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Biomedical subjects

R Johansson

Publications and source records attributed to R Johansson.

At least 109 records · Page 6Linked to original sources
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↗
PubMed1989

Dynamic performance of vibration induced anterior-posterior sway during upright posture in normal subjects.

Human postural control works as a dynamic feedback control system. The dynamic performance of postural control for anterior-posterior movements during upright posture are defined by three parameters. These parameters reflect the stiffness, the damping and the swiftness of a response to an induced perturbation. In the present study 23 normal subjects were investigated. Both with open and closed eyes, there was a negative correlation between swiftness and stiffness. With open eyes there was also a weak correlation between swiftness and damping. When the subjects were tested with open eyes there was a prominent and highly significant increase of stiffness and a reduction of swiftness of the responses. It was found that proprioceptive information from the calf muscles contributes in postural control of movements up to 1 Hz and visual information is important for movements up to 0.05 Hz. The present findings suggest that postural control changes dynamic strategies depending on the available sensory feedback.

Adolescent↗
PubMed1988

Pharmacokinetic and pharmacodynamic studies on high doses of fluphenazine.

Six chronic schizophrenics--earlier refractory to recommended doses of neuroleptic drugs but eventually responding to 250 mg fluphenazine heptanoate weekly--participated in a pharmacokinetic study. Five out of the six patients showed rather constant steady state plasma fluphenazine values on a 250 mg depot weekly. After depot drug withdrawal, the single oral dose pharmacokinetics on 400 mg fluphenazine showed the same variations in Cmax, tmax, t 1/2 and AUC as are observed when recommended doses of fluphenazine are used. We thus could not demonstrate any dose-dependent pharmacokinetics on high oral fluphenazine doses. In half the patients, a biphasic decay in the plasma concentration curve indicated at least two compartments. The patients were then studied for up to 2 years on 200-500 mg fluphenazine as a single daily dose. The fluphenazine plasma levels were rather constant in the individual patients during this period. The plasma prolactin values were related to the fluphenazine values even in the high value area, thus showing a persistent pharmacodynamic variation capacity. The clinical part of the study did not show any relevant findings.

Adult↗
PubMed1988

Tobacco smoke removal with room air cleaners.

The ability of room air cleaners to remove gases and particles from air contaminated with tobacco smoke has been studied. Thirty-one air cleaners were tested. Various air-cleaning devices were used, ie, electrostatic precipitators, electret fiber filters, ionizers, activated carbon, impregnated alumina, ionizing lamps, and an electron generator. The airflow rates were in the range of 0-500 m3/h. The measurements covered particle sizes of 0.01-7.5 microns and the following gases: carbon monoxide, ammonia, formaldehyde, nitric oxide, nitrogen dioxide, hydrocarbons, and hydrogen cyanide. No formal standard procedure exists for testing room air cleaners; therefore the tests were made in the following way. Tobacco smoke was generated and mixed in a closed room. The room air cleaner was started, and the decay rates for the gases and particles were measured. The results were calculated as equivalent airflow rates, ie, the clean airflow rate causing the same decay rate for contaminant concentrations in a room. The equivalent airflow rates were 0-360 m3/h. The rate of ozone emission by electrostatic precipitators and ionizers was also measured. One general conclusion was that it is much more difficult to remove gases than particles.

Air Conditioning↗
PubMed1988

The effect of flunitrazepam on acoustic reflex--a methodological pilot study.

Four healthy volunteers took part in this study in four sessions at one week intervals minimum. Three intravenous dose levels of flunitrazepam as well as placebo (saline) were investigated. The sessions were randomized and the study was double blind. The results show that a significant correlation exists between the serum concentrations of flunitrazepam and acoustic reflex amplitude, latency, Maddox wing readings and subjective sedation. Critical flicker fusion frequency test was insensitive in this respect. We conclude that acoustic reflex may be a new method for determination of benzodiazepine effects in man.

Double-Blind Method↗
PubMed1987

Hormonal treatment of advanced breast cancer. A randomized trial of tamoxifen versus nandrolone decanoate.

The response to tamoxifen (TAM) (10 mg to 20 mg twice orally) was compared with the response to nandrolone decanoate (NAN) (50 mg every second week or 100 mg every third week intramuscularly) in this randomized study in previously untreated women with advanced breast cancer. Patients were postmenopausal or postmenopause was induced with irradiation therapy. The two treatment groups were highly similar in different patient characteristics. Of 67 evaluable patients treated with TAM, ten (15%) had a complete or partial remission, 28 (42%) had stabilized disease and 29 (43%) had progressive disease. In the 60 patients treated with NAN, the figures were ten (17%), 22 (37%) and 28 (47%) respectively. The response rates did not differ significantly. Tam was as good as NAN in osseous metastases. Four of 34 patients responded to TAM and three of 38 patients responded to NAN. NAN had a tendency for better response in the treatment of visceral metastases. Six (43%) of 14 patients responded to NAN while only three (14%) of 21 responded to TAM (P = 0.11). The median duration of remission was 24 months in the TAM arm and 17 months in NAN (insignificant). As second line treatment, NAN after TAM gave one complete remission and three partial remissions, but none responded to TAM after NAN. The side-effects of both drugs were rare and mild. These data indicate that TAM and NAN are comparable in the treatment of advanced breast cancer.

Breast Neoplasms↗
PubMed1987

Organ and tumor distribution of (18F)-2-fluoro-2-deoxy-D-glucose in fasting and non-fasting rats.

Differences in the uptake of (18F)-2-fluoro-2-deoxy-D-glucose ((18F)FDG) in various normal organs and the Rous sarcoma of fasted and unfasted rats were studied at 5, 15, 30, 60, and 120 minutes after i.v. injection. The uptake of (18F)FDG in the tumor, spleen, and testis increased for 120 minutes, while uptake in the other organs was either level (brain, heart, white fat) or cleared off. The uptake was higher in the tumor than in the normal organs. The fraction of viable tumor tissue as measured morphometrically correlated intraindividually with the uptake of (18F)FDG--an increase of 1% of vital tumor corresponded to a 1.01-fold increase in tumor uptake of (18F)FDG. The nutritional state was of importance for the uptake of (18F)FDG into the heart, testis and brown fat. (18F)FDG is taken quantitatively up by the viable parts of the Rous tumor; this may make it possible to follow the response of treatment in individual tumors also in man with (18F)FDG and positron emission tomography (PET).

Animals↗