Signalling pathways for transactivation by dexmedetomidine of epidermal growth factor receptors in astrocytes and its paracrine effect on neurons

BACKGROUND AND PURPOSE

Stimulation of astrocytes by the alpha(2)-adrenoceptor agonist dexmedetomidine, a neuroprotective drug, transactivates epidermal growth factor (EGF) receptors. The present study investigates signal pathways leading to release of an EGF receptor ligand and those activated during EGF receptor stimulation, and the response of neurons to dexmedetomidine and to astrocyte-conditioned medium.

EXPERIMENTAL APPROACH

Phosphorylation of ERK(1/2) was determined by western blotting and immunocytochemistry, and phosphorylation of EGF receptors by immunoprecipitation and western blotting. mRNA expression of fos family was measured by RT-PCR.

KEY RESULTS

Pertussis toxin (0.2 microg ml(-1)) an inhibitor of betagamma subunit dissociation from Galpha(i) protein, and GF 109203X (500 nM), a protein kinase C inhibitor, abolished ERK(1/2) phosphorylation. PP1 (10 microM), inhibiting Src kinase and GM 6001 (10 microM), an inhibitor of Zn-dependent metalloproteinase, abolished ERK(1/2) phosphorylation by dexmedetomidine (50 nM), but not that by EGF (10 ng ml(-1)), showing Src kinase and metalloproteinase activation during the first stage only; AG 1478 (1 microM), an inhibitor of the EGF receptor tyrosine kinase, abolished ERK(1/2) phosphorylation. Dexmedetomidine-induced EGF receptor phosphorylation was prevented by AG 1478, GM 6001, PP1 and GF 109203X and its induction of cfos and fosB by AG 1478 and by U0126 (10 microM), an inhibitor of ERK phosphorylation, indicating downstream effects of ERK(1/2) phosphorylation. EGF and conditioned medium from dexmedetomidine-treated astrocytes, but not dexmedetomidine itself, induced ERK phosphorylation in primary cultures of cerebellar neurons.

CONCLUSIONS AND IMPLICATIONS

Dexmedetomidine-induced transactivation pathways were delineated. Its paracrine effect on neurons may account for its neuroprotective effects.

Influences of MxA gene -88 G/T and IFN-gamma +874 A/T on the natural history of hepatitis B virus infection in an endemic area

The influence of human genetics on the natural history of hepatitis B virus (HBV) infection may be diminished in endemic areas because infection at a young age predisposes to chronic HBV infection. The present study aimed to address this issue through the determination of the influences of single nucleotide polymorphisms (SNPs) of myxovirus resistence-1 (MxA) -88 G/T and interferon (IFN)-gamma +874 A/T on the natural history of HBV infection in endemic regions. One hundred adult patients with self-limiting HBV infection (positive for both anti-HBs and anti-HBc) and 340 adult patients with persistent HBV infection were recruited from southern China, an endemic area with an HBsAg carrier rate of 17.8%. SNPs of MxA -88 G/T and interferon (IFN)-gamma +874 A/T were typed using a protocol based on competitively differentiated polymerase chain reaction. A highly significant difference in the distribution of MxA -88 G/T was observed between those with persistent and self-limiting HBV infections. The latter displayed a lower frequency of the GG genotype (41.0% vs. 52.9%, P = 0.036) and a higher frequency of the TT genotype (16.0% vs. 2.4%, P = 0.000), compared to patients with persistent infection. These differences were not gender- or age-specific. However, a significant distribution difference of IFN-gamma +874 A/T was not observed. Between two groups of patients, respectively, the distribution frequencies of the AA genotype (65.0% vs. 72.8%, P = 0.139) and the TT genotype (2.0% vs. 1.2%, P = 0.894) were found. These results suggest that MxA gene -88 G/T and IFN-gamma +874 A/T behave differently in endemic HBV infections. Further study is necessary to clarify the influences of human genetics on endemic HBV infections.

Parameters controlling the gene-targeting frequency at the Sphingomonas species rrn site and expression of the methyl parathion hydrolase gene

AIMS

To investigate the key parameters controlling the exogenous methyl parathion hydrolase (MPH) gene mpd-targeting frequency at the ribosomal RNA operon (rrn) site of Sphingomonas species which has a wide range of biotechnological applications.

METHODS AND RESULTS

Targeting vectors with different homology lengths and recipient target DNA with different homology identities were used to investigate the parameters controlling the targeting frequency at the Sphingomonas species rrn site. Targeting frequency decreased with the reduction of homology length, and the minimal size for normal homologous recombination was >100 bp. Homologous recombination could succeed even if there were 3-4% mismatches; however, targeting frequency decreased with increasing sequence divergence. The Red recombination system could increase the targeting frequency to some extent. Targeting of the mpd gene to the rrn site did not affect cell viability and resulted in an increase of MPH-specific activity in recombinants.

CONCLUSIONS

Targeting frequency was affected by homology length, identity and the Red recombination system. The rrn site is a good target site for the expression of exogenous genes.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work is useful as a foundation for a better understanding of recombination events involving homologous sequences and for the improved manipulation of Sphingomonas genes in biotechnological applications.

Pre-clinical studies and phase I clinical trial of the anti-CD22 immunotoxin CAT-3888 (BL22) for pediatric acute lymphoblastic leukemia (ALL)

9560

Background: ALL is the most common childhood malignancy. Although highly curable, therapy is associated with multiple toxicities and ALL remains the most frequent cause of pediatric cancer mortality. Most ALL is CD22+ and we evaluated the anti-CD22 immunotoxin RFB4(dsFv)-PE38 (BL22 or CAT-3888) in the treatment of pediatric ALL. Methods: In vitro cytotoxicity was assessed on blasts from 42 children with CD22+ ALL. In vivo studies were performed using a xenograft model (SCID mouse - EU1 human ALL cell line). A pediatric phase I trial of CAT-3888 was initiated. Results: CAT-3888 induced in vitro cytotoxicity against most ALL samples (median IC50 9.8 ng/ml). A dose response was observed in murine xenografts with significant prolongation of leukemia free survival (p<0.05). 18 subjects (15 ALL, 3 lymphoma; 3 - 22 years of age) were treated on a Phase I trial at doses of 10 - 40 mcg/kg QOD for 3 - 6 doses with cycles repeated every 21 - 28 days. Treatment was well tolerated and no dose limiting toxicity was seen. Pharmacokinetics were influenced by disease burden and T1/2 showed an inverse relationship to marrow blasts (r2=0.5) consistent with rapid drug binding by CD22+ cells. All subjects were heavily pre-treated and had progressive high burden disease at the time of treatment. Transient clinical activity was observed in 16 of 18 subjects as evidenced by decreased peripheral blast count (8), decreased marrow infiltration (3), decreased extramedullary disease (2), increased platelet count (2), increased neutrophil count (1), increased reticulocyte count (1), improved PET scan (1), decreased tumor-associated pain (2), and/or peripheral blast count stabilization (3). A dose response was apparent with 4 of 9 (44%) achieving stable disease at or above doses of 30 mcg/kg. Conclusions: The majority of pediatric ALL blasts are highly sensitive in vitro to CAT-3888 at concentrations far below clinically achievable levels. CAT-3888 is well tolerated in pediatric patients and activity has been seen in most subjects treated on the phase I trial. CD22 represents a relevant target for pediatric ALL. A new higher affinity anti-CD22 immunotoxin (HA22 or CAT-8015) is in development.

No significant financial relationships to disclose.

Phase II randomized trial of docetaxel plus cetuximab or bortezomib in patients with advanced NSCLC and performance status (PS) 2—CALGB 30402

7595

Background: There is no standard treatment for patients (pts) with advanced NSCLC and PS 2. Docetaxel (D) is active and well tolerated on a weekly schedule. Cetuximab (C) and Bortezomib (B) are new agents with activity in NSCLC. We explored these two new combinations in PS 2 pts. Methods: In a multi-center randomized phase II trial, untreated pts with advanced NSCLC and PS 2 were randomized to D 30 mg/m2 d1,8,15 q. 28 days in combination with either C 400 mg/m2 week 1 then 250 mg/m2 weekly, or B 1.6 mg/m2 d1,8,15 q. 28 days for 4 cycles. Pts with CR/PR/SD were allowed to continue C or B until PD. The study was non-comparative and the primary endpoint was progression-free survival (PFS) rate at 6 months. The trial had a type I error of 0.0746 and power of 0.9 to differentiate a 6-mo PFS of <20% vs. >42%. Results: 64 pts were enrolled between 7/05 and 9/06. 5 were ineligible and 3 never received protocol treatment. Results are reported for 55 pts (27 D+C; 28 D+B). Most pts had stage IV adenoCa and 13% had brain metastases. Median age was 70 (range, 35–88) and 65% were male. Response: 10.5% for D+C and 13.6% for D+B. Median PFS was 3.1 mo for D+C and 1.8 mo for D+B. PFS rates at 4 mo (data not yet mature for 6-mo): 33% and 28%, respectively. Median survival: 3.8 mo for D+C and 3.3 mo for D+B. Gr 3/4 hematologic toxicity was 17% in both arms. Gr 3/4 non-heme toxicities were 44% in D+C and 36% in D+B arm. 5 pts died of treatment-related toxicities (3 D+C; 2 D+B). Conclusions: These results confirm the poor prognosis associated with a PS of 2. Based on our preliminary analysis, neither combination produced results that justify further research in this subset of patients. The treatment of PS 2 patients with advanced NSCLC remains a vexing problem and new approaches are urgently needed.

No significant financial relationships to disclose.

Phase II randomized study of dose-dense docetaxel (Doc) and cisplatin (Cis) every two weeks with pegfilgrastim (Pfil) and darbepoetin alfa (Darb) with and without the chemoprotector BNP7787 in patients with advanced non-small cell lung cancer (NSCLC): CAL

7617

Background: We sought to explore the toxicity, feasibility, and response rate of dose-dense Doc and Cis with growth factor support without [A] and with [B] a novel chemoprotector in patients with NSCLC. Methods: Patients with measurable disease, stage IIIB (effusion) or IV, performance status (PS) 0–1, no prior chemotherapy, and adequate organ function were eligible. Treatment with Doc 75 mg/m2 ? Cis 75 mg/m2 both IV over 1 hr day 1 with Darb 200 mcg SC day 1 and Pfil 6 mg SC day 2 randomized to without/with BNP before Cis was repeated every other week (1 cycle = 2 weeks) for up to 6 cycles. Response was determined after 3 and 6 cycles. Because of anticipated neurotoxicity (NT), the primary statistical endpoint was to differentiate between grade =2 NT rates of 30% in [A] and 10% in [B]: 90% power, two-tailed p<0.10, 76 patients per arm. Feasibility was prospectively defined as febrile neutropenia in <10% of patients and =1 treatment delay per cycles 1–3 and 4–6 in <20% of patients. Objective response rates of >35% were required to merit further investigation. Results: Between 8/04 and 3/06, 160 patients were enrolled but 5 never started therapy and 4 were ineligible: male/female, 99/52; white/black/other, 126/23/2; median age 62 (range, 30–88); PS 0/1, 69/82; stage IIIB/IV 14/137; [A]/[B], 76/75 well balanced. Sensory/motor/either NT grade =2 occurred in 28/14/32% on [A] and 19/19/29% on [B]. The incidence of febrile neutropenia was 1%. Treatment was delayed in cycles 1–3/cycles 4–6 in 3/3 patients in [A] and 1/5 patients in [B]. Completion rates for 3/6 cycles were 87/51% in [A] and 84/52% in [B]. By intent to treat, complete/partial response rates were 4/46% in [A] and 3/47% in [B]. Median estimated overall/progression-free survival times are10/6 months in [A] and 11/6 months in [B]. Overall, grade 3+4 neutropenia and thrombocytopenia occurred in =10% and anemia in 12% of patients. Non-hematologic toxicity was mild. Six deaths were thought to be treatment related. Conclusions: This dose-dense treatment regimen is feasible, tolerable, and worthy of further investigation in NSCLC. BNP did not result in significant protection from NT.

No significant financial relationships to disclose.

Depolarization-induced, glutamate receptor–mediated, and transactivation-dependent extracellular-signal regulated kinase phosphorylation in cultured cerebellar granule neurons

Depolarization of 7-8-day-old mouse cerebellar granule neurons in primary cultures, a glutamatergic preparation, by elevation of the extracellular potassium ion concentration ([K+]e) to 45 mM induces an increase of phosphorylation of extracellular-signal regulated kinase 1 and 2 (ERK1/2) at two time periods: 20 min and 60 min after the [K+]e increase. This effect can be mimicked by 5 min of exposure to 50 microM glutamate, suggesting that ERK1/2 phosphorylation in response to the depolarization is brought about by the resulting glutamate release. This concept is supported by the observation that the K+ -mediated stimulation of phosphorylation at both times is inhibited by MK-801, an NMDA antagonist, and by CNQX, an AMPA/kainate antagonist. These antagonists also inhibit the response to glutamate. Both increases in ERK1/2 phosphorylation are also inhibited by GM 6001 (a metalloproteinase inhibitor, preventing 'shedding' of growth factors), by AG 1478 (a receptor tyrosine kinase inhibitor, preventing epidermal growth factor [EGF] receptor activation), and also partly by heparin (inactivating heparin-binding epidermal growth factor [HB-EGF]), suggesting transactivation of epidermal growth factor receptors (EGFR). Transactivation is an intracellular/extracellular signal transduction pathway in which release from receptor- or depolarization-stimulated cells of EGFR ligand(s) (including HB-EGF), catalyzed by a metalloproteinase, stimulates receptor tyrosine kinases on the same (an autocrine effect) or adjacent (a paracrine effect) cells. The expression of HB-EGF as well as of transforming growth factor-alpha (TGF-alpha), two of the EGFR ligands, in the cells was confirmed by reverse transcription polymerase chain reaction, and the only partial inhibition by heparin suggests that both of these EGFR agonists are involved. Such a transactivation may play a major role in glutamate-mediated signaling and plasticity.

Chronic ethanol feeding alters the epithelial cell proliferation and apoptosis in rat gastric mucosa

We developed a chronic drinking rat model to investigate the long-term effects of ethanol feeding on cell proliferation and apoptosis in rat stomach. Adult male Sprague-Dawley (SD) rats received either an isocaloric control or drinking water containing 6% (v/v) ethanol as their only water intake for 1, 3, 7, 14 and 28 days. At the end of each feeding period, animals were sacrificed and the stomach was dissected for the sample preparation. The cell proliferation and apoptosis in gastric mucosa of rats in different groups were analyzed by flow cytometer, immunohistochemistry and computer image analysis. In the flow cytometric study, compared with the control, the cell apoptosis in gastric mucosa of the rats was enhanced during the exposure to the ethanol in 3rd to 28th day. Otherwise the cell proliferation was increased in 3rd to 14th days, and decreased in 28th days, respectively. The results were confirmed by immunohistochemistry and computer image analysis studied. This finding suggested that short-term chronic adequate alcohol intake may enhance the cell turnover of gastric mucosa. Long-term stimulus with the low concentration ethanol may cause the impairment of the cell turnover function of the gastric mucosa and may be one of the mechanisms underlying the gastric pathology associated with alcohol abuse.

Chemoradiotherapy (CRT) and gefitinib (G) in stage III non-small cell lung cancer (NSCLC): A CALGB stratified phase II trial

7046

Background: G is a small molecule inhibitor of EGFR with activity in advanced NSCLC and preclinical evidence of being a radiosenitizer. Methods: Patients with stage III NSCLC were assigned to stratum 1 (PS 0–1>5% weight loss and/or PS 2) or stratum 2 (PS 0–1weight loss < 5%). Both strata received induction paclitaxel (P) 200 mg/m2 and carboplatin (C) AUC of 6 IV every three weeks for 2 cycles plus G 250 mg PO/day. G was removed 4/05 from induction therapy as stage IV studies showed no benefit from adding G to P and C. Stratum 1 then received RT 200 cGy for 33 fractions (total dose 6,600 cGy) and G 250 mg PO /day. Stratum 2 received the same RT with concurrent G 250 mg/day, and P 50 mg/m2 plus C AUC of 2 weekly for 7 doses. Maintenance G was started after all toxicities were grade ≤2. Results: Activation was 5/02 and administrative closure 5/04 due to results from SWOG S0023. 64 patients were accrued and 59 (20 stratum 1, 39 stratum 2) were eligible and analyzed: median age 67, male 74%, adeno 30%, squamous 45%, other 25%, IIIA 51%, IIIB 49%. There was no clear increase for acute high-grade infield toxicities compared to CRT alone (reported PASCO 2004). Best response for stratum 1 was PR 29% for induction (RR 29%, 95% CI 10%-56%) and CR 5%, PR 45% full treatment (RR 50%, 95% CI 27%-73%); for stratum 2 PR 13% for induction (RR 13%, 95% CI 3%-34%) and CR 5%, PR 76% full treatment (RR 81%, 95% CI 65%-92%). Stratum 1 “poor risk” median failure free survival (FFS) was 11.5 months (95% CI 5.6–21.2), one year survival 60% (95% CI 33%-79%) and median overall survival (OS) 19.0 months (95% CI 7.2–21.2). Stratum 2 “good risk” median FFS was 9.2 months (95% CI 6.7–12.0), one year survival 47% (95% CI 30%–63%) and median OS was 12.0 months (95% CI 8.5–18.6). EGFR and Ras mutation analysis on tumor biopsies (n = 50) will be presented. Conclusions: Small sample size prevented planned data analysis. Survival of “good risk” patients on stratum 2 (CRT + G) was disappointing. The promising survival of the small number of “poor risk” patients on stratum 1 (RT + G) justifies a follow-up phase II trial of induction chemotherapy followed by RT with a concurrent small molecule EGFR inhibitor.

[Table: see text]

Induction (Ind) plus concurrent (Con) chemotherapy with high-dose (74 Gy) 3-dimensional (3-D) thoracic radiotherapy (TRT) in stage III non-small cell lung cancer (NSCLC): Preliminary report of Cancer and Leukemia Group B (CALGB) 30105

7042

Background: Combined chemoradiotherapy is the standard of care in stage III NSCLC. At standard TRT doses, local failures remain problematic and strategies exploiting the dose-response aspect of TRT are warranted. 3-D TRT allows escalation of TRT dose with acceptable toxicity (Socinski et al, J Clin Oncol 22:4341, 2004) and may enhance survival by improving loco-regional control. Methods: This is a two-arm randomized phase II trial evaluating 74 Gy with Con chemotherapy: Arm A- 2 cycles of Ind carboplatin (C) (AUC 6) and paclitaxel (P) (225 mg/m2) followed by weekly Con C (AUC 2/wk) and P (45 mg/m2) and 74 Gy; Arm B- 2 cycles of Ind C (AUC 5) and gemcitabine (G) (1000 mg/m2 d1,8) followed by Con G (35 mg/m2 twice weekly) and 74 Gy. The primary endpoint was a survival rate of ≥50% at 18 months after treatment initiation or med survival time (MST) of ≥18 mos. Results: 69 pts were entered (43 Arm A, 26 Arm B)- med age 61 yrs (39–77), 77% male, PS 0:1 42%:58%, stage IIIA:B 52%:48%. Ind therapy on both arms was well tolerated with no pts experiencing disease progression. ARM A- Overall response rate (RR) to all therapy was 61.9%. Gr 3–4 toxicities during Con therapy were anemia (15%), neutropenia (26%), esophagitis (9%), fatigue (9%), neuropathy (3%) and pulmonary (12%). There was 1 (3%) Gr 5 cardiac event. With med follow-up of 16.4 mos, the med progression-free survival (PFS) is 15.2 mos. The MST is not mature enough to estimate as only 15 deaths have occurred. ARM B- Closed early due to 3 (13%) Gr 5 pulmonary events. Overall RR to all therapy was 66.6%. Gr 3–4 toxicities during Con therapy were anemia (13%), fatigue (35%), esophagitis (35%), hemoptysis (4%), pulmonary (26% plus the 3 Gr 5 events). With med follow-up of 22 mos, the med PFS is 7.7 mos and the MST is 13.9 mos. There was a correlation between Gr 3–5 pulmonary toxicity and V20 ≥ 38% (p<0.05). Conclusions: 1) High dose 3-D TRT is feasible within CALGB, 2) the details of TRT (V20) are important with regard to toxicity, 3) the survival of pts on Arm A appears promising.

[Table: see text]

Vatalanib (V) for patients with previously untreated advanced malignant mesothelioma (MM): A phase II study by the Cancer and Leukemia Group B (CALGB 30107)

7081

Background: Targeting both vascular endothelial growth factor (VEGF) and platelet derived growth factor (PDGF) may be an appropriate therapeutic strategy in MM. MM express VEGF, PDGF, and their receptors, suggesting autocrine growth-stimulating loops. VEGF inhibitors and PDGF inhibitors have in vitro activity in MM. In MM patients (pts), high VEGF levels correlate with poor outcome. Vatalanib inhibits VEGF and PDGF receptor tyrosine kinases. Methods: We conducted a phase II trial of V in pts with unresectable, histologically-confirmed MM, measurable disease, no prior therapy, ECOG performance status (PS) 0–1. Primary endpoint: 3-month (mo) progression-free survival (PFS). V 1250 mg, was given orally daily. CT scans were obtained Q6 weeks. Baseline serum VEGF, PDGF were determined. Results: 47 eligible pts (46 evaluable) enrolled at 19 sites from 7/03–11/04. Pt characteristics: male 92%, median age 75 (range 51–92; 64% were >70). Histology: epithelial 80%, sarcomatoid 11%, biphasic 9%. Site of origin: pleura 87%, peritoneum 6%, other 6%. PS 0/1: 21%/ 79%. 261 cycles were administered, median 3, range 1–32; 2 pts continue treatment. Grade 3/4 toxicities: neutropenia 2%, lymphopenia 2%, nausea/vomiting 15%/9%, increased ALT/AST 9%/6%, hypertension 2%, gastrointestinal bleed 2%. Partial response: 11% (5 pts), stable disease 66%. 3-mo PFS: 55% (95% CI: 40%, 68%), median PFS: 4.1 mo; median survival 10.0 mo. Median baseline serum levels in 40 pts: VEGF 425 pg/mL, PDGF 22754 pg/mL. There was no correlation between baseline VEGF or PDGF levels and response, PFS, or survival. Conclusions: The study did not achieve the protocol-specified 3-mo PFS of 75%. However, the objective response rate of 11% and median survival of 10 months are similar to other active single-agents for MM, which suggests that V may warrant further study in this disease.

[Table: see text]

Quality of life (QOL) companion to CALGB 9840: A phase III study of paclitaxel (P) via weekly 1 hour (hr) versus standard 3 hour infusion every 3 weeks with trastuzumab in the treatment of patients with/without HER-2/neu-overexpressing metastatic breast cancer

674

Background: This study determined if adding trastuzumab (Herceptin, T) to P modified the QOL of HER-2 non-overexpressors and examined QOL differences between patients treated with weekly versus standard P. Methods: Of the 585 patients treated in CALGB 9840, 394 provided QOL data. Eligibility criteria and main trial results were reported, indicating greater efficacy in weekly versus standard P, but no greater efficacy with T in HER-2 negatives (Seidman AD et al., Proc ASCO 2004, Vol. 22, No 14S, abstract 512). HER-2 non-overexpressors were randomized to 1 of 4 groups: 1) P 175 mg/m2 over 3 hrs every 3 wks; 2) P 80 mg/m2 over 1 hr weekly; 3) P 175 mg/m2 over 3 hrs every 3 wks + T 4 mg/kg load, then 2 mg/kg weekly; and 4) P l 80 mg/m2 over 1 hr weekly + T 4 mg/kg load, then 2 mg/kg weekly, all IV. All HER-2 overexpressors received T and were randomized to group 3 or 4. Patients completed QOL interviews prior to randomization, and at 3, 6, and 9 months. Main outcome measures were the EORTC-C30 with the Breast Module (QLQ-BR23). Data were analyzed using general linear models for repeated measures, with the following covariates: treatment arm, assessment point, patient age, race, education, marital status, performance status, prior chemotherapy, and prior radiation therapy. Results: HER-2 negative patients receiving weekly P with/without T as compared to standard P with/without T reported better global QOL (p=.022) and fewer cancer symptoms (p=.036). No QOL differences were observed among the HER-2 overexpressors. The use of T in the HER-2 negatives, regardless of P schedule, resulted in better role (p=.002) and emotional functioning (p=.039), and fewer arm (p=.045) and breast (p=.033) symptoms than HER-2 negative patients not receiving T. No differences in physical, social, and cognitive functioning were observed across any of these treatment groups. Conclusions: Both weekly P and T improved the QOL of HER-2 negative patients. There were no QOL differences by P schedule among the HER-2 overexpressors. The higher QOL in HER-2 negatives receiving T was unexpected, inconsistent with clinical data, and needs further exploration in the dataset.

[Table: see text]

Feasibility of eliminating premixing for the production of pellets in a rotary processor

This current study aims to explore the feasibility of eliminating the premixing step for making pellets in a rotary processor. Microcrystalline cellulose (MCC) and lactose were used as starting materials. They could be loaded into the rotary processor separately using three different loading configurations (Methods I, II, and III) or as MCC:lactose blend, which was prepared in the separate mixer prior to loading (Method IV). Physical properties of the pellets prepared in Methods I-III were evaluated and compared against those prepared using a premixed blend (Method IV). The effects of loading configuration on pellet quality can be assessed by comparing the pellets prepared in Methods I, II, and III. Physical characterization of pellets included mean size, size distribution, oversized fraction, and shape. No significant difference in pellet properties could be attributed to the effect of premixing. Pellet properties were not significantly affected by the different loading configurations either. This study demonstrated that homogeneous powder blends are not required for the production of pellets in rotary processing. The tumbling action of the powders at the start of rotary processing is sufficient to ensure adequate powder mixing. However, it may be judicious to cofeed the different powders to achieve some preliminary mixing during loading under extreme processing conditions.

Predicting the onset of net carbon uptake by deciduous forests with soil temperature and climate data: a synthesis of FLUXNET data

We tested the hypothesis that the date of the onset of net carbon uptake by temperate deciduous forest canopies corresponds with the time when the mean daily soil temperature equals the mean annual air temperature. The hypothesis was tested using over 30 site-years of data from 12 field sites where CO(2) exchange is being measured continuously with the eddy covariance method. The sites spanned the geographic range of Europe, North America and Asia and spanned a climate space of 16 degrees C in mean annual temperature. The tested phenology rule was robust and worked well over a 75 day range of the initiation of carbon uptake, starting as early as day 88 near Ione, California to as late as day 147 near Takayama, Japan. Overall, we observed that 64% of variance in the timing when net carbon uptake started was explained by the date when soil temperature matched the mean annual air temperature. We also observed a strong correlation between mean annual air temperature and the day that a deciduous forest starts to be a carbon sink. Consequently we are able to provide a simple phenological rule that can be implemented in regional carbon balance models and be assessed with soil and temperature outputs produced by climate and weather models.