Modification of cell membrane in variants of chinese hamster cells resistant to abrin

Stable and heritable variants of Chinese hamster ovary (CHO) cells which are resistant to different levels (0.1, 1.0 and 10 μg/ml) of the toxin abrin have been isolated and characterized. The frequency of resistant colonies to abrin was increased with the concentration of a chemical mutagen. There was no effect of cell density or cross-feeding on the recovery of variants. In experiments using fluorescein-labeled abrin and ricin which bind to terminal (non-sialylated) galactose residues of cell-surface oligosaccharides, parental cells exhibited strong binding toward both toxins, whereas no fluorescence was observed in the resistant clones. A fluorescein-conjugated lectin, BS II, which is specific for terminal N-acetyl- -glucosaminyl residues, did not interact with the parental cells, but did with the resistant clones. This suggests that on the surface of resistant cells the number of terminal galactosyl residues of oligosaccharide chains in glycoproteins was reduced, exposing the penultimate N-acetyl- -glucosaminyl residues. The number of available endogenous acceptor sites for galactosyl transferase in the abrin-resistant clones was directly proportional to the degree of resistance. In the presence of great excess of exogenous acceptor, the rates of galactosyl transfer were similar in all the abrin-resistant cell types tested, with levels ranging from 1.4 to 1.7 times parental cell values. Studies with tetraploid cell hybrids reveal that resistance was a recessive trait. Fluctuation analysis showed that abrin resistance occurred in CHO cell populations at a rate of 4−7 × 10⁻⁸/cell/generation. The system may serve as a new marker for quantitative mutagenesis studies.     

Spectral analysis of high resolution direct-derivative melting curves of DNA for instantaneous and total base composition.

Derivative melting profiles of DNA have been obtained directly by recording the difference in absorbance between two identical solutions maintained at a small constant temperature differential. This deltaA is monitored continuously with increasing temperature in a ratio recording spectrophotometer. Resolution of complex hyperfine structure in the profiles of small homogeneous viral DNAs appears to be significantly better than has been produced by various numerical methods of differentiation. In addition, a spectral method has been modified that permits easy analysis for DNA base composition from the ratio of derivative melting curves obtained at 282 and 260 nm. Eight bacterial and three vertebrate DNAs have been analyzed for total base composition from the product of the instantaneous base composition at small temperature intervals (0.05 degrees C) throughout the entire melting region and the integrated area of the 282 nm profile. The results are in excellent agreement with values determined by traditional methods.     

Evaluation of fasciotomy and vasodilator for treatment of frostbite in the dog

Severe freezing injury was produced in the hind foot of 26 mongrel dogs. All dogs were given daily whirlpool treatment and protective bandaging for 14 days following injury. In addition, certain dogs received a vasodilator, fasciotomy, or both vasodilator and fasciotomy following injury. Deep foot temperatures, foot volumes, tissue pressures, and 14 day tissue loss-salvage scores were compared. Significant differences between fasciotomy and nonfasciotomy dogs were seen in foot temperature, volume, and tissue pressure immediately following fasciotomy. Though there was no significant difference in 14 day tissue loss, there was clinically apparent prolongation of integrity of the local vascular system for 2 to 5 days following fasciotomy, and total foot salvage in several dogs receiving fasciotomy.     

Effect of glucocorticoids on fetoprotein production by an established cell line from Morris hepatoma 8994

Glucocorticoids at concentrations equal to or higher than 10^?7M lead to an increase of alpha-fetoprotein production by an established cell line from Morris hepatoma 8994. These cells also secreted alpha_M-fetoprotein into the culture medium but only after addition of at least 4×10^?7M hydrocortisone or 5×10^?8M dexamethasone. The effects on both fetoproteins were observed in spite of a decrease of cell multiplication and an increase of cell detachment.     

Immune competence in breast cancer — Relationship of pretreatment immunologic tests to diagnosis and tumor stage

Summary The immune competence of a group of 276 patients with suspected breast cancer has been assessed using a spectrum of tests: the peripheral lymphocyte count, serum immunoglobulin levels, lymphocyte response to phytohemagglutinin (PHA), Mantoux test, and dinitrochlorobenzene (DNCB) skin test. All tests were completed prior to any form of treatment as the initial part of an ongoing, long-term assessment which will ultimately relate immune competence to prognosis. 225 patients with breast cancer were allocated into stages based on their TNM status. The remaining 51 patients proved to have benign breast disease and made up the control group. In analysis, control patients were compared with early breast cancer patients, while the effect of advancing disease was assessed by betweenstage comparisons in the cancer group.There were no significant differences between early breast cancer and control patients or between cancer stages in peripheral lymphocyte count, serum immunoglobulin levels, lymphocyte response to PHA, or Mantoux responses. Age was found to have a crucial effect on some of these parameters and some apparent differences between the various groups lost significance after appropriate allowances were made for age.Important differences seen with the DNCB test persisted after allowing for age effects. Responses to DNCB were significantly depressed in patients with early breast cancer compared to controls. Patients with disseminated cancer showed greater depression than early breast cancer patients, but surprisingly, patients with locally advanced tumors had good responses to DNCB. Possible reasons for the paradoxical preservation of DNCB reactivity in patients with locally advanced cancer are discussed.The DNCB test is the most discriminating of the five tests of immune function studied.     

Role of pelvimetry in active management of labour.

All cases referred for pelvimetry in 1970-1 and all breech presentations referred for pelvimetry in 1972-4 were reviewed. Indications for pelvimetry fell into four main categories: high head in the antenatal clinic (47-8%); high head in labour (13-9%); breech presentation (20-9%); and previous caesarean section (14-8%). In the first two categories pelvimetry rarely if ever influenced management, and it should not be performed routinely. In breech presentation and cases of caesarean section pelvimetry seemed to be of value, but in the latter group it should be performed puerperally to avoid the known radiation hazard to the fetus. A fairly close correlation between obstetric conjugate and pelvic capacity was shown, which suggested that a 3400-g baby might pass through a pelvis of obstetric conjugate of 10 cm as a cephalic trial of labour, but would need an obstetric conjugate of 11-7 cm for safe vaginal breech delivery.     

Ca2+-dependent cross-linking processes in human platelets

When platelet cytoplasmic Ca²⁺ is increased by the ionophore A23187 in the presence of the protease inhibitor leupeptin, there is the coincident appearance of a cross-linked polymer and the partial disappearance of monomeric protein and glycoprotein units. In the absence of leupeptin only 30% of the polymer was formed. The disappearance of monomeric protein bands, as detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis, is prevented by histamine, which as a pseudodonor amine is a known inhibitor of transglutaminase-catalyzed cross-linking. [¹⁴C]Histamine, at a tracer concentration, is incorporated into the polymer as well as into myosin, glycoproteins IIB and III, actin and tropomyosin. The lose of monomeric protein bands is mostly due to their conversion into polymers. Control measurements show that leupeptin effectively inhibited platelet Ca²⁺-dependent proteases. The cross-linking processes bringing about the observed increase in polymer formation are thus the result of a Ca²⁺-dependent platelet transglutaminase activity. The latter is located in the platelet cytosol and has been identified as platelet factor XIII on the basis of its specific cross-linking of fibrin. Platelet factor XIII, upon activation, may function physiologically to couple membrane proteins to cytoplasmic structural proteins. Thus, a new concept is proposed for the stabilization of platelet membranes and platelets as they form the hemostatic plug.