Metabolism of low-density lipoproteins by cultured hepatocytes from normal and homozygous familial hypercholesterolemic subjects

The profoundly elevated concentrations of low-density lipoproteins (LDL) present in homozygous familial hypercholesterolemia lead to symptomatic cardiovascular disease and death by early adulthood. Studies conducted in nonhepatic tissues demonstrated defective cellular recognition and metabolism of LDL in these patients. Since mammalian liver removes at least half of the LDL in the circulation, the metabolism of LDL by cultured hepatocytes isolated from familial hypercholesterolemic homozygotes was compared to hepatcytes from normal individuals. Fibroblast studies demonstrated that the familial hypercholesterolemic subjects studied were LDL receptor-negative (less than 1% normal receptor activity) and LDL receptor-de fective (18% normal receptor activity). Cholesterol-depleted hepatocytes from normal subjects bound and internalized 125I-labeled LDL (Bmax = 2.2 μg LDL/mg cell protein). Preincubation of normal hepatocytes with 200 μg/ml LDL reduced binding and internalization by approx. 40%. In contrast, 125I-labeled LDL binding and internalization by receptor-negative familial hypercholesterolemic hepatocytes was unaffected by cholesterol loading and considerably lower than normal. This residual LDL uptake could not be ascribed to fluid phase endocytosis as determined by [14C]sucrose uptake. The residual LDL binding by familial hypercholesterolemia hepatocytes led to a small increase in hepatocyte cholesterol content which was relatively ineffective in reducing hepatocyte 3-hydroxy-3-methylglutaryl-CoA reductase activity. Receptordefective familial hypercholesterolemia hepatocytes retained some degree of regulatable 125I-labeled LDL uptake, but LDL uptake did not lead to normal hepatocyte cholesterol content or 3-hydroxy-3-methylglutaryl-CoA reductase activity. These combined results indicate that the LDL receptor abnormality present in familial hypercholesterolemia fibroblasts reflects deranged hepatocyte LDL recognition and metabolism. In addition, a low-affinity, nonsaturable uptake process for LDL is present in human liver which does not efficiently modulate hepatocyte cholesterol content or synthesis. © 1986

A multiple catheter technique for studies or hepatic metabolism and blood flow in dogs with portacaval transposition

A technique is described for in vivo hepatic metabolic studies, employing a multiple catheterization technique in dogs with chronic portacaval transposition. The animals are studied in the unanesthetized state immediately after the insertion of catheters through peripheral cut-downs. The gradient of metabolites entering and leaving the liver can be measured concomitantly with hepatic plasma flow. Additional simultaneous gradients can be obtained across the splanchnic capillary bed, or the hindquarters. Drugs can be introduced into the circulation by a systemic route or by primary injection into the hepatic circulation. The advantages of this approach compared to other methods of evaluating moment to moment hepatic function are discussed. © 1962

Liquid chromatography-tandem mass spectrometry - Application in the clinical laboratory

This review provides a concise survey of liquid chromatography tandem mass spectrometry (LCTMS) as an emerging technology in clinical chemistry. The combination of two mass spectrometers with an interposed collision cell characterizes LCTMS as an analytical technology on its own and not just as a more specific detector for HPLC compared with conventional techniques. In LCTMS, liquid chromatography is rather used for sample preparation but not for complete resolution of compounds of interest. The instrument technology of LCTMS is complex and comparatively expensive; however, in routine use, methods are far more rugged compared to conventional chromatographic techniques and enable highthroughput analyses with very limited manual handling steps. Moreover, compared to both gas chromatographymass spectrometry (GCMS) and conventional HPLC techniques, LCTMS is substantially more versatile with respect to the spectrum of analyzable compounds. For these reasons it is likely that LCTMS will gain far more widespread use in the clinical laboratory than HPLC and GCMS ever did. In this article, the key features of LCTMS are described, method development is explained, typical fields of application are discussed, and personal experiences are related

Neuroradiologic aspects of pediatric orthotopic liver transplantation

To investigate the occurrence of neurologic symptomatology in pediatric orthotopic liver transplantation patients and to evaluate the utility of CT in uncovering the origin of their symptoms, we reviewed the medical records and head scans (when performed) of 71 patients. Neurologic problems occurred in 48%; the majority involved seizures, mental status changes, or coma. Patients who only had seizures generally had negative CT scans, except for two patients with minimal subarachnoid hemorrhages. Three-quarters of the comatose patients, however, had significant intracerebral hemorrhages defined by CT. Prominent sulci and ventricles were found in approximately one-third of the patients scanned, but did not correlate with symptomatology or steroid dose

Studies of the effects and modes of action of autonomic drugs on portal hemodynamics

The effect of epinephrine, pitressin, and Arfonad on portal pressure has been studied in dogs with special emphasis on the role of the liver in determining pressure changes. The use of dogs with portacaval transposition allowed portal pressures to be studied with the exclusion of any hepatic vascular factor. With this preparation, vena caval pressures were brought under the influence of changes in hepatic vascular resistance. By this technique, the action of epinephrine in raising portal pressure primarily seemed to be due to an increase in hepatic vascular resistance. The action of pitressin in reducing portal pressure appeared to be due to a combination of reduction of splanchnic blood flow and a reduction in hepatic vascular resistance. The effect of Arfonad in lowering portal pressure appeared to be unrelated to any changes in the liver itself. © 1962

The role of cerebral edema in ischemic cerebral neuropathy after cardiac arrest in dogs and monkeys and its treatment with hypertonic urea

1. 1. The value of hypertonic urea in forestalling the neurologic sequellae after cardiac arrest has been assessed in dogs and monkeys. Simulated cardiac arrest was produced with an inflow-outflow occlusion technique in which the blood supply to the heart was maintained during the period of complete cerebral ischemia. 2. 2. A number of factors increase the duration of cardiac arrest which can be tolerated without gross neurologic sequellae. These include the presence of an effective circulatory state before and after the arrest, the administration of 100 per cent oxygen before and after the test period, the use of an efficient respirator, and avoidance of premature efforts to promote spontaneous respirations postoperatively. 3. 3. Under optimum conditions almost all dogs and monkeys will recover completely after 12 minutes of simulated cardiac arrest. With longer occlusions, death and serious neurologic morbidity occur. 4. 4. Monkeys and dogs were subjected to simulated cardiac arrest for 14 minutes. Hypertonic urea did not materially decrease either the mortality rate or neurologic morbidity in either species, as compared to the recovery rate in controls, despite the fact that the urea-treated animals had demonstrably less brain swelling. 5. 5. From this it is concluded that cerebral edema is an overemphasized factor in the post-cardiac arrest syndrome, and that the principal deterrent to recovery is anoxic injury to the neurons which is not beneficially influenced by reduction of brain volume. © 1960

Clostridium difficile colitis in patients after kidney and pancreas-kidney transplantation

Limited data exist about Clostridium difficile colitis (CDC) in solid organ transplant patients. Between 1/1/99 and 12/31/02, 600 kidney and 102 pancreas–kidney allograft recipients were transplanted. Thirty-nine (5.5%) of these patients had CDC on the basis of clinical and laboratory findings. Of these 39 patients, 35 have information available for review. CDC developed at a median of 30 days after transplantation, and the patients undergoing pancreas–kidney transplantation had a slightly higher incidence of CDC than recipients of kidney alone (7.8% vs. 4.5%, P> 0.05). All but one patient presented with diarrhea. Twenty-four patients (64.9%) were diagnosed in the hospital, and CDC occurred during first hospitalization in 14 patients (40%). Treatment was with oral metronidazole (M) in 33 patients (94%)and M + oral vancomycin (M + V) in 2 patients. Eight patients had recurrent CDC, which occurred at a median of 30 days (range 15–314) after the first episode. Two patients (5.7%) developed fulminant CDC, presented with toxic megacolon, and underwent colectomy. One of them died; the other patient survived after colectomy. CDC should be considered as a diagnosis in transplant patients with history of diarrhea after antibiotic use, and should be treated aggressively before the infection becomes complicated