Extrachromosomal Inheritance of Carbon Dioxide Sensitivity in the Mosquito CULEX QUINQUEFASCIATUS

Mosquitoes from a laboratory colony of Culex quinquefasciatus from Matsu Island, China, develop irreversible paralytic symptoms after exposure to carbon dioxide at 1 degree. This CO2 sensitivity is caused by an inherited infectious agent, probably a virus. Crossing studies between CO2-sensitive and -resistant mosquitoes showed that the sensitivity trait is inherited extrachromosomally in a fashion strictly analogous to the hereditary transmission of sigma virus in Drosophila melanogaster. Sensitivity could be maintained through maternal transmission alone, despite nine generations of backcrossing of "stabilized" CO2-sensitive females to males from a resistant strain. CO2-sensitive males crossed to resistant females transmitted sensitivity to a portion of their F1 progeny, and only the female F1 sensitives were capable of further hereditary transmission.--Matsu, or a very similar hereditary infectious agent, is common in natural populations of Cx. quinquefasciatus on Oahu, Hawaii. Fifty-nine percent of the families reared from field-collected egg rafts contained CO2-sensitive mosquitoes, and some families contained only sensitive mosquitoes.     

Cytotype regulation by telomeric P elements in Drosophila melanogaster: evidence for involvement of an RNA interference gene

P elements inserted at the left telomere of the X chromosome evoke the P cytotype, a maternally inherited condition that regulates the P-element family in the Drosophila germline. This regulation is completely disrupted in stocks heterozygous for mutations in aubergine, a gene whose protein product is involved in RNA interference. However, cytotype is not disrupted in stocks heterozygous for mutations in two other RNAi genes, piwi and homeless (spindle-E), or in a stock heterozygous for a mutation in the chromatin protein gene Enhancer of zeste. aubergine mutations exert their effects in the female germline, where the P cytotype is normally established and through which it is maintained. These effects are transmitted maternally to offspring of both sexes independently of the mutations themselves. Lines derived from mutant aubergine stocks reestablish the P cytotype quickly, unlike lines derived from stocks heterozygous for a mutation in Suppressor of variegation 205, the gene that encodes the telomere-capping protein HP1. Cytotype regulation by telomeric P elements may be tied to a system that uses RNAi to regulate the activities of telomeric retrotransposons in Drosophila.     

Two Mutators and Their Suppressors in DROSOPHILA ANANASSAE

Assays of seven mutant stocks exposed a ten-fold range in spontaneous Minute mutation frequencies. Genetic analysis of the difference between the px (0.0006 Minutes) and bri (0.0042 Minutes) stocks revealed that each of these stocks lacks one of two complementary, autosomally transmitted, maternally expressed, dominant suppressors of a dominant 3-linked mutator present in the bri stock. Analysis of the ca; stw stock (0.0013 Minutes) with respect to the former two indicated the presence of the autosomal suppressor functions in addition to a maternally expressed, extrachromosomally transmitted, suppressor of a paternal chromosome-breaking mutator, which is also extra-chromosomally transmitted. The lesions induced by the two mutators in male carriers are probably different, but both kinds are subject to modification by the maternal suppressors soon after fertilization. The existence of these diverse controls of mutability is viewed as confirmation of Sturtevant's (1937) argument that natural selection invokes a variety of devices to minimize mutation rates while retaining mutational potential.     

Maize tertiary trisomic stocks derived from B-A translocations

Reciprocal translocations between supernumerary B chromosomes and the basic complement of A chromosomes in maize have resulted in a powerful set of tools to manipulate the dosage of chromosomal segments. From 15 B-A reciprocal translocation stocks that have the B-A chromosome genetically marked we have developed tertiary trisomic stocks. Tertiary trisomics are 2n + 1 aneuploids where the extra chromosome is a translocation element, in this case a B-A chromosome. Whereas B-A translocations produce aneuploidy in the sperm, the tertiary trisomic plant efficiently transmits hyperploid gametes maternally. Because the B-A tertiary trisomic stocks and the B-A translocation stocks from which they were derived are introgressed into the W22 inbred line, the effects of maternally and paternally transmitted trisomic B-A chromosomes can be compared. Data are presented on both the male and female transmission rates of the B-A chromosomes in the tertiary trisomic stocks.     

Impairment of cytotype regulation of P-element activity in Drosophila melanogaster by mutations in the Su(var)205 gene

Cytotype regulation of transposable P elements in the germ line of Drosophila melanogaster is associated with maternal transmission of P elements inserted at the left telomere of the X chromosome. This regulation is impaired in long-term stocks heterozygous for mutations in Suppressor of variegation 205 [Su(var)205], a gene implicated in the control of telomere length. Regulation by TP5, a structurally incomplete P element at the X telomere, is more profoundly impaired than regulation by TP6, a different incomplete P element inserted at the same site in a TAS repeat at the X telomere. Genetic analysis with the TP5 element indicates that its regulatory ability is not impaired in flies whose fathers came directly from a stock heterozygous for a Su(var)205 mutation, even when the flies themselves carry this mutation. However, it is impaired in flies whose grandfathers came from such a stock. Furthermore, this impairment occurs even when the Su(var)205 mutation is not present in the flies themselves or in their mothers. The impaired regulatory ability of TP5 persists for at least several generations after TP5 X chromosomes extracted from a long-term mutant Su(var)205 stock are made homozygous in the absence of the Su(var)205 mutation. Impairment of TP5-mediated regulation is therefore not directly dependent on the Su(var)205 mutation. However, it is characteristic of the six mutant Su(var)205 stocks that were tested and may be related to the elongated telomeres that develop in these stocks. Impairment of regulation by TP5 is also seen in a stock derived from Gaiano, a wild-type strain that has elongated telomeres due to a dominant mutation in the Telomere elongation (Tel) gene. Regulation by TP6 is not impaired in the Gaiano genetic background. The regulatory abilities of the TP5 and TP6 elements are therefore not equally susceptible to the effects of elongated telomeres in the mutant Su(var)205 and Gaiano stocks.     

The Genetic Factors Altered in Homozygous abo Stocks of DROSOPHILA MELANOGASTER

Females homozygous for the maternal-effect mutation abo (2-44.0) produce a large fraction of eggs which arrest during embryogenesis. Increasing doses of defined heterochromatic regions inherited by offspring of abo mothers from their fathers function zygotically to bring about a partial rescue of the abo-induced embryonic lethality. Another property of the abo mutation is that the severity of the maternal effect decreases when an abo stock is maintained in homozygous condition for a number of generations. Here, we show that the factors which change in homozygous abo stocks to result in the decrease in maternally induced embryonic lethality, act zygotically, dominantly and additively. More importantly, we show that the X and second chromosomes, but not the Y and third chromosomes, derived from homozygous abo stocks are, when inherited from males, more effective in promoting zygotic rescue of the abo-induced lethality than are the equivalent chromosomes derived from an abo stock maintained in heterozygous condition. The chromosomal locations of the factors maintained in the homozygous condition. The chromosomal locations of the factors altered in homozygous stock, as well as their behavior, strongly suggest that the same heterochromatic elements that are responsible for rescuing embryos from the abo-induced maternal effect are altered in homozygous abo flies in such a way that the maternal effect itself is less severe.     

THE EFFECT OF REPEATED SPRAYING OF INSECTS IN INCREASING THEIR RESISTANCE TO INSECTICIDES

During the selection of a stock of Drosophila melanogaster for resistance to DDT, in which carbon dioxide was used for purposes of anaesthesis, a sensitivity to this gas developed. The phenomena closely paralleled those shown by the CO₂-sensitive ebony stock isolated by L'Héritier and his co-workers. An experimental analysis of its effect upon DDT sensitivity was made. It was found that a stock selected for CO₂ resistance gave the same probit regression line as the original stock. A CO₂-sensitive stock, whether anaesthetized with nitrogen or carbon dioxide, gave the same regression line at a temperature of 25° C. at which CO₂ sensitivity disappeared, or at 15° C. if adjustment to the proportion of deaths in the control was made. The effect of CO₂ was therefore to limit the population from which selection is made for DDT resistance, rather than to alter the distribution of DDT resistance within the stock.     

THE EFFECT OF DIFFERENT HOST PLANTS OF POTATO VIRUS C IN DETERMINING ITS TRANSMISSION BY APHIDS

A stock of potato virus C derived from Edgecote Purple potatoes in 1945 was not then transmitted by aphids, although more than 2000 aphids were used in conditions optimal for transmitting the serologically related potato virus Y. This stock of virus C has been propagated continuously since, by manual inoculation in a series of Nicotiana glutinosa and N. tabacum , and in 1955 it was transmitted by the aphid Myzus persicae (Sulz.): about one in twenty of the aphids transmitted it compared with one in two for potato virus Y.
Virus C derived from the Edgecote Purple potatoes in 1955 was not transmitted by aphids; both stocks of virus C produced only local lesions in Majestic potato leaves, and gave similar symptoms in tobacco.
When inoculated to Majestic potatoes and then returned to tobacco plants, potato virus C usually ceased to be aphid transmitted and did not recover this property in any of the subsequent subcultures.
Transmission from stock by aphids did not isolate a strain of virus C which was any more readily transmitted by aphids, indeed, for the first two or three subcultures, aphids usually transmitted more readily from plants inoculated manually. But the few isolates which remained aphid transmissible, after a second passage through potato, were rather readily transmitted.
These results suggest that the ability of a virus to be aphid transmitted is, at least in part, determined by the host plant in which it is multiplying, but the nature of the changes which determine this ability are unknown.     

A new strain of Drosophila that inhibits the development of symptoms in imagoes infected with sigma virus

A strain of Drosophila melanogaster bearing the mutant gene ebony has been found to slow the development of symptoms (carbon dioxide sensitivity) in adult flies inoculated with sigma virus, a member of the rhabdovirus group. This inhibition is made evident by comparing mean incubation times of the virus in ebony and wild-type (Oregon) flies. The increase in mean incubation time in ebony flies has ranged from about 3 to 8 days, depending on the virus strain, amount of virus injected, and the age of the flies at the time of inoculation. This delay in development of symptoms appears to be due to a dominant autosomal gene, although further work is needed to confirm this. When accumulation of infectious virus after inoculation is compared in ebony and Oregon flies, there seems to be no inhibition of multiplication in ebony at the level of the entire fly. The relationship of this work to current theories on the mechanism of symptom production by sigma virus is discussed.     

DIRECT AND CORRELATED RESPONSES TO SELECTION ON AGE AT REPRODUCTION IN DROSOPHILA MELANOGASTER

Aging may be a consequence of mutation accumulation or of negative pleiotropic correlations between performance late and earlier in the lifespan. This study used artificial selection on flies derived from two different base stocks to produce “young” and “old” lines, propagated by breeding from young and old adults respectively. Virgin and mated adults of both sexes from the “old” lines lived longer than “young” line flies. “Young” and “old” mated females did not differ in fecundity or fertility early in the lifespan, but “old” line females had higher fecundity and fertility late in life. The results therefore suggested either that the response to selection had revealed the effect of mutation accumulation, or that pleiotropy involving characters other than early fecundity must have been involved. Development time from egg to adult was longer in the “old” lines. Competition of selected line larvae from one base stock against mutant marked larvae from the same base stock revealed that, at a wide range of larval densities, “old” line larvae showed lower survival rates than “young” line larvae. Thorax length and wet weight were significantly greater in the “old” line flies from one base stock. The results may imply that the selection regime in the “old” lines favored extended growth during development to produce a more durable adult soma, despite the cost in increased larval mortality and delayed reproduction, because the potential reproductive benefits later in life were increased. However, the differences between larvae from “old” and “young” lines could also be attributable to density differences, and this possibility needs systematic investigation.     

Amyloids, prions and the inherent infectious nature of misfolded protein aggregates

Misfolded aggregates present in amyloid fibrils are associated with various diseases known as "protein misfolding" disorders. Among them, prion diseases are unique in that the pathology can be transmitted by an infectious process involving an unprecedented agent known as a "prion". Prions are infectious proteins that can transmit biological information by propagating protein misfolding and aggregation. The molecular mechanism of prion conversion has a striking resemblance to the process of amyloid formation, suggesting that misfolded aggregates have an inherent ability to be transmissible. Intriguing recent data suggest that other protein misfolding disorders might also be transmitted by a prion-like infectious process.     

Modelling the role of urban forest in the regulation of carbon balance in an industrial area of India

The increase in greenhouse gases, especially carbon dioxide, in the atmosphere contributes to climate change. People and policy makers are becoming more interested in the role of urban trees in regulating the global carbon cycle. Carbon dioxide emissions from anthropogenic sources are mainly caused by the burning of fossil fuels, which are major contributors to the increase in greenhouse gases in the atmosphere. Therefore, a better understanding of the carbon sequestration process by urban forests and its exchange between air and soil is the first step to offsetting the impacts of climate change in urban areas.Here, a dynamic model was constructed including the carbon stock of forest, litter carbon and soil organic carbon pool. The study emphasized the relationship between the three carbon pools. The monthly dynamics of the pools were studied. A sensitivity analysis was performed followed by calibration and validation. The results showed that the mean growth rate of forest biomass was the most sensitive factor, followed by the decomposition rate and the uptake rate of organic carbon by detritivores.If the biomass of the existing forest is maintained sustainably, more carbon dioxide could be sequestered. In addition, the model showed that afforestation in the Asansol-Durgapur Planning Area would increase the carbon stocks of the forest and to some extent offset the problem of carbon dioxide release from the nearby coal mines and other factories. In the near future, the model will benefit forest managers in carrying out urban management in the Earth's tropical belt.     

Tissue Safety in View of CJD and Variant CJD

Epidemiological studies on human transmissible spongiform encephalopathies (Creutzfeldt–Jakob Disease, CJD) have shown that the agent could be transmitted by highly infectious tissues like brain, spinal cord or retina and medicinal products derived from these tissues (i.e. human growth hormone, dura mater). A few cases of transmission of CJD by neurosurgical instruments have been reported. The transmission of the agent of variant CJD, which is suspected to be transmitted by BSE-contaminated food, by blood transfusion implies that in contrast to the agent of classical CJD this agent can also be transmitted by organs and tissues other than nerve tissues. Health authorities have implemented guidelines to reduce the risk of transmission of human and animal TSE by human and veterinary medicinal products. The high resistance of TSE agents against physical or chemical treatment hamper the development of highly efficient inactivation steps in the production of medicinal products. Donor selection is considered as an efficient measure to reduce the risk of TSE transmission. However, the development of rapid, sensitive and specific diagnostic test systems is urgently required to test blood, organs and tissue of donors.     

Transitional hemizygosity of the maternally derived allele at the 6PGD locus during early development of the Cyprinid fish Rutilus rutilus

The activation of individual alleles during early embryogenesis was studied at the 6-phosphogluconate dehydrogenase gene locus of the Cyprinid fish Rutilus by means of starch gel electrophoresis. By using three alleles occurring at this locus, it was possible to discriminate between (1) maternally transmitted gene products stored in the egg cytoplasm, (2) newly synthesized protein of the maternally derived allele in the embryonic genome, and (3) newly synthesized protein of the paternally derived allele. It was found that, until the fifth day of development, maternal products were present in the embryo. By the seventh day after fertilization, these storage products were nearly exhausted, and a hemizygous phenotype for the maternally derived gene became visible. On the eighth day, the patterns of all four allelic combinations of the mating type used were demonstrable in the offspring. The findings suggest that for the alleles used in this study, the maternally derived gene is preferentially activated during embryogenesis.Supported by the Deutsche Forschungsgemeinschaft.     

Detection of replication-competent and pseudotyped human immunodeficiency virus with a sensitive cell line on the basis of activation of an integrated beta-galactosidase gene.

We have constructed a HeLa cell line that both expresses high levels of CD4 and contains a single integrated copy of a beta-galactosidase gene that is under the control of a truncated human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR). This cell line, called CD4-LTR/beta-gal, can be used to determine quantitatively the titer of laboratory-adapted HIV strains, and the method used to do so is as sensitive as the determination of viral titers in a T-cell line by end point dilution. Using this cell line as a titer system, we calculated that HIV-1 stocks contain only one infectious particle per 3,500 to 12,000 virions. Virus derived from a molecular clone of a macrophagetropic provirus will not infect this cell line. We have also cocultivated peripheral blood lymphocyte cultures from HIV-infected individuals with the CD4-LTR/beta-gal indicator cells. In a majority of primary isolates (five of eight), including isolates from asymptomatic patients, rare virus-infected cells that can activate the beta-galactosidase gene are present.     

The genetics of abnormal abdomen, incomplete abdomen, and bobbed in Drosophila buzzatii

Five stocks of Drosophila buzzatii with superficially similar abdominal disruptions including partial tergite and sternite loss were isolated by inbreeding. Three of the stocks have indistinguishable phenotypes, the inheritance of which is maternally influenced. This phenotype and its mode of inheritance bear similarities with those of Abnormal abdomen in D. melanogaster. The phenotype in the fourth stock is slightly different and is due to a single autosomal recessive gene, which we denote incomplete abdomen. In the fifth stock the trait is limited to females, and in appearance and mode of inheritance resembles bobbed in D. melanogaster. Furthermore, only in this stock are rDNA deletions evident. The combined frequencies of the three types of abdominal aberration were found to be around 1% in several samples from wild and laboratory populations of D. buzzatii.     

Establishment and maintenance of the P cytotype associated with telomeric P elements in Drosophila melanogaster

P elements inserted near the left telomere of the X chromosome are associated with the P cytotype, a maternally transmitted condition that strongly regulates the activity of the P transposon family in some strains of Drosophila. The regulatory abilities of two such elements, TP5 and TP6, are stable in homozygous stocks over many generations. However, these regulatory abilities are attenuated when the telomeric P elements are transmitted through heterozygous females, and they are utterly lost when the elements are transmitted through males. Paternally transmitted telomeric P elements reacquire regulatory ability when they pass through a female germ line. This reacquisition is enhanced if the females in which it occurs came from mothers who carried a telomeric P element. The enhancement has two components: (1). a strictly maternal effect that is transmitted to the females independently of the mother's telomeric P element ("presetting" or the "pre-P cytotype") and (2). a zygotic effect associated with inheritance of the mother's telomeric P element. One telomeric P element can enhance the reacquisition of another's regulatory ability. When X chromosomes that carry telomeric P elements are extracted through males and made homozygous by using a balancer chromosome, most of the resulting stocks develop strong regulatory abilities in a few generations. However, some of the stocks do not attain the regulatory ability of the original population.     

Cytoplasmic inheritance of temperature sensitivity in a wild stock of Paramecium primaurelia

One stock, GBC, has a maximum temperature of growth about 5 degrees C lower than other recently collected stocks of Paramecium primaurelia. The resistant stocks (R) are able to grow continuously at 35 degrees C while the sensitive stock (S) cells die within 48 h. The F1s of R X S crosses exhibited a cytoplasmic pattern of inheritance and all F2-by-autogamy lines derived from the S cytoplasmic parent are sensitive. The F2-by-autogamy lines cytoplasmically descended from the R parent were predominantly (93%) R in the initial assay. Upon reinvestigation one year later, only 64% of these lines were R, 9% were S, and 27% had a new phenotype, weak (W), intermediate between R and S. Backcrosses of W lines to both R and S strongly suggest that the W lines have normal cytoplasm (i.e. R) but also have nuclear gene(s) for temperature sensitivity that are derived from the original S stock. The delayed manifestation of the W phenotype is not understood.     

Prion protein glycosylation

The transmissible spongiform encephalopathies (TSE), or prion diseases are a group of transmissible neurodegenerative disorders of humans and animals. Although the infectious agent (the 'prion') has not yet been formally defined at the molecular level, much evidence exists to suggest that the major or sole component is an abnormal isoform of the host encoded prion protein (PrP). Different strains or isolates of the infectious agent exist, which exhibit characteristic disease phenotypes when transmitted to susceptible animals. In the absence of a nucleic acid genome it has been hard to accommodate the existence of TSE strains within the protein-only model of prion replication. Recent work examining the conformation and glycosylation patterns of disease-associated PrP has shown that these post-translational modifications show strain-specific properties and contribute to the molecular basis of TSE strain variation. This article will review the role of glycosylation in the susceptibility of cellular PrP to conversion to the disease-associated conformation and the role of glycosylation as a marker of TSE strain type.     

An orbivirus of mosquitoes which induces CO2 sensitivity in mosquitoes and is lethal for rabbits.

An orbivirus, JKT-7400, isolated from Culex mosquitoes in Indonesia, replicated to a high titer and induced cytopathic effects in Aedes albopictus cell cultures. The virus produced lethal sensitivity to carbon dioxide in Culex and Aedes mosquitoes as well as in Drosophila melanogaster fruit flies but was not the agent of the hereditary sensitivity to carbon dioxide previously described for Culex quinquefasciatus. When injected intravenously in high doses, JKT-7400 virus was lethal for rabbits, apparently without replicating to a significant extent. It was not pathogenic for adult mice inoculated intravenously or for adult or suckling mice inoculated intracerebrally and intraperitoneally. Unlike an orbivirus isolated from Culex mosquitoes in China, JKT-7400 did not interfere with the replication of Japanese encephalitis virus in mosquitoes.