A Flexible, High-Voltage (>100 V) Generating Device Based on Zebra-Like Asymmetrical Photovoltaic Cascade

The mutual conversion between light and electricity lies at the heart of optoelectronic and photonic applications. Maximization of the photoelectric conversion is a long-term goal that can be pursued via the fabrication of devices with ad-hoc architectures. In this framework, it is of utter importance to harvest and transform light irradiation into high electric potential in specific area for driving functional dielectrics that respond to pure electric field. Here, a nano-fabrication technology has been devised featuring double self-alignment that is applied to construct zebra-like asymmetric heterojunction arrays. Such nanostructured composite, which covers a surface area of 5 × 4 mm² and contains 500 periodic repeating units, is capable of photo generating voltages as high as 140 V on a flexible substrate. This approach represents a leap over the traditional functionalization process based on simply embedding materials into devices by demonstrating the disruptive potential of integrating oriented nanoscale device components into meta-material.

Construction of Laterally Asymmetric Heterojunctions with Sub-Micrometer Resolution by Hierarchical Self-Assembly of Polythiophene Nanofibers

Polymeric semiconductors are crucial candidates for the construction of next-generation flexible and printable electronic devices. By virtue of the successful preparation of monodispersed colloidal solution in orthogonal solvent, poly(3-hexylthiophene) (P3HT) nanofibers are developed into versatile building blocks for nanoelectronics and their compatibilities are verified with photolithographic lift-off technology. Then, the joint efforts from both the bottom-up hierarchical self-assembly and top-down self-alignment technology have led to the realization of lateral asymmetric heterojunctions with resolution better than 1 µm. As a result, planar photovoltaic devices incorporating N,N'-dioctyl-3,4,9,10-perylenedicarboximide and P3HT supramolecular nanowires as active components are constructed with the cathode-to-anode distance being tuned from ≈0.1 to 1-2 µm. Based on such a novel device configuration, an interesting phenomenon of channel-length-dependent photovoltaic efficiency is observed for the first time, strongly suggesting the impact of near-field light intensity on the performance of nanophotonic devices.

P103 Impact of the COVID-19 pandemic on the sleep of patients of a multidisciplinary sleep clinic

Introduction

This study aimed to assess the impact of the COVID-19 pandemic on the sleep of adult patients of a multidisciplinary sleep clinic.

Methods

Patients were invited to complete online surveys: Survey 1 in October 2020 (increased COVID-19 restrictions) followed by Survey 2 in February 2021 (after easing of restrictions for a COVIDSafe summer).

Results

Of the 746 patients invited to participate, 73 completed and 8 partially returned Survey 1 (mean age 50.1 years, range 21–83 years, 58% female). Subsequently, 46 completed and 5 partially answered Survey 2. In Survey 1, 22/74 (29.7%) reported reduced sleep quantity and 31/75 (41.3%) indicated worse sleep quality compared with prior to the pandemic. In Survey 2, 33/46 (71.7%) described unchanged sleep quantity whilst 5/46 (10.9%) reported increased sleep quantity since easing COVID-19 restrictions. 36/46 (78.3%) indicated unchanged sleep quality whereas 5/46 (10.9%) described improved sleep quality since easing restrictions. However, 9/46 (19.6%) reported that their sleep remained worse compared with pre-pandemic. For patients who completed both surveys, there was no significant change in Insomnia Severity Index scores (Survey 1 mean 13.6, Survey 2 mean 12.9, mean difference -0.67 [95%CI -2.02, 0.68], p=0.32) or PROMIS Sleep-Related Impairment 8a T-scores (Survey 1 mean 59.0, Survey 2 mean 59.5, mean difference 0.44 [95%CI -1.55, 2.42], p=0.66).

Discussion

The COVID-19 pandemic has negatively affected the sleep of 44% of patients. Following easing of restrictions, symptoms of insomnia and sleep-related impairment did not change significantly, and 19.6% reported that their sleep was not back to their pre-pandemic baseline.

Facile Synthesis of Water-Stable Multicolor Carbonized Polymer Dots from a Single Unconjugated Glucose for Engineering White Light-Emitting Diodes with a High Color Rendering Index

Tunable emission carbonized polymer dots (CPDs) are highly desirable for the preparation of optoelectronic devices, especially white light-emitting diodes (WLEDs). In most available studies, polychromatic CPDs are synthesized using aromatic molecules as precursors. However, few studies report the successful synthesis of polychromatic CPDs using two or more unconjugated precursors. In this work, we prepare multicolor fluorescent CPDs from a single unconjugated precursor, glucose, via a hydrothermal reaction. By controlling the particle size and degree of graphitization of the synthesized CPDs, their emission wavelength can be tuned in the range 440-625 nm (i.e., almost the entire visible region). Furthermore, the CPDs can be used to construct LEDs of varying colors, including WLEDs (CIE coordinates: 0.34, 0.36) with the correlated color temperature and color rendering index of 4997 K and 92.69, respectively. In brief, the strategy proposed in this study successfully converts unconjugated glucose into high-performance LEDs with great application potential.

[Comparison of modeling effects of two different 7, 12-dimethylbenz[a] anthracene induced breast cancer models in tree shrew]

Objective: To explore the feasibility of 7, 12-dimethylbenz[a] anthracene (DMBA) induced tree shrew breast cancer model, and compare the effects of two administration modes by gavage and mammary gland injection. Methods: A total of 40 tree shrews were randomly divided into two groups (20 animals per group): DMBA gavage group and mammary gland injection group. DMBA was dissolved in edible vegetable oil. For gavage group, tree shrews were administered with DMBA solutions (15 mg/kg) by gavage once a day. For mammary gland injection group, DMBA solution (10 mg/kg) was injected into the mammary fat pad of tree shrews, and the injection was performed for a total of 3 times. From the first administration of DMBA, medroxyprogesterone acetate (MPA, 100 mg/kg) was intramuscularly injected into the muscles of the lateral thighs of tree shrews at the same time, for a total of 5 times. The tumorigenesis and survival of tree shrews were monitored. The tumor histological morphology was observed by HE staining. The expression of estrogen receptor (ER), progesterone receptor (PR), cytokeratin5/6 (CK5/6) and human epidermal factor receptor-2 (HER-2) was detected by immunohistochemical staining. Results: In the gavage group, there were 10 deaths, and 4 tree shrews developed mammary tumors with 20.0% (4/20) tumor formation rate. The success rate of mammary cancer modeling was 10.0% (2/20), and the tumor formation time was 197.3±15.1 days. In the mammary gland injection group, there were 8 tree shrews died, and 9 tree shrews formed tumors with 45.0% (9/20) tumor formation rate. The success rate of mammary cancer modeling was 40.0% (8/20), and the tumor formation time was 71.8±19.0 days. There was no significant difference in mortality and tumor formation rate (P>0.05) between the two groups (all P>0.05). However, in the mammary gland injection group, the success rate of mammary cancer modeling was significantly higher than that in the gavage group (P<0.05), whereas the tumor formation time was markedly shorter than that in the gavage group (P<0.01). The pathological types in the gavage group included ductal hyperplasia, intraductal papilloma and ductal carcinoma in situ, while those in the breast injection group included intraductal papilloma and ductal carcinoma in situ. In both groups, immunohistochemical staining showed the negative expression of HER-2 but positive expression of ER, PR and CK5/6 with varying degrees. Conclusion: Both the DMBA gavage and mammary gland injection can successfully establish the tree shrew breast cancer model, and the modeling effect of mammary gland injection is better than gavage.

Inhibition of the integrin/FAK signaling axis and c-Myc synergistically disrupts ovarian cancer malignancy

Integrins, a family of heterodimeric receptors for extracellular matrix, are promising therapeutic targets for ovarian cancer, particularly high-grade serous-type (HGSOC), as they drive tumor cell attachment, migration, proliferation and survival by activating focal adhesion kinase (FAK)-dependent signaling. Owing to the potential off-target effects of FAK inhibitors, disruption of the integrin signaling axis remains to be a challenge. Here, we tackled this barrier by screening for inhibitors being functionally cooperative with small-molecule VS-6063, a phase II FAK inhibitor. From this screening, JQ1, a potent inhibitor of Myc oncogenic network, emerged as the most robust collaborator. Treatment with a combination of VS-6063 and JQ1 synergistically caused an arrest of tumor cells at the G2/M phase and a decrease in the XIAP-linked cell survival. Our subsequent mechanistic analyses indicate that this functional cooperation was strongly associated with the concomitant disruption of activation or expression of FAK and c-Myc as well as their downstream signaling through the PI3K/Akt pathway. In line with these observations, we detected a strong co-amplification or upregulation at genomic or protein level for FAK and c-Myc in a large portion of primary tumors in the TCGA or a local HGSOC patient cohort. Taken together, our results suggest that the integrin–FAK signaling axis and c-Myc synergistically drive cell proliferation, survival and oncogenic potential in HGSOC. As such, our study provides key genetic, functional and signaling bases for the small-molecule-based co-targeting of these two distinct oncogenic drivers as a new line of targeted therapy against human ovarian cancer.

Relationship between RUNX3 methylation and hepatocellular carcinoma in Asian populations: a systematic review

Runt-related transcription factor 3 (RUNX3) is a potential tumor suppressor that is frequently hypermethylated in hepatocellular carcinoma (HCC). The present meta-analysis of case-control studies was carried out to determine whether RUNX3 hypermethylation is associated with HCC. The PubMed, Embase, and Chinese National Knowledge Infrastructure databases were searched for all relevant studies published between May 2000 and May 2012. A total of 11 studies were identified, and 8 studies involving 491 patients with HCC and 409 patients without tumors were found to satisfy the inclusion criteria for the meta-analysis. All tissue samples were from Asian populations. There was significant heterogeneity between the studies. Over the entire sample, the odds ratio (OR) of RUNX3 promoter methylation was 18.5 [95% confidence interval (CI), 11.6-29.6] for HCC tissues relative to control tissues. The ORs of RUNX3 methylation were 16.6 (95%CI = 6.5-42.4) for tumor tissues relative to tumor-adjacent tissues in patients with HCC, 67.3 (95%CI = 13.0-348.5) for tumor tissues from patients with HCC relative to liver tissues from patients with non-neoplastic liver diseases, and 3.26 (95%CI = 1.54-6.90) for tissues from patients with hepatitis C virus (HCV)- related HCC relative to liver tissues from patients with HCC unrelated to HCV. There was no association between RUNX3 methylation and age, gender, pathological stage, or hepatitis B virus infection in HCC tissues. Methylation of the RUNX3 promoter strongly correlated with HCC in Asian populations, especially in individuals with HCV-related HCC, and may be a useful marker for HCC diagnosis in these populations.

Effect of influenza on cardiorespiratory and all-cause mortality in Hong Kong, Singapore and Guangzhou

1. Using a common modelling approach, mortality attributable to influenza was higher in the two subtropical cities Guangzhou and Hong Kong than in the tropical city Singapore. 2. The virus activity appeared more synchronised in subtropical cities, whereas seasonality of influenza tended to be less marked in the tropical city. 3. High temperature was associated with increased mortality after influenza infection in Hong Kong, whereas relative humidity was an effect modifier for influenza in Guangzhou. No effect modification was found for Singapore. 4. Seasonal and environmental factors probably play a more important role than socioeconomic factors in regulating seasonality and disease burden of influenza. Further studies are needed in identifying the mechanism behind the regulatory role of environmental factors.

Parathyroid hormone-induced up-regulation of connexin-43 messenger ribonucleic acid (mRNA) is mediated by sequences within both the promoter and the 3'untranslated region of the mRNA

The gap junction protein connexin 43 (Cx43) mediates communication between osteoblasts and is important for maximal PTH responsiveness. We examined the role of the Cx43 promoter and messenger RNA 3' untranslated region (UTR) in conferring responsiveness to PTH in the rat osteosarcoma cell line UMR-106. PTH induced a 4-fold increase in luciferase activity of a reporter construct containing 1.6 kb 5' of the transcription start site. Deletion analysis of the promoter localized responsive sequences to between -31 to +1 bp. PTH treatment of transgenic mice containing the 1.6 kb promoter luciferase construct induced increases in luciferase and Cx43 immunoreactivity in bone cells underlying the tibial growth plate. The full Cx43 3'UTR conferred a 3-fold response to PTH when placed 3' of a CMV-luciferase construct. Deletion analysis localized responsive sequences to between 2510 and 3132 of the 3'UTR. Cloning of this segment 5' of the CMV promoter disrupted the PTH response, indicating this sequence does not function as an enhancer. Sequences within the promoter conferred responsiveness to forskolin, whereas the 3'UTR responded to both TPA and forskolin. These data indicate that PTH responsive sequences are present in the Cx43 promoter and 3'UTR, suggesting that transcriptional and posttranscriptional pathways operate to regulate PTH-induced Cx43 expression in osteoblast cells.

Central venous catheters versus peripheral veins for sampling blood levels of commonly used drugs

BACKGROUND

Our objective was to compare the accuracy of drug levels in blood samples obtained from central venous catheters with those from peripheral blood samples taken to monitor various drug levels.

METHODS

Pediatric patients with central venous catheters receiving aminoglycosides, vancomycin, or cyclosporine had central and peripheral blood samples obtained within 5 minutes of each other and analyzed simultaneously. We ascertained how well blood levels from central venous catheters compared with those from peripheral blood (the criterion standard).

RESULTS

There were no clinically significant differences between central and peripheral values for amikacin, gentamicin, tobramycin, and vancomycin (both peaks and troughs). Preliminary data indicated that oral cyclosporine can be monitored via central venous catheter. In contrast, there was poor agreement between peripheral and central values when cyclosporine was administered by IV.

CONCLUSIONS

Amikacin, gentamicin, tobramycin, vancomycin, and probably oral cyclosporine can be monitored accurately via central venous catheter. In contrast, IV cyclosporine should be monitored via peripheral blood.

Systemic responses to SFHS-infusion in hemorrhaged dogs

Anesthetized mongrel (weight range: 16-27 Kg) dogs were prepared for monitoring hemodynamics, blood flow distribution, plasma colloid osmotic pressure and renal functional parameters at various intervals. Removal of 35 ml/Kg blood resulted in marked drop and only partial spontaneous recovery in systemic and pulmonary arterial pressures, cardiac output and organ blood flows (> 50% flow-decrements occurred in kidney, spleen, heart, gut and pancreas); plasma colloid osmotic pressure as well as urine output and creatinine clearance also fell. Group I (n = 6) of dogs was transfused after 45 minutes of hypovolemia with their own anticoagulated blood, while Group II (n = 6) received an equal volume of unmodified 6% stromafree hemoglobin solution (SFHS). Comparison of the two groups' responses to resuscitation yielded some differences. There was a significant overshoot (30 mmHg) in systemic arterial blood pressure accompanied by bradycardia in Group II only. Cardiac output recovered in both groups but was less well sustained in Group II. Cerebral blood flow rose higher and hepatic arterial flow-increment was less in Group II than in Group I; the responses to resuscitation in the other organs were comparable. Colloid osmotic pressure decreased in Group I whereas it rose immediately after resuscitation in Group II, declining thereafter with a converging trend and 30 minutes thereafter the differences were not significant between the groups. Urine excretion and creatinine clearance recovered to comparable extents in both groups, but N-acetyl-beta-D-glucosaminidase (N.A.G.) excretion rose over 10-fold higher in Group II than in Group I. These experiments have defined the response of bled animals to resuscitation with unmodified, unpurified SFHS, when compared to resuscitation with whole blood, showing a less well sustained but adequate hemodynamic and renal functional recovery while revealing indications of early renal tubular cellular injury, providing baseline comparison for testing highly purified and modified hemoglobin solutions.

Absorption of lactose, glucose polymers, or combination in premature infants

STUDY OBJECTIVE

To determine the digestion and absorption of lactose, a combination of lactose and glucose polymers, and glucose polymers alone in infants born at 28 to 42 weeks of gestation.

DESIGN

Each infant received the three carbohydrate solutions (85 gm/L concentration) in random order.

SETTING

Tertiary care urban children's hospital.

INTERVENTIONS

A double-lumen perfusion catheter was placed in the duodenum-jejunum. Absorption was defined as the disappearance of the carbohydrate and all its components (e.g., for lactose: galactose, glucose).

MEASUREMENTS AND MAIN RESULTS

Absorption of lactose was less than that of the lactose-glucose polymer combination and the glucose polymers alone. There was no relationship between lactose absorption and postnatal age, whereas absorption of the lactose-glucose polymer combination and the glucose polymers alone correlated with age. Lactose absorption was not related to the number of days that the infants received full-strength feedings or the total number of days of feeding before the study, whereas absorption of both the lactose-glucose polymer combination and the glucose polymers alone was related to both. Absorption of the three solutions was not related to gestational age or to the number of days before the initial feeding. Lactose absorption was greater in infants who received formula alone than in infants fed formula together with human milk.

CONCLUSIONS

Premature infants do not digest and absorb lactose as well as glucose polymers. However, lactose does not impair the absorption of glucose polymers. Lactose assimilation is not affected by maturation, but the type of diet may affect lactose digestion and absorption. In contrast, digestion and absorption of glucose polymers are related to both postnatal age and diet.

Oxyradical generation after resuscitation of hemorrhagic shock with blood or stroma-free hemoglobin solution

Hypovolemic states are characterized by inadequate tissue perfusion; when this state is reversed, the reintroduction of oxygen is accompanied by the excess generation of oxyradicals and these, in turn, may cause "reperfusion injury" in susceptible tissues. When hemoglobin solution is used to resuscitate the hypovolemic state, the generation of oxyradicals may be enhanced by catalytic means. The generation of oxyradicals was estimated in dogs subjected to the acute removal of 35 ml/Kg blood, and resuscitated 45 mins thereafter with an equal volume of either autologous blood (Group I, n = 6) or 6% stromafree hemoglobin solution (S.F.H.S.) (Group II, n = 6). Hepatic and pancreatic enzymes were measured in blood drawn at intervals. The hypovolemic state was characterized by profound hypotension which was reversed by resuscitation. Oxyradical generation in arterial blood samples, drawn at various times, was estimated by the generation of oxidation products (2,3- and 2,5-dihydroxybenzoic acid) of exogenously administered sodium salicylate, determined by HPLC in plasma samples extracted with diethyl ether. Salicylate oxidation products rose significantly above the baseline value in Group I dogs, whereas they rose 5-6-fold higher than the baseline values in those of Group II. The actual values attained and the increments were significantly (p < .05) greater in Group II than in Group I. In the group resuscitated with S.F.H.S., catalytically active iron concentration in plasma also rose 10-12-fold higher and was associated with spuriously elevated levels of gamma-glutamyl transferase due to interference with the assay. These findings are consistent with the hypothesis that blood-resuscitation of hypovolemic shock is accompanied by oxyradical generation of a modest degree; in contrast, S.F.H.S.-resuscitation introduces catalytically active iron and is accompanied by oxyradical generation of a significantly greater degree.

Effects of dietary sodium on central and peripheral ouabain-like activity in spontaneously hypertensive rats

High dietary Na+ intake enhances pressor and sympathoexcitatory responses in spontaneously hypertensive rats (SHR) but not Wistar-Kyoto (WKY) rats. To evaluate the possible contribution of central ouabain-like activity (OLA), brain and peripheral OLA was assessed in SHR vs. WKY rats at 4 wk of age and after 2 and 4 wk of high vs. control Na+ intake started at 4 wk of age. In SHR, hypertension developed with maturation and was exacerbated by high Na+ intake. With control Na+ intake, SHR showed higher OLA at 4, 6, and 8 wk of age in the pituitary and hypothalamus and also by 8 wk in the adrenals and left ventricle but not in plasma. High Na+ intake increased OLA in all tissues examined in both WKY rats and SHR. After 2 wk on high Na+, only OLA in hypothalamus and pituitary was higher in SHR vs. WKY rats; after 4 wk on high Na+, peripheral (i.e., adrenals, left ventricle, and plasma) OLA was also higher. These results indicate that in SHR the development of hypertension is associated early on with increases in central OLA and in a later phase with increases in peripheral OLA as well. High Na+ intake increases OLA in both SHR and WKY rats, but the higher OLA may affect sympathetic activity and blood pressure only in SHR.

Phospholipase D activity in subcellular membranes of rat ventricular myocardium

The phospholipase D (PL D), which catalyzes the formation of phosphatidic acid (PA), was studied in rat myocardium using 14C-labelled phosphatidylcholine (PC) as an exogenous substrate. Subcellular distribution experiments indicated the presence of PL D in particulate fractions only. Different procedures for the isolation of purified cardiac subcellular organelles showed the presence of PL D in sarcolemma (SL), sarcoplasmic reticulum (SR) and mitochondria with 14-, 11- and 5-fold enrichment when compared to the homogenate value, respectively. The activity of SL PL D was observed over a narrow acid pH range with an optimum at 6.5, and it showed a high specificity for PC while phosphatidylethanolamine and phosphatidylinositol showed a low rate of hydrolysis. Under optimal conditions, PA formation was linear for a 90-min period of incubation and the reaction rate was constant for 10 to 100 micrograms SL protein in the assay medium. The SR PL D displayed properties similar to those seen with the SL PL D. In membrane fractions PL D was also found to catalyze a transphosphatidylation reaction for the synthesis of phosphatidylglycerol. Assessment of the intramembranal levels of radioactive 1,2-diacylglycerol (DAG) in the absence or presence of KF suggested the presence of an active PA phosphohydrolase activity. This study indicates that a PC-specific PL D activity is localized in different membrane systems of the myocardium and may be associated with PA phosphohydrolase to act in a coordinated manner. The functional significance of PL D-dependent formation of PA in cardiac membranes is discussed.

Site-specific mutagenesis using a gapped duplex vector: a study of translesion synthesis past 8-oxodeoxyguanosine in E. coli

We have constructed a gapped plasmid vector in which a single defined lesion is introduced, site-specifically, within a single-strand region. Efficiency of translesional synthesis is determined by the number of colonies recovered following transformation of E. coli. The nucleotide sequence of progeny plasmids in the gapped region of the vector reflects incorporation of bases opposite and near the lesion. The analysis detects non-mutagenic as well as mutagenic events. This system was used to establish the mutagenic potential of 2'-deoxy-7,8-dihydro-8-oxoguanosine (8-oxodG), a lesion produced by the action of active oxygen species on DNA. The presence of 8-oxodG did not affect the number of transformants recovered. Most transformants (greater than 99%) contained G:C pairs at the site of the lesion; however, a limited number of targeted G----T transversions were observed in the presence and absence of SOS induction. Base substitutions neighboring the lesion, reported for an in vitro system, were not observed. We conclude that the 8-oxodG lesion in DNA is weakly mutagenic in E. coli.

Inhibition of cardiac phosphatidylethanolamine N-methylation by oxygen free radicals

This study was undertaken to examine the effects of oxygen free radicals on phosphatidylethanolamine (PE) N-methylation in rat heart sarcolemmal (SL) and sarcoplasmic reticular (SR) membranes. Three catalytic sites involved in the sequential methyl transfer reaction were studied by assaying the incorporation of radiolabeled methyl groups from S-adenosyl-L-methionine (0.055, 10, and 150 microM) into SL or SR PE molecules under optimal conditions. In the presence of xanthine + xanthine oxidase (superoxide anion radicals generating system), PE N-methylation was inhibited at site I and III in the heavy SL fraction isolated by the hypotonic shock-LiBr treatment method. In the light SL fraction isolated by sucrose-density gradient, a significant inhibition of PE N-methylation was seen at all three sites. These inhibitory effects of xanthine + xanthine oxidase on PE N-methylation were prevented by the addition of superoxide dismutase. Hydrogen peroxide showed a significant inhibition of PE N-methylation at site I in the heavy SL fraction, and at site I and II in the light SL fraction. Catalase blocked the inhibitory effects of hydrogen peroxide. The effects of both xanthine + xanthine oxidase and hydrogen peroxide on the SR membranes were similar to those seen for the heavy SL fraction. These results suggest that, in addition to lipid peroxidation, the oxygen free radicals may affect the function of cardiac membranes by decreasing the phospholipid N-methylation activity.

Cephalosporin penetration into soft tissue of paralyzed limbs

Poor penetration of antibiotics into paralyzed tissue may contribute to the difficulty of curing soft tissue infections in paralyzed limbs. A novel model of spinal cord hemisection was used to induce paralysis of one hind leg in mice. Five, 10, or 20 days after induction of paralysis, six groups of 10 mice were injected intravenously with a single dose or with four sequential doses of cefepime, a new broad-spectrum cephalosporin, and then sacrificed. High-performance liquid chromatography was used to compare cefepime levels in soft tissue homogenates of paralyzed and normal hind legs; no significant differences were found in any group. Factors other than antibiotic delivery may be responsible for difficulty in curing infections in paralyzed soft tissue.

Restricted infectivity of ecotropic type C retroviruses in mouse teratocarcinoma cells: studies on viral DNA intermediates

Replication of Gross strain N-tropic type C retrovirus was markedly restricted in a pluripotential undifferentiated embryonal cell line (PCC4) of murine teratocarcinoma, whereas the same virus could cause productive infection in a myoblast-derived differentiated line (PCD1) of the same tumor origin. To investigate the restriction mechanism, we compared the initial viral DNA formation in these two cell lines. Analyses by means of a modified Hirt extraction procedure and a modified Southern gel transfer method indicated that PCC4 and PCD1 cells supported the synthesis of viral DNA intermediates after inoculation of the Gross virus. In both cells, a linear DNA duplex (from III viral DNA) appeared at 4 hr, reached a maximal level at 8-9 hr, and declined rapidly thereafter, while two closed-circular supercoiled DNA duplexes (form I viral DNA) showed their appearance, increase and decline in the 8-24 hr period. During the period from 34 to 78 hr after virus inoculation, another burst of viral DNA synthesis occurred in PCD1 cells, presumably due to secondary virus infection, while at this period both form III and form I viral DNAs became undetectable in PCC4 cells. The Hirt supernatant DNAs prepared from PCD1 and PCC4 cells 10 hr after virus inoculation were equally infectious for NIH3T3 cells in a DNA transfection, although one positive result with PCD1 cells might suggest a difference between the two cell types in this aspect. These results indicate that restriction of type C retrovirus in undifferentiated embryonal carcinoma cells occurs at a step subsequent to formation and maturation of viral DNA intermediates.