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Biomedical subjects

N Mukai

Publications and source records attributed to N Mukai.

At least 55 records · Page 3Linked to original sources
PubMed1982

Effects of cyclic AMP on growth and differentiation of rat retinoblastoma-like tumor cells in vitro.

We examined the effects of cyclic AMP (cAMP) on the growth and differentiation of RAO 188 cells, a cultured cell line derived from a retinoblastoma-like tumor induced in an inbred rat by intravitreous inoculation with human adenovirus serotype 12. After adding cAMP analogs (dibutyryl cAMP and 8-bromo cAMP) and phosphodiesterase inhibitors (theophylline, amino-phylline, and 1-methyl-3-isobutyl xanthine) to the RAO 188 cell culture medium, we measured changes in cell incorporation of the DNA and RNA precursors 14C-thymidine and 3H-uridine, and we observed the morphologic alterations of RAO 188 by phase-contrast and transmission and scanning electron microscopy. Incorporation of the labeled precursors decreased with increased concentrations of cAMP analogs and phosphodiesterase inhibitors. Incorporation of the labeled precursors was inhibited shortly after the addition of dibutyryl cAMP to the culture medium. The effect was maximal at 8 hr and was sustained for up to 48 hr. Reversibility of cAMP effects on incorporation gradually decreased for 10 days; at 10 days these effects were essentially irreversible. Neuritelike processes developed shortly after cAMP analog treatment and formed a network after 24 hr. Transmission electron microscopy disclosed changes in the cell membrane and cytoplasm of cells treated with 8-bromo cAMP and theophylline: perturbation of the cell membrane and the appearance of intercellular junctional devices and microfilaments. The activity of glutamate decarboxylase, which is involved in the biosynthesis of gamma-aminobutyric acid, was increased in treated cells. These results show that cAMP decreases DNA and RNA synthesis and cell proliferation and facilitates morphologic and biochemical differentiation of RAO 188 cells.

Animals↗
PubMed1981

Complement-dependent cytotoxicity in rats bearing human adenovirus type 12-induced primary retinoblastoma-like tumor in the eye.

Using an animal model of retinoblastoma in inbred rats and cultured human adenovirus type 12-induced retinoblastoma-like tumor cells (RAO 188), complement-dependent cytotoxicity was determined by measuring release of 3H-uridine labelled RNA. Sera from rats in which tumors did not grow after adenovirus type 12 inoculation had higher cytotoxicity against RAO 188 cells than sera from rats bearing primary adenovirus type 12-induced retinoblastoma-like tumor. These results showed that the rat which could raise antibodies against adenovirus type 12-induced retinoblastoma-like tumor cells did not allow the tumor growth in the eye after virus inoculation.

Adenoviridae Infections↗
PubMed1980

Retinal tumor induced in the baboon by human adenovirus 12.

Three of 21 newborn baboons injected intraocularly with human adenovirus type 12 developed an intravitreal mass 12 to 36 months later. Two of the masses were indistinguishable from human retinoblastoma, a retinal tumor that afflicts children. To our knowledge this is the first time a retinoblastoma-like tumor has been induced experimentally by adenovirus type 12 in a nonhuman primate.

Adenoviruses, Human↗
PubMed1980

Cerebral lesions in rats with streptozotocin-induced diabetes.

We studied cerebral lesions in the streptozotocin-diabetic rat, an established model of diabetic retinopathy. A group of diabetic rats all had cerebral lesions, but showed no gross abnormalities of the brain or signs of effects on the central nervous system. Light and electron microscopy of horizontal brain sections stained by a variety of methods showed focal accumulation of collagen fibrils in the basement membranes of arteriole and capillary walls, slight degeneration of random neuronic cells (mainly in the brain stem), and no evidence of perivascular myelin pallor plaques. A marked tendency toward platelet aggregation, which leads to thrombosis, was also seen. There was no difference between results from rats killed 9 and 12 months after streptozotocin injection. The brain lesions bore a close resemblance to those seen in a nutritional encephalopathy known to be induced by a diet deficient in tocopherol and rich in oxidized oil, but differed from that encephalopathy in that the peculiar hypertrophic cerebral astroglia associated with diabetes resembled Alzheimer Type II astroglia. The differences between these cerebral astroglia and the retinal Müller cells may account for the difference in degree between the effects of diabetes on the brain and the retina.

Animals↗
PubMed1980

Ultrastructural lesions of retinal pericapillary Müller cells in streptozotocin-induced diabetic rats.

Seventeen Wistar inbred rats were made diabetic by a single injection of streptozotocin (50 mg/kg body weight) and were killed after periods of 3, 6, 9 or 12 months. Pathological changes in pericapillary Müller cells of the retina were studied using electron microscopy. Basement membrane-like material proliferated in the intercellular space of the Müller cell network and occasionally appeared to insinuate into the Müller cell cytoplasm far from capillary pericytes and endothelial cells. The part of the Müller cell that was enveloped by proliferating basement membrane-like material showed partial necrosis which was thought to contribute to the widening of the capillary wall. A breakdown of the retinal framework, which leads to capillary dilatation, was also thought to be associated with partial necrosis of Müller cells. Highly electron-dense bodies accumulated in the Müller cell cytoplasm which surrounded the retinal capillaries. Ultrastructurally, these dense bodies resembled lysosomes. Their increased number might reflect the altered metabolism of the diabetic retina.

Animals↗
PubMed1980

Ultrastructrual studies on choroidal vessels in streptozotocin-diabetic and spontaneously hypertensive rats.

Seven spontaneously hypertensive rats (SHR) and 14 Wistar inbred Kyoto strain rats (WKR) were used. Seven WKR were made diabetic by a single intravenous injection of streptozotocin (50 mg/kg body weight); the seven untreated WKR served as controls. The choroidal vessels of all rats were observed by electron microscopy after 12 months. The choroidal capillaries of control rats showed focal accumulation of basement (BM) in the subendothelial space. Two distinct types of BM lesions were noted: homogeneous thickening and sparse, interlacing branches, or ramifications, of BM. Increased BM caused indentations in the vascular wall. In diabetic rats, BM of capillaries, small arteries, and small veins showed arabesque ramification of BM which represented advanced forms of the sparse, interlacing ramifications seen in normal controls. Contiguous lesions of ramified BM, separated by narrow cytoplasmic processes projecting from the endothelial cells, resembled a scalloped border. In hypertensive rats, the arabesque ramifications were most conspicuous in the small veins. Homogeneous thickening of BM was noted in choroidal capillaries, small arteries, and small veins of SHR, although ramified BM was seen adjacent to it. Endothelial cell proliferation was seen in the small arteries of diabetic and hypertensive rats. The cytoplasm of endothelial cells at the lesion of proliferation was broadened, and cell nuclei appeared cubic or spherical. Consequently, the arterial lumina were narrowed. Complete occlusion was seldom seen in the choroidal arteries of diabetic rats, but it was observed in small arteries of SHR, accompanited by hypertrophy of medial smooth muscle cells and endothelial proliferation. Basement membrane accumulation and endothelial proliferation were common to both groups of rats, but the overall effect of pathological changes was more profound in hyptertension than in diabetes.

Animals↗
PubMed1980

Ultrastructural studies on lysosomes in retinal Müller cells of streptozotocin-diabetic rats.

Four Wistar inbred rats made diabetic by an injection of streptozotocin and four control rats were killed after an experimental period of 12 months. Eye tissues were prepared for examination and detection of acid phosphatase (AcPase) by electron microscopy. In the retina of control animals, the Müller cell cytoplasm had a small number of highly electron-dense bodies. AcPase reaction products were seen on these dense bodies and on Golgi lamellae of Müller cells. In the diabetic rat retina, a greater number of these lysosome-like bodies were seen, especially in cell processes adjacent to capillaries and in those at the vitreoretinal interface. Increased deposits of AcPase reaction products were detected on Golgi lamellae, smooth endoplasmic reticulum, and highly electron-dense bodies. The functional significance of a marked increase in lysosomal enzymes within Müller cells is uncertain. The phenomenon may occur in order to eliminate cellular debris derived from necrotic pericytes and to digest excessive glycogen accumulated in the retina under diabetic conditions.

Acid Phosphatase↗
PubMed1979

Cell origin of human adenovirus type 12-induced subcutaneous tumor in Syrian hamsters.

Single subcutaneous inoculation of human adenovirus type 12 (Ad.12), 0.05-0.1 ml of 10(8.0) TCID50 HEK cells/0.1 ml, was made on the back of 0-day-old hamsters. In 21 of 25 hamsters (84.0%), multiple solid tumors developed close to the inoculation site within 3 months. No control hamsters developed tumors. Tumor histopathology revealed the characteristic Homer Wright rosettes of neuroblastoma. Ad. 12-specific tumor antigens were demonstrable in both the primary and the cultured tumor cells by the immunofluorescein technique. Histochemical demonstration of cholinesterase and NADH oxidoreductase gave rise to a predominantly positive intracytoplasmic granule within the tumor cells. Electron microscopy showed remarkably uniform cell morphology: small, undifferentiated neuroblastic cells with poorly developed intracytoplasmic organelles; many possessed characteristic solitary cilia in a 9 + 0 tubules pattern. Intercellular junctions were poorly developed. Search for an incipient tumor cell aggregate by means of immunofluorescein T-antigen detection was carried out through a 240-h period following Ad. 12 inoculation. A sequential study in parallel with electron microscopic examination of the normal subcutaneous tissue proved that neuroblastic cells closely associated with the muscle spindle anlage could preferentially become the most sensitive target for Ad. 12 tumorigenesis.

Adenoviruses, Human↗
PubMed1977

Retinoblastoma-like neoplasm induced in C3H/BifB/Ki strain mice by human adenovirus serotype 12.

Eighty newborn C3H/BifB/Ki strain mice received a single intraocular inoculation of 0.002--0.003 ml of 10(8.0) TCID 50/0.1 ml human adenovirus 12 (AD 12), within 24 h after birth. Forty mice survived and in seven of these (17.5%) a solid retinoblastomalike neoplasm developed between 64 and 236 days. The tumors have been successfully cultured and also transplanted subcutaneously into syngeneic hosts. Morphologically, all tumors revealed characteristic features of retinoblastoma associated with the Homer Wright type of rosettes. Bizarre giant cells were commonly detectable. Ad 12-specific T-antigens were demonstrated in both the primary and cultured tumor cells using immunofluorescent techniques. Some giant cells also showed numerous T-positive filaments. Electron microscopy disclosed poorly differentiated unipolar cells possessing a large ovoid nucleus. Many tumor cells appeared to contain a well organized solitary cilium consisting of a typical ring of nine doublets with no axial (9 + 0) in close association with a pair of centrioles. Some multinucleated giant tumor cells also contained multiple cilia-centriole complexes within their broad syncytial cytoplasm. Occasional endogenous C particle-like virions unique to murine neuroblastomas were observed for the first time in virus-induced retinal tumors. This unprecedented tumor model in a pure strain mouse adds to the range of known animals sensitive to Ad 12 oncogenesis.

Adenoviruses, Human↗
PubMed1976

An assessment of the generation times of neuronal precursors in the sensory retina and subventricular zone of the newborn rat.

Generation times and the times for their respective phases were determined for neuronal precursors in the sensory retina and subventricular zone of the brain of newborn CD rats. These regions can be induced to form retinoblastoma and medulloepitheliomas, respectively, following injection of adenovirus-12. Through use of autoradiographic techniques, it was shown that the cell cycle duration in the subventricular zone was almost twice as long as in the sensory retinal layer. The G1 phase durations were found to account for the majority of the time difference.

Adenoviridae↗
PubMed1975

Retinal tumor induction by ocular inoculation of human adneovirus in 3-day-old rats.

A direct causal relationship between a human DNA virus, adeno serotype 12, and malignant transformation in target cells (sensory retinal neuronal precursors) was suggested by the development of a remarkably uniform retinoblastoma-like neoplasm in rats. In order to focus upon incipient photoreceptor differentiation, 27 3-day-old CD rats were selected for intraocular virus inoculation. A single injection of 0.03 ml of the virus fluid, 104.5 TCID50 HeLa cells/0.1 ml was given in the left eye. Within 73 to 167 days after the virus inoculation, 12 rats (44.4%) developed retinal tumors in the left eye. Although retinal tumors mimicking human retinoblastoma with true rosettes were anticipated, the highly uniform histopathologic appearance of all 12 eyes was virtually indistinguishable from that of 0-day-old rats. However, multiple foci of malignant cells fusing with the inner segment of relatively well-differentiated retinal layers were found haphazardly throughout the cases; such retinal remnants were not detectable in tumors of 0-day-old rats. Electron microscopy revealed poorly differentiated tumor cells that possessed a single cilium consisting of a typical ring of nine doublets with no axial pair (a 9 plus 0 pattern). Advenovirus-specific T-antigens detected in vivo by the immunofluorescein microscopic procedure in abortively infected or transformed cells clearly indicated that some neuronal precursors destined for part of the ganglioneuronic layer are selectively susceptible to viral oncogenesis. No preferential involvement of the photoreceptor cells was observed. No control animals developed retinal neoplasms.

Adenoviridae↗
PubMed1975

A long-term evaluation of silicone retinopathy in monkeys.

Six owl monkeys were exposed intravitreally for 6 to 28 months to Dow Corning Medical Fluid 350 in a morphologic study of silicone retinopathy. Fellow eyes of each silicone-injected animal and six eyes from three normal untreated monkeys served as controls. In addition, two eyes were treated post-mortem with silicone oil to insure that no artefact redistribution occurred. Each case was studied histochemically in frozen sections, with electron microscopy of Epon-embedded materials. All silicone-injected eyes showed numerous empty spaces in the inner segment of the retina adjacent to the vitreoretinal interface, corresponding to the intercellular spaces between Müller's filbers. These spaces contained numerous spherical bodies encircled by a homogeneous electron-opaque material, suggesting a silicone-phospholipid complex. Marked degeneration of small ganglion cells was seen. Müller's fibers appeared to be shrivelled. The lack of phospholipids in the inner segment of the visual receptors was marked, although no significant morphologic lesions were detectable. Abnormally high ATPase activity was found in both plexiform layers. There were no such lesions in the untreated control eyes, nor any detectable artefactual redistribution of silicone oil in the eyes treated post-mortem with Medical Fluid 350.

Alkaline Phosphatase↗
PubMed1975

[Viruses and brain tumors (author's transl)].

This brief review paper deals mainly with oncogenic DNA viruses originally isolated from human patients, i.e., human adenoviruses and human papova JC viruses. Human adenovirus type 12 was first isolated in 1953 in cell cultures derived from the adenoids of infected children. Since then, 32 antigenic types of human adenovirus have been identified. At least eight serotypes (12, 18, 31, 3, 7, 14, 16, and 21) are now known to be capable of producing tumors in newborn rodents. A direct causal relationship between a human adenovirus and malignant transformations in target cells (sensory neuronal precursors) has been definitely established by the development of a medullo-epitheliomatous neoplasm in the brain and spinal cord of an outbred strain of CD rats at as high an incidence as 90%. Intraocular inoculation of adenovirus in newborn rats within one week also has produced typical retinoblastomatous neoplasms. The remarkably uniform histopathologic appearance of all these malignancies in nervous tissue can be attributed to a primitive neuro-epitheliomatous neoplasm derived from sensory microneuron precursors that densely populate both the ventricular zone and the premature sensory retina at the point of virus inoculation. All of these brain and retinal tumors appear to share a common tumor phenotype, as all tumor cells contain cilia with the same morphology (a 9+0 pattern of doublets associated with a pair of centrioles). The production of adenovirus tumor-specific neoantigen (T), an earmark of the viral genome, can be regularly demonstrated by the immunofluorescein microscopic procedure. All transformed cells within both the ventricular zone and the retinal ganglion cell anlage thus appear to continue the production of (T) antigens. These findings lead us to assume that the target cell determinants in adenovirus tumorigenesis may reside in differentiating microneuron precursors ordained for the sensory neuronal complex.

Abdominal Neoplasms↗