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Biomedical subjects

R D Jackson

Publications and source records attributed to R D Jackson.

At least 19 recordsLinked to original sources
PubMed2001

The significance of platelet counts in coagulation studies.

Traditionally, the platelet count recommended for coagulation studies has been less than 10 x 10(9)/L, but the documentation for this is obscure. In the present study, platelet rich plasma (PRPs) and platelet poor plasmas (PPPs) were prepared from the same blood specimen to determine prothrombin times (PTs), International Normalized Ratios (INRs), partial thromboplastin times (PTTs), and their results compared. The measurements of all three of these parameters are not statistically or clinically significant in 100 paired comparisons. Incremented platelet count studies, selected by the number of platelets in the PRPs, showed that platelet counts of at least 199 x 10(9)/L, or perhaps even higher, did not compromise the results of PTs, INRs or PTTs. Such increased platelet counts, however, cannot be tolerated in the various studies for antiphospholipid antibodies, the Lupus Anticoagulant (LAC), or when monitoring heparin therapy with PTTs. Here, the < 10 x 10(9)/L platelet levels must be respected; otherwise the tests would be compromised by platelet-liberated phospholipid (Triplett, Brand et al., 1983) or by Platelet Factor 4, respectively.

Blood Coagulation Tests↗
PubMed2000

Involving minority and underrepresented women in clinical trials: the National Centers of Excellence in Women's Health.

Recent attention to reducing health disparities among population groups has focused on the need to include in clinical studies, especially clinical trials, participants who represent the diversity of the populations to which study results will be applied. While scientists generally applaud the goal of broadening the characteristics of participants in clinical trials, they are faced with multiple challenges as they seek to include historically underrepresented populations in their research. This article examines the historical and sociocultural context of participation by underrepresented groups, especially women and minorities, in clinical trials, identifies major barriers and challenges facing researchers, and suggests strategies for meeting these challenges. The article draws upon the experiences of the investigators affiliated with the National Centers of Excellence of Women's Health (CoEs).

Clinical Trials as Topic↗
PubMed2000

The new posterior resins and a simplified placement technique.

BACKGROUND: New heavy-body (packable) composites have been developed for use in posterior direct resin restorations. These materials are promoted as having better handling characteristics and higher physical properties than previous microhybrid composites. METHODS: The authors describe an incremental layering technique that takes advantage of the improved handling characteristics and proposed reduced shrinkage and greater depth of cure. CLINICAL IMPLICATIONS: When this new technique is used with one-bottle adhesives and improved instrumentation, posterior heavy-body composites can be placed faster, easier and possibly more predictably than when medium-body resins and previous techniques are used.

Composite Resins↗
PubMed1999

Diagnosis and treatment of glucocorticoid-induced osteoporosis.

Glucocorticoids are a mainstay in the treatment of many diseases, including pulmonary and rheumatologic disorders. Unfortunately, as many as 90% of long-term glucocorticoid recipients lose a significant amount of bone and incur an increased risk of fractures. This paper reviews the pathophysiology, diagnosis, and treatment of glucocorticoid-induced osteoporosis.

Disease Management↗
PubMed1999

Dental caries diagnosis.

As with any disease process, the early initiation of therapy for dental caries is often the most effective means to ensure resolution. However, for any therapy to be effective, early diagnosis is paramount to success. Unfortunately, current tools used in dental caries detection are not sensitive enough to diagnose the disease process in its early stages and, frequently, once a diagnosis is made restoration is the only effective means of treatment. Quantitative light-induced fluorescence, electrical conductance measurements, direct digital radiography, and direct fiber optic transillumination are methods that may offer promise as effective tools in diagnosing early dental caries. This article describes some of the research that has been performed to make these methods a reality.

Dental Caries↗
PubMed1999

Indirect resin inlay and onlay restorations: a comprehensive clinical overview.

Advances in adhesive technology and aesthetic dental materials have permitted clinicians to perform conservative preparation of the dentition for inlay/onlay restorations. The use of adhesive indirect procedures provides numerous advantages (e.g., aesthetics, reinforcement, adequate seal) to conventional restorative techniques. This article describes the indications/contraindications and material properties of aesthetic indirect restorations. It also highlights the preparation, bonding, and finishing procedures utilized to achieve an aesthetic indirect resin restoration and demonstrates the techniques with a series of case presentations.

Adult↗
PubMed1999

Modified anticoagulant therapy factor and international normalized ratio in patients in an unstable coagulation state with respect to warfarin therapy.

In our pilot study of 1997, an Anticoagulant Therapy Factor (ATF) was formulated, compared to the International Normalized Ratio (INR) and proposed to replace the INR. Statistically, replacement of the INR was reasonable; but many discrepancies occurred when the results of ATFs and INRs were compared for individual patients. The study was based on patients undergoing induction of warfarin anticoagulant therapy, so they were "unstable" with respect to warfarin. A 1998 follow-up study by Carroll and Jackson based on patients "stable" with respect to warfarin, having taken the drug for at least six weeks, was, therefore, undertaken. In this study, the ATF was modified to an MATF by both multiplying the ATF by the prothrombin ratio (PR) and adjusting the INR-ATF linear regression analysis line by analytic geometry, so that the slope was one and the line passed through the origin. These modifications achieved both statistical and individual patient concordance between INRs and ATFs. The purpose of the present paper is to apply the techniques of the 1998 study to the original 1997 pilot study to see if the reprocessed data on the "unstable" patients is, in fact, also concordant with respect to INRs and ATFs.

Blood Coagulation↗
PubMed1998

Muscle atrophy is prevented in patients with acute spinal cord injury using functional electrical stimulation.

Severe muscle atrophy occurs rapidly following traumatic spinal cord injury (SCI). Previous research shows that neuromuscular or 'functional' electrical stimulation (FES), particularly FES-cycle ergometry (FES-CE) can cause muscle hypertrophy in individuals with chronic SCI (> 1 year post-injury). However, the modest degree of hypertrophy in these already atrophied muscles has lessened earlier hopes that FES therapy would reduce secondary impairments of SCI. It is not known whether FES treatments are effective when used to prevent, rather than reverse, muscle atrophy in individuals with acute SCI. This study explored whether unloaded isometric FES contractions (FES-IC) or FES-CE decreased subsequent muscle atrophy in individual with acute SCI (< 3 months post-injury). Twenty-six subjects, 14-15 weeks post-traumatic SCI, were assigned to control, FES-IC, or FES-CE against progessively increasing resistance. Subjects were involved in the study for 3 or 6 months. Total body lean body mass (TB-LBM), lower limb lean body mass (LL-LBM), and gluteal lean body mass (G-LBM) were determined before the study, and at 3 and 6 months using dual energy X-ray absorptiometry (DEXA). Controls lost an average of 6.1%, 10.1%, 12.4%, after 3 months and 9.5%, 21.4%, 26.8% after 6 months in TB-LBM, LL-LBM and G-LBM respectively. Subjects in the FES-IC group consistently lost less lean body mass than controls, however, only 6 month G-LBM loss was significantly attenuated in this group relative to the controls. In the FES-CE group, LL-LBM and G-LBM loss were prevented at both 3 and 6 months, and TB-LBM loss was prevented at 6 months. In addition, FES-CE significantly increased G-LBM and LL-LBM after 6 months of training relative to pre-training levels. Within the control group, there was no significant relationship between LL-LBM loss (3 and 6 months) and the number of days between injury and baseline measurement. In summary, this study shows that FES-CE, but not FES-IC, training prevents muscle atrophy in acute SCI after 3 months of training, and causes significant hypertrophy after 6 months. The magnitude of differences in regionalized LBM between controls and FES-CE subject raises hopes that such treatment may indeed be beneficial in preventing secondary impairments of SCI if employed before extensive post-injury atrophy occurs.

Adult↗
PubMed1998

Warfarin monitoring by an anticoagulant therapy factor (ATF).

In a pilot study (1997) using POTENS+, our coagulation instrument, we determined that: (a) an Anticoagulant Therapy Factor (ATF) was comparable to the International Normalized Ratio (INR) for monitoring warfarin anticoagulant therapy, (b) one could use any of the four thromboplastins with which the ATF was derived with comparable results, and (c) the ATF could be proposed to monitor warfarin therapy. The ATF-INR comparisons correlated well statistically; but when individual ATF-INR comparisons were later studied, there were frequent discrepancies. The pilot study (1997) was based on hospitalized patients, so almost all patients were undergoing induction of warfarin anticoagulation. Since none of them had taken warfarin for at least six weeks, none of them could be considered "stable" on warfarin. In the present study, all patients were on warfarin therapy for at least six weeks, and the ATF equation was modified by multiplying it by the prothrombin ratio (PR) to give a corrected ATF (CATF). This CATF was then further modified to achieve agreement with the INR by adjusting the linear regression line by means of analytic geometry, so that the CATF-INR regression line now had a slope of one and passed through the origin. With these changes, the modified ATFs (MATF) and INRs correlated well and were nearly equal numerically when using two of the four thromboplastins. Reason for the discrepancies with the other two thromboplastins will be discussed.

Anticoagulants↗
PubMed1998

Protocol for predictable restoration of anterior teeth with composite resins.

The composite resins have reached a high degree of excellence and are now used with predictable results in restoring the anterior dentition. This article discusses the development of these resins and the histologic and optical considerations (polychromatic characteristics, hue translucency and opacity, chroma, value, strength and polishability). In restorative materials, the use of universal or all-purpose restorative resins is considered: i.e. materials that combine the junctional strength necessary for the posterior regions and the high gloss polishability necessary to emulate enamel in the anterior. The restorative sequence of cervical, middle, and incisal thirds describes the materials best suited for each third, along with aids to create the intricate refinement of hue, chroma, and value. The learning objective of this article is to review the principles involved in these restorations and to provide a protocol for their clinical implementation.

Color↗
PubMed1997

Forestalling fracture in osteoporosis.

When osteoporosis is imminent, simple clinical measures--risk reduction and preventive steps such as calcium supplementation and exercise--are in order. Estrogen replacement offers excellent protection in menopausal women. When disease is apparent, bone densitometry can confirm the diagnosis and therapy can be chosen from a widening palette that includes calcitonin and the bisphosphonates.

Absorptiometry, Photon↗
PubMed1997

Lack of effect of long-term fluoride ingestion on blood chemistry and frequency of sister chromatid exchange in human lymphocytes.

Two studies were conducted to assess the potential for adverse physiologic and genotoxic effects of long-term fluoride ingestion in adults residing in three communities with varying water fluoride levels (0.2 ppm, 1.0 ppm, and 4.0 ppm). All were long-time (> or = 30 years) residents of their respective communities. Plasma and urine samples were collected for fluoride analyses. Additional plasma was collected to determine blood chemistry, and plasma lymphocytes were examined to determine the frequency of sister chromatid exchange. Significant differences in urine (P = 0.001) and plasma (P = 0.0001) fluoride levels were found in the three communities. Seven of the blood parameters were statistically different among the communities, although all were within the defined normal range of the pathology laboratory. Sister chromatid exchange frequency was statistically higher in the 4.0 ppm fluoride community as compared to the other communities. Because of the higher SCE frequency in the 4.0 ppm fluoride community, a second study was performed to determine if the increased frequency was potentially related to the fluoride level of the communal water supply. Of the 58 adults recruited; 30 had used city water and 28 had used well water (< or = 0.3 ppm fluoride) as their principal water source for 30 years. Data analyses showed that the sister chromatid exchange frequency did not differ between the groups, indicating that the increased sister chromatid exchange frequency was not related to the fluoride level of the communal water. The investigation provided evidence that the long-term ingestion of water containing 4.0 ppm fluoride did not have any clinically important physiologic or genotoxic effects in healthy adults.

Adult↗
PubMed1997

Cyclical etidronate in the treatment of postmenopausal osteoporosis: efficacy and safety after seven years of treatment.

PURPOSE: To determine the efficacy and safety of cyclical etidronate for up to 7 years in the treatment of postmenopausal osteoporosis and to examine the effects of discontinuing treatment after 2 or 5 years of therapy. PATIENTS AND METHODS: Patients were randomized at entry into the original study in 1986 to blinded treatment for 2 years with either a calcium (placebo) or an intermittent cyclical etidronate regimen, which most patients continued for a third year. Following this phase of the study, patients were enrolled into an open-label, follow-up study (years 4 and 5), during which all patients received cyclical etidronate treatment. In the present double-blind study (years 6 and 7), patients were rerandomized to receive intermittent cyclical therapy with either etidronate or placebo; all patients received calcium. The treatment regimen consisted of 400 mg/day etidronate or placebo for 14 days, followed by 76 days of elemental calcium (500 mg/day); this cycle was repeated approximately 4 times in each year. Of the 193 patients who continued in years 6 and 7 of the study, 93 were randomized to receive cyclical etidronate and 100 were randomized to receive calcium only. For purposes of efficacy analyses, patients were categorized by their total years of cumulative etidronate treatment (7, 5, 4, or 2 years). There were 51, 46, 42, and 54 patients in the 7-, 5-, 4-, and 2-year groups, respectively. Annual assessments included lumbar spine bone mineral density (BMD), as measured by densitometry, and vertebral radiographs. RESULTS: The groups receiving cyclical etidronate during this 2-year study period (7- and 4-year groups) had statistically significant mean percent increases in spinal BMD of 1.8% and 2.2%, respectively (P < 0.05) at the week 104 observation time. The 5- and 2-year groups, which did not receive etidronate during this period, had mean values of 1.4% and 0.2%, respectively (not significant) at week 104. In the 7-, 5-, 4-, and 2-year groups, the increases in spinal BMD at the end of 7 years were 7.6%, 8.6%, 8.1%, and 3.9%, respectively; these values were statistically significant for all groups compared with original baseline (year 0) (P < 0.05). BMD of the femur and wrist was maintained throughout the 7-year period. The incidence and rate of vertebral fractures were lowest in patients with the longest exposure to etidronate. Etidronate was well tolerated during the study, with low incidences of gastrointestinal side effects and nonvertebral fractures. CONCLUSIONS: Long-term cyclical etidronate is a safe, effective, and well-tolerated treatment for postmenopausal osteoporosis. Bone mass is maintained for at least 2 years after treatment with etidronate is stopped; however, further gains in spinal bone mass are seen in patients who continue therapy.

Aged↗
PubMed1997

Warfarin monitoring independent of the international normalized ratio (INR): a pilot study.

Warfarin monitoring is extended to include an anticoagulant therapy factor (ATF). ATF is shown, using four different thromboplastins (Tps), to be comparable with the International Normalized Ratio (INR) mathematically; but ATF is less cumbersome and does not have the INR's poor precision with up to 13.5% error. ATF is formulated from the prothrombin time (PT), fibrinogen transformation rate (FTR) (a representation of thrombin activity), and a consideration of the fibrinogen (FBG) content of blood plasma. Each of these three components is derived from the optical density (O.D.) changes during both the monitoring of the PT and the following FBG-fibrin conversion by a potentiophotometer (PTPH), a linear-reading spectrophotometric device. Comparison of the ATF with the INR shows correlation coefficients of 0.9474, 0.9248, 0.8116 and 0.8603 using the four respective Tps, and the difference against the mean for Bland-Altman plots averages only 0.2 units more for the ATF than the INR. The ATF is independent of the Tp used, and, although Tp affects the PTs, Tp essentially only initiates the tissue factor pathway (TFP) (extrinsic clotting system) to then obtain the PT. It has no rapid direct effect on thrombin activity. For these reasons, in ATF determination, the kind of Tp used is of no consequence. The ATF is independent of the INR, and numerically almost equal to it. The ATF is, therefore, proposed as a replacement for the INR.

Anticoagulants↗