Structural and functional lability induced by diethyl ether on the sarcoplasmic reticulum membrane

Structural and functional changes occuring in sarcoplasmic reticulum vesicles following exposure to low concentrations (5–7%, v/v) of diethyl ether in aqueous media, were studied by electron microscopy and by kinetic measurements of Ca²⁺ transport and ATPase activity. Electron microscopy of thin sectioned and freeze-fractured sarcoplasmic reticulum vesicles provided detailed resolution of Ca-ATPase amphiphilic molecules displaying ‘lollipop’ portions on the outer surface of the vesicle, and non-polar moieties penetrating the membrane's hydrophobic interior. This asymmetric disposition of ATPase molecules was disrupted in vesicles exposed to ether and then centrifuged and/or resuspended in aqueous media. Such vesicles had a tendency to undergo fragmentation, and the distribution of ATPase molecules was markedly altered. The continuous fuzzy layer of lollipops became discontinuous, and the intramembranous particles became randomly distributed over both the concave and the convex freeze-fracture membrane faces. Functionally, the vesicles lost their ability to accumulate calcium in the presence of ATP, although high rates of ATPase activity were maintained. Vesicles which were simply exposed to ether, without being subjected to centrifugation and/or homogenization, did not appear altered ultrastructurally, and retained their ability to accumulate calcium. In fact, the enzyme turnover and the maximal levels of calcium uptake were increased. It is concluded that diethyl ether interferes with lipid-lipid and protein-lipid interactions in the sarcoplasmic reticulum vesicle membrane, thereby facilitating molecular motions which may be a limiting factor in the transport mechanism. On the other hand, these weakened interactions permit structural denaturation and loss of the ability to maintain a transmembrane Ca²⁺ gradient when the vesicles are subjected to mechanical perturbations which are harmless in the absence of ether.     

Laminin 332 in junctional epidermolysis bullosa

Laminin 332 is an essential component of the dermal-epidermal junction, a highly specialized basement membrane zone that attaches the epidermis to the dermis and thereby provides skin integrity and resistance to external mechanical forces. Mutations in the LAMA3, LAMB3 and LAMC2 genes that encode the three constituent polypeptide chains, α3, β3 and γ2, abrogate or perturb the functions of laminin 332. The phenotypic consequences are diminished dermal-epidermal adhesion and, as clinical symptoms, skin fragility and mechanically induced blistering. The disorder is designated as junctional epidermolysis bullosa (JEB). This article delineates the signs and symptoms of the different forms of JEB, the mutational spectrum, genotype-phenotype correlations as well as perspectives for future molecular therapies.     

锡林郭勒盟煤电基地开发生态脆弱性评价

内蒙古锡林郭勒盟国家大型煤电基地的建设,对我国华北和华东区域能源安全具有重要的作用。但随着锡盟大型煤电基地的开发,其对锡林郭勒盟这一具有重要生态屏障功能的典型草原区的生态环境造成不利影响。通过对区域生态敏感性、生态弹性及生态压力的系统研究,建立了基于生态敏感性、生态弹性及生态压力的生态脆弱性评价模型,对该区域生态脆弱性进行了评价。结果表明,锡盟地区总体生态环境质量较好,但呈现由东北向西南递减的特征。研究为锡林郭勒盟国家大型煤电基地的开发建设,区域协调发展与生态环境保护提供理论支持。     

Biophysical Characterization of <Emphasis Type="Italic">β</Emphasis>-Thalassemic Red Blood Cells

Thalassemia is the world’s most common hereditary disease; therefore, more interest has been devoted for the development of the screening procedure of this disease. In β-thalassemia major, the subject of the current study, impaired biosynthesis of beta-globin leads to accumulation of unpaired alpha-globin chain. The objective of the present study, was to examine many of the biophysical properties of β-thalassemia major red blood cells (RBCs) and to study the possibility of use of any of them as a preliminary screening tool for β-thalassemia. The percentage of normal hemolysis, osmotic fragility test, turbidity test, rheological properties, and dielectric properties, were studied in 20 regularly blood transfused thalassemia major patients who were under chelation therapy and their status were compared with those of 10 healthy subjects. There was an increase in the percentage of hemolysis for β-thalassemia by 114.6% compared to the normal RBCs. The fragility curve for β-thalassemia RBCs showed a shift toward lower NaCl concentration compared to the normal curve. The average osmotic fragility (H ₅₀: the NaCl concentration producing 50% homolysis) for β-thalassemia was found to be 3.21 ± 0.67 g/l, whereas for normal RBCs it was 5.5 ± 0.31 g/l. The turbidity curve of the β-thalassemic RBCs showed a shift toward higher detergent concentration of the normal curve, with higher value for the average membrane solubilization (S ₅₀). The viscosity value of whole blood β-thalassemia was found to be 3.916 ± 0.56 cp whereas for normal blood was 2.516 ± 0.36 cp. The relative permittivity, dielectric loss, and AC conductivity of RBCs decreased significantly compared to normal samples. This could be attributed to the loss of the insulating properties of the membrane and loss of its surface charge of thalassemic RBCs. As can be noticed, several factors showed clear difference between thalassemic and normal blood samples. Some of these parameters could be measured immediately after sample withdrawal and require short time to perform the measurements. This offers the advantages of being effective, low cost, and fast techniques, therefore, we suggest that these techniques could be applied for β-thalassemia major screening purposes.     

Biophysical and biorheological studies on the precursor cells at different stages

Splenic erythroblasts were obtained from mice during the acute disease caused by anemia-inducing virus (FVA). They were cultured in a medium containing EPO, BSA and so on. We studied their biomechanical and hemorheological behavior after 12 h, 24 h and 48 h. The results showed obvious changes in their electrophoretic mobility, osmotic fragility, membrane fluidity and membrane viscoelastic properties with the development of erythroblast. The changes were associated with the interactions of the protein and lipid and the elements of the membrane.     

Effect of 50 Hz, 0.2 mT magnetic fields on RBC properties and heart functions of albino rats

In this work the effect of sinusoidal 50 Hz, 0.2 mT magnetic fields on the red blood cells (RBCs) and heart functions of Albino rats were investigated. Twenty-four male Albino rats were equally divided into four groups, A, B, C, and D. Animals from groups B were continuously exposed to the magnetic field for 15 days; and groups C and D, for 30 days. Group A was used as control. Animals from group D were kept after exposure to the magnetic field for a period of 45 days for delayed effect studies. The osmotic fragility and shape of RBCs' membrane and hemoglobin (Hb) structure tests were carried out for all groups. The dielectric relaxation of Hb molecules was measured in the frequency range of 0.1-10 MHz and the dielectric increment (Deltaepsilon), relaxation time (tau), molecular radius (r), and Cole-Cole parameter (alpha) were calculated for all groups. The ECG was measured for all animals before and after exposure to the magnetic field. The results indicated that exposure of the animals to 50 Hz, 0.2 mT magnetic fields resulted in the decrease of RBCs membrane elasticity and permeability and changes in the molecular structure of Hb. The ECG of the exposed animals was considerably altered. The data also indicated that there was no sign of repair in the newly generated RBCs structure and the ECG after removing the animals from the magnetic field, which indicates that the blood generating system was severely injured. The injuries in the heart of the animals were attributed to the loss of some physiological functions of the RBCs as a result of exposures of the rats to the magnetic field.     

mua-6, a gene required for tissue integrity in Caenorhabditis elegans, encodes a cytoplasmic intermediate filament

Locomotion in Caenorhabditis elegans requires force transmission through a network of proteins linking the skeletal muscle, via an intervening basal lamina and epidermis (hypodermis), to the cuticle. Mutations in mua-6 result in hypodermal rupture, muscle detachment from the bodywall, and progressive paralysis. It is shown that mua-6 encodes the cytoplasmic intermediate filament (cIF) A2 protein and that a MUA-6/IFA-2::GFP fusion protein that rescues the presumptive mua-6 null allele localizes to hypodermal hemidesmosomes. This result is consistent with what is known about the function of cIFs in vertebrates. Although MUA-6/IFA-2 is expressed embryonically, and plays an essential postembryonic role in tissue integrity, it is not required for embryonic development of muscle-cuticle linkages nor for the localization of other cIFs or hemidesmosome-associated proteins in the embryo. Finally, the molecular lesion in the mua-6(rh85) allele suggests that the head domain of the MUA-6/IFA-2 is dispensable for its function.     

Protective role of vitamin E on mefenamic acid-induced alterations in erythrocytes

Erythrocyte osmotic fragility (O.F.), acetylcholinesterase (AChE) activity,and the level of malonyl dialdehyde (MDA) of control, mefenamic acid treated, and mefenamic acid with vitamin E treated rats were investigated. Administration of mefenamic acid to albino rats brought about a significant increase in the osmotic fragility of red cells and a significant (p<0.01) decrease in the activity of AChE. We have also observed increased red cell level of MDA and decreased cholesterol (Chl), hemoglobin (Hb), and reduced glutathione (GSH) content. Supplementation of vitamin E to the mefenamic acid treated rats restored the O.F., AChE activity, level of MDA, and Chl, Hb, and GSH content almost to normal. These observations suggest that mefenamic acid causes functional impairment of red cell membrane, while vitamin E shows its protective role in maintaining normal red cell functions.     

Effect of vitamin C and zinc on osmotic fragility and lipid peroxidation in zinc-deficient haemodialysis patients

Peroxidation of the membrane lipid structure of red blood cell leads to haemolysis and anaemia in haemodialysis patients. Dietary constituents of antioxidant vitamins and trace elements may play an important role in protecting against oxidant damage. In this study, the effects of supplementation of vitamin C and zinc on osmotic fragility and lipid peroxidation of erythrocytes were investigated in 34 zinc-deficient haemodialysis patients. Sixteen sex- and age-matched normal volunteers acted as controls. Patients were randomized to receive vitamin C (250 mg day(-1)), zinc (20 mg day(-1)) or a placebo treatment for 3 months. The levels of vitamin C, zinc, malondialdehyde (MDA) and osmotic fragility were measured initially and 3 months after supplementation. Mean serum concentration of vitamin C and zinc increased significantly in the groups at the end of the respective study periods. Supplementation with vitamin C and zinc improved osmotic fragility, and decreased the level of MDA in the groups, but some side-effects (i.e. nausea, vomiting, fever, muscle pain, weakness) were observed during the zinc treatment. The results showed that the supplementation of both treatments decreased osmotic fragilty and MDA in zinc-deficient haemodialysis patients. However, vitamin C treatment was found to be safer than zinc supplementation.     

Characteristics and determinants of osmotic lysis in chromaffin granules

(1) Using isolated bovine chromaffin granules, we demonstrate that osmotic lysis is not a random process and establish the osmotic pressure dependence of osmotic lysis in chromaffin granules, the so-called osmotic fragility curve. (2) We show by measuring the release of constituents of the granule core and correlating these with changes in spectroscopic parameters (turbidity and endogenous catecholamine fluorescence), that the latter can be safely used to measure lysis. (3) Within a particular granule population, noradrenaline granules lyse at higher osmolarities than adrenaline granules, suggesting a higher core osmolarity of the noradrenaline granules. (4) The size distribution of chromaffin granules as a function of lysis was determined by the use of whole mount electron microscopy. It is shown that the mean size of chromaffin granules decreases as a function of lysis. (5) On the basis of theoretical considerations three alternative models of the sequence of osmotic lysis in chromaffin granules are proposed. The experimental results best support a model which postulates that during partial osmotic lysis, granule membranes reseal into smaller vesicles after graded release of contents. The osmotic fragility would represent several cycles of lysis and resealing and would not be a reflection of the distribution of osmotic pressures in the granule population.