Thomas A. Ala

Quantitative analysis of the olfactory pathway for drug delivery to the brain

Following intranasal administration to rats, wheat germ agglutinin-horseradish peroxidase (WGA-HRP) concentrated in the olfactory nerve and glomerular layers of the olfactory bulb resulting in a mean olfactory bulb concentration of 140 nM. A negligible amount of label was detected in the olfactory bulb following intravenous administration of WGA-HRP or intranasal administration of unconjugated HRP. This is the first quantitative assessment of intraneuronal transport of a protein into the brain using the olfactory route.

Delivery of Nerve Growth Factor to the Brain via the Olfactory Pathway

Purpose: To assess the potential of delivering nerve growth factor (NGF) to the brain along the olfactory neural pathway for the treatment of Alzheimers disease. Methods: Recombinant human NGF (rhNGF) was given as nose drops to anesthetized rats. The rhNGF concentrations in the brain were determined by enzyme-linked immunosorbent assay (ELISA). Results: Following olfactory administration, rhNGF reached the brain within an hour, achieving a concentration of 3400 pM in the olfactory bulb, 660–2200 pM in other brain regions and, 240 pM and 180 pM in the hippocampus and the amygdala, respectively. In contrast, little or no rhNGF was found in the brain following intravenous administration. Conclusions: A significant amount of rhNGF can be delivered to the brain via the olfactory pathway. The detection of rhNGF by ELISA indicates that rhNGF is delivered to the brain relatively intact. The rapid appearance of rhNGF in the brain suggests that it may be transported by an extraneuronal route into the brain via intercellular clefts in the olfactory epithelium. Further work to clarify the transport mechanism is underway. The olfactory pathway is a promising, non-invasive route for drug delivery to the brain, which has potential for the treatment of neurodegenerative diseases including Alzheimers disease.

Pure hippocampal sclerosis: a rare cause of dementia mimicking Alzheimer's disease.

Objectives: To identify patients with pure hippocampal sclerosis (HS) as a cause of dementia, to determine whether they have had histories of hypotension or hypoxia, and to compare the clinical features of patients with pure HS with a control group of AD patients without HS. Methods: In a retrospective study, the authors reviewed all 1771 cases received in their dementia brain bank from 1978 through 1996 to identify those patients with pure HS, defined as severe degeneration and gliosis of the CA1 sector and subiculum of the hippocampal formation in the absence of other significant dementing disease such as Alzheimer’s changes. The control group included all patients received during the same period with severe AD without HS, infarcts, or other dementing disease. Results: Seven pure HS cases (0.4%) were identified. None had any episodes of syncope, hypotension, or hypoxia reported in association with dementia onset. Six had memory loss as the primary presenting symptom, and all became progressively demented. Forty-five AD patients without HS were identified for the control group. There were no clear clinical differences between the two groups with regard to sex, age at onset, risk factors for vascular disease, symptoms of cerebrovascular disease, treatment with tranquilizing medications, treatment for depression, or nursing home placement. There was a tendency for heart disease to be more prevalent and the duration of illness to be shorter in the patients with pure HS. Conclusions: Pure hippocampal sclerosis (HS) occurred in only 0.4% of our dementia patients. Clinically, the seven patients with pure HS were similar to our AD control group. Further research is needed to determine the causes of HS and why HS appears to mimic AD.

Is Brain Amyloid Production a Cause or a Result of Dementia of The Alzheimer's Type?

The amyloid cascade hypothesis has guided much of the research into Alzheimers disease (AD) over the last 25 years. We argue that the hypothesis of amyloid-β (Aβ) as the primary cause of dementia may not be fully correct. Rather, we propose that decline in brain metabolic activity, which is tightly linked to synaptic activity, actually underlies both the cognitive decline in AD and the deposition of Aβ. Aβ may further exacerbate metabolic decline and result in a downward spiral of cognitive function, leading to dementia. This novel interpretation can tie the disparate risk factors for dementia to a unifying hypothesis and present a roadmap for interventions to decrease the prevalence of dementia in the elderly population.

Heme from Alzheimer's brain inhibits muscarinic receptor binding via thiyl radical generation.

An endogenous inhibitor (< 3500 Da) of antagonist binding to the muscarinic acetylcholine receptor (mAChR) has been reported to be elevated 3-fold in Alzheimers disease (AD) brain. This endogenous inhibitor was found to require the presence of reducing agents such as reduced glutathione (GSH) for optimal activity. In the presence of GSH, the inhibitor was shown to generate thiyl radicals which irreversibly inhibited the mAChR. We now report that the inhibitor contains free heme, a well-established source of oxidative stress capable of generating free radicals and causing neurotoxicity. While FeSO4, microperoxidase and hemin all inhibited antagonist binding to the mAChR, only hemin shared the inhibitors requirement for GSH. Both the free radical scavengers Trolox and Mn2+, and the metal chelator, EDTA, blocked the activity of the endogenous AD inhibitor and of hemin. Heme oxygenase-1 (HO-1) markedly reduced the activity of both the endogenous AD inhibitor and hemin, indicating that the endogenous inhibitor contains heme. Mass spectrometric analysis confirmed the presence of free heme and heme fragments in fractions of the endogenous AD inhibitor. The antioxidants estrogen, vitamin E and vitamin C all protected the mAChR from irreversible inhibition by the endogenous inhibitor or hemin. These antioxidants may function to protect the integrity of the mAChR in vivo and may have therapeutic potential in AD where free heme could be a source of oxidative stress.

Ganglioside monoclonal antibody (A2B5) labels Alzheimer's neurofibrillary tangles

Ganglioside monoclonal antibody (A2B5) labels Alzheimers neurofibrillary tangles both in isolated neurofibrillary tangle-bearing nerve cells and in partially purified preparations of tangle fibers. Antibody staining was preab-sorbed by preincubation of antibody with neuronal ganglioside preparations. These results suggest that Alzheimers neurofibrillary tangles have a ganglioside associated with them.

Reversible dementia: A case of cryptococcal meningitis masquerading as Alzheimer's disease

A 70-year-old man presented to us in 1994 with a three-year history of worsening dementia. With the exceptions of a Mini-Mental State exam score of 20 and an inability to tandem walk, his physical and neurological examinations were normal. His past medical history revealed that in 1992 he had been evaluated at another institution for memory impairment and bifrontal headaches. A spinal tap had been done in 1992 showing elevated protein, reduced glucose, and a pleocytosis; his CSF fungal culture and cryptococcal antigen test were negative. He subsequently was lost to follow-up, and although his headaches had resolved, his mental status had continued to worsen. In 1994 his CSF cryptococcal antigen was positive, and his CSF fungal culture grew C. neoformans. He gradually improved with treatment for cryptococcal meningitis (CM). With the exception of mild memory impairment, in 2003 he and his family thought that his mental status had returned to normal. This case emphasizes that: 1) CM should always be kept in the differential diagnosis of dementia; 2) CM may be extremely insidious and difficult to diagnose; and 3) if one is to rule out unequivocally all possible reversible causes of dementia, one should perform a spinal tap.

Endogenous Alzheimer's brain factor and oxidized glutathione inhibit antagonist binding to the muscarinic receptor.

An endogenous inhibitor (< 3,500 Da) of antagonist binding to the muscarinic acetylcholine receptor has been extracted from Alzheimers disease (AD) brain with trifluoracetic acid. Oxidized glutathione, (GSSG) has also been found to inhibit antagonist binding to the receptor. However, in its reduced form, glutathione (GSH) like other reducing agents, markedly enhances the inhibitory effect of both GSSG and the endogenous AD inhibitor. EDTA and the free radical scavengers Mn(2+) and Trolox, a vitamin E analog, block the action of the endogenous AD inhibitor but not of GSSG in the presence of GSH. Further, while GSSG inhibition is reversible, the action of the endogenous AD inhibitor is irreversible, consistent with a free radical mechanism. The enhancement of endogenous AD inhibitor activity by GSH suggested that GSH may be involved in formation of the free radical generated by the inhibitor. The glutathione thiyl radical is shown to inhibit antagonist binding to the receptor and is, therefore, a good candidate for the free radical formed by the endogenous AD inhibitor. The ability of Trolox to block the reduction in muscarinic receptor binding caused by the endogenous AD inhibitor is encouraging and suggests that free radical scavengers, such as vitamin E, may have a potential therapeutic role in AD by protecting the integrity of the muscarinic receptor.

Validation of the NINCDS-ADRDA criteria regarding gait in the clinical diagnosis of Alzheimer disease. A clinicopathologic study.

The NINCDS-ADRDA criteria for the clinical diagnosis of probable Alzheimer disease (AD) state that “gait disturbances at the onset or very early in the course of the illness make the diagnosis of Alzheimer disease uncertain or unlikely,‘’ yet there have been few studies documenting the validity of the statement. We therefore reviewed all cases of pure autopsy-proven AD in the Ramsey Brain Bank to determine how frequently an abnormal gait was noted at time of presentation. Any reported gait disturbance was considered an abnormal gait. Only cases for which medical records were available documenting the patients presentation for dementia were included. Cases were excluded if any other pathology was present that may have contributed to the patients dementia or to a gait disorder, if neuroleptic medication had been used, or if there was a preexisting gait disorder. Clinical dementia severity at time of presentation was graded as mild, moderate, or severe per DSM-IIIR criteria. Of the 95 cases that met study criteria, none of the 36 patients with mild dementia were reported to have had an abnormal gait. Sixteen percent of the patients with moderate and 32% with severe dementia had gait abnormalities reported. This study confirms the statement regarding gait in the NINCDS-ADRDA criteria.

The characteristics of patients with uncertain/mild cognitive impairment on the Alzheimer disease assessment scale-cognitive subscale

The performances of the uncertain/mild cognitive impairment (MCI) patients on the Alzheimer Disease Assessment Scale-Cognitive (ADAS-Cog) subscale were compared with those of normal controls, Alzheimer disease patients with CDR 0.5, and Alzheimer disease patients with CDR 1.0. The Uncertain/MCI group was significantly different from normal controls and Alzheimer disease CDR 0.5 or 1.0 groups on the ADAS-Cog except on a few non-memory subtests. Age was significantly correlated with total error score in the normal group, but there was no significant correlation between age and ADAS-Cog scores in the patient groups. Education was not significantly correlated with the ADAS-Cog scores in any group. Regardless of age and educational level, there were clear differences between the normal group and the Uncertain/MCI group, especially on the total error scores. We found that the total error score of the ADAS-Cog was the most reliable variable in detecting patients with mild cognitive impairment. The present study demonstrated that the ADAS-Cog is a promising tool for detecting and studying patients with mild cognitive impairment. The results also indicated that demographic variables such as age and education do not play a significant role in the diagnosis of mild cognitive impaired patients based on the ADAS-Cog scores.