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Biomedical subjects

G Lewis

Publications and source records attributed to G Lewis.

At least 253 records · Page 14Linked to original sources
PubMed1986

Interferons and tumor necrosis factors have similar catabolic effects on 3T3 L1 cells.

The effect of a variety of cytokines on lipid metabolism in 3T3 L1 mouse fibroblasts and adipocytes was studied. Uptake of [3H]acetate by adipocytes and heparin-releasable lipoprotein lipase activity was inhibited after treatments of the cells with picomolar concentrations of recombinant human tumor necrosis factor alpha (rHuTNF-alpha), human tumor necrosis factor beta (rHuTNF-beta, also called lymphotoxin), murine interferon-gamma (rMuIFN-gamma), and a human hybrid interferon-alpha [rHuIFN-alpha 2/alpha 1 (Bgl II)]. Recombinant human interferon-gamma (rHuIFN-gamma), natural human colony-stimulating factor (HuCSF), and human interleukin 2 (HuIL-2) had no effect. Similar though less-marked suppression of [3H]acetate uptake by cytokines was seen in 3T3 L1 fibroblasts. Cytokines inhibited the incorporation of [3H]acetate into both membrane and storage lipids in the adipocytes. In addition to blocking lipid uptake and synthesis, rHuTNF-alpha and -beta, and rMuIFN-gamma stimulated the release of free fatty acid into the medium from adipocytes. Binding studies suggest that rHuTNF-alpha and rHuTNF-beta compete for the same cell-surface receptor on 3T3 L1 adipocytes, while rMuIFN-gamma binds to a separate receptor. The binding of rTNF-alpha to both adipocytes and fibroblasts can be significantly enhanced by preexposure of the cells to rMuIFN-gamma. There appear to be both high- and low-affinity receptors for rHuTNF-alpha on adipocytes, whereas fibroblasts exhibit a single class of high-affinity receptors. These results suggest that a variety of structurally distinct cytokines possess lipid mobilization activity, which may be of critical importance to the host in defense against infection or malignancy.

Acetates↗
PubMed1985

Zinc toxicity, copper deficiency and anaemia in swill-fed pigs.

Zinc toxicity, copper deficiency and an associated anaemia among weaned swill-fed pigs is described. The source of zinc was flaking galvanising from the inside of bins used to store swill before processing. The disease condition readily responded to supplementation of the diet with copper sulphate. The interactions between dietary zinc, copper and calcium are discussed with reference to the swill-feeding industry. It is concluded that supplementary copper should be routinely included in the ration of swill-fed pigs and that the use of galvanised bins for storing swill should be avoided.

Anemia↗
PubMed1985

Observers' reaction to touchers.

20 men and 20 women were shown nine photographs in which two people were interacting. The first photograph shown showed a male and a female engaged in a nontouching interaction. The remaining eight photographs showed a touching interaction. Subjects rated their affective reaction to each of the touching interactions relative to their reaction to the first (nontouch) interaction. In the latter 8 photographs, the person facing the camera was either male or female, the person with back to camera was either male or female, and the touch shown was either a hand touch or a hug. All touching interactions were rated more positively than the standard (nontouch interactions). Male and female subjects tended to show identical reactions to the photographs. More positive reactions were shown to cross-sex hugging than to same-sex hugging and interactions showing hand touch.

Adolescent↗
PubMed1984

Evaluation of brain chloride determinations in the diagnosis of water deprivation/sodium salt intoxication in pigs.

In a series of pig brains submitted from field cases where water deprivation/sodium salt intoxication was suspected, histopathological examinations and chloride determinations were performed. A poor correlation was found between brain chloride concentration and neuropathology. The ranges of chloride concentrations found were similar for brains showing the encephalopathy of water deprivation/sodium salt intoxication, brains with other neuropathological diagnoses and brains without significant histopathological lesions. A close correlation was found between brain sodium and chloride in a further similar series, suggesting that determinations of sodium would not be more helpful diagnostically than determinations of chloride. A wide range of brain chloride values was also found in a group of healthy slaughtered pigs but the significance of this was not apparent. Brain chloride determinations have little value in the diagnosis of water deprivation/sodium salt intoxication in pigs, especially when performed in isolation without concurrent neuropathology and an adequate clinical history.

Animals↗
PubMed1984

Arterial digital subtraction angiography with particulate intravascular embolization and angioplasty.

The authors are reporting their experience with arterial digital subtraction angiography to monitor particular intravascular embolization in hypervascular tumors and malformations and angioplasty. Arterial digital subtraction angiography may reduce the time of waiting for regular film developing and subtraction. The smaller amount of contrast material being used in arterial digital subtraction angiography minimizes the discomfort to the patients. It also prevents further renal damage in those patients with poor renal function. The arterial digital subtraction angiography may detect the early warning signs of embolotherapy. From the past experience, the authors have found that arterial digital subtraction angiography should be considered as a better alternative way to performing the particulate embolization and angioplasty than being monitored by conventional angiography.

Adult↗
PubMed1983

A collaborative study of the measurement of glycosylated haemoglobin by several methods in seven laboratories in the United Kingdom.

A collaborative study compared methods for measuring glycosylated haemoglobin in seven laboratories in the United Kingdom. No satisfactory standard for general use was found. Satisfactory internal quality control systems were in use for each assay which allowed the maintenance of a normal range in each participating laboratory. No satisfactory quality control system suitable for general use could be identified. Costs and convenience of the assays are reported. The technical problems with each type of assay and precautions for their use were identified, such as the need for standardization in incubation times, the practicability of automation of colorimetric assays, and the precision of pH needed for buffers in column separation methods. The relevance of the technical problems to interpretation of measurements is also considered. It is concluded that laboratories measuring glycosylated haemoglobin should maintain a normal range, use 'in-house' quality controls to monitor assay performance and keep clinical colleagues informed of the findings and of any changes in methodology that might affect the interpretation of results.

Autoanalysis↗
PubMed1982

A quantitative analysis of stereotyped gnawing induced by apomorphine.

An apparatus was designed and constructed to enable a quantitative analysis of the stereotyped gnawing produced by the dopamine agonist apomorphine. Using this apparatus it was discovered that increasing the subcutaneous dose of apomorphine increased (1) the number of animals that gnawed, and (2) the duration of gnawing in those animals that gnawed at all doses. Other aspects of apomorphine-induced gnawing, in particular the latency to respond and the frequency and duration of individual gnaws, were relatively unaffected. Likely properties of the system responsible for the organization of sterotyped gnawing are discussed.

Animals↗
PubMed1982

Locomotor activity of rats in open field after microinjection of procaine into superior colliculus or underlying reticular formation.

Whereas large lesions of the superior colliculus in rats increase locomotor activity in the open field, bilateral collicular microinjections of muscimol (an agonist of the inhibitory neurotransmitter GABA) have been reported to reduce open-field activity. This difference might be due to muscimol's acting on a subpopulation of collicular neurones, or to some feature of the microinjection technique. The issue was investigated by observing open-field behavior after reversible lesions produced by bilateral microinjections of the local anaesthetic procaine (10-300 micrograms in 0.5 microliter) into midbrain sites. Injections of procaine into the superior colliculus produced effects similar to those reported after muscimol injections: both locomotor activity and other exploratory responses were suppressed, with the rats spending much of their time motionless in an alert posture. In contrast, animals with injections of procaine into the mesencephalic reticular formation (MRF) ventral to the superior colliculus resembled rats given large collicular lesions: they showed very striking increases in locomotor activity, while their rearing and exploratory head movements were reduced. It is suggested that in some experiments large collicular lesions may have increased locomotor activity in the open field because they invaded underlying MRF. However, it is also possible that in rodents the acute effects of collicular inactivation, as assessed by microinjection of muscimol or procaine, are different from the chronic effects that are observed in experiments with electrolytic or radiofrequency lesions.

Animals↗
PubMed1981

Gnawing and changes in reactivity produced by microinjections of picrotoxin into the superior colliculus of rats.

Lesions of the superior colliculus in rats attenute the oral stereotypy produced by systemic administration of dopamine agonists. Current evidence suggest that such drugs affect the superior colliculus by reducing transmission in the inhibitory GABAergic nigrotectal pathway. To investigate whether the superior colliculus plays a direct role in producing stereotyped oral movements, the present experiment therefore examined the effects of collicular microinjections of the GABA antagonist picrotoxin on the behaviour of rats observed in an open-field. Gnawing was observed after injections of picrotoxin (25 ng) into sites in the intermediate and deep layers of the superior colliculus, consistent with the superior colliculus playing a direct part in producing the stereotyped gnawing seen after systemic administration of dopamine agonists. However, gnawing was only observed after a period in which the animal showed strong avoidance reactions to stimuli that normally evoked orienting or little reaction. This change in reactivity was observed after injections of picrotoxin into all parts of the colliculus, but the most sensitive (responding to doses as low as 12.5 ng) were mainly in the superficial and intermediate layers. It appears that there may be more than one GABAergic system within the superior colliculus.

Animals↗
PubMed1980

Fluctuations of Pa, CO2 with the same period as respiration in the cat.

1. A CO2 sensor using mass spectrometry is described. It responds linearly to O2 and CO2 with a time constant of 0.5 sec: it is not affected by pressure or flow in the physiological range: its temperature coefficient is 4 mm Hg PCO2 per degree C at 37 degrees C. 2. When this sensor and its through flow cuvette were placed in a common carotid artery-to-jugular vein loop in anaesthetized cats breathing spontaneously or being ventilated artificially, fluctuations of Pa, CO2 which had the same period as respiration were readily observed. 3. The amplitude of these fluctuations varied inversely with respiratory frequency being less than 1.5 mmHg Pa, CO2 in the range of normal respiratory frequencies in the cat, 25--35 min-1. The amplitude also varied with the mixed venous-to-end tidal CO2 difference which was altered either by giving the cat CO2 to inhale or infusing CO2 intravenously. 4. We have concluded that these fluctuations of Pa, CO2 are unlikely to provide a significant drive to ventilation at normal respiratory frequencies but they may provide a signal that gas exchange in the lung is less than optimal.

Animals↗
PubMed1978

Solanum malacoxylon toxicity to pigs.

Newly weaned pigs were given Solanum malacoxylon at dose rates of 0.2 and 1.0 g per kg body-weight per week for eight weeks. The Solanum malacoxylon was given either as an aqueous extract (SM) or as an aqueous extract incubated with fresh rumen liquor (SMLR). Tubulonephrosis, dose related in severity, was evident in all treated pigs and focal calcification in kidney and lung occurred in pigs receiving the higher dose rate. There was a marked hypercalcaemia and hypophosphataemia over the trial period; the latter feature was in contrast with the hyperphosphataemia produced in sheep. Incubation of SM with rumen liquor enhanced hypophosphataemia at both dose levels in the pig but its effect on serum calcium was equivocal.

Animals↗