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Biomedical subjects

A Keller

Publications and source records attributed to A Keller.

At least 271 records · Page 15Linked to original sources
PubMedDate not supplied

[MRI evaluation of carpal tunnel morphology after carpal tunnel release by a retinaculum lengthening technique].

AIM: The benefits of maintaining the pulley function of the flexor retinaculum in carpal tunnel release by lengthening or reconstructing it have been described. Quantitative MR imaging was used to investigate the morphological changes after open carpal tunnel release by such a retinaculum lengthening technique. METHOD: Ten patients had bilateral carpal tunnel MRI pre- and postoperatively. The MRI examinations were performed with a 1.5 Tesla imaging system and wrist coils. Carpal tunnel volume, carpal arch width, median nerve position and flexor tendon position in relation to the hamate-trapezial axis were recorded . RESULTS: Like other methods of carpal tunnel release with complete division of the flexor retinaculum, the retinaculum lengthening technique showed a significant postoperative increase of carpal tunnel volume. Carpal arch width increased only slightly. There was a significant palmar displacement of the median nerve but not of the flexor tendons. CONCLUSION: The findings support the hypothesis that maintenance of the pulley function of the retinaculum may lead to an early postoperative recovery of grip strength. In spite of some difficulties in application quantitative MR imaging may be a useful tool in evaluating the carpal tunnel morphology.

Adult↗
PubMedDate not supplied

[The Interplanta system model knee joint prosthesis. Preliminary results].

The SKI-knee joint is used since three years. Our experiences comprise 220 cases up to now. The follow-up time is still short, but the implant, which is partially designed very close to normal anatomy and on the other hand regards fundamental biomechanical aspects is showing a comparably low incidence of complications. The complications specifically due to the endoprosthetic system sums up to 10%. It is obvious that patellar complications are leading. This fact should be seen in close connexion to the anatomical design of the femoral component. With increasing experience these problems are diminished. Causes and potential elimination of patellar complications are discussed. Surgical procedure, especially advantages in comparison with other knee joints are described. The SKI-System in combination with its aligning instruments allow the surgeon anatomical reconstruction, very exact alignment of the implant and precise correction of preexisting deformities. In general the results are encouraging in comparison with formerly used knee joints after the same follow-up period.

Adult↗
PubMedDate not supplied

Short-term growth of premature infants treated with dexamethasone assessed by mini-knemometry.

AIM: The study aimed to measure the direct effect of dexamethasone (DEXA) on daily lower leg length per mini-knemometry of premature infants and to examine whether the administration of different doses is associated with alternations in growth. PATIENTS AND METHODS: We observed 20 premature children and had 276 complete mini-knemometrical and weight measurements (13.8 measurements per single child) for analysis. The gestational age of the infants was 26.8 +/- 1.9 weeks; the mean birth weight was 973 +/- 336 g. All infants underwent daily measurements of lower leg length performed by mini-knemometry. We divided the 41 DEXA administrations into three subgroups. Group I included a cumulative dose of 0.75 mg DEXA per kg bodyweight (BW), group II doses between 0.75 and 1.0 mg per kg BW and group III dosages above 1.0 mg per kg BW. RESULTS: We observed catch-up growth in group I within 24 h after stopping therapy. Groups II and III needed 48-72 h to achieve a normal level in short-term growth. CONCLUSION: Lower doses seemed to have an equivalent effect without long-term effect on lower leg length. In higher doses (groups II and III) the growth was suppressed for more than 24 h.

Anthropometry↗
PubMedDate not supplied

Intrinsic synaptic organization of the motor cortex.

Recent anatomical and electrophysiological studies of the intrinsic synaptic circuitry of the motor cortex are revealing novel aspects related to the functional organization of this cortical area. These studies demonstrate that the motor cortex is composed of modules consisting of columnar aggregates of neurons related to different aspects of the same movement. Excitatory and inhibitory connections of intracortical origin link neurons within each of these cortical modules, and also mediate interactions between different cortical modules located as far as 2-3 mm from each other. The intrinsic excitatory connections utilize glutamate, and act via both NMDA and non-NMDA postsynaptic receptors. The intrinsic inhibitory connections are GABAergic. Intrinsic cortical circuits are involved in the temporal coordination of different cortical modules for the execution of complex movement patterns. In addition, the intrinsic inhibitory and excitatory connections are involved in the plasticity of representation zones in the motor cortex, a phenomenon that occurs following nerve damage or during the acquisition of novel motor skills.

Animals↗
PubMedDate not supplied

Specific patterns of intrinsic connections between representation zones in the rat motor cortex.

The organization of intrinsic connections in rat motor cortex was studied by combining microstimulation and tract-tracing techniques. Maps of forelimb and vibrissal movements were constructed from the distribution of cortical sites from which movements were evoked in response to intracortical microstimulation. Then, a single injection of a fluorescent dextran was placed into either a vibrissal or a wrist representation zone, or into a region bordering these zones, resulting in anterograde labeling of long intrinsic, horizontal axons. Following injection into the vibrissal area, axons were largely restricted to the whisker representation zone and to the border region with the forelimb representation. Injections into a wrist zone labeled projections largely restricted to the forelimb area and to the border with the vibrissal area. Injections into a border region labeled dense projections throughout most of the forelimb and vibrissal areas. These findings indicate that intrinsic axon collaterals in the motor cortex form specific and extensive connections among representation zones related to movements of the same body part. These connections may be involved in the coordination of activity in different representation zones for the execution of complex movement patterns. The projection of axon collaterals into border regions may be the anatomical substrate for the rapid reorganization of motor cortical maps that occurs following various experimental manipulations.

Animals↗
PubMedDate not supplied

Mechanisms of LTP induction in rat motor cortex in vitro.

The motor cortex displays remarkable plasticity in response to changes in sensory and motor experience; however, the synaptic mechanisms underlying functional plasticity are not known. It is believed that synaptic processes that alter the strength of neuronal connections, such as long-term potentiation (LTP), are mechanisms by which synaptic circuits are modified by experience, resulting in functional adaptations. In the present study, we examined the mechanisms of LTP of synaptic responses in layers II/III to vertical (stimulation in layers V/VI) and horizontal (stimulation in layers II/III) inputs, in slices from rat motor cortex. Tetanic stimulation in layers V/VI or II/III induced LTP in 60% of the field potentials (n = 20) and in 73% of the intracellularly recorded postsynaptic potentials (n = 33). LTP was induced in cells with firing patterns characteristic of regular-spiking, fast-spiking, or bursting cells. LTP was expressed, for the most part, in kainate/AMPA receptor-mediated responses; however, potentiation of NMDA receptor-mediated components was also observed. Induction of LTP was prevented when either NMDA receptors or dihydropyridine-sensitive Ca2+ channels (DSCCs) were blocked, although blockade of DSCCs was less effective in preventing LTP induction. Based on the present data and previous LTP studies, we suggest that in many forms of LTP more than one mechanism participates in the induction process. The present findings may be relevant to the synaptic mechanisms underlying functional plasticity in motor cortex.

Animals↗
PubMedDate not supplied

Spontaneous dissection of the vertebral artery: MR findings.

Spontaneous (nontraumatic) dissection of the carotid and vertebral arteries, once thought to be rare, is being recognized and reported more frequently. We report one case of spontaneous dissection of the vertebral artery initially diagnosed by magnetic resonance imaging and subsequently confirmed by angiography.

Aortic Dissection↗
PubMedDate not supplied

Arginine infusion and/or acute changes of growth hormone levels do not acutely alter leptin serum levels.

UNLABELLED: Leptin, the ob gene product, is produced by differentiated adipocytes. It functions as an afferent signal to the central nervous system indicating satiety and fat mass status. It acts upon the hypothalamic-pituitary axis. Growth hormone (GH) secretion is thought to be stimulated by leptin. Conversely, leptin secretion and ob gene expression are regulated by classical neuroendocrine networks. Whether or not acute changes of GH concentrations directly alter leptin serum levels in vivo is still debated. We investigated whether or not acute changes in GH serum concentrations during arginine infusion (0.5 g/kg b. wt.) alter leptin serum levels in 45 children and adolescents (33 M, 12 F). GH and leptin serum levels were determined at -30, 0, 30, 60, 90, 120 min after arginine infusion using specific radioimmunoassays. Leptin serum concentrations remained unaltered throughout the arginine infusion in all children and adolescents whether or not GH secretion was normal. IN CONCLUSION: (1) Acute changes of GH levels do not alter leptin serum levels during acute arginine infusions over 120 min. (2) Arginine does not acutely modulate leptin secretion.

Adolescent↗
PubMedDate not supplied

A stochastic empirical model for regional heavy-metal balances in agroecosystems.

Mass flux balancing provides essential information for preventive strategies against heavy-metal accumulation in agricultural soils that may result from atmospheric deposition and application of fertilizers and pesticides. In this paper we present the empirical stochastic balance model, PROTERRA-S, that estimates heavy-metal and phosphorus accumulation in agricultural soils on the regional level. The basic units of these balances are land use systems defined by livestock production and cultivated crops. The model is designed to use available databases, such as regional agricultural statistics and soil information systems. In a case study, we assessed the phosphorus, cadmium, and zinc balances for the Sundgau region, Switzerland. The regional P requirements of crops were mainly supplied by animal manure (56%) and commercial fertilizers (40%). Net cadmium fluxes of the land use systems ranged from 1.0 g ha(-1) yr(-1) (dairy and mixed farm types) to 17.8 g ha(-1) yr(-1) (animal husbandry systems), whereas the regional net cadmium flux was only 1.4 g ha(-1) yr(-1). The regional net zinc flux was 605 g ha(-1) yr(-1). The smallest net zinc flux of 101 g ha(-1) yr(-1) was found for an arable farm type, whereas for animal husbandry systems fluxes up to 39.8 kg ha(-1) yr(-1) were estimated. Comparison of model results with reported metal balances of experimental farms shows that identification of agricultural land with high risks of heavy-metal accumulation benefits from stratification of heavy-metal balances according to land use systems while accounting for their P fertilization plans. Consequently, the model may support sustainable management of heavy-metal cycles in agricultural soils.

Agriculture↗
PubMedDate not supplied

Assessment of uncertainty and risk in modeling regional heavy-metal accumulation in agricultural soils.

Present agricultural land use and atmospheric deposition may lead to heavy-metal accumulation rates in soils that may violate soil quality standards in the future. To undertake suitable preventive measures against heavy-metal enrichment, flux balances in agroecosystems and their uncertainties have to be assessed. For this reason we developed an empirical stochastic model, PROTERRA-S, that considers heavy-metal inputs through agricultural management as well as outputs by crop removal and leaching on a regional scale. In this manuscript we describe application of PROTERRA-S to the Sundgau region in Switzerland. Considering uncertainty in informational and natural variability, large variations of the aggregated regional cadmium and zinc balances were found, with standard deviations that were of the same order of magnitude as their average values. Uncertainty in the simulated net zinc flux originated mainly from uncertainty in the zinc concentrations of manure and crops and from uncertainty in atmospheric deposition of zinc. For cadmium, the main contribution to the total uncertainty came from uncertainty in crop concentration, regression functions to estimate Freundlich parameters, atmospheric deposition, and from spatial variation of soil pH and cation exchange capacity (CEC). For both zinc and cadmium, informational uncertainty in input data were large, indicating that significant uncertainty reduction could be achieved by additional data collection campaigns. A monetary risk value for the regional zinc accumulation rate in Sundgau was calculated to be on the order of 22 million Euro.

Agriculture↗
PubMedDate not supplied

The flashlight test lacks validity as a screen for nocturnal hypoglycemia.

Though never validated, the flashlight test is a commonly used screen for nocturnal hypoglycemia. Between 2 a.m. and 4 a.m., we applied the test to 107 children at Eagle's Nest Camp for Children with Diabetes. We validated the test against simultaneously determined capillary blood glucose values (Glucoscan). An eyelid squint in response to the flashlight was considered an intact test. No significant difference existed between mean glucoses for intact and nonintact responses. Both sensitivity and positive predictive value are too low for the flashlight test to be useful in screening for nocturnal hypoglycemia.

Adolescent↗
PubMedDate not supplied

[Transcranial color Doppler estimation of blood flow parameters in respective basal cerebral arteries in healthy subjects].

Transcranial colour-coded Doppler sonography enables estimation of blood flow parameters in the basal cerebral arteries. Reference values as well as age and gender dependence of these parameters are not sufficiently established in transcranial Doppler studies. There are no reports regarding blood flow in the respective arteries of the circle of Willis. Therefore we examined 185 healthy volunteers--82 men (mean age 47, range 20-78 years old) and 103 women (mean age 47, range 22-86 years old). The subjects were divided into three age groups: 20-40 years old (group I), 41-60 years old (group II) and more than 60 years old (group III). The examinations were performed via the temporal acoustic window with a 2.5 MHz probe. Angle-corrected peak systolic, mean and end-diastolic velocities as well as impedance indices were determined in the anterior, middle and posterior cerebral arteries. In the group I mean velocity values (mean +/- SD) for the anterior, middle and posterior arteries amounted to 56 +/- 14 cm/s, 81 +/- 20 cm/s and 52 +/- 12 cm/s, respectively. In group II the values were 53 +/- 16 cm/s, 73 +/- 19 cm/s and 51 +/- 12 cm/s, and in group III the values were 44 +/- 11 cm/s, 59 +/- 11 cm/s and 40 +/- 9 cm/s. Decline in the blood flow velocities and increase in the impedance indices were found in all vessels with advancing age. This was most pronounced in subjects who were more than 40 years old. The decrease with age in blood flow velocities was more substantial in the middle cerebral arteries than in the anterior and posterior cerebral arteries. In contrast, the impedance indices increased more distinctly in the anterior cerebral arteries than in the middle and posterior cerebral arteries. We have demonstrated that the blood flow Doppler parameters are age and, in the group I (20-40 years old), also gender dependent. The range of the normal reference values of these parameters has proved to be wide. Decrease with age in blood flow velocities was found to be varied in the major cerebral arteries.

Adult↗
PubMedDate not supplied

Management information systems in maternal and child health/family planning programs: a multi-country analysis.

A diagnosis was conducted of management information systems (MIS) for maternal and child health and family planning programs in 27 African, 5 Asian, and 8 Latin American and Caribbean countries. The diagnosis covered the collection and use of information on physical infrastructure, human resources, equipment/supplies, services provided, coverage attained, and program quality and impact. It was found that many programs do not produce certain basic input and output indicators and that even among those that do, information is too infrequently brought to bear on management decision-making. Constraints under which the MIS operate in these countries are identified, and some rudimentary calculations of what would be required to improve MIS functioning are made.

Africa↗