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Biomedical subjects

D C Johnson

Publications and source records attributed to D C Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1996

A phorbol ester that activates protein kinase C mimics the action of estradiol or epidermal growth factor for initiating embryo implantation in the delayed implanting hypophysectomized rat.

In rodents an action of estrogen is required for the initiation of implantation of the blastocyst into the endometrium of a progesterone-primed uterus. Thus removal of endogenous estrogen, either directly by ovariectomy or indirectly by hypophysectomy, prevents implantation in the pregnant rat. In the present study, delayed implanting hypophysectomized progesterone-primed rats were used to test the efficacy of cyclic adenosine 3',5'-monophosphate (cAMP), epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I), which are agents that have been shown to mimic some uterine actions of estradiol, to initiate implantation. In confirmation of previous studies, EGF injected into the uterine lumen plus intravenously was effective at initiating implantation in all animals. IGF-I showed no such activity in this model system. Cyclic AMP, increased via direct activation of adenylyl cyclase by forskolin, or administration of sodium dibutyryl cAMP, did not initiate implantation. However, a ligand for protein kinase C (PKC), phorbol 12-myristate 13-acetate, was effective in augmenting the action of intrauterine EGF, or forskolin, for initiation of implantation. A phorbol ester that does not activate PKC was ineffective. The results provide circumstantial evidence for the requirement of PKC activity in the implantation initiating action of estrogens.

Animals↗
PubMed1996

Estradiol-chlordecone (Kepone) interactions: additive effect of combinations for uterotropic and embryo implantation functions.

Chlordecone (Kepone) is a polychlorinated hydrocarbon that has a low affinity for the estrogen receptor. Although the compound has been shown to be an estrogen antagonist for some responses within the central nervous system, and in hypophyseal gonadotrophic cells, such an action for other responses has not been reported. In the present study ovariectomized immature rats were used to determine the uterotropic effects of chlordecone in the presence or absence of estradiol. Administration of 30 mg/kg chlordecone per day for 3 days increased the response to 0.01, 0.1 and 1 microgram/kg per day of estradiol benzoate (EB). No additive or inhibitory effect was found with chlordecone plus 10 micrograms/kg EB. Likewise, the uterine response to 15 or 30, but not 45, mg/kg chlordecone was enhanced by the co-administration of 0.1 microgram/kg EB. A second response, initiation of embryo implantation in hypophysectomized, progesterone-primed, delayed implanting pregnant rats was tested. Subliminal doses of estradiol or chlordecone were additive for initiating normal implantation in more than 80% of the animals. The results indicate that chlordecone is not an estrogen antagonist for functions that require the action of the estrogen receptor in the uterus. The mechanism(s) involved in the additive action have not been determined but emphasize the need to consider xenoestrogen-natural estrogen interactions when assessing risks for reproductive toxins.

Animals↗
PubMed1996

Implementation and evaluation of an algorithm for isolation of patients with suspected pulmonary tuberculosis.

OBJECTIVE: To implement and evaluate an algorithm designed to assist in the consistent placement of patients with suspected pulmonary tuberculosis into negative-pressure isolation rooms (NPIRs). DESIGN: A standard algorithm was designed for the appropriate room placement of patients with suspected pulmonary tuberculosis using clinical, radiographic, and laboratory criteria and reported risk factors. A case-patient was defined as an inpatient who had at least one Mycobacterium tuberculosis culture-positive respiratory specimen from January 1, 1993, through December 31, 1994. Demographic, clinical, laboratory, case contact, and isolation and room placement data were collected prospectively on all case patients. SETTING: A 900-bed university teaching and referral center. RESULTS: During 1993 and 1994, 69 patients were evaluated for possible pulmonary tuberculosis, and 31 case-patients were identified. Of the 31 case-patients, 26 (84%) were placed on respiratory isolation in NPIRs, including 19 (61%) who were isolated within 24 hours of admission (1993, 14 of 20 [70%]; 1994, 5 of 11 [45%]). Seven case-patients (23%) were isolated in NPIRs following delays that ranged from 2 to 31 days (median, 9 days), and five case-patients (16%) never were isolated during admissions of from 3 to 28 days (median, 4 days). These 12 case-patients contributed a total of 136 patient-exposure days during their hospitalizations. Misclassification of patient risk status by user error delayed isolation of five (42%) of the 12 improperly isolated case-patients. CONCLUSIONS: The use of an algorithm incorporating radiographic, laboratory, and clinical criteria and reported risk factors may assist in the rapid isolation of patients with suspected pulmonary tuberculosis.

Adult↗
PubMed1996

Inhaled nitric oxide. A bronchodilator in mild asthmatics with methacholine-induced bronchospasm.

Nitric oxide (NO) reduces airway tone in the methacholine-treated guinea pig. We examined whether low levels of inhaled NO gas would relax airway smooth muscle tone in patients with mild asthma subjected to methacholine-induced bronchospasm. Thirteen adult volunteers with mild asthma inspired increasing concentrations of methacholine until their baseline forced expiratory volume in one second (FEV1, 3.29 +/- 0.17 L, mean +/- SEM) decreased by > or = 20% (2.33 +/- 0.18 L, p < 0.01). Thereafter, they sequentially inhaled 100 parts per million (ppm) NO, 40% O2; 40% O2; and 100 ppm NO, 40% O2 while spirometry was performed. Subsequent inhalation of isoproterenol returned the FEV1 levels to baseline. Inhaling 100 ppm NO increased FEV1 to 2.66 +/- 0.18 L (p < 0.01), and this increase was maintained after NO was discontinued. FEV1 did not change during the second period of NO inhalation. Similar results were observed for vital capacity, but no significant effect was noted on forced expiratory flow at 25% of vital capacity or peak expiratory flow. Subjects were then divided into a responder subgroup, which showed a mean increase in FEV1 after initial NO inhalation of 560 +/- 150 ml, and a nonresponder subgroup, which showed a mean increase in FEV1 of 129 +/- 29 ml. Our data suggest that inhalation of nitric oxide by patients with mild asthma with methacholine-induced bronchospasm results in a minor but significant relaxation of airway tone.

Administration, Inhalation↗
PubMed1996

Cytochrome P450 17 alpha-hydroxylase gene expression in differentiating rat trophoblast cells.

Trophoblast giant cells of the rat placenta express cytochrome P450 17 alpha-hydroxylase (P450c17) and synthesize androgens. The purpose of this study was to investigate androgen production and expression of P450c17 in the Rcho-1 trophoblast cell line. These cells are capable of differentiating along the trophoblast giant cell lineage. Androstenedione production increased approximately 70-fold as Rcho-1 trophoblast cells progressed from the proliferation to the differentiation state. P450c17 enzyme activity and mRNA also showed significant increases associated with trophoblast giant cell differentiation. To study the transcriptional regulation of the P450c17 gene, the activities of a series of P450c17 promoter-luciferase reporter constructs were evaluated following transient transfection into Rcho-1 trophoblast cells. A DNA region located-98 bp upstream of the P450c17 gene transcriptional start site was the shortest promoter DNA construct consistently possessing activity in Rcho-1 trophoblast cells. Activities of longer constructs (-156 to -1560 bp) in this population of cells were significantly greater than the -98 bp promoter-reporter construct. The -476 bp P450c17 construct showed maximal promoter activity in transiently transfected Rcho-1 trophoblast cells and was developmentally activated in stably transfected Rcho-1 trophoblast cells. Activation of the cyclic AMP/protein kinase A pathway did not significantly affect P450c17 promoter activity in Rcho-1 trophoblast cells, in contrast to its effects in mouse MA-10 Leydig cells. In summary, Rcho-1 trophoblast cells are capable of endocrine differentiation and are a useful in vitro system for studying the regulation of trophoblast androgen production and P450c17 gene expression.

Androgens↗
PubMed1995

Reproductive effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in female rats: ovulation, hormonal regulation, and possible mechanism(s).

A previous study has shown that exposure of adult rats to TCDD alters estrous cyclicity and ovulation. To further explore the mechanisms involved we employed the gonadotropin-primed immature female rat model. Single doses (0.3-60 micrograms/kg) of TCDD, dissolved in corn oil, were given orally to 22-day-old rats. Equine chorionic gonadotropin (eCG) (20 IU) was injected 24 hr later to induce follicular development. Rats were killed at various times after eCG, blood was collected, and ovarian weights were obtained. Serum concentrations of estradiol-17 beta (E2), luteinizing hormone (LH), follicle stimulating hormone (FSH), and prolactin (LTH) were measured by radioimmunoassay. Ovulation was determined 72 hr after injection of eCG by counting ova flushed from oviducts. TCDD reduced dose-dependently the increase in ovarian weight gain induced by eCG and also decreased the number of animals ovulating as well as the number of ova recovered; the ED50 was between 3 and 10 micrograms/kg of TCDD. The increase in serum E2 induced by eCG was enhanced in animals treated with TCDD. Peak serum levels of FSH and LH, but not of LTH, were decreased by TCDD. E2, as expected, decreased dramatically in control animals between 60 and 72 hr after injection of eCG, concomitant with a preovulatory surge in LH. This response was absent in TCDD-treated animals. None of these effects were related to decreased food consumption since they were absent in pair-fed controls. In hypophysectomized immature rats treated with eCG and exogenous LH the percentage of rats ovulating and the number of ova recovered were also significantly reduced by TCDD (10 and 60 micrograms/kg). These results suggest that TCDD alters reproductive function in the immature female rat model via effects on the hypothalamic-pituitary axis as well as by direct effects on the ovary.

Administration, Oral↗
PubMed1995

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on estrous cyclicity and ovulation in female Sprague-Dawley rats.

The effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on estrous cyclicity and ovulation in Sprague-Dawley rats was examined. TCDD at a single oral dose of 10 micrograms/kg resulted in irregularity of cycles, characterized mainly as prolonged periods of diestrus. In rats cycling normally this dose of TCDD reduced the ovulatory rate and the number of ova recovered. The results suggest that TCDD is a reproductive toxin also in female rats, the mechanism of which is as yet unknown.

Administration, Oral↗
PubMed1995

The role of arachidonic acid and/or its metabolites in embryo implantation initiated by epidermal growth factor (EGF).

Previous studies have shown that epidermal growth factor (EGF) can replace estrogen for initiating embryo implantation in hypophysectomized rats in which pregnancy was maintained with progesterone, provided that uterine trauma preceded the intravenous dose of the growth factor. The present study has shown that intraperitoneal administration of prostaglandin E2 (PGE2) or histamine dihydrochloride can replace the need for uterine trauma. On the other hand, indomethacin (1 mg subcutaneous), an inhibitor or prostaglandin synthase (PGHS) and phospholipase A2 (PLA2) inhibited the implantation initiated by EGF plus trauma or even EGF plus PGE2, but had no effect upon that initiated by estradiol. A much larger dose of another PGHS inhibitor, ibuprofen, did not inhibit, but appeared to enhance, the effect of EGF plus trauma. The lipoxygenase inhibitor nordihydroguairaretic acid also was ineffective at inhibiting the action of EGF plus trauma. In contrast to the ineffectiveness of these non-steroidal anti-inflammatory agents, the synthetic glucocorticoid dexamethasone inhibited implantation initiated by either EGF or estradiol. These results are consistent with the interpretation that treatment with agents known to inhibit the activity of PLA2, and thus availability of arachidonic acid, are more potent inhibitors of implantation initiated by EGF than those that only inhibit PGHS.

Animals↗
PubMed1995

Oesophageal cancer: outcome of modern surgical management.

Many clinicians still associate oesophagectomy for oesophageal carcinoma with low cure rates, poor palliation and prohibitive peri-operative mortality. Surgical advances have rendered such perceptions inaccurate. A prospective study of all patients undergoing surgery for oesophageal cancer in an Australian teaching hospital between 1979 and 1993 has been undertaken. Selection, staging, pre-operative preparation, surgical technique and postoperative care were all carefully controlled. One hundred and thirty-seven patients were explored. Twenty-one were inoperable. One hundred and sixteen underwent resection with intent to cure. Hospital mortality for oesophagectomy was 1.7%. There were no cases of clinical anastomotic leakage. Eighty-nine per cent achieved excellent to good swallowing. The median survival for all cases was 14 months and the 5 year survival was 18%. Median survival for resected cases was 18 months and the 5 year survival was 26%. The long-term survival was related to postoperative stage of the disease but not to tumour type. Oesophagectomy for oesophageal cancer will restore good swallowing in 90% of cases. Operative mortality should be less than 5% and the overall 5 year survival 20-30%. Early tumours can often be cured (ca in situ 100%, stages I and II 50-60%), indicating the benefits of early detection. Poor survival in advanced disease (stage III 15%, stage IV 0%) on a background of low surgical mortality indicate the need for better staging and more effective adjuvant therapies.

Adenocarcinoma↗
PubMed1995

Glycoproteins E and I facilitate neuron-to-neuron spread of herpes simplex virus.

Two herpes simplex virus (HSV) glycoproteins E and I (gE and gI) form a heterooligomer which acts as an Fc receptor and also facilitates cell-to-cell spread of virus in epithelial tissues and between certain cultured cells. By contrast, gE-gI is not required for infection of cells by extracellular virus. HSV glycoproteins gD and gJ are encoded by neighboring genes, and gD is required for both virus entry into cells and cell-to-cell spread, whereas gJ has not been shown to influence these processes. Since HSV infects neurons and apparently spreads across synaptic junctions, it was of interest to determine whether gD, gE, gI and gJ are also important for interneuronal transfer of virus. We tested the roles of these glycoproteins in neuron-to-neuron transmission of HSV type 1 (HSV-1) by injecting mutant viruses unable to express these glycoproteins into the vitreous body of the rat eye. The spread of virus infection was measured in neuron-rich layers of the retina and in the major retinorecipient areas of the brain. Wild-type HSV-1 and a gJ- mutant spread rapidly between synaptically linked retinal neurons and efficiently infected major retinorecipient areas of the brain. gD mutants, derived from complementing cells, infected only a few neurons and did not spread in the retina or brain. Mutants unable to express gE or gI were markedly restricted in their ability to spread within the retina, produced 10-fold-less virus in the retina, and spread inefficiently to the brain. Furthermore, when compared with wild-type HSV-1, gE- and gI- mutants spread inefficiently from cell to cell in cultures of neurons derived from rat trigeminal ganglia. Together, our results suggest that the gE-gI heterooligomer is required for efficient neuron-to-neuron transmission through synaptically linked neuronal pathways.

Animals↗
PubMed1995

Role of mannose-6-phosphate receptors in herpes simplex virus entry into cells and cell-to-cell transmission.

Herpes simplex virus (HSV) glycoprotein D (gD) is essential for virus entry into cells, is modified with mannose-6-phosphate (M-6-P), and binds to both the 275-kDa M-6-P receptor (MPR) and the 46-kDa MPR (C. R. Brunetti, R. L. Burke, S. Kornfeld, W. Gregory, K. S. Dingwell, F. Masiarz, and D. C. Johnson, J. Biol. Chem. 269:17067-17074, 1994). Since MPRs are found on the surfaces of mammalian cells, we tested the hypothesis that MPRs could serve as receptors for HSV during virus entry into cells. A soluble form of the 275-kDa MPR, derived from fetal bovine serum, inhibited HSV plaques on monkey Vero cells, as did polyclonal rabbit anti-MPR antibodies. In addition, the number and size of HSV plaques were reduced when cells were treated with bovine serum albumin conjugated with pentamannose-phosphate (PM-PO4-BSA), a bulky ligand which can serve as a high-affinity ligand for MPRs. These data imply that HSV can use MPRs to enter cells; however, other molecules must also serve as receptors for HSV because a reasonable fraction of virus could enter cells treated with even the highest concentrations of these inhibitors. Consistent with the possibility that there are other receptors, HSV produced the same number of plaques on MPR-deficient mouse fibroblasts as were produced on normal mouse fibroblasts, but there was no inhibition with PM-PO4-BSA with either of these embryonic mouse cells. Together, these results demonstrate that HSV does not rely solely on MPRs to enter cells, although MPRs apparently play some role in virus entry into some cell types and, perhaps, act as one of a number of cell surface molecules that can facilitate entry. We also found that HSV produced small plaques on human fibroblasts derived from patients with pseudo-Hurler's polydystrophy, cells in which glycoproteins are not modified with M-6-P residues and yet production of infectious HSV particles was not altered in the pseudo-Hurler cells. In addition, HSV plaque size was reduced by PM-PO4-BSA; therefore, it appears that M-6-P residues and MPRs are required for efficient transmission of HSV between cells, a process which differs in some respects from entry of exogenous virus particles.

Animals↗
PubMed1995

Herpes simplex virus glycoprotein K is known to influence fusion of infected cells, yet is not on the cell surface.

Syncytial mutants of herpes simplex virus (HSV) cause extensive fusion of cultured cells, whereas wild-type HSV primarily causes cell rounding and aggregation. A large fraction of syncytial viruses contain mutations in the UL53 gene, which encodes glycoprotein K (gK). Previously, we demonstrated that wild-type and syncytial forms of gK are expressed at similar levels and possess identical electrophoretic mobilities. Using immunofluorescence, we show that gK is not transported to the surfaces of cells infected with either wild-type or syncytial HSV. Instead, gK accumulates in the perinuclear and nuclear membranes of cells. This finding is in contrast to the behavior of all other HSV glycoproteins described to date, which reach the cell surface. When gK was expressed in the absence of other HSV proteins, using a recombinant adenovirus vector, a similar perinuclear and nuclear pattern was observed. In addition, gK remained sensitive to endoglycosidase H, consistent with the hypothesis that gK does not reach the Golgi apparatus and is retained in the endoplasmic reticulum and nuclear envelope. Therefore, although gK mutations promote fusion between the surface membranes of HSV-infected cells, the glycoprotein does not reach the plasma membrane and, thus, must influence fusion indirectly.

Animals↗
PubMed1995

Herpes simplex virus glycoprotein K promotes egress of virus particles.

Herpes simplex virus (HSV) glycoprotein K (gK) is thought to be intimately involved in the process by which infected cells fuse because HSV syncytial mutations frequently alter the gK (UL53) gene. Previously, we characterized gK produced in cells infected with wild-type HSV or syncytial HSV mutants and found that the glycoprotein was localized to nuclear and endoplasmic reticulum membranes and did not reach the cell surface (L. Hutchinson, C. Roop, and D. C. Johnson, J. Virol. 69:4556-4563, 1995). In this study, we have characterized a mutant HSV type 1, denoted F-gK beta, in which a lacZ gene cassette was inserted into the gK coding sequences. Since gK was found to be essential for virus replication, F-gK beta was propagated on complementing cells which can express gK. F-gK beta produced normal plaques bounded by nonfused cells when plated on complementing cells, although syncytia were observed when the cells produced smaller amounts of gK. In contrast, F-gK beta produced only microscopic plaques on Vero cells and normal human fibroblasts (which do not express gK) and these plaques were reduced by 10(2) to 10(6) in number. Further, large numbers of nonenveloped capsids accumulated in the cytoplasm of F-gK beta-infected Vero cells, virus particles did not reach the cell surface, and the few enveloped particles that were produced exhibited a reduced capacity to enter cells and initiate an infection of complementing cells. Overexpression of gK in HSV-infected cells also caused defects in virus egress, although particles accumulated in the perinuclear space and large multilamellar membranous structures juxtaposed with the nuclear envelope were observed. Together, these results demonstrate that gK regulates or facilitates egress of HSV from cells. How this property is connected to cell fusion is not clear. In this regard, gK may alter cell surface transport of viral particles or other viral components directly involved in the fusion process.

Adolescent↗
PubMed1995

Inhibitory and stimulatory effect of oestrogens upon ovarian 17 alpha-hydroxylase/C17,20-lyase in immature hypophysectomized rats treated with gonadotrophin.

A study was designed to compare the effects of exogenous and endogenous oestrogens upon the expression of steroid 17 alpha-hydroxylase/C17,20-lyase (CYP17) in the immature hypophysectomized rat ovary. C17,20-lyase activity was measured ex vivo using [21-14C]progesterone, while serum concentrations of androstenedione indicated in vivo activity. Immunocytochemistry was used to localize the enzyme within the ovary. Activity of CYP17 increased dramatically and remained high in thecal and interstitial cells after injection of equine chorionic gonadotrophin, even though serum oestradiol (OE2) levels exceeded 2 nmol/l. Production of comparable serum levels by the use of Silastic capsules containing OE2 greatly suppressed but did not stop, expression of the enzyme induced by repeated doses of human chorionic gonadotrophin (hCG). Subcutaneous implantation of Silastic capsules (1 cm) containing diethylstilboestrol (DES) stimulated follicular growth and increased ovarian weight by 67%, 5 days later. Injection of 50 IU hCG at various times after removal of the implant produced time-dependent changes in CYP17 activity and serum androstenedione levels, when measured 30 h later. Although the initial effect of removal of DES was an increase in CYP17 activity, delaying injection of hCG resulted in a reduced response. The results indicated that: (1) endogenous oestrogens do not inhibit CYP17 expression; (2) exogenous oestrogens only reduce the number of thecal/interstitial cells expressing CYP17 when they are exposed to hCG; (3) pretreatment with oestrogen removes the ovarian interstitial but not the thecal cell expression of CYP17 in response to hCG; and (4) oestrogens can be stimulatory for CYP17 expression in thecal cells.

Aldehyde-Lyases↗
PubMed1995

Estradiol and chlordecone (Kepone) decrease adenosine 3'5'-cyclic monophosphate concentrations in the ovariectomized immature rat uterus.

Adenosine 3'5'-cyclic monophosphate (cAMP) has been repeatedly shown to mimic some actions of estrogen in the rat uterus. However, the relationship between estrogens and uterine cAMP remains controversial. The effect of chronic exposure (3 days) to a biologically potent, long-acting estrogen, estradiol benzoate (EB), or the xenoestrogen chlordecone (Kepone), which has a long half-life in the circulation, was examined in ovariectomized immature rats. Both compounds, when administered in doses that provided equal increases in uterine weight, produced equivalent decreases in uterine cAMP content. Although the decrease in cAMP was apparent within 48 hr, it was more pronounced at 72 hr. There was no reduction in cAMP produced in response to direct stimulation of uterine adenylyl cyclase by forskolin, indicating that loss of the enzyme was not a factor in the lowering of cAMP content. The pure anti-estrogen ICI-182,780, in a dose-dependent fashion, prevented the action the estradiol benzoate and chlordecone, suggesting that the lowering of cAMP was dependent on an estrogen receptor. The physiological significance of reduced uterine cAMP with chronic estrogen treatment remains to be determined.

Adenylyl Cyclases↗
PubMed1995

The cotton swab test. Receiver-operating characteristic curves.

The purpose of this prospective, cohort study was to perform a receiver-operating characteristic (ROC) analysis of the cotton swab test and its ability to predict stress incontinence. The study was performed in a tertiary care gynecologic urology clinic over a period of 3.5 years. Two hundred sixty-three women presenting with the complaint of urinary incontinence formed the basis of the cohort. Subjects were classified as having genuine stress urinary incontinence or incontinence secondary to another factor following urodynamic testing. The cotton swab test was performed as part of the standard urogynecologic assessment. Measurement was made of the resting, straining and calculated resultant change in angle. ROC curves were calculated for each of the angles measured. The resultant ROC curves demonstrated that straining angle has the best discriminatory power in the diagnosis of genuine stress urinary incontinence. The optimum cut-off point for this discrimination is a deflection of 40 degrees from the horizontal, with a resultant sensitivity of 83%. Despite the diagnostic trend, the sensitivity of the straining angle does not allow one to confidently make a diagnosis of genuine stress urinary incontinence without a confirmatory evaluation. The test, however, can be beneficial in the counseling and triage of women with lower urinary tract complaints.

Female↗