Engineered luciferase reporter from a deep sea shrimp utilizing a novel imidazopyrazinone substrate

Bioluminescence methodologies have been extraordinarily useful due to their high sensitivity, broad dynamic range, and operational simplicity. These capabilities have been realized largely through incremental adaptations of native enzymes and substrates, originating from luminous organisms of diverse evolutionary lineages. We engineered both an enzyme and substrate in combination to create a novel bioluminescence system capable of more efficient light emission with superior biochemical and physical characteristics. Using a small luciferase subunit (19 kDa) from the deep sea shrimp Oplophorus gracilirostris, we have improved luminescence expression in mammalian cells ∼2.5 million-fold by merging optimization of protein structure with development of a novel imidazopyrazinone substrate (furimazine). The new luciferase, NanoLuc, produces glow-type luminescence (signal half-life >2 h) with a specific activity ∼150-fold greater than that of either firefly (Photinus pyralis) or Renilla luciferases similarly configured for glow-type assays. In mammalian cells, NanoLuc shows no evidence of post-translational modifications or subcellular partitioning. The enzyme exhibits high physical stability, retaining activity with incubation up to 55 °C or in culture medium for >15 h at 37 °C. As a genetic reporter, NanoLuc may be configured for high sensitivity or for response dynamics by appending a degradation sequence to reduce intracellular accumulation. Appending a signal sequence allows NanoLuc to be exported to the culture medium, where reporter expression can be measured without cell lysis. Fusion onto other proteins allows luminescent assays of their metabolism or localization within cells. Reporter quantitation is achievable even at very low expression levels to facilitate more reliable coupling with endogenous cellular processes.

Cardiac hypertrophy is not a required compensatory response to short-term pressure overload

BACKGROUND

Cardiac hypertrophy is considered a necessary compensatory response to sustained elevations of left ventricular (LV) wall stress.

METHODS AND RESULTS

To test this, we inhibited calcineurin with cyclosporine (CsA) in the setting of surgically induced pressure overload in mice and examined in vivo parameters of ventricular volume and function using echocardiography. Normalized heart mass increased 45% by 5 weeks after thoracic aortic banding (TAB; heart weight/body weight, 8.3+/-0.9 mg/g [mean+/-SEM] versus 5. 7+/-0.1 mg/g unbanded, P<0.05). Similar increases were documented in the cell-surface area of isolated LV myocytes. In mice subjected to TAB+CsA treatment, we observed complete inhibition of hypertrophy (heart weight/body weight, 5.2+/-0.3 mg/g at 5 weeks) and myocyte surface area (endocardial and epicardial fractions). The mice tolerated abolition of hypertrophy with no signs of cardiovascular compromise, and 5-week mortality was not different from that of banded mice injected with vehicle (TAB+Veh). Despite abolition of hypertrophy by CsA (LV mass by echo, 83+/-5 mg versus 83+/-2 mg unbanded), chamber size (end-diastolic volume, 33+/-6 microL versus 37+/-1 microL unbanded), and systolic ejection performance (ejection fraction, 97+/-2% versus 97+/-1% unbanded) were normal. LV mass differed significantly in TAB+Veh animals (103+/-5 mg, P<0.05), but chamber volume (end-diastolic volume, 44+/-6 microL), ejection fraction (92+/-2%), and transstenotic pressure gradients (70+/-14 mm Hg in TAB+Veh versus 77+/-11 mm Hg in TAB+CsA) were not different.

CONCLUSIONS

In this experimental setting, calcineurin blockade with CsA prevented LV hypertrophy due to pressure overload. TAB mice treated with CsA maintain normal LV size and systolic function.

Quantitative, Wide-Spectrum Kinase Profiling in Live Cells for Assessing the Effect of Cellular ATP on Target Engagement

For kinase inhibitors, intracellular target selectivity is fundamental to pharmacological mechanism. Although a number of acellular techniques have been developed to measure kinase binding or enzymatic inhibition, such approaches can fail to accurately predict engagement in cells. Here we report the application of an energy transfer technique that enabled the first broad-spectrum, equilibrium-based approach to quantitatively profile target occupancy and compound affinity in live cells. Using this method, we performed a selectivity profiling for clinically relevant kinase inhibitors against 178 full-length kinases, and a mechanistic interrogation of the potency offsets observed between cellular and biochemical analysis. For the multikinase inhibitor crizotinib, our approach accurately predicted cellular potency and revealed improved target selectivity compared with biochemical measurements. Due to cellular ATP, a number of putative crizotinib targets are unexpectedly disengaged in live cells at a clinically relevant drug dose.

Genes involved in cerebellar cell specification and differentiation

The conservation of transcriptional regulatory mechanisms across species, combined with the restricted expression of these molecules in time and space within the embryo, has offered new insights into CNS cell specification. Studies examining transcriptional control in the generation of specific cell classes within the cerebellar cortex have been particularly elucidative.

Central mineralocorticoid receptor blockade improves volume regulation and reduces sympathetic drive in heart failure

The mineralocorticoid (MC) receptor antagonist spironolactone (SL) improves morbidity and mortality in patients with congestive heart failure (CHF). We tested the hypothesis that the central nervous system actions of SL contribute to its beneficial effects. SL (100 ng/h for 28 days) or ethanol vehicle (VEH) was administered intracerebroventricularly or intraperitoneally to rats with CHF induced by coronary artery ligation (CL) and to SHAM-operated controls. The intracerebroventricular SL treatment prevented the increase in sodium appetite and the decreases in sodium and water excretion observed within a week of CL in VEH-treated CHF rats. Intraperitoneal SL also improved volume regulation in the CHF rats, but only after 3 wk of treatment. Four weeks of SL treatment, either intracerebroventricularly or intraperitoneally, ameliorated both the increase in sympathetic drive and the impaired baroreflex function observed in VEH-treated CHF rats. These findings suggest that activation of MC receptors in the central nervous system plays a critical role in the altered volume regulation and augmented sympathetic drive that characterize clinical heart failure.

Two-year outcome of social skills training and group psychotherapy for outpatients with schizophrenia

OBJECTIVE

The authors evaluated the effectiveness of behaviorally oriented social skills training and supportive group therapy for improving the social adjustment of schizophrenic patients living in the community and for protecting them against psychotic relapse.

METHOD

Eighty male outpatients with schizophrenia were stabilized with a low dose of fluphenazine decanoate (5 to 10 mg every 14 days), which was supplemented with oral fluphenazine (5 mg twice daily) or a placebo when they first met criteria for a prodromal period. (Half of the patients did so at some time during the study.) Patients were randomly assigned to receive either social skills training or supportive group therapy twice weekly for 6 months and then weekly for the next 18 months. Rates of psychotic exacerbation were monitored, as were scores on the Social Adjustment Scale II.

RESULTS

There were significant main effects favoring social skills training over supportive group therapy on two of the six Social Adjustment Scale II cluster totals examined (personal well-being and total) and significant interactions between psychosocial treatment and drug treatment for three items (external family, social and leisure activities, and total). In each case, these interactions indicated that the advantage of social skills training over supportive group therapy was greatest when it was combined with active drug supplementation. Social skills training did not significantly decrease the risk of psychotic exacerbation in the full group, but an advantage was observed (post hoc) among patients who received placebo supplementation.

CONCLUSIONS

These findings suggest that social skills training resulted in greater improvement in certain measures of social adjustment than supportive group therapy. The greatest improvement in social outcomes occurred when social skills training was combined with a pharmacological strategy of active drug supplementation at the time prodromal worsening of psychotic symptoms was first observed. However, these improvements were modest in absolute terms and confined to certain subgroups of patients.

XASH-3, a novel Xenopus achaete-scute homolog, provides an early marker of planar neural induction and position along the mediolateral axis of the neural plate

We have isolated a novel Xenopus homolog of the Drosophila achaete-scute genes, called XASH-3. XASH-3 expression is neural specific and is detected as early as stage 11 1/2, making it one of the earliest markers of neural induction so far described. Moreover, XASH-3 expression within the neural plate is regionally restricted. Transverse bands of XASH-3 mRNA mark discrete positions along the anteroposterior axis, while longitudinal bands mark a discrete position along the mediolateral axis. This latter site of XASH-3 expression appears to demarcate the prospective sulcus limitans, a boundary zone that later separates the functionally distinct dorsal (alar) and ventral (basal) regions of the spinal cord. In sandwich explants lacking any underlying mesoderm, XASH-3 is expressed in longitudinal stripes located lateral to the midline. This provides the first indication that planar or midline-derived inductive signals are sufficient to establish at least some aspects of positional identity along the mediolateral axis of the neural plate. By contrast, the transverse stripes of XASH-3 expression are not detected, suggesting that this aspect of anteroposterior neural pattern is lost or delayed in the absence of vertically passed signals. The restricted mediolateral expression of XASH-3 suggests that mediolateral patterning of the neural plate is an early event, and that this regionalization can be achieved in the absence of inducing signals derived from underlying mesoderm.

Induction and repression of mammalian achaete-scute homologue (MASH) gene expression during neuronal differentiation of P19 embryonal carcinoma cells

MASH1 and MASH2, mammalian homologues of the Drosophila neural determination genes achaete-scute, are members of the basic helix-loop-helix (bHLH) family of transcription factors. We show here that murine P19 embryonal carcinoma cells can be used as a model system to study the regulation and function of these genes. MASH1 and MASH2 display complementary patterns of expression during the retinoic-acid-induced neuronal differentiation of P19 cells. MASH1 mRNA is undetectable in undifferentiated P19 cells but is induced to high levels by retinoic acid coincident with neuronal differentiation. In contrast, MASH2 mRNA is expressed in undifferentiated P19 cells and is repressed by retinoic acid treatment. These complementary expression patterns suggest distinct functions for MASH1 and MASH2 in development, despite their sequence homology. In retinoic-acid-treated P19 cells, MASH1 protein expression precedes and then overlaps expression of neuronal markers. However, MASH1 is expressed by a smaller proportion of cells than expresses such markers. MASH1 immunoreactivity is not detected in differentiated cells displaying a neuronal morphology, suggesting that its expression is transient. These features of MASH1 expression are similar to those observed in vivo, and suggest that P19 cells represent a good model system in which to study the regulation of this gene. Forced expression of MASH1 was achieved in undifferentiated P19 cells by transfection of a cDNA expression construct. The transfected cells expressing exogenous MASH1 protein contained E-box-binding activity that could be super-shifted by an anti-MASH1 antibody, but exhibited no detectable phenotypic changes. Thus, unlike myogenic bHLH genes, such as MyoD, which are sufficient to induce muscle differentiation, expression of MASH1 appears insufficient to promote neurogenesis.

XASH genes promote neurogenesis in Xenopus embryos

Neural development in Drosophila is promoted by a family of basic helix-loop-helix (bHLH) transcription factors encoded within the Achaete Scute-Complex (AS-C). XASH-3, a Xenopus homolog of the Drosophila AS-C genes, is expressed during neural induction within a portion of the dorsal ectoderm that gives rise to the neural plate and tube. Here, we show that XASH-3, when expressed with the promiscuous binding partner XE12, specifically activates the expression of neural genes in naive ectoderm, suggesting that XASH-3 promotes neural development. Moreover, XASH-3/XE12 RNA injections into embryos lead to hypertrophy of the neural tube. Interestingly, XASH-3 misexpression does not lead to the formation of ectopic neural tissue in ventral regions, suggesting that the domain of XASH proneural function is restricted in the embryo. In contrast to the neural inducer noggin, which permanently activates the NCAM gene, the activation of neural genes by XASH-3/XE12 is not stable in naive ectoderm, yet XASH-3/XE12 powerfully and stably activates NCAM, Neurofilament and type III beta-tubulin gene expression in noggin-treated ectoderm. These results show that the XASH-3 promotes neural development, and suggest that its activity depends on additional factors which are induced in ectoderm by factors such as noggin.

Differential prenyl pyrophosphate binding to mammalian protein geranylgeranyltransferase-I and protein farnesyltransferase and its consequence on the specificity of protein prenylation

Protein geranylgeranyltransferase-I (PGGT-I) and protein farnesyltransferase (PFT) attach geranylgeranyl and farnesyl groups, respectively, to the C termini of eukaryotic cell proteins. In vitro, PGGT-I and PFT can transfer both geranylgeranyl and farnesyl groups from geranylgeranyl pyrophosphate (GGPP) and farnesyl pyrophosphate (FPP) to their protein or peptide prenyl acceptor substrates. In the present study it is shown that PGGT-I binds GGPP 330-fold tighter than FPP and that PFT binds FPP 15-fold tighter than GGPP. Therefore, in vivo, where both GGPP and FPP compete for the binding to prenyltransferases, PGGT-I and PFT will likely be bound predominantly to GGPP and FPP, respectively. Previous studies have shown that K-Ras4B and the Ras-related GTPase TC21 are substrates for both PGGT-I and PFT in vitro. It is shown that TC21 can compete with the C-terminal peptide of the gamma subunit of heterotrimeric G proteins and with the C-terminal peptide of lamin B for geranylgeranylation by PGGT-I and for farnesylation by PFT, respectively. K-Ras4B competes in both cases but is almost exclusively farnesylated by PFT in the presence of the lamin B peptide competitor. Rapid and single turnover kinetic studies indicate that the rate constant for the PGGT-I-catalyzed geranylgeranyl transfer step of the reaction cycle is 14-fold larger than the steady-state turnover number, which indicates that the rate of the overall reaction is limited by a step subsequent to prenyl transfer such as release of products from the enzyme. PGGT-I-catalyzed farnesylation is 37-fold slower than geranylgeranylation and is limited by the farnesyl transfer step. These results together with earlier studies provide a paradigm for the substrate specificity of PGGT-I and PFT and provide information that is critical for the design of prenyltransferase inhibitors as anti-cancer agents.

IgH enhancer-mediated deregulation of N-myc gene expression in transgenic mice: generation of lymphoid neoplasias that lack c-myc expression

We have generated transgenic mouse lines that carry one of three different constructs in which the murine N-myc gene is expressed under the control of the immunoglobulin heavy chain transcriptional enhancer element (E mu-N-myc genes). High-level expression of the E mu-N-myc transgenes occurred in lymphoid tissues; correspondingly, many of these E mu-N-myc lines reproducibly developed pre-B- and B-lymphoid malignancies. The E mu-N-myc transgene also appeared to participate in the generation of a T cell malignancy that developed in one E mu-N-myc mouse. These tumors and cell lines adapted from them expressed exceptionally high levels of the E mu-N-myc transgene; the levels were comparable to those observed in human neuroblastomas with highly amplified N-myc genes. In contrast, all of the E mu-N-myc cell lines had exceptionally low or undetectable levels of the c-myc RNA sequences, consistent with the possibility that high-level N-myc expression can participate in the negative 'cross-regulation' of c-myc gene expression. Our findings demonstrate that deregulated expression of the N-myc gene has potent oncogenic potential within the B-lymphoid lineage despite the fact that the N-myc gene has never been implicated in naturally occurring B-lymphoid malignancies. Our results also are discussed in the context of differential myc gene activity in normal and transformed cells.

Chronic ethanol intake and burn injury: evidence for synergistic alteration in gut and immune integrity

OBJECTIVE

Chronic ethanol (EtOH) intake and injury are both associated with increased susceptibility to infection in the host. This study examined the immune and gastrointestinal alterations induced by chronic EtOH intake and injury, and compared the effects of enteral and intravenous administration of EtOH.

DESIGN

Rats received 20% EtOH daily for 14 days by gavage [oral (PO)] or superior vena cava [intravenous (i.v.)] infusion. Mean blood EtOH concentrations at 90 minutes after administration were 95.3 mg/dL (PO) and 94.4 mg/dL (i.v.). An additional group of animals underwent a 30% total body surface area full-thickness burn injury 4 hours after the final dose of EtOH or normal saline on experimental day 14. All animals were killed 4 days after burn injury.

MATERIALS AND METHODS

Nonadherent splenic lymphocytes were tested for mitogenic responses to the T-cell mitogens concanavalin A (ConA) and phytohemagglutinin (PHA), and the B-cell mitogens lipopolysaccharide (LPS) and pokeweed. Quantitative bacterial cultures of mesenteric lymph nodes and liver were also performed. Alterations of intestinal mucosa were determined by measurement of ileal mucosal weight, DNA, protein, and diamine oxidase content. Circulating plasma endotoxin concentrations were also measured.

MEASUREMENTS AND MAIN RESULTS

Chronic PO-EtOH intake induced a significant impairment in mitogenic response to T-cell mitogens, with a fourfold reduction in ConA and a twofold reduction in PHA response (p < 0.05 by analysis of variance) and increased bacterial translocation (70% vs. 10%). Chronic EtOH administered by the i.v. route did not reduce mitogenic response to any of the mitogens studied. Histologic examination of ileal segments demonstrated that chronic PO-EtOH administration was associated with significant mucosal disruption and exfoliation. Chronic administration of PO-EtOH prior to burn injury induced a significant impairment in spleen mitogenic response to ConA, PHA, and LPS when compared with all other burn injury groups. Chronic administration of EtOH by the i.v. route prior to burn injury did not alter splenic mitogenesis. In addition, chronic PO-EtOH prior to burn injury increased bacterial translocation rates (80% vs. 33%) and prevented the normal intestinal reparative response to burn injury (demonstrated by a significant reduction in ileal mucosal weight, DNA, and diamine oxidase content).

CONCLUSIONS

Enteral but not i.v. administration of EtOH induced significant immunologic dysfunction (demonstrated by altered spleen mitogenic response) and gastrointestinal dysfunction (demonstrated by depressed ileal mucosal weight, DNA, and diamine oxidase content, and increased bacterial translocation rates). In addition, the administration of chronic enteral EtOH prior to injury resulted in significant immune suppression and impaired the host's ability for normal intestinal repair. These results suggest that this EtOH-induced reduction in immunocompetence may be gut-mediated and that the administration of alcohol prior to injury may result in a synergistic alteration of gut and immune integrity.

Late follow-up of 781 patients undergoing percutaneous transluminal coronary angioplasty or coronary artery bypass grafting for an isolated obstruction in the left anterior descending coronary artery

Seven hundred eighty-one patients with isolated left anterior descending coronary atherosclerosis treated with either coronary artery bypass grafting or percutaneous transluminal coronary angioplasty between January 1980 and December 1984 were studied to determine late survival and event-free survival. Follow-up was complete in 775 patients (99.4%). Actuarial survival at 5 years was 98% for surgical patients and 95% for angioplasty patients (p = 0.02). Five-year event-free survival (freedom from myocardial infarction, bypass grafting, angioplasty, and death) was 93% for surgical patients and 62% for angioplasty patients. This study suggests that the higher initial cost and complexity of bypass surgery may be justified by superior long-term results.

Age-related deterioration of motion perception and detection

PURPOSE

The purpose of this study was to evaluate the effect of aging on motion detection and perception.

METHODS

Forty-six subjects, ages 19-92 years, were asked to view a motion stimulus. Infrared oculography was used to objectively evaluate motion detection by documenting the presence of optokinetic nystagmus as the subjects viewed the stimulus. Subjective responses to motion perception were recorded using a computer joystick.

RESULTS

Optokinetic nystagmus was clearly detectable in all 46 subjects. Motion detection and perception thresholds showed age-related deterioration. No relationship was found to gender or age-gender interaction.

CONCLUSION

The results indicate motion detection and perception thresholds deteriorate with age. This may reflect a susceptibility to age-related degeneration in specific cortical areas responsible for motion perception as well as neurodegeneration in the retinogeniculate pathway.

A prospective evaluation of ifosfamide-related nephrotoxicity in children and young adults

BACKGROUND

Ifosfamide has been associated with proximal renal tubular dysfunction resembling Fanconi-like syndrome and leading to rickets in young children. The characteristic manifestations of this nephrotoxicity include phosphaturia and hypophosphatemia, glycosuria, aminoaciduria, renal tubular acidosis, and urinary loss of low molecular weight serum proteins. However, the relationship between acute ifosfamide nephrotoxicity, which is frequently subclinical, and long term renal damage is unclear. In this prospective study, the laboratory features of ifosfamide-induced acute nephrotoxicity were characterized further and correlated with the development of chronic nephropathy.

METHODS

The renal function of newly diagnosed children and young adults with high risk sarcomas was followed during therapy with a high dose ifosfamide-containing regimen. Serum and urine were collected regularly immediately before and after 5-day cycles of ifosfamide throughout treatment for determination of the fractional excretion of electrolytes (sodium, potassium, phosphate, magnesium, calcium) and glucose and urinary excretion of amino acids and beta 2-microglobulin.

RESULTS

Significant changes in the renal threshold of phosphate excretion, the fractional excretion of calcium and glucose, and the urinary excretion of beta 2-microglobulin were observed when comparing pretreatment values with those at the end of a 5-day treatment cycle. The median renal threshold of phosphate excretion decreased from 1.22 to 0.82 mmol/L (P < 0.0001). The median fractional excretions of calcium and glucose increased from 1.05% to 1.68% (P < 0.0001) and 0.05% to 0.08% (P = 0.0006), respectively. Beta 2-microglobulin excretion increased by 70-fold from 0.02 to 1.42 mg/mmol (P < 0.0001). Except for glucose and beta 2-microglobulin excretion, renal parameters returned to baseline before the next ifosfamide treatment cycle. Acute aminoaciduria was observed in 21 of 23 patients. Chronic nephrotoxicity, as defined by the development of a Fanconi-like syndrome or chronic tubular electrolyte loss requiring oral supplementation, developed in the three patients with the highest urinary excretion of beta 2-microglobulin after ifosfamide therapy.

CONCLUSIONS

Prospectively, high dose ifosfamide was associated with a 4% incidence of Fanconi-like syndrome; however, evidence of acute reversible subclinical nephrotoxicity was observed for all patients. Severe beta 2-microglobulinuria appeared to be a prognostic laboratory indicator for the development of chronic nephrotoxicity.

XATH-1, a vertebrate homolog of Drosophila atonal, induces a neuronal differentiation within ectodermal progenitors

XATH-1, a basic/helix-loop-helix transcription factor and a homolog of Drosophila atonal and mammalian MATH-1, is expressed specifically in the dorsal hindbrain during Xenopus neural development. In order to investigate the role of XATH-1 in the neuronal differentiation process, we have examined the effects of XATH-1 overexpression during Xenopus development. XATH-1 induces the expression of neuronal differentiation markers, such as N-tubulin, within the neural plate as well as within nonneural ectodermal progenitor populations, resulting in the appearance of process-bearing neurons within the epidermis. The related basic/helix-loop-helix genes neurogenin-related-1 and neuroD are not induced in response to XATH-1 overexpression within the embryo, suggesting that XATH-1 may activate an alternate pathway of neuronal differentiation. In further contrast to neurogenin-related-1 and neuroD, high-level expression of general neural markers expressed earlier in development, such as N-CAM, is not induced by XATH-1 overexpression. Competent ectodermal progenitors therefore respond to ectopic XATH-1 expression by initiating a distinct program of neuronal differentiation.

Structure and expression of the murine L-myc gene

We have isolated a 12 kb clone from the murine genome which we show by DNA transfection studies to contain an entire functional L-myc gene and the transcriptional promoter sequences necessary for its expression. We have also isolated a 3.1 kb cDNA sequence from a murine brain cDNA library which corresponds to most of the L-myc mRNA. We have identified the L-myc coding region within the genomic clone by a combination of S1 nuclease analyses. Northern blotting analyses and comparative nucleotide sequence analyses with the cDNA clone. The L-myc gene appears to be organized similarly to the other well-characterized myc-family genes, c-myc and N-myc. The predicted amino acid coding sequence of the L-myc gene indicates that the L-myc protein is significantly smaller than c- and N-myc, but is highly related. In particular, comparison of the N- and c-myc protein sequences reveals seven relatively conserved regions interspersed among non-conserved regions; the L-myc gene retains five of these conserved regions but lacks two others. In addition, a portion of one highly conserved region is encoded within a different region of the L-myc gene but, due to changes in the size of L-myc exons relative to those of N- and c-myc, maintains its overall position in the peptide backbone with respect to other conserved regions. We discuss these findings in the context of potential functional domains and the possibility of overlapping and distinct activities of myc-family proteins.

The pattern of cellular organization of human epidermis

Cell alignment in the stratum corneum of frozen sections of specimens of human skin was examined by light microscopy following expansion of the stratum corneum in alkaline buffer. Some degree of ordered structure was found in all specimens examined but considerable variation existed in precision of cell alignment. The typical degree of cell alignment was less precise than that typically observed in experimental animals.

The relation between vascular relaxant and cardiac electrophysiological effects of pinacidil

Pinacidil may represent an example of a new class of vasodilators that act by increasing membrane permeability to potassium ions. In the present study, the cardiac electrophysiological and venorelaxant effects of a series of pinacidil analogs in canine tissues in vitro were examined. Piacidil (3 x 10(-5) M) markedly reduced action potential duration in Purkinje fibers (82 +/- 3% decrease) and ventricular muscle (54 +/- 2% decrease) without significantly affecting maximal upstroke velocity of the action potential or conduction time. The EC50 for the reduction in Purkinje fiber action potential duration was 2.6 +/- 0.5 microM. Pinacidil also decreased barium-induced automaticity in Purkinje fibers; the concentration that decreased the rate of firing by 50% was identical to the EC50 for decreasing action potential duration. In some preparations, high concentrations of pinacidil (greater than or equal to 3 x 10(-5) M) were associated with the appearance of spontaneous action potentials that were closely coupled to the preceding driven action potential. The EC50 for pinacidil in relaxing phenylephrine-contracted cephalic veins was 0.43 +/- 0.09 microM, and in isolated cat papillary muscle, pinacidil had a direct negative inotropic effect with an EC50 of 4.1 +/- 0.7 microM. Thus, pinacidil was 6 and 10 times more potent in relaxing phenylephrine-contracted veins than in shortening action potential or decreasing cardiac contractility. There was an excellent correlation (r = 0.933, p = 0.002) between decreases in action potential duration and venorelaxation for all pinacidil analogs, as well as for BRL 34915 and nicorandil, two purported potassium channel openers. Significant correlations were also obtained between negative inotropic effects and reductions in action potential duration for the pinacidil series. Pinacidil (10(-5) M) also inhibited the venoconstrictor responses to the selective alpha 2 agonist, B-HT 920, to a greater extent than the alpha 1 agonist, methoxamine. Since a good correlation exists in vitro among all the compounds studied in reducing action potential duration, relaxing vascular tissue, and decreasing cardiac contractility, it is concluded that pinacidil as well as nicorandil and BRL 34915 affect vascular and cardiac tissues by similar mechanisms, possibly by increases in potassium ion permeability, although other mechanisms may also play a role.

Myc family of cellular oncogenes

The myc family of cellular oncogenes contains three well-defined members: c-myc, N-myc and L-myc. Additional structural and functional evidence now suggests that other myc-family oncogenes exist. The overall structure and organization of the c-, N-, and L-myc genes and transcripts are very similar. Each gene contains three exons: encoding a long 5' untranslated leader and a long 3' untranslated region. The proteins encoded by these myc genes share several stretches of significant homology. The conservation of sequences at the carboxyterminus of the L-myc protein suggests that it is also a DNA-binding, nuclear-associated protein. Each myc gene will cooperate with an activated Ha-ras oncogene to cause transformation of primary rat embryo fibroblasts. Characteristics of several new myc-family members are described.

Clinical significance of the preoperative plasma carcinoembryonic antigen (CEA) level in patients with carcinoma of the large bowel

Preoperative levels of perchloric acid extractable plasma CEA were measured in 911 patients with complaints of the digestive system. A final diagnosis of benign disease was made for 579 patients; 332 patients were found to have cancer. Data for the preoperative CEA values were examined for clinical significance as an aide to diagnosis, preoperative disease staging, and prognosis. The results of our analysis support the conclusions of many investigators that the CEA assay is not a clinically useful diagnostic test, but it shows limited value in preoperative staging and a somewhat stronger correlation with prognosis.

Characterization of distinct angiotensin II binding sites in rat adrenal gland and bovine cerebellum using selective nonpeptide antagonists

We investigated the characteristics of 125I-AII binding to rat adrenal and bovine cerebellar membranes in the presence and absence of new nonpeptide angiotensin II (AII) receptor ligands. The imidazole AII ligands, DUP753 and WL19, both produced biphasic competition curves to 125I-AII binding in rat adrenal glomerulosa and adrenal medulla particles, suggesting the existence of two distinct AII binding sites. Antagonist affinity (Ki) and binding capacity (Bmax) for each binding site was determined using nonlinear analysis of competition data fit to a two-site model. The high capacity site (68% of total specific 125I-AII bound) in glomerulosa had high affinity for DUP753 (4.6 +/- 0.8 nM) and low affinity for WL19 (29 +/- 3 microM), and the low capacity site had high affinity for WL19 (3.3 +/- 1.4 nM) and low affinity for DUP753 (51 +/- 9 microM). Conversely, in medulla, the high capacity site (77% total binding) had high affinity for WL19 (19 +/- 6 nM) and low affinity for DUP753 (29 +/- 8 microM), and the low capacity site had low affinity for WL19 (25 +/- 7 microM) but a high affinity for DUP753 (2.8 +/- 2.0 nM). In glomerulosa, binding parameters for the nonpeptide ligands at each site derived from monophasic competition curves obtained in the presence of either 0.3 microM DUP753 or WL19 to selectively block the high or low capacity binding site, respectively, were similar to values determined from the biphasic competition curves. Unlike the nonpeptide inhibitors, unlabeled AII yielded monophasic inhibition curves.(ABSTRACT TRUNCATED AT 250 WORDS)

Construction of coordinatively saturated rhodium complexes containing appended peptides

Phenanthrenequinone diimine (phi) complexes of rhodium(III) bearing appended peptides have been prepared using two complementary solid phase synthetic strategies. The first method involves the direct coupling of the coordinatively saturated rhodium complex containing a pendant carboxylate to the N-terminus of a resin-bound peptide, in a manner analogous to the chain-elongation step in solid phase peptide synthesis. The second involves coupling a bidentate chelator containing the pendant carboxylate to the resin-bound peptide, followed by coordination of [Rh(phi)2]3+ to the bidentate chelator attached to the peptide. Peptides of length 5-30 residues have been covalently attached to rhodium complexes in 5-18% yield using both methods. Despite the low overall yields, the regioselective modification of the peptide chain afforded by these strategies is a distinct advantage over solution phase methods. With coordination complexes which are stable to peptide deprotection and cleavage conditions from the resin, the solid phase synthetic strategies are convenient to apply. Amino acid analysis, electronic spectroscopy, and circular dichroism confirm the presence of the two components in the metal-peptide chimeras; the metal-peptide complexes exhibit the combined spectral properties of the parent metal complex and the appended peptide. Significantly, plasma desorption mass spectrometry reveals a novel pattern of peptide fragmentation for the metal-peptide chimeras that is not observed in the absence of the tethered metal complex; this fragmentation facilitates the sequence analysis of the appended peptide. Thus, metal-peptide chimeras may be conveniently prepared using solid phase methodologies, and features of coordination chemistry may be exploited for new peptide design and analysis.