A Three-Dimensional Skeletal Reconstruction of the Stem Amniote Orobates pabsti (Diadectidae): Analyses of Body Mass,Centre of Mass Position,and Joint Mobility

Orobates pabsti, a basal diadectid from the lower Permian, is a key fossil for the understanding of early amniote evolution. Quantitative analysis of anatomical information suffers from fragmentation of fossil bones, plastic deformation due to diagenetic processes and fragile preservation within surrounding rock matrix, preventing further biomechanical investigation. Here we describe the steps taken to digitally reconstruct MNG 10181, the holotype specimen of Orobates pabsti, and subsequently use the digital reconstruction to assess body mass, position of the centre of mass in individual segments as well as the whole animal, and study joint mobility in the shoulder and hip joints. The shape of most fossil bone fragments could be recovered from micro-focus computed tomography scans. This also revealed structures that were hitherto hidden within the rock matrix. However, parts of the axial skeleton had to be modelled using relevant isolated bones from the same locality as templates. Based on the digital fossil, mass of MNG 10181 was estimated using a model of body shape that was varied within a plausible range to account for uncertainties of the dimension. In the mean estimate model the specimen had an estimated mass of circa 4 kg. Varying of the mass distribution amongst body segments further revealed that Orobates carried most of its weight on the hind limbs. Mostly unrestricted joint morphology further suggested that MNG 10181 was able to effectively generate propulsion with the pelvic limbs. The digital reconstruction is made available for future biomechanical studies.     

Resistance training-induced muscle hypertrophy is mediated by TGF-β1-Smad signaling pathway in male Wistar rats

The TGF-β1-Smad pathway is a well-known negative regulator of muscle growth; however, its potential role in resistance training-induced muscle hypertrophy is not clear. The present study proposed to determine whether and how this pathway may be involved in resistance training-induced muscle hypertrophy. Skeletal muscle samples were collected from the control, trained (RT), control + SB431542 (CI_TGF), and trained + SB431542 (RTI_TGF) animals following 3, 5, and 8 weeks of resistance training. Inhibition of the TGF-β1-Smad pathway by SB431542 augmented muscle satellite cells activation, upregulated Akt/mTOR/S6K1 pathway, and attenuated FOXO1 and FOXO3a expression in the CI_TGF group (all p < .01), thereby causing significant muscle hypertrophy in animals from the CI_TGF. Resistance training significantly decreased muscle TGF-β1 expression and Smad3 (P-Smad3^S423/425) phosphorylation at COOH-terminal residues, augmented Smad2 (P-Smad2-L^S245/250/255) and Smad3 (P-Smad3-L^Ser208) phosphorylation levels at linker sites (all p < .01), and led to a muscle hypertrophy which was unaffected by SB431542, suggesting that the TGF-β1-Smad signaling pathway is involved in resistance training-induced muscle hypertrophy. The effects of inhibiting the TGF-β1-Smad signaling pathway were not additive to the resistance training effects on FOXO1 and FOXO3a expression, muscle satellite cells activation, and the Akt/mTOR/S6K1 pathway. Resistance training effect of satellite cell differentiation was independent of the TGF-β1-Smad signaling pathway. These results suggested that the effect of the TGF-β1-Smad signaling pathway on resistance training-induced muscle hypertrophy can be attributed mainly to its diminished inhibitory effects on satellite cell activation and protein synthesis. Suppressed P-Smad3^S423/425 and enhanced P-Smad2-L^S245/250/255 and P-Smad3-L^Ser208 are the molecular mechanisms that link the TGF-β1-Smad signaling pathway to resistance training-induced muscle hypertrophy.     

Does the MRCGP examination discriminate against Asian doctors?

OBJECTIVE--To ascertain whether the membership examination for the Royal College of General Practitioners (MRCGP) discriminates against doctors of Indian subcontinent ethnic origin ("Asian doctors"). DESIGN--Retrospective analysis of data from five administrations of the MRCGP examination (December 1988-December 1990). SETTING--United Kingdom national examination body. SUBJECTS--3686 doctors taking the examination for the first time, 244 of whom were classified as Asian, the remainder as non-Asian. MAIN OUTCOME MEASURES--Comparison of performance in each of the written and oral components of the examination between Asian doctors, identified by their names and classified into subgroups by countries of birth and primary medical training from data provided at registration, and non-Asian doctors. RESULTS--On written components of the examination (multiple choice paper mean score Asians versus non-Asians 42.3 v 48.6, modified essay paper 40.9 v 48.9, practice topic/critical reading paper 41.5 v 48.7, all p less than 0.001 by t testing). But analysis by countries of birth and primary training showed that these differences were due largely to poor performance by certain groups of Asian doctors, especially those born and trained in the Indian subcontinent or elsewhere outside the United Kingdom. Asian doctors born and trained in the United Kingdom and those born in Africa or the West Indies and trained in the United Kingdom performed similarly to the non-Asian doctors. CONCLUSIONS--The examination does not systematically discriminate against Asian doctors, but the poor performance of the two subgroups of Asians is cause for serious concern and requires investigation.     

Reduced bovine pancreatic trypsin inhibitor has a compact structure

The conformation of reduced bovine pancreatic trypsin inhibitor (R-BPTI) under reducing conditions was monitored by measurements of nonradiative excitation energy-transfer efficiencies (E) between a donor probe attached to the N-terminal Arg1 residue and an acceptor attached to one of the lysine residues (15, 26, 41, or 46) [Amir, D., & Haas, E. (1987) Biochemistry 26, 2162-2175]. High-excitation energy-transfer efficiencies that approach those found in the native state were obtained for the reduced labeled BPTI derivatives in 0.5 M guanidine hydrochloride (Gdn.HCl) and 4 mM DTT. Unlike the dependence expected for a random coil chain, E does not decrease as a function of the number of residues between the labeled sites. The efficiency of energy transfer between probes attached to residues 1 and 15 in the reduced state is higher than that found for the same pair of sites in the native state or reduced unfolded (in 6 M Gdn.HCl) state. This segment also shows high dynamic flexibility. These results indicate that the overall structure of reduced BPTI under folding (but still reducing) conditions shows a high population of conformers with interprobe distances similar to those of the native state. Reduced BPTI seems to be in a molten globule state characterized by a flexible, compact structure, which probably reorganizes into the native structure when the folding is allowed to proceed under oxidizing conditions.     

Control of K+ influx in 3T3 cells transformed by a conditional mutant of Rous sarcoma virus

Mouse 3T3 cells transformed by a conditional mutant of Rous sarcoma virus (LA90) can assume either a normal or a transformed phenotype, depending on the temperature of cultivation. These cells (LA90) were arrested at the G0/G1 phase of the cell cycle by starvation for serum growth factors at the nonpermissive temperature (39 degrees C). Release from the G0/G1 phase by serum growth factors resulted in a rapid stimulation of Rb+ influx. To investigate whether the stimulation of Rb+ influx is obligatory for cell proliferation, the cultures were released from the G0/G1 phase by a temperature decrease in the absence of serum. A temperature decrease from 39 to 32 degrees C activated the viral pp60src gene mitogenic activity. Under these conditions, no rapid stimulation of Rb+ influx was observed. These results suggest that the rapid stimulation of Rb+ influx induced by serum growth factors is not an essential signal for cell release from the G0/G1 phase. However, a delayed increase in Rb+ influx concomitant with an increase in the cell content of K+ was observed in the cultures released from the G0/G1 phase by temperature decrease in the absence of serum growth factors. We found that the LA90 cells incubated at the permissive temperature (32 degrees C) secreted a mitogenic activity into the medium. Moreover, the conditioned medium from cultures incubated at 32 degrees C, but not at 39 degrees C, stimulate Rb+ influx in G0/G1 cells. These results indicate that Rous sarcoma virus pp60src induces a slow autocrine secretion of a mitogenic activity. This mitogenic activity slowly modulates the K+ content. Therefore, the slow elevation in cellular content of K+ is proposed to be an obligatory event for proliferation in normal and transformed cells.     

Cross reactivity and enzyme sensitivity of immunoaffinity purified Sm/RNP antigens

Immunoaffinity purified Sm/RNP antigens from buffalo and goat liver were studied to determine the role of RNA and proteins towards the antigenicity of Sm and RNP antigens. A more direct approach using enzyme-linked immunosorbent assay on nylon beads has been utilized to look into the problem. The effect of enzyme treatment and the role of RNA and protein fractions in influencing antigenicity have been described. RNA seems to be involved in the maintenance of RNP specific polypeptides in suitable conformation so as to keep them in solution. Removal of RNA leads to insolubilization of RNP specific polypeptides. Antibodies to Sm and RNP antigens have been shown to cross react with poly A containing heterogeneous nuclear ribonucleoprotein with no cross reactivity with thymus RNA or DNA.