In vitro effect of branched chain amino acids on the ribosomal cycle in muscles of fasted rats.

1) The effect of a single i.p injection of branched chain amino acids on ribosomal profiles of psoas muscles was studied in rats after a 48--96 hour fast. Experimental and control animals received glucose and insulin 1--2 hours before killing. 2) The ratio of polysomes to subunits and monomers decreased progressively during the fast. 3) The administration of the three branched chain amino acids together or leucine alone significantly increased the proportion of polysomes. 4) This effect was not observed in rats fed ad libitum. 5) It is suggested that the branched chain amino acids and specifically leucine may be required for the full protein anabolic response of muscles to insulin during a prolonged fast.     

Cellular distribution of polysome populations of castor bean endosperm

The distribution of polysomes in the cells of the endosperm of very young (48 hours of germination) seedlings of castor bean (Ricinus communis var. Hale) has been examined. Seedlings exposed to 100 micromolar gibberellin A(3) for periods up to 24 hours showed increased numbers of polysomes associated with endomembranes. Cytosol-derived polysomes were generally of a shorter mean length than membrane-derived polysomes. Gibberellin did not lead significantly to increased numbers of cytosol-derived polysomes, nor did it lead to enhancement of any particular size class of polysomes.     

Possible involvement of the cytoskeleton in the regulation of barley caryopsis dormancy and germination

This study was conducted on barley cv. Ars. caryopses collected at full ripeness and divided into two batches. From one batch (dormant caryopses) polysomes were isolated from embryos immediately after harvesting and after two days of germination. From the other batch (non-dormant caryopses) the same was done after eight months storage in a dry state. A low ionic strength cytoskeleton-stabilizing buffer was used for the isolation of polysomes. Four different fractions of polysomes were examined: free polysomes (FP), membrane-bound polysomes (MBP), cytoskeleton-bound polysomes (CBP) and cytoskeleton-membrane-bound polysomes (CMBP). In germs grown from non-dormant caryopses, the first two fractions (FP + MBP) made up about 78 % of the total ribosomal material, whereas in embryos of dormant, imbibed caryopses, two last fractions (CBP + CMBP) made up about 71 %. The percentage of polysomes after 48 hours of imbibition of dormant caryopses in the FP, MBP and CBP was only about 13 % (i.e., 87 % monosomes), whereas a greater proportion (19.4 %) was found in the CMBP. The highest incorporation of ³H-uridine and ¹⁴C-amino acids (after 48 hours of germination and 0.5, 3 and 6 hrs incubation with precursors) took place in trhc CMBP both in dormant and non-dormant caryopses The major amount of the two polysome fractions associated with the cytoskeleton (CBP and CMBP) and the higher activity of CMBP in protein synthesis in embryos of dormant, imbibed triticale caryopses may indicate a significant role for polysomes associated with the cytoskeleton in the control of protein synthesis in dormant and germinating caryopses.     

Translational alterations in maize leaves responding to pathogen infection, paraquat treatment, or heat shock : polysome dissociation and accumulation of a 57 kilodalton protein

Translational alterations occur in maize (Zea mays L.) leaves stressed by pathogen infection or herbicide paraquat treatment. These translational changes include: (a) dissociation of large polysomes to small polysomes, monosomes, and subunits; (b) a decreased rate of total protein synthesis; and (c) a reduced synthesis of several proteins by polysomes in vitro. The polysome dissociation was neither due to an extraction artifact nor to degradation of RNA by RNase. The protein patterns of polysomes isolated from leaves inoculated with Bipolaris maydis at 6 to 48 hours showed an increase in the intensity of a 57 kilodalton protein. When inoculated with less virulent pathogens, such as B. zeicola, Exserohilum turcicum, or Colletotrichum graminicola, the protein was accumulated in polysomes of leaves at 24 to 48 hours after inoculation. The 57 kilodalton protein was also accumulated in polysomes of maize leaves responding to heat shock or herbicide paraquat treatments. The purified 57 kilodalton protein reassociated with polysomes isolated from healthy leaves and inhibited polysomal translation in vitro. Since the 57 kilodalton protein is rapidly accumulated in maize polysomes in response to various biological and environmental stresses and may affect protein synthesis, it may be involved in translational regulation of maize leaves during stress response.     

Dynamics of the biosynthesis of components of the protein synthesizing apparatus of the rat liver at the stage of restoration of translation, inhibited by cycloheximide

The biosynthesis of proteins, ribosomal RNA and other components of the rat liver protein-synthesizing system during the reparation and subsequent activation of translation inhibited by a sublethal dose cycloheximide (CHI, 3 mg/kg) was studied. It was found that the incorporation of labeled precursors into proteins and ribosomal rRNA isolated from free and membrane-bound polysomes is repaired already 3 hours after CHI injection. 6-9 hours thereafter, the level of component labeling reaches control values, whereas the total protein biosynthesis is retarded. After 12-24 hours, marked stimulation of ribosome biosynthesis and the integration of ribosomes into polysomes are observed together with an asymmetric accumulation of excessive amounts of newly synthesized 40S subunits into polysomes 12 hours after CHI infection. The putative mechanisms of the activation of expression of the part of the genome responsible for protein and ribosomal rRNA synthesis as well as for the synthesis of other components of the protein-synthesizing system are discussed.     

Newly Synthesized mRNA Is Translated during the Initial Imbibition Phase of Germinating Maize Embryo

RNA synthesis is activated in the cells of the plant embryo very soon after the start of seed imbibition. We previously reported that mainly heterogeneous nuclear RNA is synthesized in the radicle of Zea mays embryo during the first hours of germination. The present study was undertaken in order to detect the time of appearance of the newly synthesized messenger RNA in the polysomes of germinating maize axes.

Free polysomes were prepared from embryonic axes rehydrated for 2 hours in the presence of radioactively labeled uridine. These polysomes were shown to be labeled and to contain labeled particles sedimenting, after dissociation with EDTA, in the 10S to 40S region of a sucrose gradient. The labeled polysomal RNA migrates heterogeneously in a gel with a mean size corresponding to about 16S, and 60% of these molecules are polyadenylated.

The data indicate that the newly synthesized RNA associated with the polysomes after 2 h of germination consists of messenger RNA molecules. Analysis of the polysomes prepared 0.5 and 1 h after the start of imbibition suggests that translation of the newly synthesized messenger RNA probably occurs within the 1st hour of imbibition of the isolated axis, thus well before the completion of the initial water uptake.

     

苦参碱的提取分离及对小鼠的毒性研究

采用酸性乙醇提取、乙醚萃取、硅胶柱层析分离等方法从苦参中分离到苦参碱单体.以小鼠为实验动物进行毒性测定,小鼠的死亡主要集中在48h内,48h后无小鼠的死亡现象.小鼠对苦参碱的耐受量大于30mg.k-g1,小于140mg.k-g1,致死中量LD50为64.01mg.kg-1,回归方程Y=-3.2370+4.5602X,LD50标准误差SE=6.14.适口性的测定表明,苦参碱对小鼠有较好的适口性,可以作为杀鼠剂使用.     

Experimental infection of pups with Ancylostoma caninum larvae from an abnormal host, the chicken

The migration and distribution of Ancylostoma caninum larvae in the tissues of chickens, infected orally with 1,000 larvae, were studied. Larval yield at necropsy from different organs after digestion with artificial gastric juice revealed a 62.9% recovery four hours after inoculation, followed by a sharp decline to 5.4% at 72 hours. Larvae were found in the heart within four hours, the lungs within eight hours and the liver within 12 to 18 hours but no larvae were recovered from the spleen, kidney or brain. Migration in the muscles of head, neck, thorax and abdomen was detected at 12 hours and was maximal at 36 hours. The establishment of patent infection in the definitive host was studied by feeding infected chicks to hookworm-free pups (one chick/pup) 48 hours, 7 days and 14 days after infection. The mean worm burden at necropsy was highest (15) in the pups fed with chicks 48 hours after infection and was three and nil in the other groups respectively.     

The use of oral prostaglandin E2 in the management of intrauterine fetal death

12 otherwise healthy patients with intrauterine fetal death 1 to 6 weeks earlier were treated with oral prostaglandin E₂. 9 of the 12 patients delivered within 48 hours after treatment began. 2 others delivered within 48 hours after unsuccessful treatment ceased. In a third patient the cervix relaxed after treatment, and the uterine contents were removed by curettage. No serious complications, such as hemorrhage occurred. The uterus seemed surprisingly responsive to oral prostaglandin E₂ in cases of intrauterine fetal death.     

Effect of oculomotor and trigeminal nerve section on the ultrastructure of different myoneural junctions in the rat extraocular muscles

Summary The intramuscular nerves and myoneural junctions in the rat rectus superior, medialis and inferior muscles from 10 hours to about 10 days after section of the trigeminal and oculomotor nerves were studied with the electron microscope. Two different kinds of myoneural junctions are to be observed; one type derives from myelinated nerves and is similar to the ordinary myoneural junctions (motor end plates) of other striated skeletal muscles, while the other type derives from unmyelinated nerves, is smaller in size and has many myoneural synapses distributed along a single extrafusal muscle fibre.Section of the trigeminal nerve caused no changes in the myoneural synapses. After section of the oculomotor nerve degenerative changes occur in both the myelinated and unmyelinated nerves and in both types of myoneural junctions. In the axon terminals of both the myelinated and unmyelinated nerves the earliest changes are to be observed 10 to 15 hours after section of the nerve. First, swelling of the axoplasm, fragmentation of microtubules and microfilaments and swelling of mitochondria takes place, somewhat later agglutination of the axonal vesicles and mitochondria. The axon terminals are separated from the postsynaptic muscle membrane by hypertrophied teloglial cells about 24 hours after section of the nerve. The debris of the axon terminals is usually digested by the teloglial cells within 42 to 48 hours in both types of myoneural junction.Changes in the postsynaptic membrane are observed in the myoneural junctions of the unmyelinated nerves as disappearance of the already earlier irregular infoldings, whereas no changes take place in the infoldings of the motor end plates. The postsynaptic sarcoplasm and its ribosomal content increase somewhat.The earliest changes occur along unmyelinated axons 10 to 15 hours and along myelinated axons 15 to 24 hours after nerve section. The unmyelinated axons are usually totally digested within 48 hours, whereas the myelinated axons took between 48 hours and 4 days to disappear. The degeneration, fragmentation and digestion of the myelin sheath begin between 24 and 42 hours and still continues 10 days after the operation.The results demonstrate that in the three muscles studied structures underlying the physiologically well known double innervation of the extraoccular muscles are all part of the oculomotor system.We are grateful to Professor Antti Telkkä, M. D. Head of the Electron Microscope Laboratory, University of Helsinki, for permission to use the facilities of the laboratory.     

The use of oral prostaglandin E2 in the management of intrauterine fetal death

12 otherwise healthy patients with intrauterine fetal death 1 to 6 weeks earlier were treated with oral prostaglandin E2. 9 of the 12 patients delivered within 48 hours after treatment began. 2 others delivered with 48 hours after unsuccessful treatment ceased. In a third patient the cervix relaxed after treatment, and the uterine contents were removed by curettage. No serious complications, such as hemorrhage occurred. The uterus seemed surprisingly responsive to oral prostaglandin E2 in cases of intrauterine fetal death.     

Time- and concentration-dependent production of superoxide anion, nitric oxide, DNA damage and cellular death by ricin in the J774A.1 macrophage cells

The time- and concentration-dependent effects of ricin on some biomarkers of cellular toxicity, including production of superoxide anion (O2-), nitric oxide (NO), and DNA single strand breaks (SSB), as well as cellular death, have been examined in the J774A.1 macrophage cell cultures. Various concentrations of ricin have been added to various cell cultures, and the cells were incubated for 12, 24, 36, and 48 hours. Following 12 hour incubation, ricin did not cause significant increases in any of those biomarkers. However, time- and concentration-dependent increases were observed in the induction of all the biomarkers after incubation for 24-48 hours. Approximately twofold increases in the production of O2- were observed after incubation with 1 and 10 ng/mL of ricin for 24 and 36-48 hours, respectively. The concentrations of ricin that caused approximately twofold increases in the rate of DNA-SSB are 10 and 1-10 ng/mL after 24 and 36-48 hours incubation, respectively. Approximately twofold increases in NO production were only observed after incubation of the cultures with 1-10 ng/mL of ricin for 36-48 hours. Fifty percent reductions in cellular viability were also observed with ricin concentrations of 10-100, 10, and 1-10 ng/mL, after incubation for 24, 36, and 48 hours, respectively.     

Morphological characteristics of the small intestine and translocation of intestinal microflora in the post-resuscitation period]

Morphologic investigations were studied in rats during 1-3 hours after clinical death of the acute hemorrhage. The combination of morphologic and microbiologic methods obtained allow to describe the destruction of intestine wall and translocation of bacteria in the tissue and organs. In 3 days after clinical death the structure of small intestine regenerates, but the vital bacteria were isolated in the tissues and organs.     

Synapse-specific expression of acetylcholine receptor genes and their products at original synaptic sites in rat soleus muscle fibres regenerating in the absence of innervation.

To test the hypothesis that synaptic basal lamina can induce synapse-specific expression of acetylcholine receptor (AChR) genes, we examined the levels mRNA for the alpha- and epsilon-subunits of the AChR in regenerating rat soleus muscles up to 17 days of regeneration. Following destruction of all muscle fibres and their nuclei by exposure to venom of the Australian tiger snake, new fibres regenerated within the original basal lamina sheaths. Northern blots showed that original mRNA was lost during degeneration. Early in regeneration, both alpha- and epsilon-subunit mRNAs were present throughout the muscle fibres but in situ hybridization showed them to be concentrated primarily at original synaptic sites, even when the nerve was absent during regeneration. A similar concentration was seen in denervated regenerating muscles kept active by electrical stimulation and in muscles frozen 41-44 hours after venom injection to destroy all cells in the synaptic region of the muscle. Acetylcholine-gated ion channels with properties similar to those at normal neuromuscular junctions were concentrated at original synaptic sites on denervated stimulated muscles. Taken together, these findings provide strong evidence that factors that induce the synapse-specific expression of AChR genes are stably bound to synaptic basal lamina.     

Polyribosome formation and protein synthesis in imbibed but dormant lettuce seeds

Dormancy is maintained in Grand Rapids lettuce (Lactuca sativa) seeds imbibed on water in darkness at 25 C. Polyribosome formation and protein synthesis occur early in the imbibition phase and considerable polysomal material is also present after 24 and 48 hours, even though the seeds have failed to germinate. Incorporation of labeled leucine into protein following a 24-hour preincubation period shows that these polysomes are active in protein synthesis.     

The occurrence of Strongyloides ratti in the tissues of mice after percutaneous infection

The migration of infective larvae of Strongyloides ratti has been examined in C57Bl/6 mice after percutaneous infection of the anterior abdominal wall. Lateral migration of larvae through the skin and subcutaneous tissues was not seen. Large numbers of larvae were recovered from the muscles between 2 and 24 hours after infection and larvae were seen in the cerebrospinal fluid 24 and 48 hours after infection. Insignificant numbers of larvae were seen in the blood, serosal cavities, liver, spleen, kidneys, brain or nasopharynx. Larvae arrived in the lungs between 24 and 72 hours after infection and worms were first noted in the small intestines at 48 hours. It is concluded that larvae migrate preferentially to the muscles and CSF before passing to the lungs, but the exact mode of travel is uncertain.     

Liver aldolase as a possible target for the action of N-methyl-N-nitrosourea

The effect of N-methyl-N-nitrosourea (MNU) on the activity of cytoplasmic and reversibly bound to subcellular structures liver aldolase was studied. In vitro, the activity of aldolase purified from rabbit muscles is inhibited by MNU by 70-80% relative to fructose-1,6-diphosphate and by 50-60% relative to fructose-1-phosphate. These substrates and the competitive inhibitor ATP do not protect the enzyme against the inactivation by MNU. MNU inhibits the activity of cytoplasmic aldolase by 30-40% and 20% 2-24 hours after a single injection (80 mg/kg) in vivo. The enzyme affinity for fructose-1,6-diphosphate is markedly decreased (2-fold). Activation of cytoplasmic aldolase relative to both substrates, which is especially well-pronounced with fructose-1-phosphate after inhibition of the enzyme activity, was observed. The enzyme activity relative to both substrates was found to increase in the mitochondrial and nuclear fractions within 48 hours. MNU has no effect on the activity of aldolase bound to microsomes. MNU influences the aldolase binding to organelle membranes. MNU injections at early periods (2-168 hours) accounts for the differences in the kinetic properties of cytoplasmic and reversibly bound to subcellular structures liver aldolase. These changes persist within 168 hours after MNU administration and may result in disturbances in cell metabolism as well as in the regulation of metabolic pathways, such as glycolysis and gluconeogenesis.     

Effects of combined influence of ionizing radiation and light on the retina

The continuous irradiation of rats with a light (3500 1x) for 48 hours led to destruction of 7.5 +/- 0.43% of neurosensoric cells (the control value was 0.2 +/- (0.02%). Longer photodamage caused progressing decrease in a population of the cells, narrowing followed by disappearance of corresponding layers of retina by the 30th day of the experiment. Preliminary exposure to X-rays with a dose of 5 Gy modified light damages of retina. The combination of two factors caused death of more than 30% of neurosensoric cells and redused the number of rows of nucleis of the external nuclear layer twice for the first 48 hours of illumination. After a longer influence of light a preliminary ionizing irradiation increased the number of destructively changed neurosensoric cells, reaching minimun of 41.7% by 30th day of the experiment. At the same time after a long combined irradiation less changes in row number quantity, numerical density of nucleus of the external nuclear layer and a population of neurosesoric cells in general was observed than after only one light exposure. Changes of choriocapillaries (thrombosis, obliteration, narrowing of a gap) which were more expressed at a combination of factors, led to infringement of blood circulation and played the important role in mechanisms of retina degeneration. Radial glia and neurons of internal layers of retina showed relative resistance to the investigated influences.     

Adipose, muscle and lung tissue lipoprotein lipase activities in young streptozotocin treated rats

Lipoprotein lipase (LPL) activity was studied in adipose, muscle and lung tissues of post-weanling rats 48 and 96 hours after experimentally induced diabetes by streptozotocin administration. Weight gain was reduced, and blood glucose level increased about 3-4 fold above the control level as an indication of the diabetic state. LPL activity in brown and white adipose tissues decreased in diabetic rats to 10-30% of the control level. In soleus muscle the LPL activity was slightly enhanced 96 hours after the streptozotocin injection. In cardiac muscle the LPL activity was markedly increased already 48 hours after the administration of streptozotocin and the increase remained significant until 96 hours. There was in the pulmonary tissue also an increase of LPL activity of diabetic rats, although this was significant only 96 hours after streptozotocin treatment. The results suggest marked tissue specific variation in the LPL activity. Moreover, tissue responses to experimentally induced diabetes vary. In adipose tissue the decrease in the LPL activity suggests that lipid transport to adipocytes is decreased while an increase in skeletal and cardiac muscles and in lung tissue proposes that their lipid utilization is enhanced.