Das Problem der Sexchromatin-negativen Zellen

Zusammenfassung Die Faktoren, die für das Auftreten Sexchromatin-negativer weiblicher Zellen verantwortlich gemacht werden können, werden zusammenfassend dargestellt. In solchen Zellen ist keines der beiden X-chromosomen während der Interphase stärker kondensiert, d.h., es fehlt die in Sexchromatin-positiven Zellen zu beobachtende Heteropyknose eines X-Chromosoms.In somatischen Zellen steht des Fehlen der Heteropyknose in keinem Zusammenhang mit der DNS-Synthese-Periode, es ist auch nicht korreliert mit der Spätreplikation eines X-Chromosoms, die in allen Zellen, mit und ohne Sexchromatin, vorhanden ist. Die genetische Inaktivierung eines X-Chromosoms bleibt in Sexchromatin-negativen Zellen offenbar bestehen. Die in dieser Hinsicht gegen die Lyon-Hypothese vorgebrachten Einwände sind nicht aufrechtzuerhalten.. Da die genetische Inaktivität heterochromatischer Chromosomen nicht an die Heteropyknose gebunden ist, kann diese auch nicht die Ursache der Inaktivität sein.Eine gewisse Sonderstellung nehmen Oocyten und frühembryonale Zellen ein, bei denen die genetische Inaktivierung eines der beiden X-Chromosomen vermutlich nicht stattfindet, und die keine Heteropyknose eines X-Chromosoms erkennen lassen.Die Ausbildung eines Sexchromatinkörperchens kann durch bestimmte Faktoren, wie Zellcyclusstadium und Zelldichte beeinflußt werden. Die hier vorgelegten eigenen Befunde an ein-und mehrkernigen Zellen von Microtus agrestis ergaben aber, daß der Grad der Heteropyknose der Geschlechtschromosomen innerhalb eines Zellkernes unabhängig von äußeren Faktoren witgehend fixiert ist und bei der Mitose vermutlich auf die Tochterzellen weitergegeben wird.

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The problem of sex chromatin negative cells

Summary The factors possibly responsible for the occurrence of sexchromatin-negative female cells are reviewed. In such cells, neither of the two X-chromosomes is condensed during interphase; thus the heteropyknosis of one X-chromosome observed in sexchromatinpositive cells is absent.In somatic cells, the absence of heteropyknosis is not related to the DNA-synthesisperiod and is not correlated with the late replication of one of the X-chromosomes which occurs in all cells, with and without sex chromatin.The genetic inactivation of one X-chromosome seems to persist in sexchromatin-negative cells. Thus in this respect the objections to the Lyon hypothesis cannot be maintained. Since the genetic inactivity of heterochromatic chromosomes is not due to heteropyknosis, the latter cannot be the cause of their inactivity.Oocytes and early embryonic cells fall within a special category, in that the genetic inactivation of one of the two X-chromosomes presumably does not occur, also no heteropyknosis of one of the X-chromosomes can be observed.The formation of a sexchromatin body can be influenced by certain factors such as phase of the cell cycle and cell density. The findings in respect of single-and multi-nucleated cells of Microtus agrestis, here reported, show however that the degree of heteropyknosis of the sex chromosomes within a cell-nucleus is to a large extent fixed and independent of extrinsic factors. It is presumably transmitted through mitosis to the daughter cells.

Herrn Prof. Dr. G. Wolf-Heidegger zum 60. Geburtstag in Dankbarkeit und Verehrung gewidmet.     

Direct diagnosis of the atherosclerotic vascular wall: possibilities and limits of intravascular ultrasound]

The clinical application of intravascular ultrasound still awaits established criteria for the interpretation of normal and diseased arterial wall structures. The aim of this preclinical study was to evaluate sonographic features of normal and atherosclerotic human arteries in vitro and to correlate these findings with histological cross-sections. Seventy-four segments from 33 human postmortem arteries of various anatomic locations were studied in saline solution using a mechanical 20-MHz transducer in a 6F catheter. In normal arteries, close correlations were found between sonographic and morphometric measurements of total wall thickness (r = 0.89), lumen circumference (r = 0.99), and of lumen area (r = 0.89, all p less than 0.001). Of 29 histologically verified atherosclerotic lesions, 19 were calcified, and all of them were correctly diagnosed with IVUS; however, acoustic shadowing prevented quantitative plaque evaluation. Of 10 fibromuscular lesions, six (60%) were correctly diagnosed with IVUS, using either direct morphologic criteria (n = 4) or indirect signs of vessel wall irregularity (n = 2), while the remainder (n = 4) were missed by IVUS due to a similar echodensity compared with the surrounding tissue. Thus, there was an overall sensitivity of 86% for the detection of atherosclerotic lesions by IVUS. In animal experiments in vivo, the feasibility of high-quality-imaging in pulsatile arteries was confirmed and pathologic changes in vein grafts were visualized. We conclude that IVUS carries the potential to directly assess arterial wall changes in vivo. The method appears very sensitive in the detection of calcified plaque, whereas fibromuscular lesions may often not be readily distinguished from normal surrounding tissue. This may limit the clinical usefulness of IVUS at the present time.     

Infusion of nifedipine after coronary artery bypass grafting decreases the incidence of early postoperative myocardial ischemia

We performed a randomized study on patients undergoing elective coronary bypass grafting to examine whether postoperative infusion of nifedipine (n = 25) could reduce the incidence of isolated transient myocardial ischemia, myocardial infarction, or both. The control group (n = 25) received nitroglycerin. Hemodynamic and Holter monitoring and serial assessment of enzymatic and electrocardiographic changes were performed for all patients. Both groups showed comparable preoperative and operative data. The incidence of myocardial infarction was significantly lower in the nifedipine group (n = 1) as compared with the control group (n = 4), whereas the number of patients with isolated transient myocardial ischemia was similar in both groups (nifedipine, 3; control, 4). At the time of peak activity, levels of creatine kinase (350 +/- 129 versus 511 +/- 287 IU/mL), creatine kinase-MB (8.4 +/- 5.4 versus 17.1 +/- 11.0 IU/mL), and glutamate-oxaloacetate-transaminase (30.4 +/- 4.4 versus 41.0 +/- 7.9 IU/mL) were markedly lower in the nifedipine group (p less than 0.05). We conclude that infusion of nifedipine after elective coronary artery bypass grafting effectively decreases the incidence of myocardial infarction and the extent of myocardial necrosis during the early postoperative period.     

Vergiftungen. (Gewerbliche auch unter Gewerbehygiene)

Ohne Zusammenfassung     

Versicherungsrechtliche Medizin

Ohne Zusammenfassung     

Excitotoxic hippocampal neuron loss following sustained electrical stimulation of the perforant pathway in the mouse

Prolonged electrical stimulation of the perforant pathway in the rat evokes epileptiform discharges in dentate granule cells and irreversibly damages hilar neurons. In this in vivo study, we demonstrate that similar perforant path stimulation in C57Bl/6 mice causes the same pattern of hippocampal neuron loss. Therefore, this mouse model of seizure-induced hippocampal injury can be used for a wide variety of studies in genetically altered conditions not available in rats.     

Altersbestimmungen von Blutspuren

Ohne ZusammenfassungVorgetragen auf der 18. Tagung der Deutschen Gesellschaft für Gerichtliche und Soziale Medizin in Heidelberg, September 1929.