Augmentation of hepatic glucose uptake by a positive glucose gradient between hepatoportal and central nervous systems

To determine the role of the glucose gradient between the hepatoportal system (HPS) and the central nervous system (CNS) in regulating hepatic glucose uptake, experiments were conducted with seven conscious dogs using a hepatic venous catheterization technique. With the infusion of somatostatin (0.8 microg x kg(-1) x min(-1)), glucagon (0.65 ng x kg(-1) x min(-1)), and insulin (27 pmol x kg(-1) x min(-1)), arterial glucose levels could be maintained at 8 mmol/l by adjusting the intravenous glucose infusion (G(inf)) according to the following three periods: 1) peripheral glucose infusion period (PE), G(inf) alone; 2) portal glucose infusion period (PO), G(inf) plus constant glucose infusion into the portal vein (GIR(PV), 55.6 micromol x kg(-1) x min(-1)); 3) portal and brain glucose infusion period (PO+CNS), G(inf) and GIR(PV) plus additional glucose infusion into the unilateral carotid and vertebral arteries to abolish the positive glucose gradient between HPS and CNS. Arterial plasma glucose levels were clamped during the three periods (8.1 +/- 0.1, PE; 8.2 +/- 0.1, PO; 8.2 +/- 0.1 mmol/l, PO+CNS). During PO, when a positive glucose gradient was promoted between HPS and CNS, the net hepatic glucose balance (NHGB) determined by the difference between hepatic glucose inflow and outflow was significantly lower than that of PE (-41.5 +/- 5.3, PO vs. -7.5 +/- 3.4 micromol x kg(-1) x min(-1), PE; P < 0.01). However, this decrease in the NHGB significantly increased during PO+CNS, when the glucose gradient between HPS and CNS was minimized, compared with PO (-21.7 +/- 3.2 micromol x kg(-1) x min(-1), P < 0.05). We conclude that a positive glucose gradient between HPS and CNS is an important regulatory factor of hepatic glucose uptake, but other factors also play important roles because minimizing the glucose gradient between HPS and CNS diminished the net hepatic glucose uptake by 50%.

Mediastinoscopic extirpation of mediastinal ectopic parathyroid gland

We report a case of a 50-year-old man with hyperparathyroidism secondary to chronic renal failure who underwent extirpation of a mediastinal ectopic parathyroid gland by a transcervical approach under mediastinoscopy. This procedure provides an excellent approach to the mediastinal ectopic parathyroid gland, and is less invasive than median sternotomy or thoracotomy.

New therapeutic possibility of blocking cytokine-induced neutrophil chemoattractant on transient ischemic brain damage in rats

Earlier we indicated that neutrophilic invasion into cerebral parenchyma is an important step in rat cerebral ischemia-reperfusion injury and the production of chemotactic factors, cytokine-induced neutrophil chemoattractant (CINC) precede the neutrophilic invasion. The aim of the present study was to evaluate the role of CINC production and the therapeutic possibility of blocking CINC activity in the transient ischemic brain damage in rats. Focal transient ischemia was produced by intraluminal occlusion of the right middle cerebral artery for 60 min. An enzyme immunoassay was used to measure the brain concentration of CINC and myeloperoxidase activity in ischemic areas was measured as a marker of neutrophilic accumulation. An immunohistochemical staining technique was used to detect the immunopositive cells for anti-CINC antibody. Further, application of anti-CINC antibody or anti-neutrophil antibody to rats was used to evaluate the role of CINC production. In ischemic areas, CINC production was detected and peaked 12 h after reperfusion, which followed 60 min of ischemia. Intraperitoneal injection of anti-neutrophil antibody 24 h before and immediately after reperfusion significantly reduced the brain water content and partially reduced the CINC production in ischemic areas. Further, immunohistochemical staining showed that anti-CINC antibody was found on the endothelial surface of venules and on parts of neutrophils that had invaded the ischemic area 6 to 24 h after reperfusion. Also, treatment with anti-CINC antibody reduced ischemic edema formation 24 h after reperfusion and the size of infarction areas 7 days after reperfusion. It thus appears that CINC, mainly produced by endothelium activated by factors released from neutrophils, plays an important role in ischemic brain damage. Furthermore, the blocking of CINC activity with antibody suggests an immuno-therapeutic approach to the treatment of stroke patients.

Ultra-high-resolution scanning electron microscopy of mitochondria and sarcoplasmic reticulum arrangement in human red, white, and intermediate muscle fibers

BACKGROUND

Human skeletal muscle fibers are the red, white, and intermediate fibers. They differ in their mitochondrial structure and enzyme activity. Scanning electron microscopy (SEM) was used on specially prepared specimens to determine the distinctive features of mitochondria and sarcoplasmic reticulum (SR) in each fiber type.

METHODS

Specimens of human limb muscles were glutaraldehyde fixed, frozen, fractured, and macerated by the aldehyde-osmium-DMSO-osmium procedure to expose large areas of mitochondria and SR. Osmium-hydrazine-impregnated tissues were examined without metal coating by ultra-high-resolution SEM.

RESULTS

In white fibers, paired long, thin mitochondria encircled myofibrils at the I-band level. In red fibers, the paired rows of stubby mitochondria at the I-band level were often connected across the A-band to the next row of mitochondria by a slender mitochondrial stalk. Intermediate fiber mitochondria resembled those in red fibers but were longer and thinner. Intermyofibrillar mitochondrial columns were most common in red fibers. All three muscle types had T-tubules along the A-I junction level, and small periodic terminal cisternae formed triads or dyads. Sarcotubules from terminal cisternae formed continuous three-dimensional networks at the I-band level, but intermittent straight sarcotubules, narrow two-dimensional networks, and some axial tubules traversed the A-band. The subsarcolemmal space had continuous two-dimensional SR at the H-band level and a coarse SR network at the I-band. These two SR networks were connected by single A-band sarcotubules.

CONCLUSIONS

Mitochondrial shape and configuration were distinctive for each human skeletal muscle fiber type, but the SR was similar in all muscles examined.

Sleep characteristics of Japanese working men who score alexithymic on the Toronto Alexithymia Scale

This study examined the relationship of sleep characteristics including insomnia with scores on alexithymia in a sample of 171 Japanese working men. Levels of nonrestorative sleep and daytime sleepiness reported on a sleep questionnaire were significantly associated with scores on Depression and Confusion on the Profile of Mood States for Japanese men who had a high mean score on the Toronto Alexithymia Scale.

Ultra-high-resolution scanning electron microscopy of the sarcoplasmic reticulum of the rat atrial myocardial cells

BACKGROUND

The sarcoplasmic reticulum (SR) of mammalian ventricular and atrial muscles share common features but also differ because T-tubules are rare and extended junctional SR is exclusively seen in the atrium. This scanning electron microscope (SEM) study was undertaken to clarify the three-dimensional organization of the rat atrial SR system. Specific preparations were examined with an ultra-high-resolution SEM.

METHODS

Fixed right rat atria were frozen, fractured, and macerated by the aldehyde-osmium-DMSO-osmium method to remove myofibrils and cytoplasmic matrix. Left exposed were mitochondria, SR, and sarcolemma. Dried specimens were then impregnated by osmium-hydrazine and examined without metal coating.

RESULTS

In place of conventional T-tubules, a prominent type of sarcotubules, Z-tubules, were found at the Z-line level. Branches from these tubules joined the cisternal SR, which was 100-300 nm in diameter and localized near the Z-line, and formed extensive SR meshworks and polygonal patches. Bulbous swellings, the corbular SR, were also evident. Sarcotubular reticulum completely surrounded each myofibril. The intermyofibrillar SR, especially Z-tubules, joined the peripheral subsarcolemmal SR, which was also arranged as a meshwork and was closely apposed to the sarcolemma.

CONCLUSIONS

These SEM observations confirm the organization of the rat atrial SR system and present new, detailed, three-dimensional images of Z-tubules, cisternal SR, extended junctional SR, and peripheral SR, which provide further structural insight.

Ultra-high-resolution scanning electron microscopy of the continuity of cytoplasmic and luminal membranes in frog oxyntic cells

BACKGROUND

Despite numerous previous studies, the presumed continuity of the luminal and tubulovesicular membranes in frog oxyntic (oxyntico-peptic) cells remains to be convincingly demonstrated. This study was undertaken to clarify this question by ultra-high-resolution scanning electron microscopy of specially prepared frog stomach specimens before and during histamine stimulation.

METHODS

Fasted Japanese meadow frogs stimulated with histamine were used. Oxyntic cell cytoplasmic matrix was removed by the aldehyde-osmium-DMSO-osmium maceration procedure and impregnated with osmium-hydrazine. Specimens were examined without metal coating.

RESULTS

In the resting oxyntic cell, the luminal membrane had closely packed surface folds forming a rather flat surface with a few short microvilli. In the cytoplasm, flattened 200-500 nm vesicles were interconnected by numerous slender 20-60 nm tubules forming the tubulovesicular network. Occasional slender tubular branches were found in continuity with the luminal membrane. After histamine stimulation, the number and length of microvilli and surface folds increased, whereas the tubulovesicular membrane system decreased. Sites of clear continuity between the luminal and tubulovesicular membranes were not abundant but were clearly demonstrated in histamine-stimulated oxyntic cells. The small size of the tubules connecting the tubulovesicular system to the plasma membrane renders this observation by transmission electron microscopy very difficult. In these specimens, the clear continuity of the tubulovesicular network to the luminal plasma membrane became more evident.

CONCLUSIONS

This study confirms previous findings of increased luminal membrane and depletion of the tubulovesicle system. The demonstration of continuity between these two compartments in our SEM preparations supports the hypothesis of direct transfer of tubulovesicular membrane to oxyntic cell luminal secretory membrane.

Diabetic scleredema: a case report and biochemical analysis for glycosaminoglycans

We report a patient with the typical lesions of diabetic scleredema. Histological findings of the involved skin were thickening of the dermis, depositions of mucins, and fibrosis. Biochemical analysis revealed an increase in glycosaminoglycans in the involved skin as well as in the cutaneous lupus mucinosis. Mucinous materials were composed of hyaluronic acid.

Sensitive, selective gas chromatographic-mass spectrometric analysis with trifluoroacetyl derivatives and a stable isotope for studying tissue sorbitol-producing activity

One of the major mechanisms involved in diabetic microangiopathy is considered to be an altered polyol pathway. However, clarifying the pathophysiology is difficult due to the lack of a sensitive method for measuring the reduction of glucose to sorbitol in tissue. Here we report a sensitive and selective method for polyol measurement using trifluoroacetyl (TFA) derivatives of polyols and stable isotope-labeled D-sorbitol (U-[13C]sorbitol, 13C6H14O6, 98.7%) as an internal standard. Gas chromatography-mass spectrometry (GC-MS) using an SE-30 capillary column gave elution of TFA derivatives of sugars, polyols and U-[13C]sorbitol within 8 min, with clear separation of sorbitol. In the calibration study, the coefficients of correlation between the amount of sorbitol added and that determined in standard solutions containing 0.1-8.0 nmol sorbitol, erythrocyte mixture and liver cytosol mixture were r = 0.999, r = 0.997 and r = 0.997, respectively. The precision of the GC-MS measurement of standard solution was C.V. = 4.3%. Because glucose is used as a substrate, the method can clarify the polyol pathway under physiological conditions. With this method, Km and Vmax values of the reductase in erythrocytes were 115 +/- 19 mmol/l and 4.42 +/- nmol/min/g of hemoglobin. In human liver, on the other hand, they were 755 +/- 132 mmol/l and 0.773 +/- 0.090 nmol/min/mg of protein, respectively. This difference of Km values suggested that aldehyde reductase rather than aldose reductase is mainly responsible for reducing glucose to sorbitol in the liver. In conclusion, this newly developed method offers a highly sensitive and selective procedure for measuring low concentrations of sorbitol in various tissues and cells and should enable clarification of the kinetics of glucose reduction to sorbitol, which in turn can be used to evaluate the role of an altered polyol pathway in the pathophysiology of diabetic microangiopathy.

Glycation-dependent, reactive oxygen species-mediated suppression of the insulin gene promoter activity in HIT cells

Prolonged poor glycemic control in non-insulin-dependent diabetes mellitus patients often leads to a decline in insulin secretion from pancreatic beta cells, accompanied by a decrease in the insulin content of the cells. As a step toward elucidating the pathophysiological background of the so-called glucose toxicity to pancreatic beta cells, we induced glycation in HIT-T15 cells using a sugar with strong deoxidizing activity, D-ribose, and examined the effects on insulin gene transcription. The results of reporter gene analyses revealed that the insulin gene promoter is more sensitive to glycation than the control beta-actin gene promoter; approximately 50 and 80% of the insulin gene promoter activity was lost when the cells were kept for 3 d in the presence of 40 and 60 mM D-ribose, respectively. In agreement with this, decrease in the insulin mRNA and insulin content was observed in the glycation-induced cells. Also, gel mobility shift analyses using specific antiserum revealed decrease in the DNA-binding activity of an insulin gene transcription factor, PDX-1/IPF1/STF-1. These effects of D-ribose seemed almost irreversible but could be prevented by addition of 1 mM aminoguanidine or 10 mM N-acetylcysteine, thus suggesting that glycation and reactive oxygen species, generated through the glycation reaction, serve as mediators of the phenomena. These observations suggest that protein glycation in pancreatic beta cells, which occurs in vivo under chronic hyperglycemia, suppresses insulin gene transcription and thus can explain part of the beta cell glucose toxicity.

Involvement of the homeodomain-containing transcription factor PDX-1 in islet amyloid polypeptide gene transcription

The AT-rich cis-motif A elements of the insulin gene promoter contribute to directing the gene's expression to pancreatic beta-cells, bound by a homeodomain-containing transcription factor, PDX-1/IPF1/STF-1/IDX-1. The islet amyloid polypeptide (IAPP; amylin) gene, which is also expressed in limited tissues such as pancreatic beta- and delta-cells, contained similar AT-rich sequences in its regulatory sequences. To understand the molecular basis of IAPP gene regulation, we evaluated the possible physiological significance of the motif in human IAPP gene regulation. All of the three typical A element-like sequences that matched the CT-box consensus (AT-1, -207/-202; AT-2, -154/-142; and AT-3, -88/-83) were shown to bind specifically to a nuclear factor in the beta-cell-derived MIN6 cells, which was subsequently identified immunologically as the insulin gene transcription factor PDX-1. When the promoter activity was examined in MIN6 cells, the disruption of AT-1 or AT-3 but not of AT-2 caused a marked reduction in the IAPP gene promoter. Thus, despite the observation that all the three A element-like regions could bind to PDX-1, the AT-2 site may not be involved in mediating the PDX-1 action in vivo. These observations suggest the involvement of PDX-1 in human IAPP gene regulation, which seems to be mediated through at least two A element-like cis-motifs in the gene promoter.

Reducing sugars trigger oxidative modification and apoptosis in pancreatic beta-cells by provoking oxidative stress through the glycation reaction

Several reducing sugars brought about apoptosis in isolated rat pancreatic islet cells and in the pancreatic beta-cell-derived cell line HIT. This apoptosis was characterized biochemically by inter-nucleosomal DNA cleavage and morphologically by nuclear shrinkage, chromatin condensation and apoptotic body formation. N-Acetyl-L-cysteine, an antioxidant, and aminoguanidine, an inhibitor of the glycation reaction, inhibited this apoptosis. We also showed directly that proteins in beta-cells were actually glycated by using an antibody which can specifically recognize proteins glycated by fructose, but not by glucose. Furthermore, fluorescence-activated cell sorting analysis using dichlorofluorescein diacetate showed that reducing sugars increased intracellular peroxide levels prior to the induction of apoptosis. Levels of carbonyl, an index of oxidative modification, and of malondialdehyde, a lipid peroxidation product, were also increased. Taken together, these results suggest that reducing sugars trigger oxidative modification and apoptosis in pancreatic beta-cells by provoking oxidative stress mainly through the glycation reaction, which may explain the deterioration of beta-cells under conditions of diabetes.

PDX-1 induces insulin and glucokinase gene expressions in alphaTC1 clone 6 cells in the presence of betacellulin

The pancreatic beta- and alpha-cells are developmentally related to each other but reveal diverse gene expression patterns. Among the two important transcription factors for insulin gene expression, IEF1 is present both in alpha- and beta-cells, but PDX-1/IPF1/STF-1/IDX-1, a homeodomain-containing transcription factor, is present in beta-cells but not in alpha-cells. To elucidate the function of PDX-1 in the expression of beta-cell-specific genes, we established stable alphaTC1 clone 6 (alphaTC1.6)-derived transfectants expressing PDX-1 and examined the changes in the gene expression patterns in them. The exogenous expression of PDX-1 in alphaTC1.6 cells alone could induce islet amyloid polypeptide (IAPP) mRNA expression in the cells but not the expression of insulin, glucokinase, or GLUT2 gene. However, when betacellulin was added to the medium, the PDX-1-expressing alphaTC1.6 cells, but not the control alphaTC1.6 cells, came to express insulin and glucokinase mRNAs. This did not occur with other growth factors such as epidermal growth factor, transforming growth factor alpha, and insulin-like growth factor I. GLUT2 mRNA remained undetectable in the PDX-1--expressing alphaTC1.6 cells. These observations demonstrate the potency of PDX-1 for the expression of the insulin, glucokinase, and IAPP genes and suggest that certain regulatory factors, which can partially be modified by betacellulin, also contribute to the beta-cell specificity of gene expression.

[Evaluation of the bite block wedged between the maxillary and mandibular molars]

The purpose of this study was to compare our original bite block (T-X Block) wedged between the maxillary and mandibular molars, with the standard gum bite block, in 200 patients whose tracheas were intubated. During emergence from isoflurane anesthesia, no trouble occurred in T-X Block group (n = 100). On the other hand, lip damage and ejection of the bite block were found in 11 and 10 cases, respectively, in gum bite block group (n = 100). As another study, an opening between the maxillary and mandibular incisor edges was measured with T-X Block placed in twenty patients under general anesthesia. The inter-incisal distances in one way of using it as a smaller wedge and in the other way as a bigger one were 21.6 +/- 2.4 and 25.2 +/- 2.6 mm, respectively. Those values were significantly larger than thickness of the gum bite block. T-X Block is very useful because its use causes no complications and makes it easier to insert a naso-gastric tube as well as to clean the oral cavity with suction by giving a larger opening of the mouth.

The human glucokinase gene beta-cell-type promoter: an essential role of insulin promoter factor 1/PDX-1 in its activation in HIT-T15 cells

The glycolytic enzyme glucokinase plays a primary role in the glucose-responsive secretion of insulin, and defects of this enzyme can cause NIDDM. As a step toward understanding the molecular basis of glucokinase (GK) gene regulation, we assessed the structure and regulation of the human GK gene beta-cell-type promoter. The results of reporter gene analyses using HIT-T15 cells revealed that the gene promoter was comprised of multiple cis-acting elements, including two primarily important cis-motifs: a palindrome structure, hPal-1, and the insulin gene cis-motif A element-like hUPE3. While both elements were bound specifically by nuclear proteins, it was the homeodomain-containing transcription factor insulin promoter factor 1 (IPF1)/STF-1/PDX-1 that bound to the hUPE3 site: IPF1, when expressed in CHO-K1 cells, became bound to the hUPE3 site and activated transcription. An anti-IPF1 antiserum used in gel-mobility shift analysis supershifted the DNA protein complex formed with the hUPE3 probe and nuclear extracts from HIT-T15 cells, thus supporting the involvement of IPF1 in GK gene activation in HIT-T15 cells. In contrast to the insulin gene, however, neither the synergistic effect of the Pan1 expression on the IPF1-induced promoter activation nor the glucose responsiveness of the activity was observed for the GK gene promoter. These results revealed some conservative but unique features for the transcriptional regulation of the beta-cell-specific genes in humans. Being implicated in insulin and GK gene regulations as a common transcription factor, IPF1/STF-1/PDX-1 is likely to play an essential role in maintaining normal beta-cell functions.

The human glucokinase gene beta-cell-type promoter: an essential role of insulin promoter factor 1/PDX-1 in its activation in HIT-T15 cells

The glycolytic enzyme glucokinase plays a primary role in the glucose-responsive secretion of insulin, and defects of this enzyme can cause NIDDM. As a step toward understanding the molecular basis of glucokinase (GK) gene regulation, we assessed the structure and regulation of the human GK gene beta-cell-type promoter. The results of reporter gene analyses using HIT-T15 cells revealed that the gene promoter was comprised of multiple cis-acting elements, including two primarily important cis-motifs: a palindrome structure, hPal-1, and the insulin gene cis-motif A element-like hUPE3. While both elements were bound specifically by nuclear proteins, it was the homeodomain-containing transcription factor insulin promoter factor 1 (IPF1)/STF-1/PDX-1 that bound to the hUPE3 site: IPF1, when expressed in CHO-K1 cells, became bound to the hUPE3 site and activated transcription. An anti-IPF1 antiserum used in gel-mobility shift analysis supershifted the DNA protein complex formed with the hUPE3 probe and nuclear extracts from HIT-T15 cells, thus supporting the involvement of IPF1 in GK gene activation in HIT-T15 cells. In contrast to the insulin gene, however, neither the synergistic effect of the Pan1 expression on the IPF1-induced promoter activation nor the glucose responsiveness of the activity was observed for the GK gene promoter. These results revealed some conservative but unique features for the transcriptional regulation of the beta-cell-specific genes in humans. Being implicated in insulin and GK gene regulations as a common transcription factor, IPF1/STF-1/PDX-1 is likely to play an essential role in maintaining normal beta-cell functions.

Reactive oxygen species induce apoptosis in cultured human mesangial cells

Apoptosis is a distinct form of cell death that is observed under various physiologic and pathologic conditions, and it is thought to be important in regulating the number of glomerular cells. This study investigated the possible role of reactive oxygen species in the induction of apoptosis in cultured human mesangial cells. Fragmented nuclei with condensed chromatin, a morphologic characteristic of apoptosis, were observed by electron microscopy in mesangial cells exposed to 0.02 mM hydrogen peroxide for 4 h. Nuclear DNA extracted from mesangial cells that had been incubated with hydrogen peroxide (2 to 20 mM) or with xanthine (0.05 mM) and xanthine oxidase (5 to 100 mU/mL) showed the ladder pattern on electrophoresis that is a biochemical marker for apoptosis. Hydrogen peroxide (0.02 to 20 mM) decreased the number of viable cells, as determined by trypan blue exclusion, in a dose-dependent manner. Hydrogen peroxide or xanthine and xanthine oxidase increased the lactate dehydrogenase release from mesangial cells in a dose- and time-dependent manners. The release of lactate dehydrogenase was prevented by treatment with a free radical scavenger, catalase. Hydrogen peroxide (2 mM) also significantly increased the number of mesangial cells with fragmented DNA as detected by in situ nick end-labeling Results indicate that reactive oxygen species induce apoptosis in cultured human mesangial cells. Furthermore, apoptosis of mesangial cells induced by reactive oxygen species may contribute to the loss of such cells observed in glomerular disease.

[Atherosclerosis in subjects with mild hyperglycemia]

We have evaluated quantitatively the thickness of intimal plus median wall of the carotid arteries (IMT) in subjects with mild hyperglycemia determined by the OGTT recommendation criteria of Japanese Diabetes Association, consisting of IGT and non IGT. IMTs of IGT and non IGT hyperglycemic subjects were significantly thicker than those of normal volunteers with any decade and were quite comparable with those of diabetics. Accumulation of risk factors of atherosclerosis linearly increased IMT in subjects with mild hyperglycemia. IMT of subjects with hyperglycemia and hyperin-sulinemia after OGTT was significantly higher than that with relatively hypoglycemia and hypoinsulinemia. IMT was inversely related with insulin resistance but not with endogenous insulin secretory ability. These data indicate that insulin resistance is one of major risk factor for advancing carotid arteriosclerosis in subjects with mild hyperglycemia.

Involvement of cytokine production in pathogenesis of transient cerebral ischemic damage

The contribution of cytokines in an inflammatory cascade on cerebral reperfusion injury are characterized as typical phases; leukocytes invision, microglial activation, and remodeling. Within 1-2 days, IL-1 (interleukin-1) and TNF (tumour necrosis factor) induce the expression of adhesion molecules that cause leukocytes adhere to endothelial cells. IL-8 (CINC; cytokine-induced neutrophil chemoattractant) is a well-known chemokine that promotes invasion of these leukocytes into brain parenchyma. The activation of proteases and free radical formation by invading neutrophils induces lipid peroxidation and subsequently neuronal damage. From 2 to 7 days, microglia is activated mainly in the "reactive zone" at the boundary of the infarct, and secrete IL-1 and TNF. These cytokines induce astroglial proliferation and production of trophic factors by astroglia to limit the neuronal damage. However, excess astrogliosis exert a negative effect on neuroregeneration. From 7 to 30 days, phagocytic macrophages are observed in the core of infarction sites. The macrophages release a number of cytophylactic agents including proteases and superoxide anions to degrade the damaged areas. TGF-beta and basic FGF (fibroblast growth factor) from glial cells and macrophages induce angiogenesis to discard the debris for subsequent remodeling. These complicated cascade after cerebral reperfusion injury are indeed controlled by cytokines: IL-1 and TNF are considered to be primary mediators that work in concert with IL-8 and growth factors to initiate and regulate the local inflammation in the brain.

Inflammatory reaction after brain damage and prospective therapy against damage impending cerebral infarction

Cytokines which promote emigration of leukocytes from the vascular lumen into the injured brain tissue are produced at the site of incipient cerebral infarction. The blood-borne invaders then accelerate the decomposition of brain cells by their toxic by-products, phagocytic action, and by the immune reaction. Recently accumulated data in our laboratories and other research facilities show that depleting the amount of circulating leukocytes or administering anti-inflammatory chemicals such as cytokine blocking agents, anti-adhesion molecule antibodies, and immunosuppressants effectively minimize the size of ischemia induced cerebral infarction. Based on the fact that leukocyte invasion of the affected brain tissue occurs 6 to 24 hours after onset of ischemia, administration of an anti-inflammatory therapy may widen the therapeutic window against stroke.

Glycation and inactivation of sorbitol dehydrogenase in normal and diabetic rats

Sorbitol dehydrogenase (SDH) is involved in the polyol pathway, which plays an important role in the pathogenesis of diabetic complications. We have measured the tissue distributions of SDH mRNA, both the immunoreactive enzyme levels and the enzyme activity. SDH mRNA was especially abundant in liver, kidney and testis. Both the activity and enzyme content are high in liver and kidney but not in testis. The discrepancy between mRNA and immunoreactive enzyme levels and the activity of SDH observed in testis was also seen in livers of streptozotocin-induced diabetic rats. SDH was found to exist in both glycated and non-glycated forms, with larger amounts of the glycated protein in the diabetic liver. Moreover, after incubation of purified enzyme with glucose or fructose, its activity was markedly decreased. These results indicate that glycation causes a decrease in SDH activity in liver under diabetic conditions. The same post-transcriptional event might occur to decrease the activity of SDH in testis in normal animals.

Ultra-high-resolution scanning electron microscopy of the continuity of cytoplasmic and luminal membranes in frog oxyntic cells

BACKGROUND

Despite numerous previous studies, the presumed continuity of the luminal and tubulovesicular membranes in frog oxyntic (oxyntico-peptic) cells remains to be convincingly demonstrated. This study was undertaken to clarify this question by ultra-high-resolution scanning electron microscopy of specially prepared frog stomach specimens before and during histamine stimulation.

METHODS

Fasted Japanese meadow frogs stimulated with histamine were used. Oxyntic cell cytoplasmic matrix was removed by the aldehyde-osmium-DMSO-osmium maceration procedure and impregnated with osmium-hydrazine. Specimens were examined without metal coating.

RESULTS

In the resting oxyntic cell, the luminal membrane had closely packed surface folds forming a rather flat surface with a few short microvilli. In the cytoplasm, flattened 200-500 nm vesicles were interconnected by numerous slender 20-60 nm tubules forming the tubulovesicular network. Occasional slender tubular branches were found in continuity with the luminal membrane. After histamine stimulation, the number and length of microvilli and surface folds increased, whereas the tubulovesicular membrane system decreased. Sites of clear continuity between the luminal and tubulovesicular membranes were not abundant but were clearly demonstrated in histamine-stimulated oxyntic cells. The small size of the tubules connecting the tubulovesicular system to the plasma membrane renders this observation by transmission electron microscopy very difficult. In these specimens, the clear continuity of the tubulovesicular network to the luminal plasma membrane became more evident.

CONCLUSIONS

This study confirms previous findings of increased luminal membrane and depletion of the tubulovesicle system. The demonstration of continuity between these two compartments in our SEM preparations supports the hypothesis of direct transfer of tubulovesicular membrane to oxyntic cell luminal secretory membrane.