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Biomedical subjects

G Eisner

Publications and source records attributed to G Eisner.

At least 19 recordsLinked to original sources
PubMed2001

YidC, an assembly site for polytopic Escherichia coli membrane proteins located in immediate proximity to the SecYE translocon and lipids.

Like its mitochondrial homolog Oxa1p, the inner membrane protein YidC of Escherichia coli is involved in the integration of membrane proteins. We have analyzed individual insertion steps of the polytopic E. coli membrane protein MtlA targeted as ribosome-nascent chain complexes to inner membrane vesicles. YidC can accommodate at least the first two transmembrane segments of MtlA at the protein lipid interface and retain them even though the length of the nascent chain would amply allow insertion into membrane lipids. An even longer insertion intermediate of MtlA is described that still has the first transmembrane helix bound to YidC while the third contacts SecE and YidC during integration. Our findings suggest that YidC forms a contiguous integration unit with the SecYE translocon and functions as an assembly site for polytopic membrane proteins mediating the formation of helix bundles prior to their release into the membrane lipids.

Bacterial Proteins↗
PubMed1996

The CER3 gene of Arabidopsis thaliana is expressed in leaves, stems, roots, flowers and apical meristems.

The eceriferum3 (cer3) locus encodes one of 21 gene products known to be involved in wax biosynthesis in Arabidopsis thaliana. Mutations at these loci are readily identified by their bright, dark-green stems when compared with the more glaucous wild-type plant. Clones of a gene which encodes a 795 amino acid open reading frame have been isolated by using plant DNA flanking the site of a T-DNA insertion in line BRL1. Molecular complementation of the cer3 mutant phenotype by clones of this gene establish that it corresponds to the CER3 gene. Although the 90 kDa predicted amino acid sequence of this gene shows no homology to any other known protein, the second exon of CER3 encodes a RRX12KK nuclear localization sequence (NLS). Southern blot and DNA sequence analysis revealed that the T-DNA is inserted 89 bp downstream of the translation termination codon of this gene. Northern blot hybridization of RNA isolated from the BRL1 mutant with the CER3 cDNA probe indicated that the transcript is absent in this mutant line. Unlike other CER genes that have been cloned to date, high levels of the CER3 transcript were found in all tissues from wild-type plants, that is, leaves, stems, roots, flowers, and apical meristems.

Amino Acid Sequence↗
PubMed1996

Addition-deletion mutations in transgenic Arabidopsis thaliana generated by the seed co-cultivation method.

We have characterized three mutant alleles of the CER2 gene of Arabidopsis thaliana by sequencing polymerase chain reaction products of this gene generated with template DNA isolated from lines MK1, BRL7, and BRL17. Sequence analysis of the amplification product from line BRL17 revealed a 17-bp deletion in the CER2 gene. The CER2 gene of BRL7 differs from the wild-type sequence by a 2-base substitution and 2-base insertion. As both of these lines were isolated from the transformant populations generated by Dr. K. Feldmann and his collaborators, we suggest that these small rearrangements may be caused by unsuccessful T-DNA insertions. Comparative sequence analysis of the sequence of line MK1 and the wild type revealed a single nucleotide substitution located 360 bp downstream from the intron-exon junction that changes a tryptophan triplet TGG to TGA; i.e., an opal non-sense mutation. In accordance with these observations, the cer phenotype of line MK1 was complemented by transformation with a fusion construct of the CaMV 35S promoter and the CER2 structural gene. Comparative analysis of the deduced amino acid sequences encoded by the CER2 gene from Arabidopsis and by the glossy2 gene from Zea mays revealed a significant similarity between them. This suggests that these gene products may have a similar biochemical function.

Arabidopsis↗
PubMed1994

[Effects and side effects of the drug "Success"].

To raise the rate of success to 100% is certainly a goal worth striving for. However, the closer one approaches this ultimate success, the more one is confronted with unexpected difficulties, such as difficulties in recognizing and proving, extremely high success rates as well as ethical problems. Furthermore, in the range of a high success rate all attempts for further amelioration necessarily lead to deterioration of this success rate; this is illustrated by an example from ophthalmology. Actually, coping with success is a great challenge, and the teaching requires not only great skills but also a solid philosophical background. Teachers must meet high demands. This applies also to the general public and the authorities acting in its name who have to appoint gifted teachers and have to support their mission.

Clinical Competence↗
PubMed1994

The pseudo-posterior limiting layer syndrome: a vitreoretinal heredodegeneration with autosomal dominant transmission.

A new vitreoretinal heredodegenerative syndrome with a high incidence (> 40%) of retinal detachment is described. It has been observed in five families (altogether 27 subjects) without consanguinity. The affection is autosomal dominant, bilateral, and more often than not (> 70%) coupled with axial myopia exceeding 5 D. Peripheral retinal degenerations are found in about 90% of the eyes. The syndrome is characterized by a pathognomonic membrane-like structure in the vitreous cavity, the pseudo-posterior limiting layer. The pseudo-PLL is a purely intravitreal phenomenon: in contrast to other vitreoretinal syndromes, there are no vitreous condensations connected to the retina.

Adolescent↗
PubMed1992

[Unexpected changes in the vitreous body after posterior detachment].

After changing the position of the eye, intravitreal structures demonstrate a gravitary position at rest. As an exception the detached vitreous shows an irreversible position at rest. The vitreous tractions on retinal adhesions are therefore irregular. This could explain the asymmetric distribution of retinal tears and has to be considered for the operation techniques.

Gravitation↗
PubMed1989

[Posterior vitreous detachment].

Posterior vitreous detachments (PVDs) are common. Their complications--retinal detachment--however, are comparatively rare. PVDs without complications and those prone to complications can be differentiated biomicroscopically by morphological signs, that is by examining the posterior hyaloid and its insertion at the posterior border of the vitreous base. PVD without complications is a rhegmatogenous detachment which has been completed temporarily as well as anatomically. It has the shape of a collapsed bag whose posterior wall has been perforated and whose contents have been emptied through the hole. All other shapes of PVD are prone to complications: either an incomplete rhegmatogenous PVD with persistent vitreoretinal adhesions; or a non-rhegmatogenous PVD whose complications depend on the retinal or vascular disease which caused it.

Eye Diseases↗
PubMed1989

[Principles of the practical use of viscoelastic substances in eye surgery].

The different rheological properties of viscous and viscoelastic substances indicate different uses in surgical practice. Purely viscous substances solve manly surface-tactical problems. The stronger the elastic component, the better the substances are suitable also for space-tactical and tissue-tactical purposes. A new field of interest is the neutralization of the buoyancy of silicone oil and gas bubbles. The latter can be used for the insertion of posterior chamber lenses in cases where the lens capsule is lacking (air sandwich). The main disadvantage is the postoperative rise of intraocular pressure: but this can be managed by a release of the substance through a preplaced keratotomy.

Air↗
PubMed1985

A new contact glass for slit-lamp examination of the cornea, especially in specular reflection.

A new contact glass of 2.2X magnification for the examination of the cornea is described. With it, all three types of illumination provided by the slit lamp can be used to advantage: specular reflection, optical section, and indirect light. A precorneal chamber filled with liquid abolishes the surface reflex of the tear film, and a built-in orange filter suppresses most of the light scattered by the corneal stroma. In specular examination the necessity for a large angle between the illumination and observation beams no longer exists, so that quite small angles can be used. Since at the same time such a glass considerably widens the usable field, epi- and endothelioscopy are greatly facilitated. Handling of the glass is as easy as in routine biomicroscopy. It is shown that a contact glass of power M increases the resolution in depth by a factor of M2. Image distortion introduced by the glass is measured and found to be tolerable within the area of photographic records usable for cell density determinations. Some modifications made on the Nikon FS-2 photo slit lamp in order to improve its suitability for endotheliography are described. Clinical application of the method is documented by several examples.

Adolescent↗
PubMed1983

A contact lens for endothelial and epithelial specular microscopy.

A contact lens that facilitates specular microscopy of the corneal endothelium and epithelium with a standard slitlamp is described. It prevents blur from the superficial tear-film reflex, offers a wide field of specular illumination, and magnifies the field two times.

Cell Count↗
PubMed1983

[Contact glass for the study of the corneal endothelium and epithelium in the slit-lamp radius].

Specular endothelioscopy can be improved by an appropriate contact glass in three ways: The blurring front reflex of the cornea disappears, a two-fold magnification permits the use of routine slit-lamps for observation at higher magnification, and the field of specular illumination is increased considerably. The posterior surface of the contact glass is made plane, which offers the following advantages: a fluid chamber in front of the cornea is created which avoids any deformation of the cornea through the contact glass; the reflex of the posterior surface can be deflected by tilting the contact glass slightly so that the weak specular reflex of the epithelium becomes visible.

Corneal Diseases↗
PubMed1983

General considerations concerning viscous materials in ophthalmic surgery.

Currently available viscous substances are Methylcellulose, Chondroitin sulphate and Hyaluronic acid. All of them consist of large molecules that vary in their degree of viscosity, electrical charge and elasticity. Viscous substances are tools for spatial tactics. An analysis of the physical properties leads to the indication for their use in surgery. Like every other instrument, a special technique has to be learned in order to get maximum benefit and to avoid side effects.

Anterior Chamber↗
PubMed1982

Organization of loach ribosomal genes (Misgurnus fossilis L.).

The organization of ribosomal genes in the genome and amplified nucleoli of loach (Misgurnus fossilis L.), a teleost fish, was studied. Ribosomal DNA (rDNA) was isolated by density gradient centrifugation, digested by EcoRI endonuclease and mapped with 18S and 28S rRNAs. The transcription unit of ribosomal genes in oocyte nucleoli was investigated by an electron-microscopic visualization technique. The repeat unit of loach rDNA was shown to be split by EcoRI into two fragments: a constant fragment (3 . 10(6) daltons) and heterogeneous one (11-13 . 10(6) daltons, major type, and 7-8 . 10(6) daltons, minor type). The average size of the transcription units was found to be 2.5 +/- 0.2 microm. The lengths of nontranscribed spacers varied from 2.4 to 2.9 microm; however, shorter ones of 1.2-1.4 microm were also noticed. The data indicate that loach rDNA is organized as tandem repeat units of two types: a major fraction of 20-25 kb (14-17 . 10(6) daltons) and a minor one 15-16 kb (10-11 . 10(6) daltons). The heterogeneous length of the repeat units was predetermined by the heterogeneity of nontranscribed spacers.

Animals↗