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.     

Cryopreservation of immature spring wheat zygotic embryos using an abscisic acid pretreatment

Spring wheat (Triticum aestivum L.) zygotic embryos were successfully cryopreserved, without the addition of exogenous cryoprotectants, using only an abscisic acid (ABA) pretreatment. Optimum survival was obtained when embryos were cultured in vitro for 10 days on semisolid Murashige and Skoog (MS) nutrient medium supplemented with 0.5 mg/L (±) ABA prior to cryopreservation. The embryos resumed growth within three days when returned to MS medium devoid of ABA but containing 2mg/L 2,4-dichlorophenoxyacetic acid. The embryogenic calli produced from these embryos exhibited normal plant regeneration on auxin-free media. Changes in dw/fw ratio, as well as the esterified fatty acid and sucrose concentrations correlated positively with the development of tolerance to cryopreservation.NRCC Publication No. 33519     

Degradation of (+/-)-synephrine by Arthrobacter synephrinum. Oxidation of 3,4-dihydroxyphenylacetate to 2-hydroxy-5-carboxymethyl-muconate semialdehyde.

1. Cell-free extracts of Arthrobacter synephrinum catalyse the oxidation of 3,4-dihydroxy-phenylacetate. 2. The product of oxidation was characterized as 2-hydroxy-5-carboxymethylmuconate semialdehyde from its chemical behaviour as well as from nuclear-magnetic-resonance spectra. 3. A 3,4-dihydroxyphenylacetate 2,3-dioxygenase (EC 1.13.11.15) was partially purified from A. synephrinum. 4. The enzyme had a Km of 25 micrometer towards its substrate and exhibited typical Michaelis-Menten kinetics. 5. The enzyme also catalysed the oxidation of 3,4-dihydroxymandelate and 3,4-dihydroxyphenylpropionate, at reaction rates of 0.5 and 0.04 respectively of that for 3,4-dihydroxyphenylacetate. 6. The enzyme was sensitive to treatment with thiol-specific reagents. 7. The molecular weight of the enzyme as determined by Sephadex G-200 chromatography was approx. 282000.     

Melphalan, a second chemical for which specific-locus mutation induction in the mouse is maximum in early spermatids.

Melphalan (MLP), a bifunctional alkylating agent structurally related to the highly mutagenic chemical chlorambucil (CHL), was found to induce high frequencies of specific-locus mutations in postspermatogonial germ cells of the mouse, and to be one of only a few chemicals that is also mutagenic in spermatogonial stem cells. Productivity patterns following MLP exposures resembled those that had been found for CHL. Mutation rates in successive male germ-cell stages were measured at three MLP-exposure levels in a total of 95,375 offspring. While the induced (experimental minus historical-control) mutation rate is relatively low in stem-cell spermatogonia (1.2 x 10(-5) per locus at a weighted-mean exposure of 7.3 mg/kg), it is about 5 times higher in poststem-cell stages overall, and peaks at 26.7 x 10(-5) per locus in early spermatids at a weighted-mean exposure of only 5.7 mg/kg. This "type-2 pattern" of mutation yield (Russell et al., 1990), i.e., peak sensitivity in early spermatids, has heretofore been found for only one other chemical, CHL. Mutation-rate data earlier reported for CHL (Russell et al., 1989) were augmented in the present study for comparison with MLP-induced rates. Because of the greater toxicity of MLP, average exposures used for this chemical were only about one-half of those for CHL. When MLP and CHL mutation rates are extrapolated to equimolar doses, they appear very similar for poststem-cell stages overall. However, in the case of CHL, a somewhat higher proportion of the mutations is induced in early spermatids than in the case of MLP.     

Marine macroalgae as foods for fishes: an evaluation of potential food quality

Synopsis A revitalized view of feeding by herbivorous marine fishes is sought through two questions. First, What characteristics of major taxa of algae identify them as predictably high or low quality foods? Second, are marine algae valuable foods for fishes which do not mechanically disrupt cell walls and do not harbor specialized enzymes or microbes capable of lysing cell walls? Energy, ash and nutrient content of 16 species of marine algae were employed to assess food quality of fleshy red, green, brown and calcareous red algae. On the basis of ash, calories, total protein and total lipid content, fleshy algae should be superior to calcareous algae as foods for fishes; in addition, green algae should be superior to brown algae and brown algae superior to red algae. When the probable digestibility of storage and extracellular carbohydrates is considered, green and red algae are predicted superior to brown algae as food. Two species of damselfishes (Pomacentridae) from the Gulf of California,Eupomacentrus rectifraenum andMicrospathodon dorsalis, eat red and green algae and ignore brown and calcareous algae. They feed, therefore, in a fashion consistent with predictions based only on algal chemistry. These fishes absorb at least 20–24% of the biomass, 57–67% of the protein, 46–56% of the lipid and 37–44% of the carbohydrate contained in algae eaten in the wild. Since these damselfishes do not masticate their food, it appears that herbivorous fishes can digest major fractions of algal nutrients without mechanical destruction of algal cells.     

Direct fermentation of cellodextrins to ethanol byCandida wickerhamii andC. Lusitaniae

Summary Production of ethanol from cellodextrins, as large as cellohexose, byCandida lusitaniae andC. wickerhamii was studied.C. lusitaniae fermented only glucose and cellobiose, whereasC. wickerhamii efficiently fermented cellodextrins. Maximum ethanol yields of 29.2 g/liter from 54 g/liter cellodextrins were achieved byC. wickerhamii in 3–4 days.     

Population dynamics of daphnia pulex and utilization by the rainbow trout (salmo gairdneri)

The effect of rainbow trout (Salmo gairdneri) predation on the population dynamics of the water flea,Daphnia pulex, was examined during 1976 and 1977 in Becker Lake, a small, shallow, productive reservoir in northeastern Arizona.Rainbow trout were size-biased feeders, utilizing daphnids which were 1.3 mm in size or larger. Trout predation uponDaphnia pulex occurred mainly during winter and early spring when their numbers were relatively low but their clutch size high, suggesting that trout selectedDaphnia on the basis of brood pigmentation. By far the greatest proportion ofDaphnia mortality was due to nonpredatory sources, since generally less than 6% could be attributed to trout predation.TheD. pulex population exhibited a bimodal seasonal abundance curve which was attributed to ephippial egg production and trout predation during the winter and poor food quality/quantity during the summer.This work was supported in part by the Arizona Department of Game and Fish. The authors wish to thank Jim Novy and Joe Stone of that department for their invaluable assistance in the field collecting segment of this study.