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Biomedical subjects

S M Cohen

Publications and source records attributed to S M Cohen.

At least 109 records · Page 6Linked to original sources
PubMed1997

Long-range action of Wingless organizes the dorsal-ventral axis of the Drosophila wing.

Short-range interaction between dorsal and ventral (D and V) cells establishes an organizing center at the DV compartment boundary that controls growth and specifies cell fate along the dorsal-ventral axis of the Drosophila wing. The secreted signaling molecule Wingless (Wg) is expressed by cells at the DV compartment boundary and has been implicated in mediating its long-range patterning activities. Here we show that Wg acts directly, at long range, to define the expression domains of its target genes, Distal-less and vestigial. Expression of the Achaete-scute genes, Distal-less and vestigial at different distances from the DV boundary is controlled by Wg in a concentration-dependent manner. We propose that Wg acts as a morphogen in patterning the D/V axis of the wing.

Animals↗
PubMed1997

buttonhead does not contribute to a combinatorial code proposed for Drosophila head development.

The Drosophila gap-like segmentation genes orthodenticle, empty spiracles and buttonhead (btd) are expressed and required in overlapping domains in the head region of the blastoderm stage embryo. Their expression domains correspond to two or three segment anlagen that fail to develop in each mutant. It has been proposed that these overlapping expression domains mediate head metamerization and could generate a combinatorial code to specify segment identity. To test this model, we developed a system for targeted gene expression in the early embryo, based on region specific promoters and the flp-out system. Misexpression of btd in the anterior half of the blastoderm embryo directed by the hunchback proximal promoter rescues the btd mutant head phenotype to wild-type. This indicates that, while btd activity is required for the formation of specific head segments, its ectopic expression does not disturb head development. We conclude that the spatial limits of btd expression are not instructive for metamerization of the head region and that btd activity does not contribute to a combinatorial code for specification of segment identity.

Animals↗
PubMed1997

Indocyanine green angiography of a laser-induced retinal-choroidal venous anastomosis.

A patient with a central retinal vein occlusion and cystoid macular edema whose visual acuity was 20/200 was treated with heavy argon laser photocoagulation to a peripheral retinal vein. The patient's visual acuity improved to 20/20. An indocyanine green angiogram performed 5 months following laser therapy showed that a retinal-choroidal venous anastomosis had formed at a point where a large retinal vein crossed over a large choroidal vein. Because indocyanine green angiography can locate large choroidal veins, it may be helpful in guiding this laser treatment.

Choroid↗
PubMed1997

Endophthalmitis caused by Serratia marcescens.

BACKGROUND AND OBJECTIVE: To describe the clinical features and treatment outcomes of 10 patients with culture-proven Serratia marcescens endophthalmitis. PATIENTS AND METHODS: Records from the microbiology laboratory for the period from January 1980 through June 1993 were reviewed. Ten patients were identified who had positive anterior chamber or vitreous cultures and clinical signs of endophthalmitis. The medical records for these 10 patients were reviewed, and the patients were contacted for reexamination when possible. RESULTS: All 10 cases of S. marcescens endophthalmitis occurred after ocular surgery. Eight eyes received intraocular antibiotics and 2 eyes were primarily enucleated or eviscerated. All organisms were sensitive to aminoglycosides and to ceftazidime. Repeat vitreous cultures were positive in 5 cases despite appropriate initial therapy with intravitreal and intravenous antibiotics. Final visual acuity was 20/400 or better in 4 of 10 eyes. A total of 4 eyes were enucleated or eviscerated at final follow-up. Eyes with light perception or better visual acuity had a mean follow-up of 23 months. CONCLUSION: S. marcescens can cause persistent endophthalmitis despite appropriate intravitreal and systemic antibiotic therapy. Eyes with S. marcescens endophthalmitis have a poor visual prognosis.

Aged↗
PubMed1996

Antagonistic interactions between wingless and decapentaplegic responsible for dorsal-ventral pattern in the Drosophila Leg.

Subdivision of the limb primordia of Drosophila into anterior and posterior compartments triggers cell interactions that pattern the legs and wings. A comparable compartment-based mechanism is used to pattern the dorsal-ventral axis of the wing. Evidence is presented here for a mechanism based on cell interaction, rather than on compartment formation, that distinguishes dorsal from ventral in the leg. Mutual repression by Wingless and Decapentaplegic signaling systems generates a stable regulatory circuit by which each gene maintains its own expression in a spatially restricted domain. Compartment-independent patterning mechanisms may be used by other organisms during development.

Animals↗
PubMed1996

Two distinct mechanisms for long-range patterning by Decapentaplegic in the Drosophila wing.

Secreted signalling molecules provide cells with positional information that organizes long-range pattern during the development of multicellular animals. Evidence is presented that localized expression of Decapentaplegic instructs cells about their position along the anterior-posterior axis of the Drosophila wing in two distinct ways. One mechanism is based on the local concentration of the secreted protein; the other is based on the ability of the cells to retain an instruction received at an earlier time when their progenitors were in close proximity to the signal. Both mechanisms are involved in axis formation.

Animals↗
PubMed1996

Specification of the wing by localized expression of wingless protein.

Limb development in Drosophila depends on subdivision of the limb primordia into functional units called compartments. Cell interactions across compartment boundaries establish pattern-organizing centres that control growth and specify cell fates along the anteroposterior (AP) and dorsoventral (DV) axes of the limbs. AP subdivision of the disc primordia is inherited from the embryonic ectoderm. DV subdivision of the wing disc occurs during the second larval instar through localized expression of the apterous protein (Apterous) in dorsal cells. A third major subdivision of the wing disc into wing and body-wall compartments also occurs in the second instar. Here we show that specification of the wing primordium in early second instar depends on activity of the AP patterning system but not the DV system. These results define two distinct roles for the wingless gene: a primary role in specifying the wing primordium, and a subsequent role mediating the patterning activities of the DV compartment boundary.

Animals↗
PubMed1996

Controlling growth of the wing: vestigial integrates signals from the compartment boundaries.

In the past few years it has become apparent that the anterior/posterior (A/P) and dorsal/ventral (D/V) compartment boundaries serve as the source of long-range signals that organize the A/P and D/V axes of the Drosophila wing. Recent work suggests that the vestigial gene may function as a nodal point through which the growth-controlling activity of these two patterning systems is integrated.

Animals↗
PubMed1996

Bilaterality of idiopathic macular holes.

BACKGROUND: There has been wide variation in estimates of the incidence of bilateral idiopathic macular holes in the literature. This report of a large series of patients with macular holes provides further information regarding incidence of bilaterality, interval between onset in the first and the second eye, and visual outcome. METHODS: A retrospective chart review was done of 550 patients with idiopathic macular holes examined at the Bascom Palmer Eye Institute between 1968 and 1994. The incidence of bilaterality was estimated from 365 patients in whom the fellow eye was normal at the initial examination. The rate of onset in the fellow eye was evaluated by survival analysis. Mean follow-up was 31 months (median 17 months). RESULTS: Patients with incomplete macular holes (stage 1, aborted stage 1, lamellar) or full-thickness holes had a 19% incidence of bilaterality at 48 months follow-up. In the subset of 32 patients with full-thickness macular holes in the first eye, 13% developed full-thickness holes in the fellow eye within 48 months. The median interval between the onset in the first and in the second eye was 17.5 months. Visual acuity was excellent and stable in eyes with aborted stage 1 and lamellar holes. The visual acuity in the first eye with full-thickness macular hole decreased to 20/200 or worse in 79% of cases within 36 months' follow-up. CONCLUSION: The incidence of bilaterality and poor visual function in the majority of full-thickness idiopathic macular holes by 3 years' duration should be considered when advising patients and planning management.

Aged↗
PubMed1996

Castability optimization of palladium based alloys.

Poor or inconsistent castability often necessitates costly laboratory remakes of cast restorations. This study investigated the effects of burnout temperature and alloy investment compatibility on the castability of selected alloys. In part A nine alloy investment combinations were compared. In part B two alloy-investment combinations at four burnout temperatures were evaluated. Differences in investment, alloy, and/or burnout temperature significantly affected castability. Castability with a poorer casting investment improved with a hotter propane/oxygen fuel source compared with natural (city) gas/oxygen.

Analysis of Variance↗
PubMed1996

The effect of acetaminophen, ibuprofen, and misoprostol on prostaglandin E2 synthesis and the degree and rate of orthodontic tooth movement.

The present study compared the effect of acetaminophen, ibuprofen and misoprostol on PGE2 synthesis and orthodontic tooth movement. Guinea pigs were randomly assigned into one of three test groups or a control group. Each group received study treatments every 12 hours as an orthodontic force was applied to the maxillary incisors. Direct linear measurements of tooth separation were recorded at days 2, 4, 6, 10, and 11, and inflammatory exudate from the periodontal ligament (PDL) space was extracted and quantitatively analyzed radioimmunologically for the presence of PGE2 at days 4 and 9. Comparing the concentration of PGE2 in sample extracts, a significant difference (P = 0.001) was found among drug groups. A highly significant difference was found between the mean tooth separation among the various drug groups (P < 0.001). At day 11 the misoprostol group exhibited 4.49 +/- 0.49 mm of separation; ibuprofen 2.56 +/- 0.11 mm, and the control and acetaminophen groups exhibited similar degrees of tooth separation: 3.31 +/- 0.07 mm and 3.31 +/- 0.08 mm, respectively. A highly significant difference occurred between the mean rates of tooth separation among the various drug groups after day 8 (P < 0.001). Results of this study suggest that acetaminophen is the analgesic of choice for the relief of minor discomfort associated with orthodontic treatment.

Acetaminophen↗
PubMed1996

Analysis of differentiation-associated proteins in rat bladder carcinogenesis.

Uroplakins are the major integral membrane proteins synthesized in terminally differentiated, superficial urothelial cells. Alteration of cell differentiation during rat urinary bladder carcinogenesis was analyzed immunohistochemically for the expression of uroplakins. Expression of uroplakins was compared in N-[4-(5-nitro-2-furyl)-2-thiazolyl]-formamide (FANFT)-, uracil-, sodium saccharin- or sodium ascorbate-induced urothelial simple hyperplasia, papillary-nodular hyperplasia, papilloma and carcinoma. In controls, uroplakins were located only in superficial cells, especially the luminal surface membrane. In FANFT-induced hyperplasia, including simple hyperplasia, intermediate cells also stained and the staining pattern was disorderly and intermittent. In uracil-induced simple hyperplasia, intermediate cells were stained but in an orderly fashion. In sodium saccharin- or sodium ascorbate-induced simple hyperplasia, superficial cells were swollen but alterations were not observed in the staining pattern. In carcinoma induced by FANFT and uracil, uroplakin expression was very disorderly and focal, usually with no expression on surface cells. It appears that disorderly differentiation is an index of bladder malignancy and is an early event in FANFT-induced lesions but a late event in uracil-, sodium saccharin- and sodium ascorbate-induced lesions.

Animals↗
PubMed1996

Sternopleural is a regulatory mutation of wingless with both dominant and recessive effects on larval development of Drosophila melanogaster.

The Drosophila wingless (wg) gene encodes a secreted signaling protein that is required for many separate patterning events in both embryonic and larval development. wg functions in the development of the adult structures have been studied using the conditional mutant wgts and also using regulatory mutations of wg that reduce larval functions. Here we present evidence that Sternopleural (Sp) is another regulatory allele of wg that affects a subset of larval functions. Sp has both a recessive loss-of-function component and a gain-of-function component. The loss-of-function component reflects a reduction of wg activity in the notum and in the antenna. The gain-of-function component apparently leads to ectopic wg activity in the dorsal first and second leg disc and thereby generates the dominant Sp phenotype. Sp and other wg alleles show a complex pattern of complementation. We present evidence that these genetic properties are due to transvection. These results have implications for the genetic definition of a null allele at loci subject to transvection.

Alleles↗
PubMed1996

Use of losartan to examine the role of the cardiac renin-angiotensin system in myocardial dysfunction during ischemia and reperfusion.

To assess the role of angiotensin II (AII) in the development of myocardial dysfunction during ischemia and reperfusion, the effects of either oral pretreatment with 1 mg/kg losartan or treatment with 4.5 mu M losartan in vitro were compared with effects measured in the respective placebo or in vitro control groups in an isolated rat working-heart model. Both groups treated with losartan showed significant improvement (p < 0.005) in functional recovery following 20 min of ischemia compared with the respective control groups. Coronary flow (CF) and cardiac output (CO) were also significantly increased during reperfusion in the drug treatment groups compared with controls (p < 0.05 to p < 0.001). The recovery of mechanical function, CO, and CF was significantly more rapid in hearts from rats treated orally with losartan than in hearts treated with losartan in vitro. As measured by 31P-nuclear magnetic resonance, the changes observed in ATP levels and in intracellular pH during ischemia and reperfusion were essentially the same under either treatment regimen. This article describes the initial observation of a significant reduction in myocardial dysfunction during reperfusion following 20 min of global ischemia in the isolated perfused heart as a result of acute AII AT1 receptor antagonism by losartan administered either directly in vitro or by oral pretreatment.

Adenosine Triphosphate↗
PubMed1996

Paraproteinemias associated with serous detachments of the retinal pigment epithelium and neurosensory retina.

BACKGROUND: Serous retinal and retinal pigment epithelial detachments resembling central serous chorioretinopathy developed in three patients who had paraproteinemias. METHODS: The patients in this study were examined at two institutions, and their charts, photographs, and fluorescein angiograms were reviewed by the authors. Two patients had cryoglobulinemia and one had lgA, lgM benign gammopathy. RESULTS: These patients had decreased central visual acuity and metamorphopsia at the initial examination. All three patients were women. Two patients were taking systemic corticosteroids in tapering doses at the time of the initial examination. The multiple serous retinal pigment epithelial and retinal detachments were unilateral in one patient and bilateral in two patients. Two patients were treated with laser photocoagulation because of chronic visual loss and foveal detachments. At the most recent examination, each patient had visual acuity of 20/30 or better in both eyes and complete resolution of subretinal fluid. CONCLUSIONS: Patients with paraproteinemia may develop multiple serous detachments of the retinal pigment epithelium and of the neurosensory retina. The chorioretinopathy in these patients may have been related to their paraproteinemia, type A personality, corticosteroid use, or a combination of these factors. The final visual acuity in these three patients was good.

Adult↗
PubMed1996

Organizing spatial pattern in limb development.

Recent studies on the development of the legs and wings of Drosophila have led to the conclusion that insect limb development is controlled by localized pattern organizing centers, analogous to those identified in vertebrate embryos. Genetic analysis has defined the events that lead to the formation of these organizing centers and has led to the identification of gene products that mediate organizer function. The possibility of homology between vertebrate and insect limbs is considered in light of recently reported similarities in patterns of gene expression and function.

Animals↗