A STRAND OF CARDIAC MUSCLE : Its Ultrastructure and the Electrophysiological Implications of Its Geometry

The structure of a small strand of rabbit heart muscle fibers (trabecula carnea), 30–80 µ in diameter, has been examined with light and electron microscopy. By establishing a correlation between the appearance of regions of close fiber contact in light and electron microscopy, the extent and distribution of regions of close apposition of fibers has been evaluated in approximately 200 µ length of a strand. The distribution of possible regions of resistive coupling between fibers has been approximated by a model system of cables. The theoretical linear electrical properties of such a system have been analyzed and the implications of the results of this analysis are discussed. Since this preparation is to be used for correlated studies of the electrical, mechanical, and cytochemical properties of cardiac muscle, a comprehensive study of the morphology of this preparation has been made. The muscle fibers in it are distinguished from those of the rabbit papillary muscle, in that they have no triads and have a kind of mitochondrion not found in papillary muscle. No evidence of a transverse tubular system was found, but junctions of cisternae of the sarcoplasmic reticulum and the sarcolemma, peripheral couplings, were present. The electrophysiological implications of the absence of transverse tubules are discussed. The cisternae of the couplings showed periodic tubular extensions toward the sarcolemma. A regularly spaced array of Z line-like material was observed, suggesting a possible mechanism for sarcomere growth.     

Die Bedeutung des Nervensystems für die Regeneration bei den Insekten

Ohne ZusammenfassungHerrn Prof. Dr. O.Pflugfelder zu seinem 60. Geburtstag.     

Strukturanalytische Untersuchungen zur Altersabhängigkeit der Sensibilität

Zusammenfassung Eine Analyse der Meßwerte von Ronge (1943) über die Reizausnutzung durch das Tastsinnes-Nervensystem der Haut zeigt im Zusammenhang mit einer vorausgegangenen Studie (Scharf und Blumenthal, 1967), daß der Reizerfolg in einer transzendenten Fläche höherer Ordnung in Abhängigkeit vom Lebensalter (oder von der Anzahl der Meissnerschen Tastkörperchen pro Hautflächeneinheit) und vom Reizdruck dargestellt werden kann. In Druckrichtung steigt diese Fläche mit zunehmendem Reizdruck nichtlinear an, in Zeitrichtung oscilliert die Fläche dagegen träge um Normwerte, die beim 20jährigen Menschen realisiert sind. Dabei werden die Altersveränderungen der histologischen Hautstruktur offenbar zur Kompensation der altersabhängigen Verminderungen der Zahl der Tastkörperchen ausgenutzt.

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Summary An analysis of the observations on the Reizausnutzung by nerves of touch (Ronge, 1943) connected to a previous study (Scharf and Blumenthal, 1967) shows that the irritation result may be figured by a transcendental plane of higher order as a function of age (or number of Meissner's corpuscles per area skin) and irritation pressure. Along the pressure axis this non-linear plane is increasing non-linear in dependence on ascending pressure, but along the time axis the plane oscillates lazily round about the norm values which are realized in human beings of about 20 years of age. It seems that the age-dependent changes of histological skin structure are utilized to compensate the age-dependent diminution of touch corpuscle number.

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Mit dankenswerter Unterstützung durch einen Forschungsauftrag des Staatssekretariates für das Hochschulwesen der DDR.

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Numerische Rechnung: Tischrechner Mercedes Cellatron R 44 SM, Leitende Med. techn. Ass. Ruth Pieper (Anatomisches Institut Halle). Programmgesteuerter Digitalrechner ZRA 1, Math, techn. Ass. Friedegund Hüther (Institut für Numerische Mathematik, Halle).

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Graphik: Akad. Bildhauer Hellmut Helwin.     

Elektronenmikroskopische Untersuchungen zur Dynamik neurosekretorischer Zellen von Enchytraeus (Oligochaeta)

Zusammenfassung Von lichtmikroskopischen Befunden der Neurosekretion bei dem Oligochaeten Enchytraeus ausgehend, haben wir an zwei elektronenmikroskopisch genau bezeichneten und festgelegten Zellen bzw. Zelltypen, die bereits lichtmikroskopisch charakterisiert worden waren, Untersuchungen über die submikroskopisch faßbare Zelldynamik durchgeführt. Die beiden Arten neurosekretorischer Zellen (Q-Zelle und P-Zellen) sind elektronen-mikroskopisch schon durch ihre Lage zu erfassen. Sie können nicht nur durch die Zellgröße, sondern auch durch ihre Elementargranula, den Aufbau des endoplasmatischen Retikulums und den Golgi-Apparat eindeutig unterschieden werden. Wie schon in den lichtmikroskopischen Untersuchungen wurde die Sekretionsaktivität mit der Amputation ausgelöst. Sowohl in der Q -als auch in der P-Zelle bewirkt die Amputation eine unmittelbare Sekretentleerung. Die darauf einsetzende Phase der Sekretproduktion ist submikroskopisch durch eine erhöhte Zahl von Golgistrukturen in diesen Zellen, durch das deutlich in Erscheinung tretende granuläre endoplasmatische Retikulum und durch eine fortschreitende Vergrößerung und Verdichtung von Lysosomen in beiden Zelltypen gekennzeichnet. Für die Q-Zelle sind weiterhin die Verstärkung des diesen Zelltyp besonders noch charakterisierenden Bereiches von Membranzisternen und die dortige Ribosomenbildung typisch. Auf Grund der Feststellungen wird die Frage der Beziehung einzelner Strukturen in diesen beiden Zelltypen zur Produktion des Neuro-sekrets diskutiert. Die elektronenmikroskopische Untersuchung führte zur Entdeckung eines weiteren Zelltyps, der im Lichtmikroskop bisher nicht erkannt worden war und der sich durch besonderen Reichtum an Mitochondrien und großen Lipoid (?)-Komplexen auszeichnet (M-Zelle). Über seine Bedeutung ist jedoch noch keine Aussage möglich.

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Summary The cytophysiology of two types of neurosecretory cells (Q and P cell) in the brain of the oligochete Enchytraeus was studied at the ultrastructural level. These cell types can be identified by their location, and particularly by the size difference of their elementary granules. Amputation of the last ten segments caused a release of secretory product followed by a phase of renewed production. This was characterized by changes in the endoplasmic reticulum, the Golgi apparatus, and the lysosomes. The role of these structures in the production of neurosecretory material was discussed. Furthermore, a cell type with extraordinarily numerous mitochondria, hitherto unknown in Enchytraeus, was described. Its function has not yet been determined.

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Mit Unterstützung durch die Sächsische Akademie der Wissenschaften zu Leipzig.

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Herrn Prof. Dr. F. Seidel, Marburg, zum 70. Geburtstag gewidmet.     

Radioactive labeling of proteins in cultured postimplantation mouse embryos II. Dose and time dependency

Summary The conditions for optimum incorporation of radioactive amino acids into proteins of cultured postimplantation mouse embryos were investigated under the aspect of using these proteins for two-dimensional electrophoretic separations and fluorography. The aim was to obtain highly radioactively labeled proteins under conditions as physiological as possible. Mouse embryos of Days 8, 10, and 11 of gestation were cultured in Tyrode’s solution. Incubation time and concentration of [³H (or¹⁴C)]amino acids in the culture medium were varied over a broad range. Embryos were prepared with placenta and yolk sac or without any embryonic envelopes. After culturing, the physiologic-morphologic state of the embryos was registered on the basis of several criteria. The radioactivity taken up by the total protein of each embryo was determined and calculated in disintegrations per minute per milligram protein per embryo. To approach our aim, embryos of different developmental stages had to be cultured under different conditions. A good compromise for Day-8, Day-10, and Day-11 embryos was: embryos prepared with yolk sac (opened) and placenta, 150 μCi radioactive amino acids added per milliliter medium, incubation for 4 to 5 h. For maximum labeling of proteins it is advisable to culture Day-10 embryos without embryonic envelopes under particular conditions. This work was supported by grants from the Deutsche Forschungsgemeinschaft awarded to the project K1 237/3-2 (Systematic analysis of cell proteins).     

Single chloride channels in endosomal vesicle preparations from rat kidney cortex

Summary Endocytotic vesicles from rat kidney cortex, isolated by differential centrifugation and enriched on a Percoll gradient, contain both an electrogenic H⁺ translocation system and a conductive chloride pathway. Using the dehydration/rehydration method, we fused vesicles of enriched endosomal vesicle preparations and thereby made them accessible to the patch-clamp technique. In the fused vesicles, we observed Cl^– channels with a single-channel conductance of 73±2 pS in symmetrical 140mm KCl solution (n=25). The current-voltage relationship was linear in the range of –60 to +80 mV, but channel kinetic properties dependended on the clamp potential. At positive potentials, two sublevels of conductance were discernible and the mean open time of the channel was 10–15 msec. At negative voltages, only one substate could be resolved and the mean open time decreased to 2–6 msec. Clamp voltages more negative than –50 mV caused reversible channel inactivation. The channel was selective for anions over cations. Ion substitution experiments revealed an anion permeability sequence of Cl^–=Br^–=I^–>SO ₄ ^2– F^–. Gluconate, methanesulfonate and cyclamate were impermeable. The anion channel blockers 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS, 1.0mm) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB, 0.1mm) totally inhibited channel activity. Comparisons with data obtained from radiolabeled Cl^–-flux measurements and studies on the H⁺ pump activity in endocytotic vesicle suspensions suggest that the channel described here is involved in maintenance of electroneutrality during ATP-driven H⁺ uptake into the endosomes.     

Epidemiological analysis of acute respiratory diseases (ARD) of viral etiology in the Czech Socialist Republic (CSR] and German Democratic Republic (GDR) over the period 1979 to 1984

An analysis is made of the ARD reported in CSR and the GDR over the period July 1st, 1979 to June 30th, 1984. During that time, there were 27,810,000 cases reported in CSR in the framework of ARD epidemiological surveillance, representing 2.67 cases per one inhabitant, whereas in the GDR, the total number of reported ARD was 28,900,000 yielding 1.73 cases per person. However, the GDR reported higher morbidity per one child of preschool age. The authors believe that the differences in the reported incidence of ARD between the two countries are due to differences in the reporting systems and medical officers' activity during an epidemic and in the interim period. Approximately one third of ARD reported annually in the two countries falls to the period of influenza epidemics. The authors also analyze the etiology of the influenza epidemics which affected the two countries in 1980, 1981, 1982, 1983 and 1984. In most seasons, the causative agents and morbidity excesses were different in the two countries. The drift variant B/USSR/100/83, which caused a major epidemy in CSR in 1984, has not to date been implicated in the DGR in the etiology of ARD. The cyclic epidemic due to Mycoplasma pneumoniae occurred in the GDR already in 1979-80, while CSR experienced it a year later. There was a temporal and territorial correlation between the course of A(H1N1) influenza epidemic in the two countries in 1984.     

Application of Asymmetric Alternating Voltage Pulse Series for Investigation of the Action Potential in Chara

An alternating (asymmetric) bipolar staircase voltage clamppulse series was used to investigate the action potential inChara corallina. Using this protocol, we found that the actionpotential was present in the hyperpolarized region of the current-voltagerelationship of the whole cell membrane. Effects of strong hyperpolarizingvoltage steps, during the excitation process, can thus be studied. (Received August 22, 1989; Accepted October 14, 1989)     

Scavenging of Hydrogen Peroxide in the Endosperm of Ricinus communis by Ascorbate Peroxidase

The fat-storing endosperm of Ricinus communis L. was found tocontain an ascorbate peroxidase (EC 1.11.1.11 [EC] ), which is nearlyas active as catalase (EC 1.11.1.6 [EC] ) in degradation of hydrogenperoxide (H₂O₂) at its physiological concentrations. This ascorbateperoxidase probably functions together with monodehydroascorbatereductase (EC 1.6.5.4 [EC] ) or dehydroascorbate reductase (EC 1.8.5.1 [EC] )and glutathione reductase (EC 1.6.4.2 [EC] ) to remove the H₂O₂ producedduring the transformation of fat to carbohydrate in the glyoxysomes.The activities of these enzymes as well as the content of ascorbateand glutathione increase parallel to the activities of glyoxysomalmarker enzymes during the course of germination. Inhibitionof catalase by aminotriazole results in increases of the ascorbateperoxidase activity and of the glutathione content. All fourenzymes are predominantly localized in the cytosol of the Ricinusendosperm with low activities found in the plastids and themitochondria. The results suggest, that the ascorbate-dependentH₂O₂ scavenging pathway, which has been shown to be responsiblefor the reduction of photosynthetically derived H₂O₂ in thechloroplasts, operates also in the Ricinus endosperm. (Received June 5, 1990; Accepted July 31, 1990)