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Biomedical subjects

J L Ngu

Publications and source records attributed to J L Ngu.

At least 37 records · Page 2Linked to original sources
PubMed1985

Nephropathy in Cameroon: evidence for filarial derived immune-complex pathogenesis in some cases.

This study was carried out in two parts. Part 1 consisted of an epidemiological survey of 1011 subjects aged 3-65 yrs from 2 adjoining villages hyper-endemic for Onchocerciasis and 890 subjects in a control area, relatively free from this infection but otherwise with a similar parasitological profile. There was a significantly higher prevalence of proteinuria in subjects from the onchocercal zone than in controls (observed difference greater than 5 1/2 times its standard error). Part 2 comprised detailed investigations, including renal biopsy, of 63 consecutive patients admitted into hospital with severe proteinuria and/or renal failure from a caption area extending into the onchocercal zone. There were a variety of causative factors, but in 9 cases filarial antigen was demonstrable in the immune-complex deposits in the kidney. A plenum of renal histopathological changes were seen in patients with onchocerciasis. The significance of these findings is discussed.

Adolescent↗
PubMed1985

Serum immunoglobulin E levels in onchocerciasis: the development of a radioallergosorbent test for Onchocerca volvulus infection.

The effects of Onchocerca volvulus infection on immunoglobulin levels have been studied in subjects from three localities with different onchocerciasis prevalence rates. Infestation by O. volvulus provoked a 200-500% rise in total serum IgE levels. Immunoglobulins G, M. and A were increased less dramatically. To study further the IgE response, radioallergosorbent test (RAST) systems were developed using total extract of O. volvulus and Onchocerca supernatant (excretory-secretory) antigens. Both antigen preparations reacted with more than 80% of the onchocerciasis sera from the hyperendemic village, but the reactions were not proportionate to skin microfilarial density. There were also positive reactions with sera of some individuals whose skin biopsies showed no microfilariae, indicating prior exposure to the parasite. European control sera tested under similar conditions reacted only slightly in the RAST system. The developed RAST systems may thus be used for determining prior exposure to O. volvulus.

Cameroon↗
PubMed1983

The effects of diethylcarbamazine citrate, antihistamines and corticosteroid derivatives on skin reactivity to Onchocerca supernatants.

A single dose of promethazine or of betamethazone, either alone or compounded with dexchloropheniramine, was found to inhibit skin wheal formation in onchocerciasis patients challenged with Onchocerca supernatants. The mean wheal diameter developing 24 hours after drug administration ranged between 40-60% less than the original pre-treatment diameter but this effect had been abolished or was significantly less by 48 hours. Diethycarbamazinecitrate had only a 20% inhibitory effect on the wheal diameter of the skin reaction. It is concluded that antihistamines and corticosteroid derivates may interfere with the immunodiagnostic skin test for onchocerciasis based on skin reactivity to Onchocerca supernatants, unless measures are taken to ensure that these drugs are not consumed within the 48 hours preceding the skin test.

Adrenal Cortex Hormones↗
PubMed1981

Selective recovery of living microfilariae from Onchocerca volvulus nodules. Determination of optimal conditions for their culture in vitro for excretory/secretory products.

A method for the selective recovery of living microfilariae from Onchocerca volvulus nodules is described. The microfilariae migrate through solidified agar gel into overlayering Hanks balanced salt solution (HBSS). The highest recovery rates of the worms were obtained with 0.3 and 0.4% agar. Optimal conditions for in vitro cultures of the larvae in HBSS were established; pH range 7.0-7.5, glucose concentration 2-5 mg/ml for long term cultures, osmolality 200-309 mOsmoles/l, temperature 4 degrees C for prolonged cultures and 24-28 degrees C for overall best yield of excretory/secretory products (ESP). Subculturing of the larvae reduced contamination of ESP with human serum protein to minimal amounts after 9 recultures done within 96 h.

Animals↗
PubMed1981

A diagnostic skin test for Onchocerca volvulus infection.

Onchocerca supernatant (OS) was prepared by a technique permitting live microfilariae to migrate from nodule tissue through agar gel into sterile Hanks balanced salt/Penicillin-Streptomycin solution where they metabolized. The OS, after dialysis, was passed through Seitz viral filter and either concentrated or lyophilized. Using rabbit antiserum in immunodiffusion and immunoelectrophoresis tests, microfilariae proteins and also human protein were detected in out OS. No common antigens were found between this and somatic extracts of Loa loa, O. gutturosa, O. volvulus, L. carinii, D. immittis and A. lumbricoides. 125I labelled OS was purified by passage through protein A column and then through immunosorbent column of horse anti-human serum linked to CNB-activated sepharose 4B. Autoradiography, after sodium dodecyl sulphate polyacylamide slab gel eletrophoresis of purified OS, showed 10 protein bands in the molecular range 10,000 to 125,000. Skin prick tests with OS, shown not to be contaminated with Hepatitis B antigens, elicited immediate hypersensitivity reaction. Using our criteria, positive reactions were seen in 81% of proven onchocerca cases and only occasionally in Loasis 4.5%, ascaridiasis 13.5% or healthy controls 2.4%. The poor skin reactivity to OS in loasis was not due to immunosuppression as these patients, when also infested with ascaris, reacted just as well as onchocerca patients with ascaris to skin prick test using somatic extracts of ascaris.

Adolescent↗
PubMed1980

Circulating immune complexes in onchocerciasis.

Circulating immune complexes were detected in sera of patients with both localized and generalized onchocerciasis by a 125I-Clq binding assay but not by the IgG latex agglutination inhibition method. Gel filtration of sera demonstrated high molecular weight Clq-reactive material(greater than 2 x 10(6) Daltons) which contained IgM but no IgG. Antibody titres to Onchocerca volvulus antigen were higher in patients with generalized disease than in those with the localized form. The lack of correlation between antibody titres and levels of immune complexes suggests that these immune complexes contain antigens other than those derived exclusively from the parasite. Although few of the symptoms of this disease are likely to be due to deposition of circulating immune complexes, the depression of delayed hypersensitivity reactions to the parasite found in patients with generalized onchocerciasis may be due to IgM immune complexes exerting an immuno-regulatory role on T cell function.

Adolescent↗
PubMed1978

Immunological studies on onchocerciasis. Varying skin hypersensitivity and leucocyte migration inhibition in a clinical spectrum of the disease.

Soluble antigen was prepared from adult worms and microfilariae of Onchocerca volvulus. In 27 patients clinically characterized as having generalized type (17) and localized reaction type (10) onchocerciasis, the response to this antigen was assessed in vivo by skin testing and in vitro by leucocyte migration inhibition assay. Three varieties of skin hypersensitivity were observed: Immediate, Arthus-type and delayed or type IV hypersensitivity. The first 2 occurred in all patients, but type IV hypersensitivity was noted only in 10, eight of whom had localized reactive type onchocerciasis, whilst the other 2 had mild generalized lesions which had for the most part healed with treatment. The leucocyte migration inhibition assay showed a spectrum of responsiveness with significant inhibition in the presence of antigen in 8 patients with localized lesions and in 2 others with mild generalized disease which had largely healed.--The specificity of the skin reaction and leucocyte migration inhibition to the antigen used was confirmed by the results obtained when a control group of 18 subjects, with no evidence of previous filarial infection, was similarly tested. 16 of them showed no skin hypersensitivity and 2 had a doubtful immediate reaction. No significant inhibition of leucocyte migration in the presence of antigen was noted in this group.

Adolescent↗
PubMed1976

Immunological studies in congestive cardiomyopathy in Cameroon.

Significantly higher levels of immunoconglutinin were found in the sera of 40 Cameroonian patients aged between 15 and 80 years with congestive cardiomyopathy than in a matched group of normal Cameroonian controls. C3 values were also abnormal in the group with congestive cardiomyopathy, and a negative correlation was found between the C3 and immunoconglutinin values, indicating complement incorporation into immune complexes. Further, the levels of immunoglobulins G, M, and A were all raised, the most striking increase being of IgM, which was greater than in the normal controls and in a group with 'other cardiac disease' studied for comparison. Complement-fixing autoantibodies to cardiac muscle of the class IgG and IgM were found by immunofluorescence techniques in a significant proportion of the patients with congestive cardiomyopathy. Finally, evidence of trypanosomiasis was found by immunofluorescence tests in 27-5 per cent of patients with congestive cardiomyopathy, compared with 8-5 per cent of patients with other cardiac disease, and 1-9 per cent of normal Cameroonian controls selected randomly. We think that some cases of congestive cardiomyopathy in Cameroon may be caused by untreated subclinical attacks of African trypanosomiasis which produce immune complexes that damage the cardiac tissue where the parasite is lodged. Secondary autoimmune carditis modifies the course of the disease, with the resulting end-stage picture.

Adolescent↗
PubMed1976

Immunological studies in onchocerciasis in Cameroon.

Immunological studies were undertaken in a group of twenty patients with varying clinical manifestations of onchocerciasis. Significantly higher levels of immunoconglutinin, IgG and IgM, and alterations in C3 levels were found in the patient group than in controls. IgG and IgM complement-fixing antibodies to microfilariae of O.volvulus were detected in the sera of these patients. The lymphocyte transformation rate following PHA stimulation was high in patients with localised skin lesions in which the microfilariae were difficult to demonstrate in contrast to the low transformation rate obtained in those with diffuse lesions and in whom microfilariae were readily detected in skin biopsies. The significance of these findings is discussed.

Adolescent↗