PubMed Health⌕ Search

Biomedical subjects

N S Rafferty

Publications and source records attributed to N S Rafferty.

At least 37 records · Page 2Linked to original sources
PubMed1984

In situ localization of S1-labeled actin filaments in chick lens epithelial cells.

The actin filaments in the lens epithelial cells of three-day and eight-day post-hatched chicks have been labeled in situ with myosin subfragment 1 (S1). Labeling was accomplished by injuring the lens transcorneally with an ultramicroneedle 5 min or 24 hr before detergent treatment and incubation in S1. A band of filaments found at the epithelio-fiber junction in normal, uninjured chick lens is labeled in the 5 min and 24 hr injury. A subcapsular labeled band is found only in the 24 hr injury, and may be the result of a healing process.

Actins↗
PubMed1984

An ultrastructural study of fixation artifacts in lens epithelium.

The conditions providing for optimal preservation of the ultrastructure of the lens epithelium of embryonic and young chicks were sought, especially with regard to avoiding fixation artifacts and to enhancing the lens cytoskeleton. The optimal fixative/buffer solution for these purposes was found to consist of 2% glutaraldehyde in 0.05M phosphate buffer containing 0.2% tannic acid and 0.002% CaCl2, pH 7.2, whose total osmolarity is about 340 mOsm, and postfixation in 1% osmium. As the osmolarity was increased by use of 0.075M or 0.1M phosphate buffer, intercellular spaces and myelin-like figures appeared along the cell membranes of the epithelial cells and superficial cortical fibers. As the osmolarity was decreased, using 0.02M phosphate buffer, plasma membranes became flaccid and interrupted, nuclei underwent severe shape changes, and the cytoplasm became electron-lucent. Delays of 30 minutes or one hour before fixation caused swelling of cytoplasmic organelles and the nuclear envelope. Primary fixation in osmium resulted in interrupted cell membranes and in swollen organelles. Many of these artifacts seen in the superficial chick lens, produced merely by manipulating the tonicity or the time of fixation after death, have been previously attributed in the literature to cataractous or aging changes. Based on the present findings caution in interpreting electron micrographs of pathologic changes in lens is urged.

Animals↗
PubMed1984

Polygonal arrays of microfilaments in epithelial cells of the intact lens.

Polygonal arrays of microfilaments have been discovered to line the inner apical plasma membrane of anterior epithelial cells of the intact rabbit lens. When tangential sections are studied with the electron microscope, the polygonal arrays are seen to consist of central vertices interconnected by rays of filaments. The rays near the cell periphery insert into the lateral plasma membrane. The vertices are spaced about 1 micron apart and appear to be attached to the apical plasma membrane. The polygonal arrays have little depth as judged by stereo-pairs and are incorporated within the dense band of microfilaments seen in cross-section at the epithelio-fiber junction. The diameter of the filaments and their similarity to actin-containing polygonal arrays described by other investigators in cultured cells suggest that these structures contain actin in lens epithelial cells. The function of the polygonal arrays in relation to maintenance of lens shape or to changes in lens shape in accommodation is discussed.

Animals↗
PubMed1981

Cell population kinetics of the mouse lens epithelium.

The dividing lens epithelium of 8-week-old CF1 mice consists of a monocellular layer of about 31,000 cells and does not include the postmitotic cells of the meridional rows and another postmitotic zone of seven cell positions' width immediately anterior to the rows. The latter two populations contain approximately 3,600 and 9,000 cells, respectively, for a total of 44,000 cells in the entire lens epithelium. Autoradiographic analysis based upon mitotic index and cell cycle times indicates that the epithelium produces 207 new lens fibers a day. Throughout the 20-day period of study, labeled cells appeared almost entirely as pairs following a single dose of 3H-thymidine and clusters of labeled nuclei were not seen. Moreover, the number of labeled cells dropped only slowly with time, as did the grain counts. These observations indicate that logarithmic division "cascade" does not occur in the lens. The dividing cell population consists largely of a slowly cycling stem cell group, dividing once about every 17-20 days, and consisting of some 5,000 cells. A subpopulation may exist which undergoes two rapid consecutive divisions before becoming postmitotic, but this is too small to make a significant contribution to lens fiber production. Four days are required to transit the postmitotic zone, and an additional 43 or so are needed to transit the meridional rows and differentiate into anucleate lens fibers. Data from other laboratories indicate that the entire process, from mitosis to final differentiation, requires about 4 months. Hence, most of this time is spent in migration of nondividing cells.

Animals↗
PubMed1981

Human cataracta complicata. Clinicopathologic correlation.

Complicated cataracts of the posterior subcapsular zone may be associated with a number os systemic conditions. Cataracts from patients with retinitis pigmentosa, Turner's syndrome, myotonic dystrophy, or those who were taking corticosteroids were examined clinically and pathologically after intracapsular cataract extraction. Two major types of posterior subcapsular opacities were observed: one type had multiple vacuoles, while the other type was a more solid appearing (plaque-like or snowball) opacity clinically. The predominant morphologic counterpart (by light and electron microscopy) of the vacuolar opacity is liquefactive necrosis with aberrantly migrated epithelia cells growing into the cataract. In the plaque-like or snowball opacity, the lens fibers are generally disorganized into round globules. The clinical significance is that the vacuolar-liquified posterior subcapsular cataract may be more easily removed by extracapsular methods than the plaque-like opacity; however, the proliferative cells in the vacuolar type are probably the source of an after-cataract membrane that may require discussion.

Adrenal Cortex Hormones↗
PubMed1981

Lens transglutaminase and cataract formation.

A protein polymer characteristically present in human cataract was shown to contain significant amounts of gamma-glutamyl-epsilon-lysine isopeptides. It is proposed that these crosslinks are produced by the action of transglutaminase (R-glutaminyl-peptide:amine-gamma-glutamyl-yltransferase, EC 2.3.2.13), which is all the more plausible because lens contains the enzyme and endogenous protein substrates for it. The enzyme is similar to that obtained from liver and is Ca2+ dependent. Highest apparent activity is found in lens cortex. When cortex homogenate from the rabbit was incubated in the presence of Ca2+ with either [14C]putrescine or with dansylcadaverine, a a selective incorporation of the radioactive or fluorescent amine into the heavier subunits (Mr approximately 26,000 and 30,000) of beta-crystallins could be demonstrated. Possible modes of regulating the crosslinking activity of this enzyme in lens are discussed.

Animals↗
PubMed1980

Ultrastructure of human cataract in retinitis pigmentosa.

A second ultrastructural study of retinitis pigmentosa cataract showed differences from the previous case with respect to sex, age of cataract onset, age at time of cataract extraction, and mode of inheritance of retinitis pigmentosa. Furthermore, the cataract in the present study was limited clinically and preponderantly ultrastructurally to the posterior subcapsular area, which is typical of the location of cataracts associated with retinitis pigmentosa. The cataract was characterized by severe lens fiber disorganization, resulting in intricately distorted membrane configurations and varying cytoplasmic densities; however, "figure eight" configurations as noted in the other report were not observed. Aberrantly migrated epithelial cells were distributed unevenly in the posterior subcapsular zone. New capsular basement membrane, not mentioned in the other report, was conspicuous in our case. Thus, retinitis pigmentosa cataract may have diverse ultrastructural alterations.

Adult↗
PubMed1977

Ultrastructure of traumatic cataractogenesis in the frog: a comparison with mouse and human lens.

Normal and needle-punctured lenses of Rana pipiens were examined with the electron microscope in order to characterize the sequence of ultrastructural changes that follow the injury over a 5-month period. Results were compared with those obtained previously in experimentally injured mouse and accidentally injured human lenses. The normal adult frog lens was found to have a morphology similar to that of mammalian lenses. As in the human, frog lens epithelial cells contained scattered microfilaments and were connected by desmosomes and gap junctions. They differed from mouse cells, which had been shown to lack desmosomes and to have microfilaments organized into dense bundles. These differences are postulated to be related to the degree of accommodative deformation of the lens displayed by these species. After injury, cellular debris and fibrin, accumulated in the wound, were phagocytized by extrinsic cells derived from the blood and ocular tissues. Leucocytes, pigmented cells and fibroblasts remained in the wound for eight weeks, along with epithelial cells which proliferated and migrated from the wound margins.Epithelial cells showed an increase in those organelles associated with protein synthesis and transport, and in microfilaments. In cataractous lenses, epithelial cells showed changes in matrix, and lens fibers became organized into smaller, denser compressed units. At five months, considerable healing had taken place, but localized opacities persisted in many frog lenses.

Animals↗
PubMed1975

Ultrastructural studies of traumatic cataractogenesis: observations of a repair process in mouse lens.

Lenses of CFI mice were studied with the transmission electron microscope at frequent intervals through 13 months following a transcorneal needle injury to the lens. While this kind of injury causes a high incidence of traumatic cataract in the human and frog, it elicits a repair process in the mouse lens whereby the damaged capsule, epithelium and lens fibers are rapidly renewed and permanent lens opacity seldom occurs. Ultrastructural changes in lens epithelial cells adjacent to the wound, which precede and accompany localized cellular proliferation and production of new capsule, involve a rapid increase or enlargement of organelles associated with protein synthesis and assembly. The capsule and epithelium are repaired within a couple of months. Cortical lens fibers in the wound area undergo conformational changes into smaller, ordered arrays of "membranous sacs". These are replaced within a week by normal appearing lens fibers. There is minimal degeneration or hyperplasia noted, and except for a few fibroblastic cells on the lens surface, little evidence remains of the injury by two months. Ultrastructural differences between mouse and human lens, such as presence or absence of dense bundles of microfilaments and desmosomes are considered in relation to lens shape and tension, and susceptibility to injury-induced cataract.

Animals↗