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Biomedical subjects

G C Smith

Publications and source records attributed to G C Smith.

At least 271 records · Page 15Linked to original sources
PubMed1987

Epizootic vesicular stomatitis in Colorado, 1982: some observations on the possible role of wildlife populations in an enzootic maintenance cycle.

Sera obtained from wild ungulates, carnivores, and rodents in Colorado were tested for neutralizing (N) antibody against vesicular stomatitis, New Jersey serotype (VSNJ), virus to determine their involvement in the 1982 Colorado VSNJ epizootic in domestic animals. Viremic and N antibody responses of two local rodent species to a 1982 Colorado isolate of VSNJ were determined in the laboratory. The rodents produced only weak viremias, but all developed N antibody. N antibody prevalences for VSNJ in sera from wild ungulates was sufficiently high to indicate their involvement during the epizootic. In addition, the demonstration of N antibody in elk (Cervus elaphus) and mule deer (Odocoileus hemionus) prior to the epizootic in cattle and horses suggests that an enzootic cycle may exist in Colorado.

Animals↗
PubMed1986

Wheat germ phosphoglycerate mutase: evidence for a metalloenzyme.

Wheat germ phosphoglycerate mutase, exposed to 3.4 M guanidinium chloride at 22 degrees C and pH 7.8, slowly undergoes time-dependent inactivation which can be fully reversed by adding excess Co2+ or Mn2+ to a 50-fold dilution of the denaturing medium. Titration of the denatured enzyme with either Co2+ or Mn2+ shows that wheat germ mutase preferentially binds Co2+. Assuming 1:1 complexation between metal atom and protein, the apparent dissociation constants (Kd) for E Co2+ and E Mn2+ at 22 degrees C and pH 8.7 are approximately 1.06 and 1.84, respectively. Other metal atoms (e.g., Cr2+, Cu2+, Fe2+, Fe3+, Mg2+, and Ni2+) have no effect in restoring the apoenzyme's catalytic activity. At low concentrations (0.11-0.23 mM) Zn2+ partially restores activity, but promotes protein precipitation at elevated concentrations. Evidence suggests that all bisphosphoglycerate-independent phosphoglycerate mutases require either an intra- or an extramolecular metal atom in order to function. Attempts to characterize wheat germ mutase as a glycoprotein have yielded negative results.

Bisphosphoglycerate Mutase↗
PubMed1986

The measurement of fetal systolic time intervals: lessons from ultrasound.

Fetal systolic time intervals (pre-ejection period, iso-volumetric contraction time and ventricular ejection time) can be measured using Doppler ultrasound to detect valve movements and the fetal ECG to indicate the onset of ventricular depolarisation. Continuous recordings of FSTI, fetal heart rate and uterine activity depict changes reflecting progressive cord compression and have the potential for providing improved differentiation of late and variable decelerations. However, the continual adjustment of the ultrasound transducer required to maintain a good signal limits the technique. Recent improvements in phono indicate that this may provide a useful alternative, provided that suitable signal-processing is developed.

Electrocardiography↗
PubMed1986

Central and peripheral proglumide administration and cholecystokinin-induced satiety.

Peripheral (50 mg/ml) or central (50 micrograms/microliter) injections of proglumide were made into Sprague-Dawley rats which displayed satiety-like responses after the peripheral (100 micrograms/kg) or central (50 ng in 1 microliter) administration of cholecystokinin (CCK). The satiety produced by CCK injection into the lateral hypothalamus, area postraema and ventromedial hypothalamus was significantly reversed by proglumide injections into these areas during a 4 h food intake test. Peripheral injection of proglumide after central or peripheral CCK injection did not modify this type of CCK-induced satiety. Central proglumide injection produced a reliable decrease in water intake and this is compatible with previous findings which describe the stimulation of water intake after central gastrin administration. These results suggest that various central and peripheral mechanisms which are involved in the regulation of appetite may function independently as a 'failsafe' system.

Animals↗
PubMed1986

The amine accumulation-producing capacity of 6-hydroxydopamine and its neurochemical specificity.

There was considerable research during the 1970's addressing the problem of the neurospecificity of 6-hydroxydopamine (6-OHDA). Despite the numerous attempts to define the criteria governing the use of this drug in experimental paradigms, some believed that specific damage to catecholamine (CA)-containing neurones could be achieved only by controlling the dose injected, while others claimed that the neurotoxic effect that this drug had on non-CA systems was so severe that it contraindicated its use experimentally. The issue still remains unresolved. In the present study, we examined the degree of neurochemical specificity produced by 6-OHDA or radiofrequency (RF) lesions by comparing the quantity of amine accumulation to the amount of physical damage at the lesion site (termed non-specific damage, NSD) which each technique produced. The volume of NSD produced by 6-OHDA (2 microliter of 8 micrograms/ul) was significantly less than that produced by large RF lesions (60 degrees C for 50 sec) both of which has a similar effect on the regulation of short term body weight. Both types of lesions produced similar quantities of amine accumulation. Smaller RF lesions (45 degrees C for 30 sec) produced the same amount of NSD as did 6-OHDA but significantly less amine accumulation and had no effect on body weight regulation. The ratio of NSD to amine accumulation in 6-OHDA treated rats was 3/1 while large and small RF lesions produced a NSD/accumulation ratio of 15/1. The present results reveal that the neurochemical specificity of 6-OHDA is several magnitudes greater than with RF lesions, when using the criteria as defined in the present experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Characterization of cattle of a five-breed diallel: VI. Fat deposition patterns of serially slaughtered bulls.

Dissection and chemical analysis data from 197 bulls of 15 breedtypes were used to examine the distribution of total fat (TOTFAT) among carcass fat (CFAT), viscera fat (VIF), kidney plus pelvic fat (KPF) and blood fat (BLF). The bulls were obtained from a five-breed diallel involving Angus, Brahman, Hereford, Holstein and Jersey; reciprocal crosses were pooled. One or two bulls of each breedtype were slaughtered at each of seven ages: 6, 9, 12, 15, 18, 24 and 30 mo. An allometric equation was utilized to describe growth rate of each fat depot relative to either TOTFAT or carcass side weight (CSW). The pooled within-breedtype differential growth rates obtained from the allometric equation indicated that as TOTFAT or CSW increased, the proportion composed of CFAT and KPF increased (growth coefficients significantly greater than 1), whereas the proportion composed of VIF and BLF decreased (growth coefficients significantly less than 1). Holstein and Jersey tended to have more CFAT than Hereford, Angus and Brahman. Jersey had more KPF than other breeds. Crossbreds exhibited positive heterosis for CFAT and VIF, and negative heterosis for KPF. On a constant CSW basis, there were no significant breedtype differences in TOTFAT: nevertheless, differences in fat distribution among breedtypes persisted. There were different amounts of fat at the depots studied, but fat growth coefficients relative to TOTFAT tended to be homogeneous among breedtypes.

Adipose Tissue↗
PubMed1986

Distribution of Bunyamwera serogroup viruses in North America, 1956-1984.

We attempted to tabulate all Bunyamwera serogroup (family Bunyaviridae, genus Bunyavirus) isolates from North America. By summarizing information from the laboratories of the Centers for Disease Control, data generously shared by other laboratories, and the published literature, we were able to accumulate data regarding 1,372 Bunyamwera serogroup viruses. These were: Tensaw (664, including 8 from vertebrates), Cache Valley (396, including 6 from vertebrates), Main Drain (160, including 14 from vertebrates), Lokern (69, including 8 from vertebrates), Northway (13, including 5 from vertebrates), Tlacotalpan (7), Santa Rosa (2), Santa Cruz (1 from a horse), and 60 of undetermined serotype. Virus isolation rates by month of collection were correlated with collection efforts, but associations of viruses and arthropod vectors varied by location, vertebrate host, and arthropod distribution. Tensaw virus was isolated principally from Anopheles crucians mosquitoes (466/656 isolates from arthropods) in the southeastern United States; Cache Valley virus principally from An. quadrimaculatus (94), Coquillettidia perturbans (59), Culiseta inornata (45), Aedes sollicitans (30), Psorophora columbiae (23), An. punctipennis (18), and Ae. vexans and trivittatus (18 each) mosquitoes (total = 305/382 isolates from arthropods from all of the United States and Canada, except the southeastern United States); Main Drain virus from Culicoides variipennis (31), Culicoides (Selfia) sp. (65), and Psorophora (23) and Aedes (21) species mosquitoes in the western United States; Lokern virus from Culicoides species (55/61 isolates from arthropods) in the western United States. Relationships between vector and vertebrate host distributions are discussed briefly in regard to geographic distribution of the Bunyamwera serogroup viruses.

Aedes↗
PubMed1985

Wheat germ phosphoglycerate mutase: purification, polymorphism, and inhibition.

An improved method for purifying the bisphosphoglycerate-independent phosphoglycerate mutase from wheat germ has been devised. The method yields enzyme with a specific activity of 2,300 units/mg in 0.1 M Tris-C1 at pH 8.7 and 30 degrees C. Electrophoresis on electrofocusing and analytical polyacrylamide gels reveals only one protein band (pI = 7.3); however, under denaturing conditions (sodium dodecyl sulfate polyacrylamide gel electrophoresis), two prominent enzyme forms, with molecular masses of 63 and 74 kDa, manifest themselves along with several minor, high molecular mass components (126-141 kDa). Non-denaturing exclusion chromatography shows that both major species are catalytically active, and suggests that each species is capable of participating in reversible monomer/dimer association. Wheat germ mutase is inhibited by time-dependent reactions involving either polydentate chelators or sulfhydryl reagents.

Bisphosphoglycerate Mutase↗
PubMed1985

Microspectrofluorometric characterization of amine accumulation proximal to lateral hypothalamic lesions.

Microspectrofluorometry was employed to identify the spectral characteristics of the formaldehyde-induced fluorophore derived from amine accumulation proximal to the site of 6-hydroxydopamine injection or radiofrequency lesions in the lateral hypothalamus of Sprague-Dawley rats. The excitation and emission spectra of the accumulation were consistent with that of catecholamines in models subjected to similar formaldehyde treatment. These results indicate that while biochemical assay technique may not permit the quantification of amine accumulations, these areas do in fact represent degeneration associated increases in catecholamines which may be of functional significance.

Animals↗
PubMed1985

Effects of intravenously administered 6-hydroxydopamine on the content of monoamines in the median eminence and neurointermediate lobe of the rat.

The effects of intravenous administration of 6-hydroxydopamine (6-OHDA) on the content of catecholamines in the median eminence and neurointermediate lobe was studied in male rats. The results confirmed previous findings of a depletion of catecholamines in both regions as a result of this lesion, although the magnitude of the effect was less than that revealed by fluorescence histochemistry. Administration of desipramine before 6-OHDA injection produced a more specific lesion, depleting dopamine but leaving noradrenaline unaffected.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1985

Mandibular advancement surgery. A study of the lower border wiring technique for osteosynthesis.

A study was undertaken to evaluate the effectiveness of osteosynthesis achieved by a lower border wire technique. Fifty patients who underwent mandibular advancement surgery were examined cephalometrically during 6 weeks of maxillomandibular fixation. A detailed analysis was made of spatial changes in the proximal and distal segments following bilateral sagittal-split osteotomies.

Adolescent↗
PubMed1985

Amine accumulation in behavioural pathology.

When nigro-striatal and meso-cortical neurons degenerate there is a loss of dopamine in the terminal fields and an accumulation of amines in the axons of these systems as they traverse the hypothalamus through the medial forebrain bundle. Traditional lines of thought have attributed the occurrence of motor and consummatory deficits which occur after dopamine neuron degeneration to the loss of functional dopamine neurotransmitter in the terminal fields. However, we have hypothesized that hypothalamic amine accumulation represents an area of brain tissue where processes such as neurotransmitter release, ephaptic transmission or local axon swelling may be affecting adjacent neurons and may thereby participate in the production of behavioural deficits. There is a considerable amount of evidence from studies on both peripheral and central catecholamine-containing neurons indicating that when their axons degenerate a release of functional neurotransmitter can occur. Information from neuropharmacological studies indicates that several drugs which facilitate behavioural recovery from dopamine-depleting lesions may do so by affecting amine release or receptor sensitivity near areas of accumulation rather than depleted terminal fields. We conclude that amine accumulation is a component of dopamine neuron degeneration which should be considered when assessing the role of the central catecholamine systems in the control of various behavioural and physiological processes.

Animals↗
PubMed1985

Catecholamine-blocking drugs injected at sites of amine accumulation reverse catecholamine degeneration associated deficits.

It has been hypothesized that catecholamine (CA) accumulation in the axons of degenerating neurons may represent areas of functional neurotransmitter, and may be producing some of the consummatory and locomotory deficits which occur after central CA-depleting lesions. To test this hypothesis further, haloperidol (0.5 microliter of a 7 nM sol.), propranolol (0.5 microliter of a 175 nM sol.) or isotonic saline (0.5 microliter) were injected 1.5 h, 24 h and 48 h after the injection of 6-hydroxydopamine (6-OHDA; 2 microliter of 8 micrograms/microliters) into the lateral hypothalamus (LH) of Sprague-Dawley rats to determine if the hypothermia, motor impairment and consummatory deficits could be reversed. Although haloperidol injection significantly enhanced the hypothermia seen 1.5 h after 6-OHDA injection, open field performance and consummatory responses were significantly improved after haloperidol was injected into the LH where accumulation is known to occur. Three consecutive days of intracerebral haloperidol treatment produced a recovery of body weight regulation lasting for 6 days. Treatment with propranolol enhanced open field performance 1 day after 6-OHDA injection but failed to enhance recovery of consummatory behaviour and body weight control. These results suggest that CA released from areas of accumulation act on adjacent CA receptors to participate in the production of behavioural deficits previously attributed only to the loss of functional neurotransmitter in terminal fields in the forebrain.

Animals↗
PubMed1985

Apoprotein-B binding sites in estrogen-treated rabbit liver: quantitative immunoelectron microscopy.

Normal and estrogen-treated rabbit livers were perfused with iodinated very low density lipoproteins (125I-VLDL) and binding and cellular distribution of apolipoprotein (Apo)-B rich lipoproteins in hepatocytes was analyzed using quantitative immunoelectron microscopic and autoradiographic techniques. Apo-B containing particles were bound to and internalized through the formation of endocytotic pits and vesicles with considerably more binding to estrogen-treated specimens (2-fold). Thus, estrogen treatment stimulates Apo-B binding and subsequent internalization of the Apo-B containing particles by increasing the number of endocytotic pits. In contrast to the estrogen induced liver distribution change of Apo-E reported previously, the Apo-B distribution was not changed due to estrogen treatment.

Animals↗