Molecular mechanisms underlying sensorimotor cortex pyramidal neuron involvement in the feeding behavior of rabbits

Response in pyramidal neurons belonging to the sensorimotor cortex (37% of total nerve cells investigated in this zone) which were identified by stimulating the bulbar pyramids, were investigated during experiments on unrestrained rabbits. Pyramidal neurons having connections with the lateral hypothalamus were activated during operation of feeding behavior, while activity was inhibited in those unconnected with the lateral hypothalamus. Microiontophoretic application of a protein synthesis inhibitor to pyramidal neurons caused their ability to respond to ascending activating influences from the lateral hypothalamus to disappear. When pentagastrin was applied to these neurons following the protein synthesis blocker, they recovered their ability to participate in hypothalamic feeding reaction. It is suggested that synthesis and release of a gastrin-like peptide into the perineuronal space is required for sensorimotor cortex pyramidal neurons to participate in the organization of feeding behavior.P. K. Anokhin Institute of Normal Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 19, No. 5, 601–606, September–October, 1987.     

Monosynaptic pathway responsible for generation of bursting activity in theHelix pomatia RPal neuron

The connection between a visceral ganglia interneuron initiating bursting pacemaker activity in the RPal neuron and the RPal neuron itself was investigated inHelix pomatia. Stimulating the interneuron either initiated or intensified bursting activity in the RPal neuron, depending on initial electrical activity in this cell. Replacing calcium with magnesium ions in the extracellular fluid and adding CdCl₂ to this fluid reversibly inhibited the effect of interneuronal stimulation on the RPal neuron. The latter effect was unaffected by increasing the concentration of extracellular Ca²⁺ 10 to 70 mM. Intracellular injection of both Cs⁺ and TEA into the interneuron produced an increase in the duration of its action potentials and rendered the link connecting the neurons more effective. It is deduced that a monosynaptic chemical connection exists between the interneuron and the RPal neuron for which a peptide compound serves as transmitter.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 20–28, January–February, 1987.     

L-glutamate activated membrane conductivity in spinal cord neurons during early chick embryogenesis

Transient and steady-state components of L-glutamate-activated membrane currents were investigated using intracellular perfusion, voltage clamp, and concentration clamp techniques in spinal cord neurons of 6–11 day chick embryos. Hill's coefficient was found to equal 1 for transient and 2 for steady-state components. It was shown that the L-glutamate-activated receptors are present, which appear in the membrane of spinal neurons at the early stages of development.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 2, pp. 251–258, March–April, 1987.     

Critical considerations in the development of an assay for sulfidopeptide leukotrienes in plasma

A sensitive and specific assay has been developed for measurement of total sulfidopeptide leukotrienes (LT) in plasma. LTC4 and LTD4 in plasma are converted to LTE4 which is then extracted by C18 Sep-Pak binding and elution. Total LTE4 is resolved by reverse phase high performance liquid chromatography (RP-HPLC) and quantitated by radioimmunoassay (RIA). A [3H]LTE4 internal standard is added to the starting plasma sample to allow overall recovery to be calculated and to define the fractions from RP-HPLC to be assayed for LTE4-like immunoreactivity. The correlation between the measured increase in LTE4 concentration after addition of incremental amounts of LTC4 and LTE4 to plasma was 0.989 and 0.978, respectively, with slopes of 1.05 and 1.11. Addition of 51 pg/ml LTE4 to 5 ml plasma was detectable; the measured increase was 48 +/- 12 pg/ml (mean +/- SE, n = 7). The intra-assay coefficient of variation for 341 pg/ml of added LTC4 was 3.2% (n = 6). Sulfidopeptide leukotrienes could not be detected in blood samples taken from 12 normal volunteers in whom the theoretical detection limit, calculated from the sensitivity of the RIA, the overall recovery of LTE4, and the volume of plasma extracted, was 83 +/- 4 pg LTE4/ml plasma (0.19 +/- 0.01 pmol sulfidopeptide leukotriene/ml plasma; mean +/- SE).     

Short-term movements of chalk-stream invertebrates

SUMMARY 1. Trays of gravel were implanted for 24 h periods in several chalk streams. The trays were variously modified to monitor colonization from different sources, particularly drift (D), other downstream movements (DSM), upstream movements (USM), and all sources combined (ALL).
2. The abundance of invertebrates in the streams was high (maximum of 717 per 0.04 m²) and colonization of the trays was extensive, especially by Gammarus pulex , the predominant species in all but one of the streams (maximum number of individuals of G. pulex per tray: for D, 473; for DSM, 462; tor USM, 286; and tor ALL, 639). In some cases benthic densities were achieved in the trays in the 24 h exposure period, and in most cases any one source of colonization could provide benthic densities in a few days.
3. Patterns of movement differed between species, between size classes of G. pulex , and between sites for particular species. No one source of colonization could be regarded as generally predominant although downstream movements in total (D + DSM) usually far exceeded USM. DSM was usually an important source of colonization.
4. The extent and direction of movement appeared to be determined by local factors and were explained in terms of the high densities of invertebrates and the current and substratum characteristics of each site.
5. Estimates of the relative importance of different sources of colonization varied greatly according to the criteria used in determining proportions.     

Tension responses to increased hydrostatic pressure in glycerinated rabbit psoas muscle fibres

A method developed to study the effect of increased hydrostatic pressure on the isometric tension of a single muscle fibre is described and experiments done at room temperature (18-22 degrees C) on glycerinated rabbit psoas muscle fibres are presented. Increase of pressure (range 1-10 MPa) caused little change in tension transducer response when a muscle fibre was relaxed. However, there was a reversible depression of isometric tension with an increase of pressure when a fibre was maximally calcium-activated or in rigor; the depression was around 15% for active tension and 30% for rigor tension, for an increase of pressure of 10 MPa (ca. 100 atm).     

Attachment as a factor in the protection of Enterobacter cloacae from chlorination

Enterobacter cloacae attached to drinking water distribution particles was subjected to chlorination. Attachment resulted in the protection of these organisms from disinfection. This effect was found to be dependent upon both the level of chlorine in the system and attachment time. The results obtained in this study indicate that attached organisms may play an important role in coliform outbreaks.     

Preparation of scirpentriol and triacetoxyscirpenol in good yield from cultures of Fusarium sambucinum NRRL 13495

Crude extracts of filtrates of cultures of Fusarium sambucinum NRRL 13495 were acetylated or hydrolyzed. After chromatography on cartridge columns of silica gel and recrystallization three times from mixtures of ethyl acetate and hexane, 3,4,15-triacetoxyscirpenol (435 +/- 10 mg/liter of filtrate; mean +/- standard error [n = 3]) and the parent alcohol scirpentriol were isolated (261 +/- 29 mg/liter of filtrate; mean +/- standard error [n = 3]) in 68 and 53% yield for a 130- and 14-fold improvement, respectively, over prior reports.