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Biomedical subjects

M Kessel

Publications and source records attributed to M Kessel.

At least 91 records · Page 5Linked to original sources
PubMed1988

Three-dimensional structure of the regular surface glycoprotein layer of Halobacterium volcanii from the Dead Sea.

A three-dimensional reconstruction from electron micrographs of negatively stained cell envelopes of Halobacterium volcanii has revealed the structure of the surface glycoprotein to a resolution of 2 nm. The glycoprotein is arranged on a p6 lattice with a lattice constant of 16.8 nm. It forms 4.5 nm high, dome-shaped, morphological complexes with a narrow pore at the apex opening into a ;funnel' towards the cell membrane. The polarity of the structure was derived from freeze-etching experiments and ;edge' views. Six radial protrusions emanate from each morphological complex and join around the 3-fold axis to provide lateral connectivity. Using the primary structure of the surface glycoprotein of the closely related species Halobacterium halobium (Lechner and Sumper, 1987) and the cell envelope profile from a previous X-ray analysis of the same species (Blaurock et al., 1976) we have integrated our reconstruction into a model of halobacterial cell envelope.

Journal Article↗
PubMed1988

The cell wall structure of a magnesium-dependent halobacterium, Halobacterium volcanii CD-2, from the Dead Sea.

Cell wall preparations from the magnesium-dependent halophilic bacterium, Halobacterium volcanii, were studied by high-resolution electron microscopy complemented with image analysis and processing. For ultrastructural studies, specimens were prepared by a variety of methods, including negative staining, and metal shadowing after air-drying, freeze-drying, or freeze-fracturing and etching. All methods revealed the cell wall to be composed of a near-hexagonal lattice of unit cells having a center-to-center spacing of 15.5 nm. While negatively stained samples yielded two types variably revealed the unit cell to be composed of six protomers surrounding a central mass depression. This low-resolution unit cell morphology appears very similar to that of other bacterial cell wall S-layers studied to date.

Cell Wall↗
PubMed1988

Coding sequence and expression of the homeobox gene Hox 1.3.

We have characterized Hox 1.3 (previously described as m2), a murine homeobox-containing gene, which is a member of the Hox 1 cluster located on chromosome 6. A cloned cDNA was isolated from an Okayama-Berg library generated from the chemically transformed cell line MB66 MCA ACL6. The protein sequence of 270 amino acids was deduced from the nucleotide sequence of an open reading frame containing the homeobox. The open reading frame is interrupted at the genomic level by a 960 bp intron and is organized in two exons. The Hox 1.3 protein was found to contain extensive sequence homology with the murine homeodomain protein Hox 2.1, which is encoded on chromosome 11. There are two homology with the regions in the first exon, i.e. a hexapeptide conserved in many homeobox-containing genes and the N-terminal domain, which was found to be homologous only to Hox 2.1. Furthermore, in exon 2 the homologies of the homeodomain regions are extended up to the carboxy terminus of Hox 1.3 and Hox 2.1. During prenatal murine development, maximal expression of Hox 1.3 is observed in 12-day embryonic tissue. The two transcripts carrying the Hox 1.3 homeobox are 1.9 kb and about 4 kb in length. An abundant Hox 1.3-specific 1.9 kb RNA is also found in F9 cells which were induced for parietal endoderm differentiation, whereas F9 teratocarcinoma stem cells do not stably express this specific RNA. Induction of the transcript occurs immediately after retinoic acid/cAMP treatment and the RNA level remains high for 5 days. Thus, the kinetics are different from the previously described homeobox transcripts Hox 1.1 and Hox 3.1. Interestingly, by analogy to the F9 cell system a negative correlation between transformation and Hox 1.3 expression is observed in 3T3 fibroblasts also. Untransformed 3T3 cells carry abundant 1.9 kb Hox 1.3 RNA, whereas the methylcholanthrene-transformed MB66 and LTK- cells or 3T3 cells transformed by the oncogenes src, fos or SV40 T antigen express only low levels.

Amino Acid Sequence↗
PubMed1987

Unemployment and child abuse.

The employment state of men living in the homes of children at the time that child abuse was diagnosed was determined. The series included a wide range of abuse, including non-accidental injury, failure to thrive, neglect, and emotional deprivation. Two cohorts of children seen during 1974-9 and 1980-5 were compared; these periods were chosen because a large increase in unemployment began in Sheffield in 1980. Although the proportion of the men without work was significantly increased during the second period, this increase could not be ascribed to the rise in either long term or short term unemployment among those who had previously been in regular employment. It was accounted for by a rise in the proportions of single parent families and families in which the resident man had never had regular employment. This may reflect an increase in pregnancies among young mothers. There was no evidence to support the belief that the loss of a job in otherwise stable families leads to an increase in child abuse.

Child↗
PubMed1987

Primary structure and nuclear localization of a murine homeodomain protein.

The murine homeobox Hox 1.1 (m6) is the first of a cluster of six boxes on chromosome 6. Using probes and synthetic peptides derived from the Hox 1.1 sequence, we were able to isolate cDNAs and antibodies that allowed us to characterize the product of this homeobox-containing gene. From the open reading frame on the cDNA clone B21, a protein could be predicted, made up of 229 amino acids and having a calculated molecular weight of 25,740. A unique feature of this protein is that it has 15 glutamic acid residues as its carboxyl terminus, which gives it a very hydrophilic and acidic carboxyl terminal structure, most probably folding onto an alpha-helix. A second domain of six amino acids is present on the Hox 1.1 protein, which is conserved in other homeodomain proteins. Antibodies generated against synthetic peptides from the homeobox region were used in the immunoblotting procedure and revealed a major protein band of Mr 31,000 in extracts from 3T3 cells and F9 teratocarcinoma cells induced by retinoic acid and cAMP. The nuclear location of the protein was established by immunofluorescence. The presence of this protein in F9 cell nuclei is in faithful accordance with the kinetics established for the 2.4-kilobase Hox 1.1 transcript during differentiation into parietal endoderm cells.

Amino Acid Sequence↗
PubMed1987

Dialyzer membranes: effect of surface area and chemical modification of cellulose on complement and platelet activation.

Using an ex vivo model, the effects of membrane composition and surface area on both the complement system (as reflected by plasma C3a levels) and platelets [as indicated by plasma concentrations of thromboxane B2 (TXB2) and platelet factor 4 (PF4)] were studied. In this model, polyacrylonitrile (PAN) was associated with less complement activation than cuprammonium cellulose (CC). A new "modified cellulose" (MC) membrane, in which a small number of the free hydroxyl groups on cellulose are substituted with a tertiary amino compound, was also associated with a low degree of complement activation, similar to that with PAN. However, the extent of hydroxyl group substitution in four MC membrane subtypes did not correlate with the reduction in complement activation. In studies using CC, the amount of generated C3a correlated with the membrane surface area, although the relationship was curvilinear. Plasma concentrations at the "dialyzer" outlet of TXB2 and PF4 were similar with CC, PAN, and MC. In studies with the MC subtypes, increasing the extent of hydroxyl group substitution paradoxically increased, albeit slightly, the amount of TXB2 generation. In studies with CC, a linear relationship between membrane surface area and TXB2 generation was found. The results suggest a dissociation between platelet and complement effects among different dialyzer membranes, and underline the importance of membrane surface area.

Acrylic Resins↗
PubMed1987

Effects of blood-dialyser interaction on prostaglandins in uraemic patients and in healthy man.

The present study examines extracorporeal prostaglandin production during routine and simulated haemodialysis in healthy volunteers. The roles of dialyser membranes and alcohol washing procedures were investigated. The source of extracorporeal prostaglandin E2 was estimated by a specific platelet cyclo-oxygenase antagonist. Extracorporeal thromboxane production, with and without antagonist, was compared in an attempt to substantiate the role of the cyclo-oxygenase pathway by sources other than platelets. Clinical investigations show that prostaglandin liberation in the extracorporeal bloodstream is detectable. Additionally, laboratory results suggest an association between the type of dialyser membrane and extracorporeal prostaglandin release. The amount of prostaglandin E2 was reduced when dialysers were pre-washed with alcohol. Furthermore, it was experimentally possible to determine that a large part of extracorporeal prostaglandin E2 is released by sources other than platelets, suggesting a possible role of monocytes in extracorporeal prostaglandin production.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

The structure of the stalk surface layer of a brine pond microorganism: correlation averaging applied to a double layered lattice structure.

The surface layer of the stalk of a prosthecate halophilic microorganism is a periodic array (space group p3m1) comprised of electron dense trimers with a centre to centre spacing of 9.0 nm. The structure is reminiscent of E. coli porin. We have demonstrated that the method of correlation averaging can be effectively used to separate overlapping lattices, and that this results in a higher fidelity reconstruction, when compared to the established method of Fourier filtration. Two statistical methods are used to determine the resolution of the correlation average as a function of the number of 'windows' averaged. (i) The phase residual of spatial frequencies in Fourier space is computed between independently obtained subaverages, and (ii) a new method of Q factor analysis examines the cumulative vector sum in Fourier space as a function of the number of windows averaged. Both methods give a resolution of 1/2.1 nm-1.

Bacteria↗
PubMed1985

Nucleotide sequence analysis and enhancer function of long terminal repeats associated with an endogenous African green monkey retroviral DNA.

The nucleotide sequence and enhancer activity of the long terminal repeats (LTRs) associated with a cloned endogenous African green monkey (AGM) retroviral DNA designated as lambda-AGM-1 was studied. A unique feature of the endogenous AGM proviral LTRs was the presence of multiple copies of two types of directly repeating units in the U3 region: 16 8-base-pair (bp) repeats were present in the 5' LTR and 12 were present in the 3' LTR which were bound by a 6-bp perfect direct repeat; tandem duplication of a 32-bp sequence resulted in 3.5 copies in the 5' LTR and 2.5 copies in the 3' LTR. Nucleotide sequence homology was seen between the 8-bp direct repeats located in the AGM proviral LTRs and a 10-bp repeat unit of the deca-satellite present in AGM cellular DNA. The 32-bp repeats of the AGM proviral LTRs contained sequences which were related to the SV40 21-bp repeats and to the "core" of the SV40 72-bp enhancer element. Furthermore, the AGM provirus was distinct from known infectious retroviruses due to the presence of a primer-binding sequence complementary to the 3' terminus of mammalian tRNAGly. Functional analysis of the 3' LTR present in lambda-AGM-1 DNA by chloramphenicol acetyltransferase assay demonstrated enhancer activity associated with the 32-bp direct repeats. Sequences outside the 32-bp unit were necessary for full activator function, suggesting the presence of multiple enhancer domains in the AGM provirus.

Acetyltransferases↗
PubMed1985

Haemodynamic state in severe chronic renal failure. Pathophysiological aspects of cardiovascular function and the importance of bicarbonate dialysis.

Patients with chronic renal failure were investigated, immediately before dialysis and during haemodialysis for central and systemic haemodynamic parameters. The treatment used was changed from acetate to bicarbonate dialysis. Additionally, acid-base values were assessed and continuous long-time electroencephalographic monitoring was performed. As the severity of the cardiac dysfunction is a decided contributory determinant of the quality of dialysis, we have turned our attention to the changes in cardiac and circulatory function during the predialysis phase and the best method of treating them.

Acetates↗
PubMed1985

Ex vivo model for pre-clinical evaluation of dialyzers containing new membranes.

The ex vivo model which reflects hemodialysis modulating factors during the first twenty minutes of blood membrane interaction, is applicable as a pre-clinical test for new membranes. The biocompatibility of a new cellulosic membrane (MC) proved to be superior to regenerated cellulose and comparable to synthetic membranes such as PAN regarding complement activation.

Cellulose↗
PubMed1984

Flagella and motility behaviour of square bacteria.

Square bacteria are shown to have right-handed helical (RH) flagella. They swim forward by clockwise (CW), and backwards by counterclockwise (CCW) rotation of their flagella. They are propelled by several or single filaments arising at several or single points on the cell surface. When there are several filaments a stable bundle is formed that does not fly apart during the change from clockwise to counterclockwise rotation or vice versa. In addition to the flagella attached to the cells, large amounts of detached flagella aggregated into thick super-flagella, can be observed at all phases of growth.

Bacteria↗
PubMed1984

Modulation of enhancer activity by the hormone responsive regulatory element from mouse mammary tumor virus.

Addition of the transcriptional enhancers present in the U3 region of the Harvey murine sarcoma virus (HaMuSV) long terminal repeat (LTR) to recombinant chimeras in which the HaMuSV transforming gene (Ha-v-ras) is expressed from the mouse mammary tumor virus (MMTV) promoter increases the ability of the MMTV v-ras chimeras to transform mouse fibroblasts in culture 50- to 100-fold. Significant stimulation of transfection efficiency occurs only when glucocorticoids are present in the culture medium. Glucocorticoids also elevate the steady-state concentration of MMTV-initiated v-ras mRNA in cell lines isolated from these transfections, and MMTV-v-ras fusion transcripts are initiated at the normal MMTV cap site; potential cryptic initiation events associated with the enhancer could not be detected. The ability of the enhancer to increase the transcriptional activity of the MMTV promoter was also studied in acute transfection assays where expression of the chloramphenical acetyl transferase (CAT) gene is driven by the MMTV promoter. In this system the strong positive effect on MMTV transcription is again obtained only when the cells are hormone treated. These experiments indicate that the hormone-regulatory region is capable of modulating the function of an exogenously introduced enhancer element.

Acetyltransferases↗