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Biomedical subjects

C E Smith

Publications and source records attributed to C E Smith.

At least 109 records · Page 6Linked to original sources
PubMed1995

Comparison of fluid warmer performance during simulated clinical conditions.

The study evaluated the warming ability and flow rates associated with four fluid warming devices during pressure driven infusion and during wide open gravity driven roller clamp infusion. Warmers tested were the Astotherm, Flotem IIe, Level 1 System 250 and a modified cardioplegia heat exchanger. Fluids tested were crystalloid, red cells diluted with 200 ml, 0.9% saline, and undiluted red cells. The volume of fluid and outlet temperatures (point where i.v. tubing would be attached to the patient) were measured for each fluid and compared among warmers for each flow rate condition. For pressure driven infusion of red cells and crystalloid, the System 250, and modified heat exchanger delivered warmer fluids (33-35 degrees C) at higher flow rates (160-740 ml.min-1) than the Astotherm and Flotem (23-31 degrees C, 44-268 ml.min-1, P < 0.05). For gravity driven infusion, the System 250 delivered the warmest fluids (33-36 degrees C, P < 0.05) compared with the modified heat exchanger (29-35 degrees C), Astotherm (26-32 degrees C) and Flotem (26-27 degrees C). In conclusion, the modified heat exchanger and System 250 were moderately effective (outlet temperature > 32 degrees C) in warming crystalloid and red cells at pressure driven flow rates. Only the System 250 warmed red cells > 35 degrees C at gravity driven flow rates. The Flotem and Astotherm were not effective in warming rapidly infused solutions. None of the warmers tested was able to deliver fluids at normothermia (> 36.5 degrees C).

Blood↗
PubMed1995

Transient neonatal myasthenia gravis and pyloric stenosis.

The case report describes the occurrence of hypertrophic pyloric stenosis in a premature infant with neonatal myasthenia gravis. The infant presented for pyloromyotomy on the nineteenth day of life. Diagnosis of myasthenia gravis was made based on maternal history and clinical findings of poor muscle tone, weak suck, and weak cry. The anesthetic management is discussed with reference to the problems of newborn myasthenia gravis and pyloric stenosis as they relate to anesthetic drugs and techniques.

Anesthesia↗
PubMed1995

Functional improvement with vitamin D replenishment in a cohort of frail, vitamin D-deficient older people.

OBJECTIVE: To evaluate functional improvement in a population of frail, homebound older persons with low vitamin D status as vitamin D stores improve. DESIGN: Randomized, controlled intervention study. SETTING: Subjects' homes and a nursing facility in Baltimore, Maryland. PARTICIPANTS: The first 32 subjects (community-dwelling, homebound older subjects from the Johns Hopkins Elder Housecall Program and nursing home residents from the Johns Hopkins Geriatrics Center) entered in a longitudinal study of vitamin D replacement. MEASUREMENTS: Baseline 25-hydroxyvitamin D levels were measured and repeated at least 1 month after therapy with either placebo or vitamin D (ergocalciferol). Subjects were also administered the Frail Elderly Functional Assessment (FEFA) questionnaire, an instrument demonstrated to be reliable, valid, and sensitive to small increments of functional change in this population. MAIN RESULTS: All subjects started with 25-hydroxyvitamin D levels less than 15 ng/mL. Those subjects whose levels improved by at least 3 ng/mL (> assay coefficient of variation) also demonstrated improvement in FEFA score. Regression analysis between change in FEFA score compared with change in 25-hydroxyvitamin D was significant (r = .4; P = .02). CONCLUSIONS: In this cohort of homebound older people, improvement in vitamin D status was associated with functional improvement as measured by the FEFA questionnaire.

Aged↗
PubMed1995

HTM 2022 medical gas pipeline systems.

The new edition of HTM 2022 was published in April 1994 and supersedes HTM 22 which was last published in 1978. The new HTM was prepared following extensive consultation within the NHS and with contractors, manufacturers and other health care professionals. This article summarises the significant changes and developments which have been incorporated into the new HTM 2022. These developments are operational and technical and have considerable implications for Estates Managers. There are many significant changes in HTM 2022 for example Validation and Verification. It is strongly recommended that all staff who are in any way responsible for the operation of a medical gas pipeline system should attend an appropriate training or updating course.

Anesthetics↗
PubMed1995

Overview of morphological changes in enamel organ cells associated with major events in amelogenesis.

The formation and mineralization of enamel is controlled by epithelial cells of the enamel organ which undergo marked, and in some cases repetitive, alterations in cellular morphology as part of the developmental process. The most dramatic changes are seen in ameloblasts which reverse their secretory polarity during differentiation to allow for extracellular release of large amounts of proteins from plasma membrane surfaces that were originally the embryonic bases of the cells. Secreted enamel proteins at first do not accumulate in a layer but, in part, percolate into the developing predentin and subjacent odontoblast layer. Appositional growth of an enamel layer begins with mineralization of the dentin, and ameloblasts develop a complicated functional apex (Tome's processes) to direct release of matrix proteins, and perhaps proteinases, at interrod and rod growth sites. Once the full thickness of enamel is produced, some ameloblasts degenerate, and the surviving cells shorten in height and spread out at the enamel surface. They reform a basal lamina to cover the immature enamel, and continue producing small amounts of enamel proteins that pass through the basal lamina into the enamel. Ameloblasts also undergo cycles of modulation where apical invaginations enriched in Ca-ATPases and other enzymes are formed and shed on a repetitive basis (ruffle-ended/smooth-ended transitions). As this happens, apatetic crystals seeded earlier expand in volume by gradual layering of new mineral at the surfaces of the preformed crystals. Ameloblasts stop modulating when the crystals almost fill existing volume formerly occupied by protein and water.(ABSTRACT TRUNCATED AT 250 WORDS)

Ameloblasts↗
PubMed1994

Protein synthesis elongation factor EF-1 alpha is essential for ubiquitin-dependent degradation of certain N alpha-acetylated proteins and may be substituted for by the bacterial elongation factor EF-Tu.

Targeting of different cellular proteins for conjugation and subsequent degradation via the ubiquitin pathway involves diverse recognition signals and distinct enzymatic factors. A few proteins are recognized via their N-terminal amino acid residue and conjugated by a ubiquitin-protein ligase that recognizes this residue. Most substrates, including the N alpha-acetylated proteins that constitute the vast majority of cellular proteins, are targeted by different signals and are recognized by yet unknown ligases. We have previously shown that degradation of N-terminally blocked proteins requires a specific factor, designated FH, and that the factor acts along with the 26S protease complex to degrade ubiquitin-conjugated proteins. Here, we demonstrate that FH is the protein synthesis elongation factor EF-1 alpha. (a) Partial sequence analysis reveals 100% identity to EF-1 alpha. (b) Like EF-1 alpha, FH binds to immobilized GTP (or GDP) and can be purified in one step using the corresponding nucleotide for elution. (c) Guanine nucleotides that bind to EF-1 alpha protect the ubiquitin system-related activity of FH from heat inactivation, and nucleotides that do not bind do not exert this effect. (d) EF-Tu, the homologous bacterial elongation factor, can substitute for FH/EF-1 alpha in the proteolytic system. This last finding is of particular interest since the ubiquitin system has not been identified in prokaryotes. The activities of both EF-1 alpha and EF-Tu are strongly and specifically inhibited by ubiquitin-aldehyde, a specific inhibitor of ubiquitin isopeptidases. It appears, therefore, that EF-1 alpha may be involved in releasing ubiquitin from multiubiquitin chains, thus rendering the conjugates susceptible to the action of the 26S protease complex.

Acetylation↗
PubMed1994

Purification and characterization of a novel species of ubiquitin-carrier protein, E2, that is involved in degradation of non-"N-end rule" protein substrates.

Ubiquitin-carrier proteins (E2s, ubiquitin-conjugating enzymes, UBCs) participate in proteolysis by catalyzing transfer of activated ubiquitin to the protein substrates, which are bound to specific ubiquitin-protein ligases (E3s). Yeast UBC2 (RAD6) and the mammalian E2(14kDa) bind to the ligase that recognizes and is involved in the degradation of certain free amino-terminal substrates ("N-end rule" substrates). As such proteins are rather scarce, the role of these E2s in general proteolysis is probably limited. Here, we report the purification and characterization of a novel 18-kDa species of E2 from rabbit reticulocytes. Unlike most members of the E2 family, this enzyme does not adsorb to anion exchange resin in neutral pH, and it is purified from the unadsorbed material (Fraction 1). Thus, it is designated E2-F1. Like all members of the E2 family, it generates a thiol ester with ubiquitin that serves as an intermediate in the conjugation reaction. Sequence analysis revealed a significant homology to many known species of E2s. The enzyme generates multiply ubiquitinated proteins in the presence of an E3 that has not been characterized yet. Most importantly, the ubiquitination via this E2 leads to the degradation of certain non-"N-end rule" substrates such as glyceraldehyde-3-phosphate dehydrogenase (Val at the NH2 terminus) and to the ubiquitination and degradation of certain N-alpha-acetylated proteins such as histone H2A, actin, and alpha-crystallin. The enzyme is also involved in the conjugation and degradation of the tumor suppressor protein p53.

Amino Acid Sequence↗
PubMed1994

Synaptic transmission in a diffusion model for neural activity.

Equations for a diffusion neuronal model describing the production of nerve impulses have been derived for the case in which the noisy depolarizations of the membrane potential are restricted by the reversal potentials. Identifying neuron firing intervals with the first-passage-time distribution for the associated process allows us to compute the interspike interval statistics and relate them to the parameters characterizing the neuronal input. Methods for approximation of the first two moments of the interspike intervals are proposed. The analytical results are numerically illustrated and simultaneous computer simulations were performed for the same purpose. A comparison of the achieved results is made with those from other diffusion models or the models with discontinuous trajectories. The model is proposed mainly as an alternative to the Ornstein-Uhlenbeck neuronal model.

Action Potentials↗
PubMed1994

Isolation of Escherichia coli synthesized recombinant eukaryotic proteins that contain epsilon-N-acetyllysine.

Recombinant porcine (rpST) and bovine somatotropins (rbST) synthesized in Escherichia coli contain the amino acid, epsilon-N-acetyllysine. This amino acid was initially discovered in place of the normal lysine144 in a modified reversed-phase HPLC (RP-HPLC) species of rpST. Mass spectrometry and amino acid sequencing of a tryptic peptide isolated from this RP-HPLC purified protein were used to identify this altered residue as epsilon-N-acetyllysine. Ion-exchange chromatography was utilized to prepare low isoelectric point (pI) forms of rpST and rbST, which are enriched in epsilon-N-acetyllysine. Electrospray mass spectrometry demonstrated that the majority of the protein in these low pI fractions contained species 42 Da larger than normal. Immobilized pH gradient electrophoresis (IPG) of the ion-exchange purified low pI proteins was used to isolate several monoacetylated species of rpST and rbST. The location of the acetylated lysine in each IPG-purified protein was determined by tryptic peptide mapping and amino acid sequencing of the altered tryptic peptides. Amino acid analyses of enzymatic digests of rpST and rbST were also used to confirm the presence of epsilon-N-acetyllysine in these recombinant proteins. These data demonstrate that a significant portion of rpST and rbST produced in E. coli contain this unusual amino acid.

Amino Acid Sequence↗
PubMed1994

Waiting time after non-depolarizing relaxants alter muscle fasciculation response to succinylcholine.

The purpose of the study was to determine the effect of nondepolarizing muscle relaxants and waiting time on muscle fasciculations after succinylcholine in anaesthetized patients. Adult men and women, 60-80 kg, received pretreatment doses of atracurium 5 mg (n = 160), pancuronium 1 mg (n = 123), d-tubocurarine 3 mg (n = 97), or vecuronium 1 mg (n = 62). Waiting times between pretreatment and succinylcholine, 100 mg, ranged between 0.6 and 5 min. Data points (presence or absence of fasciculations and waiting time) were entered for each patient. Waiting time response curves were obtained between the logit transformation of the probability of no fasciculations and the log waiting time for each drug. Statistical differences between wait time response curves were determined by non-overlapping of the associated 95% confidence intervals. The frequency of muscle fasciculations was reduced with increased waiting time for all nondepolarizers tested. Following wait times of three, four and five minutes, the probability of not fasciculating was greatest with d-tubocurarine (90, 97 and 99%, respectively) and atracurium (89, 93 and 96%). Corresponding values for pancuronium were 70, 82 and 88% and for vecuronium were 74, 82 and 86%. Waiting times to prevent fasciculations in 80% and 90% of patients were shorter with d-tubocurarine (2.46 and 3.02 min, respectively) or atracurium (2.16 and 3.24 min) than pancuronium (3.77 and 5.35 min) or vecuronium (3.73 and 6.36 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

The influence of tape type and of skin preparation on the force required to dislodge angiocatheters.

The study evaluated the effects of different techniques used to secure intravenous (i.v.) catheters. An angiocatheter attached to standard i.v. tubing was taped to human forearm using a standard taping method. A calibrated piezoelectric force transducer was attached to the i.v. tubing. The force applied along the longitudinal axis to pull out the taped catheter was measured and recorded on paper. Three tape types, Curity, Leukopor and Transpore, were evaluated alone, with benzoin skin pretreatment and with mastisol pretreatment. A randomized 3 x 3 block design with 20 replications per block was utilized, and a total of 180 pullout tests were performed on two adult volunteers. Without pretreatment, the forces required to dislodge catheters were (means +/- SEM) 46 +/- 2, 37 +/- 2 and 38 +/- 2 Newtons for Curity, Leukopor and Transpore tape, respectively. Corresponding values for mastisol pretreatment (64 +/- 1, 64 +/- 3 and 52 +/- 3 Newtons) were greater (P < 0.05) for each tape compared with benzoin (54 +/- 3, 53 +/- 2 and 40 +/- 2 Newtons) and no pretreatment. The most frequent failure mode for Transpore tape was by tape fracture, for Curity tape was by separation from the skin of tape and catheter as a single unit, and for Leukopor tape was by catheter separation while tape remained attached to skin (P < 0.001). The data suggest that the application of mastisol prior to taping i.v. catheters with Curity or Leukopor tape helps to minimize the risk of accidental dislodgement.

Adhesiveness↗
PubMed1994

Rhabdomyoma of the larynx: a rare cause of stridor.

Rhabdomyomas of the larynx are rare tumours. In the literature to date 18 cases have been reported. They usually present with slowly progressive symptoms typical of their benign nature. We present a case that has many atypical features for an 'adult' type rhabdomyoma and discuss the relevant associated literature.

Female↗