Adenosine and adenine nucleotides are independently released from both the nerve terminals and the muscle fibres upon electrical stimulation of the innervated skeletal muscle of the frog

The independent release of adenosine and adenine nucleotides upon electrical stimulation was studied in the innervated sartorius muscle of the frog after blockade of the extracellular catabolism of adenosine monophosphate (AMP) through exo-AMP deaminase and ecto-5-nucleotidase. Nerve stimulation (30 min, 0.2Hz) induced the release of both adenosine (19±3 pmol) and adenine nucleotides (101±7 pmol). Experiments performed in the presence of tubocurarine (5 M) to prevent purine release due to nerve-evoked muscle twitching, or under direct stimulation of the muscle in low calcium solutions to prevent pre-synaptic release of purines, showed that there was an evoked release of adenosine and adenine nucleotides both from the nerve endings and from the twitching muscle fibres. Removal of ecto-5-nucleotidase inhibition shows that the catabolism of adenine nucleotides released during stimulation contributes in about 50% to the amount of endogenous extracellular adenosine. When only one of the enzymes catabolizing AMP (ecto-5-nucleotidase or exo-AMP deaminase) was inhibited, the evoked release of adenine nucleotides was undetectable, suggesting that each enzyme is able to catabolize all the AMP formed from adenine nucleotides released upon stimulation. It is concluded that the concentration of endogenous extracellular adenosine is under the control of the relative activities of exo-AMP deaminase and ecto-5-nucleotidase.Brief accounts of some of the results in this study have been published previously (refs. [6, 7]).     

Excitation of neuronal function in rabbit caudal ventrolateral medulla elevates plasma vasopressin

Injection of L-glutamate into the caudal ventrolateral medulla of the rabbit caused a dose-dependent increase in plasma vasopressin. Activity of the A1 noradrenergic cells within the caudal ventrolateral medulla appears to excite the vasopressin-secreting neuroendocrine cells within the hypothalamus.     

Implication of biofilm formation in the persistence of urinary tract infection caused by uropathogenic Escherichia coli

Escherichia coli is the most frequent microorganism involved in urinary tract infection (UTI). Acute UTI caused by uropathogenic E. coli (UPEC) can lead to recurrent infection, which can be defined as either re-infection or relapse. E. coli strains causing relapse (n = 27) and re-infection (n = 53) were analysed. In-vitro production of biofilm, yersiniabactin and aerobactin was significantly more frequent among strains causing relapse. Biofilm assays may be helpful in selecting patients who require a therapeutic approach to eradicate persistent biofilm-forming E. coli strains and prevent subsequent relapses.     

Simple,rapid, and accurate determination of deletion mutations by automated dna sequencing of heteroduplex fragments of the adenomatous polyposis coli (APC) gene generated by PCR amplification

Germline mutations in patients with familial adenomatous polyposis were analyzed by polymerase chain reaction (PCR) amplification of the adenomatous polyposis coli gene. PCR products from heterozygous patients for deletions of this gene formed four distinct bands on polyacrylamide gel electrophoresis. The four fragments were subsequently purified and both strands of each fragment were directly sequenced, using an automated DNA sequencer and the same primers as those for PCR amplification. It was found that the two slower migrating fragments were “bulge” heteroduplexes, while the other two were homoduplexes made up of two wild-type strands and two deletion-mutant strands, respectively. The sites of deletions in the adenomatous polyposis coli gene could be exactly determined in four of the five patients. In an attempt to identify deletion-carriers of familial adenomatous polyposis at the presymptomatic stage, a family study was also carried out, and two children were found to have the same mutations as those of their affected parents. The direct sequencing of heteroduplex fragments generated during PCR amplification is a potentially useful method for detecting mutations of not only the adenomatous polyposis coli gene but also many other genes of genetic diseases. © 1993 Wiley-Liss, Inc.     

不同方法处理的同种异体骨移植红细胞免疫功能的变化

本文道报27例同种异体骨移植兔的红细胞免疫功能指标检测结果。红细胞C_3b受体花环率变化,以异体骨花环率最高,液氮骨其次,AAA骨花环率形成率则在正常对照值范围内变化。结果提示异体骨移植能引起明显的免疫反应,液氮骨可有一定的抗原性,能引起免疫反应,冻干骨免疫反应较低下,而AAA骨则不引起免疫反应。本文对同种异体骨移植后的红细胞免疫功能变化的机理与临床意义进行了讨论。     

IL-15真核表达质粒的构建及对乙肝疫苗诱导的体液免疫应答的影响

目的 研究两种不同的IL-15真核表达质粒对乙肝蛋白疫苗诱导的免疫应答的影响。方法：构建IL-15真核表达质粒(简称pIL-15)和含有IL-12信号肽的IL-15真核表达质粒(简称pIL-2s-15)，CTLL-2细胞增殖实验验证两种质粒真核表达产物的生物学活性。将这两种质粒分别与HBsAg共免疫BALB／C小鼠，用ELISA法检测小鼠血清抗-HBs IgG及IgGl、IgG2a亚类的效价。结果：与HBsAg蛋白疫苗共免疫时，pIL-15可使HBsAg诱导的抗-HBsIgG效价升高，显著高于载体pcDNA3．1与HB—sAg共免疫对照组，pIL-2s-15对HBsAg诱导抗-HBsIgC效价没有明显影响。与HBsAg pcDNA3．1组相比，HBsAg pIL-2s-15组和HBsAg pIL-15组诱生的抗HBsIgG2a亚类均升高，但前者IgG2a／IgG1比值最高，与HBsAg pcDNA3．1组相比差别有显著性；HBsAg pIL-15组IgG2a／IgG1比值与HBsAg pcDNA3．1组相比差别无显著性。结论 pIL-15真核表达质粒可增强蛋白疫苗诱导的体液免疫应答，pIL-2s-15真核表达质粒则主要使免疫应答趋向Th1型。     

Increased production of human immunodeficiency virus (HIV) in HIV-induced syncytia formation: An efficient infection process

Syncytia or multinucleated giant-cell formation is one of the major cytopathic effects induced by human immunodeficiency virus (HIV) infection. Cell fusion results from the strong interaction of CD4 molecules on the surface of the uninfected T cells and gp120, an external envelope glycoprotein of HIV on the infected T cells. We studied the production of HIV in fusion cells between MOLT-4 and virus-infected MOLT-4/HIV cells and found that HIV production was enhanced up to three- to fivefold, which showed a good correlation with the appearance and extent of syncytia formation. Blocking the fusion by monoclonal antibody against a binding epitope of CD4 molecule to gp120 decreased the HIV production significantly. Enhancement of HIV production was observed by more than five-fold in comparison with chronically infected cells, which were fusion free 20 hr postcocultivation. Electron microscopic observation also showed the presence of abundant HIV particles inside the fused cells and on the outer surface. AZT blocked the HIV augmentation of fused cells in coculture completely. Southern blot analysis revealed that both integrated and unintegrated HIV DNA were highly accumulated in fusion cells, as compared with fusion-free MOLT-4/HIV cells. Among unintegrated DNA, circular and linear DNA were accumulated to a similar degree. Northern blot hybridization showed that rapid enhancement of all three species of HIV-specific RNA containing genomic (9.2 kb) and subgenomic (4.3 and 1.9 kb) RNAs were found 20 hr postinfection in fusion cells. These data suggest that syncytia formation is an extremely active infection process of HIV, by which multiple rounds of reinfection might take place.     

Brainstem control of sensory information: a mechanism for perception

We have proposed a theory in which pathways ascending from the brainstem reticular formation control sensory centers in the dorsal thalamus and neocortex. We assumed that the sensory messages received at a given level are transformed by a stochastic process, called Alopex, in a way which maximizes responses in central feature analyzers. Perception is seen as a process involving a close cyclic interaction between brainstem and sensory relays. We discuss the specific case of visual information flow and the proposed modification of visual images at the level of the dorsal lateral geniculate nucleus (dLGN). Computer simulations of a simple model, representing the dLGN and reafferent control emanating from the reticular formation, show that sensory features are effectively enhanced and--in the absence of sensory input--quasi-sensory features may be generated by feedback of a simple scalar variable that is formed by the non-linear superposition of the responses of any number of feature analyzers. The model proposes a specific mechanism for such processes as visual imagery, hallucinations, and dreaming, and provides a framework for further studies into the nature of cognitive brain functions.     

Vitronectin-mediated inhibition of complement: evidence for different binding sites for C5b-7 and C9.

In the activated complement system, vitronectin (complement S-protein) occupies the metastable membrane binding site of the nascent precursor complex C5b-7, so that the newly formed SC5b-7 is unable to insert into cell membranes. Some evidence also indicates that vitronectin limits on-going membrane-associated pore formation by inhibiting C9 polymerization. It has been assumed that these two stages of terminal complement complex (TCC) inhibition take place through charge interactions between the heparin-binding region of vitronectin and homologous cysteine-rich sequences of the late complement proteins C6, C7, C8 and C9. We examined SC5b-7 formation and inhibition of C9 binding in the TCC using separate haemolytic assays. The mode of action of vitronectin in these assays was compared with two 15mer peptides which span residues 348-379 of the heparin-binding region, and a heparin-affinity polypeptide, protamine sulphate. The results showed that vitronectin acts predominantly through SC5b-7 production with a lesser effect on the inhibition of C9 lytic pore formation. In contrast, protamine sulphate did not prevent C5b-7 membrane attachment, but was a potent inhibitor of C9-mediated lysis. The peptides did not inhibit C5b-7 membrane insertion and only one affected C9 binding. These data suggest that the two stages of TCC inhibition involve separate binding sites on the vitronectin molecule. The site for association with nascent C5b-7 is unknown, whereas inhibition of C9 binding and pore formation takes place through the heparin-binding region.     

Formation of ectopic neuromuscular junctions in adult rats

The formation of ectopic neuromuscular junctions between a transplanted foreign nerve (the superficial fibular nerve) and the denervated soleus muscle was examined in adult rats. Formation of new junctions was induced by denervating the soleus muscle by cutting the tibial nerve. Junctional transmission began 3 days after denervation when denervation was done 3 weeks after transplantation of the foreign nerve, and progressively later when denervation was done 8, 16 and 24 weeks after transplantation. The rate at which the transmission, once started, acquired mature characteristics was approximately the same in each case. Initially, spontaneous m. e.p. p.s were infrequent, long lasting with a skewed amplitude distribution. The e. p.p. s evoked by stimulation of the foreign nerve were then commonly below threshold for eliciting action potentials and were occasionally no larger than the size of the spontaneous m. e.p. p.s. M.e. p.p. characteristics became normal in the 2nd week after transmission had started. Fully effective evoked transmission with every innervated fibre responding with overshooting action potential occurred 1–3 months after onset of transmission.