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Biomedical subjects

J Naito

Publications and source records attributed to J Naito.

At least 19 recordsLinked to original sources
PubMed1995

Differences in dispersion of monkey optic nerve fibers according to their terminal layers in the lateral geniculate nucleus.

Dispersion of retinogeniculate fibers in the monkey optic nerve was investigated in relation to their terminal layers in the lateral geniculate nucleus (LGN) using a retrograde axonal tracer (wheat germ agglutinin conjugated to horseradish peroxidase, WGA-HRP). Dispersion of fibers projecting to the parvocellular layer of the LGN (LGNp) is clearly less extensive compared with that of fibers projecting to the magnocellular layer of the LGN (LGNm) in the most distal part of the optic nerve. The occupation rate of retrogradely labeled fibers projecting from the periphery of the nasal retina to the LGNp increases only 1.2 times in the initial part of the nerve. In contrast, the occupation rate increases up to 1.6 times for labeled fibers projecting from a similar part of the nasal peripheral retina to the LGNm in the same part of the optic nerve. The morphological features of the labeled ganglion cells indicate that these fibers arise from P beta and P alpha ganglion cells, respectively.

Animals↗
PubMed1995

Basal release of endothelium-derived nitric oxide plays an important role in the prevention of afterload mismatch in acute left ventricular dysfunction.

The basal release of endothelium-derived nitric oxide (EDNO) is considered to play an important role in regulating the vascular tone in normal subjects; however, its role in the presence of acute heart failure is unknown. This study was designed to clarify the role of a basal release of EDNO in the presence of acute heart failure. Acute ischemic left ventricular (LV) dysfunction was produced in 22 dogs by coronary microembolization. After the embolization, only saline solution was intravenously infused for sixty minutes in 10 dogs. In another 12 dogs, NG-monomethyl-L-arginine (L-NMMA), which is known to inhibit the formation of EDNO in the vascular endothelium, was intravenously infused at a rate of 20 micrograms/kg/minute for sixty minutes. Infusion of saline solution did not produce any changes in hemodynamic variables. Infusion of L-NMMA caused increases in mean aortic pressure, systemic vascular resistance, and LV end-diastolic pressure without changes in the LV peak + and - dP/dt (time constant) of LV pressure fall, and these changes were associated with a giant "v" wave in the tracing of left atrial pressure and a decrease in cardiac output. The basal release of EDNO may play an important role in the prevention of afterload elevation, subsequent cardiac output reduction, and afterload mismatch in the presence of acute heart failure.

Acute Disease↗
PubMed1995

Cell counts in peripheral blood and bone marrow of male C.B-17 scid/scid mice.

Blood cell and bone marrow cell counts were carried out for male C.B-17 scid/scid (SCID) mice aged 3, 6, 9, 18 and 26 weeks and the values were compared with those in C.B-17 +/+ (C.B-17) mice. In the peripheral blood, SCID mice had markedly low numbers of leucocytes and lymphocytes throughout the study. In the bone marrow, SCID mice had relatively low levels of erythroblasts at an early age, low levels of lymphocytes and plasma cells were absent.

Animals↗
PubMed1995

Organization of the sources of reticulospinal projections in the chicken by means of a confocal laser scanning microscope.

To investigate the manner of reticulospinal projections in chickens, two different fluorescent dyes (Fast-Blue and Diamidino-Yellow) were injected into the lumbar and sacral segments. Results showed that the main projections to the spinal segments are clearly different for the pons and medulla. The main source of the medulospinal projections was in the ventral reticular formation, and the projections from the dorsal reticular formation were sporadic. On the other hand, the main pontine projections arose from the dorsolateral tegmentum and they projected to the sacral segments. In contrast, projections to the lumbar segments were somewhat more dominant in the ventromedial tegmentum than in the dorsolateral tegmentum. Double projection neurons were observed in the ventrolateral reticular formation and dorsolateral tegmentum where there were many cells of origin of the spinal descending projections. The reticulospinal projections manner of birds was organized dorsoventrally, and it was comparable with that of mammals.

Amidines↗
PubMed1995

[Age-related changes in the retina of WBN/Kob rats--a pathological study].

Male rats of the WBN/Kob strain, which are known to spontaneously develop diabetes with aging, were examined for histopathological changes in the retina. Five rats (10 eyes) each of WBN/Kob and Wistar/ST as a control were used, and the thickness of the retinal layers, both the central region and the peripheral region of the retina, were measured on weeks 1, 2, 3, 5, 9, 13, 17, 23, 27, 36, 45, 54, 67 and 80 after birth. The rod and cone cell layer in WBN/Kob rats was under-grown, and its thickness decreased 71.7% in the central zone and 59.3% in the peripheral zone of the retina compared with that of the control. In the central and peripheral retina, the rod and cone cell layer, outer nuclear layer and outer plexiform layer, as well as the inner plexiform layer in the central retina, gradually decreased in thickness from 5-45 weeks of age. In the central and peripheral parts of the retina, the number of nuclei decreased in accordance with the thinning of the nuclear layer. The thinned layers showed only cell loss. The rod and cone cell layer of the peripheral retina was thinner than that of the central retina. We obtained the following findings in the retina of male WBN/Kob rats. First, the rod and cone cell layer is undergrown compared with that of the control. Second, the first change occurred in the rod and cone cell layer. Third, the thinning of the rod and cone cell layer appeared at 5 weeks of age, and thinning with aging was slow. And finally, the thinning of the peripheral retina was more severe than that of the central retina. From the above findings, it seems that retinal changes in WBN/Kob rats are similar to the retinal degeneration of rds mice (retinal degeneration slow mice) and that WBN/Kob rats provide a useful animal model for human retinopathy.

Aging↗
PubMed1994

Retinogeniculate projection fibers in the monkey optic chiasm: a demonstration of the fiber arrangement by means of wheat germ agglutinin conjugated to horseradish peroxidase.

The fiber arrangement of the retinogeniculate pathway was investigated in the chiasm of Japanese monkeys (Macaca fuscata) by an iontophoretic injection of wheat germ agglutinin conjugated to horseradish peroxidase into the lateral geniculate nucleus (LGN). It has been claimed that there is a distinct retinotopy in the monkey chiasm, despite lack of any clear anatomical evidence. However, the present data indicate a rather gross retinotopy or almost no discernible retinotopy. Fibers from the foveal-to-peripheral axis of the temporal retina show substantially no retinotopy owing to a marked overlap of fibers in the anterolateral and the posterocentral parts of the ipsilateral hemichiasm. In contrast, the foveal-to-peripheral axis of the nasal retina is re-formed in a gross dorsoventral order in the chiasm. That is, nasal foveal-parafoveal fibers which arise from small cells (which are P beta mode) pass in the dorsal part of the chiasm adjacent to the brain. They widely overlap nasal perifoveal fibers which cross the chiasm more ventrally with very little contact with the brain. The nasal perifoveal fibers also widely overlap nasal peripheral fibers which cross the chiasm more ventrally. Furthermore, the nasal peripheral fibers overlap nasal far peripheral fibers which arise from large cells (including many of the P alpha mode) which run near the pial surface. Fibers from the dorsal and ventral nasal retina cross the midline of the posterior and anterior parts of the chiasm, respectively, and are finally positioned in the medioventral and ventrocentral parts in the tract. Consequently, the dorsoventral retinal axis is re-formed posteroanteriorly in the midline of the chiasm and in a roughly mediolateral direction in the tract. Furthermore, the present study shows that the nasal and temporal retinal fibers coming from the same eye are acutely segregated in the prechiasmal region and the anterior part of the hemichiasm.

Animals↗
PubMed1994

Inhibition by tranilast of collagen accumulation in hypersensitive granulomatous inflammation in vivo and of morphological changes and functions of fibroblasts in vitro.

We examined the effects of tranilast, an anti-allergic agent, on hypersensitive inflammation and on morphology and functions of fibroblasts. In vivo, tranilast suppressed the content of collagen in granulation tissue of hypersensitive granulomatous inflammation induced by methylated bovine serum albumin (m-BSA) in rats. In culture, tranilast inhibited the TGF-beta-independent inflammatory exudate-induced stimulation of morphological changes of fibroblasts to myofibroblast-like cells and their proliferation. Collagen gel contraction by myofibroblast-like cells and fibroblasts was also inhibited by tranilast. Flow cytometric analysis revealed that tranilast suspended the cell cycle of fibroblasts at the G0/G1 phase. These results suggest that tranilast modulates the fibrosis and contraction of granulation tissue by inhibiting the growth of myofibroblast-like cells and fibroblasts.

Administration, Oral↗
PubMed1994

The spinal segmental and preganglionic projections from the brainstem in relation to the chicken cloaca.

Descending projections from the brainstem to the sympathetic and parasympathetic regions of the chicken spinal cord were investigated by means of the WGA-HRP method. The segmental and preganglionic injections of WGA-HRP were made into spinal segments 20-23 and 30-33 which were sympathetically and parasympathetically related to the cloaca, respectively. After injections of a large amount of WGA-HRP into each level of segments 20-23 and 30-33, the labeled SP-neurons (segmental projection neurons) were distributed mainly in the ventral half of the medulla in both cases. The distribution of these labeled neurons extended mainly to the central (20-23 segmental injections) and the lateral (30-33 segmental injections) tegmental regions of the pons. In the mesencephalon, some SP-neurons were found in the dorsomedial reticular formation and the dorsal midline area, in addition to the Ru in both cases. By iontophoretic microinjections of WGA-HRP into the preganglionic regions of these segments, the labeled preganglionic projection neurons (PP-neurons) were found in the ventromedial part of the medulla. Both distributions of the labeled PP-neurons projecting to the sympathetic and parasympathetic regions were similar in the medulla. In the pons, although the sympathetic PP-neurons were found in the ventromedial pontine tegmentum, most of the parasympathetic PP-neurons were found in the dorsolateral tegmentum, e.g., the LoC-SC region. In the mesencephalon, a few sympathetic PP-neurons were found in the midline area ventromedial to the EW, but no parasympathetic PP-neurons were observed in the mesencephalon.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Hypothalamic projections to the spinal segments and preganglionic regions by means of choleratoxin subunit B conjugated HRP in the chicken.

Hypothalamo-spinal projections were studied using the method of retrograde axonal transport of choleratoxin subunit B conjugated to horseradish peroxidase (CTb-HRP) in chickens. CTb-HRP was injected into the segmental and preganglionic regions of spinal segments 23-24 and segments 31-32 which are sympathetically and parasympathetically connected with the cloaca, respectively. Many labeled SP-neurons (segmental projection neurons) were found in the paraventricular nucleus (PVN), except in its lateral protrusion. The distribution of these labeled neurons continued to the more caudal areas such as the vicinity of the nucleus periventricularis hypothalami (PHN), areas medial to the stratum cellulare externum (SCE), the nucleus interstitialis (IS), and the posterior hypothalamic areas. Some labeled SP-neurons were also found in the lateral hypothalamic area. These labeled SP-neurons were distributed in almost the same areas in both cases of injection into segments 23-24 and 31-32. However, the number of labeled neurons was somewhat different rostrocaudally according to the spinal levels injected. In contrast, after microinjections into the spinal preganglionic regions, a small number of PP-neurons (preganglionic projection neurons) were found only in the ventral part of the PVN. These PP-neurons showed the rostrocaudally discernible segregation; PP-neurons in the rostral PVN and those in the caudal PVN were predominantly labeled by microinjections into segments 23-24 and segments 31-32, respectively. The present study suggests that the rostral PVN is more sympathetic and the caudal PVN is more parasympathetic in chickens.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

[The application of industrial endoscope to observation of the ocular-fundus in small laboratory animals].

Observation and recording methods of the ocular-fundus in small laboratory animals were studied using the industrial endoscope and VTR systems, respectively. The ocular-fundus was observed widely, brightly and clearly in the usual animal facility. In addition, the ocular-fundus was recorded easily and it was possible to examine the ocular-fundus recorded by the VTR systems.

Animals↗
PubMed1992

[Evaluation of left ventricular relaxation by mitral regurgitant curve].

To examine whether left ventricular (LV) isovolumic relaxation can be assessed noninvasively using a continuous-wave Doppler technique, we compared Doppler-determined parameters derived from mitral regurgitation (MR) velocity curve with micromanometer-derived indices of LV relaxation, peak negative dP/dt and tau, in 9 patients with MR (5 with dilated cardiomyopathy, 2 with old myocardial infarction and 2 with rheumatic MR). The rate of LV pressure decay (delta P/delta t) at aortic valve closure was calculated from the recordings of MR jet velocities based on the simplified Bernoulli equation. The time constant of LV pressure decay (tD) was determined as the time from the aortic valve closure to the point where the velocity declined by (1/e)1/2. Doppler-determined delta P/delta t correlated well with hemodynamic peak negative dP/dt (r = 0.97, p < 0.001), and tD with hemodynamic tau (r = 0.89, p < 0.005). Thus, we concluded that left ventricular isovolumic relaxation can be noninvasively assessed with a continuous-wave Doppler technique in the presence of mitral regurgitation.

Blood Flow Velocity↗
PubMed1992

Comparative studies on inflammatory reactions induced by non-immunological and immunological stimuli in an air pouch and in a carboxymethyl cellulose (CMC)-induced inflammatory pouch.

Inflammatory reactions were compared in the air pouch and the CMC pouch. Inflammation was induced by injection of CMC as a non-specific irritant, lipopolysaccharide (LPS) as an activator of macrophages, and methylated bovine serum albumin (m-BSA) as an inducer of delayed type hypersensitivity. There was no prominent difference in the inflammatory reactions following injection of 2% CMC solution into a 4-day-old air pouch and a 3-day-old CMC pouch. On the other hand, injection of 4 ml of 100 ng/ml LPS into each of the pouches enhanced the inflammatory reactions in the CMC pouch several-fold compared with those in the air pouch. A similar tendency was found in the case of an injection of 1 ml of 1 mg/ml m-BSA in rats sensitized with 1 mg of m-BSA. The enhanced inflammatory reactions induced by the injection of LPS or m-BSA were inhibited by dexamethasone, but not by indomethacin. These results indicate that the enhanced inflammatory reactions induced by CMC are related to lining tissue formation, which was a common characteristic in both pouches. Enhanced inflammatory reactions following injection of LPS and m-BSA were related to the activation of macrophages and newly formed blood vessels, which were not characteristic features in the air pouch, but were in the CMC pouch, in addition to the lining tissue. Cyclo-oxygenase products were not associated with the reactions.

Air Sacs↗
PubMed1991

A WGA-HRP study of the fiber arrangement in the cat optic radiation: a demonstration via three-dimensional reconstruction.

The fiber arrangement of the optic radiation was investigated in fourteen adult cats. The retinotopies of the lateral geniculate nucleus (LGN) were first identified electrophysiologically, and thereafter, wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was iontophoretically injected into defined positions of the LGN. These corresponded to the central (medial LGN), horizontal peripheral (lateral LGN), dorsal (rostral LGN), and ventral (caudal LGN) retina. Geniculocortical fibers from the each position of the LGN and corticogeniculate fibers projecting to these positions were always labeled reciprocally. Labeled terminals were found massively in layer IV with some extending to the lower part of layer III, but layers VI and I also contained substantial numbers. Although most of the labeled neurons were localized in layer VI, some neurons were labeled in layer V and transsynaptically in layer IV. Labeled fibers were superimposed in three-dimensionally reconstructed maps of the white matter for the easy understanding of the pathways connecting the LGN and the visual cortex. They were localized in certain zones in the white matter without wide dispersion; however, we did not obtain any findings which suggested clearly different populations of geniculocortical and corticogeniculate fibers. In agreement with previous studies, fibers from the rostral LGN and the caudal LGN projected to the striate cortex in a regular order, rostrocaudally, and fibers from the medial LGN and the lateral LGN projected to the striate cortex inversely (i.e. lateromedially). This inverse projection resulted because fibers from the lateral LGN traversed fibers from the medial LGN in a lateromedial direction; however, there was only partial crossing of these two pathways. The distribution of geniculocortical fibers together with corticogeniculate fibers formed topographic zones arrayed mediolaterally in the white matter. Thus, fibers of the medial LGN were positioned in the intermediate zone, and fibers of the rostral LGN and the lateral LGN were positioned in the rostral and caudal parts of the lateral zone, respectively. Fibers of the caudal LGN were found in the medial zone. This fiber arrangement displayed a rough centroperipheral retinotopy in that fibers representing the central area were placed between fibers representing the peripheral retina. Finally, this fiber arrangement was compared with that of the optic nerve and optic tract.

Animals↗
PubMed1991

Relation between height and the maximum conduction velocity of the ulnar motor nerve in human subjects.

The maximum motor nerve conduction velocity of the right and left ulnar motor nerve was measured in more than 650 healthy medical students of both sexes. There was no side difference in the maximum conduction velocity. The shorter person has a statistically significant higher conduction velocity than the taller person. Comparison of students of both sexes showed a slightly higher conduction velocity in females. However, with regard to its relation to height, the conduction velocity was higher in males.

Adult↗
PubMed1989

Retinogeniculate projection fibers in the monkey optic nerve: a demonstration of the fiber pathways by retrograde axonal transport of WGA-HRP.

Seven Japanese monkeys (Macaca fuscata) were used to investigate the fiber pathways of the optic nerve. Optic nerve fibers and retinal ganglion cells were retrogradely labeled by iontophoretic injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into electrophysiologically defined positions of the lateral geniculate nucleus (LGN). By gross anatomical observation, the optic nerve usually had one distinct bend, which flexed dorsally 3-4 mm from the eyeball, and occasionally another ventrally directed bend was found just behind the eyeball. In the optic nerve head, fibers from the various retinal areas were arranged in a wedge according to the fiber trajectory on the retinal surface. For about a 3 mm distance from the disc, fibers rapidly spread out radially. Subsequently, rather than scattering dorsoventrally, they progressed to the chiasm with a gradual increase in the degree of mediolateral (nasotemporal) scatter. The degree of the scatter was different depending on the retinal site from which the axons originated. Fibers from the peripheral retina spread out widely for a few millimeters behind the eyeball. Thereafter the scatter was rather limited until the chiasm. On the other hand, the scatter of fibers from the foveal and parafoveal areas progressed gradually through the nerve. The present study also suggests that the difference in scatter depends on the types of cells of origin. Fibers from large ganglion cells displayed more extensive scatter than fibers from medium-sized cells. In spite of the extensive scatter of fibers, two clear segregations were found; one was a dorsoventral segregation, which was displayed by both central and peripheral retinal fibers, and the other was a center-peripheral segregation in which the fibers from the nasal central (papillomacular) retina were located almost exclusively in the central part of the optic nerve surrounded by peripheral retinal fibers. However, the temporal central retinal fibers were located in the lateral periphery of the nerve, and they overlapped significantly with fibers from the temporal peripheral retina. Furthermore, a broad intermingling was found between nasal and temporal peripheral retinal fibers owing to their mediolateral scatter. Thus, the present findings based on more precise anatomical techniques indicate that the classical notion of the retinal quadrant topography in the monkey optic nerve probably is suspect. In addition, the "rotation" of the fiber arrangement was not demonstrated.

Animals↗
PubMed1989

Species differences in the effects of bezafibrate, a hypolipidemic agent, on hepatic peroxisome-associated enzymes.

The effects of bezafibrate on hepatic peroxisome-associated enzymes of rats, mice, guinea pigs, hamsters, rabbits, dogs and monkeys were examined. Dogs and monkeys were given bezafibrate orally at 30 mg/kg body wt daily for 2 weeks and at 125 mg/kg body wt daily for 13 weeks, respectively, and other species at 100 mg/kg daily for 2 weeks. In male rats, marked changes were observed in the activities of catalase (1.73-fold), D-amino acid oxidase (DAAO; 0.56-fold), fatty acyl-CoA oxidizing system (FAOS; 12.9-fold) and carnitine acetyltransferase (CAT; 35.8-fold); in female rats, the changes were less than in the males. In mice, there were no apparent sex differences in the responses of hepatic peroxisomal enzymes to bezafibrate and the increases in the activities of catalase, FAOS and CAT were 1.76-, 3.75- and 7.94-fold respectively. In guinea pigs, only slight increases in the activities of FAOS (3.00-fold) and CAT (2.83-fold) were observed. In hamsters, the increases in catalase, FAOS and CAT activities, were 1.23-, 2.19- and 2.77-fold respectively. Although rabbits and dogs showed slight increases in CAT activity, no significant response to the drug was observed in monkeys. Hepatomegaly and the increase of hepatic content of peroxisome proliferation-associated polypeptide (PPA-80), which has been recognized as a peroxisomal bifunctional protein in the fatty acid beta-oxidation pathway, were observed only in rats and mice. These results show that there were marked species differences in the effects of bezafibrate on hepatic peroxisomes, and that bezafibrate induced hepatic peroxisome proliferation in rodents, especially rats and mice.

Animals↗
PubMed1989

Tryptophan 2,3-dioxygenase activity in rat skin.

We have found an enzyme system that catalyzes the conversion of L-tryptophan to L-kynurenine, presumably via L-formylkynurenine, in soluble and insoluble fractions of rat skin. The enzymatic activity was stimulated by hematin, ascorbate, and catalase, but not by methylene blue. Highest activity was located in the skin of the dorsal posterior region and lowest activity in the abdominal region. The activity in plucked (depilated) skin was only about 25% of that obtained from unplucked (depilated) tissue of the same region. D-Tryptophan, 5-hydroxytryptophan, and tryptamine were not degraded by the skin enzyme and the Km for L-tryptophan determined with the crude enzyme was 1 microM. The decycling activity of rat skin and liver for L-tryptophan began to be stimulated after birth and reached the highest level at 6 weeks. But, 1 week later, most of the skin activity suddenly disappeared and the low level continued at least until 12 weeks. In contrast, the hepatic enzyme did not change so drastically. These findings suggest that an enzyme that catalyzes L-tryptophan to L-kynurenine via L-formylkynurenine is present in rat skin.

Age Factors↗