Circadian time- and sleep-dependent modulation of cortical parvalbumin-positive inhibitory neurons

Parvalbumin-positive neurons (PVs) are the main class of inhibitory neurons in the mammalian central nervous system. By examining diurnal changes in synaptic and neuronal activity of PVs in the supragranular layer of the mouse primary visual cortex (V1), we found that both PV input and output are modulated in a time- and sleep-dependent manner throughout the 24-h day. We first show that PV-evoked inhibition is stronger by the end of the light cycle (ZT12) relative to the end of the dark cycle (ZT0), which is in line with the lower inhibitory input of PV neurons at ZT12 than at ZT0. Interestingly, PV inhibitory and excitatory synaptic transmission slowly oscillate in opposite directions during the light/dark cycle. Although excitatory synapses are predominantly regulated by experience, inhibitory synapses are regulated by sleep, via acetylcholine activating M1 receptors. Consistent with synaptic regulation of PVs, we further show in vivo that spontaneous PV activity displays daily rhythm mainly determined by visual experience, which negatively correlates with the activity cycle of surrounding pyramidal neurons and the dorsal lateral geniculate nucleus-evoked responses in V1. These findings underscore the physiological significance of PV's daily modulation.

Effect of syndecan-1 overexpression on mesenchymal tumour cell proliferation with focus on different functional domains

OBJECTIVES

Syndecan-1 is a transmembrane proteoglycan involved in various biological processes. Its extracellular, transmembrane and cytoplasmic domains may all participate in signal transduction. The aim of this study was to investigate the biological roles of these domains of syndecan-1.

MATERIALS AND METHODS

We transfected cells of two mesenchymal tumour cell lines with a full-length syndecan-1 construct and three truncated variants, namely 78 construct lacking the EC domain with exception of DRKE sequence; 77 construct lacking extracellular the whole domain and RMKKK corresponding to a short cytoplasmic motif. Subcellular distribution was revealed using confocal laser microscopy. Overexpression of the constructs was verified using real-time RT-PCR and by FACS analysis and effects of syndecan-1 on cell behaviour were explored. Cell cycle analysis allowed for dissection of mechanisms regulating cell proliferation.

RESULTS

Overexpression of syndecan-1 influenced expression profile of the other syndecan members, and decreased tumour cell proliferation significantly by two mechanisms, as follows: increased length of G0/G1 phase was the most evident change in RMKKK and 77 transfectants, whereas prolonged S phase was more obvious in full-length transfectants. Overexpression of syndecan-1 changed the tumour cell morphology in an epithelioid direction.

CONCLUSIONS

Both full-length and truncated syndecan-1 inhibited proliferation of the mesenchymal tumour cells, providing new insights into the importance for cancer growth of different functional domains of this proteoglycan.

[Chromosome aberration and carcinogenicity of CHO dhfr- cells transformed by plasmid containing S+ and Pre S1 of fusion gene of hepatitis B virus]

OBJECTIVE

To investigate the chromosome aberrations and carcinogenicity of CHO-dhfr- cell induced by integration of plasmid containing S+ and Pre S1 fusion gene of hepatitis B surface antigen (HBsAg).

METHODS

The plasmid pCHBSS1G was constructed with S+ Pre S1 of HBsAg. CHO-dhfr- cells were transformed with this recombinant plasmid DNA and CHO cells lines with integrated DNA were cloned and named GdSS118. The GdSS1 18 cell lines secreting the S+ Pre S1 fusion protein of HBsAg at high level were developed by screening in increased concentration of MTX and MSX in cultured media. To make sample of cells chromosome, the cells integrated DNA were subcutaneously injected into nude mouse.

RESULTS

The CHO-dhfr- cell lines integrated with S and Pre S1 fusion protein of HBsAg were developed and named GdSS1-18 cell lines. The frequencies and type of chromosome aberrations of the GdSS1-18 cell lines with different passage generations were 11%, 56% and 29%, respectively, while that of the control CHO-dhfr- cell lines was 6%. There was no change in the mode of chromosomes, both cell lines having 20 chromosome s. Both cell lines were non-oncogenic in nude mouse.

CONCLUSIONS

The chromosome aberration of CHO-dhfr- cells with integrated DNA were obviously higher than that of the original CHO-dhfr- cells without integrated DNA. Both cell lines were non oncogenic in nude mouse.

[Analysis of herbicide-difenzoquat by reversed-phase high performance liquid chromatography (RP-HPLC)]

An RP-HPLC method for the qualitative determination of herbicide difenzoquat was developed. Operating conditions were UV-254 nm detection, Selectosil 5 C18 column 250 mm x 4.6 mm i.d., and V(methanol):V(water) = 60:40 (pH3, adjusted by H3PO4) as mobile phase. The coefficient of variation of this method was 0.41% with recoveries from 98.71% to 100.36%. The retention time was about 6.6 min. The coefficient of linear correlation was 0.9999. The method is very effective for the quality control of SP (water soluble power) products of this pesticide.