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Biomedical subjects

S Baxter

Publications and source records attributed to S Baxter.

At least 19 recordsLinked to original sources
PubMed1994

The effects of sympathomimetics on the cardiovascular system of sheep.

1. Sheep hearts have been used to study the effects of beta-adrenoceptor (beta-AR) agonists in order to better understand the effects of common asthma treatment drugs on heart rate, cardiac power output and cardiac pathology. Hearts have been examined both in vivo and in vitro. 2. In whole anaesthetized sheep, isoprenaline, fenoterol and salbutamol induced dose-dependent increases in heart rate. Hypokalaemia in response to salbutamol was accentuated in hypoxia. Many of these hearts showed significant myocardial lesions. Hypoxia alone caused no significant cardiac response. 3. As expected, the beta 1-AR agonist dobutamine caused dose-dependent increases in heart performance (heart rate and cardiac power output). Both responses were blocked by metoprolol and propranolol. The beta 2-AR agonist salbutamol caused dose-dependent increases in heart rate and although cardiac output increased, cardiac power output remained unchanged as a consequence of the fall in peripheral resistance. The heart rate changes were blocked by metoprolol. Importantly, propranolol blocked both the heart rate response and the fall in peripheral resistance. 4. Isolated atrial strips showed a right shift of their dose-response curve to isoprenaline in the presence of the highly selective beta 2-AR antagonist ICI 118,551 at concentrations above 1 x 10(-8) mol/L. 5. We conclude that the sheep heart shows many pharmacological characteristics of the human heart which makes it a good pharmacological model in addition to its being amenable to many common techniques available for humans.

Albuterol↗
PubMed1989

Sequence analysis of the major outer membrane protein gene of an ovine abortion strain of Chlamydia psittaci.

The major outer membrane protein (MOMP) gene from an ovine abortion strain of Chlamydia psittaci (S26/3) has been cloned and sequenced. The gene shows the features of other chlamydial MOMPs but comparison with the previously reported sequence for the ovine abortion isolate A22/M has revealed substantial sequence divergence which is clustered into the same four intramolecular regions as the sequence variation found between C. trachomatis serovars. Subsequent restriction enzyme analysis of A22/M DNA has shown that it has an avian-type genomic profile and thus the comparison is between types rather than between strains.

Abortion, Veterinary↗
PubMed1989

Lead toxicity and iron deficiency in Utah migrant children.

We determined the frequency of presumptive iron deficiency and lead toxicity in 198 Utah migrant children, ages 9-72 months, during the summer of 1985. There were no confirmed cases of lead toxicity. Thirteen per cent of those tested and 30 per cent of the children ages 9-23 months were iron deficient. Hematocrit determinations accurately predicted iron deficiency in only 35 per cent of the children confirmed to have this disorder via erythrocyte protoporphyrin screening.

Anemia, Hypochromic↗
PubMed1989

Acute neurohumoral response to electroconvulsive therapy during pregnancy. A case report.

The neurohumoral changes induced by electroconvulsive therapy (ECT) in pregnancy have not been described previously. In the nonpregnant adult, ECT causes an acute rise in prolactin, adrenocorticotropic hormone (ACTH), cortisol, norepinephrine, epinephrine and beta-endorphin. Because pregnancy alters the production and release of these hormones, consideration should be given to how ECT may further alter the neuroendocrine response, with possible implications for the success of treatment and the fetal response. A 30-year-old woman with a major affective disorder underwent a course of ECT beginning at 23 weeks' gestation. Serial hormonal assays of peripheral venous samples from -30 to +240 minutes were obtained during her first treatment. The prolactin, ACTH, norepinephrine, epinephrine, beta-endorphin, dopamine and oxytocin levels rose acutely and returned to baseline during observation. The maternal vital signs were stable. No increase in uterine activity or fetal heart rate abnormalities were observed during any treatment. A healthy infant weighing 2,900 g was delivered at term, with Apgar scores of 9 and 9 and no problems. We conclude that there are acute neurohumoral changes in specific hormones with ECT in pregnancy, but none of these changes appeared to adversely affect the fetus in our case.

Adult↗
PubMed1986

Cyclic AMP, the hyperresponsiveness factor from hog kidney.

The isolation and identification of a material present in the plasma of hypertensive dogs and hypertensive human patients has been under study since 1972. The earliest experiments in relation to this work, noted that plasma from hypertensive dogs cause a hyperresponse to norepinephrine when both were administered by way of the vein. Employing a rat assay system that consisted of an anesthetized rat with polyethylene catheters in the vein for giving norepinephrine and the test fractions and a catheter in the artery for blood pressure monitoring, fractions from hog kidney were tested for hyperresponsiveness activity. The active material is very comparable to cyclic AMP in molecular weight, ultraviolet spectrum, paper chromatography, Enzyme hydrolysis and activity in the anesthetized rat system. This evidence indicates that the hyperresponsiveness factor of renal origin is cyclic AMP.

Angiotensin II↗
PubMed1985

Eimeria tenella: relative survival of drug-resistant and drug-sensitive populations in floor pen chickens.

The effect was studied of introducing about equal numbers of decoquinate-sensitive or decoquinate-resistant Eimeria tenella oocysts into a floor pen of susceptible unmedicated chickens. "Sentinel" birds introduced 2, 3, 4, 5, and 6 weeks later were used to recover populations of E. tenella oocysts. In drug sensitivity tests, populations of oocysts harvested at 4 weeks were partially resistant to decoquinate medication. Oocysts obtained after 5 and 6 weeks were highly sensitive to decoquinate medication. The results indicate that drug-sensitive E. tenella parasites are more likely to dominate in absence of medication.

Animals↗
PubMed1984

Antibacterial activity of ciprofloxacin in conventional tests and in a model of bacterial cystitis.

In conventional in vitro tests and an experimental bladder model ciprofloxacin proved very active against 103 strains of enterobacteria isolated from infected urine. Nalidixic acid-resistant strains were less susceptible to ciprofloxacin than nalidixic acid-sensitive strains, and the activity of the drug was reduced under acid conditions. Nevertheless, all strains were inhibited by 4 mg/l of ciprofloxacin at pH 5.5. Streptococcus spp., Staphylococcus aureus, Pseudomonas aeruginosa and Bacteroides spp. were less susceptible than enterobacteria, although most strains were inhibited by a therapeutically achievable concentration of 2 mg/l. Under conditions simulating the treatment of bacterial cystitis, changing concentrations of ciprofloxacin well within levels achievable in urine inhibited dense bacterial cultures for periods exceeding 24 hours, and surviving bacteria did not exhibit any reduction in susceptibility.

Anti-Infective Agents, Urinary↗