Chondrocyte phenotypes on different extracellular matrix monolayers.

Chondrocytes undergo a process of dedifferentiation in monolayer culture that is characterized by a transition to a fibroblast-like phenotype. This behavioral change poses a challenge for tissue-engineered cartilage constructs, as approaches using autologous cells require expansion in vitro. Because chondrocytes express a variety of integrin receptors specific to different adhesive proteins, we hypothesized that chondrocytes expanded on various underlying protein monolayers would have different phenotypic responses. Bovine articular chondrocytes were cultured for up to 2 weeks on tissue culture plastic, fibronectin, collagen type I or collagen type II substrate in the presence or absence of ascorbate. Contrary to our hypothesis, the extracellular matrix protein substrates used in this study did not significantly alter the changes in chondrocyte morphology, gene expression, matrix formation, or cytoskeletal organization. Cells on all substrates assembled equivalent matrices, which may have subsequently regulated cell behavior. In cultures with ascorbate, populations of round and spread cells emerged after 1 week, with round cells expressing collagen type II and the differentiated phenotype and spread cells dedifferentiating. In cultures without ascorbate, chondrocytes rapidly adhered and spread onto organized fibronectin matrices via the alpha5beta1 integrin, which has been associated with survival and proliferation of chondrocytes in vitro. These findings indicate that expanding chondrocytes on protein monolayers may not be an effective solution to preventing dedifferentiation and improving autologous chondrocyte transplantation.

Testosterone supplementation improves spatial and verbal memory in healthy older men.

OBJECTIVE: To determine the relationship between exogenous testosterone administration and cognitive abilities in a population of healthy older men. BACKGROUND: Serum levels of total and bioavailable testosterone gradually decrease with age in men and are associated with reductions in muscle mass, osteoporosis, decreased sexual activity, and changes in cognition. METHODS: Twenty-five healthy, community-dwelling volunteers, aged 50 to 80 years, completed a randomized, double-blind, placebo-controlled study. Participants received weekly intramuscular injections of either 100 mg testosterone enanthate or placebo (saline) for 6 weeks. Cognitive evaluations were conducted at baseline, week 3, and week 6 of treatment by use of a battery of neuropsychologic tests. RESULTS: Circulating total testosterone was raised an average of 130% from baseline at week 3 and 116% at week 6 in the treatment group. Because of aromatization of testosterone, estradiol increased an average of 77% at week 3 and 73% at week 6 in the treatment group. Significant improvements in cognition were observed for spatial memory (recall of a walking route), spatial ability (block construction), and verbal memory (recall of a short story) in older men treated with testosterone compared with baseline and the placebo group, although improvements were not evident for all measures. CONCLUSIONS: The results suggest that short-term testosterone administration enhances cognitive function in healthy older men. However, it remains unclear whether these improvements in cognition are attributable to increased testosterone or estradiol levels, or both. The potential role of testosterone vs its metabolites on cognition requires further research.

Hypothalamic pituitary adrenocortical and sympathetic nervous system responses to the cold pressor test in Alzheimer's disease.

BACKGROUND: Increased basal activity of the hypothalamic-pituitary-adrenocortical (HPA) axis has been repeatedly demonstrated in Alzheimer's disease (AD), and some studies suggest increased basal activity of the sympathetic nervous system (SNS) in this disorder; however, the effects of AD on HPA axis or SNS responses to a standardized aversive stressor have not been examined. The neuroendocrine response to aversive stress may be relevant to the pathophysiology of AD. METHODS: Plasma adrenocorticotropic hormone (ACTH), cortisol, norepinephrine (NE), and epinephrine responses to a 1-min cold pressor test (CPT) were measured in nine medically healthy AD outpatients (age 76 +/- 2 years) and nine age- and gender-matched medically healthy cognitively normal older subjects (age 76 +/- 1 year). RESULTS: The cortisol response to CPT was increased in the AD group but the ACTH response did not differ between groups. Basal NE concentrations were higher in the AD group. Although NE responses to CPT did not differ between groups, the blood pressure response to CPT was higher in the AD subjects. CONCLUSIONS: These results suggest increased HPA axis responsiveness to CPT at the level of the adrenal cortex in AD. The results also suggest increased basal sympathoneural activity and increased cardiovascular responsiveness to sympathoneural stimulation in AD under the conditions of this experimental protocol. Increased SNS stimulatory modulation of the adrenal cortex is a possible mechanism contributing to the observed enhanced cortisol response to CPT in these AD subjects.

Effects of advanced aging on plasma catecholamine responses to the cold pressor test.

Increased basal norepinephrine (NE) concentrations have been demonstrated repeatedly in human aging, but these studies have included almost exclusively "early aging" subjects younger than age 75. We asked if "advanced aging" (over age 80) enhanced the effects of early aging on plasma NE and epinephrine (EPI) concentrations at rest and in response to the cold pressor test (CPT). Eight medically well, cognitively intact advanced aging subjects (84.4+/-0.9 years), 28 medically well cognitively intact early aging subjects (70.3+/-1.3 years), and 19 medically well young subjects (25.4+/-0.9 years) were studied. Both basal NE and the acute NE increase after CPT were significantly higher in advanced aging than in either early aging or young subjects. Plasma EPI concentrations were higher in the advanced aging group than in the other groups and an acute plasma EPI increase after CPT occurred only in the advanced aging group. These results suggest specific effects of advanced aging on both the sympathoneural and sympathoadrenomedullary components of the sympathetic nervous system.

Cerebrospinal fluid epinephrine in Alzheimer's disease and normal aging.

Central nervous system (CNS) adrenergic systems are involved in regulation of behavior and blood pressure. The effects of Alzheimer's disease (AD) and normal aging on resting CNS adrenergic activity were estimated by measuring cerebrospinal fluid (CSF) epinephrine (EPI) concentrations in 74 persons with AD, 42 cognitively normal healthy older persons, and 54 healthy young persons. The responsiveness of CSF EPI to the alpha-2 adrenergic antagonist yohimbine and the alpha-2 adrenergic agonist clonidine was measured in smaller subject groups. Resting CSF EPI was higher in AD than in older or young subjects, and increased with dementia severity in AD subjects. There was no relationship between resting CSF EPI and blood pressure. CSF EPI increased following yohimbine in AD and older subjects but not in young subjects. CSF EPI was unaffected by clonidine in all subject groups. The agitation increase following yohimbine was substantially greater in AD subjects than in older or young subjects. CNS adrenergic activity seems increased in AD, may further increase as AD progresses, and may be involved in the pathophysiology of agitation.

Effects of Alzheimer's disease severity on cerebrospinal fluid norepinephrine concentration.

OBJECTIVE: Although loss of noradrenergic neurons in the locus ceruleus has been consistently demonstrated postmortem in Alzheimer's disease, several small studies suggest that indices of central noradrenergic activity increase with the severity of Alzheimer's disease in living patients. The authors estimated the effect of Alzheimer's disease severity on central noradrenergic activity by comparing the CSF norepinephrine concentrations of subjects with Alzheimer's disease in earlier and advanced stages. The effect of normal aging on CSF norepinephrine also was determined. METHOD: Lumbar punctures were performed in 49 subjects with Alzheimer's disease of mild or moderate severity, 25 subjects with advanced Alzheimer's disease, 42 normal older subjects, and 54 normal young subjects. Advanced Alzheimer's disease was defined prospectively by a Mini-Mental State score of less than 12. Norepinephrine was measured by radioenzymatic assay. RESULTS: CSF norepinephrine concentration was significantly higher in the patients with advanced Alzheimer's disease (mean = 279 pg/ml, SD = 122) than in those with mild to moderate severity (mean = 198 pg/ml, SD = 89), normal older subjects (mean = 219 pg/ml, SD = 88), or normal young subjects (mean = 154 pg/ml, SD = 53). CSF and plasma norepinephrine levels and mean arterial blood pressure all were higher in the older subjects than in the young subjects. CONCLUSIONS: Despite the loss of locus ceruleus neurons in Alzheimer's disease, the aging-associated high concentration of CSF norepinephrine is retained in the earlier stages of Alzheimer's disease and increases further as the disease progresses. Increased brain noradrenergic activity may contribute to the agitated behaviors or cognitive deficits of patients with advanced Alzheimer's disease.