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Biomedical subjects

C Lacroix

Publications and source records attributed to C Lacroix.

At least 109 records · Page 6Linked to original sources
PubMed1996

Simple high-performance liquid chromatographic method for the quantitation of 5-fluorouracil in human plasma.

A simple, rapid, specific and sensitive high-performance liquid chromatography method has been developed for quantitation of 5-fluorouracil (5-FU) in human plasma. The method involves deproteinization of a small sample volume of plasma (150 microliters) followed by HPLC on a cation-exchange resin column, Aminex HPX-87H (300 x 7.8 mm I.D.), preceded by a similar guard cartridge with UV detection at 265 nm. This method allows a good separation of 5-FU with a retention time of 24 min and a detection limit at 25 ng/ml. The calibration curve was linear from 25 to 2000 ng/ml. The coefficient of variation was < or = 4.4% for within-day reproducibility and < or = 9.5% for day-to-day reproducibility.

Antimetabolites, Antineoplastic↗
PubMed1996

Increased serum levels of neuron-specific enolase in epileptic patients and after electroconvulsive therapy--a preliminary report.

Serum neuron-specific enolase (NSE) levels were studied by an enzymo-immunoassay method in 2 groups of patients: a group of epileptic patients, and a group of patients with refractory major depression after electroconvulsive therapy (ECT). In patients without organic neurological disease (n = 274) the mean serum NSE level (+/- S.D.) was 8.4 +/- 3.4 micrograms/l. No correlation with sex or age was observed. No significant difference was observed between epileptic patients without seizure or major electroencephalogram (EEG) abnormality, and a reference group. Significant increases were observed in 32 samples collected from patients with interictal EEG without spikes and waves before the 7th day after a seizure, in whom mean NSE was 21.5 +/- 9.4 micrograms/l, and in 26 samples from 4 patients without seizures but with spikes and waves in the interictal EEG, whose mean NSE was 20.6 +/- 11.5 micrograms/l. The increases of serum NSE levels in epileptic patients seem therefore to be linked to seizures and/or to EEG abnormalities. The consequences of these observations for the survey of epileptic patients, and for the diagnosis of cerebral tumors (mainly neuroblastoma) or for monitoring treatment after surgical resection, are discussed. In only 1 patient out of 6, an increase in serum NSE levels was observed with a peak about 12 h after ECT. No significant correlation with the ECT features (length of seizures, one- or two-sided electrodes) was observed.

Adult↗
PubMed1996

Contribution of nerve biopsy findings to the diagnosis of disabling neuropathy in the elderly. A retrospective review of 100 consecutive patients.

Peripheral neuropathy is an important factor of disability in the elderly. In order to learn more on the usefulness of intensive evaluation of patients over 65 years of age with subacute or chronic disabling peripheral neuropathy, we reviewed the clinical and nerve biopsy findings of the last 100 patients of this age group who suffered from a peripheral neuropathy severe enough to justify performance of a nerve biopsy for a diagnostic or prognostic purpose. Normal nerve biopsy findings led to the diagnosis of lower motor neuron disease in three patients and pointed to lesions of the spinal roots in six other patients. Necrotizing arteritis was demonstrated in the biopsy specimens of 23 patients, and non-necrotizing vasculitis in five. In five additional patients the diagnosis of vasculitic neuropathy was kept in spite of non-contributive biopsy findings. In two diabetic patients who had a multifocal neuropathy the biopsy also revealed the presence of vasculitis. Thus 35% of the patients included in this series had one form or another of vasculitic neuropathy. Fourteen patients had a chronic inflammatory demyelinating polyneuropathy. In 11 patients the neuropathy was associated with monoclonal gammopathy, which was benign in nine and associated with malignant plasma cell dyscrasia in two. Among the six patients with diabetes mellitus, two patients who presented with a multifocal neuropathy were found to have vasculitis in the nerve specimen; in the others the biopsy was performed because of uncommonly severe pains or motor involvement due to an extremely severe diabetic neuropathy. Six patients suffered from a long-lasting disability secondary to a drug-induced neuropathy. The remaining 15% had neuropathies of different origin, including amyloidosis, lepromatous leprosy, carcinomatous neuropathy and alcoholic neuropathy. Six patients had a mild, non-progressive or slowly progressive axonopathy of unknown origin, ageing of the peripheral nervous system may have played a role in its development. Our findings show that vasculitis is an important and treatable cause of disabling neuropathy in the elderly and that the proportion of patients with severe neuropathy of unknown origin is small.

Aged↗
PubMed1996

Pediocin 5 production and plasmid stability during continuous free and immobilized cell cultures of Pediococcus acidilactici UL5.

Continuous production of pediocin 5 from Pediococcus acidilactici UL5 was investigated in MRS medium at different pH and dilution rates during continuous free cell (FC) and immobilized cell (IC) fermentations. Pediocin 5 activity from FC operated at a dilution rate of 0.31 h-1 largely increased from 128 to 2048 AU mL-1 as pH decreased from 7.0 to 5.0. Pediocin 5 activity in IC at a dilution rate of 0.93 h-1 was much less affected by pH, varying from 256 AU mL-1 at pH 7.0 to 512 AU mL-1 at pH 5.0. At the optimum pH 5.0, the dilution rate greatly influenced pediocin 5 activity both in FC and IC. Pediocin 5 production during continuous FC culture decreased with time for all dilution rates tested except 0.31 h-1 and average activity over 144 h cultures reached a maximal value of 4915 AU mL-1 at a dilution rate of 0.26 h-1. For IC, pediocin 5 production was stable with time and increased with the dilution rate from 256 to 1024 AU mL-1 in the range of 0.47-2.28 h-1. Three Listeria strains were tested for their ability to screen low bacteriocin-producing variants (Bac+v) of Bac+ cells in FC and IC cultures by using a modified deferred antagonism method. Ten to 28% of Bac+v cells appeared after 144 h of FC cultures at dilution rates in the range 0.09-0.42 h-1 and pH control set points of 5.0-7.0 while almost no Bac+v cell was detected during 192 h IC culture in the same pH range and for dilution rates varying from 0.47 to 2.28 h-1. The Bac+v cells isolated produced eight- to 64-fold less pediocin 5 than the Bac+ cells. Although electrophoresis analysis showed no apparent difference in the plasmid profiles of Bac+v and Bac+ cells, the Bac- mutant obtained by acriflavine treatment had lost the pMJ5 plasmid encoding for bacteriocin production. The decreased quantity of plasmid DNA in Bac+v cells suggests that the decreased pediocin 5 activity of Bac+v cells resulted from a decrease in plasmid copy number.

Bacteriocins↗
PubMed1996

Effects of nifedipine and diltiazem on pharmacokinetics of cefpodoxime following its oral administration.

We compared the effects of nifedipine and diltiazem on the uptake of cefpodoxime proxetil (CP). The study was aimed at establishing the impact of increased mesenteric blood flow due to calcium channel blockers on passive transport. Twelve volunteers were given CP (200 mg) orally in a crossover design. The absorption, disposition, and elimination parameters of cefpodoxime were compared among the following three treatment groups: CP alone, CP following oral administration of diltiazem (60 mg), or CP following oral administration of nifedipine (20 mg). No statistically significant difference in pharmacokinetic parameters was observed between the three treatment groups.

Administration, Oral↗
PubMed1996

Extensive brain calcifications, leukodystrophy, and formation of parenchymal cysts: a new progressive disorder due to diffuse cerebral microangiopathy.

A new cerebral disorder, described in three unrelated children, has recognizable clinical, radiologic, and neuropathologic findings. The onset occurs from early infancy to adolescence with slowing of cognitive performance, rare convulsive seizures, and a mixture of extrapyramidal, cerebellar, and pyramidal signs. CT shows progressive calcifications in the basal and cerebellar gray nuclei and the central white matter. MRI reveals diffuse abnormal signals of the white matter on T2-weighted sequences. A special feature is the development of parenchymal cysts in the cerebellum and the supratentorial compartment, leading to compressive complications and surgical considerations. Neuropathologic examination of surgically removed pericystic samples reveals angiomatous-like rearrangements of the microvessels, together with degenerative secondary changes of other cellular elements. Both the anatomic findings and the course of the disease suggest a constitutional, diffuse cerebral microangiopathy resulting in microcystic, then macrocystic, parenchymal degeneration.

Brain Diseases↗
PubMed1995

Assay of urinary free and conjugated 3-methoxy-4-hydroxyphenylethyleneglycol by high-performance liquid chromatography with amperometric detection.

The aim of this study was to develop an analytical method for free and conjugated 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) in urine. After hydrolysis of the conjugated forms, the urinary MHPG was purified by solid-phase extraction on anion exchanger and eluted with a water-methanol (1:1, v/v) mixture. After addition of ethyl acetate to the eluate and back-extraction into acetic acid, the aqueous phase was separated on a C18 column by HPLC and detected amperometrically. The results obtained from forty healthy human subjects were compared with the literature values. The precision and accuracy of the assay were studied using 4-methoxy-3-hydroxyphenylethyleneglycol (iso-MHPG) as internal standard.

Chromatography, High Pressure Liquid↗
PubMed1995

Peripheral neuropathy with necrotizing vasculitis in rheumatoid arthritis. A clinicopathologic and prognostic study of thirty-two patients.

OBJECTIVE: To examine the clinicopathologic features of the noncompressive neuropathies in rheumatoid arthritis (RA). METHODS: We studied 32 patients with RA and peripheral neuropathy whose nerve and/or muscle biopsy specimens exhibited necrotizing vasculitis. Morphologic analysis of nerve specimens included light and electron microscopy studies and teased fiber preparation. Survival was evaluated, and the prognostic values of clinical, biologic, and pathologic features were assessed by Cox proportional hazards model. A prognostic assessment based on the significant variables was devised to estimate the probability of survival of any individual patient. RESULTS: Epi- and/or perineurial vasculitis was observed with the same frequency in the 17 patients with sensory and motor deficit and the 15 patients with sensory neuropathies and was associated with axonal degeneration of an average of 77.7% of the nerve fibers. The mean followup was 7.2 years, and the overall survival rate at 5 years was 57%. A full prolonged remission of the vasculitis was observed in 53% of the patients; relapse occurred in 25%. The factors correlated with mortality, in decreasing order of significance, were clinical cutaneous vasculitis (P = 0.0003), neuropathy affecting 3 or 4 limbs (P = 0.03), and depressed level of C4 (P < 0.05). The prognostic assessment indicated a wide range of 5-year probabilities of survival, from < 1% to 93%. CONCLUSION: Necrotizing vasculitis is responsible for the different patterns of noncompressive neuropathies in RA, including mononeuritis multiplex and distal symmetric sensory or sensorimotor neuropathy. Cutaneous vasculitis, multifocal neuropathy, and depressed C4 level were the 3 independent variables which best predicted mortality. We propose a prognostic assessment according to these variables, to stratify patients to receive more aggressive or less aggressive therapy.

Adult↗
PubMed1995

Identification of new enzyme activities of several strains of Thermus species.

New thermostable enzyme activities of seven Thermus strains were compared using the API ZYM system. All the strains exhibited high levels of alpha- and beta-glycosidases, esterase (C4) and esterase-lipase (C8) activities intracellularly. Only T. thermophilus HB8 (ATCC 27634) showed alpha-glucosidase and esterase activities in the supernatant. According to the intensity of beta-galactosidase activity, Thermus strains were divided in three groups. Group 0, which showed a weak beta-galactosidase activity, included Thermus spp. ATCC 31674 (T351) and 27978 (X-1) as well as T. thermophilus ATCC 27634 (HB8). Group I which consisted of T. aquaticus ATCC 25104 (YT-1), ATCC 25105 (Y-VII-51B) and Thermus sp. ATCC 27737 (T2), had a specific activity of approximately 40.0 U mg-1 and galactose as inducer. T. aquaticus ATCC 31558 (group 2) was particularly effective for beta-galactosidase production (2840 U) with a specific activity of 98 U mg-1. For each strain, galactose (0.5%) was a better inducer of beta-galactosidase production than lactose (1%). The detection of beta-galactosidase activity was dependent on the derivative chromogenic substrates used (naphthyl or nitrophenol coupled to sugar). Oligosaccharides were synthesized from cellobiose, lactulose, maltose or lactose as substrates at high temperature in some strains of Thermus.

Esterases↗
PubMed1995

[Experimental models of toxoplasmosis. Pharmacological applications].

Toxoplasma gondii is an ubiquitous protozoan parasite causing severe or life-threatening infections in immunocompromised patients and in congenitally infected infants. Animal models have been extensively used to describe the pathology of infection and to identify new effective drugs for the treatment of congenital infections, chrorioretinitis and toxoplasmic encephalitis. Although inherent differences between man and animal can reduce the relevance of data obtained experimentally, animal models have greatly improved our knowledge on the various aspects of toxoplasmosis. Toxoplasma infection can be easily obtained in most laboratory animals, with exception of rats which are partially resistant. According to the strain used, the resulting infection may be acute, subacute or chronic, and can be monitored either by the survival of animals, the histopathological examination of lesions or, preferably, by titration of parasites in infected tissues using subinoculation to mice or tissue culture. This latter method has proved particularly useful to describe the kinetics of infection in host tissues and to assess the efficacy of drugs, according to their pharmacokinetics and tissue distribution. The relevance of results obtained in animal models of congenital toxoplasmosis and of chrorioretinitis is more questionable, due to the marked differences between the mode of infection in humans and in animals. Experiments performed in primates provided valuable informations for the management of therapy of congenital toxoplasmosis but were of limited interest for ocular toxoplasmosis. The pathogeny of toxoplasmic encephalitis is still poorly understood, and no experimental model is fully satisfactory to produce focal encephalitic lesions as observed in immunocompromised humans. Acute infections with highly virulent strains induce disseminated infection with major pulmonary and brain involvement, and thus can be used to assess the efficacity of drugs in these tissues. Direct inoculation of tachyzoites into brain tissue can induce focal encephalitis but this model is of difficult use for large scale studies. Although cellular immunity is mainly responsible for the control of toxoplasmosis at the chronic stage, administration of immunosuppressive drugs does not usually result in focal brain reactivation; such reactivation can only be obtained using antibodies against CD8 and CD4 T lymphocytes or interferon gamma. Another experimental approach is the use of genetically immunodeficient animals: these models are of limited interest for pharmacological research since infection of nude or T depleted mice usually results in a dissemination of infection; however, using these models it could be clearly demonstrated that immunity plays a major adjunctive role in the control of acute infection. Concurrent infections between viruses and parasites is a common feature in immunocompromised patients and especially during AIDS.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Characterization of diacetin B, a bacteriocin from Lactococcus lactis subsp. lactis bv. diacetylactis UL720.

Fourteen Lactococcus lactis strains showing inhibitory activity against Listeria innocua SICC 4202 were isolated from different French raw milks and raw milk cheeses and screened for bacteriocin production by the triple layer method under conditions that eliminate the effects of lactic acid and hydrogen peroxide. Three bacteriocinogenic strains (two Lactococcus lactis subsp. lactis bv. diacetylactis UL719 and UL720 and one Lactococcus lactis subsp. lactis UL730) were selected for their high capacity to inhibit the growth of various food pathogens, including Listeria monocytogenes, Staphylococcus aureus, and clostridial strains. The inhibitory compounds from these three strains are inactivated by selected proteases, indicating their protein nature. They retained their antibacterial activity after heat treatments of 100 degrees C for 60 min and 121 degrees C for 20 min, and in the pH range from 2 to 11. The bacteriocin diacetin B produced by strain UL720 has been purified by a pH-dependent adsorption-desorption procedure, followed by reverse-phase high performance liquid chromatography, with a yield of 1.25% of the original activity. Mass spectrometry analysis indicates that the pure peptide has a molecular mass of 4292.32 or 4490.28 Da, while amino acid sequencing allowed the identification of the primary structure of the bacteriocin composed of 37 amino acid residues. The structure of the peptide did not show similarity with other known bacteriocins from lactic acid bacteria.

Amino Acid Sequence↗
PubMed1995

Role of metformin accumulation in metformin-associated lactic acidosis.

OBJECTIVE: To investigate the role of metformin accumulation in the pathophysiology of metformin-associated lactic acidosis. RESEARCH DESIGN AND METHODS: We used high-performance liquid chromatography to measure plasma metformin concentrations in 14 patients who experienced lactic acidosis (pH < 7.35 and lactate concentration 5 > mmol/l) while receiving chronic metformin treatment. Their treatment was generally based on alkalinization and dialysis therapy. RESULTS: Clinical shock and/or evidence of tissue hypoxia was found in all patients with the exception of one who had a nonsteroidal anti-inflammatory drug-induced anuria. Ten patients had significant metformin accumulation (plasma metformin concentrations 4.1-84.9 mg/l, normal value 0.6 +/- 0.5 mg/l before drug intake), generally because of failure to withdraw metformin despite intercurrent pathological conditions affecting its renal elimination (serum creatinine concentrations ranging from 269 to 1,091 mumol/l). There was no metformin accumulation (plasma metformin 0.03-0.7 mg/l) in the four other patients, who had less severe renal failure (serum creatinine 140-349 mumol/l). The severity of the patient's general condition did not predict early hospital mortality (death before discharge from the intensive care unit) even in patients in shock. Whereas it was high in those without metformin accumulation (only 1 of 4 patients recovered), early hospital mortality was low in the 10 patients with metformin accumulation and was not related to its extent (3 patients died with end-stage hepatic failure or cardiac failure). Correlation studies showed a positive correlation between serum creatinine and plasma metformin and between plasma metformin and arterial lactate but, for the latter correlation, only in patients with metformin accumulation. CONCLUSION: Metformin-associated lactic acidosis is not necessarily due to metformin accumulation; true type B (aerobic) lactic acidosis, i.e., without an apparent associated hypoxic factor, seems exceptional. Neither the severity of the clinical picture nor the degree of metformin accumulation predicted survival; rather, the prognosis was dependent upon the severity of the associated pathological conditions.

Acidosis, Lactic↗