Retinoblastoma protein (Rb) links hypoxia to altered mechanical properties in cancer cells as measured by an optical tweezer

Hypoxia modulates actin organization via multiple pathways. Analyzing the effect of hypoxia on the biophysical properties of cancer cells is beneficial for studying modulatory signalling pathways by quantifying cytoskeleton rearrangements. We have characterized the biophysical properties of human LNCaP prostate cancer cells that occur in response to loss of the retinoblastoma protein (Rb) under hypoxic stress using an oscillating optical tweezer. Hypoxia and Rb-loss increased cell stiffness in a fashion that was dependent on activation of the extracellular signal-regulated kinase (ERK) and the protein kinase B (AKT)- mammalian target of rapamycin (MTOR) pathways. Pharmacological inhibition of MEK1/2, AKT or MTOR impeded hypoxia-inducible changes in the actin cytoskeleton and inhibited cell migration in Rb-deficient cells conditioned with hypoxia. These results suggest that loss of Rb in transformed hypoxic cancer cells affects MEK1/2-ERK/AKT-MTOR signalling and promotes motility. Thus, the mechanical characterization of cancer cells using an optical tweezer provides an additional technique for cancer diagnosis/prognosis and evaluating therapeutic performance.

A phase II study of the HDAC inhibitor SB939 in patients with castration resistant prostate cancer: NCIC clinical trials group study IND195

BACKGROUND

SB939 is a potent oral inhibitor of class 1, 2, and 4 histone deacetylases (HDACs). These three HDAC classes are highly expressed in castration resistant prostate cancer (CRPC) and associated with poor clinical outcomes. We designed a phase II study of SB939 in men with metastatic CRPC.

METHODS

Patients received SB939 60 mg on alternate days three times per week for 3 weeks on a 4-week cycle. Primary endpoints were PSA response rate (RR) and progression-free survival (PFS). Secondary endpoints included objective response rate and duration; overall survival; circulating tumor cell (CTC) enumeration and safety. Exploratory correlative studies of the TMPRSS2-ERG fusion and PTEN biomarkers were also performed.

RESULTS

Thirty-two patients were enrolled of whom 88 % had received no prior chemotherapy. The median number of SB939 cycles administered was three (range 1-8). Adverse events were generally grade 1-2, with five pts experiencing one or more grade three event. One patient died due to myocardial infarction. A confirmed PSA response was noted in two pts (6 %), lasting 3.0 and 21.6 months. In patients with measurable disease there were no objective responses. Six patients had stable disease lasting 1.7 to 8.0 months. CTC response (from ≥5 at baseline to <5 at 6 or 12 weeks) occurred in 9/14 evaluable patients (64 %).

CONCLUSION

Although SB939 was tolerable at the dose/schedule given, and showed declines in CTC in the majority of evaluable patients, it did not show sufficient activity based on PSA RR to warrant further study as a single agent in unselected patients with CRPC.

Lyn tyrosine kinase regulates androgen receptor expression and activity in castrate-resistant prostate cancer

Castrate-resistant prostate cancer (CRPC) progression is a complex process by which prostate cells acquire the ability to survive and proliferate in the absence or under very low levels of androgens. Most CRPC tumors continue to express the androgen receptor (AR) as well as androgen-responsive genes owing to reactivation of AR. Protein tyrosine kinases have been implicated in supporting AR activation under castrate conditions. Here we report that Lyn tyrosine kinase expression is upregulated in CRPC human specimens compared with hormone naive or normal tissue. Lyn overexpression enhanced AR transcriptional activity both in vitro and in vivo and accelerated CRPC. Reciprocally, specific targeting of Lyn resulted in a decrease of AR transcriptional activity in vitro and in vivo and prolonged time to castration. Mechanistically, we found that targeting Lyn kinase induces AR dissociation from the molecular chaperone Hsp90, leading to its ubiquitination and proteasomal degradation. This work indicates a novel mechanism of regulation of AR stability and transcriptional activity by Lyn and justifies further investigation of the Lyn tyrosine kinase as a therapeutic target for the treatment of CRPC.

High frequency of false positive IgM immunoblots for Borrelia burgdorferi in clinical practice

Although it is known that two-tier serologic testing for Lyme disease may be associated with false positive results on the IgM immunoblot, this problem has never been systematically studied in the clinical practice setting. In a retrospective investigation of patients referred to the private adult practice of an Infectious Diseases physician for possible for Lyme disease, 50 of 182 patients (27.5%, 95% CI: 21.1-34.6) were found to have a false positive IgM immunoblot. 78.0% of these patients had received unnecessary antibiotic therapy. False positive results were not restricted to any single commercial laboratory. Research on alternative testing strategies that eliminate the IgM immunoblot entirely is warranted.

Quantitation of cell-associated borrelial DNA in the blood of Lyme disease patients with erythema migrans

Bloodstream invasion is an important event in the pathogenesis of the more serious manifestations of Lyme disease. The number of spirochetes in the blood of infected patients, however, has not been determined, and, therefore, it is unknown whether the number of spirochetes can be correlated with particular clinical or laboratory features. This study was designed to measure the level of Borrelia burgdorferi in the plasma of Lyme disease patients and correlate these levels with selected clinical and laboratory findings. Nested and quantitative polymerase chain reaction (qPCR) was employed to detect cell-associated flaB gene DNA in the plasma of untreated early Lyme disease patients with erythema migrans (EM). Twenty-nine (45.3%) of 64 patients had evidence of B. burgdorferi in their plasma by at least one of the PCR methods. For the 22 qPCR-positive patients, the mean number of flaB gene copies per mL of plasma was 4,660, with a range of 414 to 56,000. The number of flaB gene copies did not significantly correlate with any of the clinical, demographic, or laboratory variables assessed. For reasons discussed, we suggest caution in extrapolating an estimate of the number of viable Borrelia in plasma from the observed number of flaB copies.

Transition behavior in fatigue of human dentin: structure and anisotropy

The influence of tubule orientation on the transition from fatigue to fatigue crack growth in human dentin was examined. Compact tension (CT) and rectangular beam specimens were prepared from the coronal dentin of molars with three unique tubule orientations (i.e., 0 degrees , 45 degrees and 90 degrees). The CT specimens (N=25) were used to characterize fatigue crack initiation and steady-state cyclic extension, whereas the rectangular beams (N=132) were subjected to 4-pt flexure and used in quantifying the stress-life fatigue response. The transition behavior was analyzed using both the Kitagawa-Takahashi and El Haddad approaches. Results showed that both the fatigue crack growth and stress-life responses were dependent on the tubule orientation. The average Paris Law exponent for crack growth perpendicular (90 degrees) to the tubules (m=13.3+/-1.1) was significantly greater (p<0.05) than that for crack growth oblique (45 degrees) to the tubules (m=11.5+/-1.87). Similarly, the fatigue strength of dentin with 90 degrees tubule orientation was significantly lower (p<0.05) than that for the other two orientations, regardless of the range of cyclic stress. The apparent endurance strengths of specimens with 0 degrees (44MPa) and 45 degrees (53MPa) orientations were nearly twice that of the 90 degrees (24MPa) orientation. Based on these results, human dentin exhibits the largest degree of anisotropy within the stress-life regime and the transition from fatigue to fatigue crack growth occurs under the lowest cyclic stress range when the tubules are aligned with the cyclic normal stress (90 degrees orientation).

Water quality condition and trend in North Queensland waterways

The Queensland Environmental Protection Agency monitored water quality at 133 sites in North Queensland waterways between Cooktown and Bundaburg from 1992 to 2001. Condition of the waterways was rated by comparing recent data with the Queensland Water Quality Guidelines. Long-term trends were analysed using a censored regression technique that incorporates the effects of flow, temperature, seasonality and allows for long-term non-linear trends. Many sites were in good condition; those in poor condition were usually impacted by point source discharges; those in moderate condition were usually impacted by agricultural land use. There were no consistent long-term trends across the whole region. Recommendations for future programs include incorporating pressure indicators, ensuring high standards of quality assurance, including covariates such as rainfall in trend assessment and continuing programs over more than 10 years to allow detection of trends due to changes in land-use.

Multilaboratory comparison of anaerobe susceptibility results using 3 different agar media

A 5-laboratory study was performed that used the National Committee for Clinical Laboratory Standards (NCCLS) reference agar dilution method with 3 media formulations to determine whether the use of different media would affect minimum inhibitory concentration (MIC) results. Wilkins-Chalgren, Brucella-based blood agar (BRU), and Wilkins-Chalgren agar plus blood (WCB) and 6 antibiotics (clindamycin, cefoxitin, ceftizoxime, piperacillin, metronidazole, and trovafloxacin) were evaluated with 58 isolates. The MIC values were compared, and a significant correlation of >0.80 was demonstrated for all media and each antibiotic/organism group. The cumulative rate of errors for all antibiotics was 0.1%. These data indicate that a change in the NCCLS reference medium for testing of anaerobic bacteria susceptibility to either BRU or WCB will not affect the MIC results for the antibiotics and organisms evaluated.

Multilaboratory comparison of growth characteristics for anaerobes, using 5 different agar media

A multilaboratory study compared the growth of 30 fastidious anaerobes, using 5 different agar media: Wilkins-Chalgren (WC), WC with either whole or laked sheep blood, and Brucella supplemented with vitamin K(1) and hemin and either laked or whole sheep blood. The media were compared for quality and quantity of growth. Experiments were conducted either entirely in an anaerobic chamber or inoculated in ambient air with anaerobic incubation. The results showed that (1) any medium plus whole or laked blood was better than unsupplemented WC, (2) whole blood and laked blood additives gave similar results, (3) supplemented Brucella with whole or laked blood was superior to WC and WC with whole or laked blood, and (4) anaerobic and aerobic inoculation with anaerobic incubation gave similar results. Brucella agar supplemented with whole or laked blood supports the growth of fastidious anaerobic species better than the WC agars do.

Interleukin-6- and cyclic AMP-mediated signaling potentiates neuroendocrine differentiation of LNCaP prostate tumor cells

Neuroendocrine (NE) differentiation in prostatic adenocarcinomas has been reported to be an early marker for development of androgen independence. Secretion of mitogenic peptides from nondividing NE cells is thought to contribute to a more aggressive disease by promoting the proliferation of surrounding tumor cells. We undertook studies to determine whether the prostate cancer cell line LNCaP could be induced to acquire NE characteristics by treatment with agents that are found in the complex environment in which progression of prostate cancer towards androgen independence occurs. We found that cotreatment of LNCaP cells with agents that signal through cyclic AMP-dependent protein kinase (PKA), such as epinephrine and forskolin, and with the cytokine interleukin-6 (IL-6) promoted the acquisition of an NE morphological phenotype above that seen with single agents. Convergent IL-6 and PKA signaling also resulted in potentiated mitogen-activated protein kinase (MAPK) activation without affecting the level of signal transducer and activator of transcription or PKA activation observed with these agents alone. Cotreatment with epinephrine and IL-6 synergistically increased c-fos transcription as well as transcription from the beta4 nicotinic acetylcholine receptor subunit promoter. Potentiated transcription from these elements was shown to be dependent on the MAPK pathway. Most importantly, cotreatment with PKA activators and IL-6 resulted in increased secretion of mitogenic neuropeptides. These results indicate that PKA and IL-6 signaling participates in gene transcriptional changes that reflect acquisition of an NE phenotype by LNCaP cells and suggest that similar signaling mechanisms, particularly at sites of metastasis, may be responsible for the increased NE content of many advanced prostate carcinomas.

Effect of superficial heat, deep heat, and active exercise warm-up on the extensibility of the plantar flexors

BACKGROUND AND PURPOSE

Warm-up prior to static stretching enhances muscle extensibility. The relative effectiveness of different modes of warm-up, however, is unknown. The purpose of this study was to evaluate the effectiveness of superficial heat, deep heat, and active exercise warm-up prior to stretching compared with stretching alone on the extensibility of the plantar-flexor muscles.

SUBJECTS

Ninety-seven subjects (59 women, 38 men) with limited dorsiflexion range of motion (ROM) were randomly assigned to 1 of 5 groups. Female subjects had a mean age of 27.6 years (SD=7.68, range=17-50), and male subjects had a mean age of 26.8 years (SD=6.87, range=18-48).

METHODS

The first group (group 1) was a control group and did not perform the stretching protocol. The 4 experimental groups (groups 2-5) performed a stretching protocol 3 days per week for 6 weeks. Group 2 performed the static stretching protocol only; group 3 performed active heel raises before stretching; group 4 received 15 minutes of superficial, moist heat to the plantar-flexor muscles before stretching; and group 5 received continuous ultrasound for 7 minutes before stretching. Dorsiflexion ROM measurements were taken initially and after 2, 4, and 6 weeks.

RESULTS

All experimental groups increased active and passive range of motion (AROM and PROM). The mean AROM/PROM differences at 6 weeks were 1.11/1.39 degrees for group 1, 4.10/6.11 degrees for group 2, 4.16/4.21 degrees for group 3, 4.38/4.90 degrees for group 4, and 6.20/7.35 degrees for group 5. The group receiving ultrasound before performing the stretching protocol (group 5) displayed the greatest increase in both AROM (6.20() and PROM (7.35().

DISCUSSION AND CONCLUSION

Among the modalities tested, the use of ultrasound for 7 minutes prior to stretching may be the most effective for increasing ankle dorsiflexion ROM.

Relationship between functional evaluation measures and self-assessment in nonacute low back pain

STUDY DESIGN

The correlations between objective biomechanical indicators of function and self-assessment scores were examined retrospectively for 91 subjects with nonacute low back pain.

OBJECTIVES

To examine the correlation between self-assessment, trunk range of motion (ROM), velocity, and complex mechanical coordination patterns of the spine in nonacute low back pain.

SUMMARY OF BACKGROUND DATA

In low back pain, there is often little concordance between pain, physical impairment, and disability. Use of range of motion and velocity to enhance objectivity in impairment evaluations has been ineffectual. In this study, two hypotheses were examined: range of motion and velocity are controllable and inherently correlated with self-assessment; complex spinal coordination patterns such as range of lordosis cannot be controlled and are independent of self-assessment.

METHODS

Self-assessment questionnaires were administered, and indexes of spinal motion and coordination were measured through skin marker kinematics. The correlation between self-assessments and biomechanical measures was determined.

RESULTS

Self-assessments of function were significantly correlated with parameters prone to regulation: range of motion, velocity, and load lifted. In contrast, little correlation was found with measures of complex spinal coordination less susceptible to conscious or affective regulation, namely, range of lordosis and estimated segmental mobility. This effect was magnified with increased load. Self-assessment scores were significantly poorer among insurance referrals, regardless of functional status.

CONCLUSIONS

Simple parameters of the functional examination, such as range of motion and velocity, are strongly correlated with cognitive state, and thus the information they supply is less than ideal. Complex spinal coordination is a better indicator of the degree of spinal dysfunction and enhances the process of differentiating between pain, disability, and functional impairment.

Activated 3',5'-cyclic AMP-dependent protein kinase is sufficient to induce neuroendocrine-like differentiation of the LNCaP prostate tumor cell line

Neuroendocrine (NE) differentiation within prostate tumors is proposed to be a contributing factor in disease progression. However, the cellular origin and molecular mechanism controlling differentiation of prostatic NE cells are unresolved. The prostate tumor cell line, LNCaP, can reversibly acquire many NE characteristics in response to treatment with beta-adrenergic receptor agonists and activators of adenylate cyclase. In this study, we demonstrate that these treatments induce protein kinase A (PKA) activation in LNCaP cells and that ectopic expression of a constitutively activated form of the PKA catalytic subunit, CIalpha, results in acquisition of NE characteristics, including the extension of neuritic processes, cessation of mitotic activity, and production of neuron-specific enolase. Forskolin-, epinephrine-, and isoproterenol-dependent NE differentiation of LNCaP cells was significantly inhibited by expressing a dominant negative mutant of the PKA regulatory subunit, RIalpha. These results demonstrate that prostatic NE differentiation in response to these agents depends on PKA activation, and this signaling pathway may provide a therapeutic target for treating advanced forms of prostate cancer.

Acquisition of neuroendocrine characteristics by prostate tumor cells is reversible: implications for prostate cancer progression

Neuroendocrine (NE) cells occur as scattered foci within prostatic adenocarcinoma, similar to their distribution within ductal epithelial cells of the normal prostate. However, the density of NE cells is often greater in prostate carcinomas than in normal tissue, and the frequency of NE cells correlates with tumor grade, loss of androgen sensitivity, autocrine/paracrine activity, and poor prognosis. Although NE cells are nonmitotic, proliferating cells are found in direct proximity to them, suggesting that NE cells provide paracrine stimuli for surrounding carcinoma cells. In vitro, differentiation of the LNCaP and PC3M prostatic tumor cell lines to a NE phenotype can be induced by dibutyryl cyclic AMP (cAMP), suggesting that physiological agents that increase intracellular concentrations of cAMP might regulate NE differentiation in vivo. Indeed, we demonstrate in this report that LNCaP cells acquire NE characteristics in response to treatment with physiological and pharmacological agents that elevate intracellular cAMP, agents such as epinephrine, isoproterenol, forskolin, and dibutyryl cAMP. The androgen-independent LNCaP-derived cell line C4-2 also responded to these agents, indicating that cells representing later stages of tumor progression are also capable of differentiation. The NE phenotype in this study was monitored by the appearance of dense core granules in the cytoplasm, the extension of neuron-like processes, loss of mitogenic activity, and expression of the NE markers neuron-specific enolase, parathyroid hormone-related peptide, neurotensin, serotonin, and chromogranin A. However, contrary to previous reports, we observed rapid loss of the NE phenotype in both LNCaP and C4-2 cells upon withdrawal of inducing agents. Withdrawal also resulted in a rapid, dramatic increase in tyrosine kinase and mitogen-activated protein kinase activities, suggesting that activation of these intracellular signaling enzymes may be important for reentry into the cell cycle. Together, these results indicate that chronic cAMP-mediated signaling is required to block proliferation of prostate tumor cells and to induce NE differentiation.

c-Src-mediated phosphorylation of the epidermal growth factor receptor on Tyr845 and Tyr1101 is associated with modulation of receptor function

Accumulating evidence indicates that interactions between the epidermal growth factor receptor (EGFR) and the nonreceptor tyrosine kinase c-Src may contribute to an aggressive phenotype in multiple human tumors. Previous work from our laboratory demonstrated that murine fibroblasts which overexpress both these tyrosine kinases display synergistic increases in DNA synthesis, soft agar growth, and tumor formation in nude mice, and increased phosphorylation of the receptor substrates Shc and phospholipase gamma as compared with single overexpressors. These parameters correlated with the ability of c-Src and EGFR to form an EGF-dependent heterocomplex in vivo. Here we provide evidence that association between c-Src and EGFR can occur directly, as shown by receptor overlay experiments, and that it results in the appearance of two novel tyrosine phosphorylations on the receptor that are seen both in vitro and in vivo following EGF stimulation. Edman degradation analyses and co-migration of synthetic peptides with EGFR-derived tryptic phosphopeptides identify these sites as Tyr845 and Tyr1101. Tyr1101 lies within the carboxyl-terminal region of the EGFR among sites of receptor autophosphorylation, while Tyr845 resides in the catalytic domain, in a position analogous to Tyr416 of c-Src. Phosphorylation of Tyr416 and homologous residues in other tyrosine kinase receptors has been shown to be required for or to increase catalytic activity, suggesting that c-Src can influence EGFR activity by mediating phosphorylation of Tyr845. Indeed, EGF-induced phosphorylation of Tyr845 was increased in MDA468 human breast cancer cells engineered to overexpress c-Src as compared with parental MDA 468 cells. Furthermore, transient expression of a Y845F variant EGFR in murine fibroblasts resulted in an ablation of EGF-induced DNA synthesis to nonstimulated levels. Together, these data support the hypothesis that c-Src-mediated phosphorylation of EGFR Tyr845 is involved in regulation of receptor function, as well as in tumor progression.

Gonadotropin-releasing hormone pulses are required to maintain activation of mitogen-activated protein kinase: role in stimulation of gonadotrope gene expression

The present study examined the effect of alterations in GnRH signal pattern (pulsatile vs. continuous; pulse frequency) on mitogen-activated protein kinase (MAPK) activity and whether MAPK plays a role in regulating gonadotrope gene expression. Pituitary MAPK activity was measured by immunoblot, using a phospho-specific MAPK antibody, corrected to the amount of total MAPK per sample. In vivo studies were conducted in adult castrate testosterone-replaced male rats (to suppress endogenous GnRH). Animals received pulsatile or continuous GnRH (or BSA-saline for controls) via jugular cannulas. Initial studies revealed that pulsatile GnRH stimulated a dose-dependent rise in MAPK activity (30 ng, 2-fold increase; 100 ng, 4-fold; 300 ng, 8-fold) 4 min after the pulse. The effect of pulsatile vs. continuous GnRH was examined by administering 50-ng pulses (60-min interval) or a continuous infusion (25 ng/min) for 1, 2, 4, or 8 h. Pulsatile GnRH stimulated a 2- to 4-fold rise in MAPK activity (P < 0.05 vs. controls) that was maintained over the 8-h duration. In contrast, continuous GnRH only increased MAPK activity (2- to 3-fold; P < 0.05 vs. controls) for 2 h, with MAPK activity returning to baseline at later time points. The effect of GnRH pulse frequency on MAPK activation was determined by giving GnRH pulses (50 ng) at 30-, 60-, or 120-min intervals for 8 h. Maximal increases (3-fold vs. controls; P < 0.05) were seen after 120-min pulses, with faster (30- to 60-min interval) pulses stimulating 2-fold increases in MAPK activity (P < 0.05 vs. controls and 120-min GnRH pulse group). The role of MAPK activation on gonadotrope (alpha, LHbeta, FSHbeta, and GnRH receptor) gene expression was determined in vitro. Preliminary studies demonstrated that the MAPK inhibitor, PD-098059 (50 microM), completely blocked GnRH-induced increases in MAPK activity in adult male pituitary cells. Further studies revealed that PD-098059 blocked gonadotrope messenger RNA (mRNA) responses to pulsatile GnRH (100 pg/ml, 60-min interval, 24-h duration) in a selective manner, with alpha, FSHbeta, and GnRH receptor (but not LHbeta) mRNA responses being suppressed. These results show that a pulsatile GnRH signal is required to maintain MAPK activation for durations of longer than 2 h, and that slower frequency pulses are more effective. Further, MAPK plays a crucial role in alpha, FSHbeta, and GnRH receptor mRNA responses to pulsatile GnRH. Thus, divergent MAPK responses to alterations in GnRH signal pattern may be one mechanism involved in differential regulation of gonadotrope gene expression.

Characterization of graf, the GTPase-activating protein for rho associated with focal adhesion kinase. Phosphorylation and possible regulation by mitogen-activated protein kinase

Graf is a GTPase-activating protein for Rho that interacts with focal adhesion kinase and co-localizes with the actin cytoskeleton (Hildebrand, J. D., Taylor, J. M. and Parsons, J. T. (1996) Mol. Cell. Biol. 16, 3169-3178). We examined the expression and regulation of Graf as a prelude to understanding the role of Graf in mediating signal transduction in vivo. We demonstrated that Graf is a ubiquitously expressed 95-kDa protein with high levels observed in heart and brain and cells derived from these tissues. Stimulation of PC12 cells with epidermal growth factor or nerve growth factor induced a phosphatase-reversible mobility shift upon gel electrophoresis, indicative of phosphorylation. In vitro, purified mitogen-activated protein (MAP) kinase catalyzed the phosphorylation of Graf on serine 510, suggesting that Graf phosphorylation may be mediated through MAP kinase signaling. In addition, the mutation of serine 510 to alanine inhibited the epidermal growth factor-induced mobility shift of mutant Graf protein in vivo, consistent with serine 510 being the site of in vivo phosphorylation. Based on these data we suggest that phosphorylation of Graf by MAP kinase or related kinases may be a mechanism by which growth factor signaling modulates Rho-mediated cytoskeletal changes in PC12 and perhaps other cells.

CNP2 mRNA directs synthesis of both CNP1 and CNP2 polypeptides

The ribosome scanning model for translational initiation predicts that eukaryotic mRNAs should, as a rule, be monocistronic. However, cases have recently been described of eukaryotic mRNAs producing more than one protein through alternative translational initiation at several different AUG codons. The present work reports the occurrence of two translational start sites on the mRNA encoding isoform 2 of the myelin marker enzyme 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) in rat and mouse. We show that the CNP2 mRNA is able to direct synthesis of not only CNP2, but also CNP1 polypeptide. Immunoprecipitation experiments using a polyclonal antibody directed against CNP detect both CNP isoforms in tissues or cell lines expressing only the CNP2 transcript. Thus, the synthesis of CNP1 and CNP2 polypeptides must be encoded by the CNP2 transcript. In vitro translation of synthetic CNP2 mRNA demonstrates that both CNP isoforms are synthesized by initiation at different AUG codons. Furthermore, by introducing mutations to "switch off" translation from the second in-frame AUG codon in the CNP2 cDNA, and transfecting 293T cells with those constructs, we are able to correlate the production of CNP1 and CNP2 with different translational start sites. These results lead us to conclude that the CNP2 mRNA is able to produce both CNP1 and CNP2 polypeptides. This investigation has altered our understanding of the temporal expression of the CNP protein isoforms during development of the central nervous system (CNS).

Roles for protein kinase C and mitogen-activated protein kinase in nicotine-induced secretion from bovine adrenal chromaffin cells

Both the Ca2+/phospholipid-dependent protein kinases (protein kinases C, PKCs) and mitogen-activated protein kinases (MAPKs) have been implicated as participants in the secretory response of bovine adrenomedullary chromaffin cells. To investigate a possible role for these kinases in exocytosis and the relationship of these kinases to one another, intact chromaffin cells were treated with agents that inhibited each of the kinases and analyzed for catecholamine release and MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK)/MAPK activation after stimulation with secretagogues of differential efficacy. Of the three secretagogues tested, inactivation of PKCs by long-term phorbol 12-myristate 13-acetate (PMA) treatment or incubation with GF109203X had the greatest inhibitory effect on nicotine-induced catecholamine release and MEK/MAPK activation, a moderate effect on KCl-induced events, and little, if any, effect on Ca2+ ionophore-elicited exocytosis and MEK/MAPK activation. These results indicate that PKC plays a significant role in events induced by the optimal secretagogue nicotine and a lesser role in exocytosis elicited by the suboptimal secretagogues KCl and Ca2+ ionophore. Treatment of cells with the MEK-activation inhibitor PD098059 completely inhibited MEK/MAPK activation (IC50 1-5 microM) and partially inhibited catecholamine release induced by all secretagogues. However, PD098059 was more effective at inhibiting exocytosis induced by suboptimal secretagogues (IC50 approximately 10 microM) than that induced by nicotine (IC50 approximately 30 microM). These results suggest a more prominent role for MEK/MAPK in basic secretory events activated by suboptimal secretagogues than in those activated by the optimal secretagogue nicotine. However, PD098059 also partially blocked secretion potentiated by short-term PMA treatment, suggesting that PKC can function in part by signaling through MEK/MAPK to enhance secretion. Taken together, these results provide evidence for the preferential involvement of MEK/MAPK in basic secretory events activated by the suboptimal secretagogues KCl and Ca2+ ionophore and the participation of both PKC and MEK/MAPK in optimal, secretion induced by nicotine.

Tyrosine kinases are required for catecholamine secretion and mitogen-activated protein kinase activation in bovine adrenal chromaffin cells

Nicotine-induced catecholamine secretion in bovine adrenomedullary chromaffin cells is accompanied by rapid tyrosine phosphorylation of multiple cellular proteins, most notably the mitogen-activated protein kinases (MAPKs). The requirement for activation of tyrosine kinases and MAPKs in chromaffin cell exocytosis was investigated using a panel of tyrosine kinase inhibitors. Genistein and tyrphostin 23, two compounds that inhibit tyrosine kinases by distinct mechanisms, were found to inhibit secretion by > 90% in cells stimulated by nicotine, 55 mM KCl, or the Ca2+ ionophore A23187. Inhibition of secretion induced by all three secretagogues correlated with a block in both protein tyrosine phosphorylation and activation of the MAPKs and their activators (MEKs) in situ. However, neither genistein nor tyrphostin 23 inhibited the activities of the MAPKs or MEKs in vitro. These results indicate that the target(s) of inhibition lie downstream of Ca2+ influx and upstream of MEK activation. This Ca(2+)-activated tyrosine kinase activity could not be accounted for entirely by c-Src or Fyn (two nonreceptor tyrosine kinases that are expressed abundantly in chromaffin cells), because their in vitro kinase activities were not inhibited by tyrphostin 23 and only partially inhibited by genistein. These results demonstrate that an unidentified Ca(2+)-activated tyrosine kinase(s) is required for MAPK activation and exocytosis in chromaffin cells and suggest that MAPK participates in the regulation of secretion.

The Aerobic and Anaerobic Microbiology of Pustular Acne Lesions

Specimens from 32 pustular acne lesions that were inoculated on media supportive for the growth of aerobic and anaerobic bacteria showed bacterial growth. Only aerobic or facultative bacteria were recovered in 15 (47%) specimens, only anaerobic bacteria in 11 (34%) specimens, and mixed aerobic and anaerobic bacteria in 6 (18%) specimens. A total of 57 isolates, 31 anaerobes (1.0 per specimen) and 26 aerobes (0.8 per specimen) were recovered. The predominant isolates were Staphylococcus sp. (19 isolates), Peptostreptococcus sp. (15), and Propionibacterium sp. (10). Twelve (37.5%) of the comedones yielded only one organism. This retrospective study highlighted the polymicrobial nature of over two-thirds of culture positive pustular acne lesions and suggests the potential for pathogenic role of aerobic and anaerobic organisms other than P. acnes and Staphylococcus sp. in acne vulgaris.

Techniques for controlling variability in gram staining of obligate anaerobes

Identification of anaerobes recovered from clinical samples is complicated by the fact that certain gram-positive anaerobes routinely stain gram negative; Peptostreptococcus asaccharolyticus, Eubacterium plautii, Clostridium ramosum, Clostridium symbiosum, and Clostridium clostridiiforme are among the nonconformists with regard to conventional Gram-staining procedures. Accurate Gram staining of American Type Culture Collection strains of these anaerobic bacteria is possible by implementing fixing and staining techniques within a gloveless anaerobic chamber. Under anaerobic conditions, gram-positive staining occurred in all test organisms with "quick" fixing techniques with both absolute methanol and formalin. The results support the hypothesis that, when anaerobic bacteria are exposed to oxygen, a breakdown of the physical integrity of the cell wall occurs, introducing Gram stain variability in gram-positive anaerobes.

C-terminal CTII motif of 2',3'-cyclic nucleotide 3'-phosphodiesterase undergoes carboxylmethylation

Eukaryotic proteins with a carboxyl-terminal CaaX motif are modified by isoprenylation and subsequently processed by proteolysis of the three terminal amino acids and carboxylmethylation of the exposed cysteine residue. The myelination-associated 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) has a C-terminal CTII sequence and is isoprenylated; however, no examples of subsequent processing exist when threonine, a polar residue, is located adjacent to the cysteine. Here we show that CNP is capable of being carboxylmethylated in both insect cells and glioma cells. This processing is dependent upon isoprenylation of the cysteine and can be inhibited with the isoprenylated cysteine derivative, N-acetyl-S-farnesyl-L-cysteine. Although the role of the methyl group at the C-terminus of other isoprenylated proteins is not fully understood, modulation of signal transduction pathways is strongly indicated. This modification of CNP may similarly regulate cell biological processes in myelinogenesis.

Partial purification of a mitogen-activated protein kinase kinase activator from bovine brain. Identification as B-Raf or a B-Raf-associated activity

A classical biochemical approach was taken to identify mitogen-activated protein kinase kinase (MEK) activators in bovine brain. Fractionation revealed the presence of one major MEK-stimulating activity that was distinct from c-Raf-1 and MEK kinase. Similar results were obtained using bovine adrenal chromaffin cells, and in both cases, immunoblotting and immunoprecipitation experiments demonstrated co-purification of MEK activator with B-Raf. Partially purified MEK activator stimulated phosphorylation of MEK1 on residues tentatively identified as serine 218 and serine 222. Little or no MEK activator was associated with c-Raf-1 in bovine brain or chromaffin cells, although this protein was expressed, suggesting that B-Raf might be the major MEK activator in cells of neural origin.

5-lipoxygenase-activating protein stimulates the utilization of arachidonic acid by 5-lipoxygenase

5-Lipoxygenase (5-LO) and its activating protein (FLAP) are both required for cellular leukotriene (LT) synthesis, with 5-LO catalyzing both the synthesis of (5S)-5-hydroperoxy-6,8,11,14-eicosatetraenoic acid (5-HPETE) from arachidonic acid and the subsequent synthesis of LTA4 from 5-HPETE. We have previously expressed both human 5-LO and human FLAP to high levels in Spodoptera frugiperda (Sf9) insect cells, using recombinant baculoviruses. To study the mechanism by which FLAP activates 5-LO, we compared cellular 5-LO activity in Sf9 cells expressing this enzyme to that in Sf9 cells coexpressing FLAP and 5-LO. In this system, FLAP stimulates the utilization of arachidonic acid by 5-LO as a substrate, and increases the efficiency with which 5-LO converts 5-HPETE to LTA4. LT synthesis in cells coexpressing FLAP and 5-LO is inhibited by 3-[1-(p-chlorophenyl)-5-isopropyl-3-tert-butylthio-1H-indol-2-yl]-2,2- dimethyl-propanoic acid (MK-886), an LT biosynthesis inhibitor which specifically binds to FLAP. These studies in Sf9 cells, together with our recent demonstration that FLAP specifically binds arachidonic acid, suggests that FLAP activates 5-LO by acting as an arachidonic acid transfer protein.

Tyrosine phosphorylation of alpha-tubulin is an early response to NGF and pp60v-src in PC12 cells

Neuronal differentiation is accompanied by extensive reorganization of the cytoskeleton to initiate the extension of neuritic processes. We have used the rat PC12 pheochromocytoma cell line to examine the role of protein tyrosine kinase activity in the induction of these events. Immunoblotting with phosphotyrosine antibodies revealed that tyrosine phosphorylation of alpha-tubulin in PC12 cells occurred within 10 min of nerve growth factor (NGF) treatment. Tyrosine phosphorylation of alpha-tubulin also occurred on induction of pp60v-src expression in a PC12 cell line (PC12-B9) harboring an inducible v-src gene under transcriptional control of the mouse metallothionine I gene promoter. Two tyrosine phosphorylated proteins in NGF- and pp60v-src induced PC12 cells were identified as alpha-tubulin isoforms by comigration with alpha-tubulin on two-dimensional gel electrophoresis, and by immunoprecipitation with phosphotyrosine antibodies followed by immunoblotting with a monoclonal antibody specific for alpha-tubulin. These results demonstrate that alpha-tubulin is an in vivo tyrosine kinase substrate, which is phosphorylated as an early event in the neuronal differentiation pathway of PC12 cells in response to NGF or pp60v-src. Tyrosine phosphorylation of alpha-tubulin could conceivably alter microtubule dynamics during induction of neurite extension.

5-lipoxygenase-activating protein is an arachidonate binding protein

5-Lipoxygenase-activating protein (FLAP) is an 18-kDa integral membrane protein which is essential for cellular leukotriene (LT) synthesis, and is the target of LT biosynthesis inhibitors. However, the mechanism by which FLAP activates 5-LO has not been determined. We have expressed high levels of human FLAP in Spodoptera frugiperda (Sf9) insect cells infected with recombinant baculovirus, and used this system to demonstrate that FLAP specifically binds [125I]L-739,059, a novel photoaffinity analog of arachidonic acid. This binding is inhibited by both arachidonic acid and MK-886, an LT biosynthesis inhibitor which specifically interacts with FLAP. These studies suggest that FLAP may activate 5-LO by specifically binding arachidonic acid and transferring this substrate to the enzyme.

Protein tyrosine kinases in nervous system development

Protein tyrosine kinases are important mediators of intracellular signaling during nervous system development. Activation of receptor protein tyrosine kinases by neurotrophic factors are initial events in the development of discrete cell populations. The patterns of expression and characterization of substrates for nonreceptor protein tyrosine kinases indicates that they also play a crucial role in neuronal development. The observed functional redundancy among protein tyrosine kinases and their associated intracellular signaling pathways underscores the need for further characterization of these novel interactions to elucidate the mechanisms regulating nervous system development.

Neurite extension and protein tyrosine phosphorylation elicited by inducible expression of the v-src oncogene in a PC12 cell line

Tyrosine-specific protein kinase activity in neuronal differentiation was studied in a PC12 pheochromocytoma cell line (PC12-B9) produced by stable transfection with an inducible v-src gene encoding an activated tyrosine kinase (pp60v-src) under the transcriptional control of the mouse metallothionine I gene promoter. Induction of pp60v-src expression with Cd2+ and Zn2+ resulted in the reversible differentiation of PC12-B9 cells into neuron-like cells. pp60v-src elicited morphological differentiation with apparent first order kinetics at the same rate as NGF-directed neurite outgrowth in PC12-B9 cells. v-src gene expression enhanced the rate of NGF-directed neurite extension in an additive manner. Induction of pp60v-src alone constitutively increased the levels of phosphotyrosine-modified proteins (130-120, 90, 83, 65, 60/59, 36 kDa) detected by immunoblotting with phosphotyrosine antibodies. NGF treatment of PC12-B9 cells transiently increased the levels of distinct phosphotyrosine-modified proteins (108, 46, 42 kDa), as well as common substrates, including a 59-kDa protein that comigrated with alpha-tubulin. Phosphotyrosine-modified proteins were not synergistically increased in PC12-B9 cells induced for both v-src and NGF. The nonsynergistic effects of v-src gene expression on neurite outgrowth and phosphorylation suggest that pp60v-src induces PC12 cell differentiation by an intracellular signaling pathway that is largely distinct from that induced by NGF.

c-src and other proto-oncogenes implicated in neuronal differentiation

The proto-oncogene c-src has been implicated in the development and mature function of the nervous system. pp60c-src, the protein product of the c-src gene, is a tyrosine protein kinase that is highly enriched in fetal neural tissue. pp60c-src appears in two phases of neuronal development. Neuroectodermal cells of gastrulating embryos first express pp60c-src around the time of commitment to neuronal or glial pathways. Later, committed neuroepithelial cells express pp60c-src near the onset of terminal neuronal differentiation. Immunocytochemical analyses of pp60c-src in developing chick retina, telencephalon, and cerebellum show immunoreactivity concentrated in regions rich in growth cones and neurites. Moreover, pp60c-src is concentrated approximately 10-fold in a biochemical fraction from fetal rat brain that is enriched in nerve growth cone membranes. These results point toward a function for pp60c-src in neurite outgrowth. A functional role for other proto-oncogenes in the development of the nervous system was indicated from a study of the expression of a battery of proto-oncogenes during the retinoic acid-induced differentiation of the mouse embryonal carcinoma cell line P19 to a neuronal phenotype. Nuclear runoff transcription of the proto-oncogenes c-src, c-fms, c-sis, N-ras, c-myc, and c-fos was observed in proliferating and retinoic acid-treated cells.

Neutrophil uptake of vaccinia virus in vitro

We studied human neutrophils for uptake of vaccinia virus. Uptake was determined radiometrically and by electron microscopy. Vaccinia virus was labeled with 14C or 3H, incubated with neutrophils, and quantified in neutrophil pellets in a new radiometric phagocytosis assay. Better results were obtained from assays of [3H]thymidine-labeled virus; uptake increased through 1 hr and then plateaued. Phagocytosis of 3H-labeled Staphylococcus aureus was normal. Uptake of virus was serum dependent. Hexose monophosphate shunt activity was measured by two methods. No 14CO2 from [14C]1-glucose accompanied uptake of vaccinia virus, in contrast to the respiratory burst accompanying bacterial phagocytosis. Electron microscopy showed intact to slightly digested intraphagolysosomal vaccinia virus. Pock reduction assay showed a decrease in viral content due to neutrophils until 6 hr of incubation, when a modest but significant increase was observed. Thus, neutrophil uptake of vaccinia virus is distinguished from bacterial phagocytosis.

A tyrosine kinase related to pp60c-src is associated with membranes of Electrophorus electricus electric organ

A tyrosine-specific protein kinase immunologically related to pp60c-src, the cellular homolog of the Rous sarcoma virus-transforming protein, was expressed at elevated levels in the electric organ of the electric eel Electrophorus electricus. The electric organ kinase phosphorylated antibodies reactive with pp60c-src at tyrosine residues in immune complex protein kinase assays and was associated with electric organ membranes enriched in acetylcholine receptors. The protein recognized by anti-pp60c-src antibodies was phosphorylated in endogenous membrane phosphorylation reactions and was shown to have a relative molecular mass of 57 kDa by two-dimensional gel electrophoresis. In immune complex protein kinase assays the 57-kDa protein was phosphorylated at threonine by a distinct threonine kinase from the electric organ. The tyrosine kinase was purified 844-fold from electric organ membranes by chromatography on omega-aminohexyl agarose, phosphocellulose, and casein-Sepharose. Threonine kinase activity in immunoprecipitates was not observed in the tyrosine kinase fractions after the first step. Incubation of the casein Sepharose fraction with [gamma-32P]ATP-Mn2+ in solution resulted in phosphorylation of only the 57-kDa protein. Phosphorylation occurred solely at tyrosine, suggesting that the kinase is capable of autophosphorylation. The structural and functional properties of the 57-kDa electric organ kinase indicate that the 57-kDa electric organ protein is a member of the src subfamily of tyrosine kinases and is closely related to pp60c-src.

Methanol fixation. An alternative to heat fixation of smears before staining

Methanol fixation of Gram-stained smears was compared to heat fixation. Smears were prepared in duplicate from direct clinical specimens, blood culture bottles, and bacterial colonies. Results from this study show that methanol fixation is superior in every instance to heat fixation. The morphology of bacteria and tissue cells was not distorted, little or no background debris was observed, and a better Gram reaction was noted.

Distribution of fallout cesium-137 in Hawaii

The concentration of 137Cs was determined by gamma spectrometry in soils and surface-deposited volcanic sublimates from various climatic locations on the islands of Hawaii, Oahu and Maui. A distinct pattern of higher concentrations on the wetter windward sides of the islands and a correlation between 137Cs concentration and amount of rainfall were observed, which confirm the source of the 137Cs as atmospheric fallout. In the soils, the concentrations measured (to 1.93 pCi/g) are within the range reported for the continental United States and other mid-latitude locations in the northern hemisphere. In the basaltic lavas, the concentration of 137Cs was found to be variable but was overall very low, and is apparently controlled by the porosity and permeability of the lavas in addition to rainfall.

Zinc and the special senses

There is evidence that zinc is important for maintenance of the special senses: vision, taste, and smell. Rod function is impaired in zinc deficiency due partly to its role in vitamin A metabolism. However, optic nerve function may also be affected by zinc status. Microophthalmia, anophthalmia, and optic nerve abnormalities have all been found in the offspring of female rats fed zinc-deficient diets. Zinc deficiency clearly decreases taste acuity in both animals and humans. However, other nutritional and non-nutritional conditions also produce hypogeusia. There is limited evidence that zinc deficiency impairs olfactory acuity in humans. New approaches to the assessment of taste and smell abnormalities may provide reliable and reproducible associations between zinc deficiency and taste and smell defects.