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Biomedical subjects

T A Boyd

Publications and source records attributed to T A Boyd.

At least 19 recordsLinked to original sources
PubMed1992

Contributions of risk factors to elevated blood and dentine lead levels in preschool children.

The relationship between blood lead level (PbB) and an array of socio-demographic, behavioral, caregiving and environmental risk factors was investigated in a cohort of socioeconomically disadvantaged urban children at ages 2, 3 and 4 years and 10 months. The risk factors were also related to dentine lead level (PbD) from shed deciduous teeth. Strong persistent pairwise relationships with PbB and PbD were observed for maternal IQ, parental education, examiner ratings of the condition and cleanliness of the physical environment, and the HOME scale, which assesses the quality of the caretaking environment. The association between dirt pica and PbB was strong at 2 years (r = 0.30), but was less pronounced in subsequent assessments as the prevalence of pica decreased. Insignificant or weak relationships were found for maternal assessments of paint-and-plaster peeling in the home and non-dirt pica. The HOME scale and the ratings of the condition of the physical environment were significantly related to PbB and PbD even after adjustment for socio-demographic factors. These two measures were also strongly related to an array of developmental outcomes. The results indicate that statistical adjustment specifically for the quality of the caretaking environment can lead to substantial reductions in estimates of adverse lead effects.

Adult↗
PubMed1992

Thalamic amnesia: Korsakoff syndrome due to left thalamic infarction.

In order to support the concept that a lesion of the thalamus is sufficient to cause a Korsakoff syndrome, we are presenting 5 patients, all of whom developed the syndrome after sustaining a left (dominant) thalamic infarction. Two patients had pure thalamic strokes followed by a permanent Korsakoff syndrome. One of these patients was studied with neuropsychometric testing, as well as with a modern MRI scan. In 2 other patients, clinical and imaging data indicate that infarction was not limited to the thalamus. Another patient had bilateral thalamic infarcts but only a temporary Korsakoff syndrome. Neuropathological data are needed to elucidate the exact anatomical substrate of dominant thalamic Korsakoff syndrome.

Aged↗
PubMed1991

Prenatal alcohol exposure and preschool physical growth: a longitudinal analysis.

This report examines the effects of fetal alcohol exposure on size and growth in an urban cohort followed prospectively through early childhood. Indices of prenatal drinking were related to measurements of weight, stature (length), and head circumference obtained at birth and during five subsequent in-home assessments. Small but statistically significant relationships were detected between short-term recall estimates of drinking during pregnancy and weight and length at birth. The strength of these relationships diminished during the preschool assessments. However, estimates of catch-up growth associated with alcohol exposure were not statistically significant. With the exception of a single case with a profile of signs characteristic of fetal alcohol syndrome, an adverse effect of prenatal alcohol exposure on head circumference was not indicated.

Alcohol Drinking↗
PubMed1987

Psychometric validity of proration and Digit Span substitution for estimating WISC--R verbal and Full Scale IQs.

This study investigated the merits of substituting the Digit Span subtest for an invalid Verbal Scale subtest versus a proration method in calculating WISC--R Verbal and Full Scale IQ. Subjects were 93 child and adolescent psychiatric patients (67 boys and 26 girls) who ranged in age from 8 to 16 yr. Analysis indicated that the use of Digit Span as a substitute for the regularly administered Verbal subtests was inferior to the use of the comparable proration method. Although relatively few cases of misclassification occurred for either method in relation to Full Scale IQ, the rate of Verbal IQ misclassification by the Digit Span substitution method was significantly greater than with use of its proration. When faced with a choice, clinicians should attach greater validity to prorated estimates of a child's WISC--R Verbal IQ.

Adjustment Disorders↗
PubMed1979

Kidney metabolite levels and ammonia production in acute acid-base alterations in the rat.

Acute acid-base disturbances cause rapid changes in renal ammonia production in the rat. To investigate the regulation of ammonia production in acute acid-base stresses, we examined the effects of such conditions on tissue levels of metabolites such as alpha-ketoglutarate (KG), which inhibits kidney mitochondrial glutamine uptake and deamidation at physiological concentrations. In rats given low (5 mmol/kg) or high (20 mmol/kg) doses of NH4Cl by stomach tube or placed in a 10% CO2 atmosphere, kidney KG levels fell after 1-h by 44, 69, or 73%, respectively. NaHCO3 administration produced no change in KG levels. Renal glutamate and glutamine levels changed little, if at all, in any group, and renal phosphoenolpyruvate levels were not altered except for a decrease in the NH4HCO3 group. In livers of the same rats, treatments produced different patterns of metabolite changes; KG fell only in the NaHCO3 and NH4HCO3 groups. These results support the concept that KG is a specific regulator of renal ammonia production in acute acid-base stresses.

Acid-Base Imbalance↗
PubMed1979

The water provocative test in preglaucomatous chickens.

Our ability to induce glaucoma in birds provides an experimental system for exploring the mechanisms involved in the provocative water test. Waters loads of a level comparable to those used clinically produced larger intraocular pressure (IOP) changes in preglaucomatous and glaucomatous birds than in control birds. The magnitude of the response corresponded to the level of IOP before testing, that is, to the severity of the glaucoma. Changes in systemic blood pressure were not involved in the response. While hyotonicity of plasma may be the systemic determinant, the normal range of variation in this factor does not allow us at present to consider this a causal relationship.

Animals↗
PubMed1978

Senile disciform macular degeneration and smoking.

We studied the smoking habits of 114 patients with senile disciform degeneration of the macula. The mean age at onset of blindness in the first eye was 64 years in those currently smoking; this was significantly less than the mean age in those who had never smoked (71 years). We advise all patients with disciform degeneration to stop smoking.

Age Factors↗
PubMed1977

Free amino acids in tissues of the skate Raja erinacea and the stingray Dasyatis sabina: effects of environmental dilution.

Concentrations of individual free amino acids were determined in various tissues of the skate (Raja erinacea) and the stingray (Dasyatis sabina), and the relationship of cellular free amino acid concentrations to intracellular osmoregulation was investigated by adapting these elasmobranchs to half-strength seawater. Each tissue characteristically had high levels of certain specific amino acids. Skate sing muscle contained high concentrations of sarcosine and beta-alanine, skate heart had high concentrations of taurine, and skate erythrocytes had high levels of taurine and beta-alanine. Amino acid levels in skate plasma were very low. High concentrations of aturine and glutamate were found in stingray brain. Adaptation of skates and stingrays to half-strength seawater was accompanied by significant decreases in concentrations of the major free amino acids in skate wing muscle and erythrocytes and in stingray brain, but not in skate heart. The data suggest that in these elasmobranchs certain specific free amino acids are selectively involved in intracellular osmoregulatory mechanisms.

Adaptation, Physiological↗
PubMed1977

Cigarette smoking and diabetic retinopathy.

A sample of 181 diabetics with diabetic retinopathy was statistically investigated with regard to association of smoking with proliferative retinopathy. The numbers of patients with proliferative retinopathy rose with increasing tobacco consumption. In non-smokers no association existed between diabetes duration and proliferative retinopathy, but in smokers the number with proliferative retinopathy rose with increasing diabetes duration.

Adolescent↗