ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09763.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Intrinsic cardiac regulation, the direct effect of changes in right atrial pressure on heart rate, was examined in rabbits under chloralose/urethane anaesthesia. Autonomic influences on the cardiac pacemaker were eliminated by cervical vagotomy and intravenous propranolol. Right atrial transmural pressure was monitored as the difference between right atrial and pleural pressures. Blood volume expansion (5–15%) increased right atrial transmural pressure and heart rate and produced a sinus arrhythmia associated with respiration‐linked fluctuations in right atrial transmural pressure. The gain of intrinsic cardiac rate regulation was calculated as 0.96 ± 0.24 beats min‐1mmHg‐1at a heart rate of 218 ± 6 beats min‐1(values as the mean± SEM,n= 12). When heart rate was reduced by electrical stimulation of the peripheral end of the right vagus nerve, gain increased to 2.25± 0.57* and 4.61 ± 1.6* beats min‐1mmHg‐1at heart rates of 180 ± 4 and 130 ± 4 beats min‐1, respectively (n= 6 andn= 10; *P<0.05 compared with pre‐stimulation values). During vagally‐induced bradycardia, rapid infusion of blood into the left superior vena cava produced a brief marked cardiac acceleration. We conclude that right atrial pressure has a small direct influence on heart rate, and this is enhanced by background cardiac p

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09764.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The aim of this study was to determine if the adrenal medulla plays a role in mediating haemodynamic effects of hypertonic saline (HTS) resuscitation during haemorrhagic hypotension in conscious rats. Wistar‐Kyoto rats were either adrenomedullectomized (ADMX,n =11) or sham‐operated (SHAM,n =10) and implanted with intravascular catheters. Pre‐haemorrhage resting mean arterial pressure (MAP) was lower in the ADMX than in the SHAM group. Haemorrhage was performed by withdrawal of blood through the venous catheter, and a MAP of 50 mmHg was maintained for 1 h by further withdrawal when necessary. Both groups responded to haemorrhage with marked bradycardia. Plasma adrenaline (A) rose 10‐fold in response to hypotension in the SHAM group, while remaining at pre‐haemorrhage levels in the ADMX group, indicating successful adrenal demedullation. Infusion of 2.0 ml kg‐1HTS (NaCl 8.0 mg ml‐1i.v.) produced an immediate increase in MAP and heart rate (HR) in both groups, to pre‐haemorrhage values or higher. Plasma noradrenaline (NA) increased in both groups after HTS, while the high levels of A in the SHAM group slowly returned toward baseline. Plasma glucose and rate of haemodilution was higher in the SHAM group during and after hypotension. The maintenance of MAP above 60 mmHg was less effective in the SHAM group during the first 2 h after HTS, but after 24 h, pre‐haemorrhage MAP was established in both groups. In conclusion, the adrenal medulla does not play a major role in the response to

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09765.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The effects of cooling on the isometric response of rabbit isolated central ear (cutaneous) and femoral (non‐cutaneous) arteries to histamine were determined at 37oC and 24oC (cooling). Under resting tension, both types of arteries contracted to histamine (10‐7‐10‐3M), and the sensitivity of ear arteries, but not of femoral arteries was lower at 24 than at 37oC. Chlorpheniramine (10‐7M) blocked the contraction of both types of arteries to histamine at both temperatures. In ear arteries, endothelium removal or treatment with the nitric oxide synthase inhibitorNG‐nitro‐L‐arginine methyl ester (L‐NAME, 10‐5M) did not affect the contraction to histamine at 37oC, but it reversed the decreased contraction at 24oC. In femoral arteries, endothelium removal or L‐NAME (10‐5M) did not affect the response to histamine at 37 and 24oC. Ear and femoral arteries precontracted with endothelin‐1 (10‐8‐10‐7M) and pretreated with chlorpheniramine (10‐5M) relaxed to histamine (10‐7‐10‐4M), and the sensitivity of this relaxation in ear arteries, but not in femoral arteries, increased at 24oC. The relaxation of ear and femoral arteries to histamine was not modified by endothelium removal, L‐NAME (10‐5M) or meclofenamate (10‐5M), but it was blocked by cimetidine (10‐6M) at 37oC and 24oC. These results suggest: (1) ear and femoral arteries have contracting H1and relaxing H2receptors, probably located on smooth musculature, and (2) cooling reduces the contraction and increases the relaxation of cutaneous arteries to histamine: the reduction of this contraction could be caused by an augmented availability of endothelial nitric oxide, and the increment of this relaxation could be caused by an augmented sensitivity of H2receptors of smooth musculature induced by cooling. Thes

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09766.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The aim of this study was to investigate the role of vagal nerve activity for the release of oxytocin, prolactin and gastrointestinal (GI) hormones during suckling as well as for the secretion of milk in lactating rats. We have therefore performed experiments on vagotomized lactating rats. The animals were decapitated and trunk blood was collected from nonsuckling rats and from suckling rats in connection with milk ejection. Oxytocin, prolactin, vasoactive intestinal polypeptide (VIP), somatostatin, insulin, glucagon and glucose levels in plasma were measured by RIA‐technique. In addition, maternal weight as well as the weight of the litters were recorded 7 d after vagotomy. As expected, oxytocin and prolactin levels rose in response to suckling in sham‐operated controls. In vagotomized animals the suckling‐induced increase of oxytocin was blocked and prolactin levels were significantly decreased. VIP levels in plasma increased following suckling in sham‐operated animals and failed to respond after vagotomy. In contrast, somatostatin levels that rose significantly in sham‐operated rats were even more significantly raised in vagotomized animals. In addition, insulin but not glucagon levels were increased by suckling. The insulin response, however, persisted after vagotomy. Interestingly, suckling was followed by a lowering of blood‐glucose levels in vagotomized, but not in sham‐operated animals. The vagotomized rats ate as much and increased in weight as sham‐operated rats during the 7 d of vagotomy. The litters of vagotomized rats, however, gained significantly less weight in comparison with control litters. In conclusion, this study shows that vagal nerve activity is of importance for the release of oxytocin, prolactin, vasoactive intestinal polypeptide and somatostatin during suckling. In addition, vagal nerve activity was found to be of fundamental importance for adequate milk secretion, since litters of vagotomized rats increased in weight less than litters of sham‐operated

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09767.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The transport of lysine by the lactating rat mammary gland has been examined to determine whether there is an interaction between cationic and neutral amino acids. Lysine uptake was time dependent and unaffected by replacing Na+with choline. In the presence of Na+, lysine influx was inhibited by cationic amino acids (arginine, homoarginine, ornithine and lysine) and by a range of neutral amino acids (methionine, glutamine, leucine, phenylalanine, alanine, asparagine, α‐aminoisobutyric acid (AIB), 2‐aminobicyclo [2,2,1] heptane‐2‐carboxylic acid (BCH), proline and tryptophan). Leucine and glutamine also inhibited lysine influx in the absence of Na+but phenylalanine and proline did not. Lysine efflux from mammary tissue was trans‐accelerated by various cationic amino acids (lysine, arginine, homoarginine and ornithine). In addition, leucine and glutamine were capable of trans‐stimulating lysine efflux in the presence and absence of Na+. It appears that cationic and neutral amino acids stimulated lysine efflux at a

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09768.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Renal Na excretion during the 24 h following feeding was studied in sheep. A pronounced natriuresis occured 3.5‐5.5 h after feeding. Na excretion then fell to low levels in animals allowed to drink water, but was significantly elevated above this level in water‐deprived sheep for most of the remaining period. Both the post‐prandial and dehydration‐induced natriuresis were prevented by intracerebroventricular (icv) infusions of low Na concentration 0.3 mol 1‐1mannitol at 1 ml h_1, and a water diuresis also occurred. These effects were not caused by icv infusion of artificial cerebrospinal fluid (Na concentration = 150 mmol l‐1). As a result, there was a much greater increase in plasma Na concentration and osmolality in the sheep given icv mannitol. Intravenous infusion of vasopressin prevented the water diuresis induced by icv mannitol, but the inhibition of natriuresis was still observed and plasma Na concentration increased by 8 mmol l‐1over 24 h compared with an increase of 3 mmol l‐1in dehydrated sheep infused icv with artificial cerebrospinal fluid. The results show that the ambient Na concentration in the brain plays an important role in the normal homeostatic regulation of Na balance by the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09769.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In order to examine the possibility that endothelin might be important in the regulation of placental blood flow, human uteroplacental vessels were superfusedin vitroto study the contractile effect of endothelin as compared with a known strong contractor of placental blood vessels, serotonin (5‐HT). The contractile responses were compared in the presence and absence of calcium channel blocking agents, as well as in the presence of L‐NMA, an inhibitor of EDRF/nitric oxide. Endothelin (ET, 10‐510‐6M) and 5‐HT (10‐8‐10‐4M) induced contractions in the vessels. Maximal contractions in the presence of endothelin were elicited at 10‐7M, whereas 5‐HT elicited maximal contractions at 10‐5M. At 10‐7M, ET was more potent than 5‐HT. The calcium‐channel blocking agents nifedipine, diltiazem and NiCl2relaxed the vessels by 5–15% from baseline. The contractile response to ET in the presence of nifedipine or diltiazem was reduced by 55 and 67%, respectively. The response to 5‐HT in the presence of nifedipine was reduced by 58%. The contractile response to 5‐HT as well as ET in the presence of both nifedipine and NiCl2was not significantly lower than in the presence of nifedipine only. The EDRF‐inhibiting agent L‐NMA caused a small contractile response at concentrations of 10‐6–10‐5M. ET as well as 5‐HT added after pretreatment with L‐NMA produced a larger contractile response than ET or 5‐HT alone. The results show that ET has a strong contractile effect on placental blood vessels at concentrations likely to occur during labor and delivery. The mechanism whereby ET as well as 5‐HT contracts placental vessel smooth muscle appears to partly involve nifedipine‐ and diltiazem‐sensitive calcium channels, but almost half of the response

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09770.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Type II interferon is known to induce a plethora of gene expression involved in the humoral and cellular immunity. One of the multiple sites of action of γ‐IFN is the fetoplacental unit, where its role has not yet been clearly defined. We have previously shownin vitrothat γ‐IFN may induce expression of class II MHC antigens on the spongiotrophoblast layer of the murine placenta, which under physiological conditions is negative for these antigens. Indeed, the absence of class II antigens from the placenta could be part of a mechanism evoked by fetal tissues to escape a host vs. graft reaction. In the present study we show that intraperitonealin vivoadministration of low doses of recombinant γ‐IFN to pregnant females specifically induces class II antigens on the spongiotrophoblast zone, increases fetal abortion, causes retardation of eye development in the fetuses and decreases fetal weight. This treatment also affects the maternal pathology as we witness a prominent hypersplenism in the mother accompanied by low levels of haematocrit, elevated IgG production and decreased granulocytic and thrombocytic counts. These results are specifically linked to the pregnant state of the mother, since virgin females do not develop any of the above abnormalities.Our results not only point to a new dimension in γ‐IFN's role during pregnancy, but may be of clinical importance for prophylaxis since administration of γ‐IFN to a pregnant female may lead to abortion, fetal abnormalities or cause haematologic disorders

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09771.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

We have studied the effect of a novel tachykinin, neuropeptide γ(NPγ) on small intestinal motility in the rat. Experiments were donein vitroon longitudinal muscle strips of duodenum, andin vivoon the migrating myoelectric complex (MMC) of the small intestine.In vitro, contractile effects of NPγ were compared with those of a selective neurokinin 1 (NK1) receptor agonist, substance P methyl ester (SPME), and a selective neurokinin 2 (NK2) receptor agonist, Nle10‐NKA(4–10)(NleNKA). NPγ, SPME and NleNKA caused concentration‐dependent contractions (P<0.001). NPγ was eight‐fold more potent than NleNKA, and 118‐fold more potent than SPME. Contractile responses to NPγ were reduced by hexamethonium (P<0.01) and atropine (P<0.05). The non‐selective NK receptor antagonist spantide I only slightly reduced the contractile response to NPγ, as did the selective NK1 antagonist GR 82334, and the selective NK2 antagonist L‐659877 and MEN 10376.In vivo, effects of NPγ on the MMC were compared with those of the natural tachykinins substance P (SP) and neurokinin A (NKA). NPy disrupted the MMC and induced irregular spiking in a dose‐dependent manner from 25 to 100 pmol kg‐1min‐1i.v. (P<0.05). The effect of NPγ was more prominent than that of NKA at equal doses, while SP had no effect. Our findings show that NPγ exerts potent stimulatory effects on small intestinal motility, most likely mediated directly via distinct NK receptors on smooth muscle cells, but also indi

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09772.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY