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Biomedical subjects

S Collier

Publications and source records attributed to S Collier.

At least 37 records · Page 2Linked to original sources
PubMed1994

Identification of a novel family of human endogenous retroviruses and characterization of one family member, HERV-K(C4), located in the complement C4 gene cluster.

We have identified a novel family of about 10-50 human endogenous retrovirus elements (HERVs) and have characterized one family member (HERV-KC4). This retrovirus element is integrated within intron 9 of and complement C4A genes and also in some C4B genes, and is a principal contribution to interlocus and interallelic length heterogeneity of C4 genes. The HERV-K(C4) sequence has a typical retrovirus structure with elements of gag, pol and env domains, flanked by two long terminal repeats (LTRs) and is similar to type A, B and D retroviruses. Multiple termination codons preclude the existence of long open reading frames, suggesting that the HERV-K(C4) sequence is no longer functional. Zoo blot hybridization reveals that New World monkeys appear to lack sequences similar to HERV-K(C4), suggesting that integration has occurred after the divergence of Old and New World monkeys. Retrotransposition of prototype viruses is presumed to have led to the amplification and integration of the members of the family in different loci, which in humans, appear to be dispersed over several chromosomes. The absence of the HERV-K(C4) element in some C4B genes in both humans and orangutangs indicate that the retrovirus inserted into the C4A gene after the duplication of the cluster. Subsequent spread of the HERV-K(C4) sequence to C4B genes presumably occurred by interlocus sequence exchange mechanisms, such as unequal crossover and gene conversion-like mechanisms.

Animals↗
PubMed1994

Use of cyclic parenteral nutrition in infants less than 6 months of age.

Cyclic parenteral nutrition is the technique of infusing the intravenous solution in less than 24 hours, during a portion of the day or night, allowing the patient freedom from the intravenous tubing and pump apparatus. In addition, adverse effects of long-term parenteral therapy, such as liver complications, were reported to be decreased with the use of cyclic parenteral nutrition in adult patients. Literature on the method and effects of cycling in young infants is minimal. This report describes cyclic parenteral nutrition use with guidelines for cycling and the potential beneficial metabolic effects in 10 infants less than 6 months of age who required long-term parenteral nutrition support. Diagnosis, gestational age, length of time on parenteral nutrition, macronutrient intake, growth, and biochemical parameters for the patients are presented. Overall, cyclic parenteral nutrition was well tolerated without clinical symptoms of hypoglycemia, elevated capillary blood glucose concentrations, or abnormal urine glucose levels. The direct bilirubin concentrations showed a decrease or stabilization after cycling was initiated in eight of 10 patients.

Age Factors↗
PubMed1993

Sexual dimorphism in relation to big-game hunting and economy in modern human populations.

Postcranial skeletal data from two recent Eskimo populations are used to test David Frayer's model of sexual dimorphism reduction in Europe between the Upper Paleolithic and Mesolithic. Frayer argued that a change from big-game hunting and adoption of new technology in the Mesolithic reduced selection for large body size in males and led to a reduction in skeletal sexual dimorphism. Though aspects of Frayer's work have been criticized in the literature, the association of big-game hunting and high sexual dimorphism is untested. This study employs univariate and multivariate analysis to test that association by examining sexual dimorphism of cranial and postcranial bones of two recent Alaskan Eskimo populations, one being big-game (whale and other large marine mammal) hunting people, and the second being salmon fishing, riverine people. While big-game hunting influences skeletal robusticity, it cannot be said to lead to greater sexual dimorphism generally. The two populations had different relative sexual dimorphism levels for different parts of the body. Notably, the big-game hunting (whaling) Eskimos had the lower multivariate dimorphism in the humerus, which could be expected to be the structure under greatest exertion by such hunting in males. While the exertions of the whale hunting economic activities led to high skeletal robusticity, as predicted by Frayer's model, this was true of the females as well as the males, resulting in low sexual dimorphism in some features. Females are half the sexual dimorphism equation, and they cannot be seen as constants in any model of economic behavior.

Alaska↗
PubMed1993

A de novo pathological point mutation at the 21-hydroxylase locus: implications for gene conversion in the human genome.

More than two hundred characterized 21-hydroxylase deficiency alleles appear to result exclusively from sequence exchanges involving the 21-hydroxylase gene (CYP21B) and a closely related pseudogene (CYP21A). Gene conversion-like events have also been reported in many other human gene clusters, but in the absence of a de novo mutation, the alternative explanation of a multiple recombination is possible. We now report a de novo pathological mutation at the 21-hydroxylase locus. DNA sequence analysis suggests that the mutation arose by a microconversion event involving exchange of up to 390 nucleotides between maternal CYP21A and CYP21B genes. This putative de novo gene conversion event appears to be the first characterized in humans.

Adrenal Hyperplasia, Congenital↗
PubMed1992

A method for specific amplification and PCR sequencing of individual members of multigene families: application to the study of steroid 21-hydroxylase deficiency.

Mutations at the human HLA-linked CYP21B locus are responsible for 21-hydroxylase deficiency, a recessively inherited disorder of steroidogenesis. The scope for PCR-based analysis of the CYP21B gene has been restricted by the very high sequence homology between CYP21B and a closely related pseudogene, CYP21A. Here we describe a novel PCR sequencing strategy that allows the independent amplification of the entire CYP21B coding sequence and the subsequent enzyme-mediated conversion of the PCR product to a single-stranded form for dideoxy sequencing. We have used this approach to characterize the 21-hydroxylase deficiency allele associated with HLA-B55, the most frequent HLA marker associated with a CYP21B point mutation in the British population, and also an HLA-B35 associated allele of Asian origin. Allele-specific oligonucleotide (ASO) hybridization analyses have confirmed the selective amplification of CYP21B genes and the identity of the pathological mutations. The method can be adapted to permit selective amplification and PCR sequencing of individual closely related members of other multigene families and small-copy-number repetitive DNA families.

Adrenal Hyperplasia, Congenital↗
PubMed1991

Comparison of the effects of non-steroidal anti-inflammatory drugs (NSAIDs) on proteoglycan synthesis by articular cartilage explant and chondrocyte monolayer cultures.

Experiments were conducted to study proteoglycan biosynthesis by rabbit articular chondrocytes cultured in the presence of NSAIDs and 35SO4(2-) for up to 8 days. Both articular cartilage explants and confluent chondrocyte monolayer culture models were used. Medium was changed every 2 days and the [35SO4]proteoglycans which had accumulated in the medium and the extracellular matrix during the culture intervals were assayed separately. In long-term experiments, drugs were removed on day 8, and proteoglycan production during a 10-12 day culture interval also was assayed. The drugs studied were diclofenac, indomethacin, ketoprofen, piroxicam and tiaprofenic acid, at concentrations of 0, 0.1, 1, 10, 50 and 100 micrograms/mL. Whereas proteoglycan production by cell cultures was maximal early in the culture period, explants produced more proteoglycans as time progressed. The highest concentrations of all of the drugs, especially diclofenac and indomethacin, inhibited proteoglycan secretion by both cell and explant cultures. However, after removal of the drugs from the cultures, suppressed proteoglycan production reversed to levels equivalent to, or higher than controls in the cell cultures, but largely persisted in explant cultures. About 70-80% of proteoglycans produced by explants were retained in the matrix, whereas about 80-90% of proteoglycans produced by cell cultures were secreted into the medium. Where drugs inhibited proteoglycan production, the levels were reduced by approximately the same proportions in both extracellular matrix and culture medium fractions. Of the NSAIDs examined only ketoprofen demonstrated a stimulatory effect on PG synthesis in explant cultures at a physiological concentration (0.1 microgram/mL).

Animals↗
PubMed1991

Evidence of abortive recombination in ruv mutants of Escherichia coli K12.

Genetic recombination in Escherichia coli was investigated by measuring the effect of mutations in ruv and rec genes on F-prime transfer and mobilization of nonconjugative plasmids. Mutation of ruv was found to reduce the recovery of F-prime transconjugants in crosses with recB recC sbcA strains by about 30-fold and with recB recC sbcB sbcC strains by more than 300-fold. Conjugative plasmids lacking any significant homology with the chromosome were transferred normally to these ruv mutants. Mobilization of the plasmid cloning vectors pHSG415, pBR322, pACYC184 and pUC18 were reduced by 20- to 100-fold in crosses with ruv rec+ sbc+ strains, depending on the plasmid used. Recombinant plasmids carrying ruv+ were transferred efficiently. With both F-prime transfer and F-prime cointegrate mobilization, the effect of ruv was suppressed by inactivating recA. It is proposed that the failure to recover transconjugants in ruv recA+ strains is due to abortive recombination and that the ruv genes define activities which function late in recombination to help convert recombination intermediates into viable products.

Conjugation, Genetic↗
PubMed1990

Genesis by meiotic unequal crossover of a de novo deletion that contributes to steroid 21-hydroxylase deficiency.

The HLA-linked human steroid 21-hydroxylase gene CYP21B and its closely homologous pseudogene CYP21A are each normally located centromeric to a fourth component of complement (C4) gene, C4B and C4A, respectively, in an organization suggesting tandem duplication of a ca. 30-kilobase DNA unit containing a CYP21 gene and a C4 gene. Such an organization has been considered to facilitate gene deletion and addition events by unequal crossover between the tandem repeats. We have identified a steroid 21-hydroxylase [steroid, hydrogen-donor:oxygen oxidoreductase (21-hydroxylating), EC 1.14.99.10] deficiency patient who has a maternally inherited disease haplotype that carries a de novo deletion of a ca. 30-kilobase repeat unit including the CYP21B gene and associated C4B gene. This disease haplotype appears to have been generated as a result of meiotic unequal crossover between maternal homologous chromosomes. One of the maternal haplotypes is the frequently occurring HLA-DR3, B8, A1 haplotype that normally carries a deletion of a ca. 30-kilobase unit including the CYP21A gene and C4A gene. Haplotypes of this type may possibly act as premutations, increasing the susceptibility of developing a 21-hydroxylase deficiency mutation by facilitating unequal chromosome pairing.

Adrenal Hyperplasia, Congenital↗
PubMed1989

Pulsed field gel electrophoresis identifies a high degree of variability in the number of tandem 21-hydroxylase and complement C4 gene repeats in 21-hydroxylase deficiency haplotypes.

The human steroid 21-hydroxylase gene, CYP21B, and its closely homologous pseudogene, CYP21A, are each normally located centromeric to a complement C4 gene C4B and C4A respectively, in an organization suggesting tandem duplication of a CYP21 + C4 unit. Such an organization has been considered to facilitate gene deletion and addition events by unequal crossover between the tandem repeats. However, the large size (approximately 30 kb) of the individual CYP21 + C4 repeat units together with the difficulty in identifying reliable CYP21A- and CYP21B-specific markers has prevented direct monitoring of gene organization on individual haplotypes by conventional Southern analyses. In the present investigation we have sought to clarify the CYP21 and C4 gene organization in members of 32 British 21-hydroxylase deficiency families by employing additional experimental approaches, notably a long-range restriction mapping approach, which permits assessment through a VNTR type of analysis, of the number of CYP21 and C4 units on individual haplotypes. Our results show that there is a very high frequency (33%) of 21-hydroxylase deficiency haplotypes where functional CYP21B gene sequence has been removed as a consequence of CYP21 + C4 gene deletion while several haplotypes show evidence of gene addition. In each case that we have investigated the gene deletion and gene addition haplotypes differ in length from conventional haplotypes by integral multiples of approximately 30 kb, which strongly supports the involvement of unequal crossover mechanisms. Additionally, the comparatively frequent occurrence of CYP21 fusion genes which contain both CYP21A- and CYP21B-associated markers is suggested by the combined data from Southern analyses, long-range restriction mapping and characterization of selected regions of CYP21 genes which have been amplified in vitro.

Adrenal Hyperplasia, Congenital↗
PubMed1989

Evaluation of the effect of antiarthritic drugs on the secretion of proteoglycans by lapine chondrocytes using a novel assay procedure.

A new method is described for separating free 35SO4-- from 35SO4 labelled proteoglycans synthesised by rabbit articular chondrocytes cultured in the presence of excess 35SO4--. The procedure uses the low solubility product of barium sulphate to remove, by precipitation, free 35SO4-- from culture medium. Optimum recovery of 35SO4 labelled proteoglycans was achieved after papain digestion to release 35SO4-glycosaminoglycans, and addition of chondroitin sulphate before the precipitation step. Using this assay, we studied the effect of six drugs-indomethacin, diclofenac, sodium pentosan polysulphate, glycosaminoglycan polysulphate ester, tiaprofenic acid, and ketoprofen-on the secretion into the medium of labelled proteoglycans by lapine chondrocytes. The six drugs were tested at 0.1, 1, 10, 50, and 100 micrograms/ml over four consecutive 48 hour culture periods. A consistent concentration-response pattern was found for the four non-steroidal anti-inflammatory drugs (NSAIDs) studied. Generally they inhibited proteoglycan secretion at 50 and 100 micrograms/ml but had no effect at lower concentrations. Inhibition of secretion was strongest with indomethacin and diclofenac at 50 and 100 micrograms/ml. In contrast with the NSAIDs studied, the two sulphated polysaccharides (sodium pentosan polysulphate and glycosaminoglycan polysulphate ester) at low concentrations increased proteoglycan secretion by chondrocytes, with maximal stimulation occurring at 1 microgram/ml. Sodium pentosan polysulphate, but not glycosaminoglycan polysulphate ester, showed inhibitory activity at 50 and 100 micrograms/ml.

Animals↗
PubMed1988

The role of plasminogen in interleukin-1 mediated cartilage degradation.

Explants of 35SO4 labelled rabbit articular cartilage, cultured for 3 days with either 5 X 10(4) rabbit peritoneal cells (PEC) or 1:10 macrophage conditioned medium (MCM), released 30-40% of labelled proteoglycans into the medium while controls released 8-12%. The addition of 1 mM 4 aminophenylmercuric acetate (APMA) or 0.2 U/ml plasminogen increased proteoglycan release to 85%. Similar results were obtained when recombinant human interleukin-1 (IL-1) was used instead of MCM. Further, supernatant from MCM stimulated chondrocytes, incubated with dead cartilage explants for 3 days, did not significantly increase proteoglycan release above the background level of cartilage alone (7-10%), nor did the addition of 5 X 10(4) PEC to cultures of dead cartilage explants plus supernatant from MCM stimulated chondrocytes make any significant difference, indicating that supernatant from MCM stimulated chondrocytes and PEC alone had negligible cartilage proteoglycan degrading activity in these experiments. The inclusion of 0.1 mM APMA or 0.2 U/ml plasminogen in cultures of dead cartilage explants plus supernatant from MCM stimulated chondrocytes, however, increased proteoglycan release to 80-93%, with or without PEC. Our results suggest that plasminogen, activated by a product from IL-1 stimulated chondrocytes, greatly enhanced IL-1 mediated cartilage degradation by activating latent metalloproteinases.

Animals↗
PubMed1987

Synovial membrane-cartilage interactions--the role of serine proteinase inhibitors in interleukin-1 mediated degradation of articular damage.

Using a peritoneal macrophage/articular cartilage co-culture system, it was shown that the serine proteinase inhibitor derived from human articular cartilage modulated the release of 35S-labelled proteoglycan into media in a concentration dependent manner. Since the cartilage inhibitor fractions used were free of metallo-proteinase and cysteine proteinase inhibitory activity, but strongly inhibited serine proteinases, it was suggested that such enzymes may be implicated in the activation of latent metallo-proteoglycanases produced by chondrocytes on exposure to IL-1.

Animals↗
PubMed1982

Organ culture of fetal mouse and fetal human pancreatic islets for allografting.

In organ culture of fetal human and fetal murine pancreas under "conventional" conditions (10% CO2 in air), the islet cells of both species survive, proliferate and function but the acinar tissue rapidly degenerates. Fetal mouse islet cells also survive in 90% O2 and 10% CO2 but nonendocrine cells, including fibroblasts and macrophages, degenerate. Fetal mouse islets grown in 90% O2 show diminished immunogenicity when transplanted into recipients differing across the entire MHC, but a reduced allograft response by the host is frequently still present in the absence of immunosuppression. Fetal human islets, grown in 10% CO2 in air, produce insulin in vitro for prolonged periods, and as xenografts, differentiate under the kidney capsule of athymic mice, suggesting that under appropriate conditions both in vitro and in vivo, the fetal human islets can survive. However, fetal human pancreatic cells of all types are highly susceptible to high oxygen concentrations and are rapidly killed. Because of the susceptibility of fetal human pancreas to oxygen, conditions for the culture of fetal human islets for allotransplantation may need to be modified from those tolerated by fetal mouse islets. Fetal human islets may be a useful source of transplant material in human insulin-dependent diabetes, but it is likely that tissue matching and immunosuppression may be required in addition to modification of islet immunogenicity by prior organ culture.

Animals↗
PubMed1982

Isotransplantation of fetal mouse pancreas in experimental diabetes. Effect of gestational age and organ culture.

Fetal mouse pancreatic isotransplantation was performed in CBA mice, previously made diabetic with streptozotocin. Either 17- or 12-day-old fetal tissue was used, either uncultured or after 14 days in organ culture. Grafts were placed under the renal capsule, and their effect on fasting blood glucose levels was assessed over a 10-week postgraft period. The grafts and the host pancreas were then examined by light microscopy. Uncultured 12- and 17-day fetal pancreases produced poorly developed grafts with small islets, numerous ducts, and copious adipose tissue. By contrast, if organ cultured for 14 days before transplantation, both 12- and 17-day tissue resulted in large grafts composed predominantly of well-stained islet cells, few ducts, and little connective and adipose tissue. The most functionally effective grafts were derived from cultured 17-day pancreas, and a single graft per recipient always ameliorated diabetes. By contrast, grafts from single or multiple uncultured 12-day pancreases did not function, but, after culture, grafts derived from three (but not from one) 12-day pancreas lowered blood glucose levels to almost normal levels. It is concluded that grafts of fetal mouse pancreas can function in experimental diabetes provided they are first cultured and are of adequate gestational age.

Animals↗