Joseph A. Knight

The biochemistry of aging

Although philosophers and scientists have long been interested in the aging process, general interest in this fascinating and highly important topic was minimal before the 1960s. In recent decades, however, interest in aging has greatly accelerated, not only since the elderly form an ever-increasing percentage of the population, but because they utilize a significant proportion of the national expenditures. In addition, many people have come to the realization that one can now lead a very happy, active, and productive life well beyond the usual retirement age. Scientifically, aging is an extremely complex, multifactorial process, and numerous aging theories have been proposed; the most important of these are probably the genomic and free radical theories. Although it is abundantly clear that our genes influence aging and longevity, exactly how this takes place on a chemical level is only partially understood. For example, what kinds of genes are these, and what proteins do they control? Certainly they include, among others, those that regulate the processes of somatic maintenance and repair, such as the stress-response systems. The accelerated aging syndromes (i.e., Hutchinson-Gilford, Werners, and Downs syndromes) are genetically controlled, and studies of them have decidedly increased our understanding of aging. In addition, C. elegans and D. melanogaster are important systems for studying aging. This is especially true for the former, in which the age-1 mutant has been shown to greatly increase the life span over the wild-type strain. This genetic mutation results in increased activities of the antioxidative enzymes, Cu-Zn superoxide dismutase and catalase. Thus, the genomic and free radical theories are closely linked. In addition, trisomy 21 (Downs syndrome) is characterized by a significantly shortened life span; it is also plagued by increased oxidative stress which results in various free radical-related disturbances. Exactly how this extra chromosome results in an increased production of reactive oxygen species is, however, only partially understood. There is considerable additional indirect evidence supporting the free radical theory of aging. Not only are several major age-associated diseases clearly affected by increased oxidative stress (atherosclerosis, cancer, etc.), but the fact that there are numerous natural protective mechanisms to prevent oxyradical-induced cellular damage speaks loudly that this theory has a key role in aging [the presence of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, among others; various important intrinsic (uric acid, bilirubin, -SH proteins, glutathione, etc.) and extrinsic (vitamins C, E, carotenoids, flavonoids, etc.) antioxidants; and metal chelating proteins to prevent Fenton and Haber-Weiss chemistry]. In addition, a major part of the free radical theory involves the damaging role of reactive oxygen species and various toxins on mitochondria. These lead to numerous mitochondrial DNA mutations which result in a progressive reduction in energy output, significantly below that needed in body tissues. This can result in various signs of aging, such as loss of memory, hearing, vision, and stamina. Oxidative stress also inactivates critical enzymes and other proteins. In addition to these factors, caloric restriction is the only known method that increases the life span of rodents; studies currently underway suggest that this also applies to primates, and presumably to humans. Certainly, oxidative stress plays an important role here, although other, as yet unknown, factors are also presumably involved. Exactly how the other major theories (i.e., immune, neuroendocrine, somatic mutation, error catastrophe) control aging is more difficult to define. The immune and neuroendocrine systems clearly deteriorate with age. (ABSTRACT TRUNCATED)

Intraarticular carcinogenesis bioassays of CoCrMo and TiAlV alloys in rats

Wear-debris powders of cobalt-chromium-molybdenum (CoCrMo) and titanium-aluminum-vanadium (TiAlV) alloys, which are widely used for orthopedic implants (eg, hip and knee prostheses), were tested for carcinogenic activity following intraarticular administration (20 mg/rat) to groups of 44 male Fischer-344 rats (Charles River Breeding Laboratories, North Wilmington, MA). Control groups received similar intraarticular injections of either a noncarcinogen (manganese powder, negative control rats) or a potent carcinogen (nickel subsulfide powder, positive control rats). The experimental groups of 8-12 rats were observed for 24 months after injection. No local tumors developed at the injection site in the negative control rats or in rats that received the CoCrMo or TiAlV powders; poorly differentiated or pleomorphic sarcomas developed at the injection site in 10 of the 12 positive control rats that were treated with nickel subsulfide. Incidences of primary tumors distant from the injection site did not differ significantly among the experimental groups. This study shows that, under experimental conditions, any carcinogenic activity of CoCrMo or TiAlV wear-debris powders is weak in comparison to nickel subsulfide. Based on this study and observations in other laboratories, intraarticular administration of test materials to rats provides a practical, reliable, and biologically relevant method for carcinogenesis testing of biomaterials used for orthopedic implants.

Spurious hypophosphatemia in a patient with multiple myeloma

We report a patient with multiple myeloma and a prolonged history of hypophosphatemia who had remained asymptomatic. Extensive evaluation for a cause, including the search for a renal tubular disorder, oncogenous osteomalacia, or a parathyroid hormone (PTH)-related protein was unproductive. Renal biopsy showed no evidence of myeloma kidney. Subsequent mixing of the immunoglobulin G (IgG) fraction from the patients serum with normal human serum, confirmed that the observed hypophosphatemia was spurious, resulting from interference of large amounts of an abnormal IgG with a standard automated laboratory assay for phosphate.

Pulmonary Histopathology of Rats Following Parenteral Injections of Nickel Chloride

To elucidate the subacute toxic reactions to parenteral administration of Ni2+, male F-344 rats were given daily injections of NiCl2 (62.5 or 125 μmol/kg, sc) for 3 to 6 weeks. Nickel accumulation was greater in lung than in the other major organs, based upon tissue analyses by electrothermal atomic absorption spectrometry. After 5 or 6 weeks of NiCl2 treatment, severe pathological changes developed in the lungs, including a) prominent hydropic and degenerative changes of the endothelium of pulmonary arteries and veins; b) marked proliferation of alveolar lining cells, affecting Type II (granular) pneumocytes; c) thickening of alveolar walls, with proteinaceous alveolar exudate; d) hyperplasia of bronchial epithelium, with cellular atypia and mitoses; and e) focal bronchial pneumonia with intrabronchial exudates. These pulmonary responses to repeated daily injections of NiCl2 were substantially different from the pathological lesions seen 24 to 72 hours after a single sc injection of NiCl2 (500 or 750 μmol/kg), which included perivascular edema, karyorrhexis and pyknosis of mononuclear cells in focal perivascular infiltrates, and mild pulmonary congestion. This study shows that the lung is a primary site of toxicity in rats following parenteral administration of NiCl2; vascular endothelial cells, Type II pneumocytes, bronchial epithelial cells, and mononuclear cells constitute the principal cellular targets for pulmonary toxicity of Ni2+.

MENETRIER'S DISEASE IN CHILDREN: Report of a Case and Review of the Pediatric Literature

A case of Menetriers disease (giant hyperplasia of the gastric mucosa) in a 2-day-old infant is presented. The lesion was primarily confined to the gastric antrum. It resulted in outlet obstruction and necessitated partial gastrectomy. The pertinent literature is critically evaluated, and probably only 2 of the 9 previously reported cases of Menetriers disease in children qualify fully.

Primary Pulmonary Hypertension in Childhood: A Report of two Brothers

We report 2 cases of primary pulmonary hypertension in brothers, 6 and 3 years old. Their lungs contained numerous plexiform vascular lesions. The literature is reviewed involving familial cases, especially those in which siblings were affected. Several of these cases lack the pathological verification necessary for acceptance as examples of plexogenic pulmonary arteriopathy.