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W Newsome

Publications and source records attributed to W Newsome.

6 recordsLinked to original sources
PubMed2001

Isolation and characterization of the promoter region of the rat kidney-type glutaminase gene.

A lambdaEMBL3 rat genomic library was screened to clone a phage that contained the promoter region of the kidney-type mitochondrial glutaminase gene. The resulting lambdaGA1 phage contained 13.7 kb of genomic DNA that was mapped by Southern blotting and restriction analysis. The 2.22 kb and 0.83 kb SacI fragments of lambdaGA1 were sequenced and the transcription initiation site was identified by RNase mapping. The reported sequence contains 2287 bp of the promoter, the entire exon 1 (542 bp), and 223 bp of the initial intron of the glutaminase gene. The initial exon contains 141 bp of 5'-nontranslated sequence and 401 bp of coding sequence that encodes the 72-amino acid mitochondrial targeting presequence and 61 amino acids from the N-terminus of the mature 66 kDa glutaminase subunit. Various segments of the GA promoter were cloned into a chloramphenicol acetyltransferase (CAT) expression vector. The resulting GA-CAT constructs were transfected into LLC-PK(1)-F(+) kidney cells to assess the promoter function of the isolated genomic DNA. The GA(-402)CAT construct produced a 10-fold greater CAT activity than the promoter-less pCAT vector. Analysis of various deletion constructs indicated that elements located between -402 and -63 bp must act in synergy with more proximal elements to create a functional promoter. The initial 402 bp segment lacks a TATA sequence but is GC-rich and contains two CCAAT boxes and two Sp1 sites.

Amino Acid Sequence↗
PubMed1996

Anisoosmotic regulation of hepatic gene expression.

The effect of anisoosmolarity on the abundance of various mRNA species was examined in perfused rat liver and H4IIE rat hepatoma cells. Hyperosmotic exposure (385 mosmol/l) of isolated rat livers increased mRNA levels for tyrosine aminotransferase (TAT) by 246% and those for phosphoenolpyruvate carboxykinase (PEPCK) by 186%, whereas hypoosmotic exposure (225 mosmol/l) decreased their levels to 43% and 42%, respectively. mRNA levels for fructose-1,6-bisphosphatase (FBP), argininosuccinate lyase (ASL), argininosuccinate synthetase (ASS), glutamine synthetase (GS), glutaminase (GA) and glucokinase (GK) were largely unaffected. In H4IIE cells the modulation of TAT and PEPCK mRNA levels by anisoosmotic exposure was similar to that found in perfused rat liver. ASL and glutaminase mRNA levels were influenced in an opposite manner. The effects of anisoosmolarity on PEPCK mRNA levels in H4IIE cells were largely abolished in the presence of the protein kinase inhibitors H-7, H-89 and HA-1004. Other protein kinase inhibitors such as Go-6850, KN-62, Rp-8-CPT-cAMPS, rapamycin, wortmannin, genistein or herbimycin did not prevent the osmosensitivity of PEPCK mRNA levels. Also pertussis and cholera toxin, vanadate and colchicine did not affect the osmosensitivity of PEPCK mRNA levels. The data suggest that anisoosmotic exposure acts on the levels of some but not all mRNA species and that this action may involve changes in protein phosphorylation. They further indicate that the recently identified osmosensitive signal transduction pathway which involves a G-protein and tyrosine kinase dependent activation of mitogen-activated protein kinases is apparently not involved in the osmoregulation of PEPCK mRNA levels.

Animals↗
PubMed1994

Increase of c-jun mRNA upon hypo-osmotic cell swelling of rat hepatoma cells.

c-jun mRNA levels were increased in rat hepatoma cells (H4-II-E-C3) when exposed to hypotonic medium (205 mosmol/l) with a maximal induction observed after 1 h of hypotonic exposure. At this time point an approximate 5-fold increase in c-jun expression could be detected in relation to normotonic control incubations (305 mosmol/l). Hypertonic exposure (405 mosmol/l) had only a slight effect on c-jun expression. In contrast to the increased c-jun mRNA levels under hypotonic conditions, expression of the c-fos proto-oncogene was unaffected by changes in the osmolarity. The hypotonicity-induced increase in c-jun expression was also detectable in the presence of a protein kinase C (PKC) inhibitor. This indicates that PKC is not involved in the signal transduction pathway leading to c-jun expression upon hypotonic cell swelling in these cells.

Animals↗
PubMed1994

Power spectrum analysis of bursting cells in area MT in the behaving monkey.

It is widely held that visual cortical neurons encode information primarily in their mean firing rates. Some proposals, however, emphasize the information potentially available in the temporal structure of spike trains (Optican and Richmond, 1987; Bialek et al., 1991), in particular with respect to stimulus-related synchronized oscillations in the 30-70 Hz range (Eckhorn et al., 1988; Gray et al., 1989; Kreiter and Singer, 1992) as well as via bursting cells (Cattaneo et al., 1981a; Bonds, 1992). We investigate the temporal fine structure of spike trains recorded in extrastriate area MT of the trained macaque monkey, a region that plays a major role in processing motion information. The data were recorded while the monkey performed a near-threshold direction discrimination task so that both physiological and psychophysical data could be obtained on the same set of trials (Britten et al., 1992). We identify bursting cells and quantify their properties, in particular in relation to the behavior of the animal. We compute the power spectrum and the distribution of interspike intervals (ISIs) associated with individual spike trains from 212 cells, averaging these quantities across similar trials. (1) About 33% of the cells have a relatively flat power spectrum with a dip at low temporal frequencies. We analytically derive the power spectrum of a Poisson process with refractory period and show that it matches the observed spectrum of these cells. (2) About 62% of the cells have a peak in the 20-60 Hz frequency band. In about 10% of all cells, this peak is at least twice the height of its base. The presence of such a peak strongly correlates with a tendency of the cell to respond in bursts, that is, two to four spikes within 2-8 msec. For 93% of cells, the shape of the power spectrum did not change dramatically with stimulus conditions. (3) Both the ISI distribution and the power spectrum of the vast majority of bursting cells are compatible with the notion that these cells fire Poisson-distributed bursts, with a burst-related refractory period. Thus, for our stimulus conditions, no explicitly oscillating neuronal process is required to yield a peak in the power spectrum. (4) We found no statistically significant relationship between the peak in the power spectrum and psychophysical measures of the monkeys' performance on the direction discrimination task.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗