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1.
Understanding how tropical tree phenology (i.e., the timing and amount of seed and leaf production) responds to climate is vital for predicting how climate change may alter ecological functioning of tropical forests. We examined the effects of temperature, rainfall, and photosynthetically active radiation (PAR) on seed phenology of four dominant species and community-level leaf phenology in a montane wet forest on the island of Hawaiʻi using monthly data collected over ~ 6 years. We expected that species phenologies would be better explained by variation in temperature and PAR than rainfall because rainfall at this site is not limiting. The best-fit model for all four species included temperature, rainfall, and PAR. For three species, including two foundational species of Hawaiian forests (Acacia koa and Metrosideros polymorpha), seed production declined with increasing maximum temperatures and increased with rainfall. Relationships with PAR were the most variable across all four species. Community-level leaf litterfall decreased with minimum temperatures, increased with rainfall, and showed a peak at PAR of ~ 400 μmol/m2s−1. There was considerable variation in monthly seed and leaf production not explained by climatic factors, and there was some evidence for a mediating effect of daylength. Thus, the impact of future climate change on this forest will depend on how climate change interacts with other factors such as daylength, biotic, and/or evolutionary constraints. Our results nonetheless provide insight into how climate change may affect different species in unique ways with potential consequences for shifts in species distributions and community composition. 相似文献
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3.
Sequence and structural organization of the human gene encoding ciliary neurotrophic factor. 总被引:12,自引:0,他引:12
Ciliary neurotrophic factor (CNTF) is a potent polypeptide hormone whose actions appear to be restricted to the nervous system where it promotes survival, neurotransmitter synthesis and neurite outgrowth in certain neuronal populations. We have cloned the gene encoding human CNTF (hCNTF) and have characterized its structure and organization. The hCNTF gene appears to be a unique-copy gene with a simple genetic organization, since only a single intron interrupts the coding domain. The hCNTF gene is located on chromosome 11, as determined using human-hamster somatic cell hybrids. The CNTF protein is highly conserved in evolution. The amino acid (aa) sequences of rat and rabbit CNTF translated from cDNAs display approx. 85% homology with the deduced aa sequence encoding hCNTF. 相似文献
4.
David D. McPherson Chun-Tao Che Geoffrey A. Cordell D. Doel Soejarto John M. Pezzuto Harry H.S. Fong 《Phytochemistry》1985,25(1):167-170
Three new furanoditerpenoids of the caesalpin-type have been isolated from the roots of Caesalpinia pulcherrima. The structures of these compounds, vouacapen-5α-ol, 6β-cinnamoyl-7β-hydroxy-vouacapen-5α-ol and 8,9,11,14-didehydrovouacapen-5α-ol, were elucidated through interpretation of their spectral data. Sitosterol was also obtained. 相似文献
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At least 104 nucleotides are transposed from the 5' terminus of the avian sarcoma virus genome to the 5' termini of smaller viral mRNAs. 总被引:17,自引:0,他引:17
Cells producing avian sarcoma virus (ASV) contain at least three virus-specific mRNAs, two of which are encoded within the 3' half of the viral genome. Each of these viral RNAs can hybridize with single-stranded DNA(cDNA5') that is complementary to a sequence of 101 nucleotides found at the 5' terminus of the ASV genome, but not within the 3' half of the genome. We proposed previously (Weiss, Varmus and Bishop, 1977) that this nucleotide sequence may be transposed to the 5' termini of viral mRNAs during the genesis of these RNAs. We now substantiate this proposal by reporting the isolation and chemical characterization of the nucleotide sequences complementary to cDNA5' in the genome and mRNAs of the Prague B strain of ASV. We isolated the three identified classes of ASVmRNA (38, 28 and 21S) by molecular hybridization; each class of RNA contained a "capped" oligonucleotide identical to that found at the 5' terminus of the ASV genome. When hybridized with cDNA5', each class of RNA gave rise to RNAase-resistant duplex hybrids that probably encompassed the full extent of cDNA5'. The molar yields of duplex conformed approximately to the number of virus-specific RNA molecules in the initial samples; hence most if not all of the molecules of virus-specific RNA could give rise to the duplexes. The duplexes prepared from the various RNAs all contained the capped oligonucleotide found at the 5' terminus of the viral genome and had identical "fingerprints" when analyzed by two-dimensional fractionation following hydrolysis with RNAase T1. In contrast, RNA representing the 3' half of the ASV genome did not form hybrids with cDNA5'. We conclude that a sequence of more than 100 nucleotides is transposed from the 5' end of the ASV genome to the 5' termini of smaller viral RNAs during the genesis of these RNAs. Transposition of nucleotide sequences during the production of mRNA has now been described for three families of animal viruses and may be a common feature of mRNA biogenesis in eucaryotic cells. The mechanism of transposition, however, and the function of the transposed sequences are not known. 相似文献
7.
D Y Mason J L Cordell A G Tse J J van Dongen C J van Noesel K Micklem K A Pulford F Valensi W M Comans-Bitter J Borst 《Journal of immunology (Baltimore, Md. : 1950)》1991,147(11):2474-2482
Recent evidence indicates that the transmembrane form of IgM on murine and human B lymphocytes is physically associated with at least two proteins, forming a disulfide-linked dimer, which may control cell surface expression of IgM and also play a role in signal transduction after Ag binding (by analogy with the TCR-associated CD3 components in T lymphocytes). We have used mAb and polyclonal antibodies against an intracytoplasmic epitope on one of these polypeptides (previously identified in murine B cells as the product of the B cell specific mb-1 gene) to study the distribution of the IgM-associated dimer in human cells. By immunocytochemical staining of normal and neoplastic B cells, we show that the human mb-1 protein appears early in B cell differentiation, probably before expression of cytoplasmic mu-chain, and persists until the plasma cell stage, where it is seen as an intracytoplasmic component. According to immunohistologic analysis of reactive lymphoid tissue and lymphoma samples, mb-1 protein is completely B cell specific. Anti-mb-1 also labels B cell areas in tissues from seven different mammalian species. Finally, the Ig-associated dimer could be isolated from human hairy-cell leukemia cells in high purity and yield by affinity chromatography using anti-mb-1 antibody. Mice immunized with this material have produced a strong polyclonal response, so that it should now be possible to prepare a panel of new mAb reactive with different epitopes on both mb-1 and on its associated polypeptide(s). 相似文献
8.
The membrane IgM-associated heterodimer on human B cells is a newly defined B cell antigen that contains the protein product of the mb-1 gene 总被引:6,自引:0,他引:6
C J van Noesel R A van Lier J L Cordell A G Tse G M van Schijndel E F de Vries D Y Mason J Borst 《Journal of immunology (Baltimore, Md. : 1950)》1991,146(11):3881-3888
7/8embrane IgM (mIgM) on human B lymphocytes is noncovalently associated with a disulfide-linked dimer that contains phosphoproteins of 47 and 37 kDa. In this study, the biochemical properties and the identity of these Ag receptor-associated components have been addressed. Both subunits carry N-linked carbohydrate groups. After deglycosylation, the 47-kDa and 37-kDa proteins have similar molecular masses, of about 23 kDa, and relatively acidic but different isoelectric points. The accumulated data, together with a previously performed comparison of tryptic peptides, suggest that the two components are structurally distinct and possibly encoded by different genes. Indeed, a mAb, raised against a synthetic peptide that was made on the basis of the published carboxyl-terminal amino acid sequence of the human mb-1 gene product, specifically reacted with the 47-kDa but not the 37-kDa subunit. None of the established B cell-specific mAb characterized in the Fourth International Workshop on Leukocyte Antigens, including CD24, CD37, and CD72, detect the mIgM-linked heterodimer, which makes it a newly defined human B cell Ag. 相似文献
9.
Treatment of PC12 and C6 cell cultures with recombinant basic fibroblast growth factor results in approximately a five to ten-fold stimulation of beta-amyloid precursor mRNA in the C6 astrocytoma cell line but only a slight induction of precursor mRNA in the PC-12 neuronal cell line. Stimulation of expression occurred at a hormone concentration of approximately 0.5 to 1 nM and was seen after 2 days. These results suggest that basic fibroblast growth factor may contribute to amyloidosis of Alzheimer's disease. 相似文献
10.
Preparation of peroxidase: antiperoxidase (PAP) complexes for immunohistological labeling of monoclonal antibodies 总被引:12,自引:0,他引:12
D Y Mason J L Cordell Z Abdulaziz M Naiem G Bordenave 《The journal of histochemistry and cytochemistry》1982,30(11):1114-1122
The production of mouse peroxidase:antiperoxidase (PAP) complexes suitable for immunohistological use in conjunction with monoclonal antibodies is described. Three approaches were explored: 1) production of conventional polyclonal PAP complexes; 2) conversion of rabbit PAP to "pseudo-mouse PAP" by incubation with monoclonal mouse anti-rabbit immunoglobulin; 3) formation of PAP complexes from monoclonal mouse antiperoxidase. PAP complexes prepared by the latter technique gave the best immunohistological labeling reactions, being stable on storage and compatible with a wide range of human monoclonal antibodies. Gel filtration revealed that monoclonal PAP is of lower molecular weight than conventional PAP complexes (fulfilling theoretical predictions based on the monospecificity of monoclonal antibodies). 相似文献