Biomedical subjects

C Mann

Publications and source records attributed to C Mann.

6 recordsLinked to original sources

PubMed1992

Biochemical and genetic dissection of the Saccharomyces cerevisiae RNA polymerase C53 subunit through the analysis of a mitochondrially mis-sorted mutant construct.

RPC53 has previously been shown to encode an essential subunit required for tRNA gene transcription by RNA polymerase C in vivo (Mann, C., Micouin, J.-Y., Chiannilkulchai, N., Treich, I., Buhler, J.-M., and Sentenac, A. (1992) Mol. Cell. Biol. 12, in press). In this paper, we have determined that an unusual rho+ lethality associated with the rpc53::HIS3-1 disruption mutation is due to the inadvertent formation of a Pet56-C53 fusion protein. This fusion protein is missorted to mitochondria, thereby reducing the quantity of the C53 subunit available for RNA polymerase C assembly. We show that the carboxyl-terminal region of C53 contains the essential functional domain of the subunit and that a mutant RNA polymerase containing only this domain is thermolabile for its function in vivo and in vitro. The thermolability of the carboxyl-terminal C53 domain is suppressed by five different genes on multicopy plasmids, including RPC160, encoding the largest subunit of RNA polymerase C and SSD1/SRK1, which has been implicated in the activity of protein phosphatases.

Alleles↗

PubMed1992

Risk of major elective operation after myocardial revascularization.

Although an increased surgical risk of ischemic myocardial disease is widely accepted, amelioration of this risk after coronary artery bypass is poorly defined. We compared the outcomes of major elective general and peripheral vascular operations in 181 patients with prior coronary artery bypass grafting (CABG) with outcomes in an age-, gender-, and procedure-matched group without prior CABG (NOCABG). Despite the perception of a greater operative risk in the CABG patients (more CABG patients in American Society of Anesthesiologists [ASA] class III and fewer in ASA class I, p < 0.001), mortality (1.1% CABG versus 2.8% NOCABG) and morbidity (18.8% CABG versus 18.5% NOCABG) rates in the two groups were not significantly different. For patients who have undergone successful CABG, it appears that: (1) the risk of subsequent elective major general and vascular surgical operations is similar to that of an age-, gender-, and procedure-matched cohort, and (2) the mortality rate after elective operations is low.

Age Factors↗

PubMed1992

RPC53 encodes a subunit of Saccharomyces cerevisiae RNA polymerase C (III) whose inactivation leads to a predominantly G1 arrest.

RPC53 is shown to be an essential gene encoding the C53 subunit specifically associated with yeast RNA polymerase C (III). Temperature-sensitive rpc53 mutants were generated and showed a rapid inhibition of tRNA synthesis after transfer to the restrictive temperature. Unexpectedly, the rpc53 mutants preferentially arrested their cell division in the G1 phase as large, round, unbudded cells. The RPC53 DNA sequence is predicted to code for a hydrophilic M(r)-46,916 protein enriched in charged amino acid residues. The carboxy-terminal 136 amino acids of C53 are significantly similar (25% identical amino acid residues) to the same region of the human BN51 protein. The BN51 cDNA was originally isolated by its ability to complement a temperature-sensitive hamster cell mutant that undergoes a G1 cell division arrest, as is true for the rpc53 mutants.

Amino Acid Sequence↗

PubMed1991

Fluoride mobilizes intracellular calcium and promotes Ca2+ influx in rat proximal tubules.

In the renal proximal tubule, external Ca2+ ([Ca2+]o) is required for parathyroid hormone to elevate cytosolic Ca2+ ([Ca2+]i). However, other hormones increase [Ca2+]i in the absence of [Ca2+]o. These differences may arise from a diversity of signal transduction pathways acting on external and internal Ca2+ pools. However, Ca2+ influx may be necessary to expedite and maintain the rise of [Ca2+]i for a period after the initial surge. In this study, F- was used to probe the roles of intracellular Ca2+ mobilization, Ca2+ influx, and phosphoinositide (PI) hydrolysis on the surge of [Ca2+]i in rat proximal tubules. In the presence of external Ca2+; 1-20 mM F- evoked incremental rises of [Ca2+]i in tubules loaded with aequorin. Whereas 10 mM F- increased [Ca2+]i in the absence of [Ca2+]o, the time constant for the [Ca2+]i surge was increased. These findings are consistent with a role of Ca2+ influx on the effect of F- on [Ca2+]i. Indeed, 10 mM F- also enhanced the uptake of 45Ca2+, and promoted Ca2+ influx in aequorin- and fura-2-loaded, Ca(2+)-deprived tubules. In tubules, F- also activated PI hydrolysis with a time course that paralleled Ca2+ mobilization. The effect of F- on [Ca2+]i was not altered when the 39-kDa pertussis toxin substrate was inactivated with the toxin. This G protein was most likely Gi, because prostaglandin E2, an activator of Gi in tubules, dissociated the pertussis toxin-sensitive protein. The results support the notion that activation of a signal-transduction complex, the F- substrate, causes Ca2+ influx, mobilizes internal Ca2+, and activates PI hydrolysis in rat proximal tubules.(ABSTRACT TRUNCATED AT 250 WORDS)

Aequorin↗

PubMed1991

Na(+)-Ca2+ exchange and Ca2+ depletion in rat proximal tubules.

The removal of external Ca2+ ([Ca2+]o) reduces cytosolic Ca2+ ([Ca2+]i) in rat proximal tubules. In this report the role of external Na+ ([Na+]o) on the changes of [Ca2+]i and Ca2+ efflux caused by withdrawal of [Ca2+]o is described in rat renal proximal tubules. In aequorin-loaded tubules [Ca2+]i decreased from 235 +/- 25 to 48 +/- 16 (n = 4, P = 0.017), and 45Ca2+ fractional efflux ratio (45Ca2+ FER) increased from 0.94 +/- 0.03 to 1.64 +/- 0.19 (n = 6, P = 0.021) when Ca2+ was withdrawn from the bathing media of Krebs buffer (KB). The fall of [Ca2+]i, as well as the activation of 45Ca2+ FER, was reversed when [Na+]o in Ca(2+)-free KB was lowered isosmotically from 150 to 15 mM. However, when tubules were superfused with only 5 mM [Na+]o before [Ca2+]o was removed, [Ca2+]i also declined, but 45Ca2+ FER did not increase. The Na(+)-Ca2+ exchange inhibitor dichlorobenzamil (DCB) added after [Ca2+]o was removed evoked responses similar to [Na+]o removal, although DCB also inhibited internal Ca2+ release. These results are congruous with stimulation of Na+ influx in exchange for [Ca2+]i in Ca(2+)-free KB. However, even though total tubular Na+ was higher in Ca(2+)-free KB after 10 min, the initial rate of 22Na+ influx was not different without or with [Ca2+]o.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride↗

PubMed1977

Colostomy.

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Aftercare↗