The connective tissue and ligaments of the distal interphalangeal joint: a review and investigation using ultra-high field 16.4 Tesla magnetic resonance imaging.

This study reviews the literature on the anatomy of the connective tissues surrounding the distal interphalangeal joint and further characterizes the three-dimensional relationships of these structures with ultra-high field magnetic resonance imaging. Ten cadaver fingers, fixed in a solution of 5% agar and 4% formalin, were imaged utilising an ultrashield 16.4 Tesla ultra-high field magnetic resonance imaging, yielding a total of 4000 images. Images were analysed using Osirix™ (version 5.5.1 32 bit edition) for three-dimensional reconstruction. We found numerous conflicting descriptions of the connective tissue structures around the distal interphalangeal joint. Based upon our literature review and imaging studies we have defined precisely Cleland's ligaments, the oblique proximal septum, Grayson's ligaments, the dorsal plate, and the interosseous ligaments of the distal interphalangeal joint.

Spinal cord metabolism and muscle water diffusion in whiplash.

STUDY DESIGN: Case series. OBJECTIVES: To quantify spinal cord metabolites and neck muscle fast and slow water diffusion in a small sample of patients with chronic whiplash and healthy controls. SETTING: Brisbane, Queensland, Australia. METHODS: In five subjects with chronic whiplash and seven controls, we performed magnetic resonance spectroscopy (MRS) of the cervical spinal cord and diffusion-weighted imaging (DWI) of the cervical multifidus muscle. RESULTS: Significant reductions in N-acetylaspartate/creatine ratios were found in subjects with chronic whiplash when compared with healthy controls (P = 0.02). Significantly higher fast apparent diffusion coefficients (ADCs) were found in chronic whiplash when compared with the healthy controls (P = 0.01). There was no difference in slow ADCs between the two groups (P = 0.3). CONCLUSION: The potential value of MRS and DWI to quantify the presence of neuromuscular degeneration as a potential mechanism underlying chronic whiplash is recognized. Larger-scaled prospective studies are warranted and required.

Functional anatomy of the caudal thoracolumbar and lumbosacral spine in the horse.

REASONS FOR PERFORMING STUDY: Research in spinal biomechanics and functional anatomy has advanced back pain research in man. Yet, despite the performance limiting nature of back pain in horses, there are few data for the equine spine. OBJECTIVES: To describe aspects of functional anatomy of the equine thoracolumbar and lumbosacral (LS) spine and potential effects on performance. METHODS: The first study investigated variations in LS vertebral formula by post mortem examination of 120 horses. Midline vertebral transection was carried out on 65 Thoroughbred (TB), 24 Standardbred (SB) and 31 other breeds. The second study investigated morphology and biomechanics of the deep stabilising epaxial muscles of 13 horses using MRI (n = 3), anatomical dissection (n = 11) and biomechanical analysis (n = 6). The spinous process angular orientation relative to the vertebral body, was analysed at vertebrae T13, T18, L3, L5, L6 and S1. RESULTS: LS variations were found in 33.3% of the total group, 40.0% TB and 45.2% others, but 0% SB. Sacralisation of lumbar vertebra (L) 6 with LS motion between L5 and L6 occurred in 32.3% TB and 29.0% others. Five segmental multifidus fascicles were identified originating from spinous processes and vertebral laminae running craniocaudally onto the mammillary processes and lateral border of the sacrum, crossing between 1-5 intervertebral discs. Sacrocaudalis dorsalis (SCD) lateralis muscle was an extension of multifidus from L4, L5 and L6 depending on the vertebral formula whereas SCD medialis mm originated from S3. Both inserted on caudal vertebrae. Based on the location and direction of fibres, the principal action of the deep epaxial muscles was dorsoventral sagittal rotation. This action was dependent on vertebral spinous process/body orientation. We hypothesise that equine multifidus and SCD lateralis muscles act as caudal sagittal rotators of their vertebra of origin, as is the case in man, allowing dynamic stabilisation during dorsoventral motion. CONCLUSION: Equine multifidus anatomy and function are comparable to that of man. The high prevalence of anatomical variations in the LS spine may affect maximal dorsoventral motion, the stability of the LS joint and, therefore, have consequences for athletic performance. Further studies of these structures are warranted in appropriately selected poorly performing horses.

Cortical and medullary betaine-GPC modulated by osmolality independently of oxygen in the intact kidney.

Renal osmolyte concentrations are reduced during reflow following ischemia. Osmolyte decreases may follow oxygen depletion or loss of extracellular osmolality in the medulla. Image-guided volume-localized magnetic resonance (MR) microspectroscopy was used to monitor regional osmolytes during hyposmotic shock and hypoxia in the intact rat kidney. Alternate spectra were acquired from 24-microl voxels in cortex and medulla of the isolated perfused kidney. There was a progressive decrease in the combined betaine-glycerophosphorylcholine (GPC) peak intensity of 21% in cortex and 35% in medulla of normoxic kidneys between 60 and 160 min after commencing perfusion. Hypoxia had no significant effect on the betaine-GPC peak intensity in cortex or medulla, despite a dramatic reduction in tubular sodium, potassium, and water reabsorption. The results suggest that cortical and medullary intracellular osmolyte concentrations depend on osmotically regulated channels that are insensitive to oxygen and dissociated from the oxygen-dependent parameters of renal function, the fractional excretion of sodium, the fractional excretion of potassium, and urine-to-plasma inulin concentration ratio.

Regional proton nuclear magnetic resonance spectroscopy differentiates cortex and medulla in the isolated perfused rat kidney.

Volume-localized proton nuclear magnetic resonance spectroscopy was used as an assay of regional biochemistry in the isolated perfused rat kidney. This model eliminated artifacts caused by respiratory and cardiac motion experienced in vivo. Immersion of the kidney under its venous effluent reduced the susceptibility artifacts evoked by tissue-air interfaces. The rapid acquisition with relaxation enhancement imaging sequence was used for scout imaging. This gave excellent spatial resolution of the cortex, outer medulla, and inner medulla. Spectra were then acquired in 10 minutes using the volume-selective multipulse spectroscopy sequence from voxels with a volume of approximately 24 microL located within the cortical or medullary regions. Spectral peaks were assigned by the addition of known compounds to the perfusion medium and by comparison with spectra of protein-free extracts of cortex and medulla. The medullary region spectra were characterized by signals from the osmolytes betaine, glycerophosphorylcholine, and inositol. The spectra from the cortex were more complex and contained lesser contributions from osmolytes.

Serine isotopmer analysis by 13C-NMR defines glycine-serine interconversion in situ in the renal proximal tubule.

[2-(13)C]glycine metabolism was studied in freshly isolated rat renal proximal tubules. Mitochondrial coupling of the glycine cleavage complex (GC) and serine hydroxymethyltransferase (SHMT) was confirmed by the formation of three serine isotopomers, [2-(13)C]-, [3-(13)C]- and [2,3-(13)C]serine, detected by 13C-NMR. Incubation with different fractions of 13C-labelled glycine altered the labelling pattern of the serine isotopomers predictably and allowed calculation of the 13C-labelled fractions of total glycine and methylene in N5,N10-methylenetetrahydrofolate (m-THF) available for serine metabolism. Within 20 min there was a fall in labelled glycine (to 42 +/- 3, 68 +/- 3 and 93 +/- 2%, (n = 4, mean +/- S.D.) from 50%, 75% and 100% 13C-labelled added glycine respectively), followed by a slow rate of endogenous glycine formation for up to 80 min incubation. The C2 of glycine was the source of more than 90% of the methylene group of m-THF formed. Gas chromatography-mass spectroscopy (GC-MS) showed that greater than 50% of serine formed was unlabelled. GC and SHMT proceeded in the direction of serine formation. Serine isotopomer analysis by NMR and GC-MS allowed the actions of GC and SHMT and de novo contributions to glycine, serine and m-THF to be monitored in situ in fresh renal proximal tubules.

Modulation of glycine-serine interconversion by TCA and glycolytic intermediates in normoxic and hypoxic proximal tubules.

Glycine-serine interconversion is important to numerous metabolic processes and serine release by the kidney. Incubation of freshly isolated rat renal proximal tubules with 5 mM glycine 75% 13C-labelled in the 2-position resulted in 13C-labelled incorporation into serine of 69 micromol.g protein(-1) (+/- 14, n = 16) at 20 min. Addition of 5 mM glucose, 4 mM lactate, 1 mM alanine, 1 mM butyrate and 1 mM glutamate increased 13C-label incorporation into serine to 173 micromol.g protein(-1) (+/- 32, n = 4) at 60 min, 50% greater than tubules incubated with 5 mM glycine alone (P < 0.05). The increase was prevented by hypoxia. Reoxygenation for 20 min restored the rate of incorporation of 13C-label into serine. The fraction of unlabelled serine remained approximately 47% at 20, 40 and 60 min in each group. The results indicate that in the presence of oxygen, TCA and glycolytic intermediates stimulate serine synthesis via the glycine cleavage complex and serine hydroxymethyltransferase pathways and not the phosphorylated pathway. In addition, significant serine production occurs from an unidentified source, which is also tightly coupled to glycine metabolism. Both in the presence and absence of added TCA and glycolytic intermediates, glycine was the principle source of the methylene group in methylene tetrahydrofolate.

23Na NMR detects protection by glycine and alanine against hypoxic injury in the isolated perfused rat kidney.

Protection against hypoxic injury by supraphysiological glycine and alanine concentrations was investigated in the isolated perfused rat kidney (IPRK). 23Na NMR detects consistent increases in total renal Na in IPRK during hypoxic perfusion. Increasing the concentration of glycine and alanine to 5 mM each produced a 34% (p < 0.001) reduction in the increase in total renal Na following 30 minutes of hypoxia compared to a matched control group supplemented with 5 mM each of serine and glutamine. There was also a trend (p = 0.067) to improvement in the fractional excretion of sodium (FENa) in the glycine plus alanine treated group. Hypoxic alterations of other physiological parameters were not prevented by supraphysiological glycine plus alanine. This suggests that monitoring total renal Na is a more sensitive method of defining renal injury and protection than monitoring changes in FENa, fractional excretion of potassium (FEK) and inulin clearance.

23Na-NMR detects hypoxic injury in intact kidney: increases in sodium inhibited by DMSO and DMTU.

Hypoxic injury in the isolated perfused rat kidney (IPRK) was monitored using 23Na-NMR in the presence or absence of 1.5 and 15 mM dimethylthiourea (DMTU) or 15 mM dimethylsulphoxide (DMSO) before and after inducing hypoxia. Hypoxia induced a prompt exponential increase in total renal 23Na+, renal vascular resistance, and sodium excretion and decreased inulin clearance and adenine nucleotides and reduced glutathione concentrations. Lipid peroxide metabolites were unaltered. The increase in 23Na+ was significantly reduced (P < 0.001) by both DMTU and DMSO although hypoxic perturbations of function and biochemical parameters were not. Posthypoxic increases in renal 23Na+ include approximately 10% from the intratubular compartment, but principally reflect the intracellular and interstitial compartments. The results demonstrate that 23Na-NMR is a sensitive indicator of hypoxic renal injury in intact kidney and suggest that DMTU and DMSO protect against hypoxic injury by a mechanism independent of free radical-binding.