Suitability of different machine learning algorithms for the classification of the proportion of grassland-based forages at herd-level using mid-infrared spectral information from routine milk control.

As the call for an international standard for milk from grassland-based production systems continues to grow, so too do the monitoring and evaluation policies surrounding this topic. Individual stipulations by countries and milk producers to market their milk under their own grass-fed labels include a compulsory number of grazing days per year, ranging from 120 d for certain labels to 180 d for others, a specified amount of herbage in the diet or a prescribed dietary proportion of grassland-based forages (GBF) fed and produced on farm. As these multifarious policy and label requirements are laborious and costly to monitor on farm, fast economical proxies would be advantageous to verify the proportion of GBF consumed by the cows in the final product. With this in mind, we employed readily available mid-infrared spectral data (n = 1132 spectra) from routine milk controls to develop binary classification models for 4 main feed groups from a primarily forage-based diet: Total GBF (≥50% n = 955, ≥ 75% n = 599, ≥ 85% n = 356), pasture (≥20% n = 451, ≥ 50% n = 284, ≥ 70% n = 152), fresh herbage (pasture + fresh herbage indoor feeding, ≥ 20% n = 517, ≥ 50% n = 325, ≥ 70% n = 182) and whole plant corn (fresh + conserved) (≥10% n = 646, ≥ 30% n = 187), the latter as a negative control. We compared 4 machine learning methods to assess which statistical model performs best at discriminating these classes. Three of these models have not yet been tested for herd-level dietary proportion classification and all 4 follow completely different approaches: least absolute shrinkage and selection operator (LASSO), partial least squares discriminant analysis (PLS-DA), random forest (RF) and support vector machines (SVM). Seasonality has been a missing element from previous dietary herbage proportion classification models. As grazing and fresh herbage indoor feeding are highly dependent on the season, we developed an indicator to incorporate seasonality in a consistent, unbiased manner into our models. We also tested 3 sets of covariates. The first set included only mid-infrared spectra derived data, the second included mid-infrared spectra derived data plus seasonality indices and the third included mid-infrared spectra derived data, seasonality indices and additional herd specific information (DIM, breed and parity). Of the 4 machine learning algorithms tested for the binary classification of GBF proportion at herd level, LASSO and PLS-DA performed best according to evaluation metrics; however, the RF and SVM models were not far behind the best performing model evaluation metrics in each feed category. Our best performing model, the LASSO model containing seasonality indices and herd specific information, classified total GBF ≥50% with an accuracy of 78.6%, precision of 85.1%, sensitivity of 90.6%, specificity 14.1% and F1 score (harmonic mean of precision and sensitivity) of 87.7%, this was very similar to the PLS-DA model. Our results suggest that in general LASSO and PLS-DA machine learning algorithms perform better for dietary GBF classification than RF or SVM algorithms.

Robotic Heller myotomy: a safe operation with higher postoperative quality-of-life indices.

INTRODUCTION: Achalasia is a primary motility disorder of the esophagus that is treated most effectively with operative myotomy. Excellent outcomes with laparoscopic myotomy and fundoplication are well known. Heller myotomy utilizing a computer-enhanced (robotic) laparoscopic platform allows for a more precise dissection by utilizing the superior optics of a 3-dimensional camera and greater degrees of freedom provided by robotic instrumentation. How this affects outcome and quality of life is unknown. METHODS: We assessed patients' health perceptions using a standardized, validated, health-related, disease-specific quality-of-life metric. Sixty-one consecutive patients undergoing laparoscopic or robotic myotomy over a 6-year period were evaluated prospectively. All operations were performed using intraoperative manometric and endoscopic guidance and all except 5 patients had a fundoplication. The effects of the operation on health-related quality of life were evaluated with the Short Form (SF-36) Health Status Questionnaire and a disease-specific gastroesophageal reflux disease activity (GERD) activity index (GRACI) preoperatively and postoperatively. All patients completed the questionnaire at both time points. Patient scores were compared using 2-way repeated measures analyses of variance followed by the Tukey test. Operative time, estimated blood loss, duration of stay, intraoperative complication, and postoperative complications were analyzed. RESULTS: Thirty-seven patients had laparoscopic and 24 patients had robotic Heller myotomy. There was an increase in SF-36 overall evaluation of health postoperatively compared with preoperatively in both groups (P < .05). The robotic myotomy patients had better SF-36 Role Functioning (emotional) and General Health Perceptions (P < .05) compared with the laparoscopic group. The GRACI showed an equivalent improvement in severity of symptoms in both groups (P < .05). Operative time was 287 +/- 9 minutes for laparoscopic cases and 355 +/- 23 minutes for robotic cases. Estimated blood loss and duration of stay were not different between groups. There were 3 operative esophageal perforations (8%) during laparoscopic myotomy and all were repaired immediately. There were no perforations or operative complications in the robotic group. Neither group had any additional complications. CONCLUSIONS: Minimally invasive operative myotomy improves functional status and overall evaluation of health in patients with achalasia. Robotic myotomy had no intraoperative esophageal perforations compared with an 8% intraoperative rate during laparoscopic myotomy. Heller myotomy with partial fundoplication using a robotic platform appears to be a more precise and safer operation than laparoscopic myotomy with improved quality-of-life indices postoperatively compared with laparoscopic myotomy with fewer complications; this suggests that, in skilled hands, the robotic platform may be safer, with improved quality-of-life outcomes.

Synthesis and biological properties of 4-norleucine-neuropeptide Y; secondary structure of neuropeptide Y.

Neuropeptide Y (NPY) is a 36 amino acid peptide amide isolated from porcine brain. The NPY analog, 4-norleucine-NPY was synthesized by a solid-phase method and purified to homogeneity in 20% yield by reverse-phase chromatography. Investigation of the biological properties indicated that the analog is an agonist of NPY. Secondary structural analyses revealed that NPY and the analog exhibited predominantly alpha-helical and beta-sheet structures, respectively; however, experiments in trifluoroethanol indicated that the analog has the potential of assuming an alpha-helical structure. Based on circular dichroism (CD), Raman spectroscopy and Chou-Fasman analyses, a model has been proposed for the secondary structure of NPY.

Pulmonary lesions in atypical measles.

Atypical measles is a well-described entity which has a high frequency of pulmonary involvement. Resolution and shrinkage of the pneumonic infiltrates into nodular mass-like lesions have been cited only once before. Three cases of atypical measles pneumonia are described which demonstrate these pulmonary nodular sequelae. In one of the cases examined a nodular residuum has now persisted for five months. Atypical measles pneumonia should be considered as a diagnostic possibility before invasive investigations are performed in a patient who has a pulmonary nodule.

Von Hippel-Lindau disease in an adolescent.

Von Hippel-Lindau disease is a hereditary neoplastic syndrome that generally manifests in early adulthood but does present occasionally in adolescence. In the past, diagnosis and management of this disorder fell within the domain of internists and surgeons. Because pediatricians are now seeing older patients, they must learn to recognize the various components of this disorder. Additionally, they must be able to assure appropriate medical evaluation and follow-up and also arrange for genetic counseling. Pediatricians already attuned to the benefits of preventive medicine should find themselves uniquely qualified to provide the level of care that this disease requires.

Passive smoking alters lipid profiles in adolescents.

Although cigarette smoking is associated with elevation of plasma lipid levels and changes in lipoprotein distribution, it is not known whether passive smoking is associated with an alteration in lipid profiles. The relation between plasma cotinine, a marker of exposure to tobacco smoke, and lipid profiles was studied in healthy adolescents from a suburban New York high school district who were undergoing preparticipation sports physicals. Forty-four percent of the adolescents reported that one or both parents currently smoked. Eleven percent of the adolescents had plasma cotinine concentrations greater than or equal to 2.5 ng/mL, the level considered indicative of exposure. Adolescents with two smoking parents had significantly higher plasma cotinine concentrations after adjustment for other factors than adolescents whose parents did not smoke. Plasma cotinine concentration greater than or equal to 2.5 ng/mL was associated with an 8.9% greater ratio of total cholesterol to high-density lipoprotein cholesterol (P less than .003) and a 6.8% lower high-density lipoprotein cholesterol (P less than .03). These results suggest that passive smoking, like active smoking, leads to alterations in lipid profiles predictive of an increased risk of atherosclerosis.

Death due to chronic syrup of ipecac use in a patient with bulimia.

A 17-year-old girl presented with malaise, weakness, palpitations, dysphagia, myalgias, and weight loss of 1 month's duration. Within 24 hours of admission to the hospital, she had hypotension unresponsive to medical management, intractable congestive heart failure, and arrhythmias; she died. Several empty bottles of syrup of ipecac were later found among her belongings. Syrup of ipecac is commonly used to induce emesis in patients who had ingested toxic substances. The chief pharmacologic property of this agent is due to its alkaloid component, emetine. There have been many previous reports of death due to emetine poisoning in patients receiving ipecac fluid extract and in those treated for amoebic dysentery. However, the literature cites only three case reports of fatalities secondary to chronic ipecac use as a means of losing weight. This is the first report of a death due to chronic ipecac use in an adolescent patient with bulimia. Emetine persists in the body for long periods, and in patients who have ingested it chronically, emetine is extremely toxic, specifically to cardiac smooth and skeletal muscles. With an increased awareness of the importance of weight control in the adolescent age group, the physician must carefully evaluate these patients for the use of emetics.

Reduction in pulmonary function and increased frequency of cough associated with passive smoking in teenage athletes.

Previous studies have suggested that passive smoking (involuntary inhalation of tobacco smoke by nonsmokers) reduces small airways function. We evaluated the exposure to passive smoking and its effects on pulmonary function and symptoms in a group of 12- to 17-year-old high school athletes (N = 209; 119 boys and 90 girls) at their annual presport participation physical examinations. A structured interview was used to assess pulmonary symptoms, personal smoking habits, and passive cigarette smoke exposure. All athletes performed forced expiratory maneuvers on a portable spirometer. We measured forced vital capacity, forced expiratory volume in 1 second, and forced expiratory flow 25% to 75% (FEF25-75). The best of three FEF25-75 measured was used. Less than 70% of predicted FEF25-75 was considered abnormal. Of the 209 athletes, 7.7% were active smokers and were excluded. Of the remaining 193 athletes, 68.4% were currently exposed to passive smoking. We found a fourfold increase in incidence of low FEF25-75 and/or cough in athletes exposed to passive smoking compared with athletes not exposed: 18 of 132 exposed athletes (13.6%) had low FEF25-75 and/or cough compared with two of 61 unexposed athletes (3.3%) who had low FEF25-75 and cough (P = .02). Boys were more frequently exposed to passive smoking than girls (74% of boys [80/108] v 61% of girls [52/85] ), but the effects were more pronounced in girls. These data show a relationship between exposure to passive smoking and early pulmonary dysfunction in young athletes. The frequent exposure to passive smoke and the high prevalence of dysfunction in this population, generally considered to be healthy, is of particular concern.

In vivo metabolism of 3,2'-dimethyl-4-aminobiphenyl (DMAB) bearing on its organotropism in the Syrian golden hamster and the F344 rat.

The in vivo metabolism of tritiated DMAB was examined in male Syrian golden hamsters, which are susceptible to both urinary bladder and intestinal carcinogenesis by this agent and in male F344 rats in which intestinal tumors represent the main lesions. Evidence was obtained for the presence of the N-hydroxy-N-glucuronide of DMAB as a major metabolite in hamster urine and bile and in rat bile but not urine. The routes of excretion of this metabolite, which may represent a transport form of the ultimate carcinogen, correlate well with the main tumor sites in the two species. Other metabolites partially identified were the sulfates and glucuronides of C-hydroxylated DMAB and C-hydroxylated-N-acetyl DMAB.

Vocal cord paralysis in myasthenia gravis following anesthesia.

Our patient demonstrated two unusual features: (1) severe upper airway obstruction due to bilateral vocal cord paralysis at first manifestation of a myasthenic syndrome; and (2) precipitation of this syndrome following surgery and anesthesia with succinylcholine. In addition, this case illustrates use of ventilatory measurements through an endotracheal tube for documenting the patient's progress and response to medications, most dramatically during performance of an edrophonium test.

Comparison of distal and proximal splenorenal shunts: a ten-year experience.

BACKGROUND: This study evaluated the effectiveness of distal (DSRS) versus the central or proximal (PSRS) splenorenal shunts in the elective treatment of bleeding varices. METHODS: A series of 48 patients with portal hypertension and established variceal bleeding were randomized to undergo PSRS or DSRS. Preoperative evaluation included endoscopic examination, angiography, serum amino acid profile, liver chemistry studies, and neurologic evaluation. Any patient with significant ascites and hepatofugal flow underwent PSRS shunt procedures; the remainder were randomized prospectively. RESULTS: Between 1979 and 1989, 29 patients underwent PSRS and 19 underwent DSRS. The mean length of follow-up was 48 months. The groups were equivalent with regard to age, gender, child's class, number of preoperative bleeds, and cause of disease. No difference was found in any of the factors measured. In particular there were no differences in the operative mortality rate (17% PSRS; 11% DSRS), 5-year survival rate (52% PSRS; 52% DSRS), rebleeding (34% PSRS; 32% DSRS), shunt occlusion (7% PSRS; 11% DSRS), development of individual episodes of postoperative encephalopathy (28% PSRS; 26% DSRS), chronic postoperative encephalopathy (17% PSRS; 11% DSRS), or mean branched-chain/aromatic amino acid ratios (PSRS = 0.88 +/- 0.05; DSRS = 0.66 +/- 0.05). CONCLUSIONS: The results do not support the contention that DSRS is associated with either greater survival or less encephalopathy than PSRS.

Long-term evaluation of extended thymectomy with anterior mediastinal dissection for myasthenia gravis.

BACKGROUND: Thymectomy for the treatment of myasthenia gravis (MG) is well established. The extent of resection, however, remains a source for debate. Outcomes for newer surgical techniques need to be compared to more extensive procedures. METHODS: A retrospective review was done of 64 consecutive patients who underwent transsternal thymectomy with extended anterior mediastinal dissection for MG between 1979 and 2000 and who were operated on by a single surgeon. RESULTS: Fifty-six patient charts were available, providing 58 operative procedures. Three patients had died of unrelated causes. The mean age of symptom onset was 36.0 +/- 2.5 years, with a mean duration of 3.3 +/- 0.5 years until surgery was undertaken. The mean length of follow-up was 6.8 +/- 0.8 years. Operative procedures were associated with a 10.3% major morbidity rate and no mortality. Drug-free remission was achieved in 50.0% of the patients, and symptoms were absent or improved in 76.8% of the patients. Patients followed up long-term (>10 years) achieved the greatest remission rate (71.4%) and symptomatic improvement (85.7%). After thymectomy, the mean dosages of prednisone and Mestinon decreased by 69.3% and 58.8%, respectively. CONCLUSIONS: Extended thymectomy provides excellent overall symptom improvement, which is enhanced over time. This review provides a basis for long-term comparison with other less invasive and perhaps less extensive procedures.

Proximal jejunal and biliary effects on the enteroinsular axis.

The objective of this study was to investigate the roles of the proximal jejunum and endogenous bile within the proximal jejunum on the enteroinsular axis. Twelve Sprague-Dawley rats underwent proximal jejunal bypass, 11 rats underwent Roux-en-Y cholangiojejunostomies, and 12 rats underwent sham operations. After 3 months, oral glucose tolerance tests were performed in unanesthetized animals and venous blood was collected for plasma glucose and insulin measurements. The surgical procedures did not significantly affect the basal glucose and insulin levels compared with sham-operated animals. The insulin response in rats with excluded proximal jejunal segments was inhibited. The decreased insulinogenic index seen in these animals indicates a possible diabetogenic effect of this procedure. An oral glucose challenge resulted in significant hyperinsulinemia, with an increased insulinogenic index in animals that had undergone Roux-en-Y cholangiojejunostomies. These findings suggest that bile is a potential mediator in the proximal jejunal involvement in the enteroinsular axis.

Addition of glucagon to total parenteral nutrition (TPN) prevents hepatic steatosis in rats.

Hepatic steatosis is one of the two principal hepatic complications of total parenteral nutrition (TPN), the other being cholestasis. While the cause is uncertain, an excess of carbohydrate calories in rats leads to an elevated portal insulin/glucagon (I/G) molar ratio, periportal fatty infiltration, and increased total hepatic lipid content. Insulin causes fatty acid biosynthesis, whereas glucagon causes hepatic release and inhibition of fatty acid synthesis. Thus we attempted to add glucagon to lower the I/G to see if this would affect the degree of hepatic fatty infiltration by encouraging hepatic fat mobilization. Adult rats (n = 21) received internal jugular catheters; Group 1 (n = 7) was given saline solution (3 ml/h) and chow ad libitum; Group 2 (n = 7), 25% dextrose-base (D25W) TPN solution; Group 3 (n = 7), D25W TPN + 33 micrograms/100 gm/day glucagon. At 7 days portal and peripheral venous blood samples were drawn for insulin and glucagon radioimmunoassay and blood glucose determination; livers were removed for histologic study and lipid determination. Blood glucose did not differ in any group. Hepatic lipid and peripheral and portal venous I/G were increased and periportal fatty infiltration was extensive in Group 2, whereas hepatic lipid and I/G were decreased and periportal fatty infiltration was absent in glucagon-infused rats (Group 3). An abnormally high I/G ratio in portal blood elicited by high-glucose TPN may be responsible, at least in part, for hepatic steatosis. By increasing hepatic lipid export, addition of glucagon to TPN may play a major role in decreasing hepatic steatosis.

Use of omeprazole in the management of giant duodenal ulcer: results of a prospective study.

BACKGROUND: Giant duodenal ulcer (GDU) is generally thought to require surgical intervention. Proton pump inhibitors have beneficial effects in peptic ulcer disease, but their role in GDU disease is unknown. We examined the use of omeprazole in GDU management. METHODS: Twenty-eight patients were diagnosed with GDU. One patient required immediate operative intervention. The remaining 27 were placed on omeprazole (40 mg daily). When ulcer healing was documented by endoscopy, the patients were placed on oral histamine-2 receptor antagonist therapy. RESULTS: Of the 28 study patients, 20 (71.4%) did not require operative intervention, and 8 (28.6%) required operation for ulcer complications. Of the 15 patients with adherent clot or a visible vessel at initial endoscopy, 7 (46.7%) required operative intervention, as compared with 1 (7.7%) of the 13 patients without a visible vessel or adherent clot. This difference was statistically significant (P < .05). Twenty-three patients underwent antral biopsy and/or enzyme-linked immunosorbent assay for Helicobacter pylori, and 9 (39.1%) had a positive result. CONCLUSIONS: Omeprazole is effective in the treatment of GDU disease. An adherent clot or a visible vessel at endoscopy indicates a higher likelihood of complications requiring operation. The relatively low H pylori infection rate, as compared with other peptic ulcer disease, may indicate a different pathophysiology in GDU.

Management of myasthenia gravis by extended thymectomy with anterior mediastinal dissection.

BACKGROUND: Thymectomy has continued to gain acceptance as definitive treatment for myasthenia gravis. Because of the nature of thymic embryology with scattered rests throughout the anterior mediastinum, we advocate a transsternal thymectomy with extended anterior mediastinal dissection. METHODS: A series of 48 patients with myasthenia gravis treated by thymectomy between 1979 and 1991 were reviewed. RESULTS: The mean length of duration of disease from onset to operation was 48.7 +/- 11.3 months, and the mean length of follow-up was 51.6 +/- 6.5 months. The operation was associated with a 21% morbidity rate (4% major morbidity) with no deaths. Forty-five patients (94%) have improved, requiring decreased medication. The overall drug-free remission rate was 42%. Of the 20 patients in remission, three had thymomas and four had hyperplastic glands. All of the patients who achieved drug-free remission were classified as Osserman's I or II. CONCLUSIONS: An aggressive surgical approach to myasthenia gravis can result in a high percentage of overall improvements and drug-free remissions. The best results are achieved in patients with lower-stage disease. Therefore transsternal extended thymectomy for myasthenia gravis appears to be the procedure of choice and should be advocated as soon as the diagnosis is made and the patient stabilized.

Implementation of a clinical pathway decreases length of stay and hospital charges for patients undergoing total colectomy and ileal pouch/anal anastomosis.

BACKGROUND: Clinical pathways are increasingly being used by hospitals to improve efficiency in the care of certain patient populations; however, little prospective data are available to support their use. This study examined whether using a clinical pathway for patients undergoing ileal pouch/anal anastomosis, a complex procedure in which we had extensive practical experience, affected hospital charges or length of stay (LOS). METHODS: A clinical pathway was developed to serve patients undergoing elective total colectomy and ileal pouch/anal anastomosis. All operations were performed by two attending physicians (J.E.F., M.S.N.). Before implementation, 10 pilot patients were prospectively monitored to ensure that hospital charges were accurately generated. In addition, charge audits were performed by an outside agency to verify the accuracy of the hospital bills. The pathway was then implemented, and 14 patients were prospectively analyzed. RESULTS: In all patients the principal diagnosis was ulcerative colitis, with the exception of three patients with familial polyposis. Mean external audit charges were within 2% of the hospital bills; therefore the hospital bills were used in all calculations. The mean LOS decreased from 10.3 days to 7.5 days (p = 0.046) for patients on the pathway versus pilot patients. Mean hospital charges also decreased significantly, from $21,650 to $17,958 per patient (p = 0.005). CONCLUSIONS: Implementation of a clinical pathway, even for an operation in which the surgeon has much experience, is an effective method for reducing LOS and charges for patients. This is likely the result of interdisciplinary cooperation, elimination of unnecessary interventions, and streamlined involvement of ancillary services. These results support the development of clinical pathways for procedures that involve routine preoperative and postoperative care. In addition, the benefits of clinical pathways should increase proportionally with increasing case volume for a particular procedure.

Laparoscopic splenectomy by the lateral approach: a safe and effective alternative to open splenectomy for hematologic diseases.

BACKGROUND: The purpose of this study was to compare the clinical outcomes and expense of laparoscopic splenectomy by the lateral approach with open splenectomy for the treatment of hematologic diseases. METHODS: Medical records of 20 matched patients undergoing open splenectomy and lateral approach laparoscopic splenectomy were retrospectively reviewed detailing perioperative course, clinical outcome, and hospital charges. RESULTS: Patients undergoing laparoscopic splenectomy (n = 10) experienced longer anesthesia (324 versus 176 minutes; p < 0.05) and operative times (261 versus 131 minutes; p < 0.05) than those undergoing open splenectomy (n = 10). No difference was noted in both intraoperative and postoperative packed red blood cells transfused. Laparoscopic splenectomy resulted in a shorter duration of nasogastric decompression (1.2 versus 2.6 days), more rapid resumption of normal oral intake (1.9 versus 4.4 days), and earlier hospital dismissal (3.0 versus 5.8 days). Although hospital charges were not significantly higher in the laparoscopic group ($17,071.00 versus $13,196.00; p > 0.05), operative charges were always significantly higher. CONCLUSIONS: When compared with open splenectomy, lateral approach laparoscopic splenectomy allows a more rapid return of normal gastrointestinal function and shorter hospital stay. The operative expense of laparoscopic splenectomy is significantly higher; however, the overall hospital expense is not. If costs can be decreased, the lateral approach laparoscopic splenectomy will be the preferred operative approach.

The pull-through procedure: technical factors in influencing outcome, with emphasis on pouchitis.

BACKGROUND: The purpose of the study was to review those features that we believed to be critical to the successful performance of the ileal pouch-anal anastomosis, or pull-through, procedure, and specifically the complication of pouchitis. METHODS: The charts of 205 patients who successfully underwent ileal pouch-anal anastomosis procedure were reviewed. No follow-up was available in five patients; therefore, the basis of this report and its analysis was based on 200 consecutive procedures in which at least two of the three surgeons participated. Particular emphasis was placed on continence, particularly nighttime continence. The incidence of pouchitis, either a single episode or intermittent episodes, was surveyed. Particular attention was paid to the level of rectal mucosectomy and anastomosis at the top of the columns of Morgagni, thus retaining the transitional zone. RESULTS: Only 5% of patients were incontinent in the absence of pouchitis. Twenty-five patients (13%) wore a pad at night, but only nine (5%) wore a pad during the day. Of those patients with pouchitis, 6% (12) have had a single episode and 12% (23) were intermittently on medication. Therapy of pouchitis was usually carried out with ciprofloxacin 500 mg by mouth everyday or twice a day. CONCLUSIONS: Ileal pouch-anal anastomosis is an excellent procedure, provided technical details are adhered to. Satisfactory outcome with respect to nighttime continence can be achieved with rectal mucosectomy with minimal manipulation and retaining the transitional epithelium, performing the pouch anastomosis at the top of the columns of Morgagni. The incidence of pouchitis is disappointing but need not be inhibiting of either patients or carrying out this life-saving procedure in patients with ulcerative colitis and familial polyposis.

Lipid-free total parenteral nutrition and macrophage function in rats.

Certain lipids are immunosuppressive when used for nutritional support, while other lipids and nutritional additives may enhance immunologic function. We hypothesized that total parenteral nutrition (TPN) may be immunosuppressive irrespective of lipids. Twenty-four rats underwent central vein catheterization and received either intravenous saline solution and oral chow or TPN alone. At 7 or 14 days, the animals were killed. Splenic and bone marrow macrophages were isolated and cultured in either M199 medium alone or were stimulated with Escherichia coli lipopolysaccharide. The supernatants were tested for prostaglandin E2 and C3. The splenic prostaglandin E2 levels were significantly higher in the TPN group following lipopolysaccharide stimulation at 7 days but not at 14 days. Administration of TPN to rats, even without lipids, may be immunosuppressive through the release of prostaglandin E2 from splenic macrophages following a septic challenge. This effect appears to be abolished after 14 days of TPN infusion.