Observation of the 3n evaporation channel in the complete hot-fusion reaction 26Mg + 248Cm leading to the new superheavy nuclide 271Hs

The analysis of a large body of heavy ion fusion reaction data with medium-heavy projectiles (6 < or = Z < or = 18) and actinide targets suggests a disappearance of the 3n exit channel with increasing atomic number of the projectile. Here, we report a measurement of the excitation function of the reaction (248)Cm ((26)Mg,xn)(274-x)Hs and the observation of the new nuclide (271)Hs produced in the 3n evaporation channel at a beam energy well below the Bass fusion barrier with a cross section comparable to the maxima of the 4n and 5n channels. This indicates the possible discovery of new neutron-rich transactinide nuclei using relatively light heavy ion beams of the most neutron-rich stable isotopes and actinide targets.

The absence of physical-aging effects on the surface relaxations of rubbed polystyrene

Extensive experimental results are presented to reveal the relaxations of polystyrene surface deformed by rubbing with a velvet cloth. We found that surface topographic features, such as ditches and ridges created by rubbing, relax at temperatures at about 20( degrees ) C below the bulk glass transition temperature of the polystyrene for a molecular weight of 442 kg/mol, even though we estimate the Laplace Pressure driving the relaxation to be 1/500 of the yield limit. The relaxation is independent of the thermal history before the rubbing process, and post rubbing thermal history below 55( degrees ) C . In other words, physical-aging processes at 23( degrees ) C for up to 7 days and at 50( degrees ) C for 2 days, which would have drastic effects on the relaxations of bulk polymers, have little effects on the relaxations of rubbed surfaces. This is consistent with the mobility enhancement in the surface layer previously reported in the literature.

Hyperbaric oxygen for experimental intracerebral hemorrhage

Acute brain edema formation contributes to brain injury after intracerebral hemorrhage (ICH). It has been reported that hyperbaric oxygen (HBO) is neuroprotective in cerebral ischemia, subarachnoid hemorrhage, and brain trauma. In this study, we investigated the effects of HBO on brain edema following ICH in rats. Male Sprague-Dawley rats received intracerebral infusion of autologous whole blood, thrombin, or ferrous iron. HBO (100% O2, 3.0 ATA for 1 h) was initiated 1 h after intracerebral injection. Control rats were exposed to air at room pressure. Brains were sampled at 24 or 72 h for water content, ion measurement, and Western blot analysis. We found that 1 session of HBO reduced perihematomal brain edema (p < 0.05) 24 h after ICH. HBO also reduced heat shock protein-32 (HSP-32) levels (p < 0.05) in ipsilateral basal ganglia 24h after ICH. However, HBO failed to attenuate thrombin-induced brain edema and exaggerated ferrous iron-induced brain edema (p < 0.05). Three sessions of HBO also failed to reduce brain edema 72h after ICH. In summary, HBO reduced early perihematomal brain edema and HSP-32 levels in brain. HBO-related brain protection does not occur through reduction in thrombin toxicity because HBO failed to attenuate thrombin-induced brain edema. Our results also indicate that HBO treatment after hematoma lysis for ICH may be harmful, since HBO amplifies iron-induced brain edema.

Doubly magic nucleus (108)(270)Hs162

Theoretical calculations predict 270Hs (Z=108, N=162) to be a doubly magic deformed nucleus, decaying mainly by alpha-particle emission. In this work, based on a rapid chemical isolation of Hs isotopes produced in the 26Mg+248Cm reaction, we observed 15 genetically linked nuclear decay chains. Four chains were attributed to the new nuclide 270Hs, which decays by alpha-particle emission with Qalpha=9.02+/-0.03 MeV to 266Sg which undergoes spontaneous fission with a half-life of 444(-148)(+444) ms. A production cross section of about 3 pb was measured for 270Hs. Thus, 270Hs is the first nucleus for which experimental nuclear decay properties have become available for comparison with theoretical predictions of the N=162 shell stability.

Chemical investigation of hassium (element 108)

The periodic table provides a classification of the chemical properties of the elements. But for the heaviest elements, the transactinides, this role of the periodic table reaches its limits because increasingly strong relativistic effects on the valence electron shells can induce deviations from known trends in chemical properties. In the case of the first two transactinides, elements 104 and 105, relativistic effects do indeed influence their chemical properties, whereas elements 106 and 107 both behave as expected from their position within the periodic table. Here we report the chemical separation and characterization of only seven detected atoms of element 108 (hassium, Hs), which were generated as isotopes (269)Hs (refs 8, 9) and (270)Hs (ref. 10) in the fusion reaction between (26)Mg and (248)Cm. The hassium atoms are immediately oxidized to a highly volatile oxide, presumably HsO(4), for which we determine an enthalpy of adsorption on our detector surface that is comparable to the adsorption enthalpy determined under identical conditions for the osmium oxide OsO(4). These results provide evidence that the chemical properties of hassium and its lighter homologue osmium are similar, thus confirming that hassium exhibits properties as expected from its position in group 8 of the periodic table.

Macrophage-derived chemokine gene transfer results in tumor regression in murine lung carcinoma model through efficient induction of antitumor immunity

Chemokine gene transfer represents a promising approach in the treatment of malignancies. Macrophage-derived chemokine (MDC) (CCL22) belongs to the CC chemokine family and is a strong chemoattractant for dendritic cells (DC), NK cells and T cells. Using adenoviral vectors, human MDC gene was transferred in vivo to investigate its efficacy to induce an antitumor response and to determine the immunologic mechanisms involved. We observed that intratumoral injection of recombinant adenovirus encoding human MDC (AdMDC) resulted in marked tumor regression in a murine model with pre-established subcutaneous 3LL lung carcinoma and induced significant CTL activity. The antitumor response was demonstrated to be CD4+ T cell- and CD8+ T cell-dependent. Administration of AdMDC induced chemoattraction of DC to the tumor site, facilitated DC migration to draining lymph nodes or spleen, and finally activated DC to produce high levels of IL-12. Furthermore, a significant increase of IL-4 production within the tumors was observed early after the AdMDC administration and was followed by the increase of IL-12 and IL-2 production. The levels of IL-2, IL-12 and IFN-gamma in serum, lymph nodes and spleen were also found to be higher in mice treated with AdMDC as compared with that in AdLacZ- or PBS-treated mice. The antitumor response induced by AdMDC was markedly impaired in IL-4 knockout mice, suggesting an important role of IL-4 in the induction of antitumor immunity by MDC. These results suggest that MDC gene transfer might elicit significant antitumor effects through efficient induction of antitumor immunity and might be of therapeutic potentials for cancer.

Tumor rejection by disturbing tumor stroma cell interactions

The stroma of solid tumors is a complex network of different cell types. We analyzed stroma cell interactions in two tumor models during cyclophosphamide (Cy)-induced tumor rejection. In growing tumors, tumor infiltrating macrophages (TIMs) produced interleukin (IL)-10. Beginning 6 h after Cy-treatment T cells in the tumor were inactivated and TIMs switched to interferon (IFN)-gamma production. Both, IL-10 production before and IFN-gamma production after Cy-treatment by TIMs required T cells. With the same kinetics as TIMs started to produce IFN-gamma the tumor vasculature was destroyed which required IFN-gamma receptor expression on host but not tumor cells. These events preceded hemorrhagic necrosis and residual tumor cell elimination by T cells. Together, T cells regulate the function of TIMs and tumor rejection can be induced by disturbing the stroma network.

Self-assembly of polymer and sheet structures from palladium(II) complexes by hydrogen bonding between carboxamide substituents

The self-assembly of supramolecular structures from either neutral or cationic palladium(II) complexes containing primary or secondary carboxamide groups as substituents on pyridine ligands has been explored. The displacement of PhCN in trans-[PdCl(2)(PhCN)(2)] by L = N-methylnicotinamide (MNA), isonicotinamide (INA), or nicotinamide (NA) gave the corresponding complexes trans-[PdCl(2)L(2)] 1-3, respectively. Complex 1.H(2)O forms a 2D sheet network via amide-amide hydrogen bonding supported by chloride ligand-to-water hydrogen-bonding interactions. Several cationic complexes, [Pd(L'L')L(2)](2+) 4-9 and 11-16, containing the above ligands and with PPh(3), dppp, dppm, or bu(2)bipy as ancillary ligand(s) were prepared. Complex 4 (L = MNA, L'L' = dppp) forms dimers through amide-amide hydrogen bonding, forming macrocycles which further propagate to form chains via weak C-H...O=C hydrogen bonding. Complex 6 (L = NA, L'L' = dppp) forms zigzag chains connected by amide head-to-head hydrogen bonds. Complex 8 (L = INA, L'L' = dppm) gives interesting double-stranded ribbons linked by two types of amide--amide hydrogen-bonding interactions. Complex 13 (L' = PPh(3), L = NA) forms an infinite chain via complementary amide-amide hydrogen bonds. Complex 14 (L = MNA, L'L' = bu(2)bipy) forms infinite ribbons via the combination of amide hydrogen bonding mediated by a BF(4) anion and weak C-H...O=C hydrogen bonding. Complex 15 (L = INA, L'L' = bu(2)bipy) gives a ladder polymer formed through amide--amide hydrogen bonds. The structure of cis-[Pd(PPh(3))(2)(OH(2))(2)] (OTf)(2) (10) is also reported.

Refolding of beta-lactoglobulin studied by stopped-flow circular dichroism at subzero temperatures

Refolding of bovine beta-lactoglobulin was studied by stopped-flow circular dichroism at subzero temperatures. In ethylene glycol 45%-buffer 55% at -15 degrees C, the isomerization rate from the kinetic intermediate rich in alpha-helix to the native state is approximately 300-fold slower than that at 4 degrees C in the absence of ethylene glycol, whereas the initial folding is completed within the dead time of the stopped-flow apparatus (10 ms). At -28 degrees C, we observed at least three phases; the fastest process, accompanied by an increase of alpha-helix content, is completed within the dead time of the stopped-flow apparatus (10 ms), the second phase, accompanied by an increase of alpha-helix content with the rate of 2 s(-1), and the third phase, accompanied by a decrease of alpha-helix content. This last phase, corresponding to the isomerization process at -15 degrees C described above, was so slow that we could not monitor any changes within 4 h. Based on the findings above, we propose that rapid alpha-helix formation and their concurrent collapse are common even in proteins rich in beta-structure in their native forms.

Calcium-dependent stabilization of the central sequence between Met(76) and Ser(81) in vertebrate calmodulin

Spin-label electron paramagnetic resonance (EPR) provides optimal resolution of dynamic and conformational heterogeneity on the nanosecond time-scale and was used to assess the structure of the sequence between Met(76) and Ser(81) in vertebrate calmodulin (CaM). Previous fluorescence resonance energy transfer and anisotropy measurements indicate that the opposing domains of CaM are structurally coupled and the interconnecting central sequence adopts conformationally distinct structures in the apo-form and following calcium activation. In contrast, NMR data suggest that the opposing domains of CaM undergo independent rotational dynamics and that the sequence between Met(76) and Ser(81) in the central sequence functions as a flexible linker that connects two structurally independent domains. However, these latter measurements also resolve weak internuclear interactions that suggest the formation of transient helical structures that are stable on the nanosecond time-scale within the sequence between Met(76) and Asp(80) in apo-CaM (H. Kuboniwa, N. Tjandra, S. Grzekiek, H. Ren, C. B. Klee, and A. Bax, 1995, Nat. Struct. Biol. 2:768-776). This reported conformational heterogeneity was resolved using site-directed mutagenesis and spin-label EPR, which detects two component spectra for 1-oxyl-2,2,5,5-tetramethylpyrroline-3-methyl)-methanethiosulfonate spin labels (MTSSL) bound to CaM mutants T79C and S81C that include a motionally restricted component. In comparison to MTSSL bound within stable helical regions, the fractional contribution of the immobilized component at these positions is enhanced upon the addition of small amounts of the helicogenic solvent trifluoroethanol (TFE). These results suggest that the immobilized component reflects the formation of stable secondary structures. Similar spectral changes are observed upon calcium activation, suggesting a calcium-dependent stabilization of the secondary structure. No corresponding changes are observed in either the solvent accessibility to molecular oxygen or the maximal hyperfine splitting. In contrast, more complex spectral changes in the line-shape and maximal hyperfine splitting are observed for spin labels bound to sites that undergo tertiary contact interactions. These results suggest that spin labels at solvent-exposed positions within the central sequence are primarily sensitive to backbone fluctuations and that either TFE or calcium binding stabilizes the secondary structure of the sequence between Met(76) and Ser(81) and modulates the structural coupling between the opposing domains of CaM.

[The effects of Ag+ on the absorption of trace metal ion during the somatic embryogenesis of Lycium barbarum. L]

We used callus of medical plant, Ningxia Lycium barbarum. L as material to induce somatic embryo genesis, and used multitracer technique and gamma-ray energy spectrum analytical method to study different concentration of AgNO3 on some absorption of trace metal ions during the somatic embryogenesis of Lycium barbarum. L. The results show that (1) when the concentration of AgNO3 is less then 50 mg/L, with the increase of AgNO3 concentration, the absorption rate of some metal ions is increasing, but when the concentration is excess of such concentration, the effects on the absorption rate are different. Ag+ has the effect of coordination, resistance or competition on the absorption of metal ions. (2) AgNO3 in suitable concentration will promote cell differentiation and somatic embryogenesis. When the concentration of AgNO3 is less then 50 mg/L, along with the increase of the concentration, the frequency of somatic embryogenesis is increased, and Ag+ has the promotion on the somatic embryogenesis of Lycium barbarum. L. While the concentration is up to 50 mg/L, it will mostly raise somatic embryogenesis in calli, the amount of callus is about 3 times as much as that of contrast group (in which AgNO3 is not added). When excess of this concentration point, Ag+ has toxic effect, and the somatic embryogenesis is inhibited remarkably.

Decreased generation of anti-tumor immunity after intrasplenic immunization

The localization of antigen and the nature of the host antigen-presenting cells (APC) that present it to T cells are two major determinants of antigen immunogenicity. While lymph nodes appear to be the major site for T cell priming, recently the spleen was shown to provide an optimal microenvironment for direct CD8+ cytotoxic T cell (CTL) priming by tumor cells even in the absence of known costimulatory molecules on tumor cells. We analyzed whether the splenic microenvironment would support T cell priming also when host APC are involved (cross-priming) which is probably the major pathway during the generation of anti-tumor immunity. We performed immunization/challenge experiments using different tumor cells (B7.1+, B7.1- and/or beta-gal+, beta-gal-) known to induce CTL to a variable extent either exclusively by cross-priming (B7-) or at least partially by direct priming (B7+). Our results demonstrate that tumor take in the spleen required much less cells than at a subcutaneous injection site. Additionally, intrasplenic immunization was invariably ineffective compared to subcutaneous immunization. We further showed that B cells were not responsible for the inefficient intrasplenic immunization. Therefore delivering the tumor cell antigens inside the spleen by intrasplenic immunization did not improve but rather decreased the efficacy of tumor cell vaccines.

[Expression of BDNF and FGF-2 following axotomy in rat facial motoneurons]

OBJECTIVE

To study the expression and distribution of brain derived neurotrophic factor (BDNF) and fibroblast growth factor-2 (FGF-2) in normal facial motoneurons (FMNs) and in FMNs following axotomy.

METHODS

The right facial nerves were transected 6 mm distal to the stylomastoid foraman in adult Wistar rats except the normal group. Serial 20 microns cryosections were cut through the whole brainstems. Expressions of BDNF and FGF-2 mRNA as well as BDNF and FGF-2 protein were studied by in situ hybridization, immunohistochemistry and image analysis.

RESULTS

BDNF mRNA and its protein were observed in widespread areas of normal rat facial nucleus, and those increased 1 day after axotomy. In addition to neurons, glial cells were also stained. FGF-2 mRNA and its protein were mainly localized in normal FMNs of ventral facial nucleus. After axotomy, expression of FGF-2 mRNA started to up-regulate in FMNs at 7 days, however FGF-2 protein drastically reduced at 3 and 7 days.

CONCLUSION

In addition to target-supporting, there may be BDNF autocrine and paracrine mechanisms as well as FGF-2 autocrine mechanisms in normal rat FMN. When target-derived BDNF is deprived, alternative sources of BDNF support may substitute immediately after axotomy. However, deprivating of target--derived FGF-2 may result in down-regulation of FGF-2 protein in adult rat FMNs at early stage after axotomy. These suggest that the exogenous FGF-2 might provide a supportive environment for the recovery of metabolism and function of FMNs at early stage following axotomy.

[Maxillofacial vascular malformation associated with abnormal communication between external carotid and cranial arteries]

OBJECTIVE

To introduce the clinical characteristics of maxillofacial vascular malformation with abnormal communication between external carotid and cranial arteries.

METHODS

One hundred and twenty patients with maxillofacial vascular malformations had been studied by arteriography of internal and external carotid, and vertebral arteries before embolization of tumor supplying artery. Cases found to have communications between extra- and intra-cranial arteries were analyzed.

RESULTS

Fourteen patients (11.67%, 14/120) were found to have abnormal communications between external carotid and cranial arteries. Among them, 11 patients demonstrated communications between occipital and vertebral arteries, 1 patient showed ascending pharyngeal artery and vertebral artery communication, and 2 patients showed maxillary artery-ophthalmic artery communication.

CONCLUSION

Embolization of tumor supplying artery is a safe and practical method for the treatment of maxillofacial vascular malformation when done under digital subtraction angiography and superselective catheterization to avoid the abnormal communicant branches.

Assessment of arterial stenosis in a flow model with power Doppler angiography: accuracy and observations on blood echogenicity

The objective of the project was to study the influence of various hemodynamic and rheologic factors on the accuracy of 3-D power Doppler angiography (PDA) for quantifying the percentage of area reduction of a stenotic artery along its longitudinal axis. The study was performed with a 3-D power Doppler ultrasound (US) imaging system and an in vitro mock flow model containing a simulated artery with a stenosis of 80% area reduction. Measurements were performed under steady and pulsatile flow conditions by circulating, at different flow rates, four types of fluid (porcine whole blood, porcine whole blood with a US contrast agent, porcine blood cell suspension and porcine blood cell suspension with a US contrast agent). A total of 120 measurements were performed. Computational simulations of the fluid dynamics in the vicinity of the axisymmetrical stenosis were performed with finite-element modeling (FEM) to locate and identify the PDA signal loss due to the wall filter of the US instrument. The performance of three segmentation algorithms used to delineate the vessel lumen on the PDA images was assessed and compared. It is shown that the type of fluid flowing in the phantom affects the echoicity of PDA images and the accuracy of the segmentation algorithms. The type of flow (steady or pulsatile) and the flow rate can also influence the PDA image accuracy, whereas the use of US contrast agent has no significant effect. For the conditions that would correspond to a US scan of a common femoral artery (whole blood flowing at a mean pulsatile flow rate of 450 mL min(-1)), the errors in the percentages of area reduction were 4.3 +/- 1.2% before the stenosis, -2.0 +/- 1.0% in the stenosis, 11.5 +/- 3.1% in the recirculation zone, and 2.8 +/- 1.7% after the stenosis, respectively. Based on the simulated blood flow patterns obtained with FEM, the lower accuracy in the recirculation zone can be attributed to the effect of the wall filter that removes low flow velocities. In conclusion, the small errors reported in vitro may support the clinical use of this technique.

A review of therapeutic potentials in ischemic stroke

Stroke is one of the leading causes of death in the world. There are as yet no effective treatments for the ischemic cerebral lesion itself. Nevertheless, five potential therapeutic objectives can be identified. For cerebral infarction, the best treatment is prevention, including targeted preventive treatments for specific subsets of patients or individuals with different risk factors. Incidence rates and mortality rates of stroke have been successfully reduced in certain developed countries by adoption of a public health approach to the prevention and control of risk factors. To rescue the still viable but injured nerve cells, within the ischemic penumbra, effective therapy should be begun at the earliest possible time. Measures to halt or reverse programmed cell death, to enhance the intrinsic autoprotective and repair mechanisms, are under active study. The existence of down-regulated brain regions, where normal nerve cells have far less activities to perform due to interruption of information exchange with the infarct area, and the possibility to reactivate them are worthy of attention.

A caspase-3-like protease is involved in NF-kappaB activation induced by stimulation of N-methyl-D-aspartate receptors in rat striatum

Glutamate receptor stimulation reportedly activates NF-kappaB in vitro and in vivo, although underlying mechanisms remain to be elucidated. Here we evaluated the role of proteases in mediating N-methyl-D-aspartate (NMDA) receptor agonist-induced NF-kappaB activation and apoptosis in rat striatum. The intrastriatal infusion of quinolinic acid (QA, 60 nmol) had no effect on levels of NF-kappaB family proteins, including p65, p50, p52, c-Rel and Rel B. In contrast, QA decreased IkappaB-alpha protein levels by 60% (P<0. 05); other members of the IkappaB family, including IkappaB-beta, IkappaB-gamma, IkappaB-epsilon and Bcl-3, were not altered. The QA-stimulated degradation of IkappaB-alpha was completely blocked by the NMDA receptor antagonist MK-801. QA-induced IkappaB-alpha degradation and NF-kappaB activation were not affected by the proteasome inhibitor MG-132 (1-4 microg). On the other hand, the caspase-3 inhibitor Ac-DEVD.CHO (2-8 microgram) blocked QA-induced IkappaB-alpha degradation in a dose-dependent manner (P<0.05). Ac-DEVD.CHO (4 microgram) also substantially reduced QA-induced NF-kappaB activation (P<0.05), but had no effect on QA-induced AP-1 activation. Furthermore, Ac-DEVD.CHO, but not MG-132, dose-dependently attenuated QA-induced internucleosomal DNA fragmentation. These findings suggest that NF-kappaB activation by NMDA receptor stimulation involves IkappaB-alpha degradation by a caspase-3-like cysteine protease dependent mechanism. Caspase-3 thus appears to contribute to the excitotoxin-induced apoptosis in rat striatal neurons occurring at least partially as a consequence of NF-kappaB activation.

[Telomerase activity and cellular apoptosis of bladder cancers]

OBJECTIVE

To explore the relationship between clinicobiological acting, telomerase activity and cellular apoptosis of bladder cancer.

METHODS

The intensity of telomerase activity and cellular apoptosis of bladder cancer were detected by telomeric repeat amplification protocol (TRAP) and terminal deoxynucleotidyl-transferase mediated dUTP-biotin nick end labeling (TUNEL) assay respectively.

RESULTS

The positive rate of telomerase activity of bladder cancer was 89.29% and the apoptosis index of bladder cancer was (45.16 +/- 14.43)%. The intensity of telomerase activity and apoptosis index of bladder cancer were not related to patient's age, sex, size or number of tumor (P > 0.05), but to the "grade", "stage" and prognosis of bladder cancer (P < 0.01). The higher the intensity of telomerase activity or less cellular apoptosis, the poor prognosis of differentiated or more advanced bladder cancer. The intensity of telomerase activity was negatively correlated with cellular apoptosis of bladder cancer (r = -0.69, P < 0.01).

CONCLUSIONS

The intensity of telomerase activity and cellular apoptosis are correlated with the grade, stage and prognosis of bladder cancer. The detection of telomerase activity and cellular apoptosis are helpful in clinical analysis and evaluation of prognosis of bladder cancer.

Long palindromes formed in Streptomyces by nonrecombinational intra-strand annealing

Long inverted repeats (palindromes) are ubiquitous among prokaryotic and eukaryotic genomes. Earlier work has implicated both DNA breaks and short inverted repeats (IRs) in the formation of long palindromes in yeast and Tetrahymena by a proposed mechanism of intramolecular recombination. Here we report that long-palindromic linear plasmids are formed in Streptomyces following double strand DNA breakage by a nonrecombinational intra-strand annealing process that also involves IRs. By modification of palindrome-generating linear plasmids and development of a novel procedure that enables the sequencing of palindrome junctions, we show that long-palindrome formation occurs by unimolecular intra-strand annealing of IRs followed by 3' extension of the resulting DNA fold-back. The consequent hairpin structures serve as templates for synthesis of duplex linear plasmids containing long palindromes. We suggest that this model for long-palindrome formation in Streptomyces may represent a generally applicable mechanism for generating DNA palindromes.

[Expression of nm23 protein and estrogen receptor and prognosis of colorectal cancers]

OBJECTIVE

To explore the relationship between clinicobiological action and expression of nm23 protein and estrogen receptor (ER) for colorectal cancer.

METHODS

The expression of nm23 protein and ER for 209 cases of colorectal cancer was detected by immunohistochemistry assay (LSAB).

RESULTS

The expression of nm23 protein was correlated with that of ER for colorectal cancer (r = 0.5319, P < 0.01). The expression of nm23 protein and ER in colorectal cancers was not related with patient's age, sex, tumor position, pathological type, histological type, and Dukes stage (r < 0.4, P > 0.05). The expression was related with the prognosis of colorectal cancer (P < 0.01). The higher the expression of nm23 protein and/or ER the better the prognosis, whereas the less the expression of nm23 protein and/or ER the worse the prognosis.

CONCLUSIONS

The abnormal expression of nm23 protein is correlated with the disturbance of estrogen metabolism in colorectal cancer. The detection of nm23 protein and ER is helpful for the diagnosis and prognostic evaluation of colorectal cancer.

CD4+ T cell--mediated tumor rejection involves inhibition of angiogenesis that is dependent on IFN gamma receptor expression by nonhematopoietic cells

Immunity against MHC class II tumors can be mediated by CD4+ T cells in the effector phase through an unknown mechanism. We show that this is IFN gamma dependent but does not require IFN gamma receptor (IFN gamma R) expression on tumor cells, T cells, or other hematopoietic cells and that IFN gamma R expression is not necessary in the priming phase. However, tumor immunity requires IFN gamma R expression on nonhematopoietic cells in the effector phase and involves inhibition of tumor-induced angiogenesis. This shows that an effective anti-tumor response involves communication between CD4+ T cells and nonhematopoietic cells, most likely within the tumor stroma, and that tumor immunity must not entirely rely on direct tumor cell killing.

Bcr/abl+ autologous dendritic cells for vaccination in chronic myeloid leukemia

In chronic myeloid leukemia (CML) ex vivo generated DC are characterized by constitutive expression of bcr/abl and possibly other yet undefined leukemia-associated antigens, since these DC share a common progeny with leukemic cells. Induction of anti-leukemic T cell responses has been described in vitro. For a phase I vaccination study, autologous bcr/abl+ DC are generated under GMP conditions mainly from monocyte precursors in chronic phase CML patients. Lin-, CD80+, CD86+, CD83+, DR+ DC could be generated in sufficient numbers for s.c. vaccination with 1 x 10(6)-5 x 10(7) DC. Using monocyte precursors, the yield of DC per seeded PBMC was in the range of 1-6%. Furthermore, we could demonstrate in vitro that the T cell stimulatory ability of CD34+-derived DC can be augmented by a factor 2-3 by retroviral transduction with a gene coding for interleukin-7. DC-based vaccination strategies are a promising clinical approach, particularly as postremission immunotherapy in the setting of autologous stem cell transplantation.

Shear rate dependence of ultrasound backscattering from blood samples characterized by different levels of erythrocyte aggregation

The objectives were (1) to determine the effect of the erythrocyte aggregation level (wide range of aggregation) and shear rate (which also affects aggregation) on the ultrasound backscattered power, and (2) to evaluate the reproducibility of the ultrasound method. Experiments were performed under steady flow (100-1250 ml/min) in a 12.7 mm diameter vertical tube. Doppler ultrasound at 10 MHz was used to measure simultaneously the velocity and the backscattered power across the tube. For each radial position, the shear rate was computed from the derivative of the velocity profile. The backscattered power decayed exponentially as a function of the shear rate, and for a given shear rate, the power increased monotonically with the level of aggregation measured by laser reflectometry. Using blood samples simulating hypo-, normal, and hyperaggregating erythrocytes, the power of the ultrasound signal varied respectively by -7.8, -13.2, and -16.1 dB as a function of the shear rate (from 0.4 to 50 s-1). The reproducibility of the backscattered power was 5.5 dB, which is less than the variations observed as a function of the shear rate. In conclusion, ultrasound backscattering is sensitive to the level of erythrocyte aggregation. At a first glance, ultrasound seems less accurate when compared to laser reflectometry but it is suggested that this is because ultrasound backscattering may be sensitive to structural aggregate changes that are not detected by the laser method.

[Primary melanoma of the central nervous system]

OBJECTIVE

To investigate the status of diagnosis and treatment of primary melanoma of the central nervous system.

METHODS

Six patients with primary melanoma of the central nervous system underwent surgery in our department between 1969-1999. Clinical presentation, operative findings, histological diagnosis, and prognosis were reviewed.

RESULTS

No typical symptom occurred in these patients. The lesions can mimic meningiomas and acoustic neuromas in location and radiological appearance. Total removal of tumors was only achieved in one case. Histological examination showed malignant lesions in 3 cases and benign lesions in others. Five cases were followed up and only two were alive.

CONCLUSIONS

Primary melanomas are extremely rare tumors of the central nervous system. Surgical removal of the lesion may result in prolonged remission or cure.

NMDA and non-NMDA receptor-stimulated IkappaB-alpha degradation: differential effects of the caspase-3 inhibitor DEVD.CHO, ethanol and free radical scavenger OPC-14117

The excitotoxic response of striatal neurons to NMDA and non-NMDA receptor agonists involves the nuclear translocation of transcription factor nuclear factor-kappa B (NF-kappaB) due to IkappaB-alpha degradation. Resultant augmentation in c-Myc, p53 and cyclin D1 expression presages the apoptotic-like destruction of these cells in vivo. To differentiate molecular events triggered by intrastriatally injected quinolinic acid (QA, 60 nmol) and kainic acid (KA, 2.5 nmol), we compared the effects of a caspase-3 inhibitor (DEVD.CHO, 8 microgram intrastriatally), a free radical scavenger (OPC-14117; 600 mg/kg, orally) and ethanol (2.14-8.6 micromol, intrastriatally or 25-100 mmol/kg, orally) on changes induced by these glutamatergic agonists on NF-kappaB cascade components and the apoptotic death of rat striatal neurons in vivo. The results indicated that the QA-induced degradation of IkappaB-alpha is almost totally mediated by a caspase-3-dependent mechanism, while KA-induced IkappaB-alpha degradation is only partially dependent on caspase-3. OPC-14117 attenuated the effects of QA but not KA on IkappaB-alpha degradation, suggesting that oxidative stress contributes to the QA- but not the KA-induced degradation of IkappaB-alpha. In contrast, ethanol inhibited the KA- but not the QA-induced degradation of IkappaB-alpha and the ensuing DNA fragmentation and loss of striatal GABAergic neurons. It would now appear that NF-kappaB activation in striatal neurons induced by NMDA or KA receptor stimulation involves different biochemical mechanisms. Since excitotoxicity associated with NF-kappaB activation may contribute to neuronal degenerative disorders such as Huntington's disease, a more detailed understanding of biochemical events underlying ionotrophic glutamate receptor-stimulated cell death may assist in the discovery of alternative approaches to interdicting the deleterious consequences of excitotoxic insult.

Relationship between ataxin-1 nuclear inclusions and Purkinje cell specific proteins in SCA-1 transgenic mice

Spinocerebellar ataxia-1 (SCA-1), like other polyglutamine diseases, is associated with aggregation of mutant protein ataxin-1 in the nuclei of susceptible neurons. The role of ataxin-1 aggregates in the pathogenesis of susceptible neurons, especially cerebellar Purkinje cells, is unknown. The present study was initiated to determine the temporal relationship between ataxin-1 aggregation and the sequence of specific biochemical changes in Purkinje cells in SCA-1 transgenic mice (TM). Earlier, we demonstrated that SCA-1 TM with no Purkinje cell loss and no alterations in home cage behavior show decreased expression of calcium-binding proteins calbindin-D28k (CaB) and parvalbumin (PV) in Purkinje cells. To determine if increased expression of mutant ataxin-1 in TM is also associated with earlier biochemical changes in Purkinje cells, both heterozygous and homozygous (B05 line of SCA-1) TM were used. The age of onset of ataxia in SCA-1 TM was at 12 weeks in heterozygotes and 6 weeks in homozygotes. In 6 week old heterozygous TM, Western blot analysis of growth associated protein 43 (GAP-43) and synaptophysin revealed no significant alterations as compared with the age-matched nontransgenic mice (nTM), whereas CaB was significantly reduced. beta-III-Tubulin was used as a specific Purkinje cell marker protein, immunohistochemical localization showed strong beta-III-tubulin immunoreactivity (IR) in Purkinje cells in 6 week old heterozygous TM, whereas CaB and PV IR were markedly reduced in the same neurons (double immunofluorescence staining). Most Purkinje cells from heterozygous (12 weeks old) and homozygous (6 weeks old) TM contained ataxin-1 nuclear inclusions (NIs). Cells with and without visible NIs revealed reduced PV and CaB IR; however, the changes were overtly more severe in cells with visible NIs. In contrast, the same cells were strongly immunoreactive to beta-III-tubulin. CaB, which is also present in the nucleus, colocalized with ataxin-1 and ubiquitin positive NIs. Further, RT-PCR analysis of CaB mRNA in the cerebellum in 6 week old heterozygous TM demonstrated a significant decrease in mRNA in comparison with the aged-matched nTM. These data suggest that there are selective alterations in the expression of CaB and PV in Purkinje cells which possibly occur earlier than ataxin-1 aggregation. Further, we speculate that ataxin-1 aggregates may not be toxic in general; however, they may deplete specific proteins essential for Purkinje cell viability in SCA-1 TM.

[Direct determination of raw plant drugs by FTIR]

Twenty-five common raw plant drugs were determined quickly and directly with diffuse reflectance drawing sample of FTIR for the first time. The results show that the drugs with different chemical compounds are characteristics of different peaks. The category of plant drugs may be firmly identified through their respective IR characteristic absorption spectrum. Furthermore, the approach can be achieved quickly and accurately without extraction and separation of samples.

Tumor necrosis factor alpha expression produces increased blood-brain barrier permeability following temporary focal cerebral ischemia in mice

Alteration of blood-brain barrier (BBB) function occurs in both permanent and temporary cerebral ischemia. Studies in vivo and in vitro have shown that tumor necrosis factor-alpha (TNFalpha) is involved in changes of BBB permeability. However, the relationship between TNFalpha expression and BBB disruption during reperfusion is unclear. The aim of this study is to find the cell source of TNFalpha and to determine the relationship between TNFalpha expression and BBB disruption following temporary focal cerebral ischemia in mice. Adult CD-1 mice received 1 h middle cerebral artery occlusion (MCAO) followed by 2 h, 6 h, 12 h, 24 h, and 48 h of reperfusion. MCAO was achieved using an intraluminal suture technique and reperfusion was performed by the suture withdrawal. Neutralizing monoclonal anti-mouse TNFalpha antibody was administrated intraventricularly immediately after reperfusion. TNFalpha expression was determined by double labeling immunohistochemistry. BBB permeability was determined by albumin immunostaining. TNFalpha immunoreactivity (IR) was observed in the ipsilateral hemisphere from 1 h MCAO with 2 h reperfusion. TNFalpha positive cells included neurons, astrocytes, and ependymal cells. BBB disruption was detected beginning at 6 h reperfusion but was not present at 2 h of reperfusion. The areas of BBB disruption were significantly enlarged at 12 h reperfusion and plateaued at 24 h to 48 h reperfusion. BBB disruptions were significantly attenuated in the anti-TNFalpha antibody treated mice (p<0.05). Our results demonstrate that TNFalpha IR existed in neurons, astrocytes, and ependymal cells during reperfusion. TNFalpha IR following temporary focal cerebral ischemia precedes increased BBB permeability. Treatment with TNFalpha antibody reduces BBB disruption, suggesting TNFalpha may be an important mediator in altering BBB permeability during reperfusion.

[Skeletal metastasis pattern in non-small cell lung cancer and its related factors.]

BACKGROUND

To study the pattern of skeletal metastasis in non-small cell lung cancer and its associated factors.

METHODS

Six hundreds and thirty-eight patients with non-small cell lung cancer pathologically proved were retrospectively reviewed.

RESULTS

The percentage of skeletal metastasis was 35. 3 % in 638 cases. Multiple metastasis accounted for 201 cases. The sites of metastatic lesions for each patient was 3. 4. There was highly significant difference in different site of skeletal metastasis , for instance , thorax , spine , pelvis , limbs and skull in order of incidence ( P < 0. 005) . Bone metastasis rate of adenocarcinoma and adenosquamous carcinoma groups was remarkably higher than that of squamous cell carcinoma ( P < 0. 005) , which was highly significant higher in stage III - IV than that in stage I - II ( P < 0. 005) . The rate in patients with lower-differentiated lung cancer was also highly significant higher than those with well-differentiated cancer ( P < 0. 005) .

CONCLUSIONS

Skeletal metastasis is frequent in patients with lung cancer. Bone imaging should be performed routinely in all lung cancer patients , and it is helpful to estimate the stage and to make the therapeutic arrangement of lung cancer.

T helper cell type 1-associated and cytotoxic T lymphocyte-mediated tumor immunity is impaired in interleukin 4-deficient mice

It is widely accepted that cellular immune responses are induced by CD4(+) T helper 1 (Th1) cells secreting interleukin (IL)-2 and interferon (IFN)-gamma. Tumor immunity is often mediated by cytotoxic T lymphocytes (CTLs) whose activation is supported by Th1 cytokines. Since IL-4 directs Th2 development and has been shown to inhibit Th1-dominated responses, we assumed that IL-4-deficient (IL-4(-/-)) mice would develop vigorous CTL-mediated tumor immunity compared with IL-4-competent (IL-4(+/+)) mice. Surprisingly, IL-4(-/-) mice were severely impaired to develop tumor immunity to both a mammary adenocarcinoma line and a colon carcinoma line. The lack of tumor immunity in IL-4(-/-) mice was associated with reduced IFN-gamma production, diminished levels of tumor-reactive serum IgG2a, and undetectable CTL activity, indicating a defective Th1 response in the absence of endogenous IL-4. Anti-IL-4 monoclonal antibody blocked tumor immunity in IL-4(+/+) mice when administered at the time of immunization but not at the time of challenge. Additionally, tumor immunity could be induced in IL-4(-/-) mice, if IL-4 was provided by gene-modified cells together with immunizing tumor cells. These results demonstrate that tumor immunity requires IL-4 in the priming phase for the generation of effector cells rather than for their maintenance and exclude secondary, developmental defects in the "knockout" strain. Together, our results demonstrate a novel and previously unanticipated role of IL-4 for the generation of Th1-associated, CTL-mediated tumor immunity.

The effects of calbindin D-28K and parvalbumin antisense oligonucleotides on the survival of cultured Purkinje cells

The role of calcium binding proteins, calbindin D-28k (CaB) and parvalbumin (PV) in Purkinje cell survival was investigated using oligonucleotide antisense strategy. Purkinje cell enriched cultures were prepared from the cerebella of 0-1 day old Balb/c mouse pups. Purkinje cells were identified by size, asymmetric arbors, immunoreactivity to CaB and PV, uptake of gamma-aminobutyric acid (GABA) and failure to express glial fibrillary acidic protein. The cells at different days in vitro were treated with antisense or mismatched antisense phosphorothioate oligonucleotides for CaB and PV mRNA (complexed with lipofectin). Neuronal specific [3H]-GABA uptake was used as a measure of Purkinje cell survival. The cultures treated for 24 h with antisense oligos (CaB+PV) showed a significant decrease in [3H]-GABA uptake as compared with the cultures treated with lipofectin alone or with lipofectin + mismatched antisense oligos to CaB and PV mRNA. The results of the present study suggest that the expression of calcium buffering proteins CaB and PV may have a significant involvement in Purkinje cell viability.

Decrease in Ca-ATPase activity in aged synaptosomal membranes is not associated with changes in fatty acyl chain dynamics

We have examined lipid peroxidation (LPO) and fatty acid acyl chain dynamics in synaptosomal membranes isolated from aged rat (Fischer 344 x Brown Norway F1 hybrids) brains, correlating these results with measurements of enzymatic activity of the synaptic plasma membrane Ca2(+)-ATPase (PMCA). Calcium-dependent ATPase activity in these membranes exhibits progressive decreases with a maximal loss of activity with age of approximately 35%. The sensitivity of this membrane-bound ion transporter to the lipid composition of the surrounding membrane, as well as the high abundance of oxidatively sensitive polyunsaturated fatty acyl chains in synaptosomal membranes, suggests that this age-related loss in catalytic turnover may result from LPO-mediated protein modification and/or changes in the physical structure of the bilayer. However, high-performance liquid chromatography analysis of 2,4-dinitrophenylhydrazone derivatives reveals no significant age-related increases in the content of reactive aldehydes (malondialdehyde, formaldehyde, acetaldehyde or acetone) which comprise breakdown products of lipid peroxidation. Electron paramagnetic resonance measurements employing 5- and 12-stearic acid spin labels with the nitroxide reporter groups at two depths in the bilayer were used to assess the fatty acyl chain dynamics (fluidity) of synaptosomal membranes. The resulting spectra demonstrate anisotropic lipid dynamics of two populations of lipids, i.e. lipids in direct association with membrane proteins (boundary lipids) and bulk lipids that do not directly associate with proteins. The nanosecond dynamics of both lipid populations is unaltered with age indicating that any compositional changes occurring with age are insufficient to result in alterations in bilayer fluidity relevant to PMCA activity. Thus, the observed age-related decline in PMCA activity may be explained by direct modification of membrane protein.

[The treatment of rat fulminant hepatic failure by auxiliary partial heterotopic liver transplantation: experimental study]

OBJECTIVE

To confirm the effect of auxiliary partial heterotopic liver transplantation (APHLT) in the treatment of fulminant hepatic failure (FHF).

METHOD

On 30 rat models of FHF, 62% of partial liver grafts were implanted below the host residual liver with 28 successful operations. The survival rate, biochemical test for liver function, (99m)Tc-HIDA liver scintigraphy and pathological changes of the grafts and host livers were studied.

RESULT

The survival rate in 48 hours was 71.4% compared with 0% in 15 FHF animals. 14 days after the operation, the host liver regenerated obviously and the liver function recovered while the graft shrank gradually. 30 days later, the graft became fibrosis completely.

CONCLUSION

Depending on the temporary function support of the graft, the native residual liver could regenerate and restore its function while the graft tended to atrophy.

Constitutive IL-10 production accounts for the high NK sensitivity, low MHC class I expression, and poor transporter associated with antigen processing (TAP)-1/2 function in the prototype NK target YAC-1

Tumor cells that are treated with rIL-10 or transfected with the IL-10 gene show phenotypic changes. These include low but peptide-inducible expression of MHC class I, low sensitivity to specific CTL-mediated lysis, and increased NK sensitivity. In vitro-established mouse tumor lines were screened for IL-10 expression and production, and a large proportion of plasmocytomas or T cell lymphomas were found to produce IL-10. Since one of these lines was the prototype NK target cell YAC-1, we investigated whether the high IL-10 production of this cell line was related to its high NK sensitivity and its defects in MHC class I expression. The decrease in H-2 expression following the in vitro culture of in vivo-passaged YAC-1 cells was accompanied by a gradual increase in IL-10 production, whereas the reverse was found when passing in vitro-grown YAC-1 in vivo as an ascites tumor in syngenic mice. In addition, differences in YAC-1 MHC class I expression correlated with alterations in the functional activity of TAP-1/2 proteins. YAC-1 cells that were transduced with a retroviral IL-10 antisense construct (Y-IL-10 AS) only produced about half of the IL-10 that was produced by YAC-1 transduced with the control construct (Y-IL-10 Mock). Relative to Y-IL-10 Mock cells, the expression of H-2 on Y-IL-10 AS cells was markedly increased, and NK sensitivity was decreased. These data argue for a mechanism wherein IL-10 production is causally related to the low H-2 expression, decreased TAP function, and high NK sensitivity of YAC-1 cells.

Cellular localization of tumor necrosis factor alpha following focal cerebral ischemia in mice

Tumor necrosis factor alpha (TNFalpha) is a pleiotrophic cytokine with diverse proinflammatory actions. Focal cerebral ischemia induces rapid and dramatic increases in TNFalpha levels within and surrounding the focus of damaged brain both in striatum and cortex. The actions of TNFalpha during cerebral ischemia may be related to the cell types which deliver and/or accept TNFalpha signals. However, the cellular sources of TNFalpha following cerebral ischemia have not been fully elucidated. The present study was designed to determine the cellular localization of TNFalpha following permanent middle cerebral artery occlusion (MCAO) in mice. As judged by immunohistochemistry, TNFalpha expression in the ischemic hemisphere was increased at 3 h following MCAO, peaked at 6 to 12 h, and decreased at 24 h. Double immunostaining for TNFalpha and neuron specific enolase (NSE) or glial fibrillary acidic protein (GFAP) showed that TNFalpha positive neurons were observed in both the ischemic core and perifocal region, while TNFalpha positive astrocytes were observed in the outer cortical layer, the corpus callosum, the molecular layer of the hippocampus, and periventricular areas. The presence of TNFalpha immunoreactivity in neurons and nerve fibers following MCAO suggests that TNFalpha expressed in ischemic neurons might be delivered via axonal transport, while TNFalpha immunoreactivity in astrocyte end-feet and ependymal cells following MCAO suggests that TNFalpha may be involved in blood-brain barrier disruption and the initiation of inflammation in the brain.

[A study of the expression of c-myc onoprotein in laryngeal cancer and different distant adjacent mucosa]

Using citric-LSAB-microwave immunohistochemical technique, the expression of c-myc was studied in different regions of larynx including laryngeal squamous cell carcinoma (LSCC), border area, adjacent mucosa which was 0.5, 1.0, 1.5 and 2.0 cm away from cancer 30 cases and four cases of normal laryngeal mucosa. The results showed that over-expression of c-myc in LSCC was found in 29 of 30 (96.7%), which was higher than that in normal laryngeal mucosa (P < 0.01). A significant different expression of c-myc can be seen at the regions of 2.0 and 1.5 cm distant from the tumor (P < 0.05). The expression of c-myc increased as tissue progressed in sequence from normal mucosa, adjacent mucosa to carcinoma. The c-myc expression did not correlate with site of tumor, stage and histological grade (P > 0.05). The results indicate that over-expression of c-myc is involved in genesis of LSCC, and may be an early event in the development of human squamous-cell carcinoma of the larynx. The tissue adjacent to the tumor may have a potential malignancy.

Inhibition of TNFalpha attenuates infarct volume and ICAM-1 expression in ischemic mouse brain

The purpose of our study was to determine whether inhibiting the action of tumor necrosis factor-alpha (TNFalpha) attenuates brain injury and reduces inflammatory responses in the mouse during ischemia and reperfusion. Mice underwent middle cerebral artery occlusion (MCAO) for 1 h followed by 23 h reperfusion. Monoclonal neutralizing anti-murine TNFalpha antibody (mAb) was administrated intraventricularly in the mouse with temporary MCAO. Infarct volume in the anti-TNFalpha mAb treated mice was significantly smaller than that in the control group (p < 0.05). The number of intercellular adhesion molecule-1 (ICAM-1)-positive vessels in the ischemic area of the anti-TNFalpha mAb-treated group was significantly less than that in the control group. Our study demonstrated that blocking TNFalpha reduced brain injury and attenuated ICAM-1 expression during transient cerebral ischemia.

Advances in biopharmaceutical analysis in the People's Republic of China 1995-1997

The present paper is the third biannual review in succession to the author's previous publications (Z.L. Qin, Advances in biopharmaceutical analysis in the People's Republic of China: 1991-1993, J. Pharm. Biomed Anal. 13, 1995, 1-7 and Z.L. Qin, Advances in biopharmaceutical analysis in the People's Republic of China: 1993-1995, J. Pharm. Biomed. Anal. 14, 1996, 1395-1403), regarding the methodological study and progress in biopharmaceutical analysis by RP-HPLC, GC and GC-MS selected from relative journals between April 1995 and March 1997 in P.R. China. The published methods were widely adopted in pharmacokinetic and metabolic studies. Investigation on drug metabolism were conducted more deeply, both in vitro and in vivo, for searching the structure of metabolites and drug metabolic pathways. The use of high performance CZE as a new trend for the analysis of drugs and metabolites in biofluids was also reported.

Replication at the telomeres of the Streptomyces linear plasmid pSLA2

The Streptomyces linear plasmid pSLA2 initiates DNA replication bidirectionally towards its telomeres from a site located near the centre of the molecule; at the telomeres, the recessed ends of lagging strands are filled in by non-displacing DNA synthesis. Here, we report experiments that test three proposed mechanisms for lagging-strand fill-in. We present data inconsistent with recombinational or terminal hairpin models for the formation of full-length duplex pSLA2 DNA. Instead, we find that deletions in short, distantly separated homologous palindromes in the leading-strand 3' overhang prevent propagation of linear pSLA2 DNA, implicating a mechanism of palindrome-mediated leading-strand fold-back in telomere replication. We further show that circularized pSLA2 DNA molecules are opened in vivo precisely at the terminal nucleotides of telomeres, generating functional linear replicons containing native telomeres covalently bound to a protein at their 5' DNA termini. Together, our results support a model in which pairing of multiple widely separated pSLA2 palindromes anchors the 3' end of the leading-strand overhang to a site near the overhang's base -- providing a recognition site for terminal-protein-primed DNA synthesis and subsequent endonucleolytic processing. Thus, the replication of Streptomyces plasmid telomeres may have features in common with the mechanism proposed for telomere replication in autonomous parvoviruses.

B cells inhibit induction of T cell-dependent tumor immunity

Cytotoxic T lymphocyte (CTL) mediated tumor immunity against major histocompatibility antigen (MHC) class I-positive but class II-negative tumors often requires help from CD4+ T cells. These CD4 cells are activated by MHC class II-positive cells that present tumor derived antigens. Considering that different antigen presenting cells, such as B cells, macrophages and dendritic cells compete for antigen and influence the outcome of an immune response, we analyzed tumor immunity in B cell-deficient mice. These mice appear normal with regard to T cell immunity and tolerance to some pure foreign antigens. We show here that the low immunogenicity of tumors is caused by B cells whose presence in the priming phase results in disabled CD4+ T cell help for CTL mediated tumor immunity. Instead, in the presence of B cells, a non-protective humoral immune response is induced. Our results may explain the enigmatic observation that tumor-reactive antibodies occur frequently in cancer patients.