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Biomedical subjects

J Cannon

Publications and source records attributed to J Cannon.

At least 55 records · Page 3Linked to original sources
PubMed1986

Carbon source regulation of RAS1 expression in Saccharomyces cerevisiae and the phenotypes of ras2- cells.

Transcriptional analysis of the yeast RAS genes in different culture conditions suggests that the inability of ras2 mutants to grow in nonfermentable carbon sources results from the regulation of RAS1 mRNA expression. The amount of RAS1 mRNA is significantly repressed in cultures grown on the nonfermentable carbon sources ethanol and acetate. As a result, low RAS function should be expressed under these conditions in a ras2 mutant. This can explain the inability of ras2- cells to grow on nonfermentable carbon sources. This interpretation is supported by the finding that an extragenic suppressor of ras2- (sra6-15), which restores growth on ethanol or acetate, also leads to an increase in the amount of RAS1 mRNA under these conditions. The sra6-15 mutation does not alter the level of RAS1 mRNA in cells grown on glucose. The pattern of transcriptional regulation described for the RAS1 gene is not shared by RAS2, indicating differential control of the functionally homologous yeast RAS genes at the level of gene expression.

Carbon↗
PubMed1980

Experimental production of basement membrane zone antibodies.

Sera from animals immunized to basement membrane proteins were collected and studied by indirect immunofluorescence using rat skin, esophagus, kidney, urinary bladder, rabbit skin, and human skin as substrates. Serum of immunized rabbits showed indirect immunofluorescent staining at the basement membrane zone of rat skin, esophagus, glomerulus, Bowman's capsule, rabbit skin, and human skin. In addition, the connective tissue sheaths of muscle fibers showed fluorescent staining. Direct immunofluorescence of skin, esophagus, kidney, and urinary bladder obtained from immunized animals was negative in all cases. This study demonstrates the antibody-inducing capability of basement membrane zone antigens of stratified squamous epithelium and suggests the presence of an antigen common to basement membranes of stratified squamous epithelium, glomerulus, Bowman's capsule, and the connective tissue sheaths of striated muscle. Histopathologic abnormalities were not associated with these antibodies in the immunized animals.

Animals↗
PubMedDate not supplied

Evidence for neuromuscular fatigue during high-intensity cycling in warm, humid conditions.

The purpose of this study was to examine and describe the neuromuscular changes associated with fatigue using a self-paced cycling protocol of 60-min duration, under warm, humid conditions. Eleven subjects [mean (SE) age 21.8 (0.8) years; height 174.9 (3.0) cm; body mass 74.8 (2.7) kg; maximum oxygen consumption 50.3 (1.8) ml.kg.min-1] performed one 60-min self-paced cycling time trial punctuated with six 1-min "all out" sprints at 10-min intervals, while 4 subjects repeated the trial for the purpose of determining reproducibility. Power output, integrated electromyographic signal (IEMG), and mean percentile frequency shifts (MPFS) were recorded at the mid-point of each sprint. There were no differences between trials for EMG variables, distance cycled, mean heart rate, and subjective rating of perceived exertion for the subjects who repeated the trial (n = 4). The results from the repeated trials suggest that neuromuscular responses to self-paced cycling are reproducible between trials. The mean heart rate for the 11 subjects was 163.6 (0.71) beats.min-1. Values for power output and IEMG expressed as a percentage of that recorded for the initial sprint decreased during sprints 2-5, with normalised values being 94%, 91%, 87% and 87%, respectively, and 71%, 71%, 73%, and 77%, respectively. However, during the final sprint normalised power output and IEMG increased to 94% and 90% of initial values, respectively. MPFS displayed an increase with time; however, this was not significant (P = 0.06). The main finding of this investigation is the ability of subjects to return power output to near initial values during the final of six maximal effort sprints that were included as part of a self-paced cycling protocol. This appears to be due to a combination of changes in neuromuscular recruitment, central or peripheral control systems, or the EMG signal itself. Further investigations in which changes in multiple physiological systems are assessed systematically are required so that the underlying mechanisms related to the development of fatigue during normal dynamic movements such as cycling can be more clearly delineated.

Adolescent↗