Biomedical subjects

Jer R Kuszak

Publications and source records attributed to Jer R Kuszak.

4 recordsLinked to original sources

PubMed2003

Morphology and organization of posterior fiber ends during migration.

PURPOSE: To characterize structural parameters of the basal membrane complex (BMC) and to determine the arrangement and organization of posterior fiber ends during elongation/migration in lenses with branched sutures. METHODS: Lenses from normal, juvenile (4-6 week old) Sprague-Dawley rats (n=16) were utilized. Posterior fiber ends were assessed on both whole mounts of lens capsules and on decapsulated lenses. The size, shape and organization of migrating fiber ends was assessed by scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) along the entire posterior surface. The area of the BMC was measured using image analysis software and subjected to statistical analysis. RESULTS: Posterior fiber ends had a characteristic regional arrangement during elongation and migration along the capsule. These regions were termed the equatorial, the lateral-posterior (posterior from the equator to within 150 microm of the sutures), the peri-sutural (150 microm surrounding the sutures), and the sutural. The area of fiber ends (seen by SEM) was compared to the area of fluorescent F-actin profiles (seen by LSCM). There was no significant difference (p=0.324) between the average basal end area (40.21 microm2) and the average area of F-actin profiles (40.65 microm2). The average fiber end area in the lateral-posterior, peri-sutural, and sutural regions was 63.19 microm2, 71.95 microm2, and 25.75 microm2, respectively. In the equatorial region, footprints were aligned in rows oriented toward the posterior pole, consistent with the arrangement of straight, meridional rows. Initially, fiber ends within the lateral-posterior region were arranged in short irregular rows having variable orientation with respect to the posterior pole. The remainder of these ends were randomly arranged. In the peri-sutural region, fiber ends approaching suture branches were aligned in short rows oriented at angles to the posterior pole. At the sutures, fiber ends appeared to become rounded, presumably during detachment from the capsule. CONCLUSIONS: The results confirm that F-actin profiles delineate the BMC of posterior fiber ends. Furthermore, the average area, shape and arrangement of fiber ends varies in a predictable pattern during migration. The data suggests that elongating fiber ends follow defined migration patterns along the posterior capsule to their sutural destinations. This controlled process is crucial to the formation of ordered suture patterns, thereby minimizing their adverse effects on lens optical quality.

Actins↗

PubMed2003

Analysis of nuclear fiber cell compaction in transparent and cataractous diabetic human lenses by scanning electron microscopy.

BACKGROUND: Compaction of human ocular lens fiber cells as a function of both aging and cataractogenesis has been demonstrated previously using scanning electron microscopy. The purpose of this investigation is to quantify morphological differences in the inner nuclear regions of cataractous and non-cataractous human lenses from individuals with diabetes. The hypothesis is that, even in the presence of the osmotic stress caused by diabetes, compaction rather than swelling occurs in the nucleus of diabetic lenses. METHODS: Transparent and nuclear cataractous lenses from diabetic patients were examined by scanning electron microscopy (SEM). Measurements of the fetal nuclear (FN) elliptical angles (anterior and posterior), embryonic nuclear (EN) anterior-posterior (A-P) axial thickness, and the number of EN fiber cell membrane folds over 20 microns were compared. RESULTS: Diabetic lenses with nuclear cataract exhibited smaller FN elliptical angles, smaller EN axial thicknesses, and larger numbers of EN compaction folds than their non-cataractous diabetic counterparts. CONCLUSION: As in non-diabetic lenses, the inner nuclei of cataractous lenses from diabetics were significantly more compacted than those of non-cataractous diabetics. Little difference between diabetic and non-diabetic compaction levels was found, suggesting that diabetes does not affect the degree of compaction. However, consistent with previous proposals, diabetes does appear to accelerate the formation of cataracts that are similar to age-related nuclear cataracts in non-diabetics. We conclude that as scattering increases in the diabetic lens with cataract formation, fiber cell compaction is significant.

Aged↗

PubMed2003

Lens structure in MIP-deficient mice.

In this study we used correlative light, scanning, and transmission (freeze-etch) electron microscopy to characterize lens structure in normal mice and compare it with that in mice deficient in the major intrinsic protein (MIP) of fiber cells. Grossly, wild-type lenses were transparent and had typical Y sutures at all of the ages examined. These lenses had fibers of uniform shape (hexagonal in cross section) arranged in ordered concentric growth shells and radial cell columns. In addition, these fibers had normal opposite end curvature and lateral interdigitations regularly arrayed along their length. Ultrastructural evaluation of these fibers revealed anterior and posterior end segments characterized by square array membrane on low-amplitude wavy fiber membrane. Approximately 13% of the equatorial or mid segments of these same fibers were specialized as gap junctions (GJs). In contrast, heterozygote lenses, while initially transparent at birth, were translucent by 3 weeks of age, except for a peripheral transparent region that contained fibers in the early stages of elongation. This degradation in clarity was correlated with abnormal fiber structure. Specifically, although the mid segment of these fibers was essentially normal, their end segments lacked normal opposite end curvature, were larger than normal, and had a distinct non-hexagonal shape. As a result, these fibers failed to form typical Y sutures. Furthermore, the nuclear fibers of heterozygote lenses were even larger and lacked any semblance of an ordered packing arrangement. Grossly, homozygote lenses were opaque at all ages examined, except for a peripheral transparent region that contained fibers in the early stages of elongation. All fibers from homozygote lenses lacked opposite end curvature, and thus failed to form any sutures. Also, these fibers were essentially devoid of interlocking devices, and only 7% of their mid segment was specialized as GJs. The results of this study suggest that MIP has essential roles in the establishment and maintenance of uniform fiber structure, and the organization of fibers, and as such is essential for lens function.

Animals↗

PubMed2003

Knockout of the intermediate filament protein CP49 destabilises the lens fibre cell cytoskeleton and decreases lens optical quality, but does not induce cataract.

In this report, the phenotype associated with the first targeted knockout of the lens specific intermediate filament gene CP49 is described. Several surprising observations have been made. The first was that no cataract was observed despite the fact that the beaded filaments of the lens fibre cells had been disrupted. Light scatter and the lens optical properties had, however, deteriorated in the CP49 knockout lenses compared to litter mate controls. These changes were accompanied by dramatic changes in plasma membrane organisation of the fibre cells as revealed by detailed morphological examinations and providing the second surprising result. The CP49 knockout mouse is therefore an important model to study the functional link between lens transparency, the cytoskeleton and plasma membrane organisation.

Animals↗