Dermal Chromatophoies

SYNOPSIS The pigmentation of poikilotherms is based upon thepresence of deimal chiomatophoies melanophores, lndophores,and xanthophores The form function, and composition of eachchromatophore type is discussed, and variations n melano somecomposition are described Recent theories about the mechanismof melanosome movement are discussed The role of mdophores inpigmentation processes is described and their impoitance instructural coloration is evaluated Interrelationships of thepigmentary organelles of all three chromatophores are discussed,and evidence is piesented that they have a common origin Associationsof pigment cells with themselves or with other elements of theintegument are described as i basis for chromatophore function     

Absence of spirochaetes (Borrelia burgdorferi) and piroplasms (Babesia microti) in deer ticks (Ixodes dammini) parasitized by chalcid wasps (Hunterellus hookeri)

An entomophagous wasp (Hunterellus hookeri Howard) parasitizes about a third of the host-seeking nymphal Ixodes dammini Spielman et al. ticks on Naushon Island in Massachusetts (U.S.A.) where the agents of Lyme disease (Borrelia burgdorferi Johnson et al.) and human babesiosis (Babesia microti Franca) are enzootic. Following blood-feeding, wasp-parasitized ticks are destroyed by the developing wasp. The prevalence of either human pathogen in host-seeking ticks collected in wasp-infested sites is nearly 40% lower than that found in other sites. Nymphal ticks, collected early in their season of activity, are more frequently parasitized by the wasp and less frequently by the Lyme disease spirochaete than those collected later in the summer. Spirochaetes never infected wasp-infected ticks, and few wasp-infected ticks were concurrently infected by the Babesia piroplasm. Taken together, these correlations indicate that the wasp may render the tick inhospitable to both pathogens. The presence of the wasp may have reduced risk of human infection on the island by either pathogen by as much as a third.     

Plasma Equine γ-Globulin in Tolerant Adult Dogs given Anti-lymphocyte Globulin

THIS report describes a positive correlation between sequential serum concentrations of EγG and the dosage schedule of equine anti-dog-lymphocyte globulin (EADLG) in dogs in which tolerance was induced by pretreatment with ultra-centrifuged EγG (tolerogen). This was in marked contrast to results in dogs which were not pretreated with tolerogen.     

Mechanism of Zinc Absorption by Intact Bean Plants

The time course of absorption of ⁶²Zn and ³²P by roots of intactbean plants (Phaseolus vulgaris L.), and the effects of azideand amytal have been studied. The evidence indicates that zincuptake occurs mainly by a non-metabolic process.     

Aeromonas hydrophila: Ecology and Toxigenicity of Isolates from an Estuary

A microbiological survey of Aeromonas hydrophila in Chesapeake Bay and its tributaries showed that this species is ubiquitous, occurring in numbers ranging from <0.3/l to 5 × 10³/ml in the water column and ca. 4.6 × 10²/g in sediment. It was recovered from water samples collected at several locations in Chesapeake Bay representing various salinity regimes, but the numbers of A. hydrophila in higher salinity water, i.e. 15^O/OO, were low. Results of stepwise multiple linear regression analysis showed that concentrations of A. hydrophila were correlated with total, aerobic, viable, heterotrophic, bacterial counts, and, in addition, were inversely related to salinity and to concentration of dissolved oxygen. Seasonal occurrence was recorded, with fewer strains of A. hydrophila encountered during the winter months. The potential pathogenicity of A. hydrophila strains isolated from Chesapeake Bay was estimated by testing selected isolates for toxigenicity, using the Y-1 adrenal cell assay. Of 116 isolates tested, 83 (71%) produced a cytotoxic response, a characteristic found to be correlated with the lysine decarboxylase and Voges-Proskauer reactions. Eight of 11 strains tested, which elicited fluid accumulation in the rabbit ligated ileal loop assay, also provoked a cytotoxic reaction in the Y-l adrenal cell assay. Results of the study indicate that large numbers of toxigenic A. hydrophila can be found in an estuary and such strains may be pathogenic for man and/or animals.     

Nutrient Cycling in a New South Wales Subtropical Rainforest: Organic Matter and Phosphorus

Biomass and phosphorus distribution and accumulation rates wereestimated for an undisturbed subtropical rainforest in northernNew South Wales. The accumulation rates were estimated overa 16-year period. It is estimated that the steady-state above-groundbiomass for this forest is 35.0 tonne ha^–1. Most of theannual biomass production was replacing litterfall and mortality.The above-ground forest contained 52 kg P ha^–1 with agross annual accumulation of about 0.4 kg P ha^–1/yr^–1.The forest understorey and forest floor contained 4.7 kg P ha^–1and 7.9 kg P ha^–1, respectively. The annual uptake wasapprox. 4 kg P ha^–1 yr^–1. The phosphorus utilizationof this stand was compared with that of a Eucalyptus grandisplantation Sub-tropical rainforest, biomass accumulation, phosphorus cycling     

Control of Melanoblast Differentiation in Amphibia by α-Melanocyte Stimulating Hormone,a Serum Melanization Factor,and a Melanization Inhibiting Factor

A ventrally localized melanization inhibiting factor (MIF) has been suggested to play an important role in the establishment of the dorsal-ventral pigment pattern in Xenopus laevis [Fukuzawa and Ide: Dev. Biol., 129:25–36, 1988]. To examine the possibility that melanoblast expression might be controlled by local putative MIF and melanogenic factors, the effects of α-melanocyte stimulating hormone (α-MSH), a serum melanization factor (SMF) from X. laevis or Rana pipiens, and MIF on the “outgrowth” and “melanization” of Xenopus neural crest cells were studied. Outgrowth represents the number of neural crest cells emigrating from cultured neural tubes, and melanization concerns the percentage of differentiated melanophores among the emigrated cells. MSH or SMF stimulate both outgrowth and melanization. The melanogenic effect of Xenopus serum in this system is more than twice that of Rana serum. The actions of MSH and Xenopus serum on melanization seem to be different: 1) Stronger melanization is induced by Xenopus serum than by MSH, and the onset of melanization occurs earlier with Xenopus serum; 2) MSH stimulates melanization only in the presence of added tyrosine; and 3) MSH causes young melanophores to assume a prominent state of melanophore dispersion during culture, while Xenopus serum (10%) had only a slight dispersing effect and not until day 3. A fraction of Xenopus serum presumably containing molecules of a smaller molecular weight (MW <30 kDa) than that of a pigment promoting factor reported in calf serum [Jerdan et al.: J. Cell Biol., 100:1493–1498, 1985] produces the same remarkable melanogenic effects as does intact serum. While this fraction stimulates outgrowth, another fraction presumably containing larger molecules (MW > 100 kDa) does not. MIF contained in Xenopus ventral skin conditioned medium (VCM) inhibits both outgrowth and melanization dose dependently. When VCM is used in combination with MSH, the stimulating effects of MSH on both outgrowth and melanization are completely inhibited. In contrast, the stimulatory effects of Xenopus serum are not completely inhibited when combined with VCM, although melanization is reduced to approximately 40% that of controls. MIF activity was also found to be present in ventral, but not in dorsal, skin conditioned media of R. pipiens when tested in the Xenopus neural crest system. We suggest that ventrally localized MIF plays an important role in amphibian pigment pattern formation and that the interacting effects of MIF and melanogenic factors influence melanoblast differentiation, migration, and/or proliferation of neural crest cells to effect the expression of pigmentary patterns.     

Evaluations of permethrin-impregnated clothing and three topical repellent formulations of deet against tsetse flies in Zambia

Permethrin-impregnated clothing and three topical repellent formulations of deet (diethyltoluamide) were field tested against natural populations of tsetse flies, mostly Glossina morsitans centralis Machado, in central Zambia. Volunteers wore different combinations of clothing impregnated with permethrin 0.125 mg ai/cm2 and repellents while riding in a vehicle that was driven slowly (4-6 km/h), with the windows and rear door open, through fly-infested areas. The mean rate of tsetse bites was about twenty per 75 min for unprotected people. The treatment combination of permethrin-impregnated clothing (blue cotton coveralls) and either of two controlled-release deet formulations on exposed skin of face and arms provided 91% mean protection, but this was not significantly better (P greater than 0.05) than wearing deet repellent alone (76-87% protection). No significant differences of protection were observed between the three repellent treatments, although the two controlled-release formulations (intended to be more persistent) were applied at approximately half the dosage of the standard 75% deet. Wearing permethrin-impregnated coveralls alone provided relatively poor protection (34%) for the untreated and exposed skin of head and hands. However, olive drab mesh jackets treated with permethrin reduced the tsetse biting rate by 75%.