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Biomedical subjects

R J Brooks

Publications and source records attributed to R J Brooks.

At least 37 records · Page 2Linked to original sources
PubMed1987

Cholesterol hydroperoxides inhibit calmodulin and suppress atherogenesis in rabbits.

A mixture of cholesterol autoxidation products, prepared from an aged sample of cholesterol by recrystallization from methanol, inhibits calmodulin irreversibly in a Ca2+-dependent reaction. Inhibitory activity is lost after treatment with NaBH4, NaCNBH3, or NaI, from which we conclude that calmodulin inhibition is due to one or more cholesterol hydroperoxides. Partially purified cholesterol hydroperoxides, with or without cholesterol, were fed to young adult white rabbits. Cholesterol in the diet caused extensive atheroma formation in the aortas, but the addition of cholesterol hydroperoxides markedly reduced lesion formation. A cholesterol hydroperoxide preparation that was reduced by treatment with NaI was not effective in preventing atheroma formation. Cholesterol hydroperoxides did not lower cholesterol concentrations in blood plasma, liver, or heart.

Aging↗
PubMed1987

Pathogenesis of infection with Sarcocystis rauschorum (Apicomplexa) in experimentally infected varying lemmings (Dicrostonyx richardsoni).

This study describes the sequential formation of lesions associated with the endogenous development of Sarcocystis rauschorum (Apicomplexa: Sarcocystidae) in varying lemmings, Dicrostonyx richardsoni. Lethal doses of sporocysts (greater than 500) were orally administered to lemmings examined 1-6 days postinoculation (DPI) whereas sublethal doses were administered to lemmings examined subsequently. Transient necrosis and purulent inflammation, in association with precystic merogony, occurred in the liver by 4.5 DPI, peaked at 6 DPI and subsided beginning at 11 DPI with the liver returning to normal by 15 DPI. Cyst formation in skeletal and cardiac muscle was associated with purulent inflammation and sarcolemmal proliferation beginning at 9 DPI. These lesions persisted to 42 DPI. In addition, multifocal nonsuppurative meningoencephalitis was present in six of 11 infected lemmings examined between 11 and 15 DPI.

Animals↗
PubMed1987

Effects of the protozoan parasite Sarcocystis rauschorum on open-field behaviour of its intermediate vertebrate host, Dicrostonyx richardsoni.

Behaviour and activity levels were measured in varying lemmings experimentally infected with the heteroxenous parasite, Sarcocystis rauschorum to test the hypothesis that the parasite alters behaviour of this intermediate host and thereby increases probability of transmission to the definitive host, the snowy owl (Nyctea scandiaca). Measures of short-term activity levels on a running wheel indicated no effect of the parasite, either directly, or indirectly as a result of illness. We observed behaviour of infected lemmings placed in an "open field" (arena). Lemmings would increase their susceptibility to predators if they spent more time away from cover, used crypsis (stationary postures) less, spent more time exploring (especially in unfamiliar areas), or responded inappropriately to threats from predators. We found that only exploratory activity showed significant change after infection. The frequency of exploratory activity increased and became disassociated from the usual fear response. This may increase the lemmings' susceptibility to aerial predation. The mechanism for this effect is unknown, but neurological lesions have been observed. The examination of the modes of transmission of the S. rauschorum parasite within lemming populations and of a possible fecundity compensation strategy adopted by the lemmings, and their relevance to population control, are suggested as areas for future study.

Animals↗
PubMed1986

Adjuvant chemotherapy of axillary node-negative carcinoma of the breast using doxorubicin and cyclophosphamide.

One hundred fifty-six women with axillary node-negative breast cancer and primary tumors less than or equal to 5 cm in diameter (T1N0 or T2N0) were treated with a brief course of postoperative adjuvant chemotherapy consisting of doxorubicin and cyclophosphamide. Treatment was well tolerated and toxicity was minimal. With a median follow-up time of 58 months, there has been 1 relapse among 58 patients with T1 primary lesions and 15 relapses among 98 patients with T2 primary tumors. When compared with a matched historical control group receiving surgery alone, significant improvement was apparent in disease-free survival among the patients who received adjuvant chemotherapy. Prospective controlled trials are needed if we are to confirm this favorable experience with adjuvant chemotherapy in the treatment of women with node-negative breast cancer.

Adult↗
PubMed1985

Failure of strange females to cause pregnancy block in collared lemmings, Dicrostonyx groenlandicus.

The effects of exposure to unfamiliar females on pregnancy success of recently mated females were examined in collared lemmings (Dicrostonyx groenlandicus). Four days after mating, females in their home cage were exposed to strange, female intruders that were either nonpregnant or 16 days pregnant. Other recently mated females were introduced to the home cage of 16-day-pregnant females. Pregnancy success of the recently mated females was not reduced in any of these treatments. In the paired encounters, there was no relationship between dominance status and pregnancy status, nor between dominance and pregnancy success. These results do not support the hypothesis that in species in which females are aggressive and readily commit infanticide, unfamiliar females should cause other females to terminate early-stage pregnancies.

Abortion, Spontaneous↗
PubMed1984

Neurogenic pulmonary oedema.

Two young patients with head injuries subsequently developed neurogenic pulmonary oedema. The origin and pathways of the reflex response to cerebral trauma are discussed, with emphasis on the role of raised intracranial pressure and the sympathetic division of the autonomic nervous system in precipitating movement of systemic circulatory volume into the pulmonary circulation. Therapeutic measures are discussed which correct the progression of this condition by reducing intracranial pressure and blocking the systemic effects of autonomic reflex activity. This leads to the basis of a simple regime to treat future cases.

Acute Disease↗
PubMed1983

Factors affecting incidence of infanticide and discrimination of related and unrelated neonates in male Mus musculus.

Infanticide by males was examined in two strains (C57B1 and DBA) of the house mouse (Mus musculus). Males that had contact with a female within the previous 2-3 weeks rarely committed infanticide when introduced to the home cage of a female and her 1-day-old neonates, even when the female and neonates were of a different strain and from a different colony. In contrast, 90% of C57B1 males that had no contact with a female for more than 7 weeks killed pups when placed in the female's home cage, and 60% killed when a 1-day-old pup was introduced to the male's home cage. No difference in levels of infanticide occurred when grouped males were compared to isolated males. These results indicate that infanticide is not dependent upon recognition of the pups or the female, but depends on the male's previous exposure to females. Infanticidal behavior is not directly determined by genetic relationship, but the factors that inhibit this behavior reduce the probability that a male will kill his own offspring.

Animals↗
PubMed1983

Treatment of advanced breast cancer with mitomycin C combined with vinblastine or vindesine.

Mitomycin C together with either vindesine or vinblastine was given to 48 patients with previously treated advanced breast cancer. Thirteen (35%) of the 37 evaluable patients had a complete (one patient) or partial (12 patients) response. Overall median duration of response was 189 days (range, 90-700 days). Fifteen patients received mitomycin C and vindesine with six responses (40%) and a median response duration of 247 days (range, 162-700 days). Twenty-two patients received mitomycin C and vinblastine with seven responses (32%) and median response duration of 164 days (range, 90-330 days). Response duration for patients treated with mitomycin C plus vindesine was longer than that associated with mitomycin C plus vinblastine (p = 0.09). Significant toxicity included myelosuppression and neurologic symptoms, but was uncommon (less than 10% of patients). Therefore, the combination of mitomycin C and a vinca alkaloid appears to be useful in far-advanced refractory breast cancer.

Adult↗
PubMed1982

Spontaneous gastric squamous cell carcinomas and other neoplasms in Greenland collared lemmings (Dicrostonyx groenlandicus).

Malignant neoplasms were present in 39/66 Dicrostonyx groenlandicus of varying ages, examined from a laboratory colony. The presence of multiple neoplasms in some resulted in an overall average of 1.15 tumors/affected animal. Gastric squamous papillomas were present in nine, and locally invasive or metastatic gastric squamous cell carcinomas in a further 36 animals. Three mammary adenocarcinomas, one pancreatic islet cell tumor, one probable pancreatic adenocarcinoma and one adrenal cortical adenoma were also seen in lemmings with gastric tumors. Two others had mammary adenocarcinoma alone, and one animal had bilateral Harderian gland adenocarcinoma. Lesions resembling glomerulonephrosis of rats were seen in 23/51 animals whose kidneys were examined. These findings were not considered artefacts of captivity since concurrent gastric squamous cell carcinoma, mammary adenocarcinoma and glomerulonephrosis were present in the single animal examined directly from the wild at Eskimo Point, Northwest Territories.

Adenocarcinoma↗