Solution-state structure by NMR of zinc-substituted rubredoxin from the marine hyperthermophilic archaebacterium Pyrococcus furiosus

The three-dimensional solution-state structure is reported for the zinc-substituted form of rubredoxin (Rd) from the marine hyperthermophilic archaebacterium Pyrococcus furiosus, an organism that grows optimally at 100 degrees C. Structures were generated with DSPACE by a hybrid distance geometry (DG)-based simulated annealing (SA) approach that employed 403 nuclear Overhauser effect (NOE)-derived interproton distance restraints, including 67 interresidue, 124 sequential (i-j = 1), 75 medium-range (i-j = 2-5), and 137 long-range (i-j > 5) restraints. All lower interproton distance bounds were set at the sum of the van Der Waals radii (1.8 A), and upper bounds of 2.7 A, 3.3 A, and 5.0 A were employed to represent qualitatively observed strong, medium, and weak NOE cross peak intensities, respectively. Twenty-three backbone-backbone, six backbone-sulfur (Cys), two backbone-side chain, and two side chain-side chain hydrogen bond restraints were include for structure refinement, yielding a total of 436 nonbonded restraints, which averages to > 16 restraints per residue. A total of 10 structures generated from random atom positions and 30 structures generated by molecular replacement using the backbone coordinates of Clostridium pasteurianum Rd converged to a common conformation, with the average penalty (= sum of the square of the distance bounds violations; +/- standard deviation) of 0.024 +/- 0.003 A2 and a maximum total penalty of 0.035 A2. Superposition of the backbone atoms (C, C alpha, N) of residues A1-L51 for all 40 structures afforded an average pairwise root mean square (rms) deviation value (+/- SD) of 0.42 +/- 0.07 A. Superposition of all heavy atoms for residues A1-L51, including those of structurally undefined external side chains, afforded an average pairwise rms deviation of 0.72 +/- 0.08 A. Qualitative comparison of back-calculated and experimental two-dimensional NOESY spectra indicate that the DG/SA structures are consistent with the experimental spectra. The global folding of P. furiosus Zn(Rd) is remarkably similar to the folding observed by X-ray crystallography for native Rd from the mesophilic organism C. pasteurianum, with the average rms deviation value for backbone atoms of residues A1-L51 of P. furiosus Zn(Rd) superposed with respect to residues K2-V52 of C. pasteurianum Rd of 0.77 +/- 0.06 A. The conformations of aromatic residues that compose the hydrophobic cores of the two proteins are also similar. However, P. furiosus Rd contains several unique structural elements, including at least four additional hydrogen bonds and three potential electrostatic interactions.(ABSTRACT TRUNCATED AT 400 WORDS)

[Effect of anoxia on the growth of cultured neurons from embryonic chick forebrain]

Pure neurons from embryonic day 8 chick forebrain were cultured under anoxic condition (95% N2 and 5% CO2). After 24, 48 and 72 h in culture, MTT colorimetric microassay showed a reduced production of formazan, indicating that the neurons were seriously damaged. In addition, the glucose of the cultured media was significantly depleted. Even when glucose concentration was increased to 800-1,200 mg/100 ml, anoxia still caused neurons to die. The results indicate that brain neurons in embryo are sensitive to anoxia, and any protective influence of glia on anoxic neurons could not be mediated by supplying the latter with glycogen.

Spatial relationship of nebulin relative to other myofibrillar proteins during myogenesis in embryonic chick skeletal muscle cells in vitro

The developmental expression of nebulin was studied in embryonic chick skeletal muscle cells in vitro by means of immunofluorescence microscopy. Initially nebulin appeared homogeneously or in a punctate form in the cytoplasm, and then it was assembled into I-Z-I-like complexes containing actin and alpha-actinin but not myosin and connectin (titin). Striated patterns of nebulin ('singlets') in myofibrils appeared simultaneously with those of alpha-actinin (Z-bands), myosin (A-bands) and connectin ('doublets'), but earlier than those of actin. After actin striations were formed as myofibrils matured, each nebulin band started to exhibit 'droplets'. The delayed development of nebulin compared to the I-Z-I brush formation and the myofibril maturation seems to indicate that this giant myofibrillar protein is unnecessary for both the initial (formation of I-Z-I-like structures) and the subsequent (regular alignment of myofibrils) phases of myofibrillogenesis.

Influence of flexion-extension motion of lumbar spine on lumbosacral dural sac. An experimental study

To analyze the effects of flexion-extension motion of lumbar spine on the position and shape of lumbosacral dural sac, 10 flexion/extension lateral myelograms of cadaver specimens of normal lumbar spine were measured. The results showed that moving from flexion to extension both sagittal diameter and length of the dural sac decreased significantly, the dural sac moved caudally, and the sagittal diameter of the anterior epidural space decreased in the mid-vertebral level but increased in the intervertebral level. The dynamic changes of the dural sac and their influence factors and clinical relevance were discussed.

The effect of intrauterine devices (stainless steel ring, copper-T220 and levonorgestrel) on the DNA content in isolated human endometrial cells

The effect of three different intrauterine devices on the DNA content in human endometrial cells has been studied in 29 women before and after the insertion of an IUD; a stainless steel ring (9 subjects), Copper-T220 (11 subjects) and a medicated IUD releasing levonorgestrel at a rate of 2 micrograms/day (9 subjects). The material was grouped into "bleeders" (having more than 8 days of bleeding and spotting per month) and "non-bleeders" (having less than 8 days of bleeding and spotting per month). The DNA content was assessed on isolated endometrial cells smeared from thin biopsies and the amount of DNA per cell nucleus was measured by means of a Feulgen microspectrophotometric method. No significant difference was found between the "bleeders" and the "non-bleeders" as to the DNA content. Nevertheless, when the total number of subjects were pooled together, a significant increase in the DNA content was found in the post-insertion specimens in the groups of women using the SS and the T-Cu IUDs. Furthermore, a significant decrease in the DNA content was also found when the specimens obtained after the insertion of the LNG IUD were compared with those obtained after 24 months' use of the stainless steel ring and the Copper-T220 device (p less than 0.01 and p less than 0.002, respectively). It is concluded that the insertion of an inert IUD or an T-Cu IUD, induces significant alterations in the DNA content of the human endometrium adjacent to the device, whereas the use of the LNG device does not significantly modify the DNA synthesis when used for 3-10 months. No correlation was found between the DNA content per cell and the number of days of bleeding and spotting.

The effect of flexion-extension motion of the lumbar spine on the capacity of the spinal canal. An experimental study

The symptoms of lumbar spinal stenosis are often posture-dependent, and it is generally accepted that the capacity of the spinal canal is affected by flexion-extension motions of the lumbar spine. A study of spinal capacity in flexion-extension of ten cadaver specimens on the lumbar spine was done and measurements were obtained from the flexion-extension lateral myelograms. There proved to be a larger capacity of dural sac of 3.5 to 6.0 ml (4.85 +/- 0.75 ml) in flexion than in extension, and the differences were highly significant (P less than 0.001). In addition, the sagittal diameter of the dural sac and the length of the spinal canal increased from extension to flexion. Because of the effect of flexion-extension motion of the lumbar spine on the spinal capacity, we suggest that maintaining the lumbar spine in flexion is more suitable since spinal canal capacity is enlarged and symptoms may be mitigated.

[Comparison of promoting the proliferation and fusion of myoblast between conditioned media from fibroblasts of chick embryo and fetal mouse]

Conditioned media were prepared by using the collected media which had cultured fibroblasts from muscle tissue of fetal mouse (ICR) or chick embryo (Leghorn chicken). The effects of these media on the proliferation and fusion in mouse or chick myoblast were studied quantitatively. The results were as follows: (1) the conditioned medium from fibroblasts of fetal mouse promoted the proliferation of mouse or chick embryonic myoblasts by 2.65 times (P less than 0.001) or 2.35 times (P less than 0.01) as compared with control groups respectively. (2) The conditioned medium from fibroblasts of embryonic chicken promoted the proliferation of chick or mouse embryonic myoblasts by 2.66 times (P less than 0.01) or 2.17 times (P less than 0.01) respectively. (3) The conditioned medium from fibroblasts of fetal mouse enhanced the fused rate of mouse or chick myoblasts by 1.9 or 2.6 times respectively. The conditioned medium from fibroblasts of embryonic chick enhanced the rate of chick myoblast fusion by 2.1 times, but the effect on the mouse myoblast fusion was not remarkable. The results suggest that the effect of fibroblast conditioned media on myoblast proliferation is similar in the two species, but the effect on the fusion of myoblasts is somewhat species-specific.

[Comparison of the development between the satellite cells of ALD and PLD muscles of adult chicken in vitro]

Satellite cells isolated from the anterior (slow) and posterior (fast) latissimus dorsi of adult chick were cultured separately in the absence of neural factors. The cells were observed under an inverted phase contrast microscope every day. The morphological changes of satellite cells, described by other workers, were seen in these cultures. Furthermore, the difference in the time course of development of the satellite cells from different muscles was found. That is, the transformation of the satellite cells of PLD into the myoblasts and the fusion of the latter delayed about 24 h as compared with ALD. The results support the idea that there may be an intrinsic developmental tendency in the myogenic cells of bird, since it proved possible to see the difference of the myogenic cells even in mononuclear phase.

Suture and immobilization of acute peripheral injuries of the meniscus in rabbits

A comparative study of suturing or nonsuturing with or without immobilization of acute peripheral injuries to the medial meniscus of rabbits is reported. Artificial injuries to both knees of 44 male China Blue-Violet rabbits were sutured or left unsutured. One knee joint of each rabbit was immobilized postoperatively for 6 weeks. The maximum breaking strength was measured, pathologic examinations were performed, and healed areas were measured. The results showed that there was greater healed area, higher maximum breaking strength, earlier matured scar tissue formation, and more regular fiber alignment in the treatment groups with simple immobilization of the knee joint. These results were superior to suturing plus immobilization, suggesting that external immobilization of the knee joint is the key to the treatment of acute peripheral injuries of the meniscus. It may be the procedure of choice for clinical orthopedists dealing with such injuries. The measurement of the meniscus healed area and maximum breaking strength and the use of new material with this method of immobilization were introduced by the authors.