Comparative ultracytochemical study of the acrosome in four different Veneroida species from the Turkish coast.

Cytoplasmic acidic phosphoproteins and complex polysaccharides were stained with ammoniacal silver nitrate-formalin and phosphotungstic acid-chromic acid, respectively. In Cerastoderma glaucum (Cardiacea), acrosomal vesicle contents are differentiated into an apical intermediate-dense component and a basal dense region. PTA stained the apical component and silver stained the basal region and the apex of the acrosome. In Spisula subtruncata (Mactracea) the acrosome showed a PTA-stained apical component and a silver-positive basal dense region. In the Veneracea, Chamelea gallina and Pitar rudis show a tripartite acrosomal vesicle, with apical light, outer dense and inner intermediate-dense regions. In both species, the apical and inner components were stained by PTA, whereas silver stained all regions of the acrosomal vesicle in C. gallina and the apical and outer regions in P. rudis. In midpiece, only C. glaucum showed a positive silver reaction at the centriolar fossa.

Fine silver staining analysis of the nucleolar organizer regions during oogenesis in Penaeus kerathurus (Crustacea, Decapoda).

In previtellogenic oocytes, nucleoli showed segregated components, with the dense fibrillar component (DFC) appearing highly developed and presenting several fibrillar centers (FC). The granular component (GC) was less developed and formed a wide-spaced reticulum. Only the DFC appeared stained by silver, with higher intensities being found at its periphery. During early vitellogenesis, the nucleolar components were kept segregated but both the DFC and the GC enlarged, without evident changes being noticed in the silver staining pattern. In mid and late vitellogenesis, the nucleoli showed integrated components, with the DFC being intermeshed with the GC. Both nucleolar components were highly developed, no evident FC were noticed, and silver stained the DFC in a heterogeneous pattern. During cortical vesicle formation, the nuclear chromatin condensed and nucleoli appeared disintegrated, showing high levels of accelerated exportation of silver stained materials. Results suggest that the size of the DFC is kept high and the size of the GC kept low (low rDNA transcription levels and RNP exportation accelerated), in the segregated nucleoli of the previtellogenic oocyte, as the cell stores nuages but shows absence of rough endoplasmic reticulum and thus low protein svnthesis; that the size of the DFC and of the GC is increased in the segregated nucleoli of early vitellogenic oocytes (intermediate levels of rDNA transcription and of protein synthesis), which is in accordance with the appearance of the rough endoplasmic reticulum and of yolk vesicles formed with endogenous and exogenous sources; that during mid and late vitellogenesis the DFC and the GC appear highly developed and integrated (high levels of rDNA transcription and of protein synthesis) as the rough endoplasmic reticulum expands and the large yolk vesicles grow by endogenous synthesis; and that chromatin condense and nucleoli disintegrate (very low levels of rDNA transcription with accelerated RNP exportation) when cortical vesicles are formed.

Chromatin condensation during Scrobicularia plana spermiogenesis: a controlled and comparative enzymatic ultracytochemical study.

In Scrobicularia plana testis, a nuclear acid phosphatase (ACPase) activity was detected in mid and late spermatids with the improved Gomori-chloride procedure. Lead deposits were first observed in mid spermatids at focal points over condensed chromatin strands, increasing in density as chromatin further condensated. In late spermiogenesis, lead deposits became concentrated between chromatin aggregates, and after total DNA compaction were transfered to the nuclear periphery and then shed into the cytoplasm. The specificity of the nuclear ACPase was tested against different pH values (3.9, 7.2, 7.8, 9.0), substrates (TPP, IDP, TMP, p-NCS, ATP, GTP, AMP, ADP, AMP-PNP) and inhibitors (NaF, levamisole, Zn, vanadate, theophylline). To further specify the nature of this nuclear ACPase, other enzymes were comparatively studied at their optimal pH values and at pH 5.0: nucleoside-diphosphatase, thiamin-pyrophosphatase, inorganic trimetaphosphatase, lysosomal arylsulfatases A and B, ATPase, GTPase, 5'-nucleotidase, adenylate kinase, and adenylate cyclase. Several other controls were introduced to exclude artefactual deposits induced by lead ions and tissue molecules. The results showed that the enzyme has an optimal pH at 5.0, a high specific affinity for beta-GP, and is inhibited by NaF, which suggests that it behaves as a type B-ACPase, and all controls demonstrated the specificity of the enzymic activity. Because lead deposits were specifically and temporally associated with spermatid chromatin condensation, when DNA and RNA synthesis, histones, phosphoproteins and RNA molecules strongly decrease, it is possible to suggest that the nuclear ACPase could be associated with DNA processing during chromatin compaction or involved in the hydrolysis of 2' and 3' nucleotides resulting from nuclear RNase action during RNA degradation.

Ultrastructure of oogenesis in Penaeus kerathurus (Crustacea, Decapoda). I. Previtellogenic oocytes.

Although Malacostracan species represent an important alimentary human resource, the ultrastructure of oogenesis in P. kerathurus remains unknown. Previtellogenic oocytes of Penaeus kerathurus possess a large nucleus with several peripheral nucleoli. The endoplasmic reticulum (ER) is originated from expansions of the nuclear envelope (NE) and contains small dense granules, which are first formed inside the intermembranous space of the NE but are later exported to the ER lumen. Direct vesiculation from the NE and ER then give rise to the Golgi complexes. Small yolk vesicles appear to be mainly formed by vesiculation of the ER, but also receive materials from the Golgi complexes. They contain a fine fibrillar content which seems to originate from decondensation of the small dense granules. Small vesicles and small multivesicular bodies originated from the NE, ER and Golgi complexes, as also myelin figures directly shedded from the NE, fuse together to give origin to large multivesticular bodies (MVB). These organelles, which have an incomplete membrane and appear meshed within nuage materials, give origin, at a later stage, to lipid droplets that are thereafter extruded into the cytoplasm. Neighbouring oocytes exhibit intercellular bridges, the remaining of their surface being surrounded by a single layer of flattened follicular cells. These results show for the first time in Malacostraca the existence of oocyte intercellular bridges, that the ER and Golgi complexes arise from NE activity, that early yolk formation is endogenous and derives from the activity of the NE, ER and Golgi complexes, and that lipid droplets are products of intracellular membrane recycling activity occurring within large multivesicular bodies.

Flow Cytometric Analysis of Molt-Related Changes in Hemocyte Type in Male and Female Penaeus japonicus.

Hemocyte cell suspensions obtained from male and female Penaeus japonicus were individually analyzed by flow cytometry through forward and side light-scatter parameters. The hemocyte cell suspensions were further characterized after cell sorting. This type of cell analysis has several advantages over microscopy techniques. After staining with phenoloxidase and peroxidase, the hemocytes were classified into the three classic categories of hyaline, semigranular, and granular cells. Significant cyclic differences were detected among the molting stages in both sexes. The hyaline cell population was predominant before and soon after the molt, decreasing over the intermolt. This decrease was, however, more prolonged in females. Thus, the hyaline cell population was dominant in stages B, D0, and D1 in males and only in stages B and D1 in females. Semigranular cells became predominant in females during the D0 stage.

Comparison of percutaneous and surgical placement of central venous catheters in neonates.

A comparison of randomized placement of percutaneous and surgical central venous catheters was made in 53 low birthweight infants. Twenty-eight infants received percutaneous central venous lines, and 21 infants underwent surgical placement of catheters. The incidence of complications did not differ between the groups. The mean length of time the catheter was in place also was similar. Percutaneous placement of central venous catheters appears to compare favorably with the traditional surgical approach.

Ecdysteroids in the shrimp Palaemon serratus: relations with molt cycle.

Ecdysteroids were studied during the molt cycle of the shrimp Palaemon serratus using radioimmunoassay and HPLC. Continuous presence of ecdysteroids was observed in whole extracts, with two hormonal peaks: a minor peak during stage B and a major one during stage D2. The ecdysteroid titers were generally higher in females than in males. The ecdysteroid peak at stage B was more pronounced in the integument (cuticle and epidermis) than in other tissues and, at this time, 20-hydroxyecdysone was the predominant form. The observed 20-hydroxyecdysone peaks in stages B and D2 are correlatable to the previously reported rise in integumental carbonic anhydrase activity.