Development of a valid and reliable malnutrition screening tool for adult acute hospital patients

Nutrition screening identifies individuals who are malnourished or at risk of becoming malnourished and who may benefit from nutrition support. The aim of this study was to develop a simple, reliable and valid malnutrition screening tool that could be used at hospital admission to identify adult acute patients at risk of malnutrition. The sample population included 408 patients admitted to an Australian hospital, excluding pediatric, maternity, and psychiatric patients. The ability of various nutrition screening questions to predict subjective global assessment (SGA) were examined in contingency tables. The combination of nutrition screening questions with the highest sensitivity and specificity at predicting SGA was termed the malnutrition screening tool (MST), and consisted of two questions regarding appetite and recent unintentional weight loss. Subjects who were at risk of malnutrition according to the MST had significantly lower mean values for the objective nutrition parameters (except immunologic parameters) and longer length of stays than subjects who were not at risk of malnutrition. Therefore convergent and predictive validity of the MST was established. The interrater reliability of the malnutrition screening tool was high (93-97%). The MST is a simple, quick, valid, and reliable tool which can be used to identify patients at risk of malnutrition.

Dose-finding study of epidoxorubicin and docetaxel as first-line chemotherapy in patients with advanced breast cancer

BACKGROUND

Anthracyclines and taxanes are the most active drugs against breast cancer and the search after their optimal combination is under intensive investigation in both the advanced and early disease settings. A dose-finding study of epidoxorubicin (E) and docetaxel (D) was conducted in advanced breast cancer (ABC) to define the maximum tolerated dose (MTD) of the combination with and without granulocyte colony-stimulating factor (G-CSF) support and to characterise its toxicity and activity profile.

PATIENTS AND METHODS

Forty-two patients who received neither palliative chemotherapy nor adjuvant anthracyclines (55% with dominant visceral disease and 66% with > or = 2 sites involved) with measurable/evaluable lesions, were treated at four dose levels starting from E 75 mg/m2 and D 75 mg/m2 to E 120 mg/m2 and D 85 mg/m2. A maximum of four cycles of the combination was given every three weeks and four additional cycles of single agent D were allowed in responding patients. Cardiac function was monitored at baseline and at every second course by echocardiography.

RESULTS

Febrile neutropenia (two patients) and prolonged, severe neutropenia (absolute neutrophil count (ANC) < 0.1 x 10(9)/l for more than three days; one patient) defined the MTD of the combination without G-CSF support at E 90 mg/m2 and D 75 mg/m2. G-CSF was then routinely administered from the subsequent dose level of E 120 mg/m2 and D 75 mg/m2. The MTD with G-CSF support was established at E 120 mg/m2 and D 85 mg/m2 (one patient with neutropenic fever together with failure of ANC recovery at day 21, three patients with ANC less than 0.1 x 10(9)/l for more than three days, one patient with both and one patient with grade 4 thrombocytopenia and toxic death from typhlitis while neutropenic). No severe neurotoxicity, mucositis, or fluid retention were observed and there were no clinical signs of cardiotoxicity. Antitumor activity was not a primary endpoint of the study: the overall response rate (ORR) in 40 evaluable patients was 60% (95% confidence interval: 43%-75%, 58% in liver disease, 84% in soft tissue) with no apparent dose-related effect. After a median follow-up of 19 months (range 2-30+), the overall time to progression (TTP) in nine patients without maintenance hormonal therapy was five months.

CONCLUSIONS

The combination of E and D proved to be an effective and safe regimen in poor- prognosis patients with ABC. G-CSF support allowed higher doses to be delivered safely but dose escalation did not translate into improved response rates (RR). The MTD without growth factors support was used, in a phase II trial, which also included patients with previous anthracycline-containing adjuvant regimens.

Advances in cell separation: recent developments in counterflow centrifugal elutriation and continuous flow cell separation

Cell separation by counterflow centrifugal elutriation (CCE) or free flow electrophoresis (FFE) is performed at lower frequency than cell cloning and antibody-dependent, magnetic or fluorescence-activated cell sorting. Nevertheless, numerous recent publications confirmed that these physical cell separation methods that do not include cell labeling or cell transformation steps, may be most useful for some applications. CCE and FFE have proved to be valuable tools, if homogeneous populations of normal healthy untransformed cells are required for answering scientific questions or for clinical transplantation and cells cannot be labeled by antibodies, because suitable antibodies are not available or because antibody binding to a cell surface would induce the cell reaction which should be investigated on purified cells or because antibodies bound to the surface hamper the use of the isolated cells. In addition, the methods are helpful for studying the biological reasons for, or effects of, changes in cell size and cellular negative surface charge density. Although the value of the methods was confirmed in recent years by a considerable number of important scientific results, activities to further develop and improve the instruments have, unfortunately, declined.

Increased high-density lipoprotein cholesterol in patients with epilepsy treated with carbamazepine: a gender-related study

PURPOSE

Long-term treatment with carbamazepine (CBZ) may alter serum lipoprotein concentrations. Gender-related examinations, however, are rare and inconsistent in their results.

METHODS

To examine possible sex differences, serum lipoproteins were analyzed in 127 clinic outpatients (56 women and 71 men) with epilepsies with focal or secondarily generalized tonic-clonic seizures (or both) treated with a CBZ monotherapy. Results were compared with a control group of 177 blood donors (67 women and 110 men) matched for age and weight.

RESULTS

Total cholesterol, low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol were higher in both male and female patients treated with CBZ compared with controls. The known sex difference in serum lipoprotein concentrations (i.e., higher LDL cholesterol and triglycerides but lower HDL cholesterol in men) was confirmed in controls and patients treated with CBZ, with the exception of LDL cholesterol. The HDL as well as the LDL differences were significantly more pronounced in women treated with CBZ than in men when compared with their controls. These results were independent of the dose of CBZ and plasma concentrations. Lathosterol, a cholesterol precursor, and its ratio to cholesterol, an indicator of cholesterol synthesis, were not different, when compared between gender and different HDL groups.

CONCLUSIONS

The observed increase in HDL cholesterol in patients with CBZ, especially in women, might correlate with the previously reported diminished rate of death from coronary heart disease in patients with epilepsy as HDL exerts an antiatherogenic effect.

Antibodies against Helicobacter felis in sera of cats and dogs

Serum samples from 61 dogs and 49 cats were screened for circulating antibodies against Helicobacter felis by an enzyme-linked immunosorbent assay (ELISA) using sonicated bacteria as an antigen. To improve the specificity of the ELISA, sera were absorbed with Campylobacter jejuni subsp. jejuni H. pylori as well as H. felis. Sera from 26 dogs (43%) and 19 cats (39%) revealed clear positive absorbance readings determined as an optical density (OD) that was statistically significant above the OD mean value [P < 0.025 (one-tailed); log10]. The absorbance pattern of ELISA-positive sera corresponded to results obtained with bovine and human reference sera. Furthermore, a correlation between the immune response and results from histopathological examination of gastric specimens from 22 dogs was demonstrated. It could be shown that antibodies against H. felis in sera of cats and dogs can easily be detected using an ELISA. The diagnostic value of this test must be evaluated in further investigations.

A tumor necrosis factor-induced model of human primary demyelinating diseases develops in immunodeficient mice

We have reported previously that in the central nervous system (CNS) local expression of tumor necrosis factor (TNF) transgenes can trigger the development of oligodendrocyte apoptosis, primary inflammatory demyelination and neurological dysfunction, accompanied by lymphocyte and macrophage infiltration into the CNS. To distinguish between the local effects of transgene-encoded TNF and the potential encephalitogenic effects of immune infiltrates upon CNS disease pathogenesis, we have backcrossed Tg6074 TNF-transgenic mice to mice deficient in CD4, beta2-microglobulin (beta2m), immunoglobulin mu chain (Igmu) or recombination activation gene-1 (Rag-1). TNF was capable of triggering undiminished primary demyelination in all of the immunodeficient mice, in the presence of activated cells of the macrophage/microglial lineage. We conclude that TNF is sufficient to induce primary inflammatory demyelination and neurological deficits even in the absence of adaptive immunity.

Typing of clinical Mycobacterium avium complex strains cultured during a 2-year period in Denmark by using IS1245

In the present study restriction fragment length polymorphism analyses with the recently described insertion sequence IS1245 as a probe was performed with clinical Mycobacterium avium complex strains cultured in Denmark during a 2-year period. The overall aim of the study was to disclose potential routes of transmission of these microorganisms. As a first step, the genetic diversity among isolates from AIDS patients and non-human immunodeficiency virus (HIV)-infected patients was described. In addition, a number of isolates from nonhuman sources cultured during the same period were analyzed and compared to the human isolates. A total of 203 isolates from AIDS patients (n = 90), non-HIV-infected patients (n = 91), and nonhuman sources (n = 22) were analyzed. The presence of IS1245 was restricted to Mycobacterium avium subsp. avium isolates. The majority of human isolates had large numbers of IS1245 copies, while nonhuman isolates could be divided into a high-copy-number group and a low-copy-number group. Groups of identical strains were found to be geographically widespread, comprising strains from AIDS patients as well as strains from non-HIV-infected patients. Samples of peat (to be used as potting soil) and veterinary samples were found to contain viable M. avium isolates belonging to genotypes also found in humans.

Glutamate but not interleukin-6 influences the phosphorylation of tau in primary rat hippocampal neurons

Alzheimer's disease (AD) is characterized by amyloid plaques, neuritic degenerations, disturbed glutamatergic neurotransmission and a peculiar inflammatory response. Diffuse plaques develop into neuritic plaques when neurites undergo degeneration in the plaque area. Hyperphosphorylation of tau proteins is a major step in neuritic pathology. Interleukin-6 (IL-6) has been found in diffuse and neuritic amyloid plaques in AD. Therefore the question arises whether IL-6 is involved in the transformation of diffuse into neuritic plaques by affecting tau phosphorylation. We investigated the influence of glutamate and IL-6 on tau phosphorylation in cultured primary rat hippocampal neurons. Glutamate but not IL-6 induced a dephosphorylation of tau. Furthermore IL-6 did not influence the glutamate-induced dephoshorylation of tau. We conclude that the role of IL-6 in AD is not related to the phosphorylation of tau.

Advances in cell separation: recent developments in counterflow centrifugal elutriation and continuous flow cell separation

Cell separation by counterflow centrifugal elutriation (CCE) or free flow electrophoresis (FFE) is performed at lower frequency than cell cloning and antibody-dependent, magnetic or fluorescence-activated cell sorting. Nevertheless, numerous recent publications confirmed that these physical cell separation methods that do not include cell labeling or cell transformation steps, may be most useful for some applications. CCE and FFE have proved to be valuable tools, if homogeneous populations of normal healthy untransformed cells are required for answering scientific questions or for clinical transplantation and cells cannot be labeled by antibodies, because suitable antibodies are not available or because antibody binding to a cell surface would induce the cell reaction which should be investigated on purified cells or because antibodies bound to the surface hamper the use of the isolated cells. In addition, the methods are helpful for studying the biological reasons for, or effects of, changes in cell size and cellular negative surface charge density. Although the value of the methods was confirmed in recent years by a considerable number of important scientific results, activities to further develop and improve the instruments have, unfortunately, declined.

Separation of plant membranes by electromigration techniques

The review focuses on the multiple separating regimes that offers the free flow electrophoresis technique: free flow zone electrophoresis, isoelectric focusing, isotachophoresis, free flow step electrophoresis. Also, the feasibility to apply either interval or continuous flow electrophoresis is evaluated. The free flow zone electrophoresis regime is generally selected for the separation of cells, organelles and membranes while the other regimes find their largest fields of applications in the purification of proteins and peptides. The latter regimes present the highest resolution efficiency. Therefore, a large part of this review is devoted to the applicabilities of these different regimes to the purification of organelles and membrane vesicles at the preparative scale. Recent developments, both in instrumentation and procedures, are described. The major achievements in plant membrane fractionation obtained with free flow electrophoresis are outlined. The related procedures are both analytical and preparative: they separate tonoplast and plasma membrane simultaneously from the same homogenate, they discriminate for one type of membrane vesicles of opposite orientation, and process large quantities of membrane material by reason of the continuous flow mode. Recent advances using electromigration techniques that permit confirmation of the dynamic state of membranes, characterisation of complex membrane-dependent functions and discovery of new membrane-localised activities are presented.

Stability of insertion sequence IS1245, a marker for differentiation of Mycobacterium avium strains

Recently a novel insertion element, IS1245, has been described and suggested for use as a probe in restriction fragment length polymorphism studies of Mycobacterium avium strains. An important issue in this context is the stability of the insertion element. We analyzed single colonies of M. avium cultures and found frequent small one- to two-band changes. However, following repeated in vitro passages over 1 year, similar one- to two-band changes were observed in the IS1245 patterns of only six M. avium strains investigated.

Potential link between interleukin-6 and arachidonic acid metabolism in Alzheimer's disease

Prostaglandins (PGs) and cytokines, such as interleukin-1 (IL-1) and interleukin-6 (IL-6), have been implicated in the etiopathology of various inflammatory and degenerative disorders, including Alzheimer's disease (AD). Previously, we detected the presence of IL-6 in cortices of AD patients. On the other hand, non-steroidal antiinflammatory drugs (NSAIDs), potent inhibitors of prostaglandin synthesis, have been shown to be beneficial in the treatment of AD. Until now, it remained unclear whether and how these two observations were functionally connected. Here, we show that PGs are able to induce IL-6 synthesis in a human astrocytoma cell line. PGE1 and PGE2, but not PGD2 and PGF2 alpha, led to a rapid and transient induction of astrocytic IL-6 mRNA, followed by IL-6 protein synthesis. Furthermore, PGE2 potentiated IL-1 beta-induced IL-6 mRNA synthesis. These results suggest a possible link between the release of PGs from activated microglia and the astrocytic synthesis of IL-6, which itself may affect neuronal cells, as hypothesized for Alzheimer's disease. Finally we demonstrate that microglia are a strong source of PGE2 synthesis indicating that these cells may act as the origin of the pathogenic cascade.

Phase I clinical and pharmacokinetic study of the oral platinum analogue JM216 given daily for 14 days

BACKGROUND

The oral bis (acetate) ammine dichloro cyclohexylamine platinum (IV) analogue (BMS-182751) was brought into clinical development because it was shown to be cytotoxic against some human tumour cell lines and to have an antitumor activity in murine tumours at least comparable to that of parenteral cisplatin and carboplatin. In early clinical studies in which the optimal schedule of treatment was daily for five consecutive days, dose-dependent nausea and vomiting occurred in about two-thirds of patients.

PATIENTS AND METHODS

To evaluate if the use of lower daily doses for longer periods of time could result in a better tolerability, JM216 was given once daily for 14 consecutive days every four to five weeks to adult patients with solid tumors. Oral antiemetics were given prophylactically only at the highest doses. The pharmacokinetics of total and ultrafiltrable platinum were studied on days 1 and 14 of the first cycle by Inductively Coupled-Mass-Spectrometry (ICP-MS).

RESULTS

Forty-six patients were treated at doses ranging from 10 mg/m2/d to 50 mg/m2/d and 39 were evaluable for hematologic toxicity over 74 cycles. MTDs were reached at 45 mg/m2/d and 50 mg/m2/d x 14 repeated every five weeks in patients with extensive, or limited/no prior treatment, respectively. The dose-limiting toxicity was neutropenia which was delayed and variable among patients. Other non-hematological toxicities were severe vomiting (22% of cycles), diarrhea (28% of cycles) and drug-associated fever (32% of patients), controlled with paracetamol. Subjective improvement with disappearance of tumour-related pain was observed in one patient with chemotherapy-resistant metastatic prostate cancer and in one previously untreated patient with malignant mesothelioma. Cmax and AUC values of both total and ultrafiltrable platinum on days 1 and 14 were highly variable among patients. Only Cmax on day 1 was linearly related to the dose. Total and ultrafiltrable platinum were still detectable two weeks after the last dose. No relationship could be established between AUC values and toxicities.

CONCLUSIONS

Daily doses of JM216 of 40 mg/m2 and 45 mg/m2 for 14 consecutive days every five weeks with oral antiemetic prophylaxis are selected for phase II evaluation of single agent in patients with extensive or limited/no prior treatment, respectively. The administration of JM216 on a day x 14 schedule produced nausea and vomiting comparable to that observed with the day x 5 regimen but of longer duration. The variability of pharmacokinetics and pharmacodynamics, even though limited at the doses proposed for phase II evaluation of JM216 as single agent, recommend a careful monitoring of the patients.

The low density lipoprotein receptor gene family. Differential expression of two alpha2-macroglobulin receptors in the brain

LR7/8B is a member of the low density lipoprotein receptor gene family that is specifically synthesized in the brain. Here we have functionally expressed in 293 cells the splice variant harboring eight ligand binding repeats (LR8B). As assessed by confocal microscopy, the expressed receptor is localized to the plasma membrane. Importantly, in cell binding experiments, we demonstrate that this protein is a receptor for activated alpha2-macroglobulin. Because to date low density lipoprotein receptor-related protein (LRP) has been shown to be the only alpha2-macroglobulin receptor in brain, we became interested in the expression pattern of both proteins at the cellular level in the brain. LR7/8B is expressed in large neurons and Purkinje cells of the cerebellum and in cells constituting brain barrier systems such as the epithelial cells of the choroid plexus, the arachnoidea, and the endothelium of penetrating blood vessels. Anti-LR7/8B antibody stains the plasma membrane, dendrites, and vesicular structures close to the cell membrane of neurons, especially of Purkinje cells. In contrast, LRP is present in patchy regions around large neurons and most prominently in the glomeruli of the stratum granulare of the cerebellum. This suggests that, contrary to LR7/8B, LRP is expressed in synaptic regions of the neurons; furthermore, there is a striking difference in the expression patterns of LR7/8B and LRP in the choroid plexus. Whereas LRP shows baso-lateral and apical localization in the epithelial cells, LR7/8B is restricted to the apical cell aspect facing the cerebrospinal fluid. Finally, these studies were extended to cultured primary rat neurons, where double immunofluorescence labeling with anti-LR7/8B and anti-microtubuli-associated protein 2 (MAP2) confirmed the somatodendritic expression of the receptor. Based upon these data, we propose that LR7/8B is involved in the clearance of alpha2-macroglobulin.proteinase complexes and/or of other substrates bound to alpha2-macroglobulin from the cerebrospinal fluid and from the surface of neurons.

Insulin-mimetic signalling of synthetic phosphoinositolglycans in isolated rat adipocytes

A set of synthetic phosphoinositolglycan (PIG) compounds has been demonstrated to exert insulin-mimetic activity on glucose and lipid metabolism in rat adipocytes differing considerably in potency [compound 41>37>45>>7>1; W. Frick, A. Bauer, J. Bauer, S. Wied and G. Müller, G. (1998) Biochemistry 37, 13421-13436]. In the present study we examine whether these differences are based on the capability of the PIG compounds to stimulate signalling components which are thought to mediate metabolic insulin action. Studies using a tyrosine kinase inhibitor and introduction into adipocytes of anti-phosphotyrosine or inhibitory anti-insulin receptor beta-subunit antibodies demonstrated dependence on tyrosine phosphorylation but independence of insulin receptor kinase activation of the insulin-mimetic signalling and metabolic activity of the PIG compounds. The five compounds elicited in rat adipocytes a significant increase in tyrosine phosphorylation of both insulin receptor substrate 1 (IRS-1) and IRS-3 and, to a minor degree, IRS-2, in IRS-1/3-associated phosphatidylinositol 3-kinase (PI 3-K) protein as well as activity, and in protein kinase B (PKB) activity as well as phosphorylation. This was most pronounced for compound 41, approaching 65-95% of the maximal insulin response (MIR) at 20 microM, and declined in the order of compounds 37, 45, 7 and 1. The same ranking was true for the maximal inhibition of glycogen synthase kinase 3 activity (GSK-3) (41, 75% of MIR; compound 37, 65%; compound 7, 25%; compound 1, 10%) and GSK-3 autophosphorylation. The half-maximal concentrations effective for signalling (compound 41, 2-5 microM; compound 37, 10-20 microM) corresponded well to those stimulating glucose and lipid metabolism. Interestingly, compounds 37 and 41 stimulated mitogen-activated protein kinase (MAPK) and protein synthesis in rat adipocytes to only about 20-30% (at 50 microM) of MIR. We conclude that in rat adipocytes: (i) the potency of PIG compounds to regulate glucose/lipid metabolism depends on the activation of PI 3-K and PKB and inhibition of GSK-3; (ii) initiation of tyrosine phosphorylation of IRS-1/3 is sufficient and activation of the PI 3-K cascade is required for insulin-mimetic metabolic signalling; and (iii) PIG compounds are quite selective for the PI 3-K compared to the MAPK cascade, (iv) PIG compounds seem to use the same signalling components downstream of PI 3-K (including Rab4) for stimulation of glucose transport as does insulin. Thus the early signalling step(s) used by PIG, but not by insulin, may represent a target for the treatment of insulin-resistant states.

Cytokine-induced transcription of protein-tyrosine-phosphatases in human astrocytoma cells

Interleukin-1 (IL-1) and Tumor Necrosis Factor-a (TNFalpha) are potent mediators of inflammatory reactions in the brain. Although much is known about the effects of IL-1 on expression of secretory proteins, few studies have addressed the question of a selective, IL-1-dependent expression of genes involved in neuromodulatory effects of inflammation. Protein-tyrosine-phosphatases (PTP's) have been shown to regulate signal transduction and adhesion processes in the developing nervous system. They are candidates for inflammation-induced neuromodulation. Therefore, we investigated if IL-1 regulates expression of PTP's. We applied a DNA-fingerprinting method based on the PCR-amplification of conserved domains of gene families and observed IL-1-dependent induction of two PTP's, cytoplasmic PTPvarepsilon and receptor-PTPgamma, RPTPgamma, in human U373-MG astrocytoma cells. Using Northern blot analysis, we confirmed this result and also show that in addition to IL-1, TNFalpha but not IL-6 induces the transcription of cytoplasmic PTPvarepsilon and RPTPgamma in human astrocytoma cells. Given the important role for PTP's in neuromodulatory aspects such as axonal guidance and neurite outgrowth, cytokine-induced induction of PTP's may play an important pathenogenic role in the development of chronic inflammatory diseases in the brain.

[Significance of hepatic cytochrome P450 enzymes for psychopharmacology]

Nearly all psychotropic drugs are metabolized by hepatic cytochrome P450-enzymes. In humans, there are 5 isoenzymes involved in this process. The activity of these enzymes can be modulated by a number of commonly used drugs, yielding potentially hazardous interactions. Most of the recently introduced selective serotonin reuptake inhibitors are potent inhibitors of cytochrome P450 enzymes. Thus, the plasma concentrations of tricyclic antidepressants or clozapine might be elevated into toxic levels. In contrast, carbamazepine induces most of the isoenzymes. This potentiates the elimination of tricyclics and antipsychotics and might cause a serious risk for the recurrence of depressive or psychotic symptoms. Moreover, 5-10% of the population are slow metabolizers of CYP2D6. This group is prone to increased adverse effects of moderately dosed medication. This review systematically points out the reported or predicted pharmacokinetic drug interactions in psychopharmacology focussing on clinical significance.

[Resistance of bovine and porcine Pasteurella to florfenicol and other antibiotics]

The resistance pattern of 221 (89 bovine, 132 porcine) pasteurella strains isolated in 1996 against 16 antibiotics or chemotherapeutics was determined by agar diffusion. Pasteurella haemolytica showed a higher level of resistance compared to Pasteurella multocida; porcine strains were more resistant than bovine strains. Over 90% of porcine Pasteurella multocida were sensible to penicillin G, ampicillin, cephalothin, polymyxin B, enrofloxacin, chloramphenicol and florfenicol. In addition, bovine strains were at least 90% sensible to oxacillin, erythromycin, gentamycin and sulfmethoxazole-trimethoprim. More than 90% of porcine Pasteurella haemolytica were classified as sensible to polymyxin B, enrofloxacin und florfenicol; bovine strains to cephalothin, neomycin und chloramphenicol as well. In 1996, 2 years after the chloramphenicol ban for food rendering animals, only 6.3% of bovine pasteurella strains proved to be resistant against chloramphenicol compared to a 16.27% fraction in 1994. The mean MIC-values of florfenicol against pasteurella spp. were nearly the same in bovine and porcine isolates with 0.53 microgram/ml and 0.52 microgram/ml respectively. Pasteurella haemolytica, however, showed higher MIC-values (0.68 microgram/ml in bovine, 0.70 microgram/ml in porcine isolates) than Pasteurella multocida with 0.47 microgram/ml in bovine and 0.51 microgram/ml in porcine strains. No isolate had a MIC of florfenicol greater than 1.0 microgram/ml, all pasteurella strains were classified sensible to florfenicol.

The importance of fiber biopersistence and lung dose in determining the chronic inhalation effects of X607, RCF1, and chrysotile asbestos in rats

The chronic inhalation effects in rats of X607 (a rapidly dissolving synthetic vitreous fiber) were compared with those previously reported for RCF1 (a refractory ceramic synthetic vitreous fiber) and chrysotile asbestos. Of primary concern was the importance of biopersistence as a mechanism of fiber toxicity. Fischer rats were exposed to fiber aerosol by nose-only inhalation for 6 h/day, 5 days/week for 2 years. X607 and RCF1 aerosols were similar in concentration (approximately 200 fibers/cc) and average dimensions (approximately 20 x 1 microns). Chrysotile aerosol was higher in concentration (10,600 fibers/cc) and an order of magnitude smaller in average dimensions. Lung fiber deposition after 6 h inhalation was greater for X607 than for RCF1. However, at later time points, fibers/lung (especially long fibers) were much lower for X607 than for RCF1, suggesting less biopersistence for X607. X607 was neither fibrogenic nor tumorigenic and induced only minimal lung cellularity that reversed after exposure was terminated. In contrast, RCF1 and chrysotile asbestos induced pulmonary fibrosis and thoracic neoplasms (chrysotile induced 32% more pulmonary neoplasms than RCF1). Lung deposition and fiber lengths did not explain the toxicologic differences between the three fibers. Fiber biodurability, including chemical and physical parameters, appears to be a major toxicologic determinant here. Chemical analysis of lung fibers revealed rapid leaching of X607 compared to RCF1. In in vitro dissolution tests, X607 underwent rapid dissolution (kdis = 990 ng/cm2/h) and transverse fragmentation, RCF1 dissolved slowly (kdis = 6 ng/cm2/h) and did not fragment, and chrysotile dissolution was negligible (< 0.1 ng/cm2/h).

Physiological characterisation of a pyruvate-carboxylase-negative Saccharomyces cerevisiae mutant in batch and chemostat cultures

A prototrophic pyruvate-carboxylase-negative (Pyc-) mutant was constructed by deleting the PYC1 and PYC2 genes in a CEN.PK strain of Saccharomyces cerevisiae. Its maximum specific growth rate on ethanol was identical to that of the isogenic wild type but it was unable to grow in batch cultures in glucose-ammonia media. Consistent with earlier reports, growth on glucose could be restored by supplying aspartate as a sole nitrogen source. Ethanol could not replace aspartate as a source of oxaloacetate in batch cultures. To investigate whether alleviation of glucose repression allowed expression of alternative pathways for oxaloacetate synthesis, the Pyc- strain and an isogenic wild-type strain were grown in aerobic carbon-limited chemostat cultures at a dilution rate of 0.10 h-1 on mixtures of glucose and ethanol. In such mixed-substrate chemostat cultures of the Pyc- strain, steady-state growth could only be obtained when ethanol contributed 30% or more of the substrate carbon in the feed. Attempts to further decrease the ethanol content of the feed invariably resulted in washout. In Pyc- as well as in wild-type cultures, levels of isocitrate lyase, malate synthase and phospho-enol-pyruvate carboxykinase in cell extracts decreased with a decreasing ethanol content in the feed. Nevertheless, at the lowest ethanol fraction that supported growth of the Pyc- mutant, activities of the glyoxylate cycle enzymes in cell extracts were still sufficient to meet the requirement for C4-compounds in biomass synthesis. This suggests that factors other than glucose repression of alternative routes for oxaloacetate synthesis prevent growth of Pyc- mutants on glucose.

Ventricular arrhythmia and torsade de pointe: dose limiting toxicities of the MDR-modulator S9788 in a phase I trial

BACKGROUND

S9788 is a triazineaminopiperidine derivative capable of reversing multidrug resistance (MDR) in vitro. In preclinical models S9788 was several fold more potent MDR inhibitor than verapamil or cyclosporine. At P-glycoprotein (Pgp) blocking concentrations, S9788 appeared to have only very little toxicity.

PATIENTS AND METHODS

In a two step phase I trial we treated 39 patients with refractory cancer with S9788 and bolus doxorubicin. The steps differed mainly in the S9788 infusion duration; in the first part 23 patients received the MDR-reversing drug S9788 over 30 minutes, in the second step of the study 16 patients were administered S9788 over 150 minutes. The doses of S9788 were escalated in cohorts of three patients up to a dose level (DL) of 96 mg/m2 on the 30 minutes infusion, and to 144 mg/m2 on the 150 minutes infusion. The pharmacokinetics of S9788 were determined.

RESULTS

With the 30-minute infusion schedule symptomatic cardiac arrhythmia were found to be dose limiting. In all patients at the highest DL transient cardiac repolarization prolongation with a long QT-interval on ECG was demonstrated. With the 150-minute administration schedule, S9788 could be escalated up to 144 mg/m2 without subjective toxicity. However, transient QT prolongation was present in all patients. A third degree AV-block and a QT increase of about 40% occurred at the highest DL. Asymptomatic torsade de pointe (DL 96 mg/m2) was demonstrated on Holter recording in one patient. Theses repolarization disturbances with QT increase were considered dose limiting toxicity and the trial was closed. No arrhythmia related death was noted. Pharmacokinetics were similar with both infusion schedules with a mean alpha half life of 11.3 and 13.2 minutes, for the 30-minute and 150-minute infusion, and a terminal half life of 13.5 and 15 hours, respectively. QTc prolongation duration appeared to be dose-dependent.

CONCLUSIONS

With the tested infusion schedules, cardiac toxicity, in particular AV-blocks and QT prolongation, leading to ventricular arrhythmia and torsade de pointe, are the dose limiting toxicities of S9788. Our experience together with the observation of asymptomatic torsade de pointe in two other phase 1 trials of S9788 infused over six hours precluded the further clinical development of S9788.