Ultrasound assessment of the hamstrings complex of athletes with MRI correlation.

Due to anatomical complexity, ultrasound examination of the hamstring muscles is challenging, resulting in potential diagnostic uncertainty and under-confidence in the technique. This leads to a subsequent tendency to favour magnetic resonance imaging (MRI) evaluation, which can delay diagnosis and potential intervention. This article describes a comprehensive technique of ultrasound evaluation of the hamstrings complex, using key anatomical landmarks. A direct comparison of the sonographic landmarks with corresponding MRI appearances is also provided. If these landmarks can be identified successfully, the complex anatomy can be unlocked, thus improving the time and sensitivity of diagnosis of acute injuries, as well as providing a reliable framework for monitoring injury progress and helping to identify candidates for potential intervention. Many of the anatomical landmarks discussed are common areas of injury in elite athletes, encountered frequently in clinical practice.

Growth phase-dependent surface properties of Legionella pneumophila and their role in adhesion to stainless steel coated QCM-D sensors.

Legionella pneumophila cell surface hydrophobicity and charge are important determinants of their mobility and persistence in engineered water systems (EWS). These surface properties may differ depending on the growth phase of L. pneumophila resulting in variable adhesion and persistence within EWS. We describe the growth-dependent variations in L. pneumophila cell surface hydrophobicity and surface charge using the microbial adhesion to hydrocarbon assay and microelectrophoresis, respectively, and their role in cell adhesion to stainless steel using a quartz crystal microbalance with dissipation (QCM-D) monitoring instrument. We observed a steady increase in L. pneumophila hydrophobicity during their lifecycle in culture media. Cell surfaces of stationary phase L. pneumophila were significantly more hydrophobic than their lag and midexponential counterparts. No significant changes in L. pneumophila cell surface charge were noted. Morphology of L. pneumophila remained relatively constant throughout their lifecycle. In the QCM-D study, lag and exponential phase L. pneumophila weakly adhered to stainless steel surfaces resulting in viscoelastic layers. In contrast, stationary phase bacteria were tightly and irreversibly bound to the surfaces, forming rigid layers. Our results suggest that the stationary phase of L. pneumophila would highly favour their adhesion to plumbing surfaces and persistence in EWS.

Effect of aerobic conditioning on the peripheral circulation during chronic beta-adrenergic blockade.

The relation of peripheral circulatory adjustments to exercise training during long-term beta-adrenergic blockade has not been investigated. In 12 healthy men aged 22 to 34 years, blood flow in the calf was evaluated with submaximal exercise before and after a 6 week aerobic conditioning program. During conditioning, six subjects received no drug and six received propranolol, 80 to 120 mg/day in divided doses. Treated and control subjects were studied on entry and at the conclusion of a conditioning program, 72 hours after drug withdrawal in subjects given propranolol. The training was intensive and equivalent in both groups. Control subjects increased maximal oxygen uptake from 47.5 +/- 1.1 to 51.4 +/- 0.4 ml/kg per min (p less than 0.05), whereas those on propranolol did not improve. Immediately after exercise, blood flow in the calf was measured with strain gauge plethysmography after 3 minutes of supine exertion on a cycle ergometer. In control subjects, flow decreased from 15.7 +/- 1.6 to 14.0 +/- 1.4 ml/100 ml per min at 300 kg-m/min of exertion (p less than 0.05) and from 26.5 +/- 3.8 to 21.8 +/- 2.3 ml/100 ml per min at 700 kg-m/min (p less than 0.05). Vascular resistance was unchanged in these subjects at 300 kg-m/min (6.1 +/- 0.8 to 6.7 +/- 1.0 pru) (p = NS), but increased at 700 kg-m/min (4.2 +/- 0.8 to 4.8 +/- 0.7 pru) (p less than 0.05). In subjects given propranolol, no change in flow or resistance occurred after training at either work load.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydrodynamic flow in U-shaped and coiled glass loops simulating carotid arterial configurations.

The dye injection technique was used to study flow patterns in ten U-bends and two helical coils. These models were manufactured of glass and designed to simulate abnormal arterial configurations in man. In each model flow disturbances were observed below the critical Reynolds number of 2000 for flow in a straight tube with one reading as low as 250. The disturbances in the flow were sensitive to external disturbances. Their periodicity was relatively regular but the frequency increased with augmentation of flow rates and some irregularity was apparent. The results indicate that they could have applicability to the human vascular system.

Buoyancy-induced mixing during wash and elution steps in expanded bed adsorption.

Buoyancy-induced mixing occurs during expanded bed adsorption processes when the feed stream entering the bottom of the system has a lower density than that of the fluid above it. In the absence of a headspace, mixing in the expanded bed can be modeled as a single, well-mixed vessel, with first-order dynamics. In the presence of a headspace, the system exhibits second-order dynamics for the densities typically encountered in protein chromatography, and can be modeled as two well-mixed vessels (the expanded bed and the headspace) arranged in series. In this paper, the mixing dynamics of the expanded bed are described and a mathematical model of the system is presented. Experimental measurements of density changes during the dilution of sucrose and salt solutions in a STREAMLINE 25 column are presented. These show excellent agreement with predictions using the model. A number of strategies for wash and elution in expanded mode, both in the presence and absence of headspace, are discussed.

A study of the effect of legal settlement on post-concussion symptoms.

Forty-four consecutive patients with concussion for whom a medico-legal report had been written were followed up for 3-4 years after their accidents. Three cases were still pending at the end of the study. Fifty-seven per cent complained of symptoms when the medico-legal reports were written (mean interval from accident 12.9 months), 39% had symptoms at the time of settlement (mean interval 22.1 months) and 34% had symptoms one year later. When these results were compared with a general series from the same department some years earlier, it was found that the symptoms at the time of writing the reports were not significantly different from symptoms at 6 weeks in the earlier series, but the symptoms one year after settlement were almost two-and-a-half times greater than the symptoms at 12 months in the general series. No evidence could be found to suggest any organic basis for the higher symptom rate in the litigation series. It is suggested that the litigation process itself is a factor in the persistence of symptoms and this effect continues after legal settlement has been reached. Early settlement of the cases might significantly reduce morbidity.

Preparation of magnetically susceptible polyacrylamide/magnetite beads for use in magnetically stabilized fluidized bed chromatography.

Spherical polyacrylamide/magnetite (PAM) composite beads, suitable for use in a magnetically stabilized fluidized bed (MSFB), were manufactured by a suspension polymerization method. Yield of beads depended on the type and concentration of buffer used during polymerization as well as the pH. More stabilizer was needed to prevent bead agglomeration as magnetite concentration increased. Bead diameter ranged from less than 60 to 600 microm, depending on reaction conditions, and the bead mean diameter and size distribution decreased with increasing impeller speed. The density and roundness factor of the beads were 1.19 +/- 0.02 g cm(-3) and 1.08 +/- 0.03, respectively. The beads had high magnetization at a low applied magnetic field strength (60 mT at 75 kA m(-1)) and retained little residual magnetization (<2 mT) after the field was removed. Incorporation of magnetite did not significantly affect the physical strength of the beads: the beads' average elastic modulus was 14 +/- 4 kPa, similar to reported values for polyacrylamide gels (15.8 kPa). The beads were stable in a range of buffers from pH 1 to 10 and were resistant to microbial degradation. The fluidization and stabilization behavior of the beads was examined in a bench-scale MSFB. The minimum fluidization velocity (U(mf)) of the beads (0.035 mm s(-1)) allowed the MSFB to be operated at superficial velocities close to those used in HPLC systems. Against expectations, at high superficial velocities, the stabilized bed of the MSFB had a greater expansion than the unstabilized bed. The PAM beads could be derivatized and activated for soybean trypsin inhibitor immobilization by a standard carbodiimide method, and the affinity separation of trypsin from chymotrypsin was demonstrated. The PAM beads show excellent potential for use in MSFB chromatography. (c) 1997 John Wiley & Sons, Inc.

Flow through S-shaped glass models simulating arterial tortuosities.

Flow patterns in twenty-one glass models of S bends were examined using the dye-injection technique. The glass models were of different configurations designed to simulate arterial tortuosities. In each model flow disturbances were observed in the stem distal to the S bend or in the distal portion of the S bend itself at Reynolds numbers below 2000. The disturbances were periodic in nature and mostly regular, but with considerable sensitivity to external disturbances. The sharpness of the flexures appeared to be important in determining the Reynolds number at which flow disturbances occurred. The significance of the flow disturbances is their seeming applicability to the human vascular system.

Dose related remineralization using intraoral fluoride-releasing devices in situ.

Dose-related remineralization of enamel lesions was studied in situ. Enamel specimens with subsurface lesions were mounted on lower molars bilaterally and exposed to five regimens: (A) control with a F-free dentifrice three times daily; (B) NaF dentifrice brushed three times daily; (C) fluoride-releasing device (FRD; 0.07 mg F/day release rate) plus F-free dentifrice; (D) FRD (0.232 mg F/day) plus F-free dentifrice, F/day and (E) FRD (0.232 mg/F/day) plus NaF dentifrice. Resting and stimulated saliva samples were obtained for salivary flow and F content determinations. Twenty-eight subjects participated in this double-blind, random-assignment crossover study. After 50 days the enamel specimens were recovered, sectioned, microradiographed, and scanned with image analysis. Regimens D and E demonstrated approximately 30% additional remineralization as compared with to controls, and regimens B and C showed 13.7 and 10.5% increased remineralization as compared with to controls. The increased remineralization of the regimens generally paralleled the increase in salivary F and clearly demonstrated a dose-related response which was some threefold in relation to release rate, salivary F, and percent remineralization.

Exercise haemodynamic effects of beta-blockade and intrinsic sympathomimetic activity.

Beta-adrenergic blockade with intrinsic sympathomimetic activity (ISA) causes less depression of resting and submaximal heart rate (HR) than non-ISA beta-blockers. The effects of these drugs on exercise haemodynamics have not been well studied. We evaluated effects of pindolol, propranolol and placebo during rest and steady-state exercise on cardiac output, oxygen consumption, calf blood flow, HR and blood pressure in 18 healthy subjects. Pindolol 5 mg and propranolol 80 mg given twice daily, reduced maximal exercise HR by 50 and 52 beats.min-1 respectively, confirming similarity of beta 1-blockade. Resting cardiac output was unchanged in all three groups after one week of therapy. Cardiac output, measured during steady-state exercise decreased in the propranolol group (18.3 vs 15.6 l.min-1) with no significant changes in pindolol (15.7 vs 16.01.min-1) or placebo (18.6 vs 17.3 l.min-1). The rise in cardiac output, from rest to exercise, was similarly attenuated by propranolol but not by pindolol or placebo. Exercise stroke volume increased 12% on pindolol (123-140 cc) and decreased 7% on propranolol (143-133 cc). Neither drug had a detrimental effect on exercise calf blood flow compared to placebo. Thus, unlike propranolol, pindolol with ISA, maintains a normal cardiac output during submaximal exercise.