Heat-Induced Changes in the Mechanical Behavior of Passive Coronary Arteries

1995 ◽  
Vol 117 (1) ◽  
pp. 86-93 ◽  
Author(s):  
T. Kang ◽  
J. Resar ◽  
J. D. Humphrey
Keyword(s):  
Mechanical Behavior ◽  
Coronary Arteries ◽  
Axial Force ◽  
Thermal Exposure ◽  
Thermomechanical Behavior ◽  
Intraluminal Pressure ◽  
Mechanical Loads ◽  
Induced Changes

We performed in vitro pressure-diameter and axial force-length experiments on nondiseased, passive bovine coronary arteries subjected to bath temperatures from 21 to 80° C for 90 s to 4 hr. Over the strain ranges studied, we found that: (a) vessel behavior remained the same over 20 min of testing at 21 to 55° C, (b) vessels stiffened multiaxially after 5 min of exposure to 60° C and continued to stiffen over 20 min of testing, (c) dramatic multiaxial vessel stiffening and shrinkage occurred after 90 s of exposure to 70 and 80° C, and (d) heat-induced changes at 70° C depended on the intraluminal pressure during heating. Thus, passive bovine coronary arteries exhibit a complex thermomechanical behavior that depends on the temperature, duration of thermal exposure, and the mechanical loads applied during heating.

Evaluation of Peristalsis in Multiple Segments of the Guinea-pig Isolated Small Intestine: Optimisation of Tissue Use by Refined In Vitro Methodology

2003 ◽  
Vol 31 (4) ◽  
pp. 419-427 ◽  
Author(s):  
Peter Holzer ◽  
Anaid Shahbazian ◽  
Evelin Painsipp ◽  
Akos Heinemann
Keyword(s):  
Guinea Pig ◽  
Intraluminal Pressure ◽  
Drug Induced ◽  
Pressure Threshold ◽  
Pharmacological Screening ◽  
Set Up ◽  
Induced Changes ◽  
Validation Experiments ◽  
Pig Jejunum

Peristalsis is the aboral movement by which the intestine propels its contents. Since pharmacological research requires an experimental model with which drug-induced modifications of peristalsis can be reliably quantified, we set out to develop and validate an in vitro method for studying peristalsis in multiple gut segments. In our arrangement, up to four 10cm segments isolated from the guinea-pig jejunum and ileum can be set up in parallel and their lumens perfused. Peristalsis was elicited by pressure-evoked wall distension, and the peristalsis-induced changes in the intraluminal pressure were evaluated with software that determined the peristaltic pressure threshold, the frequency, maximal acceleration and amplitude of the peristaltic waves, and the residual baseline pressure. Validation experiments showed that the peristalsis parameters at baseline and after modification by morphine (0.01–10μM) did not differ between segments from the jejunum and ileum, or between segments examined in a consecutive manner. In conclusion, our work succeeded in optimising the use of the guinea-pig jejunum and ileum for multiple recordings of peristalsis in vitro, and in refining the recording and evaluation of peristaltic motility. This system promises to be particularly useful in the pharmacological screening and testing of drugs which modify peristalsis.

Systemic Effects of ADP-induced Platelet Aggregation and Their Modification by Aspirin and by Pyridinolcarbamate

1973 ◽  
Vol 30 (01) ◽  
pp. 178-190 ◽  
Author(s):  
Itsuro Kobayashi ◽  
Paul Didisheim
Keyword(s):  
Platelet Aggregation ◽  
Venous Pressure ◽  
Systemic Effects ◽  
Central Venous ◽  
Platelet Aggregates ◽  
Induced Changes ◽  
Second Wave ◽  
Carotid Arterial ◽  
Arterial Po2

SummaryADP, AMP, or ATP was injected rapidly intravenously in rats. ADP injection resulted in the f olio wing transient changes: a drop in platelet count, a rise in central venous pressure, a fall in carotid arterial PO2, bradycardia, arrhythmia, flutter-fibrillation, and arterial hypotension. AMP and ATP produced some of these same effects; but except for hypotension, their frequency and severity Avere much less than those following ADP.Prior intravenous administration of acetylsalicylic acid or pyridinolcarbamate, two inhibitors of the second wave of ADP-induced platelet aggregation in vitro, significantly reduced the frequency and severity of all the above ADP-induced changes except hypotension. These observations suggest that many of the changes (except hypotension) observed to follow ADP injection are produced by platelet aggregates which lodge transiently in various microcirculatory beds then rapidly disaggregate and recirculate.

Bio-Medico-Mechanical Behavior of Natural Artery Blood Vessel Under Constant and Variable Internal Pulsatile Pressure Flow Test In Vitro

1986 ◽  
Vol 108 (4) ◽  
pp. 295-300 ◽  
Author(s):  
A. T. Yokobori ◽  
T. Maeyama ◽  
T. Ohkuma ◽  
T. Yokobori ◽  
H. Ohuchi ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Vessel ◽  
Mechanical Behavior ◽  
Arterial System ◽  
Pressure Amplitude ◽  
Constant Amplitude ◽  
Pressure Flow ◽  
Fluctuating Pressure ◽  
Pulsatile Pressure

Studies have been carried out on the bio-medico-mechanical behavior in vitro of natural blood vessel (dogs) under constant and variable internal pulsatile pressure flow. The apparatus designed by us well simulated the arterial system. The studies were made for the case of pressure amplitude kept as constant, of the two-step-multi-duplicated pulsatile pressure and of the fluctuating pressure. For the case of the fluctuating pressure, the strength of the artery becomes considerably lower than those under constant amplitude and two-step-multi-duplicated pulsatile pressure. SEM observations of the inner walls of the artery shows that collagen fibers are more elongated under fluctuating pulsatile pressure flow. In conclusion, in order to avoid the mechanical deterioration of the artery strength, it is useful to keep the pulsatile blood pressure at constant amplitude. Even for the case of the blood pressure fluctuation, it is necessary to manage to keep the blood pressure as near a regular wave as possible, the total number of repeated pulse being equal.

scholarly journals Insulin induces rapid and specific rearrangement of the cytoskeleton of rat mesangial cells in vitro.

1996 ◽  
Vol 44 (2) ◽  
pp. 91-101 ◽  
Author(s):  
A K Berfield ◽  
G J Raugi ◽  
C K Abrass
Keyword(s):  
Mesangial Cells ◽  
Focal Adhesions ◽  
Cytoskeletal Proteins ◽  
Direct Effects ◽  
Ligand Effects ◽  
Igf I ◽  
Induced Changes ◽  
Secondary Ligand

Mesangial cells (MCs) grown without supplemental insulin (SI-MCs) express a quiescent phenotype and extracellular matrix (ECM) composition similar to MCs in vivo. In contrast, MCs routinely propagated in insulin (SI+MCs) are stimulated to proliferate, change their phenotype, and produce large amounts of collagens I and III. These effects of insulin may in part be mediated through cytoskeletal rearrangement. Differences in cytoskeletal arrangement were compared between SI-MCs and SI+MCs and 1 hr after addition of insulin (1 nM) or IGF-1 (100 nM) to SI-MCs. Cells were examined by light microscopy, electron microscopy, and immunostaining for specific cytoskeletal proteins and fibronectin. Insulin induced rapid rearrangement of stress fibers. Surface ruffling, actin aggregation, vimentin retraction, rearrangement of vinculin in focal adhesions, and fibronectin extraction were apparent. These direct effects of insulin on the SI-MC cytoskeleton occurred before insulin-induced changes in ECM composition. IGF-I induced cytoskeletal reorganization distinct from insulin. These observations demonstrate that insulin and IGF-I have unique effects on the MC cytoskeleton, which is turn may mediate secondary ligand effects on MCs.

scholarly journals Activation of two distinct Sox9-EGFP-expressing intestinal stem cell populations during crypt regeneration after irradiation

2012 ◽  
Vol 302 (10) ◽  
pp. G1111-G1132 ◽  
Author(s):  
Laurianne Van Landeghem ◽  
M. Agostina Santoro ◽  
Adrienne E. Krebs ◽  
Amanda T. Mah ◽  
Jeffrey J. Dehmer ◽  
...  
Keyword(s):  
Stem Cell ◽  
Cell Populations ◽  
Intestinal Epithelial ◽  
P53 Signaling ◽  
Reporter Mice ◽  
Radiation Induced ◽  
Molecular Phenotypes ◽  
Stem Cell Populations ◽  
Induced Changes

Recent identification of intestinal epithelial stem cell (ISC) markers and development of ISC reporter mice permit visualization and isolation of regenerating ISCs after radiation to define their functional and molecular phenotypes. Previous studies in uninjured intestine of Sox9-EGFP reporter mice demonstrate that ISCs express low levels of Sox9-EGFP (Sox9-EGFP Low), whereas enteroendocrine cells (EEC) express high levels of Sox9-EGFP (Sox9-EGFP High). We hypothesized that Sox9-EGFP Low ISCs would expand after radiation, exhibit enhanced proliferative capacities, and adopt a distinct gene expression profile associated with rapid proliferation. Sox9-EGFP mice were given 14 Gy abdominal radiation and studied between days 3 and 9 postradiation. Radiation-induced changes in number, growth, and transcriptome of the different Sox9-EGFP cell populations were determined by histology, flow cytometry, in vitro culture assays, and microarray. Microarray confirmed that nonirradiated Sox9-EGFP Low cells are enriched for Lgr5 mRNA and mRNAs enriched in Lgr5-ISCs and identified additional putative ISC markers. Sox9-EGFP High cells were enriched for EEC markers, as well as Bmi1 and Hopx, which are putative markers of quiescent ISCs. Irradiation caused complete crypt loss, followed by expansion and hyperproliferation of Sox9-EGFP Low cells. From nonirradiated intestine, only Sox9-EGFP Low cells exhibited ISC characteristics of forming organoids in culture, whereas during regeneration both Sox9-EGFP Low and High cells formed organoids. Microarray demonstrated that regenerating Sox9-EGFP High cells exhibited transcriptomic changes linked to p53-signaling and ISC-like functions including DNA repair and reduced oxidative metabolism. These findings support a model in which Sox9-EGFP Low cells represent active ISCs, Sox9-EGFP High cells contain radiation-activatable cells with ISC characteristics, and both participate in crypt regeneration.

Circumferential, not longitudinal, colonic stretch increases synaptic input to mouse prevertebral ganglion neurons

2003 ◽  
Vol 285 (6) ◽  
pp. G1129-G1138 ◽  
Author(s):  
Steven M. Miller ◽  
J. H. Szurszewski
Keyword(s):  
Synaptic Input ◽  
Muscle Tension ◽  
Circular Muscle ◽  
Longitudinal Axis ◽  
Muscle Layer ◽  
Intraluminal Pressure ◽  
Colon Wall ◽  
Mesenteric Ganglion ◽  
Ganglion Neurons

The relationship between longitudinal and circular muscle tension in the mouse colon and mechanosensory excitatory synaptic input to neurons in the superior mesenteric ganglion (SMG) was investigated in vitro. Electrical activity was recorded intracellularly from SMG neurons, and muscle tension was simultaneously monitored in the longitudinal, circumferential, or both axes. Colonic intraluminal pressure and volume changes were also monitored simultaneously with muscle tension changes. The results showed that the frequency of fast excitatory postsynaptic potentials (fEPSPs) in SMG neurons increased when colonic muscle tension decreased, when the colon relaxed and refilled with fluid after contraction, and during receptive relaxation preceding spontaneous colonic contractions. In contrast, fEPSP frequency decreased when colonic muscle tension increased during spontaneous colonic contraction and emptying. Manual stretch of the colon wall to 10-15% beyond resting length in the circumferential axis of flat sheet preparations increased fEPSP frequency in SMG neurons, but stretch in the longitudinal axis to 15% beyond resting length in the same preparations did not. There was no increase in synaptic input when tubular colon segments were stretched in their long axes up to 20% beyond their resting length. The circumferential stretch-sensitive increase in the frequency of synaptic input to SMG neurons persisted when the colonic muscles were relaxed pharmacologically by nifedipine (2 μM) or nicardipine (3 μM). These results suggest that colonic mechanosensory afferent nerves projecting to the SMG function as length or stretch detectors in parallel to the circular muscle layer.

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