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Mammals meet the increased nutritional demands of lactation through a combination of increased feed intake and a collection of adaptations known as adaptive metabolism (e.g., glucose sparing via insulin resistance, mobilization of endogenous reserves, and increased metabolic efficiency via reduced thyroid hormones). In the modern dairy cow, adaptive metabolism predominates over increased feed intake at the onset of lactation and develops concurrently with a reduction in plasma leptin. To address the role of leptin in the adaptive metabolism of early lactation, we asked which adaptations could be countered by a constant 96-h intravenous infusion of human leptin (hLeptin) starting on day 8 of lactation. Compared to saline infusion (Control), hLeptin did not alter energy intake or milk energy output but caused a modest increase in body weight loss. hLeptin reduced plasma glucose by 9% and hepatic glycogen content by 73%, and these effects were associated with a 17% increase in glucose disposal during an insulin tolerance test. hLeptin attenuated the accumulation of triglyceride in the liver by 28% in the absence of effects on plasma levels of the anti-lipolytic hormone insulin or plasma levels of free fatty acids, a marker of lipid mobilization from adipose tissue. Finally, hLeptin increased the plasma concentrations of T4and T3by nearly 50% without affecting other neurally regulated hormones (i.e., cortisol and luteinizing hormone (LH)). Overall these data implicate the periparturient reduction in plasma leptin as one of the signals promoting conservation of glucose and energy at the onset of lactation in the energy-deficient dairy cow.

MRI can provide multiparametric assessment of the cardiac allograft that can screen for common posttransplant sequelae as well as provide important prognostic information. Heart transplant recipients require lifelong screening for acute rejection and coronary allograft vasculopathy, both of which currently employ invasive screening techniques. T2-weighted MRI imaging, in particular T2 relaxation time, is an accurate predictor of acute heart transplant rejection. The serial evaluation of T2 relaxation time in heart transplant recipients could prove a useful gatekeeper to endomyocardial biopsy when screening for rejection, but randomized control trial data is needed. MRI can also screen for coronary allograft vasculopathy at macro- and microvascular levels through the use of myocardial perfusion reserve index (MPRI). MPRI outperforms invasive coronary angiography for the detection of coronary allograft vasculopathy and is strongly predictive of cardiovascular morbidity and mortality. Late gadolinium enhancement is prevalent in the heart transplant population and is associated with adverse ventricular remodeling as well as increased morbidity and mortality. The etiology of late gadolinium enhancement in this population is unclear and warrants further investigation. MRI provides uniquely accurate quantification of right ventricular volume and function, and there is emerging evidence that right ventricle volume index may be useful in screening for acute heart transplant rejection as well as posttransplant prognosis.

Translocator protein (TSPO), previously known as the peripheral benzodiazepine receptor, is a mitochondrial outer membrane protein implicated as essential for cholesterol import to the inner mitochondrial membrane, the rate-limiting step in steroid hormone biosynthesis. Previous research on TSPO was based entirely on in vitro experiments, and its critical role was reinforced by an early report that claimed TSPO knock-out mice were embryonic lethal. In a previous publication, we examined Leydig cell-specific TSPO conditional knock-out mice that suggested TSPO was not required for testosterone production in vivo. This raised controversy and several questions regarding TSPO function. To examine the definitive role of TSPO in steroidogenesis and embryo development, we generated global TSPO null (Tspo(-/-)) mice. Contrary to the early report, Tspo(-/-) mice survived with no apparent phenotypic abnormalities and were fertile. Examination of adrenal and gonadal steroidogenesis showed no defects in Tspo(-/-) mice. Adrenal transcriptome comparison of gene expression profiles showed that genes involved in steroid hormone biosynthesis (Star, Cyp11a1, and Hsd3b1) were unchanged in Tspo(-/-) mice. Adrenocortical ultrastructure illustrated no morphological alterations in Tspo(-/-) mice. In an attempt to correlate our in vivo findings to previously used in vitro models, we also determined that siRNA knockdown or the absence of TSPO in different mouse and human steroidogenic cell lines had no effect on steroidogenesis. These findings directly refute the dogma that TSPO is indispensable for steroid hormone biosynthesis and viability. By amending the current model, this study advances our understanding of steroidogenesis with broad implications in biology and medicine.

Energy balance controls the expression of the leptin receptor (Lepr) in the ruminant hypothalamus but whether similar regulation occurs in peripheral tissues is unknown. To address this issue, we measured Lepr expression in the liver and adipose tissue of dairy cows during the transition from late pregnancy (LP) to early lactation (EL). This period is characterized by the development of a profound state of energy insufficiency and is associated with reduced plasma insulin and leptin and with increased plasma growth hormone. Hepatic expression of the short (Lepr-a) and long (Lepr-b) isoforms was 40% higher during EL (8 days postpartum) than LP (30 days prepartum). A similar effect was observed when negative energy balance was induced in nonpregnant, late-lactation dairy cows by food restriction, implicating energy insufficiency as a specific cause in EL. The stimulation of hepatic Lepr expression was reversed after a 48-h period of hyperinsulinemic euglycemia in EL. Changes in hepatic Lepr expression during chronic elevation of plasma leptin in EL or plasma growth hormone in nonpregnant, late-lactation cows did not support a role for these hormones in mediating the effects of energy insufficiency on hepatic Lepr expression. In adipose tissue, Lepr expression was increased 10-fold during the transition from LP to EL. Overall, these data indicate that hypoinsulinemia is partly responsible for the induction of Lepr expression in the liver, and perhaps adipose tissue, of energy-deficient dairy cows.

Most dairy cows develop the first dominant follicle postpartum within 2 wk after calving, but only about 40% of these follicles produce sufficient estradiol to stimulate ovulation despite having normal ultrasound appearance and growth. This study aimed to characterize metabolic, endocrine, and follicular fluid profiles of cows in which the first dominant follicle postpartum will become ovulatory and those with nonovulatory follicles. Luteinizing hormone pulse frequency, follicular fluid androstenedione, and follicular fluid estradiol concentrations were lower in nonovulatory cows suggesting that the function of theca cells is impaired. In addition, nonovulatory cows had more severe negative energy balance and greater insulin resistance postpartum. This study describes for the first time the steroid hormone profile of early postpartum follicles and shows that a steroidogenic defect most likely occurs in theca cells limiting the amount of androgen precursor available for estradiol production that impairs their ovulatory outcome.

Most dairy cows develop the first dominant follicle postpartum within 2 wk after calving, but only about 40% of these follicles produce sufficient estradiol to stimulate ovulation despite having normal ultrasound appearance and growth. This study aimed to characterize metabolic, endocrine, and follicular fluid profiles of cows in which the first dominant follicle postpartum will become ovulatory and those with nonovulatory follicles. Luteinizing hormone pulse frequency, follicular fluid androstenedione, and follicular fluid estradiol concentrations were lower in nonovulatory cows suggesting that the function of theca cells is impaired. In addition, nonovulatory cows had more severe negative energy balance and greater insulin resistance postpartum. This study describes for the first time the steroid hormone profile of early postpartum follicles and shows that a steroidogenic defect most likely occurs in theca cells limiting the amount of androgen precursor available for estradiol production that impairs their ovulatory outcome.

Molecular events that regulate cellular biosynthesis of steroid hormones have been a topic of intense research for more than half a century. It has been established that transport of cholesterol into the mitochondria forms the rate-limiting step in steroid hormone production. In current models, both the steroidogenic acute regulatory protein (StAR) and the translocator protein (TSPO) have been implicated to have a concerted and indispensable effort in this cholesterol transport. Deletion of StAR in mice resulted in a critical failure of steroid hormone production, but deletion of TSPO in mice was found to be embryonic lethal. As a result, the role of TSPO in cholesterol transport has been established only using pharmacologic and genetic tools in vitro. To allow us to explore in more detail the function of TSPO in cell type-specific experimental manipulations in vivo, we generated mice carrying TSPO floxed alleles (TSPOfl/fl). In this study we made conditional knockout mice (TSPOcΔ/Δ) with TSPO deletion in testicular Leydig cells by crossing with an anti-Mullerian hormone receptor type II cre/+ mouse line. Genetic ablation of TSPO in steroidogenic Leydig cells in mice did not affect testosterone production, gametogenesis, and reproduction. Expression of StAR, cytochrome P450 side chain cleavage enzyme, 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase type I, and TSPO2 in TSPOcΔ/Δ testis was unaffected. These results challenge the prevailing dogma that claims an essential role for TSPO in steroid hormone biosynthesis and force reexamination of functional interpretations made for this protein. This is the first study examining conditional TSPO gene deletion in mice. The results show that TSPO function is not essential for steroid hormone biosynthesis.

Objective—To determine the effects of 2 conjugated linoleic acid (CLA) isomers (cis-9, trans-11 and trans-10, cis-12) on synthesis of prostaglandin (PG) E2 and F2α and expression of prostaglandin H synthase-2 (PGHS-2) of adult and fetal bovine endometrial epithelial cells in vitro. Sample—Primary cultures of endometrial epithelial cells obtained from 4 adult cows and 4 fetal bovine carcasses. Procedures—Cells were exposed to 0, 50, 100, or 200μM cis-9, trans-11 or trans-10, cis-12 CLA isomers for 24 hours. Culture media collected before and after 6 hours of stimulation of cells with phorbol 12-myristate 13-acetate were assayed to detect PGE2 and PGF2α via ELISA. After stimulation, cells were collected for western blot analysis to quantify PGHS-2. Results—Concentrations of PGF2α and PGE2 were significantly lower in culture media of adult and fetal endometrial epithelial cells exposed to any concentration of either CLA than they were in media of cells not exposed to CLAs. The trans-10, cis-12 CLA isomer seemed to decrease PG production more markedly than did the cis-9, trans-11 CLA isomer. Most concentrations of both CLAs significantly reduced culture media PGE2:PGF2α concentration ratios of cells. Exposure of cells to CLAs did not affect expression of PGHS-2 protein. Conclusions and Clinical Relevance—Results of this study indicated CLAs significantly decreased PGF2α and PGE2 concentrations and PGE2:PGF2α concentration ratios for cultures of adult and fetal endometrial epithelial cells with no apparent effect on PGHS-2 expression. Similar effects in cows could have effects on maternal recognition of pregnancy and immune function.

Thirty-two pigs (1 d old) were used to determine if exogenous glucagon and(or) free fatty acids (FFA oleic acid) would enhance gluconeogenesis and glucose homeostasis during fasting. Pigs were acquired at birth, fitted with an indwelling arterial cannula (via umbilicus) and fasted 24 h to deplete liver glycogen. A jugular cannula was inserted nonsurgically 8 to 10 h before initiation of a primed-continuous infusion consisting of control (excipient), glucagon (Glu), oleic acid (FFA), or both glucagon and oleic acid (Glu-FFA). Plasma Glu averaged 395 pg/ml preinfusion and was similar across treatments. The concentration increased fivefold (P less than .05) by 80 min for Glu and Glu-FFA pigs and remained constant thereafter (160 min: 2,379, 2,258 pg/ml; 240 min: 2,355, 2,274 pg/ml, respectively). Glucagon infusion did not alter plasma glucose after 240 min of infusion (control, 50 vs Glu, 51 mg/dl); however, Glu-FFA effected an increase (60 mg/dl, P less than .10). In contrast, pigs infused with FFA alone had a lower glucose concentration (40 mg/dl, P less than .10). Rate of glucose synthesis was determined using liver slices, acquired immediately postinfusion, with alanine and lactate as substrate (7.5 mM). The rate of synthesis was not altered by Glu or Glu-FFA infusion (2.91, 2.43 mumol glucose X g-1 X h-1 vs 2.91 for control). In contrast, exogenous FFA reduced synthesis to 1.85 mumol glucose X g-1 X h-1 (P less than .05) with lactate as substrate. It appears that Glu is not the primary factor limiting gluconeogenesis in fasting newborn pigs.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence is presented for the gas phase generation of singlet oxygen using heterogeneous photosensitization and atmospheric pressure.

O 2 ( 1 Δ g ) was generated in the gas phase at atmospheric pressure by direct laser excitation. A Holobeam model 255 Nd—YAG laser with an output at 1065 nm was used to achieve the transition O 2 ( 3 Σ g − , v = 0) → O 2 ( 1 Δ g , v = 1) The mean lifetime τ of the resulting excited oxygen species in the gas phase at atmospheric pressure was measured to be 0.124 ± 0.012 s. This corresponds to a bimolecular rate constant k 2 for the overall reaction O 2 ( 1 Δ g , v = 1) + O 2 ( 3 Σ g − ) → 2O 2 ( 3 Σ g − ) of (3.3 ± 0.4) × 10 −19 molecule −1 cm 3 s −1 , a factor of 10 below the currently accepted value for ground state oxygen deactivation of singlet oxygen. Possible reasons for this difference are discussed.