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Biomedical subjects

D Rice

Publications and source records attributed to D Rice.

At least 37 records · Page 2Linked to original sources
PubMed1997

Risk factors associated with permanent access-site infections in chronic hemodialysis patients.

OBJECTIVE: To determine the epidemiological risk factors associated with permanent access-site (PAS) infection in a population of chronic hemodialysis patients. DESIGN: Retrospective cohort analysis. SETTING: Hemodialysis unit of a 400-bed Department of Veterans' Affairs hospital. RESULTS: A cohort of 94 males (1,316 patient months) was studied. Fifty-one PAS infections in 31 patients were observed. Six patients had two PAS infections, four patients had three infections, and two patients had four infections. Twenty-nine of the 31 patients with PAS infections were bacteremic at least once. Univariate analysis identified seven factors significantly associated with PAS infection in this population: location of PAS other than forearm, type of vascular access (polytetrafluoroethylene [PTFE] versus endogenous arteriovenous [AV] fistula), limited ambulatory status, residence in a nursing home, bacterial infection at a distant site, number of access-site revisions, and number of hospitalizations. In a logistic regression analysis, only graft type and number of PTFE graft revisions were associated independently with PAS infection. The odds ratio for PAS infection in PTFE grafts compared to endogenous AV fistula was 7.8; the odds ratio for PAS infection with each PTFE graft revision was 1.5. CONCLUSIONS: PAS infections were associated independently with the type of graft and the number of PTFE graft surgical revisions.

Adult↗
PubMed1997

Transmaxillary approach to the anterior cavernous sinus: a microanatomic study.

OBJECTIVE: Several approaches to expose the anterior cavernous sinus have been used, such as frontotemporal, orbitofrontal, anterior subtemporal, and various transfacial approaches. In an effort to gain exposure to the anterior cavernous sinus without necessitating a craniotomy or wide transfacial exposure, the authors in the present study have developed a transmaxillary approach to the cavernous sinus. METHODS: The approach was developed using data obtained by performing 24 cadaveric dissections. Using a sublabial incision to expose the maxilla, maxillotomy is performed and the course of the infraorbital nerve is identified as a guide to the maxillary branch of the trigeminal nerve. After an osteotomy of the posterior sinus wall and pterygoid plate, the foramen rotundum is identified, which lies a mean of 10 mm from the posterior wall of the maxilla. A superomedial enlargement of the foramen rotundum is then undertaken to ultimately expose the anterior cavernous sinus. RESULTS: This technique offers access to all cavernous cranial nerves, as well as the entire course of the anterior loop of the internal carotid artery to the origin of the ophthalmic artery. With a mean operative range of 38 mm from the posterior wall of the maxilla to the anterior loop of the internal carotid artery, this approach offers adequate exposure with a short operative distance. CONCLUSION: The approach may be useful in limited exposure of tumors of the anterior cavernous sinus and some intracavernous vascular lesions.

Brain Mapping↗
PubMed1997

Protective effects of L-2-oxothiazolidine-4-carboxylate treatment on cyclophosphamide-induced cystitis in rats.

PURPOSE: Hemorrhagic cystitis is a therapy-limiting side effect of cyclophosphamide (CP) treatment for cancer. The purpose of this study was to investigate the potential protective effect of L-2-oxothiazolidine-4-carboxylate (OTZ; Procysteine) on CP-induced cystitis in the rat. MATERIALS AND METHODS: Thirty-six rats were divided into 6 groups: Group 1--Untreated controls, Group 2--OTZ alone (100 mg./kg., p.o.), Group 3--CP alone (68 mg./kg., i.v.), Group 4--CP + OTZ (68 mg./kg., i.v. + 100 mg.,/kg., p.o.), Group 5--CP + OTZ (68 mg./kg., i.v. + 1.0 g./kg., i.v.), and Group 6--CP + OTZ (68 mg./kg.,i.v. + 1.0 gm./kg., i.p.). OTZ was given once a day to groups 2 and 4 on the day prior to and on the day of CP administration. OTZ was given twice a day to groups 5 and 6 on the day prior to, the day of, and the day after CP administration. On the day of CP administration, CP was given 30 minutes prior to OTZ. Blood and bladder samples were taken for evaluation two days after CP administration. RESULTS: Expected depression in blood cell parameters were identified in all groups receiving CP with no differences noted between the CP-treated groups. Histologic changes (cystitis) were identified in the bladders of all CP treated groups. The lesions in the CP + OTZ groups were found to be less severe than the groups that received CP alone, with higher dosages of OTZ resulting in a significant (p < 0.05) decrease in lesion incidence and severity. CONCLUSIONS: Under the conditions of this study, L-2-oxothiazolidine-4 carboxylate caused a reduction in the incidence and severity of cyclophosphamide-induced lesions in the urinary bladder of rats. Further studies are needed to investigate optimal dosage scheme, mechanism of action, and interference with anti-tumor activity and prevention of long-term side effects of cyclophosphamide.

Animals↗
PubMed1996

Persons with chronic conditions. Their prevalence and costs.

OBJECTIVES: To determine (1) the number and proportion of Americans living with chronic conditions, and (2) the magnitude of their costs, including direct costs (annual personal health expenditures) and indirect costs to society (lost productivity due to chronic conditions and premature death). DESIGN: Analysis of the 1987 National Medical Expenditure Survey for prevalence and direct health care costs; indirect costs based on the 1990 National Health Interview Survey and Vital Statistics of the United States. SETTING: US population. PARTICIPANTS: For the estimate of prevalence and direct costs, the National Medical Expenditure Survey sample of persons who reported health conditions associated with (1) use of health services or supplies or (2) periods of disability. INTERVENTIONS: None. MAIN OUTCOME MEASURES: The number of persons with chronic conditions, their annual direct health care costs, and indirect costs from lost productivity and premature deaths. RESULTS: In 1987, 90 million Americans were living with chronic conditions, 39 million of whom were living with more than 1 chronic condition. Over 45% of noninstitutionalized Americans have 1 or more chronic conditions and their direct health care costs account for three fourths of US health care expenditures. Total costs projected to 1990 for people with chronic conditions amounted to $659 billion--$425 billion for direct health care costs and $234 billion in indirect costs. CONCLUSIONS: The prevalence and costs of chronic conditions as a whole have rarely been estimated. Because the number of persons with limitations due to chronic conditions is more regularly reported in the literature, the total prevalence of chronic conditions has perhaps been minimized. The majority of persons with chronic conditions are not disabled, nor are they elderly. Chronic conditions affect all ages. Because persons with chronic conditions have greater health needs at any age, their costs are disproportionately high.

Adolescent↗
PubMed1996

Assigning amino acid sequences to 3-dimensional protein folds.

With the advent of genome sequencing projects, the amino acid sequences of thousands of proteins are determined every year. Each of these protein sequences must be identified with its function and its 3-dimensional structure for us to gain a full understanding of the molecular biology of organisms. To meet this challenge, new methods are being developed for fold recognition, the computational assignment of newly determined amino acid sequences to 3-dimensional protein structures. These methods start with a library of known 3-dimensional target protein structures. The new probe sequence is then aligned to each target protein structure in the library and the compatibility of the sequence for that structure is scored. If a target structure is found to have a significantly high compatibility score, it is assumed that the probe sequence folds in much the same way as the target structure. The fundamental assumptions of this approach are that many different sequences fold in similar ways and there is a relatively high probability that a new sequence possesses a previously observed fold. We review various approaches to fold recognition and break down the process into its main steps: creation of a library of target folds; representation of the folds; alignment of the probe sequence to a target fold using a sequence-to-structure compatibility scoring function; and assessment of significance of compatibility. We emphasize that even though this new field of fold recognition has made rapid progress, technical problems remain to be solved in most of the steps. Standard benchmarks may help identify the problem steps and find solutions to the problems.

Algorithms↗
PubMed1996

Effect of leucine metabolite beta-hydroxy-beta-methylbutyrate on muscle metabolism during resistance-exercise training.

The effects of dietary supplementation with the leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) were studied in two experiments. In study 1, subjects (n = 41) were randomized among three levels of HMB supplementation (0, 1.5 or 3.0 g HMB/day) and two protein levels (normal, 117 g/day, or high, 175 g/day) and weight lifted for 1.5 h 3 days/wk for 3 wk. In study 2, subjects (n = 28) were fed either 0 or 3.0 g HMB/day and weight lifted for 2-3 h 6 days/wk for 7 wk. In study 1, HMB significantly decreased the exercise-induced rise in muscle proteolysis as measured by urine 3-methylhistidine during the first 2 wk of exercise (linear decrease, P < 0.04). Plasma creatine phosphokinase was also decreased with HMB supplementation (week 3, linear decrease, P < 0.05). Weight lifted was increased by HMB supplementation when compared with the unsupplemented subjects during each week of the study (linear increase, P < 0.02). In study 2, fat-free mass was significantly increased in HMB-supplemented subjects compared with the unsupplemented group at 2 and 4-6 wk of the study (P < 0.05). In conclusion, supplementation with either 1.5 or 3 g HMB/day can partly prevent exercise-induced proteolysis and/or muscle damage and result in larger gains in muscle function associated with resistance training.

Adult↗
PubMed1996

Microleakage of amalgam restorations using dentin bonding system primers.

PURPOSE: To evaluate and compare in vitro microleakage of etched and non-etched Class I amalgam restorations lined with various dentin bonding system primers to amalgam restorations with or without a Copalite liner. MATERIALS AND METHODS: Class I amalgam preparations were made in 140 extracted molars and divided into 14 groups of 10 teeth each. Permite C dispersed phase alloy restorations were placed after the following treatments: Group 1: No liner; Group 2: Lined with two coats of Copalite; Group 3(A): Lined with Amalgambond AA and 3(B): Etched with 35% Ultra-etch and lined with Amalgambond AA; Group 4(A): Lined with Scotchbond Multi-Purpose Primer and 4(B): Etched and lined with the primer; Group 5(A): Lined with ProBond and 5(B): Etched and lined with the primer; Group 6(A): Lined with All-Bond 2 Primer A & B and 6(B): Etched and lined with the primer; Group 7(A): Lined with OptiBond and 7(B): Etched and lined with the primer; Group 8(A): Lined with Permagen Primer and 8(B): Etched and lined with the primer. All primers were applied per manufacturers' specifications. After storage in water for 24 hours, all restorations were polished and then aged in water at 37 degrees C for 90 days. The specimens were then thermocycled for 300 cycles at 5 degrees C and 55 degrees C in basic fuchsin dye with a 30-second dwell time, mounted in epoxy rings, sectioned longitudinally, mesiodistally and buccolingually into four sections, then evaluated at x100 and the extent of dye penetration at the tooth/amalgam interface scored (two scores for each section, eight for each specimen). RESULTS: The unlined and Copalite-lined groups and all non-etched groups showed considerable marginal leakage. All the etched restorations were significantly more effective in reducing microleakage than the non-etched, no liner and Copalite-lined groups. Etching prior to application of the primers is significantly more effective than nonetching, however the effectiveness of the primer alone to seal the dentin needs to be evaluated. Overall, Amalgam-bond AA had the least microleakage of all the groups.

Acid Etching, Dental↗
PubMed1996

Assessing the performance of fold recognition methods by means of a comprehensive benchmark.

Recently there has been an explosion of methods for fold recognition. These methods seek to align a protein sequence to a three-dimensional structure and measure the compatibility of the sequence to the structure. In this work, we present a benchmark to assess the performance of such methods. The benchmark consists of a set of protein sequences matched by superposition to known structures. This set covers a wide range of protein families, and includes matching proteins with insignificant sequence similarity. To demonstrate the usefulness of this benchmark, we apply it here to compare different fold-recognition methods developed through the years in our group as well as several sequence-sequence substitution matrices. The results show that "global-local" alignments are superior to either local or global alignments. The most effective sequence-sequence matching matrix is the Gonnet table. The best performance overall is obtained by a method which combines the 3D-1D profiles of Bowie et al. with a substitution matrix and takes into account residue pairwise interactions.

Amino Acid Sequence↗
PubMed1995

EEG delta, positron emission tomography, and memory deficit in Alzheimer's disease.

Quantitative scalp EEG from 32 channels and the cerebral glucose metabolic rate from the 32 underlying cortical positions as assessed by positron emission tomography (PET) with 18F-2-deoxyglucose (FDG) were obtained on 36 patients with mild to moderate senile dementia of the Alzheimer type and 17 age- and sex-matched normal control subjects. Subjects performed a verbal memory task during uptake of FDG. There were significant correlations between both delta amplitude and metabolic rate and memory performance during FDG uptake. Patients with Alzheimer's disease had significantly greater left temporal delta amplitude and lower glucose metabolic rates. Both EEG delta in microvolts and metabolic rate had similar diagnostic sensitivity, but PET had fewer false positives among normals. The left amygdala had the highest sensitivity and percent correct diagnosis of any brain area. Temporal lobe EEG delta activity showed higher correlations with hippocampal metabolic rate than metabolic rate directly under the electrode.

Aged↗
PubMed1993

The 1.5-A crystal structure of plastocyanin from the green alga Chlamydomonas reinhardtii.

The crystal structure of plastocyanin from the green alga Chlamydomonas reinhardtii has been determined at 1.5-A resolution with a crystallographic R factor of 16.8%. Plastocyanin is a small (98 amino acids), blue copper-binding protein that catalyzes the transfer of electrons in oxygenic photosynthesis from cytochrome f in the quinol oxidase complex to P700+ in photosystem I. Chlamydomonas reinhardtii plastocyanin is an eight-stranded, antiparallel beta-barrel with a single copper atom coordinated in quasitetrahedral geometry by two imidazole nitrogens (from His-37 and His-87), a cysteine sulfur (from Cys-84), and a methionine sulfur (from Met-92). The molecule contains a region of negative charge surrounding Tyr-83 (the putative distant site of electron transfer) and an exclusively hydrophobic region surrounding His-87; these regions are thought to be involved in the recognition of reaction partners for the purpose of directing electron transfer. Chlamydomonas reinhardtii plastocyanin is similar to the other plastocyanins of known structure, particularly the green algal plastocyanins from Enteromorpha prolifera and Scenedesmus obliquus. A potential "through-bond" path of electron transfer has been identified in the protein that involves the side chain of Tyr-83, the main-chain atoms between residues 83 and 84, the side chain of Cys-84, the copper atom, and the side chain of His-87.

Amino Acid Sequence↗
PubMed1993

Chronic lead exposure induces ultrastructural alterations in the monkey testis.

The purpose of this study was to establish the effects of lead on the non-human primate testis. Sixteen cynomolgus monkeys maintained in environmentally controlled conditions were administered 1500 micrograms lead acetate/kg bw/day in gelatin capsules. Monkeys were randomly assigned to the following groups: control (n = 3), which received 95% glycerol and 5% distilled water (vehicle) over their lifetime for 9 years; infancy group (n = 4), exposure limited to the first 400 days of life; post-infancy group (n = 5), dosed following 300 days of life to 9 years of age; lifetime group (n = 4), dosed for nine years. All the animals were treated with lead or vehicle for the entire duration of the experiment. The organs from animals in the control group consisted of seminiferous epithelium comprised of typical Sertoli cells containing nuclei with numerous infoldings and longitudinally-oriented profiles of endoplasmic reticulum, microtubules, mitochondria, and lipid droplets that were scarce. Spermatogenic cell types at different developmental stages were observed. Seminiferous epithelium from animals of the treated groups exhibited distortion in the general architecture of the epithelium such that a marked decrease in its height was revealed. In particular, Sertoli cells contained heightened number of lipid droplets and lysosomal elements, and the basal lamina was usually stratified. The magnitude of alterations in the seminiferous tubules was indistinguishable among the three treated groups. These findings support the conclusion that lead is a potent testicular toxin.

Aging↗
PubMed1993

Chronic lead exposure induces ultrastructural alterations in the monkey seminal vesicle.

Lead is a toxic and carcinogenic metal that has been extensively associated with male reproductive abnormalities. The purpose of this study was to establish the effects of lead on the primate seminal vesicle. Sixteen cynomolgus monkeys maintained in environmentally controlled conditions were orally administered gelatin capsules containing 1500 micrograms lead acetate/kg bw/day. Monkeys were randomly assigned to the following groups: control (n = 3) which received 95% glycerol and 5% distilled water (vehicle) over their lifetime, infancy (limited to the first 400 days of life; n = 4), post-infancy (dosed following 300 days of life to 9 years of age; n = 5) and lifetime exposure (9 years; n = 4). At necropsy, the seminal vesicles from each animal were removed, fixed in glutaraldehyde, and processed for ultrastructural analysis by conventional methods. The glands from animals in the control group consisted of acini lined by two cell types, viz., tall columnar secretory cells, and round basal cells. Secretory cells possessed microvilli, basally located nuclei surrounded by much rough endoplasmic reticulum, a few lipid droplets, and supra-nuclear regions dominated by pleomorphic membrane-limited secretory granules. All the treated groups exhibited an augmentation in the number of lipid droplets within the secretory cells. In both the infancy and post-infancy groups, a marked reduction in electron-dense cores of the secretory droplets was observed in severely affected regions of the glands. These findings support the evidence that lead is a potent reproductive toxicant, however, further research is needed to determine the consequences of this damage on reproductive performance.

Age Factors↗
PubMed1992

High-sensitivity analysis of sialyl-oligosaccharide glycosylation sites in glycoproteins by miniaturized tryptic digestion and microcolumn liquid chromatography.

A highly sensitive analytical procedure was developed to assess the site of glycosylation in a model glycoprotein, bovine fetuin. First, sample cleavage with immobilized trypsin and the peptide map development are accomplished by microcolumn liquid chromatography. Second, the sialic acids content is measured fluorometrically using their precolumn conversion to quinoxaline derivatives. A unique preconcentration system was developed to secure sensitivity of the second measurement.

Amino Acid Sequence↗
PubMed1992

The HsdS polypeptide of the type IC restriction enzyme EcoR124 is a sequence-specific DNA-binding protein.

The HsdS and HsdM polypeptides of the type IC restriction enzyme EcoR124 have been purified independently and used in a set of gel retardation experiments to determine the minimum requirements for sequence-specific recognition of DNA by this enzyme. The HsdS polypeptide alone is able to bind to DNA in a sequence-specific manner. In addition, whilst the presence of the HsdM polypeptide gives rise to a stimulation of DNA binding by the HsdS subunit it is not clear whether, under the conditions of the experiments reported here, the HsdS subunit maintains the same interactions with the HsdM subunits observed in the absence of DNA.

Bacterial Proteins↗