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J Whitney

Publications and source records attributed to J Whitney.

At least 19 recordsLinked to original sources
PubMed1999

Mass spectrometry of 3,5- and 4,5-dicaffeoylquinic acids and selected derivatives

The mass spectral properties of 3,5- and 4,5-dicaffeoylquinic acids (DCQAs) and selected derivatives were examined using electron ionization (EI), fast atom bombardment (FAB) and electrospray ionization (ESI). EI analysis of the trimethylsilyl derivatives provides molecular mass (M(r)) information, but the spectrum is dominated by fragment ions of the caffeic acid group; isomers cannot be differentiated using EI. FAB analysis, in both the positive and negative ion detection modes, provides M(r) information on the free compounds, but little fragmentation is observed using normal scan conditions. The FAB mass-analyzed ion kinetic energy spectroscopic analysis of the free compounds does, however, permit differentiation of the isomers, with 3,5-DCQA showing selective loss of water, a process not observed with the 4,5-isomer. Both EI and FAB provide M(r) and some structural information when applied to the peracetate derivatives of the DCQAs. ESI of the DCQAs provides considerably more structural information, especially in the negative ion detection mode, and is the recommended method of analysis of the quinic acid esters. M(r) information, identity of the ester groups and differentiation of isomers are possible using ESI. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1996

Relationship between joint motion and flexor tendon force in the canine forelimb.

To increase in vivo tendon force and gliding after flexor tendon repair, a variety of modifications to the methods by which protective passive motion is administered have been advocated. To determine the relationship between the prime variables, wrist and digital position, muscle activation, and in vivo tendon force, a clinically relevant canine model was developed. Force was measured in the flexor tendon during several joint manipulation paradigms: single-finger flexion-extension with the wrist flexed (group 1F), single-finger flexion-extension with the wrist extended (group 1E), four-finger flexion-extension with the wrist flexed (group 4F), four-finger flexion-extension with the wrist extended (group 4E), and synergistic wrist and finger motion where wrist extension and finger flexion were performed simultaneously, followed by wrist flexion and finger extension (group SYN). In addition, tendon force was measured during electric stimulation of the proximal flexor muscle mass. Passive tendon force with the wrist extended (groups 1E and 4E) was two to three times greater than that measured with the wrist flexed, independent of the number of digits moved. With the wrist extended, peak tendon force reached 1,997 g +/- 194 g during single-digit manipulation (group 1E), compared to only 853 g +/- 104 g with the wrist flexed during the same maneuver (group 1F). Statistical comparison between means revealed that groups 1E and 4E were significantly different from groups 1F, 4F, and SYN (p < .005). There were no significant differences between groups 1E and 4E or between groups 1F, 4F, and SYN (p > .200). Active muscle force elicited by electrical stimulation and passive force varied dramatically as the wrist was flexed from full extension 3460 g +/- 766 g to full flexion 427 g +/- 239 g (p < .001). Simultaneously, passive tension decreased from 940 g +/- 143 g with wrist extended to 76 g +/- 37 g with the wrist flexed. These data indicate that wrist position has the greatest effect on flexor tendon force during motions that are commonly used to rehabilitate flexor tendon repairs. Thus, if force is to be controlled during passive motion, wrist-joint angle will have the dominant effect, while the number of digits manipulated will have much less of an effect. If the clinical goal is to minimize tendon force, rehabilitation could be carried out with the wrist flexed, whereas if the goal is to increase tendon force, rehabilitation could include exercise programs that use a greater degree of wrist extension.

Animals↗
PubMed1991

Vanillin, a potential agent for the treatment of sickle cell anemia.

Vanillin, a food additive, has been evaluated as a potential agent to treat sickle cell anemia. Earlier studies indicated that vanillin had moderate antisickling activity when compared with other aldehydes. We have determined by high performance liquid chromatography that vanillin reacts covalently with sickle hemoglobin (HbS) both in solution and in intact red blood cells. Hemoscan oxygen equilibrium curves show a dose-dependent left shift, particularly at low oxygen tensions. Rheologic evaluation (pO2 scan Ektacytometry) of vanillin-reacted HbS erythrocytes shows a dose-dependent inhibition of deoxygenation-induced cell sickling. Ektacytometry also suggests that vanillin may have a direct inhibitory effect on HbS polymer formation. Vanillin has no adverse effects on cell ion or water content. X-ray crystallographic studies with deoxyhemoglobin (HbA)-vanillin demonstrate that vanillin binds near His 103 alpha, Cys 104 alpha, and Gln 131 beta in the central water cavity. A secondary binding site is located between His 116 beta and His 117 beta. His 116 beta has been implicated as a polymer contact residue. Oxygen equilibrium, ektacytometry, and x-ray studies indicate that vanillin may be acting to decrease HbS polymerization by a dual mechanism of action; allosteric modulation to a high-affinity HbS molecule and by stereospecific inhibition of T state HbS polymerization. Because vanillin is a food additive on the GRAS (generally regarded as safe) list, and because it has little or no adverse effects at high dosages in animals, vanillin is a candidate for further evaluation as an agent for the treatment of sickle cell disease.

Anemia, Sickle Cell↗
PubMed1991

Temperature cycler evaluation: what do you need to know?

Which of the 20 different, commercially available, temperature cyclers adequately fulfill all functional requirements? How can an investigator analyze instrument function? This report describes in detail, for the first time, the characteristics of Ericomp temperature cyclers. The data show that the temperature uniformity, accuracy and maximum overshoot is +/- 0.34 degree C, less than 0.5 degree C and 0.17 degree C, respectively. Cycling temperature reproducibility is 0.1%, and cycling time reproducibility is 0.4%. These data compare very favourably to published data describing other temperature cyclers. The techniques used to obtain these data serve as a model for evaluating instruments for well-to-well uniformity, temperature accuracy and within-run reproducibility.

Biotechnology↗
PubMed1990

Surface electrical stimulation versus brace in treatment of idiopathic scoliosis.

Surface electrical stimulation using the ScoliTron device was applied to 40 adolescent patients for treatment of idiopathic scoliosis. Adequate follow-up was available for 30 of these patients. The overall failure rate was 15 of 30 or 50%. Due to curve progression while using the ScoliTron, these patients either went on to a fusion (9 of 15) or were changed to a brace (6 of 15). The remaining 15 patients were considered successes with no curve progression (10 of 30 or 33%) or successful/failures with slight curve progression not requiring a change in treatment (5 of 30 or 17%). None of the various parameters analyzed were found to be useful indicators of successful treatment using the ScoliTron device. Electrical stimulation was found to be ineffective in preventing curve progression for idiopathic scoliosis.

Adolescent↗
PubMed1986

Fast atom bombardment combined with tandem mass spectrometry for determination of bile salts and their conjugates.

Fast atom bombardment desorption of bile salts produces negative ions which show little fragmentation. The lack of fragmentation limits the utility of the method for resolving questions regarding specific structural features. This paper is a report of negative ion fast atom bombardment mass spectra and collision-activated decomposition spectra of cholate, chenodeoxycholate, lithocholate, taurocholate, taurochenodeoxycholate, taurolithocholate, 3 beta-ol-5-cholenate, taurolithocholate-3-sulfate and glycolithocholate-3-sulfate. The collision-activated decomposition spectra are useful for distinguishing bile salt structural features and for quantifying relative amounts of isomeric ions in a mixture. The negative ion mode is well suited for generating anions of bile salts and, when coupled with collisional activation, provides complementary information to the positive ion mode. The collision-activated fragmentation is also unusual as it appears to be an example of reactions occurring remote from the charge site. Furthermore, on the basis of the fragmentations, the charge site can be located in the amphiprotic form of some gas-phase diprotic bile acids such as taurolithocholate-3-sulfate and glycolithocholate-3-sulfate.

Bile Acids and Salts↗
PubMed1985

In vitro synthesis of vitamin D-3 by cultured human keratinocytes and fibroblasts: action spectrum and effect of AY-9944.

With delineation of the photochemical events occurring in the skin after ultraviolet exposure, there has been increased interest in the skin's role in the vitamin D-3-endocrine system. We provide here in vitro conditions for the generation of both labelled (from [3H]acetate) and unlabelled vitamin D-3 in cultures of human keratinocytes and fibroblasts. Sterol precursors and photoproducts in irradiated and non-irradiated cultures are identified by co-chromatography, ultraviolet absorbance spectra, thermal conversion characteristics of previtamin D-3 and mass spectrometry. Because the conversion of 7-dehydrocholesterol to cholesterol is more efficient in vitro than in vivo, the specific delta 7 inhibitor, AY-9944, was added in non-toxic doses to modulate 7-dehydrocholesterol content. Both cell types were equally capable of generating photoproducts, depending on the amount of 7-dehydrocholesterol present. The 290 +/- 5 and 295 nm filters were much more efficient than the 305 nm filter for generating previtamin D-3 and vitamin D-3 in fibroblasts. In contrast, the 305 nm filter was as efficient as the 290 +/- 5 and 295 nm filters in keratinocytes, where it yielded previtamin D-3, with much less lumisterol and tachysterol than appeared with the shorter-wavelength filters. The amount of lumisterol and tachysterol versus previtamin D-3 formed in both cell types was dependent on the total energy applied, with lower energies (less then 1 J/cm2) favoring previtamin D-3 over the other photoproducts. The use of cultured cells provides a system whereby the regulation of vitamin D-3 synthesis by extracutaneous factors can be studied in a homogeneous setting.

Aldehyde Oxidoreductases↗
PubMed1984

The relationship of membrane fluidity to calcium flux in chick intestinal brush border membranes.

To evaluate whether membrane fluidity plays a role in regulating calcium flux across the intestinal brush border, we purified brush border membranes from different regions of the chick intestine and determined the relationship of their ability to transport calcium and their fluidity parameters, as determined by diphenylhexatriene fluorescence polarization. Raising the temperature from 4 to 37 C resulted in a 3-fold increase in calcium accumulation by duodenal brush border membrane vesicles (BBMV; 2.85 to 8.70 nmol/mg protein X 12 min). This rise in temperature was associated with a decrease in degree of polarization from 0.395 to 0.290. The methyl esters of cis- and trans-vaccenic acid markedly increased calcium uptake at all temperatures studied (4, 25, and 37 C); the trans isomer was more effective. Both cis- and trans-vaccenic acid lowered the degree of polarization of the BBMV from 0.340 to 0.311 and 0.293, respectively, at 25 C. cis- and trans-vaccenic acid were effective whether BBMV were prepared from vitamin D-deficient chicks or their hatchmates given 1,25-dihydroxyvitamin D [1,25-(OH)2D]. The ability to accumulate calcium correlated to the degree of polarization when calcium uptake by and degree of polarization of BBMV prepared from duodenum, jejunum, and ileum were compared at 25 C. The duodenal BBMV had the greatest calcium accumulation (9.4 nmol Ca/mg protein X 10 min) and the lowest degree of polarization (0.336); the ileal BBMV had the least calcium accumulation (3.5 nmol Ca/mg protein X 10 min) and the greatest degree of polarization (0.375); and the jejunal BBMV were intermediate (8.2 nmol Ca/mg protein X 10 min; 0.344). This rank order was the same whether the intestine was from vitamin D-deficient chicks or their hatchmates given 1,25-(OH)2D before they were killed. 1,25-(OH)2D stimulated calcium uptake by duodenal and jejunal BBMV, reaching a maximal effect at 4 h, but no changes in degree of polarization were observed during this period. A plot of the degree of polarization as a function of the reciprocal of absolute temperature showed an inflection point at approximately 25 C. Neither the slope of the plot nor the point of the inflection was altered by 1,25-(OH)2D. We conclude that chick intestinal BBMV membrane fluidity and calcium uptake correlate in relation to the effects of temperature, changes in membrane lipids, and regional differences in the intestine. However, 1,25-(OH)2D stimulates calcium uptake by BBMV without a detectable change in membrane fluidity.

Animals↗
PubMed1983

Vitamin D3 production by cultured human keratinocytes and fibroblasts.

We have demonstrated that monolayers of human cultured newborn foreskin keratinocytes and fibroblasts elaborate vitamin D3 following exposure to UV-B. This in vitro system provides a new means to study those factors (hormones, ions, vitamin D3 metabolites, etc.) that regulate the production of vitamin D3 by human skin cells. Vitamin D3 production was enhanced greatly by using cells that were pre-treated with AY-9944, a non-toxic drug that inhibits cholesterologenesis while elevating cellular levels of 7-dehydrocholesterol, the sterol precursor of vitamin D3. The pre-D3 formed within viable, irradiated cells is transformed to D3 within a matter of hours at 37 degrees C, and keratinocytes proved to be more proficient sources of the vitamin and its metabolites than corresponding skin fibroblasts.

Acetates↗
PubMed1983

The role of conjugation reactions in enhancing biliary secretion of bile acids.

Shortening the five-carbon carboxylic acid side chain of cholic acid by one methylene group gave rise to a bile acid (norcholate) that was not a substrate for the bile acid-conjugating enzymes. The metabolism and biliary secretion of norcholate in intact liver was examined in the isolated perfused rat liver system. When rat livers were perfused with 14-20 microM solutions of norcholate for 10 min, norcholate was found in the unconjugated form in liver, venous effluent and bile. Neither tauronorcholate nor glyconorcholate was detectable by high-pressure liquid chromatography or fast-atom-bombardment mass spectrometry. The kinetics of hepatic uptake and biliary secretion of norcholate was compared with that for cholate, taurocholate and chemically synthesized tauronorcholate. The latter three bile acids were completely cleared from the perfusate and efficiently secreted into the bile. However, norcholate was incompletely extracted from the perfusate, and this was shown to be at least partially due to its relatively lower rate of hepatic uptake. Furthermore, the rate of norcholate secretion into bile was greatly reduced relative to the secretion of cholate or chemically synthesized tauronorcholate, even though the concentration of norcholate in the liver was comparatively high. These data demonstrate that the conjugation of bile acids greatly facilitates their secretion into bile.

Animals↗
PubMed1983

Human stratum corneum lipids: characterization and regional variations.

The lipids of mammalian stratum corneum are known to be important regulators of skin permeability. Since the human stratum corneum displays remarkable regional variations in skin permeability, we assessed the total lipid concentration, the distribution of all major lipid species, and the fatty acid composition in Bligh-Dyer extracts from four skin sites (abdomen, leg, face, and sole) that are known to display widely disparate permeability. Statistically significant differences in lipid weight were found at the four sites that were inversely proportional to their known permeability. In all four sites, among the polar lipids, the stratum corneum contained negligible phospholipids, but substantially more cholesterol sulfate (1-7%) than previously appreciated. As in the stratum corneum from other mammals, the bulk of the lipids consisted of neutral (60-80%) and sphingolipids (15-35%). Of the neutral lipids, free sterols (4- to 5-times greater than esterified sterols), free fatty acids, triglycerides, and highly nonpolar species (n-alkanes and squalene) predominated. n-Alkanes, which were present in greater quantities than previously appreciated, comprised a homologous series of odd- and even-chained compounds ranging from C19 to C34. The sphingolipids comprised over 80% ceramides vs. lesser quantities of glycosphingolipids. In all four sites, the sphingolipids were the major repository of long-chain, saturated fatty acids. The neutral lipid:sphingolipid ratio generally was proportional to the known permeability of each site: higher neutral lipids and lower sphingolipids generally were associated with superior barrier properties. These studies provide: 1) the first detailed, quantitative analysis of human stratum corneum lipids and 2) information about the variability in lipid composition at four skin sites with known differences in permeability. The latter results suggest that variations in neutral lipids, rather than sphingolipids, may underlie local variations in skin permeability.

Alkanes↗