Functional and Evolutionary Relationships Among the RPCH-AKH Family of Peptides

SYNOPSIS. The RPCH-AKH peptide family is a group of structurallysimilar peptides which are apparently widely distributed inarthropods, and which serve a variety of functions in differentsettings. The first three recognized members of this familywere detected and purified based on endocrine activities includingcolor change in crustaceans (RPCH) and effects on energy metabolismin insects (AKH and Compound II). The most recently identifiedfamily members, MI and Mil, were found on the basis of neuromuscularactivity as well as endocrine effects, and a combination ofhistological and physiological evidence strongly suggests thatat least some of these peptides are localized in neurons includingmotor neurons which use them as transmitters. Thus this is oneof several neuropeptide families with highly conserved structures,but diverse endocrine and neural functions. The significanceof structural similarities between family members is unclear.Fortunately the arthropod preparations in which these peptideshave been identifiedlend themselves to detailed developmental,anatomical, and physiological analysis, so there is every reasonto suppose that molecular biological and physiological investigationscurrently inprogress will shed significant light on the meaningof the phenomenon of structurally conservative peptide families.     

Frosty Spot. A Developmental Disturbance of the Tomato Leaf

Hybrids of the cross Lycopersicon esculentum x L. chilense developedfrost-like eruptions on the lower, or less frequently, the uppersides of the leaf. The eruptions consisted of large undifferentiatedcells, usually free of chlorophyll. A continuously intergradingseries of cells occurred between normal and affected regions.The spots involved any or all tissue layers. Spotting was controlledby a single dominant gene from the L. chilense parent, oftendeficient in transmission. In addition, environment influencedincidence and severity of the condition. An unstable gene controllingdevelopment is hypothesized to mutate, producing substanceswith radiating effects.     

Immunological response in rabbits infested with Rhipicephalus sanguineus

Abstract. In order to clarify the importance of humoral antibody in host resistance to ticks, in the present work we studied the immunological response of rabbits infested with larvae, nymphs or adults of Rhipicephalus sanguineus , using extracts of eggs (EE), larvae (LE), nymphs (NE), male salivary glands (MSGE), male midguts (MME), female salivary glands (FSGE) and female midguts (FME). When serum from rabbits infested with larvae or nymphs was tested using enzyme-linked immunosorbent assay, no reactions were observed with any of the extracts including the homologous LE or NE. In sera from rabbits infested with adult ticks, the reactions were observed in both homologous (MSGE, MME, FSGE and FME) and heterologous (EE, LE and NE) system. However, differences were seen regarding the type of antigen used. When the experiment was carried out using extracts from adults higher responses were found. With FSGE and FME antigens, antibody levels were systematically higher than those observed when MSGE and MME were used.