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Biomedical subjects

J Bloch

Publications and source records attributed to J Bloch.

At least 37 records · Page 2Linked to original sources
PubMed2002

[Risk factors for early bronchiolitis at asthma during childhood: case-control study of asthmatics aged 4 to 12 years].

UNLABELLED: The group of general paediatrics of the French Paediatrics Society conducted a case-control study in order to verify the link between the occurrence of an acute bronchiolitis early during the first year of life, more specifically during the first trimester, and asthma during later childhood. METHODS: Parents of 4-to-12-year-old children answered a questionnaire during a general paediatrics visit. Exposition was attested by a diagnosis of bronchiolitis mentioned on the personal health record of the child. Environmental factors and medical history, obtained from the parents and by checking the health record of the child, were studied using multivariate analysis. RESULTS: Nineteen paediatricians included 80 children with asthma and 160 controls. Fifty-four per cent of asthmatic children had a medical history of bronchiolitis during the first year of life versus 17% of control children (P < 0.001). Mean age of bronchiolitis occurrence was 6.6 months in both groups (P = 0.98). Multivariate analysis showed that occurrence of bronchiolitis during the first year of life was significantly more frequent in asthmatic children (P < 0.001, OR = 5.6, IC95 = [2.6-11.6]) but this effect was not observed during the first trimester of life. CONCLUSION: Bronchiolitis during the first year of life was significantly related to later asthma in 4-to-12-year-old children treated by general paediatricians. On the other hand, a very early bronchiolitis during the first trimester of life did not appear, in our set of data, as a contributive factor to explain asthma in later childhood.

Age of Onset↗
PubMed2002

Do prognostic factors exist for total colonic aganglionosis with ileal involvement?

BACKGROUND/PURPOSE: Total colonic aganglionosis with ileal involvement is estimated at 1 case in 50,000 living births. This pathology has a very variable prognosis, and patients often need long-term parenteral nutrition. The aim of this study is to define prognostic factors for this disease. METHODS: This is a retrospective study from 1980 to 1999, based on 26 cases of total colonic aganglionosis with ileal involvement. The authors analyzed birth term, sex, birth weight, ileal involvement in centimeters, delay to correct level enterostomy, the total parenteral nutrition duration, and the need for constant rate nutritional assistance. The authors studied the following items: Weight, height, complications, clinical state, and nutritional issues. The statistic test is: LOG RANK (analysis of censored data and comparison of survival diagram). RESULTS: The only prognostic factor is the length of ileal involvement. All the children with ileal involvement less than 50 cm, except for 2, did not need long-term nutritional assistance; for those with ileal resection over 50 cm, long-term nutritional assistance was needed. Total colonic aganglionosis is a very serious illness (2 children had a small bowel transplantation, and 2 are waiting for one). The prognosis is even worse when associated with a polymalformation syndrome (50% of the children died). CONCLUSION: The major prognostic factor is the length of small bowel not involved in the total colonic aganglionosis.

Adolescent↗
PubMed2001

High-temperature ultrafast polariton parametric amplification in semiconductor microcavities.

Cavity polaritons, the elementary optical excitations of semiconductor microcavities, may be understood as a superposition of excitons and cavity photons. Owing to their composite nature, these bosonic particles have a distinct optical response, at the same time very fast and highly nonlinear. Very efficient light amplification due to polariton-polariton parametric scattering has recently been reported in semiconductor microcavities at liquid-helium temperatures. Here we demonstrate polariton parametric amplification up to 120 K in GaAlAs-based microcavities and up to 220 K in CdTe-based microcavities. We show that the cut-off temperature for the amplification is ultimately determined by the binding energy of the exciton. A 5-micrometer-thick planar microcavity can amplify a weak light pulse more than 5,000 times. The effective gain coefficient of an equivalent homogeneous medium would be 107 cm-1. The subpicosecond duration and high efficiency of the amplification could be exploited for high-repetition all-optical microscopic switches and amplifiers. 105 polaritons occupy the same quantum state during the amplification, realizing a dynamical condensate of strongly interacting bosons which can be studied at high temperature.

Journal Article↗
PubMed2001

Nerve growth factor- and neurotrophin-3-releasing guidance channels promote regeneration of the transected rat dorsal root.

Dorsal roots have a limited regeneration capacity after transection. To improve nerve regeneration, the growth-promoting effects of the neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) were evaluated. The proteins were continuously released by synthetic nerve guidance channels bridging a 4-mm gap in the transected dorsal root. Four weeks after lesion, the regenerated nerve cables were analyzed for the presence of myelinated and unmyelinated axons. While BDNF showed a limited effect on axonal regeneration (863 +/- 39 axons/regenerated nerve, n = 6), NGF (1843 +/- 482) and NT-3 (1495 +/- 449) powerfully promoted regeneration of myelinated axons compared to channels releasing the control protein bovine serum albumin (293 +/- 39). In addition, NGF, but not BDNF nor NT-3, had a potent effect on the regeneration of unmyelinated axons (NGF, 55 +/- 1.4; BDNF, 4 +/- 0.3; NT-3, 4.7 +/- 0.3 axons/100 microm(2); n = 6). The present study suggests that synthetic nerve guidance channels slowly and continuously releasing the neurotrophins NGF and NT-3 can overcome the limited regeneration of transected dorsal root.

Animals↗
PubMed2001

Risk factors for esophageal candidiasis in a large cohort of HIV-infected patients treated with nucleoside analogues.

To assess the risk factors for esophageal candidiasis (EC), a cohort study and a case-control study were conducted using 1,368 French patients who were already participating in the Delta trial (which compared different types of antiretroviral therapy in HIV-infected patients) and who had no previous history of EC. During a median follow-up period of 19 months, 87 (6%) patients developed EC. The results of the cohort study showed an increased risk of EC associated with a low baseline CD4+ cell count (P<0.0001), a high baseline plasma HIV RNA level (P < 0.0001) and prior zidovudine therapy (P = 0.02) at entry to the study. The case-control study revealed an increased risk of EC in patients with a recent low CD4+ cell count (P < 0.0002), recent antibacterial chemotherapy (P = 0.01) and oral candidiasis (P < 0.05). Cotrimoxazole prophylaxis also increased the risk of EC (P = 0.04) in the case-control study.

AIDS-Related Opportunistic Infections↗
PubMed2001

[Reduction of complimentary prescription examinations in a pediatric emergency department].

UNLABELLED: Numerous biological tests and X-rays are prescribed though the patient's clinical status does not warrant them. They are a source of extra work, extra costs, and painful and potential measurement errors. OBJECTIVES: To reduce unnecessary tests in four frequent situations (bronchiolitis, gastroenteritis, unexplained fever in children more than three months of age, asthma attack) at the pediatric emergency department of the Robert-Debré hospital (Paris). METHODS: Using a 'before/after' intervention survey, the intervention consisted of a modification of the request forms by adding prescription recommendations. All the children presenting with any one of the four targeted pathologies were included during the two 2-week periods. RESULTS: Test requests were reduced from 0.98 test per child to 0.77 (p = 0.02). The percentage of necessary tests increased from 33 to 50% (p < 0.0001); the percentage of children who underwent unnecessary blood samples decreased from 30 to 15% (p = 0.01). At the same time, the percentage of tests which were appropriate but not prescribed did not increase during the intervention period. CONCLUSION: It is possible to reduce unnecessary tests in an emergency pediatric department by adding recommendations to the request form. Unfortunately, the effects of such intervention do not last if the recommendations are not regularly recalled.

Asthma↗
PubMed2001

[Assessment of the use of aminoglycosides at a pediatrics hospital].

MATERIALS AND METHODS: Three surveys were successively carried out regarding aminoglycoside use: one analysis of amikacine prescriptions in the most prescribing clinical wards and two surveys among nurses and physicians respectively on prescribing, administering and monitoring aminoglycosides. RESULTS: On 43 amikacine prescriptions analyzed in a month, one daily dose infusion in 30 minutes was observed in most of the patients (70%), doses and indications matched most often the official license. Half of patients treated for more than five days had no drug level monitoring. Sample collection by nurses was very erratic making results obtained not interpretable. CONCLUSION: Subsequently, guidelines regarding aminoglycoside use were designed by the interest group, approved by the drug committee and sent to all hospital prescribers and nurses.

Adolescent↗
PubMed2001

[Nutritional status and risk in hospitalized children].

BACKGROUND: A few studies report malnutrition in hospitalized patients. MATERIAL AND METHODS: This one-day cross-sectional survey performed in January 1999 assessed nutritional status and protein-energy intake in a pediatric population hospitalized in medicine or surgery units. Every child older than six months, hospitalized for more than 48 h and free of nutritional support (parenteral, enteral, or special regimens for metabolic diseases) was included. RESULTS: Fifty-eight children among the 183 present the day of the study met the inclusion criteria and were included in the statistical analysis. They were hospitalized in medicine (48%), psychiatry (31%) and surgery (21%). The body mass index (BMI) was below -2 standard deviations (DS) in 21% of them. Excluding patients with anorexia nervosa, BMI was < -2 SD, > +2 SD, or in between these limits in respectively 12, 14 and 74%. Energy intake measured at the hospital was below 75% of the recommended dietary allowances in two-thirds of the children whether malnourished or not. Fifty percent of the malnourished children had been referred to a dietician the day of the study. CONCLUSIONS: Malnutrition is frequent in a population of hospitalized children. Energy intake and referral to a dietician are insufficient.

Body Mass Index↗
PubMed2001

Patterns of EEG frequency, movement, heart rate, and oxygenation after isolated short apneas in infants.

Patterns of events occurring at the end of apneas have rarely been reported in infants. No previous studies have compared these patterns to those of spontaneous events during sleep. We examined 163 isolated apneas in 17 infants (47 +/- 4 wk postconceptional age) who underwent polysomnography for suspected upper airway problems. Mean apnea duration was 6.5+/-1.5 s (range, 5 to 11.5 s), 78% of apneas occurred in active sleep, and 67% of apneas were obstructive. We recorded the occurrence of body movement or augmented breath and analyzed changes in EEG frequency > or = 1 s, heart rate, and oxygen saturation value at the end of apneas and of a control ventilatory period defined as a period of breathing equal in duration to the apnea and preceding the apnea by 1 min. We found that 7.9% of apneas and 11.6% of control periods were followed by an augmented breath and that 14.1% of apneas and 0.5% of control periods were followed by a body movement. The percentages of motor events or no event differed significantly after the apneas (p = 0.008) compared with the control periods. A significant increase in EEG frequency was observed at the end of the apneas compared with the control periods (p < 0.04). EEG frequency increased after 61% of the apneas. Neither heart rate nor oxygen saturation value changed after the control periods. Heart rate decreased significantly after the apneas not followed by a motor event (p = 0.02) but not after the apneas followed by a body movement. We conclude that 1) at termination of isolated apneas in infants, a motor event was rare, whereas an EEG frequency increase was common; 2) event patterns at apnea termination differed from those at control period termination.

Electroencephalography↗
PubMed2000

Neurodegeneration prevented by lentiviral vector delivery of GDNF in primate models of Parkinson's disease.

Lentiviral delivery of glial cell line-derived neurotrophic factor (lenti-GDNF) was tested for its trophic effects upon degenerating nigrostriatal neurons in nonhuman primate models of Parkinson's disease (PD). We injected lenti-GDNF into the striatum and substantia nigra of nonlesioned aged rhesus monkeys or young adult rhesus monkeys treated 1 week prior with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Extensive GDNF expression with anterograde and retrograde transport was seen in all animals. In aged monkeys, lenti-GDNF augmented dopaminergic function. In MPTP-treated monkeys, lenti-GDNF reversed functional deficits and completely prevented nigrostriatal degeneration. Additionally, lenti-GDNF injections to intact rhesus monkeys revealed long-term gene expression (8 months). In MPTP-treated monkeys, lenti-GDNF treatment reversed motor deficits in a hand-reach task. These data indicate that GDNF delivery using a lentiviral vector system can prevent nigrostriatal degeneration and induce regeneration in primate models of PD and might be a viable therapeutic strategy for PD patients.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2000

Neuroprotective gene therapy for Huntington's disease using a polymer encapsulated BHK cell line engineered to secrete human CNTF.

Huntington's disease (HD) is an autosomal dominant genetic disease with devastating clinical effects on cognitive, psychological, and motor functions. These clinical symptoms primarily relate to the progressive loss of medium-spiny GABA-ergic neurons of the striatum. There is no known treatment to date. Several neurotrophic factors have, however, demonstrated the capacity to protect striatal neurons in various experimental models of HD. This includes the ciliary neurotrophic factor (CNTF), the substance examined in this protocol. An ex vivo gene therapy approach based on encapsulated genetically modified BHK cells will be used for the continuous and long-term intracerebral delivery of CNTF. A device, containing up to 106 human CNTF-producing BHK cells surrounded by a semipermeable membrane, will be implanted into the right lateral ventricle of 6 patients. Capsules releasing 0.15-0.5 microg CNTF/day will be used. In this phase I study, the principal goal will be the evaluation of the safety and tolerability of the procedure. As a secondary goal, HD symptoms will be analyzed using a large battery of neuropsychological, motor, neurological, and neurophysiological tests and the striatal pathology monitored using MRI and PET-scan imaging. It is expected that the gene therapy approach described in this protocol will mitigate the side effects associated with the peripheral administration of recombinant hCNTF and allow a well-tolerated, continuous intracerebroventricular delivery of the neuroprotective factor.

Animals↗
PubMed2000

Restoration of cognitive and motor functions by ciliary neurotrophic factor in a primate model of Huntington's disease.

Huntington's disease (HD) is an inherited disorder characterized by cognitive impairments, motor deficits, and progressive dementia. These symptoms result from progressive neurodegenerative changes mainly affecting the neostriatum. This pathology is fatal in 10 to 20 years and there is currently no treatment for HD. Early in the course of the disease, initial clinical manifestations are due to striatal neuronal dysfunction, which is later followed by massive neuronal death. A major therapeutic objective is therefore to reverse striatal dysfunction prior to cell death. Using a primate model reproducing the clinical features and the progressive neuronal degeneration typical of HD, we tested the therapeutic effects of direct intrastriatal infusion of ciliary neurotrophic factor (CNTF). To achieve a continuous delivery of CNTF over the full period of evaluation, we took advantage of the macroencapsulation technique. Baby hamster kidney (BHK) cells previously engineered to produce human CNTF were encapsulated into semipermeable membranes and implanted bilaterally into striata. We show here that intracerebral delivery of low doses of CNTF at the onset of symptoms not only protects neurons from degeneration but also restores neostriatal functions. CNTF-treated primates recovered, in particular, cognitive and motor functions dependent on the anatomofunctional integrity of frontostriatal pathways that were distinctively altered in this HD model. These results support the hypothesis that CNTF infusion into the striatum of HD patients not only could block the degeneration of neurons but also alleviated motor and cognitive symptoms associated with persistent neuronal dysfunction.

Animals↗
PubMed2000

Theory of resonant rayleigh scattering from semiconductor microcavities: signatures of disorder

We develop a self-consistent, microscopic theory of coherent resonant secondary emission from semiconductor microcavities in the normal-mode-coupling regime. Our theory provides a quantitative description of the spectral, temporal, and angular properties of the disorder-induced emission component-resonant Rayleigh scattering-and offers an intuitive physical explanation of emission properties.

Journal Article↗
PubMed2000

Prompt Optical Observations of Gamma-Ray Bursts.

The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs). A search for optical counterparts to six GRBs with localization errors of 1 deg2 or better produced no detections. The earliest limiting sensitivity is mROTSE>13.1 at 10.85 s (5 s exposure) after the gamma-ray rise, and the best limit is mROTSE>16.0 at 62 minutes (897 s exposure). These are the most stringent limits obtained for the GRB optical counterpart brightness in the first hour after the burst. Consideration of the gamma-ray fluence and peak flux for these bursts and for GRB 990123 indicates that there is not a strong positive correlation between optical flux and gamma-ray emission.

Journal Article↗
PubMed2000

Enzymatic incorporation of bioactive peptides into fibrin matrices enhances neurite extension.

Fibrin plays an important role in wound healing and regeneration, and enjoys widespread use in surgery and tissue engineering. The enzymatic activity of Factor XIIIa was employed to covalently incorporate exogenous bioactive peptides within fibrin during coagulation. Fibrin gels were formed with incorporated peptides from laminin and N-cadherin alone and in combination at concentrations up to 8.2 mol peptide per mole of fibrinogen. Neurite extension in vitro was enhanced when gels were augmented with exogenous peptide, with the maximal improvement reaching 75%. When this particular fibrin derivative was evaluated in rats in the repair of the severed dorsal root within polymeric tubes, the number of regenerated axons was enhanced by 85% relative to animals treated with tubes filled with unmodified fibrin. These results demonstrate that it is possible to enhance the biological activity of fibrin by enzymatically incorporating exogenous oligopeptide domains of morphoregulatory proteins.

Amino Acid Sequence↗
PubMed2000

Physiological parameters evaluation following apnea in healthy premature infants.

To assess responses to central and obstructive apnea, we performed 10-hour polygraphic recordings in healthy 33-34 wGA infants. Each apnea period was paired with a control period. The presence of body movements (BM) and augmented breaths (AB), the EEG, heart rate (HR), respiratory rate, phase relationships between thoracic and abdominal respiratory movements, and changes in SaO(2) were evaluated. No apnea caused awakening. Apnea were not usually followed by motor events (no significant differences with control periods), with the exception of most obstructive apnea longer than 10 s. The mean percentage of changes following apnea, normalized to baseline values, was significant for the EEG (frequency slightly increased, mainly after obstructive apnea), HR (deceleration), and respiratory rate (increased). However, the mean values masked heterogeneity across apnea in the direction of the change in each parameter. The only significant correlation was between changes in HR and SaO(2). The increases in EEG frequency and respiratory rate seen in our study can be considered markers of CNS activation, but were small and inconsistent. The heart rate decelerations and SaO(2) changes are not activation markers. Thus, mechanisms underlying restarting of breathing efforts following apnea remain unclear in premature babies. Our investigation establishes the importance of using control data to distinguish between spontaneous and apnea-related events.

Apnea↗
PubMed1999

Lentiviral gene transfer to the nonhuman primate brain.

Lentiviral vectors infect quiescent cells and allow for the delivery of genes to discrete brain regions. The present study assessed whether stable lentiviral gene transduction can be achieved in the monkey nigrostriatal system. Three young adult Rhesus monkeys received injections of a lentiviral vector encoding for the marker gene beta galatosidase (beta Gal). On one side of the brain, each monkey received multiple lentivirus injections into the caudate and putamen. On the opposite side, each animal received a single injection aimed at the substantia nigra. The first two monkeys were sacrificed 1 month postinjection, while the third monkey was sacrificed 3 months postinjection. Robust incorporation of the beta Gal gene was seen in the striatum of all three monkeys. Stereological counts revealed that 930,218; 1,192,359; and 1,501,217 cells in the striatum were beta Gal positive in monkeys 1 (n = 2) and 3 (n = 1) months later, respectively. Only the third monkey had an injection placed directly into the substantia nigra and 187,308 beta Gal-positive cells were identified in this animal. The injections induced only minor perivascular cuffing and there was no apparent inflammatory response resulting from the lentivirus injections. Double label experiments revealed that between 80 and 87% of the beta Gal-positive cells were neurons. These data indicate that robust transduction of striatal and nigral cells can occur in the nonhuman primate brain for up to 3 months. Studies are now ongoing testing the ability of lentivirus encoding for dopaminergic trophic factors to augment the nigrostriatal system in nonhuman primate models of Parkinson's disease.

Animals↗