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Biomedical subjects

H Bark

Publications and source records attributed to H Bark.

At least 37 records · Page 2Linked to original sources
PubMed1995

Demonstration of serum antiplatelet antibodies in experimental acute canine ehrlichiosis.

This report presents evidence for the presence of antiplatelet antibodies in sera of dogs experimentally infected with Ehrlichia canis, during the acute phase of the disease. Six healthy adult male beagle dogs were inoculated intravenously with blood from a longstanding infected dog with the Israel strain 611 of E. canis. Thrombocytopenia and concurrent increase in mean platelet volume were the most consistent haematological signs of the disease. The dogs developed an antibody titre to E. canis from Day 15 postinoculation. All dogs were antiplatelet antibody negative before inoculation. Twenty-four days postinoculation with E. canis, when the platelet count was at its lowest, antibodies to platelets were demonstrated, in the sera of five of the six dogs.

Acute Disease↗
PubMed1995

Trypanosoma congolense infection in two dogs.

Trypanosomiasis, caused by Trypanosoma congolense, was diagnosed for the first time in Israel in two boxer dogs imported from Kenya. The dogs developed clinical signs two days after arrival and succumbed to the disease within four days. The major clinical and clinicopathological findings included anaemia, haemorrhages, lymphadenomegaly, hepatosplenomegaly and neurological signs. Histopathology showed lymphocytic-plasmacytic infiltration in the skin, brain, meninges, kidney and liver.

Animals↗
PubMed1993

Paralytic syndrome attributed to lasalocid residues in a commercial ration fed to dogs.

Lasalocid, accidently introduced into a commercial dog food, was found to be the cause of neuromuscular toxicosis in 10 dogs. Toxicosis was confirmed in 4 principal dogs. The history, clinical signs, and pattern of onset of lasalocid-induced toxicosis in the 14 dogs were similar to those reported for botulism. The signs, which were related to a generalized lower motor neuron deficit, were generally different from ionophore-induced toxicosis reported in other species. Supportive therapy and close monitoring were sufficient to bring about a gradual improvement in all of the dogs, despite the severity of clinical signs.

Animal Feed↗
PubMed1992

Effects of hyperphosphatemia on diaphragmatic strength and endurance.

Effects of an infusion of Na2HPO4 on diaphragm strength, endurance, and magnitude of recovery were evaluated in in situ canine diaphragm strips. Results showed no effect on maximal isometric tetanic tension. Twitch tension and tension in the low- (10-Hz) frequency range were significantly increased (P less than 0.01). Time to fatigue (endurance) increased by 38 +/- 4.5% in the group that received phosphorus compared with its control and decreased by 18.5 +/- 2.5% in the group that received dextrose compared with its control (P less than 0.005). Recovery from fatigue was also significantly improved after the phosphorus infusion. Serum ATP and 2,3-diphosphoglycerate levels were unchanged throughout the experiment. The results of this study support the notion that hyperphosphatemia improves diaphragmatic endurance and recovery from fatigue. The mechanisms involved may in part be due to the phosphate-buffering effects, which limit the extent of the muscle intracellular acidosis produced with fatigue.

2,3-Diphosphoglycerate↗
PubMed1992

Effect of chronic renal failure on skeletal and diaphragmatic muscle contraction.

The changes in muscle mechanical properties caused by the myopathy of chronic uremia was examined in the soleus and the diaphragm muscles of rats in which chronic uremia was produced by subtotal nephrectomy. Using an in vitro muscle preparation in two groups of rats (moderately and severely uremic), we determined that uremia had a significant detrimental effect on both muscles with respect to the force-frequency relationships. In the diaphragm it decreased by 15% in the moderate group and by 43% in the severe group. In the soleus it decreased by 20% in both groups. Twitch characteristics behaved differently in the soleus and the diaphragm muscles in that 1/2 RT and TPT increased significantly (p < 0.05) in the soleus (severely uremic group) but not in the diaphragm. Fatigability was increased in both muscles in the moderately uremic rats and in the diaphragm in the severely uremic rats; however, the fatigability of the soleus in the severely uremic group was not different from that in the control group. Our findings suggest that the myopathic changes occurring in chronic uremia affects the function of the soleus and the diaphragm in different ways. Other findings in the severely uremic group indicate that additional factors such as marked electrolyte imbalances may also affect the excitation-contraction coupling in different ways.

Animals↗
PubMed1991

Phases of URu2Si2.

Explore the source record for details and available documents.

Journal Article↗
PubMed1991

Effect of dexamethasone on diaphragmatic and soleus muscle morphology and fatigability.

In spite of the extensive use of corticosteroids, its myopathic effect on respiratory muscle is unknown with relation to the dose and duration of therapy. The present study examined the effects of dexamethasone on the morphology and function of respiratory (diaphragm) as compared to skeletal (soleus) muscle. Control rats were compared to those that received low, high and prolonged doses of dexamethasone. Body mass was reduced proportionally to the dose and duration of therapy. Atrophy of the diaphragm was greater than that of the soleus when normalized to body mass. Absolute tension and tension as a function of cross sectional area was significantly (P less than 0.05) less in the diaphragm and soleus at the high and prolonged dosages. Dexamethasone had no effect on fatigability except in the soleus after prolonged treatment. Furthermore, after prolonged therapy, it had converse effects on the Pt and 1/2RT in the diaphragm as compared to the soleus muscle. Dexamethasone improved the recovery times in the diaphragm alone. Our data suggest that dexamethasone weakens the diaphragm and soleus by reducing its mass and apparently also through some effect on the intrinsic contractile apparatus.

Animals↗
PubMed1991

Effect of digoxin on respiratory muscle performance in patients with COPD.

The effect of 2 weeks oral digoxin administration on respiratory muscle performance (RMP) in 14 patients with chronic obstructive lung disease (COPD) was investigated in a randomized double-blind placebo-controlled cross-over study. All patients were ambulatory with severe air flow obstruction. FEV1/FVC was 0.44 +/- (SD) 0.11, FEV1 was 0.88 +/- (SD) 0.35 liter/s RMP was assessed by measuring maximal inspiratory pressure (PImax), maximal expiratory pressure (PEmax), and maximal voluntary ventilation. Although these parameters were significantly reduced in the COPD patients, 2 weeks of digoxin administration (with serum levels in the therapeutic range) did not alter any parameter of RMP or spirometry. We conclude that digoxin has no effect on RMP or spirometry in ambulatory patients with severe COPD.

Adult↗
PubMed1991

Comparison of a B2 adrenergic agonist and an anticholinergic agent given by sequential inhalation in patients with severe chronic obstructive pulmonary disease.

We evaluated the response of 15 male patients with severe chronic obstructive pulmonary disease (COPD) to sequential inhalations of an anticholinergic agent, ipratropium bromide 0.25 mg (IB) and a B2 adrenergic agonist, terbutalin 2.5 mg (TER), in a double-blind crossover study. We found no statistically significant difference in the bronchodilatory response between the two agents when comparing the change in forced vital capacity and forced expiratory volume in 1 sec. The subsequent effect of the sequential inhalation demonstrated some additional bronchodilatory response when IB was given after TER, but not when TER was given after IB. However, the end result after the two protocols was not statistically different. The results indicate that in COPD patients the two agents are equipotent. However, in order to prescribe the best treatment schedule for each patient, it is still necessary to evaluate how each individual patient responds to each of the agents. Sequential inhalation may be beneficial in some patients.

Adrenergic beta-Agonists↗
PubMed1990

Respiratory muscle performance in patients with type 1 diabetes.

Respiratory muscle strength and endurance were examined in 31 Type 1 diabetic patients and in age, sex, and weight matched control subjects. No significant difference in respiratory muscle strength was noted between the two groups. Maximal static inspiratory pressure was 92.3 +/- 33.9 (+/- SD) and 99.5 +/- 23.0% of the predicted values in the patient and control groups, respectively. Maximal static expiratory pressures were 75.1 +/- 14.3 and 77.4 +/- 14.0% of the predicted values in the patient and control groups, respectively. Respiratory muscle endurance was significantly lower in the diabetic patients 88.9 +/- 20.7 vs 103.9 +/- 15.8% predicted in the control group (p less than 0.01). Total lung capacity, vital capacity, and maximal voluntary ventilation were also significantly lower in the diabetic group and correlated with the duration of diabetes.

Adult↗
PubMed1990

Effect of codeine on the sensations elicited by loaded breathing.

The present study examined the effect of codeine, a centrally acting opiate, on the respiratory sensations elicited in normal subjects by breathing to exhaustion against externally applied inspiratory threshold loads. Subjects were tested on two separate days following the double-blind, randomized administration of either placebo or codeine (90 mg). The intensity of the sensations of effort and discomfort experienced during two loaded breathing trials (a "high" load that was 73% of the maximum inspiratory pressure (MIP) and a "low" load that was 63% of the MIP) was evaluated using category (Borg) scores on each day of study. To verify that the dosage of codeine administered was sufficient to produce analgesia, we also determined the effect of this dosage on the time that subjects could tolerate immersion of one hand in ice water. Codeine altered neither the perceived effort nor the sense of discomfort associated with breathing against external loads and had no appreciable effect on the time to exhaustion during loaded breathing trials. This dose of codeine did, however, increase the time that ice water immersion could be tolerated and reduced the rate at which the sense of discomfort increased over time during ice water trials. These results indicate that, provided the pressure-time index of respiratory muscle contraction remains constant, analgesic doses of codeine alter neither the sensations elicited by loaded breathing nor the total time that breathing against a fatiguing inspiratory load can be tolerated.

Adult↗
PubMed1990

Physiological changes in respiration associated with near drowning in the Dead Sea: a canine model.

An experimental study to elucidate the physiological changes that occur in respiration during near drowning in the Dead Sea was performed in an experimental model. Findings showed that clinical signs of respiratory failure were due to aspiration rather than ingestion of Dead Sea water and occurred within 10 min of aspiration. Physiological changes included increased ventilation, tachypnea, increased resistance, decreased compliance and hypoxia.

Airway Resistance↗
PubMed1988

Effect of chronic renal failure on respiratory muscle strength.

In 10 patients with chronic renal failure (CRF), undergoing hemodialysis, we studied respiratory muscle strength and endurance. The data obtained was compared with those acquired from 10 age-, sex-, weight- and height-matched normal volunteers. Maximal static inspiratory pressures (PImax) measured at residual volume and maximal static expiratory pressure (PEmax) measured at total lung capacity were significantly lower in the CRF group, 58.2 +/- (SD)24.9 and 50.8 +/- (SD)24.2% of predicted, respectively (p less than 0.005, p less than 0.01). There was a significant correlation between PImax and PEmax (r = 0.827, p less than 0.001), indicating similar involvement of both inspiratory and expiratory muscle groups. Maximal voluntary ventilation (MVV), although 84.4% of the predicted value in the CRF group, was significantly lower than in the control group, where it was 114% of predicted (p less than 0.001). MVV also correlated significantly with PImax and PEmax (r = 0.764, p less than 0.001 and r = 0.807, p less than 0.001, respectively). All but one CRF patient had elevated erum inorganic phosphorus levels, and a significant correlation was found between the serum inorganic phosphorus levels and PImax and PEmax (r = 0.718, p less than 0.001). These data indicate that there is an impairment of respiratory muscle strength and endurance in patients with CRF which may predispose the patient to respiratory muscle fatigue.

Adult↗
PubMed1988

Effect of hypoxia on diaphragm blood flow, oxygen uptake, and contractility.

Recent studies examining the effects of hypoxia on diaphragm function have reached conflicting conclusions, with some reports suggesting an adverse effect of even mild hypoxemia while others indicate that the diaphragm may be extremely resistant to hypoxic stress. Diaphragm tension was not, however, directly measured nor was diaphragm length controlled in these previous reports, and it seems possible that methodologic limitations may have been responsible for these discrepant results. The purpose of the present study was to examine the effects of graded, steady-state hypoxia on diaphragm blood flow, oxygen extraction, oxygen consumption, and contractility using an in situ canine diaphragm strip preparation that permitted direct and continuous measurement of diaphragm length, tension, and blood flow. Measurements were made with the diaphragm at rest, during normoxia (PaO2, 90 to 160 mm Hg), mild hypoxia (PaO2, 45 to 60 mm Hg), and severe hypoxia (PaO2, 25 to 35 mm Hg); measurements were made with the diaphragm at rest, during rhythmic contractions at a tension time index (TTI) of 0.05, and with contractions at a TTI of 0.15. Decreases in arterial oxygenation resulted in progressive increases in blood flow and in the fractional extraction of oxygen in both resting and contracting diaphragm strips. At all levels of activity tested, blood flow and fractional extraction increased sufficiently to keep diaphragm oxygen consumption constant despite reductions in arterial oxygen content. Diaphragm contractility, as assessed from the tension generated in response to a range of electrical stimuli (1 to 80 Hz), was unaffected by hypoxia for trials performed with the diaphragm at rest and contracting at a TTI of 0.05.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Xylazine and ketamine anaesthesia in the dromedary camel under field conditions.

The effects of either xylazine (0.25 mg/kg) intramuscularly, ketamine (5.5 mg/kg) intramuscularly, or a mixture of xylazine (0.15 mg/kg) and ketamine (2.5 mg/kg) intramuscularly on sedation, analgesia, cardiac and respiratory rates, body temperature and muscle relaxation were studied in the domesticated dromedary camel. Either drug used separately was suitable for sedation and analgesia in the camel. However, the mixture of xylazine and ketamine was superior to either drug used alone. Camels which received the combination of xylazine and ketamine had fewer effects on cardiac and respiratory rates and better analgesia. In addition, they showed better muscle relaxation, less central nervous system irritability and shorter recovery times than camels sedated with ketamine alone.

Analgesia↗
PubMed1987

Relationship of changes in diaphragmatic muscle blood flow to muscle contractile activity.

The effect of increases in diaphragmatic muscle contractile activity on diaphragm blood flow remains unclear. The present study examined the effect of electrically induced isometric diaphragmatic muscle contractions on diaphragmatic blood flow. Studies were performed on diaphragmatic muscle strips prepared in anesthetized mechanically ventilated dogs. Diaphragmatic contractile activity was quantitated as the tension-time index (TTI) (i.e., the product of tension magnitude and duration). Blood flow to the strip (Qdi) was measured from the volume of the phrenic venous effluent using a drop counter. The separate effects on Qdi of 30-s periods of continuous and rhythmic contractions were examined. Qdi increased with increases in TTI and peaked at a TTI of 20-30% of maximum after which Qdi fell progressively with further increases in TTI. At levels of TTI greater than 30%, the pattern of muscle contraction significantly affected blood flow. Qdi was significantly lower during activity and the postcontraction hyperemia significantly greater at a given TTI when contractions were continuous than when contractions were intermittent. Above a TTI of 30%, Qdi during contraction decreased linearly with increases in duty cycle and curvilinearly with increases in tension. We conclude that during isometric diaphragmatic contractions, diaphragmatic blood flow may become mechanically impeded, and the magnitude of the impediment in blood flow depends on the pattern of diaphragmatic contractions. With increases in contractile activity above a critical level, changes in duty cycle exert progressively greater effects on diaphragmatic blood flow than changes in muscle tension.

Animals↗