[First French-speaking days of users of decision support system in clinical pharmacy: Feedback and perspectives]

Clinical decision support systems (CDSS) are tools that have been used for several years by clinical pharmacy teams to support pharmaceutical analysis, with a perspective of contributing to the quality of care in collaboration with the other health care team members. These tools require both technical, logistical and human resources. The growing use of these systems in different establishments in France and in Europe gave birth to the idea of meeting to share our experiences. The days organized in Lille in September 2021 aimed at proposing a time of exchange and reflection on the use of these CDSS in clinical pharmacy. A first session was devoted to feedback from each establishment. These tools are essentially used to optimize pharmaceutical analysis and to secure patient medication management. This session outlined the clear advantages and common limitations of these CDSS. Two research projects were also presented to put the use of these tools into perspective. The second session of these days, in the form of workshops, addressed 4 themes that surround the implementation of CDSS: their usability, the legal aspect, the creation of rules and their possible valorization. Common problems were raised, the resolution of which requires close collaboration. This is a first step proposing a beginning of harmonization and sharing that should be deepened in order not to lose the dynamics created between the different centers. This event ended with the proposal to set up two working groups around these systems: the creation and structuring of rules for the detection of risk situations and the common valorization of the work.

Sleep and memory consolidation in aging: A neuroimaging perspective

Recently acquired information is strengthened and consolidated during sleep. For hippocampus-dependent memory, this process is assumed to occur mainly during slow wave sleep. Changes in sleep patterns in older adults can contribute to the disruption of the consolidation process during sleep and thus lead to cognitive impairment. Current findings suggest that reduced gray matter volume, particularly in frontal areas, Aβ and tau accumulation in combination with age-related changes of specific oscillations during sleep may contribute to memory deficits. This non-exhaustive review aims at providing a comprehensive picture of the associations between sleep changes and memory consolidation in aging, mainly based on neuroimaging studies. Overall, data confirm the utmost importance of sleep for healthy aging and the need to develop interventions aiming at improving sleep to reduce cognitive decline observed with advancing age.

Acceptance Factors for In-Hospital Pharmacist Interventions in Daily Practice: A Retrospective Study

Introduction: Performing pharmacist interventions (PIs) during the medication review helps to improve the quality of care. The acceptance by the physician of these PIs is a good indicator of the quality of this clinical pharmacy activity. The objective of this study was to determine, in the Amiens-Picardie teaching hospital (France), factors of acceptance in a variable environment of activity (central pharmacy, in the care units, computer assisted). Methods: All PIs transcribed by pharmacists on the Act-IP© site between November 2018 and April 2019 were analyzed using a complementary search in patient records. The environment, type, and clinical impact on patient health of each PI was collected. Linear mixed-effects models with a random pharmacist intercept were used to investigate the relationship between PI modalities and their chance of being accepted. Results: A total of 3,100 PIs were traced, of which 2,930 had been followed over time. Of these, 2,930 PIs, 1,504 (51.3%) were performed by a postgraduate pharmacist and 1,426 (48.7%) by a pharmacy resident, 1,623 (55.4%) were performed by verbal exchange, 455 (15.5%) by telephone, 846 (28.9%) by computer software, and 6 (0.2%) by paper. The clinical impact on patient health was major for 976 PIs (33.3%) and vital for 26 PIs (0.9%). According to the Anatomical Therapeutic Chemical Classification (ATC), they were mainly related to anti-infectives (30.3%), the nervous system (18.7%), and blood and blood-forming organs (17.3%). In total, 2,415 PIs (82.4%) were accepted. According to the multivariate model, a PI was more often accepted when it was transmitted orally rather than by software (+27.7%, 95% CI: +23.2 to +32.1%) and when it was transmitted to a medical resident rather than a postgraduate physician (+4.4%, 95% CI: 1.2-7.6%). In these cases, there was a major rather than a moderate clinical impact on patient health (+4.3%, 95% CI: +1.1-+7.6%). Conclusion: This study highlights the importance of the quality of the exchange with the prescriber and the prioritization of high-risk interventions as key points of medication review to improve rate of pharmacist interventions accepted by physician.

Impact of a training session for prescribers on the relative prescription of cefotaxime over ceftriaxone in elderly patients

BACKGROUND

The prescription of ceftriaxone should be limited to patients with biliary tract infections and those lacking intravenous access. A specific training session for prescribers about the clinical relevance and economic value of prescribing cefotaxime instead of ceftriaxone might decrease the use of the latter in geriatric medicine.

OBJECTIVES

To determine the clinical and economic impact of a training session for prescribers on the subsequent prescription of third-generation cephalosporin, that is, the percentage of appropriate prescriptions and the cost of third-generation cephalosporin administration before and after the training session.

METHODS

In a preliminary observational quasi-experimental, open-label study, appropriateness of cefotaxime and ceftriaxone prescription over a 4-week period immediately before the training session were compared with those during a 4-week period immediately afterwards.

KEY FINDINGS

For 46 patients (29 before the training session and 17 afterwards), the proportion of cefotaxime prescriptions increased (from 3% to 35%; P = 0.007), and the proportion of appropriate prescriptions increased at the start of treatment (from 45% to 76%; P = 0.064) and at the end (from 76% to 88%; P = 0.450). The daily per-patient cost of treatment was €8 for cefotaxime and from €1.63 to €3.42 for ceftriaxone, depending on the administration route.

CONCLUSIONS

A training session for prescribers was associated with a decrease in ceftriaxone prescriptions encouraging further studies to improve the training session and then evaluate medico-economic impact through randomized clinical trials.

Role of the community pharmacist in detecting frailty and spatio-temporal disorientation among community-dwelling older people in France

BACKGROUND

Many older community-dwelling subjects may be frail and/or disoriented, putting them at risk of adverse outcomes. We investigated the prevalence of frailty and spatiotemporal disorientation among patients aged > 65 years collecting regular medication at a community pharmacy.

METHODS

Prospective, cross-sectional study of geriatric evaluation in 218 community pharmacies in France. Regular customers aged > 65 years attending the pharmacy to receive ≥ 1 prescription drug were eligible. Spatio-temporal disorientation was assessed using a 4-item screening test; subjects were considered disoriented if they had ≥ 1 incorrect answers. Frailty was evaluated using the Short Emergency Geriatric Assessment (SEGA) grid. Subjects were considered as not frail (score < 8), or frail/very frail (score of 8 or more).

RESULTS

4090 subjects were included, average age 77.5 ± 7.6 years, 60.1% females. Overall, 1025 (25%) were frail/very frail, and 384 (9.4%) were disoriented in space or time. On average, subjects were taking 5.4 ± 3.5 medications per day. Among non-frail patients, 116/3065 (3.8%) were disoriented, of whom 87 (87/116, 75%) managed their medication alone. Among frail/very frail patients, 268/1025 (26.1%) were disoriented, of whom 46 (46/268, 16.8%) managed their medication alone. The majority of patients (77.9%) collected their medication alone at the pharmacy, but significantly fewer frail patients came to collect their drugs alone (p < 0.001).

CONCLUSION

It is feasible for community pharmacists to detect disorientation and frailty among older patients. A quarter of subjects were frail/very frail, and 3.2% were disoriented yet managing their drugs alone. Additional social support should be envisaged for these subjects.

Hemodynamic impact of molecular adsorbent recirculating system in refractory vasoplegic shock due to calcium channel blocker poisoning

OBJECTIVE

To report the hemodynamic effect of to the molecular adsorbent recirculating system (MARS™) therapy for patients in refractory vasoplegic shock due to calcium channel blocker (CCB) poisoning.

METHODS

We report a retrospective cohort of patients who were hospitalized for CCB poisoning with refractory vasoplegic shock and treated by MARS therapy, at Amiens Hospital University, from January 2010 to December 2019. Improvement in hemodynamic was assessed by dynamic changes in mean arterial pressure (MAP) and norepinephrine levels over a 24-h period after MARS therapy. Cardiac function was assessed by transthoracic echocardiography.

RESULTS

MARS therapy was performed on seven patients for CCB poisoning. CCB poisoning included nicardipine (n = 3, 43%) amlodipine (n = 3, 43%), and verapamil (n = 1, 14%). The median time to start MARS therapy was 24 [14-27] h after drug ingestion and 6 [2-9] h after ICU admission. Cardiac output was preserved for all patients. MAP values improved from 56 [43-58] to 65 [61-78] 16 mmHg (p = 0.005). Norepinephrine dose significantly decreased from 3.2 [0.8-10] µg/kg/min to 1.2 [0.1-1.9] µg/kg/min (p = 0.008) and lactate level decreased from 3.2 [2.4-3.4] mmol/l^-1 to 1.6 [0.9-2.2] mmol/l^-1 (p = 0.008). The median length of ICU stay was 4 (2-7) days and hospital stay was 4 (4-16) days. No complication related to the MARS therapy were reported. No patient died and all were discharged from the hospital.

CONCLUSION

We reported the largest case-series of MARS therapy for refractory vasoplegic shock due to CCB poisoning. We observed that MARS therapy was associated with an improvement of hemodynamic parameters.

Decreased monocyte calcium sensing receptor expression in patients with chronic kidney disease is associated with impaired monocyte ability to reduce vascular calcification

In chronic kidney disease (CKD), calcium-sensing receptor (CaSR) expression and function have been extensively studied in parathyroid tissue and vascular tissues. To examine whether similar changes occurred in other tissues, we measured total and surface CaSR expression in monocytes of patients with various stages of CKD and healthy volunteers respectively in cross-sectional studies. We further explored in vitro the impact of uremic serum on CaSR expression in monocytes (U937 and THP-1 cell lines), and whether human peripheral blood mononuclear cells or U937 and THP-1 monocytes might modify vascular calcium deposition in rat carotid arteries in vitro. CKD was associated with a decrease in peripheral blood mononuclear cell CaSR expression both in total and at the monocyte surface alone (43% and 34%, respectively in CKD stages 4-5). This decrease was associated with a reduction in the ability of monocytes to inhibit vascular calcification in vitro. Pretreatment with the calcimimetic NPSR568 of peripheral blood mononuclear cells isolated from patients with CKD significantly improved monocyte capacity to reduce carotid calcification in vitro. The fewer peripheral blood mononuclear cells expressing cell surface CaSR, the more calcimimetic treatment enhanced the decrease of carotid calcium content. Thus, we demonstrate that monocyte CaSR expression is decreased in patients with CKD and provide in vitro evidence for a potential role of this decrease in the promotion of vascular calcification. Hence, targeting this alteration or following monocyte CaSR expression as an accessible marker might represent a promising therapeutic strategy in CKD-associated arterial calcification.

Rationale for COVID-19 Treatment by Nebulized Interferon-β-1b-Literature Review and Personal Preliminary Experience

The inflammatory response to COVID-19 is specifically associated with an impaired type I interferon (IFN) response and complete blockade of IFN-β secretion. Clinically, nebulization of IFN-α-2b has been historically used in China to treat viral pneumonia associated with SARS-CoV. Very recent data show that the use of inhaled type I IFN is associated with decreased mortality in Chinese COVID-19 patients. However, IFN nebulization is currently not standard in Europe and the United States. Therefore, our group has set up a project aimed to evaluate the possibility to nebulize IFN-β-1b (a drug currently used in Europe to treat multiple sclerosis via subcutaneous injections) and to assess the safety of this new mode of administration in SARS-CoV-2 infected patients. We present here literature data that allowed us to build our hypothesis and to develop collaboration between clinical pharmacists, intensivists and nebulization engineers in order to gain first pre-clinical and clinical experience of IFN-β-1b nebulization. After validation of the nebulization method and verification of droplet size compatible with nebulization, the method has been applied to four intensive care patients treated at our university hospital, for whom none of the COVID-19 therapies initially used in France led to significant clinical improvement. All patients exhibited negative viral carriage and experienced clinical improvement 7-16 days after having initiated nebulized IFN-β-1b inhalation therapy. No side effects were observed. All patients were alive within a 90-days follow-up. Although it is not possible to draw firm conclusions on treatment efficacy based on this case report, our study shows that pulmonary IFN-β-1b administration is feasible, with a good safety profile. This procedure, which presents the advantage of directly targeting the lungs and reducing the risks of systemic side effects, may represent a promising therapeutic strategy for the care of patients with severe COVID-19. However, our preliminary observation requires confirmation by randomized controlled trials.

COVID-19 : profil patient prédisposant à une admission précoce en service de Réanimation

Introduction

Même si la majorité des patients atteints n’ont que des symptômes bénins, certains, plus graves, nécessitent une hospitalisation en service de soins voire une admission en réanimation. En raison du risque de létalité élevé, ces patients doivent être étroitement surveillés.

L’objectif de notre étude est de définir des profils patients qui pourraient favoriser une admission précoce en service de réanimation et de définir des marqueurs pouvant appuyer cette admission.

Matériels et méthodes

Étude rétrospective monocentrique du profil des patients admis en réanimation entre le 1^er mars et le 26 avril 2020. Les données démographiques des patients (âge, sexe, poids, indice de masse corporelle, statut tabagique), les données biologiques à l’admission en réanimation, les antécédents cliniques ainsi que les traitements médicamenteux ont été recueillis.

Deux groupes ont été constitués en fonction du délai entre la date de début des symptômes et la date d’entrée en réanimation : strictement inférieur à 7 jours (G1, admission précoce) et supérieur ou égal à 7 jours (G2, admission tardive). Une analyse statistique comparative par un test de Student pour les variables continues et du Chi² pour les variables catégorielle a été effectuée.

Résultats

Au total, la cohorte comprend 127 patients dont 62 dans le G1 et 65 dans le G2. L’analyse des données démographiques montre un IMC (31,5 dans le G1 vs 29,2 dans le G2 ; p = 0,04) et un âge (66,5 vs 60,6 ; p ≤ 0,01) supérieur dans le G1.

Le taux d’hypokaliémie (0,27 vs 0,09 ; p ≤ 0,01), d’hypocalcémie (0,56 vs 0,32 ; p ≤ 0,01), d’hypercréatininémie (0,42 vs 0,17 ; p ≤ 0,01) et d’hyperferritinémie (0,96 vs 0,63 ; p ≤ 0,01) semble être significativement plus élevée dans le G1.

De plus, la proportion de patients avec des antécédents cardiovasculaires (0,57 vs 0,34 ; p ≤ 0,01) et/ou diabétiques (0,25 vs 0,10 ; p = 0,02) sont plus élevés dans le G1. Le nombre de traitement moyen (4,5 vs 3,0 ; p = 0,04) et en particulier de médicaments à visée cardiovasculaire (0,60 vs 0,39 ; p = 0,02) est aussi plus fréquent dans le G1. Enfin, le taux de mortalité (0,31 vs 0,12 ; p = 0,01) est plus élevé dans le G1 que dans le G2.

Conclusion

Des profils patients se dessinent selon les données objectivées par cette étude. Les patients obèses, et en particulier en obésité morbide (avec un IMC > 35 kg/m²), ainsi que les patients âgés sont à risque d’être admis précocement en réanimation. Il en est de même pour les patients avec de nombreux antécédents cardiovasculaires et/ou diabétiques, les patients polymédiqués et notamment ceux traités par des médicaments à visée cardiovasculaire.

Parmi les éléments biologiques relevés, l’hypokaliémie, l’hyperferritinémie (avec des valeurs moyennes très hautes dans le G1), l’insuffisance rénale et l’hypocalcémie semblent favoriser une admission précoce en réanimation.

Les taux de mortalité en réanimation étant élevés (20 % à plus de 60 % selon le profil du patient), il est important de repérer les marqueurs et les facteurs prédisposant à une admission en réanimation. La priorisation de la prise en charge de ces patients permettrait d’éviter leur passage en soins intensifs et pourrait avoir un impact sur la mortalité.

Mobile Phone Text Messages and Effect on Treatment Adherence in Patients Taking Methotrexate for Rheumatoid Arthritis: A Randomized Pilot Study

OBJECTIVE

To assess the impact of weekly text messages on adherence in patients taking methotrexate (MTX) for rheumatoid arthritis (RA).

METHODS

This prospective, randomized pilot, single-site study included patients with RA stabilized using MTX alone or combined with biologics. Participants were randomized to 3 interventions: a standard consultation (controls), a 15-minute pharmacist-led counseling session, or the receipt of text message reminders. The change over time in the Compliance Questionnaire Rheumatology (CQR-19) score between baseline and 6 months was defined as the primary outcome for adherence. Multivariable analyses and final adherence (as a composite outcome of the CQR-19 score, the Girerd score, and the medication possession ratio) were probed in sensitivity tests. Rheumatologic scales, inflammation, and patient satisfaction were also analyzed.

RESULTS

A total of 96 patients (mean ± SD Disease Activity Score in 28 joints 2.42 ± 1.03) were monitored. The change over time in the CQR-19 score was significantly higher in the text message group (mean ± SD 3.32 ± 5.66; P = 0.02) than in the control group (mean ± SD 0.22 ± 6.56) and the pharmacist-led counseling group (mean ± SD -0.14 ± 7.56). Multivariable logistic regression showed that text messages remained associated with an increase in the CQR-19 score, independently of the baseline CQR-19 score (odds ratio 3.63 [95% confidence interval 1.26-10.49]; P = 0.017). In the text message group, the increase in the CQR-19 score was correlated with the Health Assessment Questionnaire score (r = -0.405, P = 0.021), and patient satisfaction was significantly higher (P < 0.01) than in the control group.

CONCLUSION

Our results showed evidence of a positive impact of text messages on adherence to MTX treatment for RA. The clinical benefit and the ideal target patient remain to be determined.

Bistability of magnetic states in Fe-Pd nanocap arrays

Magnetic bistability between vortex and single domain states in nanostructures are of great interest from both fundamental and technological perspectives. In soft magnetic nanostructures, the transition from a uniform collinear magnetic state to a vortex state (or vice versa) induced by a magnetic field involves an energy barrier. If the thermal energy is large enough for overcoming this energy barrier, magnetic bistability with a hysteresis-free switching occurs between the two magnetic states. In this work, we tune this energy barrier by tailoring the composition of FePd alloys, which were deposited onto self-assembled particle arrays forming magnetic vortex structures on top of the particles. The bifurcation temperature, where a hysteresis-free transition occurs, was extracted from the temperature dependence of the annihilation and nucleation field which increases almost linearly with Fe content of the magnetic alloy. This study provides insights into the magnetization reversal process associated with magnetic bistability, which allows adjusting the bifurcation temperature range by the material properties of the nanosystem.

P905Association of ionized serum magnesium with progression of aortic valve calcification

Background

Calcific aortic valve disease (CAVD) is the most common heart valve disease among adults. It is a progressive disease whose final step leads to severe aortic stenosis (AS). Pharmacotherapeutic strategies aimed to limit the progression of valve leaflet calcification could be beneficial to slow-down the CAVD progression and to preserve left ventricular function. Several recent clinical studies demonstrated that lower serum magnesium (Mg) level is associated with vascular calcification. Whether serum magnesium is a determinant of aortic calcific stenosis progression remains unkwown.

Methods

In an ongoing prospective cohort of AS patients (COFRASA/GENERAC) we studied the association between serum Mg with the aortic valve calcification prevalence and progression. Serum Mg was measured at baseline in both its ionized (iMg) and total (tMg) forms. AS stenosis severity was evaluated at baseline and yearly thereafter using mean pressure gradient (MPG), the aortic valve area indexed to body surface (AVAi) assessed by echocardiography and the degree of aortic valve calcification (AVC) assessed by computed tomography. Annual progression was calculated as: (final measurement − baseline measurement)/follow-up duration.

Results

We enrolled 356 patients (73.1±10 years, 73% men), the mean follow-up duration was 2.5±2 years. There was a highly significant correlation between iMg and t Mg concentrations values (r=0.85, p<0.0001). Approximately 37% and 25% of patients have respectively iMg values ≤0.45 mmol/L (normal range 0.45–0.60 mmol/L) and t Mg ≤0.80 mmol/L (normal range 0.80–0.95 mmol/L). At baseline, lower i Mg and t Mg were significantly associated with sex, diabètes, lower heamoglobin and hypertension but not with AVC neither with MPG or AVAi. After mean follow-up of 2.5±2 years, the annual mean Log AVC progression was significantly greater (p=0.01) in patients with values of iMg ≤0.45 mmol/L (2,04±0.73) as compared to patients with iMg >0,45 mmol/L (1.78±0.94). Annual Mean MGP and AVAi also progressed greater in patients with low iMg but without reaching a significant level. Similar association was not found with tMg. In multivariate analysis, iMg remained significantly associated with the progression of AVC (odds ratio per 0.1 mmol/L increment [95% confidence interval] = 0.36 [0.15–0.83]; p=0.015) independently of age, tMg, glucose, type 2 diabetes, Tobacco use, baseline AVC, MPG and AVAi.

Conclusion

In a prospective cohort of asymptomatic patients with a wide range of AS severity, low serum ionized Mg but not low total Mg was independently associated with AVC progression.

Acknowledgement/Funding

ANR -RHU-STOPAS

The electrophysiological connectome is maintained in healthy elders: a power envelope correlation MEG study

Functional magnetic resonance imaging (fMRI) studies report age-related changes in resting-state functional connectivity (rsFC), suggesting altered or reorganized connectivity patterns with age. However, age-related changes in neurovascular coupling might also partially account for altered connectivity patterns. Here, we used resting-state magnetoencephalography (MEG) and a connectome approach in carefully selected healthy young adults and elders. The MEG connectome was estimated as rsFC matrices involving forty nodes from six major  resting-state networks. Source-level rsFC maps were computed in relevant frequency bands using leakage-corrected envelope correlations. Group differences were statistically assessed using non-parametric permutation tests. Our results failed to evidence significant age-related differences after correction for multiple comparisons in the α and the β bands both for static and dynamic rsFC, suggesting that the electrophysiological connectome is maintained in healthy ageing. Further studies should compare the evolution of the human brain connectome as estimated using fMRI and MEG in same healthy young and elder adults, as well as in ageing conditions associated with cognitive decline. At present, our results are in agreement with the brain maintenance theory for successful aging as they suggest that preserved intrinsic functional brain integration contributes to preserved cognitive functioning in healthy elders.

Association between metformin use and below-the-knee arterial calcification score in type 2 diabetic patients

Background

Vascular calcification (VC) is common in type 2 diabetes, and is associated with cardiovascular complications. Recent preclinical data suggest that metformin inhibits VC both in vitro and in animal models. However, metformin’s effects in patients with diabetic VC have not previously been characterized. The present study investigated the association between metformin use and lower-limb arterial calcification in patients with type 2 diabetes and high cardiovascular risk.

Methods

The DIACART cross-sectional cohort study included 198 patients with type 2 diabetes but without severe chronic kidney disease. Below-the-knee calcification scores were assessed by computed tomography and supplemented by colour duplex ultrasonography. Data on anti-diabetic drugs were carefully collected from the patients’ medical records and during patient interviews. Biochemical and clinical data were studied as potential confounding factors.

Results

Metformin-treated patients had a significantly lower calcification score than metformin-free patients (mean ± standard deviation: 2033 ± 4514 and 4684 ± 9291, respectively; p = 0.01). A univariate analysis showed that metformin was associated with a significantly lower prevalence of severe below-the-knee arterial calcification (p = 0.02). VC was not significantly associated with the use of other antidiabetic drugs, including sulfonylureas, insulin, gliptin, and glucagon like peptide-1 analogues. A multivariate logistic regression analysis indicated that the association between metformin use and calcification score (odds ratio [95% confidence interval] = 0.33 [0.11–0.98]; p = 0.045) was independent of age, gender, tobacco use, renal function, previous cardiovascular disease, diabetes duration, neuropathy, retinopathy, HbA_1c levels, and inflammation.

Conclusions

In patients with type 2 diabetes, metformin use was independently associated with a lower below-the-knee arterial calcification score. This association may contribute to metformin’s well-known vascular protective effect. Further prospective investigations of metformin’s potential ability to inhibit VC in patients with and without type 2 diabetes are now needed to confirm these results.

N-methyl-2-pyridone-5-carboxamide (2PY)-Major Metabolite of Nicotinamide: An Update on an Old Uremic Toxin

N-methyl-2-pyridone-5-carboxamide (2PY, a major metabolite of nicotinamide, NAM) was recently identified as a uremic toxin. Recent interventional trials using NAM to treat high levels of phosphorus in end-stage renal disease have highlighted new potential uremic toxicities of 2PY. In the context of uremia, the accumulation of 2PY could be harmful-perhaps by inhibiting poly (ADP-ribose) polymerase-1 activity. Here, we review recently published data on 2PY's metabolism and toxicological profile.

Calcitriol prevents in vitro vascular smooth muscle cell mineralization by regulating calcium-sensing receptor expression

Vascular calcification (VC) is a degenerative disease that contributes to cardiovascular morbidity and mortality. A negative relationship has been demonstrated between VC and calcium sensing receptor (CaSR) expression in the vasculature. Of interest, vitamin D response elements, which allow responsiveness to 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], are present in the promoters of the CaSR gene. We hypothesized that 1,25(OH)2D3, by modulating CaSR expression in vascular smooth muscle cells (VSMCs), might protect against VC. Human VSMCs were exposed to increasing concentrations of 1,25(OH)2D3 (0.01-10 nmol/L) in noncalcifying (1.8 mmol/L) or procalcifying Ca(2+)0 condition (5.0 mmol/L). Using quantitative RT-PCR and Western blotting we observed a significant increase in both CaSR mRNA and protein levels after exposure to 1.0 nmol/L 1,25(OH)2D3. This effect was associated with a maximal increase in CaSR expression at the cell surface after 48 hours of 1,25(OH)2D3 treatment, as assessed by flow cytometry. Down-regulation of the vitamin D receptor by small interfering RNA abolished these effects. In the procalcifying condition, 1.0 nmol/L 1,25(OH)2D3 blocked the Ca(2+)0-induced decrease in total and surface CaSR expression and protected against mineralization. Down-regulation of CaSR expression by CaSR small interfering RNA abolished this protective effect. 1,25(OH)2D3 concentrations of 0.5 and 5.0 nmol/L were also effective, but other (0.01, 0.1, and 10 nmol/L) concentrations did not modify CaSR expression and human VSMC mineralization. In conclusion, these findings suggest that nanomolar concentrations of 1,25(OH)2D3 induce a CaSR-dependent protection against VC. Both lower and higher concentrations are either ineffective or may even promote VC. Whether this also holds true in the clinical setting requires further study.

Determination and modulation of total and surface calcium-sensing receptor expression in monocytes in vivo and in vitro

Expression of the calcium-sensing receptor (CaSR) has previously been demonstrated in human circulating monocytes (HCM). The present study was designed to measure CaSR expression in HCM and to examine its potential modulation by pro-inflammatory cytokines, Ca2+, vitamin D sterols in U937 cell line. Twenty healthy volunteers underwent blood sampling with subsequent isolation of peripheral blood mononuclear cells (PBMC) at 3 visits. Flow cytometry analysis (FACS) was performed initially (V1) and 19 days later (V2) to examine intra- and intersubject fluctuations of total and surface CaSR expression in HCM and 15 weeks later (V3) to study the effect of vitamin D supplementation. In vitro experiments were conducted to assess the effects of pro-inflammatory cytokines, calcidiol, calcitriol and Ca2+ on CaSR expression in U937 cell line. By FACS analysis, more than 95% of HCM exhibited cell surface CaSR staining. In contrast, CaSR staining failed to detect surface CaSR expression in other PBMC. After cell permeabilization, total CaSR expression was observed in more than 95% of all types of PBMC. Both total and surface CaSR expression in HCM showed a high degree of intra-assay reproducibility (<3%) and a moderate intersubject fluctuation. In response to vitamin D supplementation, there was no significant change for both total and surface CaSR expression. In the in vitro study, U937 cells showed strong total and surface CaSR expression, and both were moderately increased in response to calcitriol exposure. Neither total nor surface CaSR expression was modified by increasing Ca2+ concentrations. Total CaSR expression was concentration dependently decreased by TNFα exposure. In conclusion, CaSR expression can be easily measured by flow cytometry in human circulating monocytes. In the in vitro study, total and surface CaSR expression in the U937 cell line were increased by calcitriol but total CaSR expression was decreased by TNFα stimulation.

Theory of negative-refractive-index response of double-fishnet structures

A theory is presented of the negative refractive index observed in the so-called double-fishnet structures. We find that the electrical response of these structures is dominated by the cutoff frequency of the hole waveguide whereas the resonant magnetic response is due to the excitation of gap surface plasmon polaritons propagating along the dielectric slab. Associated with this origin, we show how the negative refractive index in these metamaterials presents strong dispersion with the parallel momentum of the incident light.

Potent acetylcholinesterase inhibitors: design, synthesis and structure-activity relationships of alkylene linked bis-galanthamine and galanthamine-galanthaminium salts

The syntheses, the anticholinesterase activities and structure-activity relationships of homodimeric (3a-c) and heterodimeric (6a-c) alkylene linked bis-galanthamine are reported. Compounds 6b-c were found to be more potent than galanthamine and tacrine in inhibiting AChE.

Release potency tests of hepatitis vaccines

SmithKline Beecham Biologicals produces two vaccines against hepatitis: hepatitis B (Engerix-B) introduced in 1986 and hepatitis A (Havrix) introduced in 1991. Using these two examples, we demonstrate the long and gradual transition process towards an in vitro release test for potency and a significant decrease in the number of animals needed for vaccine release.

Potent acetylcholinesterase inhibitors: design, synthesis, and structure-activity relationships of bis-interacting ligands in the galanthamine series

New galanthamine derivatives, especially bis-interacting ligands 3-5 and 7-9 were prepared in order to interact with the catalytic and the peripheral sites of acetylcholinesterase (AChE). The synthesis, the anticholinesterase activities, and the structure-activity relationships of bis-interacting ligands are reported. Compounds 4d-e were found to be more potent than galanthamine and tacrine in inhibiting AChE.

Novel splicing, missense, and deletion mutations in seven adenosine deaminase-deficient patients with late/delayed onset of combined immunodeficiency disease. Contribution of genotype to phenotype

We examined the genetic basis for adenosine deaminase (ADA) deficiency in seven patients with late/delayed onset of immunodeficiency, an underdiagnosed and relatively unstudied condition. Deoxyadenosine-mediated metabolic abnormalities were less severe than in the usual, early-onset disorder. Six patients were compound heterozygotes; 7 of 10 mutations found were novel, including one deletion (delta 1019-1020), three missense (Arg156 > His, Arg101 > Leu, Val177 > Met), and three splicing defects (IVS 5, 5'ss T+6 > A; IVS 10, 5'ss G+1 > A; IVS 10, 3'ss G-34 > A). Four of the mutations generated stop signals at codons 131, 321, 334, and 348; transcripts of all but the last, due to delta 1019-1020, were severely reduced. delta 1019-1020 (like delta 955-959, found in one patient and apparently recurrent) is at a short deletional hot spot. Arg156 > His, the product of which had detectable activity, was found in three patients whose second alleles were unlikely to yield active ADA. The oldest patient diagnosed was homozygous for a single base change in intron 10, which activates a cryptic splice acceptor, resulting in a protein with 100 extra amino acids. We speculate that this "macro ADA," as well as the Arg156 > His, Arg101 > Leu, Ser291 > Leu, and delta 1019-1020 products, may contribute to mild phenotype. Tissue-specific variation in splicing efficiency may also ameliorate disease severity in patients with splicing mutations.

A new bopyrid isopod Athelges neotenuicaudis (Crustacea: Isopoda: Epicaridea) parasitic on Pagurus kulkarnii from Visakhapatnam Coast, India

A new bopyrid isopod Athelges neotenuicaudis is reported. The new isopod is collected from the crab Pagurus kulkarnii as ectoparasite. They are found in the intertidal region of Mukkam, Visakhapatnam Coast. Andhra Pradesh, India. Athelges neotenuicaudis n. sp. is compared with A. paguri Rathke, 1843; A. tenuicaudis Rathke, 1843; and A. bilobus Rathke.

Erythrocyte deformability measurements in patients with glaucoma

Erythrocyte deformability and aggregability, fibrinogen plasma level, and hematocrit were measured in patients with primary open-angle glaucoma and in age-matched control subjects. Only one parameter, red blood cell rigidity, as evaluated by the Hanss filtration technique, was found significantly elevated in glaucoma patients. This erythrocyte abnormality, which corroborates previous data on blood viscosity, could be an important factor in the pathogenesis of optic nerve damage and could support the hypothesis of a primary oxidative stress in glaucoma.

IgG antibody response to polyethylene glycol-modified adenosine deaminase in patients with adenosine deaminase deficiency

Polyethylene glycol (PEG)-modified bovine adenosine deaminase (ADA) is used for replacement therapy of severe combined immunodeficiency disease due to inherited ADA deficiency. We monitored IgG anti-ADA antibody in 17 patients treated by intramuscular injections of PEG-ADA for 1 to greater than 5.5 yr. ELISA-detectable anti-ADA IgG appeared in 10 patients, usually between the third and eighth months of treatment. Anti-ADA levels did not correlate with trough plasma ADA activity, which averaged 1.8-5 times normal blood (erythrocyte) ADA activity, depending on dose (15-60 U/kg per wk). ELISA-detectable anti-ADA antibodies were directed primarily at bovine-specific peptide (rather than PEG-containing) epitopes. Enhanced enzyme clearance, mediated by antibody that directly inhibited native and PEG-modified bovine ADA, and native, but not PEG-modified human ADA, occurred in two patients. In one, tolerance was induced; in the second, twice weekly injections of PEG-ADA compensated for accelerated clearance. We speculate that inhibitory antibodies recognize conserved, relatively PEG-free epitope(s) encompassing the active site, and that in human, but not bovine, ADA a PEG-attachment site "shields" the active site from immune recognition. We conclude that PEG-modification largely prevents the development of high affinity, or high levels of clearing antibodies to bovine ADA, and that PEG-modified human ADA should be further investigated as a possible treatment for ADA deficiency.

Effects of two low osmolality contrast media on red blood cell filterability and aggregation in vitro

The in vitro effects of ionic ioxaglate and non-ionic iopamidol were compared. Filtration measurements were carried out on an hemorheometer; erythrocyte aggregation was evaluated by means of an erythrocyte aggregometer, and red blood cell morphology was observed with an optical microscope. Ioxaglate and iopamidol reduced erythrocyte filterability to the same extent; by contrast neither ionic nor non-ionic contrast media significantly modified aggregation or shape of red blood cells. The decrease of erythrocyte deformability observed in this study may cause clotting in catheters or syringes during angiographies investigations.

Use of site-directed mutagenesis to enhance the epitope-shielding effect of covalent modification of proteins with polyethylene glycol

Modification by covalent attachment of polyethylene glycol (PEG) can reduce the immunogenicity and prolong the circulating life of proteins, but the utility of this approach for any protein is restricted by the number and distribution of PEG attachment sites (e.g., epsilon-amino groups of lysine residues). We have developed a strategy for introducing additional sites for PEG attachment by using site-directed mutagenesis to selectively replace arginine with lysine codons and tested it with purine nucleoside phosphorylase (PNP) from Escherichia coli, an extremely stable but immunogenic enzyme, that could potentially be used to treat an inherited deficiency of PNP. A triple mutant, RK3, possessing three Arg----Lys substitutions was constructed that increased the number of lysines per PNP subunit from 14 to 17, providing an additional 18 potential PEG attachment sites per hexameric enzyme molecule. The wild-type and RK3 enzymes had similar catalytic activity, antigenicity, and immunogenicity. After PEG modification, both enzymes retained catalytic activity, the plasma half-life of both enzymes in mice increased from approximately 4 hr to 4 days, and the binding of both enzymes by antisera raised against each unmodified enzyme was markedly diminished. However, antibody raised against wild-type PEG-PNP did not bind the PEG-RK3 enzyme. PEG-RK3 PNP was also substantially less immunogenic than wild-type PEG-PNP. Accelerated antibody-mediated clearance of PEG-PNP occurred in 2 of 12 mice treated with PEG-RK3 PNP, compared with 10 of 16 mice treated with the modified wild-type enzyme. This combined use of directed mutagenesis and PEG modification is aimed at permitting the widest choice of proteins, including products of genetic and chemical "engineering," to be used for therapy of inherited and acquired disorders.

LPS-stimulated bovine aortic endothelial cells produce IL-1 and IL-6 like activities

Vascular endothelium is known to closely interact with leukocytes and immunocompetent cells. We report here that cultured bovine aortic endothelial cells (BAEC) synthesize both interleukin 1 (IL-1) and interleukin 6 (IL-6) like activities in response to bacterial lipopolysaccharide stimulation. Our results agree with previous data obtained from human venous endothelia and support the concept that IL-1 and IL-6 synthesis are properties common to endothelial cells from different vascular beds. The IL-1 activity was measured by murine thymocyte proliferation assay and by an indirect bioassay using NOB1 cells, which evidenced higher IL-1 amounts than the former. This discrepancy appeared to be partly due to the simultaneous production of one or more inhibitor(s) of the thymocyte proliferation by BAEC. The IL-6 assay was performed with the murine hybridoma cell line B9. In other respects, the cyclooxygenase inhibitor indomethacin enhanced the IL-1 like production, but was ineffective on IL-6 like production. The present study provides additional evidence that endothelial cells from large arteries may also participate in inflammatory and immunological processes.

The response time of transcription and translation of the leu-2 gene of Neurospora to its inducer, alpha-isopropylmalate, approaches the permissible minimum

The rate of transcription and translation of the leu-2 gene of Neurospora crassa was measured after induction by alpha-isopropylmalate. Little message of enzyme was found before inducer addition but transcription in the lower eukaryote was found well underway within five minutes after inducer addition, followed in a minute or two by the appearance of functional enzyme. The timing was close to the limit set by RNA synthesis and ribosome procession. As a consequence, it seems unlikely that traversal of the cell and/or nuclear membranes by the inducer and message involves intermediate synthetic reactions and that the leu-3 positive regulatory element is fully available for participation in the induction process before the inducer is added. A significant overshoot in message synthesis was found early in the induction process. This is discussed with respect to previously observed effects of the inducer on general RNA synthesis.

Change in chromosome number associated with a double deletion in the Neurospora crassa mitochondrial chromosome

The mitochondrial genome of Neurospora is usually found in a single covalently closed circular 62-kbp DNA molecule. We report here that the mitochondrial genome of a phenotypic revertant of a stopper mutant (stp-ruv) is contained primarily in two separate, nonoverlapping, autonomously replicating circular chromosomes. The circles, one about 21 kbp and the other somewhat less than 36 kbp are derived from the most frequent classes of recombinant chromosomes (21 and 41 kbp) in the chromosomal population of mitochondria in the original stopper mutant. The new, more stable chromosomal configuration, is associated with the deletion of two sequences (1 kbp and 4 kbp) at the splice junctions of the two circles. The data suggest that both deletions are likely to have originated from a single recombinational event involved in generating the 36-kbp circle. Secondary, spontaneously arising derivatives of stp-ruv have been found to yield, at high copy number, short sections of the 21-kbp circle in covalently closed supercoiled circles varying from unit length to very high multimers. The amplified segments span a common segment likely to contain the replication origin of the 21-kbp chromosome.

Consequences of terbium (III) binding on the conformation and enzymatic activity of guinea pig liver transglutaminase

Calcium ions are crucial for expression of transglutaminase activity. Although lanthanides have been reported to substitute for calcium in a variety of protein functions, they did not replace the calcium requirement during transglutaminase activity measurements. Furthermore, lanthanides strongly inhibited purified liver transglutaminase activity using either casein or fibrinogen as substrates. Terbium (III) inhibition of transglutaminase-catalyzed putrescine incorporation into casein was not reversed by the presence of 10-200 fold molar excess of calcium ions (Ki for Tb(III) = 60 microM). Conformational changes in purified liver transglutaminase upon Tb(III) binding were evident from a biphasic effect of Tb(III) on transglutaminase binding to fibrin. Low concentrations of Tb(III) (1 microM to 10 microM) inhibited the binding of transglutaminase to fibrin, whereas higher concentrations (20 microM to 100 microM) promoted binding. Conformational changes in purified liver transglutaminase consequent to Tb(III) binding were also demonstrated by fluorescence spectroscopy due to Forster energy transfer. Fluorescence emission was stable to the presence of 200 mM NaCl and 100 mM CaCl2 only partially quenched emission. Purified liver transglutaminase strongly bound to Tb(III)-Chelating Sepharose beads and binding could not be disrupted by 100 mM CaCl2 solution. Our data suggest that Tb(III)-induced conformational changes in transglutaminase are responsible for the observed effects on enzyme structure and function. The potential applications of Tb(III)-transglutaminase interactions in elucidating the structure-function relationships of liver transglutaminase are discussed.

Tb(III)-ion-binding-induced conformational changes in platelet factor XIII

Ca(II) ions are crucial during proteolytic conversion of Factor XIII zymogen into the active enzyme Factor XIIIa. Factor XIII proteolyzed by thrombin or trypsin in the presence of 5 mM-EDTA resulted in rapid inactivation of transglutaminase activity. Factor XIIIa formed by thrombin or trypsin in the presence of 40 microM-Tb(III) ions, however, was indistinguishable from Factor XIIIa formed in the presence of 2-5 mM-Ca(II) ions with respect to molecular mass and transglutaminase activity. Thrombin treatment of Factor XIII in the presence of 1-5 microM-Tb(III) ions resulted in three fragments (76 kDa, 51 kDa and 19 kDa) with simultaneous loss of transglutaminase activity. Tb(III) ions at concentrations greater than 40 microM made platelet Factor XIII resistant to proteolysis by either thrombin or trypsin. Other lanthanide(III) ions [Ln(III) ions] tested [Ce(III), La(III) and Gd(III) ions] functioned similarly to Tb(III) ions during proteolytic activation of Factor XIII. Ln(III) ions (10-100 microM) were unable to replace the Ca(II) ions required for transglutaminase activity of Factor XIIIa. Tb(III) ions also inhibited in a non-competitive manner the transglutaminase activity of Factor XIIIa (Ki 71 microM) even when measured in the presence of 200-fold molar excess of Ca(II) ions. Factor XIII selectively bound to a Tb(III)-chelate affinity column, and could not be eluted by 100 mM-CaCl2. Binding of Tb(III) ions to Factor XIII was demonstrated by fluorescence emission due to Forster energy transfer. A 10(4)-fold molar excess of CaCl2, but not NaCl, partially quenched Tb(III) fluorescence. Low concentrations (5-20 microM) of Tb(III) ions also inhibited the binding of Factor XIII to des-A-fibrinogen by about 43%, whereas higher concentrations (40-100 microM) promoted binding. Conformational changes in Factor XIII consequent to the binding of Tb(III) ions could be responsible for the observed effects on protein structure and function.

Isolation of a fibrin-binding fragment from blood coagulation factor XIII capable of cross-linking fibrin(ogen)

Purified platelet Factor XIII was radioiodinated and then partially degraded by thrombin or trypsin, and a fibrin-binding fragment was identified by autoradiography and immunoblotting following separation by SDS/polyacrylamide-gel electrophoresis. Limited proteolysis of 125I-Factor XIII by thrombin or trypsin produced an 125I-51 kDa fragment and an unlabelled 19 kDa fragment. The 51 kDa fragment was purified by h.p.l.c. on a TSK-125 gel-filtration column. Partial amino acid sequence analysis of the 51 kDa fragment indicated that it was similar in sequence to the Gly38-Lys513 segment in placental Factor XIII a-chain. More than 70% of the 51 kDa fragment bound to fibrin, whereas the 19 kDa fragment did not bind. The active site was localized to the 51 kDa fragment since this fragment expressed transglutaminase activity, cross-linked fibrin and fibrinogen and incorporated iodo[14C]acetamide into the active-site cysteine residue. Isolation of a fibrin-binding fragment expressing transglutaminase activity demonstrates that each a-chain of the dimeric Factor XIIIa could function independently to cross-link fibrin. The fibrin-binding site could play an important role in localizing Factor XIIIa to the fibrin clot.

The binding sites on fibrin(ogen) for guinea pig liver transglutaminase are similar to those of blood coagulation factor XIII. Characterization of the binding of liver transglutaminase to fibrin

The present study represents detailed investigations into the nature of interactions between an intracellular "tissue" transglutaminase and a plasma protein, fibrinogen. We demonstrate a specific, saturable, and reversible binding of transglutaminase to fibrin(ogen). The binding was time- and temperature-dependent, was independent of divalent metal ions, did not require the release of either fibrinopeptide A or B, and was partially inhibited by the presence of sodium chloride or plasma proteins, properties similar to Factor XIII binding to fibrin(ogen). Both Factor XIII and liver transglutaminase also shared similar binding sites on fibrinogen, the A alpha- and the B beta-chains. The binding characteristics of liver transglutaminase were thus similar to Factor XIII binding to fibrin, but there were also important differences. Scatchard analyses of the binding data indicated that the affinity of liver transglutaminase (Kd = 4.17 x 10(-7) M) was at least 40-fold weaker compared with the affinity of Factor XIII to fibrinogen. Consequently, a 20-fold molar excess of Factor XIII a-chains specifically and completely inhibited the binding of liver transglutaminase to des-A-fibrinogen. The association between liver transglutaminase and fibrin(ogen) was also critically controlled by the conformational states of the two proteins. Substances capable of altering the conformation of either transglutaminase (such as guanosine 5'-triphosphate) or of fibrinogen (such as the tetrapeptide Gly-Pro-Arg-Pro and Fragment D) disrupted binding. Excess CaCl2 was able to counteract the effects of guanosine 5'-triphosphate on transglutaminase binding to fibrin. In contrast, Factor XIII binding to fibrin was unaffected by either guanosine 5'-triphosphate, CaCl2, or Gly-Pro-Arg-Pro, suggesting a more stable association between the two proteins. The physiologic implications of transglutaminase-fibrin(ogen) interactions are discussed.

b-chains prevent the proteolytic inactivation of the a-chains of plasma factor XIII

While the transglutaminase activity is associated exclusively with the thrombin-cleaved a chains of plasma Factor XIII, there is little information regarding the role of the b-chains. The present investigations were undertaken to clarify the role of the b-chains during proteolytic activation of plasma factor XIII a-chains. The a-chains of platelet Factor XIII (a2) were extremely sensitive to alpha-thrombin proteolysis, especially in the presence of 5 mM EDTA, resulting in two major fragments with molecular masses 51 +/- 3 kDa and 19 +/- 4 kDa. Furthermore, fibrin enhanced the alpha-thrombin proteolysis of thrombin-cleaved platelet Factor XIII a-chains in presence of CaCl2 or EDTA, resulting in several peptide fragments with molecular masses from 51 +/- 3 kDa to 14 +/- 4 kDa. By contrast, thrombin-cleaved a-chains of plasma Factor XIII (a2b2) were not further degraded by alpha-thrombin in presence of 5 mM EDTA. Even in the combined presence of 5 mM EDTA and 0.1 mg/ml fibrin, alpha-thrombin proteolysis of plasma Factor XIIIa was limited to the formation of a 76 kDa fragment (= Factor XIIIa), a 51 +/- 3 kDa fragment and trace amounts of a 14 +/- 4 kDa species. Platelet Factor XIII proteolyzed by 500 nM alpha-thrombin in presence of 5 mM EDTA expressed less than 20% of enzymatic activity obtained when platelet Factor XIII was activated in presence of 5 mM CaCl2. In contrast, plasma Factor XIII activated by 500 nM apha-thrombin in presence of 5 mM EDTA expressed nearly 65% of original transglutaminase activity. Likewise, when plasma Factor XIII was proteolyzed by 100-1000 nM gamma-thrombin in presence of 5 mM CaCl2 or 5 mM EDTA, maximal transglutaminase activity was observed. However, when platelet Factor XIII was similarly treated with gamma-thrombin in presence of 5 mM EDTA, only one-half the original transglutaminase activity was obtained. The b-chains thus appear to mimic the function of Ca2+ in preserving transglutaminase activity of thrombin-cleaved a-chains. The b-chains of plasma Factor XIII were not degraded by either alpha- or gamma-thrombin treatment, in presence of 5 mM EDTA or 5 mM CaCl2. Both platelet and plasma Factor XIII a-chains were degraded by trypsin to fragments with molecular masses of 51 +/- 3 kDa and 19 +/- 4 kDa in presence of 5 mM CaCl2 and to fragments with molecular masses of 19 +/- 4 kDa and lower, in presence of 5 mM EDTA.(ABSTRACT TRUNCATED AT 400 WORDS)

The binding of divalent metal ions to platelet factor XIII modulates its proteolysis by trypsin and thrombin

We investigated the effect of divalent metal ions on the proteolytic cleavage and activation of platelet Factor XIII by thrombin and trypsin. In the absence of metal ions (5 mM EDTA), trypsin and thrombin rapidly degraded platelet Factor XIII (80 kDa) to low-molecular-mass peptides (50-19 kDa) with simultaneous loss of transglutaminase activity. Divalent metal ions protected Factor XIII from proteolytic inactivation with an order of efficacy of Ca2+ greater than Zn2+ greater than Mg2+ greater than Mn2+. Calcium (2 mM) increased by 10- to 1000-fold the trypsin and thrombin concentrations required to degrade Factor XIII to a 19-kDa peptide. Factor XIIIa formed by thrombin in the presence of 5 mM EDTA had one-half the specific activity of Factor XIIIa formed in the presence of calcium. Factor XIII was cleaved by trypsin in the presence of 5 mM Ca2+ to a 51 +/- 3-kDa fragment that had 60% of the original Factor XIIIa activity. A similar tryptic peptide formed in the presence of 5 mM EDTA did not have transglutaminase activity. In the presence of 5 mM Mg2+, thrombin cleaved Factor XIII to a major 51 +/- 3-kDa fragment that had 60% of the Factor XIIIa activity. Mn2+ (0.1-5 mM) limited trypsin and thrombin proteolysis. The resulting digest containing a population of Factor XIII fragments (50-14 kDa) expressed 50-60% transglutaminase activity of Factor XIIIa. Factor XIII was fully activated by both trypsin and thrombin in the presence of 5 mM Zn2+, resulting in two fragments of 76 and 72 kDa. We conclude that the binding of divalent metal ions to platelet Factor XIII induces conformational changes in the protein that alter its susceptibility to proteolysis and influence the expression of transglutaminase activity.

Factor XIII binds to the A alpha- and B beta- chains in the D-domain of fibrinogen: an immunoblotting study

The binding sites in fibrinogen for Factor XIII were localized using an immunoblotting technique. Platelet Factor XIII bound to fibrinogen and to plasmin degradation products of fibrin(ogen) including Fragments: X, D1-D3, and D-dimer, but did not bind to Fragment E. Binding of Platelet Factor XIII was independent of calcium ions but could be inhibited by the presence of 0.5 M NaCl. Binding could also be inhibited by preincubating Factor XIII with a 100-fold molar excess of fibrinogen but not by 100-fold molar excess of Fragment E. Binding of Factor XIII to fibrinogen was specific, since several other proteins tested (ovalbumin, bovine serum albumin, alpha 2-macroglobulin, beta-galactosidase, fructose kinase, lactic dehydrogenase, triose phosphate isomerase, fumarase and pyruvate kinase) did not bind Factor XIII. Furthermore, binding was not observed either when Factor XIII was left out or when antiFactor XIII antiserum was substituted with nonimmune serum. When fibrinogen was reduced prior to electrophoresis, Factor XIII bound to the A alpha and B beta chains of fibrinogen and des A,B fibrinogen, the B beta-chain of Fragment X, but not the gamma-chains. Localization of the Factor XIII binding sites to the carboxy terminal segments of the A alpha and B beta chains in the Fragment D-domain of fibrinogen could have important physiological consequences.

Differential effects of leukotrienes B4 and C4 on bovine aortic endothelial cell proliferation in vitro

The effect of leukotrienes derivated from arachidonic acid was studied on vascular endothelium proliferation. The peptido-leukotriene LTC4 (0.1 nM - 0.1 microM) promoted a dose-dependent growth of bovine aortic endothelial cells in culture with a maximal effect at 10 nM. This proliferative activity could be receptor-mediated since LTC4 specifically bound to endothelial cell membranes with a Kd value of 50 nM. The leukotriene B4 did not induce any significant proliferation in the same range of concentrations. This result was consistent with the lack of LTB4 specific binding sites. This data suggests that LTC4 could be one of the factors implicated in angiogenesis during inflammatory processes.

Critical assessment of the platelet adenylate cyclase system as a potential model for testing alpha 2 adrenergic activity

We have studied the effects of KUM 32 and CBS 1276, two clonidine-related drugs, upon the adenylate cyclase system of human platelets. Both drugs behaved as potent antagonists of epinephrine-induced platelet aggregation. [3H]Yohimbine binding studies revealed that the drugs bind to the alpha 2 adrenergic receptor of human platelets. KUM 32 and CBS 1276 also behaved as strong inhibitors of adenylate cyclase activity. This inhibition, which was not competitive with respect to ATP, is not an alpha 2 adrenergic phenomenon since it was not antagonized by yohimbine and was still observed in the absence of GTP. Moreover, pretreatment of platelet membranes with islet activating protein from Bordetella pertussis (IAP) had no effect on the inhibition by KUM 32, CBS 1276 and adenosine, although it completely reversed the effect of epinephrine and partially reversed the effect of clonidine. These results show that clonidine-like drugs may have different impacts on the adenylate cyclase system of human platelets. This system cannot be used as a pharmacological predictive test for alpha 2 adrenergic agonist activity, as various compounds, known to have central alpha 2 adrenergic agonist properties, do not behave as full agonists for the alpha 2 adrenergic receptor of human platelets.