Biomedical subjects

C Warnke

Publications and source records attributed to C Warnke.

5 recordsLinked to original sources

PubMed2006

Electrical stimulation of the energy metabolism in yeast cells using a planar Ti-Au-electrode interface.

We report on the influence of dielectric pulse injection on the energy metabolism of yeast cells with a planar interdigitated electrode interface. The energy metabolism was measured via NADH fluorescence. The application of dielectric pulses results in a distinct decrease of the fluorescence, indicating a response of the energy metabolism of the yeast cells. The reduction of the NADH signal significantly depends on the pulse parameters, i.e., amplitude and width. Furthermore, the interface is used to detect electrical changes in the cell-electrolyte system, arising from glucose-induced oscillations in yeast cells and yeast extract, by dielectric spectroscopy at 10 kHz. These dielectric investigations revealed a beta(1)-dispersion for the system electrolyte/yeast cells as well as for the system electrolyte/yeast extract. In agreement with control measurements we obtained a glycolytic period of 45 s for yeast cells and of 11 min for yeast extract.

Electric Conductivity↗

PubMed2006

Association between cardiac disorders and a decades-previous history of diphtheria.

A long, prior history of diphtheria is common among middle-aged and elder European adults. The aim of the present study was to determine whether the risk of reduced ventricular function and impaired intraventricular conduction is increased in individuals with a history of diphtheria. A study population of 2,480 subjects (1,222 women) aged 45 years or older who were recruited for the Study of Health in Pomerania were available for the present analyses. Left ventricular function was assessed by echocardiography. Intraventricular conduction blocks were diagnosed using electrocardiograms. Multivariable analyses revealed that individuals with a history of diphtheria had neither an increased odds for reduced fractional shortening (OR 1.21, 95% CI 0.69-2.11; p=0.51) nor an increased odds for intraventricular conduction blocks (OR 0.90, 95% CI 0.55-1.46; p=0.67). However, regression models revealed two-way interactions between the exposure variable and hypertension with respect to both endpoints. A history of diphtheria increased the odds for both endpoints in normotensive but not in hypertensive individuals. The findings show that a history of diphtheria several decades previously in a patient is a risk marker for reduced cardiac function and impaired intraventricular conduction in individuals at low risk for these disorders.

Adult↗

PubMed2004

Effect of interstitial stereotactic radiosurgery on behavior and subjective handicap of epilepsy in patients with gelastic epilepsy.

Patients with symptomatic epilepsy due to hypothalamic hamartomas often are compromised not only by pharmacoresistant epileptic seizures but also by behavioral disturbances and cognitive dysfunction. We report the effect of successful treatment with stereotactic interstitial radiosurgery by intrahypothalamic implantation of 125I seeds on behavior and subjective handicap. In all patients rendered seizure-free or suffering only from auras, improvement of behavior was reported by parents and colleagues or schoolteachers. Parents' ratings according to the Child Behavior Checklist showed improvements with respect to social problems and attention. Self-ratings of quality of life by adult patients showed improvements in activities, working situation, and self-perception. These improvements were not observed in patients in whom clinically manifest seizures and interictal EEG discharges persisted after radiosurgery.

Activities of Daily Living↗

PubMed2001

Morphological and functional changes of stallion spermatozoa after cryopreservation during breeding and non-breeding season.

The study compared quality and freezability of stallion semen during breeding and non-breeding seasons. Ejaculates were collected twice per week from four stallions during May (n = 24) and December (n = 24). The semen was mixed with skim milk extender, centrifuged and resuspended in fresh extender. Aliquots of this sperm suspension were separated from extender and diluted in TALP medium for sperm evaluation or with cryoextender (type "Gent" or a combination of Triladyl and skim milk). Samples of 0.5ml were cryopreserved in straws using a programmed freezer. Parameters of sperm quality were evaluated before and after freezing/thawing. These included percentages of motile spermatozoa and of morphological intact sperm. Typical injuries were demonstrated by scanning electron microscopy (S.E.M.). The acrosomal status was visualised using FITC-conjugated peanut agglutinin, and the acrosome reaction was induced by calcium ionophore A 23187. The chromatin stability was estimated by acridine orange test. In winter, the average percentages of motile and morphologically normal sperm (67 and 74.3%, respectively) were higher than during the breeding season in May (59 and 65.9%; P < 0.05). After freezing/thawing the proportions of vital and intact sperm decreased significantly. The number of motile sperm declined to 15 and 18% in May and December (range 5-40%), and of morphologically intact sperm to 51% in both seasons. Results of S.E.M. showed typical membrane ruptures in the acrosomal region and some sperm with abnormal necks. The proportion of frozen sperm with spontaneous acrosome reaction was higher during winter (86.5 versus 77.0%), suggesting a higher degree of membrane reactivity. Percentages of spermatozoa with denaturated chromatin were minimal and showed minimal differences between fresh and frozen state, stallions or seasons. An additional decondensation treatment with papain and DTE revealed a slightly enhanced number of spermatozoa with denaturable DNA after cryopreservation, especially in December (5.4 +/- 1.3%). The influence of cryoextenders was not significant for most sperm parameters, but there was a high variability between the stallions. Altogether, the influence of factors on the quality of spermatozoa has the following rank order: cryopreservation > stallion > season. Different cellular structures seem to have different susceptibilities to physicochemical stress. The cryopreservation of sperm during December results in survival rates similar to those measured during the breeding season, even more important for successful preservation is the selection of suitable semen donors.

Acrosome↗

PubMed2001

Spatio-temporal dynamics in glycolysis.

During the glycolytic degradation of sugar in a thin layer of yeast extract, travelling waves of NADH and protons can be generated that carry a state of high enzymatic activity through the system. The controlled initiation of such waves with an activator of the enzyme phosphofructokinase (PFK) and the influence of various salts and co-factors on the propagation dynamics are investigated. Furthermore a first study of the dispersion of waves is presented. The experimental characterisation of this in vitro system contributes to unravelling the possible role of glycolysis for biological information processing. In this context, the provision of chemically available energy in the absence of compartmentation by glycolysis is of primary importance.

Glycolysis↗