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Biomedical subjects

C H Smith

Publications and source records attributed to C H Smith.

At least 145 records · Page 8Linked to original sources
PubMed1986

Monoject Samplette capillary blood container with serum separator evaluated for collection of specimens for therapeutic drug assays and common clinical-chemical tests.

The Monoject Samplette (Sherwood) capillary serum-separator tube was evaluated for use in pediatric capillary blood collection. When patients' values for eight common clinical-chemical tests and five therapeutic drugs were compared with values from specimens concomitantly collected in plain Caraway tubes, only chloride and total CO2 were significantly different. The chloride differences (range 0-2 mmol/L) were considered to be clinically insignificant. Higher CO2 values in Samplette specimens were apparently ascribable to decreased loss to the atmosphere. Samplette values for therapeutic drugs were higher than corresponding Caraway values, but only the differences for digoxin were judged to be clinically significant. Both recoverable serum and the incidence of hemolysis were lower in Samplette specimens than in Caraway specimens. Storage of serum over the clots (with separator material interposed) in Samplettes for 24 h had no clinically significant effect on results for glucose or potassium. Storage of specimens for as long as 24 h had no effect on theophylline, phenytoin, and gentamicin concentrations, but phenobarbital reproducibly decreased after 24 h. We conclude that the Samplette serum-separator tube is suitable for the collection of capillary blood for many of the chemical tests commonly ordered for pediatric patients.

Adolescent↗
PubMed1985

Glucose transport across the basal plasma membrane of human placental syncytiotrophoblast.

Transfer of glucose from maternal to fetal circulations requires transport across both the microvillous (maternal-facing) and basal (fetal-facing) plasma membranes of the placental syncytium. We have previously reported transport properties of the microvillous membrane and we now report those of the basal membrane. Basal plasma membrane vesicles were prepared by selective sonication and density gradient centrifugation. Glucose or glucose analogues were rapidly transported across these membranes by facilitated diffusion. Transport was inhibited by cytochalasin B, phloretin and phloridzin. L-Glucose at 1 mM was transferred at only 1/700 of the rate of D-glucose, which indicated an insignificant nonspecific diffusion component. Transport was independent of sodium gradients, and kinetic studies under equilibrium-exchange conditions demonstrated a Km of 23 mM. Competition studies demonstrated that aldohexoses in the C-1 chair conformation were the preferred substrates. Placental steroids estriol and progesterone inhibited transport. In contrast to other polarized epithelia, the basal and microvillous membranes of the human placental syncytium possess transport systems with similar properties. Thus, the directionality and rate of transfer of glucose across the intact syncytium are likely to be direct functions of the materno-fetal concentration gradient and the total transport capacities of the two plasma membranes.

3-O-Methylglucose↗
PubMed1985

Asymmetrical effect of unilateral cortical lesions and amphetamine on DRL-20: a time-loss analysis.

Male Sprague Dawley rats received unilateral 1.5 mm diameter focal suction lesions of either the left or right orbito-frontal cortex and were tested for response to 6 doses of amphetamine sulfate ranging from 0.5 to 1.5 mg/kg on a DRL-20 schedule of reinforcement. Right hemispheric lesion animals obtained a greater number of control reinforcements and were more sensitive to amphetamine's disruptive effects, showing a greater dose-related decrease in water rewards obtained than left lesion animals. An analysis method is introduced which combines the interactive effects of premature responses and their IRT value in a way that relates directly to reinforcement attainment. Calculated total session time made unavailable for reinforcement due to premature responding, correlated negatively (r = -.942) with the number of reinforcements obtained.

Amphetamine↗
PubMed1984

Benzyl alcohol toxicity in a neonatal intensive care unit. Incidence, symptomatology, and mortality.

We unknowingly "screened" all NICU infants for elevated levels of serum benzyl alcohol (Bz-OH) over a three-month period. The fortuitous "screening" procedure resulted from the interference by Bz-OH with a routine blood CO2 assay used for all infants; validity was proved by (1) replication of the interference pattern with Bz-OH or benzoic acid; (2) confirmation of elevated benzoic acid levels in serum in two of the four screening positive infants tested but not in control infants, and (3) disappearance of the interference patterns when Bz-OH solutions were discontinued in affected infants. Screened Bz-OH-positive infants were compared to screened negative control infants, matched for weight (less than 1000 g), severity of RDS (on respirators), exposure to Bz-OH, and survival for longer than 48 hours. Intraventricular hemorrhage (IVH), metabolic acidosis appearing prior to IVH, and mortality were increased in Bz-OH-positive infants (P less than .05 in each case); hyperbilirubinemia and thrombocytopenia were not. Gasping respirations were not a major symptom. It is concluded that Bz-OH poisoning was a major cause of morbidity and mortality in NICU infants weighing less than 1000 g at birth during the three-month screening period. A retrospective review of patient records covering a 16-month period showed significant improvement in the survival rate of infants weighing less than 1000 g following the discontinuation of Bz-OH solutions.

Acidosis, Respiratory↗
PubMed1984

The effect of nutritional factors on hepatic drug and toxicant metabolism.

A variety of foreign agents, including environmental chemicals, food additives, natural food constituents, and pharmaceuticals, enter the body every day. Many of these compounds must undergo metabolism by specific enzymes within the body to facilitate their clearance. The most important of the enzyme systems, which is found in the liver, includes the cytochrome P-450 dependent mixed function oxidase, as well as several conjugation enzymes, including sulfotransferase, glucuronyl transferase, and glutathione-S-transferase. The balance of the reactions determines the rate of metabolism and clearance of the agents, as well as the degree of intracellular damage or toxicity. Specific dietary factors, such as proteins, carbohydrates, vitamins, and minerals, affect the efficiency of these reactions.

Animals↗
PubMed1984

Dietary concerns associated with the use of medications.

Medications can affect, and be affected by, nutrition. The interactions between drugs and various components in the diet are in part responsible for the erratic drug responses observed in patients. Because of the diversity of food consumption patterns among individuals and the widespread use of drugs, an array of varied and complicated side effects can occur. When vitamins, minerals, or other food components alter drug utilization or when drugs induce nutritional deficiencies, the effect poses a risk to the patient. Drugs can also affect many nutrition-related factors, such as appetite, taste acuity, and gastrointestinal function. Dietary habits or metabolic changes should be examined carefully and evaluated in any patient who unexpectedly gains or loses weight while taking drugs. Medicated patients need to be aware of good nutrition practices and to understand the importance of dietary modifications associated with certain diseases. A nutritious diet not only makes an important contribution to the health of those individuals but also reduces the risk of nutrition disorders or altered drug efficacy. Nutrition counseling should be considered for medicated patients to help them make rational decisions about their food choices.

Absorption↗
PubMed1984

Interferences with potentiometry of CO2 in the Ektachem 400 Analyzer.

We have investigated the Kodak Ektachem 400 Analyzer procedure for CO2 for interferences from benzyl alcohol, benzoic acid, and several compounds structurally similar to benzoic acid. Benzoic acid in plasma, at concentrations found in neonates intoxicated with benzyl alcohol, caused a large increase in the results for CO2, as did substantially above-normal concentrations of certain fatty acids and keto-acids, and toxic concentrations of aspirin. We observed a correlation between increasing benzoic acid concentrations (up to 17 mmol/L) and falsely increasing CO2 values (greater than 47 mmol/L) obtained with the Ektachem Analyzer for samples from a neonate in the intensive-care unit, who was receiving benzyl alcohol-preserved saline solutions. Although the Ektachem CO2 procedure is simple and rapid, and in most cases accurate, questionable results are occasionally encountered, as indicated by a low anion gap or a measured CO2 exceeding that calculated from blood gas measurements. Such results require the use of another method for verification.

Benzoates↗
PubMed1983

Isolation and partial characterization of the basal cell membrane of human placental trophoblast.

The function of the syncytiotrophoblast in maternal-fetal exchange is related to the properties of its microvillous (maternal-facing) and basal (fetal-facing) plasma membranes. We have previously reported the properties of the microvillous membrane (Smith, C.H., Nelson, D.M., King, B.F., Donohue, T.M., Ruzycki, S.M. and Kelley, L.K. (1977) Am. J. Obstet. Gynecol. 128, 190-196), and now describe the purification and partial characterization of the basal plasma membrane. Sonication and incubation with EDTA were used to isolate selectively the basal cell membrane. These steps were followed by a more conventional purification by centrifugation. The trophoblast was disrupted and its microvillous membrane and cytoplasmic contents were removed by sonication. The exposed basal cell membrane was selectively released from the underlying basal lamina by sonication in the presence of EDTA and further purified by discontinuous Ficoll gradient centrifugation. The material at the 4-10% Ficoll interface consisted of smooth membrane vesicles with internal microfilaments. It was 45-fold enriched in dihydroalprenolol binding activity and 11-fold enriched in ouabain binding activity. Other enzymatic analyses, including alkaline phosphatase, cytochrome-c oxidase, cytochrome-c reductase and galactosyl transferase indicated low contamination by other organelles. This procedure yields a preparation of relatively high purity which should be suitable for investigation of transport and other functions of the basal surface membrane of trophoblast. In principle, the purification procedures used may be applicable to other transporting epithelia.

Alkaline Phosphatase↗
PubMed1983

Logit-log calibration curves for EMIT assays.

The logit-log and four-parameter logistic procedures when appropriate for calculation of enzyme-multiplied immunoassay (EMIT) data have the advantage that they can be applied regardless of the kinetic analyzer or reaction conditions. To use these procedures correctly one must determine the change in absorbance at an infinite drug concentration (delta A infinity). The marked variation of delta A infinity with equipment and reaction conditions and the difficulty in determining this value have hindered broad use of these otherwise universally applicable procedures. We have evaluated two simple methods for determining delta A infinity, both based on its equivalence to delta A in the absence of specific antibody: (1) cross-kit reaction using antibody/substrate and enzyme-drug reagents from kits for different drugs, and (2) substitution of an antibody-free substrate reagent with composition based on direct analysis. The cross-kit procedure was tested with EMIT assays for phenobarbital, primidone, phenytoin, carbamazepine, ethosuximide, and theophylline. In some cases an unexpected type of cross-reaction occurred, giving an erroneously low value for delta A infinity. The antibody-free substrate reagent always permitted accurate determination of delta A infinity.

Anticonvulsants↗
PubMed1983

Protein kinases of the human placental microvillous membrane. Their potential role in intrasyncytial communication.

Protein phosphorylation has been shown to alter various plasma membrane functions. To investigate the role of phosphorylation in human placental trophoblast, microvillous membrane vesicles were incubated with [gamma-32-P]ATP and the phosphorylation of endogenous and exogenous protein substrates was measured. The microvillous membrane was shown to possess both adenosine 3',5'-cyclic monophosphate (cAMP)-independent and cAMP-dependent kinases. Both endogenous proteins and exogenous proteins were phosphorylated and these processes were enhanced by the presence of Triton or the ionophore alamethicin. The phosphorylation of histone and of endogenous peptides of molecular weights (MW) 147 000, 97 000 and 53 000 was increased by the addition of cAMP. cAMP stimulation required the presence of Triton or alamethicin. The cAMP-dependent kinases are apparently located at the internal (cytoplasmic) surface of the membrane. This location would allow stimulation by cAMP produced by the basal (fetal-facing) plasma membrane. cAMP-stimulated protein phosphorylation may serve as a means of communication between the syncytial plasma membranes facing the fetal and maternal surfaces.

Alamethicin↗