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At least 793 records · Page 44Linked to original sources
PubMed1977

Neurotrophic stimulation of DNA synthesis in the regenerating forelimb of the newt, Triturus.

The effect of infusions of soluble newt brain extracts on deoxyribonucleic acid (DNA) synthesis in the denervated, regenerating newt blastema has been studied. When moderate early to early regenerates are denervated for 48 hours, DNA synthesis normally drops to about 40% of that found in contralateral, innervated blastemas. Infusion of brain extract halfway through the denervation period (at 24 hours) approximately doubles the rate of DNA synthesis in denervated regenerates.

Animals↗
PubMed1979

Stages of forelimb regeneration in Ambystoma maculatum.

A series of normal stages describing the regeneration of larval A. maculatum limbs after amputation through the upper arm or wrist is described. Nine discrete stages were recognized, based on external morphological and associated histological features. These stages are Initial Dedifferentiation (ID), Early Bud (EB), Medium Bud (MB), Late Bud (LB), Early Redifferentiation (ER), Notch (N), 2-Fingerbud (2-FB), 3-Fingerbud (3-FB) and 4-Fingerbud (4-FB). Similarities and differences between this and other staging systems for urodele limb regeneration are discussed. The absence of osteoclasts was a striking feature during dedifferentiation of the wrist, in contrast to their presence in large numbers during dedifferentiation of the upper arm.

Ambystoma↗
PubMed1981

The effect of prolactin on the rate of forelimb regeneration in newts exposed to photoperiod extremes.

Four groups of bilaterally amputated newts were exposed to (1) continuous light, LL; (2) continuous light with daily prolactin injections, LL-PRL; (3) total darkness, DD; or (4) total darkness with daily prolactin injections, DD-PRL. The results confirmed that LL animals regenerate their limbs more rapidly than DD. The results also showed that LL-PRL animals do not respond to the exogenous prolactin but that DD-PRL animals do respond and in fact regenerate at a rate which exceeds not only DD but also LL and LL-PRL. The possible synergism between prolactin and photoperiod is discussed.

Animals↗
PubMed1984

Injury, nerve, and wound epidermis related electrophoretic and fluorographic protein patterns in forelimbs of adult newts.

Polyacrylamide slab gel electrophoresis and [35S]methionine fluorography were used to examine proteins in regenerating newt limbs, amputated denervated limbs, unamputated denervated limbs, and separated blastema mesodermal core and wound epidermis. A total of 27 protein electrophoretic bands were obtained from amputated limbs and 24 bands from unamputated limbs. Amputation resulted in the appearance of 4 new bands and the loss of 1 band as compared to unamputated limbs. These 5 banding differences were apparent on stained gels 3 days postamputation and were maintained through 10 weeks postamputation (complete regenerate stage). Only one band in unamputated limbs was always detectable on fluorographs, whereas virtually all of the stainable bands of amputated limbs were visible on fluorographs. Amputation clearly stimulated a marked, generalized increase in the synthesis of limb proteins. The 5 amputation induced changes were equally evident in stained gels of both innervated and denervated limbs. Amputated denervated limbs possessed a full set of fluorographic bands (including the 5 differences) through 18 days postamputation. However, denervation without amputation was not sufficient to alter the stainable banding pattern. Wound epidermis and mesodermal core both displayed the 5 banding differences and had identical banding patterns with the exception of one epidermal specific band. This band was also present in whole limb skin but was absent in unamputated mesodermal limb tissue. This was the only band of unamputated limbs that was consistently detectable by fluorography. It is concluded that amputation induces nerve independent changes in protein synthesis that are common to both mesodermal core and wound epidermis. These changes may represent preparation for cellular proliferation.

Aging↗
PubMed2003

Morphometry of Macaca mulatta forelimb. III. Moment arm of shoulder and elbow muscles.

The conversion of muscle activity into smooth, purposeful movement of the limb depends complexly on the morphometry of muscles and their mechanical action on the skeleton. Although nonhuman primates are common subjects in motor control experiments (Scott [2000] Can J Physiol Pharmacol 78:923-933), little information is available on the morphometric properties of their upper limbs. One key variable is muscle moment arm, or mechanical advantage, which defines how linear motion or force of a muscle is translated into angular motion or torque at a joint. This study reports moment arm values with respect to joint angle (flexion/extension) of 14 muscles spanning the shoulder and elbow in Macaca mulatta. The magnitude of moment arm values ranged widely across muscles. In some muscles mechanical advantage remained constant with joint angle, whereas the moment arm of others varied strongly. The angle (Theta(f)(o)) at which optimal fascicle length (L(f)(o)) occurred showed strong trends, where the elbow-spanning muscles had Theta(f)(o) values clustered at mid-flexion and the shoulder musculature Theta(f)(o) values tended to be grouped around the neutral joint angle of 0 degrees. Estimates of peak muscle torque for flexor and extensor muscle groups at each joint were surprisingly similar in both magnitude and dependency on joint angle. The present study, along with the previous two in this series (Cheng and Scott [2000] J Morphol 245:206-224; Singh et al. [2002] J Morphol 251:323-332), provides a comprehensive description of the morphology of the proximal portion of the limb suitable for the development of a musculoskeletal model of the M. mulatta upper limb.

Animals↗