A fast, convenient and rugged procedure for characterizing the selectivity of alkyl-silica columns.

Previous work has shown that the selectivity of reversed-phase columns for HPLC can be described by means of five column parameters: H (hydrophobicity), S* (steric resistance), A (hydrogen-bond acidity), B (hydrogen-bond basicity) and C (cation-exchange capacity). Values of H, S*, etc. can be determined by carrying out retention measurements for 18 test solutes under standardized conditions. The reproducibility of the latter procedure has been evaluated by comparison testing in four different laboratories and found acceptable. An alternative 10-solute test procedure which is more reproducible and convenient (but somewhat less accurate), requires only 2-3 h per column.

Midodrine: a role in the management of neurocardiogenic syncope.

OBJECTIVE: To determine the benefit of midodrine, an alpha agonist, on symptom frequency and haemodynamic responses during head up tilt in patients with neurocardiogenic syncope. SETTING: Cardiovascular investigation unit (a secondary and tertiary referral centre for the investigation and management of syncope). PATIENTS: 16 outpatients (mean (SD) age 56 (18) years; five men) with frequent hypotensive symptoms (more than two syncopal episodes and fewer than 20 symptom free days per month), and reproducible syncope with glyceryl trinitrate (GTN) during head up tilt. DESIGN AND INTERVENTION: Randomised double blind placebo controlled study. Patients were randomised to receive either placebo or midodrine for one month. Symptom events were recorded during each study month. At the end of each study month patients completed a quality of life scoring scale (Short Form 36) and a global assessment of therapeutic response. They received GTN with head up tilt for measurement of heart rate (electrocardiography), phasic blood pressure (digital photoplethysmography), and thoracic fluid index (transthoracic impedance plethysmography) during symptom provocation. RESULTS: Patients administered midodrine had an average of 7.3 more symptom free days than those who received placebo (95% confidence interval (CI) 4.6 to 9; p < 0.0001). Eleven patients reported a positive therapeutic response with midodrine (p = 0.002). All domains of quality of life showed improvement with midodrine, in particular physical function (8.1; 95% CI 3.7 to 12.2), energy and vitality (14.6; 95% CI 7.3 to 22.1), and change in health status (22.2; 95% CI 11 to 33.4). Fourteen patients who were given placebo had tilt induced syncope compared with six given midodrine (p = 0.01). Baseline supine systolic blood pressure was higher and heart rate lower in patients who received midodrine than in those who were given placebo (p < 0.05). A lower thoracic fluid index in patients administered midodrine indicates increased venous return when supine and during head up tilt. There were no serious adverse effects. CONCLUSIONS: Midodrine had a conspicuous beneficial effect on symptom frequency, symptoms during head up tilt, and quality of life. Midodrine is recommended for the treatment of neurocardiogenic syncope in patients with frequent symptoms.

The treatment of sicca features in Sjögren's syndrome: a clinical review.

Patients with SS often suffer considerable distress due to sicca symptoms and the complications of mucosal dryness. Although there are many topical treatments available, the literature on their use is scant. This paper describes the treatments available and suggests a rationale for the choice of product.

Urinary chromatographic profiles in schizophrenia.

In a series of articles, Trygstad et al. (1980) suggested that specific patterns of peptide excretion and increased levels of peptide material are found by chromatographic analysis of the urine of patients with a variety of psychiatric illness including schizophrenia. As these results have not been independently replicated in another laboratory, we conducted an investigation of urine samples from 5 DSM-III classified schizophrenic patients and 4 normal subjects using the techniques described by the Norwegian group, and with a series of modifications. The chromatographic profiles obtained differ widely from those reported by Trygstad et al. No significant differences were detected between patients with schizophrenia and controls. The methods used by Trygstad et al. are complex and we have defined several parts of the methods which are subject to variability. Our findings lend no support to the view that patients with psychiatric illness can be readily distinguished from normal subjects by the amount or profile of peptide excretion in urine.

Inhibition of oxidative metabolism in Escherichia coli by d-camphor and restoration of oxidase activity by quinones.

Oxidative metabolism in whole cells of Escherichia coli strain 82/r was inhibited by d-camphor when glucose, pyruvate, or succinate was used as substrate. Inhibition was not due to lower surface tension in d-camphor-treated cell suspensions nor was it a function of cell permeability. Succinic, lactic, and NADH-oxidase activities were inhibited in alumina powder cell-free extracts (80 mug of protein/ml) by d-camphor (1100 mug/ml). NADH: and succinic: DCPIP oxidoreductase enzymes were unaffected by d-camphor. Menadione (vitamin K3) restored succinic, lactic, and NADH-oxidase activities in d-camphor-inhibited cell-free extracts. Concentrations of menadione used to restore succinic and NADH oxidase activities were not stimulatory in non-camphor-treated extracts. Succinic oxidase activity in d-camphor-inhibited cell-free extracts was also restored by ubiquinone (Q6) but not by vitamin K1. These results are interpreted to indicate that d-camphor may affect quinone function in E. coli.