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Biomedical subjects

H Conrad

Publications and source records attributed to H Conrad.

At least 19 recordsLinked to original sources
PubMed2005

Incidence of herpes simplex virus keratitis in France.

OBJECTIVE: To assess the incidence and clinical characteristics of herpes simplex keratitis in France. DESIGN: National multicenter prospective study on herpetic keratitis. PARTICIPANTS: During a 3-month study period (September-December 2002), all cases of herpes simplex keratitis were prospectively reported by a randomly selected sample of 412 ophthalmologists representative of the 5471 French ophthalmologists in terms of gender, geographic distribution, and clinical practice. METHODS: The following set of assumptions were made to calculate the incidence of herpectic keratitis: (1) the participating (self-selected) ophthalmologists in the study could adequately represent French ophthalmologists, (2) estimates based on the 3-month study period could be used to calculate the annual incidence (i.e., no significant seasonal variations), and (3) all patients suffering from herpetic corneal lesions consult or are referred to an ophthalmologist. We calculated the incidence of herpetic keratitis by (1) estimating the average number of incident cases per ophthalmologist per year, (2) multiplying the average number of incident cases by the total number of French ophthalmologists (n = 5471), and (3) dividing the result by the French population. RESULTS: Four hundred twelve ophthalmologists reported 357 cases of herpes keratitis. We estimated that the overall incidence of herpetic keratitis during the study period was 31.5 per 100,000 person-years (95% confidence interval [CI], 25.5-37.5), and incidences were 13.2 per 100,000 person-years for new cases (95% CI, 10.4-15.9) and 18.3 per 100,000 person-years for recurrences (95% CI, 14.6-22.1). The most frequent types were dendritic keratitis (56.3%, n = 153), stromal keratitis (29.5%, n = 81), and geographic keratitis (9.8%, n = 27). Other ocular lesions were associated with keratitis in 35.0% (n = 125) of cases; the most frequent were conjunctivitis (18.8%, n = 67), uveitis (11.8%, n = 42), and/or lid involvement (8.6%, n = 31). CONCLUSIONS: This prospective epidemiological study provides an estimate of the incidence of herpes keratitis in France. Herpetic keratitis remains an epidemiologically important eye disease that justifies the need to pursue health care and research programs aimed at improving the outcome of ocular herpetic disease.

Adolescent↗
PubMed2003

Selectivity in vibrationally mediated single-molecule chemistry.

The selective excitation of molecular vibrations provides a means to directly influence the speed and outcome of chemical reactions. Such mode-selective chemistry has traditionally used laser pulses to prepare reactants in specific vibrational states to enhance reactivity or modify the distribution of product species. Inelastic tunnelling electrons may also excite molecular vibrations and have been used to that effect on adsorbed molecules, to cleave individual chemical bonds and induce molecular motion or dissociation. Here we demonstrate that inelastic tunnelling electrons can be tuned to induce selectively either the translation or desorption of individual ammonia molecules on a Cu(100) surface. We are able to select a particular reaction pathway by adjusting the electronic tunnelling current and energy during the reaction induction such that we activate either the stretching vibration of ammonia or the inversion of its pyramidal structure. Our results illustrate the ability of the scanning tunnelling microscope to probe single-molecule events in the limit of very low yield and very low power irradiation, which should allow the investigation of reaction pathways not readily amenable to study by more conventional approaches.

Journal Article↗
PubMed2001

Adsorbate-substrate vibrational modes of benzene on Ag(110) resolved with scanning tunneling spectroscopy.

Using a low temperature scanning tunneling microscope, we have detected low energy adsorbate-substrate (external or frustrated) vibrational modes of benzene molecules adsorbed on a Ag(110) surface. We demonstrate that such vibrations represent a fingerprint of the molecules' chemical state and environment; two different vibrational spectra are measured on molecules populating two different adsorption states. We also find that the distortion of the adsorption geometry of the molecules may give rise to the excitation of additional (initially hidden) modes. Important differences in the spatial distribution of the inelastic signal are also observed for these external modes.

Journal Article↗
PubMed2000

Expression of T- and L-type calcium channel mRNA in murine sinoatrial node.

At the cellular level, cardiac pacemaking which sets the rate and rhythm of the heartbeat is produced by the slow diastolic depolarization. Several ion channels contribute to this pacemaker depolarization, including T-type and L-type calcium currents. To evaluate the molecular basis of the currents involved, we investigated the cellular distribution of various low voltage activated (LVA) and high voltage activated (HVA) calcium channel mRNAs in the murine sinoatrial (SA) node by in-situ hybridization. The most prominently expressed LVA calcium channel in the SA node is Ca(v)3.1, whereas Ca(v)3.2 is present at moderate levels. The dominant HVA calcium channel transcript is Ca(v)1.2; only traces of Ca(v)1.3 mRNA are detectable in SA myocytes of mice.

Animals↗
PubMed1999

Microfibrillar structure of PGG-glucan in aqueous solution as triple-helix aggregates by small angle x-ray scattering.

The conformation of polysaccharide PGG-Glucan, isolated from yeast cell walls, in aqueous solution was investigated by small angle x-ray scattering (SAXS) and multidetector gel permeation chromatography coupled with postcolumn delivery (GPC/PCD) techniques in comparison with scleroglucan. It was shown that both polysaccharides exhibit a rigid rod-like conformation in aqueous solution by SAXS experiments. The mass per unit length (M/L) and radius (R) of rod cross section of PGG-Glucan were measured to be 6300 daltons/nm and 1.89 nm, while those of scleroglucan are 2300 and 0.83, respectively. Utilizing a GPC/light scattering technique, the average aggregation number of PGG-Glucan is 9, while that of scleroglucan is around 3. From the comparison of the M/L and R of the respective rod cross sections as well as their aggregation number data, it is concluded that PGG-Glucan is composed of triple helices, which tend to aggregate as triplets in solution, whereas scleroglucan is composed of a single triple helix. The aggregation number distribution of PGG-Glucan was found to range from 1 to about 25 determined by GPC/PCD. From the observation of a Debye-Scherrer ring type of peak in the macroscopic scattering cross section of PGG-Glucan by SAXS, the existence of a small amount of ordered clusters of PGG-Glucan can be deduced. The "lattice parameter" of these ordered fasces-like clusters is consistent with the radius of the individual triple-helical rods forming a microfibrillar superstructure. These results indicate that higher aggregated forms of PGG-Glucan containing up to 8 triple helices behave as ordered fasces-like clusters. We conclude that PGG-Glucan is triple-helix aggregates formed by rigid rods stacking together side by side. We propose a molecular structural model for PGG-Glucan conformations.

Carbohydrate Conformation↗
PubMed1995

Structural properties of native and sonicated cinerean, a beta- (1-->3) (1-->6)-D-glucan produced by Botrytis cinerea.

Cinerean, the extracellular beta-(1-->3) (1-->6)-D-glucan of the fungus Botrytis cinerea was studied. Electron micrographs of the native polysaccharide revealed quasi-endless fibrils with an estimated diameter of ca. 1.5 nm. A particle mass of 10(9)-10(10) daltons was determined from dilute solutions by low-angle laser light scattering. Sonication of increasing duration led to fragmentation of the native polymer with an approximately exponential decrease of mass in the range of average molecular masses between 250,000 and 50,000 daltons. Shadowed by platinum, cinerean fibril fragments with a weight-average molecular mass of 172,000 +/- 3000 daltons could be characterized from electron micrographs as a distribution of rods of most probable length of 45 nm and an average length of 72 nm. Small-angle X-ray scattering confirmed the fibrillar structure of the native cinerean and the rodlike structure of sonicated cinerean. A rod diameter of 1.9 +/- 0.2 nm and a mass per unit length of 2250 +/- 490 daltons/nm were found. The latter is in agreement with the value of 1830 daltons/nm calculated from the length distribution determined from the electron micrographs. These data-especially the mass per unit length-suggest a quaternary structure for the polysaccharide. Such a structure would explain the rigidity of the rods which, in turn, is responsible for the characteristic phase separation behaviour in aqueous solutions observed by nephelometry and viscometry.

Carbohydrate Sequence↗
PubMed1991

The influence of oral potassium citrate/bicarbonate on blood pressure in essential hypertension during unrestricted salt intake.

In several trials, a blood pressure lowering effect of potassium chloride could be demonstrated. However, it is not known if other potassium salts are also effective. In a randomized cross-over trial, 12 patients with essential hypertension were treated for 8 weeks with placebo and 120 mmol potassium per day. Potassium was given together with 50% citrate and 50% bicarbonate as anions. Urinary potassium excretion rose from 61.8 +/- 8.1 to 166.7 +/- 21.2 mmol/24 hours during potassium supplementation. However, blood pressure and heart rate remained unchanged when compared to placebo. Non-chloride potassium salts may not be effective in lowering blood pressure in essential hypertension. Since potassium rich foods like fruits and vegetables contain potassium mostly as non-chloride salts, it appears to be premature to recommend a high dietary potassium intake as a mean to treat elevated blood pressure.

Adult↗
PubMed1988

[Soft intraocular silicone lenses: results after a one-year follow-up].

The main advantage of phacoemulsification is lost when the 3 mm incision has to be enlarged to at least 6 or 7 mm to permit the insertion of a PMMA lens. The major reason for the development of soft IOL is their flexibility which allows them to be folded and introduced through a small incision. We began a clinical study to determine the safety and efficacy of a new silicone lens, which is a single piece, injection molded, flexible implant. 25 patients undergoing extracapsular cataract extraction were included in this study. The silicone lens was inserted flat through the wound and the desired position was sulcus fixation. After a one year follow up period, the results were compared with those of 207 patients implanted with PMMA lenses. The visual results and the mean endothelial cell loss were similar in both groups. Iris capture was seen in 4 cases of soft lenses, probably due to the minimal haptic rigidity. Long term in vivo studies in the unique environment of the eye will be necessary to establish the biocompatibility of new soft intraocular lenses.

Aged↗
PubMed1983

Neutron small angle scattering of matched proteoliposomes with incorporated F0F1 ATPase complex from Rhodospirillum rubrum FR1. An approach to the structure of membrane proteins in their natural environment.

Purified F0F1 ATPase from Rhodospirillum rubrum FR1 has been incorporated into lipid vesicles from the partially deuterated phospholipid dimyristoylglycerophosphocholine (DMPC-D54). These proteoliposomes were able to carry out energy transducing reactions. The incorporation of the membrane protein was controlled by freeze fracture electron microscopy. A method for structural research of the membrane protein in its natural environment has been developed by means of neutron small angle scattering. Using the contrast variation technique, the lipid part of the proteoliposomes was matched by adding an appropriate amount of D2O to the solvent. Thus the neutron scattering profile of F0F1 ATPase incorporated into vesicles was separated from the neutron scattering of the liposome. F0F1 ATPase incorporated in a lipid bilayer, as well as the free enzyme, yields a radius of gyration of Rg = 6.0 +/- 0.1 nm which leads to an overall diameter of 15.5 nm. This result suggests that the monomeric form of F0F1 ATPase is incorporated in DMPC-D54 membranes at 20 degrees C.

Adenosine Triphosphatases↗
PubMed1983

[Mr 1268--a new furylmethyl-substituted benzomorphan. Comparison of its effects with pentazocine and placebo in a double-blind study].

Mr 1268 (alpha-5,9-dimethyl-2(3-methyl-3-methylfuryl)-2-hydroxy-6, 7-benzomorphan) was tested in two dosages (15 mg and 30 mg) at random on a total of 200 patients with severe postoperative pain in a double blind study against pentazocine and placebo. The analgesic effect of 30 mg Mr 1268 and 30 mg pentazocine compared with placebo was statistically significant 15 min after intramuscular injection. At the dosage applied no major respiratory or circulatory effects were observed in the patients. The minimal changes in the systolic blood pressure were of no statistical significance. Side-effects observed in many patients in the verum group were miosis and transpiration. For all other side-effects there was no statistically significant difference between placebo and the verum group or among the various verum groups.

Adult↗