Dependence of the driving force of the sodium pump on rate of transport

The driving force for active transport of Na+ in the isolated toad bladder, ENa, was measured as the reciprocal slope of the change in conductance with change in short-circuit current after stimulation with antidiuretic hormone. The base-line short-circuit current was altered by change in ambient Na+ concentration or addition of amiloride, maneuvers which alter availability of Na+ at the site of active transport. In the absence of a chemical gradient for Na+ across the bladder, ENa was found to be inversely related to the rate of Na+ transport, a finding incompatible with the simple electrical analogue that has been proposed for the system. The results provide additional support for the view that ENa measured in this way has both energetic and kinetic components.     

Ultrasound findings in hepatitis

A retrospective study of ultrasound images of the liver in patients with hepatitis was undertaken. Two distinct ultrasound patterns were detected. In acute hepatitis, the predominant findings were accentuated brightness and more extensive demonstration of the portal vein radicle walls and overall decreased echogenicity of the liver. Chronic hepatitis primarily revealed decreased brightness and number of portal vein radicle walls and verall increased liver echogenicity. In addition, the pathological severity closely paralleled these ultrasound patterns. A prospective study confirmed the same acute hepatitis ultrasound findings with close correlation to the clinical severity. These distinct ultrasound patterns will help to evaluate patients with suspected acute and chronic hepatitis and more accurately define intrahepatic causes of jaundice.     

The comparative histopathology of primary and secondary lesions in murine salmonellosis

In a primary infection, Swiss-Webster mice were injected i.p. with 10(2) or 10(3) virulent Salmonella typhimurium. Multiple microscopic acute abscesses with predominantly polymorphonuclear leucocytes (PMNs) were seen in the liver and the spleen beginning on the 4th day after infection. By the 7th day, these lesions had become enlarged and were gradually transformed into granulomas with central necrosis and peripheral mononuclear cells. The animals usually died within 12 days with massive systemic infection and degeneration of the tissues. In contrast, it was necessary to inoculate 10(6) virulent salmonella i.v. into mice immunized with avirulent S. thphimurium in order to initiate microscopically observable lesions in the liver and the spleen. These secondary lesions were characterized by the early appearance of minute granulomas composed almost entirely of histiocytic cells. They remained small and isolated, usually without central necrosis. Subsequent regression of the lesions and regeneration of normal tissue occurred after the 2nd week following infection. The animals usually survived such a challenge infection.     

Pharmacokinetics and metabolic disposition of 14C-metronidazole-derived radioactivity in rat after intravenous and intravaginal administration

Urinary metabolites and the pharmacokinetics of radioactivity derived from 14C-metronidazole (14C-MTZ) were determined after intravenous (iv) or intravaginal (ivg) administration of 10 mg/kg to adult rats. Following iv or ivg administration, the disappearance of 14C from blood followed the kinetics of a two-compartment open-system model. The blood half-lives of 14C during the beta-phase were 10.9 +/- 1.6 and 13.6 +/- 4.2 hr, after iv and ivg administration, respectively. After ivg application, the MTZ-derived radioactivity was detected in tail blood at 5 min, peaked at 1 hr, declined rapidly to 6 hr and more slowly thereafter. The vaginal absorption half-life of 14C-MTZ was 0.28 +/- 0.09 hr. About 12% of the administered dose remained in the vagina after 1 hr and 1.5% after 24 hr. At 24 hr, the tissue distribution and concentration of 14C were similar in iv and ivg dosed rats, the highest 14C concentration being present in the kidneys and lowest in the fat. The percentages of the dose excreted in 24 hr in the urine and feces were 58 and 15 after iv administration, compared to 37 and 40 after the ivg route, respectively. Unchanged 14C-MTZ and five of its metabolites were detected in the urine irrespective of the route of administration. The results show that metronidazole is rapidly absorbed through the vaginal mucosa of the rat and the metabolism and excretion of this chemotherapeutic agent are influenced by the route of administration.     

Thyroid carcinoma after high-dose external radiotherapy for Hodgkin's disease: report of three cases

Three patients (two female and one male), who had received mantle irradiation for Hodgkin's disease eight, ten, and twelve years previously, developed papillary thyroid carcinoma. The radiation doses to the necks overlying the site of thyroid cancers were 3000, 4000, and 4100 rads, respectively. It has been stated that there is no risk of developing thyroid cancer with such high doses of external irradiation but apparently this complication will be encountered in a small number of patients.     

Isolation of synthetic lethal mutants of ras1 in Schizosaccharomyces pombe

Ras proteins are membrane-associated guanine nucleotide-binding proteins that serve as molecular switches for signal transduction pathways in a diverse array of organisms. Various cellular factors are known to interact with Ras proteins. In order to find the novel cellular factors that are associated with Ras function, we have constructed synthetic lethal mutants of the ras1+ gene in Schizosaccharomyces pombe and used them to identify the genes that are functionally dependent on the Ras1. We first constructed S. pombe strains in which chromosomal ras1+ gene is placed under the nmt1 promoter that is regulated by thiamine. This strain shows ras1+ phenotype in the absence of thiamine, whereas it shows ras1- phenotype in the presence of thiamine. Second, we mutated the constructed strains with ultraviolet light (UV) and selected two synthetic lethal mutants that could not grow when Ras1 function was repressed (ras1-). One of the mutants, KSC3, showed a swollen cell shape, aberrant deposition of septum materials, and aberrant nuclei. The other mutant, KSC4, showed sensitivity to hyper-osmolarity when Ras1 function is absent. These mutants, however, grow normally when Ras1 is expressed (ras1+). These two novel synthetic lethal mutants of ras1 provide the means to isolate the corresponding genes that function in association with Ras1 in S. pombe. Screening of a genomic library of S. pombe complementing the mutant phenotype allowed us to identify several novel genes associated with Ras1 of S. pombe.     

High-resolution crystal structures of delta5-3-ketosteroid isomerase with and without a reaction intermediate analogue

Bacterial Delta5-3-ketosteroid isomerase (KSI) catalyzes a stereospecific isomerization of steroid substrates at an extremely fast rate, overcoming a large disparity of pKa values between a catalytic residue and its target. The crystal structures of KSI from Pseudomonas putida and of the enzyme in complex with equilenin, an analogue of the reaction intermediate, have been determined at 1.9 and 2.5 A resolution, respectively. The structures reveal that the side chains of Tyr14 and Asp99 (a newly identified catalytic residue) form hydrogen bonds directly with the oxyanion of the bound inhibitor in a completely apolar milieu of the active site. No water molecule is found at the active site, and the access of bulk solvent is blocked by a layer of apolar residues. Asp99 is surrounded by six apolar residues, and consequently, its pKa appears to be elevated as high as 9.5 to be consistent with early studies. No interaction was found between the bound inhibitor and the residue 101 (phenylalanine in Pseudomonas testosteroni and methionine in P. putida KSI) which was suggested to contribute significantly to the rate enhancement based on mutational analysis. This observation excludes the residue 101 as a potential catalytic residue and requires that the rate enhancement should be explained solely by Tyr14 and Asp99. Kinetic analyses of Y14F and D99L mutant enzymes demonstrate that Tyr14 contributes much more significantly to the rate enhancement than Asp99. Previous studies and the structural analysis strongly suggest that the low-barrier hydrogen bond of Tyr14 (>7.1 kcal/mol), along with a moderate strength hydrogen bond of Asp99 ( approximately 4 kcal/mol), accounts for the required energy of 11 kcal/mol for the transition-state stabilization.     

p53 and K-ras status in duodenal adenomas in familial adenomatous polyposis

BACKGROUND: The genetic alterations in patients with familial adenomatous polyposis (FAP) and duodenal adenomas are poorly characterized when compared with data relating to colorectal tumorigenesis in the same patients. METHODS: Point mutation of the K-ras oncogene and point mutation and overexpression of the TP53 tumour suppressor gene were investigated in 32 duodenal polyps (seven without mucosal pathology, 23 with mildly dysplastic adenomas and two with moderately dysplastic adenomas) from 21 patients with FAP. RESULTS: K-ras mutation, TP53 mutation or positive p53 staining were not found in duodenal polyps without histological abnormality. Of 25 duodenal adenomas, K-ras mutation was found in three (two mildly dysplastic, one moderately dysplastic), 20 showed positive p53 immunostaining, and mutation of the TP53 gene was found in one moderately dysplastic adenoma. p53 protein overexpression in duodenal adenomas was significantly more frequent than mutation of either K-ras or TP53 (P < 0.01). CONCLUSION: p53 dysfunction is a hallmark of duodenal adenomas in patients with FAP. Overexpression may indicate DNA damage and thus an early step in tumorigenesis.     

Effects of dilute acetic acid on the cervical smear

BACKGROUND: Mesothelial integrity is essential for the prevention of pericardial adhesions. This study was performed to determine the effect of physical protection of the pericardium on mesothelial integrity. METHODS: A pericardial biopsy specimen was obtained at the time of pericardiotomy (0 minutes) in 10 patients undergoing a cardiac operation for the first time. The left free edge of the pericardiotomy was plicated inward to protect the mesothelium. Biopsy specimens were obtained from the protected and unprotected pericardium at 45 and 90 minutes after the start of extracorporeal circulation. Mesothelial integrity and the local inflammatory response were then assessed and graded histologically. RESULTS: The mesothelium was found to be present in the protected specimens at 0, 45, and 90 minutes, but it was found to be denuded in the unprotected specimens (p = 0.003 at 45 minutes; p = 0.004 at 90 minutes). Local inflammation was totally established in both the protected and unprotected specimens at 45 minutes. CONCLUSIONS: Physical agents appear to be the main factor that is damaging to the pericardial mesothelium, and this is an important concept to be taken into consideration when designing a method to prevent pericardial adhesions.