Location change method for imaging chemical reactivity and catalysis with single-molecule and -particle fluorescence microscopy.

In the last eight years, it has become possible to image chemical reactivity at the single-molecule and -particle level with fluorescence microscopy. This Perspective describes one of the imaging techniques that enabled this state-of-the-art application: imaging by the location change of molecules and particles. In this method, the microscope and experiment are configured to produce a signal when an individual molecule or particle changes location or changes mobility concurrently with a chemical change. This imaging technique has enabled observation of single chemical reactions and unraveled mechanisms of complex chemical and physical processes in transition metal and polymerization systems. This Perspective has three major goals: (1) to unify studies of different chemical processes or of different chemical questions, which, in spite of these differences, employ a similar microscopy detection method, (2) to explain the technique to nonexperts and those who might be interested in joining this nascent field, and (3) to highlight unique information available through this cross-disciplinary technique and the value this information has for chemical reaction development generally and catalysis specifically. To this end, application of the location change method to the investigation of polymerization reactions with radical initiators and separately with metal catalysts, and to ligand exchange reactions at platinum complexes are described.

Effects of L-carnitine fed during gestation and lactation on sow and litter performance.

Multiparous sows (n = 307) were used to evaluate the effects of added dietary L-carnitine, 100 mg/d during gestation and 50 ppm during lactation, on sow and litter performance. Treatments were arranged as a 2 (gestation or lactation) x2 (with or without L-carnitine) factorial. Control sows were fed 1.81 kg/d of a gestation diet containing .65% total lysine. Treated sows were fed 1.59 kg/d of the control diet with a .23 kg/d topdressing of the control diet that provided 100 mg/d of added L-carnitine. Lactation diets were formulated to contain 1.0% total lysine with or without 50 ppm of added L-carnitine. Sows fed 100 mg/d of added L-carnitine had increased IGF-I concentration on d 60 (71.3 vs. 38.0 ng/mL, P<.01) and 90 of gestation (33.0 vs. 25.0 ng/mL, P = .04). Sows fed added L-carnitine had increased BW gain (55.3 vs 46.3 kg; P<.01) and last rib fat depth gain (2.6 vs. 1.6 mm; P = .04) during gestation. Feeding 100 mg/d of added L-carnitine in gestation increased both total litter (15.5 vs. 14.6 kg; P = .04) and pig (1.53 vs 1.49 kg; P<.01) birth weight. No differences were observed in pig birth weight variation. Added L-carnitine fed during gestation increased litter weaning weight (45.0 vs. 41.3 kg, P = .02); however, no effect of feeding L-carnitine during lactation was observed. No differences were observed in subsequent days to estrus or farrowing rate. Compared to the control diet, feeding added L-carnitine in either gestation, lactation, or both, increased (P<.05) the subsequent number of pigs born alive, but not total born. In conclusion, feeding L-carnitine throughout gestation increased sow body weight and last rib fat depth gain and increased litter weights at birth and weaning.

Effects of L-carnitine fed during lactation on sow and litter performance.

Sows of differing parities and genetics were used at different locations to determine the effects of feeding added L-carnitine during lactation on sow and litter performance. In Exp. 1, sows (n = 50 PIC C15) were fed a lactation diet (1.0% total lysine, .9% Ca, and .8% P) with or without 50 ppm of added L-carnitine from d 108 of gestation until weaning (d 21). No differences in litter weaning weight, survivability, sow ADFI, or sow weight and last rib fat depth change were observed. Number of pigs born alive in the subsequent farrowing were not different (P>.10). In Exp. 2, parity-three and -four sows (n = 115 Large White cross) were used to determine the effect of feeding 0, 50, 100, or 200 ppm of added L-carnitine during lactation (diet containing .9% total lysine, 1.0% Ca, and .8% P) on sow and litter performance. No improvements in the number of pigs or litter weights at weaning were observed (P>.10). Sows fed added L-carnitine had increased weight loss (linear; P<.04), but no differences (P>.10) were observed in last rib fat depth change or subsequent reproductive performance. In Exp. 3, first-parity sows (n = 107 PIC C15) were fed a diet with or without 50 ppm of added L-carnitine during lactation (diet containing 1.0% total lysine). Sows fed added L-carnitine tended (P<.10) to have fewer stillborn and mummified pigs than controls (.42 vs .81 pigs). No differences were observed for litter weaning weight, survivability, or subsequent farrowing performance. Feeding 50 to 200 ppm of added L-carnitine during lactation had little effect on sow and litter performance.

Influence of intravenous L-carnitine administration in sheep preceding an oral urea drench.

Two experiments were conducted to investigate the effect of i.v. administration of L-carnitine on selected metabolites in sheep and to determine the feasibility of using L-carnitine to ameliorate the deleterious effects of hyperammonemia in sheep. In Exp. 1, i.v. L-carnitine solutions were administered at three levels in a replicated Latin square: 0 (CONT), 6.36 (CAR 1), and 12.72 (CAR 2) mmol L-carnitine/kg x (75) BW using Suffolk ewes (n = 6; average BW 75+/-3 kg). Plasma L-carnitine concentration was increased (P<.05) by treatment (51.9 vs 102.3, and 96.4 micromol/L in CONT, CAR 1, and CAR 2, respectively). Plasma glucose concentration was elevated (P<.05) in CAR 2 and CAR 1. Plasma NEFA concentration was highest (P<.05) in CAR 2. Area under the response curve for glucose was greater (P<.02) in CAR 2. In Exp. 2, Suffolk ewes (n = 16; average BW 48+/-2 kg) were used in a randomized complete block design with a 2x2 factorial treatment arrangement to determine the effects of i.v. L-carnitine administration during an oral urea load test (OULT). L-Carnitine (0 and 6.36 mmol/kg x (75) BW) was administered i.v. at 30 min, and an oral urea drench (50% wt/vol; 0 and 300 mg/kg BW) was administered at 60 min. Plasma L-carnitine was increased (P<.0001) by i.v. L-carnitine. Plasma ammonia N was highest (P<.0001) in the UREA treatment compared with the CONT, CARN, and CARN + UREA treatments (148 vs 95, 101, and 108 micromol/L, respectively). Intravenous L-carnitine administration influenced plasma glucose and NEFA concentrations in sheep and, when administered 30 min preceding an OULT, prevented the development of subclinical hyperammonemia in sheep.

Fatty acid flow to the duodenum and in milk from cows fed diets that contained fat and nicotinic acid.

Four cows fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square design; treatments were arranged in a 2 x 2 factorial. Treatments were 1) low fat diet, no nicotinic acid; 2) low fat diet, 12 g/d of nicotinic acid; 3) high fat diet, no nicotinic acid; and 4) high fat diet, 12 g/d of nicotinic acid. Cows were fed for ad libitum intake diets consisting of 35% alfalfa silage, 15% corn silage, and either 50% low fat concentrate or 40% high fat concentrate (tallow supplied 6.25% of concentrate) and 10% whole raw soybeans (dry matter basis). Intake of gross energy (104 Mcal/d) was not different among treatments. Ruminal and postruminal digestibility of energy was not altered by fat or nicotinic acid. Fatty acid intake and flow to the duodenum were increased by fat but were not affected by nicotinic acid. For all diets, flows to the duodenum of C16:0, C18:0, total C18, and total fatty acids increased, and flows of C16:1, C18:1, C18:2, and C18:3 decreased, compared with their intakes. Biohydrogenation of unsaturated C18 was decreased by fat but was not affected by nicotinic acid. Digestibilities of C18:0, C18:1, C18:2, C18:3, and total fatty acids that flowed to the duodenum were decreased by fat but were not affected by nicotinic acid. The yield of C18:0 in milk was increased, and yields of C6:0 to C16:0 fatty acids were decreased, by fat, but yields were not affected by nicotinic acid.

Supplemental fat and nicotinic acid for Holstein cows during an entire lactation.

The objectives of this experiment were to determine long-term responses to supplemental fat (from whole soybeans and liquid animal fat) and to determine whether the supplementation of nicotinic acid would enhance milk protein content or yield. From wk 4 through 43 postpartum, 44 multiparous Holstein cows (10 to 12 per treatment) were assigned to one of four dietary treatments: 1) control, 2) control plus 12 g/d of nicotinic acid, 3) supplemental fat, and 4) supplemental fat plus 12 g/d of nicotinic acid. The dry matter intake of cows did not differ among dietary treatments. Yields of milk, solids-corrected milk, and 3.5% fat-corrected milk were increased by nicotinic acid; the yield of fat-corrected milk during wk 4 to 25 was increased by supplemental fat. Contents of crude protein (CP) and true protein in milk were less for cows fed diets supplemented with fat or nicotinic acid; casein content was decreased by nicotinic acid. Intake of net energy for lactation was greater for cows fed supplemental fat; energy balance was greater during wk 4 to 25 for cows fed diets supplemented with fat. Body condition score and body weight were less when nicotinic acid was added to the control diet than when it was added to the diet supplemented with fat. Supplemental fat increased the concentration of nonesterified fatty acids (NEFA) in plasma; nicotinic acid increased NEFA when it was added to the control diet but decreased NEFA when it was added to the diet supplemented with fat. Nicotinic acid did not prevent the decrease in milk CP content that was induced by dietary fat, but it did increase milk yield and tended to increase the yield of milk CP.

Effects of dietary fat with or without nicotinic acid on nutrient flow to the duodenum of dairy cows.

Four Holstein cows, fitted with ruminal and duodenal cannulas, were utilized in a 4 x 4 Latin square design to investigate the effects of supplementing nicotinic acid to diets that contained 35% alfalfa haylage, 15% corn silage, and either 50% of a low fat concentrate or 10% whole raw soybeans and 40% of a high fat concentrate containing tallow. Treatments in a 2 x 2 arrangement were 1) low fat, no supplemental nicotinic acid; 2) low fat, 12 g/d of nicotinic acid; 3) high fat, no supplemental nicotinic acid; and 4) high fat, 12 g/d of nicotinic acid. The DMI and OM apparently and truly digested in the rumen and apparently digested postruminally were not different among treatments. Addition of fat to the diet decreased the concentration of total VFA in ruminal fluid but did not alter the molar proportions of any of the VFA; supplementation of nicotinic acid tended to decrease the molar proportion of acetate. Amounts of NAN, microbial N, nonammonia nonmicrobial N, and AA that flowed to the duodenum were similar among diets. The concentration of urea N in plasma decreased, and concentrations of cholesterol and triglycerides increased, when cows were fed supplemental fat. Milk composition and production of milk, 4% FCM, and milk components were not altered by addition of fat or nicotinic acid to the diet. Supplementation of fat or nicotinic acid to diets of dairy cows was not beneficial in this experiment.

Effect of L-carnitine and soybean oil on growth performance and body composition of early-weaned pigs.

Two experiments were conducted to evaluate the effect of dietary L-carnitine on growth performance and body composition of early-weaned pigs. In Exp. 1, 120 weanling pigs (initially 5.6 kg and 19 +/- 2 d of age) were allotted in a 3 x 2 factorial with four pigs per pen and five replications (pens) per treatment. Main effects from d 0 to 14 after weaning included dietary L-carnitine (0, 500, or 1,000 ppm) and soybean oil (0 to 10%). From d 14 to 35 after weaning, levels were reduced to 0, 250, or 500 ppm L-carnitine and 0 or 5% soybean oil. No L-carnitine x soybean oil interactions were observed (P > .10). From d 0 to 14, L-carnitine and soybean oil had no effect (P > .10) on pig performance. From d 14 to 35 and d 0 to 35, gain:feed ratio (G/F) improved (linear, P < .05) with increasing dietary L-carnitine; however, ADG and ADFI were not affected. Soybean oil improved ADG and G/F (P < .05) from d 14 to 35 and ADG from d 0 to 35. In Exp. 2, 180 weanling pigs (initially 6.0 kg and 22 +/- 2 d of age) were allotted in a 2 x 3 factorial. Pigs were fed either 0 or 1,000 ppm L-carnitine from d 0 to 14 after weaning and then pigs fed each of these diets were fed diets containing 0, 250, or 500 ppm L-carnitine from d 14 to 35. No interactions occurred between feeding L-carnitine from d 0 to 14 and performance observed from d 14 to 35. From d 0 to 14 after weaning, L-carnitine increased ADG (P < .08) and ADFI (P < .02). From d 14 to 35, ADFI decreased (linear, P < .05) and G/F increased (quadratic, P < .05) as dietary L-carnitine increased. Cumulative (d 0 to 35) ADFI decreased (linear, P < .05) and G/F increased (linear, P < .05) with increasing L-carnitine. On d 35, 14 pigs from each of four selected treatments (0 or 1,000 ppm L-carnitine from d 0 to 14 followed by either 0 or 500 ppm from d 14 to 35) were slaughtered, and carcass composition was recorded. Carcass moisture and CP percentages were not influenced (P > .10) by dietary L-carnitine. However, pigs fed 1,000 ppm L-carnitine from d 0 to 14 had less (P < .05) carcass lipid and daily lipid accretion on d 35 whether they were fed L-carnitine from d 14 to 35 or not. These results suggest that dietary L-carnitine improves G/F and reduces carcass lipid accretion in early-weaned pigs.