Biomedical subjects

I Schmidt

Publications and source records attributed to I Schmidt.

At least 19 recordsLinked to original sources

PubMed2006

Role of nitrogen oxides in the metabolism of ammonia-oxidizing bacteria.

Ammonia-oxidizing bacteria (AOB) can use oxygen and nitrite as electron acceptors. Nitrite reduction by Nitrosomonas is observed under three conditions: (i) hydrogen-dependent denitrification, (ii) anoxic ammonia oxidation with nitrogen dioxide (NO(2)) and (iii) NO(x)-induced aerobic ammonia oxidation. NO(x) molecules play an important role in the conversion of ammonia and nitrite by AOB. Absence of nitric oxide (NO), which is generally detectable during ammonia oxidation, severely impairs ammonia oxidation by AOB. The lag phase of recovery of aerobic ammonia oxidation was significantly reduced by NO(2) addition. Acetylene inhibition tests showed that NO(2)-dependent and oxygen-dependent ammonia oxidation can be distinguished. Addition of NO(x) increased specific activity of ammonia oxidation, growth rate and denitrification capacity. Together, these findings resulted in a hypothetical model on the role of NO(x) in ammonia oxidation: the NO(x) cycle.

Ammonia↗

PubMed2005

1994-2004: 10 years of research on the anaerobic oxidation of ammonium.

The obligately anaerobic ammonium oxidation (anammox) reaction with nitrite as primary electron acceptor is catalysed by the planctomycete-like bacteria Brocadia anammoxidans, Kuenenia stuttgartiensis and Scalindua sorokinii. The anammox bacteria use a complex reaction mechanism involving hydrazine as an intermediate. They have a unique prokaryotic organelle, the anammoxosome, surrounded by ladderane lipids, which exclusively contains the hydrazine oxidoreductase as the major protein to combine nitrite and ammonia in a one-to-one fashion. In addition to the peculiar microbiology, anammox was shown to be very important in the oceanic nitrogen cycle, and proved to be a very good alternative for treatment of high-strength nitrogenous waste streams. With the assembly of the K. stuttgartiensis genome at Genoscope, Evry, France, the anammox reaction has entered the genomic and proteomic era, enabling the elucidation of many intriguing aspects of this fascinating microbial process.

Anaerobiosis↗

PubMed2003

Anaerobic ammonium oxidation by marine and freshwater planctomycete-like bacteria.

Recently, two fresh water species, " Candidatus Brocadia anammoxidans" and " Candidatus Kuenenia stuttgartiensis", and one marine species, " Candidatus Scalindua sorokinii", of planctomycete anammox bacteria have been identified. " Candidatus Scalindua sorokinii" was discovered in the Black Sea, and contributed substantially to the loss of fixed nitrogen. All three species contain a unique organelle--the anammoxosome--in their cytoplasm. The anammoxosome contains the hydrazine/hydroxylamine oxidoreductase enzyme, and is thus the site of anammox catabolism. The anammoxosome is surrounded by a very dense membrane composed almost exclusively of linearly concatenated cyclobutane-containing lipids. These so-called 'ladderanes' are connected to the glycerol moiety via both ester and ether bonds. In natural and man-made ecosystems, anammox bacteria can cooperate with aerobic ammonium-oxidising bacteria, which protect them from harmful oxygen, and provide the necessary nitrite. The cooperation of these two groups of ammonium-oxidising bacteria is the microbial basis for a sustainable one reactor system, CANON (completely autotrophic nitrogen-removal over nitrite) to remove ammonia from high strength wastewater.

Anaerobiosis↗

PubMed2001

Mechanisms for LEPR-mediated regulation of leptin expression in brown and white adipocytes in rat pups.

To investigate the underlying mechanisms for leptin receptor (LEPR)-mediated regulation of leptin gene (Lep) expression in brown (BAT) and white (WAT) adipose tissue and resultant effects on plasma leptin concentrations (plasma-LEP), we examined effects of sympathetic nervous system (SNS) activity, caloric balance, and body fat content on leptin mRNA levels in BAT and WAT in 10-day-old rat pups segregating for Lepr(fa). In mother-reared pups, Lep mRNA levels were fa/fa > +/fa = +/+ in BAT and was fa/fa > +/fa > +/+ in WAT. The genotype effects on Lep expression in BAT and plasma-LEP were virtually eliminated when the differences in SNS activity between fa/fa and +/fa pups were equalized by artificial rearing of pups under thermoneutral conditions with or without oral norepinephrine (NE) administration. NE administration alone had little effect on the Lepr(fa)-dependent stratification of Lep expression in WAT. BAT-Lep mRNA was the main determinant of plasma-LEP. Metabolic rate, a surrogate indicator of SNS activity, explained 87% of the variation in BAT-Lep mRNA (R(2) = 0.93), whereas caloric balance (40%) and body fat mass (6%) accounted for most of the variation in WAT-Lep mRNA (R(2) = 0.53). We conclude that feedback regulation of Lep expression in BAT is primarily via central nervous system-mediated effects of leptin on SNS activity, whereas the control of leptin expression in WAT is more likely via mechanisms not directly dependent on SNS activity.

Adipocytes↗

PubMed2001

Leptin responsiveness of juvenile rats: proof of leptin function within the physiological range.

To bridge the gap between studies demonstrating leptin's role in protecting fat stores when food is scarce and other studies demonstrating the effects of treatment with leptin at doses that increase plasma levels to values found in overfed animals, we investigated whether leptin serves an adipostatic function within the normal range of free-feeding lean animals, i.e. within the very small range of endogenous plasma levels at which no leptin resistance occurs. For this purpose we applied recombinant leptin via mini-osmotic pumps to rats between 15 and 24 days of age and between 25 and 34 days of age and studied its dose-dependent effects on body mass and fat mass at plasma leptin concentrations extending down to the normal levels in lean animals. Using percentage change of fat mass (relative to that of saline-treated littermates) as the measure, a linear dose-response curve was found up to doses of 2 microg g(-1) day(-1), corresponding to plasma leptin concentrations between the normal physiological range and 50 ng ml(-1). In 15- to 24-day-old animals, analysis of the correlation (r = -0.89) between individual plasma concentrations and the corresponding leptin-induced changes of body fat content for a range extending down towards zero (i.e. towards the average fat content of the controls) yielded a zero value of 3.1 ng ml(-1), which was within the 2-4 ng ml(-1) range of plasma leptin concentrations found in the control pups. Likewise, regression analysis for the data from the 25- to 34-day-old pups (r = -0.88), for which the control range was 1-3 ng ml(-1), yielded a zero value of 1.9 ng ml(-1). We conclude that normal plasma leptin levels represent an adipostatic signal. Steady-state levels of plasma leptin in free-feeding lean animals thus provide a signal not only for protecting sufficiency but also for limiting increases of body fat stores.

Adipose Tissue↗

PubMed2001

Effects of gaseous NO2 on cells of Nitrosomonas eutropha previously incapable of using ammonia as an energy source.

Cells of Nitrosomonas eutropha grown under anoxic conditions with hydrogen as electron donor and nitrite as electron acceptor were initially unable to oxidize ammonia (ammonium) and hydroxylamine when transferred to oxic conditions. Recovery of ammonia and hydroxylamine oxidation activity was dependent on the presence of NO2. Under oxic conditions, without addition of NO2, ammonia consumption started after 8 - 9 days, and small amounts of NO and NO2 were detectable in the gas atmosphere. Removing these nitrogen oxides by intensive aeration, ammonia oxidation activity decreased and broke off after 15 days. Addition of gaseous NO2 (25 ppm1) led to a fast recovery of ammonia oxidation (3 days). Simultaneously, the arrangement of intracytoplasmic membranes (ICM) changed from circular to flattened vesicles, the protein pattern revealed an increase in the concentration of a 27 and a 30 kDa polypeptide, and the cytochrome c content increased significantly.

Aerobiosis↗

PubMed2001

Gaseous NO2 as a regulator for ammonia oxidation of Nitrosomonas eutropha.

Cells of Nitrosomonas eutropha strain N904 that were denitrifying under anoxic conditions with hydrogen as electron donor and nitrite as electron acceptor were unable to utilize ammonium (ammonia) as an energy source. The recovery of ammonia oxidation activity was dependent on the presence of NO2. Anaerobic ammonia oxidation activity was observed in a helium atmosphere supplemented with 25 ppm NO2 after 20 h. Ammonia oxidation activity was detected after 2-3 days using an oxic atmosphere with 25 ppm NO2. In contrast, ammonia consumption started after 8-9 days under oxic conditions without the addition of NO2; in this case, small amounts of NO and NO2 were detected and their concentrations increased with increasing ammonia oxidation activities. Hardly any ammonia oxidation was detected when nitrogen oxides were removed by intensive aeration. It would seem, therefore, that NO2 is the master regulatory signal for ammonia oxidation in Nitrosomonas eutropha. Anaerobic ammonia oxidation activity was inhibited by the addition of NO. This inhibition was partly compensated by either increasing the NO2 concentration or by using 2,3-dimercapto-1-propane-sulfonic acid as a NO binding substrate. DMPS was inhibitory to nitrification under oxic conditions, while increased amounts of NO or NO2 led to increased oxidation activities.

Aerobiosis↗

PubMed2001

The effect of leptin treatment on the development of obesity in overfed suckling Wistar rats.

OBJECTIVE: To identify the role of hyperleptinaemia in mediating the effects of early postnatal overfeeding in a rat strain known to be prone to manipulations of the early environment which result in predispositions for obesity and associated metabolic and cardiovascular disturbance in later life. DESIGN: Wistar rats were reared in normal litters (NL, 10--12 pups) or small litters (SL, four pups) from postnatal day 3 and killed for determination of body composition and plasma leptin and insulin concentrations on day 7 or day 21 after having been treated with recombinant leptin (2 x 50 (pmol/g)/day) or saline from day 1. RESULTS: Rearing in SL doubled the body fat content and plasma leptin levels in comparison to NL pups by 21 days of age. Under leptin-treatment throughout suckling age, NL pups remained leptin responsive, ie the difference in body fat content was progressively reduced relative to the controls. Until 7 days of age, despite the body fat content of untreated SL pups being 2-fold higher and their plasma leptin level 7-fold higher than that of NL pups, leptin treatment caused the same percentage decreases in body fat in SL than in NL pups. But in contrast to NL pups, the SL pups became leptin resistant thereafter. Plasma insulin levels in 7-day-old leptin-treated SL pups were 3-fold higher than in untreated littermates and 5-fold higher than in the NL groups. CONCLUSION: Prophylactic leptin treatment does not prevent hyperinsulinaemia and excessive fat deposition in SL pups. On the other hand, selective hyperleptinaemia during suckling age does not trigger leptin resistance and obesity in NL pups. Rather than hyperleptinaemia per se, other factors associated with early postnatal overnutrition, for example, the concurrent hyperinsulinaemia, seem to play a pivotal role for the development of leptin-resistance and life-long obesity risk in SL rats.

Animals↗

PubMed2001

Parvovirus B19 DNA in plasma pools and plasma derivatives.

BACKGROUND AND OBJECTIVES: Human parvovirus B19 (B19) has been transmitted by various plasma-derived medicinal products. The aim of this study was to determine the frequency and the level of B19 DNA contamination in plasma pools destined for fractionation and in a broad range of plasma derivatives. In addition, removal of B19 DNA by the manufacturing process was investigated in cases where corresponding samples from plasma pool and product were available. MATERIALS AND METHODS: Plasma pool samples and blood products were tested for B19 DNA by nested polymerase chain reaction (PCR), and the viral DNA content was determined by TaqMan quantitative PCR. RESULTS: Two-hundred and twenty two of 372 plasma pools for fractionation contained B19 DNA at concentrations of 10(2)-10(8) genome equivalents/ml (geq/ml). While approximately 65% of the DNA-positive plasma pools were only moderately contaminated (< 10(5) geq/ml), 35% contained > 10(6) geq/ml. High frequencies of contamination were detected in Factor VIII (79 of 91), prothrombin complex concentrates (38 of 43) and Factor IX (41 of 62), where the concentration of B19 DNA ranged between 102 and 107 geq/ml. A lower level of B19 DNA contamination was found in antithrombin III (five of 26 samples), in anti-D immunoglobulins (three of 37 samples) and in albumin (four of 51 samples), with levels ranging between 10(2) and 10(3) geq/ml. Furthermore, investigation of plasma pools for solvent/detergent plasma (S/D plasma), from two manufacturers, revealed B19 DNA in 15 of 66 batches at concentrations of 10(2)-10(8) geq/ml. Similar concentrations were detected in the corresponding final S/D plasma products. Anti-B19 immunoglobulin G (IgG) was found in plasma pools and S/D plasma at concentrations of approximately 40 IU/ml. CONCLUSION: Although positive PCR results do not necessarily reflect infectivity, these data show that B19 is a common contaminant in plasma pools and in plasma-derived medicinal products. Considering the resistance of animal parvoviruses to inactivation by heat and chemical agents, and the absence of specific information for B19, the risk of B19 transmission by plasma products should be considered. Physicians should be aware of this problem when treating patients of B19-related risk groups. The plasma fractionation industry should continue their efforts to avoid B19 contamination of plasma derivatives and develop methods which are effective in removing/inactivating parvovirus B19.

Blood↗

PubMed2001

The association of the involvement of financial compensation with the outcome of cervicobrachial pain that is treated conservatively.

OBJECTIVES: To examine the influence of the involvement of financial compensation on the results of physiotherapeutic McKenzie treatment on cervicobrachial pain. METHODS: A prospective study was carried out with a cohort of 60 patients referred to two spine clinics after they had experienced at least 5 weeks of neck pain radiating to the arm. Follow-up was performed 1 yr later using a validated questionnaire to measure the outcomes of neck and arm pain, disability, the use of analgesics and the perceived effect of the treatment as reported by the patient. RESULTS: At follow-up, there was no improvement in the group of patients for whom financial compensation was involved, whereas the group for whom compensation was involved showed highly significant improvement. CONCLUSIONS: Despite uniform selection criteria and similarity of complaints and treatment protocols, the involvement of financial compensation seemed to be associated with an adverse effect on treatment results for patients with cervicobrachial pain who were treated conservatively.

Adult↗

PubMed2000

Copper(II) complexes of inverted porphyrin and its methylated derivatives.

The inverted porphyrins 2-aza-5,10,15,20-tetraphenyl-21-carbaporphyrin (CTPPH2) and its methylated derivatives 2-aza-2-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrin (2-NCH3CTPPH) and 2-aza-2-methyl-5,10,15,20-tetraphenyl-21-methyl-21-carbaporphyrin (2-NCH3-21-CH3CTPPH) stabilize the rare organocopper(II) complexes (CTPP)CuII (1), (2-NCH3CTPP)CuII (2), (CTPPH)CuIIX (3-X), (2-NCH3CTPPH)CuIIX (4-X) (X = Cl-, TFA), and (2-NCH3-21-CH3CTPP)CuIICl (5). The EPR spectra recorded for 1, 2, 4, and 5 revealed typical features diagnostic of the copper(II) electronic structure. The superhyperfine coupling pattern indicates a presence of three nitrogen donors in the first coordination sphere. An addition of HX acid to 1 and 2 to yield the species 3-X and 4-X. The reaction mechanism includes protonation of the inner C(21) carbon accompanied by an axial coordination of anion. Methylation of (2-NCH3CTPP)CuII (2) with methyl iodide resulted in formation of (2-NCH3-21-CH3CTPP)CuIICl (5) which implies an existence of a sigma-carbanion-copper(II) bond in 2. The 2H NMR investigations carried out for the pyrrole deuterated derivatives (CTPP-d7)CuII, (2-NCH3-21-CH3CTTP-d7)CuIICl, and the methyl deuterated (2-NCH3-21-CD3CTPP)CuIICl one confirmed independently the copper(II) electronic structure with the considerable dx2-y2 metal orbital contribution to the SOMO. The redox properties of copper(II) inverted porphyrins were studied by the cyclic and differential pulse voltammetry. The halfwave potentials indicate a metal-centered oxidation of 1 (390 mV) and 2 (343 mV). The dimethylated homologue 5 reveals the reduction process at -224 mV attributed to the CuII/CuI transformation.

Journal Article↗

PubMed2000

[Significance of unresolved financial compensation for the course of cervical root compression].

The aim of this study was to examine the influence of claims for financial compensation on the results of physiotherapeutic McKenzie treatment for cervical nerve root compression. This study was based on prospectively collected data for quality assurance purpose with baseline classification and included a follow-up postal questionnaire to measure the outcomes: Neck and arm pain, disability, use of analgesics and the perceived effect of the treatment registered by the patient. At baseline, patients with or without compensation issues were identical in regard to their neurological and clinical signs. The study showed that 6-12 months later there was no improvement in six out of seven patients with claims for compensation involvement, in contrast to the 21 patients without claims for financial compensation who all showed significant improvement. The results applied to all five outcome measures. In conclusion, compensation involvement seems to act as a negative factor on treatment results for patients with cervical nerve root compression who were treated conservatively.

Adult↗

PubMed2000

Interaction of genetic and environmental programming of the leptin system and of obesity disposition.

Possible adverse interactions between an usually inconspicuous genetic trait and early environmental factors favoring the development of obesity were investigated in rats heterozygous for the leptin receptor defect "fatty" (fa). Pups were exposed to early postnatal overfeeding by reducing litter size from normally 10-12 to only 4. Rearing +/+ and +/fa pups from day 3 to 21 in small litters increased fat-free dry mass and body fat, but only in the latter did a significant interaction with genotype occur. Pronounced differences in the responsiveness of +/+ and +/fa pups to "prophylactic" leptin treatment (from day 1 to 21) were observed, with +/fa females from small litters being nearly as fat and unresponsive as previously reported for normally reared fa/fa pups. Clear heterozygous differences in total hypothalamic leptin binding, but no litter size effect, paralleling the differences in leptin responsiveness, were observed. By early postnatal overfeeding an usually inconspicuous genetic trait may thus become etiologic for the development of obesity via physiological changes other than the decreased leptin binding characterizing the genetic defect.

Adipose Tissue↗

PubMed2000

Confined space synthesis. A novel route to nanosized zeolites.

Confined space synthesis is a novel method in zeolite synthesis. It involves crystallization of the zeolite inside the pore system of an inert mesoporous matrix. In this way it is possible to prepare nanosized zeolites with a controlled size distribution by proper choice of the inert matrix. Here, confined space synthesis was adopted to prepare nanosized ZSM-5, zeolite Beta, zeolite X, and zeolite A with tailored crystal size distributions using mesoporous carbon blacks as inert matrices. All zeolites were characterized by X-ray powder diffraction, transmission electron microscopy, and nitrogen adsorption/desorption prior to and after removal of the carbon matrix. ZSM-5 with Si/Al ratios of 50, 100, and infinity (silicalite-1) were synthesized with controlled average crystal sizes in the range 20-75 nm. Nanosized zeolite Beta (7-30 nm), zeolite X (22-60 nm), and zeolite A (25-37 nm) were prepared similarly. Removal of the carbon matrix by controlled combustion allows a convenient method for isolation of the pure and highly crystalline zeolites. Therefore, confined space synthesis appears to be an attractive method for preparation of zeolites with a controlled size distribution.

Journal Article↗

PubMed2000

The homeodomain of Nkx2.2 carries two cooperatively acting nuclear localization signals.

NK-2 family members of homeodomain proteins have been identified as important regulators of growth and development in the ventral forebrain, heart, lung, and thyroid. In addition, Nk2.2 expression has been detected in the pancreas, where it is vital for the final differentiation of beta-cells. In our present paper, we have analyzed the domains necessary for nuclear transport of Nkx2.2. With the help of deletion mutants we identified two separate nuclear localization signals (NLS). Interestingly, both NLSs are situated in the homeodomain. They belong to the monopartite class of NLS; the proximal NLS has the sequence KKRKRR and lies at the very N-terminus of the homeodomain, while the more distal NLS RYKMKRAR is at the homeodomain C-terminus. Each NLS per se is sufficient for nuclear transport of Nkx2.2 into the nucleus, although inefficiently. Both identified NLSs act cooperatively in mediating complete nuclear transport of Nkx2.2.

Amino Acid Sequence↗

PubMed2000

Preparation and crystal structures of formato complexes of the [MIV3O4]4+ and [MIV3S4]4+ (M = Mo, W) clusters. Convenient precursors to the corresponding aqua complexes.

In the aqueous chemistry of molybdenum(IV) and tungsten(IV), trinuclear, incomplete cubane-like, oxo and sulfido clusters of the type [M3E4]4+ (M = Mo, W; E = O, S) play a central role. We here describe how formato complexes of all these cluster cores can be prepared in high yields by crystallization from methanol-water or ethanol-water mixtures. Since potassium and ammonium formate are very soluble in these alcohol-water mixtures, high formate concentrations could be accomplished in the solutions from which the corresponding salts of cluster formato complexes crystallized. The [Mo3O4]4+ compounds could be synthesized without requiring the use of noncomplexing acids in the process. Some [M3E4]4+ compounds were characterized by single-crystal structure determinations. [NH4]3.20[K]0.80[H3O][Mo3O4(HCO2)8][HCO2].H2O was triclinic, space group P1 (No. 2) with a = 11.011(2) A, b = 13.310(2) A, c = 9.993(1) A, alpha = 106.817(7) degrees, beta = 91.651(9) degrees, gamma = 88.340(9) degrees, and two formula units per cell. [K]6[W3S4(HCO2)9][HCO2].2.27H2O.0.73CH3OH was monoclinic, space group C2/m (No. 12) with a = 19.605(6) A, b = 14.458(7) A, c = 13.627(5) A, beta = 118.94(2) degrees, and four formula units per cell. Generally, the nine coordination sites of [M3E4]4+ were occupied either by a mixture of monodentate and mu 2-bridging formato ligands or by monodentate formato ligands only. By dissolution in noncomplexing strong acid, all the formato complexes immediately hydrolyzed to form [M3E4(H2O)9]4+ aqua complexes. This allows, for example, high concentrations of [Mo3S4(H2O)9]4+ in CF3SO3H to be obtained and these solutions to be used for the synthesis of bimetallic clusters containing the cubane-like motif Mo3M'S4.

Journal Article↗

PubMed2000

[The Marjolin's ulcer": a malignant and rarely complication after burn trauma of the upper extremity - a case report].

The,Marjolin's ulcer" is a malignant lesion which is developed especially at chronic wounds after burn trauma. The latency from primary trauma to the malignant transformation is about 30 years. The lesion is more aggressive than other squamous cell carcinomas. We report on the combined radiation and surgical therapy of an 65-year-old patient with this lesion on the right hand and regional lymph node metastases. The extensive tissue defect after wide excision was reconstructed with a reversal radial forearm flap.

Aged↗

PubMed2000

Rapid functional plasticity of the somatosensory cortex after finger amputation.

Recent research indicates that areas of the primary somatosensory (SI) and primary motor cortex show massive cortical reorganization after amputation of the upper arm, forearm or fingers. Most of these studies were carried out months or several years after amputation. In the present study, we describe cortical reorganization of areas in the SI of a patient who underwent amputation of the traumatized middle and ring fingers of his right hand 10 days before cortical magnetic source imaging data were obtained. Somatosensory-evoked magnetic fields (SEF) to mechanical stimuli to the finger tips were recorded and single moving dipoles were calculated using a realistic volume conductor model. Results reveal that the dipoles representing the second and fifth fingers of the affected hand were closer together than the comparable dipoles of the unaffected hand. Our findings demonstrate that neural cell assemblies in SI which formerly represented the right middle and ring fingers of this amputee became reorganized and invaded by neighbouring cell assemblies of the index and little finger of the same hand. These results indicate that functional plasticity occurs within a period of 10 days after amputation.

Afferent Pathways↗