Clinical pharmacokinetics of mycophenolate mofetil

The pharmacokinetics of the immunosuppressant mycophenolate mofetil have been investigated in healthy volunteers and mainly in recipients of renal allografts. Following oral administration, mycophenolate mofetil was rapidly and completely absorbed, and underwent extensive presystemic de-esterification. Systemic plasma clearance of intravenous mycophenolate mofetil was around 10 L/min in healthy individuals, and plasma mycophenolate mofetil concentrations fell below the quantitation limit (0.4 mg/L) within 10 minutes of the cessation of infusion. Similar plasma mycophenolate mofetil concentrations were seen after intravenous administration in patients with severe renal or hepatic impairment, implying that the de-esterification process had not been substantially affected. Mycophenolic acid, the active immunosuppressant species, is glucuronidated to a stable phenolic glucuronide (MPAG) which is not pharmacologically active. Over 90% of the administered dose is eventually excreted in the urine, mostly as MPAG. The magnitude of the MPAG renal clearance indicates that active tubular secretion of MPAG must occur. At clinically relevant concentrations, mycophenolic acid and MPAG are about 97% and 82% bound to albumin, respectively. MPAG at high (but clinically realisable) concentrations reduced the plasma binding of mycophenolic acid. The mean maximum plasma mycophenolic acid concentration (Cmax) after a mycophenolate mofetil 1 g dose in healthy individuals was around 25 mg/L, occurred at 0.8 hours postdose, decayed with a mean apparent half-life (t1/2) of around 16 hours, and generated a mean total area under the plasma concentration-time curve (AUC infinity) of around 64 mg.h/L. Intra- and interindividual coefficients of variation for the AUC infinity of the drug were estimated to be 25% and 10%, respectively. Intravenous and oral administration of mycophenolate mofetil showed statistically equivalent MPA AUC infinity values in healthy individuals. Compared with mycophenolic acid, MPAG showed a roughly similar Cmax about 1 hour after mycophenolic acid Cmax, with a similar t1/2 and an AUC infinity about 5-fold larger than that for mycophenolic acid. Secondary mycophenolic acid peaks represent a significant enterohepatic cycling process. Since MPAG was the sole material excreted in bile, entrohepatic cycling must involve colonic bacterial deconjugation of MPAG. An oral cholestyramine interaction study showed that the mean contribution of entrohepatic cycling to the AUC infinity of mycophenolic acid was around 40% with a range of 10 to 60%. The pharmacokinetics of patients with renal transplants (after 3 months or more) compared with those of healthy individuals were similar after oral mycophenolate mofetil. Immediately post-transplant, the mean Cmax and AUC infinity of mycophenolic acid were 30 to 50% of those in the 3-month post-transplant patients. These parameters rose slowly over the 3-month interval. Slow metabolic changes, rather than poor absorption, seem responsible for this nonstationarity, since intravenous and oral administration of mycophenolate mofetil in the immediate post-transplant period generated comparable MPA AUC infinity values. Renal impairment had no major effect on the pharmacokinetic of mycophenolic acid after single doses of mycophenolate mofetil, but there was a progressive decrease in MPAG clearance as glomerular filtration rate (GFR) declined. Compared to individuals with a normal GFR, patients with severe renal impairment (GFR 1.5 L/h/1.73m2) showed 3-to 6-fold higher MPAG AUC values. In rental transplant recipients during acute renal impairment in the early post-transplant period, the plasma MPA concentrations were comparable to those in patients without renal failure, whereas plasma MPAG concentrations were 2- to 3-fold higher. Haemodialysis had no major effect on plasma mycophenolic acid or MPAG. Dosage adjustments appear to not be necessary either in renal impairment or during dialysis. (ABSTRACT TRUN     

Development of a vibratory white finger prevention program for shipyard workers: an exploratory study

OBJECTIVE: To study the effects of thevetoside (TS), a cardiac glycoside, and an inhibitor of Na+, K(+)-ATPase, on tumor cells cultured in vitro. METHODS: The cytotoxic effects of TS on tumor cells were determined by trypan blue dye exclusion, neutral red vital staining and clonogenic assay. The time-effect relationship and growth inhibition of tumor cells by TS were assayed with trypan blue exclusion method. RESULTS: TS at low doses (0.005-0.1 mg.L-1), with dose dependence, was able to kill SMMC-7721, SGC-7901 and HeLa cells. IC50 values for SMMC-7721, SGC-7901 and HeLa cells were 0.007, 0.011 and 0.018 mg.L-1 by trypan blue dye exclusion test and 0.016, 0.055 and 0.078 mg.L-1 by neutral red vital staining test. TS inhibited the clonal forming rate of SMMC-7721 and SGC-7901 significantly with IC50 values of 0.021 and 0.036 mg.L-1, respectively. Only when the cells were continuously treated with TS for more than 8 hours, the drug-induced cell lethality could be displayed and strengthened quickly. The growth of tumor cells was notably inhibited after they were exposed to 0.1 microgram/ml of TS for 12 hours. All the experimental results of antitumor activity in vitro showed that SMMC-7721 was most sensitive to TS among the three kinds of tumor cells. CONCLUSIONS: TS has cytotoxic action on tumor cells cultured in vitro and this lethal effect must have an action process, in which tumor cells are not dead but suffer from deadly injury and lost the capability of unlimited proliferation.     

Relationship between expression of epidermal growth factor and simian virus 40 T antigen in a line of transgenic mice

The pattern of expression of the simian virus 40 (SV40) T antigen gene and resultant dysplasia were re-examined in a line of transgenic mice in which the T antigen gene was under the control of the SV40 early promoter. We found that T antigen expression in the kidney, and resulting dysplastic lesions, occurred exclusively in the distal convoluted tubules and the ascending limbs of Henle. Epidermal growth factor (EGF) expression in the kidney of normal mice was similarly immunolocalized. The correlation between high EGF immunoreactivity in normal mouse tissues and T antigen expression in the transgenic counterpart was also seen in the choroid plexus epithelium and in the submandibular glands of male mice. T antigen was not found in the submandibular gland of transgenic females. Similarly, EGF was only rarely detected in the normal female submandibular gland. In contrast to the correlation between T antigen expression in the transgenic mice and EGF expression in the corresponding tissues of the normal mice, within the dysplastic lesions of the transgenic mice EGF expression was severely diminished. Adenocarcinomas of the male submandibular gland from another line of transgenic mice that expresses the Int-1 transgene, showed similarly reduced levels of immunostaining for EGF. Thus, reduced expression of EGF might be a general feature of dysplasia and tumorigenesis in those tissues that normally express EGF.     

Microsatellite instability in follicle centre cell lymphoma

Fluorescent polymerase chain reaction (PCR) was used to assay 12 microsatellite markers (APC x 2, DCC, P53 x 2, RB1, NM23, WT1, D6S260, D6S262, D6S281 and TNFa) to look for evidence of microsatellite instability in 40 cases of follicle centre cell lymphoma (FCC). Evidence of novel alleles seen in the tumour tissue but not the normal uninvolved tissue was seen in seven cases (17%). In only two of these cases (5%) was more than one locus involved but in these cases multiple affected loci were seen (4/12 and 7/12 respectively). The detection of microsatellite instability indicates a DNA repair defect such as that which would be predicted to occur in cells with mutated mismatch repair genes, a novel finding in FCC lymphoma.     

Detection of alcoholism in schizophrenia using the MAST

1. alpha-toxin of Staphylococcus aureus readily permeabilized rat uterine smooth muscle after incubation for a short time. 2. The permeabilized muscle responded to Ca2+ dose-dependently and repeatedly in the same manner. 3. The threshold concentration of Ca2+ for contraction was 0.1-0.3 microM and the maximal contraction was achieved with 1 or 3 microM Ca2+. 4. GTP gamma S or GTP augmented the contractile response to Ca2+. 5. GDP beta S or GDP suppressed the contraction. 6. The role of GTP-binding protein in sensitization of Ca(2+)-induced contractile response of smooth muscle is discussed.     

Identification of nonproliferating but viable hypoxic tumor cells in vivo

We have used the combination of pimonidazole labeling of hypoxic cells, bromodeoxyuridine labeling of proliferating cells, and cell sorting based on Hoechst 33342 perfusion to directly study hypoxia and proliferation in human tumor xenografts and transplantable murine tumors in vivo. Hypoxia was largely confined to cells in regions with the least perfusion, although in tumors exhibiting transient blood flow, hypoxic cells were not as highly localized. Similarly, proliferation and hypoxia were mutually exclusive except in areas of a tumor subjected to transient changes in perfusion. By determining the clonogenic potential, pimonidazole labeling intensity, and radiosensitivity of sorted tumor cell subpopulations, we have provided direct evidence that pimonidazole identifies hypoxic tumor cells of therapeutic relevance in vivo. Given that pimonidazole exhibits few diffusion or delivery problems and no apparent cytotoxicity, it appears to be a versatile and useful label for hypoxic cells in solid tumors.     

Uptake characteristics of loracarbef and cephalexin in the Caco-2 cell culture model: effects of the proton gradient and possible presence of a distinctive second component

The mechanisms of apical (AP) uptake of cephalexin (CEPH) and loracarbef (LOR) in the absence or presence of an (extemally imposed) proton gradient were determined using well-stirred diffusion chambers that minimize the effects of the unstirred water layer. The results indicated that, compared to AP uptake in the presence of an imposed proton gradient, AP uptake in the absence of an imposed proton gradient had higher K(m) values and lower Jmax values. Furthermore, when inhibition studies were performed in the absence of a proton gradient, only natural peptides were effective, whereas the peptide analogs (e.g., enalapril) were not. In addition to the effects of concentration and competitive inhibitors, the results also indicated that (1) the AP uptake of both drugs was decreased more than 60% by FCCP, regardless of whether the proton gradient was present or absent; (2) effects of protein kinase C promoter were dependent upon the presence of a proton gradient; and (3) AP uptake in the presence of an imposed proton gradient was not affected by feeding restriction, whereas AP uptake in the absence of an imposed proton gradient was. These results showed for the first time that two substrates with similar AP uptake characteristics in the presence of an imposed proton gradient may not share those characteristics in the absence of an imposed proton gradient. Taken together, these results suggest that the AP uptake component that functions in the absence of an imposed proton gradient is distinctly different from the one that functions in the presence of an imposed proton gradient. Data generated from the present study and those in the literature lend support to the hypothesis that this distinctive component represents the second binding site on the AP peptide transporter. However, an alternative hypothesis that there are two AP peptide transporters remains to be disapproved.     

Effective shelf-life of prepared sodium hypochlorite solution

Although the tissue solvent and bactericidal properties of sodium hypochlorite are well known, the effective shelf-life of prepared sodium hypochlorite solutions is not known. The stability of sodium hypochlorite is adversely affected by exposure to high temperature, light, air, and the presence of organic and inorganic contaminants. The purpose of this study was to investigate the variables of storage conditions and time on the tissue-dissolving capacity of three different concentrations of sodium hypochlorite. Fresh frozen human umbilical cord was used as the tissue sample for this experiment. Tissue samples were dissolved at time intervals ranging from 1 day to 10 wk in 5.25%, 2.62%, and 1.0% solutions of sodium hypochlorite. The tissue-dissolving ability of 5.25% sodium hypochlorite remains stable for at least 10 wk. The tissue-dissolving ability of 2.62% and 1.0% sodium hypochlorite remains relatively stable for 1 wk after mixing, then exhibits a significant decrease in tissue-dissolving ability at 2 wk and beyond.