REACTION NORMS OF MORPHOLOGICAL AND LIFE-HISTORY TRAITS TO LIGHT AVAILABILITY IN IMPATIENS CAPENSIS

For plants, light availability is an important environmental factor that varies both within and between populations. Although the existence of sun and shade “ecotypes” is controversial, it is often assumed that trade-offs may exist between performance in sun and in shade. This study therefore investigated variation in reaction norms to light availability within and between two neighboring natural populations of the annual Impatiens capensis, one in full sun and the other in a forest understory. Seedlings were collected randomly from both populations and grown to maturity in a greenhouse under two light conditions: full light and 18% of full light. Selfed full-sib seed families were collected from plants from both populations grown in both parental light environments. To characterize family reaction norms, seedlings from each family were divided into the same two light treatments and individuals were scored for a variety of morphological and life-history traits. The maternal light environment had little impact on progeny reaction norms. However, the two study populations differed both qualitatively and quantitatively in plastic response to light availability (indicated by significant population x environment interactions in mixed-model ANCOVA). Much of this difference was attributable to population differences in light sensitivity of axillary meristem allocation patterns, which produced concurrent differences in reaction norms for a suite of developmentally linked traits. Within each population, different sets of traits displayed significant variation in plasticity (indicated by significant family x environment interactions). Thus, the genetic potential for evolutionary response to selection in heterogeneous light environments may differ dramatically between neighboring plant populations. Between-environment genetic correlations were largely positive in the woods population and positive or nonsignificant in the sun population; there was no evidence for performance trade-offs across environments or sun or shade “specialist” genotypes within either population. There was little evidence that population differences represented adaptive differentiation for sun or shade; rather, the results suggested the hypothesis of differential selection on patterns of meristem allocation caused by population differences in timing of mortality and intensity of competition.     

Organ-specific change inDolichos biflorus lectin binding by myocardial endothelial cells during in vitro cultivation

Summary Endothelial cells of the NMRI mouse strain express a cell surface glycoprotein recognized by the lectinDolichos biflorus agglutinin (DBA). This study documents a marked organ-specific increase in DBA-specific lectin binding of myocardium-derived endothelial cells (MEC) of the NMRI/GSF mouse during in vitro cultivation. An up to 20-fold increase in DBA binding sites is observed in long-term culture, an increase not found in other NMRI-derived endothelial cell lines (e.g., brain, aorta). The increase appears restricted to DBA in that binding with other lectins (PNA, WGA) was unaltered. NMRI MEC cultures maintain typical endothelial cell attributes such as cobblestone morphology on confluence, expression of endothelial cell-specific surface markers, and production of angiotensin-converting enzyme. Cultures routinely become aneuploid within 4 passages, several passages before upregulation of the DBA binding site(s). Myocardial endothelial cells sorted to obtain DBA^hi and DBA^lo cell populations generally maintained their sorted phenotype for 3 to 4 passages. Limiting dilution cloning resulted in clones varying in DBA expression. Clones for DBA^hi expression maintained their DBA affinity for at least 10 passages (>30 doublings), whereas DBA^lo clones gave rise to varying numbers of DBA^hi cells within 2 to 4 passages. We hypothesize that the change in DBA affinity accompanies in vitro aging, that the change is independent of alterations in karyotype, and that the increase in DBA affinity may reflect a change in one or more other endothelial cell properties. Additional studies will be necessary to determine whether the in vitro changes are correlated with specific functional alterations and whether they accurately reflect progressive changes of MEC in vivo.     

Comparison between cellulose and amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phases for enantiomeric separation of 17 amidotetralins

Direct enantiomeric separations of 17 chiral amidotetralins by means of high performance liquid chromatography were performed on stationary phases composed of tris(3,5-dimethylphenylcarbamate) derivatives of cellulose and amylose, coated on silica gel. The enantiomers of 15 out of 17 amidotetralins were resolved with a resolution of more than 1.5 by at least one of the chiral stationary phases. The stationary phases showed complementary results with regard to the separation of the amidotetralins, that is, pairs that did not separate on the cellulose-type column were well separated on the amylose-type column, and vice versa. There was no significant correlation between the chromatographic properties of the chiral stationary phases. © 1993 Wiley-Liss, Inc.     

Time-Dependent Effects of Progressive Gamma -Linolenate Feeding on Hyperphagia,Weight Gain,and Erythrocyte Fatty Acid Composition During Growth of Zucker Obese Rats

Obese Zucker rats (fa/fa) have low levels of arachidonic acid (AA) in liver phospholipids (PL). We have previously shown that a 70% gamma-linolenate concentrate (GLA; an AA intermediate) fed at a fixed dose (0.07 g/day) normalized hepatic PL AA and reduced weight gain selectively in the obese animals. In a follow-up study, 16 obese (fa/fa) and 16 lean (Fa/Fa) 4-week-old male rats were randomized into 4 groups of 8 each and gavaged daily with soybean oil (SOY) containing 55% 18:2ω6 (an AA precursor) or GLA, using a progressive dose (≤ 5% of total calories) based on body weight. A defined diet with 11% of energy as SOY was fed ad libitum for 60 days. GLA obese had lower body weight (p<0.0001) and 60-day cumulative food intake (p<0.05) compared to SOY obese, but neither parameter differed between the lean groups. For the last twenty days cumulative food intake was identical for GLA obese and SOY lean, whereas SOY obese consumed 18% more (p<0.05). Thus the progressive dose of GLA selectively suppressed hyperphagia in obese Zucker rats. Erythrocytes collected at 15-day intervals showed parallel increases in AA in both genotypes over time, suggesting normal AA availability during rapid growth. Thus, the reduced PL AA in the livers from the obese rats probably reflects impaired distribution in selected tissues rather than reduced hepatic production. Due to the potential health risks of enriching tissue lipids with AA, great caution is advised in considering GLA as therapy for human obesity.     

Changes in the Activities of Aldolase and of D-Glyceraldehyde-3-Phosphate Dehydrogenase during the Mitotic Cycle in Microspores of Lilium longiflorum

Microspores of Lilium longiflorum were isolated at various stages of development surrounding the mitotic interval and were analyzed for changes in the activities of D-glyceraldehyde-3-phosphate dehydrogenase and aldolase. Fructose 1,6 diphosphate was used as substrate. Activities were measured by the increase in optical density due to the reduction of diphosphopyridine nucleotide. It was found that mitosis occurs during the minimal activity of both aldolase and D-glyceraldehyde-3-phosphate, thus indicating that heightened glycolytic capacity is not necessarily related to mitosis. It was also found that soluble-SH levels were highest when the enzymes were least active. It appeared, therefore, that the "—SH enzymes" are not necessarily activated intracellularly by high concentrations of soluble thiol. These results are discussed in connection with the theory that soluble-SH compounds stimulate glycolysis and in this way initiate mitosis.     

A peptide containing a novel FPGN CD40-binding sequence enhances adenoviral infection of murine and human dendritic cells.

CD40 is a receptor with numerous functions in the activation of antigen presenting cells (APCs), particularly dendritic cells (DC). Using phage display technology, we identified linear peptides containing a novel FPGN/S consensus sequence that enhances the binding of phage to a purified murine CD40-immunoglobulin (Ig) fusion protein (CD40-Ig), but not to Ig alone. To examine the ability the FPGN/S peptides to enhance adenoviral infection of CD40-positive cells, we used bifunctional peptides consisting of an FPGN-containing peptide covalently linked to an adenoviral knob-binding peptide (KBP). One of these, FPGN2-KBP, was able to enhance adenoviral infection of both murine and human DCs in a dose-dependent manner. FPGN2-KBP also improved infection of murine B cell blasts, a murine B lymphoma cell line (L10A), and immortalized human B cells. To demonstrate that enhancement of adenoviral infection depended on the presence of CD40, we analyzed infection of the breast cancer line, SKBR3, that does not express CD40 or the adenovirus cellular receptor, CAR. Infection of SKBR3 cells was enhanced by FPGN2-KBP following transient transfection with a plasmid vector that expresses murine CD40, but not when the cells were mock-transfected. In conclusion, we have isolated a peptide that binds to murine CD40, and promotes the uptake of adenoviruses into CD40-expressing cells of both murine and human origin, suggesting that it may have potential applications for antigen delivery to CD40-positive antigen-presenting cells.     

CSP41, a sequence-specific chloroplast mRNA binding protein, is an endoribonuclease.

Correct 3' processing of chloroplast precursor mRNAs (pre-mRNAs) requires a stem-loop structure within the 3' untranslated region. In spinach, a stable 3' stem-loop-protein complex has been shown to form in vitro between petD pre-mRNA, encoding subunit IV of the cytochrome b6/f complex, and chloroplast proteins. This complex contains three chloroplast stem-loop binding proteins (CSPs), namely, CSP29, CSP41, and CSP55. Here, we report the purification of CSP41 and cloning of the csp41 gene and show that CSP41 is encoded by a single nuclear gene. Characterization of bacterially expressed CSP41 demonstrates that this protein binds specifically to the 3' stem-loop structure and a downstream AU-rich element of petD pre-mRNA and that its binding affinity is enhanced by associating with CSP55. Our data also show that CSP41 has substantial nonspecific endoribonuclease activity. These data suggest that CSP41 could be involved in 3' processing of petD pre-mRNA and/or in RNA degradation. The fact that different reaction conditions favor RNA binding over ribonuclease activities suggests a possible mode of in vivo regulation.     

The hemagglutinin envelope protein of canine distemper virus (CDV) confers cell tropism as illustrated by CDV and measles virus complementation analysis.

Measles virus (MV) and canine distemper virus (CDV) are morbilliviruses that cause acute illnesses and several persistent central nervous system infections in humans and in dogs, respectively. Characteristically, the cytopathic effect of these viruses is the formation of syncytia in permissive cells. In this study, a vaccinia virus expression system was used to express MV and CDV hemagglutinin (HA) and fusion (F) envelope proteins. We found that cotransfecting F and HA genes of MV or F and HA genes of CDV resulted in extensive syncytium formation in permissive cells while transfecting either F or HA alone did not. Similar experiments with heterologous pairs of proteins, CDV-F with MV-HA or MV-F with CDV-HA, caused significant cell fusion in both cases. These results indicate that in this expression system, cell fusion requires both F and HA; however, the functions of these proteins are interchangeable between the two types of morbilliviruses. Human-mouse somatic hybrids were used to determine the human chromosome conferring susceptibility to either MV and CDV. Of the 12 hybrids screened, none were sensitive to MV. Two of the hybrids containing human chromosome 19 formed syncytia following CDV infection. In addition, these two hybrids underwent cell fusion when cotransfected with CDV-F and CDV-HA (but not MV-F and MV-HA) glycoproteins by using the vaccinia virus expression system. To discover the viral component responsible for cell specificity, complementation experiments coexpressing CDV-HA with MV-F or CDV-F with MV-HA in the CDV-sensitive hybrids were performed. We found that syncytia were formed only in the presence of CDV-HA. These results support the idea that the HA protein is responsible for cell tropism. Furthermore, while the F protein is necessary for the fusion process, it is interchangeable with the F protein from other morbilliviruses.