Ear wax and otitis media in children.

A study was designed to find the prevalence of ear wax in children aged 3 to 10 years and to test the belief that large amounts of wax are unlikely to be seen when otitis media is present. Roughly a quarter of the children had appreciable amounts of wax, and there was a gradual decline in prevalence with age. The amount of ear wax appeared to decrease when otitis media was present. The results did not support removing wax when assessing children''s ears in general practice.     

A sensitive chemiluminescence assay for pertussis toxin and for evaluation of cell-free pertussis toxoids

Abstract Pertussis toxin (PT) inhibited luminol-enhanced chemiluminescence induced in rabbit peritoneal neutrophils by N'-formyl- l -methionyl- l -leucyl- l -phenylalanine (fMLP) at doses as low as 0.8 ng·ml⁻¹, even in the presence of a 10-fold higher concentration of filamentous haemagglutinin (FHA). A cell-free extract of Bordetella pertusis , containing predominantly PT and FHA, suppressed the neutrophil response to fMLP. After toxoiding with carbodiimide, the inhibitory activity of the extract was abolished and an enhancement of neutrophil chemiluminescence was observed due to FHA activity. Abrogation of the chemiluminescent response of neutrophils to fMLP is proposed as a sensitive, in vitro assay for PT, and may be useful for monitoring the residual toxin activity in pertussis toxoids and for determining the anti-toxic effects of anti-PT antibodies.     

Synthetic formyl-methionyl chemoattractants: A conformation-activity study of oxidized tripeptides

The two diastereomeric sulphoxides and the sulphone derived from the formyl-methionyl tripeptide chemoattractant CHO-L-Met-L-Leu-L-Phe-OMe have been synthesized and fully characterized. The diastereomeric sulphoxide tripeptides have been separated at the stage of their N-tert-butyloxycarbonyl synthetic precursors. All of the oxidized sulphur derivatives induce secretion of granule enzymes with ED₅₀s from 1–2×10⁻⁹ M with no significant differences in activity among them. They are also active to the same relative extent in inducing chemotaxis. In parallel, a solution conformational analysis has been performed in solvents of widely different polarities and capabilities of H-bond formation using circular dichroism, infrared absorption and ¹H nuclear magnetic resonance. No significant propensity for formation of intramolecularly (C=O…H-N) H-bonded folded forms has been detected in any of the four tripeptides. Intermolecular S=O…H-N interactions are postulated to tentatively explain the ¹H nuclear magnetic resonance behavior of the Met and, particularly, Leu NH resonances of the two sulphoxide tripeptides in CDCl₃ solution. The biological and conformational data agree with the recently proposed model of the chemotactic peptide receptor of rabbit neurotrophils, which involves the extended backbone of the integrity of the Met side-chain sulphide sulphur atom as a corollary point of ligand interaction.     

Regulation of beta-1, 4-Glucosidase Expression by Candida wickerhamii

Candida wickerhamii NRRL Y-2563 expressed beta-glucosidase activity (3 to 8 U/ml) constitutively when grown aerobically in complex medium containing either glycerol, succinate, xylose, galactose, or cellobiose as the carbon source. The addition of a high concentration of glucose (>75 g/liter) repressed beta-glucosidase expression (<0.3 U/ml); however, this yeast did produce beta-glucosidase when the initial glucose concentration was 相似文献   

Acetylcholine potentiation of field stimulated rat vas deferens: A pre-synaptic muscarinic mechanism?

Acetylcholine (ACh) was found to markedly enhance the nerve stimulation induced twitch response of isolated, field-stimulated rat vas deferens (RVD). The ED₂₀₀ (concentration which enhances the twitch response to 200% of control) for this potentiation was 6 × 10^?6M with the maximum twitch response being increased by more than 3 fold (325 ± 30%). Carbachol (ED₂₀₀ = 8.5 × 10^?7M) showed identical results. With each drug the potentiation was competitively antagonized by atropine (10^?7?10^?5M). Physostigmine 10^?8?10^?6M) both enhanced the basal twitch response (215 ± 8% of control at 10^?5M) and the sensitivity of the RVD to ACh (ED₂₀₀ = 3.3 × 10^?7M) but not to carbachol. Atropine, on the other hand reduced the basal twitch response by 18 ± 3% at 10^?5M. Hemicholinium (10^?4M) also reduced the basal twitch responses by 23 ± 5%. ACh (10^?7M?10^?5M) did not modify the responses of unstimulated RVD to norepinephrine or KCl suggesting a pre-synaptic site of action. Taken together these results are compatible with the presence of a pre-junctional, excitatory muscarinic mechanism in the field stimulated RVD. That this cholinergic system may be of physiological significance is supported by the observations that atropine and hemicholinium depress while physostigmine enhances the twitch response in the absence of exogenous ACh.     

Brucella-Salmonella lipopolysaccharide chimeras are less permeable to hydrophobic probes and more sensitive to cationic peptides and EDTA than are their native Brucella sp. counterparts.

A rough (R) Brucella abortus 45/20 mutant was more sensitive to the bactericidal activity of polymyxin B and lactoferricin B than was its smooth (S) counterpart but considerably more resistant than Salmonella montevideo. The outer membrane (OM) and isolated lipopolysaccharide (LPS) of S. montevideo showed a higher affinity for these cationic peptides than did the corresponding B. abortus OM and LPS. We took advantage of the moderate sensitivity of R B. abortus to cationic peptides to construct live R B. abortus-S-LPS chimeras to test the activities of polymyxin B, lactoferricin B, and EDTA. Homogeneous and abundant peripheral distribution of the heterologous S-LPS was observed on the surface of the chimeras, and this coating had no effect on the viability or morphology of the cells. When the heterologous LPS corresponded to the less sensitive bacterium S B. abortus S19, the chimeras were more resistant to cationic peptides; in contrast, when the S-LPS was from the more sensitive bacterium S. montevideo, the chimeras were more susceptible to the action of peptides and EDTA. A direct correlation between the amount of heterologous S-LPS on the surface of chimeric Brucella cells and peptide sensitivity was observed. Whereas the damage produced by polymyxin B in S. montevideo and B. abortus-S. montevideo S-LPS chimeras was manifested mainly as OM blebbing and inner membrane rolling, lactoferricin B caused inner membrane detachment, vacuolization, and the formation of internal electron-dense granules in these cells. Native S and R B. abortus strains were permeable to the hydrophobic probe N-phenyl-1-naphthylamine (NPN). In contrast, only reduced amounts of NPN partitioned into the OMs of the S. montevideo and B. abortus-S. montevideo S-LPS chimeras. Following peptide exposure, accelerated NPN uptake similar to that observed for S. montevideo was detected for the B. abortus-S. montevideo LPS chimeras. The partition of NPN into native or EDTA-, polymyxin B-, or lactoferricin B-treated LPS micelles of S. montevideo or B. abortus mimicked the effects observed with intact cells, and this was confirmed by using micelle hybrids of B. abortus and S. montevideo LPSs. The results showed that LPS is the main cause of B. abortus' resistance to bactericidal cationic peptides, the OM-disturbing action of divalent cationic chelants, and OM permeability to hydrophobic substances. It is proposed that these three features are related to the ability of Brucella bacteria to multiply within phagocytes.     

Vesicular stomatitis virus Indiana glycoprotein as a T-cell-dependent and -independent antigen.

The neutralizing immunoglobulin M (IgM) response to vesicular stomatitis virus (VSV) has been shown to be largely T-cell independent in several T-cell-deficient models of mice. By using different antigen froms of VSV, VSV antigen doses could be graded in vivo (infectious > > UV inactivated > formalin inactivated). The present study reveals a T-cell-dependent component of the neutralizing IgM response in nude mice given intravenous injections of low doses of noninfectious UV-inactivated VSV serotype Indiana (VSV-IND) only if the mice are transfused with VSV-IND-specific helper T cells. Instead, nude mice immunized with infectious VSV, which leads to greater antigen doses in vivo, were able to mount an IgM response in the absence of T cells. These results indicate that the IgM response to low doses of VSV-IND glycoprotein (G) is T-cell dependent. Nude mice immunized with infectious VSV also made a variable but low VSV-IND-neutralizing IgG response. A VSV-IND matrix (M)-specific helper T-cell line rendered this response more consistent, much higher, and longer lasting. Thus (i) VSV-G induces a mostly T-cell-independent but partially T-cell-dependent IgM (the latter can be visualized best at low doses of antigen) and (ii) the antibody response to VSV in nude mice proceeds through steps, i.e., IgM and IgG, that are dose dependent. The results suggest that the predominant role of helper T cells may be to expand and maintain the individual steps of differentiating B cells.     

Secretagogue-induced phosphoinositide metabolism in human leucocytes.

The relationship between receptor binding of the formylated peptide chemoattractant formylmethionylleucylphenylalanine (fMet-Leu-Phe), lysosomal enzyme secretion and metabolism of membrane phospholipids was evaluated in both human polymorphonuclear leucocytes (PMN) and the dimethyl sulphoxide (Me2SO)-stimulated human myelomonocytic HL-60 leukaemic cell line. In both cell types, exposure to fMet-Leu-Phe (100 nM) induced rapid lysosomal enzyme secretion (maximal release less than 30 s) and marked changes in the 32P-labelling of the inositol lipids phosphatidylinositol (PtdIns), phosphatidylinositol 4-phosphate (PtdIns4P), phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] as well as phosphatidic acid (PtdA). Specifically, levels of [32P]PtdIns and [32P]PtdIns(4,5)P2 decreased rapidly (peak decrease at 10-15s), with a subsequent increase at 30 s and later. PtdIns4P and PtdA showed only an increase. In Me2SO-differentiated HL-60 cells prelabelled with [3H]inositol for 20 h, fMet-Leu-Phe caused a net increase in the cellular content of [3H]inositol phosphates, including a rapid increase in [3H]inositol 1,4,5-trisphosphate, suggesting that PtdIns(4,5)P2 breakdown occurs by a phospholipase C mechanism. Both lysosomal enzyme secretion and changes in phospholipid metabolism occur over the same agonist concentration range with a similar time course. Binding of [3H]fMet-Leu-Phe, although occurring over the same concentration range, exhibited markedly slower kinetics. Although depletion of extracellular Ca2+ had no effect on ligand-induced polyphosphoinositide turnover, PtdIns turnover, PtdA labelling and lysosomal enzyme secretion were severely curtailed. These studies demonstrate a receptor-mediated enhancement of phospholipid turnover that correlates with a specific biological response to fMet-Leu-Phe. Further, the results are consistent with the idea that phospholipase C-mediated degradation of PtdIns(4,5)P2, which results in the formation of inositol trisphosphate, is an early step in the stimulus-secretion coupling pathway of the neutrophil. The lack of correlation between these two responses and the equilibrium-binding condition suggests that either these parameters are responsive to the rate of ligand-receptor interaction or only fractional occupation is required for a full biological response.