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Biomedical subjects

M N Hart

Publications and source records attributed to M N Hart.

99 records · Page 6Linked to original sources
PubMedDate not supplied

Effects of formaldehyde fixation on basilar artery caliber.

The external diameters of rat and rabbit basilar arteries were determined before and after formaldehyde fixation in relaxed and drug constricted vessels. Fixation usually resulted in an immediate vessel constriction followed by partial relaxation after several hours. However, the results were inconstant from vessel to vessel and from area to area of the same vessel. It is concluded that morphologic as well as morphometric assessment of formaldehyde-fixed basilar arteries is unreliable.

Animals↗
PubMedDate not supplied

Morphometry of brain parenchymal vessels following subarachnoid hemorrhage.

This study was performed to test the hypothesis that vascular spasm can occur in brain parenchymal vessels following subarachnoid hemorrhage (SAH). Five cc of autologous blood was injected into the cisterna magna of test cats and 5 cc of saline into control cats. After 2 hours, a cranial window was created and cortical tissue frozen in situ with liquid nitrogen. Statistical analysis of 124 test and 93 control arteries and arterioles showed a significantly greater mean wall to lumen ratio in the test vessels but with almost identical mean cross sectional areas for both groups of vessels. This finding provides evidence for at least vasoconstriction, if not frank spasm, in parenchymal vessels in conjunction with SAH.

Animals↗
PubMedDate not supplied

Effect of intracarotid hyperosmolar mannitol on cerebral cortical arterioles--a morphometric study.

The morphometric response of cerebral cortical arterioles to intracarotid hyperosmolar mannitol was assessed utilizing a technique of rapid freezing of rat brain tissue in vivo. A significant decrease in the wall to lumen (W/L) ratio was noted in the small parenchymal arterioles (20-49 mu) (p less than .0001) ipsilateral to the mannitol infusion. Larger arterioles showed a decreased W/L ratio but this change was not significant. Control infusion of 0.9% NaCl resulted in no change in arteriolar caliber. These results indicate that intracarotid hyperosmolar mannitol causes a direct vasodilatory response in small cerebral cortical arterioles.

Animals↗
PubMedDate not supplied

Rapid freezing and frozen sectioning as a means of preserving brain vessel morphometric characteristics.

A study was performed for the purpose of determining whether ordinary frozen sections of brain could preserve in vivo parenchymal arteriole morphometric characteristics. The results showed that flash-freezing followed by frozen sectioning is just as reliable a means of preserving brain arteriole morphometric characteristics as the time consuming process of flash-freezing followed by freeze substitution.

Animals↗
PubMedDate not supplied

Demonstration of adenosine receptors on mouse cerebral smooth muscle membranes.

Adenosine receptors have been identified on brain cortical membranes and microvascular preparations. However, they have not been demonstrated on specific microvascular elements in isolation. 2-3H-chloroadenosine was used as a ligand to investigate the presence of adenosine receptors on isolated mouse cerebral smooth muscle membranes. The binding studies reveal the presence of a high affinity binding site with a Kd value of 33.3 nM and a maximal binding capacity (Bmax) of 283 fmol/mg protein. These findings demonstrate that there is an adenosine receptor on cerebral smooth muscle membranes.

2-Chloroadenosine↗
PubMedDate not supplied

Vascular spasm in cat cerebral cortex following ischemia.

The reaction of brain parenchymal vessels in areas of no-reflow following ischemia in cats was evaluated. A method was devised by which brain biopsies following ischemia were quickly frozen at -170 degrees C, sections were cut and stained and vessel internal and external diameter measured. Vessels in the no-reflow areas had smaller internal and external diameters and thicker walls when compared to adjacent reflow areas as well as to normal control animals. By utilizing a 2-way analysis of variance in which reflow versus no-reflow vessel diameters were compared by region the differences were found to be statistically significant (p less than 0.05). The data raise the possibility that there may exist normal regional differences in the size of cerebral vessels.

Animals↗
PubMedDate not supplied

Cerebral ischemia: evaluation with contrast-enhanced MR imaging.

Eighty patients with a total of 82 ischemic lesions were examined with contrast-enhanced MR imaging 1 hr to 1 month after onset of symptoms. The studies were reviewed retrospectively to determine the presence of arterial enhancement and the patterns of parenchymal enhancement. Arterial enhancement was often detected on the initial MR examination (45%), was frequently demonstrated in cortical infarction (86%), in some cases preceded the development of signal changes on T2-weighted images, and resolved by 11 days. The presence of arterial enhancement appeared to be a better indicator of clinical severity than was the presence of proximal vessel occlusion on MR or angiographic studies. Two patterns of parenchymal enhancement were seen: progressive enhancement and early and/or intense enhancement. In patients with the progressive pattern, parenchymal enhancement on postcontrast T1-weighted images was rarely seen before 7 days, while signal abnormalities on T2-weighted images were intense during the first few days. The early and/or intense enhancement pattern was usually present within the first 3 days, approximated or exceeded the area and intensity of signal changes on T2-weighted images, and was usually associated with minimal or reversible neurologic sequelae (except when located in or near a watershed zone), suggesting a lesser degree of ischemic insult than was associated with the progressive pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Studies of the endothelial origin of cells in systemic angioendotheliomatosis and other vascular lesions of the brain and meninges using ulex europaeus lectin stains.

Ulex europaeus agglutinin I (UEA-I) is a plant lectin which binds specifically to alpha-L-fucose moieties on the surface glycoproteins of human endothelial cells. The binding is completely inhibited by preincubation of the lectin with fucose. UEA-I can be conjugated directly to fluorescein or peroxidase and can be used to stain endothelium of paraffin embedded tissues. UEA-I staining was evaluated on normal and infarcted brain, systemic angioendotheliomatosis, metastatic epidural angiosarcoma, hemangioendothelioma, hemangioblastoma, angioblastic meningioma of both the hemangioblastic and hemangiopericytic types, and vascular meningioma. The endothelium, but not neuropil of normal and infarcted brain was positive for UEA-I. The tumor cells of hemangioendothelioma and angiosarcoma also stained. However, no staining was seen in malignant intravascular cells of angioendotheliomatosis, the stromal cells of hemangioblastoma, or pericytes of angioblastic meningioma. It is concluded that the malignant cells in angioendotheliomatosis, the stromal cells of hemangioblastoma and the pericytes of angioblastic meningioma do not produce surface glycoproteins characteristic of endothelial cells.

Brain Neoplasms↗