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Biomedical subjects

A Schroeder

Publications and source records attributed to A Schroeder.

At least 37 records · Page 2Linked to original sources
PubMed1995

Verapamil increases outflow facility in the human eye.

Verapamil, a calcium channel antagonist, causes a reduction of intraocular pressure in humans. This study investigated whether verapamil's effect on intraocular pressure was related to increased outflow facility. Six pairs of human eyes were dissected and anterior segments were perfused under constant pressure with concentrations of verapamil HCl ranging from 10(-10)-10(-3) M. The maximal increase of outflow facility over baseline was 64% at 10(-9) M. These results indicate that verapamil causes a dose related increase in outflow facility in human eyes, which may account for the reduced intraocular pressure following topical administration of verapamil.

Aged↗
PubMed1994

In situ localization of the hepatocytic Na+/Taurocholate cotransporting polypeptide in rat liver.

BACKGROUND/AIMS: An Na+/taurocholate cotransporting polypeptide (Ntcp) has recently been cloned from rat liver. The aim of this study was to directly characterize the native Ntcp on the protein level and study its in situ distribution in rat liver. METHODS: A rabbit antiserum was raised against a fusion protein containing the maltose-binding protein and the C terminus of Ntcp. Native Ntcp was localized in situ by immunofluorescent techniques. Expression of Ntcp was directly correlated with taurocholate uptake measurements in stably transfected Chinese hamster ovary cells. RESULTS: Native Ntcp showed an apparent molecular weight of 51,000. After deglycosylation of isolated basolateral rat liver plasma membranes, the apparent molecular weight of Ntcp decreased to 33,500. In intact rat liver, Ntcp was selectively localized at the basolateral surface domain of hepatocytes. In short-term cultured hepatocytes, a positive surface immunoreaction was only obtained in detergent-permeabilized cell cultures. In stably transfected Chinese hamster ovary cells, the surface expression of immunopositive Ntcp was associated with Na(+)-dependent taurocholate uptake activity. CONCLUSIONS: Native Ntcp represents a glycoprotein of the basolateral hepatocyte plasma membrane with its C-terminal end facing the intracellular compartment. Furthermore, surface expression of Ntcp is a prerequisite for Na(+)-dependent taurocholate uptake to occur, thus providing further proof for its bile acid transport function in rat liver.

Animals↗
PubMed1993

[The quality of life of tumor patients as a multidimensional concept].

An important aim of supportive care for cancer patients (pts) is the maintenance or improvement of their life quality. Therefore it is interesting to measure pts' LQ while testing new cytotoxic drugs or palliative therapy like artificial nutrition. A short questionnaire also is helpful in order to inform physicians and psychooncologists about pts' needs for psychosocial intervention. Based on coping-research, gerontology and well-being-psychology we have developed a 69-item-questionnaire "Scales for Measuring LQ" with good test-statistics. This instrument emphasizes pts' life experiences and subjective appraisal of objective life conditions. Basic state, internalized life experiences and life orientations in a sample of 179 pts with chemo- or radiotherapy are more important for LQ than objective symptoms, subjectively perceived physical condition and mood. The surprisingly high LQ scores in cancer pts can best be explained by their reduced aspiration levels. Correlations with emotional and belonging support obtained from the partner or confidant are significant. Social support is before all related to our pts' positive life experiences (.68; .59) and to their life satisfaction (.58; .47).

Adolescent↗
PubMed1992

The effect of intracameral ethacrynic acid on the intraocular pressure of living monkeys.

Previous studies have shown that the sulfhydryl-reactive ethacrynic acid increases outflow facility in living monkeys when perfused via the anterior chamber. To study its potential clinical use further, living monkeys were intracamerally injected with 10 microliters of ethacrynic acid, with concentrations ranging from 0.5 to 7.5 mmol/l. The fellow control eye was injected with 10 microliters of diluent. The status of the anterior segment was monitored by slit-lamp biomicroscopy and the intraocular pressure was measured by pneumatonometry with the monkeys anesthetized with ketamine. The anterior segment of living monkeys tolerated injections up to 3.0-mmol/l ethacrynic acid without marked adverse effects. One of 13 monkey eyes injected with 3.0-mmol/l ethacrynic acid demonstrated mild reversible segmental corneal edema. The greatest mean intraocular pressure reduction in the 3.0- to 3.75-mmol/l group occurred at six hours, with the experimental intraocular pressure decreasing 2.9 mm Hg compared to a mean intraocular pressure increase of 0.1 mm Hg in the control group (n = 19). Concentrations of ethacrynic acid less than 3.0 mmol/l did not provide reliable reduction of intraocular pressure, whereas concentrations greater than 3.75 mmol/l caused a greater incidence and severity of corneal edema. We believe that the intracameral injection of ethacrynic acid can reliably and safely reduce intraocular pressure in living monkey eyes, and that this drug deserves further investigation as a potential antiglaucomatous agent.

Animals↗
PubMed1992

The axonally secreted cell adhesion molecule, axonin-1. Primary structure, immunoglobulin-like and fibronectin-type-III-like domains and glycosyl-phosphatidylinositol anchorage.

Axonin-1 is an axon-associated cell adhesion molecule (AxCAM) of the chicken, which promotes neurite outgrowth by interaction with the AxCAM L1(G4) of the neuritic membrane. Here we report the cloning and sequence determination of a cDNA encoding axonin-1. Peptides generated by enzymatic cleavage showed similarity to the AxCAM F11. Degenerated polymerase chain reaction (PCR) primers were designed and an axonin-1 fragment was amplified from mRNA of embryonic retina. Screening of a cDNA library from embryonic brain resulted in the isolation of a 4.0-kb cDNA insert with an open reading frame of 3108 nucleotides. The deduced polypeptide of 1036 amino acids includes a putative hydrophobic N-terminal signal sequence of 23 or 25 amino acids and a C-terminal hydrophobic sequence of 29 amino acids which is suggestive of sequences serving as signal for the attachment of a glycosyl-phosphatidylinositol (glycosyl-PtdIns) anchor. The putative mature form of axonin-1 comprises six immunoglobulin-like repeats, followed by four fibronectin-type III repeats. Axonin-1 exhibits 75% amino acid identity with the AxCAM TAG-1 of the rat, suggesting that it is the chicken homologue of TAG-1. Like TAG-1, axonin-1 is glycosyl-PtdIns-anchored to the neuronal membrane; in contrast to TAG-1, it does not exhibit an Arg-Gly-Asp sequence.

Amino Acid Sequence↗
PubMed1992

Effects of topical ethacrynic acid adducts on intraocular pressure in rabbits and monkeys.

We evaluated the effect of topical ethacrynic acid on rabbit and monkey intraocular pressure. In a preliminary experiment, 100-mmol/L ethacrynic acid applied topically to Dutch-Belted rabbit eyes was associated with an 8-mm Hg lowering of intraocular pressure. However, corneal edema was severe, and the corneal epithelium sloughed off. To try to maintain the pressure-lowering effect but reduce the corneal side effects, we attempted to create an adduct of ethacrynic acid by utilizing ethacrynic acid's sulfhydryl reactivity. Ethacrynic acid was mixed with equimolar cysteine to bind the sulfhydryl-reactive sites on ethacrynic acid. The goal was to expose the cornea to adducted ethacrynic acid, which might then dissociate in the anterior chamber via a retro-Michael reaction. Intraocular pressure decreased 8.9 mm Hg (n = 40) with this treatment, and corneal edema was lessened (32 of 40 eyes had mild to no edema). However, we observed that when the eye was treated before ethacrynic acid-cysteine administration with topical acetylcysteine, the corneal side effects were reduced further and the intraocular pressure effect remained. In living cynomolgus monkeys receiving a single pretreatment drop of 75-mmol/L acetylcysteine followed by two drops of 130-mmol/L ethacrynic acid and 130-mmol/L cysteine, an intraocular pressure lowering of 9.9 mm Hg was observed (n = 7). However, in three of seven eyes corneal edema developed. Pretreatment with two drops of acetylcysteine eliminated the pressure-lowering effect but did not confer any added corneal protection. Our results indicate that topical ethacrynic acid-cysteine is effective in lowering the intraocular pressure of rabbits and cynomolgus monkeys and, when combined with acetylcysteine pretreatment, may offer the potential for a new topical therapeutic regimen for use in glaucoma.

Acetylcysteine↗
PubMed1992

Indications for angled implants.

The development of dental implants has led to an expansion of indications and to perfection of implantation methods and implant systems. Angulation problems due to anatomic limitations, however, still remain. The indications for the use of angled Bonefit I.T.I. implants are described.

Alveolar Process↗
PubMed1992

Ethacrynic acid induces reversible shape and cytoskeletal changes in cultured cells.

Cell cultures derived from trabecular meshworks of human and bovine eyes and from bovine vascular endothelia were incubated at 37 degrees C for 1 hr with ethacrynic acid (ECA, 0.1-0.5 mmol/l) dissolved in culture medium. At 2 hr after the initial exposure, ECA at concentrations up to 0.4 mmol/l induced a reversible alteration in cell shape in all three cell types that was coincident with a change in the staining pattern of major cytoskeletal components including actin, alpha-actinin, vinculin, and vimentin. Distinct progressive alterations in beta-tubulin also occurred, with initial changes observed 10 min after ECA exposure. The ECA-induced changes in tubulin were blocked in part by preincubation with taxol (which stabilizes the microtubule structure), but they appeared to differ from those occurring with nocodazole (which interferes with tubulin assembly). These results suggest the possibility that ECA-induced increases in outflow facility may be mediated by alterations in the cytoskeletons of outflow pathway cells.

Adolescent↗
PubMed1991

Explantation procedure in the F-type and Bonefit ITI implant system.

The explantation technique for the ITI F-type and Bonefit implant system is described. Although implant survival rates are high, the risk of failure must be considered. In some cases implants will have to be removed for reasons other than failure of the implant itself.

Dental Implantation, Endosseous↗
PubMed1990

Dissociation between the effect of aceclidine on outflow facility and accommodation.

The dose/effect relationships for intracameral doses of aceclidine HCl and pilocarpine HCl on total facility of outflow and accommodative amplitude were compared in the cynomolgus monkey eye in vivo. The largest dose of aceclidine tested (20 micrograms), resulted in an average increase of 270% in outflow facility, whereas accommodation was limited to an average of 5 diopters. In contrast, 20 micrograms of intracameral pilocarpine (which is submaximal in increasing facility) resulted in an average of 19 diopters of accommodation. These results provide further evidence for a dissociation between the accommodative and outflow facility functions of the ciliary muscle.

Accommodation, Ocular↗
PubMed1989

ITI-system. Basic and clinical procedures.

Future development in implant prosthodontics should be based on the fundamentals of sound research and reliable clinical implementation. The goals should be to research the safety and efficacy of implants with regard to materials, host receptor site and interfacial zone; to develop acceptable uniform standards of evaluation; and to submit findings to scientific methods of analysis in determining benefit-to-risk factors. This presentation will offer a glimpse at some current developments in basic and clinical research focusing on studies in biocompatibility and host acceptance; the implant-tissue interface; processes in osteogenesis related to vascularization of host sites; and bioengineering studies related to stress analysis and dimensional accuracy of impression systems for implants. The presentation will further describe future directions in research, training and implementation of services through development of an interdisciplinary team. A center is proposed to address the need for combined efforts in clinical++ and basic science research, the broad scope of implant utilization, and the teaching of implant procedures within an academic setting and to our colleagues.

Biocompatible Materials↗