FACULTY OF BASIC MEDICAL SCIENCES
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Item Plasma glucose and thiocyanate response to different mixed cassava meals in non-diabetic Nigerians(The Macmillan Press Ltd., 1990-01) Akanji, A. O.; Adeyefa, I.; Charles-Davies, M.; Osotimehin, B. O.We measured plasma glucose and thiocyanate levels before and up to 4 h after feeding 11 overnight fasted healthy non-diabetic volunteers randomly on three occasions each with three locally consumed cassava meals: (i) gari as eba 50 g; (ii) lafun 50 g and (iii) parboiled cassava flakes 76 g. Each of these meals contained 175 kcal (0.7 MJ) and was consumed with a sauce to a total caloric value of 300 kcal (1.26 MJ). On the fourth visit, each volunteer consumed 75 g glucose. While the peak and 2-h glucose values were greatest with oral glucose (P less than 0.01), they were similar with the three cassava meals, although tended to be lowest with lafirn. Similarly, areas (incremental and total) under the glucose/time curves were highest with oral glucose (P less than 0.05), but while eba and cassava flakes were similar, lafun had the lowest values (P less than 0.05). Plasma thiocyanate levels were unchanged after ingestion of oral glucose and eba, but increased to peak values (P less than 0.05) by 14 per cent on cassava flakes and by 23 per cent on lafun. We conclude that post-prandial glycaemia and plasma thiocyanate levels after cassava meals depend on the mode of preparation of the meal and that lafun showed the least glycaemic response of the three cassava meals tested although it caused the greatest increase in plasma thiocyanate levels. These findings suggest that a cyanogenetic potential does not always reflect a tendency to hyperglycaemia.Item THE MODULATION OF RAT LIVER MICROSOMAL CALCIUM ION-PUMPING ATPase BY DICOPHANE AND LOW PROTEIN INTAKE(1992-05) ADENUGA, G. A.The effects of the liver tumour promoter, dicophane, with those of low protein intake (LPI) on the functional expression of rat liver microsomal Ca(2+) -ATPase were compared. The effects of dicophane and LPI on the activity of the microsomal enzyme after carcinogenic initiation by pretreatment with aflatoxin B (AFB), a genotoxic liver carcinogen, were also compared. The Status of membrane - bound Ca(2+) -ATPase of erythrocytes of humans having primary liver cancer (PLC) and kwashiorkor was assessed. The specific activity of membrane - bound microsomal Ca(2+) -AT Pase of the livers of untreated rats was 4.543 ± 0.857 µmole P/mg protein/hr. at pH 8.0 and was insensitive to calmodulin. The specific activity of the enzyme was significantly decreased (P < 0.01) following subcutaneous administration of a single dose of 75mg dicophane/kg body wt.; the affinity of the enzyme for Ca(2+) was however unaffected. Similarly, liver microsomal Ca (2+)-ATPase activity was significantly diminished following the ingestion of low protein diet by rats for 12 weeks. The mean Ca(2+) -ATPase activity of AFB -treated animals (in the absence of dicophane) was not significantly different (P > 0.05) from that of AFB-treated rats which subsequently received dicophane. In contrast, liver microsomal Ca(2+)-ATPase activity of animals fed low protein diet prior to and after AFB ingestion was higher (P < 0.05) than that of animals which were on low protein diet only. Basal activity of erythrocyte Ca(2+) -ATPase in paediatric controls and those having kwashiorkor (protein-energy-malnutrition) were similar (P > 0.05); similar observations were made between normal adults and those suffering from PLC. Erythrocyte Ca(2+) -ATPase of either PLC or kwashiorkor patients was however, some- what, less sensitive (15-40 %) to the stimulatory effect of calmodulin, an endogenous activator of the Ca(2+) -pump. These results suggest that liver microsomal Ca(2+) -ATPase could be a useful biochemical marker to determine the onset or occurrence of tumour promotion in liver cells. Finally, chronic dietary protein malnutrition mimics the effect of chemical liver tumour promoters and could possibly enhance the development of human PLC particularly n those areas of the tropics where malnutrition is prevalent. Future confirmatory experiments are however re-quired to fully justify this postulate.Item SOME CONSEQUENCES OF THE BINDING OF AFLATOXIN B1 WITH PLASMA MEMBRANE ON THE REGULATION OF INTRACELLULAR Ca2+ HOMEOSTASIS(1992-03) ADEBAYO, A. O.The possible influence of aflatoxin B1 a potent hepatocellular carcinogen on the regulation of intracellular Ca2+ homeostasis has been studied using the red cell as a model. Preliminary work on the interaction of the toxin with the red cell membrane using spectrofluometric analysis indicated that the toxin binds spontaneously and irreversibly to the red cell membrane. The binding is highest at pH 4 and least at pH 10. Results obtained from studies using equilibrum dialysis technique show that about 4 nmoles of the toxin bind to one microgram membrane protein. Although the exact membrane component to which aflatoxin B1 binds is not known, experiments carried out to determine the influence of aflatoxin B1 on the activity of the calcium pumping protein revealed that the toxin inhibited the calmodulin-stimulated erythrocyte membrane Ca2+ -ATPase activity by about 50 percent, while it has little or no effect on its basal activity. Kinetic analysis of the inhibition shows that, the toxin reduces the Vmax and Km of the calmodulin-stimulated enzyme by 50 percent in a non-competitive manner, On the other hand, the carcinogen had no significant influence on the kinetic parameters of the enzyme in the non-activated state. Similar results were obtained for the triton X-100 solubilized and calmodulin affinity chromatographed enzyme. In this instance aflatoxin B1 inhibited the calmodulin-stimulated purified enzyme by 50 percent with or without preincubation on ice for half an hour. Again, the toxin had little or no effect on the basal activity of the enzyme in the absence of calmodulin. Analysis of the results obtained using varying concentrations of ATP shows that the Km and Vmax of the non-activated enzyme were not altered by the toxin while both the Vmax and Km values were reduced by about 50 percent in the presence of calmodulin. In addition aflatoxin B1 inhibited Diphosphotidyl glycerol (cardiolipin) by about 28% while it has no effect on the basal activity of the enzyme. Although, the inhibition of the membrane bound or purified Ca2+ ATPase by the toxin is concentration dependent, varying concentrations of phosphatidyl serine and phosphatidyl choline do not affect the inhibition of the purified enzyme by afla toxin B1. Results obtained with triton X-100 solubilized enzyme shows that triton X-100 alone could not activate the enzyme. Thus at triton X-100: protein ratio of 2, the enzyme was stimulated by calmodulin. This activity was sensitive to inhibition by the toxin. In this instance, the calmodulin-stimulated activity was inhibited by about 50%, while at lower ratios of the triton X-100 to protein there was no significant inhibition of enzyme. Results of experiments carried out on the 124KDa fragment, which was produced as a result of exposure to calpain a Ca2+ - dependent cysteine protease, indicated that the toxin has no effect whatsoever on the activity of the fragmented enzyme, Similarly experiments on limited proteolysis of the Ca2+ ATPase by trypsin to give the 90KDa fragment which still retains its calmodulin binding domain and the 76KDa fragment which has lost its calmodulin binding domain revealed that the aflatoxin inhibited the 90KDa fragment by about 50% while the 76KDa fragment is not affected at all. Altogether, -these findings show that aflatoxin B1 inhibits the plasma membrane Ca2+ - pumping ATPase by interacting with the enzyme at the calmodulin binding domain. The nature of the exact amino acid residue to which the toxin binds is however not known. The implication of these observations is that Ca2+ extrusion may be hampered in situations where the cell is poisoned by the aflatoxinItem MALARIA PARASITAEMIA AND HUMORAL IMMUNE RESPONSES TO SOME DEFINED PLASMODIUM FALCIPARUM ANTIGENS IN NEWBORNS, INFANTS AND ADULT NIGERIANS(1994-08) ACHIDI, E. A.A cohort of mothers and then newborns at Igbo-Ora, Oyo State was studied longitudinally for 12 months to determine the incidence of malaria parasitaemia, episodes of clinical malaria and their humoral immune response to malaria infection. Cross-sectional studies were also performed on adults at the Government Technical College, Igbo-Ora and blood donors at the University College Hospital, Ibadan during the rainy and dry seasons. Peripheral and cord blood samples were collected from 116 women at delivery and maternal-newborn malariometric indices were recorded. Infants were monitored fortnightly to detect episodes of clinical malaria and serial blood samples were collected at bi-monthly clinics. Blood samples were collected from 100 volunteers at the G.T.C. Igbo-Ora in July, 1991 and 33 of these volunteers in February, 1992; 224 blood donors at the U.C.H., Ibadan between October and November, 1991 and in 192 donors in March, 1992. Immunological assays included single radial immunodiffusion assay for IgG, IgM and IgA; immunofluorescence assay for antibodies to total blood stage antigens; erythrocyte membrane immunofluorescence (EMIF) assay to detect antibodies to the Pfl55/RESA; and an enzyme-linked immunosorbent assay (ELISA) for antibodies to four synthetic peptides. Malaria parasites were detected in 2.5% of cord blood samples and in 22.4% of the parturient women. The malaria parasite rates and densities of the study infants increased significantly with increasing age. Parasite rates at the July and February surveys at the G.T.C. were similar (P>0.50) while parasite density was higher (P<0.01) at the July survey. The parasite rate of blood donors at the October-November survey was higher (P<0.001) than at the March survey while parasite density in March was higher (P<0.001) than at the October-November survey. Cord blood IgG was significantly lower than maternal IgG levels and a correlation was observed between cord and maternal IgG but not IgM levels. During the first year of life, IgM but not IgG and IgA was significantly higher in malaria positive infants compared with negative infants. Antibodies to total blood stage antigens were detected in all sera tested. Malaria-specific IgM was detected in 5.8% of cord blood samples. There was a correlation between maternal and cord blood antibody titres to the Pfl55/RESA (P<0.001) antigen. In addition a correlation was obtained between maternal and cord blood ELISA (OD405) values to the (EENV)6, LJ5 and MAP2 peptides but not (NANP)6 peptide. There was no correlation between cord blood IgG, IgM, anti- Pfl55 antibody titres, ELISA (OD405) values to the (EENV)6, (NANP)6, U5 and MAP2 peptides and duration of onset of malaria in the infant. Cord blood seropositivity for antibodies to the Pfl55/RESA and (NANP)6 antigens or (EENV)6 and (NANP)6 peptides did not influence age of onset of clinical malaria. However, infants with haemoglobin AS whose cord blood was seropositive for antibodies to the Pfl55/RESA and (NANP)6 antigens or (EENV)6 and (NANP)6 peptides showed delayed onset of clinical malaria compared with AA infants. In adults, anti-Pfl55 antibody titres and ELISA seroreactivities to the (EENV)6, LJ5 and MAP2 peptides showed a wide variation and individual levels were similar on consecutive surveys. Seroreactivity to the (NANP)6, was higher at the end of the rainy season than at the end of the dry season. The presence and level of antibodies to the Pfl55/RESA, (EENV)6, (NANP)6, U5 and MAP2 antigens did not influence the presence and density of malaria parasites. Parasitological data in infants suggest some relative protection within the first 2-3 months of life. However, maternally acquired antibodies alone may not be responsible for this observation. The presence of malaria-specific IgM in cord blood suggest intrauterine sensitization of the foetus by malarial antigens. Although no relationship was observed between malarial antibody levels and parasite rates/densities in the adult subjects, these antibodies may still play a role in immune protection against malaria.Item Human T-cell lymphotropic virus types I and II infections in mother-child paris in Nigeria(Oxford University Press, 1999) Olaleye, D. O.; Omotade, O. O.; Sheng, Z.; Adeyemo, A. A.; Odaibo, G. N."A community-based survey to determine the prevalence of human T-cell Iymphotropic type I (HTLV-I) and type II (HTLV-II) virus infections in mothers and children in south-western Nigeria was carried out using blood samples collected in 1993. A multistage cluster, random sampling procedure was used to select 460 mother-child pairs (476 children because there were 16 sets of twills) from 14 enumeration areas. A commercially available, whole HTLV-I lysate antigen-based ELISA method was used to screen for HTLV-I and HTLV-II antibodies in the samples. A synthetic peptide antigen-based ELISA was then used to differentiate between antibody reactivity to either HTLV-I or HTL V-ll. Reactivity to HTLV-I or HTLV -II antibodies was found in 43 per cent (20/460) of mothers and in 1.1 per cent (5/476) of children in both rural and urban communities and all the positive children were males. None of the 16 sets of twins in this study was positive for either HTLV-I or HTLV-ll. Also none of the mother-child paired sera tested showed concordance for either HTLV-I or HTLV-II antibody positivity. The lack of concordance between mother and child sera suggests that vertical transmission may not be the major route of transmission of HTLV infection to children in south-western Nigeria. Other modes of transmission, such as the re-use of unsterilized needles for injections and surgical knives in local scarification, which are common practices in the region, need to be investigated as they may prove to be more important than vertical transmission. These findings have important implications for any control programme for diseases that can be spread by the same routes as HTL V infection (the human immunodeficiency viruses, hepatitis B, and hepatitis C infections)."Item Human immunodeficiency virus types 1 and 2 infection in some rural areas of Nigeria(1998) Odaibo, G. N.; Olaleye, O. D.; Tomori, O.The prevelence of human immunodeficiency virus types 1 and 2 in rural areas of Nigeria was estimated using 1089 sera collected in 18 locations from 1992 to early 1994. The sera were tested with Enzyme Linked Immunosorbent Assay(ELISA) and confirmed by western immunoblotting technique. Overall, 13 (1.2%) of the 1089 sera were positive for antibodies to HIV-1 and HIV-2. Prevalence of 0.6% and 0.8% were obtained for HIV-1 and HIV-2 (50.0%) were found in Zurhlrrua and Umubuzu. A seroprevalence of 1.2% was obtained for both male and female groups tested. The highest prevalence of HIV was found among individuals 30-39 years age group. An overall increase in prevalence of HIV-1 and HIV-2 infection was obtained over the three years during which samples were collected for this study (0.7% in 1992, 1.0% in 1992 and 3.4% in 1994). In addition, two sera were positive for both HIV-1 and HIV-2. The detection of antibodies to HIV-1 and HIV-2 in the rural areas where blood samples were collected for this study shows that both virus are widespread in the rural communities of Nigeria.Item Hepatitis B and C in doctors and dentists in Nigeria(Oxford University Press, 1997) Olubuyide, I. O.; Ola, S. O.; Aliyu, B.; Dosumu, O. O.; Arotiba, J. T; Olaleye, O. A.; Odaibo, G. N.; Odemuyiwa, S. O.; Olawuyi, F."We surveyed a random sample (n=75) of doctors and dentists at University College Hospital, Ibadan, Nigeria. They were offered anonymous testing for hepatitis B surface antigen (HBsAg), hepatitis B antibodies to hepatitis B core antigen (anti-HBc) and to hepatitis C virus (anti-HCV) by enzyme immunoassay. The results suggest a high prevelance of hepatitis B virus (HBV) with a high potential of transmissibility, as well as a high prevalence of HCV infection. The majority of the doctors and dentist use universal precaution for protection against viral hepatitis on <50% of the occasion when they carry out procedures on their patients. Infection with HBV was associated with type of specialty (surgeaon, dentists) and lack of HBV vaccination (p<0.05). After logistic regression, these factors, were independently associated. with HBV infection (p<0.05). Sixty (80%) had not hepatitis received prior HBV vaccination. Unvaccinated personnel were more likely to be surgeons, dentists, <37 years of age, and have fewer years of professional activity (p<0.05). After logistic regression, only fewer years of professional activity remained independently associated with lack of vaccination (p<0.05). To reduce the occupational exposure of doctors and dentists use universal precaution must be rigorously adhered to when the doctors and dentists carry out procedures on their procedures on their patients, and all health-care workers should be vaccinated with HBV vaccine and the HCV vaccine, when it becomes available."Item Hepatitis B and C virus and hepatocellular carcinoma(1997) Olubuyide, I. O.; Aliyu, B.; Olaleye, O. A.; Ola, S. O.; Olawuyi, F.; Malabu, U. H.; Odemuyiwa, S. O.; Odaibo, G. N.; Cook, G. C."Antibody to hepatitis C virus (anti-HCV) was detected in 18.7% of patients with hepatocellular carcinoma ma (HCC)a nd in 10.9% of controls (P<0.001).The corresponding prevalences of hepatitis B surface antigen [HBsAg] were 59.3% and 50.0%(P<0.001). Using paticnts with non-hepatic disease as controls stepwise logistics regression analysis indicated that both anti-HCV (odds ratio 6-88%; 9.5% confidence interval [CI] 1.63-9-77) and HBsAg (odds ratio 6.46; 95% Cl 1.68-18:13) were independent risk factors for HCC. Calculation of the incremental odds ratio indicated no interaction between hepatitis B virus {HBV) and HCV. Blood transfusion was a significant risk factor for acquiring HCV infection with odds ratios of 5.48 (95% CI 1.07-29.0) and 2.86 (95%. CI 1.31-22.72) for HCC cases and controls, respectively. The mean age HCC cases with HBsAg and anti-HCV was lower than that of HCC patients with anti-HCV alone (p<0.01). It is concluded that there is a high rate of HBV infection, and a low rate of HCV infection, among Nigerian patients with HCC. However, HBV and HCV are independent risk factors for the developement of HCC, with HBV having an effect more rapidly. Screening of blood products for transfusion might minimize the risk of HCV transmission."