Disruption of the neural response to rapid acoustic stimuli in dyslexia: evidence from functional MRI

The biological basis for developmental dyslexia remains unknown. Research has suggested that a fundamental deficit in dyslexia is the inability to process sensory input that enters the nervous system rapidly and that deficits in processing rapid acoustic information are associated with impaired reading. Functional magnetic resonance imaging (fMRI) was used to identify the brain basis of rapid acoustic processing in normal readers and to discover the status of that response in dyslexic readers. Normal readers showed left prefrontal activity in response to rapidly changing, relative to slowly changing, nonlinguistic acoustic stimuli. Dyslexic readers showed no differential left frontal response. Two dyslexic readers participated in a remediation program and showed increased activity in left prefrontal cortex after training. These fMRI results identify left prefrontal regions as normally being sensitive to rapid relative to slow acoustic stimulation, insensitive to the difference between such stimuli in dyslexic readers, and plastic enough in adulthood to develop such differential sensitivity after intensive training.

Concurrent and independent binding of Fcgamma receptors IIa and IIIb to surface-bound IgG

Fc receptor-antibody interactions are key mechanisms through which antibody effector functions are mediated. Neutrophils coexpress two low-affinity Fcgamma receptors, CD16b (FcgammaRIIIb) and CD32a (FcgammaRIIa), possessing overlapping ligand binding specificities but distinct membrane anchor and signaling capacities. Using K562 cell transfectants as a model, the kinetics of both separate and concurrent binding of CD16b and CD32a to surface-bound IgG ligands were studied. CD16b bound human IgG with 2-3 times higher affinity than did CD32a (A(c)K(a) = 4.1 and 1.6 x 10(-7) microm(4), respectively) and both FcgammaRs had similar reverse kinetic rates (k(r) = 0.5 and 0.4 s(-1), respectively). Because CD16b is expressed on neutrophils at a 4-5 times higher density than CD32a, our results suggest that CD16b plays the dominant role in binding of neutrophils to immobilized IgG. The question of possible cross-regulation of binding affinity between CD16b and CD32a was investigated using our multispecies concurrent binding model (Zhu and Williams, Biophys. J. 79:1850-1857, 2000). Because the model assumes independent binding (no cooperation among different species), the excellent agreement between the model predictions and the experimental data suggests that, when coexpressed on K562 cells, these two FcgammaRs do not interact in a manner that alters the kinetic rates of either molecule.

Impaired growth and elevated fas receptor expression in PIGA(+) stem cells in primary paroxysmal nocturnal hemoglobinuria

The genetic defect underlying paroxysmal nocturnal hemoglobinuria (PNH) has been shown to reside in PIGA, a gene that encodes an element required for the first step in glycophosphatidylinositol anchor assembly. Why PIGA-mutated cells are able to expand in PNH marrow, however, is as yet unclear. To address this question, we compared the growth of affected CD59(-)CD34(+) and unaffected CD59(+)CD34(+) cells from patients with that of normal CD59(+)CD34(+) cells in liquid culture. One hundred FACS-sorted cells were added per well into microtiter plates, and after 11 days at 37 degrees C the progeny were counted and were analyzed for their differentiation pattern. We found that CD59(-)CD34(+) cells from PNH patients proliferated to levels approaching those of normal cells, but that CD59(+)CD34(+) cells from the patients gave rise to 20- to 140-fold fewer cells. Prior to sorting, the patients' CD59(-) and CD59(+)CD34(+) cells were equivalent with respect to early differentiation markers, and following culture, the CD45 differentiation patterns were identical to those of control CD34(+) cells. Further analyses of the unsorted CD59(+)CD34(+) population, however, showed elevated levels of Fas receptor. Addition of agonist anti-Fas mAb to cultures reduced the CD59(+)CD34(+) cell yield by up to 78% but had a minimal effect on the CD59(-)CD34(+) cells, whereas antagonist anti-Fas mAb enhanced the yield by up to 250%. These results suggest that expansion of PIGA-mutated cells in PNH marrow is due to a growth defect in nonmutated cells, and that greater susceptibility to apoptosis is one factor involved in the growth impairment.

Selective peptidic and peptidomimetic inhibitors of Candida albicans myristoylCoA: protein N-myristoyltransferase: a new approach to antifungal therapy

MyristoylCoA: protein N-myristoyltransferase (NMT) catalyzes the cotranslational covalent attachment of a rare cellular fatty acid, myristate, to the N-terminal Gly residue of a variety of eukaryotic proteins. The myristoyl moiety is often essential for expression of the biological functions for these proteins. Attachment of C14:0 alone provides barely enough hydrophobicity to allow stable association with membranes. The partitioning of N-myrisotylproteins is therefore often modulated by "switches" that function through additional covalent or noncovalent modifications. Candida albicans, the principal cause of systemic fungal infection in immunocompromised humans, contains a single NMT gene that is essential for its viability. The functional properties of the acylCoA binding site of human and C. albicans NMT are very similar. However, there are distinct differences in their peptide binding sites. An ADP ribosylation factor (Arf) is included among the few cellular protein substrates of the fungal enzyme. Alanine scanning mutagenesis of an octapeptide derived from an N-terminal Arf sequence (GLYASKLS-NH2) disclosed that Gly1, Ser5, and Lys6 play predominant roles in binding. ALYASKLS-NH2 is an inhibitor competitive for peptide [Ki(app) = 15.3 +/- 6.4 microM] and noncompetitive for myristoylCoA. Remarkably, replacement of the N-terminal tetrapeptide with an 11-aminoundecanoyl group results in a competitive inhibitor (11-aminoundecanoyl-SKLS-NH2) that is approximately 40-fold more potent [Ki(app) = 0.40 +/- 0.03 microM] than the starting octapeptide. Removal of Leu-Ser from the C-terminus generates a competitive dipeptide inhibitor (11-aminoundecanoyl-SK-NH2) with a Ki(app) of 11.7 +/- 0.4 microM, equivalent to that of the starting octapeptide. A derivative dipeptide inhibitor containing a C-terminal N-cyclohexylethyl lysinamide moiety has the advantage of being more potent (IC50 = 0.11 +/- 0.03 microM) and resistant to digestion by cellular carboxypeptidases. Rigidifying the flexible aminoundecanoyl chain results in very potent general NMT inhibitors (IC50 = 40-50 nM). Substituting a 2-methylimidazole for the N-terminal amine and adding a benzylic alpha-methyl group with R stereochemistry to the rigidifying element produces even more potent inhibitors (IC50 = 20-50 nM) that are up to 500-fold selective for the fungal compared to human enzyme. A related less potent member of this series of compounds is fungistatic. Its growth inhibitory effects are associated with a reduction in cellular protein N-myristoylation, judged using cellular Arf as a reporter. These studies establish that NMT is a new antifungal target.

In vivo qualitative changes of 31P NMR in stressed maize roots vis-à-vis carbon substrate determining the degree of stress

High resolution 31P nuclear magnetic resonance spectroscopy was used to investigate the changes in phosphate metabolism and intracellular pH in intact maize (Zea mays L) root segments to hyper osmotic shock. The results were compared with the happenings under field conditions, when the stress was given gradually. Effect of sugar substrate on adaptation of tissue to both kinds of situations was also studied. The hyper osmotic shock resulted in large vacuolar alkalinization and a decrease in pH across tonoplast membrane. There was gradual build up of phosphocholine and decrease in glucose 6P and UPDG levels. In gradual stress, the root segments were able to adapt to the stress and maintained pH gradient across tonoplast, with marginal alkalinization of vacuoles. The presence of sugar substrate reduced the impact of stress significantly, commensurate with the increased activity of plasmalemma H(+)-ATPase. The latter providing the driving force for uptake of organic molecules and ions required for osmoregulation.

The membrane anchor influences ligand binding two-dimensional kinetic rates and three-dimensional affinity of FcgammaRIII (CD16)

Kinetic rates and affinity are essential determinants for biological processes that involve receptor-ligand binding. By using a micropipette method, we measured the kinetics of human Fcgamma receptor III (CD16) interacting with IgG when the two molecules were bound to apposing cellular membranes. CD16 is one of only four eukaryotic receptors known to exist natively in both the transmembrane (TM, CD16a) and glycosylphosphatidylinositol (GPI, CD16b) isoforms. The biological significance of this anchor isoform coexistence is not clear. Here we showed that the anchor influenced kinetic rates; compared with CD16a-TM, CD16a-GPI bound faster and with higher affinities to human and rabbit IgGs but slower and with lower affinity to murine IgG2a. The same differential affinity patterns were observed using soluble IgG ligands. A monoclonal antibody bound CD16a-GPI with higher affinity than CD16a-TM, whereas another monoclonal antibody reacted strongly with CD16a-TM but weakly with CD16a-GPI. No major differential glycosylation between the two CD16a isoforms was detected by SDS-polyacrylamide gel electrophoresis analysis. We suggest a conformational difference as the mechanism underlying the observed anchor effect, as it cannot be explained by the differing diffusivity, flexibility, orientation, height, distribution, or clustering of the two molecules on the cell membrane. These data demonstrate that a covalent modification of an Ig superfamily receptor at the carboxyl terminus of the ectodomain can have an impact on ligand binding kinetics.

Cell-specific, activation-dependent regulation of neutrophil CD32A ligand-binding function

Neutrophils express 2 low-affinity FcgammaR, FcgammaRIIIB (CD16B), and FcgammaRIIA (CD32A). CD16B is a glycosyl-phosphatidyl inositol-anchored molecule, whereas CD32A is a polypeptide-anchored molecule. These 2 receptors also differ in their signaling. The biological significance of coexpression of 2 FcgammaRs with distinct membrane anchors and signaling capacities is not clearly understood. Using neutrophils from a CD16B-deficient donor and normal neutrophils treated with anti-CD16 monoclonal antibodies, the authors demonstrated that affinity modulation of CD32A is one of the mechanisms by which neutrophils regulate their FcgammaR-dependent functions. Neutrophils isolated from a CD16B(- )donor rosetted poorly with sheep erythrocytes opsonized with rabbit IgG (EA) (12% +/- 2% versus 80% +/- 6% for control) and were unable to mediate immunophagocytosis. However, activation of CD16B(-) neutrophils with fMLP, a bacterial chemotactic peptide, increased the CD32A-dependent EA rosetting to 58%. The CD32A-dependent rosetting of fMLP-activated normal neutrophils also increased nearly 5-fold, but there was no increase in CD32A expression. The CD32A-dependent immune complex (IC) binding was also increased in activated neutrophils. This affinity regulation was not observed with CD32A expressed on Chinese hamster ovary cells. These results suggest that in resting neutrophils CD32A is in a low-affinity state and that these cells primarily engage CD16B for IC binding. However, once the neutrophils are activated, the CD32A is converted to a high-affinity state that leads to CD32A-dependent ligand binding and signaling. These results suggest that neutrophils adopt a novel strategy to engage the 2 different FcgammaR selectively during physiologic and pathologic conditions to carry out their functions efficiently.

Expression and characterization of glycolipid-anchored B7-1 (CD80) from baculovirus-infected insect cells: protein transfer onto tumor cells

Tumor cells can be modified to express immunostimulatory molecules such as B7-1 by protein transfer using purified glycosylphosphatidylinositol-anchored B7-1 (GPI-B7-1). In this study recombinant baculovirus encoding GPI-B7-1 (vBacB7-1(GPI)) was established to obtain large quantities of purified GPI-B7-1 to modify tumor cells by protein transfer. vBacB7-1(GPI)-infected insect cells showed high-level cell surface expression of GPI-B7-1 that was susceptible to PIPLC treatment. GPI-B7-1 expressed in insect cells (Bac-GPI-B7-1) mediated T cell proliferation, indicating that the GPI-B7-1 retains costimulatory activity. Moreover, Bac-GPI-B7-1 was completely solubilized in Triton X-100 at 4 degrees C compared to 22% solubilization of GPI-B7-1 expressed in CHOK1 cells, suggesting that GPI-anchored proteins expressed in insect cells may not be clustered into the detergent-insoluble fraction. SDS-PAGE analysis of Bac-GPI-B7-1 showed faster mobility (45 kDa) compared to GPI-B7-1 from CHOK1 (68 kDa) and this difference may be due to a difference in glycosylation. Cell binding assays showed that immunoaffinity-purified Bac-GPI-B7-1 retained its functional ability to bind CD28(+) cells. Moreover, when human tumor cells were incubated with this functionally active purified GPI-B7-1, an efficient transfer of B7-1 onto tumor cells was observed. These results demonstrate that GPI-B7-1 can be expressed in insect cells in a functionally active form and can be used to modify tumor cells for immunotherapeutic applications.

Cortical auditory signal processing in poor readers

Magnetoencephalographic responses recorded from auditory cortex evoked by brief and rapidly successive stimuli differed between adults with poor vs. good reading abilities in four important ways. First, the response amplitude evoked by short-duration acoustic stimuli was stronger in the post-stimulus time range of 150-200 ms in poor readers than in normal readers. Second, response amplitude to rapidly successive and brief stimuli that were identical or that differed significantly in frequency were substantially weaker in poor readers compared with controls, for interstimulus intervals of 100 or 200 ms, but not for an interstimulus interval of 500 ms. Third, this neurological deficit closely paralleled subjects' ability to distinguish between and to reconstruct the order of presentation of those stimulus sequences. Fourth, the average distributed response coherence evoked by rapidly successive stimuli was significantly weaker in the beta- and gamma-band frequency ranges (20-60 Hz) in poor readers, compared with controls. These results provide direct electrophysiological evidence supporting the hypothesis that reading disabilities are correlated with the abnormal neural representation of brief and rapidly successive sensory inputs, manifested in this study at the entry level of the cortical auditory/aural speech representational system(s).

Protein transfer of glycosyl-phosphatidylinositol-B7-1 into tumor cell membranes: a novel approach to tumor immunotherapy

Modification of tumor cells with one or more costimulatory adhesion molecules has been proposed as a means to develop therapeutic cancer vaccines for use in human immunotherapy. Expression of B7-1 (CD80) in tumors by gene transfer creates an immunogenic tumor cell that induces antitumor immunity and protects mice from further challenge with wild-type tumor cells. In this report, we demonstrate that protein transfer of glycosyl-phosphatidylinositol (GPI)-anchored costimulatory molecules into tumor cell membranes could be used as an alternative to gene transfer for tumor immunotherapy. Incubation of isolated tumor membranes with purified GPI-anchored B7-1 results in stable incorporation of B7-1 on tumor cell membranes within a few hours. Immunization of C57BL/6 mice with EG7 tumor membranes modified to express GPI-B7-1 by protein transfer induces tumor-specific T-cell proliferation and CTLs. In addition, immunization with these EG7 membranes protects mice from parental tumor challenge. The protein transfer approach used here does not require foreign vectors or live tumor cells and is completed within a matter of hours. Irradiated cells or membrane preparations from fresh or frozen tumor tissue can be used. Therefore, protein transfer of glycolipid-anchored molecules provides an efficient and novel approach to modify tumor membranes for human immunotherapy. This approach is not limited to costimulatory molecules because any cell surface protein can be converted to a GPI-anchored form by recombinant techniques.

Inhaled insulin

Inhalation of regular insulin for meal time glucose control has been found to be safe, efficacious and reliable in Type I and Type II diabetics. The administration of regular insulin through the human lungs by inhalation has been conducted in at least 14 short studies in both normal and diabetic subjects beginning as early as 1925. In all studies, significant insulin absorption and lowering of blood glucose was observed in the absence of penetration enhancers. Although a concern of variable dosing was raised in early studies, the development of new reproducible delivery systems has ensured that the variability of aerosol insulin can be as good, if not better, than subcutaneous (SC) injection. In the longest controlled studies in humans to date, both Type I and Type II insulin-dependent diabetics used a novel inhaled dry powder insulin delivery system for 3 months for meal time glucose control. The study results indicate that inhaled insulin provides equivalent glucose control, measured by hemoglobin A1c, when directly compared to SC injection. Interim results from an additional study with Type II diabetics who were failing oral hypoglycemic agents suggest that adjunctive therapy with inhaled insulin markedly improved glycemic control with a low risk of hypoglycemia. In all the 3 month studies the system was efficacious, well tolerated, well liked, and resulted in reproducible results. A potential advantage of aerosol insulin is that it is more rapidly absorbed (serum peak at 5-60 min) and cleared than SC injection (peak at 60-150 min), which provides a more relevant and convenient therapy for meal time glucose control. The relative efficiency of insulin delivery by aerosol, compared to SC injection, has been estimated from the dose measured at the exit point of the aerosol device, and found to range between 8 and 25% of SC, depending on the study.

Time-frequency MEG-MUSIC algorithm

We propose a method that incorporates the time-frequency characteristics of neural sources into magnetoencephalographic (MEG) source estimation. The method is based on the multiple-signal-classification (MUSIC) algorithm and it calculates a time--frequency matrix in which diagonal and off-diagonal terms are the auto and crosstime--frequency distributions of multichannel MEG recordings, respectively. The method averages this time-frequency matrix over the time--frequency region of interest. The locations of neural sources are then estimated by checking the orthogonality between the noise subspace of this averaged matrix and the sensor lead field. Accordingly, the method allows us to estimate the locations of neural sources from each time--frequency component. A computer simulation was performed to test the validity of the proposed method, and the results demonstrate its effectiveness.

Role of Flag Leaf and Spike Emergence Stage on the Incidence of Karnal Bunt in Wheat

Removal of the flag leaf of wheat, earlier hypothesized to act as a site where secondary sporidia of Tilletia indica multiply and conjugate, reduced the severity of Karnal bunt. Evidence reported here suggests that sporidia reach the flag leaf from the soil by splashing, multiply on the surface of the flag leaf, and move with rain water or dew into the boot of the flag leaf to cause infection of the spikelets. Plants in growth stage 49 (first awns visible) were more vulnerable to infection by secondary sporidia than were plants at other growth stages. At growth stage 49, the flag leaf lamina was fully opened, compared with its preceding stages, which had tubular and closed lamina. Also, leaf posture of the flag leaf at growth stage 49 is erect and thus may facilitate movement of sporidial inoculum into the boot. Upon completion of stage 49, the flag leaf becomes droopy, leading to lesser inoculum movement into the emerging spike. Thus, maximum success can be achieved in artificial creation of Karnal bunt by inoculating with secondary sporidia before onset of growth stage 49. Genotypes whose maturity avoids coincidence of this critical stage of spike emergence with periods of weather favorable for infection by T. indica may be selected for resistance breeding.

Thyroid gland papillary carcinoma with fibromatosis-like stroma: case report

Papillary carcinoma of the thyroid may show a variable degree of fibrosis of the stroma, but proliferation of the stromal fibroblasts mimicking fibromatosis is rare. There appears to be a new variant of papillary carcinoma of the thyroid associated with exuberant proliferation of the fibroblasts resembling fibromatosis. We present one such case in a 50 year old woman and succinctly reviewed the relevant literature of this rare variant. The necessity of a diligent search for a papillary carcinoma in thyroid gland which shows a proliferative fibrous lesion is stressed.

Novel devices for the predictable delivery of nitric oxide to aqueous solutions

Nitric oxide (NO), a recently discovered biological molecule synthesized by many cells, has many physiological roles including blood pressure regulation, neurotransmission, and inhibition of platelet adhesion. However, NO and reactive species formed in the presence of oxygen and superoxide can also be cytotoxic, mutagenic, or carcinogenic. Two novel devices were developed to deliver controlled and predictable amounts of NO to aqueous solutions for studying the effects of NO on biological systems. The devices contained either a slit or a tube composed of a gas-permeable membrane. Aqueous solution flowed on one side of the membrane while the other side of the membrane was exposed to NO gas. Mathematical models were used to predict the bulk or mixing-cup NO concentration in the aqueous solution at the exit of each delivery device following exposure to NO gas. Model predictions were in good agreement with experimental values at both 25 and 37 degreesC. One of the delivery devices was also connected to a well-stirred and oxygenated chamber. Model predictions of the chamber NO concentration, which included the reaction of NO with O2, were in excellent agreement with experiments.

Stabilization of Aldehydes as Propylene Glycol Acetals

Propylene glycol (PG) acetals (substituted 1,3-dioxalans) of a few representative aldehydes are prepared according to standardized methods in yields of 80-90%. A comparative study of the regeneration of citral from the corresponding dimethyl and PG acetals under mild acidic conditions showed that, although the former readily decomposed to an extent of 85%, the latter formed a near 1:1 equilibrium mixture with the generated aldehyde.

Antiinflammatory and antipyretic activity of Michelia champaca Linn., (white variety), Ixora brachiata Roxb. and Rhynchosia cana (Willd.) D.C. flower extract

Methanolic extracts of the flowers of M. champaca, I. Brachiata and R. cana were found to possess antiinflammatory activity against cotton pellet granuloma in rats at a dose level of 100 mg/kg body weight, sc. The latter two drugs showed higher activity (AIA) as compared to that of M. champaca. They reduced the protein content, acid phosphatase, glutamate pyruvate transaminase and glutamate oxalo-acetate transaminase activities in liver and serum. A significant reduction in the ascorbic acid content in adrenals was also observed in drug-treated animals. R. cana was recorded to possess significant antipyretic activity from the first hour of administration. These pharmacological properties may be traced to the presence of flavonoids in the flowers of these plants.

Relationship between NMR relaxation characteristics and water activity in cereal leaves

The relationship of imposed water activity a(w) (equilibrium relative humidity) with conventional water status parameters and proton spin-lattice relaxation time T1 of leaf water was studied in pearl millet and wheat. The water activities of different levels were created by equilibrating the leaves in varying concentrations of PEG-6000 solutions. With decreasing a(w), relative water content and T1 decreased linearly and other variables (leaf water potential and leaf water content) decreased exponentially upto a dehydration level of a(w) approximately 0.978 for pearl millet, 0.986 for drought susceptible wheat var. HD2329 and 0.975 for tolerant wheat var. C306. Below that level there was abrupt reduction in all parameters except T1 which registered an increase. The changes in short and long components of T1 with changes in a(w) have also have been discussed for pearl millet.

The affected gene underlying the class K glycosylphosphatidylinositol (GPI) surface protein defect codes for the GPI transamidase

The final step in glycosylphosphatidylinositol (GPI) anchoring of cell surface proteins consists of a transamidation reaction in which preassembled GPI donors are substituted for C-terminal signal sequences in nascent polypeptides. In previous studies we described a human K562 cell mutant, termed class K, that accumulates fully assembled GPI units but is unable to transfer them to N-terminally processed proproteins. In further work we showed that, unlike wild-type microsomes, microsomes from these cells are unable to support C-terminal interaction of proproteins with the small nucleophiles hydrazine or hydroxylamine, and that the cells thus are defective in transamidation. In this study, using a modified recombinant vaccinia transient transfection system in conjunction with a composite cDNA prepared by 5' extension of an existing GenBank sequence, we found that the genetic element affected in these cells corresponds to the human homolog of yGPI8, a gene affected in a yeast mutant strain exhibiting similar accumulation of GPI donors without transfer. hGPI8 gives rise to mRNAs of 1.6 and 1.9 kb, both encoding a protein of 395 amino acids that varies in cells with their ability to couple GPIs to proteins. The gene spans approximately 25 kb of DNA on chromosome 1. Reconstitution of class K cells with hGPI8 abolishes their accumulation of GPI precursors and restores C-terminal processing of GPI-anchored proteins. Also, hGPI8 restores the ability of microsomes from the mutant cells to yield an active carbonyl in the presence of a proprotein which is considered to be an intermediate in catalysis by a transamidase.

Recognition of superpotent sweetener ligands by a library of monoclonal antibodies

Monoclonal antibodies (mAb) made to the superpotent guanidino sweet tasting ligand, N-(p-cyanophenyl)-N'-(diphenylmethyl)-guanidineacetic acid were examined for their molecular recognition specificities using 14 different sweetener analogues in a competitive radioimmunoassay. The effects of variations in pH on ligand binding was also examined by radioimmunoassay. Photoaffinity labelling of the binding site was accomplished using a radiolabelled azido-derivative of the parent ligand, and L-chain or H-chain labelling was easily identified in several different mAb. For two of the mAb examined in this study (NC6.8 and NC10.14), the analogue binding studies are in agreement with the known Fab-ligand crystal structures. Monoclonal antibodies to this family of sweet tasting compounds may be useful probes for the study of sweet taste chemistry and identification of novel sweet taste ligands from combinatorial chemical libraries.