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.

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.

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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.

Lack of autoantigen-specific splenic suppressor cells in mice with an X-linked B-lymphocyte defect

Male and female progeny of a cross between CBA/N female and BALB/c male mice were tested for their ability to generate autoantigen-specific suppressor cells as a result of stimulation with crossreacting rat RBC. Male mice, hemizygous for the X-linked defect, were unable to generate these antigen-specific suppressor cells, whereas their female littermates behaved like the normal (CBA/Ca x BALB/c)F1 mice.

Sex differences in the regulation of experimentally induced autoantibodies in (NZB x NZW)F1 mice

The ability to induce autoantibodies to erythrocytes in male and female (NZB x NZW)F1 mice was examined. Female (NZB x NZW)F1 mice were shown to produce significantly more autoantibody than the male (NZB x NZW)F1 mice. The regulation of this experimentaly induced autoantibody was studied by examining the ability of male and female (NZB x NZW)F1 mice to generate antigen-specific suppressor cells. A sex difference was found in the ability to generate these suppressor cells. Male mice generated antigen-specific suppressor cells in response to rat RBC which were capable to suppressing the experimental induction of red cell autoantibodies whereas female mice were unable to generate those antigen-specific suppressor cells.

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.

Specific and non-specific suppressor cell activity in NZB mice

Non-specific and specific suppressor cell activity has been examined in both young and old NZB mice and compared to normal CBA mice. Both young and old NZB mice are shown to be able to generate antigen non-specific and specific suppressor cells in response to Con A and rat RBC respectively. In addition, antigen-specific suppressor cells which suppress the experimental induction of red cell autoantibodies do not influence the spontaneous development or course of autoimmune haemolytic anaemia. Subsequent experiments showed that this is probably due to differences in specificity of induced and spontaneous autoantibodies.

Rabbit anti-EL4 serum. A reagent with specificity for a population of murine suppressor cells

Antisera against the C57B1 (H-2b) mouse lymphoma, EL4 were prepared in rabbits. After absorption with mouse liver, red cells and thymocytes the antisera appeared to be cytotoxic for a subpopulation of peripheral T cells. The absorbed antisera blocked the immunosuppressor function of Con A-stimulated splenic lymphocytes, but was unreactive against Con A-stimulated and allogeneically primed cytotoxic cells, or helper T cells. Consequently, heteroantiserum against EL4 may provide a useful reagent for the differentiation of cytotoxic from suppressor T-cell subsets.

Deficient production of anti-red cell autoantibodies by mice with an X-linked B lymphocyte defect

The production of anti-self red cell antibodies has been studied in mice bearing the CBA/N X-linked B lymphocyte defect and their phenotypically normal littermates. Defective mice produced anti-self red blood cell (RBC) antibodies at markedly reduced levels after multiple injections of rat RBC. They also failed to show significant numbers of plaque-forming cells against enzyme-treated isologous RBC. These findings are discussed in terms of the nature of the CBA/N defect and the acquisition of a complete specificity repertoire.

Activity of serum alpha-amylases in cystic fibrosis

A new method which uses a differential inhibitor to measure pancreatic and salivary type alpha-amylases (EC 3.2.1.1) was applied to serum samples from 46 cystic fibrosis (CF) patients (age range 4-14 years) and 50 controls of the same age group. The levels of pancreatic type amylase were lower in the CF patients (median 26.5 I.U./1) than the controls (median 81.5) (P less than 0.001). The results for salivary-type enzyme, however, did not support the previously reported finding of higher than usual levels in CF patients. This discrepancy is probably due to differences in analytical methods. It is felt that this procedure will be of value in the investigation of patients for cystic fibrosis and other pancreatic disorders.

Dose response, wavelength dependence and rate of excision of ultraviolet radiation-induced pyrimidine dimers in mouse skin DNA

The yield of thymine-containing dimers produced in mouse skin DNA in vivo by 290 nm ultraviolet radiation was shown to increase with dose up to around 2000 J/m2 and subsequently at a much slower rate up to 8000 J/m2. The study of wavelength dependence of dimer formation in skin indicated that 290 nm was the most effective wavelength of those investigated, followed by 300, 280 and 260 nm, with 310 nm being by far the least effective. A reduction in the number of dimers present in skin DNA was shown to occur by 24 h post-irradiation in a dose-dependent manner. A significant percentage of the dimers was, however, found to persist in the skin until at least 72 h post-irradiation.

Characterization of haemagglutinating factor produced by mouse spleen and lymph node in culture

Mouse spleen cells produce haemagglutinating activity in culture which is species specific but not strain specific. The activity is produced by all strains of mice tested including nude mice. It is produced in cultures of spleen and lymph node but not of peritoneal exudate cells. Production of the factor is not affected by macrophage depletion of the spleen. This activity is not antibody mediated.

Hyper-responsiveness in NZB mice to the experimental induction of anti-red cell autoantibody

Strain differences in ease of induction of autoantibody production were observed when mice were injected with rat RBC. Responsiveness was not linked to the H-2 locus. NZB and (NZB X BALB/c)F1 mice were hyper-responsive both in terms of the induction of autoantibody and in the production of agglutinating antibody to rat RBC. C57BL/c and (C57BL X BALB/c)F1 were poor responders. Injection of the rat RBC in FCA converted a poor responder into a good responder. Adult thymectomy and ALS treatment did not significantly enhance autoantibody production.