Search PubMed⌕ Search

Biomedical subjects

P Berg

Publications and source records attributed to P Berg.

At least 145 records · Page 8Linked to original sources
PubMed1989

[Pathogenic mechanism of contusio bulbi].

We examined experimentally the pathomechanism of ocular contusion and its damaging influence on the retina. Therefore, various jabbing instruments were used with which a definite trauma can be obtained. The physical parameters, the localization of the trauma and their importance for the injury and the intraocular pressure were analyzed. We found that the amount of energy has no special influence on the kind of ocular contusion, but that it does influence the dynamics of an injury. In direct trauma, the location where the eye is struck, e.g. the cornea or sclera, plays a decisive role in retinal damage. By means of various measurements of intraocular pressure we were able to prove that in non perforating trauma, the anterior segment, has a buffer function and protects the retina in case of corneal trauma from damage caused by contusion.

Animals↗
PubMed1989

Two stages of care for pleural effusion.

When the patient's pleural space is filled with fluid, palliative treatment measures--thoracic drainage and pleurodesis--and diligent nursing care can help her breathe easier.

Drainage↗
PubMed1988

Conservation of short patches of amino acid sequence amongst proteins with a common function but evolutionarily distinct origins: implications for cloning genes and for structure-function analysis.

Small patches of identical amino acid sequences commonly occur in proteins that have the same function but are derived from evolutionarily distant organisms. Reverse translation of such patches into degenerate pools of oligonucleotides provide useful hybridization probes for cloning the gene for the corresponding protein from other organisms. Since the conserved patches of identical amino acid sequence are probably important for the protein's biological function, they are preferred targets for reverse genetic studies aimed at defining structure-function relationships.

Amino Acid Sequence↗
PubMed1988

Introduction.

Explore the source record for details and available documents.

Journal Article↗
PubMed1988

Eyeblink-related potentials.

When the EEG is averaged time-locked to blinks, and the part of the potential that is proportional to the EOG is subtracted, a signal (the 'residuum') remains which resembles an event-related potential (ERP). The blink time-locked average (BTA) was investigated to determine whether the components of the residuum are due to a cerebral blink-related potential or to artifacts of the EOG which subtraction failed to remove. The BTA was obtained from 12 subjects using voluntary blinking in the light and in complete darkness. Differences between the potentials in light and dark indicate that a major component of the residuum is a visual evoked response elicited by the off-on light stimulus associated with blink eye closure. The results are discussed in relation to attempts to correct blink artifacts in ERP experiments and, by drawing parallels between the residuum and the lambda potential associated with saccades, similar inferences are made for the correction of eye movement artifacts.

Adult↗
PubMed1988

Homologous integration in mammalian cells without target gene selection.

Homologous integrations into a nonselectable target locus have been highly enriched for following DNA transfections into mammalian cells. The target gene, the SV40 early region in COS1 cells, provides transcription signals to activate a defective selectable marker, the gpt gene. We find that nearly half of the selected clones have integrated the gpt gene at the homologous sequence in the COS1 genome. This is an estimated 100-fold enrichment for homologous events compared with transfections in which the gpt gene is transcriptionally active. As shown for yeast integration events, a double-strand break at a position of homology between the transfected DNA and the genomic target is necessary to achieve a high frequency of homologous integrations. Furthermore, the arrangement of sequences at the integration site includes a repair of the double-strand gap, which was present on the transfected DNA, suggesting that similarities exist between yeast and mammalian integrations. The experimental design, in which a defective marker is activated following a homologous integration, may have general applications for gene targeting in mammalian cells.

Animals↗
PubMed1988

Comparison of intron-dependent and intron-independent gene expression.

Recombinant simian virus 40 viruses carrying rabbit beta-globin cDNA failed to express the beta-globin sequence unless an intron was included in the transcription unit. The addition of either beta-globin IVS1 or IVS2 caused a 400-fold increase in RNA production. Stable beta-globin RNA production required sequences in IVS2 that were very close to the splice sites and that coincided with those needed for mRNA splicing. In addition to the recombinant viruses, intron-dependent expression was observed with both replicating and nonreplicating plasmid vectors in short-term transfections of cultured animal cells. Unlike transcriptional enhancer elements, IVS2 failed to increase stable RNA production when it was placed downstream of the polyadenylation site. Using a plasmid vector system to survey different inserted sequences for their dependence on introns for expression, we found that the presence of IVS2 stimulated the expression of these sequences 2- to 500-fold. Sequences from the transcribed region of the herpes simplex virus thymidine kinase gene, a gene that lacks an intervening sequence, permitted substantial intron-independent expression (greater than 100-fold increase) in the plasmid vector system.

Animals↗
PubMed1988

Epstein-Barr virus shuttle vector for stable episomal replication of cDNA expression libraries in human cells.

Efficient transfection and expression of cDNA libraries in human cells has been achieved with an Epstein-Barr virus-based subcloning vector (EBO-pcD). The plasmid vector contains a resistance marker for hygromycin B to permit selection for transformed cells. The Epstein-Barr virus origin for plasmid replication (oriP) and the Epstein-Barr virus nuclear antigen gene have also been incorporated into the vector to ensure that the plasmids are maintained stably and extrachromosomally. Human lymphoblastoid cells can be stably transformed at high efficiency (10 to 15%) by such plasmids, thereby permitting the ready isolation of 10(6) to 10(7) independent transformants. Consequently, entire high-complexity EBO-pcD expression libraries can be introduced into these cells. Furthermore, since EBO-pcD plasmids are maintained as episomes at two to eight copies per cell, intact cDNA clones can be readily isolated from transformants and recovered by propagation in Escherichia coli. By using such vectors, human cells have been stably transformed with EBO-pcD-hprt to express hypoxanthine-guanine phosphoribosyltransferase and with EBO-pcD-Leu-2 to express the human T-cell surface marker Leu-2 (CD8). Reconstruction experiments with mixtures of EBO-pcD plasmids demonstrated that one clone of EBO-pcD-hprt per 10(6) total clones or one clone of EBO-pcD-Leu-2 per 2 x 10(4) total clones can be recovered intact from the transformed cells. The ability to directly select for expression of very rare EBO-pcD clones and to then recover these episomes should make it possible to clone certain genes where hybridization and immunological screening methods are not applicable but where a phenotype can be scored or selected in human cell lines.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1988

Cloning and characterization of a cDNA encoding human galactose-1-phosphate uridyl transferase.

We report the cloning and characterization of a cDNA that encodes a functional human galactose-1-phosphate uridyl transferase (GALT). The cDNA is 1400 bases in length and encodes a 43,000 Mr protein. The cloning strategy involved the identification of short peptide sequences conserved between the homologous enzymes from Escherichia coli and yeast, and the construction of oligonucleotide pools corresponding to the conserved patches. These patches of conserved amino acids tend to be conserved in humans as well.

Amino Acid Sequence↗
PubMed1988

Complications of prophylactic argon laser treatment of retinal breaks and degenerations in 2,000 eyes.

The decision to treat retinal breaks and degenerations prophylactically should be made with an awareness of the incidence of complications associated with argon laser photocoagulation (ALP). We evaluated retrospectively 2,000 eyes with retinal breaks and degenerations treated with ALP, with follow-up from 6 to 84 months (mean 46 months). The only complications during photocoagulation were petectal intra- and preretinal hemorrhages, which absorbed after a few days. Complications after treatment were limited to epiretinal membrane formation in the macular area in four eyes (0.2%). The applied laser energy in three of these four eyes was significantly greater (mean 34.4 mJ) than in the total 2,000 eyes (mean 7.2 mJ). This finding supports the observation by other authors that extensive photocoagulation is associated with an increased incidence of epiretinal membrane formation.

Follow-Up Studies↗
PubMed1987

Electroporation for the efficient transfection of mammalian cells with DNA.

A simple and reproducible procedure for the introduction of DNA into mammalian cells by electroporation is described. The parameters involving the cells, the DNA, and the electric field are investigated. The procedure has been applied to a broad range of animal cells. It is capable of transforming more than 1% of the viable cells to the stable expression of a selectable marker.

Acetyltransferases↗
PubMed1987

Identification and characterization of cDNA clones encoding two homologous proteins that are part of the asialoglycoprotein receptor.

The asialoglycoprotein receptor (ASGP-R) from rat liver contains the following three distinct protein species when it is analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis: RHL1 (42 kilodaltons), RHL2 (49 kilodaltons), and RHL3 (54 kilodaltons). In this paper we describe the isolation of cDNA clones encoding RHL1 and RHL2 from a cDNA library constructed from rat liver mRNA. A comparison of the predicted coding sequence for RHL2 with that for RHL1 showed that these sequences are highly homologous. The library also contained numerous cDNA clones for both RHL1 and RHL2 that were derived from unspliced precursor mRNAs. Differential splicing at the 5' end of the RHL1 transcript was inferred from the finding that two different types of RHL1 cDNA were identified, each having a different 5' terminus.

Amino Acid Sequence↗