Spin Relaxation Resonances Due to the Spin-Axis Interaction in Dense Rubidium and Cesium Vapor

Resonances in the magnetic decoupling curves for the spin relaxation of dense alkali-metal vapors prove that much of the relaxation is due to the spin-axis interaction in triplet dimers. Initial estimates of the spin-axis coupling coefficients for the dimers are 290 MHz for Rb; 2500 MHz for Cs.Comment: submitted to Physical Review Letters, text + 3 figure

Paternal effects on early embryogenesis

Historically, less attention has been paid to paternal effects on early embryogenesis than maternal effects. However, it is now apparent that certain male factor infertility phenotypes are associated with increased DNA fragmentation and/or chromosome aneuploidies that may compromise early embryonic development. In addition, there is a growing body of evidence that the fertilizing sperm has more function than just carrying an intact, haploid genome. The paternally inherited centrosome is essential for normal fertilization, and the success of higher order chromatin packaging may impact embryogenesis. Epigenetic modifications of sperm chromatin may contribute to the reprogramming of the genome, and sperm delivered mRNA has also been hythesized to be necessary for embryogenesis. There is less information about the epigenetic factors affecting embryogenesis than genetic factors, but the epigenetics of gamete and early embryogenesis is a rapidly advancing field

Spermiogenesis and spermatozoon ultrastructure of the bothriocephalidean cestode Clestobothrium crassiceps (Rudolphi, 1819), a parasite of the teleost fish Merluccius merluccius (Gadiformes: Merlucciidae)

Spermiogenesis and the ultrastructure of the spermatozoon of the bothriocephalidean cestode Clestobothrium crassiceps (Rudolphi, 1819), a parasite of the teleost fish Merluccius merluccius (Linnaeus, 1758), have been studied by means of transmission electron microscopy. Spermiogenesis involves firstly the formation of a differentiation zone. It is characterized by the presence of two centrioles associated with striated rootlets, an intercentriolar body and an electron-dense material in the apical region of this zone. Later, two flagella develop from the centrioles, growing orthogonally in relation to the median cytoplasmic process. Flagella then undergo a rotation of 90° until they become parallel to the median cytoplasmic process, followed by the proximodistal fusion of the flagella with the median cytoplasmic process. The nucleus elongates and afterwards it migrates along the spermatid body. Spermiogenesis finishes with the appearance of the apical cone surrounded by the single helical crested body at the base of the spermatid. Finally, the narrowing of the ring of arched membranes detaches the fully formed spermatozoon. The mature spermatozoon of C. crassiceps is filiform and contains two axonemes of the 9 + '1' trepaxonematan pattern, a parallel nucleus, parallel cortical microtubules, and electron-dense granules of glycogen. The anterior extremity of the gamete exhibits a short electron-dense apical cone and one crested body, which turns once around the sperm cell. The first axoneme is surrounded by a ring of thick cortical microtubules that persist until the appearance of the second axoneme. Later, these thick cortical microtubules disappear and thus, the mature spermatozoon exhibits two bundles of thin cortical microtubules. The posterior extremity of the male gamete presents only the nucleus. Results are discussed and compared particularly with the available ultrastructural data on the former 'pseudophyllideans'. Two differences can be established between spermatozoa of Bothriocephalidea and Diphyllobothriidea, the type of spermatozoon (II vs I) and the presence/absence of the ring of cortical microtubules

Spermiogenesis and spermatozoon ultrastructure of the diphyllidean cestode Echinobothrium euterpes (Neifar, Tyler and Euzet 2001) Tyler 2006, a parasite of the common guitarfish Rhinobatos rhinobatos

Spermiogenesis and the ultrastructural characters of the spermatozoon of Echinobothrium euterpes are described by means of transmission electron microscopy, including cytochemical analysis for glycogen. Materials were obtained from a common guitarfish Rhinobatos rhinobatos caught in the Gulf of Gabès (Tunisia). Spermiogenesis in E. euterpes is characterized by the orthogonal development of two unequal flagella followed by the flagellar rotation and the proximodistal fusion of these flagella with the median cytoplasmic process. The most interesting pattern characterizing the diphyllidean cestodes is the presence of a triangular body constituted by fines and dense granules without visible striation and assimilated at the striated rootlets. This pattern, only related in the Diphyllidea cestodes may be a synapomorphy of this order. Spermiogenesis is also characterized by the presence of a very short flagellum (around 1 μm long), observed in all the stages of spermiogenesis. This type of flagellum has never been commented in the diphyllidean cestodes and should be considered as an evolved character in this group. In the latest stage of spermiogenesis, this short axoneme probably degenerates. Thus, the mature spermatozoon of E. euterpes possesses only one axoneme of 9 + '1' trepaxonematan pattern. It also exhibits a single helical electron-dense crested body, a spiraled nucleus, few parallel cortical microtubules, and α-glycogen granules. Similitudes and differences between spermatozoa of diphyllideans are discussed

Endothermal fine-structure transition of metastable argon atoms passing through a micro-slit copper grating

The endothermal fine-structure transition ($^{3}P_{2} \rightarrow {}^3P_0$ —175 \un{meV}) of metastable argon atoms traversing at a velocity of 1030\un{m/s} a micro-slit copper grating the normal axis of which is set, in a first configuration, at $60^\circ$ with respect to the incident beam axis, is observed. The related differential cross-section (DCS) is sharply peaked at $60^\circ$ and its velocity dependence reveals the expected threshold at 900\un{m/s}. In a second configuration, the grating is set at an angle of $43^\circ$, allowing for a 7% transmission of the incident beam. Atoms elastically scattered by the corner edges of the grating slits are observed in the angular range $1^\circ$–$4^\circ$ and the elastic DCS is measured in relative values. In spite of such a widely unsuited geometry, the endothermal process still appears (with a magnitude 10 times smaller than before), because of the surface corrugation. The inelastic DCS is now peaked at $57.5^\circ$ with a width of about $6^\circ$, as predicted from the corrugation angle distribution deduced from the inelastic DCS of metastable \chem{N_2^*} molecules traversing the same grating

Ventilatory effects of continuous epidural infusion of fentanyl.

The effects of a continuous epidural administration of fentanyl on pain and on ventilation were studied in eight patients scheduled for orthopedic surgery of the knee. In each subject, epidural fentanyl was given by a bolus dose of 1 microgram.kg-1, followed by a continuous infusion of 1 microgram.kg-1.h-1 over 18 hours. Ventilatory measurements were performed during quiet breathing and during CO2 stimulation tests before surgery. After surgery measurements were made before epidural administration of fentanyl; 1, 2, 5, 18 hours after the start of epidural fentanyl infusion; and 6 hours after its discontinuation. Adequate pain relief was achieved in all patients during fentanyl administration. No significant change in ventilation was noted during quiet breathing. The slope of the ventilatory response to CO2 (VE/PaCO2) decreased significantly from 1.46 +/- 0.2 to 0.75 +/- 0.1 L.min-1.mm Hg-1 (mean +/- SEM; P less than 0.05) one hour after the onset of fentanyl administration, and remained stable throughout the infusion. Eighteen hours after the onset of epidural fentanyl infusion, VE/PaCO2 was still 0.76 +/- 0.14 L.min-1.mm Hg-1. At the end of fentanyl administration, plasma fentanyl levels measured in six patients had progressively increased from 0.42 +/- 0.02 ng.ml one hour after the onset of the infusion to 1.54 +/- 0.19 ng.ml at the end of the infusion. These results suggest that a continuous epidural administration of fentanyl is a technique of analgesia that can provide adequate pain relief but which is associated with ventilatory depression. However, with the doses used in this study, the ventilatory depression remained moderate and of no demonstrable clinical consequence