Transformation of UV-hypersensitive Chinese hamster ovary cell mutants with UV-irradiated plasmids

Transfection of UV-hypersensitive, DNA repair-deficient Chinese hamster ovary (CHO) cell lines and parental, repair-proficient CHO cells with UV-irradiated pHaprt-1 or pSV2gpt plasmids resulted in different responses by recipient cell lines to UV damage in transfected DNA. Unlike results that have been reported for human cells, UV irradiation of transfecting DNA did not stimulate the genetic transformation of CHO recipient cells. In repair-deficient CHO cells, proportionally fewer transformants were produced with increasing UV damage than in repair-proficient cells in transfections with the UV-irradiated hamster adenine phosphoribosyltransferase (APRT) gene contained in plasmid pHaprt-1. However, transfection of CHO cells with UV-irradiated pSV2gpt resulted in neither decline in transformation frequencies in repair-deficient cell lines relative to repair-proficient cells nor stimulation of genetic transformation by UV damage in the plasmid. Blot hybridization analysis of DNA samples isolated from transformed cells showed no dramatic changes in copy number or arrangement of transfected plasmid DNA with increasing UV dose. We conclude that the responses of recipient cells to UV-damaged transfecting plasmids depend both on the type of recipient cell and the characteristics of the genetic sequence used for transfection.     

The HCH-1 model of enzymatic cellulose hydrolysis

Solka Floc BW200 was enzymatically hydrolyzed in a batch reactor using a commercial cellulase preparation. A total of 50 different hydrolysis conditions were run within a 10-fold range in enzyme concentration and a 30-fold range in cellulose concentration. The data were evaluated in three ways using five different models. Previous literature models were not as successful in correlating the data as the HCH-1 Model derived in this work.     

Initial Phases of Starvation and Activity of Bacteria at Surfaces

The activity of the hydrophilic Vibrio sp. strain DW1 and the hydrophobic Pseudomonas sp. strain S9, which both undergo starvation-induced responses, was examined at nutrient-enriched and nutrient-deficient interfaces. The initial period of response to a starvation regime (“dwarfing” phase) is a sequence of two processes: fragmentation and continuous size reduction of the fragmented cells. This dwarfing phase is also one of intense metabolic activity as supported by O₂ uptake measurements of the endogenous metabolism and the use of inhibitors of the proton flow, the electron transport chain, and membrane-bound ATPase. Hydrophilic bacteria become even smaller at nutrient-deficient surfaces than in the liquid phase upon starvation, and this is reflected in a higher endogenous metabolism exhibited by surface-associated cells compared with those in the liquid phase. On the other hand, hydrophobic bacteria dwarfing at surfaces did not exhibit a greater size reduction and exhibited an endogenous metabolism that was only slightly higher than that of cells in the liquid phase. Bacterial scavenging of surface-localized nutrients is related to the degree of irreversible binding of dwarf and starved bacteria, which in turn may be related to the degree of cell surface hydrophobicity.     

Incidence of Dumping after Truncal and Selective Vagotomy with Pyloroplasty and Highly Selective Vagotomy without Drainage Procedure

The incidence of dumping after truncal or selective vagotomy with pyloroplasty and highly selective vagotomy without a drainage procedure was assessed both clinically and experimentally. At a gastric follow-up clinic dumping was found to be significantly less frequent in patients who had undergone highly selective vagotomy without a drainage procedure than in patients who had undergone truncal or selective vagotomy with pyloroplasty (P < 0·05 or < 0·001, respectively). Hypertonic glucose given by mouth provoked the onset of dumping in 20% of patients with duodenal ulcer before operation, in 73% after truncal vagotomy and pyloroplasty, in 80% after selective vagotomy and pyloroplasty, and in 47% after highly selective vagotomy. The test meal also produced significantly greater decreases in blood pressure and increases in pulse rate in patients who had undergone vagotomy with pyloroplasty than in patients who had undergone highly selective vagotomy.     

Factors influencing alkali-induced heat resistance in Salmonella enteritidis phage type 4

The culture of cells of Salmonella enteritidis PT4 at either 25, 30 or 37°C in media at pH values between 8.0 and 9.75 resulted in significant increases in heat resistance. At 37°C, induction was rapid and was dependent on protein synthesis, being inhibited by chloramphenicol. Thermotolerance was stable when cells were transferred from pH 9.2 to pH 7.0 and cultures only became heat sensitive again following significant multiplication at the lower pH.     

C to T and/or G to A transitions are responsible for loss of a MspI restriction site at the 5′-end of the human apolipoprotein AI gene

We detected the loss of a MspI restriction site by a C to T transition at +83 bp and a G to A transition at +84 bp of the 5-end non-coding region of the human apolipoprotein AI gene. This base change occurred at the hot spot (CCGG) for methylation, which may be important in the regulation of gene expression. The population frequency for the loss of the MspI site is 6.1%.     

Effects of intravenous infusions of prostaglandin D2 in man

Prostaglandin D₂ (PGD₂) was infused intravenously into normal male volunteers. Seven subjects received infusions of 16, 32, 64 ng/kg/min and six of these a further dose of 128 ng/kg/min. Each individual's maximum dose was limited by discomfort caused by intense facial flushing and nasal congestion. At these doses there was no significant effect on systolic or diastolic blood pressure nor on spirometric measurements. There was a small but statistically significant tachycardia at 64 and 128 ng/kg/min. Collagen- and adenosine diphosphate (ADP)-induced platele aggregation was not affected at any of the infusion rates. Infused PGD₂ is unlikely to be a useful antithrombotic agent.     

The effect of EDTA and related chelating agents on the oxidation of methanol by the methylotrophic bacterium, Methylophilus methylotrophus

The effects of EDTA and related metal-chelating agents on the respiratory system of the methylotrophic bacterium Methylophilus methylotrophus have been investigated. EDTA completely inhibited whole cell methanol oxidase activity and concomitantly decreased the aerobic steady-state reduction level of cytochrome c, but only partially inhibited methanol dehydrogenase activity. Analysis of the inhibition kinetics of EDTA and other chelating agents on methanol oxidase activity indicated that they were effective in the order CDTA greater than EDTA greater than HEDTA greater than EGTA greater than EDDA, and that they inhibited in an uncompetitive manner. Inhibition by EDTA varied as a function of the ambient cell mass in the assay, and could be partly reversed by the addition of divalent cations. EDTA had no effect on the activity of solubilised methanol dehydrogenase. These and other results indicate that EDTA binds a divalent metal ion, probably Mg2+, which is involved in the functional association of methanol dehydrogenase with the respiratory membrane. This concept is discussed in terms of the electron transfer properties and spatial organisation of the terminal respiratory chain of M. methylotrophus.     

Finite extension and torsion of papillary muscles: a theoretical framework.

We present a new analytical solution for the finite extension and torsion of a nonlinearly pseudoelastic, homogeneous, transversely isotropic, incompressible, solid circular cylinder. This solution can be used to guide the performance and interpretation of experiments, and to identify a specific functional form of a three-dimensional constitutive relation directly from data. We submit, therefore, that this solution can be used by experimentalists to quantify the multiaxial constitutive relations, including shear, of both passive and tonically activated papillary muscles for the first time.