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Biomedical subjects

J A Lewis

Publications and source records attributed to J A Lewis.

At least 109 records · Page 6Linked to original sources
PubMed1986

Expression of extracellular and intracellular human IFN-gamma in mouse L cells transformed with the human IFN-gamma cDNA gene.

Cotransformation with a plasmid containing a thymidine kinase gene (pTK2) and a plasmid encoding human IFN-gamma (pTG11) has been used to establish murine L cell lines expressing human IFN-gamma. The HuIFN-gamma gene was present in 30% of the tk+ cell lines and some of these secreted low levels of IFN into the culture medium. Two of the clones obtained after transformation were selected for detailed analysis. Clone 1-12 constitutively secreted very low levels of HuIFN-gamma in the culture medium. This antiviral activity was characterized by its species specificity and antigenicity as authentic human IFN-gamma In contrast, clone 3-47 produced a HuIFN-gamma activity which could only be detected intracellularly. This clone was resistant to infection both by Vesicular stomatitis (VSV) and Mengo viruses and contained increased levels of enzymes known to be induced by interferon. Our results suggest that clone 3-47 produces a non-secreted HuIFN-gamma like molecule which is able to trigger an antiviral state in the murine cell independent of the interaction with a specific IFN-gamma surface receptor.

2',5'-Oligoadenylate Synthetase↗
PubMed1986

Structure and expression of the Chinese hamster thymidine kinase gene.

My colleagues and I have cloned a nearly full-length Chinese hamster thymidine kinase (TK) cDNA in a lambda gt10 vector and characterized this cDNA by nucleotide sequencing. The hamster TK protein is encoded in this cDNA by a 702-base-pair open reading frame which specifies a 25,625-dalton protein closely homologous to the previously described human and chicken TK proteins. Using cDNA nucleotide sequence data in conjunction with sequence data derived from selected subclones of the hamster TK gene recombinant phage lambda HaTK.5, we have resolved the structure of the TK gene, finding the 1,219 base pairs of the cDNA sequence to be distributed through 11.2 kilobases of genomic DNA in at least seven exon segments. In addition, we have constructed a variety of Chinese hamster TK minigenes and exonuclease III-S1 derivatives of these genes which have permitted us to define the limits of the Chinese hamster TK gene promoter and demonstrate that efficient TK transformation of Ltk- cells by TK minigenes depends on the presence of both TK intervening sequences and sequences 3' to the site of mRNA polyadenylation.

Amino Acid Sequence↗
PubMed1986

Genetic determinants of growth phase-dependent and adenovirus 5-responsive expression of the Chinese hamster thymidine kinase gene are contained within thymidine kinase mRNA sequences.

We have constructed a chimeric thymidine kinase (TK) minigene, pHe delta 6Ha, which combines the complete coding and 3' noncoding regions of a Chinese hamster TK cDNA with the promoter region and 5' untranslated region of the TK gene of herpes simplex virus type 1. We have transformed rat 4 cells to Tk+ with this gene and analyzed the pattern of TK gene expression in these transformants under various conditions of in vitro cell culture. We find that TK gene expression in these Tk+ transformants is growth phase dependent, responsive to adenovirus 5 infection, and indistinguishable in character under a variety of cell culture conditions from the pattern of TK gene expression in rat 4 cells transformed to Tk+ with the genomic Chinese hamster TK gene clone lambda HaTK.5. We are led to the conclusion that the genetic elements which mediate growth phase-dependent TK gene expression are contained entirely within the sequences of the mature cytoplasmic hamster TK mRNA.

Adenoviruses, Human↗
PubMed1985

Eclampsia. IV. Neurological findings and future outcome.

Sixty-five patients with eclampsia were longitudinally evaluated regarding neurological abnormalities and maternal outcome (6 to 42 months) after eclampsia. Electroencephalograms were obtained on all patients during the subsequent 6 months. Computerized axial tomographic scans (n = 20) and cerebral arteriograms (n = 3) were obtained on patients with neurological deficits and/or those with an atypical clinical course. The electroencephalogram was abnormal in 49 patients (75%) at initial assessment but gradually returned to normal in all observed patients within 6 months. Cerebral arteriograms and computerized axial tomographic scans were normal in each patient studied. None of the patients had neurological deficits or subsequent convulsions on follow-up examination. Thirty-eight patients had one or more subsequent pregnancies without recurrent eclampsia, but 14 (37%) had pregnancy-induced hypertension. The findings suggest that neurological events of eclampsia are acute and transient and that long-term neurological deficit is rare in the properly managed patient. Computerized axial tomography and electroencephalography are rarely indicated in the management of such patients.

Adolescent↗
PubMed1985

Overproduction of the protein product of a nonselected foreign gene carried by an adenovirus vector.

We have constructed a recombinant adenovirus that carries the herpes simplex virus type I gene for thymidine kinase (EC 2.7.1.21) and expresses thymidine kinase under control of adenovirus major late promoter. A DNA fragment carrying thymidine kinase coding sequences but lacking the thymidine kinase promoter was sandwiched between a piece of adenoviral DNA and simian virus 40 early DNA on a plasmid. The aligned fragment was then inserted into the adenoviral genome, replacing internal adenoviral DNA. Hybrid viruses carrying the thymidine kinase gene were obtained by selecting for viruses that express simian virus 40 tumor antigen (T antigen) in monkey cells. The thymidine kinase gene was positioned in the third segment of the adenovirus tripartite leader downstream from the major late promoter by in vivo DNA recombination between the duplicated adenoviral sequences present in the plasmid insert and the viral vector. Levels of thymidine kinase activity in human or monkey cells infected with this hybrid virus were several times higher than in cells infected with herpes simplex virus. Infected cells produced thymidine kinase protein at very high levels, similar to those found for adenovirus late major capsid proteins. The thymidine kinase protein represented 10% of the newly synthesized protein in late infected cells and accumulated to represent 1% of total cell protein under optimal conditions. This vector system offers a procedure by which a variety of gene products that are biologically active and properly modified can be produced at high levels in mammalian cells.

Adenoviridae↗
PubMed1984

Beta blockers after myocardial infarction: have trials changed practice?

A survey of British consultant cardiologists was carried out to elicit their current practices when prescribing long term beta blockers after myocardial infarction. Sixty (72%) of the respondents reported that they used beta blockers prophylactically even in the absence of any other indications; the details of their stated policies, however, varied considerably. The favourable evidence of clinical trials in this indication appears to have been assimilated into hospital practice.

Adrenergic beta-Antagonists↗
PubMed1984

Induction of an anti-viral response and 2',5'-oligo A synthetase by interferon in several thymidine kinase-deficient cell lines.

It has previously been shown that a strain of thymidine kinase (tk)-deficient mouse L-929 cells was unable to respond to murine beta-interferon by induction of an anti-viral state and synthesis of double-stranded, RNA-dependent enzymes. Sensitivity to interferon can be restored by introducing into the cells a segment of Herpes simplex virus DNA containing the viral tk gene. It is shown here that not all Ltk(-) cell strains are resistant to interferon, suggesting that expression of a tk gene is not a prerequisite for response to interferon. Introduction of various genes into the resistant Ltk(-) strain, either alone or together with DNA containing the Herpes virus tk gene, leads to restoration of interferon sensitivity only when tk-containing DNA is inserted, showing that the activation of interferon responsiveness is not an artifact of the gene transfer, selection, and cloning procedures. The results imply that a component of the Herpes virus DNA introduced into the cells is able to activate interferon sensitivity.

2',5'-Oligoadenylate Synthetase↗
PubMed1984

Effect of magnesium sulfate on electroencephalographic findings in preeclampsia-eclampsia.

Electroencephalograms (EEGs) were recorded in 36 eclamptic, 14 preeclamptic, and 13 normotensive control patients. In the eclamptic group, EEGs were recorded while patients were receiving intravenous magnesium sulfate (MgSO4) with serum magnesium (Mg) levels of 4.5 to 11 mg/dL, and recorded again after MgSO4 was discontinued (serum Mg levels 1.8 to 2.5 mg/dL). In preeclamptic patients, EEGs were recorded before starting MgSO4, during administration of the loading dose (serum Mg levels 6 to 10 mg/dL), and eight hours through the maintenance dose (serum Mg levels 3.6 to 6.2 mg/dL). Twenty-seven (75%) eclamptic patients had abnormal EEGs, four patients showed paroxysmal spike activity, and the others showed focal or diffuse slowing (delta waves). Seven (50%) preeclamptic women had abnormal EEGs (all had generalized slowing). In preeclamptic-eclamptic patients who had serial EEG recordings, the gross EEG findings obtained during MgSO4 infusion and in the absence of MgSO4 were similar. In addition, the abnormal EEG findings were frequent despite the serum Mg levels considered therapeutic in the clinical management of these patients. Two eclamptic patients had seizure activity at serum Mg levels of 9.6 and 11 mg/dL. These findings suggested that abnormal EEGs are frequent in preeclamptic-eclamptic patients. Abnormal EEG findings in such patients are not altered by serum Mg levels achieved in the clinical management of these patients.

Adolescent↗
PubMed1983

Thymidine kinase genes and the induction of anti-viral responses by interferon.

A mouse fibroblast cell-line deficient in thymidine kinase (Ltk(-) aprt(-)) fails to show an anti-viral response when treated with interferon. After introduction of a viral tk gene into these cells the resultant clones showed normal responses to interferon. However, one such tk-containing clone (C6) spontaneously lost its ability to respond to interferon by inducing an antiviral state although it retained its ability to induce the enzyme oligo(2'-5' A)-synthetase. This sub-clone (6A) still expressed thymidine kinase activity but restriction endonuclease analysis indicated an alteration in the sequences flanking the exogenous viral tk gene. Our results suggest that a modification in the exogenous viral DNA sequences led to a loss of interferon sensitivity.

2',5'-Oligoadenylate Synthetase↗
PubMed1983

Bacteria-immune system interactions. XII. Effects of aging on Balb/c mice responsiveness to Salmonella typhimurium.

Age-associated changes in reactivity to bacteria were tested at several levels. At the level of bacteria binding to lymphocytes, there were no significant differences between young and old mice, however the lymphocytes from adults bound less bacteria than the other age groups. Similarly, the lymphocytes from spleens of adult mice were less efficient in killing bacteria than all the other age groups. The lymphocytes of young mice had higher and longer range reactivity than the ones from old mice. Bacterial stimulation did not produce significant levels of thymidine incorporation in any of the age groups tested.

Aging↗
PubMed1983

Induction of an antiviral response by interferon requires thymidine kinase.

Mouse fibroblastoid cells (Ltk-) that lack thymidine kinase (tk) activity are unable to respond to murine beta-interferon by establishing antiviral activity or inducing the double-stranded RNA-dependent enzymes, oligo[(2'-5')A] polymerase and Mr 68,000 protein kinase. In contrast, the parental L-929 cell line or clonal derivatives of Ltk- cells into which the herpes virus tk gene was introduced by DNA-mediated gene transfer respond normally to interferon in developing resistance to viral infection and in inducing double-stranded RNA-dependent enzymes. Further evidence for a role of tk in the response to interferon was obtained by isolating revertants of tk+ clones that lost the herpes virus tk gene during growth in BrdUrd-containing medium. In such revertant sublines both tk enzyme activity and viral tk genes were undetectable and treatment with interferon failed to produce an antiviral effect or induce synthesis of the double-stranded RNA-dependent enzymes. Our results indicate that the ability of mouse L cells to respond to beta-interferon is dependent upon the presence of a functional tk gene. We propose that the induction of antiviral responses by interferon stringently requires a metabolite, the level of which is determined by tk activity. The system described may provide a means for elucidating the mechanisms by which responses to interferon are induced.

Adenine Nucleotides↗
PubMed1983

Driving with epilepsy: a contemporary perspective.

A committee of concerned neurologists in cooperation with the Tennessee Department of Safety and other agencies reviewed the present state licensing rules for epileptics and offered recommendations for amendments. Epileptics, diabetics, and patients with cerebrovascular disease have an accident rate of approximately twice that of the general population. Seizures probably account for approximately .02% of all vehicle accidents and only .5% to .01% of the fatal accidents. Accidents caused by seizures involve the driver's vehicle alone or an immovable object 80% of the time and occur in less populated and developed areas than controls. The number of seizures within the first three months of therapy is a powerful prognostic indicator. With knowledgeable individual consideration, licensing epileptics to drive could be done much earlier than previously allowed, without affecting road safety. Physicians giving recommendations for licensing in good faith should be protected by law from liability for unforeseen seizure recurrence.

Accidents, Traffic↗
PubMed1983

Effects of codeine on the respiratory responses to exercise in healthy subjects.

In six healthy subjects, respiration and the sensation of breathlessness were assessed during submaximal exercise and the subsequent recovery. The overall responses were expressed by the relationship of breathlessness to minute volume. Because of the high subjective component in the assessments, validation of the method in these particular subjects was an integral part of the study. The relationship of breathlessness to ventilation during identical periods of exercise was highly reproducible and sensitivity was demonstrated by an alteration in this relationship in the presence of an inspiratory resistance. Codeine at a dose of 60 mg by mouth was compared with placebo, each treatment being given on two occasions. The study was conducted in a double-blind fashion with randomization of the order of treatments. Codeine at this dose allowed higher levels of carbon dioxide to be tolerated during breath-holding; oxygen uptakes at rest and during exercise were unaffected. Ventilation and breathlessness at the end of exercise were each slightly but significantly reduced by codeine but the relationship between breathlessness and ventilation was not changed. Codeine did not prevent detection of an inspiratory resistance.

Adult↗