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Biomedical subjects

M Bakke

Publications and source records attributed to M Bakke.

At least 37 records · Page 2Linked to original sources
PubMed1998

Morphine application to peripheral tissues modulates nociceptive jaw reflex.

This study assessed the effect of peripherally applied opioids on the electromyographic activity reflexly evoked in digastric and masseter muscles by injection of the small-fiber excitant and inflammatory irritant mustard oil (MO) into the temporomandibular joint. In 39 anaesthetized rats, local pretreatment of joint tissues with morphine (15 nmol) significantly depressed the jaw muscle responses compared with saline, and the depression was antagonized by simultaneous local injection of the opiate antagonist naloxone (2.7 nmol); systemic morphine pretreatment (15 nmol, i.v.) did not influence the muscle responses. The naloxone-reversible depression of the MO-evoked muscle responses by local, but not systemic morphine, supports the presence of peripheral opioid receptors that may have a role in modulating nociceptive responses.

Animals↗
PubMed1998

Musculoskeletal disorders among dentists and variation in dental work.

The purpose was to assess risk factors in dentistry which may contribute to musculoskeletal disorders. A questionnaire was used to identify common work tasks, and to estimate one year prevalence for troubles (65% for the neck/shoulder, 59% for the low back). In a field study working postures and electromyography (shoulder/neck) were registered during the three most common work tasks. Prolonged neck flexion and upper arm abduction were found, as well as high static muscle activity levels (splenius and trapezius muscles). No differences between work tasks were found regarding postures, frequencies of movements or muscle activity. Alterations between the three work tasks do not produce sufficient variation to reduce musculoskeletal load on the neck and shoulders.

Adult↗
PubMed1998

Involvement of NK-1 and NK-2 tachykinin receptor mechanisms in jaw muscle activity reflexly evoked by inflammatory irritant application to the rat temporomandibular joint.

An electromyographic (EMG) study was carried out in 51 anesthetized rats to assess if neurokinin, NK-1 and NK-2, receptor mechanisms and tachykinins were involved in the increased jaw muscle activity which can be reflexly evoked by injection of the small-fiber excitant and inflammatory irritant mustard oil (MO) into the temporomandibular joint (TMJ) region. A baseline level of EMG activity was recorded bilaterally for 20 min from digastric (DIG) and masseter (MASS) muscles and then each animal was treated with NK-1 or NK-2 antagonist or vehicle. In one series of experiments either the NK-1 antagonist CP-99,994 (20 microg approximately 54 nmol), the NK-2 antagonist MEN-10,376 (10 microg approximately 9 nmol or 20 microg approximately 18 nmol) or vehicle (control) was administrated into the lateral ventricle (i.c.v.); in another series the NK-1 antagonist (4 mg/kg approximately 3-4 micromol/rat) or vehicle (control) was given intravenously (i.v.). After 10 min, MO (20 microl, 20%) was applied to one TMJ (first injection) and 45 min later, MO was applied to the opposite TMJ (second injection). Pretreatment with neurokinin antagonists had little effect on the incidence of the MO-evoked EMG responses but did significantly reduce the EMG magnitude and duration. In the animals pretreated with NK-1 antagonist only the responses to the second MO injection was significantly affected whereas NK-2 pretreatment reduced the EMG responses to both MO injections to the TMJ. The systematic depression of the MO-evoked EMG responses by the NK-2 antagonist suggests that neurokinin A may be involved in the EMG responses. Since the NK-1 antagonist produced no systematic changes in responses elicited by the first MO injection, substance P does not seem to be associated directly with the initiation or maintenance of the EMG responses but may be involved if a 'central sensitization' has been induced by the first MO injection to the TMJ.

Animals↗
PubMed1998

Trigeminal responses evoked by painful electrical stimulation.

Trigeminal sensory and motor responses to high-intensity electrical stimuli were studied in 10 healthy male subjects. During contraction at 10% of maximal bite force, late exteroceptive suppression periods assessed by EMG and bite force from masseter muscles were recorded together with evoked vertex potentials. Electrical stimuli were either delivered as 1 ms single pulses or as 21 ms (5 x 1 ms, 200 Hz) train pulses at two different intensities above the pain threshold. Three different perioral regions were stimulated in random order. The duration of the masseter suppression period was significantly longer and its latency significantly shorter at higher stimulus intensities whereas the amplitude of the evoked vertex potentials remained unchanged. Both the evoked potentials and the exteroceptive suppression period in the masseter muscle differed significantly between stimulation at the three perioral regions. The present results from combined measurements of sensory and motor responses in the trigeminal system may be explained by the function of trigeminal polysynaptic reflex circuits and the central cerebral processing of afferent inputs.

Adult↗
PubMed1998

Malocclusion traits and symptoms and signs of temporomandibular disorders in children with severe malocclusion.

The present study reports the prevalence of the various traits of malocclusion, as well as the occurrence of associations between malocclusion, and symptoms and signs of temporomandibular disorders (TMD) in children selected for orthodontic treatment by the new Danish procedure for screening the child population for severe malocclusions entailing health risks. The sample comprised 104 children (56 F, 48 M) aged 7-13. Malocclusion traits were recorded at the time of selection, symptoms and signs of TMD were recorded at recall. The most prevalent malocclusion traits were distal molar occlusion (Angle Class II; 72 per cent), crowding (57 per cent), extreme maxillary overjet (37 per cent) and deep bite (31 per cent). Agenesis or peg-shaped lateral teeth were observed in 14 per cent of the children. The most prevalent symptom of TMD was weekly headache (27 per cent); the most prevalent signs of TMD were tenderness in the anterior temporal, occipital, trapezius, and superficial and profound masseter muscles (39-34 per cent). Seven per cent of the children were referred for TMD treatment. The Danish TMD screening procedure was positive in 26 per cent, while 20 per cent had severe symptoms (Aill), and 30 per cent had moderate signs (Dill) according to Helkimo (1974). Symptoms and signs of TMD were significantly associated with distal molar occlusion, extreme maxillary overjet, open bite, unilateral crossbite, midline displacement, and errors of tooth formation. The analysis suggests that there is a higher risk of children with severe malocclusions developing TMD. Errors of tooth formation in the form of agenesis or peg-shaped lateral teeth showed the largest number of associations with symptoms and signs of TMD; these associations have not previously been reported in the literature.

Adolescent↗
PubMed1997

Transcriptional regulation of the bovine CYP17 gene by cAMP.

The transcription of steroid hydroxylase genes is controlled by ACTH and cAMP in the adrenal cortex. In most instances the regulation appears to rely on transcription factors traditionally not associated with cAMP-dependent gene expression. For the non-traditional factors it remains necessary to elucidate the coupling of increases in intracellular cAMP and cAMP-dependent protein kinase (PKA) activity to the function of these proteins. The bovine CYP17 gene, which encodes the steroid 17 alpha-hydroxylase, contains two discrete DNA elements within its promoter and upstream region (CRS1 and CRS2) that individually can confer cAMP responsiveness. The CRS1 element is a target for PKA signalling and for negative regulation via the protein kinase C signal transduction pathway. The homeodomain protein Pbx1 enhances CRS1-dependent transcription, but additional CRS1-binding proteins remain to be identified. Furthermore it is not known how PKA regulates the activity of Pbx1 or its possible binding partners. Closer to the promoter, the nuclear orphan receptors SF-1 and COUP-TF have overlapping binding sites in CRS2 and they bind in a mutually exclusive manner with very similar affinities; 8 and 10 nM, respectively. SF-1 stimulates whereas COUP-TF inhibits transcription from the bovine CYP17 promoter. Together, the data suggest that cAMP-dependent control of the amounts of the activator SF-1 vs. the repressor COUP-TF could influence CRS2-dependent transcription. In addition, PKA may influence the phosphorylation of SF-1, thus increasing its activity. In vitro, PKA will elicit phosphorylation of SF-1. However, although SF-1 can be immunoprecipitated from adrenocortical cells as a phosphroprotein, we have not been able to show cAMP-dependent increase in net phosphorylation in intact cells. More careful examination of individual phosphorylation sites in SF-1 may still reveal hormone- and cAMP-induced phosphorylation of SF-1.

Animals↗
PubMed1996

Ultrasonographic assessment of the swelling of the human masseter muscle after static and dynamic activity.

Work-related fatigue, pain and disorders in skeletal muscles have been related to prolonged static and dynamic activity. Such contractions have been shown to impair blood flow and increase muscle thickness and fluid. In the present study the effect of static and dynamic activity was evaluated from changes in masseter thickness as a measure of oedema, simultaneously with assessment of perceived pain/discomfort and cardiovascular responses. As static activity, fourteen young healthy women bit at 15% maximal voluntary contraction on bite-force transducers in the molar regions until exhaustion or 20 min at maximum (median endurance time 7.1 min). For dynamic activity, the same individuals chewed gum unilaterally until exhaustion or 40 min at maximum (all endured 40 min) with a cycle time of 725 ms, an average load of 9.3% of maximal electromyographic activity (maxEMG) and a peak mean voltage of 54.3% of maxEMG. Muscle thickness was measured by ultrasonography at the mid-portion of the ipsilateral masseter. Immediately after exercise, muscle thickness was significantly increased, more after static (14.0%) than dynamic (8.6%), and returned to pre-exercise values after 20-min recovery. Visual analogue scales (VAS) revealed the concomitant occurrence of pain (static 11.9 VAS%; dynamic 5.9 VAS%), and discomfort (static 8.1 VAS%; dynamic 5.9 VAS%), and both sensations decreased to pre-exercise values after 20-min recovery. Systolic blood pressure increased significantly, more during static (12.5%) than dynamic activity (4.3%), whereas heart rate rose significantly only during dynamic exercise (13.3%). Hence, activity was associated with muscular swelling and pain, and, despite the relatively small size of the masticatory muscles, also with general cardiovascular responses.

Adult↗
PubMed1996

Efficient lipase-catalyzed preparation of long-chain fatty acid esters of bile acids: biological activity and synthetic application of the products.

A highly regioselective (3-position) and efficient (quantitative yield) acylation of bile acids catalyzed by immobilized Candida antarctica lipase was established. Methyl cholate derivatives acylated with long-chain fatty acids (C12-C16) showed an inhibitory effect on the growth of some strains of Gram-positive and -negative bacteria (27-400 micrograms/ml). The anti-bacterial activity was slightly weaker than has been observed for methyl cholate, while the increased lipophilicity and lower melting points of the present derivatives are well suited for a potential germicide which would be safe and be topically applied. This enzyme-catalyzed transesterification is also demonstrated as an expeditious route to ursodeoxycholic acid, in respect of the regioselective introduction of acyl protecting groups on the hydroxyl groups of the intermediates. 7-Ketolithocholic acid, a known direct precursor of ursodeoxycholic acid, was obtained from cholic acid via chenodeoxycholic acid in a 46% yield and 9 steps.

Acylation↗
PubMed1995

Adrenocorticotrophic-hormone-dependent regulation of a mu-class glutathione transferase in mouse adrenocortical cells.

Three different forms of glutathione transferase (GST) have been resolved in the two mouse adrenal tumour cell lines Y1 and Kin 8. Two of these belong to the mu and pi classes respectively. The third form is so far unidentified. In the Y1 cells, the levels of the mu form (mGTmu1) and the unidentified form, are both down-regulated in the presence of adrenocorticotrophic hormone (ACTH) while the pi form is unaffected. The Kin 8 cell line is derived from Y1 cells and harbours a defect in the cyclic AMP (cAMP)-dependent protein kinase, making it refractory to cAMP-dependent regulation of several enzymes. The GST levels in this cell line were unaffected by ACTH. Also, the steady-state levels of mGTmu1 mRNA were much lower in Y1 cells treated with forskolin (which activates adenylate cyclase) compared with control cells, but there was no difference in mGTmu1 mRNA levels between control and forskolin-treated Kin 8 cells. This indicates that the ACTH-dependent regulation of the mu class GST is pre-translational and that a functional cAMP-dependent protein kinase is required for the regulation. We have further shown that the difference in mRNA steady-state levels between control and forskolin-treated Y1 cells is abolished when transcription is inhibited by actinomycin D. In light of the stability of mGTmu1 mRNA, it would appear most likely that actinomycin D inhibits the transcription of short-lived factors which regulate the turn-over of mGTmu1 transcripts in response to changes in intracellular cAMP levels.

Adrenal Cortex↗
PubMed1995

CT-scanning and radiographic analysis of temporomandibular joints and cephalometric analysis in a case of Herbst treatment in late puberty.

From a consecutive sample of 100 patients treated with the Herbst appliance after the peak of puberal growth, a boy was chosen to show the total effect of the Herbst treatment. Changes in the dentofacial morphology and the structure of the temporomandibular joints (TMJ) were followed by radiologic examinations and the function of the craniomandibular system was studied by clinical examinations, and electromyographic and bite-force recordings. Treatment resulted in marked dentoalveolar changes, an increase of mandibular length, ramus height, and gonion angle. Three months after insertion of the appliance CT-scanning and orthopantomograms of the TMJ revealed new bone formation as a double contour in the fossa articularis and on the posterior part of the condylar process as a result of adaptive bone remodelling. Function was affected by treatment, but was markedly restored at control.

Adolescent↗
PubMed1995

Mutually exclusive interactions of two nuclear orphan receptors determine activity of a cyclic adenosine 3',5'-monophosphate-responsive sequence in the bovine CYP17 gene.

ACTH-dependent transcriptional activation of the bovine CYP17 gene (the gene encoding cytochrome P450 steroid 17 alpha-hydroxylase) involves two cAMP-responsive sequences (CRS1 and CRS2) located in the promoter region. Here we demonstrate that two nuclear orphan receptors, chicken ovalbumin upstream promoter transcription factor (COUP-TF) and steroidogenic factor-1 (SF-1), bind to the part of the CRS2 element that contains the repeated sequences AAGTCA and AGGTCA spaced by six nucleotides (repCRS2). Overexpression of COUP-TF and SF-1 in both steroidogenic and nonsteroidogenic cells demonstrated that SF-1 is an activator of repCRS2-dependent transcription of reporter genes. Furthermore, the SF-1-dependent transcription could be further stimulated by activation of the cAMP-dependent protein kinase. In contrast, COUP-TF alone had no effect on repCRS2-dependent reporter gene activity. Mutations that interfere with the binding of SF-1 to repCRS2 in vitro abolished the cAMP-induced activities mediated by the element in transfected Y1 cells. The mutational analysis of repCRS2 further indicated that the binding sites for the two receptors overlap, and electrophoretic mobility shift assays demonstrated that the receptors bound in a mutually exclusive manner. Overexpression of both SF-1 and COUP-TFI simultaneously demonstrated that COUP-TFI inhibited SF-1-dependent activation of reporter genes. Transient transfection experiments with a construct containing a -100/+19 base pair fragment from the bovine CYP17 gene demonstrated that SF-1 and COUP-TF had similar effects on the intact promoter as on the repCRS2/reporter gene constructs. Our data suggest that the two orphan receptors bind in a mutually exclusive manner to repCRS2 and that SF-1 is involved in the activation and COUP-TF in the repression of repCRS2-dependent transcription.

Animals↗
PubMed1993

Cooperating nonconsensus cAMP-responsive elements are mediators of adrenocorticotropin-induced VL30 transcription in steroidogenic adrenal cells.

Pituitary-derived trophic hormones regulate cell-type-specific expression of VL30 retrotransposons in tissues that are engaged in steroidogenesis. We show that adrenocorticotropic hormone and forskolin induced VL30 transcription in the steroidogenic adrenal cell line Y1 and that the transcriptional activation was cell type- and protein kinase A-dependent. Three novel cAMP-responsive elements (CREs), within the VL30 long terminal repeat, were identified and shown to activate transcription synergistically when templates bearing multiple sites were compared with templates bearing a single site. This type of regulation was evident only in forskolin-treated cells, and the response elements were found to be inactive as mediators of constitutive transcription. In vitro binding analyses indicated that a consensus CRE and the nonconsensus VL30 CREs differ with respect to binding affinity and specificity to a number of nuclear factors that were identified to be related to proteins within the CREB, Jun, and C/EBP families of transcription factors. The relatively low affinity and/or a restricted binding specificity of the VL30 CREs made it possible to detect forskolin-induced binding of CREB- and Jun-related proteins to these sequences. We suggest that cAMP-induced transcription, specific for steroidogenic cells, can be mediated by a novel type of nonconsensus CREs and that the mechanism for this type of gene regulation is distinct from that mediated through a consensus CRE. We also report the identification of a novel factor, distinct from previously characterized CRE-binding proteins, that constitutively binds to the identified CREs.

Adrenal Glands↗
PubMed1993

Mandibular elevator muscles: physiology, action, and effect of dental occlusion.

In spite of differences in embryologic origin, central nervous organization, and muscle fiber distribution, the physiology and action of mandibular elevator muscles are comparable to those of skeletal muscles of the limbs, back, and shoulder. They also share the same age-, sex-, and activity-related variations of muscular strength. With respect to pathogenesis, the type of muscular performance associated with the development of fatigue, discomfort, and pain in mandibular elevators seems to be influenced by the dental occlusion. Clinical research comparing the extent of occlusal contact in patients and controls as well as epidemiologic studies have shown reduced occlusal support to be a risk factor in the development of craniomandibular disorders. In healthy subjects with full natural dentition, occlusal support in the intercuspal position generally amounts to 12-14 pairs of contacting teeth, with predominance of contact on first and second molars. The extent of occlusal contact clearly affects electric muscle activity, bite force, jaw movements, and masticatory efficiency. Neurophysiologic evidence of receptor activity and reflex interaction with the basic motor programs of craniomandibular muscles tends to indicate that the peripheral occlusal control of the elevator muscles is provided by feedback from periodontal pressoreceptors. With stable intercuspal support, especially from posterior teeth, elevator muscles are activated strongly during biting and chewing with a high degree of force and masticatory efficiency, and with relatively short contractions, allowing for pauses. These variables of muscle contraction seem, in general, to strengthen the muscles and prevent discomfort. Therefore, occlusal stability keeps the muscles fit, and enables the masticatory system to meet its functional demands.

Dental Occlusion↗
PubMed1993

Variables related to masseter muscle function: a maximum R2 improvement analysis.

A multiple linear regression analysis, with stepwise maximum R2 improvement technique by forward selection and pair switching, was used to select the occlusal, morphologic, and histologic variables which explained most of the variation in bite force and electric masseter muscle activity. The variables comprised tooth contact and facial morphology together with thickness and fiber characteristics of the masseter muscle. The study included 13 healthy women, 21-28 yr of age, with a minimum of 24 teeth and no serious malocclusion. Significant exploratory models (R2: 0.55-0.85) were shown concerning bite force, and electromyographic amplitude during resting posture, maximal voluntary contraction (ICP), and unilateral chewing, as well as contraction time (chewing side). Muscle thickness and molar contact had a significant, positive effect on the level of forceful muscle contraction. The explorative model both demonstrated explicable relations, and offered better insight into interrelations than did univariate analysis.

Adenosine Triphosphatases↗
PubMed1993

Signal processing for hearing impairment.

Four noise reduction methods for use in sensory aids for hearing impairment were evaluated. These include a two-microphone adaptive noise canceller, short-term Wiener filtering, a transformed spectrum subtraction technique, and sinusoidal modelling. The largest improvements in speech recognition were obtained with the two-microphone adaptive noise canceller in a moderately reverberant room. Significant improvements were also obtained for short-term Wiener filtering for some hearing-impaired subjects. The transformed spectrum-subtraction technique failed to improve performance as the front-end of a hearing aid, but yielded improvements in performance as a preprocessor for the Nucleus Cochlear Implant. Sinusoidal modelling resulted in significant improvements in signal-to-noise ratio, but without a corresponding improvement in speech intelligibility.

Acoustic Stimulation↗
PubMed1992

Histochemical characterization of masseter muscle fibres in a biopsy study of normal young women.

Muscle fibres from biopsies of the anterior part of the masseter muscle (pars superficialis) were histochemically characterized in 13 healthy female students. They were 21-28 yr old with a full complement of teeth, and normal facial and occlusal relations. Before surgery, normal masseter muscle function was demonstrated by bite-force measurements and recordings of electromyographic activity. After staining for myosin ATPase activity, the relative mean areas of muscle fibres were: type I 82.9%, type IM 9.5% and type II 8.3%. The intraindividual (18-155% of mean) and interindividual (0-216% of mean) variation of the fibre size was large. The type I fibres had the largest diameter (10-80 microns, mean: 39 microns), the type II fibres (6-47 microns, mean: 21 microns) and the IM fibres (8-54 microns, mean: 28 microns) the smallest. The biopsy technique and the histochemical characterization will be suitable for reference in women with functional changes or diseases of the masseter muscle.

Adult↗
PubMed1992

Occlusal control of mandibular elevator muscles.

Occlusal stability and mandibular elevator muscle function was studied in 25 women (20-30 yr of age). They had 27-32 fully erupted teeth with few treated occlusal surfaces, and craniomandibular function including mandibular mobility was normal. The aim was to analyze the influence of natural patterns of occlusal contact on electromyographic activity, unaffected by pain and functional disorders. Occlusal stability was assessed in the intercuspal and in lateral contact positions as the number of teeth with physical contact and the number of opposing pairs of teeth in contact. Electromyographic activity was recorded by surface electrodes over anterior and posterior temporalis and masseter muscles. In general, positive correlations were found between occlusal stability in intercuspal position and moderate to strong static and dynamic contractions, most significant in masseter muscles, indicating that forceful contraction of these muscles implies stable occlusion. Systematically, the duration of activity during chewing was negatively correlated with occlusal stability in the intercuspal position, most pronounced in working-side muscles. This pointed to shorter contractions with stable occlusion and is interpreted as the result of less need for stabilizing activity. It is concluded, that the correlations between occlusal stability and elevator muscle function are probably based on feedback mechanisms from periodontal pressoreceptors.

Adult↗