Faiz Mumtaz

The effect of nitric oxide and peroxynitrite on rabbit cavernosal smooth muscle relaxation

Abstract Nitric oxide (NO) mediates penile erection by inducing cavernosal smooth muscle relaxation. Superoxide anion (O2−) can influence the activity of NO by reacting with it to produce peroxynitrite (PN). This is a highly reactive species that is known to attack a variety of biological targets. It is far more reactive and damaging than its precursors. We therefore, investigated the effect of PN on rabbit cavernosal smooth muscle relaxation and compared it to NO. Cavernosal strips from nine adult New Zealand White rabbits were excised (n=12 strips for each arm of the study) and mounted in organ baths. After pre-contraction with phenylephrine (PE) (100 μM) the strips were exposed to either NO or PN (1–100 μM) and subsequent smooth muscle relaxations monitored. Some tissues were incubated with oxadiazoloquinoxalin-1-one (ODQ; 10 μM), an inhibitor of guanylyl cyclase, before the addition of NO or PN. NO and PN induced concentration-dependent relaxations in all strips. However, PN (IC50: 26 ± 3.6 μM) was significantly less potent than NO (IC50: 11 ± 0.7 μM) [P < 0.01]. Relaxation induced by NO was immediate and short-lived, with the tension returning to its original level. In contrast, PN-initiated relaxations were of a slower onset and more prolonged, with the tissues unable to recover tension. However, after several washouts the tissues were fully responsive to PE. Both NO- and PN-mediated relaxations were inhibited by ODQ, suggesting the involvement of cGMP in this process. Although PN mediates cavernosal smooth muscle relaxation, it is much less potent than NO. As PN is thought to play a role in a variety of pathologies where erectile dysfunction is prominent, it may also contribute to the pathogenesis of erectile dysfunction.

Up-regulation of endothelin (ETA and ETB) receptors and down-regulation of nitric oxide synthase in the detrusor of a rabbit model of partial bladder outlet obstruction

Abstract Bladder outlet obstruction (BOO) is associated with altered bladder structure and function. Endothelin-1 (ET-1) has mitogenic and potent contractile properties. There are two ET receptors: ETA and ETB. Nitric oxide synthase (NOS) is the enzyme responsible for the synthesis of nitric oxide (NO) which is involved in smooth muscle relaxation. We investigated whether there are any changes in the density of ET-receptors and NOS in the detrusor and bladder neck in a rabbit model of BOO. Partial BOO was induced in adult male New Zealand White rabbits. Sham operated age-matched rabbits acted as controls. After six weeks the urinary bladders were excised and detrusor and bladder neck sections incubated with radioligands for ET-1, ETA and ETB receptors and with [3H]–l-NOARG (a ligand for NOS). NADPH histochemistry was also performed. BOO bladder weights were significantly increased (P=0.002). ET-1 binding and ETA receptor binding sites were significantly increased in the BOO detrusor smooth muscle (P=0.04, P=0.03 respectively) and urothelium (P=0.002, P=0.02 respectively). ETB receptor binding sites were also significantly increased in the BOO detrusor smooth muscle (P=0.04). However, there was no change in the BOO bladder neck. NOS was significantly decreased in the detrusor smooth muscle (P=0.003) and urothelium (P=0.0002). In the bladder neck NOS was also significantly reduced in the urothelium (P=0.003). NADPH staining was decreased in the detrusor and bladder neck. The up-regulation of ET receptors along with the down-regulation of NOS in the detrusor may contribute to the symptoms associated with BOO. Since ET-1 has a mitogenic role, especially via its ETA receptors, the increase in ETA receptors may also be involved in detrusor hyperplasia and hypertrophy in BOO. ET antagonists may therefore have a role in the treatment of patients with BOO.

Time-dependent up-regulation of neuronal 5-hydroxytryptamine binding sites in the detrusor of a rabbit model of partial bladder outlet obstruction

Abstract Serotonin (5-hydroxytryptamine; 5-HT), a vasoactive bioamine with potent contractile activity, is thought to act indirectly in the urinary bladder by the stimulation of its presynaptic receptors. This results in the release of acetylcholine (ACh), which then acts on muscarinic receptors to produce bladder contractility. Bladder outlet obstruction (BOO) can lead to detrusor instability associated with denervation supersensitivity to ACh. Using a rabbit model of partial BOO, we investigated whether there were any associated changes in the neuronal 5-HT binding sites. Partial BOO was induced in adult male New Zealand White rabbits. Sham-operated age-matched rabbits acted as controls. After 1, 3 and 6 weeks the urinary bladders were excised. Detrusor sections were incubated with [3H]-5-HT. Autoradiographs were generated and analysed densitometrically. The presence of nerves was detected using immunohistochemistry with NF200. Autoradiography demonstrated a time-dependent, significant (P < 0.0001) up-regulation of [3H]-5-HT binding sites in the detrusor smooth muscle after the induction of BOO. Immunohistochemistry confirmed that the [3H]-5-HT binding sites were neuronal. In the rabbit model of partial BOO there was a significant time-dependent up-regulation of neuronal [3H]-5-HT binding sites in the detrusor. This change may influence 5-HT-mediated ACh release, resulting in increased bladder contractility. This, in turn, may play a role in detrusor instability associated with denervation post-junctional supersensitivity. These results provide a possible rationale for further investigation into the use of 5-HT antagonists in the treatment of detrusor instability associated with BOO.

Enhanced relaxation of diabetic rabbit cavernosal smooth muscle in response to nitric oxide: potential relevance to erectile dysfunction

New Zealand white rabbit cavernosal smooth muscle strips (n=6) were mounted in organ baths. Relaxations to nitric oxide (10−7–10−4 mol/l) were measured and the same procedure was repeated on strips from rabbits 6 months after alloxan-induced diabetes (n=6). Transverse cavernosal sections were obtained from the same penises. Low and high resolution autoradiographs were prepared using [3H]-L-NG-nitroarginine (an index of nitric oxide binding sites) and analysed densitometrically. Histochemical analysis was performed on adjacent sections using NADPH diaphorase (an index of nitric oxide synthase activity).Nitric oxide relaxed control rabbit cavernosal smooth muscle strips in a concentration-dependent manner. Diabetic rabbit cavernosal smooth muscle strips were significantly (P<0.03) more sensitive to nitric oxide (mean IC50=3.9 × 10−6 mol/l). Nitric oxide synthase binding sites were localised to the cavernosal endothelium and smooth muscle. Nitric oxide synthase activity was increased in 6 month diabetic cavernosal smooth muscle. These findings suggest impairments in the L-arginine-nitric oxide pathway may play a role in the pathophysiology of diabetic erectile dysfunction.

Cascade Fumarate Hydratase mutation screening allows early detection of kidney tumour: a case report

BackgroundFumarate hydratase (FH) deficiency is a rare autosomal recessive disorder which results in a major defect in cellular metabolism. It presents in infancy with progressive encephalopathy, hypotonia, seizures and failure to thrive and is often fatal in childhood. It is caused by mutations in the FH gene (1q42.1) that result in deficiency of the citric acid cycle enzyme fumarate hydratase, resulting in accumulation of fumaric acid. Heterozygous germline mutations in the FH gene predispose to an aggressive autosomal dominant inherited early-onset kidney cancer syndrome: hereditary leiomyomatosis and renal cell cancer (HLRCC).Case presentationCascade FH mutation screening enabled the early diagnosis of a renal tumour in an asymptomatic parent of a child with fumarate hydratase deficiency, resulting in timely and possibly life-saving treatment.ConclusionWhile the theoretical risk of kidney cancer in parents of children with recessive fumarate hydratase deficiency is well recognized, to our knowledge this is the first report of a kidney tumour being detected in a parent by screening performed for this indication. This underscores the importance of offering lifelong kidney surveillance to such parents and other heterozygous relatives of children born with fumarate hydratase deficiency.

Inhibition of diabetic bladder smooth muscle cell proliferation by endothelin receptor antagonists.

Abstract Urinary bladder hypertrophy and hyperplasia are well recognised in diabetic cystopathy. The urinary bladder is known to synthesise endothelin-1 (ET-1), a potent vasoconstrictor peptide with mitogenic properties. Using diabetic New Zealand White (NZW) rabbits, we investigated the potential role of ET receptor subtypes (ETA and ETB) on the proliferation of bladder smooth muscle cells (SMC). Diabetes mellitus was induced in adult male NZW rabbits. After 6 months, control (n=6) and diabetic (n=6) bladders were removed and SMC from the dome and bladder neck were grown using standard explant methodology. At passage two, the cells were made quiescent and then further incubated in foetal calf serum (FCS), control age-matched rabbit serum (CRS) or diabetic rabbit serum (DRS) in the presence or absence of ETA-antagonist (BQ123) or ETB-antagonist (BQ788). SMC proliferation was then measured with 5-bromo-2′deoxy-uracil 24 h later and by cell counting (using a haemocytometer) at 48 h. Neither BQ123 nor BQ788 influenced detrusor or bladder neck SMC proliferation in FCS or CRS. However, in the presence of DRS, BQ123 and BQ788 significantly inhibited diabetic detrusor and bladder neck SMC proliferation at 30 and 100 nmol/l (P < 0.03 and P < 0.01, respectively). Cell counts were also significantly reduced from the diabetic detrusor and bladder neck (P < 0.01 and P < 0.03 with BQ123 and BQ788, respectively). These results suggest that ET may play a pathophysiological role in the bladder SMC hyperplasia associated with diabetes mellitus.

Robotic-assisted Laparoscopic Partial Nephrectomy in a Horseshoe Kidney. A Case Report and Review of the Literature

Horseshoe kidney is a rare renal fusion anomaly, and because of limited mobilization of the kidney and its multiple arterial blood supplies, minimally invasive surgery for renal tumors can be challenging. We describe a case of a right-side oncocytoma in a horseshoe kidney managed robotically and review the literature of robotic-assisted laparoscopic surgical resection of kidney tumors in renal fusion anomalies. Robotic-assisted laparoscopic partial nephrectomy in a horseshoe kidney is feasible. Fusion-related limited mobility during the procedure, as well as an extremely variable blood supply, require meticulous planning. Multi-phase computed tomography and interactive 3D anatomical models are helpful tools to prepare for surgery.

Intracavernosal PGE1-related penile fibrosis: possible mechanisms.

The editorial comment made by Professor Porst on penile ®brosis following intracavernosal (i.c.) prostaglandin E1 (PGE1) injection therapy for erectile dysfunction is very timely. We reported a 10% incidence of distal penile ®brosis following long-term use of i.c. PGE1. In this study, this complication was not related to the injection site as the lesions occurred distally. Since these patients achieved a grade IV erection lasting between 1±2 h, the development of ®brosis could not have been associated with inadequate erections. To explain why our patients developed distal penile ®brosis, we suggest two mechanisms. Firstly, it is well known that with aging there is signi®cant reduction of elastic ®bers in both layers of the tunica albuginea. As a result, there is a signi®cant decrease in the elasticity of both the inner and septal ®brous layers supporting the tunica albuginea. Reduction in elastic ®bres and its elasticity prevents the corpora from tolerating relatively high i.c. pressures during PGE1-induced erections. This may result in tunical tears, disruption of small blood vessels, bleeding and clot formation. This could subsequently result in ®brosis. Secondly, an ischaemic injury to the tunica albuginea may be involved in distal penile ®brosis. Assessment of blood ̄ow by duplex sonography has shown a signi®cant reduction in the blood ̄ow velocity in a proximo-distal direction following i.c. vasoactive injections. Furthermore, the cavernous oxygen tension is signi®cantly lower after i.c. injection of PGE1 in arteriogenic and venogenic groups, compared to controls. In animal experiments, there is shunting of blood from the subtunical space into the deep cavernosal circulation during both pelvic nerve and pharmacological stimulation. This shunting is more marked after pharmacological stimulation causing a greater drop in the subtunical oxygen tension in this group. These changes may be responsible for inducing relative ischaemia and may have contributed to the formation of distal ®brosis in our patients. A more careful titration of the dose of PGE1 may reduce the incidence of distal penile ®brosis. The minimally effective dose, which achieves an adequate erection for the minimum length of time needed for patient satisfaction, should be used.

Robot-assisted partial nephrectomy: How to minimise renal ischaemia

Abstract Renal ischaemia research has shown an increase in renal damage proportional to ischaemic time. Therefore, we assessed the importance of renal ischaemic times for warm and cold ischaemia approaches, and explored the different surgical techniques that can help to minimise renal ischaemia in robot-assisted partial nephrectomy (RAPN). Minimising renal ischaemia during nephron-sparing surgery (NSS) is a key factor in preserving postoperative renal function. Current data support a safe warm ischaemia time (WIT) of ≤25 min and cold ischaemic time of ≤35 min, resulting in no significant deterioration in renal function. In general, patients undergoing NSS have increased comorbidities, including chronic kidney disease, and in these patients it is difficult to predict their postoperative renal function recovery. With RAPN, efforts should be made to keep the WIT to <25 min, as minimising the ischaemic time is vital for preservation of overall renal function and remains a modifiable risk factor. Parenchymal or segmental artery clamping, early unclamping or off-clamp techniques can be adopted when ischaemic times are likely to be >25 min, but may not lead to superior functional outcome. Careful preoperative planning, tumour factors, and meticulous surgical technique are critical for optimum patient outcome.

Sign of the times: be careful what you say in the operating room.

While performing the last safety checks on pressure points of our anaesthetised patient for a major procedure requiring complex positioning, the anaesthetist noticed a small object tucked underneath the patient’s compression stockings. Initially it looked like a portable fl ash drive, but closer inspection revealed tiny printed letters spelling “mic”, a small red light, and a tiny switch which was turned on. It took a few moments for the realisation of what this device was and its intended purpose to dawn on us. Putting aside the inappropriateness of a concealed recording device in this setting, this situation raised several major concerns. First, there is the paramount issue of patient safety, with potential for pressure sore development, diathermy burns, and interference with monitoring equipment. Second, the equally key issue of patient confi dentiality, because the device might have inadvertently recorded medical staff discussions regarding other patients, making the circumstances in theatre distinct from doctor–patient consultations in the clinic. The third point of concern is that comments made by theatre staff might be misinterpreted and taken out of context, or in the worse-case scenario, be used to instigate proceedings for damages or even for a claim of awareness during anaesthesia. We will never know the real intention of a covert recording. We refer to the recent court case in Virginia, USA, where a patient accidentally recorded on his smart phone derogatory remarks made by his anaesthesiologist and medical-care team while he was anaesthetised for his colonoscopy. The patient was awarded US