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Biomedical subjects

J Valenti

Publications and source records attributed to J Valenti.

10 recordsLinked to original sources
PubMed1982

Adherence of Pseudomonas aeruginosa to the mouse cornea. Epithelial v stromal adherence.

Adherence of Pseudomonas aeruginosa to the cornea is the first step in the pathogenesis of Pseudomonas corneal ulceration. To determine the roles of epithelial and stromal adherence, a quantitative in vivo model of adherence was developed in the mouse. More than twice as many organisms were recovered from mouse corneas in which two linear abrasions were created compared with corneas totally denuded of epithelium. Scanning electron microscopy demonstrated poor adherence of Pseudomonas to bare stroma, but large numbers of organisms were seen adhering to the injured edge of epithelium. This study supports the concept that corneal trauma predisposes to Pseudomonas corneal ulceration by creating an injured epithelial edge as a site for adherence of the organisms, rather than by exposing areas of bare stroma susceptible to penetration by the organisms.

Adhesiveness↗
PubMed1981

Endothelial damage after anterior radial keratotomy. An electron microscopic study of rabbit cornea.

Anterior radial keratotomy was performed on the left eyes of 21 rabbits. Specimens were taken for electron microscopic examination at intervals during a three-month period. The corneas were acutely inflamed for three days after surgery. Some endothelial cells beneath the incisions were damaged, and distended intercellular spaces were seen. Deeper incisions seemed to produce more severe damage. With increasing time after surgery, some of the damaged endothelial cells seemed to be recovering, while others in the areas between the incisions and in the center of the cornea were degenerating. Three months after surgery, the endothelium had recovered, but some of the peripheral intercellular spaces still were distended. These findings may be the result of continuous blinking in combination with the structural weakness of the cornea, rather than a result of chronic postsurgical inflammation.

Animals↗
PubMed1981

Electron microscopic study of epithelial downgrowth after penetrating keratoplasty.

An electron microscope study of 2 cases of epithelial downgrowth after penetrating keratoplasty is presented. Several differences were observed between the normal epithelium and downgrowth epithelium at the ultrastructure level. At the advancing edge of the downgrowth a flattened and fibroblastic endothelium was still present. An interaction area was observed between these 2 tissues. The epithelial downgrowth usually has 5 to 6 layers of cells and either replaces damaged endothelium or destroys it as it advances. The attachment of this downgrowth tissue to the Descemet's membrane at the centre of the graft seemed looser than attachment of a normal epithelium to Bowman's membrane. Near the host-graft junction the downgrowth epithelium, with basement membrane, was tightly attached to a fibrous retrocorneal membrane. Clinical and histological findings suggest that the absence of endothelium assists in the advance of the epithelial downgrowth, but it is not an essential factor. The causes of this downgrowth are thought to be (1) a thin host cornea; (2) incomplete cutting and wound incarceration of Descemet's membrane; and (3) tight sutures with disruption of an old cataract wound.

Adult↗
PubMed1980

Electron microscopic study of recurrent Reis-Bücklers' corneal dystrophy.

We studied the cornea of a 51-year-old woman with recurrent Reis-Bücklers' dystrophy with the transmission electron microscope. The patient had had a superficial keratectomy nine years earlier. The epithelium removed in a second keratectomy contained distended endoplasmic reticulum and swollen mitochondria. The basal layer showed some cells in mitosis and a slight increase in the number of dark cells. The anterior portion of the removed stroma contained dense collagen fibrils, with the appearance of curly fibrils, which is characteristic of this disease. There were also severe degenerative changes in the stroma. These changes in the collagen fibers and alterations in keratocytes of the deeper layers were less severe than those of the superficial layer. A biopsy of the bulbar conjunctiva showed reduplication of the basement membrane.

Adult↗
PubMed1978

Corneal storage at room temperature.

Short-term eye banking is based mainly on moist chamber and McCarey-Kaufman medium (M-K medium) preservation. Both involve a controlled 4 C temperature for storage. Warming the cornea to room temperature, however, drastically affects the endothelial viability. On enzymatic staining and histological study, the M-K medium-stored rabbit corneas had more normal endothelium than did "moist chamber" eyes when storage was prolonged for seven days at room temperature. In human corneas that were kept at 4 C for 24 hours and then exposed to a temperature of 25 C, destruction of organelles had occurred by six hours and was increased by 12 hours. Corneas that were kept in M-K medium had relatively intact endothelium after four days, but cell disruption and vacuolation was present by the seventh day. The M-K medium, therefore, affords protection to tissue warmed to room temperature, where metabolic activity is resumed.

Adolescent↗
PubMed1977

Corneal endothelium damage with intraocular lenses: contact adhesion between surgical materials and tissue.

Intraocular lenses destroy corneal endothelial cells by contact adhesion between the acrylic lens and endothelial surfaces during cataract surgery. Glass and rubber surgical glove surfaces produce similar cell damage. This phenomenon may be important in many surgical procedures and appears to be preventable if a hydrophilic polymer interface is interposed between contacting tissue and the surfaces of materials used.

Acrylic Resins↗
PubMed1976

Scanning electron microscopy of postoperative M-K and moist chamber-stored corneas.

In the present study, using the in vivo test situation which all corneal donor material must meet, we performed penetrating keratoplastics utilizing corneal tissue stored for five days in either M-K medium or conventional moist chambers. Cat corneas stored for five days in M-K medium had a higher incidence of postoperative graft clarity along with an intact endothelial cell layer as determined by scanning electron microscopy than corneas stored in a conventional moist chamber. The endothelium of corneas immediately after moist chamber storage revealed minimal surface alteration which contrasted to the more severely stressed endothelium immediately after M-K storage. However, the M-K stored endothelium survived the trauma of penetrating keratoplasty much better than cells stored in moist chambers.

Animals↗
PubMedDate not supplied

[Effect of reinfection on the development of rats infected with Trypanosoma cruzi].

The present study was undertaken in order to demonstrate that reinfection could modify parasitemia, serum antibodies, electrocardiographic patterns and/or myocardial lesions already observed in a rat model. Experimental groups IG: rats infected at weaning with 1 x 10(6) T. cruzi; RG: same as IG plus reinoculations each 30 days until completion on day 150; IG1: 51 day old infected rats; C: controls. A high parasitemia was detected in IG and RG until day 20 showing a tendency to become negative on day 30. No parasites were observed in RG after the first reinoculation which could not be attributed to the old age of the host since there was no parasitemia in IG1. Xenodiagnosis were negative in all three groups. Serum antibodies were not significantly modified in RG in comparison with IG, except for 7S antibodies, since RG showed higher titres in some days under study. No distinct patterns of basal ECG were observed in infected rats. The ajmaline test reduced the heart rate (HR) showing no treatment dependence. The PR, QaT and QRS were significantly lengthened in all groups regarding the basal one (p less than 0.05), except for the QaT in C. Besides, the PR and QaT alterations were greater in the infected rats (p less than 0.05). There was also present a wide variety of electric axis orientations, regarding the basal value, accompanied by morphological changes more evident in the RG. The incidence of cardiac lesions histologically detected in the infected group was significantly higher than in C (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Ajmaline↗