Attosecond-pump attosecond-probe x-ray spectroscopy of liquid water

Attosecond-pump/attosecond-probe experiments have long been sought as the most straightforward method for observing electron dynamics in real time. Although there has been much success with overlapped near-infrared femtosecond and extreme ultraviolet attosecond pulses combined with theory, true attosecond-pump/attosecond-probe experiments have been limited. We used a synchronized attosecond x-ray pulse pair from an x-ray free-electron laser to study the electronic response to valence ionization in liquid water through all x-ray attosecond transient absorption spectroscopy (AX-ATAS). Our analysis showed that the AX-ATAS response is confined to the subfemtosecond timescale, eliminating any hydrogen atom motion and demonstrating experimentally that the 1b1 splitting in the x-ray emission spectrum is related to dynamics and is not evidence of two structural motifs in ambient liquid water.

Epidemiology of mastitis and interactions of environmental factors on udder health in the compost barn system

ABSTRACT This study aimed to describe the epidemiological indexes of mastitis, milk quality and udder hygiene in the Compost Barn system, as well as to search for associations between isolated pathogens from milk with compost characteristics. Three dairy herds participated in the study, and the samples were collected during different periods on each farm. Individual milk samples were collected in duplicate for SCC analysis and microbiological culture. Environmental pathogens caused most cases of clinical mastitis on farm 2, and contagious pathogens caused the most cases on farm 1. Bed moisture was not associated with the incidence of environmental pathogens. Most of the animals remained in good udder hygiene during the study. Poor udder hygiene contributed to the increased incidence of environmental pathogens in one of the farms. A higher number of animals with a hygiene score of ≥ 2 were observed during the warmer and rainfall periods. There was no association between hygiene scores and somatic cell counts. The results suggest that pathogens isolated from milk in animals confined in Compost Barn under tropical climate are like other confinement systems adopted elsewhere. The year period influenced the udder hygiene score, reinforcing the importance of bed management throughout the year.

Enhanced energy gain in a dielectric laser accelerator using a tilted pulse front laser

Using an 800 nm, 45 fs pulse-front-tilted laser we demonstrate a record 315 keV energy gain in a dual grating dielectric laser accelerator (DLA) and average accelerating gradients of 560 MV/m over 0.5 mm. These results open a new regime in DLA characterized by significant evolution of the beam distribution in the longitudinal phase space, corresponding to > 1/4 of a synchrotron oscillation. By tilting the laser wavefront we control the resonant velocity of the DLA and observe a net energy gain, indicating that a tapered optical phase could be used to achieve very high energy gain.

Double-shot MeV electron diffraction and microscopy

In this paper, we study by numerical simulations a time-resolved MeV electron scattering mode where two consecutive electron pulses are used to capture the evolution of a material sample on 10 ps time scales. The two electron pulses are generated by illuminating a photocathode in a radiofrequency photogun by two short laser pulses with adjustable delay. A streak camera/deflecting cavity is used after the sample to project the two electron bunches on two well separated regions of the detector screen. By using sufficiently short pulses, the 2D spatial information from each snapshot can be preserved. This "double-shot" technique enables the efficient capture of irreversible dynamics in both diffraction and imaging modes. In this work, we demonstrate both modes in start-to-end simulations of the UCLA Pegasus MeV microscope column.

Demonstration of Single-Shot Picosecond Time-Resolved MeV Electron Imaging Using a Compact Permanent Magnet Quadrupole Based Lens

We present the results of an experiment where a short focal length (∼1.3  cm), permanent magnet electron lens is used to image micron-size features (of a metal sample) with a single shot from an ultrahigh brightness picosecond-long 4 MeV electron beam emitted by a radio-frequency photoinjector. Magnification ratios in excess of 30× were obtained using a triplet of compact, small gap (3.5 mm), Halbach-style permanent magnet quadrupoles with nearly 600  T/m field gradients. These results pave the way towards single-shot time-resolved electron microscopy and open new opportunities in the applications of high brightness electron beams.

The circumferential resection margins status: A comparison of robotic, laparoscopic and open total mesorectal excision for mid and low rectal cancer

INTRODUCTION

Minimally invasive surgery for rectal cancer (RC) is now widely performed via the laparoscopic approach, but robotic-assisted surgery may overcome some limitations of laparoscopy in RC treatment. We compared the rate of positive circumferential margins between robotic, laparoscopic and open total mesorectal excision (TME) for RC in our institution.

METHODS

Mid and low rectal adenocarcinoma patients consecutively submitted to robotic surgery were compared to laparoscopic and open approach. From our prospective database, 59 patients underwent robotic-assisted rectal surgery from 2012 to 2015 (RTME group) were compared to our historical control group comprising 200 open TME (OTME group) and 41 laparoscopic TME (LTME group) approaches from July 2008 to February 2012. Primary endpoint was to compare the rate of involved circumferential resection margins (CRM) and the mean CRM between the three groups. Secondary endpoint was to compare the mean number of resected lymph nodes between the three groups.

RESULTS

CRM involvement was demonstrated in 20 patients (15.5%) in OTME, 4 (16%) in LTME and 9 (16.4%) in the RTME (p = 0.988). The mean CRM in OTME, LTME and RTME were respectively 0.6 cm (0-2.7), 0.7 cm (0-2.0) and 0.6 cm (0-2.0) (p = 0.960). Overall mean LN harvest was 14 (0-56); 16 (0-52) in OTME, 13 (1-56) in LTME and 10 (0-45) in RTME (p = 0.156).

CONCLUSION

Our results suggest that robotic TME has the same oncological short-term results when compared to the open and laparoscopic technique, and it could be safely offered for the treatment of mid and low rectal cancer.

Measurement in vivo of proliferation rates of slow turnover cells by 2H2O labeling of the deoxyribose moiety of DNA

We describe here a method for measuring DNA replication and, thus, cell proliferation in slow turnover cells that is suitable for use in humans. The technique is based on the incorporation of (2)H(2)O into the deoxyribose (dR) moiety of purine deoxyribonucleotides in dividing cells. For initial validation, rodents were administered 4% (2)H(2)O in drinking water. The proliferation rate of mammary epithelial cells in mice was 2.9% per day and increased 5-fold during pregnancy. Administration of estradiol pellets (0-200 microg) to ovariectomized rats increased mammary epithelial cell proliferation, according to a dose-response relationship up to the 100 microg dose. Similarly, proliferation of colon epithelial cells was stimulated in a dose-response manner by dietary cholic acid in rats. Bromodeoxyuridine labeling correlated with the (2)H(2)O results. Proliferation of slow turnover cells was then measured. Vascular smooth muscle cells isolated from mouse aorta divided with a half-life in the range of 270-400 days and die-away values after (2)H(2)O wash-out confirmed these slow turnover rates. The proliferation rate of an adipocyte-enriched fraction from mouse adipose tissue depots was 1-1.5% new cells per day, whereas obese ad libitum-fed obob mice exhibited markedly higher fractional and absolute proliferation rates. In humans, stable long-term (2)H(2)O enrichments in body water were achieved by daily (2)H(2)O intake, without toxicities. Labeled dR from fully turned-over blood cells (monocytes or granulocytes) exhibited a consistent amplification factor relative to body (2)H(2)O enrichment ( approximately 3.5-fold). The fraction of newly divided naive-phenotype T cells after 9 weeks of labeling with (2)H(2)O was 0.056 (CD4(+)) and 0.043 (CD8(+)) (replacement rate <0.1% per day). In summary, (2)H(2)O labeling of dR in DNA allows safe, convenient, reproducible, and inexpensive measurement of cell proliferation in humans and experimental animals and is well suited for slow turnover cells.

Effect of ibuprofen and acetaminophen on postexercise muscle protein synthesis

We examined the effect of two commonly consumed over-the-counter analgesics, ibuprofen and acetaminophen, on muscle protein synthesis and soreness after high-intensity eccentric resistance exercise. Twenty-four males (25 +/- 3 yr, 180 +/- 6 cm, 81 +/- 6 kg, and 17 +/- 8% body fat) were assigned to one of three groups that received either the maximal over-the-counter dose of ibuprofen (IBU; 1,200 mg/day), acetaminophen (ACET; 4,000 mg/day), or a placebo (PLA) after 10-14 sets of 10 eccentric repetitions at 120% of concentric one-repetition maximum with the knee extensors. Postexercise (24 h) skeletal muscle fractional synthesis rate (FSR) was increased 76 +/- 19% (P < 0.05) in PLA (0.058 +/- 0.012%/h) and was unchanged (P > 0.05) in IBU (35 +/- 21%; 0.021 +/- 0.014%/h) and ACET (22 +/- 23%; 0.010 +/- 0.019%/h). Neither drug had any influence on whole body protein breakdown, as measured by rate of phenylalanine appearance, on serum creatine kinase, or on rating of perceived muscle soreness compared with PLA. These results suggest that over-the-counter doses of both ibuprofen and acetaminophen suppress the protein synthesis response in skeletal muscle after eccentric resistance exercise. Thus these two analgesics may work through a common mechanism to influence protein metabolism in skeletal muscle.

Advances in the stable isotope-mass spectrometric measurement of DNA synthesis and cell proliferation

Methods for measuring rates of DNA synthesis, and thus cell proliferation, in humans had not been available until recently. We (D. C. Macallan, C. A. Fullerton, R. A. Neese, K. Haddock, S. S. Park, and M. K. Hellerstein, 1998, Proc. Natl. Acad. Sci. USA 95, 708-713) recently developed a stable isotope-mass spectrometric technique for measuring DNA synthesis by labeling the deoxyribose (dR) moiety of purine deoxyribonucleotides through the de novo nucleotide synthesis pathway. The original analytic approach had limitations, however. Here, we describe technical improvements that increase yield, stability, sensitivity, and reproducibility of the method. The purine deoxyribonucleoside, deoxyadenosine (dA), is directly isolated from hydrolysates of DNA by using an LC18 SPE column. Two derivatives were developed for analyzing the dR moiety of dA alone (without the base), an aldonitrile-triacetate derivative, and a reduced pentose-tetraacetate (PTA) derivative. The PTA derivative in particular exhibited greater stability (no degradation after several weeks), greater GC/MS signal, and much less abundance sensitivity of isotope ratios (i.e., less dependence of mass isotopomer abundances on the amount of material injected into the mass spectrometer source), compared to previous derivatives of dA. The need for complex, multidimensional abundance corrected standard curves was thereby avoided. Using the PTA derivative, dR enrichments from DNA of fully turned over cells of rodents with 2H2O enrichments in body water of 2.2-2.8% were 9.0-9.5%, and less than 1.0 microg DNA (ca. 2 x 10(5) cells) was required for reproducible analyses. In summary, these methodologic advances allow measurement of stable isotope incorporation into DNA and calculation of cell proliferation and death rates in vivo in humans and experimental animals, with fewer cells, greater reproducibility, and less labor. Many applications of this approach can be envisioned.

Increased turnover of T lymphocytes in HIV-1 infection and its reduction by antiretroviral therapy

The mechanism of CD4(+) T cell depletion in human immunodeficiency virus (HIV)-1 infection remains controversial. Using deuterated glucose to label the DNA of proliferating cells in vivo, we studied T cell dynamics in four normal subjects and seven HIV-1-infected patients naive to antiretroviral drugs. The results were analyzed using a newly developed mathematical model to determine fractional rates of lymphocyte proliferation and death. In CD4(+) T cells, mean proliferation and death rates were elevated by 6.3- and 2.9-fold, respectively, in infected patients compared with normal controls. In CD8(+) T cells, the mean proliferation rate was 7.7-fold higher in HIV-1 infection, but the mean death rate was not significantly increased. Five of the infected patients underwent subsequent deuterated glucose labeling studies after initiating antiretroviral therapy. The lymphocyte proliferation and death rates in both CD4(+) and CD8(+) cell populations were substantially reduced by 5-11 weeks and nearly normal by one year. Taken together, these new findings strongly indicate that CD4(+) lymphocyte depletion seen in AIDS is primarily a consequence of increased cellular destruction, not decreased cellular production.

Factors influencing T-cell turnover in HIV-1-seropositive patients

HIV-1 disease is associated with pathological effects on T-cell production, destruction, and distribution. Using the deuterated (2H) glucose method for endogenous labeling, we have analyzed host factors that influence T-cell turnover in HIV-1-uninfected and -infected humans. In untreated HIV-1 disease, the average half life of circulating T cells was diminished without compensatory increases in cell production. Within 12 weeks of the initiation of highly active antiretroviral therapy (HAART), the absolute production rates of circulating T cells increased, and normal half-lives and production rates were restored by 12-36 months. Interpatient heterogeneity in the absolute degree of turnover correlated with the relative proportion of naive- and memory/effector-phenotype T cells in each of the CD4+ and CD8+ populations. The half-lives of naive-phenotype T cells ranged from 116-365 days (fractional replacement rates of 0.19-0.60% per day), whereas memory/effector-phenotype T cells persisted with half-lives from 22-79 days (fractional replacement rates of 0.87-3.14% per day). Naive-phenotype T cells were more abundant, and the half-life of total T cells was prolonged in individuals with abundant thymic tissue, as assessed by computed tomography. Such interpatient variation in T-cell kinetics may be reflective of differences in functional immune reconstitution after treatment for HIV-1 disease.

Directly measured kinetics of circulating T lymphocytes in normal and HIV-1-infected humans

The dynamic basis for T-cell depletion in late-stage HIV-1 disease remains controversial. Using a new, non-radioactive, endogenous labeling technique, we report direct measurements of circulating T-cell kinetics in normal and in HIV-1-infected humans. In healthy, HIV-1-seronegative subjects, CD4+ and CD8+ T cells had half-lives of 87 days and 77 days, respectively, with absolute production rates of 10 CD4+ T cells/microl per day and 6 CD8+ T cells/microl per day. In untreated HIV-1-infected subjects (with a mean CD4 level of 342 cells/microl), the half-life of each subpopulation was less than 1/3 as long as those of healthy, HIV-1-seronegative subjects but was not compensated by an increased absolute production rate of CD4+ T cells. After viral replication was suppressed by highly active antiretroviral therapy for 12 weeks, the production rates of circulating CD4+ and CD8+ T cells were considerably elevated; the kinetic basis of increased CD4 levels was greater production, not a longer half-life, of circulating cells. These direct measurements indicate that CD4+ T-cell lymphopenia is due to both a shortened survival time and a failure to increase the production of circulating CD4+ T cells. Our results focus attention on T-cell production systems in the pathogenesis of HIV-1 disease and the response to antiretroviral therapy.

Quantification of menstrual and diurnal periodicities in rates of cholesterol and fat synthesis in humans

The mass isotopomer distribution analysis (MIDA) technique is applied here in men and menstruating women to quantify periodicities in the biosynthesis of serum cholesterol and very low density lipoprotein (VLDL)-palmitate. The isotopic enrichment of the true biosynthetic precursor (intracellular acetyl-CoA) during oral or intravenous administration of sodium[1-13C]- or [2-13C]acetate was calculated from mass isotopomer fractional abundances in free cholesterol and VLDL-palmitate, determined by gas chromatography-mass spectrometry (GC-MS). To convert fractional into absolute cholesterol synthesis rates, decay rate constants of plasma cholesterol were determined from the die-away curves of endogenously labeled high-mass isotopomers. Oral [13C]acetate was a 3-4 times more efficient means of labeling the precursor pool for VLDL-palmitate than was intravenous [13C]acetate, consistent with a splanchnic site of VLDL-fatty acid synthesis, whereas the precursor for free cholesterol had an intermediate enrichment, suggesting a contribution from extra-splanchnic tissues as well. Endogenous synthesis of serum cholesterol was 8-11 mg/kg per day (an estimated 65-75% of input into serum cholesterol); it was 1.5- to 3-fold higher at night than during the day (37-49 mg/h at night compared to 9-23 mg/h during the day) and did not vary over the menstrual cycle (608-697 mg/day). In contrast, endogenous synthesis of fatty acids made a relatively minor contribution to body fat pools (1/10-1/20) of input into VLDL-palmitate) compared to dietary fat intake; it was greater in the day-time, and was influenced by menstrual cycle (3-fold elevated in the follicular phase compared to the luteal phase), and body composition (higher in obese men than normal weight men, r2 = 0.59 for lipogenesis vs. body mass index). Factors responsible for periodicities in endogenous lipid synthesis can be studied in humans using this approach.

Effects of recombinant monokines on hepatic pyruvate dehydrogenase, pyruvate dehydrogenase kinase, lipogenesis de novo and plasma triacylglycerols. Abolition by prior fasting

1. The effects of recombinant human tumour necrosis factor alpha (TNF) and murine interleukin-1 alpha (IL-1) on the activation state of the hepatic pyruvate dehydrogenase complex (PDHa), the activity of mitochondrial PDH kinase, hepatic lipogenesis de novo and plasma triacylglycerol (TG) concentrations were studied. 2. Monokine effects depended upon prior nutritional state. In rats fasted for 20 h or 45 h before monokine administration and refeeding (orally or with intravenous glucose), PDHa, TG and hepatic lipogenesis were not increased. In rats fed ad libitum, treatment with TNF plus IL-1 increased the contribution of hepatic lipogenesis to circulating TG to 550% of control values (P = 0.03) and plasma TG concentrations to 159% (P = 0.02), whereas PDHa increased slightly to 120% (P = 0.02) and liver glycogen content fell to 45.8% (P = 0.05) of control values. 3. Intrinsic hepatic PDH kinase activity was not changed by monokine treatment in rats fed ad libitum. 4. The increased lipogenesis de novo showed no correlation (r2 = 0.05, not significant) with hepatic PDHa in individual animals fed ad libitum. 5. In conclusion, these results suggest that monokines increase pyruvate flux through hepatic PDH in vivo in rats fed ad libitum primarily by mechanisms other than covalent modification of PDH. Prior nutritional status exerts a permissive effect for monokine stimulation of PDHa and lipogenesis, consistent with a substrate-mediated action, but the mechanism of this permissive effect remains uncertain.

Mechanisms of fructose-induced hypertriglyceridaemia in the rat. Activation of hepatic pyruvate dehydrogenase through inhibition of pyruvate dehydrogenase kinase

1. The effects of purified diets containing 70% glucose or 70% fructose on the activation state of hepatic pyruvate dehydrogenase (PDHa), activity of mitochondrial PDH kinase, plasma triacylglycerols (TG) and hepatic lipogenesis de novo in rats were measured. 2. Plasma TG were significantly increased in the fructose-fed compared with the glucose-fed group (125 +/- 45 mg/dl versus 57 +/- 19 mg/dl; P less than 0.002) after 3-5 weeks on the diet despite less daily food intake. 3. Hepatic PDHa in fructose-fed rats was 144% of the value in glucose-fed rats (15.4 +/- 1.2% versus 10.7 +/- 0.5%; P less than 0.002), whereas cardiac muscle PDHa was not different (45.5 +/- 6.6% versus 41.0 +/- 7.8%). 4. Intrinsic hepatic PDH kinase activity was decreased to 34% of glucose-fed values by fructose feeding (-k = 3.56 +/- 0.39 versus 10.41 +/- 1.85 min-1; P less than 0.005). 5. The fractional contribution to very-low-density-lipoprotein palmitate from hepatic lipogenesis de novo, measured by a stable-isotope mass-spectrometric method, was 10.49 +/- 2.42% (n = 8) in fructose-fed rats versus 5.55 +/- 1.38% (n = 9) in glucose-fed rats (P less than 0.05), and 2.66 +/- 2.39% (n = 3) in chow-fed rats (P less than 0.05 versus fructose-fed group). The absolute contribution to circulating TG from lipogenesis de novo was also significantly higher in the fructose-fed than in the glucose-fed group (14.9 +/- 5.1 mg/dl versus 2.9 +/- 0.6 mg/dl; P less than 0.05) 6. Portal insulin concentrations were significantly higher in the fructose-fed rats (206 +/- 49 mu-units/ml versus 81 +/- 15 mu-units/ml; P less than 0.05). 7. In conclusion, dietary fructose appears to have a specific activating effect on hepatic PDH, mediated at least in part by inhibition of PDH kinase. These results are consistent with increased flux through hepatic PDH and synthesis of new fat, not just increased re-esterification of non-esterified fatty acids.

In vitro metabolism of 5,8-dideazafolates and 5,8-dideazaisofolates by mammalian folylpoly-gamma-glutamate synthetase

The in vitro metabolism of a variety of 5,8-dideazafolate and 5,8-dideazaisofolate analogues by pig liver folylpolyglutamate synthetase and the specificity of the enzyme for some polyglutamate derivatives of these analogues have been investigated. All 4-oxo-quinazoline analogues were metabolized to long chain polyglutamate derivatives, primarily the pentaglutamate, whereas 4-amino-quinazolines were metabolized to a lesser extent, with the accumulation of di- and triglutamate derivatives. This pattern of metabolism was consistent with the large drop in Vmax/Km and Vmax values for folylpolyglutamate synthetase observed with diglutamate derivatives of 4-aminofolate analogues. The extent of metabolism of the various analogues did not correlate with the relative substrate effectiveness of their parent monoglutamate derivatives. The 5-chloro and 5-methyl substitutions of quinazolines enhanced the addition of glutamate residues to 4-amino derivatives but markedly impaired the metabolism of 4-oxo derivatives.

Fraction of hepatic cytosolic acetyl-CoA derived from glucose in vivo: relation to PDH phosphorylation state

We measured the contribution of glucose to hepatic cytosolic acetyl-CoA in vivo in rats and compared it with the phosphorylation state of a potentially regulatory enzyme complex [pyruvate dehydrogenase (PDH)]. Xenobiotic probes were used to sample hepatic cytosolic acetyl-CoA [acetylated sulfamethoxazole (SMX)] and UDP-glucose (glucuronidated acetaminophen) in vivo during [U-14C]glucose infusions. Percent active (dephosphorylated) form of PDH (PDHa) was determined on freeze-clamped liver. First, we confirmed using liver cell elutriation that acetylation of SMX occurs in parenchymal hepatocytes. Next, the fraction of cytosolic acetyl-CoA derived from [14C]glucose in vivo was shown to depend on dietary state. Specific activity of acetyl-CoA relative to plasma glucose or hepatic UDP-glucose was lower after 48 h fasting than after overnight fasting, and glucose refeeding (25 mg.kg-1.min-1 iv) maximally increased [14C]-glucose fractional contribution to acetyl-CoA within 2 h in the overnight-fasted but not in the prolonged fasted group. Hepatic PDHa demonstrated a similar but not identical pattern. The isotopic and enzymatic parameters showed significant correlations (r2 = 0.61 in 48-h fasted-refed group, r2 = 0.28 in overnight-fasted refed group), although [14C]glucose contribution to acetyl-CoA increased disproportionately compared with PDHa as refeeding progressed. The indirect pathway of UDP-glucose synthesis correlated inversely with the fractional contribution of glucose to acetyl-CoA. In summary, the fraction of hepatic acetyl-CoA derived from glucose in vivo is influenced by acute and chronic dietary factors and is only partially explained by PDHa. Regulation of the carbon source of hepatic acetyl-CoA in vivo and interactions suggested by these results (e.g., glucose-fatty acid cycle; branch-point regulation of glucose recycling) can be addressed in a quantitative fashion using this experimental framework.