Infectious aneurysm clipping by an MRI/MRA wand-guided protocol. A case report and technical note

Infectious aneurysms are potentially deadly sequelae of multiple etiologies, typically associated with subacute bacterial endocarditis (SBE). Since these aneurysms tend to be distal, there are no consistent landmarks by which to localize them, in contrast to more typical aneurysms that occur on the circle of Willis or proximal, large cerebral vessel bifurcations. In addition, they tend to be extremely friable and may be obscured by blood if intracranial hemorrhage (ICH) has already occurred. These factors make clipping these aneurysms technically difficult, and searching for easily ruptured aneurysms without standard landmarks adds risk to the procedure. In this report, we describe the case of a 9-year-old boy with SBE and subsequent ICH secondary to a mycotic aneurysm. This aneurysm was localized to within millimeters by the MRI protocol described herein. The aneurysm was excised and the patient recovered without incident. Thus, MRI/MRA-guided frameless stereotaxy may be useful for localizing distal mycotic aneurysms, improving patient outcome by decreasing morbidity and mortality.

Malignant peripheral nerve sheath tumors associated with neurofibromatosis type 1: a clinicopathologic and molecular study of 17 patients

OBJECTIVE

To identify potential prognostic factors and criteria for early detection of malignant peripheral nerve sheath tumors associated with neurofibromatosis type 1 (NF1).

DESIGN

Retrospective study of malignant peripheral nerve sheath tumors in a cohort of 395 patients with NF1 followed up between October 1, 1988, and January 1, 1999; review of the clinical and histological characteristics of treatment and course; and analysis of p53 mutations and overexpression in tumors.

SETTING

Teaching hospital referral neurofibromatosis center for adults.

PATIENTS

Seventeen patients with NF1 (9 males and 8 females). Mean +/- SD patient age at diagnosis was 32 +/- 14 years.

MAIN OUTCOME MEASURES

(1) Clinical symptoms, (2) comparison of p53 mutations and overexpression in benign vs malignant tumors; and (3) median survival.

RESULTS

Twelve patients had high-grade tumors. All tumors except 1 developed on preexisting nodular or plexiform neurofibromas. Pain and enlarging mass were the first and predominant signs. None of the benign tumors displayed significant p53 staining or p53 mutations. Six of 12 malignant tumors significantly overexpressed p53, and 4 of 6 harbored p53 missense mutations. Median survival was 18 months overall, 53 months in peripheral locations, and 21 months in axial locations.

CONCLUSIONS

Malignant peripheral nerve sheath tumors are highly aggressive in NF1. They mostly arise from plexiform or nodular neurofibromas. Investigations and deep biopsy of painful and enlarging nodular or plexiform neurofibromas should be considered in patients with NF1. Late appearance of p53 mutations and overexpression precludes their use as predictive markers of malignant transformation.

Circulating lipoproteins and hepatic sterol metabolism in Psammomys obesus prone to obesity, hyperglycemia and hyperinsulinemia

The liver plays a central role in lipoprotein metabolism and cholesterol homeostasis. As the physiopathology of lipid disorders in non-insulin-dependent diabetes mellitus (NIDDM) is multifactorial and still imperfectly known, we evaluated its onset on plasma lipid transport and hepatic cholesterol metabolism in Psammomys obesus. This sand rat lapses into hyperinsulinemia and hyperglycemia when transferred from its native food to laboratory rodent diets. Marked hypertriglyceridemia and hypercholesterolemia developed in hyperinsulinemic (Group B) and hyperglycemic/ hyperinsulinemic (Group C), compared with normal P. obesus (Group A). Group B showed significantly (P<0.05) higher plasma VLDL-cholesterol (41.9%) and LDL-cholesterol (47.3%) concentrations, whereas Group C was characterized by an even more marked increase in VLDL-cholesterol (176%, P<0.001) compared with Group A. Lipoprotein composition was also altered, displaying impaired lipid and apolipoprotein moiety distribution in IDL, LDL, HDL(2) and HDL(3) lipoprotein fractions of Groups B and C. The activity of hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-limiting enzyme in cholesterol biosynthesis, was consistently lower in Group B (P<63.4%, P<0.001) and C (43.9%, P<0.005). In contrast, the direct measurement of microsomal acyl-CoA:cholesterol acyltransferase (ACAT), controlling the acylation of cholesterol, showed an increase averaging 53% in Group B (P<0.01) and 61% in Group C (P<0.005). Similarly, elevated activity (171.1%, P<0.05 and 291.4%, P<0.001, respectively) was related to cholesterol 7alpha-hydroxylase, the rate-limiting enzyme in bile acid biosynthesis. These alterations were accompanied with abundant deposition of triglycerides and cholesterol in the liver. Changes in circulating lipids and liver parameters were related to glucose and insulin levels, indicating the implication of insulin resistance and diabetes. Therefore, our findings demonstrate various disturbances in plasma lipid profile and lipoprotein composition, as well as in liver cholesterol metabolism during the sequential development of insulin resistance and diabetes in P. obesus rats. Furthermore, the current data point to an undoubtedly important role of the liver in the pathogenesis of metabolic disorders in the progression of nutritionally-induced insulin resistance and diabetes in P. obesus. Finally, current research shows that more marked plasma and hepatic lipid perturbations occur in insulin resistance than in diabetes, which may culminate in the development of atherosclerosis.

Modulation of intestinal and liver fatty acid-binding proteins in Caco-2 cells by lipids, hormones and cytokines

Intestinal and liver fatty acid binding proteins (I- and L-FABP) are thought to play a role in enterocyte fatty acid (FA) trafficking. Their modulation by cell differentiation and various potential effectors was investigated in the human Caco-2 cell line. With the acquisition of enterocytic features, Caco-2 cells seeded on plastic progressively increased L-FABP quantities, whereas I-FABP was not detectable even very late in the maturation process. On permeable filters that improved differentiation markers (sucrase, alkaline phosphatase, transepithelial resistance), Caco-2 cells furthered their L-FABP content and expressed I-FABP. Western blot analysis showed a significant increase in I- and L-FABP expression following an 8-hour incubation period with butyric acid, oleic acid, and phosphatidylcholine. However, in all cases, I-FABP levels were higher than L-FABP concentrations regardless of the lipid substrates added. Similarly, hydrocortisone and insulin enhanced the cellular content of I- and L-FABP whereas leptin triggered I-FABP expression only after an 8-hour incubation. Finally, tumor necrosis factor-alpha was more effective in increasing the cytosolic amount of I-FABP levels. In conclusion, our data demonstrate that I-FABP expression is limited to fully differentiated Caco-2 cells and can be more easily regulated than L-FABP by lipids, hormones, and cytokines.

Distinct properties of wild-type and the amyloidogenic human cystatin C variant of hereditary cerebral hemorrhage with amyloidosis, Icelandic type

Variant human cystatin C (L68Q) is an amyloidogenic protein. It deposits in the cerebral vasculature of Icelandic patients with cerebral amyloid angiopathy, leading to stroke. Wild-type and variant cystatin C are cysteine proteinase inhibitors which form concentration dependent inactive dimers; however, variant cystatin C dimerizes at lower concentrations and has an increased susceptibility to a serine protease. We studied the effect of the L68Q amino acid substitution on cystatin C properties, utilizing full length cystatin C purified in mild conditions from media of cells stably transfected with either the wild-type or variant cystatin C genes. The variant cystatin C forms fibrils in vitro detectable by electron microscopy in conditions in which the wild-type protein forms amorphous aggregates. We also show by circular dichroism, steady-state fluorescence and Fourier-transformed infrared spectroscopy that the amino acid substitution modifies cystatin C structure by destabilizing alpha-helical structures and exposing the tryptophan residue to a more polar environment, yielding a more unfolded molecule. These spectral changes demonstrate that variant cystatin C has a three-dimensional structure different from that of the wild-type protein. The structural differences between variant and wild-type cystatin C account for the susceptibility of the variant protein to unfolding, proteolysis and fibrillogenesis.

Immunolocalization, ontogeny, and regulation of microsomal triglyceride transfer protein in human fetal intestine

To examine the multiple stages of lipoprotein packaging during development, we studied localization, ontogeny, and regulation of microsomal transfer protein (MTP), a crucial protein for lipid transport. With the use of immunofluorescence, MTP was identified in villus and crypt epithelial cells in different regions of human fetal intestine, including colon. Staining was detected as early as the 13th wk of gestation in all gut segments and was almost entirely confined to the columnar epithelial cells of the jejunum and colon. Unlike immunofluorescence, which provides qualitative but not quantitative information on MTP signal, enzymatic assays revealed a decreasing gradient from proximal small intestine to distal, as confirmed by immunoblot. Activity of MTP in small intestinal explants cultured for different incubation periods (0, 4, 8, and 24 h) peaked at 4 h but remained insensitive to different concentrations of oleic acid. Also, a trend toward increasing MTP activity was observed at 20-22 wk of gestation. Finally, in strong contrast to jejunal efficiency, colonic explants displayed impaired lipid production, apolipoprotein biogenesis, and lipoprotein assembly, in association with poor expression of MTP. These findings provide the first evidence that human fetal gut is able to express MTP and emphasize the distinct regional distribution, regulation by oleic acid, and ontogeny of MTP.

The sequence and gene characterization of a 400-kb candidate region for IDDM4 on chromosome 11q13

Type 1 diabetes is a complex disorder with interaction of both genetic and environmental factors. One of the loci, IDDM4, has been mapped to chromosome 11q13, with evidence of association to two markers, D11S1917 and H0570polyA. To identify putative candidate genes for IDDM4, we have constructed a 400-kb clone contig in this region and sequenced the clones. We have also sequenced the orthologous DNA from mouse. Previously, we identified a cDNA for the low-density lipoprotein receptor-related protein 5 gene (LRP5) 3 kb distal to H0570polyA. We have now determined the exon-intron structure of this gene. Detailed sequence analysis has identified a further three genes in this region: the CGI-85 gene (previously identified by W.-C. Lin) and two novel genes, C11orf24 and C11orf23. The C11orf24 gene has no known similarity to other genes, and its function is unknown. C11orf23 has similarity to the SIT4 (sporulation-induced transcript 4)-associated protein (SAP) family of yeast proteins, which are involved in regulation of the cell cycle. The full-length C11orf23 cDNA is the first mammalian orthologue of the yeast SAP family to be identified. Identification of these four genes in a 400-kb region of the IDDM4 region underpins our strategy to identify the IDDM4 locus.

DEVELOPMENT OF NONINVASIVE AND QUANTITATIVE METHODOLOGIES FOR THE ASSESSMENT OF CHRONIC ULCERS AND SCARS IN HUMANS

Chronic ulcers are a significant and common cause of morbidity and mortality worldwide. They disrupt the epidermis and dermis, resulting in a loss of barrier function. Keloids and hypertrophic scars (benign cutaneous tumors) represent an abnormal healing response. These fibroproliferative disorders are characterized by an overabundance of collagen and accumulation of extracellular matrix due to an imbalance between synthesis and degradation, culminating in excessive scarring. The objectives of this study were to evaluate and compare noninvasive biophysical methods for the measurement of outstanding quantitative parameters of scars and chronic ulcers, and to establish correlations between the parameters measured and the results of conventional subjective clinical evaluations. The development of new technologies, based on ultrasonography and laser Doppler, makes possible new dermatological evaluation methods. Fifteen patients (6 females and 9 males) with 15 chronic ulcers (4 diabetic ulcers, 10 venous ulcers and 1 pressure ulcer) and 30 patients (19 females and 11 males) with 30 scars (25 hypertrophic and 5 keloids) were included in this study. Clinical evaluation was performed by a dermatologist, an aesthetic surgeon and an endocrinologist. Biophysical measurements were used to assess local blood flow by laser Doppler flowmetry (Moor DRT4), thickness and echogenicity by high frequency ultrasonography (20 MHz, Dermascan C) and ulcer linear dimensions by image analysis. Our results show that blood flow within the ulcers and scars was higher than within normal skin. Also, skin thickness of chronic ulcers was decreased when compared to normal skin; the thickness of hypertrophic scars, but not of keloids, was increased in comparison to normal skin, and presented the possibility of measuring wound and scar surfaces with precision. In summary, this pilot study established the feasibility of measuring various biophysical parameters and adapted their potential utility to research on wounds.

Hemodynamic consequences of cerebral vasospasm on perforating arteries: a phantom model study

BACKGROUND AND PURPOSE

Hemodynamics of cerebral vasospasm after subarachnoid hemorrhage remain unclear, and the discrepancy between ultrasonographic or angiographic evidence of arterial narrowing and neurological ischemic deficit is still debated. Most blood flow studies have been involved with large arteries, and thus, very little is known regarding the hemodynamic behavior of small perforating vessels. Patients with symptomatic vasospasm, however, often present with neurological signs suggesting involvement of deep-sited areas of the brain supplied by perforating arteries.

METHODS

A pulsatile pump was set to provide an outflow of 350 mL/min through a 10-mm-diameter C-flex tube at a perfusion pressure of 130/80 mm Hg. The perfusion fluid used was prepared to approximate blood viscosity. Perforating arteries were simulated by a 1-mm tube connected to the parent tube at a 90 degrees angle. Cylindrical stenotic devices of decreasing diameters were then introduced into the parent tube at the level of the aperture of the secondary tube and 1.5 diameters upstream of it. Velocity profiles both proximal and distal to the stenosis in the parent tube were obtained with a newly developed ultrasonographic flowmeter that allows for high spatial resolution.

RESULTS

Increasing stenosis resulted in decreased outflow in the main tube, although it was significant only with severe stenosis. Whenever the simulated stenosis was placed upstream of the secondary tube, flow reduction was associated with a progressive change in the velocity profile, which gradually changed from laminar conditions to a jet stream limited to the center of the lumen. Further diameter reduction was responsible for the occurrence of flow separation with retrograde flow velocities in the periphery of the lumen. In the secondary tube, flow reduction was much more pronounced and began at a lesser degree of stenosis. Increasing fluid viscosity and decreasing perfusion pressure enhanced flow separation and prominently affected the outflow in the secondary tube. Conversely, whenever the simulated stenosis involved the branching area of the secondary tube, there was a slightly progressive decrease in the relative flow in the main tube as the stenosis became tighter. When the stenosis equaled the diameter of the secondary tube, the relative contribution of the secondary tube increased markedly at the expense of the main tube outflow.

CONCLUSIONS

The present results show that local cerebral vasospasm induces changes in postvasospastic velocity profile affecting the shear rate and may eventually lead to flow separation. This phenomenon may, in turn, result in a venturi-like effect over the aperture of perforating arteries branching out of the postvasospastic portion of the affected parent artery. These alterations of cerebral hemodynamics may account for at least part of the vasospasm symptomatology, especially in the vertebrobasilar system, where vasospasm is commonly focal rather than diffuse. Furthermore, these changes proved to be affected significantly by manipulations of pressure and viscosity, supporting the use of hyperdynamic therapy in the management of cerebral vasospasm.

The adipose tissue phenotype of hormone-sensitive lipase deficiency in mice

OBJECTIVE

To directly ascertain the physiological roles in adipocytes of hormone-sensitive lipase (HSL; E.C. 3.1.1.3), a multifunctional hydrolase that can mediate triacylglycerol cleavage in adipocytes.

RESEARCH METHODS AND PROCEDURES

We performed constitutive gene targeting of the mouse HSL gene (Lipe), subsequently studied the adipose tissue phenotype clinically and histologically, and measured lipolysis in isolated adipocytes.

RESULTS

Homozygous HSL-/- mice have no detectable HSL peptide or cholesteryl esterase activity in adipose tissue, and heterozygous mice have intermediate levels with respect to wild-type and deficient littermates. HSL-deficient mice have normal body weight but reduced abdominal fat mass compared with normal littermates. Histologically, both white and brown adipose tissues in HSL-/- mice show marked heterogeneity in cell size, with markedly enlarged adipocytes juxtaposed to cells of normal morphology. In isolated HSL-/- adipocytes, lipolysis is not significantly increased by beta3-adrenergic stimulation, but under basal conditions in the absence of added catecholamines, the lipolytic rate of isolated HSL-/- adipocytes is at least as high as that of cells from normal controls. Cold tolerance during a 48-hour period at 4 degrees C was similar in HSL-/- mice and controls. Overnight fasting was well-tolerated clinically by HSL-/- mice, but after fasting, liver triglyceride content was significantly lower in HSL-/- mice compared with wild-type controls.

CONCLUSIONS

In isolated fat cells, the lipolytic rate after beta-adrenergic stimulation is mainly dependent on HSL. However, the observation of a normal rate of lipolysis in unstimulated HSL-/- adipocytes suggests that HSL-independent lipolytic pathway(s) exist in fat. Physiologically, HSL deficiency in mice has a modest effect under normal fed conditions and is compatible with normal maintenance of core body temperature during cold stress. However, the lipolytic response to overnight fasting is subnormal.

A general model of the effects of sleep medications on the risk and cost of motor vehicle accidents and its application to France

BACKGROUND

Although various prescription drugs may be equally effective in promoting sleep, some may lead to substantial impairment in psychomotor functioning and an increased risk of motor vehicle accidents.

OBJECTIVE

To develop a general model to evaluate the potential effects of sleep medications on motor vehicle accidents and costs, and apply the model to the French setting.

METHODS

Impairment in driving performance, as evaluated by randomised controlled open-road studies using the standard deviation of a vehicle's lateral position (SDLP), a measure of weaving, was expressed in terms of equivalent blood alcohol (ethanol) concentration (BAC). Epidemiological data were then used to relate BAC to the excess risk of motor vehicle accidents. Although a non-impairing medication would not increase risk, a medication that produces mild impairment in driving performance (a change of 2.5 cm in SDLP, equivalent to 0.05% BAC) would increase motor vehicle accident risk by 25%. One that leads to moderate impairment (an SDLP change of 4.5 cm, equivalent to 0.08% BAC) would roughly double this risk, and a severely impairing medication (an SDLP change of 7 cm, equivalent to 0.12% BAC) would result in up to a 5-fold increase in motor vehicle accident risk. For application to the French setting, a hypothetical cohort of 100,000 adult drivers with insomnia was assumed to be treated for 14 days either with zaleplon 10 mg, a new sleep medication that has been shown not to significantly impair driving performance, or zopiclone 7.5 mg, which has been shown to cause moderate impairment.

RESULTS

Compared with zaleplon, use of zopiclone over 14 days in France would be expected to result in 503 excess accidents per 100,000 drivers at an additional cost of 158 French francs (31 US dollars) per person (1996 values).

CONCLUSIONS

Our model illustrates the extent to which non-impairing sleep medications could reduce the burden posed by motor vehicle accidents. Our model is designed to be general, and thus can serve as the basis for similar investigations.

Codeposition of cystatin C with amyloid-beta protein in the brain of Alzheimer disease patients

Immunohistochemical analysis of brains of patients with Alzheimer disease (AD) revealed that the cysteine proteinase inhibitor cystatin C colocalizes with amyloid beta-protein (Abeta) in parenchymal and vascular amyloid deposits. No evidence of cerebral hemorrhage was observed in any of the brains studied. Immunoelectron microscopy demonstrated dual staining of amyloid fibrils with anti-Abeta and anti-cystatin C antibodies. Cystatin C immunoreactivity was also observed in amyloid deposits in the brain of transgenic mice overexpressing human beta amyloid precursor protein. Massive deposition of the variant cystatin C in the cerebral vessels of patients with the Icelandic form of hereditary cerebral hemorrhage with amyloidosis is thought to be responsible for the pathological processes leading to stroke. Anti-cystatin C antibodies strongly labeled pyramidal neurons within cortical layers most prone to amyloid deposition in the brains of AD patients. Immunohistochemistry with antibodies against the carboxyl-terminus of Abeta(x-42) showed intracellular immunoreactivity in the same neuronal subpopulation. It remains to be established whether the association of cystatin C to Abeta plays a primary role in amyloidogenesis of AD or is a late event in which the protein is bound to the previously formed Abeta amyloid fibrils.

Influence of radiographic technique and equipment on absorbed ovarian dose associated with uterine artery embolization

PURPOSE

To evaluate the influence of pulsed fluoroscopy (PF), nonpulsed fluoroscopy (NPF), and various fluoroscopic techniques on the absorbed ovarian dose (AOD) associated with uterine artery embolization (UAE) of leiomyomata.

MATERIAL AND METHODS

Ovarian location was estimated from preprocedural pelvic magnetic resonance images of 23 patients previously treated by means of UAE. The AOD was measured with thermoluminescent dosimeters (TLD) placed into an anthropomorphic phantom at the determined ovarian location. The following measurements from PF and NPF were obtained: 21.89 minutes of nonmagnified posterior-anterior fluoroscopy, 10 minutes of nonmagnified oblique fluoroscopy, 10 minutes of posterior-anterior magnified fluoroscopy, 10 minutes of combined oblique magnified fluoroscopy, and 47 simulated angiographic exposures. Numbers for nonmagnified posterior-anterior fluoroscopy time and exposure numbers were chosen from the average values from previous UAE procedures. AOD from pulsed and nonpulsed nonmagnified posterior-anterior fluoroscopy was compared to measurements from oblique magnified, posterior-anterior magnified, and oblique fluoroscopy.

RESULTS

AOD from NPF was, on average, 1.7 times higher than from PF. When compared with nonmagnified posterior-anterior fluoroscopy, the AOD from oblique magnified fluoroscopy was 1.9 times greater; the AOD from nonmagnified oblique fluoroscopy was 1.1 times greater. The AOD from oblique magnified fluoroscopy was 1.5 times higher on the side closer to the x-ray tube than on the contralateral side. AOD from serial angiographic exposures contributed only less than 7% to the total AOD for the average UAE procedure.

CONCLUSIONS

The AOD associated with UAE can best be reduced by limiting fluoroscopy time and the use of oblique or magnified fluoroscopy. Contribution of angiographic exposures to AOD is much less significant.

Software development for registration of digital subtraction angiography (DSA) images in uterine fibroid embolization

The ISIS Center at Georgetown University Medical Center has developed a comprehensive program for image-guided procedures in the spine. As part of this program, ISIS has developed a software application known as I-SPINE (ISIS's Spine Procedure Imaging Navigation Engine). I-SPINE is a Windows NT application, which is based on the Analyze/AVM libraries. The software architecture follows the Microsoft Foundation Classes (MFC) single document, multiple view paradigm. This has allowed the developers to add new visualization modules to I-SPINE that aid physicians in procedures outside the spine. One such procedure I-SPINE has been expanded for is uterine fibroid embolization. The idea is that by registering and subtracting post-embolization angiographic images from pre-treatment images the resulting image can be used to quantify the embolization effect on the fibroid circulation and predict the treatment response. The I-SPINE digital subtraction angiography (DSA) module allows the interventional radiologist to open a series of pre and post-embolization DSA images that shows the vascular structures of the uterus and the fibroid or fibroids. From these images, the radiologist selects an appropriate image from each series. The selected images are then hand registered using pixel shifting. Once the images are registered, the pixels are subtracted resulting in an image that shows the embolized arteries that were supplying the fibroids.

Roles of molecular chaperones in pancreatic secretion and their involvement in intestinal absorption

This review focuses on the contribution of molecular chaperones in the secretory process of digestive enzymes and their interaction with enterocytes. By using biochemistry and immunocytochemistry, we have shown that Grp94, Cpn10, Cpn60, and protein disulfide isomerase (PDI) are present all along the rough endoplasmic reticulum-Golgi-granule secretory pathway of the pancreatic acinar cells and are secreted into the acinar lumen. Two other molecular chaperones, Grp78 and the Hsp70, appear to be restricted to the rough endoplasmic reticulum and the trans-Golgi apparatus, respectively. We have found that chaperones can be associated with pancreatic enzymes along the secretory pathway. Indeed, double immunogold and immunocoprecipitation revealed an association between Cpn60 and the colipase-dependent lipase (CDL) and between Grp94 and the bile salt-dependent lipase (BSDL). These complexes are secreted into the acinar lumen and diverted to the duodenal lumen. These findings led us to investigate these enzyme-chaperone complexes in intestinal tissue. Grp94, Cpn60, and PDI are present on microvilli and on the endosomal compartment of enterocytes. Furthermore, we have shown that the Grp94-BSDL complexes are internalized by enterocytes through classical endocytosis. Upon dissociation of the BSDL-Grp94 complex in the late endosome, BSDL is transferred to the basolateral membrane. We propose that Grp94 interacts with specific receptors and/or could force the associated protein to adopt a specific conformation that allows its binding to corresponding membrane receptors and its internalization by enterocytes. These two hypotheses need not to be exclusive. The existence of such a pancreatic secretion-intestinal absorption link speaks in favor of a coordinated functional connection between these two entities, through molecular chaperones, in order to optimize intestinal activities.

Iron-ascorbate alters the efficiency of Caco-2 cells to assemble and secrete lipoproteins

Although oxidative stress has been implicated in development of gut pathologies, its role in intestinal fat transport has not been investigated. We assessed the effect of Fe(2+)-ascorbate-mediated lipid peroxidation on lipid synthesis, apolipoprotein biogenesis, and lipoprotein assembly and secretion. Incubation of postconfluent Caco-2 cells with iron(II)-ascorbate (0.2 mM/2 mM) in the apical compartment significantly promoted malondialdehyde formation without affecting sucrase activity, transepithelial resistance, DNA and protein content, and cell viability. However, addition of the oxygen radical-generating system reduced 1) [(14)C]oleic acid incorporation into cellular triglycerides (15%, P < 0.0002) and phospholipids (16%, P < 0.0005); 2) de novo synthesis of cellular apolipoprotein A-I (apo A-I) (18%, P < 0.05), apo A-IV (38%, P < 0.05), and apo B-48 (45%, P < 0.003) after [(35)S]methionine addition; and 3) production of chylomicrons (50%), VLDL (40%), LDL (37%), and HDL (30%) (all P < 0.0001). In contrast, increased total cellular cholesterol formation (96%, P < 0.0001), assayed by [(14)C]acetate incorporation, was noted, attributable to marked elevation (70%, P < 0.04) in activity of DL-3-hydroxy-3-methyl-glutaryl-CoA reductase, the rate-limiting enzyme in cholesterol synthesis. The ratio of Acyl-CoA to cholesterol acyltransferase, the esterifying cholesterol enzyme, remained unchanged. Fe(2+)-ascorbate-mediated lipid peroxidation modifies intracellular fat absorption and may decrease enterocyte efficiency in assembling and transporting lipids during gut inflammation.

Identification of two novel LDL receptor gene defects in French-Canadian pediatric population: mutational analysis and biochemical studies

Familial hypercholesterolemia (FH) is at least twofold more prevalent in French Canadians from Québec than in most Western populations. Although our recent data confirmed this high frequency of heterozygous FH in our pediatric population with hypercholesterolemia, none of the five established molecular defects for the French-Canadian population was detected in 29% of the unrelated French-Canadian children characterized by a persistent increase in LDL (low density lipoprotein receptor) cholesterol and a positive parental history of hyperlipidemia (Assouline et al., 1995). To probe for new mutations, six of these molecularly undiagnosed children were investigated as index patients. By using single-strand conformation polymorphism analysis and DNA sequencing, two novel mutations were identified in two of these subjects: (1) 7-base pair (bp) duplication following nucleotide 681 (according to the cDNA sequence) in exon 4 (681ins7), which causes a frameshift, the introduction of a stop at codon 208, and premature chain termination, and (2) A to G change in exon 8 substituting a tyrosine for a cysteine at amino acid 354 (Y354C). A third subject carried the recently reported exon 10 mutation (Y468X), whereas the remaining three patients demonstrated various known polymorphisms with no effect on gene product. Rapid molecular assays were developed to detect the two new mutations as well as the Y468X mutation. Screening of our cohort showed heterozygosity in 1/88, in 2/88, and in 2/88 of patients for the 681ins7, the Y354C, and the Y468X mutations, respectively.

Metabolic syndrome X: a review

Metabolic syndrome X is a multifaceted syndrome, which occurs frequently in the general population. It is more common in men than in women. A large segment of the adult population of industrialized countries develops the metabolic syndrome, produced by genetic, hormonal and lifestyle factors such as obesity, physical inactivity and certain nutrient excesses. This disease is characterized by the clustering of insulin resistance and hyperinsulinemia, and is often associated with dyslipidemia (atherogenic plasma lipid profile), essential hypertension, abdominal (visceral) obesity, glucose intolerance or noninsulin-dependent diabetes mellitus and an increased risk of cardiovascular events. Abnormalities of blood coagulation (higher plasminogen activator inhibitor type 1 and fibrinogen levels), hyperuricemia and microalbuminuria have also been found in metabolic syndrome X. This review summarizes the present knowledge of abnormalities in this syndrome. Each risk factor is reviewed, and potential criteria for diagnosis and therapeutic targets are discussed. Because patients with metabolic syndrome X accumulate cardiac risk factors, they should be given special attention in terms of diagnosis and treatment.

Use of immunoelectron microscopy and intestinal models to explore the elaboration of apolipoproteins required for intraenterocyte lipid transport

The intestine is the organ that contributes the majority of circulating alimentary lipoproteins. Intestinal epithelial cells have the unique ability to elaborate chylomicrons, the largest triglyceride-rich lipoproteins and the main vehicle for the transport of dietary lipids. The final intracellular assembly and exocytosis of chylomicrons require enterocyte-derived apolipoproteins (apo). As research on lipoprotein metabolism evolved, it has become increasingly evident that apo B is a crucial protein for the normal packaging of triglyceride-rich lipoproteins. Immunocytochemical techniques have successfully been used to demonstrate the presence of two types of apo B, the B-100 and the B-48, in different subcellular compartments of the human enterocyte. Confirmation was obtained by biochemically analyzing human lymph and intestine from pediatric patients. In addition, the immunoelectron microscopic approach revealed the location of apo A-I in the rough endoplasmic reticulum (ER) and predominantly in the Golgi apparatus and the basolateral membrane, which confirms the rapid transport of apo A-I documented by other studies. Proven utility and experimental conditions were defined to demonstrate the ability of Caco-2 cells, a colon carcinoma cell line, to esterify lipids, synthesize apo, and assemble lipoproteins. Thus, immunocytochemical and biochemical techniques can be combined with in vivo and in vitro intestinal models for the study of the intestinal lipid transport.

Developmental aspects of lipid and lipoprotein synthesis and secretion in human gut

This review article focuses on the ontogeny and the regulatory mechanisms involved in the modulation of the intracellular events governing the assembly and delivery of lipoproteins in human gut. The human fetal intestine organizes villi covered with well-differentiated enterocytes during the end of the first trimester in utero. One striking event is the formation of villi in the colonic mucosa similar to those of the small intestine. The small intestine exhibits very early (14-20 weeks) the capacity to absorb lipids, to elaborate most of the major lipoprotein classes (chylomicrons, very-low-density lipoproteins, low-density lipoproteins, high-density lipoproteins), and to efficiently export these lipoproteins from the intestinal cells. The ontogenic changes of lipid and lipoprotein synthesis are correlated with specific patterns of regulatory enzymes (HMG-CoA reductase, ACAT, MGAT) that are representative of key patterns such as the cholesterol pathway, cholesterol esterification, and neutral lipid pathway. The human fetal colon also has the capability to synthesize lipids, lipoproteins, and apolipoproteins. However, comapred with the small intestine, it is much less efficient at exporting these lipoproteins. Epidermal growth factor, insulin, and hydrocortisone, which are known modulators of the brush border digestive functions of the human gut, differentially modulate the synthesis and secretion of lipoproteins in the small intestine and colon. The use of human fetal gut represents a unique model to further our understanding of the complex biosynthetic molecular events essential for the formation and secretion of lipoproteins relevant to human intestine, both in normal or pathological conditions.

Roles of molecular chaperones in pancreatic secretion and their involvement in intestinal absorption

This review focuses on the contribution of molecular chaperones in the secretory process of digestive enzymes and their interaction with enterocytes. By using biochemistry and immunocytochemistry, we have shown that Grp94, Cpn10, Cpn60, and protein disulfide isomerase (PDI) are present all along the rough endoplasmic reticulum-Golgi-granule secretory pathway of the pancreatic acinar cells and are secreted into the acinar lumen. Two other molecular chaperones, Grp78 and the Hsp70, appear to be restricted to the rough endoplasmic reticulum and the trans-Golgi apparatus, respectively. We have found that chaperones can be associated with pancreatic enzymes along the secretory pathway. Indeed, double immunogold and immunocoprecipitation revealed an association between Cpn60 and the colipase-dependent lipase (CDL) and between Grp94 and the bile salt-dependent lipase (BSDL). These complexes are secreted into the acinar lumen and diverted to the duodenal lumen. These findings led us to investigate these enzyme-chaperone complexes in intestinal tissue. Grp94, Cpn60, and PDI are present on microvilli and on the endosomal compartment of enterocytes. Furthermore, we have shown that the Grp94-BSDL complexes are internalized by enterocytes through classical endocytosis. Upon dissociation of the BSDL-Grp94 complex in the late endosome, BSDL is transferred to the basolateral membrane. We propose that Grp94 interacts with specific receptors and/or could force the associated protein to adopt a specific conformation that allows its binding to corresponding membrane receptors and its internalization by enterocytes. These two hypotheses need not to be exclusive. The existence of such a pancreatic secretion-intestinal absorption link speaks in favor of a coordinated functional connection between these two entities, through molecular chaperones, in order to optimize intestinal activities.

Radiation-induced bone sarcoma following total body irradiation: role of additional radiation on localized areas

A 44-year-old patient who had had acute monoblastic leukemia developed an osteosarcoma of the pelvic bones 5 years after an allogeneic bone marrow transplant from his HLA-identical sister. He had additionally received superficial cutaneous radiation of the legs and pelvis, over the 3 weeks prior to total body irradiation (TBI), because of cutaneous leukemic lesions. The tumor was a fibrohistiocytomatous osteogenic sarcoma. The first lesion was in the right ilium, and a second lesion appeared 18 months later, symmetrically on the left ilium. Despite treatment, the patient died from metastases. At the time of diagnosis of radiation-induced sarcoma, the patient was free of leukemia and had several risk factors already reported to favor the development of solid tumors in stem cell recipients. These include acute leukemia, TBI and graft-versus-host disease. As he developed symmetrical lesions of the pelvic bone, and because of the histology of the radiation-induced tumor, we assumed that the additional radiation of the skin prior to TBI may have contributed to the pathogenesis of this malignant fibrous histiocytoma. Therefore, the risk/benefit ratio should be carefully considered in unusual indications. These patients should benefit from a close follow-up of the superimposed areas.

Temporal and spatial variation of inversion polymorphism in two natural populations of Drosophila buzzatii

The inversion polymorphism of the cactophilic fly Drosophila buzzatii was studied in two natural populations. We assessed the temporal changes and microspatial population structure. We observed a significant increase in the frequency of arrangement 2J at the expense of 2ST in both populations. These gene arrangements appear to affect the life-history of flies differently. Environmental heterogeneity explains the karyotype coexistence in nature. The analysis of population structure showed that differentiation of inversion frequencies among individual breeding sites, the rotting clacodes of Opuntia vulgaris, was highly significant. The karyotypic frequencies did not depart significantly from Hardy-Weinberg expectations, neither in individual rots nor in the total population. These results suggest that the observed population structure can be easily accounted by random genetic drift.

Altered lipid profile, lipoprotein composition, and oxidant and antioxidant status in pediatric Crohn disease

BACKGROUND

Growing evidence supports a role for peroxidation in the pathogenesis of Crohn disease (CD). The activation of inflammatory cells, the release of their mediators, and the excessive production of free radicals may affect circulating lipids.

OBJECTIVE

We examined the lipid profile, lipoprotein composition, and oxidant-antioxidant status of children with CD.

DESIGN

We studied 22 pediatric CD patients and 10 healthy control subjects.

RESULTS

The proportion of saturated and monounsaturated fatty acids in plasma of CD patients was higher but that of polyunsaturated fatty acids was lower than in control subjects. This resulted in higher ratios in CD patients of palmitoleic acid to linoleic acid (P < 0. 05) and of eicosatrienoic acid to arachidonic acid (P < 0.04), 2 established indexes of essential fatty acid deficiency. Hypocholesterolemia was noted in CD patients as a result of lower LDL-cholesterol concentrations than in control subjects (P < 0.02). Plasma apolipoproteins B (P < 0.02) and A-I (P < 0.02) were also lower in CD patients, whereas plasma triacylglycerols were higher (P < 0.005). Lipoprotein composition was altered in CD patients, with relative triacylglycerol depletion and protein enrichment in VLDL. In contrast, intermediate-density lipoprotein of CD patients was characterized by an increased percentage of triacylglycerol and protein (P < 0.005) and a reduced proportion of phospholipids (P < 0. 01). Additional abnormalities were observed in the chemical distribution of HDL(2) and HDL(3) moieties. Lipid peroxidation was documented by higher plasma malondialdehyde concentrations in CD patients (P < 0.05), accompanied by lower retinol concentrations (P < 0.02).

CONCLUSION

Disturbances in the lipid profile, in lipoprotein concentrations and composition, and in oxidant-antioxidant status occur in CD patients.