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121.
Synopsis Prespawning female dace were examined in 7 successive years; in 6 years mean egg size (mm3) and egg number were inversely related and hence the ovary weights of equivalent-sized females were constant. Fecundity increased logarithmically with fish length, and an index of reproductive effort (ovary weight ÷ length cubed) also increased. The number of eggs per gram of ovarian tissue decreased with fish length; this was because mean egg size (mm3) increased and not because of a change in the proportion of connective tissue in the ovary. But in 1977, both egg number and mean egg size were low, although very high somatic growth had occurred in the previous, very warm, summer of 1976. Eggs from different-sized female dace were artificially fertilized, and incubated at a constant temperature. Dry weights of larvae, egg dry weights, mean egg size and larval starvation times showed linear correlations with each other and with parental (female) lengths. The progeny from the very smallest parent died several days earlier than those from the other parents. Size-related predation rates may be of more consequence than starvation death in natural populations. The optimum position of dace along the continuum between many small eggs and fewer larger eggs may vary at different levels of reproductive effort. 相似文献
122.
123.
Christopher P. Moorhouse Barry Halliwell Martin Grootveld John M.C. Gutteridge 《Biochimica et Biophysica Acta (BBA)/General Subjects》1985,843(3)
Co(II) ions react with hydrogen peroxide under physiological conditions to form a ‘reactive species’ that can hydroxylate aromatic compounds (phenol and salicylate) and degrade deoxyribose to thiobarbituric-acid-reactive material. Catalase decreases the formation of this species but superoxide dismutase or low concentrations of ascorbic acid have little effect. EDTA, present in excess over the Co(II), can accelerate deoxyribose degradation and aromatic hydroxylation. In the presence of EDTA, deoxyribose degradation by the reactive species is inhibited competitively by scavengers of the hydroxyl radical (OH), their effectiveness being related to their second-order rate constants for reaction with OH. In the absence of EDTA the scavengers inhibit only at much higher concentrations and their order of effectiveness is changed. It is suggested that, in the presence of EDTA, hydroxyl radical is formed ‘in free solution’ and attacks deoxyribose or an aromatic molecule. In the absence of EDTA, OH radical is formed in a ‘site-specific’ manner and is difficult to intercept by OH scavengers. The relationship of these results to the proposed ‘crypto OH’ radical is discussed. 相似文献
124.
125.
Christopher E. Taylor Philip W. Stashak George Caldes Benjamin Prescott B.J. Fowlkes Phillip J. Baker 《Cellular immunology》1984,83(1):26-33
Several lectins were tested for their capacity to alter the antibody response to type III pneumococcal polysaccharide (SSS-III). The antibody response was enhanced by concanavalin A (Con A), phytohemagglutinin (PHA), as well as lectins from Phytolacca americana (Pa-2), Pisum sativum (PSA), and Lens culinaris (LCH), when these lectins were given 2 days after immunization with SSS-III; however, suppression was obtained when Con A and Pa-2 were given at the time of immunization. By contrast the lectins from Vicia villosa (VVL) and Bauhinia purpurea (BPA) did not alter the antibody response. Since the lectins PSA and LCH bind to the same monosaccharide as Con A, whereas the other lectins bind to different monosaccharides, these findings indicate that there is no relationship between nominal monosaccharide specificity and the capacity to modulate the antibody response. Substantial increases in the magnitude of the IgG1 antibody response was noted after the administration of Con A whereas profound enhancement of IgG2a antibody response was noted after PHA was given. 相似文献
126.
Friedrich Christopher A. Chakravarti Shukti Ferrell Robert E. 《Biochemical genetics》1984,22(5-6):389-394
Biochemical Genetics - 相似文献
127.
Summary The 68C puff is a highly transcribed region of theDrosophila melanogaster salivary gland polytene chromosomes. Three different classes of messenger RNA originate in a 5000-bp region in the puff; each class is translated to one of the salivary gland glue proteins sgs-3, sgs-7, or sgs-8. These messenger RNA classes are coordinately controlled, with each RNA appearing in the third larval instar and disappearing at the time of puparium formation. Their disappearance is initiated by the action of the steroid hormone ecdysterone. In the work reported here, we studied evolution of this hormone-regulated gene cluster in themelanogaster species subgroup ofDrosophila. Genome blot hybridization experiments showed that five other species of this subgroup have DNA sequences that hybridize toD. melanogaster 68C sequences, and that these sequences are divided into a highly conserved region, which does not contain the glue genes, and an extraordinarily diverged region, which does. Molecular cloning of this DNA fromD. simulans, D. erecta, D. yakuba, andD. teissieri confirmed the division of the region into a slowly and a rapidly evolving protion, and also showed that the rapidly evolving region of each species codes for third instar larval salivary gland RNAs homologous to theD. melanogaster glue mRNAs. The highly conserved region is at least 13,000 bp long, and is not known to code for any RNAs. 相似文献
128.
H. Christopher Wilson Nadine C. Milos 《In vitro cellular & developmental biology. Plant》1987,23(5):323-331
Summary This study investigates the nutritional requirements ofXenopus laevis neural crest cells and melanophores developing in vitro. A comparison is made between the growth and differentiation of cells
in serum-containing medium and a chemically defined, serum-free medium that we have designed. Our chemically defined medium
is more efficient than serum-supplemented medium in promoting proliferation of these cells. Several supplements are required
to enhance culture development. These include insulin, α-melanocyte stimulating hormone, somatotropin, luteotrophic hormone,
linoleic acid, uridine, and putrescine. In addition, collagen and fibronectin provide the most conductive environment tested
for cell migration and adhesion.
This work was supported by establishment and major equipment grants from the Alberta Heritage Foundation for Medical Research
to N. C. M. Nadine C. Milos is a Heritage Medical Research Scholar of the Alberta Heritage Foundation for Medical Research. 相似文献
129.
C. A. Lapp M. E. Stachura J. M. Tyler Y. S. Lee 《In vitro cellular & developmental biology. Plant》1987,23(10):686-690
Summary GH3 cell secretory activity was studied in long-term perifusion to define previously reported spontaneous increases in growth
hormone (GH) and prolactin production (PRL). Mechanically harvested cells (1×107/column) were perifused at 4 ml/h for 72 h. A basal period of variable duration (8 to 12 h), during which hormone secretion
was stable, was followed by steadily increasing secretion rates. Changes in cell number were not sufficient to acount for
increased jormone secretion rates: a) there was no significant change in cell count after 72 h (0.97±0.03×107;n=18); b) mean cell column DNA content increased 25.5% above the base value, whereas GH secretion rose 385% and PRL rose 178%
(n=5). Observed differences in the duration of the basal secretion period, the basal secretory rate, and the magnitude of secretory
rate increase were associated with several variables: a) variablility within a subline was a function of passage number: GH
secretion decreased and PRL secretion increased with subculture number; b) cells with identical lot and freeze numbers, but
received at different times, behaved differently; c) the presence of an antifungal agent (nystatin) altered hormone secretion
reproducibly. Conclusions: a) rates of GH and PRL secretion rise spontaneously in perifusion without a proportional increase
in GH3 cell number; b) fluctuations in the rate of GH3 cell secretion of GH and PRL are not entirely random but are determined by several definable variables.
Supported by a grant to MES from the National Institutes of Health (AM33388) and in part by the Medical Research Service of
the Veterans Administration. 相似文献
130.
The reactions of singlet oxygen (1O2) with cis and trans butenes-1,1,1-d3, at—80°C in Freon-11, show a product isotope effect (kH/kD) of 1.38 and 1.25 respectively. Isomerization of the starting materials or formation of dioxetanes were not observed during the course of the photooxygenation. Together with the isotope effects on the reactions of tetramethylethylene-d6 isomers with singlet oxygen, these results require the reversible formation of a perepoxide or charge transfer intermediate. 相似文献