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Biomedical subjects

R R Johnson

Publications and source records attributed to R R Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1995

Characterization of cDNA clones for differentially expressed genes in embryos of dormant and nondormant Avena fatua L. caryopses.

The molecular regulation of seed dormancy was investigated using differential display to visualize and isolate cDNAs representing differentially expressed genes during early imbibition of dormant and nondormant Avena fatua L. embryos. Of about 3000 cDNA bands examined, 5 cDNAs hybridized with mRNAs exhibiting dormancy-associated expression patterns during the first 48 h of inhibition, while many more nondormancy-associated cDNAs were observed. Dormancy-associated clone AFD1 hybridized with a 1.5 kb mRNA barely detectable in dry dormant and nondormant embryos that became more abundant in dormant embryos after 24 h of imbibition. Clone AFD2 hybridized with two mRNAs, a 1.3 kb message constitutively expressed in dormant and nondormant embryos and a 0.9 kb message present at higher levels in dormant embryos after 3 h of imbibition. Nondormancy-associated clones AFN1, AFN2 and AFN3 hybridized with 1.5 kb, 1.7 kb and 1.1 kb mRNAs, respectively, that were more abundant in nondormant embryos during imbibition. Expression patterns of some mRNAs in dormant embryos induced to germinate by GA3 treatment were different than water controls, but were not identical to those observed in nondormant embryos. DNA sequence analysis revealed 76% sequence identity between clone AFN3 and a Citrus sinensis glutathione peroxidase-like cDNA, while significant sequence similarities with known genes were not found for other clones. Southern hybridization analyses showed that all clones represent low (1 to 4) copy number genes.

Blotting, Northern↗
PubMed1995

Identification of Eimeria bovis merozoite cDNAs using differential mRNA display.

Differences in gene expression between Eimeria bovis sporozoites and first-generation merozoites were analyzed using the technique of differential mRNA display. Approx. 5% of the sequences detected in first-generation merozoites appear to be unique relative to sporozoites. Several of the bands corresponding to merozoite-specific gene expression were isolated and cloned. Northern blot analysis revealed that the cDNA fragments DMZ-7, DMZ-8 and NMZ-6 hybridized to mRNAs expressed at > 50-fold higher levels in merozoites relative to sporozoites. A fourth cDNA fragment, NMZ-4, hybridized to a mRNA expressed at 3-fold higher levels in merozoites. Further characterization demonstrated that expression of DMZ-8 in E. bovis-infected bovine cells begins as early as 12 h after sporozoite invasion and continues throughout the entire 14 days of first-generation schizogony. Sequence analysis of each of the four merozoite cDNAs failed to identify any significant similarity to any entries in the GenBank database, suggesting that these developmentally regulated genes may be unique to coccidian parasites.

Animals↗
PubMed1995

Computational properties of self-reproducing growing automata.

Living organisms perform much better than computers at solving complex, irregular computational tasks, like search and adaptation. Key features of living organisms, identified in the paper as a basis for their success in solving complex problems, are: self-reproduction of cells, flexible framework, and modification. These key features of living organisms are abstracted into a computational model, called growing automata. Growing automata are suited for extremely large computational problems, such as search problems. Growing automata are representatives of soft machines. Soft machines can change their physical structure as opposed to hard machines which have fixed structure. An example of a soft machine is a living organism, an example of a hard machine is an electronic computer. The computational properties of soft and hard machines are analyzed and compared. An analysis of growing automata demonstrates their advantages, as well as their limitations as compared to hard machines.

Computer Simulation↗
PubMed1994

Complex interactions at a GC-rich domain regulate cell type-dependent activity of the ornithine decarboxylase promoter.

Regulation of ornithine decarboxylase (ODC) is critical to the control of cellular growth, differentiation, and carcinogenesis. A GC-rich region in the ODC promoter contains two overlapping protein binding sites that interact to regulate basal level expression in some cell types. A perfect binding motif for transcription factor Sp1 (CCCCGCCCC) is located at nucleotides -114 to -106 relative to the site of transcriptional initiation, binds strongly to purified Sp1 protein, and forms several complexes when incubated with nuclear extracts. Only one of these complexes is recognized by Sp1-specific antibody. A new protein-binding motif (GCCCCTCCCC, located at -110 to -100) partially overlaps with the Sp1 site and analyses by DNase I protection showed that a new protein ("NF-ODC1") and the Sp1-like proteins interact with the ODC promoter in a mutually exclusive manner. Mutation of the NF-ODC1 binding motif strongly enhanced ODC promoter strength in some cell types, but had little or no influence in others. The effect of mutating the Sp1 site also varied with cell type. These cell type specificities did not correlate with the levels of Sp1 and NF-ODC1 binding activities in nuclear extracts. These results show that regulation of the ODC promoter by the Sp1 family is cell type-specific and modulated by a negative effector that we have termed NF-ODC1.

Animals↗
PubMed1994

Evidence for excitatory amino acid neurotransmitters in forward and feedback corticocortical pathways within rat visual cortex.

It is a commonly accepted notion that cells which make projections between the multiple cortical areas found in the mammalian visual system are excitatory, but there is little direct evidence that this is the case. Here we demonstrate using retrograde tracing with D-[3H]aspartate that connections in the rat which project from lower to higher visual areas (i.e. forward) and those which project from higher to lower areas (i.e. feedback) may use excitatory amino acid neurotransmitters. Following injection into the primary visual cortex, clusters of retrogradely labelled cells were found in several extrastriate areas within the cytoarchitectonic subdivisions 18a ('areas' LM, AL, PX, FLX, RL, AX) and 18b ('area' MX), and in the retrosplenial cortex. In all of these areas D-[3H]aspartate-labelled cells were surrounded by diffuse label which may represent anterograde labelling of axon terminals. This suggests that both legs of reciprocal intracortical circuits have similar chemospecificity. To directly demonstrate excitatory amino acid localization in forward projections, D-[3H]aspartate was injected into extrastriate area LM. As expected, the results revealed retrogradely labelled neurons within area 17. Outside area 17, LM injections labelled neurons in AL, PX, FLX, RL, AX and MX. Taken in the context of the hierarchy of areas in rat cerebral cortex (Coogan and Burkhalter, J. Neurosci., 13, 3749-3772, 1993), these results show that D-[3H]aspartate labels: (1) forward connections from area 17 to LM, AL, PX, RL, AX and MX, (2) feedback connections from LM, AL, FLX, PX, RL, AX and MX to area 17, (3) feedback connections from AL, PX, RL, AX and MX to LM, and (4) lateral connections between FLX and LM. These findings strongly indicate that both forward and feedback connections as well as lateral connections at several different levels of the cortical hierarchy use excitatory amino acid neurotransmitters.

Animals↗
PubMed1994

Impact of mammary grafts on coronary bypass operative mortality and morbidity. Department of Veterans Affairs Cardiac Surgeons.

The internal mammary artery is frequently used as a coronary artery bypass graft conduit because of superior long-term patency. The purpose of this study was to determine if there was also an advantage to the internal mammary artery in terms of operative mortality and morbidity. The Department of Veterans Affairs Cardiac Surgery Database was reviewed for two separate time periods, April 1987 through March 1989 and October 1990 through September 1991. During these periods, 14,172 patients underwent coronary artery bypass grafting. Univariate and multivariate logistic regression analyses were used to determine preoperative variables predictive of operative mortality and morbidity, with the independent variable of use of the internal mammary artery added to previously determined indicators. The total group was analyzed in risk quartiles according to expected mortality. Univariate analysis revealed an operative mortality of 6.8% in the early period and 6.5% in the latter period for the saphenous vein groups compared with 3.7% and 3.2%, respectively, for the internal mammary artery groups (p = 0.000). Multivariate analysis revealed an odds ratio of operative death with use of the internal mammary artery graft versus use of vein grafts of 0.78 during the first period and 0.72 during the second period, reductions of 22% and 28%, respectively. There were 29% and 37% reductions in the odds of operative mortality in the highest-risk quartile group of patients using the internal mammary artery graft. The odds ratio of developing mediastinitis with one internal mammary artery graft was 1.84 (p < 0.01) in the first time period and 1.11 in the second time period (p = not significant). However, with multiple mammary bypass grafts, the odds ratios were 3.70 (p < 0.01) and 2.96 (p < 0.01) in the respective time periods. On the basis of this study, it is concluded that internal mammary artery grafts in addition to providing superior long-term patency also decreased operative mortality after adjustment for patient risk factors. Use of the mammary artery does not consistently increase operative complications with the exception of mediastinitis when both internal mammary arteries are employed.

Analysis of Variance↗
PubMed1994

The Veterans Affairs Continuous Improvement in Cardiac Surgery Study.

The Department of Veterans Affairs Cardiac Surgery Consultants Committee is responsible for reviewing the quality of cardiac surgical treatment at the 43 Veterans Affairs cardiac surgical centers where these procedures are performed. It does so by reviewing both the unadjusted and risk-adjusted operative mortality data and the incidence of perioperative complications. These data are reviewed by the committee semiannually, and the overall summary and hospital-specific data are shared with the individual cardiac surgical program directors. Paper audits and site visits are performed when indicated by increased unadjusted and risk-adjusted operative mortality. Constructive criticism is shared with the program director and medical center administration. The relative risk of death for numerous patient risk factors has been estimated, and is now used in prospective clinical decision making. During the 7-year period that risk-adjusted outcomes have been utilized, there has been an overall significant reduction in the observed-to-expected operative mortality ratio. Although many factors could have contributed to this, including continually improving surgical techniques, it is also likely that part of this improvement has occurred because of the continuous feedback of these quality improvement data to our cardiothoracic surgeons and cardiologists.

Cardiac Surgical Procedures↗
PubMed1994

Developmental regulation of an Eimeria bovis mRNA encoding refractile body-associated proteins.

Eimeria bovis antigens defined by the monoclonal antibody (mAb) 2.4 are associated with the refractile bodies of sporozoites and are found in the parasitophorous vacuole and host cell cytoplasm during schizogony. Screening of an E. bovis oocyst cDNA library with mAb 2.4 resulted in the identification of a single unique cDNA sequence (Eb-25/50). Comparison of the predicted protein sequence of Eb-25/50 revealed a high degree of identity to an Eimeria tenella refractile body protein and mAb 2.4 was found to cross-react with refractile bodies from Eimeria acervulina, demonstrating that these proteins are highly conserved among eimerian species. Measurements of Eb-25/50 mRNA showed that the multiple proteins recognized by mAb 2.4 are encoded by a single mRNA species whose kinetics of expression during sporulation and schizogony closely correlated with protein expression. Consistent with multiple Eb-25/50 proteins arising from a single polypeptide, results from a Southern analysis of E. bovis genomic DNA indicated that Eb-25/50 mRNA is derived from a single copy gene. The presence of Eb-25/50 proteins in the host cytoplasm during schizogony, the high degree of conservation of these proteins, and the apparent complex post-translational modification raises interesting questions about the biochemistry of these proteins during eimerian development.

Amino Acid Sequence↗
PubMed1994

Two-staged breast reconstruction in patients with symptomatic macromastia requiring mastectomy.

Patients with symptomatic macromastia undergoing mastectomy for the treatment of malignant breast disease are candidates for a two-staged operation resulting in breast reconstruction and contralateral breast reduction. Five patients with symptomatic macromastia underwent a skin-sparing mastectomy for breast disease using a modified Wise incision. The first stage of the breast reconstruction was performed with a de-epithelialized transverse rectus abdominis musculocutaneous (TRAM) flap. Second-stage breast reconstruction was conducted 4 to 6 months later when revision of the TRAM reconstructed breast and concurrent contralateral breast reduction were performed with the intent of tailoring the reduced breast to approximate the revised TRAM breast mound. Excess areola from the reduced breast was harvested and used as a full-thickness graft to reconstruct the TRAM areola complex. Patients followed for 5 to 30 months postoperatively confirm resolution of macromastia symptoms, correction of the mastectomy defect, and symmetrical breast mound creation in a timely two-staged procedure. The two-staged breast reconstruction described represents an expedient plan for patients with symptomatic macromastia requiring mastectomy for breast disease. Skin-sparing mastectomy, modified Wise pattern incisions, utilization of usually discarded areola tissue, and creation of symmetrical breast mounds during the second stage of the reconstruction highlight the salient features of this patient management paradigm.

Adult↗
PubMed1993

Factors predictive of operative mortality among coronary artery bypass subsets.

As risk-adjusted outcome is increasingly being used to make clinical decisions and to assess and improve quality of care, it is important to develop simple, stable models for predicting outcome. Here we address the hypothesis that a risk factor for increased operative mortality at coronary artery bypass grafting may have differential effects in subgroups of patients defined by the presence or absence of other risk variables. We used a series of univariate and multivariate analyses to identify a group of ten patient-related preoperative characteristics independently predictive of operative death in the total population of 12,712 patients undergoing coronary artery bypass grafting at 43 Department of Veterans Affairs medical centers participating in the Department of Veterans Affairs Continuous Improvement in Cardiac Surgery Study. Separate logistic regression models were then developed for each of 14 clinically important subgroups defined by the presence or absence of seven risk variables. Odds ratios for operative death and estimated operative mortality were calculated from these subgroup regression models. Of 65 comparisons of pairs odds ratios of preoperative risk variables between the subgroups with and without a second risk variable, only five were found to be significant (p < 0.05 without adjustment for multiple comparisons); this is only slightly more than would be expected by chance alone. Risk factors for increased operative death appear to have similar odds ratios for subgroups of patients defined by a second risk variable. This finding greatly simplifies the use of predicted operative mortality in clinical decision making and quality assessment and improvement in coronary artery bypass grafting.

Aged↗
PubMed1993

Visualization of dendritic morphology of cortical projection neurons by retrograde axonal tracing.

Currently there is no reliable retrograde tracing technique for visualization of dendritic morphologies of projection neurons. Here we describe a simple and efficient method that can be used to label neurons in Golgi-like fashion. The approach relies on activity-dependent uptake of tracer. For this purpose we inject the glutamate receptor agonist N-methyl-D,L-aspartic acid (NMDA) at the tracer injection site to massively stimulate neurons and to thereby promote uptake of biocytin or biotinylated dextran amine (BDA) by axon terminals. The results show that co-injections of NMDA/biocytin and NMDA/BDA into the extrastriate lateromedial area (LM) of rat visual cortex labels large numbers of neurons in area 17 in Golgi-like fashion. Similarly injections of the lateral geniculate nucleus (LGN) lead to Golgi-like labeling of corticogeniculate neurons in area 17. The distribution of labeled neurons is highly topographic. In addition the method allows excellent preservation of ultrastructure, indicating that this approach is useful for determining the organization of neuronal circuits within the central nervous system.

Animals↗
PubMed1993

Partial mastectomy and breast reduction as a valuable treatment option for patients with macromastia and carcinoma of the breast.

The essential goals of every reconstructive procedure of the breast are to create a breast mound and establish symmetry. Breast conservation operation is now a widely accepted treatment for carcinoma of the breast. Four patients who presented with macromastia or mammary hypertrophy and a simultaneous carcinoma of the breast were treated by combined partial mastectomy and bilateral breast reduction. Incisions on the breast were made using standard Wise pattern (keyhole) markings. In each instance, the tumor was removed with a generous margin of normal surrounding mammary tissue. Two procedures used the inferior pedicle technique and two were done by resection and transplantation of the nipple. The average mammary tissue resection was 825 grams. All incisions healed primarily and necessary adjuvant chemoradiation was not delayed. Each patient is alive and well without evidence of disease with a follow-up period ranging from seven to 43 months. Postoperatively, the appearance of the breast is esthetically improved and all symptoms related to macromastia have resolved. Advantages of combining these two techniques include improved symmetry, easier postoperative self-examination of the breast and decreased radiation effect noted with larger breasts. Postoperative mammograms have been useful for patient follow-up evaluation. Combined segmental mastectomy and breast reduction represents a valuable treatment option for the patient who presents with macromastia and carcinoma of the breast. The carcinoma ablative procedure is not compromised and the improved symmetry of the breast has resulted in an excellent cosmetic outcome in these patients.

Adult↗
PubMed1992

Evidence for excitatory amino acid neurotransmitters in the geniculo-cortical pathway and local projections within rat primary visual cortex.

To examine the organization of axon collaterals of neurons that selectively take up and transport excitatory amino acids, we have used retrograde tracing with D-[3H]Aspartate after injections into different layers of rat primary visual cortex. The results show cells in the lateral geniculate nucleus retrogradely labeled from the cortex. Additional topographically precise input to the thalamic recipient layer 4 originates from neurons in the visual cortex lying in layers 2/3, 5 and 6. These inputs are reciprocated by point-to-point projections from layer 4. Layer 2/3 cells project to layers 5 and 6 in columnar fashion. Putative excitatory input to layer 2/3 originates from a vertical column of cells in layer 5 and the middle of layer 6. In addition layer 2/3 receives input via horizontal collaterals of topographically distant upper layer neurons, from more widespread projections in lower layer 6, and from very widespread projections of cells at the layer 5/6 border. Cells in the depth of layer 5 also distribute collaterals within layers 5 and 6. Our findings provide anatomical evidence that the geniculo-cortical pathway in the mammalian visual system may use excitatory amino acid transmitters. In addition, the results support the notion that most long range connections that link distant points of the topographic map are excitatory.

Animals↗
PubMed1992

Regulation of expression of proteinase inhibitor genes by methyl jasmonate and jasmonic Acid.

Gel electrophoretic analysis of the proteinase inhibitor proteins induced in tomato leaves by airborne methyl jasmonate (EE Farmer, CA Ryan [1990] Proc Natl Acad Sci USA 87: 7713-7716) revealed the new appearance of inhibitors I and II and two other, higher molecular mass proteins (63.5 and 87 kilodaltons). Northern analysis of methyl jasmonate-induced inhibitors I and II mRNAs in tomato (Lycopersicon esculentum) leaves, and of alfalfa trypsin inhibitor (a Bowman-Birk family inhibitor) mRNA in alfalfa (Medicago sativa) leaves, indicated that nascent inhibitor mRNAs were regulated in a manner similar to wounding, that is, at the transcriptional level. In tobacco (Nicotiana tabacum), transformed with a fused gene composed of the 5' and 3' regions of a wound-inducible potato inhibitor II and a chloramphenicol acetyl transferase (CAT) gene coding region, CAT activity was induced in leaves by methyl jasmonate, consistent with a transcriptional regulation of the inhibitor II gene. In tomato leaves, inhibitor I and II mRNAs and proteins accumulated in leaves distal to those exposed to methyl jasmonate or jasmonic acid to similar levels as in exposed leaves. We suggest that in response to wound signals generated by insect or pathogen attacks, linolenic acid is released into the cytoplasm from plant cell membrane lipids and is rapidly converted in cells to jasmonic acid (or perhaps a closely related derivative such as methyl jasmonate), which serves as a signal to regulate the expression of proteinase inhibitor genes.

Journal Article↗
PubMed1991

Bonding of plastic teeth to denture base resins.

This study evaluated the bond strengths of some new and traditional resin denture teeth and denture base resins. It included regular monolithic acrylic resin teeth (Bioform), monolithic acrylic resin-IPN teeth (Bioform IPN), and multilithic acrylic resin-composite resin teeth (Vivosit), with relatively new light-activated resin (Triad), conventional heat-cured resin (Lucitone 199), and autopolymerizing resin (Hygenic) denture base materials. The results of four-point flexure testing showed that the traditional materials gave the highest bond strength values. The autopolymerizing resin systems demonstrated interfacial failure with all resin denture teeth, showing that the common practice of treating teeth with the respective autopolymerizing monomer failed to produce adequate bond strength. Combinations of acrylic resin, IPN, and multilithic denture teeth with light-activated resins gave results calling for improvements in basic bonding system design, since interface debonding was prevalent. No failures occurred between the lap-ridge region of the multilithic tooth system and conventional heat-cured denture base resin.

Acrylic Resins↗
PubMed1991

Accelerator mass spectrometry: application to study of aluminum kinetics in the rat.

The advent of accelerator mass spectrometry (AMS) now permits the ultrasensitive detection of extremely long-lived isotopes, including 14C, 26Al, and 41Ca. Until now, tracer studies of aluminum kinetics have not been possible because aluminum has only two isotopes, with half-lives of 6.5 min (29Al) and 7 x 10(5) yr (26Al), neither of which is suitable for conventional studies. In a novel experiment we have employed AMS to study aluminum kinetics in a normal rat and a 5/6-nephrectomized rat over a 3-wk period of intravenous injection of a tracer dose of 26Al. Kinetics were similar in the two animals; approximately 75% of intravenously injected tracer 26Al was excreted in the urine in the first 24 h as was approximately 80% after 3 wk. Renal clearance of 26Al was approximately 0.75 ml.min-1.kg body wt-1 in both rats. The results clearly demonstrate the potential of this technique for isotope tracer studies in animals as well as in humans.

Aluminum↗
PubMed1989

Idiopathic punctate necrosis of the phalanges of the feet.

Small areas of discrete radiolucency surrounded by well-defined margins of sclerosis are incidental asymptomatic findings in the proximal phalanges of the feet, usually in young males. Histologic examination of similar lesions discovered in the feet of cadavers shows fat necrosis. Although the etiology of these lesions is as yet unproven, musculoskeletal stress is suggested.

Cadaver↗