共查询到20条相似文献,搜索用时 15 毫秒
1.
L. J. Schep I. G. Tucker G. Young A. G. Butt 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(5):370-377
The objective of this study was to assess regional variations in the permeability of the salmon posterior intestine and to
evaluate the effect of permeability enhancers as a basis for oral delivery of biologically active peptides. Proximal and distal
portions of the posterior intestine of the chinook salmon (Oncorhynchus tshawytscha) were removed, mounted as flat sheets in Ussing chambers and superfused with trout Ringer's. Intestinal permeability was
assessed under short-circuit conditions by measurement of 14C-mannitol (mucosal to serosal) flux. Tissues were treated either with the mucolytic agent dithiothreitol (10 mmol · l−1), the permeability enhancer sodium deoxycholate (5.0 mmol · l−1) or both and compared to untreated controls. Both proximal and distal control tissues had low permeabilities, but the distal
region had a lower transepithelial electrical resistance and produced significantly less mucus. Treatment with either dithiothreitol
or sodium deoxycholate alone reduced mucus adhering to tissue in both regions but did not increase permeability or change
transepithelial electrical resistance. In the distal region, sequential treatment with both agents significantly reduced adhering
mucus, decreased transepithelial electrical resistance, and increased tissue permeability. The salmon posterior intestine
can be divided into proximal and distal regions. The distal region is more likely to have the necessary permeability and responsiveness
to enhancement for the successful delivery of peptides or polar drugs.
Accepted: 14 January 1997 相似文献
2.
Takenori Onaga Shin Kubagawa Sohtetsu Lee Hitoshi Mineo Seiyu Kato Satoru Naruse Tsuyoshi Ozaki 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(5):352-360
Temporal coordination between duodenal migrating myoelectric complexes (MMC) and pancreatic exocrine secretion, and the effects
of porcine peptide YY (PYY) on gastroduodenal motility and pancreatic exocrine secretion were examined during the interdigestive
period in conscious mature sheep. Fluid and enzyme secretions from the exocrine pancreas showed a periodic pattern corresponding
to the phases of duodenal MMC, although these secretion rates were maintained at a high level during phase II in sheep. Intravenous
continuous infusion of PYY at doses ranging from 50 to 200 pmol · kg−1 · h−1 or intravenous bolus infusion of PYY at doses ranging from 50 to 200 pmol · kg−1 showed a tendency to prolong the first cycle of the duodenal MMC and significantly shorten the second cycle. However, there
was almost no effect on ruminal contractions from the PYY administration. In the pancreatic exocrine secretion, PYY could
inhibit only bicarbonate secretion at only the highest dose of 200 pmol · kg−1. These results imply that endogenous PYY may play a physiological role in the regulation of the duodenal MMC cycles in sheep
but not in ruminal contractions. PYY seems unlikely to regulate the pancreatic exocrine secretion in normal sheep, because
a supraphysiological dose of PYY was required to inhibit the pancreatic exocrine secretion.
Accepted: 3 March 1997 相似文献
3.
D. Weihrauch W. Becker U. Postel S. Luck-Kopp D. Siebers 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(1):25-37
Isolated perfused gills of stenohaline crabs Cancer pagurus adapted to seawater, brackish water-adapted euryhaline shore crabs Carcinus maenas and freshwater-adapted extremely euryhaline Chinese crabs Eriocheir sinensis were tested for their capacity to excrete ammonia. Gills were perfused with haemolymph-like salines and bathed with salines
equal in adaptation osmolality. Applying 100 μmol · l−1 NH4Cl in the perfusion saline and concentrations of NH4Cl in the bath that were stepwise increased from 0 to 4000 μmol · l−1 allowed us to measure transbranchial fluxes of ammonia along an outwardly as well as various inwardly directed gradients.
The gills of all three crab species were capable – to different extents – of active excretion of ammonia against an inwardly
directed gradient. Of the three crab species, the gills of Cancer pagurus revealed the highest capacity for active excretion of ammonia, being able to excrete it from the haemolymph (100 μmol · l−1 NH+
4) through the gill epithelium against ambient concentrations of up to 800 μmol · l−1, i.e. against an eightfold gradient. Carcinus maenas and E. sinensis were able to actively excrete ammonia against approximately fourfold gradients. Within the three crab species, the gills
of E. sinensis exhibited the greatest capacity to resist influx at very high external concentrations of up to 4000 μmol · l−1. We consider the observed capacities for excretion of ammonia against the gradient as ecologically meaningful. These benthic
crustaceans protect themselves by burying themselves in the sediment, where, in contrast to the water column, concentrations
of ammonia have previously been reported that greatly increase haemolymph levels. Electrophysiological results indicate that
the permeabilities of the gill epithelia are a clue to understanding the species-specific differences in active excretion
of ammonia. During the invasion of brackish water and freshwater, the permeabilities of the body surfaces greatly decreased.
The gills of marine Cancer pagurus exibited the greatest permeability (ca. 250 mS cm−2), thus representing practically no influx barrier for ions including NH+
4. We therefore assume that C. pagurus had to develop the strongest mechanism of active excretion of ammonia to counteract influx. On the other hand, freshwater-adapted
E. sinensis exhibited the lowest ion permeability (ca. 4 mS cm−2) which may reduce passive NH+
4 influxes at high ambient levels.
Accepted: 14 October 1998 相似文献
4.
Kwong RW Niyogi S 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2008,178(8):963-975
This study investigated the physiological characteristics of intestinal iron absorption in a freshwater teleost, rainbow trout
(Oncorhynchus mykiss). Using an in vitro gastro-intestinal sac technique, we evaluated the spatial pattern and concentration dependent profile
of iron uptake, and also the influence of luminal chemistry (pH and chelation) on iron absorption. We demonstrated that the
iron uptake rate in the anterior intestine is significantly higher than that in the mid and posterior intestine. Interestingly,
absorption of iron in the anterior intestine occurs likely via simple diffusion, whereas a carrier-mediated pathway is apparent
in the mid and posterior intestine. The uptake of ferric and ferrous iron appeared to be linear over the entire range of iron
concentration tested (0–20 μM), however the uptake of ferrous iron was significantly higher than that of ferric iron at high
iron concentrations (>15 μM). An increase in mucosal pH from 7.4 to 8.2 significantly reduced iron absorption in both mid
and posterior intestine, implying the involvement of a Fe2+/H+ symporter. Iron chelators (nitrilotriacetic acid and desferrioxamine mesylate) had no effects on iron absorption, which suggests
that fish are able to acquire chelated iron via intestine. 相似文献
5.
M. E. Forster W. Davison M. Axelsson L. Sundin C. E. Franklin S. Gieseg 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(5):345-352
Two species of Antarctic fish were stressed by moving them from seawater at −1 °C to seawater at 10 °C and holding them for
a period of 10 min. The active cryopelagic species Pagothenia borchgrevinki maintained heart rate while in the benthic species Trematomus bernacchii there was an increase in heart rate. Blood pressure did not change in either species. Both species released catecholamines
into the circulation as a consequence of the stress. P. borchgrevinki released the greater amounts, having mean plasma concentrations of 177 ± 54 nmol · l−1 noradrenaline and 263 ± 131 nmol · l−1 adrenaline at 10 min. Plasma noradrenaline concentrations rose to 47 ± 14 nmol · l−1 and adrenaline to 73 ± 28 nmol · l−1 in T. bernacchii. Blood from P. borchgrevinki was tonometered in the presence of isoprenaline. A fall in extracellular pH suggests the presence of a Na+/H+ antiporter on the red cell membrane, the first demonstration of this in an Antarctic fish. Treatment with the β-adrenergic
antagonist drug sotalol inhibited swelling of red blood cells taken from temperature-stressed P. borchgrevinki, suggesting that the antiporter responds to endogenous catecholamines.
Accepted: 22 January 1998 相似文献
6.
S. M. E. Guirguis J. C. Yee D. F. Stiffler 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(5):328-334
The skin of intact, free-swimming Xenopus laevis transports Ca2+ inwardly in a manner that is proportional to the external [Ca2+] up to about 0.3 mmol · l−1, saturates above 0.3 mmol · l−1, and is opposed to the electrochemical gradient. Efflux is relatively constant at external concentrations between 0.016 and
0.6 mmol · l−1; net flux which is negative below 0.125 mmol · l−1 becomes positive above this external [Ca2+]. Allometric analysis suggests that both Ca2+ influx and efflux scale to the 2/3 power approximately like surface area. There were no significant differences in influx
between summer and fall animals; however, efflux was greater in the fall and this resulted in a change from positive balance
in the summer to negative balance in the fall. Isolated skins were shown to support a Ca2+ uptake rate of nearly 30 nmol · cm−2 · h−1. The phenylalkylamine verapamil in the apical bathing solution significantly inhibited this at 25 μmol · l−1. The benzothiazepine diltiazem was also effective at 50 μmol · l−1 while the dihydropyradine nifedipine was ineffective up to 100 μmol · l−1. The inorganic ion La3+ was effective at blocking Ca2+ uptake at 300 μmol · l−1; Ni2+ was also effective at 500 μmol · l−1 but Co2+ was ineffective up to 500 μmol · l−1. These results suggest that apical calcium channels in Xenopuslaevis skin have properties similar to mammalian L-channels and fish gill Ca2+ channels.
Accepted: 23 January 1997 相似文献
7.
Bucking C Wood CM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(3):349-360
A diet containing an inert marker (ballotini beads, quantified by X-radiography) was used to quantify the transport of two
essential minerals, Ca2+ and Mg2+ from the diet during the digestion and absorption of a single meal of commercial trout food (3% ration). Initially, net uptake
of Ca2+ was observed in the stomach followed by subsequent Ca2+ fluxes along the intestine which were variable, but for the most part secretory. This indicated a net secretion of Ca2+ along the intestinal tract resulting in a net assimilation of dietary Ca2+ of 28%. Similar handling of Ca2+ and Mg2+ was observed along the gastrointestinal tract (GI), although net assimilation differed substantially between the cations,
with Mg2+ assimilation being close to 60%, mostly a result of greater uptake by the stomach. The stomach displayed the highest net
uptake rates for both cations (1.5 and 1.3 mmol kg−1 fish body mass for Ca2+ and Mg2+, respectively), occurring within 2 h following ingestion of the meal. Substantial secretions of both Ca2+ and Mg2+ were observed in the anterior intestine, which were attributed to bile and other intestinal secretions, while fluxes in the
mid and posterior intestine were small and variable. The overall patterns of Ca2+ and Mg2+ handling in the GI tract were similar to those observed for Na+ and K+ (but not Cl−) in a previous study. Overall, these results emphasize the importance of dietary electrolytes in ionoregulatory homeostasis. 相似文献
8.
C. Schirlo A. Bub C. Reize A. Bührer J. Kohl E. A. Koller 《European journal of applied physiology and occupational physiology》1997,75(2):124-131
To investigate the role of fluid shifts during the short-term adjustment to acute hypobaric hypoxia (AHH), the changes in
lower limb (LV) and forearm volumes (FV) were measured using a strain-gauge plethysmograph technique in ten healthy volunteers
exposed to different altitudes (450 m, 2500 m, 3500 m, 4500 m) in a hypobaric chamber. Arterial blood pressure, heart rate,
arterial oxygen saturation (S
aO2), endtidal gases, minute ventilation and urine flow were also determined. A control experiment was performed with an analogous
protocol under normobaric normoxic conditions. The results showed mean decreases both in LV and FV of −0.52 (SD 0.39) ml · 100
ml−1 and −0.65 (SD 0.32) ml · 100 ml−1, respectively, in the hypoxia experiments [controls: LV −0.28 (SD 0.37), FV −0.41 (SD 0.47) ml · 100 ml−1]. Descent to normoxia resulted in further small but not significant decreases in mean LV [−0.02 (SD 0.11) ml · 100 ml−1], whereas mean FV tended to increase slightly [ + 0.02 (SD 0.14) ml · 100 ml−1]; in the control experiments mean LV and FV decreased continuously during the corresponding times [−0.19 (SD 0.31), −0.18
(SD 0.10) ml · 100 ml−1, respectively]. During the whole AHH, mean urine flow increased significantly from 0.84 (SD 0.41) ml · min−1 to 3.29 (SD 1.43) ml · min−1 in contrast to the control conditions. We concluded that peripheral fluid volume shifts form a part of the hypoxia-induced
acute cardiovascular changes at high altitude. In contrast to the often reported formation of peripheral oedema after prolonged
exposure to hypobaric hypoxia, the results provided no evidence for the development of peripheral oedema during acute induction
to high altitude. However, the marked increase in interindividual variance in S
aO2 and urine flow points to the appearance of the first differences in the short-term adjustment even after 2 h of acute hypobaric
hypoxia.
Accepted: 27 August 1996 相似文献
9.
Juan Fuentes F. B. Eddy 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(6):438-443
Drinking in Atlantic salmon (Salmo salar) juveniles was investigated in fresh water and following transfer to sea water. There was a significant effect of fish size
on drinking, and smolts (20–30 g) imbibed about ten times less water than alevins of 0.2–0.3 g. Freshwater smolts drank at
a rate of 0.15 ± 0.03 ml · kg−1 · h−1 and administration of doses of 10 or 20 mg · kg−1 of papaverine (stimulator of the renin- angiotensin system RAS) or [Asn1, Val5]-Angiotensin II (0.4 μmol · kg−1) resulted in significant increases in drinking, while administration of the angiotensin converting enzyme inhibitor, enalapril
(50 mg · kg−1) had no effect on drinking. Transfer of Atlantic salmon smolts to 1/3, 2/3 and full strength sea water resulted in significant
increases in drinking to 1.06 ± 0.12, 1.24 ± 0.0.16 and 3.89 ± 0.28 ml · kg−1 · h−1, respectively. In sea water, stimulation of the endogenous RAS by administration of papaverine (20 mg · kg−1) resulted in a 20% increase in drinking, while administration of enalapril to doses of 50 and 200 mg · kg−1 lowered drinking to 1.99 ± 0.48 and 0.32 ± 0.06 ml · kg−1 · h−1, respectively. All treatments were without effect on blood plasma levels of Na+ and Cl− in fresh water, while in sea water smolts both stimulation and inhibition of drinking resulted in hemoconcentration of Na+ and Cl−. The role of the renin angiotensin system in control of drinking and hydromineral balance in Atlantic salmon is discussed.
Accepted: 27 February 1997 相似文献
10.
M. D. Baustian S. Q. Wang K. W. Beyenbach 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(1):61-70
Plasma and urine of toadfish (Opsanus tau) in sea water and 10% sea water were analyzed to assess responses of an aglomerular fish to hypoosmotic challenge. Following
transfer to 10% sea water, plasma osmotic pressure decreased slowly from 318 to 241 mmol · kg H2O−1, over a period of 10–15 days. Urine osmotic pressure decreased in parallel from 299 to 207 mmol · kg H2O−1, leaving urine/plasma ratios of osmotic pressure essentially unchanged. In contrast, the volume and composition of urine
changed rapidly following transfer to 10% sea water. Urine flow rate increased 110% from 3.0 to 6.3 μl · 100g−1 · h−1 and Na+ excretion increased 346%, while excretion of Mg2− and SO4
2− decreased 81% and 90%, respectively. Excretion rates for Cl− were low in seawater toadfish and decreased further in 10% sea water. An unknown sulfur-containing anion, present in the
urine of seawater toadfish, contributed significantly to the composition and ionic balance in urine of toadfish in 10% sea
water. These results suggest that the inability to produce strongly dilute urine obliges toadfish to lose salt in order to
excrete water, in hypoosmotic media. The decrease in plasma osmotic pressure may be both a strategy to reduce osmotic and
ionic gradients in dilute media and a consequence of the kidney's inability to excrete water without salt.
Accepted: 22 August 1996 相似文献
11.
Effect of meal size on postprandial metabolic response in Chinese catfish (Silurus asotus Linnaeus) 总被引:1,自引:0,他引:1
Fu SJ Cao ZD Peng JL 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2006,176(5):489-495
The effect of relative meal size (0.5–24% body mass) on specific dynamic action (SDA) was assessed in Chinese catfish (Silurus asotus Linnaeus) (30.90±1.30 g) at 25.0°C; the cutlets of freshly killed loach without viscera, head and tail were used as a test meal. There was no significant difference in either SDA duration or peak oxygen consumption (VO2) among low meal size ranges. But both increased linearly as meal size increased from 2 to 24% without reaching a plateau. Factorial metabolic scope was 5.92 in fish fed with 24% body mass, the highest documented feeding metabolic scope value in fish till now. The Peak VO2 of satiated meal size groups (175.85±10.55 mg O2 h−1) was above 80% of maximum metabolic rate during locomotion recovery process (215.48±7.07 mg O2 h−1). The relationship between energy expended on SDA (E) and energy ingested (I) was described as: E=0.0000432I
2+0.140I+2.12. The lowest value of SDA coefficient appeared at 2% body mass group. 相似文献
12.
Romano N Rossi F Abelli L Caccia E Piergentili R Mastrolia L Randelli E Buonocore F 《Cell and tissue research》2007,329(3):479-489
Real-time polymerase chain reaction (PCR) and in situ hybridization analyses were performed to investigate the occurrence
and distribution of T-lymphocytes expressing TcRβ in intestine and lymphoid tissues of the bony fish, Dicentrarchus labrax (sea bass). Immunohistochemistry with the monoclonal antibody DLT15 (pan-T-cell marker) was carried out to compare the cytology,
distribution and number of T-cells and TcRβ+ cells in the various sampled lymphoid organs. The highest TcRβ expression was revealed by real-time PCR in the thymus, with
high levels also being found in the gut. In the thymus, DLT15+ and TcRβ+ cell populations were concentrated in the cortex and TcRβ+ cells were notably reactive at the cortical-medullary border, suggesting a specialized role of this region in thymocyte selection.
The density of DLT15+ T-cells increased from the anterior to posterior intestine, whereas TcRβ+ lymphocytes were more numerous in the middle intestine compared with other segments. The existence, in fish thymus, of a
medulla and a cortex comparable with those of mammals is revealed by this study. The concentration of TcRβ+ cells in the sea bass midgut also strongly suggests a special role of this intestinal segment in antigen-specific cellular
immunity. The large population of TcRβ-/DLT15+ T-cells in the posterior gut can probably be ascribed to the TcRγδ phenotype fraction. 相似文献
13.
Smith RW Palmer RM Houlihan DF 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(2):135-144
Protein synthesis in fish has been previously correlated with RNA content. The present study investigates whether protein
and RNA synthesis rates are similarly related. Protein and RNA synthesis rates were determined from 3H-phenylalanine and 3H-uridine incorporation, respectively, and expressed as % · day−1 and half-lives, respectively. Three fibroblast cell lines were used: BF-2, RTP, CHSE 214, which are derived from the bluegill,
rainbow trout and Chinook salmon, respectively. These cells contained similar RNA concentrations (∼175 μg RNA · mg−1 cell protein). Therefore differences in protein synthesis rates, BF-2 (31.3 ± 1.8)>RTP (25.1 ± 1.7)>CHSE 214 (17.6 ± 1.1),
were attributable to RNA translational efficiency. The most translationally efficient RNA (BF-2 cells), 1.8 mg protein synthesised · μg−1 RNA · day−1, corresponded to the lowest RNA half-life, 75.4 ± 6.4 h. Translationally efficient RNA was also energetically efficient with
BF-2 cells exploiting the least costly route of nucleotide supply (i.e. exogenous salvage) 3.5–6.0 times more than the least
translationally efficient RNA (CHSE 214 cells). These data suggest that differential nucleotide supply, between intracellular
synthesis and exogenous salvage, constitutes the area of pre-translational flexibility exploited to maintain RNA synthesis
as a fixed energetic cost component of protein synthesis.
Accepted: 12 November 1999 相似文献
14.
Reed JZ Chambers C Hunter CJ Lockyer C Kastelein R Fedak MA Boutilier RG 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(1):1-10
The respiratory physiology, heart rates and metabolic rates of two captive juvenile male harbour porpoises (both 28 kg) were
measured using a rapid-response respiratory gas analysis system in the laboratory. Breath-hold durations in the laboratory
(12 ± 0.3 s, mean ± SEM) were shorter than field observations, although a few breath-holds of over 40 s were recorded. The
mean percentage time spent submerged was 89 ± 0.4%. Relative to similarly-sized terrestrial mammals, the respiratory frequency
was low (4.9 ± 0.19 breaths · min−1) but with high tidal volumes (1.1 ± 0.01 l), enabling a comparatively high minute rate of gas exchange. Oxygen consumption
under these experimental conditions (247 ± 13.8 ml O2 · min−1) was 1.9-fold higher than predicted by standard scaling relations. These data together with an estimate of the total oxygen
stores predicted an aerobic dive limit of 5.4 min. The peak end-tidal O2 values were related to the length of the previous breath-hold, demonstrating the increased oxygen uptake from the lung for
the longer dives. Blood oxygen capacity was 23.5 ± 1.0 ml · 100 ml−1, and the oxygen affinity was high, enabling rapid oxygen loading during ventilation.
Accepted: 11 August 1999 相似文献
15.
I. L. Y. Spierts H. A. Akster H. L. Granzier 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(8):543-551
Titin (also known as connectin) is a striated-muscle-specific protein that spans the distance between the Z- and M-lines
of the sarcomere. The elastic segment of the titin molecule in the I-band is thought to be responsible for developing passive
tension and for maintaining the central position of thick filaments in contracting sarcomeres. Different muscle types express
isoforms of titin that differ in their molecular mass. To help to elucidate the relation between the occurrence of titin isoforms
and the functional properties of different fibre types, we investigated the presence of different titin isoforms in red and
white fibres of the axial muscles of carp. Gel electrophoresis of single fibres revealed that the molecular mass of titin
was larger in red than in white fibres. Fibres from anterior and posterior axial muscles were also compared. For both white
and red fibres the molecular mass of titin in posterior muscle fibres was larger than in anterior muscle fibres. Thus, the
same fibre type can express different titin isoforms depending on its location along the body axis. The contribution of titin
to passive tension and stiffness of red anterior and posterior fibres was also determined. Single fibres were skinned and
the sarcomere length dependencies of passive tension and passive stiffness were determined. Measurements were made before
and after extracting thin and thick filaments using relaxing solutions with 0.6 mol · l−1 KCl and 1 mol · l−1 KI. Tension and stiffness measured before extraction were assumed to result from both titin and intermediate filaments, and
tension after extraction from only intermediate filaments. Compared to mammalian skeletal muscle, intermediate filaments developed
high levels of tension and stiffness in both posterior and anterior fibres. The passive tension-sarcomere length curve of
titin increased more steeply in red anterior fibres than in red posterior fibres and the curve reached a plateau at a shorter
sarcomere length. Thus, the smaller titin isoform of anterior fibres results in more passive tension and stiffness for a given
sarcomere strain. During continuous swimming, red fibres are exposed to larger changes in sarcomere strain than white fibres,
and posterior fibres to larger changes in strain than anterior fibres. We propose that sarcomere strain is one of the functional
parameters that modulates the expression of different titin isoforms in axial muscle fibres of carp.
Accepted: 7 May 1997 相似文献
16.
The major histocompatibility complex (Mhc) haplotype in the chicken is generally determined by the use of alloantisera in a hemagglutination assay. This method restricts
haplotype determination to antigens expressed on the surface of erythrocytes which includes class I (B – F) and class IV (B – G)
antigens as well as any other polymorphic molecules on these cells. Alloantisera can result in complex cross-reactivity patterns.
We describe here the analysis of 53 alloantisera made within Mhc-congenic lines. Each antiserum was tested by hemagglutination with erythrocytes and by flow cytometry with erythrocytes and
peripheral white blood cells of seven Mhc haplotypes; B
2
, B
5
, B
12
, B
13
, B
15
, B
19
, and B
21
. Five types of antiserum were identified based on their reactivity to different cell subpopulations of the peripheral blood
of the donor haplotype as well as in cross-reactivity for different haplotypes. RBC specific cross-reactive antigens attributed
to B – G molecules were demonstrated for the B5 : B19, B12 : B19, and B19 : B21 cross-reactions. Cross-reactive antigens detected
on RBC and thrombocytes attributable to B – G molecules on both types of cells were demonstrated for the B2 : B12, B2 : B15,
B2 : B19, and B2 : B21 cross-reactions. In addition, cross-reactive antigens occurring on RBC and WBC were attributed to B – F (or RBC and lymphocyte-expressed B – G loci) and included the B12 : B13, B13 : B19, and B15 : B19 cross-reactions. Several antisera with specificity for B cells
purportedly identifying B – L epitopes were found but their numbers were limited and cross-reactivities were not defined.
The identities described here may be useful in understanding B haplotype similarities and differences in disease resistance and immune response.
Received: 18 September 1995 / 15 November 1995 相似文献
17.
A. W. E. Dilg Giovanna Mincione Klaus Achterhold Olga Iakovleva Matthias Mentler Claudio Luchinat Ivano Bertini F. G. Parak 《Journal of biological inorganic chemistry》1999,4(6):727-741
4 S4]3 + and the reduced [Fe4S4]2 + clusters in the high-potential iron protein I from Ectothiorhodospira halophila were measured in a temperature range from 5 K to 240 K. EPR measurements and 57Fe electron-nuclear double resonance (ENDOR) experiments were carried out with the oxidized protein. In the oxidized state
the cluster has a net spin S = 1/2 and is paramagnetic. As common in [Fe4S4]3 + clusters, the M?ssbauer spectrum was simulated with two species contributing equally to the absorption area: two Fe3 + atoms couple to the “ferric-ferric” pair, and one Fe2 + and one Fe3 + atom give the “ferric-ferrous pair”. For the simulation of the M?ssbauer spectrum, g-values were taken from EPR measurements. A-tensor components were determined by 57Fe ENDOR experiments that turned out to be a necessary source of estimating parameters independently. In order to obtain a
detailed agreement of M?ssbauer and ENDOR data, electronic relaxation has to be taken into account. Relaxing the symmetry
condition in a way that the electric field gradient tensor does not coincide with g- and A-tensors yielded an even better agreement of experimental and theoretical M?ssbauer spectra. Spin-spin and spin-lattice relaxation
times were estimated by pulsed EPR; the former turned out to be the dominating mechanism at T = 5 K. Relaxation times measured by pulsed EPR and obtained from the M?ssbauer fit were compared and yield nearly identical
values. The reduced cluster has one additional electron and has a diamagnetic (S = 0) ground state. All the four irons are indistinguishable in the M?ssbauer spectrum, indicating a mixed-valence state of
Fe2.5 + for each.
Received: 15 February 1999 / Accepted: 31 August 1999 相似文献
18.
Hans Gesser William R. Driedzic Francisco Tadeu Rantin José Carlos de Freitas 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(7):474-480
Isometric force development of electrically paced preparations isolated from the systemic heart of Octopus vulgaris were utilized to examine the regulation of contractility by Ca2+. Increases in extracellular Ca2+, to the physiological level, resulted in enhancement of twitch force. For instance, at 36 beats · min−1 an increase in Ca2+ from 3 to 9 mmol · l−1 resulted in a threefold increase in twitch force development. When steady-state contraction at 12 beats · min−1 was followed by a rest period of either 5 or 10 min, the first contraction always exhibited either an increase in twitch
force or stayed unchanged such that post-rest twitch force was about 133% of the last value in the steady-state train. Ryanodine
(12.5 μmol · l−1), which is considered to be a specific inhibitor of the Ca2+ storage and release capabilities of the sarcoplasmic reticulum (SR), was applied to further assess Ca2+ handling. Twitch force fell to about 22% of the preteatment level in preparations paced at either 12 or 36 beats · min−1. In all preparations the frequency transition from 12 to 36 beats · min−1 was associated with an increase in resting tension. The␣increase␣was 37 ± 14% prior to ryanodine treatment and was significantly
elevated to 127 ± 33% following treatment. When steady-state contraction at 36 beats · min−1 was followed by a rest period of 10 s, the first contraction was not significantly different from the last beat in the train
prior to ryanodine; however, with ryanodine treatment, post-rest twitch force development significantly decreased. Twitch
force development was regular at pacing rates of up to 300 beats · min−1. Twitch force was maintained up to rates of 84 beats · min−1 but␣decreased thereafter and reached a value of about 10% at 300 beats · min−1. Resting tension increased substantially as frequency was elevated from 12 to 36 beats · min−1 and then gradually increased as frequency was further elevated to 180 beats · min−1. In conclusion, the Octopus ventricle is dependent upon extracellular Ca2+ for contraction. A post-rest potentiation of force development, the negative impact of ryanodine, and the ability to respond
regularly at high pacing rates imply a strong reliance on the SR in Ca2+ cycling based on criteria established for vertebrate hearts.
Accepted: 19 January 1997 相似文献
19.
Moro D Bradshaw SD 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(8):538-548
A laboratory study investigated the metabolic physiology, and response to variable periods of water and sodium supply, of
two arid-zone rodents, the house mouse (Mus domesticus) and the Lakeland Downs short-tailed mouse (Leggadina lakedownensis) under controlled conditions. Fractional water fluxes for M. domesticus (24 ± 0.8%) were significantly higher than those of L. lakedownensis (17 ± 0.7%) when provided with food ad libitum. In addition, the amount of water produced by M. domesticus and by L. lakedownensis from metabolic processes (1.3 ± 0.4 ml · day−1 and 1.2 ± 0.4 ml · day−1, respectively) was insufficient to provide them with their minimum water requirement (1.4 ± 0.2 ml · day−1 and 2.0 ± 0.3 ml · day−1, respectively). For both species of rodent, evaporative water loss was lowest at 25 °C, but remained significantly higher
in M. domesticus (1.1 ± 0.1 mg H2O · g−0.122 · h−1) than in L. lakedownensis (0.6 ± 0.1 mg H2O · g−0.122 · h−1). When deprived of drinking water, mice of both species initially lost body mass, but regained it within 18 days following
an increase in the amount of seed consumed. Both species were capable of drinking water of variable saline concentrations
up to 1 mol · l−1, and compensated for the increased sodium in the water by excreting more urine to remove the sodium. Basal metabolic rate
was significantly higher in M. domesticus (3.3 ± 0.2 mg O2 · g−0.75 · h−1) than in L. lakedownensis (2.5 ± 0.1 mg O2 · g−0.75 · h−1). The study provides good evidence that water flux differences between M. domesticus and L. lakedownensis in the field are due to a requirement for more water in M. domesticus to meet their physiological and metabolic demands. Sodium fluxes were lower than those observed in free-ranging mice, whose
relatively high sodium fluxes may reflect sodium associated with available food.
Accepted: 16 August 1999 相似文献
20.
Shewanella putrefaciens is a bacterium implicated in oil pipeline corrosion and fish spoilage, and is one of very few isolated microorganisms able
to use iron(III) as an electron acceptor. S. putrefaciens strain 200 produced a novel cyclic dihydroxamate siderophore, putrebactin, during aerobic growth. Putrebactin was determined
to be 1,11-dihydroxy-1,6,11,16-tetraazacycloeicosane-2,5,12,15-tetrone, a cyclic dimer of succinyl-(N-hydroxyputrescine), by 1H and 13C NMR spectroscopy, fast atom bombardment and chemical ionization mass spectrometry, and X-ray crystallography. The protonation
constants of putrebactin were determined to be 8.82 and 9.71. Potentiometric titration of the ferric complex revealed a sharp
equivalence point at 3.0 equivalents of base per mole of Fe(III), consistent with loss of 3 protons per equivalent of bound
ferric ion, while Job's method of continuous variation supported a shift from 1 : 1 to 3 : 2 complex stoichiometry as a function
of pH. Putrebactin is similar in structure to two other siderophores, bisucaberin and alcaligin, produced by unrelated bacteria.
Received: 21 May 1996 / Accepted: 9 November 1996 相似文献