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T F Freddo

Publications and source records attributed to T F Freddo.

At least 19 recordsLinked to original sources
PubMed1992

Age-related changes of sulfated proteoglycans in the normal human trabecular meshwork.

Ultrastructural changes in sulfated proteoglycans were studied in 12 pairs of normal eye-bank eyes (aged 1 day to 92 years), using the cationic dye, cuprolinic blue, in a 'critical electrolyte concentration'. Pretreatment of trabecular meshwork sections with various glycosaminoglycanases and nitrous acid served to characterize these proteoglycans. Three sizes of proteoglycan-cuprolinic blue (PG-CB) complexes were found in association with different extracellular matrix components. Small, thin PG-CB complexes were closely associated with collagen fibrils. Large, thick PG-CB complexes, although located close to collagen fibrils in a variety of places, were most commonly seen between the boundaries of the collagen bundles, where they were associated with fine filaments. Both types of collagen-associated PG-CB complexes contained chondroitin sulfate and dermatan sulfate, with dermatan sulfate predominant. Basal lamina-associated PG-CB complexes contained heparan sulfate. An age-related, progressive coalescence of collagen was found in normal trabecular meshwork in a statistically significant fashion; the regions of collagen coalescence were associated with a decrease of small, collagen-associated PG-CB complexes and an increase of a previously unrecognized matrix material. The measurement of areas of coalescence of collagen was used as an indirect indicator of small, collagen-associated PG-CB complex loss with age. Large collagen-associated PG-CB complexes and basal lamina-associated PG-CB complexes decreased from infant to young adult; no additional loss with age was found. Further studies will be needed to determine whether loss of sulfated PGs plays a role in increased aqueous outflow resistance that characterizes glaucoma.

Aging↗
PubMed1992

The source of protein in the aqueous humor of the normal monkey eye.

In vivo aqueous fluorophotometry, morphology, and computational modeling were combined to examine the source of protein and the pathway by which protein enters the aqueous humor of monkeys. A computational model was developed to determine the likelihood of a diffusional route for delivering plasma proteins from ciliary body capillaries via the iris to anterior chamber aqueous humor, bypassing the posterior chamber. Model predictions were compared to aqueous fluorophotometric data obtained from monkeys following a single intravenous injection of fluoresceinated horseradish peroxidase (F-HRP, 250 mg/kg body mass). Model predictions of the magnitude and time course of anterior chamber F-HRP concentration agree with the fluorophotometric measurements. For example, of anterior chamber F-HRP concentration as a percentage of initial plasma F-HRP concentration at 90 min and 180 min post-injection was predicted to be 0.02% and 0.05%, respectively, and was measured to be 0.01-0.03% and 0.03-0.06%, respectively. In addition, model predictions in the case of a constant plasma protein level also are consistent with experimental data. The steady-state anterior chamber total protein concentration as a percentage of plasma protein concentration was predicted to be 0.2% and was assayed to be 0.05-0.2%. As in our previous study of the normal rabbit eye, morphologic and tracer localization evidence combined with the good agreement between model predictions and experimental data lead to the conclusion that a significant amount of the plasma protein normally present in monkey aqueous humor originates in ciliary body capillaries and diffuses anteriorly through the iris and into the anterior chamber.

Animals↗
PubMed1992

Morphologic correlations with fluorophotometric data from monkey eyes with anterior uveitis.

Acute anterior uveitis was induced in monkeys by unilateral intravitreal injection of 1.0 ng of Escherichia coli endotoxin. Twenty-four hours later, each animal received an intravenous injection of 250 mg/kg body weight of fluoresceinated horseradish peroxidase (F-HRP), and fluorophotometric measurements were taken for 90 min. The animals were killed, and both eyes were processed for HRP demonstration. In the anterior chamber aqueous humor of normal control eyes, F-HRP concentrations were less than 0.002 mg/ml at 90 min. The F-HRP concentration was elevated consistently in the endotoxin-injected eyes; however, the magnitude of the effect varied. By fluorophotometry, inflamed eyes fell into two distinct groups. At 90 min, most had an anterior chamber F-HRP concentration of 0.014-0.06 mg/ml, although others had 0.39 mg/ml. In the latter group, an appreciably shorter latency was observed between the time of tracer injection and its detection in the anterior chamber. Aqueous humor protein concentrations, although highest in the most F-HRP-permeable eyes, followed more of a continuum in their distribution and identified less clearly the subpopulations seen by fluorophotometry. Normal eyes had no tracer leakage across either the ciliary epithelial or iris vascular endothelial barriers. All inflamed eyes had HRP leakage across the ciliary epithelium, but the subpopulation of eyes with shorter latencies and higher F-HRP concentrations by fluorophotometry also had iris vascular leakage.

Animals↗
PubMed1991

Oncocytoma of the caruncle: a case report and ultrastructural study.

A case of oncocytoma of the lacrimal caruncle is reported, in which extensive ultrastructural studies were completed on the surgical specimen. Individual oncocytes were columnar in shape with apical surface microvilli. Their cytoplasm was filled with two types of mitochondria. Most were very large and ovoid with cristae arranged in a wide array of patterns. A smaller number of mitochondria were long and slender with more typical cristae. Two types of granular inclusions, presumed to represent alpha- and beta-glycogen deposits, were found within a small number of the large mitochondria. Poorly differentiated desmosomes joined the lateral surfaces of adjacent oncocytes. In some cases, these junctions had mitochondria attached to their cytoplasmic surfaces. A comparison is made between ultrastructural features of oncocytes in the caruncle and those found elsewhere. The relationship noted between mitochondria and desmosomes, which occurs predominantly in secretory epithelia, is also discussed.

Adenoma↗
PubMed1990

Background-protein effects on fluorophotometric data.

Fluorescent tracers are commonly used in fluorophotometric studies of ocular fluids and tissues that contain background protein. Background-protein concentrations were found to decrease or increase significantly the measure of fluorescence emitted from solutions containing sodium fluorescein, fluorescein-labeled dextran, or fluorescein-labeled horseradish peroxidase. The effect of background protein on fluorescence was expressed as a function of the specific fluorescent tracer, tracer concentration, and background-protein concentration; it can be corrected in the analysis of fluorophotometric data. Fluorophotometric studies--particularly those in which the background-protein level is expected to be abnormally high, such as postoperative and pathologic studies--may need to include either a data correction based on measured effects of background protein on tracer fluorescence or, in the case of clinical investigations, recognize at least the potential for a range of possible interpretations.

Dextrans↗
PubMed1990

The source of proteins in the aqueous humor of the normal rabbit.

Aqueous fluorophotometric, tracer localization and modeling methods were combined to document the existence of a pathway in the normal rabbit for the diffusion of proteins from the ciliary and iridial process stromas through the iris stroma into the aqueous humor of the anterior chamber. A new custom-conjugated tracer, fluoresceinated horseradish peroxidase (F-HRP), was used. Anesthetized rabbits were injected intravenously with F-HRP (250 mg/kg). In some animals, aqueous fluorophotometric and tracer localization studies were performed on the same eyes. Anterior chamber fluorescence was detected 2-10 min post-injection and rose to concentrations of 0.01-0.05 mg/ml 60 min post-injection. Subsequent tracer localization studies of these eyes revealed that the morphologic components of the blood-aqueous barrier were intact, that is, no leakage of F-HRP from the iris vasculature or across the ciliary epithelium was observed. Separate tracer localization studies were performed to examine the time course of the route(s) by which tracer entered the anterior chamber. These studies revealed a "wave" of tracer that migrated from the ciliary and iridial process stromas, through the iris, and arrived at the anterior iris surface approximately 8 min post-injection. A pharmacokinetic model based on the diffusional pathway was developed to describe the time course of the concentration of plasma macromolecules in the ciliary body, iris and anterior chamber. Model predictions were consistent with aqueous fluorophotometric and tracer localization results. The diffusion model can account for a major fraction of protein entering the aqueous humor of normal rabbit eyes.

Animals↗
PubMed1989

Ultrastructural immunocytochemical localization of elastin in normal human trabecular meshwork.

Previous studies have suggested that hydrophobic moieties within the aqueous outflow channels might interact with certain aqueous components to retard outflow. While elastin is among the most hydrophobic proteins in the trabecular meshwork, it reacts poorly with conventional ultrastructural staining methods, so its potential role in regulating outflow could not be assessed. It was our goal to specifically localize elastin ultrastructurally using polyclonal antibodies against alpha elastin and its soluble precursor, tropoelastin. Human aorta served as a positive control. Preadsorption of the primary antibodies or their substitution with either normal rabbit serum or Tris buffer resulted in negligible labelling. With either antibody, only the electron-lucent elements in the center of elastic fibers of the trabecular meshwork were labelled, indicating that only these elements truly represent elastin. The pattern of elastin distribution within these fibers is most consistent with that found in tendons elsewhere in the body.

Adolescent↗
PubMed1989

Ultrastructural changes in the posterior layers of the cornea in Schnyder's crystalline dystrophy.

A case of central crystalline dystrophy of Schnyder is presented in which ultrastructural studies were performed on the corneal specimen after penetrating keratoplasty. Electron microscopic changes were documented not only in the anterior but in the posterior stroma and in the corneal endothelium. In the posterior stroma and at the interface between the stroma and Descemet's membrane, numerous ovoid, electron-lucent spaces were present that most likely represented foci of lipid deposition. In addition, rare, focal areas of endothelial cell degeneration were observed that produced minute discontinuities in the endothelial cell covering of Descemet's membrane. Changes in the posterior layers of the cornea in Schnyder's crystalline dystrophy may contribute to the comparatively poorer surgical results obtained with lamellar rather than full-thickness grafts in these cases.

Cornea↗
PubMed1989

Interendothelial junctions of the rabbit iris vasculature in anterior uveitis.

Ultrastructural tracer techniques and freeze-fracture electron microscopy were used to evaluate the alterations present in the tight junctions of rabbit iris blood vessels in anterior uveitis. In control animals, the iris vascular endothelial cells were seen to be joined by both tight and gap junctions. Leakage of tracer from these vessels was not observed. Freeze-fracture replicas of the tight junctions in these vessels revealed two to eight branching and anastomosing strands, the particles of which tended to remain with the E fracture face. Experimental animals received intravitreal injections of 1.0 microgram of E. coli endotoxin. Twenty-four hours later, at peak severity of the inflammatory response, the animals were sacrificed. Iris vessels from uveitic eyes were observed to leak tracer, primarily through their interendothelial clefts. In freeze-fracture replicas, junctional changes took two major forms. In most cases, junctional simplification was observed. Only one or two continuous strands were evident, with very few interstrand anastomoses. In fewer instances, focal areas of profound junctional disruption were seen. In the latter case, short strands of tight junctional particles remained but the complementary ridge and groove system characteristic of tight junctions was lost. The loss of this system is interpreted to indicate that separation of adjacent endothelial cells, and an opening of the interendothelial cell cleft, has occurred at these locations. Both junctional simplification and junctional disruption likely result in increased vascular permeability. It is not possible to judge the relative contributions to increased vascular permeability which attend widespread junctional simplification as opposed to rare, focal junctional disruptions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Mitochondria attached to desmosomes in the ciliary epithelia of human, monkey, and rabbit eyes.

In the normal ciliary epithelia of the rhesus monkey, owl monkey, albino rabbit, and human eye, a previously unreported relationship exists between mitochondria and certain desmosomes. At these sites, two mitochondria appear like "sentinels" attached to the cytoplasmic surfaces of their respective sides of a desmosome. In other instances, only one side of the junction may be afforded an associated mitochondrion. In each case the cytoplasmic filaments of the desmosome are seen to blend with the outer membrane of the mitochondrion. The relationship between desmosomes and mitochondria in the ciliary epithelium is unique among ocular tissues. A survey of ocular epithelia in the various species examined, failed to give any evidence of similar junctional/organelle complexes. Various functional roles for this relationship are discussed including the possibility that the mitochondria could control the cytoplasmic calcium ion concentration in the microenvironment of their associated desmosomal junctions.

Adult↗
PubMed1987

Influence of ethacrynic acid on outflow facility in the monkey and calf eye.

Living monkeys were perfused via the anterior chamber by the two step constant pressure technique with the sulfhydryl (SH)-reactive diuretic, ethacrynic acid (ECA) at dosages from 0.1 to 1.0 mM. Above 0.37 mM a reproducible increase in outflow facility (C) was observed. At 0.5 mM C increased 115% with ECA compared to a 22% increase in control eyes (n = 9; P less than 0.01). In three monkeys simultaneous perfusion of ECA with cysteine in 10% excess prevented this effect. In enucleated calf eyes at dosages ranging from 0.1 to 0.5 mM ECA a similar increase in outflow facility was demonstrated. Simultaneous perfusion of 0.1 mM ECA with 0.5 mM cysteine blocked this increase in facility. At high dosages (6 mM) of ECA a decrease in C of 35% was observed (P less than 0.01, n = 8). Electron microscopic studies of the perfused monkey eyes did not readily explain the observed facility effects of ECA, except for the occurrence of a small number of breaks in the inner wall endothelium of Schlemm's canal. The juxtacanalicular meshwork appeared normal. Moderate to profound trabecular endothelial cell swelling was observed with ECA alone and with simultaneous cysteine. Morphologic studies performed 4 and 11 weeks after repetitive acute exposure to ECA indicated that the tissues of the outflow pathway appeared normal. The importance of this work is that it points to a new class of drugs that may be used someday to treat glaucoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Experimental obstruction to aqueous outflow by pigment particles in living monkeys.

Pigment particles (1 X 10(6)/microliters) isolated from the iris and ciliary body of enucleated cynomolgus monkey eyes were infused into the anterior chamber of seven living cynomolgus monkeys and aqueous humor outflow facility determined by the two-step constant-pressure perfusion technique. Outflow facility acutely decreased 64% in the experimental pigment perfused eyes compared to a 76% increase in the sham-manipulated fellow eyes (P less than 0.001). However, when next measured 1 wk later, facility in the pigment perfused eyes had returned to baseline levels. Repetitive pigment perfusions similarly failed to produce any long-term abnormality in outflow facility. Gonioscopically, a well-defined band of pigment was observed in the trabecular meshwork, which decreased in density with time. Scanning and transmission electron microscopy documented pigment particle phagocytosis by trabecular endothelial cells and macrophages. Forty-two and 105 days after pigment infusion the trabecular meshwork was normal morphologically, and, despite an observed decrease in trabecular pigmentation, morphometry failed to reveal a decrease in trabecular meshwork cellularity in experimental compared to control eyes. These results suggest that factors other than, or in addition to, pigment particle accumulation in the trabecular meshwork must be involved in the mechanism of human pigmentary glaucoma.

Animals↗
PubMed1985

Bilateral acute corneal calcification.

A 38-year-old man with brittle, juvenile onset diabetes mellitus and bilateral severe dry eyes with recurrent corneal ulcers developed atypical band-shaped calcifications of both corneas during a 24-hour period. Serum calcium, phosphate, and carbon dioxide levels all were within normal limits. The patient was mildly uremic but was not in renal failure. When EDTA chelation failed to clear the deposits, partial keratectomies were performed in both eyes and the specimens were examined by light and electron microscopy, including energy dispersive x-ray analysis. Microscopic studies revealed an atypical calcific keratopathy which involved neither Bowman's layer nor the most superficial stromal lamellae. The deposits were confined to deeper lamellae in the anterior stroma and by electron microscopy were composed of extracellular crystalline aggregates. Energy dispersive x-ray analysis of these aggregates confirmed the presence of calcium and phosphate. Corneal dessication appeared to be a major contributing factor in the rapid formation of these deposits.

Acute Disease↗
PubMed1976

Future of optometric education: a student view.

With the growth of optometry and the advent of a national health insurance plan, the practice of optometry will change. As it does, so too must optometric education. This paper outlines a student's views on how admissions, curricula, new schools, and board certification must change if optometry is to fill a primary health care role.

Certification↗
PubMed1976

An assessment of the generation times of neuronal precursors in the sensory retina and subventricular zone of the newborn rat.

Generation times and the times for their respective phases were determined for neuronal precursors in the sensory retina and subventricular zone of the brain of newborn CD rats. These regions can be induced to form retinoblastoma and medulloepitheliomas, respectively, following injection of adenovirus-12. Through use of autoradiographic techniques, it was shown that the cell cycle duration in the subventricular zone was almost twice as long as in the sensory retinal layer. The G1 phase durations were found to account for the majority of the time difference.

Adenoviridae↗
PubMedDate not supplied

Differences in nuclear pore density among human choroidal melanoma cell types.

Two cases of mixed cell type choroidal melanoma were examined by means of conventional and freeze-fracture electron microscopy. Data on average nuclear pore density were readily collected from freeze-fracture replicas of spindle A, spindle B, and epithelioid cells. Highly significant (p less than 0.001) differences in pore densities were found among the three cell types. Pore density was lowest in spindle A cells, intermediate in spindle B cells, and highest in epithelioid cells. The possible relationship between nuclear pore density and nucleolar activity as well as the potential usefulness of this new finding as a prognostic indicator in cases of choroidal melanoma are discussed.

Cell Nucleolus↗