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Biomedical subjects

P Hubert

Publications and source records attributed to P Hubert.

At least 163 records · Page 9Linked to original sources
PubMed1993

[Toxicity of fire smoke. Apropos of 2 pediatric cases].

BACKGROUND: Smoke inhalation is one of the main cause of respiratory problems in fire-related accidents. CASE REPORTS: Case 1. A girl, aged 11 months, was found in her apartment 15 minutes after the start of accidental fire. She was in a stage I coma with cyanosis and covered with soot. She was placed on oxygen and given hydroxocobalamin. Aggravation of respiratory problems led to mechanical ventilation. Tracheobronchoscopy showed deposits of soots with moderate burnt lesions. Intubation was discontinued 12 hours later, but the child remained oxygen-dependent, with persistent tracheobronchitis, despite steroid therapy for 2 weeks. Case 2. Another girl, aged 4 1/2 years, was found in the same room as the preceding patient. She was also covered with soot, and in a coma (Glascow score = 11). She was intubated, placed on mechanical ventilation, and given hydroxocobalamin. Tracheobronchoscopy revealed similar changes to those seen in the preceding patient. Despite repeated tracheobronchial washings and steroid therapy, respiratory problems persisted with thoracic distension and pneumothorax. Mechanical ventilation was discontinued 16 days later but at 5 1/2 years, this child still has dyspnea and has developed bronchiectasis. CONCLUSION: Bronchopulmonary changes can be a severe complication of smoke inhalation during fires, and require early mechanical ventilation and repeated tracheobronchoscopy.

Carbon Monoxide Poisoning↗
PubMed1993

[Contribution of imaging techniques in acute neonatal renal pathology].

Ultrasound is the first imaging modality used to evaluate acute renal disease in neonates. Normal findings and abnormalities seen in venous or arterial thrombosis, hemodynamic shock, or sepsis are reviewed. Transient changes due to intoxications, tubular disorders, or congenital nephrotic syndrome are considerably less common.

Acute Disease↗
PubMed1993

[Antenatal form of Bartter's syndrome].

Six cases of tubular disorder of antenatal onset responsible for biological manifestations characteristic of Bartter syndrome and severe hypercalciuria are reported. In all six cases, severe hydramnios occurred during pregnancy between the 26th and 28th week after the last menstrual period. All six patients were born prematurely; gestational age ranged from 20 to 35 weeks. Major polyuria with dehydration occurred immediately after birth. The amounts of water and sodium needed to compensate urinary losses ranged from 280 to 370 ml/kg/day and 25 to 43 mmol/kg/d, respectively, during the first two postnatal months. Decreased serum potassium levels and increased plasma levels of renin and aldosterone were seen in all six patients. Increased urinary excretion of calcium was evidenced during the first postnatal week in three cases. Urinary calcium excretion in the six patients ranged from 15 to 30 mg/kg/d. Nephrocalcinosis developed in all six patients and two patients developed urinary lithiasis. One patient died at one month of age from necrotizing enteropathy. The five remaining patients gradually developed severe growth failure with measurements between 4 and 5.5 SDs below the mean. These five patients had evidence of hyperparathyroidism including increased serum levels of parathyroid hormone (5/5), increased serum alkaline phosphatase activity (4/5), and roentgenographic bone changes (1/5). Ionized calcium assays performed in three of the five patients disclosed low values (range 1.25-1.47 mmol/l; mean = 1.35; normal values = 1.42-1.62), although total serum calcium levels were normal or high (range 2.16-2.98 mmol/l; mean 2.61; normal values = 2.45-2.65) probably as a result of chronic dehydration.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗
PubMed1992

Compared stability of Sepharose-based immunoadsorbents prepared by various activation methods.

During the use of chromatographic supports for the purification of proteins or the selective removal of substances by immunoaffinity, leakage of the antibodies immobilized on the matrix is systematically observed. When the cleansing of blood plasma by extracorporeal circulation is concerned, it is of prime importance that the immunoadsorbents exhibit an extensive chemical stability over the whole range of experimental conditions. To study and minimize this leakage, a matrix, Sepharose CL-4B, was activated by various chemical reagents and coupled to goat anti-apolipoprotein B polyclonal antibodies. Immunoadsorbents thus prepared were compared with those obtained earlier by cyanogen bromide activation. It turns out that divinyl sulphone- and tresyl chloride-activated supports lead to similar results in terms of coupling yield and adsorption capacity, but to a significant reduction in released antibodies.

Animals↗
PubMed1992

Chromostatin receptors control calcium channel activity in adrenal chromaffin cells.

One of the functions of chromogranin A (CGA), the major soluble component of secretory granules in both adrenal medullary chromaffin cells and many other endocrine cell types appears to be that of a prohormone. CGA is the precursor of several peptides including pancreastatin, a 49-residue peptide, and a 20-residue peptide, chromostatin, which have been identified as biologically active peptides. Chromostatin produces a dose-dependent inhibition (ID50 of 5 nM) of the secretagogue-evoked catecholamine secretion from chromaffin cells. Here we report that chromostatin potently inhibits L-type calcium currents recorded with the nystatin-perforated patch technique in cultured chromaffin cells. This inhibitory effect of chromostatin on calcium currents was not observed in experiments using the classical patch-clamp whole-cell approach which induces the leakage of cytoplasmic components. Using 125I-chromostatin, we show that chromostatin exhibits a fully reversible and saturable binding to the plasma membrane of cultured chromaffin cells. Analysis of binding experiments at equilibrium indicates the existence of one class of binding sites with a Bmax of 2.7 pmol/mg of chromaffin cell proteins and an apparent Kd of 6.5 nM. This high affinity is in good correlation with the half-maximal concentration (ID50 5 nM) of chromostatin inhibiting catecholamine secretion from chromaffin cells. Specificity of the chromostatin binding was further assessed by displacement experiments with unlabeled CGA-related or -unrelated peptides. We found an excellent quantitative correlation between the affinities of the various peptides determined by binding assays and their functional potency tested on catecholamine secretion: bovine chromostatin greater than human chromostatin greater than CGA much greater than rat chromostatin, pancreastatin, CAP-14, substance P, and Leu-enkephalin. Cross-linking experiments reveal that chromostatin associates specifically with an 80-kDa plasma membrane protein. These results together with the patch-clamp experiments support the idea that chromaffin cells possess specific chromostatin receptors and that activation of such receptors leads to the inhibition of L-type voltage-sensitive calcium channels through an intracellular second messenger pathway.

Adrenal Glands↗
PubMed1992

Detergents affect insulin binding, tyrosine kinase activity and oligomeric structure of partially purified insulin receptors.

Insulin receptor activities, i.e., insulin binding and tyrosine kinase activation depend on the lipid environment of the receptor. As detergent may disrupt or interfere with this environment, we investigated the effect of various common detergents on insulin receptor properties. Experiments were carried out (i) on solubilized and partially purified insulin receptor and (ii) on the receptor reconstituted into phosphatidylcholine vesicles. The detergents tested, Triton X-100, octyl-beta-D-glucopyranoside, octyl-beta-D-thioglucopyranoside, 3[(3-cholamidopropyl)dimethylammonio]propanesulfonic acid (Chaps), and Na deoxycholate affected the insulin receptor properties differently when compared with the control receptor in the absence of detergent. On the partially purified insulin receptor, Na deoxycholate inhibited both insulin receptor activities; octyl-beta-D-glucopyranoside and octyl-beta-D-thioglucopyranoside decreased insulin binding and kinase activation as their concentration increased, particularly above their respective critical micellar concentration (CMC). Triton X-100 was the only detergent which allowed an increase of insulin binding and kinase activation throughout the whole range of concentrations assayed. Reconstitution of the receptor into phosphatidylcholine vesicles protected the receptor from the direct effects of the detergents, for both the stimulation observed with Triton X-100 and the inhibition produced by the other detergents. In order to determine the effect of detergents on the oligomeric forms of the soluble insulin receptor, we investigated a new rapid sucrose gradient centrifugation technique. Insulin receptors were detected on the gradient by 125I insulin binding. For low concentrations of detergent, i.e., near the CMC, octylglucoside, Chaps, and Triton X-100 favored the (alpha 2 beta 2)2 oligomeric form of the receptor. Higher concentrations of Triton X-100 did not modify the polymeric state of the receptor. In contrast, octylglucoside and Chaps induced an increase in the sedimentation coefficient of the receptor which appeared as (alpha 2 beta 2)3 and (alpha 2 beta 2)4 forms. These alterations in the oligomerization status of the insulin receptor may explain the deleterious effects observed with both Chaps and octylglucoside at higher concentrations.

Centrifugation, Density Gradient↗
PubMed1992

Multicentric Kaposi's sarcoma in a 5-year-old human immunodeficiency virus-negative renal allograft recipient.

We describe the clinical and pathologic features of a case of pediatric multicentric Kaposi's sarcoma (KS) associated with allograft transplantation in a human immunodeficiency virus (HIV)-negative child. A lethal polyadenopathic and visceral KS occurred in a 5-year-old Caribbean boy who had undergone an allogenic renal transplantation for diffuse mesangial sclerosis with end-stage renal failure 4 months previously. The HIV-1 and HIV-2 serologies were negative. Despite its rarity, KS must be considered as a differential diagnosis in posttransplantation polyadenopathic or multisystemic syndromes in children.

Autopsy↗
PubMed1992

Definition and estimation of lifetime detriment from radiation exposures: principles and methods.

Although the lifetable methodology is a standard tool in epidemiology and risk assessment, there are a number of differences in the way it has been applied by various advisory committees that have attempted to estimate radiation risks. The most fundamental of these differences concerns the choice of parameter to be estimated: the "excess lifetime risk" is the difference in lifetime risks between exposed and unexposed populations; the "risk of exposure-induced death" is the lifetime risk of dying of a disease attributable to exposure. These two quantities are not the same, even at low doses. Although both quantities have some utility in risk assessment, the "risk of exposure-induced death" comes closer to capturing the total impact of exposure. Other differences between reported risk estimates include details of the calculations, the baseline rates and age distributions of the exposed population, the forms of the models for excess rates, handling of organ-specific doses, and the groupings of cancer sites. These issues are discussed theoretically and illustrated with comparisons of the BEIR V and UNSCEAR reports. Although the risk estimates from these two reports are similar for most cancer sites, it is shown that this happens to be the result of an approximate cancellation of a number of differences that could be quite large.

Environmental Exposure↗
PubMed1992

Encapsulation of insulin for oral administration preserves interaction of the hormone with its receptor in vitro.

It has been shown that insulin associated with nanocapsules of isobutylcyanoacrylate retains biological activity after oral administration to diabetic rats from 6 to 21 days. Because part of this action is unexplained, we focused on the interaction of encapsulated insulin with the insulin receptor in vitro. We have shown that encapsulated insulin is able 1) to bind to insulin receptors both in rat liver plasma membranes and after solubilization from Chinese hamster ovary (CHO) cells transfected with the gene of human insulin receptor, 2) to accelerate 125I-labeled insulin dissociation from its receptor, and 3) to ensure transduction of a signal leading to stimulation of the beta-subunit phosphorylation, with parameters similar to those of native insulin. In addition, encapsulated 125I-insulin was rapidly internalized in transfected CHO cells. Analysis of cell-associated radioactivity showed that encapsulated insulin remained largely intact (greater than 80%) after 3 h, whereas native insulin was mostly degraded. These data indicate that encapsulated insulin fulfills all the earliest events at the receptor level leading to biological actions and suggests that encapsulation protects insulin against insulin degradation inside the cells.

Administration, Oral↗
PubMed1992

Site specific screening for point mutations in ornithine transcarbamylase deficiency.

Ornithine transcarbamylase (OTC) deficiency is a frequent X linked disorder of the urea cycle which is responsible for lethal neonatal hyperammonaemia in males and for various clinical symptoms in heterozygous females. In order to improve the efficiency of our screening for mutant genotypes, we focused on molecular domains of functional or structural importance in the OTC gene, namely the carbamyl phosphate binding domain (encoded by the third exon) and the MspI restriction sites (CCGG) of the coding sequence (located in exons 2 and 7 respectively), as they contain mutation hot spots (CpG doublets). Using this procedure, we were able to identify three new mutant genotypes in OTC deficient children including one nonsense mutation (E 87 K, G 50 ter, G 162 R). Since genetic counselling for OTC deficiency is frequently difficult, molecular screening directed towards specific sites of the coding sequence could allow rapid detection of mutant genotypes and help solve diagnostic problems, especially when carrier status cannot be clarified easily.

Amino Acid Metabolism, Inborn Errors↗
PubMed1992

[Kasabach-Merritt syndrome in children].

Kasabach-Merritt syndrome is a combination of thrombocytopenia, intravascular coagulation, and a rapid increase in the size of an angioma. Anemia and disseminated intravascular coagulation may develop. This infrequent syndrome is severe and may be life-threatening. Pathophysiologic mechanisms underlying the condition are incompletely understood and, consequently, many different treatments are used, including systemic corticosteroids, compression, embolization, antifibrinolytic agents, platelet aggregation inhibitors, irradiation, and others. From findings in eight personal cases, the authors review clinical and biological features, pathophysiologic hypotheses and therapeutic strategies.

Aspirin↗
PubMed1992

Subperiosteal subtemporal approach: technique and applications.

The authors describe a craniofacial surgical approach that they have used since 1987. Based on existing anatomical continuity between the subtemporal plane and the cranial periosteum, it consists of a direct subperiosteal subtemporal cleavage. Preservation of continuity between the muscle and the periosteum allows the operator to return the temporalis muscle to a normal position at the end of the operation when the scalp is sutured. This approach avoids superficial cleaving of the temporalis muscle or section and reinsertion to the fronto-orbital rim. It also allows access to the upper third of the face without jeopardizing the frontal ramus of the facial nerve.

Adolescent↗