Progression of fatigue in Parkinson's disease - a 9-year follow-up.

BACKGROUND AND PURPOSE: Although highly disabling, the pathogenesis and evolution of fatigue in Parkinson's disease (PD) is largely unknown, and no sufficiently documented treatment currently exists. The aim of the present study was to investigate the evolution of fatigue during the first 9 years after diagnosis. METHODS: This study is part of the Norwegian ParkWest collaboration, a prospective population-based longitudinal cohort study. The present study comprised 191 newly diagnosed patients and 170 control participants. Fatigue was assessed by the Fatigue Severity Scale, with examinations at baseline and then every other year up to 9 years of follow-up. Linear mixed models were applied to investigate possible variables associated with fatigue. RESULTS: It was found that there was a statistically significant increase in the proportion of PD patients with fatigue during the first 9 years after diagnosis. A large proportion of patients had a significant increase or decrease in fatigue score between consecutive visits. In addition, the relative risk of persistent fatigue and ever having fatigue was higher than for controls. There were statistically significant longitudinal associations between higher levels of fatigue and female gender, comorbidity at baseline, depressive symptoms, dependency in activities of daily living and better cognitive functioning. Lower levels of fatigue were associated with the use of dopamine agonists. CONCLUSION: Fatigue is a common, severely limiting symptom in PD. This study demonstrates associations with other factors that could yield a better understanding of the symptom and thus possible treatment strategies, although further investigations are necessary to establish causal relationships.

The value of cerebrospinal fluid α-synuclein and the tau/α-synuclein ratio for diagnosis of neurodegenerative disorders with Lewy pathology.

BACKGROUND AND PURPOSE: Parkinson's disease (PD), dementia with Lewy bodies (DLB) and Alzheimer's disease (AD) are three of the most common neurodegenerative disorders. Up to 20% of these patients have the wrong diagnosis, due to overlapping symptoms and shared pathologies. A cerebrospinal fluid (CSF) biomarker panel for AD is making its way into the clinic, but an equivalent panel for PD and DLB and for improved differential diagnoses is still lacking. Using well-defined, community-based cohorts and validated analytical methods, the diagnostic value of CSF total-α-synuclein (t-α-syn) alone and in combination with total tau (t-tau) in newly diagnosed patients with PD, DLB and AD was determined. METHODS: Cerebrospinal fluid concentrations of t-α-syn were assessed using our validated in-house enzyme-linked immunosorbent assay in 78 PD patients, 20 AD patients, 19 DLB patients and 32 controls. t-tau was measured using a commercial assay. Diagnostic performance was assessed by receiver operating characteristic curve analysis. RESULTS: Compared to controls (mean 517 pg/ml), significantly lower levels of CSF t-α-syn in patients with PD (434 pg/ml, 16% reduction, P = 0.036), DLB (398 pg/ml, 23% reduction, P = 0.009) and AD (383 pg/ml, 26% reduction, P = 0.014) were found. t-α-syn levels did not differ significantly between PD, DLB and AD. The t-tau/t-α-syn ratio showed an improved performance compared to the single markers. CONCLUSION: This is the first study to compare patients with PD, DLB and AD at the time of diagnosis. It was found that t-α-syn can contribute as a teammate with tau in a CSF biomarker panel for PD and DLB, and strengthen the existing biomarker panel for AD.

Inflammation and fatigue in early, untreated Parkinson's Disease.

OBJECTIVES: Parkinson's disease (PD)-related fatigue is a significant clinical problem, and the pathological processes that cause fatigue remain unknown. The aim of the present study was to explore the possible association of peripheral inflammation markers and fatigue in PD. MATERIALS & METHODS: We included 47 drug naïve, newly diagnosed PD patients with low (≤3.0) or high (>5.5) fatigue levels as evaluated by the Fatigue Severity Scale (FSS). Strict diagnostic criteria were applied for inclusion. Patients with possible confounding causes for fatigue were excluded. Serum concentrations of a panel of inflammatory markers (IL-8, TNF-α, MCP1, MIP-1ß, IL-6, IL-6R, p-selectin, E-selectin-1, ICAM, VCAM-1, CCL5, IL1-Ra, and TNFR1) were measured using ELISA technology in PD patients with and without fatigue to assess the potential relationships of fatigue in newly diagnosed, treatment-naïve patients. RESULTS: Fatigued PD patients had significantly higher levels of the IL-1 receptor antagonist (IL1-Ra) (1790 pg/mL (SD1007) vs 1262 pg/mL (SD379)) and of the adhesion molecule VCAM 1 (1071 ng/mL (SD276) vs 895 ng/mL (SD229)) than non-fatigued patients. A binary logistic regression model, including high or low FSS score as the dependent variable and UPDRS motor score, MADRS, MMSE, ESS, and IL1-Ra/VCAM-1 as independent variables, showed a significant effect both for IL1-Ra and VCAM-1. CONCLUSIONS: Higher serum levels of the inflammatory molecules IL1-Ra and VCAM-1 were associated with higher fatigue levels in patients with newly diagnosed, drug-naïve PD. These findings highlight an altered immune response as a potential contributor to PD-related fatigue, from the earliest clinical stages of the disease.

Fatigue in early Parkinson's disease: the Norwegian ParkWest study.

BACKGROUND AND PURPOSE: Fatigue is a common and disabling non-motor symptom in Parkinson's disease (PD). The pathogenesis is unknown, and the treatment options are limited. The aim of the present study was to investigate the development of fatigue during the first year after diagnosis. METHODS: The study design was a prospective, controlled population-based longitudinal cohort study, comprising 181 de novo, drug-naïve patients with PD and 162 control participants. PD was diagnosed according to the Gelb criteria. Fatigue was assessed by the Fatigue Severity Scale (FSS). Both groups were assessed for fatigue at baseline and after 1 year. RESULTS: Patients reported more fatigue than the control subjects at baseline and at the 1-year follow-up evaluation. The FSS scores in the patient group improved from a mean score of 4.4 (SD 1.6) to 4.0 (SD 1.6). Patients with fatigue at baseline received higher doses of dopaminergic medication during follow-up. Patients who received dopamine agonists improved slightly more than patients who received levodopa. A regression analysis did not show a correlation between an improvement in fatigue and a change in disease severity, depressive symptoms, sleep problems, apathy or cognitive impairment. CONCLUSION: Fatigue is a common symptom in PD, also in early, untreated patients. During the first year of observation, an improvement in the fatigue scores was found. The improvement could not be attributed to a change in disease severity or depressive symptoms. The results indicate a better effect of dopamine agonists than of levodopa. This may have implications for treatment in patients with PD-associated fatigue.

Autonomic symptoms and dopaminergic treatment in de novo Parkinson's disease.

OBJECTIVES: Autonomic symptoms are present in early stages of Parkinson's disease (PD), but evidence on how they are influenced by dopaminergic treatment remains unclear. The aim of this study was to investigate the impact of dopaminergic treatment on autonomic symptoms in early PD in a population-based cohort. METHODS: A total of 171 drug-naive patients with PD were investigated at diagnosis and 12 months later. Orthostatic blood pressure was measured, and autonomic symptoms were assessed by a preliminary version of the Movement Disorders Society-sponsored new version of the Unified Parkinson's Disease Rating Scale (range 0-4). RESULTS: In the 82% using dopaminergic treatment after 1 year, constipation and orthostatic blood pressure drop increased. There was a tendency towards increased orthostatic dizziness and urinary dysfunction. Dysphagia scores were reduced, and this was associated with higher levodopa-equivalent daily dose. CONCLUSIONS: Dopaminergic treatment during the first year after initiation seems to have only a minor impact on autonomic symptoms in early PD. It may increase constipation and orthostatic dizziness, while dysphagia can improve. Autonomic symptoms remained mild after 1 year of dopaminergic treatment.

Treatment in early Parkinson's disease: the Norwegian ParkWest study.

OBJECTIVES: There are limited data on treatment effect in early and drug-naïve Parkinson's disease (PD) outside of clinical trials. We sought to review the treatment effects on motor symptoms in early, unselected PD patients. METHODS: We included 183 drug-naïve patients from a longitudinal cohort (The Norwegian ParkWest study). At the time of diagnosis, motor symptoms were assessed and rated. Treatment was unrestricted, aimed at treating each patient optimally. Patients were reassessed after 12 months, and then grouped according to treatment: No dopaminergic treatment (NDT), dopamine agonists (DA) or levodopa. All strategies could be combined with monoamine oxidase B inhibitors. RESULTS: In general, the chosen treatment was coherent with current practice. During follow-up, patients given NDT (n = 40) had unaltered clinical motor symptoms, as opposed to improvement in the DA- and levodopa-treated patients (n = 140). The overall improvement in these two groups was fairly similar, but axial symptoms did not improve in levodopa-treated patients as opposed to the younger DA-treated patients. CONCLUSIONS: Twelve months after the diagnosis, motor symptoms in approximately one-fifth of PD patients remained clinically stable. Tremor, bradykinesia and rigidity improved in the dopaminergic-treated patients. Axial symptoms were more treatment resistant, and the different symptomatic effects found between treatment strategies may be age related.

Subjective sleep problems in patients with early Parkinson's disease.

BACKGROUND AND OBJECTIVE: Sleep problems are common in Parkinson's disease (PD) and increasingly so with disease progression. The frequency of these problems and the influence of dopaminergic treatment on sleep in early stages of PD remain unclear. We have therefore in this study examined the subjective experience of sleep problems in drug-naïve patients with early PD and how these problems developed after 1 year on dopaminergic treatment using the Parkinson's Disease Sleep Scale (PDSS). METHODS: In all, 138 drug-naïve patients with early PD derived from a population-based incident cohort and 138 age- and gender-matched control subjects were thoroughly assessed for Parkinsonism, cognition, depressive symptoms and sleep by structured interviews and clinical examination at the time of diagnosis and 1 year later on medication. Sleep problems were assessed using the PDSS. RESULTS: The total PDSS score for patients with PD was lower compared with controls, 119 vs. 127 (P < 0.05) at baseline and 121 vs. 128 (P < 0.005) after 1 year on drugs. Analyses of PDSS subdomains showed more nocturnal motor off symptoms both at baseline and after 1 year (P < 0.005) and increased daytime somnolence in patients compared with control subjects (P < 0.005 at baseline and P < 0.05 after 1 year). Only minor changes in sleep scores were seen after the introduction of dopaminergic treatment. CONCLUSION: Patients with early PD report only modestly increased subjective sleep problems at the time of diagnosis compared with control subjects and dopaminergic treatment during the first year in general only slightly changed the experienced sleep problems.

Fatigue in early Parkinson's disease. Minor inconvenience or major distress?

BACKGROUND AND PURPOSE: Although fatigue is recognized as a common and debilitating symptom in patients with Parkinson's disease (PD), little is known on how and when this symptom emerges during disease progression. The aim of the study was to explore the presence and severity of fatigue in patients with PD at the time of diagnosis, before dopaminergic treatment has been instituted. METHODS: The present study is part of the Norwegian ParkWest project, a large cohort study of patients with incident PD in Norway. PD was diagnosed according to the Gelb criteria. The study population comprised 199 patients with untreated, newly diagnosed PD and 172 control subjects, matched for gender and age. Fatigue was measured by the Fatigue Severity Scale (FSS). RESULTS: Fifty-five percent of the patients with PD had clinical significant fatigue (FSS > 4), compared with about 20% of the controls (RR = 2.9). The mean score in patients on the FSS was 4.4 (SD 1.7) and in controls 3.1 (SD 1.3). In addition, there were highly significant differences between patients and controls in each of the nine FSS items. In a regression analysis, only the Montgomery and Åsberg Depression Rating Scale and Unified Parkinson's Disease Rating Scale-Activities of Daily Living scores were significantly associated with fatigue. There was no correlation between fatigue and cognitive impairment and hypersomnia. CONCLUSION: Fatigue is a common symptom in PD, also in patients with early, untreated disease, and it has a negative impact on these patients' activity of daily living. Also in early PD, fatigue is an important consideration in the management of patients with the disease.

Early constipation predicts faster dementia onset in Parkinson's disease.

Constipation is a common but not a universal feature in early PD, suggesting that gut involvement is heterogeneous and may be part of a distinct PD subtype with prognostic implications. We analysed data from the Parkinson's Incidence Cohorts Collaboration, composed of incident community-based cohorts of PD patients assessed longitudinally over 8 years. Constipation was assessed with the MDS-UPDRS constipation item or a comparable categorical scale. Primary PD outcomes of interest were dementia, postural instability and death. PD patients were stratified according to constipation severity at diagnosis: none (n = 313, 67.3%), minor (n = 97, 20.9%) and major (n = 55, 11.8%). Clinical progression to all three outcomes was more rapid in those with more severe constipation at baseline (Kaplan-Meier survival analysis). Cox regression analysis, adjusting for relevant confounders, confirmed a significant relationship between constipation severity and progression to dementia, but not postural instability or death. Early constipation may predict an accelerated progression of neurodegenerative pathology.

Differential effect of environmental risk factors on postural instability gait difficulties and tremor dominant Parkinson's disease.

Both environmental and genetic factors contribute to the development of Parkinson's disease (PD). We have examined environmental risk factors in a Norwegian population of incident PD patients and controls, the Norwegian ParkWest study. All five neurological wards in the study area of Western Norway participated in the study. A 4-step diagnostic procedure was used to establish a representative cohort of patients with incident PD at a high level of diagnostic accuracy. 212 incident PD patients and 175 age- and gender-matched controls were included. PD patients and controls were asked for information on occupation, education, exposure to pesticides, tobacco, alcohol, and caffeine. Agricultural work was associated with a higher risk of PD (OR 1.75 (1.03-3.0) P = 0.009). There were no differences as to other occupations. Smoking (OR 0.63 (0.42-0.95) P = 0.016) and alcohol use (OR 0.55 P = 0.008) were associated with a lower risk for PD. Interestingly, this inverse association was only seen in postural instability gait difficulties (PIGD) PD (P = 0.046 for smoking, P = 0.07 for alcohol consumption), and not in tremor dominant (TD) PD which was similar to controls. Consumption of coffee was lower in PD patients (3.3 ± 1.8 cups per day vs. 3.8 ± 2.0 in controls P = 0.02). In the regression model including intake of alcohol, coffee, and smoke, only coffee (P = 0.007) and alcohol intake (P = 0.021) remained significant whereas smoking was no longer significant. Thus, it seems as though only coffee intake reduces the risk of PD in general while associations to alcohol and smoking differ between PIGD and TD-PD patients.

Caregiver distress associated with neuropsychiatric problems in patients with early Parkinson's disease: the Norwegian ParkWest study.

OBJECTIVES: We investigated caregiver distress associated with neuropsychiatric problems in patients with newly diagnosed Parkinson's disease (PD). MATERIALS AND METHODS: Persons who were next of kins of 198 patients and 168 healthy individuals completed the Neuropsychiatric Inventory Caregiver Distress Scale. RESULTS: Even at the time of diagnosis PD has a considerable impact on the next of kins' experience of distress. Nearly 50% reported distress, significantly more than in the control group, and more than one-quarter reported moderate severe distress. Except the more rarely reported neuropsychiatric symptoms, apathy was the symptom that most frequently caused caregiver distress in PD patient's next of kin (94.5%), followed by depression (88.2%), anxiety (86.2%) and irritability (83.3%). CONCLUSIONS: The study underlines the importance of focusing on neuropsychiatric aspects in patients and associated caregiver distress even in early PD management.

The role of APOE alleles in incident Parkinson's disease. The Norwegian ParkWest Study.

OBJECTIVES: Apolipoprotein E (APOE) gene alleles have been associated with various neurodegenerative disorders. However, there have been conflicting reports on associations between APOE alleles and Parkinson's disease (PD) and age at onset in PD. There exist no data on APOE alleles in an unselected cohort of patients with incident PD. PATIENTS AND METHODS: To determine the role of APOE alleles in PD and age of onset in PD at time of diagnosis, 203 patients with incident PD and 187 healthy control subjects from Western and Southern Norway were investigated according to their APOE allele status. RESULTS: No association was observed between any APOE alleles and susceptibility to PD or age at onset in PD. CONCLUSION: In our cohort of unselected, incident PD patients APOE alleles do not seem to play a role for development of PD. Prospective, long-term follow-up may still reveal associations between APOE alleles and clinical and neuropsychological progression in PD.

Incidence of Parkinson's disease in Norway: the Norwegian ParkWest study.

OBJECTIVE: To present the incidence of Parkinson's disease (PD) in Norway and to explore gender influences on incidence and age at onset, as well as severity and pattern of parkinsonism at the time of diagnosis in a representative drug naïve cohort with newly diagnosed PD. METHODS: In four Norwegian counties comprising a base population of 1 052 075 inhabitants, multiple sources of case ascertainment and a four step diagnostic procedure were used to establish a representative cohort of patients with incident PD at a high level of diagnostic accuracy. Of a total of 604 subjects referred to the study, 265 individuals fulfilled the clinical research criteria of PD at their latest clinical visit, at a mean 28 months after identification. RESULTS: The incidence of PD in the study area, age standardised to the 1991 European standard population, was 12.6/10(5yr-1) (95% CI 11.1 to 14.2). The overall age standardised male to female ratio was 1.58 (95% CI 1.22 to 2.06), with a consistent male preponderance throughout all age groups. Clinical onset of PD was later in women than in men (68.6 vs 66.3 years; p = 0.062) whereas severity and pattern of parkinsonism in drug naïve patients was not different between genders at the time of diagnosis. CONCLUSION: Incidence rates of PD in Norway are similar to those in other Western European and American countries. Female gender was associated with a considerably lower risk of PD and slightly delayed motor onset but had no impact on severity of parkinsonism or clinical phenotype in incident drug naïve PD, suggesting that the female gender influences on the nigrostriatal system are most pronounced in the preclinical phase of the disease.

The spectrum of neuropsychiatric symptoms in patients with early untreated Parkinson's disease.

BACKGROUND: Neuropsychiatric symptoms are common in Parkinson's disease (PD) and have important clinical consequences for patients, caregivers and society. Few studies of neuropsychiatric symptoms in early untreated PD exist. OBJECTIVE: To explore the range, clustering and correlates of neuropsychiatric symptoms in an incidence cohort of untreated subjects with PD. METHODS: All cases with incident PD identified during a 22 month period in four counties of Western and Southern Norway were included. Standardised criteria were used to diagnose PD. The Neuropsychiatric Inventory (NPI) was administered to 175 PD and 166 healthy control subjects with similar age and sex distributions. Cluster analysis was used to investigate the interrelationship of NPI items. RESULTS: The proportion with any NPI symptoms was higher in PD (56%) than in controls (22%) (p<0.001). Depression (37%), apathy (27%), sleep disturbance (18%) and anxiety (17%) were the most common symptoms. Clinically significant symptoms occurred in 27% of the PD group compared with only 3% in the control group (p<.001). Subjects with clinically significant neuropsychiatric symptoms had more severe parkinsonism than those without. Two neuropsychiatric clusters were identified, one characterised by mood symptoms and one by apathy. CONCLUSIONS: Although the majority of patients with early untreated PD do not have clinical significant neuropsychiatric symptoms, these symptoms are more common in patients than in people without PD. Both psychological stress and brain changes associated with PD are likely to contribute to the higher frequencies.

Treatment of sialorrhea in amyotrophic lateral sclerosis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a devastating progressive disease of all voluntary muscles. Bulbar symptoms with reduced ability to swallow occur frequently and may also be an early symptom. For some patients drooling may represent a severe social problem. AIM: To review the literature on treatment of sialorrhea in ALS and describe possible treatments. METHOD: PubMed was searched combining the words amyotrophic or ALS with sialorrhea or drooling. Publications more recent than 2000 were selected. RESULTS: A total of 31 publications were found. Of these, 22 are from 2000 or later. Thirteen of the 22 most recent publications are original papers whereas 9 are review articles. Of the original articles, four describe treatment of sialorrhea with radiotherapy, five describe effects of botolinum toxin injections into the salivary grands and two describe serious side-effects of botolinum toxin injections for sialorrhea in ALS. The remaining original articles are case descriptions or practice surveys. DISCUSSION: The treatment of sialorrhea in ALS is discussed in the view of current knowledge.

Radiotherapy reduces sialorrhea in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder. Sialorrhea is a frequent problem in ALS patients with bulbar symptoms, because of progressive weakness of oral, lingual and pharyngeal muscles. This prospective study aimed to investigate the putative effect of palliative single-dose radiotherapy on problematic sialorrhea in patients with ALS. Twenty patients with ALS and problematic drooling were included; 14 were given radiotherapy with a single fraction of 7.5 Grey (Gy). Five patients were treated with botulinum toxin A (BTX-A) injections (20 U) into the parotid glands; two of these were later given radiotherapy. Symptom assessment, clinical examination and measurements of salivary flow (ml/min) were performed before and after treatment (1-2 weeks, 3 months). Salivary secretion was significantly reduced after radiation treatment, with a mean reduction of 60% (1 week) and 51% (2 weeks). Three months post-treatment, 21% reduction of the salivary secretion was observed compared with salivation before treatment. Mean salivary flow was not reduced after BTX-A treatment in five patients. No serious side-effects were observed with either of the two treatment modalities. Single-dose radiotherapy (7.5 Gy) significantly reduces sialorrhea and is an effective and safe palliative treatment in patients with ALS.

Development and reversion of methionine dependence in a human glioma cell line: relation to homocysteine remethylation and cobalamin status.

We investigated the biochemical changes which accompanied the development and reversion of methionine dependence in a human glioma cell line GaMg. This cell line attained a higher proliferation rate and more malignant morphology with increasing passages in vitro. Early passages (P10, P25, and P45) were able to grow in a methionine-deficient medium supplemented with homocysteine (Met-Hcy+), while a later passage (P60) had lost this ability, i.e., it had become methionine-dependent. From P60 cells, a methionine-independent revertant (P60R) was established by exposing the cells to 5-aza-2-deoxycytidine, followed by culture in a Met-Hcy+ medium. In these genetically related cell lines, we investigated homocysteine remethylation and the functional state of cobalamin-dependent methionine synthase, the enzyme responsible for remethylation of homocysteine to methionine. The methionine synthase activity in cell extracts was similar in all cell sublines. Intact cell methionine biosynthesis and nitrous oxide-dependent homocysteine export reflect homocysteine remethylation in cells cultured in a Met-Hcy+ and methionine-containing (Met+Hcy-) medium, respectively. Both of these parameters, as well as the cellular content of the substrate 5-methyltetrahydrofolate, and the cofactor methylcobalamin, in addition to adenosylcobalamin, were high in P10, declined progressively in P45 and P60, and were restored in P60R. P25 cells had some unique features among the methionine-independent phenotypes because both homocysteine remethylation and the level of 5-methyltetrahydrofolate were low in Met+Hcy- medium. The maximal homocysteine export rate in the presence of nitrous oxide, which reflects the overall transmethylation rate, was high in P60 and even higher in P60R compared to the lower passages. The basis for development of methionine dependence during culture of this glioma cell line seems related to the combined effects of reduced methionine biosynthesis and an increased overall transmethylation rate. The single parameter which most closely correlated to the ability to use homocysteine for growth was methylcobalamin. These data support a model for methionine dependence, which implies impaired provision of cobalamin to methionine synthase.

Phosphate turnover of phosphatidylinositol in resting and thrombin-stimulated platelets.

Human platelets were pulse-labelled with [32P]Pi and extracts were analyzed for masses and radioactivities of ATP and phosphoinositides. Immediately after pulse-labelling, the specific 32P radioactivity of phosphatidylinositol (PI) was only 3.4% of that of the gamma-phosphoryl of ATP. Upon incubation of the platelets at 37 degrees C, the specific 32P radioactivity of ATP (beta- and gamma-phosphoryls) remained constant. However, specific 32P radioactivity in PI increased continuously to 17% of specific [gamma-32P]ATP at 90 min of incubation. Stimulation with 0.5 U/ml of thrombin induced a 35% decrease in mass of PI which was unaffected by the time after the pulse-labelling. In contrast, the thrombin-induced changes in [32P]PI differed markedly at the various times after the [32P]Pi-pulse. Immediately after pulse-labelling, [32P]PI initially decreased but increased thereafter to 260% of control values after 180 s. With increasing specific 32P-radioactivity in PI before stimulation, the thrombin-induced increase in [32P]PI gradually disappeared. After 90 min of incubation, thrombin induced a continuous decrease in [32P]PI that almost parallelled mass. The data are explained by an initial breakdown of PI to diacylglycerol through the PI cycle or the polyphosphoinositide cycle, followed by resynthesis of PI through phosphatidic acid. In contrast to pre-existing PI, the resynthesized PI is in full isotopic equilibrium with ATP. This allowed us to estimate that 14% of the PI that is consumed between 30 and 180 s of stimulation, is recycles. From our data we calculate that the rate of PI resynthesis increased from 2.4 to 20 nmol/min per 10(11) cells upon thrombin stimulation of platelets.

Studies on the preferential incorporation of [3H]glycerol over [32P]phosphate into major phospholipids of human platelets.

It is well known that platelets readily incorporate radioactive glycerol, but not radioactive phosphate into phosphatidylcholine (PC) and phosphatidylethanolamine (PE) in vitro, thus not in accordance with de novo synthesis according to the Kennedy pathway. In attempts to understand the reason for the discrepancy, gel-filtered platelets were incubated simultaneously with [32P]Pi and [3H]glycerol, and the specific and relative radioactivities of products and intermediates were determined. Both precursors were incorporated into phosphatidylinositol (PI) with a 32P/3H ratio similar to that in glycerol 3-phosphate (in accordance with the Kennedy pathway). However, PC and PE obtained a much lower ratio. The specific 32P radioactivity in phosphorylcholine was similar to that of the gamma-phosphoryl of ATP and 650-times higher than that of PC. The specific 32P radioactivity of phosphorylethanolamine was 20-times less than that of phosphorylcholine. Both mass and 32P labelling of CDP-choline were below the detection limits. It is concluded that the incorporation of [32P]Pi into PC via phosphorylcholine is insignificant while the preferential incorporation of [3H]glycerol could be explained by exchange of diacyl[3H]glycerol in the reversible choline phosphotransferase (CDP-choline: 1,2-diacylglycerol cholinephosphotransferase) reaction. The same mechanism would explain the preferential incorporation of 3H over 32P into PE, although dilution of 32P at the phosphorylethanolamine stage would account for part of the feeble 32P incorporation. Although other mechanisms are also possible, our results clearly show that the appearance of [3H]glycerol in PC and PE is not a reliable method of monitoring de novo synthesis of these phospholipids.

Evidence that chlorpromazine and prostaglandin E1 but not neomycin interfere with the inositol phospholipid metabolism in intact human platelets.

Human platelets that had been prelabelled with [32P]Pi were stimulated with trombin in the presence or absence of neomycin, prostaglandin E1 (PGE1) or chlorpromazine. The content of [32P]Pi in phosphatidylinositol 4-phosphate, phosphatidylinositol 4,5-bisphosphate and phosphatidic acid (PA) were determined. The data demonstrate that PGE1 and chlorpromazine but not neomycin interfere with the tight metabolic relationship that exists between the inositol phospholipids and PA in thrombin-stimulated platelets [(1989) Biochem. J. 263, 621-624]. Our results therefore indicate that neomycin does not inhibit signal transduction in intact platelets at the level of the inositol phospholipid metabolism.