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Biomedical subjects

C Thies

Publications and source records attributed to C Thies.

At least 19 recordsLinked to original sources
PubMed2004

Content-based image retrieval in medical applications.

OBJECTIVES: To develop a general structure for semantic image analysis that is suitable for content-based image retrieval in medical applications and an architecture for its efficient implementation. METHODS: Stepwise content analysis of medical images results in six layers of information modeling incorporating medical expert knowledge (raw data layer, registered data layer, feature layer, scheme layer, object layer, knowledge layer). A reference database with 10,000 images categorized according to the image modality, orientation, body region, and biological system is used. By means of prototypes in each category, identification of objects and their geometrical or temporal relationships are handled in the object and the knowledge layer, respectively. A distributed system designed with only three core elements is implemented: (i) the central database holds program sources, processing scheme descriptions, images, features, and administrative information about the workstation cluster; (ii) the scheduler balances distributed computing; and (iii) the web server provides graphical user interfaces for data entry and retrieval, which can be easily adapted to a variety of applications for content-based image retrieval in medicine. RESULTS: Leaving-one-out experiments were distributed by the scheduler and controlled via corresponding job lists offering transparency regarding the viewpoints of a distributed system and the user. The proposed architecture is suitable for content-based image retrieval in medical applications. It improves current picture archiving and communication systems that still rely on alphanumerical descriptions, which are insufficient for image retrieval of high recall and precision.

Databases as Topic↗
PubMed2002

Microencapsulation of protein particles within lipids using a novel supercritical fluid process.

Solvent-free microparticles, loaded with a model protein (bovine serum albumin: BSA) have been produced using a novel coating process based on supercritical (SC) fluid technology. Coating material consists of either trimyristin (Dynasan114) or Gelucire50-02, two lipidic compounds having a high melting point. Microparticles were characterized as regards their morphology, protein content and in vitro release profile. A discontinuous coating made of crystalline micro-needles was obtained using Dynasan114. It led to particles with an initial burst release of about 70% in 30 min at 37 degrees C. However, a prolonged release of the protein has been achieved over a 24 h period from particles coated with Gelucire50-02, which produces a more homogeneous, film-forming coating. Furthermore, it was shown that BSA does not undergo any degradation after SCCO2 treatment under the SC conditions used in the coating process.

Carbon Dioxide↗
PubMed2000

New approaches for genotyping of Helicobacter pylori based on amplification of polymorphisms in intergenic DNA regions and at the insertion site of the cag pathogenicity island.

The population of the gastric pathogen Helicobacter pylori shows a high degree of genetic diversity. It is well established that heterogeneity at the isolate level is caused by nucleotide transitions within genes, differences in the gene order, and by genetic instability of single genes as well as of a large virulence-associated genomic DNA region, the cag pathogenicity island (PAI). Analysis of intergenic regions with specific PCR-assays developed in this study, revealed that DNA polymorphisms in the noncoding DNA localized in front of the genes ribA and vacA and at the insertion site of the cag PAI contribute to the genetic diversity of H. pylori and are useful for differentiation of individual isolates. Thirteen individual genotypes were identified by PCR analysis of these polymorphic loci in 487, 241, and 182 clinical H. pylori isolates. Sequence analysis revealed that genetic variability in front of genes ribA and vacA, and in the intergenic region at the PAI insertion site is caused by insertion and deletions of so-far-unknown DNA sequences as well as by parts of the H. pylori IS elements IS605 and IS606, respectively. The new genotypes identified could be used to differentiate antrum and corpus isolates from the same patients. Their combination with vacA allele subtypes and with the cagA status allowed to differentiate 140 isolates in 51 subtypes. In 36 cases the corresponding genotype patterns were isolate specific. In summary, the results confirm that DNA polymorphisms in intergenic regions contribute to the genetic diversity of H. pylori. Although individual H. pylori genotypes were not associated with peptic ulcer disease, the PCR-based approaches for their detection developed here should be of use for further investigation of genetic diversity in H. pylori and for epidemiological purposes.

Adult↗
PubMed1999

Landscape structure and biological control in agroecosystems

Biological pest control has primarily relied on local improvements in populations of natural enemies, but landscape structure may also be important. This is shown here with experiments at different spatial scales using the rape pollen beetle (Meligethes aeneus), an important pest on oilseed rape (Brassica napus). The presence of old field margin strips along rape fields was associated with increased mortality of pollen beetles resulting from parasitism and adjacent, large, old fallow habitats had an even greater effect. In structurally complex landscapes, parasitism was higher and crop damage was lower than in simple landscapes with a high percentage of agricultural use.

Journal Article↗
PubMed1998

[Small abnormality of the middle ear--a genetically-induced defect?].

Conductive and sensorineural hearing losses are of genetic origin in 20% to 60% of cases. In general, genetic abnormalities are more often expressed as a sensorineural hearing loss than as a conductive hearing loss. At present several genes for sensorineural hearing loss have been isolated. The most common genetically transmitted forms for isolated conductive hearing losses are otosclerosis and small malformations of the ossicles. To date no genes responsible for these deformations have been isolated. We present a family with four siblings having conductive hearing losses caused by ossification of the stapedial tendon. This finding is suggestive of an autosomal recessive inheritance. The early diagnosis of an hereditary conductive hearing loss contains the possibility for permitting normal development of speech.

Adult↗
PubMed1997

Effect of maternal depression on premature infant health during initial hospitalization.

This study evaluates the effect of maternal depression on neonatal health status in premature infants during their initial hospitalization. Infants younger than 34 weeks' gestation born to nondrug abusing mothers were enrolled in the study. Thirty-one mother-infant pairs were identified. Maternal depression was evaluated by the Center for Epidemiologic Studies-Depression Scale (CES-D). Scores > or = 16 defined maternal depression. Initial infant physiologic health status was determined by the Score for Neonatal Acute Physiology (SNAP). In-hospital health status was assessed by the following variables: days receiving supplemental oxygen, days on mechanical ventilation (VENT), and days not on enteral feeding (NPO). Health status variables evaluated for long-term outcome included bronchopulmonary dysplasia at 28 days (BPD), BPD at 34 weeks' postmenstrual age (BPD-34), and intraventricular hemorrhage (IVH). Seventeen (55%) of 31 mothers manifested depression on the CES-D. No epidemiologic differences were found between this group and the nondepressed mothers. No differences in gestation or birth weight was detected between the preterm infants of depressed versus nondepressed mothers. The CES-D scores correlated significantly with SNAP (r = .36, P < .02). Infants of depressed mothers experienced significantly worse outcomes in the occurrence of BPD (P = .015), BPD-34 (P = .049), and IVH (P = .055). This study confirms that maternal depression occurs frequently in mothers of preterm infants and adversely affects the presenting neonatal health status of their babies during the initial hospitalization. Maternal depression was related to the severity of the initial neonatal illness and was significantly related to IVH and BPD. These factors may have long-term consequences for subsequent growth, neurodevelopment, and recurrence of related health problems.

Bronchopulmonary Dysplasia↗
PubMed1996

Possible autosomal recessive inheritance of progressive hearing loss with stapes fixation.

Four sibs with progressive, bilateral conductive hearing loss are presented. Symmetrical hearing loss averaging 30-60 dB (0.125-8 kHz) became apparent between 8 and 24 years of age. Tympanotomy showed a fixed stapes either through ossified stapedius tendon or through ossified stapedius tendon or through a bony bridge from the stapes to the pyramidal eminence in all patients. After surgical removal of the bony tendon hearing was normal. Both parents, four other sibs, and all grandparents had normal hearing. This family and a further published case suggest a possibly recessive inheritance of this form of conductive hearing loss.

Adult↗
PubMed1991

A physicochemical study of the morphology of progesterone-loaded microspheres fabricated from poly(D,L-lactide-co-glycolide).

Progesterone-loaded microspheres are fabricated by a solvent evaporation process from a poly(D,L-lactide-co-glycolide) (85/15 PLG) and from alpha-progesterone. Methylene chloride is used as solvent and polyvinyl alcohol and methylcellulose are used as surfactants. The microspheres are characterized by scanning electron microscopy, differential scanning calorimetry, and x-ray powder diagrams. Our study shows that the morphology and the thermal behavior of PLG microspheres can vary significantly with progesterone loading and sample thermal history. Below and at 16.5% loading the microspheres exhibit a smooth outer surface. Above 23% loading, the surface becomes rough, embedded by copolymer particles or well-defined crystals. Pores and cracks can also be observed. Below 35% the progesterone is molecularly dispersed. At 35% and above crystal domains of the steroid appear and two crystalline forms are found: alpha- and beta-progesterone. The physical state of progesterone and the nature of its crystal domains dispersed in the PLG matrix can change during storage. Also a progressive development of an endothermic peak at the Tg event of the copolymer is observed during storage. No well defined relationship of peak size to progesterone loading can be shown.

Calorimetry, Differential Scanning↗
PubMed1990

Latex nanosphere delivery system (LNDS): novel nanometer-sized carriers of fluorescent dyes and active agents selectively target neuronal subpopulations via uptake and retrograde transport.

A wide range of latex particles are described which are capable of carrying high concentrations of fluorescent dyes, drugs, and photoactive agents selectively to subpopulations of neurons in vitro and in vivo. Particle size, charge, and concentration were all found to influence uptake into cultured neurons or retrograde transport in vivo. Chromophore loadings of greater than 14% (w/w) were obtained. Incorporation of a photoactivated dye (chlorin e6) into the polymer did not compromise the ability of the dye to produce singlet oxygen following light exposure. We refer to this unique family of latex particles as the latex nanosphere delivery system (LNDS). The LNDS will be usefull for studies of neuroanatomy and nervous system development, as well as more general areas of biomedical research where it is desirable to selectively label subpopulations of cells. The LNDS also offers a means of providing targeted delivery of drugs or photoactive agents to selected subpopulations of cells; this will allow experimentation not currently possible using any existent methodology.

Animals↗
PubMed1989

Biodegradable microparticles for delivery of polypeptides and proteins.

Interest in the immobilization of polypeptides has caused various workers to develop methods for fabricating polypeptide-loaded microparticles from biodegradable polymers. A range of physical phenomena is used to form these microparticles. Thus far, all of the processes utilize a solvent or solvent combination. Selection of these solvents in such a manner that particles free of potentially harmful residual or entrapped material can be produced has not been discussed, but should receive full attention.

Biodegradation, Environmental↗
PubMed1986

The formation and characterization of hydrocortisone-loaded poly((+/-)-lactide) microspheres.

The solvent evaporation process has been used to form hydrocortisone-loaded microspheres from poly((+/-)-lactide) (PLA) and a lactide-glycolide copolymer (65/35). Methylene chloride was the casting solvent. Partially hydrolysed (88%) poly(vinyl alcohol) and methylcellulose were used as aqueous phase emulsifiers. Methylcellulose was preferred, because it gave stable emulsions as the amount of hydrocortisone being encapsulated increased whereas poly(vinyl alcohol) did not. With methylcellulose as the emulsifier, a broad size range of spherical microspheres containing up to 50% (w/w) hydrocortisone could be prepared. Thermal and X-ray analyses established that poly((+/-)-lactide) microspheres containing hydrocortisone retained thermal events characteristic of both materials. This is evidence that such microspheres contain, to some extent, crystalline hydrocortisone domains dispersed in a PLA matrix. But most of the encapsulated drug was molecularly dispersed in the PLA glass. The stability of hydrocortisone in microspheres was evaluated in different storage conditions: no degradation of drug was found. The release of hydrocortisone from 250-350 microns diameter microspheres into agitated 37 degrees C water (nitrogen atmosphere) was determined by HPLC analysis. The microspheres evaluated had initial hydrocortisone payloads of 12 to 47% (w/w). The rate of drug release increased as the initial drug payload carried by the microspheres increased. The release data are not adequately described by zero order, first order, or square-root-of-time release kinetics. Drug release from microspheres that contain 12% (w/w) hydrocortisone approached a plateau value well below the amount of drug actually carried by the microspheres. This is particularly true for hydrocortisone encapsulated in lactide-glycolide polymer.

Calorimetry, Differential Scanning↗
PubMed1984

Characterization of drug-loaded poly(d,l-lactide) microspheres.

Lomustine and progesterone have been incorporated in biodegradable poly(d,l-lactide) microspheres by evaporating dichloromethane from stirred dichloromethane-in-water emulsions. Spherical microspheres with lomustine or progesterone payloads less than or equal to 23% were obtained. Higher lomustine payloads gave irregularly shaped particles. Microspheres with less than or equal to 68% progesterone were obtained, but free drug crystals formed on the surface of such microspheres. Increased agitation rates decreased mean microsphere size. Addition of drug to the dichloromethane phase increased average particle size relative to that obtained with drug-free microspheres prepared under the same experimental conditions. Complete evaporation of the dichloromethane, while the medium was continuously stirred, promoted formation of free drug crystals in the aqueous phase. Increased emulsifier concentrations did not significantly enhance drug incorporation efficiency within the microspheres. Shelf-life stability of lomustine and progesterone was reduced by incorporation in the microspheres, presumably due to their molecular dispersion in the poly(d,l-lactide).

Crystallization↗
PubMed1983

Analysis of ventricular shape by echocardiography in normal fetuses, newborns, and infants.

Qualitative and quantitative changes in left ventricular shapes were analyzed in 14 normal fetuses, 29 normal newborns, and 12 normal infants. Qualitative observations demonstrated that most fetuses and newborns with dominant right ventricles had flattened or even indented interventricular septae, which changed left ventricular shape into an ellipse. In contrast, left ventricular shapes in infants were round, similar to shapes described in older children and adults. When changes in shape or septal distortions were gross, interobserver agreement was 100%; when changes were less altered from a circular shape, interobserver agreement was 78%. To avoid subjective misinterpretations, quantitative analyses were performed, including M mode echocardiographic comparisons of right ventricular/left ventricular dimensions and left ventricular cavity anterior-posterior/lateral diameters, as well as Fourier analysis of digitized tracings of the entire left ventricular shape. The right ventricular/left ventricular ratio, determined by M mode echocardiography, showed significant differences between fetuses (1.07 +/- 0.07) and newborns (0.62 +/- 0.12) (p less than .001). Infants had a significantly lower right ventricular/left ventricular ratio (0.45 +/- 0.01) when compared with newborns (p less than .01). Ratios of left ventricular anterior-posterior/lateral diastolic diameters were significantly lower (p less than .001) in newborns (0.66 +/- 0.08) when compared with those of infants (0.82 +/- 0.10). All diameters tended to increase (toward roundness) with systole and with aging. Fourier analysis allowed evaluation of the entire left ventricle, including that portion of the septum that qualitatively appeared most indented and could not be analyzed by either of the above techniques. Shape factor derived from idealized shapes ranging from a circle to an indented ellipse allowed comparison with digitized left ventricular tracings. This technique allowed accurate quantitation of the observed changes in shape. Fetuses had the highest diastolic shape factor (7.47 +/- 0.92), whereas infants' shape factors were lowest (2.12 +/- 0.41). A tendency toward roundness and loss of distortion occurred with aging. Systolic shape factor was lower with aging in each group studied. The Fourier technique used in this study allows evaluation of an arbitrarily large number of components of a shape, and thus a complete description of that shape is permitted. Comparisons of right ventricular/left ventricular diastolic dimensions and left ventricular anterior-posterior/lateral comparisons are subsets of this technique, which allow evaluation of only two points (circular component-first harmonic) or four points (elliptical component-second harmonic) of an overall shape.(ABSTRACT TRUNCATED AT 400 WORDS)

Echocardiography↗
PubMed1983

Seasonal variation of multiple sclerosis exacerbations in Arizona.

We studied 178 MS patients and 82 controls for 5 years. A monthly pattern in in the frequency of exacerbations in Arizona differed from the patterns seen in other regions of the world. Exacerbations were most common in warmer months. No explanation for this was found. In this prospective study, the frequency of viral infections in the MS patients was lower than in the controls.

Arizona↗
PubMed1982

RBC zinc protoporphyrin to screen blood donors for iron deficiency anemia.

We evaluated a rapid RBC zinc protoporphyrin (ZP) test in 1,147 male and 615 female blood donors to study its value in screening for evolving iron deficiency anemia. Fifteen men (1.8%) and 32 women (7.9%) who returned to donate were found to be anemic. A matched sample analysis between anemic and nonanemic donors demonstrated significant differences in serum ferritin levels, percent iron saturation, and the RBC ZP level from samples collected during the initial evaluation. Red cell ZP correlated well with the natural logarithm of serum ferritin in both men and women who later became anemic. The predictive value of RBC ZP levels compared favorably with that of the serum ferritin level. We also observed a strong association between the yearly donation frequency and RBC ZP concentration. These findings indicate that predonation RBC ZP testing may be useful in screening for iron depletion and potential risk of anemia in blood donors.

Anemia, Hypochromic↗