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91.
Chromium is an essential trace element and is associated with some biological pathways, especially with glucose tolerance.
For these reasons, we decided to determine the concentration of chromium in two sets of Brazilian medicinal plants. The first
group consisted of plants that are considered as antidiabetic, whereas the second included plants that do not have this therapeutic
property. The concentration of chromium was determined by flameless atomic absorption. All the plants analyzed contain chromium
in the normal range for this element, but the hypoglycemic plants contain more chromium than the others (1–4 μg/g compared
to 0.5–1.5 μg/g). 相似文献
92.
P. Badia A. Lorenzo T. Gomez A. Bolaños 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,157(6):865-871
Summary Ion transport processes in the ileum of the lizard,Gallotia (=Lacerta) galloti was examined in vitro by measuring Na22 and Cl36 fluxes across short-circuited preparations.In Ringer-bicarbonate solution there was both a net sodium flux (
) and a net chloride flux (
) from mucosa to serosa. The inequality between
and short-circuit current (I
sc) suggests that part of the net sodium transport is the result of an electrically neutral transport mechanism or that another electrogenic mechanism opposite in sign is contributing to the short-circuit current.In the absence of sodium, the short-circuit current and net chloride flux were abolished. In the absence of chloride, the net sodium was reduced but not abolished and the short-circuit current was unchanged.From an analysis of the effects of the inhibitors furosemide, amiloride, disulfonic stilbene (DIDS) and acetazolamide, a plausible model was developed to explain the characteristics of these transports. It is proposed that the entry of sodium into the cell across the luminal membrane occurs by two pathways. Part occurs by the antiport Na+H+ and part by an electrogenic pathway. The entry of chloride is by the antiport Cl–HCO
3
–
.Symbols and abbreviations
DIDS 4,4
diisothiocyanatostilbene-2,2-disulfonic acid
-
G
t
tissue conductance
-
I
sc
short circuit current
-
m
mucosal
-
PD
potential difference
-
s
serosal 相似文献
93.
Air-grown cells of a marine, small-celled (2 m diameter) strain of Stichococcus bacillaris contained appreciable carbonic-anhydrase activity but this was repressed when cells were grown on air enriched with 5% (v/v) CO2. Assay of carbonic-anhydrase activity using intact cells and cell extracts showed all activity was intracellular in this Stichococcus strain. Measurement of inorganic-carbon-dependent photosynthetic O2 evolution at pH 5.0, where CO2 is the predominant form of inorganic carbon, showed that the concentration of inorganic carbon required for half-maximal rate of photosynthetic O2 evolution [K0.5(CO2)] was 4.0 M for both air- and CO2-grown cells. At pH 8.3 the K0.5(CO2) was 0.3 mM for air-grown and 0.6 mM for CO2-grown cells. Sodium ions did not enhance bicarbonate utilization. Measurement of the internal inorganic-carbon pool (HCO
3
–
+CO2) by the silicone-oil-layer centrifugal filtering technique showed that air- and CO2-grown cells were able to concentrate inorganic carbon up to 20-fold in relation to the external medium at pH 5.0 but not at pH 8.3. In this alga the high affinity for CO2 and inorganic-carbon accumulation in CO2- and air-grown cells results from active CO2 transport that is not dependent on carbonic-anhydrase activity.Abbreviation Hepes
4-(2-hydroxyethyl)-1-piperazine ethanesulfonic acid 相似文献
94.
F Ure?a 《Revista de biología tropical》1988,36(1):129-137
The ultrastructure of mitotic nuclei of the promastigote Leishmania mexicana ssp. was studied by serial thin sections and three-dimensional reconstructions of each divisional stage. At the beginning of nuclear division (equatorial stage), a set of six dense plaques located about the equatorial region of the nucleus and a microtubular spindle develops in the two opposing poles of the nucleus (two sets of polar microtubules). The microtubular mitotic spindle is entirely intranuclear with the nuclear membrane persisting through mitosis. The polar spindle consists of a discrete bundle of about 50 microtubules and the equatorial spindle is formed by about 100 microtubules. The spindle may contain several continuous microtubules, but no microtubular organizing centres were observed in association with the spindle. The plaques and hemiplaques are associated with microtubular bundles; some of the spindle microtubules converge on kinetochore-like plaques. It is suggested that the spindle has a special significance in the physiology of mitosis. The two sets of hemiplaques may guide the separation of the daughter genomes. At the beginning of the elongational stage the mitotic plaques split into halves and each set of half-plaques migrates to one pole. It is concluded that the dense plaques play a kinetochore-like role and thus Leishmania mexicana ssp. may have six chromosomal units. Mitotic events of this species are essentially similar to those of Trypanosoma cruzi. 相似文献
95.
Summary Phenotypic analyses of genetic combinations involving the gene extramacrochaetae (emc) reveal its participation in the differentiation of both sensory elements and wing veins. The study of near-amorphic alleles of emc in mitotitc recombination clones indicates that it also affects cell proliferation. These clones show abnormal sizes, shapes and spatial distribution. They differentiate extra sensory elements as well as extra veins. A gain of function mutation in the gene causes opposite phenotypes in both differentiation systems. The effects of the mutant on proliferation and patterning are consistent with the emc gene being involved in the transfer of information between neighbouring cells, which leads to the spatial expression of the achaetescute gene complex and genes involved in vein formation. 相似文献
96.
Experimental aflatoxin production in Manchego-type cheese 总被引:1,自引:1,他引:0
J. L. Blanco L. Domínguez Esperanza Gómez-Lucía J. F. F. Garayzabal J. Goyache G. Suárez 《Journal of applied microbiology》1988,64(1):17-26
Manchego-type cheese, a typical Spanish cheese, was inoculated in various ways with an aflatoxigenic organism, Aspergillus parasiticus NRRL 2999, to study the production of aflatoxin. When the original milk was contaminated with a spore suspension, aflatoxin was not detected in paraffin-covered cheeses although it was present in the top layer of non-paraffin-covered cheeses after ripening at 15°C for 60 d. When the cheese surface was inoculated, no aflatoxins were detected in paraffin-covered cheeses after ripening for 60 d although they were found when the cheeses were ripened for 30 d. In non-paraffin-covered cheeses aflatoxins were detected only in the top layer and in the second 10 mm layer when cheeses were incubated after the normal ripening at 28°C for 30 d. When the centre of the cheese was inoculated, no aflatoxins were detected although Aspergillus grew slightly along the inoculation area. When cheese portions were inoculated, fungal growth was evident after incubation at 28° and 15°C for 6 d but there was no growth at 10°C after 50 d. At 28°C aflatoxins were detected at a concentration of 132 μg/g after 13 d, the highest level obtained. In cheese paste at 28° and 15°C, growth was intense, but the level of aflatoxins detected was lower than in cheese portions. At 10°C the growth was heavy, but aflatoxins were not detected. 相似文献
97.
98.
C López-García A Molowny F J Martínez-Guijarro J M Blasco-Ibá?ez J A Luis de la Iglesia A Bernabeu J M García-Verdugo 《Histology and histopathology》1992,7(4):725-746
The cerebral cortex of Squamate reptiles (lizards and snakes) may be regarded as an archicortex or "reptilian hippocampus". In lizards, one cortical area, the medial cortex, may be considered as a true "fascia dentata" on grounds of its anatomy, connectivity and cyto- chemo-architectonics of its main zinc-rich axonal projection. Moreover, its late ontogenesis and postnatal development support this view. In normal conditions, it shows delayed postnatal neurogenesis and growth during the lizard's life span. Remnant neuroblasts in the medial cortical ependyma of adult lizards seasonally proliferate. The late-produced immature neurocytes migrate to the medial cortex cell layer where they differentiate and give off zinc-containing axons directed to the rest of cortical areas. This results in a continuous growth of the medial cortex and its zinc-rich axonal projection. Perhaps the most important characteristic of the lizard medial cortex is that it can regenerate after having been almost completely destroyed. Recent experiments in our laboratory have shown that chemical lesion of its neurons (up to 95%) results in a cascade of events; first, those related with massive neuronal death and axonal-dendritic retraction and, secondly, those related with a triggered neuroblast proliferation and subsequent neo-histogenesis, and the regeneration of an almost new medial cortex that shows itself undistinguishable from a normal undamaged one. This is the only report to our knowledge that an amniote central nervous centre may regenerate by new neuron production and neo-histogenesis. Perhaps the medial cortex of lizards may be used as a model for neuronal regeneration and/or transplant experiments in mammals or even in primates. 相似文献
99.
Evidence for a role of protein kinase C zeta subspecies in maturation of Xenopus laevis oocytes. 总被引:4,自引:1,他引:3 下载免费PDF全文
I Dominguez M T Diaz-Meco M M Municio E Berra A García de Herreros M E Cornet L Sanz J Moscat 《Molecular and cellular biology》1992,12(9):3776-3783
A number of studies have demonstrated the activation of phospholipase C-mediated hydrolysis of phosphatidylcholine (PC-PLC) both by growth factors and by the product of the ras oncogene, p21ras. Evidence has been presented indicating that the stimulation of this phospholipid degradative pathway is sufficient to activate mitogenesis in fibroblasts as well as that it is sufficient and necessary for induction of maturation in Xenopus laevis oocytes. However, the mechanism whereby PC-PLC transduces mitogenic signals triggered by growth factors or oncogenes remains to be elucidated. In this study, data are presented that show the involvement of protein kinase C zeta subspecies in the channelling of the mitogenic signal activated by insulin-p21ras-PC-PLC in Xenopus oocytes as well as the lack of a critical role of protein kinase C isotypes alpha, beta, gamma, delta, and epsilon in these pathways. 相似文献
100.
We studied the behavior of the Poeciliid fishGambusia affinis after the introduction of 3 substances into their tank: a homogenization ofGambusia affinis, a homogenization of the Anabantid fishBetta splendens, and a blank made of distilled water. The response of the fish was measured as a change in their spatial distribution in
the tank after the introduction of the substance. Two sizes of fish were used, and theGambusia homogenization produced clear alarm reactions in both, the fish fleeing to the bottom of the tank. This is one of a few examples
available of recognition of alarm substances in non-ostariophysian fish. In addition, we found that the small fishes that
had recently been exposed to the alarm substance stayed in an ‘alert state’, in which they had an increased sensitivity to
mechanical and visual fright stimuli. 相似文献