[Plaque accumulation at the fitting surface and cleaning status in patients with full-arch implant-supported fixed prostheses: a cross sectional study].

Objective: To observe the plaque accumulation at the fitting surface and oral hygiene status in patients with full-arch implant-supported fixed prostheses, and explore the possible influencing factors. Methods: Twenty-eight patients [17 males and 11 females, (63.0± 10.8) years old] with 40 full-arch implant-supported fixed prostheses (18 maxillary and 22 mandibular) were collected from January 2012 to September 2020 in Department of Implantology, Peking University School and Hospital of Stomatology. Plaque accumulation at the fitting surfaces were evaluated during the follow-up visit after 6 months following definitive prostheses delivery, by analyzing the digital photographs recorded by ImageJ. Meanwhile, the cleanliness of the fitting surface of prostheses and oral hygiene status were recorded. The oral hygiene habits and the patients' satisfaction with the prostheses were investigated by questionnaire, and the difference of plaque accumulation between different cleaning habits of dentures were compared. Results: The debris index of the fitting surface of the 40 full-arch implant-supported fixed prostheses were 3.28±0.75, and the percentage of area covered with plaque was (51.6±19.0)%. The debris index and plaque accumulation of the mandibular prostheses were significantly higher than that of the maxillary prostheses (P<0.05). In most mandibular prostheses (16/22), calculus was attached to the lingual side of the anterior tooth area. The reserved cleaning space of the restoration showed more plaque accumulation than in other parts. There was no significant difference in the percentage of area covered with plaque between groups with different cleaning habits. The satisfaction survey results indicated the "clean" project had a lowest score. Conclusions: The cleanliness of patients with full-arch implant-supported fixed prostheses was poor, and the hygiene status of the mandibular prostheses was worse than that of maxillary, especially in the anterior tooth area of mandibular prostheses. The influence of different cleaning habits on plaque accumulation was not observed.

[Implant-supported fixed full-arch prostheses on oral health-related quality of life and denture satisfaction].

Objective: To assess the longitudinal changes in oral health-related quality of life (OHRQoL) and the denture satisfaction of immediate rehabilitation by implant-supported full-arch prostheses in patients of the edentulous and potential edentulous jaws. Methods: Patients in the Department of Implantology, Peking University School and Hospital of Stomatology from April 2008 to November 2020 were enrolled in the study. The treatment group (TG) consisted of 73 patients who had been treated with immediate rehabilitation by using implant-supported full-arch prostheses while the control group (CG) consisted of 31 patients who would be treated with immediate rehabilitation of implant-supported full-arch prostheses. The mean age of the patients in the treatment group was (57.5±11.1) years (ranged 31-79) and the average follow-up duration was 5.5±2.9 years (ranged 1-12). The OHRQL ratings were collected using oral health impact profile-20 (OHIP-20) and the visual analogue scales (VAS) was used to assess the denture satisfaction including stability, aesthetics, mastication, ease of cleaning, speaking and general satisfaction. Independent t-test, Mann-Whitney U-test and locally weighted scatterplot smoothing were applied for data analysis. Results: The cumulative survival rate (CSR) of the implants was 97.6% (450/461). The CSR of the prostheses was 93.3% (98/105). The average peri-implant marginal bone loss (MBL) was (0.8±0.4) mm and (1.2±0.6) mm after 1 and 5 years, respectively. The mean OHIP-20 total scores of TG and CG were 5(7) and 32.9±12.6, respectively, which had statistical difference between the two groups (P<0.001). The general satisfaction in the TG was 95.0(10.0), while the higher scores were for chewing [100.0(7.5)] stability [100.0(10.0)] and esthetics [100.0(10.0)] and the lower scores were for ease of cleaning [85.0(25.0)] and speaking ability [100.0(12.5)]. With prolonged follow-up, the total OHIP-20 score decreased significantly at first and then remained stable with minor fluctuations. Conclusions: Based on the present study, immediate rehabilitation with implant-supported full-arch prostheses was a feasible treatment program that had a long-term positive impact on OHRQoL, provided strong psychological and sociological support to the patients and restored the chewing and speech functions effectively.

[Clinical study of cervical necrotizing fasciitis accompanied with descending necrotizing mediastinitis treated with cervical double parallel incision combined with mediastinoscope or thoracoscope].

Objective: To summarize the experience of applying cervical double parallel incision combined with mediastinoscope or thoracoscope in the treatment of cervical necrotizing fasciitis (CNF) accompanied with descending necrotizing mediastinitis (DNM), so as to provide a reference for clinical practice. Methods: The clinical data of six patients with CNF accompanied with DNM who were admitted to the Department of Stomatology and the Department of Otolaryngology Head and Neck Surgery, The First People's Hospital of Changzhou from September 2014 to September 2018 were retrospectively analyzed. All of the six patients were confirmed by CT of neck and chest, among whom there were two males and four females aged from 48 to 73. Three patients were treated with cervical double parallel incision combined with mediastinoscope to be combined with cervical and thoracic drainage under general anesthesia while the other three with cervical double parallel incision combined with thoracoscope to be combined cervical and thoracic drainage under general anesthesia. The CT of neck and chest as well as infectious indicators including hematology, C-reactive protein (CRP) and procalcitonin (PCT) were reexamined during the postoperative period. Results: The cervical and thoracic combined drainage was unobstructed in all of the six patients, no secondary surgery was performed, and the infectious indicators gradually decreased. All patients had off-bed activities on the first day after the operation, were all cured and discharged after an average of 21 days (16 to 36 days) in hospital and followed up for an average of 18 months (4 to 30 months) after the operation. None of them experienced infection relapse, and they were all satisfied with the appearance of the cervical incision. Conclusions: Cervical double parallel incision combined with mediastinoscope or thoracoscope for the treatment of CNF accompanied with DNM has the advantages of complete drainage, small trauma, excellent efficacy and aesthetic operative area, thus being deserved to be clinically popularized.

[The treatment of Lemierre syndrome associated with cervical necrotizing fascitis].

Lemierre syndrome is a rare, potentially fatal condition characterized by internal jugular vein thrombosis following an acute oropharyngeal infection, often accompanied with cervical necrotizing fasciitis. This paper reviews 5 cases of Lemierre syndrome with cervical necrotizing fasciitis, extensive cervical drainage and sufficient antibiotics is crucial treatment for Lemierre syndrome, anticoagulation combined with antibiotics is safe and effective for propagation or nonresolution of the thrombus.

Detoxification, metabolism, and glutathione pathway activity of aflatoxin B1 by dietary lactic acid bacteria in broiler chickens.

Lactic acid bacteria (LAB) and the glutathione (GSH) pathway are protective against aflatoxin, but information on the effect of LAB on aflatoxin metabolism and GSH activity in farm animals is scarce. This study aimed to investigate the effects of LAB and aflatoxin B (AFB) on growth performance, aflatoxin metabolism, and GSH pathway activity using 480 male Arbor Acres broiler chickens from d 1 to 35 of age. Diets were arranged in a 2 × 2 factorial design, including AFB at 0 or 40 µg/kg of feed and LAB at 0 or 3 × 10 cfu/kg of feed, and the LAB was a mixture of equal amounts of , , and . The results showed that there were highly significant ( < 0.01) effects of AFB toxicity, LAB protection, and their interaction on ADFI, ADG, and G:F of broilers during d 1 to 35. Compared with the AFB diet, the LAB diet reduced ( < 0.05) the residues of AFB in the liver, kidney, serum, ileal digesta, and excreta on d 14 by 121.5, 80.6, 43.7, 47.0, and 26.5%, respectively, and on d 35 by 40.6, 60.2, 131.7, 37.9, and 32.9%, respectively, whereas the LAB diet increased ( < 0.05) the contents of aflatoxin M, a metabolite of AFB, in the liver, kidney, serum, and ileal digesta on d 14 by 98.2, 154.2, 168.6, 19.1, and 34.1%, respectively, and in the kidney and serum on d 35 by 32.6 and 142.2%, respectively. For the activity of the GSH pathway in the liver and duodenal mucosa, there were significant ( ≤ 0.01) effects of LAB and AFB on reduced GSH, glutathione S-transferases (GST), and glutathione reductase (GR) on d 14 and 35; compared with the control diet, the LAB diet increased ( < 0.05) GSH, GST, and GR by a range of 11.6 to 86.1%, and compared with the AFB diet, the LAB diet increased ( < 0.05) GSH, GST, and GR by a range of 24.1 to 146.9%. In the liver, there were interactions ( < 0.05) on GSH and GST on d 14 and on GSH on d 35; in the mucosa, interactions were significant ( ≤ 0.01) on GSH and GR on d 14 and on GST on d 35. It can be concluded that LAB is effective in the detoxification of AFB by modulating toxin metabolism and activating the GSH pathway in animals.

Effect of iguratimod and methotrexate on RANKL and OPG expression in serum and IL-1ß-induced fibroblast-like synoviocytes from patients with rheumatoid arthritis.

The receptor activator of nuclear factor κB ligand (RANKL)/receptor activator of nuclear factor κB (RANK)/osteoprotegerin (OPG) system plays a key role in rheumatoid arthritis (RA)-associated bone erosion. The upregulation of the RANKL/OPG ratio promotes bone erosion. The objective of this study is to explore the effects of iguratimod, a small-molecule disease-modifying antirheumatic drug (DMARD), alone or in combination with methotrexate (MTX), on RANKL and OPG expression in RA. We performed an enzyme-linked immunosorbent assay (ELISA) to investigate the modulatory effects of iguratimod, MTX, or their combination on serum RANKL and OPG levels of patients with RA before and after treatment for 12 and 24 weeks. Furthermore, fibroblast-like synoviocytes (FLS) from patients with RA were interleukin (IL)-1ß-stimulated and then treated with different concentrations of iguratimod, MTX, or both, and RANKL and OPG expressions were investigated by using ELISA, quantitative real-time polymerase chain reaction (qPCR) and western blot analysis. We found that RANKL levels and the RANKL/OPG ratio significantly decreased in both serum and IL-1ß-induced RA FLS after treatment. Moreover, combination therapy with iguratimod and MTX showed an even stronger inhibition than each drug alone did. Our results suggest that iguratimod and MTX, especially in combination, efficaciously protected against bone erosion by suppressing the production of RANKL.

Effects of Chinese herbal mixture on performance, egg quality and blood biochemical parameters of laying hens.

The aim of the study was to evaluate the effect of Chinese herbal mixture (CHM) in laying hen diets on performance, egg quality and egg nutrition components, as well as selected blood biochemical parameters. A total of 270 Lohmann Brown laying hens, 24 week of age, were randomly distributed into three dietary treatments and fed for 6 week. The CHM was used at the levels of 0%, 0.5% and 1.0% in the diets of the control and two treatment groups respectively. Each dietary treatment was divided into five replicates, comprising of 18 hens each. Hens were housed in a 3-tier battery system. Feed and water were provided ad libitum. Blood samples and eggs were collected at the end of the experiment. The results showed that dietary treatments did not affect egg weight, mortality, eggshell thickness, albumen height, Haugh units, eggshell-breaking strength and egg-shape index. Dietary supplementation of CHM significantly improved (p < 0.05) laying rate and the lowest feed conversion ratio were observed with 1.0% CHM supplementation diets. CHM supplementation decreased (p < 0.05) cracked-egg rate, egg yolk cholesterol, blood serum levels of cholesterol, triglyceride, low-density lipoprotein cholesterol (LDL-C) and alanine aminotransferase (ALT) and increased blood serum levels of high-density lipoprotein cholesterol (HDL-C). No differences in serum total protein, serum albumen, serum glucose and aspartate amino transferase (AST) were observed in hens fed CHM. In conclusion, dietary supplementation with CHM improved egg production and egg quality and reduced serum cholesterol concentrations in laying hens. Dietary supplementation of 1.0% CHM in layer diets may be a feasible means of producing eggs with lower cholesterol and higher egg yolk phospholipid contents for health conscious consumers.

Increasing production of matrix metalloproteinases, tumor necrosis factor-α, vascular endothelial growth factor and prostaglandin E2 in rheumatoid arthritis synovial fibroblasts by different adiponectin isoforms in a concentration-dependent manner.

Adipokines have been known to play a significant role in rheumatic disease via synovial fibroblasts. However, to date, the concentration effects of adiponectin isoforms on the pathophysiology of rheumatoid arthritis (RA) have not been extensively studied. Therefore, the present study examined the different effects of the adiponectin isoforms on rheumatoid arthritis synovial fibroblasts (RASF) and investigated the relations between the concentration of individual adiponectin isoforms and the production of the inflammatory factors of RASF. Articular synovial tissues were obtained from the patients fulfilled with diagnostic criteria of RA, and health people. RASF and human fibroblast—like synoviocytes (HFLS) were isolated and cultured. They were stimulated with increasing concentrations of 25 μg/ml, 50 μg/ml, and 100μg/ml of different human adiponectin isoforms. The levels of matrix metalloproteinase (MMP)—3, MMP—10, tumor necrosis factor (TNF)—α, vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE2) in culture supernatants were measured by immunoassays. The results showed the levels of MMP—3, MMP—10, TNF—α, VEGF and PGE2 were significantly increased in RASF which were treated with individual adiponectin isoforms compared to untreated RASF (p<0.01), and the increases also had significances compared to HFLS which were treated with the same conditions (p<0.05). Moreover, the effect of HMW (high molecular weight)/ MMW (middle molecular weight) was the strongest among them. In conclusion, all three adiponectin isoforms may contribute to proinflammatory effect by stimulating the production of MMP—3, MMP—10, TNF—α, VEGF and PGE2 of RASF in a concentration—dependent manner. HMW/MMW adiponectin could play an important role in matrix destroying and synovial vascular creating of the pathology of RA.

Characterization of MUSTN1 gene and its relationship with skeletal muscle development at postnatal stages in Pekin ducks.

Musculoskeletal embryonic nuclear protein 1 (MUSTN1) gene is involved in myogenic fusion and differentiation in rats. We previously showed the differential expression of MUSTN1 in week (W) 2 and W6 breast muscles of Pekin ducks. In this study, we further investigated its molecular characteristics and expression profiles in different tissues at W7 and in breast and leg muscles at W1, W3, W5, W7, and W9. The relationship between muscle development and muscle fiber areas was also investigated. A 358-bp cDNA sequence was obtained. The coding sequence of duck MUSTN1 cDNA encoded a 78-amino acid sequence, which showed high similarity with those of other species (96% similarity with zebra finch and 94% with chicken). In addition, a 6435-bp genomic DNA sequence of MUSTN1 was obtained. In total, 231 transcription factor-binding sites were found in the promoter region, and many of these transcription factors were involved in the regulation of muscle development. MUSTN1 expression in breast muscle increased from W1 to W5 and then decreased at W9. In leg muscle, the expression increased from W1 to W3 and then decreased. The relative growth rates of breast and leg muscle fibers reached their peaks at W3-W5 and W1-W3, respectively. Since the greatest relative growth rates appeared at the highest expression levels of the MUSTN1 gene, it was thought to play roles in duck muscle development. Our findings would be helpful in understanding the molecular characteristics and functions of the MUSTN1 gene in breast muscle development of ducks.

Construction of the mammalian expressing vector pEGFP-N1-P53 and its expression successful in chicken fibroblast cells and blastoderm.

The enhanced green fluorescent protein (EGFP) pEGFP-N1-P53 eukaryotic expression vector, which contains the human tumor suppressor p53, was constructed and transfected into chicken fibroblast cells and stage-X blastoderm to analyze the transfection efficiency. The complementary DNA of the human p53 gene was cloned by reverse transcription-polymerase chain reaction from human peripheral blood and inserted into the pEGFP-N1 vector by HindIII and BamHI double digestion. The pEGFP-N1-P53 vector was transfected into chicken embryo fibroblasts by Lipofectamine 2000 liposomes, and the transfection efficiency was analyzed by fluorescence microscope after 36 h of transfection. The stage-X blastoderm was also transfected by blastoderm injection using Lipofectamine 2000 liposomes at room temperature after 12-24 h; then hatching occurred until seventh day, and the transfection efficiency was analyzed by fluorescence microscope in the dead embryo. A total of 90 hatching eggs were transfected by the pEGFP-N1-P53 vector, and 20 chicken embryos expressed the reporter gene, which indicated that recombinant pEGFP-N1-P53 could be transfected and expressed in stage-X blastoderm by liposomes. Chicken embryo fibroblasts were transfected and expressed the reporter gene. The pEGFP-N1-P53 vector was constructed successfully and could be transfected and expressed in chicken embryo fibroblasts and stage-X blastoderms efficiently.

Arginine affects appetite via nitric oxide in ducks.

The objective of the study was to investigate the mechanism by which arginine regulates feed intake in Pekin ducks. In experiment 1, one hundred forty-four 1-d-old male Pekin ducks were randomly allotted to 3 dietary treatments with 6 replicate pens of 8 birds per pen. Birds in each group were fed a corn-corn gluten meal diet containing 0.65, 0.95, and 1.45% arginine. Ducks fed the diet containing 0.65% arginine had lower feed intake and plasma nitric oxide level (P < 0.05) than the other 2 groups. In experiment 2, twenty 11-d-old ducks were allotted to 1 of 2 treatments. After 2 h fasting, birds in the 2 groups were intraperitoneally administrated saline and l-NG-nitro-arginine methyl ester HCl (L-NAME) for 3 d, respectively. Feed intake (P < 0.07) and plasma nitric oxide concentration (P < 0.05) 2 h postinjection in the L-NAME administered group were lower than those of the control group. In conclusion, the study implied that arginine modifies feeding behavior possibly through controlling endogenous synthesis of nitric oxide in Pekin ducks.

Characterization of myostatin gene (MSTN) of Pekin duck and the association of its polymorphism with breast muscle traits.

Myostatin, encoded by the MSTN gene, is a negative regulator of muscle growth, and its expression level in muscle tissue is closely correlated with muscle growth and satellite cell proliferation. To identify the characteristics of the Pekin duck MSTN gene and the relationship between its polymorphism and breast muscle traits in Pekin duck, cDNA cloning and analysis and the expression pattern in breast muscle development and polymorphism were performed using molecular cloning, quantitative real-time reverse-transcription polymerase chain reaction, and molecular marker technology. The results showed that a 1320-bp sequence, including a 93-bp 5'-UTR, 1128-bp CDS, and 99- bp 3'-UTR, was obtained, and two alternative splicing isoforms were detected. The alternative splicing isoforms encoded 375- and 251-amino acid residues. The amino acid sequence of Pekin duck MSTN was similar to other vertebrates and exhibited the highest similarity to chicken. The expression pattern of MSTN in breast muscle tissue showed a tendency to increase, except for a slight decrease at 6 weeks. Three single nucleotide polymorphisms were found in the Pekin duck MSTN gene by cDNA sequencing from different individuals. The T129C had significant association with breast muscle thickness, and the T952C had significant association with the fossilia ossis mastodi length. This study reveals the molecular characteristics of the Pekin duck MSTN gene and the relationship of its polymorphism with breast muscle traits in Pekin duck. Therefore, it can provide some useful basic understanding of MSTN functions.

Developmental characteristics of pectoralis muscle in Pekin duck embryos.

To confirm the entire developmental process and transition point of embryonic Pekin duck pectoral muscle, and to investigate the association between pectoral muscle development and their regulating genes, anatomical and morphological analyses of embryonic Pekin duck skeletal muscles were performed, and the expression patterns of its regulating genes were investigated. The anatomical analysis revealed that body weight increased with age, while increases in pectoral muscle weight nearly ceased after the embryo was 20 days of hatching (E20). The developmental morphological characteristics of Pekin duck pectoral muscle at the embryonic stage showed that E20 was the transition point (from proliferation to fusion) of Pekin duck pectoral muscle. The expression patterns of MRF4, MyoG, and MSTN indicated that E19 or E20 was the fastest point of pectoral muscle development and the crucial transition for Pekin duck pectoral muscle development during the embryonic stage. Together, these findings imply that E20 is the crucial transition point (from proliferation to fusion) of Pekin duck pectoral muscle and that there is no muscle fiber hypertrophy after E20. Results of this study provide further understanding of the developmental process and transition point of Pekin duck pectoral muscle during the embryo stage.

[Non-coding RNAs and diseases].

With the completion of large scale genomic sequencing, a great number of non-conding RNAs (ncRNAs) have been discovered and capture the attention of the biological sciences community. All known ncRNAs may be divided into two groups, namely: i) small ncRNAs, which comprise microRNAs (miRNAs), PIWI-interacting RNAs (piRNAs) and short interfering RNAs (siRNAs), and ii) several thousands of long ncRNAs (IncRNAs). NcRNAs were shown to be involved in eukaryotic growth and development, cell proliferation and differentiation, apoptosis, epigenetic modifications, and also the complex control and pathogenesis of various diseases. In this paper, knowledge on the ncRNAs, which functioning is associated with human diseases, has been summarized.

Stimulation of adrenal mitochondrial cholesterol side-chain cleavage by GTP, steroidogenesis activator polypeptide (SAP), and sterol carrier protein2. GTP and SAP act synergistically.

Several factors are known to stimulate cholesterol side-chain cleavage in isolated adrenal mitochondria, including steroidogenesis activator polypeptide (SAP), GTP, and sterol carrier protein2 (SCP2). All of these reportedly function at the level of the translocation of cholesterol to the inner membrane wherein side-chain cleavage to form pregnenolone occurs. We have investigated the activating effects of these factors alone and in combination. Under conditions where exogenous cholesterol is provided and multiple turnovers of a transport system are required, GTP stimulated steroidogenesis in isolated mitochondria and in adrenal homogenates, and this effect was enhanced by a GTP regenerating system. SAP alone had little effect under these conditions, but synergized with GTP to stimulate cholesterol metabolism. A truncated SAP analog and a variant from the C terminus of the minor heat-shock protein GRP78 had similar effects, but an unrelated peptide had no effect. GTP stimulated side-chain cleavage with the same EC50 in both resting mitochondria (from dexamethasone-treated rats) and in activated mitochondria (from ether-treated rats), but SAP effects were most apparent in resting mitochondria. In contrast, SCP2 stimulation was additive with other factors, suggesting an independent mechanism of action. While the data are consistent with biological roles for these factors, the relatively small magnitude of the in vitro effects may indicate that cell disruption and mitochondrial isolation disrupt important structural or other features which are necessary for the full expression of the steroidogenic response.

Chemical synthesis, initial conformational studies, and activity of rat steroidogenesis activator peptide and a truncated analog.

A 30-residue peptide corresponding to the amino acid sequence of steroidogenesis activator peptide (SAP) from rat Leydig tumor cells has been synthesized by the solid-phase method using Boc protection. SAP is the putative cycloheximide-sensitive, cAMP-regulated mediator of ACTH-stimulated conversion of cholesterol to pregnenolone in adrenal cortex. N alpha-acetyl-SAP(11-30), an NH2-terminally truncated steroidogenesis activator peptide analog that is missing the most hydrophobic portion of SAP, was also prepared. In addition to these two peptides, N alpha-acetyl-(Cys0)SAP was synthesized in both non-radiolabeled and tritiated forms for coupling to carrier proteins for use as an immunogen to raise anti-SAP antibodies. Chain elongation during synthesis of SAP on PAM resin proceeded with an average coupling yield of 99.3% as determined by quantitative ninhydrin tests. After HF cleavage at -7 degrees, the crude products were purified by semi-preparative HPLC. Peptides were analyzed by analytical HPLC, amino acid analysis, tryptic peptide mapping, and by UV and CD spectroscopy. As determined by CD spectra, SAP showed little evidence of preferred structure either in aqueous solution in the presence of divalent cations or in micelles of reduced Triton X-100 in the absence or presence of either cholesterol or phosphatidylcholine. SAP, in conjunction with GTP, enhanced side chain cleavage activity in isolated adrenal mitochondria.

GTP stimulates pregnenolone generation in isolated rat adrenal mitochondria.

Pregnenolone synthesis from cholesterol by adrenal mitochondria isolated from ether-stressed rats exhibits a biphasic time course: upon the addition of a reducing substrate (e.g. malate), a rapid phase of pregnenolone formation occurs during the first 5 min, which has been interpreted as the metabolism of a steroidogenic pool of cholesterol, probably in the inner membrane. A slower rate follows, which is interpreted as translocation of cholesterol into the steroidogenic pool. While a 30-min preincubation of mitochondria with cholesterol alone did not affect the extent of the rapid phase, preincubation with GTP plus cholesterol extended the first phase, resulting in an up to 2-fold increase in pregnenolone synthesis by 20-30 min. The apparent Km for GTP was 0.1-0.4 mM, and stimulation was maximal with preincubation times of 10-30 min, depending upon incubation conditions. Exogenous cholesterol was not required to observe a stimulatory effect, indicating that GTP reorganizes the endogenous mitochondrial cholesterol pools. Nevertheless, stimulation was greater when exogenous cholesterol was provided, consistent with enhanced utilization of both endogenous and exogenous cholesterol. Stimulation by GTP was also seen in mitochondria isolated from cycloheximide-injected/ether-stressed rats, although the activity in these preparations was always lower than that in mitochondria from ether-stressed rats. The stimulation was specific for GTP, since many other nucleotides (e.g. ATP, GDP, and ITP) and GTP analogues (guanosine 5'-O-(3-thiotriphosphate and guanosine 5'-(beta,gamma-imino)triphosphate) had no effect. The GTP-activated state was reversible: after GTP hydrolysis by a mitochondrial GTPase, pregnenolone synthesis returned to the basal level. Sonic disruption of mitochondria abolished the stimulatory effect of GTP. These results suggest that GTP enhances pregnenolone synthesis by promoting the movement of cholesterol to the steroidogenic pool, consistent with a recently proposed general role for GTP in some vectorial transport processes (Bourne, H. R. (1988) Cell 53, 669-671).