Maximum cardiac output during incremental exercise by first-pass radionuclide ventriculography

A flow injection hydride atomic absorption spectrometric (FI-HAAS) method was developed for determining selenium in human milk and whole blood after microwave digestion of the sample. The sample (2 mL human milk or 0.25 mL blood) was introduced into the microwave vessel with 1.5 mL HNO3 and 0.25 mL H2O2 and 300 W (4 min) and 600 W (4 min) were applied. The digestion was completed by heating to 140 degrees C (2-3 h). Se (VI) was reduced to Se (IV) with hydrochloric acid. The instrumental conditions for FI-HAAS (concentrations of reducing agent and carrier acid, flow rate of argon carrier gas, and sample volume injected) were optimized. The detection limit of the proposed method was 0.23 ng/mL (assay) or 115 pg Se (absolute) in biological samples (1.15 ng/mL milk, 10.4 ng/mL blood). The precision values were 5.0% for milk and 4.0% for blood. The accuracy was evaluated with 2 reference materials, National Institute of Standards and Technology Non-Fat Milk Powder (found: 104.3 +/- 7.2 ng/g, certified: 110 +/- 10 ng/g) and Whole Blood Seronorm (found: 81 +/- 7.3 ng/mL, reference: 83 +/- 4 ng/mL). The results show the suitability of the method for selenium determination in human milk and whole blood. The method was applied to whole blood samples obtained from pregnant women and to human milk.     

The role of histone acetylation in the allelic expression of the imprinted human insulin-like growth factor II gene

This study examines the relationship between the first cycle of in-vitro fertilization (IVF) and subsequent cycles. The results of all IVF cycles conducted at The Hammersmith Hospital or The Royal Masonic Hospital between 1988 and 1995 were studied including those cycles where egg recovery was abandoned due to poor ovarian response. All patients underwent a standardized treatment protocol. Of those women who achieved a clinical pregnancy during their first IVF attempt, 33% achieved a pregnancy during their second cycle, statistically significantly different from the 24% of patients conceiving during a second cycle who had failed to conceive during their first. 36% of those who achieved a biochemical pregnancy in their first cycle became pregnant in their second. Age was an important factor in the success of IVF treatment, with pregnancy rates of 48% in the 20-25 year age group falling to 8% in those aged > or =41 years. Cumulative pregnancy rates were 26% after one cycle, increasing to 43% after two cycles and reached 80% after seven cycles. A previous pregnancy significantly improved a couple's probability of conception in a later IVF cycle. Overall pregnancy rates per cycle were constant for the first three attempts. Cumulative pregnancy rates continued to rise to 72% after six cycles. Thus the more cycles a couple undergo (up to six) the greater their chance of a pregnancy.     

Microinjection of thyrotropin-releasing hormone analogue into the central nucleus of the amygdala stimulates gastric contractility in rats

The effect on gastric contractility following bilateral microinjection of thyrotropin-releasing hormone (TRH) analog, RX 77368, into the central nucleus of the amygdala was examined in fasted, urethane-anesthetized rats. Extraluminal force transducers were used to measure gastric corpus contractility. Bilateral microinjection of RX 77368 (0.5 microgram, 1.0 microgram, n = 6 each) stimulated gastric contractility for up to 120 min post-injection, P < 0.05. Gastric contractility was not significantly stimulated by microinjection of 0.1 microgram RX 77368, 0.1% bovine serum albumin (BSA) into the central nucleus or RX 77368 (0.5 microgram, 1.0 microgram) into sites adjacent to the central nucleus. Peak responses (1.0 microgram) occurred 40 min post-injection and represented a 16-26-fold increase over basal values. The frequency of gastric contraction waves was attenuated for 0-90 min in rats receiving central amygdaloid microinjection of RX 77368 (0.1, 0.5 or 1.0 microgram) versus rats microinjected with the vehicle or RX 77368 into sites adjacent to the central nuclei. The stimulatory effect of RX 77368 (1.0 microgram) on gastric contractility was abolished by subdiaphragmatic vagotomy. These results indicate that the TRH analog, RX 77368, acts within the central amygdala to vagally stimulate gastric contractility.     

Characterization of type I 5 alpha-reductase activity in DU145 human prostatic adenocarcinoma cells

Each amino acid is represented by a vector of numerical measurements for the attributes of volume, area, hydrophilicity, polarity, hydrogen bonding, shape, and charge. Inter-residue distances are then calculated according to common metrics, and we introduce a new clustering objective function derived from information-theoretic considerations. The arguments of the function are the inter-object distances of the things to be clustered: in this case the amino acids. By means of approximating the solution of an integer programming problem, then, the residues are partitioned into clusters. The clusters obtained are compared with groups obtained in substitution/mutation studies and found to be similar. Thus, probably the strongest and most objective evidence to date is supplied for believing that physico-chemical properties account for the viability of substitutions and that the important similarities/differences are explained by a relatively small and simple set of properties.     

Cell-type-specific expression of rat steroid 5 alpha-reductase isozymes

The enzyme steroid 5 alpha-reductase (EC 1.3.99.5) is a component of an intercellular signaling pathway that determines cell fate in the primordium of the mammalian reproductive tract. During male phenotypic sexual differentiation, the dihydrotestosterone product of this enzyme binds to the androgen receptor and initiates development of the external genitalia and prostate. Genes encoding two isozymes of steroid 5 alpha-reductase with different biochemical properties and tissue distributions have recently been isolated. In the current study, we utilize in situ hybridization analysis to determine cell-type-specific expression patterns of the 5 alpha-reductase isozyme mRNAs in two androgen target tissues (regenerating ventral prostate and epididymis) and a peripheral tissue (liver). In regenerating ventral prostate, the type 1 mRNA is expressed in basal epithelial cells whereas expression of the type 2 mRNA is largely confined to stromal cells. These results were confirmed by immunohistochemical analysis and are consistent with distinct roles played by the isozymes in the prostate. In the epididymis, both 5 alpha-reductase isozyme mRNAs are expressed in epithelial cells. Only the type 1 mRNA is present in the liver. This mRNA is distributed in a striking spatial gradient extending from hepatocytes surrounding the portal triad (high expression) to those surrounding the central vein (low to absent expression). These findings demonstrate cell-type-specific expression of the steroid 5 alpha-reductase isozymes and underscore their distinct and overlapping functions in androgen physiology.     

A point mutation associated with a severe phenotype of neurofibromatosis 2

Neurofibromatosis 2 (NF2) is an autosomal dominant disease characterized by bilateral vestibular schwannomas and other nonmalignant tumors of the brain, spinal cord, and peripheral nerves. Although the average age of onset of NF2 is 20 years, some individuals may become symptomatic in childhood. We studied 5 unrelated NF2 patients who became symptomatic before age 13. All 5 had multiple tumors in addition to vestibular schwannoma, and none had a positive family history. Sequence analysis of the NF2 gene revealed identical nonsense mutation of exon 6 in 3 patients. Because this mutation destroys a restriction enzyme recognition site, genomic DNA from the 2 other children was directly tested for this change and identical alterations were detected. Although the work of our laboratory and others has not, in general, detected identical mutations in unrelated patients, this mutation seems to occur particularly frequently in the pediatric population and thus may be associated with an especially severe phenotype. Restriction analysis in children with NF2 may be a cost effective way of identifying their mutation. Further work is needed to characterize the effects of this change on the NF2 protein product and its relationship to this severe phenotype.     

Image compression in digital mammography: effects on computerized detection of subtle microcalcifications

Our previous receiver operating characteristic (ROC) study indicated that the detection accuracy of microcalcifications by radiologists is significantly reduced if mammograms are digitized at 0.1 mm x 0.1 mm. Our recent study also showed that detection accuracy by computer decreases as the pixel size increases from 0.035 mm x 0.035 mm. It is evident that very large matrix sizes have to be used for digitizing mammograms in order to preserve the information in the image. Efficient compression techniques will be needed to facilitate communication and archiving of digital mammograms. In this study, we evaluated two compression techniques: full frame discrete cosine transform (DCT) with entropy coding and Laplacian pyramid hierarchical coding (LPHC). The dependence of their efficiency on the compression parameters was investigated. The techniques were compared in terms of the trade-off between the bit rate and the detection accuracy of subtle microcalcifications by an automated detection algorithm. The mean-square errors in the reconstructed images were determined and the visual quality of the error images was examined. It was found that with the LPHC method, the highest compression ratio achieved without a significant degradation in the detectability was 3.6:1. The full frame DCT method with entropy coding provided a higher compression efficiency of 9.6:1 at comparable detection accuracy. The mean-square errors did not correlate with the detection accuracy of the microcalcifications. This study demonstrated the importance of determining the quality of the decompressed images by the specific requirements of the task for which the decompressed images are to be used. Further investigation is needed for selection of optimal compression technique for digital mammograms.     

Comparison of Etest to broth microdilution method for testing Streptococcus pneumoniae susceptibility to levofloxacin and three macrolides

When the Etest was compared to broth microdilution for susceptibility testing of Streptococcus pneumoniae, levofloxacin, erythromycin, and penicillin results correlated for both methods; azithromycin and clarithromycin showed discrepancies of > or = 2 dilutions for 95.8% and 31.5% of the isolates, respectively. Levofloxacin was active against 141 of 142 isolates (< or = 2.0 micrograms/ml), making it a potentially useful new fluoroquinolone.