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Biomedical subjects

H Imai

Publications and source records attributed to H Imai.

At least 595 records · Page 33Linked to original sources
PubMed1980

Angiotoxicity of oxygenated sterols and possible precursors.

Cell death, inflammation, and repair in rabbits' aortas and pulmonary arteries were observed at 3-, 7-, and 10-day periods after the intravenous injection of oxygenated sterols. Thus, oxygenated sterols, not cholesterol, may play the primary role in arterial wall injury and lesion development.

Animals↗
PubMed1980

Penetration of zona-free hamster eggs in vitro by goat spermatozoa preincubated in the reproductive tract isolated from a maturing gilt.

When goat spermatozoa were preincubated for 5-5.5 hr in the isolated uterus and oviduct from a maturing gilt, they developed the ability to penetrate zona-free hamster eggs in vitro. Overall penetration rates were 17% and 0%, respectively, 1 hr after insemination, and these increased to 59% and 54% 2 hr later. The penetration rates were not improved by incubation longer than 2 hr after insemination up to 5 hr. Goat spermatozoa preincubated for 5 hr in a m-KRB solution with or without goat serum penetrated zona-free hamster eggs with difficulty. The results suggest that a functional change in the ability of goat spermatozoa to penetrate zona-free hamster eggs may occur in the reproductive tract of different species.

Animals↗
PubMed1980

Inhibitory connections of nystagmus-related reticular burst neurons with neurons in the abducens, prepositus hypoglossi and vestibular nuclei in the cat.

Action potentials of inhibitory burst neurons (IBNs) were extracellularly recorded in the pontomedullary reticular formation in the cat. These neurons were identified by their burst activity coincident with the quick inhibitory phase of the contralateral abducens nerve during vestibular nystagmus and by their antidromic activation from the contralateral abducens nucleus. During extracellular recording from the soma of single IBNs, another electrode for microstimulation was systematically tracked throughout the brain stem. For each IBN investigated, the effective sites for antidromic activation were invariably found in the contralateral abducens, prepositus hypoglossi, medial vestibular nuclei and the area ventral to the prepositus hypoglossi nucleus. Stimulation of neither the ipsilateral brain stem nor the oculomotor nuclei evoked antidromic responses in IBNs. Extracellular spikes of single IBNs and neurons in the overlying projection area were recorded simultaneously. Their correlation was examined by using peri-spike time histograms. Shortly after the spikes of single IBNs, the activity of motoneurons and internuclear interneurons in the abducens nucleus, and of type II neurons in the prepositus hypoglossi and vestibular nuclei, was depressed. Connections of IBNs with ipsilateral medial rectus motoneurons were studied by spike-triggered averaging of membrane potentials of the motoneurons and action potentials of the medial rectus nerve. Single IBN spikes induced a di- or polysynaptic disfacilitation in the motoneurons. This disfacilitation was concluded to be mediated by some of the above-described interneurons which were directly inhibited by IBNs. Their depressant effect on medial rectus motoneuronal spike activity was comparable to that on the spike activity of contralateral abducens motoneurons.

Abducens Nerve↗
PubMed1980

Fertilization in vitro of hamster and mouse eggs in a chemically defined medium.

Hamster and mouse eggs with follicular cells were penetrated by epididymal spermatozoa in a modified Krebs-Ringer-bicarbonate solution known to be suitable for fertilization of rat eggs in vitro. The highest proportion (84-88%) of hamster eggs penetrated was observed when 6-30 eggs with follicular cells were introduced into 10 microliter sperm suspension. Greater volumes of sperm suspension reduced the proportions of eggs fertilized, while increased numbers of eggs in the same volume gave greater penetration rates. No fertilization was observed when 21-30 denuded hamster eggs were introduced into 10-100 microliter sperm suspension, indicating that capacitation and/or acrosome reaction of hamster epididymal spermatozoa was induced only by the post-ovulatory oviduct contents in this medium. However, when small numbers (10-20) of mouse eggs with or without follicular cells were incubated in a large volume (400 microliter) of sperm suspension 84-96% and 91% were penetrated, respectively, suggesting a lack of importance of the products of ovulation on mouse sperm capacitation. The incidence of polyspermy was very low for the hamster (0-13%) and mouse eggs (0-10%).

Animals↗
PubMed1980

Aortic lesions in nonlaying hens with endogenous hyperlipidemia.

Atherogenicity of chemically discrete cholesterol has been questioned earlier at small doses insufficient to cause hypercholesterolemia. Long-term experiments involving large doses are hindered by the propensity of cholesterol to autoxidize in air. As an alternative, aortic lesions in mature, 1- to 3-year-old laying and hereditary nonlaying hens were studied by electron microscopy. Due to spontaneous egg yolk involution, serum cholesterol values of nonlayers were high, averaging 583 mg/dL, and triglyceride values averaged 1,777 mg/dL. Respective values in layers were 106 mg/dL and 894 mg/dL. Aortic lesions in nonlayers developed earlier and were more extensive and fatty than in layers. Lipids were stainable even in the media of grossly normal segments of aorta in nonlayers. Findings suggested an important role of inhibition of hyperlipidemic components. It is unknown, however, whether large amounts of endogenous cholesterol in serum undergo autoxidation in vivo.

Animals↗
PubMed1979

Time requirement for capacitation of boar spermatozoa assessed by their ability to penetrate the zona-free hamster egg.

Boar spermatozoa were preincubated for various times in the isolated uterus and oviduct from a maturing gilt and used to inseminate zona-free hamster eggs. The proportions of eggs penetrated and activated were increased, and the interval between insemination and sperm penetration was shortened when the spermatozoa were preincubated for 4--5.5 h instead of 2--.5 h. Overall penetration rates were higher and sperm penetration occurred about 1 h earlier when the eggs were inseminated with spermatozoa preincubated in the uterus than in the oviduct. It is concluded that the change in ability of boar spermatozoa to penetrate zona-free hamster eggs is due to capcitation which requires 4--4.5 h and 5--5.5 h of preincubation in the isolated uterus and oviduct, respectively.

Animals↗
PubMed1979

Morphological alteration of aortic wall and mitotic cells after complete endothelial loss induced by repeated balloon denudation of swine aorta.

The aortic endothelium in weanling swine was rubbed ten times with an inflated balloon catheter in a repeated balloon denudation. This procedure produced more drastic, extensive and uniform changes in the aortic wall than the commonly used balloon denudation. Sequential alternations of regenerating endothelium, intimal thickening and medial reaction, and the incidence of mitotic cells were studied by scanning and transmission electron microscopy. Complete endothelial loss was confirmed from the descending thoracic aorta to the right femoral artery within 24 hr. By the third day, regenerated endothelium began to cover over the endothelial defect area from the uninjured areas such as the aortic arch and the orifices of branching arteries. Thrombus formation and fibromuscular intimal thickening were observed in the endothelial defect areas by the fifth and seventh days. Three types of mitotic cells, such as endothelial, intimal and medial cells were noted in the aortic wall. Mitotic endothelial and mitotic medial cells were most frequent at Day 3; the latter were closely associated with dead medial cells. Mitotic intimal cells initially appeared at Day 3 and were most frequent at Day 7. Mitotic intimal and mitotic medial cells were frequently present in the aortic wall subjacent to the endothelial defect areas containing interstitial blood components. The large numbers of mitotic aortic cells indicated that endothelial cells give rise to new endothelial cells, intimal cells to new intimal cells, and medial cells to new medial cells.

Animals↗