Membrane potential mediates H(+)-ATPase dependence of "degradative pathway" endosomal fusion

BACKGROUND: In recent years Tpot (potential doubling time) has been measured before treatment in human tumors in an attempt to estimate the proliferation taking place during a course of irradiation. Tpot is defined as Ts/LI, where Ts is the duration of DNA synthesis and LI is the labeling index (proportion of cells synthesizing DNA). Ts is more difficult to measure than LI, so the question arises whether variation introduced during the determination of Ts is compensated by the theoretically better relevance of the quotient Tpot than of LI alone. It is not clear from comparisons with clinical outcome whether Tpot is a useful indicator of proliferation or whether LI is more prognostic, as suggested by a currently ongoing multicenter analysis elsewhere. Therefore, we investigated intercomparisons between Tpot and its components LI and Ts in two in their proliferation rates contrasting types of tumor where multiple biopsies were taken from each tumor. MATERIALS AND METHODS: Sixty patients with esophageal carcinoma and 57 patients with breast cancer were included in this study. All patients were injected with IUdR 6-8 h before surgery. From each tumor three to five biopsies were taken at surgery. Using flow cytometry, LI and Ts were measured on all biopsies in order to calculate Tpot. Logarithmic transformations of the distributions were used to examine correlations. Kappa-tests were used to assess how reliable an LI value could be in predicting the corresponding Tpot. RESULTS: Ts and LI were not completely independent, based on the within-tumor coefficients of variation (CVw). The ratio of between-tumor coefficient of variation (CVb) to the CVw suggested that the discriminative power of Tpot was higher than LI for esophagus, but the reverse in breast tumors, which had a larger range. Pearson correlation coefficients were high for log Tpot versus log LI in both types of tumor, but the predictive power was low, as shown by kappa-values of only 0.3-0.41 starting with LI and trying to predict the corresponding value of Tpot. Increasing widths of a central 'gray zone' were investigated for improved discrimination between fast and slow proliferation. Multiples of the within-tumor standard deviation, equally on each side of the median, were used to vary the width of the gray zone. Without a gray zone no more than 70% successful matching was obtained in esophagus tumors, compared with 80% in breast tumors. However, by excluding about half of the esophageal tumors an 80% success rate was achieved. In breast tumors over 90% matching was obtained more easily, keeping 80% of the tumors classifiable. For both tumor types correlations between Ts and Tpot were weak, with a trend towards short Ts associated with short Tpot and also with low LI. The latter correlation was significant for esophageal tumors and resulted in Tpot values having a smaller range than the LIs. CONCLUSION: Although there were good correlation coefficients between Tpot and LI, the predictive power of either from the other was not reliable, except by excluding a significant number of tumors close to the medians. The predictive value of LI for Tpot was higher for breast tumors because the spread in cell kinetic measurements was wide. Until more clinical data become available on outcome in comparison with LI or Tpot, it is still worthwhile to measure Tpot and to assess the prognostic value of both LI and Tpot in relation to outcome.     

Effects of lithium on cAMP-dependent protein kinase in rat brain

The essence of the bromodeoxyuridine (BrdUrd)-flow cytometry (FCM) technique is that cells are labelled with the thymidine analogue BrdUrd. They are then allowed to progress through the cell cycle in a BrdUrd-free environment during the postlabelling time period. At a postlabelling time shorter than the length of the S phase (Ts), cells are fixed and prepared for FCM-mediated analysis of BrdUrd and DNA contents. From FCM-derived data, cell cycle kinetic parameters such as labelling index (LI), Ts, and potential doubling time (Tpot) can be calculated. Tpot is believed to be important in the evaluation of tumor aggressiveness and therapy response. Since LI is most commonly used together with Ts to calculate Tpot, it is important that both LI and Ts are independent of the time when cells are sampled. Several formulae to calculate LI and Ts have been presented. In the present paper, we deal with various formulae to calculate LI. These formulae differ in how they take into account unlabelled and BrdUrd-labelled cells in various fractions of the cell cycle. We present a new formula, which takes into consideration cells in the different fractions and thus makes LI theoretically independent of postlabelling time. Our results show that different LI values are obtained when different formulae are used to calculate LI. In addition, we show that the BrdUrd labelling period should be kept as short as possible.     

Predictive assays of radiation response in patients with head and neck squamous cell carcinoma: a review of the Institute Gustave Roussy experience

PURPOSE: The aim of the study was to present the updated Institut Gustave Roussy experience of the predictive value of three biological parameters in patients with squamous cell carcinoma of the Head and Neck (HNSCC) treated with radiation therapy. METHODS AND MATERIALS: Three parameters have been investigated independently: tumor cell kinetics (TS, Tpot and LI), oxygen tension measurements (PO2) and intrinsic radiosensitivity (SF2Gy). RESULTS: No relationship has been found between local-regional control and Tpot or LI in a series of 74 patients. Our data also support that the surviving fraction at 2 Gy, (SF2) was unlikely to predict the clinical outcome in a series of 92 patients. Differences in PO2 measurements have been observed between tumors, and tumor oxygenation was lower than that of normal tissue for the majority of patients. However PO2 measurements did not predict clinical outcome, but further investigations are needed to draw definitive conclusions, given the limited number of patients entered in our study (35 patients). In addition, we were able to measure the three parameters in 10 patients showing no correlation between PO2, SF2 and Tpot. CONCLUSIONS: The method used to evaluate Tpot and SF2 did not provide clinically relevant predictive parameters for this type of cancer. Further investigations are needed to assess the predictive value of PO2 measurements and of new biological parameters in a multiparametric approach, taking into account other possible clinical and biological confounding factors.     

Transcatheter regional urokinase therapy in the management of inferior vena cava thrombosis

The prognosis of colorectal cancer has not significantly changed during the last 30 years. While evaluation of tumour cell proliferation may provide prognostic information, results obtained so far have been contradictory Heterogeneity in tumour cell proliferation may explain these contradictions. With in vivo injection of iododeoxyuridine (IdUrd), estimation of labelling index (LI), S-phase transit time (Ts) and potential doubling time (Tpot) may be performed from a single sample. A total of 109 colorectal cancers were studied after in vivo injection of IdUrd before surgical removal. From each cancer, four to eight samples were processed for both flow cytometrical (FCM) and immunohistochemical (IHC) visualization of IdUrd incorporation. LI/IHC was morphometrically quantified at both the luminal border and the invasive margin of these tumours. LI was significantly higher at the luminal border compared with the invasive margin, although they were correlated with each other. Using combined IHC and FCM methods, rapidly growing colorectal cancers (high LI and/or low Tpot) showed an increased survival (significant for LI at the invasive margin and for Tpot at both the invasive margin and the luminal border) in the entire unselected material and for radically removed Dukes' B tumours. FCM data alone did not discriminate for survival, with the exception of Ts in diploid and radically removed Dukes' B tumours.     

Rehabilitation approach to children with sequelae of hypoxic encephalopathy

OBJECTIVES: The dependence of human prostate carcinoma growth on hormone was studied in xenotransplants in nude mice. The objective was to determine differences in cell kinetic parameters and volume growth of tumors growing with alpha-dehydrotestosterone (alphaDHT) and without alphaDHT. These differences could be used as arguments pro and contra the adaptation versus the clonal selection hypothesis. METHODS: Human prostate carcinomas were xenotransplanted into nude mice. Growth of tumors was observed in castrated male mice without and with implanted osmotic pumps secreting alphaDHT. In a further series of experiments the alphaDHT tubes were removed when the tumors had reached a volume of 0.3 cm3. Tumor volume was measured to determine tumor doubling time with and without alphaDHT. Detailed cell kinetics were analyzed using the bromodeoxyuridine (BrdUrd) method with flow cytometry. Applying the relative movement (RM) and a simulation analysis to parallel single and multiple BrdUrd labelling experimental data we determined transit times through the phases of cell cycle, potential doubling time Tpot, growth fraction (GF) and cell loss. RESULTS: Five human prostate carcinomas were xenotransplanted into nude mice. Tumor take was only achieved when androgen hormone was present. However, when alphaDHT was removed when the tumors had grown to a volume of 0.3 cm3, they continued to grow at nearly the same Td as those tumors with continued alphaDHT application. The BrdUrd experiments, on the other hand, showed considerable increase of Tc and Tpot upon withdrawal of alphaDHT in 4 out of 5 tumors. The GF and labelling index (LI) were maintained at about the same level as alphaDHT consuming tumors. CONCLUSION: While small transplanted tumor pieces do not grow without alphaDHT, larger tumors grow with the same Td after removal of alphaDHT. The slower proliferation shown by the increased Tc and Tpot is balanced by less cell loss. Since GF and LI were maintained at about the same level, we conclude that in our tumors the majority of cells adapted to hormone independence. There was no evidence for the selection model since the tumors continued to grow at about the same speed after hormone depletion. All cell kinetic parameters showed a considerable inter- and intratumoral heterogeneity. A clinical implication may be that hormone ablation therapy should always be supplemented by some other therapy.     

DNA ploidy in early gastric carcinoma (T1): a flow cytometric study of 100 European cases

DNA ploidy of 100 early gastric carcinomas (T1) was analysed by flow cytometry on archival material from five European centres and was correlated to morphological features and clinical behaviour. Tumours were classified according to the macroscopic appearance, histological type, and growth pattern. Aneuploidy was observed in 39% of tumours. Aneuploidy was more frequent in submucosal than in mucosal tumours (p = 0.04), in raised than in flat or ulcerated lesions (p = 0.001), and in the intestinal histological than in the diffuse types (p = 0.016). The presence of lymph node metastasis in 10 cases had no obvious relation to DNA ploidy. Five related deaths occurred during the follow up (6 months--16 years) of 84 patients. These results are similar to those reported in a large Japanese series suggesting no major differences between the two populations. Although follow up data were insufficient to relate DNA ploidy to tumour behaviour in this study, the Japanese experience shows that particular attention should be paid to early direction and complete surgical excision of raised intestinal type T1 carcinomas that have a Pen A growth pattern and are aneuploid.     

Chemoradiotherapy as an alternative to radiotherapy alone in fast proliferating head and neck squamous cell carcinomas

The aim of this pilot study was to explore the prognostic relevance of cell kinetics parameters on the local control of patients affected by head and neck squamous cell carcinoma (HN-SCC), randomly assigned to receive either alternating chemoradiotherapy or partly accelerated radiotherapy. Between 1992 and 1995, 40 patients with HN-SCC at stages III and IV entered the study. Multiple primary tumor biopsies were obtained 6 h after in vivo infusion of bromodeoxyuridine, an analogue of thymidine that is incorporated in DNA-synthesizing cells. In vivo S-phase fraction labeling index (LI), duration of S-phase (TS), and potential doubling time (Tpot) were obtained by analysis of the flow cytometric content of bromodeoxyuridine and DNA. Twenty patients were treated by alternating chemotherapy and conventional radiotherapy (arm A), whereas 20 other matching patients received partly accelerated radiotherapy alone (arm B). Univariate local control analysis showed that LI, TS, and Tpot were not prognostically significant in either arm. However, local control probability at 2 years for fast growing tumors, characterized by a LI of 9%, was higher for patients treated with alternating chemoradiotherapy than it was for those treated with partly accelerated radiotherapy alone (68 versus 39%). Conversely, local control probabilities for slow proliferating tumors (LI, <9%) treated in the two arms were similar. These results suggest a potential role for alternating chemotherapy and radiotherapy in HN-SCC patients with fast growing tumors.     

Determination of sedimentation coefficients for small peptides

Direct fitting of sedimentation velocity data with numerical solutions of the Lamm equations has been exploited to obtain sedimentation coefficients for single solutes under conditions where solvent and solution plateaus are either not available or are transient. The calculated evolution was initialized with the first experimental scan and nonlinear regression was employed to obtain best-fit values for the sedimentation and diffusion coefficients. General properties of the Lamm equations as data analysis tools were examined. This method was applied to study a set of small peptides containing amphipathic heptad repeats with the general structure Ac-YS-(AKEAAKE)nGAR-NH2, n = 2, 3, or 4. Sedimentation velocity analysis indicated single sedimenting species with sedimentation coefficients (s(20,w) values) of 0.37, 0.45, and 0.52 S, respectively, in good agreement with sedimentation coefficients predicted by hydrodynamic theory. The described approach can be applied to synthetic boundary and conventional loading experiments, and can be extended to analyze sedimentation data for both large and small macromolecules in order to define shape, heterogeneity, and state of association.     

Analysis of DNA content in supraglottic epidermoid carcinoma

DNA analysis by flow cytometry is considered to be of prognostic value in epidermoid carcinoma of the head and neck. However, few and contradictory studies have been made on laryngeal carcinomas. We studied 48 epidermoid carcinomas in patients subjected to horizontal supraglottic laryngectomy with a 5-year- followup. The technique described by Hedley for fixated and paraffin-embedded tumors was used. Thirteen tumors were excluded on the grounds of presenting variation coefficients in excess of 10. Of the 35 cases analyzed, 28 (80%) were diploid and seven (20%) aneuploid. No correlation was observed between tumor ploidy and patient survival, recurrence, or any of the histopathological variables studied.     

In vivo cell kinetic measurements in human oesophageal cancer: what can be learned from multiple biopsies?

The importance of intratumour variability of cell kinetics was studied in 60 patients with cancer of the oesophagus. Five biopsies per tumour were taken. The labelling index, S-phase duration and potential doubling time (Tpot) were measured using flow cytometry. The mean Tpot value was 5.56 +/- 4.43 days (+/- 1S.D.) for adenocarcinomas and 4.40 +/- 2.45 days (+/- 1S.D.) for squamous cell carcinomas. These values were statistically significantly different. Although intratumour variation in Tpot measurements occurred, the intertumour variability was more important (P < 0.00001). This feature permits classification of tumours into slow and fast proliferating groups, leaving an intermediate group of tumours that could not be unequivocally categorised. The relative distribution of tumours into these three categories depends on the intratumour and intertumour variability of Tpot, and on the cut-off values used. Increasing the number of biopsies from one to five reduces the number of non-classifiable tumours.     

Further analysis of the reliability of the posterior tangent lateral lumbar radiographic mensuration procedure: concurrent validity of computer-aided X-ray digitization

OBJECTIVE: To investigate the reliability of a specific method of radiographic analysis of the geometric configuration of the lumbopelvic spine in the sagittal plane, and to investigate the concurrent validity of a computer-aided digitization procedure designed to replace the more tedious and time-consuming manual measurement process. DESIGN: A blind, repeated-measures design was used. The results of radiographic measures derived through the traditional manual marking method were compared with measures derived by computer-aided digitization of lateral lumbopelvic radiographs. SETTING: Private chiropractic clinic. MAIN OUTCOME MEASURES: Pearson's product-moment correlation coefficients, paired sample t tests and intraclass correlation co-efficients (ICC) were used to examine intraexaminer reliability, and repeated measures of analysis of variance were used to examine interexaminer reliability for relative rotation angles for T12-L1, L1-L2, L2-L3, L3-L4, L4-L5, L5-S1, overall lordosis measurement [absolute rotation angle (ARA)] from L1-L5 and Cobb angle of overall lordosis measured from the inferior surface of T12 to the superior surface of S1, Ferguson's sacral base angle to horizontal, angle of pelvic tilt (arcuate angle) to horizontal and anteroposterior thoracic translation (Sz) in millimeters. RESULTS: ICC estimates for intraexaminer reliability were in the range of 0.96-0.98 for the L1-L5 ARA, a range of 0.87-0.99 for the arcuate angle measurement, 0.83-0.94 for the Ferguson's angle measurement, 0.88-0.95 for the Cobb angle measurement from the inferior surface of T12 compared with the superior surface of S1 and 0.98-1.00 for the translation measurement of the lower thoracic spine to S1 (Sz). The intersegmental measurement's (T12-L1, L1-L2, L2-L3, L3-L4, L4-L5, L5-S1) correlations ranged from a low of 0.55 to a high of 0.97. Examination of these findings suggests that the reliability for the three doctors is acceptable with only the T12-L1 intersegmental measure falling below 0.70 for the least experienced examiner. Average ICC of interexaminer reliability for manual and computer-aided digitizing examiners were the following: 0.96 for the L1-L5 ARA; 0.84 for the arcuate angle measurement; 0.82 for the Ferguson's angle measurement; 0.88 for the Cobb angle measurement; 1.00 for the Sz translation measurement; and values of 0.65, 0.73, 0.74, 0.75, 0.89 and 0.81 for relative rotation angle measurements T12-L1, L1-L2, L2-L3, L3-L4, L4-L5 and L5-S1, respectively. CONCLUSION: The data tend to support the reliability of this method of radiographic analysis of the geometric configuration of the lumbopelvic spine as viewed on lateral lumbopelvic radiographs. The additional data presented here tend to support the concurrent validity of the computer-aided digitization method of analysis inasmuch as the measures determined by the digitizing examiners are essentially identical to those determined by the manual method plus or minus the average standard error of measure of each value.     

Prognostic significance of proliferative activity, DNA-ploidy, p53 and Ki-ras point mutations in colorectal liver metastases

Paired colorectal liver metastases (CLM) and normal tissue samples from a consecutive series of 36 patients were studied prospectively. MIB-1 expression was studied by immunohistochemistry on paraffin-embedded sections. DNA ploidy and S-phase fraction (SPF) measurements were performed by flow cytometry on frozen tissues. Mutations within the p53 (exons 5-8) and c-Ki-ras (codons 12 and 13) genes were detected by PCR single-strand conformation polymorphism analysis followed by sequencing. A high correlation was observed between the MIB-1 LI and SPF value (rho=0.81; P<0.01). Moreover, p53 gene mutations were associated with either high MIB-1 LI and high SPF. In univariate analysis, SPF and MIB-1 levels were related to risk of death. The association between overall survival and DNA-ploidy or p53 mutations did not reach statistical significance, but a slightly better survival was observed for patients either with DNA-diploid tumours or without mutations (P=0.05 and P=0.06, respectively). SPF was shown by multivariate Cox model analysis to be an independent prognostic variable and thus it might be a useful prognostic factor in patients with CLM.     

Reproducibility and validity of a food-frequency questionnaire designed for use in girls age 7 to 12 years

This study focused on a food-frequency questionnaire (FFQ) designed to measure nutrient intake in girls aged 7 to 12 years, inclusive. The instrument's reproducibility and validity were assessed using food records (FRs) as gold standards of measurement. Log-transformed nutrient intake estimates were compared from two FFQs and between FFQs and FRs. Intraclass correlation coefficients measuring the reproducibility of the FFQ ranged from 0.11 (starch) to 0.69 (fiber). Intraclass correlation coefficients measuring agreement between FFQ and 14l-day FR data varied between 0.15 (starch) and 0.68 (vitamin B2) for the first, and between 0.06 (starch) and 0.95 (vitamin B1) for the second FFQ. FFQs were in the best agreement with FRs for the following nutrients: fiber, vitamin B1, vitamin B2, vitamin C, and beta-carotene. Joint classifications revealed that overall, 36% of subjects were similarly categorized by FFQ and FR, and 70% of those in the lowest or highest FR quartiles were were found in the lowest or highest FR quartiles were found in the lowest or highest two FFQ quartiles, respectively.     

Interactions between nurses and patients on ventilators

Image cytometric analysis of DNA ploidy status of 40 fresh primary breast carcinomas was performed in a comparative study on cytologic preparations stained directly by the Feulgen method and smears from the same tumors Feulgen-stained after Papanicolaou staining. There was a 0.82 overall concordance in diploid and aneuploid tumor classification and a good correlation (r = 0.736, P < 0.001) between the DNA indices determined by the two methods. Discordances are probably due to tumor heterogeneity. This study demonstrates that image cytometric DNA analysis on previously routine-stained cytologic preparations is feasible and reliable for pretreatment DNA analysis and suggests potential applications in retrospective studies with cytologic material from archives.     

Effect of diuresis and nephron dimensional heterogeneity on the distribution of nephron filtration rates

Conflicting data in studies of the effect of natriuresis on intrarenal single nephron glomerular filtration rate (SNGFR) redistribution may arise from the interplay of hitherto largely overlooked factors. In the present work, the effect of diuresis induced by saline, glucose or mannitol, as well as the effect of anatomical nephron heterogeneity, were studied. A highly significant positive correlation was found between the logarithm of the urine flow per gram of kidney weight (log V) and the mean superficial (S) to mean juxtamedullary (JM) SNGFR ratio. The rise in S/JM SNGFR with diuresis was primarily a function of decreased JM SNGFR. Total proximal tubular length (TPL) was used as a measure of nephron size. The distribution of nephron sizes was evaluated as S/JM TPL. The effects of urine flow and anatomical heterogeneity on S/JM SNGFR were spearated by means of multiple regression analysis, which yielded the following equation: S/JM SNGFR = -0.049 + 0.179 log V + 0.818 S/JM TPL. Both slopes were highly significant (P less than 0.001). These findings indicate that S/JM SNGFR increases with urine flow, independently of sodium homeostasis, and that anatomical heterogeneity has a marked effect and must, therefore, be controlled. Conflicting data in the literature are harmonized with the present data when appropriate correction can be made for the dimensional factor. There is no evidence that SNGFR redistributions play a role in sodium homeostasis.     

Interobserver reliability in quantitative MRI assessment of temporomandibular joint disk status

OBJECTIVE: The purpose of this study was to investigate interobserver reliability of a new technique for quantification of magnetic resonance images of temporomandibular joint disk status. STUDY DESIGN: Sixty magnetic resonance images of adolescent temporomandibular joints were randomly drawn for analysis. Four experienced observers traced the articular disk and osseous structures on sagittal magnetic resonance slice images. Quantitative measurements of disk length and disk displacement were recorded for each slice of 57 joints traced by each observer through use of a new quantification technique. Intraclass correlation coefficients were computed to assess interobserver agreement in the tracing of joint structures. RESULTS: The calculated intraclass correlation coefficient was 0.681 for disk length and 0.830 for disk displacement. In addition, the mean variability among observers was 1.041 mm for measurement of disk length and 0.972 mm for measurement of disk displacement. CONCLUSIONS: Interobserver agreement is high when the new quantification technique is used to interpret magnetic resonance images.     

Intratumoral heterogeneity of DNA ploidy in breast carcinomas: a flow cytometric assessment of sampling techniques

Intratumoral heterogeneity of DNA ploidy has been identified in breast carcinomas; however, optimal sampling methods have not been determined. In this study of 28 invasive breast carcinomas measuring more than 1.4 cm in greatest dimension, two different techniques for obtaining cells for flow cytometric DNA ploidy analysis were compared. Two solid pieces of tissue were taken from opposite halves of the tumor. A third sample was obtained by scraping multiple cut surfaces of the tumor. Heterogeneity of DNA ploidy was detected in 43% of cases. Most cases demonstrating heterogeneity contained multiple aneuploid populations. However, in five cases classification of the tumors as either DNA euploid or DNA aneuploid differed among samples. A total of 39 non-diploid populations were detected in 23 of the cases. Thirty-three (85%) were detected by scraping and 35 (90%) were detected in either one or both tissue pieces. Intratumoral DNA heterogeneity emphasizes the need for adequate sampling. The scraping technique was as effective in identifying aneuploid cell populations as the combined results of the two pieces of tissue and better than sampling a single piece of tissue. Scraping also offers the advantage of tissue conservation which may be critical when various analytic studies are performed.     

Correspondence of left ventricular ejection fraction determinations from two-dimensional echocardiography, radionuclide angiography and contrast cineangiography

OBJECTIVES: This study assessed the agreement of left ventricular ejection fraction determinations from two-dimensional echocardiography, radionuclide angiography and contrast cineangiography. BACKGROUND: Previously published reports suggest that two-dimensional echocardiography, radionuclide angiography and contrast cineangiography are equally acceptable methods of assessing left ventricular ejection fraction on the basis of high coefficients of correlation. However, correlation of methods does not necessarily imply agreement. METHODS: In a prospective analysis, 25 consecutive subjects all had two-dimensional echocardiography and radionuclide angiography performed within 10 days of each other in the cardiology department of metropolitan community hospital. A retrospective computer search (Medline) revealed seven studies, using the coefficient of correlation (r), comparing two-dimensional echocardiographic left ventricular ejection fraction (n = 268) with radionuclide angiographic (n = 174) or contrast cineangiographic (n = 119) left ventricular ejection fractions. RESULTS: The eight individual studies (n = 293) comparing two-dimensional echocardiography with either radionuclide angiography or contrast cineangiography exhibited coefficients of correlation ranging from 0.78 to 0.93. Agreement analysis using the method of Bland and Altman was performed by averaging the results obtained from the two techniques and determining how disparate any single ejection fraction was (with 95% confidence limits) from the mean value. Agreement ranged from 23% to 42% around the mean ejection fraction. The average lack of agreement between the two methods for all studies involved was 17%, with an average r value of 0.86. CONCLUSIONS: Left ventricular ejection fraction determinations by means of two-dimensional echocardiography, radionuclide angiography and contrast cineangiography exhibit high correlation and only moderate agreement. High correlation does not always imply high agreement. These results suggest that, when validated by agreement analysis, multiple studies may not be necessary in appropriate clinical situations, potentially reducing costs.     

Megakaryocytes and the heterogeneity of circulating platelets

Megakaryocytes mature to the point of cytoplasmic disintergration in three principal ploidy classes: 8n, 16n and 32n. Cells of each of these ploidy classes have been identified, using both microdensitometry and measurement of cell volume and submitted to morphometric analysis. Mature megakaryocytes of the three ploidy classes have been shown to differ in the concentration of cytoplasmic constituents which would be expected to relate to the buoyant density of their platelet progeny. Density separated platelets have been similarly analysed. Light platelets correspond with the 32n megakarycytes and are more liberally endowed with surface connected canalicular system than the progeny of the common 16n megakaryocytes; it is proposed that they have functional characteristics related to this finding. Dense platelets, which are larger in size, correspond with 8n megakaryocytes and show a greater content of granules and mitochondria than platelets of average density. These platelets most probably show specialized function relating to release of granule constituents. Fragments of cytoplasm released from megakaryocytes represent one form of "megathrombocyte" equated by others with newly formed platelets. The differences in structure between these fragments and circulating platelets are emphasized; each such fragment must undergo further disintergration into a number of platelets. It is suggested that the heterogeneity of circulating platelets with respect to both size and density stems from the origin of platelets of varying density from the different populations of megakaryocyte and their release in the form of large cytoplasmic fragments rather than as platelets.     

Computerized determination of proliferating cell nuclear antigen expression in meningiomas. A comparison with non-automated method

Proliferating cell nuclear antigen (PCNA) expression has been proven to be a significant marker of cell proliferation in meningiomas, which correlates with growth rate and, as shown by several authors, possibly provides prognostic information concerning biologic behavior. However, the current method for determining PCNA labeling index (LI) is tedious and time consuming like all the nonautomated methods for evaluating cell kinetics, presenting high interobserver and interlaboratory variability and low reproducibility. In the present study, we introduce a semi-automated computer-assisted image analysis method for determining PCNA LI in 38 meningiomas, in parallel with the current nonautomated method. Image analysis technique permits unbiased cell counting, standardizes the degree of staining intensity and provides instant results. By calculating coefficient of variability, the method proved to be highly reproducible. The correlation between the results provided by the nonautomated and the semiautomated image analysis method showed a high agreement between them, with a correlation coefficient, r, of 0.82. In conclusion, we consider that image analysis contributes to the accuracy, reproducibility, and practicality of PCNA LI determination so that along with other useful parameters this significant marker may serve to predict the clinical behavior in meningiomas.