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Biomedical subjects

E Baer

Publications and source records attributed to E Baer.

At least 19 recordsLinked to original sources
PubMed1997

A radiation hybrid map of human chromosome 5 with integration of cytogenetic, genetic, and transcript maps.

One of the major goals of the human genome project is to establish a physical map of each human chromosome with a density of sequence-tagged site (STS) markers exceeding one every 100 kb. We report here the generation of a human chromosome 5-specific radiation hybrid (RH) map that includes 556 markers. Of these markers, 132 loci are ordered with a maximum likelihood ratio of >1000:1 compared with the next most likely order. An additional 113 loci were ordered relative to these backbone markers with a maximum likelihood ratio of >10:1 but <1000:1. Together, these 245 loci form an ordered framework map for the chromosome. Using this framework, >300 more markers were localized based on two-point analysis with the ordered set. On average, there are 50 markers in common with the RH map presented here and other chromosome 5 maps included in the current whole genome cytogenetic, genetic, and physical maps. The accuracy of all the maps is evident in that there are no more than two discrepancies between any one of them and these data. All of the maps encompassing chromosome 5 complement each other providing excellent STS coverage with >2200 loci combined. The chromosome 5-specific RH map contains 20% of these independent loci. In addition, our RH map contains STSs derived from clones suitable for fluorescent in situ hybridization, allowing alignment to the cytogenetic map. Together, these maps will assist in the assembly of sequence-ready contigs and will aid in the identification of disease loci on chromosome 5 by positional cloning and positional candidate approaches.

Centromere↗
PubMed1994

Creep of a poly(etherurethane urea) in an oxidative environment.

The creep behavior of a PEUU without added stabilizers was examined in H2O2/CoCl2, an environment that simulates the biodegradation of this polymer. Creep in the control environments, air, water, and H2O2, was logarithmic with time as is characteristic of primary or viscoelastic creep. At short times, creep in H2O2/CoCl2 followed the same time dependency as creep in H2O2; however, at longer times an acceleration in the creep rate was observed. Creep in H2O2/CoCl2 was satisfactorily described by addition of a linear time term to the creep equation with an induction time, ti. The induction time was extended by stress-induced crystallization of the soft segments, but was reduced by an increase in H2O2 concentration. Oxidative degradation of the PEUU soft segments was detected by infrared and GPC analysis at times less than ti. This led to the speculation that an initial "precursor" layer was created at the surface by chain cleavage. Microcracking in a subsequent stage was postulated to be responsible for the observed effect on the creep behavior.

Biocompatible Materials↗
PubMed1989

Hierarchical structure of the intervertebral disc.

Optical microscope techniques are used to characterize the hierarchical structure of the collagenous components of the human intervertebral disc. In the anterior annulus fibrosus, the thickness of lamellae increases abruptly 2 mm inward from the edge of the disc, dividing the annulus into peripheral and transitional regions. Lamellae in the lateral and posterior aspects of the disc have a broad distribution of lamellar thicknesses throughout the annulus. In alternating lamellae, fibers are inclined with respect to the vertical axis of the spine in a layup structure. From the edge of the disc inward to the nucleus, this interlamellar angle decreases from +62 to +45 degrees. Within lamellae, the collagen fibers exhibit a planar crimped morphology. The plane of the waveform is inclined with respect to the vertical axis by the interlamellar angle. From the edge of the disc inward, the crimp angle increases from 20 to 45 degrees and the crimp period decreases from 26 to 20 um. A hierarchical model of the intervertebral disc has been developed that incorporates these morphological gradients.

Adult↗
PubMed1987

Hierarchical structure in polymeric materials.

The diversity of monomers available for synthesis of high polymers makes it possible to prepare a wide variety of long-chain macromolecular compounds. It is instructive to consider a hierarchical organization of structure in polymers at four successive levels--the molecular, nano-, micro-, and macrolevels--and to examine how interactions at and between these various levels of structure have important and often quite specific influences. Examples are drawn from semicrystalline polymers with flexible chains, liquid-crystalline polymers composed of rigid macromolecules, and amorphous polymers. Structural hierarchies in biocomposite systems are also discussed, particularly in soft connective tissues such as tendon and intervertebral disk.

Animals↗
PubMed1983

Organization of collagen fibers in the intestine.

The characteristic extinction pattern which is observed when the submucosa is viewed in the optical polarizing microscope has been analyzed in terms of the configuration and orientation of the 4 micron diameter collagen fibers. It is shown that the observed polarization effects are produced by periodic variations in orientation of fully birefringent fibers. The fiber configuration required to produce the observed polarization effects is a tilted wave configuration with a crimp period of approximately 20 micron. In the model, the tilted waveform fibers are crimped in register and form parallel arrays. The arrays are oriented in layers at approximately +30 degrees and -30 degrees to the longitudinal direction and are mirror images of each other. Analysis of the extinction pattern shows that the model satisfactorily accounts for the observed polarization effects at several different angles of the crossed polaroids. The calculated strain necessary to straighten the wavy fibers of the model correlates well with the observed strain to uncrimp the collagen fibers in the intestine. This suggests that the initial response to stress is gradual uncrimping of the collagen fibers, and concurrently, a decrease in the angle between biaxially oriented fibers, rather than extension of the straight fibers.

Animals↗
PubMed1982

Organization of collagen fibers in rat tail tendon at the optical microscope level.

The collagen fibers of tendon have a wavy configuration which is important for the mechanical function of the tissue. An investigation into the organization of collagen fibers in rat tail tendon at the level of the light microscope has led us to propose a new model for the basic tendon unit. This unit, which is termed the fascicle, is usually triangular in cross-section and 150 to 300 microns in diameter. The fibrous entities which comprise the fascicle take the planar waveform configuration seen in the polarized transmission microscope and in longitudinal histology sections. The plane of the waveform is parallel to the long side of the fascicle and adjacent planes are arranged with the waveform in registry. Other structural features observed in the microscope can be produced by defects in this ordered arrangement. Thus slip parallel to the plane of the waveform can produce the crimp reversal observed in through-focus photomicrographs. The ridges and valleys which characterize the surface of the fascicle result from out-of-plane crimping. The surface topology is probably important in maintaining registry between neighboring fascicles.

Animals↗
PubMed1979

[Microbial emission, immission and changes in the germ count in the cooling water during operation of wet cooling towers ii. communication: measuring methods, emission values and changes in the germ count in the cooling system (author's transl)].

The second in the series "Microbial emission, immission and changes in the germ count in the cooling water of wet cooling towers" describes measuring methods and results of the measurements for determining the emission values and the changes in the germ count in the cooling system. The content of colony-forming units (KBE) in the cooling water varied widely, depending on the germ content of the surface water and the preparation of the cooling water (filtration, chemical conditioning). In summer the KBE values were as a rule higher than the values recorded in winter (factor of about 10). The introduction of cooling tower water into the surface water thus did not result in any noticeable changes in germ content, either in summer or in winter. An emission rate of 8.3 10(7) KBE/s (CSA) measured at the top of the cooling tower was the maximum emission value recorded. This resulted in a total germ content in the plume of 1.2 . 10(4) KBE/m3. In order to place this finding into perspective, it should be noted that fluctuations in the KBE values of the air of considerably more than 1000 KBE/m3 can occur because of biological release and meteorological conditions alone (see IVth communication). The KBE-P values recorded (content of particles with units which are capable of forming colonies) in the plume were of the same order as the KBE values. From this it can be concluded that the drops of cooling water which are swept away with the plume are normally only charged with individual colony-forming units. It is worth noting that the KBE values of the plume are only indirectly dependent on the KBE values of the cooling water used in the cooling tower.

Air Microbiology↗
PubMed1979

[Microbial emission, immission and changes in the germ count in the cooling water during operation of wet cooling towers III. communication: laboratory tests for the determination of the reduction kinetics of Escherichia coli in cooling tower plumes (author's transl)].

The present paper reports on laboratory tests for the determination of the reduction rate of micro-organisms. The investigations were carried out with a pure culture of E. coli, a germ type from the enterobacterial group. By a suitable variation of the thermodynamic parameters it was possible to simulate the conditions through which the cooling tower plume passes inside the chimney of the cooling tower and when it mixes with ambient air. The results allow the following changes in the germ counts in the plume of a wet cooling tower to be expected: 1. As long as the cooling tower plume contains droplets, the capacity of the carried germs to form colonies does not change materially. 2. In the case of unsaturated plumes we must distinguish between two situations: a) The tests in which the germ suspension was sprayed into unsaturated air without any admixture of secondary air, did not demonstrate any dependence of the reduction rate on the relative humidity. b) In contrast to this, the tests in which the germ-carrying droplets were evaporated by admixing a stream of unsaturated secondary air, showed that the capacity to form colonies clearly decreased with diminishing relative air humidity. Case b) is of importance for the dissemination and immission of germs from cooling towers, because here, too, the visible plume initially laden with drops is dried by the admixture of unsaturated ambient air.

Escherichia coli↗
PubMed1978

The multicomposite structure of tendon.

A revised morphological model for the crimp structure of tendon is presented. The 300-500 mu diameter tendons of the mature rat tail are comprised of from one to more than ten substructures, called fascicles, of 80-320 mu diameter. Fascicles each possess a "crimp structure" demonstrable in the polarizing microscope and neighboring fascicles within a tendon usually exhibit crimp registry. The fascicle itself is shown to be a cylindrical array of planar-zig-zag crimped 500-5000 A diameter collagen fibrils. The approximate cylindrical symmetry of the fascicle is domonstrated by SEM not equal to and polarizing optical microscopy. A method of replacing native water with other liquids of refractive index near to that of collagen is utilized to reduce or eliminate light diffusion and therby greatly improve OM observations. Small bunches of collagen fibrils removed from the tendon are shown to exhibit the simple planar zig-zag morphology described in previous literature. The planar crimping of collagen fibrils and their assemblage into cylindrically symmetric fascicles is verified by small angle X-ray diffraction.

Animals↗