Microwave-And Ultrasound-Assisted Synthesis of Some Acyclonucleobases Based on a Uracil Moiety Using Dmap as Base

In this study, 1-(bromoalkanoyl)-1H-pyrimidine-2,4-diones, (2,4-dioxo-pyrimidin-1-yl)-oxo-alkanoic acids, and bis(2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-alkanones were successfully prepared via electrophilic substitution of uracil and its derivatives. High yields and pure products were obtained when microwave and ultrasound methodologies were used for undertaking the reactions. Importantly, the use of 4-dimethylaminopyridine in the present investigation gave rise to higher conversions of the starting material and afforded facile access to regioselective N-1 products.     

Low-Level Microwave Irradiations Affect Central Cholinergic Activity in the Rat

Sodium-dependent high-affinity choline uptake was measured in various regions of the brains of rats irradiated for 45 min with either pulsed or continuous-wave low-level microwaves (2,450 MHz; power density, 1 mW/cm2; average whole-body specific absorption rate, 0.6 W/kg). Pulsed microwave irradiation (2-microseconds pulses, 500 pulses/s) decreased choline uptake in the hippocampus and frontal cortex but had no significant effect on the hypothalamus, striatum, and inferior colliculus. Pretreatment with a narcotic antagonist (naloxone or naltrexone; 1 mg/kg i.p.) blocked the effect of pulsed microwaves on hippocampal choline uptake but did not significantly alter the effect on the frontal cortex. Irradiation with continuous-wave microwaves did not significantly affect choline uptake in the hippocampus, striatum, and hypothalamus but decreased the uptake in the frontal cortex. The effect on the frontal cortex was not altered by pretreatment with narcotic antagonist. These data suggest that exposure to low-level pulsed or continuous-wave microwaves leads to changes in cholinergic functions in the brain.     

Nonthermal effect of microwave irradiation on nitrite uptake in Chlamydomonas reinhardtii

When cells of the unicellular green alga Chlamydomonas reinhardtii were subjected to microwave irradiation at 2.45 GHz, nitrite uptake kinetics still obeyed the Michaelis-Menten equation, the Km of the process remaining constant, whereas V _max increased, which indicates an enhanced nonthermal permeability in irradiated cells.     

Microwave radiation absorption in the rat: frequency-dependent SAR distribution in body and tail

Experiments were conducted using twin-well calorimetry to determine the averaged whole-body specific absorption rate (SAR) for rat carcasses exposed to 360, 700, 915, and 2,450 MHz CW radiation in an anechoic chamber. All exposures were done with the long axis of the rat in an E-polarization. Additional experiments were conducted using a fiber optical temperature probe to determine local SAR in the brain, esophagus, colon, rectum, and tail during microwave exposure. The whole-body averaged SAR for the radiation frequencies examined follows a nonmonotonic function with 700 MHz as the resonant frequency. This result agrees with previous analytical estimates. Local SARs within the body and tail are nonuniform with significant frequency-specific hotspots in the colon, rectum, and tail.     

Noninvasive thermometry using multiple-frequency-band radiometry: a feasibility study

The potential use of multiple-frequency-band radiometry as a means of noninvasive sensing of one-dimensional temperature profiles is presented in this communication. The radiative energy transfer equation is solved numerically. Ideal-condition thermal noise spectra and distributions of received energy, associated with specific temperature-depth profiles, are presented. Performance characteristics are discussed.     

Brain temperature measurements in rats: a comparison of microwave and ambient temperature exposures

In an effort to understand microwave heating better, regional brain and core temperatures of rats exposed to microwave radiation (2450 MHz) or elevated air temperatures were measured in two studies. In general, we have found no substantial evidence for temperature differentials, or "hot spots," in the brain of these animals. In the first study, after a 30-min exposure, no temperature differences between brain regions either after microwave or ambient air exposure were found. However, a highly significant correlation between brain and core temperatures was found and this correlation was the same for both microwave and ambient air heating. In the second study, time-temperature profiles were measured in rats exposed to either 30 mW/cm2 or 36.2 degrees C. In this study, the 30-min exposure period was divided into seven intervals and the change in temperature during each period was analyzed. Only the cortex showed significantly different heating rates between the air heating and microwave heating; however, this difference disappeared after the initial 5 min of exposure.     

Ultrafast protein determinations using microwave enhancement

We present here microwave-based modifications of standard protein assays that dramatically reduce the time required to determine protein concentrations. Typical protein determinations involve incubation times ranging from 15–60 min. Microwave irradiation of specimens reduces this time requirement to 10–20 s without compromising accuracy or reliability. The remarkable speed with which protein determinations may be carried out using microwave enhancement greatly simplifies general laboratory procedures that depend on the estimation of protein concentrations. An erratum to this article is available at .     

Essential trace elements in humans

Serum arsenic concentrations of persons suffering from renal failure and undergoing hemodialysis treatment (n=85) and of healthy controls (n=25) were determined by hydride-generation AAS technique after microwave digestion. The results were evaluated by comparing the values of both groups, considering physiological factors and individual data, as well as comorbid conditions of the hemodialysis (HD) patients. Serum arsenic levels were diminished in the patient group compared with controls (mean values 8.5±1.8 ng/mL vs 10.6±1.3 ng/mL). Furthermore, additional diseases within the hemodialysis group, particularly injuries of the central nervous system (CNS), vascular diseases, and cancer, were correlated to occasionally markedly decreased serum arsenic concentrations. It was concluded that arsenic homeostasis is disturbed by HD treatment and certain additional diseases. Desirable arsenic concentrations in the body seem to be reasonable. This consideration results in the conclusion that arsenic could play an essential role in human health. Thus, reference arsenic concentrations in different human tissues and body fluids should be established in order to recognize not only arsenic intoxication, but also arsenic deficiency. Perhaps arsenic deficiency contributes to the increased death risk of HD patients, and therefore, arsenic supplementations for patients with extremely low serum arsenic concentrations should be taken into account.     

低强度微波辐射对人精子非热生物效应的研究

选用频率２４５０ＭＨｚ分别在３、５、７、９ｍＷ／ｃｍ２的功率密度,使用新型宽带横电磁传输室（ＢＴＥＭＣＥＬＬ）辐射人精子１小时,我们发现只有５ｍＷ／ｃｍ２的强度对人射子的活动度、存活率、畸形率又穿卵率有显著的影响,这表明在５ｍＷ／ｃｍ２附近存在明显的功率密度窗效应。同时还发现,７ｍＷ／ｃｍ２组的精子的染色体出现畸变。最后对实验结果进行了讨论。     

Effect of microwaves (2450-MHz) on the immune system in mice: studies of nucleic acid and protein synthesis

CBA/J adult male mice were given single or triple exposures to 2450-mHz microwaves in an environmentally controlled wave guide facility. The average absorbed dose rate for a single exposure varied from 12 to 15 mW/g. Sham-exposed mice served as controls. Lymphoid cells were collected and tested for metabolic activity on days 3, 6, and 9 following a single exposure, and on days 9, 12, and 16 following triple exposures on days 0, 3, and 6. Cells were cultured in vitro for four hours to seven days before their metabolic rates were assayed. Under these conditions, microwaves failed to produce any detectable change in deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and protein synthesis, as measured by the incorporation of methyl(3H)-thymidine (3H-TDR) (DNA substrate), 3H-uridine (3H-UR) (RNA substrate), and 3H-leucine (protein substrate) by spleen, bone marrow, and peripheral blood lymphocytes (PBL) in vitro. These data suggest that microwave-induced increases in the frequency of complement-receptor (CR)- or surface-immunoglobulin (sIg)-bearing cells were not associated with a concomitant increase in cell proliferation and/or protein synthesis, and favor the concept that microwaves under these conditions stimulate already existing B-cell precursors for maturation.