Plant phosphoglucose isomerase genes lack introns and are expressed in Escherichia coli

Nuclear genes that appear to encode both cytosolic and plastid isozymes of phosphoglucose isomerase (PGI), an essential glycolytic enzyme, have been isolated from three diploid species of the annual wild flower genus Clarkia (Onagraceae). The genes do not contain introns and are expressed to varying degrees in Escherichia coli when cloned in either Charon 35 phage or pUC plasmid vectors. The PGI proteins synthesized in E. coli form dimers, are catalytically active, and their electrophoretic mobilities are similar to those of appropriate Clarkia PGIs. The nucleotide sequence of a gene encoding a plastid isozyme of C. unguiculata is described.     

Alloreactivity of an OVA-specific T-cell clone

A T-cell clone (Lyl-03) derived from BALB/cBy mice, though highly specific for OVA/A^d, reacted to allogeneic spleen cells of 6 of 12 H-2 haplotypes tested. The reactivity to each particular H-2 haplotype required the expression of a non-major histocompatibility complex (MHC) gene product present on the B cells of certain strains of mice. All the alloreactive responses were MHC restricted and were inhibited by class II-specific and L3T4-specific monoclonal antibodies. The non-MHC gene product, X, is a new lymphocyte-stimulating determinant that is not expressed in mice with the xid defect. We favor a model that proposes two independent sites (or receptors) for X and the class II molecule. Contrary to previous models for alloreactivity, the anti-MHC site is not directed to a polymorphic receptor for self-class II epitope on the foreign class II molecule, but rather to a conserved determinant present on both self- and allo-class II molecules. If there is only one antigen receptor on the T-cell clone Lyl-03, then anti-X receptor must bind to a cross-reactive determinant found on immunogenic OVA and the non-MHC coded gene product expressed on the cell surface membrane. We further postulate that class II plus X recognition may be a general rule for alloreactive as well as autoreactive responses. Thus, both allo-class II and allo-class I reactive T cells are similar in that both bind a non-MHC coded gene product prior to activation.Abbreviations used in this paper: APC antigen-presenting cell(s) - Con A concanavalin A - Cl. clone - DME Dulbecco's modified Eagle's medium - FCS fetal calf serum - H-2 histocompatibility-2 - MHC major histocompatibility complex - MLR mixed lymphocyte response - Mls mixed lymphocyte stimulating - OVA chicken ovalbumin - X unknown cell-surface antigen - xid immunodeficiency mapped to the X chromosome     

Factors Determining the Frequency of the Killer Trait within Populations of the Paramecium aurelia Complex

The factors maintaining the cytoplasmically inherited killer trait in populations of Paramecium tetraurelia and Paramecium biaurelia were examined using, in part, computer simulation. Frequency of the K and k alleles, infection and loss of the endosymbionts, recombination during conjugation and autogamy, cytoplasmic exchange and natural selection were incorporated in a model. Infection during cytoplasmic exchange at conjugation and natural selection were factors that would increase the proportion of killers in a population. Conversely, k alleles reduced the proportion of killers in a population, acting through conjugation and autogamy. Field studies indicate that the odd mating type is prevalent in P. tetraurelia isolated from nature. Conjugation and therefore transmission by cytoplasmic transfer would be rare. Competition studies indicate a strong selective disadvantage for sensitives at concentrations found in nature. Natural selection must therefore be the factor maintaining the killer trait in P. tetraurelia.     

Characterization of a target-derived neuronal cholinergic differentiation factor

The sympathetic innervation of rat sweat glands undergoes a target-induced switch from a noradrenergic to a cholinergic and peptidergic phenotype during development. Treatment of cultured sympathetic neurons with sweat gland extracts mimics many of the changes seen in vivo. Extracts induce choline acetyltransferase activity and vasoactive intestinal peptide expression in the neurons in a dose-dependent fashion while reducing catecholaminergic properties and neuropeptide Y. The cholinergic differentiation activity appears in developing glands of postnatal day 5 rats and is maintained in adult glands. It is a heat-labile, trypsin-sensitive, acidic protein that does not bind to heparin-agarose. Immunoprecipitation experiments with an antiserum directed against an N-terminal peptide of a cholinergic differentiation factor (CDF/LIF) from heart cells suggest that the sweat gland differentiation factor is not CDF/LIF. The sweat gland activity is a likely candidate for mediating the target-directed change in sympathetic neurotransmitter function observed in vivo.     

Cytoplasmic organization in cerebellar dendritic spines

Three sets of filamentous structures were found to be associated with synaptic junctions in slices of cerebellar tissue prepared by rapid- freezing and freeze-etch techniques. The electron-dense fuzz subjacent to postsynaptic membranes corresponds to a web of 4-6-nm-diam filaments that were clearly visualized in rapid-frozen, freeze-etched preparations. Purkinje cell dendritic spines are filled with a meshwork of 5-7-nm filaments that were found to contact the spine membrane everywhere except at the synaptic junction, and extend through the neck of the spine into the parent dendrite. In addition, 8-10-nm microfilaments, possibly actin, were seen to be associated with the postsynaptic web and to extend into the body and neck of the spine. The arrangements and attachments of the filamentous elements in the Purkinje cell dendritic spine may account for its shape.     

Neuroendocrine and behavioral effects of dietary tryptophan restriction in healthy subjects

The neuroendocrine and behavioral effects of gradual dietary tryptophan (TRP) depletion, utilizing two magnitudes of a 10-day TRP-restriction diet (700 mg/day and 200 mg/day), were studied in 22 healthy subjects. The prolactin response to a 7 gm L-TRP infusion was measured prior to and on day 10 of the diet. Both diets significantly reduced fasting total plasma TRP by 15 to 20%, but only the 200 mg/day TRP diet led to an enhancement of the prolactin response to intravenous L-TRP. Female subjects demonstrated a more robust increase in plasma prolactin following L-TRP infusion pre-diet and exhibited a larger decrease in plasma TRP following dietary TRP restriction compared to males. There were no significant behavioral effects of either diet. Gradual dietary TRP depletion leads to an enhancement of the prolactin response to L-TRP infusion, suggestive of postsynaptic serotonin receptor supersensitivity.     

Superoxide dismutase,catalase, and U78517F attenuate neuronal damage in gerbils with repeated brief ischemic insults

Repeated ischemic insults at one hour intervals result in more severe neuronal damage than a single similar duration insult. The mechanism for the more severe damage with repetitive ischemia is not fully understood. We hypothesized that the prolonged reperfusion periods between the relatively short ischemic insults may result in a pronounced generation of oxygen free radicals (OFRs). In this study, we tested the protective effects of superoxide dismutase (SOD) and catalase (alone or in combination), and U78517F in a gerbil model of repetitive ischemia. Three episodes (two min each) of bilateral carotid occlusion were used at one hour intervals to produce repetitive ischemia. Superoxide dismutase and catalase were infused via osmotic pumps into the lateral ventricles. Two doses of U78517F were given three times per animal, one half hour prior to each occlusion. Neuronal damage was assessed 7 days later in several brain regions using the silver staining technique. The Mann-Whitney U test was used for statistical comparison. Superoxide dismutase showed significant protection in the hippocampus (CA4), striatum, thalamus and the medial geniculate nucleus (MGN). Catalase showed significant protection in the striatum, hippocampus, thalamus, and MGN and the substantia nigra reticulata. Combination of the two resulted in additional protection in the cerebral cortex. Compared to the controls, there was little protection with a dose of 3 mg/kg of U78517F. There was significant protection with a dose of 10 mg/kg in the hippocampus (CA4), striatum, thalamus, medial geniculate nucleus and the substantia nigra reticulata. The significant protection noted with SOD, catalase or U78517F with repeated ischemia supports, the hypothesis that OFRs may play a role in neuronal damage in repeated cerebral ischemia.     

Target determination of neurotransmitter phenotype in sympathetic neurons

While the majority of sympathetic neurons are noradrenergic, a minority population are cholinergic. At least one population of cholinergic sympathetic neurons arises during development by a target-dependent conversion from an initial noradrenergic phenotype. Evidence for retrograde specification has been obtained from transplantation studies in which sympathetic neurons that normally express a noradrenergic phenotype throughout life were induced to innervate sweat glands, a target normally innervated by cholinergic sympathetic neurons. This was accomplished by transplanting footpad skin containing sweat gland primordia from early postnatal donor rats to the hairy skin region of host rats. The sympathetic neurons innervating the novel target decreased their expression of noradrenergif traints and developed choline acetyltransferase (ChAT) activity. In addition, many sweat gland-associated fibers acquired acetylcholinesterase (AChE) staining and VIP immunoreactivity. These studies indicated that sympathetic neurons in vivo alter their neurotransmitter phenotype in response to novel envronmental signals and that sweat glands play a critical role in the cholinergic and peptidergic differentiation of the sympathetic neurons that innervate them. The sweat gland-derived cholinergic differentiation factor is distinct from leukemia inhibitory factor and ciliary neurotrophic factor, two well-characterized cytokines that alter the neurotransmitter properties of cultured sympathetic neurons in a similar fashion. Recent studies indicate that anterograde signalling is also important for the establishment of functional synapses in this system. We have found that the production of cholinergic differentiation activity by sweat glands required sympathetic innervation, and the acquisition and maintenance of secretory competence by sweat glands depends upon functional cholinergic innervation. 1994 John Wiley & Sons, Inc.