PubMed Health⌕ Search

Biomedical subjects

G Rumsby

Publications and source records attributed to G Rumsby.

At least 55 records · Page 3Linked to original sources
PubMed1994

The tyrosine kinase domain of the insulin receptor gene is normal in women with hyperinsulinaemia and polycystic ovary syndrome.

The cause of hyperinsulinaemia in polycystic ovary syndrome (PCOS) is unknown, but two recent reports have implicated mutations of the tyrosine kinase domain of the insulin receptor gene in two patients. We have undertaken amplification of the insulin receptor gene using the polymerase chain reaction and single-stranded conformational polymorphism analysis in 22 hyperinsulinaemic patients with PCOS. Of these patients, 50% were polymorphic in exon 17 of the insulin receptor gene, but none of the alterations in sequence has been associated with insulin resistance. The genomic sequences in exons 18-21 were normal in all patients. We conclude that mutations involving the tyrosine kinase domain of the insulin receptor gene are a rare cause of insulin resistance in the PCOS.

Base Sequence↗
PubMed1993

Problems in diagnosis and management of congenital adrenal hyperplasia due to 21-hydroxylase deficiency.

A number of biochemical tests have been utilized to assist the diagnosis of steroid 21-hydroxylase deficiency. The specificity and accuracy of plasma 17-hydroxyprogesterone assays are important. A profile of steroids in urine by gas chromatography and mass spectrometry is the definitive test. Molecular biology is not practical for the diagnosis of a new case. The ACTH stimulation test for detection of heterozygotes is a poor discriminant. Fertility in patients with congenital adrenal hyperplasia may be due to excess of progesterone as well as of androgens. Gene amplification offers the best approach in molecular biology for the prenatal diagnosis of 21-hydroxylase deficiency.

Adrenal Hyperplasia, Congenital↗
PubMed1993

Prenatal diagnosis of congenital adrenal hyperplasia by direct detection of mutations in the steroid 21-hydroxylase gene.

OBJECTIVE: Our aim was to develop a rapid and accurate method for the prenatal diagnosis of congenital adrenal hyperplasia using the polymerase chain reaction to detect mutations in the steroid 21-hydroxylase gene. These procedures will help to minimize exposure to dexamethasone treatment of either affected males or unaffected females. DESIGN AND PATIENTS: Chorionic villus biopsy samples were obtained between 10 and 11 weeks gestation from three females carrying fetuses at risk of steroid 21-hydroxylase deficiency. Blood samples were taken from parents and the index case in each family. MEASUREMENTS: Three common mutations in the 21-hydroxylase B gene were detected following DNA amplification. RESULTS: Prenatal diagnosis of congenital adrenal hyperplasia was successful in all three cases. One affected female was treated with dexamethasone to term. In the other two cases, one affected male and one carrier also male, dexamethasone was withdrawn at an early stage. CONCLUSIONS: First trimester prenatal diagnosis of steroid 21-hydroxylase deficiency was achieved in three pregnancies with a strategy based on direct detection of gene mutations.

Adrenal Hyperplasia, Congenital↗
PubMed1993

Deoxycorticosterone, 11 beta-hydroxylase and the adrenal cortex.

We report a child in whom DOC excess secondary to congenital adrenal hyperplasia (CAH, 11 beta-hydroxylase deficiency) caused malignant hypertension. Clinical and metabolic control could be achieved only by replacement of both glucocorticoid and mineralocorticoid, thus confirming in clinical practice the hypothesis that DOC is produced from both the zonae fasciculata and glomerulosa of the adrenal cortex under the independent control of the ACTH and renin-angiotensin systems respectively.

Adrenal Cortex↗
PubMed1993

Combined 17 alpha-hydroxylase/17,20-lyase deficiency caused by heterozygous stop codons in the cytochrome P450 17 alpha-hydroxylase gene.

OBJECTIVE: To determine the genetic defect underlying congenital adrenal hyperplasia due to 17 alpha-hydroxylase deficiency in a genetic female. DESIGN: Blood samples were used as a source of genomic DNA. A library of size selected genomic DNA sequences was prepared. In addition, portions of the 17 alpha-hydroxylase gene were amplified by the polymerase chain reaction and the gene products sequenced. PATIENTS: Samples were obtained from a patient with sexual infantilism, lack of secondary sexual characteristics and hypertension. Streak gonads were found on laparoscopy. RESULTS: Two point mutations were found, one in exon 3 and one in exon 4 which generate premature stop codons at codons 194 and 239 in place of glutamate and arginine respectively. The mutation in exon 3 has not previously been reported in patients with 17 alpha-hydroxylase deficiency. CONCLUSION: The protein product of these defective genes could be expected to be severely truncated with no catalytic activity. This is in keeping with the complete lack of cortisol and sex steroid output in this patient. The polymerase chain reaction provides faster access to gene sequence information than previous procedures based on library screening prior to sequencing.

Adrenal Hyperplasia, Congenital↗
PubMed1992

Genetic analysis of the steroid 21-hydroxylase gene following in vitro amplification of genomic DNA.

The 5' end of the steroid 21-hydroxylase B gene encompassing putative control regions and the first 3 exons, has been selectively amplified in vitro from a number of patients with congenital adrenal hyperplasia caused by a deficiency of this enzyme. Sequence analysis has revealed a number of isolated instances of gene conversion to the 21-hydroxylase A sequence. One mutation, a C to G transversion at the 3' end of the second intron, thought to lead to incorrect splicing of the mRNA, was found in 11 subjects all with the classical form of the disease.

Adrenal Hyperplasia, Congenital↗
PubMed1990

Low incidence of ras oncogene activation in human squamous cell carcinomas.

Activation of the ras gene family by point mutation at codons 12, 13 and 61 has been demonstrated in up to 20% of unselected series of human tumours. The present study was carried out to assess the incidence of ras activation in 37 squamous cell carcinomas of the head and neck, seven squamous cell carcinomas of the skin and eight squamous carcinoma cell lines. Oligonucleotide probes and the polymerase chain reaction were used on DNA extracted from achival paraffin embedded material. Mutations in codon 12 of the Harvey ras gene was found in a carcinoma of the larynx and a carcinoma of the lip, both of which had received prior irradiation. A cell line (LICR-LON-HN8) established from the same laryngeal cancer showed the same mutation. This study indicates that there is a low incidence of ras mutation in human squamous cell carcinomas and that activation of this family of genes is probably not a common factor in the development of this group of tumours.

Adult↗
PubMed1990

In vitro gene amplification for prenatal diagnosis of congenital adrenal hyperplasia.

A simple, rapid, non-radioactive method for detecting homozygous deletions/conversions of the steroid 21-hydroxylase gene is described. In our experience this method will be useful for first trimester prenatal diagnosis of congenital adrenal hyperplasia in 17% of families of a child with the salt losing form. This test includes an internal control to monitor the success of amplification.

Adrenal Hyperplasia, Congenital↗
PubMed1988

Heterogeneity in the gene locus for steroid 21-hydroxylase deficiency.

DNA was analysed from 33 patients with congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency. In each case Southern blots were prepared from a number of restriction enzyme digests and hybridised with probes for both the 21-hydroxylase and the adjacent fourth component of complement (C4). Evidence for deletion of the active 21-hydroxylase gene (CYP21B) was found in 13 cases and in 10 of these the deletion included the adjacent C4B gene, leading to a hybrid CYP21A/CYP21B gene. Deletion of CYP21B alone was found in one patient, the remaining two cases appearing to have the active gene replaced by the inactive pseudogene. Duplications of the CYP21A-C4B region and deletion of the pseudogene are also described. In a further 12 cases no gross abnormality could be found.

Adrenal Hyperplasia, Congenital↗
PubMed1987

Effect of temperature and sample preparation on performance of ion-moderated partition chromatography of organic acids in biological fluids.

A thorough investigation of the behavior of organic acids on the Bio-Rad Aminex cation exchange resin was prompted by both the limitations of, and a number of inexplicable inconsistencies found in, previously published papers using an identical system. In order to stabilise the elution order of various acids it was necessary to analyse samples at a higher temperature than previously recommended. This temperature (50 degrees C) decreased the retention times of all acids permitting the analysis of both aromatic and aliphatic acids within the same 45-min run. Preparation of an acidic fraction of biological fluids improved specificity, allowed direct comparison of urine and plasma profiles and by control of the conditions interference by urate could be substantially reduced. Retention data are given for more than 90 acidic metabolites including nearly 40 of clinical significance and a number derived from diet and drug therapy.

Carboxylic Acids↗
PubMed1986

Deletion of the steroid 21-hydroxylase and complement C4 genes in congenital adrenal hyperplasia.

DNA was analysed from 20 patients with congenital adrenal hyperplasia due to cytochrome P-450 steroid 21-hydroxylase deficiency. Using probes recognising sequences in both the 21-hydroxylase gene and the adjacent fourth component of complement (C4), one patient was found to have a homozygous deletion of DNA which encompassed the C4B and 21-hydroxylase B genes. Evidence is presented for this deletion arising by recombination between homologous regions of 21-hydroxylase A and B. Seven patients appeared to be heterozygous for the same deletion, but no detectable alteration in the 21-hydroxylase gene could be demonstrated in others.

Adrenal Hyperplasia, Congenital↗
PubMed1985

Expression of genes on human chromosome 21.

Gene sequences were isolated from a lambda library containing inserts originating from human chromosome 21. One phage, CP21G1, had been selected on the basis of its lack of middle-repetitive sequences and its ability to hybridize with 32P-labeled cDNA synthesized from the cytoplasmic poly A+ RNA of cultured fibroblasts. Further experiments revealed that the human insert in this phage is unique-sequence DNA, maps to the long arm of chromosome 21, and is expressed in fibroblasts and T cells. A panel of 127 "unique-sequence" phage were also selected from the lambda library and were tested for hybridization to 32P-labeled cDNA synthesized from the cytoplasmic poly A+ RNA of CCRF-HSB-2, a T-blast leukemic line. Seventeen recombinants hybridized to the probe. One of these phages, CP8, contains a human unique-sequence DNA expressed in T cells and neuroblastoma cells. One phage (CP5) in the "unique-sequence" panel that had not hybridized to cDNA from T-cell RNA was found to carry a low-repeat sequence and to hybridize specifically to RNA from a neuroblastoma line. This phage appears to carry a brain-specific gene. Many of the genomic sequences related to the low-repeat sequence contained in CP5 map to the short arm of chromosome 21. The cloned genes described here represent new markers for the detailed mapping of human chromosome 21 and may prove valuable in studying tissue-specific gene regulation.

Cell Line↗