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Biomedical subjects

D Mischke

Publications and source records attributed to D Mischke.

48 records · Page 3Linked to original sources
PubMed1987

Isolation and characterization of the gene for myosin light chain two of Drosophila melanogaster.

A recombinant lambda-phage DNA clone containing Drosophila melanogaster sequences encoding the gene for myosin light chain (MLC) two has been isolated from a library of randomly sheared DNA. The Drosophila MLC2 gene is located in region 99E1-3 on the right arm of chromosome 3, several bands removed from the site reported for the other myosin light chain gene at 98B. The MLC2 sequence at 99E1-3 appears to encode all of the isoforms of Drosophila MLC2. The polypeptide encoded at 99E was identified as MLC2 by the following criteria: the in vitro translation product is identical in size to MLC2 isolated from Drosophila muscle, and on two-dimensional gels the in vitro translation product can be separated into two or more peptides that co-migrate with isoforms of larval and thoracic MLC2. RNA encoding the polypeptide was detected in embryos only after the onset of muscle differentiation and was also abundant in adult thoracic muscle. The nucleotide sequence of cDNA generated from late embryonic RNA would be translated to yield a protein sequence with multiple regions of homology to vertebrate MLC2. (There are shorter regions of homology to vertebrate MLC1). Like a number of vertebrate muscle proteins, Drosophila MLC2 has an acetylated amino-terminus.

Acetylation↗
PubMed1987

Polymorphic keratins in human epidermis.

Human epidermal keratins from many different individuals were identified and compared by both high-resolution 1- and 2-dimensional gel electrophoresis and immunoblotting. While the polypeptide patterns obtained for keratin-enriched cytoskeletal preparations could be considered typical of normal interfollicular epidermis, they also disclosed variations, among the individuals, concerning some of the constituent protein subunits. Three sets of interindividually varying keratins could be distinguished owing to their distinct, though small, differences in electrophoretic mobility on sodium dodecyl sulfate-polyacrylamide gels and their similar or identical charge characteristics upon nonequilibrium pH gradient electrophoresis: the basic keratins 1a and 1b as well as 5a and 5b and the acidic keratins 10a and 10b. Of each set either a doublet, showing a marked 1:1 ratio of polypeptides, or the one or the other variant protein was detected together with keratin 14, which did not display any variation in a series of 148 individual tissue samples tested. Thus, the keratin composition of human epidermis could be summarized in the formula: (1a v 1b) + (5a v 5b) + (10a v 10b) + 14. The systematic appearance of the variants suggested that each protein within a set is the product of an independent allele. In support of this hypothesis we have found that the same variant is expressed in other epithelia of a given individual. Moreover, the frequency of any of the keratins in our sampling concurred with the frequency predicted by the Hardy-Weinberg relation for the distribution of alleles in a population, as did the frequency distribution of particular keratin patterns.

Alleles↗
PubMed1987

[Keratin expression in normal and malignant transformed squamous epithelium of the digestive mucosa of the head].

Keratins are alpha-type fibrous polypeptides which basically compose 10 nm thick or intermediate-sized filaments (IF) in almost all epithelial cells and tissues. Their patterns of expression in normal and malignant upper digestive tract squamous epithelium were monitored by high resolution gel electrophoresis, immunoblotting, and immunohistochemical techniques. Uninvolved epithelia, in all instances, were found to express keratins 4, 5, 6 and 13, 14 the members of the high molecular weight basic (type II or Type B) and of the low molecular weight acidic (type I or type A) subfraction, respectively. Cancers of squamous epithelial cell origin retain keratin synthesis. However, their overall patterns of keratin expression appeared aberrant when compared with those of normal epithelia. In particular, these differences result from highly proliferative tumour cells unable in most cases to synthesize keratins 4/13, a type II/type I keratin pair which specifically indicates in squamous primarily non-keratinizing epithelia completely, i.e. terminally differentiated (suprabasal or spinous) cells. The patchwise expression of acidic keratin 13 in related primaries confirms their heterogeneous phenotype, and may be explained, in part, by cancer cells no longer resistant to terminal differentiation as a result perhaps of an altered micro-environment and/or in response to various effects mediated by vitamin A. We discuss some problems pertinent to the biochemical analysis of keratin polypeptides in normal and involved epithelial tissues, and relate to the controversial question whether specific keratin members may actually candidate for markers of malignancy.

Carcinoma, Squamous Cell↗
PubMed1986

Variation and frequency of cytokeratin polypeptide patterns in human squamous non-keratinizing epithelium.

The squamous non-keratinizing epithelium of the human upper digestive tract was analyzed for keratin-like cytoskeletal proteins (cytokeratins) by both high resolution one- and two-dimensional gel electrophoresis. The Triton/high salt-insoluble portion of pure epithelial homogenates contains a number of SDS- and urea-extractable polypeptides, whose two-dimensional gel pattern (NEpHG/SDS) typically represents a defined subset of human cytokeratins. The cytoskeletal preparations of epithelial tissue samples obtained from different individuals were found to be uniform with respect to their content of cytokeratin polypeptides 55.0 kD/basic, 52.0 kD/acidic, and 49.0 kD/acidic. However, we have observed that four basic members of apparent molecular weight 60.0, 59.0, 56.5, and 56.0 kD occur at an inconstant rate. Consequently, the cytokeratin polypeptide patterns appeared highly variable as a result of the presence of constant plus compositionally different subsets of inconstant members. From the analysis of cytoskeletal portions of more than 300 individual tissue samples we demonstrate eight different keratin-like polypeptide patterns including their frequencies and propose the existence of no more than nine. These, most probably, encompass all the possible inter-individual variations to which the cytokeratins of this type of epithelium will combine for forming intermediate-sized filaments in vivo. We furthermore hypothesize that the observed variation of cytokeratin patterns may reflect a polymorphism of genes coding for the variable keratin-like polypeptide members.

Digestive System↗
PubMedDate not supplied

Lateral cervical (branchial) cyst epithelia express upper digestive tract-type cytokeratins. Polyclonal antibody studies.

The epithelial lining of lateral cervical cysts (LCCs) was analyzed for keratin polypeptide composition by means of high resolution gel electrophoresis and immunoblotting using polyclonal rabbit antikeratin antisera of defined specificity. The keratin phenotype expressed in branchial mass epithelia was found to be homologous to the profiles obtained for the squamous epithelium of corresponding palatine tonsils, but was clearly different from related polypeptide complements of both epidermis and simple (columnar) epithelium. The presence of particular keratin members (pairs 5/14 and 4/13) strongly indicates that branchial mass inner lining derives from keratinocytes that are programmed to form a stratified squamous epithelium and reveal, at least biochemically, an upper digestive tract or esophageal type of differentiation. On the basis of these data and the recent finding that a neck lymph node is involved as a target tissue in LCC formation, hypotheses concerning branchial mass histogenesis in general appear to be highly unsettled. We propose an alternative model that may explain the conflicting clinical, anatomic, and morphologic findings associated with LCC disease.

Branchioma↗
PubMedDate not supplied

The lateral cyst of the neck: congenital or acquired?

An outer rim of lymphoid tissue and an inner epithelial lining of squamous composition form the lateral (branchial) cyst of the neck. According to the particular pattern of keratin polypeptides, branchial mass inner lining is shown to be homologous to upper digestive tract (UDT) squamous epithelia. Furthermore, immunostaining of tissue sections with a polyclonal antibody highly specific for the major acidic UDT keratin 13 demonstrates that the epithelium in question is composed of both basal and normally differentiated, i.e. non-keratinizing suprabasal (spinous) cells. 'Import' into a neck lymph node, and rapid growth of oropharyngeal crypt epithelial cells is suggested to initiate a sequence of events leading to an acquired lymphoepithelial mass that may actually present as a 'branchial cyst'.

Branchioma↗