Decreased accessibility of platelet-bound fibrinogen to antibody and enzyme probes

The binding of fibrinogen to platelets is a multiphasic process leading to apparently nonreversible associations between fibrinogen and stimulated platelets. To further investigate changes in platelet- fibrinogen interactions, the present study examined the accessibility of platelet-bound fibrinogen and its GPIIb-IIIa receptor to antibody and enzyme probes as a function of time after platelet stimulation with adenosine diphosphate (ADP). Whereas only minimal changes in fibrinogen and 10E5 binding were observed within 60 minutes after platelet stimulation and equilibrium fibrinogen binding, the binding of polyclonal antifibrinogen antibodies decreased significantly (75% +/- 13%, mean +/- SD, n = 9). Similar decreases were noted with rabbit antifibrinogen Fab and F(ab')2 fragments. In addition, plasmin (32 mU/mL) added to platelets five minutes compared with 60 minutes after equilibrium fibrinogen binding dissociated 52% +/- 12% compared with 33% +/- 7% of platelet-bound fibrinogen in five minutes, and 83% +/- 15% compared with 66% +/- 14% of bound fibrinogen in 15 minutes. No difference in plasmin cleavage products was observed, however, by sodium dodecyl sulfate-polyacryl-amide gel electrophoresis (SDS-PAGE). Complete fibrinogen dissociation occurred 30 minutes after plasmin addition, confirming that fibrinogen was not internalized. In contrast, dissociation of platelet-bound fibrinogen by chymotrypsin was less affected by time after equilibrium fibrinogen binding, and minimal changes in antifibrinogen antibody recognition and plasmin-induced dissociation of fibrinogen bound to stimulated but glutaraldehyde-fixed platelets were observed. The data suggest that ADP-induced fibrinogen binding to fresh platelets is accompanied by progressive rearrangements of fibrinogen on the platelet surface.     

Histomorphometric analysis of aplastic bone disease in chronic renal failure at initiation of haemodialysis: Relation to aluminum and parathormone

SUMMARY: We studied bone histology of 134 uraemic patients without a history of vitamin D administration at the start of haemodialysis. Patients were categorized according to bone histology as follows: aplastic bone disease (ABD), ostitis fibrosa, mixed type, mild hyperparathyroidism and osteomalacia. On initiation of haemodialysis, ABD was observed in 48.5% of patients. the average age of the ABD group (50.8 ± 12.5 years) was significantly higher than that of patients with other histologies ( P <0.01). Serum parathyroid hormone (PTH) and alkaline phosphatase (ALP) concentrations were lower ( P <0.01) in the ABD group, especially in patients with diabetes mellitus. Patients with diabetes mellitus and ABD had lower serum concentrations of PTH and ALP than non-diabetic patients, suggesting that depressed PTH may be related to ABD. Eleven (55%) of the 20 patients who were receiving A1(OH)₃ also had ABD. A direct relationship was observed between serum aluminum concentration and aluminum-positive bone surface ( r =0.60; P <0.01). Aluminum staining was more frequently observed in the ABD group than in the non-ABD group ( P <0.01). Because serum intact-PTH concentrations correlate with osteoid surface area, fibrosis volume and bone formation rate, it may be a useful marker of bone histology in renal osteodystrophy. These results suggest that, in addition to conservative treatment with A1(OH)₃, other factors may be involved in the formation of ABD which is often present at the start of haemodialysis.     

Serum luteinizing hormone,follicle-stimulating hormone and oestradiol pattern in women undergoing pituitary suppression with different gonadotrophin-releasing hormone analogue protocols for assisted reproduction

Gonadotrophin-releasing hormone analogues (GnRH-a) are used widely in controlled ovarian stimulation (COS) cycles for assisted reproduction. At present, there is great debate about the influence of exogenous hormone activity on the hypothalamus–pituitary axis following pituitary desensitization. The objective of this comparative study was to investigate the pattern of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and oestradiol in women undergoing ovarian stimulation with different GnRH-a preparations. We retrospectively analysed 201 women, aged between 27 and 43 years, who were referred consecutively to our infertility clinic between January 2002 and January 2003. All women had no endocrinopathies or occult ovarian failure as assessed by day-3 hormone profile. Women were enrolled in one of the following COS protocols: depot triptorelin long protocol (n?=?38), buserelin long protocol (n?=?101) or buserelin short protocol (n?=?62). Recombinant FSH was used to induce ovulation. Treatment was monitored by transvaginal ultrasound scan and serum measurement of FSH, LH and oestradiol. Among the women initially included, 30 had cancelled cycles due to poor ovarian response. Serum LH levels were significantly higher in the short-protocol group compared with the long-protocol groups (p?<?0.001). The number of follicles, oocyte yield, number of grade-I embryos and fertilization rate were significantly lower in the short-protocol group than in the long-protocol groups. These findings showed that LH concentrations are significantly higher in women undergoing reversible medical hypophysectomy with a GnRH-a short protocol than in women treated with a long protocol. The hypothesis of an LH ceiling is confirmed.     

Receptor–receptor interactions involving adenosine A<Subscript>1</Subscript> or dopamine D<Subscript>1</Subscript> receptors and accessory proteins

Summary. The molecular basis for the known intramembrane receptor–receptor interactions among heptahelical receptors (G protein coupled receptors, GPCR) was postulated to be heteromerization based on receptor subtype specific interactions between different types of homomers of GPCR. Adenosine and dopamine receptors in the basal ganglia have been fundamental to demonstrate the existence of receptor heteromers and the functional consequences of such molecular interactions. The heterodimer is only one type of heteromeric complex and the evidence is equally compatible with the existence of higher order heteromeric complexes, where also adapter proteins such as homer proteins and scaffolding proteins can exist, assisting in the process of linking the GPCR and ion channel receptors together in a receptor mosaic that may have special integrative value and may constitute the molecular basis for learning and memory. Heteromerization of D₂ dopamine and A_2A adenosine receptors is reviewed by Fuxe in another article in this special issue. Here, heteromerization between D₁ dopamine and A₁ adenosine receptors is reviewed. Heteromers formed by dopamine D₁ and D₂ receptors and by adenosine A₁ and A_2A receptors also occur in striatal cells and open new perspectives to understand why two receptors with apparently opposite effects are expressed in the same neuron and in the nerve terminals. The role of accessory proteins also capable of interacting with receptor–receptor heteromers in regulating the traffic and the molecular physiology of these receptors is also discussed. Overall, the knowledge of the reason why such complex networks of receptor–receptor and receptor–protein interactions occur in striatal cells is crucial to develop new strategies to combat neurological and neuropsychiatric diseases.     

Reproducibility of measurements of left ventricular function with gated myocardial perfusion SPECT and comparison with blood pool radionuclide ventriculography

INTRODUCTION AND OBJECTIVE: This study was designed to evaluate the reproducibility of ejection fraction (EF) and ventricular volume measurements obtained with single photon emission computed tomography (gated-SPECT), and to assess the correlation between EF values obtained with this method and blood pool planar radionuclide ventriculography. PATIENTS AND METHOD: A total of 55 patients were included (37 men, mean age 61.3 years) upon referral to two nuclear cardiology units for diagnosis (50%) or follow-up of known coronary artery disease. In a standard 2-day protocol, patients received a dose of [99mTc]tetrofosmin (800 MBq) at stress and at rest. Two resting gated-SPECT studies were performed. QGS software was used to obtain left ventricular EF, end-diastolic volume (EDV) and end-systolic volume (ESV). Forty-nine patients agreed to undergo blood pool ventriculography on the third day. RESULTS: Interobserver variability was 0.5 (2.6)% (r=0.99) for EF, 1.9 (10.7) mL for EDV (r=0.98) and 0.5 (5.4) mL for ESV (r=0.99). Interassay variability was 2 (5.1)% (r=0.94) for EF, 4.5 (8.6) mL for EDV (r=0.99) and 3.4 (6.6) mL for ESV (r=0.99). The correlation between gated-SPECT EF and blood pool EF was suboptimal (r=0.75, 95%CI, 0.59-0.85). CONCLUSIONS: There was excellent interobserver and interassay reproducibility for left ventricular functional parameters measured with gated-SPECT and QGS software, and this method can be used for serial evaluations of ventricular function. Although the correlation between values obtained with gated-SPECT and blood pool ventriculography was acceptable, the differences show that the two techniques cannot be considered equivalent.     

Glycoprotein IIb and IIIa retention on fibrinogen-coated surfaces after lysis of adherent platelets

The platelet-membrane glycoprotein IIb-IIIa (GPIIb-IIIa) complex is essential for platelet aggregation and is involved in the attachment of platelets to thrombogenic surfaces. This study shows the retention of GPIIb and GPIIIa on immobilized fibrinogen after Triton X-100 (Sigma Chemical Co, St Louis, MO) lysis of adherent platelets. Glycoproteins were detected using subunit specific monoclonal antibodies in a modified enzyme-linked immunosorbent assay procedure. GPIIb-IIIa retention was judged to be specific relative to GPIb recovery, and was modulated by platelet activation. Platelet exposure to adenosine diphosphate or thrombin, but not A23187 or chymotrypsin, markedly enhanced GPIIb and GPIIIa recovery relative to that observed with unstimulated platelets, or prostaglandin E1-treated platelets. Moreover, lysis of adherent platelets in the presence of 10 mmol/L EDTA, under conditions promoting GPIIb-IIIa complex dissociation (pH 8.1, 60 minutes, 37 degrees C), had no effect on GPIIb or GPIIIa subunit recovery. Platelet activation with Zn+2 also enhanced GPIIb and GPIIIa recovery on fibrinogen-coated surfaces over that observed with unstimulated platelets, but GPIIb and IIIa retention was EDTA sensitive. This correlated with the EDTA-reversible nature of Zn+2- activated platelet adhesion to fibrinogen-coated surfaces. The data (1) show that platelet adhesion to fibrinogen is accompanied by the induction of high-affinity interactions between GPIIb-IIIa and immobilized fibrinogen that are EDTA-resistant and enhanced by platelet activation with some but not all agonists, and (2) implicate these interactions in stabilizing platelet contacts with fibrinogen-coated surfaces.     

Usefulness of a Collateral Channel Dilator for Antegrade Treatment of Chronic Total Occlusion of a Coronary Artery

Objectives: The aim of this study was to clarify the effectiveness of a collateral channel dilator microcatheter in antegrade percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) of a coronary artery. Background: The Corsair microcatheter, which was originally developed as a collateral channel dilator, has been reported to be useful for retrograde CTO‐PCI. Methods: We compared the success rate of the Corsair microcatheter collateral channel dilator for antegrade CTO‐PCI with a previously available microcatheter. We analyzed the data from 27 patients (32 CTOs) using the FinecrossMG (Finecross group) and the data from 31 patients (34 CTOs) using the Corsair (Corsair group). Results: There were no significant differences in the clinical or lesion characteristics between the 2 groups. The success rate for crossing the CTO by the microcatheter was 62.5% in the Finecross group and 85.3% in the Corsair group (P < 0.05). After the Corsair crossed the CTO, a 2‐mm diameter balloon catheter crossed the lesion in all the cases, but it crossed the lesion in only 17 of 20 cases in the Finecross group (85.0%, P < 0.05). The number of balloon catheters used for predilation was significantly less in the Corsair group compared with the Finecross group (P < 0.05). Conclusions: The success rate for crossing of the microcatheters and the balloon catheters through the occlusion in antegrade CTO‐PCI was better with the Corsair than with the FinecrossMG. In addition, the use of the Corsair reduced the number of balloon catheters used for predilation in antegrade CTO‐PCI. (J Interven Cardiol 2012;25:533–539)     

Direct involvement of sigma-1 receptors in the dopamine D1 receptor-mediated effects of cocaine

It is well known that cocaine blocks the dopamine transporter. This mechanism should lead to a general increase in dopaminergic neurotransmission, and yet dopamine D(1) receptors (D(1)Rs) play a more significant role in the behavioral effects of cocaine than the other dopamine receptor subtypes. Cocaine also binds to σ-1 receptors, the physiological role of which is largely unknown. In the present study, D(1)R and σ(1)R were found to heteromerize in transfected cells, where cocaine robustly potentiated D(1)R-mediated adenylyl cyclase activation, induced MAPK activation per se and counteracted MAPK activation induced by D(1)R stimulation in a dopamine transporter-independent and σ(1)R-dependent manner. Some of these effects were also demonstrated in murine striatal slices and were absent in σ(1)R KO mice, providing evidence for the existence of σ(1)R-D(1)R heteromers in the brain. Therefore, these results provide a molecular explanation for which D(1)R plays a more significant role in the behavioral effects of cocaine, through σ(1)R-D(1)R heteromerization, and provide a unique perspective toward understanding the molecular basis of cocaine addiction.     

16例脑结核瘤抗结核治疗系列观察

目的:报告16例颅内结核瘤患者的临床、影像学表现及抗结核治疗的结果.设计:本文共纳入苏丹Khartoun市全国神经系统疾病中心连续观察的16例脑结核瘤患者.诊断则依据其临床、头颅影像学特征及对抗结核治疗有效等方面.本组中共有7例具有脑组织或脑外组织的病理组织学资料.结果与结论:本组病例最常见的临床表现是头痛(100%)、全身性抽搐(68.7%)及偏瘫(56.2%).头颅横断面电子计算机体层摄影(CT)/核磁共振成像(MRI)显示单个或多个明显增强的病变及病灶周围水肿.经抗结核治疗后,多数存活患者(13/15)病变完全吸收.病变部分吸收与就诊延迟、颅内多个大病灶及晚期粟粒性结核病有关.我们主张对颅内结核瘤,即使是拟诊病例,应早期经验性试用抗结核治疗,尤其在结核病高发地区.