Simultaneous estimation of a model-derived input function for quantifying cerebral glucose metabolism with [18F]FDG PET.

BACKGROUND: Quantification of the cerebral metabolic rate of glucose (CMRGlu) by dynamic [18F]FDG PET requires invasive arterial sampling. Alternatives to using an arterial input function (AIF) include the simultaneous estimation (SIME) approach, which models the image-derived input function (IDIF) by a series of exponentials with coefficients obtained by fitting time activity curves (TACs) from multiple volumes-of-interest. A limitation of SIME is the assumption that the input function can be modelled accurately by a series of exponentials. Alternatively, we propose a SIME approach based on the two-tissue compartment model to extract a high signal-to-noise ratio (SNR) model-derived input function (MDIF) from the whole-brain TAC. The purpose of this study is to present the MDIF approach and its implementation in the analysis of animal and human data. METHODS: Simulations were performed to assess the accuracy of the MDIF approach. Animal experiments were conducted to compare derived MDIFs to measured AIFs (n = 5). Using dynamic [18F]FDG PET data from neurologically healthy volunteers (n = 18), the MDIF method was compared to the original SIME-IDIF. Lastly, the feasibility of extracting parametric images was investigated by implementing a variational Bayesian parameter estimation approach. RESULTS: Simulations demonstrated that the MDIF can be accurately extracted from a whole-brain TAC. Good agreement between MDIFs and measured AIFs was found in the animal experiments. Similarly, the MDIF-to-IDIF area-under-the-curve ratio from the human data was 1.02 ± 0.08, resulting in good agreement in grey matter CMRGlu: 24.5 ± 3.6 and 23.9 ± 3.2 mL/100 g/min for MDIF and IDIF, respectively. The MDIF method proved superior in characterizing the first pass of [18F]FDG. Groupwise parametric images obtained with the MDIF showed the expected spatial patterns. CONCLUSIONS: A model-driven SIME method was proposed to derive high SNR input functions. Its potential was demonstrated by the good agreement between MDIFs and AIFs in animal experiments. In addition, CMRGlu estimates obtained in the human study agreed to literature values. The MDIF approach requires fewer fitting parameters than the original SIME method and has the advantage that it can model the shape of any input function. In turn, the high SNR of the MDIFs has the potential to facilitate the extraction of voxelwise parameters when combined with robust parameter estimation methods such as the variational Bayesian approach.

Aiming for [18F]FDG-PET acquisition time reduction in clinical practice for neurological patients.

PURPOSE: Positron emission tomography (PET) imaging with [18F]FDG provides valuable information regarding the underlying pathological processes in neurodegenerative disorders. PET imaging for these populations should be as short as possible to limit head movements and improve comfort. This study aimed to validate an optimized [18F]FDG-PET image reconstruction protocol aiming to reduce acquisition time while maintaining adequate quantification accuracy and image quality. METHODS: A time-reduced reconstruction protocol (5 min) was evaluated in [18F]FDG-PET retrospective data from healthy individuals and Alzheimer's disease (AD) patients. Standard (8 min) and time-reduced protocols were compared by means of image quality and quantification accuracy metrics, as well as standardized uptake value ratio (SUVR) and Z-scores (pons was used as reference). Images were randomly and blindly presented to experienced physicians and scored in terms of image quality. RESULTS: No differences between protocols were identified during the visual assessment. Small differences (p < 0.01) in the pons SUVR were observed between the standard and time-reduced protocols for healthy individuals (-0.002 ±â€¯0.011) and AD patients (-0.007 ±â€¯0.013). Likewise, incorporating the PSF correction in the reconstruction algorithm resulted in small differences (p < 0.01) in SUVR between protocols (healthy individuals: -0.003 ±â€¯0.011; AD patients: -0.007 ±â€¯0.014). CONCLUSION: Quality metrics were similar between time-reduced and standard protocols. In the visual assessment of the images, the physicians did not consider the use of PSF adequate, as it degraded the quality image. Shortening the acquisition time is possible by optimizing the image reconstruction parameters while maintaining adequate quantification accuracy and image quality.

Chronological characterization of sperm morpho-functional damage and recovery after testicular heat stress in Nellore bulls.

Heat stress (HS) affects spermatogenesis and sperm maturation, decreasing sperm quality. Yet sperm morpho-functional changes caused by HS in Nellore bulls are not fully elucidated. This study aimed to show the chronological effects on sperm quality of HS during spermatogenesis and sperm maturation until recovery of the seminiferous epithelium in Nellore bulls. Nine Nellore bulls were distributed into control and heat stress (HS-scrotal bags/96 h) groups. The study was divided into five Periods: 1. Control (14-7 days before HS); 2. Stored sperm (0-7 days after HS); 3. Sperm maturation and late spermatogenesis (14-42 days after HS); 4. Early spermatogenesis (49-63 days after HS), and 5. Recovery (70-77 days after HS). Semen was collected once a week and evaluated for sperm motility, morphology, plasma, acrosome, and mitochondrial membranes, lipid peroxidation, and DNA fragmentation. Sperm characteristics were similar between groups in Periods 1 (control). During Period 2, HS increased detached normal head defect and decreased mitochondrial membrane potential, denoting effects on the sperm stored at the epididymis cauda. In Period 3, HS decreased sperm motility, plasma membrane integrity, and mitochondrial membrane potential and increased abnormal sperm, lipid peroxidation, and DNA fragmentation; reflecting the effects on sperm that were in the epididymis body and head and late spermatogenesis (spermiogenesis and meiosis). In Period 4, HS maintained a reduction in the mitochondrial membrane potential and an increase in abnormal sperm; injuries that could occur during early spermatogenesis (mitosis). Finally, in Period 5, the groups were similar, confirming the recovery of the seminiferous epithelium after HS. This study provides insights on the effects of HS on the complete process of sperm maturation and spermatogenesis, until recovery in sperm from Nellore bulls.

Changes in miRNA levels of sperm and small extracellular vesicles of seminal plasma are associated with transient scrotal heat stress in bulls.

Scrotal heat stress affects spermatogenesis and impairs male fertility by increasing sperm morphological abnormalities, oxidative stress and DNA fragmentation. While sperm morpho-functional changes triggered by scrotal heat stress are well described, sperm molecular alterations remain unknown. Recently, spermatozoa were described as accumulating miRNAs during the last steps of spermatogenesis and through epididymis transit, mainly by communication with small extracellular vesicles (sEVs). Herein, the aim was to investigate the impact of scrotal heat stress in miRNAs profile of sperm, as well as, seminal plasma sEVs. Six Nelore bulls (Bos indicus) were divided into two groups: Control (CON; n = 3) and Scrotal Heat Stress (SHS; n = 3; scrotal heat stressed during 96 h by scrotal bags). The day that the scrotal bags were removed from SHS group was considered as D0 (Day zero). Seminal plasma sEVs were isolated from semen samples collected seven days after heat stress (D+7) to evaluate sEVs diameter, concentration, and 380 miRNA levels. Sperm morpho-functional features and profile of 380 miRNAs were evaluated from semen collected 21 days after heat stress (D+21). As a control, sEVs and sperm were analyzed seven days before heat stress (D-7). Only semen parameters that were not significantly different (P > 0.05) among bulls on D-7 were addressed on D+7 and D+21. While no alterations in diameter and concentration were detected in sEVs on D+7 between CON and SHS groups, three sEVs-miRNAs (miR-23b-5p, -489 and -1248) were down-regulated in SHS bulls compared to CON on D+7; other three (miR-126-5p, -656 and -1307) displayed a tendency (0.05 < P < 0.10) to be altered. Sperm oxidative stress was higher, and the level of 21 sperm miRNAs was altered (18 down-, 3 up-regulated) in SHS bulls compared to CON on D+21. Functional analysis indicated that target genes involved in transcription activation, as well as cell proliferation and differentiation were related to the 18 down-regulated sperm miRNAs (miR-9-5p, -15a, -18a, -20b, -30a-5p, -30b-5p, -30d, -30e-5p -34b, -34c, -106b, -126-5p, -146a, -191, -192, -200b, -335 and -449a). Thus, the scrotal heat stress probably impacted testicular and epididymis functions by reducing the levels of a substantial proportion of sEVs and sperm miRNAs. Our findings suggest that miR-126-5p was possibly trafficked between sEVs and sperm and provide new insights on the mechanism by which sperm acquire miRNAs in the last stages of spermatogenesis and sperm maturation in cattle.

Heat stress effects on bovine sperm cells: a chronological approach to early findings.

Testicular heat stress affects sperm quality and fertility. However, the chronology of these effects is not yet fully understood. This study aimed to establish the early sequential effects of heat stress in bull sperm quality. Semen and blood samples of Nellore breed bulls were collected and distributed into control and testicular heat stress (scrotal bags/96 h) groups. Semen samples were evaluated for sperm motility, abnormalities, plasma membrane integrity, acrosomal membrane integrity, mitochondrial membrane potential, sperm lipid peroxidation, seminal plasma lipid peroxidation, and DNA fragmentation. Blood plasma was also evaluated for lipid peroxidation. An increase in sperm abnormalities was observed 7 days following heat stress. After 14 days, sperm lipid peroxidation increased and mitochondrial membrane function, sperm motility, and plasma membrane integrity decreased. Heat stress effects were still observed after 21 days following heat stress. An increase in sperm DNA fragmentation was observed as a late effect after 28 days. Thus, the initial effects of heat stress (i.e., increasing sperm abnormalities and lipid peroxidation) suggest the presence of oxidative stress in the semen that alters mitochondrial function, sperm motility, plasma membrane integrity, and belatedly, DNA fragmentation. Although sperm abnormalities persisted and increased over time, sperm lipid peroxidation, in turn, increased only until 21 days after heat stress. In this regard, these findings provide a greater understanding of the chronological effects of experimentally induced heat stress on bovine sperm, providing valuable insights about spermatogenesis during the first 28 days following heat stress.

Examining the factors that affect structural repetition in question answering.

We present two experiments that examine structural priming in the single-trial phone-call paradigm introduced by Levelt and Kelter (Cognitive psychology, 14 (1), 78-106, 1982). Experimenters called businesses and asked either What time do you close? or At what time do you close? Participants were more likely to produce a prepositional response (At 7 o'clock vs. 7 o'clock) following a prepositional question than following a non-prepositional question. Experiments 1 and 2 attempted to strengthen the priming effect by having the experimenters engage in a brief interaction with the participant before asking the What time…? question. The interactions did not reliably affect the observed priming effect. An analysis across experiments demonstrated that the priming effect found in this paradigm is generally smaller than the average structural priming effect (as reported in Mahowald, James, Futrell, & Gibson, Journal of Memory and Language, 91, 5-27, 2016), but within the range of the effects that are observed in different structural priming paradigms.

Effects of pentoxifylline supplementation to semen extender on post-breeding inflammation response assessed by endometrial cytology and vascular perfusion in mares.

The aim was to evaluate effects of addition of pentoxifylline to skimmed milk semen extender on uterine inflammatory response. Thirty-six estrous cycles of 15 mares were randomly divided into five groups for artificial insemination (AI): Control: mimicking the AI procedure (n = 7); Extender: deposition of skimmed milk based extender (n = 7); Extender + PTX: skimmed milk based extender plus pentoxifylline (7.18 mM; n = 8); Semen: semen diluted with extender without pentoxifylline (n = 7), and Semen + PTX: semen diluted with extender containing pentoxifylline (n = 7). Mares in estrus were examined by trans-rectal palpation and using ultrasonography, and ovulation was induced. Uterine hemodynamics were assessed immediately before ovulation induction (T-30), immediately before AI (T0), 2 (T2), 6 (T6), 12 (T12), 24 (T24) and 48 (T48) h after AI. Endometrial samples were collected 6 h after AI, and slides were stained and examined to determine percentage of PMN. Pentoxifylline had no additional effect on vascular perfusion. There was a major inflammatory response with pentoxifylline treatment that was greater than that of the control group. In the group treated with Extender + PTX, there were more PMN (57.98 ±â€¯9.42%) than in the group treated with Extender (20.20 ±â€¯6.63%) and in the Semen + PTX group more PMN (82.84 ±â€¯5.71%) than in the Semen-treated group (47.83 ±â€¯10.61%). These findings indicate the addition of pentoxifylline does not stimulate blood flow; however, it induces a greater immune defense response because more neutrophils migrate to the uterine lumen.

Inter-annual changes in fish communities of a tropical bay in southeastern Brazil: What can be inferred from anthropogenic activities?

We assessed inter-annual changes in fish assemblages of a tropical bay which experienced a heavily industrialized process in the last decades. A highly significant difference in community structure among the bay zones, and a decrease in fish richness and abundance over time were found. Changes in fish richness and abundance between the two first (1987-1988 and 1993-1995) and the two latter time periods (1998-2001 and 2012-2013) were sharpest in the inner bay zone, the most impacted bay area, and in the middle zone, whereas the outer zone remained comparatively stable over time. These changes coincided with increased metal pollution (mainly, Zn and Cd) in the bay and with the enlargement of the Sepetiba Port. Spatial changes in the fish community structure among the bay zones were related to differences in salinity, transparency and depth with this latter variable acting as a buffer stabilizing temporal community changes.

Análise quantitativa da ecogenicidade testicular pela técnica do histograma de ovinos da baixada ocidental maranhense / Quantitative analysis of testicular echogenicity by technical histogram in sheep of the western lowland region of Maranhão, Brazil

A ultrassonografia é um método de diagnóstico por imagem que permite a avaliação de diferentes órgãos e estruturas corpóreas de maneira não invasiva. No entanto, a avaliação subjetiva das imagens caracteriza um dos grandes entraves na utilização desta técnica de diagnóstico, havendo necessidade de mecanismos que minimizem a subjetividade do exame e a divergência na interpretação dos achados ultrassonográficos. Desta forma este trabalho objetivou caracterizar a ecogenicidade do parênquima e mediastino testicular de ovinos utilizando a técnica do histograma escala-cinza. Foram utilizados 30 animais divididos em três grupos de acordo com a faixa etária (FE): de três a seis meses (FE1), sete a 12 meses (FE2), 13 a 18 meses (FE3) e realizadas varreduras testiculares nos planos frontal, sagital e transversal, elaborando ao final um histograma a partir das imagens ultrassonográficas. Observou-se que tanto a ecogenicidade do parênquima quanto a do mediastino testicular aumentaram gradativamente com a progressão das idades dos animais, com média e desvio-padrão de 95,00±19,05 e 94,35±18,82 para a ecogenicidade do parênquima do antímero direito e esquerdo, respectivamente, e 127,95±12,97 para o mediastino direito e 126,59±11,78 para o esquerdo. A técnica do histograma escala-cinza demonstrou ser um método eficiente na determinação da ecogenicidade testicular, possibilitando o estabelecimento de padrões de normalidade que venham a auxiliar pesquisas futuras no monitoramento do desenvolvimento testicular bem como na detecção de patologias. Para a regimes exclusivos de criação extensiva, como na baixada maranhense, representa ferramenta valiosa para sua utilização em projetos sociais do Estado que atendem a agricultura familiar.

Ultrasound is a diagnostic imaging method that allows a no invasive evaluation of different organs and body structures. However, the personal evaluation of images is one of the major hampers in using this technique. In order to reduce this drawback, it is necessary to find out tools that can help diminish the divergence in the interpretation of sonographic findings. Therefore, this study aimed to identify features of the parenchyma's and mediastinum's testis of sheep echogenicity using the technique of gray scale histogram. 30 animals were divided into three groups according to age (FE): three to six months (FE1), seven to 12 months (FE2), 13 to 18 months (FE3). The testicular scans were performed in the frontal, sagital and transverse views, and the gray scale histograms were analyzed. It was observed that such parenchymal as the mediastinum testis echogenicity gradually increased with the aging of the animals, with mean and standard deviation of 95.00±19.05 and 94.35±18.82 for the echogenicity parenchyma of the right and left antimere, respectively, and 127.95±12.97 to 126.59±11.78, for the right and the left mediastinum. The technique of gray scale histogram was an efficient method for determination of testicular echogenicity, enabling the establishment of normal standards that may assist future research in monitoring testicular development as well as for detecting pathologies. For exclusive regimes of extensive farming, as the western lowland region of Maranhão, is a valuable tool for use in social projects of the State to attend the family farm.