Design, synthesis, in vitro and in silico evaluation of anti-colorectal cancer activity of curcumin analogues containing 1,3-diphenyl-1H-pyrazole targeting EGFR tyrosine kinase.

Recent studies have shown that monocarbonyl analogues of curcumin (MACs) and 1H-pyrazole heterocycle both demonstrated promising anticancer activities, in which several compounds containing these scaffolds could target EGFR. In this research, 24 curcumin analogues containing 1H-pyrazole (a1-f4) were synthesized and characterized by using modern spectroscopic techniques. Firstly, synthetic MACs were screened for cytotoxicity against human cancer cell lines such as SW480, MDA-MB-231 and A549, from which the 10 most potential cytotoxic compounds were identified and selected. Subsequently, the selected MACs were further screened for their inhibition against tyrosine kinases, which showed that a4 demonstrated the most significant inhibitory effects on EGFRWT and EGFRL858R. Based on the results, a4 further demonstrated its ability to cause morphological changes, to increase the percentage of apoptotic cells, and to increase caspase-3 activity, suggesting its apoptosis-inducing activity on SW480 cells. In addition, the effect of a4 on the SW480 cell cycle revealed its ability to arrest SW480 cells at G2/M phase. In subsequent computer-based assessments, a4 was predicted to possess several promising physicochemical, pharmacokinetic, and toxicological properties. Via molecular docking and molecular dynamics simulation, a reversible binding mode between a4 and EGFRWT, EGFRL858R, or EGFRG719S, remained stable within the 100-ns simulation due to effective interactions especially the hydrogen bonding with M793. Finally, free binding energy calculations suggested that a4 could inhibit the activity of EGFRG719S more effectively than other EGFR forms. In conclusion, our work would provide the basis for the future design of promising synthetic compounds as anticancer agents targeting EGFR tyrosine kinase.

Attitudes Toward Aging Among Patients With Upper Extremity Illness.

Background: An adaptive attitude toward aging might limit symptom intensity and magnitude of limitations. This study sought factors associated with attitudes toward aging (measured with the Brief Aging Perceptions Questionnaire [B-APQ]) and studied the relationship of having an age-related disease to magnitude of limitations, pain intensity, patient satisfaction, and patient comfort with completing a questionnaire about attitudes toward aging. We also looked for a subset of questions from B-APQ that maintained the construct validity and internal consistency of B-APQ, without unacceptable flooring or ceiling effects. Methods: A total of 161 upper extremity patients completed the following questionnaires: B-APQ, Patient Health Questionnaire-Short Form, Pain Self-efficacy-Short Form, Pain Catastrophizing Scale-Short Form, Patient-Reported Outcomes Measurement Information System Physical Function-Upper Extremity, pain intensity, satisfaction with the surgeon, and comfort with completing the B-APQ. We created multivariable linear regression models to test for associations. Results: Factors independently associated with less positive perceptions about aging included white race, retired work status, having nonspecific comorbidities, and more catastrophic thinking. Variation in the magnitude of limitations and pain intensity was accounted for by effectiveness of coping strategies rather than attitudes toward aging in particular. A 4-question version of the B-APQ has acceptable performance. Conclusion: Adaptive attitudes toward aging are associated with psychological and social determinants of health. We present a 4-item short form of B-APQ that could be used as a brief measure to assess attitudes toward aging. Interventions to improve adaptiveness to nociception (eg, cognitive behavioral therapy to limit catastrophic thinking) might help with adaptation to age-related changes.

Moderate and deep sedation training and pharmacology for nonanesthesiologists: recommendations for effective practice.

PURPOSE OF REVIEW: The purpose of this review is to discuss current drugs used for intravenous moderate and deep sedation by nonanesthesiologists in the United States. We also explore training expectations for moderate and deep sedation as they play key roles in anesthetic selection and preprocedural planning. RECENT FINDINGS: Although opioids and benzodiazepines are considered the standard for moderate sedation, increased interest in propofol, dexmedetomidine, and other sedative-hyptonic drugs require additional attention in terms of training providers and complying with current practice guidelines. SUMMARY: Moderate sedation providers should be familiar with titrating benzodiazepines and opioids to achieve targeted sedation. The use of propofol and ketamine is generally reserved for deep sedation by qualified professionals. However, the role of dexmedetomidine in procedural sedation continues to evolve as its use is explored in moderate sedation. Providers of all sedation types should be aware of hypotension, apnea, hypoventilation, and hypoxia that can develop and they should be able to manage the patient under these circumstances. Preprocedural planning is an integral training expectation to minimize patient risks.

The Growth of Poorly Cited Articles in Peer-Reviewed Orthopaedic Journals.

BACKGROUND: In general, journals can be divided in three categories: subscription-model, open-access, and hybrid (that is, open-access by choice). One measure of an article's impact is the number of citations it receives after publication. Open-access publishing may make articles more widely available because there is no financial barrier to a reader seeing the full-text version. As a result, we wondered whether articles published in fully open-access journals would be more likely to be cited than articles in other kinds of journals. QUESTIONS/PURPOSES: We assessed the yearly number and proportion of poorly cited articles published in orthopaedic journals and compared the proportion of poorly cited articles that were published in subscription-model journals with the proportion of poorly cited articles that were published in open-access and hybrid journals. METHODS: We identified all original articles (n = 135,029) published in orthopaedic peer-reviewed journals (n = 204) that were active from 2002 to 2012 and indexed in the Scopus® citation database. For each journal, we recorded the type of access (subscription-model, open-access, or hybrid journal), their most-recent CiteScore, the number of well- and poorly cited articles per year (more than five versus five or fewer citations after publication) calculated from the date of publication until December 31, 2017 (data collection April 2018), and then calculated if the journals themselves were poorly cited per year (defined as journals that published 75% or more articles ranked as poorly cited per year). We compared the proportion of poorly cited articles in subscription-model journals with the proportion of poorly cited articles in open-access journals. Additionally, we compared these with hybrid journals. RESULTS: In total, 48,133 (36%) articles were classified as poorly cited. The total number and proportion of poorly cited articles increased over the years, from 2121 of 7860 (27%) in 2002 to 6927 of 16,282 (43%) in 2012. The proportion of poorly cited articles in subscription-model journals increased from 226 of 395 (57%) in 2002 to 411 of 578 (71%) in 2012. The proportion of poorly cited articles in open-access journals decreased from 264 of 434 (61%) in 2002 to 296 of 801 (37%) in 2006, and then increased again to 1387 of 2259 (61%) in 2012. When we compared yearly proportions of poorly cited articles in subscription-model versus open-access journals using Mann-Whitney U tests, we only found a difference in 2012, with a higher proportion of poorly cited articles in subscription-model journals that year (median [IQR] of poorly cited article proportions for open-access, 0.61; IQR, 0.38-0.96 and subscription-model journals, 0.92; IQR, 0.54-1.0; p = 0.049). Comparisons of poorly cited articles for all three types of access showed lower proportions of poorly cited articles in hybrid journals for each year, with the lowest proportion found in 2002 (0.20; IQR, 0.09-0.67; p = 0.003). CONCLUSIONS: We found no difference in the likelihood that an article would be cited based on whether the article appeared was published in a subscription-model journal or an open-access journal. A future study might compare open-access and paywall articles on similar topics published in the same journal or investigate the characteristics of poorly cited articles, so that researchers and editorial staffs might understand which topics are more impactful and to determine if any important work is less-well appreciated. Additionally, an article-by-article analysis will provide more insight in citation rates for articles published within hybrid journals. LEVEL OF EVIDENCE: Level III, therapeutic study.

Do Patients Unconsciously Associate Suggestions for More-invasive Treatment with Better Care?

BACKGROUND: It seems common for patients to conceive of care in physical terms, such as medications, injections, and procedures rather than advice and support. Clinicians often encounter patients who seem to prefer more testing or invasive treatments than expertise supports. We wanted to determine whether patients unconsciously associate suggestions for invasive treatments with better care. QUESTIONS/PURPOSES: (1) Do patients have (A) an implicit preference and (B) an expressed preference for a physical intervention (such as a pill, an injection, or surgery) over supportive care (such as reassurance and education)? (2) What factors are independently associated with both an implicit and an expressed preference for a physical intervention over supportive care? (3) Is there a relationship between a patient's implicit preference toward or away from a physical intervention and his/her expressed preference on that subject? METHODS: In this study, we approached 129 new patients in a large urban area visiting one of 13 participating surgeons divided among six upper and lower extremity specialist offices. After excluding four patients based on our exclusion criteria, 125 patients (97%) completed a survey of demographics and their expressed preference about receiving either physical treatment or support. Treatment was defined as any surgery, procedure, injection, or medication; support was defined as reassurance, conversation, and education, but no physical treatment. Patients then completed the Implicit Association Test (IAT) to evaluate implicit preferences toward treatment or support. Although other IATs have been validated in numerous studies, the IAT used in this study was specifically made for this study. Scores (D scores) range from -2 to 2, where 0 indicates no implicit preference, positive scores indicate a preference toward receiving a physical treatment is good care, and negative scores indicate a preference toward receiving supportive care is good care. According to the original IAT, break points for a slight (± 0.15 to 0.35), moderate (± 0.35 to 0.65), and strong preference (± 0.65 to 2) were selected conservatively according to psychological conventions for effect size. Patients' mean age was 50 ± 15 years (range, 18-79 years) and 56 (45%) were men. The patients had a broad spectrum of upper and lower extremity musculoskeletal conditions, ranging from trigger finger to patellofemoral syndrome. RESULTS: We found a slight implicit association of good care with support (D = -0.17 ± 0.62; range, -2 to 1.2) and an expressed preference for physical treatment (mean score = 0.63 ± 2.0; range, -3 to 3). Patients who received both physical and supportive treatment had greater implicit preference for good care, meaning supportive care, than patients receiving physical care alone (ß = -0.42; 95% CI, -0.73 to -0.11; p = 0.008; semipartial R = 0.04; adjusted R full model = 0.13). Gender was independently associated with a greater expressed preference for physical treatment, with men expressing this preference more than women (ß = 1.0; 95% CI, 0.31-1.7; p = 0.005; semipartial R = 0.06; adjusted R full model = 0.08); receiving supportive treatment was independently associated with more expressed preference for support (ß = -0.98; 95% CI, -1.7 to -0.23; p = 0.011; semipartial R = 0.05). An expressed preference for treatment was not associated with implicit preference (ß = 0.01; 95% CI, -0.04 to 0.06; p = 0.721). CONCLUSIONS: Although surgeons may sometimes feel pressured toward physical treatments, based on our results and cutoff values, the average patient with upper or lower extremity symptoms has a slight implicit preference for supportive treatment and would likely be receptive. LEVEL OF EVIDENCE: Level II, prognostic study.

Assessment of terbium (III) as a luminescent probe for the detection of tuberculosis biomarkers.

A detection method for nicotinic acid, a specific metabolite marker of Mycobacterium tuberculosis present in cultures and patients' breath, is studied in complex solutions containing other metabolites and in biological media such as urine, saliva and breath condensate. The method is based on the analysis of the luminescence increase of Tb(3+) complexes in the presence of nicotinic acid due to the energy transfer from the excited ligand to the lanthanide ion. It is shown that other potential markers found in M. tuberculosis culture supernatant, such as methyl phenylacetate, p-methyl anisate, methyl nicotinate and 2-methoxy biphenyl, can interfere with nicotinic acid via a competitive absorption of the excitation photons. A new strategy to circumvent these interferences is proposed with an upstream trapping of volatile markers preceding the detection of nicotinic acid in the liquid phase via the luminescence of Tb(3+) complexes. The cost of the method is evaluated and compared with the Xpert MTB/RIF test endorsed by the World Health Organization.

Three new steroid biglycosides, plancisides A, B, and C, from the starfish Acanthaster planci.

Three new steroid biglycosides, plancisides A-C (1-3), were isolated from the ethanolic extract of the starfish Acanthaster planci. The structures of 1-3 were determined by extensive NMR and ESI-MS techniques, as (24S)-28-O-[ß-D-galactofuranosyl-(1-->5)-α-L-arabinofuranosyl]-24-methyl-5α-cholestane-3ß, 4ß, 6α, 8, 15α,16α, 28-heptol (1), (24S)-28-O-[α-L-fucopyranosyl-(1 --> 2)-3-O-methy-ß-D-xylopyranosy]-24-methy-5α-cholestane-3ß, 4ß,6α,8,15ß,16ß,28- heptol (2) and (24S)-28-O-[2,4-di-O-methyl-ß-D-xylopyranosyl-(1 --> 2)-α-L-arabinofuranosyl]-24-methyl-5α-cholestane-3ß,4ß,6α,8,15ß,16ß,28-heptol 6-O-sulfate (3), respectively. Compound 2 is the first steroid glycoside containing an α-fucopyranose unit found from starfish. Compound 1 slightly inhibits cell proliferation of HCT-116, T-47D, and RPMI-7951 cancer cell lines, but has no effect on colony formation of these cells in a soft agar clonogenic assay.

Elastosis perforans serpiginosa secondary to D-penicillamine therapy with coexisting cutis laxa.

Elastosis perforans serpiginosa (EPS) is a rare complication of D-penicillamine therapy. EPS has been reported in patients with Wilson disease, cystinuria, and rheumatoid arthritis after many years of high-dose therapy. We report a case of D-penicillamine-induced EPS with coexisting acquired cutis laxa in a patient with cystinuria. Although both EPS and acquired cutis laxa can be associated with D-penicillamine therapy, few cases have been reported with overlapping clinical presentations, and previously only in patients with Wilson disease. We review the characteristic clinical and histologic features of EPS and discuss the potential dermatologic manifestations of D-penicillamine therapy.

Prostaglandin E2 affects differently the release of inflammatory mediators from resident macrophages by LPS and muramyl tripeptides.

LPS and MTP-PE (liposome-encapsulated N-acetyl-muramyl-L-alanyl-D-isoglutaminyl-L-alanine-2-:[1',2'dipalmitoyl -sni-glycero-3-(hydroxy-phosphoryl-oxyl)] etylamide) induce in liver macrophages a synthesis and release of TNF-alpha, nitric oxide and prostanoids. Both agents induce an expression of mRNA's encoding TNF-alpha, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, and of corresponding proteins. LPS and MTP-PE induce a rapid activation of the extracellular regulated kinase (ERK) isoenzymes-1 and -2. Inhibition of map kinase isoenzymes leads to a decreased release of TNF-alpha, nitric oxide and prostaglandin (PG) E2 after both agents. The transcription factors NF-kappaB and AP-1 are strongly activated by LPS within 30 minutes. MTP-PE induces a weak activation of both transcription factors only after 5 hours. Inhibition of NF-kappaB inhibits the LPS- but not the MTP-PE-induced release of TNF-alpha, nitric oxide and PGE2. PGE2 release after LPS is higher than after MTP-PE. Exogenously added PGE2 inhibits the activation of map kinase and TNF-alpha release by LPS, but not by MTP-PE. Release of nitric oxide after LPS and MTP-PE is enhanced after prior addition of PGE2. PGD2 is without any effect. MTP-PE, but not LPS, induces a cytotoxicity of Kupffer cells against P815 tumor target cells. The MTP-PE-induced cytotoxicity is reduced by TNF-alpha neutralizing antibodies, indicating the involvement of TNF-alpha. Thus our results suggest that the different potencies of LPS and MTP-PE as immunomodulators probably result from different actions on Kupffer cells, resulting in differences in the amounts and kinetics of released TNF-alpha and PGE2, and that PGE2 plays an important regulatory role in the action of LPS, but not in the actions of MTP-PE.

Differential activation of transcription factors NF-kappa B and AP-1 in rat liver macrophages.

Liver macrophages (Kupffer cells) respond to many stimulations with the production of bioactive substances including cytokines, eicosanoids, and inorganic radicals. In this study the activation of transcription factors by substances inducing cytokine gene expression or superoxide formation in rat Kupffer cells was examined. Using primary cultures of rat Kupffer cells the role of NF-kappa B and activator protein 1 (AP-1) in the expression of the tumor necrosis factor-alpha (TNF-alpha) gene by lipopolysaccharide (LPS) was investigated. Both transcription factors were strongly activated but with different kinetics. Maximal DNA-binding activity was induced with 50 ng of LPS/mL of medium and persisted for at least 24 hours. At that time, NF-kappa B- as well as AP-1-DNA complexes decreased their mobilities in native gels. Among the cytokines tested only TNF-alpha and macrophage colony-stimulating factor (M-CSF) were able to activate NF-kappa B in Kupffer cells. Phorbol ester and zymosan activated AP-1 but not NF-kappa B; the treatment of zymosan yielding a modified form of AP-1. Of all substances found to interfere with TNF-alpha production by Kupffer cells (pyrrolidine dithiocarbamate, dexamethasone, prostaglandin E2, interleukin [IL]-4, IL-10, and transforming growth factor-beta [TGF-beta]) only pyrrolidine dithiocarbamate was able to completely inhibit the activation of NF-kappa B by LPS. Although not abrogating the LPS activation of NF-kappa B, dexamethasone inhibited that of AP-1. The results indicate a direct participation of NF-kappa B in the regulation of TNF-alpha synthesis and a differential effect of LPS on NF-kappa B and AP-1, respectively.

Effects of hypoxia on the oxygen-dependent metabolism of prostaglandins and adenosine in liver cells.

In this study, the capacity of hepatocytes to degrade prostaglandins diminished if the partial oxygen pressure dropped below 5%. This decrease was accompanied by an increased lactate/pyruvate ratio, a decrease in fatty acid oxidation and a drop in the ATP level. The degradation of exogenous adenosine increased with decreasing oxygen tension. At a partial oxygen pressure below 10%, the conversion of uric acid to allantoin, the final catabolite of adenosine in the rat, was strongly inhibited, resulting in the accumulation of uric acid in the medium. A good correlation was observed between the partial oxygen pressure, the oxidation of uric acid to allantoin and the degradation of prostaglandins D2 and E2, suggesting a peroxisomal pathway of hepatic prostaglandin oxidation. Subcellular fractionation of liver homogenates revealed peroxisomes as the site of degradation of prostaglandins D2 and E2 augmented by cytosolic components. The similarity of the degradation products found in the cell-free system, in hepatocytes and in the perfused liver further supports a peroxisomal degradation of prostaglandins in vivo. Stimulated liver macrophages (Kupffer cells) produced the same amount and pattern of eicosanoids at 1% and 21% O2. Even the formation of superoxide remained unaffected down to a partial pressure of 1%. At partial O2 pressures below 1%, the production of prostaglandins and superoxide became strongly inhibited. These results indicate that essential oxygenation reactions in activated Kupffer cells, including prostaglandin synthesis, possess high affinities to oxygen, while the peroxisomal pathway of prostaglandin oxidation in hepatocytes is sensitive to an O2 tension as low as 5%.

Production of tumor necrosis factor-alpha, interleukin-1 and interleukin-6 in the perfused rat liver.

The kinetics of the production and release of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) and interleukin-6 (IL-6) were investigated in the perfused rat liver and in primary cultures of Kupffer cells after stimulation with lipopolysaccharide (LPS). A small and transient accumulation of TNF-alpha could be detected immunohistochemically and by cytotoxicity assay in the intracellular space about 1 h after addition of LPS to the cultured cells. TNF-alpha release in the perfused liver followed similar kinetics as those found in the serum of LPS-treated rats and in primary cultures of rat Kupffer cells. The cytotoxic TNF-alpha activity of the perfusate attained its maximum (11.5 +/- 2.6 U/ml) 90 min after LPS stimulation and remained nearly constant for further 150 min. 2 microM dexamethasone reduced the production of TNF-alpha by 10 g of liver during 240 min from 46 to 16 x 10(3) units. The production of IL-1 and IL-6 by 10 g of liver during the initial 240 min was 3 and 530 x 10(3) IU, respectively. The maximal concentrations of IL-1 (1.4 +/- 0.7 IU/ml) and IL-6 (157 +/- 60 IU/ml) were found 240 min after LPS addition. The production of IL-1 was totally suppressed by 2 microM dexamethasone.(ABSTRACT TRUNCATED AT 250 WORDS)

The contraction of hepatic stellate (Ito) cells stimulated with vasoactive substances. Possible involvement of endothelin 1 and nitric oxide in the regulation of the sinusoidal tonus.

We have studied the contractility of liver sinusoidal stellate (Ito) cells stimulated with endothelin 1, nitric-oxide donors and eicosanoids. Contraction and relaxation of stellate cells were detected by the use of a silicone-rubber method that revealed the traction forces exerted by these cells. Endothelin 1 was a strong elicitor for stellate-cell contraction. 78, 55, 59 and 56% of stellate cells were contracted 2.5, 5, 10 and 20 min, respectively, after exposure to 10 nM endothelin 1. The effect of endothelin 1 was dose dependent and still detectable at an endothelin 1 concentration of 100 pM. Concomitantly, an endothelin-dependent formation of inositol phosphates was apparent; values of InsP, InsP2, and InsP3 were 881 +/- 99%, 1965 +/- 368%, and 791 +/- 120% of control, respectively, 20 min after addition of 10 nM endothelin 1. In addition, endothelin 1 caused a transient increase of [Ca2+]i in stellate cells from a basal value of 121 +/- 9 nM to maximal 1015 +/- 86 nM. These endothelin-1 effects were much stronger than those of the thromboxane-A2 analogue U46619 and of prostaglandin F2 alpha. In contrast, Iloprost, prostaglandin E2, and sodium nitroprusside promoted stellate-cell relaxation; for example, 82, 83 and 71% of stellate cells relaxed 5, 10, and 20 min, respectively, after addition of 500 microM sodium nitroprusside to contacted cells. Prostaglandin E2 and Iloprost led to elevation of cAMP levels in stellate cells from a basal value of 9.2 +/- 0.8 pmol/well to 55.1 +/- 8.0 and 122.2 +/- 12.2 pmol/well 10 min after addition of prostaglandin E2 (5 microM) and Iloprost (5 microM), respectively, in the presence of 3-isobutyl-1-methylxanthine (0.5 mM). However, sodium nitroprusside was a trigger for cGMP accumulation. Intracellular cGMP increased from a basal value of 0.9 +/- 0.07 pmol/well to 13.4 +/- 6.7 pmol/well 10 min after addition of 500 microM sodium nitroprusside into the medium. It is interesting that Iloprost and sodium nitroprusside also induced the disappearance of actin stress fibers in contracted cells; F-actin stress fibers became less numerous and de-aggregated; more than 90% of stellate cells were void of stress fibers after 10 microM Iloprost treatment for 30 min. Thus, endothelin 1, eicosanoids and sodium nitroprusside are able to modulate the contractility of stellate cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Regulation of endothelin-1 action on the perfused rat liver.

Endothelin-1 (ET-1) was found to be a very potent stimulus for contraction and glycogenolysis in the perfused rat liver. At 1 nM it caused a dramatic increase in portal pressure of 22.1 +/- 2.7 cm water and enhanced the glucose output up to 3-fold. Extracellular Ca2+ and protein kinase C were involved in the signal transduction of ET-1. ET-1 action does not seem to be mediated by endogenous eicosanoids. The effects of ET-1 were significantly reduced in the presence of 1 microM Iloprost, a prostaglandin I2 analogue, or by 100 microM sin-1, a nitric oxide donor. In cultured hepatocytes, glycogenolysis was also stimulated by ET-1 although to an extent too small to explain the high glucose output found in the perfused liver.

Fate of exogenous and endogenous prostaglandins D2 and E2 in the perfused rat liver.

The degradation of radiolabelled exogenous PGD2 and PGE2 was compared to that of endogenous labelled prostaglandins synthesized after stimulation with PMA in the perfused rat liver. With exogenous PGD2 and PGE2 the same degradation products were found in the perfused liver as in hepatocyte primary cultures. The major metabolite of PGD2 was dinor-PGD2 while tetranor-PGE1 was the main degradation product of PGE2. Some polar metabolites and tritiated water were also formed. The metabolites detected with endogenous prostaglandins were similar to those obtained with exogenous PGD2. Over 99% of the labelled prostaglandins were degraded in the recirculating perfusion within 40 min. In the open perfusion system, 95% of endogenous PGD2 was calculated to be degraded after a single passage through the liver, which suggests that hepatocytes play an important role in the removal of biologically active prostaglandins.

Ganglioside biosynthesis in rat liver: different distribution of ganglioside synthases in hepatocytes, Kupffer cells, and sinusoidal endothelial cells.

The activities of five glycolipid-glycosyltransferases, GL2, GM3, GM2, GM1, and GD1a synthase, were determined in a cell-free system with homogenate protein of total rat liver, isolated hepatocytes, Kupffer cells, and sinusoidal endothelial cells. In rat liver parenchymal and nonparenchymal cells ganglioside synthases were distributed differently. Compared to hepatocytes, Kupffer cells expressed a nearly sevenfold greater activity of GM3 synthase, but only 14% of GM2, 19% of GM1, and 67% of GD1a synthase activity. Sinusoidal endothelial cells expressed a pattern of enzyme activities quite similar to that of Kupffer cells with the exception of higher GM2 synthase activity. Activity of GL2 synthase was distributed unifromly in parenchymal and nonparenchymal cells of rat liver, but differed by sex. It was 1 to 2 orders of magnitude below that of all the other ganglioside synthases investigated. The results indicate GL2 synthase regulates the total hepatic ganglioside content, and hepatocytes but not nonparenchymal liver cells have high enzymatic capacities to form a-series gangliosides more complex than GM3.

Output and effects of thromboxane produced by the liver perfused with phorbol myristate acetate.

The capacity of the perfused rat liver to produce thromboxane after stimulation by phorbol myristate acetate was examined. A total of 109 +/- 20 and 155 +/- 28 pmol/g liver were found in the perfusate and in the bile, respectively, after 40 min. The amount of thromboxane recovered in the perfusate and in the bile accounted for 12.6% of the production calculated from the same number of Kupffer cells in primary cultures, indicating that a major part of thromboxane was taken up and inactivated by hepatocytes. The effect of endogenously synthesized thromboxane on the liver was assessed by using CGS 13080, a thromboxane synthase inhibitor, or BM 13.177, a thromboxane receptor antagonist. 20 nM CGS 13080 in the perfusate inhibited the synthesis of thromboxane and at the same time the elevation of portal pressure and glycogenolysis following administration of phorbol 12-myristate 13-acetate (PMA). The thromboxane receptor antagonist BM 13.177 did not inhibit the synthesis of thromboxane, but reduced the PMA-related elevation of portal pressure and glycogenolysis to the same extent (greater than 60%) as CGS 13080. Sodium nitroprusside, a vasodilator, inhibited the rise in portal pressure caused by PMA to the same extent as CGS 13080 or BM 13.177 but reduced the increase in glycogenolysis only by 25%. These results indicate that thromboxane released by stimulated Kupffer cells of the liver elevates portal pressure and glycogenolysis in the perfused rat liver, although by different mechanisms.