Lysosomal enzymes in motor neurone disease and multiple sclerosis

In nine patients with motor neurone disease the activity of acid phosphatase in cerebrospinal fluid (CSF) was higher (P<0.005) than in nine controls. The activity of this enzyme in CSF from 18 patients with multiple sclerosis did not differ from control values. The activity of arylsulphatase in CSF was the same in the motor neurone, multiple sclerosis and control groups. In the serum, the activities of the two enzymes were similar in the three groups of patients.     

Lysosomal enzymes, amino acids and acid metabolites of amines in Huntington's chorea

The activity of acid phosphatase in cerebrospinal fluid (CSF) from 7 Huntington's chorea patients tended to he higher than in 7 controls. The activity of arylsulphatase in CSF was the same in the two groups. In the Huntington's group, but not in the control group, the activity of acid phosphatase in CSF was positively correlated with age. No correlation was found between the CSF and serum levels of acid phosphatase and arylsulphatase. The concentrations of tyrosine, tryptophan, homovanillic acid and 5-hydroxyindolylacetic acid in CSF from the Huntington's chorea patients were not significantly different from control values. The concentration of tryptophan, but not of tyrosine, was significantly reduced in plasma from fasted Huntington's chorea patients.     

Echo-Tracking Technology Assessment of Carotid Artery Stiffness in Patients with Coronary Slow Flow

Coronary slow flow (CSF) in coronary angiography (CAG) is a well-recognized clinical entity. Previous studies have suggested that microvascular abnormalities and endothelial dysfunction are responsible for CSF. Accordingly, we hypothesized that the CSF phenomenon is a form of atherosclerosis including both small vessels and epicardial coronary arteries. The echo-tracking (ET) technique is a non-invasive detection method for early prediction of arterial atherosclerosis. Therefore, we investigated carotid elasticity with the ET technique in patients with CSF. Fifty patients with CSF and 50 patients with normal coronary artery blood flow, as determined by CAG, with a similar distribution of risk factors were recruited. The stiffness parameter (β), pressure–strain elastic modulus (E_p), arterial compliance (AC), augmentation index (AIx) and local pulse-wave velocity (PWV) were determined at the level of the bilateral common carotid artery (CCA) with using the ET technique. Levels of serum high-sensitivity C-reactive protein (hs-HSCRP) were determined for the two groups. β, E_p and PWV were significantly higher in the CSF group than in the control group (β: 11.4 ± 3.76 vs. 9.22 ± 3.28, p < 0.01; E_p: 153.44 ± 47.85 vs. 126.40 ± 43.32, p < 0.01; PWV: 7.26 ± 1.10 vs. 6.55 ± 1.02, p < 0.01), but AC was lower in the CSF group than in the control group (0.62 ± 0.20 vs. 0.74 ± 0.24, p < 0.01). The elasticity parameters of the bilateral common carotid artery did not significantly differ. The level of hs-HSCRP was correlated positively with β (r = 0.306, p = 0.015), E_p (r = 0.358, p = 0.005) and PWV (r = 0.306, p = 0.015), but negatively with AC (r = −0.236, p = 0.049). In conclusion, the ET technique is a simple practical method for evaluating carotid artery elasticity, and there is a significant correlation between carotid artery stiffness and level of hs-HSCRP in patients with CSF.     

Clinical,laboratory and brain Magnetic Resonance Imaging (MRI) characteristics of asymptomatic and symptomatic HIV-negative neurosyphilis patients

IntroductionThere are few studies concerning the differences between asymptomatic neurosyphilis (ANS) and symptomatic neurosyphilis (SNS). This study aimed to summarize clinical, laboratory and brain Magnetic Resonance Imaging (MRI) characteristics of HIV-negative patients with ANS and SNS.MethodsData from 43 HIV-negative patients with ANS and 59 HIV-negative patients with SNS were retrospectively collected from our hospital between December 2012 and December 2018.ResultsCompared with the ANS group, SNS group had more patients that were male, age≥45 years, had brain MRI abnormalities, and exhibited higher serum/cerebrospinal fluid (CSF) TRUST titer, CSF WBC count, CSF protein concentration (P < 0.05). Multivariate regression analysis revealed that male sex, age ≥45 years and CSF TRUST titer were risk factors for SNS [odds ratio (OR) = 7.946,P = 0.001;OR = 3.757, P = 0.041; OR = 2.713, P = 0.002; respectively]. The brain MRI findings of 78 patients without comorbidities showed that ischemic infarct lesions presented in 17/37 (45.95%) of patients with ANS; infarct ischemic stroke (73.17%) especially multiple cerebral infractions (46.34%), cerebral atrophy (48.78%) were also common presentations in the SNS group.ConclusionsPatients with HIV-negative ANS and SNS presented different clinical, laboratory and brain MRI features. Male sex, age ≥45 years and elevated CSF TRUST titer may have an increased risk of developing neurological symptoms. Brain MRI abnormalities may present prior to clinical symptoms. Multiple cerebral infarctions without explained reasons or cerebral atrophy should alert clinicians the possibility of SNS.     

Preliminary Study on the Role of Virtual Touch Tissue Quantification Combined with a Urinary β2-Microglobulin Test on the Early Diagnosis of Gouty Kidney Damage

The goal of the work described here was to evaluate the role of virtual touch tissue quantification (VTQ) combined with urinary β2-microglobulin (β2-MG) measurement in the early diagnosis of gouty kidney damage. Two hundred fifty-nine patients with gouty kidney damage and 200 healthy control subjects were tested. The shear wave velocity (SWV) of the renal parenchyma and sinus as determined with VTQ and the urinary β2-MG level of the two groups were analyzed. Although there were no significant differences in age, body mass index, creatinine level and blood urea nitrogen between the two groups (all p's > 0.05), the aforementioned parameters were higher in the group with gouty kidney damage than in the control group. Urinary β2-MG levels of the patients with kidney damage were significantly higher than those of the control subjects (t = 6.38, p < 0.01). The SWV of the renal parenchyma was higher than that of the sinus in both groups. Compared with controls, patients with kidney damage had significantly increased renal parenchyma and sinus SWVs (all p-values < 0.05). Urinary β2-MG level was positively linearly correlated with the SWV of renal parenchyma in patients with kidney damage (r = 0.442, p < 0.0001). However, there was no correlation between urinary β2-MG level and the SWV of the sinus in patients with kidney damage (r = 0). In the control group, there was no correlation between urinary β2-MG level and the SWV of the renal parenchyma or sinus. The elasticity of the kidney as determined with VTQ, combined with the urinary β2-MG level, may be helpful in the early diagnosis of gouty kidney damage.     

Hypothermia and Infection I. Influence of Hypothermia on Antibody Formation in Mice in the Secondary Response to Typhoid-H-Antigen

Öckerman, P. A. Lysosomal Acid Hydrolases in the Liver in Gargoylism. Deficiency of 4-methylumbelliferyl-β-galactosidase. Scand. J. clin. Lab. Invest. 22, 142-146, 1968.

The activites of six lysosomal acid hydrolases were measured in liver biopsy specimens from six patients with gargoylism and in post-mortem tissue from two patients. A marked diminution was noted for the activity of 4-methylumbelliferyl-β-glactosidase in all patients with gargoylism. The deficiency of β-galactosidase did not seem to be due to the presence of an inhibitor in the liver.

The activities of β-glucuronidase, β-acetylglucosaminidase, acid phosphatase and α-fucosidase were significantly increased in some of the patients. The activity of α-mannosidase was not significantly different from the values in the controls.     

Lysosomal enzyme variations in thirteen cell strains cultured from one amniotic fluid

Fifteen primary amniotic fluid cultures were established from a single sample of amniotic fluid. Three different methods were used to set up these cultures which yielded 13 cell strains. Nine lysosomal enzymes (acid phosphatase, β-glucuronidase, β-galactosidase, α-galactosidase, α-glucosidase, α-mannosidase, α-arabinosidase, $\text{N-}\text{acetyl}\text{-ß-}\text{d}\text{-}\text{glucosaminidase}$ and arylsulphatase A) were assayed in these 13 cell strains. The coefficients of variation of these enzyme levels were less than the coefficients for enzyme levels in cell strains grown from different samples of amniotic fluid but greater than those for the combined culture and assay system used. No assay values were found which could have suggested a possible enzyme deficiency disease.     

Brain atrophy evaluated by computed tomography in independent and institutionalized hip fracture patients

Purpose: To examine if there is an association between brain computed tomography (CT) findings and place of residence in a series of hip fracture patients.

Method: The CT scans taken immediately after hip fracture of 215 patients (mean age 81.6 years) living in their own homes or otherwise independently (home-dwelling group) and 95 patients (mean age 82.5 years) permanently institutionalized (institutionalized group) were analysed.

Results: The institutionalized patients had significantly more cortical cerebral (frontal, p?=?0.004; temporal, p?=?0.007; parietal, p?<?0.001) and central cerebral (third ventricle width, p?<?0.001; frontal horn width, p?<?0.001; midbody width, p?<?0.001) atrophy than the home-dwelling ones. This was also true of atrophy in the white-matter (WM) area (p?<?0.001). The institutionalized patients also had more atrophy of the cerebellar hemisphere (atrophy of the cerebellopontine angle cistern, p?=?0.002, greater fourth ventricle width, p?=?0.020). No significant difference was seen in the incidence of brain infarcts.

Conclusions: Hip fracture patients living in institutions have more brain atrophy than those living independently. The brain atrophy may be one factor in the multiple mechanism underlying their institutional admission.     

Activity of beta-galactosidase, beta-glucuronidase and N-acetyl-beta-glucosaminidase in human rectal mucosa

Activity of β-galactosidase, β-glucuronidase and N-acetl-β-glucosaminidase was determined by biopsy specimens of rectal mucosa of control subjects, cystinotic children and their parents.The studied enzymes exhibited maximal activity at pH 5.0, 4.0 and 4.5, respectively. Apparent K_m values using P-nitrophenyl-β-galactoside, p-nitrophenyl-β-glucuronide and p-nitropheny-β-glucosaminide were found to be 0.52 mM, 0.70 mM, and 0.67 mM.The activity of all three enzymes was found to be closely correlated in the 11 subjects of the control group. The values found in parents and their cystinotic children fit into these correlations, but show higher scatter of data caused by the fact that values of β-galactosidase were found to be higher and of β-glucuronidase and N-acetyl-glucosaminidase lower in the group of parents than in the other two groups.     

Effect of a hypertonic balanced ketone solution on plasma, CSF and brain beta-hydroxybutyrate levels and acid–base status

Purpose

Although glucose is the main source of energy for the human brain, ketones play an important role during starvation or injury. The purpose of our study was to investigate the metabolic effects of a novel hypertonic sodium ketone solution in normal animals.

Methods

Adult Sprague–Dawley rats (420–570 g) were divided into three groups of five, one control and two study arms. The control group received an intravenous infusion of 3 % NaCl at 5 ml/kg/h. The animals in the two study arms were assigned to receive one of the two formulations of ketone solutions, containing hypertonic saline with 40 and 120 mmol/l beta-hydroxybutyrate, respectively. This was infused for 6 h and then the animal was euthanized and brains removed and frozen.

Results

Both blood and cerebrospinal fluid (CSF) levels of beta-hydroxybutyrate (BHB) demonstrated strong evidence of a change over time (p < 0.0001). There was also strong evidence of a difference between groups (p < 0.0001). Multiple comparisons showed all these means were statistically different (p < 0.05). Measurement of BHB levels in brain tissue found strong evidence of a difference between groups (p < 0.0001) with control: 0.15 mmol/l (0.01), BHB 40: 0.19 mmol/l (0.01), and BHB 120: 0.28 mmol/l (0.01). Multiple comparisons showed all these means were statistically different (p < 0.05). There were no differences over time (p = 0.31) or between groups (p = 0.33) or an interaction between groups and time (p = 0.47) for base excess.

Conclusion

The IV infusions of hypertonic saline/BHB are feasible and lead to increased plasma, CSF and brain levels of BHB without significant acid/base effects.     

Activity of paraoxonase 1 (PON1) on HDL2 and HDL3 subclasses in renal disease

IntroductionCardiovascular complications, as the main cause of mortality in renal patients, are followed with altered lipoproteins composition. Considering that paraoxonase-1 (PON1) is an anti-oxidative enzyme located mainly on HDL particles, the current study has aim to investigate whether failure of kidney function leads to changes in the distribution of PON1 activity between different HDL subclasses.Materials and methodsIn 77 renal patients (21 chronic kidney disease (CKD) and 56 end stage renal disease (ESRD) patients on dialysis) and 20 healthy subjects PON1 activity on HDL₂ and HDL₃ subclasses was determined by zymogram method that combines gradient gel electrophoresis separation of HDL subclasses and measurement of PON1 activity in the same gel.ResultsSerum paraoxonase (p<0.01) and arylesterase activity (p<0.001) of PON1 as well as its concentration (p<0.01) were significantly lower in CKD and ESRD patients compared to controls. Relative proportion of HDL₃ subclasses was higher in ESRD patients than in healthy participants, while HDL₂ subclasses was significantly decreased in CKD (p<0.05) and ESRD (p<0.001) patients, as compared to controls. Furthermore, control subjects had higher PON1 activity on HDL₂ (CKD and ESRD patients p<0.001) and HDL₃ (CKD p<0.05; ESRD patients p<0.001) subclasses in comparison with the both patients groups. Also, significant negative correlation was found between paraoxonase activity of PON1 in serum and creatinine concentration (ρ=‐0.373, p<0.01).ConclusionsThis study showed that altered HDL subclasses distribution, changed PON1 activities on different HDL subclasses as well as diminished anti-oxidative protection could be important factors in atherosclerosis development in CKD and ESRD patients.     

Heterogeneity of acid phosphatase activity in human polymorphonuclear leukocytes

Evidence is presented indicating the existence of two acid phosphatase activities in human polymorphonuclear leukocytes. There is an acid phosphatase activity, acting preferentially on β-glycerophosphate. This enzyme has a typical lysosomal localization (p = 1.24) and is strongly inhibited by 1.5 mM (+)-tartrate and 15 mM fluoride, being insensitive to 45 mM alloxan and 0.3 M citrate. The second acid phosphatase acts preferentially on phenyl phosphate and is bound to structures of low density (p = 1.18). It is strongly activated by 0.3 M citrate and dl-tartrate, and insensitive to 15 mM fluoride. It is also extremely sensitive to 45 mM alloxan and to thiol-blocking agents, and to denaturation by preincubation under varying conditions.It was not possible to demonstrate any difference in K_m values, pH effect or response to different substances or ions between the β-glycerophospliatase or phenylphosphatase localized in the granular or supernatant fractions. It is concluded that the soluble acid phosphatase activities are similar to that of the granular fraction and may be derived from ruptured lysosomes or solubilization from other subcellular structures.     

Impaired degradation of keratan sulfate in GM1-gangliosidosis

We have prepared a new radiolabeled substrate (galactose-N-acetylglucosamine 6-sulfate-[1-³H]galactitol), from shark cartilage keratan sulfate, for an assay of acid β-galactosidase activity. Using this substrate, we found that there was a striking deficiency of β-galactosidase activity in the cultured skin fibroblasts of patients with GM₁-gangliosidosis. However, there seemed to be no quantitative differences in residual enzyme activity between type 1 and type 2 GM₁-gangliosidosis.     

Serum (1 → 3) β-d-glucan assay for discrimination between Pneumocystis jirovecii pneumonia and colonization

Polymerase chain reaction (PCR) technique is being increasingly used for the microbiological diagnosis of Pneumocystis pneumonia (PCP). As PCR is highly sensitive, it can be positive even in a patient with Pneumocystis colonization. In this study, we evaluated whether the β-d-glucan assay could be used to differentiate between PCP and Pneumocystis jirovecii colonization in immunocompromised patients with pulmonary infiltrates. We retrospectively evaluated data from 166 consecutive patients who underwent bronchoalveolar lavage for the diagnosis of PCP. Serum levels of β-d-glucan in the negative, colonization, probable PCP, and definite PCP groups were 20.2 ± 6.3, 48.8 ± 15.9, 89.9 ± 20.2, 224.9 ± 25.9 pg/mL, respectively. The β-d-glucan levels in the definite PCP group were significantly higher than those in the other 3 groups (p < 0.001). Serum β-d-glucan levels in patients with either definite or probable PCP (173.1 ± 18.8 pg/mL) were significantly greater than those in patients with colonization who had positive PCR results but improved without anti-PCP treatment (p < 0.002). The cut-off level for discrimination was estimated to be 33.5 pg/mL, with which the positive predictive value was 0.925. These results indicate that β-d-glucan is a useful marker to differentiate between PCP and Pneumocystis colonization. A positive β-d-glucan assay result might be a good indication to begin anti-PCP treatment.     

Oxidative stress and myeloperoxidase activity during bacterial meningitis: Effects of febrile episodes and the BBB permeability

ObjectiveTo investigate participation of extracellular myeloperoxidase (MPO) in oxidative stress during different courses of the bacterial meningitis (BM).Materials and methodsWe sequentially assessed WBC count, blood-brain barrier (BBB) permeability, serum and cerebrospinal fluid (CSF) lipid peroxidation (LPO), MPO and antioxidative activity (AOA) in proven pediatric BM.ResultsBM patients exhibited increased systemic and local LPO and MPO, and reduced AOA, which was exaggerated in the febrile episodes. Serum MPO and LPO products were related to the BBB permeability at the baseline. CSF hydroperoxide level was influenced by the BBB permeability, CSF albumin concentration, and serum hydroperoxide (r = 0.502; p < 0.001, and r = 0.611; p < 0.001, and r = 0.358; p < 0.001, respectively). CSF hydroperoxide and MPO correlated in complicated cases during the study.ConclusionsThese results suggest that CSF LPO and MPO were closely related in BM, had different courses if febrile episodes had occurred, but were partly influenced by the BBB permeability.     

Reverse modulation of the HDL Anionic Peptide Factor and phospholipid transfer protein activity in coronary artery disease and type 2 diabetes mellitus

ObjectivesThe high density lipoprotein Anionic Peptide Factor (HDL₃-APF) was previously described as an apolipoprotein that promotes the reverse cholesterol transport. Since phospholipid transfer protein (PLTP) is involved in such mechanism we attempted to focus on the two APF and PLTP proteins.Design and methodsWe recruited 56 type 2 diabetic patients with (n = 36) or without (n = 20) coronary artery disease (CAD) and 19 CAD patients. The three groups were compared to 39 healthy control subjects. In all groups, lipid profile was determined and plasma APF concentrations and PLTP activity were measured.ResultsIn all patients, the PLTP activity was significantly increased in comparison with controls (p < 0.01), in concomitance with a plasma APF level decrease in groups with CAD (with and without type 2 diabetes) (p < 0.01). Multiple linear regression analysis demonstrated that, when apoA-I, HDL-C, HDL-phospholipids and PLTP activity were taken into account as independent variables (after univariate regression analysis), HDL-PL was positively and independently related to APF (p < 0.0001 in whole population; p = 0.0090 in controls) and PLTP activity was negatively and independently related to APF in whole population and all patients' groups (all p < 0.05), but positively and independently associated to APF in controls (p = 0.0005).ConclusionsAPF could be considered as a specific marker against CAD and type 2 diabetes mellitus and our results confirm the atherogenic behavior of PLTP in CAD. Thus, these two proteins are likely to be regulated in a reverse manner.     

Biochemical activities of lysosomal acid hydrolases in leukemic cells

The biochemical activities of 8 lysosomal acid hydrolases in leukemic cells from 48 patients were examined. Characteristic alterations were found in α-mannosidase, β-galactosidase and N-acetyl-β-glucosaminidase activities of leukemic cells. The level of α-mannosidase activity was much higher in myelo(mono)genous leukemias (AML, AMoL, AMMoL, CML and CMMoL) than in lymphogenous ones (ALL, T-cell leukemia, hairy cell leukemia and CLL) without exception. The β-galactosidase activity also differed as a result of α-mannosidase, except in T-cell leukemia. In T-cell leukemia it was within the range of normal lymphocytes, but in the other lymphogenous leukemias it was significantly below normal. N-acetyl-β-glucosaminidase activity in myelo(mono)genous leukemic cells was above the range of normal granulocytes. The changes in these enzyme levels were consistent. The lymphocytic or myelocytic nature of three cases of acute undifferentiated leukemia could be determined by enzyme studies. In two cases it was lymphocytic and in one it was myelocytic. The enzymatic abnormalities were also found in morphologically mature neutrophils from patients with not only chronic types (CML, CMMoL) but also acute types (AMoL, AMMoL) of leukemias, and were similar to those of their respective leukemic cells. Analysis of lysosomal enzymes (at least three of those mentioned above), can elucidate one of the biochemical properties of leukemic cells and may be valuable in the differentiation of leukemias.     

Effect of β-Glucan on Drain Fluid and Amount of Drainage Following Modified Radical Mastectomy

Introduction

To reduce the seroma formation following mastectomy and axillary dissection, many different techniques and drugs have been investigated. The aim of this study is to evaluate the effects of oral β-glucan on drain fluid and efficacy of daily drainage and drain removal day in mastectomy patients.

Methods

One hundred and thirty breast cancer patients of Ankara Oncology Training and Research Hospital were divided into 2 groups by consecutive randomization (n = 65 each). β-glucan 10 mg capsules were administered to Group 1 twice a day for 10 days. Group 2 took placebos in the same manner. Age, menarche age, menopause, parity, history of oral contraceptives, comorbidities, postoperative daily drainage volumes and drain removal days were recorded and compared. Seroma samples during the first and second day of drainage were taken for analysis of Interleukin-6 (IL-6) and Tumor Necrosis Factor (TNF-α).

Results

There was no difference between groups in terms of age, menarche age, menopause period, parity, oral contraceptive use and comorbidities. Group 1 showed significantly lower daily drainage volumes between days 2 and 8. Mean drain removal day was 7.16 ± 1.72 in Group 1 and 8.59 ± 2.27 in Group 2. The difference was significant (p < 0.001). TNF-α and IL-6 levels on days 1 and 2 in Group 1 were significantly lower (p < 0.001). In addition, β-glucan significantly shortened the number of days required for the drain removal in patients who have comorbidities (p = 0.018). The earliest removal was in patients without comorbidity and who received β-glucan (p = 0.002).

Conclusion

β-glucan decreased drain discharges after mastectomy. The drains were removed earlier in β-glucan administered patients.     

Continuous inter-limb coordination deficits in children with unilateral spastic cerebral palsy

BackgroundContinuous inter-limb coordination and the ability to offset perturbations to a movement pattern (i.e., stability) are important factors in efficient motor performance. Patients with movement disorders often show deficits in coordination and stability, although little is known about these features in children with cerebral palsy. The purpose of this study was to identify the continuous inter-limb coordination and stability deficits in children with cerebral palsy and determine if improvement occurs with upper extremity intervention.MethodsChildren with cerebral palsy participated in bimanual or unimanual intensive therapy. Continuous inter-limb coordination between the arms and between the more-affected arm and leg was evaluated using relative phase analysis during four gross motor tasks, including in-place marching and standing with asymmetric and symmetric arm swing. A control group of children with cerebral palsy and a group of typically developing children were also evaluated.FindingsChildren with cerebral palsy displayed coordination deficits compared to typically developing children (p<0.01), yet both groups presented similarly poor levels of stability (p=0.39). Compared to standing, adding legs to the task negatively impacted the coordination (p<0.01) and stability (p<0.01) of all children. Both groups improved coordination between the arms post-intervention (p<0.05 for all cases), however neither group improved stability (p>0.05 for all cases).InterpretationRelative phase analysis successfully provided a sensitive measurement of coordination and stability in pathologic and non-pathologic populations. Findings indicate that all children have difficulty producing consistent movement patterns and suggest that both bimanual and unimanual interventions can improve continuous coordination in children with cerebral palsy.     

Decrease in age-adjusted cerebrospinal fluid beta-secretase activity in Alzheimer's subjects

ObjectivesTo develop a novel cerebrospinal fluid (CSF) β-secretase-1 activity assay and evaluate β-secretase-1 (BACE-1) activity as a potential biomarker in human Alzheimer's disease.MethodsThe assay consisted of an enzymatic reaction of CSF samples with an optimized β-secretase peptide substrate and the cleavage products were detected using a neo-epitope specific antibody.ResultsThe CSF BACE-1 activity assay described exhibits time, temperature, dose, and pH dependence, with sensitivity down to < 1 pM of recombinant BACE-1 enzyme, and is completely blocked by BACE-1 inhibitors. The endogenous BACE-1 enzyme in CSF appears to exist as a c-terminally truncated protein, based on both western blotting and capture-based activity assays. In a small cohort of human subjects, an age-dependent increase in CSF BACE activity was observed (~ 1.0 pM/year, p < 0.05). In Alzheimer's disease subjects, a significant decline in age-adjusted CSF BACE activity was observed compared to controls (56% in the log-transformed scale, p = 0.02).ConclusionWe have developed a robust assay to measure CSF BACE-1 activity which could serve as a potential biomarker in human Alzheimer's disease subjects.