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Biomedical subjects

M Litt

Publications and source records attributed to M Litt.

At least 163 records · Page 9Linked to original sources
PubMed1985

A study of mucus glycoproteins in secretory otitis media.

Rheologically active mucus glycoproteins (mucins) were isolated from the middle ear effusions of 282 patients (344 ears) with secretory otitis media. Middle ear mucins from those patients with no other associated pathology were compared biochemically and biophysically with mucins from patients where a specific associated pathology was present. The most striking biochemical variation was total carbohydrate content, which was lowest for mucins derived from purulent secretions in general (30.9%) and mucoid secretions from patients with cleft palates (32%). Furthermore, the carbohydrate content was correlated with the rheologic activity of reconstituted mucins, both in dilute solution and in the gel state. All mucins had high intrinsic viscosities, sensitive to ionic strength and the mucolytic N-acetylcysteine. Transport studies indicated that certain middle ear effusions, particularly those from patients with cleft palates, may not be cleared from the middle ear because of insufficient viscoelasticity.

Adolescent↗
PubMed1985

A highly polymorphic locus in human DNA revealed by cosmid-derived probes.

Human gene mapping would be greatly facilitated if marker loci with sufficient heterozygosity were generally available. As a source of such markers, we have used cosmids from a human genomic library. We have developed a rapid method for screening random cosmids to identify those that are homologous to genomic regions especially rich in restriction fragment length polymorphisms. This method allows whole cosmids to be used as probes against Southern transfers of genomic DNA; regions of cosmid probes homologous to repeated genomic sequences are rendered unable to hybridize with Southern transfers by prehybridization of the probes with a vast excess of nonradioactive genomic DNA. From one cosmid identified by this procedure, we have isolated three single-copy probes that collectively identify seven polymorphic loci. Of 56 unrelated individuals, 52 were heterozygous at one or more of these marker loci.

Chromosome Mapping↗
PubMed1985

Experimental artifacts in the study of mucociliary transport.

Mucociliary transport was studied on frog palate epithelium preparations. Three preparations were used: the detached palate preparation (prepared by detaching the upper part of the head from the frog), the live frog preparation (prepared by exposing the palate of a sedated live frog), and the thin preparation (prepared by excising a 1-mm thin section). Because the transport behavior in each of the 3 preparations is different, extirpation or sedation or excision, or all 3, introduce artifacts into the system.

Animals↗
PubMed1985

Mucociliary transport of human ear secretions in otitis media with effusion.

Rheologically active mucus glycoproteins (mucins) were isolated from the middle ear effusions of 282 patients (344 ears) presenting with secretory otitis media (SOM). The mucins were pooled according to the pathologic condition associated with the SOM. Pools were reconstituted to the same conditions and tested for ciliary transport rates with the use of the frog palate transport model. Mucin obtained from cleft palate patients showed significant differences in transport behavior in comparison with mucins from other groups of patients with SOM.

Adolescent↗
PubMed1984

Comparative studies of mucus and mucin physicochemistry.

The transport of mucus on a ciliated epithelium, and the penetration of sperm through cervical mucus, have been shown to be functions of the rheological, principally viscoelastic, properties of the secretion. These physicochemical properties, in turn, are largely determined by the composition and concentration of mucin glycoproteins, which are the principal macromolecular components of the secretion. These functions and properties of various types of mucous secretions are discussed, emphasizing both similarities and differences. Background and data are presented supporting these concepts, based on studies of human cervical and middle ear mucus, as well as bovine cervical and canine tracheal mucus. A major determinant of differences in function between mucus samples appears to be the carbohydrate composition of the mucin, after corrections are made for environmental factors such as pH, ionic strength and mucin concentration Mucin behaviour also depends on specific solutes in the secretion, such as Ca2+. Although significant differences in mucus properties and function exist, it is hypothesized that these developed as variations of the major function common to all mucous secretions, which is to maintain and control the water balance of epithelial mucosa.

Animals↗
PubMed1984

Effect of Ca++ on the structure and rheology of canine tracheal mucin.

Mucin glycoproteins are known to be the principal determinants of epithelial mucus rheology and hence of mucociliary transport rates. We are studying the structure of such glycoproteins using a model mucin purified from canine tracheal pouch secretions. Of particular interest is the effect on mucin structure of increased Ca++ such as occurs in certain disease states. Quasielastic laser light scattering was used to study the effect of Ca++ on the hydrodynamic radius of the mucin molecules. Scattering data from 0.3mg/ml mucin solutions in physiological phosphate buffer containing 0, 5 X 10(-5)M, and 5 X 10(-4)M Ca++ were analyzed to obtain an average translational diffusion coefficient and the distribution of molecular radii for the dispersion. The effect of Ca++ was to decrease the average Stokes radius. The light scattering results are supported by rheologic measures of mucin gel viscoelasticity.

Animals↗
PubMed1984

Dynamics of an oscillating viscoelastic sphere: a model of the vitreous humor of the eye.

The vitreous humor of the eye is modelled as a homogeneous viscoelastic sphere. The analysis provides a relation for the displacement amplitude and phase following oscillatory and step excitations, as functions of the storage and loss moduli of the vitreous gel, and allows calculation of the resolution requirements for a non-invasive optically-based diagnostic method for the viscoelastic properties of the vitreous.

Elasticity↗
PubMed1984

Studies of rheologically active biological macromolecules by quasielastic light scattering.

Variables which describe the structure and rheological behavior of macromolecules in both dilute solutions and gels may be determined using methods of quasielastic laser light scattering (QELS). Such parameters include diffusion coefficients, molecular size such as hydrodynamic radius, and viscoelastic moduli. If the polymer is polydisperse, the distribution of radii may be estimated. Application of the methods is illustrated with data on the size distribution of a tracheal mucin glycoprotein solution as an example of a polydisperse polymer solution of biorheological interest. A scheme for measuring shear moduli of polymer gels using dynamic laser light scattering is illustrated with data on reconstituted fibrin clots.

Animals↗
PubMed1983

Human tracheal mucin: a preliminary study of physicochemical properties and mucociliary transport.

Human tracheal secretions were collected from patients with chronic tracheostomies in the intensive care unit and through an endotracheal tube from pediatric surgical patients under general anesthesia. These secretions were dialyzed, fractionated on an agarose column, and lyophilized to recover the tracheal mucin fraction. Analysis of pooled mucin samples included determination of amino acids, carbohydrates, and sulfates. Intrinsic viscosity, microrheometry, and mucociliary transport studies were also performed. Structural and functional differences between several pools of specimens are cited with an emphasis on possible clinical correlations.

Amino Acids↗
PubMed1983

Localization of the restriction fragment length polymorphism D14S1 (pAW-101) to chromosome 14q32.1 leads to 32.2 by in situ hybridization.

The restriction fragment length polymorphism D14S1 is delineated by the cloned, single-copy DNA fragment pAW-101. This cloned fragment can therefore serve as a useful marker for gene linkage studies, and the exact location on the gene map is of great interest. pAW-101 was 3H-labeled and hybridized in situ to normal, prometaphase chromosome preparations. Analysis of the grain distribution shows this fragment to be localized to the long arm of chromosome 14 at band q32. Using lymphoid cell lines with 8;14 reciprocal translocations (q24.1;q32.3) from patients with Burkitt lymphoma, we found that the DNA fragment hybridizes to the rearranged chromosome 14 proximal to the breakpoint. These results localize D14S1 to the region 14q32.1 leads to 32.2 This is consistent with localization of this fragment utilizing somatic cell hybrids and family studies.

Burkitt Lymphoma↗
PubMed1980

Composition and functioin of human cervical mucus.

Human cervical mucus was collected from seven donors during the follicular, ovulatory and luteal phases of the ovulatory menstrual cycle. Individual mucus samples were solubilized and fractionated on Sepharose columns into excluded mucins and low-molecular-weight proteins. Mucin fractions were highly purified, as evidenced by the presence of a single N-terminal amino acid residue, threonine, and by the absence of contaminating plasma proteins. Amino acid compositions of mucins isolated during different menstrual phases of a single donor or from different donors were similar. Mucin carbohydrate compositions were also similar, except for the sialic acid-to-fucose ratio, which varied significantly between donors but not within the menstrual cycle of a single donor. An analysis of variance was applied to evaluate the contribution of mucin composition to viscoelasticity, as quantitated by microrheometry. Viscoelasticity was dependent on the donor, on the percent nondialyzable solids and on the mucin content, b ut not on the phase of the menstrual cycle during which the sample was collected. These findings suggest that mucus function (viscoelasticity) is reflected in carbohydrate composition and/or structure and that this relationship is unique for each donor. Furthermore, the absence of menstrual phase-dependent differences in mucins suggests that mucin concentration and not composition changes in response to alterations in the hormonal milieu.

Adult↗
PubMed1980

Control of specific transfer RNA concentrations in amino acid-deprived Friend leukemia cells operates at the level of RNA degradation.

In eukaryotes, the concentrations of specific tRNAs are closely correlated with the demands for their cognate amino acids in protein synthesis. To account for this phenomenon, we have proposed that the extent of aminoacylation of a given tRNA species in vivo controls the relative rate of synthesis or degradation of that species. Previously, we reported the Friend leukemia cells respond to deprivation of histidine, leucine, or tryptophan by specifically increasing the relative concentration of tRNAs cognate to the deprived amino acid (Weiser, K., and Litt, M. (1979) Eur. J. Biochem. 93, 295-300). In this paper, we show that this is also true for phenylalanine and we report studies of the relative rates of synthesis and degradation of tRNAPhe in phenylalanine-deprived and control cells. We find that deprivation of phenylalanine has no effect on the relative rate of synthesis of tRNAPhe, but does induce a decline in the relative rate of degradation of tRNAPhe which accounts quantitatively for the increase in its relative steady state concentration as measured by in vitro aminoacylation. We conclude that, in Friend leukemia cells, deacylated tRNA species are more stable than charged tRNA species.

Amino Acids↗
PubMed1980

The effect of mucolytic agents on the rheologic and transport properties of canine tracheal mucus.

The effect of several sulfhydryl and other agents on the rheologic and mucociliary transport properties of a model secretion, reconstituted canine tracheal mucus, was investigated. The mucus was obtained via the canine tracheal pouch. Rheologic properties were determined by mirorheometry, and the ciliary transport rate was determined using the frog palate technique. It was found that N-acetyl cysteine decreased the elastic modulus, leading to improved mucociliary transport at concentrations such that the mucin did not precipitate. S-carboxymethyl cysteine had no effect on either mucus properties or mucociliary transport rate, and its reported effectiveness in vivo must be due to some mechanism other than solubilization of mucin. Similar results were found with other blocked sulfhydryl compounds. Urea and potassium iodide to decrease mucus elasticity, but are harmful to cilia at the concentrations needed.

Acetylcysteine↗