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D A Samuelson

Publications and source records attributed to D A Samuelson.

At least 19 recordsLinked to original sources
PubMed2004

A new model of glaucoma filtering surgery in the rat.

PURPOSE: The most common reason for long-term failure of glaucoma filtering surgery (GFS) is scarring of the external filtering "bleb" tissues. The identification of the factors that mediate this process, as well as the development and initial testing of new therapies to limit scarring is enhanced by the use of appropriate animal models. The standard animal model for studying GFS is the rabbit but newer investigative tools that examine changes induced in biologic systems at a genetic level have made development of a rat model desirable. METHODS: Glaucoma filtering surgery was performed on 20 Sprague-Dawley rats by introducing a 30-gauge silicone cannula through a penetrating scleral tunnel, under a limbal-based conjunctival flap and suturing the conjunctiva closed. Identical GFS was performed on 3 additional rats, which underwent histologic evaluation at days 2, 5, and 11, following surgery.Fistulizing surgery was also performed on 6 Sprague-Dawley rats, for comparison, by creating a full-thickness needle sclerostomy under a limbal-based conjunctival flap and suturing the conjunctiva closed. RESULTS: Following the cannula GFS, well-elevated filtering blebs formed and these gradually failed over the course of 8 to 13 days. Needle tract sclerostomy filtering blebs formed at the site of the fistulizing surgery but rapidly failed over the course of 2 to 3 days. CONCLUSION: Cannulated filtering surgery in the rat provides a longer lasting and more predictable model than needle tract sclerostomy for studying wound healing following GFS and may facilitate the study of induced changes at the gene level.

Animals↗
PubMed2003

Localization of smooth muscle actin in the iridocorneal angle of normal and spontaneous glaucomatous beagle dogs.

PURPOSE: To date, our knowledge of the canine trabecular meshwork (TM) with regard to contractility is incomplete. It is important to understand the potential contractile capability within the TM and possible changes associated with spontaneous hypertensive glaucoma. To that end we have examined the presence of actin, including smooth muscle (SM) actin, in the normal and glaucomatous canine iridocorneal angle (ICA) morphologically and immunohistochemically. METHODS: Sections from the ICAs of 12 Beagles with inherited glaucoma (3 months to 6 years old) and age-matched normal Beagles were treated with target retrieval, protein and power blocked and sequentially incubated with the primary antibody (rat anticanine SM actin) and the secondary antibody (rabbit antirat immunoglobulin), followed by peroxidase labeled streptavidin and incubation with substrate-chromogen solution (AEC). Smooth muscle fibers that lined an artery within canine heart tissue were used as positive controls. Separate specimens were prepared for ultrastructual observation. RESULTS: Ultrastructurally, cells within the inner, posterior region of the corneoscleral TM and outer, posterior region of the uveal TM contained many microfilaments, 6 nm in diameter (i.e. actin). Immunohistochemistry demonstrated that cells within these regions possessed SM actin, having been greatest posteriorly, but extended anteriorly to a lesser extent. In the preglaucomatous affected dog the localization pattern for SM actin was identical to that seen in the normal dogs. With the progression of the disease the pattern disappeared. CONCLUSIONS: The interior presence of myofibroblastic cells within the canine ICA suggests that these cells and the smooth muscle cells of the ciliary body along the same plane of orientation function to facilitate the removal of aqueous humor and are likely to be influenced by vascular mediators. The contractile apparatus for the ICA in the dog with inherited glaucoma appeared identical to that of the normal dog prior to expression of the disease, but weakened as the disease progressed.

Actins↗
PubMed2001

Metallothionein expression protects against carbon tetrachloride-induced hepatotoxicity, but overexpression and dietary zinc supplementation provide no further protection in metallothionein transgenic and knockout mice.

Metallothionein and zinc have been implicated in cellular defense against a number of cytotoxic agents. With respect to the free radical-generating hepatotoxin carbon tetrachloride, conclusions about a defensive role were reached from in vitro studies, in vivo studies using inducers of metallothionein and studies using injections of pharmacological amounts of zinc. Metallothionein knockout (null) and metallothionein transgenic mice are more direct models to examine the effects of metallothionein expression on induced cytotoxicity. Similarly, zinc presented via the diet is a more physiological model than that presented via injection. We examined whether metallothionein-overexpressing mice or metallothionein knockout mice had altered sensitivity to carbon tetrachloride and whether supplemental dietary zinc reduced sensitivity to carbon tetrachloride in these genotypes. Metallothionein knockout mice produced no metallothionein and were unable to sequester additional hepatic zinc in response to elevated dietary zinc. Hepatotoxicity, as measured by serum alanine aminotransferase activity, histological analyses and hepatic thiol levels, was greater in the knockout mice than in controls 12 h after carbon tetrachloride treatment but not at later time points (up to 48 h). In contrast, metallothionein-overexpressing mice produced more metallothionein and sequestered more liver zinc than control mice, but hepatotoxicity was similar between genotypes. Supplemental dietary zinc had no effect on hepatotoxicity with either genotype. These data suggest metallothionein null mice were more susceptible to carbon tetrachloride-induced hepatotoxicity than were control mice. However, neither metallothionein overexpression nor supplemental dietary zinc provided further protection.

Alanine Transaminase↗
PubMed2001

Microanatomy of facial vibrissae in the Florida manatee: the basis for specialized sensory function and oripulation.

Sirenians, including Florida manatees, possess an array of hairs and bristles on the face. These are distributed in a pattern involving nine distinct regions of the face, unlike that of any other mammalian order. Some of these bristles and hairs are known to be used in tactile exploration and in grasping behaviors. In the present study we characterized the microanatomical structure of the hair and bristle follicles from the nine regions of the face. All follicles had the attributes of vibrissae, including a dense connective tissue capsule, prominent blood sinus complex, and substantial innervation. Each of the nine regions of the face exhibited a distinct combination of these morphological attributes, congruent with the previous designation of these regions based on location and external morphological criteria. The present data suggest that perioral bristles in manatees might have a tactile sensory role much like that of vibrissae in other mammals, in addition to their documented role in grasping of plants during feeding. Such a combination of motor and sensory usages would be unique to sirenians. Finally, we speculate that the facial hairs and bristles may play a role in hydrodynamic reception.

Animals↗
PubMed1998

Use of the Internet for long-term clinical follow-up.

Use of the Internet for patient-specific consultation across international boundaries has been demonstrated. This report describes the efforts of Baylor College of Medicine and NASA to conduct a telemedicine consultation with Moscow, Russia. Consultation between Russian and American physicians was performed over the Internet with a combination of real-time and store-and-forward techniques. The clinical focus involved a 65-year old Russian scientist who had undergone mitral valve replacement in the United States 5 years earlier. Development of new activity-related chest pain, dyspnea, and intermittent atrial fibrillation led to a consultation with his American cardiologist and cardiac surgeon. Real-time video was supplemented with telephone voice communication to overcome bandwidth limitations. Prior to the video link, the patient's recent history and clinical data were made available via the Internet using file transfer protocol (FTP). The patient's medications, new electrocardiographic findings, and activity status were reviewed. Specific clinical recommendations were made as a result of this telemedicine consultation. This case illustrates the technical factors, clinical implications, and confidentiality issues related to using the Internet for telemedicine consultations and demonstrates that the Internet may provide an alternative means for long-term clinical follow-up of patients.

Aged↗
PubMed1997

Photoreceptor outer segments in aqueous humor from dogs with rhegmatogenous retinal detachments.

OBJECTIVE: To determine whether photoreceptor outer segments can be found in aqueous humor from dogs with rhegmatogenous retinal detachment (RRD). DESIGN: Case series. ANIMALS: 4 dogs with unilateral RRD, 2 dogs with bilateral RRD, 1 dog with unilateral non-RRD, and 1 dog with glaucoma without retinal detachment. PROCEDURE: Aqueous humor samples were fixed in 2% glutaraldehyde and examined by means of transmission electron microscopy. RESULTS: Outer segments were found in aqueous humor from 7 of 8 eyes with RRD but were not found in aqueous humor from dogs with non-RRD or glaucoma. CLINICAL IMPLICATIONS: Photoreceptor outer segments may move into the anterior chamber of eyes with RRD.

Animals↗
PubMed1997

Immunohistochemical localization of cysteine-rich intestinal protein in rat small intestine.

Cysteine-rich intestinal protein (CRIP) is a LIM (cysteine-rich motif of leu-11, isl-1, and mec-3 genes) domain protein with a double zinc finger motif. The protein is abundantly expressed in the intestine, peritoneal macrophages, and peripheral blood mononuclear cells. The function of CRIP is not known. The purpose of this study was to determine the cellular distribution of CRIP in rat intestine, as an initial step toward eventual determination of a function. Immunohistochemical and immunogold labeling electron microscopy using a purified polyclonal rabbit antibody to a synthetic peptide representing a zinc finger domain of rat CRIP were carried out on sections of rat duodenum. Western blotting was used to detect signal specificity of the antibodies. These immunohistochemical and electron microscopy studies showed particularly high abundance of CRIP in the cytoplasmic granules of Paneth cells of the intestine. Some evidence of CRIP expression was also found in cells of the villus tip, but abundance was less than that found in the Paneth cells. The localization of CRIP in Paneth cells and its presence in mononuclear cells suggests that CRIP may be involved in host defense mechanisms and/or tissue differentiation/remodeling processes common to these cell types.

Animals↗
PubMed1996

Differential expression of cysteine-rich intestinal protein in liver and intestine in CCl4-induced inflammation.

Cysteine-rich intestinal protein (CRIP) is a double zinc finger (LIM domain) protein that is developmentally regulated but has an unknown function. CRIP is highly expressed in the intestine, but expression is low in liver. To determine if CRIP expression is regulated under altered physiological status, we used CCl4-induced injury as a model to produce hepatic injury and systemic effects associated with inflammation. Since CRIP is a zinc finger protein and zinc decreases the hepatic response to CCl4, the effect of supplemental dietary zinc (300 mg/kg diet) was also examined. Our results show that this supplemental level of dietary zinc did not affect the index of hepatic injury (plasma alanine aminotransferase), indicating zinc did not have a protective effect. Liver CRIP mRNA increased with CCl4 and CRIP protein was shown by immunohistochemistry to be localized in hepatocytes near the vascular supply. In the intestine, CCl4 caused a transient decrease in CRIP mRNA, but supplemental dietary zinc treatment prevented this decrease. These current results show that CRIP expression changes in response to cellular damage due to acute hepatic injury and are consistent with a functional role for CRIP in proliferation, differentiation, or turnover.

Animals↗
PubMed1995

Histomorphometry of the optic nerves of normal dogs and dogs with hereditary glaucoma.

The beagle dog with hereditary primary open-angle glaucoma, unlike other animal models of human glaucoma, possesses a slowly progressive, sustained elevation of intraocular pressure. The effects of this insidious elevation in intraocular pressure on the axons of the optic nerves of three beagles at early stages of glaucoma and two beagles with advanced signs of glaucoma were compared to the optic nerves of four age-matched normal dogs. Plastic embedded optic nerve cross-sections (1 micron) 1 mm posterior to the lamina cribrosa were osmicated and stained with Toluidine Blue. Axons from 0.2 to > 2.0 microns in diameter were counted and measured in 16 cross-sectional regions of equal size within the whole optic nerve using a computerized image analysis system. The mean optic nerve axon diameters in the normal, early glaucomatous, and advanced glaucomatous dogs were 1.53, 1.25 and 1.13 microns respectively. The average total optic nerve axon count in the normal dogs was 148,303. Approximately 16% of the total axonal fibers were counted in each nerve. The counts of optic nerve axons 2.0 microns or greater in diameter were reduced by up to 60% in the central regions of the optic nerves of affected beagles. The large diameter axons of the peripheral optic nerve of the beagle dogs with glaucoma were more resistant to the elevated intraocular pressure. The counts of axons > 0.6 to 0.8 micron in diameter were significantly increased in glaucomatous beagles.

Animals↗
PubMed1993

X-ray microanalysis of ocular melanin in pigs maintained on normal and low zinc diets.

Retinal-choroidal tissues were collected from older sows that were fed either control (100% Zn), intermediate zinc (59% Zn) or low zinc (21% Zn) diets for a 6-month period. The tissues were prepared for elemental energy dispersive X-ray analysis and examined by scanning transmission electron microscopy. Melanosomes of the retinal pigment epithelium and choroidal melanocytes were specifically analysed. The elemental spectra of a specific type of melanosome within a sample region were consistently similar. The elemental spectra of choroidal melanosomes differed slightly from that of RPE melanosomes, having greater levels of calcium, iron and zinc. Changes of the elemental content of both types of melanosomes were observed in the animals that were maintained on low zinc nutrition. Iron and zinc decreased in level, while copper increased. Calcium decreased in the RPE melanosomes of intermediate and low zinc diet animals. However, calcium only decreased in choroidal melanosomes of the low zinc-fed sows, having increased substantially in the intermediate zinc-fed group. Abnormal melanosomes were concomitantly seen in the melanocytes of both the intermediate and low zinc groups.

Animals↗
PubMed1993

Malabsorption of zinc in rats with acetic acid-induced enteritis and colitis.

Acute intestinal inflammation was established in rats by intraluminal administration of acetic acid into loops of distal ileum, proximal jejunum or ascending colon. The study included two control groups of intact (untreated) rats and sham-operated (saline-treated) rats for each intestinal segment. A third group of rats received acetic acid. Histological evaluation demonstrated that acetic acid treatment induced a mild inflammatory response. Two days after treatment, zinc absorption was measured using ligated 10-cm loops of each segment in which 65Zn was injected intraluminally. 65Zn absorption by the ileum, jejunum and colon was markedly reduced in those rats in which inflammation was induced by acetic acid. The liver showed the highest uptake of radioisotope, but the relative tissue distribution generally followed the amount of absorption. The surgical procedure itself seemed to reduce zinc absorption. No changes in [3H]leucine absorption were observed between sham-operated and acetic acid-treated controls. There was no significant serosal-->luminal secretion of intramuscularly injected 65Zn in any of the studied segments. Therefore, based upon the data obtained, we conclude that acetic acid-induced intestinal inflammation reduces absorption of zinc by the small and large intestine, and that a surgical procedure (laparotomy) also reduces zinc absorption. The mechanism of this inflammation is such that malabsorption shows some specificity.

Acetates↗
PubMed1993

Primary open angle glaucomas in the rhesus monkey.

Rhesus monkeys from the closed Cayo Santiago colony of the University of Puerto Rico demonstrate elevated (> or = 22 mm Hg) intraocular pressure in a pattern which significantly favours certain maternal lineage groupings. The colony had remained genetically pure since 1938. Of nine matriarchal lineages (matrilines) examined, two had an incidence of ocular hypertension of more than 40% and six of more than 10%. Information on 18 matrilines is currently located in the colony data base which identifies each individual and its vital statistics. In 1990, six animals were moved to the laboratory in Florida. Among those from a low incidence matriline, we found abnormal optic nerve cups, pallor, reduced function of (mainly peripheral) fields, progression and loss of optic nerve axons in the presence of ocular hypertension. In another individual where the cup/disc ratio for the right eye was 0.7 and left eye 0.4 and outflow facility was normal, we excluded all other causes of optic nerve atrophy, and low tension glaucoma was diagnosed. This female was from a matriline with a low incidence of ocular hypertension. Relatively rapid aging (3-4 years/human year) monkeys with ocular hypertension and familial clustering produce a near ideal glaucoma research model.

Animals↗
PubMed1992

Effect of hyaluronidase on aqueous outflow resistance in normotensive and glaucomatous eyes of dogs.

The anterior chambers in 16 dogs with normotensive eyes and 3 Beagles with glaucomatous eyes were treated with 0, 25, 50, or 100 IU of bovine testicular hyaluronidase. Aqueous outflow resistance was then determined by constant-pressure perfusion of 0.9% NaCl solution for 30 or 60 minutes. In normotensive eyes, 25, 50, or 100 IU of hyaluronidase significantly (P less than 0.02) increased the rate of constant-pressure perfusion compared with that of untreated eyes during 30- or 60-minute perfusions. Treatment of glaucomatous eyes with 25, 50, or 100 IU of hyaluronidase did not significantly increase the rate of constant-pressure perfusion over controls during a 30-minute perfusion. Bovine testicular hyaluronidase at all doses removed the staining of colloidal iron from the trabecular meshwork in normotensive eyes. In Beagles with glaucoma, the trabecular meshworks remained stained with colloidal iron when treated with the hyaluronidase, which suggested that some glycosaminoglycans were resistant to this enzyme's action.

Animals↗
PubMed1991

Analysis of eye lens-specific genes in congenital hereditary cataracts and microphthalmia of the miniature schnauzer dog.

The congenital hereditary cataracts and microphthalmia in the miniature schnauzer dog are inherited by an autosomal recessive mode. To understand the genetic basis of these diseases, the authors purified and analyzed leukocyte deoxyribonucleic acid (DNA) from affected and normal animals using a candidate gene approach. Because the genes that encode the lens-specific proteins, specifically, alpha, beta, and gamma crystallins and the membrane protein (MP26), are known to maintain the structure and function of the lens, the authors used complimentary DNA (cDNA) fragments that corresponded to the above genes to search for the mutations at their loci in the affected animals. They found no evidence of the gene deletion and rearrangement in any of the five loci. In addition, the hybridizable sequences of the dog DNA to the specific probes for the human chromosome 4 and 18 loci, which are reported to be involved in the abnormality of the human eye, seem to be unaffected. These data support the notion that the hereditary cataracts and microphthalmia in the dog may be associated with genes other than those reported for several animal systems.

Animals↗