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Biomedical subjects

R Beyer

Publications and source records attributed to R Beyer.

At least 37 records · Page 2Linked to original sources
PubMed1991

[Deterioration of pulmonary gas exchange caused by PEEP in a pulmonary vascular shunt (Rendu-Osler-Weber syndrome)].

A 25-year-old patient with headache was admitted to the neurology department. Computerized tomography revealed an intracerebral abscess of unknown origin, which was removed by craniotomy. After an uneventful operation and anesthetic low arterial oxygen tensions were noted that did not respond to increased FiO2. Angiography revealed a pulmonary arteriovenous (a-v) fistula (angioma), which was responsible for the right-left shunt. A Swan-Ganz catheter was inserted and the effects of varying levels of PEEP on the magnitude of the shunt during spontaneous breathing of 100% oxygen were determined. At zero PEEP the arterial pO2 was 211 mm Hg (AaDO2 470 mm Hg). 5 mbar PEEP caused the arterial pO2 to fall to 118 mm Hg (AaDO2 563 mm Hg). Increasing PEEP to 15 mbar caused a further decrease in arterial pO2 to 72 mm Hg (AaDO2 603 mm Hg), which resulted in arterial desaturation. The arterial pCO2 remained constant. At a virtually constant cardiac output the shunt volume increased from 23% at zero PEEP to 30% at a PEEP of 15 mbar--a relative increase of 30%. Elevating the intrathoracic pressure presumably caused redistribution of the pulmonary perfusion toward the shunt vessels, probably because the vascular resistance increased more rapidly in the normal vasculature than in the angioma. The therapeutic consequences were to reduce the PEEP and avoid mechanical ventilation. Pulmonary a-v-fistulas are not uncommonly associated with brain abscesses, probably because the normal filter function of the pulmonary vascular bed is disrupted. Therapy consists either in resecting the afflicted lung segment or in transvenous occlusion of the fistula with a silicon ballon.

Adult↗
PubMed1989

[Percutaneous mitral valvuloplasty in 6 patients].

We performed a percutaneous mitral balloon valvuloplasty in 6 patients with severe mitral stenosis, aged 21 to 50 years. The mitral valve gradient decreased from 14.7 +/- 4.9 to 6.3 +/- 4.0 mmHg, p = 0.03. Mitral valve area increased in 5 patients (0.92 +/- 0.23 to 2.32 +/- 0.26 cm2, p = 0.04). One patient developed a transient cerebral ischemic attack without sequelae and mild mitral insufficiency. The diameter of the mitral annulus as measured by echocardiography was 48.5 +/- 8.1 mm, significantly larger than that reported in other series. The curvature of the transseptal needle was selected after an echocardiographic view of the inferior vena cava and atria from the subcostal window. This allowed a successful procedure in all patients regardless of cavity size.

Adult↗
PubMed1988

Highly protective alkalinization by ammonia vapor diffusion in viscosimetric DNA damage assessment.

A method for the measurement of viscosities correlated to DNA alterations in alkaline homogenate suspensions is described. The alkaline pH shift to afford cell lysis, DNA unfolding, and denaturation is attained by gaseous ammonia diffusion, thus avoiding shear stress from mechanical mixing. At the same time a stabilizing density gradient is established. This solution is run through a plastic measuring tube that is wide enough to minimize the influence of uneven swelling of the lysing DNA-containing components. Flow times under a carefully controlled water head are registered, and their ratios to control solutions are evaluated. The relative viscosities show a strong and irreversible dependence on shear and on DNase treatment and therefore are considered as essentially DNA derived. The time dependence of the lysate viscosities with and without the DNA-damaging agent bleomycin is given and the dose:activity curves of this agent with sponge homogenates from two orders of Porifera are given with their 50% effective concentration values. The dose:activity curve of an extract from a polluted marine point source is demonstrated. The concentration changes in sponges exposed at differently polluted marine sites are shown. The idea of alkalinization through gaseous diffusion in conjunction with a simple measuring device has already proven a sensitive, reliable, and specific tool in the assessment of DNA damage produced under both laboratory and field conditions.

Ammonia↗
PubMed1987

Age-correlated DNA damage in human muscle tissue.

This investigation represents the largest study so far published on human DNA damage and aging. The subject of this investigation is damage, determined as DNA alterations which give rise to complete molecular breaks in the course of treatment of purified DNA solutions with single-strand-specific nucleases. The DNA is derived from milligram samples of human muscle of individuals mostly undergoing surgical treatment. Care has been taken to bring the muscle samples, once shut off from blood circulation to liquid nitrogen temperatures within few seconds. The DNA is prepared by a procedure keeping breaks by handling and by DNAase attack as low as possible, however pushing DNA purity, especially with respect to protein as high as possible. Highly purified DNA treated in this way has some sites which are susceptible to single-strand (ss) specific DNAase splitting (ss-events). Three different deoxyribonucleases have been used: Nuclease S1, Nuclease BAL31 and Pea Endo-Nuclease. They give very similar results, i.e. splitting of the DNA so as to yield DNA pieces of given distribution. The lengths of these double-strand (ds) pieces have been determined from their electron microscopical pictures, either by following the image contours with a magnetostrictive stylo of the projected photo on a pad, by following the contours with a mileage ruler, or by integrating the silver grains on the photo. The molecular weight averages of the ds DNA threads between two ss-events for each individual have been determined from 20 to 200 molecules. The 470 individuals contributing their data were from age groups from 1 to 91 years. The molecular weights show a considerable scatter with an average molecular weight of the DNA ds pieces between two ss-events of 43.93 MDa and a standard deviation of 17.99 MDa. Among the single-strand breaks (ssb) that split the DNA into such pieces is a fraction, the number of which increases in a highly significant fashion with the age of the donor. From this derives the fact that the average molecular weight of the DNA strand pieces between two ssb decreases with age. It is remarkable that the standard deviation of the molecular weights of such pieces increases with age significantly, too. On the basis of additional information mainly supplied by the DNA donor himself or by his parents the 470 members of the main group M where grouped according to their life-style, into: (1) abstinent people, essentially non-smokers and refraining from use of licit or illicit drugs, sub-group N.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1985

Orbital varices: a surgical approach.

Five cases of orbital varices are presented, demonstrating a surgical approach with the use of vascular clips. Three of four cases were clipped at the apex of the orbit, with no recurrence. A fourth case was clipped two-thirds of the way back in the orbit, with no progression of the varix and significant improvement of the patient's symptoms. A fifth case failed because of extensive hemorrhaging. Follow-up ranged from 2 to 9 years.

Adolescent↗
PubMed1982

The effect of benzo[a]pyrene on sponges as model organisms in marine pollution.

The majority of the investigations were performed with the marine sponge Tethya lyncurium at concentrations of 2 X 10(-8) to 1 X 10(-11) g/ml of benzo[a]pyrene (BaP). Sea-pollution was characterized as BaP equivalent activity in the Ames test. Increased activity of ornithine decarboxylase (ODC) was observed when sponges were artificially exposed at polluted marine areas for 3 weeks. In contrast to the situation in higher animals no ODC induction of the fast type was observed. Mixed function oxygenases (MFO) were not detected in sponges nor could they be induced as in vertebrates. BaP was absorbed by Tethya and concentrated 30--60-fold. In live, but not dead, artificially perfused sponges [3H]- and [14C]BaP-radiolabeled became firmly associated with DNA, RNA and protein of the sponges. The association persisted in isolated fractions, in nucleotides, in nucleosides and in protein hydrolysates. The BaP binding ratio to DNA was found to be strongly correlated to the concentration of BaP. Light modifies BaP and thus enables binding. In the dark only very low association, if any, is observed. The possible consequences of these findings are discussed.

Animals↗
PubMed1982

[Effect of difluron (dimilin) on larvae, imagines and eggs of Epilachna varivestis Muls. through application to the host plant].

Dimilin active ingredient diflubenzuron) is an insecticide influencing the chitin synthesis. The paper investigates its effect under application via the host plant. After oral intake with the food, the larvae of Epilachna varivestis Muls. (Mexican bean beetle) could not carry out the next molting and died. Imagines which had taken up Dimilin laid fewer eggs than untreated beetles, and no larvae hatched from the eggs. Direct treatment of the cluster of eggs with Dimilin also affected their development, depending on the degree of concentration. Freshly laid eggs were more susceptible than older ones. Contact with the treated non-host plant Vicia faba also caused disturbances in the development. The sensitive phase in the second instar lies between 24 and 48 hours after the previous molt. 3 to 6 hours exposition time are sufficient to inhibit the molting of the larvae, 9 hours suppressed the molting completely. The concentration limit for larvae of Epilachna varivestis lies between 1.0 and 2.5 ppm.

Animals↗
PubMed1981

Arabinosyl nucleosides. XXXII. Mechanism of inhibition of L5178y mouse lymphoma cells by 9-beta-D-arabinofuranosylguanine.

The mechanism of the growth-inhibitory action of 9-beta-D-arabinofuranosylguanine (ara-G) on mouse lymphoma cells (L5178y) at the level of nucleic acid synthesis was studied. Ara-G inhibits the cell proliferation at an ED50 concentration of 12.3 microM. The cells die because of unbalanced growth. At cytostatic concentrations ara-G inhibits the incorporation rate of dThd into DNA to a much higher degree compared to those of the precursors into RNA or proteins. Ara-G has no effect on the induction of DNA polymerase alpha occurring at the beginning of the S-phase; this compound exerts its inhibitory activity during the S-phase. Ara-G is intracellularly phosphorylated to ara-GTP. It was demonstrated that ara-G is incorporated into DNA but not into RNA; one molecule of ara-G is incorporated per 7050 molecules of deoxyguanosine. The ara-GMP moieties, incorporated into DNA of L5178y cells are not removed during a culture period of 7.7 doubling steps; compared to the controls no reduction of the viability and growth rate was observed.

Animals↗
PubMed1981

[Production of primary cells cultures by a semi-industrial technic. II. Use of active trypsin solutions for effective cell yields].

For effective cell yields in semi-industrial production of primary cell suspensions, the use of trypsin solutions with high enzyme activity has been proved to be an essential requirement. Enzyme solutions with a constant high activity may be obtained by using an optimal filtration method. Filtration results using the deep and membrane filtration method to sterilize trypsin solutions are demonstrated and discussed. A number of trypsin samples taken from the "Leidholdt-Firm" were tested concerning cell yields in the so-called 'Biomix-Procedure'. A correlation could be shown to exist between enzyme activity and cell yield. The so tested trypsin-L-samples out of the years 1976/78 were proved to be first-rate preparations for routine production of primary piglet and calf kidney cell cultures.

Animals↗
PubMed1979

[Production of primary cell cultures on a semi-industrial scale. 1. Modification of the trypsinization procedure--possible means to improve cell yield].

To produce large quantities of primary cell suspensions on efficient technique is described which is named "Biomix-Method". By this technique first tissue mince is performed automatically using tissue amounts between 300 g and 500 g. Trypsinization takes place in a three-litre trypsinization vessel using a stirring mechanism according to a defined trypsinization mode. In regard to optimal cell seeding concentration and a justifiable productivity one kidney of newborn or suckling calf yields 6--9 1 cell suspension and that of piglet 1,8-2,3 1, respectively. Proliferation behaviour and effectivity of primary cells are discussed and compared with other cell systems.

Animals↗
PubMed1978

Arabinosyl nucleosides. XII. Influence of arabino-furanosylthymine on growth of L5178y cells.

The antibiotic 1-beta-D-arabinofuranosylthymine (araThd) is a potent inhibitor of the growth of mouse lymphoma cells (L5178y). The ED50 concentration was found to be 9.8 muM. The cells die as a consequence of an unbalanced growth. The cytostatic activity of araThd can be abolished by coincubation with dThd and dUrd but not with Urd. At cytostatic concentrations araThd selectively blocks DNA synthesis; RNA- and protein synthesis are unaffected. Intracellularly araThd is rapidly phosphorylated to araTTP. This enzymic phosphorylation does not influence the synthesis of the naturally occuring, related triphosphate dTTP. AraTMP is incorporated into DNA during DNA synthesis; 1 mol of ara-TMP is incorporated/19,500 molecules of dTMP.

Arabinonucleosides↗
PubMed1978

Species-specific aggregation factor in sponges. XIII. Entire and core structure of the large circular proteid particle from Geodia cydonium.

High-molecular weight particles have been isolated from the sponge Geodica cydonium. In the "native" from these particles consist of a spherical center and have 25-30 filaments attached to it. The core structure of the particles is assembled of a central circle and 25 radially-arranged filaments. The core structure is obtained from the entire structure by incubation in a medium, containing a non-ionic detergent and EDTA. The molecular weight of the enitre structure was in the range of 1.4 X 10(9) daltons or more and of the core structure 6.1 x 10(8) daltons. Two functional proteins are released from the "native" particles: the aggregation factor and the sialytransferase.

Animals↗