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Biomedical subjects

K Winter

Publications and source records attributed to K Winter.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effects of solar ultraviolet radiation on the potential efficiency of photosystem II in leaves of tropical plants

The effects of solar ultraviolet (UV)-B and UV-A radiation on the potential efficiency of photosystem II (PSII) in leaves of tropical plants were investigated in Panama (9 degrees N). Shade-grown tree seedlings or detached sun leaves from the outer crown of mature trees were exposed for short periods (up to 75 min) to direct sunlight filtered through plastic or glass filters that absorbed either UV-B or UV-A+B radiation, or transmitted the complete solar spectrum. Persistent changes in potential PSII efficiency were monitored by means of the dark-adapted ratio of variable to maximum chlorophyll a fluorescence. In leaves of shade-grown tree seedlings, exposure to the complete solar spectrum resulted in a strong decrease in potential PSII efficiency, probably involving protein damage. A substantially smaller decline in the dark-adapted ratio of variable to maximum chlorophyll a fluorescence was observed when UV-B irradiation was excluded. The loss in PSII efficiency was further reduced by excluding both UV-B and UV-A light. The photoinactivation of PSII was reversible under shade conditions, but restoration of nearly full activity required at least 10 d. Repeated exposure to direct sunlight induced an increase in the pool size of xanthophyll cycle pigments and in the content of UV-absorbing vacuolar compounds. In sun leaves of mature trees, which contained high levels of UV-absorbing compounds, effects of UV-B on PSII efficiency were observed in several cases and varied with developmental age and acclimation state of the leaves. The results show that natural UV-B and UV-A radiation in the tropics may significantly contribute to photoinhibition of PSII during sun exposure in situ, particularly in shade leaves exposed to full sunlight.

Journal Article↗
PubMed1998

Prostate-specific antigen levels are higher in African-American than in white patients in a multicenter registration study: results of RTOG 94-12.

PURPOSE: To compare serum prostate-specific antigen (PSA) levels in a national sample of African-American and white men with prostate cancer, and to attempt to explain any differences by using self-reported individual-level socioeconomic status adjustments. METHODS AND MATERIALS: During 4 1/2 months in 1994-95, 709 patients with nonmetastatic prostate cancer were enrolled in this prospective study; 17.5% were African-American and 82.5% were white. Information about clinical stage, tumor grade, pretreatment PSA, type of insurance, and educational and income status was obtained. Serum PSA levels were measured and racial differences were found; how the differences were influenced by other patient- or tumor-related factors and if the differences could be explained by socioeconomic status disparities were determined. In univariate analyses, factors associated with the mean PSA levels were studied; log-converted values were used to yield a normal distribution. Multivariate analyses were done on log-linear models for description of association patterns among various categorical variables; a perfectly fitted model should have a correlation value (CV) of 1.0. RESULTS: The mean PSA level was higher in African-Americans (14.68 ng/ml) than in whites (9.82 ng/ml) (p = 0.001). Clinical stage (p = 0.001), Gleason sum tumor grade (p = 0.0001), educational level (p = 0.001), and household income (p = 0.03) were also associated with mean PSA levels; age, type of biopsy, and insurance status were not. Disease stage (p = 0.0001), grade (p = 0.0001), education (p = 0.07), and income (p = 0.02) were all associated with PSA levels for whites, but none of these factors were important for African-Americans (all p values > 0.1). The best fitted log-linear model (CV = 0.99) contained PSA (< 10, 10-20, and > 20), Gleason sum grade (2-5, 6-7, and 8-10), race, and two interactions: PSA by race (p = 0.0012) and PSA by Gleason sum (p = 0.0001). Models replacing race for either income (CV = 0.82) or education (CV = 0.82) or both (CV = 0.78) did not fit as well. CONCLUSIONS: African-Americans with nonmetastatic prostate cancer have higher serum PSA levels at diagnosis than whites, implying a higher tumor cell burden. Individual-level household income, education, or insurance status alone or in combination account for racial differences, but only partially.

Analysis of Variance↗
PubMed1998

Percutaneous arterial closure in severely scarred groins: a technical note.

We present a new method to enable the insertion of percutaneous suturing devices in severely scarred groins, using a peel-away sheath. This sheath stabilizes the percutaneous tract for the suturing device. It may help to salvage closure procedures, which would otherwise have to be aborted due to insufficient stiffness of the device shaft.

Catheters, Indwelling↗
PubMed1997

Androgen suppression plus radiation versus radiation alone for patients with D1 (pN+) adenocarcinoma of the prostate (results based on a national prospective randomized trial, RTOG 85-31). Radiation Therapy Oncology Group.

PURPOSE: To evaluate the effect of immediate androgen suppression in conjunction with standard external beam irradiation vs. radiation alone on a group of pathologically staged lymph node-positive patients with adenocarcinoma of the prostate. METHODS AND MATERIALS: A national prospective randomized trial (RTOG 85-31) of standard external beam irradiation plus immediate androgen suppression vs. external beam irradiation alone was initiated in 1985 for patients with locally advanced adenocarcinoma of the prostate. One hundred seventy-three of the patients in this trial had biopsy-proven pathologically involved lymph nodes. Ninety-eight of these patients received radiation plus the immediate androgen suppression (LHRH agonist), while 75 received radiation alone with hormonal manipulation instituted at the time of relapse. RESULTS: With a median followup of 4.9 years, estimated progression-free survival with PSA < 1.5 ng/ml at 5 years was 55% for the patients who received radiation plus immediate LHRH agonist vs. 11% of the patients who received radiation alone with hormonal manipulation at relapse (p = 0.0001). Because all of these patients had locally advanced disease (i.e., pathologically positive lymph nodes), stage does not explain this difference in outcome, and Gleason grade was not statistically different between the two groups. Estimated absolute survival at 5 years for the radiation and LHRH group was 73 vs. 65% for the radiation alone group who received androgen suppression at relapse. Estimated disease-specific survival at 5 years was 82% for the radiation and immediate LHRH agonist group and 77% for the radiation-alone group. CONCLUSION: Patients with adenocarcinoma of the prostate and pathologically involved pelvic lymph nodes (pN+ or clinical stage D1) should be seriously considered for external beam irradiation plus immediate hormonal manipulation over radiation alone with hormonal manipulation at the time of relapse.

Adenocarcinoma↗
PubMed1997

Clinical utility of contrast-enhanced MR angiography.

MR angiography (MRA) is a technique under ongoing discussion. Its non-invasiveness and sensitivity to flow irregularities make it an investigational technique which is easy to apply but which does not always lead to comprehensive results. It requires special skill to perform and also experience for correct interpretation of the results. The lengthiness of the procedure combined with certain physical properties tends to limit its use to mostly neurovascular applications. With the introduction of ultrafast MRA in conjunction with peripheral bolus-injection of extracellular contrast media, a new approach to the imaging of such regions as the thoracic and abdominal vasculature not to mention other vascular territories has become possible. In this paper, considerations of bolus and measurement optimization and timing protocols for dedicated indications are presented together with an overview on the experience acquired to date for CE-MRA of the carotid artery, mediastinal and pulmonary vessels, abdominal vasculature, and peripheral vessels. The main advantage of ultrafast CE-MRA is that patients are subjected to much more tolerable breath-hold investigations with the result that physiological motion such as peristalsis or major pulsation is minimised.

Adolescent↗
PubMed1997

[MR angiography of thoracic blood vessels].

Through the introduction of newly invented high-performance gradient systems to MRI, which enable for echoplanar imaging (EPI), also magnetic resonance angiography (MRA) has gained an entirely new field of applications and techniques. Ultrafast imaging techniques in MRA allow the investigation of larger vascular areas within a single breath-hold-period. Artifacts like motion induced signal misregistrations, dephasing or saturation of the vascular signal are minimized by extremely short echo times. The technique thus requires the intravenous application of a contrast media bolus, usually a gadolinium compound, which is in standard clinical use. Coordination of the bolus injection and the timing of the data acquisition is crucial for optimal results. The first pass evaluation of the contrast media resembles CTA to a certain extend. Due to the fast measurement and the high contrast in contrast-enhanced MRA (CE-MRA) new applications and indications are developed like MRA of the pulmonary vessels. The paper offers considerations and trials for optimization of thoracical CE-MRA. Besides parameter constellation also bolus-optimization is described with respect to the dedicated anatomical premises. Investigations on volunteers and on patients build a basis for suggestions of optimized CE-MRA procedures. To date, a final estimation of the clinical value of the new technique cannot be given since ongoing improvements change the optimal protocol frequently and the potential of further developments is high.

Adolescent↗
PubMed1994

[Flow cytometry detected S-phase fraction and ploidy as prognostic parameters in primary, node-negative breast cancer].

100 specimens of patients with primary node-negative breast cancer were examined by flow cytometry. 64 tumours were shown to be diploid and 36 tumours were aneuploid. The median was the cut-off level for tumours with low S-phase (< or = 10.9%) and high S-phase values (> 10.9%). Aneuploid tumours were associated with high S-phase fraction. The average length of follow-up was 42 months. In univariate analysis for disease-free survival, diploid tumours were shown to have a slightly better prognosis than aneuploid tumours (p = 0.07). This trend could not be shown in multivariate analysis. The S-phase fraction proved to be an independent prognostic factor. Patients, whose tumours had S-phase fractions < or = 10.9%, had significantly longer disease-free survival in univariate (long-rank-test: p = 0.021), as well as in multivariate analysis according to the Cox regression model (p = 0.033). Since, as already stated, the S-phase fraction is an independent prognostic factor for node-negative breast cancer, further adjuvant therapy studies should take this factor into consideration.

Adult↗
PubMed1994

Photosynthesis of a tropical canopy tree, Ceiba pentandra, in a lowland forest in Panama.

Diel (24 h) courses of CO(2) and water-vapor exchange of Ceiba pentandra (L.) Gaertn. (Bombacaceae) were studied under natural tropical conditions in the semi-evergreen moist forest of Barro Colorado Island, Panama. Measurements were conducted from early February 1991 (dry season), shortly after new leaves emerged, until mid-October 1991 (wet season), when leaves were shed. Rates of net CO(2) uptake were significantly higher in the dry season than in the wet season, and showed a linear decrease with leaf age. Leaf nitrogen concentrations and contents also decreased with age. Our estimate of annual carbon gain (2640 g CO(2) m(-2) year(-1) or 21 g CO(2) g(DW) (-1) year(-1)) is considerably higher than estimates available for temperate forest trees.

Journal Article↗
PubMed1993

[Determination of drug availability from commercial topical formulations with a multilayer membrane model].

Using the multilayer membrane system (MMS) the drug availability of four drugs from commercial topical formulations are determined. It was found that the availability differs when commercial formulations of beta-methasone-17-valerate, hydrocortisone, diclofenac-Na and clotrimazole were studied. It is shown that the drug availability for characterizing topical formulations has to be taken into account. The MMS applied in this study can be used for the determination of this parameter.

Administration, Topical↗
PubMed1992

Regulatory protein phosphorylation of phosphoenolpyruvate carboxylase in the facultative crassulacean-acid-metabolism plant Mesembryanthemum crystallinum L.

Phosphoenolpyruvate PyrP carboxylase (PyrPC) and PyrPC kinase were copurified from dark-adapted leaves of the common ice plant Mesembryanthemum crystallinum L. with crassulacean-acid metabolism (CAM). Purification by (NH4)2SO4 fractionation, chromatography on Fractogel-DEAE and hydroxylapatite resulted in a PyrPC preparation with a specific activity of 23-25 U/mg protein and a protein kinase activity of 255 mumol Pi.mol-1 PyrPC.s-1. After in vitro phosphorylation, the most prominently phosphorylated polypeptide was identified as PyrPC by immunoblotting and sequencing. Phosphorylation of PyrPC in vitro by incubation with 400 microM MgATP decreased its sensitivity towards malate. When purified in the absence of the protease inhibitor chymostatin, PyrPC lost an N-terminal sequence of 128 amino acids. Although the carboxylation reaction was unaffected, the truncated PyrPC could neither be phosphorylated in vitro nor inhibited by malate. This result and data obtained by limited proteolysis concur with the hypothesis [Jiao, J.A. & Chollet, R. (1989) Arch. Biochem. Biophys. 283, 300-305] that Ser11 is the phosphorylation site of the CAM PyrPC of M. crystallinum. At pH 7.0, the Km for ATP of the protein kinase was 25 microM; phosphorylation of PyrPC was maximal after 30 min at pH 7.0. The kinase showed also activity with histone III-S but not with dephosphorylated casein. It was inhibited by malate. The results show, that reversible protein phosphorylation is an important factor in the regulation of PyrPC in the facultative CAM plant M. crystallinum, similar to C4 and constitutive CAM plants.

Adenosine Triphosphate↗
PubMed1992

[Intrauterine pericardial effusion. Early symptom of a primary symptomatic congenital cytomegaly].

We report of a fetus who was ultrasonographically shown to have growth retardation, oligohydramnios and a pericardial effusion without other components of a hydrops fetalis at 28 weeks' gestation. At 29 weeks' gestation the child was born by cesarean section of pathological CTG. A congenital cytomegaly was diagnosed. The etiological role of the infection for the development of the pericardial effusion is discussed.

Adult↗
PubMed1991

Daily Changes in CO(2) and Water Vapor Exchange, Chlorophyll Fluorescence, and Leaf Water Relations in the Halophyte Mesembryanthemum crystallinum during the Induction of Crassulacean Acid Metabolism in Response to High NaCl Salinity.

Simultaneous measurements of net CO(2) exchange, water vapor exchange, and leaf water relations were performed in Mesembryanthemum crystallinum during the development of crassulacean acid metabolism (CAM) in response to high NaCl salinity in the rooting medium. Determinations of chlorophyll a fluorescence were used to estimate relative changes in electron transport rate. Alterations in leaf mass per unit area, which-on a short-term basis-largely reflect changes in water content, were recorded continuously with a beta-gauge. Turgor pressure of mesophyll cells was determined with a pressure probe. As reported previously (K Winter, DJ von Willert [1972] Z Pflanzenphysiol 67: 166-170), recently expanded leaves of plants grown under nonsaline conditions showed gas-exchange characteristics of a C(3) plant. Although these plants were not exposed to any particular stress treatment, water content and turgor pressure regularly decreased toward the end of the 12 hour light periods and recovered during the following 12 hours of darkness. When the NaCl concentration of the rooting medium was raised to 400 millimolar, in increments of 100 millimolar given at the onset of the photoperiods for 4 consecutive days, leaf water content and turgor pressure decreased by as much as 30 and 60%, respectively, during the course of the photoperiods. These transient decreases probably triggered the induction of the biochemical machinery which is required for CAM to operate. After several days at 400 millimolar NaCl, when leaves showed features typical of CAM, overall turgor pressure and leaf mass per unit area had increased above the levels before onset of the salt treatment, and diurnal alterations in leaf water content were reduced. Net carbon gain during photoperiods and average intercellular CO(2) partial pressures at which net CO(2) uptake occurred, progressively decreased upon salinization. Reversible diurnal depressions in leaf conductance and net CO(2) uptake, with minima recorded in the middle of the photoperiods, preceded the occurrence of nocturnal net CO(2) uptake. During these reductions, intercellular CO(2) partial pressure and rates of photosynthetic electron transport decreased. With advancing age, leaves of plants grown under nonsaline conditions exhibited progressively greater diurnal reductions in turgor pressure and developed a low degree of CAM activity.

Journal Article↗
PubMed1991

Salivary cortisol in children: correlations with serum values and effect of psychotropic drug administration.

This study compares the paired serum and salivary cortisol levels of 60 children and adolescents, obtained while performing a routine Dexamethasone Suppression Test. The results reveal significant correlations between serum and salivary cortisol levels in both drug-free (r = 0.90, p less than .001) and medicated patients (r = 0.81, p less than .001). Multiple regression analysis suggests that, while the slopes of the two regression curves are parallel (0.15 less than p less than 0.20), the intercepts are significantly different (p less than 0.05). This study supports the use of salivary measures of cortisol for children and adolescents. The authors suggest care in the use these measures while the patient is taking psychotropic medication.

Adolescent↗
PubMed1990

Inhibition of zeaxanthin formation and of rapid changes in radiationless energy dissipation by dithiothreitol in spinach leaves and chloroplasts.

Dithiothreitol, which completely inhibits the de-epoxidation of violaxanthin to zeaxanthin, was used to obtain evidence for a causal relationship between zeaxanthin and the dissipation of excess excitation energy in the photochemical apparatus in Spinicia oleracea L. In both leaves and chloroplasts, inhibition of zeaxanthin formation by dithiothreitol was accompanied by inhibition of a component of nonphotochemical fluorescence quenching. This component was characterized by a quenching of instantaneous fluorescence (F(o)) and a linear relationship between the calculated rate constant for radiationless energy dissipation in the antenna chlorophyll and the zeaxanthin content. In leaves, this zeaxanthin-associated quenching, which relaxed within a few minutes upon darkening, was the major component of nonphotochemical fluorescence quenching determined in the light, i.e. it represented the ;high-energy-state' quenching. In isolated chloroplasts, the zeaxanthin-associated quenching was a smaller component of total nonphotochemical quenching and there was a second, rapidly reversible high-energy-state component of fluorescence quenching which occurred in the absence of zeaxanthin and was not accompanied by F(o) quenching. Leaves, but not chloroplasts, were capable of maintaining the electron acceptor, Q, of photosystem II in a low reduction state up to high degrees of excessive light and thus high degrees of nonphotochemical fluorescence quenching. When ascorbate, which serves as the reductant for violaxanthin de-epoxidation, was added to chloroplast suspensions, zeaxanthin formation at low photon flux densities was stimulated and the relationship between nonphotochemical fluorescence quenching and the reduction state in chloroplasts then became more similar to that found in leaves. We conclude that the inhibition of zeaxanthin-associated fluorescence quenching by dithiothreitol provides further evidence that there exists a close relationship between zeaxanthin and potentially photoprotective dissipation of excess excitation energy in the antenna chlorophyll.

Journal Article↗
PubMed1990

Relative contributions of zeaxanthin-related and zeaxanthin-unrelated types of ;high-energy-state' quenching of chlorophyll fluorescence in spinach leaves exposed to various environmental conditions.

We have identified two rapidly relaxing components of non-photochemical fluorescence quenching which suggests that dissipative processes occur in two different sites in the photochemical system of leaves. Under a variety of treatment conditions involving different leaf temperatures, photon flux densities (PFD), exposure times, and in the presence of 5% CO(2) or 2% O(2), no CO(2), the components of nonphotochemical fluorescence quenching were characterized with respect to their sensitivity to dithiothreitol (DTT, which completely inhibits zeaxanthin formation), the effect on instantaneous fluorescence, and the rapidity of relaxation upon darkening. Under most circumstances the DTT-sensitive component (associated with a quenching of instantaneous fluorescence and correlated with zeaxanthin) represented the majority of the rapidly relaxing portion of fluorescence quenching. A DTT-insensitive (zeaxanthin-independent) component, which also relaxed rapidly upon darkening but was not associated with a quenching of instantaneous fluorescence, became proportionally greater in an atmosphere of 2% O(2) and no CO(2), at elevated leaf temperatures, and to some degree during the induction of photosynthesis (1 minute after the onset of illumination). A third component which was also DTT-insensitive and was sustained upon darkening, was largely suppressed in 2% O(2), O% CO(2). We conclude that, under conditions favorable for photosynthesis, energy dissipation occurred mainly in the chlorophyll antennae whereas, under conditions less favorable for photosynthesis, a second dissipation process, probably in or around the reaction center of photosystem II, also developed. Furthermore, evidence is presented that the zeaxanthin-associated dissipation process prevents sustained inactivation of photochemistry by excessive light.

Journal Article↗