Biomedical subjects
Publications and source records attributed to R Buchner.
The "dynamic exchange" model of ion association proposed by Watanabe and Hamaguchi, [J. Chem. Phys.123, 034508 (2005)] for aqueous solutions of MgSO4 is shown to be inconsistent with the extensive information available from Raman, relaxation, and thermodynamic studies, all of which can be explained by the Eigen equilibrium model.
A randomized clinical trial which included a follow-up of one year was applied to 118 myogenous TMD-patients. The therapies investigated were: physiotherapy of the masticatory system or splint therapy for patients without occlusal interferences, and occlusal adjustment therapy or the combination of splint and occlusal adjustment therapy for patients with pronounced occlusal interferences. Counseling, which yielded a reduction of 27% of the scored pain intensity, will most likely eliminate any further need for treatment of patients with a low level of myogenous TMD signs and symptoms. Otherwise, physiotherapy might be preferred as a starting option with respect to splint therapy because of 1. A similar efficacy; 2. A shorter treatment duration so that either chronic facial pain is earlier relieved or a patient can undergo a second type of therapy earlier; and 3. Lower costs. One third of the patients selected had pronounced occlusal interferences. Using stringent criteria it might be possible to apply occlusal adjustment therapy without involvement of splint therapy yielding a similar therapy efficacy and with advantages of a shorter treatment duration and lower costs. All types of therapy diminished not only facial pain but also pain of neck and shoulder areas.
Changes in the activity of human jaw-elevator muscles related to the mandibular stretch (jaw-jerk) reflex could be involved in the aetiology of temporomandibular disorders (TMD). In order to investigate whether there are differences in the sensitivity of the jaw-jerk reflex between myogenous TMD patients (n = 10) and gender- and age-matched controls (n = 10), jaw-jerk reflexes were elicited under standardized conditions. By measuring the reflex with bipolar surface electromyography (EMG), reflex sensitivity was determined from relations between reflex amplitude and jaw displacement from the masseter and the anterior temporalis muscles. Reflex amplitude and background EMG activity were normalized with respect to the maximal voluntary contraction (MVC) to correct for differences in the thickness of soft tissues overlying the muscle or in electrode placement. In addition to normalization with respect to MVC, for the patients, normalization was also applied with respect to a MVC that was scaled by multiplying values by the ratio of the mean MVC of controls to the mean MVC of patients. At a constant level of background EMG activity, the reflex sensitivity can be determined from the slope (reflex gain) and x-intercept (reflex threshold) of the reflex amplitude-jaw displacement relation. No significant differences between patients and controls were found for the gain or threshold values of either the masseter or the anterior temporalis muscles with a univariate analysis of variance. It is concluded that jaw-jerk reflex sensitivity is not significantly changed in myogenous TMD patients. Therefore, the fusimotor system probably does not play a part in the perpetuating myogenous TMD.
An overview is given of the most commonly investigated signs and symptoms associated with craniomandibular disorders as detected in a population of patients with craniomandibular disorders and in four defined diagnostic subgroups. The information was collected with a questionnaire and during an extensive clinical examination. Comparison of self-report and clinical data indicated that these two methods reveal different aspects of the patient's complaints and should be interpreted in their own way. The results showed that no statistically significant differences could be found between the four diagnostic subgroups with respect to occlusal factors, trauma, and clinically assessed parafunctional habits. The groups differed considerably with respect to general characteristics, pain variables, signs of craniomandibular disorders, self-reported para-functional habits, psychosocial factors, and general health factors. However, despite the reduction in clinical characteristics of the four subgroups, there was little reduction in the diversity of factors associated with craniomandibular disorders. This implicates that almost all factors associated with craniomandibular disorders may influence the initiation and perpetuation of the different disorders in the individual patient, and therefore, remain of interest in future research.
The firing pattern of the motor units (MUs) in jaw-elevator muscles was studied within a wide range of isometric contraction levels by means of changes in the frequency and broadness of the primary peak in the low-frequency (5-40 Hz) power spectral density function of the surface EMG. EMG was recorded from both masseter and anterior temporal muscles in 11 myogenous CMD patients as well as in 11 gender- and age-matched controls who clenched in intercuspal occlusion under the control of visual feedback at various levels (0.5-67% MVC for the various muscles studied). The EMG was digitized for 12 periods of 1.6 s per condition; the power spectrum was averaged and smoothed for the various clenching levels. Linear regression analysis showed that the positive slope in the peak frequency (PF)/% MVC relationship, a measure of rate modulation of the MUs, did not differ significantly between patients and controls. At a low clenching level, PF was smaller (p < 0.01) for the anterior temporal muscles of the patients, suggesting lower firing rates for a wide range of clenching levels of the patients because of a similar rate modulation for patients and controls. Furthermore, the variance in the slope values was larger (p < 0.05) for the masseteric muscles of the patients, which may be explained by more heterogeneity of the masseteric rate modulation in the patient group. The broadness of the primary peak was smallest at a low clenching level (p < 0.001) for the anterior temporal muscles of the patients, suggesting a more uniform firing rate or more synchronization between MUs.
Results obtained indicate that a site-directed polyclonal antibody specific for a synthetic peptide based on the predicted amino-terminal sequence of human C5aR (anti-C5aR(9-29)) is capable of binding to both normal human and transfected cells bearing C5aR. Flow cytometric analysis of stable murine L cell transfectants (C5aR-neo), human neutrophils, and human monocytes indicated that these cells bound anti-C5aR(9-29) in a specific manner. Moreover, F(ab')2 fragments of anti-C5aR(9-29) specifically neutralized proinflammatory and immunoregulatory activities induced by natural human C5a. This antiserum was found to block, in a dose-dependent manner, 1) zymosan-induced neutrophil chemotaxis, 2) C5a-induced enzyme release from neutrophils, and 3) C5a-induced cytokine production (IL-6 and IL-8) from human monocytes in vitro. These results suggest that this site-directed polyclonal antiserum specifically interacts with the human C5aR molecule. To the best of our knowledge, none of the existing reports in the literature provided evidence for a site-directed antiserum to C5aR that was capable of specifically blocking C5a-mediated inflammatory/immunoregulatory activities in vitro. Studies conducted with anti-C5aR(9-29) indicated that this antiserum effectively blocked C5a-mediated cell activation but by itself did not activate either neutrophils or monocytes. Combined, these data suggest that this antiserum does not interact with the C5a "effector" site but sterically interferes with C5a binding to its receptor by interacting with the extracellular amino-terminal region of the receptor.
The control of mandibular posture has been related to the activity of the anterior temporal muscles, whereas the masseter muscles have been viewed mainly as force producers. However, these groups of muscles, especially in the deep layers, are highly endowed with muscle spindles, so that a difference in function should imply a difference in the reflex sensitivity. By studying the jaw-jerk reflex by means of bipolar surface electromyogram, the reflex sensitivity was determined from relationships between reflex amplitude and jaw displacement from both groups of muscles in eight subjects. At a constant level of background muscle activity, and hence with a constant excitability of the alpha motoneurons, the reflex sensitivity can be determined from these relationships in terms of gain and threshold. In order to account for differences in thickness of the soft tissues overlying the various muscles studied, the reflex amplitude was normalized with respect to the level of maximal voluntary contraction (MVC). In experiments where the inter-electrode distance was 18 mm over both groups of muscles, the reflex gain of the anterior temporal muscles was larger than that of the masseter muscles (P < 0.05). The threshold value did not differ significantly from zero for either group of muscles. Normalization of the reflex amplitude with respect to MVC can be carried out correctly only if the reflexly activated muscle fibres are distributed uniformly within the muscle. In order to gain an insight into this distribution, control experiments were performed with three subjects in which the inter-electrode distance was varied, thus influencing the depth in the muscle from which active muscle fibres were recorded. The reflex gain of the masseter muscle with an inter-electrode distance of 22 mm, which records from deeper layers of the muscle as well as superficial ones, was larger than with a distance of 11 mm (P < 0.01-0.10 in the various subjects). No such differences were found for the anterior temporal muscle. It was concluded that the afferents of the spindles in the jaw-elevator muscles do not project uniformly upon the motoneurons, but involve mainly fibres in the deeper layers of the muscle. The difference in gain found between the masseter and the anterior temporal muscles with the same inter-electrode distance of 18 mm is likely to be due to a larger distance of the reflexly activated muscle fibres in the masseter muscle with respect to the electrodes rather than to a difference in reflex sensitivity between the muscles.(ABSTRACT TRUNCATED AT 400 WORDS)
In order to investigate whether the mandibular stretch (jaw-jerk) reflex is modulated in a task-dependent manner, jaw-jerk reflexes were elicited in eight subjects during clenching with unilateral and bilateral tooth support, respectively. The reflexes were examined in the electromyographic (EMG) activity recorded by means of surface electrodes and were elicited by means of small transient jaw displacements at a constant value of 80 microns. Low levels of background EMG were applied ranging from 1 to 30% maximal voluntary contraction (MVC) as controlled by means of visual feedback. Linear relationships were observed between reflex amplitude and level of background EMG. The slope in these relationships served as a measure of reflex gain. For the masseter as well as the anterior temporal muscles, the reflex gain, averaged over both sides, was larger during clenching with unilateral tooth support than with bilateral tooth support (P < 0.05). Furthermore, the gain was larger on the side without tooth support during unilateral clenching and larger on the side without visual feedback of elevator muscle activity during bilateral clenching. It can be concluded that the jaw-jerk reflex is modulated to subserve the stabilization of the mandible, with the reflex sensitivity being larger the more that alternative stabilizing factors such as mechanical tooth contact, visual feedback and feedback from periodontal pressure receptors around the teeth are lacking. The reflex modulation may be of functional importance in stabilizing the mandible during its movement in the chewing process, as the food is predominantly placed unilaterally between the antagonistic teeth during individual chewing cycles.
In order to investigate whether there are bilateral differences in the sensitivity of the mandibular stretch (jaw-jerk) reflex between patients with a myogenous craniomandibular dysfunction (CMD) and healthy controls free from signs and symptoms of CMD, jaw-jerk reflexes were elicited under standardized conditions in two groups of 10 gender- and age-matched subjects. The reflexes were recorded bilaterally from the masseter and the anterior temporal muscles by means of bipolar surface electromyogram (EMG). Reflex amplitudes at a mandibular displacement of exactly 80 microns and at a background muscle activity of exactly 12% maximum voluntary contraction were determined from relations between reflex amplitude and jaw displacement. These were obtained at a visually controlled, constant clenching level. For both groups, comparisons were made between reflex amplitudes from the right- and the left-hand side. In CMD patients with predominantly unilateral jaw muscle pain, comparisons were also made between the pain and non-pain sides. Although significant side asymmetries were found in many individuals, no significant differences were found among bilateral asymmetries in reflex sensitivity between patients and controls. No influence of pain side on the asymmetries was found. It was concluded that neuromuscular factors do not cause significant bilateral differences in the sensitivity of the jaw-jerk reflex between patients with myogenous CMD and controls. In a control experiment, in which eight healthy control subjects participated, the influence of a possible asymmetry in jaw displacement on the reflex sensitivity was evaluated. To achieve this, reflexes were elicited not only by means of a bilaterally imposed mandibular load, but also by means of loading via a unilateral bite-fork, so that an equal, constant jaw displacement could be imposed successively on both sides of the mandible. As no significant differences were found in bilateral asymmetries in reflex sensitivity between unilateral and bilateral mandibular loading, the influence of a possible asymmetrical jaw displacement on side asymmetries in the jaw-jerk reflex sensitivity is negligible in our experimental model.
A discriminant analysis has been applied on several electromyographic (EMG) parameters of the masseter and the anterior temporal muscles, related to clenching and the jaw-jerk reflex, to characterize jaw muscle function of patients with craniomandibular disorder (CMD) with respect to controls. The subject samples, matched for age, consisted of 20 females with myogenous CMD, and 20 symptom-free females. The jaw-jerk reflex was elicited by a downward-directed mandibular load, transmitted by a bite-fork causing a similar occlusion and bite-rise as a splint. The patients differed mainly from the controls by smaller maximum EMG activity in both muscle groups (P less than 0.05 with the bite-fork inserted). This finding was related to a smaller muscle strength as the EMG level did not improve with pain-free jaw muscles after therapy using a relaxation splint. Discriminating factors of secondary importance were an enhanced bilateral asymmetry in the muscle activity of the patients, and in the reflex amplitude normalized for background EMG activity. In all subject samples, the activity of the anterior temporal muscles decreased with respect to the masseter muscles when the bite-fork was inserted (P less than 0.05-0.001). The therapeutic effect of a relaxation splint may, in part, be related to a relief of the temporal muscles.
Using a dinitrophenylated and biotinylated peptide antigen, we have developed an affinity chromatography procedure to purify complexes of a given peptide species and a given class II major histocompatibility complex antigen away from class II molecules occupied by other peptides. We show that hen egg lysozyme peptide-I-Ed complexes purified according to this procedure have a greatly enhanced capacity to activate hen egg lysozyme-specific T cells but have lost the capacity to activate three different alloreactive T-cell hybridomas. These data demonstrate that the class II molecule in and of itself is not sufficient to activate alloreactive T cells. Rather, the data suggest that recognition of specific complexes formed between allo-class II and particular autologous peptides may be required. Alternatively, alloreactive T cells may be recognizing "empty" major histocompatibility complex molecules.
Advancement of the calcification front in the cartilage, which is a measure of the growth of the cartilage, can be determined by the administration of two dose bone-markers at specific intervals. It appears that growth still takes place in animals of 12-18 months. This growth is possible by the persistence of chondrogenic cells. The overall growth of the central part of the condyle amounts to about 2 mm over the period from 2 to 18 months. Raising of the bite in the rat has an obvious influence on the temporomandibular joint, and on the condyle in particular. Within a few days an increase of growth-rate of cartilage can be demonstrated. This extra growth is temporary, and the intensity and duration of the response is determined by the age of the animal. This adaptation is related to the presence of chondrogenic cells in the cartilaginous layer in the condyle.
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