Summary An extracorporeal circulation of rainbow trout (Oncorhynchus mykiss) was utilized to continuously monitor the rapid and progressive effects of endogenous or exogenous catecholamines on blood respiratory/acid-base status, and to provide in vivo evidence for adrenergic retention of carbon dioxide (CO2) in fish blood (cf. Wood and Perry 1985). Exposure of fish to severe aquatic hypoxia (final PwO2=40–60 torr; reached within 10–20 min) elicited an initial respiratory alkalosis resulting from hypoxia-induced hyperventilation. However, at a critical arterial oxygen tension (PaO2) between 15 and 25 torr, fish became agitated for approximately 5 s and a marked (0.2–0.4 pH unit) but transient arterial blood acidosis ensued. This response is characteristic of abrupt catecholamine mobilization into the circulation and subsequent adrenergic activation of red blood cell (RBC) Na+/H+ exchange (Fievet et al. 1987). Within approximately 1–2 min after the activation of RBC Na+/H+ exchange by endogenous catecholamines, there was a significant rise in arterial PCO2 (PaCO2) whereas arterial PO2 was unaltered; the elevation of PaCO2 could not be explained by changes in gill ventilation. Pre-treatment of fish with the -adrenoceptor antagonist phentolamine did not prevent the apparent catecholamine-mediated increase of PaCO2. Conversely, pre-treatment with the -adrenoceptor antagonist sotalol abolished both the activation of the RBC Na+/H+ antiporter and the associated rise in PaCO2, suggesting a causal relationship between the stimulation of RBC Na+/H+ exchange and the elevation of PaCO2. To more clearly establish that elevation of plasma catecholamine levels during severe hypoxia was indeed responsible for causing the elevation of PaCO2, fish were exposed to moderate hypoxia (final PwO2=60–80 torr) and then injected intraarterially with a bolus of adrenaline to elicit an estimated circulating level of 400 nmol·l-1 immediately after the injection. This protocol activated RBC Na+/H+ exchange as indicated by abrupt changes in arterial pH (pHa). In all fish examined, PaCO2 increased after injection of exogenous adrenaline. The effects on PaO2 were inconsistent, although a reduction in this variable was the most frequent response. Gill ventilation frequency and amplitude were unaffected by exogenous adrenaline. Therefore, it is unlikely that ventilatory changes contributed to the consistently observed rise in PaCO2. Pretreatment of fish with sotalol did not alter the ventilatory response to adrenaline injection but did prevent the stimulation of RBC Na+/H+ exchange and the accompanying increases and decreases in PaCO2 and PaO2, respectively. These results suggest that adrenergic elevation of PaCO2, in addition to the frequently observed reduction of PaO2 are linked to activation of RBC Na+/H+ exchange. The physiological significance and the potential mechanisms underlying the changes in blood respiratory status after addition of endogenous or exogenous catecholamines to the circulation of hypoxic rainbow trout are discussed.Abbreviations
PaCO2
arterial carbon dioxide tension
-
PaO2
arterial oxygen tension
-
Pda
dorsal aortic pressure
-
pHa
arterial pH
-
PwO2
water oxygen tension
-
RBC
red blood cell
-
Vf
breathing frequency 相似文献
A detailed study of the canine A blood group system was undertaken, resulting in the expansion of this system into a three-factor, four-allelic one with the recognition of an additional subtype, a3. The serological and extensive family data supported the proposed genetic theory of four alleles with dominance with the order being Aa1, Aa2, Aa3 and A-. Gene frequencies of the alleles were determined in various breeds of dogs with frequencies in the general Brisbane population being 0.244 (Aa1), 0.042 (Aa2), 0.045 (Aa3) and 0.669 (A-). 相似文献
Summary Human S-protein is a serum glycoprotein that binds and inhibits the activated complement complex, mediates coagulation through interaction with antithrombin III and plasminogen activator inhibitor I, and also functions as a cell adhesion protein through interactions with extracellular matrix and cell plasma membranes. A full length cDNA clone for human S-protein was isolated from a lambda gt11 cDNA library of mRNA from the HepG2 hepatocellular carcinoma cell line using mixed oligonucleotide sequences predicted from the amino-terminal amino acid sequence of human S-protein. The cDNA clone in lambda was subcloned into pUC18 for Southern and Northern blot experiments. Hybridization with radiolabeled human S-protein cDNA revealed a single copy gene encoding S-protein in human and mouse genomic DNA. In addition, the S-protein gene was detected in monkey, rat, dog, cow and rabbit genomic DNA. A 1.7 Kb mRNA for S-protein was detected in RNA from human liver and from the PLC/PRF5 human hepatoma cell line. No S-protein mRNA was detected in mRNA from human lung, placenta, or leukocytes or in total RNA from cultured human embryonal rhabdomyosarcoma (RD cell line) or cultured human fibroblasts from embryonic lung (IMR90 cell line) and neonatal foreskin. A 1.6 Kb mRNA for S-protein was detected in mRNA from mouse liver and brain. No S-protein mRNA was detected in mRNA from mouse skeletal muscle, kidney, heart or testis. 相似文献
1. 1.|Hypothalamic and rectal temperatures were recorded in 8 warm-reared (wr) and 12 control rats. Rats ran to exhaustion at a constant speed of 1.5 km h−1 but at a variable ambient temperature adjusted to stabilize their hypothalamic temperature at 38.0°C (normothermia) or 41.0°C (hyperthermia). Blood lactate concentrations were determined before and after exercise.
2. 2.|Exercise caused exhaustion in normothermic control rats after 62.08 ± 5.43 min and in wr rats after 29.64 ± 2.09 min.
3. 3.|Hyperthermia shortened to one half (to 12.24 ± 1.36 min) and to one fourth (to 16.15 ± 1.20 min) the endurance time in wr and control rats, respectively.
4. 4.|There were no correlations between lactate concentraion and hyperthermia or endurance time.
5. 5.|In conclusion, in rats and other animals which have safe refuges, hyperthermia interferes with the ability to continue exercising.
Pharmacological and biochemical characteristics of the partially purified -aminobutyric acid (GABA)B receptor using baclofen affinity column chromatography have been examined. The Scatchard analysis of [3H]GABA binding to the purified GABAB receptor showed a linear relationship and the KD and Bmax values were 60 nM and 118 pmol/mg of protein, respectively. Although GTP and Mg2+ did not affect on the GABAB receptor binding, Ca2+ significantly increased [3H]GABA binding to the purified GABAB receptor in a dose-dependent manner and showed its maximum effect at 2 mM. The enhancement of the binding by Ca2+ was found to be due to the increase of Bmax by the Scatchard analysis. The treatments with pronase and trypsin significantly decreased the binding of [3H]GABA, but phospholipase A2 had no significant effect on the binding. In addition, treatment with glycosidases such as glycopeptidase A and -galactosidase significantly decreased the binding of [3H]GABA to the purified GABAB receptor. These results suggest that purification of the solubilized GABAB receptor by the affinity column chromatography may result in the functional uncoupling of GABAB receptor with GTP-binding protein. Furthermore, the present results suggest that cerebral GABAB receptor may be a glycoprotein and membrane phospholipids susceptible to phospholipase A2 treatment may not be involved in the exhibition of the binding activity.Special issue dedicated to Dr. Eugene Roberts. 相似文献
7S-Nerve growth factor (NGF) and its alpha, beta-NGF, and gamma subunits have been purified from murine submaxillary glands and saliva by a combination of gel filtration on rigid polyvinyl gels, reversed-phase liquid chromatography on short alkyl chain supports (C4 columns), and ion-exchange chromatography on silica-based carboxymethyl columns. This technique is superior to previously used methods in that it is much more rapid and allows the purification of larger quantities of polypeptide from the same amount of starting material. Beta-NGF prepared with this method elicits the outgrowth of fibers of cells of a pheochromocytoma cell line (PC 12) in vitro, indicating that the biological activity is not impaired by the organic solvents and strong acids utilized for its isolation. 相似文献
The cytoplasmic resistivities and membrane breakdown potentials of normal (AA), sickle-cell-trait (AS), and sickle (SS) red
blood cells have been measured by the biophysical methodology of resistive pulse spectroscopy over a range of osmolalities.
At isotonicity, the average membrane breakdown potentials are virtually identical for the three types of cells occurring at
about 1150 V/cm. Average isotonic cytoplasmic resistivities are somewhat higher for the SS cells (166.7±7.49 ohm-cm) compared
to the AA (147.6±1.98 ohm-cm) or AS cells (148.7±1.79 ohm-cm). As medium osmolality is varied, the differences in resistive
properties become enlarged, especially at very low and very high osmolalities. At high osmolalities, both types of sickle
cells show a large increase in internal resistivity compared to the normals; at low osmolality, the SS samples exhibit a distinctly
different membrane breakdown characteristic, decreasing in this parameter, whereas the other two groups increase.
Of the 15 SS samples tested, three displayed much higher cytoplasmic resistivities at isotonicity: 218.2±5.25 ohm-cm, compared
to an average of 153.5±3.46 ohm-cm for the other 12. The relationship between these high resistivities and the subfraction
of irreversibly sickled cells in the sample is discussed. 相似文献
The binomial sampling to estimate population density of an organism based simply upon the frequency of its occurrence among sampled quadrats is a labour-saving technique which is potentially useful for small animals like insects and has actually been applied occasionally to studies of their populations. The present study provides a theoretical basis for this convenient technique, which makes it statistically reliable and tolerable for consistent use in intensive as well as preliminary population censuses. Firs, the magnitude of sampling error in relation to sample size is formulated mathematically for the estimate to be obtained by this indirect method of census, using either of the two popular models relating frequency of occurrence (p) to mean density (m), i.e. the negative binomial model, p=1−(1+m/k)−k, and the empirical model, p=1−exp(−amb). Then, the equations to calculate sample size and census cost that are necessary to attain a given desired level of precision in the estimation are derived for both models. A notable feature of the relationship of necessary sample size (or census cost) to mean density in the frequency method, in constrast to that in the ordinary census, is that it shows a concave curve which tends to rise sharply not only towards lower but also towards higher levels of density. These theoretical results make it also possible to design sequential estimation procedures based on this convenient census technique, which may enable us with the least necessary cost to get a series of population estimates with the desired precision level. Examples are presented to explain how to apply these programs to acutal censuses in the field. 相似文献