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Biomedical subjects

L Huber

Publications and source records attributed to L Huber.

At least 19 recordsLinked to original sources
PubMed2001

Indications for using video-assisted thoracoscopic surgery to diagnose diaphragmatic injuries after penetrating chest trauma.

BACKGROUND: Video-assisted thoracoscopic surgery (VATS) has been shown to be an accurate method for identifying diaphragmatic injuries (DIs). The purpose of this investigation was to establish specific indications for the use of VATS after penetrating chest trauma. METHODS: A retrospective review of all patients undergoing VATS after penetrating chest trauma at a level 1 trauma center over an 8-year period was performed. Logistic regression was used in an attempt to identify independent predictors of DI. RESULTS: One hundred seventy-one patients underwent VATS assessment of a hemidiaphragm, and 60 patients (35%) were found to have a DI. Five independent risk factors for DI were identified from analyzing the patient records: abnormal chest radiograph, associated intraabdominal injuries, high-velocity mechanism of injury, entrance wound inferior to the nipple line or scapula, and right-sided entrance wound. CONCLUSIONS: In the largest published series of patients undergoing VATS to exclude a DI, this review identifies five independent predictors of DI after penetrating chest trauma. A diagnostic algorithm incorporating these five factors was designed with the goal of reducing the number of unrecognized DIs after penetrating chest trauma by using VATS for patients at greatest risk for such injuries.

Adult↗
PubMed2001

First experiences with outpatient care of patients with implanted axial flow pumps.

As known from patients with pulsatile ventricular assist devices (VADs), early mobilization, physical exercise, and return to normal life are essential for optimal recovery. Recently, implantable rotary pumps became available for extended left ventricular support as bridges to transplantation. Modified procedures are essential for patient training and hospital discharge. The MicroMed-DeBakey VAD was implanted in 10 patients with end-stage heart disease. After recovery, regular ergometer training was performed with loads adapted to the patient's condition. Procedures for patient observation under outdoor conditions and a blood pressure measuring device for low pulse pressure conditions were developed. Improvement of physical condition was achieved in 8 patients. In the first 2 patients, exercise capacity was limited due to flow obstruction. In the following patients, an increase of workload on the ergometer up to 120 W was observed. Correlated with training, lactate/load relationship and heart rate decreased. Three patients were discharged from the hospital during support. The DeBakey-VAD system can support patients for extended time periods and is suitable for recovery and exercise. Under optimal patient and environmental conditions, discharge from the hospital can be obtained.

Adult↗
PubMed2000

Mice trisomic for a bacterial artificial chromosome with the single-minded 2 gene (Sim2) show phenotypes similar to some of those present in the partial trisomy 16 mouse models of Down syndrome.

The Drosophila single-minded (sim) transcription factor, is a master regulator of fruitfly neurogenesis. Recently, we have cloned and mapped a human homolog of sim, SIM2, to chromosome 21 in the so-called 'Down syndrome chromosomal region'. Three copies of SIM2 may contribute to some Down syndrome (DS) phenotypes because of the mapping position function as transcriptional repressor, temporal and spatial expression pattern of mouse Sim2, and the potentially analogous role of human SIM2 to that of Drosophila sim during neurogenesis. In order to validate this hypothesis in vivo, we have created the first bacterial artificial chromosome transgenic mice overexpressing a gene possibly involved in DS with only one or two additional copies of mouse Sim2. The transgene was shown to be expressed in the same spatial pattern as the endogenous gene. The mice develop normally, are fertile and do not show detectable histopathological abnormalities. However, detailed analysis of their behavior revealed anxiety-related/reduced exploratory behaviour and sensitivity to pain, phenotypes similar to those also present in other partial trisomy 16 mouse models of DS. Our data therefore suggest that overexpression of SIM2 contributes to some of the complex DS phenotypes.

Animals↗
PubMed2000

True imitation in marmosets.

Marmosets, Callithrix jacchus, observed a demonstrator removing the lids from a series of plastic canisters to obtain a mealworm. When subsequently allowed access to the canisters, marmosets that observed a demonstrator using its hands to remove the lids used only their hands. In contrast, marmosets that observed a demonstrator using its mouth also used their mouth to remove the lids. Since hand and mouth demonstrators brought about identical changes in the canisters, the differential test behaviour of the observer groups suggests that they learned about the demonstrator's behaviour. Furthermore, marmosets that had not been given the opportunity to observe a demonstrator prior to testing had a low probability of mouth opening, even if the canisters were previously opened by a mouth-opening demonstrator in an olfactory control experiment. Corroborating Bugnyar & Huber's (1997, Animal Behaviour, 54, 817-831) earlier findings, our results provide further evidence that marmosets can imitate. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

Natural categorization through multiple feature learning in pigeons.

Recently (Troje, Huber, Loidolt, Aust, & Fieder 1999), we found that pigeons discriminated between large sets of photorealistic frontal images of human faces on the basis of sex. This ability was predominantly based on information contained in the visual texture of those images rather than in their configural properties. The pigeons could learn the distinction even when differences of shape and average intensity were completely removed. Here, we proved more specifically the pigeons' flexibility and efficiency to utilize the class-distinguishing information contained in complex natural classes. First, we used principal component as well as discriminant function analysis in order to determine which aspects of the male and female images could support successful categorization. We then conducted various tests involving systematic transformations and reduction of the feature content to examine whether or not the pigeons' categorization behaviour comes under the control of category-level feature dimensions--that is, those stimulus aspects that most accurately divide the stimulus classes into the experimenter-defined categories of "Male" and "Female". Enhanced classification ability in the presence of impoverished test faces that varied only along one of the first three principal components provided evidence that the pigeons used these class-distinguishing stimulus aspects as a basis for generalization to new instances.

Animals↗
PubMed2000

Altered subcellular distribution of cadherin-5 in endothelial cells caused by the serum of pre-eclamptic patients.

The main clinical features of pre-eclampsia are oedema and vascular leakage. Cadherin-5 mediates endothelial cell-cell contact in the vascular endothelium and may regulate permeability as a vascular function. Therefore, we addressed the question of whether pre-eclampsia alters cadherin-5 expression and intracellular distribution. Confluent human umbilical vein endothelial cells (HUVEC) were incubated with 20% serum from patients with pre-eclampsia (n = 18), haemolysis-elevated liver enzymes-low platelet syndrome (HELLP) (n = 12), pregnancy-induced hypertension (PIH) (n = 18) or normal pregnancy (n = 10). After incubation with sera from patients with pre-eclampsia, immunostaining analyses showed cadherin-5 accumulation in vesicular and tubular structures of the Golgi apparatus. Immunoblot analyses of HUVEC after pre-eclampsia serum incubation showed an increase of the stable form of cadherin-5 while degradation products decreased. Degradation of cadherin-5 takes place at the cell membrane, so this decrease may be due to a decrease of cadherin-5 in the cell membrane. The accumulation of cadherin-5 in the vesicular and tubular structures of the Golgi apparatus indicates that targeting of cadherin-5 to the plasma membrane could be disrupted. We suggest that intracellular retention of cadherin-5 caused by serum factors in patients with pre-eclampsia may decrease the number of adhesion complexes in the cell membrane, thereby contributing to endothelial dysfunction.

Adult↗
PubMed1999

Categorical learning in pigeons: the role of texture and shape in complex static stimuli.

Pigeons are known to be able to categorize a wide variety of visual stimulus classes. However, it remains unclear which are the characteristics of the perceptually relevant features employed to reach such good performance. Here, we investigate the relative contributions of texture and shape information to categorization decisions about complex natural classes. We trained three groups of pigeons to discriminate between sets of photorealistic frontal images of human faces according to sex and subsequently, tested them on different stimulus sets. Only the pigeons that were presented with texture information were successful at the discrimination task. Pigeons seem to possess a sophisticated texture processing system but are less capable in discriminating shapes. The results are discussed in terms of the possible evolutionary advantages of utilizing texture as a very general and potent perceptual dimension in the birds' visual environment.

Animals↗
PubMed1999

The erythrocyte-perfused "working heart" model: hemodynamic and metabolic performance in comparison to crystalloid perfused hearts.

A brief period of ischemia was used to evaluate an erythrocyte-enriched Krebs-Henseleit (KH) buffer (n=8) compared to KH only (n=8) in an isolated working rabbit heart. Experimental protocol was as follows: preischemic baseline, 5 min of global ischemia followed by 45 min of reperfusion. Preischemic heart rate was identical, coronary flow was significantly lower (2.7 versus 5.6 mL/min/g wet wt, p<0.01), the other hemodynamic and biochemical values were significantly higher in erythrocyte-perfused hearts: aortic flow 23.5 versus 12.0, p<0.01; cardiac output 26.2 versus 17.6, p<0.01; all in mL/min/g wet wt; dp/dt max 1286 versus 997 mmHg/s, p<0.01; myocardial oxygen consumption 3.5 versus 2.3 micromol/min/g wet wt, p<0.05. During early reperfusion, in the erythrocyte-perfused hearts, coronary flow further increased (p<0.003), the other hemodynamic parameters returned to baseline values in both groups. High-energy phosphates showed significantly higher values (ATP 2.0+/-0.1 versus 1.3+/-0.1, p<0.05; CrP 2.0+/-0.2 versus 1.6+/-0.1, p<0.05 all in micromol/g wct wt), water content was significantly lower (81% versus 74%, p<0.05) in erythrocyte-perfused hearts. It can be concluded that the erythrocyte-perfused working heart model provides excellent oxygenation, leading to superior hemodynamic and metabolic performance. Additionally, in the erythrocyte-perfused hearts preservation of coronary flow reserve underlines the physiological competency of this preparation.

Adenine Nucleotides↗
PubMed1999

Microspheres based detoxification system: in vitro study and mathematical estimation of filter performance.

Because of the closed plasma (secondary) circuit in the Microspheres based Detoxification System (MDS), a convective blood purification system, the same amount of filtrated plasma is backfiltrated into the blood circuit. Therefore, there is no direct way to determine the ultrafiltrate production rate, which is an important factor of efficiency. The only possible way to estimate the filtration properties of the filter is to consider pressure values. In this study the pressure distribution in the filter was investigated in vitro. To explain the results and to calculate inaccessible parameters, a mathematical model was established which also considered the asymmetric behaviour of the filter membrane. The result was a linear pressure gradient, agreement with the measurements was reasonably good (calculated primary pressure loss differs <13% from measured value when using mean measured filter resistance as model parameter). Linear pressure distribution offers the possibility of easily calculating the filtration length, a parameter which can be used to estimate the filter condition. The comparison between calculated filtration and backfiltration rates offers an instrument of control for these values.

Adsorption↗
PubMed1998

The impact of a simulated immunization registry on perceived childhood immunization status.

We developed a simulated immunization registry to assess the impact on the perceived immunization status in a population-based sample of 2-year-olds living in Olmsted County, MN, in 1995. We compiled records of all immunizations by abstracting immunization data from all medical care facilities in the county. The data collected from each facility were analyzed separately to provide the immunization rate as perceived by each facility. This perceived rate was compared to the rate obtained by combining all recorded immunizations from all facilities (simulated registry). Information on children not receiving any carefrom facilities in Olmsted County was compiled from birth certificate data and community school lists. Data from the simulated registry indicated that 69.1% of all children in Olmsted County with medical records were up-to-date on their immunizations by 20 months of age. By 24 months, this increased to 74.2%. The immunization rate of 24-month-old children recorded at individual healthcare facilities in Olmsted County ranged from 24.3% to 79.5%. The addition of data from the simulated registry increased the immunization rate at each site: a 27.7% relative increase in the site with the lowest recorded immunization rate, a 14.0% increase in the site with the intermediate immunization rate, and a 6.9% increase in the site with the highest internally perceived immunization rate. The registry also identified excess immunizations in 5% of the county's 2-year-olds. Each healthcare facility in this community gained an immediate benefit from the development of a simulated immunization registry. This immediate improvement in one quality-of-care measure (up-to-date immunization rate) should be factored into the cost/benefit assessment of immunization registries.

Birth Certificates↗
PubMed1998

In vitro thrombogenicity testing of artificial organs.

Thromboembolic complications remain as one of the main problems for blood contacting artificial organs such as heart valves, bloodpumps and others. In vitro evaluation of thrombogenesis in prototypes has not previously been part of the standard evaluation of these devices. In comparison to hemolysis testing, evaluation of the thrombogenic potential is more difficult to perform because of the complexity of the blood coagulation system. We present an in vitro testing procedure that allows the accelerated examination of the thrombogenic potential of different types of blood pumps. Additionally, first results are presented that indicate the reliability of the accelerated clotting test for mechanical heart valves. Results for the centrifugal pump BioMedicus and two microaxial pumps have shown typical thrombus formation at locations such as bearings. The results indicate that the accelerated clotting test is an excellent addition to the much more expensive animal testing of artificial organs or assist devices. In vitro testing permits studies of thrombus formation to be performed at an early stage and at low costs and also facilitates a more precise investigation of device areas known to be potential hot spots for thrombus formation.

Animals↗
PubMed1997

Push or pull: an experimental study on imitation in marmosets

A laboratory experiment was conducted in order to explore the possibility of imitation, that is, response learning by observation, in marmosets, Callithrix jacchusInexperienced individuals were allowed to observe a skilful model that demonstrated one of two possible techniques (pushing or pulling a pendulum-door) to get food from inside a wooden box. Their initial manipulative actions, performed when exposed to the box in a subsequent test, were compared with those of naive control subjects (non-observers). The observers showed less exploratory behaviour than the non-observers and, more importantly, some showed a strong tendency to use the demonstrated opening technique in the initial test phase. This initial preference disappeared in the course of five test sessions and the observers converged towards the simpler, alternative solution that was generally preferred by the non-observers. Despite fundamental individual differences in the observer group and the failure to find a significant group effect, the results indicate that marmosets are capable of learning simple motor skills through conspecific observation.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour

Journal Article↗
PubMed1997

Flow measurement at the pump head of centrifugal pumps: comparison of ultrasonic transit time and ultrasonic Doppler systems.

Determination of blood flow is essential for monitoring rotary blood pumps. However, accurate measurement directly adjacent to the pump housing is difficult because of the highly irregular flow profiles near the fast spinning rotor. Therefore, a specially adapted flow probe based on the ultrasound transit time (USTT) principle was designed to evaluate the flow in centrifugal blood pumps. The probe can be directly mounted at the housing and creates 2 crossed measuring ultrasound beams. The mean value, Qm, of the 2 output signals corresponds to the blood flow and the difference, Qd, correlates to the vorticity of the flow profile in the pump outflow tract. In vitro measurements obtained an accuracy for mean flow values of better than +/-0.6 L/min in extreme working points and for vorticity values even as high as Qd = 3.5 L/min. Because of vorticity, however, the output signal contained considerable noise, and that required the application of a 10 Hz filter. Positioning of the ultrasound (US) beams parallel to the axial direction of the pump was superior to radial positioning. Additional measurement of the flow profile demonstrated that a large vorticity occurred (up to Qd equal to 3.5 L/min), and this vorticity was highly dependent upon the afterload of the pump. In vivo experiments demonstrated the reliability of the method. We concluded that USTT flow measurement can determine blood flow immediately adjacent to the pump housing with sufficient accuracy, and these measurements are superior to those from US-Doppler systems (which cannot handle the vorticity accurately enough) and electromagnetic devices (which lack zero stability).

Blood Flow Velocity↗
PubMed1997

Infectious agents in acute respiratory disease in horses in Ontario.

A study of acute respiratory disease in horses in Ontario was undertaken to determine the identity of current causative infectious agents. A nasopharyngeal swab was designed and utilized to maximize isolation of viruses, mycoplasma, and pathogenic bacteria. Serum samples were collected for parallel determination of antibody titers to equine influenza virus type A subtype 1 (H7N7) and subtype 2 (H3N8), equine rhinovirus types 1 and 2, equine herpesvirus type 1, Mycoplasma equirhinius, and Mycoplasma felis. Equine rhinovirus type 2 was recovered from 28/92 horses tested, and equine influenza virus type A, subtype 2, was recovered from 5. The mycoplasma and bacteria isolated were consistent with those commonly associated with nonspecific respiratory diseases in horses, except that Streptococcus pneumoniae capsular type 3 was isolated from 10 horses.

Acute Disease↗
PubMed1996

A physical analog of the failing left ventricle for in vitro studies of mechanical wall actuation.

Mechanical repowering of a failing heart with devices or skeletal muscle could circumvent blood-pump lining problems. Requirements are complex: indefinite support with preservation of valve competence and coronary flow, avoidance of wall coaptation, and allowance of both rapid low impedance refilling and independent left and right pressures. An accurate in vitro physical failing-heart analog could facilitate the choice and screening of surgical and engineering approaches in mock circulation experiments. Prosthetic models, transplant recipient hearts, normal animal hearts, existing in vivo animal failure models, and failing cadaver hearts all have serious limitations. One hundred and four excised porcine hearts were dilated and fixed by three iterative protocols. Geometric and passive mechanical parameters were assessed and compared with targets expected for an end-stage failing heart. For Protocol 3, Subgroup 2 (reinforcing valve support, dilatation by compliant ventricular balloon, and ethyl alcohol fixation), the left ventricular shape and capacity (ellipsoid, 201-377 ml/500 g of heart weight), passive valve function, wall flexural rigidity (Et3 range 0.101-0.331 Nm), and refilling mechanics (99 +/- 17.46 ml during 200-400 ms at < or = 10 mm Hg transmural gradient) were all within goal criteria.

Animals↗
PubMed1996

Influence of different conditioning methods on force and fatigue resistance in chronically stimulated skeletal muscles.

A study was undertaken to compare different conditioning methods for the transformation of latissimus dorsi muscle into a fatigue resistant one for application in circulatory assist. In ten sheep four electrodes were sutured to the epineurium of the left thoracodorsal nerve for indirect electrical stimulation of the latissimus dorsi muscle. In six sheep a "carousel stimulation," a special multichannel stimulation, in combination with a recently developed conditioning protocol was used for muscle conditioning (multichannel method). In four sheep, a conventional stimulation protocol using single channel stimulation was applied for transformation of the muscle (single channel method). The final experiments were carried out when fatigue resistance was obtained. The maximum tetanic forces at different preloads were determined and fatigue resistance was tested during 20 minutes of continuous stimulation. Both conditioning patterns led to fatigue-free chronic stimulation. Muscles conditioned by multichannel stimulation exhibited between 20% and 33% less force than the contralateral unconditioned muscles, whereas in the single channel group this loss was between 32% and 43%. Thus, the multichannel method revealed relatively superior in preserving muscle force for chronic stimulation.

Animals↗