Effects of inorganic phosphate on cross-bridge behavior after photorelease of ATP in permeabilized cells of rat skeletal muscle

Effects of 20 mM inorganic phosphate on the cross-bridge behavior after photorelease of ATP from caged ATP was studied by X-ray diffraction in rat skinned psoas muscle fibers at 16 degrees C. In the first 30 ms after the photorelease, tension was similar in the presence and absence of phosphate. The tension development was then suppressed in the presence of phosphate. At 500 ms after the photolysis, it was lower by about 30% in the presence of phosphate. In the presence of phosphate, the intensity of the third meridional reflection from the thick filament at 1/14.4 nm(-1) increased more slowly and was 60% of the level without phosphate at 500 ms after the photolysis. The intensities of the equatorial (1,1) reflection and the actin layer-line at 1/36 nm(-1) decreased to a lower level in the presence of phosphate. These results suggest that phosphate does not affect dissociation of myosin heads from actin, but decreases the number of myosin heads in force-generating conformation and reduces tension. Phosphate may also shift the equilibrium between the detached and attached states towards the former.     

Suppression of UV-induced mutations by wild-type p53 protein in human osteosarcoma cells

We have examined whether the tumour suppressor p53 protein suppressedUV-induced mutations in the hypoxathine-guanine phosphoribosyltransferase (HPRT) gene and in the supF gene of the shuttlevector plasmid pMY189. We used human osteosarcoma Saos-LP12cells, in which wild type (wt) p53 protein was induced by treatmentwith isopopyl-(ß-D-thiogalactopyranoside. The inductionof wt p53 protein suppressed UV-induced mutations but not spontaneousmutations in the HPRT gene. The frequency of UV-induced mutationsinduced by UV-irradiation of the plasmid was also significantlylower in cells with induced wt p53 protein than in the uninducedcells. In addition, we found that frequency of G : C to A :T transition mutations which occurred at the 3' base pair ofdipyrimidine sites were significantly lower in the cells withinduced wt p53 protein than in the uninduced cells. These findingssuggestthat wt p53 protein may play roles in modulating DNArepair pathway, resulting in the suppression of UV-induced mutations. ¹To whom correspondence should be addressed     

HIGH-GRADE SURFACE OSTEOSARCOMA OF THE LEFT ILIUM A Case Report and Review of the Literature

A rare case of high-grade surface osteosarcoma of the left ilum is reported. Trephine biopsy performed on a 31-year-old woman suffering from a huge tumor of the left buttock revealed high-grade osteosarcoma, and hemipel-vectomy was undertaken. The surgical specimen showed that the tumor was present on the surface of the left ilium. Ten months after the operation, the patient died of brain metastasis. From these results, we considered this case to be one of high-grade surface osteosarcoma. ACTA PATHOL JPN 38: 235 -240, 1988.     

Increased cancericidal activity of PTT.119; a new synthetic bis-(2-chloroethyl)amino-l-phenylalanine derivative with carrier amino acids

Summary A new synthetic tripeptide (p-F-Phe-m-bis-(2-chloroethyl)amino-Phe-Met ethoxy HCl), PTT.119, was demonstrated to have significant cancericidal activity against seven in vitro tumor cell lines of different origins and etiologies and against primary human AMML, ALL, and hairy cell leukemias. Viabilities of each murine tumor and rabbit, marmoset, and human leukemia and lymphoma line were significantly reduced by treatment with 1–50 g PTT.119 in media containing serum. Continuous 24-h exposure or pulse treatment as short as 15 and 30 min with the tripeptide resulted in irreversible damage to the tumor cells. Under identical treatment conditions, freshly isolated human leukemic cells, particularly ALL lymphoblasts, were even more susceptible to PTT.119 than any of the tested tumor cell models.Examination of the parameters of PTT.119 activity revealed that reductions of tumor cell survival were dependent on the concentration of the tripeptide. Prolongation of PTT.119 exposure from 15 min to 24 h increased the rates of tumor cell death but did not proportionally reduce the numbers of surviving cells. Assessment of tumor cell viabilities for 5 consecutive days following pulse exposure to PTT.119 demonstrated increasing reductions in tumor cell survival, which were greatest 5 days after treatment with the tripeptide.The cancericidal activity of PTT.119 was compared with its three parental components either as individual agents or as a mixture. Both the alkylator moiety, m-sarcolysin (m.L.SL) alone or together with p-fluoro-phenylalanine and l-methionine ethoxy HCl, and l-PAM (l-phenylalanine mustard), the p-isomer of m.L.SL, were 1.5- to 3-fold less cytotoxic to L1210 leukemia and MJY-alpha mammary tumor cells than PTT.119. Covalent linkage of the amino acid residues to m.L.SL yielded a molecule with greatly augmented cancericidal activity capable of acting against a broad spectrum of tumor cells.     

Double-stranded RNA and bacterial lipopolysaccharide enhance sensitivit to TNF-{alpha}-mediated cell death

The effect of double-stranded RNA (dsRNA) and bacterial lipopolysaccharideon the sensitivity to tumor necrosis factor (TNF)--medlatedcell death was studied In an In vitro system. Since secretionof TNF- Is a part of the early host response to viral and bacterialinfection, we examined whether mimicking the Infection withviral and bacterial products could affect the response of cellsto TNF-. Incubation of WEHI 164 fibrosarcoma cells with dsRNAor lipopolysaccharide (LPS) significantly increased their sensitivityto TNF--mediated lysis and to TNF-secreting inflammatory T cell-mediatedlysis. Thus, these products could induce Increased sensitivityto TNF- In cells In an inflammatory focus, possibly contributingto selective elimination of Infected but not healthy cells bythis non-specific cytokine. Additionally, our data show thatboth dsRNA and LPS, as well as TNF- Itself, rapidly Induce nuclearfactor-xB (NF-*B), a DNA-bindlng protein Implicated In regulationof gene expression. We suggest that NF-xB could regulate genescrucial for the induction of cell death by TNF-.     

Does the pineal gland play a role in neuroendocrine fear responses?

The pineal gland secretes melatonin under an influence of suprachiasmatic nucleus neurones. Pinealectomy or melatonin administration affects behavioural responses to novel stimuli. Fear or novel stimuli inhibit vasopressin (VP) and facilitate oxytocin (OT) or prolactin (PRL) release from the pituitary. Thus the suprachiasmatic nucleus-pineal gland system may modulate VP, OT and PRL responses to conditioned fear stimuli. In the present experiments with male rats, pinealectomy or melatonin administration did not significantly change VP, OT or PRL responses to conditioned fear stimuli. Electrolytic lesions of the suprachiasmatic nuclei impaired VP but not OT or PRL responses. The results show that the pineal gland is not involved in neuroendocrine responses to conditioned fear stimuli and suggest that the suprachiasmatic nucleus is necessary for the VP response to fear stimuli.     

Efficacy of the axially loaded pivot shift test for the diagnosis of a meniscal tear

Although magnetic resonance imaging (MRI) has improved the diagnostic accuracy of meniscal pathology, the authors believe that physical examination remains essential to the evaluation of knee pathology. In this study, the diagnostic accuracy of five clinical tests for meniscal pathology was prospectively evaluated in 160 patients, who thereafter underwent arthroscopy. 69% (109 knees) of the knees tested had associated ACL deficiency. There were 144 meniscal lesions in 130 of the 160 knees which were examined. The sensitivity of the tests was lower than the specificity. Conventional tests such as McMurray and Apley tests showed a low accuracy rate of 45% and 28% respectively. The diagnostic value of the axially loaded pivot shift test was significantly higher, indicating that this remains a useful diagnostic aid.     

Effects of N-ethylmaleimide on the structure of skinned frog skeletal muscles

Summary The effects of N-ethylmaleimide (NEM) and other sulfhydryl modifiers on the structure of skinned frog skeletal muscles were studied using the X-ray diffraction technique. In sartorius muscle with full overlap between the thick and thin filaments, 0.1-1.0 mM NEM changed the intensity ratio of the (1,0) and (1,1) equatorial reflections from 4.35 to 0.72, and the (1,0) spacing of the hexagonal filament lattice from 40.4 to 41.4 nm. The axial X-ray diffraction pattern showed weak myosin layer-lines after the NEM treatment but enhancement of the actin layer-lines was not observed. In overstretched semitendinosus muscle, NEM did not affect the equatorial spacing but the myosin layer-lines were weakened. These results indicate that modification of myosin by NEM destroys the helical arrangement of myosin heads around the shaft of the thick filament and that when thin filaments are available, myosin heads move towards, and possibly bind to them. This binding is different from that in rigor since the ladder-like appearance of the higher actin layer-lines, which is typical of patterns from rigor muscles, was not observed. On removal of ATP after the NEM treatment, the diffraction pattern showed features characteristic of that from normal rigor muscles but no tension was produced. The pattern showed well-defined samplings on layer-lines in the small-angle region, indicating the presence of an extensive lattice order and exact axial alignment of the filaments. The first actin layer-line did not show samplings from the superlattice of the thick filaments, which are observed on the myosin layer-lines in patterns from resting muscles. This indicates that in NEM-treated rigor muscles the pattern of binding of myosin heads to the thin filaments is not influenced by the azimuthal orientation of the thick filament.