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Biomedical subjects

R E Stevens

Publications and source records attributed to R E Stevens.

36 records · Page 2Linked to original sources
PubMed1985

Blood staining of the cornea. Light microscopic and ultrastructural features.

Eleven blood-stained corneas were examined by light and transmission electron microscopy at intervals ranging from one month to seven years after initial staining occurred. Blood staining in each case was associated with focal loss of endothelial cells or endothelial degenerative changes and elevated intraocular pressure. Globules of erythrocytic breakdown products penetrated the discontinuous endothelium and intact Descemet's membrane. Large deposits, primarily extracellular, displaced but did not interrupt the stromal lamellae. Keratocytes in blood-stained corneas contained erythrocytic breakdown products and hemosiderin, and were remarkable for extensive degenerative changes in contrast to keratocytes in areas of cleared cornea, which contained smaller amounts of hemosiderin and were relatively normal. After one year, clearing could be seen to involve peripheral and posterior stroma, and to a lesser degree, the anterior stroma. We found no evidence to support the contention that blood-derived macrophages play a role in the clearing of erythrocyte debris. The stereotyped pattern of peripheral, posterior, and anterior stromal clearing observed seems to be consistent with diffusion of hemoglobin breakdown products out of the cornea as the primary mechanism of clearing.

Blood↗
PubMed1983

Inadequacy of APUD concept in explaining production of peptide hormones by tumours.

The amine precursor uptake and decarboxylation (APUD) system of cells has been claimed to derive from the embryological neural crest. This assertion has been uncritically accepted. There is much contradictory evidence, especially about the origin of the gastrointestinal and respiratory APUD cells. There is further evidence that the embryological derivation of a particular cell does not relate to the possibility of ectopic peptide hormone synthesis by malignant tumours arising from that cell type. There are many reports of APUD activity by endodermally and mesodermally derived tumours, and of "APUDomas" with endodermal microscopic features. It seems that the concept of dedifferentiation explains the observed data much more satisfactorily and that the presence of double minute chromosomes may denote gene amplification and cellular production of peptides.

APUD Cells↗
PubMed1983

Failure of splenic implants to protect against fatal postsplenectomy infection.

Overwhelming postsplenectomy infection is not a phenomenon confined to children. In all age groups, splenic trauma that requires surgery should be managed by splenorrhaphy if possible. Autoimplantation of splenic fragments into omental pockets has been performed in the few patients we have seen who required splenectomy. A case has been presented in which these small implants failed to protect a 61 year old woman from the development of fatal pneumococcal sepsis. The patient had received a pneumococcal vaccination, and her implants had shown activity on radionuclide scanning. Concerns about critical splenic mass, blood supply to the implant, and hepatic function require further study before this technique can be considered efficacious.

Female↗
PubMed1982

Alternatives to splenectomy in adults after trauma. Repair, partial resection, and reimplantation of splenic tissue.

Splenectomy results in a lifelong risk of overwhelming infection in the adult as well as the child. This has prompted our current enthusiasm for splenic salvage in trauma patients. A number of alternatives to total splenectomy exist; however, the complications that result from splenic salvage must not exceed the risk incurred by loss of this organ. Splenorraphy can be performed safely in the majority of patients despite associated intraabdominal injuries. When splenectomy is necessary, reimplantation of splenic tissue is feasible. The efficacy of this technique is preventing postsplenectomy sepsis remains to be established.

Adolescent↗
PubMed1981

Long-term changes in corneal endothelium following intraocular lens implantation.

To understand the long-term effects of intraocular lens implantation on corneal endothelium, 52 eyes with intraocular lens implantations and 35 eyes with simple cataract extractions were studied using clinical specular microscopy. Endothelial photographs were obtained preoperatively and at least four times in the postoperative period in each case. The postoperative period ranged from 16 to 43 months. Our observations demonstrated that intraocular implants produce a greater magnitude of endothelial cell damage and iris-supported lenses have a more deleterious effect on the corneal endothelium compared with anterior chamber lenses. Seventy-one percent of the eyes with intraocular implants demonstrated precipitates on the endothelium with 16% developing guttata-like areas. All these changes were progressive with time with no such phenomenon occurring in eyes with simple cataract extractions. The progressive endothelial cell damage may be a sequel of chronic, smoldering uveitis associated with intraocular implants.

Aged↗
PubMed1980

Morphologic variations in graft endothelium.

The morphologic features of corneal endothelium were studied with clinical specular microscopy in 33 cases of clear corneal transplants. A complete morphologic profile of the corneal endothelium, which included cell density, mean cell area, and variation in cell size (polymegethism), was obtained with an automated, pattern-analysis system. Our observations demonstrated variation in all these parameters of graft endothelium with time, indicating that graft endothelium is in a state of transition during healing and that the end point to the healing process is still to be determined.

Adult↗
PubMed1979

Automated pattern analysis of corneal endothelium.

A proper understanding of the endothelial cell morphology of the cornea is of great significance to the corneal surgeon. Specular microscopy allows direct visualization of endothelial cell morphology and a proper analysis of these data needs automated computerized type of systems. Automated pattern analysis seems to offer a good option in this direction. From our experience it appears that such systems can be used with great advantage in the analysis of endothelial cell morphology. The data obtained from such analysis help to develop some indices for various facets of endothelial cell morphology.

Cell Count↗
PubMedDate not supplied

Patient, revenue and cost analyses for medical practices.

Authors Robert Stevens and Thomas Chatham write that revenue and cost analysis can be performed by medical groups from historical data they maintain. Such analysis provides the administrator with a data base for developing realistic objectives and identifying areas which should be more fully developed or even eliminated.

Costs and Cost Analysis↗
PubMedDate not supplied

A 12-week clinical trial determining the efficacy of synthetic conjugated estrogens, A (SCE), in the treatment of vasomotor symptoms in menopausal women.

OBJECTIVE: To compare the clinical effects of a new oral synthetic conjugated estrogens, A (SCE), versus placebo in a clinically relevant population on the reduction in the mean number of moderate to severe vasomotor symptoms. DESIGN: A total of 120 healthy pre- and postmenopausal women (72 active, 48 placebo) were enrolled into a randomized, placebo-controlled, double-blind, multi-center clinical trial. Women of all races were enrolled, using minimal inclusion and exclusion criteria. Each subject received either orally administered SCE, in doses of 0.3 mg, 0.625 mg or 1.25 mg per day, or placebo. Analysis of variance was performed on the primary efficacy variable (change from baseline to weeks 4, 8, and 12 in the mean number of moderate to severe vasomotor symptoms). RESULTS: Changes in moderate to severe vasomotor symptoms in the intent to treat population showed statistically significant differences between the active and placebo treatments at week 4 (P < .022), week 8 (P < .010), and week 12 (P < .010). By week 12, the mean percentage reduction in moderate to severe vasomotor symptoms was 81%, from an average baseline of 96.8, to 16.5 hot flashes per week for the active treatment group. The overall incidence of expected estrogen-related adverse effects was modest. Laboratory tests and vital sign measurements did not reveal clinically significant changes or abnormalities from screening to the final visit in either treatment group. CONCLUSIONS: The results of this study confirm the efficacy and safety of SCE in the treatment of moderate to severe vasomotor symptoms in menopausal women. In addition, the study also demonstrated that the use of more liberal entry criteria did not materially affect the efficacy outcome.

Administration, Oral↗