Linkage analysis of "necessary" disease loci versus "susceptibility" loci.

The association of some diseases with specific alleles of certain genetic markers has been difficult to explain. Several explanations have been proposed for the phenomenon of association, e.g. the existence of multiple, interacting genes (epistasis) or a disease locus in linkage disequilibrium with the marker locus. One might suppose that when marker data from families with associated diseases are analyzed for linkage, the existence of the association would assure that linkage will be found, and found at a tight recombination fraction. In fact, however, linkage analyses of some diseases associated with HLA, as well as diseases associated with alleles at other loci located throughout the genome, show significant evidence against linkage, and others show loose linkage, to the puzzlement of many researchers. In part, the puzzlement arises because linkage analysis is ideal for looking for loci that are necessary, even if not sufficient, for disease expression but may be much less useful for finding loci that are neither necessary nor sufficient for disease expression (so-called susceptibility loci). This work explores what happens when one looks for linkage to susceptibility loci. A susceptibility locus in this case means that the allele increases risk but is neither necessary nor sufficient for disease expression. It might be either an allele at the marker locus itself that is increasing susceptibility or an allele at a locus in linkage disequilibrium with the marker. This work uses computer simulation to examine how linkage analyses behave when confronted with data from such a model.(ABSTRACT TRUNCATED AT 250 WORDS)     

DNA Fragmentation Induced by Cytotoxic T Lymphocytes Can Result in Target Cell Death

Cytotoxic T lymphocyte (CTL)-mediated lysis is accompanied by fragmentation of target cell DNA into an oligonucleosome ladder, a hallmark of apoptosis. Is this a fortuitous coincidence, or could CTL be inducing lysis by activation of the suicide signal? In this report we demonstrate that CTL-mediated target cell death can be blocked with the drug aurintricarboxylic acid (ATA). The abrogation of death correlates with the inhibition of DNA fragmentation. While ATA prevented DNA fragmentation, it failed to significantly alter protein, RNA, or DNA synthesis in the cell lines over the dose range used. In addition, there was no inhibition of cell-cell interaction or granule exocytosis during CTL-mediated killing. ATA also significantly inhibited the cytolysis and DNA fragmentation mediated by isolated cytolytic granules, as well as the granular protein fragmentin. We developed an assay in which target cells could be separated from CTL after binding and programming for lysis. Once they had received the "kiss of death," target cells could be rescued from lysis (as indicated by inhibition of DNA fragmentation and increased target cell viability) by treatment with ATA. These results suggest that ATA blocks target cell death by inhibition of DNA fragmentation, and further, that chromatin degradation is a cause rather than a result of cell death in CTL-mediated lysis.     

Synthesis,characterization, and electrocatalytic behaviour of hydrothermally grown nanostructured La2O3 and La2O3/K-complex

Rare earth metals play a conspicuous role in magnetic resonance imaging (MRI) for detecting cancerous cells. The alkali metal potassium is a neurotransmitter in the sodium–potassium pump in biomedical sciences. This unique property of rare earth metals and potassium drew our attention to carry forward this study. Therefore, in this work, previously synthesized potassium (K) complexes formed by the reflux of 4-N,N-dimethylaminobenzoic acid (DBA) and potassium hydroxide in methanol, and named [(μ2–4-N,N-dimethylaminobenzoate-κO)(μ2–4-N,N-dimethylaminobenzoic acid-κO)(4-N,N-dimethylaminobenzoic acid-κO) potassium(I) coordination polymer)] were treated hydrothermally with La₂O₃ nanomaterials to obtain a nanohybrid La₂O₃/K-complex. After that, the K-complex was analyzed using single-crystal X-ray diffraction and ¹H and ¹³C NMR spectroscopy. In addition, the structural and morphological properties of the as-prepared nanostructured La₂O₃/K-complex were also characterized, which involved an investigation using X-ray diffraction (XRD)spectroscopy, Fourier transform infrared (FTIR) spectroscopy, atomic force spectroscopy (AFM), transmission electron microscopy (TEM), and energy dispersive X-ray (EDX) analysis. After this, the electrochemical redox behaviour of the synthesized nanohybrid material was studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Therefore, the results from these studies revealed that the as-prepared material was a La₂O₃/K-complex that has a promising future role in sensing various analytes, as it showed effective electrocatalytic behaviour.     

Activation of apoptosis pathways by granzyme B

Cytotoxic lymphocytes induce apoptosis of target cells by degranulating and releasing the serine protease granzyme B and the pore forming protein perforin. Granzyme B is an aspartic acid protease similar to members of the interleukin 1beta converting enzyme (ICE) family. We review the evidence for the participation members of the ICE family of proteases and cdc2 kinase in granzyme B-induced apoptosis.     

Induction of a Nerve Growth Factor-Sensitive Kinase that Phosphorylates the DNA-Binding Domain of the Orphan Nuclear Receptor NGFI-B

Abstract: Nerve growth factor (NGF) induces the synthesis and the phosphorylation of the orphan nuclear receptor NGFI-B in PC12 cells. Previous work has shown that phosphorylation, by protein kinase A, of a specific serine in the DNA-binding domain inhibits its binding to the NGFI-B response element. Also, cytoplasmic extracts from PC12 cells phosphorylate this serine, and phosphorylation is greater in extracts from cells treated with NGF. The present work describes the induction, identification, and partial purification of a kinase (termed NGFI-B kinase I) from PC12 cell extracts that catalyzes this phosphorylation. Phosphorylation of the DNA-binding domain with this purified preparation inhibits its binding to the NGFI-B response element. The kinase is rapidly activated by treatment of the cells with NGF, and the activation lasts for at least several hours. It also is activated by fibroblast growth factor and epidermal growth factor (EGF), but the activation by EGF is quite transient. The kinase requires Mg²⁺ but will use Mn²⁺. The molecular mass of the kinase is 95–100 kDa, and it is different from protein kinase A, Fos kinase, or pp90 ^rsk . Comparison with a partially purified preparation of cyclic AMP response element-binding protein kinase, however, indicates that the two are either very similar or identical.     

The hemagglutinin envelope protein of canine distemper virus (CDV) confers cell tropism as illustrated by CDV and measles virus complementation analysis.

Measles virus (MV) and canine distemper virus (CDV) are morbilliviruses that cause acute illnesses and several persistent central nervous system infections in humans and in dogs, respectively. Characteristically, the cytopathic effect of these viruses is the formation of syncytia in permissive cells. In this study, a vaccinia virus expression system was used to express MV and CDV hemagglutinin (HA) and fusion (F) envelope proteins. We found that cotransfecting F and HA genes of MV or F and HA genes of CDV resulted in extensive syncytium formation in permissive cells while transfecting either F or HA alone did not. Similar experiments with heterologous pairs of proteins, CDV-F with MV-HA or MV-F with CDV-HA, caused significant cell fusion in both cases. These results indicate that in this expression system, cell fusion requires both F and HA; however, the functions of these proteins are interchangeable between the two types of morbilliviruses. Human-mouse somatic hybrids were used to determine the human chromosome conferring susceptibility to either MV and CDV. Of the 12 hybrids screened, none were sensitive to MV. Two of the hybrids containing human chromosome 19 formed syncytia following CDV infection. In addition, these two hybrids underwent cell fusion when cotransfected with CDV-F and CDV-HA (but not MV-F and MV-HA) glycoproteins by using the vaccinia virus expression system. To discover the viral component responsible for cell specificity, complementation experiments coexpressing CDV-HA with MV-F or CDV-F with MV-HA in the CDV-sensitive hybrids were performed. We found that syncytia were formed only in the presence of CDV-HA. These results support the idea that the HA protein is responsible for cell tropism. Furthermore, while the F protein is necessary for the fusion process, it is interchangeable with the F protein from other morbilliviruses.     

Regulation of inositol monophosphatase in Saccharomyces cerevisiae

Inositol monophosphatase is a key enzyme in the de novo biosynthesis of inositol and in the phosphoinositide second-messenger signalling pathway. Inhibition of this enzyme is a proposed mechanism for lithium's pharmacological action in bipolar illness (manic depression). Very little is known about how expression of this enzyme is regulated. Because the yeast Saccharomyces cerevisiae has been shown to be an excellent model system in which to understand the regulation of inositol metabolism, we characterized inositol monophosphatase in this yeast. Lithium inhibited monophosphatase activity in vitro . Growth in the presence of inositol resulted in increased expression of the enzyme in vivo , although inositol had no effect on enzyme activity in vitro . The inositol effect was apparent when cells were grown in glucose but not in glycerol/ethanol. Monophosphatase activity was derepressed as cells entered stationary phase. This effect was apparent only during growth in glucose plus inositol. The results demonstrate that S. cerevisiae monophosphatase is inhibited by lithium and regulated by factors affecting phospholipid biosynthesis.