Analysis of Dysgenesis-Induced Lethal Mutations on the X Chromosome of a Q Strain of DROSOPHILA MELANOGASTER

The Q strain known as v6 was tested for its ability to induce X-linked lethal mutations in male and female hybrids from crosses with M strains in the P-M system of hybrid dysgenesis. All measurements of the mutation rate were made on the X chromosome derived from the v6 strain. The lethal rate for young hybrid males from the cross M female X v6 male was 1.11% per chromosome. For older males, it was only 0.44%, suggesting that there is less mutational or more repair activity in the germ cells of the older males or that mutant cells are selectively eliminated as the hybrid males age. The lethal rate for hybrid females from comparable crosses was approximately the same for both ages that were tested. However, it was substantially less than the rate for the hybrid males--only 0.26% per chromosome. Genetically identical hybrid females from reciprocal crosses also showed a low mutation rate, 0.13% per chromosome. Again, there was no difference between young and old flies. Mapping experiments established that most of the lethal mutations that were recovered from the male and female hybrids were located in two regions on the X chromosome, one between bands 14B13 and 15A9 , the other between bands 19A1 and 20A , which encompasses the maroonlike locus. More refined mapping of the lethals in the maroonlike region demonstrated that the vast majority of these affected a single gene located in band 19C4 . Cytological analysis of the lethal chromosomes revealed that several carried rearrangements, including inversions, duplications and deficiencies. Chromosome breakage occurred primarily in bands 14D1 -3 and 18F- 20A , and most of the breaks in the latter segment were located in 19C . However, rearrangements involving 19C and mutations of the gene in 19C4 were mutually exclusive events. In situ hybridization of a P element probe to the chromosomes of v6 demonstrated that P elements reside at a minimum of five sites on the X chromosome. These P element sites correspond to the mutational and breakage hot spots on that chromosome. The combined genetic and cytological data imply that most of the X-linked lethal mutations that occur in M X v6 hybrids are due to local P element action. Consideration of these and other data suggest that v6 is a weak P strain in the P-M system of hybrid dysgenesis and that other Q strains might also be regarded in this way.     

Size and organization of a multigene family encoding phaseolin, the major seed storage protein of Phaseolus vulgaris L.

Summary Solution hybridization kinetics and genomic nitrocellulose blot hybridization analyses show that the Phaseolus vulgaris L. (French bean) storage proteins (phaseolins) are encoded as a small, homologous, multigene family consisting of approximately seven members. Restriction endonuclease site mapping (EcoRI, BamHI, and BglII) of DNA regions flanking the phaseolin genes has shown that the gene family can be divided into at least three characteristic fragment size classes. Clones representative of two of these phaseolin gene classes have been isolated from a 1059 phage library.     

The effect of nematode parasitism on the osmolality and major cation concentration in the haemolymph of three larval mosquito species

Parasitism by a mermithid nematode, Romanomermis culicivorax, causes severe depletion of haemolymph carbohydrates and proteins in mosquito larvae. We undertook a study to determine if haemolymph osmolality and cation concentrations were affected also by mermithid parasitism. The haemolymph osmolality of R. culicivorax-infected and control Aedes taeniorhynchus and Culex pipiens fourth-instar larvae was not significantly different. However, the haemolymph osmolality decreased significantly in infected Anopheles quadrimaculatus. Each mosquito species demonstrated significant alterations in the haemolymph concentration of at least one cation when infected although the cation concentrations affected differed for each species. The changes observed were statistically significant but the magnitude of change was not great. Overall, despite the severe nutritional burden of the mermithid nematode, these species of mosquito larvae can continue to maintain osmoregulation.     

Tyrosine availability prevents tyramine-induced tachyphylaxis in the isolated rat heart

Isolated rat hearts perfused with Chenoweth-Koelle solution exhibit tachyphylaxis to tyramine. This tachyphylaxis was prevented if tyrosine was included in the perfusion solution. Other amino acids, including glycine, serine, phenylalanine, valine, tryptophan, glutamate, aspartate, arginine, lysine and -tyrosine, failed to prevent the tyramine-induced tachyphylaxis. Hearts from reserpinized animals showed increased chronotropy after tyramine only when tyrosine was present in the medium. This response could be blocked by , m-hydroxybenzyl-hydrazine and d,l-propanolol, indicating that it was mediated by the synthesis and release of catecholamines. These experiments suggest that sympathetic nerves in the isolated rat heart exhibit a requirement for tyrosine when catecholamine release is enhanced.     

The kinetics of abscisic acid action on root growth and gravitropism

Using an auxanometer and time-lapse cinematography we have studied the timing of abscisic acid (ABA) effects on elongation, gravitropic curvature, and hydrogen-ion efflux in several cultivars of maize (Zea mays L.). The effect of high concentrations (e.g. 0.1 mM) of ABA on root elongation is triphasic, including 1) a period of promotion lasting approximately 12 h, 2) a subsequent period of increasing inhibition lasting approximately 12h, and 3) gradual recovery to a rate within approximately 80% of the control rate. With lower concentrations of ABA (e.g. 0.1 μM) only the transient promotive phase is seen. Abscisic acid enhances ethylene biosynthesis in roots of maize but suppression of ethylene biosynthesis does not prevent the long-term inhibitory action of ABA on growth. Application of ABA (0.1 mM) to the upper surface of horizontally placed roots accelerates positive gravitropism. Application of ABA to the lower surface retards gravitropism and in some cases causes the roots to curve upward against the direction of gravity. These observations are consistent with our finding that the initial effect of ABA on root elongation is stimulatory. Since root gravitropism is rapid enough to be completed within the stimulatory phase of ABA action, the data argue against hypotheses of gravitropism based upon accumulation of ABA to inhibitory levels on the lower side of a hirizontal root.     

Purification and properties of xylanase fromAureobasidium

Summary The yeast-like fungusAureobasidium is a promising source of xylanase (EC 3.2.1.8) with an exceptionally high specific activity. For enzyme production in volumes of several liters, xylose was the preferred carbon source and inducer. Xylanase in clarified cultures was concentrated by reversible adsorption to cation-exchange matrix to 5% of the initial volume, and recovered at nearly 2 million IU/1. Selective conditions permitted 97% recovery of xylanase with a 1.8-fold enrichment in specific activity, to 70% of purity. The predominant xylanase species (20 kDa) was subsequently purified to >99% of homogeneity by gel filtration chromatography. Purified enzyme exhibited an isoelectric point of 8.5, and specific activity of 2100 IU/mg under optimal conditions, determined to be pH 4.5 and 45°C. The activity of purified enzyme was specific for polymeric xylan.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Dept. of Agirculture over other firms or similar products not mentioned.     

Specification methods for material-handling control algorithms in flexible manufacturing systems

Good methods are needed to specify, test, and debug material-handling control logic. This article surveys a number of representative methods for defining and describing control algorithms for programmable material-handling equipment used in flexible manufacturing systems. The methods are evaluated with regard to their suitability for communication between people and as bases for interfaces to automatic program generators. It is concluded that no single method is entirely satisfactory. Three methods (position diagrams, function block diagrams, and operation networks) have potential to be combined into an effective hybrid approach that minimizes the need for the user to switch between various conceptual models.     

The reproductive biology of female Père David's deer (Elaphurus davidianus)

Data for this study came from breeding records of 27 Père David's (Elaphurus davidianus) hinds maintained in large pastures and from estrous records of four hand-reared nulliparous hinds. The mean estrous cycle length ranged from 17.5 to 19.6 days. Standing estrus resembled that of other cervids, except that a low, moaning vocalization was given in response to contact, and activity (as measured by pedometers) did not increase. Mean gestation length was 183.38 ± SD 6.11 days (n = 21), and nearly all females conceived in the second and third years. The median interbirth interval was 362 days. The median birth date was April 8, and 80% of the births occurred over a 9.5-week period. Multiparous hinds gave birth an average of 20.5 days earlier in the season than primiparous hinds. There was no dimorphism in birth weight. The results are discussed in light of comparative data for other species.     

Carbon metabolism in Bradyrhizobium japonicum bacteroids

Abstract Carbon metabolism in Bradyrhizobium japonicum bacteroids is reviewed. Additionally, the bacteroid tricarboxylic acid (TCA) cycle and its regulation under oxygen-limited conditions is considered, with emphasis on possible sites of TCA cycle rate-limiting reactions. Furthermore, we consider other adaptive pathways that may be employed by these organisms while in symbiosis. These pathways include: (1) a poly-β-hydroxy-butyrate shunt, (2) a malate-aspartate shuttle, (3) an α-ketoglutarate-glutamate shunt, (4) a modified dicarboxylic acid cycle, and (5) fermentation pathways leading to lactate, acetaldehyde and ethanol. The effects of oxygen limitation on host carbon metabolism are also considered briefly.     

Sexual differentiation,gonad development,and spawning seasonality of the Hawaiian butterflyfish,Chaetodon multicinctus

Synopsis The reproductive biology of the coral reef butterflyfish,Chaetodon multicinctus, was investigated by histological examination of gonads sampled over an 18 month period from a shallow inshore population on Oahu, Hawaii. Most gonads developed directly from previously undifferentiated tissue. Ovarian development (the structural formation of lamellae and primary oocytes) was observed in fish ≥44 mm and testicular development (the formation of spermatogenic crypts) in fish ≥62 mm standard length (SL). In addition, testis formation was identified within the ovarian lamellae of several differentiated but immature fish. It is hypothesized that prematurational sex change may facilitate monogamy within the highly competitive social structure of this site attached species. Oocyte development in mature females was marked by distinct phases of primary growth, the formation of yolk vesicles, and vitellogenesis. Spawning activity was histologically identified by the maturation and hydration of fully yolked oocytes, and presence of postovulatory follicles. Recently spawned females from field collections and experimental gonadotropin-treatments exhibited postovulatory follicles that were estimated to persist at least 24 h after ovulation. Atresia of yolked oocytes was classified into four stages of cell degeneration and resorption. Monthly analyses of oocyte development and atresia within the sample population show thatC. multicinctus has a protracted annual spawning season with a major peak during the early spring and evidence of spawning activity among some individuals in the fall. Histological analyses of spawning activity provide more accurate and unambiguous information than do traditional gonadosomatic assays in this and probably other coral reef fishes.