Rheology of Naturally Deformed Antigorite Serpentinite: Strain and Strain-Rate Dependence at Mantle-Wedge Conditions.

Antigorite serpentinite is expected to occur in parts of subduction plate boundaries, and may suppress earthquake slip, but the dominant deformation mechanisms and resultant rheology of antigorite are unclear. An exhumed plate boundary shear zone exposed near Nagasaki, Japan, contains antigorite deformed at 474°C ± 30°C. Observations indicate that a foliation defined by (001) crystal facets developed during plate-boundary shear. Microstructures indicating grain-scale dissolution at high-stress interfaces and precipitation in low-stress regions suggest that dissolution-precipitation creep contributed to foliation development. Analysis of crystal orientations indicate a small contribution from dislocation activity. We suggest a frictional-viscous rheology for antigorite, where dissolution-precipitation produces a foliation defined by (001) crystal facets and acts to resolve strain incompatibilities, allowing for efficient face-to-face sliding between facets. This rheology can not only explain aseismic behavior at ambient plate boundary conditions, but also some of the contrasting behaviors shown by previous field and laboratory studies.

Messenger RNA expression and synthesis of endothelin-1 along rat nephron segments.

The kidney both produces and responds to endothelin. We examined the production and the expression of mRNA of endothelin-1 (ET-1) in tubule suspensions and microdissected nephron segments. ET-1 production was measured by RIA using an ET-1-specific antibody. We applied the reverse transcription and polymerase chain reaction (PCR) technique to detect ET-1 mRNA along the nephron segments. Stimulation of ET-1 production was observed in the presence of FCS and transforming growth factor-beta (TGF-beta) in inner medullary tubules but not in cortical or outer medullary tubule suspensions. Among dissected nephron segments, ET-1 production was observed in glomeruli and inner medullary collecting ducts (IMCD), whereas it was negligible in proximal convoluted tubules (PCT) and medullary thick ascending limbs (MAL). In addition, the PCR product of ET-1 mRNA was also higher in glomeruli and IMCD, whereas it was undetectable in PCT and MAL. Furthermore, FCS and TGF-beta increased ET-1 mRNA in microdissected glomeruli and IMCD. These data clearly demonstrated that the production sites of ET-1 are glomeruli and IMCD among the nephron segments. ET-1 is an autocrine factor in these sites.

Differential expression of mRNA for guanylyl cyclase-linked endothelium-derived relaxing factor receptor subunits in rat kidney.

Endothelium-derived relaxing factor (EDRF) has profound effects on the renal vasculature, the glomerular mesangium, and also affects renal salt excretion. EDRF stimulates guanylyl cyclases, which are thought to be heterodimers comprised of alpha and beta subunits. Two alpha and two beta isoforms have been identified thus far. However, the molecular composition of in vivo guanylyl cyclase-linked EDRF receptors is unknown. We used polymerase chain reaction to clone a portion of the rat alpha 2 subunit. Guanylyl cyclase-linked EDRF receptor mRNA was detected in microdissected renal structures using a reverse transcription/polymerase chain reaction assay. The interlobular artery/afferent arteriole contained mRNA for the alpha 1, alpha 2, and beta 1 subunits; a faint beta 2 band was found in 29% of experiments. In contrast, the cortical collecting duct contained mRNA only for alpha 1 and beta 2 subunits. We conclude that guanylyl cyclase-linked EDRF receptor subunit isoforms are independently and heterogeneously expressed in the renal vasculature and cortical collecting duct, suggesting that several different EDRF receptors exist in vivo. These data suggest that the tubule receptor is composed of alpha 1/beta 2. The vasculature may contain at least two different EDRF receptors (alpha 1/beta 1 and alpha 2/beta 1). Some beta 2 may also be expressed, allowing for even greater heterogeneity.

Renin expression in renal proximal tubule.

Angiotensinogen, angiotensin-converting enzyme, and renin constitute the components of the renin-angiotensin system. The mammalian renal proximal tubule contains angiotensinogen, angiotensin-converting enzyme, and angiotensin receptors. Previous immunohistochemical studies describing the presence of renin in the proximal tubule could not distinguish synthesized renin from renin trapped from the glomerular filtrate. In the present study, we examined the presence of renin activity and mRNA in rabbit proximal tubule cells in primary culture and renin mRNA in microdissected proximal tubules. Renin activity was present in lysates of proximal tubule cells in primary culture. Cellular renin content in cultured proximal tubule cells was increased by incubation with 10(-5) M isoproterenol and 10(-5) M forskolin by 150 and 110%, respectively. In addition, renin transcripts were detected in poly(A)+ RNA from cultured proximal tubule cells by RNA blots under high stringency conditions. In microdissected tubules from normal rats, renin mRNA was not detectable with reverse transcription and polymerase chain reaction. However, in tubules from rats administered the angiotensinogen-converting-enzyme inhibitor, enalapril, renin was easily detected in the S2 segment of the proximal tubule. We postulate the existence of a local renin-angiotensin system that enables the proximal tubule to generate angiotensin II, thereby providing an autocrine system that could locally modulate NaHCO3 and NaCl absorption.

Immunohistochemical localization of V2 vasopressin receptor along the nephron and functional role of luminal V2 receptor in terminal inner medullary collecting ducts.

We investigated immunohistochemical localization of V2 vasopressin receptor along the nephron using a specific polyclonal antibody. Staining was observed in some of thick ascending limbs and all of principal and inner medullary collecting duct (IMCD) cells. Not only basolateral but also luminal membrane was stained in collecting ducts, especially in terminal IMCD (tIMCD). To learn the functional role of luminal V2 receptor in tIMCD, we studied the luminal effects of arginine vasopressin (AVP) on osmotic water permeability (Pf), urea permeability (Pu), and cAMP accumulation using isolated perfused rat tIMCD. In the absence of bath AVP, luminal AVP caused a small increase in cAMP accumulation, Pf and Pu, confirming the presence of V2 receptor in the lumen of tIMCD. In contrast, luminal AVP inhibited Pf and Pu by 30-65% in the presence of bath AVP by decreasing cAMP accumulation via V1a or oxytocin receptors and by an unknown mechanism via V2 receptors in the luminal membrane of tIMCD. These data show that V2 receptors are localized not only in the basolateral membrane but also in the luminal membrane of the distal nephron. Luminal AVP acts as a negative feedback system upon the basolateral action of AVP in tIMCD.

Effects of oral adsorbent AST-120 on the progression of chronic renal failure: a randomized controlled study.

This prospective, randomized controlled study was designed to examine the effects of oral adsorbent AST-120 on the progression of chronic renal failure (CRF) in patients on a strict low protein diet (LPD). Twenty-six patients with CRF (serum creatinine 3.0 to 8.6 mg/dl) on a LPD were randomly assigned to a control group (N = 13) or an AST-120 group (N = 13). The 1/Cr slope and creatinine clearance (CCr) slope were used to estimate the progression rate of CRF; uremic toxins, serum and urinary indoxyl sulfate (IS), peak 2a and guanidino substrates (GS) measured by HPLC. Comparisons were made between the baseline observation period for 6 to 12 months and the treatment period (0.6 g/kg/day of LPD alone or concurrent with 6 g/day of AST-120, for the control and the AST-120 groups, respectively) for 12 to 24 months in both groups. Both the 1/Cr slope and CCr slope were significantly lessened in the treatment period only in the AST-120 group. Serum and urinary IS, but neither peak 2a nor GS were significantly decreased in the treatment period only in the AST-120 group. We conclude that AST-120 administration concurrent with LPD may be superior to LPD alone in retarding the progression of CRF by inhibiting accumulation of indoxyl sulfate.

Role of urinary arginine vasopressin in the sodium excretion in patients with chronic renal failure.

Patients with chronic renal failure show almost equal levels of sodium excreted in the urine as healthy subjects through an increase of the fractional excretion sodium (FE(Na)). The mechanisms of this adaptation, however, are unknown. Recently, urinary arginine vasopressin (AVP) has been shown to inhibit the antidiuretic action of plasma AVP in the collecting ducts of rabbits and rats. In this article, the roles of plasma and urinary AVP are examined with other hormones in the sodium excretion of 57 patients with chronic renal disease. The fractional excretion of AVP, plasma atrial natriuretic peptide (ANP) and endothelin-1 (ET-1), urinary ET-1, and FE(ET-1) correlated with the decrease of creatinine clearance (Ccr). Multiple and stepwise regression analyses showed that FE(AVP) is the major dependent determinant for FE(Na) (adjusted r2 = 0.78). These results suggest that the increase of AVP excretion per remaining nephron could be a cause of the increase of FE(Na) in patients with renal failure. Although plasma AVP works as an antidiuretic hormone, urinary AVP serves as an intrinsic diuretic, especially in patients with chronic renal failure.

A sandwich enzyme-linked immunosorbent assay for ABO blood typing of semen by using anti-p 84 monoclonal antibody as a marker of blood group substance in semen.

A blood group substance (BGS), a protein with ABH antigenic activity, was isolated from human seminal plasma and designated as p 84 (Sato, 1995). We have developed a method for determining the ABO blood type of semen by performing a sandwich enzyme-linked immunosorbent assay (ELISA) in which p 84 is captured with an anti-p 84 monoclonal antibody, and evaluated the specificity and sensitivity of this method. Although BGS activity was detected in semen sensitively by this method, it was not detected in saliva, urine, breast milk, blood or vaginal secretions. Since the concentration of p 84 in semen was independent of the secretion status, the status can be determined as non-secretor when p 84 but not BGS activity was detected. To determine the stability of BGS activity on p 84, dried stains of semen on filter paper were kept at 4, 26, and 37 degrees C for 8 months, 2 years and 1 month, respectively, and their BGS activities were examined. After 8 months at 4 degrees C, over 60% of the original BGS activity was recovered from the stain. The activity could be detected even from a square as small as 0.25 by 0.25 cm. After 1 month at 37 degrees C and 2 years at 26 degrees C, 31 and 20% of the BGS activity, respectively, still remained. It could be detected from the pieces of 1.0 by 1.0 cm and 0.5 by 0.5 cm squares, kept for 1 month at 37 degrees C and 2 years at 26 degrees C, respectively. Finally, semen was mixed with saliva or blood at varying volumetric ratios and used for the sources of dried stains. The BGS activity of p 84 could be detected in the stains until the ratio between semen and saliva or blood reached 1:4. We conclude that this sandwich ELISA offers a more sensitive and specific method for determining the ABO blood type of semen samples obtained from sexual assault victims than existing methods, such as the conventional absorption-elution and classical hemagglutination-inhibition tests.

[Gastrectomy for a patient with congenital factor VII deficiency--a case report].

A 76-year-old man with congenital factor VII deficiency was admitted to our hospital for the treatment of gastric cancer. On admission, the hepaplastin test was prolonged reaching to 21% and factor VII activity was reduced to 8%. After preoperative heat-treated prothrombin complex concentrates loading test, factor VII levels had been maintained above 20% by every four-hour infusion of concentrates during operation and the first post operative day. Bleeding tendency didn't occur, but thrombosis occurred at the left femoral vein. Pre and postoperative replacement therapy is essential to the patient with congenital factor VII deficiency for the safety of operation.

[Endoscopic examination for fistula].

We have conducted fistulous endoscopic examination in 11 cases of postoperative fistula, and discuss its clinical significance. The examination was carried out using an endoscope more than 3 weeks after the operation. The endoscopic examination of the fistula provided not only an internal observation of the fistula but also opportunity to an irrigate the fistula for removal of foreign substances. In addition, the biopsy permitted histological examination for necrotic substances and the fistulous wall. Furthermore, in 7 cases involving abscess, endoscopy made it easy to introduce a drain into the affected site and to judge when to remove the drain based on the condition of the fistula. Closure of pancreatic fistula was also attainable using fibrin glue. Consequently, the fistulas were closed within 2 months after the fistulous endoscopic examination in all cases but one, in which death resulted due to carcinoma. The endoscopic examination for fistula is a fairly easy technique as long as it is carried out only when the fistula is firmly formed. Moreover, this technique is considered to be an effective mean of testing and treatment method since it imposes less stress on the patient.

The drainage routes for aqueous humor in monkeys as revealed by scanning electron microscopy of corrosion casts.

The outflow routes for aqueous humor from the anterior chamber in cynomolgus monkeys were studied. The routes were filled with a mixture of Mercox CL2R and methyl methacrylate, 4:6, which had a low viscosity. Polymerization was delayed by cooling. Some experiments were performed after fixation with glutaraldehyde. Scanning electron microscopy was used to study the casts after dissolution of the tissue. The casts indicate inflow into the first intertrabecular space through a limited number of 10-100 microns openings. The first space is an irregular circular plexus. Subsequent uveal intertrabecular spaces also constitute complex channels. In the ciliary muscle the plastic entering from the uveal intertrabecular spaces could pass through narrow spaces into the supraciliary and suprachoroidal spaces. The intertrabecular spaces in the corneoscleral meshwork were thinner than those in the uveal meshwork. The outermost layer which tended to fill incompletely especially in fixed preparations communicated with the spaces of the juxtacanalicular tissue. In this tissue there was very limited filling even in unfixed preparations. On the casts of the canal of Schlemm there were remnants of communications with the juxtacanalicular tissue. These remnants indicated that only pores with diameters of 2-3 microns or more had been large enough to drain plastic into the canal. The collector channels formed a deep scleral plexus at many places. This plexus and direct collector channels drained into superior and inferior episcleral veins. Apparently the casting technique permitted visualization of most of the uveal and corneoscleral intertrabecular spaces and of preferential channels through the juxtacanalicular tissue and the inner wall of Schlemm's canal. The number of such channels was about 10-20/mm2 of inner wall.

Physiology of the choroidal vascular bed.

The choroidal vascular bed has many interesting features such as relatively wide but flat capillaries, fenestrated capillary walls and an enormous blood flow. The high flow rate results in a high oxygen tension in the tissue and is also of importance in the temperature control of the eye. The capillary wall is permeable to plasma proteins which is probably of great importance for the supply of vitamin A to the pigment epithelium. The permeability to low molecular weight substances is very high which results in a tissue fluid similar to plasma with respect to small molecules. It is not clear whether the choriocapillaris is normally reabsorbing fluid transported into the choroid from the retina and from the anterior chamber or if there is a net filtration from the choriocapillaris. Fluid can pass from the choroid through the suprachoroid into the episcleral tissues via the scleral substance and spaces around the blood vessels and nerves.