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Biomedical subjects

S H Day

Publications and source records attributed to S H Day.

At least 19 recordsLinked to original sources
PubMed2001

Bioactive constituents of the roots of Cynanchum atratum.

A novel biphenylneolignan, 2,6,2',6'-tetramethoxy-4,4'-bis(2,3-epoxy-1-hydroxypropyl)biphenyl (1), and two new glycosides named atratoglaucosides A (2) and B (3), were isolated from the roots of Cynanchum atratum, and their structures were determined on the basis of chemical and spectroscopic evidence. The aglycons of 2 and 3 were identified as glaucogenin C and 7-desoxyneocynapanogenin A, a new disecopregnane. A known compound, glaucogenin C 3-O-beta-D-cymaropyranosyl-(1-->4)-alpha-L-diginopyranosyl-(1-->4)-beta-D-thevetopyranoside (4), isolated from the same source, showed a significant cytotoxic effect against 212 cells. This substance also gave a significant inhibitory effect on TNF-alpha (tumor necrosis factor-alpha) formation from the RAW 264.7 mouse macrophage-like cell line stimulated with LPS (lipopolysaccharide) and on the N9 microglial cell line stimulated with LPS/IFN-gamma (interferon-gamma).

Animals↗
PubMed2000

New lignan glycosides with potent antiinflammatory effect, isolated from Justicia ciliata.

Two new lignan glycosides, 4-O-[alpha-L-arabinopyranosyl-(1' "-->2' ')-beta-D-xylopyranosyl-(1' " '-->5' ')-beta-D-apiofuranosyl]diphyllin (1), named ciliatoside A (1), and 4-O-¿[beta-D-apiofuranosyl-(1' " "-->3' ")-alpha-L-arabinopyranosyl-(1' "-->2' ')][beta-D-xylopyranosyl-(1' " '-->5' ')]-beta-D-apiofuranosyl¿diphyllin (2), named ciliatoside B (2), were isolated from the whole plant of Justicia ciliata. The structures of 1 and 2 were determined by spectral and chemical methods. Compounds 1 and 2 strongly inhibited the accumulation of NO(2)(-) in lipopolysaccharide-stimulated RAW 264.7 cells in a concentration-dependent manner with IC(50) values of 27.1 +/- 1.6 and 29.4 +/- 1.4 microM, respectively.

Animals↗
PubMed1999

Induction of cytochrome-P450 in cryopreserved rat and human hepatocytes.

Our laboratory has been routinely using suspended and cultured human hepatocytes for predicting drug metabolism and enzyme induction by drug candidates to aid drug discovery. Increasing limitation and irregular availability of human tissue has indicated the need for maximizing the use of this valuable resource. Cryopreservation of surplus hepatocytes after isolation would greatly increase the potential of this model. However, cryopreservation of hepatocytes by various methods has resulted in cells with poor metabolic activity and unacceptably low survival rates in culture. Recently, Zaleski et al. (Biochem. Pharmacol. 46 (1993) 111-116) reported that cryopreserved rat hepatocytes retained metabolic capacity similar to fresh hepatocytes when the cells were preincubated for 30 min at 37 degrees C in Krebs Ringer bicarbonate buffer prior to freezing. To further explore this methodology, both the functional capacity of the cells in culture as well as their ability to retain CYP inducibility were investigated with thawed cryopreserved hepatocytes. Although human hepatocytes were used in this study the initial work focused on rat hepatocytes as a cell model. Our results showed that while the preincubation step did not appear to effect the initial viability of cryopreserved hepatocytes, survival of the cells in culture was greatly enhanced. Plating efficiencies for nonpreincubated cryopreserved hepatocytes were decreased to approximately 15% of fresh cells after 48 h in culture. In contrast, cells that had been preincubated prior to freezing had an excellent plating efficiency (approximately 60%) and responded to classical CYP inducers dexamethasone, beta-naphthoflavone and phenobarbital in a manner indistinguishable from that of fresh hepatocytes. Experiments with human hepatocytes have also demonstrated similar results. This is the first time to our knowledge that cryopreserved hepatocytes from both rat and human have been shown to reproducibly respond to CYP inducers in culture.

Animals↗
PubMed1999

Cryopreservation of rat and human liver slices by rapid freezing.

The cryopreservation of human liver slices is a promising way to enhance the ability to test the metabolism of drug candidates. This study demonstrates the use of a novel technique for the cryopreservation of both rat and human liver slices. In this technique the slices are treated with Me2SO and sandwiched between aluminum plates separated by a thin gasket. The device is then submerged in liquid nitrogen to freeze the slices, which can then be stored until use. To thaw the slices, the apparatus is submerged in a water bath at 37 degrees C. Slices frozen and thawed in this manner were compared to those frozen in conventional cryovials. The viability of the slices was determined by incubating them in 12-well plates and measuring urea synthesis, ethoxycoumarin metabolism, and cytosolic enzyme leakage (LDH and ALT). The viability of rat slices frozen between plates approached that of fresh slices and was consistently higher than slices frozen in cryovials. Slices from two human samples gave similar results. The technique was found to work over a wide range of Me2SO concentrations (4.5 to 22% was tested) with an optimal concentration between 10 and 15%.

Aged↗
PubMed1999

Cytotoxic lignans of Justicia ciliata.

Two new naturally occurring 1-aryl-2,3-naphthalide lignans, cilinaphthalide A (1) and cilinaphthalide B (2), and nine known compounds were isolated from the whole plant of Justicia ciliata. Their structures were established by spectral analysis, and their cytotoxic activity was evaluated against several different cell lines. The known compound, justicidin A, showed potent cytotoxic effects against T-24, CaSki, SiHa, HT-3, PLC/PRF/5, and 212 cells in vitro.

Antineoplastic Agents, Phytogenic↗
PubMed1999

Molecular flexibility profiling using NMR spectroscopy.

Molecular flexibility is a factor that is not extensively studied in most pharmaceutical research efforts. When it is, the level of effort is high involving the preparation of detailed models supported by either molecular dynamics simulations and/or Nuclear Magnetic Resonance data. While these studies are both powerful and illuminating, they cannot be routinely applied in a drug discovery setting as they are time and expertise intensive. Yet there seems to be little doubt that at least in some cases, molecular flexibility plays a key role in complex formation. A simple, rapid and generally applicable flexibility profiling protocol was applied to two model systems and data describing the internal mobility of carbon atoms were obtained. The protocol utilizes the Model Free approach and NMR data to characterize the internal molecular dynamics of these compounds. The first model system consisted of fluorene and diphenylmethane where the anticipated flexibility trends were observed in the data providing a link between chemical intuition and the experimental results. Data on a second model system, which consisted of two Paclitaxel analogs, showed predictable patterns including dynamical phenyl and methyl groups and a relatively immobile taxane core. Subtle differences in the internal dynamics within the taxane core suggest that it cannot be considered as a rigid structure. Key advantages of using this approach are that no prior knowledge or supposition of dynamical features is required, the protocol can be carried out in most medicinal chemistry laboratories and the data obtained provide a common, empirically derived reference point to discuss the effects of molecular flexibility on activity.

Benzhydryl Compounds↗
PubMed1999

Ophthalmology's future in the next decade: a historical and comparative perspective.

PURPOSE: To gain a historical and comparative perspective about the future of ophthalmology within the profession of medicine. METHODS: A literature search is made of disciplines other than medicine (history, sociology, philosophy, economics, and ethics) in order to assess factors responsible for survival and healthiness of a profession. The "learned" professions (medicine, law, and theology) are assessed. Other "professional" careers valued by society (sports and classical music) are reviewed. RESULTS: From the perspective of other disciplines, the future of ophthalmology is seen as vulnerable and fragile. Survival of professions, be they classically or economically defined, is linked to societal needs, a profession's unique commitment and ability to provide services to society, and the profession's maintenance of knowledge as well as skill-based services. Historical evidence has shown erosion of a profession's power consequent to capitalist influences, government influences, access of skills by less trained individuals, and elitist posturing by a profession. Comparative evidence has shown societal acceptance of an escalation of salaries for designated superstars, increasing roles and influence of managerial personnel, and trivialization of values other than economic ones. CONCLUSION: Attention to historical and comparative trends by individual ophthalmologists as well as associations representing ophthalmologists is mandatory if ophthalmology as we know it is to survive within the profession of medicine.

Education, Medical↗
PubMed1998

Stereochemistry and biological activities of constituents from Cynanchum taiwanianum.

The stereochemistry of new acetophenones, cynandione B-D (2-4), isolated from Cynanchum taiwanianum, elucidated by computer modelling calculation and NOESY spectrum. It establishes the absolute configurations of cynandiones B-D (2-4) as 7R; 7"S, 7S; 7"S and 7R; 7"R, respectively. Cynandione B (2) strongly inhibited the release of beta-glucuronidase and lysozyme in formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated rat neutrophils in a concentration-dependent manner with IC50 values of 1.5 +/- 0.2 and 1.6 +/- 0.2 microM, respectively. 2,5-Dihydroxyacetophenone (6) strongly inhibited the aggregation of washed rabbit platelets induced by arachidonic acid in a concentration-dependent manner with an IC50 value of about 4.8 microM. In human citrated platelet-rich plasma, 2,5-dihydroxyacetophenone (6) inhibited the secondary phase, but not the primary phase, of aggregation induced by adrenaline and ADP. These results suggest that the antiplatelet effect of 2,5-dihydroxyacetophenone (6) is due to inhibition of the formation of thromboxane A2.

Acetophenones↗
PubMed1998

Electromyogram activity and mean power frequency in exercise-damaged human muscle.

Eight volunteers performed two bouts of 50 voluntary maximal eccentric contractions of the knee extensors of one leg 3 weeks apart. During maximal voluntary isometric contractions performed at intervals after each bout, electromyogram (EMG) mean power frequency declined after bout one (P < 0.01 Duncan's test), whereas integrated EMG did not change after either bout. These results suggest that unaccustomed eccentric contractions produce a temporary reduction in mean muscle activation frequency during subsequent maximal isometric contractions.

Adult↗
PubMed1998

The effect of severe eccentric exercise-induced muscle damage on plasma elastase, glutamine and zinc concentrations.

The aim of this study was to determine if severe exercise-induced muscle damage alters the plasma concentrations of glutamine and zinc. Changes in plasma concentrations of glutamine, zinc and polymorphonuclear elastase (an index of phagocytic cell activation) were examined for up to 10 days following eccentric exercise of the knee extensors of one leg in eight untrained subjects. The exercise bout consisted of 20 repetitions of electrically stimulated eccentric muscle actions on an isokinetic dynamometer. Subjects experienced severe muscle soreness and large increases in plasma creatine kinase activity indicative of muscle fibre damage. Peak soreness occurred at 2 days post-exercise and peak creatine kinase activity [21714 (6416) U x l(-1) mean (SEM)] occurred at 3 days post-exercise (P < 0.01 compared with pre-exercise). Plasma elastase concentration was increased at 3 days post-exercise compared with pre-exercise (P < 0.05), and is presumably indicative of ongoing phagocytic leucocyte infiltration and activation in the damaged muscles. There were no significant changes in plasma zinc and glutamine concentrations in the days following eccentric exercise. We conclude that exercise-induced muscle damage does not produce changes in plasma glutamine or zinc concentrations despite evidence of phagocytic neutrophil activation.

Adult↗
PubMed1998

Manipulation of knee extensor force using percutaneous electrical myostimulation during eccentric actions: effects on indices of muscle damage in humans.

Percutaneous electrical myostimulation (PES) was used to manipulate the force produced by the knee extensor muscles during eccentric exercise, thereby providing a model to investigate the role of force in muscle damage. Two eccentric exercise bouts of equal work were performed by nine subjects, using fixed voltage PES at 20 Hz (to produce moderate muscle forces) and 100 Hz (to produce high muscle forces). Muscle contractility, serum creatine kinase activity (CK) and muscle soreness (MS) were evaluated before, and up to 14 days after exercise. Data are presented as means+/-SEM, and were analysed using repeated measures analysis of variance (ANOVA), t-tests and Wilcoxon tests. Peak forces were higher during the 100 Hz bout than the 20 Hz bout for repetitions 1 (472+/-60 vs 237+/-23 Newtons), 10 (381+/-26 vs 233+/-26 Newtons), 20 (310+/-24 vs 218+/-24 Newtons), all p < 0.01, t-test and 30 (297+/-27 vs 204+/-21 Newtons), p < 0.05, t-test. Following the 100 Hz bout, maximum voluntary contractile force (MVC) was lower (p<0.01, ANOVA), and CK was higher (p<0.0001, ANOVA) than after the 20 Hz bout. Subjects also reported greater MS on days 2 to 6 (p<0.05, Wilcoxon test) following the 100 Hz bout. Despite a decline in the stimulated 20:100 Hz tetanic force ratio after each bout (p<0.01, ANOVA) there was no difference between bouts (p>0.05, ANOVA). The higher rise in CK and MS after the 100 Hz bout, together with the greater deficit in MVC, suggest that in humans, muscle force is a contributing factor to muscle injury during eccentric actions.

Adolescent↗
PubMed1998

Refinement of an in vitro cell model for cytochrome P450 induction.

Induction of cytochromes P450 (P450s) by drugs can lead to drug-drug interactions. Primary hepatocytes have been reported to retain inducible P450s. To optimize the use of primary hepatocytes for predicting induction of P450 (CYP 3A and 2B) expression in vivo, both culture conditions and expression of induction potentials were investigated. In rat hepatocytes, basal CYP 3A1/2 expression was better maintained in cells cultured on Matrigel compared with collagen when low concentrations of dexamethasone were used. However, CYP 3A1/2 induction was not affected by either matrix. In contrast, induction of CYP 2B1/2 by phenobarbital was markedly stronger in hepatocytes cultured on Matrigel. To further validate the in vitro model, Sprague-Dawley rats and isolated hepatocytes cultured on Matrigel were exposed to a series of compounds. In an attempt to minimize large variability between experiments, a novel approach for calculating induction potential was applied. In vitro results for CYP 3A1/2 and 2B1/2 induction correlated well with those observed in vivo. In contrast with rat hepatocytes, basal CYP 3A4 expression in human hepatocytes decreased rapidly in cells cultured on either Matrigel or collagen. However, CYP 3A4 inducibility was retained in cells cultured on either matrix. Interestingly, induction of CYP 3A4 in human hepatocytes by several model compounds did not correlate with the induction of CYP 3A1/2 in rat hepatocytes. This in vitro assay should facilitate the demand for a fast and reproducible method for addressing P450 induction by numerous compounds at the drug discovery stage.

Animals↗
PubMed1997

Indices of skeletal muscle damage and connective tissue breakdown following eccentric muscle contractions.

Indirect indices of exercise-induced human skeletal muscle damage and connective tissue breakdown were studied following a single bout of voluntary eccentric muscle contractions. Subjects (six female, two male), mean (SD) age 22 (2) years performed a bout of 50 maximum voluntary eccentric contractions of the knee extensors of a single leg. The eccentric exercise protocol induced muscle soreness (P < 0.05 Wilcoxon test), chronic force loss, and a decline in the 20:100 Hz percutaneous electrical myostimulation force ratio [P < 0.01, repeated measures analysis of variance (ANOVA)]. Serum creatine kinase (CK) and lactate dehydrogenase (LDH) activities were elevated (P < 0.01, repeated measures ANOVA) following the bout. The mean (SD) CK and LDH levels recorded 3 days post-exercise were 2815 (4144) IU.l-1 and 375 (198) IU.l-1, respectively. Serum alkaline phosphatase activity showed no changes throughout the study, and a non-significant increase (P = 0.058, repeated measures ANOVA) in pyridinoline was recorded following the bout. Urinary hydroxyproline (HP) and hydroxylysine (HL) excretion, expressed in terms of creatinine (Cr) concentration, increased after exercise (P < 0.05 and P < 0.01, respectively, repeated measures ANOVA). An increased HP:Cr was recorded 2 days post-exercise and HL:Cr was increased above baseline on days 2, 5, and 9 post-exercise. This indirect evidence of exercise-induced muscle damage suggests that myofibre disruption was caused by the eccentric muscle contractions. Elevated urine concentrations of indirect indices of collagen breakdown following eccentric muscle contractions suggests an increased breakdown of connective tissue, possibly due to a localised inflammatory response.

Adult↗
PubMed1997

Exercise-induced skeletal muscle damage and adaptation following repeated bouts of eccentric muscle contractions.

Repeated bouts of eccentric muscle contractions were used to examine indirect indices of exercise-induced muscle damage and adaptation in human skeletal muscle. Twenty-four subjects (18 females, 6 males) aged 20.0 +/- 1.4 years (mean +/- S.D.) performed an initial bout of either 10 (n = 7), 30 (n = 9) or 50 (n = 8) maximum voluntary eccentric contractions of the knee extensors, followed by a second bout of 50 contractions 3 weeks later using the same leg. Muscle soreness was elevated after all bouts (P < 0.05, Wilcoxon test), although the initial bout reduced the soreness associated with the second bout. Force loss and a decline in the 20:100 Hz percutaneous electrical myostimulation force ratio were observed after all exercise bouts (P < 0.01). Serum creatine kinase activity was elevated following the initial bouts of 30 and 50 repetitions (P < 0.01), but there was no increase following 10 repetitions. No increase in serum creatine kinase activity was observed in any group following the second bout of contractions (P > 0.05). We conclude that skeletal muscle adaptation can be brought about by a single bout of relatively few eccentric muscle contractions. Increasing the number of eccentric muscle repetitions did not result in an increased prophylactic effect on skeletal muscle.

Adaptation, Physiological↗
PubMed1996

Changes in human skeletal muscle contractile function following stimulated eccentric exercise.

Indices of human skeletal muscle contractile function were examined in nine subjects for up to 9 days following a single bout of stimulated eccentric exercise. Eccentric muscle actions of the knee extensor muscles were evoked by percutaneous electrical myostimulation (PES). Delayed onset muscle soreness (DOMS), elevated serum creatine kinase activity, chronic force loss, and a decline in the 20:100 Hz force ratio were observed in the days postexercise. The exercised knee extensor muscles demonstrated an impaired ability to respond to PES. This was evident by an increased time delay between the start of 100 Hz PES and the onset of contraction immediately postexercise [22.3 (SD 15.9)%, P < 0.01] and 3 days postexercise [14.9 (SD 18.1)%, P < 0.05]. Muscle relaxation rates appeared unaffected by the eccentric exercise protocol, where the muscles showed no differences in the time between the end of PES and the onset of relaxation (P > 0.05). During the days following the exercise, no significant differences were observed in the time between the start of contraction and attainment of 70% of the mean tetanic force following a single 1-s pulse of PES. Similarly, no significant differences were observed in the time between the start of relaxation and attainment of 70% of the total relaxation during the same time. The increased delay in excitation-contraction coupling observed immediately postexercise and 3 days after the exercise, may reflect a damage-induced delay in action potential propagation. Muscle relaxation rates postexercise remained unchanged, which would seem to indicate normal functioning of the sarcoplasmic reticulum, suggesting this was not the site of failure in excitation-contraction coupling.

Adult↗
PubMed1995

Activation of hepatic glutaminase by spermine.

Glutaminase activity in intact mitochondria from rat liver is activated by spermine, as indicated both by increased glutamate production from glutamine and by increased respiration with glutamine as sole substrate. Glutaminase activity assayed in membranes from frozen-thawed mitochondria, is activated by spermine about 6-fold at physiological concentrations of its other effectors (NH4+ at 0.7 mM, Pi 5 mM) and at pH 7.4. Spermine decreased the apparent Km for glutamine from 38 to 15 mM at 5 mM Pi, and increased the sensitivity of the enzyme for phosphate activation so that the concentration required for 50% stimulation decreased from 15 to 4 mM. Half-maximal spermine effects occurred at 0.15 mM, which is in the physiological range. Spermine was effective in the presence of physiological concentrations of Mg2+. We suggest that spermine may be a physiological activator of hepatic glutaminase.

Ammonium Chloride↗