Xylanase and xylosidase activities in avocado fruit

The activities of xylanase and xylosidase were demonstrated in mature avocado (Persea americana Mill.) fruits from different cultivars. When monitored on the day of harvest during the season at 1-month intervals, xylanase activity decreased and xylosidase activity increased between January and February and then remained stable until May. When monitored during the ripening process (January harvest), xylanase activity was constant, and xylosidase activity reached a peak at the climax of ethylene evolution and cellulase activity. Xylanase, which originated from Trichoderma viride and was added to the medium in which avocado discs were incubated, induced ethylene evolution.     

Zweiphasenaktivität bei der Schleiereule (Tyto alba)

Für die Schleiereule (Tyto alba) wird während der Fütterungszeit eine nächtliche Zweiphasenaktivität beschrieben. An zwei verschiedenen Brüten wurde in der Nacht eine vormitternächtliche Aktivitätsphase von etwa 2 Std. Länge und eine etwas kürzere Morgenaktivitätsphase beobachtet. Ein solcher Bigeminus war von vielen Säugetierarten, nicht aber von nachtaktiven Vögeln bekannt. Bei drei etwa 1 Monat alten Jungen muß jeder Altvogel, binnen 3 bis 3,5 Stunden, also während der Hälfte der Dunkelperiode, mindestens 5 Stück mäuse- bzw. sperlingsgroße Beutetiere erspähen und erbeuten. Die Analyse von Schädelresten aus dem Gewöllmaterial der Jungeulen ergibt kein reales Bild des Speisezettels, da die Altvögel den Kopf der Beute nicht selten abreißen, wodurch diese in den Speiballen nicht aufscheinen.     

Ultrastructural localization of silver-staining nuclear proteins at the onset of transcription in early bovine embryos.

Argyrophilic nuclear proteins, known to be functionally associated with ribosomal genes, were localized, in four-, eight-, and 16-cell bovine embryo blastomere nuclei using two different silver-staining procedures. Within the eight-cell cleavage stage by the process of embryonal nucleologenesis in the cow embryo the full-capacity ribosome-producing machinery is established. In the four-cell embryo, many patches and islands of argyrophilic (Ag+) material were detected in the nucleoplasm. The nucleolus-precursor bodies (NPBs), composed uniformly of a homogeneous compact mass, were completely devoid of any silver staining. On the other hand, clear-cut localization of argyrophilic proteins was detected during the eight-cell stage either inside the transforming NPBs or in the close vicinity, or in the already differentiated nucleolus. In compact, nonvacuolated NPB, an intensive Ag+ area was detected, in the form of a lenticle, at the periphery of the NPB. During and following vacuolation of the NPB, no Ag+ was detected inside these vacuoles. It was seen, however, in the dense fibrillar nucleolar component surrounding the smaller vacuoles formed at the time of the establishment of nucleolar structure. Ag+ areas were seen repeatedly in the vicinity of NPBs, probably a part of the nucleolus-associated chromatin or, alternatively, representing the extranucleolar bodies. In blastomere nuclei of 16-cell embryos, already possessing reticulated nucleoli known from intensively synthesizing somatic cells, the silver-staining pattern corresponded to the usual situation in differentiated cells: slight staining of fibrillar centers, heavy labelling in the dense fibrillar component, and absence of silver deposits in the granular component.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of mixed neutron-gamma irradiation in vivo on the cell surfaces of murine blood cells

Summary For studies on cell membranes, mice were exposed to mixed neutron + gamma reactor-radiation in the range of total doses from 0.5 to 4.5 Gy. Changes in functional activity of plasma membranes of erythrocytes, platelets, and lymphocytes were followed by a lectin-binding technique at various intervals afterwards. The amount of³H-concanavalin A bound to cells altered considerably during the 1st h after irradiation in all cell types. Lymphocytes and platelets, however, were more sensitive than erythrocytes as increased lectin-binding could already be observed after 0.5 Gy. The binding ability of these cells performed oscillatory behaviour. In addition, alterations in shapes and ultrastructure of cell surfaces and intracellular membranes were observed.     

Alpha-1-antitrypsin deficiency and juvenile liver disease Ultrastructural observations compared with light microscopy and routine liver tests

Sixteen children (aged between 1 month and 20 years) with alpha-1-antitrypsin deficiency (PiZ) were investigated by liver biopsy on one or more occasions. Eight patients had suffered from neonatal cholestasis, and two of them were investigated during the cholestatic period as well. The clinical status and liver function tests were compared with the light and electron microscopical findings. According to the light microscopical analyses at the latest investigation, the cholestatic and noncholestatic patients were classified as healthy, fibrotic or cirrhotic cases. All livers displayed periodic acid-Schiff positive, diastase-resistant globules in some but not all periportally located hepatocytes. By electron microscopy accumulation of retained secretory material was found in all PiZ patients. This accumulation was most conspicuous in the smooth endoplasmic reticulum of hepatocytes. alpha-1-antitrypsin deficiency seems to affect some, but not all hepatocytes. In the affected cells disappearance or hypotrophy of the Golgi complex could be observed. The intracellular transport of very low density lipoproteins (VLDL) was apparently not affected. The migration block in alpha-1-antitrypsin deficiency seems to occur before transportation to the Golgi complex. The extent of the involvement was not strictly age-dependent. There was no ultrastructural evidence of subclinical cholestasis as a possible triggering factor in the development of cirrhosis.     

The Mechanisms and Role of Photosynthetic Hydrogen Production by Green Microalgae

Microbiology - The review clarifies the mechanisms of H2 production by green microalgae and the physiological role of the [FeFe] hydrogenase in adaptation of these organisms to varying...     

Cuticular fatty acid profile analysis of three Rhipicephalus tick species (Acari: Ixodidae)

Cuticular fatty acids (CFA) are important constituents of the arthropod exoskeleton, serving as structural and defense components, and participating in intra-species communication. Here we describe for the first time a comparative analysis of the CFA profiles of three tick species of the genus Rhipicephalus: R. annulatus, R. bursa and R. sanguineus. CFA profiles were determined for R. bursa and R. sanguineus grown both on rabbit or calf, and for R. annulatus grown on calf. CFA composition was compared for each species before and after ethanol treatment, for different hosts of each species, and between the different species. Our data suggest that adsorption of the host’s fatty acids changes the apparent CFA composition. Ethanol treatment efficiently removed the unbound fatty acids from the ticks and revealed the actual composition. Comparison between ticks grown on rabbit versus calf showed significant difference in the relative abundance of fatty acids C14 and 9,12-C18:2 for R. bursa, and a difference in the relative abundance of C14 for R. sanguineus. Comparison of the CFA between the three species revealed significant differences in the abundance of fatty acids C16, 9,12-C18:2, 9-C18:1, C18 and C20. Our results show that while the host had a minor effect on CFA composition within each species, significant differences were observed in the CFA profiles of different species. We suggest that CFA profiles may be used to distinguish between related species. CFA analysis can also be used in studies of communication and defense mechanisms in ticks and other arthropods.     

Role of cuticular lipids and water-soluble compounds in tick susceptibility to Metarhizium infection

The arthropod cuticle acts as a physiochemical barrier protecting the organism from pathogens' entry. Entomopathogenic fungi actively penetrate the cuticles of arthropod hosts and are therefore directly affected by cuticle composition. Previously we have observed that Metarhizium spp. developing on resistant ticks ultimately die without penetrating tick's cuticle, suggesting that the cuticles of resistant ticks have antifungal compounds. In the present study, lipids and water-soluble cuticular components were extracted from engorged female tick cuticles, of one susceptible and one resistant tick species to Metarhizium spp. While conidia exposed to lipids from the susceptible tick, Rhipicephalus annulatus, germinated and differentiated into appressorium, conidia exposed to lipids from the resistant tick, Hyalomma excavatum, were inhibited. Soluble cuticular component extracts from both susceptible and resistant ticks stimulated conidial germination but not appressorium differentiation. A comparative analysis of the fatty acid profile in lipid extract of each tick exhibited similar compositions, but the relative abundance of C16:0, C18:0, C18:1ω9C and C20:0 was 2–5 times higher in the extracts from resistant ticks. All of these fatty acids inhibited conidial germination in vitro at 1% and 0.1% w/v concentration, but C20:0 stimulated appressorium differentiation at low concentration. This is the first report demonstrating a possible link between the presence of antifungal compounds in a specific concentration in tick cuticle and tick resistance to infection.     

A histopathological study on the Caucasian dwarf goby from an anthropogenically loaded site in Hungary using multiple tissues analyses

The present study aimed to investigate for the first time the health status of the Caucasian dwarf goby Knipowitschia caucasica (Berg, 1916, Fishes of freshwaters of Russian Empire, p. 563, Moscow, Russia: Dep. Zemledeliya) (Teleostei: Gobiidae) from an anthropogenically loaded site in Hungary using histopathological analyses on multiple tissues. For that purpose, fish were collected from the public beach at Tiszafüred near the River Tisza. Gills, liver and kidney were subjected to histopathological analyses, and the results showed different alterations in each organ, which also differed in their extent and severity. In addition, we also found lesions in the reproductive organs of both, male and female fish which, overall, we hypothesized could be due to untreated municipal wastewaters, most likely contaminated with endocrine-disrupting chemicals. The multi-organ histopathological analyses of Caucasian dwarf gobies revealed different lesions, prevalence and severity in each target organ, as follows: liver>gills>kidney>gonad (testes and ovaries). These histopathological lesions can be assessed as good indicators of contamination by endocrine-disrupting chemicals of freshwater ecosystems.