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Biomedical subjects

C Seifert

Publications and source records attributed to C Seifert.

17 recordsLinked to original sources
PubMed1992

Reciprocal inhibition of forearm flexor muscles in spasmodic torticollis.

Reciprocal inhibition between forearm extensor and flexor muscles was tested by means of an H-reflex technique in patients with spasmodic torticollis and normal controls. In both, patients and controls three different phases of reciprocal inhibition could be demonstrated with maximal inhibition at conditioning test intervals of 0 ms, 15 ms and 100 ms, respectively. However, the quantitative amount of this inhibition was different for the patients and the controls. Significantly less inhibition was found for the second and the third phase of reciprocal inhibition in the patient group. Discriminant analysis showed a clear separation between normal subjects and patients if the amount of reciprocal inhibition of the second and third phase were taken into account. We were not able to detect any side differences neither for the patients nor for the controls. The findings demonstrate a functional disturbance of motor control mechanisms of a clinically unaffected extremity in spasmodic torticollis. This is believed to reflect a bilateral disturbance most likely within the basal ganglia or their outflow. Therefore, our data support the idea, that spasmodic torticollis is associated with or even due to a generalized rather than a focal disturbance of motor control mechanisms.

Analysis of Variance↗
PubMed1989

[Endoscopic-radiologic diagnosis and therapy of the bile ducts. Results of endoscopic papillotomy].

Endoscopic-radiologic methods for demonstrating the hepatobiliary and pancreatic ducts are an integrated part of the diagnostic spectrum of gastroenterologic centers. At the Charité since 1975 we have made more than 5,500 endoscopic-retrograde cholangio-pancreaticographies (ERCP's). This method provides immediately or later an adequate therapy as an alternative to the otherwise necessary surgery. The most frequently used and basic method is endoscopic papillotomy (EPT). In most cases it precedes endoscopic removal of concrements, prosthetic drainage of biliary pathways or extracorporal shockwave lithotripsy (ESWL). Since 1977 we have carried out 2,050 EPT's at the Charité, more than 60% of these for patients of higher age (above 60). With 98.3% successful interventions complications were seen in only 4.7% of the cases. The influence of close interdisciplinary cooperation of endoscopicists and radiologists on the results of the investigation and the rate of complications is discussed.

Adult↗
PubMed1986

[Noninvasive roentgen diagnosis of right heart function in patients with recirculation disorders and chronic nonspecific lung changes].

The non-invasive x-ray functional diagnostic electroradiographic method at the large vessels near the heart may enrich the radiological preliminary diagnostics of recirculation abnormalities. In chronic unspecific pulmonary diseases it can characterize the load of the right heart. Our studies should serve as a pilot study for the in future possible, simply to be handled non-invasive video-densitometry of the vessels near the heart in the preliminary diagnostics of cardiovascular diseases.

Cardiac Output↗
PubMed1986

A summertime peak of Down's syndrome in Franklin County, Ohio.

In June, July, and August of 1984, more infants than usual were born with Down's syndrome in Franklin County, Ohio. A direct physician survey was done, and chromosome reports were reviewed, resulting in the identification of 11 infants with Down's syndrome born during that period. Using a chi 2 analysis, the expected number of affected newborns was five, making the actual number of 11 significant. Although a summertime peak was observed, the yearly incidence of 1.09 per 1000 live births was within the expected range.

Adolescent↗
PubMed1985

Properties of Vmax block of INa-mediated action potentials during combined application of antiarrhythmic drugs in cardiac muscle.

Modifications of drug-induced Vmax inhibition by the combined treatment of the cardiac membrane with several class 1 antiarrhythmic agents were studied in guinea pig's ventricular myocardium taking the depression of upstroke velocity in fast action potentials as an indicator for INa blockade. A novel analytical procedure, first beat phasic block determination, provided the opportunity to estimate phasic drug binding initiated by a single action potential. Total Vmax blockade increased in response to the addition of quinidine (1 X 10(-5) mol/l), lidocaine (3 X 10(-5) or 3 X 10(-4) mol/l) or prajmalium (2.5 X 10(-5) mol/l) to a propafenone-containing (5 X 10(-6) mol/l) medium. This intensification originated from an increase of both tonic (rested-state) and phasic (use-dependent) Vmax blockade when kinetically similar drugs such as propafenone and quinidine may interact simultaneously with Na+ channels and, thus, resembles the effects of a rise in drug concentration. Accordingly, the development kinetics of phasic Vmax blockade were accelerated but block relaxation kinetics remained unaffected. Intensification of total Vmax blockade induced by combining propafenone with the kinetically different lidocaine resulted exclusively from an increase of tonic blockade at driving rates between 0.2 and 1 Hz. Steady state phasic Vmax blockade remained within this frequency range unchanged or decreased depending on whether the lidocaine concentration in the propafenone-containing medium was low or high. Although the strength of first beat phasic Vmax block went up in both cases, the propafenone-induced fraction declined in the presence of the higher lidocaine concentration. Development and relaxation kinetics of phasic Vmax blockade became modified when Na+ channels were exposed to a mixture of kinetically different drugs, propafenone plus lidocaine or propafenone plus prajmalium. Instead of a single exponential time course, development and removal of phasic Vmax blockade consisted of two different components. The biexponential time course of phasic block onset in propafenone plus prajmalium, the biexponential time course of phasic block relaxation in propafenone plus lidocaine and the interference of one drug with the blocking action of another strongly suggest a Na+ channel-associated drug receptor. Propafenone and lidocaine very probably find a common target which might bear a single or two allosterically linked binding sites.

Action Potentials↗
PubMed1983

Quercetin stimulation of calcium release from rabbit skeletal muscle sarcoplasmic reticulum.

To elucidate the mechanism by which quercetin enhances the rate of tension development in skinned muscle fibers, effects on calcium release from longitudinal tubule-derived SR (LSR) after phosphate-supported calcium uptake were examined. In all studies, 100 microM quercetin (which inhibits initial calcium uptake velocity 85%) was added at or shortly after the time calcium content reached a maximum at various extravesicular Ca2+ concentrations (Cao). At moderate Cao (0.2-1.0 microM), where spontaneous calcium release rate depended on Cao, quercetin caused a marked stimulation of calcium release. This was accompanied by a 60% reduction in calcium influx and a 30-fold increase in calcium efflux. Thus, the previously reported quercetin-induced increase in the rate of tension development by skinned muscle fibers may result, at least in part, from sensitization of Ca2+-triggered calcium release to lower Cao.

Animals↗
PubMed1981

Aldosterone response to sodium deprivation and angiotensin II in patients with hypopituitarism.

Unknown pituitary factor(s) apart from ACTH may participate in the regulation of aldosterone (aldo) secretion in man. We investigated whether the 'sensitization' of the zona glomerulosa against angiotensin II (A II) by sodium deficiency was mediated by the pituitary gland. A II was infused in stepwise increasing doses (2, 4, 8 ng/kg/min) into 5 normal subjects (N) and into 8 patients with hypopituitarism (H) before and after 4 days on low sodium diet. Mean cumulative sodium balance after the low sodium diet was -145mM in N and -165mM in H. Plasma-aldo and aldo-excretion rate on the normal sodium diet were slightly higher in H than in N but rose less than normal during sodium depletion in H. Plasma A II and renin activity on normal sodium were slightly higher in H than in N, but the increase on the low sodium diet was blunted in H. The stimulation of plasma-aldo by A II infusion was similar in both groups on the normal sodium diet. In both groups, the response of P-aldo to A II infusion was greater in the sodium deplete than in the replete state, although 'sensitization' was slightly less marked in H than in N. This may be due to the blunted rise of plasma-A II after sodium loss in H, which may also account for abnormalities in the blood pressure response in the H group. Altogether, the results speak against a direct involvement of the pituitary gland in 'sensitization', but an indirect influence through unexplained abnormalities in renin secretion is possible.

Adrenal Glands↗