Toward defining the preclinical stages of Alzheimer's disease: recommendations from the National Institute on Aging-Alzheimer's Association workgroups on diagnostic guidelines for Alzheimer's disease.

The pathophysiological process of Alzheimer's disease (AD) is thought to begin many years before the diagnosis of AD dementia. This long "preclinical" phase of AD would provide a critical opportunity for therapeutic intervention; however, we need to further elucidate the link between the pathological cascade of AD and the emergence of clinical symptoms. The National Institute on Aging and the Alzheimer's Association convened an international workgroup to review the biomarker, epidemiological, and neuropsychological evidence, and to develop recommendations to determine the factors which best predict the risk of progression from "normal" cognition to mild cognitive impairment and AD dementia.

Developing a national strategy to prevent dementia: Leon Thal Symposium 2009.

Among the major impediments to the design of clinical trials for the prevention of Alzheimer's disease (AD), the most critical is the lack of validated biomarkers, assessment tools, and algorithms that would facilitate identification of asymptomatic individuals with elevated risk who might be recruited as study volunteers. Thus, the Leon Thal Symposium 2009 (LTS'09), on October 27-28, 2009 in Las Vegas, Nevada, was convened to explore strategies to surmount the barriers in designing a multisite, comparative study to evaluate and validate various approaches for detecting and selecting asymptomatic people at risk for cognitive disorders/dementia. The deliberations of LTS'09 included presentations and reviews of different approaches (algorithms, biomarkers, or measures) for identifying asymptomatic individuals at elevated risk for AD who would be candidates for longitudinal or prevention studies.

Eyes on the prize: federal Alzheimer's research effort aims to facilitate interventions.

The public Alzheimer's disease (AD) research enterprise began in earnest in the mid-1970s with the creation by Congress of the National Institute on Aging at the National Institutes of Health. Today, AD research is a maturing field of study, with federal effort seeking to encourage the creativity and insights of individual investigators, and targeting special areas for emphasis. It is inspired by the legacy of our friend and colleague Leon Thal, whose innovative and collaborative approach to scientific research serves as a guidepost as we move toward the discovery of new and effective ways to prevent AD or slow its progression.

Elevated levels of inducible heat shock 70 proteins in human brain.

Differential expression of heat shock genes can modulate protein folding and stress-related cell death. There have been no comparisons of their levels of expression in animals and humans. Levels of expression of heat shock 70 genes in human brain were compared to levels in non-stressed and heat-stressed brain of rat.

The future of aging therapies.

Advances in understanding aging processes and their consequences are leading to the development of therapies to slow or reverse adverse changes formerly considered to be "normal" aging and processes that underlie multiple age-related conditions. Estimating the effectiveness of candidate aging therapies, whose effects on human aging may require many years to determine, is a particular challenge. Strategies for identifying candidate interventions can be developed through multiple approaches, including the screening of molecular targets and pathways in vitro and in animal models, informed as well by evidence from human genetic and epidemiologic data.

Alzheimer's disease. Hope for the future.

It has been only two decades since researchers discovered that most "senile dementia" is the result of a specific disease process, Alzheimer's disease (AD), and not an inevitable consequence of aging. In these 20 years, scientists have accumulated an extraordinary body of research. Until recently, preventing or curing AD was considered, at best, a distant possibility.

Lesioning of the inferior olive using a ventral surgical approach. Characterization of temporal and spatial astrocytic responses at the lesion site and in cerebellum.

Activated astrocytes, intrinsic components of both local and remote (axonal target regions) central nervous system injury responses, are now recognized as active metabolic and regulatory mediators in many neurological disorders. To further define these responses, we devised a new ventral surgical approach to unilaterally lesion the inferior olivary nuclear complex, which has a single predominant remote target, the cerebellum. Activated astrocyte number, volume, and density, as well as the total volume of brainstem involved in the astrocytic response, all peaked at postlesion day (pld) 4, returning toward, but not to, unoperated control values at pld 24 (p < 0.

Differential expression of heat shock 70 proteins in primary cultures from rat cerebellum.

While a number of studies have described the heat shock response in established cell lines and in primary cultures of cells derived from the nervous system, there has been no systematic analysis comparing expression and localization of the inducible heat shock 70 (hsp70) proteins and the constitutively synthesized members of the family (hsc70) in neurons and glia. In the present communication, we utilized specific probes to compare the expression of hsp70 and hsc70 mRNAs and proteins in two types of primary cultures, astroglial and neuro-astroglial, from postnatal rat cerebellum. Conditions were adjusted to maintain physiological numbers of microglia in both types of culture, and cultures were analyzed at a number of different time points following a precisely defined heat shock.

Heat-shock 70 messenger RNA levels in human brain: correlation with agonal fever.

Systematic review of antemortem clinical information on randomly selected Alzheimer disease (AD) patients revealed that approximately 40% of the patients had a recorded fever of > or = 39.2 degrees C at or near death. Using isolation and quantitation techniques appropriate for analysis of human brain mRNAs, we found that low levels of inducible heat-shock protein 70 (hsp70) mRNAs were present in cerebellum of afebrile AD patients and that mRNA levels were usually lower in two brain regions affected in AD, i.

Developmental characterization of thymosin beta 4 and beta 10 expression in enriched neuronal cultures from rat cerebella.

The beta 4 and beta 10 thymosins are G-actin binding proteins that exhibit complex patterns of expression during rat cerebellar development. Their expression in vivo is initially high in immature granule cells and diminishes as they migrate and differentiate, ceasing altogether by postnatal day 21. Thymosin beta 4 is present in a subset of glia throughout postnatal development, and its synthesis is also induced in maturing Bergmann glia.

Cell size and the heat-shock response in rat brain.

The expression of mRNAs encoding two members of the heat-shock protein 70 family, the constitutively-expressed heat-shock cognate (hsc70) mRNA and the strictly heat-inducible (hsp70) mRNA, was quantitated in cerebellar and hippocampal cells of rats 3 h after amphetamine-induced or heat-induced hyperthermia. Intracellular heat-shock mRNA levels in specific cell types were compared with those of total polyadenylic acid [poly(A)] mRNA or 18S rRNA in the same cell type. Levels of poly(A) mRNAs, 18S rRNAs, and hsc70 mRNAs were highest in large neurons and lowest in glia.

Selective postmortem degradation of inducible heat shock protein 70 (hsp70) mRNAs in rat brain.

1. Altered mRNA levels in postmortem brain tissue from persons with Alzheimer's disease (AD) or other neurological diseases are usually presumed to be characteristic of the disease state, even though both agonal state (the physiological state immediately premortem) and postmortem interval (PMI) (the time between death and harvesting the tissue) have the potential to affect levels of mRNAs measured in postmortem tissue. Although the possible effect of postmortem interval on mRNA levels has been more carefully evaluated than that of agonal state, many studies assume that all mRNAs have similar rates of degradation postmortem.

Anomalous binding of radiolabeled oligonucleotide probes to plaques and tangles in Alzheimer disease hippocampus.

Several reports indicate that Alzheimer disease (AD) brain contains elevated levels of heat shock 70 proteins. To determine the cellular localization of the heat shock 70 mRNAs, specific oligonucleotide probes were in situ hybridized to AD and control brains. When oligonucleotides were in situ hybridized to brain sections with no AD neuropathology, hybridization was cell-specific and prior ribonuclease (RNase) treatment of adjacent sections resulted in no hybridization signal.

Effects of thymosin beta 4 and thymosin beta 10 on actin structures in living cells.

The beta-thymosins are a family of small proteins originally isolated from the thymus. Recently, two of the major mammalian isoforms, thymosin beta 4 (T beta 4) and thymosin beta 10 (T beta 10), are identified as significant actin monomer sequestering proteins which may be involved in regulating actin filament assembly. To study the cellular function of beta-thymosins, we have used isoform-specific antibodies to determine their concentration and intracellular distribution, and examined the effects of inducing overexpression of T beta 4 and T beta 10 on actin filament structures.

Alterations in actin-binding beta-thymosin expression accompany neuronal differentiation and migration in rat cerebellum.

The beta 4- and beta 10-thymosins, recently identified as actin monomer-sequestering proteins, are developmentally regulated in brain. Using specific mRNA and protein probes, we have used in situ hybridization and immunohistochemical techniques to investigate the distribution of the beta-thymosin mRNAs and their proteins in developing rat cerebellum. Early in postnatal development, both beta-thymosin mRNAs were expressed at highest levels in the postmitotic, premigratory granule cells of the external granular layer; expression diminished as granule cells migrated to and differentiated within the developing internal granular layer.

Thymosin beta 10 and thymosin beta 4 are both actin monomer sequestering proteins.

The beta-thymosins are a family of related peptides. Recently, thymosin beta 4 was identified as a significant actin monomer sequestering protein in cells. To determine if other beta-thymosins also bind actin, and how they may participate in the regulation of actin polymerization, we expressed thymosin beta 4 and its major homolog, thymosin beta 10, in bacteria and characterized their interactions with actin.

Plasticity of astroglial glutamate and gamma-aminobutyric acid uptake in cell cultures derived from postnatal mouse cerebellum.

The plasticity of astroglial glutamate and gamma-aminobutyric acid (GABA) uptakes was investigated using mouse cerebellar cell cultures. The influence of external factors, such as different sera and/or the presence of neurons, was examined. Control autoradiography experiments showed that after short-term exposure to radioactive amino acids, granule cells took up neither glutamate nor GABA, and beta-alanine predominantly inhibited astroglial GABA uptake.

Hsp70 mRNA induction is reduced in neurons of aged rat hippocampus after thermal stress.

Levels of heat-shock 70 mRNAs, relative to those of 18S rRNA, were quantitated in specific cell types of hippocampus of adult and aged rats subjected to identical heat shock regimens. Body temperature changes in response to the heat stress were no different in adult and aged rats. In control rats, as well as 3 h after initiation of heat shock in both adult and aged rats, relative levels of the constitutively synthesized heat-shock cognate 70 (hsc70) mRNA were highest in hippocampal neurons and much lower in glia.

Brain non-adenylated mRNAs.

Most eukaryotic messenger RNA (mRNA) species contain a 3'-poly(A) tract. The histone mRNAs are a notable exception although a subclass of histone-encoding mRNAs is polyadenylated. A class of mRNAs lacking a poly(A) tail would be expected to be less stable than poly(A)+ mRNAs and might, like the histones, have a half-life that varied in response to changes in the intracellular milieu.

Cloning and characterization of a testis-specific thymosin beta 10 cDNA. Expression in post-meiotic male germ cells.

Thymosin beta 10 is one of a small family of proteins closely related in sequence to thymosin beta 4, recently identified as an actin-sequestering protein. A single molecular weight species of thymosin beta 10 mRNA is present in a number of rat tissues. In adult rat testis, an additional thymosin beta 10 mRNA of higher molecular weight was identified.