PubMed Health⌕ Search

Biomedical subjects

T Walker

Publications and source records attributed to T Walker.

At least 73 records · Page 4Linked to original sources
PubMed1995

Thoracoscopy: anesthetic considerations.

Thoracoscopy is surgical procedure which was performed in the early 1900s primarily for the treatment of tuberculosis until antibiotics became the treatment of choice. Over the last two decades, thoracoscopy has experienced a rebirth as the indications for this endoscopic procedure have become numerous. Although less invasive than the thoracotomy, thoracoscopy is not without potential complications. The anesthesia provider must be alert for problems related to one-lung ventilation, lateral positioning, and pleural cavity insufflation. The anesthetic technique must be planned with the physiological changes which occur during thoracoscopy in mind.

Anesthesia↗
PubMed1994

Fc gamma receptor II stimulated formation of inositol phosphates in human platelets is blocked by tyrosine kinase inhibitors and associated with tyrosine phosphorylation of the receptor.

We report that activation of phospholipase C (PLC) by cross-linking of the platelet low-affinity Fc gamma receptor II (Fc gamma RII) is inhibited by two structurally distinct tyrosine kinase inhibitors, staurosporine and ST271. This contrasts with PLC activation induced by thrombin and U46619, a thromboxane mimetic, whose receptors have seven transmembrane domains characteristic of G-protein coupled receptors. Several proteins undergo phosphorylation on tyrosine on Fc gamma RII cross-linking upstream of protein kinase C (PKC), Ca2+ and aggregation, including the Fc gamma RII itself. The role of Fc gamma RII phosphorylation in the regulation of PLC is discussed.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1994

Medium-induced fragility of Schwanniomyces.

Schwanniomyces occidentalis has attracted interest because of its ability to metabolize starch and similar complex carbohydrates. Studies have been undertaken, mostly using defined media, to ascertain conditions for optimal production and secretion of hydrolytic enzymes. Here we demonstrate the fragility of Schw. occidentalis in many defined media. We especially examined viability in YNB (Yeast Nitrogen Base) plus 1% glucose. Without phosphate supplementation, viability was routinely very low at stationary phase (usually less than 37%), whereas viability of stationary-phase cultures in phosphate-supplemented YNB usually exceeded 97%. The negative implications of having many, presumably permeabilized, dead cells present in assays for secretion of enzymes by living yeast cells are discussed.

Culture Media↗
PubMed1993

[Differentiation of schistosome species and strains by DNA hybridization].

Genomic DNA from Schistosoma mansoni and S. japonicum adult worms was hybridized to a 32p-labelled pSM 889 probe after cleavage by restriction endonuclease BglII, BamHI, XbaI and EcoRI, or to a 32p-labelled pSM 389 probe after cleavage by EcoRI. The resulting hybridization banding patterns were significantly different between the two species. Genomic DNA from S. japonicum adult worms of Hunan, Hubei, Jiangxi, Zhejiang and Yunnan isolates was hybridized to a 32p-labelled pSM 389 probe after cleavage by EcoRI. The major hybridization bands were identical while the minor bands were more or less different among the isolates. Of them, isolates Hunan, Hubei and Zhejiang have similar minor bands while isolates Jiangxi and Yunnan have minor bands significantly different from those of the above three isolates and also markedly distinct from those of each other. These results indicate that the major hybridization banding patterns are unique to schistosome species while the minor banding patterns may serve as the basis for strain differentiation.

Animals↗
PubMed1992

Differentiation of HT-29 human colonic adenocarcinoma cells correlates with increased expression of mitochondrial RNA: effects of trehalose on cell growth and maturation.

The HT-29 human adenocarcinoma cell line has been used extensively in the study of colonic cell differentiation and colon cancer. We report here that substitution of glucose with trehalose (alpha-D-glucopyranosyl-alpha-D-glucopyranoside) depresses growth and promotes mucin-producing, goblet-like maturation of HT-29. An initial characterization of this process was made by analyzing several cDNA clones whose RNA templates were differentially expressed at elevated levels in cells grown in trehalose-containing medium. Seven of the 9 clones examined corresponded to 6 mitochondrial genes whose expression levels, relative to those from glucose-grown cells, ranged from approximately 3-fold for 16S rRNA to 8-23-fold for NADH dehydrogenase subunit 4. On the other hand, levels of mitochondrial DNA copy, measured by using NADH dehydrogenase subunit 4 cDNA as probe, were shown to be unaffected by trehalose treatment. Elevation of cellular NADH dehydrogenase subunit 4 RNA in HT-29 cultures grown in medium containing different components (sodium butyrate, galactose, no-sugar, glucose, cellobiose) generally correlated with depressed growth levels and specifically with increased numbers of mucin-producing cells present. Like butyrate, the sugar, trehalose, is an effective inducer of HT-29 differentiation, and may prove useful as a dietary therapeutic, and as a probe for elucidating mitochondrial involvement in colonic cell differentiation and transformation.

Adenocarcinoma↗
PubMed1991

The diacylglycerol kinase inhibitor, R59949, potentiates secretion but not increased phosphorylation of a 47 kDalton protein in human platelets.

We have investigated the action of a novel inhibitor of DG-kinase, R59949. This agent was found to produce partial inhibition of formation of phosphatidic acid in human platelets challenged with thrombin, DC8 or OAG. However, this effect was not associated with enhanced phosphorylation of a 47 kDa protein, a known substrate for protein kinase C. We therefore believe that this compound does not represent a major advance on its earlier prototype, R59022.

Blood Platelets↗
PubMed1991

Reperfusion modification with a simplified blood cardioplegia system compared with oxygenated crystalloid cardioplegia.

A simplified system was developed for administration of blood cardioplegia with reperfusion modification. This system utilizes a single pass stainless steel coil to eliminate the need for a separate heat exchanger circuit. This system was compared with an oxygenated crystalloid cardioplegia system which was utilized in a manner which allowed warm blood perfusion of the heart for the last three minutes of the crossclamp interval. Both of these systems were compared with regard to mortality, spontaneous defibrillation, myocardial temperature, blood usage and peak CK-MB levels. In this series of patients, no significant advantage of either system could be identified.

Blood↗
PubMed1990

The KROX-24 protein, a new transcription regulating factor: expression in the rat central nervous system following afferent somatosensory stimulation.

The expression of the protein product encoded by the Krox-24 gene was investigated immunocytochemically in the central nervous system of adult rats. Immunoreactivity (IR) of the KROX-24 protein which is a nuclear transacting transcription factor, showed a pattern of nuclear staining. Basal KROX-24-IR was visible in the superficial layers of spinal dorsal horn and trigeminal nucleus, and in many areas of the brain including the cerebellum, nucleus raphe magnus, colliculi, periaqueductal gray, hypothalamus, geniculate nuclei, caudate putamen, amygdala, hippocampus, lateral septal nucleus, olfactory tubercle and cerebral cortex. Electrical stimulation of sciatic nerve A- and C-fibers, but not of A alpha- and A beta-fibers alone, induced transient expression of KROX-24 in numerous spinal neurons in the termination area of the stimulated nerve. One hour following the onset of this stimulation of the sciatic nerve the distribution of KROX-24-IR was investigated in the brain and compared to untreated rats. In stimulated animals, the KROX-24-IR was induced in many areas including the lateral reticular nucleus, parabrachial nucleus, periaqueductal gray, hypothalamus, amygdala and lateral habenular nucleus.

Action Potentials↗
PubMed1990

Uridine kinase inhibition is involved in the vasodilator effects of minoxidil in the rat.

1. Since minoxidil is a pyrimidine derivative, its actions on vascular smooth muscle may derive from structural relationships to the uridine nucleotides, which have been shown to be vasoconstrictive in the rat. 2. Minoxidil at a low vasodepressor dose of 0.03 mg/kg per min abolished the pressor response to uridine at doses from 2 to 8 mumol/kg per min, but did not reduce the responses to uridine monophosphate or uridine diphosphate in similar pressor doses, suggesting an action on either transport of uridine into cells or on uridine kinase which catalyses phosphorylation of uridine to uridine monophosphate, the mediator of uridine's vascular actions. 3. The active metabolite of minoxidil was found to inhibit rat liver uridine kinase in vivo using an HPLC technique. 4. Plasma uridine concentration was significantly higher in 11 hypertensive patients on minoxidil compared with pretreatment values, suggesting that uridine kinase inhibition is of a degree sufficient to increase the circulating pool of uridine. 5. The data is consistent with uridine kinase inhibition being a mechanism for the vasodilator actions of minoxidil.

Animals↗