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Biomedical subjects

C D Tweedle

Publications and source records attributed to C D Tweedle.

At least 37 records · Page 2Linked to original sources
PubMed1980

Skeletal muscle fiber splitting with weight-lifting exercise in rats.

Adult male albino rats were assigned randomly to control (CON) and weight-lifting (WL) groups. The WL rats were subjected to a progressive weight-lifting program against high resistance for 8 weeks. During the last 2 weeks, each WL rat lifted a load equal to 130% of its body weight. The mean weight of the adductor longus muscle was significantly increased in the WL group ( p < 0.05). This increased muscle weight was shown to be due to an increase in the number of fibers per unit cross-sectional area ( p < 0.05), and the mean sizes of both fast-twitch oxidative glycolytic and slow-twitch oxidative fibers were significantly smaller in the WL rats than in the CON rats (p < 0.05). Light and electron microscopic examination showed that five out of eight WL rats exhibited longitudinally split muscle fibers, while only one CON rat had a few centrally placed nuclei. The splitting process appeared as either a "pinching-off" of a small segment from the parent fiber or an invagination of the sarcolemma deep into the muscle fiber in a plane parallel to the sarcomeres. There were preliminary indications that this work-induced fiber-splitting process may be a physiological adaptation of muscle to the stress of exercise.

Animals↗
PubMed1980

Cholinesterase in muscle of dystrophic hamsters (Bio-40.54).

Isozyme patterns of cholinesterase (ChE) from heart, tongue, and skeletal muscle of normal and dystrophic hamsters are presented. Two principal bands, bands 1 and 2, were evaluated. Band 1 migrates faster towards the anode than does band 2. While bands 1 and 2 stain for AChE and were found in control muscles, only band 2 was stained by a pseudocholinesterase (BuChE) and was decreased in samples from dystrophic hamsters. The decrease in BuChE was most pronounced in dystrophic heart muscle. The low level of BuChE measured for dystrophic animal tissue was similar to isozyme patterns found in embryonic tissue and in denervated muscle. BuChE obtained by acrylamide gel electrophoresis along with 16S AchE appears to be a useful biochemical marker of nerve-muscle interactions.

Animals↗
PubMed1977

Ultrastructure of lateral line organs in aneurogenic amphibian larvae (Ambystoma).

An ultrastructural study was performed to determine the ability of presumptive lateral line tissue in A. maculatum embryos to migrate and differentiate in the absence of all sensory innervation. In experimental animals, all presumptive neural tissue was surgically removed at Harrison's stage 24, leaving only the posterior portion of the post-auditory placode. At later stages, completely differentiated aneural lateral line organs were found in the midbody region of the larvae. These were morphologically similar to those of control larvae. No signs of atrophy or degeneration of the neuromasts were seen even after several weeks of nerve-free conditions.

Ambystoma↗
PubMed1977

Ultrastructural changes in rat hypothalamic neurosecretory cells and their associated glia during minimal dehydration and rehydration.

A quantitative ultrastructural study was performed to determine the changes in the neurosecretory neurons of the supraoptic (SON) and circularis (NC) nuclei following 4-24 h of water deprivation (WD) and subsequent rehydration (12 and 24 h). In both nuclei, the amount of direct soma-somatic contact increased throughout WD, apparently by retraction of fine glial processes from between the cells. Rehydration reversed these changes. The number of smaller (less than 1600 A) neurosecretory granules (NSG's) decreased in both nuclei at 4 h of WD but returned to control levels by 24 h of WD and remained so during rehydration. Larger (less than 1600 A) NSG's decreased in number at 4 h of WD in SON and then returned to control levels by 24 h of WD and remained the same throughout rehydration. In NC, these NSG's did not change in number with WD, but significantly increased between 12 and 24 h of rehydration. No cells with dilated rough endoplasmic reticulum were seen in NC during this study. In SON, however, the percentage of such cells increased at 4 and 12 h of dehydration only to decrease to control levels at 24 h of dehydration and throughout rehydration. Lysosomes decreased at 4 h of dehydration in SON and returned to control levels thereafter. In NC, lysosomes tended to decrease with dehydration and increase with rehydration. These findings indicate that detectable morphological changes take place in the course of alterations in hydration state that are well within the physiological range.

Animals↗
PubMed1972

Electrical responses of insect central neurons: augmentation by nerve section or colchicine.

Intracellular recording from the somata of central motor neurons in the cockroach Periplaneta americana normally shows little or no electrical response evoked by soma depolarization or by antidromic stimulation. Within 4 days after either cutting the axon or administration of colchicine, large action potentials can regularly be recorded from cell bodies of metathoracic motor neurons. Each experimental procedure evokes formation of a dense, perinuclear ribonucleic acid ring in the soma of neurons showing augmented electrical responses.

Action Potentials↗