Sexual differentiation,gonad development,and spawning seasonality of the Hawaiian butterflyfish,Chaetodon multicinctus

Synopsis The reproductive biology of the coral reef butterflyfish,Chaetodon multicinctus, was investigated by histological examination of gonads sampled over an 18 month period from a shallow inshore population on Oahu, Hawaii. Most gonads developed directly from previously undifferentiated tissue. Ovarian development (the structural formation of lamellae and primary oocytes) was observed in fish ≥44 mm and testicular development (the formation of spermatogenic crypts) in fish ≥62 mm standard length (SL). In addition, testis formation was identified within the ovarian lamellae of several differentiated but immature fish. It is hypothesized that prematurational sex change may facilitate monogamy within the highly competitive social structure of this site attached species. Oocyte development in mature females was marked by distinct phases of primary growth, the formation of yolk vesicles, and vitellogenesis. Spawning activity was histologically identified by the maturation and hydration of fully yolked oocytes, and presence of postovulatory follicles. Recently spawned females from field collections and experimental gonadotropin-treatments exhibited postovulatory follicles that were estimated to persist at least 24 h after ovulation. Atresia of yolked oocytes was classified into four stages of cell degeneration and resorption. Monthly analyses of oocyte development and atresia within the sample population show thatC. multicinctus has a protracted annual spawning season with a major peak during the early spring and evidence of spawning activity among some individuals in the fall. Histological analyses of spawning activity provide more accurate and unambiguous information than do traditional gonadosomatic assays in this and probably other coral reef fishes.     

Polymorphisms in human H chain V region genes from the VHIII gene family

Polymorphisms of the Ig H chain V region (VH) genes were examined with probes from the coding and flanking regions of a gene from the largest VH gene family, VHIII. The 5'-flanking probe gave the simplest pattern and revealed the largest number of polymorphic fragments. Analysis of unrelated individuals and of families identified five polymorphic loci. Two alleles were detected for each of two of the loci, whereas a polymorphic band was scored as present or absent for the other three loci. The polymorphic fragments segregated in the expected Mendelian fashion and parental haplotypes could be assigned in all cases. Comparison of the patterns obtained with the flanking and coding region probes suggests that the human VHIII gene family is highly polymorphic and may contain several hundred V genes. This method, as well as the polymorphism detected, can be used to investigate the organization and germ-line variation of H chain V genes and their inheritance in normal individuals and in individuals with immunologic disorders.     

Aneuploidy induction in human fibroblasts: comparison with results in Syrian hamster fibroblasts

The susceptibility of human fibroblast cells in culture to neoplastic transformation by chemical carcinogens is appreciably lower than that of rodent fibroblasts. We have proposed that a key step in the neoplastic progression of Syrian hamster embryo fibroblasts is the induction of aneuploidy by carcinogens. It is possible that the different sensitivity to neoplastic transformation of Syrian hamster versus human cells is due to a difference in genetic stability following treatment with chemicals inducing aneuploidy. Therefore, we measured the induction of numerical chromosome changes in normal human fibroblasts and Syrian hamster fibroblasts by 4 specific aneuploidogens. Dose- and time-dependent studies were performed. Nondisjunction, resulting in aneuploid cells with a near-diploid chromosome number, in up to 14-28% of the hamster cells was induced by colcemid (0.1 microgram/ml), vincristine (30 ng/ml), diethylstilbestrol (DES) (1 microgram/ml) or 17 beta-estradiol (10 micrograms/ml). In contrast, human cells displayed far fewer aneuploid (near-diploid) cells, i.e., 8% following treatment with colcemid (0.02 micrograms/ml) or vincristine (10 ng/ml) and only 3% following treatment with DES (6 micrograms/ml) or 17 beta-estradiol (20 micrograms/ml). The doses at which the maximum effect was observed are given. Treatment of human cells induced a higher incidence of cells with a near-tetraploid chromosome number, which was similar to the level observed in treated hamster cells except at the highest doses. These results indicate that human cells respond differently from hamster cells to agents that induce aneuploidy. In particular, nondisjunction yielding aneuploid human fibroblasts with a near-diploid chromosome number was less frequent. The magnitude of the observed species differences varied with different chemicals. The difference in aneuploidy induction may contribute, in part, to species differences in susceptibility of fibroblasts to neoplastic transformation.     

The outcome of poliovirus infections in K562 cells is cytolytic rather than persistent after hemin-induced differentiation.

K562-Mu erythroleukemia cells readily establish a long-term persistent poliovirus infection characterized by continuous virus production in the absence of complete p220 cleavage and host translation shutoff (R. E. Lloyd and M. Bovee, Virology 194:200-209, 1993). The mechanism of resistance appears to be modulated at the intracellular level and to be related to decreased virus-mediated cytopathic effects (P. A. Benton, J. W. Murphy, and R. E. Lloyd Virology 213:7-18, 1995). It is well documented that hemin induces the differentiation of K562 cells and alters the expression of several host proteins. We report here that growth of K562 cells in hemin prior to poliovirus infection results in a dose-dependent increase in virus-induced cell lysis and thereby alters the normally persistent outcome of infection to a more lytic phenotype. K562 cells infected after hemin treatment displayed increased host translation shutoff, p220 cleavage, viral protein synthesis, and viral RNA accumulation compared with nontreated cells. Since hemin treatment of K562 cells also induced the increased expression of several heat shock proteins (Hsp70, Hsc70, Hsp90, and cohort p60), we tested the hypothesis that their increased expression may play a role in altering poliovirus infection in hemin-treated K562 cells. However, neither heat stress nor oxidative stress, inducers of heat shock protein synthesis, altered the outcome (of virus infections. In addition, we report the novel finding that subunits of two translation initiation factors, p220 (eIF-4G) and eIF-2alpha, are cleaved as a result of hemin treatment of K562 cells. It is proposed that hemin alters the expression of specific host proteins in K562 cells, probably other than heat shock proteins, which changes the initial response to poliovirus infections from persistent to lytic.     

Ecology and evolution of plant mating

Plants exhibit complex mating patterns because of their immobility, hermaphroditism and reliance on vectors for pollen transfer. Research on plant mating attempts to determine who mates with whom in plant populations and how and why mating patterns become evolutionarily modified. Most theoretical models of mating-system evolution have focused on the fitness consequences of selling and outcrossing, stimulating considerable empirical work on the ecology and genetics of inbreeding depression. Less attention has been given to how the mechanics of pollen dispersal influence the transmission of self and outcross gametes. Recent work on the relation between pollen dispersal and mating suggests that many features of floral design traditionally interpreted as anti-selling mechanisms may function to reduce the mating costs associated with large floral displays.     

Effect of abscisic acid, osmolarity and partial desiccation on the development of recalcitrant mango somatic embryos

Inhibition of mango somatic embryo growth was inducedin vitro by treatments for 4 or more weeks with abscisic acid (0–100 M ABA) with and without high osmolarity provided by mannitol (0–10%). High osmolarity and ABA significantly affected somatic embryo length, precocious germination and the production of good quality secondary somatic embryos. High osmolarity also affected root elongation. Abscisic acid was more effective in suppressing growth and development of 0.5 cm-length somatic embryos than smaller somatic embryos. Development beyond the heart stage was significantly inhibited by both ABA and mannitol treatments. The recovery of good quality somatic embryos was enhanced by high levels of ABA (100 M) with and without mannitol (0–5%). Somatic embryos that had been pulsed with ABA were partially desiccated at different relative humidities. Weight loss was affected only by relative humidity; and ABA did not enhance desiccation tolerance.Abbreviations ABA Abscisic acid - 2,4-D 2,4-Dichlorophenoxyacetic acid - MM1 Mango maturation medium - RH Relative humidity     

Construction and characterization of recA mutant strains of Corynebacterium glutamicum and Brevibacterium lactofermentum

An internal fragment of the Corynebacterium glutamicum recA gene was amplified by the polymerase chain reaction (PCR) using degenerate primers corresponding to two short sequences that are well conserved homology with RecA sequences from other bacteria including the invariant and functionally conserved amino acids Leu-126, Asp-144, Gly-157, Arg-169 and Asn-193. Highest identity (91%) was shared with the gram-positive Mycobacterium tuberculosis RecA sequence. The amplified fragment was cloned into a conditional suicide vector, pBGS8, and used to generate recA deficient strains of C. glutamicum and Brevibacterium lactofermentum by insertional inactivation. These strains exhibited classical RecA phenotypes including reduced recombinational activity and increased sensitivity to DNA-damaging agents such as UV irradiation, mitomycin C and methyl-methanesulphonate.