Quantitative autoradiographic analysis of [I]-human CGRP binding sites in the dorsal horn of rat following chronic constriction injury or dorsal rhizotomy

Quantitative receptor autoradiography was used to examine the binding of [¹²⁵I]-human CGRP in the dorsal horn of the L4 spinal segment of rats with a chronic constriction injury (CCI) of the sciatic nerve or unilateral dorsal rhizotomies of spinal segments L1–L6. At the times selected for study, we found no change in the amount of CGRP binding in any areas examined following CCI. In contrast, our results showed a temporally related increase in the amount of CGRP binding in areas within laminae I–II and in lateral lamina V of the dorsal horn ipsilateral to the rhizotomies. These results indicate that CGRP binding sites are regulated, most likely, by changes in the release of CGRP. Further, our results suggest that the release of CGRP from primary afferent neurons is unchanged in animals with a CCI.     

Isolation and regional localization of a large collection (2,000) of single-copy DNA fragments on human chromosome 3 for mapping and cloning tumor suppressor genes

Summary A collection of 2,000 lambda phage-carrying human single-copy inserts (> 700 bp) were isolated from two chromosome-3 flow-sorted libraries. The single-copy DNA fragments were first sorted into 3p and 3q locations and about 700 3p fragments were regionally mapped using a deletion mapping panel comprised of two humanhamster and two-human-mouse cell hybrids, each containing a chromosome 3 with different deletions in the short arm. The hybrids were extensively mapped with a set of standard 3p markers physically localized or ordered by linkage. The deletion mapping panel divided the short arm into five distinct subregions (A-E). The 3p fragments were distributed on 3p regions as follows: region A, 26%; B, 31%; C, 4%; D, 4% and E, 35%. We screened 300 single-copy DNA fragments from the distal part of 3p (regions A and B) with ten restriction endonucleases for their ability to detect restriction fragment length polymorphisms (RFLPs). Of these fragments 110 (36%) were found to detect useful RFLPs: 35% detected polymorphisms with frequency of heterozygosity of 40% or higher, and 25% with frequency of 30% or higher. All polymorphisms originated from single loci and most of them were of the base pair substitution type. These RFLP markers make it possible to construct a fine linkage map that will span the distal part of chromosome 3p and encompasses the von Hippel-Lindau disease locus. The large number of single-copy fragments (2,000) spaced every 100–150 kb on chromosome 3 will make a significant contribution to mapping and sequencing the entire chromosome 3. The 300 conserved chromosome 3 probes will increase the existing knowledge of man-mouse homologies.     

Uptake and utilization of14C-glycine by embryos ofSebastes melanops

Synopsis The ability of embryos of the viviparous scorpaenidSebastes melanops to take up nutrients from an exogenous substrate was demonstrated by incubating embryos at various stages of development (18–30 days after fertilization) in¹⁴C-labeled glycine for 24 h. Uptake was highest for embryos at the latest stages (28–30 days) and increased at a linear rate during the incubation period. Nutrient uptake was not time dependent in embryos at the early stages (18–22 days). Nutrient utilization byS. melanops embryos was measured by the oxidation of¹⁴C-labeled glycine to¹⁴CO₂. The amount of respired¹⁴CO₂ by the oldest embryos increased significantly at a linear rate over the 24 h incubation period. There was no evidence of nutrient utilization by the youngest embryos. The developmental changes we observed in the uptake and utilization of exogenous glycine are supported by our previous findings that the oldest embryos have fully developed mouths and guts, and require additional nutrition from intraovarian sources at this stage of development.     

The Mu Transposable Elements of Maize: Evidence for Transposition and Copy Number Regulation during Development

The Mu transposon of maize exists in a highly mutagenic strain called Robertson's Mutator. Plants of this strain contain 10-50 copies of the Mu element, whereas most maize strains and other plants have none. When Mutator plants are crossed to plants of the inbred line 1S2P, which does not have copies of Mu, the progeny plants have approximately the same number of Mu sequences as did their Mutator parent. Approximately one-half of these copies have segregated from their parent and one-half have arisen by transposition and are integrated into new positions in the genome. This maintenance of copy number can be accounted for by an extremely high rate of transposition of the Mu elements (10-15 transpositions per gamete per generation). When Mutator plants are self-pollinated, the progeny double their Mu copy number in the first generation, but maintain a constant number of Mu sequences with subsequent self-pollinations. Transposition of Mu and the events that lead to copy number maintenance occur very late in the development of the germ cells but before fertilization. A larger version of the Mu element transposes but is not necessary for transposition of the Mu sequences. The progeny of crosses with a Mutator plant occasionally lack Mutator activity; these strains retain copies of the Mu element, but these elements no longer transpose.     

Limnologic consequences of the decline in hemlock 4800 years ago in three Southern Ontario lakes

Four thousand eight hundred years ago hemlock (Tsuga canadensis) populations were decimated throughout eastern North America. We have studied the effects of this loss from the terrestrial community on three Southern Ontario lakes: Little Round Lake, Sunfish Lake, and McKay Lake. This study includes the use of cladocerans, diatoms, chrysophytes, and bacterial pigments to assess the limnologic changes that occurred in these lakes. Each lake experienced a change in trophic status that coincided with the loss of hemlock from its catchment, but the change in the aquatic biota was different in each lake. The lakes' size may have been the most influential factor governing the response to this terrestrial disturbance.     

Comparison of the roles of Ostracods and Cladocerans in regulating community structure and metabolism in freshwater microcosms

Laboratory microcosms were used to compare the effects of the littoral ostracod Cypridopsis vidua and the planktonic cladoceran Daphnia magna on community structure and metabolism. Filter-feeding by cladocerans, both in the presence and absence of ostracods, greatly reduced the abundance of planktonic algae when D. magna reached peak density around day 50; rotifers and euglenids were then limited to flocculent matter on the container bottom. Both net production and community respiration rates decreased as community composition changed. Microcosms containing ostracods as the only microcrustacean showed little reduction in total algal numbers but the otherwise dominant alga, Scenedesmus spp., was replaced by Ankistrodesmus spp. when peak ostracod density was reached around day 100. Rotifers were completely eliminated but euglenids were able to coexist with ostracods. Ostracods impacted community metabolism less than cladocerans, but depressed respiration slightly more than net production.     

Dopaminergic Regulation of Cone Retinomotor Movement in Isolated Teleost Retinas: II. Modulation by γ-Aminobutyric Acid and Serotonin

In the accompanying paper we reported that 3,4-dihydroxyphenylethylamine (dopamine) induced light-adaptive retinomotor movements in teleost photoreceptors and that this effect was mediated by D2 dopamine receptors located on the photoreceptors themselves. In this study, we investigated the effects on cone retinomotor movement of three agents that have been reported by others to modulate retinal dopamine release: gamma-aminobutyric acid (GABA), 5-hydroxytryptamine (5-HT, serotonin), and melatonin. We report here that the GABA antagonists bicuculline and picrotoxin induced light-adaptive cone contraction in dark-adapted green sunfish retinas cultured in constant darkness; thus they mimic the effect of light or exogenously applied dopamine. Since their effects were blocked by either the D2 dopamine antagonist sulpiride or by Co2+, it seems likely that these agents act by enhancing retinal dopamine release. The GABA agonist muscimol produced effects opposite to those of GABA antagonists. Muscimol inhibited light-induced cone contraction in previously dark-adapted retinas and induced dark-adaptive cone elongation in light-adapted retinas. These results suggest that in green sunfish retinas, as has been reported for other retinas, GABA inhibits dopamine release. 5-HT induced light-adaptive cone contraction in dark-adapted retinas; thus 5-HT also mimics the effect of light or exogenously applied dopamine. The effect of 5-HT was blocked by sulpiride, Co2+, or the 5-HT antagonist mianserin. These results suggest that 5-HT induces cone contraction by stimulating dopamine release. Melatonin neither inhibited dopamine-induced cone contraction in retinas cultured in the dark nor induced cone elongation in retinas cultured in the light. Our results suggest that both GABA and 5-HT (but not melatonin) affect cone retinomotor movements in green sunfish by modulating dopamine release: GABA by inhibiting and 5-HT by stimulating dopamine release. We report in the companion paper that dopamine induced contraction in isolated cone fragments. Together these observations strongly suggest that dopamine serves as the final extracellular messenger directly inducing light-adaptive cone retinomotor movement, and that GABA and 5-HT affect these movements by modulating dopamine release.     

EFFECT OF TREE CANOPY REMOVAL BY GYPSY MOTH LARVAE ON THE MACROALGAE OF A RHODE ISLAND HEADWATER STREAM1

A spring-fed, headwater stream in central Rhode Island was examined during the period from June to October, 1979 to 1982. In the first two summers, a dense riparian canopy reduced the light penetration at the stream surface to a range of 5 to 18% of incident radiation. The lotic macroalgal community during this period was limited to 1 to 4 species covering < 1 to 35% of the stream bottom. However, in June and July, 1981, the surrounding leaf canopy was removed by a massive gypsy moth larval outbreak. Light penetration to the stream during this summer increased to 73% by early July, thereby resulting in a rise in water temperatures by 3.7°C. Even though there was a partial regrowth of leaves in late July and August of 1981, macroalgal cover values continued to rise to an early August peak of 80%. During the third summer, 88% of the macroalgal abundance could be attributed to illumination and water temperature. The filamentous diatom Funotia pectinalis ( O.F. Müll.) Rabh. was the predominant species in the midsummer of all four years, accounting for at least 60% of the total cover. In 1981. an important taxon was the desmid Hyalotheca dissiliens (S. Smith) Bréb., a species which was not seen in other years. A less severe gypsy moth defoliation occurred in 1982 but did not produce significant differences in light, temperature or macroalgal cover from 1979 and 1980. The results indicate that light and temperature can be limiting during the summer in spring-fed, headwater streams and that seed populations of some species are present in undetect-able levels during these periods of suboptimal growth conditions. In addition, it appears that stream macroalgal communities can be quite resilient, recovering rapidly following a major perturbation .     

Reactivity and fate of benzene and formaldehyde in culture medium with and without fetal calf serum; relevance to in vitro mutagenicity testing

Gas chromatographic-mass spectrometric analyses were performed to determine the reactivity and fate of benzene (BEN) and formaldehyde (FA) in culture medium. BEN (solubility in water: 500 ppm) does not react with culture medium, either with or without fetal calf serum, but its volatility, even in closed vials, is so great that 90% of a 250-ppm solution is lost to the head space after 1 h at 24°C. FA, as a 37% aqueous solution, is a complex mixture that changes composition after 15-min incubation at 38°C. FA is extremely reactive in culture medium containing fetal calf serum, and is much less reactive with medium components in the absence of serum. There is a dramatic increase in the number of daughter products in FA-treated medium over time, such that those seen immediately after FA is added to medium have been replaced after 60-min incubation (38°C in closed vials) by many other interaction products. Methods ensuring maximum solubilization and minimal volatilization of BEN during exposure are essential for obtaining reproducible data on the mutagenic potential of BEN. The volatilization of FA from stock formalin solutions, and, more importantly, the interaction product(s) formed by this highly reactive compound with medium components, especially those in serum, are probably the critical aspects of an effective testing protocol for FA.