Spinal 5-HT7 receptors and protein kinase A constrain intermittent hypoxia-induced phrenic long-term facilitation.

Phrenic long-term facilitation (pLTF) is a form of serotonin-dependent respiratory plasticity induced by acute intermittent hypoxia (AIH). pLTF requires spinal Gq protein-coupled serotonin-2 receptor (5-HT2) activation, new synthesis of brain-derived neurotrophic factor (BDNF) and activation of its high-affinity receptor, TrkB. Intrathecal injections of selective agonists for Gs protein-coupled receptors (adenosine 2A and serotonin-7; 5-HT7) also induce long-lasting phrenic motor facilitation via TrkB "trans-activation." Since serotonin released near phrenic motor neurons may activate multiple serotonin receptor subtypes, we tested the hypothesis that 5-HT7 receptor activation contributes to AIH-induced pLTF. A selective 5-HT7 receptor antagonist (SB-269970, 5mM, 12 µl) was administered intrathecally at C4 to anesthetized, vagotomized and ventilated rats prior to AIH (3, 5-min episodes, 11% O2). Contrary to predictions, pLTF was greater in SB-269970 treated versus control rats (80 ± 11% versus 45 ± 6% 60 min post-AIH; p<0.05). Hypoglossal LTF was unaffected by spinal 5-HT7 receptor inhibition, suggesting that drug effects were localized to the spinal cord. Since 5-HT7 receptors are coupled to protein kinase A (PKA), we tested the hypothesis that PKA inhibits AIH-induced pLTF. Similar to 5-HT7 receptor inhibition, spinal PKA inhibition (KT-5720, 100 µM, 15 µl) enhanced pLTF (99 ± 15% 60 min post-AIH; p<0.05). Conversely, PKA activation (8-br-cAMP, 100 µM, 15 µl) blunted pLTF versus control rats (16 ± 5% versus 45 ± 6% 60 min post-AIH; p<0.05). These findings suggest a novel mechanism whereby spinal Gs protein-coupled 5-HT7 receptors constrain AIH-induced pLTF via PKA activity.

Phrenic long-term facilitation after acute intermittent hypoxia requires spinal ERK activation but not TrkB synthesis.

Acute intermittent hypoxia (AIH) elicits a form of spinal respiratory plasticity known as phrenic long-term facilitation (pLTF). pLTF requires spinal serotonin receptor-2 activation, the synthesis of new brain-derived neurotrophic factor (BDNF), and the activation of its high-affinity receptor tyrosine kinase, TrkB. Spinal adenosine 2A receptor activation elicits a distinct pathway to phrenic motor facilitation (pMF); this BDNF synthesis-independent pathway instead requires new synthesis of an immature TrkB isoform. Since hypoxia increases extracellular adenosine levels, we tested the hypothesis that new synthesis of TrkB and BDNF contribute to AIH-induced pLTF. Furthermore, given that signaling mechanisms "downstream" from TrkB are unknown in either mechanism, we tested the hypothesis that pLTF requires MEK/ERK and/or phosphatidylinositol 3-kinase (PI3K)/Akt activation. In anesthetized Sprague-Dawley rats, an intrathecal catheter at cervical level 4 was used to deliver drugs near the phrenic motor nucleus. Since pLTF was blocked by spinal injections of small interfering RNAs targeting BDNF mRNA but not TrkB mRNA, only new BDNF synthesis is required for AIH-induced pLTF. Pretreatment with a MEK inhibitor (U0126) blocked pLTF, whereas a PI3K inhibitor (PI-828) had no effect. Thus, AIH-induced pLTF requires MEK/ERK (not PI3K/AKT) signaling pathways. When U0126 was injected post-AIH, pLTF development was halted but not reversed, suggesting that ERK is critical for the development but not maintenance of pLTF. Thus, there are clear mechanistic distinctions between AIH-induced pLTF (i.e., BDNF synthesis and MEK/ERK dependent) versus adenosine 2A receptor-induced pMF (i.e., TrkB synthesis and PI3K/Akt dependent).

Spinal 5-HT7 receptor activation induces long-lasting phrenic motor facilitation.

Acute intermittent hypoxia elicits a form of serotonin-dependent respiratory plasticity known as phrenic long term facilitation (pLTF). Episodic spinal serotonin-2 (5-HT2) receptor activation on or near phrenic motor neurons is necessary for pLTF. A hallmark of pLTF is the requirement for serotonin-dependent synthesis of brain-derived neurotrophic factor (BDNF), and activation of its high affinity receptor, TrkB. Activation of spinal Gs protein-coupled adenosine 2A receptors (GsPCRs) elicits a unique form of long-lasting phrenic motor facilitation (PMF), but via unique mechanisms (BDNF independent TrkB trans-activation).We hypothesized that other GsPCRs elicit PMF, specifically serotonin-7 (5-HT7) receptors, which are expressed in phrenic motor neurons. Cervical spinal (C4) injections of a selective 5-HT7 receptor agonist, AS-19 (10 µM, 5 µl; 3 × 5 min), in anaesthetized, vagotomized and ventilated male Sprague-Dawley rats elicited long-lasting PMF (>120 min), an effect prevented by pretreatment with a 5-HT7 receptor antagonist (SB 269970; 5mM, 7 µl).GsPCR activation 'trans-activates'TrkB by increasing synthesis of an immature TrkB isoform. Spinal injection of a TrkB inhibitor (k252a) and siRNAs that prevent TrkB (but not BDNF) mRNA translation both blocked 5-HT7 agonist-induced PMF, confirming a requirement for TrkB synthesis and activity. k252a affected late PMF (≥ 90 min) only. Spinal inhibition of the PI3K/AKT pathway blocked 5-HT7 agonist-induced PMF, whereas MEK/ERK inhibition delayed, but did not block, PMF. An understanding of signalling mechanisms giving rise to PMF may guide development of novel therapeutic strategies to treat ventilatory control disorders associated with respiratory insufficiency, such as spinal injury and motor neuron disease.

Spinal adenosine A2(A) receptor inhibition enhances phrenic long term facilitation following acute intermittent hypoxia.

Phrenic long term facilitation (pLTF) is a form of respiratory plasticity induced by acute intermittent hypoxia. pLTF requires spinal serotonin receptor activation, new BDNF synthesis and TrkB receptor activation. Spinal adenosine 2A (A(2A)) receptor activation also elicits phrenic motor facilitation, but by a distinct mechanism involving new TrkB synthesis. Because extracellular adenosine increases during hypoxia, we hypothesized that A(2A) receptor activation contributes to acute intermittent hypoxia (AIH)-induced pLTF. A selective A(2A) receptor antagonist (MSX-3, 8 microg kg(-1), 12 microl) was administered intrathecally (C4) to anaesthetized, vagotomized and ventilated male Sprague-Dawley rats before AIH (three 5 min episodes, 11% O(2)). Contrary to our hypothesis, pLTF was greater in MSX-3 versus vehicle (aCSF) treated rats (97 +/- 6% vs. 49 +/- 4% at 60 min post-AIH, respectively; P < 0.05). MSX-3 and aCSF treated rats did not exhibit facilitation without AIH (time controls; 7 +/- 5% and 9 +/- 9%, respectively; P > 0.05). A second A(2A) receptor antagonist (ZM2412385, 7 microg kg(11), 7 microl) enhanced pLTF (85 +/- 11%, P < 0.05), but an adenosine A(1) receptor antagonist (DPCPX, 3 microg kg(-1), 10 microl) had no effect (51% +/- 8%, P > 0.05), indicating specific A(2A) receptor effects. Intrathecal methysergide (306 microg kg(-1), 15 microl) blocked AIH-induced pLTF in both MSX-3 and aCSF treated rats, confirming that enhanced pLTF is serotonin dependent. Intravenous MSX-3 (140 microg kg(-1), 1 ml) enhanced both phrenic (104 +/- 7% vs. 57 +/- 5%, P < 0.05) and hypoglossal LTF (46 +/- 13% vs. 28 +/- 10%; P < 0.05). In conclusion, A(2A) receptors constrain the expression of serotonin-dependent phrenic and hypoglossal LTF following AIH. A(2A) receptor antagonists (such as caffeine) may exert beneficial therapeutic effects by enhancing the capacity for AIH-induced respiratory plasticity.

Respiratory plasticity following intermittent hypoxia: roles of protein phosphatases and reactive oxygen species.

Plasticity is an important property of the respiratory control system. One of the best-studied models of respiratory plasticity is pLTF (phrenic long-term facilitation). pLTF is a progressive increase in phrenic motor output lasting several hours following acute exposure to intermittent hypoxia. Similar to many other forms of neuroplasticity, pLTF is pattern-sensitive; it is induced by intermittent, but not sustained hypoxia of similar cumulative duration. Our understanding of the cellular/synaptic mechanisms underlying pLTF has increased considerably in recent years. Here, we review accumulating evidence suggesting that the pattern-sensitivity of pLTF arises substantially from differential reactive oxygen species formation and subsequent protein phosphatase inhibition during intermittent compared with sustained hypoxia in or near phrenic motor neurons. A detailed understanding of the cellular/synaptic mechanisms of pLTF may provide the rationale for new pharmacological approaches in the treatment of severe ventilatory control disorders, such as obstructive sleep apnoea and respiratory insufficiency either following spinal cord injury or during neurodegenerative diseases such as amyotrophic lateral sclerosis.

Defining practice patterns in gynecologic oncology to prevent pulmonary embolism and deep venous thrombosis.

OBJECTIVE: The goal of venous thromboembolism (VTE) prophylaxis is to reduce the morbidity and mortality associated with the development of a deep venous thrombosis (DVT) or pulmonary embolism (PE). Because women with gynecologic cancers are at high risk to develop VTE, we sought to determine the present practice patterns of gynecologic oncologists regarding their use of VTE prophylaxis. METHODS: 1073 members of the Society of Gynecologic Oncologists (SGO) were mailed surveys that asked about preferred methods to prevent the development of VTE after gynecologic oncology surgery. Data were collected by online member entry and return mail. Frequency distributions were calculated and nonparametric test used for comparisons. RESULTS: 343/1073 (34%) of SGO members and fellows responded. 142/343 (42%) preferred double prophylaxis consisting of external pneumatic compression (EPC) and an anticoagulant while 41% (n=141) preferred EPC with no additional anticoagulation. Of respondents choosing any anticoagulant, 40% preferred Enoxaparin pre- and/or postoperatively. Ovarian cancer patients were perceived by respondents to have the highest risk of developing a postoperative PE. CONCLUSIONS: Most respondents agree that women with gynecologic cancers undergoing major surgery should receive VTE prophylaxis, though there is not agreement as to which method is optimal. While 42% of members preferred double prophylaxis, 41% chose no additional measures other than EPC. Randomized studies in gynecologic oncology should be initiated in the United States to determine the optimal practice pattern.

Transurethral retrieval of a proximally dislodged ureteral stent.

A proximally migrated ureteral stent into the renal pelvis is an uncommon problem that poses a difficult technical challenge. A 32-year-old woman had her ureteral stent inadvertently dislodged into the renal pelvis at the time of stent exchange. The stent was successfully retrieved and repositioned transurethrally with a snare fed through the left ureter and into the renal pelvis. This is a relatively noninvasive method of retrograde retrieval of a proximally dislodged ureteral stent.

Stamm gastrostomy for postoperative gastric decompression in gynecologic oncology patients.

OBJECTIVE: The aim of this study was to report our experience with Stamm gastrostomy for postoperative gastric decompression on a gynecologic oncology service. METHODS: This was an observational study over the 9-year period ending in October 2000. A 24 French MIC gastrostomy with the Stamm technique was used. Criteria for a gastrostomy are outlined in the text and tubes placed for palliation were excluded. Patients were followed to determine length of open drainage, time to removal, related complications, and those who may have benefited. RESULTS: A total of 167 patients had 174 nonpalliative gastrostomy tubes placed. Nine percent of the patients had related complications with a major complication rate of 2%. Overall, approximately one-third of the patients appeared to benefit from the gastrostomy tube. CONCLUSION: The results support the safety and efficacy of the MIC gastric tube in patients undergoing extensive gynecologic cancer surgery which is likely to impact the function of the gastrointestinal tract.

Bartholin's gland carcinoma: a 15-year experience.

OBJECTIVE: Our objective was to review our experience with carcinoma of Bartholin's gland relative to treatment and oncologic outcome. METHODS: Patient names were collected from our vulvar cancer database for the period September 1985 to September 2000. The medical records were retrospectively reviewed, and data were abstracted relative to demographics, presenting symptoms, treatment, and oncologic outcome. RESULTS: We treated 12 women with Bartholin's gland carcinoma, and 11 patients are reported. Seven women presented with a painless vulvar mass, and 8 of 11 had initially been treated for an infectious process before referral to our institution. Squamous histology was most common, and the right gland was more frequently involved. Ten patients were treated with primary surgery, followed by adjuvant radiation in 7 for inadequate resection margins or lymphatic metastases. One patient was treated with primary chemoradiation. Stage I, II, III, IVA, and IVB disease was present in 3, 1, 4, 2, and 1 patient, respectively. Recurrence was suffered by 54.5% during a mean follow-up time of 73.5 months (median, 60; range, 8-180 months). Overall survival is 58.3% to date. CONCLUSIONS: Conventional therapy for Bartholin's gland carcinoma yielded a 67% 5-year survival. Seventy-one percent of women receiving adjuvant radiotherapy recurred despite this precaution. Work is needed to identify an effective systemic therapy and to better determine which patients may benefit from pelvic radiotherapy.

Diagnosis and management of vulvar and vaginal intraepithelial neoplasia.

Vulvar intraepithelial neoplasia and VAIN present unique challenges to the practicing gynecologist. VIN may produce distressing symptoms and undergo malignant conversion. A high index of suspicion and liberal use of biopsy are required to make the diagnosis. The approach to therapy for VIN has been reviewed. Treatment should be tailored to each individual patient and may include a period of expectant observation. Variations and combinations are used whenever necessary to preserve normal function and anatomy. Frequent surveillance is a must because recurrence rates are high, especially with multifocal disease in young women. Although VAIN accounts for less than 0.5% of lower genital tract neoplasia, the frequency of its detection is increasing, especially in younger patients. These lesions are most commonly found in the upper third of the vagina and are often multifocal in nature. The close proximity of the upper vagina to the rectum, bladder, and ureters makes treatment difficult. The occult invasion rate may be as high as 28%, and a wide variety of therapies are available. As is true for VIN, recurrence is not uncommon.

Accurate repair of the prolapsed vagina by use of measured lateral flaps.

OBJECTIVE: We report our experience with a technique for planning the final vaginal caliber and location of the vaginal apex in patients with severe vaginal prolapse. STUDY DESIGN: During the 2-year period ending April 1998, the technique was used in all 27 patients who were undergoing vaginal repair of prolapse performed by Mitchel S. Hoffman, MD, and who desired to retain the vagina but required at least partial excision. The major steps included determination of sites for lateral apical support, definition of the desired introital caliber, marking of the measured lateral vaginal flaps, excision of the intervening epithelium (and uterus if present, n = 14), high peritoneal closure, closure of the anterior vaginal wall, placement of apical supporting sutures, and completion of closure with tying of supporting sutures. Small flaps were designed for the 8 patients who did not anticipate further sexual intercourse. RESULTS: The only intraoperative complication was hemorrhage >1000 mL in 3 patients. Immediate anatomic results were considered excellent for 26 patients. The only early postoperative complication was hemorrhage in a patient being treated with an anticoagulant; she responded to conservative management. Follow-up was available for 24 patients (21-42 months of follow-up; mean, 29 months). All patients had complete relief of prolapse symptoms. Anatomic results remained excellent for 21 of the 24 patients; in the remaining 3 patients asymptomatic grade 2 cystoceles developed at 6 to 12 months. Three patients had new urinary symptoms that persisted. Nine patients resumed sexual intercourse, with no difficulties noted. CONCLUSION: Defining the vaginal apex and designing lateral vaginal flaps facilitate the precise creation of an anatomically and functionally appropriate vagina, with reasonable morbidity, good symptomatic relief, and mild alteration of surrounding organ function.

Accuracy of lymph node palpation to determine need for lymphadenectomy in gynecologic malignancies.

OBJECTIVE: To assess the accuracy of intraoperative lymph node palpation for identifying lymph node metastasis in gynecologic malignancies. METHODS: We prospectively evaluated 126 women who had lymphadenectomies for staging of various gynecologic malignancies from August 1995 to June 1997. Surgeries were done by obstetrician-gynecologists with subspecialty certification in gynecologic oncology from the American Board of Obstetrics and Gynecology, who had practiced gynecologic oncology for at least 5 years. Data were collected on gynecologic oncologists' opinions of lymph node status by palpation. Nodes believed to be positive were sent separately. We recorded operating time for lymphadenectomies, and intraoperative and postoperative complications. RESULTS: Mean (range) patient age was 55 (18-83) years. Mean (range) operating time was 188 (85-435) minutes. The mean (range) lymphadenectomy time was 46 (5-150) minutes. The total number of lymph nodes dissected was 2138. One hundred seven of 2138 (5%) nodes were positive for malignancy. Thirty-eight of 107 (36%) positive lymph nodes were missed by palpation. Fifty-six of 2031 (3%) negative lymph nodes were selected as positive. Sixty-nine of 107 (64%) positive lymph nodes were identified correctly. Sensitivity and specificity of palpation were 72% and 81%, respectively. The positive and negative predictive values of lymph node palpation were 56% and 89%, respectively. CONCLUSION: Intraoperative lymph node palpation has low sensitivity and positive predictive value even when done by experienced board-certified gynecologic oncologists.

Distal external iliac lymph nodes in early cervical cancer.

OBJECTIVE: To evaluate the utility of the deep circumflex iliac vein as a landmark for the caudal limit of external iliac lymphadenectomy for early cervical cancer. METHODS: During dissection of the distal (caudal), anterior (ventral) aspect of the external iliac vessels in conjunction with radical hysterectomy for carcinoma of the cervix, a careful search was made for the deep circumflex iliac vein. Lymph nodes immediately above this vein were sent as adjacent and lymph nodes caudal to the vein were sent as distal. The distance from the vein to the femoral canal was measured. RESULTS: Seventy-one women were studied over 40 months. Fifty-five had squamous cell carcinoma, 15 had adenocarcinoma, and one had adenosquamous carcinoma. The mean distance from the deep circumflex iliac vein to the femoral canal was 16 mm. Sixty-three patients had dissections distal to identified deep circumflex iliac veins and 49 (77%) of these had distal lymph nodes removed. The median number of pelvic lymph nodes removed was 24 (range nine to 68), and the median number of distal lymph nodes removed was 1.0 from each side. Lymph node metastases were found in 13 women (18%). One subject with multiple macroscopically positive nodes had a single positive distal lymph node. Thus, a small number of distal lymph nodes were found in most women with early invasive cervical cancer, and 8% of those with positive nodes had involvement of this nodal group. CONCLUSION: The deep circumflex iliac vein was an appropriate landmark for the caudal limit of external iliac lymphadenectomy.

Injury of the rectum during vaginal surgery.

OBJECTIVE: We sought to report our experience with injury of the rectum during vaginal surgery. STUDY DESIGN: A retrospective chart review of a vaginal surgery database was performed. RESULTS: Nine injuries were identified. Four patients with posthysterectomy vault prolapse incurred a rectal laceration just above the perineum during an attempt to develop the rectovaginal space. Another rectal laceration occurred just above the perineum during an attempt to develop the rectovaginal space during vaginectomy-hysterectomy for gender dysphoria. Three other injuries occurred between the vaginal cuff and peritoneum while posterior culdotomy for vaginal hysterectomy was attempted. The remaining injury was in a Schuchardt incision. All 9 injuries were recognized, repaired, and healed without complication. CONCLUSIONS: Laceration of the rectum is an uncommon complication of vaginal surgery. Prompt recognition and repair result in uncomplicated primary healing.

Lateral microscopic extension of squamous cell carcinoma of the vulva.

PURPOSE: The aim of this study was to measure the radial occult microscopic spread of tumor in patients with invasive squamous cell carcinoma of the vulva. MATERIALS AND METHODS: In the operating room the gross tumor border was marked. The pathologist took a radial section in each quadrant and measured the distance of occult lateral spread of the tumor. RESULTS: From 7/01/93 to 6/30/96, 24 tumors from 21 patients were studied. The mean maximum tumor diameter was 3. 2 cm (0.5-7.0) and the mean depth of invasion was 9.1 mm (1.1-28.0). The gross and microscopic extent correlated in 20 tumors. Maximum lateral microscopic extent of the other 4 tumors was 3.5, 5 (to the margin), 10, and 16 mm. These 4 tumors were ulcerative and infiltrative and arose from or involved mucosa. CONCLUSION: The gross and microscopic periphery of most invasive squamous vulvar cancers are approximately the same. Ulcerative tumors with an infiltrative pattern of invasion which involve mucosal epithelium may be more likely to extend beyond what is grossly apparent. Measurement of the tumor-free margin should be included in future studies.

Detection of sentinel lymph nodes with lymphazurin in cervical, uterine, and vulvar malignancies.

BACKGROUND: Identification of sentinel lymph nodes may allow prediction of metastatic disease in cancer patients. We did a prospective study to determine whether lymphazurin dye could identify sentinel lymph nodes in patients with cervical, uterine, and vulvar cancer. METHODS: In 33 patients having surgery for either uterine, cervical, or vulvar carcinoma, lymphazurin dye was injected into the respective organs before the tumor and node dissection began. Sentinel lymph nodes were identified and dissected in situ. RESULTS: The identification rate of sentinel lymph nodes was 0/8 (0%) for uterine cancer patients, 2/13 (15.4%) for cervical cancer patients, and 9/12 for vulvar cancer patients (75%). CONCLUSIONS: In a limited number of patients, lymphazurin day may be useful in identifying or assessing the sentinel nodes draining vulvar and cervical cancers. The role of this procedure in treatment planning for patients with gynecologic malignancies is yet to be determined.

Does ligation of the hypogastric artery at the time of radical hysterectomy and lymphadenectomy decrease blood loss? Results of a prospective randomized trial.

A prospective, randomized study of patients undergoing radical hysterectomy for gynecologic malignancies was undertaken from 10/95 to 11/96 to determine if ligation of the hypogastric arteries at the time of radical hysterectomy decreases blood loss. Patients were randomized to either ligation of the hypogastric artery (Group 1) or no ligation (Group 2) prior to a standard Piver type III radical hysterectomy. Surgeries were performed by Board certified gynecologic oncologists with gynecologic oncology fellows and/or OB/GYN residents. Patients were analyzed for demographic characteristics and intraoperative and postoperative parameters. Statistical analysis was performed with independent samples t-test, Mann-Whitney rank sum test, Chi square and Fisher exact test. Twenty-one patients were randomized to group 1 and 22 to group 2. Groups were similar with respect to demographics and preoperative parameters except for age. There were no differences among the groups with respect to intraoperative and postoperative parameters. The mean estimated blood loss for group 1 was 600 ml and 550 ml for group 2 (P = NS). Hypogastric artery ligation (HAL) at the time of radical hysterectomy for gynecologic malignancy does not reduce blood loss.