Clade-related phenotypic switching among fluconazole resistant Candida albicans isolates.

INTRODUCTION: C. albicans undergoes phenotypic switchng, a putative virulence trait assisting the organism to adapt to different environments. Although this switching has been studied among C. albicans isolates, not much is known about the process among various C. albicans clades (a group of genetic variants within a single species). AIM: To determine whether phenotypic switching among fluconazole resistant C. albicans isolates is clade-related. METHODS: Fifteen fluconazole resistant C. albicans isolates from different clades were studied. Phenotypic switching was determined by a method previously described. Switching behaviour and different colony morphologies among different clades were compared. RESULTS: Phenotypic switching was observed in all clades, with clade SA exhibiting the most switching (75%), and clade NG the east (5.6%). Stipple was the most dominant phenotype observed in all clades (p = 0.024), occurring mostly in clade SA (35%). Irregular wrinkle phenotype was dominant in clade SA (62%). CONCLUSION: Phenotypic switching was clade-related. Highest switching in clade SA isolates suggests better survival un der adverse conditions. Stipple and irregular wrinkle phenotypes among clade SA isolates need to be studied further.

Molecular typing of Treponema pallidum strains from patients with neurosyphilis in Pretoria, South Africa.

OBJECTIVE: To evaluate the molecular typing system for Treponema pallidum using cerebrospinal fluid (CSF) specimens obtained from patients with neurosyphilis in Pretoria, South Africa. METHODS: CSF specimens were collected from 32 men and 18 women with suspected late neurosyphilis. Typing of T pallidum involved PCR amplification and restriction analysis of the tprE, G and J genes and determination of the number of 60 base pair tandem repeats within the arp gene by PCR amplification. RESULTS: Of 13 typeable specimens, 4 strain types were identified: 2i, 3e, 14a and 17e. Subtype 14a was identified in 7 specimens (53.8%), subtype 3e in 4 specimens (30.7%) and subtypes 17e and 2i in 1 specimen (7.6%) each. CONCLUSIONS: This study shows that the typing system can be applied to specimens which may contain low numbers of spirochaetes such as CSF.

A rapid reversed phase high performance liquid chromatographic method for the determination of docetaxel (Taxotere) in human plasma using a column switching technique.

A rapid, simple and sensitive isocratic high performance liquid chromatography (HPLC) method was developed to measure the concentration of docetaxel in plasma samples with UV detection at 227 nm. The method uses a column switching technique with an Ultrasphere C18 column (75 x 4.6 mm ID, 3 mu, Altex, USA) as clean-up column and a CSC-nucleosil C8 column (150 x 4.6 mm ID, 5 mu, CSC, Montreal, Canada) as the analytical column. The mobile phase consisted of Phosphate buffer (30 mM, pH = 3)-acetonitrile (47:53, v/v) with the flow rates of 1.1 and 1.3 ml min-1 for clean-up and analytical columns, respectively. Paclitaxel was used as an internal standard. The plasma samples were extracted using a solid phase extraction method with Ammonium acetate (30 mM, pH = 5)-acetonitrile (50:50, v/v) as final eluent. The extraction method showed a recovery of 92% for docetaxel. In this system, the retention times of docetaxel and Paclitaxel were 7.2 and 8.5 min, respectively. The detection limit of docetaxel in plasma is 2.5 ng ml-1. This analytical method has a very good reproducibility (7.2% between-day variability at a concentration of 10 ng ml-1). It is applicable in clinical and pharmacokinetic studies.

Effects of PALA on the pharmacokinetics of 5-fluorouracil.

N-(phosphonacetyl)-L-aspartate (PALA) modulates the activity of 5-fluorouracil (5-FU) by inhibiting pyrimidine biosynthesis. A cross-over study was conducted to determine whether PALA affects the pharmacokinetic parameters of 5-FU in patients given 5-FU/folinic acid (FA). Six patients (3 males, 3 females) aged 63 4.3 (mean SD) years (body surface area of 1.84 18 m2) with metastatic colorectal carcinoma were given two courses of treatment. The treatment consisted of 250 mg/m2 of PALA on day 1 followed by 20 mg/m2 FA and 400 mg/m2 5-FU (5 min i.v. bolus injection) on days 2-5 in one cycle of treatment (PALA+). In another treatment cycle, these doses of 5-FU and FA were given for all 5 days without PALA (PALA-). The two courses were given four weeks apart. It was determined by random selection whether the course with PALA was given before or after the course without PALA. Blood samples were collected over a period of three hours, starting from the beginning of 5-FU infusion on days 2 and 5 of both courses. Plasma concentrations of 5-FU were determined by an HPLC technique. Pharmacokinetic parameters were calculated using a non-compartmental model. While there were no significant differences between pharmacokinetic parameters in the PALA+ vs PALA- courses, there was a trend towards a decreasing area under the curve (AUC) and increasing clearance (Cl) in PALA+ courses of treatment.

Cytotoxicity, accumulation, and efflux of cisplatin and its metabolites in human ovarian carcinoma cells.

Cisplatin (CP) is one of the most useful antineoplastic drugs. When CP is dissolved in human plasma, different metabolites are formed. Using the OV 2008 human ovarian cancer cell line, we examined the relative cytotoxicities of CP and its metabolites (aquated CP [AP], monomethionine CP [MP], bismethionine CP [BP], and a mixture of CP metabolites in ultrafiltrated human plasma [UP]) in vitro. By clonogenic assay, cell survival (percent of mean +/- SE) of OV 2008 cells exposed for 1 hr to 6.7 microM of CP was 9.8 +/- 0.7 and for its equal platinum contents of AP, MP, BP, and UP solutions were 3.3 +/- 0.7, 9.8 +/- 0.9, 15.9 +/- 1.1, 76.8 +/- 2.1, and 13.1 +/- 0.7, respectively. AP was the most cytotoxic species, and BP was the least cytotoxic species. Cellular platinum uptake (ng/10(6) cells) after addition of 0.33, 1.6, and 2.5 mM of each species for 1 hr was measured and a strong correlation was found between cytotoxicity of each CP metabolite and its corresponding cellular platinum (Pt) uptake (r = 0.997). There was a strong correlation between cytotoxicity of the CP metabolites and their DNA binding. With fractionation of these cells into DNA, nucleoplasm and cytoplasm, the highest platinum content was found on DNA. The most important factor that seems to be responsible for the cytotoxicities of the different CP metabolites is the amount of their associated intracellular accumulation, and particularly the degree of their binding to DNA.

Factors affecting platinum concentrations in human surgical tumour specimens after cisplatin.

We assessed factors which affect cisplatin concentrations in human surgical tumour specimens. Cisplatin 10 mg m-2 was given i.v. to 45 consenting patients undergoing surgical resection of neoplasms, and platinum was assayed in resected tumour and in deproteinated plasma by flameless atomic absorption spectrophotometry. By multiple stepwise regression analysis of normalised data, patient characteristics that emerged as being most closely associated (P < 0.05) with tumour platinum concentrations (after correcting for associations with other variables) were tumour 'source' [primary brain lymphomas, medulloblastomas and meningiomas ('type LMM') > 'others' > lung cancer > head/neck cancer > gliomas) or tumour 'type' (LMM > brain metastases > extracerebral tumours > gliomas), serum calcium and chloride (positive correlations) and bilirubin (negative). Tumour location (intracranial vs extracranial) did not correlate with platinum concentrations. If values for a single outlier were omitted, high-grade gliomas had significantly higher platinum concentrations (P < 0.003) than low-grade gliomas. For intracranial tumours, the computerised tomographic scan feature that correlated most closely with platinum concentrations in multivariate analysis was the darkness of peritumoral oedema. Tumour source or type is a much more important correlate of human tumour cisplatin concentrations than is intracranial vs extracranial location. Serum calcium, chloride and bilirubin levels may affect tumour cisplatin uptake or retention. CT scan characteristics may help predict cisplatin concentrations in intracranial tumours.

Factors affecting human autopsy kidney-cortex and kidney-medulla platinum concentrations after cisplatin administration.

The objective of this study was to determine factors that affect cisplatin concentrations in human kidney cortex. We used flameless atomic absorption spectrophotometry to assay platinum in autopsy specimens of kidney cortex obtained from 83 cisplatin-treated patients. Concentrations were correlated with pretreatment factors and treatment conditions using univariate nonparametric statistics. Hierarchical stepwise multiple regression analyses of transformed (to normalize) data were then used to assess which factors were most important, controlling for other factors. Kidney-cortex platinum concentrations varied from 0 to 14.8 micrograms/g (median, 2.04 micrograms/g). The cumulative lifetime dose of cisplatin ranged from 10 to 1120 mg/m2 (median, 112 mg/m2). The time from the last cisplatin dose to death was < 1-609 days (median, 38 days). According to univariate statistics, factors that correlated (P < 0.05) with kidney-cortex platinum concentrations were the cisplatin dose per course, the pretreatment serum urea level, metoclopramide use (positive correlations), the time from the last cisplatin treatment to death, and the pretreatment serum albumin value (negative correlations). Factors that approached significance (0.05 < or = P < or = 0.10) were a history of hypertension, hyperbilirubinemia (positive), the serum calcium level, and phenytoin use (negative). In the multiple regression analysis, after controlling for the cisplatin dose per course and the time from the last treatment to death, only concurrent metoclopramide and phenytoin use entered the model. The hydration volume did not affect corrected kidney-cortex or kidney-medulla platinum concentrations. The following conclusions were reached: (1) it may be feasible to use lower hydration volumes than those used routinely, (2) any effect of hydration volume on cisplatin nephrotoxicity may not be mediated via a reduction in kidney-cortex platinum concentrations, (3) higher cisplatin doses might be tolerated with new 5-hydroxytryptamine-3 (5HT-3) antiemetics than were tolerated with metoclopramide, and (4) phenytoin should be tested for its ability to reduce cisplatin nephrotoxicity.

Cisplatin and radiation in the treatment of tumors of the central nervous system: pharmacological considerations and results of early studies.

PURPOSE: To review the human central nervous system pharmacology of cisplatin, factors that affect cisplatin uptake in tumors, and use alone and with radiation for the treatment of primary brain tumors. METHODS AND MATERIALS: The authors review their own prior published and unpublished experience and data published by other groups on the above issues. RESULTS: Cisplatin is one of the most active chemotherapy drugs available for the treatment of solid tumors. It is synergistic with several other agents, including radiation. While it attains only low concentrations in the normal central nervous system, concentrations and plasma-tissue transfer constants for human intracerebral tumors are comparable to those in extracerebral tumors. Tumor type appears to be a more important determinant of platinum concentration than is tumor location, and gliomas do achieve lower concentrations than do other intracerebral or extracerebral tumors. Several other factors have also been identified that correlate with concentrations of cisplatin achieved in human tumors. While cisplatin alone and in combination with other drugs does have some degree of efficacy against primary brain tumors, combining it with cranial irradiation has generally not resulted in any substantial improvement in outcome to date, although some individual studies have been somewhat encouraging. New approaches are currently under investigation. CONCLUSION: Human pharmacology studies provide a rationale for use of cisplatin in the treatment of human brain tumors, and human and in vitro studies suggest some manipulations that might potentially further augment tumor platinum concentrations. While clinical studies suggest that cisplatin combinations may be of some value vs. human primary brain tumors and brain metastases, and while in vitro studies suggest that cisplatin potentiates radiation efficacy, no combination of cisplatin plus radiation yet tested has appeared to be superior to radiation alone.

Cisplatin neurotoxicity: the relationship between dosage, time, and platinum concentration in neurologic tissues, and morphologic evidence of toxicity.

PURPOSE: To identify the major sites of platinum accumulation within neural tissues after treatment with cisplatin and to determine the relationship between cumulative dosage, time, and the development of histopathological and clinical neurotoxicity. PATIENTS AND METHODS: Twenty-one patients treated antemortem with cisplatin had neural tissue harvested at autopsy. Neural tissues were assayed for platinum and examined for histopathologic evidence of neurotoxicity. The relationship between histopathologic neurotoxicity and various pharmacologic parameters was analyzed. RESULTS: Tissue platinum levels were found to be highest in the dorsal root ganglia and lowest in tissue protected by the blood-brain barrier. For peripheral nerve, dorsal root, and dorsal root ganglia, a linear relationship was observed between platinum levels and cumulative dose. Platinum levels in neural tissue were not observed to decrease with time. Histopathologic toxicity closely matched an index of exposure to platinum (cumulative dose and log of time). Clinical and histopathologic neurotoxicity was found to occur with higher accumulations of platinum, with the highest levels found in patients with clinical evidence of neurotoxicity. CONCLUSIONS: The dorsal root ganglia was the most vulnerable neural structure. This is consistent with the clinical presentation of sensory neuropathy in cisplatin neurotoxicity. Central structures of the spinal cord and brain were protected from platinum accumulation. The increasing histopathologic toxicity, with an index of exposure to platinum, suggests that it is retained indefinitely in an actively neurotoxic form. The pharmacologic parameters examined correlate with the development of and are consistent with the clinical and laboratory features of cisplatin neurotoxicity.