Spatial summation of perceived pressure,sharpness and mechanically evoked cutaneous pain

Psychophysically, spatial summation can be demonstrated as a decrease in threshold accompanying an increased field of stimulation. The present study examined to what extent different mechanically evoked percepts (pressure, sharpness, and pain) show spatial summation. Various probes were used to apply prescribed forces to the dorsal surface of the digits of 19 healthy subjects. The threshold for three perceptual qualities showed differing degrees of spatial summation: sharpness showed no statistically significant spatial summation; pain demonstrated some significant summation (46% on average); pressure showed the greatest degree of spatial summation (76% on average). The lack of significant spatial summation for sharpness threshold is consistent with the theory that perceived sharpness can be evoked by near threshold activity of a single nociceptor. The modest amount of spatial summation for pain implies that distinctly suprathreshold activation of nociceptors is required for mechanically evoked pain perception, and such input summates centrally, but not completely. The greater spatial summation observed for pressure vs. pain thresholds implies a greater degree of central summation for slowly adapting mechanoreceptors vs. nociceptors.     

Nitrate reductases in hexaploid and tetraploid wheats and Aegilops

Summary Nitrate reductase activity (NR activity), protein content (NR protein) and polypeptides were compared in shoots of Triticum aestivum ssp. vulgare (L.) cv Fidel (bread wheat, AABBDD genome), Triticum dicoccum cv Vernal (AABB genome), Aegilops squarrosa var. strangulata (DD genome) and the amphiploid 365 (AABBDD genome), produced by crossing T. dicoccum cv Vernal and Ae. squarrosa var. strangulata. Constitutive NR protein and activity were found in shoots of all seedlings grown without nitrate, with the highest activity in the bread wheat. The inducible NR protein and activity developed upon the addition of nitrate. A 116-K polypeptide was identified as the main component of the NR from the bread wheat, while a faint, sometimes discernable 94-K band appeared on Western blots. Only one NR polypeptide could be identified in Ae. squarrosa —the 94 K. An intermediary situation was observed with the tetraploid T. dicoccum and the amphiploid: The 94-K polypeptide was the only one separated from NR of seedlings grown in the absence of nitrate. The 116-K polypeptide appeared after the addition of nitrate. The intensity of its band on the gel increased with the duration of the nitrate treatment. When comparing Ae. squarrosa and T. dicoccum, the constitutive isozyme (94-K polypeptide) was found in the D as well as in the AB genomes, while the inducible NR (116-K polypeptide) was absent from the D genome. Addition of the D genome into the AB genome slightly reinforced the expression of the inducible form (AB genome expression) in the amphiploid wheat. We postulate that the inducible form of NR in the bread wheat resulted from an evolutionary selection pressure favoured by cultivation.     

晋西北3个树种抗旱性指数的研究

根据对海红、刺槐和柠条的ＰＶ曲线主要水分参数的测定,进行了抗旱性指数季节变化和种间排序分析。结果表明,树种的抗旱性随着年生长发育节律和环境水分条件而改变,其抗早性生长季初最弱,夏季高温干早阶段增强,秋季降雨峰期减弱,生长季末最强或很强。柠条的抗旱性与海红很接近。这对黄土高原地区果树和饲料的开发与水土保持树种的推广有重要意义。     

Coordination of changes in expression and phosphorylation of eukaryotic elongation factor 2 (eEF2) and eEF2 kinase in hypertrophied cardiomyocytes

Eukaryotic elongation factor 2 (eEF2) kinase (eEF2K) is one of the Ca²⁺/calmodulin-dependent protein kinases. Activated eEF2K phosphorylates its specific substrate, eEF2, which results in inhibition of protein translation. We have recently shown that protein expression of eEF2K was specifically increased in hypertrophied left ventricles (LV) from spontaneously hypertensive rats (SHR). However, phosphorylation state of eEF2K and eEF2 in hypertrophied LV is not determined. In the present study, we examined expression and phosphorylation of eEF2K and eEF2 in LV from SHR as well as the pressure overload (transverse aortic constriction: TAC)- and isoproterenol (ISO)-induced cardiac hypertrophy model. In LV from TAC mice, eEF2K expression was increased as determined by Western blotting. In LV from TAC mice and SHR, eEF2K phosphorylation at Ser366 (inactive site) was decreased. Consistently, eEF2 phosphorylation at Thr56 was increased. In LV from ISO rats, while eEF2K phosphorylation was decreased, eEF2K expression and eEF2 phosphorylation were not different as determined by Western blotting. In the results obtained from immunohistochemistry, however, total eEF2K and phosphorylated eEF2 (at Thr56) localized to cardiomyocytes were increased in LV cardiomyocytes from ISO rats. Accordingly, the increased expression and the decreased phosphorylation of eEF2K and the increased phosphorylation of eEF2 in hypertrophied LV were common to all models in this study. The present results thus suggest that cardiac hypertrophy may be regulated at least partly via eEF2K-eEF2 signaling pathway.     

Natural selection on the plant-water relations of Cleome serrulata growing along natural moisture gradients

Summary I investigated the extent and adaptive importance of genetically-based variation in plant water relations in two populations of the annual plant Cleome serrulata found growing along relatively short (<30 m) and mild soil moisture gradients. Field measurements of predawn plant water potentials showed that plants at the dry end of the moisture gradients had consistently lower _Plant in May and June of 1984; differences up to 0.9 MPa were seen along the gradients. Seeds were collected from maternal plants growing along the moisture gradients and then grown under well-watered conditions in the greenhouse. Pressure-volume curves were constructed for a total of 92 seedlings from 25 maternal plants when the seedlings were four weeks old.Considerable genetic variation in the four highly correlated water potential components was seen in both populations, suggesting relatively high heritabilities (h²0.5). A partial correlation analysis revealed that cell wall elasticity was higher in seedlings from maternal plants which grew in the dry portions of each site. This suggested that natural selection had acted on this character during one or more previous generations. It appears that slight variations in the physiological genotype can significantly affect overall fitness in C. serulata.     

Reversal by pressure of seed germination promoted by anesthetics

Germination of Panicum capillare L. caryopses induced by solutions of ethanol and ethyl ether was prevented by application of pressure >1 MPa during the period of exposure to the anesthetic. This effect of pressure indicates that germination is correlated with expansion at a site of anesthetic action in a cell membrane. The effects of several other anesthetics were measured on germination of P. capillare seeds. Ethanol, chloroform, and ethyl ether had the highest activity. Methanol and isopropanol were inactive. The effective compounds are thought to distribute preferentially to lipid-solution interfaces in cell membranes of the seeds.     

The kinetics of the main phase transition of aqueous dispersions of phospholipids induced by pressure jump and monitored by raman spectroscopy

The sensitivity of the melting transition temperature of aqueous dispersions of dipalmitoyl- and distearoylphosphatidylcholine to hydrostatic pressure is used to allow measurement of the rates of isothermal freezing and melting of the lipids by rapidly changing the pressure. The degree of order of the lipids is measured by monitoring a ratio of two points in the Raman spectrum of the lipids which changes sharply at the melting temperature. Use of this Raman order ratio allows correlation between the order of the sample and the rates of transition in a manner which is impossible by monitoring only turbidity. Our longest relaxation times range upwards from a few seconds for both compounds. The freezing rates are slowest when the samples are initially fully melted, and the melting rates are slowest when the samples are initially frozen. These results imply that nucleation of the growing phase dominates the kinetics of both freezing and melting.     

The role of pressure difference reception in the directional hearing of budgerigars (Melopsittacus undulatus)

In many birds, the middle ears are connected through an air-filled interaural pathway. Sound transmission through this pathway may improve directional hearing. However, attempts to demonstrate such a mechanism have produced conflicting results. One reason is that some species of birds develop a lower static air pressure in the middle ears when anaesthetized, which reduces eardrum vibrations. In anaesthetized budgerigars with vented interaural air spaces and presumed normal eardrum vibrations, we find that sound propagating through the interaural pathway considerably improves cues to the directional hearing. The directional cues in the received sound combined with amplitude gain and time delay of sound propagating through the interaural pathway quantitatively account for the observed dependence of eardrum vibration on direction of sound incidence. Interaural sound propagation is responsible for most of the frontal gradient of eardrum vibration (i.e. when a sound source is moved from a small contralateral angle to the same ipsilateral angle). Our study confirms that at low frequencies the interaural sound propagation may cause vibrations of the eardrum to differ much in time, thus providing a possible cue for directional hearing. The acoustically effective size of the head of our birds (diameter 28 mm) is much larger than expected from the dimensions of the skull, so apparently the feathers on the head have a considerable acoustical effect.Dedicated to Professor Franz Huber on the occasion of his 80th birthday.     

Mice lacking the gene encoding for MMP-9 and resistance artery reactivity

OBJECTIVES: To define the link between the deletion of gene encoding for metalloproteinase 9 and resistance artery reactivity, we studied in vitro smooth muscle and endothelial cell function in response to pressure, shear stress, and pharmacological agents. BACKGROUND: Matrix metalloproteinases play a crucial role in the regulation of extracellular matrix turnover and structural artery wall remodeling. METHODS: Resistance arteries were isolated from mice lacking gene encoding for MMP-9 (KO) and their control (WT). Hemodynamic, pharmacology approaches, and Western blot analysis were used in this study. RESULTS: The measurement of blood pressure in vivo was similar in KO and WT mice. Pressure-induced myogenic tone, contractions to angiotensin-II and phenylephrine were similar in both groups. The inhibition of MMP2/9 ((2R)-2-[(4-biphenylylsulfonyl) amino]-3-phenylpropionic acid) significantly decreased myogenic tone in WT and had no effect in KO mice. Relaxation endothelium-dependent (flow-induced- dilation 41.3+/-0.6 vs. 21+/-1.6 at 10 microl/min in KO and WT mice, respectively, P<0.05) and eNOS expression were increased in KO compared to WT mice. The inhibition of eNOS with L-NAME significantly decreased endothelium response to shear stress, which was more pronounced in KO mice resistance arteries (-26.83+/-2.5 vs. -15.84+/-2.3 at 10 microl/min in KO and WT, respectively, P<0.05). However, the relaxation to exogenous nitric oxide-donor was similar in both groups. CONCLUSION: Our study provides evidence of a selective effect of MMP-9 on endothelium function. Thus, MMP-9 gene deletion specifically increased resistance artery dilation endothelium-dependent and eNOS expression. Based on our results, MMP-9 could be a potential therapeutic target in cardiovascular disease associated with resistance arteries dysfunction.     

Pressure-dependent <Superscript>13</Superscript>C chemical shifts in proteins: origins and applications

Pressure-dependent ¹³C chemical shifts have been measured for aliphatic carbons in barnase and Protein G. Up to 200 MPa (2 kbar), most shift changes are linear, demonstrating pressure-independent compressibilities. CH₃, CH₂ and CH carbon shifts change on average by +0.23, −0.09 and −0.18 ppm, respectively, due to a combination of bond shortening and changes in bond angles, the latter matching one explanation for the γ-gauche effect. In addition, there is a residue-specific component, arising from both local compression and conformational change. To assess the relative magnitudes of these effects, residue-specific shift changes for protein G were converted into structural restraints and used to calculate the change in structure with pressure, using a genetic algorithm to convert shift changes into dihedral angle restraints. The results demonstrate that residual ¹³Cα shifts are dominated by dihedral angle changes and can be used to calculate structural change, whereas ¹³Cβ shifts retain significant dependence on local compression, making them less useful as structural restraints.