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Biomedical subjects

J Martens

Publications and source records attributed to J Martens.

At least 37 records · Page 2Linked to original sources
PubMed1992

Secondary-ion and electron production from surfaces bombarded by large polyatomic ions.

Heavy molecular ions with energies in the range 10-20 keV and masses from 276 u to 132,000 u, produced by matrix-assisted laser desorption, were used as primary projectiles to produce secondary-ion spectra from a variety of surfaces in a tandem time-of-flight mass spectrometer. In the negative mode the ratio of electron emission to secondary-ion emission was found to decrease rapidly with increasing projectile mass. Ion emission was found to dominate for primary ions larger than approximately 10,000 u. Positive or negative molecular ions and cations were observed from several organic targets of masses up to 1140 u (gramicidin S) for incident projectiles up to mass 132,000 u, i.e., for projectile speeds down to approximately 7000 m/s. Other ions characteristic of the target were also observed for these projectiles. Thus, large polyatomic ions can cause secondary-ion desorption even at very low velocity. The background ions of both polarities are similar to those found in keV particle bombardment by monatomic projectiles. The same ions are observed for all the projectiles; most can be identified with hydrocarbon background. The relative intensities of the background positive ions are largely independent of projectile, and for both polarities the ratio of the ions characterizing the target to those forming the background is approximately constant for all the projectiles. These results strongly suggest that the background ions come from the usual layer of organic impurities attached to the target surface. No direct evidence for surface-induced dissociation was observed in this mass and energy range.

Mass Spectrometry↗
PubMed1990

Importance of enantiomeric purity and its control by thin-layer chromatography.

Methods for the direct resolution of enantiomers are important and are necessary for pharmaceutical and biomedical analysis, synthetic and mechanistic studies and various other fields. The present paper deals with the results of recent approaches, such as ligand exchange, ion exchange and steric interactions, providing direct resolution of enantiomers of a variety of compounds by thin-layer chromatography. General aspects of various methods for analysis of enantiomeric purity and resolution have been compared.

Amino Acids↗
PubMed1990

A new total implantable artificial heart.

A new kind of total implantable artificial heart (TIAH), developed by the author, offers miniaturization with good hemodynamic and physiologic properties. The heart has two units of function, and each has two blood sacs, compressed and expanded by twos, that are filled from one circulation and push out the blood in the other circulation, one after the other. Therefore, the blood flow is continuous and modulated, regulated by pneumatic controlled membrane valves. Shaped plates mechanically synchronized by a pushing rod control compression and expansion of the blood sacs. Starling, atrium, Windkessel, and Anrep effects are guaranteed by construction. The heart can be used for bridging toward transplantation, for definitive substitution of the heart, and for a new kind of therapy--"extracorporeal regeneration of organs."

Heart, Artificial↗
PubMed1990

Safety and efficacy of a thymidine kinase negative equine herpesvirus-1 vaccine in young horses.

A drug induced equine herpesvirus-1 (EHV-1) mutant lacking thymidine kinase inducing activity was developed and evaluated as a vaccine. The safety and effectiveness of the vaccine to protect against experimentally induced EHV-1 respiratory disease were evaluated in weanling horses free of EHV-1 neutralizing antibody. The vaccine was safe when administered either intramuscularly or intravenously, and EHV-1 was not shed intranasally during the 12 days following administration. Intranasal challenge with virulent EHV-1 was used to evaluate vaccine efficacy. Following challenge, there was a significantly (p less than 0.05) greater increase in peak body temperatures and duration of nasal virus shedding in the nonvaccinates, and a significant (p less than 0.05) increase in serum neutralizing antibody titers in the vaccinates.

Animals↗
PubMed1989

T.l.c. enantiomeric separation of amino acids.

Resolution of enantiomers is very important particularly in the fields of asymmetric synthesis, mechanistic studies, geochronology, studies of structure-function relationship of proteins, pharmacology, and medicine. Various chromatographic methods have replaced the classical fractional crystallization, seeding and enzymatic procedures. Of these, t.l.c. provides a direct, simple, and inexpensive method for resolution of enantiomers of amino acids and their derivatives. Ligand exchange, ion exchange, and molecular inclusion complexation have been the basis of t.l.c. resolution of enantiomers of amino acids and their derivatives. The innovation of new plate types, and methods of development and detection have renewed interest in the direct resolution of enantiomers of amino acids, their derivatives and a variety of other compounds by t.l.c. The present report provides an overview of some of the more recent approaches to the direct t.l.c. resolution of amino acids and their derivatives together with special advantages and scope of t.l.c.

Amino Acids↗
PubMed1985

Application of chromatographic chiral stationary phases to pharmaceutical analysis. Enantiomeric purity of D-penicillamine.

The enantiomeric purity of the pharmaceutical D-penicillamine (I) has been determined by a novel high-performance liquid chromatographic technique involving the formation of 5,5-dimethylthiazolidine-4-carboxylic acid (III) by reaction of I with formaldehyde and separation of the optical antipodes by means of ligand exchange chromatography using the copper(II) complex of (2S,4R,2'RS)-4-hydroxy-1-(2'-hydroxydodecyl)proline, which is coated on a reversed-phase column. The limit of determination for the L-antipode is ca. 0.1%. The validation of the method is accomplished by comparison with an independent gas chromatographic procedure. Thirteen commercially available lots of I are shown to be of equally high enantiomeric purity (ca. 99.9%).

Chromatography, Gas↗
PubMed1984

[Hypophyseal adenocarcinoma in a horse. A case study].

The paper presents the case-history of a 5-year-old pony suffering from an adenocarcinoma which proceeded from the pars intermedia of the pituitary gland. Neurological and patho-morphological findings are reported.

Adenocarcinoma↗
PubMed1983

Respiratory muscle dysfunction in systemic lupus erythematosus.

An assessment of pulmonary mechanics revealed weakness of inspiratory and expiratory muscles as cause of the restrictive ventilatory defect (vital capacity: 47 +/- 10 percent predicted) in seven (ages 33 to 62 years) out of 26 consecutive patients with systemic lupus erythematosus (SLE). Maximal inspiratory transdiaphragmatic pressures were reduced mainly due to the markedly increased (more positive) esophageal pressures. During maximal expiratory efforts, esophageal and gastric pressures were grossly decreased. These abnormalities probably may be considered part of a more generalized, yet subclinical muscle disorder due to the SLE with, however, predominant involvement of the respiratory muscles. The abnormalities were not related to the use of corticosteroids or generalized inanition. The static expiratory lung compliance was reduced in all patients (55 +/- 18 percent predicted), but normalized immediately following passive inflation of the lungs to transpulmonary pressures of more than 30 cm H2O in two of the three subjects tested. The volume restriction was not progressive over a period of 38.5 patient-years.

Adult↗
PubMed1982

Rheumatoid arthritis associated with bronchiolitis obliterans and immunoblastic sarcoma.

A case is reported of a 72 year old man suffering from classical seropositive RA for 10 years. Two months before admission he experienced general illness, fever and itching. Lymph nodes enlargement and hepatosplenomegaly were found. Histologic features of lymph node biopsy were compatible with angioimmunoblastic lymphadenopathy and Lennert lymphoma. Rapidly progressive pulmonary deterioration followed with hilar invasion and honeycombing. Sternal punction, bone biopsy, bronchus biopsy and blind lung biopsy however, did not reveal lymphomatous invasion. On the contrary, lung biopsy, showed bronchiolitis obliterans, an often fatal, small airway disease whose connection with RA is discussed. Plasmapheresis induced a correction of leucopenia and thrombocytopenia. A fatal evolution evolved within six months. Autopsy revealed diffuse invasion by immunoblastic sarcoma. The clinicopathological entities angioimmunoblastic lymphadenopathy and Lennert lymphoma are referred to. The relationship with autoimmune disorders is stressed.

Aged↗
PubMed1982

Diaphragm dysfunction in mixed connective tissue disease. A case report.

A patient with mixed connective tissue disease (MCTD) presented the typical signs of respiratory muscle weakness and marked diaphragm dysfunction: reduced maximal ex- and inspiratory transrespiratory pressures (measured at FRC), maximal transdiaphragmatic pressures and transpulmonary pressures at TLC, FRC and RV. this insufficiency of the diaphragm was also responsible for the restrictive ventilatory defect and the decreased static lung compliance with high diffusing capacity per unit lung volume.

Adult↗