Increased incidence of developmental anomalies among descendants of carriers of methylenebisacrylamide-induced balanced reciprocal translocations

N,N'-Methylenebisacrylamide (MBA), a dimer of the monomeric acrylamide, was studied for induction of clastogenic effects in germ cells of male mice. It was found to be effective in inducing dominant-lethal mutations and heritable translocations in maturing sperm. The semisterile translocation carriers and their normal counterparts were used to determine the health impact of transmitted chromosomal rearrangements through anatomical analysis of their immediate descendants in utero. As expected, semisterility resulted primarily from embryonic death during the periimplantation stages presumably caused by sperm segregants with unbalanced chromosome complement fertilizing some of the eggs. Among conceptuses that survived to mid- and late-gestation stages, there was an increased incidence of developmental anomalies including fetal death and phenotypic defects. These anomalies are assumed to be caused by certain types of unbalanced segregants that are compatible with survival beyond the periimplantation period. This class of unbalanced segregants represent in humans a major health problem to the mother and her conceptus.     

Springtail postmolt vulnerability to pseudoscorpion predation: Mechanisms and implications

Arthropod prey are expected to be more vulnerable to their predators immediately following molt. The effects of springtail (Isotoma carpenteri) postmolt vulnerability on interactions with a pseudoscorpion predator were examined in the laboratory. Springtails exposed to vials pretreated with pseudoscorpions (Apochthonius minimus) delayed molting compared to those prey that were exposed to vials pretreated only with springtails. Although their escape ability (measured as distance jumped) was unaffected by molt condition, postmolt springtails were more profitable in terms of reduced predator handling time following capture. Despite this,A. minimus did not distinguish between postmolt and intermolt prey presented at either end of a T-maze.     

Studies with Differentially Labeled [11C]Cocaine, [11C]Norcocaine, [11C]Benzoylecgonine,and [11C]-and 4′-[18F]Fluorococaine to Probe the Extent to Which [11C]Cocaine Metabolites Contribute to PET Images of the Baboon Brain

Abstract: The psychostimulant drug of abuse, cocaine (benzoylecgonine methyl ester), is rapidly metabolized by cleavage of its two ester groups, to give benzoylecgonine (BE) and ecgonine methyl ester, and by N-demethylation, to give N-norcocaine (NC). The recent use of [N-methyl-¹¹CH₃]cocaine to image brain cocaine binding sites with positron emission tomography (PET) raises the question of whether PET images partially reflect the distribution and kinetics of labeled cocaine metabolites. We prepared [O-metty/-¹¹CH₃]cocaine by methylation of the sodium salt of BE with [¹¹C]CH₃l, and showed that PET baboon brain scans, as well as regional brain kinetics and plasma time-activity curves corrected for the presence of labeled metabolites, are nearly identical to those seen with [N-methyl-¹¹CH₃]cocaine. This strongly suggests that ¹¹C metabolites do not significantly affect PET images, because the metabolite pattern is different for the two labeled forms of cocaine. In particular, nearly half the ¹¹C in blood plasma at 30 min was [¹¹C]CO₂ when [N-methy/-¹¹CH₃]cocaine was administered, whereas [¹¹C]CO₂ was not formed from [O-methy/-¹¹CH₃]cocaine. Only a trace of [¹¹C]NC was detected in plasma after [O-methyl-¹¹CH₃]cocaine administration. Nearly identical brain PET data were also obtained when 4′-[N-methy/-¹¹CH₃]fluorococaine and 4′-[¹⁸F]fluoro-cocaine (prepared by nucleophilic aromatic substitution from [¹⁸F]fluoride-and 4′-nitrococaine) were compared with [N-methy/-¹¹CH₃]cocaine. In vitro assays with rat brain membranes showed that cocaine and 4′-fluoroco-caine were equipotent at the dopamine reuptake site, but that 4′-fluorococaine was about 100 times more potent at the 5-hydroxytryptamine reuptake site. The studies with positron-emitting 4′-fluorococaines thus support the lack of significance of labeled metabolites or of binding to 5-hydroxytryptamine reuptake sites to PET images taken with [N-methy/-¹¹CH₃]cocaine. [¹¹C]NC prepared by O-methylation of norbenzoylecgonine gave PET images with preferential uptake in striatum, but slower clearance from all brain regions than [O-methy/-¹¹CH₃]cocaine. [¹¹C]BE prepared by N-methylation of norbenzoylecgonine did not show brain uptake.     

Identifying plant functional types using floristic data bases: Ecological correlates of plant range size

Abstract. In an effort to identify ‘plant functional types’, the islands floras of Great Britain and Kríti (Crete, Greece) were examined separately for ecological correlates of plant range size. Plant functional types (PFTs) were defined here as categories into which plants could be grouped on the basis of attributes that predict greater or lesser sensitivity to ecological variability. Plant range size indicates commonness of a species and was assumed to be a proxy for ‘ecological flexibility’, i.e. species of larger range sizes can better withstand environmental change and differences than species of smaller range sizes. Using evolutionary comparative methods that account for the effect of taxonomic relatedness, both floras were investigated for the effects on range size of woodiness vs. non-woodiness, trees vs. shrubs, trees vs. herbs and shrubs vs. herbs. The British flora was examined additionally for the effects of wind- vs. non-wind-pollination, self vs. animal pollination and animal vs. non-animal fruit dispersal on range size. Two analyses showed significant effects on range size: for British species, trees had larger ranges than shrubs, and wind- pollinated species had larger ranges than non-wind-pollinated species. It is suggested that the lack of a similar pattern for shrubs and trees in Kríti is because the lower water availability of Kríti imbues shrubs with an ecophysiological advantage not relevant in plants of Great Britain. That trees have larger range sizes than shrubs in Great Britain is ascribed to the greater importance of competition for light when other factors are not at issue. The greater range of wind-pollinated than non-windpollinated species in Great Britain is postulated to be because both mutualists must be capable of invading new areas. This may be termed a ‘cost of mutualism’. In terms of PFTs, the results indicate that ‘life-form’ is too broad a classification category by which to differentiate relative sensitivity to environmental variability in Great Britain, in that there were significant differences in range size of trees and shrubs, but not between either of the two categories and herbs, or between woody and non-woody plants. Although pollination type may predict relative sensitivity to variation in Great Britain, dispersal type will not. Finally, differences between Great Britain and Kríti in relative range size patterns suggests that plant functional types may be specific to a region or set of conditions.     

Distribution of vasoactive intestinal peptide-like immunoreactivity in the taste organs of teleost fish and frog

Summary Using immunohistochemistry, vasoactive intestinal peptide (VIP) was visualized in taste bud cells of the carp, Cyprinus carpio, and the European catfish, Silurus glanis, by means of light and electron microscopy. Intracellular membrane systems, presumably smooth endoplasmic reticulum, of light (sensory) cells, but not of dark (supporting) cells and basal cells, were densely labelled with antibody. In the frog (four species: Rana temporaria, R. ridibunda, R. arvalis, R. pipiens), taste bud cells did not label. However, the dense basal nerve fibre plexus, some subepithelial ganglionic cells, but no ascending intragemmal fibres, were immunoreactive. In fish, the results support evidence that VIP is involved in the modulation of taste transduction at the level of receptor cells. In the frog, an indirect, possibly vasodilatatory effect on taste perception may be considered.     

Capillary recruitment and transit time in the rat lung

Presson, Robert G., Jr., Thomas M. Todoran, Bracken J. DeWitt, Ivan F. McMurtry, and Wiltz W. Wagner, Jr.Capillary recruitment and transit time in the rat lung.J. Appl. Physiol. 83(2): 543-549, 1997.Increasing pulmonary blood flow and the associated rise incapillary perfusion pressure cause capillary recruitment. The resultingincrease in capillary volume limits the decrease in capillary transittime. We hypothesize that small species with relatively high restingmetabolic rates are more likely to utilize a larger fraction ofgas-exchange reserve at rest. Without reserve, we anticipate thatcapillary transit time will decrease rapidly as pulmonary blood flowrises. To test this hypothesis, we measured capillary recruitment andtransit time in isolated rat lungs. As flow increased, transit timedecreased, and capillaries were recruited. The decrease in transit timewas limited by an increase in the homogeneity of the transit time distribution and an increased capillary volume due, in part, to recruitment. The recruitable capillaries, however, were nearly completely perfused at flow rates and pressures that were less thanbasal for the intact animal. This suggests that a limited reserve ofrecruitable capillaries in the lungs of species with high restingmetabolic rates may contribute to their inability to raiseO₂ consumption manyfold abovebasal values.

     

The thermal biology of three southern African elephant-shrews

1. 1. The thermal characteristics of Petrodromus tetradactylus, Elephantulus intufi and E. brachyrhynchus were investigated and compared with other elephant-shrews that occur in the southern African subregion.

2. 2. E. intufi and E. brachyrhynchus appear to have lower than expected basal metabolic rates (1.1185 ± 0.1623 and 0.9649 ± 0.1638 ml O₂ g⁻¹ h⁻¹, respectively) and high, narrow thermoneutral zones, similar to other elephant-shrews investigated previously. In contrast P. tetradactylus has a basal metabolic rate (0.871 ± 0.027 ml O₂ g⁻¹ h⁻¹) close to expected for body mass, and a broad, low thermoneutral zone.

3. 3. The thermal biology of macroscelids is discussed in terms of their distribution, microhabitat and body size.

     

Reduction kinetics of the photo-oxidized chlorophyll a+II in the nanosecond range: Measurements of the absorption changes at 688 nm under repetitive flash excitation

The 688 nm absorption changes (ΔA₆₈₈), indicating the photochemical turnover of chlorophyll a_II (Chl a_II) have been investigated under repetitive laser flash excitation conditions in spinach chlorplasts. It was found that under steady state conditions about 50–60% of the photo-oxidized primary donor of Photosystem II (PS II), Chl a⁺_II, becomes re-reduced with a biphasic kinetics in the nanosecond time scale with half-life times of about 50 ns and 400 ns. The remaining Chl a⁺_II becomes re-reduced in the microsecond range.