Optimised conditions for the production of hepatitis B virus from cell culture

In chronically infected patients, hepatitis B virus (HBV) particles reach numbers as large as >10(9) genome equivalents (GE)/ml of serum. However, expression of infectious HBV particles in cell culture only yields 10(5)-10(6) GE/ml, which is insufficient for many studies. HBV transcription and possibly replication is dependent on hepatocyte-specific differentiation. Thus, we tested several cell culture parameters that have been reported to enhance the expression of hepatocyte-specific markers, such as growth on different extracellular matrices, different cell culture media, low concentrations of fetal calf serum (FCS) and the addition of dimethyl sulfoxide (DMSO) to the medium. Lower concentrations of FCS, growth on collagen and inclusion of DMSO in the medium only moderately enhanced HBV production in vitro when applied individually. However, combinations of these parameters optimised cell culture conditions and reproducibly increased the release of HBV particles about 100-fold to titres >10(8) GE/ml of culture medium.

Inhibition of mitochondrial ATP generation by nitric oxide switches apoptosis to necrosis

Under pathological conditions, the mode of cell death, apoptosis or necrosis, is relevant for the subsequent fate of the tissue. Cell demise may be shaped by endogenous mediators such as nitric oxide (NO) which interfere with subroutines of the death program. Here we show that apoptosis of Jurkat cells elicited by either staurosporine (STS) or anti-CD95 antibodies in glucose-free medium is converted to necrosis by NO donors. In the presence of NO, release of mitochondrial cytochrome c was delayed and activation of execution caspases was prevented. Stimulated cells died nonetheless. The switch in the mode of cell death was due to NO-dependent failure of mitochondrial energy production. Restoration of intracellular ATP by glucose supplementation recovered the cells' ability to activate caspases and undergo apoptosis. In this system, the apoptosis/necrosis conversion promoted by NO was not mediated by cyclic guanosine monophosphate-dependent mechanisms, poly-(ADP-ribose)-polymerase (PARP) activation, or inhibition of caspases due to S-nitrosylation and glutathione depletion. In contrast, depleting intracellular ATP with rotenone, an inhibitor of mitochondrial complex I mimicked the effect of NO. The findings presented here suggest that NO can decide the shape of cell death by lowering intracellular ATP below the level required to allow the coordinated execution of apoptosis.

Nitric oxide inhibits execution of apoptosis at two distinct ATP-dependent steps upstream and downstream of mitochondrial cytochrome c release

The endogenous mediator nitric oxide (NO) blocked apoptosis of Jurkat cells elicited by staurosporine, anti-CD95 or chemotherapeutics, and switched death to necrosis. The switch in the mode of cell death was dependent on the ATP loss elicited by NO. This affected two distinct steps of the apoptotic cascade. First, the release of cytochrome c from mitochondria was delayed by NO. Second, processing of procaspases-3/7 to the active proteases was prevented even after cytochrome c had been released. Thus, NO interferes with execution steps of apoptosis both upstream and downstream of cytochrome c release.

Tumor necrosis factor-induced apoptosis during the poisoning of mice with hepatotoxins

BACKGROUND & AIMS

Treatment with tumor necrosis factor (TNF) induces murine hepatocyte apoptosis in vitro and in vivo when sensitizing concentrations of toxins are present. The aim of this study was to investigate whether endogenously formed TNF contributes to liver failure caused by hepatotoxins.

METHODS

The extent of liver damage, induced by alpha-amanitin or actinomycin D (ActD), was examined under various experimental conditions, preventing the action of TNF on hepatocytes.

RESULTS

TNF induced apoptosis of murine hepatocytes or human hepatoma cells in the presence of alpha-amanitin or ActD. TNF and alpha-amanitin induced such hepatotoxicity also in vivo in a synergistic way. After in vivo administration of high doses of ActD or alpha-amanitin alone, hepatic TNF-messenger RNA was increased and hepatocytes underwent apoptosis. A neutralizing antiserum against TNF-alpha prevented the liver injury. Hepatotoxicity of ActD or alpha-amanitin also was prevented by pretreatment of mice with low doses of the tolerizing cytokine interleukin 1. Mice deficient for the 55-kilodalton TNF receptor were protected from ActD- or alpha-amanitin-induced toxicity. Endotoxin-unresponsive C3H/HeJ mice also had liver failure after ActD treatment, and this damage was prevented by treatment with anti-TNF antiserum.

CONCLUSIONS

Hepatotoxins such as alpha-amanitin may induce liver failure by an indirect mechanism involving sensitization of parenchymal cells toward endogenously produced TNF.

Identification of a new hepatitis B virus (HBV) genotype from Brazil that expresses HBV surface antigen subtype adw4

The complete genome of a hepatitis B virus (HBV) from Brazil that expressed the subtype adw4 of HBV surface antigen (HBsAg) was cloned and sequenced. The genome, termed w4B, consists of 3215 bp. The overall genetic organization of typical hepadnaviruses with four open reading frames including the preC region was found to be conserved. When comparing the w4B sequence with 19 complete HBV genomes it was, however, found to be more divergent (15%) than any other HBV sequence thus far reported. Until now, no more than 11% divergence has been reported. Distinct from the five known HBV genotypes A to E, w4B made up a new, sixth genotype. The importance of the conserved third start codon in the HBV X gene became apparent in isolate w4B. By mutation, this ATG was out of frame, and by what appears to have been a linked mutation, a new start site two codons downstream was re-established. The significance of several other mutations is discussed.

Inhibition of gonadotrophin release in mares during the luteal phase of the oestrous cycle by endogenous opioids

Effects of the opioid antagonist naloxone on concentrations of LH and FSH in plasma were measured in mares during different stages of the oestrous cycle. During the follicular phase of the cycle, naloxone (300 mg i.v.) had no discernible effects on basal concentrations of LH and FSH. A significant increase in plasma LH (P < 0.01) and FSH (P < 0.05) concentrations was observed after naloxone in mares during the luteal phase. This response was not different between suckled and non-suckled mares. The gonadotrophin-releasing hormone analogue buserelin (0.02 mg i.v.) caused a significant (P < 0.05) LH and FSH release irrespective of the stage of the oestrous cycle and a previous naloxone treatment. The results of this study indicate that endogenous opioid peptides are involved in the inhibition of LH and FSH release during the luteal phase of the oestrous cycle in mares and may partially mediate the suppressive influence of progesterone on gonadotrophin secretion. The opioid-mediated suppression of LH and FSH release does not seem to be affected by suckling.

Hydroxylation of the native brassinosteroids 24-epicastasterone and 24-epibrassinolide by the fungus Cunninghamella echinulata

24-Epicastasterone and 24-epibrassinolide, two naturally occurring phytohormones of the brassinosteroid type, were transformed by the fungus Cunninghamella echinulata to give the corresponding 12 beta-hydroxylated compounds. The structures of these compounds were determined by spectroscopic methods, especially heterocorrelated two-dimensional nuclear magnetic resonance investigations. In the rice lamina inclination test the 12 beta-hydroxylation lowered the bioactivity at 0.1 ppm to 10% in comparison with that of the corresponding parent hormones. The described hydroxylations represent the first biotransformations of native brassinosteroids.

[On the use of laminar glow devices in pharmacies (author's transl)]

The possible uses of laminar flow devices are illustrated by some examples, and available types of these devices are indicated with a view to planing. The results from measurements of the flow conditions at working places equipped with these devices permit to draw conclusions which might be useful for their installation and operation. Some aspects of industrial hygiene are also touched.