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Biomedical subjects

H Seidel

Publications and source records attributed to H Seidel.

At least 19 recordsLinked to original sources
PubMed1999

Bioavailability of hydrocarbons during microbial remediation of a sandy soil.

The microbial degradation of hydrocarbons was studied in an artificially contaminated sandy soil, using a pilot-scale percolator system. After a short lag period, an intensive degradation occurred, which diminished in time and completely stopped in the end, despite large residual contaminations (residues of 56% diesel fuel, 20% n-hexadecane and 3.5% phenanthrene at the initial loadings of each 3000 mg/kg). The remaining pollutant content was influenced by the kind of hydrocarbon but was nearly independent of its initial loading. According to a model-aided analysis of the carbon dioxide production during remediation, the observed stagnation of degradation was caused by a limited bioavailability of the pollutants. The degradation in the soil-free aqueous phase was more extensive than in the soil, which suggests that the limited bioavailability in the soil can be attributed mainly to matrix-dependent rather than substrate-dependent influences. Generally, fine particles and organic matter are mainly responsible for the adsorption of pollutants to the soil matrix. Our sandy soil also bound hydrocarbons adsorptively although it contained neither silty material nor significant amounts of organic matter. As shown by Brunauer Emmett Teller (BET) analysis, the soil particles were covered by micropores, which enlarged the soil surface by a factor of 120 in comparison with the macroscopic surface area. The microporosity is the reason for the hydrocarbons being more strongly adsorbed to the sandy soil than expected.

Biodegradation, Environmental↗
PubMed1998

Deletion mapping by FISH with BACs in patients with partial monosomy 22q13.

Patients with deletions in 22q13 are known to have phenotypic features that include normal or accelerated growth, large hands and feet, hypotonia, delayed psychomotor development and mild facial dysmorphism. To date, very few cases have been investigated by detailed molecular genetic analysis. We have analyzed three new patients with terminal deletions in 22q. We compared the cytogenetic observations with molecular data assessed by fluorescence in situ hybridization and an array of characterized bacterial artificial chromosome recombinants. The shortest region of deletion overlap is localized in 22q13.2-qter distal to the marker D22S94, but the telomeric repeat in the deleted chromosome appears to remain intact. When parental alleles were investigated in two of the three patients, the aberrant homolog was found to be of paternal origin in both cases. Although the deleted region still spans >20 cM, molecular analysis of additional patients and screening for new genes might help in elucidating candidate genes connected with the dysmorphisms defined by deletions of 22q13.

Child, Preschool↗
PubMed1998

Controlled breathing protocols probe human autonomic cardiovascular rhythms.

The purpose of this study was to determine how breathing protocols requiring varying degrees of control affect cardiovascular dynamics. We measured inspiratory volume, end-tidal CO2, R-R interval, and arterial pressure spectral power in 10 volunteers who followed the following 5 breathing protocols: 1) uncontrolled breathing for 5 min; 2) stepwise frequency breathing (at 0.3, 0.25, 0.2, 0.15, 0.1, and 0.05 Hz for 2 min each); 3) stepwise frequency breathing as above, but with prescribed tidal volumes; 4) random-frequency breathing (approximately 0.5-0.05 Hz) for 6 min; and 5) fixed-frequency breathing (0.25 Hz) for 5 min. During stepwise breathing, R-R interval and arterial pressure spectral power increased as breathing frequency decreased. Control of inspired volume reduced R-R interval spectral power during 0.1 Hz breathing (P < 0.05). Stepwise and random-breathing protocols yielded comparable coherence and transfer functions between respiration and R-R intervals and systolic pressure and R-R intervals. Random- and fixed-frequency breathing reduced end-tidal CO2 modestly (P < 0.05). Our data suggest that stringent tidal volume control attenuates low-frequency R-R interval oscillations and that fixed- and random-rate breathing may decrease CO2 chemoreceptor stimulation. We conclude that autonomic rhythms measured during different breathing protocols have much in common but that a stepwise protocol without stringent control of inspired volume may allow for the most efficient assessment of short-term respiratory-mediated autonomic oscillations.

Adult↗
PubMed1997

On the prognostic value of systemic methotrexate clearance in childhood acute lymphocytic leukemia.

The prognostic value of systemic methotrexate clearance (ClMTX) during high-dose therapy was evaluated in a cohort of 42 children with acute lymphocytic leukemia (ALL). As part of an extensive chemotherapy protocol, they had received a total of 293 methotrexate (MTX) infusions in the 6-8 g/m2 dose range. At the termination of the study, when they had all been followed up for 3.5 years or more, 26 of these patients were still in continuous complete remission, whereas 16 had suffered relapse. The intrapatient variability in ClMTX during the eight courses was up to six-fold. In 67% of the patients, the maximum level of ClMTX reached at least twice the minimum value. The coefficients of variation for the intra- and interindividual variability in ClMTX were 9-57% and 26-41%, respectively. The cumulative probability of relapse, estimated by the Kaplan-Meier procedure, was increased for patients with a high ClMTX during the initial treatment course, but the difference was not significant on a 5% level. There was no significant relationship between high individual median ClMTX and subsequent relapse of ALL. However, ClMTX during the initial infusion, the time-dependent mean for ClMTX, and the individual patient's median ClMTX, were significant predictors for event-free survival in a Cox proportional hazards regression analysis. The present study demonstrates gross pharmacokinetic variability and unpredictable values of ClMTX in subsequent courses after standardized administration of MTX to paediatric patients with ALL. In spite of the association between ClMTX and prognosis shown by some of the analyses, estimates of ClMTX rates may not necessarily be related to disease outcome in a way that can be exploited to the benefit of the individual patient.

Adolescent↗
PubMed1997

Spectrum of clinical features associated with interstitial chromosome 22q11 deletions: a European collaborative study.

We present clinical data on 558 patients with deletions within the DiGeorge syndrome critical region of chromosome 22q11. Twenty-eight percent of the cases where parents had been tested had inherited deletions, with a marked excess of maternally inherited deletions (maternal 61, paternal 18). Eight percent of the patients had died, over half of these within a month of birth and the majority within 6 months. All but one of the deaths were the result of congenital heart disease. Clinically significant immunological problems were very uncommon. Nine percent of patients had cleft palate and 32% had velopharyngeal insufficiency, 60% of patients were hypocalcaemic, 75% of patients had cardiac problems, and 36% of patients who had abdominal ultrasound had a renal abnormality. Sixty-two percent of surviving patients were developmentally normal or had only mild learning problems. The majority of patients were constitutionally small, with 36% of patients below the 3rd centile for either height or weight parameters.

Adolescent↗
PubMed1997

Phase dependencies of the human baroreceptor reflex.

We studied the influence of respiratory and cardiac phase on responses of the cardiac pacemaker to brief (0.35-s) increases of carotid baroreceptor afferent traffic provoked by neck suction in seven healthy young adult subjects. Cardiac responses to neck suction were measured indirectly from electrocardiographic changes of heart period. Our results show that it is possible to separate the influences of respiratory and cardiac phases at the onset of a neck suction impulse by a product of two factors: one depending only on the respiratory phase and one depending only on the cardiac phase. This result is consistent with the hypothesis that efferent vagal activity is a function of afferent baroreceptor activity, whereas respiratory neurons modulate that medullary throughput independent of the cardiac phase. Furthermore, we have shown that stimulus broadening and stimulus cropping influence the outcome of neck suction experiments in a way that makes it virtually impossible to obtain information on the phase dependency of the cardiac pacemaker's sensitivity to vagal stimulation without accurate knowledge of the functional shape of stimulus broadening.

Adult↗
PubMed1996

Regional localization of two MRX genes to Xq28 (MRX28) and to Xp11.4-Xp22.12 (MRX33).

Two genes responsible for a nonspecific form of X-linked mental retardation (MRX28 and MRX33) were localized by linkage analysis with 40 highly polymorphic DNA markers situated along the entire the X chromosome. In family 1, the gene could be mapped within a 14-cM interval at Xq28, distal to the recombining marker DXS1113 (MRX28). The maximum LOD score was 2.75, with DXS52 at phi = .0. In family 2, the gene was localized within a 30-cM interval at Xp11.4-22.12 between the recombining markers DXS365 and MAOB, including the DMD gene (MRX33). Maximum LOD scores of 2.82 were obtained with markers DMD-STR49, DMD-DysII, CYBB, and DXS1068.

Child, Preschool↗
PubMed1996

Magnetic resonance imaging and neurological evaluation after treatment with high-dose methotrexate for acute lymphocytic leukaemia in young children.

This study evaluates the occurrence of permanent cerebral white matter changes and neurological abnormalities in children treated at a young age for acute lymphocytic leukaemia. Our pilot treatment protocol did not include central nervous system irradiation, but intrathecal methotrexate and high-dose methotrexate infusions followed by very intensive folinic acid rescue. We examined 12 children in complete remission and off therapy 18 months to 9.5 years after their last methotrexate infusion. They were below 5 years of age at diagnosis and therefore expected to be at special risk of neurotoxic sequelae. Cerebral magnetic resonance imaging in the 11 cases thus evaluated did not reveal white matter abnormalities or other signal changes as signs of permanent treatment-related sequelae. We did not observe any pathological clinical neurological findings likely due to methotrexate.

Age Factors↗
PubMed1995

Triosephosphate isomerase deficiency: biochemical and molecular genetic analysis for prenatal diagnosis.

Inherited deficiency of the glycolytic enzyme triosephosphate isomerase leads to a multisystem disorder characterized by progressive neuromuscular dysfunction, chronic nonspherocytic hemolytic anemia and increased susceptibility to severe infections. Most patients die within the first 6 years. We examined a family with severe triosephosphate isomerase deficiency. The 1-year-old index patient suffered from hemolytic anemia, neuromuscular impairment and pneumonias, with the necessity of intermitten mechanical ventilation. Triosephosphate isomerase activity in erythrocytes was reduced to about 20% of normal. Heat stability of the enzyme was strongly reduced; concentration of the physiological substrate, dihydroxyacetone phosphate was increased 20-fold due to the metabolic block. Direct sequencing of the triosephosphate isomerase gene revealed homozygosity for the formerly described GAG-->GAC-mutation changing 104 Glu-->Asp. During a 2nd pregnancy we examined a cord blood sample obtained in the 19th gestational week. The biochemical data on enzyme activity, heat stability of the enzyme and concentration of dihydroxyacetone phosphate were in the normal range. The molecular genetic analysis confirmed the presence of the normal triosephosphate isomerase alleles. Pregnancy was continued, resulting in the delivery of an unaffected, healthy newborn.

Anemia, Hemolytic, Congenital Nonspherocytic↗
PubMed1995

DiGeorge syndrome and partial monosomy 10p: case report and review.

DiGeorge syndrome (DGS) is predominantly caused by partial monosomy 22q11, but a subset of patients with DGS show deletions of 10p or other chromosomal abnormalities. The authors describe a 20 months old girl with DGS and a monosomy 10p bringing the number of DGS patients with this chromosomal abnormality to nine. She has a monosomy 10p13-pter and a trisomy 10q26-qter due to a meiotic recombination of a maternal inversion (10) (p13q26). The proposita's phenotype demonstrates typical features of the del (10p) syndrome which include mental retardation, abnormally shaped skull, hypertelorism, low nasal bridge, micrognathia, dysmorphic low set ears, short neck, foot abnormalities, and cardiac defect. The diagnosis of DGS was made unequivocally within the first weeks of life because of the typical features-cardiac defect, hypoplastic thymus, T-cell defect, hypocalcemia, and hypoparathyroidism. The common DGS mutation-microdeletion 22q11-was excluded by FISH analysis, and the breakpoints on chromosome 10 were mapped between D10S189 and D10S191 on the short arm and proximal to D10S25 on the long arm.

Chromosome Deletion↗
PubMed1994

The relationship between the electromyogram-amplitude and isometric extension torques of neck muscles at different positions of the cervical spine.

A group of 12 healthy men volunteered for the experiment. Electromyograms (EMG) were obtained from semispinalis capitis, splenius capitis, levator scapulae, and trapezius muscles. The flexion angle of the cervical spine was precisely adjusted to 0 degrees, 10 degrees, 20 degrees, and 30 degrees relative to the horizontal, with a constant angle of the atlanto-occipital joint. The subjects made eight short (about 2 s) vertical extension forces (6%, 12%, 18%, 24%, 30%, 36%, 42%, and 48% of maximal voluntary peak contraction force). For each position, the centre of pressure under the head was determined as the basis for the calculation of the external lever arm. The presence of motor endplate regions was ascertained by multiple surface electrodes. The slopes of individual linear regression lines for the root mean square (rms)-values were dependent on the existence of endplates in the area of the electrodes - endplates caused smaller rms values per Newton metres of external torque. Significant intersubject differences between regression equations could not be eliminated by the normalization of EMG-parameters and/or torques. The elimination of gravity, the continuous monitoring of positions, and the consideration of localization of motor endplate regions were essential prerequisites for the acquisition of reliable relationships between EMG of different neck muscles and external torques. Two important conclusions were derived for the prediction of torques from EMG measurements: firstly, individual regression equations which take into account the position of the head and neck should be used; secondly, normalization procedures do not justify the application of average regressions to a group of subjects.

Adult↗
PubMed1994

[Familial akinesia-hypokinesia sequence (Pena-Shokier phenotype)].

The Pena Shokeir phenotype (PSP) is characterised by multiple ankyloses, camptodactyly, facial dysmorphisms and lung hypoplasia with hydramnios. The basic neuromuscular defect leads, through a fetal hypokinesia-akinesia, to the development of this nonspecific phenotype and a respiratory insufficiency with early postnatal mortality. Severe central nervous anomalies are described in one-third of the reported cases. In this paper a foetus with PSP and 4 further foetuses with severe cerebral malformations and only discrete lung hypoplasia are described. It is not clear whether the cerebral malformations represent a primary or secondary developmental defect.

Abnormalities, Multiple↗
PubMed1993

Selective non-nucleoside HIV-1 reverse transcriptase inhibitors. New 2,3-dihydrothiazolo[2,3-a]isoindol-5(9bH)-ones and related compounds with anti-HIV-1 activity.

A series of substituted 2,3-dihydrothiazolo[2,3-a]isoindol-5(9bH)-ones and related compounds 1-73 were synthesized and evaluated for their ability to inhibit reverse transcriptase (RT) of the human immune deficiency virus 1 (HIV-1) and replication of HIV-1 in MT2 cells. The antiviral activity of these compounds depends on the stereoselective configuration of the substituent in position 9b. Structure-activity studies were done within these series of compounds to determine the optimum substituents for antiviral activity. The most potent inhibitors were found in the class of 2,3-dihydrothiazolo[2,3-a]isoindol-5(9bH)-ones bearing a phenyl ring system in position 9b optionally substituted with one or two methyl groups or a chlorine atom in position 8. The most active analogues (R)-(+)-1, (R)-(+)-6, (R)-(+)-13, (R)-(+)-26, and (R)-(+)-53 inhibit the HIV-1 RT with an IC50 between 16 and 300 nM and an IC50 between 10 and 392 nM in MT2 cells, respectively.

Animals↗
PubMed1993

Selected health risks caused by long-term, whole-body vibration.

The problem of a "vibration disease" caused by low-frequency whole-body vibration (wbv) is critically discussed. Disorders of the nervous, circulatory, and digestive systems are interpreted not to be predominantly wbv-specific, but to be related to the totality of working conditions. Long-term wbv exposure can probably contribute to the pathogenesis of disorders of female reproductive organs (menstrual disturbances, anomalies of position) and disturbances of pregnancy (abortions, stillbirths). Animal experiments suggest harmful effects on the fetus. WBV has a minor synergistic effect on the development of noise-induced hearing loss. Degenerative changes of the spine are more prevalent among wbv-exposed workers. Model calculations demonstrate an increased spinal load in pregnant women exposed to wbv or self-induced vibration, and illustrate a possibility for the comparison of data on stress, strain, and strength. The analysis of individual exposure-effect relationships is suggested as a future approach for evaluating potential occupation-related diseases.

Animals↗
PubMed1992

Synthetic human tRNA(UUULys3) and natural bovine tRNA(UUULys3) interact with HIV-1 reverse transcriptase and serve as specific primers for retroviral cDNA synthesis.

Full-length and 5'-truncated variants of human (h) tRNA(UUULys3) were synthesized by in vitro transcription using SP6 RNA polymerase. Bovine(b) tRNA(SUULys3) was purified from calf liver. Both full-length tRNA species were shown to be biologically active in an aminoacylation assay. Gel retardation assays revealed that both full-length tRNA species, as well as a 5'-truncated h-tRNA(UUULys3) molecule containing 24 nucleotides (nt) at the 3' end (Lys24), interact with human immunodeficiency virus (HIV)-1 reverse transcriptase (RT). Competition studies with these three tRNA species demonstrate that the 3' end of h-tRNA(UUULys3) contributes to the interaction with HIV-1 RT. Escherichia coli tRNA(UUULys) and tRNA(UUCGlu2) were also able to interact with the enzyme, whereas unrelated RNA molecules such as E. coli 5S rRNA did not bind to RT. Both b-tRNA(SUULys3) and h-tRNA(UUULys3) molecules, as well as the 5'-truncated variants, could be demonstrated to prime cDNA synthesis specifically using a HIV-1 RNA template, prepared by in vitro transcription, indicating that other viral or cellular proteins are not essential for this process. E. coli tRNA(UUULys) and tRNA(UUCGlu2), although able to interact with HIV-1 RT, failed to prime retroviral transcription. Products of cDNA synthesis were characterized by polymerase chain reaction, demonstrating that at least 18 nt at the 3' ends of h-tRNA(UUULys3) and b-tRNA(SUULys3) are still present in the cDNA product, whereas the 5' ends of both primer molecules were removed by the RNase H activity of HIV-1 RT.

Animals↗
PubMed1992

Effects of isolated and combined exposures to whole-body vibration and noise on auditory-event related brain potentials and psychophysical assessment.

Auditory event-related brain potentials (ERP) in response to two different tone stimuli (1.1 kHz or 1 kHz, 80 dB, 50 ms; given by headphones at a regular interstimulus interval of 5 s with a probability distribution of 70:30) were recorded from 12 healthy male subjects (Ss) during four different conditions with two repetitions: A-60 dBA white noise (wN), no whole-body vibration (WBV); B-60 dBA wN plus sinusoidal WBV in the az-direction with a frequency of 2.01 Hz and acceleration of 2 m.s-2 root mean square; C-80 dBA wN, no WBV; D-80 dBA wN plus WBV. Each condition consisted of two runs of about 11 min interrupted by a break of 4 min. During the break with continuing exposure, but without auditory stimuli, Ss judged the difficulty of the tone-detection task and intensity of noise by means of cross-modality matching (CMM). Vibration-synchronous activity in the electrocardiogram was eliminated by a subtraction-technique. Noise caused an attenuation of the N1 and P2 amplitudes and prolongation of P3 latencies. The WBV did not cause systematic ERP effects. Condition B was associated with higher N1 and smaller P3 amplitudes. The factor "condition" had a significant effect on the peak latencies of P3 to target stimuli and the task difficulty judged by CMM. Both effects exhibited significant linear increases in the sequence of conditions A, B, C, D. For the evaluation of exposure conditions at work, it can be suggested that noise has a strong systematic effect which can be enhanced by WBV.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1992

De novo interstitial deletion 16(q12.1q13) of paternal origin in a 10-year-old boy.

A 10-year-old boy with a de novo del(16)(q12.1q13) and many features of the deletion 16q phenotype is described. The deletion occurred in a paternal chromosome as demonstrated by DNA studies with polymorphic (AC)n microsatellite repeat markers. Comparison with published cases suggests that deletion of either of two regions (q13 and q22.1) on the long arm of chromosome 16 is associated with an apparently identical phenotype. No parental imprinting of this region was demonstrated.

Abnormalities, Multiple↗