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Biomedical subjects

D A Clark

Publications and source records attributed to D A Clark.

At least 145 records · Page 8Linked to original sources
PubMed1995

Stress-induced murine abortion associated with substance P-dependent alteration in cytokines in maternal uterine decidua.

Stress is known to induce abortions, but underlying mechanisms are unknown. Both alloimmunization and injection of antibody to the asialoGM1 determinant of natural killer cells have been shown to prevent stress-triggered abortion in mice. DBA/2J-mated CBA/J female mice were used to investigate the influence of stress during early gestation on systemic hormone levels and on cytokines in the decidua that are thought to be relevant to abortion in nonstress-related murine abortion. Lowered levels of progesterone did not occur as a result of stress. In stressed mice, increased levels of the abortogenic cytokine tumor necrosis factor alpha (TNF alpha) were associated with decreased levels of pregnancy-protective transforming growth factor beta 2-related suppressive activity in uterine decidua. In the alloimmunized animals where stress failed to boost the abortion rate, these effects were abrogated. Production of TNF alpha may be stimulated by the neurotransmitter substance P (SP); after injection of an SP receptor antagonist or SP-antibody, stress failed to increase the abortion rate above the background level. The increased levels of TNF alpha we observed in the stressed animals were completely abrogated in the animals that had received the SP receptor antagonist; stress also failed to decrease the pregnancy-protective suppressive activity in the decidua of these animals. The data indicate that stress may inhibit protective suppressor mechanisms and promote secretion of abortogenic cytokines such as TNF alpha via neurotransmitter SP.

Abortion, Spontaneous↗
PubMed1995

Stress-triggered abortion: inhibition of protective suppression and promotion of tumor necrosis factor-alpha (TNF-alpha) release as a mechanism triggering resorptions in mice.

PROBLEM: Stress adversely affects pregnancy outcome and has been implicated as an abortogen in both animals and humans. However, the mechanisms whereby stress aborts are largely unknown. Alloimmunization can prevent stress-triggered abortion, and immunization is known to increase transforming growth factor-beta 2 (TGF-beta 2)-related suppressive activity. METHOD: To investigate these mechanisms, DBA/2J males were mated to CBA/J or C3H/HeJ females, and the pregnant females were exposed to ultrasonic sound stress for a period of 24 h between day 4.5 to 8.5 of pregnancy. RESULTS: Ultrasonic stress significantly elevated the resorption rate with a peak effect on day 5.5 in the CBA/J females and on day 4.5 in the LPS-resistant C3H/HeJ females. The tumor necrosis factor-alpha (TNF-alpha) release from the decidua was also elevated and the TGF-beta 2-mediated suppressive activity was significantly decreased. The resorption rate only increased when the TNF-alpha/TGF-beta 2 ratio was increased compared to the control. CONCLUSION: These data suggest that stress may inhibit protective suppressor mechanisms and promote secretion of abortogenic cytokines such as TNF-alpha. Possible mechanisms are discussed.

Abortion, Spontaneous↗
PubMed1995

Is spontaneous resorption in the DBA/2-mated CBA/J mouse due to a defect in "seed" or in "soil"?

PROBLEM: Recurrent spontaneous resorption in DBA/2-mated CBA/J mice has been attributed to damage by NK-lineage cells and TNF-alpha beginning several days after implantation. However, some recent data have suggested CBA/J female mice have a high proportion of preimplantation embryo abnormalities resulting in defective in vitro implantation and impaired trophoblast outgrowth. Could spontaneous abortion be due to a defective embryo ("seed") rather than a hostile post-implantation uterine lining ("soil"). METHOD: Mated CBA/J females were manipulated so as to have high spontaneous abortion rates and a high percent abnormal embryos, or low resorption rates and a low percent abnormal embryos. Embryos from low aborting females were transferred into high aborting female recipients that were pseudopregnant, and vice versa. RESULTS: Abnormal embryos from females with high abortion rates implanted in low aborting females and did not show any greater tendency to resorb than normally developed embryos in these recipients. By contrast, normal embryos to some extent and abnormal embryos to a much greater extent, gave a high abortion rate when the recipient female was a high aborter. CONCLUSION: Properties of the "soil" into which embryos implant determines the likelihood of success or failure (abortion). Abnormal pre-implantation embryos can be "rescued" by "good soil"; "sick soil" damages both normal and abnormal embryos. Defining the cellular and molecular mechanisms may be useful in understanding basic mechanisms leading to aborting and nonaborting pregnancy.

Abortion, Habitual↗
PubMed1995

Amphotericin B toxicity reduced by administration in fat emulsion.

OBJECTIVE: To report a patient with intolerance to amphotericin B reversed by preparing the antifungal in fat emulsion 20% and to review the medical literature on innovative formulations of amphotericin B. CASE SUMMARY: A 51-year-old man diagnosed with acute myelogenous leukemia was treated with standard induction chemotherapy. Empiric antibiotic therapy was initiated 2 days postchemotherapy; however, the patient continued to be febrile until day 7. At this time amphotericin B 35 mg/250 mL D5W over 4 hours was administered. Despite premedication, the patient experienced severe rigors, chills, and fever. As the result of continuing infusion-related adverse events, the patient refused further therapy after the third daily dose. In an attempt to reduce the infusion-related events, a trial of amphotericin B 35 mg/35 mL of fat emulsion 20% was administered over 2 hours after patient consent was obtained. Premedication was administered and the patient tolerated therapy without adverse events. Amphotericin B dosage escalations to 50 and 70 mg were tolerated similarly. During this treatment the patient became afebrile and the serum creatinine concentration decreased to normal. DISCUSSION: Despite significant toxicities and the development of newer antifungal agents, amphotericin B remains the drug of choice for the empiric coverage of suspected fungal infection in neutropenic patients. Amphotericin B often exacerbates the nephrotoxicity of other agents characteristically prescribed in these patients. Furthermore, infusion-related events, if not intolerable, can dramatically reduce the patient's quality of life. For these reasons, novel means of amphotericin B administration are being explored. CONCLUSIONS: The delivery of amphotericin B in a lipid diluent may have substantial benefit in reducing the nephrotoxicity and infusion-related events associated with the antifungal. Prospective clinical trial comparing lipid-complexed amphotericin B with liposomal and approved formulations of amphotericin B are essential to define potential differences in toxicity and efficacy.

Amphotericin B↗
PubMed1995

Perinatal nitric oxide synthase inhibition retards neonatal growth by inducing hypertrophic pyloric stenosis in rats.

Administration of the nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) during pregnancy has been shown to compromise fetal growth. This study was designed to determine whether aminoguanidine, a predominate inhibitor of inducible NOS, affects fetal outcome. In addition, we extended the prenatal administration of L-NAME into the postnatal period (14 d) to determine whether neonatal growth and maturation were also affected. L-NAME, but not aminoguanidine, compromises fetal and placental growth. When compared with control 14-d-old pups, postnatal L-NAME compromised neonatal growth, whether it was given directly (intraperitoneally) (39.7 +/- 1.1 versus 24.1 +/- 1.0 g) or indirectly (38.6 +/- 0.5 versus 22.2 +/- 1.2 g) via maternal breast milk. Neonatal growth retardation was asymmetric, with brain sparing, suggesting a nutritional origin. L-NAME administration resulted in growth retardation that extended into adulthood, without evidence of catch-up growth. Treated neonates displayed the hallmarks of hypertrophic pyloric stenosis. Significant increases in stomach weight/pup weight (9.9 +/- 0.3 versus 8.2 +/- 0.4 x 10(3)) and stomach volume/pup weight (12.0 +/- 0.6 versus 9.4 +/- 0.6 mL/100 g) with a concomitant decrease in small intestine weight/length (2.10 +/- 0.08 versus 3.18 +/- 0.13 g/100 cm) was noted in treated versus control pups (p < 0.05). Muscularis hypertrophy at the pyloric sphincter in the L-NAME-treated pups was noted by histology. Blood pressure was elevated in the L-NAME-treated pups (93 +/- 6 versus 60 +/- 5 mm Hg in control pups, p < 0.05). These findings are consistent with inhibition of neuronal and endothelial NOS activity. We conclude that NO, formed via the constitutive isoforms of NOS, is a critical determinant of fetal and neonatal growth and maturation.

Animals↗
PubMed1995

Accumulation of chromotrope 2R positive cells in equine endometrium during early pregnancy and expression of transforming growth factor-beta 2 (TGF-beta 2).

Endometrial tissue from the gravid uterine horn of pregnant mares was examined by northern analysis and in situ hybridization for mRNA that hybridized to cDNA and RNA probes generated from a mouse TGF-beta 2 1.2 kb cDNA clone. The mouse cDNA probe hybridized to characteristic TGF-beta 2 mRNA transcripts on a northern blot of total RNA isolated from horse endometrium collected at day 45 of gestation. Two major 4.0 and 3.5 kb transcripts and possibly a minor 1.6 kb transcript were observed, consistent with specific hybridization to equine TGF-beta 2 mRNA. By in situ hybridization, riboprobes transcribed from the same fragment used in northern analysis hybridized to clusters of cells scattered between endometrial glands at days 38, 40, 42, 43, 78 and 81 of gestation. Positive cells were absent before day 38. From day 38 to day 43 there was marked hybridization over maternal leucocytes in the region of the developing endometrial cups, and at later stages (day 78 and day 81) clusters of cells positive for mRNA encoding TGF-beta 2 were localized within the dense band of leucocytes at the periphery of the degenerating endometrial cups. There was no hybridization to invasive or non-invasive trophoblast or to fully differentiated endometrial cup cells. Approximately 90% of the TGF-beta 2 positive cells detected in the sections taken at day 78 also stained with chromotrope 2R used to detect eosinophils and the morphology of approximately 50% of these cells was characteristic of eosinophils.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Phase I trial of simultaneous administration of interleukin 2 and interleukin 4 subcutaneously.

Interleukin (IL) 2 plays an important role in enhancing the immune response, whereas IL-4 has pluripotent activities which include affecting immune function. Preclinical data suggest that the combination might have enhanced immunomodulatory activity. In this Phase I trial in patients with advanced solid tumors, both IL-2 and IL-4 were given by separate s.c. injections simultaneously daily, 5 days in a row, Monday through Friday, for 3 consecutive weeks, followed by a 1-week break from treatment. Cycles could be repeated. The dose of IL-2 was kept constant at 9 x 10(6) IU/m2/injection while the dose of IL-4 was escalated beginning at 100 microgram/m2/injection and increasing by 100-microgram/m2 increments to a planned level of 400 microgram/m2/injection. Sixteen patients were entered in this study, with one patient being ineligible because of the presence of brain metastases. Of the 15 eligible patients, there were 14 males and 1 female, with a median age of 54 (range, 38-67) years and initial performance status of 0 in 5 patients and 1 in 10 patients. Patients were treated at levels of up to 300 microgram/m2/injection of IL-4 before the study was closed due to withdrawal of the drug by the manufacturer. The most commonly observed toxicities were fatigue, fever and chills, local reaction, nausea/vomiting and anorexia, headache and nasal stuffiness, and coughing, sometimes with the production of clear white sputum, more common in smokers. Duodenal ulcers occurred in one patient and one patient had grade 4 cardiac toxicity consisting of an asymptomatic minimal elevation of the creatinine phosphokinase MB isoenzyme (CPK-MB). Grade 3 hyponatremia occurred in two patients, and elevated liver function tests and creatinine occurred but were not dose limiting. Eosinophilia of unknown significance occurred in all patients. There were statistically significant elevations in absolute numbers of most T-cell subsets examined, without changes in circulating B cells. No antibodies to the IL-4 were found after one cycle. One patient with renal cell carcinoma showed a significant decrease in tumor burden after one cycle of treatment. Because of the IL-4 withdrawal, the maximum tolerated dose for this combination of drugs given by the route and schedule used here was not determined and will require additional testing. Subcutaneous IL-2 and IL-4 given simultaneously show important immunomodulatory and antitumor effects and should be tested further in cancer patients.

Adult↗
PubMed1994

Vitalethine modulates erythropoiesis and neoplasia.

Novel compounds based upon the thiol N-(carboxy)-beta-alanyl-cysteamine (vitaletheine) have strikingly potent and seemingly diverse biological activities. Concentrations of vitaletheine modulators from 1 femtograms/ml to 100 picograms/ml medium regulate RBC production from progenitors initially deprived of erythropoietin. Similarly, as little as attograms/ml concentrations of the disulfide vitalethine stimulate immunological responses of murine splenocytes toward sheep RBC in a hemolytic plaque assay. Because dosages of vitalethine as low as femtograms/kg substantially diminish tumor size and incidence and increase survival to 80% in mice inoculated with a uniformly fatal melanoma (Cloudman S-91), activities of these compounds have in vivo significance. A preliminary probe of the benzyl derivative of vitalethine in a myeloma model (NS-1) suggests efficacy (100% survival) as well. The high potencies of the vitaletheine modulators, both in cell culture and in vivo, indicate that these or similar regulatory components, if constitutively present, probably occur endogenously at vanishingly small concentrations and may be prone to deficiency resulting from metabolic imbalances, irradiation, aging, diet, pathogenic or parasitic infections, or exposure to environmental pollutants. Pathways for the biosynthesis of vitaletheine are proposed and chemical syntheses of the vitaletheine modulators are described. Possible molecular mechanisms of action, including interactions with peptidyl hormones, other endogenous effectors, and xenobiotic and pharmaceutical compounds, are explored. Indications for the treatment of other diseases are identified.

Animals↗
PubMed1994

TNF-alpha production by eosinophils in upper airways inflammation (nasal polyposis).

TNF-alpha is a cytokine with a wide spectrum of proinflammatory activities. Nasal polyps (NP), which occur in association with allergic rhinitis and asthma, are characterized by a marked infiltration of activated eosinophils, epithelial damage, and varying degrees of stromal fibrosis. By using Southern blot analysis after a reverse transcription-PCR, we detected a signal specific for TNF-alpha mRNA in five of seven NP samples, but not in control nasal mucosal samples. With in situ hybridization, we detected cells expressing mRNA specific for TNF-alpha in eight of thirteen NP samples, but not in four control samples. Counterstaining with chromotrope 2R demonstrated that virtually all cells expressing TNF-alpha message were eosinophils. The ratio of eosinophils expressing TNF-alpha to the total number of eosinophils varied greatly among tissues; as an average, we observed 24% TNF-alpha-positive eosinophils. Using a mAb against human TNF-alpha, we demonstrated TNF-alpha localization in 12 NP tissues (48.8 +/- 16.5 positive cells/mm2) but not in three control samples. Morphologically, cells localizing TNF-alpha were both mononucleated and polynucleated with only a small number of eosinophils, as determined by aniline blue counterstaining. Studies of purified blood eosinophils from a patient with hypereosinophilic syndrome and from four healthy donors indicated that TNF-alpha is produced, but rapidly secreted, so that TNF-alpha mRNA-positive cells contain little detectable protein. Furthermore, cells that retain detectable TNF-alpha may not contain sufficient TNF-alpha mRNA to be detected by using the probe developed for our studies. Together, these findings identify a novel mechanism by which eosinophils may contribute to mucosal inflammation and provide an approach to future investigation.

Eosinophilia↗
PubMed1994

Prevention of spontaneous abortion in DBA/2-mated CBA/J mice by GM-CSF involves CD8+ T cell-dependent suppression of natural effector cell cytotoxicity against trophoblast target cells.

Spontaneous resorption (abortion) that occurs at a high rate in DBA/2-mated CBA/J female mice is dependent upon asialoGM1+ natural effector-type cells, can be ameliorated by alloimmunization or administration of GM-CSF, and is augmented by in vivo injection of anti-CD8 antibody. The abortion rate was similarly augmented by administration of monoclonal anti-GM-CSF neutralizing antibody, but the GM-CSF physiologically active in preventing abortion during normal pregnancy did not appear to be derived from maternal CB8+ T cells putatively responding to antigens on the fetoplacental unit. Rather, depletion of CD8+ cells in vivo prevented GM-CSF from reducing the rate of resorptions. GM-CSF administration rapidly downregulates natural effector cells able to kill a trophoblast target cell line in vitro, and anti-CD8+ antibody boosts total splenic cytotoxic cell activity. Further, anti-CD8 completely abrogated the ability of GM-CSF to suppress anti-trophoblast killer cell activity. These cells are known to be asialoGM1+ and injection of anti-asialoGM1 reduced the abortion rate appropriately in mice that had received anti-CD8. These data suggest that GM-CSF acts indirectly to prevent abortion in DBA/2-mated CBA/J mice through a mechanism that requires CD8+ maternal T cells, and systemic regulation of the level of anti-trophoblast killer cell activity may determine the success or failure of pregnancy in this system.

Abortion, Spontaneous↗
PubMed1994

Inhibition of calcium-dependent nitric oxide synthase causes ileitis and leukocytosis in guinea pigs.

As nitric oxide reduces gut epithelial permeability, we designed a study to determine if chronic nitric oxide synthase inhibition predisposes the gut to inflammation. Nitric oxide synthase (NOS) inhibitors were administered in the drinking water ad libitum, for seven days: aminoguanidine (10 micrograms/ml), a selective inhibitor of the inducible form of nitric oxide synthase; and NG-nitro-L-arginine methyl ester (L-NAME, 1, 10, and 100 micrograms/ml), which inhibits both the constitutive and inducible forms. Control animals drank tap water only or water with D-NAME, the inactive enantiomer. After one week, circulating leukocyte count and tissue myeloperoxidase activity were measured. L-NAME (100 micrograms/ml), but not D-NAME or aminoguanidine, caused a twofold increase in a circulating leukocyte numbers. This increase in leukocyte numbers was time- and dose-dependent, but the differential count was unaltered. Tissue myeloperoxidase (MPO) activity as an index of granulocyte infiltration was comparable in all groups in the stomach, jejunum, colon, liver, lung, kidney, heart, and skeletal muscle. However, ileal MPO activity was elevated threefold in the L-NAME-(100 micrograms/ml) treated group (P < 0.05). Results in the D-NAME and aminoguanidine groups were similar to controls. L-NAME administration resulted in a reduction in NOS activity ([14C]citrulline formation) in the ileum but not jejunum, whereas cGMP levels were elevated in both ileum and jejunum. We conclude that chronic inhibition of the constitutive form of nitric oxide synthase predisposes the ileum to inflammation and leads to a progressive leukocytosis.

Amino Acid Oxidoreductases↗
PubMed1994

Nitric oxide inhibition causes intrauterine growth retardation and hind-limb disruptions in rats.

OBJECTIVE: Our purpose was to determine the effects of nitric oxide synthase inhibition on maternal and fetal health in the last third of pregnancy. STUDY DESIGN: Pregnant rats were treated from gestational day 13 to day 19 or 20 with the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester, which was administered in the drinking water ad libitum. Control animals received the inactive enantiomer NG-nitro-D-arginine methyl ester or no treatment. Maternal blood pressure, blood chemistry studies, and placenta and pup size were determined. A separate group of rats received nitroprusside sodium in conjunction with NG-nitro-L-arginine methyl ester. RESULTS: NG-nitro-L-arginine methyl ester caused a dose-dependent reduction in placenta and pup size. Amniotic fluid levels of cyclic guanosine monophosphate were significantly reduced at 0.1 mg/ml but not at higher doses. Hemorrhagic necrosis of fetal hind limbs occurred only with treatment with NG-nitro-L-arginine methyl ester and was prevented by coadministration of nitroprusside sodium. Maternal blood pressure and blood and urine chemistry studies were unaffected by NG-nitro-L-arginine methyl ester. CONCLUSION: Chronic reductions of nitric oxide production in the last third of pregnancy result in significant intrauterine growth retardation and hemorrhagic disruptions of hind limbs. Maternal complications were minimal and did not mimic preeclampsia.

Amniotic Fluid↗
PubMed1994

Obsessive intrusive thoughts in nonclinical subjects. Part II. Cognitive appraisal, emotional response and thought control strategies.

This second part of the study reports on the appraisal and thought control responses of 270 students to their most upsetting intrusive thought. Multiple regression analysis revealed that belief that one could act on the intrusive thought and perceived uncontrollability of the thought were the two most important predictors of the frequency, or persistence of the distressing intrusion. Intrusions rated as very difficult to control were also associated with increased belief that one could act on the intrusion, avoidance of situations that may trigger the intrusion, reduced success with one's most typical thought control strategy and higher thought frequency. Based on the Padua Inventory Total score, high and low obsessional Ss were selected. Highly obsessional individuals reported more unwanted obsessive intrusive thoughts and rated their thoughts as significantly more frequent and believable than low obsessive individuals. The type of thought control strategy typically used was not a factor in thought frequency and controllability, nor did it differentiate between high and low obsessional groups. The results are discussed in terms of Salkovskis' cognitive model of obsessions and intrusive thoughts.

Anxiety↗