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Biomedical subjects

N Carlson

Publications and source records attributed to N Carlson.

At least 19 recordsLinked to original sources
PubMed2002

Opening farm gates: community as educator.

This paper presents the experience of five undergraduate Bachelor of Nursing students who undertook a clinical practice placement in a rural community. This, our first engagement with nursing, was a profound learning experience. We did not expect the intense contributions the rural community as a whole would make to our understandings of rural health care in general, and rural nursing in particular. Initially, we felt like outsiders to the rural community as well as the profession of nursing. The interwoven nature of community relationships combined with our acute sense of being highly visible in the township led to us developing a sense of vulnerability. We believed we needed to portray a professional image during all social interactions with the community and this compounded our insecurities during the clinical placement. Before long, we found the rural population embracing and very supportive of our placement. However, we found ourselves questioning whether we would return to a rural community to work as nurses on the basis of our lack of privacy during this time.

Journal Article↗
PubMed2001

Neuronal nicotinic acetylcholine receptor expression by O2A/oligodendrocyte progenitor cells.

Oligodendrocyte precursor cells (O2A/OPC, A2B5(+)) were examined for expression of neuronal nicotinic acetylcholine receptors (nAChR). RT-PCR analysis and immunocytochemistry of O2A/OPCs purified from the rat corpus collusum revealed the expression of nAChR subunits alpha3, alpha4, alpha5, alpha7, beta2, and beta4. Immunoreactivity toward nAChR subunits was not detected in cells induced to differentiate into either oligodendrocytes or astrocytes. Approximately 65% of O2A/OPCs loaded with the calcium-responsive dye FURA-2 increased their intracellular free calcium in response to nicotine application. This response was sensitive to the nAChRalpha4/beta2 antagonist, dihydro-beta-erythroidine (DHbetaE), and the voltage-gated calcium channel antagonist, nifedipine. A subset of nicotine-responsive cells (37%) established DHbetaE or nifedipine-sensitive intracellular free calcium oscillations that continued in the presence of nicotine. Typical oscillations occurred at intervals of 20 to 30 s with progressively diminished amplitudes over a period of 2 to 3 min. In rare cases, oscillations persisted for as long as 10 min. O2A/OPCs exposed to carbachol or AMPA produced no oscillations despite robust increases in intracellular free calcium. The expression of nAChRs in non-neuronal glial precursor cells suggests an expanded role for this receptor system in the development of the mammalian brain. GLIA 33:306-313, 2001. Published 2001 Wiley-Liss, Inc.

Animals↗
PubMed2001

Estrogen receptor beta expression in invasive breast cancer.

The aim of this work was to determine the extent of estrogen receptor beta (ER-beta) expression in invasive breast cancer (BrCA) and whether ER-beta expression is correlated with response to adjuvant hormonal therapy with tamoxifen (AHTT). Immunohistochemical staining (IHC) for estrogen receptor alpha (ER-alpha) and ER-beta was performed on sections of formalin-fixed and paraffin-embedded tissue from 47 unselected invasive breast carcinomas (BrCA). IHC for ER-beta was also performed on sections of BrCA from 118 women who were treated with mastectomy and AHTT. Survival analysis was performed using the Kaplan-Meier method and the log-rank test. Of the 47 unselected BrCA, 17 (36%) were negative for ER-alpha and of these, 8 (47% of ER-alpha negative cases and 17% of all 47 patients) were ER-beta positive. Five of the 8 ER-alpha negative and ER-beta positive cases were positive for ER biochemically. There was no correlation between ER-beta positivity and overall survival in the unselected group. By contrast, in the group of women treated with AHTT, expression of ER-beta in more than 10% of cancer cells was associated with better survival (P = .0077), even in women with node-negative BrCA (P = .0069). In conclusion, our results show that a significant number of women with BrCA are positive for ER-beta only, and may be determined to be ER-negative when currently available IHC is used. ER-beta status is a significant predictor of response to AHTT in women with BrCA. Larger studies with multivariate analysis are needed to confirm these findings.

Blotting, Western↗
PubMed2000

Exploration of physicians' recommendations for activities in chronic low back pain.

STUDY DESIGN: A mailed survey of 142 practicing physicians (63 orthopedic spine surgeons and 79 family physicians) inquiring about their expertise and experience with chronic low back pain, their pain attitudes and beliefs, and recommendations about the appropriate level of function for chronic back pain patients. OBJECTIVES: To explore physicians' recommendations for activity and work for patients with chronic low back pain and to determine factors that might influence these recommendations. SUMMARY OF BACKGROUND DATA: Physicians continuously are asked to recommend the appropriate level of activities and work for patients with chronic low back pain. Although these recommendations can have a significant impact on patients' lives, little is known about the factors that shape recommendations. METHODS: Mailed surveys included questions inquiring about the physicians' demographics, training, and experience in low back pain, the Health Care Providers' Pain and Impairment Relationship Scale, and three vignettes of work-disabled, chronic low back pain patients. After each vignette, physicians rated their perceptions of severity of symptoms and pathology and recommendations for work and daily activities through five graded responses. Three mailings were done within 4 weeks to maximize the response rate. The association of each variable with work and activity recommendations was statistically explored. To assess the influence of clinical expertise on recommendations, the responses of orthopedic spine surgeons were compared with those of family physicians. Test-retest reliability was assessed with a second mailing of the questionnaire to all initial responders. RESULTS: Sixty-five percent of the orthopedic surgeons and 52% of the family physicians responded to the survey. Thirty-nine percent of the initial responders completed the reliability survey. The survey instrument demonstrated modest reliability, with identical recommendations for activities and work occurring 57% of the time. In general, a wide range of activities and work was recommended, with most physicians recommending avoidance of painful activities or greater restrictions. Orthopedic spine surgeons were slightly less restrictive in their activity recommendations compared with family physicians. Most physicians demonstrated some consistency in their pattern of recommendations when compared with their colleagues. Physicians' pain attitudes and belief influenced their recommendations, as did their perception of the severity of the patients' clinical symptoms. CONCLUSIONS: Physicians' recommendations for activity and work to patients with chronic back pain vary widely and frequently are restrictive. These recommendations reflect personal attitudes of the physicians as well as factors related to the patients' clinical symptoms.

Activities of Daily Living↗
PubMed2000

Relationship between dysplasia, p53 protein accumulation, DNA ploidy, and Glut1 overexpression in Barrett metaplasia.

BACKGROUND: There is a need for molecular markers of malignant progression in Barrett metaplasia (BM). The aim of this study is to determine the relationship between dysplasia, p53 protein accumulation, DNA ploidy, and Glut1 in BM. METHODS: Sections of esophageal biopsy specimens from 120 patients with BM were evaluated for dysplasia, p53 protein, and Glut1 expression by immunohistochemistry, and DNA ploidy by Feulgen stain and image analysis. In cases with diploid DNA histograms, the percentage cells in the G0G1 and G2M phases of the cell cycle were determined. RESULTS: Of 108 diploid cases 19 (28%) of 69 cases with G0G1 > or = 90% or G2M > or = 8.33% were p53-positive, in contrast to only 1 (3%) of 39 cases with lower G0G1 or G2M (P = 0.0008). Of 32 p53-positive cases 11 (32%) were aneuploid, in contrast to none (0%) of 88 p53-negative cases (P < 0.0001). Ten (91%) of 11 aneuploid cases were high-grade dysplasial adenocarcinoma (HGD/CA), compared with only 1 (1%) of 109 diploid cases (P < 0.0001). Five (45%) of 11 cases with HGD/CA were Glut1-positive, in contrast to none (0%) of 109 cases without HGD/CA (P < 0.0001). CONCLUSIONS: Our data strongly suggest that in BM, after oxidative DNA damage, as a result of gastroesophageal reflux, there is an increase in the percentage of cells in the G0G1 or G2M phases of the cell cycle to enable repair of damaged DNA; in some of these cases this is followed sequentially by p53 gene mutation and protein accumulation, DNA aneuploidy, HGD, and CA with or without Glut1 overexpression. These events can be detected in routinely processed biopsy samples.

Adenocarcinoma↗
PubMed1999

Radial neuropathy.

The radial nerve is the largest branch of the brachial plexus, and is commonly involved in upper extremity mononeuropathies. The radial nerve is primarily responsible for motor innervation of the upper extremity extensors, as well as receiving cutaneous innervation from most of the posterior arm, forearm, and hand. There are a variety of sites at which the radial nerve is susceptible to trauma and entrapment. Localizing radial nerve lesions is dependent on clinical knowledge of radial nerve anatomy, and sensory and motor examination.

Decompression, Surgical↗
PubMed1996

Responses to underwater exercise in scuba divers differing in trait anxiety.

Fifteen male scuba divers performed underwater leg ergometer exercise in an effort to determine if trait anxiety was related to their physiologic or perceptual responses. Psychologic assessment completed before exercise testing revealed that the sample exhibited positive psychologic profiles. However, five individuals possessed trait anxiety scores above the published mean (M = 46.0). Their responses to exercise were compared with the five participants with the lowest trait anxiety scores (M = 30.6). The exercise task was 20 min of steady-state underwater leg ergometer exercise. Oxygen consumption, CO2 production, minute ventilatory volume, breathing frequency, and heart rate were assessed at rest and every 5 min during exercise. Perception of effort and breathing discomfort were also determined during exercise. Each of the physiologic and perceptual variables increased (P < 0.05) with exercise. The only group main effect (P < 0.05) occurred for respiration rate. The high trait anxious group took 7.4 fewer breaths per minute (13.1 vs. 20.5) compared with low trait anxious group. These results have implications regarding the use of intervention strategies in persons at potential risk of experiencing panic while scuba diving.

Adult↗
PubMed1993

Comparison of muscle activity between conventional and neuromuscular splints.

The muscle relaxation appliance (MRA) has been used in the treatment of myofascial pain dysfunction (MPD) patients. The neuromuscular orthotic is a version of the MRA and is constructed from a three-dimensional mandibular position when muscles are in a state of minimal electromyographic (EMG) activity. The purpose of this study was to investigate the affect of two muscle relaxation appliances and a placebo (cotton rolls) on EMG activity of the functional masseter and anterior temporalis muscles. A centric relation mandibular MRA and a neuromuscular orthotic were constructed under controlled protocols for 12 women MPD patients with a mean age of 38 years. EMG measurements were taken during a 10-second clench of both appliance and placebo. No statistical difference was found between the centric relation mandibular MRA and neuromuscular orthotic. A statistically significant difference was found between the mean EMG values of the placebo and two treatment appliances.

Adult↗
PubMed1993

High levels of carbon monoxide are produced by electro-cautery of tissue during laparoscopic cholecystectomy.

Pyrolysis of tissue in a hypoxic environment can produce carbon monoxide. The atmosphere of the peritoneal cavity is rendered hypoxic during laparoscopic cholecystectomy by insufflation with 100% carbon dioxide. To determine whether carbon monoxide is produced by electrocautery of tissue during laparoscopic cholecystectomy, nine patients undergoing this procedure had the insufflation gas after use of electrocautery analyzed for carbon monoxide. Blood was analyzed for carboxyhemoglobin in these same patients to determine whether carbon monoxide was being absorbed in dangerous amounts. Carbon monoxide was present in the peritoneal cavity 5 min after use of electrocautery was initiated at a median concentration of 345 ppm (range 25-1600 ppm), and at the end of surgery at a concentration of 475 ppm (range 100-1900 ppm). This was well in excess of the 35 ppm upper limit for a 1-h exposure set by the Environmental Protection Agency. The carboxyhemoglobin concentrations (mean +/- SD) were the same at the beginning (1.3% +/- 0.7%), end (1.2% +/- 0.7%), and the day after surgery (1.1% +/- 0.6%). Although there was no evidence of significant absorption of carbon monoxide in these patients, care should be taken to scavenge the gases produced by cautery of tissues to avoid operating room contamination during laparoscopic surgery.

Adolescent↗
PubMed1991

The description of menstrual bleeding patterns: towards fewer measures.

The disturbance in menstrual bleeding induced by many methods of contraception is an important factor in their acceptability, and women participating in clinical trials of new methods are usually asked to keep a calendar record of the occurrence of bleeding. A recent WHO report recommends that, for analysis and presentation, each menstrual diary should be divided into successive periods, and the woman's bleeding pattern in each period summarized in ten indices. These indices are simple to calculate and easily understood by clinicians, but comparison of several groups is problematic because of the large number of summary statistics generated. Principal components analysis was therefore used to determine whether the indices could be reduced to a smaller number of measures. The analyses showed that three of the indices--the range and maximum value of bleeding/spotting episode lengths and the minimum bleeding-free interval--rarely measure their intended dimension of the bleeding pattern. Most of the essential information about a woman's bleeding pattern is contained in only four of the ten indices: the number of bleeding/spotting episodes, the mean lengths of episodes and intervals, and the range of bleeding-free interval lengths. Together, these indices describe the most important dimensions of a pattern: the amount, frequency and variability of the bleeding.

Contraception↗
PubMed1990

Unique anomalies in cephalothoracopagus janiceps conjoined twins with implications for multiple mechanisms in the abnormal embryogenesis.

The anatomic features of female conjoined twins with the Janiceps type of cephalothoracopagus are described. Abnormalities included bilateral clefts of the alveolar arches, shared rudimentary mandible, high, arched clavicles, multiple rib deformities, single shared foregut and small intestine, absent large intestines, omphalocele, multicystic kidneys, hypoplastic lungs, interconnected aortas and neck vessels, single ovary with elongated uterus in each twin, displaced labia, abnormal segmentation of the vertebrae, spinal dysraphism, diastasis of the symphysis pubis, malrotated lower extremity, bilateral posterior dislocation of the hips, and club feet. There were two hearts with internal anomalies. Both spinal cords had a myelocele in the lumbar region. The abnormalities noted in previous reports of conjoined twins of this type are reviewed and compared. We propose that factors associated with conjoining, dysgenetic (developmental) defects, and deformations resulting from crowding in utero all may have been important in the abnormal development in this case.

Digestive System Abnormalities↗
PubMed1988

Determinants of menstrual bleeding patterns among women using natural and hormonal methods of contraception. II. The influence of individual characteristics.

Menstrual diary records were obtained from women using either a natural method of contraception, a combined or progestogen-only oral contraceptive, a vaginal ring, or a long-acting injectable (DMPA). Within each method group, multiple regression analysis was used to examine the relationships between the subjects' bleeding patterns and their age, age at menarche, ponderal index, obstetric and contraceptive history and ethnic origin. The influence of ethnic origin was described in the preceding paper. Among combined pill users, increasing age was associated with more frequent spotting episodes. In both the untreated and combined pill groups, women with a higher ponderal index had less variable bleeding-free intervals; in the vaginal ring and DMPA groups, the more obese women had shorter bleeding/spotting episodes and longer bleeding-free intervals. Among combined oral contraceptive users, the most influential variable was the time since the end of the woman's last pregnancy: subjects who had been more recently pregnant had longer, less predictable episodes and shorter intervals. Previous oral contraceptive use was associated with more predictable bleeding patterns among women currently using either type of oral pill. In the vaginal ring and DMPA groups, subjects whose last pregnancy had ended in abortion had more bleeding/spotting days and episodes than those who had had a live birth. As reported previously, bleeding patterns were more closely related to the woman's geographical region of residence than to any other factor. The associations found with other individual characteristics were often inconsistent or difficult to interpret. A number of variables which could potentially influence menstrual bleeding patterns, such as nutritional status, were not measured and therefore could not be included in the analysis. However, contraceptive method and ethnic origin may be predominant influences, overriding any other factor.

Abortion, Induced↗
PubMed1987

Microinjection of ubiquitin: intracellular distribution and metabolism in HeLa cells maintained under normal physiological conditions.

Radioiodinated ubiquitin was introduced into HeLa cells by erythrocyte-mediated microinjection. Subsequent electrophoretic analyses revealed that the injected ubiquitin molecules were rapidly conjugated to HeLa proteins. At equilibrium, 10% of the injected ubiquitin was conjugated to histones and 40% was distributed among conjugates of higher molecular weight. Although the remaining ubiquitin molecules appeared to be unconjugated, the free pool of ubiquitin decreased by one-third and additional conjugates were present when electrophoresis was performed at low temperature under nonreducing conditions. Molecular weights of these labile conjugates suggest that they are ubiquitin adducts in thiolester linkage to activating enzymes. Despite the fairly rapid degradation of injected ubiquitin (t1/2 approximately 10-20 h), the size distribution of ubiquitin conjugates within interphase HeLa cells remained constant for at least 24 h after injection. The intracellular locations of ubiquitin and ubiquitin conjugates were determined by autoradiography, by differential sedimentation of subcellular fractions in sucrose, and by extraction of injected cells with buffer containing Triton X-100. Free ubiquitin was found mostly in the cytosolic or Triton X-100-soluble fractions. As expected, histone conjugates were located predominately in the nuclear fraction and exclusively in the Triton X-100-insoluble fraction. Although high molecular weight conjugates were enriched in the Triton X-100-insoluble fraction, their size distribution was similar to that of soluble conjugates. When injected HeLa cells were exposed to cycloheximide to inhibit protein synthesis, the size distribution of ubiquitin conjugates was similar to that found in untreated cells. Moreover, high molecular weight conjugates decreased less than 20% after inhibition of protein synthesis. These results indicate that most ubiquitin conjugates are not newly synthesized proteins which have been marked for destruction.

Erythrocytes↗
PubMed1987

Microinjection of ubiquitin: changes in protein degradation in HeLa cells subjected to heat-shock.

Ubiquitin was radiolabeled by reaction with 125I-Bolton-Hunter reagent and introduced into HeLa cells using erythrocyte-mediated microinjection. The injected cells were then incubated at 45 degrees C for 5 min (reversible heat-shock) or for 30 min (lethal heat-shock). After either treatment, there were dramatic changes in the levels of ubiquitin conjugates. Under normal culture conditions, approximately 10% of the injected ubiquitin is linked to histones, 40% is found in conjugates with molecular weights greater than 25,000, and the rest is unconjugated. After heat-shock, the free ubiquitin pool and the level of histone-ubiquitin conjugates decreased rapidly, and high molecular weight conjugates predominated. Formation of large conjugates did not require protein synthesis; when analyzed by two-dimensional electrophoresis, the major conjugates did not co-migrate with heat-shock proteins before or after thermal stress. Concomitant with the loss of free ubiquitin, the degradation of endogenous proteins, injected hemoglobin, BSA, and ubiquitin was reduced in heat-shocked HeLa cells. After reversible heat-shock, the decrease in proteolysis was small, and both the rate of proteolysis and the size of the free ubiquitin pool returned to control levels upon incubation at 37 degrees C. In contrast, neither proteolysis nor free ubiquitin pools returned to control levels after lethal heat-shock. However, lethally heat-shocked cells degraded denatured hemoglobin more rapidly than native hemoglobin and ubiquitin-globin conjugates formed within them. Therefore, stabilization of proteins after heat-shock cannot be due to the loss of ubiquitin conjugation or inability to degrade proteins that form conjugates with ubiquitin.

Autoradiography↗
PubMed1986

The degradation of guanidinated lysozyme in reticulocyte lysate.

Egg white lysozyme, treated with O-methylisourea to convert lysine to homoarginine residues, was used as a substrate for the ATP-dependent proteolytic pathway in rabbit reticulocyte lysates. Although guanidinated lysozyme was degraded by an ATP-dependent, hemin-sensitive process, ubiquitin conjugates of this protein were present at less than 5% the level of conjugates between ubiquitin and nonguanidinated lysozyme. When lysates were chromatographed on DEAE-cellulose to produce Fractions I and II of (Hershko et al. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 3107), ubiquitin-depleted Fraction II was capable of degrading nonguanidinated lysozyme, but the degradation of guanidinated lysozyme was markedly reduced or abolished. Glycerol-stabilized Fraction II, on the other hand, supported the degradation of both proteins in an ATP-dependent process stimulated by ubiquitin. The degradation of the two proteins differed, however, in that guanidinated lysozyme was more sensitive to competitive substrates, and higher concentrations of ubiquitin were required for its maximal proteolysis. Despite ubiquitin stimulation of guanidinated lysozyme degradation, only trace amounts of higher molecular weight species of guanidinated lysozyme attributable to ubiquitin conjugation were observed in ubiquitin-supplemented, glycerol-stabilized Fraction II even when special precautions were employed to preserve labile covalent bonds. These results indicate that covalent attachment of ubiquitin to the epsilon-amino group of substrate lysines is not mandatory for ATP-dependent proteolysis in rabbit reticulocyte lysates. The observation that ubiquitin stimulates proteolysis of guanidinated lysozyme, without extensive conjugation to it, suggests that ubiquitin may have essential functions for proteolysis other than direct marking of the protein substrate.

Adenosine Triphosphate↗
PubMed1983

Time course of ischemic alterations during normothermic and hypothermic arrest and its reflection by on-line monitoring of tissue pH.

Currently there are no techniques available for the intraoperative on-line assessment of the adequacy of myocardial preservation during cardiac operation. The efficacy of a new intramyocardial pH electrode in quantitating myocardial ischemic damage and monitoring myocardial preservation was investigated by correlating changes in intramyocardial pH with the time course of metabolic, histologic, and ultrastructural alterations during global ischemia. Seventeen open-chest dogs were placed on cardiopulmonary bypass and the aorta was cross-clamped for 2 hours. In Group I (n = 8), aortic cross-clamping was performed under normothermia. Group II (n = 9) received 4 degrees C potassium cardioplegia immediately after cross-clamping and consecutively every 30 minutes thereafter. Intramyocardial carbon dioxide tension (Pco2) and intramyocardial pH were measured continuously. Serial transmural biopsies were obtained before and at 5, 15, 30, 60, 90, and 120 minutes after cross-clamping for biochemical and structural analysis. During the period of cross-clamping, mean myocardial temperature was 33 degrees C in Group I and 19 degrees C in Group II. Intramyocardial pH at the end of 2 hours of anoxic arrest reached 5.39 +/- 0.08 in Group I and 6.49 +/- 0.13 in Group II (both values p less than 0.01 compared to prebypass values). Intramyocardial Pco2 rose from 41 +/- 4 to 234 +/- 13 mm Hg in Group I (p less than 0.001) and did not change in Group II. Tissue content of adenosine triphosphate (ATP) decreased by 51% in Group I and by 14% in Group II (p less than 0.01 compared to prebypass value). Tissue creatine phosphate was depleted in Group I and decreased by 48% in Group II. The degree of ischemic damage assessed by a mean ischemic score was 2.15 +/- 0.06 in Group I and 0.75 +/- 0.19 in Group II (p less than 0.001). Irreversible structural damage assessed by electron microscopy occurred in Group I 60 to 90 minutes after cross-clamping and was associated with an intramyocardial pH below 6.2. No such damage was observed in Group II. Therefore, intramyocardial pH is shown to be a reliable indicator of the severity of ischemic damage during anoxic arrest under normothermic conditions and of the adequacy of preservation under hypothermic conditions. Measurement of intramyocardial pH may provide a potentially useful tool for the intraoperative on-line monitoring of the adequacy of myocardial preservation in patients undergoing cardiac operation.

Adenosine Triphosphate↗
PubMed1981

Early pathologic detection of acute myocardial infarction.

The use of tetrazolium stains for identifying myocardial infarction during the early stages of ischemic injury has become increasingly popular in both experimental and clinical studies. However, the accuracy of these stains in delineating infarctions prior to the onset of well-defined histologic necrosis is unknown. Therefore, eight open-chested, anesthesized dogs were subjected to high left anterior descending coronary artery occlusions for six hours. The hearts were then excised and "breadloafed' into 5mm-thick transverse slices that were incubated in triphenyltetrazolium chloride (TTC) for ten minutes. Three to five tissue samples were obtained from each of three areas of two transverse ventricular slices: from TTC-unstained areas (infarction) and TTC-stained areas, both close to the infarct and remote from the infarct, for electron microscopy. All eight dogs had well-defined areas of unstained tissue that appeared pale gray next to the brick-red TTC-stained tissue. Ultrastructure of the TTC-stained tissue both close to and remote from the infarct showed only modest loss of glycogen and relaxation of myofibers. Ultrastructure of the TTC-unstained tissue in all eight dogs showed numerous mitochondrial amorphous dense bodies, intracellular edema, nuclear chromatin clumping and margination, sarcolemmal disruption, and interstitial edema. Therefore, TTC is a reliable stain for localizing myocardial cells that ultrastructurally appear irreversibly injured by ischemia.

Animals↗