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Biomedical subjects

J Yu

Publications and source records attributed to J Yu.

At least 919 records · Page 51Linked to original sources
PubMed1983

Interaction of inferior olivary nucleus with reflex bradycardia and tachycardia in the cat.

In chloralose-urethane anesthetized cats, stimulation of the ION, apart from directly producing cardioinhibition, was capable of interacting antagonistically with reflex tachycardia (induced by nitroglycerin) and synergistically with reflex bradycardia (induced by phenylephrine). The degree of the potentiation or antagonism was greater than the sum of the individually elicited responses. It was also directly related to the dose of the drugs and the intensity of the stimulating pulse frequency delivered to the nucleus. The similarity in natures of both cardio-inhibitory mechanisms of the ION and gigantocellular reticular nucleus (GRN) has been discussed. We infer that the ION, GRN, nitroglycerin-induced reflex tachycardia and phenylephrine-induced reflex bradycardia may share a final common neural mechanism which function to suppress heart rate. The neurons in the dorsal motor (DM)/solitary (SN) nuclei may be a good candidate, because bilateral vagotomy or unilateral vagotomy with a contralateral DM/SN destruction substantially abolished the cardio-inhibitory effect of both GRN and ION.

Animals↗
PubMed1983

Regional metabolic changes in the spinal cord related to spinal shock and later hyperreflexia in monkeys.

The regional metabolic rate for glucose (rMRglu) was studied in macaque monkeys after spinal cord transection at T10, both during spinal shock and after reflexes had returned. The rMRglu was measured in all Rexed layers in cord segments both caudal and rostral to the level of the transection utilizing the quantitative [14C]deoxyglucose technique. The monkeys in spinal shock exhibited a significant increase in rMRglu in Rexed layer I and a significant reduction in layers VI to IX of the lumbosacral cord. In contrast, after reflexes had returned the rMRglu was increased in all Rexed layers of the lumbosacral cord; this increase was significant in layers I, V, and VI.

Animals↗
PubMed1983

Multifocal chronic osteomyelitis of unknown etiology. Report of five cases.

Five cases of chronic, inflammatory, multifocal bone lesions of unknown etiology are reported. Although bone biopsy confirmed osteomyelitis in each case in none of them were organisms found inspite of an extensive work up. Different clinical course of the disease reflects different aetiology in respective cases. These cases present changing aspects of osteomyelitis emerging since introduction of antibiotics.

Adolescent↗
PubMed1983

Transcribed chromatin exhibits an altered nucleosomal spacing.

The nucleosomal repeat lengths of bulk chromatin and the chromatin of transcriptionally active and inactive genes were analyzed in two mouse cell lines and adult mouse spleens. The adult beta-globin gene exhibits a nucleosomal repeat length approximately 11 base pairs longer than (i) an inactive embryonic globin gene, epsilon y3; (ii) an immunoglobulin heavy chain gene, Cmu; and (iii) the bulk chromatin in murine erythroleukemia cell line DS19. The repeat length of the Cmu gene was approximately 14 base pairs longer than that of the adult beta-globin or epsilon y3 genes in the IgM-producing cell line M104E. The chromatin of several inactive genes had repeat lengths less than or equal to bulk chromatin. Individual genes were shown to vary in repeat length among the cell types examined. In addition, genes that exhibited an increased nucleosomal spacing were digested to mononucleosomes more rapidly than bulk chromatin or inactive genes with shorter repeats. Increased repeat length was also correlated with an increased sensitivity to DNase I. Thus, increased nucleosomal spacing may be a property of transcriptionally active genes or genes with the potential for transcription.

Animals↗
PubMed1983

Inhibition of RNA synthesis by deoxyadenosine plus deoxycoformycin in resting lymphocytes.

Deoxyadenosine has been implicated in the lymphocytopenia that occurs in immunodeficient children with an inherited deficiency of adenosine deaminase (ADA) and in leukemic patients treated with the ADA inhibitor deoxycoformycin. The recent reports of deoxyadenosine toxicity to nondividing lymphocytes indicates a challenge to the mechanism for deoxyadenosine toxicity, which involves the inhibition of ribonucleotide reductase by dATP, leading to the inhibition of DNA synthesis. This study provides evidence for the inhibition of transcription by deoxyadenosine as an alternative mechanism of toxicity. The incubation of resting peripheral blood lymphocytes with deoxyadenosine plus deoxycoformycin led to an inhibition of uridine incorporation. The extent of inhibition increased with the increasing time of incubation and concentration of deoxyadenosine. Replacement of deoxyadenosine with other nucleosides, adenosine or deoxyguanosine, had no effect, suggesting that deoxyadenosine-induced inhibition was not due to the reduced transport of uridine. Separation of DNA from RNA by differential alkaline hydrolysis showed that the reduction of uridine incorporation was primarily in the RNA fraction. The time sequence of the reduction in uridine incorporation coincided with that of the accumulation of dATP, but preceded that of ATP depletion and cell lysis. The phosphorylation of uridine into UTP was slightly reduced by deoxyadenosine, but this could not entirely account for the reduced incorporation of uridine into RNA. Finally, the direct measurement of RNA synthesis by the incorporation of UTP into isolated nuclei showed that RNA synthesis was inhibited to 88% and 41% of control values in lymphocytes preincubated with 20 microM deoxyadenosine for 3 and 15 hr, respectively. These findings demonstrate that deoxyadenosine plus deoxycoformycin inhibits RNA synthesis in resting lymphocytes.

Coformycin↗
PubMed1983

The effects of cerebral sensory and motor cortical 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. Subsequent unilateral or bilateral cerebral cortical lesions involving sensory and/or motor areas did not abolish this conditioned response. Since these cortical areas are essential to reflex tactile placing, the results indicate that reflex and conditioned responses can be mediated differently at the cerebral cortical level.

Animals↗
PubMed1982

Erythrocyte membrane skeletal protein bands 4.1 a and b are sequence-related phosphoproteins.

Bands 4.1 a and b are proteins of 80,000 and 78,000 molecular weight, which are both present at approximately 100,000 copies per erythrocyte ghost. Both proteins are components of the erythrocyte membrane skeleton. Bands 4.1 a and b are labeled when intact erythrocytes are incubated with [32P]orthophosphoric acid, and, therefore, are phosphoproteins. One-dimensional partial proteolytic mapping analysis of 32P-labeled bands 4.1 a and 4.1 b and two-dimensional peptide mapping analysis of 125I-labeled bands 4.1 a and 4.1 b clearly demonstrated that the two proteins are sequence-related phosphoproteins. Band 4.1 purified by standard techniques (Tyler, J. M., Hargreaves, W. R., and Branton, D. (1979) Proc. Natl. Acad. Sci. U. S. A. 76, 5192-5196) contains bands 4.1 a and 4.1 b. Bands 4.1 a and 4.1 b bind to spectrin heterodimers in solution. We conclude that the erythrocyte skeletal proteins bands 4.1 a and 4.1 b are sequence-related phosphoproteins, both capable of binding spectrin.

Electrophoresis, Disc↗
PubMed1982

The methylphenidate-induced stereotypy in the awake rat: local cerebral metabolism.

The local cerebral metabolic rate for glucose (1=CMRg) was computed in rats with methylphenidate-induced stereotypy using the quantitative 14C-2-deoxyglucose (2-DG) technique. Four rats received methylphenidate 15 mg per kilogram IP. Compared to five control animals, treated rats showed statistically significant (p less than or equal to 0.05) increases in 1-CMRg in globus pallidus, ventral lateral nucleus of the thalamus, subthalamic nucleus, red nucleus, substantia nigra, entopeduncular nucleus, inferior olivary nucleus, and the lateral cerebellar cortex. Significantly, 1-CMRg decreased in area 4 of the motor cortex. The auditory system showed no change in 1-CMRg, demonstrating the specific action of methylphenidate in the rat brain. This technique allows evaluation of the functional anatomy of the entire central nervous system and may be helpful in understanding the mechanisms of methylphenidate-induced stereotypy.

Animals↗
PubMed1982

Rehabilitation following brain damage: some neurophysiological mechanisms. Animal models of recovery with training after central nervous system lesions.

Animal studies revealed that training with techniques of instrumental conditioning produces another phase of functional recovery beyond spontaneous recovery after CNS lesions. Such conditioned behaviour is difficult to transfer to an unconditioned or another conditioned response. Conditioned and unconditioned behaviours are mediated through different pathways and mechanisms. Conditioned behaviour requires less specific pathways and can probably be achieved as long as the basic spinal mechanisms are activated. Other studies showed that reflex recovery can be maximized through non-specific training, probably by protecting the neuromuscular system from deterioration. However, such a programme does not appear to improve the reflexes beyond the level attributable to spontaneous recovery, nor to facilitate the rate of recovery. If the training is specifically directed towards augmentation of a particular reflex, the reflex can be improved beyond that seen with spontaneous recovery but may be exaggerated to a functional disadvantage. These findings have significant clinical implications.

Animals↗
PubMed1982

Effect of dexamethasone on hexamethylene bisacetamide-induced Friend cell erythrodifferentiation.

Friend erythroleukemic cells can be induced to differentiate by chemicals such as dimethyl sulfoxide and hexamethylene bisacetamide (HMBA) in a dose-dependent manner. Others have shown that dexamethasone and other steroid hormones can inhibit the differentiation induced by dimethyl sulfoxide. We show here that dexamethasone has a dual mode of action on the HMBA-induced differentiation of a Friend cell line, DS19. At concentrations above 10(-10) M, dexamethasone inhibits the HMBA-induced differentiation in DS19 cells. We further found that as the concentration of HMBA is reduced, the amount of dexamethasone required to inhibit differentiation increases. Such inhibition seems to act primarily by decreasing the probability that a cell will become committed to differentiate. Besides, dexamethasone does not inhibit hemoglobin synthesis of cells which are committed in its absence. In addition, we show that sensitivity to the inhibition by dexamethasone is inversely related to the inducibility of cell populations. The second action of dexamethasone, observed at concentrations between 10(-10) and 10(-13) M, is to increase the proportion of hemoglobin-containing cells relative to that for cells cultured in its absence. The degree of this synergistic effect for induced differentiation is inversely related to the level of induction in the absence of dexamethasone and thus is best observed in the cells cultured at low levels of HMBA. We present evidence that this synergistic effect may be due to an increased viability of the induced cells and possibly an increase in the proliferative capacity of these cells.

Acetamides↗
PubMed1981

Quantitative measurement of local cerebral metabolic rate for glucose utilizing tritiated 2-deoxyglucose.

The [14C]2-deoxyglucose (2-DG) technique has been widely utilized for quantitative measurement of local cerebral metabolic for glucose (1CMRG) in animals. The technique as presently used is limited by the energy of 14C beta-particles, which can travel relatively great distances in tissue. This results in limited audioradiographic resolution and in computed 14C concentrations which are a function of tissue section thickness. [3H]2-DG has less energetic beta-particles; hence, autoradiographs have better resolution and optical densities are independent of tissue thickness for sections greater than 5 micrometer. We have developed a method for quantitation of 1CMRG in rats using [3H]2-DG and a newly developed ultrasensitive X-ray film. Autoradiographic tissue standards were prepared by injecting rats with [3H]2-DG and assaying micro-samples of brain for 3H concentration. Ten rats were used in this study. Five rats received [3H]2-DG (300 muCi/100 g) and 5 rats received [14C]2-DG (7.5 muCi/100 g). The mean 1CMRG values for selected areas of the central nervous system demonstrated no significant difference (P greater than 0.05) between the [14C]2-DG and the [3H]2-DG groups. Values for 1CMRG from the [3H]2-DG group showed no variation attributable to inadequate microtome precision. The improved resolution obtained by utilizing [3H]2-DG is especially evident where gray matter (high 1CMRG) is immediately adjacent to white matter (low 1CMRG).

Animals↗
PubMed1981

Effects of vestibulospinal lesions upon locomotor function in cats.

We used cats to study the consequences of bilateral ablation of the vestibular complex. The animals were very severely ataxic and incapable of head support for nearly two weeks. They gradually regained the ability to stand and to walk on a treadmill, at first with a marked reduction of the extensor components of stepping. After stabilization of recovery we could not obtain decompensation by dorsal hemisection. We conclude that the key consequence of these lesions is a temporary reduction in facilitatory drive to joint extensor muscle groups. Neither the corticospinal nor the rubrospinal tracts mediate the functional recovery observed.

Animals↗
PubMed1981

Effects of corticospinal lesions upon treadmill locomotion by cats.

We studied the pattern of stepping in cats, before and after the placement of lesions in the corticospinal system. We found a deficit after the lesions, which was characterized by increased extension of the involved hindlimbs during the stance (E2--E3) phase of the step cycle. This deficit lasted two weeks or less. It may reflect loss of inhibitory influences upon extensor motoneuron pools.

Animals↗
PubMed1981

Prevalence of the tarsal tunnel syndrome in rheumatoid arthritis.

Forty-eight patients with definite of classical rheumatoid arthritis (RA) were studied for the presence of tarsal tunnel syndrome (TTS). Nerve conduction velocities and distal latencies were determined in a constant temperature room and the findings compared with a group of 35 normal, age-matched subjects. After excluding four patients with peripheral neuropathy, a definite delay in the distal motor latency of the tibial nerve was documented in 11 subjects (25%). Two of the 11 had foot symptoms suggestive of TTS. These 11 patients with prolonged distal motor latencies did not otherwise differ from RA patients without TTS in terms of disease duration or severity, treatment, or the presence of foot deformity. Thus, compressive neuropathy of the branches of the posterior tibial nerve is a relatively frequent finding in patients with definite or classical RA.

Arthritis, Rheumatoid↗