Nathan Wilkes

Phosphodiesterase-5 inhibition synergizes rho-kinase antagonism and enhances erectile response in male hypertensive rats.

To evaluate the association between hypertension, male erectile function, Rho-kinase, and cyclic GMP pathways, we monitored neurogenic erectile response in spontaneously hypertensive (SHR) vs normotensive rats. We also evaluated SHR erectile function before and after intracavernosal injection of either the specific Rho-kinase inhibitor Y-27632 or a combination of Y-27632 and the PDE5 inhibitor zaprinast to prevent cGMP degradation. SHR had lower resting baseline corpus cavernosum pressure and a higher threshold for development of tumescence than normotensive rats. In SHR, Y-27632 administration reversed hypertension-related changes in male erectile function; Rho-kinase antagonism and PDE5 inhibition in combination had a synergistic effect in improving the neurogenic erectile response. Our data indicate that hypertension is associated with impairment in the SHR neurogenic erectile response that may involve a derangement in hemodynamic mechanisms in penile erectile tissue. Rho-kinase inhibition alone or combined with PDE5 inhibition may be of value in treating hypertension-related ED.

Small intestinal submucosa as a tunica albuginea graft material.

PURPOSE We evaluated the morphological, immunological and functional response to small intestinal submucosa grafting of the tunica albuginea to determine its potential as a grafting material for penile surgery. MATERIALS AND METHODS Male New Zealand White rabbits underwent a sham procedure (6) or tunical excision and grafting with small intestinal submucosa (6). The erectile response to the intracavernous vasoactive agents sodium nitroprusside plus a papaverine, phentolamine and prostaglandin E1 combination (Sigma Chemical Co., St. Louis, Missouri) was evaluated 45-day postoperatively. The area under the graft was evaluated for stromal collagen and smooth muscle content by Massons trichrome stain. Protein expression of smooth muscle specific alpha-actin and the inflammatory markers inducible nitric oxide synthase (NOS) and transforming growth factor-beta1 (TGF-beta1) was evaluated by immunohistochemical methods. Total RNA was extracted from the corpora cavernosum underlying the small intestinal submucosa graft and reverse transcriptase-polymerase chain reaction (RT-PCR) was done using an Access system (Promega, Madison, Wisconsin) with gene specific primers for inducible NOS, TGF-beta1 and vascular endothelial growth factor (VEGF). RESULTS Grafting of the tunica albuginea with small intestinal submucosa had no significant effect on the magnitude or duration of the erectile response to intracavernous vasoactive agents. Histological examination demonstrated no inflammatory changes in the tunica albuginea or corporeal tissue underlying the area of the small intestinal submucosa graft and there was no appreciable alteration in smooth muscle or collagen content. The 2 groups showed intense positive immunostaining to alpha-actin. Weak expression of TGF-beta1 predominantly associated with smooth muscle fibers was identified in the 2 groups of rabbits by immunostaining and RT-PCR. No significant inducible NOS was detected by immunostaining or RT-PCR in either group. Strong VEGF expression was observed in grafted rabbits. The most noticeable (3-fold) increase in expression was detected in splice variant 165. CONCLUSIONS Small intestinal submucosa grafting of the tunica albuginea preserves the duration and magnitude of the erectile response to vasoactive agents. This type of tunical grafting does not stimulate a significant inflammatory response, or cause corporeal fibrosis or loss of cavernous smooth muscle content. Stimulating VEGF may facilitate wound healing and the maintenance of normal erectile function.

Electrical and mechanical recovery of cardiac function following out-of-hospital cardiac arrest

BACKGROUND Compression pauses may be particularly harmful following the electrical recovery but prior to the mechanical recovery from cardiopulmonary arrest. METHODS AND RESULTS A convenience sample of patients with out-of-hospital cardiac arrest (OOHCA) were identified. Data were exported from defibrillators to define compression pauses, electrocardiogram rhythm, PetCO2, and the presence of palpable pulses. Pulse-check episodes were randomly assigned to a derivation set (one-third) and a validation set (two-thirds). Both an unweighted and a weighted receiver-operator curve (ROC) analysis were performed on the derivation set to identify optimal thresholds to predict ROSC using heart rate and PetCO2. A sequential decision guideline was generated to predict the presence of ROSC during compressions and confirm perfusion once compressions were stopped. The ability of this decision guideline to correctly identify pauses in which pulses were and were not palpated was then evaluated. A total of 145 patients with 349 compression pauses were included. The ROC analyses on the derivation set identified an optimal pre-pause heart rate threshold of >40 beats min(-1) and an optimal PetCO2 threshold of >20 mmHg to predict ROSC. A sequential decision guideline was developed using pre-pause heart rate and PetCO2 as well as the PetCO2 pattern during compression pauses to predict and rapidly confirm ROSC. This decision guideline demonstrated excellent predictive ability to identifying compression pauses with and without palpable pulses (positive predictive value 95%, negative predictive value 99%). The mean latency period between recovery of electrical and mechanical cardiac function was 78 s (95% CI 36-120 s). CONCLUSIONS Heart rate and PetCO2 can predict ROSC without stopping compressions, and the PetCO2 pattern during compression pauses can rapidly confirm ROSC. Use of a sequential decision guideline using heart rate and PetCO2 may reduce unnecessary compression pauses during critical moments during recovery from cardiopulmonary arrest.

Selective differentiation of central nervous system-derived stem cells in response to cues from specific regions of the developing brain.

OBJECT Each region of the brain is distinguished by specific and distinct markers and functions. The authors hypothesized that each region possesses unique trophic properties that dictate and maintain its development. To test this hypothesis, they isolated central nervous system (CNS) stem cells from fetal rodents, and these rat CNS-derived stem cells (RSCs) were placed in coculture with primary cultures of the developing neonatal hippocampus and hypothalamus to determine whether region-specific primary cells would direct the differentiation of stem cells in a region-specific manner. METHODS Primary cultures were first established from the neonatal (3-7 days postnatal) hippocampus and hypothalamus. Rodent CNS stem cells, which had been genetically engineered to express green fluorescent protein, were then placed in coculture with the primary CNS cells. The expression of region-specific markers in the RSCs was then evaluated after 2 weeks using immunocytochemistry. Data from previous studies have indicated that primary adult cells lack a differentiation-inducing capacity. RESULTS When placed in coculture with primary CNS cells, RSCs began to express both neuronal (MAP2) and glial (glial fibrillary acidic protein) markers. Those that were placed in coculture with hippocampal cells expressed region-specific markers such as gamma-aminobutyric acid, whereas those placed in coculture with hypothalamic cells expressed growth hormone-releasing hormone primarily in the hypothalamus. Conclusions. Pluripotential RSCs were induced to express region-specific phenotypes on coculture with primary cells derived from the developing hippocampus and hypothalamus. The differentiation of RSCs into specific lineages on exposure to specific cell types is likely modulated through direct cell-cell contact. Secreted factors from the primary neural cells may also play a role in this induction. Such a differentiation influence is also likely age dependent.

Brain Stem Cells Adopt a Pituitary Fate after Implantation into the Adult Rodent Pituitary Gland

Fetal brain stem cells (RSCs) have been induced to express pituitary phenotypes in vitro in co-cultures with GH3 cells and by exposure to GH3-conditioned media. In the current studies, we graft RSCs into the pituitary glands of adult rat to investigate whether grafted RSCs can be induced by the native gland to acquire pituitary properties. Grafted cells survive for 4 weeks and express Pit-1, GH, FSH, LH, ACTH, TSH and to a lesser extent PRL indicating that inductive influences are operative in vivo as well. This demonstrates that pluripotential cells can be induced to acquire properties of tissues different from their organ of origin likely through the action of cell-cell contact and local tissue factors.