Functions of hepatitis B surface proteins

HBV surface proteins play a number of functional roles in cellular infection, viral synthesis and in immune responses of the host. Three coterminal proteins of differing sizes and three subdomains of the individual molecules can be recognized. In this brief review, functions of the various proteins and domains are described and their significance as potential immunogens is discussed. Although it is apparent that the surface proteins are involved in the development of persistent HBV infections, the underlying mechanisms of liver involvement remain unknown.

Stimulated Raman scattering and four-wave mixing from a mixture of carbon disulfide and phenylethanol in a hollow optical fiber

We observe, for what is to our knowledge the first time, stimulated Raman scattering and four-wave mixing in a liquid-core optical fiber filled with a mixture of carbon disulfide and phenylethanol pumped by the frequencydoubled output of a Q-switched YAG laser (lambda = 532.1 nm). The frequencies of the stimulated Raman scattering and four-wave mixing spectra are specified, and theoretical interpretations are also given.

High-order stimulated Raman scattering and nonlinear red-shifted broadening in benzyl alcohol core optical fiber

Six orders of Stokes lines and the first-order anti-Stokes line were observed we believe for the first time, in a benzyl alcohol liquid core optical fiber. All the Stokes lines were asymmetrically broadened favoring the lower frequencies. The blue-shifted broadening was only a few percent of the amount of the red-shifted broadening, and the broadening of the fifty-order Stokes line was so broadened to exceed the characteristic Raman frequency shift, 1000 cm(-1), to connect with the sixth-order Stokes line. The asymmetric broadening was discussed to be mainly due to the effect of the stimulated Rayleigh wing scattering.

Inflammation near the nerve cell body enhances axonal regeneration

Although crushed axons in a dorsal spinal root normally regenerate more slowly than peripheral axons, their regeneration can be accelerated by a conditioning lesion to the corresponding peripheral nerve. These and other observations indicate that injury to peripheral sensory axons triggers changes in their nerve cell bodies that contribute to axonal regeneration. To investigate mechanisms of activating nerve cell bodies, an inflammatory reaction was provoked in rat dorsal root ganglia (DRG) through injection of Corynebacterium parvum. This inflammation enhanced regeneration in the associated dorsal root, increasing 4-fold the number of regenerating fibers 17 d after crushing; peripheral nerve regeneration was not accelerated. A milder stimulation of dorsal root regeneration was detected after direct injection of isogenous macrophages into the ganglion. It is concluded that changes favorable to axonal regeneration can be induced by products of inflammatory cells acting in the vicinity of the nerve cell body. Satellite glial cells and other unidentified cells in lumbar DRG were shown by thymidine radioautography to proliferate after sciatic nerve transection or injection of C. parvum into the ganglia. Intrathecal infusion of mitomycin C suppressed axotomy-induced mitosis of satellite glial cells but did not impede axonal regeneration in the dorsal root or the peripheral nerve. Nevertheless, the similarity in reactions of satellite glial cells during 2 processes that activate neurons adds indirect support to the idea that non-neuronal cells in the DRG might influence regenerative responses of primary sensory neurons.

[Trace elements in the aqueous extract of twenty Chinese drugs before and after charring]

Our study on the variation of trace element contents in the aqueous extract of 20 Chinese drugs before and after charring has shown that after charring Ca ions increase noticeably in the extract of 6 drugs, increase slightly in another 6 and decrease in varying degrees in the remaining 8. In all the charred drugs no rise has been observed in the contents of trace elements, but instead, in most of them the contents tend to drop.

Retrovirus-mediated transgenic keratin expression in cultured fibroblasts: specific domain functions in keratin stabilization and filament formation

With retrovirus-mediated gene transfer, we used intact and deleted keratin proteins to investigate the molecular basis of intermediate filament function. Three levels of assembly show a different stringency for the involvement of individual keratin domains: protein accumulation requires the alpha helix domains; stable filament formation additionally requires both N- and C-terminal domains of either one of the two interacting keratins, suggesting that head to tail homotypic interaction is important for effective elongation; and higher order organization of the cytoplasmic network depends on correct type I-type II pairing of keratins. The presence of two distinct interaction sites along potentially different axes may explain the characteristic morphology of keratin intermediate filament networks.

[The isolation and structure of tripchlorolide (T4) from Tripterygium wilfordii]

A new compound named tripchlorolide was isolated from Total Glucosides (T II) extracted from the woody part of the root of Tripterygium wilfordii Hook. f. Tripchlorolide (T4) was obtained as white needle-like crystals, mp 256-258 degrees C. Its molecular formula is C20H25O6Cl. The structure of T4 was elucidated on the basis of spectral (UV, IR, MS, FTMS/SCI, 1H-NMR, 13C-NMR, 1H-1H cosy, 13C-1H cosy) analyses, X-ray and chemical evidence. In preliminary pharmacologic assay, tripchlorolide showed definite anti-inflammatory actions and strong immunosuppressive and antifertile activities, the potency of the latter being 100 times stronger than that of T II.

Cloning, characterization, and expression of the gene for the catalytic subunit of cAMP-dependent protein kinase in Caenorhabditis elegans. Identification of highly conserved and unique isoforms generated by alternative splicing

The nematode Caenorhabditis elegans expresses substantial amounts of several forms (Mr values = 39,000-41,000) of the catalytic subunit (C) of cAMP-dependent protein kinase. Approximately 65% of the total cAMP-dependent phosphotransferase activity is recovered in particulate fractions of homogenates prepared from asynchronous populations of C. elegans. The C subunit is expressed at a low level in cytosolic and particulate compartments during embryogenesis. As the nematodes progress from late embryonic stages to the newly hatched, first larval (L1) stage, C subunit content increases 15-fold. High levels of C subunits are observed in several subsequent larval and adult stages of development. Since the relative abundance of C subunit mRNA changes little with development, it appears that control of C expression is exerted the translational and/or post-translational levels. cDNAs for two types of C have been cloned and sequenced. The derived amino acid sequence of a major isoform (CeCAT alpha, 358 residues) is highly homologous (82% identical) with the murine C alpha subunit. A second, novel C subunit (CeCAT alpha', 374 residues) has a unique 56-residue carboxyl-terminal region that is generated by the alternative splicing of the C pre-mRNA. The splicing process that yields CeCAT alpha' is unusual because it converts the central portion of an apparent 1-kilobase (kb) intron to an exon. The alternative exon introduces the novel carboxyl terminus and a new translation stop signal, while simultaneously converting the coding sequence for 40 carboxyl-terminal residues in CeCAT alpha into 3'-untranslated nucleotides. The 5' end of the C. elegans C subunit mRNA is produced by the trans-splicing of the C gene transcript to a 22-base pair C. elegans leader sequence originally described by Krause, M., and Hirsh, D. [1987) Cell 49, 753-761). The 20-kb C. elegans C gene is divided into seven exons by introns ranging in size from 54 to 8000 bp. The sizes of the C. elegans C subunit gene, cytoplasmic mRNA (2.5 kb), and subunit protein are similar to the sizes of the murine C alpha gene, mRNA, and polypeptide. However, the nematode and murine C genes differ significantly in the organization of their introns and exons.

Differential screening of murine ascites cDNA libraries by means of in vitro transcripts of cell-cycle-phase-specific cDNA and digital image processing

Cell-cycle-phase-specific cDNA libraries were prepared in the lambda gt10 vector and in the in vitro transcription vector, pBluescript. Plaques of the cDNA libraries prepared in the lambda gt10 vector were differentially screened with (a) in vitro transcripts of the cell-cycle-phase-specific cDNAs cloned in the transcription vector and (b) with first-strand cDNA of mRNA from phase-synchronous cells. The results suggest that first-strand cDNA can be replaced, at least in prescreening experiments, by in vitro transcripts of representative cDNA libraries prepared in in vitro transcription vectors. The fractions of differential clones detected with in vitro transcripts (1.2%) and with first-strand cDNA (1%) were in the same order. Individual clones selected by differential hybridization with in vitro transcripts could be verified by differential hybridization with cell-cycle-phase-specific first-strand cDNA. This indicates that the pattern of stage-specific prevalences of cDNA clones is essentially retained during careful amplifications of large cDNA libraries. The application of in vitro transcripts of stage-specific cDNA for differential screening experiments is of interest in cases where the amount of biological material is either limited or difficult to prepare. It also allows standardization of the probes in repeated screening experiments. Three clones reflecting cell-cycle-phase-specific mRNA prevalences were chosen and analyzed on the sequence level. Two sequences with S-phase prevalences were identified. They code for elongation factor EF1 alpha and for glyceraldehyde-3-phosphate dehydrogenase, respectively. The third sequence reflects the first cDNA of a mRNA with significant prevalence in G2-phase cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effects of xamoterol and isoprenaline on rat cardiac beta-adrenoceptors: studies of function and regulation

1. The effects of the beta 1-selective partial agonist xamoterol and the full agonist isoprenaline on rat cardiac beta-adrenoceptors were compared in functional studies of heart rate response in vivo and in vitro. In addition, the ability of both agents to cause receptor down-regulation in the rat heart following chronic (6 days) subcutaneous infusions was assessed by radioligand binding with [125I]-pindolol. 2. In the functional studies, xamoterol produced a maximal effect equivalent to approximately 65% of that of isoprenaline and was overall less potent than the full agonist. 3. Compared to saline control, the density of beta-adrenoceptors was reduced approximately 39% in ventricular membranes prepared from animals after 6 days of isoprenaline infusion but was unaffected by xamoterol. The relative proportions of the beta-adrenoceptor subtypes were unchanged by either active treatment. 4. Plasma xamoterol level at the end of the infusion period was equivalent to that associated with maximum tachycardia in vivo and to the concentration producing maximal stimulation of the rat isolated atrium in vitro. Thus suggesting 100% beta-adrenoceptor occupancy during the period of xamoterol infusion. 5. These results indicate that in this animal model xamoterol does not induce cardiac beta-adrenoceptor down-regulation during chronic treatment, with doses that produce a maximal functional response both in vitro and in vivo.

Protective effects of sodium selenite on experimental myocardial infarction

The present study compares the protective effects of sodium selenite (Se), hyaluronidase (Hy) and anisodamine (An) on infarct size, left ventricular myocardial contractility (LVMC) and relaxation (LVMR) and myocardial hypertrophy on the 3rd, 9th and 21st days after the ligation of left main coronary artery in the rats. The results showed that Se could reduce the infarct size, so could Hy and An. However, Se could relevantly improve LVMC and LVMR at the acute phase of infarction, while Hy and An could not. On the 21st day (healing phase) of infarction the indexes of the LVMC and LVMR in Se-, Hy- or An-treated rats were significantly better than those in the control rats. Se could enhance the extent of hypertrophy in non-infarcted myocardium, while Hy and An could not. On the 21st day of this experiment the total natural mortality in the Se-treated rats was significantly lower than that in the control or in the An-treated rats. These data suggest that Se is superior to Hy and An in the treatment of acute myocardial infarction.

Construction and quality of cDNA libraries prepared from cytoplasmic RNA not enriched in poly(A)+RNA

Poly(A)+RNA and cytoplasmic RNA of Ehrlich ascites tumor cells grown in vivo were used to study the quality and efficiency of cDNA synthesis. It was found that the rates of oligo(dT)-primed and unprimed reverse transcription were very similar in both cases. The size distributions of the cDNA strands prepared from unfractionated RNA reflected the size of cytoplasmic mRNA populations including a significant fraction of long molecules up to 6 kb. The fraction of cDNAs primed on rRNAs by oligo(dT) was found to be as low as 2-3%. Following second-strand synthesis by means of RNase H-induced nick translation by DNA polymerase I the overall yields in double-stranded cDNA were slightly higher when unfractionated cytoplasmic RNA was used as starting template. In repeated experiments we obtained an average yield of 2.2 micrograms of double-stranded cDNA when 70 micrograms of unfractionated cytoplasmic RNA was used as starting material. This amount of cDNA synthesized in one assay was sufficient to construct representative cDNA libraries in different vectors. Southern hybridizations of DNA isolated from cDNA libraries with various radiolabelled probes show that the libraries constructed from cDNA synthesized from cytoplasmic RNA not enriched in poly(A)+RNA contain a high ratio of full-length cDNA clones. The results suggest that representative cDNA libraries of high quality can be constructed without pre-isolation of poly(A)+RNA fractions.