Embryotoxic effects of prenatal T-2 toxin exposure in mice.

Pregnant CD-1 mice were administered T-2 toxin by gastric intubation on day 11 of gestation at dosages of 0, 0.75 and 1.5 mg/kg. The T-lymphocyte dependent antibody response against sheep red blood cells which was evaluated in the offspring at six weeks of age was not affected by T-2 toxin exposure. Individual birth and weaning weights were not influenced by T-2 toxin, but the litter size was reduced in the high dose group, without affecting the number of implantation sites per dam. The number of female offspring produced by dams exposed to 1.5 mg/kg T-2 toxin was less compared to other treatment groups, suggesting that the female fetus was more susceptible to embryolethal effects of prenatal T-2 toxin exposure. These results suggest that prenatal T-2 toxin exposure is unlikely to be a significant health problem with respect to primary humoral immunity. At the dosages given, T-2 toxin produced substantial embryotoxicity without alteration in antibody production. The embryolethal effects are a primary limiting factor which may preclude the expression of any immunoteratological manifestations associated with humoral immunity under natural field conditions.     

The effects of acute exposure to deoxynivalenol on some inflammatory parameters in miniature pigs

Seven miniature pigs were injected intravenously with deoxynivalenol (DON) at 1 mg/kg body weight; afterward, the number of leukocytes in peripheral blood, the luminol-dependent chemiluminescence of neutrophils, the serum or plasma concentration of cytokines and acute-phase proteins were evaluated to determine the effects of acute exposure to DON on inflammatory responses. White blood cell counts were transiently increased at 3, 6, and 12 hr post-injection (PI) due to the increased number of neutrophils. The luminol-dependent chemiluminescence value of neutrophils was significantly elevated at 24 hr PI, indicating the activation of the bactericidal function of neutrophils. Significant increases of interleukin (IL)-8 and tumor necrosis factor-α at 3 hr PI and IL-6 at 6 hr PI were detected in the serum. The concentration of haptoglobin and serum amyloid A was significantly increased at 24 hr PI. These results suggest that acute exposure to DON induced a temporary recruitment of neutrophils in the peripheral blood by IL-8 and subsequent activation of the bactericidal function, and a transient increase of proinflammatory cytokines and acute-phase proteins, indicating the immunomodulatory effects of DON in pigs.     

Hematologic effects of exposure to three infective agents in rabbits

Infectious disease is typically accompanied by changes in the number and types of circulating leukocytes. To examine the effects of infectious challenge on the distribution of rabbit WBC, rabbits were inoculated IV with Streptococcus pyogenes, Escherichia coli, or Candida albicans. Blood was collected prior to and every 6 to 12 hours after inoculation for 48 hours. Infectious challenge did not substantially alter total WBC counts, but did cause neutrophilia and lymphopenia for 6 to 48 hours after inoculation. Similar patterns of leukocyte distribution were observed in rabbits with naturally developing clinical problems. Thus, high total WBC counts may not be a common characteristic of acute infectious conditions in rabbits, but differential distributions of various leukocyte populations can provide useful markers of disease in this species.     

The effects of exposure of susceptible alpacas to alpacas persistently infected with bovine viral diarrhea virus

Reports of bovine viral diarrhea virus (BVDV) infections in alpacas have been increasing in recent years but much is still unknown about the mechanisms of disease in this species. This report characterizes the transmission of BVDV from persistently infected (PI) alpacas to BVDV naïve alpacas, documents shedding patterns, and characterizes the disease effects in both PI and transiently infected alpacas. Two PI alpacas shed BVDV Type 1b virus in most body fluids, and commonly available diagnostic tests verified their status. Bovine viral diarrhea virus Type 1b transient infections produced only mild signs of disease in BVDV naïve alpacas. Viremia was detected in whole blood, but viral shedding during the acute phase was not detected and antibody appeared to be protective upon re-exposure to the virus.     

The effects of chronic intermittent noise exposure on broiler chicken performance

Effects of different noise levels (70 or 80 dB) that broilers were exposed to during the entire fattening period and also the effect of the timing of the first exposure to intermittent noise in the course of fattening (day 1 vs. day 7) were monitored. After 7 days of exposure to intermittent noise, experimental chickens already showed a significant decrease in live body weight in comparison with the control group. The difference between the group exposed to intermittent noise at 70 dB and the group exposed to 80 dB levels was not statistically significant, although the mean live body weight of broilers in the latter was lower during the entire fattening period. The chickens exposed to intermittent noise from day 1 of age showed lower mean live weight throughout the fattening period compared to chickens exposed to the same level of intermittent noise only from day 7 of age, although at the end of fattening the difference was statistically significant only in chickens exposed to the higher level of intermittent noise (80 dB).     

Masculinization of the distal tubular and external genitalia in female sheep with prenatal androgen exposure

Prenatal exposure to endogenous or exogenous androgens alters the development of the female reproductive tract. Although lesions in ovaries and external genitalia of androgenized female sheep have been reported, lesions of the tubular genitalia have not. Testosterone propionate (TP) or dihydrotestosterone (DHT) was administered by intramuscular injection twice weekly to 32 ewes from 30 to 90 days of pregnancy. The ewes lambed normally. The reproductive tracts from 24 treated and 13 control postpubertal female offspring were examined at 10 months of age. The ovaries, oviducts, and uteri were grossly and histologically normal in both TP- and DHT-exposed sheep. However, in the DHT-treated sheep, the uterus connected to a misshapen, saccular vagina that opened into the urethra; in the TP-treated sheep, it ended in a blind sac. In both TP- and DHT-treated sheep, the urethra was approximately 5 times longer than that of control sheep, and it resembled a male urethra with bilateral male accessory genital glands. The urethra terminated in a fully developed penis in both TP- and DHT-treated sheep, and a scrotal sac was present (without testes). These results show that prenatal exposure of female sheep to exogenous androgens results in masculinization of the tubular and external genitalia.     

Acute and long-term effects of exposure to sodium monofluoroacetate (1080) in sheep

Acute and long-term effects of a single, relatively high oral dose (0.25 and 0.30 mg/kg) of sodium monofluoroacetate (1080) on the survival and productivity of sheep were evaluated to establish a better understanding of 1080 poisoning and identify more specific changes diagnostic of toxicosis. In survivors, clinical signs of acute 1080 toxicosis such as salivation and lethargy were generally very mild. Fasted animals were more prone to 1080 toxicity. In animals that died, more severe signs, including tachypnoea, dyspnoea, and tremors occurred for 15-20 min prior to death. 1080 concentrations were highest in the blood > heart > skeletal muscle > liver. 1080 could not be detected in any of these organs of the animals that survived. Serum citrate concentrations were elevated for 4 days after dosing. No clinical or biochemical abnormalities were found in any animal after 4 days. Histopathological lesions were most marked in the heart and lung with inflammation, necrosis, and scattered foci of fibrous tissue in the myocardium, pulmonary oedema and inflammation of the lung. No adverse long-term effects on general health or reproductive performance were observed in any sheep that survived the first 4 days following exposure to 1080. The most reliable diagnostic indicators of 1080 exposure in sheep were measurement of its residues in blood, skeletal muscle and ruminal contents, increased serum citrate concentration, elevated heart rate, and characteristic electrocardiograph changes (up to 4 days after exposure). Death from 1080 is most likely to occur within 96 h, and animals that survived this period appeared normal.     

铅镉联合急性中毒对大鼠脏器病理组织学和超微结构的影响

按照等毒性配比法混合硝酸铅与氯化镉溶液进行急性毒性试验,采用Bliss法和Keplinger标准进行毒性评价,并应用光镜和电镜观察大鼠染毒后各脏器的显微与超微结构变化。探讨硝酸铅（Pb（NO3）2）与氯化镉（CdCl2·2．5H2O）溶液联合经口灌胃对SD大鼠的急性毒性效应。结果显示,铅镉联合作用下大鼠的绝对致死量（LD100）为5062．00mg／kg,最大耐受浓度（MTD）为1436．00mg／kg,半数致死量（LD50）为2696．54mg／kg,95％可信区间是2162．00～3362．89mg／kg。铅镉联合急性中毒的靶器官为肝脏、肾脏和脾脏,光镜下,主要表现为血管发生不同程度的充血和溶血、实质细胞发生不同程度的变性（水泡变性和颗粒变性）和坏死。电镜下,主要表现为细胞器结构破坏。结果表明,硝酸铅和氯化镉联合急性毒性为相加作用,对大鼠肝脏、肾脏和脾脏均有不同程度的急性毒性损伤。     

The effect of divergent selection for uterine capacity on prenatal survival in rabbits: maternal and embryonic genetic effects

The aim of this work was to determine whether prenatal survival depends on the genotype of the mother or of the embryo and to identify the critical periods for prenatal mortality in two lines of rabbits divergently selected by high (H) and low (L) uterine capacity. Does from H (n = 124) and L (n = 115) lines were slaughtered at 72 h of gestation. Embryos recovered at 72 h of gestation were transferred to the oviducts of recipient does from the H (n = 23) and L (n = 19) lines. Each recipient does received eight embryos from the H line into one oviduct and eight embryos from the L line into the other. Recipient does were slaughtered on d 28 of gestation. No differences were found between lines in the embryo recovery either in ovulation rate (OR) or in fertilization rate of ova recovered. Recovery rate was higher for the H line (0.80 vs. 0.72, P < 0.01). The number of embryos recovered, fitting ovulation rate as a covariate, was also higher for the H line (9.74 vs. 8.78, P < 0.05). The H line showed a more advanced embryonic stage of development, having a higher percentage of blastocysts (PB) and a lower percentage of compact morulae (PCM) (38% vs. 20%, P < 0.001 for PB, and 51% vs. 64%, P < 0.01 for PCM). The percentage of early morulae was low and similar in both lines. Neither donor nor recipient lines affected embryonic survival from 72 h to 7 d of gestation. Fetal survival was affected by the recipient line (P < 0.05). An interaction between donor and recipient was found. Embryos from the H donor line had a better fetal survival rate than embryos from the L donor line (P < 0.05) in H recipient females. Within L recipient females, embryos from H and L donor lines showed similar fetal survival. Fetal survival was divided into early (from d 7 to 17 of gestation) and late (from d 17 to 28 of gestation). The high recipient line showed a higher early fetal survival than the L recipient line (P < 0.05). The same effect was observed for late fetal survival, but the difference between H and L recipient lines was lower (P < 0.10). Thus, fetal survival depends mainly on the maternal genotype, and the embryo genotype only affects fetal survival when embryo transfer is performed to a favorable maternal environment. Selection for uterine capacity in rabbits leads to modification of early embryonic survival and of early and late fetal survival, but differences are higher for early than for late fetal survival.     

Breed prenatal, breed postnatal and heterosis effects for postweaning traits in swine

Crossfostering techniques were used to evaluate breed prenatal, breed postnatal and heterosis effects in Duroc and Yorkshire swine. Traits analyzed for these effects were: age adjusted to 104 kg (DAYS), backfat adjusted to 104 kg (AJBF), average daily gain (ADG), weight/day of age (WDA), unadjusted backfat (BF) and weight at 154 d (WT154). Breed prenatal (genetics and prenatal maternal) effects were important for BF and WT154 (P less than .10). Pigs gestated by Duroc dams tended to be fatter and weigh more at 154 d than pigs from Yorkshire dams. Breed postnatal effects were important only for AJBF (P less than .05). Pigs reared by Duroc nurses were fatter than pigs reared by Yorkshire nurses. Prenatal dam x postnatal nurse interaction effects were important for BF (P less than .10) and AJBF (P less than .05). Heterosis values were -10.2, 8.0, 13.7, 13.6, 14.1 and 7.7% for DAYS, AJBF, ADG, WDA, WT154 and BF, respectively. Differences between purebred and crossbred pigs were larger when purebred and crossbred pigs were reared in the same litter than when reared separately. These data suggest that intra-litter competition between purebred and crossbred pigs may have a detrimental effect on postweaning growth for purebred pigs.     

The response of broilers' adiposity to testosterone after embryonic exposure to androgen and tamoxifen

1. The effects of early exposure of heavy breed (HB) chicks to an anti-oestrogen (tamoxifen--TAM) and to an androgen which cannot be aromatised (5 alpha-dihydrotestosterone--DHT) on subsequent adiposity and its response to testosterone were studied. 2. Embryonic TAM administration reduced adiposity in females but not in males at 8 weeks of age. Embryonic DHT produced similar responses but to a lesser extent. 3. Testosterone propionate (TP) administration during growth had no effect on adiposity in any of the treated groups but TP reduced adiposity in males which had been exposed to DHT at the embryonic stage.     

Combined effects of diet and cold exposure on insulin responsiveness to glucose and tissue responsiveness to insulin in sheep.

Hyperglycemic clamp and hyperinsulinemic euglycemic clamp techniques were used to investigate effects of diet and cold exposure on insulin responsiveness to glucose and tissue responsiveness and sensitivity to insulin in adult rams. The sheep were fed a high-concentrate diet (80% concentrate and 20% roughage) and a high-roughage diet (20% concentrate and 80% roughage), both 70% above the ME requirement for maintenance, and were exposed to a thermoneutral environment (20 degrees C) and a cold environment (0 degrees C) for 2 wk. The estimated ME intake was greater (P < .01) for the high-concentrate diet than for the high-roughage diet. In the hyperglycemic clamp experiment, the ratio of the plasma insulin increment to the glucose infusion rate (insulin responsiveness to glucose) was lower during cold exposure than in the thermoneutral environment in sheep fed the high-concentrate diet but was unchanged in sheep fed the high-roughage diet. In the hyperinsulinemic euglycemic clamp experiment, the glucose infusion rate (tissue responsiveness to insulin) was higher (P < .01) for the high-concentrate diet than for the high-roughage diet, and it was also higher (P < .01) during cold exposure than in the thermoneutral environment, indicating that tissue responsiveness to insulin was intensified in sheep fed the high-concentrate diet during cold exposure associated with the higher energy intake. These results suggest that both reduced insulin responsiveness and enhanced tissue responsiveness to insulin in sheep exposed to cold were dependent on the type of diet.     

Early exposure to probiotics in a canine model of atopic dermatitis has long-term clinical and immunological effects

Probiotics modulate the immune response and may have protective effects against atopic dermatitis (AD). Clinical trials using dogs with spontaneous disease are limited by confounding factors such as different diets, environments and sensitizations while a more controlled evaluation is possible using experimental models. A validated model of canine AD showed that early exposure to Lactobacillus rhamnosus GG (LGG) significantly decreases allergen-specific IgE and partially prevents AD in the first 6 months of life. This study is a follow-up three years after discontinuation of LGG. Clinical signs were evaluated after allergen challenge with ragweed, timothy, Dermatophagoides farinae. Allergen-specific IgE, IL-10 and TGF-β were measured on the 1st day of challenge, before allergen exposure. Normal dogs were included as controls. Analyses included seven dogs in the non-probiotic and nine in the probiotic litter. For clinical scores, a 2-Group × 9-Time Analysis of Variance showed significant effects of group (p=0.0003, probiotic相似文献   

Pilot study to assess the effects of early flea exposure on the development of flea hypersensitivity in cats

This pilot study was to determine if early oral flea exposure reduces the incidence of flea allergy dermatitis (FAD) in cats. Eighteen kittens, assigned to three groups, received no flea exposure, oral flea exposure or flea infestation for 12 weeks. Then all the kittens were exposed continually to fleas for 31 weeks. Sensitization was monitored using intradermal testing (IDT), in vitro measurement of anti-flea saliva immunoglobulin E (IgE) and development of FAD. There was no statistically significant difference between groups in IDT reactions, in vitro data or clinical scores. The development of FAD was not associated with the presence of anti-flea saliva IgE. However, the development of a delayed reaction to flea bite was associated with symptoms after flea exposure. Although not statistically significant, the FAD scores in the oral group were lower than in the controls. Further studies are required to determine the role of oral flea exposure in the development of FAD in cats.     

Mouse epidermal development: effects of retinoic acid exposure in utero

Epidermal morphogenesis was studied in vivo following prenatal exposure to retinoic acid (RA). In pregnant mice, a single oral dose of RA on day 11.5 of gestation failed to induce histological changes in fetal epidermal development except in epidermal thickness. Epidermal thickness increased from 16.5 days post-coitum (dpc) onwards, and temporal and spatial epidermal modifications in keratins K5 and K14 related to proliferative activity of keratinocytes were observed. An RA effect on cell proliferation was supported by a statistically significant increase in the number of epidermal S-phase cells, containing BrdU-incorporated DNA in RA-exposed mice compared with nonexposed animals. The prolonged in utero action of RA on epidermal proliferative activity in fetuses and newborns suggests a long-term RA effect that may play a role on the development and evolution of diseases in adult skin.