Function of the Rho family GTPases in Ras-stimulated Raf activation

Ras plays an essential role in activation of Raf kinase which is directly responsible for activation of the MEK-ERK kinase pathway. A direct protein-protein interaction between Ras and the N-terminal regulatory domain of Raf is critical for Raf activation. However, association with Ras is not sufficient to activate Raf in vitro, indicating that Ras must activate some other biochemical events leading to activation of Raf. We have observed that RasV12Y32F and RasV12T35S mutants fail to activate Raf, yet retain the ability to interact with Raf. In this report, we showed that RasV12Y32F and RasV12T35S can cooperate with members of the Rho family GTPases to activate Raf while alone the Rho family GTPase is not effective in Raf activation. A dominant negative mutant of Rac or RhoA can block Raf activation by Ras. The effect of Rac or Cdc42 can be substituted by the Pak kinase, which is a direct downstream target of Rac/Cdc42. Furthermore, expression of a kinase inactive mutant of Pak or the N-terminal inhibitory domain of Pak1 can block the effect of Rac or Cdc42. In contrast, Pak appears to play no direct role in relaying the signal from RhoA to Raf, indicating that RhoA utilizes a different mechanism than Rac/Cdc42. Membrane-associated but not cytoplasmic Raf can be activated by Rac or RhoA. Our data support a model by which the Rho family small GTPases play an important role to mediate the activation of Raf by Ras. Ras, at least, has two distinct functions in Raf activation, recruitment of Raf to the plasma membrane by direct binding and stimulation of Raf activating kinases via the Rho family GTPases.

Structure and expression of a membrane component of the inhibin receptor system

The purification and cloning of a membrane-anchored proteoglycan with affinity for inhibin A are described. Bovine pituitary membranes were isolated, and membrane-anchored proteins were solubilized and used as an enriched source of inhibin binding protein. The extract was passed over an inhibin A affinity column, and a protein, designated p120, was identified as an inhibin-binding moiety. A partial amino acid sequence was determined for the protein, which matched two human complementary DNAs (cDNAs) in the database. The full-length cDNA predicts a 1336-amino acid glycoprotein. Full-length p120-encoding cDNAs were isolated from human testis RNA and cloned into expression vectors. Two p120 messenger RNA transcripts of 4.6 kb and 2 kb are detected in rat pituitary by RNA blot analysis. Similar analysis of rat testis RNA revealed transcripts of identical molecular mass, albeit at lower abundance. To determine the cellular localization of p120 in pituitary and testis, an antibody directed against the predicted extracellular domain of the protein was generated and used in an immunohistochemical analysis of thin tissue sections. p120 immunostaining is coincident with FSHbeta immunopositive gonadotrope cells in rat pituitary. p120 staining is intense in the testicular Leydig cells, which bind iodinated inhibin but not iodinated activin. In summary, an inhibin-binding protein has been isolated that is produced in tissues that are targets of inhibin action.

Anti-tumour activity against B16-F10 melanoma with a GM-CSF secreting allogeneic tumour cell vaccine

Genetic modification of tumour cells with the GM-CSF encoding gene renders these cells more potent, as autologous tumour cell vaccine, than their wild-type counterparts. However, autologous vaccines are impractical for wide-scale clinical use and we have therefore investigated the efficacy of the GM-CSF genetic modification approach with an allogeneic whole cell tumour vaccine. In this report, we show that the allogeneic K1735-M2 (H-2k) melanoma cell vaccine induces a specific protective anti-tumour response against the syngeneic B16-F10 (H-2b) melanoma tumour in C57BL/6J mice. In vitro T cell work demonstrated that vaccination of animals with the allogeneic cell vaccine generated cytotoxic T cells specific for the autologous tumour. In vivo T cell subset depletion experiments also illustrated that this anti-tumour effect was mediated by both CD4+ve and CD8+ve T cells, suggesting that the allogeneic vaccine may operate through the 'cross-priming' phenomenon whereby tumour antigens are processed and presented to T cells by the host's own antigen presenting cells (APC). Thus, we transduced K1735-M2 cells with a GM-CSF expressing retroviral vector and showed anti-tumour activity of the GM-CSF secreting K1735-M2 cells as a therapeutic vaccine against the syngeneic B16-F10 tumour. Our data imply that GM-CSF genetically modified allogeneic whole cell tumour vaccines could be successful in the clinic. In addition, more potent combination gene therapy strategies could be tested using this therapeutic allogeneic vaccine model.

Adoptive transfer of immature dendritic cells with autologous or allogeneic tumor cells generates systemic antitumor immunity

Dendritic cells (DCs) are potent antigen-presenting cells that are capable of priming systemic antitumor immune responses in animal tumor models. However, many of the model tumor systems tested need definition of the specific tumor antigens involved. To use DCs in situations that are more relevant to the majority of human cancers, where the antigens are unknown, we have tested the adoptive transfer of immature DCs in mouse colorectal and melanoma models of varying immunogenicity but with undefined antigens. When DCs admixed with a syngeneic primary tumor inoculum were seeded s.c., the growth of the primary tumor was unchanged; however, if the primary tumor was then surgically excised and the animal was rechallenged with the same tumor, significant protection (75%) was generated when DCs were present in the original primary inoculum of a moderately immunogenic colorectal model (CMT93tk). This effect was not observed when a nonimmunogenic melanoma (B16) was tested in an identical protocol. Next, DCs were injected directly into 6-9-mm established tumors; again, protection (55%) was achieved against a secondary tumor challenge following excision of the primary, but only in the CMT93tk model of moderate immunogenicity. To increase the clinical relevance of this approach still further, we tested irradiated allogeneic K1735 melanoma cells mixed with syngeneic DCs as a vaccine against subsequent challenge with the poorly immunogenic syngeneic melanoma B16. The allogeneic vaccine alone was ineffective, but when admixed with DCs, a significant number of animals rejected a subsequent B16 challenge, suggesting that DCs are able to prime an immune response against melanoma antigens shared between K1735 and B16. The generation of systemic antitumor immunity by adoptive transfer of DCs has significant clinical potential because it is technically straightforward and does not require the definition of specific tumor antigens.

Regulation of transforming growth factor beta1 by nitric oxide

Many tumor cells or their secreted products suppress the function of tumor-infiltrating macrophages. Tumor cells often produce abundant transforming growth factor beta1 (TGF-beta1), which in addition to other immunosuppressive actions suppresses the inducible isoform of NO synthase. TGF-beta1 is secreted in a latent form, which consists of TGF-beta1 noncovalently associated with latency-associated peptide (LAP) and which can be activated efficiently by exposure to reactive oxygen species. Coculture of the human lung adenocarcinoma cell line A549 and ANA-1 macrophages activated with IFN-gamma plus lipopolysaccharide resulted in increased synthesis and activation of latent TGF-beta1 protein by both A549 and ANA-1 cells, whereas unstimulated cultures of either cell type alone expressed only latent TGF-beta1. We investigated whether exposure of tumor cells to NO influences the production, activation, or activity of TGF-beta1.A549 human lung adenocarcinoma cells exposed to the chemical NO donor diethylamine-NONOate showed increased immunoreactivity of cell-associated latent and active TGF-beta1 in a time- and dose-dependent fashion at 24-48 h after treatment. Exposure of latent TGF-beta1 to solution sources of NO neither led to recombinant latent TGF-beta1 activation nor modified recombinant TGF-beta1 activity. A novel mechanism was observed, however: treatment of recombinant LAP with NO resulted in its nitrosylation and interfered with its ability to neutralize active TGF-beta1. These results provide the first evidence that nitrosative stress influences the regulation of TGF-beta1 and raise the possibility that NO production may augment TGF-beta1 activity by modifying a naturally occurring neutralizing peptide.

Immunocytochemical localization of latent transforming growth factor-beta1 activation by stimulated macrophages

Transforming growth factor-beta1 (TGF-beta) is secreted in a latent form consisting of mature TGF-beta noncovalently associated with its amino-terminal propeptide, which is called latency associated peptide (LAP). Biological activity depends upon the release of TGF-beta from the latent complex following extracellular activation, which appears to be the key regulatory mechanism controlling TGF-beta action. We have identified two events associated with latent TGF-beta (LTGF-beta) activation in vivo: increased immunoreactivity of certain antibodies that specifically detect TGF-beta concomitant with decreased immunoreactivity of antibodies to LAP. Macrophages stimulated in vitro with interferon-gamma and lipopolysaccharide reportedly activate LTGF-beta via cell membrane-bound protease activity. We show through dual immunostaining of paraformaldehyde-fixed macrophages that such physiological TGF-beta activation is accompanied by a loss of LAP immunoreactivity with concomitant revelation of TGF-beta epitopes. The induction of TGF-beta immunoreactivity colocalized with immunoreactive betaglycan/RIII in activated macrophages, suggesting that LTGF-beta activation occurs on the cell surface. Confocal microscopy of metabolically active macrophages incubated with antibodies to TGF-beta and betaglycan/RIII prior to fixation supported the localization of activation to the cell surface. The ability to specifically detect and localize LTGF-beta activation provides an important tool for studies of its regulation.

Expression of B7 co-stimulatory molecules by B16 melanoma results in a natural killer cell-dependent local anti-tumour response, but induces T-cell-dependent systemic immunity only against B7-expressing tumours

In an attempt to enhance the anti-tumour immune response, the co-stimulatory molecules B7-1 or B7-2 were expressed on the surface of B16 melanoma cells. B7-expressing tumours grew more slowly in both syngeneic immunocompetent mice and athymic T cell-immunodeficient nude mice. The delay in growth of B7-expressing tumours was dependent on natural killer (NK) cells, as reductions in tumour growth rates were minimized in mice depleted of NK cells. Systemic immunity to B16 melanoma was examined by vaccination with irradiated tumour cells. Inoculation with irradiated B16 B7-1 cells failed to protect against a subsequent challenge with live parental B16 cells, but conferred partial protection against challenge with live B16 B7-1 cells. In contrast to the local anti-tumour reaction, this protective response was dependent on T cells. The results presented here reveal some of the mechanisms involved in the in vivo response to a poorly immunogenic tumour modified to express co-stimulatory molecules.

Can immunotherapy by gene transfer tip the balance against colorectal cancer?

Gene therapy, in particular the transfer of genes encoding immunostimulatory molecules (cytokines and costimulatory molecules) as well as selectively cytotoxic enzymes and DNA vaccination, has the potential of enhancing cell mediated immune responses against tumours including those of colorectal origin. Genes can be transferred using viral vectors either to cultured tumour cells in vitro that can be returned to the patient as a "cancer vaccine", or directly to tumour cells in vivo. Vaccination with DNA constructs expressing specific tumour antigens characteristic of colorectal neoplasia can trigger immune recognition and destruction of tumour cells. The aim is to tip the balance from protumour to antitumour mechanisms by generating a local immune response and systemic antitumour immune memory to destroy metastases. Studies in murine models, combined with human studies, show that such approaches could become an adjunct to current treatments for human colorectal cancer in the near future.

Rapid adenoviral transduction of freshly resected tumour explants with therapeutically useful genes provides a rationale for genetic immunotherapy for colorectal cancer

To develop protocols for the molecular immunotherapy of colorectal cancer, we compared the efficacy of three separate classes of therapeutic genes to induce antitumour responses in a murine colorectal cell model. Thus, the effects of two cytokines (IL-2 and GM-CSF) were compared with those of a costimulatory gene (B7.1) and a suicide gene (HSVtk). The rank order of efficacy against primary tumour growth was HSVtk[GCV], B7.1 > puro, IL-2 > GM-CSF, neo whereas the order of efficacy in inducing antitumour immunity was GM-CSF, IL-2, > B7.1, HSVtk[GCV] > puro, neo in a prophylactic vaccination model. To exploit these data in a clinically relevant and realistic way, we also demonstrated that colorectal tumours can reproducibly be explanted and established in short-term culture. Finally, a rapid transduction protocol has been developed by which, using adenoviral vectors, as many as 90% of the cells in these fresh tumour explants can be engineered to express high levels of the clinically relevant genes (GM-CSF or IL-2) within 1-2 weeks of surgery. Adenovirus-mediated gene delivery was reproducibly and significantly more efficient than retroviral transduction using the MFG-beta-Gal retroviral vector over the time-frame of importance for vaccination. Hence, combination of the animal model data with the ex vivo modification protocol suggests that vaccination of colorectal patients of the appropriate stage will be possible and effective.

A replication-competent retrovirus arising from a split-function packaging cell line was generated by recombination events between the vector, one of the packaging constructs, and endogenous retroviral sequences

Previously we reported the presence of a replication-competent retrovirus in supernatant from a vector-producing line derived from a widely used split-function amphotropic packaging cell line. Rigorous routine screening of all retroviral stocks produced in our laboratory has not, previously or since, indicated the presence of such a virus. Replication-competent retroviruses have never previously been used in our laboratory, and stringent screening of all routinely used cell lines has not revealed the presence of any helper viruses. Therefore, it is highly unlikely that this virus represents an adventitious cross-contaminant or had been imported unknowingly with our cell line stocks. PCR studies with DNA from infected cell lines and Northern blot analysis and reverse transcriptase PCR with RNA from infected cells suggest that the helper virus arose by recombination events, at sites of partial homology, between sequences in the vector, one of the packaging constructs, and endogenous retroviral elements. These recombinations were not present in stocks of the packaging cell line or in an initial stock of the vector-producing line, indicating that these events occurred while the vector-producing line was being passaged for harvest of supernatant stocks.

Tumour cell expression of B7 costimulatory molecules and interleukin-12 or granulocyte-macrophage colony-stimulating factor induces a local antitumour response and may generate systemic protective immunity

Previously, we showed that expression of B7-1 in CMT93 murine colorectal tumour cells inhibited their growth in immunocompetent animals. However, this did not result in any significant increase in systemic protective immunity, relative to that elicited by the parental tumour. To potentiate the effects of B7-1 on systemic immunity. Interleukin-12 (IL-12) or granulocyte-macrophage colony-stimulating factor (GM-CSF) was co-expressed with this molecule. These combinations of immunostimulatory molecules were effective in eliciting systemic immunity. We also show that expression of B7-2 led to a local antitumour response as well as significantly raised systemic immunity. In another tumour model. K1735 minutes melanoma, which is moderately immunogenic, tumours secreting GM-CSF alone were as effective as the parental tumours in generating protective immunity. Previously, we described the deleterious effect of B7-1 expression on protective immunity. Co-expression of GM-CSF did not counteract this consequence of B7-1 expression. Expression of IL-12 was extremely effective in causing rejection of inoculated tumour cells, but evoked only minimal protective systemic immunity. These results suggest that combing costimulatory molecules and cytokines may be a useful therapeutic approach in some, but not all, tumours.

[Measurement of contraction force of pilot's neck muscles]

In order to discuss the function of contraction force of pilot's neck region. Contraction force of pilot's neck region was measured in 22 volunteers aged 18-35 years. The mean contraction force is 102-396 N, the mean contraction time is 28 s. Authors think that training for pilot's neck muscular power is essential.

A family of bicistronic vectors to enhance both local and systemic antitumor effects of HSVtk or cytokine expression in a murine melanoma model

The herpes simplex virus-thymidine kinase/ganciclovir (HSVtk/GCV) system produces both direct and immune-mediated tumor cell killing. Here, we compare the efficacy of HSVtk/GCV with cytokines, alone and in combination, on the tumorigenicity and immunogenicity of B16 cells. With respect to single gene modifications, only HSVtk/GCV, or high-level interleukin-2 (IL-2) secretion, completely prevented tumor growth, whereas granulocyte-macrophage colony-stimulating factor (GM-CSF) generated the best levels of long-term systemic protection. To augment both local killing and immune activation, we constructed bicistronic constructs that express HSVtk and a cytokine within the same cell. Co-expression of HSVtk with IL-2 or GM-CSF enhanced the local antitumor activity of any gene alone. In a tumor-prevention model, HSVtk killing, in an environment preprimed with GM-CSF, generated the best long-term immune protection. However, in a short-term therapy model, continued IL-2 expression was most effective against 3-day established tumors. This probably reflects differences in the activities of IL-2 and GM-CSF in generating short-term, nonspecific immune stimulation compared to long-term immunological memory, respectively. As a prelude to in vivo delivery experiments, we also demonstrated that these bicistronic cassettes can be packaged normally into retroviral (5 x 10(5) virus/ml from pooled populations) and adenoviral vectors (5 x 10(9) virus/ml) and function as predicted within virally infected cells. This family of bicistronic vectors can be used to stimulate synergy between suicide and cytokine genes, overcomes the problems of delivering two genes on separate vectors, and should allow easier preparation of vectors for the delivery of multiple genes to patients' tumor cells.

The uterine myometrium is a target for increased levels of activin A during pregnancy

Activin A is a dimeric protein hormone that regulates numerous cellular functions. A clear physiological role for this molecule in pregnancy is suggested by previous studies in the human, wherein activin A rises dramatically as women approach parturition. To determine whether the rodent is a suitable animal model for further studies of activin action during pregnancy, the serum concentration of activin A was measured in pregnant rats. Activin A was detected in the serum of pregnant rats, beginning on day 12, and the serum concentration rose progressively through gestation (22-fold) and dramatically (140-fold) in labor. The potential target tissues for circulating activin were then identified in two ways. First, iodinated activin was injected into pregnant rats, and the tissues targeted by labeled ligand were identified in vivo. A tissue targeted by activin A in the pregnant rat was the uterine myometrium. To determine the ligand specificity of the uterine myometrial cells, the uteri of pregnant rats were collected and analyzed by in situ ligand binding. 125I-activin A binding was specific for the uterus myometrium, and the ligand binding was competed by unlabeled activin A but not by inhibin A. This result suggests that the receptor in this tissue compartment is an activin-specific receptor. The production of abundant activin A and the ability of exogenous ligand to target the myometrium of the uterus provides a pathway by which activin could regulate uterine function during pregnancy.

Generation of an anti-tumour immune response in a non-immunogenic tumour: HSVtk killing in vivo stimulates a mononuclear cell infiltrate and a Th1-like profile of intratumoural cytokine expression

Direct delivery of the herpes simplex virus thymidine kinase (HSVtk) gene, in combination with the prodrug ganciclovir (GC), has been used for the treatment of localised, inoperable tumours. Several groups have shown that when rodent tumours are ablated in vivo with suicide genes, anti-tumour immunity can also be generated. Hence, this approach may also be useful in treating disseminated disease. Here we have studied the mechanisms associated with this anti-tumour immunity. In B16 HSVtk+ tumours being killed in vivo with GC treatment, we observed the induction of a pronounced intratumoural infiltrate of macrophages, CD4+ and CD8+ T cells. In addition, using reverse transcriptase polymerase chain reaction, expression of interleukin (IL)-2, IL-12, interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) and granulocyte/macrophage colony-stimulating factor (GM-CSF) but not IL-4, IL-6 or IL-10, was observed, a profile of cytokine expression which resembles that of a Th1 immune response. To complement these findings, we also investigated the mechanisms by which expression of HSVtk leads to cell death. Our data show that B16/HSVtk+ cells die predominantly by necrosis, rather than apoptosis, on exposure to GC, a process which may be associated with the generation of anti-tumour inflammatory responses. From these data we propose a model for the induction of anti-tumour immunity using suicide genes and discuss the development of improved vectors for gene therapy to augment these effects in vivo.

Expression of co-stimulatory molecules by tumor cells decreases tumorigenicity but may also reduce systemic antitumor immunity

Many tumor cells do not express co-stimulatory molecules, and this may account, in part, for their poor ability to stimulate T cells directly. One strategy to enhance immune recognition would be to express such molecules on the tumor cell. Here, we show that expression of a member of the B7 family of co-stimulatory molecules by CMT93 murine colorectal tumor or 1735 murine melanoma cells resulted in a local antitumor response in immunocompetent mice. The antitumor effect was diminished in athymic nude mice, indicating that T cells played an important part in this response. The ability of the B7-expressing tumor cells to generate systemic protective immunity was investigated by excision of tumors that developed from the initial inoculation followed by rechallenge with parental tumor cells. CMT93 is a poorly immunogenic tumor and no significant systemic immunity was elicited by the expression of B7-1 in these cells. 1735 melanoma is a mildly immunogenic tumor. Unexpectedly, the systemic immunity obtained with 1735 tumors expressing B7-1 or B7-2 was weaker than that generated by parental 1735 cells (p < 0.001, stratified logrank test), even when coexpression of interferon-gamma in the B7-1 cells produced high levels of surface MHC class I expression. These results suggest that some caution is appropriate when considering the use of these molecules in the gene therapy of cancer.

Immunotherapy III: Combinatorial molecular immunotherapy--a synthesis and suggestions

Animal models have clearly shown that tumor cells may be amenable to molecular manipulation which can result in immune activation and rejection of unmodified cells (Chapters 4 and 5). The challenge now is to design clinical trials which have a realistic chance of success, (although the definition of 'success' is itself an important issue [see Chapter 9]. How should such a strategy be formulated? A review of the previous fifteen years since the first (immune) gene transfer studies were reported, encompasses a great wealth of data. Unfortunately, far from crystallising a set of unifying principles, these diverse reports shroud us in a fog of uncertainty as to how best to proceed. However, if this technology is to have practical, widespread application in the treatment of cancer patients, it is necessary to identify certain critical immunological goals which any protocols should achieve. Clear elucidation of these goals, by unifying the huge amount of disparate experimental data, must eventually be accomplished. In this chapter, we have reviewed the literature covering the era of molecular immunotherapy. We propose four general goals around which widely applicable clinical protocols, not necessarily dependent upon tumour type or experimental bias, might be based and suggest how they may be achieved in the context of gene transfer.

Replication-competent retrovirus produced by a 'split-function' third generation amphotropic packaging cell line

We report the discovery, on routine screening, of a replication-competent retrovirus (RCR) produced from a third generation amphotropic packaging cell line, GP + envAM12. In this line, the gag-pol and env helper genes are located on separate plasmids to minimise the chances of recombination events that may lead to RCR formation. Plasmid pBabeNeo was transfected into GP + envAM12 to obtain a producer line. Supernatant from this line was used to infect two lines, B16 and 1735-puro, and stable colonies which were obtained were pooled. Supernatants from both these lines were able to transfer the neo gene to fresh cells through several passages, indicating the presence of helper virus. Rescue of puro from 1735-puro cells, which contain the pBabePuro provirus, was also achieved. Mobilisation of lacZ from TELCeB6 cells, which contain the MFGnlslacZ provirus, was also possible. The RCR was able to transfer lacZ to ampli-GPE cells, an ecotropic packaging cell line, but transfer to fresh GP + envAM12 cells was minimal, demonstrating receptor interference of the RCR by the amphotropic envelope. These observations strongly suggest that a RCR with an amphotropic envelope arose in the GP + envAM12-pBabeNeo producer line. To our knowledge, this is the first report of RCR arising from routine use of GP + envAM12 cells or any similar third generation packaging line and has important implications for the use of such lines in human gene therapy protocols.

Systemic gene therapy of murine melanoma using tissue specific expression of the HSVtk gene involves an immune component

Previously we have demonstrated safe and effective transfer of the HSVtk cytotoxic gene to primary murine melanoma tumors by direct injection of plasmid and retroviral vectors in which the HSVtk gene is driven by the tissue-specific tyrosinase promoter. However, for general clinical application such forms of therapy should, ideally, be effective against disseminated metastases. We report here that the number of recently established lung metastases of B16 melanoma in C57BL mice treated with ganciclovir is reduced compared to controls after multiple i.v. administrations of high titer retroviral supernatant encoding the HSVtk gene, but not after administration of liposome-complexed plasmid DNA. Using polymerase chain reaction analysis, integration of the provirus was observed in metastasis-bearing lungs (4 of 6 mice) and in the spleens of some ganciclovir-treated animals (2 of 6 mice) but not in the testes, brain, heart, liver, or kidney. The reduction in the number of experimental metastases in C57BL mice exceeded the anticipated extent of transduction of tumor cells, which is indicative of a marked bystander effect. This magnitude of reduction was not observed in immunodeficient athymic mice, suggesting that the immune system plays some part in the bystander effect. In support of these data, we show that, whereas the parental tumor cells are only poorly immunogenic, an effective antitumor immune response is generated following the killing of neoplastic cells in vivo as a result of treatment with ganciclovir. These effects may be responsible for augmenting the efficacy of retroviral infection. The combination of local cell killing by the HSVtk/ganciclovir system and the induction of antitumor immunity suggests new opportunities for the design of vectors for the gene therapy of cancer.

Detection of the Ki-67 antigen in fixed and wax-embedded sections with the monoclonal antibody MIB1

Novel antibodies have been generated by immunizing with bacterially expressed fragments of the repetitive motif of the Ki-67 gene. One such antibody, MIB1, recognizes a fixation and embedding resistant epitope on the Ki-67 protein if sections are previously microwaved in a citrate buffer. We have investigated the utility of this antibody as a marker of cell proliferation in archival material. The microwave technique is simple but requires careful monitoring since different tissues and fixatives require different irradiation times. Strong nuclear immunoreactivity was detected with all fixatives studied. Cytoplasmic staining was not identified. In a wide range of normal tissues the distribution and number of MIB1 immunoreactive cells matched that of cryostat sections stained with Ki-67. In nude mouse xenografts in which the growth fraction had been defined using a fraction of labelled mitosis method, the labelling index with MIB1 matched that previously determined for Ki-67 and correlated well with the growth fraction. Other markers of proliferation (e.g. proliferating cell nuclear antigen) have been shown to be expressed in DNA repair, thus we investigated expression of MIB1 immunoreactivity in situations of DNA repair in vivo--ultraviolet irradiated human skin. MIB1 staining correlated with semi-conservative DNA synthesis rather than excision repair DNA synthesis. Finally, the morphological and cell cycle distribution of MIB1 expression is identical to that of Ki-67. Thus, MIB1 represents a new anti-Ki-67 antibody which appears to be a robust marker of cell proliferation easily applicable to archival material.

Definition of a virulence-related antigen of Neisseria gonorrhoeae with monoclonal antibodies and lectins

Variants of one strain of Neisseria gonorrhoeae, grown in vivo or in vitro, that have been previously shown to differ in infectivity, serum resistance, and capsule production were compared with use of monoclonal antibodies and lectins. Monoclonal antibodies to virulent gonococci recognized an antigenic site of the lipopolysaccharide (LPS) produced in large amounts by gonococci grown in vivo but present only in a small proportion of in vitro-grown gonococci. This antigen (C-LPS) was found in all 85 different gonococcal isolates studied but not among nonpathogenic neisseriae. It was shared by group B and C meningococci but not by groups A and D. Enzyme-linked immunosorbent assay and Western blot analysis showed that N-acetylglucosamine and N-acetylgalactosamine form part of the epitope. The C-LPS antigen was shown by immunofluorescence to be present on the surface of the gonococci and also free as slime. This antigen appears to confer resistance to killing by normal sera.

Paradoxical instruction in the treatment of encopresis and chronic constipation: an experimental analysis

The purpose of the present single-case experimental investigation was to examine the efficacy of paradoxical instruction in the treatment of exacerbation-based discontinuous encopresis and chronic constipation. The subject, a 9-yr old male, complained of infrequent bowel movements and daily soiling. In addition, toileting and related activities appeared to cause considerable anxiety. An ABAB reversal design with 1-yr follow-up was used as a means of evaluating treatment effectiveness. Dependent measures included weekly parental records of soiling and appropriate bowel movements. Results indicated a clear demonstration of functional control and consistent improvement in the encopretic disturbance. These findings were maintained at 1-yr follow-up.

Dihalocarbene insertions into carbon-hydrogen bonds of hydrocarbons and ethers

Fair to moderate yields of insertion products of dichloro- and dibromo- carbenes can be achieved from aqueous reaction mixtures using the phase transfer method. Insertions are very selective; benzylic, tertiary C-H bonds of hydrocarbons and α-C-H bonds of ethers are particularly reactive. The convenience of this method makes it potentially attractive for certain synthetic applications.