Effect of nutrient deprivation on the viability of intervertebral disc cells.

There is evidence that a fall in nutrient supply leads to disc degeneration but little understanding of the effects of nutrient deprivation on the physiology of disc cells which govern the composition of the disc. We examined the effects of changes in glucose and oxygen concentration and pH on the viability and metabolism of cells from bovine nucleus pulposus. Cells isolated from bovine discs and embedded in alginate beads were cultured under oxygen and glucose concentrations from zero to physiological levels and maintained at pH 7.4, pH 6.7, or pH 6.2 for up to 3 days. Interactions between nutrient concentrations were examined in relation to cell viability and lactic acid production. Cell viability was significantly reduced in the absence of glucose, with or without oxygen. Disc cells survived at 0% oxygen, provided that glucose was present, as seen previously. Cell viability decreased if the medium was acidic, more so when combined with low glucose concentrations. The rate of lactic acid production also fell as the pH became acidic and after 24 h or more at low glucose concentrations, but it did not appear to vary with oxygen concentration under the culture conditions used here. Glucose, rather than oxygen, appears to be the nutrient critical for maintaining disc cell viability. However, in an avascular tissue such as the disc, it is unlikely that glucose deprivation will occur alone; it will almost certainly correlate with a fall in oxygen concentration and pH. These results indicate that the combined nutrient and metabolite environment, rather than concentrations of any single nutrient, should be considered when studying cellular physiology in the disc.

Intervertebral disc composition in neuromuscular scoliosis: changes in cell density and glycosaminoglycan concentration at the curve apex.

STUDY DESIGN: An analysis of the variation in glycosaminoglycan, water content, and cell density with disc level in patients with neuromuscular scoliosis. OBJECTIVES: To determine whether the composition of the apical disc differed from that of adjacent discs in the same spine. SUMMARY OF BACKGROUND DATA: Compositional differences between the convex and concave sides of scoliotic discs have been noted and are thought to be secondary to altered loading. However, there is little information on changes relative to the apex. METHODS: Intact wedges of disc obtained during anterior fusion procedures were taken from 23 discs of 6 patients with neuromuscular scoliosis. Radial profiles of glycosaminoglycan, water content, and cell density were measured. Concentrations were compared at a standard distance (5 mm) into the disc and plotted versus spinal level. RESULTS: Glycosaminoglycan and water content were lowest in the outer annulus and increased steadily toward the disc center, whereas the cell density was highest in the outer 2 mm, fell steeply and then remained constant. At 5 mm from the annulus edge, cell density was lowest in apical discs and, in most cases, was noticeably higher in adjacent discs of the same spine. At the same point, there was no consistent change in glycosaminoglycan/dry weight from disc to disc, indicating no significant proteoglycan loss. However, glycosaminoglycan/tissue water, and therefore swelling pressure, was highest in the apical discs, suggesting that these discs were the most heavily loaded. CONCLUSIONS: The loss of cells from the disc at the curve apex probably arose because this disc experiences greater mechanical stress or is more deformed than its neighbors. The decrease in cell density was not associated with major changes in tissue composition, possibly because rates of degradation and of synthesis were reduced, leaving the matrix largely unchanged.

The pathophysiology of the intervertebral disc.

After a review of disk structure, the pivotal role of disk cells in producing and renewing the extracellular disk matrix is emphasized. Disk cells rely on nutrients that diffuse through the vertebral endplates. Microelectrode methods have been developed to study nutrient diffusion and endplate permeability. Mechanical stimuli modify disk cell activity. Scoliosis is associated with decreased endplate permeability, a factor that may play a role in disk degeneration and scoliosis progression.

Efficacy of continuous extrapleural intercostal nerve block on post-thoracotomy pain and pulmonary mechanics.

To assess the efficacy of continuous extrapleural intercostal nerve block on postoperative pain and pulmonary function, a prospective, randomized, double-blind, placebo-controlled trial was conducted on 56 patients undergoing elective thoracotomy. Infusion was started before closing the chest and was continued for 5 days. Subjective pain relief was assessed on a linear visual analogue scale. Pulmonary function was measured on the day before operation and daily for 5 days. There were 29 patients in a group which received bupivacaine and 27 in a control group which received saline. The bupivacaine group had lower pain scores (P less than 0.01) and required less papaveretum (P less than 0.01) than the control group. Forced vital capacity, forced expiratory volume in 1 s and peak expiratory flow rate were maximally reduced at 24 h to median values of 56, 60 and 57 per cent, respectively, of preoperative control values in the bupivacaine group, and to 25, 30 and 32 per cent in the control group. These differences are highly significant (P less than 0.01). Restoration of pulmonary function was superior in the bupivacaine group (P less than 0.01). There were no infusion-related complications. After thoracotomy, continuous intercostal blockade with bupivacaine is a safe and effective method of pain relief which reduces the early loss of postoperative pulmonary function significantly and more rapidly restores respiratory mechanics.

Teicoplanin: Part 1. An evaluation of the concentrations seen in serum and the subcutaneous fat of the relatively ischaemic lower limb following a single intravenous bolus.

Teicoplanin is a new antibiotic currently undergoing clinical evaluation. Consecutive patients undergoing elective vascular surgery (n = 28) were randomised to receive a single intravenous bolus of 400 mg teicoplanin 1, 3, 6 or 12 h prior to surgery as prophylaxis against Gram-positive infection. Serum and fat antibiotic levels were measured and found to exceed the established MICs for common staphylococcal and streptococcal infections for at least 12 h following administration. This suggests that teicoplanin would be a useful choice of antibiotic in the prophylaxis and treatment of appropriate infections in elective surgery. By extrapolation, teicoplanin would also be of use in the prophylaxis and treatment of suitable infections seen in traumatised patients.

Teicoplanin: Part 2. Evaluation of its use in the biliary system.

Teicoplanin is a new antibiotic currently undergoing extensive investigation to evaluate its potential use in the prophylaxis and treatment of appropriate infection. To ascertain its penetration into the biliary system, 24 patients undergoing elective cholecystectomy were randomised to receive an intravenous bolus of 400 mg teicoplanin 1, 3, 6 or 12 h prior to surgery. During the operation, blood, gall bladder bile and tissue and common bile duct bile were removed for teicoplanin estimation. The results show that teicoplanin penetrates well into the gall bladder wall and bile, though less well into common bile duct bile. These results show that teicoplanin would seem to be a suitable antibiotic for the treatment of biliary infections that are known to be sensitive to the antibiotic.

The spring in the arch of the human foot.

Large mammals, including humans, save much of the energy needed for running by means of elastic structures in their legs and feet. Kinetic and potential energy removed from the body in the first half of the stance phase is stored briefly as elastic strain energy and then returned in the second half by elastic recoil. Thus the animal runs in an analogous fashion to a rubber ball bouncing along. Among the elastic structures involved, the tendons of distal leg muscles have been shown to be important. Here we show that the elastic properties of the arch of the human foot are also important.