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.

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.

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.

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.

Isolation and preliminary characterization of the Chinese hamster thymidine kinase gene

The Chinese hamster thymidine kinase (TK) gene has been isolated from a recombinant phage library constructed with genomic DNA from mouse Ltk- cells transformed to Tk+ by transfection with Chinese hamster genomic DNA. The phage library was screened by the Benton-Davis plaque hybridization technique, using as probes, subclones of recombinant phage that were isolated from mouse Ltk+ transformants by the tRNA suppressor rescue method. The Chinese hamster TK gene is contained within 13.2 kilobases of genomic DNA in the isolate designated lambda 34S4. This gene, defined by restriction enzyme sensitivity experiments, homology studies with the chicken TK gene, and mRNA blotting experiments, may extend over 8.5 kilobases. Subclones of the lambda 34S4 isolate used as hybridization probes identified a 1,400-nucleotide polyadenylated RNA as the hamster TK mRNA. The abundance of this mRNA varies dramatically in Chinese hamster cells cultured under various growth conditions, providing direct evidence that the growth dependence of TK activity may be regulated in an important way at the level of cytoplasmic TK mRNA.

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.

Beta-adrenoceptor blockade and myocardial infarction: when should treatment start and for how long should it continue?

Treatment with oral beta 1 blockade started after recovery from acute myocardial infarction and continued for approximately 2 years reduces total mortality by about 25%. It is unclear how long oral treatment should be maintained, nor is it known if stopping beta blockade increases the risk of sudden death or reinfarction. Acute i.v. administration of beta blockers has been shown to reduce indexes of infarct size. The effect of this reduction on short- and long-term survival is promising, but not conclusive.

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.

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.

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.

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.

Selective amplification of polymorphic dihydrofolate reductase gene loci in Chinese hamster lung cells

A series of antifolate-resistant Chinese hamster lung sublines that overproduce either a Mr 20,000 or a Mr 21,000 class of dihydrofolate reductase (DHFR; tetrahydrofolate dehydrogenase; 5,6,7,8-tetrahydrofolate:NADP+ oxidoreductase, EC 1.5.1.3), known to contain amplified DHFR genes, has been analyzed by DNA and RNA transfer techniques. The results suggest that the Mr 20,000 and Mr 21,000 DHFRs are encoded by at least two polymorphic DHFR genes, both of which are expressed in drug-sensitive parental cells. In drug-resistant sublines only one of the two DHFR gene types is amplified, thus accounting for the overproduction of one or the other molecular weight class of DHFR. In addition to the known differences between the DHFRs whose overproduction they direct, these allelic genes differ in restriction endonuclease profiles and in the relative abundances of their multiple mRNA transcripts.

Gene amplification accompanies low level increases in the activity of dihydrofolate reductase in antifolate-resistant Chinese hamster lung cells containing abnormally banding chromosomes

Three independently-derived, antifolate-resistant Chinese hamster lung cell lines that exhibit low level increases in dihydrofolate reductase (DHFR) activity, i.e., three- to fivefold vs. controls, have been compared with drug-sensitive cells to determine relative DHFR gene content. With a solution hybridization technique that makes use of genomic DNA and a cloned double-stranded Chinese hamster DHFR cDNA probe, it has been found that the enzyme activity increases are associated with an approximately proportionate amplification of DHFR genes. Trypsin-Giemsa staining techniques and hybridizations in situ further show that the amplified DHFR genes are located within abnormally banding regions along chromosome 2q and also suggest that, in each subline, only one chromosome 2 homolog is initially involved in the amplification process.

Confidence in results of beta-blocker postinfarction trials

Seventeen published trials of beta-blockers in myocardial infarction were scrutinised for the 95% confidence limits for the reported treatment effects. All the trials were prospective, randomised, and (except when treatment was given intravenously) placebo controlled. For analysis of pooled results the trials were divided arbitrarily according to whether treatment had been given "early" or "late" after the onset of pain. All trials were consistent with a treatment effect of just over 20%, but benefit was more apparent in trials using late intervention with beta-blockers. The pooled results of trials using early intervention showed a positive effect of 8%, whereas those using late intervention showed a 26% reduction in mortality and confidence limits of 17-35%. The results confirm that late intervention with beta-blockers after myocardial infarction reduces mortality but show that the effect of early intervention remains to be determined.

Methods to assess breathlessness in healthy subjects: a critical evaluation and application to analyse the acute effects of diazepam and promethazine on breathlessness induced by exercise or by exposure to raised levels of carbon dioxide

1. Methods were devised and evaluated for inducing breathlessness by submaximal graded exercise in healthy subjects while objective measurements of cardiorespiratory function were made. Breathlessness was assessed with serial visual analogue scales (VAS), but with various measures to enhance repeatability. 2. A high level of reproducibility was obtained in spite of the subjective nature of the assessment. Individual responses were described by the relationship between breathlessness and ventilation. The sensitivity of the method was demonstrated by the use of inspiratory resistances which disturbed this relationship and caused greater breathlessness for a given level of ventilation. 3. These methods were applied to six healthy subjects to analyse the effects of acute doses of diazepam and promethazine on breathlessness induced by graded exercise or by rebreathing carbon dioxide in a double-blind study. 4. During exercise, diazepam and promethazine did not reduce breathlessness, although there was a minor trend with promethazine. During exposure to elevated levels of carbon dioxide, diazepam and promethazine had no effect on breathlessness. Diazepam and promethazine produced similar levels of sedation, but neither drug had significant effects on the ventilatory response to carbon dioxide. These preliminary findings contrast with those reported for chronic diazepam in 'pink puffers'. 5. Raised levels of carbon dioxide caused greater breathlessness in relation to ventilation than did exercise.