Pathogenesis of distal renal tubular acidosis (incomplete form) in cirrhosis: Normal urinary Pco2 after bicarbonate loading

In liver cirrhosis, an associated defect in urinary acidification is well known but its pathophysiologic nature is not well defined. Recent studies suggest that the urine P co₂ during maximal alkalinization of the urine is an adequate index of distal hydrogen ion secretion. To evaluate the nature of distal renal tubular acidosis (distal RTA) in cirrhosis, the urine minus blood P co₂ gradient [(U – B) P co₂] in alkaline urine was determined in four patients with cirrhosis and distal RTA, and compared with that in four patients without distal RTA (control subjects), as well as with that in one patient with Sjögren's syndrome and distal RTA (subject with impaired distal acidification). As expected, the (U – B) P co₂ after sodium bicarbonate loading was low (10.6 mmHg) in the subjects with impaired distal acidification and normal (32.5 mmHg, s.e.m. = 4.8) in control subjects. By contrast, all four patients with cirrhosis and distal RTA were able to achieve a normal (U – B) P co₂ gradient (33.8 mmHg, s.e.m. = 4.0) after sodium bicarbonate loading, even in the presence of the defect in urinary acidification under acid loading. These results suggest that the pathophysiology of the urinary acidification defect in liver cirrhosis is distinct from that in ordinary distal RTA; the latter signifies a defect in H⁺ secretion (secretory or voltage-dependent RTA), whereas, in cirrhosis, an increased permeability for H⁺ may cause the inability to acidify the urine.     

Studies on the site of renal tubular defect in Bartter's syndrome

Renal tubular function was studied in an 8-month-old male infant with Bartter's syndrome, which is characterized by hypokalemic metabolic alkalosis, normotensive hyperreninemic hyperaldosteronism, and reduced pressor response to angiotensin II. Chloride transport along the diluting segment (C_H2O/C_H2O + C_Cl) was impaired. Furthermore, furosemide did not elicit normal natriuresis, which suggested impaired chloride reabsorptive capacity at the furosemide-sensitive ascending limb of Henle's loop. Loss of antidiuretic hormone-mediated urinary concentration was in support of this. These findings pointed to the thick ascending limb of Henle's loop as the site of the primary defect in this child.     

The Transport Mechanism of an Organic Cation,Disopyramide, by Brush-border Membranes. Comparison Between Renal Cortex and Small Intestine of the Rat

Abstract— The characteristics of disopyramide uptake in brush-border membrane vesicles isolated from rat renal cortex and small intestine were investigated. Transport of disopyramide into an osmotically reactive intravesicular space was observed with notable binding to the membrane surface. An outwardly directed H⁺ gradient stimulated disopyramide uptake, resulting in a transient uphill transport in both brush-border membranes. As for the renal brush-border membrane, the H⁺ gradient itself appeared to be the driving force for this stimulation of uptake. These findings suggest that disopyramide-H⁺ antiport is the mechanism of disopyramide action in renal cell membrane. The initial uptake was saturable (K_m and V_max of 680 μm and 1·25 nmol (mg protein)^?1/30 s, respectively). The stimulation of disopyramide uptake by an outward H⁺ gradient in rat intestinal brush-border membrane was due to an interior negative H⁺-diffusion potential. A K⁺-diffusion potential (interior negative) enhanced disopyramide uptake. These results suggest that there are different mechanisms of disopyramide uptake for renal and intestinal brush-border membrane vesicles.     

Extraskeletal mesenchymal chondrosarcoma of the kidney

A 61-year-old woman was referred for evaluation of an incidental mass found on the right kidney. Abdominal ultrasonography and computed tomography showed a 3-cm tumor with calcification and peripheral enhancement. Under the diagnosis of renal cell carcinoma, a transabdominal right radical nephrectomy was performed. The pathological diagnosis was extraskeletal mesenchymal chondrosarcoma of the kidney. No recurrence or metastasis occurred during a 6-year follow up. Primary renal chondrosarcoma is extremely rare, this being only the fifth case reported in the English literature, and the patient's extended survival is attributed to the small size of the tumor, as well as early diagnosis and treatment.     

A new clustering system for protein sequences and its application to constraints discovery in protein evolution

A conceptual clustering system, CLUSMOL/S, has been developed to classify protein sequences from a user-defined point of view. Given a grouping of amino acids as a viewpoint, the system constructs taxonomic trees of sequences based on minimum information criterion. Every tree node expresses itself as a generic consensus sequence that consists of specific consensus amino acids, insertionideletion points, and generic amino acids with a specified character. The resulting tree and generic sequences show the similarity-based relationships among sequences and their characteristics. Application to vertebrate cytochromes c yields an acceptable cladrogram only when amino acids are grouped by volume and length of sidechains. The result indicates that the steric factor is the most important constraint in the process of protein evolution. © Munksgaard 1995.     

Short sleep duration and long spells of driving are associated with the occurrence of Japanese drivers’ rear‐end collisions and single‐car accidents

Sleepiness and fatigue are important risk factors for traffic accidents. However, the relation between the accident type and lack of sleep as well as spells of driving has not been examined sufficiently. This study aimed to clarify that short sleep duration and long spells of driving are more associated with rear‐end collisions and single‐car accidents as compared with accidents of other types in cases of people who cause accidents. After removing drunken driving as a cause of accidents, 1772 parties involved in accidents were questioned. The quantities of rear‐end collisions and single‐car accidents were, respectively, 240 and 293. Logistic regression analysis showed that short nocturnal sleep (<6 h) and 10‐min increments of spells of driving were significantly associated not only with rear‐end collisions but also with single‐car accidents as compared with accidents of other types. Furthermore, younger age (≤25 years old) and nighttime (21:00–06:00 h) driving were significantly associated with single‐car accidents as compared with accidents of other types. To prevent such accidents, countermeasures must be considered in light of the characteristics of drivers involved in each type of accident described above.