Thyroid hormone abnormalities in serum were investigated in 47 patients with diabetes mellitus. Although no significant differences in T4 were found between normal subjects and diabetics, a group of diabetics whose fasting blood sugar levels were over 250 mg/dl showed significantly higher reverse T3 (rT3) (p less than 0.01) and lower T3 levels (p less than 0.05) than healthy controls. A significant correlation was observed between rT3 and FFA levels in diabetics. Moreover, patients in diabetic ketoacidosis showed markedly high rT3 with low T3 levels. With insulin treatment, these levels returned to normal in several days. These findings suggest that the reduction of T3 and the increase of rT3 may indicate an adaptation to limit catabolism in diabetics.

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PubMedDate not supplied

Fiber-optic laser-Doppler anemometer microscope applied to the cerebral microcirculation in rats.

We have applied our developed fiber-optic laser-Doppler anemometer microscope (FLDAM) for the study of the cerebral microcirculation in the rat. The red cell velocity in single pial microvessels was successfully measured through a closed cranial window for the vessel diameter range from 7.8 to 230 microns. The temporal resolution of the FLDAM was sufficiently high to detect the pulsation in the arterioles. Arterio-venous distributions of the temporal mean red cell velocity and wall shear rate are also described.

Animals↗

PubMedDate not supplied

Cerebral thrombosis and microcirculation of the rat during the oestrous cycle and after ovariectomy.

1. The effects of oestrogen on thrombogenesis and the cerebral microcirculation of the female rat were studied during the oestrous cycle and after ovariectomy. 2. Serum levels of oestradiol (E2) and plasma concentrations of nitric oxide (NO) metabolites were significantly greater at pro-oestrus than at dioestrus. Blood vessel diameter, mean red cell velocity, wall shear rate and blood flow at pro-oestrus were significantly higher than at dioestrus. Thrombotic tendency, assessed using a He-Ne laser-induced thrombosis model, was significantly decreased at pro-oestrus compared with dioestrus. 3. The long-term deprivation of oestrogen by ovariectomy significantly depressed serum levels of E2 and plasma concentrations of NO metabolites. Thrombotic tendency was significantly increased 4 weeks after ovariectomy. Vessel diameter, mean red cell velocity, wall shear rate and blood flow in pial arterioles were significantly reduced after ovariectomy. 4. Exogenous administration of oestrogen (17 beta-oestradiol) after surgery reversed the increased thrombotic tendency mediated by ovariectomy. 5. These results strongly indicate that oestrogen mediates beneficial effects on the cerebral microcirculation and moderates cerebral thrombotic mechanisms in the female rat.

Animals↗

PubMedDate not supplied

Cerebral prothrombotic state in spontaneously hypertensive rats of different breeds.

The thrombotic tendency in two breeds of spontaneously hypertensive rats (SHRs) was assessed by inducing occlusive thrombosis in pial blood vessels using a helium-neon laser method. A prothrombotic state was observed in the SHR of one breed as compared to the corresponding control WKY, but not in the other. Circulating platelet and erythrocyte counts and haematocrit values were significantly negatively correlated in arterioles with the number of laser pulses, which is an index of the thrombotic tendency, suggesting that the prothrombotic state was partly dependent on the counts of blood components. However, there was no correlation between the measured blood parameters and prothrombotic state in venules. The difference observed in arterioles and venules might be due to their differential haemodynamics and endothelial properties. Prothrombotic state in the SHR of one breed would be partly due to the much higher difference in blood components from its corresponding control compared to the comparatively less difference in the other breed.

Animals↗

PubMedDate not supplied

Enhanced thrombogenicity and altered hemodynamics in the cerebral microvasculature of stroke-prone spontaneously hypertensive rats.

Thrombotic potential and hemodynamic changes were assessed in the cerebral microcirculation in normal rats (WKY), non-stroke-prone spontaneously hypertensive rats (SHR) and stroke-prone spontaneously hypertensive rats (SHRSP) at the age of 4, 16 and 32 weeks. Whole blood platelet aggregation revealed that the platelet aggregability in vitro was significantly depressed in SHRSP compared to WKY at 16 and 32 weeks using 2 microg/ml collagen but was similar or higher than WKY at 32 weeks using 20 or 40 microg/ml collagen. Platelet-rich thrombi were induced using a helium-neon (He-Ne) laser technique in vivo. The numbers of laser pulses required to induce an occlusive thrombus in arterioles were similar in the three strains at the age of 4 weeks. In contrast, the numbers of laser pulses needed to induce vascular occlusion in SHR (5.5 +/- 0.7; n = 4) and SHRSP (4.9 +/- 0.3; n = 4) were lower than in WKY (7.4 +/- 0.3; n = 5) at the age of 16 weeks. Similar differences were observed at 32 weeks (SHR 5.8 +/- 0.2; n = 6; SHRSP 4.3 +/- 0.1; n = 4; WKY 7.0 +/- 0.2; n = 7). Red blood cell velocities were measured in pial arterioles using a fiber-optic laser Doppler anemometer microscope. Red cell velocities and wall shear rates in SHR and SHRSP were significantly lower than those in WKY (p < 0.05) at the age of 16 weeks and were markedly lower in SHRSP than in either WKY or SHR at the age of 32 weeks. The plasma concentration of nitrite/nitrate determined by the Griess reaction was significantly reduced in SHRSP at 32 weeks compared with 4-week-old rats. These changes could contribute to the enhanced tendency to cerebrovascular stroke in SHRSP.

Animals↗