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Biomedical subjects

D Lewis

Publications and source records attributed to D Lewis.

At least 325 records · Page 18Linked to original sources
PubMed1981

Effects of 1,2-symmetrical dimethylhydrazine on jejunocolic transposition in Sprague-Dawley rats.

In this experiment, a segment of the left colon including the upper part of the rectum was transposed to the upper jejunum, and a segment of upper jejunum was transposed to the left colon of the same animal. In another group, the same colon and jejunum segments were transsected and reanastomosed in place. A third group served as a normal control. After a recovery period, weekly s.c. 1,2-symmetrical dimethylhydrazine injections were begun. Each animal received a total of 20 injections at a dose of 20 mg/kg. Five weeks after the last 1,2-symmetrical dimethylhydrazine injection, 15 of 19 (79%) of the animals had one or more tumor(s) in the transposed colon segment, while none had tumor in the transposed jejunal segment. Transsected and reanastomosed animals showed the same distribution of tumors as did the normal control animals. All three groups had tumors at other sites in the colon and rectum. In addition, about 20% had tumors of the duodenojejunal area. These data indicate that the colonic mucosa is the primary target for the carcinogenic effect of 1,2-symmetrical dimethylhydrazine, independent of other variables such as the fecal stream.

1,2-Dimethylhydrazine↗
PubMed1981

Investigations on Babesia motasi isolated from Wales.

A number of observations were carried out on the effect of the newly isolated parasite, Babesia motasi (Wales) on intact and splenectomised sheep and on a splenectomised goat. The parasite was not pathogenic for intact animals but caused fever and anaemia in splenectomised ones. B motasi (Wales) was also studied morphologically, morphometrically and serologically. The common form of the parasite was seen to be a double pyriform, the mean length of one side being 2.23 micrometer. It appeared to be morphometrically and serologically close to the other north European B motasi strains but distinct from B motasi (Turkey). In a limited serological survey, experience of infection with B motasi appeared to be common in sheep grazing in coastal areas of North Wales, but rare in a part of South Wales known to harbour the vector tick Haemaphysalis punctata. Transovarial transmission of B motasi by H punctata took place with facility.

Animals↗
PubMed1980

Gonadal steroids: effects on excitability of hippocampal pyramidal cells.

Electrophysiological field potentials from hippocampal slices of rat brain show sex-linked differences in response to 1 X 10(-10)M concentrations of estradiol and testosterone added to the incubation medium. Slices from male rats show increased excitability to estradiol and not to testosterone. Slices from female rats are not affected by estradiol, but slices from female rats in diestrus show increased excitability in response to testosterone whereas slices from females in proestrus show decreased excitability.

Action Potentials↗
PubMed1980

Exposure of cattle immunised against redwater to tick-induced challenge in the field: challenge by a heterologous strain of Babesia divergens.

Eighteen, one-and-a-half-year-old Friesian heifers and a three-year-old Friesian bull were immunised against bovine redwater by inoculation with blood infected with a known strain of Babesia divergens which had been irradiated at 30 kilorads. Three weeks later these cattle plus 10 Friesian bullocks of the same age which served as controls were introduced to a grazing area infested with ticks able to transmit infections of a heterologous strain of B divergens. The control cattle all became infected with the heterologous strain, two severely. None of the inoculated cattle became clinically affected.

Animals↗
PubMed1980

Exposure of cattle immunised against redwater to tick challenge in the field: challenge by a homologous strain of B divergens.

A field trial was conducted in Northern Ireland to determine whether calves could be protected against babesiosis by the prior inoculation of irradiated blood infected with Babesia divergens; The trial involved 30 yearling calves. Ten were inoculated with infected blood from a donor calf after the blood had been irradiated at 25 kilorads, and 10 with blood irradiated at 30 kilorads. Their reactions to the inoculation were observed daily for a month. They were then released, along with a control group of 10 susceptible calves, into an area heavily infested with B divergens-infected Ixodes ricinus ticks for two months. Between 24 and 41 days after exposure all the control animals contracted babesiosis and six of them reacted severely. None of the immunised animals suffered clinical babesiosis although 14 had detectable low-level infections. The relative severity of the reactions of the groups of calves was reflected in their haematology.

Animals↗
PubMed1980

The isolation and characterization of human and bovine strains of Babesia divergens from Drumnadrochit, Scotland.

Strains of Babesia divergens of human and bovine origin were isolated from the same locality in Scotland. A morphometric comparison was then made between Babesia divergens parasites in blood smears made from groups of 3 splenectomized calves reacting to the inoculation of these strains. The various forms taken by the parasites of each strain were seen to be divisible into 7 categories and representatives of each category were found for each strain. More amoeboid forms were found in blood smears from calves infected with the strain of bovine origin but otherwise the frequencies of occurrence of different forms coincided. The dimensions of 3 forms of the parasites of each strain were compared and the parasites of human origin were found to be significantly larger. The reactions of the groups of calves to inoculation of the 2 strains of B. divergens were seen to be very similar, although inoculation of the bovine strain had a slightly greater effect on the animals' haematology as indicated by an an increase in erythrocyte mean corpuscular volume.

Animals↗
PubMed1980

HPLC analysis of Tc-99m iminodiacetate hepatobiliary agents and a question of multiple peaks: concise communication.

The application of high-performance liquid chromatography (HPLC) to Tc-99m-labeled iminodiacetate hepatobiliary agents is described. The method is sensitive to variations of phenyl ring structure and give different retention times for the different agents. Technetium-99m-labeled N-(2, 6-diethylacetanilide)iminodiacetate from different sources had two components in differing amounts. It was determined that the second component, which is minor at pH above 6, is major when prepared at pH 4.5 or less. Raising the pH results in rapid conversion of the second component into the first. This observation was demonstrated also in plasma and would be expected to occur when the radiopharmaceutical is injected intravenously. The kinetics of appearance of the preparations in the bile when prepared at pH 4 and pH 6 were essentially the same.

Animals↗
PubMed1979

The diagnosis and management of hairy-cell leukaemia.

Over a 4-year period 203 patients with various types of leukaemia were treated by the Haematology Unit at the Johannesburg Hospital. Ten of them were suffering from the condition known as hairy-cell leukaemia or leukaemic reticulo-endotheliosis. They were all men, and ranged in age from 29 to 67 years (mean 56 years). The majority presented with pancytopenia, and there was invariably splenomegaly, while lymphadenopathy was rare. Hairy cells were identified microscopically in the peripheral blood of 7 patients and in 5 the specific cytochemical marker, tartrate-resistant acid phosphatase, was present. In addition, in a further 2 patients this feature, which was not identified in the peripheral blood, was found in the splenic cells. The bone marrow trephine biopsy specimens characteristically showed extensive lymphoid infiltration associated with a dense disordered deposition of reticulin fibres. Electron microscopical and immunological studies proved to be of doubtful diagnostic value. Splenectomy was carried out on 9 patients, and there was tumour involvement in all the spleens removed. Two patients died from septicaemia, the one before splenectomy and the other 9 months after the operation. The 8 remaining patients have had their subjective symptoms alleviated and their peripheral blood indices have been improved by splenectomy, and none has required further treatment for periods now ranging from 7 to 41 months.

Acid Phosphatase↗
PubMed1979

The detection of rickettsia-like microorganisms within the ovaries of female Ixodes ricinus ticks.

An ultrastructural study of tick-borne fever (TBF)-infected Ixodes ricinus ticks revealed the presence of rickettsia-like microorganisms within the ooplasm and the mitochondria of developing oocytes. These microorganisms are similar in appearance to the TBF agent and it is possible that although transovarial transmission of the TBF agent apparently does not occur, the rickettsiae are at least able to establish themselves in the ovaries of infected ticks.

Animals↗