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Biomedical subjects

J Quick

Publications and source records attributed to J Quick.

At least 19 recordsLinked to original sources
PubMed2006

Identification, preparation, and characterization of several polymorphs and solvates of terazosin hydrochloride.

The phenomenon of polymorphism is prevalent in pharmaceuticals, yet it is unusual to identify more than three or four forms for any particular drug. Terazosin hydrochloride has been found to exist at room temperature in four solvent-free forms that can be isolated directly, one solvent-free form that can be prepared by desolvation of a methanolate, a methanol solvate, and a dihydrate. This study presents characterization and methods for preparation of each of these forms. Data are also presented demonstrating the relative stability of these forms.

Antineoplastic Agents↗
PubMed2002

The outer membrane localization of the Neisseria gonorrhoeae MsrA/B is involved in survival against reactive oxygen species.

The PilB protein of Neisseria gonorrhoeae has been reported to be involved in the regulation of pilin gene transcription, but it also possesses significant homology to the peptide methionine sulfoxide reductase family of enzymes, specifically MsrA and MsrB from Escherichia coli. MsrA and MsrB in E. coli are able to reduce methionine sulfoxide residues in proteins to methionines. In addition, the gonococcal PilB protein encodes for both MsrA and MsrB activity associated with the repair of oxidative damage to proteins. In this work, we demonstrate that the PilB protein of Neisseria gonorrhoeae is not involved in pilus expression. Additionally, we show that wild-type N. gonorrhoeae produces two forms of this polypeptide, one of which contains a signal sequence and is secreted from the bacterial cytoplasm to the outer membrane; the other lacks a signal sequence and is cytoplasmic. Furthermore, we show that the secreted form of the PilB protein is involved in survival in the presence of oxidative damage.

Alkaline Phosphatase↗
PubMed2001

Ritonavir: an extraordinary example of conformational polymorphism.

PURPOSE: In the summer of 1998, Norvir semi-solid capsules supplies were threatened as a result of a new much less soluble crystal form of ritonavir. This report provides characterization of the two polymorphs and the structures and hydrogen bonding network for each form. METHODS: Ritonavir polymorphism was investigated using solid state spectroscopy and microscopy techniques including solid state NMR, Near Infrared Spectroscopy, powder X-ray Diffraction and Single crystal X-ray. A sensitive seed detection test was developed. RESULTS: Ritonavir polymorphs were thoroughly characterized and the structures determined. An unusual conformation was found for form II that results in a strong hydrogen bonding network A possible mechanism for heterogeneous nucleation of form II was investigated. CONCLUSIONS: Ritonavir was found to exhibit conformational polymorphism with two unique crystal lattices having significantly different solubility properties. Although the polymorph (form II) corresponding to the "cis" conformation is a more stable packing arrangement, nucleation, even in the presence of form II seeds, is energetically unfavored except in highly supersaturated solutions. The coincidence of a highly supersaturated solution and a probable heterogeneous nucleation by a degradation product resulted in the sudden appearance of the more stable form II polymorph.

Calorimetry, Differential Scanning↗
PubMed1998

Partnerships for health in the 21st century.

This paper presents the results of a working group on partnerships in preparation for the WHO Health for All Policy for the 21st Century. The working group aimed to clarify the nature of partnerships for health, proposed six categories of partnerships and outlined principles and criteria for partnerships. It concluded that partnership building was a key strategic component of health development and underlined that WHO must increasingly see its role as one of mustering support for health from many players. In order to do so, WHO must change its organizational culture and mode of operation.

Community Networks↗
PubMed1992

The structure and biological activities of the widely used protein kinase inhibitor, H7, differ depending on the commercial source.

The protein kinase inhibitor 1-(5'-isoquinolinesulfonyl)-2-methylpiperazine (H7) has been widely used because of its ability to inhibit cyclic AMP- and cyclic GMP-dependent protein kinases (PKA and PKG) and protein kinase C (PKC) at roughly equal concentrations; it is much less potent on other kinases. Previous studies in other laboratories have found that H7 samples from different commercial sources have different properties in cellular studies and protein kinase C inhibition assays. We now report the results of chemical and biological tests which show that H7 samples also differ in chemical structure, again depending on their commercial source. Chemical synthesis and NMR spectroscopy indicate that H7 from most suppliers has the structure originally proposed for H7, while "H7" from another supplier is in fact its 3-methylpiperazine positional isomer.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1992

A strategy for promoting improved pharmaceutical use: the International Network for Rational Use of Drugs.

Over the last decade, pharmaceutical selection, procurement, distribution, and financing have improved as a result of essential drugs programs. However, despite improved availability, pharmaceuticals are frequently used irrationally. The International Network for the Rational Use of Drugs (INRUD) has been established to help address this problem. The Network joins core groups of researchers from four African and three Asian countries with support groups in Boston, Sweden, WHO, and Australia. The activities of the Network are supported by multilateral, bilateral, foundation donors and by Management Sciences for Health. INRUD functions as a participatory organization in which members are involved in decision-making. The primary objective of the Network is to identify through a coordinated set of country-based research projects a set of effective interventions to recommend as policy options for the promotion of rational drug use. In developing these research projects, INRUD stresses the importance of a multi-disciplinary perspective for adequately understanding the reasons underlying inappropriate use of drugs. To better enable country groups to utilize strong research methodologies and to blend the strengths of multiple disciplines effectively, a major activity of the Network thus far has been the building of local research capacity.

Africa↗
PubMed1992

Stimulation of erythropoietin in renal insufficiency by hypobaric hypoxia.

Patients with renal anaemia show inadequate levels of immunoreactive erythropoietin (Epo) related to the degree of anaemia. The purpose of our study is to compare the degree of stimulation of Epo by means of hypobaric hypoxia in normal controls and patients with renal anaemia. Baseline Epo concentrations were found to be 11.1 +/- 2.0 U/l in 10 healthy volunteers and 11.4 +/- 4.6 U/l in six patients with renal anaemia. After exposure to hypobaric hypoxia equivalent to 4560 m above sea level for a duration of 3.5 h, we observed a significant increase in serum Epo in healthy volunteers to 22.8 +/- 9.1 U/l (P < 0.005), while there was no increase in patients with renal anaemia: 12.3 +/- 5.2 U/l (P < 0.2). Our results show that in patients with renal anaemia serum Epo concentrations are comparable to those of normal controls, but inadequate in view of the concomitant degree of anaemia. Stimulation by acute hypobaric hypoxia was not possible in patients with renal insufficiency as opposed to normal controls. From these data it can be concluded that either Epo production is working at maximum capacity under baseline conditions, or an additional hybobaric stimulus is not able to influence a disturbed set point of the oxygen sensor regulating Epo synthesis.

Adult↗
PubMed1991

Genetic counselling for myotonic dystrophy: a comparison of lens examination and DNA linkage studies.

Genetic counselling in presymptomatic individuals with a family history of myotonic dystrophy (DM) is problematic. A genetic test to identify the presymptomatic carrier of the gene for DM would therefore be advantageous. We report studies comparing ophthalmic examination with a genetic test based on DNA linkage studies in nine DM families. The genetic test involved the use of five probes from four loci linked to the DM locus. Some discrepancies between ophthalmic and genetic tests were observed. Genetic counselling following prediction of genetic status was possible for 18 out of 20 patients from seven out of nine families.

Adolescent↗
PubMed1988

Time-resolved pulsed fluorescence immunometric assays of carcinoembryonic antigen.

A time-resolved pulsed fluorescence immunometric assay (TR-PFIA) for carcinoembryonic antigen is described in which either Eu(III) or Tb(III) chelate is used as label. Described in detail is the assay involving the well-documented format of microtiter matrix and Eu(III) fluorescence enhanced with a beta-diketone and quantified in a commercial time-resolving fluorometer. We have also used the same basic assay, but one with a Tb(III) chelate as label, and we read the fluorescence signal directly off a surface without the application of enhancement solution. The Tb(III) fluorescence is then brought into solution by using an analog of dipicolinic acid in an enhancement solution. The latter approach demonstrates the scope of the methodology, which invokes the extra complexity of enhancement only when increased sensitivity might be required. The power and versatility of the enhancement methodology are demonstrated.

Carcinoembryonic Antigen↗
PubMed1984

Novel opiates and antagonists. 6. 7-Alkyl-6,7-didehydromorphinans.

A method for preparing a variety of 7-alkyl-6,7- didehydromorphinans from the corresponding 6- morphinanones is described. The key intermediates in this sequence are the 7-formyl derivatives. The two epimeric B/C-trans-7-(1- hydroxypentyl ) morphinans ( 16a ,b) are stereochemically similar to the endo- ethanotetrahydrooripavines and are extremely potent in the mouse writhing test. The corresponding B/C-cis -7-(1- hydroxypentyl ) morphinans are inactive in this test.

Analgesia↗
PubMed1984

Protein-enhanced fluorescein chemiluminescence used in an immunoassay for rubella antibody in serum.

The chemiluminescence of fluorescein derivatives is greatly enhanced when they are conjugated to proteins. We exploited this property in devising a chemiluminescence immunoassay for rubella antibodies. In this sequential "sandwich"-type assay, tubes coated with rubella antigen are used for antibody separation and goat antibody to human IgG conjugated with fluorescein isothiocyanate is used for detection of bound rubella antibodies.

Antibodies, Viral↗
PubMed1983

Stability-indicating assay for chlorthalidone formulation: evaluation of the USP analysis and a high-performance liquid chromatographic analysis.

An investigation of the USP assay of chlorthalidone tablets showed that variable degradation of chlorthalidone occurred during assay preparation. The degradation products were isolated and identified. A stability-indicating high-performance liquid chromatographic (HPLC) assay which separates the degradation products from chlorthalidone was developed and used to examine the present USP preparation. The HPLC assay is suggested as an alternate.

Chlorthalidone↗