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Biomedical subjects

D Dive

Publications and source records attributed to D Dive.

At least 37 records · Page 2Linked to original sources
PubMed1992

Cerebral glucose utilization during stage 2 sleep in man.

Using [18F]fluorodeoxyglucose method and positron emission tomography, we performed paired determinations of the cerebral glucose utilization at one week intervals during sleep and wakefulness, in 12 young normal subjects. During 6 of 28 sleep runs, a stable stage 2 SWS was observed that fulfilled the steady-state conditions of the model. The cerebral glucose utilization during stage 2 SWS was lower than during wakefulness, but the variation did not significantly differ from zero (mean variation: -11.5 +/- 25.57%, P = 0.28). The analysis of 89 regions of interest showed that glucose metabolism differed significantly from that observed at wake in 6 brain regions, among them both thalamic nuclei. We conclude that the brain energy metabolism is not homogeneous throughout all the stages of non-REMS but decreases from stage 2 SWS to deep SWS; we suggest that a low thalamic glucose metabolism is a metabolic feature common to both stage 2 and deep SWS, reflecting the inhibitory processes observed in the thalamus during these stages of sleep. Stage 2 SWS might protect the stability of sleep by insulating the subject from the environment and might be a prerequisite to the full development of other phases of sleep, especially deep SWS.

Adult↗
PubMed1992

Endogenous superoxide dismutase activity in two Babesia species.

Babesia hylomysci and B. divergens were studied for superoxide dismutase (SOD) activity by enzyme assay and isoelectric focusing (IEF). In the two Babesia species, parasite-associated SOD is cyanide-insensitive and inhibited by H2O2, indicating that iron is the cofactor metal. Measurements of SOD activity from purified parasites show that the SOD activity detected in Babesia is, for the main part, due to an endogenous enzyme.

Animals↗
PubMed1992

Presence of human antibodies reacting with Candida albicans O-linked oligomannosides revealed by using an enzyme-linked immunosorbent assay and neoglycolipids.

In order to study the presence of antibodies directed against Candida albicans O-linked oligomannosides (oligomannosides O) in patient sera, we have developed an enzyme-linked immunosorbent assay (ELISA) involving neoglycolipids constructed with these residues (NGLO). Oligomannosides O released by mild alkaline degradation of the C. albicans cell wall phosphopeptidomannan (PPM) contained one to seven mannose residues, among which the quantitatively major components, mannobiose and mannotriose, were shown by 1H nuclear magnetic resonance to contain exclusively alpha (1-2) linkages. The pool of oligomannosides was converted to neoglycolipids by coupling them to 4-hexadecylaniline in an equimolar reaction checked by thin-layer chromatography. We have tested against these neoantigens, coated on ELISA plates, 15 pairs of sera corresponding to individual seroconversions observed in 15 patients during the course of a mycological and serological survey of candidiasis. For all patients, seroconversions resulted in an increased level of antibodies against NGLO. A significant correlation was observed between the results of ELISA-NGLO, ELISA involving the original PPM molecule, and routine antibody detection tests, indirect immunofluorescence assay, and cocounterimmunoelectrophoresis. These results therefore demonstrate the synthesis of human antibodies reactive with oligomannosides O constitutive of the C. albicans mannan molecule which have been previously described as exhibiting an inhibitory effect on human lymphocytic proliferation.

Antibodies, Fungal↗
PubMed1991

Stress protein synthesis, a potential toxicity marker in Escherichia coli.

Various chemicals were tested in Escherichia coli for the ability to modify the cellular growth rate and to induce the synthesis of heat shock and stress proteins. The toxicity of chemicals as observed by modification of the growth rate depended on concentration and duration of treatment, except for thiram. In this last case, no modification was observed up to a concentration of 10 micrograms.ml-1. In contrast, all toxicants tested enhanced the synthesis of heat shock and stress proteins. The stress response was similar but not identical. Heat shock proteins and stress proteins appear to be a more sensitive toxicity marker than growth inhibition. Suggestions for the use of stress proteins as a practical bioassay are made.

Bacterial Proteins↗
PubMed1990

Cerebral glucose utilization during sleep-wake cycle in man determined by positron emission tomography and [18F]2-fluoro-2-deoxy-D-glucose method.

Using the [18F]fluorodeoxyglucose method and positron emission tomography, we studied cerebral glucose utilization during sleep and wakefulness in 11 young normal subjects. Each of them was studied at least thrice: during wakefulness, slow wave sleep (SWS) and rapid eye movement sleep (REMS), at 1 week intervals. Four stage 3-4 SWS and 4 REMS fulfilled the steady state conditions of the model. The control population consisted of 9 normal age-matched subjects studied twice during wakefulness at, at least, 1 week intervals. Under these conditions, the average difference between the first and the second cerebral glucose metabolic rates (CMRGlu was: -7.91 +/- 15.46%, which does not differ significantly from zero (P = 0.13). During SWS, a significant decrease in CMRGlu was observed as compared to wakefulness (mean difference: -43.80 +/- 14.10%, P less than 0.01). All brain regions were equally affected but thalamic nuclei had significantly lower glucose utilization than the average cortex. During REMS, the CMRGlu were as high as during wakefulness (mean difference: 4.30 +/- 7.40%, P = 0.35). The metabolic pattern during REMS appeared more heterogeneous than at wake. An activation of left temporal and occipital areas is suggested. It is hypothetized that energy requirements for maintaining membrane polarity are reduced during SWS because of a decreased rate of synaptic events. During REMS, cerebral glucose utilization is similar to that of wakefulness, presumably because of reactivated neurotransmission and increased need for ion gradients maintenance.

Adult↗
PubMed1990

Quantitative analysis of 18/FDG-PET in the presurgical evaluation of patients suffering from refractory partial epilepsy. Comparison with CT, MRI, and combined subdural and depth. EEG.

CT, MRI, 18/FDG-PET and Depth. EEG, performed with subdural and depth electrodes were part of the presurgical evaluation in 22 patients. Statistical analysis of 18/FDG-PET was performed to compare cerebral utilization of glucose to that of normal age matched controls. The findings of CT, MRI, and quantitative analysis of PET are compared with those of ictal Depth. EEG. A positive correlation between CT and Depth. EEG was obtained in 23% of the patients and between MRI and Depth. EEG. in 50%. For both imaging techniques a negative correlation was found in 5%. Regional abnormalities were found with quantified PET in 95% of the patients and were concordant with Depth. EEG. for side of onset in 77% of the patients and for lobe of onset in 59%. A possibly false localising PET result for lobe of onset was obtained in 8 patients (36%). Limitations of PET were most apparent in patients with regional mesiolimbic or bilateral seizure onset. A favourable outcome of surgery was associated usually with positive convergence of both methods. PET may be a valuable contribution to the research and management of partial complex epilepsy, but at present cannot be considered a reliable alternative to invasive EEG methods in patients without clear unilateral focus localization on surface EEG.

Adolescent↗
PubMed1990

Reproducibility of cerebral glucose utilization measured by PET and the [18F]-2-fluoro-2-deoxy-d-glucose method in resting, healthy human subjects.

The stability of cerebral glucose utilization was examined in nine right-handed, healthy men (age, 24.88 +/- 2.93 years) using positron emission tomography (PET) and the [18F]-fluorodeoxglucose (FDG) method. Each study was run twice at intervals of 1-12 weeks with the subject at rest. The average cerebral metabolic rate for glucose (CMRGlu) was 5.40 +/- 0.71 mg/100 g per min (coefficient of variance, 13.08). The average intraindividual variation of CMRGlu was 7.91% +/- 15.46% (P = 0.13). Metabolic indices (MI: regional/mean cortical CMRGlu) were used to determine the regional cerebral metabolic distribution. The interindividual (coefficient of variance, 7.13) and intraindividual variabilities (average variation, -0.12% +/- 8.76%) of MI were smaller than those of metabolic rates. No reproducible significant asymmetry was observed. The FDG method used with subjects at rest thus yields low intraindividual variability of both cerebral glucose consumption and regional metabolic distribution, even at an interval of several weeks. Cerebral glucose utilization measured under such conditions may act as a reliable reference for determination of the influences of physiological (activation), pharmacological or pathological processes on cerebral glucose metabolism.

Adult↗
PubMed1990

Studies on synergistic toxic effects of copper and dithiocarbamate pesticides with the ciliate protozoan Colpidium campylum (Stokes).

The toxicity of seven dithiocarbamates and interactions occurring with copper were studied with the ciliate protozoan Colpidium campylum. No product was toxic at 0.1 mg liter-1. Thiram and mancozeb are the most toxic products (lethal at 1 mg liter-1) and ziram and propineb the least toxic. Concerning interactions with copper, no or slight interactions were observed with propineb and mancozeb, although a strong synergistic toxic effect was observed in a previous work with two structurally related products, maneb and zineb. On the contrary, the responses observed with alkyl-related dithiocarbamates (ferbam and ziram) and ethylene bis-related dithiocarbamates (nabam, thiram, and metiram) are in correlation with the results known in the literature. The synergistic toxic effect of copper and dithiocarbamates thus seems to be related mainly to the alkyl- or the ethylene bis-dithiocarbamate structure, but is not constant for molecules associated with metals (propineb, mancozeb, maneb, and zineb).

Animals↗
PubMed1990

Environmental and health risks of hydroquinone.

Hazard assessment of hydroquinone has been evaluated from bibliographical and original data on the physicochemical properties, the environmental behavior, and the biological effects of this aromatic compound. Hydroquinone, which is produced in large amounts and widely used, must be considered as an environmental contaminant. However, it is not persistent. The ecotoxicity of this molecule, which must be linked to its physicochemical properties, varies from species to species. Its acute and chronic toxicity toward higher terrestrial organisms is moderate. Hydroquinone is estimated to be nonmutagenic by the Ames test but induces chromosome aberrations or karyotypic effects in eucaryotic cells. Carcinogenic and teratogenic potentials have been at present inadequately studied. The study underlines the complementarity of QSAR models and experimental approaches when an attempt is made to obtain ecotoxicological profiles of pollutants.

Animals↗
PubMed1990

Interaction between components of electroplating industry wastes. Influence of the receiving water on the toxicity of the effluent.

A copper-cadmium-nickel-zinc mixture was assessed in seven different river waters to study metal toxicity to the ciliate protozoan Colpidium campylum, the interactions occurring between metals, and the influence of the receiving water on toxicity. In the range of concentrations tested, which are representative of electroplating industry wastes, the main part of the toxicity can be attributed to copper and to cadmium-copper synergy. A classification of waters, based on a principal component analysis (PCA), was used to examine the main parameters of the water, which can affect the toxicity of metal mixtures. It appears that the mineralization of the water, more than the total organic carbon (TOC), is an important parameter for the expression of toxicity. A strategy for the estimation of ecotoxicological hazard assessment, based on a simplified factorial experiment is proposed. It enables one to study, in a two-step bioassay, the toxicity of an effluent, the influence of river water on its toxicity, and the effects of contact time and dilution. By applying PCA to data from very different waters, it may be possible to estimate the ecotoxicological risk associated with the discharge of an effluent, on the basis of the chemistry of the receiving water.

Journal Article↗
PubMed1990

Identification of the side of epileptic focus with 123I-Iomazenil SPECT. A comparison with 18FDG-PET and ictal EEG findings in patients with medically intractable complex partial seizures.

123I-Iomazenil SPECT was performed in 17 patients who were considered candidates for surgery of epilepsy because of medically intractable complex partial seizures. In addition to this examination their presurgical evaluation consisted of long term ictal EEG-CCTV monitoring, CT, MRI and 18FDG PET. In eight patients intracranial ictal EEG recordings were performed. SPECT was assessed visually while PET data were analyzed quantitatively. Both SPECT and PET were compared to ictal EEG data and showed asymmetries in over 80% of patients in agreement with EEG findings. These three methods were in agreement in 65% of patients. SPECT showed abnormality contralateral to the EEG focus in one patient (6%) while PET always demonstrated ipsilateral dysfunction. It is concluded that 123I-Iomazenil SPECT may be considered a more economical and more widely available alternative to 18FDG PET in the presurgical evaluation of patients with medically intractable complex partial seizures. In this respect 123I-Iomazenil specifically reflects functional changes in the membranes of neurons while 18FDG is related to glucose metabolism not only of neurons but also of glial cells.

Adult↗
PubMed1978

Toxicity tests on ciliates--a short review.

A variety of methods has been proposed to study the toxicity of chemicals or polluted waters on ciliates as representative test organisms of the microfauna of aquatic ecosystems. These methods are based on morphological, ultrastructural, ethological, or metabolic criteria. The techniques proposed are mostly species dependent and so are their applications and restrictions. In view of a future standardization of protozoan toxicity tests a selection has been made by the authors on the basis of the applicability of the tests for routine analysis. The methods withheld are briefly described and comments are made on their advantages and limitations. The equipment involved, the operational complexity, and the accuracy of the results and their interpretation are listed in a synoptic table.

Animals↗
PubMedDate not supplied

Characterization of iron-dependent endogenous superoxide dismutase of Plasmodium falciparum.

Two main superoxide dismutase activities at isoelectric points (pI) 6.2 and 6.8 and two minor at pI 5.6 and 6.4 were found in crude extracts of Plasmodium falciparum. These activities were cyanide-resistant and hydrogen peroxide-sensitive and represented 20-30% of the total SOD activity found in the crude extract. A fragment of 424 bp, amplified from genomic DNA from P. falciparum, was cloned and sequenced. The deduced amino acid sequence identified this fragment as a coding region of an SOD gene. A cDNA corresponding to SOD was then isolated from a P. falciparum cDNA library and sequenced. The deduced amino acid sequence of SOD (197 aa) was compared with 32 known Feor Mn-SODs by the 'DARWIN' system. This analysis showed that the parasitic enzyme was related to typical Fe-SODs. The SOD subunit was purified and the N-terminal sequence, determined up to 29 residues, corresponded to that of cDNA isolated. The iron-dependent SOD activity found in Plasmodium falciparum represents the first level of the antioxidant defence system of the parasite. It is also the first SOD characterized in the parasitic Apicomplexa phylum whose sequence can be compared to equivalent iron-dependent enzymes known in other protozoa and bacteria.

Amino Acid Sequence↗