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Biomedical subjects

K R Johnson

Publications and source records attributed to K R Johnson.

At least 145 records · Page 8Linked to original sources
PubMed1992

Genetic mapping of a new homeobox gene to mouse chromosome 7.

A newly identified homeobox gene designated Dbx has been mapped to mouse Chromosome (Chr) 7. This gene is expressed in a restricted manner in developing mouse brain and spinal cord and has amino acid sequence similarities with members of the homeobox gene family such as Drosophila H2.0 and mouse Hlx. Using a fragment of the Dbx cDNA as a probe, a PstI restriction fragment length polymorphism was used to determine genotypes of 144 progeny from an interspecific backcross. Segregation analysis revealed linkage of Dbx with six prepositioned reference loci on mouse Chr 7. No recombination was observed between Dbx and Odc-rs6, indicating that Dbx lies approximately 25 cM distal to the Chr 7 centromere in a region that has conserved linkage relationships with regions of human Chrs 11 and 19.

Animals↗
PubMed1992

Breaking the structuralist barrier. Literacy and numeracy with fluency.

Behavior analysis is an example of a selection science, and behavioral programs that follow the tenets of selectionism, long advocated by B. F. Skinner, can have a large impact on social problems. This article describes the characteristics of selection sciences and their application in the Morningside Model of Generative Instruction, which addresses both adult literacy and children's learning and attention problems. School curricula are analyzed for their key component elements and underlying tool skills. Teaching procedures then establish and build these key components to fluency. New and complex repertoires then emerge with little or no instruction, producing curriculum leaps that allow students to make rapid academic advancement. Children typically gain more than two grade levels per school year, and adults advance two grades per month.

Achievement↗
PubMed1991

Masticatory-stress hypotheses and the supraorbital region of primates.

The purpose of this study is to test various masticatory-stress hypotheses about the evolution and function of well-developed browridges of higher primates. This was done by measuring and analyzing patterns of in vivo bone strain recorded from three-element rosette strain gages bonded to the supraorbital region and to other portions of the bony face of Macaca fascicularis and Papio anubis during mastication and incision. The magnitude and direction of the principal strains recorded support Endo's hypothesis that the supraorbital region during mastication and incision is bent in the frontal plane (Endo, 1966). Our data do not, however, support his hypothesis that the supraorbital region is bent more during incision than during mastication. The data also demonstrate that overall levels of supraorbital strain are not larger in more prognathic subjects. Most importantly, the data indicate that the supraorbital region of nonhuman catarrhines is strained very little during mastication and incision. This indicates that there is much more supraorbital bone than is necessary both to counter masticatory loads and to provide an adequate safety factor to failure for these loads. This in turn suggests that the macaque and baboon browridges can be considerably reduced in size and still maintain these required structural characteristics. Thus, our experiments provide no support whatsoever for those hypotheses that directly link browridge morphology to masticatory stress (cf. Endo, 1966; Russell, 1983, 1985). A recent review of Endo's original work indicates that this latter statement is also true for humans (Picq and Hylander, 1989). We conclude, therefore, that there is no good reason to believe that enlarged browridges in living and/or fossil primates are structural adaptations to counter intense masticatory forces. The evolution of browridge morphology in primates is best explained on the basis of factors related to the position of the brain relative to the orbits (Moss and Young, 1960). When these structures are widely separated, as in gorillas, the large intervening space must be bridged with bone. In addition, enough bone must be present within the supraorbital and bridged regions to prevent structural failure due to non-masticatory external forces associated with highly active primates (e.g., accidental traumatic forces applied to the orbits and neurocranium). This requirement results in both pronounced browridges and in much more supraorbital bone than is necessary to counter routine cyclical stress during mastication and incision. This in turn explains why bone strains recorded from the supraorbital region are extremely small relative to other portions of the primate face during mastication and incision.

Animals↗
PubMed1991

Function of the supraorbital region of primates.

The purpose of this study was to test the hypothesis that the functional significance of well-developed brow-ridges in primates is to counter powerful masticatory forces during chewing and biting. This was done by measuring and analysing patterns of in vivo bone strain recorded from rosette strain gauges bonded to the supraorbital region of Macaca fascicularis (the crab-eating or long-tailed monkey) and Papio anubis (the olive baboon) during mastication and incision. It was found that the supraorbital region is strained relatively little during mastication and incision. This indicates that in macaques and baboons there is much more supraorbital bone than is needed to counter masticatory loads, which in turn suggests that their brow-ridges could be considerably smaller yet still counter masticatory stress without structural failure. Therefore, there is no good reason to believe that enlarged brow-ridges in living and/or fossil primates are structural adaptations to counter powerful masticatory forces.

Animals↗
PubMed1991

MP26, a protein of intercellular junctions in the bovine lens: electrophoretic and chromatographic characterization.

We have characterized the membrane protein of apparent molecular weight 26 kD from bovine lenses (MP26 or MIP) with respect to six different electrophoretic and chromatographic procedures. These include one- and two-dimensional gel electrophoretic procedures, as well as SDS-hydroxylapatite chromatography. The two-dimensional gels include isoelectric focusing with both conventional ampholytes and buffer focusing methods. With buffer focusing, the membranes are solubilized without the use of SDS and the isoelectric focusing is performed in the absence of SDS. As specific probes for MP26, a monoclonal antibody and an anti-MP26 rabbit serum were used, the latter prepared against electrophoretically purified MP26. These separation techniques were adapted to MP26 in order to permit a more detailed characterization of this protein and to search for any heterogeneity in this size range, specifically other junctional proteins or protein fragments. We have found evidence for charge heterogeneity in MP26, but no evidence for multiple membrane proteins of Mr 26,000 in urea-treated membranes. The charge heterogeneity appears to be related to a phosphorylation of MP26. The results reported here aid the interpretation of a variety of data, especially findings on the reconstitution of MP26 in artificial membranes and results from work with polyclonal MP26 antibodies. These investigations are all designed to evaluate the proposed role of MP26 as a protein of cell-to-cell channels in the lens fiber cell.

Animals↗
PubMed1991

Characterization of cDNA clones for the beta subunit of pyruvate dehydrogenase from Ascaris suum.

The pyruvate dehydrogenase complex occupies a unique position in the anaerobic mitochondrial metabolism of the parasitic nematode Ascaris suum. This paper describes cDNA clones for the beta subunit of the pyruvate dehydrogenase component of this complex. A cDNA library has been constructed in lambda gt11 from poly(A)+ RNA isolated from adult ascarid body wall muscle. The library was screened with antiserum prepared against the beta subunit of pyruvate dehydrogenase. Full-length clones of 1.2 kb have been characterized. The first 15 amino acids determined from the purified protein match exactly those predicted from the cDNA sequence. The deduced protein sequence contains a 26-amino-acid presequence that has characteristics of mitochondrial targeting sequences. The mature protein is predicted to contain 334 amino acids and is 62% identical to the predicted sequence of the corresponding human subunit. Full-length in vitro transcripts have been translated in vitro to yield a 39-kDa polypeptide consistent with the open reading frame present in the cDNA sequence. The 90 nucleotides at the 3' end of the cDNA sequence have the potential to form a cruciform structure that may play a role in the synthesis of the enzyme.

Amino Acid Sequence↗
PubMed1991

Detection of massive pulmonary embolus-in-transit by transesophageal echocardiography.

Pulmonary embolus-in-transit represents an important cause of morbidity and mortality in the critically ill patient. Unexplained shock and acute pulmonary hypertension were evaluated with echocardiography. Standard transthoracic echocardiography failed to identify a large embolism-in-transit that was easily visualized by transesophageal imaging. A review of the literature involving emboli-in-transit suggests that early intervention in these patients may be beneficial.

Adult↗
PubMed1990

A small-scale plasmid preparation yielding DNA suitable for double-stranded sequencing and in vitro transcription.

A small-scale plasmid preparation is described that is useful for a variety of procedures from double-stranded sequencing to in vitro transcription. No specialized equipment or reagents are required. The preparation of plasmid DNA does not require the use of RNase; instead the larger RNAs are precipitated with 2.5 M ammonium acetate. The resulting plasmid DNA is used routinely for double-stranded sequencing with the Klenow fragment of DNA polymerase and has been used for generating deletions with exonuclease III. In addition, the plasmid DNA has been used to generate transcripts with T7 RNA polymerase that translate well in reticulocyte lysate.

DNA↗
PubMed1990

Expression of mRNAs encoding mammalian chromosomal proteins HMG-I and HMG-Y during cellular proliferation.

The high mobility group chromosomal proteins HMG-I and HMG-Y are closely related isoforms that are expressed at high levels in rapidly dividing, undifferentiated mammalian cells. We analyzed HMG-I/Y mRNA levels at various cell cycle stages in murine NIH/3T3 fibroblasts partially synchronized by seeding from quiescent, contact-inhibited cultures. Flow microfluorometric analysis of DNA content demonstrated a comparable degree of synchronization in such seeded NIH/3T3 cell populations as is obtained by serum deprivation or other means and has the added advantage of avoiding the use of possibly detrimental inhibitors or metabolic starvation to induce such synchrony. We show that HMG-I/Y mRNA levels gradually increase in NIH/3T3 cells during the first 16 h after seeding (G0/G1 to late S phase), but thereafter remain constant, in contrast to the cell cycle-regulated expression of the histone H3 gene. Although there is a 6-fold increase in HMG-I/Y expression during the transition from quiescent to proliferating NIH/3T3 cells, there is a much greater difference in expression (15- to 50-fold) among different cell types, possibly related to their state of differentiation. The HMG-I/Y mRNAs appear to be very stable; there was no decrease in their levels 6 h after actinomycin D transcription termination. The proportion of HMG-I to HMG-Y mRNAs was greater in the human than in the murine cells examined, appeared to be greater in proliferating than in quiescent cells, and did not always correspond with the HMG-I to HMG-Y protein ratio.

Animals↗
PubMed1990

Parathyrin assay. An analytical evaluation of two commercial Immuno Radiometric Assay kits.

We have performed a comparative evaluation of two Immuno Radiometric Assay (IRMA) kits for parathyrin against an existing Radioimmuno Assay (RIA) technique for the measurement of intact parathyrin. The analytical evaluation which was performed in line with the ECCLS recommended kit evaluation protocol showed a marginal improvement in precision with the new assays. There was a substantial improvement in the theoretical limit of detection utilising the IRMA kits although it may prove difficult to realize this improvement in practice with individual samples because of differing protein matrices. The evaluation also demonstrated the degree of parallelism and range of linearity of both kits as well as inaccuracies when compared with the International Reference Preparation for parathyrin (IRP 79/500) as the accepted standard. The demonstration of lack of agreement between measured and kit assigned results for standards when cross-over studies between kits were performed may highlight a possible contributing factor to inaccuracy. Alternatively there may be a difference of antisera avidity within the kits for intact parathyrin. Whilst minor differences in sample stability were demonstrated between the kits, the sample stability was much improved compared to that for intact parathyrin measurement by RIA. The correlation studies showed a degree of correlation consistent with other comparisons similarly performed.

Dose-Response Relationship, Drug↗
PubMed1989

Evidence for a pretranslational defect in hereditary and acquired myeloperoxidase deficiency.

Myeloperoxidase (MPO) is a heme containing enzyme involved in the oxygen-dependent microbicidal activity of human polymorphonuclear leukocytes (PMN). Complete hereditary and acquired MPO deficiencies are defined as lack of peroxidase activity in PMN. Using this criterion, we studied a patient with complete hereditary MPO deficiency, and a MPO deficient variant cell line of HL-60 (HL-60-A7), which we used as a model for acquired MPO deficiency. Western blot analysis showed complete absence of mature and precursor protein of MPO both in PMN from the patient and in HL-60-A7 cells. PMN from both parents had one half of normal levels of these proteins. To study further the molecular basis of this defect, we isolated an intron specific probe for MPO and used it and a cDNA probe. Both normal human bone marrow cells and the promyelocytic HL-60 leukemia cells contained MPO mRNA species of 2.8, 3.3, approximately 4, and greater than 8 kilobase (kb). The transcripts of greater than 8 and approximately 4 kb contained sequences hybridizing to a probe specific for intron 7 of the MPO gene. Bone marrow cells of the MPO deficient patient contained two species of heterogeneous nuclear (hn) RNA of greater than 8 and approximately 4 kb, but only trace amounts of the normal sized 3.3 kb MPO mRNA and undetectable 2.8 kb MPO mRNA. HL-60-A7 cells contained both greater than 8 and approximately 4 kb hnRNA, but only small amounts of normal sized 2.8 kb MPO mRNA and undetectable levels of the 3.3 kb mRNA. Southern blot analyses revealed no gross alteration of the MPO gene in both cases. Our results suggest that a pretranslational defect is one mechanism leading to MPO deficiency.

Adult↗
PubMed1989

Sex linkage in salmonids: evidence from a hybridized genome of brook trout and Arctic charr.

In second-generation sparctics (Salvelinus fontinalis x Salvelinus alpinus) backcrossed to S. fontinalis, we have identified tight classical linkage of phenotypic sex with Ldh-1, Aat-5, and Gpi-3. We designate this locus Sex-1 and suggest that it may be the primary sex-determining locus in salmonids. Cumulative salmonid gene-to-centromere map distances for the three biochemical loci put the order as centromere--Ldh-1--(Aat-5 and Gpi-3), with the latter two loci being tightly linked. An absence of association of phenotypic sex (presumably Sex-1) with these same three loci and other loci known to be linked to these loci is shown in splakes (S. fontinalis x Salvelinus namaycush) and cutbows (Salmo gairdneri x Salmo clarki). These data imply that the linkage of Sex-1 with these loci is found only in S. alpinus and support the view that Sex-1 lies across the centromere from these three loci in S. alpinus, representing a Robertsonian fusion not found in any of the other four species. A similar specific Robertsonian fusion is argued for S. gairdneri, where Sex-1 may be linked across a centromere to another biochemical locus (Ha). These linkage results and chromosomal observations of other investigators suggest that Sex-1 lies on an information-depauperate arm.

Animals↗
PubMed1989

The relationship between masseter force and masseter electromyogram during mastication in the monkey Macaca fascicularis.

In five adult monkeys, electromyograms (EMGs) were recorded from bipolar surface electrodes positioned over the superficial masseter and from bipolar fine-wire electrodes within both the superficial and deep masseter. Relative masseter force was estimated by measuring surface bone strain from the lateral aspect of the zygomatic arch using rosette strain gauges. Multiple step-wise regression procedures demonstrated that peak values of the averaged masseter EMG could often explain a considerable amount of the variation of peak relative masseter force during mastication, i.e. r2 values ranged from 0.23 to 0.96 for the various single-electrode models and R2 values ranged from 0.78 to 0.96 for the various multiple-electrode models. The r2 values for relative masseter force and EMG data from the surface electrodes ranged from 0.69 to 0.96, and, on average, EMG data from surface electrodes provided somewhat more information about overall relative muscle force than data from fine-wire electrodes. The R2 values for a two-electrode model, consisting of data from surface electrodes over the superficial masseter and fine-wire electrodes in the posterior portion of the deep masseter, ranged from 0.78 to 0.95. The latency between the averaged surface EMG and relative muscle force was determined and the data indicated that the surface EMG usually preceded muscle force. This latency tended to decrease gradually throughout the entire power stroke of mastication. At peak values, the surface EMG preceded muscle force by about 22 ms. Towards the end of the power stroke, i.e. the 25% of peak values during unloading, muscle force may actually precede the average EMG.

Animals↗