Caenorhabditis elegans levamisole resistance genes lev-1, unc-29, and unc-38 encode functional nicotinic acetylcholine receptor subunits

We show that three of the eleven genes of the nematode Caenorhabditis elegans that mediate resistance to the nematocide levamisole and to other cholinergic agonists encode nicotinic acetylcholine receptor (nAChR) subunits. unc-38 encodes an alpha subunit while lev-1 and unc-29 encode non-alpha subunits. The nematode nAChR subunits show conservation of many mammalian nAChR sequence features, implying an ancient evolutionary origin of nAChR proteins. Expression in Xenopus oocytes of combinations of these subunits that include the unc-38 alpha subunit results in levamisole-induced currents that are suppressed by the nAChR antagonists mecamylamine, neosurugatoxin, and d-tubocurarine but not alpha-bungarotoxin. The mutant phenotypes reveal that unc-38 and unc-29 subunits are necessary for nAChR function, whereas the lev-1 subunit is not. An UNC-29-GFP fusion shows that UNC-29 is expressed in body and head muscles. Two dominant mutations of lev-1 result in a single amino acid substitution or addition in or near transmembrane domain 2, a region important to ion channel conductance and desensitization. The identification of viable nAChR mutants in C. elegans provides an advantageous system in which receptor expression and synaptic targeting can be manipulated and studied in vivo.

Immunoprecipitation and virus neutralization assays demonstrate qualitative differences between protective antibody responses to inactivated hepatitis A vaccine and passive immunization with immune globulin

Antibodies to hepatitis A virus (anti-HAV) were measured in children from two separate vaccine trials (n = 70) 4 weeks after a dose of inactivated hepatitis A vaccine (VAQTA). The geometric mean titers (GMTs) of anti-HAV were 49.3 and 45.2 mIU/mL by immunoassay, while reciprocal GMTs of neutralizing anti-HAV were 6.5 and 15.0 by an 80% radioimmunofocus inhibition test (RIFIT) and 55.6 and 92.0 by antigen reduction assay (HAVARNA). The GMT of antibody detected by radioimmunoprecipitation (RIPA) was > or =401. These data establish serologic correlates of protection against disease and show that RIPA is most sensitive for detection of early vaccine-induced antibody. Sera collected from adults (n = 20) 7 days after administration of immune globulin contained similar antibody levels by immunoassay (45.1 mIU/mL) and slightly higher GMTs of neutralizing antibody (27.5 by RIFIT and 146 by HAVARNA) but negligible precipitating antibody (GMT, 5.6). These results are best explained by differences in the affinity of antibodies for virus following active versus passive immunization.

Seed Treatment with a Fungal or a Bacterial Antagonist for Reducing Corn Damping-off Caused by Species of Pythium and Fusarium

Bioassays were conducted under greenhouse conditions to test the efficacy of antagonists applied to corn (Zea mays) seed for protection against seed rot and seedling damping-off at 18 and 25°C in a field soil artificially infested with a combination of Pythium ultimum, P. arrhenomanes, and Fusarium graminearum. Biomass of Gliocladium virens isolates Gl-3 or Gl-21, Trichoderma viride isolate Tv-1, or peat-based slurry of Burkholderia cepacia isolates Bc-B, Bc-T, or Bc-1 was coated individually onto corn seeds in one test, and Gl-3 or Bc-B at four inoculum levels was used in another test. Seed treatments with most of the biocontrol agents, as well as with the fungicide captan, significantly (P ≤ 0.05) increased seedling stand, plant height and fresh weight, and decreased root rot severity compared with untreated seeds in pathogen-infested soil. Coating seeds with the biocontrol fungus G. virens isolate Gl-3 was the most effective treatment, resulting in greater (P ≤ 0.05) seedling stand, plant height, and fresh weight, and lower (P ≤ 0.05) severity of root rot than those parameters from seeds treated with captan or other antagonists at both temperatures. The results from the seeds treated with Gl-3 were similar to those of untreated seeds in noninfested soil. In treatments with Bc-1, Bc-T, Bc-B, or Tv-1, incubation temperature affected plant emergence, root rot severity, plant height, and fresh weight (P ≤ 0.01). Conversely, in seeds coated with Gl-3 or Gl-21, these parameters were similar at both temperatures. The minimum number of propagules needed per corn seed to obtain plant emergence comparable to that from captan-treated seeds was between 10⁴ and 10⁵ CFU for Gl-3 and >10⁸ for Bc-B. When propagules of Gl-3 were applied at a rate >10⁶ CFU per seed, seedling emergence was greater (P ≤ 0.05) than that from captan-treated seeds.

Trials to assess equivalence: the importance of rigorous methods

The aim of an equivalence trial is to show the therapeutic equivalence of two treatments, usually a new drug under development and an existing drug for the same disease used as a standard active comparator. Unfortunately the principles that govern the design, conduct, and analysis of equivalence trials are not as well understood as they should be. Consequently such trials often include too few patients or have intrinsic design biases which tend towards the conclusion of no difference. In addition the application of hypothesis testing in analysing and interpreting data from such trials sometimes compounds the drawing of inappropriate conclusions, and the inclusion and exclusion of patients from analysis may be poorly managed. The design of equivalence trials should mirror that of earlier successful trials of the active comparator as closely as possible. Patient losses and other deviations from the protocol should be minimised; analysis strategies to deal with unavoidable problems should not centre on an "intention to treat" analysis but should seek to show the similarity of results from a range of approaches. Analysis should be based on confidence intervals, and this also carries implications for the estimation of the required numbers of patients at the design stage.

Lupane derivatives from Lophopetalum wallichii with farnesyl protein transferase inhibitory activity

Chloroform-soluble extracts of the stems and of the mixed stems and stem bark of Lophopetalum wallichii were found to be inhibitory in a farnesyl protein transferase (FPTase) bioassay system. During the course of activity-guided fractionation, the known lupane-type triterpenes, ochraceolide A (1), ochraceolide B (2), betulin, and lupeol and the new lupane lactone, dihydro ochraceolide A (4), were isolated. The stereochemistry of the epoxide group of ochraceolide B (2) was determined by preparation of both epoxide isomers [2, and the new semisynthetic derivative, 20-epi-ochraceolide B (3)] from 1. The structure of 4 was established by reduction of 1 with sodium borohydride. Compounds 1 and 2 exhibited significant inhibitory activity in the FPTase assay (IC50 values of 1.0 and 0.7 microgram/mL, respectively). Lupeol was found to be weakly active (IC50 65.0 micrograms/mL) in this test system, whereas no significant inhibition was detected for betulin or compounds 3 or 4. When evaluated against a panel of human cancer cells in culture, compounds 1 and 4 were modestly cytotoxic. Compounds 2 and 3 were not active in the panel.

Inhibition of mitochondrial function by interferon

We showed previously that type I interferon causes a down-regulation of mitochondrial gene expression. We show here that IFN treatment leads to functional impairment of mitochondria. Western blot analysis indicated that interferon treatment reduces the steady-state level of cytochrome b in murine L-929 cells. Interferon produced a reduction in cytochrome c oxidase and NADH-cytochrome c reductase activities of isolated mitochondria as well as inhibiting electron transport in isolated mitochondria and in intact cells. Several mitochondrial mRNAs are affected by interferon treatment in human Daudi lymphoblastoid cells, which are highly sensitive to the antiproliferative effects of interferon. Electron transport in Daudi cells was also inhibited by interferon both in intact cells and isolated mitochondria with a dose response identical to that for the antiproliferative response. In contrast, a Daudi strain resistant to the antiproliferative effects of interferon showed no down-regulation of mRNA expression and no inhibition of electron transport. Possibly as a consequence of the inhibitory effect on mitochondrial gene expression, treatment with interferon causes a reduction in cellular ATP levels. The inhibition of cellular growth by interferon may thus be partly a consequence of a reduction in cellular ATP levels.

Analysis of cross-over trials for duration data

Survival models and cross-over designs both have an established place in biomedical research. Surprisingly, there are a few examples of proper exploitation of two in combination. A number of advantages and disadvantages of such studies are discussed. Two examples are used to illustrate the application of semi-Markov models with time-varying covariates, as standard log-linear models, to such data.

Molecular cloning and in vitro expression of C. elegans and parasitic nematode ionotropic receptors

The free living nematode, C. elegans is understood at a level of detail equalled by few other organisms, and much of the cell biology and sequence information is proving of considerable utility in the study of parasitic nematodes. Already, C. elegans provides a convenient vehicle for investigating anthelmintic drug action and resistance mechanisms. Among the ionotropic receptors, with their important roles in the behaviour and development of the organism, are targets for anthelmintics. The subunits of nicotinic acetylcholine receptors of C. elegans form a large and diverse multigene family. Members of this family are among the 11 genes associated with resistance to the anthelmintic drug levamisole.

Induction of gene expression by intracellular interferon-gamma: abrogation of the species specificity barrier

We reported previously that murine L-929 cells expressing a human interferon (IFN)-gamma cDNA lacking a signal peptide sequence synthesize but fail to secrete human IFN-gamma and support viral replication at a reduced level. These cells also had elevated levels of IFN-inducible gene products. We show here that a similar response is seen in human cells expressing a mutated murine IFN-gamma cDNA. The ability of human IFN-gamma to induce gene expression in murine cells is shown to be due to the intracellular IFN-gamma rather than to clonal variation, induction of endogenous murine IFN, or alternative mediators of antiviral activity. We have used a murine cell line, Ltk-aprt-, which is resistant to both type I and II IFNs but responsive to combined treatment with both. Ltk-aprt- cells transfected with human IFN-gamma cDNA lacking a signal sequence support virus replication at the same level as control cells. However, unlike transfectants containing only the neoR selection gene, clones expressing the mutated human IFN-gamma gene show strong protection against viral infection and elevated levels of 2,5 A synthetase mRNA and MHC class I protein after treatment with IFN-beta alone. Reverse transcriptase-PCR rules out the induction of endogenous murine IFN expression as a mediator of these effects. Thus, expression of intracellular human IFN-gamma mimics treatment with extracellular murine IFN-gamma in permitting a synergistic response to IFN-beta. Given the inability of human IFN-gamma to bind to the murine cell-surface receptor our results show that intracellular IFN-gamma can activate certain responses independent of cell-surface binding.

A sensitive biological assay for interferons

Several assays are available for interferons that either measure activity (bioassays) or protein mass (ELISAs). Bioassays generally require the use of viruses and some means of determining cell killing. Many investigators lack the expertise to work with potentially harmful viral agents and eschew this approach in favor of an ELISA assay based on a specific antibody or, to obtain the high level of sensitivity usually required, a combination of antibodies. Such immunological assays, while relatively easy, are expensive and detect protein mass which is not a reliable index of biological activity. I describe here a bioassay based on induction of a reporter gene linked to an interferon (IFN)-responsive promoter element. Production of the reporter gene product is dose-dependent in the range of 1 to approximately 100 U/ml of IFN and sensitivity is comparable to standard cytopathic effect assays. The assay can be modified to quantitate or detect other IFNs and could be applied to other cytokines.

The feasibility of collecting in-flight EEG data from helicopter pilots

An assessment of whether valid EEG data could be collected on helicopter pilots in flight was conducted. Each subject provided eyes-open/eyes-closed EEG in the laboratory and in a helicopter. During flights, EEG's were monitored on the ground in real-time via radio telemetry. Analyses were conducted on the data recorded from Fz, Cz, Pz, P3, P4, O1, and O2 from eight subjects. Delta activity at one recording site (Fz) was higher in the aircraft than in the laboratory probably because of increased eye movements. Both theta and alpha activity at several sites also were increased in the aircraft, and alpha activity at all electrodes showed the expected augmentation from eyes-opened to eyes-closed; however, there were no interactions indicative of problems detecting normal alpha changes due to eye closure in the aircraft. Beta activity recorded from Cz and O1 was elevated during flight testing, but it was concluded that at least the O1 effect was due to muscle artifact in the more active environment. While there were more recording artifacts in the helicopter than in the laboratory, the overall results show it is possible to telemeter EEG from helicopter pilots in flight. Follow-on studies are needed to assess whether recordings can be obtained while pilots are performing flight-related tasks.

The case for cross-over trials in phase III

There is a common belief that cross-over trials should not be used in phase III of drug development. This was reinforced by a statement in the draft CPMP Note for Guidance on biostatistical methodology in clinical trials which was circulated for review in March 1993: 'Hence crossover trials in patients should be avoided as far as possible'. We do not share this belief. Historically, many successful drug developments in indications such as hypertension and asthma have depended heavily on cross-over trials in their phase III programmes, leading to regulatory approval for a number of well established medicines. The evidence on which these developments were based appeared sound at the time, and has not been questioned by later experiences with these medicines. Furthermore, the general level of understanding of these medical indications is now even more well developed, and hence the circumstances under which cross-over trials may be used to advantage for new drugs in phase III are even more likely to be correctly identified. There are some well-known disadvantages of cross-over trials relative to parallel group trials. These are reviewed and the ways in which early indications of such problems might be detected in phases I and II or elsewhere will be discussed. However, there are also two key advantages, the well-known one of study size and a less well-known one arising in the context of treatment-by-patient interaction. In phases I and II these advantages lead routinely to the use of the cross-over design. Some methods of analysing cross-over trials have been criticized in a number of recent articles. We compare the properties of a number of alternative analysis strategies by means of simulation and conclude that these concerns about methods of analysis do not imply that cross-over trials should be avoided, especially if baseline measurements can be included in the design. Any small risks attached to their use should not normally concern the regulator as they will tend to diminish estimates of treatment effects rather than enhance them. In summary, cross-over trials remain a potentially valuable research tool in the development of new medicines at all stages including phase III. It is unnecessary and counterproductive to exclude them from use.

Statistical issues in the regulation of medicines

The recent release within the European Union of a draft Note for Guidance from the Commission for Proprietary Medical Products (CPMP) entitled 'Biostatistical methodology in clinical trials in applications for marketing authorisations for medicinal products' has stimulated widespread discussion of the relevant statistical issues. This discussion contains echoes of an earlier debate concerning a closely related U.S. Guideline. The areas of agreement and disagreement between the two guidelines bear close examination as they provide lessons for all statisticians involved in the design and analysis of clinical trials. Notable areas of debate include crossover designs, multi-centre trials, the intention to treat principle, pre-specification of statistical analysis and the ability to generalize results to the wider population of patients. The consequences for the routine involvement of statisticians in this area of work in general, and in the regulatory process in particular, are especially important. This is an illustration of the extent to which drug regulation has influenced, and is continuing to influence, the development of medical statistics throughout the world.

Social competence deficits in adolescents at risk for schizophrenia

Social competence in subjects at risk for schizophrenia and affective disorder and in normal-comparison subjects was examined in childhood and adolescence. Based on interviews with the parents of the subjects and with the children and adolescents themselves, subjects at risk for schizophrenia had poorer overall social competence than subjects at risk for affective disorder and comparison subjects in early adolescence and adolescence but not in childhood. In analyses of specific aspects of social competence, the adolescents at risk for schizophrenia had significantly poorer peer relationships and decreased hobbies/interests than the adolescents at risk for affective disorder and the normal-comparison adolescents. With respect to school adjustment, however, the two groups of adolescent offspring of parents with psychiatric disorders had significantly poorer adjustment than the comparison adolescents but did not differ from each other on this measure. These results suggest that various aspects of poor social competence may precede the onset of schizophrenia and play an important role in its development.

Role of areca nut in the causation of oral submucous fibrosis: a case-control study in Pakistan

A case-control study on chewing and smoking habits and oral submucous fibrosis (OSF) was undertaken in Karachi in 1989/90. Cases were patients detected with fibrous bands and leathery mucosa and hospital-based controls were matched by age and sex. Information on habits was collected by personal interview of 157 cases and 157 controls. Despite overall female preponderance, a substantial number of young men were enlisted. The male/female risks were found to be similar. Immigrants from India to Pakistan (Mohajir) had a similar risk status to local Punjabis. No differences between risks were found when comparing the three age categories, 21, 21-40, 41-60 yr. Among the cases, an increased risk was observed for areca nut chewing. This habit when practised alone appeared to have the highest risk (RR 154), followed by pan with or without tobacco (RR 64, 32 respectively). Logistic regression and discriminant analysis showed that daily consumption rates appeared to be more important with respect to risk than lifetime duration of habit. Tobacco habits were more prevalent amongst those 15 cases who presented with concurrent carcinoma and OSF: We conclude that areca nut chewing has a causal relationship with OSF: additional tobacco insult may be necessary for subsequent carcinoma development.

Alternative nurse rostering: an evaluation

An evaluative research study was conducted to determine the principles underlying the implementation of alternative nurse rostering. The results of three research studies conducted in the Western Australian health care system over a period of three years were reviewed. It was clearly demonstrated that alternative rosters are a valid management tool that will improve nursing productivity and the quality of care. A subject's age and hospital category influenced the acceptance of alternative rostering systems.

Phylogenetic relationships of dengue-2 viruses

RNA oligonucleotide fingerprinting studies on a large number of virus isolates previously demonstrated considerable genetic variation in isolates of dengue (DEN)-2 serotype. We report the entire envelope (E) glycoprotein gene and deduced amino acid sequences of 16 DEN-2 viruses and the phylogenetic relationships of these, plus 17 additional published DEN E gene sequences. Comparison of DEN-2 E glycoprotein gene sequences revealed base substitutions scattered throughout the entire gene with as much as 22% sequence divergence. Aligned E glycoprotein amino acid sequences revealed the viruses differed by as much as 10%. There appeared to be constraints on the overall structure of the E protein to maintain biological function. Clusters of amino acid substitutions were present in the hydrophobic membrane anchor region at the carboxyl terminal end of the protein. Maximum parsimony analysis of the E gene sequences allowed construction of a phylogram indicating evolutionary relationships of the virus isolates within the DEN-2 serotype. Five genetic subtypes were identified. Phylogenetic relationships of the DEN-2 serotype and other flaviviruses based on E protein sequences reflected traditional antigenic and serologic classifications.