Search PubMed⌕ Search

Biomedical subjects

J Yu

Publications and source records attributed to J Yu.

At least 937 records · Page 52Linked to original sources
PubMed1981

Effects of exercise on reflexes in paraplegic monkeys.

Eight monkeys, after complete spinal cord transection at the midthoracic level, were placed in a supine position and an exercise program was given to one hindlimb but not the other. Within 3 days, the exercised limb showed more muscle tone and more active cutaneous and proprioceptive reflexes. The difference increased progressively throughout the observation period of 11 to 36 days. These results suggest an important role of afferent influence on the recovery of spinal shock. The exercise program probably protects the neuromuscular apparatus from deterioration and thus maximize the recovery.

Animals↗
PubMed1981

Forelimb movements in cats with complete or partial bulbar pyramid lesions.

Adult cats were trained to use a forelimb to open a hinged door against resistance for a food reward. Normal cats performed the task with only toe or wrist motions. Cats with unilateral complete bulbar pyramid section showed persistent deficits in distal limb movements with toe fanning, wrist stiffness and pulling from elbow and shoulder. Partial medial or lateral pyramid lesions produced similar but less severe effects. These results suggest a significant role of the corticospinal system in distal limb movements and a lack of topographical localization of pyramid fibers related to these movements in cats.

Animals↗
PubMed1980

The effects of subcortical sensory and motor lesions on conditioned tactile placing in cats with pyramid section.

Cats after unilateral bulbar pyramid section showed permanent loss of tactile placing in the contralateral limbs. However, the cats could be trained to place the forelimb following light touch in a conditioning situation with food as a reward. This conditioned response survived subsequent unilateral red nucleus and cerebellar interposed nucleus lesions. Dorsal quadrant spinal cord lesion at the cervical level produced initial loss of the conditioned tactile placing but is recovered without retraining. Since those lesions interrupted subcortical afferent and efferent pathways essential to reflex tactile placing, these results indicate that reflex and conditioned responses involve different pathways and mechanisms. Training recruits or activates additional pathways for conditioned responses rather than strengthening those subserving the reflex responses.

Animals↗
PubMed1979

Serum proteins of mice with splenomegaly.

Our earlier serum electrophoretic study in 'lethargic' mutant mice showed that the quantity of protein in 1 band is inversely related to the size of the spleen. In this study, we demonstrate that this protein band almost entirely disappears in mice with splenomegaly following spontaneous skin infection. The results suggest that this serum protein may play a role in regulating growth of lymphoid tissue.

Animals↗
PubMed1979

Syndeins: the spectrin-binding protein(s) of the human erythrocyte membrane.

Two-dimensional tryptic and chymotryptic analyses of all the major bands in a sodium dodecyl sulfate/polyacrylamide gel of the human erythrocyte membrane show that each band has a characteristic map. However, band 2.1 (nomenclature of T. L. Steck) and several polypeptides below this band exhibit similar tryptic and chymotryptic peptide maps and thus appear to be a family of closely related proteins or degradation products. Furthermore, they all contain a subset of peptides that are accounted for by the peptides from two known spectrin-binding fragments. We show that both fragments derive from 2.1-related proteins and conclude that band 2.1 and its related proteins, which we name "syndeins", bind spectrin and connect it to the erythrocyte membrane.

Carrier Proteins↗
PubMed1979

Instrumental conditioned responses in cats with bulbar pyramid and red nucleus lesions.

Adult cats were trained to insert a forelimb into horizontally mounted transparent cylinders and then either depress a barrier or pull a sliding tray against resistance in order to receive food reward. Unilateral lesions of both bulbar pyramid and red nucleus resulted in severe neurological deficits. However, the instrumental tasks were soon accomplished at preoperative levels of rapidity and strength, although movements of the digits and wrist were reduced and adjustive movements occurred chiefly at more proximal joints. These results support our hypothesis that conditioned and unconditioned behaviors are mediated through different mechanisms.

Animals↗
PubMed1978

Cerebral influence on postural effects of cerebellar vermal zonal lesions or eighth nerve section in monkeys.

In monkeys, cerebellar vermal cortical or fastigial nuclear lesion resulted in no significant postural asymmetry. Combined decerebration (but not bulbar pyramid section) and unilateral vermal cortical or fastigial nuclear lesion gave marked ipsilateral hyperextension and contralateral hyperflexion of limbs. Unilateral eighth nerve section resulted in only ipsilateral head tilt but combined unilateral eighth nerve section and decerebration or bilateral or contralateral cerebral cortical areas 4 and 6 lesion gave also ipsilateral flexion and contralateral extension of limbs. Cervical deafferentation or postbrachial spinal cord transection did not alter these results. This study indicates a powerful cerebral influence on postural effects of cerebellar vermal zonal lesion or eighth nerve section in monkeys. Possible mechanisms mediating these effects in monkeys as compared to cats were discussed.

Animals↗
PubMed1977

Intramembrane particle aggregation in erythrocyte membranes and band 3-lipid recombinants.

The low pH-induced aggregation of intramembrane particles in human erythrocyte membranes was studied in native membranes and in a reconstituted model system. A significant difference in such aggregation was found when samples of freshly prepared ghosts were compared to ghosts receiving pretreatments that removed most of spectrin-actin from underneath the membrane. All conditions effective in aggregating particles are equally effective in precipitating extracted mixtures of spectrin and actin. In Band 3-lipid recombinants, the pH-induced aggregation of particles was duplicated only in samples containing spectrin-actin that equilibrated with these recombinants in sucrose gradients. Therefore, it was proposed that spectrin-actin components, through their associations with the underlying intramembrane particles, could impede particle lateral mobility and also determine particle redistribution in erythrocyte membrane.

Actins↗
PubMed1976

Heterogeneity in the conformation of different protein fractions from the human erythrocyte membrane.

We have isolated 5 families of proteins from human red blood cell membranes and characterized their secondary structure by ultraviolet circular dichroism measurements. The protein families were prepared by selective solubilization from ghosts under nondenaturing conditions. We find that the intact ghost has a mean alpha-helix fraction of 0.37, whereas a low-ionic-strength extract (bands 1, 2, 5, "spectrin") has a substantially higher helix fraction, 0.55. Further extraction of the ghosts with para-chloromercuribenzoate yields bands 2.1, 4.1, 4.2, and 6; their helix content is only 0.17. Finally, the major intrinsic protein, band 3, was solubilized by a non-ionic detergent. Its helix fraction is 0.38.

Blood Proteins↗
PubMed1976

Reconstitution of intramembrane particles in recombinants of erythrocyte protein band 3 and lipid: effects of spectrin-actin association.

The integral membrane protein Band 3 of the human erythrocyte, either purified or in a crude Triton X-100 extract of ghosts, was combined with egg lecithin in a cholate solution. During dialysis to remove cholate, lipid bilayer vesicles formed in which Band 3 existed as a dimer and in which intramembrane particles indistinguishable from those in the native membrane were exposed by freeze-fracturing. The recombinant vesicles were stable in both high and low salt concentrations, sedimented at a density that increased in prportion to their protein content, and bound spectrin-actin extracted from erythrocyte ghosts. When spectrin-actin was associated with the vesicles, the behavior of the recombinant intramembrane particles simulated that of the erythrocyte ghost intramembrane particles: they were dispersed at pH 7.6 and aggregrated at pH 5-5.5. Thus, some of the characteristics of the native membrane have been reconstituted in the recombinant.

Actins↗
PubMed1976

Functional recovery with and without training following brain damage in experimental animals: a review.

Review of observations on experimental animals following brain damage shows that some functions may recover spontaneously and functional accomplishment can be increased by training even with unchanged reflex status. Training consists of a combination of two basic techniques: forced use of the impaired body part, and instrumental conditional relfexes. The possible mechanisms of recovery include restoration by an alternative pathway, compensation through complicated interactions among brain structures and, with training, activation of a parallel system essential to conditioned responses. Factors, such as motivation and emotion, may complicate the course of recovery. Results of recovery with training in experimental animals strongly indicate that such training can play an active and specific role in functional improvement following brain damage in man. Future development of rehabilitation medicine in this direction is suggested.

Animals↗
PubMed1976

The effects of cerebral sensory cortical ablation on instrumental conditioned reflex in cats with cerebellar lesions.

Cats were trained to reach with their fore limbs for food placed in horizontally mounted cylinders of various diameters. The chain instrumental reflex (entering cylinder, reaching for, grasping and bringing food toward the mouth) survived cerebellar paravermal cortical ablation or interposite-dentate nuclear lesion, with some exaggerated flexor or extensor responses respectively. Movements improved with time. Cats were then subjected to ablation of cerebral sensory cortex, SI and SII. SI or compined SI and SII lesion resulted in an initial period of decompensation of cerebellar symptoms. Sensory loss was also noted for 30-40 days after SI lesion and throughout the observation period up to 53 days after combined SI and SII lesion. The conditioned responses were soon accomplished at preoperative level. Furthermore, visual occlusion did not change the performance in conditioning situation. The result indicates that the compensation of cerebellar symptoms does not depend on an intact cerebral sensory cortex. It also suggests that functional accomplishment can be obtained through training despite neurological deficits following certain brain damage.

Animals↗
PubMed1976

Interosseous muscles in claw finger.

The third and fourth fingers of the normal hands of 75 adult subjects were tested for active finger extension with the wrists in neutral position. Seventy-two of the subjects could not actively extend the interphalangeal (IP) joints when the metacarpophalangeal (MCP) joints were passively and maximally extended. However, the IP joints could be passively extended without pain in 67 subjects and with pain in 5 subjects. This indicated that the inability to actively extend the IP joints when the MCP joints were maximally extended is seldom due to tightness of the flexor tendons. Electromyographic recordings of the interossei muscles in one subject showed voluntary activity of these muscles with the MCP joints maximally extended while the IP joints remained flexed. A macrospoic study was made of the dissected third and fourth fingers of five embalmed cadaver hands and, in two of these specimens polygraphic recordings were made with the use of the strain gauge. In each of these specimens, when traction was applied in the appropriate interosseous muscle, movement of the lateral band of the extensor aponeurosis was noted when the MCP joint was at neutral or slight flexion, while no motion could be detected when the MCP joint was in maximal extension. Thus, maximal extension of the MCP joint blocks not only the action of the extensor digitorum communis tendon, as shown by Mulder and Landsmeer, but also blocks the action of the interossei in extension of the fingers. This explains the mechanism of development of claw finger in those cases without intrinsic hand muscle paralysis.

Adult↗