Biomedical subjects

S Forbes

Publications and source records attributed to S Forbes.

At least 55 records · Page 3Linked to original sources

PubMed1990

Peritracheal abscess associated with tracheal collapse and bilateral laryngeal paralysis in a dog.

Tracheal collapse and bilateral laryngeal paralysis were diagnosed in an 8-month-old Cocker Spaniel that had acute onset of dyspnea and cyanosis. Surgical exploration of the mediastinum revealed an abscess involving the ventral wall of the trachea immediately caudal to the thoracic inlet. Both recurrent laryngeal nerves were entrapped in fibrous tissue surrounding the abscess. The dog recovered after tracheal resection and anastomosis and freeing of the entrapped nerves. The peritracheal abscess was suspected to have been the result of esophageal perforation secondary to foreign body penetration.

Abscess↗

PubMed1990

Primary hypoparathyroidism in a cat.

Primary hypoparathyroidism caused by lymphocytic parathyroiditis was diagnosed in a cat. Other causes of hypocalcemia (ethylene glycol toxicosis, phosphate enema administration, pancreatitis, renal insufficiency, and malabsorption) were ruled out on the basis of history, clinicopathologic data, and lack of supportive clinical signs, which in this cat included inappetence and tetanic muscle spasms. The diagnosis was confirmed by histologic examination of a surgically excised thyroparathyroid lobe that comprised lack of recognizable parathyroid tissue and a lymphocytic plasmacytic infiltrate adjacent to the cranial pole. A treatment regimen similar to that for iatrogenic postthyroidectomy hypoparathyroidism was successful in controlling clinical signs of the disease.

Animals↗

PubMed1990

Effect of fructose 1,6-diphosphate on exercise capacity in patients with peripheral vascular disease.

Exogenous fructose 1,6-diphosphate (FDP), a glycolytic intermediate, increases blood ATP and 2,3 diphosphoglycerate levels, facilitates the dissociation of oxygen from hemoglobin, and increases red blood cell flexibility. These mechanisms explain why it has been effective in enhancing energy production in a variety of ischemic conditions. The present study was undertaken to determine whether FDP could enhance oxygen supply and thus improve exercise performance in patients with peripheral vascular disease. Ten male patients (mean age 63 +/- 5 years) with peripheral vascular disease performed symptom-limited exercise testing after randomized, double blind infusion of either 200 mg/kg body weight FDP or placebo. Data were evaluated at rest, at a matched submaximal workload (2-3 MPH/0% grade), and at peak exercise, defined as the occurrence of moderately severe claudication. No differences were observed in heart rate, blood pressure, gas exchange data, time to the onset of claudication or peak exercise, or lactate and 2,3 diphosphoglycerate levels. In contrast to previous studies performed among patients with peripheral vascular disease and other studies using more severe hypoxic conditions, FDP did not affect the respiratory gas exchange or exercise capacity of patients with exertional claudication.

Aged↗

PubMed1990

Efficacy of a topical formulation of ivermectin against naturally acquired gastro-intestinal nematodes in weaner cattle.

The efficacy of a topical formulation of ivermectin against naturally acquired gastro-intestinal nematodes in weaner cattle was evaluated. At slaughter, 14-15 days after treatment, burdens of Ostertagia spp, Trichostrongylus axei and Oesophagostomum radiatum were significantly lower in the treated calves than in the untreated controls (p<0.01). Efficacies (based on geometric mean worm burdens of treated and control groups) were 99.6%, 95.1% and 100% respectively. The sizes of the Cooperia spp and Trichuris ovis burdens in the treated group did not differ significantly at the 5% level of confidence from those in the control group.

Journal Article↗

PubMed1990

Comparison of polychlorinated dibenzodioxin levels with hepatic mixed-function oxidase induction in great blue herons.

As part of the Canadian Wildlife Service monitoring of great blue herons in British Columbia, eggs were collected from three colonies with low, intermediate, and high levels of PCDD and PCDF contamination: Nicomekl, Vancouver, and Crofton, respectively. One egg from each nest was used for chemical analysis by GC-MS; the others were hatched. Liver microsomes were prepared from the heron chicks and used for determination of cytochrome P-450-dependent activities. No erythromycin N-demethylase activity was found in any sample. Ethoxyresorufin O-dealkylase activity in the Nicomekl group was similar to that in pigeons, a control altricial species. The ethoxyresorufin activity in the herons from the Crofton colony was 2.6-fold higher than in the Nicomekl group. The Vancouver colony was intermediate. No difference among the three heron colonies was found in pentoxyresorufin O-dealkylase activity, although levels were 20-33 times that in the pigeon. Chemical analysis was carried out on paired heron eggs. Vancouver and Crofton eggs contained 13.5 and 21 times the levels of 2,3,7,8-TCDD compared to the Nicomekl group. The Crofton eggs contained higher levels of several other contaminants also. A highly significant correlation (p less than .001) was found between ethoxyresorufin O-dealkylase and 2,3,7,8-TCDD concentrations. The correlation coefficient did not change when ethoxyresorufin O-dealkylase was compared to total chemical contamination using several toxic equivalency factors. Multiple regression analysis resulted in only one predictor variable for ethoxyresorufin O-dealkylase: 2,3,7,8-TCDD.

Animals↗

PubMed1990

Hepatic copper concentrations in purebred and mixed-breed dogs.

Histomorphologic, histochemical, and atomic absorption analysis studies were performed on liver tissue from 623 clinically normal purebred and mixed-breed dogs to assess the range of hepatic copper concentrations, the histologic distribution of copper, and the histomorphologic changes associated with the various copper concentrations that were found. Atomic absorption analysis revealed a continuous numerical spectrum ranging from less than 100 parts per million on a dry weight basis (ppm dw) to more than 2,000. No decisive numerical criterion was found that could be used to separate normal from abnormal copper concentrations because of this continuous array. The threshold for histochemical demonstration of copper-containing granules using rhodanine or rubeanic acid staining was 400 ppm dw. At this concentration the copper-containing granules were located in the centrilobular hepatocytes (zone 3 of Rappaport). Copper-containing granules were found in the midzonal and periportal hepatocytes (zones 2 and 1 of Rappaport) in livers with 1,000 ppm dw and higher copper concentrations. The majority of the 623 livers were normal histomorphologically. Multifocal hepatitis characterized by mixed inflammatory cell accumulation and centrilobular distribution was found to be associated with copper concentrations in the range of 2,000 ppm dw or higher. An appropriate upper limit for normal hepatic copper concentration in the dog was not determined based on the present study.

Animals↗

PubMed1990

Effects of follicle stimulating hormone, cholera toxin, pertussis toxin and forskolin on adenosine cyclic 3',5'-monophosphate output by granulosa cells from Booroola ewes with or without the F gene.

The cAMP outputs by granulosa cells from 3-4.5 mm diameter (medium) follicles of Booroola FF ewes were similar to those by cells from greater than or equal to 5 mm diameter (large) follicles of ++ ewes with respect to time or dose of FSH, cholera toxin or forskolin. Likewise, the cAMP outputs by cells from 1-2.5 mm diameter (small) FF follicles were similar to those by cells from small and medium ++ follicles with respect to time or dose of FSH, cholera toxin or forskolin. At FSH, cholera toxin or forskolin doses of 1 microgram/ml, 0.5 microgram/ml and 10(-4) M respectively, the granulosa cell cAMP outputs of medium FF or large ++ follicles were approximately 2-fold (P less than 0.05) higher than in the respective small FF and medium ++ follicles. The effects of cholera toxin plus forskolin or FSH plus forskolin were additive irrespective of genotype or follicle size, with significant differences (P less than 0.05) observed between follicle sizes but not genotype. No differences were noted between cholera toxin plus forskolin or FSH plus forskolin on granulosa cell cAMP output. For the FSH and forskolin treatments, increased mean cAMP outputs were evident after 10 min, whereas after cholera toxin treatment they were not evident until after 20 min incubation. For all treatments the rate of cAMP production tended to slow down after 40-60 min. Pre-incubation of granulosa cells with pertussis toxin subsequently resulted in a significantly greater (P less than 0.05) FSH-induced output of cAMP relative to the untreated controls irrespective of follicle size. However, no gene-specific differences were noted when the cAMP outputs of cells from medium or small FF follicles were compared with cells from large or small-medium ++ follicles respectively. These results indicate that the activity (or composition) of the regulatory and catalytic components of adenylate cyclase in the FF granulosa cells change in a manner similar to those observed in ++ cells with the only difference being that the increases in cyclase in FF ewes occurs as follicles enlarge from 1-2.5 to 3-4.5 mm in diameter, whereas in ++ ewes they occur as follicles enlarge from 3-4.5 to greater than or equal to 5 mm in diameter. No evidence was found to link the F gene to the granulosa cell cAMP response independently of follicle size. It is suggested that the association between the F gene and the size-specific difference in follicle maturation may be unrelated to the FSH receptor/cAMP generating system.

Adenylate Cyclase Toxin↗

PubMed1990

Effect of fructose 1,6-diphosphate infusion on the hormonal response to exercise.

Exogenous fructose 1,6-diphosphate (FDP), a glycolytic intermediate, has recently been demonstrated to accelerate ATP production, prevent glycogen breakdown, stimulate glycogen synthesis, and synthesize free fatty acids in animals and humans. To assess the effects of FDP on the hormonal and metabolic response to exercise, ten trained males (34 +/- 7 yr) underwent 1 h of continuous exercise at 70% VO2max followed by 20 W.min-1 increments to exhaustion. Two hundred fifty mg.kg-1 body weight FDP or placebo was infused in randomized, double-blind, crossover fashion. No differences were observed in heart rate, blood pressure, gas exchange data, perceived effort, or glucose, insulin, free fatty acid, lactate, beta-hydroxybutyrate, glycerol, and glucagon concentration at rest, during exercise, or upon exhaustion. In contrast to the previously reported bioenergetic effects of FDP under conditions in which glycolysis is impeded (acidosis, hypoxia, and ischemia), FDP did not affect the gas exchange, hormonal, or substrate response to moderately high intensity exercise in healthy normals.

Adult↗

PubMed1989

Optimal sampling interval to estimate heart rate at rest and during exercise in atrial fibrillation.

To investigate the ideal sampling interval for the estimation of heart rate (HR) at rest and during exercise in atrial fibrillation (AF), maximal exercise testing with continuous electrocardiographic acquisition was performed in 10 patients with chronic AF (mean age 66 +/- 4 years) and 10 subjects in normal sinus rhythm (mean age 31 +/- 6 years). Measurements of HR were obtained at 9 different sampling intervals (1, 2, 3, 6, 10, 15, 20, 30 and 60 seconds) at rest and 7 different sampling intervals (1, 2, 3, 6, 10, 15 and 20 seconds) during the last 30 seconds of each minute during exercise. The HR obtained from each interval was compared with true HR (determined by a 4-minute sample at rest and by the last 30 seconds of each minute during exercise). Among patients with AF, large differences were observed between the HR obtained and true HR, both at rest and during exercise, using small sampling intervals. The mean of these differences ranged between 16 +/- 11 beats/min (range 14 to 22) using 1-second sampling intervals and 2.2 +/- 2.0 beats/min (range 1.6 to 4.4) using 20-second sampling intervals during progressive exercise. Variability of the HR obtained from a given random sample was also high when short sampling intervals were used among patients with AF. These observations were contrasted by subjects in normal sinus rhythm, among whom neither variability nor measurement error were influenced remarkably by changing the sampling interval or increasing HR.

Adult↗

PubMed1989

The effect of cardioversion on maximal exercise capacity in patients with chronic atrial fibrillation.

To evaluate the effect of cardioversion on exercise capacity, 11 male patients (59 +/- 8 years) with chronic atrial fibrillation underwent maximal exercise testing using gas exchange techniques before and after successful cardioversion to normal sinus rhythm. Testing was conducted 1 day prior to and a mean of 39 (range 10 to 95) days following cardioversion. Heart rate, blood pressure, and respiratory gas exchange responses were evaluated at rest, at a standard submaximal workload (3.0 mph/0% grade), at the gas exchange anaerobic threshold, and at maximal exertion. Cardioversion resulted in a mean decrease in resting heart rate of 37 beats/min (113 +/- 16 versus 76 +/- 10 beats/min, p less than 0.001). While mean heart rate was approximately 50 beats/min lower following cardioversion at both submaximal stages of exercise p less than 0.001), oxygen uptake was not different. At maximal exercise, heart rate was markedly reduced (192 +/- 24 to 144 +/- 21 beats/min, p less than 0.001) and maximal oxygen uptake was higher (1.86 +/- 0.5 to 2.06 +/- 0.5 L/min, p less than 0.05) after cardioversion. In addition, an improved efficiency of ventilation was observed at exercise levels exceeding 60% of maximal oxygen uptake.

Aged↗

PubMed1989

Increased exercise capacity after digoxin administration in patients with heart failure.

Failure to objectively assess the effect of digitalis on exercise capacity has resulted in controversy regarding its use in patients with chronic congestive heart failure. To clarify this situation, maximal treadmill testing with respiratory gas exchange analysis was performed on 11 patients (mean age 57 +/- 9 years) with chronic congestive heart failure with and without digoxin therapy. Ten of the 11 had a consistent third sound gallop, and the mean ejection fraction of the group was 24 +/- 10%. Rest heart rate was significantly higher (91 +/- 16 versus 102 +/- 16 beats/min; p less than 0.05) and rest systolic blood pressure was significantly reduced in the absence of digoxin (130 +/- 23 versus 121 +/- 15 mm Hg; p less than 0.05). No differences in heart rate or blood pressure were observed during exercise. Significant increases in ventilatory oxygen uptake were observed with digoxin submaximally (3.0 mph, 0% grade), at the gas exchange anaerobic threshold and at maximal exercise (mean increase of 2.6 ml/kg per min; p less than 0.02). An improvement in the estimated ratio of ventilatory dead space to tidal volume (VD/VT), an index of physiologic efficiency, occurred throughout exercise during digoxin therapy, and there was a significant negative correlation between the change in maximal oxygen uptake and change in maximal estimated VD/VT (r = -0.63; p less than 0.05). Thus, digoxin therapy is associated with a significant improvement in exercise capacity in patients with chronic heart failure, most likely due to an improved matching of ventilation to perfusion.

Adult↗

PubMed1989

Reproducibility of treadmill exercise data in patients with atrial fibrillation.

Serial submaximal treadmill tests are often used to evaluate the efficacy of therapy in patients with atrial fibrillation. Since the response to serial tests can be influenced by a 'learning phenomenon', we performed maximal exercise tests on 9 patients (mean age 63 +/- 4 years) with chronic atrial fibrillation. Points of analysis for the initial and follow-up treadmill exercise tests were 3 mph/0% grade, the gas exchange anaerobic threshold, and maximal exertion. Significant (p less than 0.05) reductions in ventilation (l/min) and oxygen uptake (ml/kg/min) were observed on follow-up at a standard submaximal work load of 3.0 mph/0% grade and at the gas exchange anaerobic threshold. There was no significant alteration in these variables at maximal exertion. A reduction in heart rate was observed throughout exercise during the follow-up test with the most marked reduction (21 beats/min) occurring at 3.0 mph/0% grade. There were no differences in respiratory exchange ratio or systolic blood pressure at any point. The reduction in submaximal heart rate and gas exchange variables without a significant change in these variables at maximal exertion is consistent with a learning effect. Therefore, studies comparing consecutive submaximal exercise test responses in patients with atrial fibrillation can be misleading.

Aged↗

PubMed1989

Studies on the fate of flocoumafen in the Japanese quail (Coturnix coturnix japonica).

1. 14C-Flocoumafen, administered to Japanese quail as a single oral or i.p. dose, was rapidly and extensively eliminated in excreta; most was eliminated within 24 h. Extensive metabolism of the rodenticide was seen, with at least 8 metabolites detected; unchanged flocoumafen comprised 9% dose. The elimination kinetics and metabolic profiles were qualitatively similar after oral and i.p. dosing. 2. The major metabolites (60% dose) were labile to beta-glucuronidase, liberating aglycones with identical chromatographic mobilities to those of the unchanged flocoumafen isomers. 3. Radioactivity was retained mostly in the liver; largely as unchanged flocoumafen associated with the mitochondrial and microsomal fractions. Elimination of radioactivity from most tissues was biphasic with an initially rapid depletion (5 days) followed by a slow terminal elimination phase. The elimination half life from liver was greater than 100 days. 4. Livers of quail receiving extended dietary exposure to flocoumafen at 5, 15 and 50 ppm had concentrations of flocoumafen (1.0 nmol/g) that were independent of dose, indicating a capacity-limited binding site. These hepatic concentrations were similar to those after a single oral dose and were also similar to those in rats. The data indicate the presence in quail liver of a saturable high affinity flocoumafin binding site with similar characteristics and capacity to that in the rat. 5. The selective toxicity of flocoumafen to rats (highly toxic) and quail (moderately toxic) appears to arise from differences in metabolism rather than from anticoagulant binding in the liver. When hepatic binding sites of rats are saturated anticoagulant action becomes lethal, whereas quail are able to survive and extensively metabolize the compound.

4-Hydroxycoumarins↗

PubMed1988

High-frequency electrocardiography: an evaluation of lead placement and measurements.

Before there is widespread clinical application of the high-frequency ECG, differences resulting from the leads used and the measurement criteria for late potentials must be resolved. Therefore 113 consecutive patients without resting QRS conduction abnormalities referred for Holter monitoring were studied. Four different lead systems were used: a standard bipolar orthogonal lead system and three bipolar lead systems mapping the left ventricle. Measurements made of late potentials included normal and high-frequency QRS duration, their difference, the duration of low-amplitude signals (less than 40 uV) in the terminal QRS, and the root mean square of the last 40 msec of the high-frequency QRS duration. We found that the left ventricular leads tended to give more abnormal measurements than the orthogonal system and that the various measurements failed to agree with each other. In addition, even in this population in which abnormalities of QRS conduction were excluded, the late potential measurements tended to be more abnormal as QRS duration lengthened. These differences in lead systems and measurement criteria must be considered when clinically applying information regarding late potentials measured from the high-frequency ECG.

Adult↗

PubMed1988

Maximal exercise testing and gas exchange in patients with chronic atrial fibrillation.

To evaluate the response of patients with chronic atrial fibrillation to exercise, 50 men (mean age 65 +/- 8 years) with atrial fibrillation underwent a maximal exercise test using respiratory gas exchange techniques. Patients were classified by the presence (n = 29) or absence ("lone atrial fibrillation," n = 21) of underlying heart disease. Responses were evaluated at a standard submaximal work load (3.0 mph, [4.8 km/h] 0% grade), at the gas exchange anaerobic threshold and at maximal exercise. For all 50 patients, the mean maximal oxygen uptake was 20.6 ml/kg per min, which approximates 85% of the aerobic capacity predicted for age-matched normal individuals. Patients with lone atrial fibrillation demonstrated normal exercise capacity in contrast to patients with atrial fibrillation and known heart disease (22.7 +/- 5 versus 19.1 +/- 5.0 ml/kg per min, p less than 0.05). The mean maximal heart rate (176 +/- 30 beats/min) was approximately 20 beats/min higher than that expected for age, was extremely variable and accounted for only 8% of the variance in maximal oxygen uptake. Maximal heart rate in subjects with lone atrial fibrillation was higher than that of subjects with atrial fibrillation and known heart disease (189 +/- 32 versus 166 +/- 24 beats/min, p less than 0.01). Stepwise regression analysis revealed that maximal systolic blood pressure accounted for 19% of the variance in maximal oxygen uptake (VO2 max), suggesting that systolic function is an important determinant of exercise performance in atrial fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1988

Treatment of seasonally anestrous Romney ewes with continuous infusion of low doses of GnRH: effects on estrus, ovulation and plasma progesterone concentration.

The aim of this study was to assess the suitability of a GnRH infusion regimen (125 ng/h or 250 ng/h) to induce estrous behaviour, ovulation and normal corpus luteum function in progesterone-primed Romney ewes each month of seasonal anestrus (i.e. September to February inclusive) over two years. None of the progesterone-primed control ewes (i.e. no GnRH treatment; N = 120 observations) ovulated, showed normal corpus luteum function or displayed estrous behaviour at any time during anestrus. Approximately 27 and 50% of the respective 125 ng/h and 250 ng/h GnRH-treated ewes (N = 120 observations per GnRH treatment) ovulated and showed normal luteal function. Of those which ovulated 59.2% and 52.4% in the respective 125 ng/h and 250 ng/h GnRH treatment groups showed estrous behaviour. There was a significant effect of GnRH dose on the median number of ovulations (250 ng/h > 125 ng/h; P<0.01) but no overall difference (when both treatment years and GnRH doses were pooled) in the median number of ovulations per month of anestrus. The frequency of ewes with an ovulation rate >2 was low with only 4/95 treated ewes with more than 2 corpora lutea (CL). Treatment of progesterone-primed ewes with 250 ng/h GnRH increased plasma LH (P<0.01) but not FSH concentrations; a significant increase in LH pulse amplitude (P<0.05) but not LH pulse frequency was observed. The plasma gonadotropin levels in the 125 ng/h GnRH treatment groups were not studied. We suggest that in breeds such as the Romney which have a strict (i.e. 5-6 month) anovulatory interval, the GnRH-infusion technique may be of limited practical use for inducing pregnancies during the non-breeding season.

Journal Article↗

PubMed1988

Blood thiamine levels in normal cattle and sheep at pasture.

Analysis of whole blood samples from 174 cattle and, 174 sheep from 3 geographical regions of New Zealand over a 10 month period showed a mean (range) thiamine level of 122 nmol/l (71-237 nmol/l) for cattle and 118 nmol/l (67-227 nmol/l) for sheep. Regional and seasonal differences were noted with levels tending to rise over the summer period. A reference range of 75-185 nmol/l is proposed for both cattle and sheep to cover these variations. Levels below 50 nmol/l are considered indicative of deficiency.

Journal Article↗

PubMed1987

Effect of beta-adrenergic blockade on exercise performance in patients with chronic atrial fibrillation.

Beta-adrenergic blocking agents are commonly used in combination with digitalis to control excessive heart rate during exercise in patients with chronic atrial fibrillation. However, little is known about the effect of beta-adrenergic blockade on exercise capacity in these patients. Accordingly, a randomized, double-blind, cross-over placebo-controlled study was performed to assess the efficacy of celiprolol, a new cardioselective beta-blocker with partial intrinsic sympathomimetic activity, on exercise performance in nine men with chronic atrial fibrillation. All but one patient was receiving maintenance digitalis during the study. Heart rate, blood pressure and gas exchange variables were measured at rest and during treadmill exercise testing while the patients were receiving maintenance celiprolol or placebo. Significant reductions in heart rate and systolic blood pressure compared with control values were observed at submaximal exercise, at the gas exchange anaerobic threshold and at maximal exertion while the patients were taking celiprolol. However, oxygen uptake at the gas exchange anaerobic threshold during celiprolol therapy was 12.3 versus 14.0 ml oxygen/kg per min during placebo administration (a 12% difference, p less than 0.01). Similarly, oxygen uptake at maximal exertion during celiprolol therapy was 17.6 versus 21.0 ml/kg per min during placebo administration (a 16% difference, p less than 0.01). Treadmill time was also reduced during the celiprolol phase compared with placebo (11.3 versus 10.3 minutes; a 19% difference, p less than 0.01). These results indicate that in patients with atrial fibrillation the major beneficial effects of beta-adrenergic blockade--reduced submaximal and maximal exercise heart rate and blood pressure--must be weighed against the decrease in exercise capacity.

Adrenergic beta-Antagonists↗