Biomedical subjects

A Parent

Publications and source records attributed to A Parent.

At least 145 records · Page 8Linked to original sources

PubMed1991

Receptors for Arg8-vasopressin, angiotensin II, and atrial natriuretic peptide in the mesenteric vasculature of pregnant rats.

Blood pressure and sensitivity of blood vessels to vasoconstrictors are decreased in term-pregnant rats (20-21 days). To determine if changes in receptors for vasoactive peptides could account for these observations, receptor kinetics were measured for Arg8-vasopressin (AVP), angiotensin II (Ang II), and atrial natriuretic peptide (ANP) in the mesenteric vascular bed of the rat throughout pregnancy. Receptors for AVP were statistically similar in the five groups of animals (nonpregnant; pregnant 9, 15, and 21 days; and postpartum). The dissociation constant (KD) for [3H]AVP varied from 0.41 to 0.52 nmol/L (NS), while receptor density (Bmax) varied from 310 +/- 110 to 455 +/- 135 fmol/mg protein for six experimental measurements. Similar observations were made for Ang II receptors where KD of 125I-labelled Sar1, Ile8-Ang II was between 0.60 and 0.97 nmol/L and Bmax between 215 +/- 30 and 250 +/- 40 fmol/mg protein in the different groups. 125I-labelled ANP (101-126) receptors were markedly modified in terms of number of sites. Bmax was significantly increased during pregnancy (9 days, 429 +/- 86; 15 days, 541 +/- 54; 20 days, 438 +/- 72) and decreased in the postpartum period (133 +/- 21) by comparison with the nonpregnant group (245 +/- 35 fmol/mg protein), while KD was similar in the different experimental groups (57 to 82 pmol/L). Despite these increases in receptor density, the vasorelaxant effects of ANP was only increased at 9 days of pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗

PubMed1990

Substantia nigra pars reticulata projects to the reticular thalamic nucleus of the cat: a morphological and electrophysiological study.

The projections of substantia nigra pars reticulata (SNr) toward the reticular (RE) thalamic complex of cat were studied morphologically and electrophysiologically. Numerous SNr cells were retrogradely labeled following injections of horseradish peroxidase conjugated to wheat-germ agglutinin (WGA-HRP) in the rostral and rostrolateral part of the RE thalamic nucleus. Iontophoretic injections of Phaseolus vulgaris leucoagglutinin (PHA-L) in the SNr confirmed that this retrograde labeling was not a consequence of tracer diffusion in neighboring structures, but reflected a genuine SNr projection to the RE thalamic nucleus. Indeed, widely branched and varicose PHA-L-positive fibers were found in the rostral and rostrolateral pole of the RE thalamic nucleus following PHA-L injections in the SNr. Furthermore, in agreement with previous data indicating that nigrothalamic cells are GABAergic, electrical stimulation of the SNr evoked a short-latency inhibitory effect acting on both spontaneous and cortically-evoked discharges of most RE thalamic neurons. These results are discussed in light of the possible role of the SNr and RE thalamic complex in attentional processes.

Action Potentials↗

PubMed1990

Evidence for interconnections between the two segments of the globus pallidus in primates: a PHA-L anterograde tracing study.

Small injections of the lectin Phaseolus vulgaris-leucoagglutinin (PHA-L) in the external segment of the pallidum (GPe) in the squirrel monkey (Saimiri sciureus) and in the rhesus monkey (Macaca mulatta) led to anterograde labeling of fibers in the internal segment of the pallidum (GPi). These fibers formed numerous large varicosities reminiscent of terminal boutons, which closely surrounded GPi cell bodies and primary dendrites. Conversely, PHA-L injections in the GPi of squirrel monkeys produced anterograde fiber labeling in the GPe. However, in contrast to fibers in GPi, those in GPe did not make prominent pericellular contacts. Instead, they displayed a rather linear course, had long intervaricose segments, and appeared to contact several GPe neurons along their course by close appositions on cell bodies and primary dendrites. These results suggest the existence of a reciprocal connection between the two pallidal segments, which may play a crucial role in the functional organization of the basal ganglia in primates.

Animals↗

PubMed1990

Immunohistochemical study of the serotoninergic innervation of the basal ganglia in the squirrel monkey.

A specific antibody raised against 5-hydroxytryptamine (5-HT) conjugated to bovine serum albumin was used to study the serotoninergic innervation of the basal ganglia in the squirrel monkey (Saimiri sciureus). At midbrain level, numerous fine 5-HT-immunoreactive axons were seen to arise from the immunopositive neurons of the dorsal raphe nucleus and less abundantly from those of the nucleus centralis superior. The bulk of these axons formed a rather loosely arranged bundle that arched ventrorostrally through the central portion of the midbrain tegmentum and ascended toward the ventral tegmental area. Several fascicles detached themselves from this bundle to reach the substantia nigra where they arborized into a multitude of heterogeneously distributed 5-HT terminals. The 5-HT innervation was particularly dense in the pars reticulata but much less so in the pars compacta of the substantia nigra. More rostrally other 5-HT fibers swept dorsolaterally and formed a remarkably dense network of varicose fibers within the subthalamic nucleus. A multitude of 5-HT axons continued their ascending course within the lateral hypothalamic area, and many of them swept laterally to invade the lenticular nucleus. At pallidal levels, the 5-HT axons arborized much less profusely in the external segment than in the internal segment, which contained numerous 5-HT varicose fibers and terminals arranged in a typical bandlike pattern. At striatal levels, the 5-HT terminals were particularly abundant in the ventral striatum, including the nucleus accumbens and deep layers of the olfactory tubercle. They also abounded in the ventrolateral region of the putamen and the ventromedial aspect of the caudate nucleus. Overall, the number of 5-HT fibers and terminals decreased progressively along the rostrocaudal axis of the striatum and several large and elongated zones rather devoid of 5-HT immunoreactivity were visualized, particularly in the caudate nucleus and the dorsal putamen. These zones of poor 5-HT immunoreactivity were in register with similar areas devoid of tyrosine hydroxylase immunoreactivity as seen on contiguous sections. These findings reveal that all the core structures of the basal ganglia in primates receive a significant serotoninergic input, but that the densities and patterns of innervation vary markedly from one structure to the other.

Afferent Pathways↗

PubMed1990

Efferent projections of the subthalamic nucleus in the squirrel monkey as studied by the PHA-L anterograde tracing method.

The organization of the efferent connections of the subthalamic nucleus was studied in the squirrel monkey (Saimiri sciureus) by using the lectin Phaseolus vulgaris-leucoagglutinin (PHA-L) as an anterograde tracer. At the level of the basal forebrain, anterogradely labeled fibers and axon terminals were mostly found in the striatopallidal complex and the substantia innominata. In cases in which the PHA-L injection sites were placed in the central or the lateral third of the subthalamic nucleus, numerous anterogradely labeled fibers were seen to arise from the injection loci and innervate massively the globus pallidus. At pallidal levels the fibers formed bands lying parallel and adjacent to the medullary laminae. The number and the complexity of the topographical organization of these bands varied with the size and the location of the PHA-L injection site. When examined at a higher magnification, the bands of subthalamopallidal fibers appeared as rich plexuses of short axon collaterals with small bulbous enlargements that closely surrounded the cell bodies and primary dendrites of pallidal cells. In contrast, PHA-L injection involving the medial tip of the subthalamic nucleus did not produce bandlike fiber patterns in the globus pallidus. Instead, the labeled fibers formed a diffuse plexus occupying the ventral part of the rostral pole of the globus pallidus as well as the subcommissural pallidal region. The substantia innominata contained a moderate number of labeled fibers and axon terminals following injection of PHA-L in the medial tip of the subthalamic nucleus. A small to moderate number of anterogradely labeled fibers were seen in the putamen after all PHA-L injections. These subthalamostriatal fibers were long, linear, and branched infrequently. At midbrain level the substantia nigra contained a significant number of anterogradely labeled fibers and axon terminals following PHA-L injection in the subthalamic nucleus. The subthalamonigral fibers descended along the ventromedial part of the cerebral peduncle and swept laterally to reach their target. Most of these fibers formed small plexuses along the base of the pars reticulata, whereas a few others ascended along the cell columns of the pars compacta that impinged deeply within the pars reticulata. More caudally in the brainstem, a small number of fibers occurred in the area of the pedunculopontine nucleus and in the periaqueductal gray. These findings indicate that besides its well-known connection with the pallidum, the subthalamic nucleus gives rise to widespread projections to other components of the basal ganglia in primates.

Animals↗

PubMed1990

The centre médian and parafascicular thalamic nuclei project respectively to the sensorimotor and associative-limbic striatal territories in the squirrel monkey.

The striatal projections of the centre médian (CM) and parafascicular (Pf) thalamic nuclei were examined in the squirrel monkey (Saimiri sciureus) by using the lectin wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) as an anterograde tracer. CM was found to project massively to the putamen, where terminal fields appeared principally in the form of oblique bands, and more diffusely to the dorsolateral border of the caudate nucleus. Striatal inputs from Pf were found more rostrally, especially in the ventromedial portion of the putamen, the entire ventromedial half of the caudate nucleus, and the ventral striatum including the nucleus accumbens and the olfactory tubercle. Pf terminal fields in the rostral striatum often displayed a patchy organization. Both CM and Pf projections were found to terminate in the matrix compartment of the striatum as defined by acetylcholinesterase staining. These results suggest that CM is more specifically involved in sensorimotor and Pf in associative and limbic aspects of basal ganglia function in primates.

Animals↗

PubMed1990

The compartmentalization of the monkey and rat cerebellar cortex: zebrin I and cytochrome oxidase.

The cerebellar cortex of mammals is composed of parasagittal zones that encompass the afferent inputs, the efferent corticonuclear and corticovestibular projections, and a number of intrinsic molecular markers. One such marker is the polypeptide antigen zebrin I that is recognized by monoclonal antibody (mab) Q113. In rodents, zebrin I immunocytochemistry reveals an array of parasagittal Purkinje cell compartments. In the present study, zebrin I has been used to reveal the molecular heterogeneity of the cerebellar cortex in the squirrel monkey (Saimiri sciureus). As in rodents, zebrin I is Purkinje cell specific in the primate cerebellum and not all Purkinje cells are immunoreactive. Immunocytochemistry on frontal or horizontal sections reveals a system of bands of zebrin I+ cells extending through the vermis of both anterior and posterior lobes. A midline (P1+) band and two more lateral bands (P2+ and P3+) are found in all lobules. The situation in the paravermis and hemispheres is similar, with alternating zebrin I+ and zebrin I- compartments, but the complex lobulation obscures the precise band pattern: it seems probable that 4 additional bands are present in the hemispheres, as in rodents. Comparison of rat and monkey cerebellums suggests that the cortex has expanded in primates by the growth of the same individual bands found in rats rather than by the addition of supplementary compartments. The zebrin I compartmentalization revealed by using mab Q113 is reproducible from individual and thus provides a stable frame of reference that has been used to compare the different chemoarchitectonic patterns found in the cerebellar cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Extrinsic connections of the basal ganglia.

Recent neuroanatomical studies undertaken with various powerful neural tracing methods have radically changed our concept of the organization of the basal ganglia. This paper briefly reviews some of the findings that have led to the conclusion that the major components of the basal ganglia can no longer be considered as single undifferentiated entities. Instead, each of these structures is characterized by several distinct afferent and efferent chemospecific subsystems by which they can modulate and convey the multifarious information that flows through the basal ganglia. This paper focuses mainly on data obtained in primates, but also stresses the importance of comparison with non-primate species.

Animals↗

PubMed1990

The monoaminergic innervation of the amygdala in the squirrel monkey: an immunohistochemical study.

The monoaminergic innervation of the amygdala of the squirrel monkey (Saimiri sciureus) was studied by using immunohistochemical methods with primary antisera raised against serotonin, and the catecholamine synthesizing enzymes tyrosine hydroxylase, dopamine-beta-hydroxylase and phenylethanolamine-N-methyltransferase. Serotonin was widely distributed within the amygdala including profuse terminal labeling in central, basolateral and cortical nuclear groups. The accessory basal and medial nuclei were the only two areas receiving relatively poor serotoninergic innervation. Tyrosine hydroxylase was more discretely distributed, with very dense to moderate terminal labeling in central, basal and lateral nuclei, but only scant labeling within accessory basal and corticomedial nuclei, except at the cortical transitional area where dense terminal labeling was noted. Dopamine-beta-hydroxylase immunoreactivity was moderate in central and corticomedial nuclei, but comparatively light in other nuclear groups. Phenylethanolamine-N-methyltransferase was only sparsely distributed in the amygdala. The findings of the present study reveal that the monoaminergic innervation of the primate amygdala is similar to that reported in rodents, although some conspicuous exceptions do exist. Whereas the noradrenergic and serotoninergic neuronal systems ramify profusely within the amygdala, the dopaminergic system appears to be more discretely and topographically organized.

Amygdala↗

PubMed1990

Role of the endothelium in adrenergic responses of mesenteric artery rings of pregnant rats.

Responses to adrenergic agents were measured on rings of mesenteric, artery of nonpregnant and pregnant rats at 21 days' gestation. In tissues from pregnant rats, norepinephrine, and phenylephrine were less sensitive than in rings from nonpregnant animals; maximum responses were not affected. The effect of isoproterenol was not modified in tissues from pregnant rats. The presence of endothelium in tissue rings was evaluated as fractional relaxation to acetylcholine. Sensitivity to phenylephrine and norepinephrine was inversely related to the effect of acetylcholine. This relationship was similar in slope in both groups but different in intercept. The sensitivity to isoproterenol was directly related to the presence of endothelium (curves similar in both slope and intercept). This demonstrates that the responses of mesenteric artery rings depends on the presence of endothelium. Furthermore, vascular endothelium is not involved in the blunted responses to adrenergic vasoconstrictor during pregnancy.

Animals↗

PubMed1990

The dopaminergic nigropallidal projection in primates: distinct cellular origin and relative sparing in MPTP-treated monkeys.

In summary, our findings revealed the existence in primates of a dopaminergic pallidal projection that arises from neurons of the substantia nigra-ventral tegmental area complex and terminates preferentially in the internal pallidum. This projection is largely distinct from the nigrostriatal dopaminergic pathway and appears to be relatively spared in parkinsonian monkeys. Thus, in addition to their potent influence at striatal levels, the midbrain dopaminergic neurons may directly modulate the activity of basal ganglia output neurons at pallidal levels.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1990

[Anatomo-physiologic substratum of akinesia in primates].

Severe akinesia can be observed in macaques following MPTP injections destroying dopaminergic nigrostriatal neurons. Akinesia also results from inhalation of toxic substances inducing bilateral lesions of the two pallidal nuclei and of the pars reticulata of the substantia nigra, and not of the pars compacta. Most of the recent studies of the anatomo-physiological substratum of akinesia used MPTP injections. Deoxyglucose studies have shown a clear increase in the neuronal activity of the medial nucleus of the pallidum and of its thalamic projection territory. Electrophysiological studies have shown a major modification of the spontaneous activity of medial pallidal neurons which is influenced in an excessive and non selective manner by sensorimotor inputs. Analysis of the relative three dimensional geometry of nervous arborizations have shown that the striato-pallido-nigral system is extremely convergent. Akinesia consecutive to nigrostriate lesions could be linked to an excessive and anarchic activation of this system. The contradiction which exists between akinesia with an abnormal activity of the medial pallidum and akinesia with bilateral pallidal lesions could only be apparent if akinesia was linked to the ineffective emission or to the interruption of messages to the thalamus.

Animals↗

PubMed1989

Neuronal activity of identified posterior hypothalamic neurons projecting to the brainstem peribrachial area of the cat.

Following horseradish peroxidase injections in the brainstem peribrachial (PB) area, massive retrograde labeling was found in the posterior hypothalamic region. Single-unit recordings posterior hypothalamic neurons with antidromically identified projections to the PB area revealed that these neurons have higher firing rates in waking than in slow-wave sleep and dissimilar discharge patterns as compared with intralaminar thalamic neurons. The results are discussed in the context of reciprocal hypothalamo-brainstem circuits.

Action Potentials↗

PubMed1989

Dopaminergic innervation of the basal ganglia in the squirrel monkey as revealed by tyrosine hydroxylase immunohistochemistry.

The organization of the dopaminergic mesostriatal fibers and their patterns of innervation of the basal ganglia in the squirrel monkey (Saimiri sciureus) were studied immunohistochemically with an antiserum raised against tyrosine hydroxylase (TH). Numerous fibers arose from midbrain TH-positive cell bodies of the substantia nigra pars compacta (group A9), the retrorubral area (group A8), and the lateral portion of the ventral tegmental area (group A10). These fibers accumulated dorsomedially to the rostral pole of the substantia nigra where they formed a massive bundle that coursed through the prerubral field and ascended along the laterodorsal aspect of the medial fore-brain bundle in the lateral hypothalamus. Some ventrally located fibers ran throughout the rostrocaudal extent of the lateral preopticohypothalamic area and could be followed up to the olfactory tubercle, whereas other fibers turned laterodorsally to invade the head of the caudate nucleus. At more dorsal levels in the lateral hypothalamus, many fiber fascicles detached themselves from the main bundle and swept laterally to reach the globus pallidus, the putamen, and the amygdala. Several TH-positive fibers coursed along the dorsal surface of the subthalamic nucleus, and some invaded the dorsomedial third of this structure. The remaining portion of the subthalamic nucleus contained relatively few TH-positive elements. In contrast, the globus pallidus received a dense dopaminergic innervation deriving mostly from two fascicles that coursed backward along the two major output pathways of the pallidum: the lenticular fasciculus caudodorsally and the ansa lenticularis rostroventrally. At the pallidal level, the labeled fibres merged within the medullary laminae and arborized profusely in the internal pallidal segment and less abundantly in the external pallidal segment. However, the caudoventral portion of the external pallidum displayed a dense field of TH-positive axonal varicosities. Other fibers ran through the dorsal two-thirds of the external pallidum en route to the putamen. The striatum contained a multitude of thin axonal varicosities among which a few long and varicosed fibers were scattered. These immunoreactive neuronal profiles were rather uniformly distributed along the rostrocaudal extent of the striatum but appeared slightly more numerous in the ventral striatum than in the dorsal striatum. The pattern of distribution of the TH-positive axonal varicosities in the dorsal striatum was markedly heterogeneous: it consisted of typical zones of poor TH immunoreactivity lying within a matrix of dense terminal labeling.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1989

Complementation of in vitro-assembled spliceosomes.

We describe the development and application of a system of in vitro-assembled splicing complexes that can be used for the identification of protein splicing factors which become associated with the spliceosome at the end of the assembly process ("late" splicing components). A splicing reaction performed in the presence of polyvinyl alcohol is interrupted after 15 to 20 minutes, before the appearance of splicing intermediates and products in significant amounts. Following low-speed centrifugation, a pellet is obtained containing splicing complexes that can be solubilized with 0.6 M-KCl. These complexes can be rapidly complemented for splicing in the presence of ATP and Mg2+ with protein factors that are present in HeLa cell nuclear extracts or in chromatographic extract fractions. Biochemical features of the complementation reactions, and conditions for reversible uncoupling of the two splicing steps, are described and discussed. These conditions are used to generate fully assembled spliceosomes in which splicing of the pre-mRNA can occur in the presence of ATP and Mg2+, but in the absence of nuclear extract ("autonomous splicing").

Adenosine Triphosphate↗

PubMed1989

Evidence for a distinct nigropallidal dopaminergic projection in the squirrel monkey.

Injections of the retrograde fluorescent tracer fast blue in the striatum (STR) and nuclear yellow in the internal segment of the globus pallidus (GPi) in the squirrel monkey (Saimiri sciureus) revealed a nigropallidal projection whose cellular origin was largely distinct from that of the nigrostriatal pathway. Neurons containing the tracer injected in GPi were scattered throughout the substantia nigra-ventral tegmental area complex where they formed approximately 20-25% of the total number of retrogradely labeled cells. Only about 5-10% of all positive neurons were double-labeled after STR-GPi injections. In experiments combining the use of the fluorescent tracer propidium iodide with immunofluorescence, the majority of neurons projecting to GPi displayed tyrosine hydroxylase immunoreactivity. Hence, in addition to their important role at striatal level, midbrain dopaminergic neurons may influence directly the output neurons of the basal ganglia at pallidal level in primates.

Animals↗

PubMed1989

Distinct afferents to internal and external pallidal segments in the squirrel monkey.

The use of retrograde fluorescence double-labeling method has revealed that the internal (GPi) and external (GPe) segments of globus pallidus in squirrel monkey receive projections from different cell populations in striatum and subthalamic nucleus. Striatal neurons projecting either to GPi or GPe formed wide and nonoverlapping cell bands oriented obliquely and covering large portions of putamen and caudate nucleus. Subthalamic neurons projecting to GPe were more abundant and more laterally located than those projecting to GPi. A few cells branching to GPi and GPe were found in subthalamic nucleus but not in striatum. Thus, different striatal and subthalamic neuronal populations influence GPi and GPe in primates.

Animals↗

PubMed1989

Blunted responses to vasoconstrictors in mesenteric vasculature but not in portal vein of spontaneously hypertensive rats treated with relaxin.

Relaxin (RLX), an ovarian polypeptide hormone that is particularly associated with gestation in viviparous species, has recently been shown to decrease blood pressure in virgin spontaneously hypertensive rats (SHR) upon chronic infusion. In this investigation, vascular reactivity to angiotensin II, arginine-vasopressin, and norepinephrine was studied in the perfused mesenteric artery and isolated portal vein of control and RLX-treated virgin spontaneously hypertensive rats. The latter received an intravenous infusion of 75 ng/hr purified rat RLX for 2 days, whereas the controls were given an equal infusion of saline. All of the animals were then killed and their tissues processed for in vitro study. In the perfused mesenteric artery, the concentration-response curves for arginine-vasopressin and norepinephrine were shifted to the right by a factor of about 2 (P less than 0.05 and P less than 0.005, respectively) after RLX treatment. In the isolated portal vein, the response to angiotensin II was not affected; the effect of norepinephrine was slightly displaced to the right (increase in EC50) and the maximum response remained unchanged. These results demonstrate that RLX treatment for 42 hr blunted the vascular response to vasoconstrictor agents in the mesenteric vasculature and are consistent with similar observations reported previously in the same tissue of 20-day-old pregnant rats. It is concluded that RLX may be involved in the blunted response to vasoconstrictor agents during gestation in the rat.

Angiotensin II↗