PubMed Health⌕ Search

Biomedical subjects

W Mackenzie

Publications and source records attributed to W Mackenzie.

11 recordsLinked to original sources
PubMed1986

Roles of urea production, ammonium excretion, and amino acid oxidation in acid-base balance.

Atkinson and colleagues recently proposed several concepts that contrast with traditional views: first, that acid-base balance is regulated chiefly by the reactions leading to urea production in the liver; second, that ammonium excretion by the kidney plays no role in acid-base homeostasis; and third, that ammonium does not stimulate ureagenesis (except indirectly). To examine these concepts, plasma ions other than bicarbonate are categorized as 1) fixed cations (Na+, K+, Ca2+, and Mg2+, symbolized M+) and anions (Cl-), 2) buffer anions (A-), 3) other anions (X-), and 4) ammonium plus charged amino groups (N+). Since electroneutrality dictates that M+ + N+ = Cl- + HCO3- + A- + X-, it follows that delta HCO3- = delta(M+ - Cl-) - delta A- - delta X- + delta N+. Therefore acid-base disturbances (changes in HCO3-) can be categorized as to how they affect bodily content and hence plasma concentration of each of these four types of ions. The stoichiometry of ureagenesis, glutamine hydrolysis, ammonium and titratable acid excretion, oxidation of neutral, acidic, and basic amino acids, and oxidation of methionine, phosphoserine, and protein are examined to see how they alter these quantities. It is concluded that 1) although ureagenesis is pH dependent and also counteracts a tendency of amino acid oxidation to cause alkalosis, this tendency is inherently limited by the hyperammonemia (delta N+) that necessarily accompanies it, 2) ammonium excretion is equivalent to hydrogen excretion in its effects on acid-base balance if, and only if, it occurs in exchange for sodium or is accompanied by chloride excretion and only when the glutamate generated by glutamine hydrolysis is oxidized.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1976

Facial and cervical injuries.

It is not commonly appreciated that mandibular and maxillary fractures are occasionally associated with fractures of cervical vertebrae. An incidence of 1-6% in a three-year survey at the Royal Brisbane Hospital is reported and the implications are discussed.

Australia↗
PubMedDate not supplied

Objective evaluation of knee laxity in children.

This study was designed to measure objectively knee laxity in children. Physical examination and the KT 1000 arthrometer were used to test the knee laxity of 150 healthy, uninjured children between 6 and 18 years of age. Data from the knee examinations and the KT 1000 measurements were compared and statistically analyzed to determine the change in knee laxity with age, laxity differences between boys and girls, and the correlation between the KT1000 measurements and subjective tests for laxity described by Carter and Wilkinson. There was no statistical difference in knee laxity between boys and girls of similar ages. We found that knee laxity, determined by measuring the millimeters of tibial translation using the KT 1000 arthrometer, was significantly greater in younger children.

Adolescent↗
PubMedDate not supplied

Wedge-shaped distal tibial epiphysis in the pathogenesis of equinovalgus deformity of the foot and ankle in tibial lengthening for fibular hemimelia.

Fibular hemimelia is associated with an equinovalgus deformity of the foot and ankle and different degrees of wedging of the distal tibial epiphysis. This deformity is often a major problem during lengthening of the shortened tibia. To determine the significance of the wedge-shaped distal tibial epiphysis in the pathogenesis of the equinovalgus deformity of the foot and ankle during and after lengthening, we reviewed 20 patients who had undergone tibial lengthening by either the Wagner or the Ilizarov technique. The mean duration of follow-up after removal of the fixator was 5.2 years (range, 2.3-9.7 years). Three types of wedge-shaped distal tibial epiphyses were identified. A mildly wedged (type I) epiphysis was found in seven patients, a moderately wedged (type II) epiphysis was found in seven patients, and a severely wedged (type III) epiphysis, in six patients. Premature fusion of the lateral part of the distal tibial physis and growth retardation of the tibia were common after lengthening in patients with the type II or type III epiphysis. After lengthening, all patients with a type II or type III epiphysis had a recurrence or aggravation of foot deformities that existed before lengthening. This usually necessitated various secondary operative procedures to obtain a plantigrade foot. We believe that after lengthening, one should anticipate varying degrees of mild growth retardation and minimal foot deformity in patients with type I epiphysis, worsened asymmetric growth retardation and progressive foot deformity in patients with type II epiphysis, and severe growth retardation and severe foot deformity in patients with type III epiphysis.

Adolescent↗
PubMedDate not supplied

Comparison of oxygen consumption measurements in children with cerebral palsy to children with muscular dystrophy.

Children with muscular dystrophy (MD) offer a unique opportunity to measure the effect of weakness on gait efficiency as they experience weakness not usually accompanied by other disabilities affecting gait. Oxygen consumption measurements were collected from eight patients with MD and eight patients with cerebral palsy (CP). A statistically significant difference in oxygen cost and oxygen consumption while walking between patients with CP and patients with MD was found despite their common inability to walk similar distances. Oxygen cost and oxygen consumption were elevated within the CP population, whereas all measurements for the MD population were within normal ranges. The measurements show that a patient can have normal oxygen cost and oxygen consumption while walking and yet be functionally limited because of weakness. Caution should be taken when using oxygen cost and oxygen consumption as sole outcome measures for patients with CP, because these measures may be insensitive to changes in strength.

Adolescent↗