Effects of Low‐Intensity Microwave Radiation on Oxidant‐Antioxidant Parameters and DNA Damage in the Liver of Rats

The continuously increasing usage of cell phones has raised concerns about the adverse effects of microwave radiation (MWR) emitted by cell phones on health. Several in vitro and in vivo studies have claimed that MWR may cause various kinds of damage in tissues. The aim of this study is to examine the possible effects of exposure to low‐intensity MWR on DNA and oxidative damage in the livers of rats. Eighteen Sprague–Dawley male rats were divided into three equal groups randomly (n = 6). Group 1 (Sham‐control): rats were kept under conditions the same as those of other groups, except for MWR exposure. Group 2: rats exposed to 1800 MHz (SAR: 0.62 W/kg) at 0.127 ± 0.04 mW/cm² power density, and Group 3: rats exposed to 2,100 MHz (SAR: 0.2 W/kg) at 0.038 ± 0.03 mW/cm² power density. Microwave application groups were exposed to MWR 2 h/day for 7 months. At the end of the exposure period, the rats were sacrificed and DNA damage, malondialdehyde (MDA), 8‐hydroxydeoxyguanosine (8‐OHdG), and total oxidant‐antioxidant parameter analyses were conducted in their liver tissue samples. It was found that 1800 and 2100 MHz low‐intensity MWR caused a significant increase in MDA, 8‐OHdG, total oxidant status, oxidative stress index, and comet assay tail intensity (P < 0.05), while total antioxidant status levels (P < 0.05) decreased. The results of our study showed that whole‐body exposure to 1800 and 2100 MHz low‐intensity MWR emitted by cell phones can induce oxidative stress by altering oxidant‐antioxidant parameters and lead to DNA strand breaks and oxidative DNA damage in the liver of rats. Bioelectromagnetics. 2021;42:76–85. © 2020 Bioelectromagnetics Society     

Organ culture of osteopetrotic (ia) rat bone: evidence that the defect is cellular.

Calvarial bone from osteopetrotic (ia) rats and normal littermates has been cultured in a chemically defined medium supplemented with homologous serum to test for the presence of inhibitors or the absence of promoters of bone resorption in mutant serum. In addition, the response of mutant and normal bone to parathyroid extract and hydrocortisone was tested in vitro. The results indicate that mutant and normal serum do not differ with respect to their ability to support bone resorption and that ia bone responds to hydrocortisone but not parathyroid extract in organ culture. These data indicate that the skeletal defect in ia rats is not humoral but cellular.     

On the Use of Microwave Radiation Energy for Brain Tissue Fixation

Abstract: Focused microwave irradiation (MWR) is an increasingly accepted method of sacrifice of laboratory animals such as the mouse or rat. By fixing the brain within a fraction of a second with heat inactivation, the investigation of fast neurochemical events may be obtained. Even though the technique is widely utilized, its application is inconsistent. This report illustrates some of the requirements necessary for the proper application of MWR for the sacrifice of animals, particularly those related to the length of time MWR is applied and the efficiency with which generated MWR power is coupled to the brain tissue. Studies were performed on the mouse, using either a 2.5 KW or 6.3 KW generator with a focused, closed system waveguide at time intervals of 350 or 500 ms or 1.4 s. During each of these intervals MWR was varied so that core brain temperatures for all groups were held between 83 and 95°C. In contrast with reported studies that used full animal restraint, all animals were minimally restrained for less than 1 s before sacrifice. Tissue content of cyclic AMP, an index of neuronal activity grossly affected by subtle changes in the activity of adenylate cyclase and/or phosphodiesterases, was monitored. No differences in tissue cyclic AMP content in any of 12 brain regions were detected after MWR, either at 350 or 500 ms. A substantial increase in cyclic AMP content occurred in 8 of 12 brain regions examined following microwave irradiation for 1.4 s. On the basis of these experiments, accurate determination of cyclic AMP in rodent brain requires that the maximum time interval of MWR exposure should not exceed 500 ms.     

Levels of cyclic nucleotides in mouse regional brain following 300 ms microwave inactivation.

Abstract— The uniformity and speed of inactivation of mouse brain adenylate cyclase, guanylate cyclase and cyclic nucleotide phosphodiesterase were measured after 6 kW microwave irradiation (MWR). Inactivation of enzymes was uniform throughout the brain during heating and 100% loss of activity was evident after 300 ms. MWR. For comparison of effects of inactivation times on levels of cyclic nucleotides measured in regional brain areas, cyclic AMP and cyclic GMP were estimated after 1.5 kW MWR requiring 4 s of heating and 6 kW MWR requiring 300 ms. Except for corpus striatum, uniformly lower levels of cyclic AMP were measured following 300 ms vs. 4s MWR . There was no change in cyclic GMP levels in regional brain areas after 4s vs. 300 ms MWR . Cyclic AMP and cyclic GMP were measured from the same regional brain tissue samples after 300 ms and ratios calculated. The finding of much lower cyclic AMP:cyclic GMP ratios than had previously been reported suggests that slow inactivation times provide for the measurement of regional brain cyclic nucleotide values which are not consistent with the in-vivo state.     

Metallothionein in male reproductive organs of adrenalectomized and hydrocortisone-treated Wistar rats

Adrenalectomy resulted in an increase in metallothionein (MT) levels in testes, caput and cauda epididymis and prostate of rats but not in seminal vesicles where its levels decreased significantly. Inspite of administration of hydrocortisone, MT in testes, prostate (1.2 mg), caput (0.3 mg days 2, 8; 0.6 mg and 1.2 mg) and seminal vesicles (0.3 mg day 2, 4; 0.6 mg and 1.2 mg) remained increased. Thus adrenal insufficiency/hydrocortisone has no direct influence on MT levels. However, the increased levels of MT can be related to its ability to protect the cells from free radical damage caused by atrophy of reproductive tissues in adrenalectomised rats. Exogenously administered hydrocortisone to ADX rats resulted in return to ADX state as hydrocortisone metabolizes (half-life < 12 hr) and hence MT levels remained increased. The observations could provide a clue for the physiological functioning of the male reproductive tissue in a state of adrenal deprivation and hormonal supplementation.     

An essential role for glucocorticoid in casein gene expression in rat mammary explants

It is demonstrated that the accumulation of 42 K casein mRNA in mammary tissue from adrenalectomized, virgin rats is almost 20x higher in the presence of exogenous hydrocortisone than in its absence. Accumulation of 25 K casein mRNA in this tissue is totally dependent on the steroid. The results indicate a much greater dependency on hydrocortisone than was appreciated previously, and also show that this dependency does not reflect a loss of cell viability in the absence of the steroid.     

Enhancement of α-lactalbumin-like activity in mammary explants from pregnant rats in the absence of exogenous prolactin

Mammary explants from pregnant rats showed a progressive increase in α-lactalbumin activity during culture with insulin, hydrocortisone and prolactin. Unexpectedly, culture with only insulin and hydrocortisone produced a similar rate of increase of α-lactalbumin-like activity, but this increase commenced about 24 hr later. The delay suggests that the enhanced activity effected by insulin and hydrocortisone is not a reflection of carry-over of endogenous mammotrophic hormones. Insulin plus hydrocortisone did not stimulate casein or fatty acid synthesis by pregnancy tissue, and did not enhance α-lactalbumin-like activity in virgin rat mammary explants. Enhancement of this activity by insulin plus hydrocortisone in pregnant tissue was constant over a wide range of glucocorticoid concentrations, but was inhibited by progesterone. Available evidence indicates that the active factor in extracts from insulin-hydrocortisone-explants is a heat-stable protein which is either α-lactalbumin itself, or another molecule with similar specifier properties.     

腺嘌呤与氢化可的松大鼠肾阳虚模型造模方法比较

目的比较腺嘌呤诱导与氢化可的松诱导的SD大鼠肾阳虚模型的优劣,从而得到临床症状、生化指标更符合中医“肾阳虚”型的动物模型,以供科研、教学使用。方法雄性SD大鼠100只,随机分成正常组、腺嘌呤造模组及氢化可的松低剂量组、中剂量组、高剂量组各20只,造模成功后检测血肌酐（Scr）、尿素氮（BUN）、尿液中17-羟皮质类固醇（17-OH）和血浆中甲状腺激素（13、T4）、睾丸酮（T）、雌二醇（E2）及模型大鼠骨密度。结果无论从症状主证方面,还是客观指标方面（除骨密度外）,腺嘌呤诱导的SD大鼠肾阳虚型动物模型在生化指标研究方面均优于氢化可的松诱导组。结论腺嘌呤诱导的肾阳虚证SD大鼠模型在症状主证方面及其相关的生化研究方面优于氢化可的松组。     

Tissue-specific differential induction of aspartate transcarbamylase by hydrocortisone in rats of various ages

The activity and induction pattern of aspartate transcarbamylase (ATCase) of the liver (a mitotic tissue) and heart (a post-mitotic tissue) of rats of various ages were studied. The activity of the enzyme of both tissues was highest in the immature rat and decreased significantly thereafter with increasing age of the animal. Adrenalectomy and hydrocortisone treatments altered the activity of liver ATCase in rats of all the ages. However, these treatments altered the heart enzyme of the immature and adult rats, but not of senescent rat. The magnitude of induction of the enzyme by hydrocortisone was highest in the immature rat. Actinomycin D inhibited the hormone-mediated induction of ATCase in both the liver and heart.     

Inhibition by dexamethasone of histamine production in allergic inflammation in rats.

In an allergic inflammation model of air pouch type in rats, histamine level in the pouch fluid and histidine decarboxylase activity of pouch wall tissues in the postanaphylaxis phase were increased. Although treatment with dexamethasone failed to inhibit histamine release from mast cells in the anaphylaxis phase, histamine production in the postanaphylaxis phase was inhibited dose dependently. Histamine production-increasing activity in the pouch fluid collected 8 h after the Ag challenge, which was estimated by an activity to stimulate histamine production by bone marrow cells, was decreased by the administration of dexamethasone at the time of the Ag challenge. The addition of steroidal antiinflammatory drugs, dexamethasone, prednisolone, or hydrocortisone, into the incubation medium inhibited the pouch fluid-induced histamine production by bone marrow cells. Hydrocortisone mesylate antagonized the inhibitory effect of dexamethasone on histamine production by bone marrow cells. However, hydrocortisone mesylate failed to recover the decrease in histamine production-increasing activity of the pouch fluid collected from dexamethasone-treated rats. In addition, the dialyzed sample of pouch fluid obtained from dexamethasone-treated nonsensitized rats did not reduce the stimulated histamine production by the pouch fluid sample obtained from the sensitized rats. However, increase in histamine production of bone marrow cells stimulated by the pouch fluid was not inhibited by cyclosporin A that inhibited histamine production induced by Con A. This observation indicates that the pouch fluid has no effect to induce production of the histamine production-increasing factor by bone marrow cells. Consequently, it is suggested that dexamethasone inhibits not only the production of histamine production-increasing factor but also the response of histamine-producing cells to this factor.     

Acute, whole-body microwave exposure and testicular function of rats

Male Sprague-Dawley rats were exposed for 8 h to continuous-wave microwave radiation (MWR, 1.3 Ghz) at a mean specific absorbed dose rate of 9 mW/g. MWR exposure and sham-irradiation took place in unidirectionally energized cylindrical waveguide sections, within which the animals were essentially unrestrained. The MWR treatment in this setting was determined to yield an elevation of deep rectal temperature to 4.5 degrees C. The animals were taken for analysis at 6.5, 13, 26, and 52 days following treatment, which corresponded to .5, 1, 2, and 4 cycles of the seminiferous epithelium. Net mass of testes, epididymides, and seminal vesicles; daily sperm production (DSP) per testis and per gram of testis; and the number of epididymal sperm were determined. The levels of circulating follicle-stimulating hormone (FSH) and leutinizing hormone (LH) were derived via radioimmunoassay of plasma samples taken at the time of sacrifice. Despite the evident acute thermogenesis of the MWR at 9 mW/g, no substantial decrement in testicular function was found. We conclude that, in the unrestrained rat, whole body irradiation at 9 mW/g, while sufficient to induce evident hyperthermia, is not a sufficient condition for disruption of any of these key measures of testicular function.     

Chemically-defined medium for growth and differentiation of mixed epithelial and connective tissues in organ culture

The effect on tissue differentiation and growth in vitro of certain of the factors implicated in collagen synthesis (ascorbic acid, α-ketoglutarate and oxygen) and the influence of hydrocortisone was studied using organ cultures of fetal mouse mandible as a mixed epithelial and connective tissue system. Using serum-free Waymouth’s MB 752/1 chemically-defined medium, addition of high levels of ascorbic acid (300 μg per ml), hydrocortisone (1 μg per ml) and oxygen (95%) enhanced differentiation in a number of tissues, in particular skin and appendages, tooth germs and bone, while osteoid and dentine production were noticeably promoted. It is suggested that an essential aspect of media design for organ culture involves the incorporation of collagen-promoting factors to the in vitro environment particularly with regard to the controlling role implicated for collagen in a variety of biological processes. Some of the work reported here was undertaken while A. H. Melcher was a member of the Department of Dental Science, Royal College of Surgeons of England, London, England.     

Effect of hydrocortisone on phenylhydrazine-induced Heinz-body anemia

The effect of hydrocortisone on phenylhydrazine-induced anemia has been examined in adrenalectomized rats. The extent of hemolysis in adrenalectomized rats treated with phenylhydrazine was significantly higher than in normal and adrenalectomized rats supplemented with hydrocortisone.     

Studies on L-arginase in developing rat small intestine, brain, and kidney. II. Effect of hydrocortisone and thyroxine

The influences of hydrocortisone and thyroxine on the developmental changes of arginase activity in intestine, kidney, and brain of suckling rats were studied. A single injection of hydrocortisone (50 mg/kg) into rats aged 9 days evoked premature increase of jejunal arginase activity due to precocious formation of arginase A4. Arginase A4 can be detected about 48 hr after hydrocortisone injection, whereas in intact rats the enzyme appears in the intestinal mucosa on the 19th-21st days of postnatal life. After hydrocortisone administration to rats aged 6 days, a similar pattern of arginase activity in jejunum was observed. Under the same conditions, the influence of hydrocortisone on kidney arginase was weaker. The hormone did not have any influence on the activity of brain arginase. Daily injection of thyroxine (2 mg/kg) to 6-day-old rats (for 6 consecutive days) caused a precocious increase of the arginase activity in intestine. Under the same conditions, only a slight increase of the arginase activity was observed in kidney, whereas in brain the activity was unaffected.     

Selective enhancement of the induction of alpha-lactalbumin activity in rat mammary explants by epidermal growth factor

Epidermal growth factor (EGF) enhances the induction of alpha-lactalbumin in mammary explants from pregnant and virgin rats in the presence of insulin (I), hydrocortisone (F) and prolactin (P). EGF also enhances the prolactin-independent induction of alpha-lactalbumin in tissue from pregnant rats and evokes prolactin-independent induction of alpha-lactalbumin in mammary tissue from virgin rats in the presence of I and F. Casein synthesis and galactosyltransferase activity are unaffected by EGF in the IFP-system, and are not induced in the IF-EGF-system. Multiplication stimulating activity, nerve growth factor, fibroblast growth factor and platelet-derived growth factor do not mimic the selective effects of EGF on rat alpha-lactalbumin. These influences of EGF on the differentiation of isolated rat mammary tissue are compared with those on mouse and rabbit tissue studied previously.     

Age-dependent effects of sodium butyrate and hydrocortisone on acetylation of high mobility group proteins of rat liver

The in vitro acetylation of high mobility group (HMG) proteins and its modulation by sodium butyrate and hydrocortisone have been studied using liver slices of young (13-) and old (114-week-old) rats. Acetylation of total HMG proteins was significantly higher in young than old rats. HMG 1, in particular, showed greater acetylation than others. Whereas acetylation of HMG 1 and 2 decreased drastically, that of HMG 14 and 17 increased in old age. In young rats, sodium butyrate and hydrocortisone stimulated acetylation of HMG 14 and 17, and decreased that of HMG 2. Butyrate had no effect on HMG 1, but hydrocortisone decreased it. In old rats, butyrate and hydrocortisone decreased acetylation of all HMGs, except HMG 17, which was stimulated to a slight extent by butyrate.     

Antidiuretic hormone content in the neurohypophysis of adult white rats after hydrocortisone administration in the early postnatal period

The age-related time-course of changes in arginine-vasopressin (AVP) content in the pituitary gland was studied in adult intact Wistar rats. In 60-day-old rats, the hormone content was measured before and after 24 h of water deprivation. In adult rats treated with a single injection of hydrocortisone at different times after birth, the content of AVP remained high in rats injected with hydrocortisone on day 2 or day 5 after birth, exceeding significantly the content of AVP in intact rats. The animals injected with hydrocortisone on day 9 or 15 manifested a more noticeable reduction in the hormone content, as was the case in intact rats. It is suggested that the first five days after birth is a critical period in the formation of the central regulation of AVP secretion with high sensitivity to short-term changes in corticosteroid balance.     

Administration of glucocorticoids markedly increases the numbers of granulocytes and extrathymic T cells in the bone marrow.

Glucocorticoids, steroid hormones, are widely used as an anti-inflammatory drug. However, clinicians have sometimes encountered adverse drug reactions such as ulcers and tissue damage. In this study, we investigated how such adverse reactions of glucocorticoids are evoked, using an experimental mice model. When hydrocortisone (0.5 or 1.0 mg/day/mouse) was administered daily for 2 weeks, severe leukocytopenia was induced in all immune system organs. However, granulocytes (Gr-1(+)Mac-1(+)) were increased in number in the bone marrow and peripheral blood. This seemed to be due to an elevated level of myelopoiesis in the bone marrow. As well as increasing in number, granulocytes were functionally activated as estimated by the Ca2+ influx and superoxide production. The proportion of primordial T cells (CD3(int)IL-2Rbeta+) in the thymus and the number of primordial T cells in the bone marrow also increased. Mice administered hydrocortisone became susceptible to stress. Thus, these mice showed gastric ulcers when they were exposed to restraint stress for 12 h. These results suggest that activated granulocytes and primordial T cells might provide a mechanism involved in steroid ulcers and tissue damage, possibly through the superoxide production of granulocytes and the autoreactivity of primordial T cells.     

The influence of caffeine on the biomechanical properties of bone tissue during pregnancy in a population of rats

The influence of pregnancy on bone tissue metabolism is not completely understood. Caffeine also has a potentially negative influence on bones. The aim of this study was the evaluation of changes in the bones of pregnant rats under the influence of caffeine. The experiment was carried out on Wistar rats. The evaluation of rats' bone tissue quality was performed based on bone density measurements and resistance examinations. It analyzed the impact of caffeine on the degree of bone tissue mineralization and the composition of the bones. The mean value of pelvises 'wet' and 'dry' densities in a group of pregnant rats with caffeine intake was lower compared to the control group. The deformation in maximal load point of the femur shaft in the experimental group was significantly higher than in the control group. In the experimental group, the percentage of water in the bones was significantly higher, while the content of inorganic phase was significantly lower compared to the control group. The changes of biomechanical parameters in the group of pregnant rats with caffeine intake indicate its negative influence on the bone. Our results show higher plasticization of the bone shafts of the animals under the influence of caffeine. Higher deformation of bone shafts may have an effect on the statics of the skeleton. The administration of caffeine significantly affected the quantitative composition of the bone.     

Effect of partial hepatectomy and hydrocortisone administration on liver and serum sialyltransferase activities.

Partial hepatectomy of rats was followed by a rise in liver sialyltransferase activity. The maximum (2.5-fold increase) was reached on the third day after the operation, after which the level started to decline, returning to normal by day 6. Determination of serum sialyltransferase in these animals showed a parallel pattern. Daily injection of 5 mg hydrocortisone to adrenalectomized rats led to a maximal 3-fold elevation in liver sialyltransferase within 3 days, but failed to elicit any change in the corresponding enzyme in the serum. Results from these two experiments suggest that the elevations of sialyltransferase in the tissue and in the circulation are independently regulated.