High-speed camera recordings uncover previously unidentified elements of zebrafish mating behaviors integral to successful fertilization

The mating behavior of teleost fish consists of a sequence of stereotyped actions. By observing mating of zebrafish under high-speed video, we analyzed and characterized a behavioral cascade leading to successful fertilization. When paired, a male zebrafish engages the female by oscillating his body in high frequency (quivering). In response, the female pauses swimming and bends her body (freezing). Subsequently, the male contorts his trunk to enfold the female’s trunk. This behavior is known as wrap around. Here, we found that wrap around behavior consists of two previously unidentified components. After both sexes contort their trunks, the male adjusts until his trunk compresses the female’s dorsal fin (hooking). After hooking, the male trunk slides away from the female’s dorsal fin, simultaneously sliding his pectoral fin across the female’s gravid belly, stimulating egg release (squeezing/spawning). Orchestrated coordination of spawning presumably increases fertilization success. Surgical removal of the female dorsal fin inhibited hooking and the transition to squeezing. In a neuromuscular mutant where males lack quivering, female freezing and subsequent courtship behaviors were absent. We thus identified traits of zebrafish mating behavior and clarified their roles in successful mating.

"Slow" skeletal muscles across vertebrate species

Skeletal muscle fibers are generally classified into two groups: slow (type I) and fast (type II). Fibers in each group are uniquely designed for specific locomotory needs based on their intrinsic cellular properties and the types of motor neurons that innervate them. In this review, we will focus on the current concept of slow muscle fibers which, unlike the originally proposed version based purely on amphibian muscles, varies widely depending on the animal model system studied. We will discuss recent findings from zebrafish neuromuscular junction synapses that may provide the framework for establishing a more unified view of slow muscles across mammalian and non-mammalian species.

Procaterol-stimulated increases in ciliary bend amplitude and ciliary beat frequency in mouse bronchioles

The beating cilia play a key role in lung mucociliary transport. The ciliary beating frequency (CBF) and ciliary bend amplitude (CBA) of isolated mouse bronchiolar ciliary cells were measured using a light microscope equipped with a high-speed camera (500 Hz). Procaterol (aβ(2)-agonist) increased CBA and CBF in a dose dependent manner via cAMP. The time course of CBA increase is distinct from that of CBF increase: procaterol at 10 nM first increased CBA and then CBF. Moreover, 10 pM procaterol increased CBA, not CBF, whereas 10 nM procaterol increased both CBA and CBF. Concentration-response studies of procaterol demonstrated that the CBA curve was shifted to a lower concentration than the CBF curve, which suggests that CBA regulation is different from CBF regulation. Measurements of microbead movements on the bronchiole of lung slices revealed that 10 pM procaterol increased the rate of ciliary transport by 37% and 10 nM procaterol increased it by 70%. In conclusion, we have shown that increased CBA is of particular importance for increasing the bronchiolar ciliary transport rate, although CBF also plays a role in increasing it.

Morphology and infectivity of virus that persistently caused infection in an AGS cell line

A recent report has indicated that proteins and genes of simian virus 5 (SV5) are detected in a human gastric adenocarcinoma (AGS) cell line, which is widely provided for oncology, immunology, and microbiology research. However, the production of infective virions has not been determined in this cell line. In this study, the morphology and infectivity of the virus particles of the AGS cell line were studied by light and electron microscopy and virus transmission assay. The virus particles were approximately 176.0 ± 41.1 nm in diameter. The particles possessed projections 8-12 nm long on the surface and contained a nucleocapsid determined to be 13-18 nm in width and less than 1,000 nm in length. The virus was transmissible to the Vero cell line, induced multinuclear giant cell formation, and reproduced the same shape of antigenic virions. In this study, the persistently infected virus in the AGS cell line was determined to be infective and form reproducible virions, and a new morphological feature of SV5 was determined.

Membrane potential modulation of ionomycin-stimulated Ca(2+) entry via Ca (2+)/H (+) exchange and SOC in rat submandibular acinar cells

Ionomycin (IM) at 5 microM mediates the Ca(2+)/H(+) exchange, while IM at 1 microM activates the store-operated Ca(2+) entry channels (SOCs). In this study, the effects of depolarization on both pathways were examined in rat submandibular acinar cells by increasing extracellular K(+) concentration ([K(+)](o)). IM (5 microM, the Ca(2+)/H(+) exchange) increased the intracellular Ca(2+) concentration ([Ca(2+)](i)) to an extremely high value at 151 mM [K(+)](o). However, with increasing [K(+)](o), the rates of Ca(2+) entry decreased in a linear relationship. The reversal potential (E (rev)) for the Ca(2+)/H(+) exchange was +93 mV, suggesting that IM (5 microM) exchanges 1 Ca(2+) for 1 H(+). Thus, depolarization decreases the Ca(2+) influx via the Ca(2+)/H(+) exchange because of its electrogenicity (1 Ca(2+) for 1 H(+)). On the other hand, IM (1 microM, the SOCs) abolished an increase in [Ca(2+)](i) at 151 mM [K(+)](o). With increasing [K(+)](o), the rate of Ca(2+) entry immediately decreased linearly. The E (rev) for the SOC was +3.7 mV, suggesting that the SOCs are nonselective cation channels and less selective for Ca(2+) over Na(+) (P (Ca)/P (Na) = 8.2). Moreover, an increase in extracellular Ca(2+) concentration (20 mM) enhanced the Ca(2+) entry via the SOCs at 151 mM [K(+)](o), suggesting depolarization does not inhibit the SOCs and decreases the driving force for the Ca(2+) entry. This suggests that membrane potential changes induced by a secretory stimulation finely regulate the [Ca(2+)](i) via the SOCs in rat submandibular acinar cells. In conclusion, IM increases [Ca(2+)](i) via two pathways depending on its concentration, the exchange of 1 Ca(2+) for 1 H(+) at 5 muM and the SOCs at 1 microM.

HCO(3) (-)-dependent transient acidification induced by ionomycin in rat submandibular acinar cells

Ionomycin (IM, 5 microM), which exchanges 1 Ca2+ for 1 H+, changed intracellular pH (pHi) with Ca2+ entry into rat submandibular acinar cells. IM-induced changes in pHi consisted of two components: the first is an HCO3--dependent transient pHi decrease, and the second is an HCO3--independent gradual pHi increase. IM (1 microM), which activates store-operated Ca2+ channels, induced an HCO3--dependent and transient pHi decrease without any HCO3--independent pHi increase. Thus, a gradual pHi increase was induced by the Ca2+/H+ exchange. The HCO3--dependent and transient pHi decrease induced by IM was abolished by acetazolamide, but not by methyl isobutyl amiloride (MIA) or diisothiocyanatostilbene disulfonate (DIDS), suggesting that the Na+/H+ exchange, the Cl-/HCO3- exchange, or the Na+-HCO3- cotransport induces no transient pHi decrease. Thapsigargin induced no transient pHi decrease. Thus, IM, not Ca2+ entry, reduced pHi transiently. IM reacts with Ca2+ to produce H+ in the presence of CO2/HCO3-: [H-IM]-+Ca2++CO2<-->{H-Ca-IM]+.HCO3-+H+. In this reaction, a monoprotonated IM reacts with Ca2+ and CO2 to produce an electroneutral IM complex and H+, and then H+ is removed from the cells via CO2 production. Thus, IM transiently decreased pHi. In conclusion, in rat submandibular acinar cells IM (5 microM) transiently reduces pHi because of its chemical characteristics, with HCO3- dependence, and increases pHi by exchanging Ca2+ for H+, which is independent of HCO3-.

Reactivation from latency displays HIV particle budding at plasma membrane, accompanying CD44 upregulation and recruitment

BACKGROUND

It has been accepted that HIV buds from the cell surface in T lymphocytes, whereas in macrophages it buds into intracellular endosomes. Recent studies, on the other hand, suggest that HIV preferentially buds from the cell surface even in monocytic cells. However, most studies are based on observations in acutely infected cells and little is known about HIV budding concomitant with reactivation from latency. Such studies would provide a better understanding of a reservoir for HIV.

RESULTS

We observed HIV budding in latently infected T lymphocytic and monocytic cell lines following TNF-alpha stimulation and examined the upregulation of host factors that may be involved in particle production. Electron microscopy analysis revealed that reactivation of latently infected J1.1 cells (latently infected Jurkat cells with HIV-1) and U1 cells (latently infected U937 cells with HIV-1) displayed HIV particle budding predominantly at the plasma membrane, a morphology that is similar to particle budding in acutely infected Jurkat and U937 cells. When mRNA expression levels were quantified by qRT-PCR, we found that particle production from reactivated J1.1 and U1 cells was accompanied by CD44 upregulation. This upregulation was similarly observed when Jurkat and U937 cells were acutely infected with HIV-1 but not when just stimulated with TNF-alpha, suggesting that CD44 upregulation was linked with HIV production but not with cell stimulation. The molecules in endocytic pathways such as CD63 and HRS were also upregulated when U1 cells were reactivated and U937 cells were acutely infected with HIV-1. Confocal microscopy revealed that these upregulated host molecules were recruited to and accumulated at the sites where mature particles were formed at the plasma membrane.

CONCLUSION

Our study indicates that HIV particles are budded at the plasma membrane upon reactivation from latency, a morphology that is similar to particle budding in acute infection. Our data also suggest that HIV expression may lead to the upregulation of certain host cell molecules that are recruited to sites of particle assembly, possibly coordinating particle production.

Intrabacterial proton-dependent CagA transport system in Helicobacter pylori

Helicobacter pylori CagA modifies the signalling of host cells and causes gastric diseases. Although CagA is injected into gastric epithelial cells through the type IV secretion machinery, it remains unclear how CagA is transported towards the machinery in the bacterial cytoplasm. In this study, it was determined that the proton-dependent intracytoplasmic transport system correlates with the priming of CagA secretion from H. pylori. The cytotoxicity of neutral-pH- and acidic-pH-treated H. pylori was examined in the AGS cell line. The amount of phosphorylated CagA in AGS cells incubated with acidic-pH- and neutral-pH-treated H. pylori was determined by enzyme immunoassay and Western blot. The production of CagA and adherence of the treated bacteria were examined by enzyme immunoassay and light microscopy, respectively. To clarify how CagA is transported towards the inner membrane of the treated bacteria, the localization of CagA was analysed by immunoelectron microscopy. The proportion of hummingbird cells in the AGS cell line rapidly increased following the inoculation of acidic-pH-treated H. pylori but increased more slowly with neutral-pH-treated H. pylori, and the phenomenon correlated with the amount of phosphorylated CagA in AGS cells. CagA was densely localized near the inner membrane in the acidic-pH-treated bacterial cytoplasm, but this localization was not observed in the neutral-pH-treated bacterial cytoplasm, suggesting that CagA shifts from the centre to the peripheral portion of the cytoplasm as a result of an extracellular decrease in pH. This phenomenon depended on the presence of UreI, a proton-dependent urea channel, but not on the presence of urea. The pH treatments did not enhance CagA production or the adherence of the bacterium to AGS cells. The authors propose that H. pylori possesses a proton-dependent intracytoplasmic transport system that probably accelerates priming for CagA injection.

Evaluation of disinfective potential of reactivated free chlorine in pooled tap water by electrolysis

Tap water is one of the causative factors of hospital infections. We examined the disinfective potential of electrolysis and mechanism of disinfection, and clarified the disinfective effect of electrolysis on tap water contaminated with bacteria, and discussed its clinical applications. Tap waters artificially contaminated with Pseudomonas aeruginosa, Escherichia coli, Legionella pneumophila, and Staphylococcus aureus could be sterilized by electrolysis at 20-30 mA for 5 min. A high-density suspension (10(6) CFU/ml) of a spore forming bacterium, Bacillus subtilis was not completely sterilized by electrolysis at 50 mA up to 30 min, but a low-density suspension (10(5) CFU/ml) was totally sterilized by electrolysis at 50 mA for 5 min. Electrolyzed P. aeruginosa changed morphologically, that is, there was bleb formation on the cell wall and irregular aggregation of cytoplasmic small granules. Moreover, cytoplasmic enzyme, nitrate reductase, was inactivated by the electrolysis. On the other hand, genomic DNA of the electrolyzed bacteria was not degenerated, therefore, their DNA polymerase activity was not completely inactivated. Consequently, the major agent in electrolysis for bactericidal action was considered to be free chlorine, and the possible bactericidal mechanism was by destruction of bacterial membranes, followed by the aggregation of peripheral cytoplasmic proteins. Electrolysis of tap water for both disinfecting contaminating bacteria and increasing the disinfectant capacity was considered effective with some limitations, particularly against high-density contamination by spore-forming bacteria. In clinical settings, electrolysis of tap water is considered effective to disinfect water for hand washing in operation theatres, and bathing water for immunocompromised hosts.