Gustatory sensitivity of the herbivore Tilapia zillii to amino acids

The gustatory sensitivity of the herbivorous fish Tilapia zillii was investigated using electrophysiological techniques. Integrated responses from facial taste nerves were recorded during stimulation by l l amino acids. All compounds proved to be effective stimuli. The relative stimulatory efficacy (RSE) determined at 1 × 10 ⁻³ m indicated that stimuli can be organized into three groups on the basis of similarity of efficacy. Effects of pH which altered the RSE of some amino acids are documented. Amino acid RSE differed to some extent from those of previously studied carnivorous fish. There was concordance between the composition of preferred food, effective feeding stimuli and the peripheral receptor responses. These observations support the hypothesis that peripheral chemosensitivity might serve as a mechanism of feeding specialization in some fish.     

A short history of nuclear activation analysis

The major developments in the field of nuclear activation analysis, from 1936 to 1989, are discussed. The developments are grouped into five consecutive time periods. The impact of various scientists on the development of the field in the first 35 years is also discussed.     

Cytogenetic characterization of 20 lymphoblastoid lines derived from human individuals differing in bleomycin sensitivity

Summary Forty lymphoblastoid (lymphoid) lines were established from 42 volunteer blood donors, including healthy individuals and patients with head and neck carcinomas. Each peripheral blood sample was split into two portions, one for the establishment of a lymphoid line and the other for short-term culture, which was used to estimate bleomycin sensitivity by cytogenetic procedures. Twenty lymphoid lines were selected at random to compare bleomycin sensitivity with data obtained from short-term lymphocyte cultures. In each set, bleomycin sensitivity of lymphoid cells was similar to that of the lymphocytes. The lymphoid lines, which can be propagated for an unlimited supply of relatively homogeneous cellular material, will be useful for a variety of future investigations. This investigation was supported by grants from the John S. Dunn Foundation, Houston, TX, the Esther Knispel Fund administered by The University of Texas M. D. Anderson Cancer Center, Houston, TX, and Department of Health and Human Services PHS grant DE 07007.     

植物冷锻炼对于胁强敏感度的影响(英文)

前文由柑桔枝条在不同低温下、不同冷冻时间的电解质外渗测定,提出胁强(stress)、作用时间与胁变(strain)之间关系的数学模型。在这个模型中共有3个参数:屈服点温度(yield point temperature),胁强敏感度(stress sensitivity)和作用时间敏感度(sensitivity to duration),用以描述植物的抗性。抗性强的植物应表现为屈服点温度较低,胁强敏感度或者时间敏感度较低。为验证此数学模型,本工作以经冷锻炼与未经冷锻炼的盆栽柑桔枝条为材料,作不同温度与时间处理的电解质外渗率的测定,研究了冷锻炼对于上述3个参数的影响。发现胁强敏感度和屈服点温度受冷锻炼影响而下降,时间敏感度未表现明显变化。对于田间柑桔、油桐与毛竹的定期测定,在固定冷冻时间下,得到了类似于盆栽柑桔的结果。入冬时,植物抗冻性提高,3种植物都表现出下列两种变化:1.胁强敏感度的明显下降;2.屈服点温度和/或时间敏感度亦下降。开春时的变化则相反。胁强敏感度的变化与后一种变化有各自的规律,且因植物种类而不同。拐点胁强(stress at inflection point)具有与半致死温度(50％killing point temperature)不同的意义,它的变化是上述两种变化的综合结果。本试验结果表明,冷锻炼对于植物胁强敏感度有明显影响,用本数学模型的3个抗性指标描述     

Ultraviolet-sensitive ooplasmic factors are responsible for the development of an endoderm-specific alkaline phosphatase in the ascidian embryo

The ascidian egg contains muscle and endoderm determinants that play critical roles in the specification of muscle and endoderm cells, respectively. Endoderm cells of the ascidian embryo express alkaline phosphatase (AP) as a tissue-specific enzyme. We obtained egg fragments from the unfertilized eggs of Ciona savignyi by means of centrifugal force. The largest fragment (red fragments) contained the egg nucleus while other small fragments (black, clear and brown fragments) were anucleate. When inseminated, only red fragments developed into partial embryos, which showed only epidermis cell differentiation and, very rarely, AP activity. When red fragments were fused with other fragments, only black fragments promoted AP expression, suggesting that endoderm determinants were concentrated in the black fragments. A lower dose (1500 J/m²) of ultraviolet (UV) light did not eliminate the AP-promoting ability of black fragments, while this dose significantly repressed the ability to promote the expression of the muscle-marker. A higher dose (4500 J/m²) of UV light markedly reduced the AP-promoting activity of black fragments. These results suggest that factors for endodermal AP development are inactivated by UV irradiation, but are more resistant than muscle determinants.     

K252a Modulates the Expression of Nerve Growth Factor-Dependent Capsaicin Sensitivity and Substance P Levels in Cultured Adult Rat Dorsal Root Ganglion Neurones

Abstract: K252a, an inhibitor of trk phosphorylation and nerve growth factor signal transduction in PC12 cells, blocked nerve growth factor-induced responses in cultured adult rat dorsal root ganglion sensory neurones. The nerve growth factor-dependent appearance of capsaicin sensitivity and accumulation of the neuropeptide substance P were inhibited when dorsal root ganglion neurones were grown in the presence of low concentrations (100 n M ) of K252a. At higher concentrations (3 µ M ), however, K252a stimulated the development of capsaicin sensitivity and the accumulation of substance P even in the absence of nerve growth factor. By using a wide dose range, therefore, we showed that K252a could either inhibit or mimic nerve growth factor's actions on sensory neurones. These results may explain the apparent paradox in the literature that some groups show a blocking effect of K252a on nerve growth factor-dependent survival of dorsal root ganglion sensory neurones, whereas others report that K252a can substitute for nerve growth factor or other trophic factors and promote neuronal survival.     

Spectral sensitivity of photoreceptors mediating phase-shifts of circadian rhythms in retinally degenerate CBA/J (rd/rd) and normal CBA/N (+/+) mice

Light-dark cycles are the most important time cue for the circadian system to entrain the endogenous circadian clock to the environmental 24 h cycle. Although photic entrainment of circadian rhythms is mediated by the eye in mammals, photoreceptors implicated in circadian photoreception remain unknown. In our previous study, retinally degenerate CBA/J (rd/rd) mice were found to have lower circadian photo-sensitivity for phase-shifting the locomotor activity rhythms than normal CBA/N(+/+) mice. In the present study, the spectral sensitivity for phase-shifting the rhythms was examined in order to characterize the photopigments involved in circadian photoreception of these mice. The spectral sensitivity of CBA/J-rd/rd mice clearly fitted to the Dartnall nomogram for a retinal₁-based pigment with a maximum at 480 nm, while the best fitted nomogram had a maximum at 500 nm in CBA/N- +/+ mice. These results suggest that circadian photopigments involved in CBA/J-rd/rd and CBA/N- +/+ mice may be different.     

神经敏感性的降低是棉铃虫对拟除虫菊酯抗药性的重要机制

用扫描电子显微镜和光学显微镜的染色观察,研究了棉铃虫Helicoverpa armigeraHubner 3龄幼虫腹部神经一肌肉的分布,表明其腹纵肌细胞适合于作电生理细胞内记录。用电生理细胞内微电极记录法研究了棉铃虫三个品系：对照品系、功夫菊酯抗性品系(Cy-R,抗性指数13.4)和氰戊菊酯抗性品系(Fn-R,抗性指数37.9)的3龄幼虫神经一肌肉材料对相应杀虫剂的神经敏感性。结果表明：用10^-6mol/L的功夫菊酯处理Cy-R,在30min内有40%的个体对药剂无反应,另外60%的个体产生反应所需的时间是对照品系的3.5倍。用10^-6mol/L的氰戊菊酯处理Fn-R,在30min内有47%的个体对药剂无反应,另外53%的个体产生反应所需的时间是对照品系的4.2倍。这些结果说明神经敏感性降低是棉铃虫对拟除虫菊酯抗药性的重要机制。     

黄皮种子发育过程中脱水敏感性与细胞膜透性的关系

黄皮（Ｃｌａｕｓｅｎａ ｌａｎｓｉｕｍ （Ｌｏｕｒ．） Ｓｋｅｅｌｓ）胚轴与完整种子的发育模式以及发育中电解质渗漏率变化有些不同． 种子生理成熟前、后的胚轴对脱水的反应也不同,前者经轻微脱水可提高萌发率和活力指数,后者不耐任何程度的脱水．活力指数的急剧下降伴随着电解质渗漏率的迅速上升．实验表明,黄皮种子在发育过程中没有形成耐脱水性． 细胞膜透性变化可反映脱水对种子的伤害程度