Protective effect of rosuvastatin pretreatment against acute myocardial injury by regulating Nrf2, Bcl-2/Bax, iNOS, and TNF-α expressions affecting oxidative/nitrosative stress and inflammation

Cardiovascular disorders are the leading cause of death globally. Rosuvastatin is a member of statins (inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase) with many pleiotropic properties. This study investigated cardioprotective effects of rosuvastatin in isoprenaline-induced myocardial injury. Male rats were given rosuvastatin (1, 5, or 10 mg/kg, oral) daily for 1 week and on seventh and eighth day isoprenaline (150 mg/kg, subcutaneous) was given to induce cardiac injury. On ninth day, rats were euthanized and different samples were harvested for analysis. Isoprenaline administration resulted in increased cardiac mass, increased cardiac injury marker levels (cTnI, CK-MB, ALT, and AST), increased lipid/protein oxidation, and increased cardiac nitrite levels. It also decreased superoxide dismutase, CAT, GST, and glutathione reductase activities, and total antioxidant activity. Isoprenaline also increased TNF-α and IL-6 levels. Decreased mRNA expression of Nrf2 and Bcl-2 along with increased mRNA expression of Bax, eNOS and iNOS genes was observed in isoprenaline treated animals. Histopathological evaluations of rosuvastatin pre-treated groups showed reduction of myocardial necrosis. Pretreatment with rosuvastatin (5 and 10 mg/kg) reduced many of these pathological changes. The current study showed that rosuvastatin significantly reduces myocardial injury induced by isoprenaline.

Genotoxic effects of drospirenone and ethinylestradiol in human breast cells (in vitro) and bone marrow cells of female mice (in vivo)

Estrogen and progesterone congeners as found in various oral contraceptive formulations have been implicated as the cause of cancer in sex and tissue-specific targets. The mechanism of carcinogenesis by sex steroids is still debatable. In this study, we evaluated the genotoxicity induced by two components of one of the commonly used oral contraceptive formulation; drospirenone and ethinylestradiol in human breast cells (MCF-7) in vitro and in bone marrow cells of female mice in vivo. DNA damage was assessed by alkaline comet assay. Both of the drugs produced DNA damage in human breast cells at exposure concentrations which are about 100-fold and above than normally found in human blood after their lowest recommended doses. The DNA damage was produced only after metabolic activation by mice liver S-9 fraction in both cases. The co-exposure with both the compounds at median exposure levels resulted in potentiation of DNA damage. In bone marrow cells of adult female mice, both the compounds produced DNA damage at human equivalent doses after exposure was carried out repeatedly for approximately one estrus cycle (5 days). The co-administration with the compounds resulted in potentiation of DNA damage as indicated by percent tail DNA in comet assay. Thus it is concluded that drospirenone and ethinylestradiol cause DNA damage in certain target specific tissue (mammary epithelial cells) and in female bone marrow cells. The co-exposure with drospirenone and ethinylestradiol results in potentiation of genotoxicity which may pose a threat of cancer development in women taking these drugs for long periods.

International Nosocomial Infection Control Consortium (INICC) report, data summary of 45 countries for 2012-2017: Device-associated module

BACKGROUND

We report the results of International Nosocomial Infection Control Consortium (INICC) surveillance study from January 2012 to December 2017 in 523 intensive care units (ICUs) in 45 countries from Latin America, Europe, Eastern Mediterranean, Southeast Asia, and Western Pacific.

METHODS

During the 6-year study period, prospective data from 532,483 ICU patients hospitalized in 242 hospitals, for an aggregate of 2,197,304 patient days, were collected through the INICC Surveillance Online System (ISOS). The Centers for Disease Control and Prevention-National Healthcare Safety Network (CDC-NHSN) definitions for device-associated health care-associated infection (DA-HAI) were applied.

RESULTS

Although device use in INICC ICUs was similar to that reported from CDC-NHSN ICUs, DA-HAI rates were higher in the INICC ICUs: in the medical-surgical ICUs, the pooled central line-associated bloodstream infection rate was higher (5.05 vs 0.8 per 1,000 central line-days); the ventilator-associated pneumonia rate was also higher (14.1 vs 0.9 per 1,000 ventilator-days,), as well as the rate of catheter-associated urinary tract infection (5.1 vs 1.7 per 1,000 catheter-days). From blood cultures samples, frequencies of resistance, such as of Pseudomonas aeruginosa to piperacillin-tazobactam (33.0% vs 18.3%), were also higher.

CONCLUSIONS

Despite a significant trend toward the reduction in INICC ICUs, DA-HAI rates are still much higher compared with CDC-NHSN's ICUs representing the developed world. It is INICC's main goal to provide basic and cost-effective resources, through the INICC Surveillance Online System to tackle the burden of DA-HAIs effectively.

Comparative oncology: Integrating human and veterinary medicine

Cancer constitutes the major health problem both in human and veterinary medicine. Comparative oncology as an integrative approach offers to learn more about naturally occurring cancers across different species. Canine models have many advantages as they experience spontaneous disease, have many genes similar to human genes, five to seven-fold accelerated ageing compared to humans, respond to treatments similarly as humans do and health care levels second only to humans. Also, the clinical trials in canines could generate more robust data, as their spontaneous nature mimics real-life situations and could be translated to humans.

Erythropoietin Reverses Sepsis-Induced Vasoplegia to Norepinephrine Through Preservation of α1D-Adrenoceptor mRNA Expression and Inhibition of GRK2-Mediated Desensitization in Mouse Aorta

We investigated the effect of erythropoietin (EPO) posttreatment on survival time and vascular functions in a mouse model of sepsis. Sepsis was induced by cecal ligation and puncture. After 20 ± 2 hours of sepsis, thoracic aorta was isolated for assessing its reactivity to norepinephrine (NE) and acetylcholine (ACh). We also measured the tissue nitric oxide (NO) level, inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), G protein-coupled receptor kinase 2 (GRK2), and α1D adrenoceptor messenger RNA (mRNA)/protein expression. In septic mice, EPO moderately improved the survival time from 19.68 ± 0.75 to 34.7 ± 3.2 hours. Sepsis significantly decreased the aortic contractile response to NE along with reduced α1D mRNA and protein expression. Erythropoietin significantly preserved the α1D receptor expression and restored NE-induced contractions to control levels in septic mice. Further, it attenuated the aortic α1D receptor desensitization in sepsis which was evident from reduced GRK2 mRNA expression. Accordingly, a selective GRK2 inhibitor markedly restored the contractile responses to NE in sepsis. Erythropoietin treatment attenuated iNOS mRNA expression and iNOS-induced overproduction of NO, but improved endothelium-dependent relaxation to ACh associated with increased eNOS mRNA expression. In conclusion, EPO seems to reverse sepsis-induced vasoplegia to NE through the preservation of α1D adrenoceptor mRNA/protein expression, inhibition of GRK2-mediated desensitization, and attenuation of NO overproduction in the mouse aorta.

Sulfasalazine induced lung toxicity masquerading as sarcoidosis--case report and review of the literature

A commonly prescribed drug for Rheumatoid Arthritis (R.A) and Inflammatory Bowel Disease (IBD) treatment, Sulfasalazine can occasionally cause lung toxicity such as interstitial pneumonitis and eosinophilic pneumonias. We report a case of a 46 year old female being treated with Sulfasalazine for Ulcerative Colitis, who developed shortness of breath and a radiographic pattern of hilar adenopathy. Biopsy showed granulomas that resembled Sarcoidosis. We review different presentations of Sulfasalazine induced lung disease and describe the first known case of Sulfasalazine lung toxicity mimicking Sarcoidosis.

Requirements for emergent neurosurgical procedures among patients undergoing neuroendovascular procedures in contemporary practice

BACKGROUND AND PURPOSE

Provisions for an emergent neurosurgical procedure have been a mandatory component of centers that perform neuroendovascular procedures. We sought to determine the need for emergent neurosurgical procedures following neuroendovascular interventions in 2 comprehensive stroke centers in settings with such provisions.

MATERIALS AND METHODS

Analysis of retrospectively collected data from procedure logs and patient charts was performed to identify patients who required immediate (before the termination of the intervention) or adjunctive (within 24 hours of the intervention) neurosurgical procedures related to a neuroendovascular intervention complication. The types of neurosurgical procedures and in-hospital outcomes of identified patients are reported as an aggregate and per endovascular procedure-type analyses.

RESULTS

We reviewed a total of 933 neuroendovascular procedures performed during 3.5 years (2006-2010). A total of 759 intracranial procedures were performed. There was a need for emergent neurosurgical procedures in 8 patients (0.85% cumulative incidence and 1.05% for major intracranial procedures) (mean age, 46 years; 7 were women); the procedures were categorized as 3 immediate and 5 adjunctive procedures. There were 5 in-hospital deaths (62.5%) among these 8 patients. Neurosurgical procedures performed were external ventricular drainage placement in 6 (6 of 8, 75%) patients, decompressive craniectomy in 1 (12.5%) patient, and both surgical procedures in 1 (12.5%) patient.

CONCLUSIONS

The need for emergent neurosurgical procedures is very low among patients undergoing intracranial neuroendovascular procedures. Survival in such patients despite emergent neurosurgical procedures is quite low.

Direct and indirect activation of cortical neurons by electrical microstimulation

Electrical microstimulation has been used to elucidate cortical function. This review discusses neuronal excitability and effective current spread estimated by using three different methods: 1) single-cell recording, 2) behavioral methods, and 3) functional magnetic resonance imaging (fMRI). The excitability properties of the stimulated elements in neocortex obtained using these methods were found to be comparable. These properties suggested that microstimulation activates the most excitable elements in cortex, that is, by and large the fibers of the pyramidal cells. Effective current spread within neocortex was found to be greater when measured with fMRI compared with measures based on single-cell recording or behavioral methods. The spread of activity based on behavioral methods is in close agreement with the spread based on the direct activation of neurons (as opposed to those activated synaptically). We argue that the greater activation with imaging is attributed to transynaptic spread, which includes subthreshold activation of sites connected to the site of stimulation. The definition of effective current spread therefore depends on the neural event being measured.

Lurcher mice exhibit potentiation of GABA(A)-receptor-mediated conductance in cerebellar nuclei neurons in close temporal relationship to Purkinje cell death

In heterozygous Lurcher mice (Lc/+), the Purkinje cells (PCs) degenerate almost totally during postnatal development. On the other hand, their projection target, the deep cerebellar nuclei (DCN), shows few signs of degeneration and seems to play an important role in maintaining a residual cerebellar function in Lc/+. We asked whether the DCN in Lc/+ develop cellular adaptations allowing them to cope with the loss of GABAergic PC input. Using whole-cell patch-clamp recordings, we measured inhibitory postsynaptic currents from DCN of Lc/+ and wild-type mice (WT). In experiments on phenotypically striking Lc/+ studied well after the onset of the PC degeneration, we found enlarged average synaptic conductances (g(syn)) compared with WT. We next investigated postnatal mice before and after the onset of PC death. In younger animals </= postnatal day (p) 13, no difference was found in g(syn) between the two groups. At p14, g(syn) in Lc/+ showed an increase, while those in WT stayed on the level found in younger animals. A peak-scaled nonstationary fluctuation analysis suggests that an increase in the average number of channels open at peak is the basis for the change in g(syn). The changes in g(syn), suitable to increase the efficacy of GABAergic transmission, occur in close temporal relationship to PC death and, thus, may reflect a functional adaptation to the loss of the DCN's main GABAergic afferents.

IgM quantification in the cerebrospinal fluid of sleeping sickness patients by a latex card agglutination test

An increased IgM concentration in cerebrospinal fluid (CSF), occurring as a consequence of massive intrathecal IgM synthesis, is a marker of interest for diagnosis of the meningo-encephalitic stage in human African trypanosomiasis. However, in current practice, IgM in CSF is not determined because of the lack of a simple and robust test that is applicable in African rural regions where the disease prevails. We describe the development of a sensitive semiquantitative card agglutination test, LATEX/IgM, for IgM quantification in CSF. The test is simple and fast and the lyophilized reagent remains stable even at 45 degrees C. CSF end-titres obtained with LATEX/IgM parallel the IgM concentrations determined by nephelometry and enzyme-linked immunosorbent assay. Detection of intrathecal IgM synthesis is the most sensitive marker for CNS involvement in sleeping sickness. At a cut-off value of >or= 8, the sensitivity and specificity of LATEX/IgM for intrathecal IgM synthesis are 89.4 and 92.7%. As a consequence, patients with LATEX/IgM end-titres >or= 8 are likely to have intrathecal IgM synthesis, thus central nervous system involvement and therefore should be treated accordingly. Further studies should concentrate on the relationship between the LATEX/IgM end-titres, presence of intrathecal IgM synthesis and occurrence of treatment failures in patients treated with pentamidine.

Two types of neurons in the rat cerebellar nuclei as distinguished by membrane potentials and intracellular fillings

Classically, three classes of neurons in the cerebellar nuclei (CN), defined by different projection targets and content of transmitters, have been distinguished. However, evidence for different types of neurons based on different intrinsic properties is lacking. The present study reports two types of neurons defined mainly by their intrinsic properties, as determined by whole-cell patch recordings. The majority of cells (type I, n = 63) showed cyclic burst firing whereas a small subset (type II, n = 7) did not. Burst firing was used to distinguish the two types of neurons because, as it turned out, pharmacological interference could not be used to convert the non-bursting cells to bursting ones. Some of the membrane potentials exclusively present in type I neurons, such as sodium and calcium plateau potentials, low-threshold calcium spikes, and a slow calcium-dependent afterhyperpolarization, were found to contribute to the generation of burst firing. Other membrane potentials of type I neurons were not obviously related to the generation of bursts. These were 1) the lower amplitude and width of the action potential during spontaneous activity, 2) a sequence of afterhyperpolarization-afterdepolarization-afterhyperpolarization following each spike, and 3) the high spontaneous firing rate. In contrast, type II neurons lacked slow plateau potentials and low threshold spikes. Their action potentials showed higher amplitude and width and were followed by a single deep afterhyperpolarization. Furthermore, they showed a lower firing rate at rest. In both types of neurons, a delayed inward rectification was present. Neurons filled with neurobiotin revealed that the sizes of the somata and dendritic fields of type I neurons comprised the whole range known from Golgi studies, whereas those of the few type II neurons recovered were found to be in the lowest range. In view of their size and scarcity, we propose that type II neurons may correspond to CN interneurons.

Distribution of mossy fibre rosettes in the cerebellum of cat and mice: evidence for a parasagittal organization at the single fibre level

Mossy fibres are the main afferent input to the granular layer of the cerebellar cortex. In this study, the spatial distribution of the mossy fibres' presynaptic enlargements - the so-called rosettes - were analysed on the single fibre level. Data obtained from the cerebella of cat and mice were compared to look for species differences, and the cerebella of the adult and young mice were also compared to look for developmental changes. The results show that there is a spatial anisotropy in all mossy fibres studied, with neighbouring rosettes being about three times further away from each other along the parasagittal axis and closer to each other in the mediolateral direction. Furthermore, these results suggest that this anisotropy is established at an early developmental stage. The anisotropic orientation of mossy fibres at the single fibre level supports the hypothesis of a timing mechanism in cerebellar function.

Exploring a critical parameter of timing in the mouse cerebellar microcircuitry: the parallel fiber diameter

Since the conduction velocity of the parallel fibers is a critical parameter for a theory of timing in the cerebellar cortex, we set out to quantify the diameter of these axons on an ultrastructural level. The overall mean of the fiber diameter was 0.18 microm. Our results confirm that the parallel fibers of the upper molecular layer are significantly thinner than those of the lower layers. Nevertheless, the difference of about 0.02 microm determined by this study is surprisingly small. In addition, the distribution of the fiber diameters of the upper layers differed slightly, but significantly from a normal distribution, partly on account of a positive skew and a positive kurtosis excess. In summary, the results show that there are fewer differences between the parallel fibers of different levels of the molecular layer than previously assumed and that these differences do not contradict a theory of timing in the cerebellar cortex.

Quantitative Golgi study of the rat cerebellar molecular layer interneurons using principal component analysis

In this study, we applied for the first time a multivariate analysis to describe the anatomy of cerebellar molecular layer interneurons. Forty variables extending over a variety of morphological features (geometrical, topological, and metrical) were obtained from a three-dimensional reconstruction of 26 rat rapid Golgi-stained neurons. The subsequent principal component analysis showed that the first principal component was strongly correlated with variables related to the depth of each cell's soma in the molecular layer. The second principal component was strongly correlated with parameters describing axonal morphology. Finally, an analysis of the distribution of these anatomical features suggested that these cells cannot be classified into distinct groups but, instead, represent one continuously varying population. Thus, the classical division of molecular layer neurons into deep basket cells and superficial stellate cells is not supported by our analysis. These results have important implications for the development of the cerebellar cortex as well as for the expected patterns of Purkinje cell activity following activation of the granule cell layer.

Mucosal immunogenicity of a holotoxin-like molecule containing the serine-rich Entamoeba histolytica protein (SREHP) fused to the A2 domain of cholera toxin

One strategy for the induction of mucosal immune responses by oral immunization is to administer the antigen in conjunction with cholera toxin. Cholera toxin consists of one A polypeptide (CTA) which is noncovalently linked to five B subunits (CTB) via the A2 portion of the A subunit (CTA2). Coupling of antigens to the nontoxic B subunit of cholera toxin may improve the immunogenicity of antigens by targeting them to GM1 ganglioside on M cells and intestinal epithelial cells. Here, we describe the construction of a translational fusion protein containing the serine-rich Entamoeba histolytica protein (SREHP), a protective amebic antigen, fused to a maltose binding protein (MBP) and to CTA2. When coexpressed in Escherichia coli with the CTB gene, these proteins assembled into a holotoxin-like chimera containing MBP-SREHP-CTA2 and CTB. This holotoxin-like chimera (SREHP-H) inhibited the binding of cholera toxin to GM1 ganglioside. Oral vaccination of mice with SREHP-H induced mucosal immunoglobulin A (IgA) and serum IgG antiamebic antibodies and low levels of mucosal anti-CTB antibodies. Our studies confirm that the genetic coupling of antigens to CTA2 and their coexpression in E. coli can produce holotoxin-like molecules that are mucosally immunogenic without the requirement for supplemental cholera toxin, and they establish the SREHP-H protein as a candidate for evaluation as a vaccine to prevent amebiasis.

The detection and generation of sequences as a key to cerebellar function: experiments and theory

Starting from macroscopic and microscopic facts of cerebellar histology, we propose a new functional interpretation that may elucidate the role of the cerebellum in movement control. The idea is that the cerebellum is a large collection of individual lines (Eccles's "beams": Eccles et al. 1967a) that respond specifically to certain sequences of events in the input and in turn produce sequences of signals in the output. We believe that the sequence-in/sequence-out mode of operation is as typical for the cerebellar cortex as the transformation of sets into sets of active neurons is typical for the cerebral cortex, and that both the histological differences between the two and their reciprocal functional interactions become understandable in the light of this dichotomy. The response of Purkinje cells to sequences of stimuli in the mossy fiber system was shown experimentally by Heck on surviving slices of rat and guinea pig cerebellum. Sequential activation of a row of eleven stimulating electrodes in the granular layer, imitating a "movement" of the stimuli along the folium, produces a powerful volley in the parallel fibers that strongly excites Purkinje cells, as evidenced by intracellular recording. The volley, or "tidal wave," has maximal amplitude when the stimulus moves toward the recording site at the speed of conduction in parallel fibers, and much smaller amplitudes for lower or higher "velocities." The succession of stimuli has no effect when they "move" in the opposite direction. Synchronous activation of the stimulus electrodes also had hardly any effect. We believe that the sequences of mossy fiber activation that normally produce this effect in the intact cerebellum are a combination of motor planning relayed to the cerebellum by the cerebral cortex, and information about ongoing movement, reaching the cerebellum from the spinal cord. The output elicited by the specific sequence to which a "beam" is tuned may well be a succession of well timed inhibitory volleys "sculpting" the motor sequences so as to adapt them to the complicated requirements of the physics of a multijointed system.

Characterization and quantification of apolipoprotein E in the genetically hypercholesterolemic rat (RICO)

The levels of apolipoprotein E (apo E) in serum and in isolated lipoprotein fractions from genetically hypercholesterolemic rats (RICO) and their normocholesterolemic controls (SW), were evaluated by immunoblotting, and their polymorphism was analyzed by isoelectrofocusing. The present results confirm previous findings from a qualitative SDS-PAGE analysis. When measured by immunoblotting, total apo E increased by 35% in the RICO rat plasma. In the different lipoprotein fractions, apo E in RICO rat increased in low density lipoproteins; LDL1, LDL2 (apo E rich HDL1) and high density lipoproteins (HDL2, HDL3). Only in the chylomicron fraction did apo E decrease. The two-dimensional electrophoretic method demonstrated that four isoproteins designated E-1, E-2, E-3 and E-4 are present at a pI range from 5.36 to 5.56 in RICO rat as well as in control SW rat.

Rapid development of resistance to clarithromycin following monotherapy for disseminated Mycobacterium chelonae infection in a heart transplant patient

Mycobacterium chelonae (formerly known as M. chelonae subspecies chelonae) is a rapidly growing mycobacterium that can cause disseminated infections, especially in immunocompromised hosts. The bacterium is typically resistant to antimicrobial agents; less than 20% of M. chelonae isolates are susceptible to trimethoprim-sulfamethoxazole, doxycycline, erythromycin, or ciprofloxacin. Findings in a recent study suggested that clarithromycin may be the drug of choice for the treatment of cutaneous (disseminated) disease due to M. chelonae. We describe a 60-year-old heart transplant patient with disseminated M. chelonae infection for whom monotherapy with clarithromycin failed because of the rapid development of resistance to the drug.

Effect of dietary cholesterol on activity and mRNA levels of hepatic lipase in rat

Female lean Zucker rats were fed for four weeks with either a control diet or the same diet enriched with 2% (w/w) cholesterol and cholic acid (0.5%, w/w). This treatment resulted in a 6-fold increase in plasma total cholesterol. A 30% decrease was observed in plasma post-heparin HL activity, in contrast with lipoprotein lipase, which was unmodified in the cholesterol/cholate-fed rats. HL activity measured in liver homogenate from these rats was also decreased (-30%, p < 0.05), as was its protein mass, quantified by immunoblot analysis (-57%, (p < 0.01), whereas HL mRNA levels were 3-fold lower in the cholesterol/cholate-fed rats. We conclude that the cholesterol/cholate-enriched diet decreases the HL gene expression by acting at the transcriptional level and/or by affecting HL mRNA stability, or both.

Lipoprotein lipase and hepatic lipase activities in a hypercholesterolaemic (RICO) strain of rat. Effect of dietary cholesterol

Hepatic lipase (HL) and lipoprotein lipase (LPL) were assayed in heparinized plasma from male normocholesterolaemic (SW) and genetically hypercholesterolaemic (RICO) rats. Both strains were fed on either a semi-purified control diet or the same diet enriched with 0.5% or 1% cholesterol. HL activity was similar in both groups of rats fed on the control diet. LPL activity was found to be significantly lower in RICO rats (35% decrease, P less than 0.05). Feeding with a high-cholesterol diet led to a decrease in HL activity (15-23%) in both groups of rats but no change was detected in LPL activity, which remained consistently lower in the RICO rats. Thus, with the control diet, LPL activity is lower in RICO rats but presumably is not rate-limiting for their triacylglycerol clearance, given the normal triacylglycerol levels present. After cholesterol feeding, however, the lower LPL activity may become rate-limiting together with the decrease in HL activity, as in these circumstances hypertriacylglycerolaemia was evident and the hypercholesterolaemia of this strain was further increased.

Inhibition of hepatic lipase activity impairs chylomicron remnant-removal in rats

[4-14C]Cholesteryl oleyl ether-labeled chylomicron remnants were injected into rats which received a specific goat antibody against rat hepatic lipase or a control serum. Chylomicron remnant cholesterol ether disappeared from circulation with a significantly higher half-life (2-fold) in antibody-treated rats than in controls (P less than 0.001). Recovered radioactivity in the liver was 2-fold lower in antibody-treated rats (22.8% (n = 6) vs. 45% (n = 4) P less than 0.01). These results clearly show that hepatic lipase may strongly promote chylomicron remnant cholesterol ether uptake by the liver.

Chylomicron-remnant uptake by freshly isolated hepatocytes. Effect of heparin and of hepatic triacylglycerol lipase

Chylomicron remnants labelled biologically with [3H]cholesterol were efficiently taken up by freshly isolated hepatocytes during a 3 h incubation in Krebs bicarbonate medium. Their [3H]cholesteryl ester was hydrolysed (74% net hydrolysis), and 0.1 mM-chloroquine could partially inhibit this hydrolysis, provided that hepatocytes were first preincubated for 2 h 30 min at 37 degrees C. This hydrolysis was also measured in preincubated cells with remnants double-labelled (3H and 14C) on their free cholesterol moiety; [3H]cholesterol arising from [3H]cholesteryl ester hydrolysis was recovered in the free [3H]cholesterol pool. A dose-response study showed saturation of remnant uptake at 180 micrograms of remnant protein/10(7) cells. Heparin (10 units/ml) increased remnant uptake by 63% (P less than 0.01), [3H]cholesteryl ester accumulation in the cell pellet by 110% (P less than 0.025) and hepatic lipase activity secreted in the medium by 2.4-fold (P less than 0.01) and by 3.3-fold (P less than 0.01) at the end of the preincubation and incubation periods respectively. Addition of 100 munits of semi-purified hepatic lipase preparation/flask stimulated remnant uptake by 44-69%, and [3H]cholesteryl ester accumulation in the presence of chloroquine by 2.1-fold (P less than 0.025). When hepatic lipase was incubated solely with the remnants, it decreased their triacylglycerol and phospholipid contents by 24% and 26% respectively. Thus freshly isolated hepatocytes may be used to study chylomicron-remnant uptake. Hepatic lipase, which seems to underly the stimulating effect of heparin, facilitates remnant uptake in vitro, and this could be mediated by at least one (or both) of its hydrolytic properties.