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Biomedical subjects

S Koch

Publications and source records attributed to S Koch.

At least 127 records · Page 7Linked to original sources
PubMed1995

Validation of the determination of the activity of adenosine deaminase in the body effusions of cats.

In order to identify parameters differentiating exudative from transudative effusions, it was postulated that the activity of adenosine deaminase (AD) (EC 3.5.4.4) might be highly correlated with granulomatous inflammatory processes of the serosa, and the activity of the enzyme in body effusions and serum from cats was examined. The method of Slaats et al (1985) for the determination of the enzyme was evaluated by using an Hitachi 705 autoanalyser, and its activity was measured in body cavity effusions of 174 cats. The activity of AD was high in effusions from cats with infectious serositis and bacterial or feline infectious peritonitis (FIP). In cases of FIP the activity of AD was very significantly different from all other cases of thoracic (P = 0.004) and abdominal (P < 0.0001) effusions. The determination of AD in the serum of cats did not contribute to the aetiological differentiation of hydrops. The increases in the activity of AD appeared to originate from the body effusion, because the ratio of the activity of the enzyme in the effusion to its activity in serum was relatively high in cases of FIP.

Adenosine Deaminase↗
PubMed1995

IT-based evaluation and automatic improvement of the quality of intraoral radiographs.

The quality of intraoral radiographs made in dental practices is too often not adequate for diagnostic purposes. This necessitates standardized measures for the quality of intraoral radiographs and controlled techniques for automatic image improvement. For the evaluation of the quality of digitized intraoral radiographs the authors have defined two parameters which enable the measurement of radiographic image quality with regard to contrast and gray value distribution. A two-dimensional feature space based on these parameters is used for separation of images with 'good diagnostic quality' from images with 'insufficient diagnostic quality'. Specific image improvement techniques based on piecewise linear gray scale transformation allow the automatic improvement of over- and under-exposed radiographs as well as the automatic improvement of suspected pathological regions of interest.

Humans↗
PubMed1995

Three-dimensional visualization of the mandible: a new method for presenting the periodontal status and diseases.

A three-dimensional representation of an ideal human jaw was reconstructed from a series of 178 digitized photographic cross-sections. The two-dimensional images were taken from the slices of an artificial skull and have been digitized by means of a high resolution scanner with a spatial resolution of 860 dots per inch. On the basis of that sequence of cross-sections, a semi-automatic segmentation algorithm was developed to reduce the information to a quadriliteral surface-representation of the teeth and the bone. An algorithm was developed which simulates the individual pathology of a patient both on the basis of the findings stored in this patient's dental record and by using the representation of the reference jaw. The results of the modeling module were automatically prepared for rendering with visualization tools compatible to the RenderMan standard. This new method of presenting periodontal situations in especially helpful for the diagnostic support of periodontologists and for dental educational purposes.

Gingiva↗
PubMed1995

The distal tendon of the biceps brachii. Structure and clinical correlations.

The structure and blood supply of 42 distal biceps tendons were investigated by means of light and electron microscopy as well as by immunohistochemistry. Possible structural causes for the rupture of the tendon are discussed. The distal biceps tendon wraps around the radius during pronation of the forearm. In this area the tendon is exposed to pressure and shearing forces in addition to those caused by tension. Two fibrocartilaginous areas were regularly observed. Large chondrocyte-like cells were found inside the fibrocartilage. As an expression of strain, the extracellular matrix is rich in acidic glycosaminoglycans and stains intensely with toluidine blue at pH 1. Electron microscopy showed a granular pericellular matrix that increases in size towards the gliding surface. Type I collagen is the main component of the distal biceps tendon. Type II collagen is found in tendon fibrocartilage but not in traction tendons. The gliding surface of the tendon is made up of reticular fibres that are equivalent to type III collagen. Monoclonal antibodies revealed the presence of dermatan-sulfate, keratansulfate and chondroitin-4- as well as chondroitin-6-sulfate. Blood vessels are usually absent in fibrocartilage, as was shown with a polyclonal antibody against the basement membrane component laminine. There are significant differences between the extracellular matrix of traction and gliding tendons, which may be responsible for the location of tendon rupture.

Adolescent↗
PubMed1995

[Functional adaptation processes of gliding tendons].

Structure and blood supply of the inserting tendons of supraspinatus and biceps brachii as well as the biceps brachii long head tendon are analyzed in respect of tendon rupture. Due to their course the three tendons investigated are gliding tendons. The part of the tendon adjacent to the pulley consists of fibrocartilage, the part looking away from the pulley having the structure of a traction tendon. The occurrence of fibrocartilage inside the investigated tendons is physiological and not a pathological finding. Development of fibrocartilage is a functional adaptation to pressure and shearing forces acting on the tendon at the pulley. In the investigated samples injection techniques and immunohistochemical methods show an avascular area in the part of the tendon that is adjacent to the pulley. The size of this area is identical with the fibrocartilage. The avascular zone in gliding tendons is due to structure, fibrocartilage is usually avascular. Localisation of rupture and fibrocartilage is nearly identical in the investigated tendons. Unphysiologically increased tensile stress which is inadequate for gliding tendons and occurs in certain kinds of sport may be responsible for the development of ruptures of the tendons of supraspinatus and biceps brachii.

Adaptation, Physiological↗
PubMed1995

Bilateral nonunited femoral neck fracture in a child with osteopetrosis.

We report a case of osteopetrosis with bilateral nonunited femoral neck and coxa vara in a 7-year-old boy. There was a history of traumatic transcervical left femoral neck fracture unsuccessfully treated by internal fixation. We performed a bilateral subtrochanteric valgus osteotomy. K-Wire fixation failed on the right side due to hardness of the bone. Finally, internal fixation with an angular plate after predrilling of the femoral neck offered stability. Bone union was achieved on both sides, resulting in full recovery of normal physical activity.

Bone Plates↗
PubMed1995

Human hexokinase II mRNA and gene structure.

This study reports the isolation and characterization of the human hexokinase II (HKII) gene. This gene is approximately 50 kilobases in length and contains 18 exons, ranging in size from 96 to 2,536 base pairs, that are exactly the same size as the corresponding exons in the rat HKII gene. A cDNA representing the entire open reading frame for HKII was synthesized using a series of polymerase chain reactions with human skeletal muscle RNA as the template, and this allowed us to deduce the complete structure of the HKII mRNA. The human HKII mRNA has 431 nucleotides (nt) of 5' noncoding sequence, 2,751 nt of coding sequence, and 2,394 nt of 3' noncoding sequence. The open reading frame encodes a protein of 917 amino acids with an estimated molecular mass of 102.4 kDa. There is a high degree of similarity in the amino acid and nt sequences of the rat and human glucokinase and HKII proteins and genes. This, coupled with the observation that the exon sizes are conserved, suggests a common evolutionary origin of the these two genes.

Amino Acid Sequence↗
PubMed1995

Quality assurance in oral radiography: computer-based methods for assessment and controlled improvement of intraoral radiographs.

The reported poor diagnostic quality of 30-50% of all radiographs made in dental practices suggests the need for standardized quality measures and appropriate image improvement procedures. We propose a new method to evaluate the quality of digital/digitized radiographs using feature vectors. This method assures the separation of over- and under-exposed radiographs from well exposed ones as clusters of "good image quality" and "poor image quality" in the resulting feature space. Automatic image improvement is accomplished by adaptive, piece-wise linear grayvalue transformation with regard to the image quality being measured. In particular, our method automatically detects grayvalue intervals which are likely to represent relevant diagnostic information as well as grayvalue intervals which are irrelevant for diagnostic purposes. Based on those intervals, a piece-wise linear grayvalue mapping function is calculated. These procedures may be used both on whole images and for the interactive improvement of suspected pathological regions of interest. Actual image quality is indicated by the simultaneous display of the defined cluster of "good image quality" and the position of the image within the feature space for visual control.

Quality Assurance, Health Care↗
PubMed1995

A virtual reality environment for enhanced oral implantology.

The quality of clinical decision making is limited by the performance of human cognitive processing of complex visual information. In the field of oral implantology, treatment planning is still based on the holistic interpretation and mental reconstruction of cross sectional 2d-image data. This surpasses widely human cognitive competence and hampers treatment planning in three dimensions that are essential in implantology. To overcome these problems, a virtual reality environment for enhanced treatment planning in oral implantology is presented, which provides a fully three-dimensional perception of an individual clinical situation. It enables the clinician to perceive and handle the objects of her work in a virtual world as needed for the task of diagnosis and treatment. Human visual decoding effort is thus reduced, and estimating the real position and orientation of implants during planning is enabled in any direction. Immersive three-dimensional perception is achieved by hybrid stereoscopic rendering techniques combined with large screen projections. The virtual world in which treatment planning takes place allows the clinician to move and interact with the individual anatomy simultaneously with three degrees of freedom. A set of virtual tools enables the clinician to perform a virtual treatment "in advance." The design and placement of implants, as it is interactively controlled by the clinician, is simulated in real-time. Thus the results of actions become immediately visible and provide visible feedback for interactive adjustment. In addition, the presented virtual reality environment for oral implant treatment planning includes algorithms for detection of inappropriate treatment in the concerned bone regions, according to the current design of the implant. These algorithms take both the individual properties of a patient's bone and the type of implants used into account.

Computer Simulation↗
PubMed1994

Both naive and memory CD4 T cell subsets become anergic during MAIDS and each subset can sustain disease.

Infection of C57BL/6 mice with the LP-BM5 mixture of retroviruses causes a severe murine acquired immunodeficiency syndrome (MAIDS). After infection, the entire CD4 T cell population shifts to a memory/activated phenotype and the CD4 cells become anergic to further stimulation. This drastic shift in phenotype could result either from a response of naive cells to the virus or its products and/or from the selective expansion of cells already having a memory phenotype. We have investigated whether both naive and memory CD4 T cells can be anergized during BM5 infection and whether each subset is sufficient for disease development. We show that V beta 3/V alpha 11 TCR transgenic mice that have > 98% CD4 T cells with naive phenotype develop MAIDS. Their spleens and lymph nodes become enlarged, their CD4 population expressing the TCR transgene shifts to a memory/activated phenotype, and the CD4 cells neither proliferate nor secrete IL-2 in response to specific Ag, a fragment of pigeon cytochrome C, or to mitogens. Adult thymectomized mice, having memory but not naive CD4 T cells, also developed MAIDS and anergy of the CD4 T cell population at a rate and extent comparable to normal control mice. Furthermore, CD4 T cells from mice primed with keyhole limpet hemocyanin 6 wk before infection with BM5 also became unresponsive to KLH during MAIDS. Thus, both naive and memory CD4 T cells are rendered anergic by the BM5 virus infection and it is likely that each subset is sufficient to sustain the development of MAIDS.

Animals↗
PubMed1994

Meningococcal Disease in Travelers: Vaccination Recommendations.

The object of the study was to determine the incidence rate of meningococcal disease in travelers originating in industrialized countries and visiting developing countries. Subjects were intercontinental travelers with meningococcal diseases acquired from 1986 to 1989. Health authorities in 108 countries were contacted; data obtained by postal survey were analyzed. The 56 replying health authorities reported 13 cases of meningococcal disease in tourist or business persons as well as 40 primary and 26 secondary cases in pilgrims in Mecca. The majority of cases were due to serogroup A. The case fatality rate in both groups of patients slightly exceeded 20%. Among the tourists and business persons, several patients had stayed in hotels; in several the onset of symptoms occurred during the flight home. The incidence rate per month of stay was estimated to be 0.4 per million travelers in this group, but 2000 per million in pilgrims to Mecca. Vaccination of pilgrims to Mecca is highly recommended, presently even compulsory. For the usual traveler to endemic countries, the risk of infection abroad seems not to exceed the one at home, thus vaccination may be limited to high-risk groups, such as trekkers.

Journal Article↗
PubMed1994

Mass spectrometry: a tool for on-line monitoring of animal cell cultures.

The magnetic sector mass spectrometer is able to detect oxygen uptake and carbon dioxide production rates from animal cell cultivations performed in 101 bioreactors. Such data have not been available with the use of classic exhaust gas analysis applying paramagnetic analyzers and infra-red sensors due to the insensitivity of the apparatus available. In the course of the present work we were able to demonstrate, that the oxygen uptake rate correlates to the number of viable cells. Additionally oxygen uptake rates supplied on-line information about the actual physiology of the cells: When the rates changed during the cultivation process, this immediately indicated the occurrence of limitations of components in the medium. The information could be useful in timing key events, such as performing splits or harvesting the bioreactor.

Animals↗
PubMed1994

The psychological development of children of epileptic parents. I. Study design and comparative findings.

We studied the genetic, neurobiological, teratogenic and psychosocial risks for the development of children born to epileptic parents in (a) children of epileptic mothers with intrauterine exposure to anticonvulsants, (b) children of epileptic mothers without intrauterine exposure to anticonvulsants and (c) children of epileptic fathers. In addition, three matched control groups were also considered. The longitudinal design of the study covered newborns to children of six years of age. A wide range of developmental and psychological tests and a structured interview for the assessment of psychiatric symptoms were used. It was shown that teratogenic factors are operant, whereas there was no indication that the condition of epilepsy in the parents per se had any effect on the developmental outcome of the children. The possible teratogenic effect of anticonvulsants should be studied in more detail.

Adult↗
PubMed1994

The psychological development of children of epileptic parents. II. The differential impact of intrauterine exposure to anticonvulsant drugs and further influential factors.

After obtaining evidence that tetratogenic effects were operant in a sample of children born to epileptic mothers, we analyzed the effects of type of medication and further influential factors. Children with prenatal exposure to polytherapy had significantly lower scores than controls for a large number of psychological tests. In addition to polytherapy, there were even stronger effects of socioeconomic status and sex was found to be less influential than polytherapy. Among further epilepsy variables, only seizure frequency of the mother during pregnancy had a modest impact on the child's developmental outcome, whereas a score of obstetric abnormality was less effective in predicting developmental outcome, as measured and defined by various standardized psychological tests.

Age Factors↗
PubMed1993

de Lange syndrome: a clinical review of 310 individuals.

Three hundred ten individuals with a clinical diagnosis of de Lange syndrome were seen and examined in conjunction with the parent support group. One hundred thirty-four males and 176 females whose ages ranged from birth to 37 years made up the study group. Examination findings were recorded for those features described by de Lange in her original report of the syndrome to determine the frequency and significance of each. In addition, questionnaires were completed by 128 of these families and medical, growth and developmental records were collected. The clinical diagnosis seems best supported by the facial features of the syndrome including the long eyelashes and confluent eyebrows (synophrys), although additional characteristics are needed. Only 27% had the upper limb deficiencies commonly associated with the syndrome. Growth was retarded in nearly all individuals, often of prenatal onset. Medical problems occurred frequently and most often involved the eye and ear, as well as the cardiac and gastrointestinal systems. Of 14 deaths, almost half were secondary to cardiac or gastrointestinal complications. The recurrence risk in 377 sibs of the patients was calculated to be less than 1%. Although development lagged significantly in speech, most individuals developed good self-help skills. The study demonstrated a higher proportion of patients affected mildly with the syndrome than is commonly appreciated. This underscores the importance of early recognition and appropriate medical and developmental support.

Adolescent↗
PubMed1993

[Cerebral symptoms in pre- or perinatally HIV-infected children].

Eight of 13 children pre- or perinatally infected with the HIV virus subsequently developed neurological symptoms. Three children also had other nonspecific symptoms (fever, lymphadenopathy, diarrhoea, hepatosplenomegaly, failure to thrive and mucocutaneous thrush). Five children developed illnesses associated with AIDS (opportunistic infections, cachexia and lymphocytic interstitial pneumonia). The neurological abnormalities predominantly affected motor functions, only later also involving sensory ones. Motor, cognitive and language development was impaired in all eight children. A loss of developmental milestones occurred in three children with HIV encephalopathy: they have since died. In all the children the HIV infection caused symptoms within the first year, progressing more quickly in the three with encephalopathy. There were no discernible risk factors to account for the difference in the course of the disease.

AIDS Dementia Complex↗