Biomedical subjects

J E Weber

Publications and source records attributed to J E Weber.

46 records · Page 3Linked to original sources

PubMed1986

Characterization of filaments within the subacrosomal space of rat spermatids during spermiogenesis.

Two types of filaments were observed within the subacrosomal space of rat spermatids. The first of these types was characterized as actin by demonstration of actin filament affinity for myosin S-1 subfragments. Actin filaments were noted in the subacrosomal space shortly after the acrosomal sac made contact with the nucleus. As the acrosome increased its surface area contact with the spermatid nucleus, the number of layers of subacrosomal filaments increased. Pre-treatment with detergent, which in addition to permeablizing cells to allow entry of S-1, also caused the acrosome to vesiculate and the subacrosomal space to widen. In such preparations filaments were more easily visualized and appeared to extend between the nuclear and acrosomal membranes, indicating, but not proving, attachment to these membranes. During spermatid clongation, the number of actin filaments in the subacrosomal space increased greatly, especially over the dorsal convex region of the spermatid head. The polarity of the majority of filaments was not ascertainable since filaments were tightly packed within the narrow subacrosomal space. In late spermiogenesis (steps 18 and 19), actin filaments were no longer detected within the subacrosomal space. A second and much thicker type of filamentous structure was observed in the subacrosomal space of spermatids at steps 14-17 of spermiogenesis. About 14 nm in diameter (10-15 nm measurement range depending on fixation protocol utilized), these filaments did not decorate with myosin S-1 subfragments and were found in subacrosomal regions not containing actin. Fourteen nanometer filaments were seen in parallel array along the ventral folded portion of the nuclear membrane and extended partially around the nucleus. Like actin filaments. 14 nm filaments were not seen in the subacrosomal space during late spermiogenesis.

Acrosome↗

PubMed1985

Ploidy pattern analysis. Statistical considerations.

Availability of large data sets of ploidy measurements makes it possible to study ploidy patterns for the diagnostic and prognostic clues they can provide. Appropriate statistical analyses can improve the accuracy and precision of these studies. Such statistical analyses include considerations of sample size requirements for the detection of different types of deviations from normal, analyses of sources of variability in ploidy patterns and assessment of the probabilities of both types of possible errors in patient classification. The advantages of statistical assessment in the classification of ploidy patterns associated with diagnostic categories are discussed in the context of these considerations.

Aneuploidy↗

PubMed1985

Test statistics for detecting aneuploidy and hyperdiploidy.

Possible approaches to the analytical evaluation of ploidy patterns are discussed and two specific problems are considered: detection of early onset of aneuploidy and detection of moderate hyperdiploidy. A statistical model for a euploid DNA pattern is formulated in terms of a mixture distribution. A test statistic for detecting deviations from this pattern is defined, and its performance is evaluated for simulated data representing differing degrees of severity of aneuploidy. An analysis based on a discriminant function using order statistics of the sample cumulative distribution functions is proposed for detecting hyperdiploidy. This procedure has the advantage of being relatively distribution-free; its performance is evaluated for simulated data and is compared with that of its classical counterparts. Although the results reported are only preliminary, they indicate that tailor-made statistical analyses can provide early detection of aneuploidy and hyperdiploidy with known and acceptable error rates using clinically reasonable sample sizes.

Aneuploidy↗

PubMed1985

Multinomial distributions in ploidy analysis.

Ploidy patterns can be summarized in the form of a vector of proportions representing the frequency of occurrence of DNA contents in specified intervals. Data represented in this way can be analyzed statistically using the multinomial distribution. Properties of the multinomial distribution and computational difficulties that arise in its application are considered. Special problems involved in formulating hypothesis tests and confidence regions for multivariate discrete distributions are discussed in the context of evaluating vectors of proportions representing DNA ploidy patterns. Construction of tailor-made critical regions for detecting specific types of deviations from normal ploidy patterns is proposed, and a detailed example is given. In this example, two critical regions are compared: a standard critical region, consisting of cases whose probability of occurrence is small, and a diagnostic critical region, consisting of cases considered to be clinically indicative of abnormality. Advantages of the diagnostic critical region are noted.

DNA↗

PubMed1984

Immobilization by Polyurethane of Pseudomonas dacunhae Cells Containing l-Aspartate beta-Decarboxylase Activity and Application to l-Alanine Production.

Whole cells of Pseudomonas dacunhae containing l-aspartate beta-decarboxylase activity were immobilized by mixing a cell suspension with a liquid isocyanate-capped polyurethane prepolymer (Hypol; W. R. Grace & Co., Lexington, Mass.). The immobilized cell preparation was used to convert l-aspartic acid to l-alanine. Properties of the immobilized P. dacunhae cells containing aspartate beta-decarboxylase activity were investigated with batch reactors. Retention of enzyme activity was observed to be as much as 100% when cell lysis was allowed to occur before immobilization. The pH and temperature optima were determined to be 5.5 and 45 degrees C, respectively. Immobilized P. dacunhael-aspartate beta-decarboxylase activity was stabilized by the addition of 0.1 mM pyridoxal-5-phosphate and 0.1 mM alpha-ketoglutaric acid to a 1.7 M ammonium aspartate (pH 5.5) substrate solution. Under conditions of semicontinuous use in a batch reactor, a 2.5% loss in immobilized l-aspartate beta-decarboxylase activity was observed over a 31-day period.

Journal Article↗

PubMed1983

Three-dimensional reconstruction of a rat stage V Sertoli cell: II. Morphometry of Sertoli--Sertoli and Sertoli--germ-cell relationships.

Sertoli--Sertoli and Sertoli--germ-cell configurational relationships were studied using morphometric techniques and direct measurements as obtained from micrographs used to reconstruct a model of a rat stage V Sertoli cell. Regional areas of the Sertoli cell surface, which faced germ cells, other Sertoli cells, or noncellular structures, were expressed as relative surface area percentages; and the absolute surface areas for these regional areas were calculated. The surface areas of the reconstructed cell, in its unmagnified state, was found to be 12,163 micron2. Cell processes were enumerated and studied using morphometric techniques. The surface area of the reconstructed Sertoli cell facing germ cells and Sertoli cells was also determined. Five Sertoli cells showed extensive contact with the reconstructed cell at the level of the Sertoli--Sertoli junctional contact region. This contact region averaged 3.51 micron in width. The relative and absolute surface area of subsurface ectoplasmic specialization of the Sertoli cell that faced germ cells and other Sertoli cells was calculated, and the extent of penetration of step 17 spermatids into the Sertoli crypts was determined. Surface relationships of the reconstructed cell to cellular and noncellular elements were depicted on outline drawings of the Sertoli cell.

Animals↗

PubMed1983

Three-dimensional reconstruction of a rat stage V Sertoli cell: III. A study of specific cellular relationships.

Specific Sertoli--Sertoli and Sertoli--germ-cell contacts and/or junctions were investigated employing micrographs used to reconstruct serially a model of a rat stage V Sertoli cell. The Sertoli--Sertoli junctional contact areas occurred in a belt-like arrangement near the base of the Sertoli cell. This configuration is consistent with their proposed function as a sealing element limiting the passage of materials toward the tubular lumen. Sertoli ectoplasmic specializations also formed a continuous belt, or band, around the reconstructed cell at the junctional contact area. Eighteen Sertoli--Sertoli tubulobulbar complexes were found; some (12 in number) invaginated the reconstructed cell, while others (6) emanated from it. Of 37 round germ cells that were sectioned in their entirety and adjoined the reconstructed cell, 23 displayed desmosome-gap junctions with either the reconstructed cell or an adjoining cell. Since there were multiple junctions connecting some germ cells to Sertoli cells, the total number of junctions was much greater (35). Desmosome-gap junctions of the Sertoli cell were numerous connecting pachytene spermatocytes, less numerous connecting type B spermatogonia, and even less numerous connecting step 5 spermatids; and none was seen joining Sertoli cells with elongate spermatids. Most desmosome-gap junctions join germ cells to the body of the Sertoli cell at its basal aspect. Their numbers and position indicate that they play a role in the maintenance of the integrity of the seminiferous epithelium and may provide a route for cell-to-cell communication. Ectoplasmic specializations of the reconstructed cell were seen facing only 3 of 37 round germ cells, and 7 ectoplasmic specializations from adjoining Sertoli cells faced these germ cells, all of which were step 5 spermatids. That there were no ectoplasmic specializations facing pachytene cells indicates that ectoplasmic specializations are not acquired as these cells pass through Sertoli--Sertoli junctions, but are acquired later in spermatogenesis.

Animals↗

PubMedDate not supplied

Giant urethral calculus: a rare cause of acute urinary retention.

We present a case of a 98-yr-old woman with acute urinary retention secondary to a large urethral calculus. This is a unique cause of obstructive uropathy for several reasons. First, urethral calculi are extremely rare in American-born Caucasian females. Second, urethral stones in females are nearly always associated with underlying genitourinary pathology; however, subsequent work up failed to reveal any strictures, diverticula, or related processes that may have predisposed this patient to urethral calculus formation. The epidemiology, pathogenesis, clinical presentation, and emergency management of large urethral calculi are reviewed.

Acute Disease↗

PubMedDate not supplied

Resource utilization in the emergency department: the duty of stewardship.

As the pool of available health care resources continues to evaporate, emergency physicians will be increasingly required to guard against the provision of expensive, unnecessary, and marginally beneficial care. This article proposes that emergency physicians embrace the ethic of prudent resource stewardship to ensure the continued availability of emergency services to all who need them. When making resource allocation decisions, emergency physicians must consider the likelihood, magnitude, and duration of benefits to patients, the urgency of the condition, and the cost and burdens of treatment to patients, payers, and society. These considerations go beyond professional duties to individual patients and suggest that ignoring the burdens of emergency department microallocation decisions is socially and morally irresponsible.

Emergency Service, Hospital↗

PubMedDate not supplied

Diagnostic decision support by inference networks.

Inference networks permit the combining of diagnostic evidence in such a fashion that the mutual dependence structure of different pieces of evidence is considered, and that a probabilistic measure of the uncertainty of the final diagnostic decision is provided. Operated in an automatic reasoning mode, an inference network allows a decoupling of the false negative rate from the false positive rate in diagnostic procedures involving rare event detection such as the prescreening for cervical cancer.

Diagnosis, Computer-Assisted↗