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Biomedical subjects

E H Campbell

Publications and source records attributed to E H Campbell.

17 recordsLinked to original sources
PubMed2000

Effects of protein kinase and phosphatase inhibitors and anti-L antisera on K+ transport in LK sheep red cells.

We investigated the role of protein phosphorylation in the action of anti-L on low potassium (LK) sheep red cells. Anti-L stimulated the Na/K pump by four- to fivefold, but Na/K pump activity in anti-L-stimulated or in control cells was unaffected by protein kinase/protein phosphatase (PK/PP) inhibitors. KCl co-transport activity was inhibited by anti-L (about 50%). Co-transport was stimulated by staurosporine; and inhibited by calyculin A, okadaic acid, tyrphostin B46 and genistein; with a similar pattem in both control and anti-L-treated cells. O2 sensitivity of KCl co-transport was similar in control and anti-L-treated cells. Neither control nor anti-L-stimulated Na/K pump activities were O2 sensitive. Incubation with urea stimulated KCl co-transport in both control and anti-L-treated cells. Inhibition of co-transport by anti-L was unaffected by low concentrations of urea but was reduced at higher urea concentrations. Na/K pump activity of control cells was unaffected by incubation with urea, but that in cells stimulated by anti-L was reduced, though not significantly. Under high hydrostatic pressure, KCl co-transport was stimulated, and the inhibitory effects of PP inhibition (okadaic acid), anti-L or combinations of the two were reduced. Results suggest that anti-L does not affect K+ transport in LK sheep red cells via protein phosphorylation.

Animals↗
PubMed1999

Oxygen-dependent K+ influxes in Mg2+-clamped equine red blood cells.

1. Cl--dependent K+ (86Rb+) influxes were measured in oxygenated and deoxygenated equine red blood cells, whose free [Mg2+]i had been clamped, to examine the effect on O2 dependency of the K+-Cl- cotransporter. 2. Total [Mg2+]i was 2.55 +/- 0.07 mM (mean +/- s.e.m. , n = 6). Free [Mg2+]i was estimated at 0.45 +/- 0.04 and 0.68 +/- 0. 03 mM (mean +/- s.e.m., n = 4) in oxygenated and deoxygenated red cells, respectively. 3. K+-Cl- cotransport was minimal in deoxygenated cells but substantial in oxygenated ones. Cl--dependent K+ influx, inhibited by calyculin A, consistent with mediation via the K+-Cl- cotransporter, was revealed by depleting deoxygenated cells of Mg2+. 4. Decreasing [Mg2+]i stimulated K+ influx, and increasing [Mg2+]i inhibited it, in both oxygenated and deoxygenated red cells. When free [Mg2+]i was clamped, Cl--dependent K+ influxes were always greater in oxygenated cells than in deoxygenated ones, and changes in free [Mg2+]i of the magnitude occurring during oxygenation-deoxygenation cycles had a minimal effect. Physiological fluctuations in free [Mg2+]i are unlikely to provide the primary link coupling activity of the K+-Cl- cotransporter with O2 tension. 5. Volume and H+ ion sensitivity of K+ influx in Mg2+-clamped red cells were increased in O2 compared with those in deoxygenated cells at the same free [Mg2+]i, by about 6- and 2-fold, respectively, but again these features were not responsible for the higher fluxes in oxygenated cells. 6. Regulation of the K+-Cl- cotransporter by O2 is very similar in equine, sheep and in normal human (HbA) red cells, but altered in human sickle cells. Present results imply that, as in sheep red cells, O2 dependence of K+-Cl- cotransport in equine red cells is not mediated via changes in free [Mg2+]i and that cotransport in Mg2+-clamped red cells is still stimulated by O2. This behaviour is contrary to that reported for human sickle (HbS) cells.

Animals↗
PubMed1998

Oxygen-dependent K+ fluxes in sheep red cells.

1. This study was designed to investigate the O2 dependence of K+ influx in sheep red cells. Influx was determined using 86Rb+ as a tracer for K+; glass tonometers coupled to a gas mixing pump were used to equilibrate cell samples to the requisite oxygen tension (PO2). 2. Both volume- and H(+)-stimulated K+ influxes in low potassium-containing (LK) sheep red cells were approximately doubled on equilibration with O2 relative to influxes measured in N2.O2-dependent influxes were abolished when Cl- was replaced with NO3-, consistent with mediation by the KCl cotransporter. At pH 7, PO2 required for half-maximal stimulation was 56 +/- 1 mmHg (mean +/- S.E.M., 3 sheep) for the O2-dependent component of K+ influx: thus PO2 values over the physiological range affected K+ influx. 3. K+ influx in fully deoxygenated sheep red cells showed substantial volume and H+ sensitivity. These residual components in N2 were also Cl- dependent, indicating that the KCl cotransporter of LK sheep red cells was active in the absence of O2. 4. Volume-sensitive K+ influxes in high potassium-containing (HK) sheep red cells responded in a similar way to those in cells from LK sheep, although much smaller in magnitude, showing that intracellular [K+] had no significant effect on the O2 dependence of the cotransporter. 5. Intracellular [Mg2+] ([Mg2+]i) was altered by incubating sheep red cells with A23187 (20 microM) and different values of extracellular [Mg2+] ([Mg2+]o). Total [Mg2+]i was determined by atomic absorption spectroscopy and free [Mg2+]i from [Mg2+]o and the Donnan ratio. Total [Mg2+]i was 1.29 +/- 0.08 mM (mean +/- S.E.M., n = 5), similar to that reported in the literature. Estimates of free [Mg2+]i showed an increase from 0.39 +/- 0.05 in oxygenated cells to 0.52 +/- 0.04 mM (mean +/- S.E.M., n = 5; P < 0.05) in deoxygenated ones. 6. Finally, although K+ influxes were altered by pharmacological loading or depletion of cells with Mg2+, the free [Mg2+]i required to affect influxes significantly was outside the physiological range. Results are difficult to reconcile with PO2 modulating KCl cotransport activity directly via changes in free [Mg2+]i or [Mg(2+)-ATP]i.

Animals↗
PubMed1998

A permeability barrier in the dorsal wall of the equine hoof capsule.

The permeability barrier in the dorsal wall of the equine hoof capsule was studied by means of horseradish peroxidase (HRP) in 0.9 N saline solution as a water soluble tracer. Section were treated with 3'3'-diaminobenzidine tetrachloride (DAB) and before dissection the quality of the horn of feet from 10 horses was assessed and given a subjective grade as either good or poor. Blocks of tissue from each horse were left in either an oven at 60 degrees C or in water for 2 weeks before treatment in HRP, sectioning and DAB solution. Regions observed were i) outer surface, ii) outermost layers of the horn, iii) cut edge of the outer layer, iv) inner layer of horn, v) cut edge of the inner layer and vi) laminae. Horn deemed to be normal horn and of good 'quality' showed very slight penetration of HRP 3-5 cell layers deep in the outer layer. The cut edge of the outer layer of the wall of the 'normal' horn also showed minimal penetration of HRP through the intercellular spaces. The cut edge of the inner layers of the wall of normal, good quality horn showed penetration of the tracer up to 20 cell layers deep, with HRP in both the intercellular spaces and within the cells. In contrast, sections of horn from horses with brittle feet showed deep cracks in the outer surface into which the HRP had penetrated. Good quality horn showed no change in the position of the permeability barrier after soaking in water for 14 days, but the brittle horn showed an increase in permeability to HRP. In brittle horn, reaction product was seen deep within the section in the intercellular spaces of the intertubular horn only. Placing horn in an oven had no effect on the permeability barrier. The permeability barrier of the dorsal wall of the equine hoof capsule differs with the layer of the wall. Horn considered to be of poor quality had a weaker permeability barrier than horn of good quality.

Animals↗
PubMed1996

Empirical, automated vocabulary discovery using large text corpora and advanced natural language processing tools.

A major impediment to the full benefit of electronic medical records is the lack of a comprehensive clinical vocabulary. Most existing vocabularies do not allow the full expressiveness of clinical diagnoses and findings that are often qualified by modifiers relating to severity, acuity, and temporal factors. One reason for the lack of expressivity is the inability of traditional manual construction techniques to identify the diversity of language used by clinicians. This study used advanced natural language processing tools to identify terminology in a clinical findings domain, compare its coverage with the UMLS Metathesaurus, and quantify the effort required to discover the additional terminology. It was found that substantial amounts of phrases and individual modifiers were not present in the UMLS Metathesaurus and that modest effort in human time and computer processing were needed to obtain the larger quantity of terms.

Medical Records↗
PubMed1988

The effect of tumour growth on liver pantothenate, CoA, and fatty acid synthetase activity in the mouse.

Enzymatic, and microbiological assays were used to determine the hepatic contents of coenzyme A, acetyl CoA, fatty acid synthetase activity, and pantothenate in livers of tumour-bearing mice. Significant decreases in CoA and acetyl CoA were found in mice bearing TLX-5 lymphoma, sarcoma 180 or a fibrosarcoma. These changes were accompanied by significant decreases in pantothenate and increases in 4-phosphopantothenate suggesting an increase in pantothenate kinase activity due to reduction of CoA inhibition of the enzyme. In contrast, large increases were found in pantothenate and 4-phosphopantothenate in mice bearing TLX-5 lymphoma, i.p. or s.c. These changes could be due to a large reduction in the rate of conversion of an intermediate in the pathway of CoA, or increased production of pantothenate or 4-phosphopantothenate from the degradation of CoA or the phosphopantetheine residue in fatty acid synthetase. Activities of fatty acid synthetase in liver of mice bearing this tumour showed marked decreases, but were insufficient to account for the increase in pantothenate, and may reflect a reduction in cytosolic CoA needed for the conversion of the apo to the holoenzyme.

Acetyl Coenzyme A↗
PubMed1967

Drug effects in squirrel monkeys trained on a multiple schedule with a punishment contingency.

The behavior of four monkeys trained on a multiple schedule was differentially sensitive to selected pharmacological agents. The three components of the multiple schedule were: (1) a variable-interval schedule in which responses were reinforced on the average of once per minute; (2) a concurrent schedule in which every tenth response was reinforced and every fifteenth response, on the average, was shocked; and, (3) a neutral stimulus in the presence of which responses were neither reinforced nor shocked. Pentobarbital, chlordiazepoxide, and meprobamate increased responding during each of the components. Scopolamine and d-amphetamine decreased variable-interval performance, had minimal effects on performance during the concurrent-schedule component, and increased responding in the presence of the neutral stimulus. Chlorpromazine decreased variable-interval responding and had slight effects on the responding during the other two components.

Animals↗