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Biomedical subjects

G Kennedy

Publications and source records attributed to G Kennedy.

At least 91 records · Page 5Linked to original sources
PubMed1989

CRE-binding proteins interact cooperatively to enhance placental-specific expression of the glycoprotein hormone alpha-subunit gene.

The 18-bp direct repeat occurring between positions -146 and -111 in the 5'-flanking region of the human alpha-subunit gene serves two functions: it mediates the transcriptional effect of cAMP and it acts in conjunction with an adjacent cis-acting element (URE) to confer properties of placental-specific expression to the alpha-subunit promoter. Functional activity of the URE and CRE requires binding of a trans-acting factor; each element binds a different factor. Analysis of saturation isotherms provides good evidence that cooperativity is involved in binding of CREB to the 18-bp direct repeat. This cooperativity could account for the synergistic effect of two CRE on both basal and cAMP-stimulated transcription. It remains to be determined whether heterotropic cooperativity is involved in binding of trans-acting factors to the URE and CRE. A major difference between the 5'-flanking region of the human alpha-subunit gene and comparable regions from bovine, rat, and mouse alpha-subunit genes is that the latter contain a single CRE homolog which appears incapable of binding the trans-acting factor that binds to the human alpha CRE. Lack of a functional CRE provides at least one explanation for inactivity of the bovine alpha-subunit promoter in choriocarcinoma cells and probably in bovine placenta as well. Yet, the same bovine promoter-regulatory region that lacks a functional CRE is capable of conferring pituitary-specific expression to the CAT gene in transgenic mice (data not shown). This suggests that the CRE is not required for pituitary-specific expression of the bovine alpha-subunit gene. Instead, another cis-acting element(s) must confer this property to the alpha-subunit promoter. While it is tempting to suggest that bovine, rat, and mouse alpha-subunit genes are not regulated by cAMP because of their inactive CRE homolog, it is also quite possible that other CRE are located further upstream. Accordingly, it will be of interest to obtain additional 5'-flanking sequence and determine whether functional homologs of the human alpha CRE are present in the bovine, rat, and mouse alpha-subunit genes, or whether another class of cis-acting elements provide cAMP-responsiveness.

Base Sequence↗
PubMed1989

Site-directed mutagenesis of the human chorionic gonadotropin beta-subunit: bioactivity of a heterologous hormone, bovine alpha-human des-(122-145)beta.

Human CG contains an alpha-subunit, common to the pituitary glycoprotein hormones, and a hormone-specific beta-subunit, but unlike the pituitary beta-subunits, hCG beta is characterized by an O-glycosylated carboxy-terminal extension. A mutant beta-subunit, des-(122-145)hCG beta, was prepared using site-directed mutagenesis, and the pRSV expression plasmids were transfected into Chinese hamster ovary cells that produce the bovine alpha-subunit (b alpha). The mutant beta-subunit binds to b alpha, and the heterologous gonadotropin, b alpha-des-(122-145)hCG beta, was capable of stimulating steroidogenesis in cultured Leydig tumor cells (MA-10) to the same extent as standard hCG. When compared with the heterologous gonadotropin, b alpha-hCG beta wild type, the hybrid hormone with the truncated hCG beta exhibited equal potency, within the accuracy of the RIAs used to determine hormone concentrations, and gave a similar time course of steroidogenesis. Interestingly, these transformed Leydig cells do not distinguish between the steroidogenic potencies (as measured by progesterone production) of hCG and human LH (hLH) as do some preparations of normal rodent Leydig cells (as measured by testosterone production). However, the MA-10 cells were able to distinguish hCG from hLH based on their cAMP response; the latter produced a greater response at both maximal and submaximal gonadotropin concentrations. The two expressed heterologous gonadotropins were equipotent in their abilities to stimulate cAMP and gave similar time courses of cAMP accumulation in MA-10 cells. Thus, the carboxy-terminal extension of hCG beta is not required for association with the alpha-subunit nor for functional receptor binding, as judged by cAMP accumulation and progesterone production in MA-10 cells.

Animals↗
PubMed1988

Cyclic AMP and phorbol esters interact synergistically to regulate expression of the chorionic gonadotropin genes.

Previous studies have shown that activators of the protein kinase A pathway increase transcription of the genes encoding the alpha- and beta-subunits of human chorionic gonadotropin (hCG) in choriocarcinoma cell lines. Here, we show that treatment of choriocarcinoma cells with activators of protein kinase C, such as phorbol myristate acetate (PMA) and dioctanoylglycerol, increases accumulation of the mRNAs for both subunits of hCG by 3-4-fold. In contrast, a phorbol ester which fails to activate protein kinase C, phorbol 12 beta,13 alpha-didecanoate, has no effect on hCG mRNA levels. To test the possibility that these two major intracellular signaling pathways interact, we treated choriocarcinoma cells with PMA, forskolin, or PMA and forskolin together. Treatment with either agent led to a 2-3-fold increase in hCG mRNA levels, whereas treatment with both agents resulted in a 9-fold increase. This synergistic response also occurred when choriocarcinoma cells were treated with PMA and 8-Br-cAMP. Furthermore, PMA did not increase intracellular cAMP levels, suggesting that these two pathways interact subsequent to cAMP generation. PMA also increased transcription of the hCG alpha- and beta-genes by 2-3-fold. Whereas transcription of the alpha subunit gene increases synergistically after treatment with both PMA and forskolin, transcription of the hCG beta-gene was limited to the increase caused by either agent alone. This latter result suggests that regulation of hCG beta mRNA accumulation is more complex than that of alpha-subunit mRNA and probably involves both transcriptional and post-transcriptional components.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1988

The time-dependent distribution of 125I-asialo-orosomucoid-horseradish peroxidase and 131I-immunoglobulin A among three endosomal subfractions isolated from rat liver.

Three discrete endosomal fractions showing a time-dependent uptake of radioactive ligand were partially purified from rat liver. The 3,3'-diaminobenzidine (DAB)-induced density-shift protocol of Courtoy, Quintart & Baudhuin [(1984) J. Cell Biol. 98, 870-876] was used to study the distribution among these three endosomal fractions of two ligands with different intracellular destinations. Rats received both 125I-asialo-orosomucoid-horseradish peroxidase (125I-ASOR-HRP) and 131I-dIgA simultaneously by intraportal injection. The liver was fractionated at various times after injection, the three ligand-containing endosomal fractions (A, B and C) were separated and each was subjected separately to the DAB-induced density-shift procedure in which only vesicles containing 125I-ASOR-HRP are increased in density. Information on whether 131I-dIgA was co-localized or segregated from 125I-ASOR-HRP was obtained. The two ligands in the A fraction were partly segregated and partly co-localized, and this distribution appeared to be relatively unchanged with time. The two ligands in the B fraction were co-localized at all times studied. We have tentatively identified the B fraction as a compartment in which vesicle fusion has occurred. The two ligands in the C fraction were also partly co-localized and partly segregated, but the 131I-dIgA became increasingly segregated with time. This represents the first report of the purification of an endosomal subfraction specifically involved in the accumulation of multiple ligands.

3,3'-Diaminobenzidine↗
PubMed1988

Administration of indomethacin for the prevention of periventricular-intraventricular hemorrhage in high-risk neonates.

One hundred twenty-two preterm infants were enrolled in a placebo-controlled, double-blind trial using intravenous indomethacin for the prevention of periventricular-intraventricular hemorrhage (PVH-IVH). Before random assignment, data on the infants were stratified according to low-weight (500 to 999 g) or high-weight (1000 to 1500 g) subgroups. Cranial sonography was used to document the absence of PVH-IVH before enrollment and the occurrence of PVH-IVH during the 7-day protocol. Indomethacin, 0.1 mg/kg, or placebo was administered before 12 hours of age and at 24, 48, and 72 hours of age. Five patients receiving indomethacin and six receiving placebo were withdrawn before completion of the study. In the remaining 111 patients, the indomethacin and placebo groups were comparable with respect to gestational ages, maternal complications, Apgar scores, ventilatory requirements, complications of prematurity, and mortality rate. PVH-IVH developed in six of 56 infants who received indomethacin and 11 of 55 infants who received placebo (P = 0.174). Analysis of the individual strata showed that the indomethacin-treated infants in the low-weight subgroup sustained a higher mortality rate (11/17 vs 3/16; P = 0.008) without a reduction in the incidence of PVH-IVH. Infants in the indomethacin-treated high-weight subgroup demonstrated a significantly lower incidence of PVH-IVH (2/39 vs 8/39; P = 0.04), but the frequency of high-grade hemorrhages was comparable for both indomethacin- and placebo-treated groups. In summary, the prophylactic administration of intravenous indomethacin for the prevention of PVH-IVH cannot be recommended for infants less than 1000 g. In preterm infants between 1000 and 1500 g birth weight, indomethacin significantly reduced the incidence of PVH-IVH.

Birth Weight↗
PubMed1984

Phases of change in the patient with Alzheimer's dementia: a conceptual dimension for defining health care management.

Since the progressive nature of Alzheimer's disease and related disorders of later life gradually imposes a series of significant limitations upon the patient, a successful clinical management program rests upon a conceptualization of changes in the patient. Postulating psychologic reactions helps professionals to understand and respond to the patient's needs and feelings at different stages of the disease. The phases discussed here provide the basis for defining treatment goals and management plans, selecting therapeutic strategies, identifying needed resources, and evolving innovative approaches to patient care.

Adaptation, Psychological↗
PubMed1982

The pharmacokinetics of vincristine in man: reduced drug clearance associated with raised serum alkaline phosphatase and dose-limited elimination.

A radioimmunoassay has been used to investigate the pharmacokinetics of vincristine in 39 cancer patients who received between 0.4 and 1.54 mg vincristine/m2 as part of standard treatment protocols. There was wide interindividual variation in both the terminal elimination half-life of vincristine (t1/2beta) and the associated volume of distribution (Vd), resulting in an 11-fold range of dose-corrected area under the plasma concentration versus time curve values (AUC0-infinity). Elevated vincristine AUC0-infinity values were observed in those patients with raised serum alkaline phosphatase at the time of vincristine estimation. The t1/2beta was significantly longer in these patients than in those with serum alkaline phosphatase within normal limits, suggesting that biochemical evidence of cholestasis is associated with reduced clearance of vincristine. Evidence is also presented to suggest that the clearance of vincristine is dose-dependent within the therapeutic dose range. We observed a disproportionate rise in vincristine plasma concentration at doses exceeding t1/2beta compared with that observed for patients receiving 1 mg vincristine/m2 or less.

Adult↗
PubMed1979

The incidence and pattern of angina prior to acute myocardial infarction: a study of 577 cases.

In order to determine the incidence and pattern of angina as a premonitory symptom of acute myocardial infarction, 577 consecutive patients with acute myocardial infarction were questioned shortly after hospital admission about the presence and pattern of chest pain prior to onset of infarction, with particular emphasis on the month prior to infarction. Two hundred and seventy-six patients (48 per cent) had no angina before infarction (Group I), whereas 301 (52 per cent) did. One hundred and seventy-nine patients (31 per cent) had a history of chronic angina, and of these, 75 had no change in the pattern of angina prior to infarction (Group II) while 104 noticed worsening of their symptoms in the month prior to infarction (Group III). One hundred and twenty-two patients (21 per cent) had new onset angina in the month prior to infarction (Group IV). The number of patients with unstable angina prior to infarction (Groups III and IV) was therefore 226 or 39 per cent of the total series. In patients with unstable angina, the increase in severity of symptoms or the development of new onset angina occurred within a period of 1 week or less in 69 per cent. Patients with a history of previous infarction or chronic angina had a higher incidence of unstable angina prior to infarction than patients without such a history (p less than 0.05). Patients with prior angina (Groups II, III, and IV) had a higher incidence of subendocardial infarction than patients without angina (p less than 0.05). The hospital mortality rate in the four groups did not differ significantly.

Age Factors↗
PubMed1976

Bromocriptine treatment in Parkinson's disease.

Thirty-one patients with Parkinson's disease were treated with the ergot alkaloid bromocriptine, a drug which stimulates dopamine receptors. Bromocriptine had a slight therapeutic effect in patients on no other treatment and an additional effect in patients on levodopa. The mean optimum dosage of bromocriptine, established over a 12 week period, was 26 mg daily. In 20 patients bromocriptine was compared with placebo in a double-blind controlled trial. Active treatment caused a significant (P less than 0.02) reduction in total disability and akinesia scores. The least disabled patients showed the greatest response. Side-effects of bromocriptine--nausea, vomiting, hallucinations, and abnormal involuntary movements--were similar to nature to those of levodopa. In most normal subjects, bromocriptine causes an increase in plasma growth hormone concentration. This was determined in 20 patients with Parkinson's disease after 1-15 mg bromocriptine. Only a single patient showed an obvious increase up to 120 minutes after dosage. Bromocriptine was not effective treatment in two patients who had not previously responded to levodopa and replacement of this drug by bromocriptine in patients with end-of-dose akinesia after chronic levodopa treatment did not totally abolish response swings.

Aged↗