[Estimation of benefits and risks of the treatment of rheumatoid polyarthritis with glucocorticoids using the health-related quality of life measurements]

The purpose of this study was to use the utility approach to evaluate the risks and benefits of corticosteroid therapy in rheumatoid arthritis patients. The utility approach provides us with a quantitative measure of the value or preference a patient attaches to his overall health status defined on a scale from perfect health (1) to death (0). Benefits and toxicity are combined into a number reflecting the patients combined assessment of the benefits of treatment and the side-effects associated with it. Utility of 3 scenarios (rheumatoid arthritis patients treated respectively with no, 5 mg/day and 15 mg/day of prednisone) were determined through the time trade-off (TTO) and thermometer scale (TS) techniques. Twenty-five rheumatoid arthritis patients selected at random among subjects attending an outpatient clinic and 25 rheumatologists were interviewed using visual aids. Treatment with 15 mg/d prednisone was assigned the highest utilities by both patients and physicians. Coefficients of correlation between thermometer scale and time trade-off utilities were 0.675 (p < 0.01) for physician-assigned utilities and 0.518 (p < 0.05) for patient-assigned utilities. Medical decisions concerning rheumatoid arthritis patients should take into account the preferences of patients and physicians.

Feasibility of utility assessment by rating scale and standard gamble in patients with ankylosing spondylitis or fibromyalgia

OBJECTIVE

To assess the feasibility of utility measurement in patients with ankylosing spondylitis (AS) or fibromyalgia (FMS). Patient derived utilities provide overall estimates of the impact of a disease on patient well being.

METHODS

The Maastricht Utility Measurement Questionnaire was applied cross sectionally to 57 patients with AS and 86 outpatients with FMS. By means of rating scale and standard gamble techniques, patients were asked to value their own health state.

RESULTS

All 143 patients completed the interview. Patients with AS valued their personal health state on the rating scale (0-100) considerably higher than patients with FMS (AS: 69 and FMS: 54). Standard gamble utility values (0-1), however, were about the same at a higher level (AS: 0.86 and FMS: 0.83). Four weeks test-retest reliability was examined in 15 patients with FMS. The intraclass correlation coefficient of the utility score for the patient's own health state was 0.56 for the rating scale and 0.66 for the standard gamble technique.

CONCLUSION

Feasibility of the Maastricht Utility Measurement Questionnaire was generally satisfactory in both patient groups. Utility values obtained by rating scale and standard gamble technique differed considerably. Our data support the view that utility measurement is sensitive to the method chosen to elicit patient well being.

Germ-line determination in Caenorhabditis and Ascaris: Will a helicase begin to unravel the mystery?

How cell lineages are established during development in higher eukaryotes is being addressed by geneticists and by developmental and molecular biologists. In Drosophila melanogaster, a gene corresponding to a germ-line-specific RNA helicase, vasa, has been shown to be a component o f the posteriorly localized germ granules o f the developing embryo. A putative RNA helicase, glh-I r which appears germ-line specific in its expression, has recently been reported from the free-living nematode Caenorhabditis elegans. Parasitologists studying the nematode Ascaris lumbricoides var. suum have found it to be a useful complement to Caenorhabditis. Deborah Roussell, Michael Gruidl and Karen Bennett predict that Ascaris will be valuable in determining the role played by germ-line helicases in development.

The population health impact of arthritis. POHEM Workshop Group

The workshop was convened to develop quantitative estimates of the incidence of progressional musculoskeletal diseases in order to estimate the population health impact of arthritis. Estimates were developed for (a) the prevalence of arthritis, (b) a weighting strategy to adjust for the quality of life for the range of health states associated with arthritis, and (c) transition probabilities to represent the likelihood of disease onset and progression through the range of possible health states. A simulation "game" was designed to follow the progression of a cohort of 200 healthy persons or persons with arthritis, creating the basis for the estimation of transition probabilities and thus generating simulated longitudinal data that allow calculation of the quantitative estimate of the burden of illness from musculoskeletal diseases within the Canadian population.

Health related utility measurement in rheumatology: an introduction

Utility measures of health-related quality of life are preference values that patients attach to their overall health status. In clinical trials, utility measures summarize both positive and negative effects of an intervention into one single value between 0 (equal to death) and 1 (equal to perfect health). These measures allow for comparison of patient outcomes of different diseases and allow for comparison between various health care interventions. There are two different approaches to utility measurement. The first is to classify patients into categories based on their responses to a number of questions about their functional status, as for instance the Quality of Well-Being questionnaire. The second approach is to ask patients to assign a single rating to their overall health by means of rating scale, standard gamble, time trade-off, or willingness to pay. The Quality Adjusted Life Year (QALY) as outcome measure includes both effects in terms of quality and quantity of life. Utilities are used as weights to adjust life years for the quality of life in order to calculate QALYs. Both QALYs and utilities are useful in decision-making regarding appropriate procedures for groups of patients.

cDNA cloning and sequence analysis of beta ig-h3, a novel gene induced in a human adenocarcinoma cell line after treatment with transforming growth factor-beta

Transforming growth factor-beta (TGF-beta) is capable of affecting the proliferation of many cell types. To identify novel genes whose protein products may mediate cellular responses to this factor, a cDNA library was made from mRNA isolated from a human lung adenocarcinoma cell line (A549) that had been treated for 3 days with TGF-beta. The library was screened by differential hybridization and a cDNA clone, beta ig-h3, was isolated. This gene was induced up to 20-fold in A549 cells after 2 days of treatment with TGF-beta 1. It was also induced in several other cell lines, including PC-3 and H2981. DNA sequence analysis of beta ig-h3 indicated that it encoded a novel protein, beta IG-H3, of 683 amino acids, which contained an amino-terminal secretory sequence and a carboxy-terminal Arg-Gly-Asp (RGD) sequence that can serve as a ligand recognition site for several integrins. beta IG-H3 also contained short amino acid regions homologous to similar regions in Drosophila fasciclin-I and four homologous internal domains, which can be folded into a potential bivalent structure and could act as a bridge between cells expressing the appropriate ligand. beta ig-h3 RNA was detected in several cell lines and tissues. COS cells transfected with plasmids encoding beta IG-H3 secreted a major 68-kD protein that was detected by immunoblotting using antipeptide antibodies. Since beta ig-h3 is induced in several cell lines whose proliferation is affected by TGF-beta 1, it may be involved in mediating some of the signals of this multifunctional growth modulator.

Quality-of-life assessment: patient compliance with questionnaire completion

BACKGROUND

Previous investigators have found that compliance with quality-of-life data collection on cancer clinical trials is poor. There is general belief that collecting complete quality-of-life data is at present an unachievable goal.

PURPOSE

We assessed the completeness of quality-of-life data collection on trials instituted by the National Cancer Institute of Canada Clinical Trials Group (NCIC CTG), since incorporation of quality-of-life outcomes into trials became mandatory for the group.

METHODS

Data from three NCIC CTG trials in which quality of life was a study end point were examined to determine the extent to which protocol specifications were met with respect to questionnaire completion. Two of the studies examined adjuvant therapies, and one examined anti-emetics. In two trials, the quality-of-life questionnaire of the European Organization for Research and Treatment of Cancer was used; in the other, the Breast Cancer Chemotherapy Questionnaire.

RESULTS

Patient compliance with questionnaire completion was unexpectedly high: More than 95% of the scheduled questionnaires were returned, and more than 99% of the questions were answered.

CONCLUSIONS

We attribute this success to a comprehensive set of measures taken to enhance compliance on these studies. Which of these measures was most contributory requires further investigation, as does the issue of whether similar results can be obtained in other circumstances.

IMPLICATIONS

It seems that the commonly held belief that quality-of-life data cannot be successfully collected in multicenter cancer trials is incorrect.

Antigen processing for presentation by class II major histocompatibility complex requires cleavage by cathepsin E

Proteolytic degradation (processing) of antigen by antigen-presenting cells is a major regulatory step in the activation of a T lymphocyte immune response. However, the enzymes responsible for antigen processing remain largely undefined. In this study we show that cathepsin E, and not the ubiquitous lysosomal cathepsin D, is the major aspartic proteinase in a murine antigen-presenting cell line, A20. This enzyme is localized to a non-lysosomal compartment of the endosomal system in these cells. Functional studies using a highly specific inhibitor of cathepsin E show that this enzyme is essential for the processing of ovalbumin by this cell line. Thus, cathepsin E, whose function was hitherto unknown, may play a major role in antigen processing.

Extending community health nursing services. The Student Learning Center

Faced with scarce resources, the Visiting Nurse Association of Omaha (VNA), Bishop Clarkson College, Creighton University, and University of Nebraska Medical Center collaborated to maintain services. Baccalaureate students learned to deliver community health nursing while serving a population in need of these services, but not coverable by funding sources. The Student Learning Center established by the VNA enabled 254 students to provide 5,035 home visits to families without funding sources.

Methodologic challenges in the development of utility measures of health-related quality of life in rheumatoid arthritis

Utility measures of health-related quality-of-life (HRQL) are unique in that they focus on patient preferences for alternative health conditions and combine benefit and toxicity into one number. This paper addresses the application of utility measurement techniques to assess HRQL in rheumatoid arthritis (RA). More specifically, the measurement issues and empirical evaluation strategies relevant to establishing the usefulness of utility measures in clinical trials and "n of 1" studies in RA are presented. First, utilities are reviewed within the context of RA and the other measures of benefit and toxicity currently in use. Second, the key methodologic challenges relevant to the development of HRQL measures of RA treatment impact are identified. Finally, a new utility instrument suitable for use in both parallel group and "n of 1" drug trials in RA is presented. The work described also addresses the interpretation of utility values and hence their acceptability to clinicians, researchers and policy makers and may aid initiatives to establish HRQL as one of the criteria for approval by federal drug regulatory agencies. Given that patient preferences constitute a central concept within the framework of HRQL, further empirical evaluation of utility measures of preference is fundamental to improving the HRQL measurement tool-kit.

A prospective, randomized trial comparing combination half-dose tissue-type plasminogen activator and streptokinase with full-dose tissue-type plasminogen activator. Kentucky Acute Myocardial Infarction Trial (KAMIT) Group

BACKGROUND

The potential benefits of combination thrombolytic agents in the treatment of myocardial infarction remain uncertain. In a small pilot study, we demonstrated that combining half-dose tissue-type plasminogen activator (t-PA) with streptokinase (SK) achieved a high rate of infarct vessel patency and a low rate of reocclusion at half the cost of full-dose t-PA.

METHODS AND RESULTS

We designed a prospective trial in which 216 patients were randomized within 6 hours of myocardial infarction to receive either the combination of half-dose (50 mg) t-PA with streptokinase (1.5 MU) during 1 hour or to the conventional dose of t-PA (100 mg) during 3 hours. Acute patency was determined by angiography at 90 minutes, and angioplasty was reserved for failed thrombolysis. Heparin and aspirin regimens were maintained until follow-up catheterization at day 7. Acute patency was significantly greater after t-PA/SK (79%) than with t-PA alone (64%, p less than 0.05). After angioplasty for failed thrombolysis, acute patency increased to 96% in both groups. Marked depletion of serum fibrinogen levels occurred after t-PA/SK compared with t-PA alone at 4 hours (37 +/- 36 versus 199 +/- 66 mg/dl, p less than 0.0001) and persisted 24 hours after therapy (153 +/- 66 versus 252 +/- 75 mg/dl, p less than 0.0001). Reocclusion (3% versus 10%, p = 0.06), reinfarction (0% versus 4%, p less than 0.05), and need for emergency bypass surgery (1% versus 6%, p = 0.05) tended to be less in the t-PA/SK group. Greater myocardial salvage was apparent in the t-PA/SK group as assessed by infarct zone function at day 7 (-1.9 SD/chord versus -2.3 SD/chord after t-PA alone, p less than 0.05). In-hospital mortality (6% versus 4%) and serious bleeding (12% versus 11%) were similar between the two groups.

CONCLUSIONS

These results suggest that a less expensive regimen of half-dose t-PA with SK yields superior 90-minute patency and left ventricular function and a trend toward reduced reocclusion compared with the conventional dose of t-PA.

The International Clinical Epidemiology Network (INCLEN): a progress report

The International Clinical Epidemiology Network (INCLEN) was established in 1982 to strengthen the research capacity of medical schools in the developing world through the development of Clinical Epidemiology Units (CEUs). The role of these units is to promote a rational approach to clinical and health care decision making, drawing on the methods of clinical epidemiology, biostatistics, health economics and health social science. This paper summarizes the evolution of the INCLEN model and the experience to date. Progress with Phase 1, the designation of sites for CEU development and the provision of advanced research training by developed country training centres has been substantial. The network now consists of 27 units: 26 in developing country medical schools in Asia, Latin America, India and Africa and 1 in France. More than 60% of the target of 270 fellows have completed training and returned to take up faculty positions in their unit. The remainder will be trained and on site by 1995. The non-return rate of fellows (2%) is very low. Research productivity is significant given only 60 fellows have been working in their CEUs for more than 3 years following the completion of training. An appropriate balance between hospital and community-based research is evident and changes in clinical and health care policy have been made based on the research conducted. The educational responsibilities of all units include courses and workshops in critical appraisal and clinical epidemiology for medical trainees and colleagues. Graduate training programs have emerged in 3 units so far. Major challenges lie ahead as we move into Phase 2 of the project--self sustainability and the transfer of training responsibility to the CEUs. The problems encountered during Phase 1 will need to be addressed. These include time protection for research, the limited availability of research funds, the low priority given to research careers and the poor linkage between health researchers and government policy makers. Our experience echos the recommendations of the recent report of the Commission on Health Research for Development, namely that donors and national governments should give increased priority to the role of health research in less developed countries. We conclude that with continuing support and special attention to the problems encountered, the INCLEN approach can contribute to ensuring that the medical establishment is part of the solution rather than the problem faced by health systems in less developed countries.

Characterization and expression of a spliced leader RNA in the parasitic nematode Ascaris lumbricoides var. suum

The parasitic nematode Ascaris spp. contains a 22-nucleotide spliced-leader (SL) sequence identical to the trans-SL previously described in Caenorhabditis elegans and other nematodes. The SL comprises the first 22 nucleotides of a approximately 110-base RNA and is transcribed by RNA polymerase II. The SL RNA contains a trimethylguanosine cap and a consensus Sm binding site. Furthermore, the Ascaris SL RNA has the potential to adopt a secondary structure which is nearly identical to potential secondary structures of similar SL RNAs in C. elegans and Brugia malayi.

Meta-analysis of injectable gold in rheumatoid arthritis

A pooled estimate of the magnitude of the benefit and side effects of injectable gold salts in rheumatoid arthritis was computed using meta-analysis based upon available evidence in the literature. Active joint count, grip strength, functional capacity, hemoglobin concentration and erythrocyte sedimentation rate (ESR) were pooled. The change in percentage in favor of gold (adjusted for placebo) was as follows: active joint count 30.1%, (p less than 0.00001), grip strength 13.7% (p less than 0.013), functional capacity 13% (p less than 0.0005), hemoglobin concentration 5.3% (p less than 0.02), and ESR 19.6% (p less than 0.02). Pooling of side effects gave the following results: side effect withdrawals were 11% (p less than 0.01), dermatitis occurred in 15% and proteinuria in 0.7% more patients than in the placebo group.

Low dose cyclosporine in rheumatoid arthritis: a pilot study

A 6 month open trial of cyclosporine (CyA) was conducted in 20 patients with active rheumatoid arthritis unresponsive to second line therapy. The dosage was monitored to achieve a serum blood level of 75-150 ng/ml. A 25% reduction in ARA joint count (baseline mean 38.2; 6 month or time of CyA withdrawal mean 28.7; p less than 0.001) was observed for all patients. Fifteen completed the 6 month CyA regimen and 5 developed toxicity requiring CyA to be permanently withdrawn. For the 15 patients completing 6 months of CyA, improvement was 36% (baseline 34.7; 6 month mean 22.2; p less than 0.001). Corresponding improvements were also observed on the other main study outcomes of pain and functional ability. Improvement occurred between 12-20 weeks, somewhat later than in other studies. Toxicity included mild hypertension (4 patients) and gastrointestinal intolerance (2). Three patients were withdrawn from CyA due to nephrotoxicity. There was a clinically significant reduction in calculated creatinine clearance but this returned to baseline within 6 months after CyA was withdrawn for all except 2 patients who took 12 months to return to baseline.

Methotrexate in rheumatoid arthritis. Indications, contraindications, efficacy, and safety

Evidence on the safety and efficacy of methotrexate as a second- or third-line agent for treating patients with rheumatoid arthritis is reviewed. Four placebo-controlled clinical trials have documented short-term benefit from methotrexate; although true remission is rare, patients receiving methotrexate showed a 26% (95% confidence interval [CI], 17% to 35%) greater improvement in their inflamed joint count and a 39% (95% CI, 26% to 51.5%) greater improvement in pain than did controls receiving nonsteroidal anti-inflammatory agents with or without prednisone. With respect to long-term benefit, improvement usually occurs within 1 month, reaching a maximum at 6 and then leveling off for the duration of treatment; in some patients, the benefit may wane after an initial satisfactory response in the first 4 to 6 months. In one third of those given methotrexate, treatment had to be discontinued because of adverse effects, less than 1% of which were life threatening. Careful baseline and follow-up monitoring is recommended until more data on the safety of methotrexate are available.

The entrapment of [14C]ascorbic acid in human erythrocytes

Radioactively labelled ascorbic acid and dehydroascorbic acid, when incubated with human blood, migrate irreversibly into human red blood cells. Isolation and characterization of the moieties trapped within the cells via infrared spectroscopy established both their identities as L-ascorbic acid. Evidence in the form of the degree of in vitro entrapment of ascorbic acid as a function of the times of incubation and the effect of incubation temperature, anion recognition site inhibitor, and active transport inhibitor on the rate of entrapment support the hypothesis that ascorbic acid is oxidized on or near the surface of the red blood cell to dehydroascorbic acid which migrates through the lipid portion of the cell wall and is reduced back to ascorbic acid within the cell. The resulting L-ascorbic acid can not pass through the cell wall and is therefore entrapped.

Guidelines for the clinical and economic evaluation of health care technologies

The health care system is routinely confronted with promising new technologies. In the past, most new technologies have been integrated into clinical practice without a rigorous demonstration of their effectiveness or efficiency. In order to provide a more rational approach to the adoption and utilization of health technology a comprehensive set of guidelines for both clinical and economic evaluation is proposed. While conceived of as an ideal that is unlikely to be universally met in practice, it is argued that decision making can be improved by striving towards this goal. The clinical guidelines stress the advantages of subjecting major new technologies to randomized controlled trials and insisting upon a demonstration of patient benefit in the application of diagnostic technologies. The economic guidelines stress comparisons with relevant alternative uses of the resources and the assessment of the impact on the quality of life. While application of the guidelines will produce rigorous and useful evidence, the final decisions concerning the allocation of health care resources must rest fundamentally on social value judgements and not solely, or even primarily, on informed expert opinion.

Trials of staphylococcal protein A-treated plasma infusions in cancer therapy: clinical effects and implications for mode of action

The data presented here indicate that patients with advanced cancer exhibit a modest but definite objective response rate to biweekly infusions of autologous plasma treated with purified, covalently bound staphylococcal protein A in a relatively nontoxic treatment program. The possibility that responses could be enhanced by alteration of treatment parameters, improved patient selection, and/or combined therapy remains to be explored. In vitro studies indicate that tumor cell killing can be produced in an ovarian cancer cell line using ascitic fluid of some ovarian cancer patients that has been treated with small amounts of protein A covalently linked to silica gel or agarose. This may be a suitable model system for exploration of possible humoral mechanisms of protein A-associated tumoricidal effects. The available literature indicates an antitumor effect of protein A-treated patient plasma in a variety of in vitro systems, as well as in animal and human tumors in vivo. Preliminary investigations of the mechanism of these effects are inconsistent and support the view that several different mechanisms of tumor cell killing may be operative in different settings.

Optical tomography: experimental verification of noise theory

Optical absorption tomography is used to map the iodine-vapor density in a plane. Two-dimensional images are obtained with 1-cm spatial resolution by using a fan-beam geometry with a 56-cm-diameter source circle. Experimental results confirm a theoretical analysis of noise in the reconstructed image, including the effects of correlated noise, position within the image, and spatial averaging.

Treatment of advanced malignancy with plasma perfused over staphylococcal protein A

A total of 14 extensively pretreated patients with advanced and progressive malignancy were given 140 infusions of autologous plasma that had been perfused over staphylococcal protein A bound to an agarose gel (Sepharose). Infusions ranged in volume from 35 ml to 260 ml (mean, 70 ml), and the quantity of protein A used ranged from 1 to 30 mg per 100 ml of plasma (mean, 10 mg). Acute toxic reactions included fever (21%), chills (18%), nausea (17%), vomiting (8%), pain (9%) and bronchospasm (2%). Four patients did not have an acute toxic reaction and no chronic or cumulative toxic effects were identified. In two patients there was objective tumor regression and in five there was stabilization of disease lasting from 4 to 12 weeks. Further study of this treatment modality is warranted.

Mutagenicity of a series of hexacoordinate chromium (III) compounds

17 chromium(III) compounds have been tested for DNA-damaging capabilities using an E. coli differential repair assay and for mutagenicity in strains of Salmonella typhimurium. 4 of these compounds were active in both assays. Another 4 compounds were positive only in the repair assay and 9 were devoid of activity in both assays. Most of the doubly active complexes contain aromatic amine ligands like 2,2'-bipyridine and 1,10-phenanthroline. Closely related complexes of ligands derived from saturated amines are much less active. It appears that chromium(III) in the proper ligand environment can have considerable genetic toxicity and could represent one of the several possible ultimate species in a mechanism for chromium mutagenesis and carcinogenesis.

Mutagenicity of a series of hexacoordinate rhodium(III) compounds

19 rhodium(III) compounds have been tested for genetic damaging capabilities using an Escherichia coli differential repair assay and for mutagenicity in the strains of Salmonella typhimurium. 10 of these were active in both assays. Presence of the plasmid pKM101 was required for mutagenicity in Salmonella. Both the composition of the ligands and the free-dimensional structures of the coordination complexes profoundly affect genetic activity. In general, the structure--activity relationships appear to favor complexes with (1) a +1 charge, (2) 2-relatively labile leaving groups with 4 more strongly bonded amine ligands, and (3) a relatively slow rate of exchange of the ligands which is characteristic of substitutionally inert coordination complexes.

Computer-controllable wedged-plate optical variable attenuator

A computer-controllable variable optical attenuator has been developed and tested that has a wide dynamic range, wide spectral range, and is suitable for applications with high peak and average power laser sources. The device is based on Fresnel transmission through two pairs of wedged plates. A 35-dB dynamic range, an insertion loss of 1%, a precision of better than 1% and beam offset and deflection of <0.5 mm and 0.5 mrad, respectively, are demonstrated.

Full-thickness transnasal flap

A method is described to reconstruct a unilateral asymmetrical defect of the tip of the nose resulting from burn scar contracture and alar loss by utilizing an appropriate full-thickness rotation of tissue of similar consistency to the defect derived from the opposite side of the nose. This transfer led to the use of similar, but normal tissue, by subtracting from the dimensions of the normal side to add to the shortage of tissue on the abnormal side. This method was designed because of the lack of normal adjacent tissue available for transfer and demonstrates a relatively simple solution to a difficult problem.

Effect of hydrocortisone on cell morphology in C6 cells

Hydrocortisone has been found to induce cell spreading in rat glial C6 cells by 24 hours after its addition. This spreading phenomenon is correlated with an increase in the fraction of the peripheral cytoplasm occupied by microfilaments. Cytochalasin B causes disorganization of microfilaments in the peripheral cytoplasm of the cells. Additionally, it also prevents cell spreading in response to hormonal stimulation. High levels of calcium prevent recovery of normal microfilament organization and cell spreading following removal of cytochalasin B, but have no effect on normal microfilament organization alone. Additionally both the hydrocortisone induced spreading of C6 cells and increases in peripheral microfilaments are shown to be dependent on RNA ans protein synthesis. The levels of protein co-electrophoresing with actin are not effected by hydrocortisone.

Reversible inhibition of the hydrocortisone induction of glycerol phosphate dehydrogenase by cytochalasin B in rat glial C6 cells

The hydrocortisone (HC) induction of glycerol phosphate dehydrogenase (GPDH; EC 1.1.1.8) in rat glial C6 cells was inhibited reversibly and in a dose-dependent manner by cytochalasin B (CB). CB had no effect on basal level GPDH, total cellular RNA, DNA or protein content nor did it act as a general inhibitor of the rate of protein synthesis. CB did not appear to be acting via dissociation of microtubules since colcemid had no effect on the induction process. The addition of an alternate energy source (sodium pyruvate) did not relieve the CB inhibition of GPDH induction suggesting that CB is not exerting its effect by blocking glucose utilization. The inhibition by CB is not dependent on the temporal sequence of the induction process since it specifically inhibited GPDH induction at any time it was added. CB did not alter the rate of degradation of GPDH in these cells and direct measurements of the specific rate of synthesis of GPDH demonstrated that CB decreased the induced rate of GPDH synthesis by about 60%. The site of inhibition was more precisely defined by experiments which demonstrated a 60% decrease in specific nuclear binding of 3H-HC even though total cellular uptake of 3H-HC was unaffected. This effect on nuclear binding of HC is sufficient to account for the decreased accumulation of GPDH activity in CB-treated cells.

Reversible inhibition of the norepinephrine induction of lactate dehydrogenase by cytochalasin B in rat glial C6 cells

The cyclic AMP mediated induction of lactate dehydrogenase (LDH: E.C. 1.1.1.27) activity by norepinephrine in the rat glial cell line C6 is inhibited by cytochalasin B. Doses of 5, 15, and 25 microgram/ml of cytochalasin B inhibited the induction equally. Twenty-five microgram/ml of cytochalasin B inhibited the induction reversibly, and had no effect on basal enzyme level. No effect of cytochalasin B on general protein synthesis was found, nor did it increase the rate of decline of enzyme activity in deinduced cells. It therefore appears to block LDH induction by selectivity inhibiting its synthesis. Cytochalasin B had no effect on the transient (intracellular and extracelllular) rise in cyclic AMP generated in response to norepinephrine treatment. Cytochalasin B was effective when added during the transcription dependent phase (first 3 hours) but not during the translation dependent phase (after 3 hours) of LDH induction. The suggestion is discussed that cytochalasin B inhibits one of the early events of the inductive process.

Desmosterol in human and experimental brain tumors in tissue culture

Desmosterol, a possible chemical indicator of brain tumors, was detected in cells of neurogenic, nitrosourea-induced rat tumors (neurinomas and gliomas, C6 cell line) and in human astrocytomas grown in lipid-poor media. A further increase in the amount of cell desmosterol was obtained when triparanol was added to media containing delipidized serum. Cholesterol was replaced almost completely by desmosterol in tumor cells grown in media containing nontoxic levels of 20,25-diazacholesterol. Desmosterol did not accumulate when these inhibitors of desmosterol-reductase were added to culture media containing cholesterol and other lipids (whole fetal calf serum). The results demonstrate that tumors of the nervous system grown in tissue culture are capable of sterol synthesis, and indicate that a central mechanism of cholesterol synthesis is operative in these cells, which may be related to the availability of exogenous cholesterol. It is concluded that these findings are relevant to clinical studies on the use of cholesterol inhibitors as tools for the detection of brain tumor activity.