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Biomedical subjects

C Hamann

Publications and source records attributed to C Hamann.

At least 19 recordsLinked to original sources
PubMed2005

[Vestibular evoked muscle potentials dependency on neural origin and the location of an acoustic neuroma].

INTRODUCTION: Most acoustic neuromas (AN) originate from the inferior vestibular nerve (IVN). Vestibular evoked myogenic potentials (VEMP) are accepted as the only unilateral test for the function of the sacculus and the IVN. METHODS: The influence of the origin from the IVN and superior vestibular nerve (SVN), and the position of the AN in relation to the internal auditory canal on VEMPs was investigated. A total of 39 patients (aged: 30-67 years, mean: 53 years) were examined. The VEMPs were recorded on the activated sternocleidomastoid muscle and averaged over 200 stimuli. Tone bursts (95 dB nHL; 500 Hz; stimulation rate 5 Hz) were used to generate the VEMPs. RESULTS: The exact origin of the AN from the SVN or the IVN could be determined intraoperatively and correlated using VEMP in 28 patients. CONCLUSION: The origin of the AN has only a marginal influence on the results of VEMP measurements. The position of the AN in relation to the internal auditory canal seems to have more influence than the origin.

Acoustic Stimulation↗
PubMed2001

[Otolith-ocular reflex in linear acceleration of low frequencies].

BACKGROUND: During constant velocity rotation about the earth's vertical axis, eccentric displacement of the head can be used to generate adequate stimulation of the otolith organs. More recently, studies have been performed with a variable radius rotatory chair, which permits a controlled modulation of the centripetal or radial acceleration, to achieve linear acceleration frequencies much lower than with a conventional linear sled. METHODS: In the present study, frequency response and threshold testing was performed using sinusoidal modulation of the chair radius. Three-dimensional eye movements were recorded with binocular video-oculography. RESULTS: The gain (0.09 degree/degree at 0.03 Hz, 0.009 degree/degree at 1 Hz) and phase relationships of the otolith-ocular response (OOR) show a low-pass characteristic over the measured range of 0.03-1.0 Hz. In comparison to the flat response of neurophysiological recordings from the otolith afferent, our findings support the idea that any low-pass filtering of otolith afferents occurs at the level of the vestibular nuclei. CONCLUSION: The OOR could be detected at acceleration levels of 0.03 m/s2, much lower than the subjective threshold for the perception of 0.08 m/s2.

Acceleration↗
PubMed2001

Measuring unilateral otolith function via the otolith-ocular response and the subjective visual vertical.

In the present study, attention is directed to the unilateral response of the otolith system to static and dynamic tilt, as reflected by subjective estimation of the visual vertical (oculogravic perception). Measurements were performed with a variable radius rotary chair, which permits controlled modulation of the centripetal, or radial, acceleration. By limiting the radius, i.e. eccentric displacement of the head by 3.5 cm during constant-velocity rotation about the earth-vertical axis, adequate unilateral stimulation of the otolith organ--predominantly the utricle--is generated, without involving the semicircular canals. This paradigm has been employed to measure the unilateral utriculo-ocular response. In contrast to the otolith-ocular response (OOR), the subjective visual vertical (SVV) reflects the processing of otolithic information in the higher brain centres (thalamus, vestibular cortex). Exploitation of these two complementary approaches provides useful information for both experimental and clinical scientists. The findings also reveal that centripetal acceleratory stimulation during constant angular velocity with the subject centred on axis is sufficient to localize peripheral otolith dysfunction by means of SVV estimation. This represents a novel test of otolith function that can be easily integrated into routine clinical testing.

Acceleration↗
PubMed2001

Prevalence of carpal tunnel syndrome and median mononeuropathy among dentists.

BACKGROUND: The authors undertook a study to determine the prevalence in dentists of abnormal sensory nerve conduction and/or symptoms of carpal tunnel syndrome, or CTS, the most common nerve entrapment syndrome. METHODS: In a cross-sectional study, dentists (n = 1,079) were screened during the American Dental Association's Annual Health Screening Program in 1997 and 1998 by means of standard electrodiagnostic measures in the dominant hand and a self-reported symptom questionnaire. The authors diagnosed a median mononeuropathy from a 0.5- or 0.8-millisecond, or ms, prolongation of the median sensory-evoked peak latency compared to the ulnar latency. They diagnosed CTS if the subject also had accompanying symptoms of numbness, tingling or pain. RESULTS: Thirteen percent of screened dentists were diagnosed with a median mononeuropathy (using a 0.5-ms prolongation as the criterion), but only 32 percent of these had symptoms consistent with CTS (4.8 percent overall). When the 0.8-ms prolongation was used as the electrodiagnostic criterion, only 2.9 percent (overall) were diagnosed with CTS. People with diabetes, rheumatoid arthritis and obesity were more likely to have a median mononeuropathy. CONCLUSIONS: The prevalence of symptoms consistent with CTS in the dominant hand among dentists was higher than the prevalence in the general population. However, when electrodiagnostic confirmation is added, the prevalence of CTS was nearly the same as that among the general population. CLINICAL IMPLICATIONS: Early recognition of CTS can lead to more effective management. Education regarding ergonomic risk factors can be an effective preventive measure.

Adult↗
PubMed2000

Synthesis of Copper(I) catenanes incorporating a disulfide bridge and their deposition on a gold surface

The synthesis of two coordinating catenates with the ability to undergo surface-confined chemistry is described. For each catenate, one of the rings includes a 2,9-diphenyl-1,10-phenanthroline unit as a coordinating moiety and a disulfide bridge, which allows adsorption of the catenate onto a gold surface, thus going from a molecular catenate to a [gold-adsorbed] species in which gold atoms are elements of one of the rings.

Journal Article↗
PubMed2000

Role of mast cells in the pathogenesis of postburn inflammatory response: reactive oxygen species as mast cell stimulators.

Thermal trauma has a direct effect on mast cells, triggering the secretion of histamine. This secretion leads to an enhanced xanthine oxidase activity and an increased production of reactive oxygen species (ROS), the latter being produced after burns through differing mechanisms. As ROS have been shown to have deleterious effects on cellular membranes, a lesion of the mast cell membrane could close the circle of autoinjury due to the vasoactive actions of mast cell mediators. Our studies were designed to assess the potentiality of ROS as stimulators of mast cell degranulation after burns by comparing two groups of rats treated, respectively, with SOD and saline solution after a scald injury. Plasma levels of tryptase and histamine were analyzed as markers of mast cell activity. A comparison of the mean increases of tryptase between baseline and 3-h postburn levels in the two groups shows significant differences (p < 0.001) (control: 0.13+/-0.04, SOD: 0.03+/-0.01). When comparing the mean increases between the baseline and 3 h postburn levels of histamine in the two groups, significant differences were also found (p < 0.001) (control group: 2.70+/-0.57. SOD group: 1.22+/-0.32). The lower levels of histamine and tryptase induced by SOD provides indirect evidence that ROS are involved in the process, causing the release of such mediators by mast cells, which may in turn suggest that ROS can act as stimulators of mast cell degranulation in burns.

Animals↗
PubMed2000

Experimental model for local application of growth factors in skin re-epithelialisation.

We did an experimental study to assess the effects of different growth factors on re-epithelialisation of skin wounds by creating a partial-thickness defect in rats with a handle dermatome. Three different growth factors that are particularly involved in the re-epithelialisation phase of wound repair (epidermal growth factor (EGF), keratinocyte growth factor (KGF), and basic fibroblast growth factor (FGF-b) n = 10 in each group) were applied locally in a hydrocolloid dressing containing solutions of the different factors (EGF 10 micrograms/ml, KGF 3.3 ng/ml, bFGF 1 microgram/ml). The dressings were changed daily. The thickness of the epithelium, the percentage of re-epithelialisation, and the maturity of the epithelium were quantified and measured morphometrically. The results showed that: the experimental model allowed us to apply the growth factors, while continuously maintaining the dose within the maximum activity of the growth factor; when EGF, KGF, and bFGF were given according to the protocol there was significant thickening of the new epidermis (p < 0.01) and acceleration of the re-epithelialisation (p < 0.05) rate compared with controls, and significantly more mature epithelium grew (p < 0.05) all of which were evident on both the third and the fifth days; and EGF and KGF cause a more epidermal thickening than bFGF.

Animals↗
PubMed2000

Comparison of the relaxation effect in vitro of nitroglycerin vs. fenoterol on human myometrial strips.

AIMS: Substance dose-related comparison of relaxation effect of nitroglycerin (GTN) and the beta 2-mimetic substance fenoterol in human myometrial tissue. METHODS: Test criterion is the isometric force development of isolated human myometrial strips. These muscle strips were removed from the lower uterine segment at cesarean section. Fenoterol in concentrations of 3 x 10(-8)-10(-5) mol/l or GTN in concentrations of 1.7 x 10(-8)-5.8 x 10(-4) mol/l were applied to the 2 x 2 x 10-mm strips, which were fixed and maintained in tissue baths. The curves were plotted on line. The integral or the "area under the curve" (AUC) served as the parameter for muscle strip activity. RESULTS: A total of 100 strips from 20 patients were used. GTN demonstrated a significant relaxation effect in the in vitro model on human myometrial strips from pregnant women already treated with oxytocin. The effect was able to be enhanced to a point where oxytocin-induced contractions were completely absent. A relatively clear connection was demonstrated between dose and effect whereby increased muscle relaxation resulted at increased concentrations. Compared to GTN application, muscle strip relaxation was less pronounced under fenoterol; a complete inhibition of myometrial activity was not achieved under fenoterol. CONCLUSIONS: With respect to relaxation of the myometrial tissue samples the NO donor GTN is at least as potent as the standard tocolytic agent fenoterol in the in vitro model.

Adrenergic beta-Agonists↗
PubMed1999

Detection of polycyclic aromatic hydrocarbon degradation genes in different soil bacteria by polymerase chain reaction and DNA hybridization.

Twenty different strains of Pseudomonas, Mycobacterium, Gordona, Sphingomonas, Rhodococcus and Xanthomonas which degrade polycyclic aromatic hydrocarbons (PAH) were characterized in respect to genes encoding degradation enzymes for PAH. Genomic DNA from these strains was hybridized with a fragment of ndoB, coding for the large iron sulfur protein (ISP alpha) of the naphthalene dioxygenase from Pseudomonas putida PaW736 (NCIB 9816). A group of seven naphthalene-degrading Pseudomonas strains showed strong hybridization with the ndoB probe, and five Gordona, Mycobacterium, Rhodococcus and Pseudomonas strains able to degrade higher molecular weight PAH showed weaker hybridization signals. Using a polymerase chain reaction (PCR) approach, seven naphthalene-degrading Pseudomonas strains showed a PCR fragment of the expected size with ndoB-specific primers and additionally ten strains of Gordona, Mycobacterium, Pseudomonas, Sphingomonas and Xanthomonas able to degrade higher molecular weight PAH were detected with degenerate primer-pools specific for the ISP alpha [2Fe-2S]-Rieske center of diverse aromatic hydrocarbon dioxygenases. This suggests a molecular relationship between genes coding for PAH catabolism in various PAH-degrading bacterial taxa, which could be used to evaluate the PAH-degradation potential of mixed populations.

Bacteria↗
PubMed1998

Regular physical exercise corrects endothelial dysfunction and improves exercise capacity in patients with chronic heart failure.

BACKGROUND: The purpose of this study was to determine the effects of systemic exercise training on endothelium-mediated arteriolar vasodilation of the lower limb and its relation to exercise capacity in chronic heart failure (CHF). Endothelial dysfunction is a key feature of CHF, contributing to increased peripheral vasoconstriction and impaired exercise capacity. Local handgrip exercise has previously been shown to enhance endothelium-dependent vasodilation in conduit and resistance vessels in CHF. METHODS AND RESULTS: Twenty patients were prospectively randomized to a training group (n=10, left ventricular ejection fraction [LVEF] 24+/-4%) or a control group (n=10, LVEF 23+/-3%). At baseline and after 6 months, peak flow velocity was measured in the left femoral artery using a Doppler wire; vessel diameter was determined by quantitative angiography. Peripheral blood flow was calculated from average peak velocity (APV) and arterial cross-sectional area. After exercise training, nitroglycerin-induced endothelium-independent vasodilation remained unaltered (271% versus 281%, P=NS). Peripheral blood flow improved significantly in response to 90 microg/min acetylcholine by 203% (from 152+/-79 to 461+/-104 mL/min, P<0.05 versus control group) and the inhibiting effect of L-NMMA increased by 174% (from -46+/-25 to -126+/-19 mL/min, P<0.05 versus control group). Peak oxygen uptake increased by 26% (P<0.01 versus control group). The increase in peak oxygen uptake was correlated with the endothelium-dependent change in peripheral blood flow (r=0.64, P<0. 005). CONCLUSIONS: Regular physical exercise improves both basal endothelial nitric oxide (NO) formation and agonist-mediated endothelium-dependent vasodilation of the skeletal muscle vasculature in patients with CHF. The correction of endothelium dysfunction is associated with a significant increase in exercise capacity.

Blood Flow Velocity↗
PubMed1998

Subjectless sentences in child Danish.

Three alternative accounts of subject omission, pragmatic, processing and grammatical, are considered from the perspective of child Danish. Longitudinal data for two Danish children are analyzed for subject omission, finite and infinitival verb usage and discourse anchorage of sentence subjects (overt and missing). The data exhibit a well-defined phase of subject omission which coincides with a well-defined phase of infinitival verbal utterances. No evidence is found for input driven accounts of subject omission. Danish adults rarely omit subjects from utterance initial position. Neither is there any evidence to support the claim that omitted subjects are anchored in previous discourse. Evidence supporting a processing constraint explanation of missing subjects is equivocal. The pattern of subject omission, infinitival usage and third person pronoun and past tense usage points to a grammatical explanation of the phenomenon. However, current grammatical accounts have difficulty accommodating several aspects of the data reported. Contrary to structure building theories, the Danish children do not exhibit a phase of development where only uninflected verb forms are used. Danish children also omit subjects from finite utterances. Furthermore, the decline of subject omissions in finite utterances coincides with decline in usage of infinitival utterances. These findings challenge tense-based accounts of children's subject omission. Finally, Danish children exhibit an asymmetry in subject omission according to verb type; subjects are omitted from main verb utterances more frequently than from copula utterances. Given the language typology associated with Danish, this asymmetry is difficult to accommodate within truncation and tense or number-based accounts of subject omission. We suggest that a proper treatment of child subject omission will involve an integration of grammatical and discourse-based approaches.

Child↗
PubMed1995

Comparison of the effects of nerve growth factor and superoxide dismutase on vascular extravasation in experimental burns.

Superoxide dismutase (SOD), a free-radical scavenger, inhibits the increase of vascular permeability in experimental burn lesions in rats. In this study the aim was to determine whether Nerve Growth Factor (NGF), which has been implicated in the modulation of some inflammatory reactions, behaves in an analogous way. The study compares the haematocrit (Ht) and haemoglobin (Hb) variations in three groups of rats treated respectively with saline solution, SOD and NGF, immediately after causing a 25 per cent dermal burn injury. Statistical comparison (Student's t test) of the Ht and Hb variations between the Control group (Ht and Hb increase) and the NGF group (Ht and Hb decrease), shows significant differences in the intervals between 15 and 60 min (P < 0.01) and between 60 and 120 min (P < 0.05). Although SOD is able to control extravasation in the immediate postburn period (basal-15 min), NGF has a comparable effect in subsequent periods. The overall action of NGF shows that this agent is able to maintain Ht and Hb values at basal levels even after 120 min postburn. These results seem to be the first evidence of an inhibitory effect of NGF on the vascular permeability in burn lesions.

Animals↗
PubMed1995

Air evacuation of critically burned patients.

We analyze the repercussions of air evacuation on the physiopathology of the critically burned patient based on the experience on 63 patients evacuated by air. Clinical repercussions are due to accelerations, vibrations, noise, and, primarily, to altitude. Accelerations are important during take-off and landing, and vibrations may be important in helicopter evacuations in the presence of craniofacial trauma. The noise, especially in helicopters, can interfere with diagnostic and therapeutic maneuvers in-flight. The altitude modifies atmospheric pressure, partial pressure of oxygen, and water concentration in inhaled air. In the aircraft we use, atmospheric pressure is between 550 and 532 mm Hg at the normal flight altitudes. This situation determines the expansion of body gases. Hypoxia seriously worsens any respiratory insufficiency, primarily in the presence of smoke inhalation. The decrease of water concentration in the inhaled air compels the increase of fluid perfusion. Pre-flight and in-flight measures are analyzed, especially with regard to smoke inhalation, pneumothorax, and parenteral perfusion.

Acceleration↗