Biomedical subjects

E H Livingston

Publications and source records attributed to E H Livingston.

At least 19 recordsLinked to original sources

PubMed2001

Biexponential model for predicting weight loss after gastric surgery for obesity.

BACKGROUND: Following gastric restrictive surgery, morbidly obese patients rarely achieve their ideal body weight defined by Metropolitan Life tables. The final body weight will depend on the initial body composition because there will be greater weight loss from fat than lean body mass. The purpose of this study was to develop a mathematical model that accurately estimates the rate and extent of weight loss following gastric bypass surgery. METHODS: Patients underwent gastric bypass followed by intensive medical therapy and serial bioelectrical impedance analysis (BIA) body composition measurements. Differential equations were derived to model weight loss. RESULTS: Weight loss in the fat and lean body compartments followed monoexponential decay kinetics with differing rate constants. Total body weight loss (W(T)) at time t was W(T) = k(f)(k(f) - k(l)) (W(f(o))e(-k(f)t) + W(l(o))e(-k(l)t)), where W(fo) and W(lo) are the initial fat and lean body masses determined by BIA and k(f) and k(l) are the rate constants for the fat and lean compartments, respectively. Following surgically induced weight loss, k(f) = 7.61 +/- 1.27 x 10(-2), and k(l) = -0.93 +/- 0.13 x 10(-2), with the ratio of residual sum of the squares to the total sum of the squares of 98.8%. CONCLUSION: Accurate prediction of weight loss depends on the initial fat and lean compartment mass since each of these loses weight at a different rate and to a different extent. When these effects are accounted for, the total body weight loss can be accurately predicted for any given time following surgery.

Adult↗

PubMed2001

Peer review.

Peer review is essential for ensuring quality medical care. In the 1980s a physician-plaintiff prevailed in lawsuit filed against peer reviewers who excluded the physician from a hospital's medical staff. The peer reviewers had acted to preserve their own economic interests. A multimillion-dollar verdict against the peer reviewers destroyed the community's only multispecialty practice and received national attention. Congress reacted by passing the Health Care Quality Improvement Act that granted sweeping, legal immunity for peer reviewers but also created the National Practitioner's Data Bank. The combination of the establishment of a public repository for physicians malpractice and medical staff privileging activity in combination with the near complete legal protection of peer reviewers has converted peer review from an evaluative to a punitive process. The peer review process and the laws that govern it should be reformed to regain its ability to improve and assure quality without being a threat to physicians.

Humans↗

PubMed2001

Human colon cancer cells deficient in DCC produce abnormal transcripts in progression of carcinogenesis.

Expressive loss of the tumor suppressor deleted in colon cancer (DCC) may be superior to lymph node status in predicting patient survival for intermediate stage colon cancer. A polymerase chain reaction (PCR)-based method for detecting DCC would be ideal as a prognostic indicator. DCC is an alternatively spliced molecule; thus, reliability of a PCR test for DCC will depend on amplifying only those regions of the molecule that are lost in the progression of colon cancer. For this reason, we studied a colon cancer cell line model at different stages of tumor progression to determine the alternative splice pattern for DCC. A commercially available colon cancer cell line system at different stages of tumor progression was used to identify which DCC exons are lost by western blot analysis, PCR, and RT-PCR techniques. Colon cancers express abnormal DCC transcripts. The proximal and distal exons are present (exons 2 and 28-29). Exons located in the center of the molecule are absent (6-7 and 18-23). This correlated to DCC protein loss in the cell lines. For clinical utility as a disease marker, exons in the middle portion of the DCC molecule that are spliced out should be utilized. Amplification of the proximal and distal regions will result in falsely concluding that DCC is present when its protein product is not expressed.

Adenocarcinoma↗

PubMed2001

Alternative mRNA splicing in colon cancer causes loss of expression of neural cell adhesion molecule.

BACKGROUND: The neural cell adhesion molecule (NCAM) has numerous isoforms resulting from alternative splicing of mRNA. The 3 major isoforms found in adult tissue are (1) a 120-kDa protein that is linked to the plasma membrane by glycosylphosphatidylinositol; (2) a 140-kDa form that has a transmembrane component and a cytoplasmic tail with unknown function; and (3) a 180-kDa isoform that has an intracellular protein that binds the cytoskeleton. NCAM is capable of homotypic binding and therefore plays a role in cell-cell adhesion for cells expressing the 180-kDa isoform by anchoring groups of cells into epithelial sheets. NCAM-180 is the isoform found in colonocytes, and loss of expression is associated with clinically aggressive colon cancers. METHODS: Western blotting and reverse transcriptase-polymerase chain reaction were used to screen commercially available cell lines for NCAM-180 expression. For cell-line pairs with differential NCAM-180 expression, exon analysis was performed with reverse transcriptase-polymerase chain reaction to determine where the molecule was spliced, culminating in failed expression. These results were confirmed with exon analysis in colon cancers harvested at the time of laparotomy. RESULTS: Analysis of a SW480 cell line (derived from a patient's primary colon cancer lesion) revealed NCAM-180 expression, whereas no expression was found in the SW620 cell line (derived from a metastatic lesion from the same patient). Exon analysis of NCAM mRNA transcripts from SW620 revealed that the transcripts were truncated after exon 12. This region correlates to an area between 2 fibronectin-III domains on the NCAM protein. CONCLUSIONS: The most common site for NCAM alternative splicing is between the 2 fibronectin-III domains corresponding to the border between exons 12 and 13 of the NCAM gene. Loss of NCAM-180 expression in aggressive colon carcinoma results from a splice defect in the same area, which may result in defective intracellular adhesion between colonocytes.

Alternative Splicing↗

PubMed2001

Body surface area prediction in normal-weight and obese patients.

None of the equations frequently used to predict body surface area (BSA) has been validated for obese patients. We applied the principles of body size scaling to derive an improved equation predicting BSA solely from a patient's weight. Forty-five patients weighing from 51.3 to 248.6 kg had their height and weight measured on a calibrated scale and their BSA calculated by a geometric method. Data were combined with a large series of published BSA estimates. BSA prediction with the commonly used Du Bois equation underestimated BSA in obese patients by as much as 20%. The equation we derived to relate BSA to body weight was a power function: BSA (m(2)) = 0.1173 x Wt (kg)(0.6466). Below 10 kg, this equation deviated significantly from the BSA vs. body weight curve, necessitating a different set of coefficients: BSA (m(2)) = 0.1037 x Wt (kg)(0.6724). Covariance of height and weight for patients weighing <80 kg reduced the Du Bois BSA-predicting equation to a power function, explaining why it provides good BSA predictions for normal-size patients but fails with obesity.

Body Height↗

PubMed2001

Reduced length of stay by implementation of a clinical pathway for bariatric surgery in an academic health care center.

Bariatric surgery is being performed in increasing numbers in an era when reimbursements are being reduced. Academic health centers bear the responsibility for training surgeons to perform these operations yet must keep costs to a minimum and retain high quality. The UCLA Bariatric Surgery Program developed a clinical pathway for the pre- and postoperative management for gastric bypass patients to achieve these goals. Medical records for 182 consecutive gastric bypass patients were retrospectively reviewed before implementation of the pathway (Group I) during the fiscal year of 1998/1999. Data on average length of stay, average intensive care unit length of stay, average standard variable cost, percentage readmission rate, and percentage return to the operating room were collected. This information was compared with the data collected prospectively from 182 patients after implementation of the pathway in July of 1999 (Group II) during the fiscal year of 1999/2000. Hospital cost per admission was reduced by 40 per cent in Group II compared with Group I (P < 0.02). The average length of stay was reduced from 4.05 days in Group I to 3.17 days in Group II (P < 0.033). Overall readmission rate was decreased from 4.2 per cent in Group I to 3.2 per cent in Group II (P < 0.05). There were no differences in morbidities between both groups. The pathway reduced costs by reducing the hospital length of stay, intensive care unit utilization, and readmission rates. Quality was maintained as evidenced by a similar pattern of postoperative morbidities yet readmission rates were reduced. Our results indicate that implementation of a clinical pathway for bariatric surgery reduces cost and improves quality of care in an academic institution.

Academic Medical Centers↗

PubMed2000

Percentage of burned body surface area determination in obese and nonobese patients.

BACKGROUND: The measurement of burn surface area is important during the initial management of burn patients for estimating fluid requirements and determining hospital admission criteria. The "rule of nines" is commonly used for this purpose. However, the proportional contribution of various major body segments to the total body surface area changes with obesity. Similarly infants have very large heads, altering the overall contribution of other body segments to the total body surface area. METHODS: Detailed body surface area measurements were made in 47 patients: 18 were of normal weight, 6 were moderately obese, and 23 were seriously obese. Published tables of similar measurements for infants were reviewed to determine how the rule of nines applied to these populations. The contribution of the major body segments to the overall body surface area was calculated and compared to estimates that would be derived for these segments from the rule of nines. RESULTS: The rule of nines provides reasonable estimates of body surface area for patients ranging from 10 to 80 kg. For obese patients weighing more than 80 kg a rule of fives is proposed: 5% body surface area for each arm, 5 x 4 or 20% for each leg, 10 x 5 or 50% for the trunk, and 2% for the head. For infants weighing less than 10 kg a rule of eights applies: 8% for each arm, 8 x 2 or 16% for each leg, 8 x 4 or 32% for the trunk, and 20% for the head. CONCLUSION: Various body parts differentially contribute to the total body surface area. Because these relationships remain relatively constant throughout growth, the rule of nines provides reasonable estimates for the determination of burned body surface area for most children and adults. These relationships break down for infants and obese adults and the proposed modifications to the rule of nines provide better estimates of surface area for these groups.

Adult↗

PubMed1998

Deletion of P15 (MTS2) in head and neck squamous cell carcinomas.

INTRODUCTION: The purpose of this study was to determine whether the multiple tumor suppressor 2 (MTS2) gene, encoding an inhibitor (p15) of cyclin D-dependent kinases 4 and 6 (cdk4, cdk6), is deleted in head and neck squamous cell carcinomas (HNSCC). There is a high frequency of LOH for the 9p21-p22 region in HNSCCs, as well as in gliomas, leukemias, and cell lines from multiple tumor types; thus, this region is suspected to contain a tumor suppressor gene or genes. P16 (MTS1), an inhibitor of cdk4 and cdk6, resides within the deleted 9p21 region in these tumors. A neighboring gene, p15 (MTS2), has biochemical properties similar to those of p16, but has not been characterized in HNSCC. METHODS: Twenty-one head and neck squamous cell carcinomas and their proximal margins were snap frozen at the time of surgical resection. DNA isolation was performed using standard phenol and chloroform extraction. Standard PCR methods were used with primers P15-1F and P15-1R, specific for exon 1 of the p15 gene, as described previously. All samples were amplified for beta-Globin as a positive control. PCR products were stained with ethidium bromide and run on 6% polyacrylamide gels. Expected sizes for the PCR products were p15, 532 bp, and beta-globin, 238 bp. Results. Of 21 proximal margins, all demonstrated normal amplification of p15 DNA, all having a visible 532bp PCR product. Of 21 HNSCC tumors, 9 showed no amplification of the p15 gene; none of these 9 neoplasms had visible PCR products. All proximal margins and head and neck squamous cell carcinomas demonstrated amplification of the beta-globin gene, indicating that the DNA used was of good quality. CONCLUSIONS: Although PCR is not a quantitative technique, densitometric analysis of PCR products showed it was unlikely that the p15 gene was present in more than a small fraction of the tumor cells. The amount of the p15 PCR product in these cells was less than 3% of that observed in reactions containing an equal amount of DNA from normal cells. We are the first to show an absence of normal p15 exon 1 gene amplification in nearly 50% of HNSCCs studied. Loss of the MTS2 gene product, p15, may contribute to the loss of cell cycle and growth regulation seen in HNSCC.

Carcinoma, Squamous Cell↗

PubMed1997

Tumor suppressor activity of neural cell adhesion molecule in colon carcinoma.

BACKGROUND AND AIMS: Neural Cell Adhesion Molecule (NCAM) is a well-characterized member of the immunoglobin superfamily. The structure of NCAM is similar to the tumor suppressor Deleted in Colon Carcinoma (DCC). NCAM has been found in some epithelial tissues and plays a role in tumorigenesis of some cancers. The purpose of the present study was to determine if NCAM is present in normal human colon. Once its presence was established, its function as a tumor suppressor was investigated. METHODS: Colon tumors and normal proximal margins were processed for reverse transcription-polymerase chain reaction (RT-PCR) of the NCAM-180 message. Immunohistochemistry of the tissue was performed to determine the distribution of NCAM. RESULTS: RT-PCR analysis demonstrated the presence of the NCAM-180 kD isoform in normal colonic epithelia. Immunohistochemistry showed NCAM on the basolateral surface of colonic epithelial cells of the villous tips. Tumors from 15 patients followed up for 4 years were studied. All seven tumors expressing NCAM-180 were from patients having a benign clinical course. Seven of eight tumors that lacked NCAM-180 were associated with aggressive clinical behaviors (presenting with obstruction, perforation or metastatic disease, or patient death within 18 months of presentation). The sole exception was in a villous adenoma excised from a patient who has had multiply recurrent polyps on follow-up. CONCLUSION: We conclude that like DCC, NCAM is an important colonic adhesion molecule that functions as a tumor suppressor.

Adenocarcinoma↗

PubMed1997

Intraislet regulation of pancreatic polypeptide secretion in the isolated perfused rat pancreas.

The present study is to determine if intraislet insulin or somatostatin regulate pancreatic polypeptide (PP) secretion in the isolated perfused rat pancreas by infusing insulin or somatostatin antisera. Isolated rat pancreata were stimulated with either 16.7 mM glucose (G) alone, G with antisomatostatin antibody (G + SA), or G with antiinsulin antibody (G + IA). G inhibited PP secretion -22 +/- 9.5 pM below basal, a decrease of 9 +/- 6.3% (n = 6; p = NS), G + IA inhibited PP secretion -10 +/- 27.2 pM below basal, a decrease of 20 +/- 15% (n = 7, p = NS), and G + SA stimulated PP secretion 18 +/- 7.1 pM above basal, an increase of 26 +/- 5% (n = 6; p < 0.05). G stimulated insulin secretion 3,144 +/- 210 pM above basal (n = 6, p < 0.05), and G + SA stimulated insulin secretion 2,695 +/- 195 pM above basal (n = 7; p < 0.05 vs. baseline, p = NS vs. G alone). G stimulated C-peptide secretion 886 +/- 175 pM above basal (n = 6; p < 0.05), G + SA stimulated C-peptide secretion 847 +/- 102 pM above basal (n = 7; p < 0.05, p = NS vs. G alone), and G + IA stimulated C-peptide secretion 834 +/- 93 pM above basal (n = 7; p < 0.05, p = NS vs. G alone). These data demonstrate that infusion of SA results in significant stimulation of PP secretion during high-G infusion, whereas IA has no effect. Infusions of SA or IA at the doses used have no effect on G-stimulated insulin or C-peptide secretion. This suggests that intraislet somatostatin may be an inhibitory regulator of PP secretion in the isolated perfused rat pancreas.

Animals↗

PubMed1995

Bicarbonate diffusion through mucus.

The mucus layer overlying duodenal epithelium maintains a pH gradient against high luminal acid concentrations. Despite these adverse conditions, epithelial surface pH remains close to neutrality. The exact nature of the gradient-forming barrier remains unknown. The barrier consists of mucus into which HCO3- is secreted. Quantification of the ability of HCO3- to establish and maintain the gradient depends on accurate measurement of this ion's diffusion coefficient through mucus. We describe new experimental and mathematical methods for diffusion measurement and report diffusion coefficients for HCO3- diffusion through saline, 5% mucin solutions, and rat duodenal mucus. The diffusion coefficients were 20.2 +/- 0.10, 3.02 +/- 0.31, and 1.81 +/- 0.12 x 10(-6) cm2/s, respectively. Modeling of the mucobicarbonate layer with this latter value suggests that for conditions of high luminal acid strength the neutralization of acid by HCO3- occurs just above the epithelial surface. Under these conditions the model predicts that fluid convection toward the lumen could be important in maintaining the pH gradient. In support of this hypothesis we were able to demonstrate a net luminal fluid flux of 5 microliters.min-1.cm-2 after perfusion of 0.15 N HCl in the rat duodenum.

Animals↗

PubMed1995

Modeling of the gastric gel mucus layer: application to the measured pH gradient.

The gastric gel mucus layer plays an important role in the defense against acid-induced injury. Previous investigations have modeled the interaction between the mucus, bicarbonate, acid moving towards the epithelial surface, and water carrying ions away from the epithelium. We measured the diffusion coefficient of protons through gastric mucus and applied this parameter to the model. Using the measured diffusion coefficient, we applied the model to previously published gastric mucus gel pH gradients to assess the relative contribution of bicarbonate or water fluxes in maintaining the gradient in the face of luminal acid. Mucus was harvested from the stomachs of anesthetized rats, mixed with bromphenol blue, and placed in capillary tubes. The tubes were submerged in 0.15 N HCl at 37 degrees C. The color change from blue to yellow was measured with time as the HCl migrated through the tube. From the distance and time data, the diffusion coefficient could be calculated. Controls of bromphenol blue in water were studied. The diffusion coefficient for water was 30.2 +/- 0.8 x 10(-6) cm2 s-1, almost identical to the standard value reported in the literature. The HCl diffusion coefficient through saline was 67.8 +/- 0.7 x 10(-6) cm2 s-1. For gastric mucus it was 5.4 +/- 1.3 x 10(-6) cm2 s-1. Application of this diffusion coefficient to the model and subsequently to observed pH gradients suggested that the most potent defense mechanism against concentrations of luminal acid is the bulk movement of water away from the epithelial surface through the mucus gel layer.

Animals↗

PubMed1994

Central vagal activation by TRH induces gastric hyperemia: role of CGRP in capsaicin-sensitive afferents in rats.

The role of calcitonin gene-related peptide (CGRP) in the vagal cholinergic-mediated increase in gastric mucosal blood flow (GMBF) induced by the stable thyrotropin-releasing hormone (TRH) analogue RX-77368 injected intracisternally (ic, 30 ng) was investigated in urethan-anesthetized rats using the hydrogen gas clearance technique. alpha-CGRP (14 micrograms.kg-1.h-1) or bethanechol (150 micrograms.kg-1.h-1) infused close intra-arterially to the stomach or RX-77368 injected intracisternally increased GMBF by 76, 102, and 131%, respectively, 30 min after administration. The CGRP antagonist, human CGRP-(8-37) [hCGRP-(8-37)], injected intravenously (15 micrograms/kg bolus and 3 micrograms.kg-1.h-1) inhibited by 100, 97, and 73% the gastric hyperemic response to alpha-CGRP, TRH analogue, and bethanechol, respectively, whereas the substance P antagonist CP-96,345 (3 mg/kg iv) had no effect. In capsaicin-pretreated rats, hCGRP-(8-37) no longer blocked the increase in GMBF induced by intracisternal RX-77368. These results suggest that the gastric hyperemic response to central vagal activation induced by intracisternal TRH analogue at 30 ng is mediated by local effector function of capsaicin-sensitive afferent fibers releasing CGRP.

Animals↗

PubMed1993

Gastric hyperemia accompanying acid secretion is not mediated by sensory nerves.

It is not known how the signal to increase gastric mucosal blood flow is passed from the gastric parietal cell layer to the resistance vessels in the submucosa. We tested the hypothesis that mucosal hyperemia accompanying stimulated gastric acid secretion is mediated by capsaicin-sensitive sensory nerves. Rats were denervated by systemic capsaicin treatment (125 mg/kg, subcutaneously, 10-14 days prior to experimentation). Acid secretion was stimulated by intravenous pentagastrin (4, 12, and 36 micrograms/kg/hr) and was measured by a continuous perfusion method. Mucosal blood flow was measured by the hydrogen gas clearance method. Sensory denervation did not affect basal blood pressure, gastric acid secretion, or mucosal blood flow. In control rats, increases in gastric mucosal blood flow and acid secretion were dose-related. With denervation, not only was there no inhibition of the blood flow response to acid secretion, but the dose-dependent rise in acid secretion was accompanied by increased mucosal blood flow that was out of proportion to the acid secretory response. The capsaicin-sensitive afferent fibers do not transmit the signal to increase gastric mucosal blood flow in response to stimulated acid secretion. It appears that sensory nerves modulate but do not mediate the mucosal hyperemic response to acid secretion.

Analysis of Variance↗

PubMed1993

Heterogeneous distribution of gastric mucosal blood flow with restraint stress in the rat.

Cold water immersion restraint (CWIR) is associated with gastric hypercontractility and gastric corpus erosions in the rat. Because the gastric blood flow response to CWIR has not been well defined, we performed the following study. Rats were implanted with force transducers, subjected to CWIR for 2 hr, and then blood flow was determined by the iodo[14C]antipyrine autoradiographic (IAP) technique. When compared to control animals, the CWIR-treated animals displayed foci of gastric corpus hyperemia with a marked and significant increase in blood flow in all layers of the gastric corpus. There was approximately a 100% increase in the mucosa and a 50% increase in the muscularis externa. The hyperemia was not uniform, but rather alternated every 2.1 +/- 0.2 mm with regions of low blood flow. Blood flow in the antrum and duodenum was unaffected by CWIR. We conclude that CWIR is associated with alternating regions of high and low blood flow only in the gastric corpus. Reduction of corpus mucosal blood flow might be due to the powerful gastric contractions associated with CWIR.

Animals↗

PubMed1993

Antisecretory and cytoprotective doses of enprostil do not alter gastric mucosal blood flow.

Prostaglandins of the E series are antisecretory and cytoprotective. Cytoprotection occurs in the deep but not superficial gastric mucosa. It has been hypothesized that the mechanism of cytoprotection involves increased gastric mucosal blood flow (GMBF). However, basal and stimulated gastric mucosal blood flow is greater in the deep than superficial corpus mucosa. The purpose of this study was to investigate the effect of a prostaglandin E2 analog, enprostil, on GMBF in the deep mucosa, where cytoprotection is observed, in both antisecretory and cytoprotective doses. Gastric mucosal blood flow in the deep half of the mucosa was measured by the hydrogen gas clearance method before, during and after intragastric perfusion of enprostil, 0.1-100 micrograms/kg, in urethane anesthetized rats. Enprostil did not alter GMBF in any of the doses tested. Therefore, the cytoprotective action of enprostil is mediated by factors other than a primary increase in GMBF.

Analysis of Variance↗

PubMed1993

The stomach as a system and the pathogenesis of experimental ulcer.

The stomach is prone to ulceration because of the hostile environment that exists within its lumen. The most important etiologic factor remains a topic of debate. We have considered the stomach as a system to lend insight into which pathophysiologic mechanisms might be most important. Systems are described by their content, hierarchy, entropy and interactions. The states of health, disease and death (i.e. ulceration) are represented by progressively increasing levels of entropy. It is argued that many of the purported causes of ulcer disease, such as acid back-diffusion or alcohol related necrosis, represent alterations in the system that affect small groups of cells that are low in the hierarchy and cause the tissue to enter the diseased state. We hypothesize that because blood flow is high within the hierarchy it represents the major homeostatic mechanism. If blood flow responds appropriately the system may return to the healthy state. If it does not the death of the system results in ulceration. Experimental evidence to support these contentions is presented.

Animals↗

PubMed1993

Cost-benefit analysis of the work-up for pancreatic cancer.

We reviewed the records of 126 patients with pancreatic cancer to assess the value of diagnostic tests. The most commonly performed studies were computed tomography (CT) (97% of patients), endoscopic retrograde cholangiopancreatography (ERCP) (44%), and fine-needle aspiration (FNA) (41%). Of 34 patients who were found to have a mass in the body or tail of the pancreas on CT, 13 underwent ERCP; the results found by ERCP did not affect the management of the patients, whereas the results of FNA in 12 patients eliminated the need for operation. Of 14 patients with suspected metastases as evidenced by CT, the results of 3 ERCPs had no impact, whereas 5 of 7 patients who had FNAs avoided operation. Of five patients with normal results on CT, three had an ERCP that identified tumor. Of 26 patients with atypical CTs, the results of 12 of 16 ERCPs and 3 of 5 FNAs confirmed cancer. In contrast, in 48 patients with a mass in the head of the pancreas and biliary dilatation, ERCP did not alter the patients' management; only 3 of 14 patients who had FNAs avoided operation. Thus, the results of ERCP rarely altered the management of the patient when the CT showed a mass but was useful when the scan was normal or atypical. FNA was helpful in patients with cancer in the body or tail of the pancreas or with suspected metastases and in confirming the diagnosis when the CT was inconclusive.

Adenocarcinoma↗