Study design: Longitudinal and cross-sectional. Objective: To determine whether, for studies of ageing with a spinal cord injury, the crosssectional di erences in outcomes across both age and years post injury (YPI) di er from the longitudinal change. Setting: Two SCI centres in England: the National Spinal Injuries Centre in Aylesbury, and the Regional Spinal Injuries Centre in Southport. Methods: A total of 315 people who sustained spinal cord injuries prior to 1971 underwent comprehensive health and psychosocial status interviews at one or more of the study assessments (1990, 1993, 1996, and 1999). A range of continuous and dichotomous outcomes was analyzed to detect both cross-sectional di erences by age and average individual changes over multiple measurements. Results: Frequently, outcomes changed longitudinally without showing any cross-sectional di erences. Cross-sectional age was more commonly associated with the worsening of a condition while cross-sectional YPI was commonly associated with improvement. After controlling for cross-sectional e ects, psychological measures generally showed minor deterioration, measures of community integration both improved and deteriorated, upper extremity pain increased, lower enxtremity pain decreased, and participants tended to quit smoking. Conclusion: Using longitudinal ®ndings that control for cross-sectional di erences produces a more complete description of ageing with a spinal cord injury.

A two-step approach to the production of well-defined protein conjugates is described. In the first step, a linker group, carbohydrazide, having unique reactivity (a hydrazide group) is attached specifically to the carboxyl terminus by using enzyme-catalyzed reverse proteolysis. Since the hydrazide group exists nowhere else on the protein, specificity is assured in a subsequent chemical reaction (formation of a hydrazone bond) of the modified protein with a molecule (chelator, drug, or polypeptide) carrying an aldehyde or keto group. The product is sufficiently stable at neutral pH, no reduction of the hydrazone bond being necessary for the hydrazones described. Protein modification is thus restricted to the carboxyl terminus and a homogeneous product results. With insulin as a model, conditions are described for producing such well-defined conjugates in good yields. The use of other linker groups besides carbohydrazide, and applications of these techniques to antibody fragments, are discussed.

Cochran's rule for the minimum sample size to ensure adequate coverage of nominal 95% con®dence intervals is derived by using the Edgeworth expansion for the distribution function of the standardized sample mean. The rule is extended for con®dence intervals based on the Studentized sample mean. The performance of the rule and Edgeworth approximations for smaller sample sizes are examined by simulation.

1 A new imidazo‐pyridine hypnotic (zolpidem 10 mg and 20 mg) was compared with placebo as premedication before general anaesthesia in female patients undergoing minor gynaecological surgery. Efficacy and tolerance before and after anaesthesia were assessed. Psychomotor testing was used to study recovery from anaesthesia. 2 Both doses of zolpidem produced good sedation pre‐operatively but only the higher dose was associated with anterograde amnesia. 3 Premorbid anxiety scores were low in the group of patients studied and were unaffected by either dose of zolpidem. 4 There were no significant effects on the course of anaesthesia. However, postoperatively there was a tendency for wake‐up to be delayed in those patients who received either dose of zolpidem. 5 Postoperative recovery, as indicated by tests of psychomotor performance, was noticeably delayed with a dose of 20 mg compared with placebo whilst psychomotor performance had returned towards baseline levels 3 h after wake‐up in those patients who had received placebo. The zolpidem 10 mg group was intermediate. 6 Zolpidem may be a suitable premedicant when hypnosis and amnesia only are required.