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Biomedical subjects

D Segal

Publications and source records attributed to D Segal.

At least 127 records · Page 7Linked to original sources
PubMed1985

The Drosophila EGF receptor gene homolog: conservation of both hormone binding and kinase domains.

Chicken v-erB probe was used to isolate a unique clone of Drosophila melanogaster DNA. It maps by in situ hybridization to position 57F on chromosome 2. A complete nucleotide sequence of the coding region has been obtained. The putative Drosophila EGF receptor protein is similar in overall organization to the human homolog. It shows three distinct domains: an extracellular putative EGF binding domain, a hydrophobic transmembrane region, and a cytoplasmic kinase domain. The overall amino acid homology is 41% in the extracellular domain and 55% in the kinase domain. Two cysteine-rich regions, a hallmark of the human ligand-binding domain, have also been conserved. Fusion of the coding sequences of the kinase and extracellular domains generating the receptor gene must have occurred over 800 million years ago.

Amino Acid Sequence↗
PubMed1985

Shortvein, a new component of the decapentaplegic gene complex in Drosophila melanogaster.

Our laboratory has been concerned with the structure and function of the decapentaplegic gene complex (DPP-C) in Drosophila melanogaster. To define the boundaries of the complex, we have studied the genetics of mutations allelic to a previously discovered mutation shortvein (shv), known to reside near decapentaplegic. We found that shortvein resides distal to Hin-d and dpp within the same polytene chromosome doublet, 22F1-2. Lesions in shv can affect not only the formation of the wing veins but also can interfere with normal development of parts of the adult and/or be lethal. Like those of dpp mutants, the shv-associated adult abnormalities affect distal epidermal structures. Some shv lesions cause a larval lethal syndrome which is associated with an unusually long larval stage (ca. five to six times its normal duration). Lesions in shv exhibit an involved pattern of complementation with dpp mutations, indicating that both shv and dpp are parts of a single gene complex. A subset of the array of mutant phenotypes displayed by shv/dpp trans-heterozygotes appear to be dpp-specific phenotypes; we interpret these as reflecting an inactivation effect of certain shv alleles on dpp functions. The other abnormalities displayed by these trans-heterozygotes appear to be shv-specific defects; we view these as indicating an inactivation effect of certain dpp mutations on shv functions. Furthermore, embryonic lethal (EL) mutations within the DPP-C exhibit allelic interactions with all shv mutations. We conclude that the shortvein region represents a newly identified integrated portion of the DPP-C.

Alleles↗
PubMed1985

Defective responsiveness of adenylate cyclase to forskolin in the Drosophila memory mutant rutabaga.

The Drosophila memory mutant rutabaga (rut) has been previously shown to have a defective subpopulation (or functional state) of the enzyme adenylate cyclase. We report here that the reduced adenylate cyclase activity is also associated with a defective responsiveness of the enzyme to forskolin. Forskolin activation isotherms of the enzyme in normal membranes reveal low- and high-affinity forskolin-interacting components; the residual enzyme in the mutant shows a smaller proportion of the high-affinity response. In addition, in mutant membrane preparations, forskolin fails to shift the Km of the enzyme for free Mg2+ and for MgATP, in contrast to the situation in the normal tissue. The defect in the responsiveness to forskolin in rut is even more pronounced in a Lubrol-solubilized enzyme preparation, and is due to intrinsic properties of the cyclase system rather than to the absence (or presence) of a soluble, or detergent solubilized, factor in rut. The reduced forskolin responsiveness maps to the X chromosomal segment 12F5-6 to 13A1-5, within the region previously reported to span the locus that controls both the abortive memory and the lack of Ca2+-stimulation of adenylate cyclase in rut17. The possible relevance of the findings to postulated molecular mechanisms of short-term memory formation is discussed.

Adenylyl Cyclases↗
PubMed1985

Functional bracing and rehabilitation of ankle fractures.

For normal daily activities, 10 degrees of ankle dorsiflexion is essential. Plantiflexion follows dorsiflexion and exceeds it by an average of 5 degrees. Normal ankle motion takes place with the talus rotating on an obliquely oriented axis distal to the tips of the medial and lateral malleolus. Mortise widening of less than 1 mm accommodates the talus with the fibula apparently rotating along its vertical axis. Ankle fractures treated nonsurgically will regain functional range of motion if immobilization in equinus is avoided and early weight-bearing with early functional bracing is applied. With the aid of a functional brace, fractures treated surgically may start weight-bearing and exercise within five to seven days, provided all fracture components have been stabilized. The functional brace allows dorsiflexion and plantiflexion via a rigid hinge and reduces rotational stresses acting on the fractured ankle.

Adult↗
PubMed1985

Clinical application of computerized axial tomography (CAT) scanning of calcaneus fractures.

CAT scanning of calcaneal fractures with the 30 degree coronal or the transverse plane provides useful information not available on conventional roentgenograms. Joint alignment, displacement of fragments, and the integrity of the medial wall are key factors in deciding whether surgical reconstruction is indicated and what surgical approach to use--medial, lateral, or both. Examples of such information obtained on eight patients with calcaneal fractures is reported comparing CAT scan results to conventional roentgenograms. CAT scans can be used also with the foot immobilized in a cast.

Calcaneus↗
PubMed1984

Silicon compounds as substrates and inhibitors of acetylcholinesterase.

Several trimethylsilyl derivatives were found to be ligands of acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7): trimethylsilylethyl acetate (III) and trimethylsilylmethyl acetate (V) are substrates of the enzyme, whereas trimethylsilylethanol (VIII) is a competitive inhibitor. The silicon compounds have kinetic parameters similar to those of their carbon analogues, except for trimethylsilylmethyl acetate, which is a substrate of acetylcholinesterase, whereas its carbon analogue is not susceptible to enzymic hydrolysis.

Binding, Competitive↗
PubMed1984

Augmentation of the atrophic maxilla with interpositional autogenous bone grafts.

Extreme ridge atrophy is a significant problem when it occurs in the maxilla, since inadequate denture function, as well as poor facial aesthetics, commonly result. Use of the Le Fort I osteotomy of the maxilla with interpositional iliac cortico-cancellous bone grafts is a predictable method of ridge augmentation in severe cases. In our experience, secondary vestibuloplasty has not been necessary prior to construction of new prostheses. Patient satisfaction has been excellent.

Alveolar Ridge Augmentation↗
PubMed1984

Playing doctor, seriously: graduation follies at an American medical school.

In American medical schools, the period of time between the announcement of internships and graduation is known as FYBIGMI, for "Fuck You Brother I Got My Internship." At University Medical School (pseudonym), as at most American medical schools, this period culminates in an elaborate musical comedy (attended by faculty and relatives) in which faculty are abused, patients are represented in terms of stigmatized stereotypes, and the students demonstrate a profane familiarity with cultural taboos. Using the analytic methods of cultural anthropology, this examination of the FYBIGMI performance at U.M.S. focuses primarily on the seniors' presentation of their newly acquired professional identity, which is constituted in the skits by recurring oppositions to socially stigmatized, medically self-destructive patients. In this oppositional logic, racial stereotypes play a particularly large role. In addition, the seniors establish their new social status by inverting their relationship to their (former) supervisors on a personal basis, and by confronting the audience with their professional ability to treat cultural taboos with profane familiarity. The FYBIGMI theatrical, and its representation of professional identity, is analyzed in relation to a proposed model of the underlying structure of the process of medical education, that is, an escalating dialectic of intimidation and self-congratulation.

Black or African American↗
PubMed1984

Displaced ankle fractures treated surgically and postoperative management.

Ankle fractures are common in young adults, often resulting from athletic activities. They can be subdivided into stable and unstable fractures. The unstable fracture consists of bone or a combined bone and ligamentous injury. In an unstable fracture the talus is displaced 2 mm or more and open reduction with internal fixation is recommended. Good functional results depend on three factors--anatomic restoration of the articulating surfaces, early range of motion, and early weight bearing. The role of early weight bearing is emphasized as a significant factor in contributing to good functional results. Based on our clinical experience with the nonathletic patient, 10 degrees of dorsiflexion is required for normal activities. Dorsiflexion has been noted to be a significant movement, and its limitation causes more disability than limited plantar flexion. A below-knee orthosis was described that enables the patient to ambulate and exercise dorsiflexion and plantar flexion, minimizing rotational forces acting on the ankle.

Ankle Injuries↗
PubMed1982

The association of amyloid deposits and osteoarthritis.

Ten of eighteen consecutive patients who underwent total knee or hip arthroplasty for osteoarthritis had amyloid present in the surgically removed articular tissues. It was found in 6 of 13 cartilage specimens, 4 of 18 articular capsules, and 2 of 16 synovial membranes. In 3 of the cartilage specimens, the amyloid was adjacent to focal deposits of calcium pyrophosphate dihydrate crystals. Therefore, deposits of amyloid are not uncommon in osteoarthritis and may be more than incidental findings.

Age Factors↗
PubMed1982

Lack of behavioral evidence for dopamine autoreceptor subsensitivity after acute electroconvulsive shock.

A single electroconvulsive shock (ECS) delivered 7 days previously produced a significant decrease in spontaneous locomotion and rearing in non-habituated rats but did not alter the inhibition of these behaviors produced by low dose apomorphine administration. As such apomorphine effects are thought to be mediated by dopamine (DA) autoreceptors, these data are not consistent with previous reports that the ECS treatment produces a persistent subsensitivity of DA autoreceptors.

Animals↗