Oxygen participation in the in vivo and in vitro aging of collagen fibres

We have examined, as a function of oxygen concentration, the in vivo and in vitro aging rates of tendon from animal species with widely differing life-spans. The results suggest that concomitant with the genetically determined aldimine type cross-linking reactions which probably are complete by the time the animal has reached physiological maturity, there is an on-going oxygen-mediated system of reactions which also effectively cross-link the structure. These reactions appear to proceed with their own intrinsic rate dependent only upon oxygen concentration, and independent of the particular species involved. They may not be required by connective tissues, but are an unavoidable consequence of the presence of free oxygen in tissues with a low rate of turnover.     

Influence of substituent ribose on transition state affinity in reactions catalyzed by adenosine deaminase

Adenosine deaminase from calf intestine hydrolyzes adenine at a limiting rate four orders of magnitude lower than that for adenosine, while Km values for these substrates are about the same (Wolfenden, R., et al. (1969), Biochemistry 8, 2412-2415). Reactivity of 6-substituents, toward nucleophilic displacement, is found to be affected only slightly by removal of ribose as a 9-substituent, in model reactions. Substituent ribose thus appears to stabilize, selectively, the transition state for enzymatic deamination. In contrast with the small influence of substituent ribose on the apparent binding affinity of substrates, removal of substituent ribose from a potential transition state analogue, 1,6-dihydro-6-hydroxy-methylpurine ribonucleoside, results in a lowering of its affinity for the enzyme by several orders of magnitude. The synthesis of the analogue and related compounds is described, and their properties compared with those of other photoadducts and of the naturally occurring inhibitors covidarabine and coformycin. Binding of these inhibitors is found to result in the appearance of ultraviolet-absorbing bands in the neighborhood of 323 nm.     

Optimal conditions for lactoperoxidase catalyzed radioiodination of external proteins on mouse erythrocytes

Optimal conditions were established for specific labelling of the surface proteins of mouse erythrocytes using lactoperoxidase-catalyzed radioiodination. The levels of H2O2 and I-, and cell concentrations required for restriction of haemoglobin labelling to less than 5% of the total 125I-protein, were different for radioiodination employing direct H2O2 addition or generation of H2O2 with glucose oxidase plus glucose. Preparation of mouse erythrocyte ghosts by hypotonic lysis caused loss of some minor labelled proteins present on intact cells and shifts to lower molecular weights of others. It is therefore important to solubilize labelled cells directly in electrophoresis buffer to avoid artifactual degradation of labelled proteins. The extent of labelling internal cell proteins was measured by a procedure suitable for the comparison of a large number of samples: solubilized radioiodinated erythrocytes were electrophoresed on 14% acrylamide gels and the radioactivity determined in the haemoglobin band which migrates separately from other proteins. The major labelled protein on the mouse erythrocytes had an apparent molecular weight of 92,000, and may be analogous to Band 3 of the human erythrocyte.     

The composition of intracellular granules from the metal-accumulating cells of the common garden snail (Helix aspersa).

Certain cells in the hepatopancreas of the common garden snail (Helix aspersa) contain intracellular granules that are sites of metal-ion accumulation. These granules have been extracted and investigated by u.v. and i.r. spectroscopy, atomic-absorption spectroscopy, X-ray microanalysis, thermogravimetric analysis, enzymic assay and microanalysis. The deposits contain about 18% (w/w) water, 5% (w/w) organic matter and 76% (w/w) inorganic material of which the main components are Ca2+, Mg2+ and P2O7(4)-. The possible origin of these granules is discussed, as is their role in detoxifying heavy-metal ions.     

Pulmonary granulomas in a patient on MER therapy

A patient with metastatic melanoma developed symmetric miliary infiltrates of the lungs while receiving injections of MER into tumor containing lymph nodes of the groin. Open lung biopsy identified the pulmonary lesions as caseating epithelioid granulomas. After cessation of MER therapy, the pulmonary lesions regressed spontaneously. The possible etiology of this so-far-unreported complication of MER therapy was briefly discussed.     

ANTERIOR MEDIASTINAL TERATOMAS IN INFANTS AND CHILDREN

This report reviews the management of five pediatric patients with anterior mediastinal teratomas, and presents a discussion of symptoms, signs, and operative management of these lesions. Surgical resection was accomplished in all cases, with three of the five patients surviving. The two who died had malignant teratomas that were treated with adjunctive chemotherapy and X-ray therapy. Age at onset appears to be a significant factor in the prognosis of the disease.     

Rat cell surface antigens: Nonidentity of the H-4 and Ag-F traits

Animals partially congenic to Lewis have been bred that differ at the locus, linked to C., which controls the Ag-F antigenic trait. Skin grafts from these animals, placed on Lewis recipients, were not rejected. This result demonstrates that Ag-F does not mediate skin incompatibility and, thus, is distinct from H-4, which was defined based on a demonstrable incompatibility and which is also linked to C.