Calcium channels in the neuromuscular junction

Chronic binge alcohol administration dysregulates global regulatory gene networks associated with skeletal muscle wasting in simian immunodeficiency virus-infected macaques

Background

There are more than 1 million persons living with HIV/AIDS (PLWHA) in the United States and approximately 40 % of them have a history of alcohol use disorders (AUD). Chronic heavy alcohol consumption and HIV/AIDS both result in reduced lean body mass and muscle dysfunction, increasing the incidence of comorbid conditions. Previous studies from our laboratory using rhesus macaques infected with Simian Immunodeficiency Virus (SIV) demonstrated that chronic binge alcohol (CBA) administration in the absence of antiretroviral therapy exacerbates skeletal muscle (SKM) wasting at end-stage SIV disease. The aim of this study was to characterize how CBA alters global gene regulatory networks that lead to SKM wasting at end-stage disease. Administration of intragastric alcohol or sucrose to male rhesus macaques began 3 months prior to SIV infection and continued throughout the duration of study. High-output array analysis was used to determine CBA-dependent changes in mRNA expression, miRNA expression, and promoter methylation status of SKM at end-stage disease (~10 months post-SIV) from healthy control (control), sucrose-administered, SIV-infected (SUC/SIV), and CBA-administered/SIV-infected (CBA/SIV) macaques.

Results

In addition to previously reported effects on the extracellular matrix and the promotion of a pro-inflammatory environment, we found that CBA adversely affects gene regulatory networks that involve “universal” cellular functions, protein homeostasis, calcium and ion homeostasis, neuronal growth and signaling, and satellite cell growth and survival.

Conclusions

The results from this study provide an overview of the impact of CBA on gene regulatory networks involved in biological functions, including transcriptional and epigenetic processes, illustrating the genetic and molecular mechanisms associated with CBA-dependent SKM wasting at end-stage SIV infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2329-z) contains supplementary material, which is available to authorized users.

Illusive transience of parvalbumin expression during embryonic development of the primate spinal cord

Parvalbumin has been located by pre-embedding light- and electron microscopic immunohistochemical techniques in the spinal cords of monkey fetuses (Macaca fasciculata), ranging from E70 to E 123, and in young (P20) and young adult (3 years) Macaque monkeys. During the time window investigated, the main developmental events of parvalbumin-containing neural elements are that parvalbumin-positive dorsal root collaterals establish intercellular networks first around nerve cells of Clarke's nucleus, then in the motoneuron pool and finally in the upper dorsal horn. In each of these areas, location of the parvalbumin-positive network is gradually shifted from medial to lateral. Whenever an intercellular network is established, nerve cells innervated by parvalbumin-positive terminals of dorsal root collaterals start to express parvalbumin. Immunoreactivity of dorsal root axons is transient; it disappears first from the intercellular networks and, afterwards, also from the dorsal columns. However, the pericellular synaptic terminals and their post-synaptic nerve cells express parvalbumin into adulthood. It is concluded that some of the large (Type A) dorsal root ganglion cells are the first ones in the spinal reflex pathway to express parvalbumin, which is elicited and gradually increased in nerve cells synaptically innervated by parvalbumin-positive axon terminals. This seems to represent a specific case of activation (or desinhibiton) of the genome. Apparent "transience" of parvalbumin is due to the specific geometry of primary sensory neurons equipped with extremely long axonal processes, and the consequent specialities of axonal transport characteristics.

Blockade of acetylcholine release at the motor endplate by a polypeptide from the venom of Phoneutria nigriventer

1. The mechanisms underlying the muscle relaxation effect of a fraction (PF3) isolated from the Phoneutria nigriventer spider venom were assessed on mouse diaphragm and chick biventer cervicis muscle preparations. 2. PF3 (0.25-4 micrograms ml-1) produced a concentration-dependent blockade of the nerve-elicited muscle twitch of the mouse diaphragm (IC50 = 0.8 micrograms ml-1) without affecting the directly induced muscle twitch. In similar preparations, the crude venom (1-10 micrograms ml-1) produced muscle contracture and blocked both the direct and indirectly induced muscle twitches. 3. In the chick biventer cervicis muscle, PF3 (1-5 micrograms ml-1) blocked the nerve stimulated muscle twitch (IC50 = 1.26 micrograms ml-1), but did not alter the postjunctional response to exogenous acetylcholine (ACh, 10 microM-10 mM). 4. PF3 (2-8 micrograms ml-1) reduced the frequency of miniature endplate potentials (m.e.p.ps) recorded intracellularly from the mouse diaphragm muscle fibers by 58 to 64%, and diminished the amplitude of m.e.p.ps by 20 to 40% of control. The relationship between log m.e.p.p. frequency and log [Ca2+]o was shifted rightwards in the presence of 4 micrograms ml-1 PF3. 5. Raising the frequency of m.e.p.ps with high K+ medium or theophylline (3 mM) did not prevent the toxin-induced depression of spontaneous ACh release. 6. The quantal content of e.p.ps (m), determined in cut-diaphragm muscle fibres, was reduced by 53% and 77% of control by 1 and 4 micrograms ml-1 PF3, respectively. At 1 microgram ml-1 the toxin shifted the relationship between log m and log [Ca2+]o towards higher values without apparent change of the slope. 7. E.p.p. trains elicited at 10 to 50 Hz in the presence of PF3 (1 microgram ml-1) exhibited irregular amplitudes and facilitation related to the frequency of nerve stimulation. 8. It is concluded that PF3 blocks neuromuscular transmission by acting prejunctionally and reducing the nerve-evoked transmitter release. The effect was related to a diminished Ca2+ entry into the nerve terminal associated with inhibition of exocytosis.