Isolation of mouse FM3A cell mutants with thermolabile thymidylate synthetase by resistance to aphidicolin

Of 625 aphidicolin-resistant clones selected at 33.5°C from mutagenized mouse FM3A cells, 13 clones could not grow at 39.5°C. Five of these clones, chosen at random, resumed growth at 39.5°C when thymidine was added to the culture medium. In hybrids, conditional thymidine auxotrophy was a recessive trait, but aphidicolin-resistance was either a codominant or recessive one depending on the mutant clone used.Thymidylate synthetase activity in crude extracts of these mutants was completely inactivated by preincubation for 30 min at 42°C, whereas that of the parent cells was not affected by the same treatment. Thus, the temperature-sensitive growth of the mutants described here seems to be due to this heat-sensitive thymidylate synthetase.     

Association of Allergic Symptoms with Dengue Infection and Severity: A Systematic Review and Meta-analysis

The relationship between the severity of dengue infection and allergy is still obscure. We conducted an electronic search across 12 databases for relevant articles reporting allergic symptoms, dengue infection, and dengue classification. These studies were categorized according to dengue severity and allergy symptoms, and a meta-analysis was performed by pooling the studies in each category. Among the included 57 articles, pruritus was the most common allergic sign followed by non-specified allergy and asthma(28.6%, 13%, and 6.5%, respectively). Despite the reported significant association of dengue with pruritus and total Ig E level(P \ 0.05), in comparison with non-dengue cases and healthy controls, there was no association between the different severe dengue group with pruritus, skin allergy, food allergy or asthma. However,removing the largest study revealed a significant association between asthma with dengue hemorrhagic fever(DHF) rather than dengue fever(DF). In comparison with DF, DHF was associated with Ig E positivity. Furthermore, specific-Ig E level was higher in secondary DF rather than primary DF. There was a possible association between allergy symptoms and dengue severity progression. Further studies are needed to clarify this association.     

Large-scale EST sequencing in rice

Large-scale cDNA analysis provides several great advantages for genome investigations in rice. Isolated and partially characterized cDNA clones have contributed not only to the construction of an RFLP linkage map and physical maps of the chromosomes but also to investigations of the mechanisms of expression of various isozymes and family genes. The ultimate aim of our large-scale cDNA analysis is to catalogue all the expressed genes of this important cereal, including tissue-specific, developmental stage-specific, and stress-specific genes. As of August 1996, the Rice Genome Research Program (RGP) has isolated and partially sequenced more than 29000 cDNA clones from various tissues and calluses in rice (Nipponbare, a japonica variety). The sequence data were translated into amino acid sequences for the 3 possible reading frames, and the similarity of these amino acid sequences to known proteins registered in PIR were examined. About 25% of the clones had significant similarities to known proteins. Some of the hit clones showed library-specific distributions, indicating that the composition of the clones in each library reflects, to some extent, the regulation of gene expression specific to differentiation, growth condition, or environmental stress. To further characterize the cDNA clones, including unknown clones, nucleotide sequence similarities of 24728 clones were analyzed and the clones were classified into around 10000 independent groups, suggesting that around a half or one third of expressed genes in rice have already been captured. These results obtained from our large-scale cDNA analysis provide useful information related to gene expression and regulation in rice.     

Starvation-responsive glycine-rich protein gene in the silkworm Bombyx mori

Four glycine-rich protein (GRP) genes were identified from expressed sequence tags of the maxillary galea of the silkworm. All four genes were expressed in the maxillary pulp, antenna, labrum, and labium, but none of the genes were expressed in most internal organs. Expression of one of the genes, termed bmSIGRP, was further increased approximately fivefold in the mouth region (including the maxilla, antenna, labrum, labium, and mandible) after 24 h of starvation. bmSIGRP expression peaked at 24 h and gradually declined during the subsequent 2 days. When a synthetic diet not containing proteins was fed, bmSIGRP expression increased significantly in the mouth region to levels similar to that observed in starved larvae. Synthetic diets that lacked vitamins or salts but contained amino acids did not significantly affect bmSIGRP expression. These results suggest that amino acid depletion increases bmSIGRP expression.     

The primary structure of human EGF produced by genetic engineering, studied by high-performance tandem mass spectrometry

The primary structure of human epidermal growth factor (hEGF), which was produced by Escherichia coli using recombinant DNA technique, has been studied by tandem mass spectrometry. The molecular weight of hEGF (about 6200 amu) was determined by fast atom bombardment mass spectrometry. Then reduced and carboxymethylated hEGF was digested by chymotrypsin into seven peptides which could cover the whole sequence of hEGF. The amino acid sequences of five of these seven peptides could be confirmed by tandem mass spectrometry with or without isolation by high-performance liquid chromatography (HPLC). After isolation by HPLC, the other two peptides were digested with trypsin or thermolysin into small peptides, and sequenced by tandem mass spectrometry.     

Fatty acid ethyl esters in the liverwort Conocephalum conicum

A series of fatty acid ethyl esters ranging from C₁₄ to C₂₄ was isolated from a hexane extract of the liverwort Conocephalum conicum, these esters accounted for 77% of the extract. The ethyl esters consisting of even-numbered fatty acids were predominant and ethyl palmitate was the major constituent.     

DNA strand scission by neocarzinostatin: molecular recognition process responsible for site-specificity

A series of hexanucleotides possessing A-T, G-C, inosine (I)-C and 2-aminoadenine (ANH2)-T base pairs at 5'-side of the target thymine were prepared and their selectivity for C-5' and C4' oxidation in the NCS-mediated degradation was investigated. Quantitative product analysis indicated that preferential C5' oxidation of deoxyribose moiety of the target T occurs at -5'-AT- and 5'-IT- sites, whereas C5' and C4' oxidation occurs competitively at T of -5'-GT- and -5'-ANH2T- sites. Based on the experimental results, an intercalation model that permits competitive hydrogen abstraction from C5' and C4' of deoxyribose moiety has been proposed.     

The transition in frequency of Y chromatin in males during the neonatal period

Summary The frequency of Y chromatin, visualized as fluorescent bodies in cell nuclei from lymphocytes in blood smears, was signficantly less in newborn males than in three-month-old male infants and adults. The frequency of Y chromatin-positive cells on day 0 was 36.16±9.11% and then increased daily. At one month after birth the frequency was 55.07±9.29%, which was not significantly different from that in adult males (57.08±5.97%).