Effect of propionyl-L-carnitine on oscillatory potentials in electroretinogram in streptozotocin-diabetic rats

The effect of propionyl-L-carnitine, an analogue of L-carnitine, and insulin on the oscillatory potentials of the electroretinogram was determined in rats with streptozotocin-induced diabetes. Propionyl-L-carnitine was administered at a daily dose of 0.5 g/kg by gavage for 4 weeks, while other rats were treated with subcutaneous injections of insulin (8-10 U/day). Both treatments shortened the peak latencies of the oscillatory potentials in the electroretinogram, which were significantly prolonged in untreated diabetic rats (O1, O2 and O3, and sigma (O1 + O2 + O3)) (P < 0.0001 vs. untreated normal rats). A significant decrease in the erythrocyte free carnitine level in diabetic rats was prevented by both treatments. Insulin produced a significant reduction of retinal glucose, sorbitol and fructose levels in diabetic rats, while propionyl-L-carnitine failed to do so. However, both treatments markedly reduced serum lipids levels in the diabetic rats. These findings provide information on the pathogenesis of diabetic retinopathy as well as suggesting the potential therapeutic value of propionyl-L-carnitine for retinopathy.

In situ ocular absorption of tilisolol through ocular membranes in albino rabbits

The purpose of this study is to characterize the in situ absorption properties of ocular membranes using a cylindrical cell. Drug disappearance in the cell was determined as in situ absorption after an application of drug solution into the cell on the comea, sclera (bulbar conjunctiva and sclera layer), or palpebral conjunctiva. Tilisolol was used as a model of an ophthalmic beta-blocker. Tilisolol disappeared from the conjunctival and scleral surfaces although hardly any disappearance of tilisolol from the corneal surface was observed. Depletion of drug from the precorneal space was much faster in situ than extrapolated from permeability measurements (in vitro) of the separate tissues. This may arise from an influence of blood flow. The in situ apparent permeability coefficient of tilisolol through the conjunctiva was almost constant at various concentrations of drug (5-100 mM), suggesting a passive diffusion of tilisolol that was affected by medium pH. A high concentration of tilisolol in the aqueous humor was observed in the corneal application although the scleral and conjunctival applications showed a slight concentration of tilisolol. The corneal route was a dominant route of access to the aqueous humor. Access to the vitreous body for tilisolol was 4 times more effective through the sclera than through the cornea. On the other hand, the corneal application showed an extremely low concentration of tilisolol in plasma compared to the scleral and conjunctival applications. Thus, the in situ method using a cylindrical cell is a useful method for investigation of the ocular absorption of ophthalmic drugs.

Effect of a novel hypoglycemic agent, KAD-1229 on glucose metabolism and fructose-2,6-bisphosphate content in isolated hepatocytes of normal rats

The effects of a novel hypoglycemic agent, calcium(2s)-2-benzyl-3-(cis-hexahydro-2-isoindolinylcarbonyl) propionate dihydrate (KAD-1229), which is a benzyl succinate derivative, on liver metabolism were investigated using isolated hepatocytes from normal rats. In the presence of 10 mM glucose, KAD-1229 increased the L-lactate production (41.1 +/- 0.9 versus 60.9 +/- 2.6 mumol of lactate/g of cells/30 min; P < 0.05) and inhibited gluconeogenesis in hepatocytes (0.94 +/- 0.02 versus 0.70 +/- 0.03 mumol of [2-14C]-pyruvate converted to glucose/g of cells/20 min; P < 0.05). These effects by KAD-1229 were accompanied by an increase in the cellular content of fructose-2,6-bisphosphate (F-2,6-P2), which is one of the important regulators of hepatic glucose metabolism, in a dose-dependent manner (0.05-2.5 mM). KAD-1229 also stimulated the oxidation of [2-14C]-pyruvate and [6-14C]-glucose in the tricarboxylic acid cycle (+18 and +31%, respectively), indicating that stimulation of tricarboxylic acid cycle activity and/or enhancement of the glycolytic flux rate had occurred. Moreover, KAD-1229 did not modify the activities of 6-phosphofructo 2-kinase or fructose-2,6-bisphosphatase, but increased significantly the accumulation of fructose 6-phosphate in hepatocytes. These results suggest that KAD-1229 has extrapancreatic effects on hepatic glucose metabolism, that its actions are mediated through the inhibition of fructose-1,6-bisphosphatase and stimulation of both the 6-phosphofructo 1-kinase reaction and tricarboxylic acid cycle activity by increasing the F-2,6-P2 content in hepatocytes, and that these multiple effects may account in part for the ability of KAD-1229 to reduce blood glucose levels in vivo.

Calcium ionophore, A23187, alters the mode of cAMP formation in wild-type S49 murine lymphoma cells

We examined the change in the adenylyl cyclase activity of S49 cells occurring after exposure to calcium ionophore, A23187. MnCl2-stimulated adenylyl cyclase activity in membrane preparations increased by 67 +/- 3% (after 24 h treatment with 0.3 microM A23187), while no significant change was found in the basal activity or NaF-, isoproterenol- or forskolin-stimulated activities. An activity sensitive to CaCl2/calmodulin, which could not be detected in membranes from untreated cells, was found in membranes from A23187-treated cells. These changes took place after treatment with 0.1-0.3 microM A23187 for a period longer than 16 h. A brief treatment of S49 cells with phorbol 12-myristate 13-acetate (PMA) enhances the activity of adenylyl cyclase (Bell, J.D. et al. (1985) J. Biol. Chem. 260, 2625-2628), but exposure of cells to PMA at the end of A23187-treatment did not affect the induction of the MnCl2-or CaCl2/calmodulin-sensitive activity. The results indicate that long-term treatment of S49 cells with calcium ionophore, A23187, induces adenylyl cyclase activity of a novel type, which is probably caused by an abnormal increase in free intracellular calcium.

Effect of gamma knife irradiation on relaxation and contraction responses of the common carotid artery in the rat

This report concerns a pilot study of the short- and long-term effects of gamma knife radiosurgery on vascular responses. The investigation was carried out on male Sprague-Dawley rats, and the relaxation and contraction responses of the right common carotid artery (CCA) were assessed following irradiation (100 Gy). The non-treated CCA of the same animals served as internal controls. Non-irradiated rats were used to control the effect of normal aging on vascular function. Isometric tension was determined on in vitro preparations of arterial rings. Acetylcholine-mediated, endothelium-dependent relaxation was impaired one month after radiosurgery, as was endothelium-independent relaxation induced by sodium nitroprusside, but the effect on the latter was minimal. The irradiated CCA was also impaired with respect to contraction responses induced by norepinephrine, endothelin-1 or phorbol dibutyrate. This impairment appeared to be biphasic, as it was evident one day after radiosurgery, followed by a partial recovery one week later, and again manifest after one month. At the light microscope level, the carotid arteries appeared to be well preserved throughout the experiment. However, obvious ultrastructural changes were noted in endothelial and smooth muscle cells of specimens obtained three months after radiosurgery. The present data indicate that high dose gamma knife radiosurgery affects the functions of both, the vascular endothelium and the vascular smooth muscles in an apparent time-dependent fashion. Because of its increasing application to patients, there is the need for studying the effects of gamma knife radiosurgery on cerebral arteries, since functional vascular changes may occur in the absence of obvious histological alterations. Our results on CCAs point to the feasibility of such experimental investigations.

Effects of caffeine on event-related potentials: comparison of oddball with single-tone paradigms

We investigated the acute effects of caffeine (500 mg) on event-related potentials (ERP) in 10 healthy subjects using standard oddball and single-tone paradigms. Event-related potentials were recorded before oral ingestion of caffeine or placebo and 30 min and 210 min after. The oddball paradigm, but not the single-tone paradigm, showed that the P300 amplitude and the area were significantly increased 30 min after ingestion of caffeine and significantly decreased 30 min after ingestion of placebo. The effects of caffeine disappeared at 210 min. Neither the P300 latency nor the reaction time changed significantly with the oddball paradigm. However, the reaction time was shortened 30 min after ingestion of caffeine with the single-tone paradigm. These findings suggest that the caffeine-induced increase in the P300 amplitude may have resulted from the increased allocation of attentional resources to the discriminating process which was not, however, accompanied by facilitation of the process and that caffeine may specifically stimulate the discriminating process involved in the oddball paradigm. In addition, the simple psychomotor performance of buttonpressing in response to a tone signal was accelerated by caffeine.

Leukemoid reaction in epidermal squamous cell carcinoma

There have been no previous concrete reports of leukemoid reactions associated with squamous cell carcinoma originating in cutaneous tissue. Here we report a case of epidermal squamous cell carcinoma of the sacral region and an associated leukemoid reaction. The tumor invaded deeply and destroyed both the sacrum and coccyx. The white blood cell count was greater than 20,000/mm3. After resection of the tumor, white blood cells transiently decreased, but did not fall under 10,000/mm3. Post-operative infection by methicillin-resistant Staphylococcus aureus and Bacteroides caccae caused sepsis and further elevation of the leukocytes to greater than 50,000/mm3. The leukemoid reaction in the case appeared to have been caused initially by direct invasion of bone by epidermal squamous cell carcinoma and later by severe infection.

Multiple segmental agenesis of the cerebral arteries: case report

A case of multiple segmental agenesis of the cerebral arteries is presented. Cerebral angiography demonstrated bilateral so-called carotid rete mirabile, a similar "rete" of the right vertebral artery and intradural duplication of the left vertebral artery. These abnormalities are thought to be caused by multiple segmental agenesis of the cerebral arteries as they penetrate the dura mater. The embryological and anatomical significance of these findings is discussed.

Immunosuppressive acidic protein (IAP) level in serum and peritoneal washings, and its implication in determining multidisciplinary treatments

In this study we examined the efficacy of the measurement of IAP (serum ancl peritoneal washings) during the treatment of colorectal cancers, and determined the possible benefits of using the IAP measurements from both serum and peritoneal washings. One hundred and six patients (peritoneal washings: 58, peritoneal fluid: 67) were investigated. Serum IAP levels were significantly higher in patients who underwent complicated surgical procedures which involved greater time and blood loss compared to those patients who underwent less involved surgical procedures with little loss of blood and time. In peritoneal washings, up to 66. 7% of cases with peritoneal dissemination showed elevated levels of IAP in the peritoneal cavity, while 37% of cases with no dissemination at surgery macroscopically had positive IAP levels (8 mg/g protein). The results suggest the value of IAP in determining the need for combined immunochemotherapy for patients in an immunosuppressive environment.

An importance of carbohydrate ingestion for the expression of the effect of alpha-glucosidase inhibitor in NIDDM

OBJECTIVE

To examine the usefulness of alpha-glucosidase inhibitors in glycemic control of patients with NIDDM. The involvement of carbohydrate ingestion in manifestation of the effects of alpha-glucosidase inhibitors was also investigated.

RESEARCH DESIGN AND METHODS

A total of 41 patients hospitalized with NIDDM (22 patients receiving sulfonylurea and 19 receiving insulin therapy) were given alpha-glucosidase inhibitors during the period when their blood glucose levels were well controlled. They were followed for 3 weeks as inpatients and for an additional 6 months as outpatients. They were retrospectively divided into two groups according to the percentage of carbohydrates in all sources of calories during outpatient management: the < 50% group and the > 50% group. Between these two groups, we compared circadian variation in blood glucose levels, HbA1c, and urine C-peptide.

RESULTS

Treatment with alpha-glucosidase inhibitors during the hospital stay markedly improved circadian variation in blood glucose levels and HbA1c and decreased urine C-peptide in both groups. While HbA1c returned to its pretreatment level at 6 months after the treatment in the < 50% group, HbA1c had further improved in the > 50% group at 6 months.

CONCLUSIONS

alpha-Glucosidase inhibitors are useful for glycemic control in patients with NIDDM and the percentage of carbohydrate in all calorie sources is an important factor for the expression of their effects.

Protection of scallop sarcoplasmic reticulum ATPase from thermal inactivation by removal of calcium from high-affinity binding sites on the enzyme

Sarcoplasmic reticulum (SR) vesicles were isolated from scallop muscle by the method of Abe et al. (J. Biochem. 112, 822-827, 1992) and their thermolability was examined in the presence and absence of Ca2+. When SR was preincubated at 38 degrees C in the presence of 0.1 mM Ca2+, Ca2+ transport activity decreased as a function of time with a half-inhibition time of about 5 min. Activities of the Ca(2+)-dependent ATPase, phosphoenzyme (EP) formation and E2 to E1 transition were decreased by the heat treatment in parallel with the Ca2+ transport activity. In contrast, when SR was preincubated at 38 degrees C in the presence of 2-5 mM EGTA, all of these activities, except for the Ca2+ transport, were markedly protected from the heat inactivation. The uncoupling between Ca2+ transport and the ATPase reaction did not lead to a rise in the Ca2+ permeability of SR membrane. Plots of the ATPase activity or steady-state level of EP against pCa in the thermal incubation medium revealed a typical sigmoidal curve with a half-inhibition concentration and Hill number of about 0.5 microM and 1.80, respectively. These results suggest that 2 mol of Ca2+ must be removed from the high-affinity Ca2+ binding sites on the ATPase to stabilize the Ca(2+)-ATPase against heat inactivation. The protection from heat inactivation disappeared if SR was preincubated at 38 degrees C after having been solubilized with a nonionic detergent, but returned when the detergent was removed to reconstitute the SR membrane. These results suggest that the protection of ATPase from thermal inactivation in EGTA may require a membrane structure in which the ATPase molecules exist in an appropriate arrangement.

In vivo regulation of acetylcholine release via adenosine A1 receptor in rat cerebral cortex

The roles of the endogenous adenosine on acetylcholine release via adenosine A1 receptor were investigated in rat cerebral cortex using brain microdialysis. Oral administration of KF15372 (8-dicyclopropylmethyl-1,3-dipropylxanthine), a novel selective adenosine A1 receptor antagonist, at doses of 1.25, 5, and 20 mg/kg, significantly increased the extracellular levels of acetylcholine in rat cerebral cortex. Selective A1 agonist N6-((R)-phenylisopropyl) adenosine (R-PIA) did not affect the extracellular level of acetylcholine by both oral (1.25 mg/kg) and intracortical administrations (0.3 microM) via dialysis probe. These results suggest that the extracellular level of acetylcholine is under tonic inhibitory control of endogenous adenosine via the A1 receptor.

Adenosine A2a receptor-mediated modulation of striatal acetylcholine release in vivo

To determine the functions of striatal adenosine A2a receptors in vivo, the effects of a selective agonist, 2-[4-(2-carboxyethyl)phenethylamino]-5'-N-ethyl-carboxamidoaden osi ne hydrochloride (CGS 21680), and an antagonist, (E)-8-(3,4-dimethoxystyryl)-1,3-dipropyl-7-methylxanthine (KF17837), on acetylcholine release were investigated in the striatum of awake freely moving rats using microdialysis. Intracerebroventricular injection of CGS 21680 (10 micrograms) increased acetylcholine release in striatum and KF17837 (30 mg/kg p.o.) antagonized the CGS 21680-induced acetylcholine elevation. To investigate the contribution of dopaminergic and GABAergic neurons on A2a receptor-mediated acetylcholine release, the effects of CGS 21680 were studied by using dopamine-depleted rats in the presence or absence of GABA antagonists. In the dopamine-depleted striatum, the intrastriatal application of CGS 21680 (0.3-30 microM) increased extracellular acetylcholine, which was significantly greater than that in normal striatum. The CGS 21680-induced elevation of acetylcholine release was still observed in the presence of GABA antagonists bicuculline (30 microM) and 2-hydroxysaclofen (100 microM) and was similar in both normal and dopamine-depleted striatum. These results suggest that A2a agonist stimulates acetylcholine release in vivo, and this effect of A2a agonist is modulated by dopaminergic and GABAergic neurotransmission.

Alpha 2-->3sialyltransferase associated with the synthesis of CA 19-9 in colorectal tumors

BACKGROUND

A novel assay method specific for alpha 2-->3sialyltransferase that seems to be responsible for the synthesis of CA 19-9 antigen was developed and the levels of the enzyme in colorectal tumor tissues were measured and compared with the levels of alpha 1-->4fucosyltransferase and the CA 19-9 antigen.

METHODS

Lacto-N-biose I (Gal beta 1-->3GlcNAc beta, Lewis(c) [Le(c)]) and 6-O-methyl-Le(c) (Gal beta 1-->3[6OMe]GlcNAc beta) were synthesized and covalently attached to bovine serum albumin (BSA). These two substrates were incubated with extracts from colorectal tissues in the presence of cytidine 5'-monophospho-N-acetylneuraminic acid (CMP-NeuAc) and their resulting products were detected by a sequential use of anti-BSA monoclonal antibody-coated beads and 125I-labelled anti-sialylated Le(c) antibody. Levels of alpha 2-->3sialyltransferase and alpha 1-->4fucosyltranferase activities and CA 19-9 antigen were measured in the extracts from colorectal tumors and their adjacent normal tissues.

RESULTS

6-O-Methyl-Le(c)-BSA showed a strong acceptor activity compared with Le(c)-BSA and was used as a specific acceptor for alpha 2-->3sialyltransferase. Similar elevation patterns alpha 2-->3sialyltransferase activities and CA 19-9 antigen levels were observed in tumor extracts but no clear correlation was present between the level of alpha 1-->4fucosyltransferase activities and CA 19-9 antigen levels were observed in tumor extracts but no clear correlation was present between the level of alpha 1-->4fucosyltransferase activities and CA 19-9 antigen levels in the same extracts.

CONCLUSIONS

The accumulation of CA 19-9 antigen in colorectal tumors might be caused mainly by the activation of alpha 2-->3sialyltransferase but not by that of alpha 1-->fucosyltransferase.

Role of protein synthesis on ethanol regulation of adenylyl cyclase activity in wild-type S49 murine lymphoma cells

Adenylyl cyclase activity was determined in membranes from wild-type S49 murine lymphoma cells that had been exposed to ethanol for 4 hr. Mn-, NaF-, and forskolin-stimulated adenylyl cyclase activities of cells-pretreated with cycloheximide, puromycin, or serum deprivation-were significantly decreased by treatment with 50 mM of ethanol. As demonstrated for Mn-stimulated activity, the decrease was dose-dependent on ethanol and was temporal; a normal activity recovered after 16-24 hr treatment, even in the presence of cycloheximide and ethanol. Studies with a cell-free membrane system of S49 cells revealed a similar activity decrease after treatment of the membranes with ethanol. In contrast, cells treated with 50 mM of ethanol in a regular culture condition showed no decrease in adenylyl cyclase activity over 24 hr. These results indicate that ethanol regulation of adenylyl cyclase activity in S49 cells depends on reduced or impaired protein synthesis.

Effects of beraprost sodium and insulin on the electroretinogram, nerve conduction, and nerve blood flow in rats with streptozotocin-induced diabetes

The effect of a prostacyclin analog, beraprost sodium, on the electroretinogram, motor nerve conduction velocity, and nerve blood flow was determined in rats with streptozotocin-induced diabetes and was compared with the effect of insulin. Beraprost sodium (0.01 mg x kg-1 x day-1 for 8 weeks) significantly shortened the peak latency of the electroretinogram b-wave, increased tail nerve conduction velocity, and increased sciatic nerve blood flow in diabetic rats (P < 0.0003, 0.0001, and 0.0001 vs. untreated diabetic rats, respectively). This was accompanied by a significant increase in the 6-keto-prostaglandin F1alpha content of the thoracic aorta and a marked increase in the cAMP content of the sciatic nerve. Beraprost sodium had no effect on the sorbitol and fructose contents of the sciatic nerve and retina, but insulin (8-10 U/day) significantly reduced both parameters. These findings suggest that beraprost sodium may be useful for prevention of vascular and neural dysfunction in the retina and peripheral nerve.

Effects of propionyl-L-carnitine and insulin on the electroretinogram, nerve conduction and nerve blood flow in rats with streptozotocin-induced diabetes

The effect of an analogue of L-carnitine, propionyl-L-carnitine, on the electroretinogram, motor nerve conduction velocity and nerve blood flow was determined in rats with streptozotocin-induced diabetes, and was compared with the effects of insulin alone or combined therapy. Oral administration of propionyl-L-carnitine (3 g/kg daily for 4 weeks) significantly increased caudal nerve motor conduction velocity and sciatic nerve blood flow in diabetic rats. There were no differences in the effects of insulin (8-10 U daily for 4 weeks), propionyl-L-carnitine and combined therapy. Although propionyl-L-carnitine significantly shortened the peak latency of the electroretinogram b-wave in diabetic rats, its effect was far weaker than that of insulin or combined therapy, with combined therapy producing the greatest improvement. These effects of propionyl-L-carnitine were accompanied by a decrease of serum lipid levels, an increase of the sciatic nerve carnitine content, and no changes of the tissue (nerve and retinal) sorbitol and myo-inositol concentrations. In contrast, insulin significantly reduced the tissue sorbitol content and markedly increased myo-inositol. These findings suggest that propionyl-L-carnitine may improve diabetic neuropathy and retinopathy without influencing the polyol pathway, and that this beneficial effect may be mediated through the amelioration of microcirculation and tissue carnitine content, thus probably increasing fatty acid oxidation.

Change in the expression of hypopharyngeal-gland proteins of the worker honeybees (Apis mellifera L.) with age and/or role

The roles of adult worker honeybees change with age; young workers nurse brood by secreting bee milk (royal jelly), and older workers forage for nectar and pollen and process nectar into honey. The electrophoretic profile of worker hypopharyngeal-gland proteins changes with age and/or role. Immunoblotting analysis using affinity-purified antibodies against three major proteins (50, 56, and 64 kDa) of the nurse-bee gland showed that they are synthesized selectively and secreted as bee-milk proteins. Immunofluorescence study showed that the proteins condense in the duct after secretion from acini. However, a major 70-kDa protein synthesized specifically in the forager-bee hypopharyngeal gland was identified as an alpha-glucosidase. Therefore, the hypopharyngeal gland seems to have two distinct states differentiated by synthesizing of different major proteins depending on the age-dependent role change.

[Clinical effects of cortisol synthesis inhibition on treatment-resistant depression]

Clinical trial with a steroid suppressive agent, metyrapone, was carried out in 6 patients with treatment-resistant depression (3 patients with major depression and 3 with bipolar disorder). Up to 2,000 mg/day of metyrapone was administered for 4 weeks, and 10 trials of the therapy were done in these patients. Most patients completed the therapy without remarkable side effects. As a result, three patients (6 trials) showed remission within 4 weeks and one patient (one trial) showed a partial response. In the remitted patients, plasma cortisol levels were suppressed below 10 micrograms/dl during the therapy and plasma ACTH levels were elevated. These results indicate that "hypercortisolemia-induced depression" similar to Cushing's disease may be present in patients with treatment-resistant depression.

Absorption characteristics of dextrans with different molecular weights from the liver surface membrane in rats: implications for targeting to the liver

We examined the importance of molecular weight on the absorption from the liver surface in rats using fluorescein isothiocyanate-dextrans (FDs) with molecular weights of 4,400 (FD-4), 9,300 (FD-10), 40,500 (FD-40) or 69,000 (FD-70). After application of FDs (5 mg) to the rat liver surface employing a cylindrical glass cell (i.d. 9 mm), each FD appeared gradually in the plasma, and the in vivo behavior was explained by two-compartment model with first-order absorption. The absorption ratios of FDs from the rat liver surface at 6 h, calculated from the amount recovered from the glass cell, decreased with an increase in the molecular weight (44.5% for FD-4, 29.3% for FD-10, 5.1% for FD-40 and 2.2% for FD-70). A linear relationship was observed between the absorption rate constant and the reciprocal value with square root of molecular weight of the model compounds. The limit of absorption from the rat liver surface was extrapolated to be at a molecular weight of 70,000. Furthermore, absorbed FDs were accumulated in the liver, as high liver/plasma concentration ratio as compared with that of i.v. administration. We clarified the molecular weight dependence of drug absorption from the liver surface in rats. Moreover, the liver surface application appeared to be a promising route with enhancing the efficacy of drug targeting to the liver.