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Biomedical subjects

D L Smith

Publications and source records attributed to D L Smith.

At least 109 records · Page 6Linked to original sources
PubMed1999

Perianal lymphoma in a heterosexual and nonimmunocompromised patient: report of a case and review of the literature.

PURPOSE: This study was conducted to report a rare case of anorectal pathology. METHODS: We report a case of perianal lymphoma in a nonimmunocompromised, heterosexual patient and review the literature. RESULTS: A 67-year-old white male was found to have an ulcerated posterior anal mass. Biopsy revealed large cell lymphoma, B cell type, immunoblastic. There was no disseminated disease. The patient denied any homosexual activity and was HIV negative. There was complete resolution with chemotherapy (cyclophosphamide, doxorubicin, vincristine, and prednisone), and he remained disease free for six years. CONCLUSIONS: Rare anorectal pathology may mimic common conditions. Biopsies should be taken to rule out malignancy.

Aged↗
PubMed1999

Accuracy of surgeon-performed gallbladder ultrasound.

BACKGROUND: Symptomatic cholelithiasis is among the most common of general surgery referrals. With an appropriate clinical presentation, definitive diagnosis requires documentation of gallstones by ultrasonography (US). The authors evaluated the accuracy of surgeon-performed US for identifying gallstones in patients with a nonacute indication for study. METHODS: Patients referred for symptomatic cholelithiasis and who provided informed consent received an US examination by one or more of the surgical investigators. Surgeon-performed US findings were correlated with radiologist US findings and pathologic diagnoses. RESULTS: Seventy-seven patients received a total of 128 examinations by the investigators. Surgeon-performed US examination agreed with the radiologist US findings for 112 of 122 studies (92%) with a sensitivity of 100% and a specificity of 95%. Surgeon-performed US findings correlated with the pathologic diagnoses for 83 of 86 studies (97%). CONCLUSIONS: Surgeons can perform gallbladder US in the nonacute setting with a high degree of accuracy.

Cholelithiasis↗
PubMed1999

Comparison of continuous and pulsed labeling amide hydrogen exchange/mass spectrometry for studies of protein dynamics.

In contrast to the rigid structures portrayed by X-ray diffraction, proteins in solution display constant motion which leads to populations that are momentarily unfolded. To begin to understand protein dynamics, we must have experimental methods for determining rates of folding and unfolding, as well as for identifying structures of folding and unfolding intermediates. Amide hydrogen exchange has become an important tool for such measurements. When urea is used to stabilize unfolded forms of proteins, the refolding rates may become slower than the rates of isotope exchange. In such cases, the intermolecular distribution of deuterium among the entire population of molecules may become bimodal, giving rise to a bimodal distribution of isotope peaks in mass spectra of the protein or its peptic fragments. When the protein is exposed continuously to D2O, the relative intensities of the two envelopes of isotope peaks give an integrated account of populations participating in the folding/unfolding process. However, when the protein is exposed only briefly to D2O, the relative intensities of the two envelopes of isotope peaks give an instantaneous measure of the folded/unfolded populations. Application of these two labeling methods to a large protein, aldolase, is described along with a discussion of specific parameters required to optimize these experiments.

Amides↗
PubMed1999

Reproducibility of resting peripheral blood flow using strain gauge plethysmography.

The purpose of this study was to examine the intra-tester and inter-tester reliability of strain gauge plethysmography (SGP) using the Hokanson EC-5R plethysmograph among three investigators. An arterial inflow test was performed by each of the investigators on fifteen college-aged volunteers at the forearm and calf sites. Intra-tester reliability was assessed by analyzing three serial measurements obtained at both sites. Intertester reliability was assessed in two ways: first, by having the three investigators obtain and analyze their own recordings, and, second, by having all three investigators (Testers 1, 2, and 3) analyze SGP recordings obtained by the most experienced investigator (Tester 1). The mean coefficient of variation (CV) for the intra-tester analysis was similar at the forearm (4.9%) and calf (4.0%) sites. The inter-tester analysis revealed that there were no significant differences among the three testers at either site when investigators obtained and analyzed their own waveforms. The CV calculated from the means of the three investigators was greater at the forearm site (10.7%) than at the calf site (2.5%). Similarly, when Testers 2 and 3 analyzed Tester 1's waveforms there were no significant differences found among testers at either site and the CV was less than when each investigator obtained his/her own waveforms. Strain gauge plethysmography blood flow measures obtained by experienced testers, under controlled laboratory conditions, are reproducible. The small variability in blood flow that exists is more attributable to variability in the acquisition of the waveforms than in the analysis of the waveforms.

Adult↗
PubMed1999

Comparison of accelerometers with oxygen consumption in older adults during exercise.

PURPOSE: The purpose of this study was to compare two commercially available accelerometers with indirect calorimetry in a group of older adults (x +/- SD; 70.6+/-3.7 yr; N = 86, 44 males and 42 females). METHODS: The accelerometers (Caltrac and Tritrac, Hemokinetics, Madison, WI) were worn while performing three submaximal, discontinuous (5 min exercise, 2 min recovery), progressive levels of treadmill walking and bench stepping. The treadmill exercise averaged 3.4 mph, at 0.4% grade, 3.0% grade, and 5.1% grade, while the stepping work rates (24 steps x min(-1)) were performed on 15.2-, 20.3-, and 25.4-cm steps. Estimated energy expenditure (EE) from the two accelerometers was compared with EE as measured by indirect calorimetry. RESULTS: The Caltrac significantly (P < 0.05) overestimated EE at the three treadmill work rates (10-52% difference) and underestimated EE at the three stepping work rates (-19% to -28% difference). When comparing the changes in EE between work rates one, two and three, the Caltrac was not sensitive to the changes (increase in EE) that occurred during graded treadmill walking but did detect some changes in the stepping exercise. The Tritrac significantly (P < 0.05) underestimated EE for the three work rates of both the treadmill and stepping exercise when compared with indirect calorimetry but did detect differences in EE among work rates during stepping exercise (P < 0.05). CONCLUSIONS: These data indicate that the magnitude of the differences between measured and estimated EE is affected by exercise mode and intensity and that caution is warranted when using the accelerometers in an attempt to quantify EE in older adults.

Aged↗
PubMed1999

Mass spectrometric characterization of oat phytochrome A: isoforms and posttranslational modifications.

At least four mRNAs for oat phytochrome A (phyA) are present in etiolated oat tissue. The complete amino acid sequences of two phyA isoforms (A3 and A4) and the N-terminal amino acid sequence of a third isoform (A5) were deduced from cDNA sequencing (Hershey et al., 1985). In the present study, heterogeneity of phyA on a protein level was studied by tryptic mapping using electrospray ionization mass-spectrometry (ESIMS). The total tryptic digest of iodoacetamide-modified phyA was fractionated by gel filtration chromatography followed by reversed-phase high-performance liquid chromatography. ESIMS was used to identify peptides. Amino acid sequences of the peptides were confirmed or determined by collision-induced dissociation mass spectrometry (CID MS), MS/MS, or by subdigestion of the tryptic peptides followed by ESIMS analysis. More than 97% of the phyA3 sequence (1,128 amino acid residues) was determined in the present study. Mass-spectrometric analysis of peptides unique to each form showed that phyA purified from etiolated oat seedling is represented by three isoforms A5, A3, and A4, with ratio 3.4:2.3:1.0. Possible light-induced changes in phytochrome in vivo phosphorylation site at Ser7 (Lapko VN et al., 1997, Biochemistry 36:10595-10599) as well at Ser17 and Ser598 (known as in vitro phosphorylation sites) were also analyzed. The extent of phosphorylation at Ser7 appears to be the same for phyA isolated from dark-grown and red-light illuminated seedlings. In addition to Ser7, Ser598 was identified as an in vivo phosphorylation site in oat phyA. Ser598 phosphorylation was found only in phyA from the red light-treated seedlings, suggesting that the protein phosphorylation plays a functional role in the phytochrome A-mediated light-signal transduction.

Amino Acid Sequence↗
PubMed1999

Sigmund Freud and the Crick-Koch hypothesis. A footnote to the history of consciousness studies.

The author describes Crick and Koch's recently developed theory of the neurophysiological basis of consciousness as synchronised neural oscillations. The thesis that neural oscillations provide the neurophysiological basis for consciousness was anticipated by Sigmund Freud in his 1895 'Project for a scientific psychology'. Freud attempted to solve his neuropsychological 'problem of quality' by means of the hypothesis that information concerning conscious sensory qualities is transmitted through the mental apparatus by means of neural 'periods'. Freud believed that information carried by neural oscillations would proliferate across 'contact-barriers' (synapses) without inhibition. Freud's theory thus appears to imply that synchronised neural oscillations are an important component of the neurophysiological basis of consciousness. It is possible that Freud's thesis was developed in response to the experimental research of the American neuroscientist M. M. Garver.

Austria↗
PubMed1999

Endomyocardial fibrosis associated with massive calcification of the left ventricle.

This is the report of a rare case of endomyocardial fibrosis associated with massive calcification of the left ventricle in a male patient with dyspnea on great exertion, which began 5 years earlier and rapidly evolved. Due to lack of information and the absence of clinical signs that could characterize impairment of other organs, the case was initially managed as a disease with a pulmonary origin. With the evolution of the disease and in the presence of radiological images of heterogeneous opacification in the projection of the left ventricle, the diagnostic hypothesis of endomyocardial disease was established. This hypothesis was later confirmed on chest computed tomography. The patient died on the 16th day of the hospital stay, probably because of lack of myocardial reserve, with clinical findings of refractory heart failure, possibly aggravated by pulmonary infection. This shows that a rare disease such as endomyocardial fibrosis associated with massive calcification of the left ventricle may be suspected on a simple chest X-ray and confirmed by computed tomography.

Adult↗
PubMed1999

Are oblique views needed for trauma radiography of the distal extremities?

OBJECTIVE: To our knowledge, few studies exist on the importance of the oblique view when radiography of the distal extremities is performed after acute trauma. Our prospective study aimed to determine whether the oblique view uniquely revealed abnormalities or clarified findings when it was obtained along with routine frontal and lateral radiographs. SUBJECTS AND METHODS: We prospectively interpreted 1461 consecutive radiographic examinations of the distal extremities in patients presenting with acute trauma to four family medicine clinics. The anatomic sites radiographed included the ankle, foot, toe, wrist, hand, finger, and thumb. Each study was interpreted and given a diagnostic certainty score using the lateral and posteroanterior or anteroposterior views only and then scored again with the oblique view added. RESULTS: The examinations included 421 with abnormal findings, 34 with equivocal findings, and 1006 with normal findings. The addition of the oblique view changed the interpretation in 70 (4.8%) of the 1461 examinations. Of these changed interpretations, 39 were changed from equivocal to either positive or negative, three from positive to negative, and 28 from negative to positive. Addition of the oblique view increased diagnostic confidence: The percentage of examinations scored as having probably normal, equivocal, and probably abnormal findings decreased from 13.9% with two views to 8.4% with three views (p < .0001). The oblique view was equally valuable in the ankle, foot, toe, wrist, hand, finger, and thumb. CONCLUSION: In the distal extremities, the oblique view uniquely reveals abnormalities and increases the confidence of the final radiographic diagnosis when the oblique view is interpreted along with frontal and lateral radiographs.

Adolescent↗
PubMed1999

Cri du chat and Turner syndrome features in a newborn girl with an unbalanced 45,X,psu dic(5;X)(p15.2;p22.1) karyotype: FISH and replication banding studies.

A newborn girl with features of Turner and Cri du chat syndromes was found to have a pseudodicentric 5;X chromosome. Her karyotype was 45,X, psu dic(5;X)(p15.2;p22.1). The net result was monosomy for 5p15.2-pter and Xp22.1-pter. Fluorescence in situ hybridization (FISH) showed the Cri du chat region was deleted. Replication banding studies to assess the X-inactivation pattern found only the X portion of the pseudodicentric chromosome to be late replicating without any apparent spread of inactivation into chromosome 5 segment. There are only two cases reported with a dicentric X; autosome. In this paper, we compare the cytogenetics of the present case and those in the literature.

Chromosome Banding↗
PubMed1999

A Phase I trial of bryostatin-1 in children with refractory solid tumors: a Pediatric Oncology Group study.

Bryostatin-1, a macrocyclic lactone, appears to elicit a wide range of biological responses including modulation of protein kinase C (PKC). PKC, one of the major elements in the signal transduction pathway, is involved in the regulation of cell growth, differentiation, gene expression, and tumor promotion. Because of the potential for a unique mechanism of interaction with tumorgenesis, a Phase I trial of bryostatin-1 was performed in children with solid tumors to: (a) establish the dose-limiting toxicity (DLT) and maximum-tolerated dose (MTD); (b) establish the pharmacokinetic profile in children; and (c) document any evidence of antitumor activity. A 1-h infusion of bryostatin-1 in a PET formulation (60% polyethylene glycol 400, 30% ethanol, and 10% Tween 80) was administered weekly for 3 weeks to 22 children (age range, 2-21 years) with malignant solid tumors refractory to conventional therapy. Doses ranged from 20 to 57 microg/m2/ dose. Pharmacokinetics were performed in at least three patients per dose level. The first course was used to determine the DLT and MTD. Twenty-two patients on five dose levels were evaluable for toxicities. At the 57 microg/m2/dose level dose-limiting myalgia (grade 3) was observed in three patients; two of those patients also experienced photophobia or eye pain, and one experienced headache. Symptoms occurred in all patients within 24-72 h after the second dose of bryostatin-1 with resolution within 1 week of onset. Other observed toxicities (grades 1 and 2) included elevation in liver transaminases, thrombocytopenia, fever, and flu-like symptoms. The bryostatin-1 infusion was typically well tolerated. Although stable disease was noted in several patients, no complete or partial responses were observed. The recommended Phase II dose of bryostatin-1 administered as a 1-h infusion weekly for 3 of every 4 weeks to children with solid tumors is 44 microg/m2/dose. Myalgia, photophobia, or eye pain, as well as headache, were found to be dose limiting.

Adolescent↗
PubMed1998

Surface topography of phytochrome A deduced from specific chemical modification with iodoacetamide.

Phytochromes are a photoreversible photochromic light switch for photomorphogenesis in plants. The molecular structure and functional mechanism of phytochromes are not fully understood. On the basis of complete mapping of total tryptic digest of the iodoacetamide-modified oat phytochrome A (phyA), the molecular surface topography of phyA was probed by specific chemical modification of cysteine residues with [14C]iodoacetamide. Under native conditions, only two cysteines (Cys-158 and Cys-311) of eleven half-cystines of the N-terminal chromophore binding domain were modified to a significant extent. In the C-terminal domain, six cysteine residues (Cys-715, Cys-774, Cys-809, Cys-869, Cys-961, Cys-995) were readily accessible to iodoacetamide. Among the reactive cysteine residues, only cysteine-311 displayed reactivity that was dependent on the photochromic form (Pr left arrow over right arrow Pfr) of the photoreceptor. Surprisingly, the modification of Cys-311 in the vicinity of the chromophore attachment site (Cys-321) did not have any detectable effect on spectral properties of phyA. Most of the cysteines of the N-terminal domain (Cys-83, Cys-175, Cys-291, Cys-370, Cys-386, Cys-445, Cys-506) are deeply buried in the core of the chromophore binding domain, as they can be modified only after denaturation of the chromoprotein. In the C-terminal domain, modification of only one cysteine residue (Cys-939) required protein denaturation. Since all 22 half-cystines can be modified with iodoacetamide without reduction of the chromoprotein, it follows that oat phyA does not have any disulfide bonds. We found that Cys-311, Cys-774, Cys-961, and Cys-995 could be easily partially oxidized under the conditions used for phytochrome isolation. The surface topography/conformation of oat phyA and its role in protein-protein recognition in phytochrome-mediated signal transduction are discussed in terms of the relative reactivity of cysteine residues.

Amino Acid Sequence↗
PubMed1998

Identification of unfolding domains in large proteins by their unfolding rates.

Three unfolding domains in rabbit muscle aldolase destabilized in 3 M urea have been identified from their unfolding rate constants (0.10, 0.036, and 0.0064 min-1). The populations of folded and various, partially unfolded forms were determined by amide hydrogen exchange and mass spectrometry. Results of this study show that unfolding domains may include multiple, noncontiguous segments of the backbone and that different regions of helices may belong to different unfolding domains. In addition, these results show that the domain unfolding most rapidly is located distant from the subunit binding surfaces and has the greatest access to the denaturant. The bimodal intermolecular distributions of deuterium found in this study show that unfolding of these domains is cooperative. It is proposed that these unfolding domains are correlated with local energy minima in the free-energy folding surface of aldolase. In addition to the three unfolding domains, there are three short segments that do not unfold in 3 M urea. These segments, which are located in the subunit binding surface, identify the most stable regions of aldolase. This study also demonstrates that it is now possible to identify and characterize unfolding domains in relatively large (Mr 158 000) proteins.

Animals↗
PubMed1998

Budding yeast Cdc20: a target of the spindle checkpoint.

The spindle checkpoint regulates the cell division cycle by keeping cells with defective spindles from leaving mitosis. In the two-hybrid system, three proteins that are components of the checkpoint, Mad1, Mad2, and Mad3, were shown to interact with Cdc20, a protein required for exit from mitosis. Mad2 and Mad3 coprecipitated with Cdc20 at all stages of the cell cycle. The binding of Mad2 depended on Mad1 and that of Mad3 on Mad1 and Mad2. Overexpression of Cdc20 allowed cells with a depolymerized spindle or damaged DNA to leave mitosis but did not overcome the arrest caused by unreplicated DNA. Mutants in Cdc20 that were resistant to the spindle checkpoint no longer bound Mad proteins, suggesting that Cdc20 is the target of the spindle checkpoint.

Amino Acid Sequence↗
PubMed1998

In vivo acetylation identified at lysine 70 of human lens alphaA-crystallin.

Posttranslational modification of protein lysyl residues that change the net charge of the molecule may alter the protein conformation. Such modifications are of particular significance among lens proteins, because conformational changes are associated with the development of cataract. A previously unidentified acetylated form of alphaA-crystallin has been isolated from the water-soluble portion of human lenses. The alphaA-crystallins were fractionated by anion exchange HPLC into seven peaks, each containing more than one form of alphaA-crystallin. The previously reported deamidated and phosphorylated forms were identified by their molecular masses, determined by electrospray ionization mass spectrometry. In addition to these modifications, approximately 5% of alphaA-crystallin had a modification that decreased the charge by one and increased the molecular mass by 42 u. This modification, identified as acetylation, was located uniquely at Lys 70. Like any modification that alters the surface charge, acetylation may affect protein conformation and intermolecular interactions, thereby altering the solubility or chaperone properties of alphaA-crystallin. Acetylation of lysine 70 is potentially significant since it is located in a region that has been implicated in the chaperone activity of alphaA-crystallin.

Acetylation↗
PubMed1998

The role of the 6 lysines and the terminal amine of Escherichia coli single-strand binding protein in its binding of single-stranded DNA.

Differential chemical modification of the lysines and amino-terminus of Escherichia coli single-strand binding (SSB) protein was used to determine their roles in the binding of SSB to single-stranded DNA (ssDNA). A combination of isotope labeling and mass spectrometry was used to determine the rates at which SSB was acetylated by acetic anhydride. First, SSB was labeled by deuterated acetic anhydride for given lengths of time in the presence or absence of single-stranded ssDNA. Then, the protein was denatured and completely acetylated by nondeuterated acetic anhydride. Enzymatic digests of the completely acetylated, isotopically labeled SSB were analyzed by electrospray ionization mass spectrometry. The intensities of the deuterated and nondeuterated forms of acetylated peptides provided accurate quantification of the reactivity of the amines in native SSB, either free or bound to ssDNA. Acetylation rate constants were determined from time course measurements. In the absence of ssDNA, the terminal alpha-amine of SSB was 10-fold more reactive than Lys residues at positions 43, 62, 73, and 87. The reactivities of Lys 7 and 49 were much lower yet, suggesting that they have very limited access to solution under any condition. In the presence of ssDNA, the reactivities of the amino-terminus and Lys residues 43, 62, 73, and 87 were reduced by factors of 3.7-25, indicating that the environments around all of these amines is substantially altered by binding of SSB to ssDNA. Three of these residues are located near putative ssDNA binding sites, whereas Lys 87 is located at the monomer-monomer interface.

Acetylation↗
PubMed1998

Age-related changes in human lens crystallins identified by two-dimensional electrophoresis and mass spectrometry.

The purpose of this study was to identify the major protein components in adult human lenses and to analyse the specific age-related changes in these proteins using two-dimensional electrophoresis, Edman sequencing, and in conjunction with the data in the accompanying manuscript, mass spectrometry. The majority of changes in the two-dimensional electrophoretic pattern of lens proteins occurred prior to 17 years of age, and included a decrease in proteins migrating to the original positions of beta B1, beta B3, beta A3, gamma C and gamma D, and the appearance of many new species with apparent molecular weights on two-dimensional electrophoretic gels similar to beta B2 and gamma S, but having more acidic pIs. These proteins were identified as deamidated forms of beta B1 and beta A3/A1 missing portions of their N-terminal extensions. With the exception of alpha B, deamidation was detected in all crystallin species. These data indicated that a major fraction of the water-soluble protein of the adult human lens is composed of truncated beta B1 and beta A3/A1 crystallins, and that nearly all human crystallins, including the, beta-crystallins, are susceptible to deamidation. The results also provided the most detailed map to date of the identities of protein species on two-dimensional electrophoresis gels of adult human lenses.

Adolescent↗