Gene-targeted B-deficient mice reveal a critical role for B cells in the CD4 T cell response

The role of B cells in promoting T cell responses is still controversial. In this study, we use JHD mice which have a targeted mutation in the JH gene and are thus rendered deficient in B cells to address this issue. We show here that immunization of JHD mice with soluble antigen fails to prime CD4 T cells, for either clonal expansion or delivery of immunological help for antibody responses. This lack of CD4 T cell priming in JHD mice corresponds to a 3- to 9-fold lower co-stimulatory activity of antigen-presenting cells (APC) from the JHD mice, as measured by anti-CD3-induced proliferative responses of CD4 T cells. This in turn is due to a defect of APC from JHD mice in response to T cell-mediated induction of co-stimulatory activity. As the development of macrophages and dendritic cells is unaffected in the JHD mice, our results demonstrate that B cells play a critical role in CD4 T cell priming, possibly by delivering a critical co-stimulatory activity for clonal expansion of CD4 T cells.

Kinetic analysis of cardiolipin synthase: a membrane enzyme with two glycerophospholipid substrates

Mitochondrial cardiolipin synthase catalyzes the transfer of a phosphatidyl moiety from phosphatidyl-CMP (PtdCMP) to phosphatidylglycerol (PtdGro) in the presence of specific divalent cations. The synthase was solubilized from Saccharomyces cerevisiae mitochondria and purified about 300-fold. The partially enzyme was part of a medium-size, mixed micelle which had to bind to a foreign substrate/detergent micelle before catalysis could occur. The kinetics of cardiolipin synthase were studied by changing the molar fraction of substrate in the micelles. The enzyme obeyed Michaelis-Menten kinetics in relation to PtdCMP with a Km of 0.03 mol%. PtdGro caused sigmoidal kinetics with a low apparent affinity. It is speculated that it was involved in docking the enzyme to the substrate/detergent micelle. Cardiolipin synthase did not catalyze isotope exchange between [14C]CMP and PtdCMP, virtually excluding a ping-pong catalytic mechanism. Mg2+ stimulated the activity by increasing the turnover number rather than the substrate affinity, a mechanism which was also found for the Co(2+)-activation of rat liver cardiolipin synthase. It is concluded that a direct association of the metal ion and the enzyme forms the active cardiolipin synthase which has a very high affinity for PtdCMP and a lower affinity for PtdGro.

The stability of amino acids at submarine hydrothermal vent temperatures

It has been postulated that amino acid stability at hydrothermal vent temperatures is controlled by a metastable thermodynamic equilibrium rather than by kinetics. Experiments reported here demonstrate that the amino acids are irreversibly destroyed by heating at 240 degrees C and that quasi-equilibrium calculations give misleading descriptions of the experimental observations. Equilibrium thermodynamic calculations are not applicable to organic compounds under high-temperature submarine vent conditions.

Small changes in cationic substituents of diphenylfuran derivatives have major effects on the binding affinity and the binding mode with RNA helical duplexes

The interactions of dicationic, 2-4, and tetracationic, 5-7, diphenylfuran analogs of 1 (furamidine) with RNA have been analyzed by thermal melting, spectroscopic, viscometric, kinetic and molecular-modeling techniques. The results of these studies indicate that most of the furan derivatives bind to RNA duplexes by intercalation in contrast to their minor-groove binding mode in AT sequences of DNA, but similar to their binding mode in GC rich regions of DNA. The highest affinity for RNA is found for an imidazoline dication, 2. With some substituents which inhibit formation of a strong intercalation complex, the results suggest a non-intercalative type of binding occurs. The non-intercalative binding probably occurs through a complex with the furan derivative bound in the narrow, deep major groove of A-form RNA helices.

Distribution and activity of calcineurin in rat tissues. Evidence for post-transcriptional regulation of testis-specific calcineurin B

Calcineurin (CN), a Ca2+/calmodulin-regulated phosphatase 2B, plays an important role in many biological processes including T-cell signal transduction. In the present study, the distribution and activity of CN were investigated in rat tissues. CN has a wide tissue distribution, as measured by enzyme-linked immunosorbent assay. CN concentrations are 0.2-0.6 micrograms/mg protein in most tissues, while the brain contains 3-10-fold higher concentrations. Immunohistochemical analyses using a monoclonal antibody to CN B subunit reveals that CN is not evenly distributed but concentrated in specific cells, especially in the brain, kidneys and testis. The specific enzymic activity of CN in tissues is around 10 pmol.min.mg protein-1, except in brain and liver (60 pmol.min-1.mg protein-1 compared to 3.6 pmol.min-1.mg protein-1). The immunosuppressants cyclosporin A and tacrolimus, but not rapamycin, inhibit the phosphatase activity of CN derived from most tissues tested, while CN activity from liver was resistant to cyclosporin A. Furthermore, transcripts and protein of the common CN B subunit and of the testis-specific form of CN B subunit were analyzed. The common CN B subunit transcripts and protein are detected in all tissues. Transcripts for the 'testis-specific' CN B subunit are also found in brain, lung, thymus and heart, while the protein is only detected in testis. This indicates that the testis-specific CN B subunit gene expression is regulated at both transcriptional and posttranscriptional levels. The findings demonstrate that CN is a widely distributed protein phosphatase and that its activity is regulated in a tissue-specific manner.

Self-pumped phase conjugation of diffusely reflected light in a KNSBN crystal

We report self-pumped phase conjugation in a Cu:KNSBN crystal for light diffusely reflected from a rough surface. We have demonstrated wave-front distortion compensation for diffuse reflection. We have experimentally studied the dependence of the phase-conjugation reflectivity on the f-number of a lens imaging the spot upon the diffuser into the crystal and on the size of the beam incident upon the diffuser surface. Finally, with a Michelson interferometer we observed the phase fluctuation of the phase-compensated wave front.

The effects of isoflurane and halothane on blood flow and 31P NMR spectra in murine RIF-1 tumors

The principal aim of these studies was to evaluate the utility of isoflurane and halothane for NMR investigations of tumor physiology. In vivo 31P and 2H NMR were used to examine RIF-1 tumors before, during, and (for 31P) after anesthesia. In tumors, halothane decreases blood flow, [PCR]:[NTP], and pH indicated by the Pi chemical shift (pHnmr), while it increases [Pi]:[NTP]; effects consistent with well-established cardiovascular effects of halothane. Isoflurane does not affect tumor blood flow or [PCr]:[NTP], but increases tumor [Pi]:[NTP] and decreases tumor pHnmr. In vivo 31P NMR measurements of normal mouse liver (upper abdomen) indicate that isoflurane has a similar effect in the liver. Although the mechanism for these effects is unknown, observation of a split Pi peak during isoflurane anesthesia suggests that a pool of Pi in a lower pH environment may become evident under isoflurane anesthesia. Regardless of the cause for increased [Pi]:[NTP] and decreased pHnmr, the utility of isoflurane anesthesia for 31P NMR studies of energy metabolism is limited.

T lymphocyte infiltration in the brain following anterior chamber inoculation of HSV-1

Following inoculation of the KOS strain of herpes simplex virus type 1 (HSV-1) into one anterior chamber of euthymic BALB/c mice, virus spreads from the injected eye to the central nervous system and from the central nervous system to the optic nerve and retina of only the uninoculated eye. In contrast, in athymic BALB/c mice or mice depleted of both CD4+ and CD8+ T cells, virus spreads to the optic nerve and retina of both the injected eye and the uninjected eye. To determine the location in the central nervous system where spread of virus to the optic nerve and retina of the injected eye is prevented, euthymic BALB/c mice were injected with a mixture of KOS and RH116, a mutant of KOS that contains the Escherichia coli beta-galactosidase (beta-gal) gene. Several animals were sacrificed each day; serial frozen sections of the brain were prepared and sequential sections were stained for beta-gal or for T cells. At all sites except the suprachiasmatic nuclei, virus and T cells arrived at approximately the same time. However, at day 5 post inoculation (PI), T cells were present in both the ipsilateral and the contralateral suprachiasmatic nuclei, but only the ipsilateral suprachiasmatic nucleus was virus-positive. Since virus spreads from the ipsilateral suprachiasmatic nucleus to the contralateral optic nerve, these results suggest that T cells infiltrating the area of the contralateral suprachiasmatic nucleus prior to the arrival of virus at this site prevent virus spread into the optic nerve of the inoculated eye.

Mutational analysis and an alternatively spliced product of B7 defines its CD28/CTLA4-binding site on immunoglobulin C-like domain

Costimulatory molecules B7 and B7-2 interact with T cell surface receptors CD28/CTLA4 and deliver a costimulatory signal essential for T cell growth. However, the structure basis of this interaction is not known. B7 and B7-2 are members of immunoglobulin (Ig) superfamily and their extracellular portion consists of an IgV- and IgC-like domain. Here we report that a naturally occurring, alternatively spliced form of B7 reveals that exon 3-encoded IgC domain is essential for CD28/CTLA4 binding. Mutational analysis of B7 demonstrates a critical role of several amino acids around loops between strands B and C and D and E, for binding CTLA4/CD28. These amino acids are clustered to form a single binding site centered at 201Y. A comparison of the effects of mutations on the binding of CD28 and CTLA4 reveals that CD28 and CTLA4 binds to the same site on B7. These results have important implications on the role of CTLA4 and CD28 in T cell costimulation. The structure of the CD28/CTLA4-binding site also provides valuable information for immune intervention targeted at the B7/B7-2-CD28/CTLA4 interactions.

[Isolation, purification and characterization of human proteinase inhibitor, alpha 2-macroglobulin]

A study of the isolation, purification and characterization of human proteinase inhibitor, alpha 2-macroglobulin (alpha 2-M) is presented. The alpha 2-M, with a purity of more than 90% and subunit molecular weight of 185kDa, was isolated by ammonium sulfate fractionated precipitation from human blood plasma and purified by DEAE cellulose DE52 column chromatography. It was found to be the same as the standard counterpart provided by sigma company. This purification procedure of alpha 2-M can be done with low cost, high efficiency and in large scale preparation.

[Modifications of gene expression by tumor promoters]

The modifications of gene expression by tumor promoters were analyzed in vitro and in vivo. The results of slot blot hybridizations showed that tumor promoter TPA induced c-fos and c-myc expressions in mouse fibroblast cell line BALB/3T3 and rat liver, decreased the levels of Rb RNA in BALB/3T3 cell line and of alpha 1-I3 RNA in rat liver. It was also demonstrated that tumor promoter phenobarbital influenced c-fos and c-myc expressions and decreased alpha 1I3 mRNA level in rat liver during a long term experiment. Phenobarbital was found to have no effect on c-fos and c-myc expressions in rat liver during a short experiment. Tumor promoters induced the expressions of c-fos and c-myc which were positively-related to cancer formation and inhibited the expressions of Rb and alpha 1-I3 which were negatively-related to cancer formation. This implied that tumor promotion played an important role in cancer development and tumor promoters exerted their effects selectively according to the attributes of different genes.

A study on immigrant labor in some enterprises in Shanghai

"This article conducts analyses of the demographic characteristics, working conditions, and welfare of the immigrant laborers currently employed in some of the enterprises in Shanghai [China], based on survey data collected on the immigrant population at the end of 1993 and a sample survey in five enterprises in Shanghai. The article also makes suggestions for the future management and utilization of immigrant labor in Shanghai."

Hodgkin disease: Hodgkin and Reed-Sternberg cells picked from histological sections show clonal immunoglobulin gene rearrangements and appear to be derived from B cells at various stages of development

Hodgkin disease (HD) is characterized by a small number of putative malignant cells [Hodgkin and Reed-Sternberg (HRS) cells] among a background of lymphocytes and histiocytes. The lineage of HRS cells is still elusive and a clonal origin of these rare cells has not formally been demonstrated. We isolated HRS cells by micromanipulation from histological sections of three cases of Hodgkin lymphoma (each representing a distinct subtype of the disease) and analyzed individual cells for immunoglobulin variable (V) gene rearrangements by PCR. In each of the three cases a single heavy-chain V (VH) (and in one case, in addition, a kappa light-chain) gene rearrangement was amplified from the HRS cells, identifying these cells as members of a single clone. A potentially functional VH rearrangement was obtained from a case of nodular sclerosis HD. Somatic mutations and intraclonal diversity in the VH genes indicate a germinal center B-cell origin of the HRS cells in a case of lymphocyte-predominant HD, whereas in a case of mixed-cellularity HD the sequence analysis revealed only nonfunctional V gene rearrangements, suggesting a pre-B-cell origin. This indicates that HRS cells can originate from B-lineage cells at various stages of development.

Synthetic laminin-like peptides and pseudopeptides as potential antimetastatic agents

This paper describes our efforts to study structure-activity relationships, improve the antimetastatic potency, and limit the in vivo enzymatic degradation of YIGSR-NH2, a synthetic peptide from the B1 chain of laminin, which reportedly has potential as an antimetastatic agent. To this end we have synthesized a series of psi (CH2NH) peptide analogs (5-9) of YIGSR-NH2 and a number of peptides in which the Tyr residue was replaced with D-Tyr (1), Phe (2), Phe (p-F) (3), and Phe(p-NH2) (4). All new peptides were assayed in vitro for their ability to promote cell attachment in both B16F10 mouse melanoma cells and HT-1080 human fibrosarcoma cells. On the basis of the in vitro assay results, peptides 3-5, 8, and 9 were tested in vivo for their ability to inhibit tumor metastasis to the lungs in mice that were coinjected in the tail vein with B16F10 melanoma cells and 1 mg of peptide. In summary, of the nine new peptides only the Phe(p-NH2) peptide 4 showed consistent in vitro cell attachment activity, but only low in vivo antimetastatic activity.

Immunohistochemical detection of bcl-2 protein in liver lesions: bcl-2 protein is expressed in hepatocellular carcinomas but not in liver cell dysplasia

A proto-oncogene, bcl-2, encodes a protein that inhibits programmed cell death (apoptosis) and may play a role in cell and tissue differentiation. As bcl-2 appears to be involved in the turn-over of stem or precursor cells, it is thought to be operational in carcinogenesis pathways. However, apart from certain lymphomas, only limited data are available on the frequency of its expression in solid tumors. Immunohistochemical analysis with an antibody specific for bcl-2 protein was used to detect the protein in hepatocellular carcinomas and in one of the putative precursor lesions, liver cell dysplasia. We detected bcl-2 protein in 5 of 37 hepatocellular carcinomas. Immunoreactivity was not related to type, grade, or extent of PCNA staining of the tumours. No bcl-2 protein staining was observed in three types of liver cell dysplasia. Thus, bcl-2 is abnormally expressed in some hepatocellular carcinomas but not in potential tumour precursor cells.

[Congenital lower lip sinuses]

Congenital lower sinuses are rare and are found often in association with cleft lip and/or palate, named Van der Woude syndrome. Although the condition per se does not always require surgical attention, its genetic character is interesting. Four cases of congenital sinuses are described and recent literature is reviewed.

An unusual pattern of lymph node involvement in mycosis fungoides simulating neoplastic follicles

We describe an unusual pattern of lymph node involvement in a case of mycosis fungoides. The neoplastic proliferation formed pale nodules composed of small, irregular lymphoid cells, features that, on routine paraffin sections, suggested neoplastic follicles and a B-cell phenotype. The correct diagnosis was established by immunohistochemical studies that demonstrated a T-cell phenotype. Polymerase chain reaction for rearrangement of the T-cell receptor gamma gene confirmed that the proliferation was monoclonal. This case demonstrates that both architectural pattern and cytologic features may be unreliable in predicting immunologic phenotype. Immunologic marker studies and careful attention to the clinical history are vital to classify lymphoproliferative disorders correctly.

Immunohistochemical analysis of p53 protein overexpression in liver cell dysplasia and in hepatocellular carcinoma

We analysed p53 protein immunoreactivity in hepatocellular carcinomas (HCCs) and in liver cell dysplasia (LCD) of patients from an area in Northern China, using five anti-p53 protein antibodies recognizing different epitopes of the protein. In HCCs, the overall prevalence of p53 protein immunoreactivity was 78.3%. However, prevalence was strongly influenced by the type of antibody used, ranging from 67.5% for antibody PAb-1801 to only 10.8% for antibodies PAb-421 and DO-7. p53 protein immunoreactivity was not related to type or grade of HCC. In contrast to former reports, p53 protein staining was restricted to nuclei only when using the CM-1 antibody, whereas two other antibodies yielded both, nuclear and cytoplasmic or membrane staining, and no nuclear staining was observed with antibodies PAb-421 and DO-7, the latter two, however, demonstrating cytoplasmic and membrane staining. For LCD, three subtypes were morphologically and karyometrically defined. Nuclei of some LCD cells were p53 immunoreactive, but positivity was restricted to the small cell variant of LCD. Positivity was different for cirrhosis with or without associated HCC, amounting to 18.9% in the former and 39.4% in the latter. Interestingly, p53 protein immunoreactivity also occurred in a set of small hepatocytes not showing the typical feature of LCD and therefore classified as simple regenerating liver cells.

Design and synthesis of RNA-specific groove-binding cations: implications for antiviral drug design

As as initial step in the design of structure-specific RNA-interactive molecules as potential antiviral agents, we have focused on the synthesis of molecules that exhibit strong and preferential binding to duplex RNA. A series of polycationic ligands have been synthesized, and the degree of preferential binding to RNA has initially been determined by thermal denaturation (delta Tm) with both RNA [poly(A).poly(U)] and DNA [poly(dA).poly(dT)] polymers at a variety of pH values. Seven compounds from the series exhibit a substantial degree of RNA-selective binding. The relatively high delta Tm values obtained suggest a specific mode of interaction between these ligands and the RNA helix. By contrast, the much lower delta Tm values with poly(dA).poly(dT) DNA reflect a more nonspecific interaction mode. A viscometric titration study with poly(A).poly(U) confirms that they do not bind by intercalation. The results, combined with the known structure and electronegative potential of duplex RNA, suggest that these molecules bind in the major groove via specific electrostatic and/or hydrogen-bonded interactions.

[The alteration of histidase catalytic activity and the expression of the enzyme protein in rat primary hepatomas]

The catalytic activity of histidase and the expression of the enzyme protein were investigated in rat hepatomas induced by diethylnitrosamine. The results indicated that the activities of histidase in the hepatomas were significantly diminished as compared with normal rat livers (P < 0.01). Western blot analysis revealed that enzyme protein levels in hepatomas were markedly reduced. It is thus inferred that some factors which control expression of histidase protein may be altered during carcinogenesis. These findings lay a foundation for studying the relationship between the regulation and expression of the histidase gene and hepato carcinogenesis.

Large-scale purification of human aspartylglucosaminidase: utilization of exceptional sodium dodecyl sulfate resistance

Deficiency of human aspartylglucosaminidase (AGA, glycosylasparaginase, EC 3.5.1.26), a lysosomal amidase, results in the lysosomal storage disease aspartylglucosaminuria (AGU). This disorder is most prevalent in the genetically isolated Finnish population. To facilitate the detailed analysis of this important enzyme, which functions in the final degradation step of glycoproteins, we developed a novel purification method which makes possible a simple five-step 5000-fold purification to apparent homogeneity of human aspartylglucosaminidase from leukocytes. This purification procedure takes advantage of the remarkable SDS resistance of aspartylglucosaminidase as SDS-sensitive proteins aggregate preferentially at low (NH4)2SO4 concentrations in the presence of SDS. This new method should be applicable to the isolation of other SDS-resistant enzymes, e.g., superoxide dismutase. The homogeneous enzyme preparation exhibited a previously unreported fully denatured 19-kDa form of the alpha-subunit of aspartylglucosaminidase on SDS-polyacrylamide gel electrophoresis as a consequence of complete coating by SDS.

Effects of oxygen free radicals and scavengers on the cardiac extracellular collagen matrix during ischemia-reperfusion

OBJECTIVE

Collagen is lysed early during ischemia-reperfusion, but whether this is due to ischemia or reperfusion injury is not known. The effect of oxygen free radicals and free radical scavengers on left ventricular hemodynamics, myocardial morphology and collagen content were studied in an isolated, Langendorff-perfused rat heart model of regional ischemia-reperfusion.

METHODS

All hearts received left anterior descending coronary artery ischemia for 20 mins. Group 1 had ischemia only; group 2 had ischemia followed by reperfusion with oxygenated Krebs-Henseleit buffer for 20 mins; group 3 had oxygen free radicals generated by hypoxanthine and xanthine oxidase during reperfusion; group 4 had free radical scavengers with superoxide dismutase plus catalase; group 5 had both oxygen free radicals and free radical scavengers during reperfusion.

RESULTS

Left ventricular developed pressure decreased significantly in group 3 during ischemia followed by reperfusion (58 +/- 3.1 mmHg versus 42 +/- 2.4 mmHg, P = 0.004), but did not change significantly in any of the other groups. Necrosis score on pathology was highest in group 3; this score also was higher than that in group 5 with free radical scavengers added (3.0 +/- 0.3 versus 2.0 +/- 0.4, P = 0.07) and higher than that of group 2 with reperfusion with buffer only (3.0 +/- 0.3 versus 1.4 +/- 0.5, P < 0.05). Collagen content decreased significantly compared with control in group 3 only with ischemia followed by reperfusion with the addition of oxygen free radicals (18.4 +/- 1.5 versus 11.9 +/- 1.7 g/mg protein, P < 0.05). The addition of free radical scavengers in group 5 mainly attenuated the collagen loss. Scanning electron microscopy revealed profound structural changes of the extracellular collagen matrix in numerous regions of 'stunning' independent of tissue necrosis.

CONCLUSIONS

We conclude that: first, oxygen free radicals trigger significant collagen damage and left ventricular dysfunction during reperfusion; second, these changes extend beyond the ischemic damage alone; and third, free radical scavengers can effectively limit oxygen free radical-induced collagen loss and left ventricular dysfunction.

Synthesis of dicationic diaryltriazines nucleic acid binding agents

- The synthesis of 2,4-bis[4-(4,5-dihydro-1H-imidazol-2-yl)phenyl]-1,3,5-triazine 6a and 2,4-bis[4-(1,4,5,6-tetrahydropyrimidin-2-yl)phenyl]-1,3,5-triazine 6b in 3 steps from either 4-bromobenzamidine or 4-(carbamoyl)benzamidine is reported. The synthesis of 4,6-bis[4-(4,5-dihydro-1H-imidazol-2-yl)phenyl]-2-dimethylamino-1,3,5-triazine 9a and 4,6-bis[4-(1,4,5,6-tetrahydropyrimidin-2-yl)phenyl]-2-dimethylamino-1,3,5-triazine 9b in 2 steps from 1,4-dicyanobenzene is also described. The compounds 6b and 9b bind strongly to DNA model sequences and inhibit topoisomerase II from 2 microbial sources. Compounds 6a and 9a bind to both DNA and RNA model sequences whereas 6b and 9b essentially do not bind to the RNA model.

Three types of liver cell dysplasia (LCD) in small cirrhotic nodules are distinguishable by karyometry and PCNA labelling, and their features resemble distinct grades of hepatocellular carcinoma

We have studied the occurrence and specific features of liver cell dysplasia (LCD) in Chinese patients showing liver cirrhosis with or without hepatocellular carcinoma (HCC). Three types of LCD (SLCD, LLCDo, LLCDe) were morphologically defined, and these types were further analyzed using karyometry, estimation of nucleic acid content and density, and PCNA immunostaining. Features found for three types of LCD were compared with those of normal hepatocytes (NLC), simple regenerating hepatocytes (SRLC), and cells of HCCs covering different grades. The results show that 1) karyometry and nucleic acid parameters allow an objective separation of LCD types both from NLC and SRLC; 2) karyometric features of LLCDe are most close to those of highly differentiated HCCs, whereas nuclear size and chromatin composition of SLCD closely reflect those of poorly differentiated HCCs; 3) the frequency of LCD clusters was higher in cirrhotic livers carrying HCC, being about double for all three LCD types; 4) the highest PCNA labelling occurred in the small cell group of LCD (SLCD), still, however, being smaller than that of simple regenerating hepatocytes. Based on these findings it is suggested that, similar to atypical adenomatous hyperplasia, LCDs of distinct morphotypes may represent precursor lesions for HCC, and some cellular forms may mimick cell types known to occur in experimental carcinogenesis.

The interaction of substituted 2-phenylquinoline intercalators with poly(A).poly(U): classical and threading intercalation modes with RNA

The interaction of a series of 2-phenylquinoline derivatives with RNA was investigated by means of viscometric, pKa, spectroscopic, binding, Tm, and kinetic methods. Compounds 1, 2, and 3 have a piperazyl substituent at the para, meta, or ortho position, respectively, while 4 has an unsubstituted phenyl ring. The pKa results suggest that 1 has three charges, 2 and 3 have more than two charges, and 4 has two charges at pH 6.2. Spectroscopic and Tm results indicate that 1 binds more strongly to RNA than 2-4. Kinetic and modeling results indicate that 1 is a threading intercalator while 2 and 4 are classical intercalators. All experimental results indicate that 3, which has a large twist between the phenyl and quinoline rings, binds weakly with RNA.

Tracing B cell development in human germinal centres by molecular analysis of single cells picked from histological sections

Germinal centres are areas of intense B lymphocyte proliferation inside primary B cell follicles in spleen and lymph nodes. Rearranged V genes from single human B cells, isolated from histological sections of two such structures by micromanipulation, were amplified and sequenced. Cells from the follicular mantle were clonally diverse and largely expressed germline V genes. Germinal centres were dominated by a few large B cell clones dispersed throughout these structures and exhibiting intraclonal diversity by ongoing somatic hypermutation. Pronounced counterselection of replacement mutations seen in one of the germinal centres may indicate a late phase of the germinal centre reaction. A polyclonal population of activated B cells expressing unmutated antibodies in the dark zone of the other germinal centre may represent the initial founder cells.

Modulated excitation of singly ligated carboxyhemoglobin

We have extended the method of modulated excitation, a small perturbation kinetic method, to study ligand binding and conformational change of hemoglobin tetramers with a single ligand bound. To restrict the excitation to the first ligand, only 1% of the hemes have bound CO, and the remainder are kept unliganded. A detailed theory is presented which agrees well with the experimental observations. This method of observing ligand recombination also provides a novel and simple method for determination of hemoglobin concentration. Additional relaxation processes are also observed. By fitting independently determined spectra to the spectra associated with the relaxations, these processes are assigned as thermal excitation and thermally driven protonation/deprotonation reactions. These added relaxations arise from the deoxy-Hb portion of the samples, and demonstrate that modulated excitation can be used effectively for temperature perturbation in the absence of photodissociation. The spectra observed are not well described by the spectra of allosteric change, however, and we conclude that there is no significant mixing of quaternary states at the first ligation step. In an appendix we present a derivation of the particular features seen in thermally modulated protonation reactions.

Differential downregulation of beta 2-adrenergic receptors in tissue compartments of rat heart is not altered by sympathetic denervation

With agonist stimulation, cardiac beta 2-adrenergic receptors (beta 2ARs) are downregulated to a much greater extent than are beta 1ARs. It has been hypothesized that this effect is due to sympathetic innervation inhibiting the downregulation of beta 1ARs. To test this hypothesis, the technique of coverslip autoradiography was used to localize and quantify beta 1AR and beta 2AR subtypes in tissue compartments of the heart in rats subjected to sympathetic denervation by two intravenous injections of 6-hydroxydopamine (50 mg/kg per dose). After denervation, the rats were infused with L-isoproterenol (400 micrograms.kg-1 x h-1 for 7 days) or vehicle (0.001N HCI) by implantation of osmotic minipumps. Sections were incubated with 70 pmol/L of the beta AR antagonist [125I]iodocyanopindolol (ICYP) alone or in the presence of 5 mumol/L DL-propranolol or 5 x 10(-7) mol/L CGP 20712A (a beta 1AR antagonist). Binding of ICYP to sections of rat hearts was saturable and stereoselective and was displaced by beta AR agonists with the rank order of potency expected for beta ARs. There was an 89% reduction in catecholamine concentration in rat ventricles after 1 week of 6-hydroxydopamine treatment, before implantation of the minipumps. Chronic infusion of isoproterenol induced significant downregulation (63% to 74%) of beta 2ARs in atrial and ventricular myocytes, coronary arterioles, and connective tissue but no change in beta 1ARs in these regions in rats with intact sympathetic innervation. Similar changes were seen in denervated animals. There was a marked reduction in beta 2ARs but small insignificant decreases in beta 1ARs, despite the fact that in the denervated animals there was upregulation of beta 1ARs in atrial and ventricular myocytes (approximately 25%). Our study suggests that beta 1ARs in the heart are not significantly downregulated by chronic agonist exposure and that this is unrelated to sympathetic innervation. The underlying mechanism of preferential regulation of beta AR subtypes remains to be elucidated but may be related to differences in the molecular structure between beta 1ARs and beta 2ARs.

"Neuroendocrine" differentiation in hepatocellular carcinomas (HCCs): immunohistochemical reactivity is related to distinct tumor cell types, but not to tumor grade

We have analyzed neuroendocrine differentiation (ND) in hepatocellular carcinomas (HCCs) of fifty patients. It turned out that ND is frequent in HCCs, and that it is not restricted to fibrolamellar hepatocellular carcinoma (FL-HCC). Multiexpression is seen in a quarter of the cases, and marker coexpression may occur within the same tumor cell. ND predominates in trabecular and mixed HCCs, but does not appear to be related to grade. Most positive cases showed a hepatocyte-like cell morphology, frequently associated with bile formation. It thus appears that the HCC cell type most likely to show ND is a hepatocyte-like one, i.e. differentiated cell, frequently polarized and producing bile, rather than a small and poorly-differentiated cell. Possible pathogenic mechanisms leading to ND in HCCs are briefly discussed.

Two-dimensional scanning laser slope gauge: measurements of ocean-ripple structures

A compact, two-dimensional scanning laser slope gauge has been developed for measuring ocean ripples, leading to the determination of their directional slope spectrum in the wavelength range of 4.5-81 mm. A telecentric scanning mechanism is used to enhance the dynamic range of slope measurements and to eliminate constraints caused by water-surface undulations associated with long waves. Successful laboratory tests and field trials have been performed; sample results are provided.

Detection of clonal B cell populations in paraffin-embedded tissues by polymerase chain reaction

A method was established to detect clonal B cell populations in frozen and paraffin-embedded tissues. The method is based on the polymerase chain reaction amplification of rearranged VH and V kappa genes using V gene family-specific primers. Monoclonal B cell populations could be detected in peripheral blood lymphocyte DNA in all 16 cases of B-CLL and immunocytoma investigated and in 8 of 10 cases of B cell non-Hodgkin's lymphoma using frozen and paraffin sections. The amplification of V kappa rearrangements in addition to the VH amplification is a useful tool to verify the results of the heavy chain rearrangement and to detect proliferation of a B cell clone in cases in which no VH product was obtained. In spite of the degradation of DNA in paraffin-embedded tissues, we were able to find amplified polymerase chain reaction products of about 350 bp length in 8 of 10 cases analyzed. The method presented here may be helpful in routine diagnosis of B cell non-Hodgkin's lymphoma using frozen or paraffin-embedded specimens.

Post-ischaemic cardiac dilatation and remodelling: reperfusion injury of the interstitium

Cardiac size and geometry have an important influence on clinical prognosis in heart disease. The cardiac interstitium would appear to play a major role in modulating muscle configuration after ischaemic insults. Ischaemic reperfusion injury of the heart should not be viewed as confined to the myocyte compartment. There are major events occurring in the interstitial compartment which could ultimately determine the long-term configuration and topography of the heart. Thus, permanent plastic changes in cardiac dimensions appear to evolve after initial alterations in the collagen matrix. The physiological, cellular, biochemical, and molecular considerations in the cardiac interstitium are quite different from those of the myocyte compartment. Accordingly, therapeutic interventions to modulate cardiac geometry and remodelling may differ.

Evaluation of a nutrition education activity for medical students in China

In China, where cancers and cardiovascular disease are the major causes of morbidity and mortality, an important role for preventive medicine has emerged. Therefore, preparing China's medical students to tackle contemporary health problems requires attention to nutrition and health promotion in the medical curriculum. To evaluate the effectiveness of a nutrition education activity for medical students, a two-group pre-test/post-test nutrition education program was conducted in a medical university in south-western China (n=300 per group). Students in another south-western Chinese medical university served as controls (n= 150 per group). Special features of the intervention were: (1) nutrition education materials developed from (a) the results of a pre-test survey of medical students and (b) discussions with medical students, faculty, and physicians; and (2) a multi-channel delivery, which included a classroom lecture-discussion; a nutrition knowledge competition; a handout providing a day's dietary allotment; campus radio and movie theatre announcements, and posters. Analysis of variance, chi-square, and t-tests showed a significant increase (P<0.05) in nutrition knowledge, but not in nutrition attitude score. The final nutrition knowledge and attitude scores were also found to be related to the students' increased exposure to the various channels (P<0.001). Also observed was an increase in the consumption of soybean and dairy products (P<0.05). It is concluded that the method is a useful and practical model for designing and developing student nutrition education activities in China, as well as demonstrating nutrition and health education methods among the medical university community.

[Effects of epidermal growth factor on growth and differentiation of rat granulosa cells]

It was known that epidermal growth factor (EGF) plays an important role in the regulation of reproduction. The present study was undertaken to investigate the effect of EGF on the proliferation and differentiation of cultured rat granulosa cells. The results showed that EGF inhibited the 3H-TdR incorporation into DNA of granulosa cells, while the progesterone production was increased due to enhanced 3 beta-HSD activity. Radioreceptor assay (RRA) suggested that there were specific receptors for EGF on the granulosa cell with a Kd of 1.83 +/- 0.30 x 10(-8) mol/L and a Bmax of 1.75 +/- 0.29 x 10(4) sites/cell. Using method of immunohistochemistry, no EGF-like immunoreactivity was found in the granulosa cells at different age or different estrous cycle, but in the theca folliculi, interstitium and corpus luteum. These results suggest that EGF can regulate the growth and differentiation of the granulosa cells in the course of maturation of the folliculi and granulosa cells.

Allosteric kinetics and equilibria of triligated, cross-linked hemoglobin

Using modulated excitation, we have measured the forward and reverse rates of the allosteric transition between relaxed (R) and tense (T) quaternary structures for triply ligated hemoglobin (Hb), cross-linked between the alpha chains at Lys 99. Oxygen, carbon monoxide, and water were used as ligands and were studied in phosphate and low Cl- bis-Tris buffers at neutral pH. Since the cross-link prohibits disproportionation, triply ligated aquomet Hb species with ferrous beta chains were specifically isolated by isoelectric focusing. Modulated excitation provides rate pairs and therefore gives equilibrium constants between quaternary structures. To coordinate with that information, oxygen binding curves of fully ferrous and tri-aquomet Hb were also measured. L3, the equilibrium constant between three liganded R and T structures, is determined by modulated excitation to be of order unity for O2 or CO (1.1 to 1.5 for 3O2 and 0.7 for 3CO bound), while with three aquomet subunits it is much greater (> or = 23). R-->T conversion rates are similar to those found for HbA, with weak sensitivity to changes in L3. The L3 values from HbXL O2 were used to obtain a unique allosteric decomposition of the ferrous O2 binding curve in terms of KT, KR, and L3. From these values and the O2 binding curve of tri-aquomet HbXL, L3 was calculated to be 2.7 for the tri-aquomet derivative. Consistency in L3 values between equilibrium and modulated excitation data for tri-aquomet-HbXL can be achieved if the equilibrium constant for O2 binding to the alpha chains is six times lower than that for binding to the beta chains in the R state, while the cooperative properties remain homogeneous. The results are in quantitative agreement with other studies, and suggest that the principal effect of the cross-link is to decrease the R state and T state affinity of the alpha subunits with almost no change in the affinity of the beta subunits, leaving the allosteric parameters L and c unchanged.

The search for structure-specific nucleic acid-interactive drugs: effects of compound structure on RNA versus DNA interaction strength

The RNA genomes of a number of pathogenic RNA viruses, such as HIV-1, have extensive folded conformations with imperfect A-form duplexes that are essential for virus function and could serve as targets for structure-specific antiviral drugs. As an initial step in the discovery of such drugs, the interactions with RNA of a wide variety of compounds, which are known to bind to DNA in the minor groove, by classical or by threading intercalation, have been evaluated by thermal melting and viscometric analyses. The corresponding sequence RNA and DNA polymers, poly(A).poly(U) and poly(dA).poly(dT), were used as test systems for analysis of RNA binding strength and selectivity. Compounds that bind exclusively in the minor groove in AT sequences of DNA (e.g., netropsin, distamycin, and a zinc porphyrin derivative) do not have significant interactions with RNA. Compounds that bind in the minor grove in AT sequences of DNA but have other favorable interactions in GC sequences of DNA (e.q., Hoechst 33258, DAPI, and other aromatic diamidines) can have very strong RNA interactions. A group of classical intercalators and a group of intercalators with unfused aromatic ring systems contain compounds that intercalate and have strong interactions with RNA. At this time, no clear pattern of molecular structure that favors RNA over DNA interactions for intercalators has emerged. Compounds that bind to DNA by threading intercalation generally bind to RNA by the same mode, but none of the threading intercalators tested to date have shown selective interactions with RNA.

Graphic analysis of relaxation times of enzyme-catalysed reactions. An extension of the graphic method of King and Altman

An extension of the graphic method of King & Altman (1956) (J. Phys. Chem. 60, 1375-1378) is applied to the analysis of relaxation times of enzyme-catalysed reactions and a simple graphic method is presented. Clear-cut graphs, simple drawing, easy operation (without the need to perform the usual complex mathematical operations), and reliable results are the main characteristics of this kind of graphic method. A system of enzyme-catalysed reactions (E <--> ES <--> EP) is used as the actual example for illustrating the graphic method.

Modulation of cytosolic-[Ca2+] oscillations in hepatocytes results from cross-talk among second messengers. The synergism between the alpha 1-adrenergic response, glucagon and cyclic AMP, and their antagonism by insulin and diacylglycerol manifest themselves in the control of the cytosolic-[Ca2+] oscillations

Hepatocytes respond to stimulation by glycogenolytic agonists acting via phosphoinositide (PI) breakdown through oscillations of the free cytosolic concentration of Ca2+ ([Ca2+]cyt.). Since the second-messenger repertoire of hepatocytes includes many other factors besides Ca2+, we investigated to what degree the regulation of [Ca2+]cyt. oscillations is integrated into these other signalling systems. [Ca2+]cyt. was recorded in single rat hepatocytes by using the Ca(2+)-indicator fura-2. Parallel stimulation with phenylephrine (an alpha 1-adrenergic agonist of PI breakdown) and glucagon resulted in a synergistic stimulation of [Ca2+]cyt. oscillations. Direct activation of the cyclic-AMP-dependent pathway with several stimuli (forskolin, 8-bromo cyclic AMP, 8-CPT cyclic AMP) mimicked the response to glucagon. In contrast, [Ca2+]cyt. oscillations induced by various combinations of these agonists could be antagonized by the glycogenic hormone insulin. As one of the options in the insulin-signalling network, we tested a diacylglycerol activator of protein kinase C, DiC8. It also acted as an inhibitor of [Ca2+]cyt. oscillations. We investigated how these observations could be reconciled with our previously introduced model of [Ca2+]cyt. oscillations in hepatocytes [Somogyi and Stucki (1991) J. Biol. Chem. 266, 11068-11077]. First of all, the effect of calmodulin inhibitors (calmidazolium and CGS 9343 B), acting at the core of our model on the feedback of Ca2+ on Ins(1,4,5)P3-induced Ca2+ release, was not altered by the new modulators. In addition, all agonists and antagonists could be used interchangeably in combination and introduced no significant change in the oscillatory pattern or spike shape. Since the response was solely limited to frequency modulation, over- or understimulation of the oscillatory system, there is no need to create a new oscillator or to introduce further reaction steps into the core of the model. We conclude that the regulation of [Ca2+]cyt. via the explored second-messenger pathways can be embedded into the oscillatory system as modulation of rate constants already present in this model.

Collagen loss in the stunned myocardium

BACKGROUND

This study was performed to biochemically assess and quantify the previously observed ultrastructural alterations in the collagen matrix of stunned myocardium.

METHODS AND RESULTS

The stunned myocardium was produced in 13 mongrel dogs by a series of 12 coronary artery occlusions of 5 minutes followed by 10-minute reperfusion periods, with a final reperfusion period of 90 minutes. Regional systolic function in the stunned myocardium was 17% of control. Relative end-diastolic length in the stunned region increased up to 8%. There was a nonuniform transmural loss of collagen. Hydroxyproline in the stunned endocardium was not different from control. The stunned midwall and epicardium demonstrated 12.5% (p less than 0.05) and 14.6% (p less than 0.005) decreases, respectively. All transmural layers in the stunned myocardium had significant increases in collagenase activity before procollagenase activation, averaging a 73.6% increase (p less than 0.025). Complete activation of all procollagenase forms with aminophenylmercuric acetate revealed no differences in fully activated collagenase between the stunned and normal regions. The lysosomal enzymes, elastase and cathepsin G, were not different between stunned and normal zone tissue. These results would tend to exclude exogenous sources of protease in the stunned myocardium at the 90-minute final reperfusion time frame. Collagen fibers were isolated from the stunned and normal zone tissue and underwent dansyl chloride reaction. Stunned collagen fibers had 9% greater dansyl labeling, suggesting greater numbers of exposed N-terminal amino acid residues on the fiber and compatible with greater enzymatic cleavage activity on the stunned collagen matrix. Tissue water content was consistently greater in the stunned region compared to the normal: a uniform transmural increase of approximately 1.7%.

CONCLUSIONS

The stunned myocardium is characterized by both systolic dysfunction and diastolic expansion or dilatation. Endogenous procollagenase is activated by the ischemic process leading to degradation of the extracellular matrix. The underlying mechanisms may be relevant in ischemic enlargement of the heart and cardiomyopathy.

Increase in myofilament separation in the "stunned" myocardium

This study explores the effects of ischemic reperfusion injury on the radial separation distance between thick and thin myofilaments. The left anterior descending coronary artery was occluded for 5 mins and reperfused for 10 mins twelve times repetitively in 6 dogs. At the end of a final 90 min reperfusion period, the hearts were fixed by perfusion with glutaraldehyde, and subepicardial and subendocardial tissue from both normal and ischemic areas were prepared for transmission electron microscopy. Quantitative analysis of inter-filament distance (IFD) was performed on micrographs of transverse sections. The center-to-center IFD was calculated from the numerical density of thick filaments at the A band level using a hexagonal array conversion formula. Sarcomere length was measured on micrographs of longitudinal sections. The results showed that center-to-center thick IFD in the stunned subendocardium was 43.9 +/- 0.8 nm which was significantly greater than the control distance of 40.6 +/- 0.4 nm (P less than 0.001) from normal zone tissue. Thick IFD in the subepicardium was also significantly different: 43.4 +/- 0.6 nm in the stunned tissue as compared with 39.0 +/- 0.7 nm in the non-ischemic tissue (P less than 0.001). Sarcomere length in the normally perfused subendocardium was 2.01 +/- 0.07 micron and was increased to 2.20 +/- 0.08 micron in the stunned subendocardium (P less than 0.005). Sarcomere length in the normal and the stunned subepicardium was also different: 2.02 +/- 0.04 vs. 2.10 +/- 0.09 micron (P less than 0.005). The significant increase in spatial separation between the contractile filaments may affect optimal cross-bridge force generation at the molecular level.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of a gene encoding a specific human sperm protein in Chinese hamster ovarian cells

The cDNA (RSD-2) encoding a human sperm protein (YWK-II) was isolated from a rat testis lambda gt11 expression library. Its nucleotide sequence was determined. The deduced polypeptide showed high identity with the transmembrane-cytoplasmic domains of A4 amyloid precursor protein of Alzheimer's disease. The RSD-2 was inserted into the EcoRI site of the pSV2-EP vector to construct the pSVRS-2 vector. Chinese hamster ovarian (CHO-dhfr) cells were cotransformed with pSV2-neo and pSVRS-2. mRNA and chromosomal DNA prepared from the transformed cells interacted with [32P]RSD-2 as probe by dot hybridization. The production of the YWK-II protein was determined by staining with the YWK-II mAb by an indirect immunofluorescence technique. There was marked staining of the cytoplasm. The RSD-2 cDNA encoding the YWK-II sperm was expressed in the transformed CHO cells. The pSV2-EP vector and the CHO cell expression system can be utilized to produce sperm proteins for antifertility studies.

Expression of a gene encoding a rabbit sperm membrane protein in mammalian cells

A general mammalian expression vector designated pSV2-EP was reconstructed by inserting an oligonucleotide fragment into pSV2-dhfr. This vector allowed insertion of cDNAs with EcoRI cohesive ends. The pSV2-EP contains a simian virus 40 (SV40) early promoter, origin for DNA replication, SV40 poly-A site, splicing site, an initiator ATG downstream from the promoter and an EcoRI site for the insertion of cDNA fragment screened from lambda gt11 expression libraries. A recombinant plasmid (pS-VRS-1) was constructed by inserting RSD-1, a cDNA encoding a rabbit sperm tail protein, into the EcoRI site of the pSV2-EP vector. Chinese hamster ovarian (CHO) dhfr-negative cells were cotransformed with pSV2-dhfr and pSVRS-1 by the calcium phosphate method. In selective culture medium without thymidine and hypoxanthine, several cell lines were obtained containing mRNA and DNA that hybridized with RSD-1. One of these transformed cell lines stained intensely with anti-rSMP-B antibodies, demonstrating that the RSD-1 was expressed in the transformed CHO cells.