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Biomedical subjects

S Marcus

Publications and source records attributed to S Marcus.

At least 109 records · Page 6Linked to original sources
PubMed1988

Neovascularization in central retinal vein occlusion: electroretinographic findings.

Electroretinograms (ERGs) were measured in 15 patients with central retinal vein occlusion (CRVO). Seven of the patients had neovascularization of the iris (NVI) at the time of testing, and two developed NVI within one month of testing; six did not have NVI or any other form of neovascularization (NV) and were no longer considered to be at risk for NV from their present occlusion. The ERGs were recorded as a function of the stimulus intensity and to a 30-Hz flickering stimulus. A Naka-Rushton-type function was fit to b-wave amplitudes, measured as a function of stimulus intensity, to evaluate changes in ERG amplitude and sensitivity. Compared with eyes in the no-NV group, eyes developing NVI had significantly reduced ERG sensitivity and amplitudes. The distributions of sensitivity values in these two groups did not overlap. All of the eyes with NV showed large a- and b-wave and 30-Hz implicit time delays, but only one eye had a b/a-wave amplitude ratio close to or less than 1. A comparison of ERG sensitivity, amplitude data, and flicker timing data with retinal fluorescein angiography in a two-alternative forced-choice analysis showed that ERG sensitivity and amplitude loss were better than retinal fluorescein angiography at discriminating eyes with CRVO and NVI from eyes with CRVO without NVI.

Electroretinography↗
PubMed1988

Vitrectomy for macular pucker. Use after treatment of retinal tears or retinal detachment.

We review our experience and present an analysis of 119 consecutive cases of macular pucker treated by vitrectomy and removal of the epiretinal tissue following treatment for acute retinal tears (16 eyes) or rhegmatogenous retinal detachment (103 eyes). Vision improved postoperatively in 104 (87%) of the 119 eyes. Final visual acuity of 20/60 or better was achieved in 38 (75%) of 51 cases in which the macula had not been detached previously and in 12 (24%) of 52 cases with prior macular detachment. Two preoperative factors were associated with a final visual acuity of 20/100 or better: (1) macula not involved by the original retinal detachment, and (2) thin epiretinal membrane.

Adolescent↗
PubMed1988

Retinal sensitivity over drusen and nondrusen areas. A study using fundus perimetry.

Elderly patients with drusen and good visual acuity have a decrease in dark-adapted retinal sensitivity in the central retina. We used the fundus camera stimulator to determine whether this sensitivity loss is caused directly by the presence of drusen. We measured retinal sensitivity over drusen and in drusen-free areas in eight patients with drusen and age-related macular degeneration (AMD). There was no significant difference in sensitivity between drusen and nondrusen areas in each patient. The sensitivity loss seen in patients with drusen thus seems to reflect a more diffuse disease of the retina and retinal pigment epithelium and is not a direct effect of drusen. More marked sensitivity losses are found in even small areas of more advanced AMD changes, suggesting that a large focal loss in retinal sensitivity may be an indicator of developing AMD changes.

Aged↗
PubMed1988

Retinal pigment epithelial tears. Patterns and prognosis.

Increasing experience with the diagnosis of retinal pigment epithelial (RPE) tears has led to expanded recognition and understanding of this clinical entity. The authors report 18 RPE tears followed for an average of 28 months; 16 were associated with age-related macular degeneration and 2 with presumed ocular histoplasmosis syndrome. Retinal pigment epithelial dehiscences fell into four categories: nine spontaneous tears associated with choroidal neovascularization, one tear associated with an RPE detachment without choroidal neovascularization, four iatrogenic tears occurring at krypton treatment of choroidal neovascularization, and four iatrogenic tears developing weeks to months after laser treatment of choroidal neovascularization. Eight patients had a final visual acuity of 20/100 or better, four were 20/200, and six were 20/400 or worse. Photocoagulation, particularly with the use of krypton red laser, may be modified on the basis of possible RPE tear formation. Heightened awareness of the possibility of inducing pigment epithelial rips should improve diagnosis and management of these cases.

Adult↗
PubMed1987

Synthesis and biological activity of amino terminus extended analogues of the alpha mating factor of Saccharomyces cerevisiae.

The synthesis and biological activity are reported for extended analogues of the secreted tridecapeptide alpha-factor (Trp-His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln-Pro-Met-Tyr) from Saccharomyces cerevisiae. Peptides with Ala, Glu-Ala, Ala-Glu-Ala, or Glu-Ala-Glu-Ala attached to the amino terminus of alpha-factor were synthesized by the solid-phase method on a (phenylacetamido)methyl (PAM) resin, using a combination of dicyclohexylcarbodiimide- and 1-hydroxybenzotriazole-accelerated active ester coupling procedures. Free peptides were obtained by hydrogen fluoride (HF) cleavage in the presence of appropriate scavengers. Normal high HF cleavage and "low-high" HF cleavage were equally effective in liberating the desired product from the PAM resin. Yields of pure peptide ranged from 9% to 17%. All of the extended alpha-factors, which represent sequences of pro-alpha-factor coded for in the MF alpha 1 structural gene, caused morphological aberrations (shmoo assay) in strain X2180-1A (MATa) the same as those caused by the tridecapeptide. The 14-peptide was equally active compared to the native alpha-factor whereas the 17-peptide was 5-10-fold less active. The analogues also arrested to various degrees (halo assay) the growth of S. cerevisiae RC629 (MATa sst1) and S. cerevisiae RC631 (MATa sst2), two supersensitive mutants, and were converted to pheromones of equal activity by treatment with V8 protease. A temperature-sensitive receptor mutant responded to all the peptides at the permissive but not the restrictive temperature. An alpha-factor antagonist, des-Trp1,Ala3-alpha-factor, inhibited activity of all extended peptides.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1987

Towards determination of the structure of the Saccharomyces cerevisiae a-factor: an acylated pentadecapeptide blocks a-factor activity.

Putative a-factor peptides YIIKGVFWADP, YIIKGVFWANP, YIIKGLFWADP, YIIKGLFWANP, YIIKGVFWDPA, and YIIKGVFWDPACVIA and several peptide derivatives were synthesized and were found to be inactive in growth arrest assays, yet they blocked the activity of biological a-factor. Antagonism was greatest with YIIKGVFWDPAC(palmitoyl)VIA. Thus, the structure of a-factor may be a lipopeptide resembling this palmitoylated pentadecapeptide.

Acylation↗
PubMed1986

Construct validity of the Kendrick Battery with institutionalized aged.

In this study, we attempted to explore the construct validity of the Kendrick Battery by using an American sample and psychometric tests as indexes of diffuse organicity, depression, and normality. Institutionalized residents (N = 53) were tested twice (6-week interval). When organicity was defined by disorientation and memory deficits, then both the Object Learning test and the Digit Copying test were accurate in differentiating preestablished criterion groups. When organicity was defined more broadly, including sensorimotor function, the Digit Copying test alone was more accurate when depression was defined in terms of irritability, restlessness, and despair. These data suggest that although the Kendrick scales appeared to be sensitive to organicity and depression in this sample, their validity varied with the criteria for each when such were defined psychometrically.

Aged↗
PubMed1986

Epithelial ion transport in rabbit corneas following myopic keratomileusis.

In isolated rabbit corneas that had undergone lamellar keratectomy or myopic keratomileusis, the stimulation of chloride transport by 10(-5) M epinephrine was completely inhibited at 1 week following surgery. At 28 days following surgery, both groups responded to 10(-7) M epinephrine. The response to 10(-5) M amphotericin B was normal both at 1 week and at 28 days following surgery. We conclude that, although the Na-K pump was not affected by the lamellar keratectomy and cryolathing, that either the epithelial beta receptors and/or the cAMP pathway were temporarily inhibited for at least 1 week following surgery. A lamellar keratectomy, therefore, can have an adverse effect on the epithelial transport system of the corneal epithelium even though the epithelium may appear normal clinically.

Amphotericin B↗
PubMed1985

Metabolism of the 1-13 sequence of gastrin 17 in humans and failure to influence acid secretion.

The metabolism and action on basal and gastrin 17 (G-17)-stimulated acid secretion of the N-terminal 1-13 sequence of G-17 was studied in human volunteers. Basal acid secretion was not changed by infusion of 1-13 G-17 in doses of 75-1000 pmol X kg-1 X h-1 which gave plasma concentrations of N-terminal G-17 immunoreactivity of 150-2020 pmol X L-1. In addition the acid response to G-17 in a dose that stimulated about 50% maximal acid output was not influenced by 1-13 G-17 (75 and 1000 pmol X kg-1 X h-1). The mean half-time for disappearance of N-terminal immunoreactivity after stopping infusion of 1-13 G-17 was 9.8 +/- 0.5 min. Gel filtration indicated a single peak of N-terminal immunoreactivity in plasma during infusion of 1-13 G-17. Ion exchange chromatography on diethylaminoethyl cellulose, however, revealed two peaks of immunoreactivity. One corresponded to 1-13 G-17, the other eluted earlier. In samples taken after stopping the infusion, the variant predominated. On high-pressure liquid chromatography the variant was resolved into a major component, which had a retention time less than 1-13 G-17, and two minor components. The variants were not produced by incubation of 1-13 G-17 with plasma in vitro. It is concluded that 1-13 G-17 is converted in the circulation to new forms with longer half-lives. Because plasma enzymes cannot account for the formation of these variants, it is possible that enzymes present on cell walls, for example, on capillaries, may be responsible.

Adult↗
PubMed1985

Metabolism of heptadecapeptide gastrin in humans studied by region-specific antisera.

The metabolism of synthetic human heptadecapeptide gastrin (G17) in vivo, and in serum in vitro, was studied by radioimmunoassay using region specific antisera, gel filtration, ion exchange chromatography, and high performance liquid chromatography. After infusion of G17 intravenously in normal human volunteers, COOH-terminal and NH2-terminal immunoreactive G17 fragments were generated. At a steady state, approximately 15% of COOH-terminal immunoreactivity was attributable to G14-like material and up to 25% of total NH2-terminal immunoreactivity was attributable to two NH2-terminal fragments; one had the chromatographic properties of 1-13 G17, and the other was less acidic and less hydrophobic. After stopping the infusion of G17, the latter fragments accounted for progressively greater proportions of total gastrin activity. When G17 was incubated in serum in vitro, there was time-dependent and temperature-dependent loss of immunoreactivity, and again COOH-terminal and NH2-terminal immunoreactive fragments were formed. Removal of the NH2-terminal pyroglutamic acid was probably the rate limiting step because synthetic 2-17 G17 was degraded more rapidly in serum (t1/2, 2-3 h) than G17 (t1/2, 3-5 h). EDTA blocked degradation at the COOH-terminus of both 2-17 G17 and G17 but cleavage at the NH2-terminus still occurred, giving rise to a G14-like peptide. The rate of conversion of G17 in serum was not enough to account for the production of fragments in vivo, and it is proposed that these are formed when G17 encounters enzymes on cell surfaces, perhaps during passage through the capillary circulation. The production of these fragments needs to be considered in interpreting studies of the identity, metabolism, and release of gastrin in health and disease.

Adult↗
PubMed1984

N-terminal tryptic fragment of big gastrin. Metabolism and failure to influence gastrin 17-evoked acid secretion in humans.

The metabolism and some biological properties of the N-terminal 1-17 sequence of human big gastrin (G-34) were studied during infusion in 5 human volunteers. Radioimmunoassay of the 1-17 fragment in plasma indicated rapid clearance (t1/2, 2.4 min). In doses of 75-1000 pmol X kg-1 X h-1, 1-17 G-34 did not, however, influence basal acid output or G-17-stimulated acid output. Gel filtration of plasma samples taken during the infusion indicated the presence of the 1-17 fragment of G-34, together with three other immunoreactive species. Two of these correspond to N-terminal G-34 immunoreactive forms previously found in human peripheral circulation. A fourth immunoreactive component that eluted late on Sephadex G50 was identified for the first time. This component also occurred in fasting human plasma, where it was the only detectable form of N-terminal G-34 immunoreactivity; its concentration increased during infusion of 1-17 G-34. The identification of this fragment and its concentrations in human circulation after feeding deserves further study. Because the fragments of 1-17 G-34 do not occur in antral extracts, and are not produced when G-34 or its N-terminal fragments are incubated in plasma in vitro, they are presumed to be generated from the 1-17 sequence by the action of peptidases found on capillary walls. The elucidation of the mechanisms involved is essential for an understanding of the metabolic pathways of gastrin.

Adult↗
PubMed1983

History of total nasal reconstruction with particular emphasis on the folded forehead flap technique.

The history of plastic surgery is identified throughout the centuries with the history of rhinoplasty. The Indian Koomas first and later the Italian surgeons found valid solutions to the problems caused by partial loss of the nasal pyramid. However, the idea of rebuilding, with a single forehead flap, the tip and columella and providing at the same time a lining of skin for the newly formed nose goes back to the middle of the nineteenth century. The Italian Natale Petrali (1842) and the Germans Johann Friedrich Dieffenbach (1845) and Ernst Blasius (1848) contend for precedence in carrying out this important procedure still used today, which, barring postoperative contracture, represented a great advance in successful total rhinoplasty.

Germany↗
PubMed1982

Macrophage and lymphocyte contributions in resistance of Candida albicans infections.

Model in vivo and in vitro experimental systems have been used to study the efficacy of specific and nonspecific immunization against Candida albicans infection induced in mice. Experiments were designed to compare the extent of resistance in specificity immunized, endotoxin treated and saline treated animals. In vitro phagocytic and postphagocytic killing (cytopepsis) of macrophages or lymphocyte-macrophage combinations from such animals were determined. In the in vitro experiments the macrophage systems destroyed the yeast cells more rapidly than did the lymphocyte-macrophage combinations. Since equivalent numbers of yeast cells were phagocytized, the differences observed were a function of cytopepsis of the organisms.

Animals↗