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Biomedical subjects

A Glasser

Publications and source records attributed to A Glasser.

At least 19 recordsLinked to original sources
PubMed2001

Effect of H-7 on cultured human trabecular meshwork cells.

PURPOSE: To determine the effect of the serine-threonine kinase inhibitor H-7, which blocks actomyosin contractility and increases outflow facility in live monkeys, on morphology, cytoskeleton, and cellular adhesions of human trabecular meshwork (HTM) cells in culture. METHODS: Cultured HTM cells were videographically recorded and evaluated before and after exposure to H-7 at different concentrations. The subcellular distribution of the actin-based cytoskeleton and associated anchor proteins including vinculin, paxillin, and beta-catenin, as well as phosphotyrosine-containing proteins were evaluated by fluorescence immunocytochemistry and digital fluorescence microscopy. RESULTS: H-7 induced pronounced but reversible HTM cell thickening toward the cell center and deterioration of the actin cytoskeletal network. Cell-extracellular matrix (ECM) and cell-cell adhesions were also affected, but the beta-catenin-rich, vinculin-containing adherens junctions were clearly more resistant than focal contacts. Phosphotyrosine labeling in focal contacts was highly sensitive to H-7. CONCLUSIONS: H-7 induces alterations in cell shape, actin cytoskeleton, and associated focal adhesions in cultured HTM cells, which may be responsible for the effects of H-7 on outflow facility in live monkey eyes.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2001

Optical and biometric relationships of the isolated pig crystalline lens.

AIM: To investigate the interrelationships between optical and biometric properties of the porcine crystalline lens, to compare these findings with similar relationships found for the human lens and to attempt to fit this data to a geometric model of the optical and biometric properties of the pig lens. METHODS: Weight, focal length, spherical aberration, surface curvatures, thickness and diameters of 20 isolated pig lenses were measured and equivalent refractive index was calculated. These parameters were compared and used to geometrically model the pig lens. RESULTS: Linear relationships were identified between many of the lens biometric and optical properties. The existence of these relationships allowed a simple geometrical model of the pig lens to be calculated which offers predictions of the optical properties. CONCLUSIONS: The linear relationships found and the agreement observed between measured and modeled results suggest that the pig lens confirms to a predictable, preset developmental pattern and that the optical and biometric properties are predictably interrelated.

Animals↗
PubMed2001

Ultrasound biomicroscopy of the aging rhesus monkey ciliary region.

Ultrasound biomicroscopy of the living rhesus monkey ocular ciliary region was undertaken to identify age-dependent changes that might relate to the progression of presbyopia. Monkeys were anesthetized and pharmacologically cyclopleged, the eyelids were held open with a lid speculum, and sutures were placed beneath the medial and lateral rectus muscles. Ultrasound biomicroscopy imaging of the nasal and temporal quadrants of the eye were performed, and the live images were recorded to videotape. Subsequent image analysis was performed to obtain objective morphometric measurements of the ciliary body region. The ciliary body inner radius of curvature, outer radius of curvature, inner arc length, area, thickness, perimeter, zonular fiber length, and circumlental space were measured. Zonular space was calculated. The circumlental space decreased with increasing age in the temporal quadrant. The other morphologic measurements were not significantly correlated with age or body weight. Most morphologic measurements were significantly different comparing temporal vs. nasal quadrants. Bifurcation of the posterior zonular fibers was frequently observed. Although temporal circumlental space was the only measurement found to change with age, ultrasound biomicroscopy of the living rhesus ciliary region did identify distinct nasal vs. temporal asymmetries, which may reflect anatomical requirements for convergence-associated accommodation.

Accommodation, Ocular↗
PubMed2001

Cycle of child sexual abuse: links between being a victim and becoming a perpetrator.

BACKGROUND: There is widespread belief in a 'cycle' of child sexual abuse, but little empirical evidence for this belief. AIMS: To identify perpetrators of such abuse who had been victims of paedophilia and/or incest, in order to: ascertain whether subjects who had been victims become perpetrators of such abuse; compare characteristics of those who had and had not been victims; and review psychodynamic ideas thought to underlie the behaviour of perpetrators. METHOD: Retrospective clinical case note review of 843 subjects attending a specialist forensic psychotherapy centre. RESULTS: Among 747 males the risk of being a perpetrator was positively correlated with reported sexual abuse victim experiences. The overall rate of having been a victim was 35% for perpetrators and 11% for non-perpetrators. Of the 96 females, 43% had been victims but only one was a perpetrator. A high percentage of male subjects abused in childhood by a female relative became perpetrators. Having been a victim was a strong predictor of becoming a perpetrator, as was an index of parental loss in childhood. CONCLUSIONS: The data support the notion of a victim-to-victimiser cycle in a minority of male perpetrators but not among the female victims studied. Sexual abuse by a female in childhood may be a risk factor for a cycle of abuse in males.

Adult↗
PubMed2000

Effect of latrunculin-A on morphology and actin-associated adhesions of cultured human trabecular meshwork cells.

PURPOSE: Determine the effects of the actin cytoskeleton disrupting compound latrunculin-A (LAT-A) on morphology, cytoskeleton, and cellular adhesions of cultured human trabecular meshwork (HTM) cells. METHODS: HTM cells were cultured to high confluence with endothelial-like morphology and treated with LAT-A at different doses and duration. Topography of living cells was evaluated by videomicroscopy. Distribution and organization of the actin-based cytoskeleton, vinculin- and paxillin-containing focal contacts, and beta-catenin-rich intercellular adhesions were determined by immunofluorescence and digital microscopy. RESULTS: LAT-A induced pronounced but highly reversible rounding of HTM cells, intercellular separation, and disruption of actin filaments. beta-catenin-rich intercellular adherens junctions were particularly sensitive to LAT-A. Vinculin- and paxillin-containing focal contacts were only partially affected and appeared to be more resistant to the drug than the intercellular interactions. CONCLUSIONS: The increase in outflow facility in the living primate eye induced by LAT-A may be due to the disorganization and disruption of the actin cytoskeleton and its associated cellular adhesions in the trabecular meshwork.

Actins↗
PubMed1999

Biometric, optical and physical changes in the isolated human crystalline lens with age in relation to presbyopia.

The biometric, optical and physical properties of 19 pairs of isolated human eye-bank lenses ranging in age from 5 to 96 years were compared. Lens focal length and spherical aberration were measured using a scanning laser apparatus, lens thickness and the lens surface curvatures were measured by digitizing the lens profiles and equivalent refractive indices were calculated for each lens using this data. The second lens from each donor was used to measure resistance to physical deformation by providing a compressive force to the lens. The lens capsule was then removed from each lens and each measurement was repeated to ascertain what role the capsule plays in determining these optical and physical characteristics. Age dependent changes in lens focal length, lens surface curvatures and lens resistance to physical deformation are described. Isolated lens focal length was found to be significantly linearly correlated with both the anterior and posterior surface curvatures. No age dependent change in equivalent refractive index of the isolated lens was found. Although decapsulating human lenses causes similar changes in focal length to that which we have shown to occur when human lenses are mechanically stretched into an unaccommodated state, the effects are due to nonsystematic changes in lens curvatures. These studies reinforce the conclusion that lens hardening must be considered as an important factor in the development of presbyopia, that age changes in the human lens are not limited to the loss of accommodation that characterizes presbyopia but that the lens optical and physical properties change substantially with age in a complex manner.

Adolescent↗
PubMed1999

The mechanism of accommodation in primates.

OBJECTIVE: To study the accommodative mechanism in primates using monkeys, in light of a recently proposed novel accommodative mechanism in primates and a concomitant controversial surgical procedure for the reversal of presbyopia, DESIGN: Experimental study. METHODS: Accommodation was induced by stimulation of an electrode surgically implanted in the midbrain and by topical ocular application of muscarinic agonists. Pharmacologic disaccommodation was achieved by topical application of a muscarinic antagonist. Movements of the lens equator and the ciliary body were imaged during accommodation and disaccommodation using ultrasound biomicroscopy and goniovideography, and the images were analyzed to determine the direction and the extent of the movements. RESULTS: Despite the systematic eye movements occurring with electrical stimulation and the nonsystematic eye movements occurring with pharmacologic stimulation, in all instances the ciliary body and the lens equator moved away from the sclera during accommodation. CONCLUSIONS: Movement of the accommodative structures is consistent with the classic mechanism of accommodation described by Helmholtz, and contrary to that recently proposed by Schachar.

Accommodation, Ocular↗
PubMed1999

The health effects of swimming in ocean water contaminated by storm drain runoff.

Waters adjacent to the County of Los Angeles (CA) receive untreated runoff from a series of storm drains year round. Many other coastal areas face a similar situation. To our knowledge, there has not been a large-scale epidemiologic study of persons who swim in marine waters subject to such runoff. We report here results of a cohort study conducted to investigate this issue. Measures of exposure included distance from the storm drain, selected bacterial indicators (total and fecal coliforms, enterococci, and Escherichia coli), and a direct measure of enteric viruses. We found higher risks of a broad range of symptoms, including both upper respiratory and gastrointestinal, for subjects swimming (a) closer to storm drains, (b) in water with high levels of single bacterial indicators and a low ratio of total to fecal coliforms, and (c) in water where enteric viruses were detected. The strength and consistency of the associations we observed across various measures of exposure imply that there may be an increased risk of adverse health outcomes associated with swimming in ocean water that is contaminated with untreated urban runoff.

California↗
PubMed1998

Presbyopia and the optical changes in the human crystalline lens with age.

Lenses from 27 human eyes ranging in age from 10 to 87 years were used to determine how accommodation and age affect the optical properties of the lens. A scanning laser technique was used to measure focal length and spherical aberration of the lenses, while the lenses were subjected to stretching forces applied through the ciliary body/zonular complex. The focal length of all unstretched lenses increased linearly with increasing age. Younger lenses were able to undergo significant changes in focal length with stretching, whereas lenses older than 60 years of age showed no changes in focal length with stretching. These data provide additional evidence for predominantly lens-based theories of presbyopia. Further, these results show that there are substantial optical changes in the human lens with increasing age and during accommodation, since both the magnitude and the sign of the spherical aberration change with age and stretching. These results show that the optical properties of the older presbyopic lens are quite different from the younger, accommodated lens.

Accommodation, Ocular↗
PubMed1998

Accommodation dynamics in aging rhesus monkeys.

Accommodation, the mechanism by which the eye focuses on near objects, is lost with increasing age in humans and monkeys. This pathophysiology, called presbyopia, is poorly understood. We studied aging-related changes in the dynamics of accommodation in rhesus monkeys aged 4-24 yr after total iridectomy and midbrain implantation of an electrode to permit visualization and stimulation, respectively, of the eye's accommodative apparatus. Real-time video techniques were used to capture and quantify images of the ciliary body and lens. During accommodation in youth, ciliary body movement was biphasic, lens movement was monophasic, and both slowed as the structures approached their new steady-state positions. Disaccommodation occurred more rapidly for both ciliary body and lens, but with longer latent period, and slowed near the end point. With increasing age, the amplitude of lens and ciliary body movement during accommodation declined, as did their velocities. The latent period of lens and ciliary body movements increased, and ciliary body movement became monophasic. The latent period of lens and ciliary body movement during disaccommodation was not significantly correlated with age, but their velocity declined significantly. The age-dependent decline in amplitude and velocity of ciliary body movements during accommodation suggests that ciliary body dysfunction plays a role in presbyopia. The age changes in lens movement could be a consequence of increasing inelasticity or hardening of the lens, or of age changes in ciliary body motility.

Accommodation, Ocular↗
PubMed1996

A history of studies of visual accommodation in birds.

Since 1813, when Crampton first described the ciliary muscle of the avian eye, there has been little agreement on how birds are able to change the focus of their eyes. Numerous later studies on the eyes of a variety of bird species contradicted earlier findings or proposed new accommodative mechanisms. The resulting confusion persists today, and a number of significant works on the avian eye perpetuate many of the myths developed during the 1800s. There is little consensus on avian accommodation; the early literature contains many accurate descriptions of the mechanisms, along with elegant experimental evidence to support them. Much of the early literature, however, is in German and has remained obscure. Further, among the mechanistic descriptions of avian accommodation are many that are incorrect. The current confusion can be attributed in part to the fact that some birds have both corneal and lenticular accommodation. It is unclear to what extent different bird species employ both mechanisms, or depend on one mechanism or the other. These facts, together with the diversity of bird species, their range of visual requirements, and the numerous anatomical differences in their eyes, make it impossible to describe a single avian mechanism of accommodation. Our own experience in studying accommodation in the chick eye has led us to review the historical literature in an attempt to provide a new foundation for future studies on visual accommodation in birds. While in relation to the anatomical arrangements [of the bird eye], these have led our knowledge pretty much to a conclusion.... There is among all these works no real difference of opinion. However, in terms of the accommodative mechanism of the bird eye, at the present time there are many different views of what is going on. Here the circumstances are very similar to what happened a few decades ago in the study of accommodation generally, but particularly with humans, when Helmholtz made the remark. "There is no other portion of physiological optics in which one finds so many differing and contradictory ideas us in the accommodation of the eye, where we have only recently actually made observations on what previously was left to the play of hypotheses".

Accommodation, Ocular↗
PubMed1995

The mechanism of lenticular accommodation in chicks.

In the chick eye, accommodation for near objects is brought about by changes in the focal length of the lens and by changes in the corneal radius of curvature. Several different mechanisms of lenticular accommodation have been proposed for the avian eye. These include a role for the ciliary muscle, a role for the iris muscle, and a role for changes in intraocular pressure. We have studied accommodation in the chick eye using electrical stimulation of the Edinger-Westphal nucleus, electric-field stimulation of enucleated eyes, in vitro measurement of changes in back vertex distance of the lens, and histology. We present evidence showing that, in the chick eye, lenticular accommodation is induced primarily by a contraction of the muscle fibers at the peripheral edge of the iris. During accommodation, the peripheral muscle fibers of the iris contract to apply a force through the ciliary processes to the anterior equatorial surface of the lens. This increases the focal power of the lens. When accommodation is relaxed, the lens is returned to its unaccommodated state by the elasticity of the pectinate ligament and the ciliary body. Contractions of the posterior ciliary muscle and changes in intraocular pressure, forces that have previously been proposed to play major roles in lenticular accommodation, are shown to be of secondary importance only.

Accommodation, Ocular↗
PubMed1995

Differences in eye growth and the response to visual deprivation in different strains of chicken.

Several laboratories studying visual deprivation myopia in the domestic chick report varying degrees of axial elongation and myopia induced by similar visual deprivation techniques. In this study we tested the hypothesis that in different strains of chick the eyes respond differently to visual deprivation. We compared under identical conditions two strains of White Leghorn chick commonly used in ocular development research--the Cornell-K strain (K) and Washington H & N Strain (H/N). The normal development of the eye was found to vary significantly between these strains of White Leghorn chicks. The K strain normally develops flatter corneas, thicker lenses, and larger eyes than the H/N strain. The response to visual deprivation also varies significantly between strains. For example, we find that 2 weeks of visual deprivation in the K strain results in less elongation of the vitreous chamber and flattening of the cornea yielding lower levels of induced myopia compared to the H/N strain. Our results show that while visual experience clearly affects normal ocular development in both strains of chick, the nature of the effect depends upon not only the type and duration of the experience but the genetics of the subject population as well.

Age Factors↗