Platelet adhesion to collagen types I through VIII under conditions of stasis and flow is mediated by GPIa/IIa (alpha 2 beta 1-integrin)

Platelet adhesion to fibrillar collagens (types I, II, III, and V) and nonfibrillar collagens (types IV, VI, VII, and VIII) was investigated in the presence of physiologic concentrations of divalent cations under conditions of stasis and flow. Under static conditions, platelet adhesion was observed to collagen types I through VII but not to type VIII. Under flow conditions, platelet adhesion to collagen types I, II, III, and IV was almost independent of shear rates above 300/s. Collagen type V was nonadhesive. Platelet adhesion to collagen type VI was shear rate-dependent and optimal at a rate of 300/s. Collagen types VII and VIII showed minor reactivity and supported platelet adhesion only between shear rates 100 to 1,000/s. Monoclonal antibody (MoAb) 176D7, directed against platelet membrane glycoprotein Ia (GPIa; very late antigen [VLA]-alpha 2 subunit), completely inhibited platelet adhesion to all collagens tested, under conditions of both stasis and flow. Platelet adhesion to collagen type III at shear rate 1,600/s was only inhibited for 85%. The concentration of antibody required for complete inhibition of platelet adhesion was dependent on the shear rate and the reactivity of the collagen. An MoAb directed against GPIIa (VLA-beta subunit) partially inhibited platelet adhesion to collagen. These results show that GPIa-IIa is a major and universal platelet receptor for eight unique types of collagen.     

Taxanes: A New Class of Antitumor Agents

Taxanes belong to a new group of antineoplastic agents with a novel mechanism of action for a cytotoxic drug. They promote microtubule assembly and stabilize the microtubules. Paclitaxel, the first agent in this group to become available, was isolated from the Pacific yew, Taxus brevifolia, in 1971. In preclinical and clinical studies, paclitaxel and its semisynthetic analog docetaxel exhibit significant antitumor activity. This review deals with the physicochemical properties, pharmacology, and results of preclinical and clinical trials of the taxanes.     

Induction of apoptosis by the ginsenoside Rh2 by internalization of lipid rafts and caveolae and inactivation of Akt

Background and purpose:

Lipid rafts and caveolae are membrane microdomains with important roles in cell survival signalling involving the Akt pathway. Cholesterol is important for the structure and function of these microdomains. The ginsenoside Rh2 exhibits anti-tumour activity. Because Rh2 is structurally similar to cholesterol, we investigated the possibility that Rh2 exerted its anti-tumour effect by modulating rafts and caveolae.

Experimental approach:

A431 cells (human epidermoid carcinoma cell line) were treated with Rh2 and the effects on cell apoptosis, raft localization and Akt activation measured. We also examined the effects of over-expression of Akt and active-Akt on Rh2-induced cell death.

Key results:

Rh2 induced apoptosis concentration- and time-dependently. Rh2 reduced the levels of rafts and caveolae in the plasma membrane and increased their internalization. Furthermore, Akt activity was decreased and consequently, Akt-dependent phosphorylation of Bad, a pro-survival protein, was decreased whereas the pro-apoptotic proteins, Bim and Bax, were increased upon Rh2 treatment. Unlike microdomain internalization induce by cholesterol depletion, Rh2-mediated internalization of rafts and caveolae was not reversed by cholesterol addition. Also, cholesterol addition did not restore Akt activation or rescue cells from Rh2-induced cell death. Rh2-induced cell death was attenuated in MDA-MB-231 cells over-expressing either wild-type or dominant-active Akt.

Conclusions and implications:

Rh2 induced internalization of rafts and caveolae, leading to Akt inactivation, and ultimately apoptosis. Because elevated levels of membrane rafts and caveolae, and Akt activation have been correlated with cancer development, internalization of these microdomains by Rh2 could potentially be used as an anti-cancer therapy.     

A new genetic isolate with a unique phenotype of syndromic oculocutaneous albinism: clinical, molecular, and cellular characteristics

An extended, highly consanguineous Israeli Bedouin family with at least 20 individuals exhibiting a unique phenotype of oculocutaneous albinism (OCA) was identified. All known OCA genes were excluded in this family. Electron microscopic analysis of platelets revealed absence of dense bodies, suggesting a diagnosis of Hermansky-Pudlak syndrome (HPS). HPS is a rare autosomal recessive disorder of lysosome-related organelle biogenesis, clinically characterized by OCA and platelet dysfunction, sometimes accompanied by other systemic pathologies. All human HPS genes (HPS1-8) and five genes corresponding to murine HPS models were evaluated. Haplotype analysis and homozygosity mapping of the HPS loci revealed linkage to chromosome 10 in the studied family. Subsequently, a novel insertion mutation, c.1066-1067insG was identified in HPS6. Most frameshift mutations generating premature termination codon cause mRNA nonsense mediated decay (NMD), while intronless genes like HPS6 are usually not monitored by NMD. Expression analysis revealed no mRNA decay in patient's fibroblasts, hence truncated protein is most probably produced. Confocal microscopy revealed abnormal distribution of LAMP-3 (lysosomal associated membrane protein-3) in fibroblasts from the patients, indicating abnormal trafficking of lysosomal lineage organelles. So far, a single HPS-6 patient phenotypically similar to HPS-3 and HPS-5 has been identified. The HPS-6 phenotype in the studied family is unique since it resembles OCA and not HPS. Therefore, our finding broadens the phenotypic definition of HPS. Two major genetic isolates of HPS-1 and HPS-3 patients were previously diagnosed in Puerto Rico. The extended Bedouin family is the largest isolate of non-Puerto Rican HPS patients.     

Maternal occupational exposure and congenital heart defects in offspring

Objectives:Congenital heart defects (CHD) are the most prevalent congenital anomalies. This study aims to examine the association between maternal occupational exposures to organic and mineral dust, solvents, pesticides, and metal dust and fumes and CHD in the offspring, assessing several subgroups of CHD.Methods:For this case–control study, we examined 1174 cases with CHD from EUROCAT Northern Netherlands and 5602 controls without congenital anomalies from the Lifelines cohort study. Information on maternal jobs held early in pregnancy was collected via self-administered questionnaires, and job titles were linked to occupational exposures using a job exposure matrix.Results:An association was found between organic dust exposure and coarctation of aorta [adjusted odds ratio (OR_adj) 1.90, 95% confidence interval (CI) 1.01–3.59] and pulmonary (valve) stenosis in combination with ventricular septal defect (OR_adj 2.68, 95% CI 1.07–6.73). Mineral dust exposure was associated with increased risk of coarctation of aorta (OR_adj 2.94, 95% CI 1.21–7.13) and pulmonary valve stenosis (OR_adj 1.99, 95% CI 1.10–3.62). Exposure to metal dust and fumes was infrequent but was associated with CHD in general (OR_adj 2.40, 95% CI 1.09–5.30). Exposure to both mineral dust and metal dust and fumes was associated with septal defects (OR_adj 3.23, 95% CI 1.14–9.11). Any maternal occupational exposure was associated with a lower risk of aortic stenosis (OR_adj 0.32, 95% CI 0.11–0.94).Conclusions:Women should take preventive measures or avoid exposure to mineral and organic dust as well as metal dust and fumes early in pregnancy as this could possibly affect foetal heart development.     

Hypoglycosylation of alpha-dystroglycan in patients with hereditary IBM due to GNE mutations

Hereditary inclusion body myopathy (HIBM) is an adult onset neuromuscular disorder associated with mutations in the gene UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE), whose product is the rate limiting bi-functional enzyme catalyzing the first two steps of sialic acid biosynthesis. Loss of GNE activity in HIBM is thought to impair sialic acid production and interfere with proper sialylation of glycoconjugates, but it remains unclear how such a defect would lead to muscle destruction and muscle weakness. Hypoglycosylation of alpha-dystroglycan, a central protein of the skeletal muscle dystrophin-glycoprotein complex, results in disturbed interactions with extracellular matrix proteins. This has recently been identified as the pathomechanism involved in several congenital muscular dystrophies. We examined the glycosylation status of alpha-dystroglycan in muscle biopsies of four HIBM patients of non-Iranian Jewish origin (one American, two Indians, and one Greek). Two of these patients carry novel compound heterozygous GNE mutations on exon 2 and exon 9. All four muscle biopsies showed absent or markedly reduced immunolabeling with two different antibodies (VIA4 and IIH6) to glycosylated epitopes of alpha-dystroglycan. Normal labeling was found using antibodies to the core alpha-dystroglycan protein, beta-dystroglycan, and laminin alpha-2. These findings resemble those found for other congenital muscular dystrophies, suggesting that HIBM may be a "dystroglycanopathy," and providing an explanation for the muscle weakness of patients with GNE mutations.     

Use and functioning of the affected limb in children with unilateral congenital below-elbow deficiency during infancy and preschool age: A longitudinal observational multiple case study

Background

Children with unilateral congenital below elbow deficiency (UCBED) lack a part of an arm, thereby lacking a part of the typical hand function. Little is known on the performance of daily activities in very young children with UCBED, usage of their affected arm with or without prosthesis during play, and neurological condition.

Aim

To explore daily activities, the use of the affected limb with or without prosthesis and neurological condition over time in young children with UCBED.

Design

A longitudinal observational multiple case study.

Methods

Four children with UCBED were assessed (first assessment at 3–16 months) every 6–8 months (follow-up 13–49 months) with a video-recorded, standardized play session and a neurological examination. Yearly, functioning in daily activities was evaluated using the Pediatric Evaluation of Disability Inventory — Dutch Version (PEDI-NL). Play behaviour was assessed with and without prosthesis, where applicable (n = 2). Video-analysis focused on achievement, exploration, variation and adaptability of the affected limb. Behavioural changes over time were plotted and analysed visually.

Results

Over time, children with UCBED showed efficient usage of their affected arm during spontaneous play. Prosthesis use seemed to be associated with reduced manipulation, exploration, variation and adaptation. Three children showed minor neurological dysfunction. Functioning in daily activities was comparable to a norm population.

Conclusion

The short limb of children with UCBED is used as an exploratory, manipulatory and fixating tool from the beginning of infancy. Its value seems to be reflected in these children's normal functioning in daily life. Prosthetic use may lead to less effective performance.