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Biomedical subjects

C Boone

Publications and source records attributed to C Boone.

53 records · Page 3Linked to original sources
PubMed1989

Effect of short lateralized signals on arousal versus activation on tasks requiring visuospatial or elementary semantic stimulus processing, a replication with a modified experimental design.

In this experiment, which is basically a replication of an earlier experiment done in 1988, we tested the hypothesis that the brain self-regulates its own arousal and activation. When subjects perform a putative right-hemisphere task (visuospatial), the effect of a supplementary information-processing load is supposed to lead to a delayed reaction. The opposite is supposed to be true in a putative left-hemisphere task (semantic). The former effect is supposed to be the result of increased arousal, the latter is that of increased activation. In the present experiment the reactions subject to experimental treatment are compared with control reactions of the same subject. This was not the case in the earlier experiment. Still other improvements of the experimental design were made. The results clearly confirm the earlier findings. Additional evidence is offered to strengthen the plausibility of the basic hypothesis.

Arousal↗
PubMed1988

Bioavailability of beta-carotene in humans.

Normal healthy volunteers were studied after they ingested various beta-carotene doses. Daily administration of 15 or 45 mg beta-carotene resulted in significant increase in plasma beta-carotene levels. The extent of increase and the pattern of plasma beta-carotene levels showed substantial interindividual variation. Absorption of beta-carotene was affected by dietary fat concentration. Individuals placed on a high-fat diet showed significant increases in plasma beta-carotene as compared with those placed on a low-fat diet. Pharmacological doses of beta-carotene (45 and 90 mg) were used in intermittent schedules (5-6 d intervals) without altering the steady state of beta-carotene plasma levels. Yellowing of the skin occasionally occurred during daily dosing with 45 mg beta-carotene without evidence of toxicity. The observed individual variation in bioavailability of beta-carotene raises questions regarding clinical use of this micronutrient. It appears that determination of target plasma beta-carotene concentrations is essential for effective use of this compound in prevention or treatment.

Adult↗
PubMed1987

A hepatitis B vaccination program in a community teaching hospital.

Prior to offering the hepatitis B (HB) vaccine, a prescreen for hepatitis B virus (HBV) antibodies was conducted in a 565 bed hospital in Pasadena, California. Antibodies to the hepatitis B virus were detected in 14.5% of 1,745 employees tested. There was a significantly higher prevalence in those with a previous history of hepatitis, blood transfusions, exposure to needlesticks, number of years in the same occupation, and in the same hospital work area. Employees of Asian extraction (33.3%) and blacks (23.1%) had a higher prevalence of antibodies to the hepatitis B virus than Hispanics (13.7%) and whites (10.2%). Anti-HBs was detected in 92.6% of 865 employees who received three doses of the hepatitis B vaccine. Only 28.6% of nonresponders receiving a fourth dose of hepatitis B vaccine produced anti-HBs. The nonresponders to the HB vaccine were older (average age 64.9 years) when compared to the responders (average age 37.5 years), and more males failed to produce anti-HBs after vaccination than females. Hepatitis B vaccination of the majority of individuals with either "low level" anti-HBs alone or anti-HBc alone did not elicit an anamnestic response after one dose of vaccine, implying that these "low level" antibodies are nonspecific and do not represent antiviral antibodies. Adverse reactions to the hepatitis B vaccine were minor and included a flu-like syndrome, sore arm, and rash and swelling at the injection site. The reasons for nonparticipation were obtained from 179 individuals, and the main issue was concern about safety of the hepatitis B vaccine.

Adult↗
PubMed1986

Yeast killer toxin: site-directed mutations implicate the precursor protein as the immunity component.

Yeast killer toxin and a component giving immunity to it are both encoded by a gene specifying a single 35 kd precursor polypeptide. This precursor is composed of a leader peptide, the alpha and beta subunits of the secreted toxin, and a glycosylated gamma peptide separating the latter. The toxin subunits are proteolytically processed from the precursor during toxin secretion. Using site-directed mutagenesis, we have identified a region of the precursor gene necessary for expression of the immunity phenotype. This immunity-coding region extends through the C-terminal half of the alpha subunit into the N-terminal part of the gamma glycopeptide. Mutations in other parts of the gene allow full immunity but produce precursors that fail to be processed. The precursor can therefore confer immunity, and we propose that it does so in the wild type by competing with mature toxin for binding to a membrane receptor.

Fungal Proteins↗
PubMed1985

Effects of short-term, high-dose prednisone treatment of patients with HBsAg-positive chronic active hepatitis.

We conducted a clinical trial to study the effects of a 10-week course of prednisone therapy and its withdrawal on serum aminotransferase levels and on hepatitis B virus (HBV) markers in patients with hepatitis B surface antigen (HBsAg) positive chronic active hepatitis (CAH-B). Eighteen patients with CAH-B were treated with prednisone, while another 18 patients matched for age, sex, race and sexual preference were followed simultaneously without treatment for the same duration. Nine of 18 prednisone-treated patients became transiently DNA polymerase positive. All nine patients developed a transient rise in serum alanine aminotransferase (ALT) levels of greater than 300 U/L above baseline values, which was associated with a drop in HBsAg levels from a mean of 186 micrograms/ml prior to therapy to 92 micrograms/ml at 6 months following treatment. Six of these patients developed fatigue, anorexia and dark urine, and four also developed either ascites or hemorrhage from esophageal varices, which was accompanied by hepatic encephalopathy. All six of these patients had histologic evidence of CAH with cirrhosis. In comparison, none of the control, untreated patients with CAH-B had any change in either HBV markers or serum ALT levels. Therefore, even a short course of prednisone in patients with CAH-B with cirrhosis is detrimental and its use should be discouraged.

Adult↗
PubMed1979

Tumorigenicity of revertant from an SV40-transformed line.

A syndrome of in vitro properties correlates with the tumorigenicity of SV40-transformed rodent cells. These properties are: plasminogen activator production, loss of large actin cables, and anchorage-independent growth. An established rat fibroblast line, its SV40 transformant, several T-antigen negative revertants, and a spontaneous retransformant isolated from one of the revertants were analyzed in vivo for their tumorigenicity and in vitro for the syndrome. The two transformed lines were highly tumorigenic, and had clearly abnormal in vitro properties. The parental rat line was weakly tumorigenic in nude mice and demonstrated a slightly transformed response in the in vitro assays. The revertants were completely nontumorigenic. Expression of the in vitro syndrome was not uniform for all revertants; however, most cell lines maintained the correlation of the syndrome and tumorigenicity.

Animals↗
PubMed1978

In vivo monitoring of the death rate of artificial murine pulmonary micrometastases.

A system is described for direct monitoring of the death rate of artificial murine pulmonary microscopic metastases in vivo. Metastatic fibrosarcoma cells or benign connective tissue cells labeled with [125I]iododeoxyuridine were injected i.v. Comparison of the long-term radioactive decay rate of these two cell types in the lung permitted identification of the portion of the decay curve reflecting the initial period of micrometastasis development and growth. About 5% of the injected tumor cells were retained in the lung in micrometastasis, and their average death rate could be monitored by loss of radioactivity from the lung. Systemic methotrexate (75.0 mg/kg) was administered as a single dose 80 hr after injection of tumor cells at a time when micrometastases had not yet become vascularized. This treatment killed about 60% of the micrometases and suppressed the appearance of gross metastases at 14 days.

Animals↗
PubMed1972

Assignment of three human genes to chromosomes (LDH-A to 11, TK to 17, and IDH to 20) and evidence for translocation between human and mouse chromosomes in somatic cell hybrids (thymidine kinase-lactate dehydrogenase A-isocitrate dehydrogenase-C-11, E-17, and F-20 chromosomes).

Independently derived man-mouse somatic cell hybrids and their derivative subclones show a positive correlation between the expression of human lactate dehydrogenase A subunits and the occurrence of the human C-11 chromosome. Data are also presented that confirm the previously reported linkage of the thymidine kinase locus to the E-17 chromosome. A translocation of the E-17 chromosome provides presumptive evidence for the assignment of the thymidine kinase locus to the long arm segment of the E-17 chromosome. This translocation also provides evidence for translocation between man and mouse chromosomes in somatic cell hybrids. A presumptive association between the human phenotype for isocitrate dehydrogenase and the human F group is also described. Identification of specific human chromosomes was achieved by the application of several new cytological techniques: measurement of chromosome arm length, in situ annealing with mouse satellite complementary RNA, constitutive heterochromatin staining with Giemsa, and quinacrine mustard fluorochromatic staining.

Animals↗
PubMedDate not supplied

A pilot study on the effects of prednisone withdrawal on serum hepatitis B virus DNA and HBeAg in chronic active hepatitis B.

We investigated the efficacy of a short course of prednisone therapy in 20 patients with histologic evidence of chronic active hepatitis B. Sixteen of 20 prednisone-treated patients who were initially serum hepatitis B virus DNA-positive had a transient elevation of their serum ALT activity on withdrawal of prednisone. Subsequently, 14 of these 16 patients (87.5%) became persistently negative for serum hepatitis B virus DNA, and 10 also lost their HBeAg. In addition, there was a significant fall in serum ALT levels and HBsAg titers up to 12 months of follow-up in the prednisone-treated group. Five of 20 (25%) prednisone-treated patients experienced a transient episode of hepatic decompensation coinciding with the peak of enzyme elevation. To contrast, only 3 of 15 (20%) initially hepatitis B virus DNA-positive matched untreated patients followed during the same time period became negative for serum hepatitis B virus DNA, and no significant changes in serum ALT values or HBsAg titers were noted over the 12-month study period. Thus, patients with chronic active hepatitis B appear to be responsive to immunologic manipulation with prednisone as indicated by a pronounced rebound immune response and clearance of hepatitis B virus DNA with improvement in liver disease activity.

Adult↗
PubMedDate not supplied

The adipose conversion process: regulation by extracellular and intracellular factors.

White adipose tissue regulates lipid metabolism and acts as a secretory organ. Because of its importance for human health and animal production, many studies have attempted to better understand its development at the cellular and molecular levels by culturing preadipose cells in vitro. This synthesis article describes our current knowledge, acquired by this approach, concerning the regulation of the different steps of the adipocyte differentiation program by extracellular (hormones, cytokines, growth factors, retinoids and fatty acids) and intracellular agents (second messengers and transcription factors). The discrepant effects that have been observed for some of these factors are also discussed. This information is very important in the perspective of a better control of fat deposits in human and breeding species.

Adipocytes↗