Toxicity of some insecticides for crowded and isolated nymphs ofGryllodes sigillatus Wlk. (Orthoptera: Gryllidae)

Summary 6 insecticides; chlordane, malathion, fenitrothion, pyrethrum, rotenone and sevin, were screened againstGryllodes sigillatus Wlk. reared under crowded and isolated conditions. Chlordane was found to be most toxic, followed by malation, fenitrothion, pyrethrum, rotenone and sevin. Insects reared under crowded conditions were more susceptible to insecticides than insects reared under isolated conditions.Acknowledgments. The authors are grateful to Dr S. C. Saxena for providing all facilities.     

Karyotypic races of the common shrew (Sorex araneus L.) from northern Poland

Summary Karyotypic races of the common shrew which differed with respect to the combinations of chromosome arms in certain 2-armed autosomes were distinguished in Poland. Two eastern races with the arm combinationik, and one western race with the arm combinationhi in the third pair of autosomes were established. In the contact area of these chromosomal forms, the fourth karyotypic race with the arm combinationhk was found.I wish to express my gratitude to my wife, A.M. Wójcik, M. Sc., for her help in catching the animals and making chromosome preparations. I must also offer my thanks to Dr J. Zima for giving me access to his as yet unpublished data, and to Prof. Z. Pucek and Dr S. Fedyk for reading the first draft of this paper.     

The genetics of phytotoxin production by plant pathogenic fungi

Little is known about the genetic control of phytotoxin production by plant pathogenic fungi. The production of host-selective toxins known to play a role in disease development has been genetically analyzed in three species ofCochliobolus. InC. heterostrophus, a single genetic locus with two alleles has been identified controlling the production of HMT-toxin. This locus appears to be at or near the breakpoint of a chromosome rearrangement. Single genetic loci have also been identified controlling the production of HC-toxin byC. carbonum and HV-toxin byC. victoriae. The locus inC. carbonum may be a cluster of tightly linked genes.     

Differences in chromosome A arrangement betweenDrosophila madeirensis andDrosophila subobscura

Summary The proximal half of the A (=X) chromosome ofD. madeirensis has a gene arrangement very similar to the A1 or A6 inversions found inD. subobscura. Polytene chromosome analysis of hybrids betweenD. madeirensis and strains ofD. subobscura homozygous for such inversions shows, however thatD. madeirensis has a gene arrangement different from any known forD. subobscura. These results provide evidence for a greater differentiation of the X chromosome in these species than has previously been described; it seems that the X chromosome is the only one that has undergone structural variation during the speciation process.     

Cholinergic control of extracardiac pulsations in insects

Summary The autonomic nerve system which controls extracardiac pulsations of hemolymph pressure appears to be quite susceptible to cholinesterase inhibitors (physostigmine, organophosphorus insecticides). In pupae ofTenebrio molitor L. andGalleria mellonella L., the treatment induced large peaks in hemolymph pressure (over 4 kPa). The peaks were repeated at more-or-less constant, 30-s intervals for several hours or days. Removal of the pupal brain neither affected extracardiac pulsations nor influenced the specific responses to the investigated drugs or insecticides.     

Cytogenetic observations on a monosomic inSesbania macrocarpa Muhl. (Leguminosae)

Summary Karyotypic analysis of a spontaneous monosomic plant isolated from a population ofSesbania macrocarpa (2n=4x=24) revealed that one chromosome of the smallest set was missing. The absence of this chromosome caused a deleterious effect on the meiotic system of the plant, resulting in total male and female sterility. The origin of the species in this context is discussed.Thanks are due to Dr B. D. Patil, Indian Grassland and Fodder Research Institute for facilities and to Dr S. K. Gupta, for valuable suggestions.     

Dominance for enzyme activity inDrosophila melanogaster

Summary A regulatory element tightly linked to theGpdh locus inDrosophila melanogaster has been isolated from a natural population. Flies homozygous for second chromosomes bearing the element,H31, have half the GPDH activity of normal homozygotes. Heterozygotes betweenH31 andF orS alleles exhibit dominance in GPDH activity. Heterozygotes betweenH31, F orS andDf(2L) GdhA have half the diploid level. The contribution of theS allele to the activity inS/H31 heterozygotes is more than four times that ofH31. The regulatory element distinguishingH31 is tightly linked to theGpdh ⁺ locus.     

Sex linkage of malic enzyme inXenopus laevis

Genetic analysis of mME variants (mitochondrial malic enzyme, E.C. 1.1.1.40) inXenopus laevis revealed sex linkage of the mMe locus and indicated a WZ/ZZ type of sex determination. Codominant mMe alleles occur on both W and Z chromosomes, with a recombination frequency of 6.1%±1.5% between mMe and the sex-determining locus (or region).     

Selection of high-level abamectin resistance from field-collected house flies,Musca domestica

Summary Abamectin is a novel, highly promising insecticide with activity against many pests. To determine if resistance to abamectin could occur, we collected house flies from several New York dairies and selected them in the laboratory. Resistance developed repidly and to a high level (36 or>60,000-fold, depending upon test technique and/or adjuvant) that could not be overcome by the synergists piperonyl butoxide orS,S,S-tributylphosphorotrithioate. There was no increase in (cross)resistance to crotoxyphos, dichlorvos, dimethoate, tetrachlorvinphos, permethrin, dieldrin or lindane following abamectin selection. Our results suggest the potential for abamectin resistance is high, at least in house flies, and that the judicious use of abamectin will be needed to prolong its usefulness as an insecticide.     

Chromsome aberrations in cattle raised on bracken fern pasture

Summary Thirteen cows maintained on natural bracken fern (Pteridium aquilinum) were analyzed cytogenetically. The frequency of structural chromosome aberrations detected in peripheral blood cells was significantly higher when compared to that detected in animals raised on pasture containing no bracken fern. We discuss the clastogenic action of fern and its synergistic action with infection by type 2 and 4 papilloma virus in the same animals.Acknowledgments. We are grateful to Dr F. J. Benesi, Dr J. L. Guerra and Dr I. L. Sinhorini for performing some of the clinical and pathological analyses; O. P. Ferraz, L. A. Tadeu Dias, L. F. Feitosa and A. M. N. Paiva for technical assistance; and to Dr N. H. C. Castro and Dr C. de Araujo Peres for critical and statistics review, respectively. Research was supported by CNPq FAPESP and CAPES.     

A human homolog of the yeast gene encoding tRNA 2′-phosphotransferase: cloning,characterization and complementation analysis

The Saccharomyces cerevisiae TPT1 gene plays a role in removing the 2-phosphate from ligated tRNA during the maturation of pre-tRNA. Here we reported the cloning and characterization of the human TRPT1 gene as a homolog of yeast TPT1. The TRPT1 gene is located at human chromosome 11q13 and encodes a polypeptide of 253 amino acids. BLAST searches with its amino acid sequence revealed the ubiquitous occurrence of TRPT1 homologs and their functional relationships with the presence of the DUF60/KptA domain. Northern analysis demonstrated that the gene is primarily expressed in heart and skeletal muscle, with lower or undetectable levels in other tissues studied. A plasmid-shuffling experiment showed that the human TRPT1 gene could complement the tpt1 mutation in S. cerevisiaeReceived 19 March 2003; received after revision 25 April 2003; accepted 22 May 2003     

Lack of mutagenicity of irradiated glucose inSalmonella typhimurium using host-mediated assay

Summary Experiments were conduced to study the ability of irradiated glucose to induce reverse, mutations inS. typhimurium by host-mediated assay. The results revealed no significant increase in the frequency of reverse mutations compared to controls.     

Sclerotial and low aflatoxigenic morphological variants from haploid and diploidAspergillus parasiticus

Summary Serial transfer of mycelial macerates of a wild type, haploid, aflatoxigenic strain ofAspergillus parasiticus in a defined liquid medium resulted in the production of three new morphological classes: a sclerotial form with high aflatoxin production, and two variant forms (fan andfluff) with lowered sporulation, no sclerotia, and attenuated levels of aflatoxin. A genetically marked diploid containing mutant markers for aflatoxin pathway intermediates yielded the same three morphological classes upon serial transfer of macerated mycelia. When these diploid variants were treated with a haploidization agent, and the phenotypes of the resultant segregants scored, a low frequency of colonies producing aflatoxin pathway intermediates was recovered. These genetic data indicate that the structural genes for the aflatoxin pathway are present but somehow attenuated in thefan andfluff strains.This work was supported by a Cooperative Agreement from the U.S. Department of Agriculture, (58-7B30-3-556).     

Distribution of sister chromatid exchanges in different types of chromatin in the X chromosome ofMicrotus cabrerae

We used the X chromosomes ofMicrotus cabrerae as a model to analyze the distribution of sister chromatid exchanges (SCEs) on different types of chromatin, because of the marked heterogeneity of the heterochromatin in the entire short arm and a portion of the long arm of this chromosome. Computer-simulated distributions, according to an algorithm that makes it possible to modify the distribution on the basis of any possible hypothesis, were compared with real distributions by log-linear models. We found that the frequency of SCEs in different types of heterochromatin was higher than that expected for a random distribution, and located an SCE hot-spot at the junction between euchromatin and heterochromatin. The possible relationship between the distribution of SCEs and base composition or chromatin accessibility are discussed.     

Laccase production byPolyporus sanguineus under different nutritional and environmental conditions

Summary Laccase production was higher in malt extract medium than in lignin, andPolyporus sanguineus appears to be better thanPolyporus versicolor andTrametes hirsuta (syn.Polyporus hirsutus) for enzyme production. Phenolic compounds, of which resorcinol was the most active, induced enzyme production; while sugars repressed it. A temperature of 37°C, pH 3 and indulin AT at a concentration of 0.2% gave the best enzyme yield.A part of Ph. D. thesis of D.S. Arora.Acknowledgments. We thank Westvaco Chemical Division, USA, and Dr P.S. Rehill, Forest Research Institute, Dehradun, India for providing lignin samples and the fungal strain, respectively. D.S. Arora further thanks University Grants Commission, New Delhi for financial assistance.     

Genotoxic evaluation of ten carcinogens in theDrosophila melanogaster wing spot test

To provide further background data on the wing spot somatic mutation and recombination assay, 10 selected carcinogens (acetamide, acrylamide, benzo(a)pyrene, cyclophosphamide, diethylstilbestrol, 4-nitroquinoline N-oxide, propyleneimine, safrole, thiourea, and o-toluidine) were tested in this assay. 72-h-old third-instar larvae, trans-heterozygous for 2 recessive wing cell markers:multiple wing hairs (mwh) andflare ³ (flr ³) were fed with 3 concentrations of each carcinogen during the rest of their development until pupation, and the genotoxic effects were measured as significant increases in the appearance of visible mutant hair clones on the adult wing blade. Our results show that 6 of the carcinogens tested produce significant increases in wing spot frequency, at least at one of the concentrations assayed. Benzo(a)pyrene, diethylstilbestrol, safrole and thiourea were the compounds that did not increase the incidence of mutant clones.     

Clinal variation and selection of MDH allozymes in honey bee populations

Latitudinal clines of malate dehydrogenase-1 (MDH-1) allozymes occur within honey bee populations on three continents: Europe, North America and South America. The North and South American populations are introduced and demonstrate that Mdh allelic clines were established within the last 150 years. The frequency of the medium electrophoretic allele increases in frequency with increasing latitude while the fast allele decreases with latitude on all the three continents. The clines are best explained by the average daily high temperature for July on all continents. These parallel clines provide evidence for selection on Mdh alleles in honey bees.     

Selection for class IIMhc heterozygosity by parasites in subterranean mole rats

Mhc organization and polymorphism have previously been studied²⁶ in the four chromosomal species of theSpalax ehrenbergi superspecies in Israel, serologically, and at the DNA, RFLP and sequence levels of class I and class II genes. Here we demonstrate that the observed heterozygosity ofMhc class II genesP₁ with 11 alleles, andQ, with at least 14 alleles, is positively and significantly correlated with infectivities of ectoparasites (gamasid mites)¹⁷ and endoparasites (helminths)¹⁸.Mhc heterozygosity is highest in the most infected area, which is in the most humid-warm region of the superspecies range, or where two zoogeographic regions overlap. We conclude that the evolutionary forces responsible for theMhc class II two-gene polymorphisms include selection for increased heterozygosity as a defense strategy against ecto- and endoparasite infections.     

La formule chromosomique deSorex minutus L. (Mammalia-Insectivora)

Summary The chromosome complement ofSorex minutus L. has been determined. The caryotype is characterized by a diploid number of 42 and by aNF (fundamental number) of 56. The sex-chromosomes are of theX−Y type usual in mammals. The origin and the evolution of the chromosome set ofS. minutus, S. unguiculatus, andS. araneus have been discussed.