In vitro activation of human herpesviruses 6 and 7 from latency.

Human herpesviruses 6 and 7 (HHV-6 and HHV-7) are prevalent lymphotropic viruses that infect more than 80% of children at infancy or during early childhood. Infection ranges from asymptomatic to severe disease. HHV-6B causes exanthem subitum. The virus can be recovered from peripheral blood mononuclear cells during the acute phase of exanthem subitum, but the host remains latently infected throughout life. In immunocompromised patients undergoing kidney, liver, or bone marrow transplantation latent HHV-6B is reactivated, at times causing severe or fatal disease. Here, we describe the establishment of an in vitro system for reactivation of HHV-6B and HHV-7 from latency. HHV-7 is reactivated from latently infected peripheral blood mononuclear cells by T-cell activation. HHV-6B could not be reactivated under similar conditions; however, the latent HHV-6B could be recovered after the cells were infected with HHV-7. Once reactivated, the HHV-6B genomes became prominent and the HHV-7 disappeared. We conclude that HHV-7 can provide a transacting function(s) mediating HHV-6 reactivating from latency. Understanding the activation process is critical for the development of treatments to control the activation of latent viruses so as to avoid these sometimes life threatening infections in transplant recipients.

Traumatic brain damage prevented by the non-N-methyl-D-aspartate antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo[f] quinoxaline.

The mechanisms of neuronal degeneration following traumatic head injury are not well understood and no adequate treatment is currently available for the prevention of traumatic brain damage in humans. Traumatic head injury leads to primary (at impact) and secondary (distant) damage to the brain. Mechanical percussion of the rat cortex mimics primary damage seen after traumatic head injury in humans; no animal model mimicking the secondary damage following traumatic head injury has yet been established. Rats subjected to percussion trauma of the cortex showed primary damage in the cortex and secondary damage in the hippocampus. Morphometric analysis demonstrated that both cortical and hippocampal damage was mitigated by pretreatment with either the N-methyl-D-aspartate (NMDA) antagonist 3-((+/-)- 2-carboxypiperazin-4-yl)-propyl-1-phosphonate (CPP) or the non-NMDA antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[f]quinoxaline (NBQX). Neither treatment prevented primary damage in the cortex when therapy was started after trauma. Surprisingly, delayed treatment of rats with NBQX, but not with CPP, beginning between 1 and 7 hr after trauma prevented hippocampal damage. No protection was seen when therapy with NBQX was started 10 hr after trauma. These data indicate that both NMDA- and non-NMDA-dependent mechanisms contribute to the development of primary damage in the cortex, whereas non-NMDA mechanisms are involved in the evolution of secondary damage in the hippocampus in rats subjected to traumatic head injury. The wide therapeutic time-window documented for NBQX suggests that antagonism at non-NMDA receptors may offer a novel therapeutic approach for preventing deterioration of the brain after head injury.

A histologically distinctive interstitial pneumonia induced by overexpression of the interleukin 6, transforming growth factor beta 1, or platelet-derived growth factor B gene.

Interstitial pneumonia is characterized by alveolitis with resulting fibrosis of the interstitium. To determine the relevance of humoral factors in the pathogenesis of interstitial pneumonia, we introduced expression vectors into Wistar rats via the trachea to locally overexpress humoral factors in the lungs. Human interleukin (IL) 6 and IL-6 receptor genes induced lymphocytic alveolitis without marked fibroblast proliferation. In contrast, overexpression of human transforming growth factor beta 1 or human platelet-derived growth factor B gene induced only mild or apparent cellular infiltration in the alveoli, respectively. However, both factors induced significant proliferation of fibroblasts and deposition of collagen fibrils. These histopathologic changes induced by the transforming growth factor beta 1 and platelet-derived growth factor B gene are partly akin to those changes seen in lung tissues from patients with pulmonary fibrosis and markedly contrast with the changes induced by overexpression of the IL-6 and IL-6 receptor genes that mimics lymphocytic interstitial pneumonia.

Twenty-five coregulated transcripts define a sterigmatocystin gene cluster in Aspergillus nidulans.

Sterigmatocystin (ST) and the aflatoxins (AFs), related fungal secondary metabolites, are among the most toxic, mutagenic, and carcinogenic natural products known. The ST biosynthetic pathway in Aspergillus nidulans is estimated to involve at least 15 enzymatic activities, while certain Aspergillus parasiticus, Aspergillus flavus, and Aspergillus nomius strains contain additional activities that convert ST to AF. We have characterized a 60-kb region in the A. nidulans genome and find it contains many, if not all, of the genes needed for ST biosynthesis. This region includes verA, a structural gene previously shown to be required for ST biosynthesis, and 24 additional closely spaced transcripts ranging in size from 0.6 to 7.2 kb that are coordinately induced only under ST-producing conditions. Each end of this gene cluster is demarcated by transcripts that are expressed under both ST-inducing and non-ST-inducing conditions. Deduced polypeptide sequences of regions within this cluster had a high percentage of identity with enzymes that have activities predicted for ST/AF biosynthesis, including a polyketide synthase, a fatty acid synthase (alpha and beta subunits), five monooxygenases, four dehydrogenases, an esterase, an 0-methyltransferase, a reductase, an oxidase, and a zinc cluster DNA binding protein. A revised system for naming the genes of the ST pathway is presented.