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Biomedical subjects

F Koch

Publications and source records attributed to F Koch.

At least 19 recordsLinked to original sources
PubMed1992

Cytokine gene expression in murine epidermal cell suspensions: interleukin 1 beta and macrophage inflammatory protein 1 alpha are selectively expressed in Langerhans cells but are differentially regulated in culture.

Epidermal Langerhans cells (LC) are considered direct yet immature precursors of dendritic cells (DC) in the draining lymph nodes. Although the development of LC into potent immunostimulatory DC occurs in vitro and has been studied in detail, little is known about their profile of cytokine gene expression. By using reverse transcriptase polymerase chain reaction analysis to screen 16 cytokines followed by Northern blotting for selected analysis, we determined the cytokine gene expression profile of murine LC at different time points in culture when T cell stimulatory activity is increasing profoundly. LC regularly expressed macrophage inflammatory proteins, MIP-1 alpha and MIP-2, and interleukin 1 beta (IL-1 beta). Both MIPs were downregulated upon culture and maturation into DC, whereas IL-1 beta was strongly upregulated in culture. MIP-1 alpha and IL-1 beta mRNA were found only in LC, but not in other epidermal cells. Apart from trace amounts of IL-6 in cultured LC, several macrophage and T cell products were not detected. The cytokine expression profile of LC thus appears distinct from typical macrophages. The exact role of the cytokine genes we found transcribed in LC remains to be determined.

Animals↗
PubMed1992

[Studies on HIV inactivation in allogeneic bone transplants using chemical disinfection and radioactive irradiation].

In our study we examined bone disinfection by ethanol and by irradiation. A 70% aqueous ethanol solution diffused through a 3 mm and a 6 mm slice of human cancellous bone against 2 ml of a HIV-sample (RTA: 300,000 cpm/ml) for 24 hours. In both cases HIV could not be inactivated. Infected T-lymphocyte cultures showed specific morphological cell changes. The Abbott HIV-antigen-EIA proved the treated HIV-samples to be infectious after cultivation in macrophage-cultures. Additional gas chromatography measurements of ethanol diffusion through 3 mm and 6 mm of human cancellous bone supported these observations: a 70% aqueous ethanol solution achieved a concentration of 25.6% (18.0%) in median after 24 hours and a thickness of 3 mm (6 mm). The effect of different doses of irradiation on HIV-samples (RTA:300,000 cpm/ml) was examined. The samples were irradiated with 2, 7, 10, 15 and 25 kGy to determine the appropriate dose for inactivation. Irradiation with 15 kGy caused HIV inactivation since no virus production could be detected in the macrophage culture (Abbott HIV-antigen-EIA). The samples irradiated with 2, 7 and 10 kGy were still infectious.

Bone Transplantation↗
PubMed1992

Effective enrichment of murine epidermal Langerhans cells by a modified(mismatched) panning technique.

A method for the enrichment of murine epidermal Langerhans cells (LC) is described in detail. It is based on positive selection of LC from pre-enriched fresh or cultured epidermal cell suspensions derived from ear skin by a modified panning technique. The method uses the interspecies cross-reactivities of anti-immunoglobulin antibodies: when LC in an epidermal cell suspension are labeled with mouse anti-major histocompatibility complex (MHC) class II antibodies they bind to petri dishes coated with anti-rat immunoglobulin antibodies. We therefore call this method "mismatched panning." After rinsing off non-adherent cells, the adherent LC can easily be dislodged by adding excess amounts of rat immunoglobulins, which effectively compete with the LC-bound mouse anti-MHC class II antibodies for binding to the petri dish. Using this modified panning technique, both fresh and cultured LC could be enriched up to more than 90% purity. From one ear, 2.0-3.0 x 10(4) fresh LC and 3.0-4.5 x 10(4) cultured LC could be obtained. Of all LC present in a primary, unenriched epidermal cell suspension, 40-60% were recovered when panned immediately after isolation of the epidermal cells and 50-75% when panned after 3 d of epidermal cell culture. Viability of panned LC was consistently more than 90%. Antigen presenting and T-cell-stimulating capacity of LC and responses to the cytokines granulocyte/macrophage colony-stimulating factor and tumor necrosis factor-alpha were not impaired by this panning procedure. The major advantage of this method compared to pre-existing panning techniques is the ease with which adherent LC can be dislodged from the panning dishes. Because the elution procedure is very gentle, virtually all panned LC are viable. As a consequence, good yields of highly enriched LC can be obtained in a reasonable time.

Animals↗
PubMed1991

Class II major histocompatibility complex molecules of murine dendritic cells: synthesis, sialylation of invariant chain, and antigen processing capacity are down-regulated upon culture.

Dendritic cells (DCs), such as Langerhans cells (LCs) of the epidermis and the DCs of lymphoid organs such as spleen, are potent antigen presenting cells. DCs express high levels of major histocompatibility complex (MHC) class II molecules, but, partly because of the low numbers of primary DCs in any tissue, there has been no detailed study of the biochemistry of their class II molecules. This information may be needed to help explain recent findings that DCs process native protein antigens when freshly isolated from epidermis and spleen. Processing ceases during culture, yet a strong accessory function for activating resting T cells develops. We studied immunoprecipitates of DC class II and invariant chain (Ii) molecules by two-dimensional gel electrophoresis. We found that (i) freshly isolated LCs synthesize large amounts of class II and Ii polypeptides; (ii) Ii molecules that are known to be involved in antigen processing display an unusually large number of sialic acids in fresh LCs; (iii) with culture, class II and Ii synthesis decreases dramatically and has virtually ceased at 3 days; and (iv) the turnover of class II in pulse/chase experiments is slow, being undetectable over a 12- to 32-hr culture period, whereas the turnover of Ii is rapid. We conclude that MHC class II molecules of DCs do not seem to be qualitatively unique. However, the regulation of class II and Ii expression is distinctive in that biosynthesis proceeds vigorously for a short period of time and the newly synthesized class II remains stably on the cell surface, whereas Ii turns over rapidly. This may enable DCs to process and retain antigens in the peripheral tissues such as skin and migrate to the lymphoid organs to activate T cells there.

Animals↗
PubMed1991

The micronucleus test in pigs: induction of micronuclei in polychromatic erythrocytes by various doses of X-rays.

This paper describes the results of a study in which pigs were used in the bone marrow micronucleus assay. In a first experiment the spontaneous frequency of micronucleated polychromatic erythrocytes (MPE) among polychromatic erythrocytes (PE) was investigated in 78 animals. It was found that it is low with individual values of 0-4 MPE/1000 PE and a group average of 1.76 +/- 1.06% (mean +/- SD). In a second set of investigations animals were exposed to 0.25, 0.5, 1.0, 1.5, 2.25 and 2.75 Gy of 9-MeV X-irradiation performed as a single whole-body exposure. Time- and dose-dependent changes in micronucleus incidence were observed. Maximal group averages appeared nearly uniform 36 h post irradiation (p.i.). Considering the 36-h values in the dose range of 0-2.25 Gy there is a marked dose-effect relationship (r = 0.971). The data yield best to a regression curve of a third-grade polynomial indicating a complex interaction between dose and micronucleus formation. In conclusion, the results demonstrate that it appears feasible to use swine as target organisms in the micronucleus test to estimate the cytogenetic damage caused by ionizing radiations or, potentially, chemical compounds.

Animals↗
PubMed1991

Giant cerebral aneurysm repair. Incorporating cardiopulmonary bypass and neurosurgery.

Since our initial experience on April 28, 1989, a total of nine patients have received treatment for giant cerebral aneurysm using cardiopulmonary bypass with deep hypothermia and circulatory arrest. The following data summarize our findings associated with these patients. The average patient's age was 46 years (range: 16 to 59 years of age). Seven patients were female, two were male. The procedure required approximately eight hours to complete with an average cardiopulmonary bypass time of 104 minutes (range: 60 to 140 minutes). Circulatory arrest time averaged 26 minutes (range, 12 to 45 minutes) with an average of 30 minutes (range: 10 to 62 minutes) required to cool the patient to below 18 degrees C (64 degrees F). An average of 54 minutes (range: 28 to 81 minutes) was required to warm the patient to a bladder temperature of 36 degrees C (96.8 degrees F). During the cooling period, five patients went into asystole spontaneously, four patients required bolus of 20 mEq of potassium chloride, and upon rewarming, spontaneous defibrillation occurred in six patients. Three patients were defibrillated without difficulty with external shock. The average number of blood products administered in each of the nine patients was 3.6 units of packed red blood cells, 3 units of fresh frozen plasma, and 6.5 units of platelets. Six patients recovered postoperatively without complication, and the recovery of three patients was affected by the complex anatomical location of the giant aneurysm. Cardiopulmonary bypass with deep hypothermia and circulatory arrest offers an alternative approach to the treatment of giant cerebral aneurysms considered inoperable by conventional techniques. The effectiveness of each procedure depends on the collaborative efforts of every member of the perioperative nursing team, the neurosurgical team, the cardiac surgical team, the neuroanesthesiology team, and the perfusionists. Careful planning and anticipation at every stage of the surgery can reduce surgical time, cardiopulmonary bypass time, and most importantly, circulatory arrest time.

Angiography↗
PubMed1991

[Lens changes following pneumatic retinopexy: preliminary results of linear densitometry image analysis of Scheimpflug photographs two months after operation].

The small degree of morbidity and a better postoperative visual acuity are the advantages of pneumatic retinopexy in comparison to encircling procedures in the treatment of retinal detachment. The injection of air or gas into the vitreous cavity can theoretically induce a cataract postoperatively. Two months after pneumatic retinopexy (SF6-gas) Scheimpflug photography and microdensitometric evaluation of the negative were performed on 22 pairs of phacic eyes showing changes in the transparency of the lens. The deterioration of transparency in the operated eye was small but higher than that of the non-operated eye. Due to the short follow up period no prognosis is possible as to the future lens transparency changes.

Cataract↗
PubMed1991

[Lens changes following intraocular tamponade in vitrectomy. Linear densitometric image analysis of Scheimpflug photographs 6 months after operation].

A complication arising from vitrectomy is the formation of cataract. As a result of an intra- and postoperative tamponade chosen (BSS, air, SF6-gas, silicon oil) the size and frequency of the cataract varies accordingly. 6 months after vitrectomy Scheimpflug photography and microdensitometric evaluation of the negatives were performed on 30 pairs of phacic eyes showing changes in the transparency of the lens. Following silicon oil tamponade a significant deterioration of transparency (t-test) was observed in the lens nucleus of the operated eye; in the area of the lens in front of the nucleus a marked but not significant deterioration of transparency was discovered following both silicon oil and SF6-gas tamponade. In the case of the area in front of the nucleus following SF6-gas tamponade as well as the whole of the lens following BSS or air tamponade a small but not at all significant difference in lens transparency was apparent after comparison of the operated to the non-operated eyes.

Cataract↗
PubMed1991

[Visually evoked cortical potentials for early detection of optic neuritis in ethambutol therapy].

Ethambutol leads to chronic, severe optic neuritis with sudden onset in approximately 5-14% of all patients. Therefore, the ability of visually (pattern) evoked potentials for the early diagnosis of ethambutol-induced optic neuritis was tested. During ethambutol therapy prolonged latency was documented in 5 of 15 cases (33%). One of these 5 cases showed a reversible decrease in visual acuity. Thus, during treatment with ethambutol visually (pattern) evoked potentials may reveal a surprisingly high percentage of subclinical optic neuritis. These patients need close supervision in order to facilitate early discontinuation of the drug when neuritis develops.

Adolescent↗
PubMed1991

[Delayed resorption of subretinal fluid after pneumatic retinopexy].

Delayed resorption of pooled subretinal fluid has been reported to cause impaired visual acuity due to involvement of the macula in up to 10% of all case. In our series of 60 eyes treated consecutively with pneumatic retinopexy for retinal detachment, 9 eyes experienced delayed absorption of subretinal fluid. Only 6 eyes showed the phenomenon of pooled, localized subretinal fluid without peripheral extension to the ora serrata. The time for complete absorption of these circumscribed subretinal bullae ranged from 8 to 52 weeks (mean 22.7 weeks). Impaired visual acuity could not be detected in any of these cases. This may be due to the location of these bullae, which never involved the macula. Therefore, we do not consider the occurrence of this phenomenon to be a reason not to carry out pneumatic retinopexy.

Adult↗
PubMed1991

[Development of lens opacities in a period of 6 months after pneumatic retinopexy].

When performing a pneumatic retinopexy, air or gas is injected into the vitreous cavity to reattach a primary, rhegmatogenous retinal detachment. SF6 gas, for examples, remains in the vitreous cavity for up to 2 weeks before it is completely absorbed. It is conceivable that the injection of SF6 gas into the vitreous cavity interferes with lens metabolism, thus causing opacities of the lens. Even minor early changes in lens transparency can be monitored by Scheimpflug photography. Two months after performing a pneumatic retinopexy, 31 out of 100 consecutive eyes showed a loss of lens transparency, which was not pronounced or statistically significant. Six months after surgery the loss of transparency was more pronounced in all lens layers, increasing from the front to the back. The increment was statistically significant for the anterior lens cortex. Further investigations are needed to determine whether lens changes are the result of the intraocular tamponade with SF6 gas or are related to other factors, such as the surgical maneuver itself.

Cataract↗
PubMed1990

Disappearance of certain acidic organelles (endosomes and Langerhans cell granules) accompanies loss of antigen processing capacity upon culture of epidermal Langerhans cells.

Freshly isolated epidermal Langerhans cells (LC) can actively process native protein antigens, but are weak in sensitizing helper T cells. During culture, when LC mature into potent immunostimulatory dendritic cells, T cell sensitizing capacity develops but antigen processing capacity is downregulated. Processing of exogenous antigens for class II-restricted antigen presentation involves acidic organelles. We used the DAMP-technique to monitor acidic organelles at the ultrastructural level in fresh, as well as cultured, mouse and human LC. We observed that the loss of antigen processing capacity with culture of LC was reflected by the disappearance of certain acidic organelles, namely endosomes (particularly early ones), and the hitherto enigmatic LC granules ("Birbeck Granules"). Our findings support the notion that endosomes are critical for antigen processing and suggest that LC granules might be involved as well.

Animals↗
PubMed1990

Tumor necrosis factor alpha maintains the viability of murine epidermal Langerhans cells in culture, but in contrast to granulocyte/macrophage colony-stimulating factor, without inducing their functional maturation.

Freshly isolated murine epidermal Langerhans cells (LC) are weak stimulators of resting T cells but increase their stimulatory capacity 10-30-fold upon 2-3 d of culture together with other epidermal cells. This maturation of LC is mediated by two keratinocyte products. Granulocyte/macrophage colony-stimulating factor (GM-CSF) maintains viability and increases function. IL-1 alone does not keep LC alive, but when combined with GM-CSF further enhances their stimulatory activity. We have now searched for a cytokine that would keep LC in a viable, but functionally immature state. When LC (enriched to greater than 75%) were cultured in the presence of GM-CSF (2 ng/ml) or murine (TNF-alpha) (plateau effect at 62 U/ml), the recovery of viable LC after 72 h was identical. The LC cultured in murine TNF-alpha, however, were 10-30 times less active in stimulating resting T cells. A series of experiments demonstrated that this phenomenon was not due to the induction of insufficient amounts of GM-CSF, the induction of a suppressor factor, or a toxic effect of TNF-alpha. Interestingly, the observed TNF-alpha activity exhibited a species preference, as human TNF-alpha was not active at comparable doses. We have observed an unexpected effect of TNF-alpha on LC in vitro. Though we found that freshly prepared epidermal cells express TNF-alpha mRNA, further studies are needed to establish whether TNF-alpha plays a role in vivo by keeping resident LC in a viable, but functionally immature state.

Animals↗
PubMed1990

Ultrastructural pathology of anterior persistent hyperplastic primary vitreous.

Using transmission electron microscopy, the fine structure of anterior persistent hyperplastic primary vitreous (PHPV) removed from the eyes of four infants was studied. The tissue mass was composed of vessels derived from or representing the tunica vasculosa lentis posterior and the vasa hyaloidea propria. They were embedded in a loose connective-tissue matrix containing many fibroblasts and mature collagen fibrils. Toward the posterior surface, the fibroblasts became more numerous, elongated and densely packed. At the point of its entry into the posterior pole of the mass, the hyaloid artery was found to be surrounded by glial cells, probably representing an extension of the wall cells of the hyaloid canal. Venous drainage of the PHPV nodules seemed to occur via the ciliary body to which they were connected by tiny vessels bridging the distance from the PHPV lump to elongated ciliary processes. The anterior surface of the tissue lump was covered with lens fragments. These remnants showed signs of very early disturbance of lens development, with a failure to form posterior lens fibers. Based on these findings, the authors suggest that PHPV may be secondary to a primary defect in lens development.

Eye Diseases↗