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C Martin

Publications and source records attributed to C Martin.

At least 703 records · Page 39Linked to original sources
PubMed1992

Phenotype-genotype correlations in X linked retinitis pigmentosa.

Retinitis pigmentosa (RP) represents a group of clinically heterogeneous retinal degenerations in which all modes of inheritance have been described. We have previously found two different clinical profiles in X linked RP as a function of age and mode of onset. The first clinical form has very early onset with severe myopia. The second form starts later with night blindness with mild myopia or none. At least two genes have been identified in X linked forms, namely RP2 (linked to DXS7, DXS255, and DXS14) and RP3 (linked to DXS84 and OTC) on the short arm of the X chromosome. In order to contribute to phenotype-genotype correlations in X linked RP, we tested the hypothesis that the two clinical profiles could be accounted for by the two different gene loci. The present study provides evidence for linkage of the clinical form with early myopia as the onset symptom with the RP2 gene (pairwise linkage to DXS255: Z = 3.13 at theta = 0), while the clinical form with later night blindness as the onset symptom is linked to the RP3 gene (pairwise linkage to OTC: Z = 4.16 at theta = 0).

Female↗
PubMed1992

Inhibition of hepatic ketogenesis by tumor necrosis factor-alpha in rats.

Tumor necrosis factor-alpha (TNF-alpha) stimulates hepatic lipogenesis. Therefore, it could play a role in the control of ketogenesis. To test this hypothesis, we measured simultaneously free fatty acids (FFA; [1-13C]palmitate) and ketone body (KB; [3,4-13C2]acetoacetate) kinetics, before and after intraperitoneal injection of saline or TNF-alpha, in postabsorptive rats or rats starved for 24 h. In both groups of rats, TNF-alpha injection did not modify insulinemia and induced a moderate increase of FFA concentrations and appearance rates (P < 0.05). Despite increased FFA availability, ketogenesis was impaired after TNF-alpha injection, as shown by lower KB concentrations and appearance rates; this effect was more important in postabsorptive than in starved rats. The percentage of FFA flux used for ketogenesis was decreased by TNF-alpha in the postabsorptive group (P < 0.05) and starved (P < 0.05) rats. In both groups, maximal liver acetyl-coenzyme A carboxylase activity and estimated phosphorylation state were not modified by TNF-alpha injection, but hepatic concentrations of citrate were increased (P < 0.05). This increased citrate level could be related to a mobilization of glucose stored as glycogen since liver glycogen was decreased by TNF-alpha injection (P < 0.05). In conclusion, TNF-alpha injection in rats decreased hepatic ketogenesis. This action could be related to an increased mobilization and utilization of carbohydrate stores.

Absorption↗
PubMed1992

Recruitment of an inotropic reserve in moderately ischemic myocardium at the expense of metabolic recovery. A model of short-term hibernation.

The regional, functional as well as metabolic consequences of inotropic stimulation on myocardium subjected to prolonged moderate ischemia were investigated. In 35 enflurane-anesthetized swine the left anterior descending coronary artery was cannulated and perfused at constant flow. The vein paralleling the left anterior descending coronary artery was cannulated for measurement of lactate and oxygen content. Transmural biopsies from the anterior myocardium were taken for the measurement of ATP, creatine phosphate, and glycogen. After control measurements, flow was adjusted to reduce regional contractile function (expressed as a work index, determined by sonomicrometry) by approximately 50%. After either 5, 25, 40, or 85 minutes of moderate ischemia, dobutamine was infused for 5 minutes into the ischemic region. In a separate group of five swine also subjected to 85 minutes of ischemia followed by infusion of dobutamine and 2 hours of reperfusion, triphenyltetrazolium chloride staining and light microscopy were used to identify infarcted tissue. Moderate ischemia (regional myocardial blood flow, 0.21 +/- 0.07 ml.min-1.g-1, determined by radiolabeled microspheres) was associated with a reduction of creatine phosphate after 5 minutes (from 9.35 +/- 2.54 to 6.43 +/- 1.06 mumol/g wet wt, p less than 0.05) and a further reduction after 25 minutes (3.18 +/- 0.69 mumol/g wet wt, p less than 0.05). Thereafter, creatine phosphate recovered despite continued ischemia (after 40 minutes, 4.95 +/- 1.37 mumol/g wet wt; after 85 minutes, 5.78 +/- 2.27 mumol/g wet wt). Lactate consumption during control conditions was reversed to production after 5 minutes of ischemia, which moderated during more prolonged ischemia. Without changing regional myocardial blood flow, infusion of dobutamine increased the work index significantly at any time point but also caused worsening of metabolic markers of ischemia. Nevertheless, even after 85 minutes of ischemia followed by the infusion of dobutamine and 2 hours of reperfusion, there was no evidence of necrosis. This experimental model provides a means of characterizing the mechanisms of short-term hibernation.

Animals↗
PubMed1992

Demonstration of a phagocytic cell system belonging to the hemopoietic lineage and originating from the yolk sac in the early avian embryo.

It is well established that hemopoietic cells arising from the yolk sac invade the avian embryo. To study the fate and role of these cells during the first 2.5-4.5 days of incubation, we constructed yolk sac chimeras (a chick embryo grafted on a quail yolk sac and vice versa) and immunostained them with antibodies specific to cells of quail hemangioblastic lineage (MB1 and QH1). This approach revealed that endothelial cells of the embryonic vessels are of intraembryonic origin. In contrast, numerous hemopoietic cells of yolk sac origin were seen in embryos ranging from 2.5 to 4.5 days of incubation. These cells were already present within the vessels and in the mesenchyme at the earliest developmental stages analyzed. Two hemopoietic cell types of yolk sac origin were distinguishable, undifferentiated cells and macrophage-like cells. The number of the latter cells increased progressively as development proceeded, and they showed marked acid phosphatase activity and phagocytic capacity, as revealed by the presence of numerous phagocytic inclusions in their cytoplasm. The macrophage-like cells were mostly distributed in the mesenchyme and also appeared within some organ primordia such as the neural tube, the liver anlage and the nephric rudiment. Comparison of the results in the two types of chimeras and the findings obtained with acid phosphatase/MB1 double labelling showed that some hemopoietic macrophage-like cells of intraembryonic origin were also present at the stages considered. These results support the existence in the early avian embryo of a phagocytic cell system of blood cell lineage, derived chiefly from the yolk sac. Cells belonging to this system perform phagocytosis in cell death and may also be involved in other morphogenetic processes.

Animals↗
PubMed1992

Performance evaluation of three vaporizing humidifiers and two heat and moisture exchangers in patients with minute ventilation > 10 L/min.

STUDY OBJECTIVE: To compare the thermal and humidification capacity of three heated hot water systems (HHWSs) and two heat and moisture exchangers (HMEs) in ICU patients submitted to minute ventilation > 10 L/min. DESIGN: Prospective, controlled, randomized, not blinded study. SETTING: ICU of a university hospital. PATIENTS: ICU patients requiring controlled mechanical ventilation with minute ventilation > 10 L/min. Patients had to be sedated and paralyzed and had to require ventilation for more than four days. INTERVENTIONS: Following a randomized order, the patients were ventilated for 24-h periods with three HHWSs (Bennett Cascade 2 humidifier, Fisher-Paykel MR 460 and MR 600) and two HMEs (Pall Ultipor and Hygrobac filter). MEASUREMENTS AND RESULTS: In each patient and for each 24-h period, absolute humidity, (AH), relative humidity (RH) of inspired gases, and tracheal temperature were obtained. Two HHWSs (Bennett and Fisher-Paykel MR 460) had a better thermal and humidification capacity than any other systems (p < 0.001). The hydrophobic HME (Pall filter) had a poor thermal and humidification capacity (RH: 79 +/- 8.7 percent; AH: 20.6 +/- 2.3 mg H2O/L). The hygroscopic filter (Hygrobac filter) had better thermal and humidification capacity than the Pall filter (RH: 92.5 +/- 3.6 percent; AH: 29.1 +/- 1.8 mg H2O/L; p < 0.001). Tracheal temperature was well preserved by all systems. The thermic and humidification capability of the Hygrobac filter declined over 24 h. Since the Pall filter could not achieve an AH > 25 mg H2O/L in any patient, it was not studied beyond the first measurement. CONCLUSIONS: The Hygrobac filter had a thermal and humidification capability closed to the two HHWSs (81 to 97 percent) but the capability declines over 24 h. The Pall filter had a poor capability (54 to 74 percent of that of HHWSs).

Adolescent↗
PubMed1992

Safety of interventional rigid bronchoscopy using intravenous anesthesia and spontaneous assisted ventilation. A prospective study.

STUDY OBJECTIVE: To investigate the safety of total intravenous anesthesia and spontaneous assisted ventilation during interventional rigid bronchoscopy (IRB). DESIGN: Prospective, noncomparative study. SETTING: A university hospital thoracic endoscopy and laser center. PATIENTS: Eighty-three patients underwent a total of 124 procedures (including Nd:Yag laser therapy, stent insertions, transbronchial biopsies/bronchoalveolar lavages (TBB/BALs) in transplant patients and others). Results of preanesthesia consultation, endoscopic and anesthesia intervention, perioperative complications, and time spent in recovery room were recorded prospectively. RESULTS: Respiratory complications occurred in 22 procedures (18 percent) and included severe intraoperative or postoperative oxyhemoglobin desaturations (19 cases), bronchospasms/laryngospasms (two cases), and one recurrent pneumothorax. These complications were mostly related to the endobronchial surgical procedure. Respiratory complications occurred more frequently in patients with American Society of Anesthesiologists (ASA) 3 and 4 status (p < 0.005) and in patients with a karnofsky Performance Scale (KPS) below 70 (p < 0.05). No cardiac complications were noted, although 13 patients had significant underlying heart disease. Propofol was used in 121 procedures. Etomidate was used 15 times for induction and three times for both induction and maintenance in patients with ASA status 4 or low blood pressure before induction. CONCLUSION: Total intravenous anesthesia and spontaneous assisted ventilation is a well-suited technique for IRB. Severe hypoxemia, however, may occur in approximately 15 percent of patients. This complication is usually related to the procedure itself and is easy to reverse. Propofol is well tolerated in the majority of patients but it must be used with care in patients with poor functional or cardiovascular status.

Adolescent↗
PubMed1992

Characterization of cDNAs encoding two isoforms of granule-bound starch synthase which show differential expression in developing storage organs of pea and potato.

We have isolated cDNA clones to two isoforms of granule-bound starch synthase (GBSS) from pea embryos and potato tubers. The sequences of both isoforms are related to that of glycogen synthase from E. coli and one, GBSSI, is very similar to the waxy protein of maize and other species. In pea, GBSSII carries a novel 203-amino-acid domain at its N-terminus. Genes encoding both proteins are expressed during pea embryo development, but GBSSII is most highly expressed earlier in development than GBSSI. Similarly, GBSSI and GBSSII are differentially expressed in developing potato tubers. Expression of both isoforms is much lower in other organs of pea than in embryos. GBSSII is expressed in every organ tested while GBSSI is not expressed in roots, stipules or flowers. The possible consequences of this differential use of GBSS isoforms are discussed.

Amino Acid Sequence↗
PubMed1992

[Anatomical limits of endonasal ethmoidectomy].

Constant anatomic boundaries of the lateral mass of the ethnoid are described, based on data from microdissections, endoscopic examinations, computed tomography imaging and histology in 12 subjects. As with surgical progression, identification of these boundaries follows the lateral orbital and superior craniofrontal surfaces. The "starred groove formation", ethmoidal roof lamina and ethmoidosphenoidal recesses are the safety beacons for endonasal ethmoidectomy under endoscopic control.

Endoscopy↗
PubMed1992

[Molecular genetics and prenatal diagnosis].

Recombinant DNA techniques have provided new insight into genetic and prenatal diagnosis during the last 10 years. Human gene mapping data are increasing exponentially due to molecular biology advances. Most analyses are possible from chorionic villi biopsy specimens as early as the 10th week of fetal life. When the gene is known and cloned, the diagnosis is regularly made by using the polymerase chain reaction technique; when the gene is unknown but mapped, the restriction fragment length polymorphism technique is used. However, these methods for prenatal assessment require a reliable diagnosis of index case disease and a preliminary familial DNA study.

Female↗
PubMed1991

Spectroscopic limits to an extragalactic far-ultraviolet background.

We use a spectrum of the lowest intensity diffuse far-ultraviolet background obtained from a series of observations in a number of celestial view directions to constrain the properties of the extragalactic FUV background. The mean continuum level, IEG = 280 +/- 35 photons cm-2 s-1 angstrom-1 sr-1, was obtained in a direction with very low H I column density, and this represents a firm upper limit to any extragalactic background in the 1400-1900 angstroms band. Previous work has demonstrated that the far-ultraviolet background includes (depending on a view direction) contributions from dust-scattered Galactic light, high-ionization emission lines, two-photon emission from H II, H2 fluorescence, and the integrated light of spiral galaxies. We find no evidence in the spectrum of line or continuum features that would signify additional extragalactic components. Motivated by the observation of steep BJ and U number count distributions, we have made a detailed comparison of galaxy evolution models to optical and UV data. We find that the observations are difficult to reconcile with a dominant contribution from unclustered, starburst galaxies at low redshifts. Our measurement rules out large ionizing fluxes at z = 0, but cannot strongly constrain the QSO background light, which is expected to be 0.5%-4% of IEG. We present improved limits on radiative lifetimes of massive neutrinos. We demonstrated with a simple model that IGM radiation is unlikely to make a significant contribution to IEG. Since dust scattering could produce a significant part of the continuum in this lowest intensity spectrum, we carried out a series of tests to evaluate this possibility. We find that the spectrum of a nearby target with higher NH I, when corrected for H2 fluorescence, is very similar to the spectrum obtained in the low H I view direction. This is evidence that the majority of the continuum observed at low NH I is also dust reflection, indicating either the existence of a hitherto unidentified dust component, or of a large enhancement in dust scattering efficiency in low-density gas. We also review the effects of an additional dust component on the far-infrared background and on extragalactic FUV observations. We conclude that dust reflection, combined with modest contributions from H II two-photon emission and from the integrated light of late-type galaxies, may account for virtually all of the FUV background in low H I column density directions.

Astronomical Phenomena↗
PubMed1991

The albedo and scattering phase function of interstellar dust and the diffuse background at far-ultraviolet wavelengths.

We have determined the scattering parameters of dust in the interstellar medium at far-ultraviolet (FUV) wavelengths (1415-1835 angstroms). Our results are based on spectra of the diffuse background taken with the Berkeley UVX spectrometer. The unique design of this instrument makes possible for the first time accurate determination of the background both at high Galactic latitude, where the signal is intrinsically faint, and at low Galactic latitude, where direct starlight has heretofore compromised measurements of the diffuse emission. Because the data are spectroscopic, the continuum can be distinguished from the atomic and molecular transition features which also contribute to the background. We find the continuum intensity to be well correlated with the Galactic neutral hydrogen column density until saturation at about 1200 photons cm-2 s-1 sr-1 angstrom-1 is reached where tau FUV approximately 1. Our measurement of the intensity where tau FUV > or = 1 is crucial to the determination of the scattering properties of the grains. We interpret the data with a detailed radiative transfer model and conclude that the FUV albedo of the grains is low (<25%) and that the grains scatter fairly isotropically. We evaluate models of dust composition and grain-size distribution and compare their predictions with these new results. We present evidence that, as the Galactic neutral hydrogen column density approaches zero, the FUV continuum background arises primarily from scattering by dust, which implies that dust may be present in virtually all view directions. A non-dust-scattering continuum component has also been identified, with an intensity (external to the foreground Galactic dust) of about 115 photons cm-2 s-1 angstrom-1. With about half this intensity accounted for by two-photon emission from Galactic ionized gas, we identify roughly 50 photons cm-2 s-1 sr-1 angstrom-1 as a true extragalactic component.

Astronomy↗