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Biomedical subjects

R F Oliver

Publications and source records attributed to R F Oliver.

At least 37 records · Page 2Linked to original sources
PubMed1990

Immunobiological studies on the alopecic (DEBR) rat.

The Dundee experimental bald rat (DEBR) has been proposed as an animal model of human alopecia areata, which is suspected of being an autoimmune disease. This study was carried out to establish whether the immunological changes observed in the lesional DEBR rat correlated with studies of human alopecia areata. The immune infiltrate was characterized using immunoperoxidase techniques on cryostat sections of vibrissa follicles. Indirect immunofluorescence was used to quantify the peripheral blood leucocytes. Some parallels were observed in the infiltration of human and DEBR rat follicles by T lymphocytes. In contrast, pre-lesional DEBR rat follicles, which are not available for investigation in human alopecia areata, were not penetrated by leucocytes and MHC class II antigens were expressed in the precortical region of the epidermal component of these follicles. Quantification of peripheral blood leucocytes showed significant increases in both T-lymphocyte subsets during lesional expression. We consider that the pre-lesional form of the rat may provide important information as a model for the pre-lesional and uninvestigated form of alopecia areata in man.

Alopecia Areata↗
PubMed1986

Whisker growth induced by implantation of cultured vibrissa dermal papilla cells in the adult rat.

Retention of the capacity to induce the growth of hair by cultured adult rat vibrissa dermal papilla cells has been investigated. Small pellets of serially cultured papilla cells were implanted into the bases of the exposed follicular epidermis of amputated adult rat vibrissa follicles. Amputated follicles that received no cell implants or implants of cultured dorsal skin fibroblasts were used as controls. Over 50% of follicles implanted with cultured papilla cells in the passage range 1-3 grew hairs. In contrast none of the follicles that received late passage cells (range 6-15) produced hairs; and spontaneous regeneration of hair occurred in only 3% of the control follicles. These results demonstrate that cultured papilla cells of early passage numbers retain their ability to induce hair growth. Histological examination confirmed that the implanted papilla cells interacted with follicular epidermis to organize the development of new, hair-producing bulbs, each containing a discrete dermal papilla. An important observation was that aggregative behaviour leading to papilla formation was only manifested by early passage papilla cell implants. This persisting embryonic characteristic appears to be an essential functional component of papilla cell activity which operates to regulate the profound morphogenetic changes that occur during the hair growth cycle.

Animals↗
PubMed1984

Observations on the relationship between nerve supply and hair positioning in the rat vibrissa follicle.

The present study has demonstrated an anatomical relationship between the position of the growing and non-growing hairs of the rat vibrissa follicle and the point where the follicular nerve supply penetrates the follicle capsule circumference. This finding may be significant in relation to the sensory function of the follicle, as physiological data have shown that the degree of stimulation of brain cells following mechanical displacement of the whisker is direction dependent. The observed relationship between the nerve entry point and the hairs, therefore, may reflect an uneven distribution of nerve endings around the upper follicle circumference. In relation to hair growth, the above observation requires that the non-growing club hair must consistently move up one side of the follicle at the end of each growth cycle. A possible clue as to the mechanism by which club hair movement is directed can be derived from observation of asymmetry, both at the base of the club hair, and in the epidermal matrix near the end of the growth cycle.

Animals↗
PubMed1984

Changes in hair growth characteristics following the wounding of vibrissa follicles in the hooded rat.

The effect on hair growth of wounding the lower region of whisker follicles, and in particular the dermal papilla, with sharply pointed tungsten needles was studied in adult hooded rats. Following injury hair growth ceased, but was subsequently resumed. While it might have been anticipated that follicle wounding would have a negative effect on whisker length, regular postoperative length measurements revealed that in follicles where cellular material was not displaced from the follicle by the original manipulation, 50% of the subsequent hairs produced were longer than their counterparts on the opposite side of the face, with 25% shorter and 25% with their length unchanged. In every case increased hair length was achieved by a prolongation of the growing period of the hair. Growth rate, when altered, was reduced. These results suggest that the factors which control the duration of the hair cycle and fibre growth rate are independent in vibrissa follicles. Since removal of most of the epidermal component by plucking of the hair just prior to injury produced equivalent hair length increases, this implicated the proximal dermal components as being mainly responsible for the observed changes.

Animals↗
PubMed1984

Histological studies of the effects of wounding vibrissa follicles in the hooded rat.

The effects of wounding the lower region of rat vibrissa follicles with a sharp tungsten needle were examined histologically, both shortly after injury and up to one year postoperatively. Following cell damage in the dermal papilla component hair growth ceased, and resumption of fibre production was always preceded by dermal papilla reformation. This papilla healing and regeneration was not associated with the production of scar tissue. In follicles undergoing no cell displacement during wounding (an effect associated with the growth of longer than normal hairs) dermal papillae were reformed from the residual papilla cell population, with recruitment of cells from surrounding mesenchyme. Follicles plucked just prior to wounding revealed little or no original epidermal matrix three days later, confirming that dermal components were primarily affected. Papilla cell counts performed on follicles which had consistently produced longer hairs gave no indication of increased papilla cell numbers. Follicles which underwent displacement of cellular material and displayed distortion of normal follicle morphology shortly after wounding (effects associated with the production of shorter than normal hairs) also revealed abnormalities at long-term biopsy. Moreover these follicles often had a history of altered fibre characteristics from one postoperative generation to the next. It is concluded that gross morphological disruption of the normal cellular relationships in the lower follicle results in a series of reorganizational difficulties with each recurring phase of the hair cycle.

Animals↗
PubMed1984

Vibrissa dermal papilla cell aggregative behaviour in vivo and in vitro.

Parallel cultures of adult rat vibrissa dermal papilla cells and skin fibroblasts revealed differences between the two cell types with respect to a number of criteria. In particular the dermal papilla cells demonstrated a distinctive single cell morphology, and at confluence formed cell aggregates radically different from regular fibroblast multilayering and patterning. This finding confirmed repeated observations of papilla cell clumping in short-term culture. The dermal papilla cells which are mitotically quiescent in situ were also shown to have a lower proliferative capacity than the skin fibroblasts. The affinity shown by papilla cells towards each other in culture reflected the behaviour demonstrated by isolated dermal papillae transplanted into ear dermis and into the collagenous capsule of the vibrissa follicle. In the absence of epidermal contact the papilla cells remained as recognizable rounded aggregates for the experimental period of up to nine months. Synthesis of extracellular material typical of that seen in situ was observed, particularly during the first weeks following transplantation. The collective behaviour of the dermal papilla cells revealed in this study may be significant for the morphogenetic activity of the papilla, and for papilla size during the hair cycle. It may also reflect the retention of embryonic-like properties by the dermal component of adult hair follicles.

Animals↗
PubMed1983

Changes in the synthesis, distribution and sulphation of glycosaminoglycans of cultured human skin fibroblasts upon ascorbate feeding.

The effect of ascorbic acid on the synthesis, distribution and sulphation of glycosaminoglycans by human skin fibroblasts has been examined. Medium was supplemented with ascorbate over several days, and cultures incubated with [3H]glucosamine and Na2(35)SO4 for 48 h, followed by analysis of the glycosaminoglycans in the medium, in collagenase and trypsin extracts, and in cell fractions. Ascorbate feeding resulted in a reduction in hyaluronate synthesis, which was the main 3H-labelled component and was distributed mainly in the medium fractions. Sulphated glycosaminoglycans showed a reduction in incorporation of 3H label, but increased sulphation following ascorbate feeding. In control cultures 53% of 3H-labelled sulphated glycosaminoglycans and 63% of 35S-labelled glycosaminoglycans were present in the medium fraction, while in ascorbate-fed cultures, 41% of 3H label and 38% 35S label were incorporated into medium-sulphated glycosaminoglycans. Ascorbate also caused an increase in cell density and in collagen production and deposition.

Ascorbic Acid↗
PubMed1983

An in vitro cytotoxicity study of aldehyde-treated pig dermal collagen.

The cytotoxicity of aldehyde-treated collagen was assayed by measuring 3H-thymidine incorporation in adult human skin fibroblasts grown in tissue culture for 1 or 3 days in the presence of pig dermal collagen cross-linked with formaldehyde or glutaraldehyde. A comparison was also made with collagen preparations washed for 2 weeks either at 15 degrees throughout or partly at 15 degrees and partly at 37 degrees. Collagen treated with both formaldehyde and glutaraldehyde proved increasingly toxic with increase in the concentrations of aldehyde used. While the maximum toxic effect was observed after 1 day culture in formaldehyde-treated collagen, with thymidine uptake ranging from 4-48% of control values with 5-0.1% formaldehyde and a 15 degrees wash, the toxic effect of glutaraldehyde treatment increased with longer exposure and at 3 days thymidine uptake ranged from 3-40% of control values with 0.05-0.001% glutaraldehyde and washing at 15 degrees. Washing partly at 37 degrees significantly reduced toxicity, the differences in thymidine uptake as compared with washing at 15 degrees alone ranging from 34-50% with 1 and 0.3% formaldehyde respectively in 1 day cultures and from 14-37% with 0.02 and 0.005% glutaraldehyde in 3 day cultures. While fibroblasts actively grew and migrated when seeded on non-cross-linked collagen, only limited cell survival occurred on aldehyde-treated collagen.

Adult↗
PubMed1982

Dermal collagen implants.

The feasibility of using preparations of cell-free, fibrous dermal collagen, prepared by trypsin-treatment of skin, for the repair of soft body tissues has been examined both as subcutaneous implants and as a replacement for dermis in skin wounds in rats. Increased collagen stability, and suppression or reduction of tissue antigenicity in collagen heterografts, was achieved by crosslinking with weak solutions of aldehydes while still allowing implant recellularization and revascularization. Tritium-labelled collagen turnover studies have shown that maintenance of collagen mass in implants crosslinked with glutaraldehyde occurs primarily by inhibition of loss of original implant collagen. Some of the in vitro growth characteristics of human fibroblasts on animal collagen preparations are also described.

Animals↗
PubMed1982

3H-collagen turnover in non-cross-linked and aldehyde-cross-linked dermal collagen grafts.

Using trypsin-purified rat dermal collagen labelled with tritiated hydroxyproline and proline, a study has been made of hydroxyproline turnover in non-cross-linked and glutaraldehyde- and formaldehyde-cross-linked collagen when implanted s.c. in unlabelled isogenic rats. Grafts cross-linked with 0.01% glutaraldehyde maintained their collagen mass over a 22-week period, loss of original collagen being balanced by the gain in new collagen (22% at 22 weeks). Cross-linking with 5% formaldehyde temporarily inhibited collagen loss as compared with non-cross-linked grafts. However, at 22 weeks both had lost some 30% of their collagen mass, the gain of new collagen (some 8%) only partially compensating for the loss of original implant collagen.

Animals↗
PubMed1981

Hydroxyproline turnover in dermal collagen grafts in reconstituted skin wounds in the rat.

Using donor skin labelled with tritiated hydroxyproline and proline, a comparative study has been made of hydroxyproline (and by extrapolation collagen) turnover in skin, dermal collagen and glutaraldehyde crosslinked dermal collagen grafts in unlabelled isogenic recipient rats. In contrast with non-crosslinked collagen and skin grafts, collagen grafts stabilized by crosslinking with 0.01% glutaraldehyde underwent little loss of original graft collagen and maintained their original collagen mass over a 22 week period. As the skin grafts acquired a similar amount of new collagen to that lost, they also maintained their original mass. However, the non-crosslinked collagen grafts showed only a small gain of new collagen and lost 57% of their original mass.

Animals↗
PubMed1980

Effect of aldehyde cross-linking on human dermal collagen implants in the rat.

The fate of s.c. implants of fibrous, trypsin-purified human dermal collagen and collagen cross-linked with formaldehyde and glutaraldehyde has been studied in rats. Dermal collagen, and untreated skin implants, underwent resorption associated with a pronounced round-cell reaction. While collagen implants cross-linked with solutions of 0.04% and 0.08% formaldehyde became reduced in size, those cross-linked with 1% formaldehyde and 0.01%, 0.02% and 0.04% glutaraldehyde, although undergoing some collagen remodelling, retained their original size over the 25-week period of study. At 5 weeks the aldehyde cross-linked implants showed their greatest cellularity, reaching a lower, more stable cell population by 18 weeks. More round cells were seen at 5 weeks, particularly after formaldehyde cross-linking, than a later times when few were present. The results indicate that aldehyde-stabilized preparations of heterograft dermal collagen could have applications in the repair of tissue defects in man.

Aldehydes↗
PubMed1979

Reconstruction of full-thickness loss skin wounds using skin collagen allografts.

Sheets of allogeneic dermal collagen measuring 20 X 15 mm and prepared by trypsin treatment of full-thickness skin were grafted under skin flaps in rats. After 2 to 5 weeks the protective recipient skin was excised and replaced by split-thickness skin isografts which remained viable on their supportive collagen beds. On average such composite grafts maintained 84 per cent of their original size over 3 to 28 weeks and in contrast with split-thickness skin grafts achieved full-thickness reconstruction of the excised skin.

Animals↗
PubMed1979

An autoradiographic study of 3H-thymidine incorporation and distribution in the dermis of healing skin incisions in the pig.

The dermal response to injury in healing incisional wounds aged from 1 to 24 days was studied by in vitro and in vivo 3H-thymidine (3HT) labelling and the use of colcemid to induce metaphase arrest. In vitro 3HT labelling provided mean numbers (+/- s.e. mean) of labelled dermal cells/section within the incision and in 3 zones in the dermis up to 0.875 mm lateral to the incision. There was a progressive increase in the numbers of DNA-synthesizing cells in the incisions as granulation tissue developed from Day 1 to Day 7, and a sharp decline by Day 9. Immediately adjacent to the incision there was a dramatic increase in the number of labelled cells on Day 2, with reduced numbers laterally. This response, which was largely maintained up to 7 days, paralleled the cellular reaction around blood vessels and skin appendages but also included labelled dermal fibroblasts. The in vivo 3HT study, taken in conjunction with the colcemid and in vitro 3HT studies, supported the idea that during the development of granulation tissue there is a continual recruitment of paraincisional cells, including dermal fibroblasts, either by direct migration or by division and then migration, as well as by continued mitosis of cells already within the incision.

Animals↗