Body mass change during altered gravity: spaceflight, centrifugation, and return to 1 G

To assess the effect of gravity on growth, immature rats (130-200 g) were studied during chronic altered gravity exposure and while transitioning between gravity fields. Body mass gain of rats (n = 12) exposed to 14 days of microgravity (spaceflight) was evaluated and compared to mass gain of 1 G controls. Spaceflight did not affect mass gain. Six rats exposed to 1 G following spaceflight, when compared to controls, experienced a significant (0 < 0.05) post-flight mass loss over 48 h of 13 g. Over subsequent days, however, this loss was compensated for, and no difference from 1 G controls was noted after 5 days. Exposure to hypergravity (2 G) for 16 days was evaluated [(n = 6/group): Centrifuge (C); On Center Control (OCC); Centrifuge Control (CC)]. Body mass of centrifuged and OCC rats was reduced within 24 h, with OCCs regaining control mass within 13 days. The mass difference (44 g) in centrifuged animals persisted, however, with no subsequent difference in rate of mass gain between centrifuged animals and controls over Days 3-16 (3.7 +/- 0.1 vs. 3.9 +/- 0.1 g/day, respectively). Transitioning from 2 G to 1 G resulted in a mass increase within 48 hours for centrifuged animals. Over Days 3-16 at 1 G, the rate of gain for centrifuged animals continued to increase (3.1 +/- 0.1 g/day compared to 2.1 +/- 0.1 g/day for controls); differences from control, however, were still noted on Day 16. Transitioning to an increase in a gravity field causes acute losses in body mass. In hypergravity, the acute reduction in body mass persists but the rate of mass gain is normal. Animals returning to 1 G, after acute changes, adjust to attain control mass.     

Effect of cell phone radiofrequency radiation on body temperature in rodents: Pilot studies of the National Toxicology Program's reverberation chamber exposure system

Radiofrequency radiation (RFR) causes heating, which can lead to detrimental biological effects. To characterize the effects of RFR exposure on body temperature in relation to animal size and pregnancy, a series of short‐term toxicity studies was conducted in a unique RFR exposure system. Young and old B6C3F1 mice and young, old, and pregnant Harlan Sprague‐Dawley rats were exposed to Global System for Mobile Communication (GSM) or Code Division Multiple Access (CDMA) RFR (rats = 900 MHz, mice = 1,900 MHz) at specific absorption rates (SARs) up to 12 W/kg for approximately 9 h a day for 5 days. In general, fewer and less severe increases in body temperature were observed in young than in older rats. SAR‐dependent increases in subcutaneous body temperatures were observed at exposures ≥6 W/kg in both modulations. Exposures of ≥10 W/kg GSM or CDMA RFR induced excessive increases in body temperature, leading to mortality. There was also a significant increase in the number of resorptions in pregnant rats at 12 W/kg GSM RFR. In mice, only sporadic increases in body temperature were observed regardless of sex or age when exposed to GSM or CDMA RFR up to 12 W/kg. These results identified SARs at which measurable RFR‐mediated thermal effects occur, and were used in the selection of exposures for subsequent toxicology and carcinogenicity studies. Bioelectromagnetics. 39:190–199, 2018. © 2018 The Authors. Bioelectromagnetics Published by Wiley Periodicals, Inc.     

Effect of 900-, 1800-, and 2100-MHz radiofrequency radiation on DNA and oxidative stress in brain

Ubiquitous and ever increasing use of mobile phones led to the growing concern about the effects of radiofrequency radiation (RFR) emitted by cell phones on biological systems. The aim of this study is to explore whether long-term RFR exposure at different frequencies affects DNA damage and oxidant-antioxidant parameters in the blood and brain tissue of rats. 28 male Sprague Dawley rats were randomly divided into four equal groups (n = 7). They were identified as Group 1: sham-control, Group 2: 900 MHz, Group 3: 1800 MHz, and Group 4: 2100 MHz. Experimental groups of rats were exposed to RFR 2 h/day for 6 months. The sham-control group of rats was subjected to the same experimental condition but generator was turned off. Specific absorption rates (SARs) at brain with 1 g average were calculated as 0.0845 W/kg, 0.04563 W/kg, and 0.03957, at 900 MHz, 1800 MHz, and 2100 MHz, respectively. Additionally, malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), total antioxidant status (TAS), and total oxidant status (TOS) analyses were conducted in the brain tissue samples. Results of the study showed that DNA damage and oxidative stress indicators were found higher in the RFR exposure groups than in the sham-control group. In conclusion, 900-, 1800-, and 2100-MHz RFR emitted from mobile phones may cause oxidative damage, induce increase in lipid peroxidation, and increase oxidative DNA damage formation in the frontal lobe of the rat brain tissues. Furthermore, 2100-MHz RFR may cause formation of DNA single-strand breaks.     

Nutrition and fetal brain maturation : II. Impact of maternal starvation on changing levels of acetylcholinesterase and enolase in vitro

The impact of maternal starvation during Days 17-20 of gestation was examined in 20-day fetal rat brain tissue cultured for 6 days in MEM and 10% adult rat serum. Acetylcholinesterase (AChE) activities were consistently greater in fetal brain cell cultures from starved mothers. When fetal tissues from starved mothers were continuously exposed to 72-h fasted serum, AChE activities increased from 1.03 +/- 0.14 to 1.59 +/- 0.21 mumol/h/mg protein (P less than 0.001). In fetal tissues from fed mothers, lower AChE activities were increased from 0.78 +/- 0.09 to 1.04 +/- 0.07 mumol/h/mg protein (P less than 0.05) when 72-h fasted serum was used to replace the fed serum during incubation. When fetal brain cell cultures from fed mothers were exposed for 6 days to graded concentrations of fed serum (2.5-15%), the activities of AChE fell reciprocally from 1.34 +/- 0.10 to 0.82 +/- 0.12 mumol/h/mg protein (P less than 0.05). The levels of AChE activity in tissues exposed to fasted serum were consistently greater, but fell similarly from 1.62 +/- 0.10 to 0.97 +/- 14 mumol/h/mg protein (P less than 0.01), when serum concentrations were increased from 2.5 to 15%. AChE activities were 30% higher in tissues incubated with cycloheximide 10(-3) M (P less than 0.02). Unlike AChE, fetal brain enolase activities were unaffected by maternal starvation. In fetal brain cell cultures from fed mothers, enolase fell from 1.85 +/- 0.10 to 1.37 +/- 0.12 mumol/min/mg protein following exposure to fasted instead of fed serum (P less than 0.02). In fetal cultures from starved mothers, enolase activities were depressed similarly from 1.76 +/- 0.08 to 1.41 +/- 0.09 mumol/min/mg protein when fasted replaced fed serum (P less than 0.02). Thus, the fetal brain cell cultures appear to maintain enzymatic realignments imposed by maternal starvation for at least 6 days. In addition, serum from fasted animals has significant growth inhibiting properties manifested by heightened activities of AChE and lower activities of enolase.     

Radiofrequency radiation and the immune system. Part 3. In vitro effects on human immunoglobin and on murine T- and B-lymphocytes

Radiofrequency radiation (RFR) altered the physical separation of immunoglobulin (Ig) and of T- and B-lymphocytes during liquid gel chromatography. Exposure of human serum to a 10 MHz electric field (8500 V/m, less than or equal to 0.134 W kg-1) during chromatography resulted in accelerated elution of the IgM, IgA and IgG fractions. This effect is consistent with an increase in steric resistance of Ig molecules to the gel pores resulting in rapid elution. The low level of absorbed power employed did not lead to measurable heating of the gel media (25.00 +/- 0.05 degrees C). Effects on lymphocyte separation were investigated by performing immunoaffinity cell chromatography during exposure to 2500 MHz RFR (194 V/m, less than or equal to 0.117 W kg-1). Murine spleen lymphocytes were fractionated at 4.0 degrees C over Ig-derivatized agarose beads into Ig- and Ig+ lymphocyte subpopulations. RFR exposures resulted in premature elution of 19 per cent of the Ig+ (B-cell) population indicating an alteration of Ig binding. Temperature excursions in excess of +/- 0.05 degree C were not observed during exposures. These in vitro results demonstrate that Ig, whether freely diffusing in solution or bound to the lymphocyte cell surface, is influenced by RFR at absorbed power levels below the current recommended safety limit of 0.4 W kg-1 (U.S.A.). A possible mode of interaction for these effects as well as the relevance of these findings to in vivo biological processes are discussed.     

A possible involvement of beta-endorphin, substance P, and serotonin in rat analgesia induced by extremely low frequency magnetic field

Most of the research concerning magnetic antinociception was focused on brief exposure less than 1 h. The main purpose of the present study was to determine the effect of extremely low frequency (ELF) magnetic field (MF) repeated exposures on rats in inducing antinociception and to find the effective analgesic "time window." Meanwhile this investigation was to examine the role of central beta-endorphin, substance P, and 5-HT in magnetic analgesia. We found tail flick latencies (TFLs) increased significantly after the rats were exposed to 55.6 Hz, 8.1 mT magnetic field for 4 days, 6 h each day. The analgesic effects seemed to decrease gradually when the rats were exposed daily for another 10 days. Their levels of TFLs decreased within 1 day when the rats were removed after a 4-day exposure. The concentrations of hypothalamus beta-endorphin, substance P, and brainstem serotonin (5-HT) were increased significantly on Day 4. However, no differences were found when rats were exposed for another 10 days, and there were no significant increases when rats were removed after the fourth day of exposure and tested for nociception on Days 5 and 7 with no changes in the biochemical markers at 7 days. These results suggest that the ELF magnetic field has analgesic effect, but only on Days 3 and 4. The effect may be associated with increases in endogenous beta-endorphin, substance P, and 5-HT stimulated by the 55.6 Hz, 8.1 mT magnetic field.     

Thermoregulatory responses of rats exposed to 9.3-GHz radiofrequency radiation

Summary Ketamine-anesthetized Sprague-Dawley rats were exposed in H orientation to far-field 9.3-GHz continuous-wave (CW) and pulsed (2 µs, 500 pps) radiofrequency radiation (RFR) at average power densities of 30 and 60 mW/cm² (whole-body average specific absorption rates of 9.3 and 18.6 W/kg, respectively). Irradiation was conducted to cyclicly increase colonic temperature from 38.5 to 39.5° C. Colonic, tympanic, and subcutaneous temperatures, ECG, blood pressure, and respiratory rate were continuously recorded during experimentation. At both power densities, the subcutaneous and tympanic temperature increases significantly exceeded the colonic temperature increase. At both exposure levels, heart rate increased significantly during irradiation and returned to baseline when exposure was discontinued. Blood pressure and respiratory rate did not significantly change during irradiation. There were no significant differences between the effects of CW and pulsed RFR exposure. The levels of subcutaneous heating and heart rate change were greater, and the times required to achieve and to recover from a 1° C colonic temperature increase were longer than in previous studies conducted at 2.8 GHz. Results of these studies indicate that the carrier frequency used during irradiation markedly affects the pattern of heat distribution and the physiological responses of RF-irradiated animals.     

Content of K+ and Na+ in seminiferous tubule and rete testis fluids from Sertoli cell-enriched testes

Seminiferous tubules of rats exposed to x-irradiation before birth were subjected to micropuncture in situ at 50 days of age to obtain samples of fluid 4 h after ligation of efferent ducts. The concentrations of cations in this fluid were: potassium, 39.7 +/- 1.2 mM, and sodium, 136.3 +/- 1.2 mM (means and standard errors, n = 5). Histologic examination revealed that germ cells constitute less than 1% of the cell population within the seminiferous tubules of these rats; the remaining cells were all Sertoli cells. Sertoli cells showed efflux of 86Rb+ with t1/2 of approximately 11 min and an active ATPase in plasma membranes. These activities were similar to those of Sertoli cells from normal rats. Germ cells from normal rats showed less rapid efflux of 86Rb+ (t1/2 greater than 60 min) and less active Na+/K+ ATPase in plasma membranes. It is concluded that Sertoli cells are responsible for the high concentration of potassium in seminiferous tubule fluid and that plasma membranes of these cells contain an active K+ pump that is not inhibited by ouabain (1 mM).     

Thermoregulatory responses of rats exposed to 9.3-GHz microwaves: a comparison of E and H orientation.

The purpose of this study was to determine the effects of exposure orientation relative to electric and magnetic fields (E and H fields) on the thermal, cardiovascular, and respiratory changes in ketamine-anesthetized rats exposed to far-field, continuous-wave, 9.3-GHz radiofrequency radiation (RFR). Irradiation (specific absorption rate = 12.5 W/kg in both orientations; power levels of 79 and 59 mW/cm2 in E and H orientations, respectively) was conducted to produce 1 degree C colonic temperature changes (38.5 to 39.5 degrees C). During experimentation, arterial blood pressure and respiratory rate, colonic (Tc) tympanic (Tt) left and right subcutaneous (Tsl & Tsr) (sides toward and away from RFR source), and tail temperatures (Tta) were continuously recorded. The Tsr change during E-orientation exposure was considerably less than the Tc change; the Tt and Tsr (H-orientation) changes approximated the Tc increase; and the Tsl and Tta changes (both orientations) were considerably greater than the Tc increase. The Tt and Tsl increases were virtually equal under the two exposure conditions; however, the Tsr increase was significantly greater during H-orientation irradiation, and the Tta increase was significantly greater during E-orientation exposure. Heart rate and mean arterial pressure increased significantly during irradiation; however the cardiovascular responses were not affected by exposure orientation. The latter findings at 9.3 GHz contrast with the marked cardiovascular response differences between E- and H-orientation exposure noted during previous studies at 0.7 to 2.45 GHz.     

Change in duration of elevated concentrations of melatonin is the major factor in photoperiod response of the tammar, Macropus eugenii

In Exp. 1, 10 quiescent non-lactating tammars were exposed to 15L:9D (Days -41 to -1), 24L:0D (Days 0 to 14), 15L:9D (Days 15 to 34) and then to ambient increasing daylength from 13L:11D on Day 35. From Days 0 to 22 they received a s.c. injection of melatonin (400 ng/kg, N -5) on the arachis oil vehicle (N = 5) in the evening (19:30 h) 2.5 h before dark. Exposure to 24L:0D abolished the nocturnal plasma melatonin rise but this was reinstated by subsequent exposure to 15L:9D. Of 5 melatonin-treated tammars, 4 gave birth on Day 45, so had failed to respond to the melatonin injection alone but reactivated when this was combined with the endogenous melatonin rise during exposure to 15L:9D. Of 5 control tammars, 4 remained quiescent until reactivated by the decrease in daylength to 13L:11D, and gave birth significantly later (Day 63.7 +/- 2.2, mean +/- s.e.m., P less than 0.05). In Exp. 2, 6 tammars were exposed to 15L:9D (Days -15 to -1) and then to 12L:12D (Days 0 to 15) by extending the dark phase by 3 h in the morning. This extended the nocturnal melatonin rise by 2-3 h in the morning and all 6 tammars gave birth on Day 31.2 +/- 1.0. A transient pulse of peripheral plasma prolactin (81.5 +/- 31.0 ng/ml) was detected at dawn during 15L:9D in all 6 tammars but was not observed in any of them 5 days after exposure to 12L:12D. Together these results do not support the time of day hypothesis but indicate that increase in duration of the nocturnal melatonin rise mediates the effects of decreased daylength on reactivation of the corpus luteum, and that the first detectable result of this may be the abolition of a transient prolactin pulse at the end of the dark phase.     

Possible effect of bromocriptine on the insulin receptor

The administration of 0.00011 mg/g weight/day of bromocriptine (CB154) for 7 days to Wistar rats, improved the peripheral glucose uptake without significant changes in plasma insulin level, during the intravenous glucose tolerance test (0.33 g/kg). The mode of the bromocriptine action on binding of 125I insulin to erythrocyte insulin receptors has been evaluated. The total number of sites was greater with bromocriptine (513.1 +/- 124.1 pM/1,CB154 815.6 +/- 107.9 pM/l) (p less than 0.01). The high affinity/low capacity compound of insulin receptor, in CB154 rats (51.8 +/- 16.8 pM/l) was higher than in normal rats (18.3 +/- 8.9 pM/l) (p less than 0.005). Additional studies indicated that CB154 had no effect on the rate of association and dissociation of 125I insulin from rats erythrocyte insulin receptors. The degradation of insulin or the erythrocyte receptor sites do not change, after the treatment with CB154.     

Alterations in lung prostaglandin synthesis and release in murine respiratory mycoplasmosis

Pathogenetic mechanisms in murine respiratory mycoplasmosis are poorly understood; however, non-specific immune responses appear to be important in controlling the growth of Mycoplasma pulmonis in vitro. To date, no study has examined the role of pulmonary prostaglandin production during the development of M. pulmonis infection. The present study was designed to determine if alterations in pulmonary prostaglandin synthesis and release occur in M. pulmonis infection and the possible role for prostaglandins in the modulation/pathogenesis of murine respiratory mycoplasmosis. Ten to 20 days after intranasal inoculation of pathogen-fee F344 rats with M. pulmonis, lung lavage concentrations of prostaglandin E (PGE) and thromboxane A2 (TxA2) were significantly elevated. To confirm a role for prostaglandins in the pathogenesis of murine mycoplasmosis we blocked the cyclo-oxygenase pathway with indomethacin. Indomethacin-treated rats had significantly lower lavage levels of PGE and TxA2 and significantly increased numbers of M. pulmonis in the lung. These data indicate that prostaglandins may be involved in the pathogenesis of murine respiratory mycoplasmosis, possibly through alteration of mycoplasmacidal and/or mycoplasmastatic mechanisms.     

Evidence for a noradrenergic transmission in the control of parturition in the rat

6-Hydroxydopamine, when injected at 14:00 h on Days 21 and 22 of pregnancy in the rat (2 X 50 mg/kg), markedly decreased plasma and uterine noradrenaline concentrations (-60% and -82% respectively; P less than 0.001). As a consequence of this treatment, there was severe disturbance in the distribution pattern of parturitions: 61% of rats had suppressed parturition and 31% of rats displayed a lengthened or interrupted labour. A bolus dose of prazosin (3 mg/kg) administered at 12:00 h on Day 22 completely blocked the normal process of parturition throughout the next 6 h, a result which is compatible with the half-life of the drug (2.9 +/- 0.8 h). Administration of phentolamine (3 mg/kg) at term induced a significant decrease of uterine activity (frequency X duration of bursts of spike potentials) as revealed by electromyographic recordings in vivo. These results suggest that noradrenaline released from sympathetic nerve terminals interacts with alpha-adrenoceptors located post-synaptically to improve the overall excitability of the myometrium at the onset of labour.     

Effects of Prenatal and Postnatal Exposure to GSM-Like Radiofrequency on Blood Chemistry and Oxidative Stress in Infant Rabbits, an Experimental Study

We aimed to investigate the potential hazardous effects of prenatal and/or postnatal exposure to 1800 MHz GSM-like radiofrequency radiation (RFR) on the blood chemistry and lipid peroxidation levels of infant rabbits. A total of 72 New Zealand female and male white rabbits aged 1-month were used. Thirty-six female and 36 male were divided into four groups which were composed of nine infants: (i) Group 1 were the sham exposure (control), (ii) Group 2 were exposed to RFR, 15 min daily for 7 days in the prenatal period (between 15th and 22nd days of the gestational period) (prenatal exposure group). (iii) Group 3 were exposed to RFR 15 min/day (14 days for male, whereas 7 days for female) after they reached 1-month of age (postnatal exposure group). (iv) Group 4 were exposed to RFR for 15 min daily during 7 days in the prenatal period (between 15th and 22nd days of the gestational period) and 15 min/day (14 days for male, whereas 7 days for female) after they reached 1-month of age (prenatal and postnatal exposure group). Results showed that serum lipid peroxidation level in both female and male rabbits changed due to the RFR exposure. However, different parameters of the blood biochemistry were affected by exposure in male and female infants. Consequently, the whole-body 1800 MHz GSM-like RFR exposure may lead to oxidative stress and changes on some blood chemistry parameters. Studies on RFR exposure during prenatal and postnatal periods will help to establish international standards for the protection of pregnants and newborns from environmental RFR.     

Alterations in lung prostaglandin synthesis and release in murine respiratory mycoplasmosis

Pathogenetic mechanisms in murine respiratory mycoplasmosis are poorly understood; however, non-specific immune responses appear to be important in controlling the growth of . To date, no study has examined the role of pulmonary prostaglandin production during the development of infection. The present study was designed to determine if alterations in pulmonary prostaglandin synthesis and release occur in infection and the possible role for prostaglandins in the modulation/pathogenesis of murine respiratory mycoplasmosis. Ten to 20 days after intranasal inoculation of pathogen-fee F344 rats with , lung lavage concentrations of prostaglandin E (PGE) and Thromboxane A₂ (TxA₂) were significantly elevated. To confirm a role for prostaglandins in the pathogenesis of murine mycoplasmosis we blocked the cyclo-oxygenase pathway with indomethacin. Indomethacin-treated rats had significantly lower lavage levels of PGE and TxA₂ and significantly increased numbers of in the lung. These data indicate that prostaglandins may be involved in the pathogenesis of murine respiratory mycoplasmosis, possibly through alteration of mycoplasmacidal and/or mycoplasmastatic mechanisms.     

Steroidogenic capacity and ultrastructural morphology of cultured ovine luteal cells

Corpora lutea were surgically collected from superovulated ewes 36 h post-injection of human chorionic gonadotropin (hCG) (Day 2), dissociated (0.2% collagenase), plated, and maintained in culture Days 2-10 in Medium 199 supplemented with 5% calf serum. Accumulation of progesterone in the cultures did not decrease (p greater than 0.05) from Day 3 (17.5 +/- 5.1 nmol/10(6) cells) to Day 10 (4.8 +/- 1.7 nmol/10(6) cells). Calf serum (5%) in the medium supported greater (p less than 0.05) progesterone production than fetal calf serum (5%) or medium without added serum. Steroidogenic cells did not increase (Days 2-10) in numbers, but increased (p less than 0.01) in mean cell diameter (Day 2, 11.7 +/- 0.4 micron; Day 10, 24.5 +/- 1.6 micron). Steroidogenic capacity on Day 10 of cells cultured Days 2-10 (in vitro) was not different (p greater than 0.05) from that of cells collected from the ovary on Day 10 (in vivo); however, steroidogenic cells recovered from plates had greater (p less than 0.01) mean cell diameters (24.5 +/- 1.6 micron, in vitro, compared to 15.2 +/- 1.0 micron, in vivo). Transmission electron microscopy revealed that cultured cells (Days 5, 10) possessed less smooth endoplasmic reticulum but more lipid droplet inclusions, ribosomes, and rough endoplasmic reticulum than cells obtained in situ (Day 10). Electron-dense secretory granules were rarely seen. Although subcellular morphology of ovine luteal cells in culture was altered, these changes did not appear to significantly affect the ability of these cells to produce progesterone.     

Promotion of Mycoplasma pulmonis growth in rat tracheal organ cultures by ammonium chloride

During exacerbation of respiratory mycoplasmosis in rats by environmental ammonia, numbers of Mycoplasma pulmonis organisms in the respiratory tract are increased. To test whether or not exposure of respiratory epithelium to ammonia in vitro promotes growth of the organism, rat tracheal organ cultures were treated with 50 mM ammonium chloride, inoculated with M. pulmonis, and quantitatively cultured. After 48 hours, treated tracheas harbored almost 10 times more M. pulmonis colony-forming units than control tracheas. Cellular lesions in the epithelium of treated tracheas resembled those in the nasal passages of rats exposed to gaseous ammonia. To determine whether or not growth-modifying factors were released from tracheal epithelium exposed to ammonium chloride, M. pulmonis growth was assessed in medium collected from ammonium chloride-treated and control tracheas. Growth in medium from treated tracheas was greater than that in medium from untreated tracheas.     

Characterization of proteins produced in vitro by periattachment bovine conceptuses

Bovine conceptuses from Days 16 (n = 4), 19 (n = 6), 22 (n = 3), and 24 (n = 4), and chorion from Day 69 (estrus/mating = Day 0) were cultured for 24 h in modified minimum essential medium (MEM) in the presence of radioactive L-leucine [( 3H] leucine) to characterize de novo synthesis and release of proteins. Proteins released into MEM were identified by two-dimensional polyacrylamide gel electrophoresis, fluorography, and gel and ion exchange chromatography. Major polypeptides identified in MEM were different from those identified in conceptus and chorionic tissues. Both uptake of [3H] leucine and quality of polypeptides produced de novo and released into MEM were related to stage of conceptus development. Percent retention of [3H] leucine in MEM was lowest (P less than 0.01) in Day 16 cultures (1.2 +/- 4.1%), increased in Days 19 (16.8 +/- 3.7%) and 22 cultures (20.9 +/- 5.8%), and decreased (P less than 0.07) in Day 24 cultures (6.9 +/- 4.1%). Complexity of polypeptides increased after Day 16. Days 16, 19, 22 and 24 conceptus culture MEM was enriched in low-Mr, acidic polypeptides (Mr/isoelectric point ranges: 22K-26K/6.5-5.6, 20K-26K/5.5-5.4, and 16K-20K/5.0-4.5), which were not prominent products of Day 29 and 69 tissues. A high-Mr (Mr +/- SEM; 735K +/- 22K) glycoprotein was produced by all conceptus and chorionic tissues. The transient nature of production of low-Mr polypeptides suggests that they may be required during the periattachment period.     

A morphometric analysis of the corpus luteum of the cow during the estrous cycle and early pregnancy

Corpora lutea were collected from cows on Days 6, 8, 10, 12, 14, 16, 18 and 19 of the estrous cycle and early pregnancy (n=2/d) and were examined by light microscopy. Mean lutein cell diameter was significantly (P<0.05) greater in pregnant than in cyclic cows on Days 6, 8, 10, 12, 16, 18 and 19 (cyclic versus pregnant: Day 6: 13.9 +/- 0.22 vs 14.9 +/- 0.24; Day 8: 13.8 +/- 0.20 vs 15.4 +/- 0.2; Day 10: 14.8 +/- 0.24 vs 17.4 +/- 0.24; Day 12: 13.2 +/-0.25 vs 17.9 +/- 0.31; Day 16: 13.9 +/- 0.28 vs 16.5 +/- 0.31; Day 18: 13.0 +/- 0.22 vs 16.5 +/- 09.36, and Day 19: 15.0 +/- 0.23 vs 17.6 +/- 0.33 mum, respectively). The distribution of cell sizes was leptokurtotic throughout the estrous cycle and the first 10 d of pregnancy, but tended towards bimodality after Day 14 of pregnancy. The proportion of lutein cell cytoplasm occupied by vacuoles was lower in pregnant than in cyclic cows from the 12th day post estrus, but there was a marked (P<0.05) increase in vacuolation of cells from cows undergoing luteolysis. Stainable intercellular collagen was also less abundant in pregnant than cyclic cows from the 12th day post estrus. The higher rate of progesterone secretion of pregnant, compared with cyclic cows may be attributed to the greater numbers and greater contribution to luteal mass of large lutein cells in the corpus luteum of pregnancy.     

Prostacyclin, prostaglandin F2 alpha and progesterone production by bovine luteal cells during the estrous cycle

Corpora lutea (CL) were collected from Holstein heifers on Days 5, 10, 15 and 18 (5/day) of the estrous cycle. Dispersed luteal cell preparations were made and 10(6) viable luteal cells were incubated with bovine luteinizing hormone (LH) and different amounts of arachidonic acid in the presence and absence of the prostaglandin (PG) synthetase inhibitor indomethacin. The concentrations of progesterone, PGF2 alpha and 6-keto-PGF1 alpha, the stable inactive metabolite of prostacyclin (PGI2), were measured. Day 5 CL had the greatest initial content of 6-keto-PGF1 alpha (1.01 +/- 0.16 ng/10(6) cells), and synthesized more 6-keto-PGF1 alpha (2.55 +/- 0.43) than CL collected on Days 10 (0.57 +/- 0.11), 15 (0.08 +/- 0.05) and 18 (0.19 +/- 0.03) during a 2-h incubation period. Arachidonic acid stimulated the production of 6-keto-PGF1 alpha by Days 10, 15 and 18 luteal tissue. PGF2 alpha was produced at a greater rate on Day 5 (0.69 +/- 0.17 ng/10(6) cells) than on Days 10 (0.06 +/- 0.01), 15 (0.04 +/- 0.02) and 18 (0.08 +/- 0.01). Arachidonic acid stimulated and indomethacin inhibited the production of PGF2 alpha, in most cases. The initial content of 6-keto-PGF1 alpha was higher than that of PGF2 alpha on all days of the cycle and more 6-keto-PGF1 alpha was synthesized in response to arachidonic acid addition. The ratio of 6-keto-PGF1 alpha content to PGF2 alpha content was 4.39, 2.30, 1.25 and 1.13 on Days 5, 10, 15 and 18, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)