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Evidence for NO-dependent vasodilation in the trout (Oncorhynchus mykiss ) coronary system 总被引:1,自引:0,他引:1
T. Mustafa C. Agnisola J. K. Hansen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(2):98-104
The effects of l-arginine, and its analogues N
ω-nitro-l-arginine methyl ester and N
ω-nitro-l-arginine on vascular resistance were investigated in the intact coronary system of an isolated non-working trout heart preparation.
l-Arginine, at 10–8 mol · l–1induced a slight vasodilatory effect (max 10%). N
ω-nitro-l-arginine methyl ester and N
ω-Nitro-l-arginine in the range 10–8–10–4 mol · l–1 caused dose-dependent increases in coronary resistance. The vasodilatory action of l-arginine was abolished when the preparation was pretreated with 10–4 mol · l–1
N
ω-nitro-l-arginine or N
ω-nitro-l-arginine methyl ester. Nitroprusside alone at 1 mmol · l–1 induced a maximum vasodilation (30%) of the coronary system. Methylene blue a known inhibitor of guanylate cyclase, induced
a strong vasoconstriction (already significant at 10–5 mol · l–1) and was able to overcome the vasodilative effect of nitroprusside. The endothelial nitric oxide agonists acetylcholine and
serotonin, established in mammalian vessels, also mediate vasodilation in trout coronary system. In 50% of preparations, acetylcholine
induced a biphasic response with vasodilation at low concentration (max 15% at 10–8 mol · l–1). Serotonin displayed a dose-response vasodilation in the range 10–8–10–4 mol · l–1 (max 20%). These vasodilative effects were reduced or abolished by 10–4 mol · l–1
l-NA. These data support the existence of NO-mediated vasodilation mechanisms in the trout coronary system.
Accepted: 1 July 1996 相似文献
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Jan Eivind Østnes Claus Bech 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):241-248
The ontogeny of deep-body cold sensitivity was studied in 1 to 12 days old Pekin ducklings Anas platyrhynchos. Deep-body cold sensitivity was determined by means of thermodes implanted in the abdominal cavity. The thermodes were perfused
with cold water for 15-min periods to lower the core temperature. Cooling of the body core elicited increases in metabolic
rate and vasoconstrictions in the legs of all the ducklings. From the changes induced in metabolic rate and core temperature,
deep-body cold sensitivity values of between −5.17 and −6.36 W · kg−1 · °C−1, were estimated. These values, which are in the range of those reported previously for adult Pekin ducks, did not change
with age, and it is concluded that deep-body cold sensitivity is fully developed at hatching. Our next aim was to investigate
whether the autonomic responses elicited by exposure of ducklings to cold ambient conditions could be explained by temperature
changes within the body core. During cold exposure, the increase in metabolic rate was not accompanied by a concomitant decrease
in core temperature. On the contrary, deep-body temperature increased slightly during the initial phase of cold exposure.
The ducklings attained a metabolic rate amounting to 85–90% of their peak metabolic rate before the core temperature fell
below the regulated level measured at thermoneutrality. Thus, despite the findings that Pekin ducklings have a highly-developed
deep-body cold sensitivity, their metabolic cold defence under natural conditions seems to be mediated primarily by peripheral
thermoreceptors.
Accepted: 7 January 1997 相似文献
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Isabelle Sendowski Gustave Savourey Yves Besnard Jacques Bittel 《European journal of applied physiology and occupational physiology》1997,75(6):471-477
To study the physiological responses induced by immersing in cold water various areas of the upper limb, 20 subjects immersed
either the index finger (T1), hand (T2) or forearm and hand (T3) for 30 min in 5°C water followed by a 15-min recovery period.
Skin temperature of the index finger, skin blood flow (Qsk) measured by laser Doppler flowmetry, as well as heart rate (HR) and mean arterial blood pressure (ˉBPa) were all monitored during the test. Cutaneous vascular conductance (CVC) was calculated as Qsk / ˉBPa. Cold induced vasodilatation (CIVD) indices were calculated from index finger skin temperature and CVC time courses. The
results showed that no differences in temperature, CVC or cardiovascular changes were observed between T2 and T3. During T1,
CIVD appeared earlier compared to T2 and T3 [5.90 (SEM 0.32) min in T1 vs 7.95 (SEM 0.86) min in T2 and 9.26 (SEM 0.78) min
in T3, P < 0.01]. The HR was unchanged in T1 whereas it increased significantly at the beginning of T2 and T3 [+13 (SEM 2) beats · min−1 in T2 and +15 (SEM 3) beats · min−1 in T3, P < 0.01] and then decreased at the end of the immersion [−12 (SEM 3) beats · min−1 in T2, and −15 (SEM 3) beats · min−1 in T3, P < 0.01]. Moreover, ˉBPaincreased at the beginning of T1 but was lower than in T2 and T3 [+9.3 (SEM 2.5) mmHg in T1, P < 0.05; +20.6 (SEM 2.6) mmHg and 26.5 (SEM 2.8) mmHg in T2 and T3, respectively, P < 0.01]. The rewarming during recovery was faster and higher in T1 compared to T2 and T3. These results showed that general
and local physiological responses observed during an upper limb cold water test differed according to the area immersed. Index
finger cooling led to earlier and faster CIVD without significant cardiovascular changes, whereas hand or forearm immersion
led to a delayed and slower CIVD with a bradycardia at the end of the test.
Accepted: 26 November 1996 相似文献
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Bernd Schröder Ina Rittmann Ernst Pfeffer Gerhard Breves 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(1):43-51
Unidirectional flux rates of Ca2+ across gastrointestinal tissues from sheep and goats were measured in vitro by applying the Ussing-chamber technique. Except for the sheep duodenum, mucosal to serosal Ca2+ flux rates (J
ms) exceeded respective flux rates in the opposite direction (J
sm) in both species and in all segments of the intestinal tract. This resulted in net Ca2+ flux rates␣(J
net = J
ms − J
sm) ranging between −2 and 9 nmol · cm−2 · h−1 in sheep and between 10 and 15 nmol cm−2 · h−1 in goats. In sheep, only J
net in jejunum, and in goats, J
netin duodenum and jejunum were significantly different from zero. Using sheep rumen wall epithelia, significant J
net of Ca2+ of around 5 nmol · cm−2 · h−1 could be detected. Since the experiments were carried out in the absence of an electrochemical gradient, significant net
Ca2+ absorption clearly indicates the presence of active mechanisms for Ca2+ transport. Dietary Ca depletion caused increased calcitriol plasma concentrations and induced significant stimulations of
net Ca2+ absorption in goat rumen. J
net of Ca2+ across goat rumen epithelia was significantly reduced by 1 mmol · l −1 verapamil in the mucosal buffer solution. In conclusion, there is clear evidence for the rumen as a main site for active
Ca2+ absorption in small ruminants. Stimulation of active Ca2+ absorption by increased plasma calcitriol levels and inhibition by mucosal verapamil suggest mechanistic and regulatory similarities
to active Ca2+ transport as described for the upper small intestines of monogastric species.
Accepted: 31 July 1996 相似文献
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Ralph Beneke Katharina Meyer 《European journal of applied physiology and occupational physiology》1997,75(3):246-251
The effect of a 3-week exercise programme on performance and economy of walking was analysed in 16 male patients with chronic
heart failure [mean age 51.8 (SD 6.9) years, height 174.9 (SD 6.3) cm, body mass 75.3 (SD 11.5) kg, ejection fraction 20.8
(SD 5.0)%]. They were submitted to a cardiopulmonary exercise test on a cycle ergometer and a 6-min walking test on a treadmill
before and after the period of exercise training. The training programme consisted of interval cycle (five times a week for
15 min), and treadmill ergometer training (three times a week for 10 min) at approximately 70% cycling peak oxygen uptake
(O2peak) and supplementary exercises (three times a week for 20 min). Compared to the pre values cycling O2peak [11.9 (SD 2.9) vs 14.0 (SD 2.3) ml · kg–1 · min–1], maximal self paced walking speed [0.68 (SD 0.33) vs 1.16 (SD 0.30) m · s–1], and net walking power [2.16 (SD 0.89) vs 2.73 (SD 0.91) W · kg–1] had increased (P < 0.01) while net energy cost [3.31 (SD 0.66) vs 2.33 (SD 0.38) J · kg–1 · m–1] had decreased (P < 0.001) after the training period. Approximately 42% of the increase of walking speed resulted from a higher walking power
output, whereas approximately 58% corresponded to a positive effect on walking economy. The improvement in walking economy
was a function of an increase in walking velocity itself and a result of a more efficient walking technique. These results
would indicate that in patients with marked exercise intolerance, adequate exercise training programmes could contribute to
favourable metabolic changes with positive effects on the economy of motion.
Accepted: 29 August 1996 相似文献
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Changes in selected aspects of immune function in the leopard frog, Rana pipiens, associated with exposure to cold 总被引:3,自引:0,他引:3
Gregory D. Maniero Cynthia Carey 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):256-263
The effect of exposure to low temperatures (5 °C) on lymphocyte proliferation, leukocyte populations, and serum complement
levels was examined in the northern leopard frog, Rana pipiens. Proliferation of T lymphocytes in response to phytohemagglutinin stimulation was significantly decreased in frogs kept for
2, 3, and 5 months at 5 °C compared to that of animals kept at 22 °C. A significant increase in the average percentage of
neutrophils and a decrease in the mean percentage of eosinophils was observed in the blood of frogs held for 5 months in the
cold compared to animals held at 22 °C for the same length of time. Mean serum complement activity after 1 month at 5 °C was
significantly reduced in comparison to animals held at 22 °C and was not detectable after 5 months in the cold. Recovery of
complement levels at room temperature (22 °C) was also examined after cold exposure. Complement levels were significantly
higher than controls (at 22 °C) in frogs returned to 22 °C for 7 and 14 days after 5 months in the cold. After frogs were
held at 5 °C for 1 month, serum complement levels increased significantly within 2 days after returning to 22 °C and continued
to rise 5 and 9 days after warming. Injections with Aeromonas hydrophila following a 5-week exposure to 5 °C failed to cause death or observable symptoms of disease in frogs that were returned to
22 °C.
Accepted: 20 November 1996 相似文献
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J. P. Costanzo J. B. Moore R. E. Lee Jr. P. E. Kaufman J. A. Wyman 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(3):169-176
This investigation examined the influence of soil moisture and associated parameters on the cold hardiness of the Colorado
potato beetle (Leptinotarsa decemlineata Say), a temperate-zone species that overwinters in terrestrial burrows. The body mass and water content of adult beetles
kept in sand at 4 °C varied over a 16-week period of diapause according to the substratum's moisture content. Changes in body
water content, in turn, influenced the crystallization temperature (range −3.3 to −18.4 °C; n = 417), indicating that environmental moisture indirectly determined supercooling capacity, a measure of physiological cold
hardiness. Beetles held in dry sand readily tolerated a 24-h exposure to temperatures ranging from 0° to −5 °C, but those
chilled in sand containing as little as 1.7% water (dry mass) had elevated mortality. Thus, burrowing in dry soils not only
promotes supercooling via its effect on water balance, but may also inhibit inoculative freezing. Mortality of beetles exposed
to −5 °C for 24 h was lower in substrates composed of sand, clay and/or peat (36–52%) than in pure silica sand (78%) having
an identical water content (17.0% dry mass). In addition to moisture, the texture, structure, water potential, and other physico-chemical
attributes of soil may strongly influence the cold hardiness and overwintering survival of burrowing insects.
Accepted: 10 September 1996 相似文献
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B. Jongsareejit R. N. Z. A. Rahman S. Fujiwara T. Imanaka 《Molecular & general genetics : MGG》1997,254(6):635-642
The gltA gene encoding a glutamate synthase (GOGAT) from the hyperthermophilic archaeon Pyrococcus sp. KOD1 was cloned as a 6.6 kb HindIII-BamHI fragment. Sequence analysis indicates that gltA encodes a 481- amino acid protein (53 269 Da). The deduced amino acid sequence of KOD1-GltA includes conserved regions that
are found in the small subunits of bacterial GOGAT: two cysteine clusters, an adenylate-binding consensus sequence and an
FAD-binding consensus sequence. However, no sequences homologous to the large subunit of bacterial GOGAT were found in the
upstream or downstream regions. In order to examine whether GltA alone can act as a functional GOGAT, GltA was overexpressed
in Escherichia coli BL21 (DE3) cells using an expression plasmid. GltA was purified to homogeneity and shown to be functional as a homotetramer
of approximately 205 kDa, which is equivalent to the molecular weight of the native GOGAT from KOD1, thus indicating that
KOD1-GOGAT is the smallest known active GOGAT. GltA is capable of both glutamine-dependent and ammonia-dependent synthesis
of glutamate. Synthesis of glutamate by KOD1-GltA required NADPH, indicating that this enzyme is an NADPH-GOGAT (EC 1.4.1.13).
The optimum pH for both activities was 6.5. However, GltA exhibited different optimum temperatures for activity depending
on the reaction assayed (glutamine-dependent reaction, 80° C; ammonia-dependent reaction, 90° C).
Received: 30 October 1996 / Accepted: 13 January 1997 相似文献
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Photoperiodic time measurement regulating larval diapause in the pitcher-plant mosquito, Wyeomyia smithii, varies in a close relationship with latitude. The critical photoperiod mediating the maintenance and termination of diapause
is positively correlated with latitude (r
2 = 0.977) among six populations from southern (30–31° N), intermediate (40° N), and northern (46–49° N) latitudes in North
America. The developmental response to unnaturally short and to unnaturally long photoperiods declines with increasing latitude,
so that longer critical photoperiods are associated with a downward rather than a lateral shift in the photoperiodic response
curve. Exotic light and dark cycles of varying period (T) with a short (10 h) photophase and a scotophase ranging from 14
(T = 24) to 62 (T = 72) h, reveal two geographic patterns: a decline in perturbability of the photoperiodic clock with increasing
latitude, and no change with latitude in the 21-h period of rising and falling development with increasing T. These results
show (1) that there is a rhythmic component to photoperiodic time measurement in W. smithii, (2) that the period of this rhythm is about 21 h in all populations, and (3) that more northern populations show decreasing
responsiveness to photoperiod and increasing stability against perturbation by exotic period lengths (T > 24). Previous studies
on W.␣smithii indicate that this single temperate species of a tropical and subtropical genus has evolved from south to north. We therefore
conclude that the evolution of increasing critical photoperiod in W. smithii during its adaptive radiation into North America has more likely involved the amplitude and not the period of the underlying
circadian pacemaker.
Received: 22 July 1996 / Accepted: 30 September 1996 相似文献
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M. Gabig M. Obuchowski S. Srutkowska G. Wegrzyn 《Molecular & general genetics : MGG》1998,258(5):494-502
It was previously demonstrated that while lysogenic development of bacteriophage λ in Escherichia coli proceeds normally at low temperature (20–25° C), lytic development is blocked under these conditions owing to the increased
stability of the phage CII protein. This effect was proposed to be responsible for the increased stimulation of the p
E promoter, which interferes with expression of the replication genes, leading to inhibition of phage DNA synthesis. Here we
demonstrate that the burst size of phage λcIb2, which is incapable of lysogenic development, increases gradually over the temperature range from 20 to 37° C, while no phage
progeny are observed at 20° C. Contrary to previous reports, it is possible to demonstrate that p
E promoter activation by CII may be more efficient at lower temperature. Using density-shift experiments, we found that phage
DNA replication is completely blocked at 20° C. Phage growth was also inhibited in cells overexpressing cII, which confirms that CII is responsible for inhibition of phage DNA replication. Unexpectedly, we found that replication
of plasmids derived from bacteriophage λ is neither inhibited at 20° C nor in cells overexpressing cII. We propose a model to explanation the differences in replication observed between λ phage and λ plasmid DNA at low temperature.
Received: 30 December 1997 / Accepted: 25 February 1998 相似文献
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T. Ruf A. I. Korytko A. Stieglitz K. R. Lavenburg J. L. Blank 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(3):185-192
We investigated pineal function as well as reproductive and energetic characteristics in male deer mice (Peromyscus maniculatus) that differentially respond to short photoperiod with full, partial or no gonadal regression. In mice at both high (23 °C)
and low temperature (1 °C), these phenotypic differences in reproductive responses to short days were not reflected by differences
in urinary excretion of 6-sulphatoxy-melatonin, the main metabolite of pineal melatonin. Neither duration nor amplitude or
phase-angle of nocturnal peaks in 6-sulphatoxymelatonin significantly differed between reproductive phenotypes at either temperature.
Differences in testis size were, however, associated with different energy requirements. In gonadally regressed males only,
food intake and body weight were significantly (P < 0.01) reduced by up to 29% and 13% respectively. Chronic cold exposure (5 °C) had no effect on the proportion of males
undergoing testicular regression under short days, but caused a general elevation in body weights among all mice (P < 0.05). Phenotypic differences in body weight and food intake were maintained in the cold. Together, these results suggest
that within-population variation of reproductive responses in male deer mice is based on post-pineal differences in the regulation of gonadal function, and that phenotypic characteristics in reproductive and energetic
responses to short days are largely unaffected by ambient temperature.
Accepted: 2 October 1995 相似文献
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S. J. Brown R. B. Child S. H. Day A. E. Donnelly 《European journal of applied physiology and occupational physiology》1997,75(4):369-374
Indirect indices of exercise-induced human skeletal muscle damage and connective tissue breakdown were studied following
a single bout of voluntary eccentric muscle contractions. Subjects (six female, two male), mean (SD) age 22 (2) years performed
a bout of 50 maximum voluntary eccentric contractions of the knee extensors of a single leg. The eccentric exercise protocol
induced muscle soreness (P < 0.05 Wilcoxon test), chronic force loss, and a decline in the 20:100 Hz percutaneous electrical myostimulation force ratio
[P < 0.01, repeated measures analysis of variance (ANOVA)]. Serum creatine kinase (CK) and lactate dehydrogenase (LDH) activities
were elevated (P < 0.01, repeated measures ANOVA) following the bout. The mean (SD) CK and LDH levels recorded 3 days post-exercise were 2815
(4144) IU · l–1 and 375 (198) IU · l–1, respectively. Serum alkaline phosphatase activity showed no changes throughout the study, and a non-significant increase
(P = 0.058, repeated measures ANOVA) in pyridinoline was recorded following the bout. Urinary hydroxyproline (HP) and hydroxylysine
(HL) excretion, expressed in terms of creatinine (Cr) concentration, increased after exercise (P < 0.05 and P < 0.01, respectively, repeated measures ANOVA). An increased HP:Cr was recorded 2 days post-exercise and HL:Cr was increased
above baseline on days 2, 5, and 9 post-exercise. This indirect evidence of exercise-induced muscle damage suggests that myofibre
disruption was caused by the eccentric muscle contractions. Elevated urine concentrations of indirect indices of collagen
breakdown following eccentric muscle contractions suggests an increased breakdown of connective tissue, possibly due to a
localised inflammatory response.
Accepted: 9 October 1996 相似文献
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The expression of the Arabidopsis heat shock protein (HSP) 18.2 promoter-β-d-glucuronidase (GUS) chimera gene was investigated in transgenic Nicotiana plumbaginifolia plants during the recovery phase at normal temperatures (20–22 °C) after a heat shock (HS) treatment. GUS activity increased
during the recovery phase after HS at 42 °C for 2 h, and maximal GUS activity was observed after 12 h at normal temperatures,
at levels 50–100 times higher than the activity immediately after HS. After HS at 44 °C, little GUS activity was observed
during the first 20–24 h at normal temperatures, but the activity increased gradually thereafter, to reach a maximum at 40–50 h.
After HS at 45 °C, no GUS activity was observed throughout the experimental period. RT-PCR analysis showed that GUS mRNA
remained for 10 h after a 2-h HS at 42 °C and for 40 h after a 2-h HS at 44 °C. These findings demonstrate that brief HS
treatment, especially at a sublethal temperature, induces a long-term accumulation of HSP-GUS mRNA during the recovery phase.
Received: 31 July 1998 / Revision received: 4 November 1998 / Accepted: 19 February 1999 相似文献
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Light response characteristics of a morphologically diverse group of southern hemisphere conifers as measured by chlorophyll fluorescence 总被引:5,自引:0,他引:5
Unlike northern hemisphere conifer families, the southern family, Podocarpaceae, produces a great variety of foliage forms
ranging from functionally broad-, to needle-leaved. The production of broad photosynthetic surfaces in podocarps has been
linked qualitatively to low-light-environments, and we undertook to assess the validity of this assumption by measuring the
light response of a morphologically diverse group of podocarps. The light response, as apparent photochemical electron transport
rate (ETR), was measured by modulated fluorescence in ten species of this family and six associated species (including five
Cupressaceae and one functionally needle-leaved angiosperm) all grown under identical glasshouse conditions. In all species,
ETR was found to increase as light intensity increased, reaching a peak value (ETRmax) at saturating quantum flux (PPFDsat), and decreasing thereafter. ETRmax ranged from 217 μmol electrons · m−2 · s−1 at a PPFDsat of 1725 μmol photons · m−2 · s−1 in Actinostrobus acuminatus to an ETR of 60 μmol electrons · m−2 · s−1 at a PPFDsat of 745 μmol electrons · m−2 · s−1 in Podocarpus dispermis. Good correlations were observed between ETRmax and both PPFDsat and maximum assimilation rate measured by gas-exchange analysis. The effective quantum yield at light saturation remained
constant in all species with an average value of 0.278 ± 0.0035 determined for all 16 species. Differences in the shapes of
light response curves were related to differences in the response of non-photochemical quenching (q
n), with q
n saturating faster in species with low PPFDsat. Amongst the species of Podocarpaceae, the log of average shoot width was well correlated with PPFDsat, wider leaves saturating at lower light intensities. This suggests that broadly flattened shoots in the Podocarpaceae are
an adaptation to low light intensity.
Received: 15 April 1996 / Accepted: 30 September 1996 相似文献