Preendocytotic alterations in cumulus cell gap junctions precede meiotic resumption in the rat cumulus-oocyte complex

Cumulus cells in the mammalian ovary are normally connected to each other and to their enclosed oocyte by an extensive network of gap junctions (GJs). We have shown that the loss of cumulus cell GJs is correlated temporally with meiotic resumption in the intact preovulatory rat follicle (Larsen et al., 1986). Here we describe morphological changes in GJ particle packing patterns (PPPs) that occur prior to GJ loss and meiotic resumption in hormonally stimulated rat cumulus-oocyte complexes (COCs). In the PMSG-primed rat, 89% of the cumulus cell GJ area detected by freeze-fracture electron microscopy consists of tightly packed junctional particles: 4% exhibit loose PPPs of randomly dispersed particles; and 7% contain a mixture of both tight and loose PPPs. One to 2 hr after stimulation with hCG, the area of GJs containing tight PPPs drops by 50%-60%, while junctions exhibiting loosely organized and mixed patterns increase concomitantly. These shifts in PPPs are accompanied by the appearance of unusual particle-free areas of puckered or ruffled nonjunctional membrane at the GJ periphery. Cumulus cell GJs from isolated COCs incubated in FSH-containing medium demonstrate a similar shift in PPPs prior to meiotic resumption. The appearance of fusing areas of particle-free nonjunctional membrane at the GJ periphery in vitro is correlated with GJ loss and is not seen in COCs treated with dihydrocytochalasin B to inhibit endocytotic removal of cumulus GJs. The structural and temporal nature of these morphological observations supports the hypothesis that interruption of junctional communication plays a role in meiotic maturation of the preovulatory oocyte.     

Bull influences on conception percentage and calving date in Angus Hereford, Brahman and Senepol single-sire herds

Bull breeding soundness parameters, semen characteristics and sexual behavior were evaluated for effects on reproductive performance in single-sire beef herds. A total of 155 cow herds (Angus, 50 herds; Hereford, 40 herds; Brahman, 46 herds; and Senepol, 19 herds) bred to bulls of the same breed were observed for 8 yr. All bulls produced adequate quality semen and had scrotal circumference (SC) >/= 30 cm. Reproductive performance was evaluated by the conception rate (CON), conception rate during the first 21 d of the breeding season (21dCON), mean calving date (MCD), and mean calving date of the first half of the herd to calve (HHCD). Correlations were determined between breeding soundness parameters and reproductive performance for all bulls combined, by breed, and by age. The Cp statistic was used to select models for the effects of parameters on CON, 21dCON, MCD and HHCD. Breeding season length and breed had significant effects. The percentages of normal cells, proximal droplets, detached heads and the semen score (motility plus percentage of normal cells) had a significant effect on CON when all bulls were considered. After the effect of season was deleted, the most significant parameter affecting CON in the Brahman was the percentage of detached sperm heads. In the Angus, motility was significantly correlated with all reproductive performance indices. In the Hereford, breeding soundness examination score (BSE) was positively correlated with 21dCON.     

Toward Practical Biological Control of Parasitic Nematodes in Domestic Animals

In a series of laboratory and field experiments where the nematophagous fungus Arthrobotrys oligospora was mixed directly with feces it has been demonstrated that it is possible to use nematophagous fungi for biological control of animal parasitic nematodes. A procedure used for selection of nematophagous fungi that can pass the digestive tract of ruminants, horses, and pigs is described. The selected fungus, Duddingtonia flagrans, has been used in further field experiments, and the results have confirmed that by the addition of D. flagrans to feed supplement it is possible to reduce the parasitic burden significantly.     

Comparison of a commercial biochemical kit and an oligonucleotide probe for identification of environmental isolates of Vibrio vulnificus

A. DALSGAARD, I. DALSGAARD, L. HØI AND J.L. LARSEN. 1996. Methods for the identification and isolation of environmental isolates of Vibrio vulnificus were evaluated. Alkaline peptone water supplemented with polymyxin B and colistin-polymyxin B-cellobiose agar were employed for the isolation of suspected V. vulnificus from water, sediment and shellfish samples. When comparing the identification of putative V. vulnificus obtained with the API 20E assay and an oligonucleotide probe, 29 API 20E profiles were obtained with only four profiles (representing 20 isolates) reaching the identification threshold of V. vulnificus among a total of 66 isolates hybridizing with the probe. The results indicated that, compared with colony hybridization, the API 20E assay was not adequate for the identification of environmental isolates of V. vulnificus .     

Arabidopsis mutants with increased sensitivity to aluminum.

Al-sensitive (als) mutants of Arabidopsis were isolated and characterized with the aim of defining mechanisms of Al toxicity and resistance. Most als mutants selected on the basis of root growth sensitivity to Al were recessive, and together the mutants constituted eight complementation groups. Also, in most als mutants, Al sensitivity appeared to be specific for Al relative to La (another trivalent cation), except als2, which was more sensitive to La than wild type. The tendency of roots on mutant seedlings to accumulate Al was examined by staining with morin and hematoxylin, dyes used to indicate the presence of Al. A significant increase in morin staining was observed in als5, consistent with its increased sensitivity to Al. Unexpectedly, als7 and als4 showed less morin staining, suggesting that the roots on these mutants accumulate less Al than wild type seedlings after exposure to Al-containing solutions. Roots of wild-type seedlings produce callose in response to AlCl3 concentrations that inhibit root growth. Only als5 accumulated more callose than wild type in response to low levels (25 mu M) of AICI3 However, als4 and als7 did not accumulate callose at this AlCl3 concentration even though root growth was significantly inhibited. The lack of callose accumulation in als4 and als7 suggests that there is not an obligatory relationship between callose deposition and Al-induced inhibition of root growth.     

The Ribosomal Database Project (RDP).

The Ribosomal Database Project (RDP) is a curated database that offers ribosome-related data, analysis services and associated computer programs. The offerings include phylogenetically ordered alignments of ribosomal RNA (rRNA) sequences, derived phylogenetic trees, rRNA secondary structure diagrams and various software for handling, analyzing and displaying alignments and trees. The data are available via anonymous ftp (rdp.life.uiuc.edu), electronic mail (server@rdp.life.uiuc.edu), gopher (rdpgopher.life.uiuc.edu) and World Wide Web (WWW)(http://rdpwww.life.uiuc.edu/). The electronic mail and WWW servers provide ribosomal probe checking, screening for possible chimeric rRNA sequences, automated alignment and approximate phylogenetic placement of user-submitted sequences on an existing phylogenetic tree.     

Spectroscopic and molecular modeling studies of caffeine complexes with DNA intercalators.

Recent studies have demonstrated that caffeine can act as an antimutagen and inhibit the cytoxic and/or cytostatic effects of some DNA intercalating agents. It has been suggested that this inhibitory effect may be due to complexation of the DNA intercalator with caffeine. In this study we employ optical absorption, fluorescence, and molecular modeling techniques to probe specific interactions between caffeine and various DNA intercalators. Optical absorption and steady-state fluorescence data demonstrate complexation between caffeine and the planar DNA intercalator acridine orange. The association constant of this complex is determined to be 258.4 +/- 5.1 M-1. In contrast, solutions containing caffeine and the nonplanar DNA intercalator ethidium bromide show optical shifts and steady-state fluorescence spectra indicative of a weaker complex with an association constant of 84.5 +/- 3.5 M-1. Time-resolved fluorescence data indicate that complex formation between caffeine and acridine orange or ethidium bromide results in singlet-state lifetime increases consistent with the observed increase in the steady-state fluorescence yield. In addition, dynamic polarization data indicate that these complexes form with a 1:1 stoichiometry. Molecular modeling studies are also included to examine structural factors that may influence complexation.     

The signal recognition particle database (SRPDB).

The SRPDB (signal recognition particle database) provides aligned SRP RNA and protein sequences, annotated and phylogenetically ordered. This release includes 82 SRP RNAs (including 22 bacterial and 9 archaeal homologs) and a total of 20 protein sequences representing SRP9, SRP14, SRP19, SRP54, SRP68, and SRP72. The offerings also include representative RNA secondary structure diagrams.