Search PubMed⌕ Search

Biomedical subjects

T Schneider

Publications and source records attributed to T Schneider.

At least 19 recordsLinked to original sources
PubMed2001

Isotope effects in underdoped cuprate superconductors: a quantum critical phenomenon.

We show that the unusual doping dependence of the isotope effects on transition temperature and zero temperature in-plane penetration depth naturally follows from the doping driven 3D-2D crossover and the 2D quantum superconductor to insulator transition in the underdoped limit. Since lattice distortions are the primary consequence of isotope substitution, our analysis clearly reveals the strong involvement of lattice degrees of freedom in mediating superconductivity.

Journal Article↗
PubMed2001

Efficient synthesis of gamma-alkylidenetetronic esters by sequential Lewis acid catalyzed.

A new approach for the synthesis of gamma-alkylidenetetronic acids and esters is reported which involves Me3SiOTf-catalyzed, regio- and stereoselective cyclization of 4-alkoxy-1,3-bis(trimethylsilyloxy)-1,3-butadienes with oxalyl chloride. The alpha-hydroxy group of the butenolides is efficiently functionalized by palladium-catalyzed cross-coupling reactions via the corresponding enol triflates.

Journal Article↗
PubMed2001

[Life threatening hypercalcemia in a young man with ALL].

HISTORY AND ADMISSION FINDINGS: A 16-year-old man experienced fatigue, vomiting and diffuse abdominal pain. Since 4 days he had myalgia in both arms and legs. On examination only a tachycardia of 110/min was noticed. INVESTIGATIONS: Laboratory tests revealed hemoglobin 12.7 g/dl, leucocytes 10,300/microliter, platelets 89,000/microliter, LDH 191 U/l, sodium 134 mmol/l, potassium 2.76 mmol/l, calcium 4.52 mmol/l (I), creatinine 1.13 mg/dl, urea 72 mg/dl, uric acid 11.2 mg/dl. The levels of PTH (0 pg/ml), PTH-related peptide, vitamin D, vitamin A, IGF-1, STH, 5-HIES and interleukin 6 were within normal limits. TNF-alpha 25.9 pg/ml (< 8.1). The electrocardiography revealed a sinus rythm with a QT-time of 0.28 s (= 100%). Multiple osteolytic bone leasions were seen in thoracic CT-scan. Abdominal sonography showed normal liver structure, multiple subhepatic lymph nodes without splenomegaly. The cytologic examination of the bone marrow demonstrated a diffuse infiltration by a common acute leukemia. TREATMENT AND COURSE: The rehydration with physiologic saline (3500 ml/d) was initiated in the ICU. Furosemide was added for further renal excretion. Additionally prednisone (100 mg/d) and calcitonin (300 I.E./d) were given. The calcium level fell within two days. No cardiac arrhythmia nor acute renal failure were seen. After definitive diagnosing the patient was treated corresponding to a specific protocol. One year later the relapsing ALL was diagnosed also by hypercalcemia (5.9 mmol/l). The level of TNF-alpha before and after correction of hypercalcemia was 20 pg/ml. CONCLUSION: The acute treatment of hypercalcemia is independent of the underlying cause (rehydration with physiologic saline, renal excretion with furosemide, inhibition of osteoclastic activity). The main causes are hyperparathyreoidism or malignancys (90%). We describe TNF-alpha as a possible marker of tumoral load of a common ALL but we are not able to reveal a correlation between TNF-alpha and the calcium level.

Adolescent↗
PubMed2001

[Benign, pulmonary metastatic leiomyoma of the uterus].

Pulmonary nodules resected in 10 patients were histologically classified as benign metastatic leiomyoma of the uterus. Hysterectomy because of myoma had been performed between 0 and 24 years earlier (median 14.9 years). Between 1 and 27 nodules were found in one or both lungs. Patients presenting with a single nodule had it resected with diagnostic intent and were followed up. Multiple nodules were resected if the loss of parenchyma was tolerable; otherwise, one lesion was resected for diagnosis. In some cases antihormonal therapy was performed postoperatively. The median duration of follow-up was 4.7 years. In this time, no local complication occurred, and no patient died of this disease. Apparently, benign metastatic leiomyoma of the uterus biologically shows benign behaviour. New manifestation or progressing growth of non-resected lesions does occur, however. Consequently, regular follow-up is required. Local complications indicate surgical intervention.

Adult↗
PubMed2001

[Sachse internal urethrotomy. Is erectile dysfuction a possible complication?].

Erectile dysfunction is reported to be a complication of direct-vision internal urethrotomy by some authors in 2.2-10.6% of cases. It is caused by injury to the cavernous nerve by direct severance with the cutting blade, late fibrosis after extravasation and infection, or by a shunt between the corpora cavernosa and corpus spongiosum. The aim of this examination was to evaluate all internal urethrotomy patients from 1990 to 1999, regarding this kind of complication. Of 184 patients, 111 had to be excluded due to preexisting erectile dysfunction, malignancy, age over 75 years, or open surgery of the urethra before internal urethrotomy. Five patients died. Of 184,68 patients did not have erectile problems before the operation and only one complained about erectile dysfunction following direct-vision internal urethrotomy. Further examination showed an impaired arterial inflow in both arteriae penis profunda; cavernosography could not prove a shunt between the corpora cavernosa and corpus spongiosum. Erectile dysfunction is a possible complication of direct-vision internal urethrotomy. External sphincterotomy at the 3- and 9-o'clock position, urethrotomy after injury or open reconstructive surgery of the urethra, and urethrotomy of long and dense strictures as well as a dilatation over 22 Chr. are known to cause this complication. To inform the patient concerning this kind of complication is recommended before urethrotomy.

Adolescent↗
PubMed2001

Does penile size in younger men cause problems in condom use? a prospective measurement of penile dimensions in 111 young and 32 older men.

OBJECTIVES: Young men often complain about problems with condom use, but very little information exists about the influence of men's age on penile dimensions and therefore on possible problems in the use of the most important means of contraception in the young. METHODS: We performed a prospective measurement of penile dimensions in 111 men,18 to 19 years old (group A), and in 32 men, 40 to 68 years old (group B). We measured penile length and width in the flaccid state and after visual and manual self-stimulation in group A and after intracavernous injection of prostaglandin E(1) in group B. RESULTS: The mean flaccid length in group A (8.60 cm) and group B (9.22 cm) was significantly different. The mean erect length in group A (14.48 cm) and group B (14.18 cm) was not significantly different. The mean flaccid width at the base was significantly different between group A (3.08 cm) and group B (2.87cm), but the mean flaccid width at the glans was not (group A, 3.02 cm; group B, 3.01 cm). The mean erect width at the base (group A, 3.95 cm; group B, 3.50 cm) and the erect width of the glans (group A, 3.49 cm; group B, 3.32 cm) were significantly different. CONCLUSIONS: Our assumption that the problems young men experience with condom use may be because of smaller penises could not be proved. To address the problems in condom use in younger men, a larger variety of condom sizes and better information about condom use may be useful.

Adult↗
PubMed2001

[Blood donation. Job description of the function of a physicion in a district subdivision].

Following the 1995 national reorganization of the transfusion system, the Nord Pas de Calais blood transfusion center has modified its blood collection organization, with the creation of four districts divided into three or four subdivisions. This change was part of Quality Assurance implementation in the center. This article provides the job description for a physician in charge of such a subdivision as well as the method chosen to design this description (inspired by the diagram of Hijman). This job was conceived as an association of human skills knowledge with the strategy of the blood center. In addition to his medical activity, the district subdivision physician becomes a manager and an organizer. The method used highlights the participation of all disciplines involved in blood donation.

Blood Banks↗
PubMed2001

Quantitative testing of liver function in relation to fibrosis in patients with chronic hepatitis B and C.

BACKGROUND/AIM: Quantitative tests of liver function may be superior to conventional tests to assess the prognosis of patients with liver diseases. There are insufficient data from quantitative testing of liver function (QTLF) for patients with chronic hepatitis B and C, particularly with regard to fibrosis. Therefore, we applied a broad panel of QTLF to these patients. METHODS: Three hundred and sixty-seven consecutive patients with chronic hepatitis B or C underwent liver biopsy and QTLF, which included tests for hepatic metabolism (aminopyrine breath test, galactose elimination capacity) and for hepatic perfusion (sorbitol clearance, indocyanine green clearance). QTLF values were correlated with liver histology (grading and staging for inflammation and fibrosis) and Child-Pugh classification for liver cirrhosis. RESULTS: In patients with no and moderate fibrosis, metabolic liver function was significantly decreased, whereas hepatic perfusion remained normal. Severe fibrosis and cirrhosis showed a significant decline in all QTLFs. Hepatic inflammation only reduced metabolic liver function, irrespective of the inflammatory grade. Viral etiology and HCV genotypes did not change QTLF. CONCLUSIONS: In summary, viral damage compromises hepatic metabolism before perfusion. Therefore, tests of metabolic liver function (aminopyrine breath test, galactose elimination capacity) should be useful to search for drugs that restore liver function in viral hepatitis irrespective of the fibrosis stage.

Adult↗
PubMed2001

Functional coupling between 'R-type' Ca2+ channels and insulin secretion in the insulinoma cell line INS-1.

Among voltage-gated Ca2+ channels the non-dihydropyridine-sensitive alpha1E subunit is functionally less well characterized than the structurally related alpha1A (omega-agatoxin-IVA sensitive, P- /Q-type) and alpha1B (omega-conotoxin-GVIA sensitive, N-type) subunits. In the rat insulinoma cell line, INS-1, a tissue-specific splice variant of alpha1E (alpha1Ee) has been characterized at the mRNA and protein levels, suggesting that INS-1 cells are a suitable model for investigating the function of alpha1Ee. In alpha1E-transfected human embryonic kidney (HEK-293) cells the alpha1E-selective peptide antagonist SNX-482 (100 nM) reduces alpha1Ed- and alpha1Ee-induced Ba2+ inward currents in the absence and presence of the auxiliary subunits beta3 and alpha2delta-2 by more than 80%. The inhibition is fast and only partially reversible. No effect of SNX-482 was detected on the recombinant T-type Ca2+ channel subunits alpha1G, alpha1H, and alpha1I showing that the toxin from the venom of Hysterocrates gigas is useful as an alpha1E-selective antagonist. After blocking known components of Ca2+ channel inward current in INS-1 cells by 2 microM (+/-)-isradipine plus 0.5 microM omega-conotoxin-MVIIC, the remaining current is reduced by 100 nM SNX-482 from -12.4 +/- 1.2 pA/pF to -7.6 +/- 0.5 pA/pF (n = 9). Furthermore, in INS-1 cells, glucose- and KCl-induced insulin release are reduced by SNX-482 in a dose-dependent manner leading to the conclusion that alpha1E, in addition to L-type and non-L-type (alpha1A-mediated) Ca2+ currents, is involved in Ca2+ dependent insulin secretion of INS-1 cells.

Alternative Splicing↗
PubMed2001

R-wave detection by subcutaneous ECG. Possible use for analyzing R-R variability.

BACKGROUND: Atrial arrhythmia (AA) discrimination remains a technological challenge for implanted cardiac devices. We examined the feasibility of R-wave detection by a subcutaneous far field ECG (SFFECG) and analysis of these signals for R to R variability as an indicator of atrial arrhythmia (AA). METHODS: Surface ECG and SFFECG (from the pacemaker pocket) were recorded in sixteen patients (61.5 +/- 11.4 years) with AA. The SFFECG was recorded with a pacemaker sized four electrode array acutely placed in the pacemaker pocket during implantation. The signals were analyzed to obtain peak-to-peak R wave amplitude and R to R interval variability (indicative of AAs). RESULTS: In sixteen patients R waves were visually discernible in all recordings. The percentage over and under detection for automatic R wave recognition SFFECG was 3 and 9%, respectively. R to R variability analysis using the SFFECG produced results concordant to those using the surface ECG. CONCLUSION: SFFECG might be a helpful adjunct in implantable device systems for detection of R waves and may be used for measurement of R to R variability.

Aged↗
PubMed2001

Heterogeneous tissue distribution of a mitochondrial DNA polymorphism in heteroplasmic subjects without mitochondrial disorders.

CONTEXT: Several maternally inherited point mutations of the mitochondrial genome cause mitochondrial disorders, but the correlation between genotype and phenotype remains obscure in many cases. The same mutation may cause various diseases, probably because of a different tissue distribution. OBJECTIVE: To assess the role of random somatic segregation in generating interperson differences by analysis of an apparently neutral polymorphism. DESIGN: Screening of 81 brain samples from subjects without mitochondrial disorders and selection of five necropsy cases showing a high level of heteroplasmy for the polymorphism. MAIN OUTCOME MEASURES: A proportion of various distinct genotypes in the mtDNA pool of the tissues, identified by fluorescent PCR products, representing a short polycytosine tract of variable length in the mitochondrial displacement loop. RESULTS: Differences were found between organs or groups of organs within subjects, pointing towards somatic segregation of mtDNA. In addition, marked differences of this organ distribution occurred between subjects, which cannot be explained by tissue specific selection. CONCLUSIONS: The observed interperson differences can be explained by somatic segregation, which occurs randomly at various developmental stages. Besides tissue specific selection, this process might participate in the distribution of pathogenic mtDNA mutations.

Adolescent↗
PubMed2001

Selective reduction of bone blood flow by short-term treatment with high-dose methylprednisolone. An experimental study in pigs.

Treatment with corticosteroids is a risk factor for non-traumatic avascular necrosis of the femoral head, but the pathological mechanism is poorly understood. Short-term treatment with high doses of methylprednisolone is used in severe neurotrauma and after kidney and heart transplantation. We investigated the effect of such treatment on the pattern of perfusion of the femoral head and of bone in general in the pig. We allocated 15 immature pigs to treatment with high-dose methylprednisolone (20 mg/kg per day intramuscularly for three days, followed by 10 mg/kg intramuscularly for a further 11 days) and 15 to a control group. Perfusion of the systematically subdivided femoral head, proximal femur, acetabulum, humerus, and soft tissues was determined by the microsphere technique. Blood flow in bone was severely reduced in the steroid-treated group. The reduction of flow affected all the segments and the entire epiphysis of the femoral head. No changes in flow were found in non-osseous tissue. Short-term treatment with high-dose methylprednisolone causes reduction of osseous blood flow which may be the pathogenetic factor in the early stage of steroid-induced osteonecrosis.

Acetabulum↗
PubMed2000

Quantification of calcium signal transmission from sarco-endoplasmic reticulum to the mitochondria.

Recent studies have shown that ryanodine and IP3 receptor (RyR/IP3R)-mediated cytosolic Ca2+ signals propagate to the mitochondria, initiating chains of events vital in the regulation of different cellular functions. However, the fraction of released Ca2+ utilized by the mitochondria during these processes has not been quantified. To measure the amount of Ca2+ taken up by the mitochondria, we used a novel approach that involves simultaneous fluorescence imaging of mitochondrial and cytosolic [Ca2+] in permeabilized H9c2 myotubes and RBL-2H3 mast cells. Communication between sarco-endoplasmic reticulum (SR/ER) and mitochondria is maintained in these permeabilized cells, as evidenced by the large RyR/IP3R-driven mitochondrial matrix [Ca2+] and NAD(P)H signals and also by preservation of the morphology of the SR/ER-mitochondrial junctions. Ca2+ was released from the SR/ER by addition of saturating caffeine or IP3 and subsequently thapsigargin (Tg), an inhibitor of SR/ER Ca2+ pumps. The amount of Ca2+ transmitted to the mitochondria was determined by measuring increases of global [Ca2+] in the incubation medium (cytosolic [Ca2+] ([Ca2+]c)). Mitochondrial Ca2+ uptake was calculated from the difference between [Ca2+]c responses recorded in the absence and presence of uncoupler or from [Ca2+]c elevations evoked by uncoupler or ionophore applied after complete Ca2+ mobilization from the SR/ER. [Ca2+]c increases were calibrated by adding Ca2+ pulses to the permeabilized cells. In H9c2 cells, caffeine induced partial mobilization of SR Ca2+ and mitochondria accumulated 26% of the released Ca2+. Sequential application of caffeine and Tg elicited complete discharge of SR Ca2+ without further increase in mitochondrial Ca2+ uptake. In RBL-2H3 mast cells, IP3 by itself elicited complete discharge of the ER Ca2+ store and the increase of the ionophore-releasable mitochondrial Ca2+ content reached 50% of the Ca2+ amount mobilized by IP3 + Tg. Thus, RyR/IP3R direct a substantial fraction of released Ca2+ to the mitochondria.

Calcium↗
PubMed2000

Rapid whole blood analysis of virus-specific CD4 and CD8 T cell responses in persistent HIV infection.

OBJECTIVES: Upon HIV infection, strong antiviral cytotoxic and helper T cell responses are generated. They are considered to be an important component in the control of HIV viral load. A simple and rapid whole blood assay was established to quantify and simultaneously characterize HIV-reactive CD4 and CD8 cells. The assay was applied to evaluate the effect of antiretroviral therapy on HIV-specific T cell responses. METHODS: Whole blood of 33 HIV-infected individuals was specifically stimulated by HIV-1 Pr55gag, and activation-induced intracellular cytokine expression in CD4 and CD8 T cells was analysed by flow cytometry. RESULTS: HIV-1-specific CD8 and CD4 T cells can be quantified simultaneously. As specific antigen, HIV-1 Pr55gag virus-like particles were superior to soluble protein, especially for the activation of CD8 T cells. In untreated individuals, a high frequency of HIV-specific T cells was observed. The frequency of CD8 T cells was consistently higher than the respective CD4 T cell response, thus demonstrating a dominance in CD8 T cell expansion in persistent HIV infection. Patients on antiretroviral therapy showed a significant reduction in HIV-specific CD4 and, even more strikingly, CD8 T cells. CONCLUSION: The whole blood assay provides a rapid estimate of the total antiviral T cell resources, and is highly suited for a clinical setting. It may thus have widespread applications for the evaluation of vaccination strategies and immunotherapy. Because antiretroviral therapy significantly reduces both HIV-specific cytotoxic and helper T cell responses, future therapeutic strategies should aim at improving cellular antiviral immunity.

Adult↗
PubMed2000

Multicenter, randomized, controlled trial of 150-J biphasic shocks compared with 200- to 360-J monophasic shocks in the resuscitation of out-of-hospital cardiac arrest victims. Optimized Response to Cardiac Arrest (ORCA) Investigators.

BACKGROUND: In the present study, we compared an automatic external defibrillator (AED) that delivers 150-J biphasic shocks with traditional high-energy (200- to 360-J) monophasic AEDs. METHODS AND RESULTS: AEDs were prospectively randomized according to defibrillation waveform on a daily basis in 4 emergency medical services systems. Defibrillation efficacy, survival to hospital admission and discharge, return of spontaneous circulation, and neurological status at discharge (cerebral performance category) were compared. Of 338 patients with out-of-hospital cardiac arrest, 115 had a cardiac etiology, presented with ventricular fibrillation, and were shocked with an AED. The time from the emergency call to the first shock was 8.9+/-3.0 (mean+/-SD) minutes. CONCLUSIONS: The 150-J biphasic waveform defibrillated at higher rates, resulting in more patients who achieved a return of spontaneous circulation. Although survival rates to hospital admission and discharge did not differ, discharged patients who had been resuscitated with biphasic shocks were more likely to have good cerebral performance.

Adult↗