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Biomedical subjects

J Perry

Publications and source records attributed to J Perry.

At least 253 records · Page 14Linked to original sources
PubMed1981

Recovery of tissue folates after inactivation of cobalamin by nitrous oxide. The significance of dietary folate.

The anesthetic gas, nitrous oxide (N2O), oxidizes the cobalt moiety in the vitamin B12 molecule and in this way inactivates methionine synthetase which requires reduced cobalamin. In rats this is followed by a disappearance of folates from the tissues, this loss being most marked in the liver. Returning the animals to a normal atmosphere leads to restoration of most of the pre-N2O folate levels within 5 days. The plasma folate, which rises on exposure to N2O, falls within several hours. The restoration of tissue folates does not take place if the rats are placed on a low folate diet after withdrawal from an N2O environment. Thus the fall in tissue folate levels is due to loss from the body either by excretion or increased catabolism and not to redistribution of folate. Return of normal folate levels requires a dietary source of folate.

Animals↗
PubMed1981

Surface versus intramuscular electrodes for electromyography of superficial and deep muscles.

The relative selectivity of surface electrodes placed over the gastrocnemius and soleus muscles in the standard manner was determined by comparing the electromyogram from these electrodes to the electromyogram from wire electrodes inserted into the soleus, gastrocnemius, and tibialis posterior muscles. Muscle activity was elicited in 11 normal subjects by performing six manual muscle tests. Three of the tests followed the standard technique and three were modifications designed to provide better differentiation of muscle action. All electromyographic data were quantified by computer integration and normalized to cancel out sampling inconsistency. None of the muscle tests totally restricted activity to the designated muscle, but the tests did determine which was the strongest participant. During the standard specific gastrocnemius and soleus muscle tests, the corresponding surface electrode provided a lower electromyogram than did the matching wire electrode; that is, the surface-to-wire-electrode ratio was less than one (gastrocnemius = 0.74, soleus = 0.58). This ratio was greater than one when the electromyogram was being recorded from one muscle while testing another muscle (gastrocnemius = 1.55, soleus = 1.92). The mathematical model relating surface-electrode values to the wire-electrode data from all three muscles identified 60 percent of the surface gastrocnemius electrode electromyogram as arising from that muscle, while only 36 percent of the soleus surface electrode data related to the activity of the soleus: Sg = .19Ws + 60Wg + .13Wt + .08Wo and Ss = .36Ws + .31Wg + .22Wt + .11Wo.

Electrodes↗
PubMed1981

Functional evaluation of Rolfing in cerebral palsy.

Rolfing is a technique which involves the use of pressure on areas of the body in which muscle tendons adhere to each other rather than sliding over one another in the normal way. In this study, a series of 10 patients with mild, moderate or severe cerebral palsy underwent Rolfing Treatment, and the results were evaluated. Mildly impaired patients made gains in velocity, stride length and cadence; the moderately impaired group made only minor gains in velocity; and the severely impaired did not improve by any of the criteria used in this study. Muscle strength and electromyography were not altered appreciably in any of the patients. While the effects of treatment on range of motion were highly variable, increased muscle tightness in the hip and knee flexors, hip internal rotators, hip adductors and plantar flexors was noted. These results indicate that Rolfing can lead to improved performance in mildly affected patients because they possess the neurological capacity to make use of increased tissue mobility, and thus avoid contractures. However, the increased muscle tightness which can occur probably outweighs any benefit which moderately or severely impaired patients may derive from the treatment.

Adolescent↗
PubMed1981

The effect of nitrous oxide-induced inactivation of cobalamin on plasma amino acid levels in the rat.

Rats were maintained in an atmosphere of equal volumes of oxygen/nitrous oxide (1/1) for up to 7 d and plasma levels of methionine, glycine, serine, histidine, homocysteine and S-methylcysteine were measured. There was a fall in plasma methionine and a rise in plasma serine levels. There were no significant changes in glycine and histidine levels. Homocysteine and S-methylcysteine were not detected in rat plasmas. The fall in plasma methionine was due to loss of cobalamin-dependent methionine synthetase activity. The rise in plasma serine may be due to decline in its metabolism via methenyltetrahydrofolate cyclohydrolase which is concerned in oxidizing the methenyl-carbon ( =CH-), initially derived as a methylene-carbon (-CH2-)from serine, to formate (-CHO).

Amino Acids↗
PubMed1981

Changes in plasma folate levels in rats inhaling nitrous oxide.

Inhalation of nitrous oxide, which inactivates vitamin B12, is followed by a rise in the plasma folate level. The concentration of plasma folate remains elevated throughout the period of exposure to nitrous oxide. Returning the rats to the air is followed by a fall to pre-exposure plasma folate levels within 24 h.

Animals↗
PubMed1981

Role of sulphasalazine in the aetiology of folate deficiency in ulcerative colitis.

Only two (2.5%) of 80 outpatients with histologically proven ulcerative colitis had folate deficiency associated with anaemia or macrocytosis. Mean folate absorption, measured using micrograms/kg body weight of a tritium-labelled physiological folate derivative, 5-methyltetrahydroteroylglutamic acid, in six newly diagnosed patients was 76.7% (normal greater than 95%) but fell to 69.4% after three months' treatment with sulphasalazine. Mean difference in individual patients was 7.5% +/- 5.2% (SD) (p less than 0.02). Mean folate absorption in four patients with megaloblastic anaemia or macrocytosis which developed during treatment with sulphasalazine was 66.3%. This rose to 82.4% after the drug was stopped. Mean difference in individual patients was 16.6 +/- 6.6% (SD) (p less than 0.001). All patients who developed anaemia or macrocytosis with sulphasalazine had additional reasons for folate deficiency. These included coeliac disease, severe nutritional deficiencies, and haemolysis. It was concluded that sulphasalazine impairs folate absorption but this only becomes significant if other reasons for folate deficiency are also present.

Adult↗
PubMed1981

EMG-force relationships in skeletal muscle.

This article reviews the history of attempts to define in quantitative terms the relationship between a processed electromyographic signal and the corresponding force produced by skeletal muscle. Numerous reports have indicated a linear relationship between isometric force and rectified, integrated EMG. These reports, the nature of their experiments, and the disagreements among them are reviewed. Particular attention is given to the effects of the signal processing in the final results, including type and location of electrodes, amplification, signal isolation, etc. The effect of joint position and level of muscular effort in the isometric case are discussed. Various proposed mathematical models of the force-EMG relationship are presented and analyzed. The concluding section of the paper summarizes the current areas of agreement and disagreement and comments on the feasibility of obtaining force-EMG relation in the presence of movement.

Animals↗
PubMed1981

Rocker shoe as walking aid in multiple sclerosis.

Evaluation of rocker shoes as a walking aid for multiple sclerosis patients included a mechanical analysis of the shoes, establishment of clinical criteria for appropriate patient selection, and laboratory gait measurements of patients with and without rocker shoes. Patient fitting demonstrated that the most significant measurement, the roll point, must be about 2cm proximal to the 1st metatarsal head. A snug fit as well as the addition of a heel strap was required to hold the shoe on the foot so its mechanical assistance was consistent. Rocker shoes were effective only in patients who still retained the ability to walk independently; retention of adequate hip and calf strength proved critical. Basic gait deficit was plantar flexion less than 15 degree while standing, leading to knee hypertension and forward trunk leaning, inadequate knee flexion and toe drag in swing, general awkwardness and fatigue. Gait improvement with the rocker shoes varied with clinical classification. Normal velocity and stride characteristic in rocker shoes were accompanied by a marked decrease in net energy cost. A mean saving of 150% of normal energy was gained with rocker shoes.

Adult↗
PubMed1980

Vitamin B12 regulates folate metabolism by the supply of formate.

Nitrous oxide (N2O) inactivates the B12 coenzyme involved in methionine synthesis and interrupts formation of the folate coenzyme (folate polyglutamate). Normal synthesis of folate polyglutamate is restored in the N2O-treated rat when folate carrying a single carbon unit is supplied at the formate level of oxidation. The activity of the enzyme, formyl synthetase, which links formate to tetrahydrofolate, is increased after exposure to nitrous oxide. Formate is normally derived from the oxidation of methyl groups, methionine being an important source. It is suggested that failure of methionine synthesis leads to a paucity of formate and in turn to inadequate formylation of tetrahydrofolate. Formyltetrahydrofolate is the required substrate for the synthesis of folate polyglutamate, and impairment of this step in turn compromises general folate metabolism.

Animals↗
PubMed1980

Utilization of [2-14C]tetrahydropteroylglutamic acid and 5-[G-3H]methyltetrahydropteroylglutamic acid as substrates for folate polyglutamate synthesis in fruit bats: effect of vitamin B-12-deficiency.

[2-14C]Tetrahydropteroylglutamic acid and 5-[G-3H]methyltetrahydropteroylglutamic acid were given intraperitoneally to fruit bats. Folate polyglutamates were formed in the liver from both substrates in different amounts and at different rates. The methylfolate pool appeared to remain separate from the tetrahydrofolate pool. More polyglutamate was formed from tetrahydropteroylglutamic acid than from 5-methyltetrahydropteroylglutamic acid. There was a fall in the folate content of the liver in the vitamin B-12-deficient bat and a more rapid incorporation of folates into polyglutamates but thereafter a more rapid loss of the labelled folate from liver.

Animals↗
PubMed1980

The effect of nitrous oxide inactivation of vitamin B12 on rat hepatic folate. Implications for the methylfolate-trap hypothesis.

Rats exposed to N20 show a decrease in liver folate to about 25% of the initial value after 10 days. There is a transient increase in the amount of 5-methylterrahydropteroylpolyglutamate in the first 24 h, but thereafter the content decreases. The level of 5-methyltetrahydropterolymonoglutamate declines without any transitory increase. The transient accumulation of 5-methyltetrahydropteroylpolyglutamate is due to failure of methionine synthetase. Thereafter the decrease in the amount of methylfolate makes it improbable that trapping of methylfolate is the explanation for failure of folate metabolism in vitamin B12 deficiency.

Animals↗
PubMed1980

Two-way shuttle box and lever-press avoidance in the spontaneously hypertensive and normotensive rat.

These experiments characterized behaviorally two strains of rat that have been selectively bred for blood pressure differences. Avoidance performances of the spontaneously hypertensive rat (SHR) and normotensive rat (WKYN) were examined under two conditions: a discrete-trial two-way shuttle box avoidance procedure and a discrete-trial lever-press avoidance procedure. The WKYN strain reached a higher level of acquisition in the two-way shuttle box task than the SHR strain, but this difference was confounded by an initial difference in pretest avoidance rate. In contrast, the SHR strain was superior in the lever-press avoidance procedure under all conditions employed. These data are interpreted as being consistent with a hypothesis offered by Satinder that strains selectively bred for some behavioral feature may also differ in central arousal which will interact with task difficulty to determine performance differences. The data clearly indicate that the selective breeding for high and low blood pressure has simultaneously influenced the behavioral properties of these two strains.

Age Factors↗
PubMed1980

Walking and wheelchair energetics in persons with paraplegia.

The energetics of walking with orthoses and wheelchair propulsion at free velocity were tested in 10 adults with low-level spinal cord injuries. Eight were subjects who customarily used wheelchairs as their primary mode of locomotion; the other two used orthoses and had discontinued use of their wheelchairs. All required bilateral knee-ankle-foot orthoses to walk. A third habitual walker also was tested during walking only. Patients walked or propelled their wheelchairs around a 60.5-meter outdoor cement track. Heart rate, respiratory rate, and step frequency were recorded and transmitted by radiotelemetry. Expired air was collected for gas analysis in a polyethylene bag during the activity after a three-minute warm-up. During wheelchair propulsion all subjects demonstrated physiological responses within normal limits. Walking was significantly more difficult to perform than wheelchair propulsion (p < .005). Subjects who customarily used orthoses walked at a mean velocity of 59 +/- 5 m/min; those who primarily used wheelchairs had a mean walking velocity of 22 +/- 13 m/min. Oxygen uptake per minute was similar for both groups. These data suggest that the wheelchair will be the primary mode of locomotion for persons with spinal cord injury who need two knee-ankle-foot orthoses to walk, unless they are willing to work under anaerobic conditions and can walk at a velocity of 54 m/min or better.

Adult↗