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PubMed1988

A simple modular tissue bath developed for 'in vitro' studies of the isolated spinal cord.

A tissue bath for studies of the mammalian spinal cord in vitro is described. The modular construction of the bath permits considerable flexibility for accommodating different tissue preparations. The individual components of the bath are easily constructed and the design permits multiple compartment baths to be simply formed. The design principle on which the bath is based may have much wider application than that described.

Animals↗
PubMed1985

tRNA-rRNA sequence homologies: evidence for an ancient modular format shared by tRNAs and rRNAs.

Homologies between tRNAs and rRNAs are identified in searches using various combinations of Escherichia coli, yeast, Halobacterium volcanii and bovine mitochondrial sequences. As in previously reported comparisons, the homologies are too frequent and long to be attributed to coincidence, and similar frequencies from inter- and intraspecies comparisons preclude evolutionary convergence as an explanation. In contrast to the earlier studies, patterns in the positioning of the homologies are now described. Graphing the positions of the homologies along orthogonal axes that represent numbers of bases in tRNA and rRNA shows recurring patterns in the alignments. Preferred spacings of integral multiples of 9 bases are found, suggesting a periodicity in the ancestral structure from which the tRNAs and rRNAs were derived. The periodicity also suggests persistence of a modular format in both classes of molecules that survived changes in sequence that occurred during evolution. A model is proposed for the generation of the ancestral molecule and the early evolution of the coding mechanism. Elongation by self-priming and self-templating gave a hairpin with a 9 base stem. Two additional cycles gave a 70-80 base tRNA-like structure. Additional cycles yielded a tandem repeat of this unit, roughly equivalent in size to the combined rRNAs of prokaryotes. The larger RNA would contain the information and materials for generating the smaller RNAs. It is proposed that multiple recombination among such molecules gave composite structures, presumed progenitors of today's t- and rRNAs. The distribution of the conserved domains among today's species argues for the existence of the ancestral molecule prior to divergence of lines leading to the various kingdoms. Their presence in the different nucleic acids suggests the existence of a nucleic acid with multiple functions prior to partitioning of these functions among the nucleic acids that exist today. The occurrence of overlaps, overlays and consensus alignments among the homologies provides the means for identifying contiguous and neighboring conserved regions and holds promise for the reconstruction of the sequence of an ancestral molecule.

Animals↗
PubMed1990

Modular organization of the lytic enzymes of Streptococcus pneumoniae and its bacteriophages.

The nucleotide sequences of genes cpl7 and cpl9 of the Streptococcus pneumoniae bacteriophages Cp-7 and Cp-9, encoding the muramidases CPL-7 and CPL-9, respectively, have been determined. The N-terminal domains of CPL-7 and CPL-9 were virtually identical to that previously reported for the CPL-1 muramidase. The C-terminal domain of the CPL-7 muramidase, however, was different from those of the host amidase and the phage Cp-1 and Cp-9 lysozymes. Whereas all enzymes studied are characterized by repeated sequences at their C termini, the repeat-unit lengths are 20 amino acids (aa) in CPL-1, CPL-9 and in the host amidase, but 48 aa in CPL-7. Six repeated sequences represent the C-terminal domains of CPL-1, CPL-9 and the host amidase, and 2.8 perfect tandem repetitions that of CPL-7. The peculiar characteristics of the structure of CPL-7 muramidase correlate with its biochemical and biological properties. Whereas CPL-1, CPL-9 and the pneumococcal amidase strictly depend on the presence of choline-containing cell walls for activity, CPL-7 is able to degrade cell walls containing either choline or ethanolamine. These results support the previously postulated role for the C-terminal domain of these lytic enzymes in substrate recognition and provide further experimental evidence supporting the notion that the proteins have evolved by an exchange of modular units.

Amino Acid Sequence↗
PubMed1990

A modular set of lacZ fusion vectors for studying gene expression in Caenorhabditis elegans.

We describe a series of plasmid vectors which contain modular features particularly useful for studying gene expression in eukaryotic systems. The vectors contain the Escherichia coli beta-galactosidase (beta Gal)-encoding region (the lacZ gene) flanked by unique polylinker segments on the 5' and 3' ends, and several combinations of a variety of modules: a selectable marker (an amber suppressor tRNA), a translational initiation region, a synthetic intron segment, the early polyadenylation signal from SV40, and 3' regions from two nematode genes. A segment encoding the nuclear localization peptide from the SV40 T antigen is incorporated into many of the constructs, leading to beta Gal accumulation in nuclei, which can facilitate identification of producing cells in complex tissues. To make functional beta Gal fusions to secreted proteins, we constructed plasmids with an alternate module encoding a synthetic transmembrane domain upstream from lacZ. This domain is designed to stop transfer of secreted proteins across the membrane during secretion, allowing the beta Gal domain of the fusion polypeptide to remain in the cytoplasm and thus function in enzymatic assays. We have used the vectors to analyze expression of several genes in the nematode Caenorhabditis elegans, and have demonstrated in these studies that lacZ can be expressed in a wide variety of different tissues and cell types. These vectors should be useful in studying gene expression both in C. elegans and in other experimental systems.

Amino Acid Sequence↗
PubMed1989

A modular stopped-flow system for use in routine pharmaceutical analysis.

A modular stopped-flow system for routine pharmaceutical analysis is presented. It consists of an inexpensive stopped-flow module which is fitted to a spectrophotometer or spectrofluorimeter and controlled by a simple computer. The automatic technique developed with this system is suitable for the individual and simultaneous determination of various pharmaceuticals (anti-asthmatics, psychotropics, hormones, analgesics, anaesthetics and antiseptics) with satisfactory results.

Autoanalysis↗
PubMed1992

Interface corrosion of a modular head total hip prosthesis.

Wear and corrosion products released from metallic prosthetic joints can stimulate adverse reactions in the surrounding tissues that may eventually require revision of the prostheses. The authors report here a case of a modular total hip prosthesis removed after 35 months that showed evidence of corrosion and fretting at the Morse taper interface between the titanium alloy femoral stem and the cobalt-chromium ball.

Aged↗
PubMed1980

Modular teaching of cardio-pulmonary resuscitation for nursing service personnel.

Hospital accrediting agencies are becoming increasingly concerned that all nursing service personnel should be proficient in the administration of cardiopulmonary resuscitation. In response, our department had instituted a modular, self-learning CPR course, based on American Heart Association standards, which yields a high quality performance and decreases instruction time.

Hospital Bed Capacity, 500 and over↗
PubMed1992

Late disassembly of a modular acetabular component. A case report.

Disassembly of metal-backed acetabular components used for total hip arthroplasty is becoming more common in both preassembled and modular designs. This complication is usually associated with a dislocation of the femoral component or other radiographic evidence of dissociation. A case of late disassembly of the acetabular component without dislocation or radiographic evidence is presented. The authors believe this complication should be considered, along with infection and aseptic loosening, in all cases of late development of pain following total hip arthroplasty.

Adult↗
PubMed1989

Modular design of synthetic protein mimics. Characterization of the helical conformation of a 13-residue peptide in crystals.

The incorporation of alpha-aminoisobutyryl (Aib) residues into peptide sequences facilitates helical folding. Aib-containing sequences have been chosen for the design of rigid helical segments in a modular approach to the construction of a synthetic protein mimic. The helical conformation of the synthetic peptide Boc-Aib-(Val-Ala-Leu-Aib)3-OMe in crystals is established by X-ray diffraction. The 13-residue apolar peptide adopts a helical form in the crystal with seven alpha-type hydrogen bonds in the middle and 3(10)-type hydrogen bonds at either end. The helices stack in columns, zigzag rather than linear, by means of direct NH...OC head to tail hydrogen bonds. Leucyl side chains are extended on one side of the helix and valyl side chains on the other side. Water molecules form hydrogen bonds with several backbone carbonyl oxygens that also participate in alpha-helix hydrogen bonds. There is no apparent distortion of the helix caused by hydration. The space group is P2(1)2(1)2(1), with a = 9.964 (3) A, b = 20.117 (3) A, c = 39.311 (6) A, Z = 4, and dx = 1.127 g/cm3 for C64H106N13O16.1.33H2O. The final agreement factor R was 0.089 for 3667 data observed greater than 3 sigma(F) with a resolution of 0.9 A.

Crystallization↗
PubMed1990

Recognizing words and pictures in sentence contexts: a test of lexical modularity.

Words or pictures completed sentence fragments to form coherent or incoherent sentences. Subjects made lexical decisions about words and object decisions about pictures. Modality was blocked in Experiment 1 and mixed in Experiment 2. In both experiments there were similar effects of context for words and pictures, contrary to the hypothesis that lexical priming produces the sentence context effect. Mixed conditions produced longer response latencies than blocked conditions but did not interact with the context effect. The finding of no interaction between the effect of context and the mixed-blocked manipulation, supports a version of lexical modularity in which context effects arise as a function of post-access integration processing.

Adult↗
PubMedDate not supplied

Voltage-sensitive dyes reveal a modular organization in monkey striate cortex.

Voltage-sensitive dyes allow neuronal activity to be studied by non-invasive optical techniques. They provide an attractive means of investigating striate cortex, where important response properties are organized in two dimensions. In the present study, patterns of ocular dominance and orientation selectivity were obtained repeatedly from the same patch of cortex using the dye merocyanine oxazolone, together with current image-processing techniques. The patterns observed agree with most established features of monkey striate cortex and suggest a new unit of cortical organization; one that is modular in structure and which appears to link the organization of orientation selectivity with that of ocular dominance.

Animals↗
PubMed1990

The Oxford modular cataract image analysis system.

A modular system of acquisition and analysis of Scheimpflug, retro-illumination and fluorescence images of the in vivo human crystalline lens is described. Image analysis is directed towards the following goals: Scheimpflug slit-images are analysed for: (1) The optical density of nuclear cataract present; (2) The dimensions of the lens and the lenticular zones; (3) The curvatures of the lens and lenticular zones. Retro-illumination images are analysed for: (1) The percentage area which is occupied by cataract; (2) A combined measure (weighted integral) describing both the amount of cataract present and its optical density. Lenticular auto-fluorescence images are analysed for the mean density (fluorescence) of the lens as a whole. A pilot study of the repeatability of the methods is presented.

Cataract↗
PubMedDate not supplied

[An alternative treatment strategy in lumbar intervertebral disk damage using an SB Charité modular type intervertebral disk endoprosthesis].

At the Department of Orthopedics, Humboldt University School of Medicine, Charité Hospital, the three-piece disk endoprosthesis SB Charité of the modular type, which works according to the low-friction principle, has been developed combining the advantages of a beneficial effect on the patient's complaints by simultaneous distraction in the vertebral segment, and of achieving movement within the physiological range. So far, this disk endoprosthesis consisting of two cover plates made of implantat steel or titanium sheet, which are fixed without cement, as well as a moveable polyethylene sliding core being vertically adjustable, has been implanted in sixteen patients. The therapeutic results show that it is possible with this method to replace the nucleus pulposus, thus providing, in addition to conventional nucleotomy and segment fusion, another therapeutic alternative for lumbar disk lesions.

Adult↗
PubMed1985

Detection of a fundamental modular format common to transfer and ribosomal RNAs: second-order spectral analysis.

Second-order spectral analysis is used to detect rigorously and to characterize the principal periodicities in the positions of conserved sequences common to tRNAs and rRNAs. It is shown that the shared periodicity having the largest spectral amplitude is 9, followed by 8 and 10, thus forming a closed triad of significant multiplets centered at 9 bases. This conclusion is proposed to reflect a closed triadic set of fundamental tandem repeat lengths in a class of ancestral macromolecules possessing a restricted sequence symmetry. The terms "remanent" and "archeomodular" are used to describe a relic modular format, traces of which are shown here to persist despite the changes that have occurred in the primary structures of ribonucleic acids during the course of their evolution.

Animals↗
PubMed1990

Chimeric phage-bacterial enzymes: a clue to the modular evolution of genes.

Pneumococcal peptidoglycan amidase (N-acetylmuramoyl-L-alanine amidase, EC 3.5.1.28) and phage CPL1 lysozyme degrade a common substrate (choline-containing pneumococcal cell walls); the former hydrolyzes the bond between muramic acid and alanine, whereas the latter breaks down the linkage between muramic acid and glucosamine. The amino acid sequences of their C-terminal domains are homologous. Chimeric genes were constructed by site-directed mutagenesis: a unique SnaBI restriction site in the cpl1 gene, coding for the phage lysozyme, was introduced at a location equivalent to the SnaBI site present in the lytA gene, which codes for the pneumococcal amidase. The resulting genes expressed lytic activities at levels similar to those of the parental genes. The gene products, which have been purified to electrophoretical homogeneity, exhibited unusual combined biochemical properties--e.g., by exchange of protein domains, we have switched the regulatory properties of these enzymes without altering their catalytic activities. Chimeric gene construction in Streptococcus pneumoniae and its bacteriophages is an excellent model to study the modular organization of genes and proteins and to help to establish evolutionary relationships between phage and bacteria. These constructions provide an experimental approach to the molecular processes involved in cassette recruitment during evolution and contribute support to the concept of bacteria as adaptable chimeras.

Amino Acid Sequence↗
PubMed1991

A modular approach to multichannel magnetometry.

A 19-channel SQUID system for biomagnetic measurements has been developed. This system differs from standard instruments in its modular approach. Various gradiometers can be coupled to the SQUIDs, the cryogenic system allows the exchange of single channels and the electronics is based on a cassette system. Problems with thermal insulation, vibrations of the gradiometers and tilted gradiometer geometries are discussed and solutions are presented.

Equipment Design↗