Nonlinear autoregressive analysis of the 3/s ictal electroencephalogram: implications for underlying dynamics

 In a previous study, nonlinear autoregressive (NLAR) models applied to ictal electroencephalogram (EEG) recordings in six patients revealed nonlinear signal interactions that correlated with seizure type and clinical diagnosis. Here we interpret these models from a theoretical viewpoint. Extended models with multiple nonlinear terms are employed to demonstrate the independence of nonlinear dynamical interactions identified in the ‘NLAR fingerprint’ of patients with 3/s seizure discharges. Analysis of the role of periodicity in the EEG signal reveals that the fingerprints reflect the dynamics not only of the periodic discharge itself, but also of the fluctuations of each cycle about an average waveform. A stability analysis is used to make qualitative inferences concerning the network properties of the ictal generators. Finally, the NLAR fingerprint is analyzed in the context of Volterra-Weiner theory. Received: 6 April 1994/Accepted in revised form: 18 November 1994     

Crystallization and X-ray analysis of a single fab binding domain from protein L of Peptostreptococcus magnus

Protein L is a multi domain cell wall constituent of certain strains of Peptostreptococcus magnus which binds to the variable domain of immunoglobulin κ-light chains. A single immunoglobulin-binding domain of M_r = 9000 from this protein has been isolated and crystallized. The crystals are of space group P4₂2₁2, with cell dimensions a = b = 66.9 Å, c = 68.3 Å, and diffract to at least 2.2 Å resolution. The asymmetric unit of the crystal contains two molecules of the protein L domain, related by a noncrystallographic 2-fold axis, as revealed by a self-rotation function calculated with native diffraction data. © 1995 Wiley-Liss, Inc.     

Refocusing revisited: An optimized,gradient-enhanced refocused HSQC and its applications in 2D and 3D NMR and in deuterium exchange experiments

Summary 2D ¹⁵N-¹H correlation spectra are ideal for measuring backbone amide populations to determine amide exchange protection factors in studies of protein folding or other structural features. Most protein NMR spectroscopists use HSQC, which has been shown to be generally superior to HMQC in both resolution and sensitivity. The refocused HSQC experiment is intrinsically less sensitive than the regular HSQC, due to T₂ relaxation during the refocusing delays. However, we show here that, when high ¹⁵N resolution is needed, an optimized refocused HSQC sequence that utilizes a semi-constant time evolution period and pulsed field gradients has better signal-to-noise ratio and resolution, and integrates more accurately, than a similar HSQC. The differences are demonstrated on a 20 kDa protein. The technique can also be applied to 3D NOESY experiments to eliminate strong NH₂ geminal peaks and their truncation artefacts at a modest cost in sensitivity.     

Isolation of virally-infected insect cells from a population containing infected and uninfected cells

A method was developed that can be used to isolate virally-infected insect cells from a mixed population containing infected and uninfected cells. Specifically, Spodoptera frugiperda Sf-9 cells infected with the Autographa californica multiple nuclear polyhedrosis virus were treated with a primary antibody specific for the gp64 protein present on the surface of virally-infected cells and a secondary antibody labeled with a fluorochrome. The resulting labeled cells were isolated by using fluorescence-activated cell sorting.     

The phosphohydrolysis of hydroxycinnamoyl-coenzyme a thioesters in plant extracts

In barley seedling extracts, p-coumaroyl-CoA is rapidly hydrolysed to p-coumaroyl-dephospho-CoA, p-coumaroyl-4′-phosphopantetheine and p-coumaroyl-pantetheine. p-Coumaroyl-4′-phosphopantetheine is active as a substrate of agmatine coumaroyl transferase in the formation of p-coumaroyl-agmatine, but p-coumaroyl-pantetheine is inactive. The phosphohydrolysis can be partly inhibited by inorganic pyrophosphate, sodium fluoride and purine nucleotides. A simplified method for the synthesis of N-hydroxysuccinimide esters of hydroxycinnamic acids, used in the synthesis of CoA thioesters, is also described.     

Changes in the surface morphology of the rabbit endometrium related to the estrous and progestational stages of the reproductive cycle

Summary Changes occurring on the surface of the uterine luminal epithelium of the rabbit during the estrous and progestational stages of the reproductive cycle were examined by scanning and transmission electron microscopy. The findings demonstrate that the uterine epithelium, or endometrium, contains two cell types: ciliated cells and nonciliated, microvillous cells. In estrous animals, ciliated cells, although not very numerous, were usually observed in small groups. However, at increasing intervals of time following mating, ciliated cells progressively disappeared from the endometrium until approximately eight to ten days post coitum, when they became scare. From several hours to four to five days following mating, extensive changes occurred on the surfaces of microvillous cells. When observed by TEM, these elements contained organelles typical of cells involved in the synthesis and secretion of glycoproteins. Furthermore, microvillous cells during this period displayed numerous apical protrusions of different sizes and shapes and containing material of varying electron density. Parallel SEM examinations of the same material confirmed the presence of these protrusions. Some of the protrusions appeared as spheroidal masses attached to the cytoplasm by means of a cytoplasmic strand. Other surface masses were clearly unattached to the cell surface and were distributed (1) on the surface of microvillous cells, (2) on the cilia of adjacent ciliated cells, and (3) on the surface of spermatozoa.Changes occurring on the luminal surface during the early postcoital period are interpreted as an expression of morphodynamic processes likely involving coupled secretion (exocytosis) and resorption (endocytosis) of luminal material. The observations presented here also demonstrate that between six and ten days post coitum, the rabbit endometrium contained increasing numbers of enlarged, nonciliated cells that probably arose by the fusion of smaller, microvillous elements.The work reported here was supported by C.N.R. contracts No. CT 760128809 and CT 77014239 (to P.M.) and NIH. Grant HD-04274 (to J.V.B.)     

Prey capture in mantids: Prothoracic tibial flexion reflex

We describe a prothoracic leg tibial flexion reflex (PTFR) of the praying mantis Tenodera aridifolia sinensis which is initiated by tactile stimulation of the movable spines of the ventro-medial border of the femur. This flexion reflex may be responsible for the continuous grasping of a captured prey by the mantid.     

Glycosidases of the guinea pig brush border membrane

The separation by polyacrylamide gel electrophoresis and subsequent enzymatic analysis of the components of the guinea pig intestinal brush border membrane revealed the presence of three enzyme complexes: maltase-gluco-amylase, maltase-sucrase-glucoamylase and maltase-sucrase. Additional bands possessing lactase, trehalase and alkaline phosphatase activity were identified but no phlorizin hydrolase or palatinase was detectable. After exposure to strong dissociating conditions the bands possessing enzymatic activity were either absent or greatly reduced in intensity.     

Inhibition by light of growth and Golgi-localized glucan synthetase in the maize mesocotyl

When dark-grown maize (Zea mays L.) seedlings were exposed to red light (R), Golgi-localized glucan synthetase activity in the mesocotyl began to decrease within 1 h, and fell by approx. 70% in 12 h. The response required at least 10^-2 mol m^-2 R and saturated at 100 mol m^-2. Far-red light (FR) alone inhibited glucan synthetase, and FR reversed the inhibition by R back to the level caused by FR alone. Density gradient fractionation indicated that of the major membrane markers only the Golgi-localized glucan-synthetase activity was affected by R. Golgi-localized latent inosine-diphosphatase activity was unaffected. The kinetics of the response, the photon fluence dependence, and the reversibility by FR all correlated with the inhibition by light of elongation of the mesocotyl, indicating that light inhibits growth and glucan synthetase activity by a similar mechanism.Abbreviations FR far-red light - GS glucan synthetase - IAA indole-3-acetic acid - R red light