Biomedical subjects
Publications and source records attributed to R A Cook.
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Detailed binding studies of the inhibitor, cytidine triphosphate (CTP), to native Escherichia coli aspartate transcarbamylase (EC 2.1.3.2) reveal significant changes in subunit interaction when enzyme concentration is altered. In contrast, similar binding studies of the activator, adenosine triphosphate (ATP), do not reveal such changes, but do indicate more complex subunit interactions than previously reported. Equilibrium dialysis studies of 4 degrees C are consistent with six binding sites for CTP and ATP per enzyme molecule of molecular weight 310 000, at all enzyme concentrations. CTP binding studies reveal a progressive change from apparent positive to negative cooperativity as the enzyme concentration is decreased. ATP binding studies reveal complex subunit interactions involving a mixture of apparent negative and positive cooperativity. Sucrose gradient studies indicate the presence of at least three enzymatically active polymeric forms of the enzyme. The preliminary sedimentation studies indicate possible ligand and enzyme concentration perturbations of a preexisting association equilibrium in the aspartate transcarbamylase system. The binding data are therefore interpreted in terms of an association model.
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Food intakes and anthropometric measurements of Head Start and nursery school children were compared in the fall and spring. Meals consumed at Head Start improved low calcium and ascorbic acid intakes. Iron intakes were low among both groups of children during both seasons. All children had high protein intakes in the fall and spring. Nursery school children consumed high levels of calcium and ascorbic acid and received more vitamin and mineral supplements. Anthropometric measurements indicated adequate and similar growth for all children during each season. Dietary intakes of mothers were less satisfactory than those of their children. Head Start mothers had the poorest diets, with frequent low intakes of energy, calcium, iron, vitamin A, ascorbic acid, riboflavin, and thiamin. Iron was the nutrient needed most by both groups of mothers. Nursery school mothers had especially high intakes of ascorbic acid, and consumed more vitamin and mineral supplements than Head Start mothers.
At the beginning of a Head Start and nursery school program in the fall, nursery school children had significantly higher hemoglobin and hematocrit levels and mean corpuscular volume than Head Start children. The latter had a higher mean corpuscular hemoglobin concentration and alpha 1 globulin level. In the spring, at the close of both preschool programs, nursery school children still had higher hemoglobin and hematocrit levels and mean corpuscular volume, and also a higher mean corpuscular hemoglobin and total iron binding capacity. Head Start children exhibiting signs of anemia in the fall were improving in iron status in the spring. Normal blood protein levels for both groups of children indicated adequate protein status. This condition was confirmed by urinary analysis of urea, creatinine, and inorganic sulfate sulfur.
Otodental dysplasia is an ectodermal dysplasia characterized by abnormal crown morphology of the teeth and sensorineural hearing loss. It was documented in six generations of a kindred of Italian extraction. Thirty-three of the 119 examined family members were affected. Twenty-six persons had characteristic dental anomalies combined with a hearing loss. Two had the dental anomalies alone, four had a hearing loss only and one of those with dental anomalies could not be tested for hearing. The teeth of the 29 with dental anomalies had large, bulbous crowns. The normal relationship between cusps and grooves was obliterated. Molars, both deciduous and permanent, were involved. Deciduous canines were large and bulbous. Absence of premolars was documented in 14 of the 29 individuals with abnormal teeth. Those premolars which were present were frequently small. Radiographs of the teeth showed denticles and taurodontia. Twenty-six of the 30 individuals with a hearing loss had concomitant dental anomalies. Of the four with isolated hearing loss, one was proven to have the syndrome. The remaining three were conjectured to be affected. The age of onset of the hearing deficit ranged from early childhood to middle age. The results of a chi-square test supported autosomal dominant inheritance. The pleiotropy in this syndrome is postualed to be due to a genetic defect in the neuroectoderm.
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The mode of sterilization (filtration or heat) was found to significantly affect the activity of trypsin solutions. Trypsin activity was substantially reduced in the initial fractions of filtrate passed through asbestos filter pads; heat-sterilized trypsin was satisfactory for transfer of cell cultures grown on glass. Heat-sterilized trypsin may be useful when elimination of filterable organisms is required.
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The recoveries of activity in the presence of mixtures of several enzymes and a cellular debris were compared with the recoveries of the pure enzymes. In the acid-dissociation experiments, no interference from foreign proteins was observed nor were any cross hybrids between subunits of different enzymes found. This suggests that the intersubunit binding sites are highly specific and have been selected over evolutionary time for correct assembly. In the urea experiments, cross hybridization and decreased yields were observed in a few cases but in most cases the "foreign" unfolded chains did not influence the recovery of the test enzyme. The results suggest that compartmentalization, temporal or spatial, will not be required as far as assembly of subunits of cytoplasmic enzymes is concerned. The results suggest some cross reaction might occur if all peptide chains were unfolding together. If folding occurs during or immediately after translation, this difficulty would be avoided.
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