Biomedical subjects

Paul Chichester

Publications and source records attributed to Paul Chichester.

22 records · Page 2Linked to original sources

PubMed2002

The functional and structural response to distention of the rabbit whole bladder in vitro.

PURPOSE: We investigated the effects of distention on intravesical pressure generation in response to stimuli in relation to its effects on bladder wall thickness and morphology. MATERIALS AND METHODS: A total of 25 New Zealand White rabbits were separated into 5 groups of 5 each. Each in vitro whole bladder preparation was filled with saline to 5% (undistended), 25%, 50%, 100% or 125% capacity (60 ml.). The effects of field stimulation, adenosine 5'-triphosphate, carbamylcholine chloride (carbachol) and KCl on intravesical pressure generation were determined. Additional bladders were similarly distended (3 at each percent of capacity), fixed in formalin and evaluated by semiquantitative morphometry. RESULTS: Pressure generation in response to field stimulation was maximal at 5% of capacity and it decreased progressively thereafter. Compared with the responses of undistended bladders, at 25% capacity the response to carbachol increased and then decreased progressively above 25%. Distention had no significant effect on the response to KCl. Interestingly pressure generation in response to adenosine 5'-triphosphate was increased more than 4-fold at 25% bladder capacity compared with 5% and it did not change significantly thereafter. Bladder wall thickness was decreased more than 50% at 25% capacity and by an additional 12% at 125% capacity. The greatest thinning was observed in the mucosa compared with the submucosa and muscularis. CONCLUSIONS: Bladder distention significantly reduced pressure generation in response to field stimulation only, indicating that distention reduced the effectiveness of synaptic transmission without altering muscarinic receptor function or membrane depolarization. The greatest change (decrease) in the response to field stimulation occurred between 5% (undistended) and 25% capacity, which was the change in distention that most affected bladder wall thinning.

Adenosine Triphosphate↗

PubMed2002

Hypoxia and an angiogenic response in the partially obstructed rat bladder.

Previous molecular and blood flow studies performed on animal models of partial bladder outlet obstruction (PBOO) caused us to propose that bladder hypoxia/ischemia was a significant effector of the cellular and functional changes that occur in the bladder as a result of this condition. To confirm the occurrence of hypoxia in the partially obstructed bladder, we obtained rat bladders at increasing intervals following PBOO and measured biomarkers of hypoxia (intracellular formation of hypoxyprobe-1 adducts and expression of hypoxia inducible factor-1 alpha [HIF-1 alpha] protein) and whether such hypoxia might elicit an angiogenic response in the tissue. Rats receiving PBOO or controls were treated with hypoxyprobe-1 at increasing intervals subsequent to surgery and their bladders were sectioned and immunostained using an antibody that detects hypoxyprobe-1 adducts. Control rat bladders were unstained, whereas intense, but regionally restricted, hypoxyprobe-1 immunostaining was detected in all obstructed bladders in a unique pattern that changed over time. Proteins were extracted from bladders removed from similarly treated rats and were analyzed for the expression of the HIF-1 alpha protein as well as for expression of angiogenic regulatory factors (vascular endothelial growth factor, angiopoietin-1, and endostatin) using Western blotting techniques. HIF-1 alpha protein was not expressed in control bladders, however, the protein was highly up-regulated over the 2-week period after PBOO. Likewise, the expression of vascular endothelial growth factor (a downstream target of HIF-1 alpha action) and angiopoietin-1 was also up-regulated in obstructed bladders confirming an angiogenic response to this hypoxia. Enigmatically, however, expression of the antiangiogenic molecule endostatin was also up-regulated by chronic PBOO. These results further support the concept that hypoxia is involved in the cellular remodeling as well as in the progressive functional impairment exhibited by the urinary bladder after PBOO.

Angiopoietin-1↗

PubMed2002

Cyr61 and CTGF are molecular markers of bladder wall remodeling after outlet obstruction.

Cysteine-rich protein (Cyr61) and connective tissue growth factor (CTGF) are key immediate early growth factors with functions in cell proliferation, differentiation, and extracellular matrix synthesis. Studies were performed to assess the gene expression profile of Cyr61 and CTGF in rat urinary bladder during growth in response to partial outlet obstruction. The mRNA levels of Cyr61 as determined by ribonuclease protection assay increased sharply after 1 day and remained elevated throughout the time period of the obstruction. This correlates well with increased bladder weight. The CTGF mRNA levels seemed to peak within the second week of the urethral obstruction and correlate well with increased type I collagen mRNA. The expression pattern of either Cyr61 or CTGF proteins corroborated that of their respective mRNAs. Immunohistochemical analyses showed that immunoreactivity of Cyr61 was confined to detrusor smooth muscle and that of CTGF was detected within both detrusor muscle and lamina propria layers. These data strongly indicate the involvement of Cyr61 and CTGF in bladder wall remodeling as a result of the outlet obstruction.

Angiotensin II↗

PubMed2002

Effects of chronic partial outlet obstruction on blood flow and oxygenation of the rat bladder.

PURPOSE: Experimental partial bladder outlet obstruction in rats and rabbits drives the bladder through 3 sequential responses, referred to as hypertrophy, compensation and decompensation. The hypertrophy phase, which is a period of rapid bladder growth, has previously been shown to be accompanied by a significant increase in bladder blood flow in rats and rabbits in a manner that likely supports the bladder cell growth process. However, chronic periods of obstruction in the rabbit have been shown to reduce significantly bladder blood flow, especially to the detrusor smooth muscle, corresponding with a loss of bladder contractile function or decompensation in these animals. We determined the effects of chronic 1 to 4-week partial outlet obstruction on rat bladder blood flow and directly correlated them with hypoxia in the rat bladder. MATERIALS AND METHODS: Rats underwent surgical partial bladder outlet obstruction under anesthesia. At weekly intervals after surgery relative blood flow to the bladder and spleen was measured by a fluorescent microsphere infusion technique. Sham operated rats were also studied 2 and 4 weeks following surgery. In a second experiment groups of similarly obstructed rats were treated with Hypoxyprobe-1 (Natural Pharmacia International, Inc., Research Triangle Park, North Carolina), a chemical probe for hypoxia, 3 days, 1 and 2 weeks after partial bladder outlet obstruction. The bladders were subsequently fixed and immunostained using a monoclonal antibody that detects Hypoxyprobe-1 adducts that are selectively formed in hypoxic cells. RESULTS: Neither bladder weight nor bladder relative blood flow was affected by sham surgery. Likewise, control and sham obstructed rat bladders were found to be free of Hypoxyprobe-1 reactive areas. In contrast, obstructed rats had significantly increased bladder weight at all time points. Relative weight of the obstructed rat bladders indicates the response to mild-moderate obstruction. Bladder relative blood flow in obstructed rats was significantly elevated 1 and 2 weeks after partial bladder outlet obstruction but it returned to almost control levels by 3 and 4 weeks. Hypoxyprobe-1 staining demonstrated a sequential transition of hypoxia from bladder mucosa and submucosal regions at 3 days to muscularis and serosal fibroblasts 1 week and finally to smooth muscle cells by 2 weeks after obstruction. CONCLUSIONS: In contrast to the rabbit model, global blood flow in the mild-moderate chronically obstructed rat bladder was found to be higher or nearly equivalent to blood flow in unobstructed control rat bladders. However, even in the presence of normal or above normal blood flow focal regions of hypoxia were still observed in obstructed rat bladders and these regions changed with time. These results provide a reason to understand better why rats are more resistant to the onset of bladder decompensation than rabbits and support the concept that hypoxia is involved in bladder remodeling as well as in progressive functional impairment of the bladder after partial bladder outlet obstruction.

Animals↗