A comparison of sperm morphology and silver nitrate staining characteristics in the domestic ferret and the black-footed ferret

Ejaculated sperm from the domestic ferret (Mustela putorius furo) and the black-footed ferret (Mustela nigripes) were compared for differences in morphological abnormalities and argentophilic protein distribution. Thawed domestic ferret sperm was also compared to fresh sperm to determine whether there were any effects on cell morphology due to cryopreservation. There were statistically significant differences between the two species of ferret in two of the categories scored. The domestic ferret had a higher frequency of cells that were bent in the midpiece and in the principal piece, and a higher frequency of headless and tailless cells when compared to the black-footed ferret. There were no statistically significant differences in cell morphology between the fresh and cryopreserved ejaculates of the domestic ferret employing a standard egg yolk cryoextender. Silver nitrate staining distribution was different between the two species in both the head and tail region.     

Stratigraphic analysis of a fossil Neogoniolithon-capped patch reef and associated facies,San Salvador,Bahamas

An unusual Pleistocene patch reef is exposed in a coastal cliff at Grotto Beach, San Salvador, Bahamas. The reef is a coralline framestone constructed mainly by Porites astreoides together with a few large heads of Diploria strigosa and Montastrea annularis, and is capped by a dense thicket of Neogoniolithon strictum that is interpreted as marking the subtidal/intertidal boundary. The reef is flanked to the northeast by laminated to low-angle cross-laminated intraclastic grainstones and to the southwest by skeletal rudstone of reefal and interreefal derivation. Uranium-series dating of pure aragonite from a Diploria corallum yielded an age of 123 000±9000 years. Reef growth began on an erosional surface underlain by steeply crossbedded eolian grainstone. As the reef grew upward, it also grew laterally over adjacent penecontemporaneous subtidal sediments. The reef was eventually buried by 2.3 m of shallow subtidal and beach sediments that apparently prograded seaward during a highstand, or possibly while sea level was still rising. The shallow subtidal sediments are mainly peloidal, ooidal and skeletal grainstones that are pervasively bioturbated. The overlying beach facies comprises predominantly laminated, sparsely burrowed grainstone. The beach and shallow subtidal facies contain boulders of fine-grained laminated grainstone that are interpreted as storm-tossed blocks of beachrock. Living analogs of the Grotto Beach fossil reef lie off East Beach, San Salvador. Several of these have a flourishing cap of Neogoniolithon that extends above low-tide level and we believe that the Neogoniolithon cap of Grotto Beach reef did likewise. Wherever found in the stratigraphic record this facies should serve to identify the subtidal/intertidal boundary. The uppermost Pleistocene beach sediments associated with Grotto Beach fossil reef lie 5.8 m above present-day mean sea level, which ist strong evidence that this portion of San Salvador has undergone little subsidence since the Grotto Beach section was deposited.     

Structural and functional analysis of a bacterial cellulase by proteolysis

CenA is an endo-beta 1,4-glucanase from the cellulolytic bacterium Cellulomonas fimi. It is a bifunctional enzyme comprising an amino-terminal cellulose-binding domain and a carboxyl-terminal catalytic domain joined by a short sequence of prolyl and threonyl residues (the Pro-Thr box). Additional structural and functional information was revealed by a detailed analysis of the products generated by proteolytic cleavage of a nonglycosylated form of CenA. An extracellular C. fimi protease attacked nonglycosylated CenA at the junctions between the Pro-Thr box and the two functional domains. A stable "core" peptide (p30), corresponding to the catalytic domain, remained after extensive proteolysis. p30 was resistant to further attack even in the presence of 2-mercaptoethanol plus urea or dithiothreitol, but treatment in the presence of sodium dodecyl sulfate allowed complete fragmentation to small peptides. Stable peptides, identical, or closely related to p30, were generated by alpha-chymotrypsin or papain. These results indicated that the catalytic domain adopts a tightly folded conformation affording protection from proteolytic attack. In contrast, the cellulose-binding domain showed a relatively loose conformation. Progressive proteolytic truncation from the amino terminus was apparent during incubation with alpha-chymotrypsin or papain, or with C. fimi protease under reducing conditions. Affinity for cellulose was retained by products missing up to 64 amino-terminal amino acids. The remaining carboxyl-proximal region of the cellulose-binding domain with affinity (47 amino acids) contained sequences highly conserved in analogous domains from other bacterial endo-beta 1,4-glucanases. By analogy with other systems, the properties of the Pro-Thr box are consistent with an elongated conformation. The results of this investigation suggest that CenA has a tertiary structure which resembles that of certain fungal cellulases.     

Mitotic Golgi fragments in HeLa cells and their role in the reassembly pathway

Immunoelectron microscopy and stereology were used to identify and quantitate Golgi fragments in metaphase HeLa cells and to study Golgi reassembly during telophase. On ultrathin frozen sections of metaphase cells, labeling for the Golgi marker protein, galactosyltransferase, was found over multivesicular Golgi clusters and free vesicles that were found mainly in the mitotic spindle region. The density of Golgi cluster membrane varied from cell to cell and was inversely related to the density of free vesicles in the spindle. There were thousands of free Golgi vesicles and they comprised a significant proportion of the total Golgi membrane. During telophase, the distribution of galactosyltransferase labeling shifted from free Golgi vesicles towards Golgi clusters and the population of free vesicles was depleted. The number of clusters was no more than in metaphase cells so the observed fourfold increase in membrane surface meant that individual clusters had increased in size. More than half of these had cisterna(e) and were located next to "buds" on the endoplasmic reticulum. Early in G1 the number of clusters dropped as they congregated in the juxtanuclear region and fused. These results show that fragmentation of the Golgi apparatus yields Golgi clusters and free vesicles and reassembly from these fragments is at least a two-step process: (a) growth of a limited number of dispersed clusters by accretion and fusion of vesicles to form cisternal clusters next to membranous "buds" on the endoplasmic reticulum; (b) congregation and fusion to form the interphase Golgi stack in the juxtanuclear region.     

Effect of recombinant murine tumor necrosis factor on hemopoietic reconstitution in sublethally irradiated mice

Intravenous bolus administration of a single 2-micrograms dose of murine rTNF-alpha to BALB/c mice 20 h before sublethal total-body irradiation (7.5 Gy) conferred significant protection against radiation-induced leukopenia. Murine rTNF-alpha administration not only reduced the decline of neutrophil and total blood cell counts after radiation, but also accelerated the subsequent normalization of peripheral blood cell counts. This was accompanied by accelerated regeneration of primitive hematopoietic progenitors, as determined by the in vivo spleen CFU assay, and the in vitro assay of the more mature hematopoietic cell compartment. This demonstrates that pretreatment with murine rTNF-alpha enhances hematopoietic reconstitution after sublethal irradiation, and indicates a possible therapeutic potential for this agent in the treatment of radiation-induced myelo-suppression.     

Mechanisms of amoeboid chemotaxis: an evaluation of the cortical expansion model

In this work we evaluate the cortical expansion model for amoeboid chemotaxis with regard to new information about molecular events in the cytoskeleton following chemotactic stimulation of Dictyostelium amoebae. A rapid upshift in the concentration of chemoattractant can be used to synchronize the motile behavior of a large population of cells. This synchrony presents an opportunity to study the biochemical basis of morphological changes such as pseudopod extension that are required for amoeboid chemotaxis. Changes in the composition and activity of the cytoskeleton following stimulation can be measured with precision and correlated with important morphological changes. Such studies demonstrate that activation of actin nucleation is one of the first and most crucial events in the actin cytoskeleton following stimulation. This activation is followed by incorporation of specific actin cross-linking proteins into the cytoskeleton, which are implicated in the extension of pseudopods and filopods. These results, as well as those from studies with mutants deficient in myosin, indicate that cortical expansion, driven by focal actin polymerization, cross-linking and gel osmotic swelling, is an important force for pseudopod extension. It is concluded that whereas three forces, frontal sliding, tail contraction, and cortical expansion may cooperate to produce amoeboid movement, the cortical expansion model offers the simplest explanation of how focal stimulation with a chemoattractant causes polarized pseudopod extension.     

Cold responses of Arabidopsis mutants impaired in freezing tolerance

Mutants of Arabidopsis thaliana L. (Heynh), characterized asdeficient in their freezing tolerance after cold acclimation,were surveyed for some of the normal responses to cold exposure.In foliar tissue, the coldinducibility of three proteins, thelevels of sucrose and glucose, the fatty acyl composition oflipids, and the accumulation of anthocyanin was examined. Fourmutations (sfr3, sfr4, sfr6, and sfr7) reduced or eliminatedthe accumulation of anthocyanin during cold acclimation. Onemutation (sfr4) prevented the normally cold-induced elevationof sucrose and glucose levels; both sfr4 and another mutation(sfr7) affected fatty acid composition after (and only after)cold acclimation. On the other hand mutations sfr1, sfr2 andsfr5 did not differ significantly from the wild type in anyof the parameters tested, suggesting that they have other, perhapshighly specific, effects on lowtemperature responses. Key words: Arabidopsis thaliana, cold acclimation, freezing tolerance, mutation     

Redescription of Vorticella oceanica Zacharias, 1906 (Ciliophora: Peritrichia) with notes on its host, the marine planktonic diatom Chaetoceros coarctatum Lauder,1864

The late-spring quantitative relationship between epiphyton and macroinvertebrates was analyzed on the basis of units of colonizable plant surface of Typha angustifolia, Phragmites australis and Nuphar lutea (floating leaves) in the shallow euthrophic Lake Loosdrecht (the Netherlands), with a high seston load. The non-predatory chironomid larvae (Glyptotendipes viridis, Endochironomus albipennis, Pentapedilum sordens, Cricotopus sylvestris agg.) dominated among the macroinvertebrate taxa, controlling the diversity and resemblance of macroinvertebrate assemblages. There was a gradient in functional feeding groups among the chironomids from continuous filtering of the seston to prevailing utilization of epiphyton. We found no direct relationship between the total macroinvertebrate abundance and the epiphyton mass on the plants surface. We attribute this to the filter feeding-strategy of the most abundant species, Glyptotendipes viridis, that utilizes seston in the eutrophicated lake.     

Cloning of a cryV-type insecticidal protein gene from Bacillus thuringiensis: the cryV-encoded protein is expressed early in stationary phase.

A CryV-type protein (CGCryV) has been isolated from supernatant fluids of Bacillus thuringiensis AB88 cultures. Previous reports have suggested the cryptic nature of the cryV-type genes on the basis of the absence of CryV-type proteins in parasporal crystals. The CryV-type protein reported here is expressed early in stationary phase, and evidence indicates that it is an exported protein. Analysis of the deduced protein sequence from this gene reveals the presence of an N-terminal domain that likely acts as a signal peptide. The CGCryV protein is the first reported case of a delta-endotoxin being a secreted protein, which may influence the biological relevance of these proteins.     

Embryonic survival in the uterus of ewes inseminated at the uterotubal junction on Day 32 post partum

Experiments were conducted to determine 1) if pregnancy initiated on Day 32 post partum would be maintained until lambing, 2) if there is a difference in the ability of the previously gravid or nongravid uterine horn to maintain pregnancy, and 3) if season has an effect on embryo loss. Estrus was induced in ewes on Day 32 post partum. At estrus, ewes were inseminated surgically at the uterotubal junction and assigned to the following groups: 1) inseminated at estrus and laparotomized on Day 3 to collect embryos for determination of fertilization rate (C), 2) inseminated in the previously gravid uterine horn (PG), 3) inseminated in the previously nongravid uterine horn (NG), and 4) inseminated when both horns were previously gravid (BG). Ewes pregnant in the PG, NG and BG groups were allowed to lamb. Conception rate in Group C at embryo collection was 70%. Embryo loss, based on concentrations of progesterone at Day 18 post insemination, was 43, 19 and 18% in the BG, NG and PG group, respectively. The high embryo loss in Group BG occurred only during the breeding season. Only 24% of the ewes that had been inseminated lambed. This was due to the prepartum loss of embryos and fetuses (47, 48 and 33% in Group BG, NG and PG, respectively. In conclusion, the detrimental effects of the uterus on embryo survival was evident within 18 d post insemination in Group BG (breeding season), and embryo loss prior to lambing was high in all the treatment groups (both seasons).