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Biomedical subjects

J Schaefer

Publications and source records attributed to J Schaefer.

At least 127 records · Page 7Linked to original sources
PubMed1980

Simultaneous recording of monophasic action potentials and contractile force from the human heart.

Cardiac monophasic action potentials (MAPs) and contractility have been simultaneously measured in man while the heart rate was being changed by right atrial pacing. A new non-suction electrode was used for safe and long-term recording of MAPs from the endomyocardium. Abrupt changes in cycle-length were followed first by a fast, then a slow response in the adaptation of MAP-duration and of contractility (LV dp/dt max) to the new steady state. After increasing the heart rate then slow phase of MAP shortening appears to be related to the slow staircase of contractility, whereas after the step decrease of frequency no such a relation could be observed. The consistency of these results with those obtained in corresponding in-vitro experiments indicates that this methodical approach may be suitable for assessing the process of E-C coupling in the human heart.

Action Potentials↗
PubMed1979

[A prospective multi-centre study of the response of metastatic gastrointestinal tumours (author's transl)].

In a prospective, multi-centre, randomized study of 109 patients with metastatic gastro-intestinal adenocarcinomas the response rate, survival time and side-effects of two drug combinations, carmustin +5-fluorouracil and carmustin + ftorafur, were compared (same carmustin dosage in both groups). Response to the treatment was 32.7% in those receiving carmustin +5-fluorouracil, 26.3% in those on carmustin + ftorafur. This difference occurred among the 42 patients with gastric adenocarcinoma (33.3% compared with 25%), as well as in 11 with pancreatic adenocarcinoma, and in 56 with colorectal adenocarcinoma (32.1% and 28.6%). Median survival time for 5-fluorouracil + carmustin was 330 days, double that for ftorafur + carmustin (163 days). Bone-marrow toxicity (leukopenia, thrombopenia) was below 10% for both drug combinations. Alopecia occurred in only a few patients. Gastro-intestinal toxicity was common (20% and 18.5%, respectively), but there was no difference between the two groups. The somewhat lower effectiveness of ftorafur compared with 5-fluorouracil was probably due to the deliberately smaller dosage of the former.

Adenocarcinoma↗
PubMed1978

Identification of young megakaryocytes by immunofluorescence and cytophotometry.

The DNA-content of fluoresceine-labeled platelet antigen containing cells of mouse bone marrow was measured. For immunofluorescence highly specific anti-mouse-platelet-serum and fluoresceine-conjugated antigammaglobuline was used, applying the "sandwich" technique. Three hundred panoptically identifable megakaryocytes served as control group. The DNA-polyploidization pattern of megakaryocytes and immunofluorescence positive cells was almost identical. However, among the immunofluorescence positive cells a considerable amount of cells showed DNA-values lower than 4c, whereas the megakaryocytes of the Pappenheim stained smears revealed no DNA-values lower than 4c. The percentages of diploid and tetraploid cells, respectively, was 6 and 7% compared with 0 and 1% of panoptically identifiable megakaryoctyes. The results suggest that young megakaryocytic cells with diploid and tetraploid DNA-values can be detected by immunofluorescence technique, indicating that the flow from the uncommited to the committed megakaryocytic precursor cell appears at this early stage of megakaryocyte production.

Age Factors↗
PubMed1978

Platelet size distribution in mice following immunothrombopenia and vincristine administration.

In the present study platelet size distribution was investigated after induction of immunothrombocytopenia by rabbit-anti-mouse-platelet-serum (RAMPS) and after vincristine-induced thrombocytopenia. The platelet size distribution after a single dose of RAMPS showed a shift to larger volumes at day 1 and 2, and a decrease to slightly smaller volumes than normal at day 8. These differences, however, were not statistically significant. After vincristine administration, a dose-dependent increase of the platelet size distribution was demonstrated, which lasted from day 1-7. It is suggested that in immune-induced thrombocytopenia the young platelets released from bone marrow megakaryocytes are not exclusively large platelets. On the other hand the early appearance of large platelets after vincristine administration points to a toxic or segregating effect of vincristine on circulating platelets. Therefore, in our experiments, the platelet size is not suitable for the differentiation of young and old platelets.

Animals↗
PubMed1978

Megakaryocyte polyploidization in May-Hegglin anomaly.

Polyploidization of megakaryocytes was studied in bone marrow aspirates from 3 patients with May-Hegglin anomaly by combined application of cytophotometric determination of the DNA content and autoradiography with 3H-TdR labeling in vitro. A marked elevation of the influx of progenitor cells into the megakaryocytic cell system as well as a decreased maturation capacity from type II to type III megakaryocytes was observed possibly contributing to the pathological platelet sequestration. The polyploidization activity as assessed by 3H-TdR labeling and nuclear DNA content was normal.

Adolescent↗
PubMed1977

[Artrial septal defect in the adult (author's transl)].

The clinical and hemodynamic findings of 96 adult patients with ostium secundum defect are presented. There are no interrelationships between the extent of symptoms and clinical state on one side and heart size, shuntvolume and other hemodynamic parameters on the other hand. Our observations do not allow firm conclusions as the the natural course of the affection. It can be stated however, that this congenital cardiac malformation can be associated with a normal life exspectancy and without severe symptoms for decades. Hence we see problems as to the indication of the surgical closure of the defect, since not much is known about the longstanding usefulness of surgery in respect to a possible prolongation of life exspectancy and diminuition of morbidity. We therefore are of the opinion that - until such data are available - the indication for surgery should not be guided by prospective nonproved assumption but by the clinical state of the patient and the severity of his symptoms.

Adolescent↗
PubMed1976

Shigellosis from swimming.

In Augsut 1974, 31 of 45 cases of Shigella sonnei infection in Dubuque, Iowa, were traced to swimming in an 8-km stretch of the Mississippi River. Comparison of the first case in each affected family with neighborhood controls showed a significant correlation between swimming and illness (P less than .0001). A significant association between diarrheal illness and swimming (P less than .0001) was also demonstrated by a retrospective survey of 60 families who had camped at a park beside the river; the attack rate for swimmers who got water in their mouths while swimming was 18%. They had been swimming in water where the mean fecal coliform count was 17,500 organisms per 100 ml; the federal recommended upper limit for swimming water is 200 per 100 ml. A water sample obtained at the park swimming area one month after authorities had banned swimming in the area yielded S sonnei with the same antibiogram, colicin type, and phage type as the isolates from six swimmers.¿

Child↗
PubMed1976

[The effect of sudden changes in the stimulation rate of the heart on peak systolic pressure (author's transl)].

The changes in systolic pressure were studied in 48 patients during artificially (by electrical stimulation) induced sudden increases and consecutive decreases in heart rate. Various patterns could be separated respective to phase A (sudden switch from low (80-120 impulses/min) to higher heart rate (140-180 impulses/min)) and to phase B (sudden switch-back from high to lower (control) beating rate): AI) The systolic peak-pressure of the first contraction after the shortened stimulation interval is very low and often stays ineffective (below the aortic opening pressure). The second contraction develops already a higher pressure than the first one, during the consecutive beats the systolic pressure increases gradually until a new steady state is reached, which is usually lower than the systolic pressure during the foregoing lower beating rate. Sometimes however it can be equal or even higher. Accordingly after an elevation of heart rate arterial mean pressure can drop, stay constant or increase. AII) The systolic peak-pressure of the first contraction after the shortened stimulation interval stays relatively high and drops continuously with the succeeding contractions until a new steady state is reached according to the higher heart rate, it is however always lower than the one at a lower stimulation rate. Therefore arterial mean pressure is always decreased. AIII) Finally we observed changes in arterial systolic pressure in some patients that could not be grouped according to one or to the other pattern described above.- BI) The systolic peak of the first contraction after the switch-back from the high to the lower (control) rate is much higher than that of the last at the higher rate. The peak pressures of the consecutive contractions are then dropping continuously to the new steady-state, that can be higher, equal or lower than that at the higher stimulation rate. BII) ....

Adolescent↗
PubMed1976

[The treatment of excessive arterial hypertension by a permanent cardiac pacemaker system: a case report concerning the possibility to influence the disturbed harmonization between the heart and the arterial system (author's transl)].

In a 63 year old female patient with a history of longstanding arterial hypertension the implantation of a permanent cardiac pacemaker system resulted in a drastic reduction of the elevated blood pressure values, allowing to reduce the formerly necessary high dosage of antihypertensive drugs. It can be assumed that in the case presented the insertion of the permanent pacemaker leads to several hemodynamic changes: firstly, the heart rate is elevated slightly, secondly, the course of the ejection of the stroke volume is changed and consequently the contour of the pulse wave. Especially the latter factor may have an influence on various regulating mechanisms of the circulatory system and thereby on the lowering of the arterial blood pressure and the consecutive reduction of the hypertrophy of the left ventricle. Most probably the baroreceptor reflex system may be of additional great importance. In addition the "desynchronization" of the spread of excitation by the cardiac pacer might be assumed to change the action of the heart in the beginning of the ejection phase into a "softer" way of pumping. The alteration of a rather "rigid" pump (during normal excitation) into a "soft" pump (during desynchronized excitation) thus may lead to a lowering of the arterial pressure a) by decreasing the speed of ejection of the stroke volume and b) by improving the matching between the heart and the arterial "Windkessel".

Blood Pressure↗