Search PubMed⌕ Search

Biomedical subjects

B G Robinson

Publications and source records attributed to B G Robinson.

At least 73 records · Page 4Linked to original sources
PubMed1996

The relationship between specific RET proto-oncogene mutations and disease phenotype in multiple endocrine neoplasia type 2. International RET mutation consortium analysis.

OBJECTIVE: Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant disorder. The 3 recognized subtypes include MEN 2A, characterized by medullary thyroid carcinoma (MTC), pheochromocytoma (pheo), and hyperparathyroidism (HPT); MEN 2B, by MTC, pheo, and characteristic stigmata; and familial MTC (FMTC), by the presence of MTC only. The purpose of this study was to establish the relationship between specific mutations and the presence of certain disease features in MEN 2 which could help in clinical decision making. DESIGN: Correlative survey study of 477 MEN 2 families. SETTING: Eighteen tertiary referral centers worldwide. PATIENTS: A total of 477 independent MEN 2 families. MAIN OUTCOME MEASURES: Association between the position and type of germline mutation in the RET proto-oncogene and the presence or absence of MTC, pheo, HPT, and/or other features in a family. RESULTS: There is a statistically significant association between the presence of any mutation at a specific position (codon 634) and the presence of pheo and HPT. The presence of a specific mutation, CGC at codon 634, has yet to be associated with FMTC. Conversely, mutations at codons 768 and 804 are thus far seen only with FMTC, while codon 918 mutation is MEN 2B--specific. Rare families with both MEN 2 and Hirschsprung disease were found to have MEN 2-specific codon mutations. Patients with Hirschsprung disease presenting with such mutations should be monitored for the possible development of MEN 2 tumors. CONCLUSIONS: This consortium analysis suggests that genotype-phenotype correlations do exist and, if made reliably absolute, could prove useful in the future in clinical management with respect to screening, surveillance, and prophylaxis, as well as provide insight into the genetic effects of particular mutations.

Carcinoma, Medullary↗
PubMed1996

Peripheral blood mononuclear cells are a reliable internal standard for the flow cytometric DNA analysis of frozen malignant breast biopsies.

DNA ploidy and S-phase estimations are widely used as prognostic indicators in treatment decisions for breast cancer patients. For accurate calculation of the DNA index there is a need to identify the G0G1 diploid peak position. This study tested the reliability of peripheral blood mononuclear cells (PBMCs) as a diploid internal standard in the flow cytometric DNA analysis of 60 frozen malignant breast tumors. For each tumor, PBMCs were added to a duplicate sample prior to staining. There were 55 tumors with interpretable histograms; 18 were DNA diploid, 37 were DNA aneuploid, and all tumors had coefficients of variation < 5.0%. For each of the 55 tumors, whether diploid or aneuploid, the addition of PBMCs gave a unimodal peak at the diploid peak position. The results show that PBMCs are a reliable standard to identify the G0G1 diploid peak position.

Aneuploidy↗
PubMed1996

Germline and somatic mutations in an oncogene: RET mutations in inherited medullary thyroid carcinoma.

Inherited cancer syndromes predispose an individual to development of specific tumors. Somatic and germline mutations in the same tumor suppressor gene, as described in Knudson's two-mutation model, are well recognized. Inherited mutations in the RET proto-oncogene, which encodes a receptor tyrosine kinase, predispose individuals to the multiple endocrine neoplasia type 2 (MEN 2) cancer syndromes. The major component tumor of these syndromes is medullary thyroid carcinoma (MTC). To date, somatic mutations in RET have not been identified in tumors from individuals with MEN 2, although they have been well documented in sporadic MEN 2-related tumors. We have identified, among 16 MEN 2 cases with well-defined RET germline mutations, a somatic missense mutation at codon 918 of RET in 3 of 15 MTCs and in a sample with hyperplastic C-cells (presumed precursor to hereditary MTC). We suggest that the presence of a somatic mutation, in addition to the preexisting germline mutation in hereditary MTCs, may contribute to tumorigenesis in vivo.

Carcinoma, Medullary↗
PubMed1996

Regulation of adhesion molecule expression by human synovial microvascular endothelial cells in vitro.

OBJECTIVE: To examine the in vitro expression of E-selectin, P-selectin, intercellular adhesion molecule 1 (ICAM-1), ICAM-2, vascular cell adhesion molecule 1 (VCAM-1), and platelet-endothelial cell adhesion molecule 1 (PECAM-1) by synovial microvascular endothelial cells (SMEC) in comparison with microvascular neonatal foreskin endothelial cells (FSE) and macrovas- cular human umbilical vein endothelial cells (HUVE). METHODS: Cultured endothelial cells were treated for 4 hours with medium alone or tumor necrosis factor alpha (TNF alpha). The expression of endothelial adhesion molecules was evaluated by flow cytometry, cell enzyme-linked immunosorbent assay, and Northern blot analysis. RESULTS: SMEC continuously expressed E-selectin under basal culture conditions, whereas FSE and HUVE did not. TNF alpha treatment of rheumatoid arthritis (RA) SMEC resulted in sustained peak expression of E- selectin for up to 24 hours, which subsequently declined but remained elevated even at 72 hours. In contrast, peak E-selectin expression in FSE and HUVE occurred between 4 hours and 16 hours after TNF alpha treatment and then declined to near basal levels by 24-48 hours. SMEC expressed significantly higher levels of ICAM-1 compared with HUVE under basal culture conditions. There was no difference between SMEC, FSE, and HUVE in the expression of P-selectin, VCAM-1, ICAM-2, or PECAM-1. Northern blot analysis demonstrated that the levels of E-selectin expression by TNF alpha stimulated endothelial cells correlated with their respective messenger RNA levels. CONCLUSION: Regulation of E-selectin and ICAM-1 expression in RA synovial endothelium is different from that in neonatal foreskin and human umbilical vein endothelium. The augmented expression of adhesion molecules in RA synovial endothelium may facilitate the recruitment of leukocytes to this site.

Agglutinins↗
PubMed1996

The identification of false positive responses to the pentagastrin stimulation test in RET mutation negative members of MEN 2A families.

OBJECTIVE: The pentagastrin stimulation test is the traditional test used for the identification of asymptomatic individuals in multiple endocrine neoplasia type 2A (MEN 2A) and familial medullary thyroid carcinoma (FMTC). The identification of mutations in the RET proto-oncogene segregating with the disease phenotype in MEN 2A and FMTC families has made it possible to re-examine the validity of using this test for the identification of affected family members. DESIGN: Sequential and single pentagastrin stimulation test data were collected following the identification of RET mutation positive and RET mutation negative members of families with MEN 2A or FMTC. PATIENTS: RET mutations were identified in 16 Australian and New Zealand MEN 2A or FMTC families. An analysis of 39 individuals from these families was included in this study. Thirty-two individuals (14 males, 18 females) had previously been determined as RET mutation negative. Seven individuals (6 males, 1 female) had previously been determined as RET mutation positive. Two RET mutation negative males had thyroidectomy based on prior pentagastrin test results. MEASUREMENTS: Serum calcitonin levels in response to stimulation with pentagastrin were measured at 0, 1, 2, 5 and 10 minutes post injection. Mutation analysis of the RET proto-oncogene was performed in all individuals. In two RET mutation negative individuals from two MEN 2A families, thyroidectomy was performed and C-cells were quantitated in order to determine the diagnosis of C-cell hyperplasia. RESULTS: There was a statistically significant difference (P < 0.013) between RET mutation negative male and female mean peak calcitonin responses of 282 +/- 236 and 96 +/- 62 (mean +/- SD) ng/l respectively. False positive responses to pentagastrin stimulation were identified in seven individuals who were RET mutation negative in two of the 16 families. Histologic examination of the thyroid glands in the two RET mutation negative individuals who had thyroidectomy demonstrated C-cell hyperplasia in one but not in the other. CONCLUSIONS: There is considerable overlap between pentagastrin test results in individuals who are RET mutation positive and those who are RET mutation negative. These results indicate a need for routine performance of RET proto-oncogene analysis on all individuals at risk of developing MEN 2A or FMTC and a coupling of pentagastrin test results and RET proto-oncogene analysis in the decision to proceed with thyroidectomy.

Adolescent↗
PubMed1996

Somatic mutations in the RET proto-oncogene in sporadic medullary thyroid carcinoma.

OBJECTIVE: We have determined the frequency of specific mutations in the RET proto-oncogene in sporadic medullary thyroid carcinomas (MTCs) and correlated the presence or absence of a codon 918 mutation with the clinical characteristics of these tumours. DESIGN: Thirty paraffin-embedded sporadic MTCs and two frozen MTCs were collected for analysis of specific mutations in the RET proto-oncogene in codons 609, 611, 618 and 620 (exon 10); 630 and 634 (exon 11); 768 (exon 13); 883 (exon 15) and 918 (exon 16). A novel primer was designed which introduced a restriction site for Rsal in the presence of the specific codon 918 mutation (ATG-->ACG) in these tumour samples. A 'clinical-genetic' correlation was performed comparing the presence of absence of the codon 918 mutation with the following clinical characteristics: age at diagnosis, tumour size, presence or absence of metastases, MTC related morbidity, and base line calcitonin levels at diagnosis or most recent follow-up. PATIENTS: Patients were classified as having sporadic MTC if there was no family history of C-cell hyperplasia, MTC, phaeochromocytoma or parathyroid disease. Retrospective review of patient records enabled complete clinical data to be obtained in 28 of 32 patients. MEASUREMENTS: Base line calcitonin levels were measured by radioimmunoassay or calcitonin enzyme linked immunoassay. Cysteine codons in exons 10 and 11, specifically codons 609, 611, 618, 620, 630 and 634, were screened for the presence of mutations by sequence analysis. Specific mutations occurring at codons 768, 883 and 918 were screened for by restriction endonuclease digestion of PCR products. RESULTS: The mutation at codon 918ATG-->ACG was found in 21 of 32 (66%) MTCs and the mutation at codon 883GCT-->TTT was found in one of 32 MTCs. Where possible, the presence of 'germline-type' mutations in codons 609, 611, 618, 620, 630 and 634 were excluded. Ten MTCs did not have a mutation in codons 768, 883 or 918 of the RET proto-oncogene. The presence or absence of the somatic mutation at codon 918 did not correlate with any of the above clinical characteristics. CONCLUSION: Somatic mutations in the RET protooncogene occur frequently in sporadic MTCs.

Adult↗
PubMed1996

Sulindac increases the expression of APC mRNA in malignant colonic epithelial cells: an in vitro study.

BACKGROUND: Sulindac is a non-steroidal anti-inflammatory drug which induces regression of colonic polyps in patients with familial adenomatous polyposis. Animal and in vitro studies have shown that both the sulphide metabolite of sulindac, which is able to inhibit cyclo-oxygenase, and the sulphone metabolite, which lacks this ability, are able to inhibit the growth of colonic carcinoma cells. The exact mechanism by which these effects occurs is not known. AIMS: To examine the effect of sulindac sulphide and sulindac sulphone on the expression of APC messenger RNA (mRNA), and on the proliferation of colonic carcinoma cells in vitro. METHODS: The colonic carcinoma cell line LIM 1215 was treated with sulindac sulphide and sulindac sulphone (10 microM or 100 microM) for 24 hours. Total RNA was extracted and APC mRNA was quantitated using competitive reverse transcription polymerase chain reaction. Measurements of cell number, cell proliferation, and prostaglandin E2 concentrations were also made. RESULTS: A significant increase in APC mRNA was observed after treatment with 10 microM of both sulindac sulphide and sulindac sulphone (control: 37.2 (19.7); 10 microM sulindac sulphide: 129 (112.8); 10 microM sulindac sulphone: 207.7 (102.9) pg/(g total RNA) (p < 0.05). Prostaglandin E2 concentrations were significantly reduced after treatment with sulindac sulphide, but not after sulindac sulphone. Both agents produced a dose dependent reduction in cell numbers and cell proliferation, which was more noticeable after treatment with sulindac sulphide. CONCLUSIONS: Both sulindac sulphide and sulindac sulphone inhibit the growth of carcinoma cells in vitro and cause an increase in APC mRNA. The effect of these agents on colonic carcinogenesis is not mediated entirely by means of an inhibition of prostaglandin biosynthesis.

Adenomatous Polyposis Coli↗
PubMed1996

Angiotensin-converting enzyme inhibitors regulate the Na(+)-K+ pump via effects on angiotensin metabolism.

Treatment of rabbits with angiotensin-converting enzyme (ACE)-inhibiting drugs increases Na(+)-K+ pump current (Ip) of isolated cardiac myocytes when intracellular Na+ is at near-physiological levels. To examine if effects of ACE inhibitors are related to angiotensin metabolism, we measured Ip in myocytes isolated from rabbits treated with the AT1 receptor antagonist losartan. Ip was increased to levels similar to those after treatment with ACE inhibitors. Exposure of myocytes from captopril-treated rabbits to 10 nM angiotensin II (ANG II) for 45 min in vitro reduced Ip to levels similar to those of myocytes from untreated control rabbits. This rapid response to ANG II suggests that treatment with captopril had induced a functional change in preexisting pump units rather than synthesis of a new population of pumps. Consistent with this, we could not detect a change in Na(+)-K+ pump subunit mRNAs during treatment with captopril. The decrease in Ip of myocytes from captopril-treated rabbits induced by ANG II in vitro was blocked by pertussis toxin, bisindolylmaleimide I, and staurosporine. Exposure of myocytes to phorbol 12-myristate 13-acetate induced a decrease in Ip similar to that induced by ANG II. Thus ACE inhibitors regulate the Na(+)-K+ pump in myocytes via an effect on angiotensin metabolism. The regulatory mechanism appears to include the AT1 receptor, a G protein, and protein kinase C.

Angiotensin II↗
PubMed1995

Quantitation of APC mRNA in human tissues.

The aim of this study was to develop a method for quantitation of APC mRNA and to measure APC mRNA levels in human tissues. This was done using a competitive reverse transcription PCR with a synthetic RNA control. APC mRNA (pg/microgram total RNA) was quantitated in the following tissues: normal colon 133.6 +/- 69.0; normal duodenum 16.6 +/- 15.7; normal thyroid 30.4 +/- 20.3; normal esophagus 65.2 +/- 58.8; colonic carcinoma 66.5 +/- 30.3; esophageal carcinoma 54.7 +/- 26.5; papillary thyroid carcinoma 55.8 +/- 32.9 and colonic adenomas from patients with familial adenomatous polyposis 46 +/- 15. APC mRNA levels were significantly lower in the duodenum and thyroid than in the colon and esophagus. The quantity of APC mRNA was lower in colonic adenomas from FAP patients than in normal colonic mucosa (p < 0.05).

Base Sequence↗
PubMed1995

Medullary thyroid carcinoma: recent advances and management update.

Medullary thyroid carcinoma (MTC) is a malignancy of the thyroid C-cells that comprises 5-10% of all thyroid cancers. MTC occurs in both sporadic and familial forms, the latter making up 25% of all MTCs and being comprised of three distinct syndromes--multiple endocrine neoplasia type 2A (MEN 2A), multiple endocrine neoplasia type 2B (MEN 2B), and familial medullary thyroid carcinoma (FMTC). To date, screening for MTC has been performed using the pentagastrin stimulation test, which is a provocative test for calcitonin release. Germline mutations in the RET protooncogene have been identified in families manifesting these syndromes and genetic screening of individuals at risk of one of these syndromes has become integral to their clinical management. The majority of the mutations associated with MEN 2A and FMTC are tightly clustered in a cysteine-rich region of the RET receptor. A single mutation associated with MEN 2B is in the the tyrosine kinase domain of the RET receptor. Somatic mutations have been identified in the tumor tissue of individuals with sporadic MTC and may prove to be helpful markers in discerning the hereditary or sporadic nature of the MTC. There is general agreement that the primary operation for MTC should include total thyroidectomy and central neck lymph node clearance. The role of microdissection for recurrent disease awaits longitudinal evaluation. External radiotherapy, radionuclide therapy, and chemotherapy may have a role in palliation, but have not been proven to have a curative value. Prognostic factors are discussed.

Animals↗
PubMed1995

Genotype-phenotype correlation in multiple endocrine neoplasia type 2: report of the International RET Mutation Consortium.

The International RET Mutation Consortium was first convened as part of the Fifth International Workshop on Multiple Endocrine Neoplasia, Stockholm, Sweden, in an attempt to analyse the relationship of RET mutation and disease phenotype in the autosomal dominantly inherited multiple endocrine neoplasia type 2 (MEN 2) syndromes. Out of 361 families studied, 41% had MEN 2A, 17.7% MEN 2B, 6.4% FMTC and the remaining subjects were unclassified. RET mutations were detected in 87.3% of families overall. Over 93% of MEN 2B families had the RET 918 ATG-->ACG mutation, while the most frequent mutation detected in MEN 2A families was cysteine codon 634 (87% of all mutations).

Carcinoma, Medullary↗
PubMed1995

Association of HincII RFLP of low density lipoprotein receptor gene with obesity in essential hypertensives.

Obese (BMI > or = 26 kg/m2; n = 51) and lean (BMI < 26 kg/m2; n = 61) Caucasian patients with severe, familial essential hypertension, were compared with respect to genotype and allele frequencies of a HincII RFLP of the low density lipoprotein receptor gene (LDLR). A similar analysis was performed in obese (n = 28) and lean (n = 68) normotensives. A significant association of the C allele of the T-->C variant responsible for this RFLP was seen with obesity (chi 2 = 4.6, P = 0.029) in the hypertensive, but not in the normotensive, group (odds ratio = 3.0 for the CC genotype and 2.7 for CT). Furthermore, BMI tracked with genotypes of this allele in the hypertensives (P = 0.046). No significant genotypic relationship was apparent for plasma lipids. Significant linkage disequilibrium was, moreover, noted between the HincII RFLP and an ApaLI RFLP (chi 2 = 33, P < 0.0005) that has previously shown even stronger association with obesity (odds ratio 19.6 for cases homozygous for the susceptibility allele and 15.2 for heterozygotes). The present study therefore adds to our previous evidence implicating LDLR as a locus for obesity in patients with essential hypertension.

Alleles↗
PubMed1995

Molecular genetics of thyroid and parathyroid neoplasia.

There have been several recent advances in the understanding of the process of carcinogenesis in the thyroid and parathyroid glands. The specific abnormal molecules are, in many instances, well understood. This review provides an overview of the molecules in the cell that regulate cell growth and proliferation and identifies the molecules that have been found to be abnormal (or mutant) in various types of thyroid and parathyroid neoplasia.

Cell Cycle↗
PubMed1994

A rapid screening method for the detection of mutations in the RET proto-oncogene in multiple endocrine neoplasia type 2A and familial medullary thyroid carcinoma families.

Multiple endocrine neoplasia type 2A (MEN2A) and familial medullary thyroid carcinoma (FMTC) are autosomal dominant inherited cancer syndromes with incomplete penetrance. Following the identification of mutations in the RET proto-oncogene that segregate with the disease phenotype in MEN2A, MEN2B, and FMTC, genetic screening of individuals with mutations in RET may be performed. We have employed restriction endonuclease digestion of polymerase chain reaction products as an alternative to sequence analysis for rapid identification of mutant gene carriers in families in which MEN2A and FMTC are segregating. Twenty-one Australasian MEN2A and FMTC families have been screened for mutations in a cysteine-rich region of the RET proto-oncogene. Seven independent mutations were identified in key individuals in 16 of these families. We have identified a mutation in codon 620, 2053 T-->C (Cys620Arg), and two mutations in codon 634 of exon 11 of RET, 2095 T-->C (Cys634Arg) and 2096 G-->A (Cys634Tyr), all three of which were present in both MEN2A and FMTC families.

Australia↗
PubMed1994

Significant relationships of plasma lipids and body mass index with polymorphisms at the linked low-density-lipoprotein receptor gene and insulin receptor gene loci (19p13.2) in essential hypertensive patients.

1. Recent molecular genetic studies have implicated the low-density-lipoprotein receptor gene locus (LDLR, at chromosome 19p13.2) in obesity in essential hypertensive patients and in the atherogenic lipoprotein phenotype. The present study examined genotypes for the obesity-associated ApaLI restriction fragment length polymorphism of LDLR, and genotypes for a hypertension-associated RsaI restriction fragment length polymorphism at the insulin receptor gene (INSR) locus, which is linked to LDLR, in relation to plasma lipids, body mass index and blood pressure in 27 obese and 57 non-obese Caucasians with severe essential hypertension, selected on the basis of having parents who were both hypertensive, and in 25 obese and 45 non-obese normotensive subjects selected on the basis of having parents who were both normotensive after the age of 50 years. 2. Plasma triacylglycerol and low-density-lipoprotein-cholesterol were elevated in hypertensive patients, but did not differ between the obese and non-obese hypertensive groups. Significant positive correlations were seen between body mass index and triacylglycerol and low-density-lipoprotein-cholesterol in the obese and non-obese hypertensive patients, respectively. In addition, obese hypertensive patients had significantly higher diastolic blood pressure than non-obese hypertensive patients. 3. The eight obese hypertensive patients who were homozygous for the obesity-associated 6.6 kb allele of the ApaLI restriction fragment length polymorphism of LDLR ('6.6. kb homozygotes') had a significantly higher body mass index [34 +/- 6.0 (SD) kg/m2] than the 18 heterozygotes (29 +/- 2.7 kg/m2) and the single subject who was homozygous for the 9.4 kb allele (29 kg/m2) (P = 0.012 by one-way analysis of variance). The body mass index of the eight hypertensive 6.6 kb homozygotes was also greater than the body mass index of 29 +/- 2.4 kg/m2 observed for the eight obese normotensive 6.6 kb homozygotes. In addition, the eight obese hypertensive 6.6 kb homozygotes had a higher plasma triacylglycerol [4.2 +/- 0.77 (SEM) mmol/l] than the 18 obese hypertensive heterozygotes (2.4 +/- 0.33 mmol/l; P = 0.045). Non-obese hypertensive patients showed no significant genotypic differences in relation to the LDLR restriction fragment length polymorphism. 4. In the normotensive group, however, the frequency of the 6.6 kb allele of the LDLR ApaLI restriction fragment length polymorphism in obese subjects (0.54) was not significantly greater than in non-obese subjects (0.48) [cf. the significantly (P = 0.004( different values of 0.63 and 0.39, respectively, in obese and non-obese hypertensive patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1994

Diverse phenotypes associated with exon 10 mutations of the RET proto-oncogene.

Mutations of the RET proto-oncogene are the underlying cause of some cases of Hirschsprung disease (HSCR) and the inherited cancer syndromes multiple endocrine neoplasia types 2A (MEN 2A) and 2B (MEN 2B) and familial medullary thyroid carcinoma (FMTC). In HSCR these mutations are dispersed throughout the gene, while in MEN 2A and FMTC, they are tightly clustered in five cysteine codons of the RET extracellular domain. HSCR and MEN 2 are usually distinct but occasional families have been reported with both diseases. In each of five families with HSCR with or without MEN 2A or FMTC, we have identified a nucleotide substitution in one of the five cysteine codons previously associated with MEN 2A or FMTC. In one family, which had HSCR as its only phenotype, we detected a Cys-->Trp mutation at codon 609 which had not been previously observed. In three families, both HSCR and MEN 2A were associated with a single Cys-->Arg mutation at either codon 618 or 620 of RET. In the fifth family, FMTC and HSCR were present but we could not determine whether HSCR arose from mutation of the RET locus. We suggest that specific mutations in cysteine codons 618 and 620 result in MEN 2A or FMTC, but can also predispose to HSCR with low penetrance.

Base Sequence↗