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Biomedical subjects

M Jahn

Publications and source records attributed to M Jahn.

At least 19 recordsLinked to original sources
PubMed2000

Candidate gene analysis of organ pigmentation loci in the Solanaceae.

Ten structural genes from the Capsicum (pepper) carotenoid biosynthetic pathway have been localized on a (Capsicum annuum x Capsicum chinense)F(2) genetic map anchored in Lycopersicon (tomato). The positions of these genes were compared with positions of the same genes in tomato when known, and with loci from pepper, potato, and tomato that affect carotenoid levels in different tissues. C2, one of three phenotypically defined loci determining pepper fruit color, cosegregated with phytoene synthase. The capsanthin-capsorubin synthase (Ccs) locus, shown previously to cosegregate with Y, another pepper fruit color locus, mapped to pepper chromosome 6. Other structural genes in pepper corresponded to loci affecting carotenoid production as follows: Ccs in pepper and the B locus for hyperaccumulation of beta-carotene in tomato fruit mapped to homeologous regions; the position of the lycopene beta-cyclase gene in pepper may correspond to the lutescent-2 mutation in tomato; and the lycopene epsilon-cyclase locus in pepper corresponded to the lycopene epsilon-cyclase locus/Del mutation for hyperaccumulation of delta-carotene in tomato fruit. Additional associations were seen between the structural genes and previously mapped loci controlling quantitative variation in pepper and tomato fruit color. These results demonstrate that comparative analyses using candidate genes may be used to link specific metabolic phenotypes and loci that affect these phenotypes in related species.

Base Sequence↗
PubMed2000

Comparative genetics of disease resistance within the solanaceae.

Genomic positions of phenotypically defined disease resistance genes (R genes) and R gene homologues were analyzed in three solanaceous crop genera, Lycopersicon (tomato), Solanum (potato), and Capsicum (pepper). R genes occurred at corresponding positions in two or more genomes more frequently than expected by chance; however, in only two cases, both involving Phytophthora spp., did genes at corresponding positions have specificity for closely related pathogen taxa. In contrast, resistances to Globodera spp., potato virus Y, tobacco mosaic virus, and tomato spotted wilt virus were mapped in two or more genera and did not occur in corresponding positions. Without exception, pepper homologues of the cloned R genes Sw-5, N, Pto, Prf, and I2 were found in syntenous positions in other solanaceous genomes and in some cases also mapped to additional positions near phenotypically defined solanaceous R genes. This detailed analysis and synthesis of all available data for solanaceous R genes suggests a working hypothesis regarding the evolution of R genes. Specifically, while the taxonomic specificity of host R genes may be evolving rapidly, general functions of R alleles (e.g., initiation of resistance response) may be conserved at homologous loci in related plant genera.

Plant Diseases↗
PubMed2000

The I gene of bean: a dosage-dependent allele conferring extreme resistance, hypersensitive resistance, or spreading vascular necrosis in response to the potyvirus Bean common mosaic virus.

The resistance to the potyvirus Bean common mosaic virus (BCMV) conferred by the I allele in cultivars of Phaseolus vulgaris has been characterized as dominant, and it has been associated with both immunity and a systemic vascular necrosis in infected bean plants under field, as well as controlled, conditions. In our attempts to understand more fully the nature of the interaction between bean with the I resistance allele and the pathogen BCMV, we carefully varied both I allele dosage and temperature and observed the resulting, varying resistance responses. We report here that the I allele in the bean cultivars we studied is not dominant, but rather incompletely dominant, and that the system can be manipulated to show in plants a continuum of response to BCMV that ranges from immunity or extreme resistance, to hypersensitive resistance, to systemic phloem necrosis (and subsequent plant death). We propose that the particular phenotypic outcome in bean results from a quantitative interaction between viral pathogen and plant host that can be altered to favor one or the other by manipulating I allele dosage, temperature, viral pathogen, or plant cultivar.

Fabaceae↗
PubMed2000

Genetic mapping of the Tsw locus for resistance to the Tospovirus Tomato spotted wilt virus in Capsicum spp. and its relationship to the Sw-5 gene for resistance to the same pathogen in tomato.

The Tsw gene conferring dominant resistance to the Tospovirus Tomato spotted wilt virus (TSWV) in Capsicum spp. has been tagged with a random amplified polymorphic DNA marker and mapped to the distal portion of chromosome 10. No mapped homologues of Sw-5, a phenotypically similar dominant TSWV resistance gene in tomato, map to this region in C. annuum, although a number of Sw-5 homologues are found at corresponding positions in pepper and tomato. The relationship between Tsw and Sw-5 was also examined through genetic studies of TSWV. The capacity of TSWV-A to overcome the Tsw gene in pepper and the Sw-5 gene in tomato maps to different TSWV genome segments. Therefore, despite phenotypic and genetic similarities of resistance in tomato and pepper, we infer that distinct viral gene products control the outcome of infection in plants carrying Sw-5 and Tsw, and that these loci do not appear to share a recent common evolutionary ancestor.

Capsicum↗
PubMed1999

The reaction of hyaluronic acid and its monomers, glucuronic acid and N-acetylglucosamine, with reactive oxygen species.

Synovial fluid is a approximately 0.15% (w/v) aqueous solution of hyaluronic acid (HA), a polysaccharide consisting of alternating units of GlcA and GlcNAc. In synovial fluid of patients suffering from rheumatoid arthritis, HA is thought to be degraded either by radicals generated by Fenton chemistry (Fe2+/H2O2) or by NaOCl generated by myeloperoxidase. We investigated the course of model reactions of these two reactants in physiological buffer with HA, and with the corresponding monomers GlcA and GlcNAc. meso-Tartaric acid, arabinuronic acid, arabinaric acid and glucaric acid were identified by GC-MS as oxidation products of glucuronic acid. When GlcNAc was oxidised, erythronic acid, arabinonic acid, 2-acetamido-2-deoxy-gluconic acid, glyceric acid, erythrose and arabinose were formed. NaOCl oxidation of HA yielded meso-tartaric acid; in addition, arabinaric acid and glucaric acid were obtained by oxidation with Fe2+/H2O2. These results indicate that oxidative degradation of HA proceeds primarily at glucuronic acid residues. meso-Tartaric acid may be a useful biomarker of hyaluronate oxidation since it is produced by both NaOCl and Fenton chemistry.

Acetylglucosamine↗
PubMed1999

Atracurium during thoracic surgery: impaired efficiency in septic processes.

OBJECTIVE: The aim of the study was to examine whether the neuromuscular blocking potency of atracurium changes in patients with a septic intrathoracic process. DESIGN: Prospective clinical study. SETTING: Community hospital. PARTICIPANTS: Thirty patients who underwent thoracic surgery for resection of a pulmonary carcinoma were examined. Fifteen patients showed typical signs of a concomitant bacterial superinfection (infection group), 15 age-matched patients without infection served as the control (no-infection) group. INTERVENTIONS: Relaxation was induced with atracurium, 0.6 mg/kg intravenously for intubation, followed by a continuous infusion to maintain a 90% neuromuscular blockade. Relaxometry was performed electromyographically using the Datex Relaxograph by stimulating the ulnar nerve next to the wrist. MEASUREMENTS AND MAIN RESULTS: The onset time was significantly longer (5.3 +/- 2.9 v 3.3 +/- 1.2 minutes; p < 0.05), and the recovery phase (DUR 10%) was significantly shorter (23.5 +/- 8.6 v 36.9 +/- 7.3 minutes; p < 0.001) in the infection group compared with the controls. The infusion rate within the first hour of continuous application was 77.4% higher in the infection group than in the control group (11.0 +/- 2.9 v 6.2 +/- 1.0 microg/kg/min; p < 0.001). CONCLUSION: The study showed that septic intrathoracic processes cause a clear reduction of the neuromuscular blocking potency of atracurium. To guarantee adequate muscle relaxation in such cases, precise neuromuscular monitoring is highly advisable.

Adult↗
PubMed1999

6-Hydroxycyclohex-1-ene-1-carbonyl-CoA dehydrogenase and 6-oxocyclohex-1-ene-1-carbonyl-CoA hydrolase, enzymes of the benzoyl-CoA pathway of anaerobic aromatic metabolism in the denitrifying bacterium Thauera aromatica.

Benzoyl-CoA is a common intermediate in the anaerobic bacterial metabolism of many aromatic substrates. Two enzymes and ferredoxin of the central benzoyl-CoA pathway in Thauera aromatica have been purified so far. Benzoyl-CoA reductase reduces the aromatic ring with reduced ferredoxin yielding cyclohexa-1,5-diene-1-carbonyl-CoA [Boll, M. & Fuchs, G. (1995) Eur. J. Biochem. 234, 921-933]. Dienoyl-CoA hydratase subsequently adds one molecule of water and thereby produces 6-hydroxycyclohex-1-ene-1-carbonyl-CoA [Laempe, D., Eisenreich, W., Bacher, A., & Fuchs, G. (1998) Eur. J. Biochem. 255, 618-627]. Here two new enzymes, which convert this intermediate to the noncyclic product 3-hydroxypimelyl-CoA, were purified from T. aromatica and studied. 6-Hydroxycyclohex-1-ene-1-carbonyl-CoA dehydrogenase is an NAD(+)-specific beta-hydroxyacyl-CoA dehydrogenase that catalyzes 6-hydroxycyclohex-1-ene-1-carbonyl-CoA + NAD(+) --> 6-oxocyclohex-1-ene-1-carbonyl-CoA + NADH + H(+). 6-Oxocyclohex-1-ene-1-carbonyl-CoA hydrolase acts on the beta-oxoacyl-CoA compound and catalyzes the addition of one molecule of water to the double bound and the hydrolytic C-C cleavage of the alicyclic ring, 6-oxocyclohex-1-ene-1-carbonyl-CoA + 2 H(2)O --> 3-hydroxypimelyl-CoA. The genes for both enzymes, had and oah, were cloned, had was overexpressed in Escherichia coli and the recombinant protein was purified. Hence, presumably all enzymes of the central benzoyl-CoA pathway of anaerobic aromatic metabolism from this organism have now been purified and studied and the corresponding genes have been cloned and sequenced.

Acyl Coenzyme A↗
PubMed1998

Blood flow measurements with [(15)O]H2O and [18F]fluoride ion PET in porcine vertebrae.

A dual positron emission tomography (PET) tracer study with [18F]fluoride and the freely diffusible tracer [(15)O]H2O was performed to measure the capillary transport of [18F]fluoride and to evaluate the potential of [18F]fluoride ion PET to quantitate bone blood flow. Under the condition of a high predictable single-pass extraction fraction (E(F)) for [18F]fluoride, the [18F]fluoride ion influx transport constant (K1F), derived from kinetic [18F]fluoride ion PET measurements, can be used to estimate bone blood flow. Bone blood flow was measured in vertebral bodies by dynamic [(15)O]H2O PET during continuous ventilation with N2O, O2, and Isoflurane (FiO2 = 0.3) in seven adult mini pigs, followed by dynamic [18F]fluoride ion PET. The mean blood flow measured by [(15)O]H2O (FlowH2O) was 0.145 +/- 0.047 ml x minute(-1) x ml(-1) and the mean K1F was 0.118 +/- 0.031 ml x minute(-1) x ml(-1), respectively (mean +/- SD). Regional analysis showed excellent agreement between FlowH2O and K1F at low flow and a significant underestimation of flow by K1F relative to FlowH2O in regions of normal and elevated flow. The observed relationship between parameters followed the Renkin-Crone distribution. The permeability-surface product was determined as 0.25 minute(-1) for vertebral bodies consisting of a mixture of trabecular and cortical bone. We conclude that [18F]fluoride ion PET can be used to estimate bone blood flow in low and normal flow regions, as long as the flow dependency of the E(F) is taken into consideration. Above blood flow values of 0.2 to 0.35 ml x minute(-1) x ml(-1), the magnitude of K1F is increasingly independent on blood flow because diffusion limits tracer transport.

Animals↗
PubMed1997

Computer aided analysis of heart rate variability in brain death.

Forty neurosurgical, artificially ventilated patients were examined. Twenty of them had been diagnosed as brain dead, while twenty non-brain-dead patients served as a control group. From a surface ECG taken over a period of five minutes the mean heart rate and various indices of heart rate variability (HRV) were determined with the help of a special computer program (ProSciCard, Medisyt, Germany). The heart rate of the brain dead was significantly higher than that of the control patients. By contrast, all parameters of HRV were drastically reduced in the brain dead individuals compared to the controls. The results show that a significant change in the course of heart rate occurs after manifestation of brain death. This would appear to be the result of the elimination of all vegetative impulses derived from the brainstem. Computer-aided, the changes can be quantified in a simple way. The method could therefore be useful in brain death diagnosis.

Adult↗
PubMed1997

Clinical performance of resin-bonded fixed partial dentures and extracoronal attachments for removable prostheses.

STATEMENT OF PROBLEM: It is important to evaluate the long-term clinical performance of resin-bonded fixed partial dentures and extracoronal attachments for removable prostheses. PURPOSE: A prospective, long-term clinical study was conducted to evaluate the success of resin-bonded fixed partial dentures since 1985 and of resin-bonded extracoronal attachments from 1987. METHODS: Until 1993, a total of 130 resin-bonded fixed partial dentures had been seated in 101 patients, as well as 12 removable partial dentures (RPDs) with 24 extracoronal retainers in 10 patients. The clinical treatment protocol and the laboratory procedures were standardized. By the end of 1993, it was possible to reexamine 98 patients with a total of 127 resin-bonded fixed partial dentures and all 10 patients with removable partial dentures. The average time in function for the resin-bonded fixed partial dentures at the time of examination was 3.4 years and 2.3 years for the removable restorations. RESULTS: During the period of observation, one retainer failed on six of the resin-bonded fixed partial dentures, which represents a failure rate of 4.7%. Debonding of extracoronal attachments was recorded for 8.3% of the total number of retainers. CONCLUSION: The resin-bonded fixed partial denture technique can be considered to be a clinically reliable method of treatment, and permits the expansion of indications beyond a classical three-unit resin-bonded fixed partial denture. Long-term clinical success of removable partial dentures with resin-bonded extracoronal retainers warrants additional clinical studies.

Adolescent↗
PubMed1997

Testosterone-regulated expression of enzymes involved in steroid and aromatic hydrocarbon catabolism in Comamonas testosteroni.

The effect of testosterone as the sole carbon source on protein expression was analyzed in Comamonas testosteroni. Testosterone simultaneously induced the expression of steroid- and aromatic hydrocarbon-catabolizing enzymes and repressed one amino acid-degrading enzyme. It is suggested that steroids play a regulative role in catabolic enzyme synthesis during adaptive growth of C. testosteroni.

Amino Acid Sequence↗