A minimal model for the respiratory sinus arrhythmia

The cardiac and respiratory rhythms in humans are known to be coupled by several mechanisms. In particular, the first rhythm is deeply modulated by the second. In this report we propose a simple operational model for heart rate variability which, taking such modulation into account, reproduces the main features of some experimental sequences of RR intervals recorded from healthy subjects in the resting condition. Also, peer analysis of the model performance allows us to answer the question whether the observed behaviour should be ascribed to phase synchronisation of the heart beating to the respiratory rhythm. Lastly, the changes of the model activity brought about by changing its relevant parameters are analysed and discussed.

[Sensorineural hearing loss in childhood: evaluation of economic impact in view of vaccine prevention of cases due to congenital cytomegalovirus infection]

Sensorineural hearing loss (SNHL) is a serious public health problem which affects 1-3% per hundred live born babies in developed countries. The congenital cytomegalovirus (CMV) infection is its most important non-genetic cause. The evaluation of the effectiveness of future programs of anti-CMV vaccination requires an assessment of the present costs of SNHL. Direct costs for the Italian public system were calculated per prosthesis child until his full age and turned out to add up to 260,000 euro. Private costs are difficult to be assessed and anyhow are highly dependent from the socio-economic level. This preliminary assessment suggests that the vaccination would be cost-saving if SNHL cases due to congenital CMV were more than 21 per year, corresponding to a congenital infection prevalence higher than 0.21%o.

Diagnosis of congenital cytomegalovirus infection by detection of viral DNA in dried blood spots

BACKGROUND

The reference method of cytomegalovirus (CMV) isolation from urine or saliva is not a feasible routine technique for all newborns, and laboratory diagnosis of this infection would be useful both for epidemiological purposes and to enable prompt institution of adequate measures to identify and correct late sequelae. Extraction and amplification of viral DNA from dried blood spots (DBS) collected from babies in the first days of life during routine screening for genetic and metabolic disorders has been proposed for the early diagnosis of viral congenital infections.

OBJECTIVES

To test the method for CMV DNA extraction from DBS and to evaluate the results obtained in newborns with and without a diagnosis of congenital infection based on viral isolation from urine and or saliva at birth.

STUDY DESIGN

DBS from Guthrie cards collected in babies who underwent virological tests for CMV infection were tested for CMV DNA by observers blinded to the virological results. DNA was extracted from DBS both in water and in cell culture medium according to Shibata et al. with minor modifications. The products of nested polymerase chain reactions (PCR) amplifying two regions in the IE1 and gp58 genes were detected by agarose gel electrophoresis. Strict control measures were adopted to avoid carryovers and contaminations.

RESULTS

DBS from the eight symptomatic and 11 asymptomatic congenitally infected babies were positive when extraction was performed in medium, whereas extraction in water failed to identify two of the asymptomatic cases. The results obtained with the two extraction methods agreed in the remaining cases; the 71 CMV negative control babies were negative and two out of 21 cases of supposed postnatal infection were diagnosed as congenital on the basis of a positive DBS. All positive cases were identified by gp58 PCR but only slightly over half of them by IE1 PCR. Extraction in medium was more efficient than in water.

CONCLUSIONS

The method of CMV DNA extraction in medium followed by amplification of the gp58 region showed 100% sensitivity and specificity compared with isolation in cell culture. Therefore, we propose this procedure to diagnose congenital CMV infection at birth and also later.

Base-sequence-dependent sliding of proteins on DNA

The possibility that the sliding motion of proteins on DNA is influenced by the base sequence through a base pair reading interaction, is considered. Referring to the case of the T7 RNA-polymerase, we show that the protein should follow a noise-influenced sequence-dependent motion which deviate from the standard random walk usually assumed. The general validity and the implications of the results are discussed.

Retrospective diagnosis of congenital cytomegalovirus infection and cortical maldevelopment

Congenital cytomegalovirus (CMV) infection can cause malformations of cortical development (MCD). It is difficult to establish CMV as a cause of MCD several months postpartum. This can now be done by detection of CMV DNA in dried blood spots (DBS test) on Guthrie cards. The authors used DBS tests to assess 10 patients with MCD of unknown cause. Four of the 10 patients were positive for CMV.

Stabilization of ratchet dynamics by weak periodic signals

We study the influence of weak periodic signals on the transport properties of underdamped ratchets. We find that the constant current intervals related to the ratchet can be significantly enlarged by a weak subharmonic signal that is in phase with the internal driver. This stabilization phenomenon is found to exist both in absence and in presence of noise. The dependence of this effect on the phase of the applied signal is also investigated.

CMV gB genotypes and outcome of vertical transmission: study on dried blood spots of congenitally infected babies

BACKGROUND

The role of the virulence of the infecting cytomegalovirus (CMV) strain in the transmission of the virus from mother to fetus and the outcome of the fetal infection has not received much attention yet. Molecular analysis of the gene coding for the surface glycoprotein B (gB) has been used to investigate the relationship between genotype and virulence in groups of immunosuppressed patients.

OBJECTIVES

(1) to assess the prevalence of different gB genotypes in babies with congenital CMV infection; (2) to investigate the possible relationship between genotype and severity of congenital CMV disease; (3) to evaluate the possibility of using dried blood on Guthrie cards (DBS) for genotyping.

STUDY DESIGN

CMV DNA was extracted from DBS and from urine/saliva samples collected in the first two weeks of life of 98 congenitally infected babies, half of which were symptomatic at birth. Genotyping was performed through RFLP analysis of the region corresponding to the cleavage site of the gB protein.

RESULTS

The most prevalent genotype was gB1 (42%) followed by gB3 (26%), gB2 (19%) and gB4 (13%). Rates of disease and CNS damages were higher among children infected by gB1 (35%, 17%) and gB3 (31%, 28%) than in those infected by gB2 and gB4 (20%, 17% and 13%, 15%, respectively). These differences however did not reach the statistical significance. The parallel typing of DBS and urine/saliva strains gave a full concordance of results.

CONCLUSIONS

All four major CMV gB genotypes (gB1-4) can cause a congenital infection but none seems to be associated to the development and the severity of disease. The possibility of using the neonatal DBS for genotyping opens a way to the examination of large numbers of cases of congenital CMV infection.

Nonlinear activity of identified Lymnaea neurons

Two long-lasting discharges of action potentials were recorded from a buccal cell of the pond snail, respectively, before and after superfusing the preparation with low-calcium solution. The corresponding sequences of interspike intervals were then analysed by the nonlinear prediction methods. The results yield evidence of a small but clear nonlinearity only in the second of analysed tachograms. This finding is evaluated and discussed.

Cytomegalovirus DNA detection in Guthrie cards: a powerful tool for diagnosing congenital infection

BACKGROUND

A simple and reliable diagnosis of congenital cytomegalovirus infection is necessary both for clinical and epidemiological purposes. This could be accomplished through the demonstration of cytomegalovirus (CMV) DNA in blood spots (DBS) on Guthrie cards.

OBJECTIVES

(1) To assess the sensitivity and specificity of the method (DBS test) in diagnosing congenital CMV infection compared with viral isolation and (2) to evaluate the applications of the test to the late diagnosis of congenital CMV.

STUDY DESIGN

The method was tested on the cards of (1) 509 babies examined through viral isolation within their third week of life (72 positive cases) and (2) 191 children studied after 3 weeks of life (25 days to 5 years). Blood was eluted from Guthrie cards and heat extracted. The products of a nested polymerase chain reaction (PCR) amplifying one region in the CMV glycoprotein B (gB) gene were detected by agarose gel electrophoresis.

RESULTS

DBS test was positive in all 72 congenitally infected babies and in four of the 437 negative at cytomegalovirus isolation (sensitivity 100%, specificity 99%). Infection in 16 of the 92 infants with a late viral isolation was demonstrated to be congenital by the test, which also detected congenital infection in 18 of 83 children in whom viral culture was not performed (13 with and five without symptoms). Fifty-six additional control cases tested negative.

CONCLUSIONS

DBS test is a reliable assay for diagnosing congenital cytomegalovirus infection and could be used as an alternative to viral culture. It is able to reveal whether ascertained CMV infection is congenital or postnatal at an age when viral isolation is not able to do so. It can assess the role of risky procedures such as transfusion and it can ascertain the etiology of morbid conditions diagnosed late or of controversial origin.

Phase locking effect and current reversals in deterministic underdamped ratchets

We study the transport properties (currents) of deterministic underdamped ratchets in terms of phase locking dynamics. The occurrence of reverse currents is interpreted in terms of different stability properties of the periodic rotating orbits and is shown to exist also in the absence of bifurcations from chaos to periodic motion. We briefly discuss the effects of noise on this phase locked dynamics.

Heart rate and blood pressure response to short-term head-down bed rest: a nonlinear approach

Although it is well-known that prolonged exposure to microgravity environment such as in space travel results in derangements of orthostasis, recent evidence suggests that even short-term exposure may have similar effects and parallels such common examples as prolonged bed rest. Whereas spectral analysis of heart rate and systolic blood pressure have been unable to detect changes, we hypothesized that nonlinear indexes may be better able to uncover such perturbations. Eighteen healthy subjects were exposed to 4-hour head-down tilt, and of these, 4 exhibited fainting. Two nonlinear indexes, mutual information and recurrence quantification were used to analyze the data. Only recurrence quantification was able to detect a "decoupling" of heart rate and systolic blood pressure at rest using discriminant analysis (p < 0.05). These results suggest that orthostatic intolerance may be due to a decoupling of heart rate from systolic blood pressure reflexive activity occurring at rest.

Immunity to poliomyelitis, diphtheria and tetanus in pediatric patients before and after renal or liver transplantation

Few studies have considered the safety, efficacy and appropriateness of vaccinations in pediatric patients before and after solid organ transplantation. The aim of this study was to evaluate the immune status after primary vaccination to diphtheria, tetanus and poliomyelitis in pediatric patients before and after hepatic transplantation and to poliomyelitis in pediatric patients before and after renal transplantation. All the patients had received a complete primary immunization schedule for diphtheria and tetanus and poliomyelitis. Immunity to the three polioviruses was evaluated in 56 patients with renal transplant, 27 on chronic dialysis and 33 controls and in 39 patients with hepatic transplant, 25 with chronic hepatic failure and their 36 controls. Immunity to diphtheria and tetanus was evaluated in 52 liver transplant patients, 29 children with chronic hepatic failure and 54 healthy children. Renal transplant patients were less protected and had lower antibody geometric mean titers than healthy controls for polioviruses 1 and 2. Whereas, protection in the children liver transplant patients was similar to that in their controls. Patients with chronic hepatic failure had higher antibody geometric mean titers to diphtheria and polioviruses 1 and 3 than their control group. Immunosuppression after transplantation has a negative influence on the immune status after primary vaccination in children with renal transplant. Whereas children with chronic hepatic failure have higher antibodies than a normal population. When possible, it could be advisable to individualize immunization schedules in patients at high risk.

A twist opening model for DNA

The real mechanisms of several biological processes involving DNA are not yet understood. We discuss here some aspects of the initiation of transcription, in particular the formation of the open complex and the activation mechanism associated to enhancer binding proteins. Transcription activation seems to be governed by underlying dynamical mechanisms related to several distortions of the double chain structure: a dynamical approach on a mesoscopic description level could then allow a deeper understanding of this complex process. Starting from the Peyrard Bishop (PB) model, that considers only the hydrogen bond stretching of each base pair, we describe here an extended DNA model, proposed in [1], that allows a rather good representation of the double helix geometry and of its structural features by the introduction of angular variables related to the twist angle. Using a generalized multiple scale expansion for the case of vectorial lattices derived elsewhere [2], we derive analytically small amplitude approximate solutions of the model which are movable and spatially localized: we present here the results of this calculation and show how the special shape of the solutions is in good agreement with what can be expected for coupled angular radial distortions in the real molecule.

Congenital cytomegalovirus infection in a northern Italian region. NEOCMV Group

Knowledge of the prevalence of congenital cytomegalovirus infection is necessary to evaluate the need for prevention. We performed a multicentre one-year study involving 11 neonatology divisions to ascertain the prevalence in Lombardy. Cytomegalovirus was isolated by culturing saliva samples from all babies born (n = 1268) of two 15-day sample periods and from 185 neonates with suspected congenital CMV based on clinical and laboratory findings and the history. The overall prevalence of congenital infection was 0.47% (6/1268) in the sample period group and 5% (9/185) in the second group. Clinical monitoring revealed sequelae in two of three children with symptomatic infection and no asymptomatic child at age two years. In a subgroup of 205 babies including 14 of the infected infants we also evaluated a test to detect cytomegalovirus DNA in the Guthrie cards obtained in neonatal screening for genetic and metabolic disorders. The test's sensitivity was 100% and specificity 98.5%, encouraging its use for early identification of infected neonates and for large epidemiological studies.

In vitro activity of acetylsalicylic acid on replication of varicella-zoster virus

Topical application of a mixture of acetylsalicylic acid (ASA) and diethyl ether is effective in the treatment of acute herpes zoster and postherpetic neuralgia. To study whether the other-than-analgesic effects of that treatment could be due to an antiviral activity of ASA the effects of the drug on the replication of varicella zoster virus (VZV) were assessed by the fluorescent focus assay on MRC5 and Vero cells. ASA caused a marked reduction in the spread of infection in MRC5 monolayers while in growing Vero cells the effective dose proved toxic. ASA concentrations (5-10 mM) which were effective in vitro against VZV are higher than the plasma concentrations attained in the standard treatment of chronic inflammatory states, but are consistent with the skin concentration attained by topical application of ASA/diethyl ether mixture. These data support similar findings relating the antiviral activity of acetylsalicylic acid to influenza virus, CMV, and HIV.

Immunization with both T cell-dependent and T cell-independent vaccines augments HIV viral load secondarily to stimulation of tumor necrosis factor alpha

Vaccination of HIV-infected individuals increases HIV viral load, reduces CD4 cell counts, and might influence disease progression. Because these deleterious effects are postulated to be secondary to a direct activation of T lymphocytes induced by the immunogen, we compared immunologic and virologic effects of a T cell-dependent and a T cell-independent vaccine. Seventeen HIV-infected children were immunized with influenza (FLU) (T cell-dependent) or pneumococcal (PNEUMO) (T cell-independent) vaccines. HIV viral load and type 1 (IL-2 and IFN-gamma) and type 2 (IL-4 and IL-10) cytokine production were evaluated before and 7, 14, and 28 days after vaccination. Slopes of CD4 cell counts analyzed 6 months before and 6 months after vaccination were not significantly different. HIV viral load increased in both groups of children despite the fact that type 1 cytokine production and the type 1-to-type 2 ratio increased in FLU-vaccinated but not in PNEUMO-vaccinated patients. Thus, an increase in HIV viral load in the absence of T cell activation (as measured by cytokine production) was observed in PNEUMO-vaccinated children. Because polysaccharides of the bacterial cell wall stimulate TNF-alpha production by monocyte-macrophages and TNF-alpha was shown to stimulate HIV replication directly on activation of NF-kappa b after binding the long terminal repeat (LTR) sequences of HIV, we measured TNF-alpha production and observed a significant increase in both groups of vaccines. These data suggest that an increase in HIV viral load can be observed in vaccinated HIV-infected children even independent of direct antigen-induced activation of T lymphocytes, and that augmented production of TNF-alpha might play a role in this phenomenon.