The human EPRS locus (formerly the QARS locus): a gene encoding a class I and a class II aminoacyl-tRNA synthetase

Glutamyl-tRNA synthetase and prolyl-tRNA synthetase belong to different classes of aminoacyl-tRNA synthetases that are thought to have evolved along independent evolutionary pathways. However, both enzymes are on one polypeptide chain encoded by a single human gene, the EPRS locus, which is transcribed as one long mRNA. We report the structure of the human EPRS gene, which consists of 29 exons spread over at least 90 kb of genomic DNA. The exons, encoding the glutamyl-specific and the prolyl-specific parts of the enzyme, are each clustered in 10-kb sections located at opposite ends of the gene. These two exon clusters are separated by a long intervening DNA section with a number of exons, encoding functions that may be involved in the organization of the mammalian multienzyme synthetase complex. The upstream gene region shows structural features of a regulated gene, and preliminary experiments suggest that the gene is expressed at specific times in growth-stimulated cultured cells. We have localized the gene to the distal long arm of human chromosome 1 and to a corresponding site in mouse chromosome 1.

The P1 family: a new class of nuclear mammalian proteins related to the yeast Mcm replication proteins

Monospecific antibodies against an oligopeptide, conserved among the Mcm class of yeast replication proteins, were used to screen a human cDNA library. Eight of the isolated cDNA clones have the potential to code for sections of proteins with high sequence similarities to the yeast proteins Mcm3 and Cdc46 from Saccharomyces cerevisiae and Cdc21 from S. pombe. Our results establish a novel and highly conserved family of nuclear proteins in mammalian cells.

Membrane potential oscillations and corticothalamic connectivity in rat associational thalamic neurons in vitro

Thalamic relay neurons were recorded from the dorsolateral and lateroposterior nuclei of the rat thalamus in a superfused explant preparation. The mean membrane potential of these cells was -67 +/- 7 mV, input resistance 114 +/- 31 M omega and spike amplitude 75 +/- 6 mV. Low-threshold slow membrane potential oscillations (1-4 Hz) were present in about 46% of the neurons. They occurred either spontaneously or following a membrane potential perturbation. In a subpopulation of cells, we also observed a high-threshold membrane oscillation when cells were depolarized above -45 mV. This oscillation consisted of bursts of low-amplitude spikes interrupted by rhythmic after-hyperpolarizations. Stimulation of the corticothalamic pathway elicited prolonged inhibitory postsynaptic potentials in associational thalamic neurons. In the presence of picrotoxin, corticothalamic input evoked prominent excitatory postsynaptic responses that showed marked short-term synaptic plasticity. Our results suggest that associational thalamic neurons maintained in vitro have a strong tendency to exhibit membrane oscillations. In addition, they receive a direct excitatory cortical input that remained functional in explant preparation.

Effects of obesity and hypertension on ventricular myocytes: comparison of cells from adult SHHF/Mcc-cp and JCR:LA-cp rats

OBJECTIVE

The aim was to compare beta adrenergic receptors, cAMP production, and Ca2+ accumulation by the sarcoplasmic reticulum in ventricular cardiomyocytes from female SHHF/Mcc-cp and JCR:LA-cp rats. Whereas rats from both strains exhibit gross obesity when the animals are homozygous for the recessive "corpulent" gene, the SHHF rats, which are hypertensive, all develop heart failure during their second year of life. The normotensive JCR:LA-cp animals do not.

METHODS

beta Adrenergic receptor number, ligand affinity, isoprenaline and forskolin stimulated cyclic AMP production, and ATP dependent, phosphate supported 45Ca2+ uptake by the sarcoplasmic reticulum were compared in ventricular cardiomyocytes isolated from 6 months old obese female SHHF/Mcc-cp and obese and lean female JCR:LA-cp rats.

RESULTS

Bmax and Kd for (-)-[125iodo]-cyanopindolol (125ICYP) binding were each approximately 50% lower in SHHF/Mcc-cp v JCR:LA-cp myocytes. Cyclic AMP production in response to isoprenaline, isoprenaline plus isobutylmethylxanthine (IBMX), and forskolin plus IBMX was also significantly depressed in the SHHF/Mcc-cp cells. In addition, sarcoplasmic reticular 45Ca2+ uptake by SHHF/Mcc-cp cells was 35% lower than in lean or obese JCR:LA-cp myocytes. Isoprenaline stimulated cAMP production and sarcoplasmic reticular Ca2+ uptake by the lean JCR:LA-cp cells were comparable to that described previously for myocytes from normal Sprague-Dawley rats. By contrast, Bmax and Kd for 125ICYP binding by the JCR myocytes differed substantially from previously described results for normal Sprague-Dawley rats, whereas values for the SHHF cells did not.

CONCLUSIONS

Declines in Ca sequestration by the sarcoplasmic reticulum of ventricular cardiomyocytes from obese, hypertensive SHHF rats are not related to their obesity. However, obesity may contribute to the decline in cAMP production. This may account, in part, for the exacerbation by obesity of cardiac dysfunction in essential hypertension.

Adenosine stimulation of AMP deaminase activity in adult rat cardiac myocytes

Using an in situ assay for analyzing AMP deaminase activity in isolated adult rat ventricular myocytes, we have shown that IMP production is stimulated approximately twofold in cardiac cells incubated with 10 microM adenosine. This effect of adenosine was not blocked by the adenosine A1-receptor antagonist 8-cyclophenyl-1,3-dipropylaxanthine (0.01-1 microM) except at a concentration (100 microM) that may inhibit adenosine transport. Similarly, in situ AMP deaminase activity was not enhanced by treatment with the specific adenosine A1-receptor agonists N6-phenylisopropyl adenosine or cyclopentyladenosine, nor was it sensitive to prior treatment of cells with pertussis toxin. The nucleoside transport blockers S-4-nitrobenzyl-6-thioinosine, dipyridamole, and papaverine inhibited adenosine-induced increases in IMP production by 75-85%, suggesting an intracellular site of action. Modulation of enzyme activity via the transmethylation pathway could not be implicated since incubation of cardiac cells under conditions known to elevate intracellular S-adenosyl-L-homocysteine had no demonstrable effect on AMP deaminase. Furthermore, a direct allosteric effect of adenosine on the partially purified rat cardiac enzyme was not observed. The results indicate that intracellular adenosine modulates rat cardiac AMP deaminase by an unknown mechanism.

[The experimental studies of the effect of Forskolin on the lowering of intraocular pressure]

The effect of the domestic Forskolin on lowering the intraocular pressure (IOP) of rabbits was studied. The results showed that the Forskolin significantly lowered the normal IOP of rabbits and blocked the ocular hypertension induced by water load in rabbits (p < 0.01). The maximum decrease value of 2%, 1% and 0.5% of the Forskolin was 0.59. 0.36 and 0.19 kPa (1 kPa = 7.5 mmHg), which showed the noticeable dose-effect relationship. Topical ocular application of Forskolin lowered IOP in 1/2 hour, reached to a peak in 2-3 hours and remained significantly for 10 hours. The pupillary diameter did not change when IOP were reduced. Furthermore, the Forskolin had potent stimulative properties to adenylate cyclase (AC). The greater the ability of the Forskolin to stimulate AC, the stronger the effect of IOP lowering.

[Culture of the sheep TMJ synovial cells in vitro-notes on cellular arrangement and ultrastructural feature]

The sheep TMJ synovial cells were cultured in virtro by tissue explantation.and the phase-contrast microscopic and electron microscopic examinations were made.The synovial cells in which they were arranged in a unique manner.It is suggested that the ultrastructural characteristics of the synovial cells in vitro can serve as the basis of cell-type classification.

NMDA receptor-mediated rhythmic bursting activity in rat supraoptic nucleus neurones in vitro

1. Intracellular recordings were obtained from 112 supraoptic nucleus magnocellular neurosecretory cells (MNCs) in superfused explants of rat hypothalamus maintained in vitro. The effects of glutamate receptor agonists and antagonists were examined at 32-34 degrees C. 2. In control solutions, spontaneously active (> 5 Hz) phasic or continuous neurones showed interspike interval distributions slightly skewed toward short intervals, but did not feature pauses in the 0.4-2 s range. Current injection to alter the rate of cell discharge shifted the histograms according to the mean firing rate, but failed to induce intermittent pauses in the 0.4-2 s range. 3. Application of N-methyl-D-aspartate (NMDA) induced a mode of firing in which bimodal interspike interval distributions reflected a high incidence of clusters of short interspike intervals (0.5-1.5 s) recurring every 1-3 s. In contrast, firing evoked by application of D,L-alpha-amino-3-hydroxy-5-methyl-4-isoxalone propionic acid (AMPA) was not associated with a clustering of impulse discharge. 4. The putative endogenous excitatory amino acid transmitters L-glutamate, L-aspartate and quinolinate all mimicked the effects of NMDA. Clustered spiking responses to these agents were reversibly blocked by D,L-2-amino-5-phosphono-valerate (APV), but not by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). In contrast, the non-NMDA receptor ligands kainate and quisqualate caused CNQX-sensitive increases in firing rate, but these responses were not associated with the appearance of clustered activity. 5. When applied to cells showing negative resting potentials (< -70 mV), or to neurones hyperpolarized by current injection, responses to NMDA consisted of rhythmic (approximately 1 Hz) voltage oscillations associated with bursts of spike discharge. In the presence of TTX, NMDA could induce subthreshold voltage oscillations in the absence of action potentials. 6. Application of a voltage clamp to potentials between -75 and -55 mV during rhythmic bursting responses failed to reveal any rhythmic oscillation of the membrane current. In all cases, rhythmic bursting activity resumed upon returning to the current-clamp mode. 7. Rhythmic bursting responses to NMDA application were abolished in Mg(2+)-free solutions, suggesting that the voltage dependence of NMDA channels served to promote regenerative voltage changes throughout the cycle. The NMDA-induced current itself, however, did not appear to decrease with time, suggesting that a distinct, outward current, was necessary to initiate the repolarizing phase of each cycle.(ABSTRACT TRUNCATED AT 400 WORDS)

Rat supraoptic neurons are resistant to glutamate neurotoxicity

Magnocellular neurosecretory cells of the supraoptic nucleus (SON) are thought to be endogenously resistant to glutamate toxicity. In this study, we sought physiological and morphological evidence of this resistance in rats that received multiple peri-nuclear injections of ibotenate. In this preparation, ibotenate produced a large necrotic zone encompassing the SON but not within the nucleus itself. Extracellular recordings in vivo from 68 'spared' SON neurons from lesioned rats revealed normal patterns of electrical activity. Intracellular analysis in vitro from 13 'spared' SON neurons indicated that their intrinsic membrane properties, osmosensitivity and spontaneous synaptic activity did not differ significantly from that of controls. We conclude that SON neurons retain both a morphological and a physiological resistance to glutamate neurotoxicity.

Correlation between levels of immunoglobulins and immune complexes in plasma of C57BL/6 and C57L/J mice infected with MAIDS retrovirus

Infection with helper-free, defective MAIDS murine leukemia virus (MuLV) caused a rapid polyclonal activation of B cells in 0.75-, 2-, and 6-month-old C57L/J mice (H-2b, Fv-1n/n), similar to that in C57BL/6 mice (H-2b, Fv-1b/b), which was recognized by elevated plasma immunoglobulin concentrations. However, changes in plasma immunoglobulin levels differed in C57BL/J and C57BL/6 mice. In C57L/J mice, infection resulted in a rapid increase in plasma IgM and IgG2a, and the elevation of IgG2a persisted undiminished for 21 weeks. Levels of IgG2b also became slightly elevated, but those of IgG1 and IgG3 were not significantly affected. Plasma of 6 to 7-month-old C57BL/6 mice contained already high levels of IgM (30-40 mg/ml), which persisted undiminished in uninfected mice but decreased progressively in infected mice to 10% of the original concentration during 25 weeks of observation. In C57BL/6 mice, plasma IgG1 and IgG2b as well as IgG2a became similarly elevated after infection but also only transiently. Their levels began to decrease progressively about 10 weeks after infection and fell to far below the maximum concentration observed. The drastic loss of plasma IgM and IgGs observed in C57BL/6 mice during the later stages of MAIDS MuLV infection did not seem to be a consequence of the polyclonal activation of B cells per se but seemed to reflect additional immunological abnormalities arising in infected C57BL/6 but not C57L/J mice. In both mouse strains these changes in plasma Ig levels correlated with the formation of Ig-containing immune complexes that bound to high-affinity, protein-binding ELISA plates in the absence of antigen coating, which may represent unusual forms of self-antigen-antibody complexes.

Immune complexes that bind to ELISA plates not coated with antigen in mice infected with lactate dehydrogenase-elevating virus: relationship to IgG2a- and IgG2b-specific polyclonal activation of B cells

We have further investigated the nature of IgG-containing complexes of 150-300 kD that rapidly appear in the circulation of mice of various strains after infection with lactate dehydrogenase-elevating virus (LDV) and are recognized and quantitated by their binding in the presence of 0.05% Tween 20 to certain enzyme-linked immunosorbent assay (ELISA) plates with high protein affinity that have not been coated with protein antigen (5). These binding complexes have been found to contain primarily IgG2a or, in some mice, IgG2b. Their isotype specificity and time course of formation correlated with those of the polyclonal production of immunoglobulins in these mice, as measured by increases in total IgG2a or IgG2b in the circulation. In contrast, anti-LDV antibodies exhibited much broader isotype specificities in all mouse strains investigated. Depletion of BALB/c mice of CD4+T cells or lack of T cells in nude Swiss mice only partly reduced the polyclonal activation of B cells and the formation of ELISA plate-binding complexes, whereas anti-LDV antibody formation was completely blocked. Only a small proportion of the total IgG2a or IgG2b formed as a result of the LDV-induced polyclonal activation of B cells was recovered in plate-binding complexes, which sedimented in sucrose density gradients between 150 and 300 kD. Diverse monoclonal antibodies of different IgG isotopes did not bind to the plates at concentrations at which LDV-induced immune complexes exhibited binding activity. We suggest that the LDV-induced immune complexes do not contain anti-LDV antibodies, but are complexes of auto-antibodies and self-antigen(s). However, additional features must be responsible for the high affinity of these complexes for ELISA plates since various immune complexes formed in vitro failed to bind to the plates, and binding activity of the immune complexes formed in LDV-infected mice could not be regenerated in vitro once the complexes had been dissociated by a low pH treatment.

Phorbol esters and cyclic AMP activate AMP deaminase in adult rat cardiac myocytes

Using rapid deenergization as a probe for adenylate deaminase activity in intact adult rat cardiac myocytes, we have previously established that IMP formation is enhanced by alpha-adrenergic agonists. In the present study, the effect of adrenergic agents on adenylate deaminase was further characterized. Phenylephrine (PE)3 increased IMP production in a dose-dependent fashion with an EC50 of 8 x 10(-7) M. The response to PE was reversed within 10 min by the alpha 1-antagonist, prazosin. Likewise, adenylate deaminase was also activated in ventricular myocytes challenged with phorbol 12-myristate 13-acetate (PMA, EC50 = 5 nM); cardiac cells presented with 100 nM PMA increased IMP production from 4.4 +/- 0.5 (control) to 15.7 +/- 0.9 nmol/mg protein when subsequently deenergized. The effects of PMA and PE were attenuated 85 +/- 5% and 96 +/- 4%, respectively, by pretreatment of cells with 150 nM staurosporine, an inhibitor of protein kinase C. Furthermore, incubation of cardiac cells with 1 microM PMA for 24 h blunted the response to both PMA and phenylephrine 85-90%. Elevating cyclic AMP (cAMP) content to greater than 15 pmol/mg by treatment with forskolin or isoproterenol plus isobutylmethylxanthine also resulted in enhanced adenylate deaminase activity, but this stimulatory effect was not abolished by 24 h incubation with 5 microM PMA. Forskolin and PMA-induced increases in IMP production appeared to be additive. However, 0.5 microM isoproterenol inhibited the cellular response to phenylephrine by about 30% but did not affect PMA-stimulated adenylate deaminase activity. We conclude that both cAMP and protein kinase C stimulate adenylate deaminase, perhaps through selective activation of different isoforms. However, cAMP also exerts partial inhibition on alpha-adrenoreceptor-mediated increases in IMP production.

Functional N-Methyl-D-Aspartate and Non-N-Methyl-D-Aspartate Receptors are Expressed by Rat Supraoptic Neurosecretory Cells in vitro

Abstract A considerable amount of evidence has accumulated to support a role for excitatory glutamatergic transmission in the regulation of the hypothalamo-neurohypophysial system. Glutamate immunoreactivity has been found in axon terminals forming asymmetric synapses on to magnocellular neurosecretory cells and kynurenic acid, a broad spectrum glutamate receptor antagonist inhibits 1) spontaneous electrical activity in vivo, 2) excitatory postsynaptic potentials in hypothalamic slices, and 3) osmotically-evoked vasopressin release from hypothalamic explants. While this provides strong evidence for glutamatergic regulation of hypothalamic magnocellular neurosecretory cells, the subtypes of glutamate receptors expressed by these cells have not been defined. We have, therefore, obtained current and voltage clamp recordings from supraoptic magnocellular neurosecretory cells in vitro to investigate the functional and pharmacological properties of their glutamate receptors. Application of micromolar concentrations of L-glutamate, or of the agonists kainate, quisqualate and N-methyl-D-aspartate (NMDA), produced reversible and dose-dependent depolarizations in all cells tested. These responses were mediated by postsynaptic receptors since they persisted during chemical synaptic blockade with Ca(2 +) -free or tetrodotoxin-containing solutions. The inward current induced by NMDA showed a marked Mg(2+)-sensitive voltage dependence, and was blocked by D, L-2-amino-5-phosphonovalerate. In contrast, currents induced by kainate and quisqualate showed linear current-voltage properties and were antagonized by 6-cyano-7-nitroquinoxaline-2,3-dione. We conclude that both NMDA and non-NMDA receptors are expressed by magnocellular neurosecretory cells of the rat supraoptic nucleus.

[Study on ursodeoxycholic acid biotransformation by three strains of clostridia]

Using the improved TLC procedure, we measured the conversion rates of ursodeoxycholic acid(UDCA) from chenodeoxycholic acid (CDCA) by 3 strains of clostridia--C. perfringens HS-10, C. butyricum DL-20 and LQ-29 isolated. The orthogonal test was used to determine the optical conditions of biotransformation for HS-10. It was found that the conversion rate of UDCA by HS-10 was over 80% during 6-48 h in RCM medium containing 0.2 mmol/L CDCA. The UDCA conversion rates were still over 70% when the CDCA concentrations were as high as 0.8-1.0 mmol/L. In addition, the WW-BCP (Waste water from bean curd production) without any supplemental nutrients was preliminarily proved to be a potential inexpensive conversion medium.

[Lower respiratory tract flora in intubated patients]

200 lower respiratory tract (LRT) aspirates were taken via endotracheal intubates in 49 respiratory failure patients for quantitative bacterial cultures. 373 strains of bacteria and fungi were isolated and 63.3% were gram negative bacilli (GNB). During intubation, the isolation rate of Pseudomonas species gradually increased. In recent years, Enterobacteriaceae species, S. pneumoniae and S. aureus as LRT flora are decreasing, but Pseudomonas species, is increasing. The bacteria in aspirates with concentration higher than 10(5)CFU/ml could be considered as etiologic bacteria. Accordingly we estimated that the GNB infection rate was 81.6% and fatality rate was 15.0% in these 49 cases. Bacteriologic survey of the patients' oropharynx, respiratory instrument and the medical workers' finger skin suggested that besides the descending of oropharynx flora, environmental bacteria may also form LRT flora via endotracheal intubates.

Excitotoxic brain injury suppresses striatal high-affinity glutamate uptake in perinatal rats

In immature rodent brain, the glutamate receptor agonist N-methyl-D-aspartate (NMDA) is a potent neurotoxin. In postnatal day (PND)-7 rats, intrastriatal injection of 25 nmol of NMDA results in extensive ipsilateral forebrain injury. In this study, we examined alterations in high-affinity [3H]glutamate uptake (HAGU) in NMDA-lesioned striatum. HAGU was assayed in synaptosomes, prepared from lesioned striatum, the corresponding contralateral striatum, or unlesioned controls. Twenty-four hours after NMDA injection (25 nmol), HAGU declined 44 +/- 8% in lesioned tissue, compared with the contralateral striatum (mean +/- SEM, n = 6 assays, p less than 0.006, paired t test). Doses of 5-25 nmol of NMDA resulted in increasing suppression of HAGU (5 nmol, n = 3; 12.5 nmol, n = 3; and 25 nmol, n = 5 assays; p less than 0.01, regression analysis). The temporal evolution of HAGU suppression was biphasic. There was an early transient suppression of HAGU (-28 +/- 4% at 1 h; p less than 0.03, analysis of variance, comparing changes at 0.5, 1, 2, and 3 h after lesioning); 1 or 5 days postinjury there was sustained loss of HAGU (at 5 days, -56 +/- 11%, n = 3, p less than 0.03, paired t test, lesioned versus contralateral striata).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotoxicity and atherogenicity of cholesterol oxides

Cholesterol in the diet can readily autoxidize and be absorbed and transported in plasma lipoproteins. Cholesterol oxides can also be endogenously produced in tissues via free-radical-induced reactions. Some cholesterol oxides, notably cholestane-3 beta, 5 alpha, 6 beta-triol and 25-hydroxycholesterol, have been shown to cause injury to vascular endothelial and smooth muscle cells, to alter LDL receptor function, to enhance cholesteryl ester accumulation, to inhibit prostacyclin production, and to induce experimental atherosclerosis alone or in combination with cholesterol. An epidemiological study examining relationships between atherosclerosis and plasma levels of cholesterol oxides as independent risk factors may provide additional insights regarding the roles of cholesterol oxides in atherogenesis.

Cholesterol oxides and carcinogenesis

Experimental evidence indicates a relationship between cholesterol alpha-epoxide and skin cancer, and exposure of skin fibroblasts to ultraviolet radiation enduces formation of significant levels of this oxide. Colon cancer is also etiologically linked to cholesterol oxidation products. Higher than normal levels of cholestanetriol have been found in patients with colon cancer and also in those with precancerous disorders such as adenomatous polyps and ulcerative colitis. Higher than normal levels of cholesterol alpha-epoxide have been found in breast fluid aspirates of women with benign breast disease, with or without atypical hyperplasia of the epithelium, and this may be a factor in the increased incidence of breast cancer associated with hyperplasia. Similarly, the observed increased levels of cholesterol alpha and beta-epoxides in prostatic fluid of men with benign prostatic hypertrophy may be associated with subsequent development of prostate cancer. Cholesterol alpha-epoxide has been found to be mutagenic to fibroblasts in culture and to induce morphological transformation in hamster embryo cells and in mouse C3H cells. 25-Hydroxycholesterol and 20 alpha-hydroxycholesterol are potent suppressors of generation and proliferation of tumor-specific cytotoxic T lymphocytes. Although investigations into the role of cholesterol oxidation products in cancer are still in the early stages, evidence to date indicates a potentially significant role in the induction of some types of cancer.