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Biomedical subjects

R H Smith

Publications and source records attributed to R H Smith.

At least 19 recordsLinked to original sources
PubMed1992

Characterization of the regulatory functions of the equine herpesvirus 1 immediate-early gene product.

Use of the translation-inhibiting drug cycloheximide has indicated that the equine herpesvirus 1 (EHV-1) immediate-early (IE) gene, the sole EHV-1 IE gene, encodes a major viral regulatory protein since IE mRNA translation is a prerequisite for all further viral gene expression (W.L. Gray, R. P. Baumann, A. T. Robertson, G. B. Caughman, D. J. O'Callaghan, and J. Staczek, Virology 158:79-87, 1987). An EHV-1 IE gene expression vector (pSVIE) in combination with chimeric EHV-1 promoter-chloramphenicol acetyltransferase (CAT) reporter constructs was used in transient transfection assays to characterize the regulatory functions of the IE gene product. These experiments demonstrated that (i) the EHV-1 IE gene product is a bifunctional protein capable of both positive and negative modulation of gene expression; (ii) the IE gene product possesses an autoregulatory function which represses the IE promoter; (iii) IE autoregulation is dependent on IE promoter sequences mapping within positions -288 to +73 relative to the transcription initiation site (+1) of the IE gene; (iv) the IE gene product can independently activate the EHV-1 tk promoter (an early promoter) by as much as 60-fold; (v) two EHV-1 beta-gamma (leaky late) promoters, those of IR5 (gene 5 in the inverted repeat) and the glycoprotein D gene, demonstrate a requirement for both the IE gene product as well as a gene product encoded within the EHV-1 XbaI G fragment for significant activation; and (vi) the IE gene product is capable of activating heterologous viral promoters.

Animals↗
PubMed1979

Role of endothelium in sequestration of lipoprotein and firbrinogen in aortic lesions, thrombi, and graft pseudo-intimas.

In the soft, gelatinous thickenings that appear to be the precursors of fibrous plaques, concentrations of plasma low-density lipoproteins (LP) and fibrinogen were three to four times higher than that in normal intima, but their concentrations of fibrin was not significantly higher. By contrast, in 60% of cholesterol-rich areas from more advanced plaques, fibrin (mean concentration 22.7 mg/100 mg lipid-extracted dry weight) was ten times higher than normal, and this was associated with a twelve-fold increase in a bound LP fraction that was released by incubation with fibrinolytic enzymes. The origin of this fibrin is uncertain, and to test similarity of fibrin in the lesion with that of mural thrombus free and bound LP, fibrinogen, and cholesterol were measured in thrombi and pseudo-intimas from prosthesis grafts. In the pseudo-intimas and the thrombi that were not covered with endothelium the concentrations of all these substances were very low, but in thrombi covered with endothelium the concentrations of free and bound LP were similar to those in intimal lesions. Thus, endothelialisation appears to promote accumulation of LP in mural thrombi.

Aged↗
PubMed1979

Pharmacokinetic model for procaine in humans during and following intravenous infusion.

A multicompartment pharmacokinetic model is presented to describe procaine distribution in humans during and following intravenous infusion. The model, based on a general perfusion model, relates individual characteristics such as sex, age, weight, height, infusion rate and duration, and hematocrit to general parameters such as drug metabolism, protein binding, ion-trapping effects, and tissue-plasma distribution coefficients to provide an individualized distribution prediction. Experimentally observed kinetics of blood procaine levels collected during intravenous procaine infusion as an adjunct to surgical anesthesia and blood lidocaine levels obtained from the literature compared very well with the model simulation.

Humans↗
PubMed1979

The origin of nitrogen incorporated into compounds in the rumen bacteria of steers given protein- and urea-containing diets.

1. Two young Friesian steers fitted with rumen cannulas were each given three different isonitrogenous and isoenergetic diets for successive periods of 2-3 weeks. The diets consisted mainly of straw and tapioca, with the nitrogen supplied mainly as decorticated groundnut meal(DCGM; diet A), in approximately equal amounts of DCGM and urea (diet B), or entirely as urea (diet C). 2. At the end of each period on a given diet, part of the dietary urea of a morning feed was replaced by a solution of [15N]urea which was infused into the rumen. Samples of rumen contents were removed just before giving the 15N dose and at 1,3,5,7 and 24 h afterwards, concentrations of ammonia and its 15N enrichment were determined and samples of mixed bacteria were prepared. Amino acids, ammonia derived mainly from amide groups, and hexosamines were prepared by ion-exchange chromatography of acid-hydrolysates of the bacteria and analysed for 15N. 3. Approximate estimates of net bacterial N synthesis were made from turnover data for rumen fluid and 15N enrichments in rumen fractions. From the determined efficiency of incorporation of urea-N into bacteria recovered at the duodenum, it was calculated that on diets A, B and C respectively 82%, 37% and 0% of the bacterial N was derived from dietary protein or other non-urea sources. 4. [15N]urea was converted rapidly to ammonia and the 15N then incorporated into bacterial amide-N; it appeared at a slower rate in total bacterial non-amide-N. Rates of incorporation into non-amide-N were highest for glutamic acid, aspartic acid and alanine, and generally lowest for proline (pro), histidine (his), phenylalanine(phe), arginine(arg), methionine(met) and galactosamine. A similar ranking was also generally observed for relative 15N abundances (15N atoms % excess in N component divided by 15N atoms % excess in total bacterial N) achieved after several hours. Relative 15N abundances in his, arg and pro increased with decreasing protein (DCGM) in the diet but those in the other protein amino acids, including the poorly labelled met, phe (and its derivative tyrosine) did not. 5. It was concluded that different extents of labelling of the amino acids (at least those present mainly in protein) indicated that different amounts of preformed units (amino acids or peptides) were used. When an adequate supply of such units was available (particularly on diet A) pro, arg, his, met and phe were derived in this way to a greater extent than the other amino acids, but whereas synthesis of pro, arg and his increased on the low-protein diet C, that of met and phe did not. Thus met and phe may be limiting for bacterial growth on diets low in protein and high in non-protein-N. 6. Differences in the extent of labelling of other bacterial N components may be due to different turnover rates.

Amino Acids↗
PubMed1978

Absorption of magnesium by the young steer.

1. Steers with rumen and simple duodenal cannulas were allowed to graze pasture or were given diets of dried grass or flaked maize with or without hay. For an experiment a solution or suspension of magnesium chloride, polyethylene glycol (molecular weight 4000) and either 144Ce (as cerous chloride) or chromic oxide was added to the rumen with a morning feed. Conditions in the rumen were sometimes modified by adding sodium chloride or hydrochloric acid. 2. Changes in magnesium:marker in samples of strained rumen contents with time interval after adding the dose were due partly to changes in Mg distribution between different phases. Results indicated, but not unequivocably, that negligible amounts of Mg were absorbed in the first few hours. 3. Relative recoveries of Mg and markers at the duodenum indicated that proportions of Mg intake absorbed (net) varied from approximately zero for pasture to 0.2--0.5 for flaked maize. Significant correlations between absorption efficiency and sodium:potassium in rumen contents (positive) and rumen pH (negative) were observed. 4. Steers with simple duodenal and re-entrant ileal cannulas were given a diet of flaked maize and hay supplemented with different amounts of magnesium oxide. Little net change in Mg relative to an unabsorbed marker was found between these sites even for a diet containing an Mg supplement of 8 g/kg dry matter.

Animals↗
PubMed1978

Intravenous procaine for general anesthesia in dogs: a new look at an old technic.

New anesthetics have been introduced during the last 25 years which are not without inherent disadvantages. They are expensive, and some produce nephrotoxicity and possibly hepatotoxicity. Although the use of procaine intravenously as an anesthetic has been discarded, probably because of a convulsive effect, it is believed this disadvantage can be controlled by concomitant use of other drugs. Hence procaine, preceded by thiamylal, was administered to dogs to test its anesthetic capability, reversibility, and effects on the cardiovascular and central nervous systems. Blood levels of procaine were measured and correlated with these physiologic responses. Convulsive doses were ten times those producing anesthesia. There were no detrimental effects which would preclude a reevaluation in humans. Intravenous procaine produces definite general anesthesia, and it has the additional advantages of being rapidly hydrolyzed and providing antiarrhythmic effects. It may prove useful in modern anesthesia.

Anesthesia, General↗
PubMed1978

Measurement of flow and sampling of digesta in the preruminant calf.

1. Methods of measuring and sampling the flow of digesta passing through intestinal cannulas in preruminant calves were studied and compared. 2. The effect of collecting digesta from a duodenal cannula on abomasal emptying in a calf given whole milk was determined. When digesta were collected and returned to the duodenum manually in large amounts (about 200 g) the outflow of abomasal contents was intermittent. When digesta were returned to the animal either manually or automatically in amounts of less than about 50 g abomasal emptying was smooth. 3. An automatic apparatus for measuring and sampling the flow of digesta continuously was developed. The device allowed effluent to be returned smoothly to an ingoing cannula at the same rate that digesta left the outgoing cannula. After a feed of whole milk abomasal contents were observed to enter the duodenum in an orderly series of gushes. Each gush consisted of about 5--30 g of digesta. 4. The apparatus was rearranged to measure the effects of composition of duodenal digesta on abomasal emptying. Replacement of duodenal digesta with a suspension containing heated soyabean flour slowed the abomasal outflow of a feed containing casein. 5. Automatic apparatus was used to collect digesta arriving at the distal ileum. Withholding effluent from the large intestine did not affect the movement of digesta from the ileum.

Abomasum↗