Die Pulvillen vonCalliphora erythrocephala (Diptera,Brachycera) als Adhäsionsorgane

Zusammenfassung Die Pulvillen vonCalliphora erythrocephala wurden licht und fluoreszenzmikroskopisch, raster- und transmissions-elektronenmikroskopisch untersucht. Das Adhäsionssekret wurde dünnschichtchromatographisch mit dem Körperoberflächen-Lipid verglichen.Die Pulvillen tragen auf der Ventralseite mehrere Tausend langer dünner Hafthaare mit sohlenartigen Endverbreiterungen. Die Kutikula des Pulvillus besteht hauptsächlich aus elastischen Kutikulatypen (Endo- und Mesokutikula) in verschiedenen, spezifischen Ausbildungsformen.Die Pulvillen enthalten ein sekretorisches Epithel ohne Ausführgänge, das Protein- und Lipideinschlüsse zeigt.Das Pulvillensekret ist eine schwerflüchtige, ölige Flüssigkeit, die nicht identisch ist mit dem Körperoberflächen-Lipid. Das Sekret wird in der homogenen Kutikala des Pulvillus gespeichert und über das Porenkanalsystem der Ventralseite nach außen geleitet.Der Zusammenhang zwischen der Struktur der Pulvillen und ihrer Rolle beim Adhäsionsvorgang wird diskutiert.

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The pulvilli ofCalliphora erythrocephala (Diptera, Brachycera) as adhesive organs

Summary The pulvilli ofCalliphora erythrocephala were examined by light microscopy, fluorescent light microscopy, SEM and TEM. The adhesive secretion was compared with the general surface lipid layer by means of thinlayerchromatography.On the ventral surface the pulvilli bare several thousand long, slender tenent hairs with solelike spatulate tips. The pulvillar cuticle is composed on the whole of elastic cuticle types (endocuticle, mesocuticle) with specific modifications of structure. The pulvilli contain a secretory epithelium without transport ducts which has lipid and proteinaceous inclusions.The pulvillar secretion is a slowly volatile oily liquid which is not identical to the general surface lipid. The secretion is stored in the homogeneous cuticle within the pulvillus and transported to the ventral surface via the pore canal system.The correlation between the structure of pulvilli and their function in the adhesion process is discussed here.

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Abkürzungen bl Basales Labyrinth - cv coated vesicle - db dense body - dlk Dichter Lamellenkörper - dw Dorsalwand - e Epithel - ef Endokutikulafasern in der Übergangszone (meso 2b) - endo 1 lamelläre Endokutikula - endo 2 homogene Endokutikula - endo 3 gelatinöse Endokutikula - ep Empodium - epi Epikutikula - exo Exokutikula - fr Fersenregion - fs Faltensaum - hh Hafthaare - hs Haarschaft - k Kutikula - kr Kralle - ku Kutikulinschicht - l Lumen - li Lipid - lr Dorsale Längsrippen - m Mitochondrium - mb Mesokutikulabalken in der Übergangszone (meso 2b) - meso 1 helle homogene Mesokutikula - meso 2a dunkle homogene Mesokutikula, kompakt - meso 2b Übergangszone, in der dunkle homogene Mesokutikulabalken mit faseriger Endokutikula verzahnt sind - mt Mikrotubulus - mvbd Dunkler multivesikulärer Körper - n Kern - pc Porenkanal - ps Proximalsklerit - pt Prätarsus - rer Rauhes endoplasmatisches Retikulum - s Schulter - sd Sehnendrüse - se Sehne - so Sohle - sr Saumregion - t Tubulus - t₅ Tarsalglied 5 - ta Tasche - td Tarsaldrüse - te Tarsalepithel - tg Taschengrund - tk Terminalkanäle - utr Unguitractor - v Heller Vesikel - va Proteinvakuole - w Wachsschicht - z Zementschicht     

Intracellular appearance of nitrite and nitrate in nitrogen-starved cells of Ankistrodesmus braunii

Summary The occurrence of heterotrophic nitrification in nitrogen-starved cells of Ankistrodesmus braunii was confirmed. The levels of nitrate and nitrite were measured over a period of four weeks. The validity of quantitative determinations in the presence of highly active nitrate and nitrite reductases is discussed. Whereas free hydroxylamine as an intermediate could not be detected, increased hydroxylamine oxidase activity was found in nitrogen-starved cultures. Nitrite reductase and hydroxylamine oxidase can be assigned to particles by sucrose density gradient centrifugation. The possible involvement of microbodies, which were found to be present in Ankistrodesmus, in metabolic processes during nitrogen starvation is discussed.Abbreviations NR nitrate reductase - NiR nitrite reductase - NNEDA N-(1-naphthyl)ethylenediaminedihydrochloride - DCPIP 2,6-dichlorophenolindophenol - EDTA ethylenediaminetetraacetic acid - TCA trichloroacetic acid - DAB 3,3-diaminobenzidine - AT 3-amino-1H-1,2,4-triazole - AMP 2-amino-2-methyl-1,3-propanediol     

Differentiation in cultures derived from embryonic chicken muscle: I. Muscle-specific enzyme changes before fusion in EGTA-synchronized cultures

It is known that myoblast fusion fails to occur in cultures containing EGTA (a calcium-specific chelator) but occurs very rapidly after EGTA medium is replaced with standard high-calcium medium. On the basis of a careful analysis of the time course of fusion in cultures switched from EGTA to standard medium, it is proposed that this method of synchronization be used routinely in studies of the timing of different processes during in vitro myogenesis. The kinetics of accumulation of total enzyme activity for creatine kinase and fructose diphosphate aldolase indicate that the increases characteristic of terminal muscle differentiation begin prior to the experimentally imposed onset of fusion in EGTA-synchronized cultures. Additionally, the accumulation of M-creatine kinase subunits, also typical for muscle differentiation, is shown by microcomplement fixation to begin before the switch from EGTA to standard medium. Creatine kinase isoenzyme patterns also show that the transition from B- to M-subunit-containing creatine kinases occurs in EGTA cultures not switched to standard medium. Like EGTA, 5-bromodeoxyuridine (BrdUrd) reversibly prevents myoblast fusion. By adding EGTA and BrdUrd in different sequences to muscle cell cultures, it is shown that they act at different stages in the course of in vitro myogenesis. Cells cultured in EGTA from 23 to 69 hr after plating fused very rapidly when switched to medium containing BrdUrd. In the reverse experiment, in which BrdUrd preceded EGTA, no fusion occurred. Parallel experiments with 5-fluorodeoxyuridine suggest that cell division is necessary to reverse the inhibitory effect of BrdUrd, but not that of EGTA; this is consistent with the observed kinetics of fusion after switching to standard medium. These data strongly support a model of myogenesis in vitro in which two processes (one BrdUrd-sensitive, the other EGTA-sensitive) occur sequentially. In the first process, myogenic cells give rise to cells capable of producing molecules necessary for (terminal) skeletal muscle differentiation, including both those required for cell fusion and specific isoenzymes. The second process, fusion itself, can occur in the presence of BrdUrd or in the absence of cell division.     

Epidemiology of yellow fever virus in humans,arthropods, and non-human primates in sub-Saharan Africa: A systematic review and meta-analysis

Yellow fever (YF) has re-emerged in the last two decades causing several outbreaks in endemic countries and spreading to new receptive regions. This changing epidemiology of YF creates new challenges for global public health efforts. Yellow fever is caused by the yellow fever virus (YFV) that circulates between humans, the mosquito vector, and non-human primates (NHP). In this systematic review and meta-analysis, we review and analyse data on the case fatality rate (CFR) and prevalence of YFV in humans, and on the prevalence of YFV in arthropods, and NHP in sub-Saharan Africa (SSA). We performed a comprehensive literature search in PubMed, Web of Science, African Journal Online, and African Index Medicus databases. We included studies reporting data on the CFR and/or prevalence of YFV. Extracted data was verified and analysed using the random effect meta-analysis. We conducted subgroup, sensitivity analysis, and publication bias analyses using the random effect meta-analysis while I² statistic was employed to determine heterogeneity. This review was registered with PROSPERO under the identification CRD42021242444. The final meta-analysis included 55 studies. The overall case fatality rate due to YFV was 31.1% (18.3–45.4) in humans and pooled prevalence of YFV infection was 9.4% (6.9–12.2) in humans. Only five studies in West and East Africa detected the YFV in mosquito species of the genus Aedes and in Anopheles funestus. In NHP, YFV antibodies were found only in members of the Cercopithecidae family. Our analysis provides evidence on the ongoing circulation of the YFV in humans, Aedes mosquitoes and NHP in SSA. These observations highlight the ongoing transmission of the YFV and its potential to cause large outbreaks in SSA. As such, strategies such as those proposed by the WHO’s Eliminate Yellow Fever Epidemics (EYE) initiative are urgently needed to control and prevent yellow fever outbreaks in SSA.     

PI Kinase-EhGEF2-EhRho5 axis contributes to LPA stimulated macropinocytosis in Entamoeba histolytica

Entamoeba histolytica is a protozoan responsible for several pathologies in humans. Trophozoites breach the intestinal site to enter the bloodstream and thus traverse to a secondary site. Macropinocytosis and phagocytosis, collectively accounting for heterophagy, are the two major processes responsible for sustenance of Entamoeba histolytica within the host. Both of these processes require significant rearrangements in the structure to entrap the target. Rho GTPases play an indispensable role in mustering proteins that regulate cytoskeletal remodelling. Unlike phagocytosis which has been studied in extensive detail, information on machinery of macropinocytosis in E. histolytica is still limited. In the current study, using site directed mutagenesis and RNAi based silencing, coupled with functional studies, we have demonstrated the involvement of EhRho5 in constitutive and LPA stimulated macropinocytosis. We also report that LPA, a bioactive phospholipid present in the bloodstream of the host, activates EhRho5 and translocates it from cytosol to plasma membrane and endomembrane compartments. Using biochemical and FRAP studies, we established that a PI Kinase acts upstream of EhRho5 in LPA mediated signalling. We further identified EhGEF2 as a guanine nucleotide exchange factor of EhRho5. In the amoebic trophozoites, EhGEF2 depletion leads to reduced macropinocytic efficiency of trophozoites, thus phenocopying its substrate. Upon LPA stimulation, EhGEF2 is found to sequester near the plasma membrane in a wortmannin sensitive fashion, explaining a possible mode for activation of EhRho5 in the amoebic trophozoites. Collectively, we propose that LPA stimulated macropinocytosis in E. histolytica is driven by the PI Kinase-EhGEF2-EhRho5 axis.     

A high degree of aneuploidy in frozen-thawed human preimplantation embryos

We have studied the chromosomal content in 68 normally fertilised freeze-thawed human embryos of good morphology from 34 patients with an average maternal age of 32,6 years. Forty embryos showed post-thaw cellular division and twenty-eight post-thaw cleavage arrest. After spreading of the embryos on microscope slides, analysis of chromosomes X, Y, 15, 16, 17 and 18 was performed using two rounds of fluorescent in situ hybridisation (FISH). According to the results, the embryos were divided into four groups: (I) normal, all nuclei uniformly diploid, (II) diploid mosaics, normal diploid blastomeres in combination with abnormal blastomeres, (III) abnormal, all nuclei abnormal, (IV) chaotic, the chromosome constitution varies randomly from cell to cell. Approximately 25% of the embryos had normal number of the chromosomes tested, while the majority of the embryos were abnormal. Most of the abnormal embryos were diploid mosaics (57%). This was true for the embryos showing cleavage division as well as the embryos showing cleavage arrest. Our data show a slightly higher incidence of abnormal embryos compared to those obtained with FISH in non-cryopreserved embryos and confirm that the majority of preimplantation embryos fertilised in vitro contain abnormal blastomeres. The results, mechanisms, significance and implications are discussed. Received: 19 November 1998 / Accepted: 4 March 1999