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Biomedical subjects

D S Latchman

Publications and source records attributed to D S Latchman.

At least 271 records · Page 15Linked to original sources
PubMed1992

The herpes simplex virus immediate-early protein ICP27 stimulates the transcription of cellular Alu repeated sequences by increasing the activity of transcription factor TFIIIC.

Infection with herpes simplex virus (HSV) results in an increase in the transcription of the endogenous Alu repeated sequence by RNA polymerase III. This effect is also observed in uninfected cells stably transformed with a plasmid expressing the HSV immediate-early protein ICP27 or in cells transfected with the gene encoding this protein. Both uninfected cells expressing ICP27 and cells infected with virus producing functional ICP27 display increased activity of the cellular transcription factor TFIIIC when compared with untreated cells. This increase is not observed, however, in cells infected with a mutant strain of virus which does not produce ICP27. Hence ICP27 induces elevated Alu transcription by activating transcription factor TFIIIC, which is the limiting factor for such transcription. This is the first report of increased activity of a cellular transcription factor during HSV infection, when most cellular gene activity is inhibited.

Animals↗
PubMed1992

The protective role of heat stress in the ischaemic and reperfused rabbit myocardium.

Cells subjected to increases in temperature induce the expression of several proteins known as heat shock or stress proteins. This process enhances the cell's ability to overcome the effects of further stress. In this respect, the effects of heat stress have been reported to protect the hearts of rats following ischaemia and reperfusion. We have confirmed and extended this observation, not only using different indices of myocardial injury but also in another species, namely the rabbit. Animals were anaesthetized and the body temperature raised to 42 degrees C for a 15-min period. Controls were treated in the same way but without heating. Twenty-four hours later the rabbits were re-anaesthetized and the hearts removed for either heat stress protein analysis or perfusion with Krebs buffer using an isolated perfused heart apparatus. Hearts were subjected to 60 min of low flow (1 ml/min) ischaemia followed by 30 min of reperfusion. All hearts subjected to heat stress showed an enhanced recovery of function upon reperfusion as measured by improvements in developed pressure (27.3 +/- 3.6 vs 16.3 +/- 3.0 mmHg) and diastolic pressure (37.3 +/- 7.4 vs 54.7 +/- 3.1 mmHg). In addition, creatine kinase release, associated with reperfusion, was significantly reduced in the heat-stressed hearts (532 +/- 102 vs 1138 +/- 73 mU/min/g wet wt). Myocardial accumulation and release of oxidized glutathione, an index of oxidative stress, was significantly reduced in the heat-stressed group (0.003 +/- 0.003 vs 0.376 +/- 0.113 nmol/min/g wet wt). The improved metabolic status of the reperfused heat-stressed hearts was further demonstrated by a significant conservation in the levels of ATP (6.1 +/- 0.9 vs 2.8 +/- 0.8 mumol/g dry wt) and CP (36.9 +/- 6.4 vs 16.4 +/- 5.1 mumol/g dry wt). Finally, isolated mitochondrial function in terms of respiratory control index (RCI) was maintained in the heat-stressed hearts (9.2 +/- 0.9 vs 5.7 +/- 0.2) and overloading with calcium was reduced. These data extend the hypothesis that heat stress protects the heart following ischaemia and reperfusion in this in vitro model, in a way as yet undetermined.

Adenosine Triphosphate↗
PubMed1992

Promoter-independent activation of heterologous virus gene expression by the herpes simplex virus immediate-early protein ICP27.

The herpes simplex virus (HSV) immediate-early protein ICP27 has been postulated to play an auxillary role in HSV. gene expression, augmenting or inhibiting the activation of different viral promoters by the other immediate-early proteins ICPO and ICP4. Here we show that ICP27 alone can up-regulate gene expression of a retroviral vector containing Moloney murine leukemia virus (MoMuLV) regulatory sequences. This is the first report of an effect of ICP27 on gene expression driven by heterologous virus regulatory sequences. The effect does not involve the region of ICP27 which inhibits gene activation of HSV early gene promoters by ICPO and ICP4, but rather is dependent on the same region of ICP27 as is required to augment the activation of HSV late gene promoters by ICPO and ICP4. This indicates that the two activation effects are likely to operate via the same mechanism. Activation by ICP27 is dependent on the 3' LTR and adjacent region of MoMuLV but is independent of the promoter in the 5' LTR which can be replaced by a heterologous promoter such as that of SV40 without affecting activation by ICP27. The significance of this effect for an understanding of the mechanism of action of ICP27 and its role in regulating the gene expression of HSV and potentially of other viruses is discussed.

3T3 Cells↗
PubMed1992

Elevation of cyclic AMP levels in cell lines derived from latently infectable sensory neurons increases their permissivity for herpes virus infection by activating the viral immediate-early 1 gene promoter.

Immortalized cell lines derived from sensory neurons are relatively non-permissive for lytic infection with herpes simplex virus (HSV) and fail to transcribe the viral immediate-early genes following infection. Treatment of these cells with agents which raise the intra-cellular level of cyclic AMP results in increased activity of the IE1 gene which contains a cyclic AMP response element within its promoter and produces a consequent increase in permissivity for HSV infection. The significance of these effects for the regulation of HSV infection of neuronal cells are discussed in the light of the finding that cyclic AMP treatment can reactivate latent HSV infections.

1-Methyl-3-isobutylxanthine↗
PubMed1992

Expression of the tissue specific splicing protein SmN in neuronal cell lines and in regions of the brain with different splicing capacities.

The SmN protein is closely related to the ubiquitously expressed SmB and B' RNA splicing proteins but is expressed in only a limited range of tissues and cell types. The expression of SmN in a range of neuronal and non-neuronal cell lines correlates with their ability to splice the calcitonin/CGRP transcript to produce the mRNA encoding CGRP rather than that encoding calcitonin. Moreover, the SmN mRNA shows a widespread distribution within the brain and spinal ganglia being present in neuronal cells in all regions which naturally produce CGRP as well as in those areas which do not naturally express the calcitonin/CGRP gene but which can correctly splice the CGRP mRNA in transgenic mice expressing the calcitonin/CGRP gene in all cell types. Interestingly however the mRNA encoding SmN is also found in a few areas of the brain which can only carry out calcitonin-specific splicing in transgenic mice, such as the Purkinje layer of the cerebellum and the inferior colliculus. The possible role of SmN in the regulation of splicing in neuronal cells is discussed in the light of these results.

Animals↗
PubMed1992

Intracellular redistribution of neuropeptides and secretory proteins during differentiation of neuronal cell lines.

We have demonstrated that the mouse neuroblastoma N18Tg2 cell line and several clones of hybrid ND cells (ND7, ND9 and ND21), derived from the fusion of neonatal rat sensory neurons with that neuroblastoma, show immunostaining to protein gene product 9.5, neuropeptide Y, C-flanking peptide of neuropeptide Y, tyrosine hydroxylase and chromogranins. Synaptophysin could only be detected in ND cells. Immunoreactivities to substance P, calcitonin gene-related peptide, galanin and somatostatin could not be detected in any of these cell lines. After three days of incubation in a differentiation medium, cell processes of various lengths were observed both in neuroblastoma and ND cell cultures. In ND7 cells there was also a redistribution of neuropeptide Y and its C-flanking peptide to the tips of cell processes. The differentiation of cell processes was also accompanied by the appearance of immunostaining to rat chromogranins in their tips. In contrast, synaptophysin expression was found mainly in cell bodies. Neuropeptide Y, its C-flanking peptide and chromogranins have been associated with secretory granules, whereas synaptophysin is a marker for small synaptic-like vesicles. Therefore, our morphological findings further support and expand the view that these markers are primarily associated with different subcellular structures. Moreover, they indicate that the regulated secretory pathway associated with chromogranins is segregated into nerve processes at an early stage of differentiation, when the synaptophysin-associated pathway is not yet mature. ND7 cells thus provide a useful model system for studying changes in the distribution of neuropeptides, cytoskeletal elements and proteins associated with cell secretion during neuronal differentiation.

Animals↗
PubMed1992

Redistribution of secretory granule components precedes that of synaptic vesicle proteins during differentiation of a neuronal cell line in serum-free medium.

Incubation of the rat sensory neuron-derived cell line ND7 in serum-free medium results in the arrest of mitosis and the appearance of numerous neuronal processes. During this differentiation event, secretory granule components such as chromogranins, neuropeptide Y and the C-flanking peptide of pro-neuropeptide Y move to the tips of the majority of the neuronal processes regardless of process length. In contrast, the synaptic vesicle component, synaptophysin, is found only at the tips of the very long processes which appear following prolonged periods of culture in serum-free medium. A similar restriction of synaptophysin to long processes is also observed following differentiation and process formation induced by other treatments such as incubation in reduced serum or treatment with cyclic AMP or phorbol myristate acetate. Hence the regulated secretory pathway associated with the chromogranins and neuropeptides appears to be segregated into the processes at an earlier stage of ND7 differentiation than the synaptophysin-associated synaptic vesicle pathway. ND7 cells therefore provide a model system for studying the processes regulating these pathways and the redistribution of their components during neuronal differentiation.

Animals↗
PubMed1992

Surface expression of heat shock protein 90 by blood mononuclear cells from patients with systemic lupus erythematosus.

Previous studies have indicated that blood mononuclear cells from 15-20% of patients with systemic lupus erythematosus (SLE) carry elevated levels of hsp90, a heat shock protein associated with steroid receptors in cells. We analysed surface expression of hsp90 on mononuclear cells (lymphocytes and monocytes) from patients with SLE by monoclonal antibody AC88 and flow cytometry. Whilst all blood mononuclear cells have intracellular hsp90, a significant proportion of patients with SLE expressed hsp90 on lymphocyte and monocyte surfaces. This was significantly higher on SLE lymphocytes than in laboratory controls and was positively correlated with disease activity. Comparison of total hsp90 with surface hsp90 in the same SLE patients' blood mononuclear samples indicated a correlation with a subgroup of patients. There was no correlation with expression of surface hsp90 by lymphocytes and activation markers. Patients with Sjögren's syndrome, rheumatoid arthritis, dermatomyositis and scleroderma were studied as disease controls and increased levels of shsp90 were detected in only three of the 53 patients studied. It is concluded that surface hsp90 expression is a feature of about 20% of patients with SLE and is correlated with high disease activity. The exposure of this hsp on the surface of some lymphocytes suggests that it is a candidate autoantigen in SLE.

Adult↗
PubMed1992

Whole body heat stress fails to limit infarct size in the reperfused rabbit heart.

OBJECTIVE: It has recently been shown that induction of heat stress proteins by whole body heat stress confers myocardial protection in the isolated in vitro rat and rabbit heart. This study extends the above studies by examining the effects of stress protein synthesis on the limitation of infarct size in the in vivo rabbit heart model. METHODS: 30 male New Zealand white rabbits were used. Six rabbits were used for measurement of heat stress protein; 10 were used for infarct size determination in a heat stress group (HS); 14 were used for infarct size determination in a control group. There were 10 exclusions. Under anaesthesia, body temperature was raised to 42 degrees C for 15 min in the HS group. Following 24 hours of recovery rabbits were reanaesthetised and the hearts subjected to a 45 min period of regional ischaemia followed by 3 h reperfusion. The risk zone was defined with fluorescent particles and the infarct area determined by tetrazolium staining. Western blotting showed an increase in the 72 KD heat stress protein in hearts in the HS group. RESULTS: Infarct size as a percent of risk area was 61.4 (SEM 6.4)% (n = 14) in control hearts and 71.8(7.3)% (n = 10) in the HS hearts. These results were not statistically significant. CONCLUSIONS: No protective effect of heat stress could be seen when infarct size was used as the end point. Either the protection seen in earlier studies using the Krebs perfused isolated heart model does not accurately reflect protection against myocardial infarction, or heat stress itself may induce injurious factors in the blood which will negate any direct protective effect to the myocardium in this model.

Animals↗
PubMed1992

The intronless mouse gene for the tissue specific splicing protein SmN is a processed pseudogene containing a stop codon after thirty-one amino acids.

The SmN protein is a component of small ribonucleoprotein particles which is closely related to the ubiquitously expressed splicing proteins SmB and B' but is expressed in only a small number of cells and tissues. We have isolated a mouse SmN-related sequence which lacks introns and contains multiple changes from the SmN cDNA sequence including a stop codon after thirty-one amino acids which would prevent it encoding functional SmN protein. This indicates that this intronless gene is a processed pseudogene and that the functional gene has yet to be isolated. In agreement with this southern blotting of mouse DNA with SmN probes reveals bands, additional to those derived from the pseudogene, which are characteristic of an intron-containing SmN gene. The relationship of the pseudogene to the functional SmN gene and to an intronless SmN-related sequence in the rat genome is discussed.

Amino Acid Sequence↗
PubMed1992

The human immunodeficiency virus tat protein increases the transcription of human Alu repeated sequences by increasing the activity of the cellular transcription factor TFIIIC.

The HIV Tat protein is able to upregulate the transcription by RNA polymerase III of cotransfected or endogenous cellular Alu-repeated sequences in both HeLa and Jurkat T cells. This effect is mediated by an increase in the activity of transcription factor TFIIIC, which binds to the B box in the RNA polymerase III Alu promoter. This is the first example of an effect of the Tat protein on the transcription of a cellular gene or on the activity of a cellular transcription factor. The significance of this effect for the life cycle of HIV and its interaction with infected cells is discussed.

Actins↗
PubMed1991

Interferon-alpha treatment of Daudi cells down-regulates the octamer binding transcription/DNA replication factors Oct-1 and Oct-2.

Treatment of Daudi cells with alpha-interferon (alpha-IFN) results in a considerable decrease in the levels of the octamer-binding DNA replication/transcription factors Oct-1 and Oct-2 and specifically inhibits gene expression by octamer-containing promoters. The inhibitory effect on octamer-binding proteins also occurs after culturing cells with phorbol 12-myristate 13-acetate but it does not occur following alpha-IFN treatment of an alpha-IFN-resistant variant of the Daudi cell line or of HeLa cells. We discuss the potential role of the decreased levels of octamer-binding proteins in the inhibition of cell proliferation.

Base Sequence↗
PubMed1991

Activation of the cellular transcription factor AP-1 in herpes simplex virus infected cells is dependent on the viral immediate-early protein ICPO.

Lytic infection with herpes simplex virus (HSV) results in the repression of most host cell protein synthesis but produces an increased activity of the cellular AP-1 transcription factor. This increase is paralleled by an increase in the transcription rate of the proto-oncogene encoding the AP-1 component, c-Jun resulting in an increase in c-Jun protein in infected cells. The increased AP-1 activity in infected cells is dependent upon the HSV immediate-early protein ICPO. Thus a mutant lacking the gene encoding this protein fails to increase AP-1 activity whilst an ICPO expression plasmid can specifically increase the activity of an AP-1 dependent promoter in co-transfection experiments. The implications of these effects in the interaction of HSV with cultured cells are discussed.

Binding Sites↗