On the fine structure of the cerebral ganglion of Sagitta (Chaetognatha)

Summary In this study the fine structure of the cerebral ganglion of Sagitta setosa (Chaetognatha) is investigated. The ganglion is flat and superficially positioned dorsally, below the basal lamina of the cephalic epidermis. It is surrounded by a specifically differentiated sheath. This sheath is made up of cells, which are interpreted as representing glial cells, and can be divided into an outer and an inner zone. The outer zone is composed of flat sheath cells with pale nuclei and few organelles. The inner zone consists of densely packed, extremely thin lamellar cellular processes. These attenuated lamellae, which still contain cytoplasm, resemble the myelin sheath of vertebrate axons. The intercellular space between the lamellae contains electron-dense material. In the sheath specialized intercellular contacts occur. The inner zone of this sheath extends at definite points into the centre of the ganglion and separates a zone of perikarya from the neuropil, as well as the single perikarya from each other. The perikarya are relatively uniform and do not form a cortex, but are concentrated mainly in lateral parts of the cerebral ganglion. Within the neuropil are axonal endings which have synaptic contacts with several postsynaptic elements. These anatomical findings are discussed with respect to their functional significance.     

Regional differences in a nematoceran retina (Insecta,Diptera)

Summary The compound eye of Psychoda cinerea comprises two types of ommatidia, arranged so as to divide the retina into distinct dorsal and ventral regions. The P-type ommatidium, in the ventral part of the eye, differs fundamentally from the other dipteran ommatidia so far described, and is regarded as a primitive ommatidium. The acone dioptric apparatus is the same in both types, with a spherical lens and four Semper cells, the processes of which expand below the rhabdom to form a ring of pigment sacs. Only the distal region of the rhabdom is surrounded by a continuous ring of screening pigment, formed by 2 primary and 12–16 secondary pigment cells. The highly pigmented retinula cells penetrate the basement membrane proximally at about the level of their nuclei; in this region they are separated from the hemolymph by glial elements. The rhabdomeres R1–6 are fused to form a tube. The two types of ommatidia are defined by the arrangement of the retinula cells R7/8: in the T type the central rhabdomeres are one below the other, in the usual tandem position, whereas in the P type only R8 is central, with R7 in the peripheral ring. In the proximal region of the retina, retinula cells with parallel microvilli in neighboring ommatidia are joined in rows by lateral processes from the R8 cells. All the rhabdomeres are short and not twisted, which suggests that the retinula cells are highly sensitive to direction of polarization. The eye can adapt by a number of retinomotor processes. These findings, together with observations of behavior, imply that the psychodids have well-developed visual abilities.     

Isolation and structural analysis of two lipid A precursors from a KDO deficient mutant of Salmonella typhimurium differing in their hexadecanoic acid content

The extraction, purification and structural characterization of two lipid A precursors (Ia and Ib) differing only in one hexadecanoic acid are described. Both precursors were synthesized at elevated temperatures by a new mutant of Salmonella typhimurium (mutant Ts5) which is conditionally defective in synthesis of the 3-deoxy-d-manno-octulosonic acid region of lipopolysaccharides.Both precursors were purified by repeated phenol/chloroform/petroleum ether (PCP) extractions followed by thin layer chromatography. Teh precursor preparation was free of lipopolysaccharides and phospholipids and contained less than 0.1% protein. Structural analysis which included chemical degradation procedures as well as positive ion laser desorption (LDMS) mass spectroscopy of dephosphorylated lipid A precursors showed together that precursor Ia represents a diphosphorylated glucosamine disaccharide containing two ester, two amide-linked residues of 3-hydroxytetradecanoic acid and lacks the ester-linked dodecanoic, tetradecanoic and hexadecanoic acid as well as 3-deoxy-d-manno-octulosonic acid. Precursor Ib has the same basic structure as precursor Ia, but contains in addition one mol of hexadecanoic acid per mol disaccharide which is linked to the 3-hydroxy group of the amide-bound 3-hydroxy-tetradecanoic acid of the reducing, terminal glucosamine residue.The structure of precursor Ib supports the conclusion that hexadecanoic acid incorporation occurs at an early stage in lipid A biosynthesis prior to the attachment of 3-deoxy-d-manno-octulosonic acid and/or other polar substituents.Abbreviations LDMS laser desorption mass spectrometry - KDO 3-Deoxy-d-manno-octulosonic acid - Ts5 Salmonella typhimurium mutant Ts5 - PCP phenol/chloroform/petroleum ether - H₂F₂ hydrogen fluoride This work is dedicated to Prof. Dr. Drews, Freiburg, on the occasion of his 60th birthday     

Thermal influences on the habitat preference and the diurnal activity in three European Rana species

The diurnal behaviour of frogs was recorded quantitatively in a habitatlike experimental environment by a new method of automatic registration via thermocouples. Three species with different habitat preferences during their summer activity period were chosen: the terrestrial common frog Rana temporaria LINNÈ and the semiaquatic water frog Rana lessonae CAMERANO and Rana ridibunda PALLAS. The activity, the location and the skin temperatures of these frogs were recorded continuously in four different temperature ranges (8.1° C–31.0° C) within the temperature span of the summer activity period. The thermal requirements and behavioural adaptations to the habitat of each species were analysed. The experimental results coincided with field observations and showed some details not yet known. The northern species R. temporaria exhibited a distinctive behavioural thermoregulation including cooling behaviour at high temperatures and warming behaviour at low temperatures during the day. In all temperatures tested these frogs remained on land changing their preferred location from the open area to the hiding places. The main activity period shifted from night to day with decreasing temperatures. The more southern species R. lessonae preferred higher temperatures than the other species showing basking behaviour during the day independent of the ambient temperature. With decreasing temperatures the preferred location changed from the shore to the water and the activity during the night almost disappeared. The closely related R. ridibunda tolerated high temperatures too, but only rarely basked. This species, however, reacted contrarily to decreasing temperatures: it changed its preference from the water to the land. This behavioural differenciation between the water frog species may be of importance for the actual habitat preference of these central european water frogs.     

In vitro studies on the subcellular location of glucosidase I and glucosidase II in dog pancreas

When programmed with yeast prepro--factor mRNA, the heterologous reticulocyte/dog pancreas translation system synthesizes two pheromone related polypeptides, a cytosolically located primary translation product (pp--F_cyt, 21 kDa) and a membrane-specific and multiply glycosylated e-factor precursor (pp--F₃, 27.5 kDa). Glycosylation of the membrane specific pp--F₃ species is competitively inhibited by synthetic peptides containing the consensus sequence Asn-Xaa-Thr as indicated by a shift of its molecular mass from 27.5 kDa to about 19.5 kDa (pp--F₀) , whereas the primary translation product pp--Fcyt is not affected. Likewise, only the glycosylated pp--F₃ structure is digested by Endo H yielding a polypeptide with a molecular mass between PP--F₀ and pp--Fcyt. These observations strongly suggest that the primary translation product is proteolytically processed during/on its translocation into the lumen of the microsomal vesicles. We believe that this proteolytic processing is due to the cleavage of a signal sequence from the pp--Fcyt species, although this interpretation contradicts previous data from other groups. The distinct effect exerted by various glycosidase inhibitors (e.g. 1-deoxynojirimycin, N-methyl-dNM, 1-deoxymannojirimycin) on the electrophoretic mobility of the pp--F₃ polypeptide indicates that its oligosaccharide chains are processed to presumbly Man₉-GlcNAc₂ structures under thein vitro conditions of translation. This oligosaccharide processing is most likely to involve the action of glucosidase I and glucosidase II as follows from the specificity of the glycosidase inhibitors applied and the differences of the molecular mass observed in their presence. In addition, several arguments suggest that both trimming enzymes are located in the lumen of the microsomal vesicles derived from endoplasmic reticulum membranes.Abbreviations dNM 1-deoxynojirimycin - N-Me-dNM N-methyl-dNM - dMM 1-deoxymannojirimycin - CCCP carbonylcyanide m-chlorophenyl hydrazone     

Lineage-specific expression of c-fos and c-fms in human hematopoietic cells: Discrepancies with the in vitro differentiation of leukemia cells

In vitro differentiation studies using the bipotential human leukemia cell line, HL60, have indicated that high levels of expression of two proto-oncogenes, c-fos and c-fms, are restricted to the myelomonocytic lineage. No such expression has been detected in induced granulocytic cells. In striking contrast to these observations, we found that c-fos mRNA levels are very high in purified human granulocytes, but barely detectable in blood monocytes and tissue macrophages. Human granulocytes contain, however, relatively low levels of c-fos protein, indicating that c-fos mRNA is inefficiently translated or that the protein is rapidly degraded in these cells. In closer agreement with the in vitro results, the level of the expression of c-fms is high in purified blood monocytes and undetectable in granulocytes. We found, however, that the evolution of monocytes into tissue macrophages is accompanied by a significant decrease in c-fms expression, suggesting that the function of c-fms is restricted to specific stages of monocytic differentiation. Our observations also show that results obtained using in vitro differentiation systems have to be regarded with caution, since they may not reflect the in vivo situation.     

Embryonic cholinesterase activity during morphogenesis of the mouse genital tract

Summary In the genital tract of male and female mouse embryos cholinesterase activity is described that is independent from innervation. The enzyme activity is localized in the mesenchyme at the junction of Wolffian and Müllerian ducts with the urogenital sinus. During male development prostate buds and vesicular glands grow out into the cholinesterase-active mesenchyme. During female development the active mesenchyme participates in the downgrowth of the vaginal anlage. Ultrastructurally the cholinesterase activity is localized in the perinuclear cisterna and in smooth endoplasmic reticulum of the mesenchymal cells. The enzyme activity disappears with definitive differentiation of the tissue. The embryonic cholinesterase is a component of a primitive muscarinic system. Its relation to the morphogenetic action of testosterone and its possible general functions are discussed.     

Sensory projections to the nucleus basalis prosencephali of the pigeon

Summary The afferent pathways to the nucleus basalis prosencephali of the pigeon were studied by use of the horseradish peroxidase (HRP) technique. It was confirmed that this nucleus receives a direct pathway from the nucleus sensorius principalis nervi trigemini and that, as in the starling, it receives a direct input from the nucleus lemnisci lateralis, pars ventralis, an auditory relay. Totally novel is the finding that the nucleus basalis prosencephali is the target of a direct pathway originating in the medullary nucleus vestibularis superior. All three pathways bypass the thalamus. From within the telencephalon the nucleus basalis prosencephali also receives fibres from the tuberculum olfactorium and the peri-ectostriatal belt, suggestive of olfactory and visual input. Marked cell bodies were also found in the neostriatum frontolaterale. It is assumed that these arose from HRP uptake by axons of the tractus fronto-archistriatalis that course through the nucleus basalis prosencephali to the anterodorsal archistriatum. Marked fibres and bouton-like formations were observed in the latter structure. The afferents to the nucleus basalis prosencephali are discussed in conjunction with the probable role of the nucleus as a sensorimotor coordinator of the pecking/feeding behaviour of the pigeon.     

Litter decomposing and ectomycorrhizalBasidiomycetes in an igapó forest

An igapó forest near the confluence of Rio Tarumã Mirim (Tarumãzinho) and Rio Negro has been studied. It is a typical ectotroph forest with a raw humus layer and suppressed litter decomposing activity by Higher (i.e., carpophore-producing) Fungi. The number of the latter is about one-fifth of that observed in the (anectotrophic) terra firme forest. All ectotrophically mycorrhizal fungi observed belonged in three families:Amanitaceae, Boletaceae, Russulaceae. Leguminosae are dominant, and of theseAldina latifolia andSwartzia cf.polyphylla were demonstrably ectomycorrhizal. The scarcity of mineral nutrients in the soils of igapó, campinarana and campina is overcome by direct cycling through ectomycorrhizae. This is in contrast to other black- and white-water inundated forest communities in Amazonia.Litter Decomposition and Ectomycorrhiza in Amazonian Forests3. Previous contributions seeSinger & Araujo (1979) andSinger & al. (1983).     

Evaluation of nongenotoxic and genotoxic factors modulating the frequency of micronucleated erythrocytes in the peripheral blood of mice

The hematological micronucleus test is regarded as an indicator of the clastogenic effect of chemicals and acute cytogenetic damage. The test can be carried out in red blood cells of the bone marrow and of the spleen, as well as in peripheral erythrocytes. We have determined the precise background values of micronucleated red blood cells for the peripheral blood of BALB/c DBA/2, and NMRI mice. Bleeding, phenylhydrazine-induced hemolysis, and splenectomy generated an increase of micronucleated erythrocytes in the peripheral blood of mice. Our data thus demonstrate that such factors should be taken into consideration when the micronucleus test is used for screening the genotoxic potential of chemicals. Furthermore, the micronucleus-inducing effect of cyclophosphamide was studied in normal and splenectomized mice and, in addition, a comparison of the sensitivity of the micronucleus test was carried out in peripheral blood and bone marrow after cyclophosphamide treatment. Our data demonstrate that the kinetics of micronucleus formation were similar in normal and in splenectomized mice in which the micronucleus levels had returned to normal. The comparison of micronucleus formation in bone marrow and peripheral blood after cyclophosphamide treatment revealed the generation of similar quantities of micronucleated red blood cells in both tissues. The physiological mechanisms of micronucleus formation and removal and the potential role of chemically induced spleen damage during this process are discussed; the usefulness of the peripheral micronucleus test as a simple, rapid, and animal-saving modification of the standard bone marrow test is evaluated.Abbreviations CP cyclophosphamide - MN micronuclei - MNCE micronucleated normochromatic erythrocytes - MNPCE micronucleated polychromatic erythrocytes - MNRBC micronucleated red blood cells - NCE normochromatic erythrocytes - PCE polychromatic erythrocytes