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Biomedical subjects

A Magora

Publications and source records attributed to A Magora.

At least 19 recordsLinked to original sources
PubMed2001

Gamma-irradiation stability of saturated and unsaturated aliphatic polyanhydrides--ricinoleic acid based polymers.

The effect of terminal sterilization by gamma-irradiation on several ricinoleic acid based polyanhydrides was investigated. The following polymers were used: poly(ricinoleic acid maleate) [P(RAM)], poly(ricinoleic acid succinate) [P(RAS)], poly(hydroxy stearic acid succinate) [P(HSAS)], poly(hydroxy stearic acid maleate) [P(HSAM)], and their copolymers with sebacic acid. The polymers were irradiated with an absorbed dose of 2.5 or 10 Mrad by means of a 60Co source under dry ice or at room temperature. No differences were found between samples irradiated under dry ice and at room temperature. Polymers prepared from monomers containing maleate residues, which contain double bonds adjusted to the anhydride linkage along the polymer chain, decreased in molecular weight, became insoluble, and showed fast hydrolytic degradation. For example, p(RAM), p(HSAM), and their copolymers with sebacic acid decreased in Mw from about 10,000 to about 2000, and from about 30,000 to about 5000, respectively, while polymers based on RAS and HSAS remained stable. This phenomenon was explained by an anhydride interchange-self-depolymerization process of the unsaturated anhydride bonds induced by gamma-irradiation. This explanation was supported by the depolymerization of another class of polymers having an anhydride bond between two double bonds, fumaric acid anhydride polymers. The anhydride bond that lies between two double bonds was found to be more sensitive to gamma-irradiation. This anhydride bond may be cleaved to form two radicals that further react with aliphatic anhydride bonds along the polymer chain to form inter- and/or intracyclization products.

Anhydrides↗
PubMed2000

Comparison of the enantioseparation of racemic uridine analogs on Whelk-O 1 and ChiralPak-AD columns.

The commercially available, brush-type (S,S)-Whelk-O 1 chiral stationary phase (CSP) has been used to separate 10 racemates of structurally related uridine analogs, potentially anti-viral agents, under various mobile phase compositions, using various temperatures. The enantioseparation was evaluated by comparing the Whelk-O 1 column performance with that of ChiralPak-AD column, reported previously. The comparison involved the role of some distinctive structural features of the racemates, type and composition of the solvent modifiers, as well as effect of temperature on the chiral discrimination. Despite the fact that both columns separate almost all the uridine analogs, significant differences were observed in their chiral recognition, as revealed from their retention, selectivity, resolution and elution order. The chiral recognition processes, responsible for enantioseparation on the Whelk-O 1 column, were relatively more systematic and easier to manipulate than on ChiralPak-AD column. Enantioseparation on the latter are of more complex nature and frequently gave results that were contradictory to the expectations. On the other hand, the performance in the ChiralPak-AD column was superior to that of the Whelk-O 1 column. Limitations in column handling and maintenance (pressure and temperatures) as well as limited solvent choice lead to the preference of the Whelk-O 1 column, in spite of its lower (but adequate) performance.

Chromatography, High Pressure Liquid↗
PubMed1996

Resolution of enantiomers of uridine analogs, potential antiviral agents.

Racemic mixtures of 5-substituted carbocyclic analogs of uracil nucleosides, 2"- and 3"-furyl, 2"- and 3"-thienyl and 2"-selenienyl, potentially anti-viral agents, were resolved using amylose tris(3,5-dimethylphenyl)carbamate as the stationary phase. The mobile phase was n-hexane with ethanol or 2-propanol. Effects of some structural features on the extent of discrimination between the enantiomers were examined through the selectivity and resolution factors as well as the elution order. The structural features were as follows; the type and position of the hetero-atom O, S or Se, in the cyclopentadienyl substituent 5 of the uracil and hydroxymethyl vs. acetoxymethyl groups on the cyclopentene moiety of the uridine analogs. It appeared that effects of the structural features on the separation were solvent dependent, with some very unusual solvent effects. For example, average retention, which did not follow the polarity of the mobile phase modifiers, was much higher when ethanol was used compared to 2-propanol. Also, the elution order of the two enantiomers of several pairs was reversed when ethanol was changed to 2-propanol. In general, ethanol affected higher selectivity and resolution of all the enantiomeric pairs.

Antiviral Agents↗
PubMed1993

Electronic pressure algometry of deep pain in healthy volunteers.

Deep pressure pain threshold (PPT) and pressure pain tolerance (PPtol) were measured by pressure algometry at the mastoid processes, external malleoli, and sternum in 24 healthy volunteers. The algometer consisted of a force displacement transducer with a 0.25 cm2 pressure tip linked to a recorder. The rate of force application was approximately 1kg/sec/0.25cm2. High intersubject variation was noted at all sites for both PPT and PPtol. Mean PPT and PPtol values at the sternum were 5.2kg +/- 2.1 and 8.1kg +/- 2.4, respectively, and significantly higher than at the other sites. PTT did not differ significantly between the sexes or between dominant and nondominant sides. PPtol, on the other hand, was lower in the women, but significantly so only at the malleoli. On repeat examination, comparison between the mean values at each site showed no statistical differences in any instance. Pressure algometry, as used in this study in healthy subjects, proved a reliable technique for the estimation of deep PPT and PPtol values. It may possibly serve for screening the response to experimental pain in various groups of pain patients.

Adult↗
PubMed1992

Diagnostic value of computer analysis of multipeaked EMG spikes.

Computer analysis of absolute number of peaks per second and the number of peaks in the multipeaked spikes/sec was carried out in the EMG interference recordings of 5 healthy, 6 myopathic and 8 neuropathic subjects. The purpose of the study was to detect diagnostically different patterns. A spike was considered multipeaked if it had 6 or more peaks. The amplitude of elimination (baseline) was examined at 1: 5, 1: 10 and 1: 15 of the average amplitude per second. Both the number of peaks and the number of peaks in multipeaked spikes in the neuropathic and myopathic muscles showed statistically significant differences when compared to healthy muscles. This technique could give an indication for the differential diagnosis of myopathic, neuropathic or healthy state of the muscle.

Arm↗
PubMed1991

Fourier series analysis of the electrophysiological pattern of fatigue in healthy human beings, after curare administration.

Real time computer analysis of the electrophysiological development of muscular fatigue after small doses of d-tubocurarine (TC), has been examined in anesthetized human beings. As compared to a decrease of frequency in the control measurements, previous studies have shown an increase of the frequency of spikes after TC administration. The present experiments were carried out on the biceps brachii of 8 healthy human volunteers maintained in isometric contraction against a constant counter load until complete fatigue occurred. The Fourier spectrum analysis showed a statistically significant shift to lower frequencies before, and a milder statistically non significant shift after TC. These results may indicate that under mild curarization the early phase of muscular contraction requires a higher number of large motor units and thus, at a later stage of the contraction the pool of available large motor units becomes smaller. This conclusion supports the hypothesis that mild curarization causes a state of initial muscular fatigue.

Action Potentials↗
PubMed1990

Comparison of the electrophysiological pattern of fatigue between athletes required to perform explosive and endurance sports.

The electrophysiological behavior of an isometric contraction sustained to fatigue, was examined in 6 long distance runners and 9 athletes involved in explosive (burst) sports, by on line computer analysis of the electrical activity of vastus medialis, rectus femoris and vastus lateralis. The experiments were carried out with a counterload of 50% of the maximal strength of the muscle. The duration of spike increased and the frequency decreased in the 3 examined muscles, in both types of sport. In the burst sports the changes of value of both parameters were statistically significant in the 3 muscles. In endurance sports the variations of duration were not significant and the changes of frequency were statistically significant only in the vastus lateralis. These results could be explained by the gradual activation of motor units of more strikingly different sizes in burst sports. Thus it may be speculated that prolonged training in burst sports may result in the automatic mobilization of higher number of small motor units, for the initiation of contraction while in endurance sports the onset of contraction is more gradual and carried out by large motor units.

Adolescent↗
PubMed1987

Proximal monomelic amyotrophy of the upper limb.

A 30-year-old patient of Central European origin, suffering from monomelic amyotrophy, is presented. The disease was characterized by proximal weakness of one upper limb, mainly of the shoulder girdle, accompanied by atrophy. The electrodiagnostic examination revealed signs of partial denervation in the presence of normal motor and sensory conduction. The disease, which is probably of the anterior horn cells, had a benign course and good prognosis, as evident from repeated examinations during a follow-up of eight years.

Adult↗
PubMed1980

Motor nerve conduction in intravenous regional anaesthesia with bupivacaine hydrochloride.

Motor nerve conduction (MNC) from proximal and distal points of the median and ulnar nerve was examined in 14 patients receiving a total of 29 i.v. regional anaesthetics (IRA) with bupivacaine hydrochloride in doses ranging from 100 to 300 mg. Conduction was tested during and following vascular obstruction, until MNC returned to pre-IRA value. After 20 min of obstruction, MNC was unobtainable in most patients, an effect which was dose-related. The action of bupivacaine on MNC persisted for up to 3 h after cuff release, depending on the dose, and paralleled voluntary movements. MNC block began at the proximal point of both nerves, the median nerve being affected earlier. Based on the clinical and electrical findings, bupivacaine 200 mg proved to be optimum dose for producing safe and prolonged IRA.

Anesthesia, Conduction↗
PubMed1980

Prolonged effect of bupivacaine hydrochloride after cuff release in i.v. regional anaesthesia.

Bupivacaine hydrochloride 0.25% and 0.50% solutions, were administered 115 times by the i.v. regional route to 64 surgical patients and in 38 subjects suffering from pain syndromes. The clinical effects were limb numbness up to 20 h following cuff release, while analgesia and weakness of the limb muscles were evident 5 h after the tourniquet. Clinical and electrophysiological findings revealed a dose relationship of the effects. Toxic signs were noted in three patients in whom the cuff was released in a one-step fashion. In 11 patients, mean arterial plasma concentrations of bupivacaine reached 3.7 micrograms ml-1 after administration of 0.5% bupivacaine 40 ml, 5 min after final cuff release, and decreased gradually thereafter. In selected conditions which do not require a bloodless field and in certain intractable pain states, i.v. regional anaesthesia with high-dose bupivacaine (200 mg of 0.5% solution) may be a simple and effective technique.

Adult↗
PubMed1980

[The pain clinic].

Explore the source record for details and available documents.

Antipsychotic Agents↗
PubMed1980

Relation between the low back pain syndrome and x-ray findings. 3. Spina bifida occulta.

The relation between LBP and SBO was studied in 1244 subjects, of which 800 had LBP and 444 served as controls. Sex, age, occupational characteristics, spine curvatures, spinal movements and work history were compared. It is concluded that SBO does not play a causative role, does not cause a proneness to LBP and does not influence the chronicity of LBP. Some data seem to indicate that the severity of LBP may be increased by SBO.

Adult↗
PubMed1980

Relation between low back pain and X-ray changes. 4. Lysis and olisthesis.

In a comparative study of 1024 low back pain and healthy subjects, prelysis was found in 16.4%, lysis in 10.5% and olisthesis in 2%. No relation between prelysis and lysis, and low back pain was found. Lysis seemed to be associated with a higher severity of low back pain. All the subjects with olisthesis suffered from low back pain. Based on these findings, it is concluded that lysis or pre-lysis should not be a ground for the exclusion of candidates to any occupation, but that olisthesis should, and that both lysis and olisthesis should be accepted as roentgenological findings in which the severity of low back pain may be higher, thus justifying a more prolonged sick leave.

Absenteeism↗
PubMed1978

Treatment of pain by transcutaneous electrical stimulation.

Two hundred and ninety-two patients suffering from a wide range of pain syndromes were treated with transcutaneous electrical stimulation (TES). Electrical stimulation of the painful area was administered on the skin by externally applied electrodes, attached to a portable battery-operated apparatus. The results, determined according to a subjective scoring system, were good in 50.7%, moderate in 24.3% and poor in 25% of the patients. TES is a non-invasive technique, has no side effects and may easily be self-administered. It is concluded that it should be tried in pain syndromes for which no specific therapy is available.

Adolescent↗
PubMed1978

Relation between the low back pain syndrome and x-ray findings. 2. Transitional vertebra (mainly sacralization).

The relation between LBP and transitional vertebra was investigated in 312 subjects; 148 healthy individuals served as controls. An overall incidence of 0.65% lumbarization and 20.8% sacralization was found; of the latter, one third were partial and two-thirds complete. The incidence was markedly lower in women. No direct relation between sacralization, partial or complete, and LBP was found; this was based on interrelation of the LBP and control groups, with or without sacralization, to age, ethnic community, occupation, number of changes of occupation or place of employment, duration of LBP, and physical occupational requirements (sitting, standing, bending, sudden maximal effort). There is some evidence that LBP, when associated with sacralization, may be more severe.

Adult↗