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At least 253 records · Page 14Linked to original sources
PubMed1990

Learning causes synaptogenesis, whereas motor activity causes angiogenesis, in cerebellar cortex of adult rats.

The role of the cerebellar cortex in motor learning was investigated by comparing the paramedian lobule of adult rats given difficult acrobatic training to that of rats that had been given extensive physical exercise or had been inactive. The paramedian lobule is activated during limb movements used in both acrobatic training and physical exercise. Acrobatic animals had greater numbers of synapses per Purkinje cell than animals from the exercise or inactive groups. No significant difference in synapse number or size between the exercised and inactive groups was found. This indicates that motor learning required of the acrobatic animals, and not repetitive use of synapses during physical exercise, generates new synapses in cerebellar cortex. In contrast, exercise animals had a greater density of blood vessels in the molecular layer than did either the acrobatic or inactive animals, suggesting that increased synaptic activity elicited compensatory angiogenesis.

Animals↗
PubMed1986

Listeria monocytogenes: a rare cause of opportunistic infection in the acquired immunodeficiency syndrome (AIDS) and a new cause of meningitis in AIDS. A case report.

A forty-two year-old male homosexual with the acquired immunodeficiency syndrome (AIDS) developed Listeria monocytogenes septicemia and meningitis. The gastrointestinal tract was the likely portal of entry. The patient was treated with intravenous ampicillin with complete and permanent resolution of his listerial infection. Although L. monocytogenes infection has been reported as an uncommon complications of AIDS, we are unaware of Listeria meningitis being previously reported in an AIDS patient. It is hoped that this case report will alert health care workers to the possibility of Listeria infection in AIDS patients, particularly since this infection responds well to readily-available antibiotic therapy. The microbiology, epidemiology, clinical, and neurologic aspects of listerial infection and general aspects of the acquired immunodeficiency syndrome are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Loss of Rhb1, a Rheb-related GTPase in fission yeast, causes growth arrest with a terminal phenotype similar to that caused by nitrogen starvation.

The Rheb GTPase is most similar in primary sequence to the Ras, Rap, R-Ras, and Ral GTPases, which regulate cell growth and differentiation in many cell types. A likely fission yeast homologue of mammalian Rheb, which we designated Rhb1, was identified by genome sequencing. Our investigation of rhb1 showed that rhb1(-) cells arrested cell growth and division with a terminal phenotype similar to that of nitrogen-starved cells. In particular, cells depleted of Rhb1 arrested as small, round cells with 1N DNA content, arrested more quickly in low-nitrogen medium, and induced expression of fnx1 and mei2 mRNA, two mRNAs that were normally induced by nitrogen starvation. Since mammalian Rheb binds and may regulate Raf-1, a Ras effector, we tested for functional overlap between Ras1 and Rhb1 in fission yeast. This analysis showed that Ras1 overexpression did not suppress rhb1(-) mutant phenotypes, Rhb1 overexpression did not suppress ras1(-) mutant phenotypes, and ras1(-) rhb1(-) double mutants had phenotypes equal to the sum of the corresponding single-mutant phenotypes. Hence, there is no evidence for overlapping functions between Ras1 and Rhb1. On the basis of this study, we hypothesize that Rhb1 negatively regulates entry into stationary phase when extracellular nitrogen levels are adequate for growth. If this hypothesis is correct, then Rhb1 and Ras1 regulate alternative responses to limiting nutrients.

Amino Acid Sequence↗
PubMed1997

Noncirrhotic portal vein thrombosis causing sudden unexpected death. A rare cause of fatally ruptured esophageal varices.

Noncirrhotic portal vein thrombosis (PVT) is a rare disease that usually presents with small nonfatal "herald bleeding" with low mortality. Classic findings of noncirrhotic PVT include esophageal varices, splenomegaly, a normal liver, and an organized thrombus of the portal vein. We present a case of previously unreported sudden unexpected death from noncirrhotic PVT in an asymptomatic elderly woman, review the literature of this entity, and examine the pathophysiology of the formation of fatally ruptured varices. The portal vein must be carefully examined in all cases where there is no coexisting cirrhosis.

Aged↗
PubMed2002

Mechanism of intervertebral disc degeneration caused by nicotine in rabbits to explicate intervertebral disc disorders caused by smoking.

STUDY DESIGN: The effects of nicotine on intervertebral discs in rabbits were studied experimentally. OBJECTIVES: To investigate the effects of nicotine on the vascular buds in rabbits for elucidating the mechanism of nicotine-induced vertebral disc degeneration. BACKGROUND DATA: Several groups have suggested that cigarette smoking is associated with low back pain, but the exact mechanism is not yet fully understood. METHODS: The pump was filled with a diluted nicotine solution, then implanted under the skin of rabbits for 8 weeks. This model was designed to maintain blood nicotine concentration at approximately 110 ng/mL. Rabbits receiving physiologic saline were used as control animals. RESULTS: Nicotine treatment resulted in necrosis and hyalinization of the nucleus pulposus in all rabbits. The anulus fibrosus showed a disturbance of the pattern of overlapping laminae with and without clefts and separation. These resulted in changes indicative of stenosis of vascular buds and perivascular calcification. Nicotine treatment resulted in hypertrophy of vascular walls, necrotic changes in endothelial cells, and narrowing of the vascular lumen. Nicotine treatment resulted in delineation of vascular buds in the vicinity of the vertebral endplate and a reduction of their numbers. However, the control animals showed a dense vascular network. The number of vascular buds decreased in nicotine treatment. CONCLUSION: The authors believe that both reduction in the density of vascular buds and narrowing of the vascular lumen result in decreased oxygen tension, leading to decreased synthesis of proteoglycan and collagen, thus facilitating degeneration of the disc.

Animals↗