Comparative population ecology of Ephydra hians Say (Diptera: Ephydridae) at Mono Lake (California) and Abert Lake (Oregon)

The population dynamics of Ephydra hians Say final instar larvae and pupae were compared over a two year period in rocky littoral habitats of two alkaline saline lakes in the western Great Basin. Relative abundance increased from 1983 to 1984 at Mono Lake (California), during dilution from ca. 90 to 80 g 1^-1 TDS (total dissolved solids). In contrast, relative abundance decreased over the same period at Abert Lake (Oregon), accompanied by a dilution of salinity from ca. 30 to 20 g l^-1 and a marked increase in the number and abundance of other benthic macroinvertebrate species. These observations are consistent with a hypothesis that proposes biotic interactions limit E. hians abundance at low salinity, and physiological stress limits abundance at high salinity.Oviposition extends from early spring to early fall. Mixed instars present throughout this period indicates multivoltine population dynamics with overlapping generations. The standing stock biomass of final instars increases exponentially in late spring and peaks in late summer or early fall. Pupae increase in proportional representation and abundance from a spring minimum to a fall maximum. The body size of adults and pupae cycle seasonally from a spring maximum to a fall minimum, and may be related to either or both food limitation, or water temperature.     

Behavioral and biochemical assessment of time-related changes in globus pallidus and striatal dopamine induced by intranigrally administered neurotensin

Microinjection of neurotensin (NT; 2 and 5 μg) into the substantia nigra zona compacta caused an increase in dopamine (DA) and DA metabolites in the rodent globus pallidus and striatum which persisted for at least 20 hours after peptide administration. Similar NT treatments given unilaterally into the nigra caused circling away from the injected side in amphetamine-pretreated rats, but were without effect when microinjected into saline-pretreated animals. Circling also occurred when the animals were given amphetamine 20 hours after intranigral NT administration. Contralateral rotation was observed with unilateral intranigral injections of gamma-hydroxybutyric acid (GHB; 400 μg) or with lower intranigral GHB doses (250 μg) in amphetamine-pretreated animals. The effects of GHB and NT differed in the manner in which the animals rotated as well as in the profile of DA and DA metabolite changes induced by these drugs. These studies indicated that: (1) dopaminergic functions of the globus pallidus are influenced, like the striatum, by manipulations of the substantia nigra; (2) NT and GHB likely act via different mechanisms to effect nigral dopamine-containing cells; and (3) NT was capable of inducing changes in dopamine neurons which had long term consequences.     

Class I and class II restriction pattern polymorphisms associated with independently derived RT1 haplotypes in inbred rats

This communication reports the DNA level identification of class I and class II sequences associated with 20 RT1 haplotypes which have been assigned previously to eight RT1 groups. Sixteen to 22 bands in genomic blots hybridized with the mouse pH-2III class I cDNA probe. Only the three RT1 ^khaplotypes associated with identical class I restriction fragment patterns. Differences in restriction bands between putatively identical RT1 haplotypes were either less than or equal to 6%, or greater than 50%, suggesting a relatively high level of recombination between serologically identified RT1.A genes and the majority of class I sequences. Restriction fragment patterns associated with three RT1 ^uhaplotypes differed by less than 6%. However, intra-RT1 ^a,intra-RT1 ^b,and intra-RT1 ^lrestriction fragment differences were between 50 and 64%. In specific cases, different RT1 haplotypes associated with identical class I restriction patterns, e.g., RT1 ^m(MNR) and RT1 ^d(MR); higher resolution confirmed the difference (two bands) between RT1 ^mand RT1 ^d.Results of hybridization with the human DC₁ probe confirmed that the AVN RT1 ^aand NSD RT1 ^bhaplotypes were generated by recombinations within the vicinity of the RT1.B : RT1.D regions. These results demonstrate that a previous classification of RT1 haplotypes was incomplete and did not include the majority of class I and class II sequences which distinguish RT1 haplotypes.     

The sporulation-specific penicillin-binding protein 5a from Bacillus subtilis is a DD-carboxypeptidase in vitro

A chemiluminescence method for determining acetylcholinesterase activity is described. It is an adaptation of the chemiluminescence assay of acetylcholine described by Israël & Lesbats [(1981) Neurochem. Int. 3, 81-90; (1981) J. Neurochem. 37, 1475-1483]. The acetylcholinesterase activity is measured by monitoring the increase in light emission produced by the accumulation of choline or by determining the amount of choline generated after a short interval. The assay is rapid and sensitive, and uses the natural substrate of the enzyme. Kinetic data obtained with this procedure for acetylcholinesterase from Torpedo and Electrophorus electric organs were comparable with those obtained by using the method of Ellman, Courtney, Andres & Featherstone [(1961) Biochem. Pharmacol. 7, 88-95]. In addition, it was shown that sodium deoxycholate totally inactivated Torpedo acetylcholinesterase but not the Electrophorus enzyme. Competitive inhibitors of acetylcholinesterase protected the enzyme from inactivation.