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Biomedical subjects

Peter Ott

Publications and source records attributed to Peter Ott.

At least 37 records · Page 2Linked to original sources
PubMed2004

Attenuated and nonproductive viral transcription in the lymphatic tissue of HIV-1-infected patients receiving potent antiretroviral therapy.

Human immunodeficiency virus type 1 (HIV-1) RNA that persists in the lymphoid tissue of patients despite treatment with highly active antiretroviral therapy (HAART) may represent extracellular virions or intracellular RNAs residing within HIV-infected cells. To further characterize residual viral transcription, tonsil biopsy specimens from patients receiving long-term HAART, untreated patients, and patients undergoing 2 weeks of structured treatment interruption were analyzed by polymerase chain reaction quantification of virion-encapsidated RNA, intracellular unspliced HIV RNA (HIV UsRNA), multiply spliced HIV RNA encoding tat and rev (HIV MsRNA), and HIV DNA. Tonsil biopsy specimens from viremic patients harbored high amounts of virions, which primarily stemmed from local production, as indicated by a strong correlation of extracellular tonsillar RNA with intracellular HIV-1 nucleic acid levels but not with plasma viremia, and as shown by phylogenetic analysis of clonal env sequences from lymphoid tissue and plasma. In patients receiving HAART, intracellular HIV UsRNA persisted at significantly decreased levels, whereas HIV MsRNA and lymphoid virion levels were depleted. Thus, residual lymphoid HIV-1 RNA in patients receiving HAART indicates attenuated viral transcription in HIV-1-infected cells that lack virion production.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Blood-brain barrier permeability to ammonia in liver failure: a critical reappraisal.

In patients with acute liver failure (ALF), hyperammonemia is related to development of cerebral edema and herniation. The present review discusses the mechanisms for the cerebral uptake of ammonia. A mathematical framework is provided to allow a quantitative examination of whether published studies can be explained by the conventional view that cerebral uptake of ammonia is restricted to diffusion of the unprotonated form (NH(3)) (the diffusion hypothesis). An increase in cerebral blood flow (CBF) enhanced ammonia uptake more than expected, possibly due to recruitment or heterogeneity of brain capillaries. Reported effects of pH on ammonia uptake were in the direction predicted by the diffusion hypothesis, but often less pronounced than expected. The published effects of mannitol, cooling, and indomethacin in experimental animals and patients were difficult to explain by the diffusion hypothesis alone, unless dramatic changes of capillary surface area or permeability for ammonia were induced. Therefore we considered the possible role of membrane protein mediated transport of NH(4)(+) across the blood-brain barrier (BBB). Early tracer studies in Rhesus monkeys suggested that NH(4)(+) is responsible for 20% or even more of the transport of ammonia from plasma to brain. In other locations, such as in the thick ascending limb of Hendle's loop and in isolated astrocytes, transport protein mediated translocation of NH(4)(+) is predominant. Many of the ion-transporters involved in renal NH(4)(+) reabsorbtion are also present in brain capillary membranes and could mediate uptake of NH(4)(+). Astrocytic uptake of NH(4)(+) is associated with increased extracellular K(+), which is a potent cerebral vasodilator. Such interference between transport of NH(4)(+) and other cations could be clinically important because increased cerebral blood flow often precedes cerebral herniation in acute liver failure. We suggest that protein mediated transport of NH(4)(+) through the brain capillary wall is a realistic possibility that should be more intensely studied.

Ammonia↗
PubMed2004

Galactose elimination capacity as a prognostic marker in patients with severe acetaminophen-induced hepatotoxicity: 10 years' experience.

BACKGROUND & AIMS: Patients with acetaminophen-induced fulminant hepatic failure may have the capacity for recovery if sufficient liver cell mass remains to allow regeneration. We investigated the prognostic potential of the galactose elimination capacity (GEC) as a noninvasive measurement of functioning liver cell mass in severe acetaminophen-induced hepatotoxicity. METHODS: All patients admitted with acetaminophen poisoning during a 10-year period were studied retrospectively. A total of 220 patients who had at least one GEC performed were included in the study. RESULTS: The GEC was lower in patients with than without hepatic encephalopathy (14.5 +/- 5.6 micromol/min/kg vs. 23.2 +/- 6.7 micromol/min/kg; P < 0.0001). Among patients with hepatic encephalopathy, the GEC was significantly higher in spontaneous survivors than in nonsurvivors (16.8 +/- 5.6 micromol/min/kg vs. 12.2 +/- 4.7 micromol/min/kg; P < 0.0001). In a logistic regression analysis, GEC was associated independently with mortality (odds ratio: 1.28 per 1 micromol/min/kg decrease in GEC; 95% confidence interval: 1.14-1.45). A threshold GEC of 16.5 micromol/min/kg to identify nonsurvivors had a sensitivity of 90%, a specificity of 72%, a positive predictive value of 49%, and a negative predictive value of 96%. None of 14 patients with hepatic encephalopathy and a GEC less than 10 micromol/min/kg survived. CONCLUSIONS: The GEC was strongly associated with development of hepatic encephalopathy and death from acetaminophen-induced fulminant hepatic failure. The GEC was too unspecific to be used alone for identification of transplantation candidates, but it may be useful as a supplement to other selection criteria.

Acetaminophen↗
PubMed2004

Two hearts and one defibrillator.

A patient who had undergone heterotopic heart transplantation and placement of an implantable cardioverter defibrillator in his native heart underwent generator change. Defibrillation testing induced ventricular fibrillation in his donor heart. To prevent this potentially lethal complication, defibrillator shock therapy must be synchronized to the donor heart R wave.

Aged↗
PubMed2004

Splanchnic metabolism in acute liver failure and sepsis.

PURPOSE OF REVIEW: A number of papers have suggested that the splanchnic circulation and oxidative metabolism are compromised in critical illness. This review discusses this hypothesis and outlines the recent advances in the understanding of splanchnic metabolism with special focus on acute liver failure and hyperdynamic sepsis. RECENT FINDINGS: Splanchnic blood flow, oxygen delivery, and consumption are increased in both acute liver failure and sepsis. The capability of the liver to extract oxygen, even under extreme conditions, renders the liver less prone to hypoxia. A common feature of acute liver failure and sepsis is a hypermetabolic state with enhanced glycolysis and production of lactate and pyruvate. Human studies on other features of intermediary metabolism are sparse, but there are indications that several intermediary processes are severely compromised in patients with acute liver failure, whereas these processes are maintained in sepsis. SUMMARY: There is increasing evidence that both acute liver failure and sepsis are accompanied by a hypermetabolic state in the hepatosplanchnic area, characterized by enhanced glycolysis and hyperlactatemia. This should not be rigorously interpreted as an indication of hypoxia. In fact, clinically important splanchnic hypoxia may be a relatively uncommon phenomenon in such patients.

Humans↗
PubMed2004

Glucose ingestion attenuates the exercise-induced increase in circulating heat shock protein 72 and heat shock protein 60 in humans.

Heat shock protein (Hsp) 72 is a cytosolic stress protein that is highly inducible by several factors including exercise. Hsp60 is primarily mitochondrial in cellular location, plays a key role in the intracellular protein translocation and cytoprotection, is increased in skeletal muscle by exercise, and is found in the peripheral circulation of healthy humans. Glucose deprivation increases Hsp72 in cultured cells, whereas reduced glycogen availability elevates Hsp72 in contracting human skeletal muscle. To determine whether maintained blood glucose during exercise attenuates the exercise-induced increase in intramuscular and circulating Hsp72 and Hsp60, 6 males performed 120 minutes of semirecumbent cycling at approximately 65% maximal oxygen uptake on 2 occasions while ingesting either a 6.4% glucose (GLU) or sweet placebo (CON) beverage throughout exercise. Muscle biopsies, obtained before and immediately after exercise, were analyzed for Hsp72 and Hsp60 protein expression. Blood samples were simultaneously obtained from a brachial artery, a femoral vein, and the hepatic vein before and during exercise for the analysis of serum Hsp72 and Hsp60. Leg and hepatosplanchnic blood flow were measured to determine Hsp72-Hsp60 flux across these tissue beds. Neither exercise nor glucose ingestion affected the Hsp72 or Hsp60 protein expression in, or their release from, contracting skeletal muscle. Arterial serum Hsp72 increased (P < 0.05) throughout exercise in both trials but was attenuated (P < 0.05) in GLU. This may have been in part because of the increased (P < 0.05) hepatosplanchnic Hsp72 release in CON, being totally abolished (P < 0.05) in GLU. Serum Hsp60 increased (P < 0.05) after 60 minutes of exercise in CON before returning to resting levels at 120 minutes. In contrast, no exercise-induced increase in serum Hsp60 was observed in GLU. We detected neither hepatosplanchnic nor contracting limb Hsp60 release in either trial. In conclusion, maintaining glucose availability during exercise attenuates the circulating Hsp response in healthy humans.

Adult↗
PubMed2003

Anti-HIV-1 activity of leflunomide: a comparison with mycophenolic acid and hydroxyurea.

BACKGROUND: Leflunomide inhibits de novo pyrimidine synthesis by inhibiting the activity of dihydroorotic acid dehydrogenase and has other immunomodulatory properties that make it a promising candidate for an anti-HIV drug. OBJECTIVES: To compare the anti-HIV activity of leflunomide with that of the immunomodulatory drugs hydroxyurea and mycophenolic acid; to assess whether there is an additive or synergistic effect when leflunomide is used in conjunction with mycophenolic acid; and to characterize the molecular mechanism of the anti-HIV activity of leflunomide. METHODS: Anti-HIV activity was examined in peripheral blood mononuclear cells. CD4 cell survival was examined in tonsillar lymphocytes by fluorescence-activating cell sorting. RESULTS: Leflunomide decreased HIV replication by approximately 75% at concentrations that can be obtained with conventional dosing. This activity was similar to that of hydroxyurea but superior to mycophenolic acid. Leflunomide and mycophenolic acid together have modest additive anti-HIV effects. Restoration of HIV replication by uridine indicates that leflunomide's primary mechanism at lower concentrations is inhibition of dihydroorotic acid dehydrogenase while at higher concentrations additional mechanisms may be involved. CONCLUSIONS: Leflunomide's anti-HIV activity and clinical profile make it an attractive candidate for further study of its effects. Since HIV RNA levels are an effective predictor of AIDS-free survival, leflunomide's partial suppression of HIV RNA may be valuable in certain patients.

Anti-HIV Agents↗
PubMed2003

Glucose ingestion attenuates interleukin-6 release from contracting skeletal muscle in humans.

To examine whether glucose ingestion during exercise affects the release of interleukin-6 (IL-6) from the contracting limb, seven men performed 120 min of semi-recumbent cycling on two occasions while ingesting either 250 ml of a 6.4 % carbohydrate (GLU trial) or sweet placebo (CON trial) beverage at the onset of, and at 15 min intervals throughout, exercise. Muscle biopsies obtained before and immediately after exercise were analysed for glycogen and IL-6 mRNA expression. Blood samples were simultaneously obtained from a brachial artery and a femoral vein prior to and during exercise and leg blood flow was measured by thermodilution in the femoral vein. Net leg IL-6 release, and net leg glucose and free fatty acid (FFA) uptake, were calculated from these measurements. The arterial IL-6 concentration was lower (P < 0.05) after 120 min of exercise in GLU, but neither intramuscular glycogen nor IL-6 mRNA were different when comparing GLU with CON. However, net leg IL-6 release was attenuated (P < 0.05) in GLU compared with CON. This corresponded with an enhanced (P < 0.05) glucose uptake and a reduced (P < 0.05) FFA uptake in GLU. These results demonstrate that glucose ingestion during exercise attenuates leg IL-6 release but does not decrease intramuscular expression of IL-6 mRNA.

Administration, Oral↗
PubMed2003

Cardiac sarcoidosis masquerading as right ventricular dysplasia.

Patients with cardiac sarcoidosis may present with clinical and morphological features similar to arrhythmogenic right ventricular dysplasia (ARVD) or cardiomyopathy (ARVC). Three cases of cardiac sarcoidosis are presented that clinically mimicked ARVD or ARVC until a pathology diagnosis of sarcoidosis was made at biopsy or autopsy. A diagnostic distinction, while often difficult to make, is important since treatment with corticosteroids may benefit those with sarcoidosis but is not expected to be useful in cases with ARVD or ARVC.

Adult↗
PubMed2003

Plasma concentration of Gc-globulin is associated with organ dysfunction and sepsis after injury.

OBJECTIVE: Clinical and experimental studies suggest that the proteins of the extracellular actin scavenger system have a role in the pathophysiological processes taking place in critically ill and injured patients. Circulating levels of Gc-globulin and gelsolin are reduced shortly after severe trauma, and admission levels of Gc-globulin are associated with survival. Herein, we sought to measure the association between admission levels of Gc-globulin and postinjury organ dysfunction and infection. We also wanted to describe the serial changes in Gc-globulin in these severely injured patients. DESIGN: Prospective cohort. SETTING: Intensive care unit at a county hospital that serves as a level one trauma center. PATIENTS: Ninety-eight consecutive trauma victims admitted to the intensive care unit for >24 hrs during a 4-month period. MEASUREMENTS AND MAIN RESULTS: Circulating levels of Gc-globulin were measured by using immunonephelometry. All patients were evaluated daily to obtain the necessary data for assessment of organ dysfunction and sepsis. The median Gc-globulin concentration at admission was 127 mg/L in patients who developed severe multiple organ dysfunction compared with 184 mg/L in patients who did not (p =.001). The admission level of Gc-globulin was comparable to known risk factors such as age and injury severity score, regarding development of organ dysfunction. Plasma concentrations of Gc-globulin remained significantly lower in patients who developed respiratory failure and sepsis, compared with patients who did not develop these complications (p =.02 and p=.015, respectively). CONCLUSIONS: Admission plasma concentration of Gc-globulin is lower in patients who develop organ dysfunction and sepsis after traumatic injury. These data, combined with the work of others, support the hypothesis that actin release and depletion of the extracellular actin scavenger system proteins are associated with, and may contribute in part to, the complications of sepsis and organ dysfunction, particularly respiratory failure and thrombocytopenia.

Adult↗
PubMed2003

Does breast feeding influence liver biochemistry?

OBJECTIVE: It is assumed that early feeding can affect liver biochemistry because breast-fed infants have a higher risk of hyperbilirubinemia than formula-fed infants. The authors sought to determine how feeding mode affected liver biochemistry in healthy term infants. METHODS: Healthy term infants were followed up during infancy with a monthly questionnaire about feeding mode. Blood samples were obtained at 2, 6, and 9 months. Liver biochemistry (serum albumin, alkaline phosphatase, lactic dehydrogenase, aspartate aminotransferase [AST], and bilirubin), total insulin-like growth factor 1 (IGF-I), and insulin growth factor binding protein 3 (IGFBP-3) were determined at all ages. RESULTS: Mean AST and bilirubin were significantly higher in breast-fed infants at 2 and 6 months. In addition, mean albumin levels were higher in breast-fed infants at 2 months. Alkaline phosphatase, IGF-I, IGFBP-3, and lactic dehydrogenase levels did not differ between the feeding groups. AST levels did not correlate significantly with bilirubin, albumin, alkaline phosphatase, or lactic dehydrogenase values. There was a strong positive association between AST and IGF-I at 2 months (r = 0.47, P = 0.004). CONCLUSION: Cytomegalovirus infection, vitamin K deficiency, and macromolecular forms of AST could be an explanation for a higher AST level among breast-fed infants. However, no other clinical or paraclinical sign of liver disease was seen, all infants were given oral vitamin K, and the AST did not rise to levels comparable to those seen in individuals with macromolecular AST. The authors speculate the most likely explanation of the elevated AST is induction of hepatocytes by factors in human milk. This is supported by the higher albumin levels in breast-fed infants and the positive association between AST and IGF-I.

Alkaline Phosphatase↗
PubMed2003

Hepatosplanchnic clearance of interleukin-6 in humans during exercise.

The cytokine interleukin (IL)-6 can increase markedly in the circulation during exercise, but whether the liver is a source of this increase is unknown. The aim of this study was to measure IL-6 flux across the hepatosplanchnic tissues in humans. To elevate systemic concentrations of IL-6, six healthy male subjects performed 120 min of semirecumbent cycling, and blood samples were simultaneously obtained from a brachial artery and the hepatic vein before and during exercise for the analysis of IL-6. Hepatosplanchnic blood flow (HBF) was measured using the indocyanine green infusion technique. Net hepatosplanchnic IL-6 balance was calculated from these measures. HBF was 1.3 +/- 0.1 l/min at rest and was not reduced throughout exercise, averaging 1.1 +/- 0.2 l/min. Arterial plasma IL-6 markedly increased (P < 0.05) from 1.8 +/- 0.6 ng/l at rest to 14.3 +/- 3.2 ng/l after 120 min of exercise. The hepatosplanchnic viscera did not contribute to this increase, since there was a net hepatosplanchnic IL-6 uptake (0.8 +/- 0.3 vs. 5.5 +/- 1.9 ng/min, rest vs. 120 min; P < 0.05). These data demonstrate that the hepatosplanchnic viscera remove IL-6 from the circulation in humans. This removal may constitute a mechanism limiting the negative chronic metabolic action of chronically elevated circulating IL-6.

Adult↗
PubMed2002

Exercise induces hepatosplanchnic release of heat shock protein 72 in humans.

Physical exercise results in the appearance of heat shock protein (HSP) 72 in the circulation that precedes any increase in gene or protein expression in contracting skeletal muscle. In rodents, exercise increases liver HSP72 expression and the hepatosplanchnic viscera are known to release many acute phase proteins. In the present study, we tested the hypothesis that the splanchnic tissue beds release HSP72 during exercise. Seven male subjects performed 120 min of semi-recumbent cycling at 62 +/- 2 % of maximal oxygen uptake. Blood samples were obtained simultaneously from a brachial artery, a femoral vein and the hepatic vein prior to and at 30, 60 and 120 min of exercise. Leg blood flow (LBF) was measured by thermodilution in the femoral vein, and hepatosplanchnic blood flow (HBL) was measured using indocyanine green dye. Net leg and net hepatosplanchnic HSP72 balance were calculated as the product of LBF and femoral venous-arterial HSP72 difference and the product of HBF and hepatic venous-arterial HSP72 difference, respectively. Arterial plasma HSP72 was only detected in one subject at rest but progressively appeared in the arterial samples throughout exercise such that at 120 min it was detected in all subjects (0.88 +/- 0.35 pg l(-1); P < 0.05 compared with rest). The contracting muscle did not, however, contribute to this increase since there was no difference in the femoral venous-arterial HSP72 concentration at any time. Rather, the increase in arterial HSP72 was accounted for, at least in part, by release from the hepatosplanchnic viscera with values increasing (P < 0.05) from undetectable levels at rest to 5.2 +/- 0.2 pg min(-1) after 120 min. These data demonstrate that the splanchnic tissues release HSP72 during exercise and this release is responsible, in part, for the elevated systemic concentration of this protein during exercise.

Adult↗
PubMed2002

Messenger RNA profiles in liver injury and stress: a comparison of lethal and nonlethal rat models.

Liver damage activates processes aimed at repairing damage; simultaneously, liver functions required for survival must be maintained. The expression of genes responsible for both in rat models of lethal (lipopolysaccharide, 90% hepatectomy, and d-galactosamine) and nonlethal (turpentine, 70% hepatectomy, and acetaminophen) liver damage and stress was measured at 3, 6, 12, and 24 h after the intervention and quantitated as the area between the control curves and the test curves (AUC). The expression of genes for cell division and remodeling was upregulated most in the lethal models. The expression of most liver-specific function genes was reduced. Positive AUC was found for ARG, ASL, CPT1, Mdr1b, Mdr2, and PEPCK. It is concluded that a high expression of genes for repair of liver damage is associated with reduced expression of genes for several liver-specific functions, possibly reflecting a limited capacity for transcriptional activity. Maintained or increased expression of selected function genes indicates that the corresponding functions have high priority. The liver sustains metabolic homeostasis ensuring that other organs in the body function normally. Simultaneously, the processes required for the integrity of its own structure and function are maintained as a result of regulated expression of the genes that produce the proteins needed to perform both set of functions.

Acetaminophen↗
PubMed2002

Heterogeneity of ductular reactions in adult rat and human liver revealed by novel expression of deleted in malignant brain tumor 1.

The regenerative capacity of mammalian adult liver reflects the ability of a number of cell populations within the hepatic lineage to take action. Limited information is available regarding factors and mechanisms that determine the specific lineage level at which liver cells contribute to liver repair as well as the fate of their progeny in the hostile environment created by liver injury. In the present study, we attempted to identify novel molecules preferentially involved in liver regeneration by recruitment of transit-amplifying, ductular (oval) cell populations. With a subtractive cDNA library screening approach, we identified 48 enriched, nonredundant gene products associated with liver injury and oval cell proliferation in the adult rat liver. Of these, only two, namely alpha-fetoprotein and a novel transcript with high homology to human DMBT1 (deleted in malignant brain tumor 1), were specifically associated with the emergence of ductular (oval) cell populations in injured liver. Subsequent cloning and characterization of the rat DMBT1 homologue revealed a highly inducible expression in ductular reactions composed of transit-amplifying ductular (oval) cells, but not in ductular reactions after ligation of the common bile duct. In human liver diseases, DMBT1 was expressed in ductular reactions after infection with hepatitis B and acetaminophen intoxication, but not in primary biliary cirrhosis, primary sclerosing cholangitis, and obstruction of the large bile duct. The expression heterogeneity in ductular reactions and multiple functions of DMBT1 homologues point to intriguing roles in regulating not only tissue repair but also fate decision and differentiation paths of specific cell populations in the hepatic lineage.

Adolescent↗