Fluorescent Stain Method for the Simultaneous Determination of Mitochondrial Potential and Integrity of Plasma and Acrosomal Membranes in Boar Sperm

The purpose of this study was to validate a technique for simultaneous evaluation of the plasma, acrosomal and mitochondrial membranes in boar spermatozoa, using an association of fluorescent probes: Propidium iodide (PI), fluorescein isothiocyanate-conjugated Pisum sativum agglutinin (FITC-PSA) and JC-1. Three ejaculates from each of four different boars, all showing motility >or=80% and abnormal morphology 相似文献   

Practical Techniques for Bovine Sperm Simultaneous Fluorimetric Assessment of Plasma, Acrosomal and Mitochondrial Membranes

This experiment was performed to develop and validate practical techniques for simultaneous evaluation of the integrity of plasma and acrosomal membranes, as well as mitochondrial function in bovine spermatozoa using associations of fluorescent probes. Four protocols of fluorescent probes association were defined: protocol 1: propidium iodide (PI), fluorescein isothiocyanate‐conjugated Pisum sativum agglutinin (FITC‐PSA) and rhodamine 123; protocol 2: PI, FITC‐PSA and MitoTracker Green FM (MITO); protocol 3: PI, Hoechst 33342 (H342), FITC‐PSA and CMXRos; and protocol 4: PI, H342, FITC‐PSA and JC‐1. Three ejaculates from each of the four bulls (n = 12) were utilized, showing sperm motility ≥80% and abnormal morphology ≤10%. The semen was diluted in Modified Tyrode’s medium (TALP) (25 × 10⁶ spermatozoa/ml) and split into two aliquots, one sample was flash‐frozen in liquid nitrogen and thawed. Samples for three treatments were prepared with the following ratio of fresh semen : flash‐frozen semen: 100 : 0, 50 : 50 and 0 : 100. Samples were stained in all four protocols and evaluated by epifluorescence microscopy. Protocol 1 did not result in a satisfactory stain, so it could not be validated. Protocols 2, 3 and 4 were validated and showed high determination coefficient to plasma membrane integrity (R² = 0.95, 0.93 and 0.92, respectively), acrosome integrity (R² = 0.95, 0.92 and 0.91, respectively) and mitochondrial function (R² = 0.84, 0.93 and R² = 0.93, respectively). These techniques are efficient for the simultaneous integrity evaluation of plasma and acrosomal membranes and mitochondrial function in bovine spermatozoa. However, JC‐1 has an advantage over MITO and CMXRos, as it separates two cell populations with high and low mitochondrial membrane potential.     

Studies on the mechanisms of fixation and release of ammonium in paddy soils after flooding. I. Effect of iron oxides on ammonium fixation

Experiments were conducted with two typical paddy soils from China and a vermiculite to study the influence of iron oxides on the fixation and release of ammonium. Removing iron oxides, especially amorphous iron oxides, from the soils favoured the release of non-exchangeable NH₄-N and stimulated the fixation of NH₄-N in the presence of added (NH₄)₂SO₄. Addition of artificial goethite and hematite to the original soils or to the soils free of iron oxides reduced the fixation of NH₄⁺-ions. This effect was also observed with vermiculite. We conclude that the coating of clay minerals with iron oxides has an impact on the diffusion of NH₄⁺-ions into and out of the interlayers of the clay minerals. The reduction and dissolution of iron oxides induced by low redox potential (E_h) after flooding of paddy soils is assumed to be an important mechanism controlling NH₄⁺-fixation in paddy fields.     

Lunar surface magnetic fields and their interaction with the solar wind: results from lunar prospector

The magnetometer and electron reflectometer experiment on the Lunar Prospector spacecraft has obtained maps of lunar crustal magnetic fields and observed the interaction between the solar wind and regions of strong crustal magnetic fields at high selenographic latitude (30 degreesS to 80 degreesS) and low ( approximately 100 kilometers) altitude. Electron reflection maps of the regions antipodal to the Imbrium and Serenitatis impact basins, extending to 80 degreesS latitude, show that crustal magnetic fields fill most of the antipodal zones of those basins. This finding provides further evidence for the hypothesis that basin-forming impacts result in magnetization of the lunar crust at their antipodes. The crustal magnetic fields of the Imbrium antipode region are strong enough to deflect the solar wind and form a miniature (100 to several hundred kilometers across) magnetosphere, magnetosheath, and bow shock system.     

Ammonium fixation by clay minerals in different layers of two paddy soils after flooding

 The influence of flooding and cellulose addition on the fixation of NH₄ ⁺ in different soil layers of two paddy soils from China (an entisol and an ultisol) was investigated. In both soils the content of total reducing substances (TRS) sharply increased during the first days after flooding and was highest in the anoxic layers. This increase, which was more pronounced in the entisol with the higher total C content, was accompanied by an increase in the concentration of non-exchangeable NH₄ ⁺ in both soils. The increase in mineralization after flooding, resulting in higher concentrations of exchangeable NH₄ ⁺, favoured the fixation of NH₄ ⁺. Although the application of cellulose resulted in higher TRS contents, the fixation of NH₄ ⁺ ions decreased, which may have been the result of microbiological N immobilization. Received: 29 April 1998     

Disulfide-dependent multimeric assembly of resistin family hormones

Resistin, founding member of the resistin-like molecule (RELM) hormone family, is secreted selectively from adipocytes and induces liver-specific antagonism of insulin action, thus providing a potential molecular link between obesity and diabetes. Crystal structures of resistin and RELMbeta reveal an unusual multimeric structure. Each protomer comprises a carboxy-terminal disulfide-rich beta-sandwich "head" domain and an amino-terminal alpha-helical "tail" segment. The alpha-helical segments associate to form three-stranded coiled coils, and surface-exposed interchain disulfide linkages mediate the formation of tail-to-tail hexamers. Analysis of serum samples shows that resistin circulates in two distinct assembly states, likely corresponding to hexamers and trimers. Infusion of a resistin mutant, lacking the intertrimer disulfide bonds, in pancreatic-insulin clamp studies reveals substantially more potent effects on hepatic insulin sensitivity than those observed with wild-type resistin. This result suggests that processing of the intertrimer disulfide bonds may reflect an obligatory step toward activation.     

Communicating food safety: Ethical issues in risk communication

This paper discusses two paradigms of risk communication that guide strategies for communicating food safety issues. Built on the principles of social utility and paternalism, the first paradigm heavily relies on science and technical experts to determine food safety regulations and policies. Risk communication, in this context, is a unidirectional process by which experts from the industry or government regulatory agencies inform or alert potentially affected publics about the hazards they face and the protective actions they can take. However, public trust and confidence in government and industry have considerably declined. Experts are being questioned about the objectivity of their assessments of risks. Policy makers are being challenged on such risk management decisions as tolerance guidelines, food labeling laws, and emergency warning systems. Concomitantly, some segments of the public, especially consumer advocates and environmental groups, are demanding increased input into the decision making process as they call for the recognition of lay perceptions and interpretations of risk as a legitimate counterpart to technically-assessed risk. Hence, instead of the linear, persuasion-oriented communication process, there are evolving efforts to shape risk communication into a more dialogical, interactive, and democratic exchange of information among different stakeholders (i.e., technical experts, government policy makers, industry, interest groups, and the general public). Reflecting a more Jeffersonian approach, this second paradigm argues that decisions about food safety are so complex and multi-dimensional that they must not be left to experts alone. However, both paradigms present ethical dilemmas. Determining the risks and relative safety of foods is not a totally objective and concise process. Since it involves social, economic, political, and personal values, how can the public not be involved in the exchange of ideas and information concerning food risks and safety? On the other hand, can we afford to let public opinion govern decisions pertaining to food risks and safety without consideration for the merits of scientific risk assessment? This paper raises questions regarding some assumptions of these two risk communication paradigms, and explores and discusses some of the salient ethical questions inherent in each framework.     

Effects of rectilinear acceleration and optokinetic and caloric stimulations in space

During the flight of Spacelab 1 the crew performed a number of experiments to explore changes in vestibular function and visual-vestibular interactions on exposure to microgravity. Measurements were made on the threshold for detection of linear oscillation, vestibulo-ocular reflexes elicited by angular and linear movements, oculomotor and posture responses to optokinetic stimulations, and responses to caloric stimulation. Tests were also conducted on the ground, during the 4 months before and on days 1 to 6 after flight. The most significant result was that caloric mystagmus of the same direction as on the earth could also be evoked in the weightless environment.     

Regulation of fasted blood glucose by resistin

The association between obesity and diabetes supports an endocrine role for the adipocyte in maintaining glucose homeostasis. Here we report that mice lacking the adipocyte hormone resistin exhibit low blood glucose levels after fasting, due to reduced hepatic glucose production. This is partly mediated by activation of adenosine monophosphate-activated protein kinase and decreased expression of gluconeogenic enzymes in the liver. The data thus support a physiological function for resistin in the maintenance of blood glucose during fasting. Remarkably, lack of resistin diminishes the increase in post-fast blood glucose normally associated with increased weight, suggesting a role for resistin in mediating hyperglycemia associated with obesity.