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Biomedical subjects

D A Clark

Publications and source records attributed to D A Clark.

At least 253 records · Page 14Linked to original sources
PubMed1990

Casein: a milk protein with diverse biologic consequences.

The consequences of bovine milk consumption are diverse, some of which are potentially deleterious. Although certain cultures shun cow's milk or milk-based products, Western societies consume large quantities of cow's milk. Although there are stronger similarities between bovine whey proteins and human whey proteins, the quantity and nature of casein in cow's milk differ markedly from human milk. We propose that the consequences of diets based on bovine casein should be more closely evaluated and certainly expanded beyond the simplistic approach of growth. What is good for the goose may be good for the gander, but what is good for the cow could be harmful to the human.

Animals↗
PubMed1990

Identification of low molecular weight immunosuppressor molecules in human in vitro fertilization supernatants predictive of implantation as a polyamine--possibly spermine.

Suppressor activity in in vitro fertilization (IVF) culture medium correlates with successful implantation. High performance liquid chromatography fractionation revealed peak(s) of inhibitory activity in the 1,000- to 5,000-Da molecular weight range. Inhibitory activity was dependent on the presence of fetal bovine serum (FBS) and was abrogated both by heat treatment of the serum and by pretreatment with monoamine oxidase inhibitors. Spermine becomes toxic when oxidized by monoamine oxidase to spermine dialdehyde or acrolein. Spermine also shows suppressive activity in the same molecular weight range as IVF supernatants. These data suggest IVF-associated inhibitory activity may be attributable to oxidation of a polyamine, possibly spermine, by monoamine oxidase in FBS. The biological significance is discussed.

Centrifugation↗
PubMed1989

Hormone-induced preimplantation Lyt 2+ murine uterine suppressor cells persist after implantation and may reduce the spontaneous abortion rate in CBA/J mice.

Immunoregulatory cells in the maternal uterine endometrium and decidua are thought to play an important role in ensuring the success of the semiallogeneic conceptus. Two phases of suppression have been described in pregnant mice. Prior to implantation, the hormonal changes triggered by mating activate or recruit a population of nonspecific Lyt 2+ suppressor cells that inhibit cytotoxic T lymphocyte generation: this suppression appears to wane at the time or implantation and 4-5 days after implantation, a non-T suppressor cell population activated or recruited by fetal trophoblast cells develops. In this paper we confirm the non-major histocompatibility complex specificity of the hormone-regulated preimplantation suppressor cell. We show that this activity persists in the uterus during the early postimplantation period where its suppressive activity is masked by an Fc-receptor-positive cell population recruited by the implanting embryo. The potential importance of the persisting suppressor cells is suggested by an increase in the rate of spontaneous abortion of DBA2-mated CBA/J mice following injection of monoclonal anti-Lyt 2+ antibody in the early postimplantation period.

Abortion, Veterinary↗
PubMed1989

The utility of MMPI subtle, obvious scales for detecting fake good and fake bad response sets.

The MMPI was administered twice to 40 graduate students to determine the utility of the Weiner subtle and obvious scales (D, HY, PD, PA, MA) for estimating how fake good and fake bad response sets might influence full scale scores. The first time, the MMPI was administered under standard conditions. Subjects then were divided randomly into two groups: fake good (complete MMPI for job application) and fake bad (qualify for psychotherapy). There were significant multivariate test effects (standard vs. response set) for the raw scores of all five obvious, subtle, and full scales. However, when raw scores were converted to T scores to ascertain practical significance, the obvious scales appeared to provide the most useful information to enhance the interpretation of full scale scores in normal populations.

Adult↗
PubMed1989

Immunosuppressive activity in human in vitro fertilization (IVF) culture supernatants and prediction of the outcome of embryo transfer: a multicenter trial.

The supernatants from cultured human oocytes fertilized in vitro contain low molecular weight factors that can suppress or stimulate the proliferative response of lymphocytes in vitro. The inhibitory and stimulatory effects are nonspecific and may be detected using cultured human or murine tumor cell lines. Using such a bioassay, we previously tested fetal cord serum-supplemented culture supernatant and found that an absence of suppression was correlated with an absence of subsequent pregnancy. To test this association further, additional samples were obtained from four different in vitro fertilization (IVF) units and studied blindly without knowledge of the pregnancy outcome. In this series, samples were obtained after the first 12-24 hr of sperm-oocyte incubation and all of the supernatants were from individual embryo cultures. The average number of preembryos transferred to those achieving pregnancy did not differ significantly from the number transferred to those not achieving pregnancy but the level of suppression was greater (8.7 +/- 1.9%) in those becoming pregnant compared to those not achieving pregnancy (0.8 +/- 1.5%). Twenty-two of 61 patients who received at least one embryo with a suppressive supernatant achieved pregnancy, whereas 0 of 19 patients received embryos lacking suppressive supernatants became pregnant. Two patients who received a single embryo from cultures with suppression became pregnant. Several problems with the bioassay method were defined. The culture medium in this series was always supplemented with adult serum, usually from the patient herself, and this serum could be suppressive.(ABSTRACT TRUNCATED AT 250 WORDS)

Blastocyst↗
PubMed1989

Histologic and immunologic study of uterine biopsy tissue of women with incipient abortion.

Biopsy specimens taken from the region of the placental bed were examined for the presence of phloxinophilic granulated mononuclear cells in women with a history of recurrent miscarriage and who would eventually miscarry a current pregnancy. They were compared with biopsy specimens from women with intact pregnancies presenting for elective termination of pregnancy and those with "missed abortion." Cells with large cytoplasmic granules (greater than or equal to 1 micron) were abundant in the group of ongoing pregnancies whereas cells with smaller granules (less than 1 micron) that were similar to large granular lymphocytes were more abundant relative to cells with large granules in the biopsy specimens from failing pregnancies. Immunosuppressive activity was tested in the supernatants of cultured biopsy samples of each group and found to be significantly lower in the incipient miscarriage group. These findings could represent alterations associated with the process of miscarriage, such as inflammation, or there may be deficient suppressor cell activity at the fetomaternal interface as the reason for "rejection" of the early embryo.

Abortion, Habitual↗
PubMed1989

Frequency as a moderating variable in self-report measures of negative cognition.

Based on responses to the Distressing Thoughts Questionnaire, subjects' most frequent depressive and anxious cognitions were selected and compared with representative low frequency thought statements. The high frequency cognitions were more emotionally intense, uncontrollable and unacceptable than the low frequency thoughts. Although high frequency anxious items were rated as more frequent than high frequency depressive statements, no differences were evident in emotional intensity and controllability. Furthermore thoughts of loss and failure were specifically predictive of dysphoria only when high frequency cognitive items were utilized. The implications of these findings for cognitive assessment issues were discussed.

Adult↗
PubMed1989

The immune function of the endometrium.

The endometrial mucosa is unique amongst mucosal sites in that it must mount an immune response against micro-organisms and resist tumour growth whilst tolerating sperm and the allogeneic fetus. Bacterial and viral infection in the uterus leads to local endometrial mucosal immune responses evidenced by the secretion of secretory component (SC), secretory IgA (sIgA) and IgG. The secretion of these molecules is under hormonal control. Trafficking of locally sensitized lymphocytes to other mucosae does not appear to occur, whereas priming at other mucosal surfaces leads to memory responses to antigen in the uterus. Proclivity to local immune function is related to sparse lymphatic supply to the endometrium together with a local distribution of antigen-presenting dendritic cells. During pregnancy, particularly in the region of the decidua and embryo, the number of Ia+ cells and the lymphatic supply become diminished. The antigenic status of sperm may lead to certain types of maternal sensitization. However, immunosuppressive factors in seminal plasma protect the sperm on its passage up the female genital tract and diminish subsequent immunogenicity. On fertilization of the oocyte, an allogenic fetus develops, that potentially could stimulate production of maternal immune effectors. Endometrial cells of various types (macrophage, decidual, NK, T cells) interact via soluble factors leading to a local immunoprotection of the fetus. Similar factors appear to operate in resisting tumour growth in the uterus.

Endometrium↗
PubMed1989

Cognitive mediation in general psychiatric outpatients: a test of the content-specificity hypothesis.

We investigated the degree of content specificity evident in the negative cognitions associated with anxiety and depression in two large samples of general psychiatric outpatients. Standardized measures of affect and cognition were analyzed in a multiple regression design. As predicted by Beck's (1967, 1976, 1987) cognitive theory of psychopathology, thoughts of loss and failure were specifically associated with depression, whereas cognitions of harm and danger were uniquely predictive of anxiety. In addition, hopelessness was specific to depression and not to anxiety. Dysfunctional beliefs showed no consistent association with either mood state. The implication of these results, as well as related findings, is discussed in terms of a cognitive perspective on the differentiation of emotional disorders. Also discussed are the methodological difficulties encountered in research on cognitive-affective relationships.

Adult↗
PubMed1989

Comparative analysis of photosynthetic light environments within the crowns of juvenile rain forest trees.

Irradiances within the crowns of saplings of two tropical tree species were simultaneously compared in primary rain forest in Costa Rica. The species examined, Minquartia guianensis Aubl., a relatively slow-growing, canopy species, and Pithecellobium pedicellare (DC) Benth., a less-tolerant, emergent species, have different crown and leaf display patterns. Crown light environments were assessed by placing arrays of quantum sensors among leaves and recording at 5-s intervals for seven days with microloggers. Median total daily quantum flux densities for saplings of both species were less than 2% of full sun and did not differ significantly. More than 90% of the measurements within the crowns of these saplings were less than 25 micromol m(-2) s(-1). Spatial variability of photon flux densities within sapling crowns was similar for the two species despite differences in leaf display patterns. In saplings of both species, photon flux densities varied significantly over the relatively short distances within crowns and from day to day. Height growth of both species was significantly correlated with total daily photon flux densities and with percentage of full sun. However, only the tolerant species, Minquartia, showed a significant correlation between diameter growth and crown light environment.

Journal Article↗
PubMed1989

Trophoblast induction of suppressor-type cell activity in human endometrial tissue.

First trimester (10-12 weeks gestation) human decidua contains small lymphocytic suppressor cells that release 22 and 43 kd soluble suppressor factors blocking the action of interleukin 2. Luteal phase endometrium, in contrast, contains large suppressor cells that do not release soluble immunosuppressive factors. However, if luteal phase endometrium from days 24 to 25 of the menstrual cycle is incubated with placental syncytiotrophoblast membrane vesicles, suppressor factors having the same molecular weight as those found in end of first-trimester pregnancy decidua are released into the supernatant. This generation of soluble suppressor activity is dependent on cells similar in size to the small lymphocytic suppressor cell population. When uterine decidua is obtained from women with tubal ectopic pregnancy (early in the first trimester), the decidual tissue releases soluble immunosuppressive factors with a 100-135 kd molecular mass and the suppressor cells are large rather than small in size. Supernatant conditioned by trophoblast dissected from ectopic implants was able to interact with large cells in luteal phase endometrium to generate additional soluble suppressor activity. A model is proposed wherein fetal trophoblast activates two suppressor cell populations (large and small) in endometrium via soluble long-range inducer and by direct contact with trophoblast membrane. The potential role of trophoblast-dependent suppressor cells in preventing rejection of the conceptus leading to occult or clinical abortion is discussed.

Decidua↗