Effect of calcium and other metal ions on pectic activities from autolysed cultures of Alternaria alternata

Abstract The effect of increasing concentrations of Ca²⁺, Mg²⁺, Cu²⁺, Zn²⁺, Na⁺ and EDTA on the pectic enzymic activities (polymethylgalacturonase, endopectinase and pectin-lyase) present in the autolytic complex from Alternaria alternata has been studied. In all cases the divalent metal ions and EDTA produced an increased inhibition correlated with increasing concentration of each ion. An opposite effect was shown by the Na⁺ ion, which produced an increase in pectic enzymic activities, principally at low concentrations.     

Effect of parasympathetic denervation on acetylcholine levels in the rat parotid gland. Is there an extraneuronal pool of acetylcholine?

Parasympathetic denervation of the rat parotid gland by avulsion of the auriculotemporal nerve caused a marked and lasting decrease in gland weight. Parasympathectomy did not change the levels of choline in the gland but decreased by 60% the levels of acetylcholine (ACh) ten days after surgery and 65% at 28 days. It is puzzling that relatively high levels of ACh remained after parasympathetic denervation. The presence of additional cholinergic nerves that innervate the gland, or pass through it en route to other structures may account for some of the remaining ACh. Also, Schwann cells from denervated nerves might have contributed to some of the ACh. The existence of an extraneuronal source of ACh is considered.     

Chemical and physiological changes in fungi during autolysis

A comparative study was done on some of the chemical changes occurring during autolysis of cultures ofAspergillus flavus in both physiologically acid and alkaline media. The mycelium ofA. flavus lost during autolysis 44 % of its maximum dry weight in the physiologically alkaline medium, whereas this loss was apparently nil in the physiologically acid medium. Nitrogen containing compounds seemed not to be affected by autolysis either in the physiologically acid or alkaline media. The disappearance of P-containing compounds in mycelium ofA. flavus autolysed in both conditions (NO ₃ ^– and NH ₄ ⁺ as N source) amounted to 64 % in the alkaline autolysis and to nearly 77 % in the acid autolysis. The results we have obtained for the acid autolysis strongly suggest that very little activity is shown by autolytic enzymes in the interval 10–133 days of incubation, when measuring autolysis by the loss in mycelial dry weight.

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Zusammenfassung Eine vergleichende Untersuchung war unternommen an einigen der chemischen Veränderungen, die während der Autolyse der Kulturen vonAspergillus flavus in physiologischen sauren und alkalischen Medien vorkommen. Die Myzelien vonA. flavus haben während der Autolyse 44 % ihres größten Trockengewichtes in physiologisch alkalischem Medium verloren, während dieser Verlust in physiologisch saurem Medium anscheinend Null gewesen ist. Stickstoff enthaltende Substanzen erschienen während der Autolyse weder in physiologisch saueren noch in alkalischen Medien beeinflußt zu sein. Das Verschwinden von P-enthaltenden Substanzen in Myzelien vonA. flavus in Autolyse unter beiden Bedingungen (NO ₃ ^– und NH ₄ ⁺ als Stickstoffquelle) erreichte 64 % in alkalischer Autolyse und beinahe 77 % in der saueren Autolyse. Die Ergebnisse, die wir in der saueren Autolyse erhalten haben legen es sehr nahe, daß autolytische Enzyme eine sehr geringe Aktivität in der Zeitspanne von 10–133 Tagen der Inkubazion zeigen, wenn die Autolyse an dem Verlust des mycelialen Trockengewichtes gemessen wird.

     

Struttura ed ultrastruttura dell'apparato genitale maschile di Drosophila melanogaster Meig.

Summary The structure of the testes of Drosophila melanogaster Meig. was re-examined by means of phase contrast and polarized light microscopy; the ultrastructure was investigated by electron microscopy. Testes from adult virgins of wild strain Varese were studied, but some observations were made also on the testes of different aged insects, of some insects examined at different times during and after mating, and on testes from sterile mutant strains.The results are summarized in the following points: 1) The testis is made up of an external wall and of an internal germinal tissue. The wall appears to be composed of two overlapping layers of very flattened cells: pigmented cells and muscle cells. 2) The ultrastructure of the muscle cells gives rise to some interesting considerations arising out of the fact that there are two kinds of filaments, but without any evident transverse band organization. 3) The testis falls into three different portions according to the organisation of the germinal tissue: the apical portion (spermatogonial zone), the middle portion (spermagenetic zone) and the terminal portion (spermatic zone). 4) The germinal tissue is made up of germinal cells and interstitial cells. The germinal cells occur in groups consisting of a fixed number of elements in a syncytial state: these groups are enveloped by interstitial cells forming the cyst. The cysts can be considered as the supracellular unit of germinal tissue.The results are discussed in relation to numerous problems, such as: the existence and meaning of the syncytial state of the germinal cells; the existence of a functional cycle of the interstitial cells associated with the maturation of germinal elements; the phagocytic and mechanical functions of terminal epithelium; the existence of various movements of germinal tissue elements along the length of the testis from the apical zone to the terminal one.The paper ends with a discussion on functional aspects of the male reproductive organs.

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Ricerche eseguite col sussidio del C.N.R. (Roma).     

Lesiones histoplasmóticas autópsicas como índice epidemiológico de la enfermedad en Los Andes Venezolanos

Resumen En 244 autopsias de los años 1961, 1962 y 1963 de sujetos de más de 2 años de edad fué encontrado un 25% de casos con lesiones histoplasmóticas, en su gran mayoría de carácter residual, en pulmones y ganglios linfáticos. Esta cifra corresponde exactamente al porcentaje de reactores positivos a la prueba de histoplasmina en la población de nuestra región. Fueron corroborados los resultados deStraub &Schwarz, quienes en Cincinnati/Ohio encontraron la misma concomitancia entre los resultados de estos métodos de estudio, ambos igualmente valiosos para determinar el indice epidemiológico de histoplasmosis en una zona determinada.Puesto que en nuestros estudios no fueron aplicadas las mismas técnicas completas como en Cincinnati las cifras positivas en nuestro ambiente pueden eventualmente ser más altas, pero no alcanzan las cifras aún más elevadas, reportadas de otras zonas de Venezuela. En nuestro material el número de casos con lesiones histoplasmóticas antiguas múltiples en el pulmón, que sugieren ser primarios, era mayor que en la primera serie deStraub &Schwarz. Parece que entre nosotros la infección tiene lugar en períodos más tempranos de la vida que en EEUU de Norteamérica.El más alto índice de infección, de casi 50%, fué encontrado en personas provenientes de la región de la Cuenca del Lago de Maracaibo, disminuyendo algo en los valles de baja altura de las montañas y llegando a cifras bajas en los lugares de mayor altura.

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Summary In 244 autopsies in patients from 2 years of age on, in 1961, 1962 and 1963 histoplasmic lesions were found in 25% of all cases, mostly residual foci in lungs and lymph nodes. This percentage is exactly the same as the percentage of histoplasmin sensitivity in our environment. Thus, the results ofStraub &Schwarz who found the same percentage of anatomic lesions and histoplasmin reactors in Cincinnati, Ohio, were confirmed in our material. Morphologic methods in autopsies are a valuable tool for epidemiologic investigations regarding histoplasmosis.Since a more exact technique of examination was applied in Cincinnati, it is probable that the positive percentage in our environment is even higher. A higher number of multiple residual histoplasmotic foci in the lungs was found in our series in comparison with the first material ofStraub &Schwarz. Multiple histoplasmic foci in some of these cases may be due to primary infection. Infection withH. capsulatum occurs apparently in our environment more frequently in younger persons.The highest infection rate of almost 50% was found in patients who lived in the tropical lowlands near the Lake of Maracaibo and the Panamerican Highway. A lower rate occurred in the mountain valleys up to approximately 3000 feet of altitude, and decreased even more in higher altitudes.

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Zusammenfassung In 244 Sektionen vom 2. Lebensjahr an aus den Jahren 1961, 1962 und 1963 wurde in 25% aller Fälle Histoplasmose in Form von Residualläsionen in Lungen und Lymphknoten gefunden. Diese Zahl entspricht genau dem Prozentsatz der Bevölkerung in unserer Gegend, die positiv auf Histoplasmin reagiert. Damit werden die Befunde vonStraub &Schwarz, die an Autopsien in Cincinnati, Ohio erhoben wurden, bestätigt. Neben der Histoplasminreaktion ist es auch mittels anatomischer Untersuchungen möglich, Aussagen über das Ausmass der Infektion mitHistoplasma capsulatum in einer bestimmten Gegend zu machen.Da bei den Untersuchungen in Cincinnati genauere Untersuchungsmethoden zur Anwendung kamen, ist es möglich, dass der Prozentsatz unserer positiven Fälle eher noch höher liegt. Die Zahl unserer Fälle mit multiplen residualen Histoplasmoseherden in den Lungen ist noch höher als in der ersten Untersuchungsserie vonStraub &Schwarz. Es könnte sich in einem Teil der Fälle durchaus um multiple Primärkomplexherde handeln. Anscheinend findet die Infektion mitH. capsulatum bei uns in früheren Lebensaltern statt.Die höchste Infektionsrate von fast 50% wurde in Personen aus den gegen den Maracaibosee zu gelegenen tropischen Gebieten gefunden. Sie war etwas geringer in den Gebirgstälern bis zu etwa 1000 m Höhe und gering in Gebieten grösserer Höhe.

     

Role of recurrent hydrophobic residues in catalysis of helix formation by T cell-presented peptides in the presence of lipid vesicles

We tested the hypothesis that the recurrence of hydrophobic amino acids in a polypeptide at positions falling in an axial, hydrophobic strip if the sequence were coiled as an alpha helix, can lead to helical nucleation on a hydrophobic surface. The hydrophobic surface could anchor such residues, whereas the peptide sequence grows in a helical configuration that is stabilized by hydrogen bonds among carbonyl and amido NH groups along the peptidyl backbone of the helix, and by other intercycle interactions among amino acid side chains. Such bound, helical structures might protect peptides from proteases and/or facilitate transport to a MHC-containing compartment and thus be reflected in the selection of T cell-presented segments. Helical structure in a series of HPLC-purified peptides was estimated from circular dichroism measurements in: 1) 0.01 M phosphate buffer, pH 7.0, 2) that buffer with 45% trifluoroethanol (TFE), and 3) that buffer with di-O-hexadecyl phosphatidylcholine vesicles. By decreasing the dielectric constant of the buffer, TFE enhances intrapeptide interactions generally, whereas the lipid vesicles only provide a surface for hydrophobic interactions. The peptides varied in their strip-of-helix hydrophobicity indices (SOHHI; the mean Kyte-Doolittle hydrophobicities of residues in an axial strip of an alpha helix) and in proline content. Structural order for peptides with helical circular dichroism spectra was estimated as percentage helicity from circular dichroism theta 222 nm values and peptide concentration. A prototypic alpha helical peptide with three cycles plus two amino acids and an axial hydrophobic strip of four leucyl residues (SOHHI = 3.8) was disordered in phosphate buffer, 58% helical in that buffer with 48% TFE, and 36% helical in that buffer with vesicles. Percentage helicity in the presence of vesicles of the subset of peptides without proline followed their SOHHI values. Peptides with multiple prolyl residues had circular dichroism spectra with strong signals, but since they did not have altered spectra in the presence of vesicles relative to phosphate buffer alone, the hydrophobic surface of the vesicle did not appear to stabilize those structures.     

Cloning, functional expression and brain localization of a novel unconventional outward rectifier K+ channel.

Human TWIK-1, which has been cloned recently, is a new structural type of weak inward rectifier K+ channel. Here we report the structural and functional properties of TREK-1, a mammalian TWIK-1-related K+ channel. Despite a low amino acid identity between TWIK-1 and TREK-1 (approximately 28%), both channel proteins share the same overall structural arrangement consisting of two pore-forming domains and four transmembrane segments (TMS). This structural similarity does not give rise to a functional analogy. K+ currents generated by TWIK-1 are inwardly rectifying while K+ currents generated by TREK-1 are outwardly rectifying. These channels have a conductance of 14 pS. TREK-1 currents are insensitive to pharmacological agents that block TWIK-1 activity such as quinine and quinidine. Extensive inhibitions of TREK-1 activity are observed after activation of protein kinases A and C. TREK-1 currents are sensitive to extracellular K+ and Na+. TREK-1 mRNA is expressed in most tissues and is particularly abundant in the lung and in the brain. Its localization in this latter tissue has been studied by in situ hybridization. TREK-1 expression is high in the olfactory bulb, hippocampus and cerebellum. These results provide the first evidence for the existence of a K+ channel family with four TMS and two pore domains in the nervous system of mammals. They also show that different members in this structural family can have totally different functional properties.     

Fusarium solani invader of the eggs of the insectPanstrongylus geniculatus in a vivarium

A strain ofFusarium solani sensu Snyder & Hansen invaded the eggs of the insectPanstrongylus geniculatus in a vivarium. None of the invaded eggs hatched. To establish experimentally the pathogenicity of thisFusarium species against the eggs ofP. geniculatus, the fungus and the eggs were incubated together under different relative humidities and temperatures. At 64% relative humidity and 26 °C, the fungus grew well colonizing and penetrating all of the chorions.Three embryos died and were also colonized byF. solani. Only 4 nymphs hatched and survived to day 20. It is concluded that the isolate ofF. solani was capable of colonizing and invading the chorion of the eggs under certain humidity and temperature conditions and cause the death of the embryos.     

Confirmational identification of Escherichia coli, a comparison of genotypic and phenotypic assays for glutamate decarboxylase and beta-D-glucuronidase.

Genotypic and phenotypic assays for glutamate decarboxylase (GAD) and beta-D-glucuronidase (GUD) were compared for their abilities to detect various strains of Escherichia coli and to discriminate among other bacterial species. Test strains included nonpathogenic E. coli, three major groups of diarrheagenic E. coli, three other non-coli Escherichia species, and various other gram-negative and -positive bacteria found in water. The genotypic assays were performed with hybridization probes generated by PCR amplification of 670- and 623-bp segments of the gadA/B (GAD) and uidA (GUD) genes, respectively. The GAD enzymes catalyze the alpha-decarboxylation of L-glutamic acid to yield gamma-aminobutyric acid and carbon dioxide, which are detected in the phenotypic assay by a pH-sensitive indicator dye. The phenotypic assay for GUD involves the transformation of 4-methylumbelliferyl-beta-D-glucuronide to the fluorogenic compound 4-methylumbelliferone. The GAD phenotypic assay detected the majority of the E. coli strains tested, whereas a number of these strains, including all representatives of the O157:H7 serotype and several nonpathogenic E. coli strains, gave negative results in the GUD assay. Both phenotypic assays detected some but not all strains from each of the four Shigella species. A strain of Citrobacter freundii was also detected by the GUD assay but not by the GAD assay. All E. coli and Shigella strains were detected with both the gadA/B and uidA probes. A few Escherichia fergusonii strains gave weak hybridization signals in response to both probes at 65 degrees C but not at 68 degrees C. None of the other bacterial species tested were detected by either probe. These results were consistent with previous reports which have indicated that the GAD phenotypic assay detects a wider range of E. coli strains than does the GUD assay and is also somewhat more specific for this species. The genotypic assays for the two enzymes were found to be equivalent in both of these respects and superior to both of the phenotypic assays in terms of the range of E. coli strains and isolates detected.