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R L Russell

Publications and source records attributed to R L Russell.

At least 73 records · Page 4Linked to original sources
PubMed1985

Properties and partial purification of choline acetyltransferase from the nematode Caenorhabditis elegans.

We have stabilized and studied choline acetyltransferase from the nematode Caenorhabditis elegans. The enzyme is soluble, and two discrete forms were resolved by gel filtration. The larger of these two forms (MW approximately 154,000) was somewhat unstable and in the presence of 0.5 M NaI was converted to a form indistinguishable from the "native" small form (MW approximately 71,000). We have purified the small form of the enzyme greater than 3,300-fold by a combination of gel filtration, ion-exchange chromatography, and nucleotide affinity chromatography. The purified preparation has a measured specific activity of 3.74 mumol/min/mg protein, and is free of acetylcholinesterase and acetyl-CoA hydrolase activities. The Vmax of the purified enzyme is stimulated by NaCl, with half-maximal stimulation at 80 mM NaCl. The Km for each substrate is also affected by salt, but in different manners from each other and the Vmax; the kinetic parameter Vmax/Km thus changes significantly as a function of the salt concentration.

Animals↗
PubMed1985

New acetylcholinesterase-deficient mutants of the nematode Caenorhabditis elegans.

We have used visual screening for a mutationally induced uncoordinated phenotype, coupled with subsequent enzymatic assay, to isolate 19 new mutations producing acetylcholinesterase (AChE) deficiencies in the nematode Caenorhabditis elegans. At least 13 of these are independent, and all fall within two genes, ace-1 X and ace-2 I, previously shown to control respectively two kinetically distinct major AChE classes, A and B. Three of the 4 new ace-1 alleles and one of the 15 new ace-2 alleles are apparently leaky; the rest are probably null. For the 3 leaky ace-1 alleles, qualitative changes in the residual class A AChE strongly support the contention that ace-1 is a structural gene. In ace-2;ace-1 mutants, marked reduction in class A and B AChE reveals a third, minor, previously unrecognized AChE class, designated C.

Acetylcholinesterase↗
PubMed1985

A novel class of acetylcholinesterase, revealed by mutations, in the nematode Caenorhabditis elegans.

In ace-2;ace-1 double mutants of the nematode C. elegans, where the major acetylcholinesterase (AChE) classes A and B have been eliminated by mutation, the animals are viable and residual AChE activity remains. This residual activity differs markedly from AChE classes A and B; its Km for acetylcholine is 1000-5000-fold lower, its resistance to eserine is 3000-260,000-fold higher, it is markedly more thermolabile, and it can be separated from classes A and B by ion exchange chromatography. It has been designated class C AChE. Class C AChE of indistinguishable properties is also present in wild type C. elegans, at levels approximating those seen in ace-2;ace-1 double mutants, suggesting that it is controlled by a third, as yet unidentified, gene. Amongst other sources examined, class C-like AChE has been detected in another nematode species, Stephanurus dentatus, but not in Drosophila melanogaster, Torpedo californica, or Rattus rattus.

Acetylcholine↗
PubMed1984

Choline acetyltransferase-deficient mutants of the nematode Caenorhabditis elegans.

We have identified five independent allelic mutations, defining the gene cha-1, that result in decreased choline acetyltransferase (ChAT) activity in Caenorhabditis elegans. Four of the mutant alleles, when homozygous, lead to ChAT reductions of greater than 98%, as well as recessive phenotypes of uncoordinated behavior, small size, slow growth and resistance to cholinesterase inhibitors. Animals homozygous for the fifth allele retain approximately 10% of the wild-type enzyme level; purified enzyme from this mutant has altered Km values for both choline and acetyl-CoA and is more thermolabile than the wild-type enzyme. These qualitative alterations, together with gene dosage data, argue that cha-1 is the structural gene for ChAT. cha-1 has been mapped to the left arm of linkage group IV and is within 0.02 map unit of the gene unc-17, mutant alleles of which lead to all of the phenotypes of cha-1 mutants except for the ChAT deficiency. Extensive complementation studies of cha-1 and unc-17 alleles reveal a complex complementation pattern, suggesting that both loci may be part of a single complex gene.

Alleles↗
PubMed1983

Multiple molecular forms of acetylcholinesterase in the nematode Caenorhabditis elegans.

Extracts of the nematode Caenorhabditis elegans contain five molecular forms of acetylcholinesterase (AChE) activity that can be separated by a combination of selective solubilization, velocity sedimentation, and ion-exchange chromatography. These are called form IA (5.2s), form IB (4.9s), form II (6.7s), form III (11.3s), and form IV (13.0s). All except form III are present in significant amounts in rapidly prepared extracts and are probably native; form III is probably derived autolytically from form IV. Most of forms IA and IB can be solubilized by repeated extractions without detergent, whereas forms II, III, and IV require detergent for effective solubilization and may therefore be membrane-bound. High salt concentrations are not required for, and do not aid in, the solubilization of these forms. For all forms, molecular weights and frictional ratios have been estimated by a combination of gel permeation chromatography and velocity sedimentations in both H2O and D2O. The molecular weight estimates range from 83,000 to 357,000 and only form II shows extensive asymmetry. The separated forms have been characterized with respect to substrate affinity, substrate specificity, inhibitor sensitivity, thermal inactivation, and detergent sensitivity. Judging by these properties, C. elegans is like other invertebrates in that none of its cholinesterase forms resembles either the "true" or the "pseudo" cholinesterase of vertebrates. However, internal comparison of the C. elegans forms clearly distinguishes forms IA, III, and IV as a group from forms IB and II; the former are therefore designated "class A" forms, the latter "class B" forms. Genetic evidence indicates that separate genes control class A and class B forms, and that these two classes overlap functionally. Several factors, including kinetic properties, molecular asymmetry, molecular size, and solubility, all suggest that a molecular model of the multiple cholinesterase forms observed in vertebrate electric organs probably does not apply in C. elegans. Potential functional roles and subunit structures of the multiple AChE forms within each C. elegans class are discussed.

Acetylcholinesterase↗
PubMed1981

Quantitative measures of aging in the nematode Caenorhabditis elegans. I. Population and longitudinal studies of two behavioral parameters.

As a first step in the quantitative characterization of senescence in the nematode Caenorhabditis elegans, we have studied movement wave frequency, defecation frequency, and whole-body water efflux as a function of age. Populations of C. elegans, strain N2, were cultured monoxenically on E. coli lawns at 20 degrees C. The median lifespan in such populations was approximately 12 days. Population mean movement wave frequency declined linearly with age (slope = -4.66 waves/minute per day). The decline in population mean defecation frequency (defecations per minute) was multiphasic, consisting of (1) a rapid decline (slope = -0.233 defecations/minute per day) from day 3 to day 6, (2) no apparent trend from day 6 to day 9, and (3) a gradual decline (slope = -0.089 defecations/minute per day) from 9 to day 14. Animals alive on or after day 15 were not observed to defecate. In longitudinal studies, individual animals exhibited linear declines in movement wave frequency and multiphasic declines in defecation frequency. For future population studies, the age-dependent declines in movement and defecation frequency appear sufficiently large and reproducible to a multiparametric description of senescence in C. elegans. One physiological parameter, 3H2O efflux, was found to be age-independent and to consist of two first-order rates. The half-times of the slow and fast efflux rates were approximately 15 and approximately 2.1 minutes, respectively. The two half-times and the fractions of 3H2O exhibiting the two half-times were invariant with age.

Aging↗
PubMed1981

An acetylcholinesterase-deficient mutant of the nematode Caenorhabditis elegans.

Within a set of five separable molecular forms of acetylcholinesterase found in the nematode Caenorhabditis elegans, previously reported differences in kinetic properties identify two classes, A and B, likely to be under separate genetic control. Using differences between these classes in sensitivity to inactivation by sodium deoxycholate, a screening procedure was devised to search for mutants affected only in class A forms. Among 171 previously isolated behavioral and morphological mutant strains examined by this procedure, one (PR946) proved to be of the expected type, exhibiting a selective deficiency of class A acetylcholinesterase forms. Although originally isolated because of its uncoordinated behavior, this strain was subsequently shown to harbor mutations in two genes; one in the previously identified gene unc-3, accounting for its behavior, and one in a newly identified gene, ace-1, accounting for its selective acetylcholinesterase deficiency. Derivatives homozygous only for the ace-1 mutation also lacked class A acetylcholinesterase forms, but were behaviorally and developmentally indistinguishable from wild type. The gene ace-1 has been mapped near the right end of the X chromosome. Gene dosage experiments suggest that it may be a structural gene for a component of class A acetylcholinesterase forms.

Acetylcholinesterase↗
PubMed1981

A second class of acetylcholinesterase-deficient mutants of the nematode Caenorhabditis elegans.

In JOHNSON et al. (1981), the Caenorhabditis elegans mutant strain PR1000, homozygous for the ace-1 mutation p1000, is shown to be deficient in the class A subset of acetylcholinesterases, which comprises approximately one-half of the total C. elegans acetylcholinesterase activity. Beginning with this strain, we have isolated 487 new behavioral and morphological mutant strains. Two of these, independently derived, lack approximately 98% of the wild-type acetylcholinesterase activity and share the same specific uncoordinated phenotype; both move forward in a slow and uncoordinated manner, and when mechanically stimulated to induce reversal, both hypercontract and become temporarily paralyzed. In addition to the ace-1 mutation, both strains also harbor recessive mutations in the same newly identified gene, ace-2, which maps to chromosome I and is therefore not linked to ace-1. Gene dosage experiments suggest that ace-2 is a structural gene for the remaining class B acetylcholinesterases, which are not affected by ace-1.--The uncoordinated phenotype of the newly isolated, doubly mutant strains depends on both the ace-1 and ace-2 mutations; homozygosity for either mutation alone produces normally coordinated animals. This result implies functional overlap of the acetylcholinesterases controlled by ace-1 and ace-2, perhaps at common synapses. Consistent with this, light microscopic histochemical staining of permeabilized whole mounts indicates some areas of possible spatial overlap of these acetylcholinesterases (nerve ring, longitudinal nerve cords). In addition, there is at least one area where only ace-2-controlled acetylcholinesterase activity appears (pharyngeo-intestinal valve).

Acetylcholinesterase↗
PubMed1978

The effect of dose, novelty, and exploration on amphetamine-produced stereotyped behavior.

Four experiments are presented. The first experiment demonstrated that the incidence of steretyped behavior was a monotonic increasing function of amphetamine dose. Variations in the form of the response to dose are described. The next two studies examined the relationship between environmental novelty and amphetamine-produced stereotypy. This behavior was observed less among subjects placed into novel environments than among subjects placed into familiar environments. The ability of novel stimuli to evoke exploratory responses incompatible with stereotypy was suggested as the basis for this effect. This interpretation was supported in a final experiment, which observed exploratory behavior and general activity, as well as amphetamine-produced stereotypy in subjects exposed to a novel stimulus in an otherwise familiar environment. All four experiments were interpreted as supporting a unified conception of amphetamine-produced and pathological sterotyped behaviors.

Animals↗