Surgery for upper cervical spine instabilities in children.

BACKGROUND: Due to the paucity of existing data with regard to surgical fusion of upper cervical spine instabilities in the paediatric population, we feel encouraged to report the results of our own series to provide additional information to the available body of literature. METHODS: Since 1991 N = 11 children underwent a total of N = 13 surgical procedures for N = 8 posttraumatic, N = 2 congenital and N = 1 postinfectious instabilities at a mean age of 10 years (range: 3-16 years). Transoral odontectomies, ventral odontoid screw-fixations, dorsal wiring or -clamping and transarticular screw-fixations were performed for stabilization and iliac crest bone graft used for fusion. Pain scores, neurological status and radiological results were documented at regular intervals (mean follow-up: 25.4 months). RESULTS: Stable fusion was achieved in all patients as documented on flexion/extension films and tomographies. At the latest follow-up N = 2 patients had improved and N = 9 were equal to their preoperative neurological status. Pain scores were improved in N = 9 patients. N = 2 children developed "bystander-fusion" after C0/2 wiring. N = 3 peri-operative complications occurred as transient neurological deteriorations. In one case this resulted from the resection of a lower brainstem tumour prior to the stabilization procedure. One was attributed to sublaminar wiring in the case of an os odontoideum and one occurred due to slippage of the halo orthosis after transoral odontectomy before definitive dorsal stabilization was carried out. INTERPRETATION: In accordance with the recent literature, we argue for the application of modern screw fixations and treatment algorithms as established for adults in upper cervical spine instabilities of older children. Techniques and indications remain problematic for those younger than 6 years and may have to be individualized in congenital instabilities.

Is elastic energy storage of quantitative relevance for the functional morphology of the human locomotor apparatus?

Elastic storage of energy in the vertebrate locomotor apparatus is supposed to be an important functional factor in cyclic and acyclic movements. In terms of physics, for humans a proof for the occurrence and quantitative relevance of this phenomenon in vivo and under physiological conditions has been missing until now. In addition to the large amount of plausible, but inconclusive information about elasticity in humans and animals, we describe a simple experiment to prove the existence of quantitatively relevant elastic energy storage in the human locomotor apparatus. Ten volunteers (5 female, 5 male) each assumed a relaxed, upright posture on a steel platform. After the release of a support, the volunteers and the platform fell for a defined distance of 33 mm. Loaded with the volunteers, the platform fell significantly (p < 0.001) faster than predicted by the laws of stiff body mechanics (50 vs. 82 ms). For a minimum time of 50 ms, the human locomotor apparatus is able to support an average external power output of more than 400 W by means of an energy transfer of more than 20 J. During the fall, no EMG activities of the ankle flexors could be recorded. We conclude that the acceleration of the platform fall is induced by elastic elements serving as energy sources. Elastic energy storage is of quantitative relevance for the functional morphology and biomechanics of the human locomotor apparatus.

Diethylpyrocarbonate inactivation of NAD-malic enzyme from Ascaris suum.

Treatment with diethylpyrocarbonate results in a first-order loss of the malate oxidative decarboxylase activity of NAD-malic enzyme. First-order plots are biphasic, with about 40-50% activity loss in the first phase. The inactivation process is not saturable, and the second-order rate constant is 4.7 M-1 S-1. Malate (250 mM) provides complete protection against inactivation (as measured by a decrease in the inactivation rate), and less malate is required with Mg2+ present. Partial protection (50%) is afforded by either NAD+ (1 mM) or Mg2+ (50 mM). Treatment of modified (inactive) enzyme with hydroxylamine restores activity to 100% of the control when corrected for the effect of hydroxylamine on unmodified enzyme. A total of 10-13 histidine residues/subunit are acylated concomitant with loss of activity while 1-2 tyrosines are modified prior to any activity loss. The presence of Mg2+ and malate at saturating concentrations protect 1-2 histidine residues/subunit. The intrinsic fluorescence of the enzyme decreases with time after addition of diethylpyrocarbonate, but the rate constant for this process is at least 10-fold too low to account for the biphasicity observed in the first order plots. The histidine modified which is responsible for loss of activity has a pK of 8.3 as determined from the pH dependence of the rate of inactivation. The histidine titrated is still modified under conditions where the residue is completely protonated but at a rate 1/100 the rate of the unprotonated histidine. The results suggest that 1-2 histidines are in or near the malate binding site and are required for malate oxidative decarboxylation.

Determination of dissociation constants for enzyme-reactant complexes for NAD-malic enzyme by modulation of the thiol inactivation rate.

Incubation of NAD-malic enzyme from Ascaris suum with the sulfhydryl reagents N-ethylmaleimide (NEM), 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), or 4,4'-dithiodipyridine (4-PDS) results in rapid and complete loss of malate oxidative decarboxylase and pyruvate reductive carboxylase activities. With DTNB, this loss of activity occurs concomitantly with the modification of about 1 thiol group per subunit. The majority of the activity is lost when 0.5 thiol per subunit is modified, indicative of possible half-site reactivity with DTNB. Complete restoration of activity follows addition of dithiothreitol to enzyme inactivated by DTNB and 4-PDS but not with NEM. With the DTNB-inactivated enzyme, replacement of the thionitrobenzoate moiety with cyanide restores activity. The presence of a divalent metal ion (Mg2+ or Mn2+) results in enhancement of the inactivation rate with all sulfhydryl reagents. However, malate alone or competitors of malate provide protection which is more effective in the presence of Mg2+, while NAD provides only about 25% protection. Thus, the Ascaris suum NAD-malic enzyme has a thiol group probably located in or near the malate binding site, which is not essential for enzyme activity. The changes in the rate of inactivation in the presence of reactants were used to determine the dissociation constants for enzyme-reactant complexes. These data suggest that all three possible binary and all three possible ternary complexes form. The binding of malate to free enzyme exhibits negative cooperativity, which is eliminated by the presence of either NAD or Mg2+.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative study of methyldopa and labetalol in the treatment of hypertension.

1 Twenty patients with essential hypertension completed a double-blind, dose-tritrated, cross-over comparison of methyldopa and labetalol. 2 Average lying BPs (systolic/diastolic) were reduced by 28/15 mmHg with methyldopa and by 23/15 mmHg with labetalol. 3 Average standing BPs (systolic/diastolic) were reduced by 29/14 mmHg with methyldopa and by 29/15 mmHg with labetalol. 4 Both lying and standing heart rates were reduced with labetalol. 5 It is concluded that the antihypertensive properties of labetalol and methyldopa are similar but that larger patient populations are needed to study the relative incidence of subjective adverse effects.

A comparative study of methyldopa and labetalol in the treatment of hypertension.

1 Twenty patients with essential hypertension completed a double-blind, dose-tritrated, cross-over comparison of methyldopa and labetalol. 2 Average lying BPs (systolic/diastolic) were reduced by 28/15 mmHg with methyldopa and by 23/15 mmHg with labetalol. 3 Average standing BPs (systolic/diastolic) were reduced by 29/14 mmHg with methyldopa and by 29/15 mmHg with labetalol. 4 Both lying and standing heart rates were reduced with labetalol. 5 It is concluded that the antihypertensive properties of labetalol and methyldopa are similar but that larger patient populations are needed to study the relative incidence of subjective adverse effects.

A multicentre open trial of labetalol in New Zealand.

1 In a multicentre open trial, labetalol was given to 128 patients in ten centres. Forty-three patients had not previously received antihypertensive therapy; the remainder (85 patients) had been on antihypertensive therapy with either unsatisfactory BP control or troublesome side-effects. 2 Thirty-two patients were withdrawn from the trial in the first 6 months of therapy, 24 (19% of the total) because of side-effects. 3 Control of BP was generally satisfactory or considerably improved. Other drugs (usually a diuretic) had to be added in 23 patients. 4 There was an abnormality of liver function in one patient; otherwise there were no biochemical or haematological problems.

Labetalol, a cross-over double blind controlled trial.

20 patients (12 female) with moderately severe essential hypertension [blood pressure during placebo treatment 181 +/- 6 (systolic), 107 +/- 3 (diastolic)] completed a double-blind, cross-over dose-titrated comparison of labetalol and methyldopa. Both drugs reduced lying and standing arterial blood pressure to a similar extent, although only labetalol reduced heart rate. Compliance was high (greater than 95%) with both drugs, and the incidence of subjective adverse effects was similar.

Dose-titrated, double-blind, cross-over comparison of a selective beta-blocker and methyldopa in the treatment of hypertension.

The efficacy and toxicity of tolamolol and methyldopa in hypertensive patients has been compared by a dose-titrated, double-blind, cross-over study. Thirteen patients completed the trial. Within the dose ranges investigated (tolamolol - 300 mg/day - 900 mg/day; methyldopa - 750 mg/day - 2250 mg/day)both drugs produced significant falls in laying and standing, systolic and diastolic blood pressures. Although the hypotensive effects of methyldopa were more marked than tolamolol, these only achieved conventional (P less than 0.05) levels of significance for lying blood pressure. There were no objective changes in haematological or biochemical indices during treatment with either drug, but patients complained of tiredness, weak limbs and mouth dryness significantly more during methyldopa treatment, than during either placebo or tolamolol therapy.

Comprehensive clinical drug information service: first year's experience.

A comprehensive clinical drug information service, established in the Northern Region in May 1975, is manned by eight doctors--all clinical pharmacologists--and is available 24 hours a day. In the first year of operation 451 inquiries were received, 354 (78-5%) of which were "consultative." Though junior hospital doctors used the service most, almost half of the inquiries about adverse reactions to drugs came from consultants.

Tay-Sachs disease: case reports with emphasis on chromatographic study of rectal biopsy.

Two South Indian Hindu children with typical clinical features compatible with Tay-Sachs disease are presented. The identification of GM2 as the major ganglioside in the lipid extract of rectal biopsy helped to confirm the clinical diagnosis.