Search PubMed⌕ Search

Biomedical subjects

C H Smith

Publications and source records attributed to C H Smith.

At least 73 records · Page 4Linked to original sources
PubMed1995

Weak extremely-low-frequency magnetic fields and regeneration in the planarian Dugesia tigrina.

Extremely-low-frequency (ELF), low-intensity magnetic fields have been shown to influence cell signaling processes in a variety of systems, both in vivo and in vitro. Similar effects have been demonstrated for nervous system development and neurite outgrowth. We report that regeneration in planaria, which incorporates many of these processes, is also affected by ELF magnetic fields. The rate of cephalic regeneration, reflected by the mean regeneration time (MRT), for planaria populations regenerating under continuous exposure to combined DC (78.4 muT) and AC (60.0 Hz at 10.0 muTpeak) magnetic fields applied in parallel was found to be significantly delayed (P << 0.001) by 48 +/- 1 h relative to two different types of control populations (MRT approximately 140 +/- 12 h). One control population was exposed to only the AC component of this field combination, while the other experienced only the ambient geomagnetic field. All measurements were conducted in a low-gradient, low-noise magnetics laboratory under well-maintained temperature conditions. This delay in regeneration was shown to be dependent on the planaria having a fixed orientation with respect to the magnetic field vectors. Results also indicate that this orientation-dependent transduction process does not result from Faraday induction but is consistent with a Ca2+ cyclotron resonance mechanism. Data interpretation also permits the tentative conclusion that the effect results from an inhibition of events at an early stage in the regeneration process before the onset of proliferation and differentiation.

Animals↗
PubMed1995

A new plastic evacuated tube with plasma separator.

A new plastic-walled, evacuated blood collection tube (Terumo Venoject II) with plasma separator was evaluated for characteristics related to the use of plastic in place of glass. Plastic tubes were highly resistant to breakage through handling mishaps or failure during centrifugation. Higher centrifugation speed (13,600g) was well tolerated, and centrifugation times as short as 3 minutes at 13,600g effectively cleared plasma of cellular components, at high plasma yield. Plastic tubes were nearly completely combustible under incineration conditions commonly used for medical waste, and plastic tubes effectively retained vacuum during the typical shelf life of evacuated blood collection tubes. Collection of carbamezepine specimens in plastic tubes decreased levels an average of 6.8% compared to a heparinized glass tube control under conditions approximating routine use; levels of other drugs (phenytoin, phenobarbital, valproic acid, theophylline, and cyclosporine) were less significantly affected. This modest decrease appeared to result from a combination of an immediate interaction with the plastic surface of the tubes and a time-dependent interaction with the olefin-based separator. Modest but clear benefits, including reduction in specimen breakage, reduced centrifugation time and reduced solid waste after incineration derive from the use of plastic in place of glass in evacuated blood collection tubes.

Adolescent↗
PubMed1995

Mast cell number and phenotype in chronic idiopathic urticaria.

BACKGROUND: Increased levels of histamine have been previously demonstrated in patients with chronic idiopathic urticaria. OBJECTIVE: The purpose of the study was to determine whether increased numbers of mast cells are present in lesional skin from such patients. METHODS: Mast cells have been quantified in lesional (n = 11) and nonlesional (n = 9) skin from patients with chronic idiopathic urticaria and compared with site-matched skin from healthy control subjects (n = 10). Mast cells were identified by using a sensitive, double-labeling immunohistochemical technique with specific monoclonal antibodies to mast cell tryptase and chymase and quantified under light microscopy. RESULTS: No significant differences in mast cell numbers from lesional, nonlesional, or control skin were observed (p > 0.1, Student's t test). In both patients with urticaria and control subjects, more than 99% of cutaneous mast cells contained tryptase and chymase. CONCLUSIONS: These data indicate that increased skin histamine in chronic idiopathic urticaria is not caused by increased mast cells and may alternatively reflect an increase in histamine content per mast cell, enhanced mast cell activation, or recruitment of basophils into skin in patients with chronic idiopathic urticaria.

Adult↗
PubMed1995

A new digoxin immunoassay substantially free of interference by digoxin immunoreactive factor.

We have evaluated the new Roche digoxin "On Line" procedure for use in a pediatric population with particular interest in the potential for interference by digoxin-like immunoreactive factor (DLIF). An initial study comparing digoxin values obtained with the new Roche procedure with determinations on an Abbott TDx, American Dade Stratus, and COBAS-FARA using Microgenics Cedia reagents, found good correlations with these established methods. The Roche method was suitably precise and utilized either serum or plasma. Interference by DLIF was assessed by analyzing specimens from patients not receiving digoxin but likely to contain DLIF, with the argument that non-zero values represent cross-reactivity of anti-digoxin antibodies with DLIF endogenous to these specimens. When specimens from neonates, women with second/third trimester pregnancies, and patients with renal and liver failure were assayed with the Roche, Stratus, and TDx methods, all three methods measured DLIF in some specimens, but the Roche method possessed the lowest overall DLIF interference. The modest extent of DLIF interference and the requirement of a small amount of specimen make the Roche method superior in monitoring digoxin in a pediatric population.

Digoxin↗
PubMed1995

Diffuse plane xanthomatosis and acquired palmoplantar keratoderma in association with myeloma.

We report a patient with diffuse plane xanthomatosis, acquired palmoplantar keratoderma, and myeloma. Although diffuse plane xanthomatosis is a recognized manifestation of paraproteinaemia, keratoderma is not. However, successful treatment of the myeloma in our patient coincided with a dramatic improvement in the keratoderma, suggesting a genuine association between the two disorders.

Aged↗
PubMed1995

Lysine uptake by human placental microvillous membrane: comparison of system y+ with basal membrane.

Transport of lysine by microvillous membranes was investigated by characterization of L-[3H]lysine uptake in membrane vesicles isolated from human placentas. At least one Na(+)-independent system was observed at 22 degrees C and two systems at 37 degrees C. Lysine concentration dependence data were fit by a one- or two-system model with a Michaelis-Menten constant (Km) of 124 +/- 28 microM and a maximum velocity (Vmax) of 33.1 +/- 7.7 pmol.mg protein-1.min-1 at 22 degrees C and with Km values of 1 +/- 0.6 and 245 +/- 51 microM and Vmax values of 0.14 +/- 0.07 and 45.8 +/- 8.7 pmol.mg protein-1.30 s-1 at 37 degrees C. In the presence of N-ethylmaleimide, the uptake (37 degrees C) data were fit by a one-system model with kinetic parameters similar to the lower Km system. Uptake of L-lysine in the absence of Na+ was inhibited completely by L-arginine, L-histidine, and L-homoarginine. In the presence of Na+, uptake was inhibited completely by these same three amino acids and L-leucine but only partially by other neutral amino acids. To compare directly microvillous and basal membrane from the same placenta, we examined the inhibition of 20 microM lysine uptake in the presence of Na+. Inhibition by L-leucine was similar in the two membranes. However, L-homoserine, L-alanine, and L-phenylalanine over a wide concentration range inhibited substantially less in microvillous (at both temperatures) than in basal membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Transport Systems↗
PubMed1995

Analytical artifacts in hematocrit measurements by whole-blood chemistry analyzers.

Compact analyzers suited to near-patient testing estimate hematocrit by measuring the conductivity of undiluted blood. We evaluated the accuracy of hematocrit determination of one such analyzer (Instrumentation Laboratory BGE analyzer) against an automated cell counter (EPC) and packed cell volume (PCV) microhematocrit. When specimens (n = 34) from outpatient and ward patients were analyzed with all three methods, the BGE analyzer correlated well with both EPC and PCV hematocrit determinations (BGE = 1.00 PCV + 0.3%, S(y)/x = 2.0%), suggesting that all three methods are similar in performance for most patients. However, a patient with increased plasma osmolality showed significant decreases in BGE and PCV hematocrits relative to the EPC method. The differences in hematocrit measurements could be reproduced by adding solutes to blood in vitro or by modifying the plasma osmolality of rats in vivo. Samples from patients undergoing cardiac surgery, whose blood had large changes in protein concentration, showed discrepancies between hematocrits by conductivity and other methods; similar effects could be produced by changes in protein concentration or in vitro addition of polyethylene glycol. We conclude that conductivity measurements provide accurate hematocrit results for physiologically normal subjects but not for some intensive-care and surgical patients.

Animals↗
PubMed1994

Selective expression of the high-affinity isoform of the folate receptor (FR-alpha) in the human placental syncytiotrophoblast and choriocarcinoma cells.

The folate receptor (FR), an essential component in the process of folate uptake in various cells, is known to exist in three isoforms, FR-alpha, FR-beta and FR-gamma, with differential tissue expression. Transfer of folate across the human placenta from mother to fetus involves participation of a folate receptor expressed in the syncytiotrophoblast, but the isoform identity of this receptor has not been established. Based on the tissue/cell type from which these isoforms have been cloned, it is currently believed that FR-alpha is the isoform expressed in adult tissues whereas FR-beta is the isoform expressed in fetal tissues including placenta. The present study, undertaken primarily to establish the isoform identity of the FR expressed in the placental syncytiotrophoblast, does not support this currently prevailing nomenclature. Reverse transcription coupled with polymerase chain reaction (RT-PCR) of total/poly(A)+ RNA from placenta, cultured trophoblast cells and JAR choriocarcinoma cells with primer pairs specific for either FR-alpha or FR-beta reveals that while both isoforms are detectable in the whole placental tissue, only FR-alpha is present in the normal trophoblast cells and in the choriocarcinoma cells. Northern analysis with probes designed to distinguish between the mRNA transcripts coding for these two isoforms corroborate the RT-PCR findings. Furthermore, the nucleotide sequences of the PCR products obtained from the trophoblast cells and JAR cells are identical to the nucleotide sequence of the FR-alpha cDNA. These studies establish that it is the FR-alpha isoform, and not the FR-beta isoform, which is selectively expressed in the placental trophoblast cells. FR-beta, which is known to be present in the placenta, most likely arises from the maternal decidua normally associated with this tissue.

Amino Acid Sequence↗
PubMed1994

Rapid measurement of serum pancreatic amylase.

A simple, rapid assay for the pancreatic isoenzyme of human serum amylase was developed. The assay utilized an immunoabsorbent prepared by coating latex beads with a monoclonal antibody specific for pancreatic amylase. Treatment of patient serum with immunoabsorbent removed pancreatic amylase, and measurement of residual amylase activity with standard total amylase methodology allowed estimation of the pancreatic amylase content. Extraction efficiency of pancreatic amylase was consistent at amylase concentrations up to 1,000 U/L (y = 0.97 x +16.7 U/L; r = 0.9995). The assay was standardized with purified pancreatic amylase added to neonatal serum (low endogenous activity). A comparison of patient specimen results with the results of a standard technique (cellulose acetate electrophoresis) yielded an excellent correlation (immunoabsorption result = 0.96 electrophoresis result + 1.2 U/L; r = 0.987). Salivary amylase did not interfere with the assay until levels exceeded 1,000 U/L. Daily analysis of a frozen serum pool yielded a coefficient of variation of 9.2% at mean pancreatic amylase value of 54 U/L (+/- 5 U/L). A normal range study found a strong influence of age, with pancreatic amylase levels increasing dramatically in the first 3 years of life, to stabilize at a range of 0-66 U/L thereafter.

Amylases↗
PubMed1994

Functional characterization of L-alanine transport in a placental choriocarcinoma cell line (BeWo).

The substrate selectivity of the neutral amino acid transport systems of the b30 clone of the choriocarcinoma cell line (BeWo) were characterized. Three transport systems were identified in undifferentiated (without forskolin) and two transport systems in differentiated syncytial cells (with forskolin). In the undifferentiated b30 cells were two sodium-dependent systems with one having substrate selectivity patterns resembling system A (e.g. sensitive to MeAIB and a broad range of neutral amino acids) and the other resembling system ASC (e.g. MeAIB insensitive and inhibited by alanine, serine and cysteine). In addition a sodium-independent system was identified with characteristics resembling system l. The differentiated syncytial cells possessed the system A and system l-like activities but not the system ASC-like activity of the system A-like or system l-like activities. The b30 clone is apparently an appropriate model for placental neutral amino acid transport systems.

Alanine↗
PubMed1994

Glutamate oxidation by trophoblasts in vitro.

Catabolism of uniformly and 1-14C-labeled glutamate was investigated in human placental cytotrophoblasts and syncytiotrophoblasts cultured on uncoated plastic or a fibrin matrix. Product-labeling experiments resulted in 14C incorporation into carbon dioxide and tricarboxylic acid cycle intermediates. 14C incorporation above background was not detected for the putative products, glutamine, amino acids, glutathione, and protein. Inhibitors of specific metabolic pathways were used to elucidate the routes of glutamate oxidation. Incorporation of 14C into carbon dioxide from [1-14C]glutamate was inhibited by the glutamate dehydrogenase inhibitor pyridine-2,6-dicarboxylic acid and aminotransferase inhibitor aminooxyacetic acid. Production of 14CO2 was higher for syncytiotrophoblast compared with cytotrophoblast and for cells on uncoated plastic compared with a fibrin matrix. Oxidation of glutamate was unaffected by added glutamine as high as 2 mM. The primary route of glutamate metabolism by placental trophoblast in vitro is oxidation to carbon dioxide utilizing both the transferase and deamination pathways.

Aminooxyacetic Acid↗
PubMed1994

Na+/Ca2+ exchange, Ca2+ binding, and electrogenic Ca2+ transport in plasma membranes of human placental syncytiotrophoblast.

To transfer a large amount of Ca2+ to the fetus, the basal (fetal-facing) plasma membrane (BPM) of human placenta must be equipped with various extrusion mechanisms. We studied one such mechanism, Na+/Ca2+ exchange, as well as related membrane potential effects and binding properties of the two membranes. Na+/Ca2+ exchange was present in BPM and absent in microvillous (maternal-facing) membrane. Uptake and efflux of Ca2+ in BPM were enhanced by Na+ when it was present on the opposite side of the membranes. Na(+)-gradient-dependent Ca2+ uptake was saturable with a Km of 19 microM and a Vmax of 0.8 nmol/min/mg. The Na+/Ca2+ exchange in BPM and the facilitated diffusion transporters in both BPM and microvillous membrane are electrogenic processes. Ca2+ binding in both BPM and microvillous membrane was affected by various monovalent cations and enhanced by Na+ more than by K+. In vivo, together with other sequestration mechanisms, Na+/Ca2+ exchange may play an important role in transsyncytial transfer and in regulating intracellular Ca2+, which is essential for a variety of physiologic mechanisms.

Biological Transport↗
PubMed1994

Detection of autoantibodies to amylase by ELISA: comparison of detection of macroamylase and free autoantibody.

New ELISAs for detecting macroamylase or free autoantibodies to amylase were tested with 48 samples that had been characterized by gel chromatography and electrophoresis. The macroamylase ELISA, with anti-IgG or anti-IgA for detection, detected macroamylase in 28 of 33 samples known to contain macroamylase (85% sensitivity), whereas the ELISA for free autoantibody to amylase was positive for only 11 samples. Specificities of both ELISAs were 93%. Among 28 true positives detected with the macroamylase ELISA, 22 contained IgA, 3 contained IgG, and 3 contained both immunoglobulins. Detection of IgM added no true positives. ELISA responses (y) were proportional to log [macroamylase concentration by chromatography (x)] from 0 to 1200 U/L: y = 5.15 x + 1.66; r = 0.72; Sy x = 1.65. As new tools for detecting macroenzymes consisting of enzyme-autoantibody complexes, the ELISAs show that some autoantibodies are detected more sensitively as antibody-antigen complexes than as free antibody.

Amylases↗
PubMed1994

Interference in ionized calcium measurements by heparin salts.

We determined the suitability of various heparin salts used for anticoagulation of whole-blood specimens for measurement of ionized calcium (iCa), blood gases, and electrolytes. We were particularly interested in a new heparin product containing both zinc and lithium cations (CNLZ heparin), in which the binding sites with greatest affinity for divalent cations are bound with zinc and low-affinity sites with lithium. In initial experiments Li heparin decreased iCa concentrations 0.07 mmol/L at the lowest heparin concentration (3000 units/L) and progressively lowered them at higher concentrations. Zn heparin initially increased iCa concentrations 0.06 mmol/L but progressively lowered them as the heparin concentration was increased. Li heparin interfered even when present in amounts (9 units per 3-mL syringe) minimally effective in preventing coagulation. Use of CNLZ heparin (36 units per 3-mL syringe; Zn 63-78 g/kg of heparin) largely eliminated interference of heparin in iCa measurements. In studies that included the effects of concentration of heparin through partial filling of syringes, specimens anticoagulated with CNLZ heparin compared well with unheparinized controls in measurements of iCa, blood gases, and electrolytes. Blood gases and iCa results on CNLZ-heparinized specimens from intensive-care-unit patients also compared well with specimens anticoagulated with a preparation of heparin (EB heparin) in which calcium has been added to balance the calcium-binding capacity. However, the presence of calcium in EB heparin significantly increased measured total calcium concentrations, whereas the new CNLZ heparin did not interfere in total calcium determinations.

Arteries↗