Occurrence of B chromosomes in Tetragonisca Latreille, 1811 (Hymenoptera, Apidae, Meliponini): A new contribution to the cytotaxonomy of the genus

Tetragonisca angustula and Tetragonisca fiebrigi have recently been listed as valid species. This study aimed to cytogenetically investigate both species, emphasizing the new registry of B chromosomes in the tribe Meliponini. We analyzed colonies of T. angustula and T. fiebrigi collected at Tangará da Serra, Mato Grosso, Brazil, through conventional Giemsa staining, C-banding, and base-specific fluorochrome staining (CMA3/DAPI). T. angustula showed 2n = 34 chromosomes in females and n = 17 in males, with karyotype formula 2K = 34AM. T. fiebrigi showed numeric variation, with chromosome number varying from 2n = 34 to 2n = 36 in females and from n = 17 to n = 18 in males, with karyotype formula 2K = 32AM+2AMc and 2K = 32AM+2AMc + 1 or 2 B-chromosomes. The B chromosomes are heterochromatic. In T. fiebrigi, the CMA3/DAPI staining revealed four chromosomes with a CMA3 positive band. All individuals from the same colony showed the same number of B chromosomes. T. angustula and T. fiebrigi showed karyotype divergence, principally due to the presence of B chromosomes, which are found only in T. fiebrigi. Our data corroborate the status of valid species for both T. angustula and T. fiebrigi, as recently proposed

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field

K+ Currents in Isolated Vestibular Afferent Calyx Terminals

Vestibular hair cells transduce mechanical displacements of their hair bundles into an electrical receptor potential which modulates transmitter release and subsequent action potential firing in afferent neurons. To probe ionic mechanisms underlying sensory coding in vestibular calyces, we used the whole-cell patch-clamp technique to record action potentials and K+ currents from afferent calyx terminals isolated from the semicircular canals of Mongolian gerbils. Calyx terminals showed minimal current at the mean zero-current potential (−60 mV), but two types of outward K+ currents were identified at potentials above −50 mV. The first current was a rapidly activating and inactivating K+ current that was blocked by 4-aminopyridine (4-AP, 2.5 mM) and BDS-I (up to 250 nM). The time constant for activation of this current decreased with membrane depolarization to a minimum value of ∼1 ms. The 4-AP-sensitive current showed steady-state inactivation with a half-inactivation of approximately −70 mV. A second, more slowly activating current (activation time constant was 8.5 ± 0.7 ms at −8 mV) was sensitive to TEA (30 mM). The TEA-sensitive current also showed steady-state inactivation with a half-inactivation of −95.4 ± 1.4 mV, following 500-ms duration conditioning pulses. A combination of 4-AP and TEA blocked ∼90% of the total outward current. In current clamp, single Na+-dependent action potentials were evoked following hyperpolarization to potentials more negative than the resting potential. 4-AP application increased action potential width, whereas TEA both increased the width and greatly reduced repolarization of the action potential