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C Estrada

Publications and source records attributed to C Estrada.

47 records · Page 3Linked to original sources
PubMed1985

Long-term serial cultivation of arterial and capillary endothelium from adult bovine brain.

Cerebrovascular endothelial cells from adult bovine brain were carried successfully in long-term, serial culture. Endothelial cells were obtained from the middle and anterior cerebral arteries and from capillaries isolated from grey matter of the cerebral cortex or caudate nucleus. Capillary cells were found to grow best in RPMI 1640 with 20% fetal bovine serum. They did not require tumor-conditioned medium or matrix-coated surfaces, although fibronectin was used to enhance the initial plating efficiency of the primary cultures. The same conditions were used to support satisfactory growth of arterial endothelial cells; however they did not grow as rapidly as the cells. Retention of endothelial-specific characteristics were shown for capillary-derived cells carried up to Passage 28, arterial-derived cells up to Passage 11, and after frozen storage of both types of cultured cells. Cultures of both arterial and capillary cells stained positively for Factor VIII antigen, exhibited a nonthrombogenic surface, and produced prostacyclin in response to arachidonic acid. Arterial endothelial cells produced more prostacyclin than capillary endothelium. The capillary cells had a unique tendency to assume a ringlike morphology after subculture and sometimes formed capillarylike networks of cell cords in dense cultures. When cultured in a three-dimensional plasma clot, capillary and arterial endothelial cells, but none of the other cell types studied, organized into tubelike structures reminiscent of capillary formation in vivo. The availability of long-term cultures of cerebrovascular endothelial cells provides an opportunity to compare properties of arterial and capillary endothelium from the same tissue and to investigate such processes as angiogenesis and blood-brain barrier induction.

Animals↗
PubMed1985

Choline acetyltransferase depletion in the rat retina after intraocular injection of neurotoxins.

The effects of kainic acid (KA), quisqualic acid (QA), and ibotenic acid (IBO) on histology of the retina and on the retinal choline acetyltransferase (ChAT) activity were studied in the rat. KA produced the highest number of altered cells in the ganglion cell layer (GCL) and in the inner nuclear layer (INL), with an almost complete depletion of ChAT activity. QA was less effective than KA in terms of both the number of altered cells and in ChAT depletion. In contrast, retinas injected with IBO showed the mildest morphological lesions together with the highest reduction in the enzyme activity. These results indicate that IBO affects nearly all the cholinergic neurons in the rat retina, whereas other populations, sensitive to KA or QA, are spared. Because of this higher specificity toward the cholinergic subpopulation, IBO may be a useful tool when cholinergic cells need to be destroyed in the retina.

Animals↗
PubMed1984

GABA receptors mediate cerebral vasodilation in the unanesthetized goat.

The effects of gamma-aminobutyric acid (GABA) and muscimol upon cerebral blood flow were evaluated in the unanesthetized goat. Cerebral blood flow was continuously measured by means of an electromagnetic flow probe chronically implanted on the internal maxillary artery after occlusion and thrombosis of the distal extracerebral vessels. Administration of GABA (1-100 micrograms) directly into the cerebral circulation produced dose-dependent increases in cerebral blood flow, without accompanying systemic effects. Muscimol mimicked the effects of GABA at doses 10 times lower. Administration of picrotoxin (1-3 mg) into the internal maxillary artery did not significantly change cerebral blood flow, but inhibited in a dose-dependent manner the vasodilation induced by GABA. Selective blockade of beta-adrenergic or muscarinic cholinergic receptors by propranolol or atropine, respectively, did not modify the cerebrovascular response to the GABAergic agonists. These results indicate that GABA increases total cerebral blood flow, acting on specific receptor sites in the cerebral blood vessels. The absence of influence of picrotoxin on resting cerebral blood flow suggests that the GABAergic receptors are not tonically activated under physiological conditions.

Animals↗
PubMed1984

Evidence for the direct effect of vasopressin on human and goat cerebral arteries.

The effects of vasopressin on the cerebral circulation were studied in conscious goats and in isolated human and goat cerebral arteries. Infusion of 1 to 12 mU of vasopressin into the internal maxillary artery of unanesthetized goats caused dose-dependent reductions in cerebral blood flow, a decrease of 36 +/- 4.7% (mean +/- S.E.) occurring with the highest dose. Cumulative application of vasopressin (10(-12) to 10(-6) M) markedly constricted human and goat cerebral arteries in vitro, the effect being more prominent in human vessels. (1-Deaminopenicillamine, 4-valine)-8-D-arginine-vasopressin, a competitive antagonist of the pressor effects of vasopressin, partially inhibited the cerebral vasoconstriction produced by vasopressin in vivo and in vitro without affecting the vasoconstrictor responses to norepinephrine, 5-hydroxytryptamine and potassium chloride. The results indicate that low concentrations of vasopressin produce constriction of cerebral vessels by direct excitatory effects on specific receptor sites. This effect should be considered in certain pathophysiological states in which vasopressin is released in amounts that could interfere with the proper blood supply to the brain.

Animals↗
PubMed1983

Biochemical evidence for cholinergic innervation of intracerebral blood vessels.

Muscarinic cholinergic receptor sites were detected with [3H]quinuclidinylbenzilate (QNB) binding techniques in two fractions of bovine intracerebral vessels; one of the fractions contained primarily small arteries and veins with some attached capillaries, and the other one was highly enriched in capillaries. The amounts of binding were similar in equivalent vascular fractions isolated from cerebral cortex, caudate nucleus and cerebellar cortex in spite of large differences among the 3 regions in [3H]QNB binding to brain tissue. The different distribution of muscarinic receptors in brain tissue and blood vessels argues against the possibility that the receptors represent a contamination of the vascular fractions by brain parenchyma. Cerebral endothelial cells, which were isolated by treating capillaries with collagenase, bound [3H]QNB to the same extent as did cerebral capillaries. This is consistent with an endothelial localization of capillary muscarinic receptors. Choline acetyltransferase (ChAT) activity, a marker for cholinergic neurons, also was present in the vascular preparations. Within each brain region, ChAT activities in capillaries and larger vessels were similar, but significant regional differences were found for vascular ChAT activity, with the highest values in the caudate. Isolated endothelial cells contained significantly lower levels of ChAT activity than intact capillaries, suggesting a periendothelial location of the enzyme, as would also be the case for attached nerve terminals. The presence of [3H]QNB binding sites and ChAT activity in intracerebral blood vessels is consistent with an innervation of the cerebral vasculature by a cholinergic system that may regulate cerebral blood flow and capillary permeability.

Acyltransferases↗
PubMed1982

Muscarinic cholinergic receptor sites in cerebral blood vessels.

Muscarinic cholinergic receptor sites in cerebral blood vessels were analyzed directly by using radioligand binding techniques with the specific muscarinic antagonist [3H]quinuclidinyl benzilate (QNB) as ligand. Specific binding of [3H]QNB to membrane preparations from isolated bovine pia-arachnoid vessels was found to be saturable, of high affinity (Kd = 5.4 X 10(-10) M) and selectively inhibited by muscarinic antagonists (atropine) and agonists (acetylcholine, carbachol and methacholine). Scatchard and Hill plot analyses of the data indicated one class of sites for the antagonists, but two independent classes of sites were revealed with the agonists. Interestingly, the high and low affinities of the agonist sites correlated with the concentrations of agonist which have been reported to produce dilation and contraction, respectively, of isolated pial artery segments. A substantial number of specific [3H]QNB binding sites also were measured in isolated bovine cerebral microvessels providing direct evidence for muscarinic receptors in intracerebral vessels. In contrast, specific [3H]QNB binding was barely detectable in mesenteric blood vessels. Choline acetyltransferase (ChAT) activity was measured in parallel with [3H]QNB binding. The relative distribution of choline acetyltransferase was correlated with that for the binding, with the highest values observed in the intracerebral microvessels. This suggests a functional innervation of the cerebrovascular muscarinic receptors.

Animals↗
PubMed1981

Relaxation of isolated middle cerebral artery induced by diazoxide.

The effect of diazoxide on isometric tension of goat middle cerebral arteries was investigated both under resting conditions and under contraction produced by 10(-6) M serotonin. In addition, the inhibitory action of diazoxide was tested against contractile effects induced by different experimental interventions such as electrical field stimulation, norepinephrine, tyramine, histamine, and KCl. Diazoxide caused dose-dependent relaxation of cerebral arteries which was more pronounced when the vessels were previously contracted. High doses of diazoxide (10(-3) M) inhibited significantly the contraction induced by electrical field stimulation and all the vasoactive agents used. This inhibitory effect of diazoxide was greater for those drugs that directly or indirectly act through alpha-adrenergic receptor stimulation. Tritium release induced by electrical field stimulation of cerebral arteries previously labelled with 3H-norepinephrine was not affected in the presence of diazoxide. We conclude that diazoxide has a dilatory effect on goat brain vessels due to direct relaxation of smooth muscle together with a possible blockade of the alpha -adrenergic receptors. This effect might explain the maintenance of cerebral blood flow observed in vivo during diazoxide-induced arterial hypotension.

Animals↗
PubMedDate not supplied

Nitric oxide-producing neurons in the neocortex: morphological and functional relationship with intraparenchymal microvasculature.

Nitric oxide is a ubiquitous intercellular messenger involved in particular functions in the cardiovascular, immunological and nervous systems. In the cerebral cortex, nitric oxide is synthetized by endothelial cells and by a discrete population of neurons and glial cells expressing nitric oxide synthase. Nitric oxide of endothelial and neuronal origin is involved in the regulation of cerebral blood flow. In this review, we have tried to combine morphological data providing information on the chemical nature of nitric oxide synthase-containing neurons and their arrangement, especially in relation to intracortical blood vessels, with functional results suggesting the participation of these neurons in the coupling between local cortical blood flow and synaptic activity.

Animals↗
PubMedDate not supplied

In vivo and In vitro studies on the cerebrovascular dilatation induced by diazoxide in normotensive and renal hypertensive goats.

We studied the in vivo and in vitro effects of diazoxide on the cerebral circulation of 8 normotensive (mean arterial pressure = 100 mm Hg) and 5 renal hypertensive (mean arterial pressure = 146 mm Hg) goats. Injections of diazoxide (0.3-27 mg) into the internal maxillary artery of unanesthetized goats produced dose-dependent increases in cerebral blood flow (electromagnetic flowmeter), this effect being significantly higher in hypertensive goats. Intravenous injection of 5 mg/kg of diazoxide into normotensive goats increased cerebral blood flow 40 ml/min/100 g and mean arterial pressure dropped 22 mm Hg whereas in hypertensive goats cerebral blood flow was unchanged and mean arterial pressure decreased 50 mm Hg. The increase in heart rate due to intravenous diazoxide was similar in normotensive and hypertensive goats (35 beats/min). Cumulative applications of diazoxide (10(-5) to 10(-3)M) on isolated middle cerebral arteries produced dilatory responses both under resting conditions and after previous tonic contraction by serotonin. This relaxation was significantly greater in arterial segments from hypertensive goats. The results indicate that diazoxide exerts powerful dilatatory effects on cerebral vessels, both in vivo and in vitro, and that these effects are particularly evident in hypertensive animals.

Animals↗