Hepatitis A, B, C, D and E viruses: structure of their genomes and general properties

Hepatitis A virus is an enteric picornavirus. Its genome is a single stranded RNA molecule of positive-strand polarity of 7478 bases. This sequence codes for a polyprotein which is processed to give rise to viral proteins VP-1, VP-2, VP-3 and others. Hepatitis B virus, a major worldwide infectious and cancer promoting agent contains a DNA genome of 3226 base pairs that replicates by a reverse transcriptase via an RNA intermediate. Extensive sequencing and expression experiments have revealed four major genes named surface, core, polymerase and X which are coded in more than one reading frame. Furthermore, within a frame, proteins are expressed from multiple initiation codons resulting in several related products. The viral genome of hepatitis C virus (nonA-nonB), an elusive major infectious agent, has recently been cloned. This genome is a single positive-stranded RNA of at least 10,000 bases which codes for several antigens, some of them associated specifically with nonA-nonB hepatitis infections. The hepatitis D (delta) viral agent, an infectious agent requiring a hepadnarious for propagation, contains a covalently closed circular single-stranded RNA genome of 1167 nucleotides. This genome encodes the protein p24 and p27 that bind specifically to antisera from patients with chronic hepatitis D infections.

Effects of captopril versus milrinone therapy in modulating the adrenergic nervous system response to exercise in congestive heart failure

The potential adverse consequences of increased adrenergic nervous system activity in patients with heart failure are now recognized. Modulation of the plasma noradrenaline response to submaximal exercise should be desirable. The long-term (9 weeks) effects of milrinone (10 mg 4 times a day) or captopril (50 mg 3 times a day) compared to placebo were evaluated in a double-blind crossover study, in 16 patients with stable, congestive heart failure receiving digoxin and furosemide. After treatment, clinical status (score range 0 to 14 points) improved significantly with both milrinone (4.4 +/- 0.5, p less than 0.01) and captopril (4.1 +/- 0.4, p less than 0.01). Plasma noradrenaline at rest was similar with both drugs and not significantly different from placebo. During submaximal exercise it increased significantly to 1,228 +/- 58 pg/ml with placebo and to 1,295 +/- 174 pg/ml with milrinone; this response was reduced significantly with captopril, to 820 +/- 100 pg/ml (p less than 0.01). Thus, long-term therapy with both captopril and milrinone improved the clinical score, but only captopril reduced the plasma noradrenaline response to submaximal exercise. These findings suggest that angiotensin-enzyme inhibition with captopril will modulate the adrenergic system response to daily activities in patients with chronic congestive heart failure and therefore could have additional salutary effects beyond vasodilatation.

[Computerized registry of medical procedures and diagnostic codification]

Retrospective analysis of clinical information requires easy access to reliably stored data. We developed a program running on a microcomputer and using codes from the International classification of diseases, to be used on line. The program stores diagnostic codes, medical actions and a summary for each case. It uses inexpensive hardware and is friendly to inexperienced users.

[Medical care to cerebrovascular syndrome]

We analyzed clinical data from all patients with a stroke admitted to the Emergency Service of a General Hospital in Santiago, from 1984 to 1986. 371 patients (196 women and 175 men) were diagnosed as having thrombosis (43%), embolic occlusion (18%), intracerebral hemorrhage (36%) and subarachnoid hemorrhage (3%). CAT scans were performed in 25% and angiography in 16%. The diagnosis was considered proven in 40% of cases. Overall hospital mortality was 46%, raising to 66% for hemorrhages. Prevention of cerebral edema was the main medical treatment. The present data suggest that primary prevention of and technological facilities to treat cerebrovascular episodes are inadequate at a general hospital level in Santiago.

Expression of three recombinant homodimeric isoforms of PDGF in Saccharomyces cerevisiae: evidence for difference in receptor binding and functional activities

Three recombinant homodimeric isoforms of platelet-derived growth factor (PDGF) were produced and purified in milligram quantities by expression of PDGF A- and B-chains in yeast cells. Structural analysis of the purified short and long variants of PDGF-AA (PDGF-AAS and PDGF-AAL) and PDGF-BB showed that they had been properly processed and assembled into dimers. PDGF-AAS and PDGF-AAL were found to bind only to the PDGF A-type receptor on human fibroblasts, with affinities of 0.1 and 0.2 nM, respectively. PDGF-BB bound to cells with A- and B-type receptors and to cells with B-type receptor only with affinities of 0.6 nM in both cases. Each fibroblast appeared to express about 4-5 times more B-type receptors than A-type receptors. The maximal mitogenic response to PDGF-BB of human fibroblasts was almost 2-fold higher than that induced by either of the two PDGF-AA forms. The three isoforms of PDGF also stimulated growth in soft agar of human fibroblasts with PDGF-BB inducing a higher maximal response.

Synthesis and assembly of a functionally active recombinant platelet-derived growth factor AB heterodimer

A Chinese hamster ovary cell line that stably expresses transfected human platelet-derived growth factor (PDGF) A and B chain precursors was established. All three dimeric combinations of PDGF chains were produced by this cell line; their biosynthesis, assembly, and processing were followed by pulse-chase analyses. PDGF-AA, PDGF-AB, and PDGF-BB were processed to Mr values of about 30,000 and were accumulated in these forms in the medium. In addition, PDGF-BB was further processed to a 24-kDa component, which remained cell-associated. The major secreted component was PDGF-AB, which was purified and shown to have structural and functional characteristics indistinguishable from PDGF-AB purified from human platelets.

Characterization of recombinant human epidermal growth factor produced in yeast

Four different forms of human epidermal growth factor (h-EGF) are found in the culture medium of a recombinant strain of Saccharomyces cerevisiae. These forms were characterized after purification using reverse-phase high-performance liquid chromatography. The most abundant form of secreted recombinant h-EGF has leucine at the carboxyl terminus and is identical with gamma-urogastrone. A second species is identical with the most abundant form except that it lacks the carboxyl-terminal leucine. This form appears to be the product of a carboxypeptidase found in the growth medium. The other two forms of recombinant h-EGF are the respective oxidation products of the above where the single methionine residue has been converted to methionine sulfoxide. These four forms of recombinant h-EGF are fully active; they bind to the EGF receptor of A431 cells as well as stimulate mitotic activity of human foreskin fibroblasts with equal specific activity. The location of the disulfide bonds in the predominant form of recombinant h-EGF was determined following digestion with thermolysin. The amino acid compositions of the resulting peptides showed that the placement of disulfide bonds in recombinant h-EGF is identical with that in murine EGF.

The yeast tRNA(Phe) gene family: structures and transcriptional activities reveal member differences not explained by intragenic promoters

Several cloned members of the yeast tRNA(Phe) gene family were transcribed in vitro using a HeLa extract and a yeast extract. The optimum DNA concentration was determined and kinetic experiments were performed for each clone to compare transcription levels. Both extract systems were able to splice the intervening sequence, but only the yeast extract produced the mature product. Some genes were not transcribed with the homologous system while they were transcribed with the HeLa extract, suggesting a control mechanism that is not operating in the heterologous system. Competition experiments demonstrated that the intragenic promoters of the inactive genes were able to bind transcription factor(s), but not as efficiently as active genes. This binding was not so strong when using linear DNA and was dependent on the presence of the 3' intragenic control region. DNA sequencing and computer analysis indicated the presence of short conserved sequences upstream from the genes. These sequences, which are not related to the intragenic promoters, are direct repeats of part of the 3' coding region in those genes that are transcribed in the homologous system. The relevance of these sequences on homologous transcription in vitro remains to be established.

Measurement of the endometrial cavity length using Wing Sound I

Parity is a factor that influences the axial length of the uterus. The knowledge of different measurements will help in the fitting of the IUD. In this paper, 657 cavimetries have been studied in relation to parity. A progressive increase of both the total uterine length and the endometrial cavity length have been observed in relation to parity, but none regarding the cervical length.

Enhancement of epidermal regeneration by biosynthetic epidermal growth factor

Epidermal regeneration depends on mitosis and migration of keratinocytes. Epidermal growth factor is known to stimulate growth of keratinocytes in vitro, thus it might be expected to promote wound healing. The results of this study show that topical application of biosynthetic human epidermal growth factor accelerates epidermal regeneration in split-thickness wounds and partial-thickness burns. The significant enhancement of epidermal regeneration suggests the potential for clinical use of epidermal growth factor for accelerating healing of burns, wounds from trauma, diabetic ulcers, skin graft donor sites, and others.

Biosynthetic human EGF accelerates healing of Neodecadron-treated primate corneas

Topical administration of biosynthetic human epidermal growth factor (h-EGF), given in combination with an antibiotic and synthetic steroid (Neodecadron) accelerated the rate of corneal epithelial regeneration and significantly increased the strength of full-thickness stromal incisions in primates. The regenerated epithelial cells of EGF-Neodecadron-treated corneas appeared normal on histologic examination and showed no evidence of hypertrophy or hyperplasia. The EGF-Neodecadron-treated stromal incisions were characterized by new collagen formation and a smaller epithelial cell plug than Neodecadron-treated control corneas. These results suggest that biosynthetic h-EGF, which lacks the immunologic potential of nonhuman proteins, may be effective in accelerating healing of corneal epithelial defects and stromal incisions in patients whose healing is suppressed by treatment with steroids.

Isolation and sequence of a rat chymotrypsin B gene

A cDNA clone encoding part of chymotrypsin B was isolated from a cDNA library prepared from rat pancreatic mRNA and used as a probe to isolate the chymotrypsin B gene. The nucleotide sequence of this gene is presented. The 4709-base pair transcribed portion of the isolated gene was inferred from the cDNA and gene sequence, and the 5' border was determined by primer extension on pancreatic polyadenylated RNA. The coding portion of the gene is interrupted by six introns. The active site residues His 57, Asp 102, and Ser 195 are encoded by separate exons. Moreover, two regions of the enzyme which form the substrate-binding pocket are also encoded by separate exons. Thus, the substrate specificity and catalytic activity of the enzyme are produced by joining several exons encoding protein segments that are intrinsically catalytically inactive. The number and location of the intron/exon junctions of the chymotrypsin gene as compared to those of other serine protease genes, as well as the location of the genes on separate chromosomes, suggest that the duplication that resulted in the formation of the chymotrypsin gene was an ancient evolutionary event.

Cloning and analysis of integrated hepatitis virus sequences from a human hepatoma cell line

We report here the isolation by molecular cloning and the analysis by heteroduplex and restriction enzyme mapping of seven distinct DNA fragments containing hepatitis B virus (HBV) sequences from genomic DNA of the PLC/PRF/5 human liver carcinoma cell line (the Alexander cell). No intact full-length HBV genomes were present. Three different patterns of organization of HBV fragments were detected. These included two linear fragments without detectable rearrangement, three other HBV fragments with internal deletions, and two HBV fragments containing long inverted duplications. HBsAg sequences are preferentially included in the integrated fragment, whereas the core gene is preferentially eliminated. Several of the integrated HBV fragments might act as templates for the synthesis of functional HBsAg mRNA, whereas only one clone could produce a full core antigen transcript.

Alpha-factor-directed synthesis and secretion of mature foreign proteins in Saccharomyces cerevisiae

Saccharomyces cerevisiae cells were transformed with plasmids containing hybrid genes in which the sequence encoding mature human epidermal growth factor was joined to sequences encoding the leader region (preprosegment) of the precursor of the yeast mating pheromone alpha-factor. These cells accurately process the hybrid protein and efficiently secrete authentic biologically active human epidermal growth factor into the medium.