Cannabinoid-serotonin interactions in alcohol-preferring vs. alcohol-avoiding mice

Because cannabinoid and serotonin (5-HT) systems have been proposed to play an important role in drug craving, we investigated whether cannabinoid 1 (CB1) and 5-HT(1A) receptor ligands could affect voluntary alcohol intake in two mouse strains, C57BL/6 J and DBA/2 J, with marked differences in native alcohol preference. When offered progressively (3-10% ethanol) in drinking water, in a free-choice procedure, alcohol intake was markedly lower (approximately 70%) in DBA/2 J than in C57BL/6 J mice. In DBA/2 J mice, chronic treatment with the cannabinoid receptor agonist WIN 55,212-2 increased alcohol intake. WIN 55,212-2 effect was prevented by concomitant, chronic CB1 receptor blockade by rimonabant or chronic 5-HT(1A) receptor stimulation by 8-hydroxy-2-(di-n-propylamino)-tetralin, which, on their own, did not affect alcohol intake. In C57BL/6 J mice, chronic treatment with WIN 55,212-2 had no effect but chronic CB1 receptor blockade or chronic 5-HT(1A) receptor stimulation significantly decreased alcohol intake. Parallel autoradiographic investigations showed that chronic treatment with WIN 55,212-2 significantly decreased 5-HT(1A)-mediated [35S]guanosine triphosphate-gamma-S binding in the hippocampus of both mouse strains. Conversely, chronic rimonabant increased this binding in C57BL/6 J mice. These results show that cannabinoid neurotransmission can exert a permissive control on alcohol intake, possibly through CB1-5-HT(1A) interactions. However, the differences between C57BL/6 J and DBA/2 J mice indicate that such modulations of alcohol intake are under genetic control.     

A Proximal Centriole-Like Structure Is Present in Drosophila Spermatids and Can Serve as a Model to Study Centriole Duplication

Most animals have two centrioles in spermatids (the distal and proximal centrioles), but insect spermatids seem to contain only one centriole (Fuller 1993), which functionally resembles the distal centriole. Using fluorescent centriolar markers, we identified a structure near the fly distal centriole that is reminiscent of a proximal centriole (i.e., proximal centriole-like, or PCL). We show that the PCL exhibits several features of daughter centrioles. First, a single PCL forms near the proximal segment of the older centriole. Second, the centriolar proteins SAS-6, Ana1, and Bld10p/Cep135 are in the PCL. Third, PCL formation depends on SAK/PLK4 and SAS-6. Using a genetic screen for PCL defect, we identified a mutation in the gene encoding the conserved centriolar protein POC1, which is part of the daughter centriole initiation site (Kilburn et al. 2007) in Tetrahymena. We conclude that the PCL resembles an early intermediate structure of a forming centriole, which may explain why no typical centriolar structure is observed under electron microscopy. We propose that, during the evolution of insects, the proximal centriole was simplified by eliminating the later steps in centriole assembly. The PCL may provide a unique model to study early steps of centriole formation.THE centriole is a cylindrical structure rich in microtubules, which are organized in a ninefold symmetry. As the template of the ciliary axoneme, the centriole transmits its symmetry to the cilium. Dividing cells contain two centrosomes at the cell poles, each containing a pair of centrioles (mother and daughter centrioles) surrounded by a thick layer of pericentriolar material (PCM). Upon differentiation, the mother centriole of each pair becomes a basal body, which acts as a template for the cilium (Azimzadeh and Bornens 2007). The function of the daughter centriole is less clear. For example, in animal spermatids, the mother centriole, known as the distal centriole, becomes a basal body and gives rise to the sperm flagellum (Krioutchkova and Onishchenko 1999; Sathananthan et al. 2001). The daughter centriole in spermatids, known as the proximal centriole, is attached to the nucleus.Unlike other animal groups, multiple ultrastructural studies of insect sperm find only one centriole that has the canonical structure of microtubules organized in a ninefold symmetry (Anderson 1967; Tates 1971; Tokuyasu 1975a,b). This centriole forms the flagellum and is therefore the homolog to the vertebrate distal centriole. During spermatid differentiation (Figure 2A), a structure, called the centriolar adjunct (CA), appears transiently around this centriole (Friedlander and Wahrman 1971; Tates 1971; Tokuyasu 1975a,b; Wilson et al. 1997). The centriolar adjunct is a very dynamic structure, which shrinks during spermatid differentiation to form a collar around the distal centriole and then disappears (Tates 1971; Wilson et al. 1997). Studies using light microscopy found that γ-tubulin localizes and redistributes around the centriole in a way similar to the CA (Wilson et al. 1997), suggesting that it may serve as its marker. Earlier electron microscopy (EM) studies describe the appearance of a centriole inside the centriolar adjunct after it obtains the collar-shape structure (Anderson 1967; Phillips 1970). But this structure is amorphous and does not exhibit the morphological features of a centriole. Interestingly, the earliest intermediate observed during centriole formation is described as an amorphous structure (Anderson 1967; Dippell 1968; Sorokin 1968; Allen 1969).Open in a separate windowFigure 2.—Ana1 labels a novel structure appearing near the mother centriole in spermatids. (A) Diagram depicting the different stages of spermatid development based on the observations of Tates (1971). (M, mitochondria; N, nucleus; Ax, axoneme). The basal body or giant centriole (Cen) is surrounded by the centriolar adjunct (CA) and, near it, we can follow the formation of the PCL. (B) We use phase-contrast pictures (unfixed testis) to determine the spermatid stage. The onion stage (stage S13) is characterized by a round nucleus (N) of the same size as the mitochondrial derivatives (M). The cell body of intermediate spermatids (stages 15 and 16) elongates, forming short protrusions (arrows), but the nucleus remains round. In late spermatid development (stage 17), the nucleus becomes oval. Ana1-GFP labels the giant centriole (Cen), and in intermediate spermatids a bulge forms on one side and becomes individualized as PCL in late spermatid development. (C) Staining with anti-γ-tubulin antibody shows that the PCL labeled by Ana1 is an entity different from the γ-tubulin collar that is reminiscent of the centriolar adjunct (CA). (D) Antibody against Ana1 labels the V-shape pair of giant centrioles in primary spermatocytes (left) and the giant centriole and PCL in spermatids (right) in flies expressing Ana1-GFP. (E) In wild-type primary spermatocytes, anti-Ana1 antibody stains the endogenous protein in the giant centrioles and colocalizes with γ-tubulin staining (left). In spermatids, the antibody labels the PCL, demonstrating that its formation is not due to centriolar protein overexpression (right).Centriole duplication provides the cell with a mechanism for tightly controlling the number of centrosomes and cilia. In most cells, the centriole duplicates once per cell cycle and a single new centriole is formed in the vicinity of each mother centriole. The mechanism ensuring that only one daughter centriole forms in the vicinity of the mother centriole is not known (Strnad and Gonczy 2008). Two major limiting factors hinder the investigation of this process: (1) the difficulty of distinguishing between the mother centriole and the forming daughter centriole and (2) the short time that it takes for the process to reach completion, which in turn hinders the identification of intermediates. Few model systems are currently available for studying this process (Pelletier et al. 2006; Kleylein-Sohn et al. 2007).Here, we demonstrate that fly spermatids contain a novel structure that is labeled by centriolar proteins and that forms in the vicinity of the proximal end of the mother centriole. Because it is reminiscent of the vertebrate proximal centriole but no morphological signatures of a centriole have been observed, we propose to call it proximal centriole-like (PCL). While studying the pan-centriolar protein Ana1, we found that it labeled the PCL. The PCL forms before γ-tubulin is redistributed as a collar, showing that it is a distinct entity. We then found that the formation of the PCL depends on the proteins SAK/PLK4 and SAS-6, which are essential early in daughter centriole formation, but not on SAS-4, which in worms is required later in the process. These observations indicate that the PCL represents an early intermediate structure in centriole formation. We also tested the involvement of the centriolar protein Bld10p/Cep135, which was found in Chlamydomonas and humans to be a component of the centriole cartwheel and wall (Hiraki et al. 2007; Kleylein-Sohn et al. 2007). We found that Bld10p is recruited to the PCL only later in the process and is not required for PCL formation. We performed a genetic screen finding that the Drosophila ortholog of POC1 is essential for the formation of normal PCL. POC1 was identified previously in a proteomic screen as a centriolar protein and is localized to the early intermediate structure in centriole/basal body formation (Keller et al. 2005, 2008; Kilburn et al. 2007). We propose to use PCL formation as a model to study the molecular pathway for centriole initiation. Our results suggest that POC1, like PLK4 and SAS-6, plays an important role early in centriole formation whereas Bld10p function is required later as SAS-4 is.     

Biopsy of the mouse prostate

Many transgenic and knockout mouse models of prostate cancer have become available over the past decade. In this paper we describe a simple biopsy technique of the murine prostate. This technique allows sequential follow-up of the prostate in an individual mouse. Its use could also reduce the number of mice used in studies of the prostate gland.     

In vitro dissociation and reassociation of the symbionts of the lichenHeppia echinulata

Summary Heppia echinulata, a heteromerous, cyanophilic lichen has been cultured on a nutrient medium containing silica gel powder.The paper describes the formation of new thalli by dissociation of the components, reversion to their free-living form and complete resynthesis accomplished as a continuous process under the same culture conditions.Part of a dissertation to be submitted by K.Marton to Tel Aviv University in partial fulfillment of the requirements for the degree of Doctor of Philosophy.     

Life-Long Hippocampal Neurogenesis: Environmental,Pharmacological and Neurochemical Modulations

It is now well documented that active neurogenesis does exist throughout the life span in the brain of various species including human. Two discrete brain regions contain progenitor cells that are capable of differentiating into neurons or glia, the subventricular zone and the dentate gyrus of the hippocampal formation. Recent studies have shown that neurogenesis can be modulated by a variety of factors, including stress and neurohormones, growth factors, neurotransmitters, drugs of abuse, and also strokes and traumatic brain injuries. In particular, the hippocampal neurogenesis may play a role in neuroadaptation associated with pathologies, such as cognitive disorders and depression. The increased neurogenesis at sites of injury may represent an attempt by the central nervous system to regenerate after damage. We herein review the most significant data on hippocampal neurogenesis in brain under various pathological conditions, with a special attention to mood disorders including depression and addiction. Special issue dedicated to Dr. Moussa Youdim.