Scientia Sinica最新文献

In this paper, we have derived an approximate "Bolus Flow" solution between two adjacent red blood cells (RBC) in a capillary, using the Galerkin method and numerical smoothing technique, and then examined in detail the effects of the ratio lambda of the diameter of the RBC to that of the capillary and those of the leakback Q in the thin lubrication layer on the Bolus Flow. Because of the simplicity of the method employed here, only a small amount of numerical calculation is involved. Furthermore, we have rectified somewhat unreasonable formulation of the boundary conditions presented previously so as to match the Bolus Flow with the flow in the lubrication layer. The results are reasonably in agreement with other theories, providing correct boundary conditions for the determination of the deformation of RBC.

Mice irradiated continuously at a low dose rate of 70 rad/day showed not only a drop of CFU-S content in the bone marrow but also an apparent functional disturbance of haemopoietic stem cells. With increase in accumulated dose of radiation, the damage of the haemopoietic microenvironment becomes evident. From the changes caused by chronical irradiation, it is believed that haemopoietic stem cells is more sensitive than haemopoietic microenvironment, and the radiation injury by hemopoiesis involves both damage of haemopoietic stem cells and microenvironment. Furthermore, in the course of recovery of hemopoietic injury, microenvironment plays as important role. In comparison of the growth curves of CFU-S from normal and irradiated bone marrow cells in irradiated recipient spleens or cultured in diffusion chambers, it is suggested that the nature of radiation damage of haemopoietic stem cells in continuous irradiation at low dose rate is mainly attributed to the deterioration of self replicative capacity of CFU-S.

Peroxidase activity of the pregerminated rice embryos collected at various stages of development has been investigated and compared with that of the embryos under the treatment of actinomycin D. Peroxidase activity gradually increases as embryo differentiation goes on, but remains more or less stable at the stage when maximum differentiation occurs. According to the investigation, the authors postulate that the peroxidase biosynthesis during rice germination is mediated by a long-lived mRNA, which is transcribed in the immature embryo at the stage of eight to nine days after anthesis. In this paper, the role of long-lived mRNA is also discussed.

The mRNA of the cytoplasmic polyhedrosis virus of silkworm Bombyx mori could be synthesized in vitro through the action of the virion associated RNA-polymerase in the presence of [3H-methyl]-methionine instead of S-adenosyl-L-methionine. The 3H-mRNA is isolated from the reaction mixture through a column of DEAE-Sephadex A-25 and digested with nuclease p1 and snake venom phosphodiesterase. The results of paper electrophoresis show that the methyl group of methionine is incorporated into the 5'-terminus of CPV mRNA. Even in the presence of S-adenosyl-L-methionine the [3H-methyl]-methionine could still function as a methyl donor for the formation of the 5'-caps of the mRNA of CPV.

Snake insulin is isolated and crystallized from the pancreas of non-venomous snake (Zaocys dhumnades dhumnades, Cantor). The crystalline form is not rhombohedral but dodecahedral. The primary structure has been determined with the aid of an LKB solid-phase sequencer. In the primary structure of snake insulin, the presence of B5 Arg, B29 Arg, B16 Phe, B25 Tyr and B18 Ile is unusual in comparison with insulins from mammals, birds and fishes. However, the snake insulin we studied is very similar to rattle snake insulin, with the exception that A15 is glutamic acid instead of glutamine and B30 is threonine instead of serine. These differences are consistent with the higher acidity of the snake insulin we studied and with the threonine and serine content in amino acid analysis. The B10 residue of the snake insulin we studied is still histidine. The formation of dodecahedral crystals of the snake insulin has been discussed in connection with the presence of this histidine.

The newly-caught stump-tailed monkeys (Macaca speciosa) with negative antibody to hepatitis A were inoculated with human hepatitis A virus. The following findings were observed in the monkeys after inoculation: (i) the elevation of activities of the serum glutamic-pyruvic transaminase, lactate dehydrogenase and its isoenzyme (LDH5), (ii) the seroconversion of antibody to hepatitis A virus. (iii) the shedding of hepatitis A antigen in feces. These findings show that the stump-tailed monkey (Macaca speciosa) is susceptible to infection of human hepatitis A virus. The virus recovered from the feces of the infected monkey, named as Hang-zhou A-1A strain of hepatitis A virus, has experienced two generations of successful transmission in monkeys.

By screening a Chinese population of 1025 unrelated persons in Beijing, three serum albumin variants were discovered, and the gene frequency of serum albumin variants of Chinese is estimated as 0.0015. These albumin variants can be distinguished electrophoretically from each other, and were named tentatively as albumin Hanzhong, albumin Changzhi and albumin LXX respectively. A polyacrylamide gel electrophoresis procedure has been developed to characterize albumin variants by determining the relative mobilities (Rm) of albumin variants in a tris-succinate buffer system.

In this article, seventy nociceptive units of dorsal horn and five preganglionic sympathetic units of spinal cord in forty-four anesthetized cats immobilized with Flaxedil were studied. The results observed were: 1. Electrophoretic administration of noradrenaline (NA) induced a remarkable depression of both evoked and spontaneous discharges of nociceptive units. Similar effects could be produced by electric stimulation of noradrenergic Al nuclei or injection of amphetamine or hand pressing of "Zusanli" (one form of acupuncture) respectively. 2. The effect of 5-hydroxytryptamine (5-HT on evoked nociceptive discharge was similar to NA, but on spontaneous discharge of nociceptive units was excitement. 3. Effects of the above-mentioned factors on the nociceptive discharges of preganglionic sympathetic neurons were similar to the nociceptive units too. 4. On the contrary, the activity of inhibited neuron by noxious stimulation was augmented by administration of NA, amphetamine, the stimulation of Al nuclei and the deep muscle. It is suggested that the noradrenergic nuclei in lower brain stem may play an important role in descending inhibitory circuits of nociceptive spinal reflex.

The NIOSH (National Institute of Occupational Safety and Health)-recommended procedure of determining quartz through X-ray diffractometry was applied to rat lungs. Using a compressed air nebulizer inside a closed chamber, 150 male Sprague-Dawley rats were exposed to monodisperse particles of quartz for varying time intervals. The rats were subsequently sacrifice by cervical dislocation and their lungs were removed for ashing inside a muffle furnace at 600 degrees C for 4 hr. The ashed materials were then filtered onto silver membranes and scanned by an /-ray diffractometer. The results, expressed in MG SiO2 were compared to standard values derived from PVC filters. The values suggested that the NIOSH method could be used by biochemists to quantify minerals and crystalline structures in organic materials.