Translational control of endogenous and recoded nuclear genes in yeast mitochondria: Regulation and membrane targeting

Mitochondrial gene expression in yeast,Saccharomyces cerevisiae, depends on translational activation of individual mRNAs by distinct proteins encoded in the nucleus. These nuclearly coded mRNA-specific translational activators are bound to the inner membrane and function to mediate the interaction between mRNAs and mitochondrial ribosomes. This complex system, found to date only in organelles, appears to be an adaptation for targeting the synthesis of mitochondrially coded integral membrane proteins to the membrane. In addition, mRNA-specific translational activation is a rate-limiting step used to modulate expression of at least one mitochondrial gene in response to environmental conditions. Direct study of mitochondrial gene regulation and the targeting of mitochondrially coded proteins in vivo will now be possible using synthetic genes inserted into mtDNA that encode soluble reporter/passenger proteins.     

Molecular genetics of the peptidyl transferase center and the unusual Var1 protein in yeast mitochondrial ribosomes

Mitochondria posses their own ribosomes responsible for the synthesis of a small number of proteins encoded by the mitochondrial genome. In yeast,Saccharomyces cerevisiae, the two ribosomal RNAs and a single ribosomal protein, Varl, are products of mitochondrial genes, and the remaining approximately 80 ribosomal proteins are encoded in the nucleus. The mitochondrial translation system is dispensable in yeast, providing an excellent experimental model for the molecular genetic analysis of the fundamental properties of ribosomes in general as well as adaptations required for the specialized role of ribosomes in mitochondria. Recent studies of the peptidyl transferase center, one of the most highly conserved functional centers of the ribosome, and the Varl protein, an unusual yet essential protein in the small ribosomal subunit, have provided new insight into conserved and divergent features of the mitochondrial ribosome.     

The multi-KH protein vigilin associates with free and membrane-bound ribosomes

The-multi-KH domain protein vigilin has been identified by ex vivo experiments as both a tRNA- and/or mRNA-binding protein. We show here that in vitro under conditions previously shown to allow tRNA binding, recombinant vigilin also binds to selected mRNA species and ribosomal RNA. An in vivo link of vigilin to mRNA and rRNA was elucidated by several approaches. (i) Coexpression/costimulation of vigilin was found with many other proteins independently of whether their mRNA was translated on free or membrane-bound ribosomes. (ii) A close codistribution of vigilin with free ribosomes was seen in the cytoplasm while nucleoli were a major organelle of vigilin accumulation in the nucleus. (iii) Furthermore, free and membrane-bound ribosomes can be enriched for vigilin which suggests that this binding does not depend on the class of mRNA translated. Therefore, we suggest that vigilin does not distinguish between free or membrane-bound ribosomes but is generally necessary for the localization of mRNAs to actively translating ribosomes.Received 20 June 2003; received after revision 25 July 2003; accepted 29 July 2003     

板材液压拉深试验装置开发

开发了一种用于板材液压拉深成形性能研究的试验装置，包括拉深模具及液压控制系统。该装置不需要复杂的外部供液系统、压边系统及凸模导向系统，在普通的单动压力机上就能实现对不同材料及尺寸板材的普通拉深和液压拉深试验。初步的试验表明，该装置结构简单、操作方便、工作可靠，满足板材液压拉深试验要求，能够有效的改善板材的成形性能。     

Ptolemy and the meta-helikôn

In his Harmonics, Ptolemy constructs a complex set of theoretically ‘correct’ forms of musical scale, represented as sequences of ratios, on the basis of mathematical principles and reasoning. But he insists that their credentials will not have been established until they have been submitted to the judgement of the ear. They cannot be audibly instantiated with the necessary accuracy without the help of specially designed instruments, which Ptolemy describes in detail, discussing the uses to which each can be put and cataloguing its limitations. The best known of these instruments is the monochord, but there are several more complex devices. This paper discusses one such instrument which is known from no other source, ancient or modern, whose design was prompted by the geometrical construction known as the helikôn. It has several remarkable peculiarities. I examine its design, its purposes, and the merits and shortcomings which Ptolemy attributes to it. An appendix describes an instrument I have built to Ptolemy’s specifications (possibly the first of its kind since the second century bc), in an attempt to find out how satisfactorily such a bizarre contraption will work; and it explains how various practical problems can be resolved.     

Invaders,weeds and the risk from genetically manipulated organisms

Invaders, weeds and colonizers comprise different but overlapping sets of species. The probability of successful invasion is low. The 10:10 rule state that 10% of introduced speices (those with feral individuals) become established, 10% of established species (those with self-sustaining populations) become pests. The rule gives an adequate fit to British plant data. The rule predicts that invaders will be rarer than natives. This is shown for British Anatidae. There is a continuous spectrum of perceived weediness. Although this spectrum is significantly related to Baker characters, neither those characters or any others can usefully predict which species will be weeds over a wide range of species. Characters tuned to sets of closely related species shown more promise. A study of BritishImpatiens shows that the characters responsible for critical ecological behaviour are still obscure. Small genetic changes can cause large ecological changes. GMOs will have characters entirely new to that species' evolutionary history. While most will have little ecological effect, a few may be ecologically and economically damaging. A sensible programme of field trials and monitoring is justified to minimize the risk.     

Biosynthesis of 1-alkenes in the defensive secretions ofTribolium confusum (Tenebrionidae); stereochemical implications

Summary The terminally unsaturated hydrocarbons of the defensive secretion ofTribolium confusum are biosynthesized from fatty acids by oxidative decarboxylation. The process involves an enantiospecific cleavage of the C–H bond of thepro-(S) C(3)–H atom and simultaneous decarboxylation of the acid into an 1-alkene and carbon dioxide via ananti-periplanar transition state geometry (anti-elimination). The stereochemistry of this biotranformation is identical in all respects with the same reaction in higher plants. The mechanism seems to be of general importance for the biosynthesis of many vinylic substructures of natural products from oxygen-containing precursors.     

Cryopreservation of parasites

Summary In this review, advances in cryopreservation of helminth parasites are reported. Our own studies demonstrate that metacestodes ofEchinococcus multilocularis can be maintained in a viable state for at least 1–2 years by appropriate deep-freezing and storage in liquid nitrogen. Infective larvae of the nematodeToxocara canis cryopreserved for 1 week in liquid nitrogen were maintained after thawing in vitro in a chemically defined medium for 35 weeks. Although motility of previously deep-frozen larvae was reduced they produced secretory/excretory antigens of similar immunodiagnostic quality as those from unfrozen larvae. Whereas infective larvae of several species of trichostrongylids can be easily cryopreserved, the infective larvae of the cattle lungworm,Dictyocaulus viviparus, and muscle larvae ofTrichinella spiralis are more sensitive to damage by subzero temperatures. Therefore, survival rates after cryopreservation are low, but improvement of the cooling schedules appears to be feasible. It is concluded that cryopreservation of certain stages of helminth and protozoan parasites is a useful technique for long-term storage of defined isolates, which can contribute considerably to reducing the number of experimental animals usually required for serial passages.     

Transfer of secondary metabolites from the spongesDysidea fragilis andPleraplysilla spinifera to the mantle dermal formations (MDFs) of the mudibranchHypserlodoris webbi

The opisthobranch molluscHypselodoris webbi is able to select, among its potential preys, sponges chemically rich in furanosesquiterpenoids. The sequestered secondary metabolites act as defensive allomones against predators and are accumulated in some dorsal glands (MDFs). This transfer from sponges to MDFs has been proven by maintainingH. webbi together with some selected sponges in an aquarium for a prolonged period.     

Gel-electrophoretic description of European populations ofTerellia virens (Loew) (Diptera,Tephritidae); implications for its use as an agent for the biological control ofCentaurea spp. (Asteraceae) in North America

Allozyme frequencies of 15 enzyme loci, 14 of which were polymorphic, were used to characterize sevenTerellia virens populations originating from three allopatrically distributedCentaurea species. The two populations whose origins were geographically furthest apart, from Israel (onC. iberica) and from Switzerland (onC. vallesiaca), showed relatively high values of genetic distance from the 5 populations sampled in Austria and Hungary (onC. maculosa) (Nei's D>0.07). The latter five displayed a high degree of genetic similarity. No diagnostic (fixed) allelic differences were observed between these three groups ofT. virens populations, but they could be well characterized by significant differences in allelic frequencies at 9 enzyme loci. Independently of this study, the populations from Switzerland (C. vallesiaca) and eastern Austria (C. maculosa) were selected as potential source populations for future introductions into North America for the biological control of introducedC. maculosa andC. diffusa. Based on the observed genetic differences and results from field experiments on the host specificity of these two potential source populations, it is argued that host specificity screening tests should be conducted separately for local (host plant) populations, as such populations might accept a different set of hosts. Biotype mismatch and the risk of spill-overs to native species could thus possibly be reduced.     

EGF receptor induction and insulin-EGF overlap inTetrahymena

Summary Offspring generations ofTetrahymena pretreated (imprinted) with insulin showed a greater binding capacity for the hormone than offspring of untreated ones. The epidermal growth factor (EGF) imprinted for insulin to a greater degree than insulin itself, and vice versa: insulin imprinted for EGF more efficiently than EGF itself. These phenomena can be explained by the overlap of insulin and EGF on one another's receptors inTetrahymena.     

Occurrence of biopterin in the wings ofMorpho butterflies

A blue fluorescent compound was isolated fromMorpho butterfly wings. Based on thin layer chromatographic, UV and CD-spectrophotometric and HPLC analyses, the blue fluorescent compound was identified as L-erythro biopterin. Biopterin is a major component of blue fluorescent pteridines in bothM. sulkowskyi andM. adonis. Pterin and isoxanthopterin can also be detected as minor components in these species. This paper is the first to report the presence of biopterin in butterfly wings.     

Pupation-temperature range in 12Drosophila species from different ecological backgrounds

Summary A comparison of pupation-temperature range was made in the laboratory on a temperature gradient (3–38°C) using 12 species ofDrosophila representing four species groups and four different ecological backgrounds (temperate-montane forest:virilis group; desert;repleta group; cosmopolitan:melanogaster group; tropical forest:willistoni group). Within groups, differences are found which usually reflect species' distributions. Comparisons of species' mating-, oviposition- and pupation-temperature ranges reveal that pupation most-often occurs at temperatures beyond those for mating and oviposition. Each species reflects a different combination of temperature effects. Individual species have different temperature-limits for mating, oviposition and pupation. Temperatures permissive for one response are not predictive of limits on other responses. Among species, temperature can affect a particular response differently. Within groups, species differences can be at high and/or low temperatures for any response, and temperature effects among closely related species can manifest themselves in one, or any combination of responses. One cannot predict which responses will be most and least limited, or at which end of the temperature scale a response will be most limited. Among groups,common, but notabsolute temperature ranges generally correspond to the geographic distributions and ecological backgrounds of the species triads. The evaluation of temperature effects on species, based on a single activity, may not be adequate for predicting adaptive strategies.     

C-band differentiation between the chromosomes of two subspecies of the chironomid midgeChironomus thummi

Summary The metaphase chromosomes ofChironomus th. thummi contain approximately 17% more pericentric C-band heterochromatin than the chromosomes ofChironomus th. piger with 11% heterochromatin. InCh. th. thummi, the proportion of heterochromatin appeared to be much larger in metaphase chromosomes than in polytene chromosomes. This discrepancy is interpreted as being due to the specific chromosome organization and not as the result of an underreplication of heterochromatin during polytenization.     

Development of DNA probes for cytotoxin and enterotoxin genes in enteric bacteria

Summary DNA probes to identify the genes encoding toxins in enteric bacteria have been developed. Use of these probes reduces the number of animals required for toxicity testing, as suspect bacteria can be directly tested for the presence of toxin. We have augmented the gene probes available by developing probes against theEscherichia coli enterotoxin LTII and shiga toxin fromShigella dysenteriae 1.The LTII gene fromE. coli 357900 was identified and characterised and a suitable internal probe was obtained. The LTII gene was found not to be common among enterobacteriae from various geographical locations. Isolates predominately of animal origin from Nigeria and Thailand hybridized with the probe.The shiga toxin gene was isolated fromS. dysenteriae 1 by a combination of in vivo and in vitro methods. An internal probe was identified and used against different serogroups ofShigella andE. coli isolated. The probe was found to hybridize withS. dysenteriae 1 isolates and also someS. flexneri andS. sonnei strains. Representatives were tested for toxin production and found to produce toxin at low levels.     

A simple test using restricted PCR-amplified mitochondrial DNA to study the genetic structure ofApis mellifera L

The COI-COII intergenic region ofApis mellifera mitochondrial DNA contains an important length polymorphism based on a variable number of copies of a 192–196 bp sequence (Q) and the completer or partial deletion of 67 pb sequence (Po). This length variability has been combined with a restriction site polymorphism to produce a rapid and simple test for the characterization of mtDNA haplotypes. This test included the amplification by the polymerase chain reaction of the COI-COII region followed by aDraI restriction of the amplified fragment. In a survey of 302 colonies belonging to 12 subspecies, 21 different haplotypes have been found which have been unambiguously allocated to one of the 3 mtDNA lineages of the species. Although all colonies of lineage C exhibit the same pattern (C1), each one of lineages A and M presents up to 10 different haplotypes, opening the way to studies on the genetic structure and the evolution of a large fraction of the species. This test also differentiates southern Spanish and South African colonies, which can be of great interest for the Africanized bee problem.     

Pheromone components of the female elephant hawk-moth,Deilephila elpenor,and the silver-striped hawk-moth,Hippotion celerio

By means of gas chromatographic and mass spectroscopic methods, and combined GC-electroantennogram and electrosensillogram techniques, (E)-11-hexadecenal and (10E, 12E)-10,12-hexadecadienal [(E,E)-bombykal is also the main constituent of the pheromone of the silver-striped hawk-mothHippotion celerio. The biological activity of the substances was demonstrated with electroantennogram and single cell recording, and the physiological efficacy of the different hexadecadienal isomers compared.Pheromones, 79; as Pheromones, 78 is taken: Wu, Cai-Hong, and Bestmann, H. J., Chinese Science Bulletin34 (1989) 1475; pheromones, 77: Attygalle, A. B., Steghaus0Kovac, S., Ahmed, V. U., Maschwitz, U., Vostrowsky, Ol, and Bestmann, H. J., Naturwissen-schaften78 (1991) 90.     

AfricanClarias catfish elicits long-lasting weak electric pulses

The African catfishClarias is generally considered to possess electroreceptors but not electric organs. It is reported here that at least one species of the genus,C. gariepinus, can produce weak monophasic discharges during aggressive interactions with conspecifics. These irregular pulse discharges are substantially longer than the electric organ discharges (EODs) of all other pulse-generating freshwater electric fishes. It is also shown that the optimal sensitivity ofClarias' ampullary receptors just corresponds to the modal pulse duration. TheClarias catfish, with its very specific EOD, may be of special interest in the evolution of the electrogenic system in the siluriforms, comprising many electroreceptive but nonelectrogenic catfish species.     

Adhesive grass spikelet with mammalian hair in Dominican amber: First fossil evidence of epizoochory

Discovery of a female spikelet of the grass genusPharus (Gramineae: Bambusoideae: Phareae) in association with mammalian hair in Dominican Republic amber provides the first fossil evidence of epizoochory. Hooked macrohairs on the lemma of the spikelet show that morphological modifications in grasses for dispersal by attachment to the surface of animals were present in the Late Eocene. The fossil also represents 1) the second-oldest undoubted macrofossil record of the Gramineae, 2) the earliest record of a fossil grass that can be assigned to an extant genus, 3) the earliest undoubted record of a member of the bamboo subfamily and 4) the only known fossil ofPharus.