Angiogenesis and vessel co-option in a mathematical model of diffusive tumor growth: The role of chemotaxis

This work considers the propagation of a tumor from the stage of a small avascular sphere in a host tissue and the progressive onset of a tumor neovasculature stimulated by a pro-angiogenic factor secreted by hypoxic cells. The way new vessels are formed involves cell sprouting from pre-existing vessels and following a trail via a chemotactic mechanism (CM). Namely, it is first proposed a detailed general family of models of the CM, based on a statistical mechanics approach. The key hypothesis is that the CM is composed by two components: i) the well-known bias induced by the angiogenic factor gradient; ii) the presence of stochastic changes of the velocity direction, thus giving rise to a diffusive component. Then, some further assumptions and simplifications are applied in order to derive a specific model to be used in the simulations. The tumor progression is favored by its acidic aggression towards the healthy cells. The model includes the evolution of many biological and chemical species. Numerical simulations show the onset of a traveling wave eventually replacing the host tissue with a fully vascularized tumor. The results of simulations agree with experimental measures of the vasculature density in tumors, even in the case of particularly hypoxic tumors.

LRU is better than FIFO under the independent reference model

Consider a two-level storage system operating with the least recently used (LRU) or the first-in, first-out (FIFO) replacement strategy. Accesses to the main storage are described by the independent reference model (IRM). Using the FKG inequality, we prove that the miss ratio for LRU is smaller than or equal to the miss ratio for FIFO.

Genetic differentiation and hybridization in two naturally occurring sympatric trout Salmo spp. forms from a small karstic lake

In this study, multiple molecular markers [genotyping of 12 nuclear microsatellite loci and the protein-coding gene ldh-c1* plus sequencing of the mitochondrial DNA (mtDNA) control region] were employed to investigate the genetic structure of the two trout forms, Salmo cettii and Salmo fibreni, inhabiting Lake Posta Fibreno, central Italy. The two forms were found to share a unique mtDNA haplotype, belonging to a widespread Mediterranean haplogroup (AD). Bayesian clustering analyses showed that these two forms correspond to well-defined autochthonous gene pools. Genetic introgression between the two gene pools, however, was observed, whose frequency appears to correlate with the environmental features of the spawning sites. The interplay of selection for the spawning sites, philopatry and natural selection can be argued to maintain genetic differentiation despite the lack of complete reproductive isolation.

“SVAROSKI”: A computerised method of assessment of rehabilitation outcomes

Introduction

The use of standardized tools for assessment and monitoring of a rehabilitation program is strongly recommended, though not so often accomplished in clinical practice.

Aims

To describe the development and feasibility of a computerised method of assessment of rehabilitation activities based on psychometrics.

Methods

The software “SVAROSKI” was implemented by means of a relational ER (Entity-Relationship) model with a user interface managed by MS-Access. The rehabilitation activities were: Physical therapy; Locomotion, Occupational Therapy and Reality-Orientation Therapy. Patients were administered at the beginning and at the end of admission the following tests: MMSE, MODA, Barthel Index, Tinetti.

The software enables processing of test data with those obtained from rating scales at each session.

Results

For each patient, two graphical reports are made available:

Punctual performance of each item divided by subject areas;

Overall pace of the three scales assessing rehabilitation (physical therapy was maintained for an evaluation board, partly qualitative, for the sake of the physiotherapist of the structure).

The software allows:

1) the rapid storage of the scores obtained from patients during the course of rehabilitation activities,

2) the real-time consultation of the development of therapeutic and rehabilitation,

3) the comparison of the iteration of several rehabilitation interventions on the patient.

Conclusions

SVAROSKY is a useful tool for analysis and monitoring of developments in the rehabilitation of the patient as a valid tool for the development of a synthesis report of the rehabilitation process.

Response of tumor spheroids to radiation: modeling and parameter estimation

We propose a spatially distributed continuous model for the spheroid response to radiation, in which the oxygen distribution is represented by means of a diffusion-consumption equation and the radiosensitivity parameters depend on the oxygen concentration. The induction of lethally damaged cells by a pulse of radiation, their death, and the degradation of dead cells are included. The compartments of lethally damaged cells and of dead cells are subdivided into different subcompartments to simulate the delays that occur in cell death and cell degradation, with a gain in model flexibility. It is shown that, for a single irradiation and under the hypothesis of a sufficiently small spheroid radius, the model can be reformulated as a linear stationary ordinary differential equation system. For this system, the parameter identifiability has been investigated, showing that the set of unknown parameters can be univocally identified by exploiting the response of the model to at least two different radiation doses. Experimental data from spheroids originated from different cell lines are used to identify the unknown parameters and to test the predictive capability of the model with satisfactory results.

The dynamics of tumour-vasculature interaction suggests low-dose, time-dense anti-angiogenic schedulings

OBJECTIVES

The administration schedule appears to be a particularly relevant factor in determining the effectiveness of an antiangiogenic drug. A better quantitative knowledge of the interactions between tumour growth and the development of its vasculature could help to design effective therapies.

MATERIAL AND METHODS

Biological and clinical inferences were derived from the analysis of a mathematical model proposed by Hahnfeldt et al. (1999), and some of its variants. In particular, we compared the effect of constant continuous infusion of an anti-angiogenic drug that induces vascular loss, to the effect of periodic, bolus-based therapy.

RESULTS AND CONCLUSIONS

The role of drug elimination rate and of dose fractionation was investigated, and we show that different schedulings, guaranteeing the same mean value of drug concentration, may exhibit very different long-term responses according to their concentration vs. time profile. For a large class of tumour growth laws, the profiles that approach the constant one are the most effective. This behaviour appears to depend on the 'cooperativity' of the tumour-vasculature interaction and on the functional form of the relationship between tumour growth and vasculature extent. Moreover, we suggest that a therapy approaching constant drug infusion might be advantageous also in the case of cytostatic anti-angiogenic drugs.

Effect of nitrous oxide on desflurane MACBAR at two target-controlled concentrations of remifentanil

BACKGROUND

The aim of this prospective, randomized, double-blind study was to determine the effect of nitrous oxide on the desflurane requirement for blunting sympathetic response following surgical incision (MACBAR) when desflurane was combined with two different target-controlled concentrations of remifentanil (1 and 3 ng/mL).

METHODS

A total of 103 patients, aged 20-50 years, ASA physical status I, scheduled to undergo general anesthesia for elective abdominal surgery, were randomly allocated to receive anesthesia with desflurane alone (Group A, n = 53), or with the addition of 60% nitrous oxide (Group N, n = 50). Patients of both groups were further assigned to receive a target-controlled plasma concentration of 1 ng/mL (Group A1, n = 27; Group N1, n = 26) or 3 ng/mL remifentanil (Group A3, n = 26, Group N3, n = 24). Sympathetic responses to surgical incision were determined after a 20 min period of constant end-tidal desflurane and target-controlled remifentanil concentrations. Predetermined end-tidal desflurane concentrations and the MACBAR for each group were determined using an up-and-down sequential allocation technique.

RESULTS

A total of 98 patients completed the study. The MACBAR of desflurane was 5.2% (95% confidence interval [CI95: 4.9-5.5%]) in Group A1 and 2.7% (CI95: 2.6-2.8%) in Group N1 (P<0.001), while in Groups A3 and N3 the MACBAR of desflurane was 2.2% (CI95:2-2.4%) and 2% (CI95:1.9-2.2%), respectively (P<0.01). When considering a minimum anesthetic concentration (MAC) value with a contribution of 60% nitrous oxide (0.55 MAC) in this population, the combined MACBAR values (expressed as multiples of the MAC) were 1.9 MAC for group A1, 1 MAC for group N1, 0.8 MAC for group A3, and 0.7 MAC for group N3.

CONCLUSION

The addition of 60% nitrous oxide reduces the MACBAR of desflurane by 52% when using a remifentanil concentration of 1 ng/mL, and reduces the MACBAR by 10% when using a remifentanil concentration of 3 ng/mL.

Cell resensitization after delivery of a cycle-specific anticancer drug and effect of dose splitting: Learning from tumour cords

After a single dose of an anticancer agent, changes due to cell death are expected to occur in the distribution of cells between proliferating and quiescent compartment as well as in the oxygenation and nutritional state of surviving cells. These changes are transient because tumour regrowth tends to restore the pretreatment status. The reoxygenation due to the decrease of oxygen consumption is expected to induce cell recruitment from quiescence into proliferation, and consequently to increase the sensitivity of the cell population to a successive treatment by a cycle-specific drug. In previous papers we proposed a model of the response of tumour cords (cylindrical arrangements of tumour cells growing around a blood vessel of the tumour) to single-dose treatments. The model included the motion of cells and oxygen diffusion and consumption. On the basis of that model suitably extended to better account for the action of anticancer drugs, we study the time course of the oxygenation and of the redistribution of cells between the proliferating and quiescent compartments. By means of simulations of the response to a dose delivered as two spaced equal fractions, we investigate the dependence of tumour response on the spacing between the fractions and on the main parameters of the system. A time window may be found in which the delivery of two fractions is more effective than the delivery of the undivided dose.

A model with 'growth retardation' for the kinetic heterogeneity of tumour cell populations

In the present paper we propose a continuous cell population model based on Shackney's idea of growth retardation. Cells are characterized by two state variables: the cell maturity x, 0 < or = x < or = 1, and a state variable T that identifies the rate of maturation along cell cycle. During their life span, cells can change T at random by jump transitions to T values corresponding to slower maturation rates, while at each jump the maturity x is conserved. Both the time evolution of the population and the exponential stationary solution are numerically computed. The distribution of the cell cycle transit time in asynchronous exponential growth is investigated by Monte Carlo simulation. An approximated formula for the distribution of cell cycle time is also provided.

Intraindividual and intraspecies variability of ITS1 sequences in the ancient asexual Darwinula stevensoni (Crustacea: Ostracoda)

The lack of variability in ITS regions within individuals and within species has been explained as the result of concerted evolution. In fact, many examples of intraindividual variation in the ITS regions have been reported. Here we report evidence of within-individual variation of the ITS1 region in the obligate parthenogenetic species Darwinula stevensoni. We analysed 46 clones obtained from 12 individuals of D. stevensoni, from three Italian sites and one site in Luxembourg. Seven nucleotides out of 366 were variable. Most variability (80%) was found among clones within individuals, and the remainder of the variability was observed among individuals. No difference was found among populations or between habitats. The low intraspecific variability and the observation of recombinant molecules are evaluated in light of the relevant literature. The high percentage of variation within individuals and the occurrence of recombination without meiosis are discussed by considering the ancient asexual "status" of the species.

[Acoustic neuroma: clinical-functional finding, results and surgical complication]

The present work provides clinical-functional findings, results and surgical complications observed in a consecutive series of 100 subjects with acoustic neuroma (AN). Analysis of the data has made it possible to draw some important conclusions. Compromised hearing is found in 90% of the ears affected by AN. Indeed the percentage of normal hearing in such cases does not exceed 5%. There is, however, no clear correlation between degree of hearing and tumor size. The symptoms of AN do not always present unilateral or asymmetrical hearing loss, unilateral tinnitus and/or dizziness. At times AN presents atypical symptoms and can even be asymptomatic. Sudden onset of unilateral hearing loss, acute vertigo, persistent monolateral tinnitus and even isolated symptoms of the V or VI cranial nerve should lead one to suspect AN. Only by applying the diagnosis of suspected AN in a large number of cases is it possible to lower the time gap between the onset of symptoms and the definitive diagnosis of AN, increasing the number of cases diagnosed while the AN is still small. Auditory brainstem responses (ABR) are still the means of choice for screening and following up subjects where AN is suspected. Reduced ABR sensitivity reported in the literature for intracanal ANs must induce further testing with magnetic resonance imaging with gadolinium in all subjects where an AN is suspected, even when the ABR is normal. Recording of transient evoked otoacoustic emissions in the presence and in the absence of contralateral white noise has proved to be a simple, inexpensive, non-invasive test for the diagnosis of suspected retrocochlear pathologies. A deficit in vestibular function is most frequently encountered when the AN is already quite large and an alteration in the smooth pursuit test is only found when the AN involves the brainstem. These data have led us to conclude that vestibular reflex studies do not play any role in early diagnosis of AN. Surgical exeresis is the treatment of choice in those cases where "watch and scan" (only hearing ear in the absence of neurological complications; AN < 0.5 cm in the ponto-cerebellar angle, particularly in elderly patients) is not indicated. The enlarged translabyrinthine approach is indicated in all cases of AN, no matter what the tumor size and extent of pre-operative hearing. Promptly and correctly treating intra and postoperative complications, most frequently encountered in patients with AN > 2 cm, reduces the mortality and morbidity to a minimum. Modern otological microsurgery and monitoring techniques make it possible to preserve the VIIth facial nerve in more than 90% of the ears, consequently preserving or nearly preserving normal VIIth nerve function 1 year after surgery in at least three out of four patients. No matter what approach is used, hearing can be preserved measurably in approximately 50% of the ears undergoing surgery and to a socially useful or nearly useful level in a significantly lower proportion of patients. In this regard the most satisfactory results are obtained when preoperative hearing is normal and the AN is < 2 cm.

[Long-term audition results in patients with chronic endolymphatic hydrops after selective vestibular neurotomy and endolymphatic sac surgery]

The purpose of the present study was to evaluate the long-term auditory results in the ears of patients suffering from unilateral Ménière's disease (Md) who had undergone retrolabyrinthine vestibular neurotomy (RVN) associated with endolymphatic sac (ES) surgery. Retrospective evaluation was performed on 45 patients with unilateral Md who had undergone RVN between 1982-1997. All patients had previously been treated with medical therapy for at least 6 months without showing any response. The forms of ES surgery performed were as follows: simple ES decompression (ESD) in 15 patients, chronic endolymphatic mastoid shunt (EMS) using a sylastic sheet in 15 ears and ES exclusion (ESE) of the proximal section in the remaining 15 patients. Evaluation of the results was performed using the parameters indicated by the "Committee on Hearing and Equilibrium"--AAO-HNS 1995. Comparison of the average post-operative and preoperative PTAs revealed a worsening of 9.2 dB (sd: +/- 17.1) in the ESE group. This variation was statistically significant (p < 0.05). When the individual patients were evaluated, the PTA remained unchanged in 10 cases (67%) in the ESD group, in 13 (87%) in the EMS group and in 10 (67%) in the ESE group. In no case did hearing improve. Statistical analysis did not reveal any significant difference between the three groups of patients. Tinnitus, present prior to surgery in all patients, disappeared or improved in 6 patients (40%) in the ESD group, in 6 (40%) of the EMS group and in 5 (33%) of the ESE group. The differences between groups were not significant. The sensation of plugged ears, present prior to surgery in 11 patients in the ESD and EMS groups and in 13 patients in the ESE group disappeared or improved respectively in 9 (82%), 10 (91) and 11 (85%) of the patients. The 10 remaining patients who did not have the sensation of plugged ears prior to surgery did not refer its appearance after surgery. Again for this symptom the difference between groups was not significant. The results of this research would appear to indicate that in patients with Md, evolution of the hearing symptoms observed after RVN can be improved by applying an EMS. This finding must be validated in a larger sampling.

[Acute cholestatic hepatitis caused by propafenone. Report of a case and review of the literature]

A case of acute cholestatic hepatitis associated with use of propafenone is reported. Hepatitis developed 3 weeks after the beginning of administration of this drug. The close time relationship between the administration of the antiarrhythmic drug and the acute onset of the liver damage, the exclusion of hepatobiliary disease and the rapid normalisation of biochemical parameters following withdrawal of the drug strongly suggest that propafenone was involved in the pathogenesis of this syndrome. Meticulous taking of patient history and clinical assessment are mandatory for the early identification of drug-induced hepatotoxicity and avoidance of more severe types of reactions, such as liver failure.

Subclinical hepatic encephalopathy: role of tryptophan binding to albumin and the competition with indole-3-acetic acid

BACKGROUND

The role of tryptophan (TRY) and its metabolites in the pathogenesis of hepatic encephalopathy is conflicting. The aim of the present study is to investigate in posthepatitis cirrhotic patients with encephalopathy the serum levels of TRY and those of its metabolite indole-3-acetic acid, as well as TRY binding curve to serum albumin and the competition with indole-3-acetic acid. The presence of a relationship between encephalopathy severity and circulating free TRY was also investigated.

METHODS

Serum TRY and indole-3-acetic acid were analyzed by HPLC; binding of TRY to serum albumin and the competition with indole-3-acetic acid was studied by equilibrium dialysis.

RESULTS

Serum-free TRY was significantly higher in cirrhotic patients (43.33 +/- 14.70 vs 28.87 +/- 8.77 mumol/L, P = 0.02). The binding capacity of albumin was reduced in cirrhotics and further decreased by the addition of indole-3-acetic (K = 6.63 +/- 0.97 x 10(3) mol/L-1, gamma = 1.16 +/- 0.45 x 10(2) mol/L-1 in normal sera vs K = 1.04 +/- 0.20 x 10(3) mol/L-1, gamma = 1.91 +/- 0.92 10(2) mol/L-1 in cirrhotic sera). A multivariate analysis showed that among the psychometric tests the only independent predictor of serum levels of free TRY was the Block Design (R2 = 0.94, B = 0.16 +/- 0.01, beta = 0.97; P < 0.0001).

CONCLUSIONS

A high percent ratio of free/total TRY and indoleacetic acid (IAA) was found in cirrhotic patients with hepatic encephalopathy. The concentrations of serum-free IAA and TRY correlated with the degree of subclinical encephalopathy, suggesting a role of these compounds in the development of mental derangement in liver cirrhosis.

Cell kinetics in a tumour cord

In some tumours, the viable cells grow around blood vessels forming cylindrical structures called tumour cords, which are surrounded by regions of necrosis. In the present paper, we propose a mathematical model for the cell kinetics in a tumour cord at the stationary state. Both proliferating cells and quiescent cells are considered, and the proliferating cell population is structured by age. Cell migration towards cord periphery is accounted for from a continuum viewpoint. The age distribution of proliferating cells, the fraction of cells in S phase, the growth fraction and the velocity along the cord radius are computed. The predictions of the model are compared with literature data obtained from two experimental rat hepatomas. The model was used to compute the profile of the oxygen tension within the cord. Possible modifications and extensions are also presented.

Paradoxical effects of contralateral white noise on evoked otoacoustic emissions in ears with acoustic neuroma

A contralateral suppression effect on evoked otoacoustic emissions (EOAEs) is usually present in normally hearing subjects and in patients with sensorineural hearing loss, while it is absent or reduced in ears to which the vestibular nerve has been cut and in ears with acoustic neuroma (AN). To date, a paradoxical effect, that is an increase in EOAE amplitude during contralateral stimulation, has been described in one ear with sensorineural hearing loss of unknown aetiology and in three ears with AN (two in the present paper). Evidence has been provided that the contralateral suppression effect on EOAEs is accomplished largely, if not entirely, via the medial olivocochlear bundle (OCB). According to clinical data the absence or the reduced amount of contralateral suppression effect on EAOEs may be attributed to a totally, or partially, damaged or malfunctioning medial OCB. The way in which a contralateral noise may increase EOAE amplitude is more difficult to explain. One attractive hypothesis is that this paradoxical effect is a result of some pathological adaptive process in the medial OCB.

Disposition of dodecanedioic acid in humans

The disposition of dodecanedioic acid (C12) was investigated in six overnight-fasting healthy male volunteers, who received a 165-min i. v. infusion of 42.45 mmol of C12 added to 150 microCi of [1-12-(14)C]C12. Blood samples were collected up to 360 min after the start of infusion, and concentration of serum labeled C12 was determined. Expired radioactivity (microCi/min) was measured up to 600 min and at 24 h. The 24-h C12 urinary excretion was around 5% of the administered amount. The percentage of C12 oxidized was 81.7 +/- 9.5% (mean +/- S.D.) of administered amount as estimated from the area under the curve of measured (14)CO(2) expiration rate. C12 kinetics was described by assuming a single compartment. A saturable rate of C12 tissue uptake (model A) and a linear rate of tissue uptake (model B) were considered. The kinetics of CO(2) produced by C12 oxidation was described by a fast pathway acting in parallel to a slow pathway modeled by first order kinetics. Parameters of model B were estimated for each subject, whereas model A was identified by fitting the pooled data of all subjects. On the basis of estimates obtained from model B, an average calorie delivery of 500 kcal/day was predicted in the plateau phase for the infusion rate of our experiments. When estimated from model A, the maximal rate of tissue uptake was 0.38 +/- 0.08 mmol/min, with a maximal calorie delivery of 750 kcal/day. These results appear promising for C12 utilization in parenteral nutrition, because C12 elimination with urine is low, whereas tissue uptake and oxidation are rather efficient.

Persistence of asexuality through mixed reproduction in Eucypris virens (Crustacea, Ostracoda)

The ostracod species Eucypris virens exhibits geographical parthenogenesis, with rare sexual populations in southern Europe and widespread asexual populations elsewhere. DNA sequence data from the nuclear ITS1 and mitochondrial COI regions have been used to estimate genetic variabilities and reconstruct phylogenies. The observed divergence was exceptionally high, with intraspecific maxima of 10.3% (ITS1) and 20.9% (COI) among European lineages, levels reported for interspecific comparisons of other taxa. Phylogenetic reconstructions reveal multiple origins of asexual clones from sexual populations. However, we argue that such data can only provide a lower limit on the number of origins of asexual reproduction, and an upper limit on the age of asexual lineages. Congruence between gene trees for different loci can provide support for the inference of long-term apomictic reproduction. Nuclear and mitochondrial data differ in their placement of some asexual clones, possibly indicating that genetic exchange has taken place between sexual and asexual lineages. Such intraspecific hybridization is one route to combine the benefits of both reproductive modes, and it might explain how asexuality managed to persist in E. virens even in long, evolutionary terms.

Pharmacokinetics of sebacic acid in rats

The pharmacokinetics of disodium sebacate (Sb) was studied in Wistar rats of both sexes. Sebacate was administered either as intra-peritoneal (i.p.) bolus (six doses ranging from 10 mg to 320 mg) or as oral bolus (two doses: 80 and 160 mg). Plasma and urinary concentrations of Sb and urinary concentrations of Sb and its products of beta-oxidation (suberic and adipic acids) were measured by an improved method using gas-liquid chromatography/mass-spectrometry. A single compartment with two linear elimination routes was selected after no increase in significance was shown by an additional compartment and after a saturable mechanism was found to be unsuitable. Both renal and non-renal elimination parameters were obtained by Marquardt non linear fitting of plasma concentrations together with urinary elimination. The data reported are calculated from the analysis on the whole population of rats and referred to an average body weight (bw) of 100 g. The Sb half-time was 31.5 min. The tissue elimination rate was 0.0122 min-1. The overall volume of distribution was found to be 26.817 ml/100 g bw. The renal clearance was 0.291 ml/min/100 g of bw, which is much less than the value of GFR reported in literature (about 1 ml/min/100 g bw), suggesting the presence of Sb reabsorption from the ultrafiltrate. The value of Sb renal clearance was found to be a concentration-independent function, suggesting the presence of a passive back-diffusion. The relative bioavailability of the oral form compared to the i.p. form was 69.09%, showing a good absorption of the drug.

Serum nitrites predict the response to prostaglandin-induced delivery at term

OBJECTIVE

To evaluate whether the clinical response to prostaglandin-induced labor is modulated by nitric oxide (NO) activity.

METHODS

Fifty-two cases of nulliparous women at term who delivered vaginally after prostaglandin E (PGE) induction of labor were enrolled. The induction was required mainly for amniotic fluid reduction or late-onset gestational hypertension. Either intracervical (0.5 mg) or vaginal (2.0 mg) PGE was administered every 12 hours, according to the Bishop score. After the third PGE application, in absence of labor onset, intravenous oxytocin was used. Nitrites/nitrates (NOx) serum levels were used as a marker of NO activity. They were measured just before the start of induction by using an enzymatic reduction and then a colorimetric evaluation. Time to delivery from the first PGE application was the main outcome variable.

RESULTS

Time to delivery ranged from 4 to 62 hours (median: 15.5). Nitrites/nitrates levels were unaffected by both gestational age, Bishop score at entry, indication allowing labor-induction, fetal position, and birth weight. In a multiple regression analysis including the previous factors, NOx levels significantly explained 33.9% of the variance of the time to delivery. Indeed, patients delivering within 15 hours (26.4 +/- 6.9) showed NOx levels significantly lower than in patients delivering after more than 15 hours (39.5 +/- 16.4) from the first PGE application.

CONCLUSIONS

A reduced level of NOx is associated with a prompt clinical response to PGE-induced labor. Provided we do not know the origin of NOx in the general circulation, these data indicate NOx levels as predictors of the response to PGE-induced delivery at term and support the hypothesis that labor onset is modulated by the endogenous NO activity.

Binding of indole-3-acetic acid to human serum albumin and competition with L-tryptophan

Indole-3-acetic acid (IAA) is a product of tryptophan (Trp) metabolism and is found to be markedly increased in uremic sera. IAA binding to defatted human serum albumin at 37 degrees C and pH 5, 7.4, and 8.5 was studied by equilibrium dialysis, and data were analyzed assuming two independent high affinity binding sites plus a class of low affinity sites. The estimated values of the association constant of dominant site were: 7.96 x 10(3) M-1 at pH 5, 11.57 x 10(3) M-1 at pH 7.4, and 6.30 x 10(3) M-1 at pH 8.5. The competition between IAA and Trp for albumin binding at pH 7.4 was investigated. The results suggest that one specific albumin site is common for IAA and Trp, but the data were not adequately predicted by a purely competitive scheme. A better prediction was achieved assuming that the binding of IAA to a site different from the common site inhibits Trp binding.

Cell loss and the concept of potential doubling time

The in vivo infusion of Bromodeoxyuridine (BrdUrd), followed by delayed biopsy and bivariate DNA-BrdUrd flow cytometry, allows the potential doubling time (Tpot) of human tumors to be estimated. According to Steel, the mathematical definition of Tpot is Tpot = ln 2/Kp, where Kp is the rate constant of cell production. All the operative formulas which allow the estimation of Tpot from flow cytometric data derive from this definition. Most authors, however, identify the potential doubling time as the doubling time that the same cell population would exhibit if cell loss were removed. We denote here as T(d)noloss this quantity. Although these two definitions are equivalent in the case of uniform random cell loss, we show, in the framework of Steel's theory of growing cell populations, that Tpot and T(d)noloss become distinct kinetic quantities when cell loss is not uniform, i.e., when loss differently affects the quiescent and the proliferative compartment. We discuss the validity of the two formulas currently used for the calculation of Tpot, one based on LI and the other on the v-function, in conditions of non-uniform cell loss. Moreover, we propose two formulas for the estimation of the cycle time T(C), which require, in addition to T(S) and LI, that a measure of the growth fraction be available.

[Cholesterol granuloma of the petrous apex]

Cholesterol granuloma of the petrous apex is a relatively rare tumor, and usually is not associated with middle ear pathology. Precise assessment of the diagnosis and extension allows the surgeon to plan the most appropriate and functional strategy. The advent of magnetic resonance imaging has helped, showing a high signal in T1 and T2 without enhancement after the administration of intravenous paramagnetic contrast. The occipito-temporal approach provides direct access to the anterior and posterior petrous apex without opening the dura, which preserves the facial and the cochlear-vestibular functions.

Steel's potential doubling time and its estimation in cell populations affected by nonuniform cell loss

The in vivo infusion of the thymidine analogue bromodeoxyuridine (BrdUrd). followed by delayed biopsy and bivariate DNA-BrdUrd flow cytometry, makes it possible to estimate Steel's potential doubling time (Tpot) of human tumors. In the present paper, the expression of Steel's Tpot for a rather general cell population model, in which the distribution of cell loss is assumed to be nonuniform, is derived in terms of the model parameters. We show that Steel's Tpot of a population can be markedly different for the doubling time that would be exhibited by the population in the absence of cell loss. These doubling times, on the contrary, are equal when loss is uniform. Moreover, we studied the influence of modes of cell loss different from the uniform random loss on the estimation of Tpot by using the labeling index or the nu-function, quantities that can be determined from the bivariate DNA-BrdUrd distribution.

Kinetics of dodecanedioic acid and effect of its administration on glucose kinetics in rats

Dodecanedioic acid (C12), a saturated aliphatic dicarboxylic acid with twelve C atoms, was given as an intraperitoneal bolus to male Wistar rats, with the aim of evaluating C12 suitability as an energy substrate for parenteral nutrition. The 24 h urinary excretion of C12 was 3.9% of the administered dose. C12 kinetics were investigated by a one-compartment model with saturable tissue uptake and reversible binding to plasma albumin. The analysis of plasma concentration and urinary excretion data from different animals yielded the population means of the kinetic parameters: renal clearance was 0.72 ml/min per kg body weight (BW) (much smaller than inulin clearance in the rat), and maximal tissue uptake was 17.8 mumol/min per kg BW corresponding to 123.7 J/min per kg BW. These results encourage the consideration of C12 as a possible substrate for parenteral nutrition. To investigate the effect of C12 administration on glucose kinetics, two other groups of rats, one treated with an intraperitoneal bolus of C12 and the other with saline, were subsequently given an intravenous injection of D[-U-14C]glucose in a tracer amount. Radioactivity data of both control and C12-treated rats were analysed by means of a two-compartment kinetic model which takes into account glucose recycling. The estimates of glucose pool size (2.3 mmol/kg BW) and total-body rate of disappearance (82.1 mumol/min per kg BW) in control rats agreed with published values. In C12-treated rats, the rate of disappearance appeared to be reduced to 36.7 mumol/min per kg BW and the extent of recycling appeared to be negligible.

Serum uremic toxins from patients with chronic renal failure displace the binding of L-tryptophan to human serum albumin

The level of free tryptophan (Trp) and its metabolites in serum appears to be related to some pathologic states, such as chronic renal failure and neuropsychiatric disorders, so that a precise characterization of tryptophan binding to serum albumin is of interest. In the present paper, the binding of L-tryptophan to defatted human serum albumin at 37 degrees C and at pH 7.4 was studied by means of equilibrium dialysis. The competition between L-tryptophan and serum solutes extracted from uremic patients undergoing hemodialysis, before dialysis treatment, was also investigated. Solutes were extracted from uremic pools of sera using two different deproteinization methods: serum ultrafiltration and heat denaturation of serum proteins followed by ultrafiltration. We found 1.10 +/- 0.03 binding sites for Trp to defatted albumin with an association constant 11.37 +/- 1.03 x 10(3) M-1. The competition experiments suggested that the number of Trp binding sites were not significantly modified by the addition of solutes obtained with the method of ultrafiltration with respect to the binding of L-tryptophan to albumin in the absence of competitors, while their affinity constant was markedly reduced (2.66 +/- 0.18 x 10(3) M-1). Moreover, a significant reduction of the affinity constant was observed when competitors for Trp were obtained using heat deproteinization associated with ultrafiltration (1.91 +/- 0.15 x 10(3) M-1 vs. 2.66 +/- 0.18 x 10(3) M-1; P < 0.005). These results might be ascribed to the fact that the last procedure has a higher yield with a more complete liberation of uremic toxins from serum proteins, so that they became probably totally free thus competing at higher extent with L-tryptophan for albumin binding sites.

Long-term GnRH-agonist administration revealed a GnRH-independent mechanism stimulating FSH discharge in humans

The present study evaluated the FSH and LH episodic discharge in different physiopathological conditions undergoing chronic GnRH-agonist administration. Four girls with true precocious puberty and five postmenopausal women were administered GnRH-agonist (3.73 leuprolide acetate every 4 weeks; Takeda Italia, Rome, Italy) for at least 4 months. Plasma LH and FSH secretory profiles were assessed before and under GnRH-agonist administration (after 21 and 120 days). Pulsatility studies were conducted for 4 h in the girls and for 6 h in postmenopausal women, with blood sampling intervals of 10 min. Pubertal and postmenopausal patients showed the distinct episodic co-secretion of LH and FSH before GnRH-agonist administration; this co-secretion disappeared in both groups after 21 and 120 days of treatment. Moreover, while LH concentrations decreased to almost undetectable levels and LH episodic release disappeared, FSH plasma levels were only partially reduced and FSH episodic secretion was detectable in both groups. In conclusion, this study demonstrated that long-term GnRH-agonist administration blocked LH but not FSH episodic release. These data enforce the hypothesis that FSH episodic discharge might be dependent not only on hypothalamic GnRH, but also on a GnRH-independent stimulatory pathway.

Pharmacokinetic analysis of dodecanedioic acid in humans from bolus data

BACKGROUND

Excretion and tissue uptake of dodecanedioic acid (C12), a proposed alternative fuel substrate, was investigated in humans by bolus experiments.

METHODS

Seven overnight-fasting healthy male volunteers received i.v. a bolus (1 g) of C12. Blood samples were collected after C12 administration at intervals of 15 minutes, and C12 serum concentration was measured by high-performance liquid chromatography. C12 excretion in 24-hour urine was measured. Binding of C12 in human serum was determined in separate equilibrium dialysis experiments by means of an isotopic compound (disodic salt of (1,12)14C-dodecanedioic acid). A two-compartment model was used for describing C12 kinetics.

RESULTS

The excreted amount of C12 in 24-hour urine was found to be, on the average, 1.62% of administered dose. The apparent number of binding sites per albumin molecule was 3.1 +/- 0.2 (estimate +/- SE) with an affinity constant of 6.4 +/- 1.8 mM-1. The distribution volume of central compartment was 5.56 +/- 3.13 L and that of peripheral compartment was 87.4 +/- 30.4 L. The rate constant of exchange between compartments was 4.60 +/- 3.50 L/min, that or urinary excretion 25.6 +2- 15.5 mL/min, and that of tissue uptake 2.17 +/- 0.86 L/min.

CONCLUSIONS

These results are promising for C12 utilization in parenteral nutrition, because C12 elimination in urine is low whereas tissue uptake appears to be rather efficient.

Well-differentiated endocrine tumours of the middle ear and of the hindgut have immunocytochemical and ultrastructural features in common

The immunocytochemical analysis of two cases of well-differentiated endocrine tumours (carcinoids) of the middle ear revealed predominant cell populations producing pancreatic polypeptide (PP)-related peptides, glucagon-related peptides, and serotonin (the latter only in one case). In consecutive sections PP- and glucagon-related immunoreactivities mainly colocalized in the same tumour cells. Ultrastructurally tumour cells were characterized by medium-sized to large granules of moderate to high density, on which PP and glicentin were localized by the immunogold technique. No amphicrine cells were found. These features are consistent with those of similar tumours in the rectal mucosa that are mainly composed of L cells coexpressing both PP-related and glucagon-related peptides. Additional tumour antigens of hindgut type detected immunohistochemically were prostatic acid phosphatase and CAR-5 mucin. Expression of the CAR-5 antigen was also found in samples of normal middle ear mucosa, in which endocrine cells have not been identified. In case 1 peritumoral mucosal invaginations showed a proliferation of endocrine cells identical immunophenotypically to tumour cells, possibly representing a precursor lesion. It is concluded that well-differentiated endocrine tumours of the middle ear are a distinct pathological entity characterized by multiple hormone production, typically involving three classes of hormones (pancreatic polypeptide-related peptides, glucagon-related peptides, and serotonin) of the hindgut endocrine system.

Cell cycle analysis by the relative movement approach: effect of variability across S-phase of DNA synthesis rate

Cell populations pulse-labelled with BrdUrd, and sampled at increasing times after the pulse, yield DNA-BrdUrd distributions from which the relative movement (RM) and the depletion function (DF) of labelled, undivided cells can be calculated. In this paper we present an extension of the equation for the time course of RM, given by White and Meistrich (Cytometry 1986, 7, 486-490), to the case in which the rate of DNA synthesis changes across S-phase. Some modalities of cell loss were also considered. Computer simulations showed that different patterns of DNA synthesis rate across S-phase can result in appreciably different RM curves. An analytical expression of the RM curve, in which the variability across S-phase of the rate of DNA synthesis is accounted for by only one parameter, was proposed. This expression was used for the simultaneous fitting of time sequences of RM and DF data of U937 cells, in order to estimate the phase transit times TS and TG2+M, and the potential doubling time Tpot. The use of the extended model gave better results than those obtained under the assumption of constant rate of DNA synthesis across S-phase.

[Transoral approaches to the skull base. An attempt of systematization]

This is a technical note concerning the classifications of the various operations possible via the buccal route towards the base of the skull and the first vertebrae. A part from the Hardy vestibulo-septal approach, mention must be made of the buccal and transpalatine approach, the direct buccal approach, the buccal approach widened downwards by transmandibular osteotomy, and finally the transmandibular and transcervical approach. These different technique enable the ablation of extradural and even intradural lesions at the level of the clivus, but are limited on the side by the pterygoid process and the large vessels.

Pharmacokinetic analysis of azelaic acid disodium salt. A proposed substrate for total parenteral nutrition

Azelaic acid was the first dicarboxylic acid proposed as an alternative energy substrate in total parenteral nutrition. In this study, the pharmacokinetics of azelaic acid were investigated in 12 healthy volunteers, 7 receiving a constant infusion (10g over 90 min) and 5 a bolus dose (1g). The 24h urinary excretion and plasma concentration in blood samples taken at regular intervals were assayed by gas-liquid chromatography. Experimental data were analysed by a 2-compartment nonlinear model that describes both tubular secretion and cellular uptake in Michaelis-Menten terms. A high value of urinary excretion (mean 76.9% of infused dose) and a mean clearance of 8.42 L/h were found, suggesting the presence of tubular secretion. Estimating the population mean of the pharmacokinetic model parameters gave a maximal cellular uptake of 0.657 g/h. The model predicts that 90% of the maximal uptake should be reached in the plateau phase of a constant infusion of 2.2 g/h. The presence of extensive and rapid losses through urinary excretion, and the low estimated value of the maximal cellular uptake, indicate that azelaic acid is not suitable as an energy substrate for total parenteral nutrition.

Study of propidium iodide binding to DNA in intact cells by flow cytometry

We studied the in situ binding of propidium iodide to DNA in fixed human lymphocytes, using flow cytometry. Experimental data of fluorescence emission vs dye concentration and vs cell concentration were obtained. Data were interpreted by means of two different mathematical models specific for the staining reaction, and the binding parameters were obtained by "best-fitting" of the data. A model based on two classes of binding sites with different affinity constants gave the most satisfactory fitting. The accessibility of the in situ chromatin turned out to be reduced with respect to the non in situ accessibility for ethidium bromide as reported in the literature. The present study shows the usefulness of the flow-cytometric technique for probing DNA structure in intact cells.

MR cisternography of the cerebello-pontine angle and internal auditory canal in diagnosis of intracanalicular acoustic neuroma

One hundred and fifteen patients, suffering from sensorineural hearing loss were tested with a 1.5 T superconducting magnet. The authors describe utility of both T1-weighted multiple slice and T2-weighted multiple echo images for the evaluation of cerebello-pontine angle, internal auditory canal and their neurovascular content. In seventy-three cases MR cisternography was normal. The remaining forty-two cases were subdivided into twenty extracanalicular masses, eleven small intra-extracanalicular and nine purely intracanalicular lesions. All the lesions were histologically proven acoustic neuromas, except one intracanalicular mass which was a meningioma. Examination was inconclusive only in two cases and decision was then made to follow the clinical course. Advantages of MR cisternography over CT and air CT cisternography, such as absence of ionizing radiation and contrast material, easy multiplanar evaluation of the region of interest and the possibility to delineate both the cisternal and canalar extremities of the tumor mass are pointed out.

Use of bispecific hybrid antibodies for the development of a homogeneous enzyme immunoassay

Hybrid bispecific monoclonal antibodies reacting with carcinoembryonal antigen (CEA) and with the E. coli enzyme beta-galactosidase (GZ) were produced by fusion of hybridomas or chemical linkage of half-antibodies. Since the original anti-GZ antibody used in these experiments was capable of protecting GZ from thermal denaturation, it was possible, by hybridizing it with two different non-competitive anti-CEA antibodies, to design a homogeneous enzyme immunoassay for quantitation of CEA. In fact, a mathematical analysis of the reaction indicates that, under appropriate concentrations of the reactants, circular complexes can be formed which contain the two hybrid antibodies, the GZ enzyme and the CEA antigen. The stability of these complexes can be expected to be substantially greater than that of the more labile CEA-free GZ-antibody complexes, prompting a significant increase in the amount of enzyme molecules which are bound to antibody and are consequently protected from thermal denaturation. These expectations were supported by experimental results: under appropriate conditions, heat-resistant enzyme activity was indeed proportional to concentration of CEA in the range up to 75 ng/ml. As predicted by theory, however, in the presence of excess CEA - in fact at CEA concentrations which are higher than those of possible clinical relevance - circular complexes tended to open up, leading to a marked prozone effect.