[Detection of microemboli by transcranial Doppler sonography after carotid endarterectomy]

Transcranial Doppler sonography (TCD), a non-invasive monitoring technique, has potential for detecting microemboli caused by the extracranial internal carotid artery. Many previous reports have shown that TCD-detected microemboli may be a risk factor for stroke. The main purpose of this study is to verify whether microemboli cease after carotid endarterectomy (CEA). TCD monitoring was performed in 43 cases before and after CEA. TCD monitoring was carried out for an hour at the ipsilateral middle cerebral artery of each case using a 2-MHz pulse-wave transcranial Doppler device, and high intensity transient signals were counted as microemboli. Microemboli were detected preoperatively in 10 cases (23.3%). Microemboli were not detected in any case immediately after CEA, in either the subacute stage (from 14 to 21 days after CEA) or in the chronic stage (more than 3 months after CEA). In the acute stage (from 3 to 7 days after CEA), microemboli were detected in three cases (7.0%). The rate of TCD-detected microembolic was always significantly reduced after CEA. TCD monitoring can be helpful in assessing the effect of CEA for prevention of stroke by removing the suspected source of microemboli.

[Analysis of factors related to microemboli in cases with internal carotid artery stenosis]

Transcranial Doppler ultrasound (TCD) has been used to detect microemboli in cases with extracranial internal carotid artery stenosis. However, the mechanism causing microemboli has remained unclear. The purpose of this study is to clarify clinical characteristics and circumstances associated with the genesis of TCD-detected microemboli. Ninety-one cases with more than 30% stenosis of the internal carotid arteries were studied. TCD monitoring was carried out for an hour at the ipsilateral middle cerebral artery of each case using a 2-MHz pulse-wave transcranial Doppler device, and high intensity transient signals were counted as microemboli. Digital subtraction angiography, magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT) were also performed in all cases. Microemboli were detected in 30 of 91 cases. Microemboli were significantly well detected in cases with a history of ischemic event and/or cerebral infarction recognized by MRI. Detection of microemboli had no relation to sex, age or clinical risk factors (hypertension, hypercholesterolemia, diabetes mellitus and smoke habituation). In contrast, detection of microemboli was significantly related to decrease in cerebral blood flow recognized by SPECT, severity of stenosis and wall irregularity of lesion recognized by angiography. Microemboli can be found in a significantly high percentage of these clinical conditions, which may be risk factors for embolic stroke caused by extracranial internal carotid artery stenosis.

Construction of a plasmid vector for transformation of Porphyromonas gingivalis

A host-vector system for transformation of Porphyromonas gingivalis was constructed using a set (1) strains that can incorporate plasmid DNA by electroporation regardless of its source and (2) stable vector plasmids with a selectable marker. First, restriction-negative mutants were isolated, because P. gingivalis possesses restriction modification systems by which DNA introduced by transformation even from heterologous strains of the same species is excluded. For screening of the mutants, plasmid pE5-2 was employed since it could be transconjugated (mobilized) to P. gingivalis from Escherichia coli and is able to replicate in this species, albeit not stably. pE5-2 DNA prepared from E coli was introduced by electroporation into chemically mutagenized P. gingivalis cells. By this method, three putative restriction-negative clones were selected. These strains exhibited a capacity for electroporation with plasmid DNAs both from E. coli and from various P. gingivalis strains at a similar efficiency. Using one of the derivatives thus obtained, YH522, we then screened for plasmids that could replicate stably in P. gingivalis. Since no plasmids were found from P. gingivalis, cryptic plasmids from other species of black-pigmented oral anaerobic rods were examined for their ability to transform P. gingivalis. A series of plasmids constructed by ligation with pBR322 for replication in E. coli and the EcoRI-B fragment from pBF4 containing erythromycin resistance were prepared from E. coli and were used for electroporation of P. gingivalis. Among these, a recombinant plasmid containing the replicon of pYHBA1 from Porphyromonas asaccharolytica, designated pYH400, was found to be incorporated into the restriction-negative P. gingivalis strain and replicated stably. This set of recipient strains and stable plasmids with a selectable marker constitutes the first practical host-vector system for this species.

[Diagnosis of shunt dysfunction after transjugular intrahepatic portosystemic shunt by color Doppler ultrasonography: usefulness change of maximum flow velocity in portal vein]

To clarify whether color doppler ultra sonography (CDUS) is useful for the diagnosis of shunt dysfunction after transjugular intrahepatic portosystemic shunt (TIPS), we investigated CDUS in 20 patients who were diagnosed as shunt dysfunction and 12 patients with patent shunt by follow-up portal pressure measurements. In patients with shunt dysfunction, maximum flow velocity in the portal vein (PV-Vmax) and maximum flow velocity in the shunt were significantly decreased in comparison to just after TIPS placement, but not in patients with patent shunt. Grade of color image of the shunt flow and flow direction in the portal vein branches were not significantly different between the shunt dysfunction group and the patent shunt group. Comparing the just after TIPS to the follow-up phase, the decreasing rate of PV-Vmax was negatively correlated with the increasing rate of portal vein pressure caused by shunt dysfunction. CDUS could detect shunt dysfunction in 95% sensitivity, 83% specificity and 91% overall accuracy on the basis of a diagnostic criterion for shunt stenosis : more than 40% decrease of PV-Vmax from just after TIPS insertion. These results suggest that follow-up observation using CDUS is useful for the diagnosis of shunt dysfunction after TIPS procedure, and PV-Vmax is an especially important indicator to detect shunt dysfunction.

[Geometrical distribution of newly formed blood vessels in diabetic retinopathy]

Outbreak sites of newly formed blood vessels (NFVs) in proliferative diabetic retinopathy (PDR) were analyzed geometrically. A montage was made of fluorescein fundus angiography photographs of 109 eyes and applied to a two dimensional x-y plane in which the center of the optic disc was taken as the origin. Thus each NFV acquired a coordinate value (x, y). After a coordinate transformation of this x-y plane designed to correct the parafoveal distortion of vascular distribution, a polar coordinate value (r, theta) of the NFV was calculated. The frequencies of NFVs were analyzed statistically relating to both theta, which is the angle around the origin, and r, which is the distance from the origin. The average theta was 2.74 +/- 1.72 (mean +/- standard deviation) radians and the outbreak frequency of NFVs showed a homogeneous distribution which was not influenced by any difference in theta. As for r, the frequency corrected as a truncated distribution at r = 0 showed a normal distribution with an average of 1.45 +/- 0.8. The outbreak of NFVs in PDR is a phenomenon in which accidental elements are strongly concerned and it is thought to be difficult to predict the site at early stage of retinopathy.

[Inhibitory effect of isosorbide dinitrate on whole blood aggregation]

Isosorbide dinitrate (ISDN) has an inhibitory effect on platelet aggregation through the generation of nitric oxide (NO). We examined the effect of ISDN on whole blood aggregation using an impedance aggregometer. Blood samples were obtained from 16 patients with acute myocardial infarction and 4 patients with angina pectoris before and after an intravenous administration of ISDN during coronary arteriography. Whole blood obtained from normal healthy donors was used for an in vitro study. Whole blood aggregation after administration of ISDN was significantly inhibited compared to that before administration (36.1 +/- 8.3 vs 43.7 +/- 8.4 omega, p < 0.001), and cyclic guanine monophosphate (c-GMP) concentration increased (5.56 +/- 2.0 vs 5.14 +/- 1.86 p mol/ml, p < 0.05). The inhibitory effect of ISDN was also observed in the in vitro study, in which the effective concentration of ISDN corresponded to the blood level of ISDN (> or = 10(-7) mol) in the clinical setting. The inhibitory effect of ISDN was diminished by the addition of methylene blue or NG-monomethyl-L-arginine monoacetate in the exo vivo and in vitro studies. The concentration of c-GMP was increased by the addition of ISDN to platelets and white blood cell suspended plasma compared to the control (1.93 +/- 0.50 vs 1.77 +/- 0.42 p mol/ml, p < 0.05), but there was no significant difference when ISDN was added to platelet-rich plasma. These results suggest that ISDN inhibits whole blood aggregation through NO generation and white blood cells are important in the mechanism of ISDN action.

Effect of aeration and unsaturated fatty acids on expression of the Saccharomyces cerevisiae alcohol acetyltransferase gene

The reduction of acetate ester synthesis by aeration and the addition of unsaturated fatty acids to the medium has been reported to be the result of the reduction in alcohol acetyltransferase (AATase) activity induced by inhibition of this enzyme. However, regulation of the AATase gene ATF1 has not been reported. In this study, ATF1 gene expression was studied by Northern analysis, and the results showed that the ATF1 gene was repressed both by aeration and by unsaturated fatty acids. The results also showed that the reduction of AATase activity is closely related to the degree of repression of ATF1 mRNA, which suggested that the gene repression is the primary means of reducing AATase activity in vivo. Using the Escherichia coli lacZ gene as a reporter gene, it was shown that a 150-bp fragment of the 5' flanking sequence played a major role in the repression by aeration and unsaturated fatty acid addition.

[Detection of microemboli in patients with extracranial carotid artery stenosis by transcranial Doppler sonography]

Embolism from a stenotic lesion of the extracranial internal carotid artery (ICS) is considered to be an important pathomechanism of cerebral infarction. The purpose of this study is to estimate the risk of cerebral infarction associated with microembolism in patients with ICS and thereby to determine the importance of TCD-detected microemboli in this condition. Seventy-one cases with more than 30% ICS and 10 cases without ICS were studied. TCD monitoring was carried out for an hour at the ipsilateral middle cerebral artery of each case using a 2-MHz pulse-wave transcranial Doppler device. High intensity transient signals were counted as microemboli. Microemboli were detected in 27 of 71 cases with ICS, but not in cases without ICS. Microemboli were detected more frequently in cases with 70% to 99% ICS (53.3%) compared with in cases with 30% to 69% ICS (12.5%). Cerebral infarctions were recognized in the ipsilateral hemisphere in 23 of 27 cases with microemboli (85.2%) by means of MRI. In contrast, cerebral infarctions were recognized only in 21 of 45 cases without microemboli (47.7%). These results suggest that a stenotic lesion of the extracranial internal carotid artery, especially high-grade stenosis, is a major source of cerebral embolism and that detection of microemboli by TCD is a useful tool capable of reliably assessing the risk of cerebral infarction due to ICS.

[Impaired glucose tolerance and branch retinal vein obstruction]

Impaired glucose tolerance (IGT) has been one of the risk factors of Branch Retinal Vein Obstruction (BRVO). In order to study the contribution of IGT to the pathogenesis of BRVO, the 75 gram oral glucose tolerance test and immunoreactive insulin (IRI) measurement were investigated in 180 BRVO patients. IGT was found in 103 patients, and about 40% of these patients showed hyperinsulinemia and secondary insulin resistance. This result suggests that IGT with BRVO are in a state of hyperinsulinemia and hyperglycemia and hyperinsulinemia play an important role in thrombogenesis, such as injury to the venous endothelial cells.

[Low-dose radiation, therapy for choroidal neovascularization in age-related macular degeneration]

The efficacy of low-dose radiation was evaluated in the treatment of eyes with subfoveal or juxtafoveal choroidal neovascularization in age-related macular degeneration. Ten eyes of ten patients received a total dose of 14 Gy of 10 MV X-rays in seven fractions and the mean follow-up time was 12 months (range 9 approximately 18 months). Thirteen control eyes of thirteen patients were followed for an average of 18 months (range 12 approximately 24 months). Visual acuity was improved in 2 eyes (20%), unchanged in 3 eyes (30%), and deteriorated in 5 eyes (50%) of treated patients, and it was improved in no eyes (0%), unchanged in 5 eyes (32%), and deteriorated in 8 eyes (50%) of the control patients at their last follow-up examinations. Funduscopic and angiographic findings were improved in 3 eyes (30%), unchanged in 2 eyes (20%), and deteriorated in 5 eyes (50%) of treated patients, and they were improved in no eyes (0%), unchanged in 5 eyes (32%), and deteriorated in 8 eyes (50%) of the control patients. These results suggested that low-dose radiation is beneficial for the management of subfoveal or juxtafoveal choroidal neovascularization in age-related macular degeneration.

[Influence of rifampicin on antihypertensive effects of dihydropiridine calcium-channel blockers in four elderly patients]

Rifamicin, an antituberculosis agent, is one of the most potent inducers of hepatic drug-oxidation enzymes. Rifampicin can reduce the efficacy of several therapeutically important drugs (including verapamil and diltiazem) by accelerating systemic elimination or by increasing hepatic first-pass metabolism. Because dihydropyridine calcium-channel blockers are mainly metabolized by the liver, rifampicin may also increase the extraction of these drugs and thereby reduce their antihypertensive effects. Here we report four possible cases of interaction between rifampicin and dihydropiridine calcium-channel blockers. Rifampicin was given to treat tuberculosis in four elderly hypertensive patients whose blood pressure was well-controlled by one or more dihydropiridine calcium-channel blockers (nisoldipine, nifedipine, or barnidipine and manidipine), shortly after the start of antituberculosis therapy, their blood pressures rose. Either much greater doses of dihydropyridines or additional antihypertensive agents had to be given to keep blood pressure under control. After withdrawal of rifampicin, blood pressure fell in all patients and the doses of the antihypertensive agents had to be reduced. These findings indicate that rifampicin may lessen the antihypertensive effects of dihydropiridine calcium-channel blockers.

Characterization of cultured rat embryonic palatal mesenchymal cells

To investigate developmental palatogenesis, the establishment of palatal cell culture in vitro is preferable to eliminate several complicated biases present in the in vivo environment. We established a primary culture of rat embryonic palatal mesenchymal cells using a special technique to dissect embryonic palatal shelves, and characterized these embryonic cells by immunohistochemical analysis against histiocytic markers. Following preparation of the maxilla of 15.5-day-old rat fetuses, a midline incision of the maxilla was established while the occiput was fixed with microforceps. This procedure allowed eversion of the maxillary process and easy dissection of the palatal shelf. The technique allowed preparation of a large number of palatal shelves with no appendages using a small number of fetuses. Cells cultured with DMEM/F-12 and 10% FBS showed multipotential nature (i.e., not only mere mesenchymal character but also neural, endothelioid, and/or myoblastoid origin were identified by immunostaining with anti-epithelium membrane antigen, keratin, vimentin, S-100 protein, factor VIII, desmin, and lysozyme antibodies, respectively). Our results demonstrated that, during several cell passages, the cultured cell gained myoblastoid characteristics in addition to a neural nature. Further in vitro studies using cultured embryonic palatal mesenchymal cells will assist in characterization of proliferation and differentiation of cells forming the palate.

Nucleotide sequences of alcohol acetyltransferase genes from lager brewing yeast, Saccharomyces carlsbergensis

The nucleotide sequences of alcohol acetyltransferase genes isolated from lager brewing yeast, Saccharomyces carlsbergensis have been determined. S. carlsbergensis has one ATF1 gene and another homologous gene, the Lg-ATF1 gene. There was a high degree of homology between the amino acid sequences deduced for the ATF1 protein and the Lg-ATF1 protein (75.7%), but the N-terminal region has a relatively low degree of homology. Southern analysis and contour-clamped homogeneous electric field analysis of Saccharomyces strains suggest that the ATF1 gene is located on chromosome XV in S. cerevisiae and that the Lg-ATF1 gene might originate from the "non-S. cerevisiae' genome of S. carlsbergensis, which is similar to that of S. bayanus and S. pastorianus.

Studies of the pathogenesis and management of thrombotic thrombocytopenic purpura

We have studied the pathophysiological signs and methods of management of thrombotic thrombocytopenic purpura (TTP) in our TTP patients. We showed that anti-platelet GP II b- III a monoclonal antibodies bound to human vascular endothelial cells (HUVEC). The binding rate of 125I-anti-platelet GP II b- III a monoclonal antibodies to HUVEC treated with TTP patients sera was decreased, compared with the value observed for HUVEC treated with normal sera. These findings showed that GP II b- III a like substances are expressed on HUVEC and that TTP patients sera appear to contain anti-platelet GP II b- III a antibodies which may attack and injure the endothelial cells. PGI2 stabilizing activity of plasma is measured by PGI2 inhibitory activity attenuation on normal platelet aggregation induced by ADP. PGI2 stabilizing activity decreases in acute phase, increases in remission, suggesting that there may be a relationship between pathogenesis of TTP and decreases of PGI2 stabilizing activity. We also showed that PGI2 analogue (beraprost sodium) was useful for prevention of relapse of TTP. Plasmapheresis has emerged as the treatment of choice of TTP. We found the effectiveness of the high molecular weight fraction (HMW-F) of plasma in chronic TTP patients. HMW-F of plasma may contain the main factor necessary for improvement of TTP.

[Medical treatment for experimental retinal vein occlusion--thrombolytic effect of nasaruplase]

The anti-thrombolytic effect of urokinase (UK), nasaruplase, and argatroban was studied using an experimental rabbit model of retinal vein occlusion (RVO). Experimental RVO was induced by transadventitial thrombin instillation. Five or fourteen days after thrombin application, the rabbits were injected with gelatin-fluorescein sodium and their eyeballs were enucleated for microscopic observation and flat preparation of the retina. Occlusion of retinal vessels was found to be less in number and distribution in the nasaruplase group than in the control group. On microscopic observation, the retinal arteries and veins of the nasaruplase group showed a vascular subendothelial space formation which suggested a process of thrombogenesis and thrombolysis in the space. The coefficiency of beraprost sodium, aspirin, and ozagrel hydrochloride to UK therapy was studied, but there was no significant difference between these groups and the control group with no after-treatment (the UK group). This result shows the effectiveness of nasaruplase for the thrombolytic therapy of RVO.

Enhancing effect of platelets on staphylokinase-mediated clot lysis and plasminogen activation

The effects of platelets on clot lysis and plasminogen activation by staphylokinase (SAK) were investigated. At concentrations ranging from 2 x 10(-7) to 1 x 10(-5)g/ml of SAK, the lysis time of platelet-rich plasma clots (PRP-clots) was shorter than that of platelet-poor plasma clots (PPP-clots). This reduction of clot lysis time was observed in a dose-dependent manner on platelet count in PRP. The activation rate of plasminogen by SAK measured by the amidolytic method using S-2251 was enhanced by the addition of washed platelets. These enhancing effects of platelets on clot lysis and plasminogen activation were not altered by pretreatment of platelets with indomethacin and theophylline, but were diminished by platelet disruption. Thus, we concluded that platelets enhance fibrinolytic activity of SAK, and this effect is not due to the release reaction or intracellular contents of platelets, but to the existence of platelet surface in the intact shape as a catalytic site for fibrinolysis.

[Pharmacological properties of chitosan-coated dialdehyde cellulose (chitosan DAC), a newly developed oral adsorbent (I). Effect of chitosan DAC in normal rats]

The effects of chitosan-coated dialdehyde cellulose (chitosan DAC), a newly developed oral adsorbent of urea and ammonia, were examined in an in vitro adsorption study and in normal rats. Chitosan DAC showed high adsorption capacity for urea and ammonia in an in vitro study using the diluted supernatant of rat gastrointestinal fluid. In contrast, Kremezin, an oral charcoal adsorbent (AST-120), had little influence on these substances. In normal rats fed diets containing chitosan DAC (1, 2, 3, 4, 5, 7, and 10% content) for three weeks, increases in fecal wet weight, fecal dry weight and fecal water content were observed in a dose-dependent manner. In addition, chitosan DAC feeding increased fecal excretion of nitrogen and electrolytes (sodium, potassium and chloride ions) and decreased the apparent protein ratio in a dose-dependent manner. There were no obvious effects in serum parameters except that increased levels of protein and albumin and decreased levels of blood urea nitrogen, cholesterol and glucose were observed in rats fed a high concentration of chitosan DAC. In conclusion, these findings suggest the possibility that chitosan DAC treatment might be effective for improving chronic renal failure.

[Pharmacological properties of chitosan-coated dialdehyde cellulose (chitosan DAC), a newly developed oral adsorbent (II). Effect of chitosan DAC on rats with chronic renal failure induced by adriamycin]

The effects of chitosan-coated dialdehyde cellulose (Chitosan DAC), a newly developed oral adsorbent of urea and ammonia, were examined in rats with progressive chronic renal failure (CRF) induced by adriamycin. CRF rats induced by repeated injections of adriamycin were fed a diet containing chitosan DAC (5% content) or Kremezin (5% content), an oral charcoal adsorbent (AST-120) under strict paired-feeding for four months. CRF rats that received both a normal diet and Kremezin showed progressive azotemia, hyperphosphatemia, hyperlipidemia, proteinuria, and anemia, and began to die from 9 weeks after feeding started. In contrast, chitosan DAC-treatment showed marked prolongation of the survival period and decreases in blood urea nitrogen, serum creatinine, and serum phosphate. In addition, chitosan DAC-treatment ameliorated anemia in CRF rats, although hyperlipidemia and proteinuria were not improved. Furthermore, fecal weight, fecal water content, fecal nitrogen and fecal sodium were markedly increased, and the apparent protein ratio was decreased in CRF rats fed a diet containing chitosan DAC for 9 weeks. In contrast, none of these effects were observed in CRF rats receiving Kremezin. These observations suggest the further possibility of using oral adsorbent therapy for CRF patients.

Purification and characterization of a major kyotorphin-hydrolyzing peptidase of rat brain

We purified a major kyotorphin (L-Tyr-L-Arg)-hydrolyzing peptidase (KTPase) from the rat brain, to electrophoretic homogeneity using conventional chromatographic techniques. KTPase was purified 1,660-fold with a specific activity of 161 mumol/min/mg protein and 6.8% recovery. The purified enzyme was composed of a single polypeptide with a molecular mass of 67 kDa and an isoelectric point (pI) of 5.5. KTPase has the ability to hydrolyze a variety of natural dipeptides. It also liberated NH2-terminal tyrosine from Tyr-Gly-Gly and Tyr-Tyr-Leu. Bestatin and arphamenine B were potent inhibitors of this enzyme, while amastatin and puromycin had little effect. An excess of anti-KTPase antibody raised in a white rabbit precipitated approximately 80% of the kyotorphin-hydrolyzing activity in the cytosol of rat brain. These data suggested that 67 kDa KTPase has a role in the degradation of kyotorphin within neuronal cells of the rat brain.

[A sporadic dentatorubral-pallidoluysian atrophy (DRPLA) diagnosed by gene analysis]

We report a 48-year-old woman with dentatorubral-pallidoluysian atrophy (DRPLA). She is the only patient in her 15 family members in two generations. She developed cerebellar ataxia and epilepsy at age 43. On admission at 48, she showed mild dementia and choreic movement in her face and extremities as well as truncal and limb ataxia. Routine laboratory examinations were normal. The point mutations in the tRNALys gene of mitochondrial DNA specific for MERRF were not found. A cranial CT scan and MRI showed mild atrophy of the cerebellum and prominent atrophy in the pons, especially in the tegmentum. Although she was thought to have DRPLA from the clinical point of view, absence of family history made the diagnosis difficult. Her parents were healthy until their 80's and died of cerebrovascular diseases and her 5 siblings had no symptoms. Hereditary DRPLA is known as an autosomal dominant disorder, with a high rate of penetrance and low rate of new mutation. According to our recent findings of a CAG repeat expansion in the DRPLA gene, this patient was diagnosed as a sporadic DRPLA. Considering the wide varieties of clinical manifestations, it is essential to examine this gene abnormality for diagnosing sporadic DRPLA.

Genetic transformation of Porphyromonas gingivalis by electroporation

Porphyromonas gingivalis was transformed by electroporation using the DNA of plasmid pE5-2, or its derivative, pYT7. Prior to transformation, pE5-2 was transferred from Escherichia coli to P. gingivalis strains by conjugation (mobilization with R751), and the plasmid DNA was purified from the P. gingivalis transconjugants. Transformation occurred when the recipient strain and the donor strain from which the plasmid DNA was purified were homologous. If they were heterologous, transformation did not take place or did so at a very low frequency. This suggested that a restriction-modification system is present in P. gingivalis strains. Plasmid pYT7 was derived by removing an 8.0 kb AvaI fragment from pE5-2 that was purified from P. gingivalis cells. It has several single-cutting restriction sites such as EcoRI, AvaI and ClaI usable for gene cloning, though it was not stable enough in P. gingivalis cells, probably because the rep gene was derived from a relatively distant species, Bacteroides eggerthii.

[Retinal ischemic changes in diabetic rats treated with pancreatic islet transplantation beneath the renal capsule]

The effect of pancreatic islet transplantation beneath the renal capsule on retinal and choroidal structure was studied using Lewis rats. Rats were divided into 3 groups: an untreated diabetic group induced by intravenous injection of streptozotocin 65 mg/kg; an islet transplanted group 1 month after induction of diabetic state; and an untreated control group. Whole retinochoroidal units were examined by light and electron-microscopy. In 6 out of 9 cases in the transplanted group, the retina showed marked destructive changes in the outer layer including pigment epithelial cells and vacuolization of the inner layer 6 months after islet transplantation. Occlusion and fibrosis of the choriocapillaris adjoining the degenerated retina were also observed. Such changes were not observed in the other groups. On electron microscopy, occlusion of capillaries and destruction of endothelial cells were frequently found in the degenerated retina. These retinal ischemic lesions appear to be caused by microvascular obstruction.