DISTRIBUTION OF PEROXISOMES (MICROBODIES) IN THE NEPHRON OF THE RAT : A Cytochemical Study

The distribution of peroxisomes (microbodies) in the rat nephron was studied cytochemically, using glutaraldehyde- or formaldehyde-fixed tissue, by means of α-hydroxy acid oxidase activity in light microscopy or oxidation of 3,3'-diaminobenzidine (DAB) at pH 9 in both light and electron microscopy.The two cytochemical methods show peroxisomes to be nearly sperical particles found only in cells of the proximal convoluted tubule. Lysosomes were identified in the same or parallel sections, with β-glycerophosphate or 5'-cytidylic acid as substrate. They are found in all cells of the nephron. These cytochemical methods visualize the two organelles for light microscopy; they also permit unequivocal differentiation of all kidney peroxisomes from lysosomes in electron micrographs. Peroxisomes are larger and more reactive in the cells of the pars descendens (P₃ segment) of the proximal convolution, located in the outer medulla and medullary rays, than in the cells of the pars convoluta (P₁ and P₂ segments), situated in the cortex. In contrast, lysosomes are much smaller in the P₃ segment and larger and more reactive in the P₁ and P₂ segments. In all cells of the proximal convolution, peroxisomes tend to be concentrated nearer the base of the cells than do lysosomes. Mitochondria in P₃ cells also show low levels of DAB oxidation at pH 6, in contrast to those in P₁ and P₂ cells. The possibility is discussed that P₃ cells possess an extramitochondrial means of oxidation in which peroxisome oxidases play an important role.     

Thirst and artificial heat acclimatization in man

The purpose of this study was to investigate the relationship between serum osmotic changes, water intake and water balance in four, fit young men during and after exercise in the heat, before and after artificial heat acclimatization. During exercise, before steady-state conditions were reached, voluntary water intakes generally paralleled but were not proportional to the serum osmotic pressure. In steady-state conditions, drinking was approximately proportional to the effective osmotic pressure of the serum. During the post-exercise recovery period, when serum osmolarity returned to normal levels, water intake also subsided even though there was a total body water (wt) deficit of about 3%. Body weight did not return to control levels until 62 to 86 hr following the exercise. This slow recovery could not be accounted for by a loss of water associated with glycogen utilization during exercise or by sweat electrolyte depletion. In general, the results supported Dill's hypothesis but plasma volume changes, in addition to osmotic factors,are very likely operative in the initiation and satiation of drinking under these conditions. Perhaps slower acting volume control mechanisms mediate the slow recovery of total body water.

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Zusammenfassung Untersucht wurde die Beziehung zwischen osmotischen Veränderungen im Serum, Wasseraufnahme und Wassergleichgewicht bei 4 gesunden,jungen Männern während und nach körperlicher Arbeit in der Hitze vor und nach künstlicher Hitzeakklimatisation. Die freiwillige Wasseraufnahme während der Arbeit, ehe ein steady state erreicht wurde, war im allgemeinen gleichlaufend, aber nicht proportional dem osmotischen Serumdruck. Im steady state war die Trinkmenge ungefähr proportional dem effektiven osmotischen Serumdruck. Wenn die Serumosmolarität während der Erholungsphase zur normalen Werten zurückkehrte, liess die Wasseraufnahme ebenfalls nach,obwohl das Gesamtkörperwasserdefizit ungefähr 3% betrug.Die Körpergewichte erreichten die Ausgangswerte 62–86 Std nach der Arbeit. Diese langsame Erholung war nicht bedingt durch einen Wasserverlust dur Glykogenverwertung während der Arbeit oder durch Elektrolytverluste beim Schwitzen. Die Ergebnisse stützen Dill's Hypothese, doch unter diesen Bedingungen wirken Plasmavolumen-Veränderungen zusätzlich zu osmotischen Faktoren sehr wahrscheinlich mit bei der Auslösung des Trinkens und der Sättiging mit Wasser. Vielleicht vermitteln langsamer wirkende Volumenkontrollmechanismen die langsame Wiederherstellung der Gesamtkörper-Wasservorräte.

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Resume On a examiné les relations existant chez 4 jeunes hommes sains entre les variations de la pression osmotiques du sérum d'une part,l'ingestion d'eau et l'équilibre acqueux du corps d'autre part et cela pendant et après un travail corporel à la chaleur tant avant qu'après une acclimatisation artificielle au chaud.L'ingestion volontaire d'eau évolue similairement à la pression osmotique du sérum, mais ne lui est pas proportionnel. Ce phénomène s'observe jusqu'à ce qu'un état dit stationnaire soit atteint. Dès ce moment, les quantités bues sont à peu près proportionnelles à la pression osmotique effective. Pendant la phase de récupération, la pression osmotique redevient normale et l'eau ingérée diminue bien que le déficit en eau pour le corps entier soit encore de 3% environ.Le poids du corps ne retrouve sa valeur initiale que 62 à 86 heures après la période de travail. Ce lent rétablissement n'est pas dû à des pertes d'eau par suite de l'utilisation de glycogènes pendant l'exercice ou par suite de la perte d'électrolytes par la sueur. Ces résultats viennent confirmer les hypothèses de Dill. Pourtant, dans ces conditions, les variations de volume du plasma agissent très vraisemblablement en plus des facteurs osmotiques dans le besoin de boire ou l'état de satiété. Il est possible que des mécanismes de contrôle du volume agissant plus lentement président aux phénomènes de rétablissement des réserves en eau dans son ensemble.

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Results were presented in part at the "Symposium on Nutrition and Physical Activity", The Swedish Nutrition Foundation, Tylösand, Sweden, 15–17 August,1966.     

Degradation of some phenols and hydroxybenzoates by the imperfect ascomycetous yeastsCandida parapsilosis andArxula adeninivorans: evidence for an operative gentisate pathway

The imperfect ascomycetous yeastsCandida parapsilosis andArxula adeninivorans degraded 3-hydroxybenzoic acid via gentisate which was the cleavage substrate. 4-Hydroxybenzoic acid was metabolized via protocatechuate. No cleavage enzyme for the latter was detected. In stead of this NADH- and NADPH-dependent monooxygenases were present. In cells grown at the expense of hydroquinone and 4-hydroxygenzoic acid, enzymes of the hydroxyhydroquinone variant of the 3-oxoadipate pathway were demonstrated, which also took part in the degradation of 2,4-dihydroxybenzoic acid byC. parapsilosis.Abbreviations HHQ Hydroxyhydroquinone (1,2,4-trihydroxybenzene) - GSH reduced Glutathione     

Controlled experiments of habitat fragmentation: a simple computer simulation and a test using small mammals

Habitat fragmentation involves a reduction in the effective area available to a population and the imposition of hard patch edges. Studies seeking to measure effects of habitat fragmentation have compared populations in fragments of different size to estimate and area effect but few have examined the effect of converting open populations to closed ones (an effect of edges). To do so requires a shift in spatial scope-from comparison of individual fragments to that of fragmented versus unfragmented landscapes. Here we note that large-scale, controlled studies of habitat fragmentation have rarely been performed and are needed. In making our case we develop a simple computer simulation model based on how individual animals with home ranges are affected by the imposition of habitat edges, and use it to predict population-level responses to habitat fragmentation. We then compare predictions of the model with results from a field experiment on Peromyscus and Microtus. Our model treats the case where home ranges/territories fall entirely within or partially overlap with that of sample areas in continuous landscapes, but are restricted to areas within habitat fragments in impacted landscapes. Results of the simulations demonstrate that the imposition of hard edges can produce different population abundances for similar-sized areas in continuous and fragmented landscapes. This edge effect is disproportionately greater in small than large fragments and for species with larger than smaller home ranges. These predictions were generally supported by our field experiment. We argue that large-scale studies of habitat fragmentation are sorely needed, and that control-experiment contrasts of fragmented and unfragmented microlandscapes provide a logical starting point.     

The Presence of (+)-S-Adenosyl-l-Methionine in the Rat Brain and Its Lack of Effect on Phenylethanolamine N-Methyltransferase Activity

Abstract: (+)-S-Adenosyl- l -methionine [(+)-SAM] was isolated from rat brain and was quantified by HPLC followed by UV spectrophotometric measurements and by ¹H-NMR. Its estimated ratio in brain is 3% of total SAM. Because of its commercial unavailability, (+)-SAM was also prepared from chemically synthesized SAM by separation of the two diastereoisomers on a preparative reverse-phase Nucleosil C8 column. The (+) diastereoisomer thus obtained was then assayed in vitro both as an inhibitor and a substrate of phenylethanolamine N -methyltransferase. Enzymatic activity was measured by HPLC analysis. It was shown that (+)-SAM has no effect on phenylethanolamine N -methyltransferase activity; therefore, it is unlikely that (+)-SAM plays any possible role in regulation of adrenaline synthesis in the brain.     

Is there hybridization between diploid and tetraploid Euphrasia in a secondary contact zone?

Premise

Strong postzygotic reproductive isolating barriers are usually expected to limit the extent of natural hybridization between species with contrasting ploidy. However, genomic sequencing has revealed previously overlooked examples of natural cross-ploidy hybridization in some flowering plant genera, suggesting that the phenomenon may be more common than once thought. We investigated potential cross-ploidy hybridization in British eyebrights (Euphrasia, Orobanchaceae), a group from which 13 putative cross-ploidy hybrid combinations have been reported based on morphology.

Methods

We analyzed a contact zone between diploid Euphrasia rostkoviana and tetraploid E. arctica in Wales. We sequenced part of the internal transcribed spacer (ITS) of nuclear ribosomal DNA and used genotyping by sequencing (GBS) to look for evidence of cross-ploidy hybridization and introgression.

Results

Common variant sites in the ITS region were fixed between diploids and tetraploids, indicating a strong barrier to hybridization. Clustering analyses of 356 single-nucleotide polymorphisms (SNPs) generated using GBS clearly separated samples by ploidy and revealed strong genetic structure (F_ST = 0.44). However, the F_ST distribution across all SNPs was bimodal, indicating potential differential selection on loci between diploids and tetraploids. Demographic inference suggested potential gene flow, limited to around one or fewer migrants per generation.

Conclusions

Our results suggest that recent cross-ploidy hybridization is rare or absent in a site of secondary contact in Euphrasia. While a strong ploidy barrier prevents hybridization over ecological timescales, such hybrids may form in stable populations over evolutionary timescales, potentially allowing cross-ploidy introgression to take place.     

Antiproliferative Activity and Ultrastructural Changes in Promastigote and Amastigote forms of Leishmania amazonensis Caused by Limonene-Acylthiosemicarbazide Hybrids

Leishmaniasis is a tropical zoonotic disease. It is found in 98 countries, with an estimated 1.3 million people being affected annually. During the life cycle, the Leishmania parasite alternates between promastigote and amastigote forms. The first line treatment for leishmaniasis are the pentavalent antimonials, such as N-methylglucamine antimoniate (Glucantime®) and sodium stibogluconate (Pentostam®). These drugs are commonly related to be associated with dangerous side effects such as cardiotoxicity, nephrotoxicity, hepatotoxicity, and pancreatitis. Considering these aspects, this work aimed to obtain a new series of limonene-acylthiosemicarbazides hybrids as an alternative for the treatment of leishmaniasis. For this, promastigotes, axenic amastigotes, and intracellular amastigotes of Leishmania amazonensis were used in the antiproliferative assay; J774-A1 macrophages for the cytotoxicity assay; and electron microscopy techniques were performed to analyze the morphology and ultrastructure of parasites. ATZ−S-04 compound showed the best result in both tests. Its IC₅₀, in promastigotes, axenic amastigotes and intracellular amastigotes was 0.35±0.08 μM, 0.49±0.06 μM, and 15.90±2.88 μM, respectively. Cytotoxicity assay determined a CC₅₀ of 16.10±1.76 μM for the same compound. By electron microscopy, it was observed that ATZ−S-04 affected mainly the Golgi complex, in addition to morphological changes in promastigote forms of L. amazonensis.     

A transformer architecture for retention time prediction in liquid chromatography mass spectrometry-based proteomics

Accurate retention time (RT) prediction is important for spectral library-based analysis in data-independent acquisition mass spectrometry-based proteomics. The deep learning approach has demonstrated superior performance over traditional machine learning methods for this purpose. The transformer architecture is a recent development in deep learning that delivers state-of-the-art performance in many fields such as natural language processing, computer vision, and biology. We assess the performance of the transformer architecture for RT prediction using datasets from five deep learning models Prosit, DeepDIA, AutoRT, DeepPhospho, and AlphaPeptDeep. The experimental results on holdout datasets and independent datasets exhibit state-of-the-art performance of the transformer architecture. The software and evaluation datasets are publicly available for future development in the field.