Effects of electromagnetic stimuli on bone and bone cells in vitro: inhibition of responses to parathyroid hormone by low-energy low-frequency fields

Low-energy electromagnetic fields pulsed at frequencies of 10-90 Hz significantly increase healing of chronic fracture nonunions in man. These fields are effective at tissue current levels several orders of magnitude lower than those required for transmembrane depolarization of normal cells. We have examined the effects of two clinically used pulsed electromagnetic fields on cultures of the osteoblast-like mouse bone cell line MMB-1. Both fields significantly reduced cellular production of cAMP in response to parathyroid hormone and osteoclast activating factor. Neither basal nor fluoride-activated levels of adenylate cyclase were altered in membranes from cells cultured in the fields; however, the same membrane preparations exhibited markedly inhibited responses to parathyroid hormone. The fields blocked the inhibitory effects of the hormone on collagen synthesis by MMB-1 cells. However, there was no effect on the inhibition of collagen synthesis by 1,25-dihydroxyvitamin D(3), which is believed to act primarily by a nuclear, rather than by a membrane-dependent, mechanism. No significant differences were noted between effects of the two fields, one generating continuous pulse trains (72 Hz) and the other generating recurrent bursts (15 Hz) of shorter pulses. We hypothesize that these field effects are mediated primarily at the plasma membrane of osteoblasts, either by interference with hormone-receptor interactions or by blocking of receptor-cyclase coupling in the membrane. These responses occurred with induced extracellular fields of 1 mV/cm or less, even though transmembrane potential gradients are typically 10(5) V/cm.

Ultrastructure of a histaminergic synapses in Aplysia

The ultrastructure of histaminergic synaptic terminals was studied by the means of intrasomatic injection of horseradish peroxidase into the identified histaminergic neuron C2 of Aplysia. The axonal tree of C2 was found to consist, in part, of varicosities that display putative release sites similar in morphology to those described in other neurons in Aplysia. The varicosities contain at least two populations of vesicles: a conspicuous class of of large vesicles with an electron-dense core that almost fills the entire vesicle and a heterogeneous class of large and small electron-lucent vesicles. The small lucent vesicles preferentially cluster near active zones.

Colorectal cancer and schistosomiasis

The risk of colorectal cancer is known to be increased in patients with long-standing schistosomal colitis. A retrospective review of clinical data and surgical specimens from 60 patients with schistosomal granulomatous disease of the large intestine but without carcinoma demonstrated that 36 of them had mild to severe grades of colonic epithelial dysplasia. This was either focal or diffuse in distribution and occurred in flat mucosa, in pseudopolyps, or in regenerating epithelium at the edges of ulcers. These dysplastic changes are regarded as the pathological basis for the malignant potential of schistosomal colitis, and they resemble the changes found in long-standing chronic ulcerative colitis.

[A case report of variant form of multiple myeloma]

Multiple myeloma is usually manifested with multiple destructive bone lesion, plasmacytosis and monoclonal protein. Here in we report a case of IgA (lambda) multiple myeloma with hepatomegaly and anemia but without bone lesions. Differential diagnostic points among lymphoma, amyloidosis, cancer and heavy chain disease are discussed.

Newcastle disease virus in Taiwan: II, Relationship between polykaryocytosis and virus virulence

Fifteen selcted local isolates and five known Newcastle disease virus strains were examined for their cytopathic effects in chick embryo kidney (CEK) cells, egg-infectious units in chick embryos (CE), virulence by mean death time, intracerebral and intravenous pathogenicity indexes for CE and chicks, and ability to cause polykaryocytosis of fusion from within (FFWI) or fusion from without (FFWO) in CEK and BHK-21 monolayer cells. The capacity of the different virus strains to induce cell FFWI at 15 hr post-infection was related to their virulence for CE and chicks, but cell FFWO did not seem to be any relationship with the virulence of the strains.

Raman spectra of ten aqueous transfer RNAs and 5S RNA. Conformational comparison with yeast phenylalanine transfer RNA

Eleven native transfer RNAs have been prepared so as to maintain their Mg2+ content. Their aqueous Raman spectra show a high, relatively constant amount of order in the ribophosphate backbone, as indicated by the ratio 1.73 +/- 0.05 for I814/I1100 in all samples. Variation in the effectiveness of stacking of guanine and adenine bases is seen, though most of the transfer RNAs studied have a comparable degree of stacking to that found in phenylalanine transfer RNA from yeast, whose tertiary structure has been determined by X-ray crystallography. The spectrum of Escherichia coli 5S RNA indicates that the stacking efficiency of the guanine bases is much higher in 5S RNA than in yeast in phenylalanine transfer RNA, while that of the adenine bases is lower.

The incidence of HLA-SD antigens in recessive retinitis pigmentosa

Eighteen patients with recessive retinitis pigmentosa were tissue typed for HLA-SD antigens. There was no evidence that a particular HLA-SD antigen was associated with autosomal recessive retinitis pigmentosa.

Laser Raman spectroscopic studies of the thermal unfolding of ribonuclease A

The reversible thermal denaturation of bovine pancreatic ribonuclease A at pH 5 in 0.1 M NaCl over the range 32-70 degrees C as studied by Raman spectroscopy proceeds in a gradual manner consistent with a stepwise unfolding process rather than as a transition between two states. Conversion of residues from helical or pleated-sheet geometry to some intermediate geometry, as followed by means of the amide I and III lines, reveals that substantial amounts of the helical and pleated-sheet conformations remain at 70 degrees C. Changes in the strength of hydrogen bonding by the tyrosyl residues are indicated by the intensity ratio of the doublet at 830-850 cm(-1) and changes in the geometry of the disulfide bridges by the frequency and half-width of the Raman line near 510 cm(-1) due to the S-S vibration. Vibrations of C-S bonds in the methionines and cystines are used to monitor conformational changes in these residues. While there are small quantitative differences in temperature dependence among these probes, all agree in placing the malting temperature at or near 62 degrees C. The Raman data are quantitatively consistent with the six-stage scheme of unfolding of A.W. Burgess and H.A. Scheraga [(1975), J. Theor, Biol. 53, 403], except that no change in the environment of the tyrosines is seen until 45 degrees C.

Chemical modification of simian virus 40 DNA by reaction with a water-soluble carbodiimide

Superhelical simian virus 40 (SV40) DNA I can be modified with N-cyclohexyl-N'-beta-(4 methylmorpholinium)ethylcarbodiimide (CMC). The reaction produces an increase in the sedimentation velocity of DNA I from 21 to 22.5S and a decrease in its buoyant density in CsCl from 1.694 to 1.688. A comparable shift in buoyant density is observed in a saturated ethidium bromide-cesium chloride gradient where form II, which has been exposed to CMC, shows no shift. The CsCl-buoyant density data allows us to estimate that 108 mol of CMC are bound per mol of SV40 DNA I. In the subsequent paper an alternative procedure has been used to locate CMC sites, and the extent of the regions available to bind CMC have been measured.

Simian virus 40 DNA replication: characterization of gaps in the termination region

A class of precursor DNA (pDNA) II molecules has been identified as the immediate precursor of simian virus 40 DNA I. A pDNA II molecule contains a strand of newly synthesized DNA with an interruption located in the region where DNA synthesis terminates (4). These pDNA II molecules have been isolated and further characterized. They are converted to covalently closed structures (simian virus 40 DNA I) only when they are treated in vitro with both T4 DNA polymerase and Escherichia coli ligase. After in vitro repair of pDNA II with T4 DNA polymerase and nucleoside triphosphates, approximately 7 mol of alpha-[32P]dATP is incorporated per mol of DNA II. Alkaline sucrose analysis of these gap-filled molecules, after they have been cleaved with Eco RI restriction endonuclease, has demonstrated that gaps are specifically located in the termination region. alpha-[32P]dATP is incorporated equally into the two labeled products that are generated by RI cleavage of these molecules. This indicates the presence of gaps in both the newly synthesized plus the minus strands. Electrophoretic analysis of the gap-filled molecules, after they have been cleaved with endonuclease Hind, has shown that gaps are localized in Hind fragments G and B and to a minor degree in fragment J. pDNA II molecules have the following properties. There is a gap in the newly synthesized linear DNA strand contained in the pDNA II molecule. Nicked pDNA II molecules cannot be detected. The two molecules that arise by segregation contain gaps in both of the complementary strands. Based on the amount of alpha-[32P]dATP incorporated and the rate of exonuclease III digestion of gap-filled molecules, it is estimated that the size of the gaps is between 22 and 73 nucleotides. Models for termination of DNA synthesis are proposed based on these findings.

Interpretation of the doublet at 850 and 830 cm-1 in the Raman spectra of tyrosyl residues in proteins and certain model compounds

The doublet at 850 and 830 cm-1 in the Raman spectra of proteins containing tyrosyl residues has been examined as to its origin and the relation of its components to the environment of the phenyl ring, the state of the phenolic hydroxyl group, and the conformation of the amino acid backbone. Raman spectral studies on numerous model molecules related to tyrosine, including certain deuterium derivatives, show that the doublet is due to Fermi resonance between the ring-breathing vibration and the overtone of an out-of-plane ring-bending vibration of the para-substituted benzenes. Further examination of the effects of pH and solvents on the Fermi doublet and of the crystallographic data demonstrates that the intensity ratio of the two components depends on changes in the relative frequencies of the two vibrations. These in turn are found to be sensitive to the nature of the hydrogen bonding of the phenolic hydroxyl group of its ionization, but much less so to the environment of the phenyl ring and the conformation of the amino acid backbone. By use of the relative intensities of the doublet in model systems where the phenolic hydroxyl group is strongly hydrogen-bonded, weakly hydrogen-bonded, free or ionized, the reported Raman intensities of the doublets observed in the Raman spectra of several proteins have been interpreted. The results are compared with those obtained by other techniques.

Raman spectra and structure of yeast phenylalanine transfer RNA in the crystalline state and in solution

Laser Raman spectra of yeast phenylalanine transfer RNA have been obtained in solution and in orthorhombic and hexagonal crystals. So far as one can tell from the spectra, which are identical in the two crystal forms, the molecular structure of the tRNA is not altered by differences in molecular packing in these two unit cells. In addition, the spectra of the two crystal forms show the same characteristic Raman frequencies and intensities as those of the tRNA in aqueous solution. Thus the structure of the tRNA molecule appears to be the same in the crystals and in aqueous solution. From the spectroscopic changes that result when Mg2+ ions are removed from the native tRNA, it is concluded that the removal of Mg2+ produces a partial disordering of the ribophosphate backbone of the molecule and a lowering of its melting temperature. The melting is shown to be a complex process in that the vibrations specific for adenine indicate a slightly lower melting temperature and those specific for guanine a slightly higher melting temperature than that of the ribophosphate backbone.

Studies of polyoma virus DNA: cleavage map of the polyoma virus genome

A small-plaque polyoma virus, MPC-1, was isolated from a mouse plasmacytoma. The DNA of this polyoma virus was cleaved with a restriction enzyme from Haemophilus influenzae (Hin d), and the molecular weights of the limit products were analyzed by electrophoresis and electron microscopy. The fragments produced by this enzyme have been ordered by analysis of partial digest products. A physical map of the polyoma virus genome was then constructed.