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Biomedical subjects

J Jenkins

Publications and source records attributed to J Jenkins.

At least 109 records · Page 6Linked to original sources
PubMed1993

Cloning of Chinese hamster DNA topoisomerase I cDNA and identification of a single point mutation responsible for camptothecin resistance.

A camptothecin-resistant (DC3F/C-10) Chinese hamster cell line that contains a catalytically altered and camptothecin (CPT)-resistant DNA topoisomerase I (top 1) (Tanizawa, A., and Pommier, Y. (1992) Cancer Res. 52, 1848-1854) and the parent cell line (DC3F) were used to compare top 1 mRNAs and cDNAs. Northern blot analysis showed a single 4.1-kilobase band without quantitative reduction between the two cell lines. We have cloned and sequenced top 1 cDNAs. DC3F and DC3F/C-10 top 1 c-DNA are 3591 and 3626 base pair long, respectively, and encode 767 amino acids. The homology of deduced amino acid sequences between Chinese hamster and mouse or human top 1 are 98.1 and 96.7, respectively. cDNAs from DC3F/C-10 and DC3F cells differ by a single base point mutation (G to A) which results in an amino acid change from Gly505 to Ser (Gly505-->Ser). G505 corresponds to Gly503 of human top 1 cDNA and is located 220 amino acids away from the presumed catalytic Tyr725. The point mutation in the Chinese hamster top 1 is located in a region that is highly conserved among all cloned top 1 cDNAs (plant ATH, vaccinia virus, Shope fibroma virus, Drosophila, Saccharomyces cerevisiae, Schizosaccharomyces pombe, mouse, and Human). A mutation of Asp533 to Gly in this same region has been shown to confer CPT resistance for human top 1. Chinese hamster top 1 protein with a Gly505-->Ser mutation that was expressed in bacteria was resistant to CPT, indicating that this single base mutation is involved in CPT resistance. Our results suggest that the highly conserved region around Gly505 plays an important role in the interactions among top 1, DNA, and CPT.

Amino Acid Sequence↗
PubMed1993

Apoptosis and its modulation in human promyelocytic HL-60 cells treated with DNA topoisomerase I and II inhibitors.

Electron microscopy studies demonstrate unequivocally that the observed oligonucleosome-sized secondary DNA fragmentation in human promyelocytic HL-60 cells treated with the topoisomerase inhibitors camptothecin and teniposide is correlated with the morphological changes in cell structure typical of programmed cell death (apoptosis). Since apoptosis has been associated with potential involvement of intracellular signaling linked to the Ca2+/calmodulin and protein kinase C transduction pathways, we also investigated the effects of signaling modulators on camptothecin- and teniposide-induced secondary DNA fragmentation in HL-60 cells. Neither calcium chelators, calcium/calmodulin inhibitors (calmidazolium or cyclosporine A), protein kinase C stimulation by TPA, protein phosphatase inhibition by okadaic acid, protein kinase inhibition by staurosporine, calphostin C, genistein or H7, nor cell cycle alterations by caffeine had any detectable effect. Interestingly, most of these intracellular signaling modulators were able to induce DNA fragmentation in HL-60 cells by themselves. These results may suggest that even though modulation of these signaling pathways was unable to prevent topoisomerase inhibitor-induced apoptosis, their sole deregulations could induce apoptosis in HL-60 cells. In contrast, aphidicolin blocked camptothecin-induced secondary DNA fragmentation, indicating that replication-induced DNA damage is required for camptothecin- but not teniposide-induced secondary DNA fragmentation. Zinc, 3-aminobenzamide, and spermine also modulated both camptothecin- and teniposide-induced secondary DNA fragmentation without significant alteration of topoisomerase-mediated primary DNA strand breaks. Hence, poly(ADP-ribosyl)ation and chromatin structure may be important in modulating oligonucleosome-sized DNA fragmentation associated with apoptosis in HL-60 cells treated with topoisomerase inhibitors.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

An attributional analysis of expressed emotion in Mexican-American families with schizophrenia.

In this study we tested an attributional model of expressed emotion (EE) among Mexican-American families. A sample of 46 key family members of schizophrenic patients were measured on three dimensions: affect toward patient, controllability attributions, and level of EE. Consistent with an attributional model, we found that high EE families (defined on the basis of critical comments) viewed the illness and associated symptoms as residing within the patient's personal control, more so than did low EE families. We also found that attributions held by family members are related to their affective reactions. Specifically, family members who perceived the patient as having control over the symptoms of schizophrenia tended to express greater negative emotions such as anger and annoyance toward the patient than did family members who viewed the symptoms as beyond the patient's personal control. An examination of the types of affects found and their relationship to EE status is discussed, along with implications for this research.

Adult↗
PubMed1993

Comparison of clinical responses to natural and synthetic surfactants.

The clinical responses to both natural and synthetic surfactants were observed in two District General Hospital Neonatal Units who were centrally randomised as part of two separate multicentre trials (OSIRIS and Curosurf 4). Forty five infants were enrolled consecutively in the OSIRIS trial using synthetic surfactant (Exosurf), while 21 infants were subsequently enrolled in the Curosurf 4 trial using natural surfactant (Curosurf). There were no significant differences between the groups for mean birth weight, gestational age, inspired oxygen (FiO2), or arterial: alveolar oxygen ratio (a/A) prior to surfactant administration. Oxygen requirements fell significantly more rapidly within the first 24 hours for patients treated with Curosurf compared to Exosurf (p < 0.001). Mean duration of > 40% oxygen requirement was significantly shorter in the Curosurf group (2.6 days) compared to 8.0 days in the Exosurf group (p < 0.01). Mean duration of oxygen therapy was also significantly shorter in the Curosurf group (10.2 days) compared to 17.1 days in the Exosurf group (p < 0.05). Ten infants (24%) in the Exosurf group developed intraventricular haemorrhage (IVH) compared to none in the Curosurf group (p < 0.05). As oxygen requirements appear to decrease more rapidly following administration of Curosurf compared to Exosurf a large prospective randomized multicentre trial needs to be performed to compare the effects of these surfactants on both short and long-term outcome.

Arteries↗
PubMed1993

A cancer day hospital: an alternative approach to caring for patients in clinical trials.

The National Institutes of Health recently established a large cancer day hospital (CDH) to address the need to support new research initiatives in the face of a shrinking research budget. By design, the CDH is very much a nursing unit. It employs a collaborative practice model of patient care delivery that emphasizes the nurses' independent clinical- and protocol-related responsibilities and roles. The CDH is designed to be budget neutral. An increased outpatient throughput and a decrease in inpatient days for at least one large protocol population (patients receiving therapy for prostate cancer) have been demonstrated. With a steadily increasing number of patients, the CDH appears to be a well-accepted and cost-effective site for the care of patients enrolled in oncology clinical trials.

Aftercare↗
PubMed1992

Crystallization and preliminary X-ray studies of the pectate lyase from Bacillus subtilis.

The pectate lyase (EC 4.2.2.9) from Bacillus subtilis has been crystallized. Crystals of form 1, grown by the hanging drop method using polyethylene glycol as precipitant, diffract to at least 2.4 A resolution. They belong to the spacegroup P2(1) with a = 132.9 A, b = 41.2 A, c = 156.8 A and beta = 114.9 degrees with probably four molecules in the asymmetric unit. A second crystal form grown from 2-methyl-2,4-pentandiol also belongs to the spacegroup P2(1) with a = 55.0 A, b = 88.1 A, c = 50.2 A and beta = 109.0 degrees. These crystals diffract to at least 2.0 A and have one molecule in the asymmetric unit. Both crystal forms are suitable for the determination of high-resolution structures.

Bacillus subtilis↗
PubMed1992

Protein engineering of xylose (glucose) isomerase from Actinoplanes missouriensis. 1. Crystallography and site-directed mutagenesis of metal binding sites.

The structure and function of the xylose (glucose) isomerase from Actinoplanes missouriensis have been analyzed by X-ray crystallography and site-directed mutagenesis after cloning and overexpression in Escherichia coli. The crystal structure of wild-type enzyme has been refined to an R factor of 15.2% against diffraction data to 2.2-A resolution. The structures of a number of binary and ternary complexes involving wild-type and mutant enzymes, the divalent cations Mg2+, Co2+, or Mn2+, and either the substrate xylose or substrate analogs have also been determined and refined to comparable R factors. Two metal sites are identified. Metal site 1 is four-coordinated and tetrahedral in the absence of substrate and is six-coordinated and octahedral in its presence; the O2 and O4 atoms of linear inhibitors and substrate bind to metal 1. Metal site 2 is octahedral in all cases; its position changes by 0.7 A when it binds O1 of the substrate and by more than 1 A when it also binds O2; these bonds replace bonds to carboxylate ligands from the protein. Side chains involved in metal binding have been substituted by site-directed mutagenesis. The biochemical properties of the mutant enzymes are presented. Together with structural data, they demonstrate that the two metal ions play an essential part in binding substrates, in stabilizing their open form, and in catalyzing hydride transfer between the C1 and C2 positions.

Actinomycetales↗
PubMed1992

Protein engineering of xylose (glucose) isomerase from Actinoplanes missouriensis. 3. Changing metal specificity and the pH profile by site-directed mutagenesis.

Aldose-ketose isomerization by xylose isomerase requires bivalent cations such as Mg2+, Mn2+, or Co2+. The active site of the enzyme from Actinoplanes missouriensis contains two metal ions that are involved in substrate binding and in catalyzing a hydride shift between the C1 and C2 substrate atoms. Glu 186 is a conserved residue located near the active site but not in contact with the substrate and not with a metal ligand. The E186D and E186Q mutant enzymes were prepared. Both are active, and their metal specificity is different from that of the wild type. The E186Q enzyme is most active with Mn2+ and has a drastically shifted pH optimum. The X-ray analysis of E186Q was performed in the presence of xylose and either Mn2+ or Mg2+. The Mn2+ structure is essentially identical to that of the wild type. In the presence of Mg2+, the carboxylate group of residue Asp 255, which is part of metal site 2 and a metal ligand, turns toward Gln 186 and hydrogen bonds to its side-chain amide. Mg2+ is not bound at metal site 2, explaining the low activity of the mutant with this cation. Movements of Asp 255 also occur in the wild-type enzyme. We propose that they play a role in the O1 to O2 proton relay accompanying the hydride shift.

Actinomycetales↗
PubMed1992

Arginine residues as stabilizing elements in proteins.

Site-specific substitutions of arginine for lysine in the thermostable D-xylose isomerase (XI) from Actinoplanes missouriensis are shown to impart significant heat stability enhancement in the presence of sugar substrates most probably by interfering with nonenzymatic glycation. The same substitutions are also found to increase heat stability in the absence of any sugar derivatives, where a mechanism based on prevention of glycation can no longer be invoked. This rather conservative substitution is moreover shown to improve thermostability in two other structurally unrelated proteins, human copper, zinc-superoxide dismutase (CuZnSOD) and D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from Bacillus subtilis. The stabilizing effect of Lys----Arg substitutions is rationalized on the basis of a detailed analysis of the crystal structures of wild-type XI and of engineered variants with Lys----Arg substitution at four distinct locations, residues 253, 309, 319, and 323. Molecular model building analysis of the structures of wild-type and mutant CuZnSOD (K9R) and GAPDH (G281K and G281R) is used to explain the observed stability enhancement in these proteins. In addition to demonstrating that even thermostable proteins can lend themselves to further stability improvement, our findings provide direct evidence that arginine residues are important stabilizing elements in proteins. Moreover, the stabilizing role of electrostatic interactions, particularly between subunits in oligomeric proteins, is documented.

Aldose-Ketose Isomerases↗
PubMed1992

Prediction of netilmicin disposition in neonates.

Multiple regression analyses of data from 33 neonates who received netilmicin therapy showed that concurrent treatment with other drugs (Drg), creatinine clearance (CLcr), gestational age (GA), and an apgar score of less than 6 at 1 min (Agl') were significant determinants of netilmicin clearance. Apparent volume of distribution was significantly affected by postnatal age (PNA), gender, the presence of ascites and/or oedema (A/O), and whether or not the neonate was small for gestational age (SGA). The following formulae were obtained: [formula: see text] The regression formulae were shown to predict netilmicin plasma concentrations with good precision and a non-significant bias in a further 15 neonates studied prospectively.

Apgar Score↗
PubMed1992

Radiolabeling of DNA can induce its fragmentation in HL-60 human promyelocytic leukemic cells.

Incorporation of radiolabeled thymidine is commonly used to investigate DNA damage. Using a filter-binding assay, we observed that the addition of various doses of [methyl-3H]thymidine (0.2 and 2 microCi/ml) or [2-14C]thymidine (0.02 and 0.2 microCi/ml) in the culture medium for 2 days, a standard method for cell-labeling, induces DNA fragmentation in HL-60 human promyelocytic cells. This effect was dose- and time-dependent and the DNA fragments were not protein-linked since the levels of DNA fragmentation were identical in the presence and in the absence of proteinase K (0.5 mg/ml). Radiolabeled thymidine-induced DNA fragmentation was associated with an inhibition of cell growth, but cells remained able to exclude trypan blue, suggesting that plasma membrane integrity was conserved, except at very high doses of [methyl-3H]thymidine (2 microCi/ml). By agarose-gel electrophoresis, the DNA-fragmentation was demonstrated to be internucleosomal with a typical ladder pattern. Addition of unlabeled thymidine to the culture medium prevented DNA fragmentation in a dose-dependent manner, indicating that radiolabeled thymidine incorporation in DNA was directly responsible for DNA fragmentation. We conclude that radiolabeling of DNA using thymidine incorporation can induce DNA fragmentation in some cell lines such as HL-60. This observation must be taken into account in methods using radiolabeling to study DNA damage in these cells.

Apoptosis↗
PubMed1992

A prospective study of nonrhabdomyosarcoma soft tissue sarcomas in the pediatric age group.

Nonrhabdomyosarcoma soft tissue sarcomas in infants and children are rare malignancies with most of the clinical data gained by retrospective analysis. In 1986, a prospective multicentered study was initiated by the Pediatric Oncology Group (POG) with a total of 75 cases now entered for epidemiologic examination. Median age of presentation was 12 years (range, newborn to 20 years). The male to female ratio was 2.3 to 1. The most common soft tissue tumor was synovial cell sarcoma (32/75, 42%), followed by fibrosarcoma (10/75, 13%), malignant fibrous histiocytoma (9/75, 12%), and malignant neurogenic tumors (8/75, 10%). Sixty-five percent of all tumors presented on the extremities (44% lower extremity, 21% upper extremity). Tumors of the trunk accounted for 28% (abdomen 15%, thorax 13%), whereas head and neck tumors were 7%. By TNMG classification, 16% presented as stage I, 21% as stage II, 33% as stage III, and 30% as stage IV. Age at presentation did not affect clinical site or stage. All upper extremity tumors presented with localized disease, whereas lower extremity tumors presented with regional nodal disease in 7% and metastatic disease (pulmonary) in 23% of the cases. Seventy-eight percent of the abdominal tumors were metastatic at diagnosis; the other 22% had extensive regional disease. In the thorax 78% had localized lesions with 22% having extensive regional disease. Ninety percent of synovial cell sarcomas were on the extremities: 84% localized disease and 12% metastatic spread at presentation. Sixty percent of the fibrosarcomas presented on the extremities with 80% having localized disease and 20% metastatic spread. Only 25% of the neurogenic tumors presented with localized disease, whereas 50% had metastases at the time of diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Biology of cancer: current issues and future prospects.

The future of cancer treatment is limited only by the rate of progress made in understanding the biology of cancer. The future will present a considerable challenge to health care professionals to learn new theories, understand new terms, and expect different toxicities. The explosion of information and technology is exciting, yet frightening. The willingness of scientists, health care professionals, and consumers to deal with the ethical, financial, and political issues generated by this progress is gratifying. Because science has created such advances, the effort to deal with the outcomes is worthwhile but still difficult. The challenge to rapidly facilitate the sharing of the scientific and clinical advances has been recognized by the nation. A legislative mandate to create a way to store and analyze the vast data related to molecular biology, biochemistry, and genetics resulted in the National Center for Biotechnology Information. The development of automated systems to analyze genetic, environmental, biological, and chemistry information can only enhance future progress in the management of cancer.

Antineoplastic Agents↗
PubMed1991

History of clinical trials.

Advances in medical treatments have occurred because of the application of new knowledge gained from clinical experiments conducted over the last 250 years. New sources of compounds with anti-tumor activity in human cancer are constantly under investigation. The development of a new drug is a complex process: screening, formulation, production, toxicology studies, FDA approval, and evaluation in phase I, II, and III clinical trials.

Antineoplastic Agents↗
PubMed1991

Monophasic action potential duration during programmed electrical stimulation.

UNLABELLED: To examine changes in monophasic action potential duration (APD) with a pacing protocol similar to that used during electrophysiological testing, action potentials were recorded in vivo from the left ventricular apical endocardium of 12 normal mongrel dogs. The atrioventricular node was ablated and the dogs paced from the anterior right ventricle at a baseline cycle length of 1000 ms between interventions. Mean steady-state APD (APDss) was 266 +/- 7 ms at a pacing cycle length (PCL) of 1000 ms. Two pacing protocols were used. The first consisted of a sudden acceleration in pacing from a cycle length of 1000 ms to one between 300 and 600 ms. The second consisted of an 8-beat train at a cycle length of 400 ms followed by a premature beat at a coupling interval of 280 ms followed by a pause. The inter-train pause varied between 1 second and 32 seconds. With a sudden acceleration in pacing rate, steady-state values for APD at the faster PCLs were significantly smaller than APDss at 1000 ms with a change to cycle lengths of 600 ms (247 +/- 29 ms), 500 ms (229 +/- 21 ms), 400 ms (220 +/- 17 ms), and 300 ms (203 +/- 31 ms; P less than 0.01 for all comparisons). The time constant of the change in APD was shorter at a PCL of 300 ms (14.9 +/- 0.8 s) than 600 ms (20.3 +/- 4.7 s; P less than 0.05). With drive train pacing and incorporating an inter-train pause, the percent drop in steady-state APD compared to APD for the first train ranged from 10.1% with a 1-second inter-train pause to 2.1% with a 32-second pause. The difference in APD between the first drive train and drive trains after at least 3 minutes of pacing when APD had stabilized was not significant for an inter-train pause exceeding 8 seconds. IN CONCLUSION: (1) with a sudden acceleration in pacing rate, endocardial APD in vivo decreases exponentially. The faster the new rate, the shorter the new steady-state APD and the shorter the time constant. (2) When pacing using an 8-beat drive train and an inter-train pause, there is a decremental shortening in APD for pause lengths shorter than 16 seconds. Thus, while performing programmed stimulation using a pause, a conditioning period of at least 2 minutes should be used prior to diastole scanning to allow APD to achieve a steady state.

Action Potentials↗