Different distribution of melanophores and xanthophores in early tailbud and larval stages inTriturus alpestris

Summary The subepidermal distribution of xanthophores and melanophores is investigated in embryos ofTriturus alpestris with a uniform (stage 28+) and a banded melanophore pattern (stage 35/36). In ultrathin head and trunk sections from stage 35/36 embryos which externally show longitudinal dorsal and lateral melanophore bands in the trunk and less compact continuations of the dorsal bands in the head, xanthophores were discovered in addition to melanophores. Melanophores contain melanosomes while xanthophores which are not externally visible, are recognized by their pterinosomes. Both chromatophore cell types are mutually exclusively distributed on the epidermal basement membrane (bm). Mesenchymal cells seemed not to be able to replace them, except on the bm of the corneal epithelium where there were only mesenchymal cells. In head and trunk sections from stage 28+ embryos which externally show a distribution of uniformly scattered melanophores on the dorsolateral halves, melanophores were found on the dorsolateral neural crest migration route. No epidermal bm was present and xanthophores were undetectable. In ventrolateral and ventral portions of embryos of both stages no chromatophores occurred. This investigation defines the histological localization of melanophores and xanthophores in embryos with a typical uniform and banded melanophore arrangement; a subsequent study analyzes when xanthophores appear and how they arrange with melanophores in alternating zones.     

Vertical migrations of herring,Clupea harengus,larvae in relation to light and prey distribution

Synopsis The influence of light and prey abundance on the vertical distribution of herring larvae was evaluated by three investigations made under calm weather conditions in the North Sea off the Scottish coast. The investigations took place at different time after hatching and the vertical distributions of three size groups of larvae (mean sizes 8,15 and 19 mm) were related to time of day and the vertical distribution of copepods. No migratory behaviour of copepods was observed but their vertical distribution differed between investigations. In the investigation on intermediate sized larvae, copepod density peaked at the pycnocline (40 m). Larvae concentrated at this depth at noon. At dawn and dusk larvae migrated towards the surface and the vertical distributions fluctuated semidielly. In the two other investigations, copepods were homogeneously distributed in the water column and after migration towards the surface at dawn larvae stayed in the upper water column during the day. The observations suggest that the daytime vertical distribution of larvae in calm weather is mainly determined by feeding conditions: the larvae move to depths were light is sufficient for feeding, and refinement within that zone is made according to a compromise between optimal light conditions for feeding and optimal prey densities.     

Changes in the distribution of gap junctions inDrosophila melanogaster wing discs during the third larval and early pupal stages of development

Summary Developmental changes in the distribution of gap junctions in early, mid and late third larval stage wing discs and in pupariation+6 h and pupariation+24 h stage wing discs fromDrosophila melanogaster were analyzed by quantitative electron microscopy. Gap junctions occur in all 12 intradisc regions examined in each of the five developmental stages. Their distribution is non-random and changes during development which suggests that they are developmentally regulated. The gap junctions are not static structures, rather they grow and regress during development. The changes tend to be gradual ones without sudden increases or decreases. Gap junctions continuously form and grow in size throughout the third larval stage and during the first 6 h following pupariation. Their surface density, number, percent of the lateral plasma membrane area, and absolute area as well as the lateral plasma membrane surface density all increase during this time. Between pupariation+ 6 h and pupariation+24 h all but one of these parameters decrease indicative of gap junctional breakdown. Gap junctions are most numerous and change least during development in the apical cell regions where intercellular contacts are close and stable. They change most in the basal cell regions where intercellular contacts tend to be looser and change during development. The most dramatic change is in the absolute area which increases by a factor of 23 between the early third larval stage and pupariation+24 h. At pupariation the rate of gap junction growth undergoes a transient increase before the phase of disassembly begins. Developmental changes in gap junction surface density are closely coupled with changes in the lateral plasma membrane surface density which suggests that these may be coregulated. Evidence from mutants suggests that when the number and density of gap junctions fail to increase in proportion to lateral plasma membrane growth, wing disc development will be abnormal. Our results support the idea that some minimum gap junction density is required for normal development and that this must increase as development proceeds. The results are consistent with the notion that gap junctions are involved in pattern formation and growth control and are discussed with respect to the acquisition of competence for metamorphosis, disc growth, disc morphogenesis and changes in the hormonal environment.     

A study of the assimilation of fluorescent pigments of microalgae Isochrysis galbana by the early larval stages of turbot and herring

The appearance of large supranuclear vacuoles in the enterocytes of 1- and 4-days post-hatch larvae of turbot and herring, respectively, revealed by the pinocytotic uptake of a fluorescent marker (FITCdextran), indicates a potential for the absorption of dissolved nutrients by the endotrophic stages of marine fish larvae. Ingestion of algal cells by turbot larvae was observed soon after hatching, but low level pinocytotic absorption of algal material was first seen during the second day. More extensive lysis of algal cells and pinocytotic absorption occurred 24 h later. Although lysis of I. galbana was shown to occur at low external osmolarities, it is unlikely that sufficiently low osmolarities present in the hind gut of turbot larvae explained the observed rupture of algae. Other mechanisms for digestion are discussed. In newly hatched herring larvae, algal cells were unable to pass beyond the constriction in the mid-gut caused by the yolk sac. When algal cells were eventually seen to pass into the hind gut, there was no evidence of algal digestion or absorption throughout the remaining endotrophic and early exotrophic stages of herring larvae, although pinocytosis was observed to occur mid-way through the endotrophic stage.     

Vulnerability of late larval and early juvenile Atlantic herring, Clupea harengus, to predation by whiting,Merlangius merlangus

Laboratory experiments investigated changes in the vulnerability of herring to predation by whiting during growth from <34 to >80mm in length, Premetamorphic herring (<50mm) failed to react to c . 50% of attacks by the predator, but this was reduced to c . 20% in postmetamorphic fish. Premetamorphic herring failing to react had c. 30% probability of survival due to unforced errors by the predator (unsuccessful attacks that did not elicit a reaction by the prey), but these errors did not occur after herring metamorphosis. The loss of the advantage of lower conspicuousness following metamorphosis was counterbalanced by increased reactivity. Antipredator benefits should increase with schooling behaviour (first evident in experiments at c . 50 mm), so predation mortality should decrease in postmetamorphic herring in the sea. Metamorphosis itself would be associated with high predation risk since conspicuousness is enhanced but reactivity and schooling behaviour are still not fully developed.     

Heavy-metal toxicity in an insect cell line. Effects of cadmium chloride, mercuric chloride and methylmercuric chloride on cell viability and proliferation in Aedes albopictus cells

We evaluated the toxicity of CdCl2, HgCl2, and MeHgCl on the C6/36 cell line of Aedes albopictus. This cell line proved to be a suitable tool for studying heavy-metal toxicity in insect cells. Since data on heavy-metal toxicity in invertebrate cell cultures are almost nonexistent, our results are discussed in relation to in vivo invertebrate and in vitro vertebrate studies. Viability and proliferation were assessed by dye exclusion and DNA quantification, respectively. Viability tests were carried out with and without 5% fetal calf serum in the medium. The three metal species decreased viability to different extents (MeHgCl>HgCl2>CdCl2), and fetal calf serum had a protective effect. In serum-deprived cultures, LD50 values were 140.20, 2.51, and 2.08 µmol/L for CdCl2, HgCl2, and MeHgCl, respectively. For cultures with fetal calf serum, LD50 values were 149.71, 12.01, and 5.47 µmol/L, respectively. The viability curve for CdCl2 under serum-free conditions suggests the induction of a cell defense system. The three metal species also inhibited cell proliferation (MeHgCl> CdCl2> HgCl2). The IC50 values were 1.75, 18.36, and 0.96 µmol/L for CdCl2, HgCl2, and MeHgCl, respectively. In summary, low MeHgCl concentrations caused both cell death and inhibition of cell proliferation; HgCl2 primarily disrupted the plasma membrane, whereas CdCl2 primarily inhibited cell proliferation.     

Role of cyclooxygenase-2 in Trypanosoma cruzi survival in the early stages of parasite host-cell interaction

Chagas disease, caused by the intracellular protozoan Trypanosoma cruzi, is a serious health problem in Latin America. During this parasitic infection, the heart is one of the major organs affected. The pathogenesis of tissue remodelling, particularly regarding cardiomyocyte behaviour after parasite infection and the molecular mechanisms that occur immediately following parasite entry into host cells are not yet completely understood. When cells are infected with T. cruzi, they develop an inflammatory response, in which cyclooxygenase-2 (COX-2) catalyses rate-limiting steps in the arachidonic acid pathway. However, how the parasite interaction modulates COX-2 activity is poorly understood. In this study, the H9c2 cell line was used as our model and we investigated cellular and biochemical aspects during the initial 48 h of parasitic infection. Oscillatory activity of COX-2 was observed, which correlated with the control of the pro-inflammatory environment in infected cells. Interestingly, subcellular trafficking was also verified, correlated with the control of Cox-2 mRNA or the activated COX-2 protein in cells, which is directly connected with the assemble of stress granules structures. Our collective findings suggest that in the very early stage of the T. cruzi-host cell interaction, the parasite is able to modulate the cellular metabolism in order to survives.     

Removal of Listeria monocytogenes dual-species biofilms using combined enzyme-benzalkonium chloride treatments

The effects of pronase (PRN), cellulase (CEL) or DNaseI alone or combined with benzalkonium chloride (BAC) against Listeria monocytogenes-carrying biofilms were assayed. The best removal activity against L. monocytogenes–Escherichia coli biofilms was obtained using DNaseI followed by PRN and CEL. Subsequently, a modified logistic model was used to quantify the combined effects of PRN or DNaseI with BAC. A better BAC performance after PRN compared to DNaseI eradicating L. monocytogenes was observed. In E. coli the effects were the opposite. Finally, effects of DNaseI and DNaseI–BAC treatments were compared against two different L. monocytogenes-carrying biofilms. DNaseI–BAC was more effective against L. monocytogenes when co-cultured with E. coli. Nonetheless, comparing the removal effects after BAC addition, these were higher in mixed-biofilms with Pseudomonas fluorescens. However, a high number of released viable cells was observed after combined treatments. These results open new perspectives of enzymes as an anti-biofilm strategy for environmental pathogen control.     

The distribution of noradrenergic nerves and small,intensely fluorescent (SIF) cells in the cat urinary bladder

Summary Fluorescence and electron microscopy have been used to study the distribution of noradrenergic nerves in the smooth muscle of the cat urinary bladder. Using the former technique, relatively few fluorescent noradrenergic nerves were observed in the body and fundus, while a rich plexus occurred adjacent to muscle cells of the bladder neck. The trigone could not be distinguished neuromorphologically from detrusor muscle in this region. Electron microscopy showed that the majority of noradrenergic terminals in the body and fundus were associated with presumptive cholinergic axons, while in the bladder neck noradrenergic terminals formed typical neuroeffector relationships with individual smooth muscle cells.Numerous ganglia occurred both in the adventitia and among the smooth muscle bundles, particularly in the bladder neck. The majority of the nerve cell bodies were non-fluorescent, although many contained bright orange autofluorescent granules, believed to be lysosomes. A small minority of ganglion cells were associated with fluorescent noradrenergic nerve terminals, thereby providing structural evidence for limited intraganglionic inhibition. In addition, occasional groups of small intensely fluorescent (SIF) cells were observed in some intramural ganglia and these were subsequently identified in the electron microscope. The possibility that these cells may provide a second inhibitory influence on bladder activity was considered.     

Ultrastructure of fibre and parenchyma cell walls during early stages of culm development in Dendrocalamus asper

BACKGROUND AND AIMS: The anatomy of bamboo culms and the multilayered structure of fibre cell walls are known to be the main determinant factors for its physical and mechanical properties. Studies on the bamboo cell wall have focussed mainly on fully elongated and mature fibres. The main aim of this study was to describe the ultrastructure of primary and secondary cell walls in culm tissues of Dendrocalamus asper at different stages of development. METHODS: The development of fibre and parenchyma tissues was classified into four stages based on light microscopy observations made in tissues from juvenile plants. The stages were used as a basis for transmission electron microscopy study on the ultrastructure of the cell wall during the process of primary and early secondary cell wall formation. Macerations and phloroglucinol-HCl staining were employed to investigate fibre cell elongation and fibre cell wall lignification, respectively. KEY RESULTS: The observations indicated that the primary wall is formed by the deposition of two distinct layers during the elongation of the internode and that secondary wall synthesis may begin before the complete cessation of internode and fibre elongation. Elongation was followed by a maturation phase characterized by the deposition of multiple secondary wall layers, which varied in number according to the cell type, location in the culm tissue and stage of shoot development. Lignification of fibre cell walls started at the period prior to the cessation of internode elongation. CONCLUSIONS: The structure of the primary cell wall was comprised of two layers. The fibre secondary cell wall began to be laid down while the cells were still undergoing some elongation, suggesting that it may act to cause the slow-down and eventual cessation of cell elongation.     

The photosynthesis of individual algal cells during the cell cycle of Scenedesmus quadricauda studied by chlorophyll fluorescence kinetic microscopy

A microscope for imaging of chlorophyll fluorescence kinetics was equipped with a chamber that allows the growth of an immobilised population of algae and their study under well-defined conditions. Single cells of the chlorococcal alga Scenedesmus quadricauda were grown and recorded for periods of whole cell cycles (up to 48 h) displaying a normal course of cell development. Heterogeneity in fluorescence yield among individual coenobia in the population and among different cells in one coenobium were analysed. Differences were observed both in the shape of Kautsky transients and in the modulation of fluorescence parameter values during the progress of the cell cycle. The extent of heterogeneity in fluorescence parameters was cell cycle dependent – in some phases of the cycle, the population was almost homogeneous, while distinct heterogeneity was observed, in particular between the protoplast division and the release of the daughter coenobia. The heterogeneity was not random but reflected developmental processes.     

Localization of chloride conductance to mitochondria-rich cells in frog skin epithelium

Summary Cell volume determinations and electrophysiological measurements have been made in an attempt to determine if mitochondria-rich (MR) cells are localized pathways for conductive movements of Cl across frog skin epithelium. Determinations of cell volume with video microscope techniques during transepithelial passage of current showed that most MR cells swell when the tissue is voltage clamped to serosa-positive voltages. Voltage-induced cell swelling was eliminated when Cl was removed from the mucosal bath solution. Using a modified vibrating probe technique, it was possible to electrically localize a conductance specifically to some MR cells in some tissues. These data are evidence supporting the idea that MR cells are pathways for conductive movements of Cl through frog skin epithelium.     

Changes of cell size distribution during the batch culture of Arthrobacter strain PI/1-95

The size distributions of an arthrobacter, approximately 1 m in diameter, were analysed using a Coulter® Multisizer II instrument thereby making it possible to distinguish between the different stages in the morphological cycle. The results indicated that at the beginning of exponential phase a shift occurred from large to smaller cells, the cell size distributions in both categories were asymmetric, skewed towards higher values than the means. During the course of the batch culture the cells in the larger class decreased in size and the two classes coalesced. The size distribution of the smaller class exhibited an additional shift towards smaller cells. After which neither the number of classes nor the size distribution changed. It was concluded that the Coulter® Multisizer II instrument provides a feasible method to extract information not only about mean cell size but also about cell size distributions.     

Stress from air emersion fails to alter chloride cell numbers in the gills of rainbow trout

Air emersion stress caused an elevation in blood plasma cortisol of rainbow trout Oncorhynchus mykiss but this acute stressor did not elicit chloride cell proliferation in the gill tissue within 2 weeks following the disturbance.     

Efficient phloem remobilization of Zn protects apple trees during the early stages of Zn deficiency

Apple trees are extensively cultivated worldwide but are often affected by zinc (Zn) deficiency. Limited knowledge regarding Zn remobilization within fruit crops has hampered the development of efficient strategies for providing adequate amounts of Zn. In the present study, Zn distribution and remobilization were compared among apple trees cultivated under different Zn conditions. Without Zn application, plants showed visible symptoms of Zn deficiency at the shoot tips after 1 year but appeared to grow normally during the first 6 months (early stage of Zn deficiency). Compared with apple plants under sufficient Zn treatment, plants suffering from early‐stage Zn deficiency showed preferential Zn distribution to young leaves and higher Zn levels in phloem, demonstrating that hidden Zn deficiency triggers a highly efficient remobilization of Zn in this species. The in vivo Zn‐nicotianamine complex in phloem tissues, combined with the significant enhanced expression of MdNAS3 and MdYSL6, suggested a positive role for nicotianamine in the phloem remobilization of Zn. These results strongly suggest that a proportion of Zn in the old leaves of apple trees can be efficiently remobilized by phloem transport to the shoot tips, partially in the form of Zn‐nicotianamine, thus protecting apple trees against the early stages of Zn deficiency.     

氯化锂对兔骨髓间充质干细胞增殖影响

目的研究Wnt/β-catenin通路激活剂氯化锂（LiCl）对兔骨髓间充质干细胞（bone marrowmesen-chymal stem cells,BMSCs）增殖的影响。方法体外纯化培养兔BMSCs,流式细胞仪检测细胞表面抗体,以不同浓度的LiCl作用兔骨髓间充质干细胞24h后,采用Cell Counting Kit-8（CCK-8）检测各组细胞的增殖活性。结果低浓度LiCl促进兔BMSCs增殖,高浓度LiCl抑制兔BMSCs增殖。结论低浓度LiCl抑制GSK3β,模拟激活Wnt/β-catenin信号途径,从而促进细胞增殖,而高浓度LiCl增加了对细胞的毒性而抑制其增殖。     

Quantitaton of gastrin and somatostatin cell populations in the antral mucosa of the rat comparative distribution and evolution through different life stages

Summary Total antral gastrin and somatostatin cell populations as well as their relative distribution pattern throughout the antrum were studied in rats with advancing age from birth time to old age. Both endocrine cell populations were estimated, after staining by immunoperoxidase technique, with a quantitative method using serial parallel strips from entire stomachs. Gastrin cells were regularly found at less than 1 h of post-natal life, but were few in number (447±82 cells). Somatostatin cells, not seen at birth, were observed in all rats at seven post-natal days; then they increased in number less rapidly but more regularly than gastrin cells. During the normal adult period, corrected gastrin cell population corresponds to about 330,000–500,000 cells and corrected somatostatin cell populations to about 130,000–200,000 cells. For the whole antrum the ratio of gastrin cell to somatostatin cell populations decreases through the rat life from 6.5 at 7 days to 1.5 in old age with a stable value, 2.5, during adult period. Examination of the topographical distribution throughout the antrum of these two populations shows that, strip per strip, their numerical ratio varies. Homogeneous values for the latter occur in the middle part of antrum and, as a rule, in each group they reflect the mean value calculated for the whole of the antrum.     

Changes to chloride and rodlet cells in gills, kidney and intestine of Dicentrarchus labrax (L.) exposed to reduced salinities

The effect of osmotic shock was investigated mainly in the chloride cells (CCs) and rodlet cells (RCs) of gills, and RCs of intestine and kidney of the European sea bass Dicentrarchus labrax obtained from a farm in the northern Adriatic Sea. During the experiment, fish were abruptly transferred from sea water to a salinity of 15 (15 SW) or to fresh water (FW). Numeric variation and ultrastructural changes of both cell types were evaluated at 24, 48 and 96 h after the transfer to lower salinity levels, using light and transmission electron microscopy (TEM). Exposure to FW produced a significant increase ( P < 0·05) in the number of branchial CCs and RCs within 96 and 24 h, respectively. Following osmotic challenge (either transfer to 15 SW or FW), kidney and intestine showed an evident increase in RC numbers. The cellular damage detected by TEM was the same for each sampling time (24, 48 and 96 h), but appeared more severe in fish exposed to FW (higher osmotic shock) than in those exposed to 15 SW. In RCs cytoplasmic vacuolizations, autophagosomes and autophagolysosomes with myelinoid bodies, dissolution and shrinkage of the typical inclusions were documented. Nevertheless, CCs showed vacuolization of endoplasmic reticulum and cytoplasmic dissolution and maintained the apical crypt typical of seawater acclimated fish. Renal tubular cells and intestinal epithelial cells showed similar changes to those reported for CCs and RCs.