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Biomedical subjects

M R Farlow

Publications and source records attributed to M R Farlow.

At least 19 recordsLinked to original sources
PubMed2006

Effects of a gamma-secretase inhibitor in a randomized study of patients with Alzheimer disease.

LY450139 dihydrate, a gamma-secretase inhibitor, was studied in a randomized, controlled trial of 70 patients with Alzheimer disease. Subjects were given 30 mg for 1 week followed by 40 mg for 5 weeks. Treatment was well tolerated. Abeta(1-40) in plasma decreased by 38.2%; in CSF, Abeta(1-40) decreased by 4.42 +/- 9.55% (p = not significant). Higher drug doses may result in additional decreases in plasma Abeta concentrations and a measurable decrease in CSF Abeta.

Alanine↗
PubMed2005

Minocycline prevents gentamicin-induced ototoxicity by inhibiting p38 MAP kinase phosphorylation and caspase 3 activation.

Aminoglycosides are commonly used antibiotics that often induce ototoxicity leading to permanent hair cell loss and hearing impairment. We hereby examined whether minocycline protects hair cells from gentamicin-induced hair cell damage. Two millimolar gentamicin significantly induced outer hair cell damage and the addition of minocycline to gentamicin-treated explants significantly increased hair cell survival in a dose-dependent manner. Additionally, we demonstrated that gentamicin induced p38 MAPK phosphorylation, cytochrome c release, and caspase 3 activation in these cells and these remarkable changes were blocked by minocycline treatments. Furthermore, we showed that the inhibitor of p38 MAPK or the inhibitor of caspase 3 only partially blocked gentamicin-induced hair cell damage, and the pretreatment of explants with the inhibitor of p38 MAPK and the inhibitor of caspase 3 together exerted a synergic protective effect against gentamicin-induced hair cell damage. Our results suggest that minocycline blocks gentamicin-induced hair cell loss possibly by inhibition of three mechanisms: p38 MAPK phosphorylation, cytochrome c release, and caspase 3 activation. This finding may explain why minocycline has protective activity in a variety of apoptotic models. Therapeutic intervention by using minocycline or related drugs may be a novel means for preventing inner ear injury following the use of aminoglycoside.

Animals↗
PubMed2004

Impact of APOE in mild cognitive impairment.

OBJECTIVE: The authors aimed to use baseline data of an ongoing large, prospective study in subjects with mild cognitive impairment (MCI) to investigate the impact of APOE genotype on the symptom profile of the condition. METHODS: Cognitive assessments included the AD Assessment Scale cognitive subscale (ADAS-cog), the Mini-Mental State Examination (MMSE), and a cognitive battery for assessment of memory, attention, and executive function. Behavioral assessments included the Neuropsychiatric Inventory and Beck Depression Inventory. Activities of daily living were assessed by the AD Cooperative Study Activities of Daily Living (ADCS-ADL) scale. Hippocampal volumes were measured with MRI. RESULTS: A total of 494 of 1,018 study subjects provided APOE data. Approximately 40% of the subjects were APOE epsilon4 carriers. APOE epsilon4 carriers had lower MMSE (p = 0.01) and higher ADAS-cog (p < 0.0001) scores than noncarriers, indicating worse cognitive impairment. APOE epsilon4 carriers also had greater deficits on New York University delayed paragraph recall and Buschke free and cued selective reminding tests, and on the ADCS-ADL scale (p < 0.001). They also had smaller hippocampal volumes (p = 0.002). Behavioral scores were similar across the subgroups. CONCLUSION: MCI subjects carrying the APOE epsilon4 allele showed distinct cognitive and imaging profiles, which appeared to resemble those of early Alzheimer patients. APOE epsilon4 genotype was associated with greater impairments in memory and functional activities as well as hippocampal atrophy.

Activities of Daily Living↗
PubMed2004

Cholesterol and APOE genotype interact to influence Alzheimer disease progression.

In this retrospective analysis of 443 Alzheimer disease (AD) patients from a 30-week tacrine trial, change in Alzheimer's Disease Assessment Scale score from baseline to final value was significantly associated with a total serum cholesterol/APOE genotype interaction. Disease progression in the no-APOE epsilon4 allele/high-cholesterol subgroup was greater than in the normal-cholesterol subgroups with or without epsilon4. Cholesterol levels and APOE genotype may interact to affect AD progression. The results are consistent with preclinical data on cholesterol's effects in AD.

Aged↗
PubMed2002

Nicotine reduces the secretion of Alzheimer's beta-amyloid precursor protein containing beta-amyloid peptide in the rat without altering synaptic proteins.

Alzheimer's disease (AD) is characterized by cerebrovascular deposition of the amyloid beta-peptide (A beta), which is derived from a larger beta-amyloid precursor protein (beta APP). Altered metabolism of beta APP, resulting in increased A beta production, appears central in the neuropathology of AD. The processing of the holoprotein beta APP by different "secretase" enzymes results in three major carboxyl-truncated species. One species, which results from the cleavage of beta APP by gamma-secretase, is secreted into the cerebrospinal fluid (CSF) and is called sAPP gamma as it contains an intact A beta domain. Moreover, AD is characterized by cholinergic dysfunction and the loss of synaptic proteins. Reports of an inverse relation between nicotine intake, due to cigarette smoking, and the incidence of AD prompted us to investigate the effects of nicotine on beta APP processing and synaptic proteins in rats and in cell culture. Nicotine, 1 and 8 mg/kg/day, doses commensurate with cigarette smoking, and a higher but well tolerated dose, respectively, was administered over 14 days to rats. Levels of sAPP in the CSF sample were evaluated by Western blot analysis. The higher dose significantly increased levels of total sAPP; however, both doses significantly reduced sAPP gamma, which contains the amyloidogenic portion of A beta. These actions were blocked by nicotinic receptor antagonism. Nicotinic antagonists alone had no effect on either total sAPP or sAPP gamma levels in CSF. Nicotine did not significantly change the intracellular levels of total beta APP in rat brain extracts, which is consistent with neuronal cell culture data. Similarly, levels of vesicular protein, such as synaptophysin, and presynaptic terminal protein SNAP-25 were unaffected by nicotine treatment both in vivo and in cell culture experiments. Taken together, these results suggest that nicotine modifies beta APP processing away from the formation of potentially amyloidogenic products, without altering the levels of synaptic proteins, and that this can potentially offer therapeutic potential for Alzheimer's disease.

Amyloid beta-Protein Precursor↗
PubMed2002

The role of the carboxyl-terminal fragments of amyloid precursor protein in Alzheimer's disease.

Two major pathological hallmarks of Alzheimer's disease (AD) are the senile plaques that are primarily composed of amyloid beta-peptide (Abeta) and neurofibrillary tangles consisting of tau aggregates. Abeta is generated proteolytically from a family of Abeta-containing precursor proteins (APP; 695-770 amino acid) by secretase enzymes to different specific carboxyl-terminal fragments (CTFs). Herein we examined APP and its products in autopsied brain sections from 10 AD and 10 non-AD control subjects immunochemically using an antibody that was raised against APP751-770 residue (O443). The O443 antibody was initially characterized by Western blot analysis and immunoprecipitation. In this study, we used this antibody for immunohistochemical analysis to determine the distribution of APP and its CTF species. In 10 brain regions showing different levels of plaques and tangles, antibody O443 stained the perinuclear region of the nucleus, plaques, and neurites. Tangle-bearing neurons also appeared to stain with the antibody, suggesting that these dysfunctional neurons continue to synthesize APP/CTF. Alternatively, the normally short-lived APP/CTF can be stabilized and persist in these neurons. Taken together, these results suggest that, in addition to the widely believed role of Abeta, CTFs may play a key role in the pathogenesis of AD. Studying their localization and biogenesis may reveal the biological activities of CTFs of APP. The present study may pave the way for possible antiamyloidogenic therapy in the treatment of AD.

Alzheimer Disease↗
PubMed2002

Do cholinesterase inhibitors slow progression of Alzheimer's disease?

In the absence of a cure for Alzheimer's disease (AD), treatment has focused on therapy to provide symptomatic benefits and to slow progression of the disease, so that patients can maintain their independence for as long as possible. New research suggests that rivastigmine, a potent, pseudo-irreversible inhibitor of both acetylcholinesterase (AChE) and butyrylcholinesterase that shows preferential selectivity for the G1 form of AChE, may provide symptomatic and disease progression slowing effects. The drug's pharmacological properties may help to slow the conversion of diffuse, benign amyloid plaques to neuritic plaques associated with clinical dementia. In 'delayed-start' paradigms--open-label extensions of placebo-controlled studies involving mild to moderate AD patients--the treatment effects of rivastigmine on cognitive and non-cognitive outcomes at 52 weeks were even greater than those observed at 26 weeks, and patients who received rivastigmine for the entire 52 weeks had better outcomes than those who received rivastigmine only for the latter 26 weeks (having received placebo for the first 26 weeks during the placebo-controlled phase). These treatment effects were even more robust in patients with moderately severe disease, indicating that the sustained long-term benefits of rivastigmine apply across the continuum of disease severity. The results seen in those patients with mild and moderately severe AD suggest that the progression of AD was being slowed in treated patients and that a disease-modifying effect may have been taking place. The effects of rivastigmine on cognition remain clinically relevant for at least 2 years, with benefits over projected placebo increasing over time. The long-term benefits of rivastigmine have also been reported in behavioural domains of patients with mild to moderate AD for 104 weeks and in patients with the Lewy body variant of AD for 96 weeks. Rivastigmine may slow AD progression, allowing patients to maintain autonomy for longer.

Alzheimer Disease↗
PubMed2001

Minocycline blocks nitric oxide-induced neurotoxicity by inhibition p38 MAP kinase in rat cerebellar granule neurons.

Minocycline, a semisynthetic second-generation tetracycline, was reported to have neuroprotective effects in models of global and focal cerebral ischemia, the R6/2 mouse model of Huntington disease, as well as glutamate-induced neurotoxicity in mixed neuronal/glial cultures. It was suggested that neuroprotective effects of minocycline resulted from inhibition of microglial/astroglial activation 'Proc. Natl. Acad. Sci. USA 95 1998 15769'. To determine whether or not minocycline is able to directly protect neurons against injury insults and to delineate its neuroprotective mechanism(s), we treated cultured rat cerebellar granule neurons (CGN) with nitric oxide (NO) in the presence or absence of minocycline. We found that minocycline protected neurons against NO-induced neuronal death in a concentration-dependent fashion. Consistent to other reports, NO was able to induce p38 MAP kinase phosphorylation at 3-6 h and such an induction could be significantly inhibited by minocycline. Furthermore, SB 203580, a p38 MAP kinase inhibitor, almost completely attenuated NO-induced neuronal death of CGN as well. These results suggest that minocycline is able to block NO-induced neurotoxicity in CGN by inhibiting NO-induced phosphorylation of p38 MAP kinase. Our finding may explain the neuroprotective mechanism of minocycline in those neurodegenerative models.

Animals↗
PubMed2001

Response of patients with Alzheimer disease to rivastigmine treatment is predicted by the rate of disease progression.

BACKGROUND: Evidence suggests that disease severity predicts the response of patients with Alzheimer disease (AD) to cholinesterase inhibitor treatment, raising the question of whether disease progression also predicts response to this treatment. OBJECTIVE: To evaluate retrospectively whether rate of disease progression during placebo treatment affects response to subsequent rivastigmine tartrate therapy for patients with mild to moderately severe AD. DESIGN: A 26-week, open-label extension study following a 26-week, double-blind, randomized, placebo-controlled trial. SETTING: Outpatient research centers at 22 sites in the United States. PATIENTS: We studied 187 of 235 patients originally randomized to receive placebo treatment in the double-blind phase of the trial who continued with open-label (rivastigmine) extension therapy. INTERVENTION: Placebo treatment for 26 weeks followed by rivastigmine treatment, 2 to 12 mg/d, for 26 weeks. MAIN OUTCOME MEASURES: Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-Cog), Progressive Deterioration Scale, Mini-Mental State Examination, and Global Deterioration Scale scores. RESULTS: Rivastigmine administration during open-label extension therapy benefited patients who had progressed slowly and those who had progressed rapidly during initial double-blind placebo treatment. Slowly progressive patients responded with a mean 1.03-point improvement in the week 26 (ie, start of open-label rivastigmine treatment) ADAS-Cog score at 12 weeks of rivastigmine treatment (week 38 of treatment; P =.02 vs week 26). However, more rapidly progressive patients had a significantly larger mean 4.97-point improvement from the week 26 ADAS-Cog score at 12 weeks (with respect to week 26 of treatment and slowly progressive patient scores, P<.001 for both). Thus, a more rapid disease progression rate while receiving placebo treatment was predictive of a significantly stronger patient response to rivastigmine therapy. This relation also was observed with the other 3 outcome measures and was still apparent when accounting for disease severity. CONCLUSIONS: Rate of disease progression for patients with mild to moderate AD seems to predict response to rivastigmine treatment. Patients with more rapidly progressive disease might be particularly likely to benefit from rivastigmine therapy.

Aged↗
PubMed2001

Biochemical characterization of a neuroserpin variant associated with hereditary dementia.

Neuroserpin isolated from inclusion bodies in the brain of a patient with a neurodegenerative disease was characterized biochemically. The protein consisted of residues 20 to 410 of the neuroserpin precursor deduced from its cDNA sequence indicating the entire molecule was deposited. A minor amount started with residue 19 of the precursor, and the carboxyl terminus was heterogeneous ending at residues 405, 407, 409, and 410. Arg was present at position 52. No normal Ser52 was found indicating that only mutant neuroserpin was present in the inclusion bodies. The three potential Asn glycosylation sites all contained carbohydrate. DNA sequence analysis of exons 2 to 9 of the neuroserpin gene in the proband showed the published normal neuroserpin sequence except for the presence of both adenine and cytosine at the first position of codon 52, that indicates heterozygosity for both the normal Ser(AGT) and variant Arg(CGT) at this position in the expressed protein. Restriction fragment length polymorphism analysis of a polymerase chain reaction product from exon 2 revealed the propositus and his affected sibling both were heterozygous for the mutation whereas 100 unaffected controls were negative. Chemical characterization of the variant neuroserpin will significantly enhance the understanding of this protein in both normal physiology and neurodegenerative diseases.

Adult↗
PubMed2001

Prion proteins with different conformations accumulate in Gerstmann-Sträussler-Scheinker disease caused by A117V and F198S mutations.

Gerstmann-Sträussler-Scheinker disease (GSS) is characterized by the accumulation of proteinase K (PK)-resistant prion protein fragments (PrP(sc)) of approximately 7 to 15 kd in the brain. Purified GSS amyloid is composed primarily of approximately 7-kd PrP peptides, whose N terminus corresponds to residues W(81) and G(88) to G(90) in patients with the A117V mutation and to residue W(81) in patients with the F198S mutation. The aim of this study was to characterize PrP in brain extracts, microsomal preparations, and purified fractions from A117V patients and to determine the N terminus of PrP(sc) species in both GSS A117V and F198S. In all GSS A117V patients, the approximately 7-kd PrP(sc) fragment isolated from nondigested and PK-digested samples had the major N terminus at residue G(88) and G(90), respectively. Conversely, in all patients with GSS F198S, an approximately 8-kd PrP(sc) fragment was isolated having the major N terminus start at residue G(74). It is possible that a further degradation of this fragment generates the amyloid subunit starting at W(81). The finding that patients with GSS A117V and F198S accumulate PrP(sc) fragments of different size and N-terminal sequence, suggests that these mutations generate two distinct PrP conformers.

Amyloid↗
PubMed2001

Pharmacokinetic profiles of current therapies for Alzheimer's disease: implications for switching to galantamine.

Although no pharmacologic treatments have been proved to alter the pathology of Alzheimer's disease, acetylcholinesterase inhibitor (AChEI) therapy offers symptomatic improvements in or delays in the progression of cognitive, behavioral, and functional deficits. Tacrine, donepezil, rivastigmine, and galantamine are the best studied agents in this class. These drugs have varying pharmacokinetic, safety, and tolerability profiles that can affect patient outcomes. Specifically, certain metabolic parameters (ie, half-life and route of metabolism/elimination) can affect a drug's tolerability and become important when a switch from one agent to another is contemplated. The mechanism of action of galantamine, the most recently approved AChEI. varies from that of the other AChEIs in that it has allosteric modulating activity at nicotinic receptors in addition to its ability to inhibit acetylcholinesterase. Benefits of this dual mode of action on the effects of the disease have been suggested.

Aged↗
PubMed2001

Olfactory-evoked regional cerebral blood flow in Alzheimer's disease.

Olfaction is impaired in Alzheimer's disease (AD). It was hypothesized that AD would reduce olfactory-evoked perfusion in mesial temporal olfactory (piriform) cortex, where neuropathology begins. Seven AD patients and 8 elderly controls (ECs) underwent olfactory threshold and identification tests and olfactory stimulation during positron emission tomography. Odor identification was impaired in AD, but threshold was not. Olfactory stimulation in ECs activated right and left piriform areas and right anterior ventral temporal cortex. AD patients had less activation in right piriform and anterior ventral temporal cortex but not in the left piriform area. Although orbital cortex did not activate in ECs, there was a significant between-groups difference in this area. Right piriform activation correlated with odor identification. Impaired odor identification likely reflects sensory cortex dysfunction rather than cognitive impairment. Given olfactory bulb projections to the mesial temporal lobe, olfactory stimulation during functional imaging might detect early dysfunction in this region.

Aged↗
PubMed2001

Assessment of dietary therapies in a canine model of Batten disease.

The neuronal ceroid lipofuscinoses (NCLs) are inherited neurodegenerative diseases that occur in a number of animal species, including dogs. A study was conducted to determine whether the resupply of nutrients lost in NCL English Setter dogs would modify the course of the disease. Carnitine and polyunsaturated fatty acids have been reported to be reduced in NCL English Setters. Therefore, the normal laboratory diets of NCL dogs were supplemented with carnitine, fish oil and corn oil and the disease progression was compared with that of an untreated litter mate. The following specific prognostic indicators of NCL were monitored: cognitive function, brain atrophy, brain glucose metabolism and lifespan. Carnitine, with or without lipid supplements, dramatically delayed the progression of cognitive decline in NCL dogs. When fish oil and corn oil only were supplied, brain atrophy was reduced. A combination of all three supplements preserved cognitive function and increased lifespan by 10%. However, brain glucose hypometabolism and cerebral atrophy were not reduced. The results in this study indicated that the effectiveness of therapeutic interventions can be assessed by non-invasive methods at a relatively early stage of the disease process. Our study suggests that dietary supplementation with carnitine is a promising new approach for delaying or preventing the cognitive decline in dogs, and perhaps, with human NCL patients.

Animals↗
PubMed2001

Ectopic white matter neurons, a developmental abnormality that may be caused by the PSEN1 S169L mutation in a case of familial AD with myoclonus and seizures.

We report clinical, neuropathologic and molecular genetic data from an individual affected by a familial Alzheimer disease (AD) variant. The proband had an onset of dementia at age 29 followed by generalized seizures a year later. He died at age 40. Neuropathologically, he had severe brain atrophy and characteristic histopathologic lesions of AD. Three additional neuropathologic features need to be emphasized: 1) severe deposition of Abeta in the form of diffuse deposits in the cerebral and cerebellar cortices, 2) numerous Abeta deposits in the subcortical white matter and in the centrum semiovale, and 3) numerous ectopic neurons, often containing tau-immunopositive neurofibrillary tangles, in the white maner of the frontal and temporal lobes. A molecular genetic analysis of DNA extracted from brain tissue of the proband revealed a S169L mutation in the Presenilin 1 (PSEN1) gene. The importance of this case lies in the presence of ectopic neurons in the white matter, early-onset seizures, and a PSEN1 mutation. We hypothesize that the PSEN1 mutation may have a causal relationship with an abnormality in neuronal development.

Adult↗
PubMed2001

New concepts in the drug therapy of Alzheimer's disease.

There are currently four compounds approved for use in the treatment of Alzheimer's disease (AD). These drugs are all cholinesterase (ChE) inhibitors, which are thought to provide predominantly symptomatic benefits by increasing the level of acetylcholine (ACh) in the synapse. Although there are slight differences in the mechanisms of action of these compounds, it remains to be determined whether any one of them has a significant therapeutic advantage over the others. Several other drugs have also been investigated for their potential use as either symptomatic or disease-modifying agents in the treatment of AD, with mixed results. Current therapeutic research is focused on addressing the underlying pathology of AD, in the hope of arresting or reversing the course of the disease. This review will provide an overview of the ChE inhibitors and other drugs used for treating the symptoms of AD, summarise the results of recent therapeutic trials, discuss directions of future research and outline the current treatment recommendations for AD.

Alzheimer Disease↗