Bioactivity and mechanical properties of PDMS-modified CaO-SiO(2)-TiO(2) hybrids prepared by sol-gel process

Hydrolysis and polycondensation of poly(dimethylsiloxane) (PDMS), tetraethoxysilane (TEOS), tetraisopropyltitanate (TiPT), and calcium nitrate gave essentially pore- and crack-free transparent monolithics of PDMS-modified CaO-SiO(2)-TiO(2) hybrids, when PDMS/(TEOS + TiPT) was larger than 26:74 in weight, under constant ratios of TEOS/TiPT of 9:1 in mol and Ca/(TEOS + TiPT) of 0.15 in mol. Their apatite-forming abilities in a simulated body fluid, which is indicative of bioactivity, increased with decreasing PDMS/(TEOS + TiPT). Their extensibility and Young's modulus decreased and increased, respectively, with decreasing PDMS/(TEOS + TiPT). The hybrids with PDMS/(TEOS + TiPT) of about 30:70 in weight showed fairly high apatite-forming ability, high extensibilities, and Young's moduli almost equal to those of the human cancellous bones. These new kind of bioactive materials with unique mechanical properties may be useful as bone-repairing materials.     

老年患者骨水泥型人工髋关节置换前后的凝血功能

背景：由于老年患者自身的高凝倾向,骨水泥型人工髋关节置换后更容易发生深静脉栓塞、弥漫性血管内凝血、肺栓塞、脑栓塞等并发症。 目的：观察老年患者骨水泥型人工髋关节置换前后凝血4项凝血酶原时间、活化部分凝血活酶时间、凝血酶时间和纤维蛋白原的变化。 方法：检测40例人工髋关节置换老年患者骨水泥植入前10 min,植入后30 min、1 h、2 h、3 h 凝血酶原时间、活化部分凝血活酶时间、凝血酶时间和纤维蛋白原各项指标。 结果与结论：与植入前10 min比较,植入后30 min凝血酶原时间明显下降(P < 0.05),纤维蛋白原明显升高(P < 0.05),植入后3 h均恢复到植入前状态(P > 0.05)。活化部分凝血活酶时间、凝血酶时间在骨水泥植入前后变化均不明显(P > 0.05)。结果表明患者在骨水泥植入后短时间内会出现高凝血状态,在植入3 h后基本消除,提示在植入骨水泥后的3 h是监测凝血的重要时间段。     

Systemic administration of antioxidants does not protect mice against the dopaminergic neurotoxicity of 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP)

We examined whether DA neurotoxicity of 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) can be prevented by combined systemic administration of antioxidants. C57 black mice were injected s.c. with (1) MPTP (30 mg/kg), once daily for two days, alone, or with ascorbic acid (1 g/kg), α-tocopherol (100 mg/kg), or dimethylsufoxide (50 μl) i.p. for two days before, two days with and two days after MPTP, and decapitated 30 days later. (2) MPTP once (30 mg/kg), alone, or with ascorbic acid (200 mg/kg) or cysteamine (75 mg/kg), two days before, one day with and 4 days after, and decapitated 10 days post-MPTP. (3) MPTP once (15 mg/kg), alone, or with ascorbic acid (500 mg/kg), α-tocopherol (100 mg/kg), cysteamine (50 mg/kg) or sodium selenite (2.5 mg/kg), 90 min before and again 90 min after MPTP, and decapitated 7 days later. In all experiments, the marked striatal DA depletions produced by MPTP alone (by 40–70% from controls) were unchanged by cotreatments with the various antioxidants. Findings do not favor intraneuronal generation of superoxides and related cytotoxic free radicals as a major factor in the DA neurotoxicity of MPTP. They suggest that if natural Parkinson's disease is caused by an MPTP-like neurotoxin, early treatment with antioxidants is unlikely to protect nigrostriatal neurons and prevent disease progression.     

Clinical evaluation of nafamstat mesilate (FUT 175). A new anticoagulant for plasmapheresis.

Nafamstat mesilate (FUT), a new anticoagulant with a short half-life of biologic activity, was used in six patients who had a history of bleeding (two from the eye, two nasally, and two orally) during plasmapheresis (PP) due to overdosage of heparin. FUT (1.2 mg/kg/hr) was injected into the arterial blood line during PP. Prothrombin time (PT), activated partial thromboplastin time (APTT), bleeding time (BT), and complete blood count (CBC) were measured before and after PP. Values of PT (17 +/- 1.4 sec) after treatment were nearly 1.5 times the levels of PT (12.5 +/- 0.8 sec) before treatment. Levels of APTT after PP (70.4 +/- 4.1 sec) were nearly double the values of APTT before PP (36.8 +/- 2.6 sec). There were no significant differences between red blood cell (RBC), hemoglobin (Hgb), or platelet counts before and after PP. No patient developed thrombosis, hemorrhage, or other side effect during PP. In conclusion, the optimal dosage of FUT was 1.2 mg/kg body weight/hr during PP. FUT is recommended as a useful anticoagulant during PP treatment of patients with an increased risk of bleeding.     

持续正压通气对阻塞型睡眠呼吸暂停综合症患者血小板活化因子表达及凝血功能的影响

探讨持续正压通气（CPAP）对阻塞型睡眠呼吸暂停综合症（OSAS）患者血中血小板活化因子（PAF）表达及凝血系统功能的影响。对40例OSAS患者治疗前及CPAP治疗30日后血小板活化因子、血栓素B2（TXB2）和凝血酶原时间（PT）、活化部分凝血活酶时间（APTT）、纤维蛋白原（FIB）水平进行了监测,并与37名正常对照者进行了比较。OSAS患者治疗前PAF、TXB2、FIB均明显高于CPAP治疗后及对照组（P〈0.01）,PT、APTT明显低于CPAP治疗后及对照组（P〈0.01）,且经CPAP治疗30日后,上述检测结果与对照组无明显差异（P〉0.05）。OSAS患者体内多存在血小板活化、表达异常及高凝状态,CPAP治疗可有效地降低PAF、TXB2水平,纠正凝血功能的异常,对减轻OSAS的临床症状及预后将起到一定作用。     

Effect of Melatonin, Ascorbic Acid, and Succinic Acid on the Cumulative Toxic Effect of Repeated Treatment with Gammafos (Amifostine)

Daily treatment of outbred albino mice with gammafos in radioprotective doses of 300 and 500 mg/kg for 4 days produced a cumulative toxic effect. This effect was not observed after decreasing the dose of gammafos to 100 mg/kg. Repeated peroral administration of melatonin and ascorbic acid in a dose of 200 mg/kg 30 min before treatment with gammafos reduced its cumulative toxic effect. Succinic acid in a dose of 100 mg/kg was ineffective under these conditions. The cumulative death time for 50% animals receiving gammafos alone or in combination with melatonin, ascorbic acid, and succinic acid was 3.08, 4.29, 4.06, and 2.97 days, respectively.     

Control of silicon species released from poly(lactic acid)-polysiloxane hybrid membranes

Novel hybrid membranes consisting of poly(L-lactic acid) (PLLA), aminopropyltriethoxysilane (APTES), and calcium carbonates were prepared for bioresorbable guided bone regeneration. A molecular chain of PLLA was bonded at the end of an organic chain in APTES through the amide bond formed between carboxy-groups in PLLA and amino-groups in ATPES. As a result, the hybrid membrane was formed. The PLLA in the membrane was an amorphous phase. By heating the membrane at 100 degrees C for 1 h, the PLLA in the membrane crystallized and some organic chains in APTES and amide bonds decomposed. Moreover, numerous pores of 0.5-1 microm in diameter were newly formed at the surface. When the membranes before and after heat treatment were soaked in simulated body fluid, the amount of silicon species in SBF released from the membrane after heat treatment was higher than that before heat treatment. A test of osteoblast-like cellular proliferation on the membrane showed that the membrane after heat treatment has much higher cell-proliferation ability than that before heat treatment.     

Hydrogels based on poly(ethylene oxide) and poly(tetramethylene oxide) or poly(dimethyl siloxane): synthesis, characterization, in vitro protein adsorption and platelet adhesion

In vitro protein adsorption, platelet adhesion and activation on new hydrogel surfaces, composed of poly(ethylene oxide) (PEO) and poly(tetramethylene oxide) (PTMO) or poly(dimethyl siloxane) (PDMS), were investigated. By varying PEO length (MW = 2000 or 3400), hydrophobic components (PTMO or PDMS) or polymer topology (block or graft copolymers), various physical hydrogels were produced. Their structures were verified by 1H NMR and ATR-IR and the molecular weights were determined by gel permeation chromatography. The hydrogels were soluble in a variety of organic solvents, while absorbed a significant amount of water with preserved three-dimensional structure by physical crosslinking. The dynamic contact angle measurement revealed that the surface hydrophilicity increased by incorporating longer PEO, PEO grafting, and adopting PDMS as a hydrophobic segment instead of PTMO. It was observed from in vitro protein adsorption study that the hydrogels exhibited significantly lower adsorption of human serum albumin (HSA), human fibrinogen (HFg), and IgG, when compared with Pellethane, a commercial polyurethane taken as a control. The hydrogels were attractive for HSA but not sensitive to HFg and IgG. And more than 65% of the proteins detected on the surfaces of the hydrogels were reversibly detached by being treated with an SDS solution. It was evident that the hydrogels synthesized in this study were much more resistant to platelet adhesion than the control, which might depend on the composition of proteins adsorbed on the surfaces and their degree of denaturation. Among the hydrogels tested, PEO3,4kPDMS exhibited albumin-rich and platelet-resistant surfaces, implying a potential candidate for biomaterial.     

In vitro bioactivity of poly(epsilon-caprolactone)-apatite (PCL-AP) scaffolds for bone tissue engineering: the influence of the PCL/AP ratio

Porous poly(epsilon-caprolactone) (PCL) is used as long-term bioresorbable scaffold for bone tissue engineering. The bone regeneration process can be enhanced by addition of carbonated apatites (AP). This study was aimed at evaluating the influence of the PCL/AP ratio on the in vitro degradation and bioactivity of PCL-AP composites. To this purpose, PCL-AP samples were synthesised with the following PCL/AP weight/weight ratios: 50/50, 60/40 and 75/25. Vibrational IR and Raman spectroscopies coupled to thermogravimetry (TG) and differential scanning calorimetry (DSC) were used to investigate the in vitro degradation mechanism in different media: 0.01 M NaOH solution (pH=12), saline phosphate buffer at pH 7.5 (SPB), esterase in SPB and simulated body fluid (SBF) at pH 7.5. The latter medium was used to evaluate the bioactivity of the composites. A control PCL sample was analysed before the addition of the AP component. As regards the untreated samples, the method of synthesis utilised for preparing the composite was found to enhance the crystallinity degree. The AP component revealed to be constituted of a B-type carbonated hydroxyapatite with a 3% carbonate content. After 28 days of treatment, the samples showed different degradation patterns and extents depending on the degradation medium, the starting PCL crystallinity and composite composition. Weight measurements, Raman and TG analyses revealed deposition of an apatitic phase on all the composites immersed in SBF. Therefore, all the samples displayed a good bioactivity; the sample which showed the most pronounced apatitic deposition was 50/50, i.e. that containing the highest amount of AP.     

Codominant translational mutants of Chinese hamster ovary cells selected with diphtheria toxin

Diphtheria toxin-resistance markers in two translational mutants, CH-RE1.22c, possessing no toxin-sensitive EF-2 (class IIa), and CH-RE1.32, with 50% toxin-sensitive and 50% toxin-resistant EF-2 (class IIb), behaved codominantly in somatic cell hybrids. There was no complementation in hybrids formed between the two resistant mutants. The mutant parents and their hybrids, except those formed by fusion of CH-RE1.32 and wild-type cells, grew in the presence of toxin. To explain these results we suggest that CHO-K1 cells possess two functional copies of the gene for EF-2 and that CH-RE1.22c and CH-RE1.32 represent the homozygous (R/R) and heterozygous (R/S) states of resistance at the EF-2 gene locus. The failure of hybrids formed between CH-RE1.32 and wild-type cells to grow in toxin is a gene dosage effect. Codominant class IIa translational resistance is a selectable marker for the isolation of hybrids. It can be combined with a second, recessive, marker to provide a cell which is a universal hybridizer (10).     

Structural analysis of poly(3-alkylthiophene)s

Poly(3-hexylthiophene) (PT6), poly(3-octylthiophene) (PT8), poly(3-decylthiophene) (PT10) and poly(3-dodecylthiophene) (PT12) were synthesized by electrochemical and chemical polymerization. Investigation of these polymers by means of gel permeation chromatography indicates that the polymers prepared from the different monomers under similar conditions do not differ substantially considering molecular weight and molecular weight distribution. Bimodal distributions were found for electropolymerized polymers, and with increasing polymerization time, the high-molecular-weight and probably highly branched fraction increased relatively to the low-molecular-weight fraction. The microstructure of the polymers was investigated by nuclear magnetic resonance, and it has been found that the polymers exhibit more types of structural units than expected from a simple coupling of adjacent thiophene moieties in 2,5′-positions. Chemical oxidation with iron trichloride in chloroform gave soluble, high-molecular-weight poly(3-alkyl-thiophene)s with a rather low amount of irregular couplings, and these more regular polymers exhibited a higher degree of crytallinity. Room temperature conductivities of the oxidized polymers were between 0,1 and 30 S/cm depending on the polymerization conditions, but these values were rather independent of the length of the alkyl substituent.     

The crystallization behavior and the mechanical properties of segmented poly(ether ester) thermoplastic elastomers

The isothermal melt crystallization of three segmented copoly(ether ester)s based on PBT as the hard and PTMO as the soft segments differing in their hard segment content was investigated. The kinetics of crystallization was studied using polarizing microscopy and DSC. Two regimes of crystallization were observed. Spherulitic structures of low crystallinity are formed via predominantly athermal nucleation in regime I at supercoolings ΔT_u < 30°C. Ill-defined aggregations of lamellae grow at ΔT_u > 30°C. The crystallization follows an apparent Avrami-equation; the Avrami-constants cannot be explained in terms of a simple model. The structure of the samples was investigated by SAXS and compared to the structure of samples crystallized by rapid quenching and subsequent annealing. Much higher long spacings are obtained on isothermal crystallization. The long spacing increases with decreasing ΔT_u. It increases at constant ΔT_u with decreasing average hard segment length contrary to the samples crystallized by subsequent annealing of the quenched melt. In this case polymers differing in composition do not differ with regard to the long spacing obtained at constant ΔT_u. The modulus in the Hookean-range as derived from stress-strain curves at T > T_g does not reflect the details of the morphology or chain architecture but it is found to depend logarithmically on the volume fraction of crystallinity in the sample. Data of pure PBT are described by the same relationship.     

Possibilities to control Ichthyophthirius multifiliis infestation with medicated feed in rainbow trout (Oncorhynchus mykiss) and chub (Leuciscus cephalus)

In the present study, the treatment of ichthyophthiriasis with medicated feed was investigated in rainbow trout, Oncorhynchus mykiss, and chub, Leuciscus cephalus. The anti-parasitics toltrazuril and imidocarb; the antibiotics doxycycline, erythromycin and sulphadiazine and the anti-inflammatory acetylsalicylic acid were tested. In vitro experiment revealed that all tested anti-parasitics and antibiotics were effective in killing the isolated trophonts and theronts. Minimum doses for killing 100 % of the viable trophonts and for inhibiting the development of theronts were 3 mg/L for doxycycline, 30 mg/L for erythromycin, 2 mg/L for imidocarb dipropionate, 30 mg/L for sulphadiazine and 20 mg/L for toltrazuril. Acetylsalicylic acid (40 mg/kg fish/day), doxycycline (3 and 6 mg/kg/day), erythromycin (40 mg/kg/day), imidocarb dipropionate (5.0 mg/kg/day), sulphadiazine (40 mg/kg/day), toltrazuril (20 and 40 mg/kg/day) and combinations of doxycycline and toltrazuril (3?+?20 mg/kg/day, 6?+?40 mg/kg/day) were tested as medicated feed. When administered as medicated feed, only doxycycline, toltrazuril and combinations of doxycycline and toltrazuril reduced the fish mortality and infestation level. Best results were obtained by feeding a combination of 6 mg/kg/day doxycycline and 40 mg/kg/day toltrazuril. In O. mykiss, this treatment reduced the mortality rate from 100 to 50?±?14 % after 10 days and the infestation level from grade 4 (≥100 trophonts per skin mucus sample) to 3.5 (50–100 trophonts). In L. cephalus, the mortality rate was decreased from 100 to 39?±?5 % and the infestation level from grades 4 to 2 (ten to 50 trophonts) after 10 days.     

Improvement of bioactivity of H(2)O(2)/TaCl(5)-treated titanium after subsequent heat treatments

Commercially pure titanium was treated with a H(2) O(2)/3mM TaCl(5) solution at 80 degrees C for various periods and a titania gel layer was formed on the surface. This gel remained amorphous when heating for 1 h below 200 degrees C and transformed to anatase after heating between 300 degrees and 600 degrees C. The anatase titania gel layers were found to be bioactive as to deposit carbonate ion-incorporated apatite within 1 day of immersion in the Kokubo solution, whereas the amorphous layers did not deposit apatite within 7 days. The apatite particles were found to nucleate preferentially inside the cracks prevailing in the thicker gel layers of 1-h chemically treated specimens. After immersing for 2 days, the titanium specimens were almost completely covered by apatite. Elimination of peroxide radicals from the titania gel and formation of anatase upon subsequent heating are considered to be responsible for the enhanced ability of apatite deposition.     

Effect of the Photoperiod and Administration of Melatonin on the Pars Tuberalis of Viscacha (Lagostomus maximus maximus): An Ultrastructural Study

The pituitary pars tuberalis (PT) is a glandular zone exhibiting well‐defined structural characteristics. Morphologically, it is formed by specific secretory cells, folliculostellate cells, and migratory cells coming from the pars distalis. The purpose of this work was to investigate differences in specific cellular characteristics in the PT of viscachas captured in summer (long photoperiod) and winter (short photoperiod), as well as the effects of chronic melatonin administration in viscachas captured in summer and kept under long photoperiod. In summer, the PT‐specific cells exhibited cell‐like characteristics with an important secretory activity and a moderate amount of glycogen. In winter, the PT‐specific granulated cells showed ultrastructural variations with signs of a reduced synthesis activity. Also, PT showed a high amount of glycogen and a great number of cells in degeneration. After melatonin administration, the ultrastructural characteristics were similar to those observed in winter, but the amount of glycogen was higher. These results suggest possible functional implications as a result of morphological differences between long and short photoperiods, and are in agreement with the variations of the pituitary‐gonadal axis, probably in response to the natural photoperiod changes through the pineal melatonin. The ultrastructural differences observed in PT, after melatonin administration, were similar to those observed in the short photoperiod, thus supporting the hypothesis that these cytological changes are induced by melatonin. Anat Rec, 293:871–878, 2010. © 2010 Wiley‐Liss, Inc.     

Purified titanium oxide with novel morphologies upon spark anodization of Ti alloys in mixed H2SO4/H3PO4 electrolytes

The spark anodization behavior of alpha/beta Ti6Al4V and Ti6Al7Nb alloys and of alpha c.p. Ti in H2SO4, H3PO4, and mixtures of these acids was studied. Chemical depth profiling revealed oxides purified with respect to the substrate alloying elements. This was particularly pronounced on Ti alloys spark anodized in H2SO4/H3PO4 mixtures, the Al content decreasing continuously towards the surface, and V and Nb hardly detectable in the outermost 200 nm. The incorporation of S was significantly reduced in mixed electrolytes, while about 8 at-% P was present. A novel oxide morphology with "worm-like" features in the micrometer range, very different from well-known nano/microporous oxides, was found in mixed electrolytes under suitable conditions. Similar but more porous-like morphologies were formed on Ti. Simple alpha/beta substrate microstructural considerations cannot explain the morphological and chemical observations. Raman spectroscopy indicated the presence of mixed anatase, rutile, and brookite phase on anodized Ti alloys. Bond strengths of 34 MPa for worm-like and 40-50 MPa for nano/microporous morphologies as well as excellent abrasion behavior were found. The compatibility of grit-blasting with the spark anodization process for creating multitopography surfaces was demonstrated. Neither the observed chemical effects, nor the observed particular morphology or the presence of brookite have been reported before.     

Preparation of poly(lactic acid) composites containing calcium carbonate (vaterite)

A new type of ceramic-polymer biomaterial having excellent apatite-forming ability in simulated body fluid was prepared by hot-pressing a mixture of poly(-L-lactic acid) (PLA) and calcium carbonate (vaterite). After PLA dissolved in methylene chloride was mixed with calcium carbonate consisting of vaterite, the mixture was dried completely and subsequently hot-pressed uniaxially under a pressure of 40 MPa at 180 degrees C. When 30 wt% vaterite was introduced, the modulus of elasticity was effectively improved by 3.5-6 GPa, which was about twice higher than the modulus of PLA. The composite showed no brittle fracture behavior and a comparably high bending strength of approximately 50 MPa. The composite containing 30 wt% vaterite formed a 5-15-microm-thick bonelike apatite layer on its surface after soaking in SBF at 37 degrees C even for 1-3d.     

Killing of naive T cells by CD95L-transfected dendritic cells (DC): in vivo study using killer DC-DC hybrids and CD4(+) T cells from DO11.10 mice

Dendritic cells (DC) play the dual task of initiating cellular immunity against potentially harmful foreign antigens (Ag), while maintaining immunological tolerance to self-Ag and environmental Ag. As an approach to induce Ag-specific suppression, we and others introduced CD95 ligand (L) cDNA into DC. The resulting "killer" DC delivered apoptotic signals, instead of activation signals, to primed CD4(+) T cells in vitro and induced Ag-specific immunosuppression in vivo. To study the impact of killer DC on naive T cells, the fate of Ag-reactive T cells and the extent of their depletion after killer DC treatment, we performed in vitro and in vivo reconstitution experiments using: (a) killer DC-DC hybrids created between CD95L-transduced XS106 DC clone (A/J origin) and splenic DC from BALB/c mice, (b) CD4(+) T cells isolated from DO11.10 transgenic mice (BALB/c background), and (c) OVA(323-339) peptide as relevant Ag. Ovalbumin (OVA)-pulsed killer DC-DC hybrids inhibited DO11.10 T cell activation triggered by conventional DC, instead of inducing their activation. Rapid apoptosis of T cells was observed after co-culture with OVA-pulsed killer DC-DC hybrids, but not with non-pulsed killer DC-DC hybrids or OVA-pulsed control DC-DC hybrids. For in vivo reconstitution, (BALB/cxA/J)F1 mice received subcutaneous administration of killer DC-DC hybrids, followed by intravenous inoculation of DO11.10 T cells. Killer DC-DC hybrids migrated preferentially to draining lymph nodes albeit with relatively low efficiency (0.5-1% recovery) and they induced significant, but incomplete (30-40%) killing of DO11.10 T cells in this location. These results document the abilities of CD95L-transduced DC to trigger apoptosis of naive T cells in an Ag-specific manner, to overrule T cell activation signals delivered by conventional DC, and to reduce local frequencies of Ag-reactive T cells in vivo. Our data also uncover two major limitations (relatively low homing efficiency and incomplete elimination of Ag-reactive T cells) that remain to be overcome for clinical application of CD95L-transduced DC strategy.     

Bulk, surface, and blood-contacting properties of polyetherurethanes modified with polyethylene oxide

The bulk, surface, and blood-contacting properties of a series of polyether polyurethanes based on polyethylene oxide (PEO) (MW = 1450), polytetramethylene oxide (PTMO) (MW = 1000), and mixed PEO/PTMO soft segments were evaluated. The effect of varying the weight percentage of PEO, and thus the overall polarity of the mixed soft segment phase, was investigated. Two polymer blends prepared from a PTMO-based and a PEO-based polyurethane were also studied. Differential scanning calorimetry (DSC) and dynamic mechanical analysis indicated that the polyurethanes based on either the PEO or the PTMO soft segments are relatively phase mixed. The degree of phase mixing in the polymers increased with increasing weight fraction of PEO. As expected, water absorption and the hydrophilicity of the polymer increased with increasing PEO soft segment content. In vacuum, the PEO-rich polymers have a lower concentration of soft segment at the surface, possibly due to the migration of the polar PEO segments away from the polymer/vacuum interface. The blood-contacting results indicated that the higher PEO-containing polymers were more thrombogenic than the pure PTMO-based polyurethane. A threshold concentration of PEO in the polyurethane appeared to be required before the blood-contacting properties were significantly affected.     

Polykaryocytosis induced by amphotropic murine C-type virus (AP129) in Sac-cells nonproductively transformed by Moloney murine sarcoma virus (MO-MSV)

Nonproducer cells of STU mouse origin (Sac) transformed with Moloney murine sarcoma virus (Mo-MSV) and superinfected with the amphotropic murine C-type virus strain AP 129 unexpectedly formed polykaryocytes. The multinuclear giant cells appeared about 30 days after AP 129 infection as confirmed in three independently performed experiments. The majority of the Sac-cells became involved in syncytium formation. The polykaryocytes disappeared during continued culture transfers. Various cell lines obtained by limiting dilution showed the same reactivity as the parental cell line. Release of sarcoma-helper virus complex was observed before and during the appearance of the polykaryocytes as well as after their disappearance at about day 50 after infection. In normal STU mouse embryo fibroblasts, normal Balb/3T3 cells or another Mo-MSV transformed nonproducer cells (MSV85 C13; Balb origin) infected with AP 129 no polykaryocytes developed. The sarcoma-helper virus complex released from AP 129 infected Sac-cells led to transformation of cultured cells from different mammalian species (mink, goat, dog). However, when observed for at least 30 days these cultures did not show polykaryocyte formation.