Search PubMed⌕ Search

Biomedical subjects

K C White

Publications and source records attributed to K C White.

At least 19 recordsLinked to original sources
PubMed1998

Evaluation of key sources of variability in the measurement of pharmaceutical drug products by near infrared reflectance spectroscopy.

Potential sources of variability in the measurement of solid oral drug products by near infrared reflectance spectroscopy were evaluated with statistical experimental design. Spectra were collected for two different tablet types according to the data collection and treatment parameters defined by the experimental design. Each tablet had three different dose-levels. Libraries were constructed using second-derivative spectra. Key figures-of-merit generated during internal and external library validation were used to calculate which parameters most strongly influence the library performance for dose-level discrimination. These responses and their corresponding experimental conditions were evaluated with the screening model in the JMP program. Segment value used for the second-derivative calculation was an an influential factor and had a complex effect. Orientation on the sampling platform also had an influential effect for embossed tablets. Collection of spectra over fewer days decreased variability within the library. More frequent reference spectrum collection improved the performance of libraries to a small degree. A larger sample population increased the range of spectral variability within a dose-level but apparently not the overall performance of the library. The number of scans averaged per spectrum was not an influential factor in this study. These results are summarized and used to recommend an approach to dose-level discrimination.

Evaluation Studies as Topic↗
PubMed1994

Hemodynamics and wall shear rate in the abdominal aorta of dogs. Effects of vasoactive agents.

Vasoactive drugs are known to affect impedance (pressure/flow) and vessel wall motion in arteries. The nonlinear theory of oscillatory flow in straight elastic vessels indicates that wall shear rate is affected by changes in impedance phase angle and wall motion. To test whether wall shear rate depends on impedance phase angle and wall motion in vivo, wall shear rate was measured in the abdominal aorta of anesthetized dogs by using a flush-mounted hot-film anemometer, and the hemodynamic state was characterized by pressure, flow, and vessel dimension measurements. Vasodilators (nitroprusside and isoproterenol) and vasoconstrictors (angiotensin II and norepinephrine) were administered acutely, and the responses of wall shear rate and hemodynamics were determined. In the control state (no drugs), peak wall shear rate was 1835 +/- 153 s-1 (mean +/- SEM). The vasodilators induced large increases in impedance phase angle and wall motion concomitant with large increases in peak wall shear rate (62.4 +/- 20.4% for nitroprusside and 68.9 +/- 28.3% for isoproterenol), which were not predicted accurately by Womersley's theory of oscillatory flow in a rigid vessel or the nonlinear theory of oscillatory flow in an elastic vessel, with measured flow and vessel dimension used as inputs. The vasoconstrictors induced small decreases in impedance phase angle and wall motion and small changes in peak wall shear rate (increase, 30.5 +/- 8.0% for norepinephrine; decrease, 18.2 +/- 7.1% for angiotensin II), which were predicted accurately by Womersley's theory. The present study shows that vasoactive drugs, particularly vasodilators, can have significant effects on wall shear rate (stress) in the abdominal aorta that appear to be related to changes in impedance phase angle and vessel wall motion. However, the effects on wall shear rate are not predicted accurately by straight-tube theory.

Angiotensin II↗
PubMed1994

Pulpal response after complete crown preparation, dentinal sealing, and provisional restoration.

This study evaluated the acute pulpal healing response following preparation, etching, and sealing of the prepared vital dentin with a 4-methacryloxyethyl trimellitate anhydride (4-META) bonding system. Adult monkey teeth received crown preparations with chamfer margins, prepared with a diamond used at ultra high speed with water cooling. Vital dentin was etched with 10% citric acid-3% ferric chloride, rinsed, and sealed with 4-META system. A provisional crown was formed with a low-viscosity light-curing adhesive resin. Teeth were fixed and evaluated histopathologically. Pulpal responses at 3 days showed only minimal disruption of the odontoblastic zone. At 7 days, the pulps presented reorganizing odontoblastoid cells, and, at 10 days, the pulps showed new odontoblastoid cells with a thin rim of reparative dentin. Pulps of crown preparations that were etched and then sealed with the 4-META system presented healing patterns similar to those of pulps associated with Class V preparations lined with calcium hydroxide, observed in (previous) similar studies.

Acid Etching, Dental↗
PubMed1994

Pulpal response to adhesive resin systems applied to acid-etched vital dentin: damp versus dry primer application.

A number of studies have reported that acid etching of dentin is toxic to the cells of the odontoblastic layer and dental pulp. Other studies report that pulpal inflammation is a consequence of bacterial microleakage. The purpose of this study was to observe the degree of pulpal healing after pretreatment of vital dentin prior to placement of All-Bond and Scotch-bond 2 composite resin adhesives. Zinc oxide-eugenol cement and an acidic cement were employed as controls. One hundred twelve Class V nonexposed cavity preparations were placed throughout the dentitions of five healthy adult rhesus monkeys and observed at 3, 25, and 80 days. Various dentinal pretreatment procedures were employed. The All-Bond Universal primer system was placed on air-dried vital dentin in 23 cavities and on damp vital dentin in 27 cavities. Scotchbond 2 was placed as per manufacturer's instructions. All treatment procedures, materials, and times were represented in all animals. Placement of silicate cement resulted in the most severe pulpal responses at all time periods. Stained bacterial profiles in the remaining dentin on the axial walls of inflamed control pulps were associated with severe pulpal inflammation. These results indicate that acid etching of vital dentin does not impair pulpal healing in deep Class V cavities.

Acid Etching, Dental↗
PubMed1994

Febrile infants at low risk for serious bacterial infection--an appraisal of the Rochester criteria and implications for management. Febrile Infant Collaborative Study Group.

OBJECTIVE: Prospective studies were conducted to test the hypothesis that infants unlikely to have serious bacterial infections (SBI) can be accurately identified by low risk criteria. METHODS: Febrile infants (rectal T > or = 38 degrees C) < or = 60 days of age were considered at low risk for SBI if they met the following criteria: 1) appear well; 2) were previously healthy; 3) have no focal infection; 4) have WBC count 5.0-15.0 x 10(9) cells/L (5000-15,000/mm3), band form count < or = 1.5 x 10(9) cells/L (< or = 1500/mm3), < or = 10 WBC per high power field on microscopic examination of spun urine sediment, and < or = 5 WBC per high power field on microscopic examination of a stool smear (if diarrhea). The recommended evaluation included the culture of specimens of blood, cerebrospinal fluid, and urine for bacteria. Outcomes were determined. The negative predictive values of the low risk criteria for SBI and bacteremia were calculated. RESULTS: Of 1057 eligible infants, 931 were well appearing, and, of these, 437 met the remaining low risk criteria. Five low risk infants had SBI including two infants with bacteremia. The negative predictive value of the low risk criteria was 98.9% (95% confidence interval, 97.2% to 99.6%) for SBI, and 99.5% (95% confidence interval, 98.2% to 99.9%) for bacteremia. CONCLUSIONS: These data confirm the ability of the low risk criteria to identify infants unlikely to have SBI. Infants who meet the low risk criteria can be carefully observed without administering antimicrobial agents.

Anti-Bacterial Agents↗
PubMed1993

Pulpal healing and dentinal bridge formation in an acidic environment.

This study was designed to observe the healing and bridging capacity of mechanically exposed pulps that were capped with silicate or zinc phosphate cements and biologically sealed with zinc oxide-eugenol cement to exclude bacteria. In six monkeys, Class V facial cavities with pulpal exposures were randomly distributed throughout 105 teeth, of which 80 were directly capped, 40 with silicate cement and 40 with zinc phosphate cement. Twenty of each group were filled to the cavosurface margin with the respective cement and 20 were surface sealed to the cavosurface margin with zinc oxide-eugenol cement. The remaining 25 exposures were capped with calcium hydroxide and amalgam as controls. Tissues were obtained by perfusion fixation after intervals of 21, 14, 10, 5 and 3 days. The 25 pulps capped with calcium hydroxide showed cell migration and organization at 5 days and dentinal matrix deposition at 10 days. At 3 and 5 days, all exposures in the experimental groups showed clot resolution. At 10 days, fibroblasts had stratified against the cement interface. At 14 days, pulps in both experimental groups showed new dentinal bridge formation directly adjacent to the acidic cements. The 21-day experimentally capped and sealed pulps presented healing similar to the controls. This study indicates that acidic components of silicate and Zinc phosphate cements are not directly responsible for pulpal inflammation or necrosis. The exposed dental pulp possesses an inherent healing capacity for cell reorganization and dentinal bridge formation when a bacterial seal is provided.

Animals↗
PubMed1992

The principal islet of the Coho salmon (Oncorhyncus kisutch) contains the BB isoenzyme of creatine kinase.

The importance of creatine kinase (E.C. 2.7.3.2) in endocrine tissues has been generally overlooked. Using a specific radiometric assay, we have demonstrated the existence of CK in the Brockmann body (principal islet) of the Coho salmon. We have purified this protein from insular tissue and concurrently purified CK from brain and muscle of the salmon. Purification characteristics, immunological cross-reactivity, and N-terminal sequence analysis have demonstrated that the predominant cytosolic CK from the Brockmann body is indistinguishable from the BB (brain) isoenzyme. Immunocytochemical studies indicated that the enzyme resides in the endocrine parenchyma. Phosphocreatine may serve as a reservoir of energy in the islet and augment its capacity to secrete hormones. The induction of CK-BB in the islet by other hormones could influence the secretion of insular hormones. Interorgan flux of the substrate creatine may be an undescribed mechanism of physiological regulation.

Amino Acid Sequence↗
PubMed1992

Reparative dentin: factors affecting its deposition.

Results of this study showed no correlation between the thickness or amount of reparative dentin deposited and the type of dental restorative material placed at either 5 or 8 weeks in controlled Class V cavity preparations in monkey teeth. Factors such as preparation trauma from the bur, operator hand instrumentation, and microleakage of bacterial toxins played a greater role in the stimulation of reparative dentin than did material irritation or toxicity. Some differences in the thickness of the reparative dentin deposited were noted when teeth were grouped according to the amount of remaining dentin.

Analysis of Variance↗
PubMed1990

Trial base adapted with sealed temporary soft liner.

Autopolymerizing acrylic resin is combined with temporary soft reline material to make a record base. Rigid acrylic resin is formed over a wax spacer. The wax is removed and the loose-fitting base is relined on the master cast with soft reline material. The soft material is cured in a pressure pot and sealed with a mono-poly mixture. Visible light-curing material can be used instead of autopolymerizing acrylic resin.

Acrylic Resins↗
PubMed1989

Two-stage impression technique for overdentures.

Overdentures are supported by hard tissue and resilient tissue. Optimum distribution of functional load between these different tissue types is a challenge. A two-stage impression technique is proposed to eliminate much of the need for finished denture base modification. A first stage impression is made of the resting form of the soft tissue and is used to make a mucostatic metal base. A second impression is developed under occlusal pressure with modeling compound applied to the border and the surfaces of the metal base overlying the abutments. This procedure establishes border seal and relates ridge tissue displacement to the abutments. A final cast is made by using the metal base and modeling compound. Heat-cured acrylic resin is processed to the metal base on this cast. Adjustment of the tissue surface of the base is limited to surfaces overlying free marginal gingivae and axial surfaces of the abutments.

Alveolar Process↗
PubMed1989

Fixed partial dentures opposing complete dentures.

When fixed partial dentures are indicated in an arch opposing a complete denture, it is best to develop the occlusal surfaces of the fixed restorations at the same time that the opposing denture teeth are arranged in wax to permit greater flexibility and reduce the compromise in developing bilateral balanced occlusion. This article describes the development of bilaterally balanced occlusion between casting patterns for fixed partial dentures and a complete denture. The technique emulates the ease of arranging maxillary and mandibular denture teeth and can be used to develop fixed restorations with metal or porcelain occlusal surfaces. Porcelain occlusal surfaces are described because the use of porcelain is more technique sensitive.

Acrylic Resins↗
PubMed1988

Professional liability. Etiology.

Once again, I find Mr. Cooper quote-worthy for his statement, "It is incumbent upon the trial bar not to support the status quo merely because it is in our economic interest. Change is in the wind, and our tort system will be blown away on the winds of change for change's sake unless we participate in correcting deficiencies in the tort system and civil jury trial process." I suggest that we cannot ask for change for our own economic interest, nor can we lay blame exclusively to the other etiologic elements. We must improve those elements within our purview. The prayer of serenity may serve us well: God, grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference. In the game of professional liability litigation as played by the rules extant there are clearly winners and losers. The winners are the legal profession, both plaintiff and defense, and the insurers, who in the face of adversity simply increase premiums or withdraw from the market. The losers are the medical profession, the patients for whom they care and, in the broadest sense, our society as a whole. So as not to close on a note of gloom, one last quote. Lawrence H. Cooke, former Chief Judge of New York State, in remarks to the April 1986 National Symposium on Civil Justice Issues stated, "Our justice systems are beset with very real problems.(ABSTRACT TRUNCATED AT 250 WORDS)

Attitude of Health Personnel↗
PubMed1985

A potentiostatic study of the corrosion behavior of anodized and nonanodized aluminum alloy.

The clinical implication of this study is that some improvement in the corrosion resistance of denture bases made with aluminum alloy D-214 may be obtained by anodization. However, since this study does not exactly duplicate an oral environment or take into consideration the variation in oral environments, it cannot be assumed that the additional corrosion resistance would be discernible in a particular patient.

Aluminum↗