Segmental release of amino acid neurotransmitters from transcranial stimulation

The present study used microdialysis techniques in an intact rabbit model to measure the release of amino acids within the lumbar spinal cord in response to transcranial electrical stimulation. Dialysis samples from the extracellular space were obtained over a stimulation period of 90 minutes and were examined using high pressure liquid chromatography. Neuronal excitation was verified by recerding corticomotor evoked potentials (CMEPs) from the spinal cord. A significant increase in the release of glycine and taurine compared to sham animals was measured after 90 minutes of transcranial stimulation. Glutamate and aspartate release was not significantly elevated. GABA concentrations were consistently low. CMEP components repeatedly showed adequate activation of descending fiber pathways and segmental interneuron pools during dialysis sampling. Since glycine, and to a lesser extent taurine, have been shown to inhibit motor neuron activity and are closely associated with segmental interneuron pools, suprasegmental modulation of motor activity may be, in part, through these inhibitory amino acid neurotransmitters in the rabbit lumbar spinal cord.     

大鼠脑胆碱能系统对血量扩张引起利尿与尿钠排泄的作用

本工作在清醒大鼠侧脑室注射胆碱能药物,观察脑胆碱能系统对血量扩张引起利尿与尿钠排泄的作用。侧脑室注射人工脑脊液后进行血量扩张引起尿流量、排钠量和排钾量显著增加(P<0.01)。侧脑室注射胆碱能 M 受体阻断剂阿托品后,血量扩张引起尿流量、排钠量和排钾量增加的效应比注射人工脑脊液组的均显著减弱(P<0.01);而侧脑室注射胆碱能 N 受体阻断剂六烃季胺后,血量扩张引起尿流量、排钠量和排钾量增加的效应与注射人工脑脊液组的相比无显著差异(P>0.05)。侧脑室注射人工脑脊液或阿托品大鼠的肾小球滤过率(GFR)与肾血浆流量(RPF)在血量扩张后均无显著变化(P>0.05)。上述结果表明:大鼠脑胆碱能M 受体参与血量扩张引起利尿与尿钠排泄反应的调节。脑 M 受体的这种作用不是通过改变GFR 和 RPF,而可能是通过未明神经液递机制直接影响肾小管对水钠的重吸收。     

Association of Lps gene with natural resistance of mouse macrophages against Legionella pneumophila

We have cloned a 1.6-kb region of chromosomal DNA from Thermoplasma acidophilum into Escherichia coli using as a probe part of the Methanococcus vannielii fus-gene. The sequence of the clone was highly homologous to part of the corresponding Methanococcus vannielii gene. By chromosome walking, a 4.7-kb EcoRI fragment containing the complete gene was isolated. Nucleotide sequencing revealed an open reading frame of 2196 nucleotides. The deduced amino acid sequence contains the known peptide sequence around the ADP-ribosylation site of T. acidophilum elongation factor 2, which unequivocally confirms that the fus-gene has been cloned. The amino acid sequence was compared to that of hamster and E. coli, as well as to known archaebacterial EF-2 sequences.     

Secretion of a new growth factor, smooth muscle cell derived growth factor, distinct from platelet derived growth factor by cultured rabbit aortic smooth muscle cells

In attempts to determine the mechanism of proliferation of arterial smooth muscle cells (SMC) in intimal atheromatous lesions, autocrine secretion of growth factors by SMC has recently received much attention. Here we report a new growth factor named smooth muscle cell derived growth factor (SDGF). Cultured rabbit medial SMC secreted SDGF for 1 week during their incubation in serum-free media only after at least 4 passages. SDGF differed from platelet derived growth factor (PDGF) physicochemically, immunologically, and biologically. The properties of SDGF also seemed different from those of other known growth factors that stimulate the proliferation of mesenchymal cells.     

Rapid Isolation of the 7S-Nerve Growth Factor Complex and Its Subunits from Murine Submaxillary Glands and Saliva

7S-Nerve growth factor (NGF) and its alpha, beta-NGF, and gamma subunits have been purified from murine submaxillary glands and saliva by a combination of gel filtration on rigid polyvinyl gels, reversed-phase liquid chromatography on short alkyl chain supports (C4 columns), and ion-exchange chromatography on silica-based carboxymethyl columns. This technique is superior to previously used methods in that it is much more rapid and allows the purification of larger quantities of polypeptide from the same amount of starting material. Beta-NGF prepared with this method elicits the outgrowth of fibers of cells of a pheochromocytoma cell line (PC 12) in vitro, indicating that the biological activity is not impaired by the organic solvents and strong acids utilized for its isolation.     

A Nerve Growth Factor-Sensitive S6 Kinase in Cell-Free Extracts from PC 12 Cells

Soluble extracts from nerve growth factor (NGF)-stimulated PC12 cells prepared by alkaline lysis show a two- to 10-fold greater ability to phosphorylate the 40S ribosomal protein S6 than do extracts from control cells. The alkaline lysis method yields a preparation of much higher specific activity than does sonication. Half-maximal incorporation of 32P from [32P]ATP into S6 occurred after 4-7 min of NGF treatment. The partially purified NGF-sensitive S6 kinase has a molecular weight of 45,000. It is not inhibited by NaCl, chlorpromazine, or the specific inhibitor of cyclic AMP (cAMP)-dependent protein kinase, nor is it activated by addition of diolein plus phosphatidylserine. Trypsin treatment of either crude extracts or partially purified S6 kinase from control or NGF-treated cells was without effect. These data suggest that the S6 kinase stimulated by NGF is neither cAMP-dependent protein kinase or protein kinase C nor the result of tryptic activation of an inactive proenzyme. Treatment of intact cells with dibutyryl cAMP or 5'-N-ethylcarboxamideadenosine also increases the subsequent cell-free phosphorylation of S6. This observation suggests that cAMP-dependent protein kinase may be involved in the phosphorylation of S6 kinase.     

Critical nuclear DNA size and distribution associated with S phase initiation

Using HeLa S-3 cells synchronized by selective detachment, in this paper we report a parallel study of nuclear morphology and autoradiography grain patterns between middle G₁ and middle S phases: Our results show two distinct [³H]-thymidine labeling patterns. The first “peripheral” labeling pattern has a characteristic nuclear size distribution, in contrast to the heterogeneous and varying size distributions of Feulgen-stained nuclei, and apparently is characteristic of very early S phase. The sizes of the second labeling pattern—homogeneous or inhomogeneous grain distribution throughout the nucleus—are equal or larger than the first and vary with S phase progression. Together, the corresponding nuclear sizes of the labeled nuclei represent the larger extreme of nuclear areas, and the labeling index closely parallels the fraction of nuclei with areas larger than the minimum size of the labeled nuclei. These results suggest a characteristic nuclear size (reflecting unique intranuclear DNA distribution) as a necessary, if not sufficient, requirement for S phase initiation. Parallel experimentation with rat liver cells—synchronized in vivo by partial hepatectomy and analyzed by thin section autoradiography—confirms the existence of a peripheral labeling pattern in both the very early part and the very late part of S phase, which reconciles our data with previous results and points to the fact that both initiation and termination sites for DNA replication are near the nuclear periphery.     

Rat hypothalamic GRF elicits its biologic action in GH3 cells by interaction with VIP- preferring receptor site(s)

GH3 cells can be used effectively to study the in vitro mechanism of action of GRF. In these cells, there is a time and concentration-dependent release of cAMP into the medium. Rat hypothalamic GRF, (rGRF) is 7 to 10 fold more active than human hypothalamic GRF (hGRF). VIP, a peptide which is structurally homologous to GRF, stimulates cAMP efflux in GH3 cells, with a higher affinity than hGRF or rGRF. We propose that in contradistinction to the normal rat pituitary, the stimulation of cAMP release by GRF in GH3 cells occurs via activation of VIP-preferring receptors and that GRF (rGRF in particular) behaves as a partial VIP agonist.     

Fine structure of wide and narrow vertebrate muscle Z-lines. A proposed model and computer simulation of Z-line architecture

A model of the structure of vertebrate Z-lines and Z-line analogs is introduced and supported by evidence from electron microscope studies of wide Z-lines (rat and feline soleus, and feline and canine cardiac muscles), narrow Z-lines (guppy, newt and frog skeletal muscles), and Z-rods (from a patient with nemaline myopathy and from cardiac muscles of aged dog). The model is based on a pair of Z-filaments (termed a Z-unit), which are linked near their centers at a 90 degrees angle and form bridges between neighboring antipolar thin (actin) filaments. A square lattice of four Z-filament pairs (the basic structure of the Z-line, termed a Z-line unit) defines the geometrical position of the I-square unit. In this native state of the Z-line, small square and large square net forms appear in cross-section. Other cross-sectional patterns of Z-lines, including basket-weave and diagonal-square net patterns, can be explained by detachment of the Z-filament from the Z-filament binding region within each Z-filament pair due to chemical or physical stress. Dissection of Z-lines and Z-line analogs with calcium-activated neutral protease provides evidence that the width of all wide Z-line structures is determined by the amount of overlap of antipolar thin filaments from adjacent sarcomeres. Longitudinal patterns of narrow and wide Z-lines are shown and described in relation to the model. To test the proposed model, the dynamics of the Z-line unit structure were computer-simulated. An attempt was made to correlate longitudinal (z direction) and cross-sectional (x and y directions) patterns and to determine the amount of movement of thin or Z-filaments that is required to explain the diversity observed in cross-sectional patterns of Z-lines. The computer simulations demonstrated that the structural transitions among the small square, and therefore large square net, as well as basket-weave and diagonal-square net forms seen in cross-sections could be caused by movements of thin filaments less than 10 nm in any direction (x, y or z).(ABSTRACT TRUNCATED AT 400 WORDS)     

Phosphate sorption isotherms for evaluating phosphorus requirement of wetland rice soils

Summary Phosphate sorption isotherms were developed for five Philippine wetland rice soils using the conventional technique and a modified one. In the conventional method, P requirements of soils varied between 280 and 810 g P/g soil. In the modified method, they varied from 160 to 540 g P/g soil at 0.2 ppm P in solution. Soils with high P-sorption capacities had vermiculite and halloysite as the dominant clay minerals. Soil reduction by flooding decreased P-sorption by 28–70 percent at 0.2 ppm P in solution. The decrease in P-sorption due to soil reduction was greatest in a crystalline soil with vermiculite and halloysite as the dominant clay minerals and least in a soil with dominant X-ray amorphous silicates in the clay fraction.Desorption of freshly adsorbed P under reduction was greater in HCO ₃ ^– solution than in CaCl₂ and it increased with level of applied P. Desorption patterns of freshly adsorbed P were similar to adsorption patterns but values of P in solution were lower at desorption. Soils varied with respect to desorption of freshly sorbed P. Desorption studies indicate that soils vary in intensity factor with respect to P and thus influence P availability to plants. Use of P-sorption and P-desorption data obtained under reduced soil condition was proposed for detecting P needs of submerged rice soils.Results of a pot study with IR36 at different levels of solution P (reduced) in one soil indicated a high degree of correlation between adjusted P levels and the measured growth parameters. About 0.12 ppm P in the soil solution or 0.46 ppm P desorbed in HCO ₃ ^– solution (equivalent to 100 mg P/kg soil) was adequate for near-maximum plant height, tiller production, total dry matter yield, plant P content, and total P uptake.