The uptake of the GABA agonist, [H]isoguvacine, by the isolated retina of the rabbit

Previous autoradiographic studies aimed at showing neurones using GABA as their neurotransmitter have been hampered by the fact that the substance is a ubiquitous metabolite and therefore accumulated by a large variety of cells, including glia. Consequently, GABA uptake markers without this widespread uptake are desirable, and one, [³H]isoguvacine, has shown promising results in autoradiographic experiments. Its uptake has now been further studied with quantitative radiochemical techniques.

The uptake of the drug was slow compared to GABA uptake and reached a tissue/medium ratio of about 3 after 120 min. The uptake could be inhibited by GABA, beta-alanine or ouabain, and by incubating the retinas at 0°C. The uptake kinetics were complex but suggested a high affinity uptake system (K_m about 10⁻⁸ M) and perhaps one or several systems with lower affinities.

The results indicate that [³H]isoguvacine and [³H]GABA are accumulated and retained by the same neurones, which most likely use GABA as their neurotransmitter.     

Estimation of parameters of a biochemically based model of photosynthesis using a genetic algorithm

Photosynthesis response to carbon dioxide concentration can provide data on a number of important parameters related to leaf physiology. The genetic algorithm (GA), which is a robust stochastic evolutionary computational algorithm inspired by both natural selection and natural genetics, is proposed to simultaneously estimate the parameters [including maximum carboxylation rate allowed by ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation rate ( V _cmax), potential light-saturated electron transport rate ( J _max), triose-phosphate utilization (TPU), leaf dark respiration in the light ( R _d) and mesophyll conductance ( g _m)] of the photosynthesis models presented by Farquhar, von Caemmerer and Berry, and Ethier and Livingston. The results show that by properly constraining the parameter bounds the GA-based estimate methods can effectively and efficiently obtain globally (or, at least near globally) optimal solutions, which are as good as or better than those obtained by non-linear curve fitting methods used in previous studies. More complicated problems such as taking the g _m variation response to CO₂ into account can be easily formulated and solved by using GA. The influence of the crossover probability ( P _c), mutation probability ( P _m), population size and generation on the performance of GA was also investigated.     

Possible Mechanism of Dantrolene Stabilization of Cultured Neuroblastoma Cell Plasma Membranes

Abstract: Some reports have suggested that dantrolene interacts directly with the membrane bilayer. We investigated effects of dantrolene on changes in membrane properties induced by compound 48/80 (C48/80), a membrane stimulator. The addition of C48/80 for 1 min elicited a rapid, dose-dependent Ca²⁺ influx, which was reduced to 14% by the absence of external Ca²⁺. Dantrolene inhibited the C48/80-induced increase in Ca²⁺ permeability of plasma membranes in a concentration-dependent manner (0.33–10 µ M , IC₅₀ value was 5 µ M ). We next examined C48/80-induced changes in structural and dynamic membrane properties by electron spin resonance (ESR). The ratio h ₀/ h ₋₁ was determined to evaluate membrane fluidity. C48/80 increased the membrane fluidity in a concentration-dependent manner (0.1–0.56 mg/ml). Dantrolene (10 µ M ) itself did not change the membrane fluidity, but it significantly reduced the C48/80-induced increase in membrane fluidity (0.56 mg/ml). Moreover, the C48/80-induced increase in fluidity was dependent on extracellular Ca²⁺. We conclude that dantrolene protects neuroblastoma cell plasma membrane from C48/80-induced membrane perturbation, which causes Ca²⁺ influx and an increase in membrane fluidity. These findings strongly suggest that dantrolene directly stabilizes the neuronal plasma membrane.     

Neurotensin. Immunohistochemical localization in central and peripheral nervous system and in endocrine cells and its functional role as neurotransmitter and endocrine hormone

The present study attempts to compile information on the possible physiologic role of the endogenous peptide neurotensin (NT) as a hormone and/or neurotransmitter. The methodological approach is immunohistochemical localization of NT in the entero-endocrine system as well as in the central and peripheral nervous systems. The results found in the three systems are first related to the pharmalogical and physiological findings in the literature. Subsequently their significance is discussed for each organ separately before attempting a final overall interpretation. Briefly, the present study reveals the following essential findings: The occurrence and distribution of NT-IR entero-endocrine cells (N-cells) in different mammals including man, as well as in representative members of all classes of vertebrates and higher invertebrates, are analyzed and evaluated morphometrically. The NT-IR cells in all investigated species are demonstrated to be of the open type. The innervation of paravertebral and prevertebral ganglia by NT-IR fibers is described; at least a portion of these fibers is thought to originate in NT-IR perikarya of the substantia intermedia of the spinal cord. The involvement of these NT-IR fibers in the regulation of systemic blood flow (hypertension) is suggested. The existence of NT-IR innervation of the gastro-intestinal tract is considered to be a general phenomenon. This notion is reaffirmed by phylogenetic investigation of the NT-IR enteric nerves. The pharmacological effects of NT in different portions of the gastro-intestinal tract, reported in the literature are related to the immunohistochemical localization of NT. In light of the present results, some of the effects of NT which were previously considered to be of an endocrine or paracrine nature - such as contraction of the guinea-pig ileum - are interpreted as effects of NT of neuronal origin. The specific NT-IR innervation of target cells in the exocrine pancreas (vascular smooth muscle, acinar cells) is demonstrated, and participation of NT-IR nerve fibers in regulation of the secretion of pancreatic juice is postulated. The innervation of the heart (coronary vasculature, myocardium, conduction system) by NT-IR fibers is demonstrated in various mammals and for the first time also in man. The cardiac NT-IR nerve fibers are thought to be the cytological substrate for different NT effects on heart action (coronary vasoconstriction, positive inotropy and chronotropy) reported in the literature.(ABSTRACT TRUNCATED AT 400 WORDS)     

Identification of target proteins of clinical immunity to Plasmodium falciparum in a region of low malaria transmission

The target molecules of antibodies against falciparum malaria remain largely unknown. Recently we have identified multiple proteins as targets of immunity against Plasmodium falciparum using African serum samples. To investigate whether potential targets of clinical immunity differ with transmission intensity, we assessed immune responses in residents of low malaria transmission region in Thailand. Malaria asymptomatic volunteers (Asy: n = 19) and symptomatic patients (Sym: n = 21) were enrolled into the study. Serum immunoreactivity to 186 wheat germ cell-free system (WGCFS)-synthesized recombinant P. falciparum asexual-blood stage proteins were determined by AlphaScreen, and subsequently compared between the study groups. Forty proteins were determined as immunoreactive with antibody responses to 35 proteins being higher in Asy group than in Sym group. Among the 35 proteins, antibodies to MSP3, MSPDBL1, RH2b, and MSP7 were significantly higher in Asy than Sym (unadjusted p < 0.005) suggesting these antigens may have a protective role in clinical malaria. MSP3 reactivity remained significantly different between Asy and Sym groups even after multiple comparison adjustments (adjusted p = 0.033). Interestingly, while our two preceding studies using African sera were conducted differently (e.g., cross-sectional vs. longitudinal design, observed clinical manifestation vs. functional activity), those studies similarly identified MSP3 and MSPDBL1 as potential targets of protective immunity. This study further provides a strong rationale for the application of WGCFS-based immunoprofiling to malaria vaccine candidate and biomarker discovery even in low or reduced malaria transmission settings.     

Molecular cloning of cDNA from foot-and-mouth disease virus C1-Santa Pau (C-S8). Sequence of protein-VP1-coding segment

cDNA segments copied from the RNA of foot-and-mouth disease virus (FMDV) C₁-Santa Pau (isolate C-S8) have been cloned in plasmid pBR322. A 998-bp DNA fragment, that includes the region coding for capsid protein VP1, the carboxy terminus of VP3, and the amino terminus of precursor protein p52 has been sequenced. Comparison of the nucleotide sequence with those from FMDV O₁K, A₁₀61, a₁₂ and C₃ Indaial (Kurz et al., Nucl. Acids Res. 9 (1981) 1919–1931; Kleid et al., Science 214 (1981) 1125–1129; Boothroyd et al., Gene 17 (1982) 153–161; Makoff et al., Nucl. Acids Res. 10 (1982) 8285–8295) indicates extensive variability between the corresponding gene segments, including short insertions and deletions. Base transversions are more frequent than transitions within the VP1 coding segment, but not in the sequence coding for the amino-terminal end of p52. The nucleotide sequence divergence is reflected in variability in both the primary and the predicted higher-order structures of the encoded VP1s.     

Effects of p-fluorophenylalanine on the induction of mutations in bacteriophage T4: I. 5-Bromouracil mutagenesis

The amino acid analogue p-fluorophenylalanine (PFPA) was found to have no mutagenic activity in the r system of bacteriophage T4. However, under standard conditions for 5-bromouracil (5-BU) mutagenesis, PFPA depressed the induced frequencies for both forward and reverse mutations. When the folate antagonist sulphanilamide (SU) was omitted from the mutagenic treatment medium or when it was replaced by Trimethoprim (TM), another folate antagonist, this depressive effect was abolished. It was proposed that PFPA alleviated the inhibitory action of SU.     

Fluoxetine, 17-β estradiol or folic acid combined with intra-lateral septal infusions of neuropeptide Y produced antidepressant-like actions in ovariectomized rats forced to swim

Folic acid is antidepressant, either alone or combined with several antidepressant drugs. However, the antidepressant-like actions of folic acid combined with intra-lateral septal (LSN) infusions of neuropeptide Y (NPY) in the forced swimming test (FST) have not been tested before. Thus, systemic injections of fluoxetine (20.0 mg/kg, P < 0.05; s.c.) or 17-β estradiol (10.0 μg/rat, P < 0.05; s.c.) or oral administrations of folic acid (50.0 mg/kg, P < 0.05; 75.0 mg/kg, P < 0.05) or NPY intra-LSN (3.0 μg, P < 0.05; 3.5 μg, P < 0.05) reduced immobility of ovariectomized Wistar rats. Subthreshold doses of: folic acid (25.0 mg/kg) or 17-β estradiol (5.0 μg/rat, P < 0.05) or fluoxetine (15.0 mg/kg, P < 0.05; s.c.) combined with subthreshold doses of NPY (2.5 μg/rat, P < 0.05; intra-LSN) and these combinations produced antidepressant-like actions; which were canceled by BIBP 3226 (a NPY-Y1 receptor antagonist). It is concluded that folic acid produced antidepressant-like effects probably through the participation of the NPY Y1 receptors found in the lateral septal nuclei.     

无机磷和叠氮钠对线粒体F_1-ATPase构象的不同影响

用εＡＤＰ作荧光探针,用荧光猝灭的方法证明无机磷（Ｐｉ）能影响Ｆ１－ＡＴＰａｓｅ的构象从而使酶结合ＡＤＰ的能力降低．用ａｕｒｏｖｅｒｔｉｎＢ作荧光探针研究了Ｐｉ和叠氮钠对Ｆ１－ＡＴＰａｓｅ构象的影响,发现Ｐｉ能影响洗去催化位点核苷酸的Ｆ１的构象,而叠氮钠对其没有影响,但却能影响结合有ＡＤＰ的Ｆ１的构象．因此Ｐｉ和叠氮钠对酶构象的影响是不同的,二者可能有不同的作用位点．