Effect of perivascular adipose tissue on arterial adrenergic contractions in normotensive and hypertensive rats with high fructose intake

The aim of this study was to investigate the effect of high fructose intake associated with moderate increase in adiposity on rat arterial adrenergic responses and their modulation by perivascular adipose tissue (PVAT). After eight-week-lasting substitution of drinking water with 10 % fructose solution in adult normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR), their systolic blood pressure, plasma triglycerides, and relative liver weight were elevated when compared to their respective control groups. Moreover, in SHR, body weight and relative heart weight were increased after treatment with fructose. In superior mesenteric arteries, PVAT exerted inhibitory influence on adrenergic contractile responses and this effect was markedly stronger in control WKY than in SHR. In fructose-administered WKY, arterial adrenergic contractions were substantially reduced in comparison with the control group; this was caused mainly by enhancement of anticontractile action of PVAT. The diminution of the mesenteric arterial contractions was not observed after fructose treatment in SHR. We conclude that the increase in body adiposity due to fructose overfeeding in rats might have prehypertensive effect. However, in WKY it might cause PVAT-dependent and independent reduction in arterial contractile responses to adrenergic stimuli, which could attenuate the pathological elevation in vascular tone.

Heterospecific female mimicry in Ficedula flycatchers

Mimicry is a widespread phenomenon. Vertebrate visual mimicry often operates in an intraspecific sexual context, with some males resembling conspecific females. Pied flycatcher (Ficedula hypoleuca) dorsal plumage varies from the ancestral black to female-like brown. Experimental studies have shown that conspecific and heterospecific (collared flycatcher, F. albicollis) individuals of both sexes respond, at least initially, to brown individuals as if they were female. We quantified the perceptual and biochemical differences between brown feathers and found that brown pied flycatcher males are indistinguishable from heterospecific, but not from conspecific, females in both aspects. To our knowledge, this is the first evidence of a visual mimetic signalling system in a sexual context where the model is heterospecific to the mimic. By only mimicking heterospecific females, brown pied flycatcher males can establish territories next to the more dominant collared flycatcher in sympatry, suffer less aggression by darker conspecifics in allopatry and preserve within-species sexual recognition throughout the breeding range. A closer look at the evolutionary history and ecology of these two species illustrates how such a mimetic system can evolve. Although likely rare, this phenomenon might not be unique to Ficedula flycatchers.

[Urotensin II--a newly discovered modulator of cardiovascular functions in vertebrates]

Peptide urotensin II was originally isolated from the urophysis of teleost fishes; later it was identified also in higher vertebrates in various organs and tissues, including cardiovascular structures. Since its discovery it has been considered as a highly potent vasoconstrictor inducing contraction of smooth muscle in subnanomolar concentrations. Its wide distribution as well as its high interspecies homology indicates that this peptide is involved in regulation of many important physiological functions in vertebrates. An effort to discover other possible functions of urotensin II was intensified by the identification of its G-protein coupled receptor and its identification in humans. Furthermore, altered levels of expression of urotensin II and its receptor were found in various disease states including hypertension, diabetes, heart and renal failure, in experimental animal models as well as in humans. Therefore, there is widely discussed question regarding the possible role of urotensin II in etiopathogeneses of these diseases, however the exact mechanisms are still unknown. The aim of this review is to summarize the current knowledge about urotensin II with emphasis to its direct and undirect effects in cardiovascular system.

Determinants of distribution and prevalence of avian malaria in blue tit populations across Europe: separating host and parasite effects

Although avian malarial parasites are globally distributed, the factors that affect the geographical distribution and local prevalence of different parasite lineages across host populations or species are still poorly understood. Based on the intense screening of avian malarial parasites in nine European blue tit populations, we studied whether distribution ranges as well as local adaptation, host specialization and phylogenetic relationships can determine the observed prevalences within populations. We found that prevalence differed consistently between parasite lineages and host populations, indicating that the transmission success of parasites is lineage specific but is partly shaped by locality-specific effects. We also found that the lineage-specific estimate of prevalence was related to the distribution range of parasites: lineages found in more host populations were generally more prevalent within these populations. Additionally, parasites with high prevalence that were also widely distributed among blue tit populations were also found to infect more host species. These findings suggest that parasites reaching high local prevalence can also realize wide distribution at a global scale that can have further consequences for host specialization. Although phylogenetic relationships among parasites did not predict prevalence, we detected a close match between a tree based on the geographic distance of the host populations and the parasite phylogenetic tree, implying that neighbouring host populations shared a related parasite fauna.

[Programming of cardiovascular phenotype by pharmacological intervention in early developmental stages: prevention of hypertension]

Cardiovascular diseases, including hypertension, represent serious medical and social problem because they affect many people in industrialized countries in the world and, unfortunately, their incidence has not decreasing tendency. Human essential hypertension is a chronic, slowly developing disease, which is a consequence of abnormalities in the development of cardiovascular system and its regulation, which are subsequently reflected in pathological rise of blood pressure. In general, blood pressure increases slowly and gradually and this may last several years. Myocardial hypertrophy and structural alterations of the vessel system frequently occur. As hypertension is already established, then complete normalization of blood pressure is difficult to obtain. Therefore, it is necessary to focus on its prevention, this means, to intervene before blood pressure elevation in individuals with significant genetic predisposition to this disease. Moreover, it is well known that cardiovascular system of the young organism is very sensitive to various environmental influences, and one can expect that it may also be more susceptible to vasoactive substances in prevention and treatment of cardiovascular diseases. Hypertension and its pharmacological treatment should therefore be studied with regard to the maturity of an individual. In accordance with the hypothesis of developmental plasticity of organisms, it may be possible (by pharmacological intervention in early ontogenetic stages of predisposed individual) to achieve such a setting of structural and functional parameters which could reduce the subsequent clinical manifestation of genetically induced hypertensive state.

Participation of nitric oxide in different models of experimental hypertension

This review concerns the role of nitric oxide (NO) in the pathogenesis of different models of experimental hypertension (NO-deficient, genetic, salt-dependent), which are characterized by a wide range of etiology. Although the contribution of NO may vary between different models of hypertension, a unifying characteristic of these models is the presence of oxidative stress that participates in the maintenance of elevated arterial pressure and seems to be a common denominator underlying endothelial dysfunction in various forms of experimental hypertension. Besides the imbalance between the endothelial production of vasorelaxing and vasoconstricting compounds as well as the relative insufficiency of vasodilator systems to compensate augmented vasoconstrictor systems, there were found numerous structural and functional abnormalities in blood vessels and heart of hypertensive animals. The administration of antihypertensive drugs, antioxidants and NO donors is capable to attenuate blood pressure elevation and to improve morphological and functional changes of cardiovascular system in some but not all hypertensive models. The failure to correct spontaneous hypertension by NO donor administration reflects the fact that sympathetic overactivity plays a key role in this form of hypertension, while NO production in spontaneously hypertensive rats might be enhanced to compensate increased blood pressure. A special attention should be paid to the modulation of sympathetic nervous activity in central and peripheral nervous system. These results extend our knowledge on the control of the balance between NO and reactive oxygen species production and are likely to be a basis for the development of new approaches to the therapy of diseases associated with NO deficiency.

Effect of chronic nifedipine treatment on blood pressure and adrenergic responses of isolated mesenteric artery in young rats with developing spontaneous hypertension

It is documented that in chronic hypertensive state there is an increased vasodepressor response to calcium channel antagonists such as the dihydropyridine derivate nifedipine. This effect is generally proportional to initial blood pressure as was demonstrated in several models of experimental hypertension. In the present study we investigated the effect of chronic nifedipine treatment on the development of cardiovascular system in young spontaneously hypertensive rats (SHR) in order to evaluate whether it could prevent the abnormalities leading to hypertensive state. Four- and eight-week-old rats were treated with nifedipine (50 mg/kg/day) for 4 weeks. Blood pressure of nifedipine-treated SHR remained at the initial level in contrast to their untreated controls where it continued to increase. In both age groups, chronic nifedipine administration reduced neurogenic contractions of isolated superior mesenteric artery, but did not significantly affect the dose-response curve to exogenous noradrenaline in 8-week-old rats. In contrast, maximum response to noradrenaline was significantly attenuated in mesenteric artery of 12-week-old nifedipine-treated SHR. We can presume that the antihypertensive effect of nifedipine is similar in both stages of spontaneous hypertension development, but the mechanisms involved might be different. It seems that chronic reduction of calcium influx during the rapid phase of pathological blood pressure increase in SHR may eliminate the effect of enhanced sympathetic tone, which may have unfavorable consequences on cardiovascular structure and function.

Inactivation of G(i) proteins by pertussis toxin diminishes the effectiveness of adrenergic stimuli in conduit arteries from spontaneously hypertensive rats

Treatment with pertussis toxin (PTX) which eliminates the activity of G(i) proteins effectively reduces blood pressure (BP) and vascular resistance in spontaneously hypertensive rats (SHR). In this study we have compared the functional characteristics of isolated arteries from SHR with and without PTX-treatment (10 microg/kg i.v., 48 h before the experiment). Rings of thoracic aorta, superior mesenteric artery and main pulmonary artery were studied under isometric conditions to measure the reactivity of these vessels to receptor agonists and to transmural electrical stimuli. We have found that the treatment of SHR with PTX had no effect on endothelium-dependent relaxation of thoracic aorta induced by acetylcholine. In PTX-treated SHR, the maximum contraction of mesenteric artery to exogenous noradrenaline was reduced and the dose-response curve to cumulative concentration of noradrenaline was shifted to the right. Similarly, a reduction in the magnitude of neurogenic contractions elicited by electrical stimulation of perivascular nerves was observed in the mesenteric artery from PTX-treated SHR. PTX treatment of SHR also abolished the potentiating effect of angiotensin II on neurogenic contractions of the main pulmonary artery. These results indicate that PTX treatment markedly diminishes the effectiveness of adrenergic stimuli in vasculature of SHR. This could importantly affect BP regulation in genetic hypertension.

Comparison of the effect of simvastatin, spironolactone and L-arginine on endothelial function of aorta in hereditary hypertriglyceridemic rats

Hereditary hypertriglyceridemic (hHTG) rats are characterized by increased blood pressure and impaired endothelium-dependent relaxation of conduit arteries. The aim of this study was to investigate the effect of long-term (4 weeks) treatment of hHTG rats with three drugs which, according to their mechanism of action, may be able to modify the endothelial function: simvastatin (an inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase), spironolactone (an antagonist of aldosterone receptors) and L-arginine (a precursor of nitric oxide formation). At the end of fourth week the systolic blood pressure in the control hHTG group was 148+/-2 mm Hg and in control normotensive Wistar group 117+/-3 mm Hg. L-arginine failed to reduce blood pressure, but simvastatin (118+/-1 mm Hg) and spironolactone (124+/-4 mm Hg) treatment significantly decreased the systolic blood pressure. In isolated phenylephrine-precontracted aortic rings from hHTG rats endothelium-dependent relaxation was diminished as compared to control Wistar rats. Of the three drugs used, only simvastatin improved acetylcholine-induced relaxation of the aorta. We conclude that both simvastatin and spironolactone reduced blood pressure but only simvastatin significantly improved endothelial dysfunction of aorta. Prominent increase in the expression of eNOS in large conduit arteries may be the pathophysiological mechanism underlying the protective effect of simvastatin in hHTG rats.

Functional and structural pattern of arterial responses in hereditary hypertriglyceridemic and spontaneously hypertensive rats in early stage of experimental hypertension

It has been shown that endothelium-derived nitric oxide (NO) plays an important role in regulation of vascular tone in the prenatal and early postnatal period. The aim of this paper was to determine the reactivity and accompanying structural changes in thoracic aorta from 4-week-old spontaneously hypertensive rats (SHR) and rats with hereditary hypertriglyceridemia (hHTG) in comparison with age-matched normotensive controls. For functional studies thoracic aorta was excised, cut into rings and mounted in organ baths for measurement of isometric contractile force. For morphological studies cardiovascular system of rats was perfused with glutaraldehyde fixative (at 100 mm Hg) via cannula placed in the left ventricle. Morphological changes of thoracic aorta were measured using light microscopy. Systolic blood pressure (SBP) in SHR (98+/-1 mm Hg) did not significantly differ from that of age-matched control rats (95+/-4 mm Hg), but was slightly increased in hHTG rats (110+/-2 mm Hg, P<0.05). Heart weight/body weight ratio was higher in SHR and hHTG rats than in control group indicating the hypertrophy of the heart in both models of hypertension. Endothelium-dependent relaxation of aorta induced by acetylcholine was preserved in all groups and did not differ from that in control normotensive rats. The maximal isometric contraction of thoracic aorta to noradrenaline (NA) was reduced in hypertensive groups and the concentration-response curves to NA were shifted to the right indicating increased sensitivity of smooth muscle to NA. The values of wall thickness and cross sectional area as well as inner diameter of thoracic aorta in SHR and hHTG rats were significantly decreased in comparison to control groups. Endothelial dysfunction seems to be absent in all young rats before development of hypertension. In conclusion, our observations indicate that in early stage of experimental hypertension NO-dependent relaxation is preserved so that putative impairment of this function provides no significant pathogenic contribution to the onset of hypertension in these two experimental models.

Hereditary hypertriglyceridemic rat: a suitable model of cardiovascular disease and metabolic syndrome?

Hypertriglyceridemia and hypertension seem to be very important cardiovascular risk factors. The Prague hereditary hypertriglyceridemic (hHTG) rat was developed as a model of human hypertriglyceridemia. It was demonstrated that these rats are not obese, they are hypertensive and insulin resistant and they have some disturbances in glucose metabolism. Several QTLs were identified for blood pressure, its particular components (dependent on major vasoactive systems) and plasma triglycerides throughout the genome of hHTG rats by using of F(2) hybrids strategy. It is evident that hHTG rats are a suitable model for the study of metabolic disturbances in relation to blood pressure as well as for the search of genetic determinants of these abnormalities. Numerous abnormalities of blood pressure regulation as well as alterations in the structure and function of cardiovascular apparatus (heart, conduit and resistance arteries) were found in hHTG rats. A special attention was paid to possible changes in the efficiency of various vasoactive systems such as nitric oxide, renin-angiotensin-aldosterone system and sympathetic nervous system, which seem to contribute substantially to cardiovascular and/or metabolic abnormalities observed in Prague hereditary hypertriglyceridemic rats.

Shear zones in granular materials: optimization in a self-organized random potential

We introduce a model to describe the wide shear zones observed in modified Couette cell experiments with granular material. The model is a generalization of the recently proposed approach based on a variational principle. The instantaneous shear band is identified with the surface that minimizes the dissipation in a random potential that is biased by the local velocity difference and pressure. The apparent shear zone is the ensemble average of the instantaneous shear bands. The numerical simulation of this model matches excellently with experiments and has measurable predictions.

Critical packing in granular shear bands

In a realistic three-dimensional setup, we simulate the slow deformation of idealized granular media composed of spheres undergoing an axisymmetric triaxial shear test. We follow the self-organization of the spontaneous strain localization process leading to a shear band and demonstrate the existence of a critical packing density inside this failure zone. The asymptotic criticality arising from the dynamic equilibrium of dilation and compaction is found to be restricted to the shear band, while the density outside of it keeps the memory of the initial packing. The critical density of the shear band depends on friction (and grain geometry) and in the limit of infinite friction it defines a specific packing state, namely the dynamic random loose packing.

Effects of environmental temperature on thyroid hormones in the barn owl (Tyto alba)

The basic patterns of thyroid hormones [thyroxine (T4) and 3,3',5-triiodothyronine (T3)] and the T4 and T3 responses induced by thyrotropin releasing hormone (TRH) are reported in captive female barn owls (Tyto alba) during the non-breeding period. The main findings of the study, conducted on a total of 10 owls, are as follow: (1) The thyroid gland of barn owl can be stimulated by the classical TRH stimulation test. (2) T3 response was much more pronounced both under cold (around 10 degrees C) and warm (around 20 degrees C) conditions, whereas T4 response ranged so widely that we could not point out any significant change in it. (3) Basal T3 plasma level was significantly (p = 0.036) higher in birds exposed to cold temperature, and they responded to TRH treatment with a lower plasma T3 elevation than the birds kept in a warm chamber. This pattern, however, cannot be explained by increased food intake, but is in agreement with the fact that enhanced T3 level may account for higher avUCP mRNA expression, which results in higher heat production on the cell level. From the results it is concluded that altering T3 plasma level plays a significant role in cold-induced thermoregulation.

Morphologies of three-dimensional shear bands in granular media

We present numerical results on spontaneous symmetry breaking strain localization in axisymmetric triaxial shear tests of granular materials. We simulated shear band formation using the three-dimensional distinct element method with spherical particles. We demonstrate that the local shear intensity, the angular velocity of the grains, the coordination number, and the local void ratio are correlated and any of them can be used to identify shear bands; however, the latter two are less sensitive. The calculated shear band morphologies are in good agreement with those found experimentally. We show that boundary conditions play an important role. We discuss the formation mechanism of shear bands in the light of our observations and compare the results with experiments. At large strains, with enforced symmetry, we found strain hardening.

Rapid temporal change in the expression and age-related information content of a sexually selected trait

The expression of sexual signals is often phenotypically plastic and also evolves rapidly. Few studies have considered the possibility that proximate determination -- the pathway between genes and trait expression -- may also be subject to both phenotypic plasticity and evolutionary change. We examined long-term patterns in size, condition- and age-dependence, repeatability and heritability of forehead patch size, a sexually selected plumage trait in male collared flycatchers. We also estimated survival and sexual selection on the phenotypic value of the trait. Forehead patch size linearly declined during the 15 years, probably due to the significantly negative survival selection. In addition, the expression of genetic variation for the ornament apparently underwent an age-limited change, which implies a change in the information content of the signal to receivers. The persistent lack of condition-dependence makes phenotypic plasticity an unlikely explanation to our results. This raises the possibility of a microevolutionary change of both expression and proximate determination during the study period.

Flycatcher song in allopatry and sympatry--convergence, divergence and reinforcement

The theory of reinforcement predicts that natural selection against the production of unfit hybrids favours traits that increase assortative mating. Whether culturally inherited traits, such as bird song, can increase assortative mating by reinforcement is largely unknown. We compared songs of pied (Ficedula hypoleuca) and collared flycatchers (F. albicollis) from two hybrid zones of different ages with songs from allopatric populations. Previously, a character divergence in male plumage traits has been shown to reinforce premating isolation in sympatric flycatchers. In contrast, we find that the song of the pied flycatcher has converged towards that of the collared flycatcher (mixed singing). However, a corresponding divergence in the collared flycatcher shows that the species differences in song characters are maintained in sympatry. Genetic analyses suggest that mixed song is not caused by introgression from the collared flycatcher, but rather due to heterospecific copying. Circumstantial evidence suggests that mixed song may increase the rate of maladaptive hybridization. In the oldest hybrid zone where reinforcement on plumage traits is most pronounced, the frequency of mixed singing and hybridization is also lowest. Thus, we suggest that reinforcement has reduced the frequency of mixed singing in the pied flycatcher and caused a divergence in the song of the collared flycatcher. Whether a culturally inherited trait promotes or opposes speciation in sympatry may depend on its plasticity. The degree of plasticity may be genetically determined and accordingly under selection by reinforcement.

Shear band formation in granular media as a variational problem

Strain in sheared dense granular material is often localized in a narrow region called the shear band. Recent experiments in a modified Couette cell provided localized shear flow in the bulk away from the confining walls. The nontrivial shape of the shear band was measured as the function of the cell geometry. First, we present a geometric argument for narrow shear bands that connects the function of their surface position with the shape in the bulk. Assuming a simple dissipation mechanism, we show that the principle of minimum dissipation of energy provides a good description of the shape function. Furthermore, we discuss the possibility and behavior of shear bands that are detached from the free surface and are entirely covered in the bulk.

Hypotensive effect of agmatine, arginine metabolite, is affected by NO synthase

The metabolites of arginine were recently shown to be involved in cardiovascular control. The study addresses the general cardiovascular response of anaesthetized rats to agmatine, a decarboxylated arginine. The relation between two arginine metabolic pathways governed by arginine decarboxylase and nitric oxide synthase was investigated. Intravenous administration of agmatine 30 and 60 microM/0.1 ml saline elicited remarkable hypotension of 42.6+/-4.6 and 70.9+/-6.5 mm Hg, respectively. The hypotension was characterized by long duration with half-time of return 171.6+/-2.9 and 229.2+/-3.8 s, respectively. The time of total blood pressure BP recovery was about 10 min. Dose-dependent relaxation to agmatine was also found in aorta rings in vitro. Both doses of agmatine administered 60-180 min after NO synthase inhibition L-NAME 40 mg/kg i.v. caused greater hypotension 59.0+/-7.6 and 95.8 8.8 mm Hg P<0.01 both compared to animals with intact NO synthase, but this was accompanied by a significant shortening of the half-time of BP return. If agmatine was administered to hypertensive NO-deficient rats treated with 40 mg/kg/day L-NAME for 4 weeks, similar significant enhancement of hypotension was observed at both agmatine doses, again with a significant shortening of half-time of BP return. It can be summarized that the long-lasting hypotension elicited by agmatine was amplified after acute or chronic NO synthase inhibition, indicating a feedback relation between the two metabolic pathways of arginine.

Hypotensive effect of agmatine, arginine metabolite, is affected by NO synthase

The metabolites of arginine were recently shown to be involved in cardiovascular control. The study addresses the general cardiovascular response of anaesthetized rats to agmatine, a decarboxylated arginine. The relation between two arginine metabolic pathways governed by arginine decarboxylase and nitric oxide synthase was investigated. Intravenous administration of agmatine 30 and 60 μM/0.1 ml saline elicited remarkable hypotension of 42.6±4.6 and 70.9±6.5 mm Hg, respectively. The hypotension was characterized by long duration with half-time of return 171.6±2.9 and 229.23.8 s, respectively. The time of total blood pressure BP recovery was about 10 min. Dose-dependent relaxation to agmatine was also found in aorta rings in vitro. Both doses of agmatine administered 60-180 min after NO synthase inhibition L-NAME 40 mg/kg i.v. caused greater hypotension 59.0±7.6 and 95.8±8.8 mm Hg P<0.01 both compared to animals with intact NO synthase, but this was accompanied by a significant shortening of the half-time of BP return. If agmatine was administered to hypertensive NO-deficient rats treated with 40 mg/kg/day L-NAME for 4 weeks, similar significant enhancement of hypotension was observed at both agmatine doses, again with a significant shortening of half-time of BP return. It can be summarized that the long-lasting hypotension elicited by agmatine was amplified after acute or chronic NO synthase inhibition, indicating a feedback relation between the two metabolic pathways of arginine.

Cardiovascular system of offsprings of hypertensive rats with defective nitric oxide production

The question was addressed of how nitric oxide synthase (NO synthase) inhibition-induced hypertension in rat parents would affect the cardiovascular system in their offsprings. Two experimental groups were set up: Group I -- offsprings of parents who had both been administered NO synthase inhibitor L-nitro-arginine methyl ester (L-NAME 40 mg/kg/day) for 5 weeks, the treatment of dams continued till week 12. Group II -- offsprings fed by dams administered L-NAME after delivery only for a period of 4 weeks. Control age-matched offsprings formed the third group. Blood pressure and heart rate in parents and in 3-week-old offsprings were determined noninvasively. In the offsprings, body and heart weight were measured and the heart/body weight ratio (HW/BW) was calculated. The NO synthase activity, and also ornithine decarboxylase activity as a marker of polyamine production, were determined in the heart. The acetylcholine-induced relaxation of aortic rings was also followed. A marked blood pressure increase with a tendency to a decreased heart rate was found in the offsprings of Group I. A significant decrease in heart weight and body weight with a decreased HW/BW ratio indicated cardiac hypotrophy that contrasted with the decrease in NO synthase activity and increase in ornithine decarboxylase activity in the heart. Noteworthy was also the finding of completely preserved relaxation of the aorta to acetylcholine. Offsprings of Group II were similarly characterized by significantly higher blood pressure, a tendency to decreased heart rate, a decrease in heart weight, but not of the HW/BW ratio. The contrasting findings of heart weight decrease on the one hand and NO synthase activity decrease and ornithine decarboxylase increase on the other, were also found in this group. Full relaxation of the aorta to acetylcholine was preserved. It can be concluded that remarkable alterations in the cardiovascular system were found in offsprings of hypertensive NO compromised parents.

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.)