DPP and DSP are Necessary for Maintaining TGF-ß1 Activity in Dentin.

Porcine dentin sialophosphoprotein (DSPP) is the most abundant non-collagenous protein in dentin. It is processed by proteases into 3 independent proteins: dentin sialoprotein (DSP), dentin glycoprotein (DGP), and dentin phosphoprotein (DPP). We fractionated DPP and DSP along with TGF-ß activity by ion exchange (IE) chromatography from developing pig molars and measured their alkaline phosphatase (ALP)-stimulating activity in human periodontal (HPDL) cells with or without TGF-ß receptor inhibitor. We then purified TGF-ß-unbound or -bound DPP and DSP by reverse-phase high-performance liquid chromatography (RP-HPLC) using the ALP-HPDL system. The TGF-ß isoform bound to DPP and DSP was identified as being TGF-ß1 by both ELISA and LC-MS/MS analysis. We incubated carrier-free human recombinant TGF-ß1 (CF-hTGF-ß1) with TGF-ß-unbound DPP or DSP and characterized the binding on IE-HPLC using the ALP-HPDL system. When only CF-hTGF-ß1 was incubated, approximately 3.6% of the ALP-stimulating activity remained. DPP and DSP rescued the loss of TGF-ß1 activity. Approximately 19% and 10% of the ALP stimulating activities were retained by the binding of TGF-ß to DPP and DSP, respectively. The type I collagen infrequently bound to CF-hTGF-ß1. We conclude that both DPP and DSP help retain TGF-ß1 activity in porcine dentin.

Micelle structure of amelogenin in porcine secretory enamel.

Even during the secretory stage of amelogenesis, enamel crystals thicken as amelogenins (the major protein component) decrease. To explain this phenomenon, we propose a model for amelogenin structure and function based upon the hypothesis that amelogenin forms micelles. Solubility and hydrophobicity analyses suggest that all but the hydrophilic amelogenin C-terminal regions aggregate via hydrophobic bonds to form a micelle core. Amelogenin micelles may form super-assemblies via their C-termini (KTKREEVD), which contain complementary positive (KTKR) and negative (EEVD) elements. Disassembly of the micelles through controlled proteolysis provides space for crystal growth. Initial cleavage (by enamelysin) removes the surface-accessible amelogenin C-terminus, exposing the middle portion to cleavage (by EMSP1). As a result, the 13-kDa amelogenin, a rod-shaped domain based upon ultrafiltration and transmission electron microscopy studies, is released. This model explains how amelogenin is able to 'space' and support the ribbon-like crystals and continuously yield space as the crystals thicken, until they are sufficiently mature to support themselves.

Antitumor effects of SEF19, a new nonsteroidal aromatase inhibitor, on 7,12-dimethylbenz[a]anthracene-induced mammary tumors in rats.

The antitumor and endocrine effects of a new nonsteroidal aromatase inhibitor, 2-(imidazol-1-yl)-4,6-dimorphorino-l, 3, 5-triazine (SEF19) were examined in female Sprague-Dawley rats bearing estrogen dependent 7,12-dimethylbenz[a]anthracene(DMBA)-induced mammary tumors, and the effects were compared with those of CGS20267. The rats bearing DMBA-induced mammary tumors within 6-15 weeks after the DMBA administration were divided into the treatment groups once a week every week, and they were treated with SEF19, CGS20267 and vehicle for 4 weeks. One hundred rats were sacrificed 4 hours after the last administration, and the remaining 60 rats were sacrificed after a 4-week recovery period. During the treatment and recovery period, the tumor size was generally smaller in the SEF19 and CGS20267-treated subgroups than in the control subgroup. Tumor sizes in the subgroups treated with high doses of SEF19 (25 mg/kg/day and 50 mg/kg/2 days) were reduced to the size of the CGS20267-treated subgroup. The CGS20267-treated rats showed decrease in the serum estradiol level and an increase in the serum testosterone level. Their uterine weights were reduced. SEF19 treatment failed to show any effect on the serum levels of estrone, estradiol, testosterone and androstenedione, but it suppressed uterine weight in a dose-dependent manner. After the recovery period, no effect was detected in the serum concentrations of steroid hormones and the weight of the organs. At every dose used in the present study the aromatase inhibitory activity of SEF19 was weaker than that of CGS20267, but the inhibitory effect on mammary tumor growth of SEF19 at high doses was comparable to that of CGS20267. We conclude that the antitumor effect of SEF19 is not due to aromatase inhibition but mainly to its direct cytotoxicity.

Potent and selective aromatase inhibitor: in vitro and in vivo studies with s-triazine derivative SEF19.

We found a potent aromatase inhibitor through the screening of agents for estrogen-dependent breast cancer. SEF19 (2-(imidazol-1-yl)-4,6-dimorphorino-1,3,5-triazine) decreased 50% of human placental aromatase activity in vitro at the concentration of 5.3 nM. In order to clarify the selectivity of SEF19 for enzyme inhibition, we determined the effect of SEF19 on the activities of four steroidogenic cytochrome P450 enzymes in porcine adrenal gland, P450SCC(side-chain cleavage of cholesterol), P450(11 beta) (11 beta-hydroxylase), P450(17 alpha)(17 alpha-hydroxylase/C17,20 lyase) and P450C21 (21-hydroxylase). SEF19 failed to inhibit the activities of porcine adrenal P450SCC, P450(17 alpha) and P450C21 up to the concentration of 100 microM and showed some inhibition on P450(11 beta) activity at 100 microM, while SEF19 completely nullified the aromatase activity at 1 microM. We also determined the potency of SEF19 for the suppression of aromatase activity in vivo. SEF19 suppressed dose-dependently the uterine hypertrophy of immature rats caused by administration of androstenedione (30 mg/kg, s.c.). The ED50 of SEF19 for the suppression of uterine hypertrophy was 0.8 mumol/kg. These results suggest that SEF19 may serve as a potent and selective agent for the treatment of estrogen-dependent breast cancer.

Blood pressure and heart rate relationships during cervical sympathetic and vagus nerve stimulation in streptozotocin diabetic rats.

Linear regressions were calculated between blood pressure and heart rate changes during the stimulation of peripheral cut end of cervical sympathetic and vagus nerve in the streptozotocin diabetic rats (65 mg/kg) and age-matched controls. Slopes of blood pressure (mmHg, abscissa)-heart rate (beat/minute, ordinate) relationships of diabetic rats (9.87 +/- 1.46, mean +/- S.E.M., n = 8) were significantly steeper (P < 0.05) than those of age-matched controls (5.12 +/- 0.63, n = 7). In the control rats, blood pressure and heart rate were rather equally changed during autonomic nerve stimulation. In contrast, in the diabetic rats, heart rate was markedly changed but blood pressure was little changed during the electrical stimulation of the cervical autonomic nerves. Chronotropic effect was exaggerated but inotropic one was disturbed in the heart of streptozotocin diabetic rat when cervical sympathetic nerve was stimulated.

Changes of substance P and somatostatin contents in the gastrointestinal tract of streptozotocin diabetic rats.

Substance P and somatostatin contents were measured in the gastrointestinal tract of streptozotocin diabetic rats, 1 month after streptozotocin administration (60 mg/kg), and of age-matched controls with radioimmunoassay. Substance P and somatostatin contents were statistically increased in the extrafundus of the diabetic stomach, but not in the diabetic fundus. Substance P was significantly decreased in the diabetic ileum and caecum. Similarly, somatostatin was decreased in the diabetic caecum. Contrarily, slight increase of somatostatin contents in the diabetic duodenum, jejunum and proximal colon was not statistically significant.

Blood pressure and heart rate changes in streptozotocin diabetic rats, with special reference to postural hypotension.

Blood pressure and heart rate changes were recorded on supine or prone head-up tilt and on carotid artery occlusion in normal and streptozotocin diabetic rats (65 mg/kg). In general supine tilt induced a larger blood pressure fall, slower blood pressure recovery from the fall and larger heart rate fall than prone tilt, both in normal and diabetic rats. Heart rate recovery from the fall was slightly larger in prone than in supine tilt in normal rats. The blood pressure fall and heart rate fall accompanying the tilt were statistically larger in diabetic than in normal rats. Furthermore, blood pressure recovery from the fall was statistically more rapid and larger in normal than in diabetic rats. The exaggerated blood pressure fall with the tilt of diabetic rats might correspond to postural hypotension. Blood pressure rise and heart rate rise with carotid artery occlusion were smaller in diabetic than in normal rats. Blood pressure changes with cervical sympathetic or vagus stimulation were almost the same in normal and diabetic rats. However, in diabetic rats such cervical autonomic nerve stimulation produced larger heart rate changes than in normal rats.

Conduction velocity of motor nerve and cervical sympathetic and vagus nerve in streptozotocin diabetic rats.

We investigated the conduction velocity of motor and autonomic nerves, motor nerve to foot interosseous muscle and cervical vagus and sympathetic nerve, in streptozotocin diabetic rats (1-3 months duration of diabetes) and compared it with that of age-matched controls. In diabetic rats, the motor nerve conduction velocity was significantly reduced but the conduction velocity of cervical vagus and sympathetic nerves was not reduced.

In vitro motor activity and compliance of the caecum in streptozotocin diabetic rats.

In order to characterize the diabetic gastrointestinal disorders such as constipation, the motor activity and the compliance of the caecum of streptozotocin diabetic rats were studied in vitro. The time course of enlargement of the caecum was also examined. Significant enlargement of the caecum was noticed in diabetic rats, 10 days after streptozotocin injection (65 mg/kg). It reached two times heavier in 30 days and three times in 90 days when compared with age-matched controls. The motor activity as studied by in vitro recording of the intraluminal pressure changes associated with spontaneous activity revealed the depression both in amplitude and frequency. The compliance was noticed to be significantly increased in the diabetic caecum as compared to age-matched controls when studied by passive Krebs solution injection. Threshold intraluminal pressure for inducing the reflex motor activity of the diabetic caecum was larger than that of the normal. These factors may contribute to the retention of content inside of the diabetic caecum.

In vitro motor activity of intestinal segments of streptozotocin diabetic rats.

The spontaneous motor activity of the isolated segments of the gut of streptozotocin-diabetic rats was studied in vitro. In normal preparations, the frequency of intraluminal pressure changes was little influenced by raising the intraluminal pressure. In contrast, in diabetic preparations, the frequency tended to increase with a rise of the intraluminal pressure, and the pressure waves were more irregular than in controls. The motor frequency with a pressure load of 3 cm H2O in the duodenum was 33/min in control rats and 21/min in diabetic rats. The motor frequencies in the other intestinal segments were also higher in normal preparations than in diabetic ones, although these differences were statistically not significant. The amplitude of intraluminal pressure changes increased according to the increase of pressure load, both in normal and diabetic preparations. These amplitudes were higher in normal than in diabetic preparations; however, the differences were statistically significant only in the jejunum. Insulin treatment (5 U/day) for one month, one to two months after streptozotocin injection, lowered the plasma glucose level to nearly normal and increased the body weight up to 80% of the normal but did not re-establish the normal motor frequency in the duodenum. Moreover, treatment of diabetic rats with aldose reductase inhibitor, ONO-2235 (per os, 50 mg/kg b.w./day for one month, one to two months after streptozotocin injection) did not re-establish the normal rhythms in duodenum. The pacemaker activity as well as mechanical properties in the intestinal tract may be disturbed in diabetic preparations.

Compliance changes of the gastrointestinal tract in streptozotocin-induced diabetic rats.

In order to elucidate diabetic gastrointestinal disorders, we measured the length, diameter, volume, and intraluminal pressure of the isolated segments of the duodenum, jejunum, ileum, and proximal colon during injection of Tyrode's solution into them, as well as wet weight. Wet weight of the stomach and of each intestinal segment of 3 cm length were similar between normal and diabetic preparations, except the duodenum. Wet weight of the diabetic duodenum was significantly heavier than that of normal. However, capacity of all diabetic gastrointestinal segments was significantly larger than that of normal ones, even after corrected for wet weight (ml/g wet weight). During saline injection, normal intestinal segments were more easily distended longitudinally than circumferentially. Contrarily, diabetic ones were distended more circumferentially than normal, as well as longitudinally. Pressure-volume relationships showed that pressure inside of the diabetic gastrointestinal tract increased much more moderately than that of normal one according to volume increase during saline injection. Similarly, tension inside of diabetic intestinal segments increased much more moderately than that of normal ones. Chord and slope compliance of diabetic gastrointestinal tract was generally larger than those of normal one. Histologically, there are no remarkable differences in cross-sectional area between normal and diabetic intestinal segments after usual fixation without intraluminal fixative injection. However, diabetic segments were much more remarkably dilated than normals were, when fixed after fixative injection. Greater compliance or distensibility of the diabetic gastrointestinal tract seemed to be one basic ground for dilatation, atony, larger appearance, transit delay, and motile disorders of the diabetic gastrointestinal tract.

Central effects of catecholamine antagonists on angiotensin-induced vasopressin secretion in conscious rats.

To evaluate the roles for catecholamines in angiotensin II (ANG II)-induced vasopressin (AVP) release, we examined in conscious rats the effects of intraventricular (ivt) administrations of catecholamine antagonists on plasma AVP responses to ivt applications of its agonists and ANG II. Plasma AVP was determined by RIA using trunk blood collected after decapitation. Dopamine (0.15 mumol), phenylephrine (an alpha-adrenergic agonist, 0.15 mumol) or ANG II (48.2 pmol) augmented plasma AVP 90 sec after the injection, whereas after isoproterenol (a beta-adrenergic agonist, 0.15 mumol) plasma AVP was unaffected. The plasma AVP responses to both dopamine and ANG II were significantly (P less than 0.01) inhibited by haloperidol (a dopamine blocker, 0.15 mumol) given 10 min before administration of these agents. Pre-administration of phenoxybenzamine (an alpha antagonist, 0.15 mumol) which was confirmed to abolish the effect of phenylephrine, or propranolol (a beta antagonist, 0.15 mumol) did not block the effect of ANG II. Administration of haloperidol, phenoxybenzamine or propranolol alone was without effect on plasma AVP level. On the basis of these results, we concluded that ANG II-induced AVP secretion may be mediated and/or modulated by dopamine.

Acetylcholine and substance P responsiveness of intestinal smooth muscles in streptozotocin diabetic rats.

We found previously that in in vitro tube form preparations of isolated intestine of streptozotocin (STZ) diabetic rats, frequency of spontaneous intraluminal pressure waves was significantly reduced in duodenum when compared with normal controls. In order to elucidate further the diabetic intestinal disorders, we examined the frequency and amplitude of spontaneous length changes and contractile responses to acetylcholine (ACh) and substance P (sP) in isolated intestinal segments of normal and experimental diabetic rats. In comparison with normal controls, we could confirm the significantly decreased frequency of spontaneous length changes in isolated longitudinal and circular muscle preparations of diabetic duodenum (1 month after STZ injection). Furthermore, amplitude of spontaneous length changes was significantly decreased in circular muscle preparations of duodenum, jejunum, and ileum but not in colon nor in longitudinal muscle preparations. Dose-response curves revealed that both ACh and sP responses were significantly decreased in longitudinal and circular muscle preparations of diabetic duodenum, jejunum, and ileum but not in colon. Mechanisms of reduced contractility of diabetic intestinal smooth muscle in response to ACh and sP were discussed.

Diurnal rhythm of water intake and plasma angiotensin II in the Japanese quail (Coturnix coturnix japonica).

A diurnal rhythm was noted in the hourly water intake of the Japanese quail exposed to a 12L:12D photoperiod. Two peaks for the water intake were observed: from 07:00 to 08:00, 1 hr after turning on the light source, and from 18:00 to 19:00, 1 hr before termination of the light source. The plasma angiotensin II (AII) concentration also showed two peaks: one at 06:00, 1 hr before the light source was turned on, and another at 18:00, 1 hr before the light was turned off. The two plasma AII peaks each occurred 1 hr before those for the water intake, respectively. The drinking rate was reduced by Captopril (SQ14225) administered at 07:05 and 18:14, when the plasma AII concentration and drinking rate were highest. The hematocrit was significantly higher during the dark period than the light period.