Search PubMed⌕ Search

Biomedical subjects

F G Diaz

Publications and source records attributed to F G Diaz.

At least 109 records · Page 6Linked to original sources
PubMed1985

"Reverse" superficial temporal artery-middle cerebral artery bypass.

A new technical variant on the superficial temporal artery-middle cerebral artery anastomosis was performed in a patient with occlusions of both the left internal and external carotid arteries and persistent ischemic symptomatology. Instead of anastomosing the proximal segment of the superficial temporal artery to the middle cerebral artery as is conventionally done, the distal segment of the superficial temporal artery was anastomosed to a cortical branch of the left middle cerebral artery. Reconstituted flow of the left superficial temporal artery via right superficial temporal artery collateral branches proved adequate to relieve the patient's ischemic episodes. "Reverse" superficial temporal artery-middle cerebral artery anastomosis should be considered in those cases where occlusive disease of the external carotid circulation renders conventional bypass procedures ineffective in the treatment of ischemic symptomatology.

Arterial Occlusive Diseases↗
PubMed1985

Cerebral angiography and neuropsychological measurement: the twain may meet.

In a sample of 31 cerebral revascularization candidates, severity and dissemination of atherosclerosis on the cerebral angiogram were correlated with two of three global indicators of neurobehavioral impairment. Additionally, the angiographic rating was correlated with age and with an index of medical risk factors, but not with duration of the longest symptomatic episode. It seems likely that several variables, particularly collateral circulation, help to determine whether a given pattern of stenoses results in neuropsychological dysfunction and what type of behavioral deficit occurs. In many cases, the configuration of neuropsychological test scores may not directly mirror the pattern of cerebrovascular stenoses.

Adult↗
PubMed1985

Middle cerebral artery reconstruction.

The authors have conducted an experimental study of the microanatomic features of the middle cerebral artery in unfixed human brains to assess the feasibility of reconstructive procedures within the Sylvian fissure. It was found that reconstructive procedures within the Sylvian fissure such as end-to-end, end-to-side, side-to-side, and grafting procedures were possible according to the anatomic data provided by our study. Possible surgical solutions to theoretical pathologic situations involving the middle cerebral artery vascular tree are highlighted and their feasibility is discussed.

Cerebral Arteries↗
PubMed1985

Quantitative electron microscopic study of calcium accumulation in cerebral ischemia mitochondria.

Formation of calcium deposits in mitochondria is a consistent feature of irreversible injury in ischemic myocardium. We studied calcium accumulation in nerve cell mitochondria in a cat model 30 and 60 minutes after cerebral ischemia localized in the anterior part of the caudate nucleus and adjacent internal capsule. In control animals, calcium deposits were visible in synaptic vesicles, Golgi apparatus, mitochondria, lysosomes, and in glial and neuronal nuclei. After cerebral ischemia, findings included astrocytic swelling and degeneration of neurons, with an increase in calcium pyroantimoniate mitochondrial deposits. Content of intramitochondrial calcium deposits is related to duration of ischemia as well as the amount of cellular lesions.

Animals↗
PubMed1985

Current management of cerebral aneurysms: is it based on facts or myths?

The overall morbidity and mortality from aneurysmal subarachnoid hemorrhage have not changed significantly over the past 30 years in spite of great progress in surgical technology and diagnostic capabilities. Most series report major morbidity and mortality figures of approximately 60%. The reason for the currently poor prognosis is due, in part, to the sometimes devastating effect of the initial hemorrhage over which we have no control. Another reason for our inability to improve these dismal statistics may be that the currently accepted treatment regimens have proven to be ineffective. Eighteen misconceptions or "myths" surrounding the treatment of aneurysmal subarachnoid hemorrhage have been identified as factors that have largely determined the currently accepted, ineffective treatment protocols, and these are discussed.

Adult↗
PubMed1985

Intraluminal thrombus and neointimal hyperplasia after microvascular surgery.

Despite advances in instrumentation, suture materials, and techniques, thrombosis and intimal hyperplasia due to myointimal cell proliferation are still problems in microvascular anastomosis. Platelet factors stimulate smooth-muscle cell proliferation and migration, but little is known about platelet-vessel wall interaction in microvascular surgery. This study evaluates the effect of the disposition of platelet or luminal thrombus, or both, in intimal evolution in autologous venous micrografts interposed in the common carotid artery of 30 rats. Three hours postoperatively, venous graft and suture line endothelium was completely denuded, and the host artery exhibited focal de-endothelialization. Thrombus deposition was observed on suture line and venous graft luminal surfaces, whereas host artery-denuded areas exhibited platelet adhesion. Two weeks postoperatively, intimal thickenings developed in venous graft and suture line, becoming narrower toward the venous graft. The distribution and size of intimal thickening did not change significantly at later observation periods (3-8 months). Intimal thrombus deposition and intimal hyperplasia, appearing in later stages of evolution, show a similar pattern of distribution.

Animals↗
PubMed1985

Possible role of endothelium in the orientation of smooth muscle cells in experimental neointima.

Myointimal cells (MIC) orientation and intimal thickening evolution, induced by grafting an autogenous venous patch onto the rat common carotid artery, were studied with light microscopy at different times until 14 months after surgery. Intimal thickenings in the venous patch were most prominent at an intermediate postoperative period, after which their mean size did not change significantly. In host artery neointima, the greatest MIC proliferation was observed at a late stage of evolution. MIC arrangement was predominantly circumferential to the blood stream in venous patch neointima, whereas it was mostly axial in the host artery. The interaction between MIC orientation and endothelial regeneration in the operated vessel is discussed.

Animals↗
PubMed1985

Complications of cerebral revascularization with autogenous vein grafts.

Autogenous veins were used for cerebral revascularization 29 times. There were 17 long grafts to the cortex and 12 shorter grafts for reconstruction of cervical vessels. Of the long cortical grafts, 5 occluded and 3 patients developed intracerebral hemorrhage. With the shorter grafts, all remained patent and there were no hemorrhagic complications. A combination of a relatively low flow rate and endothelial damage in the graft was thought to be largely responsible for early graft failure. Revascularization of an infarct and hypertension were implicated in cases with intracerebral hemorrhage.

Cerebral Angiography↗
PubMed1985

Aneurysm clip motion during magnetic resonance imaging: in vivo experimental study with metallurgical factor analysis.

Because of various mechanical, metallurgical, and commercial constraints, aneurysm clips are manufactured from different alloys, including several stainless steel and cobalt alloys. Some of the steels contain volume fractions of the crystal phase known as martensite. Martensitic alloys have body-centered cubic structure, are prone to stress corrosion failure, and are ferromagnetic. Martensitic steel can be displaced like a compass needle when exposed to a magnetic field such as that generated during magnetic resonance imaging (MRI). The force exerted by the magnetic field is proportional to the volume fraction of the magnetic phase. We investigated the martensitic content and magnetic field-induced displacement of 12 common aneurysm clips. Four clips of each of the following types were examined: Sugita, Sundt-Kees Multi-Angle, Heifetz (two types), Vari-Angle McFadden, Yasargil (two types), Scoville, Mayfield, Vari-Angle, Pivot, and Kapp. Phase homogeneity and crystal structure were analyzed by x-ray diffraction using a Phillips x-ray diffractometer. Clip deflection in an Oxford Research Systems MRI spectrometer was measured in our in vivo rat abdominal aortic aneurysm model. Results showed that the volume fraction of the martensitic phase in the various clips correlated with the magnitude of the deflection. Among the clips examined, the Yasargil, Sugita, Heifetz Elgiloy, and Vari-Angle McFadden had a nonmartensitic composition and did not deflect in the magnetic field. The Scoville contained 5% martensite and deflected only marginally. Martensite comprised 35% of the Mayfield clip, which deflected 45 degrees, and 90% of the Heifetz, Vari-Angle, Pivot, and Sundt-Kees Multi-Angle clips, which deflected approximately 70 degrees or slipped off the aneurysm.(ABSTRACT TRUNCATED AT 250 WORDS)

Alloys↗
PubMed1985

Acute inflammation and endothelial injury in vein grafts.

An experimental study of autogenous vein graft morphology 6 hours after arterial implantation was performed in dogs. The animals were divided into five groups. The first control group had veins harvested and stored but not implanted. The endothelium showed excellent preservation by routine histology and scanning electron microscopy. The second control group had grafts implanted and flow decreased to 30 to 50 ml/minute. There was a massive acute inflammatory response with subendothelial and transmural accumulation of neutrophils causing widespread endothelial sloughing. A third group had grafts implanted, but flow was not reduced (mean, 170 ml/minute). Although an inflammatory response was also present, it was much less severe than in the low flow grafts and the endothelium remained grossly intact. Two other groups had low flow grafts implanted, but were treated with either lidocaine or steroids. Lidocaine had no effect on the inflammatory response or endothelial injury. High doses of alpha-methylprednisolone succinate almost completely prevented both endothelial loss and inflammatory infiltration. This study supports the premise that an acute inflammatory response can initiate endothelial injury after autogenous grafting, an effect that is much more prominent in low flow than high flow grafts. It also demonstrated that steroids can almost totally suppress the injury during the initial 6 hours after implantation.

Animals↗
PubMed1985

Mechanical and metallurgical properties of carotid artery clamps.

The mechanical and metallurgical properties of carotid artery clamps were evaluated. The pressure plate retreat propensity, metallurgical composition, surface morphology, magnetic properties, and corrosion resistance of the Crutchfield, Selverstone, Salibi, and Kindt clamps were tested. None of the clamps showed evidence of pressure plate retreat. The clamps differed significantly in their composition, surface cleanliness, magnetic properties, and corrosion resistance. The Crutchfield clamp was the only one manufactured from an ASTM-ANSI-approved implantable stainless steel (AISI 316) and the only clamp in which the surfaces were clean and free of debris. The Selverstone clamp was made principally from AISI 304 stainless steel, as was one Salibi clamp. The pressure plate on another Salibi clamp was made from a 1% chromium and 1% manganese steel. Machining and surface debris consisting principally of aluminum, silicon, and sulfur was abundant on the Selverstone and Salibi clamps. The Kindt clamp was manufactured from AISI 301 stainless steel with a silicate-aluminized outer coating. The Crutchfield and Selverstone clamps were essentially nonferromagnetic, whereas the Salibi and Kindt clamps were sensitive to magnetic flux. In the pitting potential corrosion test, the Crutchfield clamp demonstrated good corrosion resistance with a pitting potential of 310 mV and no surface corrosion or pitting by scanning electron microscopy examination. The Selverstone clamp had lower pitting potentials and showed various degrees of corrosion and surface pitting by scanning electron microscopy. The Salibi pressure plate had a very low pitting potential of -525 mV and showed severe corrosion. By metallurgical criteria, only the Crutchfield clamp is suitable for long term implantation.

Animals↗
PubMed1985

The perforating branches of the middle cerebral artery. A microanatomical study.

The perforating branches (PFB's) of the middle cerebral artery (MCA) were studied in 34 unfixed brain hemispheres which were injected with a polyester resin and dissected under the operating microscope. Five hundred and eight vessels were identified and their site of origin, branching pattern, outer diameter (OD), and length recorded. Four hundred and two PFB's (79%) originated from the main trunk of the MCA before its division; the remaining 106 vessels (21%) had their origin from branches of the MCA as follows: superior trunk, 43 vessels (8.5%); inferior trunk, 30 vessels (6%); middle trunk, four vessels (0.8%); early temporal branch, 27 vessels (5.3%); and early frontal branch, two vessels (0.4%). The number of PFB's in each hemisphere varied from five to 29 (mean 14.9 +/- 0.7 vessels). The great majority of PFB's (96%) originated along the proximal 17 mm of the MCA. The PFB's arising in the first 10 mm had a mean OD of 0.35 +/- 0.01 mm and a mean length of 9.25 +/- 0.19 mm, and those arising from the second 10 mm had a mean OD of 0.47 +/- 0.02 mm and a mean length of 16.67 +/- 1.4 mm. A clear distinction between a medial and lateral group of PFB's was present in only 14 hemispheres (41%). In nine hemispheres (26%), perforating vessels from the anterior cerebral artery (A1 segment) and from the recurrent artery of Heubner replaced the medial group of PFB's of the MCA. In one case this group originated in an accessory MCA. In three hemispheres (9%) a small anastomosis (OD 0.2 mm) was seen between a PFB of the recurrent artery of Heubner and one of the MCA. From a total of 508 PFB's, 255 vessels (50%) originated as single vessels, while 253 vessels (50%) originated as branches of common stems. The OD of the single vessels ranged from 0.1 mm to 1.1 mm (mean 0.39 +/- 0.02 mm), and the length from 3 to 20 mm (mean 10.8 +/- 0.2 mm). The common stems ranged in OD from 0.6 to 1.8 mm (mean 0.87 +/- 0.04 mm), and in length from 1 to 15 mm (mean 4.1 +/- 0.4 mm). The clinical application of these anatomical data to the management of aneurysms and arteriovenous malformations of the MCA, and in the field of interventional neuroradiology is described. The most frequent pathological entities involving the perforating vessels are also discussed.

Adult↗
PubMed1985

Cerebral revascularization to a main limb of the middle cerebral artery in the Sylvian fissure. An alternative approach to conventional anastomosis.

Thirteen patients underwent an anastomosis of the superficial temporal artery (STA) or a saphenous vein graft to one of the secondary trunks of the middle cerebral artery (MCA). They included five patients with giant MCA trifurcation aneurysms, four patients in whom an earlier conventional STA-MCA anastomosis had become occluded, two patients who had stenosis of one of the secondary limbs of the MCA, and one patient who had a carotid-cavernous fistula. One patient had a saphenous vein graft from the common carotid artery to a secondary trunk of the MCA to bypass an occluded internal carotid artery and severely stenosed external carotid artery. The primary advantages of this procedure are that a large-caliber anastomosis to one of the secondary limbs of the MCA immediately restores flow into the MCA tree with a larger amount of vessel filling than with a standard cortical bypass, and large vessels can be used for the anastomosis. The disadvantages are that one of the secondary branches of the MCA must be occluded, the cerebral hemisphere around the Sylvian fissure must be retracted, a lumbar subarachnoid drain is needed, and the anastomosis must be performed deep within the Sylvian fissure. The procedure is a satisfactory alternative in cases in which a conventional STA-MCA anastomosis has either failed or would be less likely to succeed.

Adult↗
PubMed1985

Acute cerebral revascularization.

Fifteen patients evaluated for acute cerebral ischemia underwent acute cerebral revascularization between March, 1979, and May, 1983. Clinical presentation included crescendo transient ischemic attacks (TIA's) in eight cases, progressing neurological dysfunction in three cases, and completed nonfluctuating deficits in four cases. Nine patients received intravenous heparin but did not improve neurologically. The patients with crescendo TIA's were operated on within 4 hours of their last event; those with progressing deficits were operated on while the deficit was developing, and those with established deficits were operated on 4, 6, 9, and 12 hours, respectively, after the event began. The clinical picture for 10 patients had resolved within 10 hours after surgery. One patient with crescendo TIA's, two with progressing deficits, and two with established deficits had postoperative residual deficits, of which three were mild and two severe. One patient, who had a saphenous vein graft to the middle cerebral artery, developed an intracerebral hematoma. In this prospective noncontrolled nonrandomized study, acute cerebral revascularization was performed safely, had limited risks, and offered the potential to help some patients. Further controlled randomized studies are indicated.

Adult↗
PubMed1984

Aspects of interastrocytic gap junctions in blood-brain barrier in the experimental penumbra area, revealed by transmission electron microscopy and freeze-fracture.

Interastrocytic gap junctions in the blood-brain barrier of the experimental penumbra area were studied in the cat caudate nucleus 1 h after ischemia. Transmission electron microscopy and freeze-fracture studies revealed only slight changes in gap junctions between astrocytes, indicating that these junctions are very resistant to hypoxia.

Animals↗
PubMed1984

Pericyte endothelial gap junctions in human cerebral capillaries.

Human cerebral tissue has been ultrastructurally studied and gap junctions have been visualized between endothelial cells and pericytes that permit ion exchange. We propose that the functional interrelationship between endothelium and pericytes may play a role in the alteration of capillary diameter for the control of local cerebral blood flow.

Blood-Brain Barrier↗
PubMed1984

Corrosion of aneurysm clips: evaluation and clinical implications. Part 1: Metallurgical foundations of stress corrosion failure.

Several intracranial failures of aneurysm clips have been documented recently. Consistently, the mechanism of failure has been stress corrosion. These failures could have been anticipated if certain metallurgical properties of the clips had been known. In this paper, we review the metallurgical basis of stress corrosion failure and offer serial metallurgical tests as screening procedures to determine a clip's propensity towards failure. The importance of determining a clip's fracture toughness, a key indicator of stress corrosion resistance, is emphasized.

Corrosion↗