Combined CCNE1 high-level amplification and overexpression is associated with unfavourable outcome in tubo-ovarian high-grade serous carcinoma

CCNE1 amplification is a recurrent alteration associated with unfavourable outcome in tubo‐ovarian high‐grade serous carcinoma (HGSC). We aimed to investigate whether immunohistochemistry (IHC) can be used to identify CCNE1 amplification status and to validate whether CCNE1 high‐level amplification and overexpression are prognostic in HGSC. A testing set of 528 HGSC samples stained with two optimised IHC assays (clones EP126 and HE12) was subjected to digital image analysis and visual scoring. DNA and RNA chromogenic in situ hybridisation for CCNE1 were performed. IHC cut‐off was determined by receiver operating characteristics (ROC). Survival analyses (endpoint ovarian cancer specific survival) were performed and validated in an independent validation set of 764 HGSC. Finally, combined amplification/expression status was evaluated in cases with complete data (n = 1114). CCNE1 high‐level amplification was present in 11.2% of patients in the testing set and 10.2% in the combined cohort. The optimal cut‐off for IHC to predict CCNE1 high‐level amplification was 60% positive tumour cells with at least 5% strong staining cells (sensitivity 81.6%, specificity 77.4%). CCNE1 high‐level amplification and overexpression were associated with survival in the testing and validation set. Combined CCNE1 high‐level amplification and overexpression was present in 8.3% of patients, mutually exclusive to germline BRCA1/2 mutation and significantly associated with a higher risk of death in multivariate analysis adjusted for age, stage and cohort (hazard ratio = 1.78, 95 CI% 1.38–2.26, p < 0.0001). CCNE1 high‐level amplification combined with overexpression identifies patients with a sufficiently poor prognosis that treatment alternatives are urgently needed. Given that this combination is mutually exclusive to BRCA1/2 germline mutations, a predictive marker for PARP inhibition, CCNE1 high‐level amplification combined with overexpression may serve as a negative predictive test for sensitivity to PARP inhibitors.

(18)F-fluorodeoxyglucose positron-emission tomography-computed tomography to diagnose recurrent cancer

Background:

Sometimes the diagnosis of recurrent cancer in patients with a previous malignancy can be challenging. This prospective cohort study assessed the clinical utility of ¹⁸F-fluorodeoxyglucose positron-emission tomography-computed tomography (¹⁸F-FDG PET-CT) in the diagnosis of clinically suspected recurrence of cancer.

Methods:

Patients were eligible if cancer recurrence (non-small-cell lung (NSCL), breast, head and neck, ovarian, oesophageal, Hodgkin's or non-Hodgkin's lymphoma) was suspected clinically, and if conventional imaging was non-diagnostic. Clinicians were asked to indicate their management plan before and after ¹⁸F-FDG PET-CT scanning. The primary outcome was change in planned management after ¹⁸F-FDG PET-CT.

Results:

Between April 2009 and June 2011, 101 patients (age, median 65 years; 55% female) were enroled from four cancer centres in Ontario, Canada. Distribution by primary tumour type was: NSCL (55%), breast (19%), ovarian (10%), oesophageal (6%), lymphoma (6%), and head and neck (4%). Of the 99 subjects who underwent ¹⁸F-FDG PET-CT, planned management changed after ¹⁸F-FDG PET-CT in 52 subjects (53%, 95% confidence interval (CI), 42–63%); a major change in plan from no treatment to treatment was observed in 38 subjects (38%, 95% CI, 29–49%), and was typically associated with ¹⁸F-FDG PET-CT findings that were positive for recurrent cancer (37 subjects). After 3 months, the stated post-¹⁸F-FDG PET-CT management plan was actually completed in 88 subjects (89%, 95% CI, 81–94%).

Conclusion:

In patients with suspected cancer recurrence and conventional imaging that is non-diagnostic, ¹⁸F-FDG PET-CT often provides new information that leads to important changes in patient management.

Polar freshwater cyanophage S-EIV1 represents a new widespread evolutionary lineage of phages

Cyanobacteria are often the dominant phototrophs in polar freshwater communities; yet, the phages that infect them remain unknown. Here, we present a genomic and morphological characterization of cyanophage S-EIV1 that was isolated from freshwaters on Ellesmere Island (Nunavut, High Arctic Canada), and which infects the polar Synechococcus sp., strain PCCC-A2c. S-EIV1 represents a newly discovered evolutionary lineage of bacteriophages whose representatives are widespread in aquatic systems. Among the 130 predicted open reading frames (ORFs) there is no recognizable similarity to genes that encode structural proteins other than the large terminase subunit and a distant viral morphogenesis protein, indicating that the genes encoding the structural proteins of S-EIV1 are distinct from other viruses. As well, only 19 predicted coding sequences on the 79 178 bp circularly permuted genome have homology with genes encoding proteins of known function. Although S-EIV1 is divergent from other sequenced phage isolates, it shares synteny with phage genes captured on a fosmid from the deep-chlorophyll maximum in the Mediterranean Sea, as well as with an incision element in the genome of Anabaena variabilis (ATCC 29413). Sequence recruitment of metagenomic data indicates that S-EIV1-like viruses are cosmopolitan and abundant in a wide range of aquatic systems, suggesting they have an important ecological role.

Dynamics and Distribution of Cyanophages and Their Effect on Marine Synechococcus spp

Cyanophages infecting marine Synechococcus cells were frequently very abundant and were found in every seawater sample along a transect in the western Gulf of Mexico and during a 28-month period in Aransas Pass, Tex. In Aransas Pass their abundance varied seasonally, with the lowest concentrations coincident with cooler water and lower salinity. Along the transect, viruses infecting Synechococcus strains DC2 and SYN48 ranged in concentration from a few hundred per milliliter at 97 m deep and 83 km offshore to ca. 4 x 10 ml near the surface at stations within 18 km of the coast. The highest concentrations occurred at the surface, where salinity decreased from ca. 35.5 to 34 ppt and Synechococcus concentrations were greatest. Viruses infecting strains SNC1, SNC2, and 838BG were distributed in a similar manner but were much less abundant (<10 to >5 x 10 ml). When Synechococcus concentrations exceeded ca. 10 ml, cyanophage concentrations increased markedly (ca. 10 to > 10 ml), suggesting that a minimum host density was required for efficient viral propagation. Data on the decay rate of viral infectivity d (per day), as a function of solar irradiance I (millimoles of quanta per square meter per second), were used to develop a relationship (d = 0.2610I - 0.00718; r = 0.69) for conservatively estimating the destruction of infectious viruses in the mixed layer of two offshore stations. Assuming that virus production balances losses and that the burst size is 250, ca. 5 to 7% of Synechococcus cells would be infected daily by viruses. Calculations based on contact rates between Synechococcus cells and infectious viruses produce similar results (5 to 14%). Moreover, balancing estimates of viral production with contact rates for the farthest offshore station required that most Synechococcus cells be susceptible to infection, that most contacts result in infection, and that the burst size be about 324 viruses per lytic event. In contrast, in nearshore waters, where ca. 80% of Synechococcus cells would be contacted daily by infectious cyanophages, only ca. 1% of the contacts would have to result in infection to balance the estimated virus removal rates. These results indicate that cyanophages are an abundant and dynamic component of marine planktonic communities and are probably responsible for lysing a small but significant portion of the Synechococcus population on a daily basis.

Use of ultrafiltration to isolate viruses from seawater which are pathogens of marine phytoplankton

Viruses may be major structuring elements of phytoplankton communities and hence important regulators of nutrient and energy fluxes in aquatic environments. In order to ascertain whether viruses are potentially important in dictating phytoplankton community structure, it is essential to determine the extent to which representative phytoplankton taxa are susceptible to viral infection. We used a spiral ultrafiltration cartridge (30,000-molecular-weight cutoff) to concentrate viruses from seawater at efficiencies approaching 100%. Natural virus communities were concentrated from stations in the Gulf of Mexico, a barrier island pass, and a hypersaline lagoon (Laguna Madre) and added to cultures of potential phytoplankton hosts. By following changes in in vivo fluorescence over time, it was possible to isolate several viruses that were pathogens to a variety of marine phytoplankton, including a prasinophyte (Micromonas pusilla), a pennate diatom (likely a Navicula sp.), a centric diatom (of unknown taxa), and a chroococcoid cyanobacterium (a Synechococcus sp.). As well, we observed changes in fluorescence in cultures of a cryptophyte (a Rhodomonas sp.) and a chlorophyte (Nannochloropsis oculata) which were consistent with the presence of viral pathogens. Although pathogens were isolated from all stations, all the pathogens were not isolated from every station. Filterability studies on the viruses infecting M. pusilla and the Navicula sp. showed that the viruses were consistently infective after filtration through polycarbonate and glass-fiber filters but were affected by most other filter types. Establishment of phytoplankton-pathogen systems will be important in elucidating the effect that viruses have on primary producers in aquatic systems.

Serum withdrawal and etoposide induce apoptosis in human lung carcinoma cell line A549 via distinct pathways

The molecular events associated with apoptosis induced by two distinct triggers (1) serum withdrawal and (2) etoposide treatment were investigated in the human lung carcinoma cell line A549. Although both serum withdrawal and etoposide treatment resulted in internucleosomal DNA fragmentation, the morphologic features were distinct. Serum deprived apoptotic cells appeared small, round and refractile, with little evidence of nuclear fragmentation; etoposide-induced apoptotic cells appeared enlarged and flattened and displayed prominent nuclear fragmentation. p53 and p21/waf1 protein levels were elevated in etoposide-treated cells, but not in cells subjected to serum with-drawal. Apoptosis induced by both treatments was accompanied by a significant reduction in Rb protein levels. However, etoposide treatment led to hypo-phosphorylation of Rb, while serum withdrawal did not alter the Rb phosphorylation pattern. Serum withdrawal-induced apoptosis was correlated with activation of JNK and suppression of ERK activities, while both JNK and ERK activities were slightly elevated during etoposid- induced apoptosis. Together, these results support the hypothesis that apoptosis induced by serum withdrawal and etoposide treatment occurs through different pathways and involves distinct mediators.

KLF6, a candidate tumor suppressor gene mutated in prostate cancer

Kruppel-like factor 6 (KLF6) is a zinc finger transcription factor of unknown function. Here, we show that the KLF6 gene is mutated in a subset of human prostate cancer. Loss-of-heterozygosity analysis revealed that one KLF6 allele is deleted in 77% (17 of 22) of primary prostate tumors. Sequence analysis of the retained KLF6 allele revealed mutations in 71% of these tumors. Functional studies confirm that whereas wild-type KLF6 up-regulates p21 (WAF1/CIP1) in a p53-independent manner and significantly reduces cell proliferation, tumor-derived KLF6 mutants do not. Our data suggest that KLF6 is a tumor suppressor gene involved in human prostate cancer.

Regulation of PTEN binding to MAGI-2 by two putative phosphorylation sites at threonine 382 and 383

We have reported previously that the PTEN COOH-terminal 33 amino acids play a role in the maintenance of PTEN protein stability (Tolkacheva and Chan, Oncogene, 19: 680-689, 2000). By site-directed mutagenesis, we identified two threonine residues within this COOH-terminal region at codon 382 and 383 that may be targets for phosphorylation events. Interestingly, PTEN mutants rendered phosphorylation-incompetent at these two sites, T382A/T383A, and were found to have drastically reduced expression in cultured cells. The enhanced degradation of PTEN was most likely mediated by the proteosome-dependent pathway, we have evidence that PTEN was polyubiquitinated. More interestingly, the non-phosphorylated forms of PTEN displayed significantly greater binding affinity than the wild-type protein to a previously identified PTEN interacting partner, MAGI-2/ARIP1. On the basis of all these data, we propose that PTEN recruitment to the cell-cell junction may be regulated through the phosphorylation of its COOH terminus.

Axillary vein thrombosis secondary to congenital stricture in a left-sided superior vena cava

We describe a case of axillary vein thrombosis secondary to unusual venous anatomy. A patient with a strictured left-sided superior vena cava and axillary vein thrombosis was successfully treated with thrombolysis. The underlying stricture was treated with angioplasty and stenting.

Regulatory proteins of R-Ras, TC21/R-Ras2, and M-Ras/R-Ras3

We studied the regulation of three closely related members of Ras family G proteins, R-Ras, TC21 (also known as R-Ras2), and M-Ras (R-Ras3). Guanine nucleotide exchange of R-Ras and TC21 was promoted by RasGRF, C3G, CalDAG-GEFI, CalDAG-GEFII (RasGRP), and CalDAG-GEFIII both in 293T cells and in vitro. By contrast, guanine nucleotide exchange of M-Ras was promoted by the guanine nucleotide exchange factors (GEFs) for the classical Ras (Ha-, K-, and N-), including mSos, RasGRF, CalDAG-GEFII, and CalDAG-GEFIII. GTPase-activating proteins (GAPs) for Ras, Gap1(m), p120 GAP, and NF-1 stimulated all of the R-Ras, TC21, and M-Ras proteins, whereas R-Ras GAP stimulated R-Ras and TC21 but not M-Ras. We did not find any remarkable difference in the subcellular localization of R-Ras, TC21, or M-Ras when these were expressed with a green fluorescent protein tag in 293T cells and MDCK cells. In conclusion, TC21 and R-Ras were regulated by the same GEFs and GAPs, whereas M-Ras was regulated as the classical Ras.

Transforming growth factor-beta 1 suppresses serum deprivation-induced death of A549 cells through differential effects on c-Jun and JNK activities

Transforming growth factor (TGF)-beta1, a pleiotropic cytokine involved in regulating growth and differentiation, can exert both pro-apoptotic and anti-apoptotic effects depending on the cell type or circumstances. We observed that TGF-beta1 blocked apoptosis resulting from serum withdrawal in A549 human lung carcinoma cells. This was associated with suppression of JNK activation that occurs concomitant with the onset of apoptosis in the absence of TGF-beta1, suggesting that JNK plays an active role in the death process and that TGF-beta1 exerts its protective influence by altering JNK activity. Overexpression of a dominant negative mutant form of SEK1, an upstream activator of JNK, likewise suppressed JNK activation and inhibited apoptosis. Investigation of early events following TGF-beta1 treatment revealed an early induction and phosphorylation of c-Jun that was absent in cells subjected to serum withdrawal alone. That TGF-beta1-induced expression of c-Jun is important for survival was supported by the finding that overexpression of non-phosphosphorylatable dominant negative mutant c-Jun, c-Jun(S73A), attenuated the protective influence of TGF-beta1. Our findings suggest that JNK activation is a late but essential event in serum deprivation-induced apoptosis in A549 cells. TGF-beta1 prevents apoptosis, in part, through the early induction and phosphorylation of c-Jun, which in turn results in attenuated JNK activation.

R-Ras3, a brain-specific Ras-related protein, activates Akt and promotes cell survival in PC12 cells

The GTP-binding protein, R-Ras3/M-Ras, is a novel member of the Ras subfamily of GTPases which shows highest sequence similarity to the TC21 gene. R-Ras3 is highly expressed in both human and mouse brain and ectopic expression of a constitutively active mutant of R-Ras3 induces cellular transformation in NIH3T3 cells. To gain further insight into the normal cellular function of R-Ras3, we examined the ability of R-Ras3 in activating several known intracellular signaling cascades. We observed that R-Ras3 is a relatively weak activator of the mitogen-activated protein kinase/extracellular-signal-regulated kinases (MAPK/ERKs) when compared to the H-Ras oncogene. On the contrary, both R-Ras3 and H-Ras activated the Jun N-terminal kinase (JNK) to a similar extent. Under similar experimental conditions, R-Ras3 significantly stimulated one of the phosphatidylinositol 3-kinase (PI3-K) downstream substrates, Akt/PKB/RAC (Akt), which has been extensively implicated in mediating cell survival signaling. The activation of Akt by R-Ras3 was most likely to be PI3-K-dependent since this biochemical event was blocked by the pharmacological inhibitors, Wortmannin and LY294002, as well as by a dominant negative mutant of PI3-K. More importantly, R-Ras3 affinity-precipitated PI3-K from cell extracts in a GTP-dependent manner, and associated lipid kinase activity was readily detectable in R-Ras3 immune complexes. The biological significance of R-Ras3 in inducing Akt kinase activity is evidenced by the ability of an activated R-Ras3 to confer cell survival in the rat pheochromocytoma cell line, PC12. As expected, this biological activity of R-Ras3 was also abrogated by the addition of LY294002. Thus, R-Ras3 represents a novel G-protein which may play a role in cell survival of neural-derived cells.

Inhibition of H-Ras transformation by the PTEN/MMAC1/TEP1 tumor suppressor gene

The human PTEN/MMAC1/TEP1 (PTEN) tumor suppressor gene encodes a phosphatase with specificity towards the D3 phosphate of phosphatidylinositides. PTEN mutations have been reported in the endometrioid type of uterine tumors which are associated with frequent activations of the Ras oncogenes. In this study, we report the ability of PTEN to potently inhibit H-Ras induced morphological transformation and anchorage-independent growth in NIH3T3 cells. This novel activity of PTEN was correlated more with its ability to suppress the phosphatidylinositol 3-kinase (PI3-K)-dependent signaling cascade, but not the mitogen-activated protein kinase (MAPK) pathway. To define the minimal region in PTEN protein that is responsible for this anti-oncogenic activity, a panel of carboxyl-terminal truncation mutants was generated. While deletions of 4 and 33 amino acids do not have marked effects, removal of up to 68 amino acids drastically reduced the ability of PTEN to inhibit Ras transformation. The propensity of these mutants to suppress Ras transformation is correlated with their relative ability to dephosphorylate inositol (1,3,4,5)-tetrakisphosphate in vitro, and to suppress Akt kinase activity in cultured cells. In addition, we have evidence to suggest that the C-terminal region of PTEN contributes to the stability of the encoded gene product.

Differential roles of Akt, Rac, and Ral in R-Ras-mediated cellular transformation, adhesion, and survival

Multiple biological functions have been ascribed to the Ras-related G protein R-Ras. These include the ability to transform NIH 3T3 fibroblasts, the promotion of cell adhesion, and the regulation of apoptotic responses in hematopoietic cells. To investigate the signaling mechanisms responsible for these biological phenotypes, we compared three R-Ras effector loop mutants (S61, G63, and C66) for their relative biological and biochemical properties. While the S61 mutant retained the ability to cause transformation, both the G63 and the C66 mutants were defective in this biological activity. On the other hand, while both the S61 and the C66 mutants failed to promote cell adhesion and survival in 32D cells, the G63 mutant retained the ability to induce these biological activities. Thus, the ability of R-Ras to transform cells could be dissociated from its propensity to promote cell adhesion and survival. Although the transformation-competent S61 mutant bound preferentially to c-Raf, it only weakly stimulated the mitogen-activated protein kinase (MAPK) activity, and a dominant negative mutant of MEK did not significantly perturb R-Ras oncogenicity. Instead, a dominant negative mutant of phosphatidylinositol 3-kinase (PI3-K) drastically inhibited the oncogenic potential of R-Ras. Interestingly, the ability of the G63 mutant to induce cell adhesion and survival was closely associated with the PI3-K-dependent signaling cascades. To further delineate R-Ras downstream signaling events, we observed that while a dominant negative mutant of Akt/protein kinase inhibited the ability of R-Ras to promote cell survival, both dominant negative mutants of Rac and Ral suppressed cell adhesion stimulated by R-Ras. Thus, the biological actions of R-Ras are mediated by multiple effectors, with PI3-K-dependent signaling cascades being critical to its functions.

Control of shivering under regional anesthesia in obstetric patients with tramadol

PURPOSE

Tramadol in a dose of 1 mg x kg(-1) iv is effective in the treatment of shivering after general anesthesia. The current study aimed to investigate (1) whether tramadol was equally effective for shivering under regional anesthesia in obstetric patients and (2) whether effective treatment could be achieved with lower doses.

METHODS

In a randomised, double-blind study, 36 obstetric patients who shivered during Cesarean section under regional anesthesia and who requested anti-shivering treatment were allocated to one of three groups for iv treatment: Group T0.5 received tramadol 0.5 mg x kg(-1) (n = 12), Group T0.25 tramadol 0.25 mg x kg(-1) (n = 13) and Group NS normal saline 0.05 ml x kg(-1) (n = 11). Treatment efficacy was evaluated subjectively by the parturient as no improvement, slight improvement, or marked improvement. The attending anesthesiologist who was blinded also independently noted the time elapsed from treatment to the time shivering subsided. Side effects such as nausea, vomiting or sedation and Apgar scores of the newborn were also noted.

RESULTS

Eighty percent of parturients in Group T0.5 and 92% in Group T0.25 were judged by observers to have shivering controlled compared with 27% in Group NS (P < 0.001). The response rates of Group T0.5 and Group T0.25 were not different. There was no increased incidence of side effects in the treatment groups.

CONCLUSION

We conclude that tramadol iv was effective in the treatment of intraoperative shivering during regional anesthesia for Cesarean section. There was no demonstrable difference in response rate or incidence of side effects between the two doses of 0.5 mg x kg(-1) and 0.25 mg x kg(-1).

Renal dietitians' perspective: identification, prevalence, and intervention for malnutrition in dialysis patients in Texas

OBJECTIVE

Determine the prevalence of malnutrition per facility standards; examine interventions used to treat malnutrition; and share experiences, concerns, and solutions to problems in the management of malnutrition in dialysis patients in Texas.

DESIGN

Structured survey questionnaires.

SETTING

196 outpatient hemodialysis (HD) and 86 peritoneal dialysis (PD) programs in End-Stage Renal Disease (ESRD) Network of Texas, Inc.

PARTICIPANTS

Renal dietitians who worked in Texas dialysis facilities that treated chronic, outpatient adult, and pediatric ESRD patients on HD or PD. MEASIRES: Criteria used to identify malnourished patients, prevalence of malnutrition in dialysis recipients, prevalence and types of interventions used to manage malnourished patients, and participation in quality management activities among renal dietitians.

RESULTS

For facilities that treated both HD and PD patients in 1996: (1) a significantly greater proportion of PD patients were identified as malnourished than HD patients; (2) facilities that had a high percentage of malnourished HD patients also had a high percentage of malnourished PD patients; (3) a significantly greater proportion of PD patients received commercial nutrition supplements than HD patients; and (4) use of tube feedings, intradialytic parenteral nutrition, intraperitoneal parenteral nutrition, and total parenteral nutrition among HD and PD patients decreased significantly from the past to the current survey year. Renal dietitians shared their experiences, concerns and solutions to problems in the management of malnutrition in this population.

CONCLUSION

Results indicate a need to improve the nutritional status of malnourished dialysis patients, to increase consideration of tube feedings as viable nutrient delivery routes, and to maximize involvement of renal dietitians in the quality management process. With the cooperative effort of staff, care givers, patients, and family, early identification and appropriate interventions may improve the nutritional status and quality of life of dialysis patients. This is a US government work. There are no restrictions on its use.

Phages infecting Vibrio vulnificus are abundant and diverse in oysters (Crassostrea virginica) collected from the Gulf of Mexico

Phages infecting Vibrio vulnificus were abundant (> 10(4) phages g of oyster tissue-1) throughout the year in oysters (Crassostrea virginica) collected from estuaries adjacent to the Gulf of Mexico (Apalachicola Bay, Fla.; Mobile Bay, Ala.; and Black Bay, La.). Estimates of abundance ranged from 10(1) to 10(5) phages g of oyster tissue-1 and were dependent on the bacterial strain used to assay the sample. V. vulnificus was near or below detection limits (< 0.3 cell g-1) from January through March and was most abundant (10(3) to 10(4) cells g-1) during the summer and fall, when phage abundances also tended to be greatest. The phages isolated were specific to strains of V. vulnificus, except for one isolate that caused lysis in a few strains of V. parahaemolyticus. Based on morphological evidence obtained by transmission electron microscopy, the isolates belonged to the Podoviridae, Styloviridae, and Myoviridae, three families of double-stranded DNA phages. One newly described morphotype belonging to the Podoviridae appears to be ubiquitous in Gulf Coast oysters. Isolates of this morphotype have an elongated capsid (mean, 258 nm; standard deviation, 4 nm; n = 35), with some isolates having a relatively broad host range among strains of V. vulnificus. Results from this study indicate that a morphologically diverse group of phages which infect V. vulnificus is abundant and widely distributed in oysters from estuaries bordering the northeastern Gulf of Mexico.

Identification and characterization of R-ras3: a novel member of the RAS gene family with a non-ubiquitous pattern of tissue distribution

Members of the Ras subfamily of GTP-binding proteins, including Ras (H-, K-, and N-), TC21, and R-ras have been shown to display transforming activity, and activating lesions have been detected in human tumors. We have identified an additional member of the Ras gene family which shows significant sequence similarity to the human TC21 gene. This novel human ras-related gene, R-ras3, encodes for a protein of 209 amino acids, and shows approximately 60-75% sequence identity in the N-terminal catalytic domain with members of the Ras subfamily of GTP-binding proteins. An activating mutation corresponding to the leucine 61 oncogenic lesion of the ras oncogenes when introduced into R-ras3, activates its transforming potential. R-ras3 weakly stimulates the mitogen-activated protein kinase (MAPK) activity, but this effect is greatly potentiated by the co-expression of c-raf-1. By the yeast two-hybrid system, R-ras3 interacts only weakly with known Ras effectors, such as Raf and RalGDS, but not with RglII. In addition, R-ras3 displays modest stimulatory effects on trans-activation from different nuclear response elements which bind transcription factors, such as SRF, ETS/TCF, Jun/Fos, and NF-kappaB/Rel. Interestingly, Northern blot analysis of total RNA isolated from various tissues revealed that the 3.8 kilobasepair (kb) transcript of R-ras3 is highly restricted to the brain and heart. The close evolutionary conservation between R-ras3 and Ras family members, in contrast to the significant differences in its biological activities and the pattern of tissue expression, raise the possibility that R-ras3 may control novel cellular functions previously not described for other GTP-binding proteins.

Cooperative transformation of NIH3T3 cells by G alpha12 and Rac1

The heterotrimeric G-protein, G alpha12, together with the closely-related G alpha13, are members of the G12 class of alpha-subunits important in mediating the signaling from seven transmembrane domain-spanning receptors. Recent evidence implicating both G alpha12 and G alpha13 in the activation of signaling pathways involving members of the RHO gene family led us to examine the role of Rac1, RhoA and Cdc42Hs in the transforming properties of G alpha12. Asparagine 17 (Asn 17) dominant inhibitory mutants of Rac1, and to a lesser extent RhoA, block focus forming ability of the GTPase-deficient mutant of G alpha12 (G alpha12 Leu 229) in NIH3T3 cells. In turn, wild-type G alpha12 cooperates well with Rac1 Val 12 but not with RhoA Leu 63 mutant in transforming NIH3T3 cells. Interestingly, the morphology of foci induced by G alpha12 and RhoA mutants are strikingly similar and is distinct from those displayed by Rac1 Val 12 mutant. The fact that G alpha12's ability to induce mitogenesis in NIH3T3 cells is not significantly perturbed by C3 ribosyltransferase suggested that RhoA does not play a major role in G alpha12-induced mitogenic events. Activated mutant of Rac1 has previously been demonstrated to stimulate the activity of the stress-induced c-Jun N-terminal kinase/stress-activated protein kinases (JNK/SAPKs). Transient co-transfection of Rac1 Val 12 mutant with the wild-type G alpha12 in COS7 cells leads to the further activation of an exogenously expressed hemagglutinin(HA)-tagged JNK. Furthermore, the cooperation between G alpha12 and Rac1 in cellular transformation is correlated with their ability to stimulate transcription from c-fos serum response element (SRE).

Recovery from mivacurium block with or without anticholinesterase following continuous infusion in obstetric patients

Neostigmine antagonism after suxamethonium followed by mivacurium chloride bolus and infusion was studied. Thirty ASA group I or II patients were given mivacurium 0.15 mg/kg followed by infusion during nitrous oxide-enflurane-pethidine anaesthesia. Train of four (TOF) stimuli were applied to the ulnar nerve at the wrist and TOF twitch height and ratio measured by TOF-GUARD nerve stimulator. Mivacurium infusion was titrated to give a 90% block of first twitch height. Patients were randomized into two groups. Group I patients recovered from the mivacurium block spontaneously while Group II patients were given neostigmine 0.05 mg/kg and atropine 0.02 mg/kg. Time to reach train of four ratio (TOFR) of 25%, 50% and 70% were measured. This study demonstrated a mean infusion rate of 5.1 +/- 1.8 micrograms/kg/min to maintain a 90% neuromuscular block. In the spontaneous recovery group, time to reach TOFR of 25%, 50% and 70% were 9.3 +/- 2.7 min, 13.5 +/- 3.0 min and 16.7 +/- 3.0 min respectively while the corresponding times in the neostigmine group were 5.2 +/- 1.7 min, 10.9 +/- 2.2 min and 16.1 +/- 7.4 min respectively. There were significant differences in the time taken to TOFR of 25% (P < 0.0001) and 50% (P < 0.05) but no difference in the time taken for TOFR to return to 70%. We concluded that mivacurium is suitable for use in caesarean section despite a decrease in plasma cholinesterase activity. Neostigmine antagonism is not required as a routine.

Synergism between two growth regulatory pathways: cooperative transformation of NIH3T3 cells by G alpha 12 and c-raf-1

The alpha-subunit of the heterotrimeric G-protein, G12, has been shown to induce cellular transformation when overexpressed or oncogenically activated in rodent fibroblasts. To investigate the interaction between Galpha12 transforming pathway and the Ras-Raf-MAPK pathway, we examined the ability of mitogenic signaling molecules in cooperating with Galpha12 in transforming NIH3T3 fibroblasts. We observed a striking cooperative effect on focus-forming ability when Galpha12 and c-raf-1 cDNAs were co-transfected into NIH3T3 cells. NIH3T3 cells coexpressing both Galpha12 and c-raf-1 resulted in the constitutive activation of the mitogenic-activated protein kinase (MAPK). In addition, the levels of GTP-bound Ras were elevated in Galpha12 transformed NIH3T3 cells. Our results provide a model for studying the effects of simultaneous activation of two distinct growth regulatory pathways in cellular transformation.

Hepatocyte growth factor (HGF)/NK1 is a naturally occurring HGF/scatter factor variant with partial agonist/antagonist activity

Hepatocyte growth factor/scatter factor (HGF/SF) stimulates cell proliferation, motility, and morphogenesis by activation of its receptor, the c-Met tyrosine kinase. HGF/SF is structurally related to plasminogen, including an amino-terminal hairpin loop, four kringle domains, and a serine protease-like region. A truncated HGF/SF isoform, designated HGF/NK2, which extends through the second kringle domain and behaves as a competitive HGF/SF antagonist, was previously shown to be encoded by an alternative HGF/SF transcript. In this study, we describe a second naturally occurring HGF/SF variant, HGF/NK1, consisting of the HGF/SF amino-terminal sequence and first kringle domain. This product is encoded by a 2-kilobase alternative transcript containing intronic sequence that was contiguous with exon K1b. Analysis of baculovirus-expressed HGF/NK1 revealed that this isoform possesses the heparin binding properties of HGF/SF and modest mitogenic and scattering activity relative to HGF/SF. However, at a 40-fold molar excess, HGF/NK1 inhibited HGF/SF-dependent DNA synthesis. HGF/NK1 stimulated tyrosine phosphorylation of Met, and covalent affinity cross-linking demonstrated a direct HGF/NK1-receptor interaction. These findings establish that the HGF/SF gene encodes multiple alternative products, which include not only a mitogenic agonist (HGF/SF) and a pure antagonist (HGF/NK2) but also a molecule with partial agonist/antagonist properties.

Isolation of a novel oncogene, NET1, from neuroepithelioma cells by expression cDNA cloning

We generated a cDNA expression library from a human neuroepithelioma cell line for detection of novel oncogenes by focus formation assay in NIH3T3 cells. A morphologically unique focus was identified upon transfection and the transforming plasmid was isolated. The transforming gene, designated NET1, encoded a predicted protein species of 54 kDa containing the Dbl-Homology (DH) motif. This motif is also present in other growth regulatory molecules including Bcr, Cdc24, Vav, Ras-Grf, Ect2, Ost, Tim and Tiam1, which have been implicated as regulators of small GTP-binding proteins. NIH3T3 cells transfected with NET1 expression plasmid showed altered growth properties in vitro and were tumorigenic when injected into nude mice. In addition, a 2.5 kb cDNA was isolated from a normal human cDNA library which represented the NET1 proto-oncogene contained a 5' extended open reading frame. The fact that the proto-oncogene failed to induce transformation in NIH3T3 cells suggested that the original NET1 oncogene was activated by 5'-truncation. The 3.0 and 2.4 kilobasepair (kb) transcripts of the NET1 gene was ubiquitously expressed in all tissues examined. Using fluorescence in situ hybridization, we localized the NET1 gene to the short arm of human chromosome 10 at band p15.

A novel insertional mutation in the TC21 gene activates its transforming activity in a human leiomyosarcoma cell line

TC21 is the fourth member of the ras gene family to exhibit oncogenic activation in human tumor cells. To assess the prevalence of activated TC21 oncogenes in human tumors, we have developed sensitive single-strand conformational polymorphism (SSCP) conditions and immunological reagents for the detection of both single base alterations and/or overt overexpression in a wide spectrum of human tumor cell lines and surgical samples. In an initial examination of 33 human tumor specimens, we observed a novel nine basepair three amino acids insertion at TC21 codon 24 in one human uterine leiomyosarcoma cell line, SK-UT-1. This mutant allele when transfected into NIH3T3 cells, displayed high transforming activity comparable to that of the Leu72 oncogenic mutant identified by expression cDNA cloning from a human ovarian carcinoma cell line. Comparing the level of GTP-binding by the mutant and normal TC21 products revealed that this novel lesion increases the GTP-bound form of the TC21 molecule. These findings imply that the mechanism by which mutations activate the oncogenic properties of this ras-related molecule is analogous to that of previously known ras family members.

Fluorescently Labeled Virus Probes Show that Natural Virus Populations Can Control the Structure of Marine Microbial Communities

Fluorescently stained viruses were used as probes to label, identify, and enumerate specific strains of bacteria and cyanobacteria in mixed microbial assemblages. Several marine virus isolates were fluorescently stained with YOYO-1 or POPO-1 (Molecular Probes, Inc.) and added to seawater samples that contained natural microbial communities. Cells to which the stained viruses adsorbed were easily distinguished from nonhost cells; typically, there was undetectable binding of stained viruses to natural microbial assemblages containing >10(sup6) bacteria ml(sup-1) but to which host cells were not added. Host cells that were added to natural seawater were quantified with 99% (plusmn) 2% (mean (plusmn) range) efficiency with fluorescently labeled virus probes (FLVPs). A marine bacterial isolate (strain PWH3a), tentatively identified as Vibrio natriegens, was introduced into natural microbial communities that were either supplemented with nutrients or untreated, and changes in the abundance of the isolate were monitored with FLVPs. Simultaneously, the concentrations of viruses that infected strain PWH3a were monitored by plaque assay. Following the addition of PWH3a, the concentration of viruses infecting this strain increased from undetectable levels (<1 ml(sup-1)) to 2.9 x 10(sup7) and 8.3 x 10(sup8) ml(sup-1) for the untreated and nutrient-enriched samples, respectively. The increase in viruses was associated with a collapse in populations of strain PWH3a from ca. 30 to 2% and 43 to 0.01% of the microbial communities in untreated and nutrient-enriched samples, respectively. These results clearly demonstrate that FLVPs can be used to identify and quantify specific groups of bacteria in mixed microbial communities. The data show as well that viruses which are present at low abundances in natural aquatic viral communities can control microbial community structure.

Assignment of the human TIM proto-oncogene to 7q33-->q35

The human transforming gene TIM has been mapped to human chromosome 7 region q33-->q35 by fluorescence in situ hybridization with R-banded chromosomes. Rearrangements within this region have been reported to occur in acute myeloid leukemia cells.

Oncogenic activation of human R-ras by point mutations analogous to those of prototype H-ras oncogenes

R-ras, K-rev-1/rap and TC21, are more closely related to prototype H-ras than any other known members of the ras superfamily. We recently isolated a mutationally activated TC21 oncogene from a human ovarian carcinoma cell line. Based upon these observations, we sought to re-examine the transforming potential of R-ras, which was reported earlier to lack transforming capacity. Mutations were introduced into the R-ras gene at codons 38 or 87, analogous to positions 12 and 61, respectively, responsible for H-ras oncogene activation. While both mutations resulted in acquisition of R-ras transforming capacity for NIH3T3 cells the position 61 was shown to be more active. Transfectants expressing either R-ras mutant formed colonies in soft agar and were tumorigenic in vivo. As has been reported for H-ras, R-ras cooperated with c-raf-1 in inducing transformation of NIH3T3 cells. These results imply interactions in R-ras and c-raf-1 signaling pathways. We observed R-ras transcripts of 4.6 and 1.2 kb ubiquitously expressed in each of a variety of tissues examined. All these findings raise the possibility that R-ras, like prototype ras genes, may be mutationally activated as an oncogene in some human malignancies.

A human oncogene of the RAS superfamily unmasked by expression cDNA cloning

As an approach to identify human oncogenes, we generated an expression cDNA library from an ovarian carcinoma line. A potent transforming gene was detected by transfection analysis and identified as TC21, a recently cloned member of the RAS gene superfamily. A single point mutation substituting glutamine for leucine at position 72 was shown to be responsible for activation of transforming properties. While the cDNA clone possessed high transforming activity, the ovarian tumor genomic DNA, which contained the mutated TC21 allele, failed to induce transformed foci. Thus, expression cDNA cloning made it possible to identify and isolate a human oncogene that has evaded detection by conventional approaches.

Identification of novel genes, SYT and SSX, involved in the t(X;18)(p11.2;q11.2) translocation found in human synovial sarcoma

Human synovial sarcomas contain a recurrent and specific chromosomal translocation t(X;18)(p11.2;q11.2). By screening a synovial sarcoma cDNA library with a yeast artificial chromosome spanning the X chromosome breakpoint, we have identified a hybrid transcript that contains 5' sequences (designated SYT) mapping to chromosome 18 and 3' sequences (designated SSX) mapping to chromosome X. An SYT probe detected genomic rearrangements in 10/13 synovial sarcomas. Sequencing of cDNA clones shows that the normal SYT gene encodes a protein rich in glutamine, proline and glycine, and indicates that in synovial sarcoma rearrangement of the SYT gene results in the formation of an SYT-SSX fusion protein. Both SYT and SSX failed to exhibit significant homology to known gene sequences.

Expression cDNA cloning of a novel oncogene with sequence similarity to regulators of small GTP-binding proteins

We generated a cDNA expression library from a human mammary epithelial cell line for detection of novel oncogenes by focus formation assay in NIH3T3 cells. A morphologically unique focus was identified and the transforming plasmid was isolated. The transforming gene, designated TIM, encoded a predicted protein species of 60 kDa containing a Dbl-Homology (DH) motif. This motif is also present in other growth regulatory molecules including Bcr, Cdc24, Vav, Ras-grf, and Ect2 which have been implicated as regulators of small GTP-binding proteins. NIH3T3 cells transfected with TIM expression plasmid showed altered growth properties in vitro and were tumorigenic when injected into nude mice. The 6.5 kilobasepair (kb) transcript of the TIM gene was mainly expressed in kidney, liver, pancreas, lung, and placenta. By analysing a panel of human-hamster somatic cell hybrids, we localized the TIM gene to human chromosome 7.

Expression cDNA cloning of a serine kinase transforming gene

By ectopic expression of cDNAs derived from a Ewing sarcoma cell line in NIH3T3 cells, we isolated a transforming gene (est). Sequence analysis revealed homology to the cot oncogene, which encodes a novel serine kinase. Whereas the cot product was truncated at its carboxy-terminal end as a result of gene rearrangement during transfection, est encodes the normal cot product. Thus, this gene can be activated as an oncogene by overexpression as well as by gene rearrangement. NIH3T3 cells transfected with est formed progressively growing colonies in soft agar and were tumorigenic in nude mice. The 3.2-kb est transcript was expressed at low level in both human fibroblasts and epithelial cells. Addition of the tumor promoter, okadaic acid (OA), or cytokine, interleukin 1 (IL-1), but not serum or platelet-derived growth factor (PDGF), induced increased expression of the est transcript. Using fluorescence in situ hybridization, we localized the est gene to the short arm of human chromosome 10 at band p11.2.

Fibroblast growth factor receptor 4 is a high affinity receptor for both acidic and basic fibroblast growth factor but not for keratinocyte growth factor

A cDNA predicted to encode a transmembrane tyrosine kinase receptor with sequence features characteristic of known fibroblast growth factor (FGF) receptors was isolated from an expression library constructed from the human mammary epithelial cell line B5/589. This cDNA, designated cl44, encodes a product of 803 amino acid residues and was readily distinguishable from known FGF receptors. During the course of our studies, Partanen et al. (Partanen, J., Makela, T. P., Eerola, E., Korhonen, J., Hirvonen, H., Claesson, W. L., and Alitalo, K. (1991) EMBO J. 10, 1347-1354) isolated a new FGF receptor, designated FGFR4, from the human leukemia cell line, K562. Its amino acid sequence is identical to that of cl44 with the exception of 1 residue. The 5'-untranslated sequences of the two cDNAs diverged far upstream of the initiation codon. A myoblast line, L6E9, which lacks FGF receptors, was utilized to express high levels of FGFR4. We found, in contrast to Partenen et al., who reported only binding of acidic FGF, that FGFR4 bound both acidic and basic FGF with dissociation constants of 10-15 and 120 pM, respectively. No detectable binding of keratinocyte growth factor was observed. In studies aimed to determine whether FGF receptors contribute to the development of human tumors, we screened RNAs prepared from cell lines derived from a variety of solid tumors. High levels of the cl44 transcript were detected in 8 of 14 and 6 of 9 human mammary and kidney carcinomas, respectively, but only infrequently in other types of tumors. In contrast, FGFR1 was found to be frequently expressed in kidney, but not in breast tumor cells, suggesting a possible role for FGFR4 in human mammary cancer.

Expression cDNA cloning of a transforming gene encoding the wild-type G alpha 12 gene product

Using an expression cDNA cloning approach, we examined human tumor cell lines for novel oncogenes that might evade detection by conventional techniques. We isolated a transforming sequence that was highly efficient in transforming NIH 3T3 mouse fibroblasts. DNA sequence analysis identified the gene as the human homolog of a recently cloned alpha subunit of mouse GTP-binding protein G alpha 12. NIH 3T3 cells transfected with G alpha 12 cDNA grew in soft agar and were tumorigenic in nude mice. There were no apparent mutations in the cloned cDNA in comparison with a G alpha 12 cDNA clone isolated from a normal human epithelial cell library, implying that overexpression alone was sufficient to cause NIH 3T3 cell transformation. The observed altered growth properties mediated by G alpha 12 showed a certain degree of dependency on serum factors, and its mitogenic potential was also potently inhibited by suramin treatment.

Processing of hepatocyte growth factor to the heterodimeric form is required for biological activity

Hepatocyte growth factor is a plasminogen-like molecule with diverse biological effects. Although it is synthesized as a single chain polypeptide, it was originally purified as a disulfide-linked heterodimer which was generated by an internal proteolytic event. Subsequent work indicated that preparations consisting largely of the monomeric form also exhibited potent activity. By using a combination of protease inhibition and site-directed mutagenesis, we established that conversion of the single chain polypeptide to the heterodimer occurred during the bioassay and was required for mitogenic and motogenic activity.

Determination of ligand-binding specificity by alternative splicing: two distinct growth factor receptors encoded by a single gene

Expression cDNA cloning and structural analysis of the human keratinocyte growth factor receptor (KGFR) revealed identity with one of the fibroblast growth factor (FGF) receptors encoded by the bek gene (FGFR-2), except for a divergent stretch of 49 amino acids in their extracellular domains. Binding assays demonstrated that the KGFR was a high-affinity receptor for both KGF and acidic FGF, while FGFR-2 showed high affinity for basic and acidic FGF but no detectable binding by KGF. Genomic analysis of the bek gene revealed two alternative exons responsible for the region of divergence between the two receptors. The KGFR transcript was specific to epithelial cells, and it appeared to be differentially regulated with respect to the alternative FGFR-2 transcript. Thus, two growth factor receptors with different ligand-binding specificities and expression patterns are encoded by alternative transcripts of the same gene.

Identification of a competitive HGF antagonist encoded by an alternative transcript

We identified a naturally occurring hepatocyte growth factor (HGF) variant, whose predicted sequence extends only through the second kringle domain of this plasminogen-related molecule. This smaller molecule, derived from an alternative HGF transcript, lacked mitogenic activity but specifically inhibited HGF-induced mitogenesis. Cross-linking studies demonstrated that the truncated molecule competes with HGF for binding to the HGF receptor, which has been identified as the c-met protooncogene product. Thus, the same gene encodes both a growth factor and its direct antagonist.

Identification of the hepatocyte growth factor receptor as the c-met proto-oncogene product

Hepatocyte growth factor (HGF) is a plasminogen-like protein thought to be a humoral mediator of liver regeneration. A 145-kilodalton tyrosyl phosphoprotein observed in rapid response to HGF treatment of intact target cells was identified by immunoblot analysis as the beta subunit of the c-met proto-oncogene product, a membrane-spanning tyrosine kinase. Covalent cross-linking of 125I-labeled ligand to cellular proteins of appropriate size that were recognized by antibodies to c-met directly established the c-met product as the cell-surface receptor for HGF.

A broad-spectrum human lung fibroblast-derived mitogen is a variant of hepatocyte growth factor

A heparin-binding mitogen was isolated from conditioned medium of human embryonic lung fibroblasts. It exhibited broad target-cell specificity whose pattern was distinct from that of any known growth factor. It rapidly stimulated tyrosine phosphorylation of a 145-kDa protein in responsive cells, suggesting that its signaling pathways involved activation of a tyrosine kinase. Purification identified a major polypeptide with an apparent molecular mass of 87 kDa under reducing conditions. Partial amino acid sequence analysis and cDNA cloning revealed that it was a variant of hepatocyte growth factor, a mitogen thought to be specific for hepatic cells and structurally related to plasminogen. Recombinant expression of the cDNA in COS-1 cells established that it encoded the purified growth factor. Its site of synthesis and spectrum of targets imply that this growth factor may play an important role as a paracrine mediator of the proliferation of melanocytes and endothelial cells, as well as cells of epithelial origin.

Molecular cloning and localization to chromosome 6 of mouse INT1L1 gene

The human INT1L1 gene, which exhibits homology to the protooncogene INT1 is very closely linked to the MET gene and cystic fibrosis locus on human chromosome 7. In the present study we have isolated overlapping genomic clones that correspond to the mouse homolog of the INT1L1 gene and have used the cloned DNA as probes to examine the distribution of the mouse INT1L1 gene within a series of 35 mouse-hamster somatic cell hybrids. These analyses have localized the INT1L1 gene to mouse chromosome 6. In addition, we demonstrate that the mouse INT1L1 and MET genes are coamplified in lines of spontaneously transformed mouse NIH3T3 cells, indicating that these genes may remain closely linked within the mouse genome.

Characterization of the translocation between chromosomes X and 18 in human synovial sarcomas

Recent studies have identified a specific chromosomal translocation, t(X;18)(p11.2;q11.2), in a high proportion of human synovial sarcomas. As a first step towards characterizing the X;18 translocation we have established a synovial sarcoma cell line. Fusion of this cell line to mouse RAG cells gave rise to somatic cell hybrids that contain the derivative (X) marker chromosome in the absence of other genetic material from chromosomes 18 and X. Southern analysis of DNA from these somatic cell hybrids demonstrated that the human X chromosome markers DXS94, DXS14, DXZ1 and DXS62 were retained. In contrast DXS7, GAPDP1, ARAF1, DXS146 were not consistently present in the hybrids indicating that these markers were on the region of the X chromosome replaced by part of the long arm of chromosome 18 during the generation of the X;18 translocation. The predicted position of the translocation relative to X chromosome markers is DXS7-DXS146-X; 18-DXS14-DXZ1-DXS94.

Characterization of the mouse met proto-oncogene

The DNA sequence of cDNA clones prepared from transcripts of the mouse met proto-oncogene reveals that the mouse met gene encodes a 1380 amino acid protein with the characteristics of a growth factor receptor. This protein can be divided into several putative domains, including an intracellular protein tyrosine kinase domain, a transmembrane domain and a 929 amino acid extracellular domain, possessing a potential proteolytic cleavage site with the sequence Lys-Arg-Arg-Lys-Arg-Ser. To gain additional insights into the function of the met protein we have examined the level of met transcripts in tissues of the late-gestation mouse conceptus. Transcription of met was observed in most of the tissues analysed, but the highest levels of met mRNA were detected in the yolk sac, amnion and kidney; no transcripts were detectable in the calvaria. Chromosomal localization using a series of mouse-hamster hybrid cell lines has demonstrated that met is located on mouse chromosome 6.

Extraction from natural planktonic microorganisms of DNA suitable for molecular biological studies

We developed a simple technique for the high-yield extraction of purified DNA from mixed populations of natural planktonic marine microbes (primarily bacteria). This is a necessary step for several molecular biological approaches to the study of microbial communities in nature. The microorganisms from near-shore marine and brackish water samples, ranging in volume from 8 to 40 liters, were collected on 0.22-mum-pore-size fluorocarbon-based filters, after prefiltration through glass fiber filters, to remove most of the eucaryotes. DNA was extracted directly from the filters in 1% sodium dodecyl sulfate that was heated to 95 to 100 degrees C for 1.5 to 2 min. This procedure lysed essentially all the bacteria and did not significantly denature the DNA. The DNA was purified by phenol extraction, and precautions were taken to minimize shearing. Agarose gel electrophoresis showed that most of the final preparation had a large molecular size (>23 kilobase pairs). The DNA was sufficiently pure to allow complete digestion by the restriction endonuclease Sau3AI and ligation to vector DNA. In a sample in which the extracted DNA was quantified by binding to the dye Hoechst H33258, DNA was quantitatively extracted, and 45% of the initially extracted DNA was recovered after purification. Final yields were a few micrograms of DNA per liter of seawater and were roughly 25 to 50% of the total bacterial DNA in the sample. Alternatives to the initial harvest by filtration method, including continuous-flow centrifugation and thin-channel or hollow-fiber concentration followed by centrifugation, were less efficient than filtration in terms of both time and yield, largely because of the difficulty of centrifuging the very small bacteria typical of marine plankton. These methods were judged to be less appropriate for studies of natural populations as they impose a strong selection for the larger bacteria.

Primary structure of the met protein tyrosine kinase domain

The primary structure of the protein tyrosine kinase domain of the human met gene has been determined from cDNA clones prepared from transcripts of the activated human met gene. These analyses reveal that the met kinase domain (located on human chromosome 7) possesses unique features that distinguish met from other members of the src family of protein tyrosine kinases. The results also demonstrate that the product of the activated met gene is a fusion protein and that the amino terminal end of this fusion protein, which is encoded by human chromosome 1, exhibits homology to laminin B1.

Activation of the met oncogene in the human MNNG-HOS cell line involves a chromosomal rearrangement

In this study it is demonstrated that the activated met gene, which was originally detected in the MNNG-HOS chemically transformed human cell line, is a chimeric gene formed by the joining together of two distinct regions of DNA. Rearrangement of cellular DNA in MNNG-HOS cells was demonstrated by Southern analyses, which showed that the MNNG-HOS cell line contained unique met-related DNA fragments that were not detected in the parental cell line, HOS. Chromosomal localization using a series of rodent-human hybrid cell lines showed that the 5' end of the activated met gene is derived from human chromosome 1, in contrast to the 3' end of met which has been previously localized to human chromosome 7. The chimeric gene is transcribed to produce a 5-kb mRNA that is encoded both by regions of the gene derived from chromosome 1 and by regions of the gene derived from chromosome 7. Karyotype analysis of HOS and MNNG-HOS cells has identified several marker chromosomes that involve translocations of chromosomes 1 and 7. The possible location of the activated met locus within these rearranged chromosomes is discussed.

Cellular toxicity of pancreatic carcinogens

Azaserine (CAS: 115-02-6), streptozocin (CAS: 18883-66-4; streptozotocin), and N-nitrosobis(2-oxopropyl)amine [(BOP) CAS: 60599-38-4] produce different types of pancreatic tumors in rodents. We have investigated the toxic effects of these compounds on pancreatic tissues from Wistar rats and Syrian hamsters. Inhibition of protein synthesis was used as a measure of toxicity. Pancreatic islets and acinar cells from rat and hamster were labeled with [3H]leucine for 60 minutes in vitro in the presence of the various carcinogens. Azaserine, which produces acinar cell tumors in the rat, inhibited synthesis by all tissues; rat acinar cells, however, were most sensitive. Glutamine, but not serine, provided some protection against azaserine toxicity. Streptozocin inhibited synthesis by islets of both species and acinar cells from hamster; islets were the most sensitive. BOP and N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine, which induce ductal tumors in the hamster, had no effect on any of the tissues examined. These results indicate that the specificities of the cellular toxicities of the pancreatic carcinogens parallel, to some degree, their tumorigenic effects.

Monolayer culture of pancreatic islets from the Syrian hamster

Pancreatic islets of Langerhans of the Syrian hamster were maintained in culture for as long as 43 wk. Islets were prepared by collagenase/hyaluronidase digestion of minced pancreas. The islets quickly attached to the plastic culture flasks and lost their spherical form as they flattened out to form circular monolayers. Few fibroblastoid cells were observed. As outward migration continued, the islets became vacuolated with the ultimate formation of monolayer rings. Throughout the culture period the beta cells continued to synthesize and secrete insulin. Furthermore, the cells maintained a responsiveness to glucose stimulation with increased rates of hormone secretion in the presence of elevated concentrations of the sugar. These studies demonstrate the suitability of Syrian hamster islets for studies involving long-term culture.

Chemical reactivity of the functional groups of insulin. Concentration-dependence studies

A modification to the competitive labelling procedure of Duggleby and Kaplan [(1975) Biochemistry 14, 5168-5175] was used to study the reactivity of the N-termini, lysine, histidine and tyrosine groups of insulin over the concentration range 1 X 10(-3)-1 X 10(-7)M. Reactions were carried out with acetic anhydride and 1-fluoro-2,4-dinitrobenzene in 0.1 M-KCl at 37 degrees C using Pyrex glass, Tefzel and polystyrene reaction vessels. At high concentrations all groups had either normal or enhanced reactivity but at high dilution the reactivities of all functional groups became negligible. This behaviour is attributed to the adsorption of insulin to the reaction vessels. The histidine residues show a large decrease in reactivity in all reaction vessels in the concentration range 1 X 10(-3)-1 X 10(-5)M where there are no adsorption effects and where the reactivities of all other functional groups are independent of concentration. With polystyrene, where adsorption effects become significant only below 1 X 10(-6)M, the reactivity of the phenylalanine N-terminus also shows a decrease in reactivity between 1 X 10(-5) and 1 X 10(-6)M. In 1 M-KCl insulin does not absorb to Pyrex glass and under these conditions the histidine reactivity is concentration-dependent from 1 X 10(-3) to 5 X 10(-6)M and the B1 phenylalanine alpha-amino and the B29 lysine epsilon-amino reactivities from 5 X 10(-6) to 1 X 10(-7)M, whereas the reactivities of all other groups are constant. These alterations in reactivity on dilution are attributed to disruption of dimer-dimer interactions for histidine and to monomer-monomer interactions for the phenylalanine and lysine amino groups. It is concluded that the monomeric unit of insulin has essentially the same conformation in its free and associated states.

Chemical properties of the N-termini of human haemoglobin

The chemical properties, namely pK and reactivity, of the N-termini of oxyhaemoglobin and deoxyhaemoglobin toward acetic anhydride and 1-fluoro-2,4-dinitrobenzene (Dnp-F) were determined by the competitive-labelling approach [Kaplan, Stevenson & Hartley, (1971) Biochem. J. 124, 289-229; Duggleby & Kaplan (1975) Biochemistry 14, 5168-5175]. At physiological pH and temperature, the valine-1 alpha and valine-1-beta amino groups had unusually low pK values, but showed only minimal changes in their pK values on deoxygenation. Between pH 7.5 and pH 8.0 a deviation was observed in the pH-reactivity profiles and the apparent pK values became markedly pH-dependent. It was found that Dnp-F, but not acetic anhydride, had an abnormally high reactivity toward the N-termini. It is concluded that the valine-1 alpha and valine-1 beta N-termini make little or no contribution to the alkaline Bohr effect at physiological pH values. The high reactivity toward Dnp-F is attributed to an interaction or binding near the N-terminal region, and the discontinuity in the pH-reactivity profile at moderate alkaline pH values to a conformational change which alters the environment of these groups.