Attempts have been made to increase nutrient availability for milk production by increasing feed intake, optimizing ruminal fermentation, and supplementing nutrients to the diet that will escape ruminal degradation. Energy and N are the nutritional factors that most often limit microbial growth and milk production. Ruminal fermentation and flow of microbial and dietary protein to the small intestine are affected by feed intake and by the amount and source of energy and protein in the diet. Feeding protein and carbohydrate that are not degraded in the rumen increases the quantity of dietary protein that passes to the small intestine but may decrease the quantity of microbial protein that is synthesized in the rumen. This often results in only small differences in the total NAN that passes to the small intestine. Because microbial protein supplies a large quantity of total AA that passes to the small intestine, differences in passage of individual AA often are only slight. Additional research with cows consuming large amounts of feed are needed to identify combinations of feed ingredients that synchronize availabilities of energy and N for optimizing ruminal digestion, microbial protein synthesis, nutrient flow to the small intestine, and milk production and composition.

Estrogen and progesterone modulate gene expression in rodents by activation of intracellular receptors in the hypothalamus, which regulate neuronal networks that control female sexual behavior. However, the neurotransmitter dopamine has been shown to activate certain steroid receptors in a ligand-independent manner. A dopamine receptor stimulant and a D1 receptor agonist, but not a D2 receptor agonist, mimicked the effects of progesterone in facilitating sexual behavior in female rats. The facilitory effect of the neurotransmitter was blocked by progesterone receptor antagonists, a D1 receptor antagonist, or antisense oligonucleotides to the progesterone receptor. The results suggest that in rodents neurotransmitters may regulate in vivo gene expression and behavior by means of cross-talk with steroid receptors in the brain.

We describe the Navy Prototype Optical Interferometer (NPOI), a joint project of the Naval Research Laboratory (NRL) and the US Naval Observatory (USNO) in cooperation with Lowell Observatory. The NPOI has recently begun operations at the Lowell Observatory site near Flagsta †, Arizona, obtaining its Ðrst images, of a binary star, in 1996 May and June and its Ðrst limb-darkening observations during 1996 November to 1997 February. This paper gives an overview of the NPOI, including the characteristics of optical interferometry that a †ect its design.The NPOI includes subarrays for imaging and for astrometry. The imaging subarray consists of six moveable 50 cm siderostats feeding 12 cm apertures, with baseline lengths from 2.0 to 437 m. The astrometric subarray consists of four Ðxed 50 cm siderostats feeding 12 cm apertures (35 cm apertures to be installed in 1998), with baseline lengths from 19 m to 38 m. The shared back end covers 450È850 nm in 32 channels. The NPOI features vacuum feed and delay systems, active group-delay fringe tracking, and a high degree of automation. The astrometric subarray also includes an extensive site laser metrology system to measure the motions of the siderostats with respect to one another and to the bedrock.For imaging stellar surfaces, arrays with equal spacing between elements are superior to arrays that have been laid out to optimize (u, v) coverage and that therefore have unequal spacing. The imaging subarray of the NPOI provides a number of equally spaced conÐgurations with linear scales at ratios of B1.64. Unequally spaced conÐgurations are available for a variety of other imaging programs. Coherence across either type of imaging conÐguration is maintained by "" phase bootstrapping ÏÏ : the phases on the longest baselines, on which fringes may be too weak to track, are stabilized by tracking fringes on the shortest baselines.In principle, the four elements of the astrometric subarray provide enough independent baselines to solve for stellar positions and the array geometry simultaneously while observing each of 11 stars only once.The anticipated magnitude limit is 7 mag or better with 12 cm apertures and average seeing ; with 35 cm apertures, we expect the limit to be one or more magnitudes fainter. The anticipated wide-angle astrometric precision of the NPOI is B2 mas. The best angular resolution of the imaging subarray will be B200 kas. Our experience with the Mark III interferometer suggests that we will be able to measure stellar diameters as small as 200 kas with 1% precision and binary star separations as small as o B 65 kas (for *m B 0 mag) or o B 200 kas (for *m B 3È4 mag). With its large bandwidth and phase bootstrapping, the imaging subarray should be able to make images resolution elements across the disks Z10 of nearby late-type stars.

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Six multiparous Holstein cows (average 31 days in milk; 36.3 kg/d of milk) fitted with ruminal cannulas were used in a 6 x 6 Latin square with 21-d periods to investigate the effects of diets that varied in forage source and amount of supplemental tallow. Isonitrogenous diets in a 2 x 3 factorial arrangement were based on either high corn silage (40:10 corn silage to alfalfa silage, % of dry matter) or high alfalfa silage (10:40 corn silage to alfalfa silage, % of dry matter) and contained 0, 2, or 4% tallow. Intakes of dry matter and total fatty acids were lower when cows were fed the high corn silage diet. Tallow supplementation linearly decreased dry matter intake. Milk yield was unaffected by diet; yields of milk fat and 3.5% fat-corrected milk were higher for the high alfalfa silage diet but were unaffected by tallow. Milk fat percentage was higher for the high alfalfa silage and tended to decrease when tallow was added to the high corn silage diet. Contents of trans-C18:1 isomers in milk fat were increased by high corn silage and tallow, and tended to be increased more when tallow was fed in the high corn silage diet. Ruminal pH and acetate:propionate were lower when high corn silage was fed. Ruminal acetate:propionate decreased linearly as tallow increased; the molar proportion of acetate was decreased more when tallow was added to the high corn silage diet. Ruminal liquid dilution rates were higher for the alfalfa silage diet; ruminal volume and solid passage rates were similar among diets. Total tract apparent digestibilities of dry matter, organic matter, crude protein, starch, energy, and total fatty acids were unaffected by diet. Digestibilities of neutral detergent fiber, acid detergent fiber, hemicellulose, and cellulose were lower when high corn silage was fed. The high alfalfa silage diet increased intakes of metabolizable energy and N, and increased milk energy and productive N. Tallow decreased the amount of N absorbed but had few other effects on utilization of energy or N. Tallow linearly increased concentrations of nonesterified fatty acids and cholesterol in plasma; cholesterol was increased by high alfalfa silage. Overall, forage source had more pronounced effects on production and metabolism than did tallow supplementation. Few interactions between forage source and tallow supplementation were detected except that ruminal fermentation and milk fat content were affected more negatively when tallow was fed in the high corn silage diet.

Six cows were utilized in a 6 x 6 Latin square design with 21-d periods to determine effects of the postruminal profile of fatty acids on dry matter (DM) intake, milk yield and composition, nutrient digestibilities, and plasma metabolites. Treatments were abomasal infusions of 1) control [168 g/d of meat solubles (carrier for fatty acids) plus 10.6 g/d of Tween 80 (emulsifier)], 2) control plus 450 g/d of mostly saturated fatty acids, 3) control plus 450 g/d of palm oil fatty acids low in linoleic acid, 4) control plus 450 g/d of palm oil fatty acids, 5) control plus 450 g/d of soybean oil fatty acids, and 6) control plus 450 g/d of soybean oil fatty acids high in palmitic acid. Treatments 2, 3, 4, and 6 contained similar ratios of C16 to C18 fatty acids. Infusion of soybean oil fatty acids or soybean oil fatty acids high in palmitic acid decreased intakes of DM, organic matter, crude protein, acid detergent fiber, neutral detergent fiber, gross energy, and total fatty acids and tended to decrease yields of milk and fat-corrected milk compared with the infusion of mostly saturated fatty acids. Infusion of palm oil fatty acids low in linoleic acid or palm oil fatty acids decreased milk fat percentage compared with other treatments. Ruminal characteristics and apparent digestibilities of DM, organic matter, crude protein, acid detergent fiber, neutral detergent fiber, energy, total fatty acids, and total C18 fatty acids were not different. Infusion of fatty acids increased concentrations of cholesterol in plasma. The amount of unsaturated fatty acids passing into the small intestine may influence responses of dairy cows to supplemental fat.

Nitric oxide (NO), an active free radical formed during the conversion of arghnine to citrulline by the enzyme NO synthase (NOS), mediates vasorelaxation, cytotoxicity, and neurotransmission. The hypothalamic hypophysiotropic peptide hormone, LHRH, not only releases LH from the pituitary but also induces sexual behavior (14,17). LHRH induces lordosis after mounting by the male in estrone-primed ovariectomized (17) and estradiol benzoate-primed adrenalectomized female rats (18). These observations raise the possibility that NO might also be involved in the mediation of sexual behavior in female rats. In the present experiments, we investigated the effect(s) of agents that enhance or inhibit NO formation on the sexual behavior of female rats. The results indicate a crucial role for NO in LHRH-potentiated mating behavior as measured by the lordosis response in estrogen (E)-primed ovariectomized female rats. MATERIALS AND METHODSOvariectomized Sprague-Dawley rats (160-180 g body weight) obtained from Sasco (Houston) were housed with a 12/12-h light/dark cycle and given food and water ad libitum. All the animals were administered hormones and tested for sex behavior. 173-Estradiol benzoate (herein used as E; 10 ,ug in sesame oil) was injected subcutaneously (s.c.) followed by progesterone (P) s.c. (100 ug in sesame oil) 48 h later. Four hours after P administration, the animals were tested for sex behavior in the presence of sexually active males in a 50 x 45 x 24 cm polystyrene arena. Both proceptive (hop-darting, ear wiggling, and approaches to the male) and receptive behavior (the number of lordoses, acceptance behavior on being mounted by the male, and the number of mounts by the male) of each female rat in the presence of a male was scored and recorded. The results of all the experiments were converted to lordosis quotient (LQ), defined as a percentage of full lordosis response (perineum elevated, all four legs extended Abbreviations: NO, nitric oxide; NOS, NO synthase; LHRH, luteinizing hormone-releasing hormone; L-NMMA, NG-monomethyl-L-argliine; D-NMMA, NG-monomethyl-D-arginine; 3V, third cerebral ventricle; E, estrogen; P, progesterone; SNP, sodium nitroprusside; NE, norepinephrine; Hb, hemoglobin; NRS, normal rabbit serum; LQ, lordosis quotient; i.c.v., intracerebroventricularly. §To whom reprint requests should be addressed. 6468The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.