REGULATORY ROLE OF 20-HYDROXYECDYSONE ON HUMORAL IMMUNITY IN THE PUPAE OF THE INDIAN SILKWORM,PHZLOSAMIA CYNTHIA RICINI*

Abstract The present study shows that 20-hydroxyecdysone(20-OHE) participates in the humoral immune responses of Philosamia Cynthia ricini, either normal or debrained pupae, to the E. coli. The mode of action of 20—-OHE is multiple. It raises hemolymph protein content, makes antibacterial proteins be produced, increases lysozyme activity, and activates prophenoloxidase system. It is possible that several immune control systems are involved.     

Tagging and mapping the thermo-sensitive genic male-sterile gene in rice (Oryza sativa L.) with molecular markers

The thermo-sensititve genic male-sterile (TGMS) gene in rice can alter fertility in response to temperature and is useful in the two-line system of hybrid rice production. However, little is known about the TGMS gene at the molecular level. The objective of this study was to identify molecular markers tightly linked with the TGMS gene and to map the gene onto a specific rice chromosome. Bulked segregant analysis of an F₂ population from 5460s (a TGMS mutant line) x Hong Wan 52 was used to identify RAPD markers linked to the rice TGMS gene. Four hundred RAPD primers were screened for polymorphisms between the parents and between two bulks representing fertile and sterile plants; of these, 4 primers produced polymorphic products. Most of the polymorphic fragments contained repetitive sequences. Only one singlecopy sequence fragment was found, a 1.2-kb fragment amplified by primer OPB-19 and subsequently named TGMS1.2. TGMS1.2 was mapped on chromosome 8 with a RIL population and confirmed by remapping with a DHL population. Segregation analysis using TGMS1.2 as a probe indicated that TGMS1.2 both consegregated and was lined with the TGMS gene in this population. It is located about 6.7 cM from the TGMS gene. As TGMS1.2 is linked to the TGMS gene, the TGMS gene must be located on chromosome 8.This research was supported by the Rockefeller Foundation and China National High-Tech Research and Development Program. The first author is a Rockefeller Career Fellow at Texas Tech University     

Mutational analysis of Saccharomyces cerevisiae U4 small nuclear RNA identifies functionally important domains.

U4 small nuclear RNA (snRNA) is essential for pre-mRNA splicing, although its role is not yet clear. On the basis of a model structure (C. Guthrie and B. Patterson, Annu. Rev. Genet. 22:387-419, 1988), the molecule can be thought of as having six domains: stem II, 5' stem-loop, stem I, central region, 3' stem-loop, and 3'-terminal region. We have carried out extensive mutagenesis of the yeast U4 snRNA gene (SNR14) and have obtained information on the effect of mutations at 105 of its 160 nucleotides. Fifteen critical residues in the U4 snRNA have been identified in four domains: stem II, the 5' stem-loop, stem I, and the 3'-terminal region. These domains have been shown previously to be insensitive to oligonucleotide-directed RNase H cleavage (Y. Xu, S. Petersen-Bjørn, and J. D. Friesen, Mol. Cell. Biol. 10:1217-1225, 1990), suggesting that they are involved in intra- or intermolecular interactions. Stem II, a region that base pairs with U6 snRNA, is the most sensitive to mutation of all U4 snRNA domains. In contrast, stem I is surprisingly insensitive to mutational change, which brings into question its role in base pairing with U6 snRNA. All mutations in the putative Sm site of U4 snRNA yield a lethal or conditional-lethal phenotype, indicating that this region is important functionally. Only two nucleotides in the 5' stem-loop are sensitive to mutation; most of this domain can tolerate point mutations or small deletions. The 3' stem-loop, while essential, is very tolerant of change. A large portion of the central domain can be removed or expanded with only minor effects on phenotype, suggesting that it has little function of its own. Analysis of conditional mutations in stem II and stem I indicates that although these single-base changes do not have a dramatic effect on U4 snRNA stability, they are defective in RNA splicing in vivo and in vitro, as well as in spliceosome assembly. These results are discussed in the context of current knowledge of the interactions involving U4 snRNA.     

Distinct Requirements for Somatic and Germline Expression of a Generally Expressed Caernorhabditis Elegans Gene

In screening for embryonic-lethal mutations in Caenorhabditis elegans, we defined an essential gene (let-858) that encodes a nuclear protein rich in acidic and basic residues. We have named this product nucampholin. Closely homologous sequences in yeast, plants, and mammals demonstrate strong evolutionary conservation in eukaryotes. Nucampholin resides in all nuclei of C. elegans and is essential in early development and in differentiating tissue. Antisense-mediated depletion of LET-858 activity in early embryos causes a lethal phenotype similar to characterized treatments blocking embryonic gene expression. Using transgene-rescue, we demonstrated the additional requirement for let-858 in the larval germline. The broad requirements allowed investigation of soma-germline differences in gene expression. When introduced into standard transgene arrays, let-858 (like many other C. elegans genes) functions well in soma but poorly in germline. We observed incremental silencing of simple let-858 arrays in the first few generations following transformation and hypothesized that silencing might reflect recognition of arrays as repetitive or heterochromatin-like. To give the transgene a more physiological context, we included an excess of random genomic fragments with the injected DNA. The resulting transgenes show robust expression in both germline and soma. Our results suggest the possibility of concerted mechanisms for silencing unwanted germline expression of repetitive sequences.     

Altering Developmental Trajectories in Mice by Restricted Index Selection

A restricted index selection experiment on mice was carried out for 14 generations on rate of early postnatal development (growth rate from birth to 10 days of age) vs. rate of development much later in ontogeny (growth rate from 28 to 56 days of age). Early rate of development (E) approximates hyperplasia (changes in cell number) and later rate (L) reflects hypertropy (changes in cell size). The selection criteria were as follows: E+L0 was selected to increase early body weight gain while holding late body weight gain constant; E-L0 was selected to decrease early body gain while holding late gain constant; E0L+ was selected to increase late gain holding early gain constant; and E0L- was selected to decrease late gain holding early gain constant. After 14 generations of selection, significant divergence among lines has occurred and the changes in the growth trajectories are very close to expectation. The genetic and developmental bases of complex traits are discussed as well as the concept of developmental homoplasy.     

Aggregation of β-Amyloid Peptide Is Promoted by Membrane Phospholipid Metabolites Elevated in Alzheimer's Disease Brain

Abstract: Increased amounts of β-amyloid (Aβ) peptide deposits are found in Alzheimer's disease brain. These amyloid deposits have been implicated in the pathophysiology of this common dementing illness. Aβ peptides have been shown to be toxic to neurons in cell culture, and this toxicity is critically dependent on the aggregation of the peptide into cross-β-pleated sheet fibrils. Also, in vivo and postmortem NMR studies have shown changes in certain brain membrane phospholipid metabolites in normal aging and more extensive alterations in patients with Alzheimer's disease. The finding that membrane phospholipids affect the aggregation of Aβ suggests that the abnormalities in membrane metabolism found in Alzheimer's disease could affect the deposition of Aβ in vivo. Therefore, we examined the effect of membrane phospholipid metabolites that are altered in Alzheimer's disease brain on the aggregation of Aβ(1–40) using a light scattering method. Certain metabolites (glycerophosphocholine, glycerophosphoethanolamine, and α-glycerophosphate) augment the aggregation of Aβ. Other membrane phospholipid metabolites (phosphocholine, phosphoethanolamine, and inositol-1-phosphate) have no effect. We conclude that increased membrane phospholipid metabolite concentrations may play a role in the deposition of Aβ seen in normal aging and the even greater deposition of Aβ observed in Alzheimer's disease.     

Involvement of the fastigial nuclei in vagally mediated respiratory responses

Xu, Fadi, and Donald T. Frazier. Involvement of thefastigial nuclei in vagally mediated respiratory responses.J. Appl. Physiol. 82(6):1853-1861, 1997.Previous studies have demonstrated that thecerebellum, especially the fastigial nucleus (FN), is capable ofmodulating respiratory responses to chemical and mechanical stimuli.Because there is evidence to show projections from vagal afferents tothe FN, the goal of this study was to determine the role of the FN inthe respiratory reflexes elicited by activation of vagal afferents.Experiments were performed in anesthetized (chloralose), paralyzed, andartificially ventilated cats with an occipital exposure of thecerebellum. Administration of capsaicin (Cap; 5-10 µg/kg) viathe right external jugular vein at the end of inspiration andapplication of lung inflation (LI; 10 cmH₂O) during inspiration werecarried out to stimulate nonmyelinated and myelinated vagal afferents,respectively. The phrenic neurogram was recorded as anindex of the respiratory motor output. Control cardiorespiratoryvariables [expiratory duration(TE), arterial bloodpressure] and their immediate responses to stimuli were comparedbefore and after bilateral lesions of the FN. The results showed thefollowing. 1) Capinjection and LI resulted in a dramatic increase inTE (apnea).2) FN lesions did not significantlyalter the control TE; however,the apneic duration induced by Cap injection was prolonged.3) Neither FN lesions norcerebellectomy affected the apneic duration that resulted fromapplication of LI. 4) Cold blockadeof the vagi (6-8°C) eliminated the respiratory responses elicited by LI but not Cap injection; vagotomy abolished the responses to both stimuli. 5) FN lesions didnot change the control ABP or its responses to either LI or Capinjection. It is concluded that the FN is involved in vagally mediatedrespiratory reflexes elicited by activation of nonmyelinated (C-fiber)vagal afferents.

     

Evidence for two unlinked loci regulating total serum IgE levels.

Studies investigating the genetic control of total serum IgE levels are of major importance in understanding basic pathophysiologic mechanisms in atopy and asthma, since IgE levels predict onset and correlate with the clinical expression of these disorders. Previous analysis of data from 92 families, ascertained through a parent with asthma, showed evidence for recessive inheritance of high IgE levels with linkage to chromosome 5q. Since there was significant residual familial correlation in the one-locus segregation analysis, two-locus segregation and linkage analyses were performed. Segregation analyses provided evidence for a second major locus unlinked to the locus on 5q. Utilization of this two-locus model corroborates the previous evidence for linkage between this trait and markers on 5q31-q33. The LODs for the most informative marker D5S436 increased from 3.00 at 10% recombination to 4.67 at 9% recombination, when the two-locus model was used. Additional linkage studies are needed to map this second locus. These results demonstrate the importance of performing multilocus segregation and linkage analyses for quantitative traits that are related to the phenotype of a complex disorder. This approach has given further insight into the genetics of allergy and asthma by providing evidence for a two-locus model.     

在96孔板中进行抗脂质过氧化的微量测定

以Fe²⁺/半胱氨酸诱导大鼠肝微粒体为基本模型,根据硫代巴比妥酸(TBA)反应原理,优化不同反应条件,建立了一种在96孔板上进行抗脂质过氧化测定的一步反应方法,该方法的灵敏度不低于传统的试管法,而且还具有微量、快速、简便等优点,特别适用于大规模筛选和研究抗氧化剂.此外,也可用于其它系统诱导的抗脂质过氧化的测定.