Congenital abnormality of pituitary-thyroid axis in spontaneously hypertensive rats (SHR) and stroke-prone rats (SPR)

In an attempt to study whether TSH abnormality was genetically determined in SHR and SPR, plasma T4, T3, TSH and prolactin concentrations were measured in the animals with intervals of 1 to 3 months. Hypertension was found in 6-month-old SHR and SPR, but it was not found in younger animals. In contrast, a decrease of plasma T3 and an increase of plasma TSH were found in 15-day-old SHR. Also, an increase of TSH was found in 1-month-old SPR in spite of normal plasma T3 concentration. These abnormalities in SHR and SPR increased progressively with age. It is suggested that thyroid-pituitary abnormality was genetically determined in SHR and SPR.

Changes in vascular permeability in stroke-prone spontaneously hypertensive rats studied with peroxidase as a tracer

Cerebrovascular permeability in stroke-prone spontaneously hypertensive rats (SHR) at various ages was histologically studied using horseradish peroxidase as a tracer and such was related to the cerebrovascular lesions in the animals. An increase in permeability was demonstrated in the brain of SHR, particularly in those animals with an extremely high blood pressure. Increased cerebrovascular permeability occurred in some animals without any organic vascular change or severe parenchymal changes, although edema was present. Histologically, the SHR brain with an increase in permeability showed mild focal edema, rarefaction of tissue and necrosis with cyst formation. Thus a transitional progress was evident. Localization of the increase in permeability corresponded well with the predilection sites of cerebrovascular lesions in SHR. Constrictions and dilatations of intracerebral arterioles and small arteries were also demonstrated by the peroxidase method, and the dilated arterial walls did reveal a darker staining. From these results it is strongly suggested that certain cerebrovascular lesions, especially necrosis with cyst formation in SHR are sequelae of the increased cerebrovascular permeability caused by a chronic hypertensive state.

An elevation of plasma ISH concentration in spontaneously hypertensive rats (SHR)

Thyroid activity was tested in two substrains of SHR. Plasma level and pituitary content of TSH increased significantly in both substrains of SHR. As a result, the thyroid weight and thyroidal radioiodine uptake increased significantly. Plasma T3 concentration was decreased in Kyoto substrain but was normal in NN substrain, while plasma T4 concentration decreased significantly in both substrains. Since the pituitary content and plasma level of TSH were significantly higher in spite of the normal concentration of plasma T3, it is concluded that the pituitary "hormostat" is set at a higher level at least in the NN substrain of SHR.

Histopathological studies of the nervous system tumors in rats induced by N-nitroso-methyl-urea

Histopathological examinations were made on tumors of the nervous system induced in rats of Donryu strain by weekly intravenous injections with N-nitroso-methyl-urea (NMU) or by a single administration of NMU through the mothers. A total of 176 neural and nonneural neoplasms were produced in this study. It was suggested that the fetal nervous system of Donryu rats was also highly susceptible to the oncogenic effects of NMU. Of these tumors produced, those of the peripheral nervous system amounted to 121, comprising 68.7% of the total number of the neoplasm. Microscopically, most of the nerve tumors showed the histology corresponding to that of human neurinomas. Many tumors, however, disclosed more or less anaplastic cytological appearance. Fifteen gliomas were produced in the brain and spinal cord. Microscopically, they were classified into mixed glioma, oligondendroglioma and anaplastic astrocytoma. The commonest brain tumors produced in rats from intravenously treated group were periventricular mixed gliomas, while gliomas in rats from transplacentably treated group showed an isomorphic histology with a close resemblance to that of oligodendroglioma.

Pathogenesis and prevention of stroke in spontaneously hypertensive rats

1. A colony of stroke-prone spontaneously hypertensive rats has been developed by selective breeding. 2. These animals developed severe hypertension early in life, the magnitude of the hypertension being closely related to the incidence of stroke. 3. No evidence was obtained of any humoral factor responsible for strokes. 4. Local factors predisposing to stroke were a scanty arterial supply with characteristic recurrent branching of long and large arteries, together with increased vascular permeability, angio-necrosis, and formation of microaneurysms. 5. Strokes could be prevented by adequate antihypertensive therapy from an early age.

Requirement of heat and metabolic energy for the expression of inhibitory action of colicin K

Escherichia coli B, induced for beta-galactoside permease, can accumulate thio-methyl-beta-galactoside in the cell even at 0 degrees D. At this temperature, cells adsorb colicin K but the adsorbed colicin does not inhibit thiomethyl-beta-galactoside uptake. Inhibition by colicin K is, however, seen at 0 degrees C after exposure of the colicin K-cell complex to a high temperature: a greater degree of inhibition occurs with increasing temperature or duration or exposure. There is a transition point at around 21 degrees C in Arrhenius plots of this colicin K activation reaction. If inhibitors of energy yielding reactions are present during the heat treatment, the inhibitory action of colicin K (as measured by thiomethyl-beta-galactoside uptake after returning the colicin K-cell complex to 0 degrees C and removal of the inhibitors) is prevented. These results indicate that adsorbed colicin K is converted into the active state only in the presence of metabolic energy and that cell surface fluidity appears to be concerned in this process.

Experimental studies on the pathogenesis and prophylaxis of stroke in stroke-prone spontaneously hypertensive rats (SHR).(1) Quantitative estimation of cerebrovascular permeability

The cerebrovascular permeability quantitatively determined by the retention of 131I-human albumin in the perfused brains was increased in SHR, especially in stroke-prone SHR compared with normotensive Wistar-Kyoto, and confirmed the macroscopical or microscopical findings on the leakage into the brain or trypan blue or peroxidase injected intravenously 2 to 3 hours before sacrifice. The localization of increased vascular permeability in SHR corresponded to the predilection sites of cerebral hemorrhage or softening, which developed likely following the increased cerebrovascular permeability.

Vascular lesions in the various substrains of spontaneously hypertensive rats and the effects of chronic salt ingestion

Among different races, countries and districts there are definite differences in incidence of hypertensive vascular diseases, for example cerebral bleeding. Hereditary and dietary factors presumably play significant roles. Experimental studies under controlled conditions and utilizint suitable animals are indispensable for analysis of the related factors. For confirmation, hypertensive vascular changes in the spontaneously hypertensive rats were histopathologically studied and related to the difference of substrains. Dietary effects of sodium chloride on these vascular changes were investigated by providing the animals with 1% saline for drinking.