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Biomedical subjects

R M Davis

Publications and source records attributed to R M Davis.

At least 19 recordsLinked to original sources
PubMed1992

Morphological differentiation and proteoglycan synthesis regulate Alzheimer amyloid precursor protein processing in PC-12 and human astrocyte cultures.

A morphologically differentiated strain of rat pheochromocytoma (PC-12H) metabolically labeled with [35S]methionine and incubated with a phorbol ester displayed reduced 140-kDa and increased 15 kDa bands relative to cells incubated without phorbol ester after immunoprecipitation with antisera elicited by the C-terminal peptide of the Alzheimer amyloid precursor protein (APP). These bands correspond to glycosylated full length APP and a C-terminal fragment previously reported by Anderson et al. (Neurosci. Lett. 120:126-128, 1991) to result from a cleavage within the amyloidotic A4 region of APP, which releases a 120 kDa extracellular fragment. The 15 kDa fragment, not immunoprecipitated with an antisera elicited by the N-terminal portion of A4 amyloid, is nonamyloidogenic. Incubation of these cells with p-nitrophenylxyloside, known to inhibit proteoglycan formation, also increased this nonamyloidogenic cleavage of APP. In contrast to these results, an undifferentiated low passage PC-12-L strain constitutively displayed rapid nonamyloidogenic APP cleavage. Incubation of PC-12-L with phorbol ester did not affect the relative abundance of 140 or 15 kDa bands. Growth of PC-12-L with 7 S NGF or dibutyryl cAMP resulted in increased morphological differentiation and decreased APP cleavage which was now phorbol-inducible. Similar analyses of dividing and senescent human astrocytes and normal and F-AD fibroblasts indicate 5-fold lower rates of mid-A4 APP cleavage. Phorbol esters decreased the 140 kDa APP band without affecting the intensity of the 15 kDa band in these cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Amyloid beta-Protein Precursor↗
PubMed1991

Comparison of intraocular lens fixation techniques performed during penetrating keratoplasty.

We reviewed the charts of 41 patients who had undergone penetrating keratoplasty, anterior vitrectomy, and placement or exchange of an intraocular lens during a two-year period with a median follow-up time of 15 months (range, five to 26 months). The median preoperative visual acuity was 20/400 (range, 20/40 to hand motions). The median postoperative visual acuity was 20/70 (range, 20/25 to hand motions). Of 41 corneal grafts, 38 (93%) remained clear. New intraocular lenses were inserted by anterior chamber, iris, or transscleral fixation. The median visual acuity was 20/70 for the anterior chamber lens group, 20/100 for the iris fixation group, and 20/70 for the transscleral fixation group. Analysis of variance demonstrated no significant difference by type of fixation in postoperative visual acuity, central corneal thickness, and intraocular pressure.

Adult↗
PubMed1991

Assessing community interventions to reduce smoking.

Few major, community-based antismoking programs have undergone specific evaluation in developed countries; the number is even lower in developing countries. Yet not all evaluation need be elaborate, expensive, or overly time-consuming. Data on tobacco trade, import and export, taxation, mortality, and morbidity may already exist within government departments and can be used for evaluation. Published information from the tobacco industry may be obtained easily in trade journals and annual reports. Universities and international and overseas national health agencies may offer information, assistance, and expertise. Indirect evaluation of the importance of any particular antismoking intervention can be measured by how strongly the tobacco industry opposes that measure.

Community Participation↗
PubMed1991

Isolation and characterization of a new human microsporidian, Encephalitozoon hellem (n. sp.), from three AIDS patients with keratoconjunctivitis.

A new human microsporidian was isolated from cultures of Madin-Darby canine kidney cells incubated with conjunctival scrapings or corneal tissues from three AIDS patients with keratoconjunctivitis. The three isolates were morphologically similar to Encephalitozoon cuniculi. The spores averaged 1 x 1.5-2.0 microns, had six to eight polar filament coils, displayed monokaryotic nuclei, and possessed relatively thick endospores with irregularly shaped exospores. Organisms developed within a parasitophorous vacuole. By SDS-PAGE analysis, the three isolates appeared to be identical but were different from E. cuniculi. Identical banding patterns on Western blots of the three isolates were expressed by each patient's serum. By Western immunoblotting, murine antisera to E. cuniculi reacted to several antigens of the new AIDS-related microsporidian, whereas murine antisera bound weakly to Nosema corneum. The name Encephalitozoon hellem (n. sp.) is proposed to identify this new human microsporidian.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Ciliary sulcus anatomical dimensions.

Trans-scleral ciliary sulcus and iris suture fixation of posterior chamber intraocular lenses (IOLs) in eyes without posterior capsular support are techniques gaining wider acceptance. Primary indications are IOL exchange in pseudophakic bullous keratopathy and secondary IOL insertion in aphakia. Accurate placement of the posterior chamber lens loops within the ciliary sulcus is based on knowledge of ciliary sulcus anatomy. Nineteen postmortem eyes were sectioned in the coronal plane to expose the posterior iris border and the ciliary body. Ciliary sulcus diameters were measured, and the mean diameter was 11.0 +/- 0.37 mm. The mean limbus-ciliary sulcus distance was then measured by passing 26-gauge needles through the ciliary sulcus and sclera. The mean limbus-ciliary sulcus distance was 0.9 mm. These measurements may guide ophthalmic surgeons in choosing appropriate IOL designs for IOL exchange or secondary IOL procedures.

Ciliary Body↗
PubMed1991

National programs for smoking cessation.

The smoking cessation effort has made tremendous progress since the 1964 Report of the Surgeon General described the health hazards of smoking. The impact of these efforts on smoking is particularly impressive when the current smoking level is compared with levels of smoking projected from trends apparent before that 1964 report, levels that might have been reached if there had been no national stop-smoking campaign. Because of the campaign, an estimated 35 million Americans were nonsmokers in 1985 who would otherwise have been smokers. If these figures are projected to the year 2000, the campaign will have postponed more than 2 million deaths. Therefore, reducing the prevalence of smoking in adults from about 40% in 1964 to 29% in 1987 can be considered a tremendous public health achievement. Among those who did take up smoking, there is also reason for some optimism. By 1987, more than 38 million Americans had quit smoking; this figure represents nearly half of all living adults who ever smoked. The 1990 Report of the Surgeon General gave a positive message to the 50 million Americans who continue to smoke by describing the health benefits of quitting for all the major smoking-related diseases.

Female↗
PubMed1990

Human neuroectoderm-derived cell line secretes fibronectin that shares the HNK-1/10C5 carbohydrate epitope with neural cell adhesion molecules.

A human malignant melanoma cell line, Melur, secretes several glycoproteins that contain a unique carbohydrate epitope shared by neural cell adhesion molecules and recognized by the monoclonal antibodies HNK-1, L2, and 10C5. In this report, we present evidence that one of the major melanoma glycoproteins containing the HNK-1/10C5 epitope is the cell adhesion molecule, fibronectin, or a fibronectin-like molecule. Melanoma-derived fibronectin was isolated from serum-free conditioned medium by gelatin-Sepharose affinity adsorption and shown to react with monoclonal antibodies HNK-1 and 10C5 in Western blot analysis. HNK-1-containing fibronectin was purified on a gelatin-Sepharose column followed by an affinity column using a monoclonal antibody against the HNK-1 carbohydrate. The purified HNK-1-fibronectin then could be incorporated into the extracellular matrix of hamster fibroblasts in vitro, and such a matrix was detectable using the HNK-1 monoclonal antibody in an immunofluorescence assay. Of the seven neuroectoderm-derived tumor cell lines tested, only the Melur melanoma cell secreted fibronectin containing the HNK-1 carbohydrate. Identification of human neuroectoderm-derived fibronectin as a potential carrier of the HNK-1 carbohydrate suggests a new role for fibronectin in neural development and regeneration, and represents a new model for studying the function of this carbohydrate domain in neural cell adhesion.

Antigens, Differentiation↗
PubMed1979

Production of anti-rubratoxin antibody and its use in a radioimmunoassay for rubratoxin B.

Rubratoxin B was coupled to ovalbumin using 1-ethyl-3-(3-dimethyaminopropyl) carbodiimide HCl (ECDI) in high concentration at pH 8.0. Under these conditions it was possible to couple 13 moles of rubratoxin B per mole of ovalbumin. The conjugate was used for immunization of rabbits, and anti-rubratoxin antibody was produced. A radioimmunoassay for rubratoxin B was developed which could detect 0.1 microgram to 10 microgram of toxin using 0.21 microgram of [14C] rubratoxin (0.47 Ci/mole, 2.0 x 10(9) dpm/microgram) and 0.125 ml of anti-rubratoxin antibody.

Animals↗
PubMed1979

Production of [14C]rubratoxin B.

[14C]rubratoxin B was produced by culturing Penicillium rubrum Stoll for 13 days at 22 degrees C in medium containing [14C]glucose. The most efficient incorporation of glucose into rubratoxin occurred when Raulin-Thom medium enriched with 2.5% malt extract was supplemented with 2.5% added glucose. The presence of 1.0 mCi of radioactivity in 50 ml of medium with 2.5% added glucose resulted in the production of 38 mg of labeled, chromatographically pure rubratoxin with a specific activity of 0.47 Ci/mole.

Animals↗
PubMed1979

Development of the tibiotarsus in the chick embryo: biosynthetic activities of histologically distinct regions.

The dynamics of the histological changes which occur in the distal half of the tibial portion of the embryonic chick tibiotarsus from day 8 to day 18 of incubation are correlated with the capacities of histologically distinct zones to incorporate isotopic precursors into mucopolysaccharides and collagen. At the distal end of the tibia, which abuts the suture line formed by the fusion of the two tarsals with the tibia, there persists throughout embryonic development a narrow band of small, round or oval, rapidly dividing chondrocytes which synthesize chondroitin SO4 and collagen at low rates. Just proximal to this zone is a broader zone of flattened, disc-shaped chondrocytes which divide more slowly and are extremely active in chondroitin SO4 and collagen synthesis. Proximal to the zone of flattened chondrocytes is a zone of non-dividing, hypertrophied chondrocytes which are large and round and increase continually in size going from the distal to the proximal end of the zone. The biosynthetic activities of the cells in this zone fall sharply with their distance from the zone of flattened chondrocytes. Finally, there is a fourth zone, the marrow cavity, formed by a proximal to distal disintegration of the hypertrophied chondrocytes, starting at mid-diaphysis. The marrow cavity is surrounded by a shell of periosteal and intra-membranous bone which extends to the distal end of the zone of hypertrophied chondrocytes. Our data suggest that as the tibiotarsus grows in length the small, round rapidly dividing cells of the tibia differentiate first to flattened chondrocytes which synthesize matrix at a high rate and ultimately to low activity, hypertrophying chondrocytes. This sequence proceeds in a linear fashion.

Animals↗
PubMed1977

Lightning injuries.

The course of three patients apparently struck by lightning is reviewed. The circumstances of the injury and the power of the lightning discharge are uncontrollable variables affecting morbidity and mortality. Immediate cardiopulmonary resuscitation followed by careful clinical monitoring and aggressive treatment of involved organ systems will help most patients to complete recovery.

Adult↗
PubMed1977

Visualization of the medullary rays on excretory urography in experimental ureteric obstruction.

Excretory urography occasionally delineates striations of alternating density in the renal parenchyma. Experimental observations on a dog model of ureteric obstruction show that the dense striations have the same dynamic alterations as the obstructive nephrogram. They become progressively more dense to a plateau and then fade with relief of obstruction. Previous obstruction is shown to facilitate visualization of the striations presumably by having dilated the tubules. Previous obstructive episode, previous symptoms, or chronic obstruction were present in each of the clinical cases collected which show a similar striation pattern. We conclude that the dense striations represent shadows produced by hyperconcentrated contrast material which has accumulated in dilated collecting ducts or groups of ducts within the medullary rays.

Acute Disease↗
PubMed1977

Extraperitoneal inguinal endometriosis.

Two instances of extraperitoneal inguinal endometriosis are presented with a review of the previous reports of proven diagnosis. A high index of suspicion is needed to avoid needless prolonged observation. The diagnosis must be considered in any woman of childbearing age especially if the groin mass is associated with menstrual variability in size and in tenderness of the mass. Excision is curative and should result in permanent relief of pain.

Adnexa Uteri↗