Chronic graft-versus-host disease as a model for scleroderma. II. Mast cell depletion with deposition of immunoglobulins in the skin and fibrosis

We explored the pathologic changes in the skin of mice undergoing a chronic graft-versus-host (GVH) reaction. In rodents and in man, chronic GVH includes the deposition of excess collagen in the skin-a reaction which resembles idiopathic scleroderma. GVH disease across minor histocompatibility barriers was produced by injecting B10.D2 cells into irradiated BALB/c mice. These strains are identical at the H-2 and Mls loci but differ in minor histocompatibility antigens. Control BALB/c mice received irradiation and BALB/c cells. Serial skin biopsies were taken and studied for histological changes characteristic of chronic GVHD, for mast cell density, and for the deposition of immunoreactants. GVHD was produced in B10.D2----BALB/c mice as measured by body weight loss and the production of skin changes including dermal fibrosis, loss of fat and appendages, and a mononuclear cell infiltrate. Dermal mast cells, assessed by toluidine blue staining, were normal at Day 11, but had disappeared by Days 21-63 and returned to normal by Day 104. Immunoglobulins IgG, IgA, and IgM appeared at the dermo-epidermal junction and along the basement membrane zone of hair follicles. This deposition was maximal at Day 42 and waned thereafter. Thus the appearance of immunoglobulins in the skin was maximal when mast cell staining was minimal. The changes in this GVHD model leading to a scleroderma-like picture in the skin are compatible with an immune etiology for the fibrosis. Vasodilation following liberation of mast cell mediators would facilitate the deposition of immunoglobulins. The disappearance of mast cell staining may be caused by extensive degranulation. We postulate an interaction between GVHD-activated T cells, mast cell stimulation, fibroblast activation, and fibrosis.     

Mass characteristics of DNA obtained from chromosomes of a human carcinoma cell line

Sedimentation studies of DNA from chromosomes extracted from human mitotic cells showed that highmolecular-weight DNA can be obtained if cell hypotonic treatments and prolonged metaphase blocks are avoided. Two types of large double-stranded DNA were observed. One of these (M _r = 2.5×10⁸) appeared as a size class with characteristics reminiscent of the chromosomal DNA subunit hypothesis. However, this DNA is the decay product of larger molecules, whose minimum molecular weight is 6×10⁸.     

Isotope-exchange enhancement studies of Escherichia coli glutamine synthetase

Isotope-exchange enhancement studies, a variation on positional isotope-exchange enhancement as described by Raushel and Garrard [Raushel, F. M., & Garrard, L. J. (1984) Biochemistry 23, 1791-1795], are used to establish the point in the biosynthetic reaction of Escherichia coli glutamine synthetase at which gamma-glutamyl phosphate is formed. In these experiments, the behavior of the reverse biosynthetic reaction, i.e., the reaction of ADP, L-glutamine, and phosphate to form NH4+, L-glutamate, and ATP, is examined as a function of the concentration of ammonium ion. By varying the concentration of NH4+, the ratio of the velocity of isotope exchange to the velocity of net reaction, as measured by the rate of 18O depletion from labeled phosphate and the rate of production of L-glutamate, respectively, can be modulated in a mechanism-dependent manner. Evidence is presented demonstrating the presence of a branch point in the mechanism. The enzyme-ATP-glutamate complex may partition in two ways, one involving binding of ammonium ion and the other involving the chemical transformation to form the enzyme-ADP-gamma-glutamyl phosphate complex. The alternate pathways then rejoin upon formation of the enzyme-ADP-NH4+-gamma-glutamyl phosphate complex. Because of the branch point, there is no absolute requirement that ammonium ion be absent or present in order for the formation of gamma-glutamyl phosphate to occur. At high concentrations of ammonia, one pathway through the branch can be eliminated, effectively making that portion of the pathway ordered, with ATP, L-glutamate, and NH4+ binding consistent with our previously reported steady-state kinetic mechanism [Meek, T. D., & Villafranca, J. J. (1980) Biochemistry 19, 5513-5519].     

Aluminium salts accelerate peroxidation of membrane lipids stimulated by iron salts

Aluminium salts do not themselves stimulate peroxidation of ox-brain phospholipid liposomes, but they greatly accelerate the peroxidation induced by iron(II) salts at acidic pH values. This effect of Al(III) is not seen at pH 7.4, perhaps because Al(III) salts form insoluble complexes at this pH in aqueous solution. Peroxidation of liposomes in the presence of Al(III) and Fe(II) salts is inhibited by the chelating agent desferrioxamine, and by EDTA and diethylenetriaminepentaacetic acid at concentrations greater than those of Fe(II) salt. Aluminium salts slightly stimulate the peroxidation of peroxide-depleted linolenic acid micelles, but they do not accelerate the peroxidation induced by addition of iron(II) salts to the micelles at acidic pH. Aluminium salts accelerate the peroxidation observed when human erythrocytes are treated with hydrogen peroxide at pH 7.4. Desferrioxamine decreases the peroxidation. We suggest that Al(III) ions produce an alteration in membrane structure that facilitates lipid peroxidation, and that the increased formation of fluorescent age pigments in the nervous system of patients exposed to toxic amounts of Al(III) may be related to this phenomenon. The ability of desferal to bind both iron (III) and aluminium(III) salts and to inhibit lipid peroxidation makes it an especially useful chelating agent in the treatment of 'aluminium overload'.     

The survival of anaerobes during sewage treatment employing biological filter beds

During the passage of sewage through a typical treatment plant employing biological filter beds and operating under dry weather flow conditions, about 7% of the input of anaerobic organisms survive to be released in the effluent. The greatest fall in numbers occurs in the first of two primary settling tanks operating in series and during passage through the filter beds. The predominant organisms were Bacteroides species, gram-positive cocci and clostridial species. There is no significant difference in the rate of survival of any of the genera through the different stages of treatment.     

Primary structure of pilin protein from Bacteroides nodosus strain 216: comparison with the corresponding protein from strain 198

The amino acid sequence of pilin protein from Bacteroides nodosus strain 216 was determined. The protein had a calculated molecular weight of 15962 and contained the same number of amino acid residues (151) as the pilin from the previously sequenced strain 198. The sequence of the first 44 residues was common to both strains, including the unusual amino-terminal amino acid, N-methylphenylalanine. Of the remaining 107 residues, 37% of them differed between the two strains. Comparison of hydrophilicity profiles constructed from the sequence data indicated that a conserved region around residues 71-72 was probably the site of an antigenic determinant.     

Therapeutic potential of rat monoclonal antibodies: isotype specificity of antibody-dependent cell-mediated cytotoxicity with human lymphocytes

The ability of rat monoclonal antibodies to promote antibody-dependent cell-mediated cytotoxicity with human effector cells was tested by using a variety of antibodies against different human and mouse leukocyte antigens. It was found that only IgG2b antibodies were effective. This isotype has already been shown to be efficient in fixing human complement, which suggests that among rat monoclonal antibodies, the IgG2b subclass might be a good choice for attempts at serotherapy. Further studies with other antibody-mediated effector mechanisms as well as suitable clinical trials are merited.     

The putative dopamine autoreceptor agonist B-HT 920 decreases nigral dopamine cell firing rate and prolactin release in rat

Recent behavioural and biochemical investigations have suggested that the alpha-2 receptor agonist B-HT 920 is also a centrally acting dopamine (DA) agonist with a selectivity for autoreceptors. It is presently demonstrated that B-HT 920, in contrast to the structurally related alpha-2 agonist B-HT 933, effectively reduces the firing rate of nigral DA neurons both after intravenous and microiontophoretic administration. Furthermore, B-HT 920, but not B-HT 933, decreases plasma levels of prolactin in reserpine pretreated rats. The electrophysiological as well as the neuroendocrine effects of the drug were antagonised by DA antagonists but not by alpha-2 receptor antagonists. The data support the contention that B-HT 920 acts as an agonist at central DA autoreceptors. Furthermore, they reinforce the hypothesis that lactotroph DA receptors are more similar to DA autoreceptors than to postsynaptic DA receptors in the brain.