Isolation, localization, and cloning of a kainic acid binding protein from frog brain

Excitatory amino acids (EAA) are major neurotransmitters in the vertebrate central nervous system. EAA receptors have been divided into three major subtypes on the basis of electrophysiological and ligand binding studies: N-methyl-D-aspartate, kainate, and quisqualate receptors. To understand their molecular properties, we undertook a project aimed at isolation and cloning of these receptor subtypes. We purified a kainate binding protein (KBP) from frog brain, in which kainate binding sites are about fortyfold more abundant than in rat brain, using domoic acid affinity chromatography, and made monoclonal and polyclonal antibodies to the purified protein. These antibodies immunoprecipitate the frog KBP but not KBPs from other species. Immunocytochemical analyses show that KBP has a synaptic and extrasynaptic localization in frog optic tectum, with most labeling being extrasynaptic. The cDNA encoding frog brain KBP was isolated by screening a frog brain cDNA library with oligonucleotide probes that were based on the amino acid sequence of the purified protein. The deduced amino acid sequence of the KBP has a hydrophobic profile similar to those of other ligand-gated ion channel subunits, such as the nicotinic acetylcholine receptor, the GABAA receptor, and the glycine receptor. Frog brain KBP is very similar (36% amino acid identity to the carboxyl half) to rat brain kainate receptor, suggesting that these two proteins evolved from a common ancestor. The function of KBP in frog brain remains a major question. Preliminary results showed that Xenopus laevis oocytes injected with KBP RNA did not produce a detectable electrophysiological response when perfused with kainate. These results suggest that additional subunits may be required to form a functional receptor or that KBP is not functionally related to a neurotransmitter receptor.

Solubilization and partial purification of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid binding sites from rat brain

alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) binding sites were solubilized from rat brain membranes using 1% Triton X-100 in 0.5 M potassium phosphate buffer containing 20% glycerol. The solubilized binding sites were stable, permitting biochemical and pharmacological characterization as well as partial purification. Pharmacological and binding analyses indicated that the solubilized binding sites were similar to the membrane-bound sites. Both the solubilized and the membrane-bound preparations contained high- and low-affinity AMPA binding sites in the presence of potassium thiocyanate. A similar rank order for inhibition of [3H]AMPA binding by several excitatory amino acid analogs was obtained for the soluble and membrane-bound preparations. [3H]AMPA binding to both soluble and membrane-bound preparations was increased in the presence of potassium thiocyanate. The solubilized AMPA binding sites migrated as a single peak with gel filtration chromatography, with an Mr of 425,000. Beginning with the solubilized preparation, AMPA binding sites were purified 54-fold with ion-exchange chromatography and gel filtration. The characterization and purification of these soluble binding sites is potentially useful for the molecular characterization of this putative excitatory amino acid receptor subtype.

Age-dependent changes in brain glycine concentration and strychnine-induced seizures in the rat

Glycine levels and receptor binding were measured in the medulla and spinal cord of 2-month, 10-month, and 24-month-old Fischer 344 rats. The behavioral response to the administration of the glycine antagonist, strychnine, was also evaluated in 2- and 24-month-old animals to investigate the relevance of these parameters to the susceptibility to seizures. Significant reductions in glycine in both the spinal cord and medulla occurred from 2 to 24 months of age. The glycine precursors, serine and threonine, were decreased only in the spinal cord. [3H]Strychnine binding was also decreased by 38% and 34% in the medulla and spinal cord, respectively, of 24-month-old rats compared to 2-month-olds. [3H]GABA binding was similarly reduced while no age-related changes in [3H]diazepam binding in the spinal cord were detected. Comparison of 2- and 24-month-old animals after systemic injection of 1.75 mg/kg strychnine showed that senescent animals have a higher incidence of seizures and mortality compared to young animals. Decreases in glycinergic neurotransmission may lower strychnine seizure threshold in the aged animal.

A highly sensitive and specific radioimmunoassay for quantitation of plasma fluphenazine

Antisera of high sensitivity and selectivity were obtained from rabbits immunized with conjugates of hemisuccinylated fluphenazine and porcine thyroglobulin. The antiserum selected (titer 1:6000) for the development of the RIA was obtained after a priming dose and a single iv booster injection three months later. This antiserum had negligible crossreactivity with known available metabolites of fluphenazine (FPZ) and an affinity constant of 2 X 10(10) L/mol. Tritiated FPZ was further purified by HPLC and used as a ligand. The method detects as little as 20 pg/mL of plasma (4 pg/RIA tube) after 1 mL of plasma is extracted. The extraction was performed at a basic pH with heptane: isoamyl alcohol (99:1); the solvent was then back extracted using an acetic phosphate buffer. Recoveries were uniformly high (88.6 +/- 2.1%), and this aqueous buffer extract was used directly in the RIA procedure. The assay has intra- and interassay coefficients of variation of 5.8 and 8.2%, respectively, in a plasma concentration of 95 pg/mL. Results using this procedure have been cross validated against an HPLC procedure (r = 0.952, slope = 1.032, intercept = 0.009, n = 18). In a single-dose FPZ study (10 mg, po), plasma FPZ levels in 25 normal volunteers could be monitored greater than 48 h post dose. Single plasma level profiles, after an initial injection of 12.5 mg of FPZ decanoate, could be measured greater than 36 d, and, in some cases, up to 100 d post dose.

Erythrocyte catechol O-methyltransferase activity in schizophrenia: analysis of family data

The authors determined the erythrocyte catechol O-methyltransferase (COMT) activity of 38 chronic schizophrenic patients, 69 of their first-degree relatives, and 39 normal controls. COMT activity did not distinguish patients from controls. Within families, COMT activity was not associated with schizophrenia spectrum disorders. The data suggest that COMT activity is not an indicator of vulnerability to schizophrenia.

Assay of human erythrocyte catechol-o-methyltransferase activity with naturally occurring catecholamines as substrates

This report describes a simple and sensitive radiometric assay for catechol-o-methyltransferase activity in human erythrocytes and other tissues. Saturating concentrations of the endogenous catecholamines and S-adenosylmethionine are used under optimum assay conditions. Erythrocyte catechol-o-methyltransferase activity is also dependent on storage conditions, as activity was lost at -20 degrees C but not at -80 degrees C.

Complete remission of idiopathic pure red cell aplasia. Case reports

Two patients with pure red cell aplasia of undetermined aetiology are in sustained, complete remission after immunosuppressive therapy. In the first, short-term supplementary plasmapheresis was used during initial chemotherapy, and in the second, anabolic androgens were administered. In both patients haematopoietic recovery was temporally related to the withdrawal of the cyclophosphamide used to cause immunosuppression in the patients over a 4- and 6-month period respectively.

Idiopathic fatty liver of pregnancy with maternal and fetal survival

A case of idiopathic fatty liver of pregnancy with survival of mother and child is reported. The management of this condition is essentially supportive; coagulation disturbances may require special attention. Maternal survival should be the major consideration and is favourably influenced by early delivery. Fetal monitoring aids obstetric management and may indirectly improve fetal survival. Evidence from the literature suggests that the condition does not usually recur in subsequent pregnancies.

Histone-histone propinquity by aldehyde fixation of chromatin

Histones have been fixed within the chromatin complex using either formaldehyde or glutaraldehyde. Evidence is presented which argues that in short time periods formaldehyde fixation leads to the formation of reversible covalent bonds between histone and DNA. On the other hand, fixation of chromatin with glutaraldehyde leads initially to the formation of polymers of F1 histone, and at a later stage of multiple small oligomers of the remaining histones. There oligomers then increase in size until they become too large to detect by polyacrylamide gel electrophoresis. Exclusive formation of histone dimers or tetramers was not observed. The simplest model for histone distribution on DNA which encompasses these observations is one in which histones are organized as a fairly extensive linear overlapping array.

Growth of the heart and lungs in hypoxic rodents: a model of human hypoxic disease

1. Rats and mice were kept in a decompression chamber at 52 kPa (390 mmHg) for 1–4 weeks and their hearts and lungs were compared with littermate control animals. In both species growth was retarded in the hypoxic environment.

2. In both species small peripheral lung vessels became thickened, developing two elastic laminae with a muscular coat between. A method was developed for assessing these changes in large numbers of animals. The number of thick-walled vessels was still high after 4 weeks' recovery in a normal environment. Pulmonary vascular resistance, measured by a perfusion method, increased in animals kept in the decompression chamber.

3. Mouse lungs became heavier than controls; the increase was not due to a greater fluid content. Rat lungs were heavy in relation to body weight but not heavier than controls; there may have been slight thickening of alveolar walls. Chest areas, measured from radiographs, were large relative to body weight in hypoxic rats.

4. The relationship between right and left ventricular weight and body weight was studied in normal rats and mice. The left ventricle grew about four times more quickly than the right. Changes in ventricular weights during exposure in the decompression chamber and subsequent recovery in a normal environment were related to these normal growth curves.

5. In both species the right ventricle grew abnormally fast in the decompression chamber. It was absolutely heavier than that of controls and relative to body weight was extremely heavy. After 4 weeks' recovery the relationship between right ventricular weight and body weight was nearly normal; this was achieved by retarded growth or actual loss of weight.

6. In mice the left ventricle grew normally in the decompression chamber and was heavy in relation to body weight. In rats its growth was retarded in the chamber and was normal in relation to body weight.

7. Morphometry of the hypertrophied right ventricle showed that muscle fibre size and total muscle mass had increased in hypoxic rats. There had been no increase in nuclear mass, but the perinuclear sarcoplasm had increased. All layers of the myocardium participated in the hypertrophy.

The effects of hypoxia on the caudal vertebrae of growing mice and rats

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Changes in skeletal proportions of the rat in response to hypoxic stress

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Changes in the capacity for protein-synthesis in embryonic axes of hazel fruits during the breaking of dormancy by GA3

Embryonic axes of hazel seeds sown on GA3 (non-dormant) show a higher rate of protein synthesis than those of seeds sown on water (dormant). Associated with this increased protein synthesis are changes in tRNA and aminoacyl-tRNA synthetases. These changes appear to be consequences of changes at the transcriptional level which have previously been described.