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报道了内蒙古清水河黄土丘陵地区发现的紫萼藓科1新变种——缨齿藓菱形变种[Jaffueliobryum wrightii(Sull.)Thér.var.rhombicumX.L.BaiSarula],该变种与干旱山地岩面生境中的原变种缨齿藓[Jaffueliobryum wrightii(Sull.)Thér.]相似,生境的变化导致其形态发生变化,主要表现在上部细胞菱形和细胞壁背部强烈加厚,未分化的叶上部边缘细胞、中肋横切面细胞不分化,叶片长0.7~0.8mm,毛尖长0.8~1.3mm。文中对缨齿藓及其新变种的形态学特征,分布和生境进行了描述,并提供了显微照片,另外,列出了缨齿藓属5个种的检索表。 相似文献
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Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves 总被引:4,自引:0,他引:4
A puzzling population-genetic phenomenon widely reported in allozyme
surveys of marine bivalves is the occurrence of heterozygote deficits
relative to Hardy-Weinberg expectations. Possible explanations for this
pattern are categorized with respect to whether the effects should be
confined to protein-level assays or are genomically pervasive and expected
to be registered in both protein- and DNA-level assays. Anonymous nuclear
DNA markers from the American oyster were employed to reexamine the
phenomenon. In assays based on the polymerase chain reaction (PCR), two
DNA-level processes were encountered that can lead to artifactual genotypic
scorings: (a) differential amplification of alleles at a target locus and
(b) amplification from multiple paralogous loci. We describe symptoms of
these complications and prescribe methods that should generally help to
ameliorate them. When artifactual scorings at two anonymous DNA loci in the
American oyster were corrected, Hardy-Weinberg deviations registered in
preliminary population assays decreased to nonsignificant values.
Implications of these findings for the heterozygote-deficit phenomenon in
marine bivalves, and for the general development and use of PCR-based
assays, are discussed.
相似文献
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The initial steps in taste and olfaction result from the activation by
chemical stimuli of taste receptor cells (TRCs) and olfactory receptor
neurons (ORNs). In parallel with these two pathways is the chemosensitive
trigeminal pathway whose neurons terminate in the oral and nasal cavities
and which are activated by many of the same chemical stimuli that activate
TRCs and ORNs. In a recent single unit study we investigated the responses
of rat chorda tympani and glossopharnygeal neurons to a variety of
bitter-tasting alkaloids, including nicotine, yohimbine, quinine,
strychnine and caffeine, as well as capsaicin, the pungent ingredient in
hot pepper. Here we apply many of these same compounds to cultured rat
trigeminal ganglion (TG) neurons and measure changes in intracellular
calcium [Ca2+]i to determine whether TG neurons will respond to these same
compounds. Of the 89 neurons tested, 34% responded to 1 mM nicotine, 7% to
1 mM caffeine, 5% to 1 mM denatonium benzoate, 22% to 1 mM quinine
hydrochloride, 18% to 1 mM strychnine and 55% to 1 microM capsaicin. These
data suggest that neurons from the TG respond to the same bitter-tasting
chemical stimuli as do TRCs and are likely to contribute information sent
to the higher CNS regarding the perception of bitter/irritating chemical
stimuli.
相似文献
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The histological effect on and stress response of post juvenile Clarias gariepinus exposed to Qua Iboe crude oil and rig wash were investigated. Fish weighing 60–90 g and measuring 16–18 cm were exposed for 7–28 days to 8.00 ml?1 Qua Iboe crude oil and 0.0018 ml–1 rig wash, both being 0.1 of the 96 hr LC50. Blood samples of C. gariepinus were collected every seven days and evaluated for stress by measuring cortisol concentration. The gills and liver were studied and scored for Gill Alteration Index (GAI) and Hepatic Alteration Index (HAI), respectively. There was an increase in cortisol level up to the 7th and 14th day among the group exposed to Qua Iboe crude oil, with a decrease on the 21st and 28th day. The rig wash group increased in cortisol level up to the 7th day and decreased slightly on the 14th day, after which the trend became irregular. The toxic effects of the Qua Iboe crude oil and rig wash were time dependent, as shown by the histopathological alteration index (HAI) of gill and liver. After 28 days of exposure, the gills had irreparable damage due to high frequency of cellular necrosis and degeneration, whereas the liver had from moderate to severe damage due to the high frequency of cellular degeneration and inflammation. Qua Iboe crude oil and rig wash are both toxic to C. gariepinus, therefore their indiscriminate discharge to the environment must be discouraged. 相似文献
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