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。     

Osmotic responses of unicellular blue-green algae (cyanobacteria): changes in cell volume and intracellular solute levels in response to hyperosmotic treatment

Abstract Changes in cell volume and solute content upon hyperosmotic shock have been studied for six unicellular blue-green algae (cyanobacteria): Synechococcus PCC 6301, PCC 6311; Synechocystis PCC 6702, PCC 6714, PCC 6803 and PCC 7008. The extent of change in volume was shown to be dependent upon the solute used to establish the osmotic gradient, with cells in NaCl showing a reduced shrinkage when compared to cells in media containing added sorbitol and sucrose. Uptake of extracellular solutes during hyperosmotic shock was observed in Synechocystis PCC 6714, with maximum accumulation of external solutes in NaCl and minimum solute uptake in sucrose solutions. Conversely, solute loss from the cells (K⁺ and amino acids) was greatest in sucrose-containing media and least in NaCl. The results show that these blue-green algae do not behave as ‘ideal osmometers’ in media of high osmotic strength. It is proposed that short-term changes in plasmalemma permeability in these organisms may be due to transient membrane instability resulting from osmotic imbalance between the cell and its surrounding fluid at the onset of hyperosmotic shock.     

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.     

Trypanosoma congolense. I. Clinical observations of experimentally infected cattle

The course of disease was studied in 8 cattle infected with Trypanosoma congolense. Although the onset of patency was dependent on the numbers of infecting organisms, the duration of the infection was not. High fevers were present on the day of or the day after initial patency. Succeeding peaks of parasitemia, and a progressive weight loss of over 30% occurred. A decrease in packed cell volume (PCV) beginning the first week after infection was observed. Early in the course of the developing anemia, many polychromatophilic erythrocytes and occasional normoblasts were found in the blood. A leucopenia persisted for the duration of the disease. Total serum protein concentrations fell sharply during the first 5 weeks of infection, then gradually increased to low normal levels. Serum albumin levels followed a similar pattern for the first 5 weeks, and remained at a relatively low level. Although gamma globulin levels also declined during the first 5 weeks, their levels gradually surpassed those of preinfection samples. No marked changes in serum glucose were noted. A mild elevation of serum urea nitrogen values occurred early during infection, but subsided. The animals dying early after infection developed elevated total bilirubin levels.     

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.