Field potential mapping of neurons in the lumbar spinal cord activated following stimulation of the mesencephalic locomotor region

The spinal neurons involved in the control of locomotion in mammals have not been identified, and a major step that is necessary for this purpose is to determine where these cells are likely to be located. The principal objective of this study was to localize lumbar spinal interneurons activated by stimulation of the mesencephalic locomotor region (MLR) of the cat. For this purpose, extracellular recordings of MLR-evoked cord dorsum and intraspinal field potentials were obtained from the lumbosacral enlargement during fictive locomotion in the precollicular-postmammillary decerebrate cat preparation. Potentials recorded from the dorsal surface of the cord between the third lumbar (L3) and first sacral (S1) segments typically showed four short-latency positive waves (P1-P4). These P-waves were largest between the L4-L6 segments. The amplitude of the P2-4 waves increased with the appearance of locomotion and displayed rhythmic modulation during the locomotor step cycle. Microelectrode recordings from the L4-L7 spinal segments during fictive locomotion revealed the presence of both positive and negative short-latency MLR-evoked intraspinal field potentials, and were used to construct isopotential maps of the evoked potentials. Positive field potentials were observed throughout the dorsal horn of the L4-L7 spinal segments with the largest amplitude potentials occurring in laminae III-VI. Negative field potentials were found in laminae VI-X of the lumbar cord. The shortest latency negative field potentials were observed in lamina VII and at the border between laminae VI and VII and were considered to be evoked monosynaptically from the arrival of the descending volley. Short-latency mono- and disynaptic negative field potentials were also observed in lamina VIII. Longer latency, tri- and polysynaptic field potentials were observed in laminae VII and VIII. Many of the longer latency negative waves observed in laminae VII and VIII followed shorter latency negative potentials recorded from the same location. Laminae VII and VIII negative field potentials were largest in the L5-6 and L4-5 spinal segments, respectively. Negative field potentials were also evoked in the motor nuclei of the L4-7 spinal segments. The segmental latencies for these potentials indicate that they were evoked di- and trisynaptically.(ABSTRACT TRUNCATED AT 400 WORDS)

Cleavage of an amide bond by a ribozyme

A variant form of a group I ribozyme, optimized by in vitro evolution for its ability to catalyze magnesium-dependent phosphoester transfer reactions involving DNA substrates, also catalyzes the cleavage of an unactivated alkyl amide when that linkage is presented in the context of an oligodeoxynucleotide analog. Substrates containing an amide bond that joins either two DNA oligos, or a DNA oligo and a short peptide, are cleaved in a magnesium-dependent fashion to generate the expected products. The first-order rate constant, kcat, is 0.1 x 10(-5) min-1 to 1 x 10(-5) min-1 for the DNA-flanked substrates, which corresponds to a rate acceleration of more than 10(3) as compared with the uncatalyzed reaction.

[Effect of xiaopiling granules on muscular histochemistry of gastric precancerous changes in rats]

The effect of Xiaopiling Granules on muscular histochemistry of gastric precancerous changes in rats was observed quantitatively. The activity of SDH and M-ATPase as well as the content of muscular glycogen in model groups were found significantly lower than those of the normal groups (p < 0.01), and in this decrease Xiaopiling Granules had markedly played a preventive and therapeutic role.

The lipids of slugs and snails: evolution, diet and biosynthesis

There is a considerable gap in current knowledge of the lipid composition of snails and slugs, both of which belong to the phylum Mollusca. We have therefore analyzed the sterol and fatty acid compositions of three species of slugs and three species of snails. The sterols of slugs included eight different sterols: cholesterol contributed 76-85% of the total sterols, brassicasterol accounted for 4-13%; other sterols we identified were lathosterol, 24-methylene cholesterol, campesterol, stigmasterol, sitosterol and sitostanol. In contrast, snails contained two additional sterols, desmosterol and cholestanol. Of the polyunsaturated fatty acids in slugs, linoleic (18:2n-6) and arachidonic acids (20:4n-6) were the major n-6 fatty acids, while linoleic (18:3n-3) and eicosapentaenoic acids (20:5n-3) were the predominant n-3 fatty acids. Docosahexaenoic acid (22:6n-3), the end product in the n-3 fatty acid synthetic pathway and an important membrane fatty acid of mammals, fish and birds, was absent in both slugs and snails. However, the analogous product of n-6 fatty acid synthesis, 22:5n-6, was found in both snails and slugs. This raises speculation about preference for n-6 fatty acid synthesis in these species. Our data show the unique sterol and fatty acid compositions of slugs and snails, as well as similarities and differences in sterol composition between the two. The results between the two land mollusks are contrasted with those of marine mollusks, such as oysters, clams and scallops.

Experimental study of a bow-tie-shaped optical fiber ring resonator with two 2 × 2 fiber couplers

An experimental study of a bow-tie-shaped double-coupler fiber ring resonator is presented. Multiple resonances of the transmitted output intensity and the splitting of the main resonance dip or peak have been observed. The experimental results are discussed and compared with theoretical results. The observed output property suggests the possible applications of the resonator as periodic Butterworth-like, narrow-band passing, and blocking filters.

Initial characterization of an antineoplastic, polysaccharide-rich extract of Mycobacterium bovis BCG, Tice substrain

A purified hot-water extract from Mycobacterium bovis (BCG vaccine) has been found to have significant antitumor activity against a murine sarcoma in vivo, but not in vitro, suggesting that the active compound is behaving as an immunostimulant. The material, termed PS1, has an average molecular weight of 22.4 kDa, is freely soluble in water, but has low solubility in acetone or ethanol, and is remarkably heat-stable, as is the parent BCG vaccine in terms of high-dose antitumor activity. PS1 contains at least 50% carbohydrate, consisting mainly of glucose, galactose and mannose, and about 10% lipid that may correspond to phosphatidylinositol. It shares chemical and biological properties with an arabinomannan isolated from M. tuberculosis, but it contains only trace quantities of lipoarabinomannan (LAM). Crossed immunoelectrophoresis indicated that PS1 contains the mycobacterial antigen 89, but only a single, non-migrating precipitin arc appeared on immunoelectrophoresis against a standard anti-BCG serum. PS1 appears to be non-toxic in mice up to a dose of 5 mg/kg, while as little as 70 micrograms/kg is sufficient to inhibit tumor formation significantly.

Optical-fiber double-loop resonator with a nonplanar 3 × 3 fiber coupler

We present for the first time to our knowledge a new and simple single-mode optical-fiber double-loop resonator. The double-loop resonator consists of two fiber loops constructed from a nonplanar 3 × 3 directional fiber coupler and two fiber delay lines. When the lengths of the fiber loops are different, additional periodic-resonance notches appear. The depths and the positions of these notches depend on the difference between the phase changes, and the coupling of the two fiber loops. This double-loop resonator can be used as a spectral filter and a sensor.

Intracellular calcium increases with hyperactivation in intact, moving hamster sperm and oscillates with the flagellar beat cycle

At some time before fertilization, mammalian sperm undergo a change in movement pattern, termed hyperactivation. There is evidence that hyperactivation offers an advantage to sperm for detaching from the oviductal mucosa, for penetrating viscoelastic substances in the oviduct, and for penetrating the zona pellucida. Hyperactivation is known to require extracellular calcium, but little else is known about the mechanisms by which calcium affects sperm movement. The calcium-sensitive fluorescent dye indo-1 was used to follow intracellular calcium levels ([Ca2+]i) in individual moving sperm. Sperm were loaded with 10 microM of the acetoxymethyl ester form of the dye and then rinsed. The dye was excited at 340 nm by using a filtered xenon stroboscope, and images at the 405-nm and 490-nm excitation maxima were simultaneously digitized at 30 per sec for 2.1 sec. [Ca2+]i was significantly higher in the acrosomal and postacrosomal regions of the head and in the flagellar midpiece (the principal piece could not be measured) in hyperactivated than in nonhyperactivated sperm (P < 0.0001). [Ca2+]i oscillations were detected in the proximal half of the midpiece that were identical in frequency to the flagellar-beat-cycle frequency in 12 of 17 hyperactivated sperm (median, 3.5 Hz). Rapid [Ca2+]i oscillations were also detected in the acrosomal and postacrosomal regions, as well as in the distal midpiece. Oscillations were not eliminated by dampening the flagellar bending with methyl cellulose. The [Ca2+]i oscillations detected in sperm are significantly more rapid than oscillations detected in other cell types.

The effects of intrathecal administration of excitatory amino acid agonists and antagonists on the initiation of locomotion in the adult cat

Development of pharmacological strategies for the control of locomotion in patients with spinal cord injury or disease requires an understanding of the neuroactive substances involved in the activation of the spinal cord neural systems for the control of locomotion. Studies using the in vitro preparations of the lamprey, frog embryo, and newborn rat indicate that excitatory amino acids (EAAs) are involved in the initiation of locomotion. The present study determines whether spinal EAA receptors play a role in locomotion in an in vivo, adult mammalian preparation. Experiments were performed on precollicular, postmammillary decerebrate cats, some of which were spinalized at the 13th thoracic segment. Cannulas for drug infusions were positioned intrathecally in the lumbar region of the spinal cord. A ligature around the spinal cord at the level of the 13th thoracic segment prevented rostral diffusion of the drugs. Locomotion was monitored with electromyograms in treadmill locomotion experiments and electroneurograms in fictive locomotion experiments. Intrathecal infusion of either the NMDA receptor antagonist 2-amino-5-phosphonovaleric acid or the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione blocked hindlimb treadmill and fictive locomotion induced by electrical stimulation of the mesencephalic locomotor region (MLR) of the midbrain. Intrathecal administration of NMDA elicited hindlimb fictive locomotion in resting animals similar to that evoked by electrical stimulation of the MLR. At lower concentrations, NMDA evoked either independent bursting activity in the various nerves or loosely organized rhythmicity showing little reciprocity between antagonists. In contrast, administration of the EAA uptake blocker dihydrokainic acid (DHK) evoked intermittent periods of bursting activity characterized by a variable duration and a high degree of reciprocity between flexors and extensors. Given together at low concentrations, NMDA and DHK produced a well-coordinated locomotor pattern. Kainate and quisqualate were ineffective in producing fictive locomotion. These results are consistent with the suggestion that EAAs play a role in the initiation of mammalian locomotion. Furthermore, the results are consistent with those obtained from the neonatal rat in vitro preparations.

Life security of the elderly: rural population control

"This article will examine the life security among the elderly in rural China and its impact on the population control in those areas." Data are from a fertility survey conducted in five rural villages in 1990.

[Effects of 3 Chinese medical prescriptions on alkaline reflux gastritis in rats]

The experimental alkaline reflux gastritis in rats was established after 9 weeks of anastomosis between stomach and jejunum. The experiment shows that xiangsha liujunzi decoction, xiaochaihu decoction and dahuang gancao decoction all help to inhibit edema, hyperamia and extravasted blood, as well as depress inflammatory infiltration and hyperplasia. The number of intestinal metaplasia in the group treated with xiangsha liujunzi decoction is decreased. All the three prescriptions are not able to lower the contents of bile acid in the stomach.

[Regulation of purine biosynthesis. I. Isolation of add:: MudJ (lacZ, Kanr) insertions and genetic mapping]

Report here is the isolation of adenosine deaminase deficient mutants and genetic mapping. Engineering transposon MudJ (lacZ, Kanr) was used for mutagenesis and six add:: MudJ were obtained among 20,000 Kanr transductants. Adenosine deaminase activity of these mutants were assayed and all are negative. Cotransduction analysis of add::MudJ indicated that add is 70% linked to pmi(31') and 37% linked to zxx1900::Tn10d-tet insertion which is 10% linked to purR(30'). Three points cross showed that add is located between pmi and Tn10d-tet insertion. Therefore the gene order is purR-zxx1900::Tn10d-tet-add-pmi.

Hyperactivation enhances mouse sperm capacity for penetrating viscoelastic media

A movement pattern known as hyperactivation has been observed among sperm recovered from the periovulatory oviduct of several species. In culture medium, hyperactivated sperm swim in a pattern that is far less progressive than that of freshly ejaculated sperm. In the oviduct, sperm encounter highly viscoelastic substances, such as mucus and the cumulus matrix. We have previously reported that hyperactivated hamster sperm become more progressive in vitro when the viscosity of medium is increased. In the present study, we tested the effect of increasing the viscosity and viscoelasticity of the medium on the swimming progressiveness of mouse sperm. Caudal epididymal sperm were incubated in a medium that produced hyperactivated motility in 60 min. Swimming velocities of sperm incubated for 60 min were compared with those of fresh sperm after addition of one of the following to culture medium: solutions of 1.8% methylcellulose (high viscosity), 1.8% long chain polyacrylamide (high viscoelasticity), or culture medium alone (low viscosity). In culture medium, hyperactivated sperm had significantly lower mean straight-line velocities than fresh sperm (p = 0.004); this difference disappeared in methylcellulose (p = 0.085) and was reversed in polyacrylamide (p = 0.004). This and other velocity measurements indicated that hyperactivated mouse sperm penetrate viscoelastic media more efficiently than fresh sperm and therefore may be more efficient at penetrating oviductal mucus and cumulus matrix in vivo.

[Effect of sodium valproate on bicuculline-induced epileptiform activity in rat hippocampal slices in vitro]

Experiments were conducted on the rat hippocampal slices in vitro with the superfusion of bicuculline (Bcl, 10 mumol/L) and stimulation of Schaffer collaterals by single pulse to produce epileptiform activity of the pyramidal cells in CA1 area. In these experiments the effect of constant microinjection of sodium valproate onto the surface of slice on the epileptiform activity was studied. The results showed that the valproate, in concentration of 20, 30, 50 and 100 mmol/L, inhibited the Bcl-induced epileptiform activity in a manner of dose-dependence. It was deduced that the inhibition of epileptiform activity by the valproate is possibly related to the recovery of and increase in the inhibition mediated by GABAergic neurons and may be also to the non-synaptic mechanism of the valproate in rat hippocampus.

Differential theophylline inhibition of alkaline phosphatase and 5'-nucleotidase of bovine milk fat globule membranes

1. The effects of theophylline (1,3-dimethylxanthine) on alkaline phosphatase and 5'-nucleotidase activities of bovine milk fat globule membranes (MFGM) were examined. 2. Theophylline inhibited MFGM alkaline phosphatase in a concentration-dependent manner with 50% inhibition produced by 99 +/- 28 microM theophylline. 3. The 5'-nucleotidase activity was resistant to theophylline inhibition with 50% inhibition produced by 33.9 +/- 3.1 mM theophylline. 4. Theophylline was an uncompetitive inhibitor of MFGM alkaline phosphatase with a Ki of 126 +/- 15 microM. 5. The extent of theophylline inhibition of alkaline phosphatase activity was independent of the substrate utilized in the assay. 6. The effect of theophylline on bovine MFGM alkaline phosphatase was similar to theophylline effects on other mammalian alkaline phosphatases of liver/bone isoenzyme origin.

[The finite element analysis of the bicuspid and molar of mandible]

Recently, the finite element method has been adopted in the study of tooth structure as well as the stress distribution of dental prosthesis. In order to understand the loading state of the supporting tissues and the stress distribution of the teeth in various shapes under the pressure of loading, the author of this essay has applied the two-dimensional finite element method to the study of the stress distribution of the periodontal supporting tissues at the time when the second bicuspid and the second molar are vertically and obliquely loaded. Finally, the results of the quantitative analysis are obtained and a curve of the stress distribution of the teeth is also drawn up. The conclusion is as follows: 1. When the vertical loading is applied to the occlusal surface of the bicuspid and molar, the stress distribution of periodontal supporting tissues is uniform. 2. The stress concentration is on the marginal ridge and thedistal apex of bicuspid under the oblique loading. 3. When the oblique loading is applied to the occlusal surface of the molar, the stress concentration is only on the marginal ridge, and it is small.

Genetic diversity of six isozyme loci in cultivated barley of Tibet

A random sample of 463 accessions of cultivated barley from the Tibet Hordeum germplasm collection was assayed electorphoretically for genetic diversity at six isozyme loci. Two loci (Acp-1 and Got-1) were found to be monomorphic and extensive variation was detected at the remaining four loci (Est-1, Est-2, Est-3 and Est-4). The allelic composition of Tibetan barley appeared to be distinct as compared to the results of previous studies of barleys from other parts of the world. Partitioning of genetic diversity showed that approximately 96% of the total variation was maintained at the within-subregion level and only about 4% was accounted for by differentiation among the eight subregions. Analysis of multilocus genotypes revealed non-random association of the alleles at the four loci, both in the entire sample and in all the subregions, although the four major multilocus genotypes did not show significant departure from the expectation based on complete random association. The possible causes for the establishment of these multilocus associations were discussed.

Bovine mitochondrial rhodanese is a phosphoprotein

The mitochondrial sulfurtransferase, rhodanese, has been analyzed for phosphate content. Significant amounts of protein-bound phosphate (30-40%) were measured in the six rhodanese preparations examined. Chromatographic experiments followed by phosphate analyses done on two of the preparations indicated that rhodanese A and rhodanese B, two enzyme forms that were previously resolved on DEAE-Sephadex by Blumenthal and Heinrikson (Blumenthal, K., and Heinrikson, R. L. (1971) J. Biol. Chem. 240, 2430-2437), correspond to dephospho- and phosphorhodanese, respectively. The phosphorylation of rhodanese by [gamma-32P]ATP is catalyzed by cAMP-dependent protein kinase. The stoichiometry of 32P incorporation based on the amount of dephosphorhodanese in the enzyme preparation approaches 1.0. The phosphorylation site is accessible in rhodanese that is free of substrate sulfur but not in the covalent enzyme-sulfur intermediate which is formed as an obligatory step during the course of catalysis. Because the cellular localization of cAMP-dependent protein kinase makes it unlikely as the physiologic modulator of rhodanese activity, liver extracts have been tested for a rhodanese kinase that does not require cAMP. Rhodanese kinase activity which is independent of cAMP is observed in extract fractions resolved by Affi-Gel Blue chromatography and freed from endogenous rhodanese by chromatography on Sephadex G-100. These results together with previous findings from this and other laboratories have led to a working model of a bicyclic cascade system that can modulate the rate of mitochondrial respiration. The essence of the model is a transduction and amplification of cellular signals into the altered covalent phosphorylation of rhodanese. Rhodanese, in turn, serves as a converter enzyme which directly alters the rate of the respiratory chain and, thus, ATP production by the reversible sulfuration of key iron-sulfur centers. The model, when expanded to include signal pathways initiated by hormones or neurotransmitters, represents a mechanism by which mitochondria can recognize and meet changing energy demands.

The transposition properties of Tn2 in E. coli

We report the characterization of Tn2 transpositions into the chromosome and into an F' lacproB episome of E. coli. When Tn2 transposes into the chromosome a proportion of the insertions result in auxotrophy. These insertions can revert to prototrophs and lose ampicillin resistance concomitantly. However, Tn2 insertions in F' lacproB are often associated with deletions, and it seems probable that insertion and deletion occur simultaneously.