Oral Ultrastructure and Oral Development of the Misaligned Undulating Membrane Mutant of Tetrahymena thermophila1

The misaligned undulating membrane (mum) mutant of Tetrahymena thermophila is a non-conditional, single gene recessive mutation. The major effect of the mum mutation is the production of multiple undulating membrane (UM) fragments in the oral apparatus (OA). The ultrastructure of the UM fragments of mum OAs is identical to that of the single UM of wild-type OAs. Analysis of OA development at midbody using a combination of light microscopy of protargol-stained cells and SEM of demembranated whole cells showed that the phenotypic effect of the mum mutation first becomes evident during mid to late stage 4 and is fully manifested in early stage 5. The effect of the mutation involves a proliferation of excess basal bodies in the UM field. Subsequent events in the development of the mum OA from mid to late stage 5 are identical to those in wild-type OAs. This study suggests that the mum mutation establishes conditions that allow the production of multiple UMs and thus reveals that the UM field is competent for the complete and coordinated development of several adjacent UMs. This level of regional control is not clearly evident when a single UM is present. The comparison of development of wild-type and mum OAs required an extensive reanalysis of stages 4 and 5 of normal oral development. On the basis of current and previous observations, we propose a new and more subdivided staging system for oral development in Tetrahymena.     

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.     

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.