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D L Hasty

Publications and source records attributed to D L Hasty.

62 records · Page 4Linked to original sources
PubMed1980

Specific cleavage of human type III collagen by human polymorphonuclear leukocyte elastase.

Purified polymorphonuclear leukocyte elastase degraded native human liver type III collagen at 27 degrees C by making a cleavage through the triple helix. The enzyme had no effect on human type I collagen. The reaction was inhibited by phenylmethanesulfonyl fluoride (PhCH2SO2F) but not by EDTA. The collagen reaction products were identical with those generated by human rheumatoid synovial collagenase when analyzed by polyacrylamide gel electrophoresis and gel filtration. NH2-trminal sequence analysis indicated that the enzyme cleaved at an isoleucyl-threonyl bond located 4 residues on the carboxyl side of the established cleavage site for animal collagenases. Therefore, it is likely that in pathologic states, type III collagen can be selectively depleted from the matrix by this enzyme.

Amino Acid Sequence↗
PubMed1978

Freeze-fracture studies of the developing cell surface. II. Particle-free membrane blisters on glutaraldehyde-fixed corneal fibroblasts are artefacts.

We describe, in sections and by freeze-fracture, four classes of intramembrane particle (IMP)-free membrane blebs or "blisters" associated with glutaraldehyde-fixed embryonic corneal fibroblasts: (a) Single blisters attached to the cell membrane; (b) free (detached) vesicles; (c) myelin figures; (d) multivesicular protrusions which resemble the "mounds" described by others on nerve growth cones. The IMP-free, membrane-bounded blisters contain no ground cytoplasm or organelles, in contrast to blebs on trypsin-isolated fibroblasts, which we show here do contain cytoplasm and IMP-rich membranes. That the IMP-free membrane blisters in embryonic corneas are artefacts of fixation is demonstrated by (a) their absence in replicas of fibroblasts frozen and fractured without prior aldehyde fixation and (b) their absence in sections of fibroblasts fixed in a combination of glutaraldehyde and osmium tetroxide. We suggest that the addition of osmium prevents postfixation movement of membrane lipids, especially the negatively charged "fluid" lipids which others have shown are capable of considerable mobility after aldehyde fixation alone. Recent literature has implicated membrane blistering in secretory processes and in growth of nerves, but before the functional significance of such IMP-free blisters is assessed, membrane mobility of the type shown here should be taken into consideration.

Cell Membrane↗
PubMed1978

Development of glucose-mediated insulin release response in organ cultured rat pancreas.

In the Sprague-Dawley rat, glucose concentration dependent insulin release first appears 2 days after birth. If pancreatic explants from 19-, 20- or 21-day fetal rats are organ cultured to a period corresponding to the 4th postnatal day, 120 min stimulus with glucose (100 or 300 mg/dl) fails to produce glucose-dependent insulin release. When explants from 20-day fetal pancreas are cultured, glucose-mediated insulin release develops after 12 h to 2 days of culture, and persists for up to 2 days. Explants from 3 day postnatal pancreas retain glucose-dependent insulin release for at least 2 days culture. High tissue insulin levels and continued release of immunoreactive insulin into culture medium are maintained throughout the culture period studied. Our data show that glucose-mediated insulin release can develop in organ culture, and suggest that this development, after the 19th fetal day, does not require extrapancreatic neural or endocrine factors.

Animals↗
PubMed1977

Freeze-fracture studies of the developing cell surface. I. The plasmalemma of the corneal fibroblast.

The freeze-fracture technique was used to study changes in the corneal fibroblast cell membrane during morphogenesis in chick embryos. Fibroblasts migrate into the acellular primary corneal stroma on day 6 of embryogenesis, moving between the orthogonal layers of collagen fibrils which serve as their substratum. Morphometric analysis of the intramembrane particles (IMP) reveals their concentration on the P face to decrease from 756 to 534/mum2 from day 6 to day 14. After day 14, fibroblast migration and cell division cease and the stroma condenses due to dehydration, so that by day 18 all of the layers of fibroblasts are extremely flattened and the cornea has taken on its mature, transparent form. The cell membranes of the terminally differentiated, highly compacted fibroblasts are rich in IMP (1,300/MUM2, P face). In seeking to relate the particle increase to cell differentiation, we analyzed synthetic events taking place at this time, but no correlation, we analyzed synthetic events taking place at this time, but no correlation with 25SO4 or proline-3H incorporation was found. The event which seems best correlated with the doubling of P face particles between days 15 and 18 is the dehydration and condensation of the stroma, an event which is associated with cessation of both cell division and migration. Thyroxine stimulates premature condensation of the stroma, whereas thiouracil delays condensation, but neither of these treatments affects IMP concentration. Interestingly, IMP concentration on the filopodia of migrating fibroblasts is similar to that on the cell bodies, suggesting that the new membrane has the same composition as the pre-existing membrane. Observations are also presented on tight and gap junctions between fibroblasts and on the relation of extracellular matrix to the outer etched surface of the fibroblast plasmalemma.

Animals↗
PubMedDate not supplied

Attachment of Streptococcus pyogenes to mammalian cells.

Accumulated evidence indicates that lipoteichoic acid (LTA) is centrally involved in the attachment of group A streptococci to epithelial cells of the host. The binding of LTA to a variety of host cells is mediated by the glycolipid end of the LTA molecule, which can form ionic complexes with streptococcal surface proteins, permitting the reorientation of the LTA to expose some of its lipid ends toward the surface of the organism. The ability of albumin to block the adherence of streptococci to epithelial cells and to bind to LTA-M protein but not deacylated LTA-M protein complexes supports the idea that the lipid ends remain free to interact with cell membrane receptors. The cell membrane receptors appear to consist of a lipid-binding region(s) on fibronectin molecules on the surfaces of oropharyngeal epithelial cells. Although streptococci exhibit LTA-sensitive binding to phagocytic cells in a serum-free system, in the presence of serum, they do not; rather, complement bound to the streptococcal cell surface is required for recognition by phagocytes. The binding of fibrinogen to the M protein on the surface of M-rich streptococci specifically blocks the recognition of the organisms by opsonic complement components. The attachment of M-rich streptococci to phagocytic cells requires the development of antibodies directed specifically toward regions of M protein not blocked by fibrinogen.

Adhesiveness↗