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Biomedical subjects

F Koch

Publications and source records attributed to F Koch.

At least 73 records · Page 4Linked to original sources
PubMed1994

A light and electron microscopic study of the healing of pars plana incisions in the rhesus monkey.

Pars plana incisions were made in 11 rhesus monkey eyes. Six animals had injections of 0.1 ml of blood into the vitreous cavity with a 25-gauge needle and five animals had vitrectomy through a 4-mm incision with a multifunction vitrectomy probe. Six to 13 years later the scars in the pars plana were found to consist of fibrous tissue and blood vessels which extended from the episclera into the vitreous. The intravitreous scar was shaped by the incarceration of vitreous strands in the internal aspect of the wounds. There were quantitative, but no qualitative differences between the two types of incision. The ultrastructural features were those of mature scar tissue: fibroblasts, adult collagen, uveal melanocytes, macrophages, myelinated and non-myelinated nerves, and capillaries with non-fenestrated endothelium. There were associated proliferative ciliary epithelial changes, but no evidence of ciliary epithelial metaplasia.

Animals↗
PubMed1994

Variations in ploidy among isolates of Botrytis cinerea: implications for genetic and molecular analyses.

Field isolates and laboratory strains of Botrytis cinerea, an ascomycetous fungus causing considerable economic losses, e.g., as "grey mould" of vine, were compared for differences in ploidy level by determining their DNA content per nucleus. Strain SAS56, an ascospore line used routinely for genetic analyses, is probably polyploid, since treatment with benomyl causes a significant reduction in DNA content per nucleus. This conclusion is substantiated by the increased sensitivity of the putative haploid derivatives to mutagens (UV and EMS). Molecular analyses (RAPD) of the haploidized strains indicate a very limited degree of heterozygosis of the parent strain SAS56. Analysis of field isolates of B. cinerea showed that their DNA content per nucleus varied considerably, indicating that aneuploidy/polyploidy is a widespread phenomenon in this species. This can explain both the variability and phenotypic instability of many field isolates of this fungus and the unusual difficulties faced by researchers in recovering stable recessive laboratory mutants. Since the haploid derivatives of SAS56 resemble the parent strain in their parasitic and physiological properties they should provide a good basis for classical and molecular genetic studies.

Base Sequence↗
PubMed1993

Interleukin 7 is produced by murine and human keratinocytes.

Interleukin 7 (IL-7) was originally identified as a growth factor for B cell progenitors, and subsequently has been shown to exert proliferative effects on T cell progenitors and mature peripheral T cells as well. Constitutive IL-7 mRNA expression so far had been demonstrated in bone marrow stromal cell lines, thymus, spleen, and among nonlymphoid tissues in liver and kidney. Here we show that both murine and human keratinocytes express IL-7 mRNA and release IL-7 protein in biologically relevant amounts. The physiological or pathological relevance of keratinocyte-derived IL-7 is presently unknown. Our finding that keratinocytes can produce IL-7 in concert with reports that IL-7 is a growth factor for in vivo primed antigen-specific T cells, as well as for T lymphoma cells suggests, however, that keratinocyte-derived IL-7 is important in the pathogenesis of inflammatory skin diseases and cutaneous T cell lymphoma.

Animals↗
PubMed1993

The architecture of human accessory lacrimal glands.

Human accessory lacrimal glands were examined both light and electron microscopically and their gross architecture was reconstructed from serial sections. Every accessory lacrimal gland nodule is an individual organ with its own connective tissue coat and excretory duct. Within the gland proper, the excretory duct ramifies to form intralobular ducts, which are connected to the secretory glandular epithelia. The secretory epithelia are composed of elongated tubules terminating in short end pieces with lumina of variable width. True acini are absent. Thus, the accessory lacrimal glands are tubular glands. The cells of tubules and end pieces contain large secretory granules suggestive of a regulated mechanism of secretion. The content of organelles and the amount of secretory material present in neighboring cells can show pronounced differences. Both end pieces and tubules and, to a lesser extent, the intralobular ducts are surrounded by myoepithelial cells. The interstitial connective tissue contains blood vessels, free cells, and fibroblasts. Axons of nonmyelinated nerve fibers are in close spatial contact to vascular endothelial cells, connective tissue cells, free cells, and glandular epithelial cells. A few axons with parasympathetic characteristics and, less frequently, with sympathetic characteristics were identified between the epithelial cells of both secretory epithelium and intralobular ducts.

Blepharoptosis↗
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↗