RESUMO
By inserting a microlens array at the intermediate image plane of an optical microscope, one can record four-dimensional light fields of biological specimens in a single snapshot. Unlike a conventional photograph, light fields permit manipulation of viewpoint and focus after the snapshot has been taken, subject to the resolution of the camera and the diffraction limit of the optical system. By inserting a second microlens array and video projector into the microscope's illumination path, one can control the incident light field falling on the specimen in a similar way. In this paper, we describe a prototype system we have built that implements these ideas, and we demonstrate two applications for it: simulating exotic microscope illumination modalities and correcting for optical aberrations digitally.
RESUMO
We have characterized the 5'-end (3218 bp) of the rat phenylalanine hydroxylase (PAH) gene. Within this PAH promoter sequence, we have identified a number of putative regulatory sites analogous to those present in the human and murine PAH promoters. In particular, potential HNF 1 binding sites and a CRE have been identified. These sequences respectively bind HNF1 and CREB transcription factors present in rat nuclear extracts and may be significant in the tissue-specific and hormonal control of PAH expression.
Assuntos
Fenilalanina Hidroxilase/genética , Regiões Promotoras Genéticas/genética , Ratos/genética , Região 5'-Flanqueadora/genética , Animais , Sequência de Bases , Dados de Sequência Molecular , Alinhamento de Sequência , Análise de Sequência de DNARESUMO
Phenylalanine hydroxylase catalyzes the major regulatory step of the phenylalanine degradation pathway. In view of the glucogenic nature of phenylalanine breakdown, and hence its potential contribution to glucose homeostasis, we have investigated the impact of streptozotocin-induced diabetes upon the expression of rat phenylalanine hydroxylase. Northern blot analysis revealed that induction of diabetes was associated with an increase in the in vivo abundance of hepatic phenylalanine hydroxylase-specific mRNA. This increase in mRNA abundance was maintained for at least 8 hr in liver cells isolated from diabetic animals. In contrast, phenylalanine hydroxylase immunoreactivity and enzymic activity decreased, over the 8 hr incubation period, to levels similar to those observed in liver cells from normal animals. These changes were retarded, but not prevented, by the presence of dexamethasone in incubation media. In liver cells from normal animals the abundance of phenylalanine hydroxylase-specific mRNA, immunoreactivity and enzymic activity, were largely insensitive to treatment with dexamethasone and/or glucagon over an 8 hr incubation period. It is concluded that, whereas diabetes-related alterations in phenylalanine hydroxylase-specific mRNA abundance persist after isolation of liver cells, changes in phenylalanine hydroxylase protein abundance do not. Additionally, in contrast to certain other enzymes (e.g. phosphoenolpyruvate carboxykinase) it is not possible to mimic diabetes-related alterations in the expression of phenylalanine hydroxylase, in liver cells from normal animals, by simple hormonal manipulation of incubation media. This implies that other additional factors must also contribute to diabetes-related alterations in hepatic enzyme expression.
Assuntos
Diabetes Mellitus Experimental/enzimologia , Regulação Enzimológica da Expressão Gênica , Fígado/enzimologia , Fenilalanina Hidroxilase/metabolismo , RNA Mensageiro/metabolismo , Animais , Northern Blotting , Células Cultivadas , Dexametasona/farmacologia , Diabetes Mellitus Experimental/genética , Diabetes Mellitus Experimental/metabolismo , Glucagon/farmacologia , Immunoblotting , Insulina/farmacologia , Rim/enzimologia , Rim/metabolismo , Fígado/metabolismo , Masculino , Fenilalanina Hidroxilase/genética , Fosfoenolpiruvato Carboxilase/genética , Fosfoenolpiruvato Carboxilase/metabolismo , Ratos , Ratos WistarRESUMO
We have characterized the immediate (465 bp) 5'-flanking region of the rat phenylalanine hydroxylase (PAH)-encoding gene. This sequence shows considerable similarity to the 5'-flanking region of the human PAH gene [Konecki et al., Biochemistry 31 (1992) 8363-8368]. Both sequences lack obvious TATA elements; however, putative regulatory sites, including a potential cyclic AMP-response element and glucocorticoid response elements, are present.
Assuntos
Fenilalanina Hidroxilase/genética , Sequências Reguladoras de Ácido Nucleico/genética , Animais , Sequência de Bases , Clonagem Molecular , AMP Cíclico/fisiologia , Glucocorticoides/fisiologia , Humanos , Dados de Sequência Molecular , Ratos , Análise de Sequência de DNA , Homologia de Sequência do Ácido NucleicoAssuntos
Diabetes Mellitus Experimental/enzimologia , Fígado/enzimologia , Fenilalanina Hidroxilase/biossíntese , Fosfoenolpiruvato Carboxiquinase (GTP)/biossíntese , RNA Mensageiro/metabolismo , Vanadatos/farmacologia , Animais , Diabetes Mellitus Experimental/tratamento farmacológico , Insulina/uso terapêutico , Fígado/efeitos dos fármacos , Masculino , Ratos , Ratos Wistar , Valores de ReferênciaRESUMO
Induction of diabetes in rats is associated with a significant elevation in the phenylalanine hydroxylating capacity of the liver. This phenomenon reflects an increase in the abundance of both phenylalanine hydroxylase protein and phenylalanine hydroxylase-specific mRNA. These changes can be abolished by insulin-dependent control of diabetes. We show here that the control of diabetes by oral administration of sodium orthovanadate will also nullify the diabetes-related alterations in phenylalanine hydroxylase expression. In addition, diabetes-induced changes in the extent of phosphorylation of phenylalanine hydroxylase are reversed by either insulin or vanadate treatment in vivo. These treatments also abolished the diabetes-related, approx. 30-fold, decrease in glucagon sensitivity of phenylalanine hydroxylation in isolated liver cells.
