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Biomedical subjects

J E McMahon

Publications and source records attributed to J E McMahon.

18 recordsLinked to original sources
PubMed1988

Onchocerciasis transmission levels and Simulium damnosum complex biting activity at riverside and rice field sites in Sierra Leone.

Biting densities of the Simulium damnosum Theobald complex of blackflies and their levels of parasitism by Onchocerca volvulus (Leuckart) were compared at two ecologically contrasted sites in the Southern Province of Sierre Leone, West Africa: by the Tabe riverside close to Gbaiima village where onchocerciasis is hyperendemic (63.1% positive skin-snips) and in open rice fields 2 km from the mesoendemic (54.9%) village of Senehun. Using a combination of morphometric and enzyme electrophoresis techniques, the primary vector was found to belong to the S.sanctipauli subcomplex and was most probably S.soubrense 'B' (sensu Post, 1986). In the wet season biting activity took place throughout the day at the village, but had morning and evening peaks in the rice fields. Transmission of O.volvulus was detected at the village in all months except February-April, while in the rice fields it was detected only during September-November and May at one tenth the level of the village. There was a significant difference between the two sites in the proportion of parous flies carrying third stage larvae in the head, but not of other larval stages.

Animals↗
PubMed1988

Isolation and in vitro translation of Onchocerca volvulus mRNA.

Adult Onchocerca volvulus recovered for excised nodules by dissection or treatment with collagenase have been used as a source of RNA for in vitro translation experiments. RNA was purified using either the hot phenol/SDS procedure or the guanidine isothiocyanate protocol. Immunoprecipitation experiments performed on in vitro products demonstrate a marked heterogeneity in responses by individed human infection sera. Further immunoprecipitation experiments demonstrate cross reactivity between O. volvulus and other filarial nematodes.

Animals↗
PubMed1979

Praziquantel: a new schistosomicide against Schistosoma haematobium.

The effectiveness of the new schistosomicide praziquantel was assessed in African schoolchildren infected with Schistosoma haematobium. They were stratified according to the severity of their infection and were then randomly allocated to treatment with two single-dose regimens (30 and 40 mg/kg) and a split regimen of two doses of 20 mg/kg given four hours apart. All three regimens were highly effective and produced few side effects. Children who initially had very high pretreatment egg loads showed a poorer therapeutic response at all dose levels, and further investigations are necessary to find the optimum dose. Because of its effectiveness in a single dose and lack of toxicity, praziquantel may prove to be the ideal schistosomicide.

Adolescent↗
PubMed1979

Bancroftian filariasis: a comparison of microfilariae counting techniques using counting chamber, standard slide and membrane (nuclepore) filtration.

Three techniques were compared for counting microfilariae of Wuchereria bancrofti in blood specimens--a standard slide method, the counting chamber technique (CCT) and a membrane filtration technique (MFCT). The CCT was much more sensitive than the slide method, the difference in sensitivity between these two methods probably being due mainly to the loss of microfilariae during the dehaemoglobinizing process prior to staining in the standard slide method. There was good correlation between the techniques when 0.1 ml of finger-prick blood was examined by the CCT and 1 ml of venous blood by the MFCT. The number of additional positives revealed by the MFCT was ten of 275 (3.6%) subjects examined. The use of venepuncture for MFCT is impractical for field surveys in East Africa whereas a microfilarial count on 0.1 ml of finger-prick blood meets most of the criteria required of a field technique. The method is simple, quantitative and acceptable to the population. The results are reproducible, can be readily checked, the technique provides a useful and practical method for obtaining prevalence information following control schemes. The finding of a relatively low prevalence of microfilariae seen by both MFCT and CCT in children aged five to nine years from a highly endemic filariasis area agrees with the results of previous East African surveys carried out by blood smear and CCT.

Adolescent↗
PubMed1979

Preliminary screening of antifilarial activity of levamisole and amodiaquine on Wuchereria bancrofti.

A single dose of levamisole of 3 mg/kg had a marked microfilaricidal effect in some persons harbouring Wuchereria bancrofti, but there was considerable variation in the response. In some cases blood examinations for microfilariae remained negative or at a low level for several months. Persons with high pretreatment microfilaraemias responded less to therapy than did those with low counts. The main side-reaction to levamisole was fever, which began six to eight hours after treatment. Combined DEC-levamisole therapy appears to have no advantage over the use of DEC alone. Amodiaquine in a total dose of 40 mg/kg appears to be macrofilaricidal, but because of the slight possibility of blood dyscrasias, mass chemotherapy with this dosage could not be recommended. Some amodiaquine congeners shown to be effective in experimental infections against adult filarial worms may prove to have a higher chemotherapeutic index than amodiaquine against W. bancrofti in man.

Adolescent↗
PubMed1979

Tanzania Filariasis Project: a provocative day test with diethylcarbamazine for the detection of microfilariae of nocturnally periodic Wuchereria bancrofti in the blood.

In coastal Tanzania, an area where the microfilariae (mf) of Wuchereria bancrofti exhibit nocturnal periodicity, the administration of 2 mg diethylcarbamazine (DEC) per kg body weight in the daytime provoked mf to enter the peripheral blood. In persons on normal daily activities the daytime DEC provocative method proved to be as sensitive in detecting microfilaraemia as was the examination of night blood. Its use in routine surveys is therefore justified. Although mf densities by day and night were highly correlated (r = 0.83) they tended to be lower after provocative daytime DEC than in the corresponding night blood, except in very light infections. This method was also useful in assessing the parasitological response to mass chemotherapy with DEC, but, in comparison with the results of the night blood examinations, the sensitivity and magnitude of the counts in persons remaining positive progressively decreased as the period of DEC administration increased. A correction factor has to be calculated to take account of this, and/or additional night blood samples must be taken.The dose of 2 mg of DEC per kg body weight used was readily acceptable to the people in coastal East Africa, whose cooperation is difficult to obtain for night blood surveys. Apart from W. bancrofti, the only human filarial infection occasionally encountered in this area was Dipetalonema perstans. Because of the risk of a severe Mazzotti reaction the test is contraindicated in onchocerciasis endemic regions. Severe reactions may also occur in subjects with loaiasis.

Circadian Rhythm↗
PubMed1979

Tanzania filariasis project. Survey methodology and clinical manifestations of bancroftian filariasis.

In a Bancroftian filariasis survey on the coast of Tanzania microfilaria rates rose with age reaching 53% in the 60-69 year group followed by a slight fall above this age. The most important clinical manifestations were hydrocoele, funiculitis and elephantiasis, with hydrocoele presenting the most serious public health problem. Hydrocoele rates increased with age reaching 90% above the age of 70. The highest proportion of large hydrocoeles were also in the older age groups. A satisfactory methodology was established for the planning of future surveys leading to control.

Adolescent↗
PubMed1978

Treatment of schistosomiasis. Factors affecting chemotherapy and reflections on ideal drug treatment.

The blood concentration of certain known schistosomicides or their active metabolites never reaches levels high enough to prove lethal to the parasite. The chemotherapeutic response is a function of the relations of the triad-drug, parasite and host. This article reviews the multiple factors which influence the chemotherapeutic response in schistosomiasis with references to researchers in this wide field. An understanding of these complex interactions is a basis for the design of drug trials in the search for the ideal schistosomicide.

Animals↗
PubMed1978

Metrifonate in onchocerciasis and lymphatic filariasis.

Metrifonate, in doses of 10 mg/kg for 3 consecutive days, demonstrated partial microfilaricidal activity against Onchocerca volvulus in humans. Higher doses were not investigated because of the toxic reactions obtained and the absence of monitoring of the blood cholinesterase levels. Spaced doses of 10 mg/kg every 2 weeks or once monthly up to 3 doses showed neither micro- nor macrofilaricidal activity against Wuchereria bancrofti.

Adolescent↗
PubMed1977

Total hip replacement in disseminated neoplastic disease.

Between 1972 and 1975, 11 total hip replacements were performed on ten patients with advanced neoplastic disease. Eight of ten patients survived more than one year after total hip replacement. Eight of 11 hips were rated as having excellent or good functional results six months postoperatively. We suggest that total hip arthroplasty be considered an appropriate procedure in the operative management of patients with advanced neoplastic disease involving the hip.

Adult↗
PubMed1975

Method for predicting RNA secondary structure.

We report a method for predicting the most stable secondary structure of RNA from its primary sequence of nucleotides. The technique consists of a series of three computer programs interfaced to take the nucleotide sequence of any RNA and (a) list all possible helical regions, using modified Watson-Crick base-pairing rules; (b) create all possible secondary structures by forming permutations of compatible helical regions; and (c)evaluate each structure for total free energy of formation from a completely extended chain. A free energy distribution and the base-by-base bonding interactions of each possible structure are catalogued by the system and are readily available for examination. The method has been applied to 62 tRNA sequences. The total free-energy of the predicted most stable structures ranged from -19 to -41 kcal/mole (-22 to -49 kJ/mole). The number of structures created was also highly sequence-dependent and ranged from 200 to 13,000. In nearly all cases the cloverleaf is predicted to be the structure with the lowest free energy of formation.

Base Sequence↗