Biomedical subjects
Publications and source records attributed to J A Lawrence.
Rhipicephalus zambeziensis was shown experimentally to transmit Theileria parva parva in cattle from nymph to adult and Theileria parva lawrencei, Theileria parva bovis and Theileria taurotragi from larva to nymph and nymph to adult. In a single trial the tick failed to transmit Theileria mutans. The tick is believed to be a vector of T. parva lawrencei in the field in Zimbabwe.
One pathogenic and 4 mild bovine Theileria strains from southern Africa, all transmitted by Rhipicephalus appendiculatus, were compared amongst themselves as well as to bovine and buffalo strains of the T. parva complex from eastern and southern Africa and to bovine strains of T. taurotragi from Tanzania considered to be derived from eland antelope. Criteria used were parasitological, clinical, serological and cross-immunity characters. The mild strains are similar to bovine T. taurotragi. Serological evidence suggested that T. taurotragi is also infective to sheep. The pathogenic strain belongs to the T. parva complex; the latter consists of a series of types with different behaviour ranging from the lawrencei-type (of buffalo) causing Corridor disease, through the bovis-type causing Rhodesian malignant theileriosis to the parva-type causing classical East Coat fever. Seven cattle-tick passages of a bovis-type strain did not result in transformation into a parva-type. Four species of bovine Theileriae are now known to occur in southern Africa: T. parva (lawrencei- and bovis-types) and T. taurotragi, both transmitted by R. appendiculatus, and T. mutans and T. velifera both with Amblyomma spp. as vectors.
A hypothetical dilemma on resuscitation of an intensive care patient was presented to nurses at a workshop on ethics of critical care nursing. Nurses responded to separate questionnaires about what a charge nurse should do, and what they themselves would do in relation to ten considerations arising from the dilemma. Nurses were agreed that legal consequences, patient wishes and rights, and physician authority should and would be considered, and that peer influence should not. Nurses were divided in their attitudes to following procedure and personal moral beliefs, and to job risk. The most contentious issues were related to the nurse's role as a decision-making member of the health care team. Implications for regarding nurses as independent decision-makers are discussed.
There is a marked increase in sialyltransferase activity (EC 2.4.99.1) in serum and a profound change in the endogenous acceptor property of sialyltransferase in the intestine of colchicine treated rats (Fraser, Ratnam, Collins and Mookerjea, (1980) J. Biol. Chem. 255, 6617-6625). To ascertain the contribution of intestine as a source of this elevated serum enzyme, sialyltransferase and other enzymes activities were measured in intestinal lymph before and after colchicine treatment. There was a 4-fold increase of the enzyme activity in lymph 3 h after treatment. The lymph flow rate, protein concentration and composition as measured by polyacrylamide gel electrophoresis were not affected. The kinetic properties of lymph sialyltransferase (protein and time dependence, pH optima and Km values for the substrate CMP-sialic acid) were essentially unchanged after treatment and were similar to the serum sialyltransferase. Alkaline phosphatase and lactic dehydrogenase activities remained unchanged. Although intestinal lymph sialyltransferase was increased by colchicine, enterectomy did not prevent the rise of serum sialyltransferase suggesting that the intestine is not a major source of the serum enzyme.
The effects of natural porcine and synthetic secretin, given by intravenous bolus or infusion, on intestinal lymph flow and protein composition in unanaesthetized rats were studied. Both forms of secretin increased lymph flow and protein output from the lymph fistula; dose-response relationships were determined. No change was observed in protein concentration in lymph or in the relative concentrations of large and small protein molecules during secretin-induced enhanced lymph flow, compared with the basal state. These results are in keeping with an increase in the functional exchange vessel area of the small intestine produced by secretin. It is possible that secretin may play a part in the hyperaemia and augmented intestinal lymph flow which occurs in the post-prandial period.
The disruption of veterinary services in the tribal areas of Rhodesia (now Zimbabwe) during seven years of conflict resulted in serious epidemics of disease. The cessation of dipping was followed by the death of an estimated one million cattle from tick-borne disease. Heavy mortality followed the disruption of control measures for trypanosomiasis. Foot-and-mouth disease and anthrax spread widely in the tribal areas. Rabies, normally restricted to areas bordering Botswana and Mocambique, became widespread. A marked increase in human deaths from anthrax and rabies occurred.
Cerebrospinal fluid from 582 persons was analyzed by a double-antibody radioimmunoassay for the presence of material cross-reactive with peptide 43-88 of human myelin basic protein (BP). In a group of 104 patients with multiple sclerosis (MS), 23 of 33 individuals clinically judged to have had an exacereation within two weeks prior to the time CSF was obtained had detectable material ranging from 2 to 200 ng/ml. In the remaining 71 MS patients who either were stable or had had an exacerbation more than two weeks before, only 1 patient had a marginally elevated level of immunoreactive material. CSF from 53 persons with cerebrovascular disease was studied, and 13 of 29 with recent infarctions had values of 2 to 540 ng/ml. The degree of elevation in strokes generally paralleled the predicted volume of the lesion, but the amounts detected did not correlate quite so closely temporally with onset as they did with the periods of active disease in MS. Of the remaining 425 patients, 29 had immunoreactive material of 2 to 400 ng/ml in their CSF. Most of these patients with detectable material had acute diseases known to affect the myelin sheath. Eight of 10 persons with acute disseminated encephalomyelitis had no detectable material. The presence in CSF of material cross-reactive with BP peptide 43-88 does not have diagnostic specificity for MS but can be used as a means for determining recent myelin injury. The type of BP peptide formed and mechanisms for clearance of BP and BP peptides may be important in determining the biological consequences following release of this potentially immunogenic material from the central nervous system.
Nine Dorper lambs infected with 3000 cercariae of Schistosoma mattheei showed inappetence, reduced growth rate, anaemia, hypoalbuminaemia, hyperglobulinaemia and an intermittent eosinophilia. A marked granulomatous reaction in the intestinal mucosa was associated with the deposition and accumulation of eggs. The disease was progressive for the first 25 weeks and three sheep died or were slaughtered in extremis between 12 and 24 weeks after infection. In those animals that survived, the disease became chronic with no evidence of recovery up to 67 weeks after infection. The number of egg-laying females in the sheep and their output of eggs showed no reduction over the period of observation. Daily egg output was estimated at 692 eggs per female per day.
It is currently thought that the following species or sub-species of Theileria occur in cattle in southern Africa: Theileria parva parva (East Coast fever), Theileria parva lawrencei (Corridor disease), Theileria parva bovie (Rhodesian theileriosis), Theileria mutans proper (transmitted by Amblyomma species), so-called Theileria mutans (a non-pathogenic species transmitted by Rhipicephalus appendiculatus, possibly identical with Theileria taurotragi) and Theileria velifera. The parasites can be differentiated on serological, morphological and epidemiological grounds. The four true species are serologically distinct. T. mutans proper and T. velifera show morphological differences from the other two species in some stages of their development. The T. parva group are the only parasites that are commonly pathogenic. Differentiation of the three members of this group is based on differences in the numbers of schizonts and piroplasms present and on differences in the epidemiology of the diseases they cause.
A syndrome characterised by the birth of lambs with varying degrees of rigidity of the limbs and spine has been encountered on several occasions in Rhodesia. Outbreaks have occurred in autumn-born lambs from Dorper ewes grazing heavily fertilised Star grass cv No 2 (Cynodon aethiopicus) pastures. The condition appears to be exacerbated by the application of sulphur to the pasture and is partly prevented by the administration of selenium and vitamin E to the ewes before lambing. The aetiology is unknown.
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Thirty-eight sera from cattle from a herd in Rhodesia naturally infected with Theileria lawrencei were titrated with the indirect immunofluorescent test against schizont antigens of T parva (Muguga) and T lawrencei from Rhodesia. T lawrencei was found to be indistinguishable from T parva with the test.
Twenty-eight Friesian calves were infected between seven and 11 months of age with 5000 to 45,000 cercariae of Schistosoma mattheei. They developed anaemia, lymphopaenia and hypoalbuminaemia during the period of acute clinical illness after the infection became patent, and lymphocyte counts remained depressed after clinical recovery. Neutrophil counts rose and later fell before returning to normal. Eosinophilia and hypergammaglobulinaemia were marked during the period of recovery. The changes in haemoglobin, neutrophils and serum proteins were proportional to the level of infection. The eosinophil response was reduced in animals subjected to nutritional stress. The aetiology of the changes is discussed.
Thirty Friesian steers were infected with Schistosoma mattheei and the antibody response was followed for up to 76 weeks by the complement fixation (CF), indirect haemagglutination (IH) and indirect immunofluorescent (IF) tests. CF and IF antibodies rose to a peak at about 25 weeks and then fell, while IH antibodies rose more slowly and remained high. Peak IH and IF titres were proportional to the level of infection. Peak CF titres were reduced in animals on a low plane of nutrition. There was a strong cross-reaction to Fasciola gigantica and Paramphistomum microbothrium in the CF test while the IH and IF tests were specific. The IF test proved of value in the diagnosis of naturally occurring clinical schistosomiasis.
Twenty-eight Friesland calves were infested at 7 to 11 months of age with 5 000-45 OOO cercariae of Schistosoma mattheei. At 7 to 8 weeks post-infestation the majority developed an acute intestinal syndrome characterised by diarrhoea or dysentery, anorexia and loss of condition, from which they recovered spontansously. The severity and duration of illness was proportional to the level of infestation. Two heavily infested animals on a low plan of nutrition developed a subacute syndrome in which the initial acute disease was succeeded by prolonged unthriftiness, without diarrhoea, from which recovery occurred when the nutritional status was improved. Both acute and subacute forms of the syndrome were encountered in natural outbreaks.
A Friesland steer infested on four occasions at intervals of 4--6 weeks with 20 000 cercariae of Schistosoma mattheei developed progressive hepatic failure and died after 74 weeks. The condition was characterised by enlargement and induration of the liver with portal fibrosis, inflammation of the portal veins and "piecemeal necrosis", and was associated with a severe circulating eosinophilia and hypergammaglobulinaemia. Similar cases were encountered in two natural outbreaks. The syndrome is considered to be of immunological origin, initiated by the reaction in the portal veins to antigen from schistosomes killed by the immune response of the host. It is usually seen in animals exposed to repeated heavy infestation but may occur occasionally after light infestation.