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Biomedical subjects

J Perry

Publications and source records attributed to J Perry.

At least 235 records · Page 13Linked to original sources
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↗
PubMed1980

Marrow cells from patients with untreated pernicious anaemia cannot use tetrahydrofolate normally.

Folate analogues were added to human bone marrow cells to determine their effect on deoxyuridine utilization in the deoxyuridine suppression test. Formyltetrahydrofolates fully corrected the impairment of dU utilization in pernicious anaemia marrows but tetrahydrofolate was relatively ineffective. All these analogues were effective in megaloblastic marrows from folate deficient patients. Formyltetrahydrofolates also enhanced dU utilization by normal human marrows whereas methyltetrahydrofolate reduced its use. In terms of the methylfolate trap hypothesis, the expectation that cobalamin-deficient marrows would be able to use tetrahydrofolate normally was not realized.

Anemia, Megaloblastic↗
PubMed1980

Inactivation of methionine synthase by nitrous oxide.

Exposure of rats to a 50% N2O/oxygen mixture led to a rapid loss of methionine synthase activity in both liver and brain. This enzyme has vitamin B12 as a cofactor. There was impaired conversion of deoxyuridine to deoxythymidine by bone marrow cells and this defect followed loss of methionine synthase activity. There was no homocystinuria. Withdrawal of N2O was followed by a relatively slow recovery of methionine synthase activity over four days. The inactivation of vitamin B12 by N2O promises to be a valuable tool in the study of vitamin B12 metabolism.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1980

Dynamic gait electromyography study in Duchenne muscular dystrophy (DMD) patients.

Preoperative and postoperative dynamic gait electromyography (EMG) weas performed on 15 patients 8 to 13 year of age with Duchenne's muscular dystrophy who underwent Achilles tendon lengthening and posterior tibial tendon transfer anteriorly through the interosseous ligament for correction of equinus and equinovarus foot deformities. The muscles tested preoperatively (anterior tibial, soleus, gastrocnemius, posterior tibial, peroneal longus, and peroneal brevis) showed phase changes. It is believed that patients with weakened leg muscles fire multiple muscle groups out of phase in an attempt to overcome the action of the stronger muscles, thus stabilizing the limb for ambulation. Postoperative EMGs, performed with the patients walking in long leg braces after the deformity had been corrected, showed little activity in the muscles tested. As the patients became dependent on the brace, the need for the muscles to be active out of phase was eliminated. The transferred posterior tibial muscle appeared to be active both clinically and electromyographically.

Achilles Tendon↗
PubMed1980

Functional evaluation of the pes anserinus transfer by electromyography and gait analysis.

The effectiveness of the pes anserinus transfer, proposed by Slocum and Larson to control anteromedial rotatory instability of the knee, depends on the pes anserinus muscles contracting at times when the instability threatens the patient's function. To examine the activity of the transferred pes anserinus muscles, quantitated dynamic electromyography, isometric testing of muscle strength, and gait-analysis techniques were employed. Seven normal subjects and nine patients who had undergone pes anserinus transfer for anteromedial rotatory instability were tested. In contrast to the normal subjects, who demonstrated pes anserinus muscle activity primarily during swing phase, the patients displayed conspicuous activity of the semitendinosus, gracilis, and sartorius tendons during stance phase. Quantitated electromyography indicated that the pes anserinus muscles worked harder in the patients than in the normal subjects, and more effort was required from the muscles of patients with poor results than from those of patients with good results. All of the patients also demonstrated reduction of single-limb support time, as well as a shorter stride length and reduced gait velocity. We concluded that the pes anserinus transfer is kinetically sound. Since instability of the knee is a functional defect that is present during stance, the finding of marked activity of the pes anserinus muscles during stance phase in the patients but not in the normal subjects suggests that these muscles were being used to control the instability.

Adolescent↗
PubMed1979

Characterization of endogenous folate and incorporation of labelled folates into the brain of the South African fruit bat.

Folate in the brain of the South African fruit bat consists of 10-formyltetrahydropteroyglutamic acid and the tri-, tetra- and penta- forms of 5-methyltetrahydropteroylglutamic acid. Following parenteral injection, only 5-[3H]-methyltetrahydropteroylglutamic acid was taken up by the brain, but none of a dose of 14C-labelled tetrahydropteroylglutamic acid was detectable. Only trace smounts of the 5-methyltetrahydropteroylglutamic acid were converted into the formyl compounds and a small amount of methyltetrahydropteroyltriglutamic acid appeared after 96 h. There was no significant difference in vitamin B-12-deficient animals.

Animals↗
PubMed1979

Dynamic electromyography and decision-making for surgery in the upper extremity of patients with cerebral palsy.

Seventeen children with cerebral palsy were selected for improvement in upper extremity function. Each had normal or nearly normal intelligence; each hand had good or mildly impaired sensibility; each arm had relatively good placement. Electromyograms with wire electrodes were utilized to study the patterns of activity of the planned tendon transfers. Only muscles with isolated activity in grasp were utilized to transfer in hands with weak grasp. Only muscles with isolated activity in release were utilized to transfer in hands with poor release.

Adolescent↗
PubMed1979

Stiff-legged gait in hemiplegia: surgical correction.

Selective tenotomy of one or two heads of the quadriceps based on electromyographic criteria improved knee flexion in hemiplegic patients who walked with a unilateral stiff-legged gait. The improvement was greatest in eight patients in whom the rectus femoris was released, either with or without release of the vastus intermedius, with activity in pre-swing stance and initial swing confined to those heads of the quadriceps; in these patients knee flexion improved an average of 20 degrees. Knee flexion improved an average of only 8 degrees in five patients in who activity was present in one head of the quadriceps that was not surgically released. No improvement in knee flexion occurred in seven of eight patients in whom activity was present in two or more of the quadriceps heads that were not surgically released.

Electromyography↗
PubMed1978

Selective inactivation of vitamin B12 in rats by nitrous oxide.

Exposure of rats to nitrous oxide rapidly inactivated the cytosol enzyme, methionine synthetase, but the mitochondrial enzyme, methylmalonyl CoA mutase, seemed to be unaffected, although both enzymes require vitamin B12.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗