Catabolic fate of dietary trilinoleoylglycerol hydroperoxides in rat gastrointestines

To elucidate whether dietary lipid peroxides are absorbed in the body, the catabolic fate of trilinoleoylglycerol hydroperoxides (TL-OOH), in the gastrointestines of rats was examined. Oxidized trilinoleoylglycerol with a peroxide value of 1000 meq/kg, 0.5 or 20 mg, was dosed intragastrically to rat together with 59.5 or 40 mg unoxidized trilinoleoylglycerol, respectively. The fate of TL-OOH in gastric and intestinal lumina was determined by high-performance liquid chromatography periodically until 240 min after treatment. At low dose, TL-OOH was soon broken down to linoleic acid hydroperoxides (LA-OOH) and hydroxyls, probably through gastric lipases, whereas at high dose, TL-OOH was retained in the stomach. In both cases, TL-OOH did not reach the intestines, though the unoxidized lipids moved to the intestines. When LA-OOH was given intragastrically, the lipids decomposed in the stomach, and linoleic acid hydroxyls, hexanal, 9-oxononanoic acid, and two novel compounds were detected 30 min after treatment. The novel compounds were identified to be epoxyketones, 11-oxo-12,13-epoxy-9- and 11-oxo-9,10-epoxy-12-octadecenoic acids. Thus, dietary TL-OOH was broken down in the stomach releasing, LA-OOH which decomposed further, and did not reach the intestines.

Antimutagenicity of flavones and flavonols to heterocyclic amines by specific and strong inhibition of the cytochrome P450 1A family

We found the mechanism in flavonoids that can strongly suppress the mutagenicity of one of the food-derived and carcinogenic heterocyclic amines, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). The antimutagenicity was evaluated by IC50 value, the amount required for 50% inhibition of the mutagenicity of 0.1 nmol Trp-P-2, with Salmonella typhimurium TA98 strain in the presence of S9 mix. The flavones and flavonols were two orders stronger as antimutagens that such antimutagenic phytochemicals as chlorophylls and catechins. We had previously found flavonoids to be a desmutagen to neutralize Trp-P-2 before or during attack of DNA, because they had no effect on either the ultimate mutagenic form of Trp-P-2 (N-hydroxy-Trp-P-2) or the mutated cells. The desmutagenicity of the flavonoids did not depend on the hydroxy number or position that should be associated with antioxidative potency, and was also unaffected by the solubility of Trp-P-2 in the assay solution. The inhibitory effect of the flavonoids on the metabolic activation of Trp-P-2 to N-hydroxy-Trp-P-2 was almost in parallel with the antimutagenic IC50 value, when determined with a Saccharomyces cerevisiae AH22 cell simultaneously expressing both rat cytochrome P450 1A1 and yeast reductase. The Ki values of flavones and flavonols for the enzyme were less than 1 microM, while the K(m) value of Trp-P-2 was 25 microM. The antimutagenicity of the flavones and flavonols was thus concluded to be due to inhibition of the activation process of Trp-P-2 by P450 1A1 to the ultimate carcinogenic form. They were also able to act as antimutagens toward other indirect mutagens that were activated by P450 1A1.

Usefulness of K-ras gene mutation at codon 12 in bile for diagnosing biliary strictures

Point mutations of the K-ras gene at codon 12 are often detected in the pancreatic juice of patients with pancreatic cancer. Detection of these mutations may, thus, have diagnostic implications. K-ras mutations may also have diagnostic potential for other biliary tumors. We sought to detect K-ras mutations in DNA obtained from bile in patients with biliary tract cancers, pancreatic cancer and benign biliary disease but who had obstructive jaundice. In 35 patients, bile was collected during percutaneous transhepatic choledocal drainage (PTCD) catheters. K-ras gene mutations at codon 12 in the samples were examined using mutant-allele-specific-amplification (MASA). We compared these results with cytological analyses of bile. K-ras mutations at codon 12 in bile were detected in 11 of 14 (79%) of the patients with biliary duct cancer, 3 of 9 (33%) with pancreatic cancer but not in patients with gallbladder cancer (n=3), papilla of Vater's cancer (n=3) or benign biliary diseases (n=6). In the patients, where cytological evaluation did not reveal malignant cells, K-ras mutations in bile were detected in 5 of 7 (71%) patients with biliary duct cancer and 2 of 5 (40%) with pancreatic cancer. This approach, when used in conjunction with bile cytology, may improve the yield in diagnosing suspected malignant tumors of the pancreatic-biliary system.

[A case of multiple organ failure with massive intestinal bleeding caused by methicillin-resistant Staphylococcus aureus in a postcystectomy patient--efficacy of mask continuous positive airway pressure training and intraarterial embolization]

A 51-year-old man underwent radical cystectomy with tubeless cutaneous ureterostomy. Methicillin-resistant Staphylococcus aureus (MRSA) enteritis developed postoperatively. MRSA caused critical infections such as pneumonia and sepsis, which subsequently progressed to adult respiratory distress syndrome, massive melena and multiple organ failure. The patient was rescued by intensive management including mask continuous positive airway pressure, systemic vancomycin administration and intraarterial embolization to stop jejunal bleeding.

Xenobiotic tolerance of primary cultured hepatocytes in rats fed a high-fat or high-protein diet

The diet and nutritional status dominate a tolerance to environmental xenobiotics. In this study, the cytotoxic action of carbon tetrachloride (CCl4) and 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), one of the dietary carcinogens, was investigated using primary cultured hepatocytes from rats fed a high-fat (23% corn oil) or high-protein (50% casein) diet for three weeks. Both chemicals showed strong cytotoxicity to hepatocytes, which was judged by measurement with the MTT-test and lactate dehydrogenase leakage test. A dietary effect on cytotoxicity was observed; hepatocytes from rats fed the high-protein diet were more susceptible to cytotoxicity than the cells from rats fed a standard diet. On the other hand, ureogenesis, as a cellular function of hepatocytes, was markedly decreased in the cells from rats fed the high-fat diet. These activities were affected in the CCl4-treated cells but not in the Trp-P-1-treated cells. The same trend of both diet and chemical effects was observed in gluconeogenesis from fructose. We conclude that the hepatocytes from rats fed a high-protein diet have high susceptibility to the cytotoxicity of CCl4 and Trp-P-1, but cytotoxicity was not related to the reduction of cellular functions.

Visual influence on the magnitude of somatogravic illusion evoked on advanced spatial disorientation demonstrator

BACKGROUND

The somatogravic illusion (SGI) is a kind of spatial disorientation caused by a linear sustained acceleration. Pilots believe that visual cues, such as a visible horizon or texture flow, reduce this illusion. This study was performed to evaluate the influence of visual stimuli on the SGI using the Advanced Spatial Disorientation Demonstrator (ASDD).

METHODS

There were eight healthy males who were exposed to a 0.58 g x axis linear acceleration on the ASDD, where the direction of the resultant gravitoinertial force was equivalent to 30 degrees pitch-up. One of the following visual stimuli was presented during each acceleration: BLANK (no visual cues); HORIZON (a visible horizon without motion); and TEXTURE (vertical lines moving toward the subject evoking vection). The subjective magnitude of the SGI in ordinal scale was observed; and in interval scale, the deviation of the moving point kept at the subjective horizon was observed. The differences among visual stimuli were analyzed.

RESULTS

The subjective magnitude of the SGI (p < 0.01) and the deviation of the moving point (p < 0.05) were significantly smaller in HORIZON than in BLANK and TEXTURE. No difference was demonstrated between BLANK and TEXTURE. The linear vection produced by the TEXTURE stimulus did not affect the SGI.

CONCLUSION

The data indicated that the presence of a visible horizon reduced the magnitude of the SGI. On the other hand, the presence of a vection stimulus did not influence the magnitude of the SGI.

Acute mesenteric ischemia. CT and plain radiographic analysis of 26 cases

The purpose of this study was to assess the computed tomography (CT) and plain radiographic findings of acute mesenteric ischemia, in an effort to elucidate its poor prognostic signs. The study group consisted of 26 cases with pathologically or angiographically proven mesenteric ischemia. The pathologically proven longitudinal extent of the bowel ischemia was graded using six degrees, and correlated with the radiographic findings. The mortality of the patients depended primarily on the extent of infarctions and the age of the patient. Patients with bowel dilation or abnormal gas in the bowel wall or portal system were prone to have wider extents of ischemia.

An evaluation of splenopancreatic disconnection as a modification of the distal splenorenal shunt, studied in nonalcoholic patients by sequential angiography

To evaluate the validity and complications of modifying the distal splenorenal shunt (DSRS) by performing splenopancreatic disconnection (SPD), hemodynamic changes in the portal system were assessed by visceral angiography in 93 patients with nonalcoholic portal hypertension during early postoperative follow-up after DSRS. There were 40 patients who underwent DSRS alone and 53 who underwent DSRS plus SPD. Early follow-up angiography showed that portal vein perfusion was well maintained, and that the diameter of the portal vein had decreased significantly by the same degree in both groups. Hepatofugal collaterals for the shunt had developed to a greater extent in the DSRS group, while they were almost completely absent in the DSRS with SPD group. Nevertheless, partial portal vein thrombosis was not detected in the DSRS group, although it was seen in seven (13.2%) of the patients who underwent DSRS plus SPD, in whom the left proximal splenic vein was not visible. The proximal splenic vein was seen in significantly less of the DSRS with SPD patients (47.2%) than the DSRS group patients (85%). In conclusion, SPD more effectively prevented the early postoperative development of collateral pathways for the shunt compared with standard DSRS; however, the possible stagnation of blood flow in the left proximal splenic vein may predispose to a risk of partial portal vein thrombosis developing during the early postoperative period after DSRS with SPD.

Effects of dietary lipid peroxidation products on hormonal responses in primary cultured hepatocytes of rats

Dietary lipid peroxidation products cause endogenous lipid peroxidation with hepatic dysfunction. In this study, we isolated and cultured hepatocytes of rats that were given secondary autoxidation products of linoleic acid (p.o., 400 mg/rat/day for 3 days), and examined the hormonal responses of these hepatocytes. An increase in thiobarbituric acid reactive substances and a depletion of vitamin E persisted in hepatocytes from treated rats for at least 24 h in culture as compared to those from control rats. As markers for hepatic dysfunction, the activities of six enzymes were measured. In each case, there was an initial decrease in the enzyme activity in hepatocytes from the treated rats, and all activities were restored by 48 h in culture. Then, we measured the hormonal responses of these hepatocytes. The responses to insulin or glucagon in hepatocytes from secondary products-treated and control rats were the same. In contrast, the response to dexamethasone was significantly lowered in hepatocytes from secondary products-treated rats as measured by the induction of tryptophan 2,3-dioxygenase and tyrosine aminotransferase. We conclude that primary cultured hepatocytes from the rats treated in vivo with dietary lipid peroxidation products retained symptoms of oxidative stress and had a low response to glucocorticoids.

What is the Transition Point between Static and Dynamic Motion Aftereffects?

The motion aftereffect (MAE) measured with a dynamic test pattern (eg a counterphase-flickering grating) is distinguishable by a number of properties from the classical MAE obtained with a static test pattern. For a dynamic MAE, however, it is not sufficient simply to introduce dynamic properties into the test pattern. In two experiments we attempted to determine the transition point in the temporal-frequency domain at which a dynamic MAE becomes distinguishable from the static MAE. First, we examined the interocular transfer (IOT) of the MAE with conventional first-order (luminance) gratings. The amount of IOT increased with temporal frequency, and was almost complete at 1 Hz and above. In addition, the IOT of a dynamic MAE shows a drastic reduction in the peripheral visual field, possibly reflecting difficulties in feature tracking or the loss of involuntary attention. Second, we examined the MAE with second-order motion as the adaptation stimulus (contrast modulation of two-dimensional static noise). Under these conditions, similar results were obtained for first-order and second-order test gratings: MAE was not observed at low temporal frequencies and a substantial MAE was observed only at 1 Hz and above. The results agree with recent findings which showed a gradual loss of spatial-frequency selectivity with increasing temporal frequency of the test pattern (Mareschal et al, 1997 Vision Research37 1755 – 1759). The present results support the idea that two mechanisms underlie the different kinds of MAE: a low-level mechanism responsible for the MAE observed at low temporal frequencies, and a high-level mechanism operating predominantly at high temporal frequencies with a transition point at about 1 Hz.

Linking lower and higher stages of motion processing?

The spatial frequency selectivity of motion detection mechanisms can be measured by comparing the magnitude of motion aftereffects (MAEs) as a function of the spatial frequency of the adapting and test gratings. For static test gratings, narrow spatial frequency tuning has been reported in a number of studies. However, for dynamic test patterns, reports have been conflicting. Ashida & Osaka [(1994). Perception, 23, 1313-1320] found no tuning whereas Bex et al. [(1996) Vision Research, 36, 2721-2727] reported a narrow tuning. The main difference between the two studies was the temporal frequency of the test pattern. In this study we measured the spatial frequency tuning of the MAE using test patterns for a range of temporal frequencies. The results confirmed that there was narrow spatial frequency tuning when the test pattern was counterphasing at a low temporal frequency. However, the spatial frequency selectivity broadened as the temporal frequency of the test pattern was increased.

Red cell survival in patients with nonalcoholic liver cirrhosis before and after distal splenorenal shunt

We previously reported severe hemolysis in one patient immediately after distal splenorenal shunt (DSRS). The purpose of the present study was to evaluate changes in red cell survival after DSRS. In ten patients with nonalcoholic cirrhosis in whom DSRS was performed for esophageal varices, red cell survival and splenic quantitative hemodynamic studies were performed before and after DSRS. The splenic venous blood flow per unit volume (flow/volume ratio) was calculated. The red cell survival was significantly (P < 0.05) shortened after DSRS; the apparent half-life survival time (T 1/2) before and after DSRS was 24.6 +/- 5.9 (mean +/- SD) and 16.3 +/- 8.5 days, respectively. After DSRS, the spleen volume was significantly (P < 0.05) decreased, whereas the splenic venous blood flow was slightly increased. The spleen flow/volume ratio was significantly (P < 0.05) increased after DSRS. There was a significant and negative correlation (r = -0.684, P < 0.05) between the postoperative percentage change in T 1/2 and the spleen flow/volume ratio. These findings suggest that the red cell survival period is significantly decreased, after DSRS in patients with nonalcoholic cirrhosis, and that the increased splenic blood flow per unit spleen volume after DSRS may play an important role in the hemolytic reaction in the spleen after this procedure.

Contrast dependencies of two types of motion aftereffect

We examined the effects of adaptation and test contrasts on the duration of two types of motion aftereffect (MAE) that presumably reveal different levels of motion processing: MAE with a static test stimulus (static MAE), and that with a counterphasing test stimulus (flicker MAE). MAE duration increased with increasing adaptation contrast. When the test contrast was low, it increased rapidly, and saturated at a low adaptation contrast. When the test contrast was high, however, it gradually increased over a wide range of adaptation contrasts. These complex effects of stimulus contrasts could be well described by a dependency on adaptation contrast normalized by test contrast on a logarithmic axis. Little difference was found between the results for two types of MAE. The interaction between adaptation and test contrasts leads us to reject the idea that the shape of adaptation contrast dependency of MAE duration reflects that of the sensitivity function of motion detecting mechanisms. The results also suggest a functional similarity between the processes underlying static and flicker MAEs with regard to their responses to contrasts.

[MR imaging of spontaneous spinal epidural hematoma]

Spontaneous spinal epidural hematoma is a rare entity. Sudden onset of nuchal or back pain is a common presentation. Clinical diagnosis is often difficult because of its non-specific symptomatology. Irreversible neurological deficits of spinal cord may result, due to delay in initiating proper treatment. We present two cases of spontaneous spinal epidural hematoma, one in the cervical and the other in the thoracic spine. MR imaging was helpful to confirm the diagnosis and for pre-surgical planning. Both patients were treated surgically and the MR findings confirmed. MR imaging accurately localized and characterized the epidural lesions. We stress that MR imaging is a valuable examination for the diagnosis of spinal epidural hematoma.

Linear motion aftereffect induced by pure relative motion

The effect of adaptation to pure relative motion was investigated for the motion aftereffect (MAE) of linear translation motion. In experiment 1, MAE induced by adaptation in the surrounding area was tested. The relative motion signal significantly increased the magnitude of MAE while local MAE in the surrounds was not affected. In experiment 2, MAE observed in the same adapted area was examined while local adaptation was cancelled out. Substantial MAE was found only when the test stimuli included the surroundings, which is considered to be favourable for relative motion mechanisms. These results clearly indicate that MAE is induced by adaptation to pure relative motion as well as by local motion. MAE should be regarded as a composite phenomenon reflecting multiple sites of adaptation including the local and the relative motion levels. The results also provide evidence for the existence of independent detecting mechanisms for relative motion processing.

A case of gross hematuria arising during embolization for renal arteriovenous malformation

A cirsoid type of arteriovenous malformation was treated successfully by superselective embolization using a platinum micro coil and absorbable gelatin sponge. During the procedure, as soon as the arteriovenous shunt had disappeared, an arteriopelvic shunt appeared. The pyelogram showed that the high pressure arterial blood flow drained directly into the pelvic cavity. Massive gross hematuria occurred immediately accompanied by a sudden blood pressure drop to 60 mm Hg, necessitating blood transfusion. Fortunately this complication was managed successfully. To our knowledge, there are only a few reported cases that make reference to gross hematuria occurring on embolization. We discuss the possible causes of this complication and the mechanism of occurrence of gross hematuria in renal arteriovenous malformation.

Re-evaluation of local adaptation for motion aftereffect

A motion aftereffect (MAE) can be induced by stimuli moving in surrounding areas. This suggests the relevance of mechanisms for relative motion, rather than early-level motion detectors, which are considered to work locally. Experiments are reported in which the role of local adaptation in the MAE with a stimulus configuration comprising relative motion has been discussed. Sinusoidal gratings were presented in three rectangular windows: a centre window, and two windows one above and one below the central one. The surrounding top and bottom windows, which were divided into left and right halves, had gratings presented in only one of the two halves. The MAE duration was measured after adaptation to motion either in the central or in the surrounding windows, by controlling the regions with the gratings. From this, the regions of surrounding gratings were found not to have a significant effect with adaptation in the centre window. With adaptation in the surrounds, however, these regions did affect the MAE; the MAE duration was reduced when the adapted region had no gratings in the test phase. Thus, for an MAE it is necessary for the adapted area to be covered with stimuli in the test phase, which indicates the dominance of local adaptation for the MAE even when relative motion is relevant in producing the MAE.

Cooperative Interaction between Change in Disparity and Size for the Perception of Motion in Depth

While an object is moving in depth, its retinal disparity and size are cooperatively changing along the viewing distance. We examined the effect of a cooperative relation between the two cues for the perception of motion in depth—changes in disparity and size—with the Wheatstone stereoscopic display. In experiment 1, we used a stereoscopic stimulus whose disparity and size were independently modulated with sine-wave form, but at different frequencies (0.7 Hz vs 0.8 Hz, and vice versa). So, the cooperative and the uncooperative phases between the two cues repeatedly followed each other. The subjects continuously pushed a response key when the stimulus was clearly perceived to be moving in depth. In general, the impression of motion in depth was clear when the two cues were simultaneously modulated in similar phase, but not in different phase. In experiment 2, we measured the perceived distance of a stimulus that is moving in depth, when the two cues were moderated in the same phase and in counterphases. The perceived distance was increased when the two cues moved in the same phase. We found that not only the effect of each cue, but also the effect of the cooperative change of the two cues was affecting the perception of motion in depth. These results suggest that the cooperative interaction of two cues, that is their relative phase, is important for the perception of motion in depth.

Evoked Magnetic Field Elicited by Motion and Motion Aftereffect

Motion aftereffect (MAE) is a negative aftereffect caused by prolonged viewing of visual motion: after gazing at a moving grating for a while, a stationary image will appear to move in the opposite direction (Ashida and Osaka, 1995 Vision Research35 1825). Evoked magnetic field (magnetoencephalogram: MEG) was measured on a human subject observing visual motion and MAE. Magnetic evoked field (80 averagings) was measured from 37 points over occipital and parietal areas (Magnes SQUID biomagnetometer, BTi) during watching a horizontally moving sinusoidal grating with low spatial frequency (2 cycles deg−1 with 5 Hz: motion condition) and immediately after stopping the moving grating (MAE condition). Dipole estimates based on equal magnetic field contour suggest that the main loci subserving visual motion and MAE appear to be the surrounding region over occipital and parietal areas in the human brain. Further analysis is now underway. In general, this appears to be in good agreement with another study using fMRI-based MAE measures [Tootell et al, 1995 Nature (London)375 139] in which a clear increase in activity in these areas was observed when subjects viewed MAE.

[Prospective randomized trial comparing 1/2 FAM (5-fluorouracil (5-FU) + adriamycin + mitomycin C) versus palliative therapy for the treatment of unresectable pancreatic and biliary tract carcinomas (the 2nd trial in non-resectable patients). Japanese Study Group of Surgical Adjuvant Therapy for Carcinomas of the Pancreas and Biliary Tract]

The efficacy of 1/2 FAM, which consists of 5-fluorouracil (5-FU), adriamycin (ADM) and mitomycin C (MMC), was compared with that of palliative treatment in patients with unresectable pancreatic and biliary tract carcinomas in a multicenter randomized trial. The patients assigned to 1/2 FAM group were treated with 5-FU 200 mg/m2/day IV, ADM 15 mg/m2/day IV and MMC 5 mg/m2/day IV. These 3 drugs were given concurrently as the initial dose within a week after palliative operation, and this regimen was repeated for at least 2 whole courses, at 4-week intervals before the next course of therapy. Those randomized to the control group were subjected to palliative treatment alone. Completely eligible for analysis were 42 cases of the 1/2 FAM group and 41 of the control group. There was no significant difference between the groups with respect to the overall and differentiated survival times according to the tumor sites and the clinical efficacy. As for the duration of 50% inhibition of tumor progression, a significantly better outcome was obtained in 1/2 FAM group. Tumor progression was most significantly inhibited in patients with gallbladder carcinoma. In 1/2 FAM group, tumor reduction was achieved in 1 CR and 2 PR patients. The most frequent adverse reaction was gastrointestinal manifestations, along with diarrhea and alopecia. 1/2 FAM did not contribute to the life prolongation, but inhibited the tumor progression for a significantly longer duration and, to a lesser extent, reduced the tumor size in unresectable pancreatic and biliary tract carcinomas. This regimen is suggested to be useful particularly in the treatment of the latter carcinoma.

Protective action of dehydroascorbic acid on the Ah receptor-dependent and receptor-independent induction of lipid peroxidation in adipose tissue of male guinea pig caused by TCDD administration

The effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on lipid peroxidation, 3H-Me-glucose (3H-Me-glu), and 14C-dehydroascorbic acid (14C-DHA) uptakes were studied in adipose tissue of male guinea pig. Under in vitro test conditions, using isolated adipose tissue in a culture medium (explant culture), TCDD reduced the uptake of 3H-Me-glu and 14C-DHA in a dose- and time-dependent fashion. The IC50 values of TCDD's action were 0.04 and 2 nM on 14C-DHA and 3H-Me-glu uptakes, respectively. TCDD (10 nM) also suppressed glucose transporting activity within 15 minutes in explant-cultured adipocytes. Cytochalasin B (CB) and nonlabeled D-glucose inhibited 14C-DHA uptake also in a dose-dependent manner. In addition, TCDD was found to induce lipid peroxidation in explant-cultured adipose tissue. This effect of TCDD was similar to that of a typical lipid peroxidation inducer, CCl4, and it was dose and time dependent. TCDD caused a statistically significant rise in lipid peroxidation at a concentration as low as 0.1 nM after 60 minutes of treatment in explant culture. Unexpectedly, the Ah receptor partial antagonists, 4,7-phenanthroline and alpha-naphthoflavone, did not fully antagonize TCDD-induced lipid peroxidation in explant-cultured adipocytes. In vivo treatment of TCDD also induced lipid peroxidation. Among seven organs of male guinea pig tested, the levels of lipid peroxidation in adipose tissue and in liver increased at 1 and 40 days following a single i.p. dose of TCDD (1 microgram/kg). The results of an in vivo time-course study indicated that such an effect of TCDD was most pronounced after 40 days of treatment. Finally, we have tested the protective role of some antioxidants on TCDD-induced lipid peroxidation under explant-culture conditions. The results indicated that DHA, but not ascorbic acid, could completely abolish TCDD-induced lipid peroxidation. The protective effect of DHA on TCDD-induced lipid peroxidation was stronger than that of alpha-tocopherol and uric acid, and this effect was blocked by CB. We conclude from these studies that TCDD acts in this guinea pig tissue through two different routes: one is the Ah receptor-dependent route causing the reduction of the level of glucose transporters and subsequent decrease of cellular uptake of DHA and the other, the Ah receptor-independent route causing the overall lipid peroxidation. Nevertheless, it appears likely that both events are antagonized by DHA.

Formation of lyso-glycosphingolipids by Streptomyces sp

The actinomycete strain Streptomyces sp. H37 produces a novel glycosphingolipid-degrading enzyme. This strain was capable of converting ganglioside GM1 to lyso-GM1. After cultivation for 5 days in medium containing GM1, peptone, and detergent, GM1 was found to be almost completely converted to lyso-GM1. The product was purified on a DEAE-Sephadex A-25 column and thin layer chromatographies. The purified lyso-GM1 was hydrolyzed by endoglycoceramidase, and the released oligosaccharide moiety was identified as that of GM1 by HPLC using the pyridylaminoderivative method. The counterpart sphingosine moiety was confirmed with TLC. Moreover, the structure of lyso-GM1 was ascertained by 1H-NMR analysis. The maximum formation of lyso-GM1 was found in 50 mM potassium phosphate buffer (pH 7.5) containing 0.1% glycodeoxycholate. Various lyso-glycoshingolipids, including those of ganglio-, neolacto-, and globo-types, were formed from their parent glycosphingolipids using this strain.

Protein kinase C inhibitors affect induction of long-lasting potentiation in the somatosensory cortex

The effects of protein kinase C (PKC) inhibitors on the induction of long lasting potentiation (LLP) of field potentials in the feline somatosensory cortex were studied. LLP was induced by high frequency stimulation (HFS, 200 Hz) of the ventral posterolateral thalamic nucleus. First, the effects of a protein kinase inhibitor, H-7, and a specific PKC catalytic domain inhibitor, chelerythrine, on the LLP in the secondary somatosensory cortex (SII) were investigated. Intracortical microinjections of H-7 and chelerythrine at 30 min before HFS inhibited induction of LLP in SII, while an injection of chelerythrine at 60 min after LLP induction had no effect on the potentiation. Second, changes in PKC activity in the presence of calcium and phosphatidylserine were investigated in SII after induction of LLP. Triton-soluble membrane fractional PKC activity had increased to 350% of the control value with low frequency test stimulation (0.1 Hz) by five min after HFS. In contrast, PKC activities of cytosolic fractions decreased to 25.6% of the control value. At 60 min after HFS, the PKC activity level returned to the control value, despite persistent potentiation in all cases. PKC activation is considered to be one of the factors required for induction of LLP but not for maintenance in SII.