The relationship between ovarian follicular steroidogenesis and insulin-like growth factor binding protein (IGFBP) activity was evaluated during the follicular phase of the bovine estrous cycle. In experiment 1, follicles were collected from cyclic cows (n = 11) slaughtered at 48 h after administration of prostaglandin F2 alpha (PGF; 35 mg i.m.). In experiment 2, cows were injected twice daily with saline (control) or FSH (FSH cows; total dosage = 42 mg) from Day 2 to Day 6 (estrus = Day 0) and with PGF (35 mg i.m.) on Day 7; follicles were collected from control cows (n = 20) slaughtered at 0, 24, 48, or 72 h and from FSH cows (n = 8) at 0 and 48 h after PGF. Follicular fluid was assayed for estradiol (E2), androstenedione (A4), progesterone (P4), and insulin-like growth factor-I (IGF-I) by RIA and for IGFBP activity by ligand blotting and densitometry. Intensities of the 34-kDa (IGFBP-2), 29-27-kDa, and 22-kDa IGFBP bands in follicular fluid were nondetectable or were lower (p < 0.01) in the fluid of large (> or = 8 mm) E-active (E-A; E2 > 50 ng/ml and > P4) follicles than in large E-inactive (E-I), medium (5-7 mm), or small (< 5 mm) follicles. IGFBP-3 (44-40-kDa doublet) was unaffected by follicle stage in experiment 1, but IGFBP-3 was lower (p < 0.01) in follicular fluid of E-A vs. E-I large follicles in experiment 2. Profiles of IGFBP activity were similar in follicular fluid of small, medium, and E-I large follicles. In experiment 2, E2 concentrations in large E-A follicles increased (p < 0.01) from 0 to 48 h after the PGF injection for control cows but decreased (p < 0.01) for FSH cows, whereas follicular fluid IGFBP-2 binding activity decreased from 0 to 48 h after PGF in controls and increased in FSH cows (treatment x time, p < 0.05). IGFBP-3 binding was unaffected by FSH treatment or time after administration of PGF. Profiles of IGFBP activity in homogenates of granulosa or theca cells were similar to follicular fluid profiles except for the absence of IGFBP-3 binding activity. The disappearance of binding activities for IGFBP-2 and smaller-molecular-mass IGFBPs in E-A follicles suggests a possible regulatory role for IGFBPs in follicular maturation and on aromatase activity.(ABSTRACT TRUNCATED AT 400 WORDS)

1. Two experiments were conducted to assess the effects of lighting regime, dietary calcium source and sodium bicarbonate on production variables and egg shell quality of White Leghorn hens. In both experiments, hens were assigned to one of three lighting programmes that provided evening, morning or intermittent (midnight) lighting supplements in addition to natural daylight. Experimental diets used in the first study were formulated to contain (1) ground oyster shell flour, (2) limestone flour, or (3) and (4) the same +2/3 of the calcium source as hen-size oyster shell grit. The same 4 diets plus those containing hen-size limestone or hen-size limestone and oyster shells were used in experiment II. Additionally, diets in the first experiment contained either 0 or 10 g/kg sodium bicarbonate. 2. Hen-day egg production and food consumption were not affected by any of the experimental treatments. Hens fed on oyster shell diets or exposed to intermittent lighting regimes laid eggs of the highest specific gravity. Shell quality, as measured by specific gravity, was not affected by the addition of dietary sodium bicarbonate. 3. As expected, elevated temperatures (greater than 32 degrees C) significantly reduced egg shell quality. However, this effect was variable particularly in experiment II which used younger hens. 4. The shell quality of eggs from hens exposed to intermittent lighting in experiment II was significantly higher in each of the 4 sampling periods: morning (08.00-12.00), afternoon (12.00-16.00), evening (16.00-20.00) and night (20.00-08.00). 5. It is suggested that midnight lighting programmes provide a means of supporting egg shell quality of older laying hens during the summer months without a significant reduction in egg production.

The influence of life span-prolonging dietary energy restriction on hepatic expression of glucose-regulated protein 78 and 94 (GRP78 and GRP94) RNA was investigated in female C3B10RF1 mice. Mice were either fed ad libitum or fed diets reduced 20 or 40% in energy but containing approximately equivalent amounts of protein, fats, vitamins and minerals. Aging produced no changes in GRP mRNA. However, GRP78 and GRP94 mRNA levels were reduced approximately 50 and 40%, respectively, by 40% energy restriction. This level of energy restriction produced a 43% reduction in the mean plasma glucose levels of young and old mice. The changes in GRP mRNA expression appear to be specific, because the levels of these RNAs were normalized to the level of polyadenylated RNA, and no changes were detected in the levels of a number of other mRNAs. Although extreme glucose deprivation increases GRP mRNA levels in cultured cell lines, physiologically relevant reductions in blood glucose had the opposite effect in the liver, in vivo. The regulatory pathway responsible for these effects is not known. GRP mRNA levels are elevated by agents that increase the level of malfolded proteins in the endoplasmic reticulum. Thus, energy restriction may act to reduce malfolded proteins in the endoplasmic reticulum of hepatic cells.