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Biomedical subjects

R M Lavker

Publications and source records attributed to R M Lavker.

105 records · Page 6Linked to original sources
PubMed1980

Patterns of mast cell alterations and in vivo mediator release in human allergic skin reactions.

Patterns of in vivo histamine release in skin sites challenged with ragweed antigen were compared in five human subjects sensitive to this antigen and four nonallergic individuals, using a newly developed skin-chamber technique. These findings were compared with inflammatory cell responses in the reaction sites and patterns of ultramicroscopic mast cell alterations in biopsy specimens of skin tests in the same subjects. Definite mast cell alterations occurred within 15 sec and appeared maximal within 5 to 10 min after antigen injection. Histamine levels in appended chambers increased after a lag of 10 to 30 min and were elevated for at least 60 min after antigen challenge. Eosinophils accumulated only in antigen-induced reaction sites. However, there was no precise quantitative correlation among the degree of change in these three measurements. These appear to be promising approaches to further in vivo studies of human allergic reactions.

Antigens↗
PubMed1980

Changes in skin surface patterns with age.

Cyanoacrylate skin surface biopsies from protected and exposed regions were obtained from two age cohorts (20 to 25 vs 68 to 75) and skin surface patterns were studied by light microscopy. The patterns were markedly altered in exposed areas of the older subjects, whereas protected skin showed only slightly altered patterns with aging.

Adult↗
PubMed1979

A new method for scanning electron microscopic visualization of dermal elastic fibres.

Autoclaving sections of dermis for 8 h followed by fixation, dehydration and xylol-air drying yields a pure preparation of elastic fibres for scanning electron microscopy which retains the native architecture of this component. Elastic fibres were intertwined in a complex fashion with numerous branches. Fibres were predominantly cylindrical in the upper dermis and became larger and more elliptical in the deeper dermis. This method produces a means to study of organization of elastic fibres in a variety of disorders in which dermal changes are prominent.

Adult↗
PubMed1975

Lipid synthesis in chick epidermis.

Lipid synthesis in newborn chick epidermis was studied by electron microscopic autoradiography after injection of tritiated palmitate. The labeled lipid product in the tissue was identified as mostly triglyceride. At the earliest time after injection (6 hr), the radioactive precursor was taken up by all viable cells of the epidermis. Grain density was heaviest over basal cells, moderate over spinous cells, and slight over granular cells; thus lipid incorporation is highest in the basal and spinous regions of the chick epidermis. As time after injection progressed, the increasing amounts of grains over the granular and horny cells and decreasing amounts over the basal and spinous cells reflected the continuous upward displacement of cells from one layer into the next. From the distribution of silver grains within the epidermal cells, it has been concluded that, with the passage of time, triglycerides synthesized by the epidermal cells were mainly located in lipid droplets. The numerous grains associated with the elements of the endoplasmic reticulum indicated that this organelle is involved in aggregating triglyceride molecules into lipid droplets. The fact that grains were seen within the horny cells indicated that part of the horny cell consists of lipid probably derived from the lipid droplets retained by the cells during keratinization.

Animals↗
PubMed1970

Formation of horny cells: the fate of cell organelles and differentiation products in ruminal epithelium.

Epithelial cells changing from the granular stage of differentiation to the horny stage are more numerous, and reveal sequential events of transformation in finer detail in the rumen epithelium than in other keratinizing epithelia thus far studied in the electron microscope. Studies of such cells indicate that transformation is initiated by the release of hydrolytic enzymes, as evidenced by the appearance of lysosomes. As lysosomes increase in number, the nucleus, ribosomes, mitochondria, Golgi apparatus, and mucous granules are gradually degraded. Furthermore, marked changes occur in permeability of the plasma membrane as voluminous amounts of the lysed cell components pass through and accumulate in the intercellular space in the form of an amorphous mass. Filaments, keratohyalin granules, and the content of the ER (ER-protein) are not lysed, revealing the action of released enzymes to be specific. During transformation, filaments become displaced toward the cell periphery and keratohyalin granules disperse and mix with the ER-protein in the cell center. Subsequently, the keratohyalin-ER-protein complex infiltrates the filament network whereby a fibrous-amorphous cell content is formed. Loss of fluids through the plasma membrane leads to reduction of cell volume and consolidation of the remaining cell content. The deep interdigitations formed between the cells ultimately interlock the outer part of the epithelium into a cohesive and protective stratum corneum.

Animals↗
PubMedDate not supplied

An ultrastructural study of the effects of topical tretinoin on microcomedones.

It has been hypothesized that topical tretinoin prevents inflammatory acne lesions by loosening follicular impactions (microcomedones) and clearing the follicular canal of retained keratin. To lend support to this hypothesis, 15 volunteers applied 0.1% tretinoin cream once daily for 12 weeks to one side of the face and an emollient cream to the other side. During the 12-week treatment period, samples of microcomedones were obtained using the follicular biopsy technique. By 6 weeks, the number of microcomedones was reduced approximately 50% from baseline on the side treated with tretinoin and approximately 80% at the end of the study. Only a minimal reduction in the number of microcomedones was seen on the emollient side, even after 12 weeks of application. Morphologic examination showed a progressive loss of the cohesiveness of the microcomedones and ultrastructural alterations in the epithelial cells treated with tretinoin. The microcomedones changed from well-developed keratinous plugs containing many bacteria to a few wispy layers of keratin containing few bacteria. This study confirms the microcomedolytic activity of tretinoin and provides evidence that this activity is associated with changes in the differentiation of the follicular epithelial cells.

Acne Vulgaris↗