卧床前后压力感受性反射机能变化的研究

许多数据表明长期失重以后立位耐力降低可能与压力感受性反射功能的改变有关。本文比较了两组被试者15天低动力卧床前后的立位耐力。以血压调节模型为基础分析了两种不同方式卧床前后单纯立位和下身负压加立位时压力感受性反射功能的改变,并用颈部加压及下身负压对中枢调节功能改变进行了观察。结果表明严格的头低位卧床后,立位耐力下降及压力感受性反射功能改变明显大于半日平卧半日倚坐者。而压力感受性反射功能的改变,特别是中枢神经系统调节功能的紊乱,是卧床后立位耐力降低的主要原因。从这种考虑为基础,作者提出了改变失重或模拟失重状态下的血液分布,调整对压力感受器的刺激,可能是预防心血管失调的有效方法。     

Absence of female-specific protein in the hemolymph of stable fly Stomoxys calcitrans (L.) (Diptera: Muscidae)

Changes, during the reproductive cycle, in fat body, hemolymph, and ovarian proteins of the stable fly Stomoxys calcitrans were characterized quantitatively and qualitatively using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Protein content of all three tissues increased after blood feeding. Fat body protein increased first, followed by hemolymph and ovarian proteins. SDS-PAGE failed to identify vitellogenin in both female hemolymph and fat body samples. No single protein or group of proteins predominated at any stage of the reproductive cycle. Comparisons between male and female stable fly hemolymph and fat body proteins failed to detect female-specific proteins. Female-specific proteins, however, were detected in the hemolymph of four other species of Diptera.     

Vitellin and vitellogenin concentrations during oögenesis in the first gonotrophic cycle of the house fly,Musca domestica

The house fly, Musca domestica, contains at least two native vitellin and two vitellogenin proteins. Both vitellins appear to have an identical vitellogenin partner. The major native vitellin has a mol. wt of 281 K Daltons, and the major native vitellogenin has a mol. wt of 283 K Daltons. These proteins are composed of three subunits with mol. wt of 48, 45 and 40 K Daltons. The relationship of the subunits to the native proteins is not known.Haemolymph vitellogenin levels are cyclical during oögenesis with no detectable amounts in previtellogenic flies and low levels in postvitellogenic flies. The highest level of vitellogenin, 10.5 μg/μl, occurred in flies with stage-7 ovaries. The vitellogenin levels during oögenesis fit a parabolic curve and the fat body vitellogenin content during oögenesis showed this same pattern.Uptake of vitellogenin into the ovary during each stage of oögenesis also fit a parabolic curve and produced a high linear correlation with haemolymph vitellogenin levels. The greatest uptake was 37 μg/stage and occurred during stage 6.     

Virus particle packaging in baculovirus and cytoplasmic polyhedrosis virus inclusion bodies

The structure of the inclusion bodies (IBs) of three multiply enveloped nuclear polyhedrosis viruses (MNPVs), one singly enveloped NPV (SNPV), two granulosis viruses (GVs) and one cytoplasmic polyhedrosis virus (CPV) were compared. A method was devised to calculate the numbers of virus particles and nucleocapsids in IBs using data from light microscopy and thin sections. The three MNPVs, from Agrotis segetum (English and Polish virus isolates) and Mamestra brassicae had similar concentrations of virus particles ranging from 17.3 to 19.6 per μm³ of IB. Plusia gamma SNPV had a higher density of 59.6 virus particles per μm³ of IB, which partly compensated for its having smaller IBs (mean volume 0.65 μm³) than the MNPVs (2.60–9.71 μm³). The English A. segetum MNPV isolate had the most nucleocapsids in each virus particle (mean, 4.04) and the largest IBs (mean volume, 9.71 μm³), giving 674 nucleocapsids per IB on average. The GVs, from A. segetum and Pieris brassicae, mainly contained one nucleocapsid per IB. P. gamma CPV IBs had a much higher density of virus particles than the baculoviruses (260 per μm³ compared with 17–60 per μm³). These data are discussed in relation to the biological properties of these viruses, and possible adaptational advantages of alternative IB designs are considered.     

Biogenic Amine-Stimulated Cyclic Adenosine-3'',5''-Monophosphate Formation in the Rat Carotid Body

The subcutaneous injection of isoprenaline, salbutamol, histamine, and adrenaline to rats, which were subsequently killed by microwave irradiation, resulted in a rapid increase in the cyclic AMP content of the carotid body. On the other hand, noradrenaline, dopamine, adenosine, and 5-hydroxytryptamine, at doses at least 100 times greater than that of isoprenaline, did not significantly alter the cyclic nucleotide content in vivo. The response to isoprenaline was dose related, with an ED50 of 15 micrograms X kg-1, and reached a peak level 1-1.5 min after injection. Incubation of intact carotid bodies with isoprenaline (10(-5) M) in vitro also resulted in a 10-fold increase in cyclic AMP content. The in vivo response to isoprenaline could be blocked stereo-selectively by propranolol, and ICI 118.551, a beta 2-selective antagonist, blocks the isoprenaline-elicited increase in cyclic AMP completely at a dose of 30 micrograms X kg-1; whereas betaxolol, a beta 1-selective antagonist, was ineffective, even at a dose of 300 micrograms X kg-1. Hypoxia (5% oxygen in 95% N2) did not result in a significant increase in the cyclic AMP content, nor did it significantly alter the isoprenaline-stimulated increase in the cyclic AMP content of the rat carotid body. These results suggest that some catecholamines may stimulate cyclic AMP formation by interacting with a beta 2-adrenoceptor in the rat carotid body.     

An observation of an association between adaptive pigmentation and thermal tolerance of fish

Replidated experiments indicate an association between thermal tolerance of juvenile bluegill sunfish and adaptive pigmentation to background color. Bluegills exposed to black backgrounds were able to survive higher temperatures longer than those exposed to blond backgrounds, when water temperatures were raised at a rate of 0.1°C/h from 24 to 36°C. Plausible explanations are considered which involve heat radiation effectiveness (by the fish) related to the black body concept, and stress associated with adaptive pigmentation.     

An unusual ultrastructural association of smooth membranes and glycogen particles: The glycogen body

Summary An electron microscope study of the epithelium of rabbit fallopian tube demonstrated a rarely described intracytoplasmic structure consisting of an array of smooth membranes associated with glycogen particles. This organelle is seen exclusively in the ciliated cells. A three-dimensional reconstruction of these glycogen bodies has been made from serial sections. The peripheral localization of the rough-surfaced membranes in continuity with intra-corpuscular smooth membranes, which have lost their granules, suggests a possible role for the rough membranes in the genesis of the smooth membranes of these glycogen bodies. The role of both the smooth and the rough membranes in glycogenesis and glycogenolysis is discussed.This investigation was made in part in the Laboratoire d'Hormonologie et de Cytologie Expérimentale, Hôpital Broca, Paris.     

Temperature-related divergence in experimental populations of Drosophila melanogaster. II. Correlation between fitness and body dimensions

From a laboratory stock of Drosophila melanogaster (Oregon), reared for more than 20 years at 18° C, a new population was derived and maintained at 28° C for 8 years. The chromosomal and cytoplasmic contribution to genetic divergence between the two populations was estimated. Six body traits and reproductive fitness were taken into account. The third chromosome is responsible for the adaptive difference for temperature between the two lines. Temperature-selected genes which control body size are located on the second and third chromosomes, although the contribution of each chromosome depends on the environment in which the flies develop. The correlation between the chromosomal and cytoplasmic contributions to different traits and fitness, changes with temperature. At 28° C the correlation between fitness and each body trait is proportional to the response to selection exhibited by each of them, but this is not true at 18° C. Body size has, therefore, an adaptive significance in relation to temperature, which is expressed only in the environment where selection occurs. Cytoplasmic genes affect almost all characters to an extent similar to that of chromosomal genes. Inter-chromosomal and nucleo-cytoplasmic interactions are present and also change with temperature. In general, genes selected in a given environment produce greater phenotypic changes in that environment than in another. The population that experienced both temperatures is fitter in both environments, suggesting that the capacity to adapt to warm temperatures depends on genes other than those which are involved in the adaptation to cold.     

Ultrastructure of Sporozoites and Zoites of Hammondia heydorni

The ultrastructure of sporozoites and zoites of Hammondia heydorni was studied in cultured bovine cells. In addition to ultrastructural features typical of coccidian parasites, H. heydorni sporozoites and zoites contain rhoptries that are located posteriorly as well as anteriorly. Also, sporozoites contain a posteriorly located crystalloid body (1.2 μm in diameter); a small crystalloid body (0.5 μm in diameter) was occasionally seen in the anterior end. Zoites resulting from the 1st division of endodyogeny contain a posteriorly located crystalloid body, which is absent in zoites formed by subsequent divisions. Zoites contain posteriorly located amylopectin granules and a relatively large anterior vacuole which is not present in sporozoites. During penetration, the host cell plasmalemma ballooned laterally around the sporozoite creating a large cavity, which later disappeared. Sporozoites and zoites undergoing cell penetration usually exhibit partially empty anterior rhoptries; no changes occur in posterior rhoptries. Lysosomes fuse with the par-asitophorous vacuole surrounding killed sporozoites but not live sporozoites.