Formation and persistence of N7-methylguanine DNA adducts in the target pyloric tissue following chronic exposure to N-methyl-N′-nitro-N-nitrosoguanidine

Outbred 7-week old male Wistar rats were exposed for 21 days to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) via the drinking water and N7-methyl deoxyguanosine 3'-monophosphate (N7-MedGp) levels in DNA from the pyloric mucosa (target tissue) and white blood cells (wbc: non-target tissue) were determined by ³²P-postlabelling. Exposure to MNNG resulted in the non-linear, dose-related formation of N7-medGp in both tissues. Adduct levels in the pyloric mucosa were determined to be 1058, 5.4 and 1.1 μmole N7-medGp mole^-1 deoxyguanosine 3'-monophosphate (dGp) after exposure to 4.1, 0.62 and 0.006 mg MNNG kg^-1 day^-1 respectively whereas adduct levels in the wbc DNA were lower at 5.2, 0.52 and 0.68 μmoles N7-medGp mole^-1 dGp after exposure to 4.1, 0.62 and 0.062 mg MNNG kg^-1 day^-1 respectively. In addition, the persistence of N7-medGp was investigated. Loss of adduct occurred rapidly, with a decrease of 87 and 97% respectively in target tissue and wbc DNA by 48 h after cessation of 4.1 mg MNNG kg^-1 day^-1 exposure; 14 days post-MNNG treatment, however, N7-medGp was still detectable (0.46 μmole N7-medGp mole^-1 dGp) in pyloric mucosal DNA. The quantitation of N7-medGp after exposure to low doses of carcinogen, i.e. 0.006 mg MNNG kg^-1 day^-1, approaching environmentally relevant levels has not been previously reported, and indicates that the ³²P-postlabelling assay developed here possesses sufficient sensitivity to quantitate N7- medGp in human DNA arising from environmental exposure to methylating agents.     

A new subgenus and species of Glyptomorpha (Hymenoptera: Braconidae) from Arabia, Egypt, Pakistan and Yemen, with a reappraisal of the status of Teraturus

Abstract A new subgenus and species, Glyptomorpha (Zanporiu) egyptiaca from Egypt, Arabia, Yemen and Pakistan are described and illustrated. G. Zanporia differs from G. Glyptomorpha in the form of the scapus and the lengh of the ovipositor. The status of Teraturus Kokujev is reconsidered and it is proposed that it should be treated as a subgenus of Glyptomorpha Holmgren, The relationship of Glyptomorpha to Rhadinobracon Szépligeti and Victoroviella Tobias is also discussed.     

Rapid indexing of the sunblotch disease of avocados using a complementary DNA probe to avocado sunblotch viroid

A routine procedure has been established for the sensitive and specific detection of avocado sunblotch viroid in partially purified nucleic acid extracts of avocado leaves by hybridisation analysis with ³²P-complementary DNA prepared against the purified viroid. Avocado sunblotch viroid was shown to be present in 12 avocado trees that had indexed positive in a biological test for sunblotch disease but was absent from 10 trees that indexed negative. The complete correlation between sunblotch disease and the presence of viroid indicates that the complementary DNA hybridisation assay procedure can be used for the indexing of sunblotch disease. The overall procedure of leaf extraction and hybridisation analysis can be completed in 5 days and is to be compared with up to 2 yr required for indexing by biological methods. The level of avocado sunblotch viroid in partially purified nucleic acid extracts of a number of different sources of sunblotch infected avocado leaves was found to vary 10 000-fold from 0.2% to 2 × 10^-5% by weight. The lower limit of detectability of the viroid by the hybridisation assay is considered to be about 10^-5% by weight; this is at least 10³ times more sensitive than the detection of the viroid by polyacrylamide gel electrophoresis of the leaf nucleic acid extracts followed by staining.     

Three-Dimensional Structure of Macronuclei from Paramecium Determined by Scanning Electron Microscopy*

SYNOPSIS. Macronuclei of Paramecium primaurelia were isolated and examined by scanning electron microscopy. These nuclei consisted of a closely packed array of chromatin bodies measuring ～ 0.2 μm in diameter. We estimated there were ～ 30,000 such bodies/macronucleus, 20 times more than the number of unit genome equivalents. This suggests that a unit genome is physically shared by several chromatin bodies.     

Managing for Elevated Yield of Moose in Interior Alaska

ABSTRACT Given recent actions to increase sustained yield of moose (Alces alces) in Alaska, USA, we examined factors affecting yield and moose demographics and discussed related management. Prior studies concluded that yield and density of moose remain low in much of Interior Alaska and Yukon, Canada, despite high moose reproductive rates, because of predation from lightly harvested grizzly (Ursus arctos) and black bear (U. americanus) and wolf (Canis lupus) populations. Our study area, Game Management Unit (GMU) 20A, was also in Interior Alaska, but we describe elevated yield and density of moose. Prior to our study, a wolf control program (1976–1982) helped reverse a decline in the moose population. Subsequent to 1975, moose numbers continued a 28-year, 7-fold increase through the initial 8 years of our study (λ_B1 = 1.05 during 1996–2004, peak density = 1,299 moose/1,000 km²). During these initial 8 hunting seasons, reported harvest was composed primarily of males ( = 88%). Total harvest averaged 5% of the prehunt population and 57 moose/1,000 km², the highest sustained harvest-density recorded in Interior Alaska for similar-sized areas. In contrast, sustained total harvests of <10 moose/1,000 km² existed among low-density, predator-limited moose populations in Interior Alaska (≤417 moose/1,000 km²). During the final 3 years of our study (2004–2006), moose numbers declined (λ_B2 = 0.96) as intended using liberal harvests of female and male moose ( = 47%) that averaged 7% of the prehunt population and 97 moose/1,000 km². We intentionally reduced high densities in the central half of GMU 20A (up to 1,741 moose/1,000 km² in Nov) because moose were reproducing at the lowest rate measured among wild, noninsular North American populations. Calf survival was uniquely high in GMU 20A compared with 7 similar radiocollaring studies in Alaska and Yukon. Low predation was the proximate factor that allowed moose in GMU 20A to increase in density and sustain elevated yields. Bears killed only 9% of the modeled postcalving moose population annually in GMU 20A during 1996–2004, in contrast to 18–27% in 3 studies of low-density moose populations. Thus, outside GMU 20A, higher bear predation rates can create challenges for those desiring rapid increases in sustained yield of moose. Wolves killed 8–15% of the 4 postcalving moose populations annually (10% in GMU 20A), hunters killed 2–6%, and other factors killed 1–6%. Annually during the increase phase in GMU 20A, calf moose constituted 75% of the predator-killed moose and predators killed 4 times more moose than hunters killed. Wolf predation on calves remained largely additive at the high moose densities studied in GMU 20A. Sustainable harvest-densities of moose can be increased several-fold in most areas of Interior Alaska where moose density and moose: predator ratios are lower than in GMU 20A and nutritional status is higher. Steps include 1) reducing predation sufficient to allow the moose population to grow, and 2) initiating harvest of female moose to halt population growth and maximize harvest after density-dependent moose nutritional indices reach or approach the thresholds we previously published.