Showing papers in "Cellular and Molecular Life Sciences in 1993"

The melatonin rhythm: both a clock and a calendar.

Abstract: The paper briefly reviews the data which shows that the circadian production and secretion of melatonin by the pineal gland can impart both daily, i.e., clock, and seasonal, i.e., calendar, information to the organism. The paper summarizes the 3 patterns of nocturnal melatonin production that have been described. Clearly, regardless of the pattern of nocturnal melatonin production a particular species normally displays, the duration of nightime elevated melatonin is proportional to the duration of the night length. Since daylength under natural conditions changes daily the melatonin rhythm, which adjusts to the photoperiod sends time of year information to the organism. The melatonin receptors which subserve the clock message sent by the pineal gland in the form of a melatonin cycle may reside in the biological clock itself, namely, the suprachiasmatic nuclei (SCN). The melatonin receptors that mediate seasonal changes in reproductive physiology are presumably those that are located on the pars tuberalis cells of the anterior pituitary gland. Besides these receptors which likely mediate clock and calendar information, melatonin receptors have been described in other organs. Interestingly, the distribution of melatonin receptors is highly species-specific. Whereas the clock and calendar information that the melatonin cycle imparts to the organism relies on cell membrane receptors, a fact that is of some interest considering the high lipophilicity of melatonin, recent studies indicate that other functions of melatonin may require no receptor whatsoever.

The structure of scytonemin, an ultraviolet sunscreen pigment from the sheaths of cyanobacteria.

Abstract: Despite knowledge of the existence of the pigment called scytonemin for over 100 years, its structure has remained unsolved until now. This pigment, the first shown to be an effective, photo-stable ultraviolet shield in prokaryotes, is a novel dimeric molecule (molec. wt. 544) of indolic and phenolic subunits and is known only from the sheaths enclosing the cells of cyanobacteria. It is probable that scytonemin is formed from a condensation of tryptophan-and phenylpropanoid-derived subunits. The linkage between these units is unique among natural products and this novel ring structure is here termed the ‘scytoneman skeleton’. Scytonemin absorbs strongly and broadly in the spectral region 325–425 nm (UV-A-violet-blue, with an in vivo maximum at 370 nm). However, there is also major absorption in the UV-C (λ max=250nm) and UV-B (280–320 nm). The pigment has been recently shown to provide significant protection to cyanobacteria against damage by ultraviolet radiation. The pigment occurs in all phylogenetic lines of sheathed cyanobacteria and possibly represents a UV screening strategy far more ancient than that of plant flavonoids and animal melanins. How diverse organisms deal with UV radiation is considered of vital importance to global ecology.

Compatible solutes of halophilic eubacteria : molecular principles, water-solute interaction, stress protection

Abstract: Compatible solutes are best described as organic osmolytes responsible for osmotic balance and at the same time compatible with the cells' metabolism. A comprehensive survey (using HPLC and NMR methods) on halophilic/halotolerant eubacteria has revealed the full diversity of compatible solutes employed in nature. Molecular principles derived from the spectrum of compounds found in the bacterial world may be summarized as follows. Compatible solutes are polar, highly soluble molecules and uncharged at physiological pH. With the exception of proline (a proteinogenic amino acid) they are characterized as amino acid derivatives of the following types: betaines, ectoines, N-acetylated diamino acids and N-derivatized carboxamides of glutamine. Using nearinfrared spectroscopy we have also been able to demonstrate that compatible solutes are strong water-structure formers and as such probably excluded from the hydration shell of proteins. This “preferential exclusion” probably explains their function as effective stabilizers of the hydration shell of native proteins (protection against heating freezing and drying). Hence these typical products of halophilic eubacteria have a considerable potential as stabilizing/protecting agents on both molecular and whole-cell level. Thorough understanding of common structural principles and fundamental water-solute interactions will ultimately enable us to design novel highly efficient stress protectants and stabilizers of biomolecules.

The contribution of extrapineal sites of melatonin synthesis to circulating melatonin levels in higher vertebrates

Abstract: While the production of melatonin in higher vertebrates occurs in other organs and tissues besides the pineal, the contribution of extrapineal sites of melatonin synthesis such as the retina, the Harderian glands and the gut to circulating melatonin levels is still a matter of debate. The amount of melatonin found in the gastrointestinal tract is much higher than in any other organ including the pineal and the gut appears to make a significant contribution to circulating melatonin at least under certain conditions. The gut has been identified to be the major source of the elevated plasma concentrations of melatonin seen after tryptophan administration and of the changes of circulating melatonin level induced by the feeding regimen. Whereas the circadian and circannual fluctuations of the concentration of melatonin in the blood seem to be triggered by changes of the photoenvironment and its effect of pineal melatonin formation, basal daytime melatonin levels and the extent of their elevation at nighttime appear to be additionally controlled by nutritional factors, such as the amount and the composition of ingested food and therefore availability of tryptophan as a rate-limiting precursor of melatonin formation by the enterochromaffin cells of the gastrointestinal tract.

Heat balance modelling.

Abstract: The only way to describe the effects of the thermal environment on the human body completely is to do it by means of an energy balance equation. In such an equation all relevant meteorological parameters, behavioral characteristics (activity and clothing) and body measurements can be considered. Using Fanger's comfort equation and the models MEMI and IMEM as examples, the problems of energy balancing and ways of solving them are described. The value of energy balance models is documented by examples from the field of application.

Nervous tissue proteoglycans.

Abstract: The structure, biosynthesis, localization, and possible functional roles of nervous tissue glycosaminoglycans and proteoglycans were last reviewed several years ago70,74. Since that time, there has been an exponential increase in publications on the neurobiology of proteoglycans. This review will therefore focus on reports which have appeared in the period after 1988, and especially on those concerning the properties of individual characterized nervous tissue proteoglycans. Related areas such as the regulation of glycosaminoglycan biosynthesis and the roles of cell surface proteoglycans in adhesion and growth control are covered in other contributions to this special topic issue.

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

Abstract: 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.

A method for chromosome preparations from large fish specimens using in vitro short-term treatment with colchicine

Abstract: This paper describes a new technique for preparing mitotic fish chromosomes using short-term in vitro treatment with colchicine. The results show that a large number of good quality metaphases (many suitable for chromosome banding) can be obtained by this technique, which requires an average of 1 h and 30 min for all steps. The procedure considerably reduces the time normally required for chromosome preparations in fish.

Calmodulin mediates melatonin cytoskeletal effects

Abstract: In this article, we review the data concerning melatonin interactions with calmodulin. The kinetics of melatonin-calmodulin binding suggest that the hormone modulates cell activity through intracellular binding to the protein at physiological concentration ranges. Melatonin interaction with calmodulin may allow the hormone to modulate rhythmically many cellular functions. Melatonin's effect on tubulin polymerization, and cytoskeletal changes in MDCK and N1E-115 cells cultured with melatonin, suggest that at low concentrations (10−9 M) cytoskeletal effects are mediated by its antagonism to Ca2+-calmodulin. At higher concentrations (10−5 M), non-specific binding of melatonin to tubulin occurs thus overcoming the specific melatonin antagonism to Ca2+-calmodulin. Since the structures of melatonin and calmodulin are phylogenetically well preserved, calmodulin-melatonin interaction probably represents a major mechanism for regulation and synchronization of cell physiology.

Cyanobacterial symbiont biosynthesis of chlorinated metabolites from Dysidea herbacea (Porifera)

Abstract: The tropical marine spongeDysidea herbacea contains large numbers of a symbiotic filamentous cyanobacterium identified on the basis of a detailed ultrastructural study asOscillatoria spongeliae. We report the flow-cytometric separation of the symbiont from the sponge cells, and demonstrate by chemical analyses that a unique group of polychlorinated compounds isolated from the whole sponge tissue is limited to the cyanobacterial filaments, whereas the accompanying sesquiterpenoids are found only in the sponge cells. This is the first demonstration that secondary metabolites ascribed to a sponge are localized in prokaryotic symbiont cells.

Non-viraemic transmission of tick-borne encephalitis virus: a mechanism for arbovirus survival in nature

Abstract: The vectors of arthropod-borne viruses (arboviruses) become infected by feeding on the viraemic blood of an infected animal. This theory is based on transmission studies involving artificial infection of vertebrate hosts by syringe inoculation. To reproduce natural conditions of virus transmission, infected and uninfected vectors (ticks) of tick-borne encephalitis virus, the most important arbovirus in Europe, were allowed to feed together on uninfected wild vertebrate hosts. The greatest numbers of infected ticks were obtained from susceptible host species that had undetectable or very low levels of viraemia. The results suggest that ‘nonviremic transmission’ is an important mechanism for the survival of certain arboviruses in nature.

The impact of climate change on human health: Some international implications

Abstract: The objective of this study is to discuss the potential impact of a global warming on various aspects of human health. Changes in heat-related mortality are estimated for four countries: the United States, Canada, the People's Republic of China and Egypt. In addition, the potential confounding impact of increased air pollution is considered. Finally, a framework to analyze two vector-borne diseases, onchocerciasis and malaria, which may spread if temperatures increase, is discussed. Our findings suggest that heat-related mortality is estimated to rise significantly in all four countries if the earth warms, with the greatest impacts in China and Egypt. The most sensitive areas are those with intense but irregular heat waves. In the United States, air pollution does not appear to impact daily mortality significantly when severe weather is present, although it seems to have a slight influence when weather conditions are not stressful.

Melatonin: presence and formation in invertebrates

Abstract: In vertebrates, it is now clearly demonstrated that the pineal gland is implicated in conveying photoperiodic information via the daily pattern of melatonin secretion Invertebrates, like vertebrates, use photoperiodic changes as a temporal cue to initiate physiological processes such as reproduction or diapause How this information is integrated in invertebrates remains an unsolved question Our review will be an attempt to evaluate the possible role of melatonin in conveying photoperiodic information in invertebrates It is now well demonstrated in both vertebrates and invertebrates that melatonin as well as its precursors or synthesizing enzymes are present in various organs implicated in photoreceptive processes or in circadian pacemaking Melatonin, serotonin or N-acetyltransferase have been found in the head, the eyes, the optic lobe and the brain of various invertebrate species In some species it has also been shown that melatonin is produced rhythmically with high concentrations reached during the dark period Moreover, the physiological effects of melatonin on various periodic processes such as rhythmic contractions in coelenterates, fissioning of asexual planarians or reproductive events in flies have been reported in the literature All these results support the hypothesis (refs 36, 37) that melatonin is not solely a pineal hormone but that it may be an evolutionary conservative molecule principally involved in the transduction of photoperiodic information in all living organisms

Proteoglycans of basement membranes

Abstract: Proteoglycans carrying either heparan sulfate and/or chondroitin sulfate side chains are typical constituents of basement membranes. The most prominent proteoglycan (perlecan) consists of a 400–500 kDa core protein and three heparan sulfate chains. Electron microscopy and cDNA sequencing show a complex and elongated domain structure for the core protein which in part is homologous to that of the laminin A chain. This structure may be varied by alternative splicing and proteolysis. Integration into basement membranes probably occurs by heparan sulfate binding to laminin and collagen IV, core protein binding to nidogen and by limited self assembly. The proteoglycan is in addition a cell-adhesive protein which is recognized by β1 integrins. Several more proteoglycans with smaller core proteins (10–160 kDa) apparently exist in basement membranes but are less well characterized. Biological functions include control of filtration through basement membranes and binding of growth factors and protease inhibitors.

The link proteins

Abstract: Aggregates of chondroitin-keratan sulfate proteoglycan (aggrecan) and hyaluronic acid (hyaluronan) are the major space-filling components of cartilage. A glycoprotein, link protein (LP; 40–48 kDa) stabilizes the aggregate by binding to both hyaluronic acid and aggrecan. In the absence of LP, aggregates are smaller (as estimated by rotary shadowing of electron micrographs) and less stable (they dissociate at pH 5) than they are in the presence of LP. The proteoglycan aggregate, including LP, is dissociated in the presence of chaotropes such as 4 M guanidine hydrochloride. On removal of the chaotrope, the complex will reassociate. This forms the basis of the isolation of LP from cartilage and has been described in detail elsewhere. Tryptic digestion of the proteoglycan aggregates results in a high molecular weight product that consists of hyaluronic acid to which is bound LP and the N-terminal globular domain of aggrecan (hyaluronic acid binding region; HABR) in a 1∶1 stoichiometry. The amino acid sequences of LP and HABR are surprisingly similar. The amino acid sequence can be divided into three domains; an N-terminal domain that falls into the immunoglobulin super-family and two C-terminal domains that are similar to each other. The DNA structure echoes this similarity, in that the major domains are reflected in three separate exons in both LP and HABR. The two C-terminal domains are largely responsible for the association with HA and are related to two recently described hyaluronate-binding proteins, CD44 and TSG-6. A variety of approaches, including analysis of the forms of LP found in vivo, rotary shadowing and analysis of the sequence in the immunoglobulin-like domain, have shed considerable light on the structure-function relationships of LP. This review describes the structure and function of LP in detail, focusing on what can be inferred from the similarity of LP, HABR and related molecules such as immunoglobulins and lymphocyte HA-receptors.

Neuromodulation by serotonin and octopamine in the honeybee: behaviour, neuroanatomy and electrophysiology

Abstract: The biogenic amines serotonin (5HT) and octopamine (OA) exist in the bee and can modulate neuronal activity and behaviour. 5HT-like and OA-like immunoreactivities can be found in most neuropils of the brain. Binding sites for the two amines are also present in most brain neuropils. The highest density of binding sites for [3H]serotonin and [3H]octopamine was found in the mushroom bodies. In some brain areas, especially the mushroom bodies, mismatches exist between binding sites and immunoreactivities, suggesting that the two amines also bind to neuropils which are not directly innervated by 5HT-like or OA-like immunoreactive neurons. The action of the two amines on behaviour in the bee is antagonistic. In the antennal pathway, proboscis and antennal responses to olfactory and gustatory stimuli are enhanced by OA and reduced by 5HT. In olfactory conditioning experiments, storage and retrieval of the learned signal can be enhanced by OA and reduced by 5HT. The specificity of these effects depends on the site of amine application in the neuropil. In the visual system the direction specificity of the visual antennal response is enhanced by OA and reduced by 5HT after topical application or injection into the lobula, the third optic ganglion. Correlates for the behavioural modulation can be found in higher-order visual interneurons. While OA application can mimic the stimulation of the bee with sugar water, the behavioural conditions leading to the release of 5HT are not yet known.

Altered proteoglycan gene expression and the tumor stroma

Abstract: Tumor stroma is a specialized form of tissue that is associated with epithelial neoplasms. Recent evidence indicates that significant changes in proteoglycan content occur in the tumor stroma and that these alterations could support tumor progression and invasion as well as tumor growth. Our main hypothesis is that the generation of tumor stroma is under direct control of the neoplastic cells and that, via a feedback loop, altered proteoglycan gene expression would influence the behavior of tumor cells. In this review, we will focus primarily on the work from our laboratory related to the altered expression of chondroitin sulfate proteoglycan and its role in tumor development and progression. The connective tissue stroma of human colon cancer is enriched in chondroitin sulfate and the stromal cell elements, primarily colon fibroblasts and smooth muscle cells, are responsible for this biosynthetic increase. These changes can be reproduced in vitro by using either tumor metabolites or co-cultures of human colon carcinoma cells and colon mesenchymal cells. The levels of decorin, a leucine-rich proteoglycan involved in the regulation of matrix assembly and cell proliferation, are markedly elevated in the stroma of colon carcinoma. These changes correlate with a marked increase in decorin mRNA levels and a concurrent hypomethylation of decorin gene, a DNA alteration associated with enhanced gene expression. Elucidation of decorin gene structure has revealed an unexpected degree of complexity in the 5′ untranslated region of the gene with two leader exons that are alternatively spliced to the second coding exon. Furthermore, a transforming growth factor beta (TGF-β)-negative element is present in the promoter region of decorin gene. This regulatory domain is likely to be implicated in the silencing of decorin gene by TGF-β and may contribute to the regulation of this matrix gene in the tumor stroma.

Invaders, weeds and the risk from genetically manipulated organisms

Abstract: 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.

Genotypic variation in foraging responses to environmental stimuli by honey bees,Apis mellifera

Abstract: We experimentally tested a model predicting that colony-level genotypic diversity contributes to colonylevel foraging flexibility in honey bees. We established a colony into which we placed individually marked workers from three genetically distinct groups. The colony was placed in an enclosure that contained feeding stations with pollen and sugar syrup. Foraging resources, stores of pollen and the quantity of brood within the colony were varied temporally. Individual foragers switched between resource types in response to changes in relative resource quality and colony need, demonstrating flexibility in resource choice at the individual level. However, genetic groups within the colony varied in their tendency to collect pollen versus nectar, and in lability of response to changes in foraging stimuli. Our data suggest that within-colony genotypic diversity contributes to a resilient foraging response to environmental variation.

Biology of halophilic bacteria, Part II. Membrane lipids of extreme halophiles: biosynthesis, function and evolutionary significance.

Abstract: Archaebacteria (archaea) are comprised of three groups of prokaryotes: extreme halophiles, methanogens and thermoacidophiles (extreme thermophiles). Their membrane phospholipids and glycolipids are derived entirely from a saturated, isopranoid glycerol diether, sn-2,3-diphytanylglycerol ('archaeol') and/or its dimer, dibiphytanyldiglyceroltetraether ('caldarchaeol'). In extreme halophiles, the major phospholipid is the archaeol analogue of phosphatidylglycerolmethylphosphate (PGP-Me); the glycolipids are sulfated and/or unsulfated glycosyl archaeols with diverse carbohydrate structure characteristic of taxons on the generic level. Biosynthesis of these archaeol-derived polar lipids occurs in a multienzyme, membrane-bound system that is absolutely dependent on high salt concentration (4 M). The highly complex biosynthetic pathways involve intermediates containing glycerol ether-linked C20-isoprenyl groups which are reduced to phytanyl groups to give the final saturated polar lipids. In methanogens, polar lipids are derived both from archaeol and caldarchaeol, and thermoacidophiles contain essentially only caldarchaeol-derived polar lipids. The function of these membrane polar lipids in maintaining the stability, fluidity and ionic properties of the cell membrane of extreme halophiles, as well as the evolutionary implications of the archaeol and caldarchaeol-derived structures will be discussed.

Clinical aspects of the melatonin action: impact of development, aging, and puberty, involvement of melatonin in psychiatric disease and importance of neuroimmunoendocrine interactions

Abstract: During the last decade we have learned much on physiological changes in the secretion of the pineal hormone melatonin (MLT) in man. Reportedly, there is little or no MLT secreted before age 3 months. Then MLT production commences, becmes circadian, and reaches highest nocturnal levels at the age of 1–3 years. During all of childhood nocturnal peak levles drop progressively by 80% until adult levels are reached. This alteration appears to be the consequence of increasing body size in face of constant MLT production during childhood. The biological significance of this MLT alteration is presently unknown. Because of conceptual considerations, major depressive syndrome (MDS) and seasonal affective disorder (SAD) have been in the focus of pineal research for several years. Although in these disorders alterations in MLT levels could not be substantiated, light therapy, a consequence of this research, was discovered as an effective treatment for SAD and perhaps for MDS. In addition, there is some recent evidence for low MLT levels in schizophrenia. Finally, the potential effect of MLT in neuroimmunoendocrine interactions is presently explored. Reportedly, in vitro studies and animal experiments give evidence for a modulatory role of MLT in the immune response. However, the exact way of this possible action of MLT remains to be clarified. Clinical studies are too scant for a meaningful estimation of MLT's involvement in human neuroimmunoendocrine interactions.

Hormonal control of pheromone responsiveness in the male black cutworm Agrotis ipsilon

Abstract: In Lepidoptera, reproduction is linked to chemical communication between conspecific partners. When exposed to the female sex pheromone, males respond by exhibiting typical sexual behaviour which leads to mating. Here we show that presence of the juvenile hormone producing gland (corpora allata) of the male black cutworm,Agrotis ipsilon, is necessary for pheromone responsiveness. Allatectomized males do not show any sexual behaviour, although their antennal olfactory system is functional. Allatectomized males implanted with active corpora allata recover full pheromone receptivity. It is suggested that reproductive processes are synchronized in males and females through endocrine control; timing of the mating activity could serve as an adaptive strategy linked to the migratory behaviour of this species.

Exopolysaccharide production byVolcaniella eurihalina

Abstract: The application of microbial extracellular polymers began in the 1960s, and since then there has been a remarkable increase in their commercial use. They are used in the food, textile, pharmaceutical, agricultural, paint and petroleum industries.Volcaniella eurihalina, a moderately halophilic eubacterium, produces an extracellular polysaccharide whose physical and chemical properties could be of interest for various industrial applications. The aim of this investigation is to analyze the different environmental parameters which influence the production of polysaccharide, and to study its chemical composition and the rheological properties of its solutions.

Towards an understanding of the role of glutamate in neurodegenerative disorders: energy metabolism and neuropathology.

Abstract: It is thought that impairment, of energy metabolism that results in deterioration of membrane function, leading to loss of the Mg2+ block on NMDA receptors, and allowing persistent activation of these receptors by glutamate, might be a cause of neuronal death in neurodegenerative disorders. Studies in rodents using mitochondrial respiratory chain toxins, such as aminooxyacetic acid, 1-methyl-4-phenylpyridinium, malonic acid and 3-nitropropionic acid, suggest that such processes may indeed be involved in neurotoxicity. Striatal and nigral degeneration induced by mitochondrial toxins in rodents resembles the neuropathology seen in humans suffering from Huntington's or Parkinson's disease, and can be prevented either by decortication or by NMDA receptor antagonists. Such experimental observations suggest that glutamate may be involved in neuronal death leading to neurodegenerative disorders in humans. If so, glutamate antagonists may offer a therapeutic approach for retarding the progression of these disabling disorders.

Urban bioclimatology : Human biometeorology. II

Abstract: This article deals with the part of urban climatology which is of particular relevance to human beings. Presented first is a summary of all human biometeorologically effective complexes, as well as other factors which are relevant to urban planning and which depend on atmospheric conditions in urban structures in a direct or indirect manner. Later, methods for human biometeorologically significant assessment of thermal and air pollution components of the urban climate are discussed in detail, because these components can be strongly influenced by urban planning. The application of these methods is illustrated by some results of appropriate investigations in urban areas

Ecology and physiology of phototrophic bacteria and sulfate-reducing bacteria in marine salterns

Abstract: Marine salterns are habitats for a large variety of halophilic bacteria. In the anoxic zones, halophilic sulfur bacteria develop mainly at the sediment surface, but only a few of them have so far been isolated from such environments. Among the phototrophic sulfur bacteria that sometimes form purple layers underneath the green cyanobacterial layers, members of the generaEctothiodhodospira, Chromatium (C. salexigens), Thiocapsa (T. halophila) were isolated. They grow by using sulfide as an electron donor. In the marine salterns, sulfide originates from active sulfate reduction. Among the halophilic sulfate-reducing bacteria, onlyDesulfovibrio halophilus andDesulfohalobium retbaense have so far been isolated. The ecology and physiology of both kinds of bacteria are discussed in this paper.

Cantharidin production in a blister beetle

Abstract: Cantharidin, a potent defensive chemical, is present in all ten life stages of the blister beetleEpicauta funebris. The first five larval stages accumulate cantharidin as they feed and grow in size. When disturbed, they exude cantharidin in a milky oral fluid, not in hemolymph which adult beetles reflexively discharge from leg joints. Two subsequent larval stages and the pupa do not feed, grow, regurgitate, or change in their defensive reserves (110 μg cantharidin/insect, regardless of sex). Adult beetles kept in isolation for 60–90 d exhibit a pronounced sexual dimorphism in cantharidin production: the male biosynthesizes about 17 mg of the toxin, representing 10% of his live weight, whereas the female actually loses most of her defensive reserves. But in the wild a female beetle repeatedly acquires cantharidin as copulatory gifts from her mates.

PCR jumping in clones of 30-million-year-old DNA fragments from amber preserved termites (Mastotermes electrodominicus).

Abstract: DNA from 30-million-year-old amber preserved termites (Mastotermes electrodominicus) was PCR amplified with nuclear ribosomal RNA small subunit primers and cloned into the TA vector (INVITROGEN). We obtained several classes of recombinant clones as a result. Authentic Mastotermes electrodominicus clones were identified. The source of other classes of clones was identified as contaminants of the ancient DNA template. Several of the clones appeared to be chimeric in structure with half of the clone identical to the termite sequence and the other half identical to contaminant sequences. The phenomenon of PCR jumping was identified as a possible source for the chimeric clones.

Mediation by nitric oxide of neurally-induced human cerebral artery relaxation.

Abstract: Human cerebral artery strips relaxed in response to non-adrenergic, non-cholinergic vasodilator nerve stimulation by electrical pulses or nicotine. The relaxation response was abolished by treatment with NG-nitro-L-arginine, a nitric oxide synthase inhibitor; the inhibitory effect was reversed by L-, but not D-, arginine. Nitric oxide-induced relaxation was unaffected. These findings support the hypothesis that nitric oxide plays a crucial role, possibly as neurotransmitter, in transmitting information from vasodilator nerve to smooth muscle in human cerebral arteries.

Avoidance of competition by spruce bark beetles, Ips typographus and Pityogenes chalcographus

Abstract: Bark beetles,Ips typographus andPityogenes chalcographus, attracted by synthetic or natural pheromone to Norway spruce logs,Picea abies, preferred to colonize uninfested logs rather than logs occupied by these beetles, probably as a means of avoiding intra-and interspecific competition. The aggregation pheromone components ofP. chalcographus, chalcogran and methyl (E, Z)-2,4-decadienoate, inhibited the attraction response ofI. typographus to its pheromone components (methyl butenol andcis-verbenol), while the converse was not true. However, verbenone released from colonized bark inhibited pheromonal response ofP. chalcographus.