Increased expression of the retinoblastoma gene in human colorectal carcinomas relative to normal colonic mucosa.

We report the first evidence of increased levels of the retinoblastoma (Rb) message in a majority of colorectal cancers when compared with normal mucosa. Southern blot analysis showed an increase in Rb gene copy number in at least 28% of colorectal carcinomas relative to normal mucosa. These results plus previous reports of nonrandom chromosome 13 gains in approximately 50% of colorectal cancers suggest that an increase in Rb gene copy number occurs frequently in these tumors. Possible mechanisms pertaining to overexpression of the Rb gene are discussed in relation to its role as a recessive cancer gene.

Carbohydrate and energy metabolism during the evolution of hypoxic-ischemic brain damage in the immature rat.

The brain damage that evolves from perinatal cerebral hypoxia-ischemia may involve lingering disturbances in metabolic activity that proceed into the recovery period. To clarify this issue, we determined the carbohydrate and energy status of cerebral tissue using enzymatic, fluorometric techniques in an experimental model of perinatal hypoxic-ischemic brain damage. Seven-day postnatal rats were subjected to unilateral common carotid artery ligation followed by 3 h of hypoxia with 8% oxygen at 37 degrees C. This insult is known to produce tissue injury (selective neuronal necrosis or infarction) predominantly in the cerebral hemisphere ipsilateral to the carotid artery occlusion in 92% of the animals. Rat pups were quick-frozen in liquid nitrogen at 0, 1, 4, 12, 24, or 72 h of recovery; littermate controls underwent neither ligation nor hypoxia. Glucose in both cerebral hemispheres was nearly completely exhausted during hypoxia-ischemia, with concurrent increases in lactate to 10 mmol/kg. During recovery, glucose promptly increased above control values, suggesting an inhibition of glycolytic flux, as documented in the ipsilateral cerebral hemisphere by measurement of glucose utilization (CMRglc) at 24 h. Tissue lactate declined rapidly during recovery but remained slightly elevated in the ipsilateral hemisphere for 12 h. Phosphocreatine (P approximately Cr) and ATP in the ipsilateral cerebral hemisphere were 14 and 26% of control (p less than 0.001) at the end of hypoxia-ischemia; total adenine nucleotides (ATP + ADP + AMP) also were partially depleted (-46%).(ABSTRACT TRUNCATED AT 250 WORDS)

Postnatal development of efferent synapses in the rat cochlea.

The development of olivocochlear efferent axons and their contacts in the postnatal cochlea was studied after DiI applications to the olivocochlear bundle in the ipsilateral brainstem of rats from 0 to 10 days of age (P0-10). Light microscopic analyses showed that labeled axons reached the vicinity of inner hair cells by P0 and outer hair cells by P2. Electron microscopic analyses demonstrated that labeled immature efferent axons are present among supporting cells of the greater epithelial ridge as well as inner hair cells at P0. The first efferent contacts that contacted inner hair cells contained a few irregularly sized vesicles and, occasionally, mitochondria. Postsynaptic specializations within inner hair cells apposed to labeled efferent axons included subsynaptic cisterns, irregularly sized vesicles, and synaptic bodies. Similar features were present in unlabeled profiles, presumed to be afferents, indicating that immature efferent axons could not be reliably distinguished from afferents without positive labeling. Efferent axons synapsed with outer hair cells by P4 and had synapse-like contacts at the bases of Deiters' cells at P4 and P6. Contacts between afferents and efferents were observed frequently in the inner spiral bundle from P6. As they matured, efferent axon terminals contacting hair cells contained increasing numbers of synaptic vesicles and were typically apposed by well-defined postsynaptic cisterns, thus acquiring distinctive profiles.

Electron microscopic differentiation of directly and transneuronally transported DiI and applications for studies of synaptogenesis.

The neuronal tracer DiI is a lipophilic dye which diffuses along the lipid bilayer of membranes and sometimes will move transcellularly. We used this tracer to study the development of olivocochlear synapses in the auditory system in rats and chickens by applying DiI directly to severed axons in the olivocochlear bundle. Observations with epi-fluorescent microscopy showed that DiI had labelled efferent axons directly and had labelled spiral ganglion cells and hair cells transneuronally. Ultrastructural analysis of photoconverted DiI tissue in rats revealed that transneuronal diffusion occurred when the plasma membrane of directly labelled axons made contact with the plasma membrane of their target structure. Directly and transneuronally labelled profiles can be distinguished easily at the electron microscopic level. In directly labelled profiles, all plasma, nuclear, endoplasmic reticulum, and outer mitochondrial membranes and cell cytoplasm are labelled leaving only the mitochondrial matrix unstained. However, in transneuronally labelled cells the endoplasmic, nuclear, and immature synaptic membranes are labelled but mitochondrial and non-synaptic plasma membranes are not labelled. This labelling pattern can be explained by diffusion through continuous membranes. These characteristics make DiI diffusion a powerful technique for identifying and studying early events in neuronal development and synapse formation.

Regional cerebral blood flow following hypothermic circulatory arrest in newborn dogs.

A model of hypothermic circulatory arrest has been developed in newborn dogs which simulates the procedure used for the operative repair of congenital cardiac defects in human infants. Hypothermic circulatory arrest for 1.0 h causes no brain damage, whereas cardiac arrest for 1.75 h results in damage of the cerebral cortex, basal ganglia and to a lesser extent the claustrum and amygdaloid nucleus. In the present study, we determined regional cerebral blood flow (rCBF) during 24 h of recovery from hypothermic circulatory arrest. Newborn nitrous oxide anesthetized and artificially ventilated dogs were cooled to 20 degrees C and subjected to cardiac arrest by the i.v. injection of KCl for either 1.0 or 1.75 h. Thereafter, animals were resuscitated, rewarmed to 37 degrees C, and rCBF measured with [14C]iodoantipyrine at either 2 or 18 h of recovery. Control animals were rendered hypothermic to 20 degrees C without cardiac arrest for 1.0 or 1.75 h prior to rewarming. No alterations in CBF at either 2 or 18 h of recovery were present in any of 16 analyzed structures in animals previously subjected to hypothermic circulatory arrest compared to controls rendered hypothermic alone. A direct linear correlation existed between mean arterial blood pressure and blood flow within frontal, parietal and occipital cortex, occipital white matter, hypothalamus and cerebellar vermis in puppies arrested for 1.75 h and recovered for 2 h, suggesting a loss of CBF autoregulation at this interval. No such association between blood pressure and CBF was apparent at 18 h of recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Cumulative incidence of colorectal and extracolonic cancers in MLH1 and MSH2 mutation carriers of hereditary nonpolyposis colorectal cancer.

The extracolonic tumor spectrum of hereditary nonpolyposis colorectal cancer (HNPCC) includes cancer of the endometrium, ovaries, stomach, biliary tract, and urinary tract. This study was designed to determine the penetrance of colorectal and extracolonic tumors in HNPCC mutation carriers. Forty-nine patients (22 females and 27 males) were identified with an MSH2 germline mutation, and 56 patients (28 females and 28 males) were identified with an MLH1 I mutation. Cumulative incidence by age 60 (lifetime risk) and mean age of cancer diagnosis were compared. The lifetime risk of extracolonic cancers in MSH2 and MLH1 carriers was 48% and 11%, respectively (P = 0.016). Extracolonic cancer risk in MSH2 females and males was 69% and 34%, respectively (P = 0.042). Mean age of extracolonic cancer diagnosis was significantly older for MSH2 males than females (55.4 vs. 39.0, P = 0.013). No difference was observed in colorectal cancer risk between MLH1 and MSH2 carriers (84% vs. 71%). Colorectal cancer risk was 96% in MSH2 males compared to 39% in MSH2 females (P = 0.034). No differences in colorectal and extracolonic cancer risks between MLH1 females and males were identified. The risk of extracolonic cancer by age 60 was greater in MSH2 mutation carriers than in MLH1 carriers. Gender differences in colorectal and extracolonic cancer risk were observed for MSH2 carriers only. These phenotypic features of HNPCC genotypes may have clinical significance in the design of genotype-specific screening, surveillance, and follow-up for affected individuals.

Rectopexy without resection for rectal prolapse.

Forty-three patients underwent simple posterior suture rectopexy for repair of rectal prolapse. Follow-up was obtained in 42 patients (mean 28 months). The recurrence rate was 2 percent (one patient). Postoperative morbidity and mortality were 20 percent and 0, respectively. The proportion of continent patients increased from 36 percent preoperatively to 74 percent postoperatively. Constipation increased after suture rectopexy but was managed conservatively. We believe that simple suture rectopexy offers a safe and effective alternative to other, more complex procedures for the treatment of rectal prolapse.

Transrectal ultrasound of rectal tumors.

Since preoperative staging of rectal tumors is important in planning treatment, we evaluated transrectal ultrasound (TRUS) staging of rectal neoplasms. In 35 consecutive rectal tumors, we compared TRUS staging results with final pathologic staging. TRUS predicted the degree of tumor invasion in 19 of 24 patients (79%) and the presence or absence of lymph node metastasis in 11 of 15 patients (73%). TRUS overestimated the degree of tumor invasion in four patients (17%) and underestimated invasion in one patient (4%). The depth of tumor invasion was correctly predicted in all 14 tumors located within 6 cm from the anal verge, but, beyond 6 cm, only 5 of 10 tumors (50%) were staged correctly (p = 0.005). In the group of 11 patients who underwent preoperative radiotherapy, pretreatment TRUS predicted the depth of tumor invasion in only six patients (55%) and overestimated tumor invasion in five patients (45%), suggesting that nearly half of these tumors were downstaged by radiotherapy. TRUS accurately predicts the degree of tumor invasion, especially in tumors closer to the anal verge, allowing for better treatment planning in patients with low to middle rectal neoplasms.

Preoperative chemoradiation downstages locally advanced ultrasound-staged rectal cancer.

BACKGROUND: This prospective study assessed the effect of preoperative radiation and chemotherapy on the pathologic staging of advanced rectal cancer. METHODS: Twenty patients with rectal cancer were treated with combined chemoradiation prior to operation, after pretreatment staging of all lesions with transrectal ultrasound (TRUS). Perirectal fat invasion served as minimal criteria for preoperative neoadjuvant therapy. The pretreatment stage of these rectal lesions as defined by TRUS was then compared with the pathological stage of the surgical specimen following resection. Cancers were treated with high-dose radiation (45 to 54 Gy) in 19 of 20 patients. One patient received in excess of 60 Gy because of tumor characteristics. Chemotherapy consisted of 5-fluorouracil delivered as a continuous infusion or bolus therapy. Four to 8 weeks after neoadjuvant therapy, 13 abdominal perineal resections, 5 low anterior resections, and 2 completion proctectomies were performed. RESULTS: Following resection, rectal cancer was downstaged in 14 of 20 patients. No tumor was present in the rectal wall in 8 of 20 patients. Complete pathological response was present in 7 of 20 patients. Local recurrence occurred in 2 of 20 patients. Disease-free survival in the remaining 17 of 20 patients ranges from 9 to 51 months (average 26). CONCLUSIONS: Preoperative chemoradiation in the surgical management of advanced rectal cancer results in demonstrable tumor downstaging.

Manometric diagnosis of anal sphincter injuries.

A manometric technique of anal pressure vectography has been developed for the detection of anal sphincter injuries. Manometric symmetry of the anal sphincter can be visualized on the pressure vectorgram and quantified as a vector symmetry index. The mean vector symmetry index in asymptomatic women was 0.76, compared with 0.33 in incontinent women with a known sphincter injury (p = 0.0001). Among women who were incontinent without having a recognized sphincter injury, nearly half of those who had a previous episiotomy had subnormal (less than 0.60) vector symmetry indices (p = 0.0003). The values were in the same range as those from known injuries, suggesting the presence of an occult sphincter injury. In contrast, normal symmetry indices were found in all those who had never had an episiotomy or who presented with outlet constipation. We conclude that the vector symmetry index can expose occult anal sphincter injuries and may have a role in the selection of patients for sphincter repair.

Clinical use of the self-expanding metallic stent in the management of colorectal cancer.

PURPOSE: This report describes our experience with the use of self-expanding metallic stents (SEMS) in the management of obstructing colorectal cancer. METHODS: A retrospective chart review of all patients undergoing placement of SEMS between May 1997 and January 2000 was performed. RESULTS: Insertion of SEMS was attempted in 12 patients. Successful stent placement was achieved in 10 of the 12 patients. The locations of lesions were hepatic flexure (2), splenic flexure (1), left colon (1), sigmoid colon (4) and rectum (4). The intended uses of SEMS were for palliation in 3 patients and as a bridge to elective surgery in 9. In the latter group, SEMS placement allowed for preoperative bowel preparation in 4 patients and administration of neoadjuvant therapy prior to elective surgery in 2 patients. One patient died prior to definitive surgery. Stent placement was unsuccessful in 2 patients. Three SEMS-related complications occurred; 1 stent migrated and 1 stent obstructed secondary to tumor ingrowth. One patient died 13 days after stent placement and colonic decompression. CONCLUSION: SEMS represent a useful tool in the management of obstructing colorectal neoplasms. As a bridge to surgery, SEMS provide time for a complete preoperative evaluation and a mechanical bowel preparation and may obviate the need for fecal diversion or on-table lavage. It may also allow for time to administer neoadjuvant therapy when indicated. As a palliative measure, SEMS can eliminate the need for an operation.

Nature, time-course, and extent of cerebral edema in perinatal hypoxic-ischemic brain damage.

To ascertain the nature, time-course, and extent of the cerebral edema that accompanies perinatal hypoxic-ischemic brain damage, 7-day postnatal rats were subjected to unilateral right common carotid artery ligation followed by exposure to hypoxia with 8% oxygen for up to 3 hours. Some rat pups were sacrificed during hypoxia-ischemia or recovery for determination of cerebral hemispheric water content and percentage of brain swelling. Other animals were sacrificed and their brains processed either for determination of cerebral cortical edema and infarct volume or for horseradish peroxidase staining. The results indicated that cerebral edema occurs even during the course of hypoxia-ischemia and that the extent and duration of edema formation during the recovery period is dependent upon the severity of tissue injury. The data also disclosed a direct, linear correlation between infarct volume and the extent of cerebral edema. Accordingly, the greater the severity of cerebral edema, the proportionately greater the extent of infarction. Horseradish peroxidase staining, a reflection of vasogenic edema, occurred in 17 of 19 brains in a distribution which corresponded closely to the distribution of neuropathologic alterations observed histologically. The findings indicate that cerebral edema can occur in the absence of consequent infarction and that when infarction does occur, the associated edema contributes little or nothing to the severity of the ultimate brain damage.

Myocardial contusion: new concepts in diagnosis and management.

Myocardial contusion is diagnosed with one or a combination of four diagnostic procedures: electrocardiography, echocardiography, creatine kinase MB fractions and/or radionuclide procedures. This article presents a critical review of 18 recent studies addressing the utility, sensitivity and specificity of these tests. Careful review suggests that clinically significant myocardial contusions as a result of blunt trauma are rare and may be detected simply and inexpensively using electrocardiography and careful physical examination. Serum myocardial enzymes and radionuclide studies are nonspecific and are not predictive of cardiac complications. Echocardiography is useful in the management of myocardial decompensation but not as a primary screening tool in blunt cardiac injury. Cost comparisons, resource allocation and implications for critical care practice are discussed.

Comparing arterial and end-tidal carbon dioxide values in hyperventilated neurosurgical patients.

BACKGROUND: Hyperventilation is a frequently used method for inducing hypercarbia in neurosurgical patients. This practice requires careful carbon dioxide monitoring that might be replaced by a less expensive and less invasive alternative to arterial blood gas monitoring. OBJECTIVE: To determine the accuracy of end-tidal carbon dioxide monitoring in hyperventilated neurosurgical patients. METHODS: Nineteen adult patients requiring hyperventilation for the reduction of intracranial pressure following head injury or neurosurgery were enrolled from the surgical intensive care unit of a level I trauma center. A correlation design was used to compare arterial carbon dioxide tensions and end-tidal carbon dioxide measurements during specific periods; secondary analysis with bias and precision estimates was performed. Also, changes in arterial carbon dioxide tensions were compared with simultaneous changes in end-tidal carbon dioxide values. RESULTS: End-tidal carbon dioxide values showed a moderately acceptable correlation with arterial blood gas measurements. However, changes in end-tidal carbon dioxide values failed to correlate with simultaneous changes in arterial carbon dioxide tension measures. Bias and precision measures confirmed these findings. CONCLUSION: In this patient sample, changes in end-tidal carbon dioxide values did not accurately reflect changes in arterial carbon dioxide tension levels in the intensive care setting. Further technological advances in noninvasive carbon dioxide monitoring may lead to a significant cost savings over traditional arterial blood gas analysis.

Hetastarch: an alternative colloid in burn shock management.

Hetastarch is a synthetic polysaccharide colloid that has been used clinically in the management of multiple trauma, hypovolemic shock, and postoperative cardiac patients. Our objective was to determine whether hetastarch is a safe alternative to blood products in burn shock resuscitation. Twenty-six patients received hetastarch during the colloid phase of resuscitation and were compared to matched historical controls who received either albumin or fresh frozen plasma. Clinical and laboratory parameters were measured on admission and for 4 days after the burn. There was no significant difference in hemodynamics, respiratory status, incidence of bleeding, or renal or liver function among the three colloid groups. The advantages of hetastarch include immediate availability, no dependence on human blood donor population, no risk of serum-transmitted diseases, and lower cost. It can be safely recommended for those patients who object to blood products for resuscitation, in those situations where human donors are few, and when cost is a consideration.

Alcohol, head injury, and pulmonary complications.

The purpose of this study was to determine the difference in rates of pulmonary complications (e.g., aspiration, pneumonia) in head-injured patients with and without concomitant alcohol intoxication. The records of 98 consecutive patients admitted over a 1-year period to a Level I Trauma Center were reviewed. The patients were grouped into three subsets: acutely intoxicated (n = 26), acutely intoxicated with a diagnosis of chronic alcoholism (n = 14), and non-intoxicated (n = 58). Alcohol intoxication was defined as a blood alcohol level (BAL) > or = 0.08 mg/dl. Admission BALs and Glasgow Coma Scale (GCS) scores were tabulated at admission. Frequency of arterial blood gas (ABG) measurements, need for an artificial airway/mechanical ventilation, and length of stay (LOS) were analyzed by using one-way analysis of variance. Intergroup differences in breath sounds were compared by using the nonparametric Kruskall-Wallis technique. We found no statistical difference between groups in terms of pulmonary sequelae despite the remarkably high BALs observed in the study groups. Similarly, there was no statistically greater LOS in the groups with alcohol intoxication than in alcohol-free cohorts. Despite a great deal of BAL science research to support our hypothesis, we failed to demonstrate a significantly higher rate of pulmonary problems in inebriated individuals with head injuries. We found that our strict exclusion criteria (no concomitant chest, abdominal, or pelvic trauma) limited the sample to only those patients without significant intracranial bleeding, whereas most complications in blood alcohol neuroscience research have been associated with much larger mass lesions (e.g., epidural or subdural hematomas). In addition, we found the characterizations of patients as chronically alcoholic were cumbersome and inaccurate in many cases. Future research should allow for a greater range of concomitant injuries that might suggest a positive or negative relationship to acute intoxication.

Oxidative stress potentiates BACE1 gene expression and Abeta generation.

Alzheimer's Disease (AD) is the most common neurodegenerative disorder leading to dementia and its prevalence increases with age. The pathological features of AD are characterized by the beta-amyloid protein (A(beta)) deposits in the core of neuritic plaques and abnormal neurofibrillary tangles in the brain of AD patients. BACE1 is the major beta-secretase to cleave the beta-amyloid precursor protein (APP) to generate A(beta). Oxidative stress has been shown to affect A(beta) generation in the AD pathogenesis and the mechanism of such effect is unknown. In this report we generated a novel promoterless enhanced green fluorescent protein (EGFP) reporter gene cloning vector and cloned a 1.9-kb BACE1 gene promoter fragment in this vector. The BACE1 promoter fragment can efficiently activate EGFP or luciferase gene transcription. Oxidative stress induced by hydrogen peroxide resulted in significant increase in the BACE1 promoter activity. Furthermore, hydrogen peroxide treatment facilitated beta-secretase activity and A(beta) generation. Thus, upregulation of BACE1 transcription by oxidative stress may contribute to the pathogenesis of Alzheimer's disease.

Regional cerebral blood flow and glucose utilization during hypoglycemia in newborn dogs.

To assess alterations in regional cerebral blood flow and glucose utilization during perinatal hypoglycemia, newborn dogs (2-7 days postnatal age) were anesthetized with halothane, tracheostomized, paralyzed, and artificially ventilated with 70% N2O-30% O2 to maintain arterial normoxia and normocapnia (arterial PO2 greater than 60 mmHg; arterial PCO2: 35-42 mmHg; arterial pH: 7.35-7.45). Regional cerebral blood flow (rCBF) and glucose utilization (rCGU) were determined with iodo-[14C]antipyrine and 2-deoxy-[14C]glucose as the radioactive tracers, respectively. Hypoglycemia with blood glucose concentrations averaging 0.9 mmol/l was achieved within 90-120 min in 10 animals using intermittent intravenous injections of regular insulin; 10 control animals received 0.9% saline (blood glucose = 9 mmol/l). During hypoglycemia, mean arterial blood pressure was 81% of control, whereas heart rate was unchanged. Arterial O2 and acid-base balance were well maintained (arterial PO2 = 68 mmHg; PCO2 = 37 mmHg; pH = 7.35). Hypoglycemia was associated with significant increases in rCBF in all of 16 analyzed structures, ranging from 172% (parietal white matter) to 249% (thalamus) of control values (17-65 ml.100 g-1.min-1). During hypoglycemia, rCGU was relatively unchanged from normoglycemic values in 11 of 16 brain structures. Significant reductions in rCGU were seen only in occipital white matter (-31%) and in the cerebellar vermis and hemisphere (-31 and -43%, respectively). CGU actually increased slightly in the pons and medulla (+12 and +19%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)