The prognostic value of lymph node ratio after neoadjuvant chemoradiation and rectal cancer surgery.

BACKGROUND: Neoadjuvant chemotherapy decreases total lymph nodes harvested and possibly affects lymph node staging after total mesorectal excision in patients with rectal cancer. OBJECTIVE: This study aimed to compare staging by lymph node ratio with staging by absolute number of positive lymph nodes. DESIGN: This study is a retrospective cohort review. SETTING: : A tertiary care referral center was the setting for this investigation. PATIENTS: A total of 281 consecutive patients who underwent neoadjuvant chemoradiation and total mesorectal excision after histologically confirmed rectal cancer between January 1, 1998 and December 31, 2008 were included in this study. MAIN OUTCOME MEASURES: Lymph node ratio is the number of positive lymph nodes divided by the total number of lymph nodes within one sample. Risk categories of low (0 to < 0.09); medium (0.09 to < 0.36); and high (≥ 0.36) for lymph node ratio were chosen by significance with the use of Cox proportional hazards models. These categories were then used in a reclassification table and compared with positive lymph node stage: low (0 positive nodes), medium (1-3 nodes), and high (> 3) by 5-year mortality rates. RESULTS: The majority (87%) of patients were concordant in risk assessment. Thirty patients were downstaged to lower risk lymph node ratio categories without showing actual lower mortality rates. Seven patients were upstaged to a high-risk lymph node ratio category with a supporting higher 5-year mortality rate. When limiting the analysis to those with fewer than 12 nodes, 136 (95%) patients were concordant in risk assessment; all 30 incorrectly downstaged patients were removed, but the 7 correctly upstaged patients remained. CONCLUSIONS: Patients who undergo neoadjuvant chemoradiation before rectal cancer surgery frequently have fewer than 12 lymph nodes harvested despite maintaining vigorous surgical standards. Lymph node ratios may provide excellent prognostic value and are possibly a better independent staging method than absolute positive lymph node counts when less than 12 lymph nodes are harvested after neoadjuvant treatment.

Matrix polysaccharide precursors in Arabidopsis cell walls are synthesized by alternate pathways with organ-specific expression patterns.

The expression pattern of the single-copy gene UDP-glucose dehydrogenase (Ugd) was analysed in transgenic Arabidopsis plants by promoter:GUS and GFP fusions, Western blots, activity assays and histochemical activity staining. The enzyme oxidizes UDP-glucose to UDP-glucuronic acid and thus directs carbohydrates irreversibly into a cell wall-specific pool of nucleotide sugars. UDP-glucuronic acid is the central intermediate in the interconversion pathway to other nucleotide sugars, including the UDP-derivatives of arabinose, xylose, apiose and galacturonic acid which account for half the biomass of a typical Arabidopsis leaf cell wall. These activated sugars are needed as substrates for the biosynthesis of matrix polysaccharide polymers. In plants up to 5 days old the Ugd gene is strongly expressed in young roots, but very little in hypocotyls. Older plants show a more uniform expression pattern with a preference for the vascular system. A complex expression pattern was observed in flowers with high activity in the stamen, stigma and nectaries. Meristems in the leaf axil of rosette and inflorescence leaves exhibit a high level of activity of the Ugd gene. Although many of the growing tissues show high activity levels of the Ugd gene, others such as the hypocotyl and the cotyledons of young seedlings do not. Instead these tissues efficiently incorporate 3H-inositol into their cell walls. This indicates the biosynthesis of UDP-glucuronic acid through an alternative pathway via the oxidation of inositol to glucuronic acid and subsequent activation to the nucleotide sugar. The data strongly suggest two alternative pathways for matrix polysaccharide precursors with spatial and developmental regulation.

Biotransformation of the fungicide chlorthalonil by glutathione conjugation.

The biotransformation of the nephrotoxic fungicide chlorthalonil (2,4,5,6-tetrachloroisophthalonitril) has been studied in the rat and in rat liver subcellular fractions. In rat liver cytosol, chlorthalonil was rapidly transformed to 4,6-bis(glutathion-S-yl)-2,5-dichloroisophthalonitril in the presence of glutathione in a reaction catalysed by glutathione S-transferases. 4-(Glutathion-S-yl)-2,5,6-trichloroisiphthalonitril was observed as an intermedite in the glutathione-dependent biotransformation of chlorthalonil. In the bile of rats dosed with chlorthalonil (0.18 mmol/kg, orally) 4,6-bis (glutathion-S-yl)-2,5-dichloroisophthalonitril was recovered as a minor metabolite. In rats, chlorthalonil was transformed to 4,6-bis (N-acetyl-cystein-S-yl)-2,5-dichloroisophthalonitril. This metabolite was excreted in small amounts in the urine of rats dosed orally with chlorthalonil (0.66 and 2.64 mmol/kg). In all experiments, a major part of the dose was recovered as unchanged chlorthalonil in feces. Oral administration of chlorthalonil (0.66 and 2.64 mmol/kg) resulted in a slight increase in the urinary excretion of gamma-glutamyltranspeptidase, indicative of nephrotoxicity. Other parameters indicative for renal proximal tubular damage (urinary glucose and protein excretion) were not changed by acute chlorthalonil administration. Very minor renal lesions were observed in chlorthalonil-dosed animals by histopathological examination.

Comparative metabolism of the renal carcinogen 1,4-dichlorobenzene in rat: identification and quantitation of novel metabolites.

1. The metabolism of 1,4-dichlorobenzene has been studied in the male and female Fisher 344 rat over 72 h after oral administration of 14C-1,4-dichlorobenzene (900 mg = 96.8 microCi/kg). No covalent binding of radioactivity could be detected in samples of liver, kidney, lung and spleen. The major route of excretion was with urine accounting for 41.3% of the dose for male and 37.8% of the dose for female rat within 72 h after dosing. 2. Urinary metabolites of 1,4-dichlorobenzene were identified and quantified. The major metabolites identified in the urine of both the male and female rat, were the sulphate and glucuronide of 2,5-dichlorophenol. Minor amounts of 2,5-dichlorohydroquinone were excreted as an unidentified conjugate. 3. 2-(N-acetyl-cysteine-S-yl)-1,4-dichlorobenzene and 2-(N-acetyl-cysteine-S-yl)-2,3-dihydro-3-hydroxy-1,3-hydroxy-1,4-dich lorobenzen e were minor metabolites excreted in the urine of both sexes. 4. A novel biotransformation pathway for 1,4-dichlorobenzene may be postulated, leading to the urinary excretion of a mercapturic acid of chlorophenol. 5. No marked differences in the distribution and excretion of metabolites of 1,4-dichlorobenzene were observed between the male and female Fisher 344 rat.

p-aminophenol nephrotoxicity: biosynthesis of toxic glutathione conjugates.

p-Aminophenol causes necrosis of the pars recta of the proximal tubules in rats, and its nephrotoxicity may be due to glutathione-dependent bioactivation reactions. We have investigated the hepatic metabolism of p-aminophenol in Wistar rats and the cytotoxicity of formed glutathione S-conjugates in rat renal epithelial cells. After ip application of p-aminophenol (100 mg/kg), the following metabolites were identified in rat bile: 4-amino-2-(glutathion-S-yl)phenol, 4-amino-3-(glutathion-S-yl)-phenol, 4-amino-2,5-bis(glutathion-S-yl)phenol, 4-amino-2,3,5(or 6)-tris(glutathion-S-yl)phenol, an aminophenol conjugate (likely a sulfate or glucuronide), acetaminophen glucuronide, and 3-(glutathion-S-yl)acetaminophen. 4-Amino-3-(glutathion-S-yl)phenol, 4-amino-2,5-bis(glutathion-S-yl)phenol, and 4-amino-2,3,5(or 6)-tris(glutathion-S-yl)phenol induced a dose- and time-dependent loss of cell viability in rat kidney cortical cells. Cell killing was significantly reduced by inhibition of gamma-glutamyl transpeptidase with Acivicin. p-Aminophenol was also toxic to renal epithelial cells. Coincubation of p-aminophenol with tetraethylammonium bromide, a competitive inhibitor of the organic cation transporter, and with SKF-525A, an inhibitor of cytochrome P450, protected cells from p-aminophenol-induced toxicity. p-Aminophenol would thus be accumulated in the kidney mainly by organic cation transport systems, which are concentrated in the S-1 segment of the proximal tubule. However, p-aminophenol toxicity in vivo is directed toward the S-2 and S-3 segments, which are rich in gamma-glutamyl transpeptidase. These results and the observation that biliary cannulation and glutathione depletion reduce p-aminophenol nephrotoxicity suggest that the biosynthesis of toxic glutathione conjugates is responsible for p-aminophenol nephrotoxicity in vivo. The aminophenol glutathione S-conjugates formed induce p-aminophenol nephrotoxicity by a pathway dependent on gamma-glutamyl transpeptidase.

Prilocaine-induced methemoglobinemia in a child with Shwachman syndrome.

A case of methemoglobinemia after injection of prilocaine in a patient who had Shwachman syndrome (Shwachman-Diamond syndrome) is presented. The report reinforces the need to be cognizant of dose/weight/mass relationships in patients receiving medications capable of oxidizing hemoglobin.

Cation-anion gap and choleretic properties of rat bile.

To investigate whether bile contains choleretic anion(s) other than bile salts (BS) that could account for the observed cation-anion gap in bile, the choleretic properties of bile were investigated in the rat. Infusion of bile increased bile flow significantly more than did taurocholate (TC) (P less than 0.005). By contrast, TC increased BS excretion more substantially (P less than 0.01). This effect was dose dependent for both bile and TC. The choleretic principle had a molecular weight of less than 1,000 as estimated by ultrafiltration of bile. Infusion of bile that had been chromatographed on BioBeads SM-2 still elicited choleresis, whereas bile that had been chromatographed on Dowex 1 x 50W did not. Administration of bile in vivo did not affect Na+-K+-stimulated ATPase activity in liver plasma membrane fractions. These results suggest that bile contains anion(s) other than 3-hydroxy-BS, which increase bile flow in a dose-dependent fashion without affecting the permeability of the biliary tree. This putative choleretic appears to be anionic in nature, heat stable, and has an apparent molecular weight of less than 1,000. This finding suggested that bile salt-independent bile flow partly depends on the excretion of a currently undefined anion.