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Biomedical subjects

A Kaplan

Publications and source records attributed to A Kaplan.

At least 73 records · Page 4Linked to original sources
PubMed1998

Three year results of photoastigmatic refractive keratectomy for mild and atypical keratoconus.

PURPOSE: To evaluate the long-term effect of photoastigmatic refractive keratectomy (PARK) on mild keratoconus. SETTING: Laser Unit, Ein Tal Eye Center, Tel Aviv, Israel. METHODS: Eight eyes of 6 patients with stable compound myopic astigmatism and topography features of keratoconus were treated with a VISX Twenty-Twenty excimer laser. The laser beam slit width ranged between 4.8 and 5.0 mm according to the degree of cylinder. Preoperative slitlamp examination did not reveal significant thinning, ectasia, or scarring. Astigmatism ranged between -2.00 and -7.50 diopters and follow-up, between 36 and 48 months. RESULTS: In 7 of 8 eyes, uncorrected visual acuity (UCVA) before PARK ranged between 6/30 and finger counting. After PARK, it ranged between 6/9(-) and 6/15, and patients could manage in most of their daily activities without using spectacles. In 2 eyes, the final UCVA was 6/15(-) and 6/15. In 1 eye, treatment failed to improve UCVA and corneal topography revealed progression of the keratoconus. CONCLUSIONS: Photoastigmatic keratectomy was partially effective in eyes with mild stable keratoconus. However, the long-term results may be altered by progression of corneal thinning and ecstatic disease. In addition to the mild nature of the keratoconus, this is a small series and further studies are needed to confirm these results.

Adult↗
PubMed1998

Sialic acid in childhood renal diseases: correlation with clinical and laboratory indices.

There are many kinds of glycoproteins that have sialic acid residues and it has been reported that these are elevated in some renal diseases and their significance in the pathogenesis of several renal diseases has been investigated. In the present study the serum and urine levels of sialic acid were measured in healthy controls and in children with either poststreptococcal acute glomerulonephritis (PSAGN) or minimal change nephrotic syndrome (MCNS) to test if there is any correlation with clinical and laboratory indices. In PSAGN and MCNS patients the serum and urine sialic acid concentrations at onset and relapse were significantly different from healthy controls (Mann-Whitney U-test P < 0.005). There was not a significant correlation between the clinical severity, serum creatinine and complement C3 levels and serum sialic acid concentrations in PSAGN patients. Also there was not a significant correlation between edema, serum albumin, IgG, transferrin, alpha-1-antitrypsin and serum sialic acid concentrations in MCNS patients. Although high serum and urine sialic acid levels were found in both PSAGN and MCNS patients, it does not have any clinical significance nor is it important as a diagnostic or prognostic marker.

Acute Disease↗
PubMed1997

Sustained net CO2 evolution during photosynthesis by marine microorganisms.

BACKGROUND: Many aquatic photosynthetic microorganisms possess an inorganic-carbon-concentrating mechanism that raises the CO2 concentration at the intracellular carboxylation sites, thus compensating for the relatively low affinity of the carboxylating enzyme for its substrate. In cyanobacteria, the concentrating mechanism involves the energy-dependent influx of inorganic carbon, the accumulation of this carbon--largely in the form of HCO3(-)-in the cytoplasm, and the generation of CO2 at carbonic anhydrase sites in close proximity to the carboxylation sites. RESULTS: During measurements of inorganic carbon fluxes associated with the inorganic-carbon-concentrating mechanism, we observed the surprising fact that several marine photosynthetic microorganisms, including significant contributors to oceanic primary productivity, can serve as a source of CO2 rather than a sink during CO2 fixation. The phycoerythrin-possessing cyanobacterium Synechococcus sp. WH7803 evolved CO2 at a rate that increased with light intensity and attained a value approximately five-fold that for photosynthesis. The external CO2 concentration reached was significantly higher than that predicted for chemical equilibrium between HCO3- and CO2, as confirmed by the rapid decline in the CO2 concentration upon the addition of carbonic anhydrase. Measurements of oxygen exchange between water and CO2, by means of stable isotopes, demonstrated that the evolved CO2 originated from HCO3- taken up and converted intracellularly to CO2 in a light-dependent process. CONCLUSIONS: We report net, sustained CO2 evolution during photosynthesis. The results have implications for energy balance and pH regulation of the cells, for carbon cycling between the cells and the marine environment, and for the observed fractionation of stable carbon isotopes.

Bicarbonates↗
PubMed1997

Twentieth-Century Sea Surface Temperature Trends

An analysis of historical sea surface temperatures provides evidence for global warming since 1900, in line with land-based analyses of global temperature trends, and also shows that over the same period, the eastern equatorial Pacific cooled and the zonal sea surface temperature gradient strengthened. Recent theoretical studies have predicted such a pattern as a response of the coupled ocean-atmosphere system to an exogenous heating of the tropical atmosphere. This pattern, however, is not reproduced by the complex ocean-atmosphere circulation models currently used to simulate the climatic response to increased greenhouse gases. Its presence is likely to lessen the mean 20th-century global temperature change in model simulations.

Journal Article↗
PubMed1997

D2 dopamine receptor A1 allele in Alzheimer disease and aging.

BACKGROUND: The apolipoprotein E4 (APOE*4) allele is a major risk factor for the common forms of late-onset Alzheimer disease (AD), but does not account for all the genetic variation in late-onset AD; hence, other genetic markers must be examined. The D2 dopamine receptor (DRD2) A1 allele is associated with abnormal brain function and decreased DRD2s. These receptors are decreased in hippocampus and amygdala in AD, and allele frequencies may vary with age. OBJECTIVE: To study APOE and DRD2 genotypes in patients with AD and cognitively intact controls of varying ages. DESIGN: The DRD2 and APOE genotypes were examined in 832 unrelated white subjects, including 554 patients with AD (486 sporadic; 68 familial) and 278 controls. Logistic regressions tested A1 allele effects on disease status and age, and DRD2 linkage with AD was investigated in 60 families with late-onset AD. SETTING: University medical centers. SUBJECTS: Patients (mean +/- SD age, 74.6 +/- 8.1 years; range, 52-98 years) had probable AD, according to standard consensus diagnostic criteria; controls (mean +/- SD age, 69.2 +/- 8.6 years; range, 50-93 years) were cognitively intact. MAIN OUTCOME MEASURES: Disease status, age, and DRD2 linkage with AD. RESULTS: No association between the DRD2 and APOE alleles was found, and the presence of the A1 allele did not increase the risk for AD. There was also no evidence of linkage between DRD2 and AD. Age analyses, including both patients and controls, indicated a decrease in A1 allele frequency with age. CONCLUSIONS: The A1 allele does not contribute to AD risk, alone or in combination with the APOE*4 allele. The DRD2 A1 allele frequencies decrease with age in both patients and controls. Thus, studies of DRD2 disease association need to control for age.

Aged↗
PubMed1997

Quantitative evaluation of local drug delivery using the InfusaSleeve catheter.

BACKGROUND: Restenosis is the most common long-term complication after angioplasty. Local delivery of pharmacologic agents at the site of angioplasty holds promise as a means of achieving higher concentrations of drug in the arterial wall than can be obtained by systemic infusion. In this study, a novel local drug delivery catheter system, the InfusaSleeve catheter, was evaluated in a porcine coronary balloon injury model. The purpose of the study was to evaluate the efficacy of solute transfer to the arterial wall and the influence of varying supporting angioplasty balloon pressure. METHODS AND RESULTS: Ten pigs (total of 22 arterial segments) underwent overstretch balloon injury (artery/balloon ratio 1:1.29) with a standard angioplasty balloon. In 7 animals (16 arterial segments) horseradish peroxidase (HRP; 10 mg/ml) was administered locally after injury, by tracking the local infusion catheter as a sheath over the angioplasty balloon to the intended site of arterial drug delivery. Supporting angioplasty balloons were inflated to one of the three different pressures. In 3 pigs HRP (10 mg/ml) was administered intravenously. No significant arterial injury caused by the local delivery device was evident on histological examination (disruption of the internal lamina elastica, arterial media, or thrombosis). Radial concentrations of the HRP reaction product in the first 150 microns of the arterial wall were quantified against known standards by measurement of light transmission through tissue sections. Mean HRP concentrations were not significantly different from those obtained by intravenous infusion using a supporting pressure of 1 atm or a supporting pressure of 3 atm of the underlying angioplasty balloon. However, a supporting pressure of 6 atm resulted in a 6-fold greater mean HRP concentration in the arterial wall than that which could be achieved by systemic administration of an equal volume of tracer (P < 0.001). CONCLUSION: Thus solute can be delivered throughout the coronary media by the InfusaSleeve, with the magnitude of wall uptake related to support pressure. Local delivery at 6 atm support pressure produced substantially greater uptake than did systemic delivery.

Angioplasty, Balloon, Coronary↗
PubMed1997

The Effect of Achievement Goals: Does Level of Perceived Academic Competence Make a Difference?

Researchers using a goal orientation framework have hypothesized that learning goals are associated with adaptive patterns of behavior, regardless of the level of perceived ability. In contrast, perceived ability is hypothesized to moderate the relation between performance goals and patterns of adaptive or maladaptive behavior. We examined this hypothesis in two samples of seventh grade middle school students, focusing on the math domain in one sample and on the English domain in the other. Using two different statistical methods, median split and multiple regression, we found only little support for the role of perceived competence as a moderator between performance goals and patterns of behavior. Contrary to what has been suggested, we found some evidence that perceived competence moderated the relation between learning goals and behavior. Implications of these findings for recent efforts to use goal theory to reform classrooms and schools are discussed. Copyright 1997Academic Press

Journal Article↗
PubMed1997

The effect of metabolic acidosis on serum apolipoprotein A I and apolipoprotein B levels in children with chronic renal failure.

In this report serum apolipoprotein A I (Apo A I) and apolipoprotein B (Apo B) levels were determined in children with chronic renal disease (CRD) during metabolic acidosis, after the correction of metabolic acidosis and in healthy children to look for the effect of metabolic acidosis on Apo A I and B levels. It was found that Apo A I levels were significantly decreased during metabolic acidosis (p < 0.05) but Apo A I/Apo B ratios were not affected before and after the correction of acidosis in the CRD group (p > 0.05) although it was significantly different from those in the controls (p < 0.01).

Acidosis↗
PubMed1997

1,25-Dihydroxyvitamin D3 and a new analogue, 22-oxacalcitriol, modulate proliferation and interleukin-8 secretion of normal human keratinocytes.

Vitamin D3 is a new therapeutic agent for psoriasis. Hyperproliferation of epidermis and over-secretion of IL-8 by keratinocytes are the characteristic features of psoriasis. The present study was conducted to determine whether a new vitamin D3 analogue, 22-oxacalcitriol, could be effective in inhibiting the proliferation and IL-8 secretion of normal human epidermal keratinocytes. Cell proliferation was measured colorimetrically by the MTS assay. IL-8 secretion was measured with ELISA. Proliferation of cultured normal human epidermal keratinocytes was inhibited in the presence of 1,25-dihydroxyvitamin D3 at the concentrations of 1 x 10(-8) to 1 x 10(-6) M and 22-oxacalcitriol at concentrations of more than 1 x 10(-9) M at 48 h. IL-8 secretion from normal human epidermal keratinocytes was augmented by TNF-alpha, or synergistically by TNF-alpha and IFN-gamma. 1,25-Dihydroxyvitamin D3 and 22-oxacalcitriol inhibited cytokine-stimulated IL-8 production dose dependently after 24 h incubation without inhibition of cell proliferation. 1,25-Dihydroxyvitamin D3 and 22-oxacalcitriol are considered to inhibit the proliferation of keratinocytes directly and indirectly with inhibition of the secretion of IL-8 from keratinocytes. The inhibition of IL-8 secretion from keratinocytes by vitamin D3 could modulate the behaviour of immunocompetent cells infiltrating in the skin.

Calcitriol↗
PubMed1997

Mnemonics usage and cognitive decline in age-associated memory impairment.

To determine predictors of cognitive deterioration, the authors performed baseline and 1- to 5-year follow-up (mean +/- SD = 2.5 +/- 1.2 years) neuropsychological assessments on 36 persons (mean age +/- SD = 62.1 +/- 8.0; range = 50 to 81 years) with age-associated memory impairment. Subjects were recruited from a larger group of volunteers, had minimal medical comorbidity, and 25 of them had a family history of Alzheimer's disease. Baseline age and a subjective memory measure indicating reported frequency of mnemonics usage were significant decline predictors. Subjects reporting more frequent mnemonics use at baseline were more likely to show objective cognitive decline at follow-up. Baseline full-scale IQ, educational level, and family history of Alzheimer's disease failed to predict decline. These findings suggest that although age is the strongest decline predictor in some people with age-associated memory impairment, self-perception of memory function may also predict subsequent cognitive loss.

Abbreviations as Topic↗
PubMed1996

Subcellular distribution of "intersecting' beta-N-acetylglucosaminyltransferase in Dictyostelium discoideum. A likely marker for the Golgi apparatus.

Glycoprotein processing in Dictyostelium discoideum is characterized by enzyme catalyzed steps not reported in other organisms. One of these is the formation of a beta 1 --> 4 linkage between GlcNAc and the mannose linked to the core mannose in the alpha 1 --> 6 position of N-glycosides. A simple and sensitive assay for this GlcNAc transferase activity, using a tri-mannose acceptor and a low concentration of UDP-GlcNAc, was developed. Homogenates of the organism were subjected to sub-cellular fractionation by centrifugation in discontinuous sucrose gradients. The specific activity was enriched 4-5-fold in a crude membrane fraction. The transferase was purified 10-12-fold in a membrane fraction that bands on top of 1.1 M sucrose. This fraction was also enriched in nucleotidyldiphosphatase. The enriched fraction was deficient in glucose-6-phosphatase, an endoplasmic reticulum marker. Approx. 80% of the transferase activity was latent, and unavailable to protease. Purified membranes were either subjected to phase separation in Triton X-114, or sodium carbonate extraction or sonication. In each case, the transferase behaved as an intrinsic membrane protein. Several secreted and lysosomal proteins are modified by the enzyme. These data support the idea that the GlcNAc transferase is present as an integral Golgi membrane protein and that at least the catalytic center of the transferase is on the lumenal side of the vesicles.

Acid Anhydride Hydrolases↗
PubMed1996

Quantitative evaluation of the role of a putative CO2-scavenging entity in the cyanobacterial CO2-concentrating mechanism.

This paper assesses the contribution of a postulated CO2-scavenging system to the efficient operation of the CO2-concentrating mechanism (CCM) in cyanobacteria. A quantitative model for the CCM is presented which incorporates an energy-dependent carbonic anhydrase-like entity located at or near the inner surface of the plasma membrane. This entity, which converts CO2 to HCO3- against the thermodynamic potential, scavenges CO2 leaking outward from the carboxysomes, and, further, converts CO2 entering from the medium to HCO3-, thus maintaining an inward diffusion gradient along which CO2 enters passively. The model resembles our earlier models in postulating that CO2 and HCO3- are not at equilibrium throughout the greater part of the cell, and that CO2 is generated in high concentration at carbonic anhydrase sites within the carboxysomes. The model further takes into account the concentric thylakoid membranes which surround the carboxysomes, and events in the periplasmic space and the unstirred layer surrounding the cell. Implications of the predicted steady state fluxes of CO2 and HCO3-, and of their steady state concentrations in various cellular compartments, are discussed. The plasma membrane carbonic anhydrase-like activity lowers the photosynthetic Km for external Ci, as well as decreasing the inorganic C 'leak', but it may not save on energy expenditure.

Bicarbonates↗
PubMed1996

In vitro NMR proton T1 measurements in peritoneal ascites.

The proton spin-lattice relaxation rate (1/T1) in malignant and non-malignant ascites was measured with an FT NMR spectrometer operating at 60 MHz. The mean relaxation rate in non-malignant ascites was significantly smaller than that of malignant ascites. However, the 1/T1 of malignant ascites overlaps with that of non-malignant ascites over all concentrations of total protein (TP) in samples. The 1/T1 in non-malignant ascites correlates strongly with TP, whilst the 1/T1 in malignant ascites shows only a moderate correlation. T1 measurements before and after addition of ascorbic acid (reductant) suggest that there is a small paramagnetic contribution of ions to the 1/T1 in malignant ascites. The least-squares fitting of 1/T1 versus TP for non-malignant data gives a linear relationship, and suggests that the T1 mechanism in non-malignant ascites is caused by a fast chemical exchange of water molecules between protein-bound water and free water.

Ascites↗
PubMed1996

Mycobacterium avium infection in a patient with acquired immunodeficiency syndrome and a solid silicone buttock implant.

A 31-year-old female patient with both acquired immunodeficiency syndrome and a solid silicone buttock implant presented with fever. Using ultrasound-guided aspiration of the periprosthetic space, a diagnosis of Mycobacterium avium complex infection involving the implant was made. The implant was surgically removed and the patient had a resolution of her fevers while treated with ethambutol, rifabutin, ciprofloxacin, and clarithromycin.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Preliminary report of the activity of docetaxel in advanced or recurrent squamous cell cancer of the cervix.

Eighteen patients with squamous cell cancer of the cervix were treated with i.v. docetaxel 100 mg/m2 over 1 h every 21 days. No patient received prior chemotherapy, except as a radiation sensitizer. Median age was 42 years (range 30-58) and Zubrod performance status was 1 (0-2). Ten (59%) patients had prior surgery and 11 (65%) had prior radiation therapy. Sixteen patients were evaluable for response. Two patients had a partial response (13%; 95% CI 0-32%) and eight (50%; 95% CI 23-77%) had stable disease. Dose reduction to 75 mg/m2 was required in 10 patients and to 55 mg/m2 in one patient. Granulocytopenia was the major hematopoietic toxicity (31% grade 3 and 44% grade 4). Docetaxel is active in patients with squamous cell cancer of the cervix and may be tolerable at this dose schedule.

Adult↗