Interactions between size and temperature influence fecundity and longevity of a tortricid moth,Zeiraphera canadensis

Females of Zeiraphera canadensis Mut. & Free., the spruce bud moth, were reared in the laboratory at constant and alternating temperatures, and in an outdoor insectary, to (1) determine the effects of temperature, age and size on several reproductive parameters and, (2) to test the hypothesis that body size-temperature interactions influence longevity and realized fecundity. Egg maturation was linearly related to age and large moths developed eggs at a higher rate than small ones. Mcan lifetime oviposition rate reached a maximum and remained stable at temperatures 20° C while the mean lifetime rate of egg maturation increased linearly with temperature, indicating that higher temperatures adversely affect oviposition. The production of nonviable eggs increased with age but also with temperature, suggesting high temperature (25° C) reduces egg quality and/or hinders fertilization. The realized fecundity and longevity of females reared under an alternating temperature regime (mean 20° C) was significantly less than that of females reared at constant 20° C. Similar realized fecundity, longevity and mean lifetime oviposition rates for females reared at temperatures alternating between 10 and 25° C (mean 20° C) and those at constant 25° C reflected the inability of females to recover from elevated diurnal temperatures. Longevity was positively related to female body size at constant 15 and 20° C but the relationships were negative for moths exposed to diurnal temperatures equal to or exceeding 25° C. Due to the reduced longevity of large moths at high temperatures, linear regressions between size and realized fecundity were only significant at constant temperatures 20° C. At higher temperatures, the size-fecundity relationship became curvilinear as a result of the diminished reproductive output of large individuals. Reduced fecundity and longevity of large females at high temperatures may have been due to elevated internal temperatures of large-bodied moths. Large females in a controlled-environment chamber maintained at 25° C developed an internal temperature excess (i.e. temperature above ambient) of nearly 2° C while small-bodied females exceeded ambient by only 0.3° C. However, when held at 20° C, the temperature excess of large-bodied moths was much less than 1° C and small-bodied females did not differ from ambient. Such interactions between temperature and body size suggest that there should be stabilizing selection toward moderate-sized individuals and may explain the absence of size-related effects on fecundity and longevity previously reported for several other lepidopterans.     

Defining phosphorus efficiency in plants

The many different definitions for "nutrient efficiency" make the use of the term ambiguous. We evaluated nutrient efficiency using data from a study of response to phosphorus (P) supply in white clover (Trifolium repens L.) and lucerne (Medicago sativa L.). Application of various criteria identified in the literature as measures of nutrient efficiency did not clarify differences between purportedly P efficient and inefficient germplasm. Germplasm differed in maximum shoot and total dry mass and in solution P concentration ([P]_s) required to achieve 80% maximum yield, but not in P concentration of tissue ([P]_t), internal P utilization, or P uptake per unit of fine root dry mass. Differences in yield may have resulted from factors other than efficient use of P. To reduce the confounding effects that other factors have on nutrient efficiency, it is essential that equivalent yields of germplasm be demonstrated where nutrients are not limiting. Mechanisms that enable enhanced nutrient efficiency can be identified less ambiguously using this approach.Joint contribution of the Minn. Agric. Exp. Stn. and the USDA-ARS     

NAD(P)H-ubiquinone oxidoreductases in plant mitochondria

Plant (and fungal) mitochondria contain multiple NAD(P)H dehydrogenases in the inner membrane all of which are connected to the respiratory chain via ubiquinone. On the outer surface, facing the intermembrane space and the cytoplasm, NADH and NADPH are oxidized by what is probably a single low-molecular-weight, nonproton-pumping, unspecific rotenone-insensitive NAD(P)H dehydrogenase. Exogenous NADH oxidation is completely dependent on the presence of free Ca²⁺ with aK _0.5 of about 1 µM. On the inner surface facing the matrix there are two dehydrogenases: (1) the proton-pumping rotenone-sensitive multisubunit Complex I with properties similar to those of Complex I in mammalian and fungal mitochondria. (2) a rotenone-insensitive NAD(P)H dehydrogenase with equal activity with NADH and NADPH and no proton-pumping activity. The NADPH-oxidizing activity of this enzyme is completely dependent on Ca²⁺ with aK _0.5 of 3 µM. The enzyme consists of a single subunit of 26 kDa and has a native size of 76 kDa, which means that it may form a trimer.     

Two Transduction Pathways Mediate Rapid Effects of Abscisic Acid in Commelina Guard Cells

Commelina guard cells can be rapidly closed by abscisic acid (ABA), and it is thought that this signal is always transduced through increases in cytosolic calcium. However, when Commelina plants were grown at 10 to 17[deg]C, most guard cells failed to exhibit any ABA-induced increase in cytosolic calcium even though all of these cells closed. At growth temperatures of 25[deg]C or above, ABA-induced closure was always associated with an increase in cytosolic calcium. This suggests that there may be two transduction routes for ABA in guard cells; only one involves increases in cytosolic calcium. Activation of either pathway on its own appears to be sufficient to cause closure. Because the rates of ABA accumulation and transport in plants grown at different temperatures are likely to be different, we synthesized and microinjected caged ABA directly into guard cells. ABA was released internally by UV photolysis and subsequently caused stomatal closure. This result suggests a possible intracellular locale for the hypothesized ABA receptor.     

Gangliosides Inhibit Platelet-Derived Growth Factor-Stimulated Receptor Dimerization in Human Glioma U-1242MG and Swiss 3T3 Cells

Abstract: We previously showed that gangliosides inhibit DNA synthesis in Swiss 3T3 cells stimulated with platelet-derived growth factor (PDGF) in a dose-responsive manner. This correlated with the inhibitory effects of several gangliosides (except GM3) on tyrosine phosphorylation of the PDGF receptor (PDGFR). [³⁵S]Methionine-labeled Swiss 3T3 cells were incubated either with or without gangliosides and stimulated with PDGF, and proteins were cross-linked with bis(sulfosuccinimidyl) suberate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that two protein bands (170 and 350 kDa) were specifically immunoprecipitated with an anti-PDGFR antibody. Using both Swiss 3T3 and human glioma U-1242MG cells, western blots with anti-PDGFR and anti-phosphotyrosine antibodies confirmed that these bands were the PDGFR monomer and dimer, respectively, and that phosphotyrosine was present in these bands only after cells were stimulated with PDGF. Of the gangliosides tested, GM1, GM2, GD1a, GD1b, GD3, and GT1b, but not GM3, inhibited the formation of the 350-kDa band. These results demonstrate that all gangliosides tested, except GM3, probably inhibit PDGF-mediated growth by preventing dimerization of PDGFR monomers. Loss of more complex gangliosides in human gliomas would permit unregulated activation of the PDGFR, contributing to uncontrolled growth stimulation. We propose that ganglioside inhibition of receptor dimerization is a novel mechanism for regulating and coordinating several trophic factor-mediated cell functions.     

Linkage studies with 17q and 18q markers in a breast/ovarian cancer family.

Genes on chromosomes 17q and 18q have been shown to code for putative tumor suppressors. By a combination of allele-loss studies on sporadic ovarian carcinomas and linkage analysis on a breast/ovarian cancer family, we have investigated the involvement of such genes in these diseases. Allele loss occurred in sporadic tumors from both chromosome 17p, in 18/26 (69%) cases, and chromosome 17q, in 15/22 (68%) cases. In the three familial tumors studied, allele loss also occurred on chromosome 17 (in 2/3 cases for 17p markers and in 2/2 cases for a 17q allele). Allele loss on chromosome 18q, at the DCC (deleted in colorectal carcinomas) locus, was not as common (6/16 cases [38%]) in sporadic ovarian tumors but had occurred in all three familial tumors. The results of linkage analysis on the breast/ovarian cancer family suggested linkage between the disease locus and 17q markers, with a maximum lod score of 1.507 obtained with Mfd188 (D17S579) polymorphism at 5% recombination. The maximum lod score for DCC was 0.323 at 0.1% recombination. In this family our results are consistent with a predisposing gene for breast/ovarian cancer being located at chromosome 17q21.     

A large, dominant pedigree of atrioventricular septal defect (AVSD): exclusion from the Down syndrome critical region on chromosome 21.

We describe a large pedigree of individuals with autosomal dominant atrioventricular septal defect (AVSD). The pedigree includes affected individuals and individuals who have transmitted the defect but are not clinically affected. AVSDs are a rare congenital heart malformation that occurs as only 2.8% of isolated cardiac lesions. They are the predominant heart defect in children with Down syndrome, making chromosome 21 a candidate for genes involved in atrioventricular septal development. We have carried out a linkage study in the pedigree by using 10 simple-sequence polymorphisms from chromosome 21. Multipoint linkage analysis gives lod scores of less than -2 for the region of trisomy 21 associated with heart defects, which excludes a locus within this region as the cause of the defect in this family.     

The effects of calcium deficiency on Cucurbita pepo L. hypocotyl cells: A 31P nuclear-magnetic-resonance study

Calcium deficiency in zucchini (Cucurbita pepo L.) is associated with reduced growth and a reduced ability to transport auxin (Allan and Rubery, 1991, Planta 183, 604–612). An investigation of the effects of calcium-deficiency on zucchini hypocotyl cells was made using weak-acid uptake and ³¹P-nuclear-magneticresonance (³¹P-NMR) spectroscopy in vivo and in tissue extracts. Calcium-deficient tissue had the same cytoplasmic and vacuolar pHs as normal tissue when extracellular pH was near neutral. At acidic external pH the vacuolar pH was lower in deficient tissue. Adenine nucleotides were present predominantly as ATP in both control and calcium-deficient tissues. Addition of calcium to calcium-deficient tissue, under conditions which cause recovery of auxin transport induced no changes in the ³¹P-NMR spectra of deficient tissue. The content of mobile, phosphorylated metabolites was reduced in calcium-deficient tissue in comparison to control tissue. However, a substantial increase in the content of phosphorylcholine occurs in calcium-deficient tissues compared with controls; this may reflect changes in lipid turnover in calcium-stressed cells. We wish to thank Drs. Terry Moore and Jamie Vandenberg for technical assistance and Professor Peter Morris for providing the gated oxygen device. A.C.A. thanks the Cambridge Commonwealth Trust for a Prince of Wales Scholarship and the O.R.S. Awards Scheme for an award.     

A Method for Determining the Activity State of Hair Follicles

A histological method is described for determining the proportion of growing hair follicles h skin samples. A variation of the Sacpic staining method, modified for bulk processing, produces high contrast staining of the principal tissue types present in skin. In particular, the inner root sheath is accentuated, facilitating detection of active follicles. Skin preparations from a range of species are used to illustrate structural characteristics of follicles viewed in cross section at various stages of the hair cycle and to establish criteria for classification of the state of activity of follicles. The hair cycle may be divided into quiescent and active states at the points of rapid transition (early pronanagen and mid catagen). Data from repeated skin biopsies from ferrets and goats are also used to demonstrate quantitative estimation of follicle activity, change in compound follicle size, and the relationship between follicle type and fiber medullation.     

DNA/DNA hybridization studies of carnivorous marsupials. III. Relationships among species ofDidelphis (Didelphidae)

We report three sets of DNA hybridization experiments conducted to determine relationships among species ofDidelphis (D. albiventris, D. marsupialis, D. virginiana). The 1989 and 1991 sets had fewer replicates per cell than the 1990 series (3.4 and 5.4 vs 9), but in 1991 we distinguished two populations ofD. marsupialis and utilized several individuals for each heterologous comparison. BothPhilander opossum andLutreolina crassicaudata were used as outgroups in 1989, but onlyLutreolina was included in subsequent sets. For each set, we calculated all four standard indices of thermal stability (T _mode,T _m,T ₅₀ H, and NPH) and constructed trees by least-squares (FITCH) and neighbor-joining methods, both before and after correction for asymmetric reciprocal cell values. Subsets of the 1989 data lacking eitherPhilander orLutreolina were analyzed similarly. To explore measurement imprecision, the corrected and uncorrected matrices for each of the four indices were bootstrapped 100 times for the 1989 set and subsets and 1000 times for the 1990 and 1991 sets. Again, for the 1990 and 1991 data, an additional 100 bootstrapped distances were fitted to user trees representing the three possible pairings ofDidelphis spp. to determine the significance of the FITCH branch lengths. The successive experimental sets generated increasingly consistent evidence for pairingD. marsupialis withD. albiventris. The 1989 experiments involved just 85 comparisons, and only T _mode's pairedD. marsupialis withD. albiventris (at bootstrap percentages of 70% or above), but did so whetherPhilander orLutreolina or both were included as the outgroup(s). FITCH and neighbor-joining trees had identical topologies for T _mode's but sometimes differed for the other measures. In contrast, all but one of the corresponding FITCH and neighborjoining trees matched for the 1990 and 1991 data, and three of the four distance measures (T _mode, T _m, and T ₅₀ H) unitedD. marsupialis withD. albiventris at bootstrap percentages averaging 81%; NPH gave a different result for 1990, associatingD. marsupialis withD. virginiana. Further, all but 2 of the 16 matrices for 1990 and 1991 gave mean bootstrapped branch lengths for a consensus pairing that were positive and at least one standard deviation from zero, despite the very short internodes recovered. These results illustrate that the potential of DNA hybridization for resolving very close relationships depends on both the index and the experimental design employed. We conclude that of the three species,D. albiventris andD. marsupialis shared a more recent common ancestor and estimate thatDidelphis spp. have diverged at about 0.39% in nucleotide sequence per myr.Deceased.