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151.
Guanethidine treatment or adrenal medullectomy significantly inhibited the elevation in blood pressure induced by Clostridium perfringens beta toxin, and the combination of the two drastically reduced the pressure rise, to less than 19% of that in control rats. When rats were pretreated with tetrodotoxin or hexamethonium, the toxin-evoked rise was significantly inhibited. Elevation in blood pressure induced by the toxin in spinal rats tended to be less than that in control rats. When investigated by a microscopical technique, arteriolar constriction in the mesenteric vasculature was observed after the blood pressure elevation induced by the toxin reached a maximum. Blood flow in the skin decreased with an increase in blood pressure following intravenous injection of the toxin. It is concluded that beta toxin acts on the autonomic nervous system and produces arterial constriction. 相似文献
152.
The catalytic mechanism of porcine pancreatic alpha-amylase (1,4-alpha-D-glucan glucanohydrolase, EC 3.2.1.1) has been examined by nuclear magnetic resonance (NMR) at subzero temperatures by using [1-13C]maltotetraose as substrate. Spectral summation and difference techniques revealed a broad resonance peak, whose chemical shift, relative signal intensity and time-course appearance corresponded to a beta-carboxyl-acetal ester covalent enzyme-glycosyl intermediate. This evidence supports a double-displacement covalent mechanism for porcine pancreatic alpha-amylase-catalyzed hydrolysis of glycosidic linkages, based on the presence of catalytic aspartic acid residues within the active site of this enzyme. 相似文献
153.
Siddhartha Kumar Bhaumik Manoj Kumar Singh Subir Karmakar Tripti De 《Glycoconjugate journal》2009,26(6):663-673
As compared to cutaneous leishmaniasis, vaccination against visceral leishmaniasis (VL) has received limited attention. In
this study, we demonstrate for the first time that an UDP-Galactose: N-acetylglucosamine β 1–4 galactosyltransferase (GenBank Accession No. EF159943) expressing attenuated LD clonal population (A-LD) is able to confer protection against the experimental challenge with the virulent LD AG83 parasite. A-LD was also effective in established leishmania infection. The vaccinated animals showed both cell mediated
(in vitro T-cell proliferation, and DTH response) and humoral responses (Th1 type). These results demonstrate the potential of the
attenuated clones as an immunotherapeutic and immunoprophylactic agent against visceral leishmaniasis. 相似文献
154.
155.
Mamta Singhvi Dipti Joshi Shalaka Gaikaiwari Digambar V. Gokhale 《Indian journal of microbiology》2010,50(1):97-100
Method for production and regeneration of Lactobacillus delbrueckii protoplasts are described. The protoplasts were obtained by treatment with a mixture of lysozyme and mutanolysin in protoplast
buffer at pH 6.5 with different osmotic stabilizers. The protoplasts were regenerated on deMan, Rogosa and Sharpe (MRS) with
various osmotic stabilizers. Maximum protoplast formation was obtained in protoplast buffer with sucrose as an osmotic stabilizer
using a combination of lysozyme (1 mg/ml) and mutanolysin (10 μg/ml). Maximum protoplast regeneration was obtained on MRS
medium with sucrose (0.5 M) as an osmotic stabilizer. The regeneration medium was also applicable to other species of lactobacilli
as well. This is, to our knowledge, the first report on protoplast formation and efficient regeneration in case of L. delbrueckii. 相似文献
156.
It is generally perceived that landscape patterns or textures in a given protected area are spatially stationary. The findings
of this study suggest that this common perception is only partially correct. Over the course of 52 years, equilibrium in landscape
shifting was detected using digital data for the Lassen Volcanic National Park (USA). Vertical aerial photographs taken of
the park in 1941 were geo-referenced with the digital orthophoto quarter quadrangle (DOQQ) images of the same area from 1993
to identify landscape compositions and to measure change. Spatial analysis was used to observe pattern changes over time.
The results suggested that landscape development maintained equilibrium while patches were in various stages of a successional
sequence. The total area of each landscape component held steady, although over time patches throughout the landscape changed—a
shifting-mosaic steady state (SMSS). These findings reflect the limitations of contemporary environmental conservation theory.
They also suggest the importance of considering landscape change in policies that currently govern park planning and management. 相似文献
157.
158.
James A. Simmons Andrea Megela Simmons 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(5):585-594
Widely divergent vertebrates share a common central temporal mechanism for representing periodicities of acoustic waveform
events. In the auditory nerve, periodicities corresponding to frequencies or rates from about 10 Hz to over 1,000 Hz are extracted
from pure tones, from low-frequency complex sounds (e.g., 1st harmonic in bullfrog calls), from mid-frequency sounds with
low-frequency modulations (e.g., amplitude modulation rates in cat vocalizations), and from time intervals between high-frequency
transients (e.g., pulse-echo delay in bat sonar). Time locking of neuronal responses to periodicities from about 50 ms down
to 4 ms or less (about 20–300 Hz) is preserved in the auditory midbrain, where responses are dispersed across many neurons
with different onset latencies from 4–5 to 20–50 ms. Midbrain latency distributions are wide enough to encompass two or more
repetitions of successive acoustic events, so that responses to multiple, successive periods are ongoing simultaneously in
different midbrain neurons. These latencies have a previously unnoticed periodic temporal pattern that determines the specific
times for the dispersed on-responses. 相似文献
159.
Primož Pirih Bodo D. Wilts Doekele G. Stavenga 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(10):987-997
The males of many pierid butterflies have iridescent wings, which presumably function in intraspecific communication. The
iridescence is due to nanostructured ridges of the cover scales. We have studied the iridescence in the males of a few members
of Coliadinae, Gonepteryx aspasia, G. cleopatra, G. rhamni, and Colias croceus, and in two members of the Colotis group, Hebomoia glaucippe and Colotis regina. Imaging scatterometry demonstrated that the pigmentary colouration is diffuse whereas the structural colouration creates
a directional, line-shaped far-field radiation pattern. Angle-dependent reflectance measurements demonstrated that the directional
iridescence distinctly varies among closely related species. The species-dependent scale curvature determines the spatial
properties of the wing iridescence. Narrow beam illumination of flat scales results in a narrow far-field iridescence pattern,
but curved scales produce broadened patterns. The restricted spatial visibility of iridescence presumably plays a role in
intraspecific signalling. 相似文献
160.