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M Yaar

Publications and source records attributed to M Yaar.

70 records · Page 4Linked to original sources
PubMed1988

Normal human keratinocytes contain an interferon-like protein that may modulate their growth and differentiation.

Epidermal growth and differentiation is a complex process which depends upon a balance between positive and negative growth signals, and in normal skin the majority of the cells in the germinative basal layer do not proliferate unless stimulated. Using the indirect immunofluorescent method, it can be demonstrated that purified polyclonal epidermis in cross sections of normal skin and to the basal layer of cultured keratinocyte colonies. Furthermore, extracts of keratinocyte cultures contain interferon bioactivity. With Western blot analysis, antibodies to interferon recognize a band of approximately 40 kD both in keratinocyte lanes and in recombinant interferon lanes that give in addition a band of approximately 20 kD. Addition of interferon to rapidly growing keratinocytes inhibits their growth by as much as 90% and promotes their terminal differentiation. The growth inhibitory effect of interferon is completely reversible. These data demonstrate that interferon or a closely related protein is present in human epidermis and suggest that this protein may act as a physiologic modulator of keratinocyte growth and differentiation.

Antibodies↗
PubMed1988

Human nevocellular nevus cells are surrounded by basement membrane components. Immunohistologic studies of human nevus cells and melanocytes in vivo and in vitro.

Dermal nevus cells in the skin are surrounded by electron-dense deposits resembling a basement membrane (BM), and epidermal melanocytes rest on the epidermal BM. Using antibodies directed against various BM components, we have determined that the BM-like structure surrounding nevus cells in vivo contains type IV collagen, laminin, and BM-1 proteoglycan, analogous to BM throughout the body, but not bullous pemphigoid antigen or epidermolysis bullosa acquisita antigen that are keratinocyte-associated proteins present in the epidermal BM. Moreover, in vitro, both nevus cells and melanocytes derived from adult donors display intracellular and extracellular fibronectin, BM-1 proteoglycan, type IV collagen, and laminin. In contrast, newborn melanocytes maintained under identical culture conditions display none of these BM components, emphasizing the influence of donor age on cell behavior. The data suggest that dermal nevus cells manufacture a BM in vivo, as do certain other neural crest-derived cells. The apparent shared ability of cultured nevus cells and melanocytes to synthesize BM components, coupled with other previously noted behavioral and morphologic similarities in vitro, suggests that these cell types are very closely related; and that morphologic or histochemical differences present in vivo are the result of environmental influences rather than intrinsic differences.

Adult↗
PubMed1986

Normal human epidermis contains an interferon-like protein.

Interferons have been postulated to participate in growth regulation of normal body tissues and are known to inhibit growth of human epidermal keratinocytes in vitro. Polyclonal antibodies to recombinant human interferon-alpha, purified by passage over an affinity column (Sepharose coupled to the recombinant interferon), used in the indirect immunofluorescent method specifically stained the proliferative (basal) compartment of human epidermis in histological cross-sections of normal skin and in cultured keratinocyte colonies. Extracts prepared from healthy nonvirally infected keratinocyte cultures contained interferon activity as determined by viral plaque inhibition assay. Using the Western blotting technique column-purified antibodies and antisera to recombinant human interferon-alpha recognized a band of approximately 40 kD when reacted with both extracted keratinocyte proteins and recombinant human interferon-alpha standards, that gave in addition a band of approximately 20 kD. The above findings suggest that interferon or a closely related protein is present in the proliferative compartment of normal epidermis in the absence of viral infection and therefore may serve as a physiological modulator of epidermal growth.

Antibodies↗
PubMed1986

Characteristics of cultivated adult human nevocellular nevus cells.

Nevus cells are of biologic interest because of their uncertain relationship to epidermal melanocytes and of clinical interest because of their statistical association with melanoma. We report a technique that allows reliable cultivation of nevus cells from small acquired and congenital nevi and permits in vitro characterization of this cell type. Morphologically, cultured nevus cells were found to closely resemble epidermal melanocytes from the same or comparably aged donors, manifesting marked dendricity and specific ultrastructural features characteristic of melanocytes; but could be distinguished by the presence of occasional large binucleate or trinucleate cells and by the frequent finding of grouped melanosomes in nevus cell cytoplasm. Growth kinetics were also similar for nevus cells and epidermal melanocytes, with population doubling times of 1-2 weeks in hormone-supplemented serum-free medium, and substantial growth enhancement by fetal bovine serum. As previously noted for epidermal melanocytes, nevus cells in serum-free culture demonstrated striking substrate responsiveness, with far greater attachment rates and degree of cytoplasmic spreading on fibronectin or type I/III collagen than on laminin, type IV collagen, or uncoated plastic. These strong similarities in vitro suggest that morphologic and behavioral differences observed between epidermal melanocytes and nevus cells in the skin may result from local environmental influences rather than from intrinsic cellular differences. The availability of a satisfactory culture system for nevus cells may facilitate future investigations into their malignant potential and other biologic features.

Adult↗
PubMed1985

Substrate influences human epidermal melanocyte attachment and spreading in vitro.

Previous culture systems for melanocytes have employed serum-supplemented medium and uncoated plastic dishes, prohibiting examination of possible substrate influences on cellular morphology and function. We now report, using a sensitive serum-free system and a quantitative procedure for evaluating cellular morphology, that modification of the plating surface affects human epidermal melanocyte attachment rate and subsequent morphology in vitro. Melanocytes attach and spread more rapidly on surfaces coated with fibronectin or Type I/III collagen or on surfaces previously conditioned by human keratinocytes, dermal fibroblasts, melanocytes, or melanoma cells than do melanocytes on untreated control surfaces. Type IV collagen and laminin, although minimally beneficial for cell attachment, do support a characteristic melanocyte morphology that differs from that seen either on the other coated surfaces or on uncoated plastic controls. Addition of fetal bovine serum at the time of inoculation has no appreciable effect on attachment but markedly improves cell spreading on untreated surfaces, while addition of nerve growth factor with or without serum to this system fails to affect cell attachment or spreading. Our data establish that human epidermal melanocytes are indeed capable of responding morphologically to substrate signals. The ability of several biochemically unrelated surfaces to enhance melanocyte attachment rate and spreading suggests that melanocytes have surface receptors with a variety of specificities. This work is relevant to the development of improved culture systems for melanocytes in vitro and to understanding melanocyte behavior in vivo.

Cell Adhesion↗
PubMed1985

Effects of alpha and beta interferons on cultured human keratinocytes.

Interferons (IF) are a family of glycoproteins known for their antiviral activity and the ability to inhibit growth and alter behavior of various normal and transformed cell types, both in vivo and in vitro. Because cultured human keratinocytes (HK) produce IF in response to viral infection, we undertook studies of alpha-IF and beta-IF effects on HK. Cloned human IF were added at time of seeding and at each feeding to paired dishes of keratinocytes maintained in serum-free hormone-supplemented medium. At 7 days significant inhibition of growth was observed for both alpha-IF and beta-IF, as determined by cell counts, total protein, and appearance of stained colonies, and was sustained for at least two weeks during continuous IF exposure. The inhibition was substantially blocked by prior addition of cholera toxin to the medium, consistent with competition for a common cell surface receptor. Growth of a single human epidermal carcinoma cell line was much less affected by IF than was growth of the normal keratinocytes. IF also promoted terminal differentiation of keratinocytes as assessed by desquamation rate of cells from the colony surface and by proportion of total cells having cornified envelopes. IF effect on both growth and differentiation was completely reversible within days of its removal from medium. These findings suggest that IF may function as a physiologic regulator of epidermal growth in vivo with properties of a negative growth factor or chalone.

Cell Differentiation↗
PubMed1983

Abortion in mice induced by intravenous injections of antibodies to type IV collagen or laminin.

Purified antibodies to laminin or Type IV collagen administered intravenously to pregnant mice were found to localize in the basement membranes of all maternal tissues as well as the parietal and visceral yolk sacs and trophoblast basement membranes but not in embryonic tissues. Antibodies to Type IV collagen induced a higher incidence of abortions, retroplacental hematomas and fetal deaths. When administered intraamniotically, both antiserums were embryotoxic. The functional consequences of the attachment of antibodies to these specific basement membrane antigens appear to be hemorrhage within the parietal and visceral yolk sacs and separation of fetal from maternal tissues. Complement activation appears to play an important role in the interruptions of pregnancy, because this was not observed in strains of mice lacking C5, the fifth component of complement, in mice depleted of C3 by administration of cobra venom factor, or in mice injected with the F(ab) fragments of antibody to Type IV collagen or laminin.

Abortion, Induced↗
PubMed1982

Stimulation of retinoic acid of synthesis and turnover of basement membrane in mouse embryonal carcinoma-derived endoderm cells.

The effect of retinoic acid on the synthesis and degradation of basement membrane components by endoderm cells derived from mouse embryonal carcinoma (EC) cells was studied in a serum-free, defined medium. By immunofluorescence these cells accumulate type IV collagen, laminin, and fibronectin after growth in media containing epidermal growth factor (EGF), fibroblast growth factor (FGF), insulin, transferrin, and Pedersen fetuin. Collagen accounted for 2 to 4% of the newly synthesized proteins, of which 90% were found in the culture media. This collagen was identified as Pro-type IV be gel electrophoresis and enzymatic susceptibility. The EC cells preferentially attached to type IV collagen in vitro and such attachment was mediated by laminin. Treatment of EC cells with retinoic acid caused an increased accumulation of collagen (10 to 15% of secreted proteins) and also stimulated the elaboration of latent protease which degraded laminin and type IV collagen. The laminin-degrading activity was plasminogen dependent. The type IV collagen-degrading activity was a metal protease which could be activated by trypsin or plasmin. It is likely that at least part of the laminin degrading activity is plasmin (mediated through plasminogen activator), since highly purified plasmin is shown to degrade native laminin.

Animals↗
PubMed1982

Laminin and bullous pemphigoid antigen are distinct basement membrane proteins synthesized by epidermal cells.

We sought to determine if laminin, a high molecular weight glycoprotein of basement membrane, is synthesized by epidermal cells and whether it is distinct from bullous pemphigoid (BP) antigen, another high molecular weight-protein of basement membrane. By indirect immunofluorescence we detected laminin in cultures of Pam cells ( a mouse keratinocyte cell line) and normal human epidermal cells. To directly demonstrate its biosynthesis, we labeled the cells with radioactive amino acids and then extracted the cell layers with nonionic detergent. Using immunoprecipitation followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and fluorography to identify radiolabeled laminin, we could precipitate the 2 chains of laminin from cell culture medium and extracts of the cell layers. BP antigen, immunoprecipitated from the cells, did not comigrate with laminin on SDS-PAGE. In addition, BP antigen could be immunoprecipitated from the cell extracts depleted of laminin, and conversely, laminin could be immunoprecipitated from cell extracts depleted of BP antigen. We conclude that laminin is synthesized by epidermal cells (specifically, keratinocytes) and is distinct from BP antigen.

Animals↗
PubMed1982

Long-lasting cerebral functional changes following moderate dose x-radiation treatment to the scalp in childhood: an electroencephalographic power spectral study.

EEG tracings were compared in 44 young adults who received scalp x-radiation treatment for tinea capitis during childhood and 59 non-irradiated control subjects. The irradiated subjects were exposed, over 20 years previously, to a mean dose of 130 rads to the brain. Visual analysis of the EEG revealed an insignificant excess of abnormalities among the irradiated subjects compared to the controls. Power spectral density function analysis showed increased power values among the irradiated subjects, particularly in the beta wave frequencies. This finding provides further evidence for suspecting that x-irradiation during brain maturation may cause long-lasting damage to the brain tissue.

Adolescent↗
PubMed1982

Pemphigus antibodies identify a cell surface glycoprotein synthesized by human and mouse keratinocytes.

Pemphigus is an antibody-mediated autoimmune skin disease in which loss of cell-to-cell contacts in the epidermis results in blister formation. Patients with pemphigus develop antibodies that bind to the keratinocyte cell surface, the site of primary pathology. The purpose of this study was to characterize the antigen(s) to which pemphigus antibodies bind. Because we could detect pemphigus antigen by indirect immunofluorescence on the surface of multiply-passaged cells in cultures of both a spontaneously transformed mouse keratinocyte cell line (Pam) and normal human epidermal cells, we used these cells as a source of antigen. In order to demonstrate biosynthesis of antigen and to characterize the antigen(s), we radiolabeled cell cultures with [(14)C]glucosamine or d-[2-(3)H]mannose and used different pemphigus sera to immunoprecipitate antigen from nonionic detergent extracts of these labeled cells. Specifically precipitated radiolabeled molecules were identified using sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and fluorography. Sera from five of seven pemphigus patients specifically precipitated (from extracts of both Pam cells and human epidermal cells) a molecule that, when reduced, was approximately 130 kD, whereas seven normal human sera and two pemphigoid sera did not precipitate this molecule. The findings that (a) these precipitated molecules comigrated on SDS-PAGE and that (b) the 130-kD molecule could no longer be precipitated from cell extracts that had been previously reacted with a pemphigus serum, indicate that reactive pemphigus sera bind the same molecule. The molecule was not detected in the culture medium of these cells. This finding, along with the cell surface immunofluorescence pattern, suggests that the antigen is bound to the cell surface. Cultured mouse and human fibroblasts do not synthesize the antigen. The antigen contains protein because it was degraded by V8 protease and chymotrypsin, and it could also be labeled with [(14)C]amino acids. It is probably not a sulfated proteoglycan because it did not label with (35)SO(4). Taken together, these data indicate that some, but not all, pemphigus sera bind a specific cell surface glycoprotein that is synthesized by keratinocytes.

Animals↗
PubMed1982

The Goodpasture-like syndrome in mice induced by intravenous injections of anti-type IV collagen and anti-laminin antibody.

Laminin and Type IV collagen are both components of basement membrane. Antibodies to these two proteins, when injected into mice, were found to accumulate in all basement membranes examined, but at highest levels in kidney, liver, and spleen. An acute respiratory distress syndrome was noted shortly after injection. A transient segmental proliferative glomerulonephritis was observed both in the heterologous (early) and autologous (late) phase. The glomerular basement membrane of mice injected with anti-Type IV collagen antibodies was observed to be thickened and to contain dense deposits in the lamina rara externa and lamina rara interna.

Animals↗
PubMed1981

Retinoic acid delays the terminal differentiation of keratinocytes in suspension culture.

The effect of retinoic acid (RA) on the terminal differentiation of guinea pig keratinocytes maintained in suspension culture was studied. Keratinocytes obtained from trypsinized guinea pig skin were suspended in medium containing 20% calf serum and 1.2% methyl cellulose. RA, which was added at the beginning of culture, delayed differentiation as judged by a decrease in the percent of cells that developed disulfide cross-linked keratin (sodium dodecyl sulfate insoluble cells) and cornified envelopes (sodium dodecyl sulfate and 2-mercaptoethanol insoluble cells). RA inhibited differentiation maximally at 5 microgram/ml on day 3 of 5 day culture; concentrations as low as .005 microgram/ml were also inhibitory. Because the disulfide cross-linking of keratin and the formation of cornified envelopes are thought to occur when the cell membrane becomes permeable, we determined whether RA inhibited these processes by stabilizing the cell membrane. Two agents (ionophore X537A and Triton X-100) which permeate cell membranes rapidly reversed the inhibitory effect of RA on cornified envelope formation. In addition, when cultured with RA, the percent of cells which became permeable to trypan blue was reduced, also suggesting that RA acts on the cell membrane. These studies show that RA can inhibit keratinocyte differentiation by stabilizing the cell membrane thereby delaying transition from a living epidermal cell to a dead cornified cell.

Animals↗
PubMed1981

Immunopathological and clinical studies in herpes gestationis.

Herpes gestationis is a recurring pruritic, vesiculobullous disease of pregnancy and puerperium. Recently, Lawley et al (1979) reported a high frequency (38 per cent) of fetal morbidity and mortality in 40 cases of immunologically proven herpes gestationis. This study was undertaken to determine whether the antibody to skin basement membrane (found in most patients with herpes gestationis) is able to bind to the placenta basement membranes and thereby to threaten the pregnancy. We were unable to detect this antibody in the placental basement membranes of a patient with herpes gestationis, nor could we demonstrate that the anti-basement membrane antibody, found in the sera of herpes gestationis patients, binds to homologous or autologous placentas and fetal membranes. The importance of an accurate diagnosis and appropriate treatment of this condition is discussed.

Basement Membrane↗
PubMed1980

Distribution and immunoelectron microscopic localization of laminin, a noncollagenous basement membrane glycoprotein.

Laminin is a noncollagenour glycoprotein isolated from a transplantable mouse tumor producting basement membrane (BM). Purified antibodies to laminin do not cross-react with other known BM antigens including type IV collagen, fibronectin, bullous pemphigoid antigen, and a BM proteoglycan. Using immunofluorescence, laminin is localized in the BM zones of those human, chick, guinea pig, bovine, monkey, rat, and mouse tissues examined. Epithelial and endothelial cells in culture synthesize laminin while mesenchymal cells do not. By immunoelectron microscopy, laminin was localized to the lamina lucida of human epidermal BM and of mouse esophagus epithelial BM. The wide distribution of laminin among diverse tissues and species, and in early stages of embryonic development suggests that laminin is an ubiquitous component of basement membranes.

Animals↗