Biomedical subjects

J Naito

Publications and source records attributed to J Naito.

At least 55 records · Page 3Linked to original sources

PubMed1996

Ultrasonic myocardial tissue characterization in patients with dilated cardiomyopathy: value in noninvasive assessment of myocardial fibrosis.

Dilated cardiomyopathy (DCM) is usually diagnosed from the left ventricular functional viewpoint by the detection of dilated ventricular cavity and depressed myocardial contractility. Although histologic analysis of the myocardium no doubt provides clinically important information, it is possible only with microscopic examination of biopsy specimen of the myocardium. The objective of this particular study is to clarify the comparative values of the measures of ultrasonic tissue characterization, that is, calibrated myocardial integrated backscatter (IB) and the magnitude of cyclic variation in IB, with conventional echocardiographic parameters in assessing histologic condition of the myocardium. The magnitude of cyclic variation in IB and myocardial IB at end-diastole calibrate with the power of Doppler signals from the blood were measured in addition to conventional echocardiographic parameters in 14 patients with DCM. Calibrated myocardial IB was higher in patients with more fibrosis in the biopsy specimen of the heart tissue, whereas the magnitude of variation in IB or conventional echocardiographic parameters did not significantly correlate with a histologic estimate of myocardial fibrosis. Calibrated myocardial IB provides information about the myocardial fibrosis that cannot be assessable with conventional echocardiographic parameters. Calibrated myocardial IB and the magnitude of cyclic variation of IB are likely to reflect somewhat different acoustic properties of the myocardium.

Adult↗

PubMed1996

Endothelial dysfunction in the early stage of atherosclerosis precedes appearance of intimal lesions assessable with intravascular ultrasound.

The objective of this study was to clarify whether morphologic evaluation of the in vivo artery with intravascular ultrasound provides as sensitive a marker as endothelial dysfunction or microscopic histologic assessment. Endothelial dysfunction assessed with the changes in the vessel diameter during acetylcholine infusion has been used as a more sensitive marker of atherosclerosis than the angiographic estimates of morphologic structure of the vessel. Recent advent of intravascular ultrasound has provided such high-resolution images of the vessels that morphologic changes in the vessel structure are sensitively and accurately detected. Twenty-two rabbits were divided into three groups: six rabbits fed a cholesterol-rich diet for 2 weeks as the hypercholesterolemia group, eight rabbits fed with the diet for 8 weeks as the atherosclerosis group, and eight rabbits fed a normal diet as the normal group. After evaluating the atherosclerotic lesions by intravascular ultrasound, the cross-sectional area was measured in the baseline and during the infusion of acetylcholine (0.05, 0.5, and 5 micrograms/kg/min) and nitroglycerin (5 micrograms/kg/min). No atherosclerotic lesions were detectable with intravascular ultrasound in any rabbit despite the presence of microscopic intimal lesions in the vessels in the rabbits of the atherosclerosis group. The cross-sectional area increased during acetylcholine infusion in the rabbits of the normal and the hypercholesterolemia groups. In contrast, in the rabbits of the atherosclerosis group, the cross-sectional area did not significantly increase during acetylcholine infusion at the rate of 0.5 microgram/kg/min and even tended to decrease at the rate of 5 micrograms/kg/min (-3.8% +/- 3.7%, P < 0.05 vs the normal group). Dilating responses to nitroglycerin infusion were similar among all three groups. In conclusion, impairment of the endothelium-dependent vasodilating response assessed with intravascular ultrasound in the in vivo vessel precedes the appearance of echographic atherosclerotic findings. Thus intravascular ultrasound, if used in combination with drug intervention to assess endothelial function, would provide even more accurate assessment of the vessels than conventional intravascular ultrasound alone.

Acetylcholine↗

PubMed1996

Myocardial integrated ultrasonic backscatter in patients with old myocardial infarction: comparison with radionuclide evaluation.

The purpose of our study was to clarify whether the abnormalities in integrated backscatter may be used to assess myocardial viability in patients with old myocardial infarction by comparing these integrated backscatter parameters with conventional radionuclide and echocardiographic estimates of myocardial viability. Two myocardial integrated backscatter parameters, the magnitude of cyclic variation in integrated backscatter and the myocardial integrated backscatter calibrated with the power of Doppler signals from the blood along the same ultrasound beam (calibrated myocardial integrated backscatter), were measured in 21 normal persons and 33 patients with old anteroseptal myocardial infarction. Calibrated myocardial integrated backscatter was higher and the magnitude of cyclic variation in integrated backscatter was lower in the infarct septum compared with the septum of normal subjects. Percent thallium uptake, as assessed in scintigraphic images taken at rest or after reinjection, correlated well with the calibrated myocardial integrated backscatter (r = -0.72, p < 0.01) and more weakly but significantly with the magnitude of cyclic variation in integrated backscatter (r = 0.55, p < 0.05) in 16 of 33 patients. The measurement of calibrated myocardial integrated backscatter, in addition to the magnitude of cyclic variation of integrated backscatter, may likely be valuable in the noninvasive assessment of myocardial viability.

Adult↗

PubMed1996

Somatostatin-14 and somatostatin-28 in chicken pancreatic islet D-cells.

Somatostatin (SST)-14 and mammalian (m) SST-28[1-14] immunoreactivities of chicken pancreatic islets were investigated by using light microscopic immunohistochemistry. Chicken D-cells in both A- and B-islets showed immunoreactivity to SST-14, but not to mSST-28[1-14]. The acid-extract from both splenic and ventral lobes of pancreas was fractionated by reverse-phase high-performance liquid chromatography, and the SST-like immunoreactivity was measured in the radioimmunoassay using anti-SST-14 serum. In both lobes, the SST-like immunoreactivity was detected in the fraction which corresponded to that of SST-14 standard, but was not found in that of mSST-28 standard. Immunohistochemically, pancreatic endocrine D-cells of 1 amphibian, 4 reptiles and 12 birds showed the same immunostaining property as chicken D-cells. By contrast, both SST-14- and mSST-28[1-14]-immunoreactive D-cells were observed in the pancreatic islets of 16 mammals. From these results, we concluded that chicken islet D-cells contain only SST-14-like peptide, but not SST-28-like peptide, and that this phenomenon may be common to the avian species.

Amphibians↗

PubMed1996

Role of basal release of nitric oxide in the presence of acute left ventricular dysfunction: comparative study with normal condition.

The basal release of nitric oxide (NO) plays an important role in the regulation of vascular circulation in the presence of acute left ventricular dysfunction. It is not clear, however, whether the role is as important in the presence of acute left ventricular dysfunction as it is in the normal condition. In addition, the effects of flow rate on the role of basal NO have not been clarified in the presence of acute left ventricular dysfunction. This in vivo study was attempted to compare the contribution of the basal release of NO to the regulation of vascular circulation and the effects of a mechanically reduced basal flow rate on the contribution of basally released NO between the normal condition and acute left ventricular dysfunction. In eight anesthetized dogs, the responses of femoral artery blood flow to NG-monomethyl-L-arginine (L-NMMA, 10(-5)M) were observed with and without a reduction in basal flow. The same observation was performed after the production of acute left ventricular dysfunction by coronary microembolization. Without the reduction in basal flow, the L-NMMA-induced decrease in femoral artery flow was significantly larger in acute left ventricular dysfunction than in the normal condition (-40 +/- 12% vs-17 +/- 6%, P < .01). Under the reduction in basal flow, there was no significant change in flow during the infusion of L-NMMA in the normal condition and only a small decrease in acute left ventricular dysfunction. There was no significant difference in the L-NMMA-induced changes in flow between these conditions. The contribution of basally released NO to the regulation of vascular circulation is larger in the presence of acute left ventricular dysfunction than in the normal condition; however, the role of basal NO is reduced with a decrease in basal flow rate.

Acetylcholine↗

PubMed1996

Muscle representation within the hypoglossal nucleus of the chicken studied by means of horseradish peroxidase.

The distribution in the chicken of motoneurons innervating the hyolingual muscles, i.e. the Mm. hyoglossus rostralis (HR), hyoglossus obliquus (HO), ceratoglossus (CG), interceratobranchialis (CB), stylohyoideus (YH), serpihyoideus (PH) and cricohyoideus (CR), and the laryngotracheal muscles, comprising the Mm. tracheolateralis (TL), cleidohyoideus (CL) and sternotrachealis (ST), was examined by retrograde transport of horseradish peroxidase conjugated with wheat-germ agglutinin. Labelled motoneurons are only found in the hypoglossal nucleus. The rostrocaudal distributions of motoneurons projecting to hyolingual muscles are restricted in the hypoglossal nucleus cranial to the obex, and those projecting to laryngotracheal muscles are distributed in the more caudal part of hypoglossal nucleus. Detailed analysis of the data showed that the most rostrally positioned motoneurons in the hypoglossal nucleus supplied to the PH, followed by the CG, CB, HR, YH, HO, CR, TL, CL and ST in that order, overlapping each other. In the hypoglossal nucleus motoneurons innervating the PH and YH have the smallest perikarya. Of the motoneurons in the hypoglossal nucleus, those supplying the laryngotracheal muscles (CL and TL) have the largest perikarya. Motoneurons innervating the other muscles are intermediate in size.

Animals↗

PubMed1996

Coronary back flow pressure is elevated in association with increased left ventricular end-diastolic pressure in humans.

To clarify the effect of left ventricular (LV) diastolic pressure on the coronary pressure-flow relation in humans, the instantaneous diastolic coronary pressure-Doppler flow velocity relation was analyzed at rest and during papaverine-induced maximal vasodilation in 15 patients with angiographically normal coronary arteries. The values for slope (alpha PF) and zero-flow pressure intercept (Pzf index) of the instantaneous diastolic coronary pressure-flow velocity relation were obtained by a linear regression analysis. Although alpha PF did not correlate with LV end-diastolic pressure (EDP), the Pzf index correlated positively with LVEDP both at rest and during maximal vasodilation (r = 0.64, P < 0.05 and r = 0.58, P < 0.05, respectively). Thus, the back pressure to coronary inflow, as indicated by the Pzf index, may be elevated in patients with increased LVEDP, resulting in the rightward shift of the maximally dilated coronary pressure-flow relation and decreased maximal coronary flow and reserve at any given perfusion pressure.

Adult↗

PubMed1995

Digital subtraction high-frame-rate echocardiography in detecting delayed onset of regional left ventricular relaxation in ischemic heart disease.

BACKGROUND: Because left ventricular (LV) diastolic function is impaired before systolic function in patients with ischemic heart disease and because ischemic heart disease is constituted of regional rather than global abnormalities of the left ventricle, measures of LV regional diastolic dysfunction, if possible, should provide the most sensitive assessment of the coronary involved region. The objectives of this study are to clarify whether high-frame-rate two-dimensional echocardiography, combined with digital subtraction image processing, may be used to visualize regional LV relaxation abnormalities in patients with ischemic heart disease and to clarify whether this technique provides a measure for the noninvasive assessment of the coronary involved region. METHOD AND RESULTS: In 30 normal subjects and 59 patients with ischemic heart disease, two-dimensional echocardiograms obtained at a rate of 60 frames per second were provided on line for digital subtraction analysis, with which digitized images were continuously subtracted on a frame-by-frame basis. The subtracted images were analyzed to determine the onset of the segmental outward motion of the LV wall in early diastole in each of 16 segments per subject. Regional relaxation index, defined as the interval from the second heart sound to the onset of outward wall motion, was significantly prolonged in the coronary involved segments compared with the normal segments (36.3 +/- 18.0 versus 101.2 +/- 34.0 ms, P < .01). The prolongation in the regional relaxation index was observed even in the coronary involved segments without reduction in systolic wall motion. When a cutoff level of 50.0 ms was used, coronary involved segments could be distinguished from normal or border segments with a sensitivity of 92% and a specificity of 81%. CONCLUSIONS: Digital subtraction high-frame-rate echocardiography may be used to visualize regional LV relaxation abnormalities in patients with ischemic heart disease. The time interval from the second heart sound to the onset of the segmental outward motion of the LV wall (regional relaxation index) obtained with this technique provides a noninvasive and accurate measure for assessing coronary involved regions.

Adult↗

PubMed1995

Noninvasive assessment of left ventricular relaxation using continuous-wave Doppler aortic regurgitant velocity curve. Its comparative value to the mitral regurgitation method.

BACKGROUND: The most established parameters of left ventricular (LV) relaxation are peak negative value of the first derivative of LV pressure (-dP/dtmax) and the time constant of isovolumic LV pressure fall. The instantaneous pressure gradient between the aorta and the LV during diastole can be calculated from the continuous-wave Doppler aortic regurgitant velocity spectrum. Because the fluctuation of aortic pressure during LV isovolumic relaxation is negligibly minor and because LV minimal pressure is negligibly low, LV pressure during the isovolumic relaxation period may be derived from the continuous-wave Doppler aortic regurgitant velocity spectrum. This study was designed to clarify whether analysis of continuous-wave Doppler aortic regurgitation recording provides accurate measures of LV relaxation over a wide range of LV function and to determine comparative values of aortic and mitral regurgitation methods in the assessment of LV relaxation. METHODS AND RESULTS: In eight mongrel dogs with acute ischemic LV dysfunction, the continuous-wave Doppler aortic regurgitant velocity spectrum was recorded simultaneously with high-fidelity LV and aortic pressures, while the continuous-wave Doppler mitral regurgitant velocity spectrum was recorded simultaneously with high-fidelity left atrial and LV pressures. The aortic regurgitant velocity spectrum was provided for the determination of Doppler-derived mean rate of LV pressure fall in 20 ms after the onset of aortic regurgitation (delta P/delta t-AR) and the time interval from the onset of aortic regurgitation to the point at (1-1/e)1/2 of the maximal aortic regurgitant velocity as an estimate of the time constant. The mitral regurgitant velocity spectrum was provided for Doppler-derived mean rate of LV pressure fall in 20 ms after the point of -dP/dtmax (delta P/delta t-MR) and the time interval from the point of -dP/dtmax to the point with mitral regurgitant velocity of (1/e)1/2 of the mitral regurgitant velocity at the point of -dP/dtmax as an estimate of the time constant. delta P/delta t-AR and delta P/delta t-MR correlated well with catheter-derived -dP/dtmax (r = .92, r = .98, P < .01, respectively). The time constant derived from aortic and mitral regurgitant velocity spectra (tau-AR and tau-MR) also correlated well with catheter-derived time constant (r = .84, r = .76, P < .01, respectively). However, a mean difference of the catheter-derived time constant minus tau-MR was larger than tau-AR (29 +/- 30 versus 4 +/- 17 ms, P < .01, presented as mean +/- 2 SD). CONCLUSIONS: LV relaxation can be assessed from the continuous-wave Doppler aortic regurgitant velocity spectrum. The aortic regurgitation method provides an even more accurate estimate of the time constant compared with the mitral regurgitation method, particularly in the presence of LV dysfunction.

Animals↗

PubMed1995

Intraventricular dispersion of early diastolic filling: a new marker of left ventricular diastolic dysfunction.

Mitral flow velocity patterns are frequently "normalized" by the alteration in the loading condition even in the presence of left ventricular (LV) diastolic dysfunction. In addition, a simple index, the ratio of mitral peak early diastolic flow velocity to mitral peak flow velocity at atrial contraction, is not obtainable in patients with atrial fibrillation (Af). Thus these limitations hamper the value of analyzing the mitral flow velocity pattern in the assessment of abnormal LV diastolic characteristics. This study was designed to elucidate the hypothesis that peak early diastolic flow velocity decreases progressively from the base to the apex in patients with LV diastolic dysfunction. Regional diastolic flow velocity patterns at 1, 2, or 3 cm from the mitral tip toward the apex were simultaneously recorded with the mitral flow velocity pattern by using multigate pulsed Doppler echocardiography in 42 subjects with normal LV function (31 normal volunteers and 11 patients with Af only), 17 patients with hypertensive heart disease, and 22 patients with dilated cardiomyopathy. In the normal subjects early diastolic flow velocity at the mitral tip was maintained at the positions 1 to 3 cm away from the tip into the LV cavity. In contrast, regional peak early diastolic flow velocity progressively decreased toward the apex in patients with hypertensive heart disease and dilated cardiomyopathy. These findings were observed even in patients with a normalized mitral flow velocity pattern or those with Af. Thus the assessment of the intraventricular decrease in peak early diastolic flow velocity may be useful in detecting LV diastolic dysfunction, particularly in patients with Af or a "normalized" mitral flow velocity pattern.

Adult↗

PubMed1995

Doppler echocardiographic pulmonary venous flow-velocity pattern for assessment of the hemodynamic profile in acute congestive heart failure.

The hemodynamic profile of congestive heart failure (CHF) is best described in terms of its two primary sets of hemodynamic parameters, that is, left atrial pressure and cardiac output, each of which has a specific and independently variable hemodynamic cause. To assess whether analysis of the mitral and/or pulmonary venous flow-velocity patterns provides valuable information in the noninvasive assessment of the hemodynamic profile of CHF, these patterns were obtained by using the transthoracic approach in 18 patients with acute CHF with simultaneous measurements of catheter-derived mean pulmonary capillary wedge pressure and thermodilution cardiac index. Measurements were repeated on two occasions in each case: at the acute stage of CHF and 1 to 5 days after treatment. Peak diastolic pulmonary venous forward flow velocity was higher, the ratio of pulmonary venous systolic to diastolic peak forward flow velocity was lower, and the ratio of mitral early diastolic to late diastolic flow velocity was greater in patients with higher mean pulmonary capillary wedge pressure (r = 0.80, n = 36, p < 0.01; r = -0.69, n = 36, p < 0.01; r = 0.71, n = 36, p < 0.01). Peak systolic pulmonary venous forward flow velocity and time-velocity integral of the systolic pulmonary venous flow wave were greater in patients with larger cardiac index (r = 0.80, n = 36, p < 0.01; r = 0.62, n = 36, p < 0.01). In conclusion, two primary sets of hemodynamic parameters, that is, left atrial pressure and cardiac output, can be estimated with Doppler pulmonary venous flow parameters in patients with acute CHF.

Acute Disease↗

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

Validation of transthoracic myocardial ultrasonic tissue characterization: comparison of transthoracic and open-chest measurements of integrated backscatter.

To investigate whether myocardial integrated backscatter (IB) can be measured through the chest wall, myocardial IB parameters were measured in five adult mongrel dogs with a newly developed IB imaging system capable of measurements of myocardial IB relative to backscatter from the blood. There was no significant difference in the calibrated myocardial IB between the closed chest and the open chest conditions either in the septum or in the posterior wall if a 2.5- or 3.5-MHz frequency transducer was used. There was no significant difference in the magnitude of cyclic variation in IB between the closed chest and the open chest conditions independent of the frequency of the transducer used. These data suggest that we can accurately measure not only the magnitude of cyclic variation in IB but also the calibrated myocardial IB through the chest wall with a 2.5- or 3.5-MHz frequency transducer. Such data may validate measurements of myocardial IB parameters through the chest wall even in humans.

Algorithms↗

PubMed1995

Degree of external force to the left ventricle determines hemodynamic response to nitroprusside in failing hearts: comparison with the response to dobutamine.

Vasodilators frequently, although not always, increase cardiac output (CO) in patients with congestive heart failure (CHF) despite a decrease in left ventricular (LV) diastolic pressure. In patients with CHF, vasodilator-induced decrease in LV diastolic pressure without decrease in "preload" plays an important role in the vasodilator-induced increase in CO failure that may be caused by a vasodilator-induced reduction in external force to the LV. To clarify the hypothesis that a hemodynamic response to vasodilators depends on the degree of external force to the LV in failing hearts before drug administration and to examine whether the degree of the external force also affects a hemodynamic response to positive inotropic agents, we produced in 17 dogs two different conditions of LV dysfunction with high LV end-diastolic pressure (EDP: > or = 15 mm Hg), i.e., 1 with high right ventricular (RV) EDP (condition 1) and the other with lower RVEDP than condition 1 (condition 2), and compared hemodynamic effects of nitroprusside or dobutamine between these two conditions. Condition 1 was produced by the injection of a small dose of microspheres into the left coronary artery and intravenous infusion of dextran. Condition 2 was produced only by the injection of a large dose of microspheres. The nitroprusside-induced decrease in LVEDP was associated with a greater decrease in RVEDP and lesser decreases in mean left atrial pressure and LV end-diastolic diameter in condition 1 than in condition 2. CO increased in condition 1; however, CO then decreased in condition 2. The nitroprusside-induced changes in CO inversely correlated with those in RVEDP (r = 0.65, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

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↗