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Biomedical subjects

T Eckert

Publications and source records attributed to T Eckert.

At least 19 recordsLinked to original sources
PubMed2005

Increased pre-SMA activation in early PD patients during simple self-initiated hand movements.

The slowness of movement, termed bradykinesia, is one of the main symptoms of Parkinson's disease (PD). This symptom may be due to the inability of PD patients to maximise the speed of internally driven movements. The mesial premotor areas and in particular the pre-supplementary motor area (pre-SMA) seem to play a crucial role in the temporal initiation of movements in humans and animals. However, this activation seems to be debatable in imaging studies of PD patients. We performed a motor paradigm with temporally self-initiated movements in nine de novo PD patients before and after initiation of dopaminergic medication. The main finding was an increased activation of the pre-SMA in de novo PD patients compared with healthy age-matched control subjects. This result indicates the contribution of the pre-SMA in the temporal initiation of self-generated movements and in the disease pathology of PD. Increased bilateral activation of the superior cerebellum, mainly on the ipsilateral side, and a decreased activation of the ipsilateral inferior cerebellum in PD patients were also present. These findings provide new insights into the activation pattern of the cerebellum in PD patients.

Aged↗
PubMed2003

The effect of free polymer on the interactions and the glass transition dynamics of microgel colloids.

By studying the phase behaviour and the short range order of polystyrene microgel colloids in a good solvent we demonstrated that these particles can be considered as hard spheres or nearly hard spheres if the internal cross link density is made sufficiently high. A binary mixture of 1:50 crosslinked (1 crosslink per 50 monomers) particles with a size ratio R(small)/R(large) = 0.83 and a number ratio N(small)/N(large) = 2.7 was characterized with respect to the short range order and glass transition dynamics. We found that this mixture can be mapped onto a one-component hard sphere system with an effective polydispersity of 11%, even though for the particle interactions an inverse power potential u(r) alpha r(-35) was established. The only significant difference observed was a shift of the glass transition to a higher volume fraction of 0.595. Thus, the binary mixture was used as a non-crystallizing reference system to study the effect of free polymer on interactions and glass transition dynamics. Addition of linear polystyrene with a size ratio delta = R(g,polymer)/R(colloid) = 0.054 induced short-ranged depletion attractions between microgel particles. In the case of a glassy sample already a rather small amount of polymer leads to melting of the glass and a re-entrant glass transition is observed at high polymer content. From the difference of the line shapes of the density autocorrelation functions on approaching the different transition lines. measured over the full dynamic range, a change of the freezing mechanism from a packing-driven glass transition at low polymer content to a bonding-driven glass transition at high polymer content was deduced.

Journal Article↗
PubMed2002

Re-entrant glass transition in a colloid-polymer mixture with depletion attractions.

Performing light scattering experiments we show that introducing short-ranged attraction to a colloid suspension of nearly hard spheres by addition of a free polymer produces new glass-transition phenomena. We observe a dramatic acceleration of the density fluctuations amounting to the melting of a colloidal glass. Upon increasing the strength of the attractions the system freezes into another nonergodic state sharing some qualitative features with gel states occurring at lower colloid packing fractions. This re-entrant glass transition is in qualitative agreement with recent theoretical predictions.

Journal Article↗
PubMed2001

Motivation for smoking cessation: what role do doctors play?

PRINCIPLES: Cigarette smoking causes an estimated 13% of all deaths in Switzerland. Though most smokers will eventually become ex-smokers of their own volition, physicians play an important role in accelerating the process of quitting among smoking patients. Even brief advice from physicians is effective in doing so. The purpose of this study was to investigate which smokers were asked about their smoking habits, and how often, whether they received advice to quit, and how this correlates with the patient's desire to quit. METHODS: Telephone interviews were carried out with a random sample of smokers and ex-smokers from the German-speaking Swiss population (n = 993). We collected information on personal characteristics, smoking habits, and recall of physicians' advice. Data was analysed descriptively and by logistic regression. RESULTS: 88% recalled being asked by a doctor about their smoking habits. In contrast, only 34% of smoking patients recalled being advised to stop. Women, older people and those in poor subjective health were asked more frequently. Heavier smokers and those in poor subjective health were advised more frequently. Current smokers more frequently express the desire to quit if they are heavier smokers and have been advised to quit by their physician, compared with those who have not received such advice. CONCLUSIONS: Similarly to the international findings, smoking patients in Switzerland receive brief advice with insufficient frequency. Action should therefore be taken to encourage health professionals not only to question all smoking patients but to advise and motivate them to quit smoking.

Adolescent↗
PubMed2000

[Blood titanium levels before and after oral administration titanium dioxide].

The normal titanium levels in the blood of males between 24 and 66 years of age were found to be 11.2 micrograms/l (rsd 4.1). After oral administration of titanium dioxide containing capsules or as powder (anatas) it could be observed that the material can be absorbed from the gastro-intestinal tract. If two titanium dioxide qualities, having different mean particle sizes (0.16 micron and 0.38 micron), are administered orally, the latter shows less absorption, most likely due to agglomeration phenomena. The blood concentration/time correlation shows the type of curves which are characteristic for a persorption mechanism of absorption and reveal a high individual fluctuation. An increase of the administered dose by twice the amount shows only a tendentious response in the corresponding blood levels. The method of analysis was ICP-AES. A pretreatment of the samples in order to eliminate the organic matrix is necessary.

Administration, Oral↗
PubMed1999

Tight binding of bulky fluorescent derivatives of adenosine to the low affinity E2ATP site leads to inhibition of Na+/K+-ATPase. Analysis of structural requirements of fluorescent ATP derivatives with a Koshland-Némethy-Filmer model of two interacting ATP sites.

A Koshland-Némethy-Filmer model of two cooperating ATP sites has previously been shown to explain the kinetics of inhibition of Na+/K+-ATPase (EC 3.6.1.37) by dansylated ATP (Thoenges, D., and Schoner, W. (1997) J. Biol. Chem. 272, 16315-16321). The present work demonstrates that this model adequately describes all types of interactions and kinetics of a number of ATP analogs that differ in their cooperativity of the high and low affinity ATP binding sites of the enzyme. 2',3'-O(2,4,6-trinitrophenyl)ATP binds in a negative cooperative way to the E1ATP site (Kd = 0.7 microM) and to the E2ATP site (Kd = 210 microM), but 3'(2')-O-methylanthraniloyl-ATP in a positive cooperative way with a lower affinity to the E1ATP binding site (Kd = 200 microM) than to the E2ATP binding site (Kd = 80 microM). 3'(2')-O(5-Fluor-2,4-dinitrophenyl)-ATP, however, binds in a noncooperative way, with equal affinities to both ATP binding sites (Kd = 10 microM). In a research for the structural parameters determining ATP site specificity and cooperativity, we became aware that structural flexibility of ribose is necessary for catalysis. Moreover, puckering of the ring atoms in the ribose is essential for the interaction between ATP sites in Na+/K+-ATPase. A number of derivatives of 2'(3')-O-adenosine with bulky fluorescent substitutes bind with high affinity to the E2ATP site and inhibit Na+/K+-ATPase activity. Evidently, an increased number of interactions of such a bulky adenosine with the enzyme protein tightens binding to the E2ATP site.

Adenosine↗
PubMed1999

The effect of combined oestrogen and progesterone replacement on the renal responses to oxytocin and vasopressin in ovariectomized rats.

OBJECTIVE: Renal responsiveness to the neurohypophyseal hormones, oxytocin and vasopressin, has been shown in the rat to vary during pregnancy and lactation. A study was performed to determine whether ovarian steroids could contribute to the observed changes. DESIGN: Using a previously validated method, fluid excretion during infusion of oxytocin or vasopressin was monitored in ovariectomized animals with and without chronic administration of oestrogen and progesterone. METHODS: After 14 days treatment with vehicle or 12.5 mg hydroxyprogesterone caproate and 0.25 mg oestradiol valerate injected every 3 days, rats were infused with 0.077 mol/l NaCl for an equilibration period of approximately 2.5h. Timed urine collections for the determination of volume and electrolytes were then made during a control period of at least 45 min and for 60 min while the infusate was supplemented with vasopressin (40 fmol/min) or oxytocin (50 fmol/min). Further observations were made for a final 90 min of hypotonic saline infusion. In control infusions saline alone was given. RESULTS: Treatment with ovarian steroids did not affect the volume of urine excreted during hormone infusion. Electrolyte excretion, however, was affected with lower concentrations of sodium and chloride on oxytocin infusion being seen in the steroid-treated animals. During vasopressin infusion, peak electrolyte concentrations were also achieved later in this group of animals. CONCLUSION: The increased circulating concentrations of oestrogen and progesterone seen during pregnancy could contribute to variations in the natriuretic response to neurohypophyseal hormones observed in the rat.

Animals↗
PubMed1997

Suspected malignant hyperthermia in a 13-month-old: today's "typical" episode--a case report.

A case of suspected malignant hyperthermia in a 13-month-old female, to whom succinylcholine was not administered, is presented. The patient presented for a repair of the right radial nerve under general anesthesia. Induction was accomplished with halothane, nitrous oxide, and oxygen. Tracheal intubation was facilitated with intravenous vecuronium. Controlled ventilation was initiated, and anesthesia was maintained with isoflurane, nitrous oxide, oxygen, morphine sulfate, and vecuronium. At the conclusion of the surgical procedure, an abrupt increase in ETCO2, an elevation in body temperature, and a mixed acidosis was observed. Resolution of symptoms followed the administration of dantrolene sodium. The patient underwent an uneventful postoperative recovery and was discharged home. It was felt that the patient was too young to undergo a muscle biopsy for a caffeine-halothane stimulation test.

Age Factors↗
PubMed1996

[Outcome of corneal astigmatism after pars plana vitrectomy with or without simultaneous cataract extraction].

Changes in corneal astigmatism induced by pars plana vitrectomy (PPV) (group I, 44 eyes) and PPV combined with no-stitch cataract surgery (group II, 20 eyes) were studied prospectively for a period of at least 3 months. The amount and orientation of the keratometric cylinder and the surgically induced astigmatism (according to the methods of Jaffe and Clayman or Naeser) were analysed. In the first postoperative week both groups exhibited a marked against-the-rule to oblique astigmatism (in group I up to 3.65 +/- 1.40 D, in group II up to 3.05 +/- 1.60 D, according to Jaffe). After 3 months this had declined in group I to 0.40 +/- 0.27 D, whereas a slight induced astigmatism (0.97 +/- 0.41 D) persisted in group II. Gas endotamponade did not significantly aggravate the postoperative astigmatism in either group. Computerized video-keratography generally revealed an asymmetric bowtie pattern during the first week. Our results show that PPV alone induces no appreciable long-term corneal astigmatism. Optical rehabilitation, however, can be delayed by a marked short-term postoperative astigmatism. PPV with simultaneous no-stitch cataract surgery, by contrast, was found to induce a persisting slight astigmatism against the rule.

Adult↗
PubMed1983

[Micelle formation as the origin of the cut-off phenomenon in a homologous series of local anesthetics].

On the example of the surface anaesthetic homologous series of 4-alkoxybenzoic-diethylaminoethylester-HCl (parethoxycaine) the so-called "cut off"-effect was studied. The "cut off"-effect is the phenomenon, that a weaker efficiency or an inefficiency is observed on the higher homologues of therapeutic substances. It is demonstrated that the "cut off"-effect is referred to the micellisation and aggregation of the higher homologues of the local anaesthetics in aqueous solution. This has the consequence, that the higher homologues cannot diffuse on the pain receptors and so the efficiency is reduced. By the addition of urea the aggregation will be reduced and the chain length-efficiency curve will take a different course.

Anesthetics, Local↗