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Biomedical subjects

C Allen

Publications and source records attributed to C Allen.

At least 37 records · Page 2Linked to original sources
PubMed1989

Behavior of human RPE cultured on Bruch's membrane and on necrotic debris.

Degeneration and necrosis of the retinal pigment epithelium (RPE) is found in several conditions associated with reactive alteration of the cell layer, and is probably involved in the formation of drusen and age-related macular degeneration. In the current study we describe a novel system for culturing human RPE. This system permits evaluation of the effect of necrotic material between the epithelium and Bruch's membrane, of drusen, and of other alterations in Bruch's membrane on the behavior of the RPE. In this system, dissociated RPE cells were seeded onto isolated Bruch's membrane. Cell behavior was assessed in areas with and without drusen, and also in areas covered with necrotic cells and fragmented debris. On both exposed Bruch's membrane and on the membrane covered with debris, the cells developed a polygonal shape, with a varying density of apical microvilli. The cultures were monolayered with some overlapping. In areas containing fragmented debris and dead cells, seeded RPE cells were found to adhere to the apical surface of necrotic cells, but were also seen to intrude between the necrotic debris and underlying Bruch's membrane, appearing to clear the membrane of such debris. Our study demonstrates the stability of epithelial histology of human RPE under not previously tested conditions. Further, it shows that the present system permits exposure of these cells to several in vivo physiological and pathological changes in a controlled in vitro environment.

Cells, Cultured↗
PubMed1988

Kikuchi's disease--apparent malignancy of a neck mass.

We report a case of Kikuchi's disease presenting as cervical lymphadenopathy in an adolescent. The original histological diagnosis in this case was a metastatic neoplasm. We wish to highlight the importance of this rare condition because of its potential for mimicking malignancy.

Adolescent↗
PubMed1988

The morphology of human cells from the choroid and retinal pigment epithelium grown in vitro on isolated Bruch's membrane.

Cells from samples of human choroidal tissue were collected and seeded onto isolated Bruch's membrane in vitro, and the morphology of the developing cultures was examined by light-, scanning electron- and transmission electron-microscopy. In early cultures, the cells showed a flattened, spread out appearance with short surface villi and a low degree of cellular overlapping. After 48 h, a shift towards a more elongated cell form was observed, and one week old cultures were composed of predominantly elongated cells with a pronounced degree of overlapping. In contrast, human retinal pigment epithelial cells seeded onto sheets of Bruch's membrane maintained a spread out epithelial morphology with a varying degree of overlapping throughout the culture period. The present system permits comparative studies on the behavior of choroidal and pigment epithelial cells under controlled conditions. It may serve as an in vitro model for disorders characterized by growth of these cells on Bruch's membrane in vivo.

Cell Membrane↗
PubMed1988

The effect of a pulsed neodymium-YAG laser on chorioretinal monolayered cell cultures.

The effect of a pulsed YAG laser on monolayers of chorioretinal cells maintained in vitro on plastic surface was examined. At the energy levels used, phase contrast microscopic visible lesions were observed at all focus distances up to 2 mm. Scanning electron microscopy demonstrated curling of detached sheets of cells, displacement of single cells, clustering of cells, and severe cell membrane damage at the edge of the lesions. The present system permits evaluation of the effect of different laser characteristics and application modes on the extent and morphology of damage in monolayers of human cells under easily controlled conditions.

Cells, Cultured↗
PubMed1988

Gonadotropin-producing pituitary adenoma in a man with long-standing primary hypogonadism.

Pituitary adenomas that secrete gonadotropins are generally believed to arise spontaneously rather than as a response to chronic primary gonadal failure. However, two women who were found to have gonadotroph adenomas several years after ovarian ablation have been reported. We describe a middle-aged man who developed bitemporal hemianopia and was found to have a large pituitary tumor 35 yr after castration. He had never received any replacement therapy. The tumor was considered to be a primary gonadotroph adenoma, rather than secondary gonadotroph hyperplasia, on the basis of its secretory capabilities, its reticulin patterns, and its specific immunostaining for human FSH beta, human LH beta, and alpha-subunit. Furthermore, the tumor did not decrease appreciably in size after 12 months of testosterone treatment, although plasma gonadotropin levels decreased. Unless the association of primary gonadal failure with a gonadotroph adenoma was coincidental, it suggests that some human gonadotroph adenomas may be secondary to failure of the gonads.

Adenoma↗
PubMed1987

The use of monoclonal antibodies UCH beta and UCH gamma for the antenatal diagnosis of beta-thalassaemia.

Monoclonal antibodies for the beta-globin chain of human HbA (UCH beta) and the gamma-globin chain of human HbF (UCH gamma) have been made. UCH beta indirectly labelled with rhodamine-labelled goat anti-mouse Ig and directly flouresceinated UCH gamma have been used, via double labelling immunofluorescence microscopy, to assay for the presence of beta-chains in fetal erythrocytes obtained at fetoscopy from fetuses at risk for beta-thalassaemia major. The results from 111 cases demonstrate that beta-chain synthesis of as low as 1.8% can be detected in fetal erythrocytes. The immunochemical labelling can be rendered more sensitive by the use of biotinylated UCH beta and avidin-FITC conjugates. This method is rapid and can be used for a sample that is highly contaminated with maternal erythrocytes.

Antibodies, Monoclonal↗
PubMed1986

Macrophage antigens and the effect of a macrophage activating factor, interferon-gamma.

Molecules characteristic of mononuclear phagocytes have been identified using monoclonal antibodies (MAb). MAb 3.9 reacts with a 150/95 000 dalton heterodimer which is found exclusively on monocytes and macrophages and appears to be the third member of the lymphocyte function-associated (LFA) family of molecules. In contrast, the reactivity of MAb 24, which bonds to a 175 000 dalton protein, is most highly expressed on the macrophages in lymphoid tissue. Both 3.9 and 24 detect the interdigitating cells in the T cell areas of these tissues, which strongly suggests that this cell type belongs to the macrophage family. A third MAb, 10.1, reacts selectively with a set of macrophages outside lymphoid tissue, particularly on Kupffer cells, alveolar macrophages and microglia. Thus subsets of tissue macrophages are proving easy to identify whereas it appears that circulating monocytes are not easily subdivided. None of the MAbs detected either Langerhans' cells, dendritic reticulum cells of B cell areas, or osteoclasts, indicating that these cells are not mononuclear phagocytes. As a first step towards identifying macrophage molecules which have a biological function, we have investigated the effect of macrophage-activating factor, interferon-gamma, on the expression of macrophage membrane molecules. There was greatly increased expression of only two out of ten molecules detected with anti-myeloid antibodies.

Antibodies, Monoclonal↗
PubMed1986

Human retinal pigment epithelium in long term explant culture.

Explants of human retinal pigment epithelium were maintained in culture in various types of media, and examined by light and transmission electron microscopy. After one month in vitro, the central areas showed a monolayered configuration with distinct polarity and presence of ruthenium red stainable material on the apical surface. On the peripheral areas of Bruch's membrane, multilayered lesions were observed to develop and to extend from the monolayered epithelium and past the cut edge in Bruch's membrane. Cells in these lesions contained little melanin and generally lacked an apico-basal polarity. Ruthenium red staining revealed the presence of electron dense material on the apical surface of the lesions as well as in the extracellular space between cells in the various layers. Development of multilayered lesions with deposition of extracellular material are seen in various chorio-retinal disorders, including senile macular degenerations and also subsequent to laser and cryo-therapy. The findings in the present study point to the explant culture system as a valuable tool in the study of important aspects of chorio-retinal pathology.

Aged↗
PubMed1986

Requirement for two or more Erwinia carotovora subsp. carotovora pectolytic gene products for maceration of potato tuber tissue by Escherichia coli.

Several genes encoding enzymes capable of degrading plant cell wall components have been cloned from Erwinia carotovora subsp. carotovora EC14. Plasmids containing cloned EC14 DNA mediate the production of endo-pectate lyases, exo-pectate lyase, endo-polygalacturonase, and cellulase(s). Escherichia coli strains containing one of these plasmids or combinations of two plasmids were tested for their ability to macerate potato tuber slices. Only one E. coli strain, containing two plasmids that encode endo-pectate lyases, exo-pectate lyase, and endo-polygalacturonase, caused limited maceration. The pectolytic proteins associated with one of these plasmids, pDR1, have been described previously (D. P. Roberts, P. M. Berman, C. Allen, V. K. Stromberg, G. H. Lacy, and M. S. Mount, Can. J. Plant Pathol. 8:17-27, 1986) and include two secreted endo-pectate lyases. The second plasmid, pDR30, contains a 2.1-kilobase EC14 DNA insert that mediates the production of an exo-pectate lyase and an endo-polygalacturonase. These enzymes are similar in physicochemical properties to those produced by EC14. Our results suggest that the concerted activities of endo-pectate lyases with endo-polygalacturonase or exo-pectate lyase or both cause maceration.

Cell Wall↗
PubMed1985

Prevalence and clinical associations of intraocular pressure changes in Graves' disease.

We investigated an unselected series of 55 patients with treated or untreated hyperthyroid Graves' disease, assessing their clinical and laboratory status and ophthalmological findings, including the difference in intraocular pressure (dIOP) between upgaze and straight gaze using applanation tonometry. An increased dIOP (greater than 2 mm Hg) was detected in only 22% of Graves' patients [who had a mean dIOP of 3.5 +/- 1.6 (+/- SEM) mm Hg]. dIOP did not correlate with age, sex, age at disease onset, duration of disease, mode of antithyroid treatment, or thyroid function testing at the time of examination. Mean Hertel exophthalmometry measurements in patients with a dIOP greater than 2 mm Hg were 22.0 +/- 2.9 mm compared with 18.4 +/- 3.7 mm in those with a dIOP less than 2 mm Hg (P less than 0.027, by Wilcoxon rank sum test). Only 58% of patients with increased dIOP had clinical exophthalmos, but all had other evidence of Graves' eye disease. Computed tomographic scanning revealed significant proptosis and/or orbital muscle involvement in all of the patients with increased dIOP.

Adult↗
PubMed1979

State of unesterified fatty acids in skim milk.

By a multiple extraction procedure the unesterified fatty acids of skim milk have been shown in at least three entities: a) free dissociated and undissociated fatty acids, b) fatty acids associated with the membrane material in skim milk, and c) fatty acids of unknown origin requiring acidification to pH 1.5 for extraction.

Animals↗
PubMed1979

Photodegradation of riboflavin in milks exposed to fluorescent light.

Photodegradation of riboflavin in 50-ml samples of fluid milks exposed to fluorescent light (2690 lux) followed first-order reaction kinetics, and the reaction rate (s-1) averaged 1.86 x 10(-5) in skim milk and 1.47 x 10(-5) in whole milk. Additional evidence led us to conclude that photodegradation of riboflavin proceeds prior to the appearance of a light-induced off-flavor.

Animals↗
PubMed1978

Vasopressin in the rat with spontaneous hypertension.

Because vasopressin is one of the most potent naturally occurring pressor agents, and because of its importance in the regulation of blood volume and composition, we have undertaken a study of the role of vasopressin in the pathogenesis of the hypertension in the Okamoto-Aoki spontaneously hypertension (SH) rat. In SH rats, systolic blood pressure increased from 135 +/- 3 (SE) mmHg at age 33 days to 184 +/- 3 mmHg at age 75 days (P less than 0.01). In the Wistar-Kyoto (WKY) control rats, blood pressure increased from 100 +/- 2 to 120 +/- 2 mmHg (P less than 0.01). The differences in blood pressure between the SH and WKY rats at all ages were significant (P less than 0.01). During the age period 33-75 days, the 24-h urinary excretion of vasopressin in the SH rat was consistently more than twofold greater (P less than 0.01) than in the WKY rat. Plasma vasopressin concentration and pituitary vasopressin content were also elevated in the SH rat (P less than 0.01 and P less than 0.02, respectively). Changes in systolic blood pressure in the SH rat, however, were not paralleled by changes in the urinary excretion of vasopressin. The data indicate that the secretion of vasopressin is elevated in the SH rat. However, the magnitude of this elevation, in and of itself, may not be sufficient to account for the rising blood pressure in the young SH rat.

Animals↗