Detection of Nonlinearity in the Healthy Heart Rhythm

Sequences of interbeat intervals from two groups of subjects, 24 in relaxed and 10 in sleeping condition were analyzed by the nonlinear predictor method as well as by a method, proposed recently, able to directly estimate the time series nonlinearity. The nonlinear predictability of the R-R intervals is tested by using surrogate data. The results obtained with both methods show that nearly all the sequences exhibit a statistically meaningful degree of nonlinearity. This raises the question whether such nonlinearity encodes information about the physiological condition of the examined subjects.

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.

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.

Gap junctions promote synchronous activities in a network of inhibitory interneurons

By using a single compartment biophysical model of a fast spiking interneuron the synchronization properties of a pair of cells, coupled by electrical and inhibitory synapses, are investigated. The inhibitory and excitatory synaptic couplings are modeled in order to reproduce the experimental time course of the corresponding currents. It is shown that increasing the conductance value of the electrical synapses enhances the synchronization between the spike trains of the two cells. Moreover, increasing either the decay time constant of the inhibitory current or the firing frequency of the cells favours the emergence of synchronous discharges.

Sciatic nerve block with lateral popliteal approach for hallux vagus correction. Comparison between 0.5% bupivacaine and 0.75% ropivacaine

AIM

In this study the authors compared the clinical profile of 2 local anesthetic drugs in the sciatic nerve block used during hallux valgus correction, a surgical procedure known to be post-operatively extremely painful. Since hallux valgus correction is painful post-operatively, many attempts have been tried to ensure a long-lasting analgesia. Block of the sciatic nerve appears to be the right choice balancing ease to performance, satisfaction of the patient and duration of action.

METHODS

The authors investigated the use of 20 ml of 0.5% bupivacaine or 0.75% ropivacaine regarding the speed of onset, quality and length of duration of sciatic nerve block performed with a lateral popliteal approach. Sixty ASA I-III patients (aged 19-73 years) were enrolled in this trial. Written informed consent was asked and obtained. A 20 G 50 mm Teflon coated Crawford needle, delivering 0.5 mA at 2 Hz, was used to locate and block the sciatic nerve in the popliteal fossa with a lateral approach.

RESULTS

Patients in the ropivacaine group required about 13 minutes to achieve a complete block and about 16 minutes were needed in the bupivacaine group for the anesthesia to be complete. The length of analgesia was 16 h for the ropivacaine group and 13 h for the bupivacaine group. This kind of approach to block the sciatic nerve appeared to the authors to be very easy to perform, with the patient lying in a natural position. Surgical anesthesia required less than 30 min in both groups to be ready, while the ropivacaine group had a longer length of analgesia compared to the bupivacaine group.

CONCLUSIONS

Patient satisfaction was high in both groups.

Head-down bed rest reduces the breathing rate short-term variability in subjects with orthostatic intolerance

Orthostatic intolerance is the most serious symptom of cardiovascular deconditioning induced by microgravity. We have showed that in symptomatic subjects the baroreflex control of sinus node is affected by short term simulated microgravity. At present the influence of the respiration on the cardiovascular system in this condition is not clear. The aim of the present study was to examine the behaviour of the Breathing Rate (BR) in 5 Non-Symptomatic (NS) and 3 Symptomatic (S) subjects before and after 4 hours of head-down bed rest (HD).

Long- and short-time analysis of heartbeat sequences: correlation with mortality risk in congestive heart failure patients

We analyze RR heartbeat sequences with a dynamic model that satisfactorily reproduces both the long- and the short-time statistical properties of heart beating. These properties are expressed quantitatively by means of two significant parameters, the scaling delta concerning the asymptotic effects of long-range correlation, and the quantity 1-pi establishing the amount of uncorrelated fluctuations. We find a correlation between the position in the phase space (delta, pi) of patients with congestive heart failure and their mortality risk.

The use of remifentanil for bloodless surgical field during vertebral disc resection

BACKGROUND

A short hospital stay is nowadays desirable and affordable for a wide range of surgical pathology, respecting safety of care and home discharge. In the present study, the Authors investigated the use of TIVA with propofol/remifentanil during microsurgical vertebral disc resection to maintain a controlled vascular hypotension for bloodless surgical field aiming to reduce the operating time and consequently recovery room length of stay and morbility related to anaesthesia.

METHODS

The study took place in a 300 bed Orthopaedics hospital over a period of 3 months and 50 ASA I-II patients were enrolled in this trial; further data are presented for comparison of 50 ASA I-II patients homogeneous for age and sex to the studied population, operated under a standard TIVA with propofol and boluses of fentanyl. Duration of anaesthesia and surgery, time for awakening after cessation of TIVA, incidence of postoperative nausea and vomiting (PONV), amount and quality of postoperative analgesia, length of stay in the recovery room are reported in statistical presentation.

RESULTS

Time of surgery and anaesthesia were reduced in the remifentanil group compared with the fentanyl group, thanks to an easily reachable and durable state of controlled hypotension in the first group without the use of any other drug. The recovery profile was shorter in the remifentanil group the drug being rapidly metabolised by plasma cholinesterase.

CONCLUSIONS

No difference occurred between the two groups regarding quality and amount of postoperative analgesia, while PONV presented more in the fentanyl group and shivering more in the remifentanil group.

Mutual information detects a decreased interdependence between RR and SAP in orthostatic intolerance after microgravity condition

Orthostatic intolerance is the most serious symptom of cardiovascular deconditioning induced by microgravity. However, the exact mechanisms underlying these alterations have not been completely clarified. Several methods for studying the time series of systolic arterial pressure and RR interval have been proposed both in the time and in the frequency domain. However, these methods did not produce definitive results. In fact heart rate and arterial pressure show a complex pattern of global variability which is likely due to non linear feedback which involves the autonomic nervous system and to "stochastic" influences. Aim of this study was to evaluate the degree of interdependence between the mechanisms responsible for the variability of SAP and RR signals in subjects exposed to head down (HD). This quantification was achieved by using Mutual Information (MI).

0.25% levo-bupivacaine for interscalene block during shoulder surgery. A survey on 20 patients

BACKGROUND

Interscalene brachial plexus block (ISB) is an alternative procedure to general anaesthesia for shoulder surgery, and consents the anaesthetist to easily control postoperative pain that, indeed, is known to be intense and often requires strong analgesic administration. The introduction of regional anaesthesia for this type of surgery, contributed to the relief of acute postoperative pain occurring in the recovery room since the analgesic effects of block persist for several hours after surgery depending upon the selected drug. The aim of this study was to determine the effects of 40 ml of 0.25% levo-bupivacaine, a local anaesthetic derived from the racemic mixture of bupivacaine, on the speed of onset, quality and duration of ISB.

METHODS

Twenty adult ASA I-II patients, undergoing shoulder surgery for various pathologies, were enrolled in this study. All patients were examined before surgery and were given a full explanation; written informed consent was asked for and obtained. ISB was placed with the classic Winnie approach and the plexus was localised by means of a 40 mm, 22G Teflon(R) coated needle connected to an electro neural stimulator distributing 0.5 mA at 2 Hz. Once twitching was observed, 16 ml of 0.25% levo-bupivacaine were injected on shoulder lift, 12 ml on forearm abduction and 12 ml on forearm adduction. Monitoring: the time elapsing from last injection to loss of sensibility of pin-prick on the shoulder area, degree of motor block expressed on a 4 points scale, surgery time, as well as total time of analgesia were recorded for statistical analysis.

STATISTICS

data were analysed at the STATISTICS Department of the University of Messina (Italy) and results are expressed as means and standard deviations.

RESULTS

Eighteen patients were operated under ISB and light sedation while 2 patients were scheduled for interscalene block plus deep sedation, the position being very discomforting and surgery supposed to last more than 60 min (shoulder arthroscopy). Less than 9 min were required for the block to be complete with satisfactory muscle relaxation, optimal intraoperative anaesthetic condition and more than 13 hours of postoperative analgesia occurred.

CONCLUSIONS

Levobupivacaine is a newly developed local anaesthetic derived from a bupivacaine racemic mixture from which the right isomer has been eliminated. Levo-bupivacaine, compared to racemic mixture, is acknowledged to be less cardiotoxic, faster at equal dosage, and ensures a longer analgesic interval. Zero point twenty-five percent concentration was preferred in this study in order to inject large volumes (40 ml) with a minimal anaesthetic amount (100 mg), resulting in short time for obtaining loss of sensibility, optimal intraoperative conditions and long lasting block with adequate postoperative analgesia.

Average magnitude of heartbeat fluctuations in healthy subjects after exposure to 4 hours head down bed rest

Orthostatic intolerance, induced by microgravity exposure, has been hypothesized to be related to a disorder of the autonomic control of the cardiovascular system. Non-invasive measurement of Heart Rate Variability (HRV) have been used as a valuable tool to characterize the ability of the autonomic system to modulate the cardiovascular function by analyzing the spontaneous fluctuations of arterial pressure and heart period on a beat-to-beat basis. Concerning this, conflicting results have been reported on the heart rate and blood pressure variability responses during exposure to microG. These differences seem to be due to different experimental designes used. Moreover, the different behavior of normal subjects in response to orthostatic stress after HD, i.e. Symptomatic (S) or Non Symptomatic (NS), could play some role in producing these discrepancies [correction of dicrepancies]. In this study we suggest the analysis of "magnitude" or "volatility" as a new method to study HRV variability. The volatility is a measure of the beat-to-beat excursion capability of the heart, regardless to its direction (positive or negative): the higher the volatility, the greater the excursion. The aim of the present study was to examine R-R volatility before and after 4 hours of HD -6 degrees in normal subjects.

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.

Effect of 4 hours HD -6 degrees on heart rate variability in symptomatic and non symptomatic subjects

Orthostatic intolerance is the most serious symptom of cardiovascular deconditioning induced by microgravity exposure. In fact the neural control mechanisms of the cardiovascular system are significantly affected by this condition. Non-invasive measurement of Heart Rate Variability (HRV) have been used as a valuable tool to characterize the ability of neuroendocrine regulatory systems to modulate the cardiovascular function by analyzing the spontaneous fluctuations of arterial pressure and heart period on a beat-to-beat basis. Concerning this, conflicting results have been reported on the heart rate and blood pressure variability responses during exposure to microgravity. These differences seem to be due to different experimental designs used. Moreover, the different behavior of normal subjects in response to orthostatic stress after HD, i.e. Symptomatic (S) or Non Symptomatic (NS), could play some roles in producing these discrepancies. Therefore the aim of the present study was to examine BP and HR variability before and after 4 hours of HD in two groups of normal subjects with and without symptoms of orthostatic intolerance to orthostatic stress.

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.

Effect of aging on responses to autonomic cardiovascular tests

Cardiovascular deconditioning (CD) and orthostatic intolerance represent some of the major disturbances experienced by astronauts returning on Earth after micro-G exposure. The orthostatic intolerance observed in crew members after space missions has been hypothesized to be related to a disorder of the autonomic control of the cardiovascular system. There is evidence that advanced acing itself may alter the cardiovascular mechanism that underlie the CD. Due to involvement of elderly subjects in space flights it is mandatory to verify how age affects the cardiovascular autonomic neural regulation. In order to assess age-related differences in autonomic cardiovascular regulation our aim is to analyze the cardiovascular responses to 3 different autonomic tests that explore baroreceptor (tilt and deep breathing) and non-baroreceptor (isometric exercise) afferent pathways, in two goups of normal subjects characterized by significant different age.

Interleukin-12 and interleukin-10 production by mononuclear phagocytic cells from breast cancer patients

Interleukin-10 (IL-10) and Interleukin 12 (IL-12) generation may be regulated by a complex monocyte and macrophage-derived cytokine network and an impairment of the immune system can be observed in neoplastic disease. In this study, we examined the production of these cytokines by phagocytic cells, obtained from breast cancer (BCa)-bearing patients. Our results suggest that an increased IL-10 formation may represent an important regulatory pathway of IL-12 production by BCa mononuclear cells. In this report, we show that mononuclear cells of patients affected by breast cancer have a defective IL-12 production capability while generating higher amounts of IL-10.

[Clinical study of residual function and recurrence in patients undergoing partial thyroidectomy for euthyroid nodular goiter]

The different surgical options for the treatment of non toxic nodular goiter led the Authors to study the residual thyroid function following conservative surgery (subtotal thyroidectomy, lobectomy and enucleation). Follow-up showed an overall recurrence rate of 49%, with a higher rate after lobectomy and enucleation than after subtotal thyroidectomy. On the other hand, subclinical hypothyroidism was higher in patients who underwent subtotal thyroidectomy. No significative correlation was found between high plasmatic levels of TSH and recurrences.

Detection of nonlinearity in the healthy heart rhythm

Sequences of interbeat intervals from two groups of subjects, 24 in relaxed and 10 in sleeping condition were analyzed by the nonlinear predictor method as well as by a method, proposed recently, able to directly estimate the time series nonlinearity. The nonlinear predictability of the R-R intervals is tested by using surrogate data. The results obtained with both methods show that nearly all the sequences exhibit a statistically meaningful degree of nonlinearity. This raises the question whether such nonlinearity encodes information about the physiological condition of the examined subjects.

Ring wave solutions of a n+1-dimensional Sine-Gordon model

The dynamical properties of the ring wave solutions of the model psi(tt)- nabla (n) (2)psi+sin psi+ varepsilon sin (psi/2)+alphapsi(t)=0 (0</= varepsilon <<1,0</=alpha<<1) are studied analytically and numerically for spatial dimension (n=2,3). The model is obtained as a continuum approximation of a multidimensional Frenkel-Kontorowa lattice. We will show that in the case varepsilon >0, alpha=0 (or alpha>0) the return effect of the ring wave does not occur only for well defined values of varepsilon. It will be shown numerically that the dissipative perturbation alphapsi(t) (alpha>0) stabilizes both the velocity and the wave profile of the ring wave when the return effect does not occur. (c) 1997 American Institute of Physics.

In vitro effects of lithium chloride on TNF alpha and IL-6 production by monocytes from breast cancer patients

It is well known that lithium chloride (LiCl) is able to trigger human monocytes to release tumor necrosis factor alpha (TNF alpha). In this study we have evaluated the in vitro effect of LiCl on TNF alpha and interleukin-6 (IL-6) release by monocytes from patients affected by non-metastatic (BCa/M0) and metastatic breast cancer (BCa/M1), preincubated with autologous serum (sPt). Our data demonstrate that monocytes from cancer patients (BCa) treated with LiCl released lower amounts of TNF alpha compared to those from healthy donors (HD). Preincubation in autologous serum (sPt) impaired TNF alpha production by monocytes from BCa with LiCl. On the contrary, our data indicate that IL-6 production by monocytes treated was not impaired. Moreover, the results obtained from the same cells, preincubated in sPt and treated with LiCl, indicate that serum factors may synergize with LiCl treatment in releasing IL-6.

[Esophageal leiomyoma: ultrasonographic endoscopic diagnosis]

Leiomyoma is the most frequent benign neoplasia of the esophagus. It is generally diagnosed, accidentally during a radiologic examination (filling defect with clear and regular margins) or endoscopically (sessile, hemispheric, covered by pink mucosa). Recently, to the above conventional exams, endoscopic ultrasonography has been added allowing to identify the single layers of the esophageal wall, thus furnishing useful informations on the morpho-structural characteristics of the leiomyoma. From October '94 to May '96, at the Endoscopy Service of the Institute of Oncology of the University of Messina, 12 patients, 8 males and 4 females, ranging from 39 to 69 years of age (median age 55.4) underwent EUS for suspect leiomyoma. An Olympus EU-M20 echoendoscope was used with a radial scan transducer of 12 Mhz. In 8 patients the leiomyoma was located in the III mid-esophagus, while in 4 patients the III inferior portion was interested. The Authors observed lesions ranging in size from 0.5 to 2.5 cm. In their experience, a suspect of leiomyoma represents a good indication for an endoscopic ultrasonography, which shows high sensitivity and specificity.

Dynamics of the neural discharge in snail neurons

Spike trains recorded under weak sinusoidal driving from central neurons of Lymnaea stagnalis appear quite irregular and envisage the possibility of an underlying chaotic process. Therefore, the sequences of interspike intervals are analyzed in the framework of non-linear dynamics. Since, for several reasons, these sequences are rather short, the analysis is performed by using methods of non-linear forecasting. To reject the null hypothesis that the original time series is a realization of a linear stochastic process with the same autocorrelation function, the results obtained on the original data are compared with those from surrogate data sets. Some 'non-linear' predictability occurs only in narrow regions of the space of stimulus parameters and the frequency of perturbation is critical in determining it. Moreover, it is shown that such behavior can be qualitatively mimicked by the FitzHugh-Nagumo model driven by a weak sinusoidal signal plus noise. It is argued that the narrowness of the non-linear predictability regions renders quite unlikely the detection of deterministic dynamics in the activity of these neurons.

Dynamics of analog-to-frequency transduction in sensory receptors

We analyze the analog-to-frequency transduction by sensory neurons in vivo. Spatially extended neural models are made to fire by applying the stimulus to the membrane potential at the boundary of the trigger zone. The membrane property that provides a broad dynamical range of frequency is a prolonged hyperpolarizing afterpotential. In support of this PDE model, we study the stimulus-dependent location of pulse-initiation in crayfish stretch receptors Ringham (1971).

[Sedation in endoscopic diagnosis: rationale of the use of specific benzodiazepine antagonists]

The aim of this study was to evaluate the best clinical use of Flumazenil, a specific antagonist of benzodiazepines, during endoscopic exams. Two-hundred patients were studied: 120 were treated with Flumazenil and 80 with placebo. The patients were prepared for the endoscopic exam with local anaesthesia and i.v. Diazepam administration. Controls performed at the end of the exam and at 5, 30, 120 e 240 minutes from the administration of Flumazenil and placebo, allowed to evaluate the state of awakeness, the level of conscience and the capacity of time-space orientation. Significantly statistical differences between the two groups were obtained at 5, 30 and 120 minutes after Flumazenil administration, while both groups had retrograde amnesia. The drug was well tolerated and there were no undesiderable side effects or reactions. The Authors therefore affirm that Flumazenil, in virtue of its competitive action toward benzodiazepine receptors, interrupts sedation with immediate awakening and improvement of the state of consciousness. Such drug, thus, permits the Day Hospital performance of endoscopic procedures which otherwise would require hospitalization, at the same time allowing the surgeon to use benzodiazepines at doses more adequate for surgical necessities.

[Gynecomastia: diagnosis and therapy update]

The Authors report their experience in the management of gynaecomastia. Physiologic, pathologic and iatrogenic causes of the lesion, as well as possible interfering mechanisms, and diagnostic protocol are examined. When there is no spontaneous regression or when the precipitating factors are eliminated surgery is the therapeutical choice, also because it helps in resolving the related psychological problems affecting these patients.

Effects of lithium carbonate on cytokine production in patients affected by breast cancer

It has been reported that lithium salt compounds influence hematopoiesis, which is known to be regulated by a number of cytokines, including tumor necrosis factor (TNF), interleukin-1 (IL-1) and interleukin-6 (IL-6). Since lithium can induce TNF production in human monocytes, we wished to determine if lithium carbonate treatment of neutropenic patients affected by breast cancer results in increased cytokine production. Serum levels of TNF alpha, IL-1 and IL-6 were measured before and at 7 and 180 days after treatment with lithium carbonate. Results indicate that this therapy produced TNF alpha and IL-6, but not IL-1 alpha, elevations in patients affected by unmetastasized breast cancer. Conversely, TNF alpha, but not IL-6, elevations were detected in metastatic patients. Studies are under way to investigate the mechanisms by which lithium salts affect cytokine production in monocytes from cancer patients.

Generation of superoxide anion and candidacidal activity by lipopolysaccharide-treated macrophages from patients affected by neoplasia

Macrophages, derived from in vitro cultured monocytes from both healthy donors and patients affected by metastatic breast cancer, treated or not with Escherichia coli lipopolysaccharide (LPS), were tested for phagocytosis and intracellular killing of Candida albicans and superoxide anion release. We found a marked impairment in intracellular killing closely linked to the lack of superoxide production in macrophages from patients affected by neoplasia treated or not with LPS. On the other hand, the LPS treatment significantly enhanced the phagocytic activity of all the macrophage populations tested, except for phagocytes obtained from patients affected by neoplasia and differentiated in autologous serum.

Modulation of the intrinsic antiviral activity by Escherichia coli endotoxin in macrophages from patients with neoplasia

Macrophages from patients with breast cancer showed an impairment of their antiviral activity. The capability to hinder herpes simplex virus type 2 replication of macrophages from healthy donors and from patients with breast cancer was compared to the in-vitro treatment with Escherichia coli lipopolysaccharide (LPS). The LPS showed a dose-dependent effect on the different macrophage populations studied. Nevertheless, macrophages from healthy donors appeared to be more sensitive to LPS in comparison with macrophages from the patients under our observation. On these cells LPS treatment was not able to modify the antiviral property, when these macrophages were differentiated in autologous serum.

Role of exogenous interferons on intrinsic antiviral activity of macrophages from patients affected by neoplasia

Macrophages derived from in vitro cultured monocytes were infected with herpes simplex virus type 2. A marked impairment in the intrinsic antiviral activity was found in macrophages obtained from patients with breast cancer or melanoma. Moreover, the antiviral activity of macrophages from healthy donors, differentiated in serum from patients with neoplasia, was also impaired. The aim of this work was the evaluation of alpha, beta, gamma exogenous interferon in restoring the intrinsic antiviral activity of macrophages from patients affected by breast cancer or melanoma under different conditions. Pretreatment of macrophages with alpha, beta interferons, but not gamma interferon, restored their impaired intrinsic antiviral activity.

Analysis by simulation of the transient rectification in molluscan neurons

Central neurons of Lymnaea stagnalis exhibit, by the dne of a hyperpolarizing current pulse, a breaking-off of the rise of the membrane potential to the resting level. By using an electrical model of the membrane, this effect is accounted for by the activation of the fast outward current.

Interferon release by LPS-treated macrophages from patients affected by neoplasia

Concerning the modulatory role of LPS on immunocompetent cells, the production of interferon by macrophages primed with human gamma interferon (HUIFN gamma), was studied. In particular the production of IFN from primed macrophages of patients affected by breast cancer, differentiated in presence of autologous serum or in serum from healthy donors, was compared with the IFN production from macrophages of healthy donors. The levels of endotoxin-induced IFN were enhanced by priming macrophages with HUIFN gamma. The "in vitro" treatment with Escherichia coli LPS restores the interferon production of primed macrophages, obtained from patients affected by breast cancer, differentiated in presence of serum from healthy donors. Moreover, LPS treatment of primed macrophages from patients, differentiated in autologous serum, did not influence the interferon production of these cells. Nevertheless, primed macrophages from healthy donors appeared to be more sensitive to LPS treatment in comparison with primed macrophages from patients affected by breast cancer.

Evaluation of macrophage antiviral activity in patients affected by neoplasia

The intrinsic antiviral activity of macrophages has been studied in healthy donors and in patients affected by breast cancer and melanoma. In vitro differentiated macrophages from blood-derived monocytes were infected with measles virus, herpes simplex virus type 2 and adenovirus 17. The challenge was carried out with different multiplicities of infection and the synthesis of virus was tested by evaluating the single cycle growth curve in 24 h. The results obtained show that the restriction of virus infectivity by macrophages is strongly influenced by the multiplicity of infection. This was particularly evident with the adenovirus 17. Moreover, macrophages from patients with melanoma and breast cancer showed an impairment of the intrinsic antiviral activity in comparison with normal subjects.

[Serum levels of copper and zinc in patients with lung cancer]

Serum copper levels (SCL) and serum zinc levels (SZL) were measured in two groups of lung cancer patients divided according to disease extension. SCL was higher, SZL was lower and SCL/SZL ratio was more raised in patients extensively affected by the disease. It is confirmed that SCL, SZL and the SCL/SZL ratio play an important role in indicating the stage of lung cancer development.

[Behavior of serum sialic acid levels at various stages of neoplastic disease]

Serum sialic acid levels were measured at two different stages of neoplasia (active and non-active phases). CEA levels were also assayed at the same time. 98 patients suffering from different neoplastic diseases and a group of healthy controls were studied. Serum sialic acid levels were always significantly higher in the neoplastic patients. When neoplastic disease were divided into active and non-active groups, it was observed that the level of this glycoprotein was specific in the non-active (NA) phase only for breast tumours and lymphomas. Correlation with CEA levels was also significant in these cases. It is concluded that serum sialic acid assay may be useful only for melanomas, breast tumours and lymphomas where the level of this membrane protein undergoes significant changes according to the stage of the tumour.

Effects of current pulses on the sustained discharge of visual cells of Limulus

Current pulses were used in the eccentric and retinular cells of the Limulus lateral eye to produce changes in the interspike interval of the discharge sustained by a constant light level. The effects on the interspike interval of hyperpolarizing and depolarizing perturbations, applied at various delays from the previous spike, were measured for different intensities and durations of the current pulse. The results show that when the perturbations were applied in the first part of the interval, effects contrary to what is normal were produced (i.e, hyperpolarizing pulses decreased the interspike interval instead of increasing it and vice versa for depolarizing pulses). Here we discuss briefly the implications on neural encoding models.

Resonant response of a neural model and of Limulus ommatidia to double frequency stimulation

Signals which are the sum of two sinusoids of frequencies v1 and v2 are used to stimulate: i) an electronic analog of the leaky integrator neural model, ii) the visual neurons of the Limulus lateral eye. This makes it possible to investigate the resonant amplification of the impulse density modulation for v1 + v2 which approaches the free-run discharge rate; this resonance is predicted by the Volterra series representation of the leaky integrator (Poggio and Torre, 1977). The resonant responses obtained look very similar for the simulated discharge and for the experimental one.

Phase-locked responses in the Limulus lateral eye. Theoretical and experimental investigation

The 1:1 phase locking of the neural discharge to sinusoidally modulated stimuli was investigated both theoretically and experimentally. On the theoretical side, a neural encoder model, the self-inhibited leaky integrator, was considered, and the phase of the locked impulse was computed for each frequency in the locking range by imposing the condition that the "leaky integral" u(t) of the driving signal should reach the threshold for the first time one stimulus period after the preceding impulse. As u(t) can be a nonmonotonic function, this approach leads to results that sometimes differ from those reported in the literature. It turns out that the phase excursion is often much smaller than the values of about 180 degrees predicted from previous analysis. Moreover, our analysis shows a peculiar effect; the phase locking frequency range narrows when the input modulation depth increases. The theoretical predictions are then compared with phase-locked discharge patterns recorded from visual cells of the Limulus lateral eye, stimulated by sinusoidally modulated light or depolarizing current. The phases of the locked spikes at each of a number of modulation frequencies have been measured. The predictions offered by the model fit the experimental data, although there are some difficulties in determining the effective driving signal.