Hyaluronan, fluid pressure, and stromal resistance in pancreas cancer.

Pancreatic ductal adenocarcinomas (PDAs) are notoriously aggressive and resistant to treatment. They distinguish themselves further by their robust fibroinflammatory, or desmoplastic, stromal reaction and degree of hypovascularity. Recent findings have revealed multiple mechanisms of stromal complicity in disease pathogenesis and resistance. In this review, we focus on altered physicomechanics as one mechanism of what we term as 'stromal resistance' in PDA. Extremely high interstitial fluid pressures and a dense extracellular matrix combine to limit the delivery and distribution of therapeutic agents. We discuss the genesis and consequences of altered fluid dynamics in PDA and strategies to restore them.

Matrix density-induced mechanoregulation of breast cell phenotype, signaling and gene expression through a FAK-ERK linkage.

Mammographically dense breast tissue is one of the greatest risk factors for developing breast carcinoma, yet the associated molecular mechanisms remain largely unknown. Importantly, regions of high breast density are associated with increased stromal collagen and epithelial cell content. We set out to determine whether increased collagen-matrix density, in the absence of stromal cells, was sufficient to promote proliferation and invasion characteristic of a malignant phenotype in non-transformed mammary epithelial cells. We demonstrate that increased collagen-matrix density increases matrix stiffness to promote an invasive phenotype. High matrix stiffness resulted in increased formation of activated three-dimensional (3D)-matrix adhesions and a chronically elevated outside-in/inside-out focal adhesion (FA) kinase (FAK)-Rho signaling loop, which was necessary to generate and maintain the invasive phenotype. Moreover, this signaling network resulted in hyperactivation of the Ras-mitogen-activated protein kinase (MAPK) pathway, which promoted growth of mammary epithelial cells in vitro and in vivo and activated a clinically relevant proliferation signature that predicts patient outcome. Hence, the current data provide compelling evidence for the importance of the mechanical features of the microenvironment, and suggest that mechanotransduction in these cells occurs through a FAK-Rho-ERK signaling network with extracellular signal-regulated kinase (ERK) as a bottleneck through which much of the response to mechanical stimuli is regulated. As such, we propose that increased matrix stiffness explains part of the mechanism behind increased epithelial proliferation and cancer risk in human patients with high breast tissue density.

Application of nonlinear viscoelastic models to describe ligament behavior.

Recent experiments in rat medial collateral ligament revealed that the rate of stress relaxation is strain dependent and the rate of creep is stress dependent. This nonlinear behavior requires a more general description than the separable quasilinear viscoelasticity theory commonly used in tissue biomechanics. The purpose of this study was to determine whether the nonlinear theory of Schapery or the modified superposition method could adequately model the strain-dependent stress-relaxation behavior of ligaments. It is shown herein that both theories describe available nonlinear experimental ligament data well and hence can account for both elastic and viscous nonlinearities. However, modified superposition allows for a more direct interpretation of the relationship between model parameters and physical behavior, such as elastic and viscous nonlinearities, than does Schapery's theory. Hence, the modified superposition model is suggested to describe ligament data demonstrating both elastic nonlinearity and strain-dependent relaxation rate behavior. The behavior of the modified superposition model under a sinusoidal strain history is also examined. The model predicts that both elastic and viscous behaviors are dependent on strain amplitude and frequency.

Microstructural morphology in the transition region between scar and intact residual segments of a healing rat medial collateral ligament.

This study used a rat model to investigate the microstructural organization of collagen through the transition from scar to intact residual segments of a healing medial collateral ligament (MCL). Twenty-two male retired breeder Sprague-Dawley rats were randomly separated into two groups. Eleven underwent surgical transections of both MCLs and were allowed unrestricted cage activity until euthanized two weeks post surgery. The remaining eleven rats were used as normal controls. All 44 MCLs were harvested including intact femoral and tibial insertions and prepared for scanning electron microscopy (SEM) imaging. At harvest the scar region in the healing ligaments was more translucent than the normal tissue. Ligaments were viewed from femoral to tibial insertions at magnifications of 100X through 20,000X. Tissue away from the scar region in the transected MCLs was indistinguishable from normal tissue in uninjured ligaments. Collagen fibers and fibrils in these tissues were more aligned along the longitudinal axis of the ligament than in the scar tissue. Continuity of collagen fibers and fibrils were consistently observed from the residual portions of the transected ligament through the scar region. Bifurcations/fusions, but no anastomoses, in fibers and fibrils were observed in both normal and scar tissues of ligaments. Qualitatively, bifurcations were encountered more frequently in scar tissue. In the transition region, larger diameter fibers from the residual tissue bifurcated into smaller diameter fibrils in the scar. This connection between larger diameter and smaller diameter fibers and fibrils indicates that bifurcations/fusions are likely to be the dominant way in which force is transmitted from a region with larger fibrils (residual ligament) into and through a region with smaller fibrils (scar).

Nonlinear ligament viscoelasticity.

Ligaments display time-dependent behavior, characteristic of a viscoelastic solid, and are nonlinear in their stress-strain response. Recent experiments (25) reveal that stress relaxation proceeds more rapidly than creep in medial collateral ligaments, a fact not explained by linear viscoelastic theory but shown by Lakes and Vanderby (17) to be consistent with nonlinear theory. This study tests the following hypothesis: nonlinear viscoelasticity of ligament requires a description more general than the separable quasilinear viscoelasticity (QLV) formulation commonly used. The experimental test for this hypothesis involves performing both creep and relaxation studies at various loads and deformations below the damage threshold. Freshly harvested, rat medial collateral ligaments (MCLs) were used as a model. Results consistently show a nonlinear behavior in which the rate of creep is dependent upon stress level and the rate of relaxation is dependent upon strain level. Furthermore, relaxation proceeds faster than creep; consistent with the experimental observations of Thornton et al. (25) The above results from rat MCLs are not consistent with a separable QLV theory. Inclusion of these nonlinearities would require a more general formulation.

Interaction between naloxone, chlordiazepoxide and valproic acid evaluated by emotional operant behaviour in the rat.

The effects of chlordiazepoxide (CDP, 5 mg/kg i.p.), the sodium salt of valproic acid (VPA, 200 mg/kg i.p.) and naloxone (Nx, 1 mg/kg s.c.) alone and CDP-Nx, VPA-Nx association on schedule controlled behaviour with signalled unpunished and punished periods, were investigated. Our results show that CDP and VPA under both the unemotional (variable ratio reinforcement schedule 20%) and the emotional (continuous reinforced schedule associated with electric shock) components significantly increase responding in the Skinner box. Nx, on the multiple schedule, non-significantly reduces responding under both components. With CDP-Nx association the increase in responding under the unemotional component is less than in the case of the benzodiazepine alone, while under the emotional component the increase in responding is not appreciably affected. With the VPA-Nx association the responding rate is lower than that of the control under the unemotional component while under the emotional component the increase in responding is reduced compared to the VPA alone. The higher rates of unemotional and emotional responding with both CDP and VPA depend on the dipsogenic and disinhibiting effects by both drugs. The different rate of emotional and unemotional responding with CDP-Nx and VPA-Nx associations indicates a specific influence on GABAergic and other systems by CDP and VPA.

Effect of single and repeated treatment of chlordiazepoxide and sodium valproate on water intake in the rat and their influence on the antidipsogenic action of naloxone.

The action of single and repeated treatment with chlordiazepoxide (CDP) (5-10 mg/kg i.p.) and sodium valproate (VPA) (100-200 mg/kg i.p.) on water intake of rats adapted to a daily 23-h water deprivation schedule was investigated. The influence exerted by single or repeated treatment of the two drugs on the antidipsogenic effect of naloxone (Nx) (1 mg/kg s.c.) was studied too. Our results show that with single treatment of CDP the dipsogenic effect is lower and not further modified by increasing dose and by the time-course of the session; with repeated treatment the dipsogenic effect is greater and further enhanced by increasing dose and by the time-course of the session. Single or repeated treatment with VPA does not significantly affect the water intake. Single treatment of CDP enhances the antidipsogenic effect of Nx, while CDP, after repeated treatment, reverses the antidipsogenic effect of Nx. With VPA-Nx association, the response is univocal (antidipsogenic effect) independent of the experimental conditions. The results are briefly discussed.

Antidipsogenic action of naloxone under different water deprivation conditions.

Naloxone (1 mg/Kg s.c.), in the light phase of the daily light-dark cycles during the 30 and 60 min of the test, shows an antidipsogenic effect of the same intensity in chronically water-deprived rats which drink more (+ 176% and + 162%) than the acutely water-deprived animals. In chronically water-deprived rats, the time interval from the drug introduction (5, 30, 60 and 90 min) is not critical for the intensity of the antidipsogenic action of naloxone. When water intake is controlled by a 20% variable ratio schedule that does not allow the animals to satisfy, during the session, more than 50% of their thirst, the time interval from the introduction of naloxone is critical. When the rats can drink freely for 30 min in their home-cage after they satisfied their thirst partially by means of bar-pressing, naloxone, paradoxically shows a weaker and not significant antidipsogenic action. The results and the usefulness of the behavioural test are briefly discussed.

Further assessment of benzodiazepine-tricyclic antidepressant interaction. Effectiveness of combined treatment with ketazolam-nortriptyline on conflict behaviour in rats.

Using Geller and Seifter's conflict behaviour test, ketazolam in rat increases the rate of responses emitted both with and without punishment. Nortriptyline decrease the non-punished component of the schedule without influencing the punished one. With combined treatment, nortriptyline does not modify the effects of ketazolam on punished responses while nortriptyline, 1 h after administration, decreases, though not significantly, the facilitating action of ketazolam. After 24 h it significantly increases the depressant action of this benzodiazepine. The results suggest that with the combination tricyclic anti-depressant-benzodiazepine, as with these two categories of drugs, there is not always an increase in disinhibiting action, while depressant action has characteristics closely dependent on the properties of the benzodiazepine used.

Influence of the suspension of continued treatment with flurazepam and amobarbital on two discrimination learning schedules.

The authors have studied the effect of the suspension of chronic treatment with flurazepam and amobarbital on the operant behavior of rats that for the first time were in the presence of two fixed-interval discrimination schedules. With the sound discrimination schedule, the responses emitted by the treated animals had charactistics similar to those of control animals. With the temporal discrimination schedule, though it is not possible to distinguish between learning rates, modifications in the intensity of the effect (increases in lever pressing) indicate that, considering the doses, the action of flurazepam is slight and that of amobarbital clear and statistically significant.

Chemistry and pharmacology of arginine pyroglutamate. Analysis of its effects on the CNS.

By studying the influence of the arginine pyroglutamate on the CNS its variations were evidenced which are clearly identifiable through the analysis of the interaction with molecules having either a depressive or excitatory action. In the case of pentobarbital the antagonistic effect of the compound on the general anaesthesia is very intense and is equally present even when medazepam and flurazepam are associated. Equally obvious is the antagonism with barbiturate in the case of spontaneous motility but much less so with the two benzodiazepines. As far as the specialized behaviour is concerned, arginine pyroglutamate does not alter the sound discrimination capacity (responses in Sdelta punished) at fixed intervals (F.I.) nor does it influence the learning of a sound discrimination (responses in Sdelta punished) at varied intervals (V.I.). The process of learning is instead moderately accelerated in the case of a temporal discrimination and of a conditioned avoidance response (CAR) in the shuttle-box. No effect was found when the same amino acids were introduced alone or in random association. The hypothesis is proposed that the phenomena described depend on the different pharmacokinetics of arginine pyroglutamate that ensures brain concentrations sufficient to block the activity of depressive compounds but is not capable of influencing in a significant way the spontaneous and specialized behaviour of normal animals.

Charge-transfer complexes of hematoporphyrin having a pharmacological interest.

Complexes formed by hematoporphyrin with donor molecules were prepared and isolated. Among these complexes particular attention is given to that formed by reacting dimethylaminoethanol with hematoporphyrin. Some data are reported on the chemical evidence of formation like u.v. spectra. The product, named Hematodeanol, determines some sufficiently specific effects on the CNS; it remarkably cuts down the depression induced by pentobarbital, moderately hinders convulsions by metrazole, delays hypothermia by reserpine, facilites the learning of conditioned avoidance response (CAR) and improves the learning of a sound discrimination at variable interval. The actions become evident when tests are carried out after a continuous treatment for 7 days and according to the data of the investigation of pharmacokinetic kind, the phenomenon may be attributed to the fact that the drug concentration in the nervous tissue, when it is administered several times at intervals of 24 h, inclines to increase progressively.