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Biomedical subjects

P L Yap

Publications and source records attributed to P L Yap.

At least 19 recordsLinked to original sources
PubMed1992

Virus infections of the respiratory tract in HIV-infected children.

In order to determine whether the rates of respiratory viral infection and the severity of respiratory symptoms in HIV-infected children were higher than those in noninfected children, nose and throat swabs for viral isolation were taken at 3-month intervals during the first 2 years of life from 50 children born to HIV-infected women. Similar samples were obtained during the first year of life from 19 control children born to HIV seronegative mothers. Of the 50 children, five proved to be HIV-infected while 45 were presumed to be uninfected. HIV-infected children had significantly more respiratory symptoms and a higher proportion of samples from which viruses were isolated than the non-HIV-infected children. Also, more infected episodes required admission to hospital in the HIV-infected group. There was no such difference between the non-HIV-infected and the control children. Three HIV-infected children received intravenous immunoglobulin therapy. Among these the proportion of positive samples for viral isolation was greater before than after treatment began. These results suggest that HIV-infected children are more susceptible to recurrent viral infection and that passive immunotherapy may be of benefit to such children.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Applications of intravenous immunoglobulin in haematology.

Intravenous immunoglobulin (IVIgG) has many potential applications in haematology both as antibody replacement therapy and as an immune-modulater in autoimmune disorders. Antibody replacement appears to be of value in the prophylaxis of infection in low-grade B-cell malignancies, in bone marrow transplant recipients and in children with AIDS, although optimal treatment strategies have not been assessed and determining which patients are likely to derive greatest benefit has been problematic. IVIgG appears to be effective in the prevention or amelioration of CMV-related pathology if given frequently and has also dramatically improved the survival of patients with established interstitial pneumonia when used in combination with ganciclovir. Intriguingly, IVIgG appears to moderate the severity of GVHD in adult transplant recipients. IVIgG has short term efficacy in most patients with ITP but, as long term remissions are uncommon, it has become necessary to be more selective in the use of IVIgG in this disorder. The response to IVIgG in other immune-mediated cytopenias is similar with generally transient improvement but also with occasional spectacular cures. The treatment of the acquired haemophilias with IVIgG has yielded in vivo and vitro evidence to support the idiotype-antiidiotype theory of IVIgG immune-modulation and has also demonstrated significant differences in the sensitivity of coagulation factor autoantibodies and alloantibodies to IVIgG therapy. IVIgG has several roles in pregnancy related disorders, including the management of both mother and fetus in ITP during pregnancy, the antenatal and postnatal management of platelet alloimmunisation and also in the management of severe rhesus isoimmunisation. IVIgG is safe and well tolerated. The expense of this therapy should be balanced against the likely gains and the overall costs of alternative approaches.

Adjuvants, Immunologic↗
PubMed1992

The influence of dietary essential fatty acids on uterine C20 and C22 fatty acid composition.

The effect of dietary fatty acids on uterine fatty acid composition was studied in rats fed control diet or semi-synthetic diet supplemented with 1.5 microliter/g/day evening primrose oil (EPO) or fish oil (FO). Diet-related changes in uterine lipid were detected within 21 days. Changes of 2- to 20-fold were detected in the uterine n-6 and n-3 essential fatty acids (EFA) and in certain saturated and monounsaturated fatty acids. The FO diet was associated with higher uterine C20 and C22 n-3, and the EPO diet, with higher uterine n-6 fatty acid. High uterine C18:2 n-6 was detected in neutral lipid (NL) of rats fed high concentrations of this fatty acid, but there was little evidence of selective incorporation or retention of C18:2 n-6 by uterine NL. The incorporation of EFA into uterine phospholipids (PL) was greater than NL EFA incorporation, and uterine PL n-3/n-6 ratios showed greater diet dependence. Tissue/diet fatty acid ratios in NL and PL also indicated preferential incorporation/synthesis of C16:1 n-9, and C16:0, and there was greater incorporation of C12:0 and C14:0 into uteri of rats fed EPO and FO. Replacement of 50-60% of arachidonate with n-3 EFA in uterine PL may inhibit n-6 EFA metabolism necessary for uterine function at parturition.

Animals↗
PubMed1992

Developmental changes in the fatty acids of rat uterus and the influence of dietary essential fatty acids.

The effect of age on uterine fatty acid composition was studied in rats fed diets of differing fatty acid composition. Uteri of newly weaned 23-day rats had a higher fatty acid content and a higher proportion of short-chain (less than or equal to C18) fatty acids. Higher incorporation of C less than or equal to 18 fatty acids into neutral lipid (NL) and phospholipid (PL) of young 42-day rats compared with adult 240-day rats was detected. Uterine NL incorporated predominantly C less than or equal to 18 fatty acids which may be an important metabolic energy store in developing uterine tissue. Incorporation of C less than or equal to 18 fatty acids by uterine PL and NL was relatively unselective. In contrast, there was selective retention of arachidonic acid (AA) and docosahexanoic acid (DHA) throughout uterine development. An effect of dietary EFA on uterine n-3 and n-6 EFA was detected in each age group. There was marked retention of uterine AA when dietary supplies of n-6 EFA were low, but the total AA, eicosapentaenoic acid (EPA) and DHA in uterine PL remained constant in the three diet groups, and a constant content of AA, EPA and DHA was maintained throughout uterine development, regardless of diet. The degree of n-3 substitution achieved in this study inhibited uterine release of PG and parturition in adult rats.

Aging↗
PubMed1992

Analysis of a new hepatitis C virus type and its phylogenetic relationship to existing variants.

Sequences obtained in the 5' non-coding region (5'NCR) of hepatitis C virus (HCV) were obtained from Scottish blood donors and compared with previously published HCV sequences. Phylogenetic analysis revealed the existence of three distinct groups of sequences; two of these corresponded to the recently described HCV types 1 and 2 variants, while viral sequences detected in around a third of the blood donors formed a separate phylogenetic group that probably represents infection with a novel virus species. Nucleotide sequences of this latter group differed from all previously published 5'NCR sequence variants by at least 9%. This new virus type also differed considerably from previously published variants in other regions of the viral genome (core, NS-3 and NS-5), with corrected nucleotide distances of 15, 43 and 49% respectively from the prototype HCV-1 sequence. Formal phylogenetic analysis of each of the coding regions confirmed that HCV type 1 variants could be clearly differentiated into regional variants (Far East and U.S.A./European), in contrast to the clearly overlapping geographical distributions of the main HCV types in U.K. blood donors. We discuss the evidence for and against the hypothesis that the three main phylogenetic groups identified in this study represent separate species of HCV.

Amino Acid Sequence↗
PubMed1992

Pathways controlling the superoxide response during phagocyte differentiation: involvement of arachidonic acid and Ca2+ in the response to bacterial endotoxin.

In contrast to the phorbol ester oxidative response, which only develops during dimethylsulphoxide (DMSO)-induced differentiation of the human leukemic myeloblast HL-60 cell-line, the endotoxin response was observed in undifferentiated and differentiated cells. The Ca2+ response to endotoxin, detected in both differentiated and undifferentiated HL-60 cells, consisted of a transient 10-50 nM increase in intracellular Ca2+. A very slow, irreversible increase in intracellular Ca2+ was detected at high 1-100 micrograms/ml endotoxin concentrations, and this effect, and the inositol phosphate response, correlated with the surfactant activities of various endotoxins and Lipid A. Arachidonic acid and sodium arachidonate 1-50 microM stimulated a large 200-500 nM and transient Ca2+ response in undifferentiated HL-60 cells, which was significantly greater than that elicited by 1-50 microM eicosapentaenoic acid, and was not observed at similar concentrations of arachidonic acid methyl ester or myristic acid. These concentrations (1-50 microM) of arachidonic acid were observed to have surfactant activities on the plasma membrane. At lower arachidonic acid concentrations a marked potentiation of both Ca2+ and oxidative responses to the chemotactic peptide fMet-Leu-Phe was detected. It is possible that the arachidonic acid released during phospholipase A2 activation of neutrophils may be involved in cellular cross-talk and, at higher concentrations, in directly activating Ca2+ and superoxide production. It is also possible that previously reported effects of endotoxin at high concentrations are an in vitro artefact of surfactant properties of endotoxin.

Arachidonic Acid↗
PubMed1992

Use of serum from patients with polycythaemia or haemochromatosis for laboratory external quality assurance exercises.

Some External Quality Assessment Schemes (EQAS) require large volumes of human serum. During a one year period, 595 units of blood were obtained from 87 patients with haemochromatosis and polycythaemia, who underwent therapeutic venesection at the Edinburgh and South East Scotland Blood Transfusion Service. Serum from 59% of these donations was used in the EQAS for peptide hormones and related substances. The cost of the serum collection was 109 pounds/litre, but was only 33 pounds/litre of serum if the cost of the actual venesection was excluded. Results from tests on the sera were satisfactory in a variety of immunoassays for several different hormones. EQA schemes with requirements for large volumes of serum should consider therapeutic venesection as a cost effective means of obtaining serum.

Adult↗
PubMed1992

Zidovudine therapy in combination with intravenous immunoglobulin in HIV infected children.

There is little published data on concomitant use of zidovudine and intravenous immunoglobulin (IV IgG). In this paper we review our experience of four HIV-1 infected children treated with zidovudine for periods of 19-33 months (mean 26.5 months) subsequent to starting IV IgG for period of 18-20 months (mean 19 months). In these children the only clear benefit we found was in one child who had developed HIV encephalopathy which resolved after starting zidovudine. The respective roles of zidovudine and intravenous immunoglobulin in HIV-1 infected children need to be clarified in larger comparative trials.

CD4-Positive T-Lymphocytes↗
PubMed1991

Use of intravenous immunoglobulin in acquired immune deficiency syndrome.

Patients infected with the human immunodeficiency virus (HIV) may have an antibody deficiency and a deficiency of cellular immunity. Intravenous immunoglobulin (IVIG) preparations may benefit HIV-infected children and adults with recurrent bacterial infections at doses of 200 to 400 mg/kg every 2 to 4 weeks. In addition, IVIG (1 to 2 g/kg) is effective at raising platelet counts to hemostatic levels in HIV-infected patients with idiopathic thrombocytopenic purpura and life-threatening bleeding. Indirect evidence also suggests that IVIG may be effective in preventing Pneumocystis carinii pneumonia. Finally, recent studies suggest that specific anti-HIV antibody preparations may have a therapeutic role, either as immunoglobulin concentrates or as immunoadhesions and immunotoxins. However, further investigations are needed to exclude antibody enhancement of HIV infection by the Fc receptor or the complement receptor.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Lack of specificity for antibodies to double stranded DNA found in four commercial kits.

Four commercially available kits (three enzyme linked immunosorbent assays and one modified Farr radioimmunoassay) were compared for their ability to detect specifically autoantibodies to double-stranded DNA (dsDNA) using 66 patient sera. This was assessed by comparing the results of the kits with those from an ELISA specifically measuring antibodies against highly purified dsDNA, single-stranded DNA (ssDNA), native DNA and histones. The RIA and two of the ELISAs seemed equally efficient at detecting antibodies to dsDNA, but all three also detected anti-ssDNA (the RIA being particularly bad for this). The need for highly purified dsDNA was clearly shown. The results obtained with one ELISA did not correlate with any variable investigated in this study. A total of 220 sera were assayed with the IDS RIA, of which 130 were recorded as positive. Of these, 50 sera seemed to contain no identifiable autoantibodies. This very high false positive rate may be due, at least in part, to precipitation of nonspecifically bound labelled DNA.

Antibodies, Antinuclear↗