The locomotion, shape and pseudopodial dynamics of unstimulated Dictyostelium cells are not random

The dynamic periphery of unstimulated, preaggregation, hunger-stage Dictyostelium discoideum amoebae was investigated by time-lapse videomicroscopy and digital image processing. Circular maps (i.e. of each of 360 radii around the cell transformed upon Cartesian coordinates) were constructed around the centroid of individual cell images and analysed in time series. This novel technique generated spatiotemporal structures of various degrees of order in the maps, which resemble classical wave interference patterns. The patterns thus demonstrate that cell movement is not random and that cells are intrinsically vibrating bodies, transited by self-organized, superpositioned, harmonic modes of rotating oscillatory waves (ROWS). These waves appear to depend upon spatiotemporal oscillations in the physicochemical reactions associated with actin polymerization, and they govern pseudopodial movements, cell shape and locomotion generally. ROWS in this case are unrelated to the cyclic-AMP-regulated oscillations, which characterize later, aggregative populations of Dictyostelium. However, the exposure of aggregation-stage cells to a pulse of the chemoattractant cyclic-AMP induces a characteristic sequence of changes in the global cellular concentration and spatiotemporal distribution of fibrillar (F-)actin. This reaction begins with what appears to be a phase resetting of ROWS and it may, therefore, underlie the cellular perception of and response to chemotactic signals. We also develop here an analytical mathematical description of ROWS, and use it to simulate cell movements accurately.

Possibility of signal transduction through microfilaments below the membrane following ligand-receptor interaction

In this paper, we describe the changes of microfilament assembly and 3H-TdR incorporation in mouse ascites liver cancer cells under the action of concanavalin A (ConA) and laminin (LN). We have also studied the variation of 3H-TdR incorporation induced by destroying microfilaments with cytochalasin B (CB) following ConA and LN binding with their membrane receptors. It was found that ConA and LN interactions with their membrane receptors could induce the assembly of microfilaments below the membrane and promote DNA synthesis in these cells, but this effect was inhibited when microfilaments were destroyed by CB treatment. These results suggest that microfilaments might play a role in transferring signals from the membrane to the nucleus.

Pathogenesis of craniofacial and body wall malformations induced by ochratoxin A in mice

Ochratoxin A (OA), a mycotoxin commonly found in soils and on moldy food such as cereal grains, is a potent teratogen. The present investigation was designed to examine the teratogenicity of OA administered acutely at early post-implantation stages in mice, with particular emphasis on the pathogenetic basis of induced malformations. Maternal OA administration on gestational day (GD) 7 or 8 resulted in excessive amounts of cell death in selected cell populations. After a single dose of 2-4 mg/kg, excessive cell death was notable within 6 hours, and persisted to 36 hours post-treatment. As observed in GD 14 or 18 fetuses, the spectrum of induced craniofacial malformations included exencephaly, midfacial clefting, cleft lip, as well as hypotelorism, and synophthalmia associated with holoprosencephaly. Body wall defects involved either the abdominal wall alone, or in combination with the thoracic wall, resulting in partial or complete exposure of the viscera. Potential mechanisms for OA-induced selective cell killing are discussed.

Potentiation by the beta subunit of the ratio of the ionic current to the charge movement in the cardiac calcium channel

The voltage-activated rabbit cardiac calcium channel alpha 1 subunit was expressed in Xenopus oocytes. The charge movement of its voltage sensor was measured and related to the opening of the ion-conducting pore. The half-activation potential for charge movement was 35 millivolts more negative than that for pore opening. Coexpression of the cardiac calcium channel beta subunit reduced this difference without affecting charge movement. Thus, intramolecular coupling between the voltage sensor and the channel pore opening can be facilitated by a regulatory subunit.

Application of cDNA selection techniques to regions of the human MHC

Identification of transcribed sequences by cDNA selection is a potentially rapid and efficient way of scanning large genomic DNA fragments for the presence of genes. To evaluate this approach further, we have applied it to three yeast artificial chromosomes (YACs) and examined the products obtained from a total of about 1100 kb from two regions of the human major histocompatibility complex (MHC). One YAC was derived from an extensively studied portion of the Class II region of the MHC. The cDNAs recovered from this YAC included representatives of the previously described genes as well as one or more cDNA clones not described in the databases. A second YAC spanned about 330 kb of DNA surrounding the Class I gene HLA-A. In addition to Class I clones, 10 distinct cDNA products were identified from this YAC. A third YAC contained about 700 kb of human DNA, including 260 kb of overlap with the second YAC, and recovered an additional cDNA complementary to YAC B30 H3 DNA. Overall, the method is shown to be able to detect very scarce cDNAs and to detect a large fraction of coding sequences in YAC clones. Advantages and limitations of the approach are discussed.

Cloning and expression of a neuronal calcium channel beta subunit

Although pharmacological and electrophysiological studies have demonstrated the existence of multiple types of voltage-dependent calcium channels in neuronal tissue, the subunit composition of these channels is not well known. Here, we report the cloning and expression of a new rat brain beta subunit (beta 4). Northern blot analysis indicates that beta 4 mRNA is expressed almost exclusively in neuronal tissues, with the highest levels being found in the cerebellum. Coexpression studies indicate that rat beta 4 can interact with rabbit cardiac muscle alpha 1, rabbit skeletal muscle alpha 1, and calcium channels endogenous to Xenopus oocytes. beta 4 modulation of alpha 1 activity is similar to the modulation induced by beta 1, beta 2, or beta 3. The most striking effect of beta subunits is their ability to increase functional alpha 1 activity, which can be measured as either increased dihydropyridine binding to membranes from transfected COS cells or increased calcium channel activity in Xenopus oocytes.

The effect of laminin on molecular motion in the cell membrane and on cell motility

We have studied the variation of lateral diffusion of proteins in the cell membrane, of membrane lipid fluidity and of the electrophoretic motility (EPM) of macrophages after treatment with extrinsic laminin. The results showed that the lateral diffusion coefficient D value of membrane proteins, the fluidity of membrane lipids and the EPM of macrophages were decreased after laminin had bound to its membrane receptor on the macrophages. These results are important for developing an understanding of the early reaction of plasma membranes and cells in the presence of laminin.

[Clinical application of electro-retinographic C-wave]

We studied electro-retinographic c-wave in several fundus diseases. Compared with the normal controls of 65 eyes, the amplitude extinguished and lowered respectively were 71.4% and 25% in retinal detachment (28 eyes), 72.5% and 22.5% in tapetal degeneration (40 eyes), 30.8% and 38.4% in uveitis (13 eyes), 18.2% and 50% in high myopia (22 eyes), 8.6% and 44.3% in diabetics (70 eyes). We conclude that the ERG-C-wave can be a very simple and practical method for helping the clinical diagnosis in several obscured fundus diseases, if the patient cooperates.

[Alterations of protein kinase C activity in rat myocardium and aorta smooth muscle during endotoxemia]

A decline of cytosol protein kinase C activity was observed in rat myocardial cells at 4 and 8 h after endotoxin administration, and membrane-associated protein kinase C activity rose at the same time. The activity of membrane protein kinase C in aortic smooth muscle cells at 0.5 and 4 h after endotoxin injection was higher than that in control, while cytosol protein kinase C activity was lower. The results indicate that protein kinase C was activated in myocardial cells and aortic smooth muscle cells during various phases of endotoxemia.

The effect of tocainide on theophylline metabolism

The effect of 5 days of oral tocainide (400 mg every 8 h) on the kinetics of theophylline given as a single 5 mg kg-1 i.v. infusion over 30 min was investigated in eight healthy male nonsmokers. Treatment with tocainide decreased the plasma clearance of theophylline from 37.5 +/- 6.9 (mean +/- s.d.) to 33.7 +/- 5.0 ml kg-1 h-1 (difference -3.8, 95% CI, -1.7 to -5.9; P = 0.004) and increased its terminal elimination half-life from 9.7 +/- 2.5 to 10.4 +/- 2.1 h (difference 0.7, 95% CI, 0.2 to 1.2; P = 0.011). Tocainide decreased the formation clearances of 3-methylxanthine and 1-methyluric acid, but the formation clearance of 1,3-dimethyluric acid was unaltered. These data indicate that tocainide exerts a modest inhibitory effect on theophylline metabolism. The magnitude of this change is substantially smaller than that reported to be produced by mexiletine.

Cardiovascular effects of microinjections of thyrotropin-releasing hormone, oxytocin and other neuropeptides into the rostral ventrolateral medulla of the rat

Thyrotropin-releasing hormone, oxytocin, neurotensin, calcitonin gene-related peptide and neuropeptide Y have been proposed as putative neurotransmitters in the rostral ventrolateral medulla of the rat. To investigate the modulation of the basal blood pressure by neuropeptides, we microinjected these neuropeptides into the rostral ventrolateral medulla of the rat and examined their effects on basal blood pressure. Male Wistar rats were anesthetized with urethane, paralyzed and artificially ventilated. Thyrotropin-releasing hormone (0.01-1 ng), oxytocin (1 and 10 ng), neurotensin (0.1-10 ng), calcitonin gene-related peptide (1 and 10 ng) and neuropeptide (1 and 10 ng) produced increases in blood pressure and/or heart rate. Ganglion blockade with hexamethonium (10 mg/kg, i.v.) blocked the pressor responses to thyrotropin-releasing hormone (0.1 ng), oxytocin (10 ng) and neurotensin (10 ng), while methylatropine (1 mg/kg, i.v.) did not affect these responses. Corticotropin-releasing factor (0.1-10 ng) and atrial natriuretic peptide (1 and 10 ng) were ineffective. These findings indicate that many neuropeptides can modify basal blood pressure when injected into the rostral ventrolateral medulla. Whether these neuropeptides play a role in the blood pressure regulation within this brain region remains to be established.

Cloning and expression of a third calcium channel beta subunit

The skeletal muscle dihydropyridine receptor/Ca2+ channel consists of five distinct subunits (alpha 1, alpha 2 delta, beta 1, and gamma). Homologous alpha 1, alpha 2 delta, and beta 2 subunits are expressed in heart and brain. The present study reports the cloning and expression of a third beta subunit, beta 3, which is expressed predominantly in brain. Its open reading frame encodes a protein with 484 amino acids with a predicted molecular mass of 54,571 Da. Coexpression of beta 3 with a cardiac alpha 1 in Xenopus oocytes induces similar changes in Ca2+ channel activity as beta 1 and beta 2, that is, it increases peak currents, modulates the voltage dependence of activation, and accelerates activation. In addition, beta 3 accelerates the rate of inactivation at positive test potentials.

Characterization and autoradiographic localization of the cannabinoid binding site in rat brain using [3H]11-OH-delta 9-THC-DMH

The binding of [3H]11-OH-delta 9-tetrahydrocannabinol-1, 1-dimethyl-heptyl (THC-DMH), a recently synthesized cannabinoid analog, was characterized in an in vitro brain slice binding assay and compared to that obtained with [3H]CP-55,940, the radiolabeled ligand used originally to characterize cannabinoid binding sites. The binding of both [3H]CP-55,940 and [3H]11-OH-delta 9-THC-DMH exhibited high affinity (Kd of 19 +/- 3 and 29 +/- 9 nM, respectively), and was saturable, reversible and specific. Values of maximal concentration of receptors determined for [3H]11-OH-delta 9-THC-DMH and [3H]CP-55,940 were 4.0 +/- 0.3 and 3.0 +/- 0.5 pmol/mg of protein, respectively. The distribution of [3H]11-OH-delta 9-THC-DMH and [3H]CP-55,940 binding in 30-microns rat brain sections was then compared by autoradiographic analysis. The binding of both ligands was densest in the basal ganglia (substantia nigra pars reticulata, globus pallidus, entopeduncular nucleus and regions of the caudate putamen) and cerebellum (molecular layer). Low levels of binding were observed in discrete brain regions including the brain stem (medulla and pons), thalamic nuclei, hypothalamus, corpus callosum and the deep nuclear layer of the cerebellum. Intermediate levels of binding were seen in layers I and VI of the cortex, and the dentate gyrus and CA pyramidal cell regions of the hippocampus. The ability of selected cannabinoid analogs to compete with [3H]11-OH-delta 9-THC-DMH binding was determined. The Ki's were correlated to the in vivo potencies for producing catalepsy, antinociception, hypothermia and decreasing spontaneous locomotor activity in mice (correlation coefficients > 0.86).(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of lipopolysaccharide on protein kinase C activity in human erythrocytes]

Membrane-associated protein kinase C activity was significantly increased after normal human erythrocytes were incubated with lipopolysaccharide. The effect was dose and time dependent. The results indicate that protein kinase C is activated by lipopolysaccharide in intact human erythrocytes.

Cloning of a novel alpha 1-subunit of the voltage-dependent calcium channel from the beta-cell

To study the molecular regulation of voltage-dependent Ca2+ channels (VDCCs) in the beta-cell, we have cloned a cDNA for the alpha 1-subunit from a hamster insulin-secreting cell line (HIT-T15). The cDNA (HCa3a) encodes a 1610-amino acid protein with four repeating membrane domains and an overall structure characteristic of other alpha 1-subunits. Although the cDNA shows a high degree of sequence homology (97%) with a rat brain alpha 1-subunit (RB alpha 1), the C-terminal 15 amino acids of HCa3a share no similarity with any cloned alpha 1 protein. High stringency Northern blot analysis revealed a single transcript of approximately 8.6 kilobases in HIT cells and hamster pancreas. A similarly sized species was detected in hamster brain, heart, and skeletal muscle. Using polymerase chain reaction and a primer set unique to HCa3a, this alpha 1 isoform was found to be expressed in islet cell lines derived from rat, mouse, and hamster. The HIT cell alpha 1-subunit is also expressed in discrete regions of the rat central nervous system, including the cortex, cerebellum, hypothalamus, and brain stem. The expression of two alpha 1 isoforms (HCa3a and cardiac) in the HIT cell underscores the possible complexity of VDCCs in the regulation of beta-cell signal transduction. With its widespread tissue distribution, HCa3a does not conform to the current classification system used for L-type VDCCs; this suggests that an alternative system of classification is required.

[Experimental studies on growing seedlings of Morinda officinalis How]

By using the techniques of growing seedlings in bowshaped shed covered with plastic sheeting plus treatment with plant growth regulator, vegetative and generative propagation tests have been made of Morinda officinalis. Scientific evidences have thus been provided for growing seedlings of Morinda officinalis.

Glucose and glucosamine regulate growth factor gene expression in vascular smooth muscle cells

We have investigated the regulation of the expression of two growth factors found in vascular smooth muscle, transforming growth factor alpha (TGF alpha) and basic fibroblast growth factor (bFGF). Cells cultured in medium containing 30 mM glucose exhibited a 2-fold increase in TGF alpha mRNA and a 3-fold increase in bFGF mRNA compared with cells grown in normal (5.5 mM) glucose. Glucosamine was more potent than glucose, leading to a 6-fold increase in TGF alpha mRNA. TGF alpha protein levels were also increased by glucosamine treatment, and the predominant species present was the membrane-bound precursor form of TGF alpha. To examine further the regulation of growth factors by sugars, cultured rat aortic smooth muscle cells were transfected with a plasmid construct consisting of a 1.2-kilobase-pair fragment of the TGF alpha promoter linked to a luciferase reporter gene. Increasing the concentration of glucose in the culture medium from 5.5 mM to 30 mM led to a rapid, 1.7-fold increase in the activity of the TGF alpha promoter. Glucosamine was much more potent than glucose in this stimulation, with 2 mM glucosamine causing a 12-fold increase in TGF alpha promoter activity. Insulin had no effect on luciferase activity in either the presence or the absence of added sugars. The glucose response element of the TGF alpha gene maps to a 130-base-pair segment that includes three potential binding sites for the transcription factor Sp1. We conclude that high glucose concentrations such as are reached in diabetes mellitus can stimulate the transcription of the genes for growth factors in vascular smooth muscle cells. This signaling pathway apparently involves the metabolism of glucose to glucosamine. This effect could be representative of nutritional regulation of a family of genes and could contribute to the toxicity of hyperglycemia and the vascular complications of diabetes.