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Biomedical subjects

K Rasmussen

Publications and source records attributed to K Rasmussen.

At least 343 records · Page 19Linked to original sources
PubMed1984

Some behavioral effects of hallucinogens are mediated by a postsynaptic serotonergic action: evidence from single unit studies in freely moving cats.

Although central serotonergic systems appear to be linked importantly to the mechanism of action of a variety of hallucinogenic drugs, the nature of this interaction has remained unclear. In the present study, the question of whether the critical link is presynaptic or postsynaptic was examined in cats. Behaviorally inactive doses (1.0 mg/kg) of the serotonin receptor antagonists mianserin, ketanserin or metergoline effectively blocked behavior, as measured by the cat limb flick response, elicited by either LSD (50 micrograms/kg) or DOM (250 micrograms/kg) but not that resulting either from lisuride (50 micrograms/kg) or a high dose of apomorphine (4 mg/kg). Pretreatment with 1.0 mg/kg of mianserin, which completely attenuated LSD's behavioral effect, failed to alter LSD-induced depression of mesencephalic serotonergic neuron discharge. These results demonstrate that at least some of the behavioral effects of LSD can be blocked by pharmacological antagonism of postsynaptic serotonin receptors which leaves LSD's presynaptic effect unaffected. Thus, the behavioral, and possibly psychoactive, effects of hallucinogens appear to be attributable to an action at 5HT2 receptors, presumably located postsynaptically.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMed1984

Regulation of nuclear binding of the avian oviduct progesterone receptor. Changes during estrogen-induced oviduct development, withdrawal, and secondary stimulation.

The progesterone receptors from various stages of estrogen induced oviduct development, estrogen withdrawal, and secondary stimulation with estrogen were examined. The progesterone receptors were characterized for their biological function (i.e. capacity for nuclear translocation, nuclear binding, and effects on RNA polymerase II activity) as well as certain physical properties. The progesterone receptors from the undeveloped or partially developed oviducts (0 to 8 days of estrogen treatment) displayed little or no nuclear translocation and binding in vivo or in vitro. Similarly, progesterone showed little or no effect in vivo on RNA polymerase II activity at the early stages of development. As development progressed from 8 to 12 days of estrogen treatment, the above parameters rapidly increased to maximal levels and plateaued through day 23 of estrogen treatment. A marked decrease in these parameters occurred within 1 day of estrogen withdrawal. The reverse series of events occurred during secondary estrogen stimulation of 10-day-old withdrawn chicks. While the receptor concentrations increased rapidly to maximum values by 2 days of restimulation, receptor function did not return until day 4. Similarly, the effects of progesterone on RNA polymerase II activity reached maximal values by day 4. The progesterone receptor isolated from oviducts during development, estrogen withdrawal, and restimulation, displayed similar patterns of cell-free binding to chromatin and nucleoacidic protein as that observed in vivo supporting the nativeness of the in vitro binding assay. In contrast, the cell-free binding of these same progesterone receptor to pure DNA were not similar to the in vivo binding, i.e. no patterns (differences) in progesterone receptor binding were observed. These data support that protein DNA complexes and not pure DNA represent the native acceptor sites for oviduct progesterone receptor. Comparison of the progesterone receptor between the functional and nonfunctional states revealed no differences in the steroid affinity for the receptor, in the apparent pI of the species, or in the sedimentation of the receptor under high salt conditions. However, the nonfunctional receptors consistently displayed a deficiency in one of the two monomer molecular species (the B species) as determined by isoelectric focusing. These results suggest that both monomer species of progesterone receptor are required for biological activity. Interestingly, the 7S "aggregate" species of the progesterone receptor was constantly detected even when only one of the monomer species was present.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1984

Individual recognition of female hamsters by males: role of chemical cues and of the olfactory and vomeronasal systems.

Sexually satiated male hamsters preferred to investigate and to mount an anesthetized, estrous, novel female over a similarly presented female with which the male had become satiated (the Coolidge effect); likewise, such males preferred a novel female recently mated with another male over the familiar female but showed no preference between fresh and mated novel females. Thus the Coolidge effect is at least partly dependent on discrimination of a new female by chemical cues. Another experiment indicated that transfer of a male's own scent during mating is not involved in discrimination between familiar and novel females. Flank gland secretion of females were sufficient for individual discrimination by males, whereas head region scents and vaginal secretions were not sufficient. The presence of female's flank glands was not, however, necessary for such discrimination. Lesions of or removal of the vomeronasal organ did not disrupt the preferences of sexually satiated males for a novel female, but elimination of main olfactory system function by ZnSO4 treatment of the olfactory mucosa did abolish such preferences. Thus olfactory cues are sufficient for individual discrimination of novel females by sexually satiated male hamsters, and such recognition leads to increased sexual arousal. These processes are mediated by the main olfactory system but not the vomeronasal accessory-olfactory system.

Animals↗
PubMed1984

Activity of serotonin-containing neurons in nucleus centralis superior of freely moving cats.

Serotonergic neurons were recorded in the nucleus centralis superior (NCS) in freely moving cats and were initially identified on-line by their slow and regular spontaneous activity (mean 2.55 +/- 0.21 spikes/s). Discharge rates of NCS serotonergic neurons were highest during active waking (AW) (mean 2.94 +/- 0.28 spikes/s), decreased during slow-wave sleep (middle of SWS: mean 1.38 +/- 0.18 spikes/s), and were lowest during REM sleep (mean 0.46 +/- 0.13 spikes/s). The activity of serotonergic NCS neurons did not significantly increase during transient elevations of the EMG during AW but did significantly decrease immediately preceding, and during the occurrence of, SWS spindles. These neurons were responsive to phasic auditory and visual stimuli, with most neurons showing excitatory responses. In response to a small dose of the serotonin-specific agonist 5-methoxy-N,N-dimethyltryptamine (50 micrograms/kg, i.m.), NCS serotonergic neurons responded with a mean decrease in unit activity of 43.9 +/- 6.1%. Among the NCS serotonergic neurons a subpopulation differed from the remaining serotonergic neurons in that they showed a much smaller decrease in unit activity across the sleep-wake cycle and responded with an inhibition of activity to phasic auditory and visual stimuli. The results of this study are compared with those previously reported for serotonergic neurons in the dorsal raphe nucleus, nucleus raphe pallidus, and nucleus raphe magnus of freely moving cats.

Acoustic Stimulation↗
PubMed1984

Intracardiac electrography in patients before and after surgical repair of secundum atrial septal defect.

Nine patients (mean age 32 years, range 9-58) with a secundum atrial septal defect (ASD) were investigated by intracardiac electrography before and, on an average, 14 months after circumclusion of the defect. Postoperatively, four patients developed atrial fibrillation or flutter requiring treatment. After the repair, sinus node recovery time and the H-V interval increased significantly. The P-A interval, the A-H interval, sinoatrial conduction time, and the effective refractory period of the atrium (ERPA) remained unchanged. In the patients who developed atrial tachyarrhythmias, the mean preoperative ERPA was significantly longer than in the remaining patients; in patients with ERPA less than 220 ms, no atrial arrhythmias occurred. Our findings suggest that circumclusion of a secundum ASD has a sustained deleterious effect on sinus node function and His-Purkinje conduction. Preoperative determination of ERPA might be of value for the prediction of postoperative atrial arrhythmias in patients submitted to ASD repair.

Adolescent↗
PubMed1984

Prevalence of vasospastic ischaemia induced by the cold pressor test or hyperventilation in patients with severe angina.

We performed coronary artery spasm provocation, using the cold pressor test (CPT) and hyperventilation (HVT) in 105 patients (87 males, 18 females) with mean age 51.9 years (range 25-69) consecutively admitted for coronary angiography due to attacks of chest pain. A positive response to spasm provocation (ST segment elevation or depression greater than or equal to 0.1 mV or pseudonormalization of negative T-waves) was seen in 25 patients (23.9%) (group A), with 8 patients responding to CPT and 23 to HVT. In the remaining patients (group B) a negative response was found. Of 80 patients with coronary artery stenosis (diameter reduction greater than 50%), 22 (27.5%) showed a positive response. During CPT and HVT the rate pressure product increased 25% and 16%, respectively in group A versus an increase of 139% during exercise testing in the same patients. This suggests that ischaemia induced by CPT or HVT is not caused by increased myocardial oxygen demand. Repeat spasm provocation was performed during coronary angiography in 14 patients from group A and 14 from group B. The induced reduction in the diameters of the ischaemia related vessels was on average 48.3% in group A versus a 9.9% reduction of the left anterior descending artery in the patients from group B (P less than 0.01). In group A 88% had a history of nocturnal angina versus 38.8% in group B (P less than 0.001). A positive exercise test was found in 87% and 35.6% in group's A and B respectively (P less than 0.0005).

Adult↗
PubMed1984

Assessment of left ventricular filling pressure in myocardial infarction using the first derivative of the apexcardiogram.

We recorded the apexcardiogram (ACG) and its first derivative (dA/dt) in 24 patients with acute or recent myocardial infarction. From dA/dt, an index I = X 10 dRFW/dS was defined (dRFW and dS = peaks of dA/dt corresponding to the rapid filling wave and to the systolic upstroke of the ACG). A significant correlation was found between I and pulmonary capillary wedge pressure (PCW, mmHg). PCW = 2.3 X I + 6.5 (r = 0.80, p less than 0.001). Normal PCW was found in 15 patients who all had an I less than 2.8. Elevated PCW was found in 9 patients who all had an I greater than 2.8. Thus the ability of I to predict elevated PCW was 100% (95% confidence limit greater than 66.4%). The ability to predict normal PCW was 100% (95% confidence limit greater than 76.2%). No significant correlation was found between I and cardiac index (r = 0.29, p greater than 0.1).

Adult↗
PubMed1984

HV interval in calcific aortic stenosis. Relation to left ventricular function and effect of valve replacement.

Intracardiac electrography and 24 hour ambulatory electrocardiographic monitoring were carried out in 20 patients with calcific aortic stenosis (mean pressure gradient 86 mm Hg) to investigate (a) the role of bradycardia and tachycardia in the pathogenesis of syncope in aortic stenosis, (b) the relation between haemodynamic data and electrophysiological abnormalities, and (c) whether valve replacement corrects electrophysiological abnormalities. Intracardiac electrograms showed impaired sinus node function in five patients and a prolonged HV interval (greater than or equal to 50 ms) in 11 but there was no difference in the findings of 13 patients with syncope and seven without. Ambulatory monitoring showed short pauses in three patients and brief episodes of tachycardia in four, but there was no difference in the findings of patients with and without syncope. The HV interval correlated inversely with the left ventricular ejection fraction, whereas no correlation was found between the HV interval and the pressure gradient. Nine patients were re-evaluated 15 months after aortic valve replacement. No change was found in sinus node function, but the HV interval had increased by 7.8 ms. It is concluded that in calcific aortic stenosis neither bradycardia nor tachycardia is shown to be a frequent cause of syncope, a prolonged HV interval is a frequent finding and further prolongation occurs after valve replacement, and contractility and conductivity appear to deteriorate in parallel.

Adult↗
PubMed1984

Cardiomyopathy in western Denmark.

A retrospective study was carried out to assess the incidence of cardiomyopathy in western Denmark (Jutland and Funen) (population 2 798 000) during a two year period (1980-81). The WHO/ISCF classification was strictly followed, and rigid criteria for exclusion and inclusion of patients were adopted. Thus cases in which specific heart muscle disorders (myocarditis, alcoholic heart disease, hypertension etc) were merely suspected were excluded. Forty one patients had dilated cardiomyopathy (overall incidence 7.3/10(6) population/year) and 20 hypertrophic cardiomyopathy (overall incidence 3.6/10(6) population/year). In men aged 40-59 years the occurrence of dilated cardiomyopathy was 23.4/10(6) population/year. Only one case of Löffler's endomyocardial disease was diagnosed during the study period. Since the investigation was retrospective and was a study of diseased persons and not a population, and since a specific set of criteria for exclusion and inclusion was rigidly applied, the results represent the minimum frequency of these diseases.

Adolescent↗
PubMed1984

Clinical experience with porcine xenografts in the mitral position.

In a 7-year period, 120 porcine xenografts, 16 of Hancock and 104 of Carpentier-Edwards type, were implanted in the mitral position in patients with isolated mitral valve disease. The operative mortality was 4.2%. The actuarial survival after 5 years was 93%. Death during the observation period was valve-related in two cases. Three valves had to be exchanged, one because of calcification and two because of prosthetic endocarditis. The risk of contracting prosthetic endocarditis was 0.38% per patient year. All the patients received peroral anticoagulant medication indefinitely. Two minor embolic episodes occurred, both in the first 6 post-operative months. The probability of freedom from thromboembolism was thus 98.2% after 7 years. In functional evaluation of 92 patients observed for at least 6 months, more than 90% were in NYHA class I or II. Porcine xenograft is a good valve substitute in the mitral position with a low incidence of complications, especially of thromboembolism, in patients on maintenance anticoagulant therapy. Long-term observations of this type of valve substitute are not yet available, however.

Adolescent↗
PubMed1984

A hemodynamic study of the Carpentier-Edwards and Hancock porcine xenografts in the mitral position.

A hemodynamic study was performed on 11 female and 3 male patients with porcine xenograft (9 Carpentier-Edwards, 5 Hancock) in mitral position on average 32.5 months (range 10-65 months) after the operation. In comparison with the preoperative values, the following parameters showed statistically significant post-operative decrease (mean values): wedge pressure (from 22.9 to 13.7 mmHg), pulmonary artery pressure (33.6-21.7), right atrial pressure (7.1-4.2) and pulmonary vascular resistance (3.6-1.9 mmHg/l/min). In a supine bicycle exercise test the mean wedge pressure rose to 27.8 (range 15-44) mmHg. The transvalvular average diastolic gradient showed a mean value of 6.9 (range 4-12 mmHg). The corresponding figures for the calculated valve area were 2.0 (1.0-3.5) cm2. A biplane left ventriculography showed no valvular or paravalvular regurgitation to the left atrium in any patient. The wedge pressures during exercise were significantly correlated with graft diameters. The results were compared with previous reports on mechanical and biological mitral prostheses, and it was concluded that implantation of a porcine xenograft in the mitral position is a satisfactory procedure in severe mitral disease.

Adult↗