Stimulation of the de novo pathway for the biosynthesis of platelet-activating factor (PAF) via cytidylyltransferase activation in cells with minimal endogenous PAF production

Treatment of Ehrlich ascites cells with 2 mM oleic acid causes a greater than 10-fold increase in the formation of platelet-activating factor (PAF; 1-[3H]alkyl-2-acetyl-sn-glycero-3-phosphocholine) from the de novo precursor of PAF, 1-[3H]alkyl-2-acetyl-sn-glycerol. Under these conditions, CTP:phosphocholine cytidylyltransferase activity, which is known to catalyze the rate-limiting step in phosphatidylcholine biosynthesis, was stimulated 32% (p less than 0.001) over control cells. Surprisingly, the dithiothreitol-insensitive choline-phosphotransferase activity, which catalyzes the final step in PAF biosynthesis, was reduced approximately 95% in membranes isolated from cells that were pre-treated with 2 mM oleic acid. However, calculations of product formation at this reduced cholinephosphotransferase activity revealed that it was still sufficient to accommodate the increased synthesis of PAF observed in the intact oleic acid-treated cells. Kinetic studies and experiments done with cells treated with phenylmethylsulfonyl fluoride (an acetylhydrolase inhibitor) indicate the various metabolic products formed are derived through the following sequence of reactions: 1-alkyl-2-acetyl-sn-glycerol----1-alkyl-2-acetyl-sn-glycero-3- phosphocholine----1-alkyl-2-lyso-sn-glycero-3-phosphocholine----1-alkyl- 2(long-chain) acyl-sn-glycero-3-phosphocholine. These results indicate PAF is the source of alkylacylglycerophosphocholine through the action of an acetylhydrolase and a transacylase as shown in other cell systems. The relative amounts of PAF, lyso-PAF, and alkylacylglycerophosphocholine produced after treatment of the cells with oleic acid in the absence of the phenylmethylsulfonyl fluoride inhibitor indicate that the acylation rate for lyso-PAF is considerably slower (i.e. rate-limiting) than the deacetylation of PAF by acetylhydrolase. We further conclude that the final step in the de novo pathway for PAF biosynthesis is under the direct control of CTP:phosphocholine cytidylyltransferase, which emphasizes the importance of this regulatory (rate-limiting) step in the biosynthesis of both phosphatidylcholine and PAF.

Adrenocortical pregnenolone-binding protein: identification and antibody development

Pregnenolone-binding activity isolated from the cytosol of the guinea pig adrenal cortex appears to correspond to a Mr 34,000 protein when examined by SDS-polyacrylamide gel electrophoresis during different stages of purification. To verify this finding the Mr 34,000 protein band was eluted from the SDS gel and used to generate a polyclonal antibody. Immobilized anti 34,000 IgG on protein A-Sepharose was found to extract pregnenolone-binding activity from solution in contrast to pre-immune IgG and an antibody raised against a Mr 30,000 protein isolated simultaneously. In addition, protein eluted from the protein A-anti 34,000 IgG complex exhibited the expected molecular weight of 34,000 when examined on an SDS gel. These results, thus, confirm that the pregnenolone-binding protein is indeed a protein of Mr 34,000.

Evaluation of the L5178Y mouse lymphoma cell mutagenesis assay: quality-control guidelines and response categories

A data-based approach to formulating quality-control criteria for the mouse lymphoma cell forward mutation assay is described. Quality-control guidelines for solvent controls, positive controls, and compound-treated cultures were developed based on analysis of over 800 experiments. Frequency distributions of experimental parameters of control cultures, such as mutant frequencies, cloning efficiencies, and suspension growths, were examined. Cloning efficiency and relative total growth affected the variability only when the test chemical was highly toxic. This information was used to generate the quality-control criteria, which were applied to an experiment before it was evaluated for a response. The response categories for classifying the effect of test chemicals on the assay system are defined in terms of (1) the statistically significant differences in average mutant frequency between solvent control cultures and cultures exposed to a chemical and (2) the trend of the dose-related responses.

Kinetics and mechanisms of etodolac degradation in aqueous solutions

The extent and mechanisms of etodolac (1; 1,8-diethyl-1,3,4,9-tetrahydropyrano[3,4-b]-indole-1-acetic acid) decomposition, as a function of pH and temperature, were investigated. Three main degradation products derived from 1 are identified as 7-ethyl-2-(1-methylenepropyl)-1H-indole-3-ethanol (2), the decarboxylated product of etodolac (3), and 7-ethyltryptophol (4). The main pathway for the degradation of 1 is followed by consecutive first-order kinetics: 1----2 in equilibrium 3----4. No appreciable buffer effect on the degradation of 1 is observed for any of the buffer species in the study. The rate-pH profile exhibits a specific acid catalysis at acidic (kH) and neutral (k'H) pH regions, and an inflection point at pH 4.65 corresponding to the pKa value. From Arrhenius plots, the activation energies (Ea) for kH and k'H were found to be 26 and 24 kcal/mol, respectively. The small positive entropy of activation (delta S) indicates that a unimolecular decomposition mechanism is favored for the decomposition reaction of 1.

Effect of cycloheximide or puromycin on induction of thermotolerance by heat in Chinese hamster ovary cells: dose fractionation at 45.5 degrees C1

While studying the quantitative relationship between hyperthermia-induced heat shock proteins (HSPs) and thermotolerance (TT), we observed that heat induced a family of HSPs, particularly an HSP 70 family, that might be involved in the development of TT. When cells were heated for 10 min at 45.5 degrees C, they became thermotolerant to a second heat exposure at 45.5 degrees C, with a thermotolerance ratio of 5-6 at 10(-3) isosurvival at 12 h after heating. In parallel, during the 12-h interval, heat shock resulted in a 2-fold relative increase in the synthesis of three major HSP families (Mr = 110,000, 87,000, and 70,000). Rate of synthesis was expressed relative to total protein synthesis, as studied with one-dimensional polyacrylamide gels analyzed by counting radioactivity in selected protein bands. The increase of unique HSPs, if studied with two-dimensional gels, would probably be much greater. Furthermore, even though the development of TT was partially suppressed by treatment with cycloheximide (10 micrograms/ml) or puromycin (100 micrograms/ml) at concentrations that inhibited total protein synthesis by 96 or 99%, respectively, a family of HSP 70 was still preferentially synthesized. Nevertheless, when cells were labeled for 3 days, the total level of HSP families did not change either when TT developed after a triggering heat treatment or as the development of TT was partially inhibited by suppressing protein synthesis with cycloheximide or puromycin. Thus, TT could still occur when total levels of HSP families did not change and when synthesis of HSP families was less than in unheated control cells, which may imply that TT is unrelated to HSPs. However, the finding that the amount of TT increased with increased synthesis of both total protein and HSP families, as studied with different concentrations of cycloheximide or puromycin, suggests that heat-inducible proteins, in particular the observed preferential synthesis of the HSP 70 family, may be necessary for the development of TT.

Protection of Chinese hamster ovary cells from heat killing by treatment with cycloheximide or puromycin: involvement of HSPs?

Cycloheximide (CHM) or puromycin (PUR) added for 2 h before heating at 43 degrees C followed by either PUR or CHM during heat greatly protected cells from heat killing. This protection increased with inhibition of protein synthesis. Since treatment with a drug both before and during heating was required for heat protection, and since one drug could be exchanged for the other after the 2-h pretreatment without affecting the heat protection, a common mode of action involving inhibition of protein synthesis is suggested for the two drugs. Drug treatment reduced the synthesis of heat-shock proteins (HSPs) as studied by one-dimensional gel electrophoresis by 80-98% relative to 37 degrees C untreated controls. Synthesis of large molecules (greater than 30 kDa) was preferentially inhibited by PUR but not by CHM. Also for CHM, but not for PUR treatment, a 42 kDa band appeared along with a great reduction in the 43 kDa actin band during CHM treatment at both 37 and 43 degrees C. Furthermore, during CHM or PUR treatment, incorporation of [35S]methionine into HSP families 70, 87, or 110 was not increased relative to incorporation into total protein. However, synthesis of the 70 kDa HSP family was selectively suppressed when cells were incubated at 37 degrees C after CHM treatment, but when cells were incubated at 37 degrees C after treatment at 43 degrees C with CHM, synthesis of the 70 kDa HSP family resumed. When cells were labeled for 3 days, there was no preferential accumulation or turnover of HSP families during heating with or without CHM. Therefore, heat protection caused by treatment with CHM or PUR apparently involves a common mode of action not associated with changes in either total levels or synthesis of HSP families during drug treatment before and during heating. The significance of the changes observed in the synthesis of the HSP 70 family after heat is unknown. As thermotolerance developed during 5 h at 42 degrees C without drugs, synthesis of HSP families 70, 87, and 110, as studied with one-dimensional gels, increased 1.4-fold relative to synthesis of total protein, but compared to HSP families in cells labeled for 5 h at 37 degrees C incorporation was reduced by 40%. The increase of unique HSPs, if studied with two-dimensional gels, would probably be much greater.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of cyclosporine on anesthetic action

The effects of a single dose of cyclosporine on anesthetic actions of pentobarbital and fentanyl were studied in mice. Mice given pentobarbital 2 hr after receiving cyclosporine, 60 mg/kg, slept a statistically significant 2.3 times longer than did controls. In a second study, each of two dose levels of cyclosporine was given before each of four dose levels of fentanyl. The analgesic effect of fentanyl, measured with the abdominal constriction test, was dose-dependent. Cyclosporine significantly increased the analgesia produced by fentanyl and did so in a dose-dependent manner. Cyclosporine by itself did not produce analgesia. Plasma levels of fentanyl and binding of fentanyl by plasma proteins were unchanged by cyclosporine treatment. The results show that a single dose of cyclosporine can increase pentobarbital hypnosis and fentanyl analgesia in mice but do not establish the mechanism of these interactions.

Solid-phase extraction of chloramphenicol with graphitized carbon black

The sorption and desorption properties of graphitized carbon black (GCB) were evaluated for enrichment of highly polarizable chloramphenicol (CP) from biological fluids. The distribution of CP between GCB and water lay strongly toward GCB. Among the organic solvents examined, methanol gave the lowest adsorption coefficient. The optimum packing amount of GCB, and the optimum volume and flow-rate of the eluent were deduced from the breakthrough curve and methanol elution curve, respectively. The inner diameter of GCB extraction columns was chosen from the sorption efficiency curve obtained by plotting CP recovery against column inner diameter. The solid-phase extraction method using GCB was applied to the assay of CP in serum samples in the concentration range of 5 to 50 micrograms/ml.

Effect of cycloheximide or puromycin on induction of thermotolerance by sodium arsenite in Chinese hamster ovary cells: involvement of heat shock proteins

After sodium arsenite (100 microM) treatment, the synthesis of three major heat shock protein families (HSPs; Mr = 110,000, 87,000, and 70,000), as studied with one-dimensional gels, was enhanced twofold relative to that of unheated cells. The increase of unique HSPs, if studied with two-dimensional gels, would probably be much greater. In parallel, thermotolerance was observed as a 100,000-fold increase in survival from 10(-6) to 10(-1) after 4 hr at 43 degrees C, and as a thermotolerance ratio (TTR) of 2-3 at 10(-3) isosurvival for heating at 45.5 degrees C. Cycloheximide (CHM: 10 micrograms/ml) or puromycin (PUR: 100 micrograms/ml), which inhibited total protein synthesis and HSP synthesis by 95%, completely suppressed the development of thermotolerance when either drug was added after sodium arsenite treatment and removed prior to the subsequent heat treatment. Therefore, thermotolerance induced by arsenite treatment correlated with an increase in newly synthesized HSPs. However, with or without arsenite treatment, CHM or PUR added 2-6 hr before heating and left on during heating caused a 10,000-100,000-fold enhancement of survival when cells were heated at 43 degrees C for 4 hr, even though very little synthesis of heat shock proteins occurred. Moreover, these cells manifesting resistance to heating at 43 degrees C after CHM treatment were much different than those manifesting resistance to 43 degrees C after arsenite treatment. Arsenite-treated cells showed a great deal of thermotolerance (TTR of about 10) when they were heated at 45 degrees C after 5 hr of heating at 43 degrees C, compared with less thermotolerance (TTR of about 2) for the CHM-treated cells heated at 45 degrees C after 5 hr of heating at 43 degrees C. Therefore, there are two different phenomena. The first is thermotolerance after arsenite treatment (observed at 43 degrees C or 45.5 degrees C) that apparently requires synthesis of HSPs. The second is resistance to heat after CHM or PUR treatment before and during heating (observed at 43 degrees C with little resistance at 45.5 degrees C) that apparently does not require synthesis of HSPs. This phenomenon not requiring the synthesis of HSPs also was observed by the large increase in thermotolerance to 45 degrees C caused by heating at 43 degrees C, with or without CHM, after cells were incubated for 6 hr following arsenite pretreatment. For both phenomena, a model based on synthesis and redistribution of HSPs is presented.

Induction of heat shock proteins in Chinese hamster ovary cells and development of thermotolerance by intermediate concentrations of puromycin

During 4 hr after puromycin (PUR: 20 micrograms/ml) treatment, the synthesis of three major heat shock protein families (HSPs: Mr = 110,000, 87,000, and 70,000) was enhanced 1.5-fold relative to that of untreated cells, as studied by one-dimensional gel electrophoresis. The increase of unique HSPs, if studied with two-dimensional gels, would probably be much greater. In parallel, thermotolerance was observed at 10(-3) isosurvival as a thermotolerance ratio (TTR) of either 2 or greater than 5 after heating at either 45.5 degrees C or 43 degrees C, respectively. However, thermotolerance was induced by only intermediate concentrations (3-30 micrograms/ml) of puromycin that inhibited protein synthesis by 15-80%; a high concentration of PUR (100 micrograms/ml) that inhibited protein synthesis by 95% did not induce either HSPs or thermotolerance. Also, thermotolerance was never induced by any concentration (0.01-10 micrograms/ml) of cycloheximide that inhibited protein synthesis by 5-94%. Furthermore, after PUR (20 micrograms/ml) treatment, the addition of cycloheximide (CHM: 10 micrograms/ml), at a concentration that reduces protein synthesis by 94%, inhibited both thermotolerance and synthesis of HSP families. Thus, thermotolerance induced by intermediate concentrations of PUR correlated with an increase in newly synthesized HSP families. This thermotolerance phenomenon was compared with another phenomenon termed heat resistance and observed when cells were heated at 43 degrees C in the presence of CHM or PUR immediately after a 2-hr pretreatment with CHM or PUR. Heat protection increased with inhibition of synthesis of both total protein and HSP families. Moreover, this heat protection decayed rapidly as the interval between pretreatment and heating increased to 1-2 hr, and did not have any obvious relationship to the synthesis of HSP families. Therefore, there are two distinctly different pathways for developing thermal resistance. The first is thermotolerance after intermediate concentrations of PUR treatment, and it requires incubation after treatment and apparently the synthesis of HSP families. The second is resistance to heat after CHM or PUR treatment immediately before and during heating at 43 degrees C, and it apparently does not require synthesis of HSP families. This second pathway not requiring the synthesis of HSP families also was observed by the increase in thermotolerance at 45.5 degrees C caused by heating at 43 degrees C after cells were incubated for 2-4 hr following pretreatment with an intermediate concentration of PUR.

Antiviral antibodies in the sera of homosexual men: correlation with their lifestyle and drug usage

Healthy homosexual men between the ages of 21 and 65 years, from the Washington, DC (n = 162), and New York City (n = 89) areas, were studied for antibodies in the serum against cytomegalovirus (CMV), herpes simplex virus (HSV) types 1 and 2, and Epstein Barr virus (EBV) viral capsid antigen (VCA). CMV-specific antibodies were assayed by enzyme-linked immunosorbent assay (ELISA), anti-HSV-1 and -2 antibodies were measured by indirect hemagglutination (IHA), and antibodies to EBV VCA were measured by the immunofluorescence assay. Antibodies to human T lymphotrophic virus III (HTLV-III) were detected by ELISA and Western blot procedures. T lymphocytes were enumerated using OKT4 monoclonal antibody. Healthy male volunteer blood donors (n = 90) matched for age range and race proportions were used as controls. The percentage of seropositive individuals in the homosexual group was higher (90-98%) for all the viruses tested than in the control group (47-87%). Comparisons of the geometric mean titers, expressed as reciprocal serum dilutions, of seropositive individuals in homosexual (H) vs control (C) group were as follows: CMV-IgG (ELISA) H = 1:794, C = 1:68; HSV-1 (IHA) H = 1:248, C = 1:14; HSV-2 (IHA) H = 1:56, C = 1:17; EBV-VCA (IFA) H = 1:385, C = 1:131. The homosexual group also showed a higher frequency of individuals with elevated titers than the control group. The CMV IgM antibody was prevalent in 17.7% of the homosexual group and 5% of the control group; arithmetic means for ELISA values for CMV IgM were 0.207 for the homosexual group and 0.05 for the control group. In the homosexual group, the anti-CMV antibody titers increased with age (P = 0.01) and with numbers of sex partners (P = 0.06). Both anti-HSV-1 and anti-HSV-2 antibodies correlated with the number of sex partners (P = 0.04 and P = 0.05, respectively). Neither age nor partner number correlated with response to EBV, and no particular sex act was related to the EBV VCA titer level. HTLV-III seropositivity was associated with higher herpes virus group antibody titers, probably because of life style cofactors. Among the HTLV-III-seropositive subjects, those with less than or equal to 400 T-helper lymphocytes/mm3 had lower antibody titers than those with greater than 400 T-helper lymphocytes/mm3 counts, suggesting an impaired immune response secondary to immunosuppression.

Changes of plasma angiotensin-converting enzyme activity during hemodialysis

Plasma angiotensin-converting enzyme activity was measured by spectrophotometer in normal subjects and in patients with end stage renal failure, serially during a routine hemodialysis. Patients on maintenance hemodialysis tended to be associated with elevated plasma angiotensin-converting enzyme activity versus normal subjects. Plasma angiotensin-converting enzyme activity was significantly elevated in patients with chronic renal failure after 5 hours of hemodialysis(p<.001). Plasma angiotensin-converting enzyme activity corrected for hemoconcentration was also significantly increased(p<.05). There was a significant correlation between the increase in plasma angiotensin-converting enzyme activity after 5 hours of hemodialysis and the decrease in white blood cell count at one hour of hemodialysis (r = 0.51, p<.05). It is suggested that plasma angiotensin-converting enzyme analysis may prove to be a method for assessing transient pulmonary dysfunction during hemodialysis.

Reye's syndrome. Salicylate metabolism, viral antibody levels, and other factors in surviving patients and unaffected family members

To investigate possible etiologic factors for Reye's syndrome (RS), five survivors and their unaffected family members were studied. This study showed low salicylate levels among the patients with RS compared with siblings and parents when challenged with three doses of aspirin. Thus, the patients with RS, three to ten years after having had RS, exhibited normal or increased ability to metabolize aspirin. We found significantly higher antibody levels to influenza A and varicella among the patients with RS, further supporting the importance of these viral infections in the etiology of the syndrome.

Survey on the management of febrile seizures

A survey regarding the management of the child with febrile seizures was mailed to 10 000 child neurologists, neurologists, pediatricians, and family and general practitioners. The response rate varied by specialty; overall, slightly more than half the physicians responded. One third or less of physicians prescribed anticonvulsive therapy only at the time of febrile illness, although this practice was much less common among recent graduates. If children had lengthy or focal seizures, the majority of physicians in all specialties either prescribed long-term treatment or referred for consultation. Long-term daily anticonvulsant therapy was prescribed most frequently by child neurologists and least often by general practitioners, who most often referred for consultation. Rate of hospitalization also differed according to specialty. The results of the survey indicate that the management of a child with febrile seizures may differ depending on the specialty of the attending physician.

Protection of Chinese hamster ovary cells from hyperthermic killing by cycloheximide or puromycin

Cycloheximide (CHM) and puromycin (PUR) were used at various concentrations up to maxima of 10 micrograms/ml and 100 micrograms/ml, respectively, which inhibited protein synthesis by 95% without any cytotoxicity. The drugs were added to the cells for a maximum period of 7 h, with various combinations for treatment before, during, and after heating. Maximum protection, i.e., a 10,000-fold increase in survival from 5 X 10(-6) to 5 X 10(-2) after 4 h at 43 degrees C, required both 1-2 h of treatment before heating and 1-2 h of treatment during heating. For treatments at 45.5 degrees C, the protection was less, i.e., a 100-fold increase in survival from 10(-5) to 10(-3). Little or no protection was observed if after treatment, the drug was removed before heating, or if the drug was added at the start of heating and left on for 5 min to 3 h after heating. For both drugs, the amount of protection increased as inhibition of protein synthesis increased. However, the amount of protection from the drugs was the same only at about 95% inhibition; at 60-85% inhibition, CHM afforded more protection than PUR. Therefore, the modes of action of the drugs might be common at high drug concentrations, but different when intermediate concentrations are used.

Schizophrenia and cerebral laterality

Investigators have suggested that schizophrenic patients have reversals of abnormal structural abnormalities and abnormal left hemisphere function. The authors attempted to know of the pattern of cerebral asymmetry in schizophrenic patients and controls on the computerized tomography scans of thirty right-handed schizophrenic patients and thirty right-handed control subjects. Compared to thirty right-handed controls, the schizophrenic patients had a significantly increased frequency of frontal and occipital reversals. This result suggests that reversals of neuroanatomical asymmetries, and by implicating the abnormalities of lateralization, are relevant to some schizophrenics. Statistics were done by the Chi square method.

Radiation-enhanced resistance to oxygen: a possible relationship to radiation-enhanced longevity

Shortly after gamma-irradiation, flour beetles (Oklahoma strain of Tribolium confusum) exhibited a decline in resistance to oxygen toxicity. Beginning about two weeks after irradiation, however, the LD50 exposure time in pure oxygen was much greater than that of nonirradiated beetles, and this enhanced resistance persisted for about 6 months. The magnitude of the enhancement was a function of dose, and decreased with increasing age at irradiation. These characteristics of a radiation-enhanced resistance to a stress are comparable to the characteristics of radiation-enhanced longevity in Tribolium, in that after irradiation mortality rate is less than that of controls for about 6 months, the magnitude of the effect is dose-dependent, and older beetles are refractory to the effect. Irradiation under anoxic conditions reduced the development of oxygen resistance to the same degree that it reduced acute radiation lethality, suggesting that the amount of biological damage is the critical factor. These results are discussed in terms of the "induced repair" theory of radiation-enhanced longevity of insects.

Rapid detection of herpes simplex virus in clinical specimens by use of a capture biotin-streptavidin enzyme-linked immunosorbent assay

A sensitive enzyme-linked immunosorbent capture assay with biotin and streptavidin (capture B/SA ELISA) was developed to detect herpes simplex virus (HSV) antigen. Rabbit anti-HSV antibody (immunoglobulin G fraction) was coated on flat-bottom, irradiated, 96-well polystyrene microtiter plates and served to capture HSV antigen. Clinical specimens from patients with genital herpes were added. Biotin-linked rabbit anti-HSV immunoglobulin G was used as the second antibody. The antigen-antibody complex was detected with alkaline phosphatase-conjugated streptavidin, which linked to the biotin. With clinical specimens, the test had a sensitivity of 95.6% and a specificity of 91.4% when compared with the tissue culture method. The presence of HSV antigen in specimens devoid of infectivity was confirmed by blocking the reaction with unlabeled rabbit and human antibody to HSV. The level of antigen detected by the capture B/SA ELISA did not necessarily correlate with the infectivity titer of the specimens. HSV antigens could be detected by the capture B/SA ELISA when the virus infectivity was destroyed at 37 degrees C, by UV irradiation, or by Triton X-100 treatment, but not when hypochlorite treatment was used. Greater sensitivity was obtained when HSV-1- and HSV-2-specific antibody reagents were used simultaneously in each test. The capture B/SA ELISA provides a relatively rapid method (4.5 h) which is quite sensitive and specific when compared with other non-tissue culture, direct assay methods.

Quick and simple approximation of sample sizes for comparing two independent binomial distributions: different-sample-size case

Given the ratio, k, of two sample sizes, sample sizes for comparing two independent proportions can be approximated from the sample size for the equal-sample-size design. The proposed method is compared to the method of Fleiss , Tytun and Ury (1980, Biometrics 36, 343-346). Methods for choosing the ratio are also presented.

Evaluation of various plastic microtiter plates with measles, toxoplasma, and gamma globulin antigens in enzyme-linked immunosorbent assays

Seventeen lots of microtiter plates which differed in lot, batch, plastic type, or manufacturer were evaluated as solid-phase carriers in enzyme-linked immunosorbent assays for antibodies to measles, toxoplasma, and human gamma globulin. Most plates of polystyrene or polyvinyl chloride were found to give acceptable binding. The final choice depended on the antigen to be attached. Variations in binding between lots, batches, and types of plastic were found. Well-to-well variation was found to be of greater statistical significance than edge effect and should be a consideration in selection of a plate lot for enzyme-linked immunosorbent assays. Lots of plates should be pretested by the investigator to determine whether there is good binding of the antigen to be used and whether there is low plate-to-plate and well-to-well variation.

Reduced mutant yield at high doses in the Salmonella/activation assay: the cause is not always toxicity

In the Salmonella/activation assay developed by Ames et al [1973, 1975] toxicity is not measured, though it is recognized by the loss of a cloudy appearance on the plate. One approach to the measurement of toxicity is described here and uses a microscope-linked automated colony counter to estimate the number of microcolonies formed by histidine auxotrophs that stop growing after the depletion of histidine. This technique was used to evaluate the effect of toxicity on the revertant count for 16 mutagens, most of which were chosen because, from previous experience, their dose-response curves manifested a maximum at an intermediate dose tested. One of the sixteen, 2-nitrofluorene, was not toxic up to the maximum dose tested. The relationship between mutation and toxicity for the remaining fifteen allowed them to be grouped into two categories: (1) compounds that induced decreases in survival at the same dose at which the number of mutants decreased, and (2) compounds that induced toxicity, but survival was reduced at dose levels higher than those required to reduce the number of mutants. Possible explanations for this reduction of mutant counts occurring with little apparent concomitant increase in toxicity are examined. These results may be significant for attempts to estimate mutagenic potency and, to a lesser extent, construct mathematical models of the Ames test.

Mathematical model of L5178Y mouse lymphoma forward mutation assay

A mathematical model of the biological protocol for the Mouse Lymphoma L5178Y Forward Mutation Bioassay is presented. The model relates the mutant progenitor frequency (MPF), the number of cells per million surviving cells with DNA damage after exposure to the chemical, to the mutant frequency (MF), the number of TFT-resistant cells per million survivors. For a given expression time, the deterministic relationship is linear and the proportionality constant depends on the relative suspension growth factor (rg) and relative cloning efficiencies (rc) of mutants to those of wild type cells: MF = (rg X rc) X MPF. Experimental noise leads to variations in the values of rg and rc and lack of reproducibility in the system. If mutant progenitors and their progeny grow as well as wild-type cells and if all of the parental mutant progenitors express the mutant phenotype, then rg = 1/2 and rc = 1. Biological mechanisms, such as differential growth characteristics of mutant and wild-type cells or DNA repair, can make the mutant frequency an inaccurate estimate of the MPF. For the assay to be useful as a screen for the mutagenic activity of chemicals, rg X rc has to be reasonably constant from chemical to chemical.

Age and sensitivity to oxygen in the flour beetle, Tribolium confusum

Sensitivity of Tribolium confusum males and females to pure oxygen at one atmosphere was measured as a function of adult age. Sensitivity to oxygen increased markedly with age; the reciprocal to the LD50 exposure time was a linear function of age. The sensitivity to oxygen increased more rapidly with age in males than in females; this may be related to the greater longevity of females in this species. Thus the LD50 exposure time represents an index of physiological age. Sublethal exposure to pure oxygen, unlike equivalent exposure to ionizing radiation, did not affect longevity. This suggests that the age-associated increase in oxygen sensitivity is a non-specific stress effect, rather than additivity of acute oxygen damage with cumulative atmosphere-induced lesions.

Oligoclonal IgG bands in cerebrospinal fluid in various neurological diseases

We studied the frequency of oligoclonal immunoglobulin G bands in the cerebrospinal fluid (CSF) of patients with various neurological diseases. We used a micromethod employing sodium dodecyl sulfate polyacrylamide gel electrophoresis that required only 50 microliters of unconcentrated CSF. Oligoclonal bands were detected in the CSF of 95% of the patients with multiple sclerosis, 90% with subacute sclerosing panencephalitis, and 100% with herpes simplex encephalitis, but less frequently in other central nervous system infections. No oligoclonal bands were detected in the CSF of patients with Parkinson, Huntington, Creutzfeldt-Jakob, or herniated disc diseases. Bands were detected in some patients with Alzheimer disease, cerebrovascular accident, idiopathic vertigo, idiopathic seizures, amyotrophic lateral sclerosis, polyneuropathy, and central nervous system glioma. Patients with other conditions infrequently had positive bands. The determination of oligoclonal bands is a useful aid in the diagnosis of multiple sclerosis, subacute sclerosing panencephalitis, and herpes simplex encephalitis. The presence of oligoclonal bands indicates an immunological response but is not diagnostic for a particular condition.

High concentrations of dimethylamine and methylamine in squid and octopus and their implications in tumour aetiology

The levels of the common secondary amines in various squid, in octopus and in 17 other seafoods were determined by HPLC. Ammonia and dimethylamine were found in all of the seafoods tested and some of them also contained methylamine and/or ethylamine. Particularly high levels of dimethylamine (946-2043 ppm) and methylamine (38-255 ppm) were detected in various species of squid and in the octopus. Reaction of nitrite in acidic medium with aqueous extract of squid yielded appreciable amounts of N-nitrosodimethylamine. The optimum pH for this reaction was around 2.4. Dimethylamine in dried squid tissues was readily extracted with water or 1% sodium carbonate solution. Heat treatment of dried squid at 200 degrees C was found to increase its amine content dramatically. It appeared that pyrolytic decarboxylation of some amino acids might cause this increase. Squid is a popular seafood in Japan and other oriental countries. The high incidence of stomach cancer in Japan and China is thought by epidemiologists to be associated with traditional Japanese and Chinese diets. Our present finding that squid and other seafoods contain unusually high levels of dimethylamine and other amines adds to the evidence that dietary factors may have an important role in the aetiology of stomach cancer and other gastro-intestinal tumours.

Teratogenic effects of valproic acid and diphenylhydantoin on mouse embryos in culture

Teratogenic effects of the anticonvulsant drugs valproic acid (VPA) and diphenylhydantoin (DPH) on the development of mouse embryos during early organogenesis were studied using the whole embryo culture technique. Embryos with one to seven somites were exposed in vitro to 50-375 micrograms/ml VPA or 15-135 micrograms/ml DPH for up to 42 hours and compared to control embryos cultured in 80% rat serum without either drug. For both VPA- and DPH-treated embryos, a dose-dependent increase in the frequency of abnormal embryos and a decrease in viability were found. VPA and DPH produced a similar pattern of defects. Drug-induced anomalies included open neural tubes in the cranial regions, abnormal body curvature, craniofacial deformities, and yolk sac defects. Ultrastructural changes were noted in the neuroepithelium of exencephalic VPA-treated embryos. Growth and development were retarded in embryos exposed to greater than 35 micrograms/ml DPH or greater than 50 micrograms/ml VPA as indicated by the decrease in protein and DNA content and the reduction in somite number, crown-rump length, and yolk sac diameter. On a molar basis DPH was potentially more teratogenic than VPA, which correlates with the higher lipid solubility of DPH. With VPA, susceptibility to the drug depended on the developmental stage; e.g., at 150 micrograms/ml VPA the frequency of malformations was 70% in embryos with one to four somites as compared to 35% in embryos with five to seven somites.

Interim recruitment goals in clinical trials

The recruitment rate or duration of a clinical trial must be so determined that the required number of patients may be assured within the given design frame. Establishing interim recruitment goals in clinical trials will not only help keep the clinical investigator from falling too far behind in recruitment but will also enable the sponsor of the study to decide in the early stages of the study whether the investigator can achieve the final recruitment goal. We propose statistical methods for determining a proper recruitment rate, duration and interim recruitment goals. A method of projecting the final recruitment at interims and a method of adjusting the recruitment duration at interims are discussed. Seasonal adjustment methods are also noted.

Small cell lung cancer: analysis of treatment factors contributing to prolonged survival

Seventy-one consecutive patients with small cell lung cancer (SCLC) were treated in the Radiation Oncology Branch of the National Cancer Institute using six different radiation regimens in combination with cyclophosphamide, vincristine and doxorubicin chemotherapy. Patients treated with concurrent chemotherapy-irradiation (CT-RT) experienced better local tumor control than patients treated with sequential CT-RT. Maximum survival with minimum toxicity occurred in the group given a three-week course of concurrent CT-RT. Although concurrent therapy appeared more toxic than sequential therapy, it also appeared to result in more effective tumor control. Precise details of the timing of CT and RT represent important variables in study design of combined modality therapy for SCLC. Carefully controlled clinical trials should be undertaken to define the optimal timing and sequencing of CT-RT, as well as the optimal dose of RT.

Small cell lung cancer: analysis of treatment factors contributing to prolonged survival

Seventy-one consecutive patients with small cell lung cancer (SCLC) were treated in the Radiation Oncology Branch of the National Cancer Institute using six different radiation regimens in combination with cyclophosphamide, vincristine and doxorubicin chemotherapy. Patients treated with concurrent chemotherapy-irradiation (CT-RT) experienced better local tumor control than patients treated with sequential CT-RT. Maximum survival with minimum toxicity occurred in the group given a three-week course of concurrent CT-RT. Although concurrent therapy appeared more toxic than sequential therapy, it also appeared to result in more effective tumor control. Precise details of the timing of CT and RT represent important variables in study design of combined modality therapy for SCLC. Carefully controlled clinical trials should be undertaken to define the optimal timing and sequencing of CT-RT, as well as the optimal dose of RT.

Prognostic factors in Burkitt's lymphoma: importance of total tumor burden

In 42 patients with African Burkitt's lymphoma, we have studied biochemical and clinical correlations with prognosis. Clinical stage and anti-EA titer were the best predictive factors, but lactic dehydrogenase (LDH) and uric acid (UA) concentrations also correlated with stage and prognosis, whereas lactic acid (LA), which was significantly elevated in Stage D, did not significantly correlated with prognosis or with LDH and UA levels. All of these factors with the possible exception of LA reflect the total body burden of tumor. We conclude that the tumor burden is the single most important prognostic factor in Burkitt's lymphoma, and that this is reflected directly by LDH and UA concentrations, and probably indirectly by anti-EA titer.

Two-stage plans for patient accrual in phase II cancer clinical trials

This paper considers two-stage patient-accrual plans for phase II trials of anticancer drugs. The purpose is to identify the therapeutic level of drugs as either above or below a reference response rate. Using such a plan, decisions concerning the future disposition of drugs can be made more formally and objectively. The tables used to implement the plan are prepared for a 20% reference response rate, due to its wide acceptance in the design of phase II clinical trials.

Analysis and interpretation of response rates for anticancer drugs

A statistical method for interpreting data on the efficacy of anticancer agents is proposed. Tables were prepared for the retrospective analysis of studies evaluating the activity of anticancer agents against individual tumor types. The number of responding patients and the number of patients entered in the study were used to more objectively and formally determine the future disposition of the drug. Several examples of clinical studies show that use of our tables allows a more satisfactory and reliable classification than is often currently reported.

Pyridinium- and quinolinium-2-dithioacetic acid zwitterions: antiradiation and anticancer activities

Pyridinium-, quinolinium-, and one pyrimidinium-2-dithioacetic acid zwitterions were prepared by condensation of the N-methyl heterocyclic anhydro bases with carbon disulfide. Reaction of the 2-methylpyridine methiodide anhydro base with carbon disulfide resulted in replacement of the 2-methyl group to give the 1-methylpyridinium-2-dithioacetic acid zwitterion. The 1,6-dimethylquinolinium-2-dithioacetic acid zwitterion showed appreciable anticancer activity against P-388 lymphocytic leukemia in mice, but the other zwitterions tested showed no activity. No antiradiation activity was found for 1-methyl-pyridinium-2-dithioacetic acid zwitterion.

Intracerebral arterial aneurysm in a newborn

Angiographic diagnosis of an intracerebral aneurysm in a neonate was made on the 13th day of life following persistent neurological symptoms that began at birth. Rupture of the aneurysm probably occurred within the first day of life. This unusual condition should be considered in newborn infants with unexplained neurological signs or intracranial hemorrhage.

A paper chromatoelectrophoresis method for the determination of bilirubin binding to serum protein

A technique is described in which paper chromatoelectrophoresis is used to measure the bilirubin binding capacity of albumin in serum. It is equivalent to the Sephadex G-25 method and its results are highly reproducible. From a single pool of serum, multiple determinations indicated the mean bilirubin binding capacity to be 23.7 +/- 0.76 (SD) mg/dl and the greatest difference between any two values was 2 mg/dl. This new technique can determine the bilirubin binding capacity of a serum sample in 15 min. Highly skilled technicians are not needed and very small quantities of serum are required, which gives it a definite advantage over the Sephadex G-25 method.