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G S Heard

Publications and source records attributed to G S Heard.

18 recordsLinked to original sources
PubMed1992

Magnetic resonance imaging of traumatized ligaments of the ankle.

The clinical examination of acute soft tissue injuries of the ankle does not necessarily help to delineate the extent of injury. Ankle stress radiographs and arthrography have been applied for a more accurate assessment of the actual degree of ligamentous damage. However, these studies do not define the level of the ligament tear of the relationship of torn ligament ends to one another. This information would seem to be valuable in deciding whether a conservative or surgical approach would be advisable. The following study evaluated the possible role of magnetic resonance imaging in assessment of these injuries. The ability to assess ankle ligaments was first undertaken. Once this was successfully performed, magnetic resonance imaging was used to assess the degree of ligament damage in 15 patients. Magnetic resonance imaging proved to be comparable to arthrography. It also provided additional valuable information.

Adult↗
PubMed1991

Effects of age and biotin status on postnatal development of plasma biotinidase activity in rats.

Biotinidase activity was measured in plasmas of 1-, 7-, 14-, and 21-day-old rats from control dams and dams that had been fed a biotin-depleting diet from Day 15 of gestation. Biotinidase activity increased significantly in the plasma of rats from control and depleted mothers until Postnatal Day 14, after which there was a small but significant decline at Day 21. Differences between the mean activities of the two groups of pups on each sampling day were not significant and there were no significant differences in activity levels attributable to sex. Plasma albumin concentrations increased from birth until Day 21, and plasma biotinidase activity and albumin concentration were significantly correlated (r = +/- 0.43). We suggested that these two proteins may be controlled by a common mechanism in the early postnatal period, and that biotin deficiency does not affect the development of biotinidase activity. Because biotin-depleted neonatal pups show developmental changes in biotinidase activity similar to those of human newborns, and they can be produced reliably by depleting dams from Day 15 of gestation, they may be useful models for studying the developmental abnormalities associated with human biotinidase deficiency.

Age Factors↗
PubMed1990

Biotinidase.

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Amidohydrolases↗
PubMed1990

Fatty acid alterations and carboxylase deficiencies in the skin of biotin-deficient rats.

Full-thickness biopsies of haired and alopecic skin of biotin-deficient rats had less subcutaneous fat and showed lipophilic follicular plugging, vascular engorgement, epidermal hyperplasia, and abnormal keratinization. Mean activities of the three mitochondrial biotin-dependent carboxylases in the skin of biotin-deficient animals were reduced to 3-18% of control whereas the cytosolic enzyme, acetyl-CoA carboxylase, was reduced only to 38-61%. The total fatty acid content of haired and alopecic skin of deficient rats was 30% of those in the corresponding skin sites of control animals. Skin from deficient rats contained less of several long-chain fatty acids (16:0, 16:1, 18:0, 18:1, and 18:2) and more very-long-chain fatty acid, particularly 24:1 and 26:1. These alterations in fatty acids in biotin-deficient rats suggest that the skin findings in biotin and biotinidase deficiencies in humans may be due to similar fatty acid changes.

Animals↗
PubMed1990

Screening for biotinidase deficiency in newborns: worldwide experience.

Between January 24, 1984, and December 31, 1988, 29 screening programs for biotinidase deficiency in newborns were established in 12 countries, and 4,396,834 newborns were screened. The worldwide incidence is based on screening programs in Australia, Austria, Canada, Italy, Japan, Mexico, New Zealand, Scotland, Spain, Switzerland, The United States, and West Germany. Biotinidase deficiency was detected in 72 newborns; 32 had profound biotinidase deficiency (less than 10% of mean normal activity level) and 40 had partial deficiency (10% to 30% of mean normal activity level). The combined incidence of profound and partial deficiency was 1 case per 61,067 live births (1:49 500 to 1:79 544; 95% confidence interval), the estimated frequency of the recessive allele was 0.0040, and the frequency of heterozygosity was estimated to be 1:123. Profound deficiency occurred in 1 per 137,401 live births (1:109,300 to 1:211,200), and partial deficiency in 1 per 109,921 live births (1:86,600 to 1:159,700). Most available parents of children with profound and partial deficiency had biotinidase activity levels intermediate between zero and mean normal activity levels. Six children with profound deficiency were symptomatic at, or soon after, the time of diagnosis; no infant with partial deficiency has become symptomatic, but little is known about the natural history of infants with partial deficiency. Most children whose biotinidase deficiency was detected by newborn screening were white, one was black, and one Hispanic; biotinidase deficiency has not been detected in Oriental children. Although 8 pilot programs have terminated, 21 will continue either indefinitely or until predetermined targets are reached, and 3 new programs were scheduled to begin in January 1989.(ABSTRACT TRUNCATED AT 250 WORDS)

Amidohydrolases↗
PubMed1989

An automated procedure for measuring biotinidase activity in serum.

In this automated procedure for quantifying biotinidase activity in human serum, a manual colorimetric method that measures conversion of the enzyme's artificial substrate N-biotinyl p-aminobenzoate was modified for use with a Technicon AutoAnalyzer II. The intra-run replicate precision (CV) was 2.1% and the day-to-day CV was 4.6% for quality-control sera. Results were linearly related to biotinidase activity in serum over the complete range of clinically relevant values, 0.2 to 11.0 U/L. Moreover, results of the automated assay were not significantly different from those of the manual assay. Because the automated procedure is faster and more precise, we recommend it for population-based studies and some screening studies.

Amidohydrolases↗
PubMed1986

Neonatal screening for biotinidase deficiency: results of a 1-year pilot study.

We screened 81,243 infants born in Virginia during the 1-year period beginning Jan. 24, 1984, for deficiency of the enzyme biotinidase. A simple colorimetric screening procedure was used to detect the presence or absence of biotinidase activity on the same blood-soaked filter paper cards that are currently used in most neonatal metabolic screening programs. Two newborn infants with biotinidase deficiency were identified during the 12-month pilot study. In addition, two affected siblings of one of the newborn infants were detected through secondary family screening. On the basis of these results, the disorder appears to be at least as frequent as several others for which newborn screening is currently conducted. There were no known false-negative test results, and only 0.09% false-positive results that necessitated requests for second blood samples. False-positive test results can be readily identified by the use of a quantitative assay, which can also be used to confirm the diagnosis and to detect heterozygous family members in the case of true positives. On the basis of currently recognized criteria, biotinidase deficiency should be considered for inclusion among the metabolic disorders for which screening is performed in the neonatal period.

Age Factors↗
PubMed1986

Gastrointestinal absorption of vitamin B-6 in the chicken (Gallus domesticus).

The absorption of vitamin B-6 from the gastrointestinal tract of the chicken (Gallus domesticus) was studied by using ligated segments in vivo, everted jejunal sacs in vitro, and in intact birds. [3H]Pyridoxine hydrochloride ([3H]PN . HCl) was absorbed from all sections of the small intestine, from the cecum and the crop, although absorption from the latter two segments was minimal. Absorption was independent of fasting and the vitamin B-6 concentration in the rearing diet. Concentration-dependence was demonstrated for absorption from ligated jejunal segments (24 microM-24 mM) and for 4-min uptake of [3H]PN . HCl by everted sacs (0.01-10,000 microM). Unidirectional flux of 2 microM PN . HCl was reduced by ouabain, iodoacetate and Na+-free media but not by 4-deoxy PN . HCl, D- and DL-penicillamine, anoxia or glucose-free media. Absorption of vitamin B-6 from the lumen to the intestinal epithelium of the chicken occurs by simple diffusion. Free, added vitamin B-6 was almost completely absorbed. In contrast, vitamin B-6 in food ingredients became available only as digestion proceeded and was in no case completely available. The vitamin B-6 concentrations in the contents of the cecum, lower ileum and rectum were similar. Incomplete absorption of dietary vitamin B-6 could explain the presence of the vitamin in the cecum. An enterohepatic route accounting for the recycling of approximately 1% of normal daily vitamin B-6 intake was identified, and the vitamin B-6 concentration in bile increased with vitamin B-6 in the diet. Pyridoxal, pyridoxamine (and their phosphate esters), pyridoxine, and 4-pyridoxic acid were measured in blood, but only the pyridoxal concentration in blood responded noticeably to increases in dietary vitamin B-6.

Animals↗
PubMed1986

Biotinidase deficiency: accumulation of lactate in the brain and response to physiologic doses of biotin.

Biotinidase deficiency is the most common cause of late onset, biotin-responsive multiple carboxylase deficiency (MCD). We studied the two oldest known boys with this disorder who had high CSF content of lactate that could have contributed to the clinical disorder. The symptoms of these patients implied that near physiologic, rather than pharmacologic, doses of biotin may be sufficient for treatment.

Amidohydrolases↗
PubMed1985

Clinical findings in four children with biotinidase deficiency detected through a statewide neonatal screening program.

Four children with biotinidase deficiency were identified during the first year of a neonatal screening program for this disease in the Commonwealth of Virginia. Two unrelated probands were identified among the 81,243 newborn infants who were screened. In addition, two siblings of one of these infants were found to be affected. Both probands had mild neurologic symptoms at two and four months, respectively, and the two older children had more severe neurologic abnormalities, cutaneous findings, and developmental delay at two and three years of age. However, none of the affected children had acute metabolic decompensation. Previous studies have shown that the administration of biotin to affected children can be a lifesaving procedure that can reverse acute symptoms and prevent irreversible neurologic damage. Our findings demonstrate that subtle neurologic abnormalities may appear as early as at two months of age and that developmental abnormalities may occur even in the absence of episodes of overt metabolic decompensation. Since screening and treatment are both inexpensive and effective and the incidence of the disease is well within the range of that of other metabolic diseases for which screening is performed, biotinidase deficiency should be added to the group of metabolic diseases for which screening is done in the neonatal period.

Amidohydrolases↗
PubMed1985

Biotinidase deficiency: initial clinical features and rapid diagnosis.

Biotinidase deficiency is the primary defect in most individuals with late-onset multiple carboxylase deficiency. We have reviewed the presenting clinical features of 31 children with the disorder. Seizures, either alone or with other neurological or cutaneous findings, are the most frequent initial symptom observed. Other neurological symptoms, such as hypotonia, ataxia, hearing loss, optic atrophy, and developmental delay, are seen, in addition to skin rash and alopecia. The disorder is also characterized by ketolactic acidosis and organic aciduria. Biotinidase activity may be diagnosed using a simple, rapid, semiquantitative colorimetric procedure. Samples of whole blood spotted on the same filter paper used by most states to screen for phenylketonuria and other inborn errors of metabolism may be sent to an appropriate reference laboratory. None of the common anticonvulsants or sedatives used to treat newborns and children interfere with the test. Because biotinidase deficiency can be treated readily with biotin, this disorder should be considered in children with infantile seizures, especially in the presence of other characteristic neurological or cutaneous features.

Acidosis↗
PubMed1985

Biotinidase deficiency: a novel vitamin recycling defect.

The recent finding that biotinidase deficiency is the primary biochemical defect in late-onset multiple carboxylase deficiency was stimulated new interest in the inherited disorders of biotin-dependent carboxylases. The clinical and biochemical features of biotinidase deficiency are discussed. We also speculate about two exciting areas currently being investigated: the localization of action biotinidase, and the possible role of the enzyme as a binding or carrier protein for biotin.

Adult↗
PubMedDate not supplied

Antibiotic-impregnated bone cement: an in vitro comparative analysis.

This manuscript examines the in vitro antibacterial activity of eight different antibiotics when mixed with polymethyl methacrylate. Two different parameters are presented as being important considerations in the choice of antibiotic. One parameter is the bacterial inhibition created by the direct contact of the antibiotic-impregnated bone cement. The second parameter is the bacterial inhibition produced by diffusion of antibiotic from the bone cement into the surrounding liquid medium. These two experimental models were created to establish the contiguous and remote antimicrobial effects of antibiotic-impregnated bone cement.

Anti-Bacterial Agents↗
PubMedDate not supplied

Peripheral neurotoxicity testing by pairs of stimuli.

At the present time the best electrophysiological test of peripheral nerve function for purposes of evaluating neurotoxicity in humans is the analysis of the response to pairs of stimuli. This test is a more sensitive measure of axonal conduction deficit than is the single-action potential of standard clinical technique. While not as sensitive a measure as a train of stimuli at any given frequency of stimulation, the paired stimulus technique has the following advantages. The interpretation of responses to trains of impulses can be made inaccurate by alternate blocking. Under such conditions the pairs response will already have shown impaired conduction, The method is sufficiently sensitive that the second response of the pair is decreased in normals. Thus the test will show any neurotoxic impairment which is additive to such normal physiological decrement. The method has already been reported in the literature as being sensitive to a number of different peripheral and central neuropathies in humans, including segmental demyelination and axonal degeneration. The equipment required is often already in the standard clinical facility, or can be added at reasonable cost. Stimulation with pairs is more acceptable to the subject since it is not as painful as presentation of stimulus trains.

Electrodiagnosis↗