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21.
The rooting of hypocotyl cuttings from 20-day-old seedlings of Pinus sylvestris L. cultured in vitro is discussed. About 40% of the cuttings cultured on medium lacking activated charcoal produced roots during the first two months. When activated charcoal was added to the medium, either root formation (75% formed roots) or wound tissue growth (95% formed large wound tissues) was stimulated in different experiments. These large wound tissues did not develop any roots. The anatomical changes in the basal part of the cuttings were similar during the first two weeks in all the cuttings studied. A vascular cylinder composed of short tracheids with many pores developed. Thereafter the differentiation process became varied. The amount of wound tissue produced and the time for rooting differed among the cuttings. Tracheid nests which were in contact with the vascular system in the hypocotyl via short tracheids were observed after three weeks. Subsequently, roots developed from the tracheid nests. The longer root formation was delayed, the larger the wound tissue became.
Short tracheids were found close to the wound tissue surface. Their ability to adsorb nutrients and water is discussed. 相似文献
Short tracheids were found close to the wound tissue surface. Their ability to adsorb nutrients and water is discussed. 相似文献
22.
Somatomedin serum levels of congenitally vasopressin-deficient Brattleboro rats were determined postnatally between day 1 and 55, and compared with heterozygous control values. Assays were performed with a radioimmunoassay of insulin-like growth factor 1 (IGF-1). A transient enhancement of immunoreactive IGF-1 levels between day 8 and 21 of age and a reduction in adulthood was found. This observation shows that the early growth impairments of the Brattleboro mutant are not due to a deficiency of IGF-1. 相似文献
23.
Mordechai Schreiber Leon Fogelfeld Miry C. Souroujon Fortune Kohen Sara Fuchs 《Life sciences》1983,33(15):1519-1526
Spiroperidol was covalently conjugated to bovine serum albumin (BSA). Conjugated spiroperidol was almost as efficient as free spiroperidol in its binding capacity to dopamine receptor. Antibodies to spiroperidol were produced in rabbits following repeated immunizations with the conjugate of spiroperidol and BSA. The obtained antibodies have an apparent KD of 0.02 nM for [3H]-spiroperidol. These antibodies bind also to other butyrophenones with IC50 values three to four orders of magnitude higher than the IC50 obtained with unlabeled spiroperidol. Antibodies were purified from anti-spiroperidol sera by affinity chromatography. Anti-idiotypic antibodies were raised in rabbits by immunization with the purified anti-spiroperidol antibodies. Some rabbits produced anti-idiotypic antibodies which bind to rat and calf striatum. 相似文献
24.
Gabriella Goldberg Daria Mochly-Rosen Sara Fuchs Yoram Lass 《The Journal of membrane biology》1983,76(2):123-128
Summary Monoclonal antibodies directed against the cholinergic binding site of the acetylcholine receptor were found to alter the ion channel properties in cultured chick myoballs. Time and dose dependent reduction in acetylcholine sensitivity was observed. Noise analysis experiments indicated a decrease in the mean single channel conductance and an increase in the mean single channel open time. 相似文献
25.
The effect of osmotic `shock'' on the swelling pattern and respiratory control of rat-liver mitochondria 总被引:2,自引:2,他引:0
1. Rat-liver mitochondria suspended in 0.25m-sucrose were exposed for a few seconds to strongly hypo-osmotic conditions, and then the osmolarity of the medium was raised again to 0.25 with the aid of tris chloride (osmotic ;shock'). 2. Mitochondria after hypo-osmotic pretreatment lost their capacity for slow energy-dependent swelling in iso-osmotic tris buffer and showed no respiratory control. 3. Swelling could be induced in the ;shocked' mitochondria by ATP but not by addition of respiratory substrates. 4. It was shown that cytochrome c is lost from ;shocked' mitochondria when they come into contact with the tris buffer present in the assay medium, and that the changes observed in the pattern of swelling, as well as in respiratory control, are directly connected with this loss of cytochrome c. 5. The results of the investigation are discussed with regard to the role of cytochrome c in swelling and respiratory control. 相似文献
26.
The 5-fluorouracil (5 FU) technique for the phenotypic reversion of amber mutants was used to demonstrate that under certain circumstances, in the presence of putrescine or spermidine, early mutants have an enhanced response to 5 FU, whereas late mutants have a delayed response. Bacteria infected by T4D wild-type bacteriophage did not produce phage in the presence of high putrescine concentrations. Pulse treatments with putrescine showed that the production of lysozyme depends on a putrescine-sensitive process that begins immediately after infection at 26 C and ends at 36 min or even later. The addition of putrescine at any time during the critical period between 0 and 36 min led to a corresponding delay in lysozyme synthesis after the inhibitor was removed. Intracellular phage maturation was delayed by the addition of 100 mumoles of putrescine per ml. Early enzymes were not affected by the diamine, but the level of phage deoxyribonucleic acid was considerably decreased by the inhibitor. The putrescine-sensitive process that affects the timing of maturation is suggested to be the natural process controlling the T4 "clock." 相似文献
27.
1. Three random linear copolymers composed of two or three of the amino acids d-tyrosine, d-glutamic acid, d-alanine and d-lysine, and a branched multichain copolymer with a poly-d-lysine backbone and polymeric side chains of d-tyrosine and d-glutamic acid, were found to be non-antigenic in rabbits, by precipitin and passive cutaneous anaphylaxis, and in guinea pigs, by delayed hypersensitivity tests. The corresponding four copolymers of l-amino acids were shown to be antigenic by all the three criteria. 2. No immunological cross-reactions were observed between the polypeptides composed of d-amino acids and the corresponding l-amino acid copolymers. 3. Similarly, an azobenzenearsonic acid conjugate of poly-d-tyrosine was shown to be non-antigenic in guinea pigs, in contrast with an analogous conjugate of poly-l-tyrosine. Animals sensitized with the conjugate of poly-l-tyrosine did not exhibit delayed skin reactions, when cross-tested with the d-conjugate. 4. A linear polymer composed of d-tyrosine, l-glutamic acid and l-alanine was found to be immunogenic and to cross-react with the corresponding polymer composed exclusively of d-amino acids. 相似文献
28.
Hillard S. Kaplan Jane B. Lancaster Sara E. Johnson John A. Bock 《Human nature (Hawthorne, N.Y.)》1995,6(4):325-360
Our objective is to test an optimality model of human fertility that specifies the behavioral requirements for fitness maximization
in order (a) to determine whether current behavior does maximize fitness and, if not, (b) to use the specific nature of the behavioral deviations from fitness maximization towards the development of models of evolved
proximate mechanisms that may have maximized fitness in the past but lead to deviations under present conditions. To test
the model we use data from a representative sample of 7,107 men living in Albuquerque, New Mexico, between 1990 and 1993.
The model we test proposes that low fertility in modern settings maximizes number of grandchildren as a result of a trade-off
between parental fertility and next generation fertility. Results do not show the optimization, although the data do reveal
a trade-off between parental fertility and offspring education and income.
We propose that two characteristics of modern economies have led to a period of sustained fertility reduction and to a corresponding
lack of association between income and fertility. The first is the direct link between costs of investment and wage rates
due to the forces of supply and demand for labor in competitive economies. The second is the increasing emphasis on cumulative
knowledge, skills, and technologies in the production of resources. Together they produce historically novel conditions. These
two features of modern economies may interact with evolved psychological and physiological mechanisms governing fertility
and parental investment to produce behavior that maximizes the economic productivity of lineages at the expense of fitness.
If cognitive processes evolved to track diminishing returns to parental investment and if physiological processes evolved
to regulate fertility in response to nutritional state and patterns of breast feeding, we might expect non-adaptive responses
when returns from parental investment do not diminish until extremely high levels are reached. With high economic payoffs
from parental investment, people have begun to exercise cognitive regulation of fertility through contraception and family
planning practices. Those cognitive processes maynot have evolved to handle fitness trade-offs between fertility and parental investment.
A preliminary presentation of this data was published in R. I. M. Dunbar, ed.,Human Reproduction Decisions: Biological and Social Perspectives. New York: St. Martin’s Press, 1995. Support for the research project, “Male Fertility and Parenting in New Mexico,” began
with two seed grants from the University of New Mexico’s Biomedical Research Grants Program, 1988 and 1989, and one from the
University of New Mexico Research Allocations Committee, 1988. Further seed money as well as interim funding came from the
William T. Grant Foundation (#89130589 and #91130501). The major support for the project came from the National Science Foundation
from 1990 to 1993 (#BNS-9011723 and #DBS-911552). Both National Science Foundation grants included Research Experience for
Undergraduates supplements.
Hillard S. Kaplan is an Associate Professor of Anthropology at the University of New Mexico. His earlier research and publications
focused on food sharing, time allocation, parental investment, and reproductive strategies among Ache hunter-gatherers in
Paraguay, Machiguenga and Piro forager-horticulturalists in Peru, and villagers of several ethnicities in Botswana. New research
and theory concern fertility, parental investment, and mating strategies in developed and developing nations. This research
formulates a new theory of reproductive decision-making and the demographic transition, integrating human capital and parental
investment theory in a synthesis of economic and evolutionary approaches.
Jane B. Lancaster is a Professor of Anthropology at the University of New Mexico. Her research and publications are on human
reproductive biology and behavior, especially human parental investment; women’s reproductive biology of pregnancy, lactation,
and child-spacing; and male fertility and investment in children. Current research with Hillard S. Kaplan is on male life
history strategies among a large sample of men in New Mexico. She has coedited three books on human parental investment:School-Age Pregnancy and Parenthood (with B. Hamburg),Parenting across the Life Span (with J. Altmann, A. Rossi, and L. Sherrod), andOffspring Abuse and Neglect (with R. Gelles). She is scientific editor of a quarterly journal,Human Nature: An Interdisciplinary, Biosocial Perspective published by Aldine de Gruyter. She is also a council member of the newly formed Human Behavior and Evolution Society.
John A. Bock is Andrew W. Mellon Post-Doctoral Fellow in Epidemiology and Population Health at the National Centre for Epidemiology
and Population Health, The Australian National University. His research focuses on the allocation of parental investment and
the determinants of children’s activities, integrating aspects of economic and evolutionary theory. He has ongoing field research
with Bantu and Bushmen agro-pastoralists and forager-horticulturalists in the Okavango Delta, Botswana. He is also collaborating
with Lancaster and Kaplan on the determinants of progeny distribution and homosexuality among New Mexican men.
Sara E. Johnson is a Ph.D. candidate at the University of New Mexico. Her major research trajectory focuses on trade-offs
in life history characters. Her research experience includes participation in a study of variation in growth and development
among children in a multi-ethnic community in the Okavango Delta, Botswana, in addition to her dissertation work on individual
variation in growth and mortality among juvenile baboons. She is collaborating with Lancaster and Kaplan on the association
between survival and fertility among Albuquerque men. 相似文献
29.
Jorge J. Casal R. Alejandra Mella Carlos L. Ballaré Sara Maldonado 《Physiologia plantarum》1994,92(4):555-562
Etiolated Vicia faba seedlings were exposed to continuous red light to investigate whether changes in extracellular peroxidase activity were correlated in time and localization with changes in extension growth and/or lignin content in the subapical region of the epicotyl. Continuous red light: (a) increased extracellular peroxidase activity after a lag of ca 0.5 h, followed by a maximum peak after 2.5 h due to slightly acidic isoforms (pI = 6–6.5, according to isoelectrofocusing gels), a minimum after 4 h and a second maximum after 8 h due to acidic isoforms (pI=4–5), (b) increased lignin content and epicotyl resistance to bending after a lag of ca 4 h, i.e. simultaneously with changes in acidic extracellular peroxidase activity, and (c) reduced extension growth to a stable rate after a lag of ca 1 h, not coinciding with the kinetics of any of the extracellular peroxidase isoforms. These effects of continuous red light were at least partially mediated by phytochrome. Tissue printing and anatomical studies revealed red light effects on extracellular peroxidase activity and lignin content mainly in the outer cortical parenchyma. The results are consistent with the involvement of phyto-chrome-mediated effects on extracellular peroxidases (acidic isoforms) in the transduction chain leading to lignin responses to red light. 相似文献
30.
Anna Tramontano Elisabetta Bianchi Sara Venturini Franck Martin Antonelo Pessi Maurizio Sallozzo 《Journal of molecular recognition : JMR》1994,7(1):9-24
Conformationally constraining selectable peptides onto a suitable scaffold that enables their conformation to be predicted or readily determined by experimental techniques would considerably boost drug discovery process by reducing the gap between the discovery of a peptide lead and the design of a peptidomimetic with a more desirable pharmacological profile. With this in mind, we designed the minibody, a 61-residue β-protein aimed at retaining some desirable features of immunogloblin variable domains, such as tolerance to sequence variability in selected regions of the protein and predictability of main chain conformation of the same regions, based on the ‘canonical structures’ model. To test the ability of the minibody scaffold to support functional sites we also designed a metal binding version of the protein by suitably choosing the sequences of its loops. The minibody was produced both by chemical syntyhesis and expression in E. coli and charactgerized by size exclusion chromatography, UV CD (circular dichroism) spectroscopy and metal binding activity. All our data supported the model, but a more detailed structural characterization of the molecule was impaired by its low soubility. We were able to overcome this problem both by further; mutagenesis of the framework and by addition of a solublizing motif. The minibody is being used to select constrained human IL-6 peptidic ligands from a library displayed on the surface of the f1 bacteriophage. 相似文献