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Biomedical subjects

R Johansson

Publications and source records attributed to R Johansson.

At least 19 recordsLinked to original sources
PubMed1992

Evaluation of some nonrecursive digital filters for signals of auditory evoked responses.

Auditory brain stem evoked responses are routinely used in audiology and otoneurology. Because recordings include more or less noise, the signals of evoked responses need digital filtering to suppress the noise. Nonrecursive digital filters are often the best since they can be organized to have no phase shift, which is essential in order not to distort sensitive parameters, as latency, in evoked responses. We have studied effects of some nonrecursive digital filters on the latency parameters of evoked responses. It turned out that digital filtering can have considerable influence on latencies, and thus the choice of appropriate filters is crucial.

Evaluation Studies as Topic↗
PubMed1992

Studies on the individual and combined diuretic effects of four Vietnamese traditional herbal remedies (Zea mays, Imperata cylindrica, Plantago major and Orthosiphon stamineus).

Herbal remedies are widely used in Vietnam alongside modern drugs. We assessed the diuretic effect of four traditional Vietnamese herbal remedies from Zea mays, Imperata cylindrica, Plantago major and Orthosiphon stamineus, all claimed to produce an increase of diuresis. No influence was recorded for the 12- and 24-h urine output or on the sodium excretion for any of the drugs when tested under standardized conditions in a placebo controlled double-blind crossover model. The present study indicates the need for critical review of the present recommendations regarding therapy with plant materials in countries relying on empiric traditions.

Adult↗
PubMed1991

Optimal coordination and control of posture and locomotion.

This paper presents a theoretical model of stability and coordination of posture and locomotion, together with algorithms for continuous-time quadratic optimization of motion control. Explicit solutions to the Hamilton-Jacobi equation for optimal control of rigid-body motion are obtained by solving an algebraic matrix equation. The stability is investigated with Lyapunov function theory, and it is shown that global asymptotic stability holds. It is also shown how optimal control and adaptive control may act in concert in the case of unknown or uncertain system parameters. The solution describes motion strategies of minimum effort and variance. The proposed optimal control is formulated to be suitable as a posture and stance model for experimental validation and verification. The combination of adaptive and optimal control makes this algorithm a candidate for coordination and control of functional neuromuscular stimulation as well as of prostheses.

Algorithms↗
PubMed1991

Delayed onset of ototoxic effects of gentamicin in patients with Meniére's disease.

In treatment of Meniére's disease, installations of gentamicin are continued until there are signs of disturbance of vestibular or cochlear function. However, since it has been demonstrated that gentamicin is eliminated slowly from the inner ear, a continuing ototoxic effect may be suspected. The present study aimed to investigate the delay of onset of symptoms of ototoxic effects. Five patients with Meniére's disease and disabling vertigo were treated with intratympanic installation of gentamicin. The patients received two installations at two consecutive days, after which the treatment was abated, although no patient showed any symptoms of affection of the vestibular or cochlear end organs. All patients, however, developed vertigo and nystagmus beating toward the not treated ear within 3 to 5 days after the last installation. At 3 months and 1 year later, the treated ear showed no reaction on bithermal caloric stimulation and all patients had a complete relief of attacks of vertigo but hearing levels were about the same compared to before treatment. The present findings demonstrate a delayed onset of ototoxic effects and it is suggested that gentamicin treatment should not be carried on until symptoms develop. Furthermore, extremely low dose treatment may produce loss of vestibular function with the desired relief of vertigo and with less hazards of affecting the hearing level.

Adult↗
PubMed1991

Effects of restrained cervical mobility on voluntary eye movements and postural control.

The effects of restrained cervical mobility on pursuit eye movements (PEMS), voluntary saccades and postural control, as measured by posturography, were studied in 11 healthy subjects whose cervical spine movement had been restrained for 5 days by means of a rigid neck-collar. At day 5 mean peak velocity of voluntary saccades at amplitudes of 40 degrees and 60 degrees was significantly reduced, as was mean peak gain of PEMs at a stimulus velocity of 50 degrees/s; the variance of body position in vibration-induced body sway was significantly increased, but there was no difference in variance of galvanically-induced body sway or in velocity of vibration-induced body sway. The results suggest that restriction of cervical movements per se affects voluntary eye movements, a conclusion also consistent with findings in patients with tension headache. Restriction of cervical movement only marginally affects postural control.

Adult↗
PubMed1991

Human postural dynamics.

The study of posture dynamics is important not only to understand disorders of impaired equilibrium and protective reactions to unexpected displacements of the human body, but also to the design of prosthesis and functional neuromuscular stimulation as aids to patients with impaired postural stability and locomotion. Coordinated control of the body segments is a complex aspect of motor behavior, owing to the multiple degrees of freedom of the controlled system. Several interacting subsystems are involved in the dynamics of human posture and locomotion, including the skeletal, neuromuscular, and sensory systems. Human posture control is maintained by somatosensory, vestibular, and visual feedback, integrated within the locomotor and central nervous systems. Studies of posture dynamics and stability therefore entail the study of mechanical aspects of the human body, its sensory systems, and the principles governing coordination in motion control. In this paper is reviewed some of the research done in the field of human posture dynamics, including such topics as biomechanics, equilibrium, stability, motion coordination, neural feedback, neural control systems modeling, motion strategies, optimality of motion, and adaptation. We consider experimental approaches and theoretical models, as well as the gap between them. Principles for the experimental investigation of control systems are considered.

Animals↗
PubMed1990

Predictive value of tumor estrogen and progesterone receptor levels in postmenopausal women with advanced breast cancer treated with toremifene.

The predictive value of estrogen receptor (ER) concentrations was evaluated in a group of 113 postmenopausal patients with estrogen-receptor-positive (ER greater than 7 fmol/mg protein) advanced breast cancer. In 103 patients, tumors were also sampled for progesterone receptor (PgR) determination. All patients were treated with toremifene, a novel antiestrogen, 60 mg daily. The median ER in 51 responders was 78 fmol/mg protein, and in 62 nonresponders, 51 fmol/mg protein; the median PgR levels were 40 and 37 fmol/mg protein, respectively. The response rate in patients with ER less than 50 fmol/mg protein was 38%, and 51% in the group with ER greater than 50 fmol/mg protein (not significant [NS]). The response rate in patients with PgR less than 10 fmol/mg protein was 42%, and in patients with greater than 10 fmol/mg protein, 44%. The duration of response in patients with ER greater than 50 fmol/mg protein was significantly longer than with lower ER levels (P = 0.002). PgR was not associated with the duration of response. In Cox's multiple regression analysis, ER was an independent prognostic factor (P = 0.005) for response duration. Thus, the ER concentration of tumor tissue predicts the duration of response but not the response rate to toremifene in patients with advanced breast cancer. The PgR status does not predict the response rate or the duration of response.

Aged↗
PubMed1990

High dose toremifene (240 mg daily) is effective as first line hormonal treatment in advanced breast cancer. An ongoing phase II multicenter Finnish-Latvian cooperative study.

The efficacy of high dose toremifene (240 mg daily) in postmenopausal women with advanced breast cancer is investigated in this ongoing study. At present, 38 patients are fully evaluable. Ten patients have CR (26%), 16 PR (42%) (objective response rate 68%), 8 NC (21%), and 4 PD (11%). Most objective responses are in soft tissue tumors (14/17, 82%). The response rate is equally high in patients with positive or unknown estrogen receptor (ER) status. Median duration of responses and survival are not yet evaluable. Of 48 patients evaluable for side-effects, 22 (46%) experienced some kind of toxicity, which was mild in 64% of cases, moderate in 29%, and mostly of estrogenic type. The study will continue to confirm the results thus far obtained.

Aged↗
PubMed1990

The effects of hypoxic hypoxia on brain stem mediated stapedial reflex in healthy volunteers.

The stapedial reflex is routinely used both in hearing evaluation and to distinguish cochlear from retrocochlear lesions. The present study was carried out on seven healthy volunteers in the hope of obtaining basic information about the physiological variables of stapedial reflex using hypoxic hypoxia. The results show that a short-term hypoxic hypoxia affects, for the most part, the muscle contraction velocity and the amplitude of the reflex, whereas the latency remains unchanged. This finding indicates that the arterial O2-saturation may have an influence when studying the effects of breathing depressive drugs or in patients with decreased ventilation capacity.

Adult↗
PubMed1989

Hearing of dentists in the long run: a 15-year follow-up study.

Pure tone audiograms from 68 dentists with a minimum of 10 yr in dental practice were taken in 1973 and a follow-up was carried out in 1988. The aim was to study whether the dental occupation carried a risk for hearing handicap or not. Allowance for age and sex was made by using the presbyacusis values of SPOOR as the reference. At the speech range of frequencies dentists did not differ from the reference. At higher frequencies of 4, 6, and 8 kHz dentists tended to have higher hearing thresholds than expected. At 6 kHz, both male and female dentists had highly significantly greater hearing thresholds than expected by the corresponding references in both the studies. This difference remained essentially similar over the follow-up period, indicating that dental drill noise was insufficient to cause continuous loss of hearing. While mild NIHL was very common and tended to appear earlier in male than in female dentists, there was in the long run no continuous loss of hearing in either sex other than that attributable to the natural development of presbyacusis.

Adult↗
PubMed1989

Determination of characteristic parameters of human postural dynamics.

Posture control performance was quantified in three variables (swiftness, stiffness, damping). Subjects were tested with a force platform recording body sway induced by vibrators attached to the calf muscles. Parameter estimation was made with identification of a transfer function representing the stabilized inverted pendulum. It is conjectured that the state feedback parameters identified are suitable for use in assessing ability to maintain posture.

Adult↗