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1.
2.
A method by which virus penetration through condoms can be tested with simple, inexpensive equipment is described. The method uses chi X174 bacteriophage as the challenge virus and physiologically relevant pressure. Penetration by 0.1 microliters (or less) of challenge suspension can be readily detected. As examples, latex and natural-membrane condoms were examined. 相似文献
3.
Roy E. Crabtree Edward C. Cyr Renée E. Bishop Laura M Falkenstein John M. Dean 《Environmental Biology of Fishes》1992,35(4):361-370
Synopsis Leptocephali were collected in June 1981 and July 1989 over the continental shelf and slope of the Florida west coast. Tarpon larvae ranged 5.5–24.4 mm standard length (SL) and were the second most abundant leptocephalus species. Sagittae examined with compound microscopes and scanning electron microscopy had increments that were presumed to be formed daily. Increment counts made using the two microscopic techniques were not significantly different. Estimated ages ranged 2–25 days with a growth rate (± standard error) of 0.92 ± 0.04 mm d–1 The least squares linear regression equation SL = 2.78 + 0.92 (age in days) best described the relationship between estimated age and length. Adult tarpon appear to undergo a substantial spawning migration from inshore areas frequented during spring and summer to offshore spawning grounds. Spawning occurs during May, June, and July, although the spawning season may be of greater duration. 相似文献
4.
Neurons require a large amount of intracellular transport. Cytoplasmic polypeptides and membrane-bounded organelles move from
the perikaryon, down the length of the axon, and to the synaptic terminals. This movement occurs at distinct rates and is
termed axonal transport. Axonal transport is divided into the slow transport of cytoplasmic proteins including glycolytic
enzymes and cytoskeletal structures and the fast transport of membrane-bounded organelles along linear arrays of microtubules.
The polypeptide compositions of the rate classes of axonal transport have been well characterized, but the underlying molecular
mechanisms of this movement are less clear. Progress has been particularly slow toward understanding force-generation in slow
transport, but recent developments have provided insight into the molecular motors involved in fast axonal transport. Recent
advances in the cellular and molecular biology of one fast axonal transport motor, kinesin, have provided a clearer understanding
of organelle movement along microtubules. The availability of cellular and molecular probes for kinesin and other putative
axonal transport motors have led to a reevaluation of our understanding of intracellular motility. 相似文献
5.
The survival, development and mycorrhizal efficiency of a selected strain of Laccaria bicolor along with naturally occurring ectomycorrhizal fungi in a young plantation of Douglas fir was examined. Symbionts were identified and their respective colonization abilities were determined. Eight species of symbiotic fungi, which may have originated in adjacent coniferous forests, were observed on the root systems. Mycorrhizal diversity differed between inoculated (5 taxa) and control (8 taxa) seedlings. Ectomycorrhizal fungi which occurred naturally in the nursery on control seedlings (Thelephora terrestris and Suillus sp.) did not survive after outplanting. Both inoculated and naturally occurring Laccaria species, as well as Cenococcum geophilum, survived on the old roots and colonized the newly formed roots, limiting the colonization by other naturally occurring fungi. Other fungi, such as Paxillus involutus, Scleroderma citrinum and Hebeloma sp. preferentially colonized the old roots near the seedling's collar. Russulaceae were found mainly in the middle section of the root system. Mycorrhizal colonization by Laccaria species on inoculated seedlings (54%) was significantly greater than on controls (13%) which were consequently dominated by the native fungi. Significant differences (up to 239%) were found in the growth of inoculated seedlings, especially in root and shoot weight, which developed mainly during the second year after outplanting. Seedling growth varied with the species of mycorrhizae and with the degree of root colonization. Competitiveness and effectiveness of the introduced strain on improving growth performances of seedlings are discussed. 相似文献
6.
Stability of Bradyrhizobium japonicum Inoculants after Introduction into Soil 总被引:4,自引:3,他引:1 下载免费PDF全文
Brigitte Brunel Jean-Claude Cleyet-Marel Philippe Normand Rene Bardin 《Applied microbiology》1988,54(11):2636-2642
Bradyrhizobium japonicum USDA 125-Sp, USDA 138, and USDA 138-Sm had been used as inoculants for soybean (Glycine max (L.) Merr.) in soils previously free of B. japonicum. At 8 to 13 years after their release, these strains were reisolated from soil samples. A total of 115 isolates were obtained through nodules, and seven colonies were obtained directly by a serological method. The stability of the inoculants was confirmed by comparing the reisolated cultures with their respective parental strains which had been preserved by being lyophilized or stored on a yeast extract-mannitol agar slant at 4°C. Comparisons were made on morphological and serological characters, carbon compound utilization (8 tested), intrinsic antibiotic resistance (9 tested), and enzymatic activity (19 tested). Mucous and nonmucous isolates of serogroup 125 were analyzed for symbiotic effectiveness and restriction fragment hybridization with a DNA probe. Our data suggest that the B. japonicum inoculants have survived for up to 13 years in the soils without significant mutation except for two reisolates with a slightly increased kanamycin resistance level. 相似文献
7.
Plasmids in Frankia sp. 总被引:6,自引:0,他引:6
P Normand P Simonet J L Butour C Rosenberg A Moiroud M Lalonde 《Journal of bacteriology》1983,155(1):32-35
A method to achieve cell lysis and isolate Frankia sp. plasmid DNA was developed. A screening of Frankia sp. strains belonging to different host compatibility groups (Alnus sp., Elaeagnus sp., Ceanothus sp.) showed that, of 39 strains tested, 4 (strains Cp11, ARgN22d, ArI3, and EUN1f) possessed plasmids ranging in size from 7.1 to 32.2 kilobase pairs as estimated from agarose gel electrophoresis and electron microscopy. A total of 11 plasmids were detected. 相似文献
8.
Genetic and developmental analysis of an X-linked vital locus vnd was undertaken. Embryos hemizygous for the original allele vnd did not hatch and exhibited a disorganized ventral nervous system (VNS). The mutation maps in the region 1B6-7 to 1B9-10, a subregion of an area previously shown to be essential to normal neural development. In this paper, we report isolation of five new alleles at the locus vnd. Genetic complementation analysis of all mutations at the vnd locus, with lethal alleles at adjacent loci, indicates that all lesions at the locus vnd affect only one vital gene function in the region. Four of the five alleles are embryonic lethal; one allele is subvital and behaves like an hypomorphic mutation. Hemizygous embryos for three of the four embryonic lethal alleles were inspected in histological sections; all exhibited disorganized VNS similar to the original allele. The developmental analysis in gynandromorphic genetic mosaics shows that (1) vnd+ gene function is not essential in most imaginal-disc cell derivatives, (2) only about 30% of the mosaic zygotes survive as adults, (3) mosaic zygotes with mutant tissue close to the head cuticle are least likely to survive, and (4) mutant tissue in the thoracic ganglion in the adult is not necessarily lethal. The mosaic data are consistent with the vnd+ gene function being necessary in neural cells derived from the anterioventral region of the blastoderm. 相似文献
9.
Summary The glucoamylase gene from Lactobacillus amylovorus was cloned and expressed in Escherichia coli. A genomic DNA library from Lactobacillus amylovorus was prepared by partially digesting genomic DNA with EcoRI and ligating random fragments to the EcoRI digested cloning vector, pZErO-1.1. Three E. coli transformants expressing glucoamylase were identified using a probe prepared from the STA2 glucoamylase gene from Saccharomyces cerevisiae var. diastaticus. The physical maps of the recombinant plasmids were constructed. These plasmids contained inserts of about 5.2 Kb, 5.9 Kb and 6.4 Kb respectively. Temperature and pH optima of 45°C and 6.0, respectively, were obtained for both recombinant and purified wild type glucoamylases. Also, the enzymes were found to be thermolabile at temperatures above 50°C. 相似文献
10.