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61.
Crossing over frequency was determined for five marked regions covering most of a chromosome arm. The results of a 12th backcross were compared with previously published results from the noninbred f1. Exchange frequency increased significantly following inbreeding. Chiasma interference remained positieve, but was somewhat less intense in b12.Supported in part by Public Health Service Research Grants AI 01462 and GM 1882-01, by a National Science Foundation Faculty Fellowship to H. R. C., and by Public Health Service Research Career Award K6-GM-4899 to D. D. P.Technical Paper No. 2054, Oregon Agricultural Experiment Station, Corvallis. 相似文献
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Aspects of the life cycle of marine nematodes 总被引:1,自引:0,他引:1
Summary 1. Life cycles of approximately one month are recorded for laboratory maintained cultures of chromadorid, monhysterid and oncholaimid nematodes.2. Amphimictic and parthenogenetic reproduction occurs in the species investigated. Reproduction inMonhystera parelegantula is by parthenogenesis.3. The chromadoridChromadorina epidemos and the oncholaimidViscosia macramphida are able to reproduce by either amphimixis or parthenogenesis.4.Acanthonchus cobbi, Chromadora macrolaimoides andEuchromadora gaulica are amphimitically reproducing species.
Aspekte des Lebenszyklus mariner Nematoden
Kurzfassung Bei einigen marinen Nematoden, die in Biscayne Bay (Florida) gesammelt und im Labor gezüchtet worden sind, vollzieht sich der gesamte Lebenszyklus ungefähr innerhalb eines Monats. BeiAcanthonchus cobbi, Chromadora macrolaimoides undEuchromadora gaulica ist zweigeschlechtliche Fortpflanzung festgestellt worden.Monohystera parelegantula vermehrt sich parthenogenetisch. Ein möglicherweise durch Umwelteinflüsse bedingter Wechsel von bisexueller und parthenogenetischer Fortpflanzung tritt beiChromadora epidemos undViscosia macramphida auf.相似文献
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66.
Summary 1. Studies of the broad-leafed turtle grass,Thalassia testudinum
König, have revealed a diverse range of fungal infestation different in generic composition and dynamics of attack from that found on submerged wood. Certain of the fungi, notably the AscomyceteLindra thalassiae, initiate considerable degradation of leaf tissue and show a developmental cycle in nature related to the physiological state of the host plant.2. Use of fungal-cellulose mats as a trapping substrate has been extremely effective for discernment of ecologically significant shifts in nematode concentrations, especially those of the omnivorous species,Metoncholaimus scissus.3. Patterns of activity ofM. scissus, as well as those of various foliicolous nematodes, suggest that loci of organic material, such as fungal infested leaves and decaying plant tissue, significantly affect biological activity of these animals.4. Laboratory analysis of degraded cotton cellulose filters show a striking incidence of fungal reproduction of the ascomycetous fungusLulworthia, along with development of a considerable associated nematode fauna, especially species ofViscosia (V. macramphida) andLeptolaimus (L. plectoides). Successional patterns in nematode development are noted with continued degradation of the cotton cellulose matrix.
Contribution No. 768 from the Institute of Marine Science, University of Miami, Miami, Florida, and from the Canada Department of Agriculture, Ottawa, Canada. This work was supported at the IMS by grant GM 12842 from the National Institutes of Health, USA. 相似文献
Studien über marine Pilz-Nematoden-Assoziationen und Pflanzendegradation
Kurzfassung Untersuchungen am SeegrasThalassia testudinum König haben ergeben, daß sich hier Pilzinfektionen hinsichtlich der Komposition der beteiligten Gattungen und der Dynamik des Befalls von den am untergetauchten Holz festgestellten Infektionen unterscheiden. Bestimmte Pilze, insbesondere der AscomycetLindra thalassiae, leiten eine erhebliche Degradation des Blattgewebes ein und zeigen einen Entwicklungszyklus, welcher in Beziehung steht zum physiologischen Zustand der Wirtspflanze. Die Anwendung von Pilz-Zellulose-Matten als Einfangsubstrat war außerordentlich erfolgreich für das Erkennen ökologisch signifikanter Verschiebungen in den Nematodenkonzentrationen, insbesondere bei der omnivoren ArtMetoncholaimus scissus. Die Aktivitätsmuster vonM. scissus — ebenso wie die verschiedener foliicolöser Nematoden — deuten darauf hin, daß pilzinfizierte und zerfallende Pflanzenteile in entscheidendem Maße die biologische Aktivität dieser Tiere beeinflussen. Laboratoriumsanalysen degradierter Wollzellulosefilter lassen eine überraschend starke Vermehrung des AscomycetenLulworthia erkennen und gleichzeitig die Entwicklung einer beachtlichen Fauna assoziierter Nematodenarten, insbesondere vonViscosia macramphida undLeptolaimus plectoides. Im Verlaufe der weiteren Degradation der Wollzellulosematrix kommt es bei der Nematodenfauna zu entsprechenden Sukzessionen.
Contribution No. 768 from the Institute of Marine Science, University of Miami, Miami, Florida, and from the Canada Department of Agriculture, Ottawa, Canada. This work was supported at the IMS by grant GM 12842 from the National Institutes of Health, USA. 相似文献
67.
When male mouse spleen cells were incubated with a combination of platelet activating factor (PAF, 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) and sera from female mice in oestrus, the cells displayed a markedly increased rosette inhibition titre (RIT) when subsequently tested in the rosette inhibition assay. Neither PAF nor oestrous mouse sera alone could induce this effect, the combined action was required. Lyso-PAF could not substitute for the PAF, nor could male mouse sera nor the sera from females in dioestrus or metoestrus substitute for the oestrous mouse serum requirement. Pro-oestrous mouse sera could replace oestrous mouse sera but were less effective in their dose-responses. Studies on the mechanism of action of the PAF and oestrous mouse serum components suggested that the PAF stimulated the production and release of soluble factors (termed S2 factors) which by themselves could induce increased RIT values when applied to fresh spleen cells. The PAF-stimulated cell populations were rendered refractory to the action of these S2 factors and did not display increased RIT values, unless oestrous mouse serum was added. This serum acted to reverse the refractory state, allowing the S2 factors to exert their effect, and so cells treated with PAF and oestrous mouse serum displayed increased RIT values. 相似文献
68.
Function of the human immunodeficiency virus types 1 and 2 Rev proteins is dependent on their ability to interact with a structured region present in env gene mRNA. 总被引:15,自引:10,他引:5 下载免费PDF全文
The interaction of the human immunodeficiency virus type 1 (HIV-1) Rev protein with a structured region in env mRNA (the Rev-responsive element [RRE]) mediates the export of structural mRNAs from the nucleus to the cytoplasm. We demonstrated that unlike HIV-1 Rev, which functions with both the HIV-1 and HIV-2 RREs, HIV-2 Rev functions only with the HIV-2 RRE. Rev-RRE binding studies suggested that the lack of nonreciprocal complementation stems from the inability of HIV-2 Rev to interact with HIV-1 RRE RNA. Maintenance of RNA secondary structure, rather than the primary nucleotide sequence, appeared to be the major determinant for interaction of both HIV-1 and HIV-2 Rev with the HIV-2 RRE. Moreover, the binding domain of the HIV-2 RRE recognized by HIV-1 Rev was dissimilar to the binding domain of the HIV-1 RRE, in terms of both secondary structure and primary nucleotide sequence. Our results support the hypothesis that function of HIV Rev proteins and possibly the functionally similar Rex proteins encoded by the human T-cell leukemia viruses (HTLVs) HTLV-I and HTLV-II is controlled by the presence of RNA secondary structure generated within the RRE RNA. 相似文献
69.
Summary Prader-Willi syndrome (PWS) is a sporadic disorder in which about half of cases have a 15q12 deletion. Although a small number of cases have other rearrangements involving 15q12, the rest of the cases appear to have normal chromosomes. Clinical similarities among all these patients regardless of the karyotype strongly suggests a common etiology. To investigate the nature of this common etiology, we analyzed sister chromatid exchange (SCE) at the 15q11-13 region in 10 PWS patients with the chromosome deletion, 12 PWS patients with normal chromosomes, and 11 normal control individuals. While SCE at the q11-13 region was absent on the 15q12 deleted chromosome, the percentage of SCE on chromosome 15 at q11 was statistically higher for PWS with normal chromosomes (10.1%) compared to that for normal controls (1.9%) and the normal homologue (2.2%) in deleted patients (2=7.7982, df=2, P<0.025). The data suggest relative instability of DNA at the 15q11 region in PWS patients. 相似文献
70.
Chromosome numbers for 26 different species of the generaPiper, Peperomia andPothomorphe (Piperaceae) are reported. The basic chromosome numbers are 2n = 26, x = 13 (Piper, Pothomorphe) and 2n = 22, x = 11 (Peperomia), polyploid series are characteristic forPiper andPeperomia. Piper has the smallest chromosomes and prochromosomal interphase nuclei,Peperomia the largest ones and mostly reticulate to euchromatic nuclei.Pothomorphe is intermediate in both characters. The karyomorphological differences betweenPothomorphe andPiper underline their generic separation. Interspecific size variation of chromosomes occurs inPiper andPeperomia. Infraspecific polyploidy was observed inPiper betle. C-banding reveals different patterns of heterochromatin (hc) distribution between the genera investigated. The genome evolution is discussed. 相似文献