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Biomedical subjects

C E Smith

Publications and source records attributed to C E Smith.

At least 145 records · Page 8Linked to original sources
PubMed1992

Correlated biochemical and radioautographic studies of protein turnover in developing rat incisor enamel following pulse-chase labeling with L-[35S]- and L-[methyl-3H]-methionine.

The movement of proteins into and out of enamel was followed over time using a highly sensitive microprecipitation technique to quantify the amount of TCA-insoluble radioactivity present within small pieces of freeze-dried enamel and cells (enamel organ) dissected from the mandibular incisors of rats injected with L-[35S]-methionine. Conventional image processing techniques were also used to estimate the number of silver grains over enamel and cells in radioautographs of mandibular incisors from rats similarly injected with L-[methyl-3H]-methionine. Data from both techniques indicated that the average half-life for labeled proteins secreted into enamel was about 8.9 days. Typically, radioactive proteins accumulated in increasing amounts for 8 hours after which they were lost slowly up to 4 days and more rapidly thereafter when enamel formed during the secretory stage underwent maturation. The half-life for radioactive proteins in cells was only about 20.7 hours. No significant accumulation of radioactivity could be detected in the TCA-soluble or TCA-insoluble fractions of cells as enamel development proceeded. Results from this study suggest that radioautographs provide an accurate estimate of changes occurring to proteins in enamel and cells except at early time intervals (less than 1 hour) when a high percentage of total radioactivity is present within the TCA-soluble fraction of cells.

Animals↗
PubMed1992

Immunolocalization of enamel proteins during amelogenesis in the cat.

Amelogenesis in the cat has been suggested to closely resemble enamel formation in human teeth. In order to further characterize the sequence of events leading to enamel formation in the cat, the expression and distribution of enamel proteins throughout amelogenesis were examined by postembedding immunocytochemistry using an antibody to mouse amelogenins and the high resolution protein A-gold technique. Enamel proteins were first immunodetected in ameloblasts and in the extracellular matrix during the presecretory stage. Secretory stage ameloblasts showed the most intense cellular reactivity. In these cells, protein synthetic organelles, secretory granules, and large lysosome-like structures were all intensely labeled. Extracellularly, numerous gold particles were observed over enamel and over patches of material found at the baso-lateral surfaces of these ameloblasts. During the early maturation stage, the protein synthetic organelles and secretory granules of ameloblasts still showed some immunoreactivity, although the most conspicuous labeling at this later stage was found over enamel and over material present among the extensive apical membrane infoldings of ruffle-ended ameloblasts. Qualitative analysis of lysosome-like elements in ameloblasts suggested that their frequency and immunoreactivity in the maturation stage were relatively lower than in the secretory stage, where some groups of cells often showed numerous large labeled structures. The enamel matrix was intensely labeled at all stages; however, cervical-occlusal and surface-depth gradients were readily apparent by conventional staining and by quantitative analysis of immunolabeling in the late secretory and early maturation stages. These data suggest that the cellular and extracellular distribution of enamel proteins in the cat is generally similar to that reported in other species, although some particularities were observed, perhaps reflecting variation in the timing of developmental parameters.

Amelogenesis↗
PubMed1992

Isolation and characterization of porcine somatotropin containing a succinimide residue in place of aspartate129.

Aspartate129 in porcine somatotropin was converted into a cyclic imide residue (succinimide) under acidic solution conditions. Reversed-phase high performance liquid chromatography was utilized to isolate and quantitate this altered species, which accounted for approximately 30% of the total protein. The molecular mass of this modified species was determined by electrospray mass spectrometry to be 18 Da less than normal porcine somatotropin, indicative of a loss of 1 H2O molecule. Tryptic peptide mapping demonstrated that the peptide composed of residues 126-133 was altered in this modified protein. Amino acid analysis, amino acid sequencing, mass spectrometry, and capillary zone electrophoresis were used to demonstrate that aspartate129 in this peptide had been converted into a succinimide residue. Further confirmation that this peptide contained a succinimide was obtained by hydrolyzing the modified peptide at pH 9.0, which yielded both the aspartate and isoaspartate peptides.

Amino Acid Sequence↗
PubMed1992

Effects of afterhyperpolarization on neuronal firing.

Stein's model for a neuron is studied. This model is modified to take into account the effects of afterhyperpolarization on the neuronal firing. The relative refractory phase, following the absolute one, is modelled by a time-increasing amplitude of postsynaptic potentials and it is also incorporated into the model. Besides the simulation of the model, some theoretical results and approximation methods are derived. Afterhyperpolarization tends to preserve the linearity of the frequency transfer characteristic and it has a limited effect on the moments of the interspike intervals in general. The main effects are seen at high firing rates and in the removal of short intervals in the interspike interval histogram.

Animals↗
PubMed1992

A severe, unusual reaction to trimethoprim-sulfamethoxazole in patients infected with human immunodeficiency virus.

The clinical features of three patients with a life-threatening reaction to trimethoprim-sulfamethoxazole (TMP-SMZ) are presented along with seven other cases from the literature. All patients developed sudden fever and hypotension immediately after the administration of TMP-SMZ; usually this reaction occurred within approximately 2 weeks of completion of a previous course of the drug. All but one patient had a rash. Most patients were hypoxemic and developed diffuse pulmonary infiltrates. All patients responded rapidly to supportive care, while bacterial cultures remained negative. The presence, absence, or character of previous adverse reactions to TMP-SMZ did not predict subsequent severe reactions. Although its mechanism remains unclear, this reaction has features of both IgE-mediated anaphylaxis and cytokine (tumor necrosis factor)-mediated effects. We advise extreme caution, with close observation, when this drug is first readministered to patients who have experienced any TMP-SMZ-associated toxicity within the previous 6-8 weeks.

Adult↗
PubMed1992

OSHA's final rule on occupational exposure to bloodborne pathogens.

This report is intended as a brief review of some of the key points of the new OSHA rule. It should not be used in place of the complete rule, and you should contact your legal advisor with any questions about interpretations of the rule. Because circumstances of occupational exposure vary among employers, it is advisable that employers be thoroughly acquainted with all requirements of the rule. The preamble to the rule, starting on page 64004 of the December 6, 1991 Federal Register, may provide helpful background information for understanding specific provisions of the rule.

Blood↗
PubMed1991

Non-ketotic hyperglycinaemia in a neonate. A case report.

Non-ketotic hyperglycinaemia was diagnosed in a newborn infant presenting with lethargy, apnoea, hiccoughs and myoclonic seizures. The typical findings of raised cerebrospinal fluid:plasma glycine ratio, a burst suppression pattern on electro-encephalography, hypodense areas seen on computed tomography and lack of acidosis, ketosis and serum organic acid abnormality confirmed the diagnosis. Prenatal diagnosis by investigating the glycine cleavage enzyme system from a chorionic villus sample is not yet available.

Amino Acid Metabolism, Inborn Errors↗
PubMed1991

Functional and structural characterization of peptidylamidoglycolate lyase, the enzyme catalyzing the second step in peptide amidation.

Carboxy-terminal amidation is a prevalent posttranslational modification necessary for the bioactivity of many neurohormonal peptides. We recently reported that in addition to peptidylglycine alpha-monooxygenase (PAM), a second enzyme, which we now call peptidylamidoglycolate lyase (PGL), functions in the enzymatic formation of amides [Katopodis et al. (1990) Biochemistry 29, 4551]. The monooxygenase first catalyzes formation of the alpha-hydroxyglycine derivative of the glycine-extended precursor, and the lyase subsequently catalyzes breakdown of the PAM product to the amidated peptide and glyoxylate. We report here the first primary sequence data for PGL, which establish that it is part of the putative protein precursor which also contains PAM. We also show that PAM and PGL activities are colocalized in the secretory granular fraction of neurointermediate pituitary as would be expected for enzymes sharing the same precursor. Time course studies of the amidation reaction using purified soluble pituitary PAM and PGL indicate that both enzymes are essential for enzymatic amidation. Finally, PGL has no effect on the substrate or inhibition kinetics of PAM, and purified pituitary PAM has an acidic pH optimum consistent with its known localization in secretory granules.

Amidine-Lyases↗
PubMed1991

Hemophagocytic syndrome: a cause of pancytopenia in human ehrlichiosis.

A 67-year-old white man with human ehrlichiosis infection complicated by pancytopenia, hemophagocytic syndrome, disseminated intravascular coagulopathy and septic shock is presented. The patient had been on a three-week camping trip to California, Colorado, Utah, and New Mexico. The diagnosis of human ehrlichiosis was confirmed by sixteen-fold rise in antibody titer to Ehrlichia canis, and supported by the characteristic cytoplasmic inclusions. Human ehrlichiosis should be considered in the differential diagnosis in patients with fever and cytopenia associated with hemophagocytosis. Pancytopenia associated with ehrlichiosis is transient; however, it may be severe, and appears to be associated with destruction of normal blood elements.

Aged↗
PubMed1991

Differential expression of calbindin-D 28 kDa in rat incisor ameloblasts throughout enamel development.

Calbindin-D 28 kDa (CaBP 28 kDa), a vitamin D-dependent calcium-binding protein, has been associated with calcium handling by cells. We have investigated the expression of this protein in the rat incisor enamel organ, an epithelium interposed between a mineralizing matrix and connective tissue rich in blood vessels, by radioimmunoassay (RIA), Western blotting, and quantitative protein A-gold immunocytochemistry with antibodies to rat kidney CaBP 28 kDa. RIA of cytosolic extracts showed that enamel organs contained relatively high concentrations of CaBP 28 kDa (compared to kidney; see review by Christakos S., C. Gabrielides, and W.B. Rhoten 1989 Endocr. Rev., 10:3-25). Immunoblotting of proteins extracted from enamel organ strips revealed an intensely-stained band near 28 kDa throughout amelogenesis following ameloblast differentiation. Immunocytochemically, CaBP 28 kDa was localized exclusively within ameloblasts. The density of labelling increased from the presecretory stage to the secretory stage and fluctuated across the maturation stage in relation to ameloblast modulation. Ruffle-ended ameloblasts consistently showed the most intense immunoreaction. Gold particles were present throughout the cytoplasm and nuclei of ameloblasts but regions rich in rough endoplasmic reticulum or cell webs showed a higher immunolabelling. Some gold particles were also associated with the external face of the rough endoplasmic reticulum. Multivesicular bodies in maturation stage ameloblasts were occasionally immunoreactive. These data suggest that the intracellular concentration of CaBP 28 kDa is regulated throughout amelogenesis reflecting a stage-specific control of calcium homeostasis in ameloblasts.

Ameloblasts↗
PubMed1991

Pindolol decreases prolactin and growth hormone responses to intravenous L-tryptophan.

The effects of pindolol on the prolactin (PRL) and growth hormone (GH) responses to intravenous tryptophan (LTP) were studied in eight healthy male volunteers. Pindolol pretreatment (40 mg over 48 h) markedly attenuated the GH response to LTP and modestly, but significantly, reduced the LTP-induced increase in plasma PRL. The disposition of LTP following infusion was not altered by pindolol. While the data are consistent with 5-HT1A receptor mediation of PRL and GH responses to LTP, the intrinsic sympathomimetic actions of pindolol might also be involved in the attenuation of the endocrine responses to LTP.

Adult↗
PubMed1991

Characterization of the genome of rice tungro bacilliform virus: comparison with Commelina yellow mottle virus and caulimoviruses.

Rice tungro disease is caused by an infection of two different viruses, rice tungro spherical virus (a (+) sense RNA virus) and rice tungro bacilliform virus (RTBV) with a genome of circular double-stranded DNA. The genome of an RTBV isolate from the Philippines was cloned, sequenced, and found to be 8000 bp in length. It contains four open reading frames (ORFs) on a single strand, with ORF 1 having an internal termination codon (TAA). The 5' and 3' ends of a polyadenylated viral RNA transcript, of genome length, were mapped by primer extension and cDNA sequence analysis, respectively. The transcript is terminally redundant by 265-268 nucleotides. Purified virus particles contain two major proteins with molecular masses of 37 and 33 kDa, although only the 37-kDa protein was detected in the infected rice tissues. The N-terminal amino acid sequence of the 33-kDa protein was determined and its coding region was identified on the RTBV genome. The identity of the coat protein gene was further confirmed by expressing a region of the genome in Escherichia coli, the products of which reacted with anti-RTBV antibody. The unusually long ORF 3 of RTBV is predicted to encode a polyprotein of 194.1 kDa that includes: the coat protein(s), viral proteinase, reverse transcriptase, and ribonuclease H. The sections of the polyprotein show varying degrees of similarity to the counterparts of Commelina yellow mottle virus (a member of the proposed badnavirus group) and caulimoviruses. The functions of the other three ORFs are unknown.

Amino Acid Sequence↗
PubMed1991

Altered in vitro adaptive responses of lymphocyte Na+,K(+)-ATPase in patients with manic depressive psychosis.

When lymphocytes from healthy subjects are incubated in lithium (8 mM) or ethacrynate (1 microM) they show a time-dependent adaptive response, which consists of a significant increase in the number of Na+,K(+)-ATPase molecules in the lymphocyte membrane. We have studied the lymphocytes from nine euthymic drug-free patients with a history of manic depressive psychosis, and have found that this normal adaptive response was absent. It was also absent from the lymphocytes of euthymic patients taking lithium. We conclude that this altered in vitro adaptive response of lymphocyte Na+,K(+)-ATPase represents an enduring trait marker in manic depressive psychosis.

Bipolar Disorder↗
PubMed1991

Response of glioblastoma cell lines to low dose rate irradiation.

Glioblastoma U251 and U87 cells irradiated with single fraction high dose rate radiation (1.1 Gy/min) were relatively insensitive to inactivation of colony forming ability, similar to other glioblastoma cell lines. Initial rates of cell kill with continuous low dose rate irradiation (0.075 Gy/hr to 0.49 Gy/hr) were low, but at times greater than 20 hours and with dose rates of 0.25 Gy/hr or higher, the rate of cell kill increased. Population doubling times for these cell lines were about 24 hours, suggesting that cell cycle redistribution may be responsible for the increased sensitivity. DNA histograms obtained by flow cytometry support this hypothesis, with cells accumulating in the G2 and M phases of the cell cycle. These results suggest that low dose rate irradiation may be effective in treating glioblastomas. Optimization of time intervals between radiation treatments as well as dose rates used for glioblastoma patients may be influenced by these findings, resulting in better integration of continuous low-dose-rate irradiation (radioactive antibodies and implants) and high-dose-rate irradiation (fractionated external beam) into therapeutic programs.

Cell Cycle↗
PubMed1991

Effects of propranolol on myocardial performance during acute normovolemic hemodilution.

The effects of propranolol and hemodilution on myocardial performance and oxygen delivery were evaluated in 36 anesthetized rats. Oral propranolol treatment consisted of 64 mg/kg/d for 6 weeks prior to the experiments, whereas intravenous (IV) propranolol treatment consisted of 5 micrograms/kg/min for 60 minutes after hemodilution. The hematocrit was reduced to 20% by a hetastarch-for-blood exchange. Animals were divided into six equal groups as follows: (1) no oral drug (water), no hemodilution, no IV drug (saline); (2) oral water, hemodilution, IV saline; (3) oral water, no hemodilution, IV propranolol; (4) oral water, hemodilution, IV propranolol; (5) oral propranolol, no hemodilution, IV saline; and (6) oral propranolol, hemodilution, IV saline. Left ventricular (LV) pressure, maximal dP/dt, ascending aortic blood flow, and response to preload (peak cardiac and stroke volume indices) and afterload (LV-developed pressure) stress were measured. In group 2, hemodilution significantly increased cardiac index, stroke volume index, and dP/dt, and decreased blood pressure, peripheral resistance, and oxygen delivery compared with group 1. Compared with group 2, IV propranolol after hemodilution in group 4 significantly decreased cardiac index, dP/dt, LV-developed pressure, and peak cardiac index, and increased peripheral resistance. Stroke volume index and peak stroke volume index after preload stress remained elevated in group 4, despite the negative inotropic effects of IV propranolol. Oral propranolol in group 6 did not prevent the hemodilution-induced increase in stroke volume index and peak stroke volume index in response to preload stress, although it did decrease cardiac index and dP/dt compared with group 2. Oxygen delivery was reduced in the hemodiluted animals in proportion to the decrease in hemoglobin, regardless of propranolol treatment. It is concluded that reduced myocardial contractility and cardiac performance by nonselective pharmacological beta-adrenoceptor blockade does not interfere with the compensatory increase in stroke volume index after hemodilution.

Administration, Oral↗
PubMed1991

Secretion of active bovine somatotropin in Escherichia coli.

We have expressed a chimeric protein, comprising the LamB secretion signal sequence fused to mature bovine somatotropin (bST), in Escherichia coli. Plasmid constructs with the recA promoter showed significant protein accumulation prior to induction and cell lysis occurred after induction. In contrast, the lacUV5 promoter was tightly regulated. With the lacUV5 promoter, temperature and inducer concentration had significant effects on the total amount of recombinant protein produced and the fraction processed to mature bST. Quantitation of bST from shake flask cultures showed that 1-2 micrograms/ml/OD550 could be released from the periplasm by osmotic shock. N-terminal sequence analysis of the purified protein indicated that the majority of the secreted bST was correctly processed. The bST present in the osmotic shock fraction was judged to be correctly folded by comigration with oxidized methionyl-bST standard on a non-reducing polyacrylamide gel and activity in a bovine liver radioreceptor assay. These results provide a rapid method to produce bST for use in structure-function studies.

Amino Acid Sequence↗