GAD1 alternative transcripts and DNA methylation in human prefrontal cortex and hippocampus in brain development, schizophrenia.

Genetic variations and adverse environmental events in utero or shortly after birth can lead to abnormal brain development and increased risk of schizophrenia. γ-Aminobutyric acid (GABA), the major inhibitory neurotransmitter in the mammalian brain, plays a vital role in normal brain development. GABA synthesis is controlled by enzymes derived from two glutamic acid decarboxylase (GAD) genes, GAD1 and GAD2, both of which produce transcript isoforms. While the full-length GAD1 transcript (GAD67) has been implicated in the neuropathology of schizophrenia, the transcript structure of GAD1 in the human brain has not been fully characterized. In this study, with the use of RNA sequencing and PCR technologies, we report the discovery of 10 novel transcripts of GAD1 in the human brain. Expression levels of four novel GAD1 transcripts (8A, 8B, I80 and I86) showed a lifespan trajectory expression pattern that is anticorrelated with the expression of the full-length GAD1 transcript. In addition, methylation levels of two CpG loci within the putative GAD1 promoter were significantly associated with the schizophrenia-risk SNP rs3749034 and with the expression of GAD25 in dorsolateral prefrontal cortex (DLPFC). Moreover, schizophrenia patients who had completed suicide and/or were positive for nicotine exposure had significantly higher full-length GAD1 expression in the DLPFC. Alternative splicing of GAD1 and epigenetic state appear to play roles in the developmental profile of GAD1 expression and may contribute to GABA dysfunction in the PFC and hippocampus of patients with schizophrenia.

The development of a new service for older adults.

In July, 1986, Wesley Long Community Hospital, Greensboro, North Carolina, opened its Older Adult Unit. Staffed to accommodate twelve patients, the unit is often operating at capacity. Key to the success of the unit is the process the hospital followed in its development. The hospital tested its preliminary concept for the unit with its consumer populations and tailored the concept to address the needs specifically identified by the populations. In addition, the hospital recognized the importance of an educational role in the promotion of a new service and incorporated this in its marketing strategy. This article outlines the steps followed in the development and successful introduction of the unit.

Role of calcium as an inhibitor of rat liver carbamylphosphate synthetase I.

The mechanism of Ca2+ inhibition of carbamylphosphate synthetase I has been investigated using purified enzyme obtained from livers of rats fed a high protein diet. Binding of Mn2+ to the enzyme was measured by EPR techniques at pH 7.8, and Scatchard plots of the data indicated one Mn2+-binding site with a K'd of 13 microM. From competition studies between Mn2+ and Ca2+ or Mg2+ binding, values of 180 microM were obtained for K'd (Mg) and 193 microM for K'd (Ca). A nonlinear least squares curve fitting program was used to calculate the K'm for MgATP2- at the metal-nucleotide binding sites using a simplified rate equation of the enzyme reaction mechanism. Values of 140 and 2420 microM were obtained for K'm (MgATP) at the first and second sites, respectively, at pH 7.8, with a free Mg2+ of 1 mM and other substrates and activators present at saturating concentrations. Variations of the bicarbonate, N-acetylglutamate, and ammonia concentrations in the absence and presence of different amounts of total calcium, from which free Ca2+, free Mg2+, MgATP2-, and CaATP2- concentrations were calculated, permitted values for K'i (CaATP) to be obtained by graphic procedures. Mean values of 375 and 120 microM were obtained for K'i (CaATP) at the first and second sites, respectively. Using the above kinetic constants, a computer model of the enzyme reaction was constructed and tested using two further sets of kinetic data obtained by varying the concentrations of Mg2+, Ca2+, MgATP2-, and CaATP2-. Poor fits were obtained unless the formation of a mixed complex involving CaATP2- competition with MgATP2- at the second metal-nucleotide-binding site was incorporated into the rate equation. Nonlinear least squares curve fitting of both sets of experimental data gave a well determined value of 124 microM for this final CaATP2- inhibitory constant. Sensitivity tests for variation of the primary kinetic constants with the computer model showed that the inhibitory effect of free Ca2+ was weak and that the observed calcium inhibition of carbamylphosphate synthetase can be accounted for primarily by competitive interaction of CaATP2- at the second MgATP2- binding site. With 1 mM free Mg2+ and 5 mM MgATP2-, half-maximal inhibition of enzyme activity was obtained with 0.2 mM CaATP2-.