The mature embryo sac of the sugar beet, Beta vulgaris: A structural investigation

The mature embryo sac of Beta vulgaris consists of one egg cell, one persistent and one degenerated synergid, one cental cell with two fused polar nuclei, and five to six antipodals. The degeneration of one of the synergids appears before pollination in the maturing process. The two fused polar nuclei are located in the chalazal part of the central cell. The antipodals may have secretory activities. It is suggested that the embryo sac of the sugar beet completes the maturing process independently of pollination.     

The development of the human spleen

Summary Splenic tissue of human fetuses from the 14^th to the 24^th week of gestation (menstrual age) were investigated by light- and electron microscopy to describe the development of the red and white pulp in close relationship to the differentiation of the vascular tree. Special interest is focussed on the differentiation of the T-cell- and the B-cell regions and their specific stationary cells.The preliminary stage, here called the primary vascular reticulum, lasts up to the 14^th gestational week (gw). Numerous erythrocytes, normoblasts and macrophages are seen among a network of mesenchymal cells and argyrophilic fibers. Hematopoiesis, especially erythropoiesis, can be recognized.The characteristic organ structure becomes established during the subsequent transformation stage of the fetal spleen, beginning with the 15^th gw. Splenic lobules begin to form during the 15^th to 17^th gw. They consist of a central artery, surrounded by a sheath of lightly stained stationary cells which resemble myofibroblasts. At the periphery of these lobules the red pulp forms. Initially mobile cells are distributed throughout the reticulum. Soon they begin to accumulate in the venous sinuses, which develop from lacunae among the reticular network and come into contact with the venous system. The endothelial wall of these sinuses remains discontinuous, confirming the theory of the open vascularization of the spleen. The development of the larger veins is correlated with the differentiation of the splenic trabeculae.The development of the white pulp is correlated with the stage of lymphoid colonization within the spleen, beginning around the 18^th gw. An accumulation of lymphocytes around the central arteries can be recognized during the 19^th and 20^th gw. These lymphoid cells show morphological and immunohistochemical characteristics of T-precursor cells. Within the now assembling periarterial lymphoid sheath (PALS) a few precursors of interdigitating cells (IDC) are recognizable, giving evidence for the differentiation of the T-cell region.Around the 23^rd gw the assemblage of primary follicles is discernible at the periphery of the PALS. Precursors of the follicular dendritic reticulum cell (FDRC), the specific stationary cell of the B-cell region, have been recognized. This observation leads to the conclusion that the small primary follicles represent the beginning formation of the B-cell region.The significance of the vascular system for the differentiation of the specific splenic organization is discussed.This investigation was supported by grants from the Deutsche Forschungsgemeinschaft (Sonderforschungsbereich 111)The authors appreciate the contribution of human fetal material from Dr. von Hollweg and Dr. Körner from the Hospital Heidberg, Hamburg, and the excellent technical assistance of Mrs. H. Hansen, Mrs. I. Knauer, Mrs. M.v. Kolszynski, Mrs. J. Quitzau, Mrs. H. Siebke and Mrs. H. Waluk     

The Effect of Nonanal on Dipodascus aggregatus

Biotin can not replace nonanal for Dipodascus aggregatus. The growth-promoting effect of nonanal (80 μW) remained unchanged when the concentration of biotin was increased from 2 μm per 1 to 200 μm per I. Oleic acid stimulated the growth of D. aggregates. However, unlike nonanal, oleic acid promoted growth even if cells from the exponential phase of growth were used as inoculum. The concentrations of oleic acid required to produce growth–stimulation were considerably higher than the concentrations of nonanal required to promote growth. The growth-stimulating effect f nonanal seems to be different from t he effect of oleic acid. The incorporation of ₁C-ghtCOM by D. aggregates was stimulated by the addition of nonanal (80μm) to the growth medium. The uptake of glucosamine was not affected by nonanal (80 or 160 μM in the presence of ethanol, 0.8 to 100μ in the absence of ethanol). Hexokinase activity in cell-free homogenates was not affected by the addition of nonanal over a concentration range from 0.0059 to 1250μM.     

Elektronenmikroskopische Autoradiographie mit H3-Thymidin an der Thymusrinde der Maus

Zusammenfassung Ultradünnschnitte durch die Thymusrinde erwachsener männlicher Mäuse wurden mit einer Einkristallschicht von Ilford-L 4-Photoemulsion überzogen. In elektronenmikroskopischen Autoradiogrammen können die mit H³-Thymidin markierten Zelltypen besser erkannt werden als in lichtmikroskopisch-autoradiographischen Untersuchungen am gleichen Gewebe.Den größten Anteil der freien Zellen stellen die kleinen Lymphocyten mit dichten, von wenigen Ausnahmen abgesehen, unmarkierten Kernen und schmalem Zytoplasmasaum. In der subkapsulären Zone finden sich gehäuft große Lymphozyten und ihre Vorstufen mit einem umfangreichen, nicht so dichten Kern und einem breiteren, freie Ribosomen enthaltenden Zytoplasmasaum. 83% der Kerne dieser Zellen sind deutlich markiert. Die epithelialen Retikulumzellen im Inneren der Rinde und das Randepithel haben unmarkierte Kerne. Nur vereinzelt werden markierte Retikulumzellen unmittelbar unter dem Randsaum gefunden. Plasmazellen sind in der Rinde nur selten zu finden. Ihre Kerne weisen keine Markierung auf. Die lichtmikroskopisch-autoradiographisch erhobenen Befunde von Hinrichsen (1963, 1965) werden elektronenmikroskopisch bestätigt: Bei der Maus stellt die unmittelbar unter der Kapsel liegende Randzone des Thymus die Keimschicht zur Bildung von Thymuslymphozyten dar.

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Summary Sections of the thymus of adult male mice were covered with Ilford-L 4 photographic emulsion. In electron microscopic autoradiograms, the labelled cell types after H³-thymidine injection — can be more easily identified than with light microscopic autoradiographic methods.Most of the free cells are small lymphocytes with dense, mostly unlabelled nuclei and scanty cytoplasm. In the sub-capsular zone larger lymphocytes with a bigger, but not so condensed nucleus and more extensive cytoplasm containing free ribosomes can be found. 83% of their nuclei are labelled with tritiated thymidine. The nuclei of epithelial reticulum cells in the inner cortex and the surface epithelium are unlabelled. Only very few labelled reticulum cells can be found immediately under the connective tissue layer. Plasma cells are rarely found in the cortex. Their nuclei are not labelled. The light microscopic autoradiographic findings by Hinrichsen (1963, 1965) are electronmicroscopically confirmed: the lymphocytes of the mouse thymus originate in the immediately sub-capsular cortex of the thymus.

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Herrn Professor Bargmann zum 60. Geburtstag gewidmet.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Karyotypes of some species of Hyacinthaceae from Ethiopia and Kenya

Karyotypes for 8 different species of Hyacinthaceae from Ethiopia and Kenya are presented. Five represent new chromosome information: Drimia macrocarpa (2n = 20 + 4 B), Ledebouria revoluta (2n = 28), L. somaliensis (2n = 30), L. urceolatu (2n = 20), Ornithogalum grucillimum (2n = 24). A table summing up the present chromosome information from tropical East and North East-Africa are given.     

A structural investigation of the ovule in sugar beet, Beta vulgaris: Integuments and micropyle

The micropyle and the integuments of sugar beet (Beta vulgaris) ovules have been investigated by light and electron microscopy during differentiation and maturation of the ovule. The micropyle itself is formed by the inner integument which is surrounded by the outer integument at its base. The micropyle containts a fibrillar PAS+ substance and is often covered by a thin sheet or hymen. Both integuments are cuticle-covered thin sheets, each 2-few cell layers in thickness. In the outer integument an increase in starch accumulation occurs during ovule maturation and probably functions as nutrient storage for embryo development. The inner epidermis of the inner integument differentiates as the most conspicuous cell layer of the beet ovule. During growth and maturation of the ovule a system of small perinuclear vacuoles containing dense material increases steadily in these cells. At maturity this system fills up more than half of each cell and very dense material has accumulated in each vacuole. This vacuole content is highly refractive and contains tannins and/or polyphenols.     

Calcitonin gene-related peptide and its receptor in the thymus

Calcitonin gene-related peptide (CGRP), a 37-amino acid residue neuropeptide, was immunostained in rat thymus at two sites: a subpopulation of thymic epithelial cells, namely subcapsular/perivascular cells, were heavily stained besides some nerve fibers surrounding arteries and arterioles. The administration of nanomolar concentrations of rat -CGRP dose-dependently raised intracellular cyclic adenosine monophosphate (cAMP) levels in isolated rat thymocytes (half-maximum stimulation 1 nM) but not in cultured rat thymic epithelial cells. Peptides structurally related to CGRP (i.e., rat calcitonin or amylin) had no effect. CGRP(8–37), an N-terminally truncated form, acted as an antagonist. Peripheral blood lymphocytes did not respond to CGRP, suggesting that receptors are present only on a subpopulation of thymocytes but not on mature T cells. This was substantiated by visualization of CGRP receptors on single cells by use of CGRP-gold and -biotin conjugates of established biological activity: only a small proportion of isolated thymocytes was surface labeled. In situ, the CGRP conjugates labeled receptors on large thymocytes residing in the outer cortical region of rat thymus pseudolobules. Thus, immunoreactive CGRP is found in subcapsular/perivascular thymic epithelial cells and acts via specific CGRP receptors on thymocytes by raising their intracellular cAMP level. It is suggested that CGRP is a paracrine thymic mediator that might influence the differentiation, maturation, and proliferation of thymocytes.     

Prostaglandins contribute to the vasodilation induced by nicotinic acid

The significance of endogenously formed prostaglandins in the vasodilation induced by nicotinic acid (NIC) was investigated. The forearm venous plasma level of radioimmunoassayed PGE (R-PGE) and the forearm blood flow (FBF) were measured in 13 healthy male volunteers at rest and during infusion of NIC. Each subject was subsequently re-studied after pretreatment with the PG synthesis inhibitor, naproxen. In the absence of naproxen, NIC infusion resulted in an almost four-fold rise in the release of R-PGE and a 60% increase in FBF. Pretreatment with naproxen did not affect the basal release of R-PGE or the basal FBF but inhibited both the release of R-PGE and the increase in FBF following NIC. The data support the hypothesis that the vasolidating effect of NIC is largely dependent upon an increased vascular formation of PG.