Search

Contents The gonadotropin-releasing hormone (Gn RH) stimulation test is a common procedure used to investigate normality of the pituitary-gonadal axis in mammals. There is very little information on the technique, its efficacy and side effects in small animals and in particular no information for male cats. In dogs, such test is performed by intravenous ( IV) administration. With cats, the number of times the animal needs to be restrained for blood sampling should be the least possible. The purpose of this study was to assess efficacy and side effects of the Gn RH stimulation test in tomcats comparing the IV with the intramuscular ( IM) route of administration. A Gn RH stimulation test was performed in eight adult tomcats through IM or IV administration of 50 μg gonadorelin. The response of the pituitary-gonadal axis was assessed by measuring serum testosterone on blood samples collected prior to and 1 hr following treatment. When considering each single group of cats, the post-stimulation serum testosterone values were significantly higher than the pre-treatment ones ( p < .05). When comparing the two groups of cats, basal testosterone concentrations did not differ, and also post-Gn RH testosterone concentrations did not differ. In conclusion, in the cats of our study, the Gn RH stimulation test produced the same results following the IM or the IV route of administration. Therefore, in tomcats, the IM route can be considered as effective as the IV one and should be preferred when doing a Gn RH test. [ABSTRACT FROM AUTHOR]

Cell function and energy redistribution are influenced by lipid classes (phospholipids (PLs), free fatty acids (FFAs), triglycerides (TGs), and cholesterol esters (CEs)). The aim of this study was to investigate metabolic alterations that are related to changes in lipid classes according to different levels of energy deficits in early lactating Mediterranean buffaloes (MBs). Sixty-three MBs were enrolled at the beginning of lactation using an observational study with a cross-sectional experimental design. Serum β-hydroxybutyrate (BHB) levels were used to group the animals into a healthy group (Group H; n = 38; BHB < 0.70 mmol/L) and hyperketonemia risk group (Group K; n = 25; BHB ≥ 0.70 mmol/L). Statistical analysis was performed using a linear model that included the effect of the group and body condition score to assess differences in fatty acid (FA) concentrations. A total of 40 plasma FAs were assessed in each lipid class. Among the FAs, eight PLs, seven FFAs, four TGs, and four CEs increased according to BHB levels, while three FFAs, three TGs, and one CE decreased. The changes among lipid class profiles suggested the influence of inflammatory response, liver metabolism, and the state of body lipid reserves. In addition, the possible similarities of buffaloes at risk of hyperketonemia with ketotic cows suggest the necessity of further investigations in these ruminants.

We evaluated the performance of a third-generation fluorescence enzyme immunoassay kit (FEIA; Tosoh Bioscience) for progesterone (P4) measurement in canine serum to identify the day of luteinizing hormone (LH) peak and ovulation in bitches. We conducted P4 assays on 54 serum samples using a FEIA and a chemiluminescence immunoassay (CLIA; Siemens). For the FEIA kit, the linearity test, recovery test, inter- and intra-assay CVs, and total error observed (TEo) were calculated. Serum samples from 28 bitches were used to evaluate the association of P4 concentration with the day of LH peak and the day of ovulation based on P4 thresholds (P4 ≥ 2 ng/mL, and doubling at 4-8 ng/mL in the following 48 h), and with pregnancy length. Linearity was 75-97% and 86-94% for high (37.0 ng/mL) and medium (3.8 ng/mL) pool serum samples, respectively. Recovery was 86.4-119%. Intra-assay CVs were 2.6%, 3.3%, and 5.2% for low (0.23 ng/mL), medium (6.24 ng/mL), and high (38.3 ng/mL) pool concentrations. Inter-assay CVs were 2.22% and 2.53% for P4 concentrations of 2.70 ng/mL and 8.2 ng/mL, respectively. TEo was 8.72% and 22.7% for P4 concentrations of 2 and 8 ng/mL, respectively. The mean pregnancy length from the day of LH peak and ovulation were 64.6 ± 1.7 and 63.3 ± 1.1 d, respectively. The third-generation FEIA kit that we tested was highly reliable.

The transition from late pregnancy to early lactation is characterized by marked changes in energy balance of dairy ruminants. The mobilization of adipose tissue led to an increase in plasma non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHB). The aim of this study was to analyze the total plasma fatty acids of healthy and hyperketonemic dairy ewes in early lactation through gas chromatography (GC) to evaluate metabolic alterations. An observational study was used with a cross-sectional experimental design. Forty-six Sarda dairy ewes were enrolled in the immediate post-partum (7 ± 3 days in milk) and divided into two groups according to serum BHB concentration: non-hyperketonemic group (n = 28; BHB < 0.86 mmol/L) and hyperketonemic group (n = 18; BHB ≥ 0.86 mmol/L). A two-way ANOVA included the effect of group and parity was used to evaluate differences in fatty acids (FA) concentrations. A total of 34 plasma FA was assessed using GC. 12 out of 34 FA showed a significant different between groups and 3 out of 34 were tended to significance. Only NEFA concentration and stearic acid were influenced by parity. The results may suggest possible links with lipid metabolism, inflammatory and immune responses in hyperketonemic group. In conclusion, GC represents a useful tool in the study of hyperketonemia and primiparous dairy ewes might show a greater risk to develop this condition., (© 2022. The Author(s).)

Nutrient loading from conventional row-crop production systems impairs surface waterbodies in the mid-southern United States. This study was conducted to determine whether minimum tillage and winter cover crops can decrease nutrient loading in surface runoff from conventionally tilled row-crop fields. The effects of winter cover crops and minimum tillage on N and P loading from a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation system were investigated on production fields in northwestern Mississippi using a split-field approach. As measured at the edge of the field, minimum tillage with cover crops had no effect on surface runoff from production fields regarding N or P loading (p > .10 for all nutrient loads), discharge (p > .10), or loss of suspended solids (p > .10). Minimum tillage and cover crops decreased sediment and nutrient concentrations in runoff for total N (p = .05) and total P (p = .09) but had no effect on other nutrients of interest. Although these practices decreased total N concentration by 36% in surface runoff to receiving waters, this reduction was only seen when aboveground cover crop biomass was present (p = .07). Regardless of the time of year, minimum tillage with cover crops decreased total P concentration in surface runoff by 27% (p = .09). These data indicate that it is unlikely that minimum tillage and cover crops will affect N and P loading while transitioning to a conservation production system in the mid-southern United States., (© 2022 The Authors. Journal of Environmental Quality published by Wiley Periodicals LLC on behalf of American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.)

The period from late gestation to early lactation is characterized by changes in energy metabolism. The aim of the current study was to analyze the plasma total lipid fraction using gas chromatography (GC) analysis, in order to highlight metabolic changes from the pre-foaling to post-foaling periods. Eleven pluriparous dairy jennies (mean age of 11.88 ± 3.79 years) belonging to the Amiata donkey breed were enrolled. Blood sampling was performed at 15 days before foaling (T0), and 15 (T1), 30 (T2), 60 (T3), and 90 (T4) days after foaling, for biochemical and GC analysis. A total of 37 fatty acids were identified in plasma samples: 4 medium chain (MCFA), 24 long chain (LCFA), and 9 very-long chain (VLCFA) fatty acids. Among them, 20 fatty acids changed significantly, and two fatty acid showed a trend toward significance. Furthermore, the LCFA, saturated, unsaturated, monounsaturated, and polyunsaturated ω-3 fatty acids changed significantly during the study period. The main alterations were between T0 and the other time points and appeared to be related to lipid metabolism, cellular structure and function, and inflammatory and immune responses. Our findings reveal greater energy requirements at the end of gestation compared to early lactation in donkeys.

Ketosis is a metabolic disease of pregnant and lactating ewes linked to a negative energy balance which can cause different economic losses. The aims of this study were to understand the metabolic status of the early-lactating ewes and to identify biomarkers for early diagnosis of subclinical ketosis. Forty-six Sarda ewes were selected in the immediate post-partum for the collection of the biological samples. A blood sample from the jugular vein was used to determine β-Hydroxybutyrate (BHB) concentrations. Animals were divided into two groups: BHB 0 or healthy group ( n = 28) with BHB concentration < 0.86 mmol/L; and BHB 1 or subclinical ketosis ( n = 18) with a BHB concentration ≥ 0.86 mmol/L. Ten mL of pool milk were collected at the morning milking for the analyses. The concentration of 34 milk fatty acids was evaluated using gas chromatography. Two biochemical parameters and 11 milk fatty acids of the total lipid fraction presented a p -value ≤ 0.05. The study revealed different relationships with tricarboxylic acid cycle, blood flows, immune and nervous systems, cell functions, inflammatory response, and oxidative stress status. Eight parameters were significant for the receiver operating characteristic (ROC) analysis with an area under the curve greater than 0.70.

C-reactive protein (CRP) is a major acute-phase protein, and it is produced by the liver in response to a pro-inflammatory stimulus. Given that human and canine CRP have a similar molecular structure, the assays used for human CRP detection have been used to measure CRP concentrations in dogs. We evaluated the use of a human CRP assay (Biotecnica CRP assay) and validated its application in dogs. We analyzed 91 canine serum samples with a fully automated analyzer. Our validation was based on the evaluation of imprecision, limits of linearity, limits of quantification, and an evaluation of interferences. The new assay was also compared with the Randox CRP assay, a validated assay for the measurement of CRP. Intra- and inter-assay repeatability were <8% and <11%, respectively. The tested assay proportionally measured canine CRP in an analytical range up to 60 mg/L; however, hemoglobin, triglycerides, and bilirubin interfered with the determination. Good agreement, with the presence of proportional systematic bias, was observed between Biotecnica and Randox assays. The Biotecnica CRP assay provides reliable measurement of CRP in canine serum, provided that samples are free of interferents.

Platelet-rich plasma (PRP) is known to play a crucial role in skin wound healing, in both Human and Veterinary Medicine. Remarkably, until now, no studies have reported PRP treatment in subacute full-thickness skin wounds of the dog. The aim of this study was to evaluate the effects of two consecutive applications of autologous PRP, with the second application after 15 days, in 6 dogs showing large subacute skin wounds. The percentage of contraction, re-epithelialization and healing in all treated patients indicated that no complications or side effects, associated with consecutive PRP treatments, occurred in any patient and all wounds achieved complete closure and re-epithelialization. Our results suggest a positive effect of repeated autologous topical PRP treatments in large cutaneous subacute wounds of different etiology. Therefore, this PRP treatment could represent a simple, cost-effective, and valid alternative to promote healing processes in subacute large wounds cases in dogs., (Copyright © 2020 Iacopetti, Patruno, Melotti, Martinello, Bedin, Badon, Righetto and Perazzi.)

The aim of this study was to extend the limited research available on the association between the concentration of milk fatty acids and the elevated plasmatic value of β-hydroxybutyrate (BHB) in early lactation of dairy cows. Fifty-four Holstein Friesian dairy cows were enrolled in the study. All animals were classified on the basis of their blood BHB concentration: BHB ≥ 1.0 mmol/L (BHB-1, sick group) and BHB ≤ 0.99 mmol/L (BHB-0, healthy group). Using Thin Layer Chromatography (TLC), four lipid classes (cholesterol esters -CE-, phospholipids -PL-, free fatty acids -FFA- and triacylglycerols -TAG-) were separated, and then the fatty acid (FA) composition was determined by High Resolution Gas Chromatography coupled with Flame Ionization Detector/Mass Spectrometer (HRGC-FID/MS). The FA profiles were used to investigate the diagnostic potential value of milk fatty acids for the correct classification of cows with BHB concentration above the established threshold (BHB < 1.0 mmol/L). Boruta Test and Receiver Operating Characteristic curves (ROC) were used to identify which FA and their thresholds of concentration could be used when animals presented hyperketonemia. The research has identified fourteen FA, belonging to CE, FFA, and TAG classes, useful for an association with BHB-1. These compounds, with predictive value for the development of hyperketonemia, could be considered valuable biomarkers. Further studies on a wider sampling, based on clinical and therapeutic approach, will be necessary to confirm, by bioanalytical chromatographic approaches, if these predictive FA will change between healthy and sick animals. New approaches in relation on the administration of different diets or supplements, and administration of drugs might improve the prevention of hyperketonemia., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The transition period is a central moment in dairy cows breeding because metabolic disorders may occur in relation to a dramatic increase in energy demand. This research aimed to identify new biomarkers for the diagnosis of hyperketonemia in bovine in early lactation phase with different value of plasmatic non-esterified fatty acid (NEFA). The profile of plasma fatty acids (FAs) divided into four lipid classes was evaluated using thin layer chromatography and gas chromatographic techniques (TLC-GC). A group of 60 multiparous Holstein-Friesian dairy cows were recruited in the present study. Blood samples were collected from the coccygeal vein and NEFA and the β-hydroxybutyrate (BHB) were evaluated. All animals were divided in 2 groups based on NEFA, NEFA0 group had as mean value 0.24 ± 0.12 mEq/L and NEFA1 group had as mean value 0.87 ± 0.23 mEq/L. Plasma FA concentrations were analyzed separately in free fatty acids, cholesterol esters, phospholipids and triglycerides. Six FAs demonstrated a predictive value in the hyperketonemic dairy cows. In the free fatty acid class, the predictive FAs were C14:0 (AUC = 0.77), C18:1 ω 9 (AUC = 0.72), C18:1 ω 7 (AUC = 0.70) and C18:3 ω 3 (AUC = 0.68). In the phospholipids class the predictive parameters were C12:0 (AUC = 0.78) and C8:0 (AUC = 0.73). In cholesterol, esters and triglycerides lipidic classes no FA had a predictive function.

Excessive mobilization of adipose tissue in high milk producing dairy cows predisposes to metabolic diseases. The aim of this research was to identify the plasma fatty acids in four lipid classes as biomarkers for the diagnosis of hyperketonemia in bovines using thin layer chromatography and gas chromatographic techniques (TLC-GC). Sixty multiparous Holstein-Friesian dairy cows were enrolled in the study. Blood samples from the coccygeal vein were collected and β-hydroxybutyrate (BHB) was evaluated. All animals were divided into three groups on the basis of ketonemia: BHB < 0.50 mmol/L, 0.50 < BHB < 1.0 mmol/L, and BHB > 1.0 mmol/L. Plasma fatty acid concentrations were evaluated in four lipid classes: Free Fatty Acids (FFA), Triglycerides (TG), Cholesterol Esters (CE) And Phospholipids (PL). The concentration of fatty acids was analyzed using TLC-GC. The results showed the following significance in the lipid classes: 19 fatty acids were significant ( p < 0.053) in FFA, nine fatty acids were significant ( p < 0.050) in TG, eight fatty acids were significant ( p < 0.050) in CE and three fatty acids were significant ( p < 0.049) in PL. Eleven parameters were considered as predictive fatty acids related to animals in hyperketonemia. The FFA increased simultaneously with blood BHB levels, although the identified predictive fatty acids related to the TG and CE lipid classes decreased, meanwhile the BHB values increased. In the PL lipid class, no fatty acids were predictive.

Serum protein distribution and concentration can be affected by different physiological and pathological conditions. The aim of this study was to evaluate the changes in the concentration of serum protein fractions and haptoglobin in clinically healthy dairy buffaloes during late pregnancy and early lactation. Blood and milk samples were collected from 30 buffaloes at around 7 d before expected calving (blood only) and 7, 30 and 50 d after calving. In serum samples, the total protein, haptoglobin, albumin, α1-, α2-, β1-, β2-, γ-globulins, and albumin/globulin ratio (A/G) values were evaluated. In milk, fat%, protein%, lactose%, somatic cell score (SCS) were assessed, along with milk yield (MY) and daily milk production (DMP). The peripartum period significantly influenced (P < 0.005) total protein, albumin, haptoglobin, α2-, β2- and γ-globulins (P < 0.005). Milk yield, DMP and fat% changed significantly throughout the monitoring period (P < 0.005). Milk yield and DMP were positively correlated with total protein, albumin, β2-globulins and A/G ratio, and negatively correlated with haptoglobin and α2-globulins. These results provide new knowledge about the serum protein electrophoretic pattern in Italian Mediterranean Buffaloes during the last phase of pregnancy and early stages of lactation.

Objectives: The objective of this study was to assess duration of efficacy, side effects and return to fertility following use of the 9.4 mg deslorelin implant (Suprelorin 12; Virbac) in cats, and test whether efficacy and duration of action are influenced by implantation site (interscapular vs periumbilical)., Methods: Sixteen healthy adult tom cats were checked with (1) reproductive examination, (2) gonadotropin-releasing hormone stimulation test and (3) semen collection until achievement of sterility, then with (1) and (2) only at 2, 4, 6 and 12 months, and every 6 months thereafter until treatment effect disappeared., Results: Serum testosterone reached basal levels by 7 days post-treatment. Semen quality improved initially then started to worsen by 1 month post-treatment and after 70 days post-treatment all cats were sterile. Early in the third month post-treatment there was a significant decrease in testicular volume and penile spikes. Testicular histology was normal upon neutering performed after resumption of fertility. No injection site lesions or treatment-related side effects were observed. There was no difference between periumbilical and interscapular placement for all criteria, but there was a trend for the decrease in testicular volume to last longer and for the regression of penile spikes to start sooner after interscapular administration. One of 16 cats did not respond to treatment. Six cats were lost at variable times during the study while fully responding to treatment. In the cats that completed the study, normal fertility was regained after 805 days, on average, but with a variable duration of effect from 750-850 days., Conclusions and Relevance: Treatment with a 9.4 mg deslorelin implant in male cats was effective for a period of 750-850 days, which is 1.5-2 times longer than the effect of the 4.7 mg deslorelin implant. Fertility (based on serum testosterone production and the presence of penile spikes) was regained at the end of the study. Placing implants in the intrascapular vs periumbilical location did not affect duration of suppression of testosterone production. The interscapular location may be characterised by a better efficacy, although further studies are needed to clarify this issue.

Pregnancy and lactation are physiological periods that result in an increased metabolic demand that, if not satisfied, could provoke a threat to homeostasis. In this study changes in the values of Non-Esterified Fatty Acids (NEFA) and β-hydroxybutyrate (BHB), glucose, insulin, thyroid hormones, milk composition and yield were investigated in buffaloes during the late pregnancy and early lactation. From a total of 50 buffaloes, blood samples were collected -7±5 days before expected calving; +7±5; +30±5 and +50±5 days post-partum; milk samples were collected at the same post-partum time points. On serum samples, the values of Non-Esterified Fatty Acids (NEFA), β-hydroxybutyrate (BHB), glucose, insulin, Triiodothyronine (T3), Thyroxine (T4) and Thyroid-stimulating hormone (TSH) were evaluated. On milk, fat %, protein %, lactose %, somatic cells score (SCS), milk yield and daily milk production (DMP) were assessed. Peripartum period significantly influenced all studied parameters (P<0.05). Milk constituents and productivity statistically changed throughout monitoring period (P<0.005). Milk yield resulted positively correlated with insulin and TSH values, negatively correlated with NEFA and BHB. Insulin was negatively correlated with lactose % and positively correlated with SCS. The obtained results showed that the peripartum period and lactation are accompanied by marked changes in some biochemical variables and in the thyroid hormones values in Italian Mediterranean Buffaloes. Moreover, the relationship found between TSH values and milk yield seems to suggest a possible role of thyroid gland on the maintenance of lactogenesis. This study underlines the importance of monitoring the hormonal status of buffalo during the transition period in order to understand when adjustments of regulatory mechanisms break through physiological limits predisposing the buffalo to metabolic problems.

Background: Saliva in dogs, as in humans, is a complex fluid secreted by different salivary glands in the oral cavity to protect the oral mucosa and teeth. The use of saliva as a substitute for blood in diagnosing and prognosticating disease in humans is widely accepted. Salivary biochemistry has also been used as a marker for periodontal disease in humans. No studies have as yet investigated the relation between salivary biochemistry and periodontal disease in dogs, however; neither has the salivary composition of healthy dogs with no oral disease been assessed. The purpose of this study was to obtain an overview on pH distribution and a set of salivary biochemical analytes (calcium, phosphorus, lactate dehydrogenase, lysozyme and amylase) commonly related to oral health in humans in a subset population of healthy young dogs with no periodontal disease or previous oral disease. Data were analyzed to gather salivary reference ranges for pH and each parameter and to assess a possible correlation between salivary and serum analytes., Results: Twenty-nine adult client-owned dogs were recruited for the study. Lactate dehydrogenase and lysozyme showed higher concentrations in saliva than in serum, whereas amylase showed the contrary. Salivary biochemistry values did not differ between males and females or between non-neutered and neutered individuals. No significant correlations between salivary and serum calcium, phosphorus, lactate dehydrogenase, amylase and lysozyme were identified in this study. Data allowed intervals for the salivary pH and other analytes investigated to be obtained from healthy dogs with healthy oral conditions., Conclusions: These preliminary data can contribute to enlarge our understanding of the functional role of saliva and its relation to oral health in dogs.

Surfactant-associated protein B (SP-B) is critical to the biophysical function of pulmonary surfactant. No information is available on SP-B synthesis and kinetics in humans. We administered a 24-h i.v. infusion of 13C-valine as metabolic precursor of SP-B to six newborn infants (weight 3.5+/-0.5 kg; age 12 d, range 1-43 d). Three of the study infants also received i.v. 2H-palmitate to label surfactant disaturated phosphatidylcholine (DSPC). SP-B and DSPC were isolated from tracheal aspirates, and their respective 13C and 2H enrichments were measured by gas chromatography-mass spectrometry. SP-B kinetics was measured successfully in all six infants. SP-B median (range) fractional synthesis rate was 30% per day (20-78% per day), secretion time was 4.5 h (1-9 h), time to peak was 24 h (12-36 h), and half-life was 21 h (8-35 h). The ascending part of the SP-B kinetic curve was similar to the DSPC curve, suggesting similar secretion pathways. SP-B half-life seemed to be shorter than DSPC half-life. These results agree with existing animal data. We conclude that the measurement of SP-B kinetics is feasible in vivo in humans by stable isotope technology.

We studied surfactant kinetics on Day 1 of life in 11 preterm infants on mechanical ventilation by infusing stable isotope labeled palmitic (PA) and linoleic acid (LLA). Six infants received exogenous surfactant for the treatment of respiratory distress syndrome (RDS) and five did not meet treatment criteria because of minimal or no disease. The isotopic enrichment of plasma free PA and LLA and of surfactant phosphatidylcholine PA (PC-PA) and LLA (PC-LLA) from tracheal aspirates was measured by mass spectrometry. Significant isotopic enrichment could be measured in PC-PA and PC-LLA from all patients. The fractional synthesis rate (FSR) of PC-LLA was higher than that of PC-PA (22.7 +/- 15.9 versus 12.1 +/- 7.7% per day, p = 0.018). Half-life (HL) of PC-PA was longer than that of PC-LLA (94.7 +/- 18.8 versus 46.6 +/- 32.6 h, p = 0.028). Patients who received exogenous surfactant had longer secretion times (ST) and delayed peak times (PK) but FSR and HL were unaffected. We concluded that: (1) surfactant kinetics can be measured in preterm infants with stable isotope labeled lipids; (2) surfactant FSR and HL calculated with PA and LLA gave different results; (3) patients treated with exogenous surfactant had similar FSRs compared with the nontreated subjects but had longer ST and delayed PK; (4) FSR from plasma free fatty acids (present study) was higher than that from plasma glucose in our previous work (Bunt JEH, Zimmermann LJI, Wattimena D, van Beek R, Sauer PJJ, Carnielli VP. Am J Respir Crit Care Med 1998;157:810-814) in a comparable population of preterm infants with RDS.

Little is known about surfactant metabolism in newborn infants, since radioactive isotopes cannot be used in humans. We describe here a new method for studying exogenous surfactant pharmacokinetics in vivo. We measured surfactant half-life, pool size, and turnover time in eight preterm infants (gestational age: 30 +/- 2 wk; birth weight: 1,416 +/- 202 g) who were mechanically ventilated because of infant respiratory distress syndrome. We administered two doses of 100 mg/kg each of a natural porcine surfactant with (13)C-labeled dipalmitoylphosphatidylcholine as a tracer. The (13)C enrichment of surfactant disaturated phosphatidylcholine (DSPC) was measured in serial tracheal aspirates by gas chromatography-mass spectrometry. The DSPC half-life was 34.2 +/- 9.4 h (mean +/- SD; range: 21.8 to 45.9 h). The apparent DSPC pool sizes were 5.8 +/- 6.1 mg/kg (range: 0.1 to 17.0 mg/kg) and 17.3 +/- 13.6 mg/kg (range: 3.3 to 41.0 mg/kg) at the time of the first and second surfactant doses, respectively. We present a novel and safe method that allows the tracing of exogenous surfactant phosphatidylcholine, the major lipid component of pulmonary surfactant, in infants who receive exogenous surfactant. This method could be a valuable tool for studying: (1) therapies that enhance lung/surfactant maturation; (2) the dosing and timing of surfactant therapy in different lung diseases; and (3) the comparison of different surfactant preparations.

Little is known about endogenous surfactant metabolism in infants, because radioactive isotopes used for this purpose in animals cannot be used in humans. We developed a novel and safe method to measure the endogenous surfactant kinetics in vivo in humans by using stable isotope labeled fatty acids. We infused albumin-bound [U-13C]palmitic acid (PA) and [U-13C]linoleic acid (LLA) for 24 h in eight critically ill infants (mean+/-SD: weight: 3.7+/-1.3 kg: age: 51.3+/-61.6 d) who required mechanical ventilation. The 13C enrichment of PA and LLA in surfactant phosphatidylcholine (PC), obtained from tracheal aspirates, was measured by gas chromatography combustion interface-isotope ratio mass spectrometry. We measured a significant incorporation of both 13C-PA and 13C-LLA into surfactant PC. PC-PA and PC-LLA became enriched after 8.7+/-4.9 h (range: 3.4-17.3) and 10.0+/-7.2 h (range: 3.0-22.4), respectively; the times at maximum enrichment were 49.2+/-8.9 and 45.6+/-19.3 h, respectively. The fractional synthesis rate of surfactant PC-PA ranged from 0.4 to 3.4% per h, whereas the fractional synthesis rate of PC-LLA ranged from 0.5 to 3.8% per h. The surfactant PC-PA and PC-LLA half-lives ranged from 16.8 to 177.7 and 23.8 to 144.4 h, respectively. This method provides new data on surfactant metabolism in infants requiring mechanical ventilation. We found that synthesis of surfactant from plasma PA and LLA is a slow process and that there were marked differences in PC kinetics among infants. This variability could be related to differences in lung disease and could affect the clinical course of the respiratory failure.

Lipolysis has been measured in humans by means of stable isotope techniques using labeled palmitic acid (PA) or glycerol as tracers. If other fatty acids (FA) such as linoleic acid (LLA) have the same rate of appearance (Ra) as PA and therefore contribute equally to oxidative and nonoxidative metabolism is unknown. We infused albumin-bound [U-13C]PA and [U-13C]LLA in seven critically ill infants (weight 3.6 +/- 1.3 kg, age 57 +/- 64 d) receiving 20.9 +/- 5.4 kcal. kg-1.d-1 of i.v. glucose only, and measured simultaneously the Ra of PA and LLA from the isotopic enrichment of plasma FFA by mass spectrometry. A needle biopsy of the s.c. adipose tissue was obtained for FA composition. PA in adipose tissue was higher than LLA (40 +/- 6.7 versus 5.4 +/- 3.2 mol %, p < 0.001). The Ra values of PA and LLA were 5.73 +/- 2.79 and 1.34 +/- 0.92 mumol.kg-1.min-1, respectively (p = 0.005). However, the ratio of the FA's Ra to their respective mol% values in adipose tissue was lower for PA than for LLA (0.15 +/- 0.06 versus 0.25 +/- 0.06, p = 0.02). The Ra of LLA acid was higher than could be expected from the FA composition of adipose tissue, thus indicating a preferential release of LLA during lipolysis. In critically ill infants receiving only i.v. glucose, the contribution of LLA to the oxidative and nonoxidative metabolism may be larger than what assumed from the FA composition of plasma and adipose tissue.