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Biomedical subjects

W E Koch

Publications and source records attributed to W E Koch.

At least 19 recordsLinked to original sources
PubMed1993

Examination of the development of chicken embryos following exposure to magnetic fields.

1. Studies of effects produced by magnetic fields on developing chickens have been reviewed. 2. Compilations of the variety of field conditions utilized, and of the consequences of the tested conditions on the embryo, are reported in tabular form for comparison. 3. The developmental consequences, if any, of the fields are also reported, as are those aspects of timing and morphogenesis deemed important in this area. 4. More recent information on biochemical changes in embryos exposed to magnetic fields is included and given weight as a growing aspect of this scientific field of study.

Animals↗
PubMed1990

Development of chicken embryos in a pulsed magnetic field.

Six independent experiments of common design were performed in laboratories in Canada, Spain, Sweden, and the United States of America. Fertilized eggs of domestic chickens were incubated as controls or in a pulsed magnetic field (PMF); embryos were then examined for developmental anomalies. Identical equipment in each laboratory consisted of two incubators, each containing a Helmholtz coil and electronic devices to develop, control, and monitor the pulsed field and to monitor temperature, relative humidity, and vibrations. A unipolar, pulsed, magnetic field (500-microseconds pulse duration, 100 pulses per s, 1-microT peak density, and 2-microseconds rise and fall time) was applied to experimental eggs during 48 h of incubation. In each laboratory, ten eggs were simultaneously sham exposed in a control incubator (pulse generator not activated) while the PMF was applied to ten eggs in the other incubator. The procedure was repeated ten times in each laboratory, and incubators were alternately used as a control device or as an active source of the PMF. After a 48-h exposure, the eggs were evaluated for fertility. All embryos were then assayed in the blind for development, morphology, and stage of maturity. In five of six laboratories, more exposed embryos exhibited structural anomalies than did controls, although putatively significant differences were observed in only two laboratories (two-tailed Ps of .03 and less than .001), and the significance of the difference in a third laboratory was only marginal (two-tailed P = .08). When the data from all six laboratories are pooled, the difference in incidence of abnormalities in PMF-exposed embryos (approximately 25 percent) and that of controls (approximately 19 percent), although small, is highly significant, as is the interaction between incidence of abnormalities and laboratory site (both Ps less than .001). The factor or factors responsible for the marked variability of inter-laboratory differences are unknown.

Animals↗
PubMed1988

Relative growth rates of maxillary mesenchyme in the chick embryo.

Chick embryos were injected with [3H]-thymidine at days 3-7 of incubation and were fixed and embedded in plastic. The embryos were divided into three stage groupings of development [Hamburger and Hamilton: J Morphol 88:49-92, 1951], and labeling indices were determined for each of the following delineated regions within the maxillary process at each stage: region 1, subepithelial mesenchyme located at the medial side of the maxillary process adjacent to the roof of the stomodeum; region 2, subepithelial mesenchyme at the ventral tip of the maxillary process (as seen on cross section); region 3, subepithelial mesenchyme at the lateral portion of the maxillary process below the eye; and region 4, interior mesenchyme defined as the central portion of the maxillary process and separated from the epithelium by the three other regions. Results indicated that differences exist among the regions examined and that these differences were stage specific. At stages 19-21 and stages 24-25 1/2, growth rates were higher in subepithelial regions than interiorly. At stages 28-29, however, a statistically significant difference among the regions was not found. These results suggested that there is an association between growth rates in the maxillary process mesenchyme and its proximity to the overlying epithelium and that these effects are related to the stage of development.

Animals↗
PubMed1985

A genetically determined murine model of infantile polycystic kidney disease.

We have evaluated a congenic strain of mice with congenital polycystic kidney disease in which the disease process appears to closely resemble human infantile polycystic kidney disease. Cysts formed first in the proximal tubules of the nephron and appeared, by light microscopy, to be preceded by vacuolization of the cells. These spaces, as seen by electron microscopy, occurred between adjacent cells. The pancreas was severely involved with reduction of both exocrine and endocrine elements. Cyst formation in the liver was minimal. Serum samples evaluated for urea nitrogen and creatinine were significantly elevated in affected mice. Serum glucose was within normal limits.

Animals↗
PubMed1984

Development of the embryonic murine kidney in normal and congenital polycystic kidney disease: characterization of a proximal tubular degenerative process as the first observable light microscopic defect.

The current report presents findings from a comparative histological and histochemical investigation of murine congenital polycystic kidney disease. The studies revealed that the morphological changes are initiated in the developing proximal tubules of the nephron; differences from control sections first become evident at 16 days' gestation. As the disease progresses, obvious changes include hyperplasia and dilation of the tubule, cellular vacuolization, and alterations in the apical cell brush border. Included among the latter changes are decreases in enzyme (alkaline phosphatase) staining and decreases in glycoprotein staining (periodic acid Schiff). All such changes continue until the kidney is markedly cystic and apical cell cytochemical staining is absent. Some cellular vacuolization, assumed to be a normal developmental event, is also seen within the same segment of the proximal tubule at 17 days' gestation through the 1st postnatal day. Dilation of the collecting duct is noted to be a later or secondary change evident after the initial onset of the disease.

Animals↗
PubMed1984

Development of the iris in the chicken embryo. I. A study of growth and histodifferentiation utilizing immunocytochemistry for muscle differentiation.

The development of the iris was studied in chicken embryos from 4 days of incubation through hatching and in chicks up to 17 days posthatching. Serial sections of the eye were stained routinely or by immunocytochemical methods using myosin antiserum to enhance detection of differentiating muscle by light microscopy. Eyes from embryos at each stage were also examined by scanning electron microscopy. Outgrowth of the iris occurs in a sequential pattern around the eye, beginning at 6 1/2 days of incubation in the region temporal to the choroid fissure and proceeding around the eye. Since differentiation of the iris follows the same pattern, similar areas of the iris were compared at each stage of development. At 6 1/2 days of incubation, pigment granules can be seen in the anterior epithelium at the root of the iris, but it is not until 8 days of incubation that pigment is identified in the same area of the posterior epithelium. As development proceeds, the pigmentation of both epithelial layers progresses from the root of the iris to the pupillary margin. Early features of the development of the sphincter muscle can first be recognized in the 7-day embryo, when epithelial buds form from the anterior epithelium adjacent to the pupillary margin. Cells from these buds detach from the epithelium and populate the entire irideal stroma; these cells are the precursors of the sphincter muscle. The epithelial buds increase in size and distribution, and coalesce into a continuous ridge of cells around the iris by 10 days of incubation. The first muscle cells differentiate at 11 days of incubation when striated fibres can be identified by immunocytochemistry. The first striated fibres of the dilator muscle are seen in the 13-day embryo. Differentiation of the dilator muscle begins near the root of the iris and proceeds toward the pupillary margin, ultimately arising from the entire anterior epithelium except near the pupillary margin. Further differentiation of the sphincter and dilator muscles continues throughout incubation and for several weeks beyond hatching.

Animals↗
PubMed1984

Development of the iris in the chicken embryo. II. Differentiation of the irideal muscles in vitro.

The developmental capabilities of the iris rudiment in the chicken embryo, as well as the role of tissue interactions in the differentiation of the iris, were investigated in vitro. Sectors of the intact iris from 7 1/2- through 9-day embryos (stages 32 through 35) lost their morphological organization in vitro, but were capable of normal histodifferentiation. The pigmentation of the epithelium increased, and muscle differentiation occurred. Developing muscle was identified using immunocytochemistry with antiserum against chicken muscle myosin; this procedure permitted positive identification of myoblasts, myotubes, and muscle fibres in cultures in which histological features alone were equivocal. The proportion of irideal explants which developed muscle increased with the age of the embryo, and correlated with the incidence of epithelial buds and epithelial cells in the stroma. Irideal mesenchyme from stage-32 through stage-35 embryos was already populated with stromal epithelial cells when isolated, but growth and muscle differentiation in these cultures compared poorly with that in the intact iris in vitro. Isolated irideal epithelium (stages 32 through 37) demonstrated even more limited muscle differentiation in vitro, suggesting reciprocal interaction between irideal epithelium and mesenchyme during development. Irideal epithelium was also cultured in direct association with non-irideal mesenchyme from various embryonic organ rudiments, but muscle differentiation was not enhanced.

Animals↗
PubMed1980

Utilization of the chick chorioallantoic membrane for in vitro growth of the embryonic murine kidney.

Previous experimental investigations of embryonic kidney development with in vitro organ-culture techniques have been limited by the short duration of graft viability and lack of detailed anatomic development. In a modified application of the chick chorioallantoic-membrane (CAM) grafting technique, we have transplanted 11-day-old undifferentiated embryonic murine kidney rudiments and studied their differentiation and early morphogenesis. Surviving grafts, maintained for 5-10 days on the CAM, demonstrated well-developed convoluted secretory tubules and highly branched collecting ducts. Definitive glomeruli were also identified in these grafts by the presence of efferent tubules, visceral and parietal epithelium, capillary tuft, and Bowman's space. In vitro branching of the ureteric bud preceded formation of definitive tubules. Sections of the CAM grafts appeared histologically comparable to the 14-15-day in vivo embryonic metanephros. Grafts of 10-day-old rudiments showed minimal kidney development; fewer grafts survived, fewer tubules were formed, and fewer glomeruli developed. Our results indicate that the CAM is an efficient site for in vitro murine kidney development with both vascularization of the explant and extensive maturation, including the appearance of primitive nephron units.

Animals↗
PubMed1977

In vitro development of palatal tissues from embryonic mice. II. Tissue isolation and recombination studies.

The epithelial and mesenchymal tissues of the secondary palate from 12-, 13-, and 14-day embryonic mice were enzymatically separated and cultured in isolation and in homochronic and heterochronic recombinations. In both homochronic and heterochronic recombinations, epithelial differentiation was similar to that in vivo. In heterochronic recombinations, epithelium differentiated according to a schedule appropriate for the age of the epithelium rather than for the age of the mesenchyme, suggesting that differentiation of palatal epithelium is temporally 'determined' as early as 12 days of gestation. Palatal epithelium cultured in isolation was capable of limited differentiation. Potential for differentiation therefore exists within the isolated palatal epithelium at an early stage of palatal development, and epithelial-mesenchymal interactions are required during palatal development to support full epithelial differentiation.

Agar↗
PubMed1976

The efficacy of general anesthesia for cataract surgery.

This is a report of 259 consecutive cataract extractions performed under general anesthesia over a two-year period. The age of the patients ranged from 6 to 93 with an average of 71. The purpose of this paper is to reiterate the safety of modern general anesthesia for cataract extraction in the elderly, and to demonstrate it can provide a very soft eye in a completely immobilized patient. It offers the most ideal conditions to the surgeon for lens extraction and careful wound closure without the necessity of retrobulbar block, digital massage or osmotic agents.

Adolescent↗
PubMed1975

A comparison of secondary palate development with different in vitro techniques.

Palatal processes from 14-day fetal C57BL mice were cultured under varying conditions for 48 hours and prepared for light and electron microscopy. Disruption of the epithelium along the medial border occurred when single palatal processes were explanted onto Millipore filters, plasma clots, or lens paper in subjacent contact with nutrient medium. Paired processes under the same culture conditions demonstrated typical midline epithelial disruption and mesenchymal fusion. Regions of mesenchymal necrosis occurred in processes grown on nutrient agar in a dish or submerged in nutrient medium. In similar cultures medial epithelial disruption did not occur in single processes and mesenchymal fusion of paired processes was either delayed or did not occur. Disruption of the epithelium along the medial border in single palatal processes, and mesenchymal fusion in paired palatal processes, occurred when palates were grown on nutrient agar supported above but in contact with nutrient medium. The results indicated that responses of palatal epithelium and mesenchyme may be altered by different in vitro procedures. These observations emphasize that many factors must be considered in interpreting developmental changes in palatal processes grown in vitro.

Agar↗
PubMed1975

In vitro development of palatal tissues from embryonic mice. I. Differentiation of the secondary palate from 12-day mouse embryos.

Single palatal processes or homotypic paired palatal processes from 12-day mouse embryos (strain C57Bl) were grown in organ culture on Millipore filters. The epithelium along the medial edge of each palatal process became disrupted, and, by 72 hours of culture, paired palatal processes achieved mesenchymal fusion at the site of disruption. The nasal epithelium of paired palatal processes became a recognizable pseudostratified ciliated columnar epithelium by 96 hours of culture, and the oral epithelium became a recognizable stratified squamous epithelium by 120 hours of culture. These events correspond temporally to the differentiation of palatal tissue in vivo. Differentiative changes of single palatal processes followed the same schedule as double processes. Observations also suggest that the epithelium at the tip of the vertically oriented young palatal process corresponds to the medial epithelium of the more advanced horizontal process-these observations have bearing on the mechanism of palatal movement. In addition, the results suggest that a re-evaluation of the terminology "potential for fusion" is necessary.

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