Rapid determination of benzalkonium chloride in pharmaceutical preparations with flow injection liquid-liquid extraction

Benzalkonium chloride was assayed by on-line extraction of the benzalkonium ion with picrate to chloroform. The absorbance of picrate was measured. The extractions were performed with a home-made flow injection extraction unit. Calibration curves (1.5-180 x 10(-4)% w/v) were straight lines (r = 0.9993) and the relative standard deviation of a series of injections was less than or equal to 2%. Pharmaceutical benzalkonium preparations, containing xylometazoline, timolol, phenylephrine or carbachol could also be assayed. The method was compared with a modified HPLC assay.     

Application of a radioimmunoassay for determination of levels of zalcitabine (ddC) in human plasma, urine, and cerebrospinal fluid.

A specific and sensitive radioimmunoassay for the determination of levels of zalcitabine in human plasma, urine, and cerebrospinal fluid has been developed. Commercially available radiolabel and antiserum (Sigma Chemicals) were used after dilution in assay buffer. Prior to the immunoassay, standard and patient samples were subjected to solid-phase extraction on silica columns in order to obtain purified samples. The lower limit of quantitation was determined to be 1 ng/ml. Intra- and interassay variations were less than 11% for a number of quality control samples of drug in plasma and urine. Results from parallelism studies with plasma and urine demonstrated that samples outside the standard range (1 to 30 ng/ml) could be diluted by blank plasma or assay buffer, respectively. A large number of related compounds and potentially coadministered drugs were tested for cross-reactivity. Stability tests showed that heat treatment for 30 min at 60 degrees C or storage for 1 month at -30 degrees C did not affect zalcitabine concentrations in plasma or urine. The radioimmunoassay with solid-phase extraction for sample cleanup discussed here has been successfully applied in a pharmacokinetic study of a single patient, demonstrating its applicability for clinical pharmacokinetic research with zalcitabine.     

Longitudinally orientated smooth muscle cells in rabbit arteries

Intima formation in vessels, spontaneous or experimentally induced, is generally characterized by the presence of longitudinally orientated smooth muscle cells (LSMC). During an experiment of neo-intima induction in carotid arteries in rabbits, by application of a nonconstrictive silastic cuff, a study was performed to investigate the presence of LSMC in the systemic and pulmonary circulations, in both elastic and muscular arteries. Three patterns could be distinguished: intimai cushions in muscular arteries, single or small groups of LSMC in the intima in elastic and larger muscular arteries, and intra-medially located layers or columns of LSMC in the aorta, the pulmonary artery, at the bifurcation of the aorta and around orifices of branches. In order to understand this peculiar orientation a biomechanical approach was used: this showed that near the lumen the circumferential stress is 4.5 times higher than the longitudinal. Because the cell surface of the smooth muscle cells exposed to this stress per unit vessel length is much less in the longitudinal than in the circular direction we conclude that the LSMC align in the direction which allows them to cope most effectively with the mechanical stresses.     

Translational accuracy and sexual differentiation in Chlamydomonas reinhardtii

Summary A renewal of ribosomes has been previously reported to occur during gametogenesis in C. reinhardtii. In order to further characterize these new ribosomes, we performed pulse-labelling experiments on whole cells of C. reinhardtii, during gametogenesis and in the presence of various aminoglycosides known to alter translational accuracy: Hygromycin and Paromomycin are assumed to increase the rate of translational errors at the level of 80S and 70S ribosomes whereas Kasugamycin is assumed to induce the opposite effect. Three lines of evidence support an increased inaccuracy in protein translation during gametogenesis: (1) gamete cells displayed a higher sensitivity than vegetative cells to Hygromycin and Paromomycin; 4 g/ml Hygromycin cancelled cytoplasmic protein synthesis in gametes but not in vegetative cells; Paromomycin induced the synthesis of new polypeptides of high molecular weight and of nuclear origin in gametes but not in vegetative cells. In addition, chloroplast protein synthesis was more sensitive to Hygromycin and Paromomycin in gametes than in vegetative cells. (2) Kasugamycin-sensitive alterations of thylakoid membranes were detected during gametogenesis. (3) ³⁵S-misincorporation in the OEE3 polypeptide, of nuclear origin and normally devoid of sulphur containing amino acids, was more than three times higher in gametes than in vegetative cells. This increase was prevented by Kasugamycin, suggesting that 80S translation in gametes was more inaccurate than in vegetative cells. The possible significance of these changes occurring during gametogenic differentiation is discussed in light of the importance of a modulation of translational accuracy at particular stages of the life cycle in other lower eukaryotes.Abbreviations Hm Hygromycin B - Pm Paromomycin - Ks Kasugamycin - CAP Chloramphenicol - OEE Oxygen evolving enhancer     

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Synthesis,physical properties and microbiological activities of more water soluble silver sulfadiazine derivatives

In this study the preparation of five hydrophilic derivatives of sulfadiazine is reported. The common structural element in the compounds is the 2-sulfonamidopyrimidine moiety. Three of these compounds are suitable for the preparation of a photostable 1∶1 silver compound. These silver compounds are five to ten times more water soluble than silver sulfadiazine. TheIr,¹H- and¹³C-Nmr data point to a similar co-ordination of silver in these compounds as with silver sulfadiazine. The microbiological activity of these silver compounds againstSt. aureus is slightly lower.     

Impaired antigen-presenting cell function contributes to T-cell hyporesponsiveness in stable lung transplant recipients

BACKGROUND: Peripheral blood mononuclear cells (PBMC) of stable renal or cardiac transplant recipients were previously shown to respond to allogeneic cells but not to soluble protein antigens. The aim of the present study was to assess the T-cell and antigen-presenting cell (APC) functions of stable lung transplant (LT) recipients. METHODS: We obtained PBMC from 38 stable LT recipients. PBMC from healthy volunteers served as controls. PBMC were stimulated with either anti-CD3 monoclonal antibody, allogeneic PBMC, or tetanus toxoid (TT). T-cell activation was assessed by determination of interleukin (IL)-2 levels in culture supernatants; in some experiments, interferon-y levels were also determined. Patients' APC function was tested in a mixed leukocyte reaction using patients' PBMC as stimulators. The expression of class II MHC, B7.2, and CD40 molecules on patients' APC was determined by flow cytometry, and their production of IL-10 and IL-12 at the basal state and upon CD40 ligation was also measured. RESULTS: Patients' T cells produced normal amounts of IL-2 in response to anti-CD3 monoclonal antibody and allogeneic PBMC. In contrast, the response of memory T cells to TT was severely blunted both in terms of IL-2 and interferon-y production. Patients' PBMC were poor stimulators in mixed leukocyte reaction, and class II MHC expression on patients' monocytes was significantly reduced. Patients' APC presented a modest but significant increase in basal IL-10 production and produced significantly less IL-12 upon CD40 ligation than control APC. CONCLUSIONS: T cells from stable LT recipients respond normally to stimuli that do not depend on autologous APC. The major impairment in the T-cell response to TT is caused by APC dysfunction, which involves decreased class II MHC expression and deficient IL-12 synthesis.