Spontaneous recovery of excitation and inhibition.

In two conditioned suppression experiments with rats as subjects, the authors examined two classes of accounts of spontaneous recovery of excitation and inhibition. One view suggests that spontaneous recovery occurs due to greater temporal instability of inhibitory associations, whereas the other posits that spontaneous recovery occurs due to greater temporal instability of second-learned associations. These accounts diverge in predictions concerning spontaneous recovery when the first-learned association is inhibitory and the second-learned association is excitatory. Using different designs, Experiments 1 and 2 found spontaneous recovery of both excitation and inhibition. The results support the view that spontaneous recovery occurs due to faster waning of second-learned associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Initiation of spontaneous epileptiform activity in the neocortical slice

Cortical local circuitry is important in epileptogenesis. Voltage-sensitive dyes and fast imaging were used to visualize the initiation of spontaneous paroxysmal events in adult rat neocortical slices. Although spontaneous paroxysmal events could start from anywhere in the preparation, optical imaging revealed that all spontaneous events started at a few confined initiation foci and propagated to the whole preparation. Multielectrode recording over hundreds of spontaneous events revealed that often two or three initiation foci coexisted in each preparation (n = 10). These foci took turns being dominant; the dominant focus initiated the majority of the spontaneous paroxysmal events during that period. The dominant focus and dynamic rearrangement of foci suggest that the initiation of spontaneous epileptiform events involves a local multineuronal process, perhaps with potentiated synapses.     

关于预防硫化矿床矿石氧化自燃的措施

通过对硫化矿石自燃发生的机理分析，论述了硫化矿石氧化自燃的鉴别性指标，提卅了预防和控制硫化矿石氧化自燃的措施。     

Spontaneous cognition and HIV risk behavior.

Theories of cognitive processes and risk behavior have not usually addressed spontaneous forms of cognition that may co-occur with, or possibly influence, behavior. This study evaluated whether measures of spontaneous cognition independently predict HIV risk behavior tendencies. Whereas a trait-centered theory suggests that spontaneous cognitions are a by-product of personality, a cognitive view hypothesizes that spontaneous cognitions should predict behavior independently of personality. The results revealed that spontaneous cognition was an independent predictor of behavior tendencies in cross-sectional analyses. Its predictive effect was stronger than drug use, a frequently emphasized correlate of HIV risk behavior in the literature, and comparable with sensation seeking in magnitude. The results suggested that a relatively spontaneous form of cognition may affect HIV risk behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

DNA sequence analysis of spontaneous mutagenesis in Saccharomyces cerevisiae

To help elucidate the mechanisms involved in spontaneous mutagenesis, DNA sequencing has been applied to characterize the types of mutation whose rates are increased or decreased in mutator or antimutator strains, respectively. Increased spontaneous mutation rates point to malfunctions in genes that normally act to reduce spontaneous mutation, whereas decreased rates are associated with defects in genes whose products are necessary for spontaneous mutagenesis. In this article, we survey and discuss the mutational specificities conferred by mutator and antimutator genes in the budding yeast Saccharomyces cerevisiae. The implications of selected aspects of the data are considered with respect to the mechanisms of spontaneous mutagenesis.     

Hazelden''s model of treatment and its outcome

1. Effects of d-amphetamine on the frequency of spontaneous contraction of the longitudinal muscle of the portal vein were studied in Wistar rats. Its effects on the circular muscles of the pulmonary artery and stomach also were tested. 2. d-Amphetamine increased the frequency of the spontaneous contraction of the portal vein. The ratio of the frequency of the spontaneous contraction of the portal vein before and after d-amphetamine treatment also was increased. The effect was not affected in the presence of prazocin, (+)-lysergic acid diethylamide, atropine and haloperidol. These results that the d-amphetamine-elicited response was not due mainly to the activation of adrenergic, serotoninergic (5-HT), cholinergic or dopaminergic receptors. 3. Increasing extracellular calcium or sodium ion concentrations decreased the frequency of the spontaneous contraction of the portal vein. However, the ratios of the frequency of the spontaneous contraction of the rat portal vein before and after d-amphetamine treatment in media containing different extracellular calcium or sodium concentrations were not significantly altered. Tetrodotoxin did not alter the effect of d-amphetamine on the frequency of spontaneous contractions. It appeared that calcium and sodium ions may not take part in the effects of d-amphetamine on the frequency of the portal vein. 4. An increase in extracellular potassium ion concentrations increased the frequency of the spontaneous contractions of the portal vein. In addition, the ratios of the frequency of the spontaneous contractions of the rat portal vein before and after d-amphetamine treatment in media containing different extracellular potassium ion concentrations were significantly altered. Tetraethylammonium chloride (TEA) and 4-aminopyridine (4-AP) increased the spontaneous contractions of the portal vein. However, TEA and 4-AP did not increase the d-amphetamine-elicited increasing effect on the frequency of spontaneous muscle contractions. 5. Levochromakalim, a potassium channel opener, decreased the frequency of the spontaneous contractions of the portal vein. Levochromakalim also decreased the effect of d-amphetamine on the frequency of spontaneous contractions of the muscle. It appeared that potassium ion may be associated with the effects of d-amphetamine on the activity of the portal vein. 6. d-Amphetamine potentiated, whereas prazosin decreased, the noradrenaline-elicited contracture of the rat pulmonary artery in a dose-dependent manner. 7. d-Amphetamine elicited contracture of the circular muscle of rat stomach, whereas it did not alter the frequency of the spontaneous contraction of the muscle. 8. Both 5-HT and d-amphetamine elicited the contracture of the circular muscle of rat stomach. Ketanserin decreased the 5-HT-elicited response, whereas it did not alter the d-amphetamine-elicited response in the muscle. d-Amphetamine did not alter the frequency of the spontaneous contraction of the stomach. 9. It is concluded that d-amphetamine has different effects on the frequency of spontaneous smooth muscle contractions. It increased the frequency in the portal vein, but it did not alter the frequency in stomach circular muscle.     

Prevalence of NIDDM and impaired glucose tolerance in a rural and an urban population in Cameroon

PURPOSE: We wished to determine the effects of seizure type, age at onset, and family history of epilepsy on risk of spontaneous abortion in the pregnancies of adults with idiopathic/cryptogenic epilepsy. METHODS: We examined pregnancy outcomes in 812 adults with idiopathic/cryptogenic epilepsy who had ever had or fathered a pregnancy and 250 of their same sex siblings who had ever had or fathered a pregnancy. We compared the likelihood of spontaneous abortion before and after onset of epilepsy with the likelihood of spontaneous abortion among same sex siblings. RESULTS: Risk of spontaneous abortion was not increased before onset of epilepsy. After onset of epilepsy, risk of spontaneous abortion was significantly increased in the pregnancies of wives of men who had localization-related epilepsy with age at onset <10 years or who did not have a family history of epilepsy. In women after onset of epilepsy, risk of spontaneous abortion was significantly increased for pregnancies of women with localization-related epilepsy with age at onset < or =20 years and for those of women with or without a family history of epilepsy. Risk of spontaneous abortion was greatest in the pregnancies of women with a positive family history of epilepsy odds ratio, (OR = 2.12, p < 0.05). CONCLUSIONS: Risk of spontaneous abortion in the pregnancies of men and women with idiopathic/cryptogenic epilepsy varied with the clinical characteristics of their epilepsy. The increased risk of spontaneous abortion in women with a family history of epilepsy may influence the observed risk of epilepsy in their live-born offspring.     

黄铁矿自燃机理及其预防

在地下开采中 ,黄铁矿常温下在空气中极易发生自燃 ,产生大量的热和SO2 ,不仅给作业人员带来职业危害 ,而且可能造成严重的事故。本文通过分析黄铁矿自燃的化学反应过程 ,硫铁矿含硫量与自燃性关系 ,以及崩矿量及其允许堆放时间 ,得出了对黄铁矿自燃的一些规律性认识。在此基础上 ,提出了加强分析化验、现场管理以及粉尘检测等工作的预防对策。     

Spontaneous central nervous system remyelination in strain A mice after infection with the Daniel's (DA) strain of Theiler's virus

Intracerebral infection of susceptible SJL/J (H-2s) mice with the Daniel's strain of Theiler's murine encephalomyelitis virus produces chronic, progressive, inflammatory central nervous system demyelination, with minimal spontaneous remyelination. To assess the role of host genetic factors in spontaneous myelin repair following chronic infection with the Daniel's strain of Theiler's virus, we examined demyelination and spontaneous remyelination in strain A mice after infection with Theiler's virus. We found that A.BY/SnJ (H-2a), and A.SW/SnJ (H-2s) mice all developed chronic demyelination with substantial spontaneous remyelination 90 days after infection. In the spinal cords of both A/J and A/WySnJ mice, one quarter of the total lesion area showed spontaneous remyelination, whereas in A.SW/SnJ mice, the extent of remyelination increased to two thirds of the total lesion area. The spontaneous remyelination seen in strain A mice was consistent with myelin repair by oligodendrocytes and Schwann cells, and occurred despite the presence of persistent virus antigen. These results indicate that host-pathogen interactions play an important role in myelin regeneration after virus-induced demyelination, and suggest that host genetic factors influence spontaneous remyelination.     

Seasonal variation in spontaneous abortions

Using a national sample of hospital discharges, we found identical seasonal patterns for spontaneous abortions and conceptions but no significant seasonal variation in the rate of spontaneous abortions per 1,000 conceptions. The differences between our findings and those of previous investigators of spontaneous abortion may reflect our more comprehensive definition of spontaneous abortion, our more complete estimate of the monthly number of conceptions, and our more rigorous statistical analysis. The periodic regression analysis (PRA) reported in our study may be useful in other studies that monitor short-term trends.     

Cocaine and tobacco use and the risk of spontaneous abortion

BACKGROUND: Cigarette smoking and cocaine use may be risk factors for spontaneous abortion, but data supporting such a link are limited. METHODS: We studied the associations between cocaine and tobacco use and spontaneous abortion among pregnant adolescents and women (age range, 14 to 40 years) who sought care at an inner-city emergency department. A total of 400 adolescents and women had spontaneous abortions either at study entry or during follow-up (which lasted until 22 weeks' gestation), and 570 adolescents and women remained pregnant past 22 weeks' gestation. Cocaine use was measured at base line by self-reports and analysis of urine and hair samples. Cigarette smoking was measured by self-reports and urine analysis. RESULTS: The adolescents and women in both groups were predominantly black and of lower socioeconomic status. Among those who had spontaneous abortions, 28.9 percent used cocaine on the basis of hair analysis and 34.6 percent smoked on the basis of a urine cotinine assay, as compared with 20.5 percent and 21.8 percent, respectively, of the adolescents and women who did not have spontaneous abortions. The presence of cocaine in hair samples was independently associated with an increase in the occurrence of spontaneous abortion (odds ratio, 1.4; 95 percent confidence interval, 1.0 to 2.1) after adjustment for demographic and drug-use variables. However, the use of cocaine as measured by self-reports and by urine analysis was not. The presence of cotinine in urine was also independently associated with an increased risk of spontaneous abortion (odds ratio, 1.8; 95 percent confidence interval, 1.3 to 2.6). Twenty-four percent of the risk of spontaneous abortion could be related to cocaine or tobacco use. CONCLUSIONS: Cocaine and tobacco use were common in our study population and were associated with a significant risk of spontaneous abortion.     

Serum deprivation, but not inhibition of growth per se, induces a hypermutable state in Chinese hamster G12 cells

Spontaneous mutagenesis is thought to play a crucial role in spontaneous carcinogenesis. We recently described a new mathematical model for estimation of the spontaneous mutation rate (mutation/gene/generations) based on the assumption that mutations are fixed in the S-phase of the cell cycle. With this definition, the spontaneous mutation rate should be independent of the growth rate. In the present study, we tested this hypothesis, using cell line G12, a transgenic Chinese hamster V79 derivative, which contains a single copy of the Escherichia coli gpt gene as a target for mutagenesis. The growth rate was modulated by varying the serum concentration or the seeding density, or by addition of suramin, transforming growth factor beta, or dichlorobenzimidazole riboside to the medium. Significant increases in the spontaneous mutation rate occurred when cell proliferation was blocked by serum deprivation. Density-dependent inhibition of growth and inhibition of growth by suramin, transforming growth factor beta, or dichlorobenzimidazole riboside did not result in significant increases in spontaneous mutation rates. The level of oxidants in cells cultivated in the presence of low concentrations of serum was higher compared to control cells, suggesting that the increases in the spontaneous mutation rates under low serum conditions may be partly a result of oxidative stress due to a lack of serum antioxidants. This was shown to be the case, because spontaneous mutation rates were significantly reduced in serum-depleted cells when antioxidants were added to the medium. We suggest that during carcinogenesis, when tumors are in a prevascularized state, the spontaneous mutation rate may be elevated, and this process may contribute to the genetic instability of the tumor cells.     

Influence of spontaneous activity and visual experience on developing retinal receptive fields

BACKGROUND: The role played by early neural activity in shaping retinal functions has not yet been established. In the developing vertebrate retina, ganglion cells fire spontaneous bursts of action potentials before the onset of visual experience. This spontaneous bursting disappears shortly after birth or eye opening. In the present study, we have investigated whether the outgrowth of receptive fields in turtle retinal ganglion cells is affected by early spontaneous bursting or by early visual experience. RESULTS: Ganglion cells normally stop bursting spontaneously 2-4 weeks post-hatching, the time when receptive-field areas reach adult size. When turtles are reared in the dark, the spontaneous bursting persists. Concomitantly, receptive-field areas expand to more than twice those observed in normal adults. To test whether chronic blockade of spontaneous bursting inhibits the expansion of developing receptive-field areas, we have exposed the retina to curare, a nicotinic cholinergic antagonist, because spontaneous bursting by ganglion cells requires acetylcholine. Curare was released from Elvax, a slow-release polymer that was implanted in the eye. When spontaneous bursting was chronically blocked with curare in hatchlings, dark-induced expansion of receptive fields was abolished. Moreover, receptive fields of ganglion cells exposed to curare in hatchlings reared in normal light and dark cycles were smaller than normal. CONCLUSIONS: These results strongly suggest that early, acetylcholine-dependent spontaneous bursts of activity control the outgrowth of receptive-field areas in retinal ganglion cells. The onset of visual experience induces the disappearance of the immature spontaneous bursts, resulting in the stabilization of receptive-field areas to their mature size.     

Rhabdomyolysis after infection and taking a cold medicine in a patient who was susceptible to malignant hyperthermia

OBJECTIVE: To investigate the role of human parvovirus B19 (Parvo B19), cytomegalovirus (CMV) and human papilloma virus (HPV) viruses in the aetiopathogenesis of spontaneous abortions. STUDY DESIGN: Abortion material from 102 cases of women with spontaneous abortions were analysed for the presence of Parvo B19, CMV and HPV DNA using the polymerase chain reaction (PCR) technique. Serological assays were used for the detection of specific IgM and IgG antibodies against Parvo B19 virus and CMV in the maternal sera. RESULTS: Parvo B19 virus genome was detected in two cases of spontaneous abortion, by PCR amplification, while CMV and HPV genomes were not observed. Serological markers were indicative for Parvo B19 virus and CMV infection in ten and four cases, respectively. CONCLUSIONS: PCR is a useful method for investigating the viral contribution to the aetiopathogenesis of spontaneous abortions and for detecting the viral genome in the abortion material. This study of 102 cases of spontaneous abortion does not implicate CMV and HPV in the aetiopathogenesis of spontaneous abortion, although it indicates a possible abortional role for Parvo B19 virus.     

Functional studies of human decidua in spontaneous early pregnancy loss: effect of soluble factors and purified CD56+ lymphocytes on killing of natural killer- and lymphokine-activated killer-sensitive targets

Inappropriate leukocyte activation and disturbance of the delicate cytokine balance within the uterus during early human pregnancy may initiate spontaneous abortion. The purpose of the present study was to assess whether decidual soluble factors from women suffering sporadic spontaneous early pregnancy loss could enhance the cytotoxic activity of peripheral blood lymphocytes (PBL), and to investigate the lytic activity of endometrial granulated lymphocytes (eGL) purified from decidua against natural killer (NK)- and lymphokine-activated killer (LAK)-sensitive targets. Decidual cell culture supernatants from sporadic spontaneous abortion cases did not have any effect on PBL cytotoxic activity against the NK-sensitive target cells K562. Endometrial GL purified from decidua of spontaneous aborters were unable to lyse the LAK-sensitive target cells Raji and, in contrast with eGL from decidua of first-trimester therapeutic aborters, approximately 50% of the cases also failed to kill K562 cells. These results do not provide evidence to implicate either cell-mediated or cytokine-mediated cytolytic mechanisms in early spontaneous pregnancy loss, thus strengthening the possibility that other damaging effects are operating. Nevertheless, the deficient cytotoxic activity in a proportion of spontaneous abortion decidua merits further investigation.     

Spontaneous orbital hemorrhage in pregnant women treated with subcutaneous heparin

PURPOSE: To describe two pregnant women who developed spontaneous orbital hemorrhage following treatment with subcutaneous heparin. METHOD: Case histories and subsequent management of spontaneous orbital hemorrhage. RESULTS: Both women developed severe unilateral visual loss. CONCLUSION: In spontaneous orbital hemorrhage, anticoagulation therapy such as heparin may contribute to severe hemorrhage and visual loss.     

Iatrogenic multiple pregnancy. Higher risk than a spontaneous one?

OBJECTIVE: To determine if spontaneous and induced multiple pregnancies have similar outcomes. STUDY DESIGN: We compared the results of antepartum and intrapartum surveillance and fetal outcome in spontaneous multiple gestations (group A) with induced multiple gestations (group B) at Albert Szent-Gy?rgyi Medical University, Szeged, Hungary, in a six-year period. RESULTS: Between January 1, 1991, and December 31, 1996, there were 13,131 births; the number of multiple pregnancies was 307 (2.34%). There were 232 spontaneous and 48 induced twin pregnancies, 8 spontaneous and 16 induced triplet pregnancies, and 3 quadruplet pregnancies, all induced. Higher incidences of gestational diabetes and cervical insufficiency were found in group B. The incidences of prematurity in the induced and spontaneous groups were similar. The incidences of low birth weight and perinatal mortality were higher in induced triplet pregnancies than in spontaneous ones. Fetal outcome, with respect to Apgar score and umbilical cord blood pH, was much poorer in both induced groups. CONCLUSION: Iatrogenic multiple pregnancy following ovulation induction or assisted operative reproductive techniques may increase the incidence of pathologic events in the antepartum, intrapartum or postpartum period. Careful counseling before assisted reproductive techniques is of paramount importance.     

Decreased type IV collagen expression by human decidual tissues in spontaneous abortion

To provide some insight into the etiology of spontaneous abortion, the expression of type IV collagen was investigated in human decidual tissues obtained after spontaneous abortion (n = 17) and normal pregnancy (n = 22). Indirect immunofluorescent staining was performed for type I, III, and IV collagen as well as laminin, and Northern blot analysis was conducted to assess the expression of messenger ribonucleic acid for the alpha 1(IV) chain. Immunohistochemical analysis did not reveal any significant differences between normal pregnancy and spontaneous abortion with respect to interstitial collagens (type I and III collagen) and laminin in the decidual tissue. However, although pericellular immunostaining for type IV collagen was recognized around the decidual cells in normal pregnancy, very weak or no staining was observed in spontaneous abortion. Northern blot analysis revealed that the decidual expression of messenger ribonucleic acid for the alpha 1(IV) chain was significantly reduced in spontaneous abortion compared to that in normal pregnancy (P < 0.001). These results suggest that type IV collagen might play an important role in the maintenance of pregnancy and that decreased expression of this collagen could be associated with spontaneous abortion.     

Urodilatin, a natriuretic peptide with clinical implications

Little is known about endogenous processes causing spontaneous mutagenesis in mammalian cells. To study this problem, a mathematical model and method developed previously in our laboratory was used to measure the spontaneous mutation rate in mammalian cells at the transgenic gpt locus in Chinese hamster G12 cells. We found that spontaneous mutagenesis increased when cells were cultured in low (<0.25%) serum. These cells also contained higher oxidant levels, measured by dichloroflourescein (DCF) fluorescence, suggesting that the elevated spontaneous mutagenesis resulted from endogenous oxidants which are normally quenched by serum antioxidants. This was found to be the case. Spontaneous mutagenesis was significantly reduced in serum-depleted as well as control cells when catalase (100 ng/ml) or the antioxidants ascorbate (50 microg/ml) or mannitol (100-500 microg/ml) were added to the medium. Overexpression of metallothionein in these cells also suppressed spontaneous mutagenesis and mutagenesis induced by oxygen radical-generating compounds. Cells expressing metallothionein antisense RNA become mutators. Taken together, these results suggest that the major cause of spontaneous mutagenesis in mammalian cells is endogenously-generated oxidative DNA damage which can be blocked by metallothionein or by dietary antioxidants carried by the blood supply.