Innervation und zentralnervöse Verbindungen des Frontalorgans von Rana temporaria und Rana esculenta

Zusammenfassung Mit neurohistologischen Techniken (Nauta-Verfahren) wurde der Anteil des Stirnorgans von Rana temporaria und Rana esculenta an der zentralnervösen Projektion des lichtempfindlichen Pinealkomplexes geprüft. Nach operativer Unterbrechung des Nervus pinealis im dorsalen Lymphsack lassen sich degenerierende Nervenfasern sowohl im Tractus pinealis als auch im stirnorgannahen Stumpf des Nervus pinealis nachweisen. Die ersteren werden als cerebropetale (afferente), die letzteren als zum Stirnorgan ziehende (efferente) Faserelemente gedeutet. Es ist gelungen, die hirnwärts gerichteten Nervenfasern des Stirnorgans bis in die unmittelbare Umgebung des sekretorischen Subcommissuralorgans zu verfolgen; zerfallende Faserfragmente liegen dicht der Basis des Subcommissuralorgans an. Anders als nach Durchtrennung des Tractus pinealis (vgl. Paul, Hartwig und Oksche, 1971) ließen sich nach Unterbrechung des Nervus pinealis keine Degenerationszeichen im mesencephalen Zentralen Grau darstellen.

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Innervation and central nervous connexions of the frontal organ in Rana temporaria and Rana esculenta Fiber degeneration after surgical interruption of the pineal nerve

Summary The contribution of the frontal organ of Rana temporaria and Rana esculenta to the central nervous projections of the light-sensitive pineal complex has been investigated with neurohistological techniques (Nauta-method). After surgical transection of the pineal nerve within the dorsal lymph sac, degenerating nerve fibers have been observed within the pineal tract and also in the proximal stump of the pineal nerve. Those in the pineal tract have been interpreted as cerebropetal (afferent) connexions of the frontal organ, and those in the pineal nerve as fibers directed towards the frontal organ (efferent elements). The cerebropetal fibers of the frontal organ have been traced to the subcommissural region where they degenerate in close juxtaposition with the secretory subcommissural organ. In contrast to the findings obtained after transection of the pineal tract (see Paul, Hartwig and Oksche, 1971), no degenerating fibers have been observed in the mesencephalic central grey after surgical interruption of the pineal nerve.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Weitere experimentelle und neuroanatomische Untersuchungen an den Nervenbahnen des Pinealkomplexes der Anuren

Zusammenfassung Der Epiphysenkomplex von 32 Fröschen der Arten Rana temporaria, Rana esculenta und Rana catesbeiana wurde zuerst elektrophysiologisch, anschließend neuro-histologisch bzw. elektronenmikroskopisch untersucht. Auf Belichtung des Stirnorgans lassen sich vom Nervus pinealis (= Tractus frontalis) zwei Arten von Antworten ableiten. Antidrome elektrische Reizung des Tractus pinealis zeigt im Nervus pinealis fortgeleitete Aktionspotentiale und damit Nervenfasern, die vom Stirnorgan bis zum Mittelhirn durchgehen. Elektrophysiologisch wurden außerdem Fasern ermittelt, die die Epiphysis cerebri nicht erreichen. Weitere Fasern enden in der Epiphyse. Neben den vom Stirnorgan zum Gehirn ziehenden afferenten Fasern kann man im extracranialen Teil des Nervus pinealis auch efferente Fasern nachweisen.Histologisch ist in allen Fällen der Durchtritt des Nervus pinealis durch das Schädeldach zu beobachten. Der Durchmesser des Nerven nimmt jedoch wahrend seines Verlaufs kontinuierlich ab. Elektronenmikroskopisch konnte gesichert werden, daß diese Durchmesserabnahme auf einem Faserverlust beruht. Bei einer Rana catesbeiana wurden kurz vor Eintritt des Nervus pinealis in die Epiphyse — im Vergleich zum extracranialen Nervenabschnitt —nur noch die Hälfte der markhaltigen und 1/3 der marklosen Nervenfasern gezählt. Bei den verbleibenden markhaltigen Fasern war außerdem die Dicke der Markscheide stark reduziert. Der Nervus pinealis fächert sich in Epiphysennähe auf; seine Fasern treten dorsomedian einzeln durch die Basalmembran in das Parenchym des rostralen Epiphysenabschnittes ein. Gemeinsam mit den Neuriten der Epiphysennervenzellen bilden sie den Tractus pinealis (s. auch Paul u. Mitarb., 1971). Eine synaptische Umschaltung der Fasern des Nervus pinealis konnte in der Epiphyse nicht nachgewiesen werden. Bei einer Rana esculenta betrug der Faseranteil des Nervus pinealis am Tractus pinealis nur etwa 2%. Die Befunde werden im Zusammenhang mit der Entstehung und Leitung der chromatischen und achromatischen Antwort im Epiphysenkomplex diskutiert.

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Further experimental and neuroanatomical investigations of the nerve tracts of the pineal complex in anura

Summary The pineal systems of 32 frogs of the species Rana temporaria, Rana esculenta, and Rana catesbeiana were studied first electrophysiologically and then with histological and electron microscopical methods. The nervus pinealis (= tractus frontalis) showed two kinds of responses to photic stimulation. Uninterrupted conduction of nerve impulses from the frontal organ to the midbrain was demonstrated by antidromic electrical stimulation of the intracranial pineal tract and recording of action potentials from the extracranial pineal nerve. Beside the uninterrupted fibres from the frontal organ to the tractus pinealis, other fibres of the nervus pinealis either did not reach the pineal organ or ended in the pineal organ. The extracranial part of the nervus pinealis contained afferent as well as efferent fibres.Morphologically it was shown in 32 investigated animals that the nervus pinealis penetrates the skull and runs to the pineal organ. During its course, the diameter of the pineal nerve became smaller, which was related to a decrease of the number of myelinated and unmyelinated fibres as revealed by the electron microscope. In comparison with the extracranial portion of the pineal nerve, the intracranial portion of the nerve near the pineal organ contained only half of the myelinated and one third of the unmyelinated fibres counted in one specimen of Rana catesbeiana. The thickness of the myelin sheats of the residual myelinated fibres was much reduced. The nervus pinealis entered the rostral region of the pineal organ, and single nerve fibres were seen to penetrate the basal lamina of the pineal organ reaching its parenchyma dorsomedially. These fibres, and axons of the nerve cells of the pineal organ, constituted the pineal tract (see also Paul et al., 1971). In one specimen of Rana esculenta, only 2% of the nerve fibres of the tractus pinealis originated in the frontal organ. The results have been discussed in relation to the generation and conduction of the chromatic and achromatic responses in the pineal system.

Herrn Prof. Dr. Dr. h. c. W. Bargmann, Kiel, in Dankbarkeit gewidmet.     

Acetylcholinesterase-positive intrapineal neuronal system in the palm squirrel Funambulus pennanti (Wroughton)

A well-developed acetylcholinesterase (AChE)-positive neuronal system could be demonstrated in the pineal organ of the palm squirrel. There are two longitudinal nerve tracts which run all along the margin of the pineal organ from its distal to proximal regions. These nerve tracts are confluent distally. Another short, but deep tract was seen in the middle part of the pineal organ which joins one of these tracts. A large number of AChE-positive neurons whose processes actually form the tracts are present all along the pineal organ. They are distinguished into multipolar and pseudounipolar/unipolar neurons. A few neurons seen outside the nerve tract form a network of nerve fibres among the pinealocytes and also link the main tracts. The nerve tracts appear wavy, irregular and tortuous. A large number of round ring-like bodies seen in close association with neuronal perikarya and nerves may represent the axo-somatic and axo-dendritic contacts.     

Elektronenmikroskopische Untersuchungen am Stirnorgan von Anuren

The ultrastructure of the frontal organ (pineal end-vesicle, Stirnorgan) of Rana temporaria L. and Rana esculenta L. is similar to the submicroscopic organization of the retina and other photosensitive organs. There are five different cell types in the frontal organ: sensory (receptor) cells, ependymal cells, ganglion cells, glial cells and epithelial cells. The ependymal cells may be secretory. There is no evidence for a typical pigment epithelium. The sensory cells have inner and outer segments. The inner segments contain numerous mitochondria, a Golgi complex, filaments, lipid droplets, two centrioles and a fibrillar apparatus (within the connecting piece). The mitochondria are very abundant in the Ellipsoid and Ersatzellipsoid areas (Holmgren) of the inner segment. The outer segment consists of about 60 to 110 discs formed by infoldings of the cell membrane. Most of the sensory cells are cone-like, but there are some elements with rod-like structures. Plexiform areas of the frontal organ contain terminations of the receptor cells, and processes of the nerve cells and glia cells. Synaptic structures have been determined within these areas. Non-medullated and medullated nerve fibers with adjacent glial satellites are observed in the pineal nerve (Nervus pinealis). The anatomical findings are described in detail and discussed in respect to the physiological results of Dodt and Heerd (1962) in Rana temporaria and Rana esculenta.

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Durchgeführt mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Developmental changes in the fatty acids of synaptic membrane phospholipids: Effect of protein malnutrition

The acyl-linked fatty acid composition of the major phospholipid species in rat cortical synaptic membranes was determined at various stages of development. For most species there was a decrease during development in the short chain saturated fatty acids, 140 and 160, an increase in 180 and 226 (n-3) and an increase in the ratio of 226 (n-3)/225 (n-6). Pups were protein deprived by feeding the dams a 12% casein diet as compared to the 24% casein control diet. Protein malnutrition markedly affected the composition of acyl-linked fatty acids in the synaptic membranes. The increases in the ratio of 226 (n-3)/225 (n-6) fatty acids were especially compromised.Abbreviations used (PC) Phosphatidylcholine - (PE) phosphatidylethanolamine - (EP) ethanolamine plasmalogen - (PS) phosphatidylserine - (PI) phosphatidylinositol - (SP) sphingomyelin - (t.l.c.) thin layer chromatography - (BHT) butylated-hydroxytoluene     

Modification of the properties of a translocation in the German cockroach by selection

Summary A stock of Blattella germanica bearing the interchange T(3; 12)/3;12 was subjected to close inbreeding with selection for random disjunction at metaphase I. After 3–4 generations of selection, interchange quadrivalent chiasma frequency decreased, variability in free bivalent chiasma frequency increased sharply, and individuals with either random or directed disjunction were present in the stock. Random disjunction was modified from a ratio of 2112 (adj.-1; alt.-1; adj.-2; alt.-2) to a ratio of 1111. After 7–8 generations of selection, chiasma frequency appeared to stabilize at lower than normal levels and variability decreased for both quadrivalents and free bivalents. Directed disjunction was modified from a ratio of 2114 to 1112, and no individuals with the original high level of directed disjunction were detected. Chains-of-four tended to orient randomly, especially in individuals where the ring quadrivalents showed directed disjunction. Relaxation of inbreeding, but not selection, produced an increase in chiasma frequency and variability in both free bivalents and quadrivalents, but the modified ratios for both random and directed disjunction were retained. These results are discussed with respect to inbreeding effects and genetic control of chiasma frequency and metaphase I disjunction in interchange quadrivalents.     

Toxigenic fungi and the deterioration of Nigerian poultry feeds

Growth of toxigenic strains of Aspergillus clavatus Des. and Aspergillus flavus Link at 30°C on milled poultry feeds led to a considerable decrease in the protein, oil and crude fibre contents of the feed substrate. A corresponding increase in the free fatty acid fractions of the feeds due to the activities of these microbes was also recorded. Rapid degradation of the feedstuff by both species was recorded at a temperature of 25°C and 30°C and a pH range of 4.8–6.4. When grown on feed infusion broth at 30°C, the highest amounts of mycelial production with sporulation of both fungal species occurred within the 8-day incubation period. A determination of their extra-cellular enzyme profile showed the production of amylases, pectate lyase, cellulases, proteases, lipases, xyalanases, DNase and RNase.All the carbon and nitrogen sources used (except L-sorbose and DL-tryptophan), supported good mycelial growth with sporulation. An optimal CN ratio of 5.04.5 and 7.53.0 was recorded for growth and sporulation of A. clavatus. For A. flavus, a CN ratio of 7.54.5 was found best for growth and 5.03.0 for sporulation.     

Thiol-dependent passive K:Cl transport in sheep red blood cells: X. A hydroxylamine-oxidation induced K:Cl flux blocked by diethylpyrocarbonate

Summary Hydroxylamine, a potent oxidizing agent used to reverse carbethoxylation of histidine by diethylpyrocarbonate, activated Cl-dependent K flux (KCl cotransport) of low K sheep red blood cells almost sixfold. When KCl cotransport was already stimulated by N-ethylmaleimide, hydroxylamine caused an additional twofold activation suggesting modification of sites different from those thiol alkylated. This conclusion was supported by the finding that hydroxylamine additively augmented also the diamide-induced KCl flux (Lauf, P.K. 1988.J. Membrane Biol. 101:179–188) with dithiothreitol fully reversing the diamide but not the hydroxylamine effect. Stimulation of KCl cotransport by hydroxylamine was completely inhibited by treatment with diethylpyrocarbonate also known to prevent KCl cotransport stimulation by N-ethylmaleimide, both effects being independent of the order of addition. Hence, although the effect of carbethoxy modification on KCl flux cannot be reversed by hydroxylamine and thus excludes histidine as the target for diethylpyrocarbonate, our finding reveals an important chemical determinant of KCl cotransport stimulation by both hydroxylamine oxidation and thiol group alkylation.     

The paracellular pathway in toad urinary bladder: Permselectivity and kinetics of opening

Summary Determination of serosa-to-mucosa fluxes of Na, K, and Cl yields information about the properties of the shunt pathway in toad urinary bladder. We show that measurement of these fluxes at 30-sec intervals following an abrupt increase in mucosal osmolality yields evidence on the rate of opening of the path and of its permselectivity. The relationship between the fluxes of any pair of these ions indicates that the shunt is paracellular both before and after the increase in conductance effected by hyperosmolality and that the transepithelial PD affects the permselectivity properties (at 0 mV,P _K/P _Na/P _Cl= 10.710.57; at +25 mV,P _K/P _Na/P _Cl=10.710.99). The relationship between any of the fluxes and the total transepithelial conductance is linear and yields an estimate of cellular conductance (the intercept of this regression on the conductance axis) which is in accord with that measured electrically. These studies provide information on tight junction permeability to nonelectrolytes, as well. Finally, they provide new information about the role of the shunt path as a controlling influence on transepithelial sodium transport and raise the possibility that, in both leaky and tight epithelia, differences in transepithelial conductance from tissue to tissue, organ to organ, and species to species may be due, in the absence of edge damage, to changes in conductance of the paracellular pathway.     

Bioassembly of acyl lipids in microspore-derived embryos of Brassica campestris L.

The native lipid composition and the capacity of cell-free extracts to biosynthesize acyl lipids in vitro were determined for the first time using the recently reported microspore-derived (MD) embryo system from the Brassica campestris low erucic acid line BC-2 (Baillie et al. 1992). The total lipid fraction isolated from midcotyledonary stage MD embryos (21 days in culture) was composed primarily of triacylglycerol (76%) with an acyl composition quite similar to that of mature BC-2 seed. When incubated in the presence of glycerol-3-phosphate, ¹⁴C 181-CoA, and reducing equivalents, homogenates prepared from 21-day cultured MD embryos were able to biosynthesize glycerolipids via the Kennedy pathway. The maximum in vitro rate of triacylglycerol biosynthesis could more than account for the known rate of lipid accumulation in vivo. The homogenate catalyzed the desaturation of 181 to 182 and to a lesser extent, 183. The newly-synthesized polyunsaturated fatty acids initially accumulated in the polar lipid fraction (primarily phosphatidic acid and phosphatidylcholine) but began to appear in the triacylglycerol fraction after longer incubation periods. As expected for a low erucic acid cultivar, homogenates of MD embryos from the BC-2 line were incapable of biosynthesizing very long chain monounsaturated fatty acyl moieties (201 and 221) from 181-CoA in vitro. Nonetheless, embryo extracts were still capable of incorporating these fatty acyl moieties into triacylglycerols when supplied with ¹⁴C 201-CoA or ¹⁴C 221-CoA. Collectively, the data suggest that developing BC-2 MD embryos constitute an excellent experimental system for studying pathways for glycerolipid bioassembly and the manipulation of this process in B. campestris.Abbreviations CPT sn-1,2-diacylglycerol cholinephosphotransferase - DAG diacylglycerol - DGAT diacylglycerol acyltransferase - DGDG digalactosyldiacylglycerol - G-3-P glycerol-3-phosphate - G-3-PAT glycerol-3-phosphate acyltransferase - LPA lyso-phosphatidic acid - LPAT lyso-phosphatidic acid acyltransferase - LPC lyso-phosphatidylcholine - LPCAT acyl-CoA: lyso-phosphatidylcholine acyltransferase - LPE lyso-phosphatidylethanolamine - MGDG monogalactosyldiacylglycerol - PA phosphatidic acid - PA Phosphatase, phosphatidic acid phosphatase - PC phosphatidylcholine - PE phosphatidylethanolamine - PG phosphatidylglycerol - TAG triacylglycerol - 181-CoA oleoyl-Coenzyme A - 181 oleic acid, cis-9-octadecenoic acid - 182 linoleic acid, cis-9,12-octadecadienoic acid - 183 -linolenic acid, cis-9,12,15-octadecatrienoic acid - 201 cis-11-eicosenoic acid - 221 erucic acid, cis-13-docosenoic acid; all other fatty acids are designated by number of carbon atoms: number of double bonds National Research Council of Canada Publication No. 35896     

Nutrient proportions in foliage of semi-mature loblolly pine

Summary Nitrogen and phosphorus limitations to growth are common in many loblolly pine (Pinus taeda) stands. Interactions of these nutrients may complicate interpretation of foliar nutrient analysis for predicting response to forest fertilization. Proportions of foliar nutrient concentrations (and the changes in these proportions following fertilization) were examined in 36 semi-mature loblolly pine plantations in the southeastern United States. Mean proportions of nutrient concentrations (NPKCaMg) for non-fertilized stands were 1009.336.517.29.2. Potassium and phosphorus were higher. Nitrogen fertilization generally decreased the PN ratio and enhanced growth, indicating a nitrogen deficiency in most stands under study. Additions of nitrogen and phosphorus together yielded a significant increase in the PN ratio. Effects of fertilization effects on other nutrient concentration ratios were also examined.Paper No. 9401 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695.     

Glycerolipid-fatty-acid desaturase deficiencies in chloroplasts from fruits of Capsicum annuum L.

Chloroplasts from fruits and leaves of Capsicum annuum cv. Bell Tower were purified on sucrose gradients, and the lipids were separated by column and thin-layer chromatography. The glycerolipids mono- and digalactosyldiacylglycerol (MGDG, DGDG), sulfoquinovosyldiacylglycerol (SQDG), and phosphatidylglycerol (PG) were quantified, and the fatty-acid composition at the 1 and 2 positions of the glycerol moiety (sn-1 and sn-2) was determined after hydrolysis with position-specific lipases. In fruit chloroplasts, ³-trans hexadecenoate (trans-3-161) was absent and replaced by palmitate (160) at sn-2 of PG, and ^7,10,13-hexadecatrienoate (163) at sn-2 of MGDG was greatly reduced and largely replaced by linoleate (182). The ratio of 182 to linolenate (183) was consistently greater in glycerolipids from fruit compared with leaf chloroplasts. The lower percentage of C-16 fatty acids at sn-2 indicated that prokaryotic molecular species were reduced by 15% in DGDG, 40% in SQDG, and 90% in MGDG, in fruit compared with leaf chloroplasts. The MGDGDGDG ratios in fruit and leaf chloroplasts were 1.21 and 2.21, respectively. Taken together, the data indicate that chloroplasts in Capsicum fruit are deficient in three desaturases: those that convert 1) 160 to ³-trans-161 at sn-2 of PG, 2) 160 to ⁷–cis-161 at sn-2 of MGDG, and 3) 182 to 183 at both sn-1 and sn-2 of various chloroplast glycerolipids.Abbreviations Chl chlorophyll - DGDG digalactosyldiacylglycerol - FS free sterol - GL galactolipid - MGDG monogalactosyldiacylglycerol - PE phosphatidyl ethanolamine - PG phosphatidylglycerol - PL phospholipid - SQDG sulfoquinovosyldiacylglycerol We are grateful to Dr. Roger Calza for providing us with the tobacco gt11 cDNA expression library and to Dr. Eric Huttner for his advice throughout the screening procedure. We also wish to thank M. Gosse for his assistance in growing and maintaining our plants. T.W.B. was supported by a BAP research grant from the Commission of the European Communities.     

Sex determination in Sarotherodon (tilapia)

Summary The simplest possible model of the sex determination process adding autosomal influence to a minimal number of sex chromosomes was developed to explain matings of Tilapia (Sarotherodon) species. Eighteen different genotypes, each having two autosomes (AA, Aa, or aa) and two sex chromosomes (WX, WY, WW, XY, XX or YY) involved in sex determination, are predicted by the theory. Their sex (10 males and 8 females) were determined using a series of directed graphs, showing the relative strength of the chromosome pairs, developed on the basis of Chen's sex ratio results (Chen 1969). This theoretical model predicts eight different sex ratios (01, 13, 35, 11, 97, 53, 31, 10 ); three of them are not predicted by the WXYZ theory. The greatest part of these sex ratios have been obtained experimentally in extensive series of crosses between related species of Tilapia and their hybrids, carried out by several authors. The theory succeeds in explaining all of Chen's results, including those ratios 53 and 01 seen in certain crosses but not predicted by the WXYZ theory. The importance of the autosomes is seen in comparisons of the genotype pairs (AaWY, aaWY), (AaXY, aaXY) and (AAWW, AaWW) in which the first genotype in each case is male while the second is female as proven by the sex ratio results. The members of the pair differ only in the substitution of one autosome for the other. To test the theory, experiments consisting of hormonal sex reversion and a series of crosses are proposed. Finally, theoretical and practical implications of the theory are discussed.     

Cellular fatty acid composition of six fastidious,gramnegative, xylem-limited bacteria from plants

Composition of cellular fatty acids was determined for strains of fastidious, Gramnegative, xylem-limited bacteria causing or associated with Pierce's disease of grapevine, phony disease of peach, plum leaf scorch, stunt of ragweed, elm leaf scorch, and periwinkle wilt. The most abundant fatty acids were straight-chain 150, 160, 170, and 180, unsaturated 161, 181, and unsaturated 17-and 19=carbon homologs. Minor fatty acids included straightchain 120, 140, 190, and 200; an unsaturated 15-carbon homolog; hydroxy-substituted 2-OH 120, 3-OH 120, and 3-OH 140; and branched chain iso-140 and iso-200. Cyclopropane acids were not detected. Physiological age had no effect on fatty acid composition. Class analysis of data indicated relative uniformity within the group. Saturated even-carbon chains comprised 31%–42%, unsaturated acids 41%–52%, saturated odd-carbon chains 10%–18%, hydroxysubstituted chains 2%–7%, and branched-chains 1%–4% of total fatty acids. The ratio of saturated-unsaturated acids ranged from 0.8 to 1.2.     

Neurone und zentralnervöse Verbindungen des Pinealorgans der Anuren

Zusammenfassung Das Problem der Zwischenneurone nimmt bei der Deutung der chromatischen und achromatischen Antworten der pinealen Sinnesorgane eine Schlüsselstellung ein. Frühere Ergebnisse schienen darauf hinzuweisen, daß der nervöse Apparat des Pinealorgans (Epiphysis cerebri) vonRana temporaria undRana esculenta bineuronal organisiert ist. Mit modifizierten Methylenblau- und Golgi-Methoden gelang es jetzt, die nervösen Strukturen der pinealen Rezeptoren und Nervenzellen präziser darzustellen. Das neurohistologische Bild der Epiphysis cerebri enthält auch Nervenzellen, die an Zwischenneurone denken lassen. Diese diffus verstreuten kleinen Elemente unterscheiden sich von den klassischen Typen der retinalen Bipolar-, Horizontal- und Amakrinzellen. Der Tractus pinealis vonR. temporaria undR. esculenta wird von Axonen großer multipolarer und kleiner, wenig verzweigter Ganglienzellen gebildet. Die zentrale Projektion dieser pinealofugalen (afferenten) Bahn ist von großem funktionellem Interesse. Nach vollständiger Unterbrechung des Tr. pinealis finden sich degenerierende Faserelemente innerhalb und am unteren Rand der Comm. posterior, in der Area praetectalis und in den Kernarealen des sog. Zentralen Graus. Keine degenerierenden Tractusfasern sind in der subependymalen Schicht und in den aminergen Kerngebieten des Mesencephalon zu beobachten. Die beschriebenen Verbindungen des Tr. pinealis könnten die anatomische Basis einiger lichtabhängiger (phototaktischer) Reflexe darstellen. Weitere Untersuchungen über die zentralnervöse Projektion des Tr. pinealis sind im Gang.

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Neurons and central nervous connexions of the pineal organ in anura

Summary The problem of interneurons appears to be very important for the functional interpretation of the chromatic and achromatic responses of pineal sense organs. Previous results seemed to indicate a bineuronal chain in the pineal organ (epiphysis cerebri) ofRana temporaria andRana esculenta. Precise images of pineal receptors, neurons and their connexions were obtained in the present studies using methylene-blue and Golgi methods. A limited number of interneurons probably exist in theepiphysis ofR. temporaria andR. esculenta: the images of these scattered neurons were observed to differ from the classical bipolar, horizontal and amacrine cells of the amphibian retina. The pineal tract of R. temporaria andR. esculenta is formed by the axons of large multipolar and smaller scarcely ramified nerve cells. The central projection of this pinealo-fugal (afferent) pathway is of great functional interest. After complete surgical interruption of the pineal tract degenerating nerve fibers were traced in Nauta (Fink-Heimer) preparations. Degenerating fibers were observed within and beneath the posterior commissure, in the pretectal region and in the nuclear areas of the periventricular gray. The subependymal layer and the basal aminergic nuclei of the frog mesencephalon were always free of degenerating fibers. The anatomical connexion of the pineal tract described in this paper could serve as a basis for some light-dependent (phototactic) reflexes. Further investigations concerned with the central projections of the pineal tract are in progress.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft. — Eine Kurzfassung der Befunde wurde auf dem Symposium The Pineal Gland der Ciba Foundation in London (30. 6.–2. 7. 1970) vorgetragen (s. Oksche, 1971).     

Osmotropotaxis inDrosophila melanogaster

Summary Drosophila melanogaster is able to perform osmotropotaxis under open-loop conditions. With an optimal stimulus the average turning tendency to the side of higher concentration corresponds to a circular track with radiusr=0.8 cm. The response amplitude does not decrease within 1 or 2 h. Unilaterally antennectomized flies in an homogeneous odor field show a permanent turning tendency towards their intact side.The smallest concentration ratio to elicit osmotropotaxis in normal flies ranges between 610 and 910 at high and between 210 and 510 at an about 50 times lower odor intensity. No negative tropotaxis (i.e. turning to the side of lower concentration) is observed, even with strong repellents.     

Diverse effects of essential (n−6 andn−3) fatty acids on cultured cells

Fatty acids (FAs) have long been recognized for their nutritional value in the absence of glucose, and as necessary components of cell membranes. However, FAs have other effects on cells that may be less familiar. Polyunsaturated FAs of dietary origin (n–6 andn–3) cannot be synthesized by mammals, and are termed essential because they are required for the optimal biologic function of specialized cells and tissues. However, they do not appear to be necessary for normal growth and metabolism of a variety of cells in culture. The essential fatty acids (EFAs) have received increased attention in recent years due to their presumed involvement in cardiovascular disorders and in cancers of the breast, pancreas, colon and prostate. Manyin vitro systems have emerged which either examine the role of EFAs in human disease directly, or utilize EFAs to mimic thein vivo cellular environment. The effects of EFAs on cells are both direct and indirect. As components of membrane phospholipids, and due to their varying structural and physical properties, EFAs can alter membrane fluidity, at least in the local environment, and affect any process that is mediated via the membrane. EFAs containing 20 carbons and at least three double bonds can be enzymatically converted to eicosanoid hormones, which play important roles in a variety of physiological and pathological processes. Alternatively, EFAs released into cells from phospholipids can act as second messengers that activate protein kinase C. Furthermore, susceptibility to oxidative damage increases with the degree of unsaturation, a complication that merits consideration because lipid peroxidation can lead to a variety of substances with toxic and mutagenic properties. The effects of EFAs on cultured cells are illustrated using the responses of normal and tumor human mammary epithelial cells. A thorough evaluation of EFA effects on commercially important cells could be used to advantage in the biotechnology industry by identifying EFA supplements that lead to improved cell growth and/or productivity.Abbreviations AA arachidonic acid (20 carbons: 4 double bonds,n–6) - BHA butylated hydroxyanisole - BHT butylated hydroxytoluene - cAMP cyclic adenosine monophosphate - CHO Chinese hamster ovary - DAG diacylglycerol - DGLNA dihomo--linolenic acid (203,n–6) - DHA docosahexaenoic acid (226,n–3) - EFA essential fatty acid - EGF epidermal growth factor - EGFR epidermal growth factor receptor - EPA eicosapentaenoic acid (205,n–3) - FA fatty acid - FBS fetal bovine serum - GLNA -linolenic acid (183,n–6) - LA linoleic acid (182,n–6) - LNA -linolenic acid (183,n–3) - LT leukotriene - MDA malondialdehyde - NAD nicotinamide adenine dinucleotide - NDGA nordihydroguaiaretic acid - OA oleic acid (181,n–9) - PG prostaglandin - PKC protein kinase C - PUFA polyunsaturated fatty acid - SFM serum-free medium - TX thromboxane     

A new type of phosphoglycolipid fromPseudomonas cepacia

A new type of phosphoglycolipid was found inPseudomonas cepacia. A ratio of glucosamine/phosphoric acid/polar fatty acid/nonpolar fatty acid was resolved to be 1 1 1 1, and the molecular weight of the phosphoglycolipid was determined to be 777 by mass spectrometry. An amino group of the glucosamine was free, and both a phosphoric acid and two kinds of fatty acids were bound directly to the glucosamine.     

Pineal regeneration in the frog, Rana pipiens, following embryonic extirpation

This report describes the capacity of larvae of the Leopard frog, Rana pipiens, to regenerate pineal tissue after embryonic pinealectomy, and presents experimental evidence for frontal organ dependence on the epiphysis. In addition, it was found that the “brow spot,” a pigment-free region located in the epidermis betweeen the eyes, is dependent on the frontal organ for its formation. This report also substantiates that the absence of the pineal organ in larval animals does not affect growth or development through metamorphosis.     

Comparative mapping in F2∶3 and F6∶7 generations of quantitative trait loci for grain yield and yield components in maize

This study was conducted to compare maize quantitative trait loci (QTL) detection for grain yield and yield components in F₂₃ and F₆₇ recombinant inbred (RI) lines from the same population. One hundred and eighty-six F₆₇ RIs from a Mo17×H99 population were grown in a replicated field experiment and analyzed at 101 loci detected by restriction fragment length polymorphisms (RFLPs). Single-factor analysis of variance was conducted for each locus-trait combination to identify QTL. For grain yield, 6 QTL were detected accounting for 22% of the phenotypic variation. A total of 63 QTL were identified for the seven grain yield components with alleles from both parents contributing to increased trait values. Several genetic regions were associated with more than one trait, indicating possible linked and/or pleiotropic effects. In a comparison with 150 F₂₃ lines from the same population, the same genetic regions and parental effects were detected across generations despite being evaluated under diverse environmental conditions. Some of the QTL detected in the F₂₃ seem to be dissected into multiple, linked QTL in the F₆₇ generation, indicating better genetic resolution for QTL detection with RIs. Also, genetic effects at QTL are smaller in the F₆₇ generation for all traits.Abbreviations RFLPs Restriction fragment length polymorphisms - QTL quantitative trait loci - RIs recombinant inbreds Journal Paper no. J-16261 of the Iowa Agric and Home Economics Exp Stn Project no. 3134