Cellules riches en glycogène dans l'épendyme du ventricule latéral du cerveau de rat

Summary The ependyma of the lateral ventricle of the rat brain was investigated at different ages from 20 days to adulthood.A particular cell type occurs in the external wall of the ventricle, where the proliferative subependymal layer is present. These cells found at all ages studied, are characterized by a high content of glycogen, and a structure different of typical ependymal cells.A large number of nerve endings is situated in close vicinity of these cells, either free in the ventricle lumen, or sometimes ensheathed in the cells. No synapse was found between these endings an the glycogen-rich cells.These glycogen-rich cells undergo several modifications with age: their glycogen content is reduced in the adult, and they acquire a few cilia and gliofilaments. It is suggested that they represent a transitory differentiation of the ependyma, functionally linked with the proliferative subependymal layer.

     

Pituitaries of rats neonatally treated with oestrogen

Summary Pituitaries of male and female rats neonatally treated with oestradiol dipropionate were examined with light and electron microscopy, disc electrophoresis and in vitro C¹⁴-leucine incorporation.Single dose of oestradiol administered shortly after birth to male rats has an prolonged stimulative effect on LTH synthesis and release. This is expressed in the cell hypertrophy, proliferation of ER, increase of corresponding band density and higher rate of ¹⁴C-leucine incorporation. In females this effect was less pronounced.STH cell in the treated male pituitaries were degranulated, corresponding hormone band density significantly lowered and incorporation of ¹⁴C-leucine was reduced. This could be considered as an inhibitory effect of oestradiol on STH synthesis and release. Such effect was more expressed two than four months after treatment and is more pronounced in male than in female rats.The technical assistence of Slobodanka Selimovi is gratefully acknowledged.     

Untersuchungen zur Fettresorption im Dünndarm der Ratte,unter besonderer Berücksichtigung der Tagesrhythmik

Zusammenfassung Die vorliegende Untersuchung will klären, welche Rolle die Mikropinocytose bei der Fettresorption spielt und ob die Fettresorption tagesrhythmische Schwankungen aufweist. Zu diesem Zweck wurde Fett zu verschiedenen Tages- und Nachtzeiten in abgebundene Jejunumabschnitte von Ratten injiziert, das Darmgewebe in verschiedenen Abständen licht- und elektronenmikroskopisch untersucht und die Zahl der mikropinocytotischen Invaginationen der Enterocyten bestimmt. Folgende Resultate wurden erzielt:Die Häufigkeit der Mikropinocytose (mikropinocytotische Invaginationen/100 Mikrovilli) beträgt bei Hungertieren 4,78, bei Normaltieren 5,06, 1 min nach Gabe von Mazolachymus 3,55, 1/16 m NaCl-Lösung 4,37, Butterschmalz 5,50, Rindertalg 7,16, Schweineschmalz 7,66 und Mazola 9,25; 2 1/2 min nach Mazolagabe 8,23, nach 5 min 7,67, nach 10 min 6,76. Zwischen 10 und 15 min wird der Ausgangswert erreicht. Aufgrund statistischer Auswertung der Befunde wird geschlossen, daß Fett vor allem in den Frühstadien der Fettresorption durch Mikropinocytose aufgenommen werden könnte. Ferner zeigt sich, daß die Mikropinocytosehäufigkeit entscheidend von der chemischen Zusammensetzung und dem physikalischchemischen Zustand der verabreichten Fette beeinflußt werden dürfte. — Lichtmikroskopisch wurde nachgewiesen, daß die Fettresorption charakteristische, tagesrhythmische Schwankungen aufweist. Um 2.00 Uhr ist sie am stärksten, um 14.00 Uhr am geringsten. Es wird diskutiert, worauf die tagesrhythmischen Unterschiede zurückzuführen sind.

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Investigations of fat absorption, with special reference to circadian rhythm

Summary The present study attempts to elucidate (a) to what extent micropinocytosis is involved in the process of fat absorption and (b) whether fat absorption shows a circadian rhythm. For this purpose rats were given 0.1 to 0.15 ml of fat directly into the upper jejunum at various times of the day and night. 20 sec to 20 min after administration of fat small pieces of the jejunum were rapidly dissected out, the tissue examined by means of light- and electron microscopy, and the number of micropinocytotic pits occurring in the enterocytes during fat absorption was determined. The following results were obtained:The frequency of micropinocytosis (micropinocytotic pits/100 microvilli) is as follows: in starved rats 4.78, in normal rats 5.06, 1 min after administration of corn oil chyme 3.55, 1/16 m NaCl-solution 4.37, clarified butter 5.50, ox tallow 7.16, lard 7.66, corn oil 9.25; 2 1/2 min after administration of corn oil 8.23, after 5 min 7.67, and after 10 min 6.76. Between 10 and 15 min the number of micropinocytotic pits reverses to normal. From statistical analysis of the results it is concluded that micropinocytosis can play a significant role in the early stages of fat absorption. The experiments show in addition that micropinocytosis is greatly influenced by the chemical composition and the physico-chemical state of the administered fat.—Light microscopic studies indicate that fat absorption varies considerably during the 24 hr period. The highest absorption was found at 2 a.m., the lowest at 2 p.m.

Untersuchung unter der Leitung von Univ.-Doz. Dr. L. Vollrath.     

Arterio-venöse Kurzschlüsse mit Klappenmechanismen im Bereich der dorsalen Haut der Rattenhinterpfote

Zusammenfassung In der dorsalen Haut der Hinterpfoten von Ratten wurden Klappen am Abgang kleinerer Gefäße von großen Arterien beobachtet. Diese Arterien verlaufen in einer subkutanen, größere Gefäße und Nerven führenden Bindegewebsschichte über den Streckersehnen.Die kleineren Gefäße haben den Wandbau einer Vene und zweigen etwa im rechten Winkel von der Arterie ab. An ihrer Abgangsstelle ist neben den Klappen manchmal ein sphinkterartiger Muskelring ausgebildet.Diese Gefäßabschnitte werden für arterio-venöse Anastomosen gehalten und auf die Bedeutung solcher an dieser Stelle bisher nicht beschriebenen Verschlußeinrichtungen für die Regulation der Kurzschlüsse wird hingewiesen.

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Arteriovenous anastomoses with valve mechanisms in the dorsal skin of the hindpaw of rats

Summary In the dorsal skin of the hindpaws of rats valves were observed at those sites where smaller vessels branched from larger arteries. These arteries run in a subcutaneous layer of connective tissue, which lies above the extensor tendons and in which the larger vessels and nerves are found.These smaller vessels, the walls of which resemble those of veins, were seen branching off at approximate right angles to their artery of origin. Besides the valves a sphincterlike muscle ring was observed in some cases at the point of branching.These vascular segments are held to be arteriovenous anastomoses. Such locking devices at these points have not been described until now and seem to be important in the regulation of arteriovenous shunts.

     

On the innervation of the rat and pig adrenal cortex

Summary The innervation of the adrenal cortex of the rat and the pig is investigated with the electron microscope. Nerve fibers containing synaptic and two types of dense-cored vesicles come into contact with endocrine cells. There are no specialized pre- and postsynaptic membranes. The synaptic cleft is about 200 Å wide. Generally the basement membrane between nerve and cell is absent. These observations are discussed on the base of more recent experimental findings. Small fibers having an average diameter of about 0.2 to 0.5 and containing only tubules and filaments are considered to represent parts of an afferent nervous system.Dedicated to Prof. v. Kügelgen on the occasion of his 60th birthday.Supported by the Deutsche Forschungsgemeinschaft.     

The effect of extreme temperatures and starvation on the body proportions of the rat

The effects of extremely cold and hot environments on body proportions of rats were studied. These effects included changes in the length of the tail, trunk, extremities, cranio-facial and nasal dimensions, in bone robusticity and bone shape, in the size of the ear and in some characteristics of the skin and hair. Since animals in both extreme temperatures fail to gain normal body weight, all changes were also studied in a group of starving rats. Because of the lower body weight and its concomitant reduction of body measurements, absolute values were avoided for analysis and all parameters were related to neurocranial length and trunk length. Such a triple experimental approach (response to cold, heat, and starvation) combined with a two-fold frame of reference (neurocranial length and trunk length), as well as statistical corrections for body weight loss, made it possible to differentiate between nutrition-specific and temperature-specific responses under conditions of extreme temperature exposure. Moreover, some attention was given to endocrine pathways involved in some morphological changes. The methodological advantages of a multi-experimental approach over a single-experimental technique were demonstrated.     

A radioautographic study of the transport of 125I-labeled serum lipoproteins in rat aorta

Summary The transport of ¹²⁵I-labeled serum lipoproteins through the aortic endothelium was studied by radioautography. Rat aorta and heart was perfused in vitro with a medium containing human very low density (VLDL), low density (LDL), high density lipoprotein (HDL), delipidated HDL apolipoprotein or rat HDL. In all lipoproteins more than 95% of the radioactivity was TCA precipitable and lipid radioactivity was from 2–4% in HDL, 4–6% in LDL, 7–15% in VLDL. After 18–60 min of perfusion and wash with unlabeled medium, most of the aortic radioactivity was TCA precipitable and the percent of lipid counts was similar to that in the original lipoprotein. Following perfusion with VLDL, LDL, or HDL the radioautographic reaction was seen over the endothelium, the subendothelial space and the inner media, and was separated by an unlabeled zone from the reaction present over the adventitia. Uniform labeling of the entire wall was found after perfusion with HDL apolipoprotein. The presence of silver grains over endothelial cells in regions rich in plasmalemmal vesicles suggested that these organelles participate in the transport of the labeled lipoprotein, as was shown for lactoperoxidase (Stein and Stein, 1972). The present data indicate that cholesterol may enter the aortic wall as a constituent of lipoprotein particles. Since an HDL particle carries less than 1/20 of the cholesterol present in a LDL particle, it seems that the lower susceptibility of the female to atheromatosis might be related to the higher ratio of HDL to LDL particles in the female serum.The excellent technical help of Miss R. Ben-Moshe, Mrs. A. Mandeles, Mr. G. Hollander and Mrs. Y. Dabach is gratefully acknowledged. This study was supported in part by grants from National Institute of Health (No. 06-101-1), United States Public Health Service; Delegation Generale a la Recherche Scientifique et Technique of the French Government and from the Ministry of Health, the Government of Israel.     

Karyometrische Untersuchungen am Nucleus suprachiasmaticus geblendeter Ratten

Zusammenfassung Radioaktiv markierte Aminosäuren werden bei Säugetieren nach intraokulärer Injektion nicht nur zu den primären optischen Kerngebieten, sondern auch in den Nucleus suprachiasmaticus des Hypothalamus transportiert (Moore und Lenn, 1972; Hendrickson, Wagoner und Cowan, 1972; Moore, 1973). Dieser Befund macht eine direkte Verknüpfung zwischen der Netzhaut und dem sekretorisch aktiven Nucleus suprachiasmaticus wahrscheinlich, obwohl mit Silbertechniken eine solche Verbindung nicht sicher nachgewiesen werden konnte. Karyometrische Studien am Nucleus suprachiasmaticus männlicher Wistar-Ratten zeigen 6 Tage nach beidseitiger Blendung eine signifikante Abnahme der Zellkerndurchmesser. Dieses Ergebnis spricht für eine Aktivitätsänderung der Neurone im Nucleus suprachiasmaticus geblendeter Ratten.

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Karyometric investigations of the suprachiasmatic nucleus in blinded rats

Summary Intraocular injection of labeled amino acids results, in different mammals, in an accumulation of radioactive material not only in the primary optic centers but also within the hypothalamic suprachiasmatic nucleus (Moore et al., 1972; Hendrickson et al., 1972; Moore, 1973). This finding argues in favour of a direct connection between the retina and the secretory suprachiasmatic nucleus although silver techniques do not show such a pathway. In male Wistar rats the nuclear diameter of the suprachiasmatic neurons decreases significantly 6 days after bilateral experimental ablation of the retina. These results indicate an alteration in activity of the suprachiasmatic neurons in blinded rats.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft (Arbeitskreis Prof. Dr. A. Oksche).     

The ultrastructure of the duct system in the rat extraorbital lacrimal gland

Summary The duct system of the rat exorbital lacrimal gland consists of intercalated ducts, interlobular ducts and excretory ducts. The morphological changes from one type of duct to the next are gradual. At the light microscopical level this consists of a change from a bilaminar epithelium in the intercalated ducts to an epithelium, consisting of approximately three layers — which may be pseudostratified — in the excretory ducts. The basal layer of the intercalated ducts consists of myoepithelial cells, whereas the inner epithelial cells may have both a secretory and an electrolyte transporting function. The interlobular duct epithelium contains many cells with deep infoldings of the basolateral plasma membranes and associated mitochondria, suggesting a similar function to the striated duct epithelium in salivary glands. Numerous basal cells in this epithelium have tentatively been interpreted as unusual myoepithelial cells. Nerve terminals have been observed in the ductal epithelium.This work was supported by the National Health and Medical Research Council of Australia. — We wish to thank Mrs. Eva Vasak for her expert technical assistance.