Small-molecule auxin inhibitors that target YUCCA are powerful tools for studying auxin function

Auxin is essential for plant growth and development, this makes it difficult to study the biological function of auxin using auxin-deficient mutants. Chemical genetics have the potential to overcome this difficulty by temporally reducing the auxin function using inhibitors. Recently, the indole-3-pyruvate (IPyA) pathway was suggested to be a major biosynthesis pathway in Arabidopsis thaliana L. for indole-3-acetic acid (IAA), the most common member of the auxin family. In this pathway, YUCCA, a flavin-containing monooxygenase (YUC), catalyzes the last step of conversion from IPyA to IAA. In this study, we screened effective inhibitors, 4-biphenylboronic acid (BBo) and 4-phenoxyphenylboronic acid (PPBo), which target YUC. These compounds inhibited the activity of recombinant YUC in vitro, reduced endogenous IAA content, and inhibited primary root elongation and lateral root formation in wild-type Arabidopsis seedlings. Co-treatment with IAA reduced the inhibitory effects. Kinetic studies of BBo and PPBo showed that they are competitive inhibitors of the substrate IPyA. Inhibition constants (Ki ) of BBo and PPBo were 67 and 56 nm, respectively. In addition, PPBo did not interfere with the auxin response of auxin-marker genes when it was co-treated with IAA, suggesting that PPBo is not an inhibitor of auxin sensing or signaling. We propose that these compounds are a class of auxin biosynthesis inhibitors that target YUC. These small molecules are powerful tools for the chemical genetic analysis of auxin function.

Mucosal damage and recovery of the intestine after prolonged preservation and transplantation in dogs

BACKGROUND

Although much is known about the mucosal damage that occurs after intestinal warm ischemia and reperfusion and its recovery, little is known about the effect of cold preservation and transplantation on the mucosa. We studied the electrophysiological, biochemical, and histological changes of the intestinal mucosa after preservation for 24 hr and subsequent transplantation.

METHODS

The small intestines from adult mongrel dogs were harvested. The intestines were orthotopically autotransplanted immediately (control group) or after preservation for 24 hr (preservation group). Jejunal and ileal tissues were taken before harvesting, at the end of preservation, 1 hr after reperfusion, and on postoperative days 3, 7, 14, and 28. The Ussing chamber method was used to study the electrophysiologic changes. Tissue maltase, diamine oxidase, and ornithine decarboxylase were measured. A histological analysis was also performed.

RESULTS

Control group grafts showed no evident deterioration in electrophysiology, biochemistry, or morphology. In contrast, preservation group grafts exhibited electrophysiological and biochemical degradation, complete denudation of the villi, and crypt injury (especially in the ileum) after reperfusion. Electrophysiologic function and the mucosa biochemical marker recovered within 3 days in the jejunum and within 7-14 days in the ileum; however, histological recovery of mucosal injury required 28 days in the jejunum and more than 28 days in the ileum.

CONCLUSIONS

Our study showed that despite severe destruction of mucosal integrity by prolonged preservation and transplantation, the intestinal mucosa has an enormous regenerative capacity. Our study also showed that regeneration was more pronounced in the jejunum than in the ileum.

Measurement of serum hyaluronate as a predictor of human liver failure after major hepatectomy

Serum hyaluronate can be used as an index of hepatic sinusoidal endothelial cell function. This study was designed to evaluate its application as a predictor of liver failure after major hepatectomy. Thirty-six patients who underwent right liver lobectomy after percutaneous transhepatic right branch portal vein embolization were divided into two groups based on their postoperative clinical course (groups 1 and 2, with and without postoperative liver failure, n = 6 and n = 30, respectively). We serially measured serum hyaluronate levels using a sandwich binding protein assay system before and after hepatectomy and determined relations with progression of the underlying chronic liver disorder, portal venous pressure, and liver growth of the left lobe after portal embolization. Serum hyaluronate levels were significantly elevated, in line with the degree of severity of the underlying chronic liver disorder, and correlated well with the portal venous pressure and the hypertrophic ratio of the left lobe subsequent to portal embolization. Serum hyaluronate levels in group 1 were significantly higher than those in group 2 before surgery and increased steeply during the early period after hepatectomy. These results suggest that the serum hyaluronate reflects the hepatic functional reserve, and serial measurement of this parameter after hepatectomy can serve as a simple indicator for early detection of posthepatectomy liver failure.

Microsomal cytochrome P-450 monooxygenase system and its drug-metabolizing activity after partial portal vein ligation in the Rat

Percutaneous transhepatic portal vein embolization (PTPE) has been used to decrease the risk of hepatic failure after hepatectomy in patients with poor liver function. The effect of PTPE on hepatic drug-metabolizing activities is not clear. Therefore we examined the effect of portal vein branch ligation, a model of PTPE, on hepatic drug-metabolizing activities in Sprague-Dawley rats. Ligated and nonligated lobes were harvested separately. Drug-metabolizing activities and concentrations of components of the microsomal cytochrome P-450 monooxygenase system were examined. In ligated lobes, drug-metabolizing activities (lidocaine and aminopyrine) and enzymatic concentrations of the microsomal cytochrome P-450 monooxygenase system gradually decreased over 10 days. In nonligated lobes these functions were depressed rapidly to 60% of those before PBL but then recovered 10 days after PBL. From the viewpoint of drug metabolism, hepatic dysfunction occurred in both ligated and nonligated lobes.

Morphological and functional alterations to sinusoidal endothelial cells in the early phase of endotoxin-induced liver failure after partial hepatectomy in rats

Liver failure following major hepatectomy is characterized pathologically by massive hepatic necrosis, which is thought to begin with injury of sinusoidal endothelial cells (SECs). To examine the early events of SECs leading to hepatic damage, we performed time-course analyses of the morphological and functional perturbation of SECs after endotoxin administration to hepatectomized rats. At 1.5 h after endotoxin injection, when hepatocellular damage was not yet evident, SECs showed augmented expression of intercellular adhesion molecule-1, with frequent adherence of infiltrating leucocytes and ultrastructural features of defenestration and hypertrophied cytoplasm enriched with cell organelles. The serum level of hyaluronate, as an indicator of the functional state of SECs, was significantly elevated. At 3 h, SECs underwent necrosis and disruption, accompanied by fibrin deposits with concomitant hepatocellular necrosis. The morphological and functional alterations of SECs precede necrotic changes in hepatocytes and SECs in endotoxin-induced liver failure after partial hepatectomy.

Spontaneous degeneration of testicular germ cells in congenitally athymic nude mice of four strains: a light microscopical observation

Many hormonal studies have demonstrated that the presence of thymic factors affects testicular function. However, morphological studies on the testis in the absence of thymic factors are very limited. In the present study, seminiferous tubules of nude mice of four strains were light microscopically observed in order to investigate the effect of congenital athymia on germinal cell components. Testes obtained from congenitally athymic nude mice of CD1, BALB/c-nu/nu, LASAT, and KSN strains were fixed in Bouin's solution, dehydrated, and embedded in plastic. The samples were cut and their sections were stained with hematoxylin and eosin. The results showed that degeneration of testicular germ cells was focally observed in all four strains of athymic mice. The degenerating morphology was characterized by karyopyknosis and karyolysis of immature germ cells, multinuclear giant cell formation, and severe depletion of epithelial components with remaining Sertoli cells and/or some spermatogonia. KSN nude mice showed the most severe degenerative changes among the four strains of nude mice examined. Their significant degenerative changes first appeared at 2 weeks of age. In contrast, CD1 nude mice showed very slight degenerative features even at 20 weeks of age. BALB/c-nu/nu and LASAT nude mice had more degenerated epithelia than did CD1 nude mice; however, their significant degenerative changes were apparent at 20 but not at 10 weeks of age. Therefore, the severity and the onset of spontaneous degeneration and depletion of testicular germ cells in congenitally athymic mice were different among the four strains examined.

Protective effects of antithrombin III supplementation on warm ischemia and reperfusion injury in rat liver

The effect of antithrombin III (AT III) supplementation on energy status, microcirculation, cytoprotection, and prostacyclin (PGI2) production during and after a period of warm ischemia of the rat liver was investigated. AT III supplementation (250 units/kg) stimulate prostaglandin I2 (PGI2) production from 1 hour after administration, with maximal production observed at 3 hours. Ischemia was induced by occluding the hepatoduodenal ligament for 30 minutes, and experiments were continued for 60 minutes after reperfusion. The rats received AT III (250 units/kg IC) 30 minutes before induction of liver ischemia (AT III group). In the AT III group, recovery of the beta-ATP/inorganic phosphate ratio measured by 31P nuclear magnetic resonance showed significant improvement (p < 0.01), and the recovery of tissue blood flow markedly improved (p < 0.01) compared to the saline-treated group (control group). Leakages of aspartame aminotransferase, alanine aminotransferase, and lactate dehydrogenase were mitigated in the AT III group (p < 0. 05). Ultrastructural alterations of sinusoidal endothelial cells were markedly reduced in the AT III group. The PGI2 level at the end of reperfusion was significantly elevated (p < 0.01) in the AT III group compared to the control group. The results of this study indicated that pretreatment with AT III significantly improved the energy status and microcirculation, as well as histologic damage, after liver ischemia and reperfusion. One of the fundamental effects of AT III might be mediated through the production of prostacyclin.

Effect of rejection on electrophysiologic function of canine intestinal grafts: correlation with histopathology and Na-K-ATPase activity

To investigate whether electrophysiologic changes can detect the early onset and progress of intestinal rejection, changes in in vitro electrophysiologic function, intestinal histopathology, and Na-K-ATPase activity were studied in dogs. Adult mongrel dogs of both sexes, weighing 18-24 kg, were used for auto and allo small bowel transplantation. The entire small bowels, except for short segments at the proximal and distal ends, were switched between a pair of dogs (allograft). Animals receiving intestinal autotransplantation were used as controls. Allograft recipients were sacrificed 3, 4, 5, 7, or 9 days after transplantation, and autograft recipients were sacrificed 3, 7, or 14 days after transplantation. Immunosuppression was not used. Electrophysiologic measurements were done with an Ussing chamber. Histological analysis was performed blindly using whole thickness sections. Na-K-ATPase activity in the mucosal tissue, which is said to regulate the potential difference, was also measured. Potential difference, resistance, and Na-K-ATPase activity of the allograft intestine decreased with time and were significantly lower 7 and 9 days after transplantation compared to host intestine, normal intestine, and graft intestine of controls (autograft). Potential difference, resistance, and Na-K-ATPase activity of the native intestinal tissue and the autografts did not decrease with time. Detection of histologically mild rejection of the intestine, which is important for appropriate immunosuppressive treatment in clinical cases, could not be achieved based on electrophysiology or Na-K-ATPase activity. Deterioration of electrophysiologic function during rejection correlated with the histological rejection process and Na-K-ATPase activity; however, electrophysiology may not be a reliable tool for monitoring grafts, since it cannot detect early intestinal rejection.

The effect of FK506 on warm ischemia and reperfusion injury in the rat liver

The protective effect of FK506 on hepatocytes against ischemia and reperfusion injury was examined by evaluating the following: the high energy phosphorus metabolism obtained using 31P magnetic resonance spectroscopy (31P-MRS) and the tissue blood flow of the liver in ischemia and the reperfusion process, mitochondrial glutamic oxaloacetic transaminase (m-GOT) and glutamic pyruvic transaminase (GPT), the survival rates of the animals, a histological study and immunohistological staining for intercellular adhesion molecule-1 (ICAM-1) in the liver after ischemia. The rats were treated with FK506 1 mg/kg/day i.m. for 4 days before testing. Ischemia was induced by clamping the hepatoduodenal ligament for 30 min. In 31P-MRS, the recovery of the hepatic energy status after ischemia, evaluated by beta-ATP/inorganic phosphate (Pi), was significantly better in the FK506 group. It also coincided with the recovery of tissue blood flow monitored with a laser Doppler flowmeter. In the histological examination, the congestion observed in the periportal region of the control group was mild, while there was less induction of ICAM-1 in the endothelial cells of the portal veins and hepatic veins in the FK506 group. From these findings, we concluded that FK506 had a protective effect on hepatocytes against warm ischemia and reperfusion injury, and the mechanism for this could partially be attributed to improved tissue blood flow after ischemia by the modulation of immunological events.

[Warm ischemia and reperfusion injury in the regenerating rat liver]

The effect of warm ischemia and reperfusion injury in the regenerating rat liver after portal vein branch ligation (PBL) was examined by monitoring hepatic high energy phosphorous metabolism using in vivo Phosphorus-31 Magnetic Resonance Spectroscopy (31P-MRS). On 14 days after 70% occlusion of the portal vein, energy metabolism of non-occluded lobe of the liver was evaluated by measuring the ratio of beta-ATP to Pi obtained using 31P-MRS. During 30min-ischemia, beta-ATP/Pi dropped down similarly below the limit of observation in both of control and regenerating liver. However, after reperfusion, in the regenerating liver, the earlier and better recovery of beta-ATP/Pi was observed compared with the control. In the any examination of m-GOT, GPT, increase in enzyme level was apparently restrained in the PBL group. On the pathological examination, centrilobular necrosis and hepatocyte degeneration were remarkable in the normal liver, while in the regenerating liver, these changes were slight. In conclusion, these results suggest that reperfusion injury observed in the regenerating liver seems to be reduced compared with that in the normal liver. Functional and structural changes in the regenerating liver could be claimed as a course of this observation. However, to understand the mechanism, further study will be needed both in morphological and biochemical aspect.

[31P-NMR study on the high energy phosphate metabolism in warm ischemic rat liver caused by hepatic artery and portal vein occlusion]

An effect on normothermic ischemia on the rat liver metabolism was examined using in vivo 31P-NMR spectroscopy. Energy metabolism was monitored by measuring the ratio of beta-ATP/Pi and changes were compared between two groups, untreated rats (Group A) and rats of which spleens were subcutaneously transposed to perform portosystemic collaterals (Group B). In group A, beta-ATP/Pi reduced to 0.18 after occlusion of both portal vein and hepatic artery for 10 min, and recovered to 0.97 at 120 min after reperfusion was initiated. In the case of 30 minischemia, however, it recovered only to 0.53 even at 120 min after reperfusion. In contrast to group A, it recovered to 0.81 at 120 min after reperfusion following 30 min-ischemia in group B. Furthermore, when 10 min-ischemia was repeated 3 times with intervals of 10 min-perfusion in group B, it recovered to 0.87 as early as 20 min after initiation of reperfusion. These results clearly indicate that the prevention of the portal congestion improves recovery from energy metabolic disorder and, in addition, division of total ischemic time with moderate intermission is effective to diminish the metabolic disorder due to occlusion of both hepatic artery and portal vein. However without the prevention of the portal congestion the effect of division of total ischemic time was significantly reduced.

[A case of cardiac myxoma associated with long-term lasting symptoms of mitral stenosis]

We reported a case of 70-year-old woman whose left atrial myxoma was resected. She had been suffered from low cardiac output due to mitral stenosis for 15 years or more. Resection of the myxoma corrected mitral stenosis completely. Cardiac output and pulmonary wedge pressure, however, were not improved following the operation. Postoperative echo- and angiocardiography revealed marked early closure of the mitral valve. These findings indicate that left ventricular compliance should be reduced if inflow stenosis continued for a long period and it is difficult to improve depressed ventricular function even if mitral stenosis is completely removed.