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1.
Mogens L. Glass Atsushi Ishimatsu Kjell Johansen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1986,156(3):425-430
Summary The snake-head fish (Channa argus) is an obligate air-breather inhabiting fresh waters in the temperate zone of East Asia.Ventilation of the air-breathing organ and aerial gas exchange were measured in 1 to 2 kg specimens at 15 and 25°C. Additionally, the ventilatory responses to hypoxia and hypercapnia were studied. Aerial ventilation increased from 1.1 to 2.9 mlbtps·kg–1·min–1 when temperature rose from 15 to 25°C. Concomitantly, O2-uptake through airbreathing increased from 0.1 mlstpd·kg–1·min–1 (15°C) to 0.28 mlstpd·kg–1·min–1 (25°C), whereas aerial gas exchange was less important for CO2-climination as evident from low gas exchange ratios (0.16 at 15°C, 0.29 at 25°C).Ventilation increases only slightly in response to inspiration of hypercapnic gas mixtures or to hypoxic conditions in water. By contrast, inspiration of hypoxic gas mixtures caused marked increases of ventilation in particular at the higher temperature.Aerial ventilation inChanna is low compared to values for ectothermic pulmonary breathers. However, its ventilatory responses to hypoxia strikingly resemble those of reptiles: The most marked ventilatory response to hypoxia occurs at the higher temperature where the demands for O2 are greatest. 相似文献
2.
Cardiac output and stroke volume were estimated for a 200 g largemouth blackbass (Micropterus salmoides) by a modified whole-body thermodilution method using the relation between thermal equilibration rates and heartbeat frequencies. The reciprocal of the thermal time constant, k (min–1), was related to the heartbeat frequency, F (beats min–1), by the equation k=0.00146 F + 0.309; the slope is the weight-specific stroke volume (ml g–1) and the intercept is the weight-specific heat transfer constant (cal °C–1 min–1 g–1). Stroke volume was 0.292 ml (0.00146 ml/g body weight), yielding cardiac output values ranging from 44 ml kg–1 min–1 (at 30 beats min) to 158 ml kg–1 min–1 (at 108 beats min–1), or 4.4 to 15.8% of body weight. Active (convective) heat transfer due to blood flow constituted an estimated 11 to 34% (mean 22.5%) of total heat transfer, depending on heartbeat frequency; this variability constitutes physiological thermoregulation. 相似文献
3.
A. Quirion L. Laurencelle L. Paulin A. Therminarias G. R. Brisson A. Audet S. Dulac P. Vogelaere 《International journal of biometeorology》1989,33(4):227-232
This study was designed to clarify the effects of cold air exposure on metabolic and hormonal responses during progressive incremental exercise. Eight healthy males volunteered for the study. Informed consent was obtained from every participant. The following protocol was administered to each subject on three occasions in a climatic chamber in which the temperature was 20°, 0° or –20°C with relative humidity at 60%±1%. Exercise tests were conducted on an electrically braked ergocycle, and consisted of a propressive incremental maximal exercise. Respiratory parameters were continuously monitored by an automated open-circuit sampling system Exercise blood lactate (LA), free fatty acids (FFA), glucose levels, bicarbonate concentration (HCO
3
–
), acidbase balance, plasma epinephrine (E) and norepinephrine (NE) were determined from venous blood samples obtained through an indwelling brachial catheter. Maximal oxygen uptake was significantly different between conditions: 72.0±5.4 ml kg–1 min–1 at 20°C; 68.9±5.1 ml kg–1 min–1 at 0°C and 68.5±4.6 ml kg–1 min–1 at –20°C. Workload, time to exhaustion, glucose levels and rectal Catecholamines and lactate values were not significantly altered by thermal conditions after maximal exercise but the catecholamines were decreased during rest. Bicarbonate, respiratory quotient, lactate and ventilatory thresholds increased significantly at –20°C. The data support the contention that metabolic and hormonal responses following progressive incremental exercise are altered by cold exposure and they indicate a marked decrease in maximal oxygen uptake, time to exhaustion and workload.This study was supported by grants from CSR, Univesité du Québec; FIR, Université du Québec à Trois-Rivières and NATO no, 86.0435. 相似文献
4.
M. L. Glass K. Johansen A. S. Abe 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1981,142(4):509-514
Summary Pulmonary CO-diffusing capacity (D
l
CO), lung volume, pulmonary perfusion and O2-uptake were measured by non-invasive techniques in the lizardsVaranus exanthematicus andTupinambis teguixin (mean body weight 2.2 kg for both species).The CO-diffusing capacity was at 25–27°C 0.059 mlstpd·kg–1·min–1·Torr–1 inVaranus, which is 47% greater than the value of 0.040 mlstpd·kg–1·min–1·Torr–1 inTupinambis. The lung volume ofVaranus was 36 ml·kg–1 and that ofTupinambis 20 ml·kg–1. At 35–37°C the diffusing capacity of lizard lungs are about 25% of those for mammals of comparable size.InVaranus pulmonary CO-diffusing capacity increased with temperature from 0.027 mlstpd·kg–1·min–1·Torr–1 at 17–19 °C to 0.075 mlstpd·kg–1·min–1·Torr–1 at 35–37 °C. This change closely matched a concomitant increase of O2-uptake. Pulmonary perfusion increased from 27 ml·kg–1·min–1 to 55 ml·kg–1·min–1 within this temperature range.The study emphasizes that pulmonary diffusing capacity cannot be fully evaluated without information on pulmonary perfusion and O2-uptake. In reptiles and other ectotherms diffusing capacity must be reported at specified body temperature. 相似文献
5.
John H. Gee 《Environmental Biology of Fishes》1986,16(4):269-278
Synopsis Four species of Australian Eleotridae from hypoxic habitats were examined in the laboratory to study buoyancy control in hypoxic water (<10 torr) when performing aquatic surface respiration (ASR; irrigating gills with upper millimeter of surface water). A conflict can arise here because O2 can be reabsorbed from the swimbladder (reducing buoyancy) at a time when additional lift may be required to perform ASR. Three species were negatively buoyant and initially performed ASR while resting on the bottom in shallow water. After 24 h swimbladder lift increased to nearly neutral and ASR was performed while fish were pelagic. The fourth species remained pelagic at near neutral buoyancy in hypoxic water. With sudden exposure to hypoxia these physoclists reabsorbed between 5–27% (depending on species) of swimbladder volume (standard pressure) during the initial 30–90 min exposure to hypoxia. Additional experiments on one species (Hypseleotris galii) showed such loss to occur at O2 tensions below 68 torr and when O2 declined rapidly (2.17 torr min-1). Secretion of gas compensated for losses under slower, natural rates of nocturnal O2 decline. Eleotrids appear to reduce the conflict between respiration and buoyancy control in hypoxia by restricting gas reabsorbtion from the swimbladder and by rapidly secreting gases into the swimbladder. 相似文献
6.
Seymour RS Farrell AP Christian K Clark TD Bennett MB Wells RM Baldwin J 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(5):579-587
The Pacific tarpon is an elopomorph teleost fish with an air-breathing organ (ABO) derived from a physostomous gas bladder.
Oxygen partial pressure (PO2) in the ABO was measured on juveniles (238 g) with fiber-optic sensors during exposure to selected aquatic PO2 and swimming speeds. At slow speed (0.65 BL s−1), progressive aquatic hypoxia triggered the first breath at a mean PO2 of 8.3 kPa. Below this, opercular movements declined sharply and visibly ceased in most fish below 6 kPa. At aquatic PO2 of 6.1 kPa and swimming slowly, mean air-breathing frequency was 0.73 min−1, ABO PO2 was 10.9 kPa, breath volume was 23.8 ml kg−1, rate of oxygen uptake from the ABO was 1.19 ml kg−1 min−1, and oxygen uptake per breath was 2.32 ml kg−1. At the fastest experimental speed (2.4 BL s−1) at 6.1 kPa, ABO oxygen uptake increased to about 1.90 ml kg−1 min−1, through a variable combination of breathing frequency and oxygen uptake per breath. In normoxic water, tarpon rarely breathed
air and apparently closed down ABO perfusion, indicated by a drop in ABO oxygen uptake rate to about 1% of that in hypoxic
water. This occurred at a wide range of ABO PO2 (1.7–26.4 kPa), suggesting that oxygen level in the ABO was not regulated by intrinsic receptors. 相似文献
7.
Oxygen consumption (VO2) of juvenile Arctic cod (Boreogadus saida) was investigated at low tempera tures (six temperatures; range -0.5 to 2.7°C). Small (mean wt. 6–8 g) and large (mean wt. 14 g) fish were acclimated, or adjusted to a constant temperature (0.4°C), for 5 months and then tested for metabolic cold adaptation (elevated metabolic rates in polar fishes). Short-term (2 weeks) acclimated fish showed elevated VO2 similar to previously established values for polar fishes, but there was no such evidence after longterm acclimation. Long-term acclimation caused VO2 values to drop significantly (from 86.0 to 46.5 mg O2·kg–1·h–1, at 0.4°C), which showed that metabolic cold adaptation was a phenomenon caused by insufficien: acclimation time for fish in respiration experiments. We also measured the effects of temperature and feeding on VO2. A temperature increase of 2.3°C resulted in relatively large increases in VO2 for both longand short-term acclimated fish (Q10 = 6.7 and 7.1, respectively), which suggests that metabolic processes are strongly influenced by temperature when it is close to zero. Feeding individuals to satiation caused significant increases in VO2 above pre-fed values (34–60% within 1–2 days after feeding). Respiration budgets of starved and fed Arctic cod at ambient temperatures in Resolute Bay N.W.T., Canada, were used to model annual respiration costs and potential weight loss. Low respiration costs for Arctic cod at ambient temperatures result in high growth efficiency during periods of feeding and low weight loss during periods of starvation. 相似文献
8.
D. A. Gray T. Erasmus 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1989,158(6):651-660
Summary The osmoregulatory effects of intravenously (i.v.) administered angiotensin II (AII) at dose rates of 5, 15 and 45 ng · kg–1 · min–1 were examined in kelp gulls utilizing salt glands and/or kidneys as excretory organs.In birds given i.v. infusion of 1200 mOsmolal NaCl at 0.3 ml · min–1 and utilizing only the salt glands to excrete the load, infusion of AII for 30 min consistently inhibited salt gland function in a dose-dependent manner.In birds given i.v. infusion of 500 mOsmolal NaCl at 0.72 ml · min–1 and utilizing both salt glands and kidneys to excrete the load, each dose of AII given for 2 h inhibited salt gland function but stimulated the kidney, so that the overall outputs of salt and water were enhanced and showed significant (2P<0.01) positive correlations with plasma AII.In birds given i.v. infusion of 200 mOsmolal glucose at 0.5 ml · min–1 and utilizing only the kidneys to excrete the load, low doses of AII (5 and 15 ng · kg–1 · min–1) caused renal salt and water retention, whereas a high dose (45 ng · kg–1 · min–1) stimulated salt and water output.The actions of plasma AII in kelp gulls support the concept that this hormone plays a vital role in avian osmoregulation, having effects on both salt gland and kidney function. Elevation of plasma AII consistently inhibits actively secreting salt glands, but its effects upon renal excretion depend primarily on the osmotic status as well as on the plasma AII concentration. In conditions of salt and volume loading doses of AII stimulate sodium and water excretion. With salt and volume depletion, the action of AII is bi-phasic with low doses promoting renal sodium and water retention but high circulating levels causing natriuresis and diuresis. 相似文献
9.
Production of fructose via a continuous glucose isomerization process was optimized using response surface methodology. Glucose isomerization was performed using immobilized glucose isomerase in a flow-through tubular reactor. Process factors eg pH (7.0–7.8), temperature (50–60°C), flow rate (5–17 ml min–1) and glucose content (30–50% w/w) of the feedstock solution were simultaneously tested according to a central composite experimental design. Measured responses such as % isomerization, and fructose yield (gh–1) has an excellent correlation with tested factors. The highest desirability,D, (geometric mean of % isomerization and fructose yield) was obtained when the feedstock (56–60°C) had 34–36% glucose, a pH of 7.4–7.8 and was pumped at 15 ml min–1. 相似文献
10.
Exercise metabolism in two species of cod in arctic waters 总被引:2,自引:2,他引:0
The northern range of Atlantic cod (Gadus morhua), overlaps the southern range of the Greenland cod (Gadus ogac), in the coastal waters of Western Greenland. The availability of a temperate water species (G. morhua) in the same area and oceanographic conditions as a polar species (G. ogac) presented us with the ideal circumstances to test the hypothesis of metabolic cold adaptation (MCA) since many of the problems associated with MCA studies (adaptation of the animals beyond their normal temperature range or mathematical extrapolation of data to common temperatures) could thus be avoided. We therefore used a swim tunnel to measure oxygen consumption in fish at 4°C over a range of swimming speeds and following exhaustion, monitored the size of the oxygen debt and time of oxygen debt repayment. There were no significant differences in standard (60–72 mg O2 kg–1· hr–1), routine (76 mg O2 kg–1·hr–1), active (137mg O2 kg–1·hr–1), or maximal (157 mg O2 kg–1·hr–1) metabolic rate, metabolic scope (2.5) or critical swimming speed (2.2 BL·s–1) between the two species. Following exhaustive swimming, however, the half-time for oxygen debt repayment in G. ogac (43 min) was almost twice that of G. morhua (25 min). Despite its circumpolar distribution, therefore, there was no evidence of MCA in G. ogac. 相似文献
11.
Synopsis The toxicity of zinc to rainbow trout was determined and the 72 h median lethal concentration was found to be 2.00 mg l–1 in freshwater, hardness 7.50 mg l–1 as calcium. An insignificant increase in zinc concentration of internal tissues occurred in fish exposed to 1.52 mg l–1 in freshwater for 72 h. However, there was a significant uptake of zinc by gills and the body surface. Fish exposed to 10 mg l–1 zinc for 72 h in two-thirds sea water showed significant zinc uptake by liver, rectum and muscle, when compared to control fish. Drinking rate decreased from 1.43 to 0.26 ml kg–1 h–1 when zinc sulphate was added to freshwater. Trout adapted to two-thirds sea water showed no decrease in drinking, about 7 ml kg–1 h–1 when zinc was added to the water. 相似文献
12.
Ronald K. Gratz 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1978,127(4):299-305
Summary Simultaneous measurements of pulmonary and cutaneous oxygen and carbon dioxide exchange, pulmonary ventilation and heart rate were made on the diamondback water snake,Natrix rhombifera at 28°C using body plethysmography. Resting lung volume, maximum lung volume and tracheal volume were also measured.The following mean values were measured in undisturbed snakes breathing room air: total (pulmonary and cutaneous) O2 uptake 46 mol · (kg min)–1; total CO2 output, 49 mol · (kg min)–1; tidal volume, 12 ml (BTPS) · kg–1; ventilatory rate, 6.9 min–1; heart rate, 42 min–1. From the measurements of tracheal volume, the effective (alveolar) ventilation was estimated as approximately 70% of total ventilation resulting in effective pulmonary
and
of 130 Torr and 20 Torr respectively. Cutaneous exchange accounted for 8.1% of the total
and 12.4% of the total
.Resting lung volume of anaesthetized snakes was 75 ml (BTPS) · kg–1, maximum lung volume was 341 ml (BTPS) · kg–1 and tracheal volume was 3.9 ml (BTPS) · kg–1. 相似文献
13.
A. T. Marshall P. D. Cooper 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,157(6):821-827
Summary The lachrymal salt glands ofChelonia mydas were functional when hatchlings emerged from the nest. Osmotic concentrations up to 720 mosmol kg–1 were recorded in spontaneously produced tears (salt gland secretions). When injected with a Na+ load (1500–2700 mol (100 g)–1) newly emerged hatchlings produced tears ranging in osmotic concentration from 1000–1900 mosmol kg–1 with Na+ secretion rates from single glands of 200–475 mol (100 g·h)–1. In these circumstances the rate of sodium excretion, via the salt glands, was equivalent to the sodium content of 0.2 to 0.5 ml of sea water per hour. Since the apparent drinking rate of hatchlings within the first two days of entering sea water was approximately 0.5 to 1.7 ml per day, the excretion of Na+ imbibed by drinking is well within the secretory capacity of the lachrymal salt glands.In feeding hatchlings extraordinarily high Na+ secretion rates were induced by Na+ loading. Hatchlings which were loaded with Na+ by injection (1500–5400 mol (100 g)–1) produced tears having osmotic concentrations between 1500 and >2000 mosmol kg–1. The Na+ secretion rates from single glands were 750–4185 mol (100 g·h)–1 with extremely high short term rates of 10700 mol (100 g·h)–1 (50 mol min–1 for 28 g hatchlings).In terms of gland mass the highest long term secretion rate translates into 21 mmol of Na+ per gram of salt gland per hour and is the highest secretion rate yet recorded for a reptilian salt gland. This rate is almost three times the highest rate recorded for sea snakes (8 mmol g·h–1) and is similar to rates commonly observed in avian salt glands (25 mmol g·h–1).Secretion by the lachrymal salt glands was initiated by increased blood concentrations of Na+ or K+, K+ being as effective as Na+ but with the composition of the teras being virtually unchanged compared to tears from Na+ stimulated hatchlings. Preliminary experiments indicated that secretion was not initiated by increased Cl– concentration in the blood or by increased volume or osmotic concentration of the blood.Abbreviation
O.P.
osmotic pressure 相似文献
14.
Calegario FF Cosso RG Fagian MM Almeida FV Jardim WF Jezek P Arruda P Vercesi AE 《Journal of bioenergetics and biomembranes》2003,35(3):211-220
The CO2 evolution of intact potato tubers (Solanum tuberosum, L., var. Bintje) was analyzed during a 10-day period of their warm (25 ± 2°C) or cold (5 ± 1°C) storage, to evaluate cold-stress effects on expression and activities of plant uncoupling mitochondrial protein (PUMP) and alternative oxidase (AOX). CO2 evolution rates were analyzed at 20°C, to reflect their possible capacities. The 20°C CO2 production declined from 13 to 8 mg kg–1 h–1 after 2 days of warm storage and then (after 3 to 7 days) decreased from 8 to 6.5 mg kg–1 h–1. In contrast, 20°C CO2 evolution did not change after the first day of cold storage, increased up to 14.5 mg kg–1 h–1 after 2 days, and decreased to about 12 mg kg–1 h–1 after 3 to 7 days of cold storage. Cold storage increased PUMP expression as detected by Western blots and led to elevated capacities of both PUMP (44%) and CN-resistant AOX (10 times), but not the cytochrome pathway. Since we found that cold storage led to about the same mitochondrial respiration of 40 nmol O2 min–1 mg–1 attributable to each of the respective proteins, we conclude that both AOX and PUMP equally contribute to adaptation of potato tubers to cold. 相似文献
15.
Markus M. Bischoff James Duffin 《European journal of applied physiology and occupational physiology》1995,71(1):65-70
Detection of the ventilatory threshold during an incremental load exercise test by eye can be difficult. Although various alternative methods employing information other than the ventilation can be used to assist in determining the ventilatory threshold, they rely on underlying assumptions about the physiological basis for the ventilatory threshold. The method presented here (CUSUM) uses only the ventilation data, and therefore avoids such assumptions. Twelve subjects performed a total of 47 incremental exercise tests to exhaustion. Determinations of the ventilatory thresholds made by eye from the ventilation data (mean of three independent observers) were used as a standard for comparison with determinations using the modified V-slope method and the CUSUM method. A mean (SD) difference of 0.6 (2.84) ml·min–1·kg–1 was found between the standard ventilatory thresholds and those determined using the modified V-slope method. A similar comparison between the standard ventilatory thresholds and those determined using the CUSUM method yielded a difference of –0.11 (2.35) ml min–1·kg–1. It was concluded that the CUSUM method was a useful aid for the detection of the ventilatory threshold using the ventilation data alone. 相似文献
16.
D. L. Jones L. C. -H. Wang 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1976,105(2):219-231
Summary The metabolic and cardiac responses to temperature were studied in two species (four subspecies) of western chipmunks (genusEutamias), inhabiting boreal and alpine environments. A specially designed (Fig. 1) implantable biopential radiotransmitter was used to measure heart rate in unrestrained animals. The estimated basal metabolic rates (EBMR) were 1.78 (E. minimus borealis), 1.64 (E. m. oreocetes), 1.50 (E. m. operarius), and 1.69 ml O2 g–1 h–1 (E. amoenus luteiventris), or 839, 752, 698, and 628 ml O2 kg–0.75 h–1, respectively, for the four subspecies (Table 1). The two alpine species (E.m.or. andE.m.op.) had significantly lower EBMR than both of their boreal counterparts. The EBMR from all animals are 120–135% of the predicted values based on body weights of the animals. The thermal neutral zone for the four subspecies ranged from 23.5 to 32°C and the minimum thermal conductances were 0.113, 0.111, 0.112 and 0.112 ml O2 g–1 h–1 °C–1, respectively, or 54.4, 54.0, 50.4 and 52.1 ml O2 kg–0.75 h–1 °C–1, respectively (Fig. 2). No interspecific diffence in conductance was observed. These values are 72 to 85% of their weight specific values. The body temperature ranged between 35.0 and 39.5°C and was usually maintained between 36 and 38°C in all subspecies between ambient temperatures of 3 and 32°C. The estimated basal heart rates were 273, 296, 273 and 264 beats/min, respectively, for the four subspecies, 49–55% of their predicted weight specific values. The resultant oxygen pulses (metabolic rate/heart rate) were 5.49, 4.50, 4.48 and 5.56×10–3 ml O2/beat, respectively, which are 2 to 2.4 times their weight specific values (Table 2).The observed reduction of basal heart rate without the corresponding decreases of basal metabolic rate and body temperature indicate sufficient compensatory increases in stroke volume and/or A-V oxygen difference at rest. Such cardiovascular modifications provide extra reserves when demand for aerobic metabolism rises during bursts of activity typically observed in the western chipmunk.Abbreviations A-V
arterio-venous
- EBMR
estimated basal metabolic rate (ml O2 g–1 h–1)
- HR
heart rate (beats/min)
- MR
metabolic rate (ml O2 g–1 h–1)
- OP
oxygen pulse (ml O2/heart beat)
- Ta, Tb
ambient and body temperature (°C) 相似文献
17.
Ivar R?nnestad Einar Thorsen K?re Segadal Arvid Hope 《European journal of applied physiology and occupational physiology》1994,69(1):32-35
In diving, pulmonary mechanical function is limited by the increased density of the gas breathed. Breathing cold and dry gas may cause an additional increase in airways resistance. We have measured forced vital capacity, forced expired volume in 1 s (FEV1) and forced midexpiratory flow rate (FEF25%–75%) before and after breathing dry or humid gas at 29–32°C during a standardized exercise intensity on a cycle ergometer at an ambient pressure of 3.7 MPa. The atmosphere was a helium and oxygen mixture with a density of 6.8 kg · m–3. Six professional saturation divers aged 26–37 years participated in the study. There were no significant differences in convective respiratory heat loss between the exposures. The mean evaporative heat loss was 67 W (range 59–89) breathing dry gas and 37 W (range 32–43) breathing humid gas, corresponding to water losses of 1.7 g · min–1 (range 1.5–2.2) and 0.9 g · min–1 (range 0.8–1.1), respectively. There was a significant reduction in FEV1 of 4.6 (SD 3.6)% (P<0.05), and in FEF25%–75% of 5.8 (SD 4.7)% (P<0.05) after breathing dry gas. There were no changes after breathing humid gas. By warming and humidifying the gas breathed in deep saturation diving bronchoconstriction may be prevented. 相似文献
18.
A. M. Beal 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1989,159(5):601-608
Summary Intracarotid infusion of isoprenaline, either alone or in combination with acetylcholine infusion was used to stimulate salivation by the mandibular glands of anaesthetized red kangaroos. Isoprenaline alone (0.20–1.25 mol·kg–1·min–1) elicited flow rates ranging from 0.014 to 0.239 ml·min–1 (1.21–28.1 l·g gland–1·min–1). Salivary concentrations of sodium, chloride, phosphate and urea were negatively correlated with flow, whereas potassium, calcium, magnesium, hydrogen ion, bicarbonate, protein, and osmolality were poorly correlated with flow. Relative to cholinergic saliva produced at equivalent flow rates, isoprenaline-evoked saliva had higher osmolality, saliva/plasma urea ratios and concentrations of protein, potassium, magnesium, bicarbonate, and phosphate, but lower sodium, chloride and hydrogen ion levels. At a steady salivary flow (0.5 ml·min–1), superimposition of isoprenaline infusion (0.15 mol·kg–1·min–1) on a pre-existing acetylcholine infusion reduced the rate of acetylcholine administration necessary to maintain flow, increased osmolality and the concentrations of protein, urea, potassium, calcium, magnesium, bicarbonate and phosphate and decreased sodium, chloride and hydrogen ion in the saliva. Salivary amylase activity was low and highly variable and the amylase activity/protein ratio fell substantially during isoprenaline stimulation. These results support the conclusion that the enzyme is of extrinsic origin. The response of the kangaroo mandibular gland to isoprenaline stimulation was very similar to that reported for rat mandibular gland, suggesting that the same ion transport phenomena underlie mandibular secretion in both species and probably in therian mammals generally. 相似文献
19.
Sandra A. G. Visser Chantal J. G. M. Smulders Werner W. F. T. Gladdines Hubertus Irth Piet H. van der Graaf Meindert Danhof 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2000,745(2):160
This report describes a rapid and sensitive analytical method for the quantification of the neuroactive steroids alphaxalone and pregnanolone in rat plasma using derivatization with dansyl hydrazine as fluorescent label. The method involves protein precipitation, alkaline derivatization and extraction of the compounds and internal standard pregnenolone with dichloromethane, followed by isocratic reversed-phase high-performance liquid chromatography on a 3-μm Microsphere C18 column with fluorescence detection at wavelengths 332 nm and 516 nm for excitation and emission, respectively. The mobile phase consists of a mixture of 25 mM acetate buffer (pH 3.7)–acetonitrile (45:55, v/v for alphaxalone and 40:60, v/v for pregnanolone) with a flow-rate of 1 ml/min. The total run time was 35 min. In the concentration range of 0.010–10 μg ml−1, the intra- and inter-assay coefficients of variation were less than 17% for both methods. In 50 μl plasma samples the corresponding limits of detection were 10 ng ml−1 (signal-to-noise ratio=3). The utility of the analytical method was established by analyzing plasma samples from rats, which had received an intravenous administration of 5 mg kg−1 alphaxalone or pregnanolone. Values for clearance, volume of distribution at steady state and terminal half life were 71.9 ml min−1 kg−1, 814 mg kg−1 and 13.5 min for alphaxalone and 69.2 ml min−1 kg−1, 1638 ml kg−1 and 27.8 min for pregnanolone, respectively. Due to its simplicity and sensitivity this method can be used on a routine basis for pharmacokinetic analysis of neuroactive steroids. 相似文献
20.
Jens Peter Lomholt Kjell Johansen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1976,107(2):141-157
1. | Gas exchange and blood gas transport has been studied in the amphibious teleost,Amphipnous cuchia. A. cuchia is a bimodal breather. Respiratory gas exchange takes place in a pair of specialized air sacs extending from the pharyngeal cavity. Aquatic and aerial gas exchange also takes place in vestigial gills, across buccopharyngeal surfaces and in the skin. All blood draining the air sacs is returned via systemic veins to the heart before systemic distribution. |
2. | Oxygen uptake in fish kept in water with access to air was 33.3±8.0 ml O2STP·kg–1·h–1. About 65% of this uptake resulted from air breathing. Upon removal from water the O2 uptake rose to 44.6±15.7 ml O2· kg–1·h–1, while confinement to water breathing reduced the O2 uptake to 16.4±2.7 ml O2·kg–1·h–1. The latter value was 50% higher than aquatic O2 uptake when air breathing was available. |
3. | Amphipnous practices periodic breathing and normal breathhold periods last 8–10 min. In the early phase of breathholding the gas exchange ratio (RE) was close to 0.7 but declined to low levels with breathholding. Mean RE for an average breathhold was 0.2. The low RE of the air sacs results from a high cutaneous CO2 elimination in water as well as in moist air. Estimated blood flows to the air sacs indicate flow of about 20 ml min–1 shortly after an air breath declining to 5 ml·min–1 late in a breath-hold period. |
4. | Due to the shunting of air sac blood to systemic venous (jugular vein) blood, the jugular vein P\textO2 P_{{\text{O}}_2 } carried the most oxygenated blood averaging 35.2 mm Hg, the dorsal aorta 23.4 mm Hg and the hepatic vein 18.6 mm Hg. |
5. | A. cuchia blood has a very high Hb concentration and O2 capacity reaching 15.5 gram % and 22 vol%, respectively. TheP 50 value was 7.9 mm Hg at pH 7.6. The Bohr factor, was –0.57, then-value 2.05 and the temperature sensitivity of the O2-Hb binding expressed by H=–13.1 Kcal·mole Hb–1. Buffering capacity was high: 34.1 mM HCO3 –·1–1. |
6. | The vascular configuration inA. cuchia suggests a low efficiency of gas transport. A high blood O2 capacity and O2 affinity and a high cardiac output reduce the efficiency loss and permit the fish to suspend with air breathing for up to 30 min with a modest reduction in arterial O2 saturation from near 90% to 60%. The high blood O2 affinity allows breathholding to occur at reduced rates of systemic blood flow due to the large O2 stores available in venous blood during normal breathing. |
7. | Ventral aortic blood pressure fell from about 60 mm Hg systolic value to 40 mm Hg in the dorsal aorta indicating considerable vascular resistance in the shunt connecting these vessels. The pressure gradient across the shunt remained unchanged with the breathhold cycle and is thus not part of the vasomotor activity controlling blood flow to the aerial gas exchanger. |
8. | The data are discussed in relation to other air breathing fishes, notably the electric eel,Electrophorus electricus, and the African lungfish,Protopterus aethiopicus. |