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1.
V. G. Borkhvardt 《Russian Journal of Developmental Biology》2000,31(3):154-161
The development of the fin and limb buds involves a balance of centrifugal (active) and centripetal (passive) mechanical forces,
the first of which acts to move the walls of these structures away from each other and the second of which holds them together.
When the volume of the mesodermal core increases, the generated force meets with the resistance of the basal membrane, and
as a result, the limb bud has a tendency to acquire a cylindrical shape. Collagen fibers, individual mesenchymal cells, and
their groups hold together the dorsal and the ventral wall of the limb bud, prevent the movement of these walls away from
each other, and in this way direct bud growth along the proximodistal and the anteroposterior axes. The balance of the forces
which stretch the ectodermal layer and those which constrain it has also been observed in the development of other body parts. 相似文献
2.
Ian R. Brown 《Journal of neurochemistry》1983,40(5):1490-1493
Abstract: Analysis of the cell-free translation products of polysomes isolated from fetal brain and other organs indicates that elevation of maternal body temperature induces the synthesis of a heat shock protein of molecular weight 74,000 (74K). The newborn mammal is particularly sensitive to induction of the 74K protein. As early postnatal development proceeds, higher body temperatures are required to induce synthesis of the 74K heat shock protein. 相似文献
3.
Chien-Hung Liu Wen-Ming Chen Jo-Shu Chang 《World journal of microbiology & biotechnology》2007,23(5):633-640
Acidic lipase finds its commercial values in medical applications and bioremediation of food wastes. In this work, approaches
for rapid screening of lipase-producing bacteria were developed and the feasibility assessment of the screening methods was
performed. From food waste samples, the proposed screening procedures allowed isolation of sixteen pure bacterial strains
expressing higher lipase activity at acidic pH (pH 6.0) than at alkaline pH (pH 9.0). To enhance the accuracy of lipase activity
determination under acidic conditions, a novel assay procedure was also developed by deactivating lipase activity by microwave
treatment prior to back titration. This additional step could minimize interferences arising from residual lipase activity
during conventional direct back-titration methods in measuring lipase activity at acidic pH. Using the four strategies proposed
in this work, the best acidic-lipase-producing isolate was obtained by strategy C (SSC) and was identified as Aeromonas sp. C14, displaying an optimal lipase activity of 0.7 U/ml at an acidic pH of 6.0. 相似文献
4.
Dicoumarol derivatives were synthesized in the InCl3 catalyzed pseudo three-component reactions of 4-hydroxycoumarin with aromatic aldehydes in excellent yields. The reactions were performed in water under microwave irradiation. All synthesized compounds were characterized using NMR, IR, and UV–Vis spectroscopy, as well as with TD-DFT. Obtained dicoumarols were subjected to evaluation of their in vitro lipid peroxidation and soybean lipoxygenase inhibition activities. It was shown that five of ten examined compounds (3e, 3h, 3b, 3d, 3f) possess significant potential of antilipid peroxidation (84–97%), and that compounds 3b, 3e, 3h provided the highest soybean lipoxygenase (LOX-Ib) inhibition (IC50 = 52.5 µM) and 3i somewhat lower activity (IC50 = 55.5 µM). The bioactive conformations of the best LOX-Ib inhibitors were obtained by means of molecular docking and molecular dynamics. It was shown that, within the bioactive conformations interior to LOX-Ib active site, the most active compounds form the pyramidal structure made of two 4-hydroxycoumarin cores and a central phenyl substituent. This form serves as a spatial barrier which prevents LOX-Ib Fe2+/Fe3+ ion activity to generate the coordinative bond with the C13 hydroxyl group of the α-linoleate. It is worth pointing out that the most active compounds 3b, 3e, 3h and 3i can be candidates for further examination of their in vitro and in vivo anti-inflammatory activity and that molecular modeling study results provide possibility to screen bioactive conformations and elucidate the mechanism of dicoumarols anti-LOX activity. 相似文献
5.
Summary The Bacillus subtilis cdd gene encoding cytidine/2-deoxycytidine deaminase has been located by transduction at approximately 225 degrees on the chromosome, and the gene order rpC-lys-cdd-aroD was established. The gene was isolated from a library of B. subtilis DNA cloned in D69 by complementation of an Escherichia coli cdd mutation. Minicell experiments revealed a molecular mass of 14000 dalton for the cytidine deaminase subunit encoded by the cloned DNA fragment. The molecular weight of the native enzyme was determined to be 58000, suggesting that it consists of four identical subunits. The nucleotide sequence of 1170 bp, including the cdd gene, was determined. An open reading frame encoding a polypeptide with a calculated molecular mass of 14800 dalton was deduced to be the coding region for cdd. The deduced amino acid composition of the 136-amino acid-long subunit shows that it contains six cysteine residues. A computer search in the GenBank DNA sequence library revealed that the 476 bp HindIII fragment containing the putative promoter region and the first ten codons of cdd is identical to the P43 promoter-containing fragment previously isolated by Wang and Doi (1984). They showed that the fragment contained overlapping promoters transcribed by B. subtilis 43 and 37 RNA polymerase holoenzymes during growth and stationary phase.Abbreviations SDS
sodium dodecyl sulphate
- Ap
ampicillin resistance
- Tetr
tetracycline resistance
- Kmr
kanamycin resistance 相似文献
6.
Gender difference in the relationship of performance in the handgrip and standing long jump tests to lean limb volume in young adults 总被引:1,自引:0,他引:1
B. N. Davies Elizabeth J. Greenwood S. R. Jones 《European journal of applied physiology and occupational physiology》1988,58(3):315-320
Groups of young, adult males and females performed the handgrip and standing long jump tests. Their total forearm and leg volumes were calculated from a series of circumference and length measurements, and the lean volumes (bone + muscle) calculated by taking the skinfold thickness into consideration. In the handgrip, the mean female performance was 298 N compared with 496 N for the males. In the standing long jump, mean performance expressed as distance x body mass was 87.3 kg.m for females compared with 137.7 kg.m for males. These superior performances of males could simply reflect their greater muscle mass, as the mean lean volumes of female and male limbs respectively were 0.54 l and 0.89 l for forearms, and 11.82 l and 14.82 l for the two legs. However, when the performances of males and females were grouped by lean limb volume, it was found that while in both tests there were linear relationships, males and females did not share a common line. In both tests the male relationship was at a higher level than the female; therefore, for a given lean volume, the male performance was significantly superior to that of the female. The gender difference found in this study has not been seen in other studies in which the performance of skeletal muscle has been related to the cross-sectional area of the active muscles and the possible reasons for the differences are considered. 相似文献
7.
Summary In order to study mitogenic control during axolotl limb regeneration, we have developed a primary blastema cell culture as a very sensitive bioassay for blastema mitogens. Transferrin, an iron-binding glycoprotein which has been shown to be the neurotrophic factor for muscle cells, is the mitogen which has been analysed in the present report. Addition of approximately 2 g human transferrin/ ml of serum-free culture medium enhances blastema cell proliferation 11-fold over control levels and 2-fold over that produced by the addition of nerve extracts or purified growth factors extracted from nerve tissues (basic and acidic fetal growth factor, FGF). At a higher concentration (20 g/ml), transferrin alone has no mitogenic effect unless the medium is also supplemented with FeCl3 (100 M). The results are discussed with regard to the sensitivity of the blastema cell culture bioassay and in the context of the neurotrophic theory of urodele limb regeneration. 相似文献
8.
Fully adult partial skeletons attributed to Australopithecus afarensis (AL 288-1, “Lucy”) and to Homo habilis (OH 62, “Lucy's child”), respectively, both include remains from upper and lower limbs. Relationships between various limb bone dimensions of these skeletons are compared to those of modern African apes and humans. Surprisingly, it emerges that OH 62 displays closer similarities to African apes than does AL 288-1. Yet A. afarensis, whose skeleton is dated more than 1 million years earlier, is commonly supposed to be the ancestor of Homo habilis. If OH 62, classified as Homo habilis by its discoverers, does indeed represent a stage intermediate between A. afarensis and later Homo, a revised interpretation of the course of human evolution would be necessary. 相似文献
9.
Shingo Kurabuchi 《Development genes and evolution》1992,201(6):376-382
Summary The relationship between the size and shape of regenerative outgrowth and the quantity of innervation was studied in adult Xenopus laevis. The forelimbs, of which the nerve supply was artificially altered, were amputated midway through the stylopodium and were kept for 1 year. The regenerative outgrowths that formed in normal limbs with an intact nerve supply were mainly spike-shaped and occasionally rod-shaped. However, when the nerve supply to the distal part of the forelimb was augmented by surgically diverting ipsilateral sciatic nerve bundles, the quantity of innervation was increased to about two and a half times that of the normal limb. These hyperinnervated outgrowths were somewhat larger than those of the normally innervated outgrowths and the majority of them were oar-shaped, a type hardly ever encountered in normal regeneration. In contrast, when partial denervation was performed concomitantly with limb amputation, by ablation of the N. radialis at the shoulder joint, the quantity of innervation decreased to about one half that of the normal limb. The outgrowths obtained were spike-shaped in all cases, with their size being about half that of the normally innervated outgrowths. Furthermore, when both the N. radialis and N. ulnaris were ablated in the same way, the amputated limbs were mostly non-regenerative, but some of them regenerated small conical outgrowths. Based on these results, a discussion is presented concerning the relationship between a regenerative outgrowth and the innervation of the forelimb in Xenopus. 相似文献
10.
Male, Fischer strain 344 adult rats were given various doses (25-100 mg/kg) of p,p'-DDT by oral gavage, and levels of biogenic amines, their metabolites, and amino acid neurotransmitters, tremor activity, and rectal temperature were measured at several intervals (2, 5, 12, and 24 h) after dosing. Dose-related increases in rectal temperature and in tremor activity were observed at 50-100 mg/kg 12 h after dosing. Tremorigenic doses of DDT increased the 5-hydroxyindoleacetic acid (5-HIAA) level in hypothalamus, brainstem, and striatum, whereas doses of 75 and 100 mg/kg increased the 3-methoxy-4-hydroxyphenylglycol (MHPG) level in hypothalamus and brainstem and the 3,4-dihydroxyphenylacetic acid level in striatum. Six amino acids were assayed in the brainstem, hypothalamus, and striatum; aspartate and glutamate levels were increased only in brainstem at 25-100 mg/kg. No consistent changes in concentrations of taurine, glutamine, glycine, or gamma-aminobutyric acid were observed in any of the regions assayed. Time-related increases in rectal temperature were seen 2-12 h after dosing, and the presence of tremor was observed 5-12 h after dosing; for both the time of peak effect was at 12 h. The DDT-induced hyperthermia and tremor were associated with dose- and time-related increases in levels of 5-HIAA, MHPG, aspartate, and glutamate. It is suggested that an increase in the turnover rate of 5-hydroxytryptamine (5-HT) may be responsible for the DDT-induced hyperthermia, whereas increases in the metabolism of 5-HT and norepinephrine may be involved in the tremor. 相似文献