Search PubMed⌕ Search

Biomedical subjects

L Larson

Publications and source records attributed to L Larson.

At least 73 records · Page 4Linked to original sources
PubMed1992

Modulation of human natural killer cell activity by exposure to uncontrollable stress.

Changes in natural killer cell (NK) activity and proportions of circulating T and NK lymphocyte subsets were assessed in adult males immediately after exposure to controllable or uncontrollable stress (noise) as well as 24 and 72 h later, in order to track the time course of the effects of stress. The role of control-relevant personality variables as moderators of the stress-immunosuppression relationship was considered. Subjects who perceived they had control over the noise as well as no-noise "control" subjects showed no reduction in NK activity. By contrast, subjects who perceived that they had no control over the stressor showed reduced NK activity immediately after the conclusion of the first 20-min stress session, and the reduced NK activity was found as long as 72 h later. Optimism and one's desire to be in control enhanced the negative impact of uncontrollable noise on NK activity. No differences between conditions were found on number of NK cells or a variety of T cell subsets. The results suggest the importance of perceived control in moderating the short- and long-term effects of stress on NK activity.

Adolescent↗
PubMed1991

Regulation of prostaglandin biosynthesis by luteinizing hormone and bradykinin in rat preovulatory follicles in vitro.

Luteinizing hormone (LH) stimulates prostaglandin biosynthesis and steroidogenesis in preovulatory (PO) follicles prior to ovulation. Since the ovulatory process shares many similarities with an inflammatory reaction, mediators of the inflammatory response, such as bradykinin (BK) have been suggested to modulate the effects of LH. In the present study the effect of BK (5 microM) on: 1) prostaglandin biosynthesis (PGE2, PGF2 alpha and 6-keto-PGF1 alpha), 2) the levels of two enzymes in the cyclo-oxygenase pathway, prostaglandin endoperoxide synthase (PGS) and prostacyclin synthase (PCS), and 3) cyclic adenosine 3'5'-monophosphate (cAMP) and progesterone response of PO follicles incubated in vitro were examined. LH (0.1 microgram/ml) stimulated the accumulation of cAMP and progesterone in the medium, while BK had no effect on these parameters. BK exerted a slight stimulatory effect on PGE2, and PGF2 alpha, (p less than or equal to 0.01) but not on 6-keto-PGF1 alpha synthesis, but no changes in PGS or PCS levels could be detected. The effect of LH on prostaglandin biosynthesis was much more pronounced, with an increase of PGE2, PGF2 alpha and 6-keto-PGF1 alpha. LH also induced PGS. The combination of LH and BK did not alter these responses compared to that of LH alone. This study demonstrates that BK stimulates prostaglandin biosynthesis in PO follicles. In contrast to LH, this effect of BK does not seem to involve the adenylate cyclase system, since BK did not stimulate cAMP production. BK did not affect the levels of PGS or PCS, and the stimulatory effect of BK is suggested to involve an increase in the availability of substrate for the cyclo-oxygenase pathway.

Animals↗
PubMed1991

Stimulatory effects of bradykinin on the ovulatory process in the in vitro-perfused rat ovary.

The role of bradykinin in the ovulatory process was investigated using an in vitro-perfused rat ovary model. Stimulation with LH (0.1 micrograms/ml) resulted in 2.6 +/- 0.5 (mean +/- SEM) ovulations per ovary, whereas no ovulations occurred in the nonstimulated control group. Bradykinin (5 microM) added to the perfusion system hourly for 10 h induced 2 of 5 ovaries to ovulate, with 2 and 3 ovulations, respectively. When bradykinin (5 microM) was given as a single dose at 5 or 10 h after LH, the ovulation rate was significantly increased to 11.0 +/- 2.8 and 8.6 +/- 2.0 ovulations per ovary, respectively. A competitive bradykinin antagonist, phenylalanine bradykinin, inhibited the bradykinin-induced increase in LH-stimulated ovulations. The addition of LH, but not of bradykinin, increased the levels of prostaglandin endoperoxide synthase in granulosa cells, but the levels of the enzyme in the residual ovarian tissue were negligible. In contrast, prostacyclin synthase was predominantly located in the residual ovarian tissue. This enzyme was not affected by LH or bradykinin. LH increased the tissue levels of prostaglandins, predominantly prostaglandin E2 (PGE2), at 7 h, whereas the stimulatory effect of bradykinin was smaller, with a preferential increase in prostacyclin (prostaglandin I2) levels. This study indicates a modulatory role of bradykinin, possibly involving prostacyclin late in the ovulatory process, in the rat.

Animals↗
PubMed1989

Turnover of epidermal growth factor binding sites in mouse mammary epithelial cells.

An in vitro method of studying epidermal growth factor (EGF) receptors in mouse mammary epithelial cells in serum-free collagen gel culture has been developed. Binding of EGF averaged 108 +/- 19 fmol/mg DNA in cells isolated from freshly dissociated virgin mammary tissue. Initial binding values were maintained in cells cultured in the presence of 0.1 ng/ml EGF, but decreased in either 0 ng/ml or 10 ng/ml EGF. Addition of either chloroquine (100 microM) or ammonium chloride (10 mM) to the culture medium increased receptor levels 10-fold. Cycloheximide (0.1 microgram/ml), ouabain (3 mM), and actinomycin D (5 x 10(-2) micrograms/ml) each decreased receptor levels, in some cases by as much as 80%. Both methylamine (10 mM) and dinitrophenol (0.1 mM) had no significant effect. These studies suggest that the net level of EGF receptors in these target cells is the result of an equilibrium between synthesis and degradation. The difference between the effects of the compounds tested on either receptor degradation or synthesis in comparison to cell growth, may be indicative that receptor degradation is not linked to cell proliferation.

Animals↗
PubMed1989

Regulation of prostaglandin endoperoxide synthase by cyclic adenosine 3',5'-monophosphate in the in vitro-perfused rat ovary.

The preovulatory regulation of two enzymes in the prostaglandin biosynthetic pathway, prostaglandin endoperoxide synthase (PGS) and prostacyclin synthase (ISN), was examined in granulosa cells and residual tissue of rat ovaries perfused in vitro. Ovaries from rats primed with pregnant mare's serum gonadotropin (20 IU) were perfused for up to 20 h starting the morning of induced proestrus. The amounts of PGS and ISN present were analyzed with immunoblotting techniques. Soluble extracts from granulosa cells and residual ovarian tissues were obtained at different times (0 h, 3 h, 7 h, 12 h) after treatment in vitro with luteinizing hormone (LH, 0.1 microgram/ml) and 3-isobutyl-1-methylxanthine (IBMX; 0.2 mM) and at 7 h in untreated control ovaries or after treatment with forskolin (30 microM) or LH (0.1 microgram/ml). The levels in the perfusion medium of cyclic adenosine 3',5'-monophosphate (cAMP), progesterone, testosterone, and estradiol were measured and the number of ovulations were examined. The levels of PGS after treatment with LH + IBMX increased up to 7 h and remained high at 12 h, a time that is close to the time of ovulation. The increase was more pronounced in the granulosa cells than in the residual tissue. Treatment with forskolin induced synthesis of PGS in granulosa cells, and the levels at 7 h were similar to those after stimulation with LH + IBMX. The levels of PGS were lower in granulosa cells of the group stimulated with LH alone than in granulosa cells from ovaries stimulated with LH + IBMX or forskolin.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗
PubMed1988

Vitamin E in the treatment of tardive dyskinesia: the possible involvement of free radical mechanisms.

One of the major problems associated with long-term neuroleptic treatment is persistent tardive dyskinesia (TD), for which there is no satisfactory treatment. We have recently proposed that some cases of TD are associated with neuronal dysfunction resulting from excess free radical production occurring during catecholamine metabolism. We therefore decided to assess the efficacy of a powerful free radical scavenging agent, alpha-tocopherol (vitamin E), on the clinical signs of TD. We treated 15 patients with persistent TD with alpha-tocopherol and matched placebo in a randomized crossover design. Patients demonstrated a significant overall reduction in scores on the Abnormal Involuntary Movements Scale (AIMS) after treatment with alpha-tocopherol, but not after placebo. The mean reduction in the AIMS score with alpha-tocopherol was 43 percent, with seven patients showing a greater than 50 percent reduction in their dyskinesia. There was also a trend for a decrease in scores on the Brief Psychiatric Rating Scale, but no change was observed in scores on the Simpson-Angus Scale for Extrapyramidal Side Effects. Our findings are consistent with the possibility that alpha-tocopherol is beneficial in the treatment of some patients with TD, but further research is necessary to establish the efficacy of this agent.

Antipsychotic Agents↗
PubMed1988

Complete trisomy 17p a relatively new syndrome.

A patient with a de novo duplication of 17p is described. A comparison with five other published cases indicates several features in common that seem characteristic of the syndrome. Primary features include, low birth weight, small size, severe mental and motor retardation, heart defect, failure to thrive and peculiar facial traits. The prominent facial features are, a tendency for round and flat mid face, small palpebral fissures, hypertelorism, microcephaly and low set prominent ears.

Abnormalities, Multiple↗
PubMed1987

Long-term alterations in histology and steroid receptor levels of the genital tract and mammary gland following neonatal exposure of female BALB/cCrgl mice to various doses of diethylstilbestrol.

The relation of the dosage of diethylstilbestrol (DES) administered neonatally to the incidence and severity of genital tract and mammary gland lesions and to the levels of sex hormone receptors was examined using a mouse model for human intrauterine DES exposure. Female BALB/cCrgl mice received various doses of DES (ranging from 5 X 10(-1)-10(-5) micrograms daily for the first 5 days of life) or the sesame oil vehicle alone. In the vagina, at all ages examined (1, 2, 6, and 12 months) cytosolic estrogen receptors are consistently decreased after high doses of neonatal DES (10(-1) and 1 microgram). In contrast, at the same ages, vaginal cytosolic progestin receptors increase after identical doses. In the uterus, the 1-microgram dose of neonatal DES also consistently decreases cytosolic estrogen receptors while increasing cytosolic progestin receptors at 1, 2, and 6 months of age. Histologically, neonatal doses of 5 X 10(-2) micrograms DES result in vaginal lesions at 2 months. With age, this threshold level decreases, implying interaction with an altered hormonal milieu. The uterus shows a sensitivity similar to that of the vagina in regard to the histopathological effects of neonatal DES. The ovary and mammary glands are 10- to 100-fold more sensitive to neonatal DES exposure.

Age Factors↗
PubMed1987

Growth of mouse vaginal epithelial cells in culture: functional integrity of the estrogen receptor system and failure of estrogen to induce proliferation.

Normal mouse vaginal epithelial cells isolated from ovariectomized ca. 40-day-old BALB/cCrg1 mice were purified by Percoll density gradient centrifugation and grown in primary culture using a collagen gel matrix and a serum-free complete medium. During the 9-day culture period, a 6-fold increase in cell number was observed. Addition of estrogen to the medium did not enhance epithelial cell proliferation. In fact, all doses of estrogen (180 fM to 18 nM) were inhibitory, resulting in only a 3- to 4-fold increase in cell number by day 9 of culture. Continuous exposure to estradiol (1.8 nM) for 9 days in the serum-free complete medium resulted in a decrease in cytosolic estrogen receptors with associated nuclear accumulation of estrogen receptors. A corresponding increase of cytosolic progestin receptors was also observed, indicating that no qualitative modification of the estrogen receptor system had occurred. Thus, despite its effectiveness in specific product synthesis (progestin receptors), estrogen does not stimulate proliferation of vaginal cells in this culture system, but rather inhibits epithelial cell proliferation.

Animals↗
PubMed1986

Pseudomonas cepacia colonization and infection in intensive care units.

Pseudomonas cepacia has become a prominent epidemic nosocomial pathogen over the past 15 years. Between December 1982 and September 1983 it was isolated from 29 patients in two intensive care units (ICUs) at one hospital. Twelve infections--five bacteremias, four pneumonias and three urinary tract infections--occurred. Most of the isolates (25/29) were from the respiratory tract, and most (23/29) had the same antibiogram as the only environmental isolate, which was cultured from a contaminated ventilator thermometer, a previously unrecognized source of nosocomial infection. The ventilator thermometers were calibrated in a bath whose water had not been changed for months and contained P. cepacia. Despite elimination of this reservoir, P. cepacia was eradicated from the ICUs only after intensive infection control efforts were instituted.

Aged↗
PubMed1986

Somatomedin-C substitutes for insulin for the growth of mammary epithelial cells from normal virgin mice in serum-free collagen gel cell culture.

We investigated the effect of somatomedin C (SM-C) on the growth of mouse mammary ductal epithelial cells in collagen gel culture. Epithelial cells, isolated by collagenase digestion of whole glands, were placed into primary serum-free collagen gel cell culture for 10-12 days, during which SM-C was added alone or in combination with other growth-promoting factors. Previous work has shown that these cells require a superphysiological concentration of insulin (10 micrograms/ml) for optimum growth in serum-free medium (a 1:1 mixture of Ham's F-12 and Dulbecco's Modified Eagle's medium) containing epidermal growth factor (EGF). When SM-C (1-250 ng/ml) alone was added to serum-free basal medium containing EGF, it stimulated growth (at concentrations greater than 25 ng/ml) to at least the same extent as insulin at 10 micrograms/ml. There was no additive stimulation of growth when optimal concentrations of insulin and SM-C were added together. The nonadditive stimulation at optimal concentrations of these hormones may indicate that the previous requirement for a superphysiological concentration of insulin for maximum growth was due to low affinity binding of insulin to the SM-C receptor. Rat insulin-like growth factor II (Collaborative Research) at 50-200 ng/ml did not stimulate growth in the presence or absence of insulin. SM-C could not stimulate growth alone. The presence of EGF or mammogenic hormones (progesterone and PRL) was required.

Animals↗
PubMed1986

Heterogeneity in the hormonal responsiveness of clones derived from the 13762NF rat mammary tumor.

The transplantable hormone-responsive rat mammary adenocarcinoma 13762NF was dissociated with collagenase and hyaluronidase. Cells were cloned directly or lines were established from mass cultures and cells from these lines were cloned. Clones differed in cellular morphology, colony morphology on plastic or in collagen gel, growth rate, growth response to hormones, and hormone receptor levels. Growth response to prolactin, estradiol, progesterone, cortisol, and epidermal growth factor (EGF) was determined by culturing the cells within collagen gel and using a serum-free medium base of DME/F12 (1:1) with insulin, linoleic acid, and BSA. The clones varied in their hormone responses, with all 20 of the clones tested responding to cortisol in combination with EGF. Some clones would respond to EGF, cortisol, or progesterone when used alone. None of the clones tested could be stimulated by prolactin or estradiol. Receptor levels for estradiol, progesterone, glucocorticoids, and EGF were assessed in 3 selected clones differing in their hormone responsiveness. Receptor levels appeared to correlate with hormonal sensitivity. Selected clones transplanted into female F344 rats produced carcinomas with histopathologies similar to the original tumor.

Adenocarcinoma↗
PubMed1985

Regulation of estrogen and progesterone receptor levels in mouse mammary epithelial cells grown in serum-free collagen gel cultures.

The effect of collagenase dissociation of virgin mouse mammary glands on the level of mammary epithelial cytosolic estrogen receptors (ER) and progesterone receptors (PR) was assessed. After cell dissociation, ER was present in mammary epithelial cells at concentrations similar to those found in the whole gland. However, PR appeared to be affected by the collagenase treatment. The regulation of ER and PR in mouse mammary epithelial cells isolated by collagenase dissociation and grown within collagen gels was then determined. After 7 days in culture under serum-free conditions inside a collagen gel, PR and, to a lesser extent ER, as characterized by high affinity binding and specificity, were present in the epithelial cells. Although at a low level, the ER were determined to be functional, since estradiol (E2) was able to promote nuclear accumulation of ER and to induce PR. PRL was able to increase cytosolic ER and PR concentrations. The combination of progesterone (P) and PRL was more effective than PRL or P alone in increasing PR. The induction of PR by P and PRL was inhibited when epidermal growth factor was present in the culture medium. Previous studies have shown that P, PRL, and epidermal growth factor, but not E2 (either alone or in combination with these factors) are able to stimulate cell proliferation in vitro. We conclude that the effects of E2 on protein synthesis and proliferation are dissociated in vitro. The difference between the effect of E2 and PRL or P on growth may be related either to the initial concentrations of their respective receptors or estrogen may stimulate growth indirectly.

Animals↗
PubMed1985

Epidermal growth factor receptor levels in mouse mammary glands in various physiological states.

Experiments were undertaken to demonstrate and characterize specific receptors for epidermal growth factor (EGF) in mammary glands of female BALB/c mice in various physiological states. The results of an in vitro desaturation technique are also presented which allow estimation of the total EGF-binding sites per mg membrane protein. Binding of the ligand [125I]iodo-EGF is both time and temperature dependent. Maximum binding to the membrane is achieved after 6 h of incubation with [125I]iodo-EGF at 23 C. Scatchard analysis of equilibrium binding using membrane preparations of mammary glands from virgin mice yields two classes of high affinity receptors with Kd values of 0.8 +/- 0.1 and 5.0 +/- 0.4 X 10(-10) M and receptor concentrations of 10 +/- 1.2 and 23.5 +/- 2 fmol/mg protein, respectively. Membrane preparations of mammary tissues from cycling, gestating, and lactating mice were used to correlate cellular receptor levels to the physiological state of the animal. Beginning at weaning, there is a constant decrease in high affinity receptor level with increasing age, as well as through the early stages of both gestation and lactation. On day 10 of gestation, receptor levels increase, reaching 15.2 +/- 1.6 fmol/mg protein, followed by a decrease to 3.8 +/- 0.9 fmol/mg protein on day 10 of lactation. We conclude that membrane preparations from the mouse mammary gland contain specific high affinity receptors for EGF, and that receptor levels are characteristic of the physiological state.

Aging↗
PubMed1984

Correlation between in vitro growth and regulation of estrogen and progesterone receptors in rat mammary epithelial cells.

The present studies examine 1) the effect of enzymatic cell dissociation on the level of cytosolic estrogen receptor (ER) and progesterone receptor (PR) for normal rat mammary tissue, 2) the concentrations of ER and PR in rat mammary epithelial (RME) cells cultured within collagen gel, and 3) correlations that may exist between receptor concentration and cultured RME cell proliferation after hormonal stimulation in vitro. After cell dissociation, ER was present in mammary cells at higher concentrations than those found in the whole gland, whereas PR concentrations were similar to those in the whole gland. As characterized by Scatchard analysis, PR and, to a lesser extent, ER can be maintained in cells cultured in serum-free medium within a collagen gel matrix. ER is apparently functional at relatively low levels, since estradiol did induce PR synthesis, and cytosolic ER was reduced by estrogen administration. However, estradiol had no mitogenic effect on RME cells in this system, supporting the hypothesis that there may be a dichotomy between estrogen's effect on growth and progesterone receptor synthesis. PRL plus progesterone act synergistically to induce cell proliferation in our system, and this correlates with increased concentrations of progesterone receptors. Thus, the collagen gel system appears to provide a useful in vitro model for the study of receptor regulation and cell proliferation.

Animals↗
PubMed1983

Human chromosome analysis: methodology and applications.

This issue focuses on the rapidly developing field of human cytogenetics. The first article discusses the methodology used in the study of human chromosomes as well as its application in the diagnosis of chromosomal disorders. The second article discusses the application of chromosome analysis to the diagnosis and prognosis of hematologic malignancies, and the final article illustrates clues found on a peripheral blood smear that lead to the diagnosis of a chromosomal disorder.

Chromosome Aberrations↗