Sawfishes stealth revealed using computational fluid dynamics

Detailed computational fluid dynamics simulations for the rostrum of three species of sawfish (Pristidae) revealed that negligible turbulent flow is generated from all rostra during lateral swipe prey manipulation and swimming. These results suggest that sawfishes are effective stealth hunters that may not be detected by their teleost prey's lateral line sensory system during pursuits. Moreover, during lateral swipes, the rostra were found to induce little velocity into the surrounding fluid. Consistent with previous data of sawfish feeding behaviour, these data indicate that the rostrum is therefore unlikely to be used to stir up the bottom to uncover benthic prey. Whilst swimming with the rostrum inclined at a small angle to the horizontal, the coefficient of drag of the rostrum is relatively low and the coefficient of lift is zero.

Finite element analysis of a micromechanical model of bone and a new 3D approach to validation

Finite Element Analysis (FEA) is now widely used to analyse the mechanical behaviour of bone structures. Ideally, simulations are validated against experimental data. To date, validation of Finite Element Models (FEMs) has been 2 Dimensional (2D) only, being based on comparison with surface-mounted strain gauge readings. In this study we present a novel 3-Dimensional (3D) approach to validation that allows comparison of modelled with experimental results between any two points in 3D space throughout the structure, providing magnitude and direction data for comparison, internally and externally. Specifically, we validate a FEM of a rat tibia, including trabecular network geometry, using a material testing stage housed within a microCT scanner. We further apply novel landmark based morphometric approaches to more effectively compare modelled and experimental results. 542 landmark points on the cortical and trabecular bone surfaces of the model were selected and validated in 3D against experimental data. This approach may hold considerable potential in fields wherein a better understanding of the mechanical behaviour of trabecular networks is important, e.g., the studies of osteoporosis and trabecular loss after orthopaedic implant insertion.

NMR structure of the N-terminal domain of Saccharomyces cerevisiae RNase HI reveals a fold with a strong resemblance to the N-terminal domain of ribosomal protein L9

In addition to the conserved and well-defined RNase H domain, eukaryotic RNases HI possess either one or two copies of a small N-terminal domain. The solution structure of one of the N-terminal domains from Saccharomyces cerevisiae RNase HI, determined using NMR spectroscopy, is presented. The 46 residue motif comprises a three-stranded antiparallel beta-sheet and two short alpha-helices which pack onto opposite faces of the beta-sheet. Conserved residues involved in packing the alpha-helices onto the beta-sheet form the hydrophobic core of the domain. Three highly conserved and solvent exposed residues are implicated in RNA binding, W22, K38 and K39. The beta-beta-alpha-beta-alpha topology of the domain differs from the structures of known RNA binding domains such as the double-stranded RNA binding domain (dsRBD), the hnRNP K homology (KH) domain and the RNP motif. However, structural similarities exist between this domain and the N-terminal domain of ribosomal protein L9 which binds to 23 S ribosomal RNA.

D-dimer in the early diagnosis of thromboembolic disease in acute spinal injuries

The role of monitoring plasma levels of D-dimer (XDP) as a diagnostic aid for thromboembolic disease was investigated in 267 patients admitted for acute care to the Prince Henry Hospital Spinal Unit. Elevated plasma XDP levels were found in 103 patients (39%) and a diagnosis of thromboembolic disease was made in 33. Thromboembolic disease was not found in patients whose XDP levels remained normal.

Tongue size, oral cavity size and speech

Methods of measuring tongue size are evaluated, and protruded tongue size is related to sex, malocclusion, and speech. Significant correlations are found with sex and speech.

Effects of pollen extract upon adolescent swimmers

Many competitive sportsmen in this country regularly use pollen extract as a dietary supplement in the belief that it can lead to an improvement in performance. We have investigated the effects of a six-week course of pollen extract administration on a variety of physiological parameters in a group (n = 20) of adolescent swimmers. At the time of the study, all subjects were training on a daily basis. During the course of the study, maximum oxygen uptake increased in both the treatment group and the placebo group, no difference between the response of the two groups being observed. Vital capacity showed a significant increase in the treatment group, but not in the placebo group. The results indicate that no positive benefit was obtained from the use of pollen supplementation. However, the number of training days missed due to upper respiratory tract infections was much less in the pollen treatment group (4 days) than in the placebo group (27 days). In a study of longer duration, this difference could lead to an improved performance by the pollen treatment group due to fewer interruptions to training.

The role of the gut flora in the reduction of sulphinpyrazone in the rat

Sulphinpyrazone underwent both reduction to a sulphide and oxidation to a sulphone after parenteral administration to normal Wistar rats. Oral administration was associated with a bioavailability of about 75% and with a 3-fold greater formation of the sulphide. However, no sulphide was detected in the plasma after oral administration of sulphinpyrazone to germ-free (BD/X) rats or normal rats treated with oral antibiotics. In vitro studies showed that the major site of reduction of sulphinpyrazone was the contents of the hind gut with little activity detected in the liver or other tissues. The sulphide was oxidised in vivo to sulphinpyrazone and small amounts of sulphone, while the latter underwent only slight reduction to sulphinpyrazone, but did not give detectable levels of the sulphide. These data suggest that the gut microflora are the main site of reduction of sulphinpyrazone in the rat in vivo.

The estimation of late fetal and perinatal age from limb bone length by linear and logarithmic regression

This paper describes an attempt that was made to confirm the suggestion that limb bone length may be a good indicator of perinatal age. Gestational (menstrual) age was regressed on: (i) the lengths of the ossified shafts of the femur, humerus and radius of 17 subjects of mixed sex aged between 27 and 46 weeks; and (ii) the femur, tibia, humerus, radius and ulna of a second, larger, sample of 65 subjects (29 male; 36 female) aged between 24 and 40 weeks. Age was regressed on single bones and combinations thereof, e.g. humerus, radius and ulna. The data were analyzed both in their raw form and as logarithms, the latter yielding very slightly, but not significantly, better results than the former in the case of sample (ii) but not in (i).

In vitro platelet abnormality in adenosine deaminase deficiency and severe combined immunodeficiency

The platelets of an infant with severe combined immune deficiency and adenosine deaminase deficiency showed markedly diminished responses to ADP-induced aggregation in vitro. This abnormality was corrected by the addition of purified adenosine deaminase in vitro. Exogenous adenosine added to platelet-rich plasma caused markedly prolonged inhibition of ADP-induced aggregation. This was shown by isotopic studies to be due to slow clearance of adenosine and hence persistence of this nucleoside. Direct assay for adenosine deaminiase in plasma and platelet lysates of the patient confirmed the very low activity of this enzyme. Raised cAMP levels were demonstrated in his platelets. The deranged adenosine metabolism and raised cAMP in the platelets of this child with severe combined immunodeficiency may explain the altered response to ADP. Despite the in vitro platelet aggregation abnormality, the patient had no clinical evidence of impaired hemostasis.