Identification of an interleukin HP1-like plasmacytoma growth factor produced by L cells in response to viral infection

We have recently purified and partially sequenced a new T cell-derived lymphokine with growth factor activity for B cell hybridomas and plasmacytomas, which we named interleukin HP1 (HP1). Here we show that, in response to viral infection or after treatment with poly(rI).poly(rC), L cells produce a factor that is capable of supporting the in vitro growth and survival of HP1-dependent cell lines. Serologic and structural evidence is presented in favor of the identity between the fibroblast factor and HP1, demonstrating that non-T cells can make HP1-related molecules.     

Alterations in tissue Mg++, Na+ and spinal cord edema following impact trauma in rats

Alterations in water content and total tissue Na+ and Mg++ of rat spinal cord tissue were followed over time after a 100 g-cm impact injury to the T-9 spinal cord segment. Rats subjected to laminectomy but not trauma served as controls. In the injured segment there was a progressive increase in water content with increased Na+ and decreased Mg++ at 1 hour and 24 hours after trauma. At seven days, water and Na+ content remained elevated, whereas Mg++ levels had returned to preinjury baseline values. Because of its important role in many metabolic and physiological regulatory processes the early decline in Mg++ concentration after trauma may contribute to the development of secondary tissue damage after spinal cord injury.     

Decline in intracellular free Mg2+ is associated with irreversible tissue injury after brain trauma

Much of the tissue damage resulting from trauma to the central nervous system appears to result from secondary, delayed biochemical changes that follow primary mechanical injury. However, the early biochemical events remain to be elucidated. In the present studies, we have used phosphorus (31P) magnetic resonance spectroscopy (MRS) to examine in vivo, the temporal changes in brain intracellular free Mg2+ concentration following fluid percussion head injury in rats. We report that injury caused a profound and rapid decrease in intracellular free Mg2+ which was significantly correlated with the severity of injury. At high levels of injury, the decrease in intracellular free Mg2+ concentration was associated with a decrease in total Mg2+ concentration as determined by atomic absorption spectrophotometry. Prophylactic treatment with MgSO4 prevented the post-traumatic decrease in intracellular free Mg2+ and resulted in a significant improvement in acute neurological outcome. Because magnesium is essential for a number of critical enzyme reactions, including those of glycolysis, oxidative and substrate level phosphorylation, protein synthesis, and phospholipid synthesis, changes in free Mg2+ after brain trauma may represent a critical early factor leading to irreversible tissue damage.     

Integration of human immunodeficiency virus types 1 and 2 DNA in vitro by cytoplasmic extracts of Moloney murine leukemia virus-infected mouse NIH 3T3 cells.

An essential step in the life cycle of the human immunodeficiency virus (HIV) is integration of a DNA copy of the viral RNA into the genome of the infected cell. We show here that this step can be faithfully accomplished in vitro by the enzymatic machinery of another retrovirus, Moloney murine leukemia virus (MoMLV). Mini-HIV substrates, which are linearized plasmids with long terminal repeat sequences at their ends, were incubated with cytoplasmic extracts of MoMLV-infected NIH 3T3 cells and target DNA. The MoMLV integration apparatus carried out integration of the mini-HIV substrates correctly; the terminal nucleotides of the viral substrate were removed, and a 4-base-pair duplication of the target DNA flanked the inserted viral DNA (C. Shoemaker, S. P. Goff, E. Gilboa, M. Paskind, S. W. Mitra, and D. Baltimore, Proc. Natl. Acad. Sci. USA 77:3932-3936, 1980). Our experiments show that the substrate sequence requirements for integration in vitro were limited to a few nucleotides, as the similarity between HIV and MoMLV long terminal repeat ends is minimal.     

Acute and Prolonged Alterations in Brain Free Magnesium Following Fluid Percussion-Induced Brain Trauma in Rats

Abstract: Several studies have reported declines in brain total and free magnesium concentration after a traumatic insult to the CNS. Although the evidence suggests that this magnesium decline is associated with eventual neurologic outcome after trauma, the duration of free magnesium decline and its impact on related bioenergetic variables are relatively unknown. The present study has therefore used phosphorus magnetic resonance spectroscopy to determine the length of time that free magnesium remains suppressed after traumatic brain injury in rats. Immediately after the traumatic event, brain intracellular free magnesium declined to <60% of preinjury values and remained significantly depressed (50 ± 8%; p < 0.001) for 5 days before recovering to preinjury levels by day 8. Cytosolic phosphorylation ratio and mitochondrial oxidative capacity also significantly decreased ( p = 0.008) and increased ( p = 0.002), respectively, after trauma. However, unlike the time of maximum magnesium change, the maximum changes in these bioenergetic variables occurred at 16–24 h after trauma and thereafter remained stable until after the magnesium had recovered. We conclude that free magnesium decline after trauma precedes changes in bioenergetic variables. Furthermore, therapies targeted at reestablishing magnesium homeostasis after trauma may require administration over a 1-week period.     

Structure of the rat cytomegalovirus genome termini.

The lytic replication cycle of herpesviruses can be divided into the following three steps: (i) circularization, in which, after infection, the termini of the linear double-stranded viral genome are fused; (ii) replication, in which the circular DNA serves as template for DNA replication, which generates large DNA concatemers; and (iii) maturation, in which the concatemeric viral DNA is processed into unit-length genomes, which are packaged into capsids. Sequences at the termini of the linear virion DNA are thought to play a key role in both genome circularization and maturation. To investigate the mechanism of these processes in the replication of rat cytomegalovirus (RCMV), we cloned, sequenced, and characterized the genomic termini of this betaherpesvirus. Both RCMV genomic termini were found to contain a single copy of a direct terminal repeat (TR). The TR sequence is 504 bp in length, has a high GC content (76%), and is not repeated at internal sites within the RCMV genome. The TR comprises several small internal direct repeats as well as two sequences which are homologous to herpesvirus pac-1 and pac-2 sites, respectively. The organization of the RCMV TR is unique among cytomegaloviruses with respect to the position of the pac sequences: pac-1 is located near the left end of the TR, whereas pac-2 is present near the right end. Both RCMV DNA termini carry an extension of a single nucleotide at the 3' end. Since these nucleotides are complementary, circularization of the viral genome is likely to occur via a simple ligation reaction.     

Formation of a stable complex between the human immunodeficiency virus integrase protein and viral DNA.

The integrase (IN) protein of the human immunodeficiency virus (HIV) mediates two distinct reactions: (i) specific removal of two nucleotides from the 3' ends of the viral DNA and (ii) integration of the viral DNA into target DNA. Although IN discriminates between specific (viral) DNA and nonspecific DNA in physical in vitro assays, a sequence-specific DNA-binding domain could not be identified in the protein. A nonspecific DNA-binding domain, however, was found at the C terminus of the protein. We examined the DNA-binding characteristics of HIV-1 IN, and found that a stable complex of IN and viral DNA is formed in the presence of Mn2+. The IN-viral DNA complex is resistant to challenge by an excess of competitor DNA. Stable binding of IN to the viral DNA requires that the protein contains an intact N-terminal domain and active site (in the central region of the protein), in addition to the C-terminal DNA-binding domain.     

Ultrastructural evidence for a triple structure of the lateral element of the synaptonemal complex.

This study describes composition and localization of several substructures of the synaptonemal complex (SC) using different techniques. The techniques which were used were surface spreading, critical point drying of isolated SCs, and sectioning of Lowicryl embedded testis material. The lateral elements (LEs) of the SC appear to be composed of three lateral substructures: two morphologically identical major strands and a third strand which is considerably thinner. The thinner strand is localized on the inner side of the two major strands of the lateral element. In late pachytene/early diplotene stages when the SC starts to disintegrate more than three strands can be observed in the LEs. A model is presented and the function of the different substructures is speculated upon.