In vivo replication of the hamster polyomavirus genome and generation of specific deletions in the process of lymphomagenesis.

Hamster polyomavirus (HaPV) causes lymphomas when injected into newborn hamsters. These tumors are virus-free but accumulate large amounts of deleted extrachromosomal viral genomes. In order to identify the major sites of virus replication in animals, we have monitored the HaPV DNA present in different organs at various times after injection. The data demonstrate that viral replication preferentially occurs in lymphoid organs. Lymphoma-associated viral genomes display specific deletions. PCR analysis shows that such viral genomes are the only variants detectable in infected animals, suggesting that they are generated by a specific cellular mechanism. We have tested the possible role of the lymphoid cell-specific V(D)J recombination activity in the generation of these specific variants. Our results indicate that this mechanism is not solely responsible for the viral genome rearrangement, if involved at all.     

Germline and somatic mosaicism in a female carrier of Duchenne muscular dystrophy

The family of a male with Duchenne muscular dystrophy (DMD) and a deletion within the dystrophin gene has been studied. Polymerase chain reaction analysis of ectopic mRNA from peripheral blood T+B lymphocytes and the use of (CA) _n repeat polymorphisms in and around the deleted region showed the proband's mother to be both a germline mosaic and a somatic mosaic for the deletion seen in her son. The mutation therefore occurred as a mitotic event early in embryogenesis.     

Linkage analysis of schizophrenia with five dopamine receptor genes in nine pedigrees

Alterations in dopamine neurotransmission have been strongly implicated in the pathogenesis of schizophrenia for nearly 2 decades. Recently, the genes for five dopamine receptors have been cloned and characterized, and genetic and physical map information has become available. Using these five loci as candidate genes, we have tested for genetic linkage to schizophrenia in nine multigenerational families which include multiple affected individuals. In addition to testing conservative disease models, we have used a neurophysiological indicator variable, the P50 auditory evoked response. Deficits in gating of the P50 response have been shown to segregate with schizophrenia in this sample and may identify carriers of gene(s) predisposing for schizophrenia. Linkage results were consistently negative, indicating that a defect at any of the actual receptor sites is unlikely to be a major contributor to schizophrenia in the nine families studied.     

Reproductive activity of ruffed lemurs (Varecia variegata variegata) in a Madagascar rain forest

Mating activity was observed during four breeding seasons in two groups of black and white ruffed lemurs (Varecia variegata variegata) living in lowland rain forest on Nosy Mangabe island, Madagascar. The onset of the May-July breeding season was signalled by behavioral changes in adult males. Males made forays outside their usual home ranges, were more aggressive to other males, and performed appetitive and other sex-specific behaviors more frequently. Females showed receptive and proceptive behaviors during a 1-2 day behavioral estrus. Ruffed lemurs mated monogamously, polyandrously, and polygynously. These observations do not support previous assertions that they live only in monogamous families. Limited evidence suggests females exercised mate choice and may have preferred familiar males. © 1993 Wiley-Liss, Inc.     

Impact of Holoshestes heterodon Eigenmann (Pisces: Characidae) on the plankton community of a subtropical reservoir: the importance of predation by Chaoborus larvae

We analyzed the effects of planktivorous Holeshestes heterodon Eigenmann (Characidae) predation on the plankton community of a small subtropical reservoir, using four enclosures (volume about 17.5 m³), open to the sediment, established in the littoral zone. Two enclosures were stocked with fish (mean TL 5.7 cm), at a density of about 4–5 fish m^–3 (approx. 8 g m^–3), whereas two remained fishless. The experiment lasted a little longer than one month. In the fish enclosures, most Crustacea and Chaoborus larvae remained scarce, probably as a result of visually selective fish predation. In both fishless enclosures, Chaoborus larvae became abundant. However, in only one of these did large individuals become relatively numerous; this discrepancy in the demographic structure of the Chaoborus populations between the two fishless enclosures is unexplained. Only in the fishless enclosure without appreciable numbers of large Chaoborus did densities of Crustacea increase greatly. It is suggested that in the enclosure containing large Chaoborus individuals, crustacean populations were prevented from developing due to predation pressure, while the small Chaoborus larvae of the other enclosure could not readily consume these prey. Rotifers were low in abundance in the absence of fish, probably as a consequence of Chaoborus predation. Phytoplankton density increased in all four enclosures, due probably to the lack of water flow. Only in the fishless enclosure with high densities of crustaceans did phytoplankton abundance decrease markedly at the end of the experiment, perhaps because of grazing losses.     

CARBON FIXATION IN CULTURED MARINE BENTHIC DIATOMS1

The enzyme activity of ribulose 1, 5-bisphosphate carboxylase-oxygenase (RuBisCO) and phosphoenolpyruvate carboxylase (PEPC) was measured in four species of marine benthic diatoms isolated from subtidal sediments of Graveline Bayou, Mississippi. Enzyme activities were measured in cultures of Amphora micrometra Giffen, A. tenerrima Aleem and Hustedt, Nitzschia fontifuga Cholnoky, and Nitzschia vermicularis Grunow that were grown at light levels supporting μ_max and at light-limiting irradiances. All four species exhibited similar RuBisCO: PEP ratios (range = 1–1.8) at μ_max the lowest ratio (0.4) was observed in A. micrometra. Reduced light levels increased PEPC relative to that measured at μ_max in two species. Two-dimensional paper chromatography was used to determine the first products of carbon fixation in A. micrometra After a 15 s incorporation period, the first product of photosynthetic carbon fixation was 3-phosphoglycerate even though this alga had a PEPC activity that was three times higher than that of RuBisCO. After 30 s, over 50% of the recovered radioactivity was still in this compound. Stable carbon isotope analyses of a mixture of the four pennate diatoms also suggest the predominant carbon fixation pathway in these benthic diatoms was similar to C3 plants.     

The promotive effect of smoke derived from burnt native vegetation on seed germination of Western Australian plants

Exposure of dormant seed to cold smoke derived from burnt native vegetation had a positive influence on germination in one or more seed provenances in 45 out of 94 species of native Western Australian plants that are normally hard to germinate. When tested under controlled conditions some species showed earlier germination in smoke treatments than controls; in others smoke-treated seeds continued to germinate for several weeks after controls had achieved full germination. In the remainder, treated and control seeds germinated to similar time schedules. A group of 23 species which responded positively had previously been recorded as extremely difficult or impossible to germinate using conventional techniques. These included members of the genera Geleznowia (Rutaceae), Hibbertia (Dilleniaceae), Stirlingia (Proteaceae), Verticordia (Myrtaceae), Actinostrobus (Cupressaceae) and Pimelea (Thymelaeaceae). Both large- and small-seeded species were encountered amongst the positively responding taxa, which encompassed representatives of 15 families and 26 genera of dicotyledons, 5 families and 8 genera of monocotyledons and the gymnosperm Actinostrobus acuminatus. Sowing seeds on smoke-fumigated filter papers or watering with aqueous eluates of smoke elicited similar degrees of stimulation of germination, as did exposure to gaseous smoke in a readily germinating species Anigozanthos manglesii (Haemodoraceae) and the normally intractable species Lysinema ciliatum (Epacridaceae). Exposing recently burnt and unburnt natural bushland sites to smoke, smoked water or smoked dry sand elicited a significant germination response in 15 species. Over one third of the species sampled in the burnt site exhibited germination additional to that caused by the fire. Data are discussed in relation to previous germination studies on Australian and other taxa.