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Jonathan Whitfield

Publications and source records attributed to Jonathan Whitfield.

7 recordsLinked to original sources
PubMed2006

Specific requirement for Bax, not Bak, in Myc-induced apoptosis and tumor suppression in vivo.

Bax and Bak comprise the mitochondrial gateway for apoptosis induced by diverse stimuli. Loss of both bax and bak is necessary to block cell death induced by such stimuli, indicating a great degree of functional overlap between Bax and Bak. Apoptosis is the major intrinsic pathway that limits the oncogenic potential of Myc. Using a switchable mouse model of Myc-induced apoptosis in pancreatic beta cells, we have shown that Myc induces apoptosis in vivo exclusively through Bax but not Bak. Furthermore, blockade of Myc-induced apoptosis by the inactivation of Bax, but not Bak, eliminates all restraints to the oncogenic potential of Myc, allowing the rapid and synchronous progression of invasive, angiogenic tumors.

Animals↗
PubMed2005

The neuroprotective action of JNK3 inhibitors based on the 6,7-dihydro-5H-pyrrolo[1,2-a]imidazole scaffold.

Imidazole-based structures of p38 inhibitors served as a starting point for the design of JNK3 inhibitors. Construction of a 6,7-dihydro-5H-pyrrolo[1,2-a]imidazole scaffold led to the synthesis of the (S)-enantiomers, which exhibited p38/JNK3 IC50 ratio of up to 10 and were up to 20 times more potent inhibitors of JNK3 than the relevant (R)-enantiomers. The JNK3 inhibitory potency correlated well with inhibition of c-Jun phosphorylation and neuroprotective properties of the compounds in low K+-induced cell death of rat cerebellar granule neurones.

Animals↗
PubMed2004

Methods for culturing primary sympathetic neurons and for determining neuronal viability.

Developing nerve growth factor (NGF)-dependent sympathetic neurons are one of the best-studied in vitro models of neuronal apoptosis and have been used to identify key components of the neuronal cell death pathway. This chapter describes how to prepare purified cultures of primary sympathetic neurons and how to induce apoptosis by NGF deprivation. In addition, a simple method for measuring neuronal viability based on the live/dead assay is also described. This can be used for assessing the effect of small molecule inhibitors of protein kinases, caspases and other enzymes, on NGF withdrawal-induced death.

Animals↗
PubMed2004

Immunocytochemical techniques for studying apoptosis in primary sympathetic neurons.

Developing sympathetic neurons, which depend on nerve growth factor for survival, are one of the best studied in vitro models of neuronal apoptosis and have been extensively used for cellular and molecular studies of the neuronal death pathway. Important apoptotic events after nerve growth factor withdrawal include the release of proapoptotic proteins, such as cytochrome c, from the mitochondria and the activation of caspases, followed by nuclear DNA fragmentation and chromatin condensation. In this chapter, we describe immunocytochemical techniques for studying apoptotic DNA fragmentation, changes in nuclear morphology, and mitochondrial cytochrome c release at the single cell level using sympathetic neurons cultured on glass coverslips.

Animals↗
PubMed2003

High-throughput methods to detect dimerization of Bcl-2 family proteins.

Members of the Bcl-2 family are critical regulators of apoptosis. Antiapoptotic family proteins such as Bcl-2 and Bcl-x(L) function, at least in part, by binding proapoptotic members such as Bax and Bak and thereby preventing release of apoptotic proteins, including cytochrome c, from the mitochondria. "BH3-only" members of the family disrupt this interaction by binding, via their BH3 domain, to a hydrophobic pocket on the surface of the antiapoptotic members. Disruption of heterodimerizations by small-molecule inhibitors could be used to modulate cell death in both cancer (to increase apoptosis) and degenerative disorders (to decrease apoptosis), and assays are necessary to screen compound libraries. Fluorescence polarization and enzyme-linked immunosorbent assay-based methods to detect Bcl-2 protein interactions have been described. Here, two further methods that are rapid, "mix and read," homogeneous reactions, insensitive to compound autofluorescence, and amenable to high-throughput screening, are described: a scintillation proximity assay and a time-resolved fluorescence resonance energy transfer assay (HTRF). The assays are designed using tags such that different Bcl-2 family members or BH3 domain peptides can be readily applied to either format, as exemplified by the use here of histidine-tagged Bcl-x(L) and biotinylated BH3 peptides.

Amino Acid Sequence↗
PubMed2003

Clinical effects of L-carnitine supplementation on apnea and growth in very low birth weight infants.

OBJECTIVE: Systemic carnitine deficiency may present with apnea, hypotonia, and poor growth. Premature infants often manifest these symptoms and are at risk of developing carnitine deficiency because of immaturity of the biosynthetic pathway, lack of sufficient predelivery transplacental transport, and lack of sufficient exogenous supplementation. This study was undertaken to examine the effect of carnitine supplementation in premature infants. METHODS: Eighty preterm infants <1500 g were enrolled in a prospective, double-blind, placebo-controlled study of carnitine supplementation within 96 hours of delivery. Growth, length of hospital stay, and frequency and severity of apnea were the primary outcome measures. RESULTS: Weight gain and change in length, fronto-occipital head circumference, mid arm circumference, and triceps skinfold thickness were similar between the carnitine-supplemented and placebo groups. The amount and severity of apnea and the overall length of hospitalization were also similar between the 2 groups. The carnitine levels in the supplemented group were significantly higher than in the placebo group at 4 and 8 weeks after study entry. CONCLUSION: Although preterm infants <1500 g have low carnitine levels, routine supplementation with carnitine has no demonstrable effect on growth, apnea, or length of hospitalization and thus seems to be unnecessary.

Apnea↗