Analytical performance of the Tandem-R free PSA immunoassay measuring free prostate-specific antigen

The analytical performance of the Tandem-R free PSA assay available from Hybritech Inc. was evaluated. Comparison of recoveries of purified free (unbound) prostate-specific antigen (PSA) diluted in female serum in the Tandem-R free PSA assay and the Tandem-R (total) PSA assay demonstrated a link in calibration between the assays and an accurate determination of percent free PSA. The cross-reactivity of the assay to purified PSA-alpha 1-antichymotrypsin was determined to be < 1%. The minimum-detectable concentration was < 0.05 microgram/L. The within-run and between-day CVs were < or = 5% for samples with > 0.3 microgram/L free PSA. Dilution and recovery showed no significant deviations from linearity across the assay range. The assay was insensitive to interference from blood components. The Tandem-R free PSA kit was shown to be an accurate, precise, and reliable assay for the measurement of free PSA.     

Characterization of recombinant soybean leghemoglobin a and apolar distal histidine mutants

The cDNA for soybean leghemoglobin a (Lba) was cloned from a root nodule cDNA library and expressed in Escherichia coli. The crystal structure of the ferric acetate complex of recombinant wild-type Lba was determined at a resolution of 2.2 A. Rate constants for O2, CO and NO binding to recombinant Lba are identical with those of native soybean Lba. Rate constants for hemin dissociation and auto-oxidation of wild-type Lba were compared with those of sperm whale myoglobin. At 37 degrees C and pH 7, soybean Lba is much less stable than sperm whale myoglobin due both to a fourfold higher rate of auto-oxidation and to a approximately 600-fold lower affinity for hemin. The role of His61(E7) in regulating oxygen binding was examined by site-directed mutagenesis. Replacement of His(E7) with Ala, Val or Leu causes little change in the equilibrium constant for O2 binding to soybean Lba, whereas the same mutations in sperm whale myoglobin cause 50 to 100-fold decreases in K(O2). These results show that, at neutral pH, hydrogen bonding with His(E7) is much less important in regulating O2 binding to the soybean protein. The His(E7) to Phe mutation does cause a significant decrease in K(O2) for Lba, apparently due to steric hindrance of the bound ligand. The rate constants for O2 dissociation from wild-type and native Lba decrease significantly with decreasing pH. In contrast, the O2 dissociation rate constants for mutants with apolar E7 residues are independent of pH, suggesting that hydrogen bonding to the distal histidine residue in the native protein is enhanced under acid conditions. All of these results support the hypothesis that the high affinity of Lba for oxygen and other ligands is determined primarily by enhanced accessibility and reactivity of the heme group.     

Localization of ROMK channels in the rat kidney

Renal potassium secretion occurs in the distal segments of the nephron through apically located secretory potassium (SK) channels. SK may correspond to the ROMK channels cloned from rat kidney. In this study, the localization of ROMK at the cellular level in the rat kidney was examined using an affinity-purified polyclonal antibody raised against a C-terminal peptide of ROMK. The specificity of the antibody was demonstrated by immunoblots of membranes of Xenopus oocytes expressing ROMK2. Immunoblots of homogenates from rat renal outer medulla and cortex revealed predominant bands of 70 to 75 kD, which were ablated by preadsorption with an excess of peptide. These bands were specific for the rat kidney. Immunolocalization studies revealed that ROMK is expressed in specific nephron segments in both the cortex and medulla. In the cortex, ROMK was found in the apical domain of the thick ascending limb of Henle's loop, the connecting tubule, and in some, but not all, cells of cortical collecting tubules. In the medulla, expression in the apical membrane of the thick ascending limbs of Henle's loop was strong, whereas outer medullary collecting ducts were weakly stained. Expression in the thick ascending limb was also heterogeneous; some cells that expressed the Na-K-Cl cotransporter were weakly stained with the anti-ROMK antibody. No staining of glomeruli, proximal tubules, or inner medullary collecting ducts was found. The localization of ROMK agrees well with the findings of SK in patch-clamp studies and supports the view that ROMK is the SK channel of the distal segments of the nephron.     

A digital model of pattern and productivity in an agroforestry landscape

Agroforestry is an approach to land-use which offers much promise in addressing many of the inter-related problems associated with rural development and land degradation (Scherr, 1992; Nair, 1993). This research incorporates remotely sensed agroforestry landscape information within a computerized model that relates spatial structure at the field and landscape scale to maize production. Remote sensing, cartographic modeling as well as landscape ecological theory and methods of analysis figure prominently in the work. The study area is in the coffee zone on the southern footslopes of Mount Kenya. The research tests the hypotheses that: there is a correlation between landscape, field structure and crop production. Specifically, it is hypothesized that spatial configuration at the field scale, (e.g. patch size, shape and adjacency relationships etc.) as well as at the landscape scale (density of trees and hedgerows) can be significantly correlated with productivity. The central hypothesis is that spatial variability across the landscape, at scales both at and beyond that of the field, can explain a significant amount of the variability in yields. In order to carry out the work, a recent innovation in remote sensing, the Compact Airborne Spectrographic Imager (CASI), has been used in the project. The CASI was used to acquire a detailed digital image of the site at a high spatial resolution (1.75 m pixel size). Six spectrally narrow width bands were acquired with the purpose of determining chlorophyll density as well as crop type and vigor. Findings indicate that the spatial measures that were undertaken at the landscape scale do not explain enough crop variability to be statistically significant. Rather, it is far better explained at the individual field level. Here it was demonstrated that the distance from shelter plantings is inversely and curvilinearly related to crop vigor as measured by the relationship between the Near Infra Red and Red wavelengths. Findings indicate that the positive effects of trees in the study landscape are limited to within 25 m of the canopy and may increase production as much as 32% at the optimal distance. An optimum hedgerow inter-distance of 40 m is suggested in order to maximize crop vigor. The impact of both the existing conditions as well as two possible alternatives are evaluated for their total landscape wide impacts on maize yields and wood production. It was determined that removal of the existing hedgerows (50% of all the trees in the area) by a disturbance such as a pest outbreak would cause a 5% reduction in maize production. A second alternative, which identified under-utilized planting niches throughout the landscape, is predicted to result in a modest increase in maize production and a doubling of wood products.     

ACTH-producing carcinoma of the pituitary with haematogenic metastases

Two laboratories equipped with CAS 200 (Becton Dickinson Image Cytometry Systems, San Jose, CA) instruments participated in this study of variability of DNA analysis of bladder tumor specimens. Formalin fixed paraffin embedded specimens were disaggregated and centrifuged onto microscope slides from ten bladder tumor specimens and two specimens of normal urothelium. Sources of variability considered were Specimen, Slide, Run, Laboratory, and Error. Slides were systematically scanned and 200 cells measured followed by the operator selecting 100 nuclei with abnormal morphology. DNA index (DI) and hyperdiploid fraction (HDF) were calculated from the DNA frequency distributions. For systematic sampling, 92% of the variability was due to Specimen indicating that differences in HDF values between specimens reflect biological differences. With selective sampling, only 67% of the variability in HDF is due to Specimen differences. Other factors, Laboratory, Error, and Laboratory x Specimen interaction each accounted for approximately 10% of the variability. Similarly variability of DI with selective sampling was also higher, and less specimen dependent than systematic sampling. It is important that sampling schemes and selection criteria be carefully documented in order to control variability. Enriched (or selective) sampling for abnormal cells has the potential to increase sensitivity but specimen classification based on these measurements must depend on determination of the frequency of such cells in the total population.     

Bacteremia associated with extracorporeal shockwave lithotripsy of gallbladder stones

BACKGROUND/AIMS: The possible induction of bacteremia by extracorporeal shock wave lithotripsy (ESWL) of gallbladder stones was studied. MATERIALS AND METHODS: Seventy-six patients undergoing a total of 107 ESWL treatments were studied. RESULTS: Twenty-four (22%) of the 107 treatments were associated with bacteremia. Staphylococcus epidermidis was cultured during and/or after 23 (96%) of the treatments associated with bacteremia. The ESWL-induced tissue damage of the skin in the pass-way of the shock-waves was the most likely cause of bacteremia in these patients. There was no correlation between the occurrence of bacteremia and the age or body mass index of the patients. Neither was there any correlation of bacteremia related to the duration of the treatment, the number of shock waves, the energy delivered, the stone volume or the occurrence of calcified stones. No patient developed sepsis or endocarditis. Transient fever shortly after treatment was recorded in 5 patients (5%), one of whom had bacteremia. CONCLUSIONS: Routine antibiotic prophylaxis is not indicated in patients undergoing ESWL for gallbladder stones. The question whether such prophylaxis should be given to patients at special risk, for instance patients with artificial heart valves or known valvular heart disease, remains to be answered in larger controlled and randomized studies.     

Mucosal addressin cell adhesion molecule-1 (MAdCAM-1). Its binding motif for alpha 4 beta 7 and role in experimental colitis

The integrin alpha 4 beta 7 and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) are molecules involved in the normal recirculation of lymphocytes between the blood and the gastrointestinal tract. These molecules may play a complementary and significant role in animal models of colitis. We have investigated the structural interaction between alpha 4 beta 7 and MAdCAM-1. Site-directed mutagenesis studies of the MAdCAM-1 molecule has led to the identification of the amino acid residue (LDT) in the loop between beta strands C and D of the Ig-superfamily-like folds being involved in the adhesive and cell activation functions of MAdCAM-1 with alpha 4 beta 7.     

Paraoxonase (PON1) gene in mice: sequencing, chromosomal localization and developmental expression

PURPOSE: To retrospectively examine the optic disc photographs of a glaucoma population for optic disc haemorrhages, vascular occlusions and vascular abnormalities. METHODS: The optic disc photographs of 906 eyes of glaucoma and suspect glaucoma patients were examined. Optic disc photographs were taken annually, where possible, with the follow-up period varying between 1 and 14 years duration (mean, 2.89). Glaucoma patients are regularly reviewed every 4-6 months and glaucoma suspects every 1-2 years, depending on the ophthalmologist. Low-tension glaucoma patients were reviewed more frequently (mean, every 2.6 months). The results of the findings were compared to a control group of 39 subjects with a mean follow-up period of 7 years, using Fisher's exact test. RESULTS: It was found that during the period under review, 7.4% (n = 67) of eyes had optic disc haemorrhages. The highest frequency of optic disc haemorrhages (37.5%) was found in the low tension glaucoma group (P = 0.0001) followed by 11% of primary open-angle glaucoma eyes (P = 0.03). In the normal group there were three eyes with optic disc haemorrhages and one with a disc collateral, which constitutes 5.1% vascular changes in this sub-group. Of the study eyes 2.8% had central retinal vein occlusions, 1.3% branch vein occlusion, 1.2% disc vessel abnormalities (loops) and 1.1% disc collaterals. Discrete nerve fibre layer haemorrhages and microaneurysms were found in 0.8% and 1.8% of eyes, respectively. CONCLUSIONS: A total of 16.8% of the eyes observed in this study had either disc haemorrhages or vascular changes. The underlying trend of vascular and haemorrhagic changes in glaucoma are demonstrated in this sample, which is in general agreement with previous studies. The high percentage of optic disc haemorrhages in low tension glaucoma is highlighted. The presence of microaneurysms and nerve fibre layer haemorrhages is interesting but of unknown significance.     

Interpretation and arousal in the counseling process.

We tested whether level of arousal affects the delivery of interpretations. Sixty undergraduate participants were assigned to high or low arousal or to control conditions. Participants in arousal conditions received a 30-min counseling interview for procrastination, which included two interpretations. Arousal was manipulated by interventions made before the interpretations, either confrontations (high arousal) or reflections (low arousal). Galvanic skin response measures confirmed the arousal manipulation (p?p?p?