A CLADISTIC ANALYSIS OF PARKIA (LEGUMINOSAE: MIMOSOIDEAE)

A cladistic analysis of the tropical mimosoid genus Parkia was undertaken to examine relationships among the 31 species and to test the monophyly of the three recognized sections. The implications of the cladogram to the evolution of bat-pollination and biogeography were also explored. The analysis, based on 52 morphological characters, resulted in 408 most parsimonious trees. A consensus tree supports the monophyly of sections Parkia and Platyparkia, but section Sphaeroparkia is paraphyletic. The latter section is distinguished by a capitulum of all fertile flowers, a plesiomorphic attribute in this analysis. Characters supporting the monophyly of section Platyparkia include an inflorescence with distal nectar flowers having exserted styles, and fruits with seeds in two rows. Section Parkia is characterized by having sterile basal flowers with nectar flowers just above them, and calyx lobes included in bud. Bat-pollination was mapped onto one of the most parsimonious cladograms to examine the evolution of pollination syndromes within the genus. Our phylogeny is consistent with a single origin of bat-pollination and indicates that entomophilous species of Parkia are basal rather than secondarily derived. Sections Platyparkia and Parkia are separate lineages within the bat-pollinated clade and have independently developed capitulum types adapted to chiropterophily. Characters that are associated with chiropterophily include specialized nectar-producing flowers and basifixed anthers. Several characters, including presence of a staminodial fringe, a nectar ring, and pollen with verrucate sculpturing on the exine, probably represent increasing specialization for bat-pollination. The cladogram supports a South American origin for Parkia but is not consistent with a Gondwanan vicariance event as is usually hypothesized to explain its amphi-Atlantic distribution.     

The Severe Perinatal Form of Autosomal Recessive Polycystic Kidney Disease Maps to Chromosome 6p21.1-p12: Implications for Genetic Counseling

Autosomal recessive polycystic kidney disease (ARPKD) is a one of the most common hereditary renal cystic diseases in children. Its clinical spectrum is widely variable with most cases presenting in infancy. Most affected neonates die within the first few hours of life. At present, prenatal diagnosis relies on fetal sonography, which is often imprecise in detecting even the severe form of the disease. Recently, in a cohort of families with mostly milder ARPKD phenotypes, an ARPKD locus was mapped to a 13-cM region of chromosome 6p21-cen. To determine whether severe perinatal ARPKD also maps to chromosome 6p, we have analyzed the segregation of seven microsatellite markers from the ARPKD interval in 22 families with the severe phenotype. In the majority of the affected infants, ARPKD was documented by histopathology. Our data confirm linkage and refine the ARPKD region to a 3.8-cM interval, delimited by the markers D6S465/D6S427/D6S436/D6S272 and D6S466. Taken together, these results suggest that, despite the wide variability in clinical phenotypes, there is a single ARPKD gene. These linkage data and the absence of genetic heterogeneity in all families tested to date have important implications for DNA-based prenatal diagnoses as well as for the isolation of the ARPKD gene.     

Membrane protein trafficking through the common apical endosome compartment of polarized Caco-2 cells.

By raising monoclonal antibodies to the apical surface of Caco-2 cells we have identified a membrane protein (p100) that internalizes and recycles constitutively between the apical plasma membrane and endosomes in the apical cytoplasm. By applying tracers bound to the transferrin receptor, which internalizes and recycles back to the basolateral border, we demonstrate that the apical endosomes containing p100 include a subset of multivesticular bodies (MVB), which are also accessible to proteins arriving from the basolateral endosome. Tracers bound to EGF receptors and alpha-2-macroglobulin, which internalize from the basolateral border and are degraded, probably in lysosomes, also pass through the p100-containing MVB. These studies therefore suggest that the apical cytoplasm of Caco-2 cells contains a population of MVB capable of receiving membrane proteins trafficking in from both apical and basolateral borders and then routing them to a variety of cell surface and intracellular destinations. The differential distribution of apical and basolateral tracers within the 50-nm-diameter tubules connected to these p100-positive apical MVB suggests that the destination of proteins trafficking from the MVB back to apical and basolateral surfaces is determined by the tubules to which they gain access.     

The NF-kappa B binding site is necessary for efficient replication of simian immunodeficiency virus of macaques in primary macrophages but not in T cells in vitro.

We demonstrate here that the nuclear factor-kappa B (NF-kappa B) binding site in the simian immunodeficiency virus (SIVmac) long terminal repeat is essential for efficient virus replication in primary alveolar macrophages but dispensable for efficient replication in primary T cells. Mutation of the NF-kappa B site does not seriously impair replication of a T-cell-tropic SIVmac239 or a macrophagetropic SIVmacEm* in peripheral blood lymphocytes or established CD4+ cell lines; however, mutation of the NF-kappa B site prevents efficient SIVmacEm* replication in primary alveolar macrophages. These data suggest that efficient replication in primary macrophages requires both envelope and long terminal repeat determinants.     

A new class of promoter mutations in the lactose operon of Escherichia coli

The isolation and genetic characterization of a number of mutations that are located in the promoter region of the lac2 operon are described. These mutations have reduced levels of lac operon expression in a wild, type (crp⁺cya⁺) genetic background. Three of the mutations also have lower levels of lac operon expression than lacP⁺ in a crp^?cya^? genetic background, that is in the absence of the catabolite activator protein and 3′,5′-adenosine cyclic monophosphate. These three mutations are located nearest to the lac operator. They define a second essential site in the promoter region.     

Immunochemical and spectroscopic evidence for protein conformational changes in phytochrome transformations

Phytochrome was examined by immunochemical and spectroscopic techniques to detect differences between the protein moieties of red- and far red-absorbing phytochrome (P_r and P_fr). No differences in the reaction of P_r and P_fr with phytochrome antibody were discernible on Ouchterlony double diffusion plates. However, the microcomplement fixation assay showed a greater degree of antibody reaction with P_fr than with P_r, indicating some difference in the surface characteristics of the two forms. Circular dichroism spectroscopy between 300 and 200 nanometers revealed differences between P_r and P_fr which may reflect differences in the protein conformation. The circular dichroism spectrum of P_r showed a negative band at 285 nanometers which was not present in the spectrum of P_fr, and the large negative circular dichroism band at 222 nanometers with P_fr, associated with the α-helical content, was shifted 2 nanometers to shorter wave length with P_r although there was no change of magnitude of this band. The absorbancy of P_r and P_fr is very nearly the same in the 280 nanometer spectral region, but sensitive difference spectra between P_r and P_fr did reveal spectra which were similar to solvent perturbation spectra obtained by others with different proteins. In total, the experiments indicate that there are conformational differences between the protein moieties of P_r and P_fr but that these differences are rather slight from a standpoint of gross structure.     

Regulation of gonadotropin secretion in the anterior pituitary

Studies on the regulation of gonadotropin secretion in dissociated pituitary cell cultures are described. Initial studies employing a ferritin-labelled analogue of gonadotropin hormone releasing hormone (GnRH) to localize its receptor sites on the gonadotropin cell surface that while these receptor sites initially have a random monodisperse distribution, binding of the ligand causes coarse aggregation and internalization of the GnRH receptor. These events are not due to the multivalency of the ligand and probably reflect redistributive events in vivo. By using an octapeptide analogue GnRH that binds to the GnRH receptor but lacks gonadotropin releasing activity in conjunction with sequence-specific antisera it is shown that antibodies that bind the octapeptide can induce the octapeptide to release gonadotropin. These data suggest that receptor aggregation is important in GnRH stimulation. Finally immunocytochemical studies are described in which golg-protein-A-antibody complexes are used to identify gonadotropins on ultrathin frozen sections of porcine pituitary cells. These studies indicate that in porcine gonadotropin cells the majority of the secretory granules contain both luteinizing hormone and follicle-stimulating hormone.