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Biomedical subjects

A Schmidt

Publications and source records attributed to A Schmidt.

At least 631 records · Page 35Linked to original sources
PubMed1984

Inhibition of human natural killer cell reactivity by exogenous adenosine 5'-triphosphate.

The presence of micromolar concentrations (5 to 100 microM) of adenosine 5'-triphosphate (ATP) in cytotoxicity assays of human natural killer (NK) cells with K562 targets resulted in marked inhibition of NK activity. NK activity of peripheral blood mononuclear cells (PBL) and of purified NK cells (i.e., large granular lymphocytes (LGL] were similarly sensitive to inhibition by ATP. The inhibitory activity was specific to ATP and was not demonstrated with GTP, UTP, CTP, or with other adenosine compounds. This inhibitory activity resulted from an effect of ATP on the effector cells and was not dependent on serum components. ATP did not inhibit binding of the LGL to target cells, and therefore the inhibition by ATP is presumed to be related to some post-recognition metabolic events. Some physiologic role in regulation of NK activity by ATP seems possible, because nonspecific phosphatases (bacterial alkaline phosphatase or human alkaline phosphatase) stimulated NK activity and partially reversed the ATP-induced inhibition of reactivity.

Adenosine↗
PubMed1984

[Skeletal muscle reaction to the loading limit. III. Changes in the contractile apparatus].

A description is given of the changes in the contractile apparatus of the skeletal muscle following extreme long-term exercise. In detail, they include Z-stripe dehiscences, myofibril disintegrations and destructions of single sarcomer . These findings are known from myopathology . A characteristic feature is their subsarcolemmic localisation. The pathogenesis is discussed. In connection with the alterations of the sarcolemma and the mitochondria as well as the increased endo- and exocytosis of the muscle fibre, the cause is seen in a local intracellular catabolism. At the same time, the possible importance to the effluence of enzymes, especially of creatine phosphokinase, is pointed out.

Adult↗
PubMed1984

Binding and degradation of proteoglycans by cultured arterial smooth muscle cells. I. Endocytosis and intracellular translocation of proteoglycan-gold conjugates.

Proteoglycans (Mr approximately 200 000) isolated from bovine arterial tissue were decorated with 17 nm diameter gold particles for tracing in electron microscopic thin sections and surface replicas. Lysine and arginine residues of their proteoglycan protein core are assumed to be essential for gold conjugation. The resulting proteoglycan-gold conjugates, which appear as pearl string-like gold strands of about 170 nm in length were used to visualize binding, endocytosis and intracellular translocation of proteoglycans by homologous cultured arterial smooth muscle cells. The proteoglycan-gold conjugates bind to coated as well as to non-coated cell surface membrane areas at 4 degrees C. This is followed by the formation of membrane invaginations. Postincubation at 37 degrees C leads to a time-dependent uptake of proteoglycan-gold conjugates via non-coated and coated vesicles which after fusion are translocated to multivesicular bodies and to large sized vesicles within 1 h. After conversion of these vesicles to lysosomal compartments the gold particles are uncoupled from the proteoglycans and are concentrated within residual vacuoles. From these vacuoles the gold particles are extruded. In contrast to the surface-bound proteoglycan-gold conjugates the released gold particles are condensed to bulky aggregates. The results, which include competition, inhibition and pulse chase experiments, extend biochemical data on endocytosis and degradation of proteoglycans.

Animals↗
PubMed1983

Wheat germ eIF2 and CoeIF2. Resolution and functional characterization in in vitro protein synthesis.

A factor that binds Met-tRNAiMet in a ternary complex (eucaryotic initiation factor (eIF2) ) and an auxiliary component that strongly stimulates the activity of the binding factor (CoeIF2) have been purified from extracts of wheat germ. The molecular weights of the two factors, as determined by glycerol gradient centrifugation and sodium dodecyl sulfate gel electrophoresis, are 88,000 and 20,000, respectively. Incubation of wheat germ eIF2 with gamma-[32P]ATP and alpha-subunit kinase results in the phosphorylation of a Mr = 40,500 subunit, while no specific phosphorylations are found when the eIF2 is incubated with the beta-kinase. These data are interpreted to suggest that CoeIF2 is a monomer of Mr = 20,000 while eIF2 may be a dimer, containing subunits of Mr = 40,000 and 50,000. Both eIF2 and CoeIF2 are strongly required for in vitro amino acid polymerization, providing the first direct demonstration of the function of CoeIF2 in protein synthesis.

Electrophoresis, Polyacrylamide Gel↗
PubMed1983

Altered visual-evoked potentials in congenitally deaf adults.

Visual-evoked potentials recorded from the scalp of congenitally deaf adults were significantly larger over both auditory and visual cortical areas than in normal hearing adults. Over temporal and frontal areas peripheral stimuli presented at long intervals elicited N150 components which were larger in deaf than in hearing subjects. Over occipital and parietal areas peripheral and foveal stimuli elicited larger P230 components in deaf than in hearing subjects. These results imply that early auditory experience influences the organization of the human brain for visual processing.

Adult↗
PubMed1983

Fractionation and partial characterization of the protein synthesis system of wheat germ. I. Resolution of two elongation factors and five initiation factors.

Wheat germ S100 supernatant was resolved into 10 components, all of which are required for tobacco mosaic virus RNA-directed incorporation of amino acid into protein. Two of the components, C2b and C2a, are, respectively, elongation factors 1 and 2, having molecular weights of 51,000 and 72,000. A third factor (C2e) binds Met-tRNA in a GTP-requiring reaction and is absolutely required for the formation of both 40 S ribosome.Met-tRNAiMet and 80 S ribosome.Met-tRNAiMet complexes. This factor is considered to be eucaryotic initiation factor 2. Formation of 80 S ribosome Met-tRNAiMet complexes is augmented 2 to 3-fold by the simultaneous addition of an mRNA, factor C1, and fraction D2(a + b). Factor C1 also reverses the inhibition of translation by an increased concentration of monovalent cations and promotes the translation of a "competitively inhibited" mRNA. These observations suggest that factor C1 and either factor D2a and D2b (or both) function in mRNA attachment reactions. Factor C1 has a molecular weight of 115,000 and appears to be made up of two or three subunits. Factor D2b has been purified to essential homogeneity and has a molecular weight of 55,000. Its interaction with mRNA and its molecular weight suggest that this factor is the wheat germ equivalent of reticulocyte eucaryotic initiation factor 4A.

Amino Acids↗
PubMed1983

Fractionation and partial characterization of the protein synthesis system of wheat germ. II. Initiation factors D1 (eucaryotic initiation factor 3), D2c (eucaryotic initiation factor 5), and D2d (eucaryotic initiation factor 4C).

This report characterizes three components of the fractionated wheat germ protein synthesizing system, factors D1, D2c, and D2d. FActor D1 has a molecular weight of about 420,000 and is comprised of 7-10 components varying in molecular mass between 28,000 and 105,000 daltons. The factor is absolutely required for the formation of both 40-S ribosome.Met-tRNAiMet and 80 S ribosome.Met-tRNAiMet complexes except at low Mg2+ concentration, where significant 40 S ribosome complex formation can be obtained without D1, provided the reaction products are fixed with glutaraldehyde. Factor D1 can be shown to interact with the 40-S ribosome subunit in two ways: the change in sedimentation of the ribosome subunits that occurs when ribosomes are incubated with the factor under dissociating conditions and the prevention of the reformation of 80 S ribosomes by a prior incubation of ribosome subunits with the factor. Factor D2c has a molecular mass of about 100,000 daltons and is absolutely required for the conversion of 40 S ribosome.Met-tRNAiMet complexes to 80 S ribosome.Met-tRNAiMet. Factor D2d strongly augments the D2c-dependent formation of 80S ribosome.Met-tRNAiMet complexes, with the requirement for D2d most apparent when the complexes are fixed with glutaraldehyde, a treatment that labilizes the 80 S ribosome-bound Met-tRNAiMet. Addition of factor D2d to a 40 S ribosome.Met-tRNAiMet synthesizing system also increases the amount of complex obtained 2-5-fold. Consideration of these characteristics establishes components D1, D2c, and D2d as wheat germ eucaryotic initiation factors 3, 5, and 4C, respectively.

Eukaryotic Initiation Factor-1↗
PubMed1983

Unilateral split hand in one of monozygotic twins.

Atypical split hand (left) was observed in one of monozygotic twins. The probability for monozygosity was 0.997 as based on 18 autosomal loci (11 blood groups and 7 enzymes and serum proteins). This observation supports the thesis that atypical split hand is not genetically determined and must be distinguished from autosomal dominant ectrodactyly.

Diseases in Twins↗
PubMed1983

The genetic significance of accessory bisatellited marker chromosomes.

Ten new cases of accessory bisatellited marker chromosomes examined in different laboratories are reported. As a basis for genetic counseling in the context of prenatal diagnosis a cytogenetic categorization of such marker chromosomes is proposed and an estimation of the genetic risk associated with each category is carried out. The results are as follows: There is no increased risk for offspring with abnormal phenotype born to a healthy carrier of an accessory bisatellited marker chromosome with either a single or two closely adjacent C-bands (Category AI or AII). The unbiased sample of cases with de novo accessory bisatellited marker chromosomes of categories AI and AII is too small to allow a satisfactory estimation of the actual risk that, in case of such a prenatal finding, the foetus may not show a normal phenotype as a consequence of the marker chromosome. There is, however, evidence that this risk may be lower than 10%. Accessory bisatellited marker chromosomes showing a discrete pattern of G- and R-bands situated between two distant C-bands (Category AIII) usually indicate a chromosomal imbalance giving rise to an abnormal phenotype. Mosaic carriers of such dicentric marker chromosomes may, however, present a normal phenotype.

Abortion, Spontaneous↗
PubMed1983

Short-term physical training in bronchial asthma.

The effect of two types of physical training on patients with perennial asthma were compared in a blind, controlled, randomized study. Eleven of 27 adults with asthma performed a physical training programme which did not change their oxygen consumption (control group). The remaining 16 asthmatics performed a physical training programme which improved their maximal oxygen consumption (training group). Both of the training programmes were performed for 1 hour, twice a week during a period of 2 months. No complications were reported during the performance of the training programmes. The doses of all medicines apart from beta 2-agonist aerosol were unchanged during the training period. The patients inhaled beta 2-agonist aerosol if their peak expiratory flow (PEF) was less than 60% of their maximal PEF. The training group decreased their use of aerosol from an average of 4.94 puffs per day to 3.41 puffs per day (P less than 0.05). The control group did not change their use of beta 2-agonist aerosol significantly. It is concluded that physical exercise which improves the maximal oxygen consumption decreases the use of beta 2-agonist spray and that heavy exercise is well tolerated by asthmatics.

Adrenergic beta-Agonists↗
PubMed1983

An auditory evoked potential study of consonant perception in different vowel environments.

Auditory evoked responses (AER) to series of consonant--vowel syllables were recorded from temporal and parietal scalp locations from 20 right-handed female college students. Averaged AERs were submitted to principal components analysis and analysis of variance. Seven components of the group's AERs were found to reflect various aspects of the stimulus parameters. One component reflected changes over only the left hemisphere to different consonants independent of the following vowel sound. A second component changed systematically over both hemispheres in response to only consonant changes. A third component systematically changed for the different consonants depending on the following vowel.

Adolescent↗
PubMed1983

Is hostility linked with affiliation among males and with achievement among females? A critique of Pollak and Gilligan.

This investigation attempted to replicate and to clarify methodologically an investigation by Pollak and Gilligan (1982). Those investigators reported sex differences in violence imagery to Thematic Apperception Test (TAT) pictures depicting affiliation and achievement situations. Pollak and Gilligan concluded that men perceive danger in situations of affiliation whereas women perceive danger in situations of achievement. It was demonstrated in the present study that Pollak and Gilligan incorrectly classified TAT cards into motivational categories, which may have resulted in incorrect inferences. In addition, their findings could not be replicated when using four different systems for classifying TAT cards into motivational categories. Other potential sources of error in their research, including a restrictive scoring scheme for hostility, unusual instructions, and failure to control for sex role in the TAT pictures, did not influence the pattern of results.

Achievement↗
PubMed1983

Eukaryotic initiation factor 4A is the component that interacts with ATP in protein chain initiation.

Protein synthesis in a resolved homogenate of wheat germ requires ATP and eight factors functioning at the level of protein chain initiation. To identify the component(s) interacting with ATP, the different factors were treated with the ATP affinity analogue 5'-p-fluorosulfonylbenzoyladenosine (FSBA) and tested for their function in protein synthesis. The activity of eukaryotic initiation factor 4A (eIF4A) was strongly curtailed, whereas all other factors were unaffected. At a concentration of 250 microM, AMP, ADP, and ATP protected eIF4A against FSBA inactivation, whereas at a concentration 50 microM, protection was afforded only by ATP. GTP did not protect at a concentration of 250 microM. In another approach, the substrate analogue 2',3'-O-(2,4,6-trinitrophenyl)adenosine 5'-triphosphate (TNP-ATP) was found to inhibit protein synthesis in a manner, at least in part, competitive with ATP. Supplementing a TNP-ATP inhibited reaction with eIF4A substantially reversed the inhibition. Except for a small effect by factor C1, no reversal was obtained with any other component. Finally, a preincubation of ribosomes with ATP, mRNA, and eIF4A resulted in the formation of a complex capable of TNP-ATP-resistant amino acid incorporation. These data are interpreted to indicate that the primary interaction of ATP is with eIF4A. A model is proposed reconciling this conclusion with other observations relevant to the mRNA . ribosome attachment reaction.

Adenosine Triphosphate↗
PubMed1983

Pretreatment of exercise-induced asthma with sequential inhalations of fenoterol as aerosol and as powder (first of two parts).

Fifteen adult asthmatics participated in a controlled open randomized study to compare the efficacy on exercise-induced asthma of pretreatment with 1 mg fenoterol administered as inhalation powder and from a pressurized aerosol. Both types of treatment were inhalations of 5 single doses of 0.2 mg fenoterol over a period of 10 minutes. A run of 6 minutes was carried out on a treadmill in a climate chamber 30 minutes after the beginning of the pretreatment, at the same time of day on three days. After pretreatment with the pressurized aerosol a fall was seen in peak expiratory flow of 28% (+/- 5%, SEM) and after pretreatment with inhalation powder the fall was 18% (+/- 4%). This is a statistically significant difference (p less than 0.01).

Adult↗
PubMed1983

Double-blind pretreatment of exercise-induced asthma with sequential inhalations of fenoterol from an aerosol and as a powder (second of two parts).

Eighteen adult asthmatics participated in a placebo controlled, double-blind, randomised study comparing the efficacy of pretreatment with fenoterol administered by pressurized aerosol and as a dry powder on exercise-induced asthma. The dosages used were 0.6 mg and 1.0 mg as both pressurized aerosol and dry powder. The pretreatment was given over a period of 10 min. Six min of treadmill-running was performed in a climate chamber 30 min after pretreatment on five successive days. The lung function was assessed by peak expiratory rate. The decrease in lung function following pretreatment with placebo was 32% (average +/- (SEM) (2). Falls of 9% (2) and 8% (1) were seen after pretreatment with 0.6 and 1.0 mg from a pressurized aerosol. The falls following pretreatment with 0.6 and 1.0 mg of dry powder were 8% (2) and 8%, respectively. It is concluded that pretreatment of exercise-induced asthma with a beta-2-agonist is equally effective whether dosed from a pressurized aerosol as when given as a dry powder. A dose of 0.6 mg is just as effective as a dose of 1.0 mg when inhaled over a period of ten min.

Adult↗
PubMed1983

Pretreatment of exercise-induced asthma in children using disodium cromoglycate and fenoterol inhalation powder.

The effect of pretreatment with inhalation powder containing fenoterol, sodium cromoglycate, fenoterol plus sodium cromoglycate and placebo, in the prevention of exercise-induced asthma was compared in a randomized, double-blind, cross-over investigation including 17 asthmatic children with exercise-induced asthma. Six minutes of treadmill running was carried out in a climate chamber 30 minutes after pretreatment on the four test days. The post-exercise fall in PEF after pretreatment with fenoterol was 7%, with sodium cromoglycate 20%, with fenoterol plus sodium cromoglycate 6% and after placebo 27%. Both sodium cromoglycate and fenoterol provided protection against exercise-induced asthma (p less than 0.05 and p less than 0.001). Fenoterol gave significantly better protection than sodium cromoglycate (p less than 0.001), and it is concluded that the treatment of choice for the prevention of exercise-induced asthma is the inhalation of a beta 2-agonist.

Adolescent↗