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1.
Chemotactic responses by motile bacteria 总被引:3,自引:0,他引:3
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Locusts jump by rapidly releasing energy from cuticular springs built into the hind femur that deform when the femur muscle contracts. This study is the first to examine the effect of temperature on jump energy at each life stage of any orthopteran. Ballistics and high-speed cinematography were used to quantify the energy, distance, and take-off angle of the jump at 15, 25, and 35°C in the locust Locusta migratoria. Allometric analysis across the five juvenile stages at 35°C reveals that jump distance (D; m) scales with body mass (M; g) according to the power equation D = 0.35M
0.17±0.08 (95% CI), jump take-off angle (A; degrees) scales as A = 52.5M
0.00±0.06, and jump energy (E; mJ per jump) scales as E = 1.91M
1.14±0.09. Temperature has no significant effect on the exponent of these relationships, and only a modest effect on the elevation, with an overall Q10 of 1.08 for jump distance and 1.09 for jump energy. On average, adults jump 87% farther and with 74% more energy than predicted based on juvenile scaling data. The positive allometric scaling of jump distance and jump energy across the juvenile life stages is likely facilitated by the concomitant relative increase in the total length (L
f+t; mm) of the femur and tibia of the hind leg, L
f+t = 34.9M
0.37±0.02. The weak temperature-dependence of jump performance can be traced to the maximum tension of the hind femur muscle and the energy storage capacity of the femur''s cuticular springs. The disproportionately greater jump energy and jump distance of adults is associated with relatively longer (12%) legs and a relatively larger (11%) femur muscle cross-sectional area, which could allow more strain loading into the femur''s cuticular springs. Augmented jump performance in volant adult locusts achieves the take-off velocity required to initiate flight. 相似文献
5.
Injection of metallic tin powder causes intense proliferation of plasma cells in draining lymph nodes of Lewis rats. Pretreatment orally with soluble tin salts prevents this response to subsequently injected metallic tin. In the present work, pretreatment with tin salts by parenteral injection was just as effective as addition to the drinking water. This new approach made the following experiments possible. Poorly soluble tin compounds were found to be inhibitory when injected parenterally. Tin salts injected parenterally into one of two rats joined in parabiotic union prevented the plasma cell response to metallic tin in both parabionts. The transfer of the inhibitory effect via the cross-circulating blood represents significant progress toward understanding the mechanisms involved. The evidence suggests the possibility that tin salts elicit an intermediary substance or process that is responsible for inhibition of the plasma cell response to metallic tin. 相似文献
6.
Seymour Kaufman 《Neurochemical research》1991,16(9):1031-1036
Tetrahydrobiopterin and the folate coenzymes can reciprocally interact in ways that would be useful to the metabolic pathways subserved by both of these coenzymes. Thus, through one of the reactions catalyzed by methylene tetrahydrofolate reductase, 5-CH3-H4-folate can regenerate BH4 from q-BH2 and q-BH2 can provide an escape from the methyl trap.Special issue dedicated to Dr. Louis Sokoloff 相似文献
7.
Human B cell development. II. Subpopulations in the human fetus 总被引:19,自引:0,他引:19
M Bofill G Janossy M Janossa G D Burford G J Seymour P Wernet E Kelemen 《Journal of immunology (Baltimore, Md. : 1950)》1985,134(3):1531-1538
In man, during fetal development the B cell populations show distinct phenotypes at different tissue sites. The pre-B and B lymphocytes of the fetal liver and bone marrow express IgM and B cell markers, B1 (CD20) and BA-1 (CD24). These "early" cells are negative with a number of other reagents, anti-IgD, RFB4 (CD22), RFB6 (CD21), and RFA-2, which on the other hand recognize peripheral B cells. These peripheral B lymphocytes in the developing fetus are heterogeneous. The diffusely distributed B cells in the earliest lymph node samples, 16 to 17 wk of gestational age, and from 16 to 21 wk in the spleen, are strongly IgM+ (IgD+,RFB4+,RFB6+, and RFA-2+) but lack T cell-associated markers such as T1 (CD5, p 67,000 dalton equivalent of murine Ly-1) and Tü-33. In fetal lymph nodes, primary nodules develop around the follicular dendritic (FD) cells from 17 wk onward, and contain a virtually pure population of B cells; B1+,BA1+,RFB4+,RFB6+,RFA-2+, which simultaneously express IgM,IgD together with T1 (CD5), a T cell-associated antigen. A sizeable subpopulation of these IgM+,T1+ cells are also positive for Tü-33, another T cell-associated marker. In the spleen, the B cells of the IgM+,IgD+,T1+ type appear in smaller numbers and only relatively late around wk 22. These cells are diffusely distributed at first, and start accumulating around the small FD cell clusters as soon as these emerge about the 23rd gestational wk. At that time, the IgM+,T1+B cells can also be washed out from the peritoneal and pleural cavities. The T1+,IgM+B cells may represent the normal equivalent cells of B chronic lymphoid leukemia and centrocytic lymphoma, and appear to be the counterpart of Ly-1+,IgM+B cells in the mouse. 相似文献
8.
Walter W. McAlhaney Naren L. Banik Seymour Greenfield Edward L. Hogan 《Neurochemical research》1986,11(2):173-183
Six proteolytic enzymes were assayed for activity in quaking CNS in examining the hypothesis that increased proteolytic activity contributes to the hypomyelination characteristic of this mutant. Cathepsin B-like enzyme, cathepsin D, neutral proteinase, calcium-activated neutral proteinase, prolyl endopeptidase, and diaminopeptidase II were assayed in whole homogenate of brain or spinal cord and each was found to have activity similar to that in normal mice. These results do not support a relationship between proteolysis and the genetic defect and suggest that other factors should be investigated to delineate the pathogenesis of this mutant. 相似文献
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10.
Michael B. Rabinowitz Harvey C. Gonick Seymour R. Levin Mayer B. Davidson 《Biological trace element research》1983,5(6):449-466
Chromium (Cr) deficiency in experimental animals and in humans sustained by prolonged total parenteral nutrition has been shown to cause diabetes mellitus. Prior trials in humans indicated that Cr supplements, in either inorganic or organic form, may improve carbohydrate utilization. We report here a clinical double-blind, random cross-over trial of inorganic chromium trichloride, a brewer’s yeast that contained Cr as glucose-tolerance-factor (GTF), a brewer’s yeast extract without GTF, and a placebo. Forty-three outpatient diabetic men received three of these supplements for 4 months each. Subgroups included 21 ketosis-prone, 7 ketosis-resistant non-obese, and 15 ketosis-resistant obese men. Cr levels were followed pre- and post-treatment in hair, red blood cells, plasma, and urine. Response of carbohydrate metabolism to treatment was assessed in terms of change in insulin requirements, fasting plasma glucose, plasma cholesterol, and triglycerides, as well as the change in plasma glucose, glucagon, and insulin or C-peptide levels in response to a standard meal. In some men, these parameters were also measured after iv tolbutamide. Both the inorganic and organic oral Cr supplements increased measurable body pools of Cr in hair and red blood cells by about 25%. However, fasting plasma glucose and lipids and the glucose response to either the standard meal or to tolbutamide were not significantly altered by any of the treatments. 相似文献