The organic cation transporter OCT2 mediates the uptake of beta-adrenoceptor antagonists across the apical membrane of renal LLC-PK(1) cell monolayers

Previous studies have shown that beta-adrenoceptor antagonists may be substrates of organic cation transporters in kidney and lung. In this study we examined the transport of the beta-adrenoreceptor antagonists propranolol and metoprolol, in renal LLC-PK(1) cell monolayers. Experiments with BCECF (2', 7'-bis(2carboxyethyl)-5(6)-carboxyfluorescein) loaded LLC-PK(1) cell monolayers demonstrated that metoprolol and propranolol flux across the basolateral membrane was consistent with non-ionic diffusion. Flux across the apical membrane consisted of both non-ionic diffusion and the uptake of the cationic form of the beta-adrenoceptor antagonists. Uptake of the cationic form of metoprolol across the apical membrane was Na(+)-independent, electrogenic and sensitive to external pH. Furthermore, uptake was sensitive to inhibition by Decynium-22 and the organic cations TEA (tetraethylammonium) and MPP(+) (1-methyl 4-phenylpyridinium). These results, allied with the apical location of the uptake mechanism suggest that beta-adrenoceptor antagonists may be substrates for the organic cation transporter, OCT2. To confirm beta-adrenoceptor antagonists as substrates for OCT2, we demonstrate, in cells transiently transfected with an epitope tagged version of hOCT2 (hOCT2-V5):(1) Decynium-22 sensitive [(14)C]-propranolol uptake, (2) cis-inhibition of OCT2 by a range of beta-adrenoceptor antagonists and (3) metoprolol induced intracellular acidification.

Characterization of MPP+ secretion across human intestinal Caco-2 cell monolayers: role of P-glycoprotein and a novel Na(+)-dependent organic cation transport mechanism

1. In the kidney, a number of transport proteins involved in the secretion of permanently charged organic cations have recently been cloned. To evaluate the possible similarities between intestine and kidney in the handling of organic cations we investigated the transport of 1-methyl-4-phenylpyridinium (MPP+) across monolayers of intestinal Caco-2 cells. MPP+ is a prototypic substrate of the cloned organic cation transporters hOCT1 and hOCT2. 2. In Caco-2 cell monolayers, the basolateral to apical flux of MPP+ was significantly greater than the apical to basolateral flux, consistent with net secretion of MPP+. 3. Net secretion of MPP+ was abolished by addition of either 10 microM cyclosporin A or 100 microM verapamil to the apical membrane. In contrast, secretion of MPP+ was unaffected by addition of either TEA (2 mM) or decynium-22 (2 microM) to either apical or basolateral membranes. These results suggest that MPP+ secretion is mediated primarily by P-glycoprotein located at the apical membrane. We found no evidence of a role for hOCT1 or hOCT2 in the secretion of MPP+. 4. In addition to net secretion of MPP+, we found evidence of a Na(+)-dependent MPP+ uptake mechanism at the apical membrane of Caco-2 cells. 5. Na(+)-dependent MPP+ uptake was sensitive to inhibition by the organic cations; decynium-22 (2 microM), TEA (2 mM) and cimetidine (5 mM) but not by carnitine, guanidine or proline. 6. These results suggest that net secretion of MPP+ across the apical membrane of Caco-2 cells is a function of the relative contributions of MPP+ secretion mediated by P-glycoprotein and MPP+ absorption mediated by a novel Na(+)-dependent transport mechanism.

Early events in naphthalene-induced acute Clara cell toxicity: comparison of membrane permeability and ultrastructure

Naphthalene causes severe dose- and site-selective injury to mouse nonciliated bronchiolar (Clara) epithelial cells. Toxicity is characterized by exfoliation of injured Clara cells into the airway lumen 24 h after exposure. The purpose of this study was to define the temporal pattern of intracellular changes immediately following naphthalene treatment, with the goal of identifying critical early events involved in cytotoxicity. Mice were injected with naphthalene or carrier and were killed 1, 2, 3, and 6 h after treatment (PT). Loss of membrane integrity was assessed by ethidium homodimer-1 permeability and confocal microscopy. Cell morphology and ultrastructure were evaluated using high-resolution light and electron microscopy. Permeable cells were found only in terminal bronchioles and increased in abundance with time PT. At 2 and 3 h PT, when most Clara cells had early signs of injury, few permeable cells were detected. Many Clara cells had apical membrane blebs that contained abundant, swollen, smooth endoplasmic reticulum (SER) and few other organelles. By 6 h PT many Clara cells were membrane-permeable. However, many permeable Clara cells lacked apical blebs and SER was less abundant in these cells. Cytoplasmic blebbing may be a mechanism to protect the cell by isolating and removing damaged SER. We conclude that the early stages of injury include SER swelling and bleb formation which precede increases in cell membrane permeability after acute naphthalene injury to bronchiolar Clara cells in vivo.

The global topography of Mars and implications for surface evolution

Elevations measured by the Mars Orbiter Laser Altimeter have yielded a high-accuracy global map of the topography of Mars. Dominant features include the low northern hemisphere, the Tharsis province, and the Hellas impact basin. The northern hemisphere depression is primarily a long-wavelength effect that has been shaped by an internal mechanism. The topography of Tharsis consists of two broad rises. Material excavated from Hellas contributes to the high elevation of the southern hemisphere and to the scarp along the hemispheric boundary. The present topography has three major drainage centers, with the northern lowlands being the largest. The two polar cap volumes yield an upper limit of the present surface water inventory of 3.2 to 4.7 million cubic kilometers.

Phosphorylated serine422 on tau proteins is a pathological epitope found in several diseases with neurofibrillary degeneration

Neuronal inclusions with bundles of abnormal filaments made of tau polymers are found in numerous diseases with neurofibrillary degeneration. Tau proteins are the basic components of paired helical filaments (PHF) in Alzheimer's disease (AD), and are abnormally phosphorylated. A disease-specific phosphorylation site at serine422 was demonstrated on PHF, but not on tau proteins from biopsy-derived brain samples. In the present study, we report the characterization of a polyclonal antibody (988) against the serine422 phosphorylation site. By using biochemical and immunohistochemical methods, we confirmed that it is not found on tau proteins from biopsy- or autopsy-derived control samples, and we investigated the presence of this epitope on tau proteins in several neurodegenerative disorders, including AD, Down syndrome (DS), Guamanian amyotrophic lateral sclerosis/Parkinsonism-dementia complex (ALS/PDC), corticobasal degeneration (CBD), progressive supranuclear palsy (PSP), postencephalitic parkinsonism (PEP) and Pick's disease (PiD). By Western blotting, antibody 988 labeled the characteristic tau triplet (tau 55, 64, 69) in AD, DS, Guamanian ALS/PDC and PEP. PSP and CBD exhibited their typical tau doublet (tau 64, 69), whereas the doublet tau 55 and 64 was detected in PiD. In all of these neurodegenerative disorders, antibody 988 clearly labeled NFT and dystrophic neurites, as well as Pick bodies in PiD cases, whereas no staining was observed in control cases. These data indicate that phosphorylation of serine422 on tau proteins is a common feature among neurodegenerative disorders and is therefore not specific of AD. Moreover, phosphorylation of this epitope permits the distinction between normal tau proteins and pathological tau proteins.

Characterization of the analgesic and anti-inflammatory activities of ketorolac and its enantiomers in the rat

The marked analgesic efficacy of ketorolac in humans, relative to other nonsteroidal anti-inflammatory drugs (NSAIDs), has lead to speculation as to whether additional non-NSAID mechanism(s) contribute to its analgesic actions. To evaluate this possibility, we characterized (R,S)-ketorolac's pharmacological properties in vivo and in vitro using the nonselective cyclooxygenase (COX) inhibitors [indomethacin (INDO) and diclofenac sodium (DS)] as well as the selective COX-2 inhibitor, celecoxib, as references. The potency of racemic (R,S)-ketorolac was similar in tests of acetic acid-induced writhing, carrageenan-induced paw hyperalgesia, and carrageenan-induced edema formation in rats; ID50 values = 0.24, 0. 29, and 0.08 mg/kg, respectively. (R,S)-ketorolac's actions were stereospecific, with (S)-ketorolac possessing the biological activity of the racemate in the above tests. The analgesic potencies for (R,S)-, (S)-, and (R)-ketorolac, INDO, and DS were highly correlated with their anti-inflammatory potencies, suggesting a common mechanism. (R,S)-ketorolac was significantly more potent than INDO or DS in vivo. Neither difference in relative potency of COX inhibition for (R,S)-ketorolac over INDO and DS nor activity of (S)-ketorolac at a number of other enzymes, channels, or receptors could account for the differences in observed potency. The distribution coefficient for (R,S)-ketorolac was approximately 30-fold less than for DS or INDO, indicating that (R,S)-ketorolac is much less lipophilic than these NSAIDs. Therefore, the physicochemical and pharmacokinetics properties of (R,S)-ketorolac may optimize the concentrations of (S)-ketorolac at its biological target(s), resulting in greater efficacy and potency in vivo.

Anti-peptide antibodies specific to rat endothelin-converting enzyme-1 isoforms reveal isoform localisation and expression

Endothelin-converting enzyme-1 (ECE-1) is a critical enzyme in the biosynthesis of the potent vasoconstrictor peptide endothelin and exists in several isoforms. Anti-peptide antibodies raised against epitopes in the distinct N-terminal cytoplasmic tails of the rat ECE-1 isoforms have been obtained. By using these antibodies in Western blot analysis and immunofluorescence studies, we have shown that cultures of transformed rat lung vascular endothelial cells treated with the metalloprotease inhibitor phosphoramidon and untreated cells express ECE-1alpha only, whereas human umbilical vein endothelial cells express ECE-1alpha and ECE-1beta. The ECE-1 isoforms expressed in CHO-K1 cells transfected with rat cDNA to ECE-1alpha and ECE-1beta could be immunoprecipitated by using the appropriate isospecific antibody.

Ethylene oxide dosimetry in the mouse

Ethylene oxide (EO) is a direct-acting mutagen and animal carcinogen used as an industrial intermediate and sterilant with a high potential for human exposure. Understanding the exposure-dose relationship for EO in rodents is critical for developing human EO exposure-dose models. The study reported here examined the dosimetry of EO in male B6C3F1 mice by direct determination of blood EO concentrations. Steady-state blood EO concentrations were measured during a single 4-h nose-only inhalation exposure (0, 50, 100, 200, 300, or 400 ppm EO). In addition, glutathione (GSH) concentrations were measured in liver, lung, kidney, and testis to assess the role of the GSH depletion in the saturable metabolism previously observed in mice (Brown et al., Toxicol. Appl. Pharmacol. 136, 8-19, 1996). Blood EO concentrations were found to increase linearly with exposure concentration up to 200 ppm. Markedly sublinear blood dosimetry was observed at exposure concentrations exceeding 200 ppm. An EO exposure concentration-dependent reduction in tissue GSH levels was observed, with both liver and lung GSH levels significantly depressed at EO exposure concentrations of 100 ppm or greater. Our results also indicate that depletion of GSH is likely responsible for nonlinear dosimetry of EO in mice and that GSH depletion corresponds with reports of dose-rate effects in mice exposed to EO.

Surgical margins for excision of primary cutaneous melanoma

BACKGROUND

A major controversy in the treatment of melanoma is the width of the surgical margin necessary for complete excision. Although surgical margins have decreased in recent years, the current recommendations are mainly based on arbitrary choices, only two of which have been tested in clinical trials.

OBJECTIVE

Our purpose was to use prospective data, measuring the extent of subclinical melanoma extensions, to develop guidelines for predetermined surgical margins for the excision of cutaneous melanoma.

METHODS

A prospectively collected series of 535 patients with 553 primary cutaneous melanomas was studied. All melanomas were excised by means of the fresh tissue technique of Mohs micrographic surgery with frozen section examination of the margin. The surgical margin needed for excision of melanoma was determined by measuring the invisible extensions of tumor around the melanoma. The minimum surgical margin was 6 mm and the total margin was calculated by adding an additional 3 mm for any melanoma requiring a subsequent stage to remove the tumor completely.

RESULTS

Eighty-three percent of melanomas were successfully excised with a 6 mm margin; 9 mm removed 95% of the melanomas; and a 1.2 cm margin was necessary to remove 97% of all melanomas. Margins to remove melanomas on the head, neck, hands, and feet were wider than those on the trunk and extremities. Margins to remove melanomas that were more than 2 to 3 cm in diameter were wider than for smaller melanomas.

CONCLUSION

Predetermined surgical margins for excision of melanoma or melanoma in situ by standard surgical techniques should include 1 cm of normal-appearing skin for melanomas on the trunk and proximal extremities that are smaller than 2 cm in diameter, or a 1.5 cm margin for tumors larger than 2 cm in diameter. For melanomas on the head, neck, hands, and feet, a minimum surgical margin of 1.5 cm is recommended or a margin of 2.5 cm for melanomas larger than 3 cm in diameter. Mohs micrographic surgery is a useful alternative to standard surgery when more narrow margins are desired, particularly for melanomas on the head, neck, hands, and feet, or melanomas larger than 2.5 cm in diameter, or for melanomas without distinct clinical margins.

Cardiovascular health risks related to overweight

Cross-sectional surveys of the civilian noninstitutionalized population of the United States, including in-home interviews and clinical examinations, were employed to examine trends in consumption of energy and fat, prevalence of overweight in the population, the association of overweight with levels of blood pressure and blood cholesterol, and the prevalence of high blood pressure and high blood cholesterol among the overweight compared with the nonoverweight. Data from participants 20 years of age and older are reported. Study results suggest that total mean energy intake, although generally accepted to be underreported in dietary surveys, may have increased. Total fat and saturated fat intake as a percent of energy decreased, but remained above recommended levels. Overweight has increased in the population, despite decreases in the prevalence of high blood pressure and high blood cholesterol levels. Increased levels of overweight, reported as body mass index, are associated with increased cardiovascular risk factors of high blood pressure and high blood cholesterol. These data suggest the need for health care practitioners to emphasize the requirement for energy balance (or weight loss if overweight, ie, not at a "healthy weight"). A focus on fat intake alone without emphasis on energy balance is inadequate for achieving and maintaining recommended weight.

Osteochondritis dissecans of the patella: arthroscopic fixation with bioabsorbable pins

Osteochondritis dissecans of the patella is a relatively rare condition. Surgical treatment has been recommended for those patients who fail conservative treatment, or who present with mechanical symptoms or loose bodies. In an attempt to preserve the patellofemoral articulation, we describe a new technique to arthroscopically fix osteochondritic lesions of the patella using bioabsorbable pins. This technique avoids the morbidity of a formal arthrotomy as well as the complications associated with metallic hardware.

Metabolism and testicular toxicity of 1,3-dinitrobenzene in the rat: evaluation of the stage-synchrony model

Because many testicular toxicants cause damage to specific stages of spermatogenesis, the present study has investigated the utility of a model in which the testis is synchronized to contain only a few closely related spermatogenic stages. The susceptibility of different stages to 1,3-dinitrobenzene (1,3-DNB) toxicity was investigated in rats, the testes of which had been stage synchronized by a vitamin A depletion/repletion (VADR) procedure. 1,3-DNB (25 mg/kg, IP) or vehicle was injected 58, 61, or 78 d after vitamin A readministration, and testicular histopathology was evaluated 48 h later. At the time of sacrifice, testes in the three groups were synchronized to stages I-VI, VII-IX, or X-XIV+I. The data indicated that tubules in all stages of spermatogenesis, in both synchronized and unsynchronized animals, demonstrated histopathologic changes in response to 1,3-DNB. However, the lesion seen in synchronized animals was more severe and less stage specific than that seen in weight-matched, unsynchronized animals. This increase in degree of susceptibility could be partially explained by differences in toxicokinetics. Stage-synchronized testes could provide unique insights into stage-specific cellular and molecular events, especially for in vitro studies where the stage enrichment could be maximally exploited. However, results obtained from in vivo toxicity studies using animals subjected to VADR should be interpreted carefully in light of the confounding physiologic/metabolic perturbations potentially induced by the VADR procedure.

Chloride channel blockers decrease intracellular pH in cultured renal epithelial LLC-PK1 cells

The effects of chloride channel blockers upon intracellular pH (pHi) were examined in renal epithelial monolayers of LLC-PK1 cells. A significant intracellular acidification was found with addition of 100 microM 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB), niflumic acid, flufenamate and diphenylamine-2-carboxylate (DPC) but not with 4,4'-diisothiocyanatostilbene-2-2'disulphonic acid (DIDS). The effects of these agents upon pHi was dose-dependent with apparent K0.5 values of: 16.7 +/- 0.3 microM, 34.2 +/- 0.9 microM and 740 +/- 13 microM for niflumic acid, flufenamate and DPC respectively. The results indicate that at concentrations commonly used to block channel activity these chloride channel blockers have profound effects upon pHi.

Mediation of cimetidine secretion by P-glycoprotein and a novel H(+)-coupled mechanism in cultured renal epithelial monolayers of LLC-PK1 cells

1. Previous studies have shown that the weak base, cimetidine, is actively secreted by the renal proximal tubule. In this study we have examined the transport of cimetidine by renal LLC-PK1 epithelial cell monolayers. 2. In LLC-PK1 cell monolayers the basal-to-apical flux of cimetidine was significantly greater than the apical-to basal flux, consistent with net secretion of cimetidine in a basal-to-apical direction. 3. Net secretion of cimetidine was significantly (70%) reduced by the addition of either 100 microM verapamil or 100 microM nifedipine to the apical membrane. The reduction in net secretion was the result of an inhibition of basal-to-apical flux; these agents had no effect upon flux in the apical-to-basal direction. These results suggest that cimetidine secretion is mediated primarily by P-glycoprotein located in the apical membrane. In addition we found no evidence of a role for organic cation antiport in the secretion of cimetidine. 4. In the presence of an inwardly directed proton gradient across the apical membrane (pH 6.0), cimetidine secretion was significantly reduced compared to that measured at an apical pH of 7.4. The reduction in net secretion at pH 6.0 was the result of a stimulation of cimetidine uptake across the apical membrane. This pH-dependent uptake mechanism was sensitive to inhibition by DIDS (100 microM). 5. Experiments with BCECF (2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein) loaded monolayers demonstrated that cimetidine influx across the apical membrane was associated with proton flow into the cell and was sensitive to inhibition by DIDS. 6. These results suggest that net secretion of cimetidine across the apical membrane is a function of the relative magnitudes of cimetidine secretion mediated by P-glycoprotein and cimetidine absorption mediated by a novel proton-coupled, DIDS-sensitive transport mechanism.

In vivo and in vitro kinetics of ethylene oxide metabolism in rats and mice

Ethylene oxide (EO) is a direct-acting mutagen and animal carcinogen used as an industrial intermediate and sterilant with a high potential for human exposure. Kinetics of EO metabolism in rodents can be used to develop human EO dosimetry models. This study examined the kinetics of EO metabolism in vivo and in vitro in male and female F-344 rats and B6C3F1 mice. In vivo studies measured blood and tissue EO levels during and 2-20 min following whole-body inhalation exposure (4 hr, 100 or 330 ppm EO). At 100 ppm EO, the half-life of elimination (t1/2) in rats was 13.8 +/- 0.3 (mean +/- SD) and 10.8 +/- 2.4 min for males and females, respectively, compared to a t1/2 in mice of 3.12 +/- 0.2 and 2.4 +/- 0.2 min in males and females, respectively. On exposure to 330 ppm EO, the t1/2 in mice increased approx twofold, while no change in t1/2 was observed in rats. In vitro kinetic parameters (Vmax and KM) of EO metabolism were determined using tissue cytosol and microsomes. EO metabolism in vitro occurred primarily via cytosolic glutathione S-transferase-mediated EO-GSH conjugation (cGST-EO), with highest activity in the liver. Liver cGST-EO activity (Vmax) was 258 +/- 86.9 and 287 +/- 49.0 nmol/mg protein/min (mean +/- SD) in male and female mice, respectively, compared to 52.7 +/- 10.8 and 29.3 +/- 4.9 in male and female rats, respectively. In rats, but not mice, there was a statistically significant (p < 0.05) gender difference in the Vmax for liver cGST. The KM for liver cGST-EO was approximately 10 mM in both species. The higher Vmax values observed in mice are consistent with the more rapid elimination of EO observed for this species in vivo compared to rats.

Metabolism and testicular toxicity of 1,3-dinitrobenzene in the rat: effect of route of administration

Studies investigating the testicular toxicity of 1,3-dinitrobenzene (1,3-DNB) have utilized both the oral (po) and intraperitoneal (ip) routes of administration. These two administration routes could be expected to produce different pharmacokinetic profiles and, potentially, different degrees of toxicity. In the present work, the effect of route of administration upon 1,3-DNB disposition and susceptibility to testicular damage has been investigated. Male Sprague-Dawley rats were given 25 mg/kg 1,3-DNB either ip or po. Metabolites were quantitated in blood, urine, and feces, and methemoglobin levels were determined. Peak blood levels of 1,3-DNB and its major metabolite were three times higher in ip-dosed rats than in po-dosed rats. While the lower blood levels seen after po administration were maintained for greater than 6 hr, blood levels fell rapidly after ip dosing, reaching po levels at 6 hr postadministration. Peak methemoglobin levels in ip-dosed animals were twice that of po-dosed animals. Route of administration had a minor effect on the levels of urinary metabolites, while there was a significantly higher excretion of metabolites in the feces of po-dosed animals. Despite the markedly higher 1,3-DNB blood levels after ip administration, there were only subtle differences in testicular damage. The data raise the possibility that above a threshold level of 1,3-DNB in the blood, only the duration of testicular exposure to the toxicant may govern susceptibility to testicular toxicity.

Choice of wound dressings and ointments

Over the last several decades, methods for wound dressing have dramatically changed. This article reviews the effects of wound dressing, antiseptics, and antimicrobials on the process of wound healing and on the incidence of wound infection. A set of guidelines is provided to help the surgeon decide what to apply topically to wounds and which dressing to select to achieve the best possible outcome in wound healing.

pH-dependent transport of procainamide in cultured renal epithelial monolayers of OK cells: consistent with nonionic diffusion

1. Previous studies suggest that procainamide is a substrate for organic cation/proton antiport. In order to study the coupling between procainamide flux and proton flux in greater detail we investigated the effects of extracellular procainamide addition upon intracellular pH in cultured monolayers of renal OK cells. Intracellular pH was monitored by use of BCECF as a probe. 2. Apical addition of procainamide (10 mM) caused a significant alkalinisation of intracellular pH. Basolateral addition of procainamide was equally effective in raising intracellular pH. A similar alkalinisation was found in two other renal cell lines: MDCK strain 1 and LLCPK1. 3. In contrast, both tetraethylammonium and N-methylnicotinamide, archetypal substrates for organic cation/proton antiport were without effect upon intracellular pH. 4. At physiological pH values, procainamide exists as a neutral weak base (B) and its conjugate weak acid (BH+). To test which species of procainamide was responsible for the alkalinisation, experiments in which [B] was kept constant whilst [BH+] was varied from 1.15 mM to 7.25 mM were performed. The results suggested that the neutral weak base (B) was the permeant species. 5. Procainamide efflux from procainamide-loaded cell monolayers resulted in a significant acidification of intracellular pH. As with procainamide uptake, this result could be ascribed to the movement of neutral weak base. 6. These effects of procainamide upon intracellular pH are consistent with nonionic diffusion of procainamide rather than an interaction of procainamide with the organic cation/proton antiporter. In addition, the results suggest that organic cation/proton antiport is not highly expressed in OK cells.

Isolated systolic and diastolic ventricular interactions in pacing-induced dilated cardiomyopathy and effects of volume loading and pericardium

BACKGROUND

Interactions between the closely coupled right and left ventricles are known to play important roles as determinants of ventricular function, and the purpose of this study was to evaluate their effects in a model of heart failure.

METHODS AND RESULTS

A dilated cardiomyopathy resulting in congestive heart failure (CHF) was produced in pigs by rapid ventricular pacing at 230 beats per minute for 1 week. Blood was rapidly withdrawn from the left ventricular (LV) apex into a prosthetic ventricle, and the instantaneous effects on the right ventricle were studied during volume loading and before and after pericardiectomy. The systolic interaction gain between the right and left ventricles (Gs) was calculated as the ratio of changes in mean systolic pressure during isolated systolic LV unloading. Diastolic ventricular interaction gain (Gd) was calculated as the ratio of changes in mean diastolic pressures during LV unloading in the last 150 ms of diastole. With the pericardium closed, all interaction gains were significantly increased during volume loading from a right ventricular end-diastolic pressure of 3 to 9 mm Hg: Gs from 0.045 +/- 0.014 to 0.063 +/- 0.020 mm Hg/mm Hg (normal pigs) and from 0.077 +/- 0.040 to 0.103 +/- 0.019 (CHF pigs) and Gs from 0.196 +/- 0.116 to 0.493 +/- 0.117 mm Hg/mm Hg (normal pigs) and from 0.174 +/- 0.101 to 0.341 +/- 0.165 (CHF pigs). When the pericardium was opened, Gd was significantly reduced to 0.145 +/- 0.071 and 0.129 +/- 0.026 mm Hg/mm Hg (normal and CHF pigs, respectively), but Gs showed no significant change (0.067 +/- 0.027 and 0.109 +/- 0.012 mm Hg/mm Hg for normal and CHF pigs, respectively), and both were also significantly increased during volume loading. Gs was significantly greater in CHF versus normal pigs under all conditions, but there were no differences in Gd between CHF and normal pigs.

CONCLUSIONS

These results suggest that dilated cardiomyopathy increases systolic but not diastolic interactions, that the pericardium increases diastolic but not systolic ventricular interactions, and that volume loading with and without the pericardium opened increases both systolic and diastolic interactions.

Erythropoietin in diabetic macular edema and renal insufficiency

Erythropoietin was administered to five anemic azotemic diabetic subjects for 1 year to assess the effect of increasing red cell mass on clinical well-being and the course of renal functional decline. None of the subjects manifested worsened hypertension or cerebrovascular or cardiovascular complications despite an increase in mean hematocrit from a baseline mean of 29.6% to a mean of 39.5%. The serum creatinine concentration after 1 year of treatment with erythropoietin was 3.7 mg/dL, which was unchanged from the baseline value of 3.5 mg/dL. Plasma viscosity remained constant as red cell mass increased. Although the viscosity of whole blood rose as the hematocrit increased, it was within the range of normal blood viscosity for an equivalent hematocrit. The favorable impact of erythropoietin treatment on three diabetic subjects who had macular edema and anemia is described. One hypothesis to explain the benefit of a raised hematocrit on both diabetic nephropathy and retinopathy is that the metabolic, hormonal, and hemodynamic components of the diabetic syndrome, in concert, produce tissue and cellular hypoxia that is ameliorated in part by the greater oxygen-transporting capacity of a raised red cell mass. The pseudohypoxia of diabetes may be implicated in the pathogenesis of diabetic neuropathy, retinopathy, muscular dysfunction, and nephropathy.

Reduction of lipoprotein(a) following treatment with lovastatin in patients with unremitting nephrotic syndrome

Pharmocologic treatment of the hyperlipidemia associated with the nephrotic syndrome with lovastatin has been previously shown to be safe and effective. However, there is no information on the effect of lovastatin treatment on plasma lipoprotein(a) [Lp(a)] levels in patients with the nephrotic syndrome. We administered lovastatin (40 to 80 mg/day) to 20 adult patients with unremitting nephrotic syndrome for 8 weeks to assess its effect on plasma Lp(a) and other plasma lipid concentrations. Apoprotein(a) (apo(a)) phenotype was determined in all patients. Patients were grouped according to their plasma Lp(a) levels. Those with elevated plasma Lp(a) (> or = 30 mg/dL) were placed in group I and those with normal Lp(a) levels (< 30 mg/dL) were placed in group II. Mean total cholesterol and LDL cholesterol were similarly and significantly reduced in groups I and II (-35.9% and -43.3%, P < 0.0005, P < 0.0005 group I, and -31.0% and -42.0%, P < 0.02, P < 0.03 group II, respectively). The median reduction in plasma Lp(a) was -32% (P < 0.003) in nephrotic patients in group I, whereas the median decline in plasma Lp(a) levels in nephrotic patients in group II was only -8.0% (P = 0.052). The overall frequency of the high molecular weight (M(r)) apo(a) phenotype S4 was 70% in nephrotic patients. There was no correlation between plasma Lp(a) and apo(a) phenotype. Treatment with lovastatin results in a favorable response in terms of total and low-density lipoprotein cholesterol lowering in patients with the nephrotic syndrome; however, plasma Lp(a) levels are uniformly and significantly reduced only in nephrotic patients with elevated baseline plasma Lp(a) concentrations. There was no correlation between plasma Lp(a) concentration and other lipid and biochemical parameters.

The prognosis and treatment of true local cutaneous recurrent malignant melanoma

BACKGROUND

The prognosis and treatment of true local cutaneous recurrent malignant melanoma is presently unknown. We define this entity as melanoma bearing an in situ component that recurs contiguous with the scar of the primary excision. Although previously uncommon, the incidence of true local recurrent melanoma may rise due to the recent use of more narrow margins for excision of thin primary melanoma.

OBJECTIVE

We hypothesized that there is a difference in prognosis between true local cutaneous recurrent melanoma versus local recurrence from satellite or in-transit metastases. Also, we defined guidelines for the surgical management of true local cutaneous recurrent melanoma.

METHODS

We calculated the surgical margin necessary to reach a tumor-free plane using Mohs surgery in 50 patients with true local recurrent melanoma. Patient survival was determined by the Kaplan-Meier method.

RESULTS

Seventy-six percent of the tumors were completely excised using a margin of less than 1 cm. However, a margin of up to 2 cm was required to successfully treat all 50 patients. Thicker tumors did require significantly larger margins. The Kaplan-Meier 5-year overall and melanoma survival rates were 89% and 98%, respectively. The 5-year disease-free survival rate was 66%.

CONCLUSION

The prognosis of true local recurrent melanoma is related to tumor thickness. We recommend full-thickness excision of the entire old scar including a 2-cm margin or Mohs surgery if a narrower margin of resection is desired.

Na-K-Cl cotransport in villus and crypt cells from rat duodenum

The aim of the present study was to examine the possibility that Cl- uptake into both villus and crypt epithelial cells of rat duodenum occurs via an electroneutral Na-K-Cl coupled-transport mechanism. Sheets of villus cells and whole crypts were isolated using a Ca2+ chelation technique combined with continuous vibration at low temperatures. Structurally intact, viable epithelia from defined regions along the villus-crypt axis were produced. Uptake of 86Rb+ (as a proxy for K+) into both villus and crypt cells appeared to depend on a coupled process, as evidenced by the inhibition of 86Rb+ uptake by bumetanide and by the removal of either Na+ or Cl- from the bathing media. We report an improved method of isolation of viable enterocytes from defined regions along the villus-crypt axis. We demonstrate the presence of Na-K-Cl cotransport in both villus and crypt duodenal enterocytes.

Metabolism and testicular toxicity of 1,3-dinitrobenzene in rats of different ages

Susceptibility to 1,3-dinitrobenzene (1,3-DNB)-induced testicular damage is known to increase with age. The present study investigated the possibility that age-dependent differences in metabolism and disposition could account for differences in toxicity. [14C]1,3-DNB (25 mg/kg, ip) was administered to Sprague-Dawley rats which were 31, 75, or 120 days of age. Levels of 1,3-DNB and 1,3-DNB metabolites were determined in blood and urine. As animal age increased, peak blood concentrations of 1,3-DNB were lower and declined more slowly indicating an age-dependent decrease in rate of metabolism and a possible increase in volume of distribution. In younger animals, faster elimination rates were associated with higher blood levels of metabolites. Urinary metabolites were generally similar for all age groups with the exception of the diacetamidobenzene metabolite which was significantly lower in the urine of 31 days old rats. There were clear differences in the toxicokinetic profile for 1,3-DNB between the 31 day old rats and the other two age groups. However, differences between the 75 and 120 day old animals were less marked. Testicular damage induced by 1,3-DNB (25 mg/kg, ip) was hardly detectable in the youngest animals, while the intermediate age group showed a moderate lesion particularly in later stages of spermatogenesis. For the oldest animals, testicular damage was more severe, particularly in the earlier stages of spermatogenesis. Overall, the rapid elimination rate could account for the lack of 1,3-DNB toxicity in very young animals. However, simple metabolic differences were less likely to adequately explain the increase in testicular damage found as animal age increased from 75 to 120 days.

Cyclosporin A has divergent effects on plasma LDL cholesterol (LDL-C) and lipoprotein(a) [Lp(a)] levels in renal transplant recipients. Evidence for renal involvement in the maintenance of LDL-C and the elevation of Lp(a) concentrations in hemodialysis patients

Cardiovascular disease is the major cause of mortality in renal transplant recipients. Plasma levels of low-density lipoprotein cholesterol (LDL-C) are often elevated following renal transplantation, and the immunosuppressant cyclosporin A has been implicated as a predisposing factor for posttransplantation hyperlipidemia. Lipoprotein(a) [Lp(a)] is an LDL-like lipoprotein particle; elevated levels of Lp(a) provide an independent and significant risk factor for cardiovascular disease. Plasma concentrations of Lp(a) vary greatly among individuals, and the mechanisms that govern changes in their levels in transplant patients are unknown. The effect(s) of cyclosporin A on Lp(a) was studied in two groups of renal transplantation patients. In group I plasma lipoproteins including Lp(a) were measured before and after successful renal transplantation; this group received both prednisone and cyclosporin A for immunosuppression. Group II patients were studied after renal transplantation and received prednisone alone for immunosuppression. Following surgery, group I patients demonstrated increased plasma concentrations of LDL-C (mean +/- SEM range, 111 +/- 6 to 142 +/- 17 mg/dL; P < .005). In contrast, plasma Lp(a) levels for this group were markedly decreased after renal transplantation (median, 34.3 to 19.7 mg/dL). Patients not treated with cyclosporin A (group II) exhibited mean LDL-C and median Lp(a) levels (118 +/- 42 and 33.1 mg/dL, respectively) that were remarkably similar to those observed before renal transplantation (group I). These data confirm that hyperlipidemia following renal transplantation is associated with cyclosporin A therapy and show that this drug has opposing effects on plasma Lp(a) and LDL-C accumulations.(ABSTRACT TRUNCATED AT 250 WORDS)