Compliance with good practice guidelines for the prevention of vascular access infections: the multi-centre PHYDEL survey in French haemodialysis units

BACKGROUND

French guidelines for the prevention of vascular access infections in a haemodialysis setting were released in 2005. Compliance with these guidelines is currently unknown. The aim of this study was to assess compliance with the guidelines for vascular access infection prevention in French haemodialysis units, and to describe the difficulties reported.

METHODS

A cross-sectional survey was conducted between March and December 2019 in 200 haemodialysis units in France, selected at random. Data were collected via questionnaire, completed by telephone interview with an infection control practitioner. A practice was deemed compliant when >85% of units declared that they always complied with the guidelines.

RESULTS

In total, 103 units (51.5%) agreed to participate. Most practices complied with the guidelines; however, some practices did not reach the 85% compliance threshold for working in pairs when connecting central venous catheter (CVC) lines, performing hand hygiene before disconnecting lines, rinsing antiseptic soap before painting CVC exit site or arteriovenous fistula (AVF) puncture site, allowing antiseptic paint to dry, handling CVC branches with antiseptic impregnated gauze, performing hand hygiene after AVF compression with gloves, wearing protective eyewear when connecting/disconnecting CVC or when puncturing AVF, and wearing a gown when puncturing AVF. The most frequently reported difficulties were understaffing, difficulties with skin preparation because of exit site skin damage, and lack of buttonhole technical expertise.

CONCLUSIONS

Despite good overall compliance, this survey highlights some shortcomings in compliance with infection prevention guidelines, which could be associated with either higher risk of vascular access infection or increased blood-borne virus transmission.

Lack of effect of a poster-based intervention to reduce the number of blood culture samples collected

OBJECTIVE

To reduce the number of blood culture samples collected.

PATIENTS AND METHOD

We performed a cluster randomized controlled trial in adult acute care, and subacute care and rehabilitation wards in a university hospital in France. A poster associating an image of eyes looking at the reader with a summary of blood culture sampling guidelines was displayed in hospital wards in the intervention group. The incidence rate of blood cultures per 1000 days during pre- and post-intervention periods was calculated.

RESULTS

Thirty-one wards participated in the study. The median difference in blood cultures/1000 days between periods was -1.863 [-11.941; 1.007] in the intervention group and -5.824 [-14.763; -2.217] in the control group (P=0.27).

CONCLUSION

The intervention did not show the expected effect, possibly due to the choice of blood cultures as a target of good practice, but also to confounding factors such as the stringent policy of decreasing unnecessary costly testing.

Localization of phosphodiesterase-4 isoforms in the medulla and nodose ganglion of the squirrel monkey

Pre-clinical and clinical studies are currently underway to evaluate the potential of phosphodiesterase-4 (PDE4) inhibitors for the treatment of chronic obstructive pulmonary disease and other inflammatory conditions of the airways. The most common side effect associated with this class of compounds is emesis. The squirrel monkey provides a model for evaluating the efficacy of PDE4 inhibitors and their emetic potential. The distribution of three PDE4 isoforms (A, C and D) has been investigated in the squirrel monkey medulla and nodose ganglion to determine which isoform(s) could be responsible for the emetic adverse effects. The distribution of PDE4 isoforms was delineated using immunohistochemistry with antibodies specific for PDE4A, PDE4C and PDE4D and by in situ hybridization with isoform-selective riboprobes. PDE4A was present in the medulla where expression was mostly restricted to glial cells and the vasculature. PDE4C was not detected in either the medulla or nodose ganglion. Finally, the PDE4D isoform was localized to neurons in the nodose ganglion and found through many structures of medulla including the area postrema, neurons of the nucleus tractus solitarius and locus coeruleus. These data are consistent with a role for PDE4D in the emetic response.

Moderate intake of n-3 fatty acids is associated with stable erythrocyte resistance to oxidative stress in hypertriglyceridemic subjects

BACKGROUND

The important triacylglycerol-lowering capacity of n-3 fatty acids is counterbalanced by their inherent sensitivity to oxidation. Inconsistent results about the latter have been reported in hypertriglyceridemic individuals. After incorporation into cell membranes, n-3 fatty acids may alter membrane-related functions. In view of the distinct composition of hypertriglyceridemic membranes and the prooxidant status in this condition, it can be surmised that cell enrichment with the oxidizable n-3 fatty acids will be associated with an increased hemolytic process.

OBJECTIVE

We sought to evaluate the effect of fish oil consumption on n-3 fatty acid incorporation into erythrocyte membranes and subsequent ex vivo oxidative-stress-induced hemolysis in normotriglyceridemic and hypertriglyceridemic subjects.

DESIGN

Sixteen normotriglyceridemic and 12 hypertriglyceridemic subjects were given 6 g fish oil/d for 8 wk. Blood samples were collected before and 4 and 8 wk after treatment. Resistance to 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced hemolysis was assayed in fresh erythrocyte suspensions, and erythrocyte samples were stored at -70 degrees C for later analysis of cholesterol, hemoglobin, fatty acids, vitamin E, and glutathione peroxidase activity.

RESULTS

Fish oil supplementation induced n-3 fatty acid incorporation in normotriglyceridemic and hypertriglyceridemic erythrocyte membranes without decreasing their resistance to AAPH. n-3 Fatty acids significantly protected normotriglyceridemic but not hypertriglyceridemic erythrocytes against hemolysis. In normotriglyceridemic subjects only, the higher resistance to hemolysis correlated with changes in cell vitamin E.

CONCLUSION

Although they exhibit a high susceptibility to oxidation, n-3 fatty acids may preserve membrane integrity and represent an added benefit in the treatment of hypertriglyceridemic patients.

Characterization of CHO-K1 cells stably expressing PDE-IV enzymes. Whole-cell cAMP determinations vs broken-cell enzymatic assays

A CHO-K1 cell line stably expressing a recombinant full-length human PDE-IVa (HSPDE4A4B) enzyme was established under hygromycin B selection. Full-length expression of the protein was determined by Western blot analysis, which revealed the presence of a 125-kDa immunoreactive band using rabbit anti-PDE-IVa antibodies. The potency of inhibitor compounds was examined by their ability to increase cAMP in the whole-cell, and by their ability to inhibit cAMP hydrolysis in a 100,000 g supernatant (soluble enzyme preparation) obtained from the same cell line. Inhibition of the expressed PDE-IVa activity by selective PDE-IV inhibitors--(R) and (S)-rolipram, RS 14203, and CDP 840--at 100 nM substrate demonstrated that RS 14203 and CDP 840 were the most potent with IC50 = 9 nM, followed by (R)-rolipram (IC50 = 110 nM) and (S)-rolipram (IC50 = 420 nM). The rank order of potencies of the inhibitors in elevating cAMP in the whole-cell assay was quite different from that on the soluble enzyme. RS 14203 was still the most potent compound in elevating cAMP. Moreover, the relative rank order of potencies between CDP 840 and (R)-rolipram changed dramatically, such that (R)-rolipram was more potent than CDP 840 = (S)-rolipram. An apparent 30-fold stereoselectivity between (R)- and (S)-rolipram was also noted. The whole-cell rank order of potencies was also maintained when PKA activity ratios were measured in place of cAMP levels. The ability of the compounds to elevate cAMP in the stable CHO-K1 cells appeared to track better with the potency of the compounds against the high-affinity (Sr) conformer of the enzyme rather than the low-affinity catalytic state.

Airway responsiveness and bronchial-wall thickness in asthma with or without fixed airflow obstruction

To determine whether asthmatic subjects have an increase in airway wall thickness that could enhance airway narrowing during bronchoprovocation, we examined the relationship between airway responsiveness and bronchial wall thickness measured by high-resolution computed tomography (HRCT). We studied 24 nonsmokers with asthma, of whom 13 had a fixed component of airflow obstruction (Group 1) and 11 had an optimal FEV1 of 80% or more of the predicted value (Group 2). These subjects were compared with a control group of 10 nonasthmatic subjects (Group 3). Measurements were taken of each subject's expiratory flows, bronchodilator response, lung volumes, and methacholine responsiveness. All subjects used an inhaled beta 2-agonist on demand, and 19 also used inhaled steroids (13 in a Group 1 and six in Group 2). HRCT sections were obtained at the top and base of the lung and at the level of the intermediary bronchus (IB), although only this last level was found adequate for analysis. The ratio of IB wall thickness to outer diameter (T/D) showed a negative relationship with the outer diameter in Group 1 only. The mean T/D ratio of IB was not significantly different in Groups 1, 2, and 3, with respective values of 0.16 +/- 0.01, 0.15 +/- 0.01, and 0.18 +/- 0.01 at TLC, and 0.16 +/- 0.01, 0.20 +/- 0.01, and 0.19 +/- 0.01 at FRC. In subjects with a fixed component of airflow obstruction, the thicker the airway wall in relation to its diameter, the lower was the PC20 for methacholine. This was not observed in the other study groups. No correlation was found between the T/D ratio and baseline FEV1.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dexamethasone on antigen-induced high molecular weight glycoconjugate secretion in allergic guinea pigs

The ovalbumin-sensitized guinea pig is commonly used as a small animal model of allergic asthma. This animal model exhibits many of the hallmark characteristics observed in patients afflicted with asthma including nonspecific airway hyperreactivity, airway eosinophilia, early and late phase bronchoconstriction, and plasma extravasation into the airways. In addition, mucous hypersecretion in the airways of asthmatic patients is thought to be responsible for the plugging of distal airways and to contribute to the morbidity and mortality associated with the disease process. In this study we examined whether the allergic guinea pig model exhibits an increase in airway high molecular weight glycoconjugate (HMWG) secretion in response to an antigen challenge and whether dexamethasone exerts any modulatory effects upon the response. Ovalbumin (OVA) -sensitized guinea pigs were challenged with OVA 2 wk following the initial exposure. Trachobronchoalveolar lavages (TBAL) were performed, and the samples were assayed for total eosinophil cell number, eosinophil peroxidase activity (EPO), and both acidic and neutral HMWG content. Morphometric analysis of mucous-containing cells was also performed on tissue sections prepared from the trachea, mainstem bronchus, and three lobes of the left lung. Within 24 h of an antigen challenge, TBAL samples obtained from the allergic guinea pigs exhibited increases in eosinophil cell number, measured EPO enzyme activity, and acidic HMWG content compared to TBAL samples prepared from vehicle-exposed animals. These antigen-induced changes were dependent on the concentration of aerosolized OVA administered. Exposing the animals to 0.3% OVA provoked a 6.23-fold increase in airway eosinophils, 15-fold elevation in TBAL EPO enzyme activity, and 175% increase in TBAL acidic HMWG. No significant changes in TBAL neutral HMWG were measured. The changes in measured EPO activity correlated with the levels of acidic HMWG found in the TBAL samples (r = 0.73, P < or = 0.001). The measured increase in TBAL acidic HMWG was time dependent and was found to be maximal at 2 h post-antigen challenge. Morphometric analysis of Alcian blue (pH 2.5) -stained airway sections showed a decline in stored mucosubstances following the antigen exposure, supporting the notion that the allergic guinea pig model exhibits a mucosecretory component. Pretreating the animals with dexamethasone attenuated the antigen-induced release of HMWG and changes in measured EPO activity. In conclusion, these data indicate that the allergic guinea pig may be a useful model for examining the neural and cellular mechanisms underlying mucus hypersecretion in individuals afflicted with bronchial asthma.

Increased airway responsiveness to inhaled methacholine in a rat model of chronic bronchitis

Chronic exposure of rats to high concentrations of SO2 gas causes pathologic changes in airway similar to those seen in human chronic bronchitis. The purpose of this study was to examine the pulmonary mechanical correlates of these changes and to quantify the extent of mucous hypersecretion by measuring changes in mucous glycoproteins. Female Sprague-Dawley rats were exposed to 250 ppm SO2 gas, 5 h/d, 5 d/wk, for a period of 4 wk. Control rats were exposed to air only. On the day after the last SO2 exposure, rats were anesthetized, instrumented for the measurement of pulmonary resistance (RL) and dynamic compliance (Cdyn), and ventilated. Chronic SO2 exposure caused a small but significant increase in RL and decrease in Cdyn. Airway responsiveness to inhaled aerosolized methacholine was increased in SO2-exposed rats, as indicated by approximately 6.6- and 4.6-fold decreases respectively, in the doses of inhaled methacholine required to double RL or decrease Cdyn to 50% of baseline. SO2 exposure had no effect on the contractile response of the trachea measured in vitro. Tracheae and lungs from SO2-exposed animals exhibited 140 and 535% increases in measured neutral mucous glycoproteins, respectively, and 33 and 37% increases in acid glycoproteins. Our results indicate that this animal model of chronic bronchitis mimics the mucous hypersecretion, airway obstruction, and increased airway responsiveness observed in human bronchitis and may allow us to begin to probe their mechanistic basis.

Hyperplastic effects of aerosolized sodium metabisulfite on rat airway mucus-secretory epithelial cells

The ability of aerosolized sodium metabisulfite to induce hypertrophic and hyperplastic changes in rat airway secretory epithelial cells was investigated. A 10% solution of sodium metabisulfite was aerosolized into a Plexiglas exposure chamber, using an ultrasonic humidifier. The level of SO2 gas generated by this apparatus was measured to be 500 ppm. Measured levels of neutral and acidic mucous glycoproteins in extracts from tracheal and lung tissue were used as indices of hypertrophic (increases in mucus content per cell) and hyperplastic (increased numbers of cells containing mucus per gram of tissue) changes occurring in mucus-secreting cells of the airways. Exposing rats to sodium metabisulfite for 3 weeks resulted in profound increases in total neutral mucous glycoproteins found in tracheal and lung tissue (6.2-fold and 10.1-fold, respectively), compared with the H2O-treated counterparts. Total acidic mucous glycoproteins were significantly elevated in lung tissue only (13.5-fold). In addition, neutral and acidic mucous glycoproteins were elevated 20-fold and 9-fold, respectively, in bronchoalveolar lavage samples prepared from sodium metabisulfite exposed animals. These results indicate that aerosolized sodium metabisulfite may be a useful agent for developing small animal models of mucus hypersecretion.

Influence of probucol on enhanced LDL oxidation after fish oil treatment of hypertriglyceridemic patients

The susceptibility of low-density lipoprotein (LDL) to oxidation was studied in hypertriglyceridemic men (5 with type III and 5 with type IV) at baseline on a low-saturated-fat, low-cholesterol diet, after 6 weeks of dietary supplementation with fish oil (Promega, 12 g/d), and after 6 weeks of fish oil combined with probucol (500 mg BID). The relative content of n-3 polyunsaturated fatty acids in plasma and LDL was increased during the two treatment periods, and a low alpha-tocopherol to n-3 polyunsaturated fatty acids ratio was observed. Plasma thiobarbituric acid-reactive substances (TBARS) levels were unchanged after 6 weeks of fish oil, but the ratio of lipid peroxides to the reduced triglyceride (TG) levels (MDA:TG) was significantly higher (P < .01). Addition of probucol lowered both absolute levels of TBARS (P < .01) and the MDA to TG ratio (P < .001). The susceptibility of LDL to Cu(2+)-catalyzed oxidation was evaluated over a 5-hour time course by determining TBARS formation, free amino group levels, and changes in LDL electrophoretic mobility. TBARS levels that were higher in native LDL (1.019 < d < 1.050 g/mL) after 6 weeks of fish oil than at baseline (P < .01) were reduced 52.3 +/- 11.3% by the addition of probucol (P < .001). With fish oil alone, TBARS production after exposure of LDL to Cu2+ for 5 hours was increased 17.0 +/- 5.8% compared with corresponding baseline values (P < .001), whereas a 64.1 +/- 14.3% reduction from the previous period was observed with fish oil + probucol (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution and threshold expression of the tRNA(Lys) mutation in skeletal muscle of patients with myoclonic epilepsy and ragged-red fibers (MERRF)

We investigated the distribution and expression of mutant mtDNAs carrying the A-to-G mutation at position 8344 in the tRNA(Lys) gene in the skeletal muscle of four patients with myoclonus epilepsy and ragged-red fibers (MERRF). The proportion of mutant genomes was greater than 80% of total mtDNAs in muscle samples of all patients and was associated with a decrease in the activity of cytochrome c oxidase (COX). The vast majority of myoblasts, cloned from the satellite-cell population in the same muscles, were homoplasmic for the mutation. The overall proportion of mutant mtDNAs in this population was similar to that in differentiated muscle, suggesting that the ratio of mutant to wild-type mtDNAs in skeletal muscle is determined either in the ovum or during early development and changes little with age. Translation of all mtDNA-encoded genes was severely depressed in homoplasmic mutant myoblast clones but not in heteroplasmic or wild-type clones. The threshold for biochemical expression of the mutation was determined in heteroplasmic myotubes formed by fusion of different proportions of mutant and wild-type myoblasts. The magnitude of the decrease in translation in myotubes containing mutant mtDNAs was protein specific. Complex I and IV subunits were more affected than complex V subunits, and there was a rough correlation with both protein size and number of lysine residues. Approximately 15% wild-type mtDNAs restored translation and COX activity to near normal levels. These results show that the A-to-G substitution in tRNA(Lys) is a functionally recessive mutation that can be rescued by intraorganellar complementation with a small proportion of wild-type mtDNAs and explain the steep threshold for expression of the MERRF clinical phenotype.

Phenotypic heterogeneity associated with defective apolipoprotein B-100 and occurrence of the familial hypercholesterolemia phenotype in the absence of an LDL-receptor defect within a Canadian kindred

Of 163 individuals with a diagnosis of heterozygous familial hypercholesterolemia (FH), only one subject was found to be positive for familial defective apo B-100 (FDB). The eight-member kindred ascertained through this subject who presented with both a clinical phenotype of FH and the FDB apo B-100 (Arg3500----Gln) mutation was studied. Plasma lipid and lipoprotein profiles, apo E phenotypes, apo B gene markers at the 3' hypervariable region and LDL-receptor haplotypes (ApaLI, PvuII, NcoI), were determined, together with LDL-receptor activity on freshly isolated blood lymphocytes. The FDB mutation, present in four relatives, was associated with three different phenotypes: FH and severe hypercholesterolemia, moderate hypercholesterolemia and normolipidemia. The FH phenotype occurred in the absence of any functional LDL-receptor defect. In homozygotes for the absence of the PvuII cutting site who had the apo B mutation, LDL-cholesterol levels were low in the presence of the apo E3/2 phenotype and high in the presence of the apo E4/4 phenotype. None of the major known environmental influences accounted for the wide range of variation in LDL-cholesterol among the affected members. Further observations in the spouse and offspring of the normolipidemic FDB subject confirmed the association of apo E4, the FDB mutation and the PvuII(-/-) genotype with high cholesterol levels. It is concluded that the phenotypic expression of the FDB mutation may vary widely as a function of the genetic environment within a family.(ABSTRACT TRUNCATED AT 250 WORDS)

Fish oil supplementation reduces beta-very low density lipoprotein in type III dysbetalipoproteinemia

beta-Very low density lipoproteins (beta-VLDLs) are atherogenic, cholesterol-rich chylomicron and VLDL remnants that accumulate in the plasma of type III dysbetalipoproteinemic subjects. To evaluate the effect of fish oil supplementation on plasma beta-VLDL concentrations, we compared the lipid and lipoprotein responses in nine type III and nine type IV hyperlipidemic subjects. Each individual received 6 g/day omega-3 fatty acids for 12 weeks. Before treatment, the mean total cholesterol, total triglyceride, VLDL triglyceride, low density lipoprotein (LDL) cholesterol, and high density lipoprotein (HDL) cholesterol levels were not different between groups. Conversely, VLDL cholesterol, intermediate density lipoprotein (IDL) cholesterol, and IDL triglycerides were higher in type III than in type IV subjects. Fish oil supplementation was associated with significantly lower levels of cholesterol (-50%), triglycerides (-50%), and apolipoprotein B (-50%) in the d less than 1.006 g/ml ultracentrifugation plasma fraction in both groups, compatible with a reduction in VLDL in type III and type IV subjects, and in beta-VLDL in type III subjects. This finding was confirmed by analysis of the plasma zonal ultracentrifugation profile and the agarose gel electrophoretic pattern of lipoproteins, which showed a reduction in but not a disappearance of remnant particles, suggesting that not all beta-VLDL had been cleared after treatment. The levels of IDL cholesterol and IDL triglycerides (1.006 less than d less than 1.019 g/ml) were not affected in either group. Initially low LDL cholesterol (1.019 less than d less than 1.063 g/ml) and HDL cholesterol levels rose significantly in both groups. In type III hyperlipidemics, all LDL cholesterol values remained below 120 mg/dl, whereas they were higher than 150 mg/dl after treatment in two individuals with type IV hyperlipidemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipoprotein composition changes induced by fenofibrate in dysbetalipoproteinemia type III

Fenofibrate (300 mg daily) was given to 9 subjects (7 men, 2 women) with dysbetalipoproteinemia type III. The treatment brought about important plasma level reductions in cholesterol (-35%), triglycerides (-56%), VLDL-cholesterol (-63%) and VLDL-triglycerides (-59%). The VLDL-C/TG ratio, which was 0.40 before treatment, was 0.30 after 4 weeks of fenofibrate, still suggestive of type III. LDL-C, when measured by conventional methods, was unchanged but isolation of the IDL (1.006-1.019 g/ml) fraction from the 1.006 g/ml infranatant revealed that true LDL-C levels actually increased in 6 individuals while IDL-C decreased considerably. The total HDL-C increase was mostly due to a 33% HDL3-C change. Apolipoprotein levels were considerably modified, notably apo B, C-III and E which were decreased, as well as the lipoprotein particles containing combinations of these apolipoproteins, namely LpE:B and LpC-III:B. Apo A-I was slightly modified as LpA-I: A-II particle levels increased and LpA-I decreased. There were marked compositional modifications of apo B-containing lipoproteins which corresponded to changes of the whole lipoprotein profile. Some abnormal classes of lipoproteins (e.g., beta-VLDL, dense LDL), characteristic of this disease, tended to disappear and were in some cases replaced by material of different size and density.

Mistranslation in twelve Escherichia coli ribosomal proteins. Cysteine misincorporation at neutral amino acid residues other than tryptophan

The misincorporation of cysteine (codon: UGU/C) into twelve ribosomal proteins devoid of cysteine has been studied. Although it is generally assumed that cysteine is misincorporated at arginine and tryptophan residues (codons: CGU/U and UGG respectively), our results are consistent with the idea that cysteine is also misincorporated at phenylalanine residues (codon: UUU/C) through a second-position C:U mismatch. Cysteine was found in ribosomal proteins L29, L32/L33 and S10, under conditions where only its misincorporation at neutral residues was measured. Since these proteins contain no tryptophan, the date imply that cysteine has replaced a neutral amino acid other than tryptophan. Because there was a statistically significant correlation between the total level of cysteine in the twelve proteins under study and their content of phenylalanine and arginine residues, we conclude that there is a likelihood of cysteine misincorporation at phenylalanine residues, in addition to its misincorporation at arginine and tryptophan residues. Our measurements are consistent with the existence of a cluster of ribosomal proteins having an average mistranslation frequency of 2.5 X 10(-4)/residue and another having an average mistranslation frequency of 10(-3)/residue. There was three times less cysteine misincorporated into ribosomal protein L1 than into L7/L12, although the L1 mRNA contains eleven CGU/C codons and four UUU/C codons while the L7/L12 mRNA contains only one arginine and two phenylalanine codons (both proteins are free of tryptophan). Furthermore, the mRNAs for both L1 and L7/L12 contain a CGU codon located in the context GUA-codon-GG and there was as much cysteine incorporated at this codon in L7/L12 [Bouadloun, F., Donner, D. and Kurland, C.G. (1983) EMBO J. 2, 1351-1356] than in the whole of L1. This suggests that, relatively speaking, little cysteine is to be found at the phenylalanine and the other ten arginine positions of L1 and that the phenylalanine residues of L7/L12 are particularly error-prone.

Effects of amino acids on the transport and cytotoxicity of melphalan by human bone marrow cells and human tumor cells

In human tumor cells freshly obtained from patients with breast cancer, ovarian cancer, or adenocarcinoma of unknown etiology and in normal human bone marrow cells, the cell-to-medium ratio (intracellular/extracellular concentration) in vitro of 5.42 microM melphalan rose rapidly to levels of 6-17 after 35 min at 37 degrees C in Dulbecco's phosphate-buffered saline containing bovine serum albumin and glucose. Only patient C (breast cancer) had received chemotherapy. In all cells studied, L amino acids (1 mM) such as leucine, glutamine, tyrosine, and methionine reduced the cell-to-medium ratio of melphalan at 3 and 35 min. There was a good correlation between the reduction of melphalan transport at 35 min in the heterogeneous nucleated bone marrow cell population by amino acids and their effect on melphalan cytotoxicity in the CFU-C system. Aminoisobutyric acid (A1B), a specific substrate of the A system of amino acid transport, at a concentration between 1 and 50 mM had no significant effect on melphalan uptake at 3 min in any of the human cells studied except those of patient C. At 35 min A1B (10 or 50 mM) significantly reduced the intracellular melphalan concentration in normal bone marrow cells and tumor cells from patients B and C. At 2 mM, 2-aminobicyclo-(2, 2,1)-heptane-2-carboxylic acid (BCH), a specific substrate of the L system of amino acid transport, reduced the cell-to-medium ratio to 70% of control at 3 and 35 min in human bone marrow cells. In tumor cells from patients A, B, D, and F, 2 mM BCH had no significant effect on melphalan uptake at 3 min; it slightly decreased uptake in tumor cells from patient C. At 35 min, 2 mM BCH significantly reduced melphalan transport in tumor cells from patients C and F only. The lack of a BCH-suppressible component to melphalan uptake into human tumor cells freshly obtained from previously untreated patients contrasts with the presence of this component in murine L1210 leukemia cells, murine P388 leukemia cells, and human tumor cell lines. This suggests that minor differences in melphalan transport may exist amongst species and also between human tumor cells which are freshly obtained and cell lines maintained in culture.

Plasma cholesteryl sulfate in Friedreich's ataxia

Alteration of membrane fluidity and anomalies of membrane structural proteins have been suspected in Friedreich's ataxia. Plasma lecithin:cholesterol acyltransferase (LCAT) activity is also lowered in this disease, presumably because of a substrate effect. The membrane-stabilizing effect of cholesteryl sulfate (CS) and its inhibitory effect on LCAT activity prompted us to measure this substance in the plasma of Friedreich's ataxia patients as well as in normal subjects and in patients with Charlevoix-Saguenay disease. Plasma cholesteryl sulfate concentrations were significantly higher in Friedreich's ataxia, with levels above the upper limit of normal in nearly half of the cases. This increase was unrelated to age, sex or plasma cholesterol levels, but closely associated with the severity of the disease and thus considered to be secondary. A similar phenomenon (except the association with severity) was observed in Charlevoix-Saguenay ataxia. Levels also tended to be higher in first-degree relatives of Friedreich cases. The significance of these findings is discussed in the light of recent knowledge and experimental data obtained in this laboratory on rats made deficient in essential fatty acids. The highest concentrations of CS observed in Friedreich's ataxia (1097 micrograms/dL, 6 times the normal mean) was only 25% as high as the concentrations reported to inhibit LCAT activity.

Pharmacokinetics of clofibrate in familial hypercholesterolemia

Some patients with familial hypercholesterolemia (FHC, type II) are highly responsive to the cholesterol-lowering effect of clofibrate, while others are not only resistant to this effect but may even show an increase in plasma beta-lipoproteins. In an attempt to find an explanation for these striking differences, we have studied the pharmacokinetics of clofibrate in FHC patients at both extremes of responsiveness. The results disclosed several major differences between the two groups. Plasma clofibric acid (CPIB) measured during the chronic administration of the drug was significantly higher in the responders than in the non-responders, whether all patients in each group or only those with tendon xanthomas were considered. Plasma CPIB concentrations were negatively correlated with body weight in the responders but not in CPIB-resistant patients. They were also inversely proportional to decreases in plasma beta-lipoprotein cholesterol after chronic clofibrate administration in the responsive group, but directly proportional to increases in the non-responders. Increasing the dose of clofibrate from 2 to 3 g/day in CPIB-resistant patients always resulted in an increase in plasma CPIB levels, but this was followed in some patients by a decrease and in others by an increase in plasma beta-lipoprotein cholesterol concentrations, so that the overall effect was not statistically significant. The half-life of plasma CPIB was measured over 48 h after a single 1-g dose of clofibrate in patients who had not received this drug for at least 3 weeks. Half-life was significantly longer in the responsive patients. In addition, the bioavailability and the rate of absorption of clofibrate tended to be higher in this group than in the resistant patients. We suspect that both groups differ not only in the metabolic handling of clofibrate but also in some aspect of their beta-lipoprotein cholesterol metabolism.