Development of GABAergic inputs controls the contribution of maturing neurons to the adult hippocampal network

New neurons are continuously generated in the dentate gyrus (DG) in the adult hippocampus, and new granule cells (GCs) have been shown to be necessary for several aspects of learning and memory. Nonetheless, the limited information available regarding the anatomical and physiological development of synaptic inputs onto maturing neurons has restricted our understanding of how new GCs affect cognition. Here, we use photostimulation to demonstrate the time course by which anatomically isolated inhibitory inputs develop onto maturing GCs. We then show that the gradual development of inhibition is sufficient in a computational model to drive learning of novel information in young neurons. Finally, we validate this model observation by using slice physiology to show how inhibition regulates firing probability and plasticity in young GCs. Combined, these data demonstrate that the unique connectivity of immature GCs affords them a functional role that is different from mature neurons in the DG circuit, a distinction that potentially underlies many of the proposed functions of new neurons in the hippocampal network.     

The homopolymerization of 2,3-dimethyl-1,3-butadiene and the copolymerization of 1,3-butadiene/2,3-dimethyl-1,3-butadiene using the catalyst system AlEt2Cl-Co(acac)2. A structural investigation of the products

The homopolymerization of 2,3-dimethyl-1,3-butadiene with the catalyst system AlEt₂Cl-Co(acac)₂ affords polymers consisting of about 81% cis-1,4-units and 19% 1,2-units. The copolymerization of 1,3-butadiene/2,3-dimethyl-1,3-butadiene using the same system is of the ideal type and the composition of the copolymers is practically identical with that of the monomer mixture. The structure of the copolymers depends on their composition. The butadiene units, which are more than 95% cis-1,4 in the homopolymer, become partially 1,2 in the copolymers; their amount increases with increasing dimethylbutadiene content. Conversely, the fraction of dimethylbutadiene units with 1,2-structure decreases in the copolymers with increasing butadiene content. In the copolymers containing more than 50% of butadiene, the dimethylbutadiene units are practically all cis-1,4. The analysis of sequence distribution shows that the 1,2-butadiene units in the copolymers are not randomly distributed but are mostly adjacent to dimethylbutadiene units. The results obtained with dimethylbutadiene are compared with those reported for the homopolymerization of isoprene and the copolymerization of isoprene/butadiene using the same catalyst system.     

Polymerization of 4‐Methyl‐1,3‐pentadiene with Catalysts Based on Cyclopentadienyl Titanium Chlorides: Effect of anti/syn Isomerism of the Allylic Group on the Chemoselectivity and the Role of Backbiting Coordination in 1,3‐Diene Polymerization

Summary: Homopolymerization of 4‐methyl‐1,3‐pentadiene (MP) and copolymerization of 4‐methyl‐1,3‐pentadiene with alkenes (ethylene, 1‐pentene, 4‐methyl‐1‐pentene) were performed to investigate the effect of the so‐called backbiting coordination on the chemoselectivity of 1,3‐diene polymerization. Three homogeneous catalyst systems were used: CpTiCl₃‐MAO, Cp₂TiCl₂‐MAO and Cp₂TiCl‐MAO. Backbiting coordination is possible with the first catalyst, but not with the other two. The three catalysts gave similar results, which indicates that backbiting has no effect on the polymerization chemoselectivity, contrary to what has been reported in recent literature. An interpretation is presented for the formation of 1,4 units in MP/alkene copolymers. This interpretation is based on the fact that allyl groups have predominantly a syn configuration in MP homopolymerization, whereas allyl groups of anti configuration are formed in MP/alkene copolymerization. The role of backbiting in diene polymerization is discussed.

The effect of anti/syn isomerism on the chemoselectivity in the different polymerizations.     

Laparoscopic surgery of the liver: state of the art

Laparoscopic hepatic surgery has recently claimed its place among the minimally invasive techniques. Adequate technologies and experience both in laparoscopy and liver surgery are essential for its correct use. A review of the English literature on this subject is presented and the present state of the art discussed. Various topics are considered: staging, treatment of cystic lesions and treatment of benign and malignant primary and secondary tumours. Over the past five years various groups have published papers regarding case series, mainly concerning hepatic resection. More correct indications for the use of laparoscopy in liver surgery have been defined. In particular, laparoscopy is of great importance in the staging of primary and secondary liver cancer and in the treatment of cystic and benign lesions, mainly of the anterior segments. Less univocal are surgeons' attitudes towards the treatment of primary and secondary liver cancers. Laparoscopic liver surgery is gradually gaining wider and clearer acceptance in the treatment of hepatic lesions, while it has now virtually consolidated its role in the treatment of cystic lesions and in the staging of primary and secondary liver cancer.     

Segmental analysis of neuropeptide concentrations in normal human spinal cord

We concurrently measured, by radioimmunoassay, levels of substance P (SP), somatostatin (SST), methionine-enkephalin (Met-Enk), cholecystokinin (CCK), peptide hystidyl-isoleucine (PHI), vasoactive intestinal polypeptide (VIP), and neuropeptide Y (NPY) in the ventral and dorsal gray matter at each segment of the cervical, thoracic, lumbar, and sacral spinal cord, obtained within 6 hours of death from 4 subjects (ages 17 to 55) with no neurologic disease. Levels (pmol/g gray matter) of SP, SST, and Met-Enk throughout and PHI, VIP, and NPY in lumbar and sacral cord were significantly higher in dorsal than in ventral gray matter. PHI, VIP, and NPY were significantly higher in lumbar and especially sacral cord than in cervical and thoracic segments. In rats, a postmortem delay of up to 8 hours did not affect SP, Met-Enk, PHI, or NPY and decreased SST, CCK, and VIP levels. Thus, there is a characteristic profile of neuropeptide distribution in gray matter, which emphasizes the neurochemical heterogeneity along the rostrocaudal and dorsoventral extent of normal human spinal cord.     

A small molecule accelerates neuronal differentiation in the adult rat

Adult neurogenesis occurs in mammals and provides a mechanism for continuous neural plasticity in the brain. However, little is known about the molecular mechanisms regulating hippocampal neural progenitor cells (NPCs) and whether their fate can be pharmacologically modulated to improve neural plasticity and regeneration. Here, we report the characterization of a small molecule (KHS101) that selectively induces a neuronal differentiation phenotype. Mechanism of action studies revealed a link of KHS101 to cell cycle exit and specific binding to the TACC3 protein, whose knockdown in NPCs recapitulates the KHS101-induced phenotype. Upon systemic administration, KHS101 distributed to the brain and resulted in a significant increase in neuronal differentiation in vivo. Our findings indicate that KHS101 accelerates neuronal differentiation by interaction with TACC3 and may provide a basis for pharmacological intervention directed at endogenous NPCs.