Existence of capsaicin-sensitive glutamatergic terminals in rat hypothalamus.

Capsaicin has been suggested to act not only on thin primary afferents but also on the hypothalamus, but the neurotransmitter(s) of central capsaicin-sensitive neurons are unknown. The present study was conducted to determine whether any central, especially hypothalamic, glutamatergic terminals were sensitive to capsaicin. Capsaicin evoked glutamate release from slices of hypothalamus and lumbar dorsal horn, but not cerebellum. Such capsaicin action was Ca2+ dependent and inhibited by the capsaicin antagonist capsazepine. Vanilloid receptor subtype 1 mRNA was widely distributed in the brain, with a marked level in the hypothalamus and cerebellum, but not in the spinal cord. The results suggest that there are glutamatergic terminals sensitive to capsaicin in the hypothalamus.

Tumor growth inhibition and nutritional effect of D-amino acid solution in AH109A hepatoma-bearing rats.

We examined the inhibitional and nutritional effects of total parenteral nutrition (TPN) containing D-amino acids (D-phenylalanine, D-Phe; D-valine, D-Val; D-leucine, D-Leu; D-methionine, D-Met) on tumor growth in AH109A hepatoma-bearing rats. Five experimental groups were examined: a control amino acid solution group (control group), D-Phe group, D-Val group, D-Leu group and D-Met group. The analysis of tumor volume and weight revealed significant tumor growth inhibition in the D-Val group as compared with the control group. In the D-Val group, decreases of DNA and protein contents in the tumor tissues were also observed. The D-Leu and D-Met groups showed a tendency toward tumor growth inhibition. The protein content in the liver tissues of these two groups was significantly higher as compared with the control group. The DNA content in the liver tissue was also significantly higher in the D-Met group. The body weight including the tumor (on the final day of TPN) was significantly lower in the D-Val group as compared with the control group, but there was no significant difference in the groups for body weights not including tumors (carcass body weight). The hematocrit and hemoglobin values, indicators of anemia, were significantly higher in the D-Val group as compared with the control group. From these results, regarding tumor growth inhibition, the D-Val solution had the strongest inhibitory effect with no negative influence on the host, and improvement of nutritional status was also suggested in the rats that received the D-Leu or D-Met solutions.

Degeneration and regeneration of Ruffini corpuscles in the joint capsule.

The Ruffini corpuscle is a highly-differentiated sensory corpuscles which consists of complexly-arborized axon terminals surrounded by Schwann cells. The present study examined by electron microscopy the morphological changes of Ruffini corpuscles in rat joint capsule during their degeneration and regeneration, following nerve crush. Initial sign of axonal degeneration was seen as early as one day after nerve crush, and by day 3, axon terminals disappeared from Ruffini corpuscles, Schwann cells became shrunken and atrophic by day 5. Regenerating small-diameter axons first appeared about 10 days later in the denervated corpuscles, and they gradually thickened, developing into matured terminals. At the same time, atrophic Schwann cells recovered their original vigorous state about 30 days after nerve crush. No findings were obtained that suggested the neogenesis of the corpuscle by regenerating nerves. These findings show that regenerating axons enter the original denervated corpuscle and, by associating with remaining atrophic Schwann cells, develop into axon terminals as in the normal corpuscle.

Peripheral and central actions of capsaicin and VR1 receptor.

Vanilloid receptor subtype 1 (VR1), a capsaicin receptor, is expressed in primary sensory neurons and vagal nerves. Heat and protons as well as capsaicin activate VR1 to induce the influx of cations, particularly Ca2+ and Na+ ions. Characteristic effects of capsaicin are the induction of a burning sensation after acute administration and the desensitization of sensory neurons after large doses and prolonged administration. The latter feature made capsaicin cream applicable for the treatment of chronic pain and pruritus. Capsaicin alters several visceral functions, which may be mediated by action on vagal nerves and central neurons. Capsaicin affects thermoregulation after intra-hypothalamic injection and releases glutamate from the hypothalamus and cerebral cortex slices, while VR1-like immunoreactivity is not apparent in these regions. These findings taken together suggest the existence of other subtypes of vanilloid receptors in the brain.

Nutritional effects of a D-methionine-containing solution on AH109A hepatoma-bearing rats.

The effects of a D-methionine-containing solution (DMCS) on the nutritional status of AH109A hepatomabearing rats receiving total parenteral nutrition were studied. The DMCS solution inhibited the decrease of transferrin in the plasma of tumor-bearing rats when compared with the effect of an L-methionine-containing solution. The survival time was also significantly prolonged in the DMCS-treated rats. These results indicate that DMCS had a beneficial effect on the malnutrition induced in tumor-bearing rats and would be a useful amino acid solution for the nutritional support of cancer patients.

Effects of D-methionine-containing solution on tumor cell growth in vitro.

The effects of a nutrition therapy with D-methionine (Met)-containing solution were investigated in cell cultures of the AH109A cell line. The growth of AH109A hepatoma cells in culture media with D-Met-supplemented medium, L-Met-supplemented medium (control) and Met-free medium was compared. The D-Met-supplemented medium inhibited the cell growth to an extent similar to that manifested in the Met-free medium. The total free amino acid concentrations in the control medium decreased by approximately 40% on day 6 post-culture. However, the free amino acid concentrations in D-Met-supplemented and Met-free media did not change. Furthermore, alanine, which was not added to RPMI-1640, was detected in the control medium on day 6 post-culture. These results suggest the possibility of application of D-Met-containing solution to cancer patients receiving total parenteral nutrition.

Molecular cloning and characterization of Drosophila genes encoding small GTPases of the rab and rho families.

We have isolated eight genes from Drosophila, small GTPases. They can be classified into three rab family genes (Drab2, Drab5, Drab11) and five rho family genes (Drac1a, Drac1b, Drac3, Dcdc42, DrhoA). While Drac3 is a novel type of rac gene, others are homologues of known mammalian genes for small GTPases. Northern blot analyses showed that all the genes are expressed throughout all developmental stages from embryo to adult. In situ hybridization to embryos revealed that Drab2, Drac1b, and Drac3 are highly expressed in the nervous system, in the trunk mesoderm, and in the cephalic mesoderm, respectively. Since hemocytes are derived from the cephalic mesoderm, we carried out double stainings using a hemocyte marker anti-peroxidasin antibody and Drac3 in situ hybridization. We found that Drac3 is expressed in hemocyte precursor cells. In the Drac3 deficiency embryos, the hemocyte precursor cells start to differentiate normally, but never develop into mature hemocytes, indicating that Drac3 is essential for their maturation. The DrhoA and Dcdc42 genes complemented S. cerevisiae rho1 and cdc42 mutations in the same manner as human rhoA and CDC42, respectively. These results suggest functional similarity between Drosophila and mammalian small GTPase genes.

Immunocytochemical localization of salivary peptide P-C in human submandibular gland.

Human saliva contains a proline-rich polypeptide, salivary peptide P-C, which potentiates insulin release and reduces glucagon release from perfused rat pancreas to decrease blood glucose level. To elucidate the process of secretion into humoral fluid of this peptide morphologically, we investigated ultrastructural localization of P-C in human submandibular gland by immunogold technique with anti-peptide P-C whose specificity to P-C was confirmed by immunoblotting. The labeling with gold particles which represents the distribution of P-C-like-immunoreactivity (P-C-LI) was detected in the secretory granules and rough endoplasmic reticula of the acinar serous cells and in few mucosa cells. P-C-LI was also observed in the lumen of striated duct but not intracellularly in the ductal cells themselves, indicating that P-C is not probably reabsorbed there. These results suggest that salivary peptide P-C is present in acinar serous cells, is secreted into the oral cavity, and may be reabsorbed through the digestive tract to modulate the blood glucose level after feeding.

Axonal transport of VR1 capsaicin receptor mRNA in primary afferents and its participation in inflammation-induced increase in capsaicin sensitivity.

Capsaicin receptors are expressed in primary sensory neurons and excited by heat and protons. We examined the inflammation-induced changes of the level of VR1 capsaicin receptor mRNA in sensory neurons and the sensitivity of primary afferents to capsaicin. Carrageenan treatment induced axonal transport of VR1 mRNA, but not that of preprotachykinin mRNA, from the dorsal root ganglia to central and peripheral axon terminals. The sensitivity of central terminals to capsaicin, which was estimated by measuring the capsaicin-evoked release of glutamate from the dorsal horn, was increased by peripheral inflammation, and such an increase was suppressed by inhibiting the RNA translation in the dorsal horn with cycloheximide and an intrathecal injection of VR1 antisense oligonucleotides. Thus, peripheral inflammation induces the axonal transport of VR1 mRNA, which may be involved in the hypersensitivity of primary afferents to capsaicin and the production of inflammatory hyperalgesia.

Reduction of incretin-like salivatin in saliva from patients with type 2 diabetes and in parotid glands of streptozotocin-diabetic BALB/c mice.

AIM: Diabetic xerostomia is a typical syndrome in diabetic complication. We have reported that salivatin (salivary peptide P-C) derived from human saliva potentiates glucose-stimulated insulin release and inhibits arginine-stimulated glucagon release. The present study is aimed to gain further evidence on the physiological role by investigating the diabetic state-induced change in the amount of salivatin. METHODS: The amount of salivatin was measured in saliva taken from patients with type 2 diabetes with ELISA and with rabbit antiserum against human salivatin immunocytochemically in sections of parotid glands from streptozotocin-diabetic BALB/c mice. RESULTS: The amount of salivatin after a meal was reduced by diabetes in both human saliva and in the serous secretory granule of mouse parotid gland acinar cells. CONCLUSIONS: The above results suggest that salivatin lowers hyperglycaemia after meal and sustains the normal blood glucose levels by incretin-like mechanisms. The function may be damaged by diabetes, and this in turn might make the diabetes worse.