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941.
Irradiation of etiolated leaves leads to their greening. Although this problem has a long history, the question of whether
the intermittent irradiation (IMI) grown plants have fully functional reaction centres as well as the oxygen clock, before
exposure to continuous irradiation (CI), had not been resolved. To answer this question, as well as to analyze the development
of the two photosystems, the following parallel measurements were made: (1) Emission spectra at 77 K; (2) OJIP chlorophyll (Chl) a fluorescence transient; (3) period 4 oscillation in the flash number dependence of initial fluorescence F0 (at 50 μs) and FJ (at 2 ms); and (4) P700. In the 1-ms-flash (FL) grown pea, that has a different biogenesis of the photosynthetic apparatus, delayed light emission
(DLE) and Chl a fluorescence transient were measured in parallel. Quantitative analysis of Chl a fluorescence values provided the following conclusions: (1) IMI, not FL, plants have almost fully developed reaction centres and the oxygen clock. (2) Further greening of IMI plants under CI involves two phases: (a) during 3-4 h of CI, the number of PS2 units and connectivity between them increase, and then (b) light-harvesting antenna increases. (3) In FL, 10 min CI activates fully the oxygen clock.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
942.
943.
India is one of the countries where sericulture is being practiced traditionally. Due to the higher economic return and the greater employment potential, attempts are being made to increase the productivity by developing high yielding mulberry varieties. At the present, Mysore local, Bomaypiasbari, Kanva-2, Bilidevalaya, Kajli, S1, BC(2)59, C776, RFS-175, S-36 and Victory-1 are being cultivated extensively in different parts of India for rearing the silkworm Bombyx mori L. Using 17 random amplified polymorphic DNA (RAPD) and 11 inter-simple sequence repeat (ISSR) primers the genetic relationships among these varieties were analyzed. The RAPD and ISSR primers revealed more than 75% polymorphism among the varieties. The genetic similarity estimated from RAPD markers varied from 0.645, between Kajli and Victory-1 to 0.887, between Kanva-2 and Bilidevalaya. Similarly, the genetic similarity estimated from the ISSR markers ranged from 0.600, between Kajli and Victory-1, to 0.873 between Kanva-2 and BC(2)59. The dendrogram constructed from these markers grouped the varieties into three major groups comprising the low yielding, medium yielding and high yielding. The low genetic similarity between the group of varieties originating from the eastern regions with that of the southern region encourages formation of extensive breeding programs between these groups as to transfer the high yield potential of the southern varieties to the low yielding but highly adaptive eastern varieties. 相似文献
944.
Rapid micropropagation through adventitious shoot induction from in vitro raised leaf explants of Clerodendrum aculeatum (Verbenaceae), was successfully achieved for the first time. Basal portion of the leaves showed highest regeneration potential when grown on MS medium supplemented with BA (5.0 mg/l) and NAA and IBA (0.5 mg/l of each). Shoots after elongation in growth regulator-free medium, were rooted in MS medium containing 0.5 mg/l of NAA and IBA. Aqueous leaf extract of in vitro raised plants, induced high degree of resistance against viruses in susceptible healthy hosts when applied prior to virus inoculation. Upon purification from leaves of cultured plants, the resistance inducing protein, showed molecular mass of 34 kDa. Amount of resistance inducing protein obtained from leaves of cultured plants, was consistent throughout the year, as compared to the protein isolated from leaves of field grown plants, which showed marked seasonal fluctuation. The purified 34 kDa protein from in vitro raised plants, was serologically related to field grown plants and possessed similar characteristics. The micropropagated plants were successfully established in earthen pots under greenhouse conditions. 相似文献
945.
946.
The mammalian oocyte is surrounded by an extra-cellular matrix, the zona pellucida (ZP), composed of three major glycoproteins (ZP1, ZP2 and ZP3). The ZP glycoproteins, by virtue of their tissue specificity and critical role during mammalian fertilization, have emerged as potential candidate antigens for the development of an immunocontraceptive vaccine. Molecular characterization of ZP glycoproteins from several species, reveals a variable degree of homology among the deduced primary amino acid sequences, which provided an opportunity to undertake active immunization studies in heterologous animal models. Active immunization of various animal species with either native ZP glycoproteins or those obtained by recombinant DNA technology led to the inhibition of fertility. Thus ZP glycoproteins based immunocontraceptive vaccines offer an attractive proposition for controlling wild life population. To make it a practical proposition, additional research inputs are required to optimize and devise novel strategies for vaccine delivery. Observed ovarian dysfunction, often associated with immunization by ZP glycoproteins is one of the major stumbling blocks for their use in humans. Ongoing studies to delineate appropriate B cell epitopes of ZP glycoproteins that are devoid of oophoritogenic T-cell epitopes, which will inhibit fertility without concomitant oophoritis, will be critical to determine their feasibility for human use. 相似文献
947.
The predation and searching efficiency of fourth instar of predatory C. septempunctata at various densities of mustard aphid, Lipaphis erysimi (Kaltenbach) and predator was investigated under laboratory conditions. The feeding rate of predatory stage decreased at increased prey- and predator densities. Highest percent (92.80%) prey consumption was observed at initial prey density and lowest percent (40.86%) prey consumption at highest prey density by the fourth instar, though the total prey consumption increased with increase in either prey- or predator densities. Similarly, the individual prey consumption was also highest at initial predator density and lowest at highest predator density owing to the mutual interference between the predators at higher densities. The area of discovery (searching efficiency) also decreased with increase in prey- and predator densities. Handling time of predator was highest at lower prey densities, which decreased with increased prey densities. The highest percentage of prey consumption at the prey density of 50 revealed that 1:50 predator-prey ratio was the best to reduce the pest population. 相似文献
948.
Ephrin-B2 reverse signaling is required for axon pathfinding and cardiac valve formation but not early vascular development 总被引:1,自引:0,他引:1
Cowan CA Yokoyama N Saxena A Chumley MJ Silvany RE Baker LA Srivastava D Henkemeyer M 《Developmental biology》2004,271(2):263-271
Vascular development begins with the formation of a primary vascular plexus that is rapidly remodeled by angiogenesis into the interconnected branched patterns characteristic of mature vasculature. Several receptor tyrosine kinases and their ligands have been implicated to control early development of the vascular system. These include the vascular endothelial growth factor receptors (VEGFR-1 and VEGFR-2) that bind VEGF, the Tie-1 and Tie-2 receptors that bind the angiopoietins, and the EphB4 receptor that binds the membrane-anchored ligand ephrin-B2. Targeted mutations in the mouse germline have revealed essential functions for these molecules in vascular development. In particular, protein-null mutations that delete either EphB4 or ephrin-B2 from the mouse have been shown to result in early embryonic lethality due to failed angiogenic remodeling. The venous expression of EphB4 and arterial expression of ephrin-B2 has lead to the speculation that the interaction of these two molecules leads to bidirectional signaling into both the receptor-expressing cell and the ligand-expressing cell, and that both forward and reverse signals are required for proper development of blood vessels in the embryo. Indeed, targeted removal of the ephrin-B2 carboxy-terminal cytoplasmic tail by another group was shown to perturb vascular development and result in the same early embryonic lethality as the null mutation, leading the authors to propose that ephrin-B2 reverse signaling directs early angiogenic remodeling of the primary vascular plexus [Cell 104 (2001) 57]. However, we show here that the carboxy-terminal cytoplasmic domain of ephrin-B2, and hence reverse signaling, is not required during early vascular development, but it is necessary for neonatal survival and functions later in cardiovascular development in the maturation of cardiac valve leaflets. We further show that ephrin-B2 reverse signaling is required for the pathfinding of axons that form the posterior tract of the anterior commissure. Our results thus indicate that ephrin-B2 functions in the early embryo as a typical instructive ligand to stimulate EphB4 receptor forward signaling during angiogenic remodeling and that later in embryonic development ephrin-B2 functions as a receptor to transduce reverse signals involved in cardiac valve maturation and axon pathfinding. 相似文献
949.
BACKGROUND: Hydatidosis occurs due to infestation with the larval stage of the Echinococcus species. Humans are incidental hosts. Symptoms and signs in humans are a slowly growing mass lesion, especially in the central nervous system. Diagnosis depends on the appropriate presentation and history with corroborative radiology and serology. Microscopic detection of characteristic parasitic scolices and hooklets is confirmatory. CASE: A 10-year-old girl presented with complaints of headaches and convulsions for the preceding several months. Computed tomography findings showed asymmetric dilatation of the right lateral ventricle by an intraventricular, focally calcified mass. The radiologic suspicion was an intraventricular tuberculoma, hydatid cyst or choroid plexus papilloma. Cytologic examination of cerebrospinal fluid (CSF) smears revealed characteristic echinococcal components. CONCLUSION: Intracranial hydatid cyst is a fairly uncommon manifestation of an echinococcal infestation and shares clinicoradiologic features with several intracranial, space-occupying lesions. Cytologic examination of CSF samples may be employed to detect confirmatory evidence of a clinical/radiologic suspicion. 相似文献
950.
Goyal HO Robateau A Braden TD Williams CS Srivastava KK Ali K 《Biology of reproduction》2003,68(6):2081-2091
The effects of neonatal exposure to different doses of diethylstilbestrol (DES) on the reproductive functions of male rats at adulthood were evaluated. Sprague-Dawley rats (5-8/group) received sc injections of 25 microl olive oil containing DES (Sigma Chemical Co., St. Louis, MO) at a dose of 10 microg, 1 microg, 100 ng, 10 ng, or 1 ng per rat on alternate days from Postnatal Days 2-12. Control animals received olive oil only. All animals were allowed to develop until 83-91 days of age; however, when they were 70 to 80 days old, four male rats each from the 10 microg, 1 microg, 100 ng, and control groups were cohabited with untreated 60- to 70-day-old females (1:1) for 12 days. At the end of cohabitation, both mated and unmated male rats were weighed, and blood and tissue samples were collected and processed. Results revealed that although sperm motility patterns and sperm morphology were adversely affected in the 10- microg group, other reproductive parameters, including 1). daily sperm production (DSP)/testis; 2). absolute and relative weights of the testis, epididymis, and seminal vesicle; and 3). sperm numbers in both regions of the epididymis declined significantly in a dose-dependent manner in the 10- and 1- microg groups. Conversely, in the <1- microg groups, none of these parameters (except DSP/testis and weight of the epididymis in the 100-ng group, and sperm numbers in the epididymis of the 100- and 10-ng groups) was different from controls. Generally, plasma testosterone levels decreased in the 10- and 1- microg groups, FSH level increased in the 10-microg group, and prolactin and LH levels were unaltered. In the fertility study, although each male in the 1-microg, 100-ng, and control groups produced a copulatory plug and impregnated a female, none could do so in the 10-microg group. The mean number of pups per litter was reduced to eight in the 1-microg group, in contrast to 15 each in the 100-ng and control groups. In conclusion, exposure of neonatal male rats to DES altered sperm motility patterns, sperm fertility (as evident from the reduced number of pups in the 1-microg group), and sexual behavior (as evident from the absence of copulatory plugs in the 10-microg group) and reduced weights of reproductive organs, DSP/testis, and sperm numbers in the epididymis. Whether these alterations/reductions persist in older rats (6-8 mo of age) is under investigation. 相似文献