Rapid spectral variability of a giant flare from a magnetar in NGC 253.

Magnetars are neutron stars with extremely strong magnetic fields (1013 to 1015 gauss)1,2, which episodically emit X-ray bursts approximately 100 milliseconds long and with energies of 1040 to 1041 erg. Occasionally, they also produce extremely bright and energetic giant flares, which begin with a short (roughly 0.2 seconds), intense flash, followed by fainter, longer-lasting emission that is modulated by the spin period of the magnetar3,4 (typically 2 to 12 seconds). Over the past 40 years, only three such flares have been observed in our local group of galaxies3-6, and in all cases the extreme intensity of the flares caused the detectors to saturate. It has been proposed that extragalactic giant flares are probably a subset7-11 of short γ-ray bursts, given that the sensitivity of current instrumentation prevents us from detecting the pulsating tail, whereas the initial bright flash is readily observable out to distances of around 10 to 20 million parsecs. Here we report X-ray and γ-ray observations of the γ-ray burst GRB 200415A, which has a rapid onset, very fast time variability, flat spectra and substantial sub-millisecond spectral evolution. These attributes match well with those expected for a giant flare from an extragalactic magnetar12, given that GRB 200415A is directionally associated13 with the galaxy NGC 253 (roughly 3.5 million parsecs away). The detection of three-megaelectronvolt photons provides evidence for the relativistic motion of the emitting plasma. Radiation from such rapidly moving gas around a rotating magnetar may have generated the rapid spectral evolution that we observe.

Sevoflurane-Induced Dysregulation of Cation-Chloride Cotransporters NKCC1 and KCC2 in Neonatal Mouse Brain.

The cation-chloride cotransporters Na+-K+-2Cl--1 (NKCC1) and K+-2Cl--2 (KCC2) critically regulate neuronal responses to gamma-aminobutyric acid (GABA). NKCC1 renders GABA excitatory in immature neurons while expression of KCC2 signals GABA maturation to its inhibitory role. Imbalances in NKCC1/KCC2 alter GABA neurotransmission, which may contribute to hyperexcitability and blunted inhibition in neurocircuitry after neonatal exposure to anesthesia. Thus, we hypothesized that anesthetics may dysregulate NKCC1 and/or KCC2 in developing brain. We exposed postnatal day (PND) 7 mice to sevoflurane or carrier gases and assessed NKCC1 and KCC2 expression across three brain regions 6 h and 24 h after initial exposure. To test differences in behavior, we challenged pups receiving sevoflurane or carrier gases on PND7 with propofol on PND8 and recorded parameters of anesthesia induction and maintenance. Sevoflurane exposure increased cortical NKCC1 at 6 h (p = 0.03) and decreased cortical and hippocampal KCC2 at 24 h (p = 0.009 and p = 0.007, respectively). NKCC1/KCC2 ratio was significantly increased at both 6 h (p = 0.02) and 24 h (p = 0.03) in cortex and at 24 h (p = 0.02) in hippocampus. After propofol challenge on PND8, pups previously exposed to sevoflurane on PND7 regained righting reflex significantly faster than their non-exposed cohort (p < 0.001). Disturbing NKCC1/KCC2 balance may underlie circuit hyperexcitability and contribute to neurodevelopmental impairments we have observed in previous studies of neonatal anesthesia exposure. Human infants previously exposed to anesthesia may require higher concentrations of anesthetic drugs, potentially compounding their susceptibility for neurodevelopmental sequalae.

Leydig cell cytoplasmic content is related to daily sperm production in men.

The relationship between the abundance of specific Leydig cell organelles and daily sperm production (DSP) was determined. Testes from 10 men (26-53 years of age) were obtained at autopsy within 10 h of traumatic death or heart failure and fixed by vascular perfusion. Testicular tissue was processed for light and electron microscopy. DSP/testis and Leydig cell cytoplasmic volume/testis were determined by stereology of histologic sections. The Leydig cell organelle content was determined by point counting electron micrographs for smooth endoplasmic reticulum (SER), rough endoplasmic reticulum, mitochondria, lipofuscin pigment, lipid, Golgi bodies, and Reinke crystals. Men were divided equally into two groups based on DSP/testis. Men with low DSP/testis had less SER volume density (P less than 0.01) and lower SER volume per testis (P less than 0.05) than men with high DSP. Other organelles were unrelated to DSP. When all men were combined, the volume density of SER (r = 0.80; P less than 0.01), the volume SER per testis (r = 0.69; P less than 0.05), and the volume SER per Leydig cell (r = 0.84; P less than 0.01) were significantly related to DSP. Hence, there appears to be a significant relationship between Leydig cell SER and the level of spermatogenesis in men.

Stability and electrophoretic characteristics of creatine kinase BB extracted from human brain and intestine.

Creatine kinase (CK; EC 2.7.3.2) isoenzyme BB extracted from brains of rats reportedly undergoes modification at 37 degrees C, leaving an electrophoretic variant that accounts for most of the residual CK activity. This variant, called CK-BB', migrates on electrophoresis similarly to creatine kinase isoenzyme MB. Using electrophoresis and immunoinhibition with antiserum to creatine kinase isoenzyme MM, we found CK-BB to be the only identifiable cytoplasmic isoenzyme in surgical samples from human brain and intestine. In contrast, we found that some samples of brain obtained at autopsy contain CK-BB'. We also found that CK-BB extracted from human brain was converted to CK-BB' upon incubation in serum or plasma at 37 degrees C. We found a similar development of CK-BB' in incubation mixtures of serum or plasma containing CK-BB obtained from surgical samples of human intestine. The development of CK-BB' during infarction of the gastrointestinal system may thus be a source of false-positive CK-MB in the laboratory verification of myocardial infarction when electrophoresis is used as the only method to identify CK isoenzymes.