Search PubMed⌕ Search

Biomedical subjects

D Carter

Publications and source records attributed to D Carter.

At least 91 records · Page 5Linked to original sources
PubMed1997

Cloned and native guinea pig 5-ht7 receptors. Characterization using an integrated approach.

Structural criteria, i.e., primary sequence homology, indicates a unique 5-HT subtype. Operational criteria suggest that this is also true, although no selective agonist or antagonist is available to fully define the receptor, and thus its function in vivo. Transductional data provide perhaps the weakest criterion to define the receptor, since at least two other subtypes (5-HT4 and 5-ht6) signal via the same second messenger. These criteria, taken together, suggest that the cloned sequence represents an endogenously expressed 5-HT receptor and should be referred to as "5-HT7" receptors, rather than "5-ht7".

Amino Acid Sequence↗
PubMed1997

Recognition of activated CSF-1 receptor in breast carcinomas by a tyrosine 723 phosphospecific antibody.

The macrophage colony stimulating factor receptor (CSF-1R), the product of the c-fms proto-oncogene, plays an important role in regulating the normal proliferation and differentiation of macrophages and trophoblasts. However, the abnormal expression of CSF-1R transcripts and protein by human breast carcinomas has been shown to correlate with advanced stage and poor prognosis. Ligand activated CSF-1R dimers transphosphorylate several tyrosines in their cytoplasmic domains which provide recognition sites for various effector proteins in multiple signal transduction pathways. In cells transformed by the c-fms oncogene, one of the major CSF-1R phosphotyrosines, pTyr723 is important for phenotypic expression of anchorage-independent growth and metastasis. In order to investigate the relationship between receptor activation/phosphorylation and cellular phenotypes in vitro and in vivo, we prepared a CSF-1R phosphorylation-state specific antibody raised against a specific phosphopeptide of CSF-1R, which included phosphorylated tyrosine 723. On immunoblots of lysates from cells expressing CSF-1R, this antibody recognizes phosphorylated CSF-IR in CSF-1 stimulated cells but not in unstimulated cells. As an immunohistochemical reagent, this antibody stained 52% of invasive human breast tumors (72% of CSF-1R positive cases) in a sample of 114 cases and 38% of carcinoma in situ. This data represents the first direct evidence of in vivo phosphorylation of CSF-1R in human breast carcinomas.

Amino Acid Sequence↗
PubMed1997

Molecular and biochemical studies on the hypoxanthine-guanine phosphoribosyltransferases of the pathogenic haemoflagellates.

All genera of protozoan parasites are auxotrophic for purines, and thus, purine acquisition from the host is a nutritional necessity for the survival and growth of these pathogens. Many of these parasites, including Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp., access host purines by phosphoribosylating purine bases via purine phosphoribosyltransferase (PRT) enzymes. The trypanosomatid hypoxanthine-guanine phosphoribosyltransferase (HGPRT) enzyme has been implicated as a critical enzyme of purine salvage in members of the Trypanosomatidae family. Moreover, the HGPRT enzymes of Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp. can also initiate the metabolism of certain cytotoxic purine base analogs that have little effect on the mammalian host. This implies that either inhibitors or substrates of HGPRT might serve as efficacious and selective agents for the treatment of diseases for which trypanosomatids are the etiologic agent. The hgprt genes from Trypanosoma brucei, Trypanosoma cruzi and Leishmania donovani have all been cloned, sequenced and overexpressed in E. coli, and the recombinant proteins have all been purified to homogeneity and characterized with respect to kinetic parameters and physicochemical properties. This paper presents an overview of recent molecular and biochemical studies on trypanosomatid HGPRT proteins and future efforts to validate HGPRT as a rational target for the chemotherapeutic manipulation of African sleeping sickness, Chagas disease and leishmaniasis.

Amino Acid Sequence↗
PubMed1997

Expression, purification, and characterization of uracil phosphoribosyltransferase from Toxoplasma gondii.

The coding region derived from a full-length CDNA spanning the uracil phosphoribosyltransferase (UPRT) gene of Toxoplasma gondii has been ligated into a bacterial expression vector and overexpressed in E. coli. Recombinant UPRT protein migrated with a molecular mass of 27 kDa on SDS polyacrylamide gels and was purified to homogeneity by conventional protein purification techniques. In solution, UPRT behaved as a monomer and exhibited K(m)app values of 3.5 microM for uracil and 243 microM for phosphoribosylpyrophosphate, respectively. Other naturally occurring pyrimidine or purine bases were not recognized as substrates. [14C]Uracil phosphoribosylation was inhibited by 5-fluorouracil with a Ki value of 25 microM and was not activated by GTP. Ample quantities of recombinant enzyme are now available for biochemical and structural studies, facilitating evaluation of UPRT as a possible therapeutic target.

Animals↗
PubMed1997

Repression of vasopressin gene expression by glucocorticoids in transgenic mice: evidence of a direct mechanism mediated by proximal 5' flanking sequence.

Glucocorticoids are known to exert multiple effects upon neuronal systems and neuronal gene expression but the molecular mechanisms through which these effects are mediated are largely undefined. In this study, a transgenic mouse model that expresses a bovine vasopressin transgene was used to investigate the mechanisms by which this neuropeptide gene is repressed by glucocorticoids. Using both northern analysis and a reverse transcriptase polymerase chain reaction assay, depletion of glucocorticoids with the 11,beta-hydroxylase inhibitor metyrapone was shown to result in a dexamethasone-reversed increase in ectopic adrenal transgene messenger RNA levels. This result shows that sequences within the confines of the 3.5 kb transgene are sufficient to mediate repression by glucocorticoids, and indicates the involvement of a type II glucocorticoid receptor mechanism which is independent of cellular context. Evidence for the involvement of cis-acting repressive elements in the proximal 5' flanking sequence was obtained in further studies in which bovine transgene constructs were shown to be negatively regulated by dexamethasone in 293 cells. The further demonstration that recombinant glucocorticoid receptor binds to a vasopressin promoter fragment in an in vitro electrophoretic mobility shift assay provided additional evidence of a direct mechanism of repression. Both in vitro studies were consistent with the presence of a glucocorticoid regulatory element within the region -300 to 155 of the transcription start site. The use of an in vivo transgenic system combined with in vitro analyses of gene promoter fragments enabled the characterization of the molecular mechanisms which effect physiological changes in vasopressin gene expression, and provided evidence of a direct mechanism of repression mediated by sequences within the vasopressin gene promoter.

Animals↗
PubMed1997

Minimally invasive thoracoscopically assisted coronary artery bypass surgery.

OBJECTIVE: Minimally invasive techniques have been widely used in other surgical fields including video-assisted thoracic surgery (VATS) in thoracic surgery. These concepts are now being applied to cardiac surgery. The opportunities to make cardiac surgery less invasive include elimination of the median sternotomy incision, elimination of cardiopulmonary bypass and no manipulation of the aorta. MATERIALS AND METHODS: From January 1992 through September 1996, various aspects of minimally invasive cardiac surgery have been examined in the inanimate endoscopic trainer, animal model, human cadaver and in human clinical studies. Techniques of endoscopic sutured anastomosis as well as alternatives to suturing were first perfected in the inanimate trainer. Twenty animals then underwent endoscopic coronary artery bypass using the left internal mammary artery to the left anterior descending with circulatory support from an axial flow pump. Fifty eight minimally invasive coronary artery bypass procedures have been performed in humans using thoracoscopic assistance for internal mammary artery harvest. RESULTS: One hundred fifty endoscopic coronary anastomoses were performed in the inanimate trainer with the endoscopic suturing technique being the preferred method. Time required to perform an anastomosis decreased from greater than 60 min to a mean of 20 min as technique and instruments were developed. In animals, methods of access as well as enabling surgical instruments to allow crossclamp of the aorta and performance of the anastomosis were developed. Fifty-eight humans underwent coronary artery bypass using the left internal mammary artery placed to the left anterior descending under direct vision through a limited anterior thoracotomy on a beating heart. The procedure was successful in 52 patients with conversions required in six patients. Techniques were developed for immobilization for performance of the anastomosis. DISCUSSION: The ability to perform an endoscopic anastomosis still remains the rate limiting step for totally endoscopic coronary artery bypass surgery. The present MIDCAB (minimally invasive direct coronary artery bypass grafting) procedure is a significant advance in cardiac surgery, but still has limitations that make performance of an exact anastomosis still somewhat difficult and applicable only to single-vessel disease. Present efforts are directed toward extending the MIDCAB procedure by various immobilization and circulatory support devices and combining the MIDCAB procedure with catheter techniques for treating more advanced disease.

Animals↗
PubMed1997

Mutations in Plasmodium falciparum dihydrofolate reductase and dihydropteroate synthase and epidemiologic patterns of pyrimethamine-sulfadoxine use and resistance.

To assess the relationship between mutations in Plasmodium falciparum dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) and clinical pyrimethamine-sulfadoxine resistance, polymerase chain reaction surveys and analyses for new mutations were conducted in four countries with increasing levels of pyrimethamine-sulfadoxine resistance: Mali, Kenya, Malawi, and Bolivia. Prevalence of mutations at DHFR codon 108 and a new mutation at DHPS 540 correlated with increased pyrimethamine-sulfadoxine resistance (P < .05). Mutations at DHFR 51, DHFR 59, and DHPS 437 correlated with resistance without achieving statistical significance. Mutations at DHFR 164 and DHPS 581 were common in Bolivia, where pyrimethamine-sulfadoxine resistance is widespread, but absent in African sites. Two new DHFR mutations, a point mutation at codon 50 and an insert at codon 30, were found only in Bolivia. DHFR and DHPS mutations occur in a progressive, stepwise fashion. Identification of specific sets of mutations causing in vivo drug failure may lead to the development of molecular surveillance methods for pyrimethamine-sulfadoxine resistance.

Africa↗
PubMed1997

Seasonality of symptoms in women with late luteal phase dysphoric disorder.

OBJECTIVE: Both late luteal phase dysphoric disorder (LLPDD) and seasonal affective disorder are cyclical disorders often manifested by "atypical" depressive features. The goal of this study was to determine whether patients with LLPDD demonstrate substantial seasonal variation in symptoms. METHOD: Consecutive female patients attending a subspecialty clinic in a university teaching hospital were assessed by means of DSM-III-R criteria. All subjects completed the Seasonal Pattern Assessment Questionnaire, modified to include items on the seasonality of premenstrual symptoms. The results were compared with those of a group of female nonclinical subjects (N = 50). RESULTS: One hundred patients met the DSM-III-R criteria for LLPDD. Compared to the nonclinical group, the LLPDD patients had a significantly higher mean global seasonality score (an index of seasonality of mood and vegetative symptoms) and a significantly higher rate of seasonal affective disorder (38% versus 8%) as determined by Seasonal Pattern Assessment Questionnaire criteria. Twenty-five percent of the LLPDD group rated their seasonal variation in premenstrual symptoms as marked or severe, while 30% considered seasonal changes in overall symptoms to be a marked or severe problem. CONCLUSIONS: These results suggest that patients with LLPDD have substantial seasonal patterns in mood and premenstrual symptoms. These seasonal patterns have implications for the clinical assessment and treatment of LLPDD. For example, light therapy may be beneficial for women with seasonal worsening of LLPDD.

Adult↗
PubMed1997

Prolonged asymptomatic micro-embolism after hip or knee arthroplasty.

We studied the time course of micro-embolism by recording high intensity transient signals (HITS) on Doppler venous blood flow studies during a 7-day period in 57 of 63 consecutive patients after hip or knee replacement. No HITS were found before surgery, or in the non-operated leg after surgery. In the operated leg, the median number of HITS per minute showed an exponential decrease with time; a 50% reduction in the number of HITS took 72 minutes. Regardless of the duration and severity of HITS, we found no clinically apparent embolic event. Colour Doppler imaging at days 8 to 10 after operation showed a deep venous thrombosis in 17% of our patients with one thrombosis of the long saphenous vein. The presence or severity of HITS did not predict the venous thrombi. Although we found no pulmonary complications, we detected micro-emboli over a longer period after surgery than is usually reported. Spectral analysis of the Doppler venous signal is a repeatable and non-invasive monitoring technique in the post-surgical period. We failed to prove a correlation between deep venous thrombi and micro-emboli detected by this method.

Aged↗
PubMed1996

Tonic suppression of adrenal AP-1 activity by glucocorticoids.

The AP-1 transcription factor is a variable complex of Fos and Jun nuclear phosphoproteins that is induced in many cell types. AP-1 interacts with transcription factors of different classes, including the nuclear steroid hormone receptors, an interaction that is often mutually antagonistic and thereby serves to integrate different cellular signalling events. In addition to direct, molecular interactions between AP-1 and glucocorticoid receptor (GR), there is also evidence that the two signalling pathways may interact at different levels, but in vivo interactions of this nature have not been well characterized. We have investigated a unique cellular context for GR/AP-1 interactions, namely in the adrenal gland of the rat where the production of glucocorticoids leads to extremely high local levels of glucocorticoids, and where high constitutive AP-1 activity (as determined by in vitro DNA binding activity) has been demonstrated. We have now shown that depletion of glucocorticoid production in rats with the 11-beta-hydroxylase inhibitor, metyrapone, results in increased adrenal AP-1 activity. The demonstrated 5-fold increase is reversed by prior treatment with the glucocorticoid agonist, dexamethasone, and is largely localized to the adrenal medullary region. Further experiments have shown that c-Jun and JunD are the principal components of adrenal AP-1 in the basal state, but a change in jun-B expression appears to underly the metyrapone-induced increase in AP-1 activity. In situ hybridization analysis has shown that glucocorticoid depletion is associated with a dramatic increase in adrenal medullary junB mRNA, and using immunoblotting we have demonstrated a similar increase in nuclear levels of both the 43 kD JunB protein, and an associated phosphorylated JunB. Our use of a pharmacological intervention to demonstrate tonic suppression of adrenal medullary JunB expression by glucocorticoids has provided evidence of a nuclear mechanism that may have physiological relevance as an adaptive response to fluctuating levels of glucocorticoids.

Adrenal Glands↗
PubMed1996

Microscopic and biochemical analysis of the viability and permeability of guinea pig amnion and chorion leave in vitro.

Tissue viability and permeability of guinea pig amnion and chorion leave were analyzed microscopically and biochemically. The vital dyes T1111 and fluorescein diacetate were used to locate and determine the integrity of cell plasma membranes in early and late tissue in vitro using confocal laser scanning microscopy and scanning electron microscopy. Early amnion and chorion laeve were each found to contain a single epithelial cell layer, composed of membrane-intact cells. In contrast, plasma membrane lesions were present throughout the epithelium of late amnion. Late chorion laeve contained both regions of intact and damaged epithelial cells on its maternal side. There was also a layer of membrane-intact squamous cells on the fetal side of late chorion laeve. ATP measurements confirmed that early fetal membranes were viable after incubation in isotonic salt solutions at physiological pH. Late amnion was depleted of ATP stores while late chorion laeve retained its capacity for generating energy. These viability markers indicate that late guinea pig amnion is not a viable tissue in vitro, while late chorion laeve is a viable but probably degenerating tissue. Confocal X-Z scans were used to trace the movement of T1111 through the tissue as an indication of permeability to free solutes. Whereas dye will permeate across the main thickness of early amnion and chorion leave, it did not pass between cells, but was blocked, presumably by a line of tight junctions. Late amnion was characterized by the complete permeability to T1111. Late chorion leave contained regions where solute migration was blocked, but overall was a permeable tissue. These results provide an important context for the interpretation of molecular movement across fetal membranes.

Adenosine Triphosphate↗
PubMed1996

Evaluation of HER-2 neu oncoprotein expression as a prognostic indicator of local recurrence in conservatively treated breast cancer: a case-control study.

PURPOSE: The purpose of this study is to determine the prognostic significance of overexpression of the HER-2 neu oncoprotein with respect to local relapse following conservative surgery and radiation therapy (CS + RT). METHODS AND MATERIALS: Twenty consecutive patients who sustained a local recurrence as the first and only site of failure following CS + RT comprised the case population base for this study. Only patients who received no adjuvant systemic chemotherapy or tamoxifen were selected for analysis. Following the identification of 20 consecutive local-relapse patients, the patient database was searched for 20 matching control patients who did not sustain a local relapse. Each control patient was matched to the index case with respect to age, menopausal status, follow-up, primary histology, axillary nodal status, and primary tumor size. Both index cases and the matched control group received full course radiation therapy, to a total dose of 64 Gy to the tumor bed. The paraffin-embedded blocks of the original primary tumor of the local-relapse cases and the primary tumor of 20 matched controls were processed for immunohistochemical staining of the HER-2 neu oncoprotein. Each slide was rated on the 3-point scale, 0 representing no stain, 1+ indicating light staining, and 2+ denoted heavy staining (overexpression). RESULTS: Of the 20 index cases, with each of the matched controls, 16 were evaluable for analysis. The 4 cases that were eliminated had inadequate paraffin-embedded material in either the case or the match control for adequate staining. By design of the study, the index case group and control group had similar ages (52 years index vs. 51.4 control), follow-up (10.8 years index vs. 10.5 years control), and histologies. For the immunostaining, a value of 2+ was considered to denote high activity and overexpression, and 0 and 1+ were considered negative values. Using these criteria, a total of 9 of the 16 index cases (56%) exhibited overexpression of HER-2 neu oncoprotein, and only 3 of the 16 control cases (18%) demonstrated high immunoreactivity. The difference in immunostaining between the index and control cases was statistically significant by a Pierson chi-square analysis at the p = 0.03 level. CONCLUSIONS: In this matched case-control study, overexpression of the HER-2 neu oncoprotein appears to have prognostic significance with respect to local relapse in the conservatively treated breast. The correlation of overexpression of HER-2 neu by multivariable analysis with other prognostic factors for local recurrence warrants further investigation. The clinical implications of the study are discussed.

Adult↗
PubMed1996

Insertional tagging, cloning, and expression of the Toxoplasma gondii hypoxanthine-xanthine-guanine phosphoribosyltransferase gene. Use as a selectable marker for stable transformation.

A nonhomologous integration vector was used to identify the Toxoplasma gondii hypoxanthine-xanthine-guanine phosphoribosyl transferase (HXGPRT) gene by insertional mutagenesis. Parasite mutants resistant to 6-thioxanthine arose at a frequency of approximately3 x 10(-7). Genomic DNA flanking the insertion sites was retrieved by marker rescue and used to identify molecular clones exhibiting unambiguous homology to H(X)GPRT genes from other species. Sequence analysis of vector/genome junction sites reveals that integration of the linearized vector occurred with minimal rearrangement of either vector or target sequences, although the addition of filler DNA and small duplications or deletions of genomic sequences at the transgene termini was observed. Two differentially spliced classes of cDNA clones were identified, both of which complement hpt and gpt mutations in Escherichia coli. Kinetic analysis of purified recombinant enzyme revealed no significant differences between the two isoforms. Internally deleted clones spanning the genomic locus were used to create "knock-out" parasites, which lack all detectable HXGPRT activity. Complete activity could be restored to these knock-out mutants by transient transformation with either genomic DNA or cDNA-derived minigenes encoding both enzyme isoforms. Stable HXGPRT+ transformants were isolated under selection with mycophenolic acid, demonstrating the feasibility of HXGPRT as both a positive and negative selectable marker for stable transformation of T. gondii.

Amino Acid Sequence↗
PubMed1996

Surgical research.

Explore the source record for details and available documents.

General Surgery↗
PubMed1996

Surgical biopsy findings in patients with atypical hyperplasia diagnosed by stereotaxic core needle biopsy.

PURPOSE: To correlate the stereotaxic core needle biopsy results with those of surgical biopsy in patients with atypical lobular or ductal hyperplasia (atypical hyperplasia) diagnosed at stereotaxic core needle biopsy (SCNB). METHODS: We retrospectively reviewed the mammograms and pathology reports of 358 consecutive SCNBs performed in 323 patients. The results of SCNBs of 22 lesions reported as atypical hyperplasia were correlated with histologic findings at surgical biopsy. RESULTS: A histologic diagnosis of atypical hyperplasia at SCNB was found to be a poor predictor of the final surgical results. In the 19 patients with 22 lesions, surgical biopsy and SCNB results were in disagreement in 16, partial agreement in two, and complete agreement in only four lesions. Furthermore, five cases of atypical hyperplasia were shown to have invasive carcinoma on open biopsy, and five had ductal carcinoma in situ in the surgical biopsy, none of which was present on SCNB. CONCLUSION: Given the frequent occurrence of malignancy in patients diagnosed with atypical hyperplasia by SCNB, it is recommended that all such patients undergo excisional biopsy.

Biopsy, Needle↗