Characterization of Mouse Pmel 17 Gene and Silver Locus

Pmel 17 cDNA clones, isolated from wild-type and si/si murine melanocytes, were sequenced and compared. A single nucleotide (A) insertion was found in the putative cytoplasmic tail of the si/si Pmel 17 cDNA clone. This insertion is predicted to alter the last 24 amino acids at the C-terminus and to extend the Pmel 17 protein by 12 residues. The mutation was confirmed by the sequence of the PCR-amplified genomic region including the mutation site. Silver Pmel 17 was not recognized by antibodies directed toward the C-terminal amino acids of wild-type Pmel 17, indicating a defect in this region. These results indicate that silver Pmel 17 protein has a major defect at the carboxyl terminus.     

The brain of Echiniscus viridissimus Peterfi, 1956 (Heterotardigrada): a key to understanding the phylogenetic position of tardigrades and the evolution of the arthropod head

The brain of Echiniscus viridissimus , Peterfi, 1956 is composed of a series of orthogonally arranged neuropils. The most anterior neuropils are rireumbuccal, positioned dorso-and ventrolateral to the buccal tube and are associated with ganglia for sensory receptors of the mouth cone. Posterior to these are neuropils and ganglia for the (1) internal cirri and (2) cephalic papillae, external cirri, cirri A and clavae. They are joined by two pairs of vertical tracts to neuropils lateral to the buccal tube. A model based on the postcephalic organization of the tardigrade nervous system is used to propose a transformation of segmental ganglia that gives an arrangement congruent with the pattern of neuropils in the brain. The analysis suggests that the brain is derived from nervous elements of four segments with the fourth segment having contributed paired dorsal ganglia and their connecting vertical tracts to the first trunk ganglia of the ventral chain. The organization of the head of tardigrades is compared with that of other lobopods and arthropods and several possible key evolutionary innovations are offered. In addition homologous characters for the heads of tardigrades and other lobopods and arthropods are proposed and the nomenclature for the tardigrade cephalic nervous system is discussed.     

Cytotaxonomic observations in tropical Vaccinieae (Ericaceae)

Chromosome numbers are reported for 36 accessions representing 31 species from nine genera of the tribe Vaccinieae, family Ericaceae. The plants are tropical and come from Southeast Asia and Central and South America. The taxonomy of the tribe is outlined in these regions. Genera are often poorly defined and taxa were chosen to reflect the range of variation of the Vaccinieae. Most Southeast Asian Vaccinium species were diploid (2n= 24) as were those of Agapetes subgenus Agapetes (apart from the Himalayan A. flava), Agapetes scortechinii and Costera endertii. All other accessions were found to be polyploid. The correlation between polyploidy, geographical distribution and the possession of an ‘anatomical complex’ of the leaf and stem in Vaccinieae of New Guinea and the neotropics is discussed.     

A comparison of spike and spikelet survival in mainstem and tillers of barley

Initiation and abortion of spikelet primordia on primary tillers and mainstem were compared for plants of spring barley, Maris Mink, sown on two sowing dates during 1983, in plots at the Scottish Crop Research Institute (SCRI) and at Long Ashton Research Station (LARS). Sowing date had no effect on the number of spikelets initiated on either mainstem or surviving tillers and many more spikelets were initiated on equivalent stems at LARS than at SCRI but more spikelets aborted at the former site. The final number of spikelets produced was eventually similar. Spikelet abortion was complete by anthesis and coincided with the period of rapid stem and rachis elongation and with the time over which tiller death occurred. Despite the fact that plants at SCRI produced fewer fertile tillers they outyielded those at LARS because much heavier grains were produced on the mainstem and tiller 1 of plants at the Scottish site. An interval of 2 wk between sowing had only small effects on the components of yield.     

Suppression of Stomatal Opening in Leaves Treated with Abscisic Acid

Small doses of abscisic acid (approximately 0.02 µg cm^-2of leaf) applied to the leaf surface as a 10^-4 M solution causedmarked stomatal closure in Xanthium pennsylvanicum, and theeffect persisted for up to 9 days after application. Similareffects were found when 10^-4 M abscisic acid was supplied todetached tobacco leaves via their petioles. CO²-free air didnot cause a reversal of the closure, and it was therefore concludedthat the effect was not due simply to an increase in the intercellularCO²concentration; a more direct effect on the stomatal apparatusis suggested. It is considered that abscisic acid could playan endogenous role in the control of stomatal aperture, andthat this, and/or related substances, might be more useful as‘anti-transpirants’ than the phytotoxic substancescurrently employed for this purpose.     

Sporozoites of Rodent and Simian Malaria, Purified by Anion Exchangers, Retain their Immunogenicity and Infectivity

SYNOPSIS. Sporozoites of rodent malaria, Plasmodium berghei , and simian malaria, Plasmodium knowlesi and Plasmodium cynomolgi , were partially separated from mosquito debris and microbial contaminants by passage of Anopheles material through a DEAE-cellulcse column. In addition to eliminating most of the contaminants (80–90%), this simple technic has made it possible to recover rapidly large numbers of viable sporozoites (55–75% yield), which have retained their infectivity, immunogenicity, and capacity to react with known antisera. Mice injected with varying doses of column-purified sporozoites (CS) of P. berghei produced infections which paralleled those seen in the controls. Total protection against challenge with a potentially lethal dose of viable sporozoites was acquired by mice inoculated twice with irradiated CS of P. berghei. CS of P. berghei and P. cynomolgi gave positive circumsporozoite precipitation (CSP) reactions, upon inoculation with the respective immune sera. The preservation of the surface antigens of CS was documented by immunofluorescence.
It was shown that differences in elution behavior exist among sporozoites of certain species of Plasmodium as well as among sporozoites of the same species derived from different organs of the mosquito. These results may be attributed to differences in the surface charge of the sporozoites or conditions in sample media.
Purified sporozoites obtained by the method described in this report provide an adequate source of parasites for a variety of in vitro studies.     

THE FUNGICIDAL CONTROL OF LETTUCE DOWNY MILDEW, CAUSED BY BREMIA LACTUCAE

Protection experiments carried out in the greenhouse showed that preparations of thiram, zineb, ferbam and ziram were superior to cuprous oxide and copper oxy-chloride preparations, in controlling downy mildew of lettuce and in lack of phytotoxic effect.
Tests made in winter on lettuce seedlings grown in Dutch lights, showed that Bremia lactucae attack reduced the stand of seedlings, diminished their size and weight, and, when the crop was planted out into the open ground, reduced survival in the field and slightly delayed the date of reaching maturity. The best overall results in protecting foliage against downy mildew were given by thiram and zineb preparations.     

Nerium oleander as an alternative host plant for south Florida milkweed bugs, Oncopeltus fasciatus

Abstract.

• 1 Life history data were gathered for south Florida Oncopeltus fasciatus reared from eggs on Nerium oleander seeds and milkweed seeds in the laboratory.
• 2 Milkweed seeds were found to be a superior food source since O.fasciatus grew faster, laid more clutches, and has a higher total fecundity on milkweed seeds.
• 3 Fruiting N.oleander was found to be a better food source than nonfruiting milkweeds in a summer field study in south Florida since no nymphs survived to the adult stage on nonfruiting milkweeds but some did on N.oleander.
• 4 O.fasciatus adults and nymphs are abundant on N.oleander in the summer in south Florida when N.oleander is fruiting; no O.fasciatus nymphs are found in the summer on the milkweeds which are not fruiting.
• 5 O.fasciatus leave N.oleander in the autumn when milkweeds start to fruit and can then be found on fruiting milkweeds.