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Results for “BLOOD VESSELS, PERIPHERAL”

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PubMed1998

Cyclooxygenase-2 is induced in brain blood vessels during fever evoked by peripheral or central administration of tumor necrosis factor.

Cyclooxygenase-2 (COX-2) is an inducible type of enzyme that is involved in prostaglandin biosynthesis. In the present study, we examined whether or not COX-2 is involved in fever that is induced by tumor necrosis factor-alpha (TNF-alpha) and, if so, where in the brain COX-2 is induced by this factor. Intraperitoneal (i.p.) injection of TNF-alpha into rats evoked a fever that started 1 h after the TNF injection, peaked 3 h after the injection, and then gradually declined. The fever was suppressed by pretreatment with a COX-2-specific inhibitor. With a time course similar to that of fever, COX-2 mRNA was induced in brain blood vessels. On the other hand, in some of the telencephalic neurons, COX-2 mRNA was constitutively expressed under the normal condition; but its level gradually decreased during the course of fever. Fever was also evoked by an intracerebroventricular (i.c.v.) injection of TNF-alpha. This febrile response was also suppressed by a COX-2 specific inhibitor and was associated with the induction of COX-2 mRNA in the brain blood vessels. On the other hand, the telencephalic neurons did not show consistent change in COX-2 mRNA level after i.c.v. injection of TNF-alpha or saline. COX-2-like immunoreactivity was found in some cells of the brain blood vessels 3 h after the TNF-alpha injection by either i.p. or i.c.v. route. Most of the COX-2-like immunoreactive cells were endothelial cells since COX-2-like immunoreactivity was colocalized with von Willebrand factor, an endothelial cell marker, in the same cells. These results suggest that the brain blood vessels are the major sites where TNF-alpha enhances PG biosynthesis after peripheral as well as after central injection, and provides further evidence supporting the hypothesis that COX-2 induced in the brain blood vessels is involved in fever.

Animals↗
PubMed1993

A comparison of tumor and normal tissue microvascular hematocrits and red cell fluxes in a rat window chamber model.

This laboratory has previously used a window chamber model to measure red blood cell velocity in mammary tumors and normal granulation tissues of the F-344 rat. Because red cell flux and hematocrit more accurately reflect the oxygen carrying potential of blood, we used this model to measure these parameters. Red blood cells were labelled with fluorescein isothiocyanate, and 0.2 ml. packed cells were injected intravenously into rats bearing an 8 to 10 day old R-3230 mammary carcinoma. beta-phycoerythrin (0.15 mg.) was also injected and served as a plasma dye to outline the blood vessels. A sample of peripheral blood was then taken and analyzed by flow cytometry to determine the labeled fraction of red blood cells. Flowing tumor and normal tissue vessels were recorded onto a VCR, and these video images were used to determine vascular length and diameter, RBC flux and velocity, and hematocrit. Median vessel diameter and loge (red blood cell flux) were significantly greater in tumors than in normal tissues (p = 0.007 and p < 0.025, respectively). After controlling for these variables, the median tumor hematocrit of 19% was not significantly greater than the median normal tissue hematocrit of 15%. This technique provides a nontoxic and reproducible method that is now being used to assist in the in vivo definition of tumor oxygenation.

Animals↗
PubMed1998

Effect of octreotide on 24-h blood pressure profile in acromegaly.

The aim of the study was to investigate the effect of octreotide, a somatostatin analog drug potentially able to inhibit growth hormone (GH), on the circadian blood pressure profile in a group of patients with acromegaly. Ten patients with GH-secreting pituitary adenoma were studied before and 6 months after treatment with subcutaneous octreotide 0.2 to 0.6 mg/day. Twenty-four hour blood pressure and heart rate were measured every 15 min at daytime (07:00 to 22:59) and every 30 min at nighttime (23:00 to 06:59) using a TM-2420 recorder. No correlation was found between GH levels and 24-h blood pressure in baseline conditions. Untreated patients had a significant nocturnal decrease of both systolic and diastolic blood pressure (P < .01), and all showed a circadian systolic or diastolic blood pressure rhythm. During octreotide treatment, 24 h as well as nighttime systolic and diastolic blood pressures significantly increased (P < .05), whereas daytime systolic and diastolic blood pressures did not change. Treated patients did not have a nocturnal decline in both systolic and diastolic blood pressures (P = NS), and eight lost their systolic or diastolic blood pressure rhythm. In conclusion, blood pressure circadian rhythm seems to be maintained in acromegaly. Octreotide treatment is associated with an increase of 24-h and nighttime blood pressure, and with loss of circadian blood pressure rhythm. Splanchnic vasoconstriction by this drug, shifting blood to peripheral vessels, may explain this phenomenon.

Acromegaly↗