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Biomedical subjects

A Winnberg

Publications and source records attributed to A Winnberg.

7 recordsLinked to original sources
PubMed1988

Head posture and hyo-mandibular function in man. A synchronized electromyographic and videofluorographic study of the open-close-clench cycle.

Synchronized electromyography and videofluorography (lateral projection) were used to investigate the influence of altered head posture on hyo-mandibular movements, suprahyoid muscle length, suprahyoid working angle, and timing of suprahyoid and masseter muscle activity. Twelve adult male subjects with normal dentofacial morphology were investigated during the open-close-clench cycle. Using upright head position (Frankfort horizontal) as reference, several statistically significant observations were made during forward flexion and backward extension of the head. The results indicate that head posture is a significant factor in studies of mandibular and hyoid bone movements, and masseter and suprahyoid muscle function.

Adult↗
PubMed1987

Suprahyoid biomechanics and head posture. An electromyographic, videofluorographic and dynamographic study of hyo-mandibular function in man.

Suprahyoid and masseter muscle function was studied in 49 adult males with normal dentofacial morphology and normal soft tissue profiles, with special reference to head posture. The different parameters were investigated by EMG during chewing, by EMG synchronized to an opening force dynamograph during static and dynamic conditions, and by EMG synchronized to videofluorography during the open-close-clench cycle. Cephalometry was applied to evaluate the videofluorographic images of the hyo-mandibular complex. The EMG amplitude for the entire group did not vary significantly between different test occasions with an interval of 5-24 hours. The individual variation was large, however. Repeated EMG registrations within such time intervals should therefore be reliable for groups of individuals. Hook electrodes gave about 10% higher maximal EMG compared to surface electrodes. Registrations with the two types of electrodes could therefore not be directly compared. An increased interelectrode distance resulted in larger EMG amplitudes. The interelectrode distance should therefore be standardized. Head posture influenced the EMG amplitude and should therefore also be standardized. The electrical activity in suprahyoid muscle contraction preceded the mechanical activity. During opening, a time- lag of approximately 200 msec was found between the peak EMG activity of the anterior belly of the digastric muscle and the maximal opening force. A direct correlation existed between the IEMG activity of the digastric muscle and force during static (r = 0.89) and dynamic (r = 0.72) conditions. The maximal recorded force of the opening muscles of the mandible was found to be 70 N. No absolute reciprocity existed between opening and closing EMG activity. During chewing, suprahyoid maximal IEMG activity was less than one-third of that from the masseter. Maximal IEMG activity was reduced for the masseter during forward flexion, and for the suprahyoid muscle group during backward extension. Head posture is an important factor in EMG registrations of opening and closing muscle function during chewing. During upright head posture, the hyoid bone exhibited on average an elliptical movement pattern and reached its most elevated position at the start of opening and its most depressed position at the start of closing. A small movement before opening an upward and forward direction and before closing in a further downward and backward direction was found. Suprahyoid EMG activity was registered before start of opening, during opening and during the first half of the open phase.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1986

Masticatory muscle activity and hyoid bone behavior during cyclic jaw movements in man. A synchronized electromyographic and videofluorographic study.

Synchronized electromyography (EMG) and videofluorography were used to relate the EMG activity from the suprahyoid and masseter muscles and the movement of the hyoid bone to different phases of the jaw open-close-clench cycle. The subjects investigated comprised 19 adult males with normal dentofacial appearances. Five subjects were excluded from the analyses because of a uniform suprahyoid EMG pattern during cyclic jaw movements. The results from the remaining fourteen subjects revealed that mandibular opening was preceded by suprahyoid EMG activity and movement of the hyoid bone in an upward-forward direction. During jaw opening and the first half of the jaw-open phase, EMG activity was registered exclusively from the suprahyoid muscles. The hyoid bone was moved downward-backward during jaw opening. Mandibular closing was preceded by masseter EMG activity and movement of the hyoid bone in a further downward-backward direction. During jaw closing the hyoid bone moved upward and forward. Discrete EMG bursts from the suprahyoid muscles were occasionally registered simultaneously with the masseter EMG activity during jaw closing. No absolute reciprocity existed between suprahyoid and masseter muscle activity during cyclic jaw movements. A period of no EMG activity from either the suprahyoid muscle group or the masseter muscle was noted during the jaw-open phase and the occlusal phase.

Adult↗
PubMed1986

The trophic effect on the pancreas of long-term continuous intravenous infusion of secretin and a cholecystokinin-like peptide in rats.

Rats were treated for 5 days with continuous intravenous infusion of different doses of secretin and Thr28Nle31CCK25-33 (CCK-LP) alone and combined. The trophic effect on the pancreas was evaluated by means of pancreatic weight and contents of DNA, RNA, and protein. The acute effects on pancreatic protein secretion were studied in anesthetized rats. The findings generally confirmed the trophic effects of secretin and CCK-like peptides on the pancreas. No convincing evidence of potentiation was found between small doses of secretin and CCK-LP for either pancreatic growth or protein secretion. The maximal dose of CCK-LP was the same for pancreatic growth and for protein secretion (2.5 micrograms/kg-h). Potentiation was demonstrated between secretin and the maximal dose of CCK-LP for protein secretion. The maximal effect of CCK-LP on pancreatic growth, however, was not enhanced by secretin.

Animals↗
PubMed1985

Effects of a cholecystokinin-like peptide on DNA and polyamine synthesis in the rat pancreas.

The trophic effect of one or multiple subcutaneous injections of two different doses of a cholecystokinin-like peptide (CCK-LP) on the rat pancreas was evaluated by determination of ornithine decarboxylase (ODC) activity, the concentrations of the polyamines putrescine, spermidine, and spermine, and the activities of DNA polymerase and thymidine kinase, in addition to the contents of DNA, RNA, and protein. ODC activity was increased 10- to 20-fold already 2 h after a single injection of CCK-LP. The activity thereafter decreased and approached the control level after 6 to 8 h. The concentration of putrescine also showed a marked increase after a single injection, approaching maximum at 8 h. A slight increase was found for spermidine as well. DNA polymerase and thymidine kinase increased after 2 days of treatment. The DNA content was still normal at that time. The study suggests that the trophic effect of CCK is initiated very early. It shows that ODC activity and putrescine concentrations are early and sensitive determinants of the effect of CCK on the pancreas.

Animals↗