Bronchial reactivity: interaction between vagal stimulation and inhaled histamine

The interaction between the effects of vagal stimulation and inhaled histamine on the bronchi was studied in anesthetized dogs. Reactivity was assessed by measuring changes in bronchial caliber visualized with tantalum bronchograms. In seven vagotomized dogs the bronchoconstrictor response to a combination of electrical stimulation of the vagus nerves and inhaled histamine solution produced a mean reduction in airway diameter (Daw) of 2.21 mm which was significantly greater than the additive results of the two stimuli applied separately (mean decrease in Daw 0.29 +/- 0.91 mm). In three dogs the effect of vagal stimulation was to produce a shift in the dose-response curve to inhaled histamine. These results indicate that the effect of the base-line bronchomotor tone must be considered in the evaluation of the effect of vagal blockade on airway reactivity. An increase in the resting degree of bronchomotor tone may contribute to the hyperreactivity observed in patients with asthma.     

The dependence of HNO2 mutagenesis in phage T4 on ligase and the lack of dependence of 2AP mutagenesis on repair functions

A temperature sensitive ligase allele of phage T4 reduced or eliminated HNO2 induced reversion of am mutants. Since at the temperatures used, the ligase mutant is defective in the repair of some types of lethal lesions (i.e., UV, MMS and EMS induced lesions) these results indicate that HNO2 mutagenesis may occur through a ligase dependent repair pathway. In contrast, 2AP induced mutation was not inhibited by mutants defective in the gene 30 ligase or in genes 32, 39, 41, 42, 44, 45, 46, 47, 49, 52, 56, 58-61 and v. This indicates that 2AP mutagenesis probably does not depend on a repair pathway in phage T4.     

Synthesis and bioreductive potential of a mono N-oxide derivative of the alkylating agent chlorambucil

Chlorambucil N-oxide (CHLN-O) was synthesized and evaluated for in vitro bioreductive antitumor activity. A time-dependent hypoxic differential was observed when EMT6 cells were exposed to CHLN-O in the presence of rat liver microsomes and reducing equivalents. The cytotoxicity of the N-oxide was potentiated under hypoxia, and augmented further by a combination of low pH and hypoxia. Metabolic studies were also undertaken, which utilized previously described HPLC methodology for the analysis of CHLN-O loss from biological fluids. These demonstrated the requirement for microsomal enzymes and reducing equivalents, and also illustrated the time-dependent manner of CHLN-O loss from isolated microsomal preparations.     

Directing phage selections towards specific epitopes

It is possible to direct selections from antibody repertoires displayed on filamentous phage towards unique epitopes on protein antigens by competing with related molecules. A phage display repertoire of human single chain Fvs (scFvs) was panned three times against foetal haemoglobin (HbF). The selection was dominated by one clone with a Kd of 10 nM but yielded at least 17 others, all of which bound HbF but crossreacted with adult haemoglobin (HbA). To direct selection towards HbF-specific epitopes, the repertoire was preincubated with HbA in solution before each panning. Crossreactive scFvs can form complexes with the soluble HbA and thereby be prevented from binding the immobilized HbF. Four clones with preferential binding to HbF emerged under these conditions. One of these (Hb-1), with a Kd of 6 microM, had exquisite specificity for HbF and could distinguish cells expressing HbF from those expressing HbA by immunocytochemistry and flow cytometry. This antibody has an affinity that is 600-fold lower than the dominant crossreactive clone, and so only emerged under conditions of 'competitive deselection'. Thus, competitive deselection is a viable means for directing selections towards useful epitopes. It permits a more effective 'search' of phage display repertoires and allows the emergence of lower affinity clones with useful specificities. These clones may be useful in themselves or may serve as leads for in vitro affinity maturation.     

Development of endometrial cancer in women on estrogen and progestin hormone replacement therapy

The presenting symptoms, hormonal regimens, treatment modalities, tumor pathology, and follow-up of 25 women developing endometrial cancer while receiving postmenopausal estrogen and progestin therapy were investigated retrospectively. Patients were interviewed and hormone therapies were confirmed through medical records. Pathology specimens were reviewed. Patients received conjugated estrogens (n = 20) or another estrogen (n = 5). For those on conjugated estrogens, the mean daily dose was 0.68 mg, monthly duration was 24.9 days, and monthly dose was 17.0 mg. Women also received medroxyprogesterone acetate (n = 23) or norethindrone acetate (n = 2). The most common regimen was sequential medroxyprogesterone acetate, at a mean daily dose of 7.5 mg, monthly duration of 9.3 days, and monthly dose of 68 mg (mean duration = 5.7 years). Most tumors were low stage and grade, with few demonstrating grade 3 disease (n = 2) or greater than 50% myometrial invasion (n = 2). Twenty-three (92%) had disease limited to the uterus, while two had stage IIIA disease. All are alive and disease-free after a median follow-up of 26 months. Estrogen and progestin therapy does not prevent endometrial cancer in all patients. Women who developed this tumor on sequential therapy in general received less than the recommended guidelines for daily dosage and monthly duration of progestin. Most patients had early-stage and low-grade disease. Continued vigilance in the care of women on hormone replacement therapy is necessary even when combination therapy is prescribed.