Morphometric investigations of the colon mucosa in chronicTrypanosoma cruzi infected rats

The objective of this investigation was to study the morphometry of the epithelial mucosa in the chronic phase ofT. cruzi infection. Nine young female Wistar rats were inoculated withT. cruzi. Ten months after inoculation the animals were sacrificed and the proximal colon was collected for morphometric measurements of the thickness of the muscle layers, the number of neurons in the myenteric plexus, the crypt cell population (CCP), crypt cell production per crypt (CCPC) and turnover time (TT) of the epithelium. There was no muscle layer hypertrophy but there was significant denervation in the group inoculated withT. cruzi, which also showed hyperplasia of the epithelium. The data suggest that denervation of the myenteric plexus did not induce hypertrophy of the propria muscle layer itself but altered the morphometry of the colonic epithelium inT. crwzi-infected animals, with increased development of CCP and TT. It is possible that this epithelial hyperplasia, as a consequence of a longer crypt cell TT, increased the absorption and secretion activities of the colon, which in turn may participate in the genesis of the enteromegalies observed in the chronic phase of Chagas’ Disease.     

A visually evoked escape response of the housefly

Summary Flies (Musca domestica) avoid danger by initiating a rapid jump followed by flight. To identify the visual cues that trigger the escape response in the housefly, we measured the timing and probability of escapes when the fly was presented with a variety of visual stimuli created by moving targets toward it. Our results show that an escape response is triggered by an approaching dark disk, but not by a receding dark disk. On the other hand, a bright disk elicits escape only when it recedes. A disk with black and white rings is less effective at eliciting escape than is a dark solid disk of the same size. This indicates that the darkening contrast produced by an approaching stimulus is a more crucial parameter than expansion cues contained in the optical flow. Escape is also triggered by a horizontally moving dark edge, but not by a moving bright edge or by a grating. An examination of several visual parameters reveals that the darkening contrast, measured from the onset of stimulation to the start of escape is nearly constant for a variety of stimuli that trigger escape reliably. Thus darkening contrast, coupled with motion may be crucial in eliciting the visually evoked escape response. Other visual parameters such as time-to-contact or target angular velocity seem to be relatively unimportant to the timing of escapes.Abbreviations P _s Probability of successful escape - r _disk radius of disk target - r _arena radius of shielding arena - v _disk linear velocity of disk target - v _edge linear velocity of edge - d _disk angular velocity of disk target boundary - _edge angular velocity of edge - _escape target distance at escape - d _start target distance before onset of target movement - h _edge height of the edge above fly - x _start distance from corner of triangle to start position of edge (0 or 50 mm) - x _escape distance from corner of triangle to the position of the edge when the fly escapes - x _center distance from corner of triangle to point above the center of the pad - x _total distance from the corner of the triangle to the base (height of triangle = base of triangle)     

Dioecy inMikania (Compositae:Eupatorieae)

For the first time dioecy inMikania and in the tribeEupatorieae is described and discussed. The condition is known only in members of theMikania swartziana Griseb. complex, a group of eight species, all endemic to the Greater Antillean Islands of Cuba, Hispaniola, and Jamaica.     

Horizontal distribution of crustaceans in Lake Glubokoe

A study has been made on the distribution of crustaceans along a profile of 6–9 stations from depths of less than 2 m to 20 m, in summer, autumn and early spring. The species composition, abundance, size-frequency distribution, biomass and diurnal dynamics were estimated. Many species abundant in the pelagic zone were found to be absent or scarce out to depths of 5 m. In the daytime, at depths out to 3 m, crustaceans greater than 1.0 mm were seldom found, while those 0.15–0.40 mm long were most abundant. At depths out to 5 m, not only was the total average size of crustaceans found to be smaller, but also that of individual species, including small ones: Ceriodaphnia and Chydorus. The biomass of crustaceans in shallow water and in the open lake differs in summer by more than 100 times, and in late autumn and early spring by more than 10 times. At the depth of 1 m, in none of the seasons did it exceed 0.026 mg l^-1. All the crustaceans except for nauplii and Chydorus considerably increased in numbers in the shallow water at night. The impoverishment of the littoral plankton in Lake Glubokoe is regarded as a specific case of the well-known phenomenon of ‘avoidance of the littoral’ by euplankton (Hutchinson, 1967; Kiselyov, 1980). It is pointed out that there is a possible relationship between diurnal horizontal migrations of plantivorous fish and the impoverishment of plankton near the shore. An attempt has been made to substantiate the assumption that the ‘avoidance of the littoral’ by pelagic crustaceans is due to high numbers of fish in shallow water.     

Complete resistance to challenges with Hymenolepis nana cysticercoids derived from mouse, rat and beetle in mice

and 1986. Complete resistance to challenges with Hymenolepis nana cysticercoids derived from mouse, rat and beetle in mice. International Journal for Parasitology 16: 623–628. When BALB/c and dd strains of mice were given eggs of Hymenolepis nana, they all became completely resistant not only to challenge with mouse-derived cysticercoids but also to challenges with rat-derived and beetle-derived cysticercoids. Serum IgG antibodies at 47–60 days post egg inoculation reacted strongly with these three different host-derived cysticercoids when examined by IFA test, but IgA and IgM isotypes reacted very weakly. Antibodies of infected mouse sera (IgG, IgM and IgA were examined) reacted not only with the protoscolex (scolex of the excysted juvenile) but also with the outer cyst wall. By contrast, uninfected mouse sera and immune sera prepared seven days post cysticercoid inoculation did not react at all. Antigens of both cyst wall and protoscolex appeared to be of parasite origin and not of host origin, and appeared similar in parasites from the different host species.     

Ethanol directly stimulates dihydrotestosterone conversion to 5 alpha-androstan-3 alpha, 17 beta-diol and 5 alpha-androstan-3 beta, 17 beta-diol in rat liver

The present results demonstrate for the first time in rat liver, that low ethanol concentrations (2.2 and 22 mM) directly stimulate dihydrotestosterone conversion to 5 alpha-androstan-3 alpha, 17 beta-diol and 5 alpha-androstan-3 beta, 17 beta-diol. Because this effect was blocked by 4-methylpyrazole, an alcohol dehydrogenase inhibitor, or by the addition of a saturating NADH concentration, this action probably is mediated by hepatic alcohol dehydrogenase activity through elevation of the NADH/NAD+ ratio. It remains to be determined whether this effect of ethanol actually reduces circulating and/or target tissue dihydrotestosterone levels; nevertheless, it is tempting to speculate that this action, in part, is responsible for the reported adverse effects of alcohol on male reproductive functions.     

The frequency of mutants in human fibroblasts UV-irradiated at various times during S-phase suggests that genes for thioguanine- and diphtheria toxin-resistance are replicated early

Human cells deficient in rate of excision repair of DNA damage induced by UV-radiation, i.e., xeroderma pigmentosum (XP) cells, are much more sensitive to the mutagenic effect of UV than are cells from normal persons. The lower frequency of mutants in the latter cells has been attributed to the fact that, unlike XP cells, they excise most of the potentially mutagenic lesions before these can be converted into mutations. If semi-conservative DNA synthesis on a template still containing unexcised lesions is responsible for introducing mutations and if replication of the gene of interest, e.g., hypoxanthine (guanine)phosphoribosyltransferase (HPRT) for thioguanine resistance or the elongation factor 2 (EF-2) for diphtheria toxin resistance, occurs at a particular time during S-phase, it should be possible to shorten the time available for such repair by synchronizing cells and irradiating them just as the gene is to be replicated. The predicted result would be a much higher frequency of mutants at one part in the S-phase than at other times. To test this, cells were synchronized using the alpha-polymerase inhibitor aphidicolin, which blocks cells at the G1/S border. Autoradiography, cytofluorimetry, and incorporation of tritiated thymidine studies showed that DNA synthesis started immediately after release from aphidicolin and was completed in 8-10 h. Cells irradiated with 6 J/m2 at various times post-release were assayed for survival and mutations. The frequency of thioguanine- or diphtheria toxin-resistant cells in the population was highest in cells irradiated during the first fifth of the S-phase, i.e., 0-1.5 h post-release. It was significantly lower in cells irradiated at later times. In contrast, UV-induced cytotoxicity showed no significant time dependence during S-phase. These data suggest that the HPRT and EF-2 genes are replicated early in S-phase.     

Immunochemical detection with rabbit polyclonal and mouse monoclonal antibodies of different pools of phytochrome from etiolated and green Avena shoots

While two monoclonal antibodies directed to phytochrome from etiolated oat (Avena sativa L.) shoots can precipitate up to about 30% of the photoreversible phytochrome isolated from green oat shoots, most precipitate little or none at all. These results are consistent with a report by J.G. Tokuhisa and P.H. Quail (1983, Plant Physiol. 72, Suppl., 85), according to which polyclonal rabbit antibodies directed to phytochrome from etiolated oat shoots bind only a small fraction of the phytochrome obtained from green oat shoots. The immunoprecipitation data reported here indicate that essentially all phytochrome isolated from green oat shoots is distinct from that obtained from etiolated oat shoots. The data indicate further that phytochrome from green oat shoots might itself be composed of two or more immunochemically distinct populations, each of which is distinct from phytochrome from etiolated shoots. Phytochrome isolated from light-grown, but norflurazon-bleached oat shoots is like that isolated from green oat shoots. When light-grown, green oat seedlings are kept in darkness for 48 h, however, much, if not all, of the phytochrome that reaccumulates is like that from etiolated oat shoots. Neither modification during purification from green oat shoots of phytochrome like that from etiolated oat shoots, nor non-specific interference by substances in extracts of green oat shoots, can explain the inability of antibodies to recognize phytochrome isolated from green oat shoots. Immunopurified polyclonal rabbit antibodies to phytochrome from etiolated pea (Pisum sativum L.). shoots precipitate more than 95% of the photoreversible phytochrome obtained from etiolated pea shoots, while no more than 75% of the pigment is precipitated when phytochrome is isolated from green pea shoots. These data indicate in preliminary fashion that an immunochemically unique pool of phytochrome might also be present in extracts of green pea shoots.Abbreviation ELISA enzyme-linked immunosorbent assay - mU milliunit - Pfr far-red-absorbing form of phytochrome - Pr red-absorbing form of phytochrome     

Subcellular localization of the common shikimate-pathway enzymes in Pisum sativum L.

5-Enolpyruvylshikimate 3-phosphate (EPSP) synthase (3-phosphoshikimate 1-carboxyvinyltransferase; EC 2.5.1.19), 3-dehydroquinate dehydratase (EC 4.2.1.10) and shikimate: NADP⁺ oxidoreductase (EC 1.1.1.25) were present in intact chloroplasts and root plastids isolated from pea seedling extracts by sucrose and modified-silica density gradient centrifugation. In young (approx. 10-d-old) seedling shoots the enzymes were predominantly chloroplastic; high-performance anion-exchange chromatography resolved minor isoenzymic activities not observed in density-gradientpurified chloroplasts. The initial enzyme of the shikimate pathway, 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (EC 4.1.2.15) was also associated with intact density-gradient-purified chloroplasts. 3-Dehydroquinate synthase (EC 4.6.1.3) and shikimate kinase (EC 2.7.1.71) were detected together with the other pathway enzymes in stromal preparations from washed chloroplasts. Plastidic EPSP synthase was inhibited by micromolar concentrations of the herbicide glyphosate.Abbreviations DAHP 3-deoxy-d-arabino-heptulosonate 7-phosphate - DEAE diethylaminoethyl - DHQase 3-dehydroquinate dehydratase - DTT dithiothreitol - EPSP 5-enolpyruvylshikimate 3-phosphate - SORase shikimate:NADP⁺ oxidoreductase     

Immigration of the brown planthopper, Nilaparvata lugens, exhibiting various responses to density in relation to wing morphism

Considerable inherent variations in the relation between macropterous and brachypterous wing forms, and nymphal density were found in field populations of the brown planthopper, Nilaparvata lugens Stål (Homoptera: Delphacidae), collected from various locations in Japan. When compared under uniform laboratory rearing conditions, most of the female populations exhibited higher ratios of macropters with increasing nymphal density, but some showed extremely high proportion of brachypters and the others were highly macropterous, over broad ranges of density. These results indicate the possibility that the planthoppers in Japan, which are known not to persist in winter, are derived from different migration sources.About ten generations of successive selection for brachyptery from a population showing usual density-dependent wing morphism generated populations similar to highly brachypterous ones mentioned above. Genetic analysis of the inheritance of wing morphism revealed that brachyptery in the females was controlled by a single pair of dominant alleles. However, in the males wing forms did not segregate so clearly in the crossing experiments. This suggests that wing morphism in N. lugens in under sex-limited inheritance.

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Einwanderung von Nilaparvata lugens mit unterscheidlicher Reaktion auf Populationsdischte bei der Flügelausbildung

Zusammenfassung In Feldpopulationen von Nilaparvata lugens Stål., welche in verschiedenen Regionen Japans gesammelt wurden, bestand in der Beziehung zwischen makropteren bzw. brachypteren Flügelformen und der Larvendichte eine beträchtliche Variation. Unter einheitlichen Zuchtbedingungen im Laboratorium stieg der Makropterenanteil bei den meisten Weibchenpopulationen mit steigender Temperatur; bei einigen Populationen hingegen war entweder der Brachypterenanteil oder der Makropterenanteil extrem hoch und zwar über weite Dichtebereiche. Dies deutet auf die Möglichkeit hin, dass die Zikade in Japan, wo sie bekanntlich nicht überwintert, jeweils aus verschiedenen Quellen einwandert.Wenn eine Population mit der üblichen dichteabhängigen Flügelausbildung 10 Generationen lang auf Brachypterie selektioniert wurde, entstanden Populationen, die den erwähnten hochbrachypteren Populationen aus dem Feld glichen. Die genetische Analyse der Vererbung der Brachypterie ergab, dass bei Weibchen ein einzelnes dominantes Allel verantwortlich ist. Bei Männchen dagegen trennten sich bei Kreuzungsexperimenten die Flügelformen nicht so klar. Dies deuted auf Unterschiede zwischen den Geschlechtern bei der Vererbung der Flügelformen.