Requirement for Brn-3.0 in differentiation and survival of sensory and motor neurons

Specific families of transcription factors mediate events in the sequential maturation of distinct neuronal phenotypes. Members of one such family, the class IV POU domain transcription factor Brn-3.0, and two highly related factors Brn-3.1 and Brn-3.2, are differentially expressed in the developing and mature mammalian nervous system. The expression pattern of Brn-3.0 suggested that it has an important role in the development of sensory ganglia, as well as red nucleus, inferior olive, and nucleus ambiguus. Analysis of mice null for the Brn-3.0 locus shows that Brn-3.0 is required for the survival of subpopulations of proprioceptive, mechanoreceptive and nociceptive sensory neurons, where deletion of the gene affects neurotrophin and neurotrophin-receptor gene expression. Deletion of Brn-3.0 also alters either differentiation, migration or survival of specific central neuronal populations.

Psychological long-term effects of sterilization on anxiety and depression

Two-thousand cases (500 women and 500 men with sterilization; 500 women and 500 men without sterilization) in two counties and two cities in Sichuan, China, were investigated between 15 September 1992 and 30 April 1993. Information was obtained about their age, parity, marriage, contraceptives, social behavior, and present psychological characteristics. CES-D, SAS, and E.P.Q. scales were used to assess the depressive symptomatology, anxiety, and personality of the subjects. The results revealed that sterilization psychologically affected the depressive symptoms and anxiety under the neutral personality. In addition, depressive symptoms and anxiety were related to the subjects' age, educational level, income, operative doctors' attitudes to sterilization acceptors, and subjects' understanding of the sterilization.

Effect of hypoxia on DNA synthesis and c-myc gene expression of pulmonary artery smooth muscle cells

The neonate is particularly susceptible to the development of hypoxic pulmonary hypertension. The present study was undertaken to observe the effect of hypoxia on DNA synthesis and c-myc gene expression between newborn calf and adult bovine PASMC in vitro. DNA synthesis measured by 3H-TdR incorporation was increased after hypoxic challenge for 24h. Hypoxia enhanced the increment in 3H-TdR incorporation induced by EGF. Northern blot analysis revealed that PASMC cultured in both normoxia and hypoxia expressed c-myc gene transcript of 2.2Kb, but there is a higher 2. 2Kb mRNA expression in hypoxic PASMC than that in normoxia. We speculate that newborn calf PASMC exhibited potential response to hypoxia than adult, which was augmented by EGF. Enhanced c-myc gene expression may lead to a great understanding of the mechanism of PASMC growth in the development of pulmonary hypertension.

[Expression of retroviral transmembrane envelope protein p15E in human malignant cells]

Malignant tumor growth is always accompanied with immune suppression. Tumor-derived immuno-suppressive factors, among others, are thought to be responsible, but their nature is not well defined. The paper reports on the expression of an immuno-suppressive retroviral transmembrane envelope protein p15E at different levels in human cancer cells. By using immunohistochemistry, enzyme-linked immunosorbent assay, flow cytometry and in situ hybridization, p15E expression could be demonstrated in cancers of the esophagus, nosopharynx, rectum, ovary (including malignant effusion and cell lines), stomach and breast. Enhanced expression of p15E was also observed in activated lymphocytes of cancer patients as shown by RT-PCR technique. The results indicate that p15E of tumor origin, and perhaps that from activated lymphocytes, may contribute to the immune suppression associated with malignancy.

Localization of ATP-gated ion channels in cerebellum using P2x2R subunit-specific antisera

The distribution of the P2x2 purinoceptor subunit protein, which forms ATP-gated ion channels by homo- and hetero-multimeric assembly, was examined in the adult rat and guinea-pig cerebellum using two novel antisera generated against separate 18 amino acid sequences located in the predicted extracellular domain of this subunit. These antisera, the first available for labelling the P2x2R subunit protein, were validated by selective labelling of a fusion protein containing the target amino acid sequences, and in cerebellum, by peptide specific block of immunoreactivity and by comparison with the distribution of P2x2R mRNA. P2x2R-like immunoreactivity was seen in Purkinje cells, specifically the soma and dendrites, neurons in the granular and molecular layers and deep cerebellar nuclei. The identification of P2x2R-like immunoreactivity within the cerebellar neural circuitry is consistent with a role for extracellular ATP acting as a fast neurotransmitter in motor learning and coordination of movement. Additionally, labelling of neuroglia and fibre tracts supports a diverse role for extracellular ATP in CNS homeostasis.

ATM mutations in cancer families

Ataxia-telangiectasia (A-T) is a multisystem recessive disease characterized clinically by cerebellar ataxia, oculocutaneous telangiectasias, immunodeficiency, sensitivity to radiomimetic agents, and cancer predisposition. This pleiotropic disorder is caused by mutations in the ATM (mutated in A-T) gene, which is located in the human chromosomal region 11q22-q23. The ATM gene product is a member of a novel family of large proteins implicated in the regulation of the cell cycle and response to DNA damage. Heterozygosity for A-T was previously suggested to be associated with an increased risk of tumors, particularly female breast cancer. Because of loss of constitutional heterozygosity at 11q22-q23 is a frequent event in breast and other tumors, suggesting the presence of a tumor suppressor gene(s) in this region, we screened blood DNA samples from 88 unrelated breast cancer patients of Swedish cancer families for ATM mutations using single-strand conformation polymorphism analysis. All patients had a family history of tumors previously associated with A-T heterozygosity or homozygosity. We demonstrate the first three germ-line mutations in ATM identified by screening of breast cancer patients. Two mutations were previously found in A-T homozygotes and one mutation was a 1-bp insertion. All mutations were found in families with a large number of tumors, however, they did not cosegregate with malignancies. Although the proportion of A-T carriers in this sample seems to be higher than expected by chance, larger studies and pooled data sets will be required to establish that an A-T allele confers cancer susceptibility in heterozygotes.

Effects of inefficient cleavage of the signal sequence of HIV-1 gp 120 on its association with calnexin, folding, and intracellular transport

The HIV-1 envelope glycoprotein gp120 displays inefficient intracellular transport, which is caused by its retention in the endoplasmic reticulum. Coexpression in insect cells (Sf9) of HIV-1 gp120 with calnexin has shown that their interaction was modulated by the signal sequence of HIV-1 gp120. gp120, with its natural signal sequence, showed a prolonged association with calnexin with a t1/2 of greater than 20 min. Replacement of the natural signal sequence with the signal sequence from mellitin led to a decreased time of association of gp120 with calnexin (t1/2 < 10 min). These different times of calnexin association coincided both with the folding of gp120 as measured by the ability of bind CD4 and with endoplasmic reticulum to Golgi transport as analyzed by the acquisition of partial endoglycosidase H resistance. Using a monospecific antibody to the HIV-1 gp120 natural signal peptide, we showed that calnexin associated with N-glycosylated but uncleaved gp120. Only after dissociation from calnexin was gp120 cleaved, but very inefficiently. Only the small proportion of signal-cleaved gp120 molecules acquired transport competence and were secreted. This is the first report demonstrating the effect of the signal sequence on calnexin association.

Increased expression of PDGF and c-myc genes in lungs and pulmonary arteries of pulmonary hypertensive rats induced by hypoxia

The role of growth factors and proto-oncogene in pulmonary vascular structural remodelling is not well known. The present study examined gene expression of platelet-derived growth factor (PDGF)-A and -B chain and proto-oncogene, c-myc, in lung tissue and pulmonary artery of rats exposed to hypoxia and compared to those levels of gene expression in normal rats. Normal lungs and pulmonary artery expressed PDGF-A chain transcript of 1.7 kb and PDGF-B chain transcript of 3.5 Kb. The c-myc transcript of 2.2 kb was expressed as well. After hypoxic exposure for 7 and 14 days mRNA levels of PDGF-B chain and c-myc were elevated significantly compared with those of control rats. PDGF-A chain mRNA increased after hypoxia for 7 days, and then declined. These results suggest that activation of autocrine and/or paracrine is important in proliferation mechanism of pulmonary artery smooth muscle cells in hypoxic pulmonary hypertensive rats.

Are Leydig cell steroidogenic enzymes differentially regulated with aging?

Previous studies have shown that the ability of Brown Norway rat Leydig cells to produce testosterone declines significantly with age. To address the possible mechanism(s) by which aging Leydig cells lose steroidogenic function, we determined the effect of age on the steady-state levels of the mRNAs for the steroidogenic enzymes P450 cholesterol side-chain cleavage (P450scc), delta 5-3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase (3 beta-HSD), and 17 alpha-hydroxylase/C17-20 lyase (P450(17) alpha), and on the levels of immunoreactive steroidogenic enzyme proteins and enzyme activities. Northern blot analysis revealed that the levels of P450scc and P450(17) alpha mRNAs in Leydig cells isolated from the testes of aged (22-month-old) Brown Norway rats were reduced from their levels in young (4-month-old) rats, but that 3 beta-HSD mRNA was not reduced. Western blot analysis, however, revealed that cellular levels of each of the P450scc, P450(17) alpha, and 3 beta-HSD proteins were reduced with aging. The activities of the steroidogenic enzymes, assessed by incubating Leydig cells in culture with substrate and then summing all steroidogenic reaction products through testosterone, similarly revealed that P450scc, 3 beta-HSD, P450(17) alpha, and additionally 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD), were all reduced with aging. We conclude that age-related loss of steroidogenic function results at least in part from reductions in the levels and activities of each of the steroidogenic enzymes responsible for converting cholesterol to testosterone, and not by differential regulation of these enzymes.

APPL, the Drosophila member of the APP-family, exhibits differential trafficking and processing in CNS neurons

The Drosophila Appl gene encodes a transmembrane protein that is expressed exclusively in neurons. Amino acid comparisons show that APPL protein is a member of the amyloid precursor protein (APP)-like family of proteins. Similar to mammalian APP-family proteins, APPL is synthesized as a transmembrane holoprotein and cleaved to release a large secreted amino-terminal domain. Using immunocytochemical methods, we have analyzed the distribution of APPL in the Drosophila CNS. Surprisingly, although APPL is present in all neuronal cell bodies, the neurophil shows sterotypic differential distribution. Double-labeling experiments with different neuronal markers were used to distinguish between APPL associated with neuronal processes or extracellular matrix. The distribution of APPL protein produced from transgenes encoding wild-type (APPL), secretion-defective (APPLsd), and constitutively secreted (APPLs) forms was analyzed in an Appl-deficient background to determine which APPL form is associated with different neuropil regions. We found that APPLsd protein is enriched where APPL immunoreactivity coincides with neuronal processes. In contrast, APPLs preferentially localizes to those parts of the neuropil that show a diffuse APPL signal that rarely colocalizes with processes, and thus seems to be a component of the extracellular matrix. These data indicate that proteolytic cleavage and trafficking of APPL is differentially regulated in different neuronal populations. Through metamorphosis, APPL is especially abundant in growing axons and in areas where synapses are forming. Interestingly, in adult brains, APPL protein is enriched in the mushroom bodies and to a lesser extent in the central complex, structures involved in learning and memory.

The relation between codon usage, base correlation and gene expression level in Escherichia coli and yeast

Based on the investigation of the relation between gene expression and the usage of synonymous codons, a method of classifying and predicting the gene expression level is proposed which is called the Self-consistent Information Clustering (SCIC). Using the modified Codon Adaption Index (CAI) values, we have accomplished the linear regression analysis on the relation between base composition, base correlation and gene expression level in Escherichia coli and yeast. The assumption of Expression-Enhancing-Network Site (EENS) is proposed, the existence of which can be demonstrated by the linear equations between gene expression and base correlations in a codon, in adjacent codons and in non-adjacent codons. The modes of base correlation of E. coli and yeast which are important to gene expression have been found and listed in this paper.

The ATM gene and susceptibility to breast cancer: analysis of 38 breast tumors reveals no evidence for mutation

Heterozygosity for ataxia-telangiectasia (A-T), a cancer-prone recessive syndrome, has been associated with an increased risk of breast cancer. The gene for A-T (ATM) is located at chromosomal region 11q22-q23, a region of frequent loss of constitutional heterozygosity in breast and other tumors. Loss of constitutional heterozygosity at 1lq22-q23 was found in 47% of informative cases in the series of primary tumors analyzed in this study. To investigate the role of ATM in breast cancer, we have determined the complete genomic organization of the gene, developed an exon-scanning PCR single-strand conformation polymorphism (PCR-SSCP) assay for mutation detection of ATM, and screened 38 consecutive breast tumors for mutations using both genomic DNA- and cDNA-based assays. In addition to common ATM polymorphisms detected both in the coding sequence and in flanking introns, seven unique SSCP alleles were identified in six tumor DNAs. Sequence analysis of these alleles revealed rive nucleotide substitutions that were predicted to change the encoded amino acid. However, PCR-SSCP and nucleotide sequencing analysis of the paired blood samples and of an extended sample size of a total of 224 chromosomes indicated that these SSCP patterns represent constitutional rare polymorphisms with a frequency between 0.005 and 0.023. Because the majority of A-T mutations are null mutations and none of the ATM alleles found in breast cancer samples would lead to the truncation of the translation product, we conclude that, in this initial sample of sporadic breast cancer patients, there was no evidence for an increased number of A-T carriers. In addition, because no somatic mutations were found, our study rules out the ATM gene as the frequently altered tumor suppressor gene at 11q23.

Role of transcription factors Brn-3.1 and Brn-3.2 in auditory and visual system development

The neurally expressed genes Brn-3.1 and Brn-3.2 (refs 1-6) are mammalian orthologues of the Caenorhabditis elegans unc-86 gene that constitute, with Brn-3.0 (refs 1-3,8,9), the class IV POU-domain transcription factors. Brn-3.1 and Brn-3.2 provide a means of exploring the potentially distinct biological functions of expanded gene families in neural development. The highly related members of the Brn-3 family have similar DNA-binding preferences and overlapping expression patterns in the sensory nervous system, midbrain and hindbrain, suggesting functional redundancy. Here we report that Brn-3.1 and Brn-3.2 critically modulate the terminal differentiation of distinct sensorineural cells in which they exhibit selective spatial and temporal expression patterns. Deletion of the Brn-3.2 gene causes the loss of most retinal ganglion cells, defining distinct ganglion cell populations. Mutation of Brn-3.1 results in complete deafness, owing to a failure of hair cells to appear in the inner ear, with subsequent loss of cochlear and vestibular ganglia.

A follow-up study of first trimester induced abortions at hospitals and family planning clinics in Sichuan province, China

Four-thousand women aged 18-40 underwent an early induced abortion at hospitals and family planning clinics in six counties in Sichuan province, China, between 1 July 1990 and 30 June 1991. The subjects were followed-up three times, on days 15, 90 and 180 after the operation. Information was obtained about their age, parity, contraceptive use, social behaviors, and gynecological and psychological characteristics before and after the abortion. The results indicate that induced abortion is safe when provided by medically trained personnel in health facilities such as hospitals or clinics. Depressive symptomatology was assessed by the CES-D and SCL-90 scales. The depressive symptoms declined over time. A substantial proportion of the abortions were to unmarried women or resulted from non-use of contraception or contraceptive failure, implying that the incidence of unintended pregnancies and induced abortions could be reduced by more effective and accessible contraception.

[The pharmacokinetics of pancuronium bromide in infants, children and adults]

Twenty-four patients scheduled for elective plastic surgery were selected to study the pharmacokinetics of pancuronium bromide under enflurane anesthesia. The patients were divided into three groups by their ages; Group 1 consisted of 5 infants (0.75-2.95 years); Group 2 contained 13 children (4-14 years); Group 3 included 6 adults (16-27 years). An improved fluorimetric assay was used to measure the plasma concentrations of pancuronium bromide after administration of pancuronium bromide at a dose of 100 micrograms/kg. The results showed that the disposition of pancuronium bromide may be best described mathematically by a two-compartment open model in all patients. The younger the patients, the larger the distribution volumes and the higher the Cl. There were significant differences among the three groups with regard to V1, V2, Vdss, Cl, AUC. The T1/2 beta and MRT were longer in Group 1 than in Group 2 and Group 3.

Synthesis and ligand binding of eta(6)-(2beta-carbomethoxy-3beta-phenyltropane) transition metal complexes

The transition metal complexes [eta(6)- (2beta-carbomethoxy-3beta-phenyltropane)]tricarbonylchromium (3) and [eta(6)-(2beta-carbomethoxy-3beta-phenyltropane)] [eta(5)-(pentamethylcyclopentadienyl)]ruthenium(II)triflate (4) were synthesized from 2beta-carbomethoxy-3beta-phenyltropane (2, WIN 35,065) to further elucidate the influence of substituents on the 3beta-aryl on the affinity of the ligand for cocaine-binding sites at the dopamine transporter. The compounds were tested for their ability to displace bound [(3)H]WIN 35,428 (5) from rat caudate putamen tissue and for their ability to inhibit [(3)H]dopamine uptake. The binding affinity for 3 was 2-fold greater than those observed for cocaine (1) and 2, while the binding affinity for 4 was found to be 100-fold less than those of 1 and 2. In addition, 3 was equipotent with 1 and 2 in [(3)H]dopamine uptake inhibition studies, while 4 was 10-fold less potent. The potencies of the complexes 3 and 4 correlated well with the structure-activity relationships of other 2beta-carbomethoxy-3beta-aryltropane derivatives. These data further support a pharmacophore model in which the region occupied by the aryl ring is a lipophilic pocket with electropositive character.

Effects of enflurane and isoflurane anesthesia on the pharmacokinetics of pancuronium in adult patients

OBJECTIVE

To evaluate the effects of 1 MAC of enflurane or isoflurane anesthesia on the pharmacokinetics of pancuronium.

METHODS

Eighteen adult patients undergoing the elective plastic surgery were randomly divided equally into 3 groups, namely, Group 1 (control group), Group 2 (enflurane group) and Group 3 (isoflurane group). Anesthesia was maintained with thiopental and 67% N2O-O2 in Group 1, 1 MAC enflurane in Group 2 and 1 MAC isoflurane in Group 3. After administration of a bolus of pancuronium 100 micrograms/kg, an improved fluorimetric assay was used to determine the serum concentrations of pancuronium and the pharmacokinetic variables of pancuronium were calculated with a 3P87 program.

RESULTS

The disposition of pancuronium may be well described mathematically by a two-compartment open model. The results showed that in comparison with the control group, patients in Group 2 and Group 3 had a longer T1/2 beta and MRT. The patients in Group 2 had the slower K10 and lower CL than those in the control group. There were no significant differences among the three groups in T1/2 alpha, V1, V2, Vdss, V beta, K21, K12 and AUC.

CONCLUSION

During enflurane and isoflurane anesthesia, CL of pancuronium decreased, and T1/2 beta and MRT of pancuronium were prolonged in our patients, so duration of the effective plasma concentrations of pancuronium was much longer. As a result, the effects of enflurane and isoflurane of the pharmacokinetics of pancuronium may be part of reason why two drugs extended the duration of neuromuscular depression produced by pancuronium.

Differential effects of the Rac GTPase on Purkinje cell axons and dendritic trunks and spines

Neurons contain distinct compartments including dendrites, dendritic spines, axons and synaptic terminals. The molecular mechanisms that generate and distinguish these compartments, although largely unknown, may involve the small GTPases Rac and Cdc42, which appear to regulate actin polymerization. Having shown that perturbations of Rac1 activity block the growth of axons but not dendrites of Drosophila neurons, we investigated whether this also applies to mammals by examining transgenic mice expressing constitutively active human Rac1 in Purkinje cells. We found that these mice were ataxic and had a reduction of Purkinje-cell axon terminals in the deep cerebellar nuclei, whereas the dendritic trees grew to normal height and branched extensively. Unexpectedly, the dendritic spines of Purkinje cells in developing and mature cerebella were much reduced in size but increased in number. These 'mini' spines often form supernumerary synapses. These differential effects of perturbing Rac1 activity indicate that there may be distinct mechanisms for the elaboration of axons, dendrites and dendritic spines.

Exon-scanning mutation analysis of the ATM gene in patients with ataxia-telangiectasia

Using a polymerase chain reaction single strand conformation polymorphism (PCR-SSCP) assay, which amplifies individually all coding exons of the ATM gene deficient ataxia-telangiectasia (A-T), we have analyzed 10 patients with A-T for ATM mutations. Mutation were detected in 9 patients. We describe the first ATM mutation in the splice junction found in the 5' splice site of intron 17, leading to exon skipping. However, most mutations were small deletions or insertions resulting in premature termination of the translation product. The development of DNA-based methods for detection of unknown mutations and further characterization of ATM mutation pattern will facilitate identification of A-T carriers and assessment of their cancer risk.

Small GTPases in axon outgrowth

We propose that small GTPases in the Rho/Rac/Cdc42 subfamily play a central role in signaling pathways from cell surface receptors to actin cytoskeleton changes in the growth cone. The proposal is based upon the following evidence. First, the Rho/Rac/Cdc42 subfamily GTPases have been shown to regulate various aspects of cytoskeletal organization from budding yeast to mammalian fibroblasts. Second, perturbation of GTPase activities of Rac and Cdc42 in neurons by constitutively active and dominant negative mutants results in specific defects in axon and dendrite outgrowth. In addition to reviewing existing experimental evidence, we will discuss the implications of such a model and the potential relationship with other signaling pathways.

Differential effects of pre-treatment with intrathecal or intravenous morphine on the prevention of spinal cord hyperexcitability following sciatic nerve section in the rat

The effect of intrathecal (i.t.) and intravenous (i.v.) morphine on spinal hyperexcitability following unilateral section of the sciatic nerve was studied in decerebrate, spinalized, unanesthetized rats. Sciatic nerve section evoked a biphasic, prolonged hyperexcitability of the flexor reflex. Either i.v. (0.2, 1 or 10 mg center dot kg-1) or i.t. (3 or 10 mu g) morphine was administered prior to sciatic nerve section. All doses of morphine significantly depressed the baseline flexor reflex and abolished the less intense prolonged second component of reflex hyperexcitability. One and 10, but not 0.2, mg center dot kg-1 i.v. morphine significantly depressed the first phase of spinal cord sensitization. However, both 3 mu g and 10 mu g i.t. morphine were significantly more effective than i.v. morphine in suppressing spinal cord hyperexcitability. The present results suggest that moderate doses of i.t. morphine decrease spinal hyperexcitability following nerve transection more than even extremely large i.v. doses. The poorer effect of i.v. morphine on preventing spinal hyperexcitability may be due to low spinal concentration after systemic administration.

Detection of mRNA encoding guanylate cyclase A/atrial natriuretic peptide receptor in the rat cochlea by competitive polymerase chain reaction and in situ hybridization

Expression of mRNA encoding guanylate cyclase A (GC-A)/atrial natriuretic peptide (ANP) receptor in the rat cochlea was examined by polymerase chain reaction (PCR) and in situ hybridization (ISH). After reverse-transcription, PCR amplification, subcloning, and sequencing, we found that GC-A mRNA with sequence identical to that previously cloned from the rat brain (Chinkers et al., 1989) was expressed in the rat spiral ligament as well as in the spiral ganglion. However, GC-A mRNA was not detected in the stria vascularis. Competitive PCR using internal standard DNAs indicated that the expression of GC-A in the cochlea occurred at a level approximately 16 times less than that measured in kidney cortex. ISH histochemistry using a 35S-labeled antisense riboprobe showed the highest level of expression of GC-A mRNA to be in oligodendrocytes of the cochlear nerve root. The results suggest that ANP may play a role in the cochlear nerve function.

Structural and electronic similarity but functional difference in methylmalonyl-CoA mutase between coenzyme B12 and the analog 2',5'-dideoxyadenosylcobalamin

The cofactor analog 2',5'-dideoxyadenosylcobalamin (ddAdoCbl) differs from the natural cofactor coenzyme B12 [5'-deoxyadenosylcobalamin (dAdoCbl)] by lacking only one oxygen atom. The 1H and 13C NMR spectra of ddAdoCbl have been assigned unambiguously by homonuclear and heteronuclear 2D NMR techniques. The 1H, 13C, and 31P chemical shift values for ddAdoCbl were compared with those of another organocobalamin, namely dAdoCbl. This assessment shows that the analog is very similar both electronically and structurally to the natural cofactor. The effectiveness of ddAdoCbl as a cofactor for both the human and Propionibacterium shermanii methylmalonyl-CoA mutases was compared with that of the natural cofactor. ddAdoCbl was found to be a competitive inhibitor with respect to dAdoCbl. Similar binding affinities to both enzymes were found for both the ddAdoCbl analog and the natural cofactor. However, in the presence of ddAdoCbl, the rate of conversion of methylmalonyl-CoA to succinyl-CoA was only 1-2% of that seen with the natural cofactor. There were no changes with time in the visible absorption spectrum of the bound cofactor analog in the presence of substrate, suggesting that the Co-C bond was not cleaved. The CD (circular dichroism) spectra of dAdoCbl and ddAdoCbl are very similar, consistent with the NMR results. The CD spectral changes upon binding to P. shermanii methylmalonyl-CoA mutase are large compared to those reported on the binding of dAdoCbl to ethanolamine ammonia lyase. Furthermore, the CD spectra of both enzyme-bound cobalamins are very similar, suggesting that similar changes in the conformation or structure in these cobalamins occur on binding to the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of non-NMDA glutamate receptor mRNAs in the developing rat cochlea

In situ hybridization was used to document the distribution of mRNA encoding six subunit isoforms of non-N-methyl D-aspartic acid (NMDA) glutamate receptors (GluR1, GluR2, GluR3, GluR4, GluR5 and GluR6) in the inner ears of embryonic, postnatal and adult rats. GluR2 and GluR3 expression in the spiral ganglion appeared well before birth, and reached adult levels several days before the onset of function in the cochlea. In the spiral limbus, expression of GluR2 and GluR3 mRNA reached very high levels at around the time of birth, then declined after a few days. Low levels of GluR1, GluR4 and GluR6 expression were detected in various tissues of the cochlea during development. In the adult cochlea, GluR expression was limited to GluR2 and GluR3 mRNAs in the spiral ganglion neurons and GluR2 mRNA in fibrocytes of the spiral limbus, a non-neural tissue. The ontogenetic expression of additional GluR subunit genes and their appearance in different cochlear tissues could reflect different roles for these genes during development, or less precise regulation of gene expression within the GluR family. In particular, the very high levels of GluR gene expression in the spiral limbus during the perinatal period support a non-neural function, perhaps as cell surface receptors during tissue differentiation.

CDC42 and Rac1 control different actin-dependent processes in the Drosophila wing disc epithelium

Cdc42 and Rac1 are members of the rho family of small guanosinetriphosphatases and are required for a diverse set of cytoskeleton-membrane interactions in different cell types. Here we show that these two proteins contribute differently to the organization of epithelial cells in the Drosophila wing imaginal disc. Drac1 is required to assemble actin at adherens junctions. Failure of adherens junction actin assembly in Drac1 dominant-negative mutants is associated with increased cell death. Dcdc42, on the other hand, is required for processes that involve polarized cell shape changes during both pupal and larval development. In the third larval instar, Dcdc42 is required for apico-basal epithelial elongation. Whereas normal wing disc epithelial cells increase in height more than twofold during the third instar, cells that express a dominant-negative version of Dcdc42 remain short and are abnormally shaped. Dcdc42 localizes to both apical and basal regions of the cell during these events, and mediates elongation, at least in part, by effecting a reorganization of the basal actin cytoskeleton. These observations suggest that a common cdc42-based mechanism may govern polarized cell shape changes in a wide variety of cell types.

Effect of administration of high dose intrathecal clonidine or morphine prior to sciatic nerve section on c-Fos expression in rat lumbar spinal cord

The effects of moderate and high intrathecal doses of clonidine, an alpha 2 adrenoceptor agonist, or a high dose of morphine on sciatic nerve section-induced expression of c-Fos-like immunoreactivity was studied in laminae I and II of the dorsal horn and laminae VIII and IX of the ventral horn of rat lumbar spinal cord. c-Fos-like immunoreactivity was examined by immunohistochemistry in normal rats (group 1), rats implanted with an intrathecal catheter with its tip on the lumbar spinal cord (group 2), injected with 10 micrograms (group 3) or 50 micrograms (group 4) clonidine intrathecally 3 h before being killed. In other groups, saline, 10 or 50 micrograms clonidine or 30 micrograms morphine was injected 1 h before unilateral nerve section, and the expression of c-Fos-like immunoreactivity was examined 2 h after axotomy. Few labeled neurons were found in normal controls. The intrathecal catheter itself caused a significant increase in bilateral c-Fos-like immunoreactivity in spinal dorsal and ventral horn compared to normals. The level of c-Fos-like immunoreactivity after 10 or 50 micrograms intrathecal clonidine was similar as in the intrathecal catheter group. Sciatic nerve section caused a significant ipsilateral increase in c-Fos-like immunoreactivity in the dorsal horn compared to the intact side in rats injected with saline. Pretreatment with 10 or 10 micrograms clonidine did not reduce sciatic nerve section-induced expression of c-Fos-like immunoreactivity, but instead caused a significant bilateral increase in c-Fos-like immunoreactivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Mouse mammary hyperplasias and neoplasias exhibit different patterns of cyclins D1 and D2 binding to cdk4

Deregulated expression of G1 cyclins D1 and D2 is a feature of some neoplasias. This study examined the altered expression of D1 and D2 cyclins, both the total pool and as associated with cdk4 and cdk2, at different stages of mouse mammary tumorigenesis. Three different mammary hyperplastic outgrowth lines, TM2, TM10 and TM12, and their respective tumors were examined. Increasing levels of the cyclin D1 protein pool, D1 binding to cdk4 and cdk2 and cdk4 kinase activity were closely correlated with tumorigenesis. In constrast, cyclin D2 binding to cdk4 was predominant in hyperplasias and much less in tumors, where cyclin D1 became predominant. However, the cyclin D2 pool showed increases of 15-65 times in hyperplasias compared with normal gland and further increases of 11-15 times in two of three different tumors. The message level for cyclin D1 increased only 2-3 times in tumors compared with normal gland. Cyclin D2 mRNA was highest in normal tissue and decreased only marginally in tumors. These results suggest that cyclin D2 functions uniquely from cyclin D1 in the early stages of mouse mammary tumor development. Cyclin D2 bound to cdk4 may act to guarantee a low level of kinase activity in hyperplasias and may be an attempt to direct the mammary epithelial cells through differentiation rather than proliferation. This interaction may be one of the negative regulatory mechanisms in the early stages in mouse mammary tumor development, until cyclin D1 totally replaces cyclin D2 binding to cdk4, which would activate the high levels of cdk4 kinase activity observed in neoplasias.

Disassembly of the Mu transposase tetramer by the ClpX chaperone

Mu transposition is promoted by an extremely stable complex containing a tetramer of the transposase (MuA) bound to the recombining DNA. Here we purify the Escherichia coli ClpX protein, a member of a family of multimeric ATPases present in prokaryotes and eukaryotes (the Clp family), on the basis of its ability to remove the transposase from the DNA after recombination. Previously, ClpX has been shown to function with the ClpP peptidase in protein turnover. However, neither ClpP nor any other protease is required for disassembly of the transposase. The released MuA is not modified extensively, degraded, or irreversibly denatured, and is able to perform another round of recombination in vitro. We conclude that ClpX catalyzes the ATP-dependent release of MuA by promoting a transient conformational change in the protein and, therefore, can be considered a molecular chaperone. ClpX is important at the transition between the recombination and DNA replication steps of transposition in vitro; this function probably corresponds to the essential contribution of ClpX for Mu growth. Deletion analysis reveals that the sequence at the carboxyl terminus of MuA is important for disassembly by ClpX and can target MuA for degradation by ClpXP in vitro. These data contribute to the emerging picture that members of the Clp family are chaperones specifically suited for disaggregating proteins and are able to function with or without a collaborating protease.

[Effects of gu chi san on cultured human gingival fibroblasts]

The present study demonstrates that Gu Chi San is able to increase the bone density in the clinical and animal tests. This study finds that Gu Chi San has no cytotoxicity on HGFs, and 1g/L Gu Chi San extracts can stimulate the mitosis and enhance the DNA synthesis of HGFs. The results indicate that certain substances are present in Gu Chi San.

[Relationship between chlamydial infection in female genital tract and tubal infertility]

OBJECTIVE

To detect the incidence of chlamydial infection in female genital tract and it's relationship with tubal infertility.

METHODS

Fourty-eight infertile women underwent laparoscopies were divided into study group (n = 32) and control group (n = 16). Samples were taken from the upper genital tract (including endometrium, tubal fimbriae, peritoneal fluid and pelvic adhesion) and lower genital tract (cervix). The monoclonal direct immunofluorescent method was used to assay chlamydia trachomatis the results of these two groups were compared.

RESULTS

The positive percentage of cervical clamydial infections between the two groups were not significant lydifferent (P > 0.05). But there showed a significant difference between the two groups if compared by the incidence of the whole genital tract 32.5% and 10.2% (P < 0.01). The tubal positive percentage is 66.7% in the study group. Which is the highest among other locations such as cervix, endometrium, etc (P < 0.05).

CONCLUSION

This study indicates that fallopian tube is a high prevalent site of chlamydial infection, and chlamydial infection in female genital tract is a principal pathogenic factor of tubal infertility. Early laparoscopy for tubal infertility and chlamydia trachomatis sampling is the key method for early diagnosis and treatment of chlamydia trachomatis.

Fuzzy classification of nucleotide sequences and bacterial evolution

A new method for reconstructing evolutionary relationship among bacteria by use of rRNA sequence data is proposed. The method is based on the concept of fuzzy classification of probabilities p(i), p(i/j) and p(i/j*) (i = A, G, C, U) of each sequence. The resulting partition tree shares common features of previous works but has some new peculiarities.

Thyrotropin-releasing hormone and c-fos/c-jun genes are colocalized in rat anterior pituitary cells: stimulation of transcription by glucocorticoids

We recently reported that glucocorticoids (GC) enhance the level of TRH peptide and messenger RNA in anterior pituitary cells. However, the regulating mechanism is as yet unclear. The protooncogenes c-fos/c-jun belong to the class of immediate early genes that are activated in neurons by a variety of stimuli, including GC. Fos protein acts as an intracellular third messenger, regulating gene transcription of neurotransmitters. To determine whether c-fos/c-jun are involved in regulating the effect of GC on TRH in rat anterior pituitary cells, the coexpression and nuclear transcription activity of TRH and c-fos/c-jun after dexamethasone (DEX) stimulation (7 days) were investigated. The double labeled in situ hybridization results demonstrated that TRH and c-fos/c-jun are coexpressed in anterior pituitary cells and that DEX (10(-8) M) enhanced the cell intensity for TRH and c-fos/c-jun. The mean cell intensity of treatment vs. control was 2.4-fold for TRH, 1.4-fold for c-fos, and 1.4-fold for c-jun (n = 24; P < 0.01). The Northern blot analysis also showed that DEX increased the messenger RNA level of TRH 5.1-fold (n = 4; P < 0.01), that of c-fos 1.8-fold (n = 5; P < 0.01), and that of c-jun 4.2-fold (n = 4; P < 0.01). The nuclear run-on analysis indicated that DEX increased the nuclear transcription activity of TRH 3.3-fold, that of c-jun 3.2-fold, and that of c-fos 3-fold (n = 3; P < 0.01) vs. the control value. The coexpression of TRH and c-fos/c-jun in anterior pituitary cells as well as the enhancement of transcription after DEX treatment raise the possibility that c-fos/c-jun could mediate the effect of GC on TRH gene transcriptional activity.

Children's development effecting blood oxygen desaturation following apnea

One hundred and fifty-six children aged from 4 months to 12 years undergoing elective plastic surgery were included in this study. All children were ASA physical status I, under normal development, ranging from 64 to 140 cm in body height and from 6.0 to 41.0 kg in body weight. Following 2-minute preoxygenation, the time when SpO2 dropped to 95% and 90% in apneic period had a close correlation with age, weight and height of children by means of linear and non-linear regression analysis. The smaller the children's weight, the higher the incidence of severe arterial desaturation after reinstitution of manual ventilation with 100% oxygen at SpO2 of 90%. It is suggested that younger children are more susceptible to hypoxemia than older ones during apnea and provided no problem existing other than oxygen delivery, an SpO2 of 95% might be the safe limitation of apnea in pediatric anesthesia induction.

Expression of acidic FGF mRNA in rat auditory brainstem during postnatal maturation

In situ hybridization was used to investigate the mRNA distribution of acidic and basic fibroblast growth factor (aFGF and bFGF) in the auditory brainstem of neonatal and adult rats. bFGF mRNA was not detected at any age. In adult rats, aFGF mRNA was strongly expressed in the principal neurons of the anteroventral and posteroventral cochlear nuclei, but not in the octopus cells. In the dorsal cochlear nucleus, aFGF mRNA was seen only in scattered smaller vertical cells. aFGF was strongly expressed in the nucleus of the trapezoid body and in all periolivary cell groups, but not in the medial and lateral olivary nuclei. No expression was observed in the lemniscal nuclei or in the central nucleus of the inferior colliculus, but large neurons in the external zone of the colliculus were labeled. Developmentally, low levels of aFGF expression appeared in the cochlear nuclei and olivary nuclei between P0 and P6. This expression increased rapidly during the onset of hearing, between P10 and P14, and reached adult level by P14-P17. Labeling in collicular neurons appeared slightly later. The results suggest that the appearance of strong aFGF mRNA expression is related to the onset of function.

The maximum information principle and the evolution of nucleotide sequences

The probability distributions of bases in nucleotide sequences are deduced from the maximum information principle by maximizing the entropy (due to random mutation of bases) under certain constraints (Markovian entropy, G + C content, etc, due to selection). Two formulations are given with respect to different selective constraints. The deviations of theoretical distributions from experimental data are lower than 10% for most sequences. It is shown that the Lagrange multipliers change from species to species systematically--i.e. selective constraints correlate with evolution.

The effects of pretreatment with tachykinin antagonists and galanin on the development of spinal cord hyperexcitability following sciatic nerve section in the rat

The effects of acute section of the sciatic nerve on the excitability of the flexor reflex was examined in decerebrate, spinalized, unanaesthetized rats. In control experiments without drugs, the excitability of the flexor reflex was dramatically increased in two phases following axotomy. An early intense, brief reflex hyperexcitability was followed by a less intense, prolonged period of facilitation. The selective NK1 tachykinin receptor antagonist CP-96,345 injected intrathecally at lower (1.2-2.4 nmol) and higher (12 nmol) doses blocked both components of spinal sensitization. The selective NK2 tachykinin receptor antagonist Men 10376 at a dose of 2.4 nmol also reduced both response components, as did the same dose of the inhibitory neuropeptide galanin. Thus, antagonists of excitatory neuropeptides released during and after nerve section, such as substance P and neurokinin A, can block the spinal response to peripheral nerve injury. Furthermore, the inhibitory neuropeptide galanin also reduced spinal cord sensitization.

[Enhancing effects of the supernatant of pulmonary alveolar macrophages stimulated by BCG on proliferation on pulmonary fibroblasts]

The supernatant of pulmonary alveolar macrophages (PAM) stimulated by 7.5-60mg/L of BCG could significantly enhance proliferation of pulmonary fibroblasts (PFB), and the supernatant contained high level of TNF. This result indicated BCG could stimulate PAM to produce TNF in vitro. On the other hand, the supernatant of PAM stimulated by 50mg/L of SiO2 could also enhance proliferation of PFB, but the level of TNF in the supernatant was very low and it demonstrated the ingredient in the supernatant enhancing proliferation was not TNF. TNF showed synergistic effect with this ingredient for enhancing proliferation of PFB. Therefore, TNF produced by tuberculosis bacteria-stimulated PAM might be an important factor enhancing the development of fibrosis of silicotuberculosis.

Induced abortion among unmarried women in Sichuan province, China

This report describes the social and demographic characteristics of 457 unmarried women who underwent a first trimester induced abortion at hospitals and family planning clinics in Sichuan province, China. The data show a very low level of medical complications. However, improved access to contraception for unmarried women is needed in order to reduce the incidence of unintended pregnancies and induced abortion.

Genes encoding the group I intron-containing tRNA(Leu) and subunit L of NADH dehydrogenase from the cyanobacterium Synechococcus PCC 6301

A part of the tRNA(Leu)(UAA) gene containing a 240-nucleotide group I intron was amplified by PCR from cyanobacterium Synechococcus PCC 6301 genomic DNA. The pre-tRNA synthesized from the cloned PCR product was efficiently self-spliced in vitro under physiological conditions. The gene encoding the tRNA(Leu)(UAA), trnL-UAA, was isolated from a Synechococcus PCC 6301 genomic library and the nucleotide sequence of a 2,167-bp portion was determined. The trnL-UAA consists of a 34-bp 5' exon, a 240-bp group I intron and a 50-bp 3' exon. In addition, three open reading frames (ORF1, ORF2 and ORF3) were found in the 5' and 3' flanking regions of trnL-UAA. The predicted protein sequence of ORF3, which is located 74-bp upstream from trnL-UAA on the opposite strand, shows 66.2% amino acid identity to that of the Synechocystis PCC 6803 gene encoding subunit L of NADH dehydrogenase (ndhL).

Mapping of functional domains for HIV-2 gag assembly into virus-like particles

The human immunodeficiency virus type 2 gag precursor protein, pr41, self assembles as virus-like particles (VLP) when the gag gene is expressed in insect cells. To map the functional domains for HIV-2 gag VLP formation, a series of deletion mutants was constructed by removing sequentially the C-terminal region of HIV-2 gag precursor protein and expressing the truncated gag genes in SF9 insect cells by means of recombinant baculoviruses. We found that deletion of up to 143 amino acids at the C-terminus of HIV-2 gag, leaving 376 amino acids at the N-terminus of the protein, did not prevent VLP formation. However, an additional four amino acids deletion from the C-terminus, which represents 372 amino acids at the N-terminus, made gag protein fail to form VLP. There is a proline-rich region at amino acid positions 372 and 377 of HIV-2 gag. To analyze the role of these proline residues, we generated five mutants in which proline was changed sequentially into leucine. Our results showed that replacement of one or two prolines did not stop gag VLP formation, whereas replacement of all three prolines by leucine residues completely abolished VLP assembly. Our data demonstrate that the C-terminal p12 region of HIV-2 gag precursor protein and the zinc finger domain are dispensable for gag VLP assembly, but the presence of at least one of the three proline residues located between amino acid positions 372 and 377 of HIV-2NIH-Z is required.

Toward functional magnetic stimulation (FMS) theory and experiment

This paper examines the use of magnetic fields to functionally stimulate peripheral nerves. All electric fields are induced via a changing magnetic field whose flux is entirely confined within a closed magnetic circuit. Induced electric fields are simulated using a nonlinear boundary element solver. The induced fields are solved using duality theory. The accuracy of these predictions is verified by saline bath experiments. Next, the theory is applied to the stimulation of nerves using small, partially occluded ferrite and laminated vanadium permendur cores. Experiments demonstrate the successful stimulation of peripheral nerves in the African bullfrog with 11 mA, 153 mV excitations. These results offer a new vista of possibilities in the area of functional nerve stimulation. Unlike functional electric stimulation (FES), FMS does not involve any half cell reactions, and thus would not have the commensurate FES restrictions regarding balanced biphasic stimulation, strength duration balances, and oxidation issues, always exercising care that the electrodes remain in the reversible operating regime.

Complete transposition requires four active monomers in the mu transposase tetramer

A tetramer of Mu transposase (MuA) cleaves and joins multiple DNA strands to promote transposition. Derivatives of MuA altered at two acidic residues that are conserved among transposases and retroviral integrases form tetramers but are defective in both cleavage and joining. These mutant proteins were used to analyze the contribution of individual monomers to the activity of the tetramer. The performance of different protein combinations demonstrates that not all monomers need to be catalytically competent for the complex to promote an individual cleavage or joining reaction. Furthermore, the results indicate that each pair of essential residues is probably donated to the active complex by a single monomer. Although stable, tetramers composed of a mixture of mutant and wild-type MuA generate products cleaved at only one end and with only one end joined to the target DNA. The abundance of these abortive products and the ratios of the two proteins in complexes stalled at different steps indicate that the complete reaction requires the activity of all four monomers. Thus, each subunit of MuA appears to use the conserved acidic amino acids to promote one DNA cleavage or one DNA joining reaction.

Control of expression, glycosylation, and secretion of HIV-1 gp120 by homologous and heterologous signal sequences

The HIV-1 gp120 signal sequence of 30 amino acids is longer than most glycoprotein signal sequences and contains an average of 5 positively charged amino acids. The HIV-1 gp120 gene with its natural signal sequence expressed in any prokaryotic or eukaryotic expression systems showed extremely low levels of synthesis and secretion. However, deletion of the HIV-1 gp120 signal sequence results in production of large quantities of a nonglycosylated form of gp120 in Spodoptera frugiperda cells. Substitution of the gp120 natural signal sequences with the signal sequences from honeybee mellitin or murine interleukin 3 promotes a high level of expression of a glycosylated form of gp120 and efficient secretion. These heterologous signal sequences contain one (mellitin) or no (IL-3) positively charged amino acids and led us to investigate the role of the positively charged amino acids in the signal sequence of HIV-1 gp120. Four charge-altered forms of the gp120 signal sequence of HIV-1 were constructed by site-directed mutagenesis in which the positively charged amino acids were sequentially substituted with neutral amino acids. The results of these experiments showed that the expression and secretion of gp120 was progressively increased by eliminating the positively charged amino acids in a stepwise fashion. However, the substitution of all positively charged amino acids resulted in the accumulation of nonglycosylated gp120 within the cells with decreased amounts of the glycosylated form of gp120. These results demonstrate that the positively charged amino acids in the signal sequence of HIV-1 gp120 are key factors in determining its poor expression and secretion. Analyses of intracellular transport and folding of gp120 further indicate that the presence of a highly charged, uncleaved signal sequence is an important factor limiting transport of gp120 from the rough ER to the Golgi apparatus.

Distinct morphogenetic functions of similar small GTPases: Drosophila Drac1 is involved in axonal outgrowth and myoblast fusion

The small GTPases of the Rac/Rho/Cdc42 subfamily are implicated in actin cytoskeleton-membrane interaction in mammalian cells and budding yeast. The in vivo functions of these GTPases in multicellular organisms are not known. We have cloned Drosophila homologs of rac and CDC42, Drac1, and Dcdc42. They share 70% amino acid sequence identity with each other, and both are highly expressed in the nervous system and mesoderm during neuronal and muscle differentiation, respectively. We expressed putative constitutively active and dominant-negative Drac1 proteins in these tissues. When expressed in neurons, Drac1 mutant proteins cause axon outgrowth defects in peripheral neurons without affecting dendrites. When expressed in muscle precursors, they cause complete failure of, or abnormality in, myoblast fusion. Expressions of analogous mutant Dcdc42 proteins cause qualitatively distinct morphological defects, suggesting that similar GTPases in the same subfamily have unique roles in morphogenesis.

The spinal analgesic role of alpha 2-adrenoceptor subtypes in rats after peripheral nerve section

Two putative agonists of subtypes of alpha 2-adrenoceptors, guanfacine (alpha 2A) and ST-91 ([2,6-dicthylphenylamino]-2-imidazoline, alpha 2C), were applied intrathecally and their effects on autotomy behaviour and on the flexor reflex before and after sciatic nerve section were examined. Neither drug influenced autotomy during a 17-day observation period. Both drugs dose dependently depressed the flexor reflex in rats with intact sciatic nerves. After axotomy, the sensitivity of the flexor reflex to guanfacine and ST-91 was moderately increased compared to normals. ST-91 i.t. at high doses evoked motor discharges, an effect which was reversed by the alpha 1-adrenoceptor antagonist, WB4101 (2-[2,6-dimethyoxyphenoxyethyl]-aminomethyl-1,4-benzodioxane). Thus, the effect of i.t. clonidine on the flexor reflex and autotomy behaviour observed previously may not involve its action on alpha 2A- and alpha 2C-adrenoceptors. Furthermore, due to its motor effect which may involve activation of alpha 1-adrenoceptors, ST-91 may not be a suitable tool to study the physiological function of spinal alpha 2C-adrenoceptors.

The effects of intrathecal morphine and clonidine on the prevention and reversal of spinal cord hyperexcitability following sciatic nerve section in the rat

We have previously shown that intrathecal (i.t.) morphine, but not the alpha 2-adrenoreceptor agonist clonidine, administered prior to sciatic nerve section, reduced the level of autotomy in rats, which is a behavioural model of neuropathic pain. Neither drug was effective when administered 15 min after nerve section. We now examined the effects of i.t. morphine and clonidine on the development of flexor reflex hyperexcitability following sciatic nerve section in acute physiological experiments. The flexor reflex was recorded from the hamstring muscles in decerebrate, spinalized, unanesthetized rats. The effect of sciatic nerve section on the flexor reflex without drugs was compared with axotomy performed 60 min after i.t. injection of 3 micrograms or 30 micrograms morphine, as well as 50 micrograms clonidine. The effect of these drugs on reversing reflex hyperexcitability was also examined. Both doses of morphine administered prior to sciatic nerve section profoundly depressed the baseline reflex and the higher dose almost completely abolished reflex hyperexcitability following nerve section. In contrast, clonidine pre-administration was less effective in depressing the baseline reflex and blocked reflex hyperexcitability less than morphine. Both morphine and clonidine administered 15 min after nerve section reversed spinal hyperexcitability. Thus, the ability of morphine to prevent the occurrence of autotomy may be related to its effectiveness in blocking axotomy-induced hyperexcitability. These physiological data suggest that even a short period of spinal cord hyperexcitability following nerve injury may lead to the development of neuropathic pain.

Identification of residues in the Mu transposase essential for catalysis

A tetramer of Mu transposase (MuA) cleaves the phage Mu DNA and joins these ends to a target DNA to catalyze transposition. Substitution mutations at Asp-269 or Glu-392 within MuA destroy both the DNA cleavage and joining activities without blocking tetramer assembly, indicating that the mutations specifically affect catalysis. Although inactive under standard reaction conditions (10 mM Mg2+), the mutant proteins are partially resuscitated by 10-20 mM Mn2+, concentrations 5- to 10-fold higher than optimal for wild-type MuA. Amino acid sequence alignment and the similar effects of mutations suggests that Asp-269 and Glu-392 of MuA may be analogs of the first Asp and final Glu of a conserved triad of acidic amino acids present in many transposases and the retroviral integrases (the D-D-35-E motif). The higher Mn2+ optima observed with MuA derivatives altered at these positions supports a role for the conserved acidic amino acids in coordinating divalent metal ions in the active sites of transposases.

[Effect of crystal no. 4 of polygonum cuspidatum on the viability of island flaps with venous stasis: an experimental study]

The effects of crystal No. 4 of Polygonum cuspidatum on microcirculatory changes of island flaps in rats following resumption of blood flow after venous occlusion of six hours were observed with a special TV set with magnification of 500X. The pathological events and survival rate of flaps were recorded as well. The results showed that the survival rate, amount of open capillaries, amount of blood flow, and velocity of blood flow of flaps treated by crystal No. 4 of polygonum cuspidatum were much higher than those of untreated control flaps. The white thrombosis and endothelial damage of dermal vessels were alleviated by administration of crystal No. 4 of polygonum cuspsidatum. The experiment also showed that there were no differences between flaps treated with crystal No. 4 of polygonum cuspidatum preoperatively and flaps treated with it postoperatively.

Genetic factors may influence the development of spinal reflex hyperexcitability following sciatic nerve section in the rat

We compared changes in the excitability of the hamstring flexor reflex evoked by electrical stimulation of the sciatic nerve before and after section of the peroneal, tibial and sural branches of the nerve in Sprague-Dawley (SD) and spontaneously hypertensive (SHR) rats. In both rat strains, the flexor reflex exhibited a biphasic hyperexcitability lasting over 120 min after nerve section. The initial brief, intense increase in reflex excitability was similar in SD and SHR rats. The second prolonged phase, which may represent hyperalgesia, was significantly greater in SHR than SD rats. These results indicate that genetic differences may have a role in the development of central sensitization.