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Biomedical subjects

G Smith

Publications and source records attributed to G Smith.

At least 847 records · Page 47Linked to original sources
PubMed1979

[3H]Uridine uptake by target monolayers as a terminal label in an in vitro cell-mediated cytotoxicity assay.

A terminal labelling method is described for measuring cell-mediated cytotoxicity based on the ability of surviving target cells to incorporate [3H]uridine into their RNA precursor pools. Parameters of the system were examined using whole and damaged embryonic mouse fibroblast monolayers. This assay is less laborious than direct cell counting and gives increased sensitivity at low target to effector cell ratios. The labelling time is short and, unlike similar techniques, it allows target cell monolayers to remain intact after completion of the radioassay and available for histological examination. This is important where heterogeneous target populations are employed since it allows assessment of differential cell killing and eliminates the need for duplicate cultures. The assay was used in conjunction with a well defined mouse popliteal lymph node assay to investigate the appearance of cytotoxic cells during a localised graft versus host response. Results showed a direct correlation between proliferative index and the development of highly specific cell-mediated cytotoxicity.

Animals↗
PubMed1979

Primary postoperative wound infection due to Staphylococcus pyogenes.

Using S. pyogenes as a tracer organism, an examination of the importance of air-borne infection of clean wounds in the modern, plenum-ventilated operating room has been made. It appears that, for most surgical procedures, additional ultra-clean air installations are not necessary. It has been shown that even if the air is sterile, the skin remains a possible source of infection. This is especially so as far as the patient's skin is concerned. It will remain so, since the skin cannot be sterilized. Indeed, until the ecology of the skin is better understood, rigorous efforts directed toward its disinfection may compromise its inherent defense mechanisms and its protective bacterial flora. It will be argued by some that operating rooms with ultraclean air should be afforded for certain specialized procedures in sugery; for example, those in which prosthetic materials are being implanted or in which the patient's immune mechanisms are depressed. Although not disagreeing with this, I wish to note that the only controlled trial on this aspect of surgery that exists to date shows no advantage for patients randomly apportioned to have hip arthroplasty, either in an isolator or in the same modern operating room but without the isolator. From this experience, I believe that any further trial of this nature, if it is to be controlled to a similar high level, will require very large numbers of patients to show even a marginal advantage for ultraclean air or isolator installations over the modern, plenum-ventilated and meticulously managed operating suite. The verdict on the need to install ultraclean air plant for operating rooms must, therefore, be couched in the third alternative that exists under Scots Law-- "not proved." I suggest the money could be better spent on devising methods to keep skin pathogens out of surgical wounds. Perhaps more urgently, there is a need to discover how to increase the defense mechanisms of the wound milieu to implanted harmful bacteria. There is also a pressing need to improve the ward environment with the aim of diminishing secondary infections of surgical wounds.

Air Microbiology↗
PubMed1979

Effect of nitrous oxide on the cardiovascular system and coronary circulation of the dog.

A comparison was made in seven dogs anaesthetized with pentobarbitone of cardiovascular measurements during ventilation with 65-70% nitrous oxide in oxygen and ventilation with 65-70% nitrogen in oxygen. The substitution of nitrous oxide for nitrogen was found to be associated, after 15 min, with a significant decrease in cardiac output and significant increases in right atrial and left ventricular end-diastolic pressure and systemic vascular resistance. There was no significant change in mean coronary artery flow, coronary vascular resistance or myocardial oxygen consumption.

Animals↗
PubMed1979

Threshold concentration of nitrous oxide affecting psychomotor performance.

Using audiovisual reaction times, no effects were found in 12 subjects exposed to 1, 2, 4, or 8% nitrous oxide. In subsequent studies on 30 subjects, a positive effect on performance was found at a concentration of between 8 and 12% nitrous oxide. In addition, there was no difference in mean reaction time in 12 subjects exposed to air or 8% nitrous oxide. It is concluded that the threshold concentration of nitrous oxide for an effect on psychomotor performance as assessed by choice reaction times probably lies between 8 and 12%.

Adult↗
PubMed1979

Canine coronary blood flow responses to hypoxaemia: the influence of halothane.

Electromagnetic flow meters were used to measure blood flow in the coronary and pulmonary arteries of six anaesthetized dogs following thoracotomy. Halothane 1% (v/v) caused a reduction in arterial pressure, coronary artery flow, cardiac output and myocardial and total body oxygen consumption and an increase in coronary vascular resistance. Hypoxaemia caused large increases in coronary artery flow during both cardiac systole and diastole, but not until PaO2 was less than 5.3 kPa. This response was not influenced by the presence of halothane. Although myocardial oxygen availability and consumption were maintained during hypoxaemia, total body oxygen availability and consumption were markedly reduced.

Animals↗
PubMed1979

Effect of hypotension induced with sodium nitroprusside on canine coronary arterial flow.

In seven dogs anaesthetized with pentobarbitone, coronary and pulmonary artery blood flows were measured using electromagnetic flow meters. The infusion of a 0.01% solution of sodium nitroprusside caused an initial small increase in mean coronary artery flow which returned to control as the arterial pressure decreased. No changes were noted in cardiac output nor were further changes observed in coronary flow. Heart rate was increased consistently during the hypotension and left ventricular dp/dt max was reduced as were coronary and total peripheral resistances. There were no significant changes in myocardial or total body oxygen extraction or consumption.

Animals↗
PubMed1979

Response of mean and phasic coronary arterial blood flow to graded hypercapnia in dogs.

An electromagnetic flow meter was used to assess the changes in coronary blood flow in response to four levels of increased PaCO2 in six dogs. Mean, diastolic and systolic flow all increased during hypercapnia, the increase being maximal at mean PaCO2 11.3 KPa. Mean and diastolic coronary vascular resistances decreased progressively as PaCO2 increased, but systolic resistance, although decreasing with the lower levels of hypercapnia, returned to control at the greatest PaCO2. Although the oxygen available to the myocardium was increased markedly during hypercapnia, coronary sinus PO2 increased also, reflecting a reduction in myocardial oxygen extraction; thus myocardial oxygen consumption was unchanged. Cardiac output was increased significantly only at the greatest PaCO2. Total body oxygen handling was not altered significantly.

Animals↗
PubMed1979

The effect of pupil size on visual acuity in uncorrected and corrected myopia.

The effect of pupil size on the relation between Snellen visual acuity and corrected and uncorrected myopia was examined for 22 young subjects with degrees of myopia ranging from 0.75 D to 7.5 D. Effective pupil size was varied by inducing mydriasis and then placing artificial pupils of between 1.0 and 8.0 mm diameter before the eye. Both a constant chart luminance of 120 cd/m2 and a constant retinal illuminance of 2150 trolands were used. There was little difference in results for the two lighting conditions. For the corrected myopes considered as a group, maximum visual acuity occurred for 2--3 mm diameter pupils, but larger pupils reduced acuity only marginally. For the uncorrected myopes, variation in pupil size produced a large variation in visual acuity, and for refractive errors greater than about 1.5 D, the optimum pupil diameter was less than 1 mm. For uncorrected myopes of 3.0 D or less, visual acuity was nearly as good with a 1-mm pupil as for corrected myopes. The presented data are a useful guide to the clinician.

Adult↗
PubMed1979

Variation of image vergence with change in object distance for telescopes: the general case.

Three formulas are given and derived which can be used to evaluate the relationship between image vergence and object position for any two-lens system and will be very useful in the special case of telescopes. A corresponding formula for afocal telescopes has been published previously. The formulas presented here are applicable to all non-afocal (focal) telescopes, including particular types such as near point telescopes. All that is required for their evaluation is the positions of one pair of conjugate planes, the corresponding magnification, and the lens separation. The formulas can be used to estimate such quantities as a working or useful depth of field and accommodation demand, particularly when the optical system is not used at its design conjugates. A numerical example is presented.

Accommodation, Ocular↗
PubMed1979

The effects of ketamine on the canine coronary circulation.

Systemic and coronary haemodynamic measurements have been made in six healthy greyhounds anaesthetized with trichloroethylene. The administration of ketamine in bolus doses of 5 mg/kg, 10 mg/kg and 5 mg/kg followed by an infusion 0.1 mg/kg/min was found to be accompanied by a decrease in arterial pressure and an increase in cardiac output produced by an increase (84%) in stroke volume. Coronary blood flow increased greatly as did myocardial oxygen consumption and there was no change in myocardial oxygen extraction.

Animals↗
PubMed1979

Tumor inhibitory and non-tumor inhibitory L-asparaginases from Pseudomonas geniculata.

Two enzymes that catalyze the hydrolysis of l-asparagine have been isolated from extracts of Pseudomonas geniculata. After initial salt fractionation, the enzymes were separated by chromatography on diethylaminoethyl-Sephadex and purified to homogeneity by gel filtration, ion-exchange chromatography, and preparative polyacrylamide electrophoresis. The enzymes differ markedly in physicochemical properties. One enzyme, termed asparaginase A, has a molecular weight of approximately 96,000 whereas the other, termed asparaginase AG, has a molecular weight of approximately 135,000. Both enzymes are tetrameric. The asparaginase A shows activity only with l-asparagine as substrate, whereas the asparaginase AG hydrolyzes l-asparagine and l-glutamine at approximately equal rates and it is also active with d-asparagine and d-glutamine as substrates. The asparaginase A was found to be devoid of antitumor activity in mice, whereas the asparaginase AG was effective in increasing the mean survival times of both C3H mice carrying the asparagine-requiring Gardner 6C3HED tumor line and Swiss mice bearing the glutamine-requiring Ehrlich ascites tumor line. These differences in antitumor activity were related to differences in the K(m) values for l-asparagine for the two enzymes. The asparaginase A has a K(m) value of 1 x 10(-3) M for this substrate whereas the corresponding value for the AG enzyme is 1.5 x 10(-5) M. Thus the concentration of asparagine necessary for maximal activity of the asparaginase A is very high compared with that of the normal plasma level of asparagine, which is approximately 50 muM.

Animals↗
PubMed1978

Trisomy 9p with an isochromosome of 9p.

An 18 1/2-year-old female is described with moderately severe mental retardation, the phenotype of the trisomy 9p syndromy, and an isochromosome for the short arm of a chromosome 9, contained in an unique karyotype, 46,XX,-9,t(7q9q),+ iso 9p.

Adolescent↗