Expression of topoisomerase II alpha, Ki-67 and p53 in early stage laryngeal carcinomas not featuring vocal cord fixation

AIM

To determine whether topoisomerase II alpha (topoIIa) expression is an additional prognostic marker for less advanced stage laryngeal cancers first treated without surgery. Ki-67 and p53 protein levels were also assessed for comparison.

EXPERIMENTAL DESIGN

Formalin-fixed, paraffin-embedded tumor material from 63 cases of squamous cell carcinoma (SCC) of the larynx (glottis, stages 0,1,2) was immunohistochemically stained for topoIIa, Ki-67 (MIB-1) and p53 (DO-7) and the results were compared with clinicopathologic findings.

RESULTS

There were 7 stage 0 (TisN0M0), 33 stage I (T1N0M0), and 23 stage II (T2N0M0) SCCs with the TNM classification. Significant differences between carcinomas and normal mucosa were found for the topoIIa-LI, Ki-67-LI, and topoIIa-to-Ki-67 ratio. Regarding histologic grade, a significant difference in topoIIa-to-Ki-67 ratio was evident between well or moderately and poorly differentiated lesions. There were 19 cases of recurrence and 44 cases of nonrecurrence, but no significant differences were found for either of the indices or their ratio. No significant variation with p53 positivity was evident with reference to histologic differentiation, T-factor, clinical course, or proliferation.

CONCLUSIONS

The results demonstrate that the topoIIa-to-Ki-67 ratio is a more sensitive parameter reflecting proliferation, for histologic grading of less advanced laryngeal SCCs, than topoIIa- or Ki-67-LIs.

The prognosis of intraductal papillary mucinous tumors of the pancreas

BACKGROUND/AIMS

Intraductal papillary mucinous tumors of the pancreas have been recognized as a distinct clinical entity. However, their biological behavior has not been clearly defined. The aim of this study was to examine the prognosis of this tumor, to clarify the biological behavior and determine the most appropriate treatment.

METHODOLOGY

Correlations between prognosis of operated cases and histopathologic features were investigated.

RESULTS

In 105 patients with characteristic clinical features of intraductal papillary mucinous tumors, the lesions were classified as hyperplasias in 21%, intraductal tumors in 48% and invasive carcinomas in 31%. Minimal invasion was apparent in 25%, lymph node metastasis in 21%, and fistula formation in 31% of the invasive lesions. Non-invasive and minimally invasive intraductal papillary mucinous tumors were essentially free from risk of tumor recurrence. Other invasive intraductal papillary mucinous tumors showed a significantly poor prognosis.

CONCLUSIONS

Because of the variation in pathological characteristics, patient outcome and the possibility of differential diagnosis, the treatment might be recommended as follows: the case of hyperplasia can be followed-up with close surveillance. Non-invasive and minimally invasive intraductal papillary mucinous tumors should be operated with function-preserving minimal pancreatectomy. For patients with invasive intraductal papillary mucinous tumors evident with preoperative imaging modalities, radical operations with lymph node dissection might be needed.

Functional characterization of organic cation drug transport in the pigmented rabbit conjunctiva

PURPOSE

To characterize carrier-mediated organic cation drug transport in the rabbit conjunctiva.

METHODS

The transport of [14C]guanidine, the model substrate, in the excised pigmented rabbit conjunctiva was evaluated in the modified Ussing chamber. Tetraethylammonium (TEA) transport also was investigated to determine substrate specificity.

RESULTS

The apparent permeability coefficient for guanidine and TEA in the mucosal-to-serosal (ms) direction was 5.4 and 49.6 times greater than that in the serosal-to-mucosal (sm) direction, respectively. Guanidine transport in the ms (but not sm) direction revealed temperature and concentration dependency over 0.02 to 10 mM with an apparent Michaelis-Menten constant of 3.1 mM and a maximal flux of 11.4 nmol/(cm2 x h). Net guanidine transport measured at 0.1 mM across the conjunctiva was decreased by 71% or 82%, respectively, on the addition of 1 microM valinomycin (a K+ ionophore) in both bathing fluids or in a high K+ buffer in the mucosal fluid. Interestingly, net guanidine transport was reduced, rather than enhanced, by 63% upon acidifying the mucosal bathing fluid. By contrast, net guanidine transport was not affected by the serosal presence of 0.5 mM ouabain (a Na+, K+-ATPase inhibitor), by the mucosal and serosal presence of 0.1 microM monensin (a Na+ ionophore) or 0.3 microM carbonyl cyanide p-(trifluoromethoxy)phenyl-hydrazone (FCCP, a H+ ionophore). Guanidine transport in the ms direction was polyspecific, as indicated by the 48% to 82% inhibition by structurally diverse amines. In particular, guanidine ms transport was inhibited by the antiglaucoma drugs dipivefrine (72%), brimonidine (70%), and carbachol (78%).

CONCLUSIONS

A carrier-mediated organic cation transport process appears to exist in the conjunctiva, mediating the absorption of organic amines, including certain amine-type ophthalmic drugs. This process may be driven by an inside-negative apical membrane potential difference.

In situ localization of S-phase-specific histone (H3) mRNA in Bowen's disease

PCNA and Ki-67 immunohistochemistry has been used to assess cell proliferation in place of tritiated thymidine or BrdU labeling of S-phase cells. Recently, it has been possible to reliably demonstrate histone H3 mRNA by in situ hybridization in formalin-fixed and paraffin-embedded tissue sections. We have compared this new proliferation marker with Ki-67 and PCNA with regard to distribution of positive cells and labeling indices (LI%) for 22 cases of Bowen's disease. In normal skin, Ki-67-IHC positive cells and histone mRNA positive cells were observed in the basal and suprabasal layers of the epidermis. In Bowen's disease, positive cells with each marker were more frequent in upper neoplastic epidermis than in suprabasal layers, and the average LI%s were markedly elevated with all markers, the scores decreasing in the following order: PCNA-IHC, Ki-67-IHC and H3mRNA-ISH. However, the results of double staining demonstrated that S-phase cells do not necessarily show exactly the same distributions as with PCNA and Ki-67-IHC labeling. H3mRNA-ISH showed three different degrees of reaction with significantly different LI%s, whereas PCNA and Ki-67 LI% did not vary essentially in the same areas. These results strongly suggest that Bowen's disease, which is well known as a low-grade neoplastic state with malignant potential, also demonstrates clear intratumoral heterogeneity of S-phase cells using the H3mRNA-ISH method.

Histopathological assessment of localized proliferation in cases of Bowen's disease using immunostaining and a laser cytometer

In order to evaluate the localized proliferative activity of intratumor cells in Bowen's disease using tissue sections, skin specimens from ten patients were compared with skin samples from seven normal individuals for their expression of proliferating cell nuclear antigen (PCNA), Ki-67 immunostaining and intranuclear DNA contents, quantitated with a laser cytometer (LCM). In normal epidermis, the largest proportion of PCNA- and Ki-67-positive cells was observed in the basal cell layer, with the amounts decreasing through the suprabasal cell layer towards the prickle cell layer. Examination by LCM also revealed the highest average fluorescence intensity of individual nuclei in the basal cell layer and, as with the immunohistological parameters, reducing towards the upper layer of the epidermis. In the Bowen's disease tissue sections, the largest proportion of PCNA- and Ki-67-positive cells was found in contact with the basement membrane (base of the tumor), with lower amounts in the center of the tumor nest and in the marginal epidermis. The average fluorescence intensities of individual nuclei were in line with these results. These results show that tumor cells distributed in Bowen's disease tumor nests have different proliferative activities depending on their location.

Carrier-mediated transport of monocarboxylate drugs in the pigmented rabbit conjunctiva

PURPOSE

To determine whether an Na+-dependent monocarboxylate transport process exists on the mucosal side of the pigmented rabbit conjunctiva and to evaluate how it may contribute to the absorption of ophthalmic monocarboxylate drugs.

METHODS

L-lactate was used as a model substrate. The excised pigmented rabbit conjunctiva was mounted in a modified Ussing chamber for the measurement of short-circuit current (Isc) and 14C-L.-lactate transport.

RESULTS

When added to the mucosal side at 37 degrees C and at pH 7.4, applications of as much as 40 mM L- and D-lactate increased Isc in a saturable manner. By contrast, no change in Isc was observed at 4 degrees C or under the mucosal Na+-free condition. 14C-L-lactate transport in the mucosal-to-serosal (m-s) direction at 0.01 mM revealed directionality, temperature dependency, Na+ dependency, and ouabain sensitivity, but not pH dependency. L-lactate transport in the m-s direction consisted of a saturable Na+-dependent process by the transcellular pathway and a nonsaturable process by the paracellular pathway. For the saturable process, the apparent Michaelis-Menten constant was 1.9 mM, the maximum flux was 8.9 nanomoles/cm2 per hour, and the apparent Na+ :L-lactate coupling ratio was 2:1. 14C-L-lactate transport in the m-s direction was significantly inhibited (46% to 83%) by the mucosal presence of various monocarboxylate compounds, but not by dicarboxylate compounds, zwitterionic compound, D-glucose, amino acids, and peptidomimetic antibiotics. Monocarboxylate nonsteroidal anti-inflammatory drugs and the antibacterial fluoroquinolones inhibited 14C-L-lactate transport by 40% to 85%, whereas prostaglandins and cromolyn had no effect.

CONCLUSIONS

An Na+-dependent monocarboxylate transport process that may be used by non-steroidal anti-inflammatory and fluoroquinolone antibacterial drugs for transport appears to be present on the mucosal side of the pigmented rabbit conjunctiva. A possible physiologic role for the Na+-dependent monocarboxylate transport process may be to salvage tear lactate.

Pharmacokinetics of aniracetam and its metabolites in rats

The pharmacokinetics of aniracetam (AP), a new cognitive performance enhancer, and its main metabolites was investigated after intravenous (iv) and oral administrations to rat. The plasma levels of AP, 4-p-anisamidobutyric acid (ABA), and p-anisic acid (AA) were determined simultaneously by the HPLC method. The plasma concentrations of the parent drug and ABA quickly declined in a biexponential manner, with rapid terminal decay and a small mean residence time. However, AA yielded nonlinearly high levels at the initial times and the plasma concentrations of 2-pyrrolidinone (PD) were sustained over a relatively long time. When AA was administered intravenously, nonlinearity of the plasma concentrations was also found at higher doses. To describe the time course of the plasma levels of AP and its metabolites after iv administration, a pharmacokinetic model with seven compartments was applied, which included 10 first-order rate constants and one Michaelis-Menten constant. An approximate fit was obtained between the observed and calculated curves based on the model, except for the plasma concentrations of ABA. The plasma concentration-time profiles of AP and its metabolites following oral administration of AP (50 and 100 mg/kg) were similar to those after iv dosing, with the exception of PD, which showed much lower plasma levels than those after iv administration. Elimination of AP and ABA was rapid after oral dosing, and the bioavailability of AP was extremely small (11.4 and 8.6%). As a result, AP was largely metabolized to ABA, AA, and PD in rat.

Carrier-mediated transport of NG-nitro-L-arginine, a nitric oxide synthase inhibitor, in the pigmented rabbit conjunctiva

In this study, the transport mechanism of NG-nitro-L-arginine (L-NA), a nitric oxide synthase inhibitor that may be useful for alleviating intraocular inflammation, was characterized in the pigmented rabbit conjunctiva. L-NA, when applied to the mucosal side of the conjunctiva, led to dose-dependent increases in the short-circuit current (Isc) at 37 degrees C but not at 4 degrees C or under the Na+-free condition. Serosally added 1 mM L-NA did not elicit any change in the Isc. Mucosally added 1 mM L-NA elicited a net absorptive Na+ flux of 0.09 microEq/(cm2.hr), comparable with the Isc change. L-NA transport at 0.1 mM in the mucosal-to-serosal (ms) direction was 22 times greater than that in the serosal-to-mucosal direction. There was a good correlation between the ms flux of L-NA and the Isc changes elicited by L-NA under the same experimental conditions. L-NA transport was saturable, with a Km of 0.35 mM and a maximal flux of 290 pmol/(cm2.min). Hill analysis of L-NA flux observed at 0.1 mM L-NA in response to varying Na+ concentrations in the mucosal bathing fluid yielded a Hill coefficient of 0.98, suggesting a 1:1 coupling between Na+ and L-NA. Moreover, ms 3H-L-NA transport was inhibited by basic amino acids (L-Arg and L-Lys) and a neutral amino acid (L-Leu), but not by an acidic amino acid (L-Glu) and the D-stereoisomer of L-NA. In the case of L-Arg, inhibition was competitive with a Ki of 0.034 mM. Taken together, the above findings are consistent with the involvement of the L-Arg transport system B0,+ in the conjunctival transport of L-NA.

Nucleoside transport mechanisms in the pigmented rabbit conjunctiva

PURPOSE

To elucidate the mechanisms of nucleoside transport in the pigmented rabbit conjunctiva using [3H]uridine as the substrate.

METHODS

Excised pigmented rabbit conjunctiva was mounted in a modified Ussing chamber for measurement of short-circuit current (Isc) and [3H]uridine transport.

RESULTS

[3H]Uridine transport in the mucosal-to-serosal direction at 10 microM exhibited directionality, temperature dependency, and phlorizin sensitivity. Uridine transport appeared to be mediated via saturable Na(+)-dependent and nitrobenzylthioinosine-insensitive Na(+)-independent processes. The corresponding Michaelis-Menten constants (K(m)) were 1.9 microM and 200 microM, and the maximal uridine fluxes (Jmax) were 29.3 and 46.7 pmol/cm2 per minute. When added to the mucosal side containing 141 mM Na+, uridine increased the Isc in a dose-dependent manner from 0.005 mM to 1.0 mM at 37 degrees C. The K(m) value was 7.6 microM, and the maximal increase in Isc was 0.71 microA/cm2. Hill analysis of uridine transport at 10 microM in the presence of varying Na+ concentrations in the mucosal bathing fluid yielded a Hill coefficient of 1.1, suggesting a 1:1 coupling between Na+ and uridine. Na(+)-dependent uridine transport was inhibited by 10 microM adenosine, guanosine, and inosine, but not by thymidine, suggesting that the transport process may be mainly selective for purine nucleosides. Moreover, 2'-deoxyuridine, 5-iodo-2'-deoxyuridine, and 5-(2-bromovinyl)-2'-deoxyuridine were potent inhibitors of Na(+)-dependent uridine transport.

CONCLUSIONS

Na(+)-dependent and Na(+)-independent nucleoside transport processes appeared to be localized on the mucosal aspect of the pigmented rabbit conjunctiva. One or more Na(+)-coupled uridine cotransport processes exhibited a 1:1 stoichiometry and an apparent preference toward purine nucleosides.

Kinetic evidence for Na(+)-glucose co-transport in the pigmented rabbit conjunctiva

PURPOSE

To obtain kinetic evidence for the existence of a Na(+)-coupled glucose co-transport process on the mucosal (tear) side of the pigmented rabbit conjunctiva.

METHODS

The excised pigmented rabbit conjunctiva was mounted in the modified Ussing chamber for measurement of 22Na and 3H-3-O-methyl-D-glucose (3-O-MG) fluxes.

RESULTS

In the presence of 5 mM glucose, the conjunctival tissue showed net Na+ absorption in the mucosal-to-serosal direction at an approximate rate of 0.15 microEq/cm2/h. This net Na+ absorption was abolished by serosally added 0.5 mM ouabain, but not affected by mucosally added 0.1 mM or 1 mM amiloride. There was a 40-60% reduction in net Na+ absorption under the glucose-free condition or in the mucosal presence of 0.5 mM phlorizin. Moreover, serosally added ouabain and mucosally added phlorizin (both at 0.5 mM) significantly decreased the 3-O-MG permeability coefficient in the mucosal-to-serosal direction by about 70%, whereas mucosally instilled 0.1-1.0 mM amiloride was without any effect. Three-O-MG absorption in the mucosal-to-serosal direction appeared to be coupled with Na+ transport with a 1:1 stoichiometry. In addition, this process exhibited temperature dependency, saturability, and directionality.

CONCLUSION

Our findings are consistent with Na(+)-glucose cotransport as being one of the mechanisms for mucosal Na+ entry into the epithelial cells of the pigmented rabbit conjunctiva.

Na(+)-dependent L-arginine transport in the pigmented rabbit conjunctiva

The objective of this study was to characterize Na(+)-coupled L-arginine (L-Arg) transport in the pigmented rabbit conjunctiva. The excised pigmented rabbit conjunctiva was mounted in the modified Ussing chamber for measurement of short-circuit current (Isc), 3H-L-arginine (3H-L-Arg) flux, and 22Na flux. L-Arg when added to the mucosal side led to 0.32-2.65 microA cm-2 increases in the Isc at 37 degrees C, but not at 4 degrees C or in a Na(+)-free solution. L-Arg at 1 mM stimulated net Na+ absorption by 0.12 microEq cm-2 h-1. The evidence for carrier-mediated transport of L-Arg includes: (1) temperature dependence and saturability over 0.01-10 mM, (2) Na+ dependence and ouabain sensitivity, (3) 84 +/- 2% reduction in the apparent permeability coefficient (Papp) of 3H-L-Arg in the presence of excess unlabeled L-Arg (1 mM), and (4) 16-fold difference in L-Arg transport (at 0.1 mM) between the mucosal-to-serosal and the serosal-to-mucosal direction. Moreover, L-Arg transport was inhibited by basic amino acids, large neutral amino acids, and nitric oxide synthase inhibitors, but not by acidic and small neutral amino acids. Kinetic analysis revealed the possible existence of both high and low affinity processes for L-Arg transport. A half maximal concentration (Km) and maximal L-Arg flux (Jmax) values of the low and high affinity processes were 5.90 and 0.07 mM, and 1,248 and 111 pmol cm-2 min-1, respectively. Hill analysis of L-Arg transport at 0.1 mM in the presence of varying Na+ concentrations in the mucosal bathing fluid yielded a Hill coefficient of 0.93, suggesting a 1:1 coupling between Na+ and L-Arg. In conclusion, Na(+)-coupled transport process(es) for L-Arg in accordance with a 1:1 stoichiometry appear to be present on the mucosal side of the pigmented rabbit conjunctiva. The pattern of inhibition by basic and large neutral amino acids and Na+ dependency are suggestive of system B0,(+)-mediated L-Arg transport.

Ras gene point mutations in gallbladder lesions associated with anomalous connection of pancreatobiliary ducts

BACKGROUND/AIMS

The present study was undertaken to investigate possible changes in the K-ras oncogene in patients with gallbladder lesions (carcinoma, adenoma or hyperplasia) in relation to the presence or absence of an anomalous connection of pancreatobiliary ducts (ACPBD).

METHODOLOGY

Gallbladder specimens were obtained from 44 patients with lesions that were either with or without ACPBD, and DNA samples were analyzed using PCR-SSCP. Point mutations in codons 12, 13 and 61 were analyzed by direct sequencing methods with oligonucleotide primers.

RESULTS

The K-ras codon 12 was detected in 83.3% (5/6) of carcinomas the one adenoma tested and in 35.7% (5/14) of hyperplastic lesions with ACPBD, as opposed to only 36.4% (4/11) of carcinomas without ACPBD. The one case of gallbladder adenoma and 11 cases of normal gallbladder without ACPBD studied demonstrated no point mutations in the K-ras oncogene.

CONCLUSIONS

Alteration of the K-ras oncogene appears to be involved in the early stages of gallbladder carcinogenesis when in association with ACPBD. The results further suggest that hyperplasia in cases with ACPBD may be a significant pre-cancerous lesion.

Polar solute transport across the pigmented rabbit conjunctiva: size dependence and the influence of 8-bromo cyclic adenosine monophosphate

PURPOSE

To characterize the conjunctival permeability to polar solutes ranging from 182 to 167,000 daltons in molecular weight (m.w.).

METHODS

Solute transport across the excised pigmented rabbit conjunctiva with a baseline transepithelial electrical resistance (TEER) of 1,285 +/- 46 ohm.cm2 was evaluated in the modified Ussing chamber under open-circuit conditions. The model solutes were mannitol (m.w. 182), 6-carboxyfluorescein (m.w. 376), and fluorescein isothiocyanate-labeled dextrans (FD4, m.w. 4,400-FD150, m.w. 167,000).

RESULTS

For a given solute, the apparent permeability coefficient (Papp) was independent of solute concentration and direction of transport. As expected, the Papp decreased with solute size, from 27.7 x 10(-8) cm/sec for mannitol to 0.31 x 10(-8) cm/sec for FD150. When the experimental temperature was lowered from 37 degrees C to 4 degrees C. Papp decreased by approximately 50% for FD4 through FD40 and by > 80% for both FD70 and FD150. Equivalent pore analysis, assuming restricted solute diffusion via cylindrical, water-filled pores across the isolated tissue, revealed a radius of 5.5 nm at a pore density of 1.9 x 10(8) pores per cm2. The addition of 1 mM 8-bromo cyclic adenosine monophosphate (8-BrcAMP), known to stimulate Cl- secretion and decrease TEER, to the mucosal side of the conjunctiva increased the transport of mannitol, FD4, and FD40 by 28%, while not affecting FD150 transport.

CONCLUSIONS

Our findings suggest that polar solutes up to FD40 traverse the conjunctival epithelial barrier primarily by restricted diffusion through equivalent pores of 5.5 nm radius and that solute movement is affected by reduction of TEER. On the other hand, polar solutes of the FD70 or larger may cross the barrier primarily via non-diffusional pathways such as non-specific endocytosis.

Effect of collagen cross-linking in collagen corneal shields on ocular drug delivery

It is well known that some ocular diseases can be treated more effectively with a collagen shield containing drug. The influence of collagen cross-linking on drug delivery is not known. We determined if collagen cross-linking affects ofloxacin bioavailability at three different collagen shield dissolution times. In this study, the collagen shields were not impregnated in drug but an eye drop was simply instilled after application of collagen shield. A non-cross-linked collagen shield, with a dissolution time of 12 h, disappeared more rapidly from the rabbits' eyes due to proteolysis after application in vivo. On the other hand, the cross-linked collagen shields, with dissolution times of 24 and 72 h, served as an ofloxacin depot and enhanced topical ofloxacin penetration into the cornea and the aqueous humor. As the dissolution times for the cross-linked collagen shield are longer than those of the non-cross-linked type, they serve as drug reservoirs. Therefore, cross-linked collagen shields might be useful ocular drug delivery devices because they can allow drug concentrations to achieve higher levels in the cornea and aqueous humor.

[Transcatheter arterial chemoembolization to hepatic metastases from colorectal cancer]

Response of transcatheter arterial chemoembolization (TAE) and transcatheter arterial infusion chemotherapy to hepatic metastases was reported in 25 cases of colorectal cancer. The severity of liver metastases was H1 in 12 cases, H2 in 9 cases, and H3 in 4 cases. Liver metastases were found during surgery in 12 of these patients, and 13 showed metastases or recurrence in the liver after resections of primary lesions. Catheters were inserted selectively to the proper hepatic artery by Seldinger's method, followed by injection of embolizing agents (gelfoam particles of Lipiodol) with adriamycin or 5-FU + leucovorin in most cases. Response was assessed by blood CEA levels, diagnostic imaging, and period of survival. In 5 cases in whom liver resections were performed following TAE, response was assessed by histopathological findings of the resected specimens. Two patients showed partial response (PR), 12 no change (NC) and 11 progressive disease (PD) by diagnostic imaging. Blood CEA levels fell to less than 50% of pre-treatment levels in 26% of cases. Histological changes by TAE were confirmed in 4 of 5 cases after liver resections, but viable cancer cells were observed in all cases. A case of mucinous cancer showed no change histologically. As the other case of mucinous cancer showed PD by diagnostic imaging, TAE was not suggested to be suitable to treat cases of mucinous cancer. More improvements in the dosage, drugs and times of treatment were suggested to yield a better response rate in TAE therapy for liver metastases from colorectal cancer.

A patient with early gallbladder cancer derived from a Rokitanski-Aschoff sinus

We present herein a case of a 40-year-old male with early gallbladder cancer derived from a Rokitanski-Aschoff sinus (RAS). The patient originally presented at our hospital with epigastric discomfort, following which a diagnosis of adenomyomatosis (ADM) of the gallbladder was made, and a cholecystectomy performed. Histopathological examination of the resected specimen revealed a 7-mm well-differentiated papillo-tubular adenocarcinoma in the RAS epithelium in the body of the gallbladder. The RAS extended to the "pm" layer but the adenocarcinoma was an in situ lesion localized within the RAS epithelium. Considering the difficulties in making an early diagnosis of gallbladder cancer, active surgery should be performed for patients in whom ADM is seen in the gallbladder.

Inhibitory effect of valproic acid on metabolic clearance of carbamazepine epoxide

In order to clarify the inhibitory effect of valproic acid (VPA) on the metabolic clearance of carbamazepine-10,11-epoxide (EPO), an active metabolite of carbamazepine, in rat, the disposition of EPO from plasma and the in vitro hydration of EPO were measured in the presence of VPA, in addition to estimating the effect of the antiepileptic on uridine 5'-diphosphoglucuronyltransferase (UDPGT) activity. It was found that the elimination of EPO from plasma was hardly affected by the pretreatment of VPA (100 mg/kg/d for 7 d). However, the elimination was significantly delayed by VPA at steady-state concentration, maintained by the repeated oral administration of the drug, with a 38% decrease in total clearance and a 52% increase in the fraction of EPO eliminated unchanged in urine. The in vitro hydration of EPO was inhibited competitively by VPA at the concentrations comparable to the in vivo levels. The UDPGT activity of hepatic microsomes was also partly inhibited by VPA. These results suggest that VPA at steady state interferes with the metabolic clearance of EPO, by inhibiting the hydration of EPO and glucuronidation of carbamazepine-trans-diol, a hydrated metabolite.

Effects of anticonvulsants on plasma levels and entero-hepatic circulation of valproic acid and on hepatic drug metabolizing enzyme activities in rats

To clarify the interaction between valproic acid (VPA) and anticonvulsive drugs such as phenytoin (DPH), phenobarbital (PB) and carbamazepine (CBZ), the effects of these anticonvulsants on the plasma levels and enterohepatic circulation of VPA and on drug metabolizing enzyme activities in liver in relation to their inductive effects were investigated in rats. After intravenous (i.v.) or oral administration, plasma VPA rapidly decreased, and this was followed by a secondary increase in plasma level of VPA due to enterohepatic circulation. When the drug was repeatedly coadministered with DPH or CBZ, the initial VPA elimination from plasma up to 1 h after dosing was less than with VPA alone, while PB significantly enhanced the disappearance of VPA. Judging from the decrease in the area under plasma VPA concentration-time curve from 2 to 9 h (AUC2-9), the enterohepatic circulation of VPA was also decreased by PB, but not by DPH and CBZ. The in vitro and in vivo protein binding of VPA was almost unchanged in the presence of DPH. Cytochrome P-450 content and glucuronyltransferase activity were enhanced following repeated coadministration with PB, DPH or CBZ. These enzyme activities in the animals treated with VPA alone at various dosage levels, however, remained unchanged, indicating that VPA did not inhibit the hepatic drug metabolizing enzyme activities in rats.

Gravitational Separation of Gases and Isotopes in Polar Ice Caps

Atmospheric gases trapped in polar ice at the firn to ice transition layer are enriched in heavy isotopes (nitrogen-15 and oxygen-18) and in heavy gases (O(2)/N(2) and Ar/N(2) ratios) relative to the free atmosphere. The maximum enrichments observed follow patterns predicted for gravitational equilibrium at the base of the firn layer, as calculated from the depth to the transition layer and the temperature in the firn. Gas ratios exhibit both positive and negative enrichments relative to air: the negative enrichments of heavy gases are consistent with observed artifacts of vacuum stripping of gases from fractured ice and with the relative values of molecular diameters that govern capillary transport. These two models for isotopic and elemental fractionation provide a basis for understanding the initial enrichments of carbon-13 and oxygen-18 in trapped CO(2), CH(4), and O(2) in ice cores, which must be known in order to decipher ancient atmospheric isotopic ratios.