Energetic characteristics of the new transthyretin variant A25T may explain its atypical central nervous system pathology

Transthyretin (TTR) is a tetrameric protein that must misfold to form amyloid fibrils. Misfolding includes rate-limiting tetramer dissociation, followed by fast tertiary structural changes that enable aggregation. Amyloidogenesis of wild-type (WT) TTR causes a late-onset cardiac disease called senile systemic amyloidosis. The aggregation of one of > 80 TTR variants leads to familial amyloidosis encompassing a collection of disorders characterized by peripheral neuropathy and/or cardiomyopathy. Prominent central nervous system (CNS) impairment is rare in TTR amyloidosis. Herein, we identify a new A25T TTR variant in a Japanese patient who presented with CNS amyloidosis at age 42 and peripheral neuropathy at age 44. The A25T variant is the most destabilized and fastest dissociating TTR tetramer published to date, yet, surprising, disease onset is in the fifth decade. Quantification of A25T TTR in the serum of this heterozygote reveals low levels relative to WT, suggesting that protein concentration influences disease phenotype. Another recently characterized TTR CNS variant (D18G TTR) exhibits strictly analogous characteristics, suggesting that instability coupled with low serum concentrations is the signature of CNS pathology and protects against early-onset systemic amyloidosis. The low A25T serum concentration may be explained either by impaired secretion from the liver or by increased clearance, both scenarios consistent with A25T's low kinetic and thermodynamic stability. Liver transplantation is the only known treatment for familial amyloid polyneuropathy. This is a form of gene therapy that removes the variant protein from serum preventing systemic amyloidosis. Unfortunately, the choroid plexus would have to be resected to remove A25T from the CSF-the source of the CNS TTR amyloid. Herein we demonstrate that small-molecule tetramer stabilizers represent an attractive therapeutic strategy to inhibit A25T misfolding and CNS amyloidosis. Specifically, 2-[(3,5-dichlorophenyl)amino]benzoic acid is an excellent inhibitor of A25T TTR amyloidosis in vitro.     

Desensitization of acetylcholine induced inositol 1,4,5-trisphosphate formation in neuroblastoma SH-SY5Y cells following repetitive acetylcholine stimulations

In this study, the desensitization of acetylcholine-induced inositol 1,4,5-trisphosphate [I(1,4,5)P₃] formation, upon short-time prestimulations, was investigated in cultures of human neuroblastoma SH-SY5Y cells. Four repeated stimulations for 10 seconds with 10 μM acetylcholine were necessary to induce a desensitization of the I(1,4,5)P₃ formation. The desensitization was observed 4 hours after the initiation of repetitive stimulations. The same effect was obtained by a single prestimulation with 1 mM acetylcholine. Preincubation of the cells with phorbol 12-myristate 13-acetate (PMA) markedly down-regulated the acetylcholine-induced I(1,4,5)P₃ formation. However, the protein kinase C (PKC) inhibitors H7 and staurosporine did not influence the desensitization induced by four repeated stimulations with 20 μM acetylcholine. These results indicate that the signal transduction can be desensitized following repeated stimulations with sub-maximal concentrations of receptor agonist and although activation of PKC can induce the same down-regulation, PKC is most likely not involved in the desensitization induced by repetitive acetylcholine-stimulations.     

Terbutaline Depot Tablets in Asthma

A sustained release preparation of terbutaline sulphate has been formulated (Bricanyl® depot tablets) in order to extend the duration and accordingly change the dosage regimen to twice a day. This presentation gives a summary of a clinical trial performed in order to study effect and side effects of terbutaline depot tablets 7.5 mg twice a day compared to terbutaline tablets 5 mg three times a day.
Patients suffering from perennial asthma and with daily requirement of asthma medicine were accepted for the study. The trial was a double-blind cross-over, double dummy and randomized. The tablets were given in two consecutive periods of 7 day's duration each. The effect of terbutaline depot tablets was equal to the effect of the ordinary terbutaline tablets. The indication for using depot tablets in the basic treatment of bronchial asthma is a better patient compliance due to medication twice a day. Furthermore in patients with unstable bronchial asthma and in patients with morning dips in PEF the more stable plasma concentration may perhaps keep the patients in a more steady state.     

Myeloperoxidase in human lung lavage

Bronchial wash and bronchoalveolar lavage were performed in 12 healthy subjects (five smokers), in order to elucidate whether or not material of neutrophil origin may be phagocytized by lung macrophages in vivo. Cells from different levels in the bronchial tree were obtained by sequential injection and subsequent aspiration of either four 50-ml or five 10-ml aliquots. Each aliquot was used for the determination of total and differential cell counts. The proportion of myeloperoxidase-positive alveolar macrophages was determined by specific immune histochemical staining. The percentage of myeloperoxidase-positive macrophages was highest (median 94.8%, range 37-98.5%) in the 10-ml aliquots and lowest in the last three 50-ml aliquots (median values 1-2.5%) (P less than 0.001). A significant correlation was obtained between the fraction of myeloperoxidase-positive macrophages and the percentage count of bronchoalveolar lavage neutrophils (r = 0.466, P less than 0.05). Furthermore, the cellular myeloperoxidase showed a significant inverse correlation (r = -0.46, P less than 0.05) to the viability of the bronchoalveolar lavage cells. Our findings are compatible with previous demonstrations in animals of neutrophil phagocytosis by lung macrophages and show that this phenomenon in particular occurs in the more proximal airways. The internalization of neutrophils or neutrophil components by airway macrophages may be an important scavenger mechanism for protection of the lung from the deleterious effects of activated neutrophils.     

Meiotic and cytoplasmic maturation of oocytes collected in stimulated cycles is asynchronous

Oocytes collected in stimulated cycles are more readily fertilizedafter preincubation than are oocytes inseminated immediatelyafter collection. It has not been ascertained, however, whetherthis increase in the fertilization rate is due to extrusionof the first polar body (meiotic maturation) during this period,or to some conclusive cytoplasmic maturation subsequent to thepolar body extrusion. When analysing oocytes with a polar body(n = 14) by transmission electron microscopy, differences wereobserved in the appearance of cytoplasmic features which werecorrelated to the total durations both of systemic human chorionicgonadotrophin influence before collection and of oocyte culture.These differences were manifested as a delayed formation inaggregates of the smooth endoplamic reticulum in the ooplasmof oocytes having a polar body and might have signified a cytoplasmicmaturation. The degree of synchrony in the oocytes varied andthis could explain why some oocytes can be fertilized when inseminatedshortly after collection and others not until 8 h or even moreafter collection. Thus, although meiotic and cytoplasmic maturationis likely to be synchronized at ovulation of an oocyte in anatural cycle, they appear to be mainly asynchronous in oocytescollected in stimulated cycles.     

Genetics of the low density lipoprotein receptor:

Fibroblast association (plasma membrane binding plus intracellular accumulation) and degradation of radioiodinated low density lipoprotein (125I-LDL) index plasma membrane LDL receptor activity. Cultured fibroblasts from 23 subjects affected with familial hypercholesterolemia (HC) and from 95 subjects without HC (non-HCs) were tested for 125I-LDL association and degradation. Both LDL receptor activity indices were twice as high in non-HC and HC heterozygous cell strains. This is compatible with a major gene effect on LDL receptor activity. However, a considerable overlap between non-HC and HC heterozygous values was found in the 125I-LDL association assay [median (range) 970 (330-2500), and 450 (250-490), respectively] and in the degradation assay [median (range) 810 (280-2020), and 470 (160-790), respectively]. The values are expressed as ng 125I-LDL X mg cell protein-1 X 4.5 h-1. These great overlaps in the LDL receptor activity indices support the view that the influence of LDL receptor activity on the HC phenotype may be smaller than believed previously. Furthermore, for the diagnosis of HC, these LDL receptor activity assays are far more expensive and have less sensitivity and specificity than simple serum cholesterol determination. The LDL receptor-dependent 125I-LDL association values for the HC heterozygous individuals clustered into four groups. Family data supported the hypothesis that this variation could be due to four different LDL receptor variants, each coded for by different alleles at the LDL receptor locus. If confirmed, this finding may have implications for the understanding of the variable expression of HC and also of the genetic impact on lipoprotein metabolism and susceptibility to atherosclerosis in non-HCs.     

Longitudinal Split of the Peroneus Brevis Tendon and Lateral Ankle Instability: Treatment of Concomitant Lesions

OBJECTIVE: To describe the clinical picture, pathophysiology, and treatment of concomitant lesions of the peroneus brevis tendon and lateral ligament injuries to the ankle. BACKGROUND: In some cases, chronic lateral ankle instability is associated with a longitudinal partial tear in the peroneus brevis tendon. Patients who suffer from this lesion usually have atypical posterolateral ankle pain combined with signs of recurrent ligament instability ("giving way"). The tendon injury is often overlooked because it is combined with the ligament injury, and the injury mechanisms are similar. DESCRIPTION: Tears or laxity in the superior peroneal retinaculum allow the anterior part of the injured peroneus brevis tendon to ride over the sharp posterior edge of the fibula, leading to a longitudinal tear in the tendon. This combined injury should be suspected in patients with recurrent giving way of the ankle joint and retromalleolar pain. The diagnosis can be established using either ultrasonography or magnetic resonance imaging. DIFFERENTIAL DIAGNOSIS: Ligament injury, tenosynovitis, peroneus longus tendon lesion, os peroneum fracture, distal peroneus brevis tendon tear, or anomalous peroneus tertius tendon. TREATMENT: The tendon injury and the ligament insufficiency should be repaired at the same time. CONCLUSIONS: We recommend reconstruction of the superior peroneal retinaculum, combined with repair of the tendon, using side-to-side sutures and anatomical reconstruction of the lateral ankle ligaments.     

Molecular analysis in Japanese patients with Charcot-Marie-Tooth disease: DGGE analysis for PMP22, MPZ,and Cx32/GJB1 mutations

Charcot-Marie-Tooth disease (CMT) is a heterogeneous disorder and is traditionally classified into two major types, CMT type 1 (CMT1) and CMT type 2 (CMT2). Most CMT1 patients are associated with the duplication of 17p11.2-p12 (CMT1A duplication) and small numbers of patients have mutations of the peripheral myelin protein 22 (PMP22), myelin protein zero (MPZ), connexin 32 (Cx32/GJB1), and early growth response 2 (EGR2) genes. Some mutations of MPZ and Cx32 were also associated with the clinical CMT2 phenotype. We constructed denaturing gradient gel electrophoresis (DGGE) analysis as a screening method for PMP22, MPZ, and Cx32 mutations and studied 161 CMT patients without CMT1A duplication. We detected 27 mutations of three genes including 15 novel mutations; six of PMP22, three of MPZ, and six of Cx32. We finally identified 21 causative mutations in 22 unrelated patients and five polymorphic mutations. Eighteen of 22 patients carrying PMP22, MPZ, or Cx32 mutations presented with CMT1 and four of them with MPZ or Cx32 mutations presented with the CMT2 phenotype. DGGE analysis was sensitive for screening for those gene mutations, but causative gene mutation was not identified in many of the Japanese patients with CMT, especially with CMT1. Other candidate genes should be studied to elucidate the genetic basis of Japanese CMT patients.