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Biomedical subjects

W Silverman

Publications and source records attributed to W Silverman.

32 records · Page 2Linked to original sources
PubMed1989

Alzheimer-type neuropathology and clinical symptoms of dementia in mentally retarded people without Down syndrome.

Postmortem morphometric analyses of Bielschowsky stained sections from brains of 70 mentally retarded people without Down syndrome, age 65 and over when they died, indicated Alzheimer-type neuropathology in 22 cases (31%) and a majority with at least presence of some Alzheimer-type lesions. Based upon information abstracted from clinical histories, however, old-age-associated dementia proved to be difficult to judge reliably. Nevertheless, for otherwise healthy individuals (n = 25), loss of motor skills, development of problem behaviors, and a 10-point drop in IQ appeared to be likely indicators of Alzheimer's disease. Prevalence estimates of Alzheimer-type neuropathology among nonretarded people and the present sample appear comparable, and projections must be made to address the special needs of this rapidly growing population of retarded people.

Aged↗
PubMed1987

Localization of phospholipid synthesis to Schwann cells and axons.

Quantitative electron microscopic autoradiography was used to detect and characterize endoneurial sites of lipid synthesis in mouse sciatic nerve. Six tritiated phospholipid precursors (choline, serine, methionine, inositol, glycerol, and ethanolamine) and a protein precursor (proline) were individually injected into exposed nerves and after 2 h the mice were perfused with buffered aldehyde. The labeled segments of nerve were prepared for autoradiography with procedures that selectively remove nonincorporated precursors and other aqueous metabolites, while preserving nerve lipids (and proteins). At both the light and electron microscope levels, the major site of phospholipid and protein synthesis was the crescent-shaped perinuclear cytoplasm of myelinating Schwann cells. Other internodal Schwann cell cytoplasm, including that in surface channels, Schmidt-Lanterman incisures, and paranodal regions, was less well labeled than the perinuclear region. Newly formed proteins were selectively located in the Schwann cell nucleus. Lipid and protein formation was also detected in unmyelinated fiber bundles and in endoneurial and perineurial cells. Tritiated inositol was selectively incorporated into phospholipids in both myelinated axons and unmyelinated fibers. Like inositol, glycerol incorporation appeared particularly active in unmyelinated fibers. Quantitative autoradiographic analyses substantiated the following points: myelinating Schwann cells dominate phospholipid and protein synthesis, myelinated axons selectively incorporate tritiated inositol, phospholipid precursors label myelin sheaths and myelinated axons better than proline.

Animals↗
PubMed1983

The strength of association between fragile (X) chromosome presence and mental retardation.

In order to obtain a quantitative estimate of the degree of association between presence of fragile X chromosome (fra(X] and mental retardation (MR), existing data from nonretarded males were analyzed. Clearly, fra(X) occurs less frequently among nonretarded compared to MR males. However, incidence estimates for fra(X) based upon existing data hold open the possibility that there may be significant numbers of nonretarded males with fra(X). Additional analyses of data from families with a pattern of fra(X) linked MR showed: (a) the probability that nonretarded male offspring will have fra(X) is very small, and (b) the probability that MR male offspring will have fra(X) is very large. Thus, accurate prognostic decisions can be based upon prenatal diagnosis of fra(X) presence, especially in families with a pattern of fra(X) linked MR.

Female↗
PubMed1982

Reaction time and mild mental retardation: high speed scanning reexamined.

When observers judge whether a probe is contained within a small positive set, reaction time (RT) increases linearly with set size (Sternberg, 1969b). Slope and intercept of the function relating RT to positive set size are believed to reflect durations of different processing stages. As results of several investigations suggested inverse slope/intercept relationships, however, studies using "high-speed scanning" tasks to compare retarded with nonretarded individuals were reexamined. When slope was correlated with points along the RT function (intercept, Positive Set Sizes 1, 2, and 4), results showed no interdependencies for nonretarded adults. Slope and intercept were negatively correlated for retarded and nonretarded adolescents, whereas slope and Positive Set Size 1 values apparently were unrelated. These results seem to contradict theoretical expectations, and specification of processing stages where efficiency varies across populations may not be possible based on results from high speed scanning tasks.

Adolescent↗
PubMed1975

Utilization of redundant information by EMR and nonretarded adults.

When stimuli differed on two dimensions (size and shape), either of which furnished enough information for a correct response, retarded subjects were faster to discriminate than when stimuli differed on only one dimension. This result was also found with nonretarded subjects, and the data were taken to support the argument that both populations process information in this type of speeded visual discrimination in similar ways; whatever feature-testing model accommodates the data from nonretarded subjects also describes the data from retarded subjects.

Adolescent↗
PubMedDate not supplied

Genetic and other factors that contribute to variability in cytogenetic expression in fragile X males.

Variability in cytogenetic expression of fragile X has been observed by many investigators. One recent study of families of fragile X brothers concluded that frequency of expression was almost completely controlled by genetic factors. We investigated the extent of genetic control over frequency of expression by evaluating fragile X families from 3 different sources using hierarchal analysis of variance model to calculate the intraclass correlation and the index of heritability, h2. Proportion of variance attributable to families was computed from 2 estimation procedures: 1) a least squares method and 2) a maximum likelihood technique. Results were comparable with one another and indicated that, although genetic factors were significant, differences between laboratories contributed a larger proportion of the total estimated variance. These results partly confirmed previous findings but indicated that the degree of genetic control over the proportion of affected cells was lower than recently suggested.

Analysis of Variance↗
PubMedDate not supplied

Effect of prophylactic main pancreatic duct stenting on the incidence of biliary endoscopic sphincterotomy-induced pancreatitis in high-risk patients.

Pancreatitis is a common complication of endoscopic sphincterotomy. Cautery-induced papillary edema has been implicated as a possible cause. The objective of this study was to determine whether prophylactic stenting of the main pancreatic duct after endoscopic sphincterotomy in high-risk patients would reduce the incidence of pancreatitis. High-risk patients were defined as those with sphincter of Oddi dysfunction, small common bile duct diameter (< 10 mm), or those requiring pre-cut sphincterotomy. Patients were studied in a prospective fashion from October 1990 to April 1992 and were randomized to receive either a main pancreatic duct stent or no stent after biliary sphincterotomy. The stents were generally removed 10 to 14 days after placement. Fifty patients were randomized to the no-stent group and 48 patients were randomized to the stent group, but in five patients stent placement was unsuccessful. Pancreatitis occurred in 18% of patients in the no-stent group compared with 14% of patients in the stent group. Most cases of pancreatitis were mild, occurring in 10% of patients in the no-stent group and 12% of patients in the stent group. Moderate to severe pancreatitis occurred with an increased frequency in patients in the no-stent group (8%) compared with that in patients in the stent group (2%). Mean number of hospital days required to treat pancreatitis was 9.5 days in the no-stent group compared with 2.8 days in the stent group; however, none of these differences reached statistical significance. Small common bile duct diameter (< 6 mm) was found to be an independent risk factor for pancreatitis after endoscopic sphincterotomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Common Bile Duct↗
PubMedDate not supplied

Diagnostic criteria for the neuropathological assessment of Alzheimer's disease: current status and major issues.

A Consensus Conference focusing on Alzheimer's disease (AD) took place in November 1996 to recommend uniform evaluation procedures and diagnostic criteria, co-sponsored by the National Institute on Aging and the Reagan Institute of the Alzheimer's Association. In conjunction with this conference, we reviewed diagnostic practices in current use, together with various neuropathological criteria proposed since 1985. Difficulties were identified in developing "gold standard" criteria for diagnosis and case classification of AD based upon the current state of knowledge. Working criteria for use within research contexts were proposed that acknowledged the realities of scientific limitations by inclusion of a broad and heterogeneous category of "uncertain" cases. (Eventually, methods will be developed for identifying these cases as preclinical AD, dementia due to multiple causes or non-AD, but this is not now possible.) Within applied contexts, the use of CERAD guidelines was supported. Finally, recommendations generated at the Consensus Conference were discussed, emphasizing the rapid pace of recent scientific advancement and the need for ongoing empirical reevaluation and modification of the Group's proposal.

Adult↗