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Biomedical subjects

R J Barrett

Publications and source records attributed to R J Barrett.

At least 91 records · Page 5Linked to original sources
PubMed1989

Effect of bopindolol on renin secretion and renal excretory function in rats.

We investigated the effects of the new beta-adrenoceptor antagonist, bopindolol, on stimulated renin secretion and on renal function in conscious rats. Intravenous doses of 10, 31.6, and 100 micrograms/kg of bopindolol antagonized the rise in plasma renin activity (PRA) induced by the administration of isoproterenol (10 micrograms/kg, s.c.). Peak PRA, evident at 15 min after isoproterenol, reached 27 +/- 3 ng/ml/h with bopindolol (100 micrograms/kg) pretreatment vs. 105 +/- 7 ng/ml/h in saline controls. Antagonism by bopindolol (100 micrograms/kg, i.v.) of isoproterenol-stimulated rise in PRA persisted through 12 h. Within this dosage range, bopindolol itself had no significant effect on PRA. Significant antagonism of beta-adrenoceptor-induced hypotension resulted with 31.6 and 100 micrograms/kg of i.v. bopindolol. Orally administered bopindolol produced significant antagonism of isoproterenol-induced increase in PRA at a dose of 316 micrograms/kg; however, oral doses of 31.6-316 micrograms/kg of bopindolol failed to significantly alter furosemide-stimulated increase in PRA. Bopindolol alone had little effect on renal excretory function but caused a slight attenuation of furosemide-induced diuresis and electrolyte excretion. Plasma electrolytes and osmolarity were unaffected by bopindolol alone or in conjunction with furosemide. These results indicate that bopindolol (a) is a potent, long-acting, orally active, antagonist of beta-adrenoceptor-stimulated renin secretion in the rat, (b) is ineffective in antagonizing furosemide-induced rise in PRA, (c) does not elevate basal levels of PRA by virtue of its intrinsic sympathomimetic activity, and (d) does not cause dramatic alteration of renal excretory function at effective beta-blocking doses.

Adrenergic beta-Antagonists↗
PubMed1989

A phase II evaluation of mitolactol in patients with advanced squamous cell carcinoma of the cervix: a Gynecologic Oncology Group Study.

Sixty patients with advanced squamous cell carcinoma of the cervix (SCC) who had received no prior chemotherapy were entered onto a study of mitolactol (dibromodulcitol [DBD]). The drug was administered orally at an initial dose of 180 mg/m2 per day for 10 days and repeated every 4 weeks. There were 55 evaluable patients, of whom one (2%) had a complete response (CR), and 15 (27%) had a partial response (PR), (CR plus PR, 29%). A 95% confidence interval for the true response rate is 18.8% to 42.1%. Myelosuppression was appreciable at this dose and schedule, with 13 patients experiencing life-threatening thrombocytopenia and two drug-related deaths. The level of activity in this disease encourages us to determine a tolerable dose of this drug in combination with cisplatin for further study.

Adult↗
PubMed1989

Primary melanoma of the vagina: a clinicopathologic analysis.

Primary melanoma of the vagina is a rare tumor associated with a poor prognosis. The clinical and pathologic features of 15 patients treated at the University of Michigan Medical Center and Bowman Gray School of Medicine are reviewed. The presenting symptom of bleeding was noted in 80% of the patients. The cumulative 5-year survival was 17.4%. Two patients survived more than 5 years. All melanoma tumors were of the nodular type, 66% were located in the lower one-third of the vagina, and all patients were found to have invasion greater than 3 mm at the time of diagnosis. The majority of recurrences were located in the pelvis, with the lung being the most common metastatic site. Data from the literature were incorporated with these patients' data in a meta-analysis. Tumor thickness (6 mm or less) significantly (P = .015) affected the disease-free interval. Tumor size (less than 3 cm) significantly (P = .024) influenced survival, whereas age, stage, tumor location, and tumor thickness did not. There was no significant difference in survival among patients treated by surgical resection, irradiation, or surgical resection plus irradiation. The type of surgery, whether radical or conservative, also did not influence survival. One patient had a complete response to high-dose irradiation fractions (greater than 400 cGy), and this form of irradiation in conjunction with surgical resection is presented as a treatment option.

Aged↗
PubMed1988

Tenckhoff catheter cytology in patients with ovarian cancer.

In order to expose malignant cells to high concentrations of cytotoxic chemotherapeutic agents, drugs can be instilled directly into the peritoneal cavity of patients with ovarian carcinomas through a Tenckhoff catheter. The peritoneal dialysate removed during such therapy can be examined cytologically for the presence of carcinoma cells. The cytologic specimens from Tenckhoff catheters from 40 consecutive patients with primary ovarian (39) and tubal (1) cancer who received intraperitoneal chemotherapy have been reviewed retrospectively. A total of 237 specimens yielded 78 (33%) positive, 138 (58%) negative, and 21 (9%) inconclusive or suspicious fluids. The major diagnostic problem was the marked mesothelial atypia, which may be related to the high concentrations of cytotoxic agents intimately in contact with the peritoneum. Of the 15 patients who had tissue examined after placement of the catheter (mean interval, 5 months), results agreed with those of the catheter cytologic specimens in ten patients. The catheter cytologic specimen was never positive when histology was negative. Of the 36 patients with evaluable follow-up (mean, 19 months), agreement between the clinical course and the catheter cytologic results was found in 27 patients (75%). Again, interpretation of the catheter specimens was never positive in the face of a benign clinical course. Thus, evaluation of catheter specimens by cytologic examination has a diagnostic sensitivity and specificity of 59% and 100%, respectively. Tenckhoff catheter cytology has proven to be a rather valuable tool to monitor persistent or recurrent intraperitoneal ovarian carcinoma.

Adult↗
PubMed1988

The evaluation of HBDH and LDH isoenzymes in cardiac cell necrosis of the rat.

The total LDH, HBDH and LDH isoenzyme activities were assessed in a number of rat tissues. HBDH did not correlate with LD1 and LD2 isoenzyme activity in tissues with high HBDH activity. HBDH therefore cannot be used as a marker for cardiac necrosis in the rat. In rats treated with isoprenaline and SK&F 94120 at doses producing myocardial necrosis, only the LD1 isoenzymes showed any significant change but only within the first 24 h of treatment. No statistically significant differences were seen in the plasma AST, CK, CK-MB and total LDH activities.

Animals↗
PubMed1988

Clinical writing and the documentary construction of schizophrenia.

Psychiatric practice involves writing as much as it involves talking. This study examines the interpretive processes of reading, writing and interviewing which are central to the clinical interaction. It is part of a broader ethnographic study of an Australian psychiatric hospital (which specializes in the treatment of patients with a diagnosis of schizophrenia). The paper examines two major types of written assessment of patients--the admission assessment and the 'complete work-up.' Writing is analyzed as performance, thereby focusing on the transformations that are effected in patients, their perceptions of their schizophrenia, and their total identity. One crucial transformation is from 'person suffering from schizophrenia' to 'schizophrenic.' The paper aims to show that as much as psychiatry is a 'talking cure' it is also a 'writing cure.'

Adult↗
PubMed1988

Time dependent pentylenetetrazol-like cues subsequent to diazepam administration.

Seventy male Sprague-Dawley rats were trained to discriminate which of two levers to press for milk reinforcement on a VI-20 schedule of reinforcement on the basis of whether they were injected subcutaneously with 0.75 mg/kg diazepam or 10.0 mg/kg pentylenetetrazol. Following discrimination acquisition, a dose-response function was generated for each drug during 5-min extinction periods. Subjects were then assigned to one of seven groups on the basis of their per cent responding during saline testing. Each group was injected with 5 mg/kg diazepam and then given a 5-min extinction test at intervals of 2, 4, 6, 8, 12, 16, 20, or 24 h subsequent to injection. The results indicated that at the shorter time intervals the animals responded on the diazepam lever. However, as the time interval between injection and testing lengthened, responding on the PTZ bar gradually increased until by 12 h following injection with diazepam the animals were responding as though they had received an injection of 5 mg/kg PTZ. Following this period of rebound, choice behavior returned to baseline by 24 h post-injection.

Animals↗
PubMed1988

Amphetamine's effects on food consumption and body weight: the role of adaptive processes.

Three experiments were conducted to characterize the time course of amphetamine's effects on food consumption using procedures that would allow both decreases and increases in eating to be evident relative to control levels. In Experiment 1 we measured eating over 12 postinjection hr in rats. Orderly changes in within-day temporal patterns of eating over the 12 days of amphetamine administration suggest the role of conditioned adaptive processes. In Experiment 2, animals were not presented food until 2 hr after drug administration. Initial anorexia and subsequent hyperphagia were produced by repeated administration of amphetamine. Experiment 3 assessed both within-day and over-day changes in body weight and food consumption and showed that in addition to the drug's anorectic effect, amphetamine also reduces body weight via other mechanisms. In interpreting tolerance to anorectic drugs, it is necessary to evaluate such changes in body weight that indicate shifts in hunger that occur over days as well as shifts in within-day temporal patterns of eating that indicate the presence of conditioned adaptive changes. It is proposed that these two adaptive mechanisms account for pharmacodynamic tolerance.

Animals↗
PubMed1988

Cardiovascular and renal actions of calcium channel blocker chemical subgroups: a search for renal specificity.

The diuretic and natriuretic responses to structurally distinct classes of Ca2+ channel blockers have been compared, to determine whether any agent provoked K+-sparing natriuresis, and to assess the relation of such responses with drug effects on blood pressure. Conscious normotensive Sprague-Dawley rats received vehicle or one of the following drugs in an oral saline load (40 mL kg-1) nifedipine, nimodipine, nitrendipine, prenylamine, cinnarizine, flunarizine, diltiazem, verapamil, hydrochlorothiazide, amiloride, or hydralazine, at doses from 0.316 to 100 mg kg-1. Urine was collected for 6h. Blood pressure was monitored directly in parallel studies. Diltiazem (31.6, 100 mg kg-1) and flunarizine (100 mg.kg-1) enhanced urine and electrolyte excretion in spite of marked hypotension; diltiazem was the only drug to produce dose-related renal responses. In contrast, equihypotensive doses of hydralazine and nifedipine produced overt urine and electrolyte retention. Nitrendipine and prenylamine (0.316 mg kg-1 each) produced slight diuresis or natriuresis without altering blood pressure; higher doses had no effect. The 31.6 mg kg-1 doses of verapamil, nitrendipine, and nimodipine markedly reduced blood pressure, but neither enhanced nor limited urine and electrolyte excretion. Cinnarizine failed to produce any cardiovascular or renal effects. Diuretic responses evoked by the Ca2+ channel blockers were not class-specific, showed no tendency towards sparing K+, were generally weaker than those produced by low doses of amiloride or hydrochlorothiazide, and were dissociable from drug-induced changes in blood pressure.

Amiloride↗
PubMed1988

An improved simple technique for the collection of blood samples from rats and mice.

The technique of blood collection from the lateral caudal vein has been improved. The method requires only moderate skill and no anaesthesia is necessary. Collection of blood samples causes little trauma and can be repeated at frequent (8 h) intervals thus making the method particularly suitable for pharmacokinetic and hormonal studies. Blood samples are uncontaminated by tissue fluids. Large volumes can be obtained, in mice up to 1.5 ml and in Wistar rats over 4 ml.

Animals↗
PubMed1988

Cervicovaginal psammoma bodies. The initial presentation of the ovarian borderline tumor.

Psammoma bodies associated with cancer cells of ovarian and endometrial origins have been previously described in cervicovaginal smears, as have psammoma bodies from totally benign processes. We describe the presence of numerous psammoma bodies in the cervical smear, endometrial curettage, and peritoneal wash specimens from a patient with subsequently discovered bilateral, ovarian, borderline serous tumors. We morphologically traced the transit of these psammoma bodies and their associated cytologically benign tumor cells through the entire female genital tract.

Fallopian Tubes↗
PubMed1987

Neuroendocrine features in poorly differentiated and undifferentiated carcinomas of the cervix.

Neuroendocrine or argyrophil cell carcinoma of the cervix has recently been accepted as a distinct clinical-pathological entity. The histologic pattern of these carcinomas is usually poorly differentiated or undifferentiated. Twenty patients with a histologic diagnosis of small cell carcinoma, undifferentiated carcinoma, poorly differentiated adenocarcinoma, or poorly differentiated, adenosquamous carcinoma of the cervix were evaluated for neuroendocrine features. The results of studies to detect neurosecretory granules were positive in seven of the 20 cases. Not only small cell carcinomas, but also tumors classified as undifferentiated carcinoma and poorly differentiated, adenosquamous carcinoma contained cytoplasmic granules consistent with neuroendocrine carcinoma of the cervix. The prognosis for survival appears poorer for patients having tumors with neurosecretory granules after controlling for stage and histologic grade of the neoplasm.

Adenocarcinoma↗
PubMed1987

Involvement of dopamine receptor subtypes in dopaminergic modulation of aldosterone secretion in rats.

The postulation that dopamine (DA) may tonically inhibit aldosterone (ALDO) secretion has arisen from the finding that metoclopramide, a non-selective DA receptor antagonist with prominent non-dopaminergic actions, stimulates ALDO secretion. Experiments were performed to determine: (a.) the ability of several non-specific and subtype-specific DA receptor antagonists to stimulate ALDO secretion, (b.) the subtype DA receptor involved in regulating ALDO secretion, and (c.) if ALDO responses were associated with changes in plasma Na+(pNa), K+(pK), or osmolality (pOsm). Blood samples were withdrawn from carotid arterial catheters in conscious, fasted male Sprague-Dawley rats before and following intra-arterial administration of lactated Ringer's placebo, furosemide (10 mg/kg), or one of several DA receptor antagonists. Furosemide stimulated ALDO, decreased pK, and left pNa and pOsm unchanged. The non-selective DA receptor antagonists metoclopramide (0.2, 0.6 mg/kg), rs-sulpiride (0.2 mg/kg), and haloperidol (0.1 mg/kg), and the DA-2 receptor antagonists domperidone (0.1 mg/kg) and s-sulpiride (0.1 mg/kg) each stimulated ALDO, and left pNa, pK, and pOsm unchanged. Conversely, the DA-1 receptor antagonists SCH 23390 (0.03, 0.1 mg/kg) and r-sulpiride (0.1 mg/kg) failed to stimulate ALDO, and left pNa, pK, and pOsm unaltered. These studies suggest that ALDO secretion in rats is modulated by a mechanism involving DA-2, but not DA-1 subtype receptors, and that the ALDO responses to DA receptor antagonism are independent of changes in pNa, pK, and pOsm.

Aldosterone↗
PubMed1986

Myocardial and vascular actions of amiloride in spontaneously hypertensive rats.

Experiments were conducted to characterize the cardiovascular actions of the potassium-sparing diuretic amiloride in spontaneously hypertensive and normotensive Wistar-Kyoto rats. Amiloride produced dose-dependent and sustained reductions in blood pressure in spontaneously hypertensive, but not Wistar-Kyoto rats. In intact spontaneously hypertensive rats, amiloride reduced blood pressure, heart rate and myocardial oxygen consumption, and increased simultaneously myocardial contractility. The antihypertensive response was unaltered by bilateral nephrectomy, atropine, cimetidine plus mepyramine, sulpiride and ouabain, but was prevented by phentolamine, hexamethonium and reserpine. Pressor responses to norepinephrine, tyramine, phenylephrine and clonidine were depressed significantly after amiloride, suggesting that amiloride interfered with alpha adrenoceptor-mediated vasoconstriction; vascular reactivity to arginine vasopressin, isoproterenol, histamine and acetylcholine was unaltered. The bradycardic response to amiloride persisted in all groups of animals in spite of surgical or pharmacological pretreatments; positive chronotropic responses to isoproterenol were unaltered by amiloride. The positive inotropic responses to amiloride were evident in the presence of bradycardia, and under conditions in which afterload remained constant or was allowed to decrease. The negative chronotropic and positive inotropic actions of amiloride were due to a direct action of the drug on myocardial tissues, and occurred independently of the antihypertensive effect.

Amiloride↗
PubMed1985

Lack of renal tubular and hemodynamic effects of non-selective and delta-opioid receptor antagonism.

The renal pharmacological actions of the non-selective opioid receptor antagonist naloxone and the selective delta (delta)-opioid receptor antagonist ICI 154,129 were examined in conscious dogs. Neither naloxone nor ICI 154,129 altered glomerular filtration rate, renal blood flow, blood pressure, heart rate, or renal excretion of water, Na+, K+, or Cl-. In addition, urine and plasma osmolality and electrolyte concentrations and hematocrit were unchanged, suggesting that neither agent produced physiologically significant alteration in plasma vasopressin levels. These data suggest that (a) naloxone and ICI 154,129 exert no renal pharmacological effects in dogs and (b) under resting physiological conditions, delta-opioid receptors, as well as other opioid receptor subtypes, probably are not involved in the tonic regulation of renal hemodynamics or tubular function.

Animals↗
PubMed1985

Amphetamine-haloperidol discrimination: effects of chronic drug treatment.

Rats responding for food reinforcement were trained in a 2-lever drug discrimination task. Groups of rats were trained to discriminate one of four doses of amphetamine (0.0, 0.1, 0.3, or 0.5 mg/kg) from haloperidol (0.02 mg/kg). Both the rate of acquisition and level of discrimination at asymptote were a function of amphetamine training dose. Following acquisition of this discrimination, choice behavior was assessed in the absence of drug during two test sessions. Twenty-four hours following the second drug-free test session, chronic drug treatment commenced. Half of the animals received 10 mg/kg amphetamine for 10 consecutive days while the other half received 1 mg/kg haloperidol during the same period. Choice behavior was assessed during three 2.5-minute unreinforced drug-free test sessions 24, 48, and 72 hours following the chronic drug regimen. Following chronic haloperidol, animals responded as though a small dose of amphetamine had been administered, while following chronic amphetamine, they responded as though a small dose of haloperidol had been administered. Collectively, these results suggest that animals trained to discriminate amphetamine from haloperidol respond on the basis of a continuum of dopaminergic function. Further, this continuum can be used to elucidate the net effect of pharmacologically-induced alterations in dopaminergic function, as well as the effect of nonpharmacological manipulations that may result in dopaminergic changes.

Amphetamine↗