Editorial

The need for multiple time points in aging studies

With advancing age, a decline in the main sensory modalities including touch sensation and perception is well reported to occur. This review mainly outlines the peripheral components of touch perception highlighting ageing influences on morphological and functional features of cutaneous mechanical transducers and mechanosensitive ion channels, sensory innervation, neurotransmitters and even vascular system required to ensure efferent function of the afferent nerve fibres in the skin. This, in conjunction with effect of ageing on the skin per se and central nervous system, could explain the tactile deficit seen among the ageing population. We also discuss appropriate tools and experimental models available to study the age-related tactile decline.

Plant derived products are consumed by a large percentage of the population to prevent, delay and ameliorate disease burden; however, relatively little is known about the efficacy, safety and underlying mechanisms of these traditional health products, especially when taken in concert with pharmaceutical agents. The flavonoids are a group of plant metabolites that are common in the diet and appear to provide some health benefits. While flavonoids are primarily derived from soy, many are found in fruits, nuts and more exotic sources, e.g., kudzu. Perhaps the strongest evidence for the benefits of flavonoids in diseases of aging relates to their effect on components of the metabolic syndrome. Flavonoids from soy, grape seed, kudzu and other sources all lower arterial pressure in hypertensive animal models and in a limited number of tests in humans. They also decrease the plasma concentration of lipids and buffer plasma glucose. The underlying mechanisms appear to include antioxidant actions, central nervous system effects, gut transport alterations, fatty acid sequestration and processing, PPAR activation and increases in insulin sensitivity. In animal models of disease, dietary flavonoids also demonstrate a protective effect against cognitive decline, cancer and metabolic disease. However, research also indicates that the flavonoids can be detrimental in some settings and, therefore, are not universally safe. Thus, as the population ages, it is important to determine the impact of these agents on prevention/attenuation of disease, including optimal exposure (intake, timing/duration) and potential contraindications.

The pain and aging subfield has grown dramatically, including a 6-fold increase in publications over the last 2 decades. This subfield is based on the assumption that pain in older and younger adults differs in clinically and theoretically significant ways. If this were not the case, data from younger groups could be generalized to older persons, and the subfield would not be needed. This article considers the evidence for this assumption. Possible interpretations of the discrepant findings of age-related increases, decreases and stability in pain, including methodological limitations, challenges of gerontological research, and the possibility of nonuniform age-related variation, are discussed. Evidence is presented for several unique characteristics of geriatric pain: difficulty using Visual Analog Scales, increased vulnerability to neuropathic pain, decreased vulnerability to acute pain related to visceral pathology, prolonged recovery from tissue and nerve injury, including prolonged hyperalgesia, and differences in the relationships among psychosocial factors important in adjustment to chronic pain. However, without a theoretical framework, it is difficult to integrate these results in a heuristic manner. Further research is needed to elucidate the characteristics of geriatric pain, to examine the mechanisms for age-related patterns, and to develop and test the efficacy of age-tailored interventions.

This article reviews the emerging subfield of pain and aging, discusses the interpretation of age-related patterns in pain, and presents several avenues for future research and subfield development. This could contribute to the continued growth of this subfield.

Studies on the normal pattern of development and post-natal maturation of the recurrent laryngeal nerve in rats are scanty. The aim of the present study was to investigate the normal microscopic aspects of the recurrent laryngeal nerve myelinated fibers in the post-natal developing rat, with special attention to longitudinal morphology and lateral symmetry. Fifteen male rats were divided into experimental groups according to age 20, 55, 76, 150 and 250 days. A female group aged between 76 and 150 days was also used. Right and left RLN were studied by light microscopy at proximal, medium and distal segments and morphometric data comparisons were made between sides, segments, ages and gender. Our results showed that the left recurrent laryngeal nerves were significantly longer than the right in all ages studied and this difference increased with ageing. There was a slight decrease in the myelinated fiber number, according to proximal to distal gradient, but a significant decrease was observed only on older animals (ages 55 (both sides), 76 (left side), and 150 (left side) days). This difference was also observed for female rats (left side). No differences between ages were observed. There was an age-dependent difference on ranges and histograms form (younger animals showed a unimodal histogram while older animals showed a bimodal one), with no significant differences between segments or sides, in all groups studied. Also, no differences between males and females of the same age were observed. In conclusion, the RLN alters its morphology due to development and ageing and the present study describe normal patterns of the recurrent laryngeal nerve development in rats that can be useful for a better understanding of pathological alterations on experimental neuropathies involving the laryngeal nerves.

The aim of this study was to determine the existence of a relation between the fascicular area and total vessel area on the cervical vagus nerve of Wistar-Kyoto female rats. Animals aged 30, 180 or 360 days had their right vagus nerves prepared for epoxy resin embedding and light microscopy study. Semithin serial sections were studied every 100 μm of the longitudinal extension of the nerve. The fascicular area and the total endoneural vessel area were obtained for each nerve segment (proximal, middle and distal) and compared between segments and ages. The relation between fascicular area and endoneural vessel area was accessed by linear regression analysis and correlation coefficient calculations. No significant relationship between the two variables was detected in all nerves studied. This suggests that the entrance of blood vessels to the endoneural space is not accompanied by an increase in the fascicular area and this may have implications on the fiber density calculations since, in the presence of large vessels, this density can be underestimated if the vessel area is not discounted. The endoneural vessel area increased from proximal to distal in all groups but got smaller with ageing, suggesting that older animals may be more susceptible to nerve ischemia.