A novel pancreatic endocrine tumor suppressor gene locus on chromosome 3p with clinical prognostic implications.

The molecular pathogenesis of pancreatic endocrine tumors is largely unknown. Such tumors are more likely to develop in individuals with the von Hippel-Lindau (VHL) syndrome. We sought to determine whether allelic loss of the recently identified VHL tumor suppressor gene on chromosome 3p25-26 occurs in the more common sporadic forms of these tumors. Allelic loss on chromosome 3p was identified in 33% of 43 patients with endocrine tumors of the pancreas. The smallest common region of allelic loss, however, centered not at the VHL locus, but rather at 3p25, centromeric to VHL. Furthermore, no mutations of the VHL gene were identified in these tumors. Loss of alleles on chromosome 3p was associated with clinically malignant disease, whereas tumors with retained 3p alleles were more likely to be benign. Thus, the VHL gene does not appear to play a pathogenic role in the development of sporadic pancreatic endocrine tumors. Instead, a locus at chromosome 3p25 may harbor a novel pancreatic endocrine tumor suppressor gene, and allelic loss of this chromosomal region may serve as a molecular marker that helps distinguish benign from clinically malignant disease.

Regulation of vascular endothelial growth factor by the Wnt and K-ras pathways in colonic neoplasia.

Angiogenesis is not restricted to advanced stages of tumor development but is also observed in benign precursor lesions. Vascular endothelial growth factor (VEGF) is a key regulator of tumor angiogenesis, but the genetic mechanisms controlling its expression in premalignant lesions are poorly described. The Wnt signaling pathway, which is commonly mutated in benign colonic adenomas, was found to strongly up-regulate VEGF. A T-cell factor-4-binding element at -805 bp in the VEGF promoter is an important mediator of this effect. Signaling through the K-ras oncogene, also frequently mutated in benign colonic polyps, up-regulated VEGF in a phosphatidylinositol 3-kinase-dependent manner. Furthermore, K-ras activation appeared to enhance Wnt signaling, which suggests a unique interaction between these two pathways. These studies thus identify VEGF as a novel target of the Wnt pathway in early colonic neoplasia and serve to underscore the importance of angiogenesis in premalignant disease.

Cables enhances cdk2 tyrosine 15 phosphorylation by Wee1, inhibits cell growth, and is lost in many human colon and squamous cancers.

Cyclin-dependent kinase 2 (cdk2) is a small serine/threonine kinase that regulates cell cycle progression. Cdk2 activity is tightly controlled by several mechanisms, including phosphorylation and dephosphorylation events. Cables is a recently described novel cdk-interacting protein. In proliferating cells, Cables was predominantly localized in the nucleus by cell fractionation and immunostaining. Expression of Cables in HeLa cells inhibited cell growth and colony formation. Cables enhanced cdk2 tyrosine 15 phosphorylation by the Wee1 protein kinase, an inhibitory phosphorylation, which led to decreased cdk2 kinase activity. The gene encoding Cables is located on human chromosome 18q11-12, a site that is frequently lost in squamous, colon, and pancreas cancers. We found that Cables was strongly expressed in normal human epithelial cells including squamous and glandular mucosa. Breast and pancreatic cancers show strong Cables expression; however, loss of Cables expression was found in approximately 50-60% of primary colon and head and neck cancer specimens. Lack of Cables expression was associated with loss of heterozygosity on chromosome 18q11. The data provide evidence for a Cables-mediated interplay between cdk2 and Wee1 that leads to inhibition of cell growth. Conversely, loss of Cables may cause uncontrolled cell growth and enhance tumor formation.

Localization of putative tumor suppressor loci by genome-wide allelotyping in human pancreatic endocrine tumors.

Only two tumor suppressor gene loci, one on 3p25 and the MEN1 gene on 11q13, have thus far been implicated in the pathogenesis of sporadic human pancreatic endocrine tumors (PETs). A genome-wide allelotyping study of 28 human PETs was undertaken to identify other potential tumor suppressor gene loci. In addition to those on chromosomes 3p and 11q, frequent allelic deletions were identified on 3q (32%), 11p (36%), 16p (36%), and 22q (29%). Finer deletion mapping studies localized the smallest regions of common deletion to 3q27, 11p13, and 16p12.3-13.11. Potential candidate genes at these loci include WT1 (11p13), TSC2 (16p13), and NF2 (22q12), but no known tumor suppressor gene localizes to 3q27. The mean fractional allelic loss among these human PETs is 0.126, and no correlation was observed between allelic loss and clinical parameters, including age, sex, hormonal subtype, and disease stage. These findings highlight novel locations of tumor suppressor gene loci that contribute to the pathogenesis of human PETs, and several of these on 3p, 3q, and 22q are syntenic with loci on mouse chromosomes 9 and 16 that are implicated in a murine transgenic model of PETs.

Overexpression of cyclin D1 occurs frequently in human pancreatic endocrine tumors.

The molecular pathogenesis of human pancreatic endocrine tumors (PETs) is poorly understood. Three independent animal models have pointed to the pivotal role of the G1/S cell cycle transition in pancreatic endocrine cell proliferation. We thus hypothesized that the cell cycle regulator cyclin D1 may contribute to the pathogenesis of human PETs. Overexpression of cyclin D1 was identified in 43% of cases, and no correlation was observed with clinical phenotype. The novel observation of frequent overexpression of cyclin D1 suggests that this established oncogene may be implicated in the pathogenesis of human PETs. The absence of detectable alterations in cyclin D1 genomic structure suggests that the mechanism for its oncogenic activation in PETs may be transcriptional or posttranscriptional.

Adenovirus-mediated gene transfer of ornithine aminotransferase in cultured human retinal pigment epithelium.

PURPOSE: To evaluate the efficacy of adenovirus mediated transfer of ornithine delta-aminotransferase (OAT) into human retinal pigment epithelial (RPE) cells. METHODS: Adenovirus-mediated gene transfer into primary cultures of human RPE was evaluated by measurement of enzyme activity in whole cell extracts and by Western blot analysis. To assess mitochondrial integrity, succinate dehydrogenase activity was measured in transduced RPE cells. Expression of adenovirus early genes was evaluated using reverse transcription-polymerase chain reaction. RESULTS: OAT activity, which was 65 nmol/mg.hour in untransduced cells, could be increased to levels in excess of 20,000 nmol/mg.hour using an adenovirus vector carrying the OAT cDNA. There was, however, a significant reduction in succinate dehydrogenase activity associated with OAT activity greater than 12,000 nmol/mg.hour. Transduced human RPE displayed an altered morphology that appears to be a response to the vector because similar changes could be induced by an adenovirus vector that does not carry the OAT cDNA. Adenovirus early gene expression was detected in transduced RPE. CONCLUSIONS: This study represents a first step in the development of intraocular gene replacement therapy for the treatment of gyrate atrophy. The authors demonstrate that adenovirus is an efficient vehicle for the delivery of OAT into human RPE and that RPE will tolerate greater than a 150-fold increase in OAT-specific activity. Evidence for disruption of mitochondria when OAT activity exceeds 12,000 nmol/mg.hour and vector-induced toxicity indicate that more controlled transgene expression and refinement of the vector systems is needed.

Importance of breath size in calibrating the respiratory inductive plethysmograph.

The usual method of calibrating the respiratory inductive plethysmograph (RIP) is to have the subject breathe over a rather narrow volume range, either resting tidal volume or into a bag containing a fixed larger volume, in both the standing and supine positions. During a previous study in our laboratory using the RIP to quantify ventilation during sleep in young and elderly adults, we began to observe that the accuracy of the RIP measurements could be improved if we calibrated using a wider range of tidal volumes which encompassed the smaller breath sizes we were measuring during sleep. We therefore decided to investigate whether the size of the breaths used for calibrating the RIP was indeed important in improving the accuracy of the device. Eight healthy, nonsmoking young adult men participated in the study. Three sets of calibration factors for the RIP were determined based on low (300 to 500 ml), normal (500 to 800 ml) and high tidal volume (over 800 ml) breaths. Each of these sets of calibration factors were then used to validate three different sets of supine tidal volumes (low, normal, high). For all volumes tested, the RIP values most closely approximated the spirometric volumes when the calibration breaths and validation breaths were of the same size.

Ventilatory and arousal patterns during sleep in normal young and elderly subjects.

Since elderly subjects have lower chemosensitivity, we postulated that ventilation might be more state dependent in the elderly. To address this we investigated the changes in ventilation, measured by respiratory inductive plethysmography, with sleep in 12 healthy young (19-29 yr) and 13 elderly (greater than 65 yr) subjects. Ventilation was measured in representative periods in each sleep state. These data showed that there is no difference between the elderly and the young either in mean ventilation or in the variability of ventilation awake or in the different states of sleep. In both groups ventilation was variable in stage 1-2 sleep and least variable in stage 3-4 sleep. The variability in stage 1-2 sleep was due to periodic breathing (cycle time approximately 45 s) in both age groups. Although within a sleep state no differences were observed, over the night of study the elderly behaved differently from the young. Apneas occurred more frequently in the elderly, and 5 of 13 elderly met the criteria for sleep apnea syndrome compared with 1 of 12 young subjects. Apneas tended to occur predominantly in stage 1-2 sleep and seem to be an exaggeration of the periodicity that is typical of this state. Four of the elderly with apnea remained in this stage of sleep throughout the night of study. The apneic episodes usually terminated with an electroencephalogram arousal that occurred prior to or simultaneously with the onset of ventilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in compartmental ventilation in association with eye movements during REM sleep.

The effect of phasic eye movement activity on ventilation during rapid-eye-movement (REM) sleep was studied in seven healthy young adults by use of the respiratory inductive plethysmograph. Mean ventilation (VE) and ventilatory components during REM sleep were not significantly different from that seen in either stages 1-2 or 3-4 sleep. The percent of rib cage contribution to ventilation in REM sleep, 29.3 +/- 5.1%, was reduced compared with 54.4 +/- 5.8% in stage 1-2 and 52.2 +/- 4.3% in stage 3-4 sleep (P less than 0.005). When one separated breaths by the degree of associated phasic eye movement activity, it became apparent that breathing during REM sleep is very heterogeneous. Increasing eye movement activity was associated with inhibition of ventilation with a reduction in VE from 5.1 +/- 0.3 to 3.8 +/- 0.3 l/min. Tidal volume and frequency both fell, whereas inspiratory duration was unchanged. Compartmental ventilation was also affected, with the fall in the rib cage contribution from 37.8 +/- 6.4 to 15.3 +/- 5.6%. Chest wall and abdominal movement became more asynchronous as phasic-eye-movement activity increased and frank paradoxical breathing was seen.

Spectral analysis of ventilation in elderly subjects awake and asleep.

We studied the periodicities of ventilation in elderly subjects using digital comb filtering. Two groups of subjects were studied, those with and without sleep apnea. Measurements were made in wakefulness, stage 1-2 sleep, and where possible in stage 3-4 sleep. For each of the digital filters we calculated the average power of the oscillatory output. To compare subject groups we first specifically determined the average power in the filter with the maximum output. The mean of this measurement was greater in elderly subjects with apnea compared with those without apnea, both during wakefulness and stage 1-2 sleep. In both groups of subjects the cycle time of the major ventilatory oscillations was on the order of 40-60 s. There was no difference in this cycle time between the two groups of subjects in wakefulness or stage 1-2 sleep. Thus, whereas similar oscillatory processes occur in subjects with and without apnea, it is the magnitude of the oscillation that differs between the two groups. These conclusions are supported by analysis of the output of individual filters of the digital comb filter. In both groups, stage 1-2 sleep produced significantly increased oscillations in ventilation. Both in wakefulness and stage 1-2 sleep, significantly greater periodicities occurred in the apneic compared with the nonapneic group. In the few subjects who had sufficient data in stage 3-4 sleep for spectral analysis, ventilatory oscillations were virtually absent in this state. Our data suggest that subjects who develop apnea during sleep have an increased propensity for periodic breathing even while awake.

Gabapentin for the treatment and prophylaxis of cluster headache.

BACKGROUND AND OBJECTIVES: Cluster headache is an uncommon debilitating condition for which effective management remains a challenge. We describe the use of gabapentin in the treatment and prophylaxis of cluster headache in a patient who was refractory to other treatments. CASE REPORT: A 38-year-old man had a history of intermittent right-side headaches for 24 years, diagnosed as cluster headache. He received only partial relief from a range of conventional treatments. A trial with gabapentin 300 mg twice daily was tried and found to be effective in treatment and prophylaxis of his headaches. CONCLUSION: Gabapentin was effective in the treatment of a patient with cluster headache. Further investigation of gabapentin compared with conventional treatments and placebo is warranted.

Airway difficulties caused by improperly applied cricoid pressure.

Cricoid pressure, when properly applied, may prevent gastric regurgitation and may improve the view of laryngoscopy. When improperly applied, however, it can impede laryngoscopy and mask-ventilation. When faced with a "cannot intubate" or "cannot mask-ventilate" situation, clinicians should reevaluate the manner with which the assistant is applying cricoid pressure and must be prepared to adjust or even to release it.

A bougie improves the utility of the UpsherScope.

STUDY OBJECTIVE: To assess the alignment of the tube-guide and visual-guide channels of the UpsherScope and to evaluate methods to improve the success of tracheal intubation. DESIGN: In-vitro observation followed by clinical series. SETTING: Tertiary care, academic medical institution. PATIENTS: 56 surgical patients. MEASUREMENTS AND MAIN RESULTS: In an in-vitro study, cross-marked concentric circles were used as the target for the tracheal tube. It confirmed that the tube-guide channel of the UpsherScope directs the tip of the tracheal tube posteriorly and to the right of the visual field when the tube was loaded into the guide channel, according to the manufacturer's recommendations. Of five other methods used for maneuvering the tracheal tube to the target, use of a bougie within the lumen of the tube resulted in the highest success rate. When this method was assessed in a clinical setting, it was successful in directing the tracheal tube into the trachea of 95% of the patient population. Two failures were due to secretions obscuring the view, and one, to a broken bougie. CONCLUSIONS: There is a functional misalignment between the long axes of the tube-guide and visual-guide channels of the UpsherScope. Use of a bougie will minimize this potential problem.

"Apnea-volume" warning during normal ventilation of the lungs: an unusual leak in the Narkomed 4 Anesthesia System.

We report a case of an unusual breathing circuit leak in the Narkomed 4 Anesthesia System due to a loose retaining ring at the junction of the expiratory valve assembly and the Spiromed Respiratory Volume Monitor. In the presence of the leak, the monitor panel displayed the messages "apnea volume" and "minute volume low," yet the low airway pressure alarm was not triggered and other parameters and clinical signs pointed to normal ventilation of the lungs. These conflicting data led to some delay in localizing the leak. After conclusion of the case, we found that occult loosening of this ring without causing leaks large enough to fail the FDA generic or manufacturer-recommended leak checks can occur. We recommend checking the tightness of this ring during routine leak checks and after rotating the expiratory valve assembly during re-positioning of the anesthetic system.

Absorption of lidocaine during aspiration anesthesia of the airway.

STUDY OBJECTIVE: To determine the optimal solution to use when anesthetizing the airway by aspiration of lidocaine. DESIGN: Randomized, double-blind clinical study. SETTING: University hospital. PATIENTS: 96 adult ASA physical status 1,II, and III patients, scheduled for diagnostic flexible bronchoscopy. INTERVENTIONS: Patients were randomized to receive one of 5 solutions of lidocaine: Group A (n = 16): 1% lidocaine, 0.2 mL. kg(-1); Group B (n = 16): 1.5% 0.2 mL. kg(-1); Group C (n = 32): 2% 0.2 mL. kg(-1); Group D (n = 16): 1% 0.3 mL. kg(-1), and Group E (n = 16): 2% 0.3 mL. kg(-1). Fiberoptic bronchoscopy was performed after the airway was anesthetized with this aspiration technique, using the assigned lidocaine solution. The scope was manipulated in the trachea to test for anesthesia. MEASUREMENTS AND MAIN RESULTS: Successful airway anesthesia was determined by tolerance to bronchoscopy without sustained coughing, and also by the number of lidocaine supplements, if any, that were given via the bronchoscope. Arterial plasma concentrations of lidocaine were measured in 33 patients from Groups C, D, and E. All solutions provided equally effective anesthesia of the airway. All patients tolerated endoscopy through the vocal cords, and 94 patients required no supplementary anesthesia, or only one dose of lidocaine, during bronchoscopy to the carina. The highest peak plasma concentrations of lidocaine were 5.02 and 6.28 microg. mL. No patient had signs of toxicity. CONCLUSIONS: This technique produced anesthesia of the airway to the carina, safely, suitable for awake intubation, in 94 of 95 patients. The use of 1% lidocaine, 0.2 to 0.3 mL. kg(-1), so that the volume is 10 to 20 mL, is recommended.