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J D McKinney

Publications and source records attributed to J D McKinney.

At least 19 recordsLinked to original sources
PubMed2004

Cost efficiency in the prospective diagnosis and follow-up of polyomavirus allograft nephropathy.

Evaluation of urine cytology (UC) for decoy cells and quantitative determinations of viruria (urine viral load [UPCR])and viremia (viral load in blood [VLB]) have been proposed as surrogate markers of polyomavirus allograft nephropathy (PVAN). In this study, we present the experience with the concurrent evaluation of UC, UPCR, and VLB in 349 patients (940 sets of samples). Results were correlated with each other and with a previous, concurrent, or subsequent biopsy diagnosis of PVAN. Patients were followed up for a mean of 27 months posttransplantation. We conclude that both UC and UPCR are useful for screening of renal transplant recipients. Simultaneous performance of both UC and UPCR does not add useful clinical information. In patients with positive UC, performance of UPCR, however, can allow for the distinction between BK and JC polyoma viruses. Quantitative measurement of viremia is not indicated in patients lacking viruria because no patients with PVAN present with this combination of findings. In patients with viruria, a positive viremia strongly correlates with PVAN. Rationale selection of screening protocols based on the current knowledge of the infection and tailored to the available laboratory capabilities in each transplantation center can optimize the use of resources.

Biopsy↗
PubMed2003

Effects of a mixture of polychlorinated biphenyls (Aroclor 1254) on the transcriptional activity of thyroid hormone receptor.

Polychlorinated biphenyls (PCBs) are environmental contaminants which may affect thyroid function. PCBs may reduce serum thyroid hormone (TH) concentrations by either displacing T4 from TH transport proteins or increasing its hepatic metabolism. The reduced serum T4 causes neurological and growth defects in animals exposed to PCBs during the perinatal period, which can partially be reverted by T4 administration. In addition to a hypothyroid-like syndrome, a direct action of PCBs on TH-sensitive genes has been postulated. In the present study the effects of Aroclor 1254 (ARO), a mixture of PCBs, on transcription of TH-dependent genes were investigated. A reporter plasmid containing the TH-responsive element (TRE) of malic enzyme (ME) gene was used in transient transfections to assess the responsiveness to ARO. ARO (10 microM) reduced the CAT activity by about 50% and competed with T3 to reduce the induction of transcription. Cotransfection of TH receptor (TR) and a wild type TRE was required to reveal ARO inhibitiry effect, which was abolished by a mock reaction not containing TR or by a mutated TRE. ARO reduced the 125I-T3 binding to TR by 30%, but did not affect the interaction of TR with a 32P-labeled TRE in gel shift assay. ARO is likely to produce a conformational change in in vitro translated TR, leading to its increased proteolysis by trypsin. These results demonstrate that ARO interacts with TR, thereby affecting the transcription of TH-sensitive genes, and provide a molecular basis to further explain the complex effects of PCBs on TH disruption.

Animals↗
PubMed2000

Persistence of Mycobacterium tuberculosis in macrophages and mice requires the glyoxylate shunt enzyme isocitrate lyase.

Mycobacterium tuberculosis claims more human lives each year than any other bacterial pathogen. Infection is maintained in spite of acquired immunity and resists eradication by antimicrobials. Despite an urgent need for new therapies targeting persistent bacteria, our knowledge of bacterial metabolism throughout the course of infection remains rudimentary. Here we report that persistence of M. tuberculosis in mice is facilitated by isocitrate lyase (ICL), an enzyme essential for the metabolism of fatty acids. Disruption of the icl gene attenuated bacterial persistence and virulence in immune-competent mice without affecting bacterial growth during the acute phase of infection. A link between the requirement for ICL and the immune status of the host was established by the restored virulence of delta icl bacteria in interferon-gamma knockout mice. This link was apparent at the level of the infected macrophage: Activation of infected macrophages increased expression of ICL, and the delta icl mutant was markedly attenuated for survival in activated but not resting macrophages. These data suggest that the metabolism of M. tuberculosis in vivo is profoundly influenced by the host response to infection, an observation with important implications for the treatment of chronic tuberculosis.

Animals↗
PubMed2000

Assessing the role of ortho-substitution on polychlorinated biphenyl binding to transthyretin, a thyroxine transport protein.

ortho-Substituted polychlorinated biphenyls (PCBs) make up a large part of the PCB residue found in the environment and human tissues. Our laboratory as well as others have demonstrated that ortho-substituted congeners exhibit important biological activities by aryl hydrocarbon (Ah) receptor-independent mechanisms, including changes in second messenger systems necessary for normal cell function and growth. Previous structure-activity relationship (SAR) studies on second messengers and transthyretin (TTR; prealbumin) binding focused little attention on the ortho-substituted PCBs. Disruption of thyroid hormone (TH) transport is one potentially important mechanism by which PCBs can alter TH homeostasis. A more systematic study of PCB binding to TTR, a major TH transport protein, was undertaken, in which the role of ortho-substitution was more thoroughly investigated. Results from this study indicated that the ortho-only substituted series showed significant binding activity and the relative affinities were 2,2',6 > 2,2' = 2,6 >> 2 = 2,2',6, 6'. As anticipated on the basis of steric considerations, bromine was shown to be more active as an ortho-substituent where the relative affinity of 2,2'-Br was equivalent to 2,2',6-Cl. The congener patterns (di-meta-substitution in one or both rings) most closely resembling the diiodophenolic ring of thyroxine (T(4)) showed the highest binding activity. Multiple ortho-substituents were shown to decrease binding activity in such patterns. Congener patterns (single meta-substitution in one or both rings) more closely resembling the monoiodophenolic ring of T(3) showed significantly lower binding activity, consistent with the relatively low binding activity of T(3) and smaller size of chlorine compared to iodine. The addition of ortho-substitution to such patterns gave variable results depending on the substituent relationship (adjacency or nonadjacency) to the pattern. Some patterns such as 2, 2',4,4',5,5' showed good binding activity and represent common congeners in the commercial Aroclor mixtures and in the environment. The binding potencies of ortho-PCBs to TTR may represent a signature SAR that predicts specific biologic/toxic effects. In this regard, the binding potencies were consistent with measured biological activities of these PCBs, including effects on cell dopamine content, Ca(2+) homeostasis, and protein kinase C translocation in neuronal cells and brain homogenate preparations.

Aroclors↗
PubMed2000

Structure of isocitrate lyase, a persistence factor of Mycobacterium tuberculosis.

Isocitrate lyase (ICL) plays a pivotal role in the persistence of Mycobacterium tuberculosis in mice by sustaining intracellular infection in inflammatory macrophages. The enzyme allows net carbon gain by diverting acetyl-CoA from beta-oxidation of fatty acids into the glyoxylate shunt pathway. Given its potential as a drug target against persistent infections, we solved its structure without ligand and in complex with two inhibitors. Covalent modification of an active site residue, Cys 191, by the inhibitor 3-bromopyruvate traps the enzyme in a catalytic conformation with the active site completely inaccessible to solvent. The structure of a C191S mutant of the enzyme with the inhibitor 3-nitropropionate provides further insight into the reaction mechanism.

Amino Acid Substitution↗
PubMed2000

In vivo veritas: the search for TB drug targets goes live.

The term 'microbial persistence' describes a phenomenon whereby microorganisms which are drug-susceptible when tested outside the body are nevertheless capable of surviving within the body despite intensive therapy with the appropriate antimicrobial drug. In clinical practice this phenomenon obviously has to do with the post-treatment 'carrier state' and with post-treatment relapse. In short, it is this phenomenon which is responsible for our inability to eradicate an infection from a person or a community by the use of drugs. - Walsh McDermott, The Yale Journal of Biology and Medicine 30, 257 (1958).

Antitubercular Agents↗
PubMed2000

The practice of structure activity relationships (SAR) in toxicology.

Both qualitative and quantitative modeling methods relating chemical structure to biological activity, called structure-activity relationship analyses or SAR, are applied to the prediction and characterization of chemical toxicity. This minireview will discuss some generic issues and modeling approaches that are tailored to problems in toxicology. Different approaches to, and some facets and limitations of the practice and science of, SAR as they pertain to current toxicology analyses, and the basic elements of SAR and SAR-model development and prediction systems are discussed. Other topics include application of 3-D SAR to understanding of the propensity of chemicals to cause endocrine disruption, and the use of models to analyze biological activity of metal ions in toxicology. An example of integration of knowledge pertaining to mechanisms into an expert system for prediction of skin sensitization to chemicals is also discussed. This minireview will consider the utility of modeling approaches as one component for better integration of physicochemical and biological properties into risk assessment, and also consider the potential for both environmental and human health effects of chemicals and their interactions.

Animals↗
PubMed1996

Increased [3H]phorbol ester binding in rat cerebellar granule cells and inhibition of 45Ca2+ sequestration in rat cerebellum by polychlorinated diphenyl ether congeners and analogs: structure-activity relationships.

Our previous reports indicate that ortho-substituted non-coplanar polychlorinated biphenyl (PCB) congeners perturbed neuronal Ca2+-homeostasis in vitro, altered agonist-stimulated inositol phosphate accumulation, and caused protein kinase C (PKC) translocation. The structure-activity relationship (SAR) with 24 PCB congeners was consistent with a chlorination pattern that favored non-coplanarity while those with chlorination that favored coplanarity were less active. To test the hypothesis that coplanarity (or lack thereof) is a significant factor in the activity of PCBs, studies with related classes of chemicals such as the polychlorinated diphenyl ethers (PCDEs), in which coplanarity is more difficult to achieve regardless of degree and pattern of chlorination, were initiated. The selected PCDEs and their analogs are predicted to be active, since they are non-coplanar in nature. The effects of these chemicals were studied using the same measures for which PCBs had differential effects based on structural configuration. These measures include PKC translocation as determined by [3H]-phorbol ester ([3H]PDBu) binding in cerebellar granule cells and 45Ca2+ sequestration as determined by 45Ca2+ uptake by microsomes and mitochondria isolated from adult rat cerebellum. All the PCDE congeners studied, increased [3H]PDBu binding in a concentration-dependent manner. The order of potency was 2,4,4'-trichlorodiphenyl ether > 4,4'-dichlorodiphenyl ether > diphenyl ether, 3,3',4,4'-tetrachlorodiphenyl ether and, 2,2',4,4',5- and 2,3',4,4',5-pentachlorodiphenyl ethers. The structurally related diphenyl ether nitrofen and diphenyl ethanes o,p'-1,1,1-trichloro-2,2-bis[p-chlorophenyl]ethane (DDT) and p,p'-DDT increased [3H]PDBu binding to a similar extent (28-35% stimulation at 100 microM). All PCDE congeners and their analogs inhibited 45Ca2+ sequestration by microsomes and mitochondria. Of all the chemicals, unchlorinated diphenyl ether was the least active. These results are in agreement with previous SAR findings in which non-coplanar PCBs are active and support our hypothesis that the extent of coplanarity determined by a pattern of chlorination on certain aromatic hydrocarbons can weaken their potency in vitro, although the extent of chlorination is also important.

Animals↗
PubMed1996

Inhibition of microsomal and mitochondrial Ca2+-sequestration in rat cerebellum by polychlorinated biphenyl mixtures and congeners. Structure-activity relationships.

Recent studies from our laboratory indicate that polychlorinated biphenyl (PCB) congeners in vitro perturbed signal transduction mechanisms including cellular Ca2+-homeostasis and protein kinase C translocation. We have now investigated the structure-activity relationship (SAR) of three PCB mixtures, 24 PCB congeners and one dibenzofuran for their effects on microsomal and mitochondrial Ca2+-sequestration in rat cerebellum. Ca2+-sequestration by these intracellular organelles was determined using radioactive 45CaCl2. All three mixtures studied, Aroclor 1016, Aroclor 1254 and Aroclor 1260, were equally potent in inhibiting microsomal and mitochondrial Ca2+-sequestration with IC50 values of 6-8 microM. 1,2,3,7,8-Pentachlorodibenzofuran had no effect on Ca2+-sequestration by these organelles. The SAR among the congeners revealed: (1) congeners with ortho-/meta- or ortho-, para-chlorine substitutions were the most potent in inhibiting microsomal and mitochondrial Ca2+-sequestration (IC50 = 2.4-22.3 microM); (2) congeners with only para- but without ortho-substitutions were not effective in inhibiting Ca2+-sequestration by microsomes and mitochondria; (3) increased chlorination was not related to the effectiveness of these congeners. The present SAR studies indicate that the effects of most PCB congeners in vitro may be related to an interaction at specific sites having preference for low lateral substitution or lateral content (meta- or para) in the presence of ortho-substitution.

Animals↗
PubMed1996

Ste12 and Mcm1 regulate cell cycle-dependent transcription of FAR1.

The transcripts of many genes involved in Saccharomyces cerevisiae mating were found to fluctuate during the cell cycle. In the absence of a functional Ste12 transcription factor, both the levels and the cell cycle pattern of expression of these genes were affected. FUS1 and AGA1 levels, which are maximally expressed only in G1-phase cells, were strongly reduced in ste12- cells. The cell cycle transcription pattern for FAR1 was changed in ste12- cells: the gene was still significantly expressed in G2/M, but transcript levels were strongly reduced in G1 phase, resulting in a lack of Far1 protein accumulation. G2/M transcription of FAR1 was dependent on the transcription factor Mcm1, and expression of a gene with Mcm1 fused to a strong transcriptional activation domain resulted in increased levels of FAR1 transcription. The pattern of cell cycle-regulated transcription of FAR1 could involve combinatorial control of Ste12 and Mcm1. Forced G1 expression of FAR1 from the GAL1 promoter resorted the ability to arrest in response to pheromone in ste12-cells. This indicates that transcription of FAR1 in the G1 phase is essential for accumulation of the protein and for pheromone-induced cell cycle arrest.

Base Sequence↗
PubMed1996

Reactivity parameters in structure-activity relationship-based risk assessment of chemicals.

New approaches to the risk assessment process are needed that might be more definitive and satisfying to the scientific community, interest groups, and the public at large. This commentary examines an alternative approach that is based on understanding the relationships of chemical structure and reactivity properties to the toxicokinetic behavior of chemicals in biological systems. This approach is based on the likelihood that there is a limited number of triggering (reactivity) mechanisms by which chemicals can express their toxicity at the molecular level. The fundamental importance of electrophilic character of chemicals as a determinant of their critical molecular reactivities and interactions with biological material in the expression of toxicity is supported. Such an approach also takes advantage of the maturing field of theoretical/computational chemistry in understanding important molecular recognition and reactivity processes (both qualitatively and quantitatively) for chemicals that can underlie their biological/toxicological activity. A process that permits assessment of reaction equivalents delivered to biological systems may hold promise for grouping chemicals by common triggering mechanisms with clearly delineated toxicological endpoints.

Animals↗
PubMed1996

Modeling the cytochrome P450-mediated metabolism of chlorinated volatile organic compounds.

Comparative molecular field analysis (CoMFA), a three-dimensional quantitative structure-activity relationship (3D-QSAR) paradigm, has been used to analyze the metabolic rates, as intrinsic clearance, of a series of chlorinated volatile organic compounds (VOCs). A comparison between 3D-QSAR and conventional Hansch-type QSAR is provided. To develop predictive 3D-QSARs for metabolism, the standard CoMFA model based on steric and electrostatic potential fields must be supplemented with hydropathic and molecular orbital information also in the form of three-dimensional fields. A mechanistic interpretation of chlorinated VOC metabolism by cytochrome P450 isozymes is provided as a rationalization for the inclusion of multiple fields in the CoMFA 3D-QSAR model. Models of this type have practical utility in the development of generalized physiologically-based pharmacokinetic models, as well as the rational, structure-based, design and/or selection of compounds for use in the in vivo and in vitro metabolic studies.

Cytochrome P-450 Enzyme System↗
PubMed1995

Increased [3H]phorbol ester binding in rat cerebellar granule cells by polychlorinated biphenyl mixtures and congeners: structure-activity relationships.

Our previous reports indicate that polychlorinated biphenyl (PCB) congeners in vitro perturbed cellular Ca2+ homeostasis and protein kinase C (PKC) translocation. We have now studied the structure-activity relationship (SAR) of 3 PCB mixtures, 24 PCB congeners, and 1 dibenzofuran for their effects on PKC translocation by measuring [3H]phorbol ester ([3H]PDBu) binding in cerebellar granule cells (7 days in culture). All the PCB mixtures studied increased [3H]PDBu binding significantly and in a concentration-dependent manner. However, Aroclor 1016 and Aroclor 1254 were more potent than Aroclor 1260. Of the 24 congeners studied, di-ortho congeners such as 2,2',5,5'-tetrachlorobiphenyl (-TeCB), 2,2',4,6,6'-pentachlorobiphenyl (-PeCB), 2,2',4,6-TeCB, and 2,2'-dichlorobiphenyl (-DCB) were the most potent (E50 = 28-43 microM) while non-ortho congeners such as 3,3',4,4'-TeCB and 3,3',4,4'5-PeCB were not effective. The potential contaminant of PCB mixtures, 1,2,3,7,8-pentachlorodibenzofuran had no significant effect on [3H]PDBu binding. The SAR among these congeners revealed: (i) congeners with ortho-chlorine substitution such as 2,2'-DCB (EC50 = 43 +/- 3 microM) or ortho-lateral (meta, para) chlorine substitution such as 2,2',5,5'-TeCB (EC50 = 28 +/- 3 microM) and 2,2'4,6-TeCB (E50 = 41 +/- 6 microM) were most potent; (ii) congeners with only para-substitution such as 4,4'-DCB or high lateral content in the absence of ortho-substitution such as 3,3',4,4',5,5'-HCB were not effective; and (iii) increased chlorination was not clearly related to the effectiveness of these congeners, although hexa- and heptachlorination was less effective than di- and tetrachlorination. Low lateral substitution, especially without para-substitution, or lateral content in the presence of ortho-substitution, may be the most important structural requirement for the in vitro activity of these PCB congeners in neuronal preparations.

Analysis of Variance↗
PubMed1995

Three-dimensional quantitative structure-activity relationships of dioxins and dioxin-like compounds: model validation and Ah receptor characterization.

In the present study we have utilized comparative molecular field analysis (CoMFA), a three-dimensional quantitative structure-activity relationship paradigm, to explore the physico-chemical requirements for binding to the Ah (dioxin) receptor. Recent developments by Gillner et al. [(1993) Mol. Pharmacol. 44, 336-345] prompted us to review and revise our previous CoMFA/QSAR model [Waller, C. L., and McKinney, J. D. (1992) J. Med. Chem. 36, 3660-3666] to include a structurally-diverse training set of Ah receptor ligands ranging in size from naphthalene to indolo[3,2-b]carbazole nuclei. An exhaustive validation process utilizing external test sets and hierarchical cluster analysis routines was employed during model construction and is discussed herein. The limitations of the approach presented herein are discussed with respect to predictive ability of the CoMFA/QSAR models, which is demonstrated to be dependent on a balance between structural diversity and redundancy in the molecules comprising the training set. The results of our modified CoMFA/QSAR model are consistent with and unify all previously established structure-activity relationships established for less structurally-diverse training sets of Ah receptor ligands. As a result of the more complete nature of the series of molecules under examination in the present study, the CoMFA/QSAR steric and electrostatic field contour plots as well as the essential and excluded volume plots provide for a more detailed characterization of the molecular binding domain of the Ah receptor. The implications of the CoMFA/QSAR model presented herein are explored with respect to quantitative hazard identification of potential toxicants.

Binding Sites↗
PubMed1995

FAR1 and the G1 phase specificity of cell cycle arrest by mating factor in Saccharomyces cerevisiae.

Significant accumulation of Far1p is restricted to the G1 phase of the Saccharomyces cerevisiae cell cycle. Here we demonstrate yeast cell cycle regulation of Far1p proteolysis. Deletions within the 50 N-terminal amino acids of Far1p increase stability and reduce cell cycle regulation of Far1p abundance. Whereas wild-type Far1p specifically and exclusively promotes G1 phase arrest in response to mating factor, stabilized Far1p promoted arrest both during and after G1. The loss of the G1 specificity of Far1p action requires elimination of FAR1 transcriptional regulation (by means of the GAL1 promoter) as well as N-terminal truncation. Thus, the cell cycle specificity of mating factor arrest may be largely due to cell cycle regulation of FAR1 transcription and protein stability.

Amino Acid Sequence↗
PubMed1994

Role of Swi4 in cell cycle regulation of CLN2 expression.

Expression of the Saccharomyces cerevisiae CLN1 and CLN2 genes is cell cycle regulated, and the genes may be controlled by positive feedback. It has been proposed that positive feedback operates via Cln/Cdc28 activation of the Swi4/Swi6 transcription factor, leading to CLN1 and CLN2 transcription due to Swi4 binding to specific sites (SCBs) in the CLN1 and CLN2 promoters. To test this proposal, we have examined the effects of deletion either of the potential SCBs in the CLN2 promoter or of the SWI4 gene on CLN2 transcriptional control. Deletion of a restriction fragment containing the identified SCBs from the promoter does not prevent cell cycle regulation of CLN2 expression, although expression is lowered at all cell cycle positions. A promoter containing a 5.5-kb plasmid insertion or an independent 2.5-kb insertion at the point of deletion of the SCB-containing restriction fragment also exhibits cell cycle regulation, so involvement of unidentified upstream SCBs is unlikely. Neither Swi4 nor the related Mbp1 transcription factor is required for cell cycle regulation of the intact CLN2 promoter. In contrast, Swi4 (but not Mbp1) is required for correct cell cycle regulation of the insertion/deletion promoter lacking SCB sites. We have extended previous genetic evidence for involvement of Swi4 in some aspect of CLN2 function: a mutant hunt for CLN2 positive regulatory factors yielded only swi4 mutations at saturation. Swi4 may bind to nonconsensus sequences in the CLN2 promoter (possibly in addition to consensus sites), or it may act indirectly to regulate CLN2 expression.

Alleles↗