Vaccination against typhoid fever: present status.

Typhoid fever remains an underestimated important health problem in many developing countries, causing more than 600,000 deaths annually in the world. Because of the reactogenicity of the parenteral, killed whole-cell vaccine, research has been oriented towards vaccination orally using live organisms and purified antigen. Live vaccine Ty21a, given by the oral route, has been extensively tested in several studies in developing countries. Its liquid formulation was the most effective, providing more than 60% protection after 7 years of follow-up. A Vi polysaccharide vaccine has been elaborated and provided more than 65% protection; after 3 years of follow-up the Vi antibody level was still at a high level. These two vaccines are therefore candidates for use in public health control programmes. Before such use, however, they need further evaluation for safety and protective efficacy when administered to the EPI-targeted age groups. The question of whether typhoid fever vaccines interfere with the response to simultaneously administered measles vaccine must also be studied. New live vaccines, given by the oral route in one dose, have been constructed through genetic engineering. The first results are promising, but they must be improved before use in a large-scale study. These strains could be used as live vector to deliver foreign antigens to the intestinal mucosa.     

Reductive activation and radical formation in a series of substituted benzoquinones: Thermodynamic and quantum chemical studies

The reduction of the quinone moiety, which is found in many anti-cancer agents, is still a poorly understood process. It is commonly assumed that the reduction of a quinone by the uptake of two electrons and two protons leads to the active hydroquinone form. For a better understanding of these reactions electrochemical data, obtained for a series of substituted benzoquinones, were analyzed. In addition quantum chemical calculations on the STO-3G level were performed to obtain data for the one- and two-electron reduction.From the electrochemical experiments, thermodynamic data can be obtained which show that the unfavourable free energy of electron uptake is overcome by the favourable binding of protons. Both reactions are influenced by the electronic properties of the substituents, as demonstrated by Hammett-type relationships between the free energy of these reactions and the sigma-para character of these substituents. In these relationships the reaction constant of the electron uptake process has an absolute value which is five times higher than that of the proton uptake.Quantum chemical calculations yielded energy values for the one-electron uptake, as expressed by U(LUMO), and for the total reduction process. Most of the results from these calculations are in accord with the thermodynamic study. The calculations also revealed a conformational change to take place upon reduction of NH₂ and N(CH₂)₂ substituted benzoquinones, which might be important for chemical and biological activity.     

Do local anaesthetics interact with dihydropyridine binding sites on neuronal L-type Ca2+ channels?

We have examined the interaction of procaine, prilocaine, lignocaine, bupivacaine, amylocaine and R(+) and S(-) ropivacaine with L-type voltage-sensitive Ca2+ channels in rat cerebrocortical membranes. Membranes were prepared in Tris HCl 50 mmol litre-1, pH 7.4, by homogenization and centrifugation. Binding assays were performed in 1- ml volumes of Tris HCl 50 mmol litre-1, pH 7.4, for 90 min at room temperature using approximately 200 micrograms of protein. Non-specific binding was defined in the presence of nifedipine 10(-5) mol litre-1, and bound and free radioactivity were separated by vacuum filtration. The effects of local anaesthetics were determined by displacement of [3H]PN200-110 (approximately 0.2 nmol litre-1), a radiolabelled 1,4- dihydropyridine (DHP) L-channel antagonist. The concentration of displacer producing 50% displacement was corrected for the competing mass of [3H]PN200-110 to yield the affinity constant, K50. All local anaesthetics displaced [3H]PN200-110 in a dose-dependent manner with a rank order potency of (K50, mmol litre-1) bupivacaine (0.48), amylocaine (0.74), lignocaine (1.09), prilocaine (2.06) and procaine (2.09). Ropivacaine enantiomers did not show stereo-selective displacement, with K50 values of 0.99 and 0.92 mmol litre-1 for R(+) and S(-) ropivacaine, respectively. There was a significant correlation between pK50 and p (octanol:buffer partition coefficient) (r2 = 0.872, P = 0.020), pK50 and p (local anaesthetic potency) (r2 = 0.816, P = 0.036), pK50 and p (relative conduction blocking potency) (r2 = 0.843, P = 0.028) and between pK50 and p (IC50 for inhibition of cardiac output) (r2 = 0.897, P = 0.015). These data suggest that DHP binding sites may be involved in both the mechanism of local anaesthesia and the cardiotoxicity of these agents.      

Convergence of occipital nerve and superior sagittal sinus input in the cervical spinal cord of the cat

Co-existence of facial and occipital pain may occur in occipital neuralgia, migraine and cluster headache; suggesting convergence of trigeminal and cervical afferents. Such convergence has been shown in humans and other animals, but the site and extent of this are uncertain. In anaesthetized adult cats, the superior sagittal sinus and occipital nerve were stimulated electrically, and extracellular recordings made in the dorsolateral area of the upper cervical cord using glass-coated tungsten electrodes. Of 49 units in 10 cats, 33 (67%) had input from the superior sagittal sinus and the occipital nerve. Thirteen (27%) had superior sagittal sinus input and 3 (6%) had occipital nerve input. Convergent receptive fields were identified mechanically in 7 units. These experiments in cats show convergent input from occipital nerve and superior sagittal sinus on dorsolateral area units in two-thirds of cases studied. This experimental site of trigeminocervical convergence may relate to referral of pain in occipital neuralgia and other headaches.     

Enhancing psychotherapy outcomes via providing feedback on client progress: a replication

Several systems have been developed to monitor and feedback information about a client's responses to psychotherapy as a method of enhancing client outcome. The current study divided 1020 clients into four groups (two experimental and two control) to determine if feedback regarding client progress, when provided to a therapist, affected client outcome and number of sessions attended. Results showed that feedback increased the duration of treatment and improved outcome for clients identified as potential treatment failures thereby replicating an earlier study using nearly identical methodology. Nearly twice as many clients in the feedback group achieved clinically significant or reliable change and fewer were classified as deteriorated by the time treatment ended. For those clients who were predicted to have a positive response to treatment, feedback to therapists resulted in an equal number of treatment sessions and equivalent outcomes compared to the no feedback controls. The results are discussed in terms of quality management in routine clinical practice and the need to base treatment decisions on clients' response to treatment rather than arbitrary session limits. Suggestions for additional research aimed at enhancing the effects of feedback on client outcome are made. Copyright © 2002 John Wiley & Sons, Ltd.     

Crosslinking of fibrinogen and fibronectin by free radicals: a possible initial step in adhesion formation in osteoarthritis of the temporomandibular joint.

PURPOSE: Adhesion formation in osteoarthritis (OA) of the temporomandibular joint (TMJ) typically results in a sustained limitation of joint movement. We propose the hypothesis that free-radical-mediated crosslinking of proteins underlies this adhesion formation in affected joints. Free radicals may cause oxidative modification of proteins, creating an opportunity for the formation of intramolecular and intermolecular crosslinks via covalent bonds. This may stabilize protein aggregates, rendering them more resistant to degradation. In this study, the free-radical-mediated crosslinking of model proteins (fibrinogen and fibronectin) was investigated to test our hypothesis that free radicals contribute to adhesion formation via this mechanism in OA of the TMJ. MATERIALS AND METHODS: Physiological clot formation of fibrinogen by thrombin and free-radical-induced crosslinking of fibrinogen and of fibronectin were analyzed using spectrophotometric turbidity measurements, light-scattering techniques, polyacrylamide gel electrophoresis (PAGE), and rotary shadowing. RESULTS: Fibrinogen was shown to aggregate after free radical treatment, as detected using turbidity measurements and light-scattering techniques. Using PAGE, fibrinogen as well as fibronectin was shown to degrade under low oxidative stress. Under high oxidative stress, however, fragments from both proteins were found to be covalently crosslinked, resulting in high-molecular-weight protein aggregates. The aggregation was shown to be at random with rotary shadowing. CONCLUSION: The study shows that high oxidative stress contributes to the formation of crosslinked proteins that may serve as an initial scaffolding for the development of adhesions frequently seen in OA of the TMJ.     

Comparative effects of stimulation of the trigeminal ganglion and the superior sagittal sinus on cerebral blood flow and evoked potentials in the cat

The superior sagittal sinus (SSS) and the trigeminal ganglion (Vg) of anesthetized cats were stimulated electrically and field potentials in the upper cervical spinal cord and regional cerebral blood flow were recorded. Stimulation of the entire ganglion produced smaller field potential changes in two regions (medioventral area (MVA); dorsolateral area (DLA] of the upper spinal cord than did stimulation of the sagittal sinus (Vg/SSS response ratio = 17% for the MVA and 48% for the DLA). Stimulation of the trigeminal ganglion increased blood flow in only the frontal and parietal cortices (+93% and +33%), whereas stimulation of the sinus produced both larger changes in these areas (+137% and +139%) and also produced changes in regional cerebral blood flow in the thalamus (+122%).     

Missense mutations and evolutionary conserved amino acids at the human hypoxanthine phosphoribosyl-transferase locus.

Molecular characterization of in vivo mutation at the human hypoxanthine phosphoribosyltransferase (hprt) locus has revealed a broad spectrum of mutation, both with regard to germ-line mutation in Lesch-Nyhan and gout patients, and somatic mutation in 6-thioguanine resistant T-lymphocytes from healthy individuals. The pattern of missense mutation shows a non-random distribution with a preferential location to codons for amino acids which are identical in human and the two parasites Schistosoma mansoni and Plasmodium falciparum. Although these 'evolutionary conserved' amino acids account for only 32% of the amino acids in the human hprt protein, they are involved in 76% of the missense mutations at the hprt locus in human T-lymphocytes, 67% in Lesch-Nyhan patients (with severe hprt-deficiency), but only 43% in gout patients (with partial hprt deficiency). This observation supports the notion that evolutionary conserved amino acids constitute functionally important sites in the hprt enzyme, and missense mutations affecting these amino acids will often lead to complete loss of enzyme activity. Substitutions of 'non-conserved' amino acids cause less severe hprt-deficiency (as seen in the gout patients), or may even escape clinical diagnosis. These considerations are important for the understanding of structure-activity relationships in the hprt protein, possible differences between hprt mutational spectra in germ-line and somatic cells, and the mutational spectra induced by specific exogeneous mutagens.