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Biomedical subjects

M E Rogers

Publications and source records attributed to M E Rogers.

At least 19 recordsLinked to original sources
PubMed1996

Laser induced bubble formation in the retina.

BACKGROUND AND OBJECTIVE: The immediate thermodynamic effects of absorption of a laser pulse in the retina are theoretically studied to understand underlying physical damage mechanisms at threshold fluences. Damage is most likely to occur at threshold levels in the retinal pigment epithelium due to the strong absorption by the melanosomes. METHODS: The retinal pigment epithelium is modeled as an aqueous environment with absorption occurring at small spherical sites with absorption coefficients representative of melanosomes. For laser pulse durations of less than 10(-6) seconds, heat conduction is negligible during energy deposition and the resulting large energy density in the melanosomes will cause vaporization of the medium immediately surrounding a melanosome. RESULTS: We developed expressions for calculating the size of bubbles produced as a function of pulse characteristics and melanosome properties. We show that for pulse durations between 10(-6) and 10(-9) seconds, bubble formation will occur for laser fluences that are smaller than those required to cause Arrhenius-type thermal damage. CONCLUSION: Bubble formation is likely to be the mechanism of threshold damage to the retina for laser pulses durations in the time regime between 10(-6) and 10(-9) seconds.

Absorption↗
PubMed1996

Ontogeny of odorant receptor gene expression in zebrafish, Danio rerio.

We cloned three putative odorant receptor (OR) genes from the zebrafish to use as in situ hybridization probes to follow the temporal patterns of neurons expressing OR genes through a developmental progression from embryo (12 h postfertilization) to adult. The identification of these genes is supported by sequence homology to previously reported ORs and by the morphology and location of labeled cells in in situ hybridization experiments. Cells expressing OR mRNA were first observed in the olfactory placodes between 31 and 38 h after fertilization (fish reared at 26 degrees C). Initially, only single cells were observed to hybridize the probe; the number of labeled cells increased throughout the remainder of embryogenesis and through postembryonic growth and morphogenesis of the olfactory organ. At all ages, the positively hybridizing cells were scattered throughout the olfactory epithelium but not in the nonsensory epithelium of the olfactory organ.

Amino Acid Sequence↗
PubMed1996

Melanin granule model for laser-induced thermal damage in the retina.

An analytical model for thermal damage of retinal tissue due to absorption of laser energy by finite-sized melanin granules is developed. Since melanin is the primary absorber of visible and near-IR light in the skin and in the retina, bulk heating of tissue can be determined by superposition of individual melanin granule effects. Granules are modeled as absorbing spheres surrounded by an infinite medium of water. Analytical solutions to the heat equation result in computations that are quick and accurate. Moreover, the model does not rely on symmetric beam profiles, and so arbitrary images can be studied. The important contribution of this model is to provide a more accurate biological description of sub-millisecond pulse exposures than previous retinal models, while achieving agreement for longer pulses. This model can also be naturally extended into the sub-microsecond domain by including vaporization as a damage mechanism. It therefore represents the beginning of a model which can be applied across the entire pulse duration domain.

Animals↗
PubMed1995

Interdialytic weight gain and nutritional parameters in chronic hemodialysis patients.

The extent of interdialytic weight gain (IDWG) in chronic hemodialysis patients is usually attributed to the level of compliance with fluid restriction. However, in view of the substantial water content of food (and caloric content of beverages), IDWG also may be a function of calorie and protein intake and may reflect the nutritional state of patients. To investigate this theory, the relationship between 2-day IDWG and body weight, normalized protein catabolic rate (nPCR), serum albumin, and delivered Kt/V urea was assessed in a prospective, randomized study of 860 chronic hemodialysis patients in 56 dialysis units. Compared with patients having < 2 kg IDWG (n = 378), patients with > 3 kg IDWG (n = 138) weighed more (dry weight, 76.8 v 61.7 kg), had higher nPCR (1.15 v 0.96 g/kg/d), and had higher serum albumin levels (3.96 vs 3.79 g/dL) (all P < 0.001) but did not have different levels of Kt/V (1.04 v 1.06). When IDWG was assessed as a function of dry weight, patients with IDWG > 4.5% of dry weight (n = 151) had higher nPCR (1.17 v 0.94 g/kg/d) but weighed less (60.1 v 70.0 kg) and had a higher Kt/V (1.14 v 1.01) than patients with IDWG < 3% of dry weight (n = 355) (all P < 0.001). Artifactual association between IDWG and nPCR attributable to an accentuated two-pool effect from differing ultrafiltration requirements was unlikely as assessed by the relationship between modeled Kt/V and prescribed Kt/V determined using an anthropometric urea volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary Proteins↗
PubMed1994

Identification and characterization of O-biotinylated hydroxy amino acid residues in peptides.

Recent findings have indicated that certain hydroxyl groups of peptides have enhanced intrinsic chemical reactivity and can be O-acylated by N-hydroxysuccinimide esters of biotin. Analytical procedures are described for the identification of O-acylated derivatives of seryl, threonyl, and tyrosyl residues after reaction with the N-hydroxysuccinimide ester of biotin containing the extended spacer arm 6-aminohexanoic acid. The identification and chemical characterization of O-biotinylated residues included amino acid analysis, peptide sequence determination, and mass spectrometric analysis. The application of these analytical procedures provided unequivocal identification of O-biotinylated residues for a number of peptides investigated. In a separate study, we also show that O-biotinylated amino-terminal seryl residues occurring after proteolysis of peptides or proteins can rapidly undergo an O-->N acyl shift resulting in blockage of sequence analysis by the Edman degradation procedure.

Amino Acid Sequence↗
PubMed1994

Deficiencies in delivered hemodialysis therapy due to missed and shortened treatments.

The frequency of missed and shortened hemodialysis treatments was assessed in a randomly selected sample of 860 ESRD patients from 54 dialysis units. Data were collected for three sequential 4-week periods covering 28,108 treatments. During each of these 4-week periods, 5.1% to 7.6% of patients missed at least one treatment, 26.8% to 32.3% of patients had at least one shortened treatment, and 6.6% to 7.9% of patients missed 10% or more of their prescribed therapy. Over the entire 12-week period, 50% of patients had either missed or shortened treatments (or both). Missed and shortened treatments are prevalent enough to account for clinically important deficiencies in delivered dialysis for a significant number of patients.

Female↗
PubMed1994

The effect of dialyzer reuse on dialysis delivery.

It is well documented that the reprocessing of dialyzers may reduce their solute clearance capabilities. However, the effect of dialyzer reuse has never been assessed in an uncontrolled clinical practice setting. We addressed this issue in a prospective 436-patient, 34-center study. All patients underwent formal urea kinetic modeling monthly, usually for 3 sequential months. Dialyzers were reprocessed and reused in the usual manner for each unit. As a result, urea kinetic modeling was performed in individual patients using dialyzers with differing numbers of prior uses. For each patient, Kt/V urea for the treatment using the dialyzer with the most reuses (mean, 13.8) was compared with that with the treatment using the dialyzer with the fewest reuses (mean, 3.8). The mean Kt/V delivered for high reuse treatments was significantly lower than that for low reuse treatments (1.05 v 1.10, P = 0.002). Prescribed Kt/V in high and low reuse treatments was identical. Individual centers appeared to differ substantially (P = 0.06) in the effect of reuse on delivered Kt/V. Of the 23 centers using formalin-based reprocessing, an average difference of > or = 0.12 (mean, 0.17) in Kt/V between high and low reuse treatments was seen in 10 centers. Dialyzer reprocessing significantly impairs dialysis delivery, an effect that may be related to the methods and procedures in individual dialysis centers.

Acetic Acid↗
PubMed1994

The science of unitary human beings: current perspectives.

This article explicates current perspectives on Rogers' science of unitary human beings. Possibilities for nursing in the 21st century are elaborated upon. Attention is called to the increasingly rapid social changes which will have an impact on nursing science.

Forecasting↗
PubMed1994

Ultrashort laser pulse effects in ocular and related media.

Relatively little experimental and theoretical data exist on the retinal hazards of ultrashort laser pulses operating in the visible and near infrared spectral regions. Because of potential nonlinear effects that can occur from high-peak irradiance, ultrashort laser pulses propagate from the cornea to the retina, we have developed four projects within our Ultrashort Pulse Effects program. First, we discuss preliminary ED50 threshold values for nanosecond (ns), picosecond (ps), and femtosecond (fs) single pulses for in-vivo ocular exposures in Dutch Belted Rabbits using pulses in the visible spectral region. Then we examine two experiments that study nonlinear absorption using water tubes and measure the nonlinear refractive index of ocular tissue using the Z-Scan technique. Finally, we determine laser-induced breakdown thresholds in ultrahigh purity water. These studies give reasonable estimates of the damage thresholds and insight into the biophysics of how ultrashort pulses interact with ocular media.

Animals↗
PubMed1993

The Lewis x epitope is a major non-reducing structure in the sulphated N-glycans attached to Asn-65 of bovine pro-opiomelanocortin.

The N-terminal glycopeptide of pro-opiomelanocortin (POMC), designated as the 16K fragment, is highly conserved throughout vertebrates from amphibians to mammals and is likely therefore to have an important functional role. In this paper, we report the first structural characterization of N-glycans attached to asparagine-65 of a 16K glycopeptide. The 16K fragment was isolated from bovine pituitaries and the N-glycans were analysed using fast atom bombardment mass spectrometry together with sugar and linkage analysis. Sulphated-N-acetylgalactosamine-capped antennae, typical of the pituitary glycohormones, were present in the major acidic components. The POMC oligosaccharides are distinct from those of the pituitary glycohormones because the sulphate is exclusively located on the 3-arm of biantennary structures and, in addition, a significant proportion of the molecules carry the Lewis x epitope. It is probable that these differences reflect the absence of a tripeptide motif in POMC which fully conforms to the criteria previously defined for the recognition sequence for the N-acetylgalactosamine transferase that is specific for the pituitary glycohormones [Smith and Baenziger (1992) Proc. Natl. Acad. Sci. USA, 89, 329-333]. It remains to be seen whether the Lewis x epitope is involved in selectin-mediated events, but previous studies suggest that the sulphated moieties are unlikely to play a major role in clearance. The Lewis x epitope is also present in the neutral N-linked oligosaccharides, together with a variety of other antennae including a rarely found fucosylated GalNAc-GlcNAc structure.

Acetylgalactosamine↗
PubMed1992

Observations on an outbreak of anthrax in pigs in north Wales.

Nineteen pigs in a 500 sow herd died from anthrax over a period of 95 days. This paper describes some of the problems encountered and how they were dealt with, including the risks to public health, the disposal of slurry and the cleansing and disinfection of the premises after the herd was slaughtered.

Animals↗
PubMed1992

Decrease in erythrocyte glycophorin sialic acid content is associated with increased erythrocyte aggregation in human diabetes.

1. Sialic acid moieties of erythrocyte membrane glycoproteins are the principal determinants of the negative charge on the cell surface. The resultant electrostatic repulsion between the cells reduces erythrocyte aggregation and hence the low shear rate viscosity and yield stress of blood. 2. Using g.c.-m.s., a decrease in sialic acid content has been observed in the major erythrocyte membrane glycoprotein, glycophorin A, obtained from nine diabetic patients compared with that from seven normal control subjects [median (range): 3.30 (0.01-11.90) versus 18.60 (3.20-32.60) micrograms/100 micrograms of protein, P less than 0.02]. 3. Erythrocyte aggregation, measured by viscometry as the ratio of suspension viscosity to supernatant viscosity (LS/S) in fibrinogen solution, was increased in ten diabetic patients compared with ten normal control subjects (mean +/- SEM, 37.6 +/- 1.3 versus 33.8 +/- 0.6, P less than 0.02). 4. In the patients in whom both viscometry and carbohydrate analysis were performed, the decrease in erythrocyte glycophorin sialylation and the increase in erythrocyte aggregation in fibrinogen solution were related statistically (LS/S correlated negatively with glycophorin sialic acid content, r = 0.73, P less than 0.05). 5. Decreased glycophorin sialylation provides an explanation at the molecular level for increased erythrocyte aggregation and it may be important in the pathogenesis of vascular disease in diabetes.

Adult↗
PubMed1992

Nursing science and the space age.

This article presents the basic elements of Rogers' science of unitary human beings. It defines science, explicates nursing as a science and an art, addresses the meaning of the principles of hemodynamics, and discusses the building blocks of these principles. Several theories arising from the science of unitary human beings are elaborated, and noninvasive therapeutic modalities are discussed as part of nursing practice.

Homeostasis↗
PubMed1992

The linkage between stimulus frequency and covert peak areas as it relates to monaural localization.

Head-related transfer functions for differently centered narrow noise bands were obtained on 6 subjects. Derived from these measurements were covert peak areas (CPAs), defined as the spatial constellation of loudspeakers that generates maximal sound pressure at the entrance of the ear canal for specific bands of frequency. On the basis of previous data, we proposed that different frequency bands served as important spectral cues for monaural localization of sounds from different loci and that location judgments were directed toward the CPAs associated with the different bands. In the first study, the stimuli were bandpass filtered so that they contained only those frequencies whose associated CPAs occupied either the monaural listener's "upper" or "lower" spatial regions. Loudspeakers, separated by 15 degrees, were stationed in the left hemifield, ranging from 0 degree to 180 degrees azimuth and -45 degrees to 60 degrees elevation. Subjects reported the loudspeaker from which the sound appeared to originate. Judgments of the sound's elevation were in general accord with the CPAs associated with the different frequency segments. In the second study, monaural localization tests were administered in which different 2.0-kHz-wide frequency bands linked with specific CPAs were notch filtered from a 3.5-kHz highpass noise band. For the control condition, the highpass noise was unfiltered. The data demonstrated that filtering a frequency segment linked with specific CPAs resulted in significantly fewer location responses directed toward that particular spatial region. These results demonstrate in greater detail the relation between the directional filtering properties of the pinna and monaural localization of sound.

Attention↗
PubMed1991

Characterisation of the N-linked oligosaccharides of the light chain of human glycoprotein IIb by f.a.b.-m.s.

The glycosylation of the light chain (GPIIbL) of glycoprotein IIb, one of the glycoproteins constituting the receptor for fibrinogen, fibronectin, and the von Willebrand factor on platelet cell surfaces, was investigated using fast-atom-bombardment mass spectrometry (f.a.b.-m.s.). Complex-type N-glycans were observed, attached to Asn-60. The most abundant oligosaccharide is a disialylated biantennary structure substituted with fucose on the chitobiose core. Mono-sialylated biantennary, and di- and tri-sialylated triantennary structures were found as minor constituents of the N-glycan population. The amino acid sequence of GPIIbL was fully mapped by f.a.b.-m.s., thereby providing the first direct evidence for the absence of O-glycosylation.

Amino Acid Sequence↗
PubMed1991

Foraging profiles of sympatric lowland gorillas and chimpanzees in the Lopé Reserve, Gabon.

Comparison of the diets of sympatric gorillas and chimpanzees allows an analysis of niche separation between these two closely related species. Qualitatively, their diets are similar, being dominated by an equally diverse array of fruit species complemented with vegetative plant parts, seeds and insects. Gorillas eat more vegetative plant parts than do chimpanzees, but niche separation is most obvious in periods of fruit scarcity when the two species show different strategies that reduce competition for food. Their abilities to overcome mechanical and physical plant defences appear to differ, as gorillas are able to subsist entirely on abundant vegetative foods. Chimpanzees show social adjustment, foraging alone or in small groups, to reduce intra-specific competition for scarce fruit resources. Thus it seems that subtle physiological differences have far-reaching repercussions, defining potential evolutionary pathways for social organization and allowing sufficient niche separation between species.

Animals↗