Interaction of direct afferent and recurrent signals in cat motor cortex neurons

Intracellular activity was recorded from the functionally identified motor cortex neurons (MI, area 4) in acute experiments on myorelaxin-immobilized cats under calypsol anesthesia. Changes in neuronal responses to testing stimulation of the ventrolateral thalamic nucleus or pyramidal tract fibers were studied; the same or another input was used for a conditioning stimulation. Excitatory and inhibitory components of test responses of variousMI neurons were found to be either facilitated or depressed. The facilitation of orthodromic excitation was more frequent in the case of thalamic testing stimulation. The depression of both excitatory and inhibitory components of the response was more pronounced with paired stimulation of the pyramidal tract fibers. The peculiarities of interaction between direct afferent and recurrent signals in theMI neurons are thought to be determined by different distribution of thalamocortical fiber terminals and recurrent collaterals of corticofugal axons in the cortex and nonuniform localization of their synapses on dendrites and somata of the studied cells. It seems possible that these peculiarities also are connected with different chemical mechanisms of synaptic transmission in the above synapses and different properties of postsynaptic membrane receptors.Neirofiziologiya/Neurophysiology, Vol. 26, No. 3, pp. 203–210, May–June, 1994.     

A study of air particulate pollution in colombo using a nuclear-related analytical technique

Air particulate matter of two size fractions (coarse [2.5–10 Μm] and fine [less than 2.5 Μm]) were collected at an urban residential site (Colombo University ground) over a period of 12 mo during 1996 using a Gent PM10 stacked filter unit. Seventy-five sets of samples collected during this period were analyzed for 10 elements: Al, Si, K, S, Ca, Ti, Fe, Zn, Br, and Pb by energy-dispersive X-ray fluorescence, which is a multielement analysis. This is a highly sensitive technique enabling quantitative analysis of very low masses. The average concentrations of lead, sulfur, and bromine, which are generally associated with combustion products of automotive exhausts, dominate the fine fraction in this study. The minimum and maximum concentration of lead resulting in an annual average of 0.09 Μg/m³ was found to be 0.0042 and 0.441 Μg/m³ in particulate matter with less than 10 Μm equivalent aerodynamic diameter. The maximum concentration determined is well below the limits set by the World Health Organization (0.5–1.0 Μg/m³). The recommended value for Pb in Sri Lanka is 0.5 Μg/m³. Al, Si, Ca, Ti, and Fe exhibited enhanced concentrations in the coarse fraction, which probably originate from disturbed soil as a result of wind and traffic.     

Escape responses of hauled out ringed seals (Phoca hispida) to aircraft disturbance

Arctic marine mammals may be subject to human-induced disturbance from various air traffic, mostly in connection with exploration and exploitation of non-renewable resources. The escape responses (i.e. leaving the ice) of hauled out ringed seals (Phoca hispida) to a low-flying (150 m) fixed-wing twin-engine aircraft (Partenavia PN68 Observer) during strip censuses in eastern Greenland (June 1984) and to a low-flying (150 m) helicopter (Bell 206 III) during reconnaissance in northwestern Greenland (May 1992) were recorded. Overall, 6.0% of the seals (N _tot = 5040) escaped as a reaction to the fixed-wing aircraft. Seals escaped less than about 600 m in front of the aircraft. The overall probability of escaping was 0.21 within a 200-m-wide centre zone, 0.06 on the side of the aircraft (100–300 m from the flight track), and 0.02 between 300 and 500 m from the track. The probability of escaping was found to be influenced by the time of day, relative wind direction and wind chill. Overall, about 49% of all seals (N _tot = 227 cases) escaped as a response to the helicopter. Seals entered the water a maximum of about 1250 m in front of the aircraft. At wind chill values below 1100 kcal/m² h, the probability of escaping was 0.79 in the 200-m-wide centre zone. On the sides the probability of escaping decreased up to about 500 m from the flight track whereafter it remained constant at about 0.30 up to about 1450 m. During the helicopter surveys wind chill was the only environmental factor found to have an additional effect on the probability of escaping. The study indicated that the risk of scaring ringed seals into the water can be substantially reduced if small-type helicopters do not approach them closer than about 1500 m, and small fixed-winged aircraft not closer than about 500 m. Accepted: 27 August 1998     

Contribution of root respiration to soil respiration in a C3/C4 mixed grassland

The spatial and temporal variations of soil respiration were studied from May 2004 to June 2005 in a C₃/C₄ mixed grassland of Japan. The linear regression relationship between soil respiration and root biomass was used to determine the contribution of root respiration to soil respiration. The highest soil respiration rate of 11-54 Μmol m^-2 s^-1 was found in August 2004 and the lowest soil respiration rate of 4.99 Μmol m^-2 s^-1 was found in April 2005. Within-site variation was smaller than seasonal change in soil respiration. Root biomass varied from 0.71 kg m^-2 in August 2004 to 102 in May 2005. Within-site variation in root biomass was larger than seasonal variation. Root respiration rate was highest in August 2004 (5.7 Μmol m^-2 s^-1) and lowest in October 2004 (1.7 Μmol m^-2 s^-1). Microbial respiration rate was highest in August 2004 (5.8 Μmol m^-2 s^-1) and lowest in April 2005 (2.59 Μmol m^-2 s^-1). We estimated that the contribution of root respiration to soil respiration ranged from 31% in October to 51% in August of 2004, and from 45% to 49% from April to June 2005.     

A novel cottong ovule culture: Induction, growth, and characterization of submerged cotton fibers (Gossypium hirsutum L.)

Summary The growth of submerged cotton (Gossypium hirsutum L.) fibers from cultured ovules has been investigated. The results indicate that exogenous plant hormone levels regulate the induction of submerged fiber growth. The age of ovules at induction is also important. Cell diameter, wall thickness, and cell length of submerged fibers were measured and compared with air-grown fibers and fibers grown in vivo (produced by cotton plants grown in the greenhouse). Various cellwall thickening patterns were observed among submerged fibers, while only one predominant cell-wall deposition pattern was produced in air-grown fibers and in fibers produced in vivo. The diameter of submerged fibers was about the same as that of air-grown fibers but about 22% less than that of fibers grown, in vivo. It appears that the secondary cell wall thickenings are initiated earlier in submerged fibers. The cell-wall thickness of submerged fibers, at 41 d post anthesis (DPA), was 51% greater than that of fibers grown in vivo, whereas the cell-wall thickness of air-grown fibers was 42% less than that of fibers produced in vivo. The cell length of submerged fibers was approximately half that of fibers grown in vivo. and the air-grown fiber length was about two-thirds of fibers grown in vivo. The age of ovules at induction affects the outcome of the air-grown fiber-cell length, but does not appear to affect the length of submerged fiber cells. To produce submerged fiber growth, we found that the optimal age of ovules at induction was 0 DPA, and the optimal medium (with a GA₃ of 0.5 μM and an IAA range of 5-20 μM) depends on the time of ovule induction (−2 to+2DPA). We conclude that conditions leading to submerged cotton fiber growth have great potential for (a) direct monitoring of growth and making precise, detailed measurements during fiber growth and development; (b) producing cellulose and fibers in vitro more efficiently than earlier ovule-culture methods; and (c) using these unique cultures to obtain a better understanding of signal transduction and gene expression leading to growth, development, and programmed cell death in the life history of the cotton fiber.     

Increased serum copper and decreased serum zinc levels in children with iron deficiency anemia

In order to evaluate serum copper and zinc status in children with iron deficiency anemia (IDA), 60 children with IDA aged 1–14 yr and 64 healthy children as controls aged 1–14 yr were included the study. Serum copper levels were higher in children with IDA (189 ± 49 (Μg/dL) than those of controls (163 ± 37 Μg/dL) (p = 0.001). Serum zinc levels were lower in the patient group (109 ± 59 Μg/dL) than those of control subjects (135 ± 56 Μg/dL) (p = 0.017). In addition, there were statistically significant negative correlations between hematological parameters and serum copper levels in the patient group, but not in controls. No correlation between hematological parameters and serum zinc levels were found in both patient and control groups, except positive correlation between mean corpuscular volume (MCV) and serum zinc level in patients. It was concluded that at the time of managing children with IDA, zinc deficiency must be borne in mind and if necessary treatment should be initiated with zinc.     

Mercury ions inhibit photosynthetic electron transport at multiple sites in the cyanobacteriumSynechococcus 6301

Inhibition of electron transport activities in the spheroplasts ofSynechococcus 6301 by HgCl² is dependent on the concentration of mercury ions. The inhibition of whole chain electron transport activity occurs at low concentration of Hg²⁺ (6 ΜM@#@). This inhibition occurs mostly due to interaction of Hg²⁺ on plastocyanin. At an elevated concentration (24 ΜM@#@), mercury induces inhibition chiefly in photosystem II catalyzed electron transport. At this concentration it also alters both the absorption and emission characteristics of the phycocyanin. The photosystem I catalyzed electron transport was inhibited by 50% only at high concentrations (36 ΜM@#@) of HgCl₂. However, electron transport catalyzed by photosystems I and II from reduced duroquinone to methylviologen which involves intersystem electron transport is extremely sensitive to mercury (low concentration 6–9 ΜM) like that of whole chain assay indicating that the observed inhibition in whole chain electron transport at low concentrations is mostly contributed by the damage involving other intersystem electron transport carrier(s) like plastocyanin. Thus mercury ions depending on the concentration affects the electron transport at multiple sites in the spheroplasts ofSynechococcus.     

Spatial distribution of extractable organohalogens in northern pink shrimp in the North Atlantic

Extractable organohalogens (EOX) are organic compounds that contain chlorine, bromine and/or iodine, which can be separated from the matrix by liquid/liquid or liquid/solid extraction. A combination of instrumental neutron activation analysis (INAA) and solvent extraction methods has been developed for the determination of EOX from the shrimpPandalus borealis. Levels of EOX were evaluated for spatial trends for shrimp caught in several areas off the Labrador coast, off the coast of Nova Scotia, and off the coast of Maine. Muscle contained 1.09–6.05 Μg EOCl/g tissue and 105–498 Μg extractable organochlorine (EOCl)/g lipid; 0.0607–0.288 Μg extractable organobromine (EOB)r/g tissue and 4.74-10.5 Μg EOBr/g lipid; and 0.014–0.048 Μg extractable organoiodine (EOI)/g tissue and 1.03–1.76 Μg EOI/g lipid, respectively. The levels of EOC1 in roe were 1.60–12.34 Μg/g tissue and 39.0-146 Μg/g lipid. In roe, the EOBr levels were 0.707–1.03 Μg/g tissue and 6.96–13.5 Μg/g lipid; and EOI levels were 0.123–0.349 Μg/g tissue and 1.42–4.11 Μg/g lipid. The EOCl, EOBr, and EOI levels in roe increased noticeably from north to south along the coast of Labrador. Samples taken from the coast of Maine and from Canso Hole were typically higher in EOCl levels than those taken from Labrador. The results for EOBr and EOI were in the same range as those from Labrador.     

Limits of detection of a total reflection x-ray fluorescence system with double reflection module

An X-ray tube with a Mo target and Zr filter, operated at 45 kV/20 mA, was used to excite samples (5 ΜL deposited on a quartz support) and the total reflection angle condition was obtained with a double reflector module built with two 10-cm-long 7-mm-thick quartz crystals placed 50 Μm apart. A high-resolution spectrometer based on a Si(Li) detector coupled to a multichannel analyzer was used for X-ray detection and the spectra were interpreted with the AXIL software. The system was calibrated with standard chemical solutions containing Cr, Fe, Cu, Zn, and Pb, and Y was used as an internal standard to correct eventual geometric errors and high-voltage instabilities of the X-ray generator. The limits of detection were 19, 9, 5, and 4 ng/mL for Cr, Fe, Cu, and Zn, respectively, analyzed through characteristicKk _α X-rays, and 7 ng/mL for Pb, throughLk _α X-rays, considering 50 ΜL samples deposited and dried on a quartz support, to be excited/ detected for 1000 s.     

Effect ofCalotropis latex on laticifers differentiation in callus cultures ofCalotropis procera

Laticifers differentiation in callus cultures of Calotropis procera (Asclepiadaceae) as affected by own latex and its fractions incorporated in Murashige and Skoog (MS) medium is described. Callus cultures have been maintained on MS medium with 2.3 ΜM 6-furfurylaminopurine (FAP) and 3.0 ΜM 1-naphthylacetic acid (NAA). Marked increase in laticifers differentiation (from 10.1 to 28.4 %) was observed on this medium supplemented with 1 % (v/v) of latex. Latex fractions containing proteins + complex polysaccharides or inorganic salts also increased laticifers differentiation (by 21.8 % and 24.1 %, respectively). Other fractions (free amino acid + saccharides, phenols and terpenes + sterols) had no marked effect on laticifers differentiation while alkaloid fraction inhibited it. Effect of latex on laticifers differentiation was much more profound than the reported optimal concentration of plant growth regulators (4.6 ΜM FAP + 1 ΜM IAA). This research was supported by grant-in-aid for research from the University Grants Commission (No. F3-65/91SR II), New Delhi, to Dr. KG. Ramawat.     

Evaluation of mutagenicity of the antitubercular naphthylglycine hydrazides insalmonella typhimurium

N-(2-naphthyl)glycine hydrazide and N-methyl-N-(2-naphthyl) glycine hydrazide, which inhibitMycobacterium tuberculosis H₃₇ R_V and show activity against experimental tuberculosis, were evaluated for their mutagenic potential inSalmonella typhimurium. Both the compounds at concentration ranges from 0.1 Μgplate to 1000 Μg/plate failed to induce mutations at the histidine locus either directly or after treatment with rat liver homogenate fraction-“S-9”. N-(2-naphthyl)glycine hydrazide and its N-methyl derivative elicited toxicity at concentrations of 500 Μg/plate and 1000 Μg/plate. However, in the presence of the liver homogenate system, reduction in toxicity was noticed probably due to detoxification and/ or conjugation of the compounds. Under the assay conditions employed, standard mutagens like 4-nitroquinoline-N-oxide, 9-aminoacridine and benzo(a)pyrene were positive. The non-mutagenic nature of N-(2-naphthyl)glycine hydrazide and N-methyl-N-(2-naphthyl)glycine hydrazide should enhance their potential for inclusion in treatment protocols for management of tuberculosis     

Spinal mechanisms of electric organ discharge synchronization in Gymnotus carapo

Summary The duration of the electric organ discharge (EOD) in Gymnotus carapo is brief and independent of fish size. Spinal mechanisms involved in electrocyte synchronization were explored by recording spontaneous action potentials of single fibers from the electromotor bulbospinal tract (EBST). Using the field potential of the medullary electromotor nucleus (MEN) as a temporal reference we calculated the orthodromic conduction velocity (CV) of these fibers (range: 10.7–91 m/s).The CVs (in m/s) of fibers recorded at the same level of the spinal cord were significantly different in small and large fish; this difference disappeared when CV were expressed as percentage of body length/ms. Plotting these values against conduction distance (also in %) showed that low CV fibers predominate in the rostral cord while only fast fibers are found at distal levels. Moreover, antidromic stimulation of the distal cord was only effective on high CV fibers. The orthodromic CVs in the distal portion of the recorded fibers were calculated by collision experiments; no significant differences were found between proximal and distal portions.The spatial distribution of CV values within the EBST is proposed to play the main role in synchronizing the electromotoneurons' activity along the spinal cord.Abbreviations EOD electric organ discharge - EO electric organ - EBST electromotor bulbospinal tract - MEN medullary electromotor nucleus - CV conduction velocity - EMN electromotoneuron     

An acid stable trypsin-chymotrypsin inhibitor from horse gram (Dolichos biflorus)

An inhibitor of trypsin and chymotrypsin was purified from horse gram (Dolichos biflorus) beans. The concentration of the inhibitor which provided total inhibition was 0.27 Μg/Μg tryptic enzyme and 0.46 Μg/Μg chymotryptic enzyme. The inhibitor was stable at 37‡C between pH of 3 to 11 and at 97‡C, upto pH 5.0 only. While the activities were rapidly lost in 0.1N NaO H the loss was only 5 0% in 0.1N HCl when kept for 2 h at 97‡C. On heating at pH 7.8, it remained stable upto 80‡C with a gradual loss in activities at 97‡C and a total loss occurring by autoclaving at 15 psi for 10 min. Reduction of disulphide bonds by 2-mercapto-ethanol, pronase digestion and boiling in the presence of 1 M NaCl led to reduction in the activities. However, the inhibitor was resistant to the action of pepsin and subtilisin and to urea at 37‡C.     

Diameters and conduction velocities of fibers in the cat auditory pathways

The diameters of nerve fibers in the brachium colliculi inferioris and geniculo-cortical tract were measured. The thickness of these fibers ranges from 0.5 to 6.0 µ, and in 82–88% of them it is 1.0–3.0 µ. About 100,000 nerve fibers were found in cross-sections through the brachium colliculi inferioris. The velocity of conduction along centripetal fibers of the geniculo-cortical tract was determined. It varied from 11 to 28.6 m/sec in different fibers, and in 71% of them it was between 15 and 22 m/sec. The composition of the fibers of the geniculo-cortical tract was compared relative to their thickness and conduction velocity.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 6, pp. 608–611, November–December, 1972.     

Character of activation of medullary reticulospinal neurons by collaterals of pyramidal fibers

The character of activation of medullary reticulospinal neurons by collaterals of pyramidal fibers was investigated in cats anesthetized with pentobarbital (40 mg/kg) or a mixture of chloralose (45 mg/kg) and pentobarbital (15 mg/kg). The experiments were carried out on animals after preliminary destruction of the contralateral red nucleus and division of the ipsilateral dorsolateral fasciculus in segment C₄. A conditioning technique showed that pre- and postsynaptic effects arising in the medullary gigantocellular nucleus to stimulation of the cortex and of the isolated dorsolateral funiculus are due to activation of collaterals of pyramidal fibers projecting into the brain stem. In most reticulospinal neurons tested, stimulation of the fasciculus induced monosynaptic EPSPs. Their generation was due to influences transmitted via fast- and slow-conducting pyramidal fibers. Pyramidal fibers with different conduction velocities are distributed irregularly in the pyramidal tract in the cervical region of the spinal cord. Mainly slowly-conducting fibers are found in its medial zones and fast-conducting pyramidal fibers in its lateral zones. The results are evidence that in cats fibers of the pyramidal tract, running into the spinal cord, can activate medullary reticulospinal neurons directly.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 495–503, September–October, 1977.     

Effect of plant growth regulators and basal media onin vitro shoot proliferation and rooting ofMyrtus communis L.

The influence of macronutrients and growth regulators on in vitro shoot proliferation and rooting of an East Spanish population ofMyrtus communis L. were studied. Preincubation of field material on a medium without mineral salts prevented the browning from phenolic exudates. For multiplication, nodal segments of 5 mm fromin vitro produced shoots were cultured on Murashige and Skoog (MS), Schenk and Hildebrandt (SH) and Heller (H) media (full strength or diluted to 1/2 or 1/4), with 6-benzylaminopurine (BAP) at concentrations 4.4, 13.3 and 22.2 ΜM or kinetin (K) at concentrations 4.7, 14.0 and 23.2 ΜM. The optimum shoot proliferation was on quarter-strength MS medium with 4.4 ΜM BAP, whereas the maximum number of nodal segments was produced on half-strength MS medium with 4.4 ΜM BAP. Rooting of shoots was obtained by adding 2.5 – 24.6 ΜM indole-3-butyric acid (IBA) and broad range of macronutrients; Lloyd and McCown (WPM) and Gresshoff and Doy (GD) media both full strength or diluted to 1/2 were optimum. No rooting was obtained in the presence of α-naphthaleneacetic acid (NAA). Acknowledgements: This study was supported by a grant from Conselleria de Cultura, Educació i Ciència de Ia Generalitat Valenciana. The authors are grateful to Man Cannen Perea for her helpful comments.     

Mother plant age and seasonal influence on in vitro propagation of <Emphasis Type="Italic">Quercus euboica</Emphasis> Pap., an endemic,rare and endangered oak species of Greece

A micropropagation method for Quercus euboica Pap. was developed. Nodal explants from seedlings gave higher multiplication rates than explants from adult plants. Cultures initiated at the beginning of May produced the highest percentage of shoot forming explants and multiplication rate. Woody Plant Medium (WPM) salts, with 100 mg l⁻¹ myoinositol, 1 mg l⁻¹ thiamine, 0.5 mg l⁻¹ pyridoxine, 0.5 mg l⁻¹ nicotinic acid and 3% sucrose was used as basal medium and several cytokinins at various concentrations were evaluated for their effect on shoot multiplication. The highest shoot multiplication rate was obtained with 4.44 μΜ BA. IBA at 9.84 μΜ in the culture medium during the first week of culture, and if followed by culture in hormone-free medium, gave the best rooting results. Darkness at the beginning of the rooting period did not improve rooting. The use of plastic wrap as a cover material of the culture vessels enhanced rooting percentage and root number. Plantlets acclimatized ex vitro in soil from the natural environment of the species survived at a higher percentage (up to 93%) and had more vigorous growth than plantlets grown in a compost–perlite (2:1 v/v) medium (up to 36%).     

Pigmented Nanoflagellates Grazing on <Emphasis Type="Italic">Synechococcus</Emphasis>: Seasonal Variations and Effect of Flagellate Size in the Coastal Ecosystem of Subtropical Western Pacific

We investigated seasonal variation of grazing impact of the pigmented nanoflagellates (PNF) with different sizes upon Synechococcus in the subtropical western Pacific coastal waters using grazing experiments with fluorescently labeled Synechococcus (FLS). For total PNF, conspicuous seasonal variations of ingestion rates on Synechococcus were found, and a functional response was observed. To further investigate the impact of different size groups, we separated the PNF into four categories (<3, 3–5, 5–10, and >10 μm). Our results indicated that the smallest PNF (<3 μm PNF) did not ingest FLS and was considered autotrophic. PNF of 3–5 μm in size made up most of the PNF community; however, their ingestion on Synechococcus was too low (0.1–1.9 Syn PNF⁻¹ h⁻¹) to support their growth, and they had to depend on other prey or photosynthesis to survive. The ingestion rate of the 3–5 μm group exhibited no significant seasonal variation; by contrast, the ingestion rates of 5–10 and >10 μm PNFs showed significant seasonal variation. During the warm season, 3–5 μm PNF were responsible for the grazing of 12% of Synechococcus production, 5–10 μm PNF for 48%, and >10 μm PNF for 2%. Taken together, our results demonstrate that the PNF of 3–10 μm consumed most Synechococcus during the warm season and exhibited a significant functional response to the increase in prey concentration.     

Residual stress in the adult mouse brain

This work provides direct evidence that sustained tensile stress exists in white matter of the mature mouse brain. This finding has important implications for the mechanisms of brain development, as tension in neural axons has been hypothesized to drive cortical folding in the human brain. In addition, knowledge of residual stress is required to fully understand the mechanisms behind traumatic brain injury and changes in mechanical properties due to aging and disease. To estimate residual stress in the brain, we performed serial dissection experiments on 500-mum thick coronal slices from fresh adult mouse brains and developed finite element models for these experiments. Radial cuts were made either into cortical gray matter, or through the cortex and the underlying white matter tract composed of parallel neural axons. Cuts into cortical gray matter did not open, but cuts through both layers consistently opened at the point where the cut crossed the white matter. We infer that the cerebral white matter is under considerable tension in the circumferential direction in the coronal cerebral plane, parallel to most of the neural fibers, while the cerebral cortical gray matter is in compression. The models show that the observed deformation after cutting can be caused by more growth in the gray matter than in the white matter, with the estimated tensile stress in the white matter being on the order of 100–1,000 Pa.     

Uridine 5′-diphosphate glucose 4-epimerase from ehrlich ascites carcinoma cells

Uridine 5′-diphosphate glucose 4-epimerase (EC 5.1.3.2) from Ehrlich ascites carcinoma cells was purified to apparent homogeneity using conventional procedures and NAD-hexane-agarose affinity chromatography. The protein had a molecular weight of 96,000. The ascites enzyme had an absolute requirement for exogenously added NAD (10 ΜM) for stability. This appears to be a unique feature of ascites epimerase since epimerase from other mammalian sources did not exhibit such a dependence. Exogenously added NAD was also needed for catalysis with an apparentK _m value of 2.5 ΜM. NADH was a very potent competitive inhibitor (K _i = 0.11 ΜM with respect to NAD) of the enzyme activity at pH values close to intracellular pH. The dependence of the enzyme on NAD for stability and its inhibition by NADH may have some potential significance in tumor metabolism