Effects Of Age-related Changes Research Articles

Mechanical approach to aging and wrinkling of human facial skin based on the multistage buckling theory

A wrinkle formation mechanism with cutaneous aging is addressed through a mechanical calculation of linear buckling. Skin is divided into five mechanically distinct layers in this study. In general, the outer layer is stiffer than the inner layer, so buckling occurs in the outer layer against the uniform compression caused by muscle contraction. This buckling damages the skin and affects the formation of permanent wrinkles. We propose a multistage buckling theory for evaluation of the wrinkle property, namely, the specific wrinkle size and critical strain in three stages. The specific wrinkle size is derived as the wavelength of the minimum-buckling mode for infinite-length skin. A sensitivity analysis is carried out to investigate the effect of age-related changes of the mechanical parameters on the wrinkle property. We employ some aging hypotheses and prepare two sets of mechanical parameters, one for young and one for aged skin. The numerical results show that the buckling mode switch from Stage I to Stage II is the main reason why pronounced wrinkles suddenly appear in aged skin.

Maculoplasty for age-related macular degeneration: Reengineering Bruch's membrane and the human macula

Age-related macular degeneration (AMD) is the leading cause of blindness in the western world. Over the last decade, there have been significant advances in the management of exudative AMD with the introduction of anti-VEGF drugs; however, many patients with exudative AMD continue to lose vision and there are no effective treatments for advanced exudative AMD or geographic atrophy. Initial attempts at macular reconstruction using cellular transplantation have not been effective in reversing vision loss. Herein we discuss the current status of surgical attempts to reconstruct damaged subretinal anatomy in advanced AMD. We reinforce the concept of maculoplasty for advanced AMD, which is defined as reconstruction of macular anatomy in patients with advanced vision loss. Successful maculoplasty is a three-step process that includes replacing or repairing damaged cells (using transplantation, translocation or stimulation of autologous cell proliferation); immune suppression (if allografts are used to replace damaged cells); and reconstruction or replacement of Bruch's membrane (to restore the integrity of the substrate for proper cell attachment). In the current article we will review the rationale for maculoplasty in advanced AMD, and discuss the results of initial clinical attempts at macular reconstruction. We will then discuss the role of Bruch's membrane damage in limiting transplant survival and visual recovery, and discuss the effects of age-related changes within human Bruch's membrane on the initial attachment and subsequent proliferation of transplanted cells. We will discuss attempts to repair Bruch's membrane by coating with extracellular matrix ligands, anatomic reconstitution of the inner collagen layer, and the effects of Bruch's membrane reconstruction of ultrastuctural anatomy and subsequent cell behavior. Lastly, we will emphasize the importance of continued efforts required for successful maculoplasty.

Anisotropy of age-related toughness loss in human cortical bone: A finite element study

A mechanistic understanding of the role of bone quality on fracture processes is essential for determining the underlying causes of age-related changes in the mechanical response of the human bone. In this study, a previously developed cohesive finite element model was used to investigate the effects of age-related changes and the orientation of crack growth on the toughening behavior of human cortical bone. The change in the anisotropy of toughening mechanisms with age was also studied. Finite element method (FEM) simulations showed that the initiation toughness decreased by 3% and 8%/decade for transverse and longitudinal crack growth, respectively. In contrast, fracture resistance curve slope for transverse and longitudinal crack growth decreased by 2% and 3%/decade, respectively. Initiation fracture toughness values were higher for the transverse than for the longitudinal for a given age. On the other hand, propagation fracture toughness values were higher for longitudinal than for transverse crack growth for a given age. With respect to age, the toughness ratio for crack initiation decreased by 6%/decade, but that for propagation showed almost no change (less than 1%). In light of these findings, an analytical model evaluating the crack arresting feature of cement lines, is proposed to explain the factors that determine crack penetration into osteons or its deflection by cement lines.

Bruch Membrane Aging Alters the Gene Expression Profile of Human Retinal Pigment Epithelium

We investigated the effects of age-related changes within the Bruch membrane on the gene expression profile of the RPE. Immortalized human ARPE-19 cells were seeded onto acellular human Bruch membrane from younger and older donors and harvested 72 hr later; total RNA was isolated and the gene expression profile was determined using the Affymetrix Human Genome U95A gene chip. Twelve genes were upregulated and 8 genes were downregulated with Bruch membrane aging; RT-PCR confirms that Bruch membrane aging upregulates genes in RPE cells encoding for transforming growth factor alpha and downregulates genes for vitronectin and the membrane transporter ABCC5. The role of these changes in the pathogenesis of age-related diseases such as macular degeneration remains to be elucidated.

Effect Of Segmental Growth On The Force Construction Of Pedaling As A Function Of Speed

Motor skill acquisition is characterized by improvements in the application of taskappropriate forces. Muscular and non-muscular forces act in concert to produce a resultant force that complies with the goal of the task. Non-muscular forces are directly dependent on the anthropometry of the performer. If the resultant force to be produced is the same between performers, inter-participant differences in anthropometry might require muscular adjustments to changing non-muscular forces. This effect might depend on movement speed as it also influences non-muscular forces. Differences in the application of muscular forces may therefore represent functional adjustments needed to account for changes in anthropometry. Such adjustments could pose confounds if age-related differences in muscular forces are to be attributed to features of the neuro-motor system. PURPOSE The purposes of this study were to determine (a) the effect of age-related changes in anthropometry on the application of muscular forces and (b) how this effect depends on movement speed. METHODS A torque-driven biomechanical model of two-legged pedaling was developed. The model tracked experimental kinematics and forces obtained from an experienced adult cyclist who signed informed consent before participating. The anthropometrics of the model were modified according to Jensen (1989). Segmental mass proportions, center of mass locations, and radii of gyration were scaled to children's dimensions (5, 7.5, and 10 years of age). Pedaling at 60 rpm and 120 rpm at a moderate resistance was simulated. The forces to be produced were scaled in proportion to body mass, and the kinematics were held constant across all simulations. This procedure enabled us to isolate the effect of differences in anthropometry on muscular force application. The muscular contribution to crank power was compared across age groups using ANOVAs (alpha=.05) and effect sizes (ES). RESULTS Relative changes in anthropometry between 5 and 10 years of age did not significantly influence muscular power production neither at 60 rpm nor at 120 rpm (p>.05). In addition, the effect sizes quantifying differences between age groups were small (mean ES=0.16). CONCLUSIONS The results demonstrate that during pedaling at a moderate resistance, changing anthropometry during childhood does not influence the force construction in pedaling over a broad range of movement speeds. It can therefore be concluded that during pedaling at these cadences, age-related differences in muscular force application can be attributed to features of the neuro-motor system. Supported by the National Science Foundation under Grant 9986221

Effect Of Segmental Growth On The Force Construction Of Pedaling As A Function Of Speed

Motor skill acquisition is characterized by improvements in the application of taskappropriate forces. Muscular and non-muscular forces act in concert to produce a resultant force that complies with the goal of the task. Non-muscular forces are directly dependent on the anthropometry of the performer. If the resultant force to be produced is the same between performers, inter-participant differences in anthropometry might require muscular adjustments to changing non-muscular forces. This effect might depend on movement speed as it also influences non-muscular forces. Differences in the application of muscular forces may therefore represent functional adjustments needed to account for changes in anthropometry. Such adjustments could pose confounds if age-related differences in muscular forces are to be attributed to features of the neuro-motor system. PURPOSE The purposes of this study were to determine (a) the effect of age-related changes in anthropometry on the application of muscular forces and (b) how this effect depends on movement speed. METHODS A torque-driven biomechanical model of two-legged pedaling was developed. The model tracked experimental kinematics and forces obtained from an experienced adult cyclist who signed informed consent before participating. The anthropometrics of the model were modified according to Jensen (1989). Segmental mass proportions, center of mass locations, and radii of gyration were scaled to children's dimensions (5, 7.5, and 10 years of age). Pedaling at 60 rpm and 120 rpm at a moderate resistance was simulated. The forces to be produced were scaled in proportion to body mass, and the kinematics were held constant across all simulations. This procedure enabled us to isolate the effect of differences in anthropometry on muscular force application. The muscular contribution to crank power was compared across age groups using ANOVAs (alpha=.05) and effect sizes (ES). RESULTS Relative changes in anthropometry between 5 and 10 years of age did not significantly influence muscular power production neither at 60 rpm nor at 120 rpm (p>.05). In addition, the effect sizes quantifying differences between age groups were small (mean ES=0.16). CONCLUSIONS The results demonstrate that during pedaling at a moderate resistance, changing anthropometry during childhood does not influence the force construction in pedaling over a broad range of movement speeds. It can therefore be concluded that during pedaling at these cadences, age-related differences in muscular force application can be attributed to features of the neuro-motor system. Supported by the National Science Foundation under Grant 9986221

Effect of Age-Related Changes in Gastric Physiology on Tolerability of Medications for Older People

Studies specifically examining the effect of age upon the stomach are limited and frequently uncontrolled for the high prevalence of Helicobacter pylori in this age group. Age-related changes in gastric physiology such as reduced mucosal protection, gastric blood flow and impaired repair mechanisms may all impact upon gastrointestinal adverse effects and how older people tolerate medicines. Understanding how the upper gastrointestinal tract changes with advancing age could allow interventions that lead to more appropriate prescribing for older people, potentially reduce adverse effects, increase compliance with treatment regimens, and may allow older people to take medications that they would not otherwise tolerate. This review emphasises how the stomach changes with age, and how understanding this will aid clinicians when prescribing medications with potential gastrointestinal adverse effects to older people.

Age differences in orbitofrontal activation: an fMRI investigation of delayed match and nonmatch to sample

Several investigations have suggested that the orbitofrontal cortex (OFC) may be particularly vulnerable to the effects of age-related changes. We recently reported behavioral data indicating greater age differences in orbitofrontal tasks when directly compared to tasks tapping dorsolateral prefrontal functions. The present study was designed to investigate the neural underpinnings of age differences in OFC functioning. Event-related functional magnetic resonance imaging (fMRI) was performed during delayed match and nonmatch to sample tasks, previously shown to differentially activate medial and lateral OFC in young adults. Sixteen healthy younger [age = 26.7(5.6)] and 16 healthy older individuals [age = 69.1 + 5.6] with similar levels of education and general cognitive functioning participated in the experiment. Participants chose the stimulus from a pair of stimuli matching a previously viewed target (match to sample) or chose the nontarget item (nonmatch to sample) depending upon a trial-specific instruction word. Consistent with previous studies, SPM99 analyses of the younger age group revealed activation for medial OFC regions during the match task compared to the nonmatch task and lateral OFC activation during the nonmatch task compared to the match task. In contrast, older adults showed prefrontal activation only during the match relative to the nonmatch task and posterior temporal and limbic involvement during the nonmatch relative to the match task. Between-group analyses confirmed within-group results suggesting differential age-related recruitment of prefrontal regions when performing match and nonmatch tasks. Results suggest that OFC recruitment during these cognitive tasks changes with age and should be evaluated within the context of other prefrontal subregions to further define differential age effects on frontal functions.

Creating Text for Older Audiences

Creating Text for Older Audiences

Attention and the control of posture and gait: a review of an emerging area of research.

Research on the relationship between attention and the control of posture and gait is a new and expanding area with studies on young adults revealing the role of cognitive factors in the control of balance during standing and walking. The use of dual task paradigms to examine the effect of age related changes in attentional requirements of balance control and age-related reductions in stability when performing a secondary task has shown that these are important contributors to instability in both healthy and balance-impaired older adults. The attentional demands of balance control vary depending on the complexity of the task and the type of secondary task being performed. New clinical assessment methods incorporating dual-task paradigms are helpful in revealing the effect of disease (e.g. Parkinson's disease) on the ability to allocate attention to postural tasks and appear to be sensitive measures in both predicting fall risk and in documenting recovery of stability.

The Effect of Age-Related Changes and Loss of Molar Teeth on Hippocampal Pyramidal Cells in Senescence-Accelerated Mouse (SAM)

The Effect of Age-Related Changes and Loss of Molar Teeth on Hippocampal Pyramidal Cells in Senescence-Accelerated Mouse (SAM)

Heart rate variability during sleep: effects of aging and cardiac denervation

Cardiac vagal predominance increases RR interval (RR) and RR high frequency (HF) variability during non rapid-eye- movement sleep (non-REM, stage I-IV) in young subjects. Aging suppresses deep sleep but effects of age-related changes in sleep architecture on RR are unknown. Whether mechanical effects of changes in the breathing pattern on the sinus node during sleep affect RR variability is unclear. Methods: Polygraphic sleep recordings, RR and RR spectral profiles were determined in 8 young (22.5±3.3 yr.) and 8 older healthy volunteers (55.0±7.3 yr.). HF oscillations in RR of 8 cardiac denervated transplant recipients (HTR) determined mechanical effects of respiration on the sinoatrial node during sleep. Transition from wake to non-REM sleep increased RR in young and older subjects and increased the HF variability of RR in the young (p<0.05) but not in the older subjects. Older subjects disclosed a faster RR (p<0.01) and a lower HF variability (p<0.05) during non-REM sleep than the young subjects. Aging did not affect light and REM sleep but decreased deep sleep (stage IV) from 39±23 min to 6±6 min (p<0.001). Reduction in sleep stage IV with aging blunted the increase in RR and in RR HF variability during non-REM sleep (r>+0.55, p<0.05). Transition from wake to non-REM sleep doubled the markedly reduced HF variability of RR in the HTR (p<0.05). Conclusion: Disappearance of deep sleep with aging impairs nocturnal increase in cardiac vagal activity. Mechanical effects of changes in breathing pattern during sleep favor increases in HF oscillations of RR during non-REM sleep.

Effects of Aging and Cardiac Denervation on Heart Rate Variability During Sleep

Cardiac vagal predominance increases the RR interval and RR high-frequency (HF) variability during non-rapid eye movement (non-REM) sleep (stages I through IV) in young subjects. Aging suppresses deep sleep, but effects of age-related changes in sleep architecture on RR are unknown. Whether mechanical effects of changes in the breathing pattern on the sinus node during sleep affect RR variability is unclear. Polygraphic sleep recordings and RR and RR spectral profiles were determined in 8 young (22.5+/-3.3 years) and 8 older (55.0+/-7.3 years) healthy volunteers. HF oscillations in RR of 8 cardiac-denervated heart transplant recipients determined mechanical effects of respiration on the sinoatrial node during sleep. Transition from wakefulness to non-REM sleep increased the RR interval in young and older subjects and increased the HF variability of RR in the young (P:<0.05) but not in the older subjects. Older subjects disclosed a faster RR (P:<0.01) and a lower HF variability (P:<0.05) during non-REM sleep than the young subjects. Aging did not affect light and REM sleep but decreased deep sleep (stage IV) from 39+/-23 to 6+/-6 minutes (P:<0.001). Reduction in sleep stage IV with aging blunted the increase in RR and in RR HF variability during non-REM sleep (r>0.55, P:<0.05). Transition from wakefulness to non-REM sleep doubled the markedly reduced HF variability of RR in the heart transplant recipients (P:<0.05). Disappearance of deep sleep with aging impairs nocturnal increase in cardiac vagal activity. Mechanical effects of changes in breathing pattern during sleep favor increases in HF oscillations of the RR interval during non-REM sleep.

The Effect of Age-Related Changes and Loss of Molar Teeth on Learning and Memory in Senescence-Accelerated Mouse (SAM)

The Effect of Age-Related Changes and Loss of Molar Teeth on Learning and Memory in Senescence-Accelerated Mouse (SAM)

Aging and sensory senescence.

The aging process typically is associated with decline in function for the various senses. A decline in sensory ability may simulate an intellectual decline that is not present. Sensory decline can lead to depression, social isolation, and even to hallucinations. I reviewed the medical literature via computer, focusing on recent findings. Sensory changes with aging are common yet often go unrecognized and untreated. Declines in sensory function often reflect the combined effect of age-related changes in both the sensory organ and the central nervous system processing of sensory information. Combinations of defects in several sensory modalities are often found in the older individual. Correct diagnosis is important for management so that correctable causes of sensory decline are not overlooked.

Modeling the mechanical behavior of vertebral trabecular bone: Effects of age-related changes in microstructure

Age-related reductions in the thickness and number of trabeculae in vertebral trabecular bone have been documented by several workers, yet the relative effects of these changes on mechanical properties are not known. We developed a two-dimensional model of human vertebral trabecular bone and investigated its mechanical behavior using finite element analysis. The stress-strain behavior, failure mode, and strain distributions predicted using the model were consistent with those observed for vertebral trabecular bone under compressive loading. Random reductions in the number of trabeculae reduced the modulus and strength of the models two to five times more than uniform reductions in the thickness of trabeculae that caused the same loss of bone volume. For example, randomly removing longitudinal trabeculae to achieve a reduction in density of 10% reduced the strength by approximately 70%, whereas removing the same amount of bone by uniformly reducing the thickness of the longitudinal trabeculae only reduced the strength by approximately 20%. For a simulation of aged bone, in which the thickness and number of trabeculae were reduced concurrently, the strength was 23% of its intact (“young”) value. When the bone mass of the aged model was restored to its intact level by increasing the thickness but not the number of trabeculae, the strength increased by 60%, but was still only 37% of its intact value. These combined findings, based on a two-dimensional, idealized model of vertebral trabecular bone, illustrate the importance of maintaining trabecular number and suggest that it may not be possible to restore bone strength following a period of advanced bone loss if a substantial number of trabeculae have been resorbed. Thus, until treatments exist that can increase trabecular number, the most effective treatment strategy is to prevent the degradation of bone strength by maintaining the number of trabeculae at a healthy level.

Age-Related Changes in Rat Interstitial Matrix Hydration and Serum Proteins

Measurements of effects of age-related changes on loose connective tissue protein concentrations and water are lacking. Tissue hydration is an important determinant of tissue protein diffusion coefficients and hydraulic conductivity. Sprague-Dawley rats (ages 11, 30, 57, and 89 wk) were anesthetized. Blood and mesenteric tissue samples were taken. Tissue water content was determined by microgravimetric technique. Protein content was determined by electrophoresis. Tissue hydration decreased 18% between 11 and 89 wk with one-half the fall occurring between 57 and 89 wk. Tissue albumin concentration decreased 37% between 11 and 89 wk. Serum albumin increased 22% between 11 and 30 wk and then decreased by 37% to 1.4 g/dl in 89-wk rats. Serum total protein concentration increased by 13% between 11 and 89 wk, whereas tissue total protein concentration decreased 30% with age to 1.9 g/dl at 89 wk. The results suggest that age-related tissue dehydration is due, in part, to a shift in the colloid osmotic pressure components of Starling equilibrium favoring fluid reabsorption.

Recent advances in geriatric psychopharmacology.

Psychopharmacotherapy of the elderly must take into account the effects of age-related changes in the structure and function of the brain and various organs. In general, older people are more sensitive than young people to both the therapeutic and toxic effects of psychotropic medications, necessitating lower doses and longer dosage intervals. This holds true for the treatment of 5 major types of psychiatric illness (depression, bipolar disorder, anxiety, psychotic disorders and dementia). The tricyclic antidepressants, although efficacious, inexpensive, and backed by 30 years of experience, are less well tolerated by the elderly than are newer antidepressants such as the selective serotonin uptake inhibitors. Problems with monoamine oxidase (MAO) inhibitors, including orthostatic hypotension and restrictions in diet and other medication use, have been overcome by the advent of reversible selective inhibitors of MAO-A, but the efficacy of these in the elderly has yet to be proven in clinical trials. Lithium remains the mainstay for the treatment of bipolar disorder. However, careful dosing and monitoring of plasma lithium concentrations are required in the elderly due to changes in pharmacokinetics and pharmacodynamics which make older patients very sensitive to the toxic effects of this medication. Similarly, age-related changes in the pharmacokinetics and pharmacodynamics of the benzodiazepines, the most frequently prescribed medications for anxiety in the elderly, result in recommendations for lower doses and preferential use of those agents metabolised by conjugation (e.g. oxazepam). Buspirone, a partial serotonin 5-HT1A-agonist which is better tolerated than benzodiazepines in the elderly, may be used as an alternative. The elderly are extremely sensitive to extrapyramidal adverse effects which the typical antipsychotics (neuroleptics) exhibit to varying extents. The selection of a suitable agent for the treatment of a psychotic disorder should be based upon the adverse effect profile of the drug and the specific symptoms and situation of the patient. The newer atypical antipsychotics, clozapine and risperidone, have yet to be well-studied in the elderly. Dementia, exemplified by Alzheimer's disease, is almost exclusively an illness of the elderly. Only one medication, tacrine, has been approved for its treatment, based on extensive basic research and positive results of several clinical trials. Its long-term benefits have yet to be determined and it has several adverse effects, including a tendency to increase liver enzymes to the extent that the medication has to be discontinued.(ABSTRACT TRUNCATED AT 400 WORDS)

Psychophysics of Reading--x. Effects of Age-related Changes in Vision

This study examined the influence of age-related changes in vision on reading performance. Maximum reading speed was measured in groups of young (n = 16, mean age 21.6 years) and old (n = 14, mean age 68.3 years) subjects, all with acuities of 20/32 or better. A psychophysical procedure was used for measuring reading speed that has proven reliable and sensitive to visual factors in previous research. Data were collected for character sizes ranging from .15 degrees to 12 degrees. Research revealed that old subjects who were free of eye disease read as fast as the young subjects for character sizes ranging from .3 degrees to 1.0 degrees. This is the range in which reading speed is maximum for young subjects. Research also revealed that old subjects showed a deficit when reading text composed of very small or very large characters. Their speeds dropped to about 70% of the young adult speeds. These deficits may be due to age-related losses in visual contrast sensitivity.

Onset of symptoms of rheumatoid arthritis in relation to age, sex and menopausal transition : J. Rheumatol. 1990 17/12 (1620–1622)

In a population of 564 patients with rheumatoid arthritis (RA), the onset of symptoms has been studied in relation to age, sex and last menstrual period for women. Median age of menopause was 49 years (3rd percentile: 32 years and 97th percentile: 56 years). Median age of first symptoms was 45 years in women and 50 in men. The individual interval between menopause and first symptoms has a Gaussian distribution with mean at time 0, implying that the average woman develops the first symptoms at the time of her menopause. The F:M ratio of all patients was 2.3; with increasing age the F:M ratio decreased from 3.7 before 30 years of age to 1 after the 6th decade of life, with a peak at the age of 40-44 years. A possible effect of age related changes in sex hormone levels on the pathogenesis of RA is suggested.