Biomedical subjects

E Galperin

Publications and source records attributed to E Galperin.

8 recordsLinked to original sources

PubMed2001

Association of insulin-like growth factor 1 receptor with EHD1 and SNAP29.

Ligand-induced receptor-mediated endocytosis plays a central role in regulating signaling conveyed by tyrosine kinase receptors. This process depends on the recruitment of the adaptor protein 2 (AP-2) complex, clathrin, dynamin, and other accessory proteins to the ligand-bound receptor. We show here that besides AP-2 and clathrin, two other proteins participate in the endocytic process of the insulin-like growth factor receptor (IGF-1R); they are EHD1, an Eps15 homology (EH) domain-containing protein 1, and SNAP29, a synaptosomal-associated protein. EHD1 and SNAP29 form complexes with alpha-adaptin of AP-2 and co-localize in endocytic vesicles, indicating a role for them in endocytosis. EHD1 and SNAP29 interact directly with each other and are present in complexes with IGF-1R. After IGF-1 induction, EHD1 and IGF-1R co-localize intracellularly. Overexpression of EHD1 in Chinese hamster ovary cells represses IGF-1-mediated signaling, as measured by mitogen-activated protein kinase phosphorylation and Akt phosphorylation, indicating that EHD1 plays a role as a down-regulator in IGF-1 signaling pathway.

3T3 Cells↗

PubMed2001

Red eye syndrome: clinical and experimental experience in a new aspect of diffuse eosinophilic infiltration?

Twenty-two of 24 hemodialysis patients dialyzed simultaneously with a new batch of cellulose acetate dialyzers promptly developed a spectrum of symptoms and physical signs including red eyes, hearing loss, tinnitus, and bone pain, previously described as red eye syndrome. We subsequently injected 4 rabbits with an eluate from a dialyzer of the same or a control batch. Six hours following exposure, the animals developed, in addition to red eyes, diffuse eosinophilic infiltration of various organs as well as myopathic changes and moderate brain edema. On the basis of these data, we suggest that it cannot be concluded whether the underlying pathophysiological mechanisms were toxic, allergic or both and that the occurrence of relevant symptomatology in 2 or more simultaneously dialyzed patients is a strong argument against unnecessary diagnostic or therapeutic procedures. Finally, a second exposure in a given patient should be avoided.

Animals↗

PubMed2001

Vitamin B(6) therapy does not improve hematocrit in hemodialysis patients supplemented with iron and erythropoietin.

BACKGROUND/AIM: Pyridoxine deficiency may be the cause of failure to respond appropriately to iron and erythropoietin (EPO) administration in hemodialysis patients. METHOD: We studied 36 patients on chronic hemodialysis amply supplemented with iron and EPO, who failed to raise hematocrit levels >33%. Patients were divided into three equal groups and evaluated for 6 months as follows: Group A -- no additional therapy; group B -- supplemented with oral pyridoxine 50 mg/day, and group C received 100 mg/day pyridoxine orally. RESULTS: In all our patients, erythrocyte pyridoxine levels were initially within reference range for a healthy population and did not vary significantly during the study period. Likewise, ferritin levels and iron saturation values remained normal and constant. Hemoglobin and/or hematocrit levels remained practically unchanged in all three groups. CONCLUSIONS: The results indicate that in hemodialysis patients with normal pyridoxine status who, despite appropriate supplementation of iron and EPO, fail to reach optimal hematocrit levels, additional pyridoxine treatment does not produce any hematocrit elevation.

Adult↗

PubMed2000

Proliferative responses of mesangial cells to growth factors during compensatory versus dietary hypertrophy.

While the bulk of renal hypertrophy induced by contralateral nephrectomy or a high-protein diet consists of tubular cell growth, there is some evidence suggesting that mesangial cells play a role in this phenomenon. Previous data suggest that this role of mesangial cells is associated with their proliferation. We, therefore, undertook this investigation to assess the proliferative responses of mesangial cells, originating from single remaining kidneys or from kidneys of rats fed a high-protein diet, to epinephrine, endothelin, arginine vasopressin, neo-synephrine, or epidermal growth factor (EGF). All agents significantly enhanced the proliferation of normal mesangial cells, though the responses to neo-synephrine and EGF were significantly lower as compared with the other growth promoters. The mitogenic effects of the first three agents on single kidney mesangial cells were significant, but blunted as compared with control cells. This blunting was not evident in the case of the latter two mitogens. A significant enhancement of proliferation of mesangial cells originating from protein-fed rats was produced by epinephrine, neo-synephrine, and EGF. These effects were statistically not different from those observed in normal mesangial cells. The proliferative response to each of the mitogens used in the study proved highly specific for each mitogen, since it was abolished by respective specific inhibitors. Mesangial cells may play a role in the activation and later in progressive inhibition of renal hypertrophy in vivo.

Animals↗

PubMed1999

Evaluation and molecular characterization of EHD1, a candidate gene for Bardet-Biedl syndrome 1 (BBS1).

Bardet-Biedl Syndrome (BBS) is an autosomal recessive disorder characterized by developmental abnormalities including mental retardation, obesity, retinitis pigmentosa, polydactyly, short stature, and hypogenitalism. To date, five BBS loci have been identified. BBS1, located on 11q13, is reported to be the most prevalent form of BBS in the Caucasian population. A positional cloning approach is being used to identify the gene responsible for BBS1. EHD1, a new member of the EH-domain containing proteins, was identified in this study as lying within the BBS1 disease interval. RNA analysis of many tissues revealed that expression of EHD1 is ubiquitous, with elevated levels in the testis. The genomic structure of EHD1 was elucidated by direct BAC sequencing. Following identification of the intron/exon boundaries, mutational analysis was performed by single strand conformation polymorphism and direct sequencing of affected individuals from several large kindreds linked to the BBS1 locus, as well as a cohort of unrelated probands. No disease-causing mutations were identified in this analysis, but several polymorphisms were found.

Amino Acid Sequence↗

PubMed1999

EHD1--an EH-domain-containing protein with a specific expression pattern.

A cDNA that is a member of the eps15 homology (EH)-domain-containing family and is expressed differentially in testis was isolated from mouse and human. The corresponding genes map to the centromeric region of mouse chromosome 19 and to the region of conserved synteny on human chromosome 11q13. Northern analysis revealed two RNA species in mouse. In addition to the high levels in testis, expression was noted in kidney, heart, intestine, and brain. In human, three RNA species were evident. The smaller one was predominant in testis, while the largest species was evident in other tissues as well. The predicted protein sequence has an EH domain at its C-terminus, including an EF, a Ca2+ binding motif, and a central coiled-coil structure, as well as a nucleotide binding consensus site at its N-terminus. As such, it is a member of the EH-domain-containing protein family and was designated EHD1 (EH domain-containing 1). In cells in tissue culture, we localized EHD1 as a green fluorescent protein fusion protein, in transferrin-containing, endocytic vesicles. Immunostaining of different adult mouse organs revealed major expression of EHD1 in germ cells in meiosis, in the testes, in adipocytes, and in specific retinal layers. Results of in situ hybridization to whole embryos and immunohistochemical analyses indicated that EHD1 expression was already noted at day 9.5 in the limb buds and pharyngeal arches and at day 10.5 in sclerotomes, at various elements of the branchial apparatus (mandible and hyoid), and in the occipital region. At day 15.5 EHD1 expression peaked in cartilage, preceding hypertrophy and ossification, and at day 17.5 there was no expression in the bones. The EHD1 gene is highly conserved between nematode, Drosophila, mouse, and human. Its predicted protein structure and cellular localization point to the possibility that EHD1 participates in ligand-induced endocytosis.

Amino Acid Sequence↗

PubMed1999

Failure of acute hyperinsulinemia to alter blood pressure is not due to baroreceptor feedback.

It is well documented that acute insulin administration stimulates the sympathetic nervous system in both humans and animals. Despite marked sympathetic activation during acute hyperinsulinemia, blood pressure is generally not increased because it is overridden by the vasodilator action of insulin. The maintenance of blood pressure in the face of sympathetic activation is unknown. A possible mechanism includes feedback regulation by the baroreceptor reflex arc. In normotensive states, hyperinsulinemic-induced sympathetic activation may tend to elevate blood pressure, but this change is rapidly sensed by the baroreceptors in the carotid arteries (and aortic arch), and a counterbalancing increase in vasodilation could return blood pressure to normal. Thus, it can be speculated that, in the event of diminished baroreceptor sensitivity and suppressed vasodilator actions of insulin, common abnormalities in hypertension, acute insulin infusion would be expected to increase blood pressure. We undertook the present study to determine whether the baroreceptor reflex arc modulated the blood pressure response to acute hyperinsulinemia. To this end, six normotensive dogs underwent saline or insulin infusions before and after deactivation of the carotid and aortic baroreceptors. Baroreceptor dysfunction was documented after denervation in all cases by an abnormal response to phenylephrine injections. Before denervation, insulin infusions caused a slight but nonsignificant rise in mean arterial pressure (MAP; 110 +/- 5 to 120 +/- 5 mm Hg; P = 0.13). Baroreceptor denervation caused a marked variability in blood pressure. However, basal mean arterial pressure was not significantly altered. Neither saline nor insulin infusions (105 +/- 10 v 105 +/- 8 mm Hg, basal v steady state) caused a significant change in MAP in denervated dogs. Likewise, insulin and saline did not change heart rates significantly in intact or denervated animals. Furthermore, glucose metabolism was similar in both groups of animals. This study demonstrates that the baroreceptor reflex arc does not mediate the blood pressure response to acute hyperinsulinemia.

Acute Disease↗

PubMed1997

Identification of factors regulating the expression of the human glucocerebrosidase gene.

Gaucher disease, the most prevalent sphingolipid disorder, is characterized by an accumulation of sphingolipids mainly in cells of the reticuloendothelial cells, and is due to decreased activity of the lysosomal enzyme glucocerebrosidase (GCase). The corresponding gene is expressed differentially, namely in different cell types there are different GCase steady-state mRNA levels. Electrophoretic mobility shift assays, DNase footprinting and chloramphenicol acetyl transferase assays were employed in order to unravel some of the transcription factors responsible for the differential expression of the glucocerebrosidase (gcs) gene. The results indicate that OCTA binding protein, AP-1, PEA3 and a CAAT binding protein participate in regulating the expression of the gcs gene. The availability of the transcription factors seems to control the level of transcription of the gcs gene.

Binding Sites↗