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Biomedical subjects

J Weiss

Publications and source records attributed to J Weiss.

At least 379 records · Page 21Linked to original sources
PubMed1984

Effects of naloxone and naltrexone on drug-induced hypothermia in mice.

The hypothermia produced by injecting apomorphine into mice was potentiated by morphine; it was antagonized by haloperidol, by naloxone and by naltrexone. The hypothermic responses to morphine, chlorpromazine and ethanol were also blocked by naltrexone. However, naltrexone potentiated the hypothermic response to pentobarbital. Tolerance to morphine, produced by subcutaneous implantation of a morphine pellet, was accompanied by cross-tolerance to apomorphine-induced hypothermia. Animals made tolerant to apomorphine were not tolerant to morphine-induced hypothermia. The dopamine supersensitivity resulting from chronic treatment with haloperidol potentiated the hypothermic response to apomorphine but not to morphine. These results suggest that endogenous opioids may serve as mediators in the control of thermoregulation by dopamine.

Animals↗
PubMed1984

Conspecific urine marking in male-female pairs of laboratory rats.

Male-female pairs of rats were observed during social interactions for conspecific markings where an animal deposits urine on the body of a second animal. Injections of sodium fluorescein were used to change urinary color and provide a visible mark on the back of a conspecific. The general hypothesis tested in the three experiments was that a female would mark males differently dependent upon her hormonal status and upon the relative hormonal integrity of the males. Results of Experiment 1 were that males marked females more frequently than vice versa and female marking decreased during her estrus. Moreover, a diestrous female marked an aggressive male more than she marked a non-aggressive male (Experiment 2), and a diestrous female marked a castrated male receiving 800 micrograms testosterone propionate (TP) injections more copiously than she marked a castrated male receiving 200 micrograms TP injections (Experiment 3). Finally, aggressive and non-aggressive males marked females similarly, though the 800 micrograms TP males marked females more than the 200 micrograms TP males. These data were compared with findings from research on environmental marking in rodents, and an hypothesis was suggested that female rats use conspecific marking to identify and select males with preferred behavioral and endocrine characteristics.

Aggression↗
PubMed1984

Electrophysiologic basis for the suppression by amiodarone of orthodromic supraventricular tachycardias complicating pre-excitation syndromes.

Ten patients with refractory recurrent supraventricular tachycardia were found by electrophysiologic study to have bypass tracts and orthodromic atrioventricular reentrant tachycardia. All had failed to respond to conventional antiarrhythmic therapy and were therefore treated with oral amiodarone (1,600 to 2,000 mg/day for 2 weeks, then 800 to 1,200 mg/day for another 2 weeks with subsequent 200 to 600 mg/day maintenance doses). During or after the fourth week of therapy, electrophysiologic study was repeated. In 9 of 10 patients, supraventricular tachycardia could not be reinduced by programmed stimulation. In the remaining patient, nonsustained supraventricular tachycardia (greater than 10 beats, lasting less than 30 seconds) with a slower basic cycle length than that during the control period was provoked. Significant increases in the effective refractory period of the accessory pathway in both the anterograde (+26%, p less than 0.05) and retrograde (+40%, p less than 0.02) directions were noted, the magnitude of change being independent of the control effective refractory period. There were also significant increases in the effective refractory period of the right atrium (+24%, p less than 0.01) and the right ventricle (+15%, p less than 0.01) during long-term therapy with amiodarone. Over a mean follow-up period of 20 months, symptomatic control of the arrhythmia occurred in all patients; in only one patient treatment with amiodarone could not be continued because of side effects. These data establish the electrophysiologic basis for the effectiveness of amiodarone in the prophylactic control of refractory paroxysmal supraventricular tachycardia complicating the bypass tract syndromes.

Adult↗
PubMed1984

A new type of ventriculo-atrial gap phenomenon in man.

A new type of ventriculo-atrial (V-A) gap phenomenon was observed in a patient who underwent a cardiac electrophysiology study and had complete antegrade infranodal A-V block but intact V-A conduction. During ventricular extrastimulus testing, a split retrograde His potential emerged from the ventricular electrogram. As the prematurity of the extrastimulus was increased, the later of the two retrograde His deflections disappeared suddenly at a critical coupling interval and V-A conduction was interrupted. More premature extrastimuli resulted in progressive delay in the His-Purkinje system and delayed appearance of the earlier retrograde His deflection. As a result of this delay, conduction through the His bundle eventually resumed, the second (split) retrograde His reappeared and conduction to the atria resumed. Thus, the initial site of block during the V-A gap phenomenon in this patient was located in the His bundle, with proximal delay occurring in the distal His-Purkinje system. The results indicate that the classic mechanism of gap phenomenon is operative. To our knowledge, this type of V-A gap phenomenon has not been previously described in man.

Aged↗
PubMed1984

Dual atrio-ventricular nodal pathways and atrial fibrillation.

The determinants of the ventricular rate during atrial fibrillation were studied in a group of eleven patients demonstrating dual A-V nodal pathways during atrial stimulation. The shortest R-R interval and the mean ventricular cycle length during at least 1 min of pacing-induced atrial fibrillation were compared: a) to the effective and functional refractory period of the fast pathway; b) to the effective refractory period of the slow pathway determined during atrial stimulation, at two or more different basic cycle lengths of pacing; and c) to the shortest cycle length during atrial stimulation followed by 1:1 A-V conduction. A group of 8 patients not demonstrating dual A-V nodal pathway-curves during atrial stimulation was used as a control. In both groups the shortest R-R interval during atrial fibrillation was best predicted by the shortest cycle length followed by 1:1 A-V conduction during atrial stimulation. The mean ventricular cycle length during atrial fibrillation was not accurately predicted by any of the variables studied. The similar results in patients with and without dual A-V nodal pathways suggest that concealed conduction from one to another A-V nodal pathway does not play a role in determining the ventricular response during atrial fibrillation in patients with dual A-V nodal pathways.

Adolescent↗
PubMed1984

Role of acidosis in early contractile dysfunction during ischemia: evidence from pHo measurements.

To investigate the contribution of acidosis to contractile dysfunction during early myocardial ischemia, miniature intramyocardial pH electrodes (0.2 mm tip diam) were used to correlate changes in extracellular pH (pHo) with tension in the isolated arterially perfused rabbit interventricular septum. A number of findings argue against acidosis as the major cause of contractile failure during early ischemia. During hypoxia without glucose present, the rate and pattern of tension decline was very similar to total ischemia, suggesting that a common mechanism is involved. Throughout the initial period in which tension declined by 50%, however, pHo increased in the six of eight preparations during hypoxia without glucose. During hypoxia with glucose present, tension fell less rapidly than during hypoxia without glucose despite a significantly greater fall in pHo in the former case. The maximal rate of relaxation (-dT/dt) was markedly more sensitive to ischemia, hypoxia, or exposure to inhibitors of aerobic metabolism (2,4-dinitrophenol and Na azide) than the maximal rate of force development (+dT/dt). In contrast, +dT/dt and -dT/dt decreased almost symmetrically during exposure to respiratory acidosis. During ischemia, the change in pHo associated with 50% reduction in tension was 0.11 +/- 0.04 units. During respiratory acidosis, this value was 0.45 +/- 0.02 units. From these observations we concluded that acidosis is unlikely to be a major factor in the early decline of tension during ischemia.

Acidosis↗
PubMed1984

Extracellular pH and tension during ischemia in the isolated rabbit ventricle.

To investigate the factors determining the rate of H+ accumulation during early ischemia, miniature intramyocardial pH electrodes (tip diam 0.2-0.5 mm) were used to record extracellular pH (pHo) in the isolated arterially perfused rabbit interventricular septum. Changes in pHo and the rate of fall of tension during global ischemia were compared under control conditions (37 degrees C, heart rate 75 beats/min) and after exposure to the following interventions: reduced heart rate (36 beats/min), hypothermia (27 degrees C), verapamil (0.5 microM), reduced extracellular Ca2+ concentration [( Ca2+]o 0.5 mM), norepinephrine (0.5 microM) in normal and catecholamine-depleted preparations, norepinephrine and reduced [Ca2+]o, and theophylline (4 mM). Under control conditions pHo declined by 0.61-0.73 pH units after 10 min of ischemia. The negative inotropic interventions and reduced temperature significantly decreased [H+]o accumulation during ischemia. Positive inotropic interventions did not affect the rate of [H+]o accumulation during ischemia except in reserpinized preparations. All of the interventions except for reduced temperature significantly altered the relationship between tension and pHo during ischemia.

Acidosis, Respiratory↗
PubMed1984

The influence of various housing conditions on the ocular fundus in Wistar rats.

Examinations of ocular fundi were performed on male Wistar rats which were housed for 2 years individually or in groups of 3, 5 or 10 animals per cage. Photographs were taken to make the data objective and provide a permanent record. The results indicated no differences between the various groups, although there were marked differences between individual rats.

Animals↗
PubMed1984

Testicular hormones and intermale aggressive behaviour in the presence of a female rat.

A hypothesis was examined that increased levels of available testicular hormones are responsible for the increased aggressiveness of males in the presence of a female. In the first of two experiments intact male rats were injected with the androgen antagonist flutamide before exposure to oestrous, dioestrous or no females. Consistent with the hypothesis, flutamide-injected males were less aggressive than the respective control males which had been injected with oil alone. Yet the antiandrogen did not fully block the increased aggressiveness between males exposed to an oestrous female. In experiment 2 the aggressive behaviours of male rats in the presence of an oestrous female were observed after castration and restoration therapy with different amounts of testosterone propionate (TP). Neither a physiological amount (200 micrograms) nor an unusually large amount (800 micrograms) to TP could adequately mimic the effects of a gonadally intact male exposed to a sexually receptive female. These data suggest that differences in androgens available to target tissues influence aggressiveness among males exposed to a female. However, there are other factors involved, presumably the chronic morphological-physiological-behavioural changes that are provoked by copulatory experience.

Aggression↗
PubMed1984

The role of lipopolysaccharides in the action of the bactericidal/permeability-increasing neutrophil protein on the bacterial envelope.

The killing of gram-negative bacteria by the bactericidal/permeability-increasing protein ( BPI ) of neutrophils requires surface binding, and is accompanied by a discrete increase in outer membrane permeability to small hydrophobic substances. This outer membrane alteration appears to be related to perturbation of outer membrane lipopolysaccharides (LPS). BPI causes extracellular release of LPS, but only at supra-saturating doses. Nevertheless, because the organization of LPS in the outer membrane is altered by pretreatment of bacteria with saturating doses of BPI (producing maximal bactericidal and permeability-increasing effects), the amount of LPS released during Tris-EDTA treatment is reduced by 80%. BPI markedly (approximately 50%) and selectively stimulates biosynthesis of LPS, suggesting an attempt by BPI -killed bacteria to repair outer membrane damage. The removal of surface-bound BPI by 40 mM Mg2+ initiates time- and temperature-dependent repair of the outer membrane permeability barrier and a further increase (approximately 170% of control) in LPS synthesis, even though the bacteria are no longer viable. Mg2+-induced repair is blocked when: 1) a temperature-sensitive mutant (Salmonella typhimurium HD50 ) with a conditional defect in LPS synthesis is incubated at the nonpermissive temperature (42 degrees C); and 2) LPS synthesis is selectively inhibited by a diazaborine derivative (Sandoz drug No. 84474). In contrast, repair is normal by the mutant at permissive temperatures (30 degrees C) and by the parent strain (S. typhimurium AG701 ) at both 30 degrees C and 42 degrees C. Inhibition (greater than 85%) of protein synthesis by chloramphenicol has little or no effect on repair. These findings indicate that the repair of the permeability barrier after the removal of BPI from the surface requires newly made LPS, but apparently no biosynthesis of other outer membrane constituents, which strongly suggests that the effects of BPI on LPS are mainly responsible for the break-down of the outer membrane permeability barrier.

Animals↗
PubMed1984

Verapamil as maintenance treatment in bipolar illness: a case report.

The authors report the successful maintenance treatment of a bipolar woman with verapamil. Whereas the patient had previously demonstrated multiple antidepressant-induced manias despite prophylactic lithium treatment, she was able to maintain on verapamil plus trazodone without manic or depressive episodes over a 1-year period. It is suggested that verapamil may have a place in the maintenance treatment of bipolar patients.

Adult↗
PubMed1983

[Chemotherapy in pretreated Hodgkin's disease with lomustine, bleomycin, vinblastine and dexamethasone].

A combination of lomustine (120 mg/m2 day 1), bleomycin (15 mg day 1 and 22), vinblastine (6 mg/m2 day 1 and 22) and dexamethasone (3 mg/m2 day 1 up to 21) was used in 20 patients with Hodgkin's disease stage II B (n = 2), III B (n = 4) and IV B (n = 14). These patients had not responded to earlier standard chemotherapy or had had a relapse within one year. Treatment cycles were repeated six-weekly. Nine cases showed complete and six cases partial remission. No change was seen in two cases and progression occurred in three patients. The median time of remission was 10 months. Multiple extranodal involvement had a particularly unfavourable prognosis: only one out of five patients showed remission. Two out of 7 patients with progression during COPP and 3 out of 5 patients with progression during ABVD remitted completely, indicating a slight cross resistance only among the three combinations of chemotherapeutics. Treatment was well tolerated and can be done on an out-patient basis.

Adult↗
PubMed1983

Light and scanning electron microscopic study of testosterone-restored penile papillae in castrated rats.

Structural changes in various penile tissue from rats with differing circulating androgen levels were analyzed with light and scanning electron microscopy. Adult males were castrated and daily injected for 6 weeks with one of four physiologic amounts of testosterone propionate (TP). Results indicated that epithelium, subepithelial connective tissue, and the papillae protruding from the surface of the glans penis responded, more or less, in a dose-dependent fashion to the steroid. The least androgen-sensitive penile tissue was the epidermal stratum corneum, more sensitive was the maligiphian layer, and more sensitive still was the subepithelium. The penile papillae and their follicles were the most androgen-sensitive tissue. Specifically, the high testosterone, 400 micrograms and 800 micrograms TP, males experienced papillae that were thicker, taller, more densely arranged, and more highly keratinized than the lower testosterone, 100 micrograms and 200 micrograms TP, males. The function of the papillae may be to provide the female with the mechanical stimulation necessary to ensure a proper hormonal milieu for successful impregnation.

Animals↗
PubMed1983

Control of sudden recurrent arrhythmic deaths: role of amiodarone.

Patients resuscitated after out-of-hospital cardiac arrest have electrical instability of the myocardium, with 30% to 40% propensity for recurrent arrest in the first year. About 85% to 90% of such patients have complex ventricular ectopy and runs of ventricular tachycardia; in 70% to 80%, ventricular tachycardia or fibrillation are inducible by programmed electrical stimulation. The attempt to control recurrent cardiac arrest using these parameters and conventional antiarrhythmic drugs has yielded conflicting or variable results. Amiodarone was therefore studied in 40 consecutive patients (with previous cardiac arrests) in whom conventional antiarrhythmic therapy had proved ineffective or was not tolerated. The mean ejection fraction of the group was 0.29 +/- 0.12. At a mean follow-up of 16 months (range 5 to 40 months) six patients had died, three from heart failure, one from liver failure (not drug induced), and two from sudden (presumably arrhythmic) death. Late occurrences of arrhythmia were found in two patients (complicated by digitalis intoxication in one). Ambulatory ECG recordings showed that amiodarone had a potent suppressant effect on ventricular ectopy and runs of VT, but electrophysiologic studies demonstrated that it did not inhibit inducible VT/VF in greater than 65% despite an excellent clinical outcome. Limiting adverse reaction was seen in only one patient; other relatively minor side effects occurred in 10% to 15% of patients receiving maintenance therapy. Our data provide further evidence for the effectiveness of amiodarone in life-threatening ventricular arrhythmias, with a potential for the prolongation of survival in patients resuscitated after out-of-hospital cardiac arrests.

Amiodarone↗
PubMed1983

Acceleration of wound healing by topical application of honey. An animal model.

Commercial unboiled honey was applied topically to open wounds of 12 mice. Twelve other mice served as a control group and their wounds were dressed with saline solution only. Wound healing was judged histopathologically by measuring the thickness of granulation tissue, epithelization from the periphery of the wound, and the size of the open wounds. The animals were killed 3, 6, and 9 days from the day they were wounded and treated, and their wounds were examined histopathologically. According to the three mentioned criteria, wounds of the honey-treated animals healed much faster than the wounds of the control animals (p less than 0.001). Unboiled commercial honey seems to accelerate wound healing when applied topically due to its energy-producing properties, its hygroscopic effect on the wound, and its bacteriocidic properties. Our results suggest that honey applied topically on open wounds accelerates the healing process.

Administration, Topical↗
PubMed1983

Use of nitrofurantoin macrocrystals after transurethral prostatectomy.

A prospective randomized study of 223 consecutive patients with sterile urine undergoing transurethral prostatectomy was undertaken to examine the effects of nitrofurantoin macrocrystals on postoperative urine cultures. Patients were divided into 3 groups; group 1 received no postoperative antibiotics, group 2 received nitrofurantion for 5 days postoperatively and group 3 received nitrofurantoin for 10 days postoperatively. Nitrofurantoin decreases the incidence of short-term (24 hours after catheter removal) postoperative bacteriuria, while having no effect on long-term (4 weeks) bacteriuria following transurethral prostatectomy. The use of postoperative nitrofurantoin is supported by its tendency to reduce the incidence of short-term urinary infection in patients with the same organisms found in cultures of the prostatic tissue. However, there was no long-term advantage in prolonging therapy for greater than 5 days. There was no difference in morbidity in the immediate postoperative period among the 3 groups.

Bacteriuria↗