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Biomedical subjects

R J Goss

Publications and source records attributed to R J Goss.

At least 19 recordsLinked to original sources
PubMed1995

Future directions in antler research.

Through a series of interrogatories, unsolved problems of antler evolution, anatomy, development, physiology, and pathology are probed, with commentaries, on the following prospects for future research: 1. How could these improbable appendages have evolved mechanisms to commit suicide, jettison the corpse, and regenerate new ones every year? 2. By what developmental processes are antlers able to prescribe their own morphogenesis with mirror image accuracy year after year and in some cases produce deliberate asymmetries? 3. What causes the scalp to transform into velvet skin as a deer's first antlers develop? 4. Why do healing pedicle stumps give rise to antler buds instead of scar tissue? 5. How is the unprecedented rate of antler elongation related to the diameter and length of the structure to be grown? 6. How come wound healing by pedicle skin is held in abeyance for several months until new growth resumes? 7. How is it that tropical deer regenerate antlers at any time of year, while in temperate zones deer do so in seasonal unison? 8. How do deer find enough calcium to make such massive antlers in only a few months? 9. What is the nature of the bizarre tumors that some antlers grow following castration?

Animals↗
PubMed1994

Why study ageing in cold-blooded vertebrates?

Homeotherms exhibit programmed ageing correlated with their determinate mode of growth and the natural attrition of irreplaceable functional units in vitally essential organs. Poikilotherms are potentially capable of indefinite growth, can supplement their populations of functional units, and may therefore not be subject to the inherent depreciations of ageing. Comparative studies may enable us to determine which group is the exception to nature's rule.

Aging↗
PubMed1992

The mechanism of antler casting in the fallow deer.

The process by which antlers are detached from their pedicles was examined histologically in fallow deer castrated in the autumn to induce precocious casting. Osteoclastic erosion across an abscission line between the dead bone of the antler and the living bone of the pedicle was found to be responsible for the separation of the 2. As early as 3 days after castration, osteoclasts and associated lacunae were present on the sides of the pedicle bone. These were then found in progressively deeper locations, by 2 weeks extending across the entire width of the pedicle. Concomitant with the centripetal spread of osteoclasts was the enlargement of Haversian canals, the surfaces of which became lined with osteoclasts. These widening vascular channels within the bone were filled with connective tissue, which in precasting stages formed a mesodermal pad about 1 mm thick. In later stages, a circumferential cleft was excavated beneath the antler burr, and connective tissues from the surrounding pedicle skin invaded the space between the antler and pedicle. After casting, the ingrowing integumental tissues fused with the mesodermal tissues derived from the vascular channels of the pedicle to give rise to an incipient antler bud beneath the scab. The ingrowth of epidermis capable of de novo hair follicle formation gave rise to the future velvet skin that envelops the elongating antler.

Animals↗
PubMed1992

The evolution of regeneration: adaptive or inherent?

If regeneration were adaptive, it would have arisen autonomously by natural selection from non-regenerative antecedents. Unless each episode coincidentally reinvented the same method of regeneration independently, one would expect the various lineages to differ basically from each other, which they do not. On the other hand, if regeneration were inherent to metazoan life, a derivative of embryogenesis, its various expressions should be as much like each other as they resemble the development of embryonic appendage buds, which they do. It follows that the uneven distribution of regeneration must have been due to its extinction here and there, not as a negative adaptation by natural selection but as a pleiotropic epiphenomenon linked to more useful adaptations with which it was incompatible. In vertebrate evolution, these adaptations have included the transition from aquatic to terrestrial habitats and the modification of poikilothermic to homeothermic metabolism. The former advance rendered the regeneration of weight-bearing limbs impractical; the latter favored rapid wound healing and scar formation which effectively precluded blastema formation. If the latent capacity for regeneration persists in non-regenerative appendages, as would seem to be the case, then the restoration of its overt expression should be possible if the mechanisms of its inhibition could be discovered and eventually rendered ineffectual.

Adaptation, Physiological↗
PubMed1992

Epimorphic vs. tissue regeneration in Xenopus forelimbs.

Postmetamorphic froglets of Xenopus laevis regenerate hypomorphic unbranched spikes from amputated arm stumps. These are composed primarily of cartilage, produced from blastemalike structures sparsely populated with cells and rich in connective tissue. Some consider these outgrowths to be an example of epimorphic regeneration produced from blastemas, albeit deficient ones. Others interpret them as a case of tissue regeneration derived from fibroblastemas augmented by chondrocytes and periosteal and perichondrial fibroblasts. To resolve these alternatives, forelimbs were amputated proximal to the wrist, skinned, and inserted through the body wall into the abdominal cavity. In the absence of skin, epidermal wound healing failed to occur and blastemas could not develop. After 2 months, by which time controls had regenerated spikes averaging 3.38 mm long, the denuded stumps had not given rise to outgrowths. They typically developed cartilaginous caps on the severed ends of the radius-ulna, and in rare cases formed amorphous growths of cartilage. If blastema formation is considered diagnostic of epimorphic regeneration and tissue regeneration can proceed in the absence of epidermal wound healing and blastema formation, these findings lead to the conclusion that Xenopus limb regeneration is epimorphic.

Animals↗
PubMed1990

Tumor-like growth of antlers in castrated fallow deer: an electron microscopic study.

Male deer regenerate new sets of antlers each year. When fully grown, rising levels of testosterone promote antler ossification, cutting off the blood flow and causing the velvet integument to be shed. After the mating season, the old antlers fall off to be replaced by new ones. When the adult fallow deer is castrated in autumn or winter, its bony antlers are shed and replaced by usually shorter regenerates that remain permanently viable and in velvet. If prevented from winter freezing, these antlers continue to grow thicker each year, eventually giving rise to amorphous outgrowths, or antleromas, from their sides. These growths mushroom out from the antler as clusters of nodules, developing in unpredictable locations, but commonly at the bases and ends of the antlers. Their integument contains numerous hair follicles. Internally, antleromas are composed of masses of collagen together with fibroblasts actively engaged in ribonucleic acid and protein synthesis. Thin basal laminae surround the blood vessels, and in the skin separate the overlying epidermis from the collagenous substance of the antleroma. Despite their superficial resemblance to hypertrophic scars, antleromas lack many of the characters by which they are diagnosed. They may be classified as benign tumors, at least in the generic sense. Antleromas would appear to represent a sustained expression of antler regeneration uncoupled from those morphogenetic influences responsible for the configurations into which deer antlers normally develop.

Animals↗
PubMed1986

Correlations between phases of deer antler regeneration and levels of serum keratan sulfate.

A sensitive and highly specific enzyme-linked immunosorbent assay with an inhibition step was used to monitor the concentration of keratan sulfate, a cartilage-related glycosaminoglycan, in the serum of three adult male deer. During the course of one complete annual antler regeneration cycle, keratan sulfate levels were found to fluctuate predictably in relation to the growth and maturation of the antlers: levels are substantially elevated during the growth phase and drop precipitously when growth ceases and the antlers become fully mineralized. In addition, an unanticipated elevation of serum keratan sulfate was observed in early spring prior to casting of the preceding year's antlers and the initiation of regrowth. This suggests that changes in cartilage metabolism occur concomitantly, with this phase of the antlerogenic cycle. These results show predictable and physiologically regulated variation in serum keratan sulfate levels which correlate directly with specific phases of the antler regeneration cycle. Furthermore, the findings provide additional support for the assertion that measurements of keratan sulfate levels in serum can provide useful information about changes in cartilage metabolism in normal as well as diseased states.

Animals↗
PubMed1985

Induction of deer antlers by transplanted periosteum. I. Graft size and shape.

When discs of frontal periosteum from presumptive antler sites of 6-8 month old male fawns of the fallow deer are grafted beneath the foreleg skin, they will differentiate into pedicle bones and induce small antlers in the overlying integument. These antlers shed their velvet in the fall, and in succeeding years are replaced by larger outgrowths not exceeding 7 cm in length. Periosteal transplants 1.5 cm in diameter gave rise to ectopic antlers in 100% of the grafts, while discs measuring 1.05 cm, 0.75 cm and 0.4 cm did so in only 20% of the cases. Conversely, the donor sites produced antlers in 20-23% of the cases following removal of 1.05 cm or 1.5 cm of periosteum, while 80% and 100% grew antlers after deletions of 0.75 cm and 0.4 cm discs of periosteum, respectively. Semicircular grafts of periosteum induced antler development in most cases, especially when derived from the lateral halves of the antlerogenic region on the frontal bone. These findings confirm that the histogenesis of a deer's first pedicle and antler resides in the frontal periosteum over an area about 1.5 cm wide. They also show that leg skin is capable of antlerogenic development under the inductive influence of frontal periosteum, and that integumental wounding may enhance inductive interactions.

Animals↗
PubMed1984

Photoperiodic control of antler cycles in deer. VI. Circannual rhythms on altered day lengths.

Groups of sika deer were exposed to light and dark periods of equal lengths but different from 12 hr. Light cycles were 4.94L/4.94D, 6L/6D, 8L/8D, and 21L/21D. In all experiments, deer underwent circannual cycles of antler replacement, testis size, molting, and coat color. The results indicate that the previously reported abolition of circannual cycles on 12L/12D was due to the 12-hr duration of the light or dark periods, not their equivalence. They also eliminate the possibility that the circannual cycle might be the sum of 365 circadian cycles. Circannual antler cycles appear to be expressed under artificial light cycles to which the deer cannot entrain.

Animals↗
PubMed1980

Photoperiodic control of antler cycles in deer. V. Reversed seasons.

Newborn and weanling fawns were held under reversed annual light cycles to learn if the subsequent replacement of their antlers would coincide with the anniversary of their births, as occurs in nature, or adapt to the artificial seasons of increasing day lengths even when these fall at the "wrong" time of year. The first sets of antlers developed at approximately the normal age when the deer were yearlings. These antlers, however, were shed and replaced half a year earlier than would otherwise have occurred under natural environmental conditions. It is concluded that the onset of renewed antler growth is not a response to every other time the photoperiod increases or decreases, but is triggered by lengthening days, irrespective of the age of the deer.

Age Factors↗
PubMed1980

Prospects of regeneration in man.

Reports of fingertip regrowth in children are interpreted in the perspective of epimorphic regeneration in lower forms and in relation to a few other examples in mammals. The latter include cases of antler replacement in deer as well as ingrowth from the margins of holes cut in bat wing membranes and in the external ears of rabbits, pikas, cats, and echolocating bats. It is suggested that the relative inadequacy of regeneration in warm-blooded vertebrates may be attributed to the precocity with which they tend to form dermal scars in healing wounds, scars that are believed to preclude blastema production. Wound healing around the margins of rabbit ear holes is uniquely characterized by the development of prominent epidermal downgrowths adjacent to the severed sheets of dermis in the integument on either side of the ear. If these downgrowths act as epidermal blockades preventing scar formation in favor of allowing blastema cells to accumulate, a logical approach to the experimental induction of regeneration in normally nonregenerating mammalian appendages would involve manipulation of the mechanisms by which epidermis heals amputation stumps.

Amputation, Traumatic↗
PubMed1976

Photoperiodic control of antler cycles in deer. III. Decreasing versus increasing day lengths.

Deer were exposed for three years to photoperiods which increased or decreased two hours every four months, starting at 4L/20D or 20L/4D, respectively. Under both sets of conditions, antlers were repeatedly shed and replaced, usually in synchrony with every other time the day lengths were changed. On decreasing days, antler cycles were omitted as the photoperiod passed the equinox (12L/12D). On increasing days, the equinoctial photoperiod induced prolonged episodes of antler growth. The tendency for the antler replacement cycle to lock onto alternate changes in artificial photoperiods is consistent with the seasonal growth of antlers every other time the day lengths change in the natural environment. It is suggested that antler replacement is triggered neither by shortening nor lengthening days, but by the alternation of such changes irrespective of the direction of the shift in the photoperiod.

Animals↗
PubMed1975

Epidermal downgrowths in regenerating rabbit ear holes.

Rabbits are unique among mammals in that their ears can regenerate tissues from the margins of full thickness holes which grow in and completely fill the opening in about two months. The circular blastema that forms around the edges of the hole differentiates a new sheet of cartilage as it regenerates in a centripetal direction. Similar holes in other mammals fail to regenerate and form scar tissue instead of a blastema. Histological studies of the healing around the edges of rabbit ear holes reveal that during the second week, when the epidermis is completing its migration across the wound from the opposite sides of the ear, conspicuous tongues of epidermal cells grow down into the underlying tissues at the edges of the wound. These epidermal downgrowths are situated between the original intact dermis of the skin and the more central tissues which give rise to the blastema. Such downgrowths are of a transient nature, and are no longer found once the blastema rounds up toward the end of the second week. Since they are not found in the healing of similar wounds in rabbit ears prevented from regenerating by prior removal of their cartilaginous sheets, nor in the naturally nonregenerating ears of sheep and dogs, it is considered that these downgrowths of healing epidermis may play a role in the unusual regenerative response of ear tissues in the rabbit.

Animals↗
PubMed1975

Induction of extra nephrons in unilaterally nephrectomized immature rats (38525).

The normal number of glomeruli per kidney in the rat rises from about 10-4 at birth to approximately 35 times 10-3 at 50 days of age. When one kidney is removed at birth the remaining one produces an average of 63% more nephrons than normal by 70 days. Unilateral nephrectomy of successively older rats results in progressively less augmentation of the nephron complement in the remaining kidney up to 50 days, beyond which age the kidney loses its ability to produce new nephrons.

Age Factors↗