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Biomedical subjects

E Fuchs

Publications and source records attributed to E Fuchs.

At least 289 records · Page 16Linked to original sources
PubMed1987

Extragonadal germ cell tumor: the preoperative urological evaluation.

Primary extragonadal germ cell tumors were diagnosed in 4 patients in whom surgical or postmortem examination of the testis failed to reveal germ cell tumor. A fifth patient underwent serial examination with testicular ultrasound without evidence of any abnormalities and he remains free of disease following chemotherapy. Based on our experience and a literature review, it is our opinion that orchiectomy is not indicated unless there is a palpable testicular abnormality, recent change in testicular size or consistency, abnormal testicular ultrasound or history of cryptorchidism, or if the primary tumor is choriocarcinoma.

Adult↗
PubMed1987

Retinoids as important regulators of terminal differentiation: examining keratin expression in individual epidermal cells at various stages of keratinization.

When human epidermal cells were seeded on floating rafts of collagen and fibroblasts, they stratified at the air-liquid interface. The suprabasal cells synthesized the large type II (K1) and type I (K10/K11) keratins characteristic of terminal differentiation in skin. At earlier times in culture, expression of the large type II keratins appeared to precede the expression of their type I partners. At later times, all suprabasal cells expressed both types, suggesting that the accumulation of a critical level of K1 keratin may be a necessary stimulus for K10 and K11 expression. Expression of the terminal differentiation-specific keratins was completely suppressed by adding retinoic acid to the culture medium, or by submerging the cultures in normal medium. In submerged cultures, removal of vitamin A by delipidization of the serum restored the keratinization process. In contrast, calcium and transforming growth factor-beta did not influence the expression of the large keratins in keratinocytes grown in the presence of retinoids, even though they are known to induce certain morphological features of terminal differentiation. Retinoic acid in the raft medium not only suppressed the expression of the large keratins, but, in addition, induced the synthesis of two new keratins not normally expressed in epidermis in vivo. Immunofluorescence localized one of these keratins, K19, to a few isolated cells of the stratifying culture. In contrast, the other keratin, K13, appeared uniformly in a few outer layers of the culture. Interestingly, K13 expression correlated well with the gradient of retinoid-mediated disruptions of intercellular interactions in the culture. These data suggest that K13 induction may in some way relate to the reduction in either the number or the strength of desmosomal contacts between suprabasal cells of stratified squamous epithelial tissues.

Cell Differentiation↗
PubMed1987

The expression of mutant epidermal keratin cDNAs transfected in simple epithelial and squamous cell carcinoma lines.

We have deleted cDNA sequences encoding portions of the carboxy-terminal end of a human type I epidermal keratin K14, and examined the molecular consequences of forcing the expression of these mutants in simple epithelial and squamous cell carcinoma lines. To follow the expression of our mutant products in transfected cells, we have tagged the 3' end of the K14 coding sequence with a sequence encoding an antigenic domain of the neuropeptide substance P. Using DNA transfection and immunohistochemistry (with an antibody against substance P), we have identified a collection of mutants that have a wide range of morphological effects on the endogenous keratin filament networks of transfected cells. Mutants that are missing most of the nonhelical carboxy-terminal domain of K14 incorporate into the endogenous keratin filaments without any visible perturbations on the network. In contrast, mutants that are missing as few as 10 of the 310 amino acids of the central alpha-helical domain of the polypeptide cause gross alterations in the keratin network. In some cases, the entire cytoskeletal network of keratins was disrupted, leaving no evidence of 8-nm filaments. These results reveal the existence of a dynamic exchange between newly synthesized subunits and preexisting keratin filaments.

Amino Acid Sequence↗
PubMed1987

Regulation of human mesothelial cell differentiation: opposing roles of retinoids and epidermal growth factor in the expression of intermediate filament proteins.

We report here the discovery that retinoids are potent regulators of epithelial morphology and keratin expression in cultured human mesothelial cells. When LP-9 cells are cultured in medium supplemented with vitamin A-depleted serum, they grow with an extreme spindle-shaped morphology and synthesize abundant levels of vimentin, but very little keratin. When retinoic acid is added to the medium at 1 X 10(-8) to 1 X 10(-6) M, keratin synthesis is increased, vimentin synthesis is decreased, and the cells assume an epithelioid morphology. Keratin synthesis, but not epithelioid morphology, seems to be dependent on cell density as well: even when vitamin A is present, sparse cultures cannot fully maintain keratin synthesis. In contrast, epidermal growth factor (EGF) acts in an antagonistic fashion to suppress both keratin synthesis and epithelial morphology. The effects of vitamin A, EGF, and cell shape on intermediate filament (IF) expression seem to occur in a growth-independent manner, and they appear to be at the level of transcription or mRNA stability. Even so, their effects on IF expression do not appear to be rapid ones, and hence it is unlikely that these agents interact directly at the gene level to cause changes in IF gene expression.

Actins↗
PubMed1987

Nascent secretory polypeptides synthesized on Escherichia coli ribosomes are not translocated across mammalian endoplasmic reticulum.

Cell-free protein-synthesizing systems from Escherichia coli and wheat germ were compared for their capacity to support the translocation of secretory proteins across microsomal membranes derived from mammalian endoplasmic reticulum. Three different secretory proteins, two of bacterial and one of eucaryotic origin, were tested in this respect. In all three cases a contrast between the results in the eucaryotic and procaryotic protein-synthesizing systems was revealed. Whereas the eucaryotic system, as expected, supported the translocation of nascent secretory proteins across the microsomal membranes, the procaryotic system failed to do so. This failure was not due to the absence of a translocation-promoting activity or the presence of a translocation-blocking activity in the procaryotic system. These results demonstrate a specificity in the requirement of components of the protein-synthesizing machinery for protein translocation. These components might participate in forming a functional ribosome-membrane junction during protein translocation. The nascent secretory chain alone is not sufficient for making this junction, which might involve the postulated binding of the ribosome to the signal recognition particle or another component of the membrane.

Bacterial Proteins↗
PubMed1987

An Epstein-Barr virus transforming protein associates with vimentin in lymphocytes.

The Epstein-Barr virus (EBV) latent infection membrane protein (LMP) is likely to be an important mediator of EBV-induced cell proliferation, since it is one of the few proteins encoded by the virus in latent infection and since production of this protein in Rat-1 cells results in their conversion to a fully transformed phenotype. LMP was previously noted to localize to patches at the cell periphery. In this paper we examine the basis of LMP patching in EBV-infected, transformed lymphocytes. Our data indicate that LMP is associated with the cytoskeletal protein vimentin. Although LMP is fully soluble in isotonic Triton X-100 buffer, only 50% of it is extracted from cells in this solution. The rest remains bound to the cytoskeleton. LMP undergoes phosphorylation, and phosphorylated LMP is preferentially associated with the cytoskeleton. As judged by both immunofluorescence and immunoelectron microscopy, the vimentin network in EBV-transformed lymphocytes or EBV-infected Burkitt tumor lymphocytes is abnormal. Vimentin and LMP often colocalize in a single patch near the plasma membrane. In response to Colcemid treatment of EBV-infected cells, vimentin reorganizes into perinuclear rings, as it does in uninfected cells. LMP is associated with these perinuclear rings. Vimentin (or a vimentin-associated protein) may be a transducer of an LMP transmembrane effect in lymphoproliferation.

Burkitt Lymphoma↗
PubMed1986

Release rates of catecholamines, GABA and beta-endorphin in the preoptic area and the mediobasal hypothalamus of the rhesus monkey in push-pull perfusates: correlation with blood hormone levels.

Push-pull cannulae were implanted into the preoptic area and into the mediobasal hypothalamic median eminence complex of ovariectomized rhesus monkeys. After recovery, perfusion of the implanted areas was performed over a period of 56 h before and following estradiol benzoate treatment. This treatment results in a drop of LH levels followed by an increase. Catecholamine (norepinephrine, epinephrine and dopamine) concentrations in perfusates collected at 15 min intervals fluctuated tremendously prior to treatment with the estrogen. These fluctuations were largely reduced in perfusates of both structures following the estrogen treatment. They reoccurred at the time of increasing LH levels. beta-endorphin and GABA concentrations were also measured in the perfusates of both structures. Occasional secretory bursts were observed without any obvious relation to the estrogen treatment. It is concluded that catecholamine release in the preoptic area and in the mediobasal hypothalamic median eminence complex is of a pulsatile nature in ovariectomized rhesus monkeys. This pulsatility is largely reduced or abolished following estrogen treatment. The reduced pulsatility may bear a signal character for the release of LH.

Animals↗
PubMed1986

Postnatal development of transmitter systems: sexual differentiation of the GABAergic system and effects of muscimol.

The development and sex differences of the central nervous GABAergic system were examined by measuring GABA (gamma-aminobutyric acid) in discrete brain nuclei of the hypothalamus, as well as the nigrostriatal and the limbic systems of male and female rats on the day of birth and on days 5, 10, and 15. The highest concentrations were found in the hypothalamic and nigrostriatal nuclei; the lowest in the limbic system. Sex differences were observed only on day 10 in the medial preoptic area, with GABA being higher in males than in females; and also in the substantia nigra, where female GABA levels were higher than male. These results suggested an involvement of GABA in the sexual differentiation of the brain. As a control, concentrations of the GABA precursor glutamate were determined. No sex differences in glutamate concentrations were found in any brain region during the first 15 days postnatally. Since a GABA mimetic substance applied during the critical period of brain differentiation could disturb the development of the GABAergic system, the consequences of a perinatal treatment with the GABA agonist muscimol were investigated. Significant reduction of GABA concentrations by muscimol were observed in the hypothalamic and nigrostriatal systems at specific times postnatally. On day 5, GABA concentrations were diminished only in the medial preoptic area, then on day 10, in the anterior hypothalamus and the substantia nigra, and still later, on day 15, in the caudato putamen. In contrast, the effects of muscimol on glutamate concentrations could be observed over a longer postnatal period. Glutamate was already diminished on day 5 in 7 areas of the hypothalamic, nigrostriatal, and limbic systems.

Aging↗
PubMed1986

Evidence for posttranscriptional regulation of the keratins expressed during hyperproliferation and malignant transformation in human epidermis.

Keratin K6 is a protein that is expressed in human skin under conditions of hyperproliferation (e.g., wound-healing, psoriasis, and cell culture) and malignant transformation (e.g., squamous cell carcinomas). When induced, the appearance of K6 is rapid: if skin tissue is placed in radiolabeled culture medium, this protein can be detected within an hour. The regulation of K6 seems to be controlled partly by a posttranscriptional mechanism: At least two K6 genes are actively transcribed both in vivo, when the protein is not made, as well as in vitro, when abundant levels of the protein are expressed. Substantial levels of K6a and K6b RNAs can be detected in skin by Northern Blot analysis, and these RNAs are largely, if not fully translatable in vitro. In situ hybridizations reveal that the RNAs are distributed throughout the living layers of the epidermis. The rapid induction of K6 expression through a posttranscriptional regulatory mechanism suggests that this keratin may play an important role in designing a cytoskeletal architecture that is compatible with the hyperproliferative state.

Cell Differentiation↗
PubMed1986

Three tightly linked genes encoding human type I keratins: conservation of sequence in the 5'-untranslated leader and 5'-upstream regions of coexpressed keratin genes.

We have isolated and subcloned three separate segments of human DNA which share strong sequence homology with a previously sequenced gene encoding a type I keratin, K14 (50 kilodaltons). Restriction endonuclease mapping has demonstrated that these three genes are tightly linked chromosomally, whereas the K14 gene appears to be separate. As judged by positive hybridization-translation and Northern blot analyses, the central linked gene encodes a keratin, K17, which is expressed in abundance with K14 and two other type I keratins in cultured human epidermal cells. None of these other epidermal keratin mRNAs appears to be generated from the K17 gene through differential splicing of its transcript. The sequence of the K17 gene reveals striking homologies not only with the coding portions and intron positions of the K14 gene, but also with its 5'-noncoding and 5'-upstream sequences. These similarities may provide an important clue in elucidating the molecular mechanisms underlying the coexpression of the two genes.

Base Sequence↗
PubMed1986

Decreased number and affinity of rat atrial natriuretic peptide (6-33) binding sites in the subfornical organ of spontaneously hypertensive rats.

Binding sites for rat atrial natriuretic peptide (6-33) were quantified by incubation of brain sections with (3-[125I]iodotyrosyl28) rat atrial natriuretic peptide (6-33), followed by autoradiography with computerized microdensitometry. Spontaneously hypertensive rats present lower numbers and lower affinity of binding sites than normotensive controls, Wistar-Kyoto rats, in the subfornical organ (binding capacity 61.7 +/- 8.9 and 124.3 +/- 10.7 fmol/mg protein; affinity constant 4.25 +/- 0.55 and 11.10 +/- 1.67 X 10(9) M-1, respectively). In the choroid plexus, hypertensive rats have lower numbers of sites than normotensive rats (binding capacity 72.7 +/- 10.5 and 173.6 +/- 22.8 fmol/mg protein, respectively), but there was no difference in the binding affinity (affinity constant 6.28 +/- 0.82 and 7.60 +/- 2.06 X 10(9) M-1, respectively). Our results suggest that discretely localized brain binding sites for rat atrial natriuretic peptide (6-33) may have a physiological function in genetically hypertensive rats.

Animals↗
PubMed1986

Fatty-acid biosynthesis in man, a pathway of minor importance. Purification, optimal assay conditions, and organ distribution of fatty-acid synthase.

Fatty-acid synthase has been purified to homogeneity from human liver by a 3-step procedure including protamine sulfate/ammonium sulfate fractionation, affinity chromatography on 2',5'-ADP-Sepharose 4B and gel filtration on Sephacryl S-300. Both the human and rat fatty-acid synthase had similar characteristics regarding molecular mass, subunit structure, amino-acid composition, and substrate affinities. In order to measure the fatty-acid synthase activities in small tissue samples it was necessary to improve the sensitivity of an isotopic assay using [14C]malonyl-CoA as tracer. Special attention was paid to the dual role of free CoASH as an activator and inhibitor of the enzyme. Considerable differences existed between the specific activities of the fatty-acid synthase complex measured in human and rat lipogenic organs. Only negligible values of about 1 mU/mg protein were found in human liver and adipose tissue, while the corresponding activities were 10- to 50-fold higher in young lean rats. Less pronounced but still remarkable differences were determined for the activity of the acetyltransferase which catalyses the initial primer reaction of the fatty-acid synthase complex. In some selected cases under long-term fat-free diet (alcoholism, parenteral nutrition) elevated values of fatty-acid synthase activities were detected in human tissues. Under usual diet, with a relatively high fat content of up to 40 percent, and even after a carbohydrate-rich diet for three days, fatty-acid synthase activity remained low. It is concluded that under the dietary conditions, common for the industrialized world, de novo lipogenesis in man is negligible.

Adipose Tissue↗
PubMed1985

The sequence of a type II keratin gene expressed in human skin: conservation of structure among all intermediate filament genes.

We report here the coding sequence of the gene for a 56-kDa type II keratin (designated K6b). Using a subclone specific for a unique 3' noncoding region of the encoded mRNA, we have shown that this gene is one of at least two 56-kDa keratin genes expressed in abundance in human epidermis. Segmenting the coding portion of this gene are eight introns, six of which are identically positioned with those of a distantly related type III intermediate filament gene (vimentin), and five of which are identically positioned with those of a distantly related type I gene (50-kDa keratin). These results indicate a common ancestral origin for all three classes of intermediate filament genes. All of the highly conserved intron positions are located within, but do not demarcate, the four central alpha-helical domains common to all intermediate filament polypeptides, suggesting that these genes were probably not created piecemeal by recombination-mediated linkage of separate structural domains as they presently are known.

Amino Acid Sequence↗