Surface alterations in calf lymphocytes oxidized by sodium periodate.

In order to investigate alterations in surface structure in transformed lymphocytes, calf submandibular lymph node cell suspensions were oxidized with NaIO4. Oxidezed lymphocytes were morphologically transformed and had higher rates of DNA synthesis by 2 days after treatment. These results were prevented by reduction of the cell suspension with NaBH4, or by neuraminidase treatment of cells prior to oxidation. The amount of 125I-labeled Agaricus bisporus lectin bound to cells immediately after oxidation and the affinity constant for binding were increased over 2-fold, while cells immediately following oxidation and reduction showed decreased receptors with still higher affinity for the lectin compared to untreated cells. The amount of Phaseolus vulgaris lectin bound to oxidezed cells was also increased, but affinity was unchanged. Immediately following oxidation and reduction, these receptor sites were unchanged in number and affinity from untreated cells. In contrast, the number and affinity of receptors for concanavalin A were not changed immediately after oxidation or oxidation and reduction. In order to define the extent of compositional changes in surface glycoprotein receptors, plasma membranes were isolated from frozen calf submandibular lymph nodes. Compared to untreated plasma membranes, oxidezed membranes had similar contents of galactose, mannose, N-acetylglucosamine, N-acetylgalactosamine, fucose, and amino acids. Sialic acid content of oxidized membranes was reduced when measured by thiobarbituric acid assay. Sialic acids of untreated plasma membranes co-chromatographed with N-glycolylneurominic acid and N-acetylneuraminic acid, while those of oxidized membranes co-chromatographed with N-glycolylneuraminic acid and 5-acetamido-3,5-dideoxy-L-arabino-7-aldehydo-2-heptulosonic acid. Therefore, specific surface conformational changes in certain classes of membrane glycoproteins are associated with mild Malapradian oxidation of membrane sialic acids. These temporally precede NaIO4-induced transformation of calf lymphocytes. This is consistent with an hypothesis of membrane-mediated stimulation of lymphocyte transformation.     

Surface alterations of fertilized surf clam (Spisula solidissima) eggs induced by concanavalin A

Fertilized Spisula eggs, incubated in ConA, were examined at periodic intervals to determine the effects of lectin binding on events of fertilization and cleavage. ConA was localized to specific regions of the vitelline layer and plasma membrane by reacting lectin-treated eggs with horseradish peroxidase and diaminobenzidine. In contrast to eggs, little reaction product was associated with the plasma membrane of spermatozoa. Sperm that fused with ConA-treated eggs failed to move into the cortex of the ovum and were observed as bulbous appendages at the surface of the zygote. Reorganization of sperm nuclei was inhibited, and male pronuclei failed to develop. ConA also inhibited polar body formation and cleavage. The maternally derived chromatin underwent meiosis, and the chromosomes normally taken into the first and second polar bodies were retained within the zygote. All of the maternally derived chromatin was organized within four or more female pronuclei which subsequently entered mitosis. The effects of ConA binding on events at the surface of fertilized Spisula eggs were abrogated by α-methyl-d-mannoside; succinyl-ConA only partially inhibited fertilization-related processes. The effects of ConA are discussed in terms of possible cross-linking of surface components of fertilized Spisula eggs which may inhibit deformation of the zygote cortex.     

Ultrastructural alterations in extrinsic eye muscles induced by vincristine.

A comparative morphological analysis of the effects of vincristine on particular types of muscle fibres of the eye and selected trunk muscles of the mouse was performed. Great resistance of the mouse organism to the action of sublethal doses of vincristine has been found. Degenerative changes of great intensity (atrophy of myofibrils, disturbances of the Z line) and the appearance of new changes, not mentioned hitherto among the vincristine myopathies (megamitochondria, intermembranous inclusions, glycogen in mitochondria and very large vacuoles) were observed in the trunk muscles of mice. The eye muscles are seem to be more resistant to the action of vincristine. The intensity of changes in the eye muscles was connected with the types of muscle fibres. Red fibres, rich in mitochondria, underwent relatively greatest changes, whereas the smallest changes were found in tonic fibres, poor in mitochondria and sarcotubular system, i.e. these structures from which spheromembranous bodies, most characteristic of the pathogenic effects of vincristine arise.     

Surface EMG in advanced hand prosthetics

One of the major problems when dealing with highly dexterous, active hand prostheses is their control by the patient wearing them. With the advances in mechatronics, building prosthetic hands with multiple active degrees of freedom is realisable, but actively controlling the position and especially the exerted force of each finger cannot yet be done naturally. This paper deals with advanced robotic hand control via surface electromyography. Building upon recent results, we show that machine learning, together with a simple downsampling algorithm, can be effectively used to control on-line, in real time, finger position as well as finger force of a highly dexterous robotic hand. The system determines the type of grasp a human subject is willing to use, and the required amount of force involved, with a high degree of accuracy. This represents a remarkable improvement with respect to the state-of-the-art of feed-forward control of dexterous mechanical hands, and opens up a scenario in which amputees will be able to control hand prostheses in a much finer way than it has so far been possible. This work is partially supported by the project NEURObotics, FP6-IST-001917.     

Surface EMG signal processing during isometric contractions

This paper provides an overview of techniques suitable for the estimation, interpretation and understanding of time variations that affect the surface electromyographic (EMG) signal during sustained voluntary or electrically elicited contractions. These variations concern amplitude variables, spectral variables and muscle fiber conduction velocity, are interdependent and are referred to as the ‘fatigue plot'. The fatigue plot provides information suitable for the classification of muscle behavior. In addition, the information obtainable by means of linear electrode arrays is discussed, and applications of mathematical models for the interpretation of array signals are presented. The model approach provides additional ways for the classification of muscle behavior.     

Mutational alterations induced in yeast by ionizing radiation

The cyc1-9 ochre (UAA) mutant and the cyc1-179 amber (UAG) mutant of the yeast Saccharomyces cerevisiae were reverted with X-rays and -particles. The amino acid sequence changes of iso-1-cytochromes c from 36 of the intragenic revertants were determined by amino acid analysis and peptide mapping, aided by partial amino acid sequencing of 4 revertants. In addition, the DNA segments encompassing 3 unusual mutations with complex changes were cloned and sequenced. This study and previous studies of 16 other revertants of cyc1-9 and cyc1-179 revealed that ionizing radiation primarily induces single base-pair substitutions; 47 of the 52 revertants arose by transversions and transitions without any apparent preference. However, the A·T→T·A substitution at the first base pair for the cyc1-179 UAG codon, leading to the normal protein, was not detected, nor was it found previously in 32 revertants of cycl-179 obtained spontaneously or induced with various other mutagens; apparently, there is a prohibition of certain base-pair substitutions at certain sites in DNA. In addition, 5 of the 52 revertants arose by multiple changes within a short region of 11 base pairs. These consisted of the deletion of 6 base pairs, the substitution of 3 base pairs, and 3 different kinds of substitutions of two base pairs. Compared to other mutagens previously tested with the cyc1 system, ionizing radiation produces the most random types of base-pair substitutions.     

Mitochondrial alterations induced by 532 nm laser irradiation

Mitochondrial alterations were monitored after low power green laser (532 nm, 30 mW) irradiation in the case of whole cells (B-14) and isolated mitochondria (from Wistar rat heart). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide (MTT) assay products were significantly higher (by 8%) in irradiated B-14 cells as compared to non-irradiated controls. Mitochondrial transmembrane potential of B-14 cells, measured by means of a fluorescent probe 3,3'-dihexyloxacarbocyanine iodide (DiOC6(3)), significantly increased (by 13%) after exposure to green laser irradiation. Another MTT assay was used for isolated mitochondria suspensions in order to examine the effect of green laser irradiation on stimulation of processes related to oxidative phosphorylation. It revealed 31.3%-increase in MTT assay products in irradiated mitochondria as compared to controls. Laser irradiation of isolated mitochondria suspension did not significantly change 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence anisotropy, indicating that mitochondrial membrane fluidity was not affected by laser light. Fluorescence emission spectra of irradiated as well as non-irradiated mitochondria suspensions showed fluorescence maximum at 635 nm, corresponding to emission of Protoporphyrin IX, which was significantly lower (by 20.7%) in irradiated sample.     

Nuclear alterations in mammalian cells induced by L-canavanine

Mammalian cells treated four hours with the L-arginine analogue, L-canavanine (Cana), develop alterations in nuclear architecture characterized by the formation of irregular aggregates of nucleoplasmic contents, frequently attached to the nuclear membrane. On the basis of previous studies showing that Cana is incorporated into nuclear proteins and inhibits DNA synthesis over similar periods of exposure, it is postulated that the formation of canavanyl protein-DNA aggregates interfere with DNA replication.     

Regulatory light chain influences alterations of myosin head induced by actin.

The effect of magnesium-for-calcium exchange and phosphorylation of regulatory light chain (LC2) on structural organization of rabbit skeletal myosin head was studied by limited tryptic digestion. In the presence of actin, exchange of magnesium bound to LC2 by calcium in dephosphorylated myosin accelerates the digestion of myosin and heavy meromyosin heavy chain and increases the accumulation of a 50 kDa fragment. This effect is significantly diminished in the case of phosphorylated myosin. Thus, both phosphorylation and cation exchange influences the effect of actin binding on the structural organization of myosin head.     

Ultrastructural alterations of the myocardium induced by doxorubicin

Morphologic changes in Doxorubicin (DXR)-induced cardiomyopathy are characterized by marked dilatation of the sarcoplasmic reticulum (SR). DXR was administered to New Zealand White rabbits for 5 or 8 weeks and the three-dimensional structure of the sarcotubular system in cardiac muscle cells from each rabbit was examined under a field-emission type scanning electron microscope (SEM) after removal of cytoplasmic matrices by the osmium-DMSO-osmium procedure. Five weeks after the initial injection of DXR, partial dilatation of the SR and damaged mitochondria with lysis of cristae were observed three-dimensionally. After 8 weeks, the three-dimensional structure of the SR showed extensive spherical ballooning which could be seen clearly in bold relief. Thus, we could directly visualize structural alterations of the sarcotubular system in DXR-induced cardiomyopathy using the SEM.