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Biomedical subjects

K Choi

Publications and source records attributed to K Choi.

123 records · Page 7Linked to original sources
PubMed1975

Transient ischemic attacks due to atherosclerosis. A prospective study of 160 patients.

Patients with transient ischemic attacks (TIAs) due to atherosclerosis were studied by aortocranial arteriography. Onset of TIAs was before age 55 in 24% and between 55 and 64 in 47%. Men exceeded women by two to one. Of 160 patients, 77 were treated medically and 82 surgically. Five died in the immediate postoperative period. In the survivors, mortality has been the same in the medically and surgically managed groups. For patients with multiple lesions, surgical reconstruction of the carotid arteries was associated with very high surgical risk. In the medically treated group, anticoagulant therapy reduced the frequency of TIAs, but did not appear to protect patients from stroke. Mortality was 23% at four years, 57% of deaths being attributable to myocardial infarction and 38% to stroke.

Adult↗
PubMedDate not supplied

Examination of compact bone microdamage using back-scattered electron microscopy.

A new staining technique using heavy metals (lead-uranyl acetate) has been developed to allow visualization of bone microdamage using both light microscopy and scanning electron microscopy operated in its back-scattered mode (BSE). At the light microscopic level, the number of microcracks counted in sequential sections of human ribs is the same for both the traditional basic fuchsin method of differentially staining microcracks and the new lead-uranyl acetate procedure. With BSE study, however, the number of microcracks observed is significantly reduced in all samples, because of the reduction of projection effect error associated with surface based imaging techniques. Application of the lead-uranyl acetate staining technique to ex vivo-loaded crack propagation specimens showed an extensive ultrastructurally disrupted region associated with the crack path through bone, consistent with the damage process zone around cracks in toughened composite materials.

Adult↗
PubMedDate not supplied

Three-dimensional reconstruction of human femur using consecutive computer tomography images and simulated implantation system.

This study is concerned with the construction of a simulated implantation system (SIS) for a human femur using various algorithms of image processing and computer graphics. The SIS is the software which performs 3D visualization as well as various numeric analyses between the patient's femur and the artificial hip joint through certain stages of processing on consecutive CT images and projected images. We present the concrete methods that were to be implemented into the suggested prototype of SIS and the corresponding experimental results will also be shown.

Algorithms↗
PubMedDate not supplied

Modification of Cotrel-Dubousset's original hook constructs for idiopathic scoliosis.

We performed a retrospective review of 41 patients (ages 9-18 years) who underwent posterior spinal fusion with either Isola or Cotrel-Dubousset (CD) instrumentation to determine whether the presence of an apical hook on the thoracic convexity affected initial and long-term sagittal and coronal correction in adolescent idiopathic scoliosis surgery. A study group of 38 female and three male patients was evaluated (2-5 years of follow-up). Twenty-three patients (Group A) were treated with an up-going hook at the convex apex of the thoracic curve, and 18 patients (Group B) with similar curves were instrumented without an apical hook. Results showed that Group A's average preoperative coronal curve of 48 degrees decreased to 17 degrees , whereas Group B's preoperative average of 52 degrees decreased to 25 degrees . At follow-up, no statistical significance was noted in either coronal curve correction (p = 0.203) or sagittal kyphosis (p = 0.38) between Groups A and B. We conclude that omission of the up-going hook at the apex of the thoracic convexity can reduce postoperative discomfort in patients undergoing posterior spinal fusion, without sacrificing curve correction or balance.

Adolescent↗
PubMedDate not supplied

Association of comorbidity with depressive symptoms in community-dwelling older persons.

BACKGROUND: Depression in later life poses a serious threat to mental health and well-being of older persons burdened with medical illnesses. Comorbid medical conditions independently, as well as through interactions, may influence the degree of depressive symptoms manifested by the elderly. Insight into the role medical comorbidity plays in the manifestation of depression may help to better address both physical and mental health care needs of the depressed elderly. OBJECTIVE: To examine independent and synergistic effects of comorbid medical conditions in the presentation of depressive symptoms among older adults living in the community. METHODS: Data from a national survey of community-dwelling older persons aged 60 years and over (n = 2,058) in Korea were used. The levels of depression were assessed using an eleven-item Center for Epidemiological Studies Depression Scale. Comorbidity was defined as the number of chronic medical conditions and the combination of disease pairs. Sociodemographic characteristics, self-rated health, physical functioning, history of hospital admission in the past year, frequency of contact with friends or neighbors, and emotional support were used as covariates. RESULTS: Overall, persons with a medical condition compared to those without tended to show a higher depressive symptom score. Comorbidity, in terms of the number of medical conditions, tended to show a significant linear association with depression, controlling for confounders. More important, independent effects of medical conditions as well as a tendency to synergy among specific medical conditions were found, with notable gender differences. CONCLUSION: Given the significant but complex association of comorbid medical conditions with depressive symptoms in aged persons, clinicians should exercise care to address their physical and mental health needs within a common therapeutic context.

Aged↗
PubMedDate not supplied

Homogenized stress analysis in a dental implant system.

In this study, the stress state occurring at each trabecular due to three different types of dental implant is investigated by a homogenization technique, in which the trabecular structure is assumed to be composed of repeating hexagonal units. This technique helps make a proper material model of bone and to analyse such a non-homogeneous structure at the level of an individual microstructural unit. Stress analyses with the homogenization technique show a much higher stress level in the sponge bone, compared to those with conventional FEM. It also shows that even a minor lateral force results in crucial stresses in the dental implant system. The stress states of the mandible with a hemisphere-rooted implant and a wedge type implant show similar levels, while those with a rectangular-rooted implant result in higher stresses. It is suggested that the distance between the implant tip and cortical bone be kept far enough apart to prevent stress concentrations in the mandible.

Dental Implants↗
PubMedDate not supplied

Modulation of N-nitrosomethylurea induced mammary tumorigenesis by dietary fat and voluntary exercise.

The effect of dietary fat and exercise on N-nitrosomethylurea [NMU:CAS:684-93-5]-induced mammary tumorigenesis in female F344 rats was investigated. Rats were fed the NIH-07 diet until NMU administration on day 50 of age, when they were transferred to four treatment groups. Three sedentary groups were fed either high-fat (20% wt/wt), medium fat (10%) or low fat (5%) diets (HF, MF, LF, respectively), and a fourth group was fed a HF diet but allowed free access to an activity wheel (HFEX). Tumor yields among the three sedentary groups were significantly greater in the HF and MF groups when compared to the LF group. Voluntary exercise reduced tumor yields and delayed time of tumor appearance in HFEX animals to levels similar to those found in LF sedentary animals. Animals with voluntary access to exercise wheels averaged between 1.03 and 2.85 miles/day, consumed more food (+ 18%) and exhibited greater weight gain (+ 13%) than their sedentary counterparts. No differences in weight gains were detected among the HF, MF, and LF groups, despite widely varying amounts of fat intake. Body composition studies indicated that body fat content was not influenced by the quantity of fat consumed in the diet, but was significantly reduced by voluntary exercise (-20%). Since exercise and fat intake have been associated with alterations in endocrine status, circulating bioactive and immunoactive prolactin were assessed at termination. No significant changes were found in either form of prolactin among the four experimental groups, casting doubt on mediation by this pituitary hormone.

Animals↗
PubMedDate not supplied

Rocky Mountain spotted fever in Georgia, 1961-75: analysis of social and environmental factors affecting occurrence.

For the period of 1961 through 1975, 10 geographic and sociologic variables in each of the 159 counties of Georgia were analyzed to determine how they were correlated with the occurrence of Rocky Mountain spotted fever (RMSF). Combinations of variables were transformed into a smaller number of factors using principal-component analysis. Based upon the relative values of these factors, geographic areas of similarity were delineated by cluster analysis. It was found by use of these analyses that the counties of the State formed four similarity clusters, which we called south, central, lower north and upper north. When the incidence of RMSF was subsequently calculated for each of these regions of similarity, the regions had differing RMSF incidence; low in the south and upper north, moderate in the central, and high in the lower north. The four similarity clusters agreed closely with the incidence of RMSF when both were plotted on a map. Thus, when analyzed simultaneously, the 10 variables selected could be used to predict the occurrence of RMSF. The most important variables were those of climate and geography. Of secondary, but still major importance, were the changes over the 15-year period in variables associated with humans and their environmental alterations. Detailed examination of these factors has permitted quantitative evaluation of the simultaneous impacts of the geographic and sociologic variables on the occurrence of RMSF in Georgia. These analyses could be updated to reflect changes in the relevant variables and tested as a means of identifying new high risk areas for RMSF in the State. More generally, this method might be adapted to clarify our understanding of the relative importance of individual variables in the ecology of other diseases or environmental health problems.

Climate↗
PubMedDate not supplied

A controlled trial of disease surveillance strategies.

Active surveillance techniques using routine telephone contacts with providers improved the reporting of measles, rubella, salmonellosis, and hepatitis by a factor of 4.6 among private physicians in Monroe County, New York, and increased reporting for these target diseases from all sources by 51 percent. The timeliness of reporting was not improved by active surveillance. Reporting patterns varied by disease and source of report, suggesting the desirability of various approaches to surveillance based on local resources and priorities. Although reporting rates were higher for diseases among persons from census tracts of low socioeconomic status, physicians providing care to persons living in low-income areas responded no differently to active reporting than did those providing care to patients from middle- and high-income areas.

Hepatitis↗
PubMedDate not supplied

Effect of varying proportions of dietary fat on the development of N-nitrosomethylurea-induced rat mammary tumors.

The influence of diets varying in their relative proportions of dietary fat on N-nitrosomethylurea (NMU)-induced mammary tumorigenesis, was assessed. Animals were initiated on day 50 of age with 25 mg/kg NMU and then placed on casein-based AIN-76A diets containing 5, 10, 16 and 23% corn oil (wt/wt). There were 30 animals/group and the experiment was terminated 22 weeks post-NMU. It was found that animals fed diets containing 16 and 23% corn oil exhibited tumor incidences between 2 and 3 times that of animals fed diets containing 5 and 10% corn oil. No differences in tumor incidence could be detected between the 5 and 10% groups or the 16 and 23% groups, suggesting that a threshold occurs at some point between 10 and 16% fat (or 20 and 33% of total calories as fat). The results of this study suggest that the tumor-promoting effects of dietary fat are manifested in terms of a threshold, rather than a linear dose-response effect.

Animals↗
PubMedDate not supplied

[New method of epidemiological surveillance of influenza mortality in the USA].

This paper describes a new method of forecasting the expected number of pneumonia and influenza (P and I) deaths on the basis of time-series analysis of historical mortality data. The new method is different in three aspects from the regression method developed by Serfling and used by the Centres for Disease Control (CDC) since 1963 in that it uses the ratio of P and I deaths to deaths from all causes in lieu of the total number of P and I deaths in forecasting the expected numbers. Also, instead of deleting epidemic periods in the forecast, these weeks are replaced by expected numbers. Finally, forecasting is done with a time-series model instead of the regression model.

Adolescent↗
PubMedDate not supplied

The role of infusional chemotherapy and radiation in organ preservation.

Chemotherapeutic agents, used alone or in combination, have had a largely palliative effect in the treatment of solid tumors. The curative ability of these agents has been limited to about 15% of cases, in large measure due to chemotherapy's failure to accomplish locoregional control, leaving surgery or irradiation for local control of primary disease as modes of treatment. In many cases, however, surgery is not a feasible alternative, and radiation therapy may fail because of radioresistance. Whether this is caused by anoxia or by the innate radioresistance of the tumor cell, radiation oncologists have tried a number of methods to overcome the resulting insensitivity. Experience with the continuous concomitant infusion of various cytotoxic agents and radiation therapy in the treatment of advanced malignancies has been encouraging. The resultant radiosensitization has let to an increased rate of locoregional clearance of advanced carcinomas with a worthwhile increase in survival rates. The use of infusion chemo- and radiation therapy also has allowed the use of an organ-sparing program in all but the most advanced stages. There are already encouraging reports on successful organ-sparing treatment programs for carcinoma of the anus, esophagus and bladder. (ABSTRACT TRUNCATED)

Antineoplastic Combined Chemotherapy Protocols↗