[Otoacoustic distortion products in infants and adults: a comparative study]

Distortion Products (DP) are otoacoustic emissions evoked by emitting two pure tones. The principle advantage of this method vs. transient evoked otoacoustic emissions is the specificness of frequency. The purpose of the present work was to determine whether this technique could be applied in objective study of cochlear function in infants. This was done by setting standard data for infants and comparing them with the data obtained in a control population of adults. The input/output functions of the DP and the DP audiograms for 8 f2 frequencies ranging from 696 to 6006 Hz were studied in a group of 15 healthy, full-term infants. The data obtained were statistically compared to the data taken from a control group of 8 normal hearing adults. The infants showed significantly more intense DPs in the intermediate frequencies, with a greater detection threshold and dynamic range. On the other hand, at the high frequencies the amplitude of infant DPs was the same or lower than (f2 = 5005) those found in the adults. These differences can partially be attributed to the fact that the outer auditory channel is smaller in infants thus the probe and the middle ear are better matched. There is significantly greater background noise in infant DPs, particularly at low frequencies. This may be due to the fact that the skin of the outer auditory duct--which acts as a low-pass filter allowing suction and movement of the cervical muscles to contaminate the tracing--is thinner in infants. In conclusion, the study of DPs has shown its potential in the study of cochlear function in infants because it is non invasive and objective, it can be performed quickly and shows frequency specificness. Unfortunately, it cannot be considered a valid method for determining cochlear function at the low frequencies.

Association between longevity and allelic forms of human leukocyte antigens (HLA): population study of aged Italian human subjects

Several arguments support the idea of a link between longevity and heredity, both in humans and in experimental animals. We have therefore investigated the possibility of an association between the human leukocyte antigens (HLA) and longevity in two groups of Italian subjects: 108 healthy subjects over 85 years old, and 749 healthy blood donors (controls). Only four antigens showed a higher frequency in the elder group: HLA-A31(19), B7, Cw7 and DQ1. These findings suggest an involvement of HLA antigens in human longevity, but the real biological meaning of these results is still unclear.

Solution structure of glutathione bound to human glutathione transferase P1-1: comparison of NMR measurements with the crystal structure

The conformation of the bound glutathione (GSH) in the active site of the human glutathione transferase P1-1 (EC 2.5.1.18) has been studied by transferred NOE measurements and compared with those obtained by X-ray diffraction data. Two-dimensional TRNOESY and TRROESY experiments have been performed under fast-exchange conditions. The family of GSH conformers, compatible with TRNOE distance constraints, shows a backbone structure very similar to the crystal model. Interesting differences have been found in the side chain regions. After restrained energy minimization of a representative NMR conformer in the active site, the sulfur atom is not found in hydrogen-bonding distance of the hydroxyl group of Tyr 7. This situation is similar to the one observed in an "atypical" crystal complex grown at low pH and low temperature. The NMR conformers display also a poorly defined structure of the glutamyl moiety, and the presence of an unexpected intermolecular NOE could indicate a different interaction of this substrate portion with the G-site. The NMR data seem to provide a snapshot of GSH in a precomplex where the GSH glutamyl end is bound in a different fashion. The existence of this precomplex is supported by pre-steady-state kinetic experiments [Caccuri, A. M., Lo Bello, M., Nuccetelli, M., Nicotra, M., Rossi, P., Antonini, G., Federici, G., and Ricci, G. (1998) Biochemistry 37, 3028-3034] and preliminary time-resolved fluorescence data.

Proton release upon glutathione binding to glutathione transferase P1-1: kinetic analysis of a multistep glutathione binding process

The fate of the thiol proton coming from the ionization of the sulfhydryl group of GSH in the active site of glutathione transferase P1-1 has been studied. pH changes caused by the binding of GSH to the enzyme in the absence of any inorganic buffer indicate that the thiol proton leaves the active site when the binary complex is formed. The amount of protons released is stoichiometric to the amount of GSH thiolate formed in the G-site. The apparent pKa value for the bound GSH, calculated with this potentiometric approach, is 6.18 +/- 0.09; very similar values are found by spectrophotometric (6.20 +/- 0.12) and by kinetic (6.00 +/- 0.08) experiments. Binding of S-hexylglutathione does not cause any proton release. Stopped-flow data obtained by means of an acid-base indicator show that the proton extrusion process (apparent t1/2 = 1.1 +/- 0.1 ms at 15 degrees C) is not rate limiting in turnover (apparent t1/2 = 34 +/- 4 ms at 15 degrees C). By comparing the kinetic behavior of three distinct events occurring during the binding of GSH to the enzyme, i. e., proton release, ionization of bound GSH and quenching of intrinsic fluorescence, it appears that the binding process follows a multistep mechanism possibly involving the conformational transition of a weak precomplex into the final Michaelis complex. This step is modulated by helix 2 motions and may be rate limiting at physiological GSH concentrations. These findings, coming from kinetic studies, are consistent with NMR data [Nicotra, M., Paci, M., Sette, M., Oakley, A. J., Parker, M. W., Lo Bello, M., Caccuri, A. M., Federici, G., and Ricci, G. (1998) Biochemistry 37, 3020-3027] and time-resolved fluorescence experiments [Stella, L., Caccuri, A. M., Rosato, N., Nicotra, M., Lo Bello, M., De Matteis, F., Mazzetti, A. P., Federici, G., and Ricci, G., manuscript in preparation].

Junctional contacts between Sertoli cells in normal and aspermatogenic rat seminiferous epithelium contain alpha6beta1 integrins, and their formation is controlled by follicle-stimulating hormone

The distribution of alpha6beta1 integrins at the level of cell-to-cell contacts within the rat seminiferous epithelium was investigated. Double fluorescence experiments using phalloidin staining of actin filaments and anti-integrin subunit antibodies showed that the receptor belongs to the Sertoli cell lateral domains engaged in the characteristic junctional structures known as ectoplasmic specializations (ES), at the level both of inter-Sertoli junctions and of the contacts between Sertoli cells and elongating spermatids. In the seminiferous epithelium of aspermatogenic testes, obtained through X-irradiation in utero (Sertoli-cell-only testes), at the level of inter-Sertoli junctions both ES and alpha6beta1 integrins are present. In order to study the dependence of alpha6beta1 receptors and ES formation upon FSH stimulation during development, 9-day-old testes were grown in organ culture in basal as well as FSH-supplemented conditions. FSH stimulation, which is necessary for the progression of spermatogenesis to early meiotic stages, appears to be required for the development of inter-Sertoli junctional structures containing ES and alpha6beta1 integrins. These observations indicate that the receptor belongs to the inter-Sertoli junctional machinery and that its expression at that level is not dependent on active spermatogenesis but requires FSH stimulation.

Catalytic mechanism and role of hydroxyl residues in the active site of theta class glutathione S-transferases. Investigation of Ser-9 and Tyr-113 in a glutathione S-transferase from the Australian sheep blowfly, Lucilia cuprina

Spectroscopic and kinetic studies have been performed on the Australian sheep blowfly Lucilia cuprina glutathione S-transferase (Lucilia GST; EC 2.5.1.18) to clarify its catalytic mechanism. Steady state kinetics of Lucilia GST are non-Michaelian, but the quite hyperbolic isothermic binding of GSH suggests that a steady state random sequential Bi Bi mechanism is consistent with the anomalous kinetics observed. The rate-limiting step of the reaction is a viscosity-dependent physical event, and stopped-flow experiments indicate that product release is rate-limiting. Spectroscopic and kinetic data demonstrate that Lucilia GST is able to lower the pKa of the bound GSH from 9.0 to about 6.5. Based on crystallographic suggestions, the role of two hydroxyl residues, Ser-9 and Tyr-113, has been investigated. Removal of the hydroxyl group of Ser-9 by site-directed mutagenesis raises the pKa of bound GSH to about 7.6, and a very low turnover number (about 0.5% of that of wild type) is observed. This inactivation may be explained by a strong contribution of the Ser-9 hydroxyl group to the productive binding of GSH and by an involvement in the stabilization of the ionized GSH. This serine residue is highly conserved in the Theta class GSTs, so the present findings may be applicable to all of the family members. Tyr-113 appears not to be essential for the GSH activation. Stopped-flow data indicate that removal of the hydroxyl group of Tyr-113 does not change the rate-limiting step of reaction but causes an increase of the rate constants of both the formation and release of the GSH conjugate. Tyr-113 resides on alpha-helix 4, and its hydroxyl group hydrogen bonds directly to the hydroxyl of Tyr-105. This would reduce the flexibility of a protein region that contributes to the electrophilic substrate binding site; segmental motion of alpha-helix 4 possibly modulates different aspects of the catalytic mechanism of the Lucilia GST.

The structures of human glutathione transferase P1-1 in complex with glutathione and various inhibitors at high resolution

The human pi-class glutathione S-transferase (hGST P1-1) is a target for structure-based inhibitor design with the aim of developing drugs that could be used as adjuvants in chemotherapeutic treatment. Here we present seven crystal structures of the enzyme in complex with substrate (glutathione) and two inhibitors (S-hexyl glutathione and gamma-glutamyl- (S-benzyl)cysteinyl-D-phenylglycine). The binding of the modified glutathione inhibitor, gamma-glutamyl-(S-benzyl)cysteinyl-D-phenylglycine, has been characterized with the phenyl group stacking against the benzyl moiety of the inhibitor and making interactions with the active-site residues Phe8 and Trp38. The structure provides an explanation as to why this compound inhibits the pi-class GST much better than the other GST classes. The structure of the enzyme in complex with glutathione has been determined to high resolution (1.9 to 2.2 A) in three different crystal forms and at two different temperatures (100 and 288 K). In one crystal form, the direct hydrogen-bonding interaction between the hydroxyl group of Tyr7, a residue involved in catalysis, and the thiol group of the substrate, glutathione, is broken and replaced by a water molecule that mediates the interaction. The hydrogen-bonding partner of the hydroxyl group of Tyr108, another residue implicated in the catalysis, is space-group dependent. A high-resolution (2.0 A) structure of the enzyme in complex with S-hexyl glutathione in a new crystal form is presented. The enzyme-inhibitor complexes show that the binding of ligand into the electrophilic binding site does not lead to any conformational changes of the protein.

Long-term evaluation of cellular immunity during antiretroviral therapy and immunization with human immunodeficiency virus type 1 (HIV-1) Env glycoprotein in HIV-1-infected persons

Cellular immune responses to human immunodeficiency virus type 1 (HIV-1) antigens, microbial recall antigens, and CD3 monoclonal antibody were studied in HIV-1-infected asymptomatic patients in a phase II, double-blind trial of immunization with recombinant HIV-1 gp160 in or not in association with zidovudine. A vigorous and persistent lymphoproliferative response (LPR) to HIV-1 Env antigens was observed in vaccinated patients. Neither Env-specific lymphocyte cytotoxicity nor LPR to recall antigens was significantly influenced by gp160 administration. The induction of LPRs to HIV-1 envelope proteins did not show positive effects on the course of HIV-1 infection. Patients treated with zidovudine alone or in combination with the immunogen showed improvement of T lymphocyte responses and transient reduction of viremia. These results suggest that antiretroviral therapy is more beneficial than immunization with gp160 and should always be considered in association with future vaccination and immunotherapeutic interventions in HIV-1-infected subjects.

Factors associated with gallstone disease in the MICOL experience. Multicenter Italian Study on Epidemiology of Cholelithiasis

The epidemiological associations of gallstone disease were evaluated in a general population sample of 29,584 individuals (15,910 men and 13,674 women; age range, 30-39 years) belonging to 14 cohorts examined between December 1984 and April 1987. Subjects were screened for the presence of gallstones by gallbladder ultrasonography, completed a questionnaire, and underwent a physical examination and blood chemistry tests. Participants were considered to have gallstone disease if they had already had cholecystectomy or gallstones. Statistical associations were established by univariate analysis of the age-standardized data and by stepwise multiple logistic regression. Increasing age and body mass index and a maternal family history of gallstone disease were the most consistent associations (both at univariate and multivariate analysis and in both sexes) found in this study. Personal history of dieting was associated with gallstone disease in men, and at univariate analysis, in women. Decreasing serum total cholesterol levels and increasing serum triglycerides were associated with gallstone disease in both sexes in the multivariate analysis. In women, associations were also found with a number of pregnancies and paternal family history of gallstone disease. A slight but negative association with contraceptive pill use was identified only at multivariate analysis. Associations (investigated at univariate analysis) were also found with diabetes, cirrhosis, angina or myocardial infarction, and peptic ulcer. There was no association with smoking habits and use of aspirin or antirheumatic drugs.

Epidural lipomatosis with lumbar radiculopathy in one obese patient. Case report and review of the literature

Idiopathic epidural spinal lipomas are rare: only 13 cases have been described in the literature. We report a further case in an obese patient without known etiological factors. Diagnosis of epidural lipomatosis was performed by MRI. Weight reduction was obtained by conservative treatment, reserving surgery in case symptoms did not disappear. Of the 8 obese patients with idiopathic epidural spinal lipomatosis described in the literature, 3 were treated conservatively, with complete regression of symptoms in 2 cases, partial in the other one. In our patient, the radicular symptomatology disappeared once he had lost weight.

Olive oil and the Mediterranean diet: implications for health in Europe

At a meeting convened by the European Commission at the Italian National Research Council in Rome, 11 April 1997, European nutrition, cardiology, lipidology and public health specialists gathered to reach a health consensus on olive oil and the Mediterranean diet.

Multifunctional role of Tyr 108 in the catalytic mechanism of human glutathione transferase P1-1. Crystallographic and kinetic studies on the Y108F mutant enzyme

The possible role of the hydroxyl group of Tyr 108 in the catalytic mechanism of human glutathione transferase P1-1 has been investigated by means of site-directed mutagenesis, steady-state kinetic analysis, and crystallographic studies. Three representative cosubstrates have been used, i.e. ethacrynic acid, 7-chloro-4-nitrobenz-2-oxa-1,3-diazole, and 1-chloro-2,4-dinitrobenzene. In the presence of ethacrynic acid, the enzyme follows a rapid equilibrium random bi-bi mechanism with a rate-limiting step which occurs after the addition of the substrates and before the release of products. The replacement of Tyr 108 with Phe yields a 14-fold decrease of k(cat), while it does not change appreciably the affinity of the H site for the substrate. In this case, it would appear that the role of the hydroxyl function is to stabilize the transition state for the chemical step, i.e. the Michael addition of GSH to the electrophilic substrate. Crystallographic data are compatible with this conclusion showing the hydroxyl group of Y108 in hydrogen bonding distance of the ketone moiety of ethacrynic acid [Oakley, A. J., Rossjohn, J., Lo Bello, M., Caccuri, A. M., Federici, G., & Parker, M. W. (1997) Biochemistry 36, 576-585]. Moreover, no structural differences are observed between the Y108F mutant and the wild type, suggesting that the removal of the hydroxyl group is solely responsible for the loss of activity. A different involvement of Tyr 108 appears in the catalyzed conjugation of 7-chloro-4-nitrobenz-2-oxa-1,3-diazole with GSH in which the rate-limiting step is of a physical nature, probably a structural transition of the ternary complex. The substitution of Tyr 108 yields an approximately 7-fold increase of k(cat) and a constant k(cat)/Km(NBD-Cl) value. Lack of a critical hydrogen bond between 7-chloro-4-nitrobenz-2-oxa-1,3-diazole and Tyr 108 appears to be the basis of the increased k(cat). In the 1-chloro-2,4-dinitrobenzene/GSH system, no appreciable changes of kinetics parameters are found in the Y108F mutant. We conclude that Y108 has a multifunctional role in glutathione transferase P1-1 catalysis, depending on the nature of the electrophilic cosubstrate.

Coagulation and fibrinolysis changes in normal pregnancy. Increased levels of procoagulants and reduced levels of inhibitors during pregnancy induce a hypercoagulable state, combined with a reactive fibrinolysis

OBJECTIVE

To establish the physiologic changes in the coagulation and fibrinolytic systems during normal pregnancy and puerperium.

STUDY DESIGN

One hundred and seventeen normal pregnant women were investigated in a longitudinal study involving five measurements: blood samples were collected at 10, 20, 30, 36 weeks and on the second day puerperium and were assayed for prothrombin time (PT expressed in INR), activated partial thromboplastin time (PTT), fibrinogen (FBG), antithrombin III activity (AT III), protein C activity (PC), protein S activity (PS), prothrombin fragments 1+2 (F1+2), type 1 plasminogen activator inhibitor activity (PAI) and tissue-plasminogen activator antigen (t-PA). Student t-test, One Way Analysis of Variance (ANOVA) and Bonferroni test were used for statistical analysis. P<0.05 (two tails) was assumed to indicate a significant difference.

RESULTS

Fibrinogen concentrations were always increased with respect to controls (P<0.001), while protein S was always decreased, with values averaging 60% of those of controls from the 10th week of pregnancy onwards (P<0.001). Variance analysis showed a statistically significant increase with gestational age for procoagulant factors (INR: P<0.001; FBG: P<0.001), a reduction for anticoagulants (PC: P<0.0001; PS: P<0.0001), and a rise for F1+2 (P<0.0001). With regard to fibrinolysis, there was an increase both for t-PA (P<0.0001) and PAI-1 (P<0.0001) during pregnancy. The t-PA values were always comprised in the normal range. PAI-1 were increased with respect to control values starting from 31st week. The most significant variations in the procoagulants (expressed by PT and FBG) were recorded up to the 20th week (P<0.001); from the 30th week onwards, they remained stable until after the delivery. The same was true for protein S levels (P<0.001), except that the difference between the 10th and the 20th weeks was not statistically significant. The level of F1+2 gradually increased throughout pregnancy (P<0.001), and then fell in the puerperium (P<0.001).

CONCLUSIONS

The parameters showing the greatest variation during pregnancy were PT, FBG, PS, F1+2 and PAI-1. The existence of a hypercoagulable state in pregnancy was suggested by the increased levels of F1+2.

Inhibition of human placenta glutathione transferase P1-1 by the antibiotic calvatic acid and its diazocyanide analogue--evidence for multiple catalytic intermediates

The inhibition mechanism of the dimeric human placenta glutathione transferase (GST) P1-1 by calvatic acid and the reaction intermediates, i.e. the diazocyanide analogue of calvatic acid, has been investigated at pH 7.0 and 30.0 degrees C. Experiments performed at different molar ratios of inhibitor/GST P1-1 indicate that 1 mol calvatic acid inactivates 1 mol GST P1-1, containing two catalytically equivalent active sites. However, 2 mol of the diazocyanide analogue of calvatic acid inactivate 1 mol GST P1-1. Two disulfide bridges/dimer, probably between Cys47 and Cys101, have been formed during the reaction of GST P1-1 with calvatic acid and its diazocyanide analogue. The apparent second-order rate constants for GST P1-1 inactivation by calvatic acid and its diazocyanide analogue are 2.4+/-0.3 M(-1) s(-1) and (8.5+/-0.7) x 10(3) M(-1) s(-1), respectively. The reaction of calvatic acid with free L-cysteine can be described by a simple process with an apparent second-order rate constant of (5.0+/-0.4) x 10(1) M(-1) s(-1). In contrast, a transient species occurs during the reaction of the diazocyanide analogue of calvatic acid with free L-cysteine. Kinetics may be described by a second-order process [the rate constant being (8.0+/-0.5) x 10(3) M(-1) s(-1)] followed by a first-order decay [the rate constant corresponding to (1.2+/-0.1) x 10(1) s(-1)]. Calvatic acid represents an enzyme inhibitor acting much slower than its reaction intermediates (i.e. its diazocyanide analogue).

[Results and considerations regarding auditory neonatal screening based on the use of transient evoked otoacoustic emission]

The authors present a 5-year clinical experience in audiological screening performed at the neonatal center of the Policlinico of Perugia, Italy. The study was performed using an IL088 Otodynamics unit produced by Bray & Kemp. A total of 1328 newborns (2656 ears) were tested on the 4th day of life and during spontaneous sleep. None of the children had any audiological risk factors. The test was repeated one month later for all subjects who lacked Transient Evoked Otoacoustic Emissions and in many cases ABR testing was performed by 3 months of age. The authors present the undoubted advantages of the present method which include the fact that it is a) easy to perform, b) non invasive, c) sensitive and d) effective. They then discuss the main problems which arose during the course of the screening and advance some solutions. For the most part these problems involved the high number of false positives (13.1%) and the high percentage of subjects who were lost to subsequent controls (approximately 6% of the total population). The number of false positives could be reduced by using a linear acoustic stimulation (rather than the non-linear stimulation which is the default parameter for the machine). Such a linear stimulation can improve the signal-to-noise ratio, thus making it possible to adopt a reproducibility index lower than the 70% presently used (however, this brings with it the risk of including a certain number of false negatives). Finally, they discuss the possibility of only retesting those subjects with bilateral lack of TEOAEs, thus reducing the number of check-ups to be performed a month later.