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Biomedical subjects

G Fuchs

Publications and source records attributed to G Fuchs.

At least 73 records · Page 4Linked to original sources
PubMed1997

Anaerobic metabolism of L-phenylalanine via benzoyl-CoA in the denitrifying bacterium Thauera aromatica.

The anaerobic metabolism of phenylalanine was studied in the denitrifying bacterium Thauera aromatica, a member of the beta-subclass of the Proteobacteria. Phenylalanine was completely oxidized and served as the sole source of cell carbon. Evidence is presented that degradation proceeds via benzoyl-CoA as the central aromatic intermediate; the aromatic ring-reducing enzyme benzoyl-CoA reductase was present in cells grown on phenylalanine. Intermediates in phenylalanine oxidation to benzoyl-CoA were phenylpyruvate, phenylacetaldehyde, phenylacetate, phenylacetyl-CoA, and phenylglyoxylate. The required enzymes were detected in extracts of cells grown with phenylalanine and nitrate. Oxidation of phenylalanine to benzoyl-CoA was catalyzed by phenylalanine transaminase, phenylpyruvate decarboxylase, phenylacetaldehyde dehydrogenase (NAD+), phenylacetate-CoA ligase (AMP-forming), enzyme(s) oxidizing phenylacetyl-CoA to phenylglyoxylate with nitrate, and phenylglyoxylate:acceptor oxidoreductase. The capacity for phenylalanine oxidation to phenylacetate was induced during growth with phenylalanine. Evidence is provided that alpha-oxidation of phenylacetyl-CoA is catalyzed by a membrane-bound enzyme. This is the first report on the complete anaerobic degradation of an aromatic amino acid and the regulation of this process.

Acetaldehyde↗
PubMed1997

Impact of a single megadose of vitamin A at delivery on breastmilk of mothers and morbidity of their infants.

OBJECTIVES: To evaluate the effect of vitamin A supplementation 24 h after delivery on breastmilk retinol concentration. METHODS: Fifty low income women were randomly assigned to a single oral dose of 209 micromol of Vitamin A or none at delivery. Maternal serum and breastmilk retinol levels and infant morbidity and anthropometry were serially assessed. RESULTS: Mean (95% CI) serum retinol levels increased in the supplemented mothers at 2.77 (2.3, 3.2) compared to 1.15 (0.9, 1.4) micromol/l in controls (P < 0.05) and remained at a significantly higher level of 1.59 (1.4, 1.8) micromol/l compared to 1.33 (1.8, 1.5) micromol/l in the control group (P < 0.001) up to a period of three months. Breastmilk retinol concentration was also greater at 24 h after supplementation, mean (CI) 11.34 (9.0, 13.7) micromol/l, compared to 2.95 (2.3, 3.6) micromol/l in the control group (P < 0.0001), and remained higher for the next six months at 1.06 (0.9, , 1.3) micromol/l compared to 0.73 (0.6, 0.8) micromol/l in the control group (P < 0.02). Infants of the supplemented mothers had reduced mean duration of respiratory tract infection of 3.1 (2.7, 3.5) days compared to 3.7 (3.3, 4.2) days (P < 0.03) and mean incidence of febrile illness 0.1 (0.1, 0.1) compared to control infants 0.3 (0.3, 0.3) days, (P < 0.002). CONCLUSION: Vitamin A supplementation of malnourished mothers maintains higher breastmilk retinol concentration for at least six months and reduces the duration of respiratory tract infection and febrile illness in their breastfed infants.

Adult↗
PubMed1997

Helicobacter pylori: prevalence, transmission, and serum pepsinogen II concentrations in children of a poor periurban community in Bangladesh.

The aim of this study was to determine the age-specific prevalence of Helicobacter pylori infection in infants and children aged 1-99 months from a poor periurban community in Bangladesh. We also examined the frequency of infection among infants and their 53 immediate family members and evaluated the relationship between infection and fasting serum group II pepsinogen (pepsinogen II) concentration in 76 children. Sixty-one percent of 1-3 month-old infants tested positive for H. pylori; this rate declined steadily to 33% in children aged 10-15 months and then increased to 84% in children aged 5-8 years. The H. pylori infection rate was 2.5 times higher in children with illiterate mothers. No difference in infection rate was detected among the family contacts of infected vs. noninfected infants. H. pylori-infected children had significantly higher serum pepsinogen II concentrations than did noninfected children (P < .001). We conclude that infection with H. pylori is highly prevalent and occurs at an early age. An environmental factor or factors, rather than or in addition to intrafamilial spread of this infection, are important in poor communities of Bangladesh. The higher levels of serum pepsinogen II in H. pylori-positive children might indicate the presence of gastritis in such asymptomatic children.

Bangladesh↗
PubMed1997

Randomised controlled trial of zinc supplementation in malnourished Bangladeshi children with acute diarrhoea.

OBJECTIVE: To evaluate the impact of zinc supplementation on the clinical course, stool weight, duration of diarrhoea, changes in serum zinc, and body weight gain of children with acute diarrhoea. DESIGN: Randomised double blind controlled trial. Children were assigned to receive zinc (20 mg elemental zinc per day) containing multivitamins or control group (zinc-free multivitamins) daily in three divided doses for two weeks. SETTING: A diarrhoeal disease hospital in Dhaka, Bangladesh. PATIENTS: 111 children, 3 to 24 months old, below 76% median weight for age of the National Center for Health Statistics standard with acute diarrhoea. Children with severe infection and/or oedema were excluded. MAIN OUTCOME MEASURES: Total diarrhoeal stool output, duration of diarrhoea, rate of weight gain, and changes in serum zinc levels after supplementation. RESULTS: Stool output was 28% less and duration 14% shorter in the zinc supplemented group than placebo (p = 0.06). There were reductions in median total diarrhoeal stool output among zinc supplemented subjects who were shorter (less than 95% height for age), 239 v 326 g/kg (p < 0.04), and who had a lower initial serum zinc (< 14 mmol/l), 279 v 329 g/kg (p < 0.05); a shortening of mean time to recovery occurred (4.7 v 6.2 days, p < 0.04) in those with lower serum zinc. There was an increase in mean serum zinc in the zinc supplemented group (+2.4 v -0.3 mumol/l, p < 0.001) during two weeks of supplementation, and better mean weight gain (120 v 30 g, p < 0.03) at the time of discharge from hospital. CONCLUSIONS: Zinc supplementation is a simple, acceptable, and affordable strategy which should be considered in the management of acute diarrhoea and in prevention of growth faltering in children specially those who are malnourished.

Acute Disease↗
PubMed1997

[Laser Doppler data analysis during interstitial laser thermotherapy with magnetic resonance control within the scope of an animal experiment study].

The aim of the present study was to investigate, using laser Doppler (LD) flowmetry, the phases immediately prior to and following experimental, neurosurgical laser therapy in animals. Two statistical models obtained on the basis of discriminant analysis are described. These models should enable the user to classify the sets of parameters calculated from the LD signals. With both models which contain 3 and 5 parameters, respectively. 100% discrimination of the two phases was attained. The usefulness of the models could be validated by results obtained with other models.

Animals↗
PubMed1997

Coping with chronic neurological impairment: a contrastive analysis of Parkinson's disease and stroke.

This study aimed at a contrastive analysis of coping strategies and psychosocial alterations in patients with Parkinson's disease (PD) and stroke (CVA) and their relatives. Fifty-four PD and 50 CVA patients were investigated with a standardized semistructured interview to assess the severity of psychosocial changes following illness, the Freiburg Questionnaire on Coping with Illness, the Cornell Depression Scale and instruments to assess motor impairment. Psychosocial alterations were most prominent in the professional and emotional-cognitive domains. Degree of depression correlated with familial and emotional-cognitive alterations in both patient groups. Active problem-oriented coping and distraction predominated as coping styles. Religious relief and quest for sense were significantly more important for the PD patients. Coping styles did not correlate with degrees of depression, motor impairment or psychosocial alterations.

Adaptation, Psychological↗
PubMed1997

[The suicide conference. An instrument for support of involved teams after inpatient suicides].

This is a report on the authors' experience over two years in developing a new way to deal with patient suicides in a District Psychiatric Hospital. The main aim of the Suicide Counselling Session is to help the involved hospital ward teams to overcome the strain, doubt and psychological burden often caused by the suicide of a patient. The authors describe the institutional conditions and setting in which a Suicide Counselling Session takes place. The method is characterised by a special attitude and the ideas of "Reflecting Team" to bring the involved stress factors into the open.

Adaptation, Psychological↗
PubMed1997

[An unusual case of a foreign body in the maxillary sinus].

An unusual case of a foreign body in the maxillary sinus was presented with a 13-year-old boy. The boy led a sewing needle into the maxillary sinus through a tooth destroyed by caries. Trying to remove the needle, the boy broke it. The existence of the foreign body was proved by an X-ray picture. The operation was conducted according to the Caldwell-Luc's method. A two centimeter piece of the needle was extracted. The interior of the sinus was cleaned and inflammated mucous membrane, and granulation were removed. The cause tooth was extracted. The tooth-socket was sewn and the fistula at the bottom of the sinus was covered with a peduncular layer of mucous membrane of the nasal duct. Post-operational conduct without any complications.

Adolescent↗
PubMed1996

Evidence that anaerobic oxidation of toluene in the denitrifying bacterium Thauera aromatica is initiated by formation of benzylsuccinate from toluene and fumarate.

Toluene is degraded anoxically to CO2 by the denitrifying bacterium Thauera aromatica. Toluene first becomes oxidized to benzoyl-CoA by O2-independent reactions. Benzoyl-CoA is then reduced to non-aromatic products by benzoyl-CoA reductase. We set out to study the reactions employed for the initial activation of toluene and its oxidation to the level of benzoate. Evidence is provided for a novel way of toluene degradation based on experiments with cell-free extracts and with whole toluene-grown cells: Cell-free extracts oxidized [14C]toluene to [14C]benzoyl-CoA via several radioactive intermediates. This reaction was strictly dependent on the presence of fumarate, coenzyme A and nitrate as electron acceptor; acetyl-CoA and ATP were not necessary for the reaction. The first product formed in vitro was benzylsuccinate; (2H8)toluene was converted to (2H7)benzylsuccinate. Formation of benzylsuccinate from toluene was independent of coenzyme A and nitrate, but it required the presence of fumarate. Other tricarboxylic acid cycle intermediates were converted to fumarate in cell extracts and therefore could partially substitute for fumarate. [14C]Benzylsuccinate was oxidized further to [14C]benzoyl-CoA and [14C]benzoate in cell extracts if coenzyme A and nitrate were present. No benzyl alcohol and benzaldehyde and no phenylpropionate could be detected as intermediates. In isotope trapping experiments with cell suspensions, two intermediates from [14C]toluene were detected, benzoate and benzylsuccinate. This corroborates the sequence of reactions deduced from in vitro experiments. A hypothetical degradation pathway for the anaerobic oxidation of toluene to benzoyl-CoA via an initial addition of fumarate to the methyl group of toluene and following beta-oxidation of the benzylsuccinate formed is suggested.

Acyl Coenzyme A↗
PubMed1996

Depression in Parkinson's disease: biogenic amines in CSF of "de novo" patients.

INTRODUCTION: Etiology of depression in Parkinson's disease (PD) is associated with serotonergic dysfunction. Previous studies, supporting this hypothesis, were performed on patients treated with antiparkinsonian drugs. To eliminate the influence of parkinsonian drug therapy and to elucidate significance of different biochemical pathways in PD associated with depression we determined levels of biogenic amines in cerebrospinal fluid (CSF) of 26 untreated "de novo" Parkinsonian patients. MATERIAL AND METHODS: Patients were scored with the Hamilton depression scale (HD) and subdivided into groups with HD score > or = 18 and HD score < 18. Diagnosis of depression was made according to DSM III R. Both groups were matched for age and motor disability. RESULTS: In both groups no significant differences appeared between CSF levels of dopamine, noradrenaline, 3,4-dihydroxyphenylacetic acid, homovanillic acid, 3-methoxy-4-hydroxyphenylglycol and 5-hydroxyindole acetic acid, determined by high-performance liquid chromatography. DISCUSSION: In contrast to previous studies on treated Parkinsonian patients no sign of altered serotonin metabolism especially in context with severity of depression in early stages of PD was found. Due to our results, we suggest, that biochemical markers of depression in CSF of PD may be influenced by antiparkinsonian therapy and that depression in PD may respond to serotonin reuptake inhibitors mainly in later stages of PD.

Aged↗
PubMed1996

Ultrasonographic evaluation of the anterior recess in the normal hip: a prospective study on 166 asymptomatic children.

PURPOSE: To redefine the ultrasonographic features of the normal hip joint in children and to establish a normal value for the neck-capsule distance (NCD) of its anterior recess. MATERIALS AND METHODS: 332 hips of 166 asymptomatic children were examined sonographically. In a sagittal section plane the maximum distance between the anterior surface of the femoral neck and the anterior limit of the articular capsule (NCD-A) was measured. RESULTS: The hypoechoic synovial membrane occupying the anterior recess could always be differentiated from the capsule. An additional thin layer of synovial fluid was detected in 12% of probands. The configuration of the capsule varied with different rotation positions of the legs. In small children the mean NCD-A increased from 2.5 mm at 65 cm height to 5 mm at 100 cm height. In larger children the mean NCD-A was 5.5 mm. The mean right-to-left difference was 0.5 mm with a pathological limit of 2 mm. CONCLUSIONS: The pathological limit of the NCD-A increases from 3.5 to 7.5 mm in relation to the height. Sonographic investigation of the pediatric hip joint must include detailed demonstration of anatomical structures to avoid misinterpretations.

Adolescent↗
PubMed1996

Anaerobic metabolism of 2-hydroxybenzoic acid (salicylic acid) by a denitrifying bacterium.

The anaerobic metabolism of 2-hydroxybenzoic acid (salicylic acid) was studied in a denitrifying bacterium. Cells grown with 2-hydroxybenzoate were simultaneously adapted to degrade benzoate. Extract of these cells formed benzoate or benzoyl-CoA when incubated under reducing conditions with salicylate, MgATP, and coenzyme A, suggesting a degradation of 2-hydroxybenzoate via benzoate or benzoyl-CoA. This suggestion was supported by enzyme activity measurements. In extracts of 2-hydroxybenzoate-grown cells, the following enzyme activities were detected: two CoA ligases, one specific for 2-hydroxybenzoate, the other for benzoate, and two different enzyme activities catalyzing the reductive transformation of 2-hydroxybenzoyl-CoA. These findings suggest a degradation of salicylic acid by two new enzymes, 2-hydroxybenzoate-CoA ligase (AMP-forming) and 2-hydroxybenzoyl-CoA reductase (dehydroxylating), catalyzing (1) 2-hydroxybenzoate + MgATP + CoASH --> 2-hydroxybenzoyl-CoA + MgAMP + PPi (2) 2-hydroxybenzoyl-CoA + 2[H] --> benzoyl-CoA + H2O Benzoyl-CoA was dearomatized by reduction of the ring. This represents another case in which benzoyl-CoA is a central intermediate in anaerobic aromatic metabolism.

Anaerobiosis↗
PubMed1995

Benzoyl-coenzyme A reductase (dearomatizing), a key enzyme of anaerobic aromatic metabolism. ATP dependence of the reaction, purification and some properties of the enzyme from Thauera aromatica strain K172.

Anoxic metabolism of many aromatic compounds proceeds via the common intermediate benzoyl-CoA. Benzoyl-CoA is dearomatized by benzoyl-CoA reductase (dearomatizing) in a two-electron reduction step, possibly yielding cyclohex-1,5-diene-1-carboxyl-CoA. This process has to overcome a high activation energy and is considered a biological Birch reduction. The central, aromatic-ring-reducing enzyme was investigated for the first time in the denitrifying bacterium Thauera aromatica strain K172. A spectrophotometric assay was developed which was strictly dependent on MgATP, both with cell extract and with purified enzyme. The oxygen-sensitive new enzyme was purified 35-fold with 20% yield under anaerobic conditions in the presence of 0.25 mM dithionite. It had a native molecular mass of approximately 170 kDa and consisted of four subunits a,b,c,d of 48, 45, 38 and 32 kDa. The oligomer composition of the protein most likely is abcd. The ultraviolet/visible spectrum of the protein as isolated, but without dithionite, was characteristic for an iron-sulfur protein with an absorption maximum at 279 nm and a broad shoulder at 390 nm. The estimated molar absorption coefficient at 390 nm was 35,000 M-1 cm-1. Reduction of the enzyme by dithionite resulted in a decrease of absorbance at 390 nm, and the colour turned from greenish-brown to red-brown. The enzyme contained 10.8 +/- 1.5 mol Fe and 10.5 +/- 1.5 mol acid-labile sulfur/mol. Besides zinc (0.5 mol/mol protein) no other metals nor selenium could be detected in significant amounts. The enzyme preparation contained a flavin or flavin-like compound; the estimated content was 0.3 mol/mol enzyme. The enzyme reaction required MgATP and a strong reductant such as Ti(III). The reaction catalyzed is: benzoyl-CoA + 2 Ti(III) + n ATP-->non-aromatic acyl-CoA + 2 Ti(IV) + n ADP + n Pi. The estimated number n of ATP molecules hydrolyzed/two electrons transferred in benzoyl-CoA reduction is 2-4. In the absence of benzoyl-CoA the enzyme exhibited oxygen-sensitive ATPase activity. The enzyme was specific for Mg(2+)-ATP, other nucleoside triphosphates being inactive (< 1%). Mg2+ could be substituted to some extent by Mn2+, Fe2+ and less efficiently by Co2+. Benzoate was not reduced, whereas some fluoro, hydroxy, amino and methyl analogues of the activated benzoic acid were reduced, albeit at much lower rate; the products remain to be identified. The specific activity with reduced methyl viologen as the electron donor was 0.55 mumol min-1 mg-1 corresponding to a catalytic number of 1.6 s-1. The apparent Km values under the assay conditions (0.5 mM for both reduced and oxidized methyl viologen) of benzoyl-CoA and ATP were 15 microM and 0.6 mM, respectively. The enzyme was inactivated by ethylene, bipyridyl and, in higher concentrations, by acetylene. Benzoyl-CoA reductase also catalyzed the ATP-dependent two-electron reduction of hydroxylamine (Km 0.15 mM) and azide. Some of the properties of the enzyme are reminiscent of those of nitrogenase which similarly overcomes the high activation energy for dinitrogen reduction by coupling electron transfer to the hydrolysis of ATP.

Acyl Coenzyme A↗
PubMed1995

Hydroxybenzoyl-CoA reductase: coupling kinetics and electrochemistry to derive enzyme mechanisms.

Hydroxybenzoyl-CoA reductase (HBCR) is an iron-sulfur protein that is involved in the metabolism of aromatic compounds. It catalyzes the two-electron reduction of hydroxybenzoyl-CoA to benzoyl-CoA. In the work described here, kinetic schemes were derived for HBCR and for several classes of redox enzymes and redox-activated enzymes. Introduction of the Nernst equation into the rate laws led to the development of novel relationships between the ambient redox potential, the midpoint potential of the enzyme active site, and the kinetic parameter, V/K. By coupling electrochemistry and steady-state kinetics, mechanistic information could be obtained that could not be determined by either method alone. For HBCR, the relationship between the kinetic parameter V/K and the ambient electrochemical potential of the assay mixture was found to be: apparent V/Km = Vmax/(Km(1 + exp[nF/RT(E - E(o)e)])), where n is the number of electrons involved in the redox process, F is the Faraday constant, R is the gas constant, T is the temperature in K, E is the applied potential, and E(o)e is the redox potential of a redox-active catalytic site on the enzyme. Coupling kinetics with electrochemistry yielded the E(o)e (-350 mV vs NHE) for HBCR and maximum values under optimal redox conditions for kcat and kcat/Km (9 s-1 and 1.8 x 10(5) M-1 s-1, respectively). In addition, theory was developed that could distinguish a single two-electron transfer mechanism from one involving two successive one-electron transfers. HBCR was found to be in the latter class. Interestingly, the derived mechanism for HBCR is similar to that of the Birch reduction, the classical organic chemical reaction for reductive dehydroxylation of phenolic compounds. The methodology described here represents a novel approach that should help elucidate the mechanisms of other oxidoreductase and redox-activated enzymes.

Acyl Coenzyme A↗