Aging: The Continuous Process From Birth To Death

“Highlighted Topics” Series Examines the Physiological Processes  Involved in Aging; Reports Published in the October-December 2003 Editions of the Journal of Applied Physiology

November 29, 2003 (Bethesda, MD) -- A special series, “Highlighted Topics on The Physiology of Aging,” appears in the October through December 2003 editions of the Journal of Applied Physiology, the flagship publication of the American Physiological Society (APS). The series examines the physiological changes associated with aging based on a systems approach, and theories of the aging process and underlying mechanisms are explored.

Two featured articles are published in the October 2003 edition:  

• The first, entitled “Bone Adaptation with Aging and Long-Term Caloric Restriction in Fischer 344 x Brown-Norway F1-hybrid Rats,” is from the study conducted by Jeremy M. LaMothe, Russell T. Hepple, and Ronald F. Zernicke, all of the University of Calgary, Calgary, Alberta, CN. Using a specific rat model and a caloric restriction paradigm, the investigators examined the effects of age and caloric restriction on bone geometry and the mechanics of the vertebrae and tibiae. They found that aging produced small changes in bone mechanics and geometry in ad libitum-fed animals, while caloric restriction effected bone’s mechanical and geometrical properties to a greater extent. Caloric restriction-induced body mass reductions accounted for changes in vertebral structural properties, but the alterations in tibial structural properties were independent of body mass. Thus, the researchers conclude that caloric restriction adversely and differently influenced axial and appendicular bones in late-middle-aged animals. Despite the salutary life-extending effects of caloric restriction, their results also offer a cautionary note suggesting that caloric restriction may have possible adverse effects on the structural and mechanical properties of bone.   

• The second report, “Effects of Aging on Cerebrovascular Tone and [Ca²⁺]_i,” examines whether cerebral artery tone and intracellular Ca²⁺ concentration ([Ca²⁺)_i] are affected by aging, using the isolated cerebral arteries of rats for investigation. The conclusions of the research team Greg G. Geary and John N. Buchholz, both from the School of Medicine, Loma Linda University, Loma Linda, CA, suggest that aging alters cerebral artery tone and [Ca²⁺]_i responses through endothelial-derived nitric oxide synthase-sensitive and insensitive mechanisms. They conclude that the combined effect of greater cerebral artery tone with less endothelium-dependent modulation may, in part, contribute to the age-dependent shift in cerebral blood flow autoregulation.

The November 2003 selected contributions include the following:  

• In a study entitled “Aging Impairs Nitric Oxide and Protacyclin - Mediation of Endothelium-Dependent Dilation in Soleus Feed Arteries,” researchers assess the notion that aging impairs endothelium-dependent vasodilation of feed arteries in the soleus muscle of rats. Such feed arteries play an integral role in control of blood flow to this muscle during exercise; with age, the ability to increase the soleus muscle’s blood flow during exercise decreases. The investigation, conducted by Christopher R. Woodman, Elmer M. Price and M. Harold Laughlin, of the Departments of Biomedical Sciences and Physiology and The Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, concludes that endothelium-dependent vasodilation, stimulated by increases in intraluminal flow and acetylcholine, was impaired in aged rats. The results also indicate that the age-related decrement endothelium-dependent vasodilation was the result of impaired release of nitric oxide and protacyclin by the endothelium in the senescent arteries. An improved understanding of the cellular mechanisms that account for age-related endothelial dysfunction may offer therapeutic approaches to ease or reverse the detrimental effects of age on skeletal muscle blood flow.

• The “Identification of Differentially Expressed Genes Between Young and Old Rat Soleus Muscle During Recovery From Immobilization-Induced Atrophy,” is the subject of an investigation conducted by J. Scott Pattison, Lillian C. Folk, Richard W. Madsen, and Frank W. Booth, all of the University of Missouri at Columbia, Columbia, MO. Utilizing immobilized hindlimbs of young and old rats to cause atrophy, then assessing age-related variation in gene expression, they found that while skeletal muscle from older rats exhibited little to no regrowth following ten days of hindlimb arrest, the muscles of the young rats returned to precontrol size within 30 days of postimmobilization. To assess candidate genes potentially responsible for the defective re-growth following atrophy in the aged rats, researchers used oligonucleotide microarrays assaying 24,000 transcripts. They found that during recovery from immobilization, young and old rats expressed 64 mRNAs differently. Real-time PCR confirmed 3 (Elfin, amphilregulin and clusterin) of the 64 new candidates whose inappropriate gene expression could play some role in the failure of old skeletal muscle to regrow to its preatrophy mass after ending immobilization.

The articles featured in the December 2003 edition are as follows:

• The study, “Long-lived Drosophila melanogaster Lines Exhibit Normal Metabolic Rates,” was conducted by Wayne A. Van Voorhies, of the Molecular Biology Program, New Mexico State University, Las Cruces, NM, and Aziz A. Khazaeli and James W. Curtsinger, both from the Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN. Their large-scale study examined the relationship between metabolic rate and longevity in the fruit fly (Drosophila melanogaster). The metabolic rates of approximately 3,000 individual fruit flies or various ages were measured in an effort to identify genes affecting longevity.

• The final study, entitled “Chronic Intermittent Hypoxia Enhances Respiratory Long-Term Facilitation in Geriatric Female Rats,” was performed by A.G. Zabka, G.S. Mitchell, E.B. Olson, Jr., and M. Behan, all of the University of Wisconsin, Madison, WI. In their study, they demonstrate that hypoxic phrenic and hypoglossal (XII)  nerve responses are similar in geriatric and young female rats. However, the expression of both phrenic and hypoglossal long-term facilitation was decreased from the responses previously observed in middle-aged female rats.

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Source: October-December 2003 editions of the Journal of Applied Physiology. The Journal is one of the 14 scientific publications published each month by the American Physiological Society (APS). 

The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.

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Editor’s Note: A copy of the research article is available in pdf format to the press. Members of the press are invited to obtain a pdf copy of the study and to interview members of the research team. To do so, please contact Donna Krupa at 703.527.7357 (direct dial), 703.967.2751 (cell) or djkrupa1@aol.com.