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Biomedical subjects

M Fink

Publications and source records attributed to M Fink.

At least 145 records · Page 8Linked to original sources
PubMed1995

Susceptibility of cloned K+ channels to reactive oxygen species.

Free radical-induced oxidant stress has been implicated in a number of physiological and pathophysiological states including ischemia and reperfusion-induced dysrhythmia in the heart, apoptosis of T lymphocytes, phagocytosis, and neurodegeneration. We have studied the effects of oxidant stress on the native K+ channel from T lymphocytes and on K+ channels cloned from cardiac, brain, and T-lymphocyte cells and expressed in Xenopus oocytes. The activity of three Shaker K+ channels (Kv1.3, Kv1.4, and Kv1.5), one Shaw channel (Kv3.4), and one inward rectifier K+ channel (IRK3) was drastically inhibited by photoactivation of rose bengal, a classical generator of reactive oxygen species. Other channel types (such as Shaker K+ channel Kv1.2, Shab channels Kv2.1 and Kv2.2, Shal channel Kv4.1, inward rectifiers IRK1 and ROMK1, and hIsK) were completely resistant to this treatment. On the other hand tert-butyl hydroperoxide, another generator of reactive oxygen species, removed the fast inactivation processes of Kv1.4 and Kv3.4 but did not alter other channels. Xanthine/xanthine oxidase system had no effect on all channels studied. Thus, we show that different types of K+ channels are differently modified by reactive oxygen species, an observation that might be of importance in disease states.

Animals↗
PubMed1995

Molecular properties of neuronal G-protein-activated inwardly rectifying K+ channels.

Four cDNA-encoding G-activated inwardly rectifying K+ channels have been cloned recently (Kubo, Y., Reuveny, E., Slesinger, P. A., Jan, Y. N., and Jan, L. Y. (1993) Nature 364, 802-806; Lesage, F., Duprat, F., Fink, M., Guillemare, E., Coppola, T., Lazdunski, M., and Hugnot, J. P. (1994) FEBS Lett. 353, 37-42; Krapivinsky, G., Gordon, E. A., Wickman, K., Velimirovic, B., Krapivinsky, L., and Clapham, D. E. (1995) Nature 374, 135-141). We report the cloning of a mouse GIRK2 splice variant, noted mGIRK2A. Both channel proteins are functionally expressed in Xenopus oocytes upon injection of their cRNA, alone or in combination with the GIRK1 cRNA. Three GIRK channels, mGIRK1-3, are shown to be present in the brain. Colocalization in the same neurons of mGIRK1 and mGIRK2 supports the hypothesis that native channels are made by an heteromeric subunit assembly. GIRK3 channels have not been expressed successfully, even in the presence of the other types of subunits. However, GIRK3 chimeras with the amino- and carboxyl-terminal of GIRK2 are functionally expressed in the presence of GIRK1. The expressed mGIRK2 and mGIRK1, -2 currents are blocked by Ba2+ and Cs+ ions. They are not regulated by protein kinase A and protein kinase C. Channel activity runs down in inside-out excised patches, and ATP is required to prevent this rundown. Since the nonhydrolyzable ATP analog AMP-PCP is also active and since addition of kinases A and C as well as alkaline phosphatase does not modify the ATP effect, it is concluded that ATP hydrolysis is not required. An ATP binding process appears to be essential for maintaining a functional state of the neuronal inward rectifier K+ channel. A Na+ binding site on the cytoplasmic face of the membrane acts in synergy with the ATP binding site to stabilize channel activity.

Adenosine Triphosphate↗
PubMed1995

Heterologous multimeric assembly is essential for K+ channel activity of neuronal and cardiac G-protein-activated inward rectifiers.

The family of G-protein-activated inward-rectifiers K+ channels presently comprise at least 3 cloned members called GIRK1, GIRK2 and GIRK3. A close structural parent of GIRK channels has recently been described as being an ATP-sensitive K+ channel. This paper shows that Xenopus expression of this new channel that we call GIRK4 does not produce an ATP-inhibitable activity with a pharmacological activation by pinacidil as previously described but instead a G-protein activated inward-rectifier. While oocyte expression of single subunits is infrequent and relatively modest in intensity, expression of GIRK1,2, GIRK1,4 and GIRK2,4 mixtures leads to routine and robust expression of K+ channels indicating that heterologous subunit assembly is necessary for activity. Activity of GIRK1,2, GIRK1,4 and GIRK2,4 channels required the presence of ATP acting as an activator at the cytoplasmic face and is further activated by the beta gamma subunits.

Adenosine Triphosphate↗
PubMed1995

Genotype-phenotype correlation in multiple endocrine neoplasia type 2: report of the International RET Mutation Consortium.

The International RET Mutation Consortium was first convened as part of the Fifth International Workshop on Multiple Endocrine Neoplasia, Stockholm, Sweden, in an attempt to analyse the relationship of RET mutation and disease phenotype in the autosomal dominantly inherited multiple endocrine neoplasia type 2 (MEN 2) syndromes. Out of 361 families studied, 41% had MEN 2A, 17.7% MEN 2B, 6.4% FMTC and the remaining subjects were unclassified. RET mutations were detected in 87.3% of families overall. Over 93% of MEN 2B families had the RET 918 ATG-->ACG mutation, while the most frequent mutation detected in MEN 2A families was cysteine codon 634 (87% of all mutations).

Carcinoma, Medullary↗
PubMed1995

ECT and non-memory cognition: a review.

The literature on the effects of electroconvulsive therapy (ECT) on non-memory cognitive functions is reviewed. It is concluded that with early methods of ECT administration (sine wave, high dose), these effects are larger than those of depression. They are less pronounced, and usually do not exceed the effects of depression, when modern methods of ECT administration (brief pulse, moderate or low dose) are used. Following ECT, these functions progressively improve. At one week to seven months after ECT, performance is better than before ECT, probably because of the alleviation of both the effects of depression and of ECT. The time course to full recovery of the non-memory effects resembles that of the recovery of amnesic effects, although the latter are more pronounced. With bilateral ECT, as with right unilateral ECT, there is evidence that right hemisphere effects are more pronounced. The results of this review argue that clinicians should take the non-memory cognitive effects of ECT into account, and patients should be informed of their existence before they sign consent for ECT.

Cognition Disorders↗
PubMed1995

Assessment of treatment outcomes in neuropsychiatry: a report from the Committee on Research of the American Neuropsychiatric Association.

The ANPA Committee on Research conducted a survey of its members and those of the British Neuropsychiatry Association to determine the extent to which neuropsychiatrists employ formal measures of clinical outcome. Results revealed that although respondents endorsed the practice of outcome assessment, formal diagnostic evaluations and outcome measures were rarely applied consistently to the broad range of neuropsychiatric conditions encountered clinically. These findings have implications for clinical research and managed care in neuropsychiatry and will form the basis for future work by the Committee on Research.

Cognition↗
PubMed1995

Convulsive therapy in delusional disorders.

Delusions are psychopathologic expressions associated with schizophrenia, affective disorders, and systemic and toxic illnesses. In each condition, the efficacy of ECT is well defined. For some illnesses, such as major depression with psychosis, manic delirium, and catatonia, ECT is effective in relieving the delusional states. This activity of ECT as an antidelusional agent compels us to consider the mode of action of ECT as broader than as an antidepressant treatment alone. The experience also compels greater consideration of the unitary classification of severe mental disorders.

Delusions↗
PubMed1994

Cloning provides evidence for a family of inward rectifier and G-protein coupled K+ channels in the brain.

MbIRK3, mbGIRK2 and mbGIRK3 K+ channels cDNAs have been cloned from adult mouse brain. These cDNAs encode polypeptides of 445, 414 and 376 amino acids, respectively, which display the hallmarks of inward rectifier K+ channels, i.e. two hydrophobic membrane-spanning domains M1 and M2 and a pore-forming domain H5. MbIRK3 shows around 65% amino acid identity with IRK1 and rbIRK2 and only 50% with ROMK1 and GIRK1. On the other hand, mbGIRK2 and mbGIRK3 are more similar to GIRK1 (60%) than to ROMK1 and IRK1 (50%). Northern blot analysis reveals that these three novel clones are mainly expressed in the brain. Xenopus oocytes injected with mbIRK3 and mbGIRK2 cRNAs display inward rectifier K(+)-selective currents very similar to IRK1 and GIRK1, respectively. As expected from the sequence homology, mbGIRK2 cRNA directs the expression of G-protein coupled inward rectifier K+ channels which has been observed through their functional coupling with co-expressed delta-opioid receptors. These results provide the first evidence that the GIRK family, as the IRK family, is composed of multiple genes with members specifically expressed in the nervous system.

Amino Acid Sequence↗
PubMed1994

Possible effect of medroxyprogesterone acetate (MPA) in lymphoid blast crisis of chronic myelogenous leukemia.

A patient with a lymphoid blast crisis of a chronic myelogenous leukemia (CML) was treated with vindesine, vincristine and prednisone. Blasts disappeared from the peripheral blood but persisted at a level of 60% in the bone marrow. After 5 weeks of continuous therapy, the patient became thrombopenic, and 2 weeks later blasts rose to 31%. After 7 weeks, 1 g MPA was given daily p.o. and weekly vincristine treatment was resumed. Blasts disappeared again from the peripheral blood, thrombocytes rose to a maximum of 274 g/l, and a remission with less than 5% blasts was demonstrated in the bone marrow. In another relapse after withdrawal of MPA, estrogen and progesterone receptors (PR) were found in the leukemic cells. Thus, a remission was seen during treatment with vincristine, prednisone, and MPA after a deterioration with vincristine and prednisone alone in a PR-positive leukemia, and an effect of MPA in this lymphoid blast crisis of a CML has to be discussed.

Blast Crisis↗
PubMed1994

A rare leucine 40/arginine40 polymorphism on platelet glycoprotein IIIa is linked to the human platelet antigen 1b.

A rare polymorphism on glycoprotein (GP) IIIa is reported. Sequencing of a 482-base-pair (bp) PCR product of the genomic DNA of GPIIIa revealed a single-base exchange of a G<==>T polymorphism at base 12,569 that created an additional restriction site for MspI. This single-point mutation (frequency in Caucasians 0.00386) is on the HPA-1b gene (HPA-1bvar) and codominantly inherited. The exchange of a G for a T results in a leucine-to-arginine substitution at amino acid 40 from the NH2 terminus. The binding of anti-HPA-1a and -1b antibodies to HPA-1bvar platelets is not influenced.

Arginine↗