Sequence analysis of two exons from the murine dystrophin locus

We have isolated two genomic clones from the murine dystrophin locus, containing single exons encoding protein sequence from the putative actin-binding domain of the amino-terminus and the terminal portion of the triple helical domain. Using interspecific backcross progeny mice, both clones were shown to be X-linked. Sequence analysis indicated that the amino-terminal clone contains a 173 bp exon exhibiting 90% nucleotide sequence identity to human dystrophin exon 6, whilst the C-terminal clone contains a 61 bp exon with 93% nucleotide sequence identity to the human cDNA sequence.

     

Lymphocyte activation and serine-esterase induction following recombinant interleukin-2 infusion for lymphomas and acute leukaemias

Summary C57BL mice inoculated with radiation leukemia virus (RadLV) develop preleukemic cells long before the onset of leukemia. These cells are potentially immunogenic but fail to elicit an immune response in the host because of the appearance of virus-specific suppressor T cells. We have studied the effect of polysaccharide K (PSK) on the generation of RadLV-specific cell-mediated immune responses in vitro. Long-term exposure to PSK in culture potentiated the ability of immunized T cells to respond to a RadLV-induced lymphoma. It also abrogated the suppressive activity of suppressor T cells and simultaneously boosted the ability of reactive T cells to respond. The dual immunostimulating activity of PSK resulted in the generation of T cytotoxic lymphocytes that could lyse lymphoma cells in vitro. The results suggest that PSK could be used as a prophylactic immune response modifier in preleukemia.     

Dopamine acts through a D2-like receptor on a jellyfish motor neuron

Summary Dopamine, which is present in nerve-rich tissues of the hydromedusa Polyorchis penicillatus, produces membrane hyperpolarization in identified motor neurons from this jellyfish. In this study we demonstrate that the inhibitory action of dopamine is mediated by conventional drug-receptor interactions which are reversible, saturable and specific. When 10 M dopamine was applied by micro-spritzing onto voltage-clamped (holding potential, –20 mV), cultured swimming motor neurons, an outward current of about 1 nA was evoked. Using this technique, we established a potency order for several amines: dopaminenorepinephrine>tyramine >octopamine>-phenylethylamine. Dopamine is effective at concentrations betweeen 1 × 10^-8 and 1 × 10^-3 M. Several dopamine receptor blockers such as fluphenazine, haloperidol and spiperone reduced the dopamine-induced current in a concentration-dependent manner. Although propranolol, a -adrenergic blocker, reduced the dopamine response and SKF 83566, a D₁ blocker, increased the response, it appears that the dopamine receptors in these jellyfish neurons share pharmacological properties with mammalian D₂ dopamine receptors.     

Enzyme-linked immunosorbent assays for detecting antibodies to Shiga-like toxin I,Shiga-like toxin II,andEscherichia coli O157:H7 lipopolysaccharide in human serum

Shiga-like toxin-producingEscherichia coli O157:H7 are important causes of bloody diarrhea and hemolytic uremic syndrome. To facilitate the epidemiologic study of these organisms, we developed enzyme-linked immunosorbent assays (ELISAs) for antibodies to Shiga-like toxin I (SLT I), Shiga-like toxin II (SLT II), andE. coli O157 lipopolysaccharide (LPS). We tested serum samples from 83 patients in two outbreaks ofE. coli O157:H7 diarrhea and from 66 well persons. Forty-three patients (52%) had at least one serum sample positive for anti-O157 LPS antibodies; among 26 culture-confirmed patients, 24 (92%) had at least one positive serum sample. Two (3%) of 66 control sera had positive anti-O157 LPS titers. ELISA results for SLT I and II were compared with those of HeLa cell cytotoxicity neutralization assays on both patient and control sera. Neutralization assays detected anti-SLT I antibodies in at least one serum sample from each of 17 (20%) patients and 7 (10.6%) controls, while 16 (19%) patients and 7 controls had positive titers by anti-SLT I ELISA. Although all serum samples, including control sera, showed nonspecific neutralization of SLT II, no antibody titers to SLT II were detected by either neutralization or ELISA. These results indicate that ELISAs for SLT I and SLT II antibodies are comparable to HeLa cell cytotoxicity neutralization assays. Both the ELISAs and neutralization assays are insensitive in detecting infected patients. However, the ELISA for antibodies toE. coli O157 LPS is both sensitive and specific, and may be more useful than assays for antitoxic antibodies in detecting persons withE. coli O157:H7 infection.     

Elemental and isotopic analyses of mammalian fauna from Southern Africa and their implications for paleodietary research

Elemental analyses of mammalian bone (e.g., strontium-calcium ratios, or Sr/Ca) distinguish between herbivores and carnivores; however, the relationships among herbivores are unclear. To study this question, a modern faunal sample from the Nagupande Tsetse Control Area (Zambezi drainage, Northwestern Zimbabwe) was used. This collection has the advantage of well-established geographical controls in addition to a varied fauna, which includes both bovids and suids. The grazing/browsing dietary status of each species was ascertained by means of isotopic analysis of carbon. Clear differences were seen in the δ¹³C of grazing and browsing animals; a specialized grazer was found to have significantly lower Sr/Ca than less specialized grazers and browsers. In this study it was also possible to examine differences in Sr/Ca by sex; female warthogs were found to have significantly lower Sr/Ca than males. The variation in certain animal groups was found to be abnormal. Implications for reconstruction of prehistoric human diets using trace-element techniques are discussed.     

Glycosaminoglycans vary in accumulation along the neuraxis during spinal neurulation in the mouse embryo

We have utilized the method of whole embryo culture for metabolic labeling of mouse embryos with [3H]glucosamine during closure of neural folds at the posterior neuropore (27- to 29-somite stage). Accumulations of newly synthesized glycopeptides, lactosaminoglycans, hyaluronate, and sulfated glycosaminoglycans (GAG) were assessed by ion-exchange chromatography of glycoconjugates isolated from labeled embryos. Accumulation of hyaluronate and sulfated GAG was greatest in the posterior neuropore and decreased progressively toward the hindbrain where neurulation was already complete. Hyaluronate comprised a progressively smaller proportion of total newly synthesized glycoconjugate from the posterior neuropore toward the cranial region and glycopeptides showed the opposite trend. Sulfated GAG and lactosaminoglycans showed no consistent differences in relative abundance along the neuraxis. Autoradiographic analysis of newly synthesized glycoconjugates revealed especially heavy incorporation into developing basement membranes, beneath the neuroepithelium and around the notochord, in the posterior neuropore and recently closed neural tube regions, but not at more cranial levels of the neuraxis. Predigestion of sections with a specific hyaluronidase showed a significant quantity of this glycoconjugate to be hyaluronate. These results are consistent with a role for neuroepithelial and notochordal basement membrane hyaluronate in spinal neurulation.     

Effect of photoperiod and temperature on the life-cycle of different populations of the peacock butterfly Inachis io

The variation in response to photoperiod and temperature of different populations of the peacock butterfly, Inachis io (L.) (Lepidoptera: Nymphalidae), was investigated to test the extent to which species can adjust their response to the environment, and therefore maximise their reproductive potential. The photoperiodic (adult) diapause induction response varies between populations, and appears to be finely tuned to the local conditions. There is however variation within populations and the response can be adjusted in a population by selective breeding. The developmental rate is not significantly different between three latitudinally distinct populations, over the range of temperatures tested, and pupal weights are similar at given temperatures. However, pupal weights increase with decreasing development temperature. The implications of these findings are discussed with reference to modelling life history strategies.

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Résumé Inachis io (L.), observable dans une grande partie de l'Europe, y présente des différences quant au cycle biologique, au voltinisme et à la durée du développement. Trois populations provenant de la zone de transition entre monovoltinisme et bivoltinisme ont été échantillonnées pour examiner les différences de réponses à la photopériode et à la température, et pour évaluer l'étendue des possibilités d'adaptation de cette espèce à l'environnement et ainsi optimaliser son potentiel reproductif. L'induction photopériodique de la diapause est de type jour long pour toutes les souches examinées, mais la photopériode critique 50 (CPh50) varie suivant les populations et paraît étroitement ajustée aux conditions locales. Il y a cependant assez de variabilité à l'intérieur des populations pour que le seuil puisse être rapidement abaissé dans chaque population par des expériences d'élevage sélectif. Par contre, la vitesse de développement ne varie pas significativement entre les populations pour la gamme de température: 15–27°C. Les poids de chrysalides ne diffèrent pas suivant les populations, bien qu'ils augmentent quand la température de dévelppement diminue. On peut penser que des modèles, prédisant que la diminution du nombre de générations pendant une saison sera accompagnée d'une prolongation de la durée de développement et d'une augmentation de la taille, et que ceci est d'origine génétique et non le résultat seul du refroidissement de l'environnement, ne tiendront pas compte de l'absence de variation entre populations dans la relation entre température et développement.

     

Interactions amongst species in a guild of subtidal benthic herbivores

Summary The subtidal coralline flats of northeastern New Zealand support a characteristic guild of grazing herbivores. The most important members of this guild are an echinometrid echinoid, patellid, turbinid and trochid gastropods. Densities of these herbivores fluctuate through time. Interactions within and among the different species of echinoids and gastropods were investigated experimentally. Different combinations of species were caged at densities up to 5 times that of ambient for a 24 week period in an experiment designed to differentiate between intra- and interspecific competition.The echinoidEvechinus chloroticus and the turbinid gastropodCookia sulcata exhibited reduced mean dry weight with increasing intraspecific densities. There was little evidence of density-related mortality in these species. The limpetCellana stellifera showed comparatively large losses of weight and enhanced mortalities in intraspecific experimental treatments but this was not related to density.Investigation of interspecific interactions amongstEvechinus andCookia revealed no evidence of a negative influence of one species on the other. In terms of dry weight,Cookia was indifferent to the presence ofEvechinus, andEvechinus benefited in the reciprocal interaction.Cookia also enjoyed an enhanced mean dry weight when in the presence ofCellana compared to the equivalent intraspecific treatments. There were no coherent trends in proportional mortality in any treatments with enhanced interspecific densities. Cellana, in the presence ofCookia, exhibited a dramatic decrease in mortality rate and increase in mean dry weight. The presence of the turbinid gastropod was clearly beneficial to the limpet when compared to the intraspecific treatments with enhanced intraspecific densities and the control cages containingCellana at ambient density. We suggest that subtidal areas constitute poor habitats for limpets in the absence of agents such asCookia which may provide or maintain suitable sites for attachment and grazing.For the combinations of densities and species investigated there was a consistent trend towards positive interspecific interactions. It seems unlikely that at the sites investigated interspecific competition could act to restrict distributions, or limit abundances of species.     

Critical nuclear DNA size and distribution associated with S phase initiation

Using HeLa S-3 cells synchronized by selective detachment, in this paper we report a parallel study of nuclear morphology and autoradiography grain patterns between middle G₁ and middle S phases: Our results show two distinct [³H]-thymidine labeling patterns. The first “peripheral” labeling pattern has a characteristic nuclear size distribution, in contrast to the heterogeneous and varying size distributions of Feulgen-stained nuclei, and apparently is characteristic of very early S phase. The sizes of the second labeling pattern—homogeneous or inhomogeneous grain distribution throughout the nucleus—are equal or larger than the first and vary with S phase progression. Together, the corresponding nuclear sizes of the labeled nuclei represent the larger extreme of nuclear areas, and the labeling index closely parallels the fraction of nuclei with areas larger than the minimum size of the labeled nuclei. These results suggest a characteristic nuclear size (reflecting unique intranuclear DNA distribution) as a necessary, if not sufficient, requirement for S phase initiation. Parallel experimentation with rat liver cells—synchronized in vivo by partial hepatectomy and analyzed by thin section autoradiography—confirms the existence of a peripheral labeling pattern in both the very early part and the very late part of S phase, which reconciles our data with previous results and points to the fact that both initiation and termination sites for DNA replication are near the nuclear periphery.