THE LOCOMOTION OF LIMAX : I. TEMPERATURE COEFFICIENT OF PEDAL ACTIVITY.

Pedal progression of the slug Limax maximus was studied to obtain relations between wave velocity on the sole of the foot, wave frequency, the advance due to a single wave, and the velocity of vertically upward creeping. Each of the first three quantities is directly proportional to the simultaneous velocity of progression. Under comparable conditions, that is when work is done at a constant rate, the frequency of pedal waves is influenced by the temperature according to the equation of Arrhenius, with µ = 10,700 (Q ₁₀ for 11° to 21° = 2.1). The velocity of a single wave must have very nearly the same "temperature characteristic," which is found also in another case of nerve net transmission (in Renilla).     

THEORY AND MEASUREMENT OF VISUAL MECHANISMS : VIII. THE FORM OF THE FLICKER CONTOUR

Flicker response curves (man) obtained with images formed entirely within the fovea are like those secured with lower animals having only one general class of retinal receptors. They are normal probability integrals (F vs. log I_m), and the properties of their parameters agree with those for visually simplex animals and for the "cone" portions of contours exhibiting visual duplexity. By several different procedures, involving experimental modifications of the "cone" curve, the "rod" part of the typical human duplex curve can be obtained free from overlapping by the extrapolated "cone" curve. It then has the probability integral form which the lower segment does not directly exhibit when combined with "cone" effects. These results are discussed with reference to the statistical nature of the fundamental form of the flicker contour and to the interpretation of duplex curves produced by the neural integration of two independently modifiable groups of sensory effects.     

Axial Diffusivity of the Corona Radiata at 24 Hours Post-Stroke: A New Biomarker for Motor and Global Outcome

Fractional anisotropy (FA) is an effective marker of motor outcome at the chronic stage of stroke yet proves to be less efficient at early time points. This study aims to determine which diffusion metric in which location is the best marker of long-term stroke outcome after thrombolysis with diffusion tensor imaging (DTI) at 24 hours post-stroke. Twenty-eight thrombolyzed patients underwent DTI at 24 hours post-stroke onset. Ipsilesional and contralesional FA, mean (MD), axial (AD), and radial (RD) diffusivities values were calculated in different Regions-of-Interest (ROIs): (1) the white matter underlying the precentral gyrus (M1), (2) the corona radiata (CoRad), (3) the posterior limb of the internal capsule (PLIC) and (4) the cerebral peduncles (CP). NIHSS scores were acquired at admission, day 1, and day 7; modified Rankin Scores (mRS) at 3 months. Significant decreases were found in FA, MD, and AD of the ipsilesional CoRad and M1. MD and AD were also significantly lower in the PLIC. The ratio of ipsi and contralesional AD of the CoRad (CoRad-rAD) was the strongest diffusion parameter correlated with motor NIHSS scores on day 7 and with the mRS at 3 months. A Receiver-Operator Curve analysis yielded a model for the CoRad-rAD to predict good outcome based on upper limb NIHSS motor scores and mRS with high specificity and sensitivity. FA values were not correlated with clinical outcome. In conclusion, axial diffusivity of the CoRad from clinical DTI at 24 hours post-stroke is the most appropriate diffusion metric for quantifying stroke damage to predict outcome, suggesting the importance of early axonal damage.     

Onchocerciasis in British cattle: a study of Onchocerca gutturosa and O. lienalis in North Wales

Onchocerca gutturosa and O. lienalis infections in British cattle were studied by examination of cattle post-mortem originating from North Wales and Cheshire (north west England). In 463 adult animals, the microfilarial (mf) prevalence was 28.5%. In 95.3% of the mf infected animals, gravid worms could not be found at either the ligamentum nuchae or the gastro-splenic omentum. Dermal mf at the head were identified as O. gutturosa on the basis of their highly significant association with the presence of gravid O. gutturosa at the ligamentum nuchae, which were found in only 3.2% of cattle. Mfs were isolated from different skin sites and from adult worms and a minimum of 10 mfs from each isolate were examined for width and acid phosphatase (AP) staining pattern. The width of O. gutturosa dermal mf was less than 4 micron (4 isolations), narrower than that of putative O. lienalis mf isolated from umbilical skin of cattle without evidence of O. gutturosa, which were in 20/22 isolations greater than 4 micron wide. The dermal mf were also distinguished on the basis of different AP staining patterns which, for each species, correlated closely with that of hatched intrauterine mf from their respective adult female worms. Based on the criteria of morphology and AP staining patterns the mf species prevalences in the survey population were estimated as O. lienalis 24.1% and O. gutturosa 2.2%, with a further 2.2% of cattle infected with both species. The results indicate that the predilection site of adult O. lienalis is not the gastro-splenic omentum. In North Wales, the distribution of the two species was different; O. lienalis was widely distributed in all cattle rearing areas both lowland and upland, whereas O. gutturosa was largely restricted to valleys close to major rivers.     

Production of gibberellins and indole-3-acetic acid by Rhizobium phaseoli in relation to nodulation of Phaseolus vulgaris roots

Similar ranges of gibberellins (GAs) were detected by high-performance liquid chromatography (HPLC)-immunoassay procedures in ten cultures of wild-type and mutant strains of Rhizobium phaseoli. The major GAs excreted into the culture medium were GA₁ and GA₄. These identifications were confirmed by combined gas chromatographymass spectrometry. The HPLC-immunoassays also detected smaller amounts of GA₉- as well as GA₂₀-like compounds, the latter being present in some but not all cultures. In addition to GAs, all strains excreted indole-3-acetic acid (IAA) but there was no obvious relationship between the amounts of GA and IAA that accumulated. The Rhizobium strains studied included nod ^– and fix ^– mutants, making it unlikely that the IAA- and GA-biosynthesis genes are closely linked to the genes for nodulation and nitrogen fixation.The HPLC-immunoassay analyses showed also that nodules and non-nodulated roots of Phaseolus vulgaris L. contained similar spectra of GAs to R. phaseoli culture media. The GA pools in roots and nodules were of similar size, indicating that Rhizobium does not make a major contribution to the GA content of the infected tissue.Abbreviations EIA enzyme immunoassay - GA_n gibberellin A_n - GC-MS gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - IAA indole-3-acetic acid - Me methyl ester - RIA radioimmunoassay - TLC thin-layer chromatography     

The biosynthesis and conjugation of indole-3-acetic acid in germinating seed and seedlings ofDalbergia dolichopetala

Germinating seed ofDalbergia dolichopetala converted both [²H₅]l-tryptophan and [²H₅]indole-3-ethanol to [²H₅]indole-3-acetic acid (IAA). Metabolism of [2-¹⁴C]IAA resulted in the production of indole-3-acetylaspartic acid (IAAsp), as well as several unidentified components, referred to as metabolites I, II, IV and V. Re-application of [¹⁴C]IAAsp to the germinating seed led to the accumulation of the polar, water-soluble compound, metabolite V, as the major metabolite, together with a small amount of IAA. Metabolites I, II and IV were not detected, nor were these compounds associated with the metabolism of [2-¹⁴C]IAA by shoots and excised cotyledons and roots from 26-d-oldD. dolichopetala seedlings. Both shoots and cotyledons converted IAA to IAAsp and metabolite V, while IAAsp was the only metabolite detected in extracts from excised roots. The available evidence indicates that inDalbergia, and other species, IAAsp may not act as a storage product that can be hydrolysed to provide the plant with a ready supply of IAA.Abbreviations HPLC-RC high-performance liquid chromatography-radiocounting - IAA indole-3-acetic acid - IAAsp indole-3-acetylaspartic acid - IAlnos 2-O-indole-3-acetyl-myo-inositol - IEt indole-3-ethanol     

Opiate modulation of the stress-induced increase of vasoactive intestinal peptide (VIP) in plasma

Vasoactive intestinal peptide (VIP) has a variety of extra-intestinal actions which are typical of the body's reaction to stress, such as lipolysis, glycogenolysis and modulation of anterior pituitary hormone secretion. Serial VIP plasma concentrations in patients undergoing major laparotomies were determined. The influence of the mu-receptor agonist, fentanyl, on intra-operative changes was investigated and compared to a control group receiving halothane anesthesia. Plasma levels of typical "stress hormones" cortisol and catecholamines were also monitored for additional information on the extent of perioperative stress. VIP levels increased intraoperatively in the halothane group from 5.9 +/- 4.6 to 15.3 +/- 5.3 pmol/l. Cortisol and catecholamine levels showed a similar increase. The intraoperative VIP increase in the fentanyl group was significantly smaller: 3.5 +/- 1.9 to 7.3 +/- 3.6 pmol/l. Anesthesia itself did not affect VIP concentrations as shown by constant levels during a 30 minute preoperative control period. The observed increases of VIP plasma concentration are thought to reflect a possible role for VIP in the hormonal metabolic response to stress. The attenuation of the increase by fentanyl might be due to a direct opiate action on VIP release.     

Correlations of understory herb distribution patterns with microhabitats under different tree species in a mixed mesophytic forest

Summary This study examines the role of canopy trees in the formation and maintenance of different herb microhabitats in a mixed mesophytic forest stand. Herb abundance and reproductive success were recorded in 54 circular plots under seven species of canopy trees and in 15 circular control plots>2 m from any tree. Soil moisture, soil nutrient levels, litter depth, and light intensity were measured in a subset of these plots. Ordination of plots by both herb relative abundance and by reproductive success of common species indicated that herb assemblages under most canopy tree species were similar to those away from trees. However, herb assemblages under Fagus grandifolia trees differed moderately from the others while plots under Quercus alba trees supported significantly different herb assemblages. Analyses of variance revealed that several herb species occurred at significantly closer mean distance to the base of Q. alba or Fagus trees or at higher densities under these tree species. Soils around Q. alba trees had significantly higher concentrations of calcium and sulfate ions, and higher pH than plots under other tree species and control plots. This correlated closely with Q. alba stemflow which had higher concentrations of calcium and sulfate ions and lower concentrations of hydrogen ions than stemflow from other trees at this site. The slightly lower soil pH near the base of Fagus trees may have been related to the high volumes of stemflow produced by this species. Stepwise regression showed significant correlations between abundances of five common herb species and soil nutrient patterns. Maintenance of spatial heterogeneity in forest floor resources by the presence of different species of canopy trees may therefore be important in the maintenance of diversity in these understory herb communities.     

Characterization of gibberellins from dark-grown Phaseolus coccineus seedlings by gas-liquid chromatography and combined gas chromatography-mass spectrometry

Summary An extract from 6000 dark-grown Phaseolus coccineus seedlings was purified by countercurrent distribution and G-10 Sephadex followed by gradient elution from a silicic acid partition column with increasing amounts of ethyl actetate in n-hexane. 25 fractions were collected and tested with the barley-aleurone, Tan-ginbozu dwarf-rice, lettuce, cucumber, dwarf-pea, d-1, d-2, d-3 and d-5 maize, oat first-internode, and sugarcane-spindle bioassays. Major gibberellin (GA)-like activity was detected in fractions 4 (500g GA₃-equivalents) and 12–13 (270 g GA₃-equivalents) with smaller amounts in fractions 6, 8–9, 15–16, 18, 20, 23 and 25. The extracts were also applied to AMO-1618=dwarfed Ph.-coccineus seedlings. Fractions 4, 8 and 12 promoted the growth of both light- and dark-grown seedlings. GA₁, GA₃, GA₄ and GA₈ were active in the Phaseolus bioassay but GA₈-glucoside was inactive.The biological and chromatographic properties of fractions 4, 8–9 and 12–13 correspond with those of GA₄, GA₁₉ and GA₁. The identity of GA₄ in fraction 4 was conclusively established by combined gas chromatography-mass spectrometry (GC-MS) of the methyl ester and the trimethylsilyl ether of the methyl ester. Gasliquid-chromatography peaks corresponding to these derivatives of GA₁₉ and GA₁ were detected on QF-1 and SE-33 columns but their intensities were too weak to permit conclusive identification by GC-MS.Supported by an S.R.C. StudentshipSupported by a NATO Grant.Supported by NRC Grant A-5727.