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Biomedical subjects

A A Mohamed

Publications and source records attributed to A A Mohamed.

At least 19 recordsLinked to original sources
PubMed2003

Study of larvivorous fish for malaria vector control in Somalia, 2002.

An intervention study was conducted on the introduction of the larvivorous fish Oreochromis spilurus spilurus as a method of malaria vector control in Kalabeydh village, northern Somalia. This species is resistant to chlorine in water up to a concentration of 1.0 mg/L. Fish were introduced into 25 berkit (reservoirs). After 1 month the number of larvae in each berkit was reduced by between 16.5% and 78.6% (mean 52.8%). Community acceptance and participation was good. The introduction of larvivorous fish is a cheap method of malaria vector control, but its sustainability needs special consideration and education of the community is important, especially to cover the dry season, when most of the berkit dry up.

Animals↗
PubMed2002

Amelioration of experimental allergic encephalitis (EAE) through phase 2 enzyme induction.

The multiple sclerosis (MS) lesion is characterized by an inflammatory cell mediated attack on white matter. Oxidative stress appears to play a role in the onset and progression of MS. We reasoned that decreasing oxidative stress might ameliorate MS. One way of decreasing oxidative stress is to induce phase 2 enzymes. The model chosen to test this hypothesis was experimental allergenic encephalomyelitis (EAE) induced in the Lewis rat. The 26 animals were placed into two groups: 1) those on normal rat chow, 2) those on rat chow containing 250 mumoles t-butylhydroxyanisole (BHA)/kg. After 2 weeks, animals were administered 100 micrograms guinea pig myelin basic protein and examined daily in a blinded fashion. Twenty-nine days later, animals were sacrificed, blood collected for glutathione (GSH) measurements and tissues collected for histology. Six of the 13 control chow animals developed hindlimb weakness or paralysis while 5 developed tail weakness only. Only 1 BHA fed animal exhibited symptoms--hindlimb weakness. Clinical symptoms correlated well with the extent of perivascular lymphocyte infiltration. Animals with BHA in the diet had 20% higher red cell GSH indicting induction of phase 2 enzymes. We conclude that dietary phase 2 enzyme inducers should be examined for their ability to ameliorate MS.

Animals↗
PubMed2001

Type II tumour necrosis factor-alpha receptor (TNFR2) activates c-Jun N-terminal kinase (JNK) but not mitogen-activated protein kinase (MAPK) or p38 MAPK pathways.

The pleitropic actions of tumour necrosis factor-alpha (TNF) are transmitted by the type I 55 kDa TNF receptor (TNFR1) and type II 75 kDa TNF receptor (TNFR2), but the signalling mechanisms elicited by these two receptors are not fully understood. In the present study, we report for the first time subtype-specific differential kinase activation in cell models that respond to TNF by undergoing apoptotic cell death. KYM-1 human rhabdomyosarcoma cells and HeLa human cervical epithelial cells, engineered to overexpress TNFR2, displayed c-Jun N-terminal kinase (JNK) activation by wild-type TNF, a TNFR1-specific TNF mutant and a TNFR2-specific mutant TNF in combination with an agonistic TNFR2-specific monoclonal antiserum. A combination of the TNFR2-specific mutant and agonistic antiserum elicited maximal endogenous or exogenous TNFR2 responsiveness. Moreover, alternative expression of a TNFR2 deletion mutant lacking its cytoplasmic domain rendered the cells unable to activate JNK activity through this receptor subtype. The profile of JNK activation by TNFR1 was more transient than that of TNFR2, with TNFR2-induced JNK activity also being more sensitive to the caspase inhibitor, benzyloxycarbonyl-Val-Ala-DL-Asp-fluoromethylketone. Conversely, only activation of the TNFR1 could stimulate mitogen-activated protein kinase (MAPK) or p38 MAPK activities in a time-dependent manner. The role of TNFR2 activation in enhanced apoptotic cell death was confirmed with agonistic monoclonal antisera in cells expressing high levels of TNFR2. Activation of TNFR2 alone elicited cell death, but full TNF-induced death required stimulation of both receptor types. These findings indicate that efficient activation of TNFR2 by soluble TNFs is achievable with co-stimulation by antisera, and that both receptors differentially modulate extracellular signal-regulated kinases contributing to the cytokine's cytotoxic response.

Antigens, CD↗
PubMed2001

Modulated kinase activities in cells undergoing tumour necrosis factor-induced apoptotic cell death.

Tumour necrosis factor-alpha (TNF) has a variety of cellular effects including apoptotic and necrotic cytotoxicity. TNF activates a range of kinases, but their role in cytotoxic mechanisms is unclear. HeLa cells expressing elevated type II 75 kDa TNF receptor (TNFR2) protein, analysed by flow cytometry and Western analysis, showed altered c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38MAPK; but not MAPK) protein content and activation. There was greater JNK activation, but reduced p38MAPK activation in dying cells compared to those still to enter TNF-induced apoptosis. Moreover, cells displaying more rapid apoptosis possess higher levels of type I 55 kDa TNFR1 receptor isoform, but less TNFR2. These findings reveal differential kinase activation in TNF-induced apoptotic death.

Antigens, CD↗
PubMed2001

Catalytic spectrophotometric determination of vanadium in seawaters based on the bromate oxidative coupling reaction of metol and 2,3,4-trihydroxybenzoic acid.

A new, simple, sensitive and selective catalytic method is developed for the determination of vanadium in natural and sea waters. The method is based on the catalytic effect of V(V) and/or V(IV) on the bromate oxidative-coupling reaction of metol with 2,3,4-trihydroxybenzoic acid (THBA). The reaction is followed spectrophotometrically by tracing the oxidation product at 380 and/or 570 nm after 5 min of mixing the reagents. The optimum reaction conditions are 6.4 x 10(-3) mol l-1 of metol, 2.0 x 10(-3) mol l-1 of THBA and 0.16 mol l-1 of bromate at 35 degrees C and in the presence of an activator-buffer solution of 1 x 10(-2) mol l-1 of tartrate (pH = 3.10). Following the recommended procedure, V(V) and/or V(IV) can be determined with linear calibration graphs up to 0.75 ng ml-1 and detection limits, based on the 3Sb criterion, of 0.008 and 0.018 ng ml-1 at 380 and 570 nm, respectively. The developed method was successfully applied, without any separation or preconcentration processes, to the determination of vanadium in natural and seawaters following the direct calibration and standard addition techniques, respectively.

Journal Article↗
PubMed2000

Evaluation of a national eye care programme: re-survey after 10 years.

AIM: To re-survey the Gambia after an interval of 10 years to assess the impact of a national eye care programme (NECP) on the prevalence of blindness and low vision. METHOD: Comparison of two multistage cluster random sample surveys taking into account the marked increase in population in the Gambia, west Africa. Samples of the whole population in 1986 and 1996 were taken. The definition of blindness is presenting vision less than 3/60 in the better eye, or visual fields constricted to less than 10 degrees from fixation. Low vision is less than 6/18 but 3/60 or better. Causes of blindness were determined clinically by three ophthalmologists. RESULTS: The crude prevalence of blindness fell from 0.70% to 0.42%, a relative reduction of 40%. During the same 10 year period, the population increased by 51% from 775 000 to 1 169 000. When the results were standardised for age, a west to east gradient was found for changes in risk of blindness over the 10 year period. This matched the phased west to east introduction of the NECP interventions. There was a modest but significant increase in the risk of low vision across the whole country. CONCLUSIONS: The overall reduction in risk of blindness, in those areas where the NECP has been active, appears to justify the programme and the support of donor organisations. The low vision cases due to cataract must now be addressed.

Blindness↗
PubMed1999

Study of factors affecting growth of Leishmania in cultures.

The rate of growth of Leishmania major and L. infantum in El-On's culture media supplemented with human, dog, rat and avian blood was studied in vitro. Rabbit blood was used as a control. The effect of culture with these types of blood on the infectivity of both Leishmania strains to albino mice was also studied. The results showed that a good yield of both L. major and L. infantum parasites can be obtained in culture by using avian blood as substitute for rabbit blood in El-ON's medium. In addition, rat blood gave good results with L. infantum. The morphological forms of L. major and L. infantum on all types of blood supplemented media: elongated promastigotes, spindle promastigotes, paramastigotes and amastigoes were present all through the culture period with variable percentages. The infectivity to experimental animals was not affected by culture of both Leishmania strains on rabbit, human, rat, dog as well as avian blood supplemented media.

Animals↗
PubMed1998

Epidemic optic neuropathy in primary school children in Dar es Salaam, Tanzania.

BACKGROUND: An epidemic of bilateral optic neuropathy is affecting large numbers of people aged between 10 and 40 in Dar es Salaam, the capital city of Tanzania. The disease is characterised by acute onset of bilateral visual impairment, bilateral impairment of colour vision, and a characteristic temporal pallor of the optic discs. The disease often occurs in association with peripheral neuropathy and sensorineural hearing loss. This report presents the first data on disease prevalence in adolescents, based on a rapid assessment of schoolchildren. METHODS: Three schools in Dar es Salaam were visited and all children aged between 10 and 16 were screened for the disease. RESULTS: The prevalence of bilateral optic neuropathy among the schoolchildren is estimated to be 1.0% (95% CI 0.5-1.4%). This suggests that 5000 children (95% CI 2600-7300) aged 10-16 in Dar es Salaam may have the disease. CONCLUSION: The results of this rapid assessment indicate this epidemic is a major public health problem. The prevalence of the disease in the community is likely to be far higher than found in this survey because children with the disease may have withdrawn from school. As the disease predominantly affects young adults, resulting in impaired vision and hearing, the economic and social consequences are enormous.

Adolescent↗
PubMed1998

Trachoma in The Gambia.

BACKGROUND: As part of the second National Survey of Blindness and Low Vision in the Gambia carried out in 1996, all survey participants were examined for signs of trachoma. The findings were compared with the results of the first survey in 1986, which used the same sampling strategy. METHODS: A multistage stratified cluster random sample, with proportional probability sampling, was obtained. Stratification included settlement size (less than 400 residents, and 400 and more residents). All subjects were examined for trachoma using the simplified WHO grading system. RESULTS: Of the sample of 14,110 people, 13,047 (92.5%) were examined. Active inflammatory trachoma (grade TF or TI) was found in 3.0% of all age groups and 5.9% of children aged 0-9 years old. Trichiasis was found in 3.3% and trachomatous corneal opacities in 0.9% of adults aged 30 and over. The prevalence of blinding trachomatous corneal opacities was 0.02%, compared with 0.10% 10 years previously. CONCLUSION: Compared with a previous national survey undertaken in 1986, prevalence of active trachoma has fallen by 54%. There has been an 80% relative reduction in blinding trachomatous corneal opacities over the 10 year period.

Adolescent↗
PubMed1998

Patterns of injury associated with automobile airbag use.

The wide use of automobile airbags has undoubtedly reduced the mortality and the incidence of serious injuries from motor vehicle accidents. However, automobile airbags appear to be associated with a variety of injuries including fatal injuries, ocular injuries, upper limb and chest injuries. Further improvements in airbag design together with education of the general public in their use should help reduce airbag-related injuries.

Accidents, Traffic↗
PubMed1998

[Association of HLA-DQB1 alleles and the susceptibility to beta-thalassemia in Guangxi Chinese Zhuang nationality].

OBJECTIVE: To investigate the relationship between HLA-DQB1 allele and susceptibility to beta-thalassemia in Guangxi Chinese Zhuang nationality. METHODS: The polymorphism of the HLA-DQB1 loci in 64 randomly selected, unrelated Guangxi Zhuang individuals with beta-thalassemia was investigated by PCR-SSP. RESULTS: Compared with normal controls, the frequency of HLA-DQB1*0604 allele was significantly increased in the patient group, with a relative risk(RR) of 9.9(chi 2 = 20.78, P < 0.005), while the frequencies of other HLA-DQB1 alleles did not in the patient group. CONCLUSION: The susceptibility to beta-thalassemia in the Guangxi Zhuang individuals is associated with HLA-DQB1*0604 allele.

Adult↗
PubMed1997

Reduction of trachoma in a sub-Saharan village in absence of a disease control programme.

BACKGROUND: Trachoma is a leading cause of blindness in the developing world and is most prevalent among people who live in poor rural communities in arid locations. METHODS: We analysed the results of surveys of trachoma prevalence in Marakissa, a rural village in The Gambia. These surveys were undertaken in 1959, by the Medical Research Council, and in 1987 and 1996 by the Gambian National Eye Care Programme. FINDINGS: During this 37-year period, the prevalence of active inflammatory trachoma among children aged 0-9 years fell from 65.7 cases per 100 children in 1959 to 2.4 cases per 100 children in 1996. The prevalence also fell dramatically among people of 10-19 years (52.5 to 1.4 per 100) and among people of 20 years and older (36.7 to 0 cases per 100). INTERPRETATION: The dramatic fall in disease occurrence was paralleled by improvements in sanitation, water supply, education, and access to health care in the village. Of particular importance is that the decline in trachoma occurred without any trachoma-specific intervention.

Adolescent↗
PubMed1996

Kinetics of interleukin-6 production after experimental infection of mice with Schistosoma mansoni.

It has been reported that interleukin-6 (IL-6) is expressed in cells of acute inflammatory granulomas experimentally induced in mice by eggs of Schistosoma mansoni. Moreover, in vitro IL-6 was shown to enhance the cytotoxic activity of human platelets against larvae of S. mansoni. To elucidate further a proposed biological significance of this cytokine during the course of schistosomiasis, we studied the kinetics of IL-6 production and concomitantly performed a histopathological analysis of the livers in BALB/c mice subcutaneously infected with S. mansoni cercariae. Over a period of 24 weeks postinfection (p.i.) we monitored serum IL-6 levels, IL-6 production in vitro by pokeweed mitogen (PWM)-stimulated spleen cells as well as IL-6 mRNA expression in livers, spleens and kidneys. We found significantly elevated IL-6 levels in PWM-stimulated spleen cell-conditioned media (SCM) at weeks 6 to 20 p.i., peaking at week 10 p.i. In contrast, serum IL-6 concentrations started to rise not before week 8 but remained significantly elevated above normal control values until week 24 p.i. The time pattern of enhanced IL-6 mRNA expression detected in spleens and livers, but not in kidneys, as well as the rises of IL-6 in SCM and with a delay of 2 weeks in serum samples correlated with the onset of the egg-induced inflammatory reactions as well as the incidence and the number of the granulomas observed histopathologically in the livers of infected mice. Our data emphasize both a local and a systemic role of IL-6 in the host immune response following infection of mice with S. mansoni.

Animals↗
PubMed1996

Schistosoma mansoni infection in mice augments the capacity for interleukin 3 (IL-3) and IL-9 production and concurrently enlarges progenitor pools for mast cells and granulocytes-macrophages.

Mast cells and granulocytes-macrophages (GM) are components of the host defense system against worm infections, including schistosomiasis. Here we report the kinetics of changes in the number of colony-forming cells (CFC) for mast cells and GM during the course of a primary experimental infection of mice with Schistosoma mansoni cercariae over a period of 24 weeks postinfection (p.i.). Concurrently, we measured known myelopoietic and/or mast cell-stimulating cytokines (i.e., interleukin 3 [IL-3] and IL-9) in pokeweed mitogen-activated spleen cell-conditioned medium. Our results show that during the acute phase of the hepatic granulomatous reaction, the numbers of both mast-CFC and GM-CFC were significantly elevated in bone marrow. However, while femoral GM-CFC numbers had returned to normal control values at week 16 p.i., femoral and splenic mast-CFC numbers remained significantly elevated until week 20 p.i., which corresponds to the chronic fibrotic phase of hepatic granulomatous inflammation. Increased GM-CFC numbers correlated with elevated IL-3 levels, while increased mast-CFC numbers paralleled the increased IL-9 concentrations in spleen cell-conditioned medium. By the reverse transcription-PCR method, enhanced expression of IL-3 and IL-9 transcripts was found in RNA samples obtained from livers and spleens of infected mice. Our data demonstrate that during the course of infection of mice with S. mansoni, the coordinate need for mast cells and GM is at least partly regulated at the stage of progenitor cell commitment in the bone marrow and spleen. It appears that IL-3 and IL-9 help to promote at this stage the ultimate generation of mature effector cells.

Animals↗
PubMed1996

Piracetam is useful in the treatment of children with sickle cell disease.

The management of children suffering from sickle cell disease [sickle cell anaemia (SCA) and sickle cell beta degree-thalassaemia (S beta degree-thal.)] has been the concern of all clinicians caring for these patients. Several agents have been tried for treatment, often limited by toxic side effects. Piracetam (2-oxo-l-pyrrolidine acetamide, Nootropyl), a cyclic derivative of gamma-amino butyrate, used for the treatment of psychosenescent syndromes with no known side effects, was considered as a possible therapeutic agent for sickle cell disease. Interest was focused on the use of piracetam when it was shown that it had an antisickling effect, both in vivo and in vitro. We initiated multicentre double-blind investigations in two groups of children suffering from sickle cell disease ranging in age from 3-6 to 6-12 years. The total number of patients included in the study were 87 (SCA = 79 and Hb S beta degree-thal. = 8) in 13 centres in 10 different regions of Saudi Arabia. Coded boxes of the drugs were received from the company (UCB) and were administered as intravenous infusion during crises and orally during the follow-up, for a period of up to 1 year. After decoding the code at the end of the study, the patients were grouped into those receiving placebo (n = 39), i.e. controls, or piracetam (n = 48), i.e. study cases. In terms of age, weight, height and severity index, number of blood transfusions received and number of hospitalization, both groups were statistically homogenous. Data analysis showed that the clinical severity of the disease, the number of crises, the extent of hospitalization and the blood transfusion requirements significantly decreased during piracetam treatment (p < 0.001), though no statistically significant changes occurred in the placebo group. However, in the levels of the haematological and biochemical parameters no significant changes were documented in both groups. In addition, the improvement in the clinical presentation of the disease continued even several months after discontinuation of the drug in the majority of the children, as judged from the low severity index value. Though our results point to the recommendation that piracetam can be used for the treatment of children suffering from sickle cell disease, both SCA and S beta degree-thal, it is advisable to conduct long-term and close follow-up treatment programmes using piracetam to establish its therapeutic value particularly in adults and to ascertain that there are no long-term toxic side effects.

Anemia, Sickle Cell↗
PubMed1995

Visceral leishmaniasis in Somalia. Circulating antibodies as measured by DAT, immunofluorescence and ELISA.

Sera from patients with visceral leishmaniasis (VL) (n = 26), healthy residents of Mogadishu (n = 157), inhabitants of a village in an endemic area (n = 276) and healthy Swedes (n = 60) were examined using the direct agglutination test (DAT), immunofluorescence (IF) and ELISA for antibodies against Leishmania donovani. The study was carried out in order to provide baseline data for antibody responses in visceral leishmaniasis as existing in Somalia and to explore which one of these methods would be most suitable for diagnosis of clinical cases as well as for epidemiological population studies in Somalia. All patients had high levels of circulating antibodies, however, lower values were recorded in the early stages of the disease. High reactivity in ELISA was seen first after one year. All three tests distinguished well between sera from VL patients and healthy controls. Approximately 10% of the sera from villagers were reactive above the cut-off levels in the three tests. DAT is the simplest to perform and does not require much equipment. ELISA can be made simple and economic if performed in one serum dilution and read visually. IF requires more expensive and specialized equipment and is not suitable for large scale examination of sera. A complete evaluation of the three tests should also include the analysis of sera from various stages and manifestations of the disease.

Adolescent↗