Influence of 50 Hz electric and magnetic fields on the pulse rate of human heart

This investigation studied the effects of 50 Hz electric and magnetic fields on the pulse rate of the human heart. The ECG (electrocardiograms) of 41 male volunteers were recorded with a Holter recorder. Twenty-six subjects were measured in and outside real fields, and 15 subjects were measured in and outside “sham” fields. The blood pressure and EEG (electroencephalogram) were also measured, but this article presents only the results of ECG recordings. The measurements took 3 h. The subjects were first sitting for 1 h outside the fields, then 1 h in the real or “sham” fields, and then, again, 1 h outside the fields. The electric field strength varied from 3.5 to 4.3 kV/m and the magnetic flux density from 1.4 to 6.6 μT. An analysis of the ECG recordings showed that the subjects' pulse rates were the same in and outside the fields. No response occurred when the subjects were exposed to real or “sham” fields. © 1994 Wiley-Liss, Inc.     

Aphid activities during sieve element punctures

Aphid salivation in sieve elements and phloem sap ingestion were linked to waveforms in the Electrical Penetration Graph (EPG). Non-viruliferousRhopalosiphum padi (L.) (Hemiptera, Aphididae) on barley yellow dwarf virus (BYDV) infected wheat could acquire the virus, which was used as an indication for phloem sap ingestion, whereas virus inoculation by viruliferous aphids on healthy plants was associated with salivation in sieve elements or other phloem cells. Probing was monitored and the waveforms recorded were related to ELISA results of test plants. The EPG patterns A, B, and C are indicative of the stylet pathway phase, whereas patterns E1 and E2 reflect the phloem (sieve element) phase with an unknown activity (E1) or with ingestion and concurrent salivation (E2). Aphids showing pathway and E1 rarely acquired virus, suggesting that little or no phloem sap ingestion can occur during these patterns, whereas those showing additionally pattern E2 did so substantially, indicating phloem sap ingestion. The main pattern related to virus inoculation was E1, although some aphids were able to inoculate plants during pathway. Pattern E1 clearly reflects the most important salivation into sieve elements. Pattern E2 had no clear contribution to virus inoculation, supporting the present hypothesis that during this pattern the saliva is mixed with the phloem sap in the single canal at the stylet tips and ingested immediately, without reaching the plant tissue. Sustained sap ingestion did not affect virus inoculation. So, BYDV inoculation mainly occurs during the first period of a sieve element puncture which is always formed by E1. Implications on persistent virus transmission are discussed.     

Oscillations in the electrical resistance of Nitellopsis obtusa nodes

Oscillatory changes of the electrical resistance across the nodal complex of Nitellopsis obtusa (Desv. in Lois) J. Gr. were observed in experiments performed for 40–150 min with the use of external electrodes and microelectrodes. Three main patterns of node resistance oscillations were similar to those found for membrane potential and resistance. The presented findings indicate an oscillatory behaviour of the plasmodesmata system at the node, which may be connected with e.g. pulsatile variations in the number of open plasmodesmata.     

The early ontogeny of the southern mouthbrooder,Pseudocrenilabrus philander (Pisces,Cichlidae)

Synopsis The early development of the southern mouthbrooder,Pseudocrenilabrus philander, is documented from activation until the early stages of the juvenile period. The duration of the embryonic period is about 14 days at 25°C. Development is direct and there is accelerated exogenous feeding into the embryonic period. The pattern of development and the timing of ontogenetic events and structure formation are a reflection of both internal and external environmental conditions. During mouthbrooding, oxygen uptake is facilitated by embryonic respiratory plexuses and flapping of the pectoral fins. At the time of first release from the buccal cavity, the embryos are in an advanced state of development. The switch-over from the temporary embryonic respiratory system to the adult branchial system has occurred. The yolksac serves as a supplemental source of nutrition as the embryos develop their external food-gathering abilities. The skeletal and sensory systems are sufficiently developed to allow the young to return to the safety of the female's buccal cavity. Pigmentation may provide disruptive colouration. The rate and pattern of development of another mouthbrooding cichlid,Oreochromis mossambicus, is similar to that ofP. philander despite their phylogenetic differences, and may be a consequence of similar life-history styles.     

USE OF BIOELECTRICAL IMPEDANCE ANALYSIS TO ASSESS BODY COMPOSITION OF SEALS

Abstract: Bioelectrical impedance analysis (BIA) measures resistance and reactance of a current as it passes through an organism. The validity of using BIA as a tool to measure body water content, and hence body composition and condition, was tested on harp and ringed seals. The resistance and reactance readings from BIA were compared to estimates of total body water (TBW) determined via tritiated water dilution. The relationship between resistance and TBW (% of body mass) was linear after logarithmic transformation and the two variables were highly correlated. We describe the electrode configuration and placements which provide reliable results in these seals. Our findings indicate that BIA has considerable potential as an inexpensive, rapid, and reliable technique for estimating body composition of phocid seals.     

Aluminum enhancement of plant growth in acid rooting media. A case of reciprocal alleviation of toxicity by two toxic cations

The generally rhizotoxic ion Al³⁺ often enhances root growth at low concentrations. The hypothesis that Al³⁺ enhances growth by relieving H⁺ toxicity was tested with wheat seedlings ( Triticum aestivum L.). Growth enhancement by Al³⁺ only occurred under acidic conditions that reduced root elongation. Al³⁺ increased cell membrane electrical polarity and stimulated H⁺ extrusion. Previous investigations have shown that Al³⁺ decreases solute leakage at low _pH and that the alleviation of H⁺ toxicity by cations appears to be a general phenomenon with effectiveness dependent upon charge (C³⁺>C²⁺>C^l+). Alleviation of one cation toxicity by another toxic cation appears to be reciprocal so that Al³⁺ toxicity is relieved by H⁺. It has been argued previously that this latter phenomenon accounts for the apparent toxicity of ALOH²⁺ and Al(OH)⁺₂. Reduction of cell-surface electrical potential by the ameliorative cation may reduce the cell-surface activity of the toxic cation.     

Rapid neurotrophic actions of an ACTH/MSH(4–9) analogue after nigrostriatal 6-OHDA lesioning

ACTH peptide fragments demonstrate potent neurotrophic effects on peripheral nerves in situ, central neurons in culture, and have been implicated to have effects on central neurons in vivo. Neurotoxic lesioning of the nigrostriatal system, which depletes the striatum of dopamine, provides a feasible model of central regeneration in which to test these peptides. Male Sprague-Dawley rats were lesioned unilaterally with 6-hydroxydopamine (8 μg/4 μl), infused into the substantia nigra. They were subsequently treated with 10 μg/kg IP of Org 2766 [ACTH/MSH(4–9) analogue] or saline every 24 h starting immediately after the infusion and were observed for 2 weeks. Rotational behavior data indicate that Org 2766 significantly decreases ipsiversive turning (p < 0.05), induced by amphetamine (2 mg/kg), as well as accelerating the onset of denervation supersensitivity induced by apomorphine (0.05 mg/kg). Evaluation of dopamine immunohistochemistry, using an anti-tyrosine hydroxylase antibody, demonstrates an enhanced intensity of staining in the ORG 2766-treated tissue compared to its saline counterpart. This difference is confirmed and quantified through specific high-affinity dopamine uptake. Dopamine uptake is about 17% higher in the striata of animals treated with Org 2766. Higher dopamine uptake levels in these ACTH-treated animals correlate with greater fiber density in this group. Therefore, it appears that treatment with the ACTH/MSH(4–9) analogue Org 2766 (10 μg/kg/24 h) offers a protective effect from 6-OHDA lesions in the substantia nigra as well as accelerating various compensatory mechanisms involved in functional recovery.     

人血红细胞酪氨酸蛋白磷酸酶（PTPP）的研究Ⅱ·胞浆PTPP的分离纯化及其主要性质

人血红细胞胞浆部分经（ＮＨ_４）_２ＳＯ_４沉淀,ＤＥＡＥ－纤维素（ＤＥ５２）柱层析,磷酸纤维素柱层析（Ｐ１１）得到部分纯化的ＰＴＰＰ,产率：５．７％,提纯１０７５倍。以（３２）￣Ｐ－Ｔｙｒ－Ｐｏｌｙ（Ｇ_４：Ｔ）作底物,测得其表征Ｋｍ约为０．５－０．８μｍｏｌ／Ｌ,该酶的最适ｐＨ和最适温度分别为７．０－７．８及３７－４０℃。Ｚｎ￣（２＋）等二价金属离子及Ｎａ_３ＶＯ_４等酸根基团对其活性有明显的抑制作用;ＥＤＴＡ、甘油及ＤＴＴ、巯基乙醇等则对其有强烈激活作用;而氟化物、酒石酸等对ＰＴＰＰ活性基本无影响。此外,某些蛋白质、氨基酸、核苷酸及抗肿瘤药物等对ＰＴＰＰ活性也都有不同程度的影响。特别是一些ＰＫｓ及ＰＰｓ在体外对ＰＴＰＰ活性也具有不同的作用。     

Fire and competition in Australian heath: a conceptual model and field investigations

Abstract. We describe a model of heath vegetation, in which species were classified into five functional groups based on characteristics of their propagule pools, post-fire growth, timing and mode of reproduction and competitive status. The model assumes no recruitment without fire and a simple competitive hierarchy based on vertical stature. A critical feature of the model is an initial post-fire window of 5–6 yr in which competition from overstorey species on understorey species is reduced. Understorey functional groups differ in their ability to exploit this window. In the field, we tested five predictions derived from the model: (a) overall species richness of understorey varies inversely with overstorey density as a result of a trend in richness of woody species, but not in herbaceous species; (b) where an overstorey was present in the previous fire interval, post-fire population density is reduced in a functional group of understorey serotinous resprouting shrubs, but not in a group of understorey obligate-seeding shrubs with soil seed banks; (c) in understorey serotinous resprouting shrubs, post-fire regrowth in resprouting individuals is adversely affected by the presence of an overstorey in the preceding fire interval; (d) in understorey serotinous resprouting shrubs, levels of pre-fire propagules are lower in the presence of an overstorey, reducing the density of post-fire recruits; and (e) in understorey serotinous resprouting shrubs, recruitment relative to the pre-fire population is unaffected by overstorey species within the window of reduced competition. Of these, three tests (a,b,d) supported the model, one (e) may support the model, but the results were inconclusive and one (c) did not support the model. Limitations and further applications of the model are discussed. Our results suggest that maintenance of high densities of overstorey populations is in conflict with conservation of some understorey species. Models of the type we propose will help identify and resolve such conflicts and promote the judicious use of fire to maintain full species diversity of plant communities.