Platelet adhesion and thrombus formation on subendothelium in platelets deficient in glycoproteins IIb-IIIa, Ib, and storage granules

Patients whose platelets are deficient in glycoprotein (GP) Ib, IIb- IIIa (thrombasthenia), or granule substances (storage pool deficiency, SPD) were studied to define further the properties of platelets that mediate platelet adhesion and thrombus formation on subendothelium. Both nonanticoagulated and citrated blood were exposed to everted, de- endothelialized rabbit vessel segments under controlled flow conditions and shear rates varying from 650 to 3,300 sec-1. Morphometry was used to measure platelet thrombus dimensions and the percentage of the subendothelial surface covered with contact (C) or spread (S) platelets. Adhesion was defined as C + S. The results in SPD demonstrated (1) reduced thrombus dimensions in delta-SPD (pure dense granule deficiency) in proportion to the magnitude of the dense granule defect; (2) an even greater reduction in thrombus dimensions in patients with combined deficiencies of alpha and dense granules (alpha delta-SPD); and (3) impaired platelet adhesion at several conditions in alpha delta-SPD and, in delta-SPD, a hematocrit-dependent impairment of adhesion in citrated blood at 2,600 sec-1. In thrombasthenia, platelets were present as a monolayer on the subendothelial surface in both nonanticoagulated and citrated blood, indicating an absolute requirement for GPIIb-IIIa in promoting platelet-platelet interaction at all shear rates and perfusion times. Two types of abnormalities in platelet-vessel wall interactions were observed. In nonanticoagulated blood, the percentage of platelets in the C phase was consistently increased at all shear rates, but C + S values were normal. These observations indicate that platelets deficient in GPIIb-IIIa do not spread normally on the subendothelial surface exposed to nonanticoagulated blood. With citrated blood, the C + S value in thrombasthenia was reduced at both 800 and 2,600 sec-1, as in von Willebrand's disease, and a similar degree of reduction (about 50%) was observed in normal blood treated with a monoclonal antibody to GPIIb- IIIa. The findings, together with theoretical considerations, are consistent with an hypothesis that GPIIb-IIIa mediates the spreading of platelets on subendothelium following the initial attachment through GPIb and that GPIIb-IIIa may be considered an adhesion site on the platelet membrane. Abnormalities of GPIIb-IIIa may, depending on the conditions of study, result in either increased values of C platelets or decreased values of C + S. The results of the study further suggest that a complex interaction of platelet granule factors and membrane GP mediate platelet adhesion and thrombus formation.     

Rab geranylgeranyl transferase alpha mutation in the gunmetal mouse reduces Rab prenylation and platelet synthesis

Few molecular events important to platelet biogenesis have been identified. Mice homozygous for the spontaneous, recessive mutation gunmetal (gm) have prolonged bleeding, thrombocytopenia, and reduced platelet alpha- and delta-granule contents. Here we show by positional cloning that gm results from a G-->A substitution mutation in a splice acceptor site within the alpha-subunit of Rab geranylgeranyl transferase (Rabggta), an enzyme that attaches geranylgeranyl groups to Rab proteins. Most Rabggta mRNAs from gm tissues skipped exon 1 and lacked a start codon. Rabggta protein and Rab geranylgeranyl transferase (GGTase) activity were reduced 4-fold in gm platelets. Geranylgeranylation and membrane association of Rab27, a Rab GGTase substrate, were significantly decreased in gm platelets. These findings indicate that geranylgeranylation of Rab GTPases is critical for hemostasis. Rab GGTase inhibition may represent a new treatment for thrombocytosis and clotting disorders.     

Cerebral palsy is characterized by protein mediators in cord serum

Cerebral palsy (CP) is a major neurodevelopmental disability in childhood. An association between intrauterine infection and CP has been reported. We examined the relationship between inflammatory mediators in cord serum and CP in term and preterm children. Regional multicenter study was conducted on 19 CP children and 19 gestation-matched paired controls. CP children (n = 27) were further compared with controls of similar gestation at birth (n = 25). Serum levels of 78 protein mediators were analyzed. Eleven analytes correlated with the length of gestation both in cases and controls. In paired analysis, B-lymphocyte chemoattractant, ciliary neurotrophic factor, epidermal growth factor, interleukin (IL)-5, IL-12, IL-13, IL-15, macrophage migration inhibitory factor, monocyte chemoattractant protein-3, monokine induced by interferon gamma, and tumor necrosis factor-related apoptosis-inducing ligand were higher in children with CP (p < or = 0.05). Preterm infants with CP showed higher epidermal growth factor and lower levels of granulocyte-macrophage colony-stimulating factor, IL-2, macrophage-derived chemokine, and pulmonary and activation-regulated chemokine than their paired controls. Inflammatory mediators and growth factors serve as a footprint of the fetal response to an insult manifesting after birth as a permanent brain damage. The cytokine patterns at birth differ between premature and term infants who develop CP.     

Change in neoadjuvant chemotherapy could alter the prognosis of patients with pancreatic adenocarcinoma: A case report

BACKGROUNDNeoadjuvant treatment has become a standard of care for borderline or locally advanced pancreatic cancer and is increasingly considered even for up-front resectable disease. The aim of this article is to present the case of a 62-year-old patient with locally advanced pancreatic adenocarcinoma who was successfully treated with gemcitabine plus nab-paclitaxel after the failure of the first line treatment.CASE SUMMARYComputerized tomography scan and magnetic resonance imaging demonstrated a nodular lesion of ill-defined limits in the body of the pancreas, measuring approximately 4.2 cm × 2.7 cm, with an infiltrative aspect. The tumor had contact with the superior mesenteric vein, splenomesenteric junction and the proximal segment of the splenic artery, causing focal reduction of its lumens. Due to vascular involvement, neoadjuvant chemotherapy treatment with eight cycles of “folinic acid, 5-fluorouracil, irinotecan and oxaliplatine” (FOLFIRINOX) were performed. At the end of the cycles, surgery was performed, but the procedure was interrupted due to finding of lesions suspected of metastasis. Gemcitabine plus nab-paclitaxel was then successfully used for neoadjuvant treatment with subsequent R0 surgical resection.CONCLUSIONGemcitabine plus nab-paclitaxel may be effective as an alternative regimen when FOLFIRINOX fails as the first line of treatment, suggesting the need for further studies to identify which patients would benefit from each type of therapeutic approach.     

EFFECT OF EXERCISE ON GLUTAMINE SYNTHESIS AND TRANSPORT IN SKELETAL MUSCLE FROM RATS

• 1 Reductions in plasma glutamine are observed after prolonged exercise. Three hypotheses can explain such a decrease: (i) high demand by the liver and kidney; (ii) impaired release from muscles; and (iii) decreased synthesis in skeletal muscle. The present study investigated the effects of exercise on glutamine synthesis and transport in rat skeletal muscle.
• 2 Rats were divided into three groups: (i) sedentary (SED; n = 12); (ii) rats killed 1 h after the last exercise bout (EX‐1; n = 15); and (iii) rats killed 24 h after the last exercise bout (EX‐24; n = 15). Rats in the trained groups swam 1 h/day, 5 days/week for 6 weeks with a load equivalent to 5.5% of their bodyweight.
• 3 Plasma glutamine and insulin were lower and corticosterone was higher in EX‐1 compared with SED rats (P < 0.05 and P < 0.01, respectively). Twenty‐four hours after exercise (EX‐24), plasma glutamine was restored to levels seen in SED rats, whereas insulin levels were higher (P < 0.001) and costicosterone levels were lower (P < 0.01) than in EX‐1. In the soleus, ammonia levels were lower in EX‐1 than in SED rats (P < 0.001). After 24 h, glutamine, glutamate and ammonia levels were lower in EX‐24 than in SED and EX‐1 rats (P < 0.001). Soleus glutamine synthetase (GS) activity was increased in EX‐1 and was decreased in EX‐24 compared with SED rats (both P < 0.001).
• 4 The decrease in plasma glutamine concentration in EX‐1 is not mediated by GS or glutamine transport in skeletal muscle. However, 24 h after exercise, lower GS may contribute to the decrease in glutamine concentration in muscle.