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Biomedical subjects

A J Ammann

Publications and source records attributed to A J Ammann.

At least 19 recordsLinked to original sources
PubMed1992

Human recombinant transforming growth factor-beta 1 modulation of biochemical and cellular events in healing of ulcer wounds.

The effects of recombinant human transforming growth factor beta 1 (rhTGF-beta 1) on wound healing were examined in a rabbit ear ulcer model in which rhTGF-beta 1 was applied to full-thickness biopsy ulcers on the ears. The influence of perichondrium on healing was studied by comparing ulcers with and without perichondrium on 1) formation of total healing wound area (HWA, the newly formed connective and granulation tissues within the ulcer) over time and 2) the amount of collagen synthesized by the wound tissue at day 5. The HWA of ulcers with intact perichondrium increased sharply with time and reached a plateau at day 7, whereas a slower healing occurred in the perichondrium-free model where maximal HWA appeared at day 14. Topical application of 100 ng of rhTGF-beta 1 per wound accelerated healing by increasing HWA in both models. The enhancement of healing by rhTGF-beta 1 was associated with increased collagen synthesis. The percent collagen synthesis in the rhTGF-beta 1 was doubled in the perichondrium-intact ulcers and increased 40% in the perichondrium-free ulcers. DNA synthesis in the perichondrium-intact ulcers was not altered by rhTGF-beta 1 when measured at day 5 by in vitro labeling with [3H]thymidine ([3H]TdR). Autoradiography indicated that the primary cells labeled in the wound tissue were epithelial cells and rhTGF-beta 1 enhanced the migration of these cells from the wound margin towards the center. To evaluate the effects of rhTGF-beta 1 on fibroblasts derived from the granulation tissue of the wound, cells were treated with increasing concentrations of rhTGF-beta 1 and DNA and collagen synthesis were determined. rhTGF-beta 1 elicited a biphasic change in percent collagen synthesis with a maximal increase of 50% at 20 pM followed by a decline. A twofold increase in [3H]TdR incorporation that plateaued at 1 nM was also observed. Our results indicate that the cellular responses to rhTGF-beta 1 differ in vivo and in vitro. The perichondrium-intact ulcers contain more wound tissue and have larger responses to rhTGF-beta 1 stimulation, which allows better examination of biochemical and cellular events. The in vivo mechanisms are multi-factorial, which may involve cell migration and recruitment as results of numerous cell/cell and cell/matrix interactions.

Animals↗
PubMed1992

An intraosseous device for studies of bone-healing. The effect of transforming growth-factor beta.

A novel implantable device, the analytic bone implant, was used in order to establish a model for studies of bone-healing and the evaluation of factors that augment the process, such as transforming growth-factor beta (TGF-beta). This device was implanted into the tibiae of four baboons. After healing, bone was removed from the center chamber. Recombinant human TGF beta-1 was then delivered to the core of the device. After twenty-two days of healing, the device was disassembled and the newly formed bone was removed from the core of the implant for histomorphometric analysis. An analysis of the bone revealed a substantial effect of TGF-beta on osteoblastic activity and proliferation compared with that seen in control and placebo groups. However, despite increased osteoblastic activity, trabecular bone volumes at twenty-two days were equivalent among the groups. The number of osteoclasts and the erosion of the surface were also increased, although not significantly so. Substantial endochondral formation of bone was seen in the supraperiosteal tissues directly over the implants that contained TGF-beta but not over the implants in the control and placebo groups. These data demonstrate the utility of this bone-implant model for studies of bone-healing with minimally invasive methods. In addition, use of the device provided the first in vivo data on the effects of TGF-beta at an intermediate (twenty-two-day) time-point in the healing process in a non-human primate.

Animals↗
PubMed1991

In vivo induction of bone by recombinant human transforming growth factor beta 1.

A single application of recombinant human transforming growth factor beta 1 (rhTGF-beta 1) adjacent to cartilage was found to induce bone formation in rabbit ear full-thickness skin wounds. At doses that optimally promote soft tissue healing, 25-100 ng rhTGF-beta 1 per wound caused osseous tissue formation starting 21 days after wounding to reach a peak incidence and area of bone formation at day 42. Bone formation was followed by active remodeling, resulting in lower incidence and area of bone formation at days 56 and 70. The early phase of bone formation was located overlying the cartilage and involved perichondrial cells that appeared to differentiate directly into osteoblasts forming bone matrix without a cartilage precursor. Cartilage was replaced with bone at later time points. rhTGF-beta 1 was able to increase the ratio of osteoblasts to osteoclasts lining the trabecular surface of bone and thus increase the net amount of bone formation. The present studies suggest a potential therapeutic role for rhTGF-beta 1 in hard tissue repair.

Animals↗
PubMed1979

Multiple biotin-dependent carboxylase deficiencies associated with defects in T-cell and B-cell immunity.

Three siblings presented in early childhood with central-nervous-system (CNS) dysfunction, candida dermatitis, keratoconjunctivitis, and alopecia. Two were studied immunologically and had absent delayed-hypersensitivity skin-test responses and absent in-vitro lymphocyte responses to candida antigen. One of them had selective IgA deficiency and no antibody response to pneumococcal polysaccharide immunisation, and the other had a subnormal percentage of T lymphocytes in peripheral blood. The first two siblings died with progressive CNS deterioration and overwhelming infection. The third child, who presented with a periorificial candida dermatitis, alopecia, keratoconjunctivitis, and intermittent ataxia at eighteen months of age, had intermittent lactic acidosis and raised excretion of beta-hydroxyproprionate, methylcitrate, beta-methylcrotonylglycine, and beta-hydroxyisovalerate in urine. After four days of oral biotin, 10 mg/per day, the metabolites in her urine were significantly reduced, suggesting a biotin-responsive multiple carboxylase deficiency. These findings, taken with previous reports of immune defects in patients with disorders of branched-chain aminoacid catabolism, suggest a new biochemical basis for primary immunodeficiency disease.

Alopecia↗
PubMed1979

Milk precipitins in selective IgA deficiency.

Precipitating antibody to cow milk's antigens (commonly bovine IgM) is found in 40-50% of selective IgA deficient patients. These precipitins may obscure the diagnosis of selective IgA deficiency by formation of anti-antiserum precipitin rings in radial immunodiffusion. Abnormal immunoregulatory function along with excess absorption of milk antigens in the absence of secretory IgA may be predisposing factors. Elimination of dietary cow's milk results in disappearance of these antibodies.

Animals↗
PubMed1978

Further characterisation of a spontaneously occurring antibasement membrane antibody.

A spontaneously occurring antibasement membrane antibody has been further characterised according to antigenic specificity, immunoglobulin class, and tissue localisation using immunofluorescent and immunoelectron microscopic techniques. The autoantibody reacted with the basement membrane of kidney tubules, Bowman's capsule, and the epithelial portion of ileum but not with the basement membrane of skin, cornea, glomerulus, or oesophagus. It also reacted with bile canaliculi, sarcolemmal sheath, and salivary duct. On electron microscopy the antibody was distributed along the basement membrane of Bowman's capsule and renal tubules. Some reactivity against collagen was observed. Antibody activity was found in both IgG and IgM fractions. In immunodeficiency disorders, the autoantibody was found only in patients with selective IgA deficiency.

Autoantibodies↗
PubMed1978

Deoxyguanosine triphosphate as a possible toxic metabolite in the immunodeficiency associated with purine nucleoside phosphorylase deficiency.

Purine nucleoside phosphorylase (PNP) deficiency is associated with a severe defect in thymus-derived (T)-lymphocyte function combined with normal bone marrow-derived (B)-lymphocyte function. To investigate the role of this enzyme deficiency in the resulting immune dysfunction, we measured the levels of ribonucleoside and deoxyribonucleoside triphosphates in erythrocytes from two unrelated PNP-deficient, T-lymphocyte-deficient patients. Both PNP-deficient patients have abnormally high levels of deoxyguanosine triphosphate (deoxy-GTP) in their erythrocytes (5 and 8 nmol/ml packed erythrocytes). In contrast, normal controls and adenosine deaminase-deficient, immunodeficient patients do not have detectable amounts of deoxyGTP (<0.5 nmol/ml packed erythrocytes). We propose that deoxyguanosine, a substrate of PNP, is the potentially lymphotoxic metabolite in PNP deficiency. The mechanism of toxicity involves phosphorylation of deoxyguanosine to deoxyGTP, which acts as a potent inhibitor of mammalian ribonucleotide reductase.

Adenosine Deaminase↗