Chronic hypoxia diminishes pregnancy-associated DNA synthesis in guinea pig uteroplacental arteries.

Enlargement of the uterine artery (UA) during pregnancy is diminished in women residing at a high altitude. We asked whether chronic hypoxia alters the rise in DNA synthesis in uteroplacental vessels and, if so, whether the reduction is related to the intrauterine growth retardation (IUGR) observed under conditions of chronic hypoxia. We used bromodeoxyuridine (BrdU) labelling to measure DNA synthesis in all vascular layers of the UA, mesometrial arteries (MA), thoracic aorta and mesenteric artery of guinea pigs, residing throughout pregnancy at a low (1600 m) or high (3962 m) altitude. Pregnancy increased DNA synthesis throughout the UA at both altitudes, yet the maximal value was less at high than low altitude (P<0.05). Likewise, pregnancy increased DNA synthesis throughout the MA, yet at high altitude pregnancy elevated levels returned to non-pregnant values after 42 days of gestation, whereas at low altitude DNA synthesis continued to be elevated until near term. Fetal weights were lower (P=0.01) and placental/fetal weight ratios tended to be greater in high than low altitude, near term pups (P = 0.09). We conclude that a diminished growt response by the uteroplacental vasculature to pregnancy may contribute to the previously reported reduced uterine artery blood flow and resulting IUGR at high altitude.

Relaxin stimulates uterine edema via activation of estrogen receptors: blockade of its effects using ICI 182,780, a specific estrogen receptor antagonist.

Relaxin's ability to stimulate uterine growth is well established. The mechanisms by which relaxin exerts this effect, however, remain unclear. In light of previous work demonstrating peptide growth factor activation of estrogen receptors (ERs), the present study was conducted to determine if relaxin similarly stimulates ERs. Twenty-five day-old female Sprague-Dawley rats were bilaterally ovariectomized and treated with estradiol or porcine relaxin alone or in combination with the ER antagonist ICI 182,780. Following treatment with 17beta-estradiol or relaxin alone, the uterine weight/body weight ratio (UtW/BW) increased significantly over control values (+98% and +77% respectively, p<0.0003). Pre-treatment of animals with ICI 182,780 (3 microg/g BW) prior to either estradiol or relaxin treatment completely inhibited the hormone-induced increases in uterine weight (p<0.0005). ICI 182,780 alone had no significant effect. Histological analysis of uterine cross-sections revealed that the edema present in the endometrium of animals treated with estradiol or relaxin alone was completely absent in the uteri of animals pre-treated with ICI 182,780. These data indicate that relaxin-induced uterine edema and growth is mediated by ERs.

In vitro cytotoxicity of amalgams made with binary Hg-In liquid alloys.

OBJECTIVE: Mercury vapor release from amalgams during setting significantly decreases when the amalgams are prepared with binary Hg-In liquid alloys. The objective of this study was to compare the cytotoxicity of amalgams made with experimental Hg-In alloys with that of amalgam without In and a commercial In-containing amalgam. METHODS: Amalgam specimens were prepared by triturating a high-Cu alloy powder (Tytin, Kerr) with pure Hg or Hg-In liquid alloy containing 5, 20 or 50% In and also by triturating an In-containing high-copper alloy powder (Indiloy, Shofu) with pure Hg. After the specimens were aged for 2 wk, a cylindrical specimen of each amalgam was immersed consecutively in cell culture medium for 0-8, 8-48 and 48-72 h. The cytotoxicity of the extracts was determined by placing them in contact with Balb/c 3T3 mouse fibroblasts for 24 h, after which the succinic dehydrogenase (SDH) activity was measured and expressed as a percentage of the Teflon negative controls. The results were statistically compared using ANOVA and Tukey's test (alpha = 0.05). The concentration of elements released into the extracts was determined by atomic absorption spectrophotometry and evaluated by Kruskal-Wallis and nonparametric multiple comparisons. RESULTS: For the 0-8 h and 8-48 h intervals, the 20% In amalgam was significantly (p < 0.05) less toxic than the other amalgams, and not different from the Teflon control. Results for the other amalgams were only slightly depressed compared to the Teflon control. For the 48-72 h interval, all amalgams were essentially no different from the control. Copper was the element dominantly released into the medium from all the amalgams tested. SIGNIFICANCE: For amalgam tested after aging, alloying indium to mercury did not deleteriously affect the cytotoxicity of the resultant amalgam compared to the amalgam without indium.

Determination of the flavor attributes of cooked beef from cross-bred Angus steers fed corn- or barley-based diets.

Eighteen commercial Angus cross-bred feedlot steers of similar hip height and live weight were randomly assigned to one of three dietary treatment groups: corn-, corn/barley, or barleybased diets (n = 6 per treatment). Steers were fed for 102-103 days on their respective diets prior to slaughter. Live animal performance traits, carcass characteristics, total lipid and descriptive flavor and descriptive palatability attributes of beef strip loin steaks were determined. End live weight (P = 0.88) did not differ between dietary treatments. Beef carcasses from steers fed corn-, barley-, and corn/barley-based diets did not differ in hot carcass weight (P = 0.18), ribeye area (P = 0.21), kidney, pelvic and heart fat (KPH) (P = 0.35), and yield grade (P = 0.14). However, adjusted preliminary yield grade was higher (P = 0.03) for carcasses from steers fed corn/barley-based diets than carcasses from steers fed barley as the dietary energy source. These data suggest that carcasses from steers fed barley-based diets were lower in external fat. Quality grade characteristics were not different in beef carcasses from steers fed either corn-, barley-, or a corn/barley-based diet. Cook time (P = 0.37), cooking loss (P = 0.83), descriptive meat palatability attributes (P > 0.27), Warner-Bratzler shear force (P = 0.25), and descriptive sensory flavor attributes (P ≥ 0.17) did not differ for steaks from steers fed the three diets prior to slaughter. The Japanese have claimed that feeding cattle barley-based high energy diets result in beef with different flavor than when cattle are fed high-energy corn-based diets. These results indicated that the eating quality, tenderness and flavor attributes of beef steaks were not influenced by the dietary grain source fed to young steers in this study prior to slaughter.