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Biomedical subjects

H Erickson

Publications and source records attributed to H Erickson.

14 recordsLinked to original sources
PubMed1996

Articular chondrocyte tenascin-C production and assembly into de novo extracellular matrix.

Tenascin-C is an oligomeric glycoprotein of the extracellular matrix that is expressed in a variety of processes including development, tissue remodeling, wound healing, cell adhesion/antiadhesion, and cell/matrix interactions. Tenascin has recently been acknowledged as a component of the extracellular matrix of articular cartilage, but its function remains unclear. In this study, bovine articular chondrocytes were grown in alginate beads for 35 days to examine the kinetics of tenascin synthesis and incorporation into de novo extracellular matrix. During the culture period, 6 harvest days were established in which culture medium was recovered, alginate beads were dissociated with an EDTA solution, and chondrocytes were collected and lysed by sonication. Total DNA determination performed on the cell lysates demonstrated chondrocyte survival and proliferation. Western blotting performed on the medium, EDTA/alginate, and lysate samples demonstrated the production of both the 220 and 320 kDa tenascin size variants and their differential compartmentalization within the culture system. Tenascin was incorporated into the alginate bead matrix at a constant rate of 3.8 micrograms/day. The 320 kDa variant was produced in higher quantity, but the 220 kDa fragment was twice as likely to be incorporated into the de novo matrix. Methylene blue/acid fuchsin staining and tenascin immunohistochemistry demonstrated the incorporation of tenascin into a progressively expanding matrix surrounding the chondrocytes. The results suggest a role for tenascin in the assembly of the chondrocyte matrix and as a soluble mediator of chondrocytes with possible diverse functions for the tenascin size variants.

Animals↗
PubMed1995

Single-headed myosin II acts as a dominant negative mutation in Dictyostelium.

Conventional myosin II is an essential protein for cytokinesis, capping of cell surface receptors, and development of Dictyostelium cells. Myosin II also plays an important role in the polarization and movement of cells. All conventional myosins are double-headed molecules but the significance of this structure is not understood since single-headed myosin II can produce movement and force in vitro. We found that expression of the tail portion of myosin II in Dictyostelium led to the formation of single-headed myosin II in vivo. The resultant cells contain an approximately equal ratio of double- and single-headed myosin II molecules. Surprisingly, these cells were completely blocked in cytokinesis and capping of concanavalin A receptors although development into fruiting bodies was not impaired. We found that this phenotype is not due to defects in myosin light chain phosphorylation. These results show that single-headed myosin II cannot function properly in vivo and that it acts as a dominant negative mutation for myosin II function. These results suggest the possibility that cooperativity of myosin II heads is critical for force production in vivo.

Amino Acid Sequence↗
PubMed1995

Cardiovascular, respiratory and metabolic effects of interval training at VLA4.

The purpose of this study was to determine if training with short intervals at the velocity producing a lactate level of 4 mmol/l (VLA4) is sufficient to induce adaptations and better exercise tolerance. Five Standardbred mares (4-8 years) were interval trained on a treadmill 3 days a week for 12 weeks and subsequently detrained for 4 weeks. Standardized exercise tests were performed before, during and after the training period and muscle biopsies were taken. Measurements were made of heart rate, oxygen consumption, stride frequency, blood volume and blood lactate. Plasma volume was reduced after 2 weeks of training but then increased to the approximate pre-training value throughout the remaining training and post-training periods. No change was detected in the total cell volume whereas the total blood volume varied in consequence with the plasma volume variation. A significant reduction in heart rate response to exercise was seen after 4 weeks of training. VLA4 increased after 2 weeks of training and remained higher than the baseline value during the rest of the training period. Consequently, the blood lactate at 8 m/sec was decreased compared to baseline concentration after 8 and 12 weeks of training. The post-training VLA4 did not differ significantly either from the end of training or from the pre-training value. Mass specific oxygen consumption (VO2-200/BW) at V200 increased with training and decreased with detraining. The respiratory quotient at a velocity of 8 m/sec decreased from 1.18 +/- 0.02 before training to 1.07 +/- 0.02 (P < 0.05) at the end of training. No changes were found in muscle histo- or biochemical parameters. The results indicate that training at VLA4 is sufficient to cause adaptational changes in exercise tolerance related parameters.

Animals↗
PubMed1995

Body weight, heart weight, and heart-to-body weight ratio in greyhounds.

Heart and body weights were obtained from 230 Greyhounds during necropsy. Sex and age were recorded for each Greyhound. Twenty-nine racing and 21 nonracing Greyhounds among the 230 dogs were compared. Heart-to-body weight ratio was calculated. Statistical analysis was done to determine the effects of age, sex, and racing on heart and body weights and heart-to-body weight ratio. In adult Greyhounds, mean +/- SD body weight was 28.4 +/- 3.1 and 31.5 +/- 2.8 kg, heart weight was 355.6 +/- 52.8 and 381.4 +/- 50.8 g, and heart-to-body weight ratio was 1.3 +/- 0.2 and 1.2 +/- 0.2% for females and males, respectively. Heart and body weights were significantly different between sex and age groups and among nonracing and racing males. However, heart-to-body weight ratio was not significantly different among age, sex, or racing groups.

Aging↗
PubMed1993

Ventral tegmental microinjections of quinpirole decrease ethanol and sucrose-reinforced responding.

The effects of microinjections in the ventral tegmental area (VTA) of the dopamine D2/D3 agonist quinpirole on ethanol- and sucrose-reinforced responding were tested. Two groups of Long-Evans rats were trained to lever press on a fixed-ratio 4 schedule with 10% ethanol (v/v) (n = 8) and 75% sucrose (w/v) (n = 10) presented as the reinforcer. Weekly bilateral injections of quinpirole were tested in the ethanol group (0.0, 0.001, 0.01, 0.1, and 1.0 micrograms/microliters) and sucrose group (0.0, 0.01, 0.1, 1.0, and 10.0 micrograms/microliters). Quinpirole dose dependently decreased ethanol- and sucrose-reinforced responding, but the dose-effect curve for sucrose was shifted two orders of magnitude to the right of the ethanol curve. Temporal response patterns during control sessions for both reinforcers were characterized by initial high rates that terminated after approximately 10 min. VTA injections of quinpirole dose dependently delayed the onset of the first response and the initial high rate period, and resulted in an early termination of responding following onset. These data support the hypothesis that dopamine activity in the VTA is involved in the regulation of ethanol-reinforced responding in a manner similar to that of other reinforcers.

Animals↗
PubMed1990

Mobilizing self-care resources: a nursing intervention for hypertension.

This study was undertaken to assess the potential for mobilizing self-care resources in 10 persons with hypertension. Modeling and role-modeling theory provided the conceptual base for the experimental group. Ten persons with hypertension were matched with a comparison group. The results provide some evidence that theoretically sound nursing interventions can assist clients to mobilize self-care resources needed to enhance their well-being. Although further research with larger, randomly assigned samples is indicated, these findings suggest that nursing the person rather than the symptom might help people with hypertension contend with stressors, reduce stress, and deal with loss and grief.

Adaptation, Psychological↗
PubMed1988

Enhancer-origin interaction in plasmid R6K involves a DNA loop mediated by initiator protein.

Initiation of DNA replication from ori beta of plasmid R6K requires the presence of the ori gamma sequence in cis. We demonstrate that binding of initiator protein to the seven strong, tandem binding sites in gamma increases binding of the protein at the very weak binding site present in ori beta by cooperativity at a distance. The gamma-beta interaction via the initiator results in a DNA loop, as revealed by the novel technique of cyclization enhancement and as confirmed by exonuclease III protection, electron microscopy, and chemical footprinting. The protein-mediated gamma-beta interaction in vitro suggests that the cooperative interaction of gamma-bound protein with the beta sequence by DNA looping is an early step in the initiation of DNA replication at the beta origin of R6K.

Allosteric Regulation↗
PubMed1988

Detection of DNA looping due to simultaneous interaction of a DNA-binding protein with two spatially separated binding sites on DNA.

We describe different and relatively rapid biochemical techniques to detect protein-mediated DNA looping. These techniques, based on enhancement of DNA knotting and that of ligase-catalyzed cyclization, were used to show that the replication initiator protein of plasmid R6K can bring together two intramolecular gamma origin of replication sequences located as far apart as 2 kilobases. The site-site interaction causes looping out of the intervening DNA sequence as visualized by electron microscopy. Because the autoregulatory sequence of the initiator cistron also binds initiator protein, we investigated whether the gamma origin-bound protein can participate in autoregulation by interaction of the two sites through a protein bridge. We discovered that the two sites do not interact in vitro at their natural locations when on opposite faces of the double helix. Moving the two sites to the same face of the double helix by introducing a half turn into the intervening sequence allows protein-mediated site-site interaction to occur.

DNA Replication↗
PubMed1987

Evidence for a junctional feet-ryanodine receptor complex from sarcoplasmic reticulum.

Heavy sarcoplasmic reticulum vesicles, labelled with the Ca2+ release channel probe [3H]ryanodine, were solubilized in detergent, then centrifuged through sucrose gradients. A single peak of ryanodine binding activity was observed with an apparent sedimentation coefficient of 30S. Electron microscopy of the peak fraction showed disk structures of 25-28 nm diameter and 10 nm thickness. Proteins specifically enriched in the peak fraction were the Mr 160,000 and 260,000 and junctional feet proteins (Mr 320,000 and 300,000). This suggests that the feet proteins and ryanodine receptor may be specifically associated into a large oligomeric complex comprising subunits of Mr 160,000-320,000.

Alkaloids↗
PubMed1983

Coping with new systems.

The main purpose for the course was to facilitate students in adaptive growth producing changes. Feedback from students has indicated that they found the seminars very helpful. Group outcomes of the seminars were also noted. Of those students who participated in this project, several joined forces and organized the RN Council. This Council has been very influential in our school in the administration of the RN studies program. Most of these students have gone on for graduate education. This approach appears successful in enhancing continued growth. However, no systematic data have been collected about this intervention model. Sufficient interest has been generated in others so that a study is being developed and will be implemented in the new academic year. The purpose of this controlled study is to determine whether or not such a planned support group will facilitate goal attainment. Such data will add to the knowledge base of the nurse educator interested in the RN student, the RN student who returns to school, and peers who attempt to facilitate that process. In the meantime, the Old-Now-New You Process Model is being utilized to facilitate students, clients, and faculty in decision making in futuristic goal setting.

Adaptation, Psychological↗
PubMed1982

A model for assessing potential adaptation to stress.

The purposes of this study were to determine if hospitalized medical-surgical patients could be classified reliably according to their potential to adapt to stress; and to explore the relationship between their adaptive potential and length of hospital stay. Forty-six patients were selected for participation by use of a table of random numbers. Three classes of significantly different adaptive potential were identified: the Alarm and Impoverished states were considered as stress states, while the state of Equilibrium was considered a nonstress state. Although it was possible to distinguish stress from nonstress states, using only physiological parameters, psychological parameters were required to distinguish between the two stress states. The differentiation among the three coping states was used to predict subjects' potential for mobilizing adaptive resources. Length of hospitalization was then related to classification of adaptive potential.

Adaptation, Psychological↗
PubMed1980

Fibrin assembly: a comparison of electron microscopic and light scattering results.

To test the validity of a proposed two step fibrin assembly mechanism and directly visualize the molecular species present at various stages of fibrin formation, we have carried out an electron microscopic investigation. Assembly conditions duplicated those of a recent light scattering study and specimens were prepared at different time points with the use of a negative staining technique recently employed to visualize the trinodular structure of fibrinogen. Under near-physiological buffer conditions, protofibrils structurally similar to those postulated by Ferry have been found at early stages of fibrin assembly. In parallel with the light scattering results, a dramatic increase in fiber diameter was found in specimens prepared during the postulated lateral association stage of gelation. Light scattering and electron microscopic results both showed that high ionic strength reduces the rate and extent of fiber formation. Reptilase cleavage is shown to result in typical cross striated fibrin.

Batroxobin↗