Development of gabaergic connections in vitro: Increasing efficacy of synaptic transmission is not accompanied by changes in miniature currents

Development of inhibitory synaptic transmission was studied using a dissociated cell culture from the superior colliculus of neonatal rat. Patch-clamp recordings in the whole-cell configuration were performed to measure evoked (single-cell-activated) inhibitory postsynaptic currents (IPSCs), miniature IPSCs and current responses to maximal concentrations of exogenous γ-aminobutyric acid (GABA). Over a period of 3 weeks in vitro (DIV3-24), the fraction of synaptically coupled neurons raised from 0% to 76%. Evoked IPSCs were first observed at DIV5. They had an average amplitude of 33.9 pA during the first week (n = 13) and 129.7 pA during the fourth week (n = 48). This increase by a factor of 3.8 represents a significant rise in the efficacy of GABAergic transmission during in vitro development. However, no developmental change has been observed in the average amplitudes of miniature somatic IPSCs. The latter remained at an average level of about 9 pA (symmetrical chloride concentration and a driving force of 68 mV). No increase was found also in whole-cell current densities induced by saturating concentrations of exogenous GABA. Our results suggest that under the given conditions, synapse maturation was primarily the result of presynaptic sprouting. This conclusion is further supported by bouton counts in immunostained collicular cultures, where the number of axosomatic and axodendritic GABAergic contacts per neuron increased from 0.54 and 0.37, respectively, at DIV3, to 13.84 and >23.1, at DIV24. The overall density of GABAergic neurons decreased during this period from about 41,000/cm² to 15,600 cm², indicating that a growing number of contacts is formed by a declining number of presynaptic neurons. © 1992 John Wiley & Sons, Inc.     

Active, inactive and in vitro synthesized forms of polyphenoloxidase during leaf development

Polyphenoloxidase (PPO; EC 1.14.18.1) activity decreased 8-fold from young to mature Vicia faba L. Moensch (cv. Long pod) leaves. The K_m for catechol remained relatively constant from young to mature leaves. Electrophoretic separation and analysis showed that only one active form was present in extracts from various leaf sizes. The amount of this form appeared to decrease with leaf size/age. In extracts which had not tanned, electroblotting and immunostaining indicated that one enzyme form was present with a molecular mass of 45 kDa. Two leaf categories contained greater amounts of this immunological cross-reacting PPO than other leaf categories. When extracts were allowed to darken, immunoblotting detected three enzyme forms with molecular masses of 45, 59 and 63 kDa. The latter two immunological crossracting species had no detectable enzyme activity. Poly-A⁺ mRNA was isolated from six leaf sizes and translated in vitro. A product corresponding to PPO was present in all leaf categories. Greater amounts of this translation product were observed in medium-sized leaves than in very young or mature leaves. These results suggest that: (1) enzymatic assays for PPO are not reliable indicators of the total amount of PPO protein present in developing leaves, (2) immunoblotting can detect inactive enzyme forms, (3) only one active form of the enzyme is present at all developmental stages, and (4) mRNA corresponding to PPO is present at all developmental stages but appears to be more abundant in certain leaf sizes/ages.     

Schistocephalus solidus and Ligula intestinalis: Pinocytosis by the tegument

Using ruthenium red as a macromolecule, endocytosis was demonstrated in the plerocercoid of Ligula intestinalis and adult Schistocephalus solidus. Uptake, transport across the tegument, and exocytosis across the basal plasma membrane occurred within 6 min. The types of vesicles in the tegument of L. intestinalis are redescribed and their former classification is modified. The vertical and longitudinal distribution of pinosomes in the tegument of adult S. solidus and L. intestinalis plerocercoids were determined. The possible role of macromolecular uptake in the economy of pseudophyllidean tapeworms is discussed with particular reference to growth and defence of an unencysted larval stage in the tissues of the intermediate host.     

Albino inflorescence proliferation of Dendrocalamus latiflorus

Summary Inflorescence proliferation is a plant tissue culture technique that, can be used to obtain in vitro inflorescences year-round without the intervening development of vegetative organs. In this study, we used albino mutant inflorescences of Dendrocalamus latiflorus as the original explant material to investigate, the effect of plant growth regulators on long-term inflorescence proliferation. The albino inflorescences proliferated on solidified Murashige and Skoog (MS) basal medium supplemented with thidiazuron (TDZ), and the optimal concentration for successful long-term inflorescence proliferation was 0.45 μM TDZ. A combination of α-naphthaleneacetic acid (NAA) with 0.45 μM TDZ inhibited the inflorescence proliferation. Inflorescences cultured on a TDZ-free medium supplemented with 26.82 μM NAA rooted in 21 d, vegetative shoots formed by 42 d and, in one case, flowering occurred after 63 d. The auxins 2,4-dichlorophenoxyacetic acid (2,4-D, 4.52 μM) and pieloram (4.14 μM) induced shoot formation. The protocol described can be used to produce large numbers of mutant inflorescences within a relatively short period of time.     

LIFE HISTORY AND IN SITU GROWTH RATES OF ALEXANDRIUM TAYLORI (DINOPHYCEAE, PYRROPHYTA)

Alexandrium taylori Balech is a phototrophic marine dinoflagellate. It produced recurrent blooms during the summer months (July and August) of 1994 to 1997 in La Fosca beach (NW Mediterranean). In addition to a motile vegetative form, A. taylori had two benthic forms: temporary cysts and resting cysts. Temporary cysts were a temporally quiescent stage produced from the ecdysis of the vegetative cell in both natural populations and laboratory cultures. Temporary cysts may divide to form motile cells. Resting cysts had a thicker wall than the temporary cysts and had a red accumulation body. Gametes and planozygotes were also observed in laboratory cultures. Alexandrium taylori showed in situ diurnal vertical migration with an increase of vegetative cells in the water column in the morning through midday, with concentrations peaking in the afternoon followed by lower levels at night. Most vegetative cells lost their thecae and flagella, and with them their motility, turning into temporary cysts that settled in the early evening. The number of temporary cysts in the water column rose in the evening and at night. The temporary cysts gave rise to motile cells the following morning. Synthesis of DNA occurred in vegetative cells at night, and a preferential period of cell division occurred at sunrise. The estimated division rate in the field was 0.4–0.5 vegetative cells·day⁻¹. Temporary cysts had twice the DNA of a G₁ vegetative cell. The minimum in situ division rate of the temporary cysts was 0.14 day⁻¹. The role of the resting and temporary cyst population in the annual recurrence and maintenance of the A. taylori bloom is discussed.     

The relationship between iron status and lead absorption in rats

The absorption of lead from loops of small intestinein situ was investigated in rats in which iron absorption was increased by stimuli varying in type, intensity, or duration. Lead absorption was increased by a short period of severe iron restriction before any change in hematological indices became apparent. A period of hypoxia, which markedly increased iron absorption, did not influence absorption of lead. An extended period of moderate iron restriction resulted in a marked reduction in liver iron stores and increased iron absorption throughout the 17-wk experiment. Under these conditions lead absorption was initially also increased, but after 12 wk, when iron intake had become adequate to meet essential requirements, lead absorption was similar to that in iron-supplemented rats. These results are discussed in the light of evidence for a receptor-mediated absorption process for iron.     

Viscoelastic characteristics of protein solutions and the micromechanics of their motion in porous carriers

The interactions of model proteins with porous matrices in biosensors are considered. The viscoelastic properties of casein and albumin were assessed by a dynamic method of a piezoquartz resonator by applying thin layers of the studied solutions to a piezocrystal. The experimental data on the viscoelastic characteristics of protein solutions of various concentrations were compared with the characteristics of their tangential motion in the porous carriers of cellulose nitrate. It was demonstrated that the parameters of dynamic viscosity correlated with the motion time of the protein solutions in the porous polymeric carrier.     

DISC1 gene polymorphisms and the risk of schizophrenia in an Iranian population: A preliminary study

Background: Schizophrenia, schizoaffective disorder, and bipolar illness are common psychological disorders with high heritability and variable phenotypes. The disrupted in schizophrenia 1 ( DISC1) gene, on chromosome 1q42, has an essential role in neurite outgrowth and cell signaling. The purpose of this study was to investigate the association of three single-nucleotide polymorphisms (SNPs; rs6675281, rs2255340, and rs2738864) with schizophrenia disorder. These three SNPs were chosen as they had been used in most of the previous studies. Methods: In a case-control study of Iranian population for the first time 778 blood samples were collected including, 402 schizophrenic patients and 376 healthy controls. Genomic DNA was extracted from peripheral blood using DNA extraction kit (BioFlux Co). The genotypes of rs6675281, rs2255340, and rs2738864 were detected by nested allele-specific multiplex polymersae chain reaction (PCR). Results: Our data revealed that the three SNPs are significantly associated with schizophrenia (rs2255349 C>T: confidence interval (CI), 2.115 to 3.268; P = 0.0000 OR: 2.629; rs2738864 C>T: CI, 1.538 to 2.339; P = 0.0000 OR: 1.897; rs6675281 C>T: CI, 2.788 to 4.662; P = 0.0009241 OR: 3.605). Through applying the expectation-maximization (EM) algorithm, we calculated the haplotype frequency, and finally performed haplotype analysis with Bonferroni correction and data preprocessing methods and the results showed rs66875281 to have the highest association. Discussion: Our findings primarily showed that DISC1 gene polymorphisms contribute to schizophrenia risk and have a significant association with this disorder among Iranian population. The strategy was found to be easy, rapid, specific, and consistent for the co-occurring detection of the DISC1 polymorphisms. We could finally confirm that the polymorphisms are related to schizophrenia studied in Iranian population.