Normalizing the thermal effects of radiofrequency radiation: body mass versus total body surface area

The current guideline for exposure to radiofrequency radiation (RFR) was developed through assessment of the biological effects data collected primarily from the rat. The consensus that a lack of hazardous biological effects occurred below a whole-body-averaged specific absorption rate (SAR) of 4.0 W/kg led to the proposition of a 0.4 W/kg guideline with a built-in safety factor of 10. This paper demonstrates that if the RFR absorption rate in the rat had been normalized with respect to total body surface area rather than body mass, the exposure guideline would be 2.3 W/m2, which translates to an SAR of approximately 0.06 W/kg for an adult human. It is further shown that a given RFR absorption rate, normalized as a fraction of a species' heat loss per unit of surface area, is independent of body mass over a range of 0.03-100 kg; however, a normalization of the RFR absorption rate to heat loss per unit of body mass is highly dependent on the species' mass. Normalizing the rate of RFR absorption to the surface area of the rat indicates that the current RFR exposure guideline of 0.4 W/kg may be too high.     

A finite-difference electromagnetic deposition/thermoregulatory model: comparison between theory and measurements

The rate of the electromagnetic energy deposition and the resultant thermoregulatory response of a block model of a squirrel monkey exposed to plane-wave fields at 350 MHz were calculated using a finite-difference procedure. Noninvasive temperature measurements in live squirrel monkeys under similar exposure conditions were obtained using Vitek probes. Calculations exhibit reasonable correlation with the measured data, especially for the rise in colonic temperature.     

Effect of Hirschmanniella caudacrena on the Submersed Aquatic Plants Ceratophyllum demersum and Hydrilla verticillata

In vitro pathogenicity tests demonstrated that Hirschmanniella caudacrena is pathogenic to Ceratophyllum demersum (coontail). Symptoms were chlorotic tissue, deformed stems, and, finally, death of the plant. Inoculum densities of 500 nematodes per 5-cm-long cutting in a test tube containing 50 ml of water resulted in death and decay of some of the cuttings within 8 weeks; 100 nematodes killed the plants in 12 weeks, and 50 and 25 nematodes killed them in 16 weeks. The lowest inoculum level of 10 nematodes did not seriously affect the plants at 16 weeks when the experiment was terminated. A second test conducted outdoors in glass jars containing 3 liters of water and two cuttings weighing a total of 15 g fresh weight showed damage, but results were not statistically significant. Hydrilla verticillata inoculated with H. caudacrena was not affected seriously.     

Influence of leaf surfaces on movements by the hymenopterous parasitoid Trichogramma exiguum

Walking speeds of female Trichogramma exiguum Pinto & Platner were fastest on maize and soybean (12 cm/min), intermediate on tomato (8 cm/min), and slowest on woolly mullein, Verbascum thapsus (3 cm/min). Similarly, rates of turning along the paths of walking T. exiguum were smallest on maize (median angle=0°±15°), intermediate on soybean and tomato, and greatest on V. thapsus (median angle=30°±15°). Leaf trichome density and morphology influenced walking behavior. Walking was slowed and flight initiation delayed for T. exiguum walking on Amaranthus hybridus leaves compared to either maize or filter paper. When inundative releases are conducted, the effects of plant surfaces on searching rates and arrestment should be considered in determining release rates of Trichogramma spp.

---

Résumé La vitesse de marche a été déterminée en lâchant des individus sur chaque substrat végétal et en traçant leur parcours sur une plaque de verre placée à 9 mm au dessus du sujet. Les déviations angulaires de portions successives des tracés, longues de 1 mm, ont été utilisées pour mesurer les taux de changement de direction. Dans une deuxième expérience, des individus ont été lâchés au milieu d'une cercle de 40 mm de diamètre sur chaque substrat et les temps écoulés avant l'envol ou pour atteindre le bord du cercle à la marche ont servi à évaluer respectivement la propension au vol et la vitesse de déambulation.Les vitesses de marche ont été plus rapides sur maïs et soja (12 cm/min), moyennes sur tomate (8 cm/min) et les plus lentes sur Verbascum thapsus (Scrophulariaceae) (3 cm/min). De le même façon, les angles de changement de direction au cours des marches effectuées par T. exiguum ont été plus petits sur maïs, moyens sur soja et tomate, et plus grands sur V. thapsus. Chez T. exiguum marchant sur des feuilles d'Amaranthus hybridus L. (Amaranthaceae), la marche a été plus lente et l'envol plus tardif que sur maîs ou papier filtre.Lors de lâchers inondatifs, les effets des surfaces végétales sur les vitesses d'exploration et d'arrêt devraient être pris en compte pour déterminer les vitesses de lâcher des Trichogramma spp.

     

Nucleosomal organization of a BPV minichromosome containing a human H4 histone gene

Summary When the body temperature of rats is elevated to 42°C, four heat shock proteins, with the molecular weights of 70000, 71000, 85000, and 100000 (hsp 70, hsp 71, hsp 85, and hsp 100, respectively), are induced in various tissues of rats (Fujio et al., J Biochem 101, 181–187, 1987). Heat shock proteins are induced by various stresses other than heat in varieties of cultured cells, so we studied whether heat shock proteins are induced in intact rats by different treatments. Analysis of the translation products of poly(A) + RNA isolated from the livers of rats recovering from ischemia of the liver showed that mRNAs for hsp 70, hsp 71, and hsp 85 were induced. These hsp-mRNAs were also induced in the livers of rats 6 h after a partial hepatectomy, and had returned to control levels 24 h after the surgery. These results suggested that heat shock proteins have not only the function of protection against various stresses but also physiological functions in the normal growth and development of animals.     

Polygalacturonase activity and variation in ripening of papaya fruit with tissue depth and heat treatment

Effects of tissue position (viz. outer vs inner mesocarp) and heat treatment (48°C, 20 min) on variations in polygalacturonase (EC 3.2.1.15 and EC 3.2.1.67) activity and ripening of fruits of Carica papaya L. cv. Backcross Solo were investigated. Polygalacturonase activity increased during ripening concomitantly with an increase in tissue softness and soluble polyuronide level. Throughout ripening, inner mesocarp tissue was softer and contained higher polygalacturonase activity than outer mesocarp tissue. Titratable acidity as well as ß-galactosidase (EC 3.2.1.23) activity also increased during ripening; however, unlike polygalacturonase, their level or activity was lower in inner than in outer mesocarp. Ascorbic acid could partially account for the increase in titratable acidity during ripening but contributed very little to the differences in titratable acid levels between outer and inner mesocarp. Heat treatment had no effect on either fruit softness or titratable acidity, but it markedly reduced the increase in ascorbic acid and polygalacturonase activity during ripening. Ripening, as reflected by changes in tissue softness and polygalacturonase activity, progressed outwardly from the interior towards the exterior of the fruit. The effect of heat treatment in suppressing polygalacturonase activity was relatively greater in inner than in outer mesocarp, suggesting that sensitivity of the enzyme to heat treatment may vary with stage of ripeness of the tissue.     

Physicochemical characterization of alpha-crystallins from bovine lenses: hydrodynamic and conformational properties

A detailed investigation of hydrodynamic and conformational behavior has been made of the HM-crystallin and -crystallins of bovine lens. Results from this study indicated that HM (high-molecular-weight -crystallin) and (low-molecular-weight -crystallin) possess considerable size and charge heterogeneities in their native structures and subunit polypeptides, respectively. Sedimentation velocity showed a heterogeneous polydisperse system of HM with an average sedimentation coefficient of about 50 S and a more homogeneous system of -crystallin of 20 S. Viscosity and circular dichroism studies pointed to a compact and globular shape of dominant -sheet conformation for -crystallin, yet a highly asymmetrical and aggregated form for HM. The conformational stability of -crystallin was investigated in the presence of various denaturants. The evidence presented shows that hydrogen bonding is the main force in maintaining the quaternary structure of compact native -crystallin. Conformational flexibility of -crystallin demonstrated in the equilibrium unfolding study indicated a multistep transition that made the extraction of thermodynamic data from the heat denaturation study difficult. Temperature perturbation on -crystallin suggested the possible involvement of hydrophobic interaction in the aggregation process, leading to the formation of HM from -crystallin. The comparison of conformational properties between HM and -crystallin strongly indicated that HM is a denatured form of -crystallin.     

Heat shock proteins in Sorghum bicolor and Pennisetum americanum I. genotypic and developmental variation during seed germination

Abstract The capacity to synthesize heat shock proteins (HSPs) during seed germination of sorghum (Sorghum bicolor) and pearl millet (Pennisetum americanum) has been examined. HSP synthesis is detectable in a thermotolerant genotype of sorghum during the first hour of imbibition of the seed under high temperature stress. A non-coordinate control of HSP synthesis during germination was revealed. Genotypic differences were manifest in the stage of germination at which the ability to synthesize HSPs was first apparent and this related to the thermosensitivity of that genotype.     

Microscopic observations on the interaction of the mycoparasite Verticillium biguttatum with Rhizoctonia solani and other soil-borne fungi

The mycoparasitic interactions of Verticillium biguttatum with Rhizoctonia solani and with a variety of other soil-borne fungi were investigated in dual cultures. V. biguttatum interacted with various soil fungi by appressed growth along the host hyphae and infrequent penetrations. Intracellular growth and subsequent sporulation, however, only occurred with R. solani, a few binucleate Rhizoctonia and Ceratobasidium spp., and Sclerotinia sclerotiorum. Effective mycoparasitism on sclerotia was restricted to those belonging to R. solani.Electron-microscopic observations revealed that V. biguttatum can penetrate the host cell with infection tubes. This process is probably mediated by enzymatic hydrolysis of the cell wall. Subsequently, trophic hyphae develop within the host cytoplasm, ultimately resulting in death of the host cell.