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ABSTRACT:Intrinsic viscosities [11] for sodium hyaluronate in aqueous sodium chloride at 25°C were determined for 12 samples ranging in weight-average molecular weight Mw from 3.8 x 10 3 to 3.5 x 10 5 at NaCl concentrations C, between 0.005 and 2.5 M. They were analyzed on the basis of the Yamakawa-Fujii-Yoshizaki theory for [11] ofan unperturbed wormlike chain combined with the Yamakawa-Stockmayer-Shimada theory for excluded-volume effects to estimate the total persistence length q and the excluded-volume strength B as functions of C,. At any C, studied, excluded-volume effects on [11] became appreciable when Mw exceeded 1 x 10 4~2 x 10 4 . The C, dependence of q yielded 4.0 nm for q0 (the intrinsic persistence length) of the polysaccharide chain at infinite ionic strength. It was found that the values of q-q0 (i.e., the electrostatic contribution to q) at C,<0.02M were roughly 70% larger than predicted by the Le Bret theory and the Odijk-Skolnick-Fixman theory. On the other hand, the estimated B values agreed fairly well with Fixman and Skolnick's theory for the excluded-volume interaction between a pair of charged rodlike segments unless C, was lower than 0.05 M, KEY WORDS Polyelectrolyte / Hyaluronic Acid / Wormlike Chain / Chain Stiffness / Electrostatic Persistence Length/ Excluded-Volume Effect/The current polyelectrolyte theory 1 -4 predicts that the persistence length q of a charged linear polymer in aqueous salt increases with lowering salt concentration c., provided the polyelectrolyte is modeled by the Kratky-Porod wormlike chain. 5 This prediction for the electrostatic stiffening effect seems to be substantiated experimentally for intrinsically stiff polymers undergoing no appreciable intramolecular excluded-volume effect. Notably for double-stranded DNA, 6 almost quantitative agreement was obtained between theoretical and experimental values for the electrostatic persistence length q.1 (the electrostatic contribution to q).On the other hand, our understanding of q. 1 for polyelectrolytes with intrinsically weak stiffness is far from satisfactory. The primary difficulty in the experimental determination of q. 1 or q for those polymers is that the effects of chain stiffness and volume exclusion on measured properties can hardly be separated without resort to a relevant excluded-volume theory. Some previous workers 7 -9 deliberately or undeliberately ignored the latter effect in their estimation of q and discussed apparent values so estimated for q or q. 1 • Others 10 -12 took account of volume effects, but they invoked the Fixman-Skolnick theory 13 for the electrostatic binary cluster integral and early theories 14 · 15 for the radius expansion factor a. based on the random flight model.Here, °' • is defined as the ratio of the perturbed to unperturbed radius of gyration. It is probably fair to say that no established way of estimating the chain stiffness is as yet known for intrinsically flexible or weakly stiff polyelectrolytes unless the ionic strength is high enough. We note that although scatt...

[reaction: see text] N-Acyliminium cation of prolines was efficiently generated to accumulate in an undivided cell at 0 degrees C by an anodic oxidation of N-acylprolines or alpha'-phenylsulfanylated N-acylproline derivatives in a lithium perchlorate/nitromethane solution. The iminium cation intermediates gave modified prolines by a reaction with nucleophiles under mild conditions.

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We performed CT myelography in 38 patients with cervical myelopathy before and after laminoplasty to enlarge the canal. The sagittal and transverse diameters, the cross-sectional area, and the central point of the spinal cord were measured.After cervical laminoplasty, the mean sagittal diameter of the spinal cord at C5 increased by 0.8 mm, but the mean transverse diameter decreased by 0.9 mm. The mean cross-sectional area of the cord increased by 7.4% and that of the dural sac and its contents by 33.8% at C5. The centre of the spinal cord moved a mean 2.8 mm posteriorly at this level.Enlargement of the spinal canal is sufficient to decompress the spinal cord, but posterior movement may be the limiting factor in determining the decompressive effect of laminoplasty. [Br] 1998;80-B:33-7. Received 28 April 1997; Accepted after revision 8 July 1997 In patients with cervical myelopathy, anterior interbody fusion or laminoplasty is performed to expand the canal. In some cases, both anterior and posterior operations are done at the same time. We usually undertake laminoplasty for patients who have developmental spinal stenosis. There are many variations of the technique 1-7 and good clinical results have been reported for all of them. Our method is the 'open-door' type which uses the spinous processes as bone blocks, thereby requiring no additional theatre time for taking grafts from the iliac crest and avoiding the complications of iliac-crest bone donor sites. Moreover, central laminar osteotomies to enlarge the spinal canal are very safe since the spinous processes have been previously resected. J Bone Joint SurgAfter laminoplasty, the spinal cord is decompressed and also moves posteriorly (Fig. 1) Patients and MethodsWe performed laminoplasty in 38 patients, 26 men and 12 women. Their mean age was 56 years (29 to 85) at the time of the operation. Nineteen patients had cervical myelopathy and 17 had ossification of the posterior longitudinal ligament. The remaining two had hypertrophy of the posterior longitudinal ligament and calcification of the ligamentum flavum.The laminoplasty was performed from C3 to C7 in 36 patients, from C3 to T2 in one, and from C2 to T2 in one. Operative technique (Fig. 2). The patient is placed prone and a straight midline skin incision is used. The paravertebral muscles are resected from the spinous processes and the posterior surfaces of the laminae are exposed. The insertion of the semispinalis muscle to C2 is preserved.The spinous processes are resected so that their bases are longer than 5 mm, and their remnants are split with a highspeed drill. At the transitional portion of the laminae and facet joints, the laminae are thinned enough to allow them to be pushed laterally, the 'open-door' technique. The widths of the lateral gutters are determined by CT myelography (CTM) before the operation.The laminae are opened and any adhesions to the dura mater are dissected off. Bone blocks approximately 10 to 15 mm long from the spinous processes are then inserted at the site of the lamin...