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Biomedical subjects

R Felder

Publications and source records attributed to R Felder.

17 recordsLinked to original sources
PubMed1998

Robotic automation of coagulation analysis.

Laboratory automation systems (LAS) have been installed in over 22 sites across North America providing automation of many preanalytical and analytical tasks in clinical laboratories. Only a few laboratories have automated the analysis of citrated whole blood for the diagnosis of hemostasis disorders. The analysis of coagulation factors in citrated blood requires a large amount of labor in order to provide rapid turnaround; thus automation of this analytical process is attractive. Therefore, we have created an automated coagulation workstation using a systematic approach to automation design and engineering. First, we used discrete event simulation to calculate potential throughput and to identify possible bottlenecks for the proposed coagulation workcell. We then created a three-dimensional animated computer model of the workstation to simplify workstation design. Finally, we constructed a prototype workcell using a mobile robot, an articulated robotic arm, and a coagulation analytical system.

Blood Coagulation Disorders↗
PubMed1995

[Satisfaction of paid thrombocyte donors with instrumental thrombocytapheresis].

OBJECTIVE: The increasing need for single-donor platelet concentrates makes it necessary to motivate platelet donors to donate regularly. The authors examined the contentment of existing donors in order to create a basis for improvements and to raise the attractiveness of donation. DESIGN: Open empirical data acquisition. SETTING: Institute for Transfusion Medicine at the General Hospital Vienna. PARTICIPANTS: 211 platelet donors. INTERVENTIONS: Interview with a self-developed questionnaire. RESULTS: Whereas donors rate the work of the staff as being very good, they are less content with the surroundings in the pheresis unit. Younger and higher-educated donors as well as persons who have been donating for less than 5 years show more negative ratings than comparable groups. The financial compensation is important to ensure a high donation frequency. CONCLUSIONS: The attractiveness of donation could be raised by improving certain aspects of donation. In order to ensure a high donation frequency donors should be granted a financial compensation, as otherwise particularly younger donors, who are more likely to be seronegative for antibodies to CMV, would not donate any more or at least not that often.

Adult↗
PubMed1994

Dexterity testing as a predictor of oral care ability.

OBJECTIVE: To examine a spectrum of elderly people to determine if hand function/dexterity measures can predict oral care ability. DESIGN: A series of dental, hand function, and dexterity measures were assessed by blinded examiners. Plaque scores were used as the criterion standard to assess plaque removal ability. PATIENTS: A convenience sample of 52, predominately male, elderly patients were recruited from the patient population of the Portland Veteran Affairs Medical Center and a community nursing home. Entry into the study required that the patient be able to give consent, be age 65 or older, have a minimum of six contiguous teeth or a minimum of 12 teeth total, be medically stable, have grossly adequate vision, and be able to hear and understand spoken instructions. OUTCOME MEASURES: The primary outcome measure was plaque score, as defined by the Turesky modification of the Quigley-Hein index. This was related to four dexterity tests (Jebsen-Taylor Hand Function test, Nine-hole Peg test, Box and Block test, Toothbrushing Ability test), a grip strength measure, and a cognitive measure (Allen Cognitive Level Test). RESULTS: Oral hygiene was significantly impaired among institutionalized elderly compared with outpatient elderly (P < 0.001), as was dexterity (P < 0.001). All dexterity tests correlated significantly with plaque score (Spearman rho: 0.49-0.77; P < 0.000). Forward stepwise regression analysis identified the Toothbrushing Ability Test (P < 0.0001) and the time spent brushing (P = 0.007) as the most significant predictors of plaque score. CONCLUSIONS: Results suggest oral hygiene ability is decreased among long term care residents, that dexterity tests can help identify patients unable to perform adequate oral self-care, and that these tests could be used to estimate brushing ability among elderly compromised patients.

Aged↗
PubMed1993

Developmental regulation of the alpha 1B-adrenoceptor in the sheep kidney.

The expression of renal alpha 1B-adrenoceptor (alpha 1B-AR) mRNA was studied and contrasted with the expression of renal renin mRNA in fetal and newborn sheep. Fetal sheep between 90 and 91, 116 and 118, and 139 and 141 d gestation (term is 145 d gestation) as well as newborn lambs between 1 and 2 d old and 8 and 10 d old were studied (n = 3 for each age range). The role of the renal nerves in regulating changes in alpha 1B-AR gene expression was also investigated by measuring renal cortical alpha 1B-AR mRNA levels and receptor kd and maximum number of binding sites in 24-h-old lambs that were either denervated (n = 6) or sham-operated (n = 5) 3 d before birth. During development, renal alpha 1B-AR mRNA levels show a marked increase in term fetuses; this increase persists into the first 2 d of life and is distinct from the developmental pattern seen for renal renin mRNA levels. Denervation of term fetuses does not alter the expression of renal alpha 1B-AR mRNA in newborn lambs when compared with sham-operated controls but decreases significantly the expression of the renin gene (p < 0.05). These results suggest that the alpha 1B-AR gene is developmentally regulated in the kidney in a pattern distinct from that seen for renin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Subclinical pregnancy loss in clomiphene citrate-treated women.

OBJECTIVE: To ascertain the subclinical pregnancy loss rate in clomiphene citrate (CC)-treated infertile women compared with women of normal fertility. DESIGN: Following a prospective format, serum samples were taken during the luteal phase of 92 menstrual cycles associated with CC treatment and 47 cycles in normal women. Human chorionic gonadotropin (hCG) assay sensitivity was 0.25 IU/L. Human chorionic gonadotropin assay was validated against 95 nonpregnant cycles. Criterion for pregnancy was a single serum sample greater than or equal to 0.5 IU/L. SETTING: All subjects were under clinical management at the University of Virginia Health Sciences Center. PATIENTS AND PARTICIPANTS: Patients undergoing CC induction of ovulation with satisfactory ovulatory response were candidates for the study group (n = 34). Control subjects of proven normal fertility were recruited (n = 22). Nonpregnant control subjects were sexually abstinent or had been surgically sterilized (n = 89). INTERVENTION: A serum sample was taken during the late luteal phase of all subjects. RESULTS: Thirteen percent of CC-treated cycles and 4.3% of normal control cycles were subclinical losses (P = 0.09). Fifty percent of CC-induced pregnancies were subclinical losses compared with 16.6% of normal control pregnancies (P = 0.05). Of CC patients who had at least one subclinical loss 47.6% later conceived a term pregnancy compared with 15.3% who did not have a subclinical loss (P = 0.06). CONCLUSION: Subclinical pregnancy loss is more common in CC-treated women than normal women and may be a predictor of subsequent normal conception.

Abortion, Spontaneous↗
PubMed1990

Vaginal sonography findings and hCG dynamics of early intrauterine and tubal pregnancies.

Early intrauterine gestational sac recognition by ultrasound is useful for discriminating between intrauterine and tubal pregnancies. Transvaginal ultrasound offers improved resolution in the imaging of the uterus and adnexa. Seventy-four women with normal intrauterine pregnancies, 18 women with spontaneous abortions, and 34 women with tubal pregnancies were evaluated by transvaginal ultrasound and serial hCG determinations. Intrauterine pregnancies were followed within the first 50 days of gestation. In women with a normal uterus and singleton pregnancy, sacs were consistently recognized in association with an hCG level greater than 2004 mIU/mL (First International Reference Preparation). Two-to three-millimeter sacs were recognized in association with an hCG level of 2032 +/- 1253 on cycle day 36.1 +/- 2.0. When sacs were less than 5 mm in mean diameter, 33% exhibited a prominent echogenic rim, 38% exhibited a partial echogenic rim, and 29% exhibited no echogenic rim. Fetal cardiac activity was recognized in association with an hCG level of 27,284 +/- 11,479 on cycle day 45.0 +/- 2.9. The hCG doubling time was 1.46 +/- 1.0 days. Apparent loss of multiple gestational sacs was observed in five normal pregnancies. Apparent bleeding in the intrauterine cavity was observed in eight patients and associated with a 38% abortion rate. One false-positive sac was observed among 34 tubal pregnancies (3%). The extrauterine sonographic finding of a solid adnexal mass or cul-de-sac fluid was specific but not sensitive for the diagnosis of tubal pregnancy. The hCG doubling time in tubal pregnancies was 7.69 +/- 9.8 days. Transvaginal ultrasound and serial hCG determinations are useful for the early recognition of tubal pregnancy.

Abortion, Spontaneous↗
PubMed1986

D-2 dopamine receptor-mediated inhibition of pro-opiomelanocortin synthesis in rat intermediate lobe. Abolition by pertussis toxin or activators of adenylate cyclase.

Stimulation of the D-2 dopamine receptor inhibits pro-opiomelanocortin (POMC) synthesis in isolated rat intermediate lobe tissue. Intermediate lobe tissue was incubated in the absence or presence of various dopaminergic compounds, and then its capacity to incorporate [3H]tyrosine into POMC was tested. D-2 dopaminergic agonists caused a dose-dependent inhibition of POMC synthesis; the maximal inhibitory effect was approximately a 50% reduction in the amount of POMC synthesized. D-2 dopaminergic antagonists blocked the inhibitory effect of each agonist. Pretreatment of the tissue with pertussis toxin abolished the D-2 dopaminergic inhibition of POMC synthesis. The potency of pertussis toxin in abolishing the dopaminergic inhibition of POMC synthesis corresponded to its potency in abolishing the D-2 dopaminergic inhibition of adenylate cyclase activity. Cholera toxin, forskolin, and 8-bromo-cAMP, compounds that activate the cAMP pathway, enhanced the capacity of intermediate lobe tissue to synthesize POMC and counteracted the dopaminergic inhibition of POMC synthesis. Incubation of intermediate lobe tissue for 24 h with bromocriptine, a D-2 dopaminergic agonist, decreased the POMC mRNA content by 46% as determined by hybridization of RNA to a 32P-labeled probe. Incubation of intermediate lobe tissue with forskolin increased the level of POMC mRNA; incubation of the tissue with a combination of bromocriptine and forskolin also resulted in an increase in the level of POMC mRNA. It is proposed that Ni, the inhibitory guanyl nucleotide binding protein, and possibly adenylate cyclase mediate the dopaminergic inhibition of POMC synthesis.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1986

D-2 dopaminergic agonists and adenosine 3',5'-monophosphate directly regulate the synthesis of alpha-melanocyte-stimulating hormone-like peptides by cultured rat melanotrophs.

When placed in short term (2-day) tissue culture, the melanotrophs from the intermediate lobe of the rat pituitary gland synthesize a proopiomelanocortin-like material (POMC-LM). Exposure of these cells to bromocriptine (CB 154), an agonist upon their D-2 dopamine receptor, reduces the synthesis of POMC-LM; spiroperidol, an antagonist of the D-2 receptor, prevents this effect of CB 154. Cultured melanotrophs secrete an alpha MSH-like material. The amount of this alpha MSH-like material, either stored intracellularly or secreted into the culture medium, can be quantified in a specific RIA; the material identified in this manner is designated immunoreactive alpha MSH (IR-alpha MSH). CB 154 inhibits the secretion of IR-alpha MSH from these cells. Either spiroperidol or 8-bromo-cAMP prevent this inhibitory effect of CB 154. The capacity of these cells to synthesize alpha MSH-like molecules and release them into the culture medium can be assessed by incubation in the presence of [3H]tyrosine, followed by immunoprecipitation with an antibody directed against alpha MSH. This newly synthesized immunoprecipitable material is designated immunoprecipitable alpha MSH (IP-alpha MSH) and should be distinguished from IR-alpha MSH. Both CB 154 and quinpirole, a selective D-2 agonist (but not SKF 38393, a selective D-1 agonist), inhibit the synthesis and secretion of IP-alpha MSH. YM-09151-2, a selective D-2 antagonist (but not SCH 23390, a selective D-1 antagonist), blocks the inhibitory effects of quinpirole. Several compounds affecting cAMP metabolism (cholera toxin, forskolin, 8-bromo-cAMP, and 3-isobutyl-1-methylxanthine) can also prevent the inhibitory effect of CB 154 on the synthesis of IP-alpha MSH. We conclude the following. The D-2 receptor in the intermediate lobe directly regulates the synthesis and secretion of IP-alpha MSH. cAMP can regulate either the synthesis of POMC-LM or the processing of this substance into alpha MSH-like peptides.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Elder abuse.

Explore the source record for details and available documents.

Aged↗
PubMed1984

Mechanism of directional selectivity in simple neurons of the cat's visual cortex analyzed with stationary flash sequences.

The properties of simple neurons showing selectivity to direction of motion in area 17 of the cat cortex were examined. We analyzed in particular a sample of cells receiving a projection from 0 to 10 degrees in visual angle from the area centralis of the cat retina. Three categories of simple neurons were examined: directionally asymmetric (DA) neurons, directionally selective neurons of the unimodal type (DS1), and bimodal types (DS2). Poststimulus time histograms (PSTH) were obtained to moving white and black bars as well as to static onset sequences and static offset sequences. Our analysis involves a comparison of responses to single static flashes at various receptive-field locations with responses to sequence pairs of static flashes at those same locations. We find that DA neurons are not sensitive to the direction in which a pair of stimuli are presented. Inhibitory and excitatory responses show properties of linear summation whatever the direction of the stimulus sequence. Their behavior is reminiscent of retinal and LGN neurons. The synergy model accounts well for a DA neurons's directional asymmetry. If pairs of stimuli are close enough (usually an interstimulus distance of 20' or less for the central 10 degrees of the cat's visual field), then DS neurons show striking departures from linear summation. Specifically, this departure entails an anisotropic distribution of inhibition. The directional selectivity of DS neurons cannot be explained on the basis of a simple linear combination of their on and off region's responses. Directional selectivity is produced entirely within an on-excitatory discharge region or entirely within an off-excitatory discharge region. The excitatory discharge center of even the simplest unimodal DS neuron can be shown to be decomposable into subunits smaller than that discharge center. The fact that the spread of this anisotropy of inhibition is often much more restricted than the entire extent of the DS neuron's excitatory discharge center argues strongly that underlying subregions or modules are contributing their inputs to DS neurons. A DS neuron does not analyze motion as an isolated unit; to the contrary, it is probably embedded in a pool of mutually "cooperative" DS neurons. The basic module of directional analysis is responsive either to an on-on sequence or an off-off sequence but not to both. It is not selective to an on-off sequence. Therefore, unimodal DS neurons (DS1) are performing an analysis of single moving edges.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Comparison of coding and spacer region sequences of chromosomal rRNA-coding genes of two sequevars of Pneumocystis carinii.

Two distinct sequevars, denoted Pc1 and Pc2, of the opportunistic pathogen Pneumocystis carinii have been previously identified based on the sequence of their 26S rRNA genes, the location of group I self-splicing introns and pulsed field electrophoretic patterns of chromosomal DNA. This study shows that the sequences of 16S and 5.8S rRNA genes also vary between these sequevars, and that greater variation was seen in the internal transcribed spacer regions. Polymerase chain reaction and restriction analysis can distinguish between these sequevars.

Animals↗
PubMedDate not supplied

Testing toothbrushing ability of elderly patients.

An individual's ability to perform adequate oral care may become jeopardized by medical and physical insults associated with the aging process. Declines in oral care abilities may be difficult to identify, and usually go unnoticed and unaddressed. This study examined a tool developed to assess toothbrushing ability in elderly patients. The Toothbrushing Ability Test (TAT) was examined for its ability to predict brushing effectiveness (measured by plaque levels) and to determine its interrater and intrarater reliability. Fifty-eight dentate subjects, age 65 and older, from the Portland Veterans Affairs Medical Center and a community nursing home participated. Results showed highly significant Spearman correlations between TAT scores and plaque levels (r = 0.719; p < 0.000). Correlations also revealed high interrater (r = 0.87) and intrarater reliability (r = 0.82). The results suggest that the TAT is a practical and effective screening tool for assessing oral self-care ability in the elderly.

Aged↗