The functional morphology of Mactrinula reevesii (Bivalvia: Mactroidea) in Hong Kong: adaptations for a deposit-feeding lifestyle

The shallow subtidal mactrid bivalve Mactrinula reevesii is a deposit-feeder in the southern and south-eastern oceanic waters of Hong Kong. Buried obliquely, large quantities of fine sediment are taken into the mantle cavity and sorted on enormous labial palps. The small ctenidia probably have little value in collecting material, amounts taken in being too large. The mid gut is long and complexly folded inside the visceral mass. It is also capable of distension, although superficial visceral muscles maintain internal tonus. The rectum is narrow and creates compact faecal pellets.
Most interest is in the ventral mantle margin which is, posterior to the pedal gape and the base of the inhalant siphon, united by a sheet of cuticle. There is no fourth pallial aperture. There are, however, two pairs of flaps extending along the posterior third of the internal ventral mantle surface. These arch over left and right mantle rejection tracts which transfer unwanted material to the base of the inhalant siphon for final expulsion. The mantle flaps prevent such material from being returned to the anterior end of the mantle cavity, for palp reprocessing, when new material arrives. They, thus, maximize sorting efficiency by separating unsorted from sorted and rejected material.
Other mactrids have similar mantle flaps which they use in different ways, including the channelling of unwanted material to a fourth pallial aperture for expulsion, as in Lutraria lutraria. The Mactridae have thus evolved a unique method of increasing the efficiency of pseudofaecal waste rejection which has thereby facilitated the deposit-feeding lifestyle by the diverse representatives of this family.     

Anaerobic Biodegradation of Alkylbenzenes in Laboratory Microcosms Representing Ambient Conditions

A microcosm study was performed to document the anaerobic biodegradation of benzene, toluene, ethylbenzene, m- xylene, and/or o-xylene in petroleum-contaminated aquifer sediment from sites in Michigan (MI) and North Carolina (NC) and relate the results to previous field investigations of intrinsic bioremediation. Laboratory microcosms, designed to simulate ambient conditions, were constructed under anaerobic conditions with sediment and groundwater from source, mid-plume, and end-plume locations at each site. The general patterns of biodegradation and electron acceptor utilization in the microcosms were consistent with field data. At the MI site, methane was produced after a moderate lag period, followed by toluene degradation in all sets of microcosms. At the NC site, biodegradation of the target compounds was not evident in the source area microcosms. In the mid-plume microcosms, toluene and o-xylene biodegraded first, followed by m-xylene and benzene, a pattern consistent with contaminant decay along the plume length. Chemical extraction of microcosm sediment at the beginning and end of me incubation indicated that iron-reducing conditions were dominant and iron reduction occurred on a sediment fraction not extracted by 0.5N HC1. In the end-plume microcosms, degradation of benzene, toluene, and xylene isomers occurred but was variable between replicates. Consistent with field data, dissolved concentrations of the target contaminant(s) persisted at low but detectable levels (0.05 to 0.25 μM) in microcosms from both sites where biodegradation was measured.     

Development of a chronically catheterized maternal-fetal macaque model to study in utero mother-to-fetus HIV transmission: A preliminary report

Abstract: The lack of a representative animal model that permits frequent in utero fetal blood sampling is a major limiting factor for the study of maternal-fetal HIV transmission. Therefore, we have developed a maternal-fetal virus infection model using chronically catheterized macaques to simultaneously study the time-course of viral infection in the mother and the response of the fetus to maternal HIV infection. Pregnant macaques were infected with 10³ infectious units of HIV-2₂₈₇; every 3 days blood samples from both the mother and the fetus as well as amniotic fluid samples were collected. We found a varying degree of peak and time-to-peak virus load, virus-infected PBMCs, and free virus (determined by QC-RNA-PCR method) in maternal blood. Two of the three mothers with more than 10⁸ copies of viral RNA/ml of plasma at peak viremia transmitted the virus to their fetuses at about 14 days post-infection. As observed with HIV-2₂₈₇ infected mothers, virus-infected fetuses also produced a rapid rate of CD4⁺ cell decline in utero.     

Genetic variation of morphological characters within a single isolate of the endomycorrhizal fungus Glomus clarum (Glomaceae)

The nature of variation in morphological characters in spores of arbuscular endomycorrhizal fungi (Order Glomales, Class Zygomycetes) has received little attention, despite the importance of these characters in modern taxonomy of the order. We tested the hypothesis that genetic variation exists in spore size and color (presumably important taxonomic characters) within a single isolate of the glomalean fungus Glomus clarum. Phenotypic variation in size and color of spores was determined from a pot culture population (designated P). A 10% selection pressure was imposed on replicate pot cultures of the first progeny culture generation (G1) by selecting the smallest, largest, yellowest, and whitest spores from the P generation and inoculating Sorghum bicolor plants. The experiment was repeated for another generation (G2), but with a 5% selection pressure. In both the G1 and G2 generations, significant differences in spore size and color were observed among the various treatments, indicating substantial genetic variation in these characters. Despite efforts to keep the physical environment constant across generations, we observed variation in the overall means of spore size and color among the generations (regardless of treatment), indicating a strong nongenetic influence on character expression. This study provides empirical evidence that will help delimit species boundaries among isolates of Glomus clarum and similar morphospecies. It also demonstrates a promising method to help elucidate the nature of character diversity in obligately asexual fungi.     

EVIDENCE FOR A COMMON EVOLUTIONARY ORIGIN OF LIGHT-HARVESTING FUCOXANTHIN CHLOROPHYLL a/c-PROTEIN COMPLEXES OF PAVLOVA GYRANS (PRYMNESIOPHYCEAE) AND PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE)1

A fucoxanthin-chlorophyll a/c-protein complex has been isolated from the prymnesiophyte Pavlova gyrans. Thylakoid membranes were treated with the mild anionic detergent sodium taurodeoxycholate followed by sucrose density gradient centrifugation. The brown fraction produced by this procedure was treated with Triton X-100 followed by a second sucrose density gradient centrifugation. A brown fraction isolated from this gradient was shown to be a light-harvesting complex nearly identical to that which is present in the diatom Phaeodactylum tricornutum. The complexes from the two organisms have nearly identical absorption and flourescence spectra, both complexes contain fucoxanthin and two other carotenoids, both contain four polypeptides of similar molecular weights, and polypeptides from both complexes cross react with antibodies raised to polypeptides of the Phaeodactylum tricornutum complex. Results suggest a common evolutionary origin for these light-harvesting complexes, in apparent contrast to the great differences in cell structure between prymnesiophytes and diatoms.     

Olfactory sensitivity in tsetse flies: a daily rhythm

The diurnal tsetse Glossina morsitans morsitans bites especially in early morning and late afternoon; around midday feeding is at a low. In laboratory apparatus that measures the amount of locomotion under constant conditions over the photophase, the flies display a similar patterning of activity levels. The profile of daily rhythms for G. morsitans reported in the literature includes a number of motor and sensory motor systems that fluctuate cophasically. Lacking is a study on the patterning of the senses' response levels. In this paper we present the first instance of a daily modulation in the sense of smell. We stimulated the antennae with concentration series of host-derived odours and measured the spiking rate of cells at different times during the photophase. The concentration-response curves suggest that the sensitivity of antennal olfactory cells flows in parallel with the other daily rhythms. This was also reflected in electroantennograms (EAGs). The electroantennography was extended to G. fuscipes fuscipes, whose level of spontaneous locomotor activity--instead of following a U- shaped pattern--rises gradually over the photophase. Again, the EAGs appeared to parallel the species' locomotor activity. What we believe happens is that the organism tones down the sensitivity of its odour receptors during periods of anticipated inactivity for reasons of economy.      

Combined segregation and linkage analysis of Graves disease with a thyroid autoantibody diathesis.

Combined segregation and linkage analysis is a powerful technique for modeling linkage to diseases whose etiology is more complex than the effect of a well-described single genetic locus and for investigating the influence of single genes on various aspects of the disease phenotype. Graves disease is familial and is associated with human leukocyte antigen (HLA) allele DR3. Probands with Graves disease, as well as close relatives, have raised levels of thyroid autoantibodies. This phenotypic information additional to affection status may be considered by the computer program COMDS for combined segregation and linkage analysis, when normals are classified into diathesis classes of increasing thyroid autoantibody titer. The ordinal model considers the cumulative odds of lying in successive classes, and a single additional parameter is introduced for each gene modeled. Distributional assumptions are avoided by providing estimates of the population frequencies of each class. Evidence for linkage was increased by considering the thyroid autoantibody diathesis and by testing two-locus models. The analysis revealed evidence for linkage to HLA-DR when the strong coupling of the linked locus to allele DR3 was considered (lod score of 6.6). Linkage analysis of the residual variation revealed no evidence of linkage to Gm, but a suggestion of linkage to Km.     

Analysis of the interaction between human interleukin-5 and the soluble domain of its receptor using a surface plasmon resonance biosensor

A surface plasmon resonance (SPR) biosensor was used to study the interaction of human interleukin-5 (hIL5) with its receptor. IL5 is a major growth factor in the production and activation of eosinophilis. The receptor for IL5 is composed of two subunits, α and β. The α subunit provides the specificity for IL5 and consist of an extracellular soluble domain, a single transmembrane region and a cytoplasmic tail. We expressed the soluble domain of the human IL5 receptor α subunit (shIL5Rα) and human IL5 (hIL5) in Drosophila. Both hIL5 and shIL5Rα were immobilized separately through amine groups onto the carboxylated dextran layer of sensor chips of the BIAcore? (Pharmacia) SPR biosensor after N-hydroxysuccinimide/carbodiimide activation of the chip surface. Interactions were measured for the complementary macromolecule, either shIL5Rα or hIL5, in solution. Kinetics of binding of soluble analyst to immobilized ligand were measured and from this the association rate constant, dissociation rate constant and equilibrium dissociation constant (K_d) were derived. With immobilized shIL5Rα and soluble hIL5, the measured K_d was 2 nM . A similar value was obtained by titration calorimetry. The K_d for Drosophila expressed receptor and IL5 is higher than the values reported for proteins expressed in different systems, likely due to differences in the methods of interaction analysis used for differences in protein glycosylation. Receptor-IL5 binding was relatively pH independent between pH 6.5 and 9.5. Outside this range the dissociation rate increased with compressibility little increased in association rate. The values obtained for the interaction of hIL5 and shIL5Rα were found to depend on which component was immobilized; the K_d was 5.5 nM with immobilized hIL5 and soluble shIL5Rα. The SPR biosensor provides a unified methodology to measure the interaction properties of shIL5Rα and hIL5 derivatives, mutants and mimetic as well as to evaluate potential antagonists of the receptor-cytokine interaction.     

Both VH and VL regions contribute to the antigenicity of anti-idiotypic antibody that mimics melanoma associated ganglioside GM3

Previously we developed a murine monoclonal anti-idiotype (antiid) antibody (4C10) that mimics the melanoma-associated ganglioside antigen GM₃, that is, it carries the internal image of GM₃. 4C10 was made against the human monoclonal antibody (HuMAb) L612, which reacts with several types of human cancer cells, including melanoma and breast cancer. To reduce mouse components of 4C10, the constant region was replaced by a human constant domain to form the murine/human chimeric anti-id antibody TVE-1. In the present study, we sought to determine which chain (V_H or V_L) of the anti-id is responsible for the antigenicity of GM₃. The TVE-1 V_H and V_L expression vectors were simultaneously transfected with either the V_H or V_L expression vector of a murine-human chimeric IgG antidansyl haptenic antibody, resulting in the construction of three different combinations of V_H and V_L chimeric antibodies. These IgG molecules were produced from the transfectomas, and their reactivity to HuMAb L612 was tested. Neither of the IgG proteins that had cross-combined the V_H-V_L pair showed positive results, suggesting that both heavy and light chains are required to express the antigenicity. The in vivo antigenicity of this chimeric anti-id was confirmed by skin tests in melanoma patients receiving active specific immuntherapy.