Biomedical subjects
Publications and source records attributed to N Francis.
Image analysis of isolated F-actin filaments shows that the actin helix can be described by a constant rise per subunit but a considerably variable and randomized twist (number of units per turn). The ability of actin subunits to rotate through angles of the order of 10 degrees from their helically ideal positions helps to explain actin's capacity to form many different polymorphic structures.
1. Copper concentrations were low in many organs of Moblo/Y mice, but very high in the gut. Absorption of 64Cu was seen to be very low when related to the absorption of cyano[57Co]cobalamin. The results in Moblo/+ mice were intermediate. 2. Copper therapy temporarily ameliorated many effects of the mutation in Moblo/Y mice, but did not improve the rate of weight gain as has been achieved previously in Mobr/Y mice. Lower capacity for a 'depot dose' effect at the site of injection may explain the difference. 3. The distribution of 64Cu after administration into the bloodstream of Moblo/Y mice altered from an initially normal state to one that resembled the abnormal distribution of pre-existing copper by 48 h. This indicated that the later mechanisms of copper distribution were at fault. Moblo/+ mice were equally affected. 4. The alteration of copper homoeostasis in blotchy mice was similar to that observed in brindled mice previously and in the present studies, although generally less severe. This is consistent with allelism of the two mutations.
Three-hundred Aboriginal people five to 70 yr have been studied at three missions in the north west of Australia-Beagle Bay, Lombadina and One Arm Point. The prevalence of hypozincaemia and hypercupraemia (a departure of more than 2 S.D. from the expected normal) has been assessed. Plasma iron concentration was determined. Half of the individuals had hypozincaemia and for some age groups the prevalence was greater (almost 100% for 15 to 20-year-old females at Lombadina). Hypercupraemia was prevalent and ranged from 70 to 100% for most age groups. Hypoferraemia was detected frequently. By the use of anthropometric methods the children were found to be growth retarded and to have reduced weight for height. These people are known to be infected with intestinal parasites which cause bleeding into the bowel or malabsorption which can cause losses of zinc or failure of adsorption. They prefer unleavened bread which contains phytic acid which inhibits zinc absorption. The soil is zinc deficient and the climate conducive to large losses of zinc in sweat. Geophagia is practiced and pica is found to occur in children. Preliminary evidence of elevated copper status is available. We speculate that growth failure may be related to zinc deficiency or copper toxicity.
1 Self-stimulation to lever pressing and capacitance probe touching was obtained in Mongolian gerbils (Meriones unguiculatus) from electrode placements within the medial forebrain bundle. 2 Lever pressing was more sensitive to the decremental effects of a central depressant, pentobarbitone, than capacitance probe touching, suggesting its greater responsiveness to disturbances of motor function. 3 Spiperone (0.005 to 0.05 mg/kg) attenuated capacitance probe touching and lever pressing equally, a finding explained by action on either reward pathways or on the ability to initiate responding. 4 This same dose range of spiperone (0.005 to 0.05 mg/kg) attenuated locomotor activity, whether spontaneous or evoked by non-contingent electrical stimulation, and produced catalepsy. 5 The spiperone-induced attentuation of self-stimulation was not necessarily a result of its action on dopaminergic reward pathways since the effects could equally well be explained by a failure to initiate responding.
Explore the source record for details and available documents.
A randomized, double-blind, placebo-controlled community-based trial of oral iron supplementation (200 mg ferrous sulphate daily) administered to multigravid pregnant women by traditional birth attendants (TBAs) was carried out in a rural area of The Gambia. Iron supplementation led to a significant reduction in the prevalence of anaemia and of iron deficiency. Iron supplementation was not accompanied by increased susceptibility to malaria infection; there was no difference in the prevalence and severity of peripheral blood or placental malaria infection between the 2 groups of women. The birth weight of children born to women who received iron prophylaxis was increased by an average of 56 g. It is concluded that oral iron prophylaxis can be successfully delivered through TBAs integrated into a primary health care programme. This simple intervention can produce significant beneficial effects on the health of the mother without inducing increased susceptibility to malaria and has the potential for reducing perinatal mortality by increasing birth weight.
The harmful effects of malaria are most pronounced during first pregnancies and chemoprophylaxis is most effective when given at this time. However, restriction of chemoprophylaxis to first pregnancies might lead to enhanced susceptibility to malaria during second pregnancies. We have investigated this possibility by studying the outcome of second pregnancies in 165 Gambian women who had received either malaria chemoprophylaxis with Maloprim or placebo during their first pregnancy. Many of these primigravidae did not present until the third trimester of pregnancy so that some are likely to have experienced a malaria infection before they started medication. The prevalence of malaria infection of the blood and of the placenta during second pregnancies was similar in women who had received chemoprophylaxis during their first pregnancy and in those who had not, and the mean birth weights of babies born to women in each group were almost identical. Thus, in areas where the epidemiology of malaria is similar to that of The Gambia and where most women present relatively late in pregnancy, it may be possible to restrict malaria chemoprophylaxis to first pregnancies with consequent savings in cost and a reduction in drug pressure on Plasmodium falciparum.
The influence of haemoglobin genotype on the response to iron supplementation was studied in a randomized, double blind, placebo-controlled trial involving 497 multigravid pregnant women from a rural area of The Gambia. Women were randomly allocated to receive either oral iron (60mg elemental iron per day) or placebo. At 36 weeks of pregnancy, women who had received oral iron during pregnancy had higher mean haemoglobin, packed cell volume, plasma iron and ferritin levels than did women who received placebo. Iron supplementation of pregnant women with the AA haemoglobin genotype also resulted in increases in the packed cell volume (PCV) and haemoglobin level measured after delivery, and in the birth weight of the infant. However, in AS women PCV and haemoglobin level at delivery were lower in the supplemented group and supplementation was also associated with reduced birth weights. In malaria endemic areas, pregnant women with the haemoglobin genotype AS may not benefit from iron supplementation during pregnancy.
In 1992, the Gambian national impregnated bed net programme (NIBP) introduced insecticide treatment of bed nets into half of the primary health care villages in The Gambia. One component of the evaluation of this programme was the determination of whether it had any impact on the outcome of pregnancy in primigravidae. From February 1992, 651 primigravidae were recruited into the study. Less than 50% of them used an insecticide-treated bednet. During the rainy season the prevalence of Plasmodium falciparum among primigravidae was lower, fewer babies were classified as premature, and the mean birth weight was higher in villages where treated bed nets were used than in control villages. Therefore, during the rainy season, despite the low use of insecticide-treated bed nets by Gambian primigravidae, the NIBP had some impact on the outcome of pregnancy, particularly on the percentage of premature babies, and this was probably due to the decreased risk of malaria infection achieved during this period.
Although a ubiquitous pathogen, cytomegalovirus (CMV) is very rarely thought to be the cause of significant gastrointestinal infection in the immunocompetent child. We report the case of a 2-month-old infant who presented with bloody diarrhoea and severe dehydration, which was subsequently diagnosed as CMV enterocolitis and resolved spontaneously without antiviral treatment.
We describe an infant with a congenital form of non-Langerhans cell histiocytosis with clinical and pathologic features of both disseminated juvenile xanthogranulomatosis and benign cephalic histiocytosis. The findings in this case support the concept of these non-Langerhans cell histiocytoses forming part of a spectrum of disease rather than being separate pathologic entities.
Explore the source record for details and available documents.
The incidence of cryptosporidiosis in our unit has increased over the last 6 years, being diagnosed in approximately 5 per cent of all patients with HIV infection and in 21 per cent of those with AIDS, but a marked seasonal variation occurs. We have studied the course of the infection in 128 patients and identified four clinical patterns of disease: transient (28.7 per cent), chronic (59.7 per cent), fulminant (7.8 per cent) and asymptomatic (3.9 per cent). Transient disease occurred in patients with a wide range of CD4 lymphocyte counts, but was more common in less immunosuppressed patients. Fulminant disease, defined by the passage of more than 2 l of stool/day from the time of presentation, only occurred in patients with a CD4 count less than 50/mm3. This group had lost more than 7 kg in weight at presentation and more commonly had other intercurrent gastrointestinal infections. They survived for a median of only 5 weeks, compared with 20 weeks for those with chronic diarrhoea and 36 weeks for those with transient infection. The survival was unaffected by any treatment other than zidovudine. Cryptosporidiosis in HIV-infected individuals is a heterogeneous disease.
Hepatitis in the context of HIV infection is commonplace, but the causative agent is not always readily identifiable. This review highlights the differential diagnosis of hepatitis in that context, examining the interrelationships and interactions between the four main hepatitis viruses and HIV.