Occupational medicine in Canada and Poland in the 1990s

The protocol describes (i) methods for the investigation of neuropeptide catabolism in the central nervous system (CNS), (ii) the identification of the neuropeptidases involved, and (iii) methods for the determination of neuropeptide stability in vitro. These methods are applicable also to study the degradation of peptide hormones by peripheral cells or tissues. To identify peptide degradation products, nanomolar amounts (micromolar concentrations) of peptides are incubated in synthetic media with cell or tissue cultures. Aliquots of the supernatants are withdrawn after different times, peptide fragments separated and fractionated by reversed-phase HPLC, and identified by peptide chemical methods. The peptidases responsible for this degradation can be identified by the use of specific inhibitors listed in the protocol. For receptor binding assays or the study of peptide effects in physiological, nanomolar concentrations the stability of the peptides in an in vitro system should be checked by addition of radiolabeled peptides (femtomolar or nanomolar concentrations) and monitoring the peptide degradation by a procedure analogous to that established for unlabeled peptides. The addition of more or less specific peptidase inhibitors enhances peptide stability in vitro, and thus it can be assured that a given peptide concentration is maintained during biological assays.     

Cardiovascular and biochemical evidence of stress during major surgery associated with different techniques of anaesthesia

The relative merits of a potent narcotic and a spinal analgesic to affect the stress response to a standard operation have been assessed. Forty-five fit patients scheduled for abdominal hysterectomy were allocated at random to three groups, referred to as standard (i.v. anaesthesia alone), spinal (spinal plus i.v. anaesthesia) and fentanyl (fentanyl plus i.v. anaesthesia) groups. In the doses used, fentanyl produced the most effective attenuation of the cardiovascular, hormonal and metabolic responses to stress, but had the disadvantage of prolonged respiratory depression. Spinal anaesthesia gave only a modified blockade of the response to stress and did not obtund the response to intubation.     

A simple method for determining static parameters of large signal semiconductor diode and transistor models

A simple on-line interactive computing methodology for determining static parameters of large-signal semiconductor models is described. The procedure makes use of: (1) an automatic data collection scheme, (2) a single search, three-parameter optimization method for computing diode parameters, and (3) a partitioning scheme to separate the defining transistor equations into two single search, three-parameter problems which are solved by the diode optimization method described in (2).

The method is described by means of the CIRCUS diode and transistor models, and is compared experimentally with Sokal's method [1,2]. The new approach is shown to be superior.     

A matrix of kappa-type coefficients to assess the reliability of nominal scales

To investigate the reliability of nominal scales, Kraemer proposed a measurement model from which kappa coefficients could be derived. More recently she suggested a matrix of coefficients as a comprehensive summary of reliability, contrasting this with use of a single summary kappa statistic. The main diagonal of the matrix consists of binary kappa coefficients for each category which measure the reliability of each category relative to all others, while the off-diagonal elements are correlation coefficients for pairs of categories. The off-diagonal elements were suggested as measures of confusion between categories. Schouten also suggested coefficients to assess confusion between pairs of categories, which might be used as alternative off-diagonal elements in a summary matrix. The two types of off-diagonal element will be compared. It will be shown that Schouten's coefficients can be expressed in terms of the parameters of Kraemer's measurement model and that they are more easily interpreted as measures of confusion. First, the maximum value for Schouten's coefficient is one. Secondly, for any pair of categories, Schouten's coefficient equals the proportionate reduction in the probability of classifying a subject in one category of the pair having previously classified them in the other. Thirdly, where the coefficient for a pair of categories is less than the summary kappa statistic, it will be shown that combining these two categories will increase the value of the summary kappa statistic. The methods of analysis are applied to data from a study of the reliability of psychiatric diagnosis and used to identify pairs of classifications between which there is substantial confusion.     

Is diurnal variation of mood associated with parasympathetic activity?

70 patients older than 50 years (mean age: 60.2 years) underwent a CD-spondylodesis from 1987 to 1991 for degenerative changes of the lumbar spine, and were followed for 2 years. 88.2% improved, but only 47.1% showed a good-to-excellent result. Patients with fair and poor outcomes had had significantly more operations on the lumbar spine (p < 0.001), had a greater extent of preoperative lumbar kyphosis (p < 0.05), motor weakness (p < 0.05), had less vertebral slips (p < 0.01), had less posterior distraction postoperatively (p < 0.001), and had a greater extent of postoperative motor weakness compared to patients with good-to-excellent outcomes. Age, sex, duration of back/leg pain, taking of analgetic drugs, preoperative pain status, profession, range of walking, time of operation, number of fused segments, blood loss, blood transfusion, postoperative profile of the spine did not show any significant influence upon clinical results. Already at 6-months-follow-up there was significant difference of the clinical outcome (p < 0.001), making improvement of a then fair or poor result unlikely.     

In vitro and in vivo antipseudomonal activity, acute toxicity, and mode of action of a newly synthesized fluoroquinolonyl ampicillin derivative

Compounds N-(6,7-difluoroquinolonyl)-ampicillin (AU-1) and N-(6-fluoroquinolonyl)-ampicillin (FQ-1), synthesized by coupling of the carboxyl group of 6,7-difluoroquinolone (FP-3) and 6-fluoroquinolone (FP4), respectively, with the alpha-amino-group of ampicillin side chain, exhibit antipseudomonal activity similar to and lower acute toxicity than that of norfloxacin, whereas neither ampicillin nor the fluoroquinolone moieties, compound FP-3 or FP4, alone have such activity. Also, AU-1 and FQ-1 are active against tested clinical isolates of Pseudomonas aeruginosa that are highly resistant to norfloxacin, gentamicin, or both. The therapeutic efficacies of FQ-1 and norfloxacin were assessed and compared in neutropenic mice infected with a 90% lethal dose of P aeruginosa. Mice intraperitoneally administered FQ-1 (10 mg/kg) 4, 8, 24, and 48 hours after infection had survival rates as high as 80%, comparable to those of mice treated with norfloxacin at the same dosage and dosing schedule. The study of protoplast formation revealed that FQ-1 did not inhibit cell-wall biosynthesis but did induce cell filamentation of Bacillus subtilis at a level close to its minimal inhibition concentration. Both AU-1 and FQ-1 were able to intercalate into the double-stranded DNA. However, that FQ-1 lost such activity after it was treated with penicillinase suggests that the lactam-ring structure in ampicillin moiety of FQ-1 was hydrolyzed by penicillinase and that the hydrolyzed structure of FQ-1 does not own DNA-intercalation activity.