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Biomedical subjects

H Barker

Publications and source records attributed to H Barker.

18 recordsLinked to original sources
PubMed1994

Release of gastric inhibitory polypeptide from cultured canine endocrine cells.

Canine intestinal duodenal and jejunal epithelial cell preparations enriched for endocrine cells were obtained by sequential collagenase digestion and centrifugal elutriation and maintained in culture for a 40-h period. Adherent cells contained a total cell content (TCC) of 11.5 +/- 2.5 ng (mean +/- SE) immunoreactive gastric inhibitory peptide (IRGIP)/well and 1.4 +/- 0.2 ng immunoreactive somatostatin (IRS)/well. Release experiments were performed by incubation of the cells with various stimuli over a 2-h period. Basal release of IRGIP in 5 mM glucose-5 mM K+ was 2.7 +/- 0.4% TCC. Incubation with concentrations of K+ > 20 mM or glucose > 15 mM significantly increased IRGIP release, as did the addition of a somatostatin immunoneutralizing antibody to the basal media. The addition of the Ca2+ ionophore, A-23187 (10 microM), or the adenylate cyclase activator, forskolin (100 microM), resulted in an IRGIP output greater than four times basal. Porcine gastrin-releasing peptide (GRP), at 1-100 nM, significantly stimulated IRGIP release in a concentration-dependent fashion. IRS release was increased significantly by 55 mM K+, 20 mM glucose, 10 microM A-23187, 100 nM GRP, or 100 microM forskolin.

Animals↗
PubMed1994

Experimental arthritis and uveitis in rats associated with Mycobacterium butyricum.

OBJECTIVE: To determine if the anterior uveitis associated with adjuvant arthritis (AA) in the rat can be passively transferred with arthritis to syngeneic recipients using spleen cells or T cell lines prepared from animals given complete Freund's adjuvant (CFA) and Mycobacterium butyricum (M. butyricum) in incomplete Freund's adjuvant (IFA). METHODS: Spleen cells from Lewis or Lewis SsN rats given IFA, CFA, type I collagen in IFA (CI-IFA), or type II collagen in IFA (CII-IFA) were administered to naive rats or rats treated with pertussis toxin or bacterial endotoxin. Three CD4+ T cell lines, propagated from CFA injected rats and maintained in vitro with M. butyricum (M-1), bovine proteoglycan (PR-1) or an extract of M. butyricum (MBE-1) were administered to naive or immunosuppressed rats. The arthritogenic and uveitogenic properties of these cell preparations and intradermal MBE-IFA, CII-IFA and intraperitoneal (ip) M. butyricum without adjuvant were evaluated. RESULTS: Uveitis was observed in 15/69 (22%) arthritic rats given CFA. Spleen cells prepared from CFA injected rats caused arthritis in 55 (82%) and uveitis in 2 (3%) of 67 cell recipients. Uveitis occurred in 2/6 cell recipients pretreated with bacterial endotoxin. Neither uveitis nor arthritis was observed in rats given IFA (0/6) or spleen cells prepared from rats given IFA (0/27), CI-IFA (0/6), or CII-IFA (0/28). CII-IFA produced polyarthritis in 5/6 rats, but no uveitis. CII-IFA induced arthritis associated uveitis in 1/15 animals receiving spleen cells from rats given CII-IFA, but not those given CI-IFA (0/3) or IFA (0/13). Uveitis was observed in one recipient of the M-1 T cell line and in 2 recipients of the PR-1 T cell line. Immunization with 400 micrograms of MBE-IFA induced uveitis but not arthritis in 3/11 animals. The MBE specific T cell line was neither arthritogenic nor uveitogenic. A high frequency (5/6) of uveitis accompanied arthritis in male Lewis rats given ip M. butyricum. Arthritis occurred in 4/10 female Lewis rats given ip M. butyricum and 2 arthritic animals also developed uveitis. CONCLUSION: Uveitis occurs infrequently in arthritic rats given spleen cells from CFA injected animals. The ip administration of M. butyricum constitutes a novel disease model in which the immunopathological relationships between arthritis and uveitis may be more reliably studied.

Animals↗
PubMed1990

Failure of mature dendritic cells of the host to migrate from the blood into cardiac or skin allografts.

Precisely where sensitization occurs after transplantation is uncertain, but it has been immunological dogma that sensitization to skin grafts occurs "centrally" in the draining lymph nodes. On the other hand, sensitization to fully-vascularized organs (kidney, heart, etc.) has been thought to occur "peripherally" within the graft itself. We have previously shown that mature dendritic cells migrate from the blood into the spleens of normal mice in a T cell-dependent manner, raising the possibility that circulating host dendritic leukocytes might be recruited from the blood into allografts where T cells had accumulated. This would provide a precedent for peripheral sensitization after transplantation. We examined whether 111indium-labeled mature DC host strain could migrate from the blood into cardiac or skin grafts. We were unable to detect migration into either allografts or isografts of these tissues, and found instead that the cells migrated to the spleen as in unmanipulated animals. This was despite the fact that accumulation of resting T cells was readily demonstrable in cardiac or skin allografts. In addition, we found that T cells sensitized against donor or third-party alloantigens had equal access to cardiac allografts, indicating that their migration into transplants is independent of their antigen specificity. The data of this study are discussed in the light of our other recent findings that donor DL migrate from fully-vascularized allografts into the recipients' spleens. Our current hypothesis is that allograft rejection is predominantly initiated centrally in host lymphoid tissues.

Animals↗
PubMed1982

Dermal collagen implants.

The feasibility of using preparations of cell-free, fibrous dermal collagen, prepared by trypsin-treatment of skin, for the repair of soft body tissues has been examined both as subcutaneous implants and as a replacement for dermis in skin wounds in rats. Increased collagen stability, and suppression or reduction of tissue antigenicity in collagen heterografts, was achieved by crosslinking with weak solutions of aldehydes while still allowing implant recellularization and revascularization. Tritium-labelled collagen turnover studies have shown that maintenance of collagen mass in implants crosslinked with glutaraldehyde occurs primarily by inhibition of loss of original implant collagen. Some of the in vitro growth characteristics of human fibroblasts on animal collagen preparations are also described.

Animals↗
PubMed1982

3H-collagen turnover in non-cross-linked and aldehyde-cross-linked dermal collagen grafts.

Using trypsin-purified rat dermal collagen labelled with tritiated hydroxyproline and proline, a study has been made of hydroxyproline turnover in non-cross-linked and glutaraldehyde- and formaldehyde-cross-linked collagen when implanted s.c. in unlabelled isogenic rats. Grafts cross-linked with 0.01% glutaraldehyde maintained their collagen mass over a 22-week period, loss of original collagen being balanced by the gain in new collagen (22% at 22 weeks). Cross-linking with 5% formaldehyde temporarily inhibited collagen loss as compared with non-cross-linked grafts. However, at 22 weeks both had lost some 30% of their collagen mass, the gain of new collagen (some 8%) only partially compensating for the loss of original implant collagen.

Animals↗
PubMed1981

Glycemic index of foods: a physiological basis for carbohydrate exchange.

The determine the effect of different foods on the blood glucose, 62 commonly eaten foods and sugars were fed individually to groups of 5 to 10 healthy fasting volunteers. Blood glucose levels were measured over 2 h, and expressed as a percentage of the area under the glucose response curve when the same amount of carbohydrate was taken as glucose. The largest rises were seen with vegetables (70 +/- 5%), followed by breakfast cereals (65 +/- 5%), cereals and biscuits (60 +/- 3%), fruit (50 +/- 5%), dairy products (35 +/- 1%), and dried legumes (31 +/- 3%). A significant negative relationship was seen between fat (p less than 0.01) and protein (p less than 0.001) and postprandial glucose rise but not with fiber or sugar content.

Adult↗
PubMed1981

Hydroxyproline turnover in dermal collagen grafts in reconstituted skin wounds in the rat.

Using donor skin labelled with tritiated hydroxyproline and proline, a comparative study has been made of hydroxyproline (and by extrapolation collagen) turnover in skin, dermal collagen and glutaraldehyde crosslinked dermal collagen grafts in unlabelled isogenic recipient rats. In contrast with non-crosslinked collagen and skin grafts, collagen grafts stabilized by crosslinking with 0.01% glutaraldehyde underwent little loss of original graft collagen and maintained their original collagen mass over a 22 week period. As the skin grafts acquired a similar amount of new collagen to that lost, they also maintained their original mass. However, the non-crosslinked collagen grafts showed only a small gain of new collagen and lost 57% of their original mass.

Animals↗
PubMed1980

Formaldehyde as a pre-treatment for dermal collagen heterografts.

The preparation, stability both in vitro and in vivo and resistance to bacterial collagenase of trypsin-purified pig dermal collagen cross-linked with a range of concentrations of formaldehyde in phosphate-buffered saline, was studied using 14C-labelled formaldehyde as a tracer. Washing in phosphate-buffered saline at 37 degrees C produced rapid loss of formaldehyde over 6 weeks before stability was reached. After 19 weeks washing, 12-20% of the initial radioactivity remained, representing 6, 18 and 35 mumol formaldehyde/g of collagen after 21 days reaction with 0.1, 1 and 5% formaldehyde, respectively. Collagen, incorporating stable-bound formaldehyde arising from reaction with formaldehyde in concentrations of 0.5% or over, was totally resistant to bacterial collagenase. The stabilizing effect of formaldehyde cross-linking was also demonstrated by implants of fibrous pig dermal collagen in rats. After 8 weeks a significant constant amount of formaldehyde was retained in all implants. There was no net loss of mass over a 24 week period when pre-treated with 1% formaldehyde but some loss when pre-treated with 0.1% formaldehyde.

Animals↗
PubMed1980

Rate of digestion of foods and postprandial glycaemia in normal and diabetic subjects.

Carbohydrate portions (2 g) of lentils, soya beans, and wholemeal bread were incubated for three hours with human digestive juices and the effect of digestibility on blood glucose examined. Lentils and soya beans released only 39% and 8% respectively of the sugars and oligosaccharides liberated from bread. In healthy volunteers 50 g carbohydrate portions of cooked lentils and soya beans raised blood glucose concentrations by only 42% (p < 0.001) and 14% (p < 0.001) of the bread value. There was a similar response in diabetics. These results suggest that rate of digestion might be a important factor determining the rise in blood glucose concentration after a meal and that supplementing chemical analysis with in-vitro and in-vivo food testing might permit identification of especially useful foods for diabetics.

Adult↗
PubMed1977

The actions of cyclic AMP, its butyryl derivatives and Na butyrate on the proliferation of malignant trophoblast cells in vitro.

Cyclic AMP, and its derivatives N6-monobutyryl cyclic AMP and dibutyryl cyclic AMP, have been found to inhibit the proliferation of trophoblast cells of the BeWo cell line in vitro. Sodium butyrate (1 mM), a possible degradation product of the butyrate derivatives, also inhibited cell proliferation, giving similar growth rates to equimolar dibutyryl cyclic AMP. The inhibition by butyrate was however, not sufficient to account for the action of 1 mM N6-monobutyryl cycli AMP, which, like cyclic AMP, completely inhibited cell proliferation. The potency, specificity and toxicity of the substances were compared. The results suggest different modes of action for cyclic AMP and dibutyryl cyclic AMP.

Bucladesine↗
PubMed1977

RNA and protein components of maize streak and cassava latent viruses.

Polyacrylamide gel electrophoresis indicated that maize streak (MSV) and cassava latent (CLV) viruses each contain one species of protein and two of RNA. The estimated protein mol. wt is 28000 for MSV and 34000 for CLV. The mol. wts obtained for the two RNA species using formamide-containing gels were the same for the two viruses: 1-7 X 10(6) and 1-3 X 10(6). It is suggested that the viruses have a two-part genome and that the tendency of their nucleoprotein particles to form pairs favours the delivery of complete genomes to sites of infection.

Genotype↗
PubMedDate not supplied

Enhancement of resistance to potato leafroll virus multiplication in potato by combining the effects of host genes and transgenes.

Four potato clones with host gene-mediated resistance to potato leafroll virus (PLRV) multiplication were transformed with the PLRV coat protein (CP) gene. Plants of lines expressing high levels of transcript were highly resistant to PLRV multiplication; virus concentration was only 20-40 ng/g of leaf, which is approximately 1% of the concentration reached in susceptible cultivars. The effects of the transgenic and host-derived resistance genes appear to be additive.

Capsid↗
PubMedDate not supplied

Immunity to potato mop-top virus in Nicotiana benthamiana plants expressing the coat protein gene is effective against fungal inoculation of the virus.

Nicotiana benthamiana stem tissue was transformed with Agrobacterium tumefaciens harboring a binary vector containing the potato mop-top virus (PMTV) coat protein (CP) gene. PMTV CP was expressed in large amounts in some of the primary transformants. The five transgenic lines which produced the most CP were selected for resistance testing. Flowers on transformed plants were allowed to self-fertilize. Transgenic seedlings selected from the T1 seed were mechanically inoculated with two strains of PMTV. Virus multiplication, assayed by infectivity, was detected in only one transgenic plant of 98 inoculated. T1 plants were also highly resistant to graft inoculation; PMTV multiplied in only one plant of 45 inoculated. Transgenic T1 seedlings were challenged in a bait test in which they were grown in soil containing viruliferous spores of the vector fungus Spongospora subterranea. In these tests only two plants out of 99 became infected. Of the five transgenic lines tested, plants of three lines were immune to infection following manual, graft, or fungal inoculation.

Base Sequence↗