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Biomedical subjects

J M Rogers

Publications and source records attributed to J M Rogers.

At least 55 records · Page 3Linked to original sources
PubMed1997

Methanol causes posteriorization of cervical vertebrae in mice.

Inhalation of methanol by pregnant mice before gestation day nine (gd 9) produces fetal skeletal alterations, principally in the cervical region. The appearance of these defects suggests homeotic shifts in segment identity, patterning, or both. To explore this possibility, detailed morphological analyses of the effects of methanol on fetal skeletal development were done. Pregnant mice were gavaged with 0, 4.0, or 5.0 g/kg methanol (MeOH) split in two doses on gd 7, the most sensitive day for induction of skeletal alterations with methanol. Dams were killed on gd 18 and the fetuses were counted, weighed, and examined externally. Fetuses were double stained with alcian blue and alizarin red for examination of cartilaginous and ossified vertebral and rib characteristics, and in selected fetuses cervical vertebrae were disarticulated for more detailed analysis. Observations indicative of methanol-induced homeotic transformations were as follows: [tabular data: see abstract volume] Examination of disarticulated vertebrae revealed foramina and other distinguishing characteristics on vertebrae anterior to those on which they normally appear. These results demonstrate that maternal methanol exposure can alter segment patterning in the developing mouse embryo, producing posteriorization of cervical vertebrae.

Abnormalities, Drug-Induced↗
PubMed1997

Critical periods of sensitivity to the developmental toxicity of inhaled methanol in the CD-1 mouse.

Exposure of pregnant CD-1 mice to methanol (MeOH) by inhalation on gestation days (gd) 6-15 results in dose-related increases in fetal cleft palate, exencephaly, and skeletal defects. Here, critical periods for the developmental toxicity of MeOH were assessed in pregnant CD-1 mice exposed to 10,000 ppm MeOH or filtered air for 7 hr/day on 2 consecutive days during gd 6-13, or to single day (7 hr) exposures to 10,000 ppm MeOH during gd 5-9. Mice received water but not food during exposure. Maternal blood MeOH was determined at times during, at the end of, and subsequent to a single 7 hr exposure on gd 7. On gd 17, remaining mice were weighed, killed, and gravid uteri removed. Live, dead, and resorbed fetuses were counted, and live fetuses were examined, weighed, and preserved in 70% ethanol. All fetuses were examined externally and for cleft palate, eviscerated, and stained with Alizarin red for skeletal examination. Pregnant mice lost an average of 0.3-2.9 g during 7 hr exposure to either filtered air or MeOH, but a MeOH treatment effect was evident only with 2-day exposure on gd 7-8. Peak maternal blood MeOH concentration (at the end of exposure) was approximately 4 mg/ml, and MeOH was cleared from maternal blood within 24 hr. Some fully resorbed litters were observed with 2-day MeOH exposures on gd 6-7 or 7-8, or 1-day exposure on gd 7. With 1-day MeOH exposure on gd 7, the number live was lower than with exposure on any other day. As previously reported, cleft palate, exencephaly, and skeletal defects were the fetal anomalies observed in this mouse strain. Cleft palate occurred with 2-day exposures on gd 6-7 through gd 11-12 (peak on gd 7-8), and with 1-day exposure on gd 5 through gd 9 (peak on gd 7). Exencephaly occurred with 2-day exposures on gd 6-7 through gd 8-9 (peak gd 6-7) or 1-day exposure on gd 5 through gd 8 (peak on gd 7). Skeletal elements malformed included the exoccipital (peak gd 6-7, gd 5), atlas (peak gd 6-7, gd 5,6), axis (peak gd 6-7, gd 7), cervical vertebra 7 with a rib (peak gd 6-7, gd 7), and lumbar vertebra 1 with a rib (peak gd 7-8, gd 7). An increased incidence of fetuses with 25 presacral vertebrae (normal = 26) was observed with methanol exposure on gd 5, whereas an increased incidence of fetuses with 27 presacral vertebrae was observed with MeOH exposure on gd 7. These results indicate that gastrulation and early organogenesis represent a period of increased embryonal sensitivity to methanol.

Abnormalities, Drug-Induced↗
PubMed1997

Nucleoside-mediated mitigation of 5-fluorouracil-induced toxicity in synchronized murine erythroleukemic cells.

5-Fluorouracil (5-FU) is a chemotherapeutic agent known to retard embryonic growth and induce cleft palate and limb deformities. The predominant mechanism underlying its toxic action is thought to be inhibition of thymidylate synthetase (TS), and hence thymidine triphosphate (dTTP) synthesis, resulting in alteration of the balance of deoxynucleotide (dNTP) pools and disruption of DNA synthesis. Indeed, previously we demonstrated retarded cell-cycle progression concurrent with a 60% decrease in TS activity in rat whole embryos following maternal exposure to 40 mg/kg 5-FU on Gestational Day 14 and in the murine erythroleukemic cell (MELC) suspension culture following exposure to 5-25 microM 5-FU for 2 hr. In the study described herein, we used high-performance liquid chromatography (HPLC) to demonstrate in both of these model systems that 5-FU exposure results in similar patterns of dNTP perturbations: a prolonged decrease in dTTP and dGTP levels and an increase in dCTP and dATP. In addition, we used centrifugal elutriation to synchronize MELC in the phases of the cell cycle (G0/G1 and early S) most sensitive to 5-FU to investigate the ability of nucleoside supplementation to mitigate 5-FU-induced toxicity. Our data indicate that following a 2-hr exposure to 5-25 microM 5-FU, supplementation with 1-10 microM thymidine (TdR) for 24 hr partially reverses 5-FU-induced toxicity as evidenced by increased cellular proliferation and cell-cycle progression and amelioration of 5-FU-induced perturbations of protein synthesis and cellular membrane permeability compared to unsupplemented 5-FU-exposed cells. However, TdR concentrations >/=100 microM inhibited growth or were cytotoxic. In comparison, supplementation with 10 microM-10 mM of deoxycytidine (CdR) was not toxic, but effected a dose-dependent recovery from 5-FU-induced toxicity. At 1-100 microM, neither deoxyadenosine nor deoxyguanosine supplementation reduced 5-FU-induced toxicity; at higher concentrations, both purine nucleotides inhibited cell growth. Although these results support the hypothesis that 5-FU disrupts the MELC cell cycle by depleting dTTP (a perturbation that is reversible by TdR supplementation), they also indicate that CdR supplementation offers an additional recovery pathway.

Animals↗
PubMed1997

Equivalent efficacy and reduced occurrence of diarrhea from a new formulation of amoxicillin/clavulanate potassium (Augmentin) for treatment of acute otitis media in children.

OBJECTIVE: To compare the safety and efficacy, in treating acute otitis media (AOM) in children, of a new formulation of amoxicillin/clavulanate potassium (Augmentin) oral suspension providing 45/6.4 mg/kg/day and administered twice daily (bid) for 5 and 10 days, respectively, with the safety and efficacy of the original formulation providing 40/10 mg/kg/day and administered three times daily (tid) for 10 days. STUDY DESIGN: Eight hundred sixty-eight children ages 2 months to 12 years with AOM were randomly assigned to one of the three treatment groups. Stringent criteria were used for the diagnosis of AOM and for determinations of "cure" and "improvement." Subjects were reexamined on Days 12 to 14 and 32 to 38. RESULTS: Among subjects whose treatment and follow-up conformed fully to protocol, the proportion of treatment successes (clinically cured or improved) on Days 12 to 14 was 78.8% (149 of 189) in the tid 10-day group, 86.5% (154 of 178) in the bid 10-day group and 71.1% (140 of 197) in the bid 5-day group. Corresponding values on Days 32 to 38 were 64.2% (95 of 148) in the tid 10-day group, 63.1% (94 of 149) in the bid 10-day group and 57.8% (93 of 161) in the bid 5-day group. None of the differences between the tid 10-day regimen and either of the 2 bid regimens were statistically significant, but the bid 10-day regimen was significantly more effective than the bid 5-day regimen in younger subjects. In the study population as a whole, results were similar to those in per protocol subjects. Overall the incidence of protocol-defined diarrhea was 26.7% (74 of 277) in the tid 10-day group, compared with 9.6% (27 of 280) in the bid 10-day group (P < 0.0001) and 8.7% (25 of 286) in the bid 5-day group (P < 0.0001). CONCLUSIONS: In comparison with the original formulation of Augmentin administered tid for 10 days in the treatment of AOM in children, the new formulation administered bid for 10 days provides at least equivalent efficacy and causes substantially less diarrhea. Administration for 5 days appears not to provide equivalent efficacy, but the difference appears limited to younger children and the margin of difference is small.

Acute Disease↗
PubMed1997

The mental health of informal caregivers in Ontario: an epidemiological survey.

OBJECTIVES: This study describes the mental health status, disability, physical health, and mental health service utilization of informal care-givers under the age of 65 in the province of Ontario. METHODS: The study analyzed data collected in the 1991 province-wide, population-based mental health supplement to the Ontario Health Survey. Diagnoses from the Diagnostic and Statistical Manual of Mental Disorders, 3rd edition, revised, were generated on the basis of a structured diagnostic interview. Caregivers and noncaregivers are compared here on past-year prevalence of psychiatric disorder, physical illness, disability, and utilization of mental health services. The possible confounding effects of age, sex, employment status, and economic disadvantage are explored. RESULTS: Informal caregivers (n = 1219) constituted 15.0% of the sample. Caregivers had higher rates of affective (6.3% vs 4.2%) and anxiety (17.5% vs 10.9%) disorders than noncaregivers and used health services for mental health problems at nearly twice the rate. CONCLUSIONS: Documentation of the prevalence of caregiving and the increased prevalence of psychiatric disorders, disability, and service utilization among caregivers is of critical importance as governments continue to move toward community-based care. To accomplish this goal, the needs of caregivers must be acknowledged and met by the establishment of appropriate and readily accessible support services.

Adolescent↗
PubMed1996

Influence of maternal folate status on the developmental toxicity of methanol in the CD-1 mouse.

Methanol, which is detoxified via a folic acid-dependent pathway, has been shown to be teratogenic in mice. Given recent observations that the level of dietary folic acid intake may be inversely related to the occurrence of select birth defects in humans, we tested the hypothesis that dietary folic acid intake would influence the developmental toxicity of methanol. Virgin female mice were fed one of three diets containing 400 (low), 600 (marginal), or 1,200 (adequate) nmol folic acid/kg diet for 5 weeks prior to and following mating. On gestation days (GD) 6-15, dams were administered by gavage either vehicle (distilled, deionized water) or methanol at 2.0 or 2.5 g/kg body weight, twice daily. On GD 18, mice were weighed and killed and the liver, kidneys, and gravid uteri removed and weighed. Implantation sites, live and dead fetuses, and resorptions were counted; fetuses were weighed individually and examined for cleft palate and exencephaly. One third of the fetuses in each litter were examined for skeletal morphology. Maternal liver folate concentrations were approximately 40-50% lower in the low dietary folic acid groups than in the marginal and adequate groups; methanol did not affect maternal liver folate concentration at term. Maternal net gestational weight gain was lowest at the lowest dietary folate level but was not affected by methanol. Gravid uterus weights were lowest in the low dietary folic acid groups exposed to the high methanol dose and the number of live fetuses per litter was lowest in the low folic acid groups. Fetal body weights were lowest in the low folic acid groups and significantly lower in the methanol groups relative to vehicle-treated animals. Fetal crown-rump lengths were shorter in the methanol-treated groups; this parameter was not affected by folic acid treatment. Both methanol and low dietary folic acid increased the incidence of cleft palate, with the highest number of affected litters in the low dietary folic acid group. These results support the concept that maternal folate status can modulate the developmental toxicity of methanol.

Abnormalities, Drug-Induced↗
PubMed1996

A three-dimensional finite element method for large elastic deformations of ventricular myocardium: I--Cylindrical and spherical polar coordinates.

A three-dimensional Galerkin finite element method was developed for large deformations of ventricular myocardium and other incompressible, nonlinear elastic, anisotropic materials. Cylindrical and spherical elements were used to solve axisymmetric problems with r.m.s. errors typically less than 2 percent. Isochoric interpolation and pressure boundary constraint equations enhanced low-order curvilinear elements under special circumstances (69 percent savings in degrees of freedom, 78 percent savings in solution time for inflation of a thick-walled cylinder). Generalized tensor products of linear Lagrange and cubic Hermite polynomials permitted custom elements with improved performance, including 52 percent savings in degrees of freedom and 66 percent savings in solution time for compression of a circular disk. Such computational efficiencies become significant for large scale problems such as modeling the heart.

Animals↗
PubMed1995

Biological modeling of 5-fluorouracil developmental toxicity.

A biologically-based dose-response (BBDR) model is a mathematical description of the biological events leading to expression of a toxic response. As an alternative to current approaches in non-cancer risk assessment, such models will reduce uncertainty in that they will provide a more comprehensive description of toxicity. We are involved in construction of a BBDR model for the developmental toxicity of 5-fluorouracil (5-FU) in the rat using multiple approaches. First, to identify critical events in the pathogenesis of 5-FU developmental toxicity, thymidylate synthetase (TS) inhibition and alterations in cell kinetics and growth were examined in embryos following maternal administration of 5-FU on day 14 of gestation. A dose-related decline in TS activity was observed within 1 h; however, maximal inhibition and recovery were similar at 10, 20 and 40 mg/kg. Dose-dependent cell cycle alterations were observed within 4 h after exposure and were maximal at 8 h. Hindlimb growth reduction was observed 24 h after exposure to 40 mg/kg, but not at lower doses. At term hindlimb defects were observed at doses above 30 mg/kg. An integrated dose-response model for hindlimb defects was derived from empirical relationships among these events. The resultant dose-response somewhat over-predicted the developmental toxicity of 5-FU, although results of a Monte Carlo simulation indicated that these data were not incompatible with model predictions. Overall, the results suggest that TS inhibition is a key component of the mechanism of 5-FU developmental toxicology, but the model does not capture all of the critical events in the induction of hindlimb defects. A preliminary mechanistic model for the inhibition of embryonic TS, DNA synthesis and cell cycle following maternal exposure to 5-FU, independently derived from literature data to further examine the potential role of this pathway in its developmental toxicity, predicted a dose-response for TS inhibition and DNA synthesis that closely reflected the observed patterns. These results further suggest that TS inhibition, resultant deficits in DNA synthesis and cell cycle perturbations represent a critical mechanistic pathway in the developmental toxicity of 5-FU.

Animals↗
PubMed1995

Flow cytometric detection of abnormal fetal erythropoiesis: application to 5-fluorouracil-induced anemia.

We sought to determine whether flow cytometric analysis of circulating fetal blood cells could be used to rapidly detect perturbations of fetal erythropoiesis. In addition, we wanted to determine whether this approach would allow sample collection by exsanguination instead of fetal cardiac puncture, a difficult technique used to prevent contamination of samples with maternal erythrocytes. To monitor fetal erythropoiesis from gestational day (GD) 14-20, we analyzed the cell size, RNA content, and percentage of circulating liver-derived reticulocytes relative to yolk-sac-derived erythroblasts. As a model toxicant, we chose 5-fluorouracil (5-FU), since we previously observed that maternal administration at 20-40 mg/kg on gestational day (GD) 14 produced fetal anemia on GD 16-17, as evidenced by dose-dependent decreases in the cell counts, hematocrit, and hemoglobin content of fetal blood obtained by cardiac puncture. We report herein that 48 hr after maternal 5-FU administration, both cardiac and peripheral blood samples exhibited a dose-dependent decrease in the relative percentage of reticulocytes, indicating a reduced rate of reticulocyte release from the fetal liver. Moreover, at 30 and 40 mg/kg, reticulocytes exhibited increased size and reduced RNA content on GD 16, but elevated RNA content (indicative of premature release) by GD 18. These data suggest that 5-FU inhibits both erythroid cell proliferation and RNA synthesis reversibly, resulting in an anemia that triggers compensatory release of immature reticulocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia↗
PubMed1995

Maternal zinc deficiency, but not copper deficiency or diabetes, results in increased embryonic cell death in the rat: implications for mechanisms underlying abnormal development.

The mechanisms underlying the teratogenicity of maternal copper deficiency, zinc deficiency, and diabetes are largely unknown. Here we investigated whether these insults are associated with altered patterns of cell death in gestation day (GD) 11.0 rat embryos. Four weeks prior to mating, rats in the copper-deficient group (CuD) were fed a copper-deficient diet supplemented with the chelator, triethylenetetramine, to facilitate the depletion of tissue copper stores. Rats in this group were switched to a triethylenetetramine-free copper-deficient diet 1 week prior to mating. Dams in the diabetic and control groups were fed a control (8 micrograms copper, 25 micrograms zinc/g) diet throughout the study. On GD 3.0, one subset of the control dams was assigned to the zinc-deficient group (ZnD) and fed a zinc-deficient diet. A second subset of control dams was assigned to a restricted fed group and fed the control diet in quantities consumed by the zinc-deficient dams. Litters were taken by cesarean section on GD 11.0. Embryos were examined for gross morphology and assessed for patterns of cell death using Nile blue sulfate. Embryos from the CuD dams were characterized by edematous hindbrain. Embryos from the diabetic group were characterized by delayed development. Altered patterns of cell death were only detected in embryos from the ZnD dams. Within the ZnD group, embryos were either characterized by small size, edematous head region, and control patterns of cell death, or normal size, normal morphology, and increased cell death. These different patterns of morphology and cell death in the embryos of ZnD dams were associated with different patterns of maternal food intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Developmental toxicity of formate and formic acid in whole embryo culture: a comparative study with mouse and rat embryos.

Acute methanol (MeOH) toxicity in primates is attributed to the conversion of MeOH to formate and the resulting acidosis. MeOH has been shown to be developmentally toxic in mice and rats both in vivo and in vitro, but rodents neither accumulate formate nor develop acidosis after MeOH exposure. To further assess the potential human developmental toxicity of MeOH exposure, we evaluated the developmental effects of sodium (Na) formate and formic acid in rodent whole embryo culture (WEC). Day 9 rat embryos were cultured for 24 or 48 hours and day 8 mouse embryos were cultured for 24 hours in the presence of Na-formate or formic acid. Rat and mouse embryos exposed to either agent for 24 hours exhibited a trend toward reduced growth and development and the number of abnormalities increased at the higher concentrations. Rat embryos exposed for 48 hours to either Na-formate or formic acid showed a trend toward reduced growth and development with increasing concentration. Embryo lethality and incidence of abnormal embryos were also increased at the higher concentrations. The anomalies observed in both species after exposure to either compound were primarily open anterior and posterior neuropore with less frequent incidence of rotational defects, tail anomalies, enlarged pericardium and delayed heart development. Exposure to Na-formate or formic acid for comparable periods of time results in comparable degrees of embryotoxicity at concentrations (mMolar) at least 4-fold lower than those previously reported for methanol exposure.

Abnormalities, Drug-Induced↗
PubMed1995

Teratogenicity of low doses of all-trans retinoic acid in presomite mouse embryos.

This study was designed to examine the developmental dose response for all-trans retinoic acid (TRA) administered at presomite stages in mouse embryos. Previous studies using hamsters [Shenefelt (1972) Teratology 5:103-118] have shown that developmental stages corresponding to those present early on gestational day (GD) 7 in mice are most sensitive to retinoid-induced teratogenesis. Our preliminary studies showed that at this treatment time, gavage dosages of 7.5 mg/kg maternal body weight administered to C57B1/6N mice, an inbred strain, resulted in severe craniofacial malformations representing the holoprosencephaly, aprosencephaly spectrum. Additionally, in an outbred mouse strain, CD-1, exencephaly was induced by dosages of 2.5 mg/kg TRA and above. Readily detectable abnormalities of the eyes, including anophthalmia and severe microphthalmia and iridial colobomata, were induced by even lower doses cf TRA in the C57B1/6N strain. Incidences of micro/anophthalamia were 6.7%, 8.1%, 12.9%, and 32.4% at 0, 0.313, 0.625, and 1.25 mg/kg, respectively. The dosages required to induce significant incidences of exencephaly (2.5 mg/kg) and severe ocular abnormalities (1.25 mg/kg) on GD 7 in mice are approximately 50-100-fold less than those that are commonly used to examine the teratogenicity of this compound at later developmental stages in this species. The trend toward an increase in the incidence of severe ocular malformations at the lowest dose examined and the fact that subtle ocular malformations were not taken into account for this study suggest that even lower dosages may be effective.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Drug-Induced↗
PubMed1995

Utility of fluorescence microscopy in embryonic/fetal topographical analysis.

For topographical analysis of developing embryos, investigators typically rely on scanning electron microscopy (SEM) to provide the surface detail not attainable with light microscopy. SEM is an expensive and time-consuming technique, however, and the preparation procedure may alter morphology and leave the specimen friable. We report that by using a high-resolution compound epifluorescence microscope with inexpensive low-power objectives and the fluorochrome acridine orange, we were able to obtain surface images of fixed or fresh whole rat embryos and fetal palates of considerably greater topographical detail than those obtained using routine light microscopy. Indeed the resulting high-resolution images afford not only superior qualitative documentation of morphological observations, but the capability for detailed morphometry via digitization and computer-assisted image analysis.

Animals↗
PubMed1995

Zinc deficiency causes apoptosis but not cell cycle alterations in organogenesis-stage rat embryos: effect of varying duration of deficiency.

Zinc deficiency is teratogenic in all species in which it has been examined. Zinc is an essential component of enzymes involved in DNA synthesis and cell proliferation, and may play an as yet undetermined role in apoptosis. To further our understanding of the role of zinc in normal development, we examined cell death and cell cycle parameters in embryos of pregnant rats fed a zinc-deficient diet for 2 to 10 days (0.5 microgram zinc/g diet; zinc-adequate diet was 25 micrograms zinc/g). To elucidate sensitive periods of development and susceptible cell populations, dams were fed the zinc-deficient diet from gestation day 1, 3, 7, or 9 and killed on day 11. Embryos were examined for morphology and developmental stage. From each litter, 2-3 embryos were stained with Nile blue sulfate (NBS) to visualize cell death, 3 embryos were frozen for flow cytometric cell cycle analysis and cell counts, and selected embryos were preserved for histological examination. Dams fed the zinc-deficient diet for more than 3 days reduced their food intake through gestation day 8 but increased food intake on day 9. Maternal plasma zinc dropped to 10-25% of control levels in the zinc-deficient groups. Zinc deficiency from gestation day 1 or 3 resulted in two categories of affected litters on day 11. One category had embryos which were morphologically normal but displayed extensive NBS staining in the visceral arches, neural tube, and somites. The second category had developmentally retarded or maldeveloped embryos which showed little NBS staining. Zinc deficiency from gestation day 7 produced cell death in the posterior dorsal midline in the area of premigratory neural crest cells, which was confirmed by histological examination. Zinc deficiency from gestation day 9 did not affect morphology or NBS staining. Percentages of cells in the G0/G1, S, and G2M phases of the cell cycle on gestation day 11, determined by flow cytometry, were similar to controls in all groups. This study shows that as few as 4 days of maternal zinc deficiency can produce excess embryonal cell death, and that neural crest cells may be particularly sensitive.

Animals↗
PubMed1995

Health risks associated with prenatal metal exposure.

A symposium entitled Health Risks Associated with Prenatal Metal Exposure was held at the 33rd Annual Meeting of the Society of Toxicology (SOT) in Dallas, Texas. The symposium was cosponsored by the Metals and Reproductive and Developmental Specialty Sections of SOT and was designed to elaborate the health risks associated with in utero exposure to metals commonly found in the workplace and/or ambient environment on the mother and developing offspring. Epidemiological and toxicological evidence that demonstrates the health effects and underlying mechanisms associated with exposure to arsenic (As), lead (Pb), and methyl mercury (MeHg) were discussed, as well as the legal ramifications and personal implications associated with prenatal metal exposure. The following is a summary of each of the individual presentations.

Animals↗
PubMed1995

Specific competitive inhibitor of secreted phospholipase A2 from berries of Schinus terebinthifolius.

Two structurally related triterpenoids 1 and 2 from pink peppercorn (berries of Schinus terebinthifolius) are identified and characterized as active site-directed specific competitive inhibitors of the three classes of secreted 14 kDa phospholipase A2. The inhibitors not only protect the active site histidine from alkylation but also inhibit the action of secreted phospholipase A2 from pig pancreas, human synovial fluid, and bee venom. Detailed X-ray crystallographic results on the structures of the inhibitors are provided. By physical methods and X-ray crystallography the triterpenoids were identified as masticadienoic acid and masticadienolic acid (schinol). Several other triterpenoids were ineffective as inhibitors of phospholipase A2; however certain ganoderic acid derivatives showed noticeable inhibition. Results show that the side chain of these acidic tetracyclic terpenoids can access the catalytic-site region of phospholipase A2, whereas the acyclic nucleus is at the interfacial recognition region. The selectivity of the assay protocol used here is demonstrated by the fact that the original screen of ethyl acetate extracts of 60 commercially available spices and herbs was carried out with phospholipase A2 from pig pancreas, and only one extract showed inhibitory action on the hydrolytic activity in the scooting mode. Under such assay conditions the enzyme remains tightly bound to the surface of the substrate vesicles. In this way, nonspecific effects of additives that promote desorption of the enzyme from the substrate vesicle surface, under conditions in which the binding of the enzyme to the vesicle is weak, are avoided. The assay protocol is useful for the kinetic characterization of the inhibitors of phospholipase A2, and it does not give false positive results with amphiphilic and hydrophobic compounds, as is the case with virtually all assay systems in use.

Animals↗
PubMed1995

Tumor necrosis factor-alpha alters maternal and embryonic zinc metabolism and is developmentally toxic in mice.

We tested the hypothesis that tumor necrosis factor-alpha (TNF-alpha) would be teratogenic in mice due in part to its effects on zinc metabolism. In Experiment 1, nonpregnant mice were injected with a single dose of TNF-alpha (40,000 U) or PBS and then received a 65Zn-labeled meal. Mice killed 10 h after TNF-alpha treatment had high liver 65Zn and low plasma 65Zn, compared with controls. In Experiment 2, gestation day 8 (GD 8) mice were injected with PBS or TNF-alpha and then received a 65Zn-labeled meal. Dams killed 10 h after TNF-alpha treatment had higher liver and kidney 65Zn and lower plasma and embryonic 65Zn accumulation than controls. In Experiment 3, TNF-alpha dosing from GD 7-12 was associated with high maternal liver Zn and metallothionein concentrations on GD 13 and a high frequency of exencephaly on GD 18. In Experiment 4, dams fed diets containing 4.5, 12.5 or 50.0 micrograms Zn/g were given PBS or TNF-alpha on GD 7-12. Gross fetal defects were not observed in the PBS-treated litters evaluated on GD 18. In contrast, TNF-alpha-treated litters were characterized by multiple defects, with the incidence and severity being highest in the low Zn diet group. In Experiment 5, embryos cultured in serum from TNF-alpha-treated animals exhibited a high frequency of defects; the developmental toxicity of this serum was ameliorated when it was supplemented with Zn. Thus, the developmental toxicity of TNF-alpha is due in part to its influence on Zn metabolism.

Abnormalities, Drug-Induced↗