The genetics of levamisole resistance in the nematode Caenorhabditis elegans

We have characterized a small group of genes (13 loci) in the nematode Caenorhabditis elegans that, when mutated, confer resistance to the potent anthelmintic levamisole. Mutants at the 7 loci conferring the most extreme resistance generally possess almost identical visible and pharmacological phenotypes: uncoordinated motor behavior, most severe in early larval life, extreme resistance to cholinergic agonists and sensitivity to hypo-osmotic shock. Mutants with exceptional phenotypes suggest possible functions for several of the resistance loci. The most extreme mutants can readily be selected by their drug resistance (211 mutants, as many as 74 alleles of one gene). The more common resistance loci are likely to be unessential genes, while loci identified by only a few alleles may be essential genes or genes conferring resistance only when mutated in a special way. We propose that these mutants represent a favorable system for understanding how a small group of related genes function in a simple animal. The extreme drug resistance of these mutants makes them useful tools for the genetic manipulation of C. elegans. And, as the most resistant class of mutants might lack pharmacologically functional acetyl-choline receptors (LEWIS et al. 1980), these mutants may also be of some neurobiological significance.

Antifolate-resistant Chinese hamster cells. Evidence for dihydrofolate reductase gene amplification among independently derived sublines overproducing different dihydrofolate reductases

Purification of a cDNA probe specific for dihydrofolate reductase mRNA has allowed the relative quantification of dihydrofolate reductase gene numbers and mRNA levels between a line of Chinese hamster lung fibroblasts sensitive to the antifolate drugs methotrexate and methasquin and sublines which by virtue of their overproduction of the target enzyme dihydrofolate reductase are cross-resistant to these site-specific inhibitors. Previous results have shown that resistant sublines could overproduce one of two molecular weight forms of dihydrofolate reductase, one parental-like (Mr = 21,000) and one nonparental-like (Mr = 20,000), each encoded by a different mRNA present in elevated amounts in resistant cells (Melera, P. W., Wolgemuth, D., Biedler, J. L., and Hession, C. (1980). J. Biol. Chem. 255, 319--322). The cDNA-RNA and cDNA-DNA hybridization experiments reported here confirm the elevated levels of dihydrofolate reductase-specific mRNA in resistant cells and show that the overproduction of either molecular weight form of dihydrofolate reductase is accompanied by amplification in dihydrofolate reductase gene number.

Multicentre post-infarction trial of propranolol in 49 hospitals in the United Kingdom, Italy, and Yugoslavia

A multicentre study of survivors of an anterior myocardial infarction is reported. The trial consisted of 720 patients and was a double-blind, placebo-controlled study with propranolol 40 mg three times a day. Trial entry was at two to 14 days (mean 8.5 days) and follow-up at one, three, and in most centres, six and nine months. The trial was designed to detect a 50 per cent reduction in mortality and this was not shown. The non-fatal reinfarction rate was similar in both groups. Subgroup analysis identified several prognostic risk factors for death, none of which interacted with treatment.

The effects of amino acid starvation on regulation of polypeptide chain initiation in Ehrlich ascites tumor cells

The ratio of initiation of protein synthesis in Ehrlich ascites tumor cells in culture is reduced by over 60% in the absence of a single essential amino acid. Cell-free extracts prepared from control and amino acid-starved cells retain some of the translational characteristics of these cells and are able to form [40 S.Met-tRNAfMet] initiation complexes. Studies with inhibitors show that up to 63% of the translation directed by endogenous mRNAs in vitro depends on reinitiation of polypeptide chains. Amino acid starvation inhibits this activity, as well as protein synthesis due to in vitro polysomal run-off, by up to 75%. Analysis of [40 S.Met-tRNAfMet]initiation complexes formed in vitro on native 40 S subunits shows that amino acid starvation causes up to a 77% decrease in the concentration of these complexes relative to the corresponding fed controls. This difference is eliminated by the addition of highly purified eukaryotic initiation factor eIF-2. Factor eIF-3 also stimulates [40 S.Met-tRNAfMet] formation in the cell extracts but does not abolish the difference between fed and starved preparations. Mixing experiments have not so far revealed any inhibitor of initiation complex formation in the starved cell extracts.

Influence of soil texture on survival and saprophytic activity of Rhizoctonia solani in soils

Survival of Rhizoctonia solani in precolonized tablebeet seed was greater in a light-textured sandy loam (SL 1) than in a heavy-textured silty clay loam (SiCL). Reduction in survival as well as competitive saprophytic activity of the pathogen resulted when clays (kaolinite and montmorillonite) were added to SL to prepare soils of heavier texture. Survival and activity of R. solani, however, were not increased when sand was added to SiCL (suppressive to R. solani survival) to make this soil lighter in texture. In natural soils of different textures, activity of R. solani was maintained longer in two light-textured sandy loam soils than in a light-textured loamy sand or loam. During investigation of soil chemical and biological influences on R. solani survival, high K2O content in soil was significantly correlated with low saprophytic activity of the pathogen. In all instances where soil microbial activity as determined by a dehydrogenase assay was high, low saprophytic activity was found. Since high microbial activity or K2O content in soil were not associated with any particular soil type, biological or chemical factors may be more important than soil texture in influencing survival and activity of R. solani in soil.

Neuropsychological impairment with schizophrenia vs. acute and chronic cerebral lesions

Performed detailed neuropsychological evaluations with 25 recently hospitalized schizophrenics in whom systematic neurologic workups had failed to reveal CNS disease. Efforts were made to minimize possible effects of drug-induced extrapyramidal symptoms on test performance. Although the schizophrenics showed some neuropsychological impairment relative to 25 normals, their deficits were not as severe as those of patients known to have either acute or chronic brain disorders (N = 25). The diagnostic accuracy achieved by the tests supports their use in short-term treatment facilities when the differential diagnosis includes schizophrenia and brain disorder, especially acute brain disorder. Schizophrenics' neuropsychological impairment was more correlated with degree of EEG abnormality than with degree of psychosis, which suggests a possible organic basis for the deficits that they showed on testing.

Deanol in minimal brain dysfunction

The literature on minimal brain dysfunction is confused, confusing and controversial. The statements that the condition exists, needs treatment, and that treatment may be pharmacological, are more expressions of faith than accepted fact. We believe they are true (within limits not discussed in the article). Furthermore, there is evidence that some patients with MBD are hypo-aroused, while others are not. The role of deanol in the treatment of MBD is still unclear, because of the complexities of identifying appropriate patients in terms of levels of arousal, as well as identifying appropriate measures of response. There is sufficient support for an effect of deanol in the literature to justify further investigation. Further studies should attend to important methodological problems as discussed.

Specific neuroanatomical changes in chemosensory mutants of the nematode Caenorhabditis elegans

Eight of nineteen chemotactic mutants of the nematode Caenorhabditis elegans have morphological defects in the sensory endings of neurons at the tip of the head. The mutants were obtained as worms swimming away from attractant or found amongst male potency mutants or mutants exhibiting erratic behavior. The nineteen mutants fall into at least twelve complementation groups. Mutants E1034 and E1035, alleles of che-1, show morphological alterations in the sensory endings of amphidial neurons and inner labial type 2 neurons, both prospective chemosensory neurons. Both mutants contain non-complementing ts sterile mutations linked to the chemosensory mutation. E1066 shows abnormalities in all the sheath cells associated with the sensory neurons and in the bundling pattern of the amphidial neurons. E1126 is structurally abnormal only in the sensory endings of inner labial type 2 neurons, supporting a chemosensory role for these neurons. E1033 (che-2) and E1124 (che-3) cause defects in the ciliary structure of all but one type of ciliated sensory neuron in the head. E1062 is grossly defective in head structure and the structure of the male copulatory organ, suggesting these opposite ends of the nematode rich in sensory structures share gene functions in embryogenesis. Our study illustrates the possibilities for genetic dissection of the development of a small set of nerves in a simple organism.

Production of volatiles from decomposing plant tissues and effect of these volatiles on Rhizoctonia solani in culture

Volatiles, of which NH3 is a major component, were evolved from decomposing immature corn tissue (c:n9) and affected R. solani in culture two ways: they supplied additional nitrogen to the growth medium so that fungal mycelial growth increased; and they raised substrate pH from 5.5 to 8.2 which induced melanization of mycelium. Volatiles increased fungus growth and pigmentation within 2 weeks of amendment addition to soil. Increases were concomitant with NH3 production from corn tissue. More NH3 evolved from decomposing corn tissues of C:N9 and 17 than from those of C-N 33 and 81. More growth and pigmentation occurred in flasks through which volatiles from decomposing corn (C:N9) were passed than in flasks through which volatiles from nonamended soil or decomposing corn (C:N81) were passed. Carbon dioxide from decomposing tissues did not affect growth or pigmentation. Twice as much NH3 evolved from corn tissue (C:N9) which decomposed in saturated soil than from tissue which decomposed in soil at 50% of its water-holding capacity. Pigment production doubled under saturated conditions.

Methyldopa and propranolol or practolol in moderate hypertension

The effect of a low dose of methyldopa combined with (a) a non-selective and (b) a selective beta-adrenoceptor antagonist was studied in a double-blind crossover trial in 24 carefully selected patients with moderate hypertension (mean initial lying blood pressure 189/117 mm Hg). Each patient received methyldopa 750 mg/day, propranolol 240 mg/day, practolol 600 mg/day, methyldopa 750 mg/day combined with propranolol 240 mg/day, methyldopa 750 mg/day combined with practolol 600 mg/day, and placebo for four weeks each according to a random sequence. After four weeks of therapy the most effective treatment, methyldopa combined with propranolol, reduced lying and standing blood pressures by 36-5/21-4 mm Hg and 44-7/25 mm Hg respectively. Thic combination had similar effects to those of the combination of methyldopa with the cardioselective agent practolol except that it reduced lying diastolic pressure further. The combination was more effective than either treatment alone. No significant differences were found between the effects of propranolol, practolol, or methyldopa at the doses used.

Propranolol in hypertension: a dose-response study

The effect of propranolol was studied in a double-blind crossover trial in 24 carefully selected hypertensive outpatients. Each patient received propranolol 60 mg/day, 120 mg/day, 240 mg/day, and placebo for four weeks each according to a randomised sequence. Propranolol 60 mg/day was no better than placebo in reducing blood pressure. The effects of propranolol 120 mg/day and 240 mg/day were not significantly different. Both doses reduced lying blood pressure by about 20/10 mm Hg from an initial level of 173/104 mm Hg. No difference was detected between the effects of the different doses of propranolol and placebo on weight or on the occurrence of adverse reactions.

Morphological and biochemical changes in the hepatic endoplasmic reticulum and golgi apparatus of male Xenopus laevis after induction of egg-yolk protein synthesis by oestradiol-17 beta

This report describes morphological and biochemical changes accompanying oestrogen induced synthesis of the egg-yolk protein precursor, vitellogenin, in male Xenopus liver. Extensive proliferation of the rough and smooth endoplasmic reticulum and the Golgi apparatus occurs between 3 and 9 days after administration of oestradiol-17 beta. Subcellular fractionation showed that microsomal fractions have an increased number of ribosomes available for protein synthesis, hormone treatment enhances the in vitro protein synthetic capacity per unit of RNA; both in microsome and ribosome preparations. Polypeptides synthesized in vitro by ribosome preparations show an enrichment in serine content after hormone treatment and an increased proportion of ribosomes can be immunoprecipitated by antibodies directed against vitellogenin. Our data are consistent with the proposal that vitellogenin is synthesized on the ribosomes of the rough endoplasmic reticulum and processed and packaged for secretion in the smooth endoplasmic reticulum and Golgi apparatus. Response to hormonal induction of vitellogenin involves an early phase in which membrane proliferation occurs in order to increase the cellular capacity to synthesize, process and secrete large quantities of egg-yolk protein precursor.

Laser heating of an optical fiber

For use in absorption measurements in low-attenuation glass fibers, we calculate the periodic temperature rise at the surface of a glass cylinder heated by a chopped laser beam. Specifically, we give the mean temperature, setting the operating temperature of the experiment, and the peak-to-peak temperature, determining the sensitivity of the measurements.

Atenolol and bendrofluazide in hypertension

The effect of atenolol, a new beta-1-adrenergic receptor blocking agent, was studied in a double-blind cross-over trial in 24 carefully selected hypertensive outpatients. After a four-week run-in period on matching placebo each patient received atenolol 200 mg/day, atenolol 400 mg/day, a combination of atenolol 200/mg day with bendrofluazide 5 mg/day, and bendrofluazide 5 mg/day alone, according to a random sequence. Atenolol at either dose produced a significantly greater reduction in all blood pressure levels except standing systolic pressure than bendrofluazide alone. There was no statistically significant difference between the effects of the two atenolol doses on either blood pressure or pulse rate. The addition of bendrofluazide to atenolol resulted in a further significant lowering of the blood pressure. A significant effect of thiazide on weight was noted. The study shows that atenolol, a cardioselective beta-blocker of similar potency to propranolol in animals but without membrane-stabilizing or partial agonist acitivity, is an effective and well-tolerated hypotensive agent.

Experiences with electrical stimulation devices for the control of chronic pain

The results of a study involving the treatment of pain syndromes by electrical stimulation in 98 patients are reported. Advantages and disadvantages of three electrostimulation techniques--transcutaneous stimulation, peripheral nerve stimulation, and dorsal cord stimulation--are discussed. Also included is a brief discussion of the possible mechanism of suppression of pain stimuli.

Deanol and methylphenidate in minimal brain dysfunction

Deanol, a putative acetylcholine precursor, has been used as a treatment for childhood hyperactivity for years. Efficacy has not been satisfactorily established, however. Seventy-four children referred for problems with learning, including many with hyperactivity, were screened for neurological or psychiatric illness, then given deanol, methylphenidate, or placebo in a double-blind fashion for 3 months. Maintenance dose for methylphenidate was 40 mg daily; for deanol, 500 mg. Behavior rating forms, reaction time, and a series of standard psychometric tests were given before and after treatment. Both drugs showed significant improvement on a number of tests; the pattern and degree of change differed slightly for the two. In this paradigm, deanol thus appeared to improve performance in children with learning and behavior disorders. The mechanism of action remains speculative; proof that deanol increases acetylcholine is scanty, and there is a theoretical basis for actually assuming an anticholinergic effect. Further clinical studies on deanol are indicated.

Extraction of Polychlorinated Biphenyls: Evaluation of a Column Technique Applied to Polar Bear and Seal Tissue

A column extraction procedure was evaluated for the extraction of polychlorinated biphenyls (PCB) from polar bear and seal liver and fat tissue. DDE (2,2-bis (p-chlorophenyl)-l,l-dichloroethylene) was also present in these tissues, and was quantitated for comparative purposes. Two solvent systems were compared: hexane and chloroform-methanol. The chlorinated hydrocarbons were also separated from the liver and fat by digestion of tissue in hot perchloric-glacial acetic acid, and treatment of tissue with acetone and hot isopropanol (considered to be an exhaustive extraction method for lipid). Six replicate extractions were performed for each of the 4 procedures applied to the 4 tissues. The results suggest that the column technique is excellent for extraction of these chlorinated hydrocarbons from animal tissue. Hexane eluted through a sodium sulfate- tissue mixture in a column was as effective in extracting PCB and DDE from polar bear and seal fat as the standard method of comparison (acetone-isopropanol), and slightly less effective (2—4%) in recovering them from liver. These results also indicate that PCB and DDT compounds are associated with the nonpolar lipid component in the cell. A fraction collection study with polar bear liver and fat shows that hexane removes the compounds rapidly from the 2 tissue types. Most of the PCB and DDE is eluted in the first 50 ml.

A Rapidly Sedimenting Fraction of Rat Liver Endoplasmic Reticulum

Balance-sheet experiments carried out to account for the distribution of endoplasmic reticulum fragments during subcellular fractionation of rat liver showed that a large proportion of these fragments are present in the pellets of low-speed centrifugation. Using glucose-6-phosphatase and RNA as markers we found that approximately 50% of the fragments of endoplasmic reticulum sedimented in the pellet of a 640-g centrifugation, 10% in that of a 6000-g centrifugation and 35% in the pellet of a 105000-g centrifugation. Starvation of the animals before use did not alter this distribution, nor did the use of more vigorous homogenization conditions. We have developed a procedure for removing nuclei and erythrocytes from the material sedimenting at 640g to give a fraction (rapidly sedimenting ER fraction or RS-ER) similar to the standard microsomal preparation. Centrifugation of this RS-ER fraction over 1.3 M sucrose yields subfractions of high and low RNA content analogous to the rough and smooth microsomal fractions. Electron-microscopic studies showed that, whereas the rough microsomal fraction consisted of ribosome-studded vesicles of varying size and content density, the rough RS-ER fraction contained a mixture of mitochondria and double lamellar membranes with ribosomes attached. These double lamellar membranes closely resemble the endoplasmic reticulum of intact rat liver. The double lamellar membranes are frequently observed grouped in stacks and in close association with the mitochondria. The significance of the association between endoplasmic reticulum and mitochondria of the RS-ER fraction and the relation between it and the standard microsomal preparation are discussed.

Heterogeneous distribution of glucose 6-phosphatase in rat liver microsomal fractions as shown by adaptation of a cytochemical technique

1. A novel technique for the subfractionation of rat liver smooth and rough microsomal fractions according to their content of glucose 6-phosphatase is described. This technique, based on the Gomori lead histochemical procedure, involves incubation of smooth and rough microsomal fractions with low concentrations of Pb(NO(3))(2) and glucose 6-phosphate. Control experiments, in which enzyme was assayed in the presence of various amounts of Pb(NO(3))(2) or in which microsomal fractions were reisolated after incubation with low concentrations of Pb(NO(3))(2) and glucose 6-phosphate, showed that lead does not interfere with glucose 6-phosphatase activity. 2. Discontinuous sucrose-density-gradient centrifugation of microsomal fractions which had previously been incubated with various amounts of Pb(NO(3))(2) and glucose 6-phosphate showed that it is possible to subfractionate both smooth- and rough-microsomal fractions into several bands, owing to a differential modification of the density of the microsomal vesicles by the trapping of lead phosphate within them. 3. When the material in the bands obtained by density-gradient centrifugation of incubated microsomal fractions was assayed for glucose 6-phosphatase activity, it was found that the modification of the density of the microsomal fractions was directly related to their relative enrichment in glucose 6-phosphatase activity. Control experiments, in which microsomal fractions were incubated with Pb(NO(3))(2) and glucose 6-phosphate and then treated with EDTA, showed that the subfractionation was not due to aggregation of microsomal vesicles, lead and glucose 6-phosphate. Thus the resolution of microsomal preparations into subfractions with different glucose 6-phosphatase activities is interpreted as indicating heterogeneity of glucose 6-phosphatase distribution in the microsomal vesicles. 4. Electron micrographs of both smooth- and rough-microsomal subfractions show deposits of lead phosphate within the microsomal vesicles. The frequency and extent of these deposits correlate with the different amounts of glucose 6-phosphatase activity measured biochemically. 5. The nature of the heterogeneous distribution of glucose 6-phosphatase is discussed and the more general applicability of the technique for studying membrane fractions containing a heterogeneous distribution of phosphatases is indicated.