Biomedical subjects

R C Crane

Publications and source records attributed to R C Crane.

6 recordsLinked to original sources

PubMed1996

Energy balance in asymptomatic HIV infection.

OBJECTIVES: Body weight is regulated by the balance between energy intake and energy expenditure, but the influence of HIV infection on energy balance has not been fully examined. The main objectives of this study were (1) to assess the effect of HIV on energy balance, (2) to examine the relationship of parameters of immunodeficiency to energy balance, and (3) to examine the interrelationship of different components of energy balance in asymptomatic HIV-seropositive men. DESIGN: A cross-sectional study of nutrition and metabolism in asymptomatic HIV-seropositive men METHODS: Components of energy balance were examined in 104 asymptomatic HIV-seropositive men (CD4 count 4-482 x 10(6)/l) and 57 age-matched HIV-seronegative male controls. Energy and protein intake were measured using 5-day diaries, and small bowel absorption and permeability was assessed using four sugar probes. Resting energy expenditure was calculated from indirect calorimetry and nitrogen loss estimated from 24 h urine collection. Four methods were used to assess the effect of HIV infection on body composition (anthropometry, dual energy X-ray absorptiometry, bioelectrical impedance and 24 h urine creatinine). RESULTS: Resting energy expenditure per kilogram of fat-free mass was raised (P < 0.0001), fat mass was decreased (P = 0.001), fat-free mass was increased (P = 0.05), energy intake was higher (P = 0.05), absorption of L-rhamnose (P = 0.01) and 3-O-methyl-D-glucose was decreased (P = 0.003), and small bowel permeability was increased (P < 0.0001) in HIV-seropositive men compared with HIV-seronegative controls. HIV-seropositive subjects with a CD4 count less than 100 x 10(6)/l had decreased absorption of L-rhamnose (P < 0.05), D-xylose (P < 0.05) and 3-O-methyl-D glucose (P < 0.05) compared with HIV-seropositive subjects at higher CD4 counts, and had a similar resting energy expenditure to HIV-seronegative controls. Protein intake, carbohydrate, fat and protein oxidation. 24 h nitrogen excretion and appendicular muscle mass were similar in HIV-seropositive men and controls. CONCLUSION: HIV infection exerts a direct effect on parameters of energy balance that varies with the severity of immunosuppression.

Adult↗

PubMed1996

Intestinal inflammation, ileal structure and function in HIV.

OBJECTIVES: This study examines small intestinal absorption-permeability, intestinal inflammation and ileal structure and function in HIV-positive male homosexuals. METHODS: Thirty HIV-seropositive male homosexuals at various stages of disease underwent intestinal absorption permeability and 111indium leukocyte studies (for quantification of intestinal inflammation). Twenty-six men with AIDS had a dual radioisotopic ileal function test (whole body retention of tauro 23-[75Se]-selena 25-homocholic acid and 58cobalt-labelled cyanocobalamine), and 17 underwent ileocolonoscopy with terminal ileal biopsy. RESULTS: Well, HIV-infected, subjects had normal intestinal absorption-permeability, but both functions were impaired upon the development of AIDS. The median faecal excretion of 111indium in well patients (0.66%) did not differ significantly (P > 0.5) from controls (0.46%), but subjects with AIDS who were well or who had diarrhoea had significant (P < 0.005) intestinal inflammation (1.33% and 2.18%, respectively). The median 7-day retention of tauro 23-[75Se]-selena 25-homocholic acid in well patients with AIDS (38.9%) did not differ significantly (P > 0.2) from controls (39.3%), whereas the absorption of 58cobalt-labelled cyanocobalamine was significantly (P < 0.05) lower than controls (32.1% and 59.4%). Patients with AIDS-diarrhoea had significant (P < 0.001) malabsorption of both the bile acid (7.7%) and vitamin B12 (8.9%) which was more severe than in Crohn's ileitis (14.2% and 30.3%, respectively). Morphometric analyses of ileal biopsies were unremarkable in AIDS. CONCLUSIONS: These studies demonstrate a low-grade enteropathy in patients with AIDS, severe ileal malabsorption in patients with AIDS diarrhoea and relatively minor ileal morphologic changes. Malabsorption of bile acids may play a pathogenic role in patients with AIDS and diarrhoea.

Acquired Immunodeficiency Syndrome↗

PubMed1985

Lack of effect of 1-methylisoguanosine on sleep in rats.

The dose-response effects of intracerebroventricular (i.c.v.) administration of 1-methylisoguanosine (MIG) on sleep in rats were examined. Not even the largest dose (100 nmol/rat) of 1-methylisoguanosine produced significant hypnotic effects, whereas doses of 10 and 100 nmol/rat suppressed rapid eye movement sleep in rats. The only statistically significant effect of 1-methylisoguanosine on sleep latencies was an increase in the latency of S2 after intracerebroventricular administration of 100 nmol/rat of the drug. These effects of 1-methylisoguanosine on sleep were unlike those of both adenosine and the benzodiazepines, suggesting that, contrary to earlier speculations, 1-methylisoguanosine does not interact with central adenosine or benzodiazepine receptors.

Adenosine↗

PubMed1984

Aluminum effect on slow axonal transport: a novel impairment of neurofilament transport.

Administration of aluminum (Al) produces accumulation of neurofilaments (NF), called neurofibrillary tangles (NFT), in neuronal cell bodies and proximal axonal segments. This study was undertaken to investigate whether these changes are associated with impairment of the slow axonal transport. Local administration of AlCl3 induced the formation of NFT in 90 to 100% of the rabbit hypoglossal neurons. [35S]Methionine was then administered to the hypoglossal nerve nuclei. The hypoglossal nerves were processed 18 or 28 days later for one- and two-dimensional SDS-polyacrylamide gel electrophoresis and fluorography. Labeled NF polypeptides and a polypeptide of 57 kilodaltons (Kd) were not detectable beyond the proximal 9-mm segment of the hypoglossal nerve in Al-treated rabbits 18 days after labeling, whereas they were present up to 27 mm from the medulla in controls. Tubulin and polypeptides migrating with slow component b were not significantly affected. In rabbits sacrificed 28 days after labeling, accumulation of NF subunits within the proximal 9 mm of hypoglossal nerve was less dramatic, and labeled NF were present up to 30 mm from the medulla whereas they were detectable up to 45 mm in controls. Morphological studies demonstrated the presence of enlarged axons filled with NF in the proximal 9 mm of the hypoglossal nerve. In nerve segments immediately distal, axons were markedly reduced in size and contained no NF but an apparently normal number of microtubules and other organelles. Transport of NF and of a 57-Kd polypeptide is markedly but reversibly slowed down or blocked within the proximal 9-mm segments of the hypoglossal nerve following Al administration to the hypoglossal nucleus. It is suggested that NF transport is maintained distally, resulting in lack of NF in axonal segments immediately distal to the block. Local Al intoxication provides a novel model of impairment of NF transport.

Aluminum↗

PubMed1983

Antibodies to neurofibrillary tangles of Alzheimer's disease raised from human and animal neurofilament fractions.

Antibodies reacting with neurofibrillary tangles (NFT) of Alzheimer's disease were consistently obtained using neurofilament (NF) fractions as antigen. NF fractions were obtained from normal human spinal roots or guinea pig peripheral nerves and used to immunize BALB/c mice. Mice receiving a total dose of 300 to 600 micrograms of protein developed antibodies that were indistinguishable with immunostaining of tissues and of polypeptides separated on sodium dodecyl sulfate-polyacrylamide electrophoresis gels. These antibodies reacted with NFT from cases of Alzheimer's disease and with NFT induced with aluminum, as well as with structures rich in NF such as central and peripheral axons and cerebellar basket fibers. When used to immunostain polypeptides separated by sodium dodecyl sulfate-polyacrylamide electrophoresis, all antisera recognized the three NF subunits. Absorption of the antisera with 5 micrograms/ml of purified human NF proteins blocked immunostaining of Alzheimer's NFT. It is concluded that human and animal NF fractions are excellent antigens to produce antibodies that consistently react with NFT of Alzheimer's disease. The present findings further support existing evidence that the paired helical filaments of Alzheimer's disease share antigenic determinants with normal NF.

Alzheimer Disease↗

PubMedDate not supplied

Accuracy of fast spin echo magnetic resonance imaging in the diagnosis of vestibular schwannoma.

PURPOSE: An ideal screening test is noninvasive, inexpensive, and has a high specificity and sensitivity. Auditory brain-stem response testing has been the usual screening test for the diagnosis of vestibular schwannoma, although its accuracy in diagnosing small vestibular schwannomas has caused its effectiveness as a screening test to be questioned. Magnetic resonance imaging (MRI) with gadolinium has a high sensitivity and specificity for the diagnosis of vestibular schwannoma. Its use as a screening test for vestibular schwannoma has been limited due to its high cost. Fast spin echo MRI is a technique that provides T2-weighted images with excellent contrast between fluid and neural structures, and its cost is a fraction of a gadolinium MRI scan. This study compares the accuracy of fast spin echo MRI to gadolinium MRI in the diagnosis of vestibular schwannoma. MATERIALS & METHODS: Twenty-five patients (50 ears) in whom there was a clinical suspicion of vestibular schwannoma were scanned with both modalities. All studies were read independently and scored as positive, negative, or indeterminate. RESULTS: There were 11 true positives and 39 true negatives. There were no false positives or negatives, resulting in a sensitivity of 100% and a specificity of 100%. CONCLUSION: Fast spin echo MRI appears to be an excellent choice as a screening test for vestibular schwannoma due to its low cost, noninvasiveness, and high sensitivity and specificity.

Cranial Nerve Neoplasms↗