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Biomedical subjects

G Johnston

Publications and source records attributed to G Johnston.

At least 19 recordsLinked to original sources
PubMed1992

Changing perspective on gastrointestinal complications in patients undergoing cardiac surgery.

There has been a documented shift towards increasing age and severity of illness in the patient population undergoing cardiac surgery. To determine if there was a coincident change in frequency, gastrointestinal (GI) complications were prospectively recorded in a consecutive series of 5,438 patients undergoing cardiac surgery from 1983 to 1991. There were 73 complications in 69 patients (incidence = 1.4%) defined as any GI condition that required transfer to an acute care unit, surgical intervention, blood transfusion, or treatment that prolonged the hospital course. Fourteen patients died, a mortality rate of 20% for patients with GI complications (p less than 0.001 versus patients without GI complications). The most frequent complications were those of gastric ulceration despite routine use of H2-receptor blocking agents. Thirty-six patients had upper GI (UGI) bleeding from gastric ulceration with 4 patients requiring operative intervention to control hemorrhage and 6 fatalities in patients with UGI bleeding. Two additional patients died of septic complications following gastroduodenal perforation or penetration. Six patients experienced bowel obstruction or prolonged bowel dysfunction (three Ogilvie's syndrome) with two requiring laparotomy. There were four cases of cholecystitis, two cases of pancreatitis, and the remaining cases were equally divided among common septic complications (diverticulitis and ischemic injury among others). Three patients with massive intestinal infarction died. GI complications were significantly associated with older patients (p less than 0.01) and valve surgery (p = 0.002) but were not more common in women. When considered as a separate group, patients with acid-peptic complications had longer perfusion times, increased use of vasopressors, and more frequent utilization of the intra-aortic balloon pump. In contrast to prior studies, this investigation indicates that GI complications associated with acid-peptic erosion of the UGI tract tend to occur in a different patient group than those with other GI complications. Older patients and/or those with a prior history of peptic ulcer symptoms, as well as those who experience prolonged perfusion times, low cardiac output, or prolonged ventilatory support, should be under rigorous gastric pH surveillance and receive aggressive prophylactic treatment with high-dose H2 antagonists, antacids, and/or sucralfate.

Aged↗
PubMed1992

The minimum effective dose of lignocaine to prevent injection pain due to propofol in children.

In a single-blind study of 100 children aged 1 to 10 years, the minimum effective dose of lignocaine required to prevent injection pain due to propofol was 0.2 mg.kg-1 when veins on the dorsum of the hand were used. This is more than twice the adult value. We concluded that injection pain should not limit the use of propofol in children if an adequate amount of lignocaine is mixed immediately prior to injection.

Anesthesia, Intravenous↗
PubMed1992

Influence of cigarette smoking on the outcome of coronary care unit admissions with chest pain.

We studied the effect of current smoking habits in the period immediately before admission to hospital in 90 consecutive patients presenting with chest pain, 50 of whom were shown to have myocardial infarction. Urine cotinine/creatinine (cot/creat) ratio measured within 4 hours of admission was used as an objective marker of cigarette smoking in the preceding 18 hours. Fifty-seven patients had urine cot/creat ratios suggesting recent smoking, although four of these denied smoking. Patients with myocardial infarction had higher median cot/creat ratios (3.31 micrograms/mg, range 0-17.8) compared with patients with non-infarct chest pain (0.5 microgram/mg, range 0-37.2). Sixteen patients with cardiac rhythm disturbances following infarction had significantly higher cot/creat ratios than the 34 infarct patients without this complication (median and range 8.34 micrograms/mg; 0-17.8 V. 1.87 micrograms/mg; 0-16.4, P < 0.01). Tobacco use in the 24 hours before myocardial infarction may predispose to cardiac rhythm disturbance, irrespective of infarct size.

Adult↗
PubMed1992

An evaluation of prototype school-based peer counseling program.

This study reports short-term outcome evaluation results of a school-based peer counseling (PRC) program as implemented by North Forsyth High School during January 1990-February 1991. The PRC program is evaluated in terms of: 1) the content of the program as evaluated by the PRC trainees; 2) the quality of the PRC instructor as perceived by these trainees; 3) several instrumental objectives deduced from the PRC training program; and 4) the degree to which the program was able to reach other students at North Forsyth during the time the PRC was in operation. In the absence of a control group, the treatment effect of the program is determined in terms of individual growth curve models. Through the multiple evaluation designs employed in this research, it has been learned that a significantly larger proportion of students in the PRC group had more favorable attitude toward the content of the PRC program when compared to the content of what they learned from their regular school curricula. Furthermore, a significantly larger proportion of students in the PRC program reported more favorable attitude toward their instructor than their regular school teachers. The PRC program was able to elicit an improvement of trainee self-esteem (p less than .01) and their social values (p less than .05) between pre and post of the Peer Training Evaluation Instrument. In terms of client access, 18.4 percent of the totality of potential clients at North Forsyth have been reached through sixty-one peer counselors sanctioned by the school.

Adolescent↗
PubMed1991

An evaluation of radiation and dust hazards at a mineral sand processing plant.

This three-part article discusses the results of a 2-y study on radiation and dust hazards in a mineral sand processing plant involving: (1) evaluation of external gamma radiation levels and determination of isotopic composition of the different sand products; (2) evaluation of radiation carried in long-lived radioactive dust (LLRD) particles; (3) evaluation of Rn gas concentrations within the working environs of the plant. Gamma radiation levels had a mean value of approximately 40 nSv h-1, and monazite sand returned the highest activity concentrations of 0.16% and 3.4% for 238U and 232Th, respectively. Low volume gross respirable dust sampling revealed an average long-lived airborne alpha activity concentration of 0.07 +/- 0.02 Bq m-3 and an average dust mass concentration of 3.3 +/- 2 mg m-3. Gamma spectroscopy applied to high-volume air samples showed average airborne 232Th and 238U activities of 0.012 +/- 0.004 Bq m-3 and 0.005 +/- 0.002 Bq m-3, respectively, giving an airborne 232Th: 238U ratio of 2.4:1. Air sampling using a high volume, five-stage cascade impactor indicated an average activity median aerodynamic diameter (AMAD) of 3.2 microns with an associated average geometric standard deviation (GSD) of 2.8. Average radiation dose arising from the inhalation of LLRD was estimated to be 7 mSv per annum. CR-39 (polycarbonate plastic) nuclear track detectors indicated that Rn gas concentrations in the environs of the processing plant dry mill and main product warehouse ranged from 30 Bq m-3 to 220 Bq m-3, with an average value of 100 Bq m-3, which presents a possible inhaled dose from Rn daughters of 1.5 mSv y-1 (assuming an equilibrium ratio of 0.5).

Air Pollutants, Radioactive↗
PubMed1990

Preparation of xenon-133 in a lipid emulsion for tissue perfusion studies.

A simple, inexpensive technique for concentrating xenon-133 in a medium suitable for intravenous use is reported. The method uses a 20% lipid emulsion, standard syringes, an oscillating motor, and xenon-133, which is available commercially. Typically, 43% of the xenon-133 combines with the lipid emulsion and remains stable for more than 24 hours in vitro.

Fat Emulsions, Intravenous↗
PubMed1988

Osteogenesis in two marsupial species, the bandicoot Isoodon macrourus and the possum Trichosurus vulpecula.

Skeletal development of two marsupial species, the bandicoot, Isoodon macrourus and the brushtail possum, Trichosurus vulpecula, has been examined in whole mount preparations using a technique of clearing and differential staining of cartilage and bone. Both marsupials possess a complete cartilaginous skeleton at birth and ossification begins in the maxilla, mandible and certain bones of the forelimb soon after birth. The general pattern of ossification in these marsupials is similar to that in eutherians but the long bones of the forelimbs, and the thoracic vertebrae, have a precocious development when compared with that of eutherian mammals. This difference may be due to the requirement of the marsupial forearms for the passage of the young from the cloaca to the pouch. Accelerated rib development occurs, and is possibly related to respiratory movements which are initiated at a very much earlier stage than in eutherian mammals.

Aging↗
PubMed1987

Selection of an animal model for resurfacing hip arthroplasty.

This study was done to determine whether sheep provide a better model of resurfacing hip arthroplasty than dogs. Eighteen sheep were subjected to unilateral resurfacing arthroplasty. Fifty-eight percent developed femoral loosening by 10 months. This reflects the clinical situation in humans: loosening has been the leading cause of failure. By contrast, reports of experiments with dogs describe very low loosening rates. Sheep provide a more stringent test of hip arthroplasty than dogs. The critical difference appears to be activity level. Sheep allowed free activity on a farm more closely simulate the situation of active patients than do dogs housed in small enclosures in conventional research facilities. New techniques of prosthetic hip arthroplasty that lend themselves to animal models should be studied in sheep before being studied in humans.

Animals↗
PubMed1987

Sodium-dependent D-glucose transport in brush-border membrane vesicles from isolated rat small intestinal villus and crypt epithelial cells.

Differentiation and maturation of enterocytes occur with migration from the crypt to villus compartments. To investigate the effect of epithelial cell differentiation on sodium-dependent D-glucose transport, brush-border membrane vesicles were prepared from small intestinal epithelial cell suspensions selectively isolated from villus and crypt populations. Enterocytes were isolated with a morphologically monitored sequential cell dissociation method. Thymidine kinase, sucrase, and alkaline phosphatase activities were measured as differentiation markers of specific cell populations. Brush-border membrane vesicles were purified and their kinetic characteristics defined with a rapid filtration method under conditions of a zero-trans, 100 mM cis-NaSCN gradient. Typical "overshoot" phenomena characteristic of sodium D-glucose cotransport were observed for both villus (five- to eight-fold equilibrium values) and crypt brush-border membrane vesicles (two- to four-fold equilibrium values). Kinetics analyses of the initial D-glucose flux in brush-border membrane vesicles suggested the presence of at least two sodium-dependent D-glucose carriers in the villus and only a single carrier in the crypt compartments. These data indicate that sodium D-glucose cotransport occurs in brush-border membranes of both villus and crypt populations. Moreover, quantitative and qualitative differences between these two membrane populations suggest that epithelial D-glucose transport processes are differentiation dependent and reflect the degree of enterocyte development.

Animals↗
PubMed1987

Boxer's fractures--conservative or operative management?

Sixty-three consecutive patients presented during an 18-month period with isolated closed fractures of the fifth metacarpal neck. Follow-up ranged from 3 to 20 months. Forty were recalled for study and divided into a conservative group (25 patients) and an operative group (15 patients). Both groups were statistically comparable. All patients obtained good results. Subjectively, no patient had long-term pain or dissatisfaction with the functional or cosmetic result. Objectively, all patients regained full joint motion and normal grip strength. Mild rotatory malalignment was present in both groups, but the conservative group had less extensor lag. The main difference between the two groups centered on residual dorsal angulation. This cosmetic deformity was considerably less in the operative group, although the cost of this improvement was significantly longer rehabilitation. Failure to correct dorsal angulation was not associated with functional disability.

Adult↗
PubMed1985

Seasonal variations in plasma testosterone concentrations in the male marsupial bandicoot Isoodon macrourus in captivity.

Although bandicoots in Queensland mate throughout the year, the majority of births occur in late winter and spring. To ascertain whether this seasonality in mating is manifest in the male reproductive system; body weight, testes size, and plasma testosterone concentration were examined in eight bandicoots throughout the year. The size of the testes increased with age in all bandicoots and there was no evidence of seasonal variation. Plasma testosterone concentrations fluctuated from 0.1 to 70.0 ng/ml and a seasonal cycle was observed, with a nadir in concentrations in March and a peak in September. The peak in testosterone concentration coincided with the period of the year when the majority of births occurred. Subsequent statistical analysis suggested that the annual plasma testosterone profile correlated well with the rate of change of day length.

Acclimatization↗