Comparative Physiology of the Vasomotor Effects of Neurohypophysial Peptides in the Vertebrates

The neurohypophysial peptides are vasopressor or depressor inaction depending on the species. Isotocin, mesotocin and oxytocinconstrict the branchial vessels in fish and induce a reflexvasodilation in the systemic vasculature. The vasodilation haspersisted in some higher vertebrates and is particularly prominentin the snakes and birds where vasotocin and arginine vasopressinalso are vasodepressor but are much less potent than mesotocinand oxytocin. In other vertebrates including fish, vasotocinand vasopressin are pressor and exert their effects mainly onthe peripheral resistance. The newt, toads and soft-shell turtlegave pressor responses to all neurohypophysial peptides, withvasotocin showing the highest potency. The frogs, big-headedturtle and lizards were intermediate with vasotocin being pressor,mesotocin being pressor and oxytocin exhibiting a dual effect.     

Crystalline Ferredoxin from a Blue-Green Alga, Nostoc sp.

Ferredoxin isolated from a blue-green alga, Nostoc sp., was purified and crystallized. The absorption spectrum of Nostoc ferredoxin had, in the oxidized state, peaks at 276, 331, 423, and 470 nm, a pattern characteristic of chloroplast-type ferredoxin. The 423:276 absorption ratio was 0.57. The midpoint oxidation-reduction potential of Nostoc ferredoxin was found to be –406 mV, at pH 7.5. Nostoc ferredoxin mediated the photoreduction of NADP by isolated Nostoc chromato-phores and spinach chloroplasts from which the native ferredoxin was removed. The molar ratio of Nostoc ferredoxin to chlorophyll a was about 1:50, a ratio higher than usually found in photosynthetic cells. The possible evolutionary significance of the properties of Nostoc ferredoxin compared with those of ferredoxins from other photosynthetic organisms is discussed.     

Histochemical Localization of Citral Accumulation in Lemongrass Leaves (Cymbopogon citratus(DC.) Stapf., Poaceae)

Lemongrasses (Cymbopogonspp., Poaceae) are a group of commerciallyimportant C₄tropical grasses. Their leaves contain up to 1.5%(d.wt) essential oils with a typical lemon-like aroma, consistingmainly of citral (a mixture of the isomeric acyclic monoterpenealdehydes geranial and neral). To specifically locate the sitesof citral accumulation in lemongrass we employed Schiff's reagent,which reacts with aldehydes and gives a purple-red colorationwith citral. Using this technique, single oil-accumulating cellswere detected in the adaxial side of leaf mesophyll, commonlyadjacent to non-photosynthetic tissue, and between vascularbundles. Cell walls of these oil cells are lignified. Our resultssuggest that citral accumulation takes place in individual oilcells within the leaf tissues.Copyright 1998 Annals of BotanyCompany Lemongrass;Cymbopogon citratus; Poaceae; oil cells; histochemistry; citral; aldehydes; Schiff's-reagent.     

Dioecy and wind pollination in Pernettya rigida (Ericaceae) of the Juan Fernández Islands

Pernetttya rigida is endemic to the Juan Fernández archipelago. Although all flowers are complete, with seemingly fertile stamens and pistils, differences in fruit production and detailed field, anatomical, and morphological studies indicate they are functionally unisexual, and the species is consequently dioecious. A comparison of 15 features demonstrated sigdicant differences between the sexes. The populational sex ratio is 1:1. Nectaries located between the filaments produce small amounts of floral nectar with similar sugar composition in both sexes. There are =33,357 (or = 133,429) pollen tetrads (or pollen grains)/male flower and =109 ovules/female flower. No tetrads in either hand self-pollinated or open pollinated male flowers showed any pollen germination. Tetrads on open- and hand-pollinated female flowers germinate. Female flowers do not show autogamy or apomixis. During more than 80 hours of field observation, we recorded only seven floral visitors (representing three insect species). In spite of this, openpollinated female flowers have abundant fruit and seed-set. Thus, we conclude that pollen is transferred abiotically and the ever-present wind over the exposed ridges of the islands is the likely dispersal agent. A number of anemophilous features, such as dry pollen and exposed habitat, support this conclusion. Thus, dioecy and anemophily have evolved independently, in situ , in this species in this remote locality. Preservation of habitat and elimination of competitive invasives are the primary conservation challenges.     

A self-medicating applicator for control of ticks on deer

Abstract. A self-medicating applicator for killing ticks on deer and domestic ungulates by passive transfer of acaricides during feeding is described. The applicator consists of a barrel divided into a food bin (above) and a sealed self-contained acaricide reservoir (below) with a vertical, centrally-located ceramic column that extends from the reservoir into the food bin. Acaricide is drawn up the column from the sealed reservoir by absorption. Animals attracted to the food in the device acquire the acaricide during feeding when they contact the uppermost portion of the column.
White-tailed deer (Odocoileus virginianus) readily utilize the applicator in penned and natural conditions. In a field study, examination of hunter-killed deer demonstrated that animals from a treated site were infested with many fewer Ixodes scapularis (3.4 ± 1.1) than those from a control site (10.8 ± 3.0). Chromatographic analysis of hair samples revealed traces of permethrin on three of the four animals examined, suggesting use of applicators by these deer. In a study using penned goats {Capra hircus) infested with Amblyomma americanum ticks, treatment efficacy reached 86.4% within 4 days of exposure to the applicators. Visual observations confirmed that all animals used the applicators. Gas chromatographic analysis of goat hair samples indicated that permethrin was detectable on all of the treated animals exposed to the device.     

Mouthparts, antennae and genitalia of intersex Culicoides stellifer parasitized by mermithid nematodes

Abstract A 12-month study of Culicoides in Bulloch County, Georgia, U.S.A., revealed that twelve of 23 ,859 specimens (0.05%) of C.stellifer were intersexes as a result of being parasitized by mermithid nematodes. Of these, eleven had male genitalia and female type antennae and one had female genitalia with male type antennae.     

Naegleria Actin Elicits Species-Specific Antibodies1

ABSTRACT. Actin, the major protein of amebae of Naegleria gruberi, proved to be strongly immunogenic in rabbits. The resulting precipitating antibodies are specific to actin of Naegleria. In a competitive solid-phase radioimmunoassay, these antibodies bound similarly to Naegleria G- and F-actin. Actins from amebae of Acanthamoeba and Dictyostelium, plasmodia of Physarum, sea urchin eggs, and vertebrate muscles gave no competition in the radioimmunoassay. Estimates of the amount of actin in Naegleria amebae ranged from a minimum of 5% of the total cell protein by radioimmunoassay to a maximum of 16% by electrophoresis. The unusual species specificity of these antibodies indicates that Naegleria actin, although conserved in many properties, is different enough to have unique antigenic determinants.     

The Prothoracicotropes: Source of the Prothoracicotropic Hormone

SYNOPSIS. An in vitro assay for the insect prothoracicolropichormone (PTTH) has been developed which measures the rate ofecdysone synthesized by Manduca sexta prothoracic glands (PG)stimulated in vitro by PTTH. This assay has been used to quantifyPTTH in single neurosecretory cells (NSC) resulting in the identificationof one NSC in each hemisphere of the brain as the prothoracicotrope,source of PTTH. The axonal and dendritic distribution of theprothoracicotrope has been determined by cobalt filling withsilver intensification. From a comparison of the titers of PTTHin brains, corpora cardiaca and corpora allata during larval-pupaldevelopment, the corpus allatum has been identifiedas the neurohemalorgan for PTTH. Electron microscopic analyses suggest that theacellular sheath surrounding the corpus allatum contains theaxon terminals of the prothoracicotropes. There is at least one form of PTTH, {small tilde}22,000 molwt (big PTTH), and possibly a smaller form of about 7,000 molwt (small PTTH). Bioassay and PTTH hemolymph titer data duringthe head critical period (HCP) for larval-larval developmentreveal that big PTTH is released as a single peak lasting {smalltilde}6 hr. By contrast, during the first HCP of the last larvalinstar PTTH is released over a period of {small tilde}18 hrin three bursts, but its molecular weight has not been establishedwith certainty. The kinetics of PG activation by these two formssuggest that big PTTH may function to activate the PG dramaticallyand thereby elicit molting, while small PTTH may activate thePG minimally at the time of cellular reprogramming.     

Nutation of growing and georsacting roots

Abstract. Growth and geocurvature of the primary roots of maize (cv. LG 11) were analyzed by a filming technique allowing continuous recording, root by root. Typical nutations, in vertical growth and following the downward curvature of the roots, have been observed. The possible relations between these nutations, the elongation, the georeaction and the hormonal mechanisms which control georeaction, are discussed.