Search PubMed⌕ Search

Biomedical subjects

J Hopkins

Publications and source records attributed to J Hopkins.

At least 127 records · Page 7Linked to original sources
PubMed1992

Effect of caffeinated coffee on running speed, respiratory factors, blood lactate and perceived exertion during 1500-m treadmill running.

Using a motorized treadmill the study investigated the effects of the ingestion of 3 g of caffeinated coffee on: the time taken to run 1500 m; the selected speed with which athletes completed a 1-min 'finishing burst' at the end of a high-intensity run; and respiratory factors, perceived exertion and blood lactate levels during a high intensity 1500-m run. In all testing protocols decaffeinated coffee (3 g) was used as a placebo and a double-blind experimental design was used throughout. The participants in the study were middle distance athletes of club, county and national standard. The results showed that ingestion of caffeinated coffee: decreases the time taken to run 1500 m (P less than 0.005); increases the speed of the 'finishing burst' (P less than 0.005); and increases VO2 during the high-intensity 1500-m run (P less than 0.025). The study concluded that under these laboratory conditions, the ingestion of caffeinated coffee could enhance the performance of sustained high-intensity exercise.

Adolescent↗
PubMed1992

Plasma and serum von Willebrand factor antigen concentrations in connective tissue disorders.

Concentrations of serum and plasma von Willebrand factor antigen were measured in over 200 patients with a variety of connective tissue diseases, and in control samples from over 200 asymptomatic individuals. This comprehensive study found the highest concentrations of von Willebrand factor antigen in patients with vasculitis, Sjögren's syndrome, Felty's syndrome, giant cell arteritis and polyarteritis nodosum. Raised values were also found in rheumatoid arthritis, systemic lupus erythematosus, polymyalgia rheumatica, systemic sclerosis, Raynaud's syndrome, Takayasu's arteritis and Wegener's granulomatosis, but not in oesteoarthritis. It is possible that the difference in von Willebrand factor antigen concentrations in two sub-groups of systemic necrotising arteritis (Wegener's granulomatosis and polyarteritis nodosum) may imply different disease processes. The large numbers involved have allowed us to confirm or question smaller studies of the role of this molecule in connective tissue disease.

Biomarkers↗
PubMed1991

Characterization of the binding site for nevirapine (BI-RG-587), a nonnucleoside inhibitor of human immunodeficiency virus type-1 reverse transcriptase.

Nevirapine (BI-RG-587) is a potent and specific non-nucleoside inhibitor of human immunodeficiency virus type-1 reverse transcriptase. The compound is non-competitive with respect to template, primer, and nucleoside triphosphates indicating that BI-RG-587 does not act directly at the catalytic site. The binding site for this inhibitor was investigated by employing an azido photoaffinity analogue, BI-RJ-70, to covalently label the enzyme. The resulting photoadduct was subjected to enzymatic digestion by trypsin and endoproteinase lys-C and a single, highly labeled peptide was identified as residues 174-199. Sequencing of this peptide identified Tyr-181 and Tyr-188 as labeled residues.

Affinity Labels↗
PubMed1991

Detection of border disease virus in sheep efferent lymphocytes by immunocytochemical and in situ hybridisation techniques.

The prefemoral efferent lymphatics of four sheep persistently infected with a non cytopathic (NCP) isolate of border disease virus (BDV) were cannulated. Recovered lymphocytes were examined for the presence of virus by an immunocytochemical technique employing a pool of monoclonal antibodies which recognise the 120K non-structural polypeptide of NCP BDV. The results revealed that 9.5% of the lymphocytes carried virus antigen. Lymphocytes from two of the sheep were studied by in situ hybridisation using a viral antisense RNA probe complementary to the region of the BDV genome coding for the 120K polypeptide. This showed that 70-80% of the cells were infected, confirming the greater sensitivity of the in situ hybridisation technique.

Animals↗
PubMed1991

Retroviral arthritis: phenotypic analysis of cells in the synovial fluid of sheep with inflammatory synovitis associated with visna virus infection.

A phenotypic analysis on synovial fluid cells from the carpal and tarsal joints of sheep with visna virus-induced inflammatory synovitis was performed. The results showed increased representation of cells bearing lymphocyte, macrophage, and dendritic cell markers compared to equivalent synovial fluid cells from normal uninfected age-matched controls. In infected sheep, CD8+ T cells tended to predominate over CD4+ cells, while the numbers of gamma delta T cells varied from being absent in some samples to constituting the major T cell subset in others. B cells were found in relatively smaller numbers. Analysis of the large mononuclear cells showed that they stained with monoclonal antibodies that recognize macrophages and afferent lymph dendritic cells. Major histocompatibility complex (MHC) class II+ macrophage/dendritic cells were found in normal joints, but significantly elevated proportions of such cells were present in the carpal joints of infected sheep. The intensity of MHC class II staining was also significantly elevated in infected animals compared to control animals. A high proportion of these cells also stained for CD1 in both normal and infected animals, but were significantly elevated in number in the carpal joints of infected sheep. The elevated proportion of cells expressing molecules associated with accessary cell function and the increase in the numbers of accessory molecules per cell suggests an enhanced capacity for presenting antigen to a variety of T cell subsets within the joints of infected sheep, which could initiate or perpetuate potentially damaging local synovial inflammatory responses.

Animals↗
PubMed1991

Analysis of the CD1 cluster in sheep.

The anti-CD1 monoclonal antibodies submitted to the 1st International Workshop on Leucocyte Differentiation Antigens of Cattle, Sheep and Goats were tested for their reactivity on sheep skin, thymus and lymph node and for their reactivity with sheep efferent and afferent lymph and peripheral blood. With the exception of 20-27 they all stained that same cell populations. The antibodies precipitated molecules with a heavy chain of 46,000 apparent molecular weight and a light chain of 14,000 apparent molecular weight. VPM5 and CC14 antigens were purified by affinity chromatography. All the antibodies cross-reacted with these molecules. The results show that 20-27 recognises the same molecules as the other antibodies and suggest that 20-27 is a pan CD1 monoclonal antibody and the other monoclonal antibodies are homologues of the human CD1b molecules.

Animals↗
PubMed1991

Immunohistology of lymph nodes draining local skin reactions (chancres) in sheep infected with Trypanosoma congolense.

Marked enlargement of lymph nodes draining local skin reactions (chancres) occurred in sheep following intradermal inoculation of cultured metacyclic forms of Trypanosoma congolense. Histologically, these lymph nodes were characterized by follicular hypertrophy and hyperplasia, compression and relative reduction of the paracortical areas and expansion of the medullary regions. Immunohistochemical staining with monoclonal antibodies to ovine lymphocyte subsets and Fc receptor (FcR) bearing macrophages, revealed increased expression of B cells (CD45R+), major histocompatibility complex (MHC) Class II, FcR+ macrophages, and CD1+ cells in the cortical and paracortical areas. The paracortical areas were found to be sparsely populated by CD5+, CD4+ and CD8+ cells, while the medullary areas contained numerous CD8+ cells and FcR+ macrophages. FcR+ macrophages were also present in cortical trabecular and subcapsular sinuses. As the chancre regressed, lymph node reactivity also subsided and fewer B cell follicles were observed and there was decreased expression of CD45R+ and MHC Class II+ cells.

Animals↗
PubMed1991

Identification of a putative cellular receptor for the lentivirus visna virus.

One mechanism by which viral tropism may be controlled is by the expression of a specific virus receptor on the cell surface. This paper reports the identification of a putative cellular receptor for visna virus, the prototype virus of the family Lentiviridae. Using a virus overlay protein blot assay we identified a group of polypeptides of apparent Mr 30K to 33K which interacts with visna virus and is present on permissive but not non-permissive cells. A rat polyclonal anti-ovine major histocompatibility complex (MHC) class II antigen (Ag) serum raised to immunopurified MHC class II Ag, but not preimmune serum, blocked the interaction of visna virus with these polypeptides. In an ELISA, immunopurified MHC class II Ag bound to visna virus but not to bovine parainfluenza 3 virus. Preincubation of visna virus with immunopurified soluble MHC class II Ag resulted in a marked decrease in virus-induced syncytium formation, i.e. preincubation with class II Ag inhibited infection with visna virus, but we have been unable to inhibit infection using class II Ag-specific antisera. These results suggest that ovine MHC class II Ag acts as a component of a cellular receptor for visna virus. This is of particular interest owing to the close similarities between visna virus and human immunodeficiency virus (HIV), and the relationship between MHC class II and CD4, the cellular receptor for HIV. It is also of relevance to recent reports that a growing number of viruses utilize polypeptides of the Ig supergene family as receptors.

Animals↗
PubMed1991

Use of DNA fingerprinting in paternity analysis of closely-related Exmoor ponies.

DNA fingerprinting techniques were used to try to resolve the parentage of an Exmoor pony foal. Three young Exmoor ponies, one female and two males, shared a paddock and the female subsequently became pregnant. The two possible sires were three-quarter siblings and were also half-siblings to the dam. Southern hybridisation of Exmoor pony DNA with human mini-satellite probes resolved the disputed parentage in spite of the fact that there was a 70 per cent band share between the individuals involved. Colt M6 was 2.06 times more likely to be the father than an uncle, and Colt M3 was 477 times more likely to be an uncle than the father.

Animals↗
PubMed1990

Uptake of antigen by afferent lymph dendritic cells mediated by antibody.

Dendritic cells isolated from sheep afferent lymph were examined for their ability to bind soluble protein and peptide antigens labeled with fluorescein both in in vitro assays and following intradermal injection of antigen in vivo. Analysis of dendritic cells by flow cytometry revealed weak direct binding of proteins and peptide antigens. However, the degree of uptake was greatly enhanced in the presence of specific antibody in vitro or if antigen was injected intradermally into antigen-primed sheep. About 60% of dendritic cells possessed the ability to take up antigen in both the in vitro and in vivo experiments. The uptake of antigen occurred very rapidly, reaching maximum values in terms of cell numbers and fluorescence intensity in less than 5 min in vitro and 20-40 min following in vivo challenge. Both sheep IgG subclasses could mediate this effect, but F(ab')2 fragments were ineffective. Procedures adopted to remove complement components from the in vitro test mixtures did not result in any reduction in the binding of antigen by dendritic cells. Two-color flow cytometry analysis of the dendritic cell population further showed that 43% of cells taking up the antigen/antibody complexes were CD1+, suggesting a relationship between these cells and Langerhans' cells or other dendritic cells in skin. The results, thus, indicate that approximately two thirds of sheep afferent lymph dendritic cells bind antigen/antibody complexes via an Fc receptor, a mechanism which could be important in the accentuated accessory function of these cells known to occur following secondary antigen challenge.

Animals↗
PubMed1990

Stability of metacyclic variable antigen types (M-VATs) during the early stages of infection with Trypanosoma congolense.

Expression of nine metacyclic variable antigen types (M-VATs) of Trypanosoma congolense in chancres from infected rabbits was determined using monoclonal antibodies raised against metacyclic forms of trypanosomes. Trypanosomes present in chancres 7-9 days post infection expressed M-VATs present in metacyclic populations of the parasites. The majority of M-VATs expressed showed little proportional change from those observed on metacyclic trypanosomes during this period although expression of one M-VAT increased, and another decreased. Although trypanosomes in chancres continued to express M-VATs, other VATs, not present in the M-VAT repertoire were also expressed and neutralization tests showed that new VATs appeared by 7 days after infection. In infected sheep neutralizing antibodies against M-VATs were detected by day 14 in lymph from efferent lymphatics draining lymph nodes in the region of chancres. Neutralizing antibodies directed against metacyclics were also present in the serum by day 14 and were still detectable for up to 35 days post infection. Hence, it is likely that in the vertebrate host the trypanosomes multiplying in the skin at the site of tsetse bit express all M-VATs characteristic of that particular serodeme, enabling the host to develop immunity to all antigen types present in the M-VAT repertoire.

Animals↗
PubMed1990

Monoclonal antibodies to the sheep analogues of human CD45 (leucocyte common antigen), MHC class I and CD5. Differential expression after lymphocyte activation in vivo.

This paper describes three anti-sheep monoclonal antibodies. The tissue distribution and apparent molecular weight of the antigens detected by these antibodies is consistent with them reacting with sheep leucocyte common antigen (CD45 (VPM18], MHC class I (VPM19) and CD5 (VPM29). An ELISA method is described that permits the cross-reactivity of different antibodies to be assessed, this confirms the identity of the antigens detected by VPM18, VPM19 and VPM29. This method is also of value as either a positive or a negative screen in the construction of further monoclonals. A study of the expression of these three antigens on efferent lymph small lymphocytes and antigen-activated lymphoblasts shows that the density of CD45 on lymphoblasts (activated either in vivo or in vitro) is approximately half that of small lymphocytes whereas the density of MHC class I is the same in both populations. Furthermore, about 75% of small lymphocytes express CD5 but less than 10% of lymphoblasts are positive. Cell membrane CD5 expression is lost on lymphocyte activation. It does not seem to be linked to cell membranes via phosphatidylinositol and the loss is not due to the breaking of that link.

Animals↗