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Biomedical subjects

C B Williams

Publications and source records attributed to C B Williams.

At least 19 recordsLinked to original sources
PubMed1992

Alleles of the rat T-cell receptor beta chain gene complex.

Inbred rat strains provide a rich source of genetic diversity in immunologically relevant genes. We have characterized the alleles of one of these genes, encoding the rat T-cell receptor C beta 1 chain, by Southern blots and nucleic acid sequencing. The Cb1 gene segments from DA and LEW rats display complex allotypic variation: both coding and noncoding regions contain multiple nucleotide substitutions. In addition, there is a polymorphic insertion of a rat repetitive LINE element 3' to the coding region. The Cb1 alleles are one part of larger Tcrb haplotypes, containing V beta, D beta, and J beta elements; complete Cb1 genomic nucleotide sequences, and a partial list of the strain distribution of the two alleles, are described in this report.

Alleles↗
PubMed1992

The real magic.

Explore the source record for details and available documents.

Adult↗
PubMed1992

Congenital hypertrophy of retinal pigment epithelium in patients with colonic polyps associated with cancer family syndrome.

Congenital hypertrophy of retinal pigment epithelium (CHRPE) has been shown to be a frequent extracolonic manifestation of adenomatous polyposis coli (APC). The presence of CHRPE in patients with adenomatous polyps from families with cancer family syndrome suggests possible involvement of the APC gene locus in syndromes associated with less florid polyp formation than seen in APC. It also emphasises that caution must be exercised in using the presence of CHRPE clinically as a marker for APC in isolated at-risk individuals.

Adenoma↗
PubMed1992

Rectal polyposis as a guide to duodenal polyposis in familial adenomatous polyposis.

Almost all patients with familial adenomatous polyposis (FAP) develop duodenal polyps, the severity of which is graded stage 1 (minor) to stage V (cancer). Regular endoscopy is recommended for all patients with FAP. To test whether the development of severe duodenal polyposis could be predicted in another way, rectal and duodenal polyp severity were compared in 91 patients with FAP. The fulguration ratio (number of rectal fulgurations divided by number of years since colectomy) supplied the rectal polyp severity index. Patients with stage V duodenal polyposis had significantly higher fulguration ratios (median 0.38) than did patients with stage 1 disease (median 0; P = 0.009). However, the wide scatter of results means that rectal polyp severity cannot be used as a guide to duodenal polyp severity in individual patients. The coexistence of populations with severe duodenal and rectal polyposis suggests that environmental factors are important in phenotypic expression in FAP.

Adenomatous Polyposis Coli↗
PubMed1992

A computer model to predict empty body weight in cattle from diet and animal characteristics.

A computer model was developed to predict empty BW in cattle as a function of diet (forage NDF, physical form of forage [hay vs silage and pasture], proportion of dietary concentrates) and animal (full BW) characteristics. The model was empty BW = full BW * (1 - GFILL), where GFILL is gut fill expressed as a fraction of full BW. An equation obtained from published data (GFILL = .05354 + .329 * NDF) was used to provide a base prediction of GFILL from the fraction of NDF in the forage. Predicted GFILL was then corrected for full BW, physical form of forage, and fraction of concentrates using multiplicative factors obtained from published data. The model was evaluated with data from 11 published experiments. Several breeds of cattle, a wide range of forage types, and diets with 0 to 93% concentrates were represented in these data. Observed values for empty BW were compared to model-predicted values and to values predicted by systems published by the Agricultural Research Council (ARC) and National Research Council (NRC). Sums of squared deviations of predicted values from observed (n = 64) were 3,074, 37,327, and 25,920 for the model, ARC, and NRC systems, respectively. After fitting predicted empty BW values to observed values, proportion of concentrates and forage NDF accounted for a significant (P less than .01) amount of the residual variation with the ARC and NRC systems, but not for the model. This finding suggests that the model will predict empty BW more accurately than the ARC and NRC systems with diets similar to those used in the evaluation.

Animal Feed↗
PubMed1992

A computer model to predict the effects of level of nutrition on composition of empty body gain in beef cattle: I. Theory and development.

A computer model was developed to simulate differences in the composition of empty body gain of beef cattle resulting from differences in postweaning level of nutrition that are not associated with empty BW. Differences in rate of empty body gain of cattle of similar genotype reflect differences in the level of nutrition; hence, empty body gain was used to represent level of nutrition. The model was based on four assumptions: 1) as animals mature, the proportion of fat is greater in gain than in body weight, 2) effects on body composition caused by plane of nutrition that are not associated with empty BW are predictable from rate of empty BW gain, 3) effects resulting from changes in nutrition are not exerted immediately nor are they permanent, and 4) cattle approach an empty body composition equilibrium when empty body gain is zero. Six parameters were used to characterize mature fat-free matter, rate of change to body composition equilibrium, minimum and maximum fractional growth rate relative to fractional growth rate for empty BW, time lag of response to change in nutrition, and influence of stage of maturity and nutrition on rate of change for fat-free matter. Two parameters were specific for genotype and gender. Using results from the model, we were able to explain conflicting results obtained from compensatory gain experiments.

Adipose Tissue↗
PubMed1992

A computer model to predict the effects of level of nutrition on composition of empty body gain in beef cattle: II. Evaluation of the model.

A computer model developed to predict composition of empty body gain of beef cattle fed at different levels of nutrition was evaluated with data from one unpublished and seven published experiments. These experiments used several breeds of beef cattle growing at rates that varied from negative to fast and various combinations of these growth rates. There was close agreement between observed and simulated absolute treatment means for fatness, except when animals were fed diets low in protein. In this case, experimental animals fed inadequate protein grew at slower rates and became fatter than contemporaries fed adequate protein, whereas the model predicted the opposite. Ability of the model to predict effects of nutrition not associated with changes in BW was evaluated using the proportion of residual variation in experimental fat percentage accounted for by the model, after fitting linear and quadratic terms for empty BW. The model accounted for 13.8 to 56.2% of the residual variation in observed fatness in four experiments in which significant differences in fatness were observed among nutritional treatments after accounting for differences in empty BW. Regression of observed fatness on model-simulated fatness resulted in regression coefficients that were positive and close to 1 in these four experiments. This suggests that the model can accurately predict some of the effects of nutrition on fatness that are not associated with changes in empty BW.

Adipose Tissue↗
PubMed1991

Organization and nucleotide sequence of the rat T cell receptor beta-chain complex.

We have characterized four overlapping genomic clones containing the DA rat TCR C beta complex, which span a total of 23 kb and bear two closely related complexes of gene segments. The D beta 1-J beta 1-C beta 1 and the D beta 2-J beta 2-C beta 2 complexes each contain a single diversity segment, six joining segments and four exons that encode the C region. All gene segments appear to be functional except J beta 2.5, which has a 5-bp frame-shifting deletion. This organizational pattern is identical to that of the mouse, and the homologous rat and mouse coding regions share about 92% nucleotide sequence identity. Our sequence comparisons indicate that a localized gene correction event has homogenized the sequences of the first exons of C beta 1 and C beta 2 in the evolutionary time since rats and mice became separate species. We have identified three repetitive elements, each flanked by short direct repeats, present in the region "brain-specific" identifier (ID) sequences, another is a truncated member of the LINE I class of repetitive elements, and the third is a member of the Alu type 2 family. The insertion of at least two, and probably all, of these elements has occurred since the time of rat/mouse divergence. We have identified a substantial number of "cryptic" rearrangement signals (heptamer/nonamer) in the C beta locus, which match the consensus sequence as well or better than authentic signals, and may represent sites of nonfunctional rearrangements.

Animals↗
PubMed1991

Retention of nondeflating balloon in small bowel. Case report and review of the literature.

Intubation of the upper gastrointestinal tract with balloon catheters has a role in the diagnosis, treatment, and research of many gastrointestinal conditions. A potential complication of this procedure, albeit rare, is failure of the balloon to deflate, thereby preventing removal of the intestinal tube. We describe a case where this problem arose and the series of maneuvers that were attempted to resolve it. Attempts at overdistending the balloon, reaching it via endoscopy, and ultrasound localization of the balloon all failed. The tube was successfully removed following CT-guided percutaneous needle puncture of the impacted balloon. The published experience with nondeflating catheter balloons in hollow viscera has been reviewed and the suggested methods for deflation or puncture are discussed.

Adult↗
PubMed1991

Malignant colorectal polyps: venous invasion and successful treatment by endoscopic polypectomy.

We reviewed the pathology of 81 malignant colorectal polyps in 80 patients treated by endoscopic polypectomy and assessed the importance of carcinomatous invasion of veins in the stalk (submucosa). All the patients were followed up for at least five years. Venous invasion was present in 30 of the polyps (37%). The histological features of lymphatic invasion were considered too subjective to be of value. Most of the tumours were well or moderately differentiated adenocarcinomas, one was poorly differentiated, and one was a signet ring cell carcinoma. Seventy one patients were treated by polypectomy alone, and 58 of these were alive and well five years later, with no evidence of recurrence. Nine died of unrelated causes within five years, but four died of carcinomatosis: one with recurrent tumour, one with a possible metachronous caecal cancer, and in two patients there was late development of malignancy of uncertain nature. The remaining nine patients underwent surgical resection after initial endoscopic polypectomy because of incompleteness of excision, poor differentiation of the tumour, or a decision by the surgeon. Tumour was not present in the resection specimens apart from a single lymph node deposit in the patient with signet ring cell carcinoma. These nine patients were alive and well without evidence of recurrence five years later. The results reemphasize the necessity of good cooperation between endoscopist and pathologist, meticulous laboratory technique, strict histopathological criteria including examination of resection margins and degree of differentiation of the tumour, and regular endoscopic follow up. Endoscopic polypectomy of pedunculated and sessile malignant polyps is adequate treatment if the lesion can be removed in one piece, the tumour is well or moderately differentiated, and local excision is judged complete by endoscopic and histological criteria. Patients with histologically incompletely excised polyps, containing well or moderately differentiated carcinoma, can be safely managed by conservative treatment provided the endoscopist is certain there is no residual tumour. Venous invasion by tumour is a common finding in malignant colorectal polyps and seems to have no prognostic importance.

Adult↗
PubMed1991

Primary B-cell immunoblastic lymphoma of pancreas.

Extranodal lymphoma may present as an abdominal mass without evidence of disease elsewhere. Predominant pancreatic involvement with lymphoma is rare. Presenting as a pancreatic mass, it may be difficult to differentiate if from carcinoma. Ultrasound-guided fine needle biopsy and immunocytochemistry are helpful in establishing a histological diagnosis. It is important to differentiate lymphoma from carcinoma, because lymphoma is treated differently and has a better prognosis.

Adult↗
PubMed1990

A family of three mouse potassium channel genes with intronless coding regions.

To understand the molecular mechanisms responsible for generating physiologically diverse potassium channels in mammalian cells, mouse genomic clones have been isolated with a potassium channel complementary DNA, MBK1, that is homologous to the Drosophila potassium channel gene, Shaker. A family of three closely related potassium channel genes (MK1, MK2, and MK3) that are encoded at distinct genomic loci has been isolated. Sequence analysis reveals that the coding region of each of these three genes exists as a single uninterrupted exon in the mouse genome. This organization precludes the generation of multiple forms of the protein by alternative RNA splicing, a mechanism known to characterize the Drosophila potassium channel genes Shaker and Shab. Thus, mammals may use a different strategy for generating diverse K+ channels by encoding related genes at multiple distinct genomic loci, each of which produces only a single protein.

Amino Acid Sequence↗