Naloxone and TRH affect regional blood flows in the anesthetized rabbit

The cardiovascular effects of IV naloxone and a subsequent administration of TRH IV were studied in the rabbit. Naloxone caused a vasodilation in the myocardium and adrenal glands. Naloxone elicited an increment in cerebral blood flow in several regions which attenuated the cerebrovasodilating effect of TRH in a few regions. The blockade of endogenous opioids with naloxone did not modify the peripheral vasoconstricting effect of TRH or affect the vascular effects of TRH mediated by the peripheral sympathetic nerves. The results indicate that naloxone has a vasodilating effect in the myocardium and CNS in anesthetized rabbits. The major part of the cardiovascular effect of TRH is not dependent on mechanisms sensitive to naloxone.     

Circulation,metabolic rate,and body size in mammals

Summary This paper attempts to explain Kleiber's rule, which relates metabolic rate of mammals to their body mass, from the structure and function of the blood circulation system.Abbreviations a scaling factor - fractal dimension - hydrodynamic conductivity - l _n length of an arterial blood vessel at bifurcation level n - M body mass - N maximal number of bifurcation levels - p pressure - Q flow - r size of Bohr effect - r _n radius of an arterial blood vessel at bifurcation level n - V volume - VO ₂ rate of oxygen unloading - Z _n number of arterial blood vessels at bifurcation level n     

Statistical analysis of the migration component of genetic drift

Statistical methods are introduced for analysis of the migration component of genetic drift, i.e., of the stochastic changes that affect allele frequencies during migration between local groups. Attention focuses on alpha M, a parameter that measures the extent to which this component of drift departs from the ideal of independent random sampling, and which can be interpreted as a measure of the extent to which migration is kin-structured. It is shown that alpha M can be estimated from genetic data, even in the absence of information about the genealogical relationships of migrants, and Monte-Carlo simulations are used to approximate the sampling distribution of the estimator under the null hypothesis of independent random sampling. Application of these methods to data from the Aland Islands, Finland, shows that the migration pattern there is consistent with the hypothesis of independent random sampling.     

夏季高温对水牛瘤胃代谢的影响

利用南京地区夏季炎热的自然条件,连续两年在高温季节(7—8月)进行实验。第一年(系列Ⅰ)的实验动物为四头装置瘤胃瘘管的空怀母水牛,研究高温初期(27.5～33.4℃)和持续高温期(28.0～35℃)对水牛瘤胃消化代谢的影响。第二年实验(系列Ⅱ)利用三头装置瘤胃瘘管的海仔母水牛重复高温(26～35.3℃)实验。 夏季高温期间,实验水牛的呼吸率、瘤胃温度和直肠温度升高,采食量减少,饮水量增加,瘤胃液流速减缓。高温初期出现瘤胃代谢升高[总挥发性脂肪酸(TVFA)和氨氮(NH_3-N)浓度及乙酸/丙酸(A/P)比率升高]。但在持续高温情况下,水牛的采食和瘤胃代谢均明显抑制。采取瘤胃内降温措施(投入冰袋)或冷水淋浴,均能迅速降低呼吸率、直肠和瘤胃温度,恢复采食和反刍,并缓解瘤胃代谢的抑制。提示动物机体参与调节瘤胃代谢的变化,并为改善水牛夏季的饲养管理提供生理学依据。     

Altered growth kinetics precede calcium-induced differentiation in mouse epidermal cells

Summary Primary cultures of newborn mouse epidermal cells proliferate rapidly and with a high growth fraction for several months when grown in medium with low calcium (0.02 to 0.1 mM). Addition of calcium to levels generally used in culture medium (1.2 mM) was followed by rapid changes in the pattern of proliferation. By using a combination of technics (a stathmokinetic method, autoradiography, [³H]thymidine incorporation into DNA, DNA flow cytometry) it was found that cell flux was blocked for 5 to 6 h, followed by a short rise in the mitotic rate at 10 h, and a gradual fall in all growth parameters until about 32 h after the calcium switch. There was no accumulation of cells in any particular cell cycle phase. The results indicate that the calcium switch is followed by a strong reduction in cell flux from G₁ whereas the majority of the cells that had left G₁ at the time of the switch completed one cell division before cessation of all proliferative activity. Both before and after the switch the primary epidermal cultures consisted of one diploid and one tetraploid G₁ DNA stemline that seemed to react in the same way to calcium. This work reported in this paper was undertaken during the tenure of an American Cancer Society-Eleanor Roosevelt-International Cancer Fellowship awarded by the International Union Against Cancer (K. E.). The project was supported by funds partly provided by the International Cancer Research Data Bank Program of the National Cancer Institute, National Institutes of Health, Bethesda, MD, under contract N01-C0-65341 (International Cancer Research Technology Transfer) and partly by the International Union Against Cancer (O.P.F.C.).     

The effects of antibiotics on hemolytic behavior of red cells

Human blood was sheared between rotating polyethylene disks and plasma hemoglobin measured at intervals to produce kinetic hemolysis curves (KHC), plotted as free hemoglobin concentration vs time. The KHC produced by blood samples incubated in the presence of penicillin, streptomycin, gentamicin, and amikacin lie always below those for control samples, indicating a reduction in hemolysis; this reduction was greater as the drug concentration was increased. Explanations in terms of alterations in red cell structure were sought by several characterization tests of amikacin-loaded blood samples. Drug-localization studies demonstrated that significant fractions of the total dosage were associated with the red-cell membrane. Resistive pulse spectroscopy was used to show how amikacin affected cell size, deformability, and osmotic fragility; results were sensitive to storage age of the blood. In all cases, the effect of shearing was to reduce cell size, deformability, and osmotic fragility. Mechanisms for hemolytic protection by drugs are proposed.     

Biomass: Is it a useful tool in paleocommunity reconstruction?

In general, more of the biomass of the community is preserved than is its numerical abundance. Thus, the paleontologist, on the average, works with more of the community when biomass is used. Community characteristics such as taxon dominance and habitat proportions are at least as accurately derived from biomass as numerical abundance. The use of biomass is clearly more appropriate in describing energy flow and trophic proportions. Whenever possible, biomass should be used as a complement to numerical abundance in future paleoecologic reconstructions.     

Pollen flow, population composition, and the adaptive significance of distyly in Linum tenuifolium L. (Linaceae)

The function of distyly as a device promoting inter-morph pollination was proposed by Darwin over a century ago, though only recently have experimental studies been undertaken to test this hypothesis. These studies are unrealistic since they assume regular spatial distribution of morphs within a population and fail to consider intra-flower pollination in assessing distyly's effects. Pollen flow in two populations of Linum tenuifolium L. was investigated using a fluorescent-dye marker technique. One population was dimorphic and self-incompatible; the other was monomorphic and self-compatible. In both populations pollen dispersal was leptokurtic with over 75% of grains detected within 5 m from the source. Intra-flower pollinations comprised a large proportion of individual stigma loads (42% for the dimorphic form; 49% for the monomorphic form). Total stigmatic loads for the dimorphic population showed equal proportions of pin and thrum pollen on both long-style and short-style stigmas, though variation in individual loads was marked. Values ranging from 34.2 to 61.5% legitimate pollen were recorded. The irregular distribution of morphs observed at the dimorphic site will reduce the efficiency of heterostyly as a device promoting intermorph pollination. The reduction in intra-flower pollination suggests adaptive significance of this floral dimorphism in increasing the efficiency of pollen dispersal to the individual.     

Effects of DDT on photosynthetic electron flow in Secale species

Following a survey of a range of varieties of rye, mainly Secale cereale, for reaction to DDT, the mode of action of the pesticide in a susceptible variety was studied. Two sites of interaction of DDT with the photosynthetic electron transport chain were demonstrated. The first site of inhibition was on the oxidizing side of photosystem 2, between the sites of electron donation from diphenylcarbazide at pH 6.0 and pH 8.0 in Tris-washed chloroplasts. The second site of DDT inhibition was in the intermediate electron transport chain, and was demonstrated by using dichlorophenol-indophenol and phenyldiamines as electron donors in chloroplasts where electron flow from photosystem 2 was inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The sites are distinct from those characteristic of herbicides which affect photosynthetic electron flow.