The action of glutamate and the problem op the “extracellular space” in the retina

Summary Turtle's retinae were incubated in isotonic Ringer and then studied with the electron microscope in order to determine if in these conditions an extracellular space appeared. In the incubated retinae, as in the normal ones no extracellular space was observed. The distance between adjacent membranes is of 120–250 Å and is filled with a cementing material.The Müller cell of the turtle's retina is described. The existence, at the choroidal end of this cell, of villous projections filled with vesicles and the accumulation of mitochondria under these projections would suggest that a process of micropinocytosis takes place in this site, and that it may be metabolically more active. After incubation, Müller cells showed no appreciable changes, in contrast with what happens to astrocytes in incubated slices of CNS (Gerschenfeld et al. 1959).The addition of sodium-l-glutamate to the incubation medium determined a marked swelling of the nervous endings in the inner synaptic layer and a similar though less pronounced change in the ganglion cells. This would indicate that the surcharge of water, sodium and chloride produced by glutamate (Ames 1956) is localized in this layer.The selective action of glutamate on the inner synaptic layer, in contrast with the excellent preservation of the outer synaptic layer, is probably linked to differences in biochemistry and physiology of synapses in these two strata.Work supported by a research grant from the Air Force Office of Scientific Research (5–60), U.S.A.     

Analysis and use of the perforated patch technique for recording ionic currents in pancreaticβ-cells

Summary To investigate the voltage dependence of the Na^–/K^– pump, current-voltage relations were determined in prophasearrested oocytes ofXenopus laevis. All solutions contained 5mm Ba^2– and 20mm tetraethylammonium (TEA) to block K^– channels. If. in addition, the Na⁺/K⁺ pump is blocked by ouabain, K⁺-sensitive currents no larger than 50 nA/cm² remain. Reductions in steady-state current (on the order of 700 nA/cm²) produced by 50 m ouabain or dihydro-ouabain or by K⁺ removal, therefore, primarily represent current generated by the Na^–/K^– pump. In Na^–-free solution containing 5mm K⁺, Na⁺/K⁺ pump current is relatively voltage independent over the potential range from –160 to +40 mV. If external [K⁺] is reduced below 0.5mm, negative slopes are observed over this entire voltage range. Similar results are seen in Na⁺- and Ca²⁺-free solutions in the presence of 2mm Ni²⁺, an experimental condition designed to prevent Na⁺/Ca²⁺ exchange. The occurrence of a negative slope can be explained by the voltage dependence of the apparent affinity for activation of the Na⁺/K⁺ pump by external K⁺, consistent with the existence of an external ion well for K^– binding. In 90mm Na⁺, 5mm K⁺ solution, Na⁺/K⁺ pump current-voltage curves at negative membrane potentials have a positive slope and can be described by a monotonically increasing sigmoidal function. At an extracellular [K⁺] of 1.3mm, a negative slope was observed at positive potentials. These findings suggest that in addition to a voltage-dependent step associated with Na⁺ translocation, a second voltage-dependent step that is dependent on external [K⁺], possibly external K⁺ binding, participates in the overall reaction mechanism of the Na⁺/K⁺ pump.     

Contributions to the mathematical theory of epidemics—II. The problem of endemicity

(1) A mathematical investigation has been made of the prevalence of a disease in a population from which certain individuals are being removed as the result of the disease, whilst fresh individuals are being introduced as the result of birth or immigration. Allowance is made for the effects of the immunity produced as the result of an attack of the disease, but the effect of deaths from other causes is not taken into account, and the action of the disease is supposed to be independent of the age of the individual. (2) As a special case of the above, results have been obtained for a closed population in which no deaths occur and to which no fresh individuals are added, but in which the individuals after being infected acquire immunity, and then may be again infected. A threshold density of population exists analogous to that described in the previous paper, which is such that no disease can exist in a population, the density of which is below the threshold. (3) In other special cases investigated when either immigration or birth is operative in the supply of fresh individuals, as well as in the general case, only one steady state of disease is possible. To reach this state the population must be of a certain density which will be determined by the functions characterizing the infectivity, morbidity, etc., of the disease. (4) Increase of the immigration rate or of the birth-rate results in an increase in the rate of infection of the healthy individuals and also in the percentage rate of infection, the percentage of sick, and in the percentage of mortality from the disease. This result is, of course, a necessary consequence of our assumption that the disease is the only cause of death. (5) More particular results have been obtained by substituting constants in the place of the undetermined functions assumed in the general theory. Further, under these conditions the nature of the steady states has been more fully investigated and it has been shown that in all cases, except one, the steady states are stable ones. In the exception, a disturbance would result in purely periodic oscillations about the steady state.     

Water relation parameters of the CAM plant Kalanchoë daigremontiana in relation to diurnal malate oscillations

Summary In the CAM plant Kalanchoë daigremontiana, kept in an environmental rhythm of 12 h L: 12 h D in a growth chamber at 60% relative humidity and well watered in the root medium, decreasing water potentials and osmotic potentials of the leaves are correlated with malate accumulation in the dark. In the light increasing water and osmotic potentials ( _W and _S ) are associated with decreasing malate levels. Transpiratory H₂O loss is high in dark and low in light.In continuous light, the CAM rhythm rapidly disappears in the form of a highly damped endogenous oscillation. Malate levels, and water and osmotic potentials of the leaves remain correlated as described above. However, transpiration is very high as malate levels decrease and water and osmotic potentials increase.It can concluded, that water relation parameters like total water potential ( _W ) and osmotic potential ( _S ) change in close correlation with changes of malic acid levels. As an important osmotically active solute in CAM plants, malic acid appears to affect water relations independently of and in addition to transpiration. The question remains open, whether turgor ( _P ) is involved in CAM regulation in intact plants in a similar way as it determines malate fluxes in leaf slices.Abbreviations CAM Crassulacean Acid Metabolism - L Light - D Dark     

A critical review of the ‘neugliederung’ concept in relation to the development of the vertebral column

Summary The literature on the early embryonic development of the vertebral column in various animal species was analyzed to evaluate so many unrelated or contradictory observations. The recurring problems are described. One of the first was the lack of correspondence between the metameric boundaries of the primitive vertebral bodies arising from the somites and those of the adult vertebral bodies, as presumably shown by their relationship to the vertebral processes and spinal nerves. A century ago, Remak introduced the concept of Neugliederung, according to which the ultimate vertebral body boundaries are determined by a shift of a half segment in comparison with the earlier segment boundaries.     

Thiamine requirement in relation to cytokinin in “normal” and “mutant” strains of tobacco callus

Summary High concentrations of kinetin (400–2,000 g/l) permit continuous growth of tobacco callus cultures (Nicotiana tabacum, var. Wisconsin No. 38) in the absence of exogenous thiamine. On the optimum concentration (1,000 g/l) the tissue has been maintained through 21 bimonthly passages without change in vigor or other growth characteristics.The effect of kinetin is general, not mutagenic, because tissue returned to low-kinetin, thiamine-free medium failed to grow.Kinetin-thiamine interactions in cytokinin mutant strains which were grown without cytokinin in light and darkness suggest that the endogenous content of cytokinins may markedly affect the requirement for thiamine and possibly the tissue content of this vitamin and other growth factors.The viability of tissue on low-kinetin media in enhanced by thiamine, but the addition of this vitamin does not eliminate the requirement for a cytokinin.The great divergence in minimum kinetin concentrations required for growth of the tissue in the presence and absence of thiamine indicates that the growth promoting action of cytokinin must be different in the two cases.     

The short—term variation of asthma in Brisbane: Its relation to the weather and other factors

In the cooler portions of the six years 1961–1966, there were 22 weeks in which the night attendances for asthma at the Royal Brisbane Hospital Casualty Department were much higher than would be expected from the seasonal and annual variation, 23 weeks in which they were much lower, and 114 intermediate weeks. The high-asthma weeks differed significantly from intermediate weeks in having on the average a greater decrease from the previous week in mean and minimum temperature, dew point, relative humidity and rainfall, and a greater increase in hours of sunshine. There was a significant association with the arrival of a cold dry change. No significant difference was found with smoke density, fungal elements or pollens. In many of the individual high-asthma weeks the increase in asthma occurred within 48 hours after a definite fall in minimum temperature or dew point or both. However, in some of the weeks, particularly in spring, there had not been a cold or dry change, and many cold dry changes were not followed by an increase in asthma. The low-asthma weeks differed significantly from intermediate weeks in having on the average a higher dew point and relative humidity, more rainy days, a lower temperature range and fewer hours of sunshine. This applied particularly to autumn. In autumn and spring, rain was significantly less frequent on days with asthma attendances than on days with none. These relationships are largely the converse of those with high-asthma weeks.

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Zusammenfassung Während der kühleren Jahreszeiten in 6 Jahren (1961–1966) waren 22 Wochen in denen die Anzahl der nächtlichen Einlieferungen wegen Asthma im Royal Brisbane Hospital weit höher war als die erwartete Anzahl, 23 Wochen in denen sie wesentlich geringer war, und 114 Wochen mit einer mittleren Anzahl Fälle. Die Wetterbedingungen während der Wochen mit vielen Asthmafällen waren signifikant unterschieden von denen mit mittlerer Häufigkeit. Im Mittel waren die mittlere und die Minimaltemperatur tiefer als in der vorausgegangenen Woche, es waren weniger Regen, niedrigere Luftfeuchtigkeit und mehr Stunden Sonnenschein. Es bestand eine signifikante Beziehung zu dem Eintreffen kalter trockener Luft. Dagegen bestand keine Beziehung zur Dichte der Luftverunreinigung und der Menge Pilzsporen und Pollen in der Luft. In vielen Wochen trat Asthma innerhalb 48 Stunden nach dem Fall der Temperatur und Feuchtigkeit auf. Während einiger Wochen dagegen, besonders im Frühling, lag dieser Wetterwechsel nicht vor und in vielen Fällen bewirkte der Wechsel keinen Anstieg der Asthmahäufigkeit. Während der Wochen mit niedriger Asthmahäufigkeit waren im Mittel die Feuchtigkeit erhöht, ein geringerer Temperaturwechsel, weniger Regen und weniger Sonnenscheinstunden, besonders im Herbst. Im Herbst und Frühling war signifikant weniger Regen an Tagen mit als an Tagen ohne Asthmameldungen. Diese Beziehungen waren weitgehend umgekehrt von denen in Wochen mit hoher Asthmahäufigkeit.

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Resume Des statistiques de la permanence du "Royal Brisbane Hospital" il appert que durant les périodes froides des années 1961 à 1966, on a dénombré 22 semaines pendant lesquelles, la nuit, les entrées d'urgence causées par des crises d'asthme furent beaucoup plus nombreuses que ne le laissaient supposer les variations saisonnières et annuelles. Durant les mêmes laps de temps, on en a décompté 23 pendant lesquelles les crises nocturnes d'asthme étaient moins fréquentes et 114 qui occupent une position intermédiaire. Les semaines à haute fréquence d'asthme présentent des moyennes de température, des minimums journaliers, des points de rosée, des humidités relatives et des précipitations inférieurs et une durée d'insolation supérieure à la normale et cela de façon significative. On a pu déceler une relation significative entre les crises d'asthme et des invasions d'air froid et sec. On n'a par contre pas pu déceler de différences en ce qui concerne le taux de fumée ou le nombre de spores et de grains de pollen. Dans bon nombre de semaines avec de hautes fréquences d'asthme, le déclenchement des crises se produit 48 heures après la chute du minimum de la température ou du point de rosee, voire des 2 ensemble. Pourtant, quelques unes de ces semaines — au printemps surtout — n'ont pas connu d'invasion d'air froid et sec et de nombreuses invasions de ce type ne furent pas suivies d'une augmentation du nombre de crises. Les semaines de faible fréquence se distinguent de façon significative de la classe intermédiaire en ce sens qu'elles présentent en moyenne des points de rosée et une humidité plus élevés, plus de jours avec précipitations, une température plus basse et moins d'heures d'insolation. Ceci est valable surtout en automne. En automne et au printemps, la pluie fut moins fréquente les jours où l'on note des crises d'asthme qu'à ceux où il n'y en a pas. Cette relation est en général inverse à celle que l'on rencontre durant les semaines à haute fréquence de crises d'asthme.

     

The ultrastructure of the “difference factor” in the myelin

Summary Electron-microscopic studies of peripheral nerves as prepared by the freezeetching method show the myelin lamella to be 185 Å thick. This is the same dimension found by x-ray diffraction analysis of natural myelin. In contrast to the appearance of osmiumfixed material, the cytoplasmic surfaces of the paired membranes in the myelin lamella are apposed to two fine, separate lines, while the outer membrane sides are fused into a broader single line. The finding of a decidedly different structure for the outer and for the inner membrane surfaces appears to be the cause of the difference factor.This work was supported by the Swiss National Foundation (Nr. 4065). — Acknowledgement: We thank the Balzers AG. (9496 Balzers, Fürstentum Liechtenstein) for providing us with the High Vakuum Device.     

The metabolism of benzyladenine in Spathiphyllum floribundum ‘Schott Petite’ in relation to acclimatisation problems

In Spathiphyllum floribundum Petite, which was cultured on medium containing benzyladenine (BA), uptake of this cytokinin and its conversion to 9-ß-D-ribofuranosyl-benzyladenine (9R-BA) or 9-ß-glucopyranosyl-benzyladenine (9G-BA) was monitored. BA and extremely large quantities of 9G-BA were exclusively located in the basal part of the plant (callus and meristems). 9R-BA was found in the basal part, the petioles and the leaf blades. After an acclimatisation period of 9 weeks the plants still contained high levels of 9G-BA, but BA and 9R-BA could no longer be detected after one week. The possible role of BA and its derivatives on inhibition of root initiation or irreversible chloroplast deficiency is discussed.Abbreviations 3G-BA 3-ß-glucopyranosyl-benzyladenine - 7G-BA 7-ß-glucopyranosyl-benzyladenine - 9G-BA 9-ß-glucopyranosyl-benzyladenine - 9R-BA 9-ß-D-ribofuranosyl-benzyladenine - au absorption units - HPLC high-performance liquid chromatography - LC-MS liquid chromatography—mass spectrometry - MeOH methanol - NaFeEDTA ethylenediaminetetra-acetic acid - NH₄Ac ammonium acetate - PAR photo-synthetic active radiation - UV ultra-violet     

Phylogenetic position of the ectomycorrhizal basidiomycete Tricholoma dulciolens in relation to species of Tricholoma that produce “matsutake” mushrooms

Tricholoma dulciolens is an ectomycorrhizal basidiomycete that produces “matsutake”-like mushrooms in association with Picea abies in Fennoscandia. The phylogenetic position of T. dulciolens relative to matsutake species is, however, unknown. In the present study, we demonstrated that T. dulciolens is phylogenetically independent from T. matsutake and its allied species. In addition, herbarium specimens identified as T. caligatum from Abies alba forests in Spain were phylogenetically related to but distinct from T. dulciolens. Based on ribosomal internal transcribed spacer DNA sequence data, T. dulciolens appears to exist in North America, as well. This is the first phylogeny of T. dulciolens in Fennoscandia and its related species in southern Europe.     

The dependence of the duration of sperm motility in Ob–Irtysh basin coregonidae on temperature

The duration of sperm motility in four whitefish species in the Ob–Irtysh basin, namely, Coregonus tugun, the river and lake forms of C. peled, C. lavaretus pidschian, and C. nasus, has been studied. It is shown that the duration of sperm motility in these species has a statistically significant inversely proportional dependence on the temperature of the water that is used for activation. The total duration of sperm motility at the spawning temperature in the range from 0.1 to 5.0°C amounts to 331 ± 107 s, on average, while the duration of forward movement amounts to 149 ± 44 s, on average. At temperatures that exceed the spawning values (above 7.1°C), these parameters constitute 190 ± 47 and 86 ± 15 s, respectively. The highest interspecific variability in the duration of sperm motility was observed within the temperature range from 0.1 to 2.5 and above 7.1°C. C. tugun shows less dependence of the duration of sperm motility on temperature than the other species under study. At a temperature of 0.7°C, the total duration and duration of the forward movement of C. tugun sperm are 201 and 108 s, respectively. When the temperature was increased to 13.4°C, these parameters decreased by 1.2 and 1.1 times only, i.e., to 172 and 100 s, respectively.     

The shape of things to come in the study of the origin of species?

Perhaps Darwin would agree that speciation is no longer the mystery of mysteries that it used to be. It is now generally accepted that evolution by natural selection can contribute to ecological adaptation, resulting in the evolution of reproductive barriers and, hence, to the evolution of new species (Schluter & Conte 2009 ; Meyer 2011 ; Nosil 2012 ). From genes that encode silencing proteins that cause infertility in hybrid mice (Mihola et al. 2009 ), to segregation distorters linked to speciation in fruit flies (Phadnis & Orr 2009 ), or pollinator‐mediated selection on flower colour alleles driving reinforcement in Texan wildflowers (Hopkins & Rausher 2012 ), characterization of the genes that drive speciation is providing clues to the origin of species (Nosil & Schluter 2011 ). It is becoming apparent that, while recent work continues to overturn historical ideas about sympatric speciation (e.g. Barluenga et al. 2006 ), ecological circumstances strongly influence patterns of genomic divergence, and ultimately the establishment of reproductive isolation when gene flow is present (Elmer & Meyer 2011 ). Less clear, however, are the genetic mechanisms that cause speciation, particularly when ongoing gene flow is occurring. Now, in this issue, Franchini et al. ( 2014 ) employ a classic genetic mapping approach augmented with new genomic tools to elucidate the genomic architecture of ecologically divergent body shapes in a pair of sympatric crater lake cichlid fishes. From over 450 segregating SNPs in an F2 cross, 72 SNPs were linked to 11 QTL associated with external morphology measured by means of traditional and geometric morphometrics. Annotation of two highly supported QTL further pointed to genes that might contribute to ecological divergence in body shape in Midas cichlids, overall supporting the hypothesis that genomic regions of large phenotypic effect may be contributing to early‐stage divergence in Midas cichlids.