Criterion for phase separation in one-dimensional driven systems

A general criterion for the existence of phase separation in driven density-conserving one-dimensional systems is proposed. It is suggested that phase separation is related to the size dependence of the steady-state currents of domains in the system. A quantitative criterion for the existence of phase separation is conjectured using a correspondence made between driven diffusive models and zero-range processes. The criterion is verified in all cases where analytical results are available, and predictions for other models are provided.

Impaired endothelial function of thoracic aorta in hereditary hypertriglyceridemic rats

OBJECTIVE

Hereditary hypertriglyceridemia (hHTG) in rats was found to be associated with metabolic abnormalities and elevation of blood pressure. There is controversy regarding the relation between hHTG and vascular function. The aim of this study was to determine the reactivity and accompanying structural changes in thoracic aorta from hereditary hypertriglyceridemic rats and hHTG rats that were given, for a long time, N(G)-nitro-l-arginine methyl ester (L-NAME) with and without simultaneous captopril treatment.

METHODS

Isolated rings of thoracic aorta were mounted in organ chambers for isometric tension recording or for measurement of endothelium-dependent relaxation. Morphological changes of thoracic aorta (wall thickness, diameter) were measured using light microscopy.

RESULTS

Endothelium-dependent relaxation (EDR) to acetylcholine (ACh, 10(-5) M) was significantly attenuated in the hHTG group compared to control Wistar rats (59.3 +/- 8.5% vs. 95.8 +/- 6.5%, p < 0.001), but normalized after pretreatment with captopril. EDR to ACh was further inhibited in hHTG rats treated with L-NAME (36.0 +/- 2.3%, p < 0.001). Maximum residual relaxation was only partly restored with captopril treatment (72.4 +/- 5.8%, p < 0.001). Hypertriglyceridemia did not significantly alter the sensitivity of the thoracic aorta to exogenous noradrenaline. The diameter/wall thickness (D/W) ratio in aortas of control Wistar rats averaged 16.25 +/- 0.57. This ratio was significantly lower in hHTG rats (12.52 +/- 0.38, p < 0.01) and was not altered after treatment with captopril. In the hHTG rats treated with L-NAME, the D/W ratio was further significantly decreased (8.25 +/- 0.30, p < 0.001). Simultaneous captopril treatment attenuated the decrement of this ratio (9.80 +/- 0.75, p < 0.05).

CONCLUSIONS

Results showed that hHTG is accompanied by functional and morphological alterations in the rat thoracic aorta. These changes in hHTG and in hHTG rats treated with L-NAME could be, at least in part, protected by captopril treatment.

[Effect of the parents' dental fear on the child's oral health]

There are various factors which influence the oral status, among them the dental fear. Dental anxious individuals are likely to have more missing teeth and fewer filled ones. This study examined the association between dental anxiety and oral health status in parents and indirectly in children. The authors found that there is positive correlation between dental fear and missing teeth in the older generation. These tendency can also be seen in younger ones.

[Attention deficit hyperactivity disorder. Literature review for the pediatric dentist]

The purpose of this review was to give a complete summary of the ADHD (Attention Deficit Hyperactivity Disorder) for dentists, especially for those who deal with dental traumatology. Children with ADH disorder show symptoms of restlessness, hyperactivity, impulsive behaviour and inattention often resulting in serious dental accidents. The article summarizes the literary data concerning ADH-Syndrome, presents a typical case and also deals with the dental considerations.

Remarkably reduced transplant-related complications by dibromomannitol non-myeloablative conditioning before allogeneic bone marrow transplantation in chronic myeloid leukemia

A non-myeloablative conditioning protocol containing dibromomannitol (DBM/cytosine arabinoside/cyclophosphamide) has been applied to 36 chronic myeloid leukemia (CML) patients followed by bone marrow transplantation (BMT) from sibling donors. Risk factors include: accelerated phase (10 patients), older age (17 patients over >40 years) and long interval between diagnosis and BMT (27 months on average). Severe mucositis did not occur. Venoocclusive liver disease was absent. Infectious complications were rare. Although grade II-IV acute graft-versus-host disease (GVHD) was present in 9 (25%) cases, there were only 2 serious (III-IV) ones. Chronic GVHD occurred in 25 (69%) cases, preceded by acute GVHD in 9 of the 25 affected patients. Early hematological relapse, 7-29 weeks after BMT, developed in 6 patients (17.6%). No relapse was noted in the completely chimeric patients, however molecular genetic residual disease was observed in 6 patients, in most of them after transient short-term mixed chimeric state. Overall actual survival rate is 83.3% for the 36 cases, and leukemia-free survival is 72.2% for the 34 engrafted patients.

[Goltz syndrome - a case report]

The Goltz (Goltz-Gorlin) syndrome or focal dermal hypoplasia is a relatively rare disease. Its clinical manifestation shows a great variety. The syndrome characterized by anomalies of cutaneous, osseous, dental and ocular structures. The authors present the case of a six-year-old girl with typical anomalies of Goltz-Gorlin syndrome with special respect to the dental problems.

Silver Nanoparticles by PAMAM-Assisted Photochemical Reduction of Ag(+)

The photochemical synthesis of Ag(0) nanoparticles in the presence of amino- and carboxylate-terminated PAMAM dendrimers is reported. The formation of Ag(0) nanoparticles was followed spectrophotometrically and by transmission electron microscopy (TEM). According to TEM investigations Ag(0) nanoparticles with the average size of about 7 nm in diameter were produced. Based on the present investigation a possible mechanism for the Ag(0) nanoparticles formation is proposed. Copyright 2000 Academic Press.

Histamine-induced relaxation in pulmonary artery of normotensive and hypertensive rats: relative contribution of prostanoids, nitric oxide and hyperpolarization

The aim of this study was to determine the relative contribution of nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF) and prostanoids in histamine-induced relaxation of isolated pulmonary artery from normotensive and hypertensive rats. The hypertension was induced by oral administration of NO synthase inhibitor N(G)-nitro-L-arginine methylester (L-NAME, 50 mg/kg/day) to normotensive rats for 8 weeks. In phenylephrine-precontracted arterial rings the histamine-induced relaxation was significantly reduced in L-NAME-treated rats compared to the controls. Indomethacin (cyclooxygenase inhibitor) and glibenclamide (ATP-sensitive K+-channel blocker) did not inhibit the relaxation response in either control or hypertensive rats. On the other hand, tetraethylammonium (TEA), a K+-channel blocker with a broad specificity, significantly reduced histamine-induced relaxation in the pulmonary artery from both groups examined. The TEA-resistant relaxation was completely abolished by additional administration of L-NAME to the incubation medium. The results indicate that histamine-induced relaxation of the pulmonary artery in both normotensive and hypertensive rats is mediated mainly by nitric oxide, whereas EDHF seems to play a minor role.

Contemporary activation of different endothelial receptors accounts for a reserve mechanism of nitric oxide-mediated relaxation

The aim of this study was to investigate whether the inhibition of one of the endothelial receptor sites in the rat pulmonary artery (muscarinic, histaminergic, purinergic, alpha2-adrenergic) affects the NO-mediated relaxation induced by the activation of the other type of receptors. Acetylcholine (ACh)-, histamine (Hist)-, adenosine (Ade)-, and clonidine (Clon)-induced endothelium-dependent relaxations were reduced by the administration of specific antagonists of muscarinic, H1-histaminergic, purinergic or alpha2-adrenergic receptors, respectively. The inhibition of H1-histaminergic receptors by chlorphenyramine did not prevent ACh-induced relaxation. Similarly, the inhibition of muscarinic receptors by atropine did not prevent the relaxations to histamine, adenosine and clonidine. On the other hand, the relaxations induced by acetylcholine, histamine, adenosine or clonidine were regularly reduced by NO-synthase inhibitor N(G)-nitro-L-arginine methyl ester (10(-4) mol/l). These results suggest that the inhibition of NO-synthase abolished arterial relaxations induced by all agonists. After inhibition of one type of the endothelial receptors, the NO-dependent relaxation could still be evoked by activation of one of the others.

Passive smoking impairs endothelium-dependent relaxation of isolated rabbit arteries

The aim of the present study was to examine the effect of prolonged passive smoking (lasting 3 weeks) on plasma catecholamine levels and reactivity of isolated rabbit arteries. Plasma noradrenaline, adrenaline and dopamine levels were determined radioenzymatically. Isolated rings of the thoracic aorta and carotid artery were suspended in organ chambers and connected to a force transducer for the recording of isometric tension. Plasma noradrenaline levels were found to be significantly elevated in rabbits subjected to passive smoking for 3 weeks. Plasma adrenaline and dopamine levels were not changed. Transmural nerve stimulation of arterial rings evoked frequency-dependent contractions. Prolonged passive smoking did not affect neurogenic contractions of the arteries tested. On the other hand, endothelium-dependent relaxations of phenylephrine-precontracted arteries were significantly impaired. Furthermore, hypertrophy of the left ventricle was observed. In conclusion, passive smoking impairs endothelium-dependent relaxations but not neurogenic contractions of systemic arteries. The impaired relaxations of arteries may be, at least in part, mediated through the degradation of released nitric oxide by superoxide anions derived from cigarette smoke.

Sex-dependent risk taking in the collared flycatcher, Ficedula albicollis, when exposed to a predator at the nestling stage

An increased mortality rate is a cost of parental care, and can be high during the provisioning phase of altricial nestlings. When a parent stops feeding the nestlings temporarily after seeing a predator, it can reduce its own predation risk, but the suspension of parental care may also reduce its offspring's chances of surviving. We modelled this situation by exposing a stuffed sparrowhawk near collared flycatcher nests and removing it when both parents had seen it. We measured the time (return time) between the removal and when each parent entered the nestbox. The parents' risk taking and the return time are assumed to be inversely related. We studied which brood variables the parents take into account when deciding how much risk they are willing to take during the provisioning period. Males took more risk for older and better-quality nestlings and earlier broods. The females' behaviour was opposite to that of the males: they took significantly less risk for older and better-quality offspring and visited the nestbox later for earlier broods. The males' behaviour supported the reproductive value hypothesis, that risk taking is related to brood value and survival chances, whereas the females' behaviour supported the harm to offspring hypothesis, that risk taking is related to the broods' vulnerability. Copyright 2000 The Association for the Study of Animal Behaviour.

[A new radiation-free conditioning in bone marrow transplantation and dibromo-mannitol therapy in chronic myeloid leukemia]

A new, radiation-free, conditioning protocol, containing the original Hungarian mitobronitol (DBM) (DBM/ cytosine arabinoside/cyclosphosphamide) has been applied to 36 chronic myeloid leukemia (CML) patients followed by bone marrow transplantation (BMT) from HLA identical sibling donors between 1990-1997. In spite of some prognostically disadvantageous factors (half of them were above 40 years, 10 out of 36 patients were in accelerated phase, the disease history was longer than 2 years in average) the overall survival (30/36) and the leukemia free survival rate (26/36) were in accordance with the best international results. Transplantation-related toxicity was remarkably reduced in comparison to bone marrow transplantation performed by total body irradiation/cyclophosphamide (TBI/Cy) or busulphan/cyclophosphamide (Bu/Cy) conditioning protocols. Acute graft versus host disease was present in lower percentage (9/36) and the number of serious cases was only 2/36. Chronic GVH disease, generally known to be associated with antileukemic effect (GVL), occurred in 25 of cases. Early haematological relapse among the 34 patients with functioning graft occurred in 6 patients which rate is slightly higher than reported after TBI/Cy or Bu/Cy conditioning treatment. There was no relapse among patients transplanted within one year post-diagnosis and patients having CML with accelerated phase. The leukemia free post-transplant period was in association with the chronic GVH disease and full chimeric state.

Developmental dynamics of endothelial and neurogenic control of canine thoracic aorta

The purpose of the study was to confront the range of endothelial relaxation and neurogenic contraction of the thoracic aorta in fetuses (1 week before birth), puppies (1, 2, 4 and 6 weeks old), and in adult dogs. Isometric tension of aortic rings was monitored in organ bath. Acetylcholine-induced dose-dependent relaxation of aortic rings precontracted by phenylephrine was pronounced already in fetuses and puppies and significantly larger than in adults. Indomethacin, a cyclooxygenase inhibitor, did not affect the magnitude of aortic relaxation to acetylcholine. Transmural nerve stimulation induced but very slight contractions of the thoracic aorta in fetuses, while in puppies the extent of contractions was increasing with increasing age, reaching its maximum in adults. Contractile responses of aortic rings induced by KCl were fully detectable in fetuses and puppies and increased with increasing age of the animals. Thus in ontogenesis, the extent of endothelium-dependent relaxation and neurogenic contraction of the thoracic aorta displayed an opposite trend. The acetylcholine-induced relaxation was fully operative already in fetuses and puppies and its extent was declining toward adulthood, whereas the neurogenic contraction was hardly detectable in fetuses, increasing in puppies, and showed the highest values in adults.

[The role of endothelial nitric oxide in neurogenic contractions of the carotid artery in rabbits during cooling]

The role of endothelial nitric oxide in contractions induced by endogenous noradrenaline released by transmural nerve stimulation (TNS) and by exogenous noradrenaline (NA) was studied in isolated rings of rabbit carotid artery during cooling. At 37 degrees C, TNS produced frequency-dependent contractions of artery. Endothelium removal or inhibition of nitric oxide synthase by NG-nitro-L-arginine methyl ester (L-NAME) significantly enhanced TNS-induced contractions. The magnitude of maximal contraction to exogenous NA was increased in L-NAME-treated intact rings. Cooling the incubation bath from 37 degrees C to 26 degrees C increased the magnitude of neurogenic contractions in intact rings. L-NAME increased further the magnitude of neurogenic contractions at 26 degrees C in intact, but not in denuded arterial rings. Similarly, L-NAME increased contractions induced by exogenous NA during cooling. The results suggest that the response of the carotid artery to noradrenergic stimulation is modulated by nitric oxide originating from endothelial cells at normal as well as reduced temperature. (Tab. 1, Fig. 6, Ref. 19.)

Vascular responses after long-term inhibition of nitric oxide synthesis in newborn dogs

The effect of long-term inhibition of nitric oxide synthase on the relaxation and contraction ability of the thoracic aorta, carotid and pulmonary arteries was studied in the early postnatal period. Starting from the fifth day after birth, puppies were administered NG-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg/day subcutaneously) for 6 weeks. After this period, mean blood pressure increased from the control value of 94 +/- 14 mm Hg to 168 +/- 5 mm Hg (P < 0.01) and the heart/body weight ratio from 6.22 +/- 0.25 to 8.23 +/- 0.45 (P < 0.01). In control arterial rings precontracted by phenylephrine (10(-5) mol/l), acetylcholine caused dose-dependent relaxations; the maximal values were reached in the range of 10(-8) to 10(-6) mol/l. In arteries from L-NAME treated puppies, acetylcholine also induced dose-dependent relaxations, the maximum values in the thoracic aorta (81.0 +/- 2.9%) and carotid artery (87.2 +/- 6.9%) were significantly reduced, not, however, in the pulmonary artery (76.4 +/- 7.8%). Dose-response curves to acetylcholine in all the examined arteries from L-NAME-treated animals were shifted to the right indicating a decrease in sensitivity to acetylcholine. Neurogenic contractions, induced by electrical stimulation of adrenergic nerves, were not significantly altered in the thoracic aorta and carotid artery. However, in the pulmonary artery the contractions were greater at high frequency of stimulation. The findings that (i) submaximal doses of L-NAME attenuate acetylcholine-induced relaxation only slightly, and (ii) that it does not appreciably influence adrenergic contractions justify the hypothesis that the endothelium of vessels in newborn dogs is very probably endowed with a high content of nitric oxide synthase.

Histamine H1-receptor antagonists do not prevent the appearance of endothelium-dependent relaxation to acetylcholine in rat pulmonary artery

The purpose of this study was to determine the relaxant effects of acetylcholine after inhibition of vascular histaminergic receptors. In isolated rings of the rat pulmonary artery precontracted by phenylephrine (10(-5) mol/l) both histamine (10(-7) to 10(-4) mol/l) and acetylcholine (10(-8) to 3 x 10(-5) mol/l) produced concentration-dependent relaxations. The arterial relaxations induced by either histamine or acetylcholine were markedly reduced or abolished by administration of NO synthase inhibitor NG-nitro-L-arginine methyl ester (10(-5) mol/l). Relaxant responses to histamine were not influenced by cimetidine, histamine H2-receptor antagonist, but were significantly decreased or abolished by treatment with chlorphenyramine or diphenhydramine, histamine H1-receptor antagonists. On the other hand, chlorphenyramine and diphenhydramine did not prevent the appearance of endothelium-dependent relaxation to acetylcholine. The results suggest that relaxation to histamine in the rat pulmonary artery is mediated by H1-histaminergic receptors and their inactivation does not interfere with the endothelial capability to produce and/or release nitric oxide by the activation of other types of receptors.

Restriction of nitric oxide rather than elevated blood pressure is responsible for alterations of vascular responses in nitric oxide-deficient hypertension

The responsiveness of isolated high-pressure (aorta, renal artery) and low-pressure vessels (pulmonary artery) was compared during systemic hypertension induced by chronic inhibition of nitric oxide synthesis by NG-nitro-L-arginine methyl ester (L-NAME) in rats. L-NAME (40 mg/kg/day) was given to animals in their drinking water. After 4 weeks of L-NAME treatment, systolic blood pressure increased by 37% as compared with that in the control group. Chronic L-NAME treatment resulted in significant reduction of endothelium-dependent relaxation to acetylcholine (10(-8) to 3 x 10(-6) mol/l) in both types of vessels. The reduced relaxation was not influenced by acute pretreatment with indomethacin (10(-5) mol/l), however, it was further reduced by acute pretreatment with additional L-NAME (10(-4) mol/l). L-arginine (10(-4) mol/l) improved the reduced relaxation. Endothelium-independent relaxation to sodium nitroprusside (10(-9) to 10(-6) mol/l) was unaffected by L-NAME treatment. beta-adrenoceptor-mediated relaxation to isoprenaline (10(-8) to 3 x 10(-6) mol/l) was also not influenced by chronic L-NAME treatment. Similar alterations in the responsiveness of high- and low-pressure vessels indicate rather the decisive role of nitric oxide restriction than that of elevated blood pressure in their development.

Drug utilization study during pregnancy

The history of drug registration in most developed countries has been strongly influenced by the dramatic thalidomide disaster. A systematic hand search identified all women who delivered between September 1st 1993 and June 1st 1994. A total of 2389 mothers were set against the Australian Classification of Drugs with respect to their known or suspected risks in pregnancy. According to the interview after delivery, and from the hospital files, the prescription rate of all drugs increased from 15% in period-1 (two months before pregnancy), to an average of 65.66% during pregnancy. We could divide the groups of drugs used during pregnancy into major and minor groups according to the number of women who ingested drugs in the different trimesters. 1. In the first trimester, women received major amounts of blood-forming drugs, vitamins and electrolytes, hormones, anxiolytics, antibiotics and GI drugs. 2. In the second trimester, women received major amounts of blood-forming drugs, vitamins and electrolytes, anti-infectives, anxiolytics, tocolytics and antihypertensive. 3. In the third trimester, women received major amounts of blood-forming drugs, vitamins and electrolytes, tocolytics, anxiolytics, anti-infectives, antithrombotics and antihypertensive. The drug groups mentioned above have been set according to it's decreasing use respectively.

Morphological and functional alterations in endothelium, smooth muscle, and nerve fibers in rabbit aorta after storage at 4 degrees C

Structural and implied functional changes in endothelial cells (EC), smooth muscle cells (SMC), and nerve fibers (NF) in rabbit aorta were studied after storage in cold Krebs solution. Rings from the thoracic aorta were stored for 2, 4, 6, and 8 days in a refrigerator at 4 degrees C. Subsequently they were examined after 6 h in an organ bath at 37 degrees C and processed for transmission electron microscopy. The earliest and most prominent structural changes were observed in NF and varicosities. These changed after 2 days and were completely destroyed after 6 days. Less remarkable changes in both the intensity and the timeliness of alterations were found in EC. The majority of them showed changes after 4 days. After 8 days they were seriously destroyed, but still formed a relatively continuous layer. The most resistant cells were SMC, showing only slight alterations during the whole period. Contraction of aortic rings in response to transmural nerve stimulation (8 Hz) gradually decreased with the length of cold storage. After 4 days contraction was about 10% of the control value, while after 6 days it was entirely abolished. Maximal relaxation of noradrenaline-precontracted rings in response to acetylcholine was decreased to 46% after 4 days of storage, while after 8 days it was only 15% of the control value. The contractile response of aorta to exogenous noradrenaline did not change during the whole period except for Day 4 when the response was significantly increased. These results showed the different susceptibilities of the EC, the SMC and the NF of the thoracic aorta to cold storage at 4 degrees C (NF > EC > SMC). The observed structural changes were in close agreement with their functional expressions.

Endothelium-dependent relaxation in rabbit aorta after cold storage

The extent of preservation of endothelial, smooth muscle and neurogenic function following cold storage was studied in rabbit thoracic aorta. Relaxation responses to acetylcholine and sodium nitroprusside were compared between fresh aortic rings and rings that had been stored in a refrigerator for 2-8 days at 4 degrees C. In fresh aortic rings, the addition of acetylcholine to precontracted vessels resulted in dose-dependent relaxation. The magnitude of relaxation was gradually decreased after 4-8 days of cold storage. Relaxation in response to sodium nitroprusside did not change. Following cold storage contractions of aortic rings in response to noradrenaline and phenylephrine were not reduced. Contractile responses induced by transmural nerve stimulation were gradually attenuated with the length of cold storage. Electron microscopy after 4 days showed partial damage of endothelial cells (slightly vacuolized mitochondria). After 8 days, endothelial cells were destroyed; only membranous material was present. The structure of smooth muscle cells was only partially changed even after 8 days. Sympathetic nerve endings on the 4th day were partially, but on the 8th day completely destroyed. These results suggest that after cold storage of rabbit aorta, the gradual reduction of endothelium-dependent relaxation is probably caused by a decrease in production of the endothelium-derived relaxing factor due to the destruction of endothelial cells.

[Comparison of the inhibitory effect of diltiazem on neurogenic contractions in the mesenteric arteries and veins]

The effect of diltiazem on the magnitude of isometric contractions induced by electric stimulation of intramural nerves (4Hz) was studied on isolated rings of the mesenteric artery and vein of the dog and rabbit. Diltiazem in concentrations of 10(-5) mol/l and above inhibited neurogenic contractions of the mesenteric artery and vein of the dog in a dose-dependent manner. Inhibition of contractions of the mesenteric vein was found to be more pronounced than that of contractions of the mesenteric artery. In the mesenteric vessels of the rabbit, diltiazem in concentrations of 10(-6) and above inhibited neurogenic contractions, and again more markedly in the veins than in the arteries. On comparing the inhibition of contractions in the two animal species studied, the contractions of the mesenteric vein of the rabbit were found to be more intensely inhibited than those of the dog vein. Diltiazem inhibited also phentolamine-resistant neurogenic contractions of the mesenteric artery. The established differences in the magnitude of neurogenic contraction inhibition may presumably be accounted for by quantitative differences in adrenergic innervation of mesenteric arteries and veins, as well as by differences in the magnitude of the contraction component dependent on extracellular calcium which is greater in the veins than in the arteries. This may also explain the more pronounced inhibition of neurogenic contractions in the veins compared to arteries.

[The effect of cadmium on neuromuscular transmission in rabbit blood vessels]

Influence of cadmium on contractions of isolated v.portae of a rabbit, elicited by transmural nerve stimulation and by exogene norepinephrine, has been studied. Low concentrations of cadmium (10(-6) mol/l) potentiated contractions of the vessels in response to transmural nerve stimulation but they did not influence the magnitude of response to norepinephrine. Higher concentrations of cadmium (10(-5) - 10(-4) mol/l) inhibited contractions of v.portae elicited by both adrenergic stimuli. The results indicate that the effect of cadmium on contractions induced by transmural nerve stimulation is realized predominantly pre-synaptically, probably by influence on homeostasis of calcium in the nerve ending. Potentiation of responses of v.portae indicates a mechanism by which ions of cadmium could contribute to the development of hypertension.

[Absence of the inhibitory effect of ATP and adenosine on adrenergic neurotransmission in the portal vein in guinea pigs]

Influence of purin substances ATP and adenosine on the magnitude of contractile response induced by transmural nerve stimulation (TNS) and exogene norepinephrine (NE) has been investigated on isolated segments of v.portae of a foetus, newborn and grown guinea pig. ATP and adenosine had no inhibitory effect on adrenergic contractions of v.portae of the guinea pig of all three investigated groups. In concentrations of 0.03-0.3 mol/l which inhibit neurogene contractions of v.portae in rabbits and in rats they potentiated contractions in response to TNS and exogene NE in newborn as well as grown animals. Absence of an inhibitory effects indicates lack of presynaptic P1 purinergic receptors in the area of adrenergic terminals of guinea pig's v.portae. Potentiation is probably caused by activation of postsynaptic purinergic receptors.

[Functional and morphologic changes in adrenergic innervation of the portal veins in guinea pigs towards the end of the prenatal period]

Contractions induced by transmural nervous stimulation were studied on isolated preparations of the portal vein of newborn and adult guinea pigs and the walls of the studied vessels were examined by electron microscopy. Transmural nervous stimulation elicited contractions of the portal vein in all developmental types yet with a higher threshold frequency for inducing contractions in fetuses than in newborn animals. Guanethidine and phentolamine reduced while cocaine enhanced the neurogenic contractions, indicating their adrenergic nature. Electron microscopic studies revealed uncompleted differentiation of the tunica media of the fetal portal vein into the inner circular and outer longitudinal layer. The region of the adventitio-medial border locates the external nervous plexus from which already in the fetus nerve fibers penetrate between the longitudinal and circular layer of the tunica media to constitute there inner nervous plexus. The vesicles in the nerve endings displayed the same characteristics in all the developmental types studied. The obtained results indicate a high degree of morphological and functional maturation of the adrenergic regulation of the portal vein already in the fetus at the end of the prenatal period in guinea pigs. (Fig. 9, Ref. 16.)