Effect of cross-linking on the secondary structure of DNA I. Cross-linking by photodimerization

An investigation has been made into the effect produced by photo-induced pyrimidine cross-links upon the secondary structure of DNA. We have studied the effect of uv irradiation upon the B in equilibrium A transition in DNA brought about by a change of solvent from 70 to 80% ethanol. Circular dichroism (CD) was used to monitor the conformational changes. However, we first showed by means of laser Raman spectroscopy that CD is a reliable monitor of the conformational change, even though the DNA is aggregated in 80% alcohol solutions. It is suggested that this aggregation stabilizes the A form through lateral interaction between the helices. The uv irradiation experiments show that pyrimidine-dimer cross-links induced into the B-form DNA will lock it irreversibly into that conformation and prevent it from going to the A form in 80% EtOH solution. The A-form DNA can tolerate a few cross-links but converts cooperatively to the B form if a larger number of cross-links is introduced. Irradiation-induced pyrimidine cross-links create locally denatured regions in B-form DNA. Upon continued irradiation, the entire DNA moelcule becomes denatured.     

Ouabain-insensitive salt and water movements in duck red cells. III. The role of chloride in the volume response

Duck red cells in hypertonic media experience rapid osmotic shrinkage followed by gradual reswelling back toward their original volume. This uptake of salt and water is self limiting and demands a specific ionic composition of the external solution. Although ouabain (10(-4)M) alters the pattern of cation accumulation from predominantly potassium to sodium, it does not affect the rate of the reaction, or the total amount of salt or water taken up. To study the response without the complications of active Na-K transport, ouabain was added to most incubations. All water accumulated by the cells can be accounted for by net salt uptake. Specific external cation requirements for reswelling include: sufficient sodium (more than 23 mM), and elevated potassium (more than 7 mM). In the absence of external potassium cells lose potassium without gaining sodium and continue to shrink instead of reswelling. Adding rubidium to the potassium- free solution promotes an even greater loss of cell potassium, yet causes swelling due to a net uptake of sodium and rubidium followed by chloride. The diuretic furosemide (10(-3)M) inhibits net sodium uptake which depends on potassium (or rubidium), as well as inhibits net sodium uptake which depends on sodium. As a result, cell volume is stabilized in the presence of this drug by inhibition of shrinkage, at low, and of swelling at high external potassium. The response has a high apparent energy of activation (15-20 kcal/mol). We propose that net salt and water movements in hypertonic solutions containing ouabain are mediated by direct coupling or cis-interaction, between sodium and potassium so that the uphill movement of one is driven by the downhill movement of the other in the same direction.     

A new technique for measuring velopharyngeal orifice area during sustained vowel production: an application of aerodynamic forced oscillation principles

A new technique for measuring velopharyngeal orifice area during sustained vowel production is described. The technique is based on a simple oscillatory flow balancing procedure between two aerodynamic branches, a mechanical model of the human upper airway and the subject's upper airway. The area of the velopharyngeal orifice in the model is adjusted until identical oscillatory flows traverse it and the subject's velopharyngeal orifice in response to a common forced oscillatory pressure. When identical oscillatory flows are observed, the area of the adjusted orifice is taken as a measure of the area of the subject's velopharyngeal orifice.     

Efficacy of oxibendazole against adult and larval nematodes of cattle

Calves which were artificially infected with Haemonchus, Ostertagia, Trichostrongylus, Cooperia, and Oesophagostomum but which were also carrying natural infections of Nematodirus and Trichuris were treated with 15.0 mg of oxibendazole (methyl-5-n-propoxy-2-benzimidazole-carbamate)/kg of body weight at 3 days, 7 days, and 42 days after exposure to the infective trichostrongylid and strongylid larvae. Efficacies against adult populations of these genera treated on day 42, except Trichostrongylus, exceeded 98%. The chemical was highly effective against immature nematodes of the genera, except Oesophagostomum (0%). Data were not obtained on Trichostrongylus. The oxibendazole premix was palatable, and toxicosis due to the chemical was not seen in these calves.     

Effect of wet corn gluten feed, supplemental protein, and tallow on steer finishing performance

Two trials evaluated the effects of level of wet corn gluten feed (WCGF), type of supplemental protein, and supplemental tallow on steer finishing performance. In Trial 1, WCGF was fed at 0, 25 (two diets), or 50% of the dietary DM replacing dry-rolled corn (DRC), molasses, and a portion of the supplement. The DRC control diet and one 25% WCGF diet were supplemented with a combination of protein sources. The second 25% WCGF diet was supplemented with urea alone. The 50% WCGF diet contained no additional protein supplementation. No differences in DMI (P > .10) were observed. Calves fed 25% WCGF plus a combination of protein sources or 50% WCGF gained faster (P < .10) and more efficiently (P < .10) than calves fed the DRC control. Calves fed 25% WCGF plus urea gained faster (P < .10) and tended (P = .14) to be more efficient than calves fed the DRC control. In Trial 2, WCGF was fed to replace 0 or 50% of the DRC and the molasses-urea supplement (DM basis). Both diets were fed with or without 3% tallow. Steers fed WCGF gained faster (P < .01) and more efficiently (P < .01) than steers fed DRC. Inclusion of 3% tallow increased gain (P < .05) and improved efficiency (P < .05). Feed efficiency is improved by the addition of WCGF or tallow to DRC finishing diets.     

Plasma c-erbB-2 levels in breast cancer patients: prognostic significance in predicting response to chemotherapy

PURPOSE: To determine the significance of plasma c-erbB-2 levels to assess the extent of disease spread and to predict the response to chemotherapy in node-positive breast cancer patients. METHODS: We determined plasma levels of c-erbB-2 in 79 stages II and III breast cancer patients who received cyclophosphamide, methotrexate, and flourouracil (CMF)/cyclophosphamide, methotrexate, fluorouracil, vincristine, and prednisone (CMFVP) chemotherapy. All patients had a minimum follow-up of greater than 60 months or until disease recurrence. Plasma samples were obtained before and after chemotherapy. Plasma c-erbB-2 levels were quantified by enzyme-linked immunoassay. c-erbB-2 levels were analyzed in relation to the patients' axillary lymph node status, menopausal status, disease status, disease-free survival (DFS), and steroid receptor status of tumor. RESULTS: Plasma c-erbB-2 levels varied widely in breast cancer patients. In general, when all patients were included in the analyses, plasma c-erbB-2 levels before chemotherapy correlated significantly with the number of positive axillary lymph nodes and with postchemotherapy c-erbB-2 levels. No association was observed between pre- or postchemotherapy c-erbB-2 levels and other variables (patients' age at diagnosis, receptor status of the tumor, or disease status). The prognostic significance of different factors (ie, nodal status [one to three v > three positive nodes], menopausal status [pre- v postmenopausal women], estrogen receptor [ER] status [ER+ v ER-], and pre- and postchemotherapy c-erbB-2 levels) in predicting DFS was determined in all study patients. Among the variables examined, nodal status was the strongest predictor of DFS in these patients. The second most significant prognostic marker was postchemotherapy c-erbB-2 level. Prechemotherapy c-erbB-2 levels showed prognostic significance for DFS in a subset of breast cancer patients (ie, patients with > three positive nodes). Patients with greater than three positive lymph nodes and those with greater than 100 fmol/mL of plasma c-erbB-2 levels before therapy had significantly shorter DFS than did those patients with 100 fmol/mL or less c-erbB-2 levels. CONCLUSION: In breast cancer patients, determination of c-erbB-2 levels before therapy is an important biomarker to assess the extent of disease spread in the lymph nodes. Postchemotherapy c-erbB-2 levels are also a prognostic indicator for DFS in patients who receive chemotherapy. Finally, in a subgroup of patients with greater than three positive nodes, prechemotherapy c-erbB-2 levels are a prognostic marker for response of patients to standard chemotherapy.