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Biomedical subjects

A Pfeiffer

Publications and source records attributed to A Pfeiffer.

At least 181 records · Page 10Linked to original sources
PubMed1982

Delta versus mu receptors: cardiovascular and respiratory effects of opiate agonists microinjected into nucleus tractus solitarius of cats.

The cardiovascular and respiratory responses to relatively specific mu or delta agonists microinjected (0.5 microliter/kg) into the region of the nucleus of tractus solitarius (NTS) were examined in anesthetized cats. Blood pressure, heart rate, and respiratory rate were monitored for 30 min after the microinjection of opioid compounds or saline vehicle. The delta agonist, (D-Ala2,D-Leu5)-enkephalin (10-100 nmol/kg) elicited dose-dependent decreases in blood pressure, heart rate, and respiratory rate which were naloxone reversible. In contrast the mu agonists, morphine (10-54 nmol/kg) and morphiceptin (100-320 nmol/kg) had no effect on blood pressure or respiratory rate; yet, naloxone elicited pressor responses in animals pretreated with these mu agonists. A receptor-binding assay demonstrated a predominance of mu sites in the NTS. These data show that the delta opiate agonist is more effective than mu agonists in modifying cardiovascular variables in the NTS; we suggest caution in relating specific cardiovascular function to receptor subtypes defined by binding assays.

Animals↗
PubMed1982

Discrimination of three opiate receptor binding sites with the use of a computerized curve-fitting technique.

The presence of different types of opiate binding sites was investigated with the use of a computerized, weighted, nonlinear least-squares regression program. The experimental data were obtained from four groups. Each of three labeled opiate ligands was displaced using each of the same unlabeled ligands. The resulting nine different ligand combinations of each group were evaluated by use of a curve-fitting program. The four groups consisted of the kappa ligand ethylketocyclazocine, the sigma ligand SKF 10047, and the oripavine derivatives etorphine and diprenorphine, each in conjunction with the delta opiate receptor ligand (D-Ala2,D-Leu5)-enkephalin and the mu opiate receptor ligand dihydromorphine. The binding model which best fitted each of the four groups suggested the existence of three different binding sites in the rat brain homogenate. Two of these sites conform to the previously described mu and delta sites. A third site (R3) displayed high affinity for ethylketocyclazocine, SKF 10047, etorphine, and diprenorphine but very low affinity for dihydromorphine and [D-Ala2,D-Leu5]enkephalin. Naloxone, cyclazocine, and dynorphin-(1--13) had high affinity for R3. Behavioral data support the interpretation that the R3 site may represent a kappa site at which SKF 10047 acts antagonistically.

Animals↗
PubMed1982

Differential regulation of the mu-, delta-, and kappa-opiate receptor subtypes by guanyl nucleotides and metal ions.

The effects of Na+, guanyl-5'-yl imidodiphosphate (Gpp(MH)p), and Mn2+ on the binding of dihydromorphine, ethylketocyclazocine, D-Ala2, D-Leu5-enkephalin, and diprenorphine to the opiate receptor were investigated. Three distinct binding sites, mu, delta, and kappa sites, were identified with the use of multiple tracer displacement curves. Moreover, this approach was used to determine the effects of Gpp (NH)p and metal ions on each individual binding site. At the mu and delta sites, Na+ and Gpp(NH)p each decreased and Mn2+ increased agonist binding affinities, with the exception of D-Ala2, D-Leu-enkephalin affinity which was not affected by Gpp(NH)p. None of these conditions markedly altered dihydromorphine and D-Ala2, Leu5-enkephalin binding to kappa sites, whereas the affinity of ethylke-tocyclazocine for kappa sites was decreased by Gpp(NH)p. Sodium ions lowered the capacity of mu sites and Gpp(NH)p reduced that of delta sites, while both agents increased the capacity of apparent kappa sites. These results demonstrate that each of the kinetically distinguishable binding sites is regulated differentially by metal ions and guanyl nucleotides. Simultaneous addition of Na+ and Gpp(NH)p greatly reduced the binding affinity of all three agonists at their respective high affinity sites (dihydromorphine at the mu site, D-Ala2, D-Leu5-enkephalin at the delta site, and ethylketocyclazocine at the kappa and mu sites). This result confirms previous observations that agonist binding is characterized by a large affinity reduction in the presence of both Na+ and guanyl nucleotides, and it extends this concept to each of the opiate receptor subtypes.

Animals↗
PubMed1979

[Radionuclide determination of the left ventricular ejection fraction under stress: comparison with angiocardiography].

Left ventricular ejection fraction (LVEF) determined by first pass radionuclide (Nucl.) and biplane contrast angiocardiography (Angio.) was compared in 62 patients with suspected coronary artery disease under resting conditions and in 32/62 patients during bicycle ergometry at identical work load. At rest both methods correlated with r = 0.81 with similar heart rates in both determinations. The mean value of LVEF (Nucl.) was lower than the mean value of LVEF (Angio.), at 50 +/- 2 (SE) % and 58 +/- 2% respectively (p less than 0.001). During exercise a significant correlation between the two methods was again found (r = 0.76). This time no difference was detected between the mean values for LVEF (50 +/- 3% [Nucl.] vs 48 +/- 2% [Angio.], n.s.), which may be explained by the higher heart rates during the invasive study (123 +/- 5/min [Angio.] vs. 108 +/- 4/min [Nucl.], p less than 0.001), resulting in a higher degree of ischemia and hence a lower LVEF. The interobserver variability did not differ between the two methods.

Adult↗
PubMed1979

[Thallium 201 myocardial scintigraphy. Clinical use and value].

Thallium-201 exercise myocardial perfusion scintigraphy, a new, non-invasive screening method, serves to visualize stress-induced ischemic regions and scarred tissue. As compared to the exercise electrocardiogram, the method shows higher sensitivity and specificity in detecting coronary artery disease. Moreover, it makes it possible to localize the predominant defects. Even though myocardial scintigraphy cannot replace coronary arteriography in establishing the precise morphologic situation of the coronary arteries, it is of help in deciding whether an arteriogram should be carried out or not. Thus, important indications for myocardial stress scintigraphy are atypical chest pain and an abnormal electrocardiogram without pain. Furthermore, the method is useful for evaluating patients with uninterpretable electrocardiograms during exercise, and in assessing the outcome of coronary artery bypass surgery.

Coronary Artery Bypass↗
PubMed1979

[On cyclic rejuvenation of life in change of generations (author's transl)].

Various cellular processes are discussed which might be able to reduce in protozoa as well as in higher organisms the accumulation of "errors" in protein synthesis by the interplay of error accumulation and cell division frequency or by katabolic effects after a generative process of one kind or another. Some of these processes also may be regarded as decisive for the time dependence of mass growth of higher organisms.

Aging↗
PubMed1978

[Nuclear medical determination of the ejection fraction and the regional wall movements of the left ventricle].

Left ventricular ejection fraction was determined in 114 patients by radionuclide and contrast angiocardiography. The correlation coefficient (r) amounted to 0.66. Exclusion of patients with arrhythmias and with a difference in heart rate exceeding 15 beats per minute between the two determinations of the ejection fraction increased r to 0.80 (61 patients). In patients with coronary artery disease and cardiomyopathies (n = 35), r was higher (0.88) than in patients (n = 26) with acquired valve disease or congenital heart disease (0.60). Comparison of first pass radionuclide angiocardiography and gated blood pool scanning with contrast angiocardiography in 19 patients elicited an r-value of 0.82 for the first pass method and of 0.31 for gated blood pool scanning. Visual assessment of local wall motion by gated blood pool scanning in 15 patients showed agreement with cineangiographically quantitated segmental motion (normo-, hypo- or a-kinesis) in 50 of 60 (= 83%) evaluated segments.

Angiocardiography↗
PubMed1978

[Fundamental problems of ageing (author's transl)].

Issuing from the second theorem of thermodynamics a cybernetical schema and a corresponding system of differential equations are proposed, describing dehydration and diminishing metabolism rate of the aging cell. With respect to the organism as a whole, there results the well known vitality formula of Beier, but with an altered expression for F(t).

Aging↗
PubMed1978

[To the process of registration of ageing process (author's transl)].

A cybernetical scheme and a corresponding system of differential equations, describing the dehydration and the diminishing metabolism rate of the aging cell as well as of the whole of the organism, are generalised to adapt them also to other phenomena of aging. The resulting expressions are tested by comparison with a number of representative theoretical and experimental dates of various aging processes.

Adaptation, Biological↗
PubMed1977

[Disordant monozygotic twins with Mayer Rokitansky Kütser syndrome (author's transl)].

Two patients with vaginal agenesis are reported. Each had a normal twin. In one case, a Mayer Rokitansky Küster syndrome could be diagnosed by laparoscopy. In the other case it was probably the same syndrome. Monozygocy of the two pairs of twins was shown by examination of features of serum proteins, serum enzymes and erythrocytes with a probability of 99,8% and 99,1%. Only three other cases of discordant twins with MRK syndrome were reported in the literature, at least two of them monozygotic. Extremely rare cases of familial MRK syndrome were also found. Discordance of monozygotic twins makes a genetic etiology unlikely.

Adolescent↗
PubMed1977

[Neurocybernetic basis of hallucinations and related illusions].

Present concepts of circuits of neurons involved in the development of regular perception are used as a basis for discussing possible processes proceeding in these circuits and producing hallucinations and other illusions and false perceptions in mental patients or normal subjects.

Affective Symptoms↗