Predictive value of palpation per rectum for detection of the CL in Zebu cattle as evaluated by progesterone concentrations and ultrasonography

The main objective of this study was to calculate the predictive value of the positive and negative diagnosis of the presence of a corpus luteum by palpation per rectum in Zebu cattle. Gyr breed (n = 16) heifers were palpated by a veterinarian every 3 d during March and April, and every 5 days during May. The presence or absence of a CL was recorded for 442 examinations. A blood sample was obtained after each examination, and a functional CL was considered to be present if plasma progesterone concentrations were above 1 ng/ml. Progesterone results were used as the reference to calculate the sensitivity and specificity of palpation per rectum for the diagnosis of a functional CL on different months. Predictive values for the positive and negative diagnoses were calculated using different hypothetical rates of the prevalence of CL. To evaluate the morphological basis of an erroneous diagnosis, ultrasonographic scanning of the ovaries was performed in 264 cases and the physical presence or absence of a CL was registered. The calculations were repeated using the ultrasonographic findings as the reference to evaluate the sensitivity and specificity of the diagnosis of a structural CL by per rectum palpation. Several heifers were not cyclic in March but began to cycle during the study. Thus, the prevalence of both functional and structural CL increased with time. As a result, the proportion of palpation diagnoses classified as true positives increased in May, while the proportion of true negatives decreased. Although the values of sensitivity and specificity remained constant from month to month, the predictive values changed markedly in May, when the predictive value of the positive test increased while the predictive value of the negative test decreased. These changes were due to differences in the prevalence of a CL and not to differences in the palpable characteristics of CLs in different months. The prevalence of a structural CL was always higher than that of a functional CL. The Cohen's Kappa test for concordance revealed better correspondence between palpation per rectum and ultrasound (k = 0.82) than between progesterone and either ultrasound (k = 0.68) or palpation (k = 0.66). These results show that a large proportion of the errors imputed to deficient palpation when progesterone concentrations are used as a reference are in fact the result of lack of correspondence between the physical and functional presence of a CL.

B- and C-RAF display essential differences in their binding to Ras: the isotype-specific N terminus of B-RAF facilitates Ras binding

Recruitment of RAF kinases to the plasma membrane was initially proposed to be mediated by Ras proteins via interaction with the RAF Ras binding domain (RBD). Data reporting that RAF kinases possess high affinities for particular membrane lipids support a new model in which Ras-RAF interactions may be spatially restricted to the plane of the membrane. Although the coupling features of Ras binding to the isolated RAF RBD were investigated in great detail, little is known about the interactions of the processed Ras with the functional and full-length RAF kinases. Here we present a quantitative analysis of the binding properties of farnesylated and nonfarnesylated H-Ras to both full-length B- and C-RAF in the presence and absence of lipid environment. Although isolated RBD fragments associate with high affinity to both farnesylated and nonfarnesylated H-Ras, the full-length RAF kinases revealed fundamental differences with respect to Ras binding. In contrast to C-RAF that requires farnesylated H-Ras, cytosolic B-RAF associates effectively and with significantly higher affinity with both farnesylated and nonfarnesylated H-Ras. To investigate the potential farnesyl binding site(s) we prepared several N-terminal fragments of C-RAF and found that in the presence of cysteine-rich domain only the farnesylated form of H-Ras binds with high association rates. The extreme N terminus of B-RAF turned out to be responsible for the facilitation of lipid independent Ras binding to B-RAF, since truncation of this region resulted in a protein that changed its kinase properties and resembles C-RAF. In vivo studies using PC12 and COS7 cells support in vitro results. Co-localization measurements using labeled Ras and RAF documented essential differences between B- and C-RAF with respect to association with Ras. Taken together, these data suggest that the activation of B-RAF, in contrast to C-RAF, may take place both at the plasma membrane and in the cytosolic environment.

Increased expression levels of human telomerase reverse transcriptase (hTERT) mRNA correlates with poor prognosis in resected non-small cell lung cancer (NSCLC) patients

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Background: Telomerase adds hexameric TTAGGG nucleotide repeats onto the ends of chromosomal DNAs to compensate for losses of each cell replication. In several tumors, telomerase is expressed in a way that tumoral cell proliferates indefinitely. Correlation between telomerase level expression, clinico-pathological characteristics and survival of lung cancer is not well established in NSCLC. Methods: We studied 149 consecutive patients (140 men/9 women) with resected NSCLC: 37.6% adenocarcinoma, 59 % squamous cell, and 3.4% large cell carcinoma. Pathological stage: I (36.9%), II (32.3%) and III (30.8%). Reverse transcription-polymerase chain reaction (RT-PCR) analysis was used for the detection hTERT expression in lung cancer tissues immediately snap-frozen in liquid nitrogen at -80 °C. Results: Median and mean values of hTERT mRNA were 18.27 and 475.29 (SE 309.76). There were no significant differences on expression according to sex, histology, smoking history and pathological stage (ANOVA). Patients with highest values of hTERT mRNA expression (percentile 95, cut-off value >353) had worse median progression free survival (PFS) (p=0.024) and overall survival (OS) (p=0.020), using Kaplan-Meier method. Multivariate analysis by Cox regression yielded that hTERT level > 353 independently predicted a worse PFS (HR=0.39; 95% CI 0.17–0.93, p=0.034) and OS (HR=0.32; 95% CI 0.12–0.82, p=0.017). Conclusions: A high level of telomerase expression in tumoral tissue is strongly associated with increased risk of recurrence and mortality in resected NSCLC. The level of hTERT mRNA would predict the prognosis of lung cancer patients.

No significant financial relationships to disclose.

First-line docetaxel (Dx) and capecitabine (Cap) in advanced head and neck cancer

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Background: Dx and Cap are useful drugs in head and neck cancer. Our purpose was to establish the efficacy and safety of this combination in non selected patients (pts) with advanced or metastatic (M1) head and neck cancer. Methods: : Between Apr 2005 and Nov 2006, 33 pts with squamous cell locally advanced or M1 head and neck cancer received the following chemotherapy (Ct) schedule: Dx 75 mg/m2 day 1 and Cap 950 mg/m2/12h days 2–14, every 3 weeks.30 pts (90.9%) had received previous local radiotherapy, 11 of them with concomitant Ct. Results: Mean age was 60 years old (range 46–75). M/F: 32/1. PS 0/1/2: 1/29/3. Location of disease: only local 49%; local and M1 36%; only M1 15% (Main M1 site: lung 76.5%, nodes 11.8%, bone 5.9%, soft tissue 5.9%). Mean number of Ct cycles: 4 (range 1–7). Worst hematologic toxicities per patient G3/G4 (%): neutropenia 6/39; febrile neutropenia 36/0; anemia 3/0; trombopenia 3/3. Non-hematologic toxicities G2/G3 (%): vomiting 3/3; neuropathy 6/0; asthenia 33/6; diarrhea 21/3; mucositis 33/18; nail changes 12/0; hand foot syndrome 3/12. Other events to remark: 4 pts had neumonia (2 toxic deaths), 1 pts had angor and required a different Ct schedule, 2 pts had massive hemorrage (1 exitus). There were 7 pts not evaluable for response (4 not yet evaluated, 1 early death due to massive hemorrage, 1 toxic death due to neumonia, 1 early disphagia). Among the evaluated pts, responses were: 2 CR (7.7%), 10 PR (38.5%), 9 SD (34.6%) and 5 PD (19.2%). Median TTP was 21 weeks (95%CI 17.5 - 24.2). Median OS was 39.8 weeks (95%CI 32.4 - 47.4) by Kaplan-Meier method. Conclusions: This combination appears to be active in pts with advanced or M1 head and neck cancer. Main toxicities were neutropenia, febrile neutropenia, mucositis and asthenia. Global toxicity was important with two toxic deaths documented

No significant financial relationships to disclose.

Nasopharyngeal carcinoma: Comparison of concomitant chemoradiotherapy with neoadjuvant chemotherapy in the caucasian population

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Background: Nowadays, concomitant chemoradiotherapy (CT-RT) is the standard treatment for nasopharyngeal carcinoma (NPC). Neoadyuvant chemotherapy (CT) has been investigated without definitive conclusions. The aim of this study is to compare results of patients(pts) treated with neoadyuvant CT with those treated with concurrent CT-RT. Methods: 38 pts with histologically proven NPC stage II-IVb (PS 0–2) were treated. 27 pts (71.1%) (Group A) (June 1994-May 2000) received Cisplatin (P) 100 mg/m2, Epirrubicin (E) 70 mg/m2, Bleomicin (B) 15 mg D1 and B 12 mg/m2 continous infusion (c.i) for 5 days every 3 week with sequential RT. The other 11 pts (28.9%) (Group B) (June 2002-August 2006) received P 100 mg/m2 D1, D22 and D43 concurrent with RT followed by adyuvant CT P 80 mg/m2 and 5-Fluorouracil 1,000mg/m2/d D1-D4 c.i every 28 day for 3 cycles. Results: 38 pts: 30 male(79%), 8 female(21%). Median age: 53(range 15–75). Stages:II:7, III:11, IVA:12, IVB:8(AJCC 2002). Histology:WHO I-II:11, WHO III:27. Overall response rate: Group A: 25/27 (92.5%), Group B: 10/11 (90.9%) p=0.65. Group A: CR: 17/27 (62.9%); PR: 8/27 (29.6%); PD: 1/27( 3.7%). Group B: CR: 8/11(72.7%); RP: 2/11 (18.1%). 1 pts of each group was not evaluated. Median overall survival (OS) was 34 months (m) in Group A and has not been reached in Group B. Estimated 3 years OS was 48% in GroupA and 80% in GroupB. Median progression free survival (PFS) was 42 m in Group A and 45 m in Group B p=0.72. Estimated 3 years PFS was 50.6% and 66.7% respectively. In the multivariate analysis concurrent CT-RT (HR=5.94 p=0.03) and stage (HR=0.17 p=0.01) were associated with OS. There was 2 toxic death in Group A. The most common toxicities was; Group A: bone marrow suppresion, nausea; Group B: mucositis. Conclusions: These data suggest that P based concomitant CT-RT improves OS and PFS compared with neoadyuvant CT (BEC) followed by RT.

No significant financial relationships to disclose.

Las amiloidosis cerebrales y las demencias

Amyloid deposit in the brain causes neurologicaldiseases characterized by dementia. These depositsare constituted by fibrilar proteins with beta-planarshape whose origin is due to mutations, infectionsor exogenous alterations. Treatment of cerebralamyloid angiopathy depends on the cause and atpresent, the manipulation of the synthesis of theresponsible peptides, their chemical solubilizationor extraction outside of the nervous system, arebeing investigated.

Ras activation in response to phorbol ester proceeds independently of the EGFR via an unconventional nucleotide-exchange factor system in COS-7 cells

Ras is a major mediator of PE (phorbol ester) effects in mammalian cells. Various mechanisms for PE activation of Ras have been reported [Downward, Graves, Warne, Rayter and Cantrell (1990) Nature (London) 346, 719-723; Shu, Wu, Mosteller and Broek (2002) Mol. Cell. Biol. 22, 7758-7768; Roose, Mollenauer, Gupta, Stone and Weiss (2005) Mol. Cell. Biol. 25, 4426-4441; Grosse, Roelle, Herrlich, Höhn and Gudermann (2000) J. Biol. Chem. 275, 12251-12260], including pathways that target GAPs (GTPase-activating proteins) for inactivation and those that result in activation of GEFs (guanine nucleotide-exchange factors) Sos (son of sevenless homologue) or RasGRP (RAS guanyl releasing protein). However, a biochemical link between PE and GAP inactivation is missing and GEF stimulation is hard to reconcile with the observation that dominant-negative S17N-Ras does not compromise Ras-dependent ERK (extracellular-signal-regulated kinase) activation by PE. We have addressed this controversy and carried out an in-depth biochemical study of PE-induced Ras activation in COS-7 cells. Using a cell-permeabilization approach to monitor nucleotide exchange on Ras, we demonstrate that PE-induced Ras-GTP accumulation results from GEF stimulation. Nucleotide exchange stimulation by PE is prevented by PKC (protein kinase C) inhibition but not by EGFR [EGF (epidermal growth factor) receptor] blockade, despite the fact that EGFR inhibition aborts basal and PE-induced Shc (Src homology and collagen homology) phosphorylation and Shc-Grb2 (growth-factor-receptor-bound protein 2) association. In fact, EGFR inhibition ablates basal nucleotide exchange on Ras in growth-arrested COS-7 cells. These data disclose the existence of two separate GEF systems that operate independently from each other to accomplish PE-dependent formation of Ras-GTP and to maintain resting Ras-GTP levels respectively. We document that COS-7 cells do not express RasGRP and present evidence that the PE-responsive GEF system may involve PKC-dependent phosphorylation of Sos. More fundamentally, these observations shed new light on enigmatic issues such as the inefficacy of S17N-Ras in blocking PE action or the role of the EGFR in heterologous agonist activation of the Ras/ERK pathway.

Live-cell imaging of endogenous Ras-GTP illustrates predominant Ras activation at the plasma membrane

Ras-GTP imaging studies using the Ras-binding domain (RBD) of the Ras effector c-Raf as a reporter for overexpressed Ras have produced discrepant results about the possible activation of Ras at the Golgi apparatus. We report that RBD oligomerization provides probes for visualization of endogenous Ras-GTP, obviating Ras overexpression and the side effects derived thereof. RBD oligomerization results in tenacious binding to Ras-GTP and interruption of Ras signalling. Trimeric RBD probes fused to green fluorescent protein report agonist-induced endogenous Ras activation at the plasma membrane (PM) of COS-7, PC12 and Jurkat cells, but do not accumulate at the Golgi. PM illumination is exacerbated by Ras overexpression and its sensitivity to dominant-negative RasS17N and pharmacological manipulations matches Ras-GTP formation assessed biochemically. Our data illustrate that endogenous Golgi-located Ras is not under the control of growth factors and argue for the PM as the predominant site of agonist-induced Ras activation.

Elderly patients with advanced non-small cell lung cancer (nsclc). Results of chemotherapy and comparison with younger patients

18505

Background: Lung cancer is increasingly diagnosed in elderly patients and is the first cause of cancer death. Treatment of this subset represents a challenge to medical oncologists. Methods: We retrospectively reviewed clinical characteristics, co-morbidity (Charlson Index), toxicity and results of all patients ≥ 65 years (y) old, diagnosed of advanced NSCLC. We compared these results with younger patients’. Results: From January-95 to June-02, we treated 477 patients (pt), 176 ≥ 65 years, 301 < 65 y. Treatment: 177 pt, MIC (mitomycine + ifosfamide + cisplatin), 60 ≥ 65 y and 117 < 65 y; 156, CG (Cisplatin + Gemcitabine), 52 > 65 y and 104 < 65 y; 144, CP (Cisplatin + Paclitaxel), 64 ≥ 65 y and 120 < 65 y. Characteristics: median age 60 (31–78); 428 male, 49 female; ECOG 0/1/2/3: 83/312/71/5, Stage IIIA, IIIB and IV: 72/199/206, Histology: squamous carcinoma 215, adenocarcinoma 190, large cell 19, bronchioloalveolar 7, undifferentiated 45 pt. No significant differences between the two groups. Overall response rate: 39% (CR, 32.9%, PR, 6.1%), Stable disease 26.4% and Progressive disease, 26.4%. Patients ≥ 65 y: CR 5.7%, PR 45.5%, SD 23.3% and PD 18.2%. Patients < 65 y: CR 6.3% PR 25.6%, SD 28.2% and PD 31.2%. Predictive factors for response: ECOG and stage. Response rate was superior in patients ≥ 65 y and in patients ≥ 70 y. Overall survival: 38.29 weeks (w): < 65 y, 38.57 w; 65–70 y, 37.71 w and ≥ 70 y, 37 w. Multivariate analysis: ECOG, stage and sex were prognostic factors; age, histology, Charlson index and schedule treatment were not significant. Grade 3/4 episodes of toxicity: ≥ 65 y, 184/17, and < 65 y, 232/8. Treatment delays: ≥ 65 y, 115 and < 65 y, 100. Hospitalization due to toxicity: >≥ 65 y, 34 and < 65 y, 23. Treatment was stopped in 13 pt >≥ 65 y and in 7 pt < 65 y. Conclusions: Age is not a predictive factor for response to chemotherapy, neither a prognostic factor for survival. Charlson index does not seem to be useful for these patients. Although toxicity is superior, cisplatin-based schedules are safe and active.

No significant financial relationships to disclose.

Biweekly schedule of cisplatin with prolonged infusion of gemcitabine in advanced non small cell lung cancer (NSCLC)

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Background: Firstly, we conducted a phase I of a biweekly schedule of cisplatin with prolonged infusion of gemcitabine (10 mg/m2/min) and stablished the dose to perform a phase II. We present final results of a phase II with this combination. Methods: Patients with cytologically or histologically confirmed NSCLC stage IIIB and IV were included. Treatment consisted of Cisplatin 50 mg/m2 days 1 and 15 with Gemcitabine 1600 mg/m2 in 160 minutes (10 mg/m2/min), days 1 and 15 every 28 days. Chemotherapy was administered to a maximum of 6 cycles; if radiotherapy was planned, patients received 4 cycles. Results: From March-04 to January-05, 55 patients were included. Patient characteristics: Median age 59 years (35–75). Gender: 51 male 4 female. ECOG performance status 0/1/2: 8/43/4. Histology: Squamous cell carcinoma 26 (47.3%), adenocarcinoma 22 (40%), large cell carcinoma 2 (3.6%), undifferentiated 5 (9%). Stage: IIIA 2 (3.6%), IIIB 27 (49.1%) and IV 26 (47.3%). Treatment compliance: Administrations: Mean 6.7 and median 8 (1–12). Dose intensity: Cisplatin 20.35 mg/m2/week (81%) Gemcitabine 632.61 mg/m2/week (79%). Toxicity: Extrahematological toxicity grade 3/4 per patient: nausea 10/0, emesis 6/0, asthenia 31/1, anorexia 14/0, mucositis 1/0, diarrhoea 1/1, infection 4/0, hepatic 2/0, vascular 0/1 (pulmonary thromboembolism). Neurotoxicity grade 1, 13 pt and grade 2, 1 pt. Hematological toxicity grade 3/4: anemia 1/0, thrombocytopenia 5/1, neutropenia 21/9 and neutropenic fever 4/0. Nine patients were hospitalised due to toxicity. There was one toxic death. Response rate: Response was evaluated in 52 pt (3 pt died after first cycle). Overall response rate was 38.1% (95% CI 50.93–25.26%). Complete response 2 (3.6%), Partial response 19 (34.5%), Stable disease 23 (41.8%), Progressive disease 8 (14.5%). Survival: Overall median survival was 9.6 months (95% CI 7.76–11.43): stage III 10.46 and stage IV 8.8. Overall progression-free survival was 8.06 months (95% CI 5.95–10.18): stage III 8.9 and stage IV 6.3. Conclusions: Biweekly cisplatin with prolonged infusion of gemcitabine is an active regimen for advanced NSCLC with a good toxicity profile. This better rational way of gemcitabine infusion should be more profoundly explored.

No significant financial relationships to disclose.

Concurrent chemoradiotherapy (crt) with weekly docetaxel (d) for advanced head and neck cancer

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Background: Concomitant CRT has become a standard treatment for advanced head and neck cancer. The aim of this study was to evaluate the efficacy and toxicity of concurrent CRT with D in patients (pts) with advanced squamous cell carcinoma of head and neck (SCCHN). Methods: Patients with untreated and unresectable stage III or IV (M0) squamous cell carcinoma of head and neck were included. Treatment consisted of D 20 mg/m2 weekly with concomitant radiotherapy 70 Gy (2 Gy per day, 7 weeks). Results: From September 03 to October 05, sixty-four pts with advanced SCCHN, were recruited. Gender: 61 male, 3 female. Mean age: 56.5 years old (range 42–77). ECOG PS 0/1/2: 0/57/7. Primary sites of disease: oral cavity 8, oropharynx 26, hypopharynx 15 and larynx 15. Stage III 16 pts and stage IV 48 pts. Compliance: 393 administrations of D were given, median 6, mean 6 (range 1–8). Fifty-five pts (86%) completed the radiotherapy dose planned (mean dose of RT was 66 Gy). One refused more treatment with D after first administration. Nineteen pts required supportive percutaneous gastrostomy or nasogastric tubes previously or during therapy. Grade 2/3/4 toxicity per patient: anemia 4/2/0, mucositis 21/24/0, dermatitis 21/20/0. Neither thrombopenia nor neutropenia were observed. Four pts died of aspiration pneumonia during treatment, one of gastric perforation and two of unknown causes. Fifty-six pts were evaluable for response: CR 28 (44%), PR 23 (36%), SD 2 (3%), PD 3 (5%), with an overall response rate of 80%. Median overall survival was 74.86 weeks (95% CI: 40.40–109.32) and median progression free survival was 48 weeks (95% CI: 18.80–77.20). With a median follow up of 40 weeks 34 pts (53%) were alive and 21 of them (33%) remained free of disease. Conclusions: Concurrent weekly D with conventional radiotherapy showed a high response rate. Toxicity was manageable and allowed maintaining radiotherapy administration. Taking into account poor prognostic factors of our series, survival results seem promising.

No significant financial relationships to disclose.

Value of postoperative adjuvant chemotherapy (ac) for patients with completely resected hepatic (hm) and/or pulmonary metastases (pm) from colorectal cancer (crc): retrospective analysis of 146 patients

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Background: AC is indicated for stage III and high risk stage II colon cancer, as well as for stages II-III rectal cancers combined with RT. Moreover, chemotherapy improves survival in metastatic disease. There are no randomised trials evaluating the role of systemic AC after resection of metastases from CRC. Methods: We retrospectively reviewed patients with completely (R0) removed HM and/or PM from CRC, analysing prognostic factors for overall survival, including AC. Kaplan-Meier method with log rank test was used to assess and compare survival curves. Cox regression model was applied for multivariate analysis. Results: From Jan 1993 to Jun 2004, 146 patients were identified: 98 (67%) with HM, 39 with PM (27%) and 9 (6%) with both HM and PM. Gender (M/F): 102/44. Median age: 65.5 y-o (39.3–82.6). Primary CRC: rectum 62 (42.5%), pN+ 87 (60%), stage IV at diagnosis 57 (39%). Number of metastatic nodules resected: mean 2.25 (1–10). Size of the largest metastasis: mean 4 cm (0.5–18). Mean serum CEA value before surgery 20.6 (0–332): normal 73 (50%), increased 45 (31%), missing data 28 (19%). Ninety seven patients (66.5%) received postoperative AC (5FU/LV: 81, CPT11: 15, FOLFOX 1), 10 patients were not treated because of postoperative death (1) or early progression (9), and 39 due to several causes: not referred, medical contraindication or patient refusal. Median overall survival was 46.4 m, with a 3, 5 and 7-year survival probability of 59%, 35% and 22%. At univariate analysis, number (2 vs >2) of metastases resected (60.1 vs 38.3m, p=0.0004) and AC (54.3 vs 31.2m, p=0.0001) were significant prognostic factors. Increased CEA (p=0.088), involved nodes in the primary (p=0.0618) and PM+HM (p=0.0538) showed a trend towards worse survival. In multivariate analysis (excluding patients with early death/progression) AC was associated with longer survival probability (HR 2.049, 95%CI 1.149–3.656, p=0.015). Conclusions: In our retrospective series AC seems to improve survival after resection of liver and/or lung metastases from CRC. The best use of chemotherapy (adjuvant, neoadjuvant or both) in patients with resectable metastatic CRC should be evaluated in a randomised fashion.

No significant financial relationships to disclose.

Use of the Ras binding domain of c-Raf for biochemical and live-cell analysis of Ras activation

Small modular GBDs (GTPase-binding domains) derived from GTPase-effector proteins are useful tools for the selective detection of the active GTP-loaded GTPase conformation, be it in biochemical assays or for imaging purposes. Use of GBD probes requires careful consideration of all features of the GDB-GTPase interaction. It is innate to the strong and specific interaction with the GTP-loaded GTPase, that GBDs will protect their partner GTPases from GAP (GTPase-activating protein) action. This feature is likely to cause an increase in cellular Ras-GTP levels, in particular in leucocytes and other cells with high steady-state Ras-GDP/GTP cycling rates. By the same token, high levels of GBD expression will interrupt GTPase-initiated signalling, with implications for the activation of the very same GTPase since feedback regulatory mechanisms can impinge on this process.

Influence of nutrient intake and body fat on concentrations of insulin-like growth factor-I, insulin, thyroxine, and leptin in plasma of gestating beef cows1

Pregnant Angus x Hereford cows (n = 73) were used to determine the effects of amount of nutrient intake and BCS on concentrations of IGF-I, insulin, leptin, and thyroxine in plasma. At 2 to 4 mo of gestation, cows were blocked by BCS and assigned to one of four nutritional treatments: high (H = a 50% concentrate diet fed ad libitum in a drylot) or adequate native grass pastures and one of three amounts of a 40% CP supplement each day (M = moderate, 1.6 kg; L = low, 1.1 kg; or VL = very low, 0.5 kg; as-fed basis). After 110 d of treatment, all cows grazed dormant native grass pasture and received 1.6 kg/d of a 40% CP supplement. At 68, 109, and 123 d of treatment, cows were gathered, and plasma samples were collected by tail venipuncture (fed sample). After 18 h without feed and water, a second plasma sample was collected (fasted sample). At 109 d of treatment, BCS was greatest (P < 0.05) for H cows, similar for M and L cows, and least for VL cows. Concentrations of insulin and leptin were greater (P < 0.05) for H cows than for M and VL cows at 68 and 109 d, but similar for all groups at 123 d. Thyroxine in plasma was greatest (P < 0.05) for H cows at 68 d and similar for cows on all treatments at 123 d. Concentrations of IGF-I, insulin, and leptin in fed and fasted cows were positively correlated with BCS at 109 d. Body condition was predictive of concentrations of IGF-I, insulin, and leptin when cows had different nutrient intakes, but BCS accounted for less than 12% of the variation in plasma concentrations of IGF-I, insulin, and leptin when nutrient intake was the same for all cows. We conclude that amount of nutrient intake has a greater influence than body energy reserves on IGF-I, insulin, and leptin concentrations in the plasma of gestating beef cows.

Quantification of absolute Ras-GDP/GTP levels by HPLC separation of Ras-bound [(32)P]-labelled nucleotides

Ras guanine nucleotide binding protein (GTPase) activation is a widely assessed readout in cell biological studies. We describe an improved approach for the quantitative analysis of total GDP and GTP bound to Ras. The present method involves HPLC separation and online detection/quantitation of Ras-bound [(32)P]-labelled GDP/GTP. As compared to standard approaches that are time consuming and/or provide only semi-quantitative data, this technique allows the rapid processing of large numbers of samples for the quantitative determination of Ras-bound GDP and GTP.