Chromium concentrations in serum, blood clot and urine from patients following total hip arthroplasty

Chromium released from implant alloys may be incorporated into organometallic complexes as Cr3+ [Cr(III)] or CR6+[Cr(VI)]. Since Cr(VI) is far more biologically active than Cr(III), there is considerable interest in identifying the valence state that predominates in corrosion products, either in vitro or in vivo. It is known that erythrocytes display a unidirectional uptake of Cr(VI) while effectively excluding Cr(III). Thus it was felt that a study of the chromium content of blood clot, in comparison to chromium concentrations in serum and urine, could shed light on the valency question. Fourteen patients who received conventional polymethylmethacrylate cemented cobalt-chromium alloy/ultra high molecular weight polyethylene total hip replacements as well as seven control patients who underwent orthopaedic procedures without implantation were studied. Blood and urine specimens were obtained preoperatively, post-operatively and, for total hip patients, at routine early follow up. Chromium content was determined by electrothermal atomic absorption spectroscopy. A significant post-operative rise in serum chromium content was observed for total hip replacement patients, as previously reported, but not for control patients. Unexpected day-to-day variations in clot chromium content, without significant increases, were also observed. Longer time studies are required to determine chromium valence states in corrosion products in this model.     

Electron delocalization in the S1 and T1 metal-to-ligand charge transfer states of trans-substituted metal quadruply bonded complexes

The singlet S₁ and triplet T₁ photoexcited states of the compounds containing MM quadruple bonds trans-M₂(TⁱPB)₂(O₂CC₆H₄-4-CN)₂, where TⁱPB = 2,4,6-triisopropylbenzoate and M = Mo (I) or M = W (I^′), and trans-M₂(O₂CMe)₂((N[ⁱ Pr ])₂CC ≡ CC₆H₅)₂, where M = Mo (II) and M = W (II^′), have been investigated by a variety of spectroscopic techniques including femtosecond time-resolved infrared spectroscopy. The singlet states are shown to be delocalized metal-to-ligand charge transfer (MLCT) states for I and I^′ but localized for II and II^′ involving the cyanobenzoate or amidinate ligands, respectively. The triplet states are MoMoδδ* for both I and II but delocalized ³MLCT for I^′ and localized ³MLCT for II^′. These differences arise from consideration of the relative orbital energies of the M₂δ or M₂δ* and the ligand π^∗ as well as the magnitudes of orbital overlap.     

The relationship between the binding of primary antibody to solid-phase antigen in microtiter plates and its detection by the ELISA

Radioiodinated monomeric and dimeric M315 (mM315 and dM315) prepared from BALB/c ascites fluid by gel filtration and affinity chromatography were used to study the relationship between primary antibody binding to solid-phase dinitrophenylated gelatin in microtiter ELISAs and its indirect detection by enzyme-antibody conjugates and complexes. The relationship between the amount of mM315 or dM315 which binds to dinitrophenylated gelatin to the amount added is linear over a nearly 3-log range with a slope of 1; the amount of M315 which binds in this linear range after 24 h represents all of the active antibody in the system. On a binding site basis, mM315 was inhibited by a significantly lower amount of dinitrophenyl-(DNP)glycine than was dM315. The indirect detection of bound M315 over the same 3-log range using ELISA yielded a sigmoidal titration curve which encompassed a short linear region that had a slope of 0.9 or less. Plateauing of the titration plots at high input of both mM315 and dM315 was shown to be progressively exaggerated in direct relationship to the size of the enzyme-antibody conjugate used for their detection. The data show that the upper region of the sigmoidal ELISA titration plot is the result of steric hindrance of the detection system. Through the combined use of an 131I-enzyme-antibody immune complex (EIC) detection system and 125I-M315, it was shown that the deviation from the linear binding of 125I-M315 observed during its indirect detection in the so-called linear region of the ELISA titration curve was the result of changing ratios of bound EIC: bound primary antibody, not altered enzymic activity.     

Polysaccharide conjugate vaccine protein carriers as a “neglected valency” – Potential and limitations

The development of vaccines against polysaccharide-encapsulated pathogens (e.g. Haemophilus influenzae type b, pneumococci, meningococci) is challenging because polysaccharides do not elicit a strong and long-lasting immune response (i.e. T-cell independent). This can be overcome by conjugating the polysaccharide to a protein carrier (e.g. tetanus toxoid, cross-reacting material 197 [CRM]), which vastly improves the immune response and induces memory to the polysaccharide (T-cell dependent). Although it is well documented that protein carriers additionally induce an immune response against themselves, this potential “additional valency” has so far not been recognized. The only exception is for the protein D carrier (derived from non-typeable Haemophilus influenzae [NTHi]) used in a pneumococcal conjugate vaccine, which may have a beneficial impact on NTHi acute otitis media. In this review, we describe the immunogenicity of various protein carriers and discuss their potential dual function: as providers of T-cell helper epitopes and as protective antigens. If this “additional valency” could be proven to be protective, it may be possible to consider its potential effect on the number of required immunizations. We also describe the potential for positive or negative interference between conjugate vaccines using the same protein carriers, the resulting desire for novel carriers, and information on potential new carriers. The range of conjugate vaccines is ever expanding, with different carriers and methods of conjugation. We propose that new conjugate vaccine trials should assess immunogenicity to both the polysaccharide and carrier. Ultimately, this so-far “neglected valency” could be an exploitable characteristic of polysaccharide conjugate vaccines.     

The electrosorption valency and partial charge transfer

The electrosorption valency as usually defined is an extra-thermodynamic and self-contradictory concept.     

适合治疗给药的大鼠抗肾小球基底膜肾炎模型的建立与应用

目的建立适合治疗给药的大鼠抗肾小球基底膜(GBM)肾炎模型。方法采用家兔多点sc大鼠肾小球基底膜与弗氏佐剂乳化物的方法进行免疫,两周1次,共5次,制备抗血清;分次给大鼠iv抗血清,检测血清循环免疫复合物(CIC)水平、肾小球基底膜免疫荧光强度、肾脏及肾小球基底膜病变,确定适合治疗给药的抗血清效价、免疫剂量、方式及时间。以固肾2号为治疗药物,验证模型的可行性。结果使用效价为1∶4的兔抗大鼠GBM血清4 m L,分3 d 4次iv免疫,免疫第6、8、10天,均能形成大鼠抗肾小球基底膜肾炎,免疫第6天,病变相对较轻,免疫第8天及第10天,病变基本稳定。验证实验结果显示,连续给药30 d,固肾2号显著降低模型大鼠24 h尿蛋白排出,减轻肾脏病变,对大鼠抗肾小球基底膜肾炎有明显治疗作用。结论使用效价为1∶4的兔抗大鼠GBM血清4 m L,分3 d 4次iv免疫,免疫后8 d,能形成适合治疗给药的大鼠抗肾小球基底膜肾炎模型。     

Dimerization of Fab fragments enables ready screening of phage antibodies that affect hepatocyte growth factor/scatter factor activity on target cells

A number of applications of antibodies in diagnosis and therapy require multivalent reagents either because of the polymeric nature of the antigens or because biological activity depends on an effect on the formation of homodimeric species. Here, we report a procedure for mass screening of phage-derived monomeric antibody fragments that depend on valency for activity. As a model system, a set of 13 phage-derived human Fab fragments were first selected against mouse and human recombinant hepatocyte growth factor/scatter factor (HGF/SF), a high molecular weight polypeptide growth factor related to the blood protease plasminogen and involved in development and cancer. These Fab fragments were subsequently screened for an effect on HGF/SF activity either as monomeric fragments or after dimerization with a monoclonal antibody (9E10) directed against a peptide tag on the fragments. Fab were identified that either inhibited or enhanced HGF/SF activity on target cell lines, but dimerization was required for this effect. The approach proposed should facilitate mass screening of phage-derived antibody fragments that depend on multiple valency for activity.     

Permeation of chromium salts through human skin in vitro

Chromium permeation studies were performed on full thickness human skin in diffusion cells. All samples were analysed for the total chromium content by graphite furnace Zeeman-corrected atomic absorption spectrometry. Some samples were analysed by an ion chromatographic method permitting the simultaneous determination of Cr(VI) and Cr(III) as well. The amounts of chromium found in all skin layers were significantly higher when potassium dichromate was applied to the skin compared with chromium chloride or chromium nitrate. Chromium could only be detected in the recipient phase after application of the dichromate solution. Chromium skin levels increased with increasing concentrations of applied chromium salts up to 0.034 M Cr. The amount of chromium in recipient phase and skin layers increased with increasing pH when the applied solution contained potassium dichromate. This was ascribed to a decreased skin barrier function of the skin. The amount of chromium found in all skin layers after application of chromium chloride decreased with increasing pH due to lower solubility of the salt. The % of chromium found in the recipient phase as chromium(VI) increased with increasing total chromium concentration indicating a limited reduction ability of the skin in vitro.     

Human antibodies from phage libraries: neutralizing activity against human immunodeficiency virus type 1 equally improved after expression as Fab and IgG in mammalian cells

Human antibodies against HIV-1 have been sought to study neutralization events on the molecular level, and for possible use in passive immune intervention. The development of phage display techniques has opened the possibility of rapidly generating human monoclonal antibodies with desired specificities. We and others have isolated human HIV-1 neutralizing antibody fragments using this technique. Bacterial expression of isolated clones does, however, differ broadly both in expression levels and functional activity. In addition, intact IgG cannot be expressed in bacteria. By transferring the genes of isolated Fab clones to a mammalian expression system we could perform a comparison of functional activity between Fab expressed in bacterial and mammalian cells, as well as Fab and whole IgG. Fab fragments expressed in mammalian cells showed increased virus neutralizing activity compared to the same Fab clones expressed in Escherichia coli, underlining the inefficiency of procaryotic expression. No difference in HIV-1 neutralizing capacity was detected between monovalent (Fab) and divalent (whole antibody) reagents expressed in CHO cells. Thus, bivalency does not always confer improved neutralization efficacy.