Sevoflurane inhibits neuronal apoptosis and expressions of HIF-1 and HSP70 in brain tissues of rats with cerebral ischemia/reperfusion injury.

OBJECTIVE: To observe the influences of sevoflurane on neuronal apoptosis and expressions of hypoxia-inducible factor 1 (HIF-1), and heat-shock protein 70 (HSP70) in brain tissues of rats with cerebral ischemia/reperfusion (I/R) injury. MATERIALS AND METHODS: A total of 60 Sprague-Dawley rats were selected and divided into sham-operation group (Sham group, n=20), cerebral I/R model group (Model group, n=20), and 3% sevoflurane treatment group (Sevoflurane group, n=20). The rats in each group received neurological scoring, and the blood and brain tissues were collected to detect the concentrations of serum K+, Na+ and glucose (Glu). Enzyme-linked immunosorbent assay (ELISA) was adopted to measure the levels of inflammatory factors [tumor necrosis factor-ß (TNF-ß) and interleukin-6 (IL-6)] and oxidative stress [catalase (CAT), malondialdehyde (MDA) and superoxide dismutase (SOD)]. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay was performed to determine the nerve cell apoptosis in the brain tissues. The gene and protein expressions of Caspase-3, HIF-1, and HSP70 in the brain tissues were measured via quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) and Western blotting. RESULTS: In Sevoflurane group, the content of serum Glu and Na+ was decreased markedly, that of K+ was increased notably, and the levels of TNF-ß, IL-1 and IL-6 were lowered remarkably compared with those in Model group (p<0.05). Moreover, the neurological score was reduced evidently (p<0.05). Model group had significantly strengthened the activity of MDA and CAT and decreased SOD content, while Sevoflurane group exhibited the opposite results. TUNEL staining showed that there were distinctly more apoptotic cells that were dominated by glial cells in Model group and fewer apoptotic cells in Sevoflurane group. It was indicated in gene assay that the messenger ribonucleic acid (mRNA) expression levels of HIF-1, HSP70, and Caspase-3 in Model group were remarkably higher than those in Sham group and Sevoflurane group (p<0.05). According to the results of Western blotting, the protein expressions of HIF-1 and HSP70 in Sevoflurane group were markedly lower than those in Model group. CONCLUSIONS: Sevoflurane can reduce the content of inflammatory factors, inhibit apoptosis, and reduce the expressions of HIF-1 and HSP70 in the case of cerebral I/R injury, thus exerting protective effects on rats with cerebral I/R injury.

Lipase-catalyzed modification of the flavor profiles in recombined skim milk products by enriching the volatile components.

The purpose of this study was to modify the amount and composition of volatile components in bovine milk products, in an attempt to create a recombined skim milk product with full-fat milk flavor but with only 0.5% fat. The experimental plan included lipase-catalyzed hydrolysis and esterification reactions using Palatase 20000L (Novozymes, Bagsværd, Denmark). The results, measured by the methods of volatile compositional analysis and sensory evaluation, showed that the flavor profiles of the optimal recombined milk products were effectively modified in this way, possessing intensified characteristic volatile flavor components with rather low level of fat contents, and the sensory characters were quite realistic to natural whole milk flavor.

Compound C induces the ramification of murine microglia in an AMPK-independent and small rhogtpase-dependent manner.

Microglial cells are the pivotal immune cells of the central nervous system. Adult microglia cells under physiological conditions are in a ramification state with extensively branched processes. Upon disease stimulation, they retract their processes and become activated. Induction of ramification is an attracting strategy to terminate the excessive activation of microglia. Here, we investigated the influence of compound C (CC) on microglial shape. Results showed that CC reversibly induced a ramification of murine microglia in both basal and inflammatory conditions. These pro-ramification effects were independent of adenosine 5'-monophosphate-activated protein kinase (AMPK) inhibition as both AMPKα1 and AMPKα2 silence failed to induce microglial ramification. The ramification state of microglia induced by CC was associated with a decrease in pro-inflammatory factors and an increase in brain-derived neurotrophic factors (BDNF) protein and phagocytic activity. Mechanistic studies confirmed that the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt) signal, extracellular signal-regulated kinase 1/2 (ERK1/2) or small RhoGTPase activation mediated the effect of CC on microglial shape change based on the following observations: (i) CC induced a significant activation of the small RhoGTPase Rac1 and Cdc42; (ii) CC promoted the phosphorylation of ERK1/2 and Akt; (iii) inhibition of Rac1, Cdc42, ERK1/2, or the PI3K-Akt signal abolished the effect of CC on microglial shape change. These signal mechanisms were also ascertained in primary microglia. Our results explore a potential agent that promotes microglial ramification, and provide an alternative explanation for the neuroprotective effects of CC in various disease models such as brain ischemia and subarachnoid hemorrhage.

Right-sided congestive heart failure in a dog because of a primary intracavitary myocardial lymphoma.

CASE REPORT: A 9-year-old female intact Cocker Spaniel was presented with a history of acute-onset dyspnoea and abdominal distension of 3 days' duration. Ultrasonography revealed pleural, peritoneal and pericardial effusions. Abdominal fluid analysis was consistent with a modified transudate. Echocardiography revealed a large, hypoechoic space-occupying mass within the right atrium. The dog was euthanased and the postmortem examination showed a solid, 40 × 35 × 20 mm broad-based mass arising from the right atrial wall and occluding approximately 90% of the right atrial lumen. Histopathology revealed myocardial lymphoma. There were histologically similar, focal nodules in the lung parenchyma without involvement of other extracardiac sites. There was gross and histological evidence of hepatic congestion and marked distension of the caudal vena cava, consistent with secondary right-sided congestive heart failure. CONCLUSION: This case highlights the need to consider lymphoma as a differential diagnosis for an intra-atrial mass and as a cause of congestive heart failure in the dog.

Fracture characteristics to distinguish between accidental injury and non-accidental injury in dogs.

Non-accidental injury (NAI) refers to trauma arising from deliberate physical abuse and is increasingly recognised as an important differential diagnosis in veterinary medicine. Given the sensitivity and importance of identifying NAI, clinicians, pathologists, and veterinary forensic experts need clear scientific evidence to support their diagnosis. The aim of this study was to investigate fractures occurring in accidental and NAI in dogs by comparing the radiographic features of fractures in 19 dogs with abuse fractures and 135 dogs with accidental fractures. Radiographic findings indicated that the following five features should raise the index of suspicion of and support a diagnosis of NAI: (1) the presence of multiple fractures; (2) fractures occurring on more than one region of the body (forelimb, hindlimb, or axial); (3) transverse fractures; (4) fractures presenting at a later stage of healing (delayed presentation); and (5) multiple fractures at different stages of healing. Staffordshire bull terriers were over-represented in the NAI group. Many findings in this study correlate with patterns seen in human NAI fractures. However some aspects show significant differences, serving as a reminder that veterinary forensics cannot rely on data from existing human studies.

Fatal arrhythmogenic right ventricular cardiomyopathy in 2 related subadult chimpanzees (Pan troglodytes).

Cardiovascular disease is increasingly recognized as an important cause of morbidity and mortality in captive chimpanzees (Pan troglodytes). This report records 2 cases of sudden cardiac death in closely related subadult captive chimpanzees with marked replacement fibrosis and adipocyte infiltration of the myocardium, which resemble specific atypical forms of the familial human disease arrhythmogenic right ventricular cardiomyopathy. Changes were consistent with left-dominant and biventricular subtypes, which are both phenotypic variants found within human families with familial arrhythmogenic right ventricular cardiomyopathy. Previously reported fibrosing cardiomyopathies in chimpanzees were characterized by nonspecific interstitial fibrosis, in contrast to the replacement fibrofatty infiltration with predilection for the outer myocardium seen in these 2 cases. To the authors' knowledge, this case report is the first to describe cardiomyopathy resembling arrhythmogenic right ventricular cardiomyopathy in nonhuman primates and the first to describe left-dominant arrhythmogenic cardiomyopathy-type lesions in an animal.

Tanshinone-1 induces tumor cell killing, enhanced by inhibition of secondary activation of signaling networks.

Tumor multidrug resistance (MDR) can result from overexpression of drug transporters and deregulation of cellular signaling transduction. New agents and strategies are required for overcoming MDR. Here, we report that tanshinone-1, a bioactive ingredient in traditional Chinese medicine, directly killed MDR tumor cells and their corresponding parental cells, which was potentiated by inhibition of secondary activation of signaling networks. Tanshinone-1 was slightly more potent at inducing cytotoxicity and apoptosis in MDR cells than in corresponding parental cells. Tanshinone-1-induced MDR cell killing was independent of the function and expression of drug transporters but was partially correlated with the phosphatase-dependent reduction of phospho-705-Stat3, which secondarily activated p38-, AKT-, and ERK-involved signaling networks. Cotreatments with p38, AKT, and ERK inhibitors potentiated the anti-MDR effects of tanshinone-1. Our study presents a model for MDR cell killing using a compound of natural origin. This model could lead to new therapeutic strategies for targeting signaling network(s) in MDR cancers as well as new strategies for multitarget design.

Hollow fiber liquid-phase microextraction for the determination of nimesulide in human plasma and its application to a pharmacokinetic study.

A hollow fiber liquid-phase microextraction (HF-LPME) method in combination with HPLC-UV for the determination of nimesulide in human plasma was developed and validated. A small volume of dihexyl ether contained within a polypropylene hollow fiber was used for the extraction of nimesulide from acidified plasma solutions. Factors affecting the extraction efficiency were optimized and discussed. With HPLC-UV as the end analysis technique, the procedure was validated for nimesulide in the concentration range of 50-5000 ng/mL. The intra- and inter-assay precisions were less than 9.1%, and accuracy was within 3.2%. The lower limit of quantification (LLOQ) was 50 ng/mL. Enrichment factor from 144-fold to 156-fold was achieved at three quality control (QC) concentrations. The mean extraction recovery was greater than 41.2%. This method was successfully applied for the evaluation of pharmacokinetics of nimesulide after single oral doses of 100 mg nimesulide to six healthy Chinese volunteers.

Transcriptional regulation of alpha1-adrenoceptor gene in the rat liver during different phases of sepsis.

Changes in alpha1-adrenoceptor (alpha1AR) gene expression in the rat liver during different phases of sepsis were studied. Sepsis was induced by cecal ligation and puncture (CLP). Septic rats exhibit two metabolically distinct phases: an initial hyperglycemic phase (9 h after CLP, early sepsis) followed by a hypoglycemic phase (18 h after CLP; late sepsis). The [3H]prazosin binding studies show that the density of alpha1AR was increased by 30% during the early phase while it was decreased by 24% during the late phase of sepsis. Western blot analyses reveal that alpha1AR protein level was elevated by 48% during early sepsis but was decreased by 55% during late sepsis. Northern blot analyses depict that the steady-state level of alpha1bAR mRNA was enhanced by 21% during the early phase but was declined by 29% during the late phase of sepsis. Nuclear run-off assays show that the transcription rate of alpha1bAR gene transcript was increased by 76% during early sepsis while it was decreased by 29% during late sepsis. The actinomycin D pulse-chase studies indicate that the half-life of alpha1bAR mRNA remained unaffected during the early and the late phases of sepsis. These findings demonstrate that during the early phase of sepsis, the increase in the rate of transcription of alpha1bAR gene paralleled with the elevations in the alpha1bAR mRNA abundance and alpha1AR protein level, while during the late phase of sepsis, the decrease in the rate of transcription of alpha1bAR gene coincided with the declines in the alpha1bAR mRNA abundance and the alpha1AR protein level in the rat liver. These observations indicate that the altered expression of alpha1AR genes in the rat liver during the progression of sepsis was regulated transcriptionally.

Phospholipase A2 activities are decreased during early but increased during late phases of sepsis in rat heart.

BACKGROUND: Changes in the activities of secretory phospholipase A2 (sPLA2) and cytosolic phospholipase A2 (cPLA2) in the rat heart during early hyperdynamic and late hypodynamic phases of sepsis were studied in an attempt to understand the pathophysiology of cardiac dysfunction during sepsis. METHODS: Sepsis was induced by cecal ligation and puncture (CLP). Experiments were divided into three groups: control, early sepsis, and late sepsis. Early and late sepsis refers to those animals sacrificed at 9 and 18 h, respectively, after CLP. PLA2 activity was measured based on the rate of hydrolysis of 1-palmitoyl-2-[1-(14)C]-oleoyl phosphatidylcholine. RESULTS: The results show that under physiological conditions, sPLA2 and cPLA2 activities were time and protein dependent. The optimal Ca2+ concentrations for sPLA2 and cPLA2 activities were 3 mM and 40 microM, respectively. During sepsis, sPLA2 activity was decreased by 25% (P < 0.01) during early phase while it was increased by 49% (P < 0.01) during late phase of sepsis. Similarly, cPLA2 activity was decreased by 23% (P < 0.01) during early sepsis while it was increased by 60% (P < 0.01) during late sepsis. CONCLUSIONS: Since PLA2 functions to maintain cell membrane integrity and function, a biphasic change in sPLA2 and cPLA2 activities may contribute to the development of the two cardiodynamically distinct phases during the progression of sepsis.

GTP-binding protein mediated phospholipase A2 activation in rat liver during the progression of sepsis.

Effects of GTP-binding proteins on the activation of secretory phospholipaseA2 (sPLA2) and cytosolic phospholipaseA2 (cPLA2) in rat liver during two different phases of sepsis were studied. Sepsis was induced by cecal ligation and puncture (CLP). Experiments were divided into three groups: control, early sepsis, and late sepsis. Early and late sepsis refers to those animals sacrificed at 9 and 18 h, respectively, after CLP. The results show that in the absence of G-protein modulator, hepatic sPLA2 and cPLA2 activities were activated by 40.8-46 and 91.6-105.8%, respectively, during early and late phases of sepsis. GTPgammaS and fluoroaluminate (AlF4-) stimulated sPLA2 and cPLA2 activities within each experimental group, i.e., control, early sepsis, and late sepsis. The GTPgammaS and AlF4(-)-stimulated sPLA2 and cPLA2 activities remained significantly elevated during early phase (22.3-65.6% increase) and late phase (32.5-109.1% increase) of sepsis. Further analyses demonstrate that cholera toxin significantly stimulated sPLA2 and cPLA2 activities within each experimental group, and that the cholera toxin stimulated sPLA2 and cPLA2 activities remained significantly higher during early phase (23.5-37% increase) and late phase (56.7-70% increase) of sepsis. In contrast, pertussis toxin significantly inhibited sPLA2 and cPLA2 activities within each experimental group, and that the pertussis toxin-inhibited sPLA2 and cPLA2 activities remained significantly higher in early septic (57-68.5% increase) and late septic (34.6-45.5% increase) experiments. These data demonstrate that cholera toxin-sensitive G alpha s and pertussis toxin-sensitive G alpha i were both involved in the activation of sPLA2 and cPLA2 activities in rat liver during the progression of sepsis.

Group II phospholipase A2 gene expression is transcriptionally regulated in rat liver during sepsis.

Changes in group II phospholipase A2 (PLA2) gene expression in rat liver during different phases of sepsis were studied. Sepsis was induced by cecal ligation and puncture (CLP). The results show that PLA2 activity was increased by 41 and 92% during early hyperdynamic phase (9 h after CLP) and late hypodynamic phase (18 h after CLP) of sepsis, respectively. Western blot analysis reveals that group II PLA2 protein levels were elevated by 53 and 95% during early and late sepsis, respectively. Northern blot analysis depicts that the steady-state levels of group II PLA2 mRNA were enhanced by 39 and 114% during early and late sepsis, respectively. Nuclear run-off assay shows that the transcription rates of group II PLA2 gene transcript were stimulated by 36 and 74% during early and late sepsis, respectively. The actinomycin D pulse chase study indicates that the half-life of group II PLA2 mRNA remained unaffected during early and late phases of sepsis. These results demonstrate that group II PLA2 gene transcripts were overexpressed in rat liver during the progression of sepsis and that the overexpression was a result of the enhanced synthesis of group II PLA2 mRNA. Because PLA2 plays an important role in the maintenance of cell membrane integrity, our findings may contribute to the understanding of the pathogenesis of hepatic dysfunction during the progression of sepsis.

Assessment of autoimmunity in patients with chronic urticaria.

BACKGROUND: The etiology of chronic urticaria is unknown, and an exogenous allergen cannot be identified as the cause in the vast majority of subjects. Thus the concept has evolved that it might be autoimmune. OBJECTIVE: We have prospectively assessed sera obtained from 50 consecutive patients with chronic urticaria for the presence of autoantibodies that could be pathogenic. METHODS: We tested sera for their ability to release histamine from human basophils and to activate rat basophil leukemia cells that were transfected with the alpha subunit of the IgE receptor. We also tested selected sera for anti-IgE antibodies and for IgG anti-Fc epsilon RI alpha by Western blot. RESULTS: Sera from 38 of 50 patients with chronic urticaria released beta-hexosaminidase from transfected rat basophil leukemia cells, whereas only one of 20 control sera did so (p < 0.001); in 30 subjects this could be attributed to IgG anti- Fc epsilon RI alpha. When human basophils were used, sera from 20 of 50 patients with chronic urticaria released a significant quantity of histamine compared with one of 20 control subjects (p < 0.01). Six patients with chronic urticaria and one control subject had IgG anti-IgE. In selected sera we could demonstrate IgG anti-Fc epsilon RI alpha by Western blot; however, some sera are positive for histamine release but do not demonstrate such binding. CONCLUSION: A large fraction of patients with chronic urticaria have antibody directed to Fc epsilon RI alpha that is functional (60%). A smaller number have IgG anti-IgE (10%). A third group may also have circulating factors capable of activating basophils or mast cells of which the identity is unknown. Thus chronic urticaria may be autoimmune in origin.

[Endothelin-stimulated proliferation of thoracic artery smooth muscle cells involves activation of mitogen-activated protein kinase].

Endothelin (ET) is a potent vasoconstrictor whose responses are mediated through a common G-protein coupled receptor. So far little is known concerning its potential mitogenic capacity. In the present study, experiments were conducted to determine the role of mitogen-activated protein kinase (MAPK) activation in the rabbit thoracic artery smooth muscle cells (VSMC) in response to stimulation by ET-1. It was found that ET-1 produced concentration- and time-dependent increases in 3H-TdR incorporation and in MAPK activity of these cells. All the increases were inhibited by protein kinase C (PKC) inhibitors, such as Staurosporine (STP) and H-7 and by ETA receptor antagonist BQ123, but not by specific tyrosine kinase inhibitor Herbimycin A (Herb). Pre-treatment with PKC activator PMA (phorbol myristate acetate) for 24 h (PKC downregulation) significantly attenuated ET-1-induced MAPK activation. These results indicate that: (1) ET-1-stimulated proliferation of VSMC involves the activation of MAPK and (2) ET-1-induced MAPK activation is mediated through ETA receptor and PKC.

Role of regulatory peptide in pathogenesis of shock.

The present study evaluated the pathogenetic roles of three kinds of regulatory peptide. The results showed that (i) plasma endothelin (ET) level elevated significantly in septic shock rats, persistent intravenous drip of low doses ET caused development of shock state in normal rats and the irreversible outcome of light hemorrhagic shock. Furthermore, i. v. administration of specific ET-antiserum was significantly effective to septic shock rats. (ii) Plasma calcitonin gene-related peptide (CGRP) increased by 260% in septic shock rats, i. v. drip of low doses CGRP both in early and late sepsis were effective to shock rats. (iii) Angiotensin-II (ANG-II) contents of heart and aorta increased dramatically both in early and late septic shock, and inhibiting its increase with Captopril in late sepsis significantly improved the shock state, but results were inverse in early sepsis. It could be concluded that ET was one of the most important factors participating in the pathogenesis of shock, CGRP had a compensatory regulatory role in shock and the role of tissue ANG-II was different during different periods of shock.

[Changes of calcium transport capacity of myocardium and myocardial mitochondria during sepsis].

On the isolated perfused heart model of septic rats, the present study showed that: (1) Calcium content and 45Ca-influx of myocardium increased 190%, 208% (P < 0.01) and that of mitochondria elevated 332%, 178% (P < 0.01) respectively with no change of myocardial 45Ca-release during sepsis. (2) 10(-8) mol/L calcitonin gene-related peptide (CGRP) or 10(-7) mol/L atriopeptin (ANP) added into the Krebs-Henseleit solution could effectively reduce 45Ca-influx to myocardium and mitochondria with no effect on myocardial 45Ca-release. (3) The calcium uptake reserve of mitochondria evaluated in vitro showed that the maximal calcium uptake and uptake velocity of mitochondria during sepsis were reduced 34.6%, 33.3% (P < 0.01) respectively. The data suggested that the net increase of myocardial Ca2+ content resulted from increase of 45Ca-influx with no change of 45Ca-efflux and the reduction of mitochondrial Ca2+ buffering capacity during sepsis were key events in the pathogenesis of intracellular Ca(2+)-overload. CGRP and ANP could effectively alleviate Ca(2+)-overload of myocardium and mitochondria. This may have some cellular protection action during sepsis.

[Expression of cytokine messenger RNA in mice in physiological conditions]. / Expression de l'ARN messager des cytokines chez la souris dans des conditions physiologiques.

The expression of the cytokine genes was studied under physiological conditions in normal adult mice using RT-PCR method capable of detecting low levels of mRNA. Total RNA was prepared from brain, spinal cord, lung, spleen, liver and kidney of 6 to 8 week-old specific pathogen-free BALB/c mice by acid guanidinium thiocyanate-phenol-chloroform (AGPC) method. cDNA was synthesized by M-MLV reverse transcriptase, and amplified using the specific oligonucleotide primers for IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, TNF-alpha, IFN-alpha, IFN-beta and IFN-gamma by PCR method. Although IL-1 mRNA was detected in all the organs, IL-3 mRNA was not detected in any organs tested. IL-2 or IL-4 mRNA and IL-5 mRNA were produced only in spleen and lung, respectively. However, IL-6, TNF-alpha and IFN mRNA were detected in some different organs. These results suggest that many kinds of cytokine mRNA were produced in vivo under physiological conditions in normal mice.

[Induction of messenger RNA of cytokines by Herpes simplex virus infection in mice]. / Induction de l'ARN messager des cytokines par l'infection de l'Herpès simplex virus chez la souris.

The induction of the cytokine mRNA after infection with Herpes simplex virus (HSV) was studied using RT-PCR method capable of detecting low levels of mRNA. Total RNA was prepared from spleen lymphocytes 3 h after infection with HSV-1 (+GC virulent variant and -GCr attenuated variant of Miyama strain) by acid guanidinium thiocyanate-phenol-chloroform (AGPC) method. cDNA was synthesized by M-MLV reverse transcriptase, and amplified using the specific oligonucleotide primers for IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, TNF-alpha, IFN-alpha, IFN-beta and IFN-gamma by PCR method. After HSV-1 infection, IFN-alpha, IFN-beta, IFN-gamma, IL-1 beta, IL-4, IL-6 and TNF-alpha mRNA were significantly induced, but IL-2, IL-3 and IL-5 mRNA were not induced. Although IFN-alpha, IFN-gamma and IL-6 mRNA were more strongly induced by infection with +GC virulent variant than -GCr attenuated variant, there was no significant difference in the expression of other cytokine mRNA between two variants. These results demonstrate that cytokine mRNA in addition to IFN was induced by HSV infection, and suggest that cytokines as well as IFNs may play a role in the defense mechanism against HSV infection.

[Expression of cytokine messenger RNA in murine placenta]. / Expression de l'ARN messager des cytokines dans le placenta de la souris.

The expression of the cytokine genes in normal placenta was studied using RT-PCR method capable of detecting low levels of mRNA. Total RNA was prepared from placenta of specific pathogen-free BALB/c mice at the 16th day of gestation by acid guanidinium thiocyanate-phenol-chloroform (AGPC) method. cDNA was synthesized by M-MLV reverse transcriptase, and amplified using the specific oligonucleotide primers for IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, TNF-alpha, IFN-alpha, IFN-beta and IFN-gamma by PCR method. IL-1 beta, IL-6, TNF-alpha, IFN-alpha, IFN-beta and IFN-gamma mRNA were detected in all the placentas tested. On the other hand, the expressions of IL-2, IL-3, IL-4, and IL-5 mRNA were not detected at all. These results suggest that these cytokines may play a role in the evolution of pregnancy.

Enhancement of the growth of human osteosarcoma cells by human interferon-gamma.

It is well known that interferons inhibit cell growth. However, we found that human interferon-gamma (HuIFN-gamma) enhanced the growth of human osteosarcoma cells, HOS-Y1 cells, in a dose-dependent manner. This enhancing effect was found only under the following conditions: when the cells were precultured for 2 or 3 days and then treated with HuIFN-gamma for 2, 3, or 4 days, and when the cells were seeded at a density of 1,000 or 2,000 cells/well. The degree of enhancement of cell growth was maximum when the cells were precultured at a density of 1,000 cells/well for 3 days and then treated with HuIFN-gamma for 2 days. The enhancing effect of HuIFN-gamma disappeared in the presence of anti-HuIFN-gamma antibody. In addition, it was found that the conditioned medium from HOS-Y1 cells enhanced the growth of HOS-Y1 cells, and that the conditioned medium from HOS-Y1 cells cultured with HuIFN-gamma enhanced the cell growth more than that from cells cultured without HuIFN-gamma. Epidermal growth factor (EGF), acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF), and transforming growth factor-beta 1(TGF-beta 1) did not enhance the growth of HOS-Y1 cells. These results suggest that HuIFN-gamma enhanced the cell growth by augmenting the production of unknown growth factor(s) in HOS-Y1 cells via an autocrine mechanism.