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Biomedical subjects

J Ellenberg

Publications and source records attributed to J Ellenberg.

30 records · Page 2Linked to original sources
PubMed1998

The REACH Project of the Adolescent Medicine HIV/AIDS Research Network: design, methods, and selected characteristics of participants.

PURPOSE: To describe the Reaching for Excellence in Adolescent Care and Health (REACH) Project of the Adolescent Medicine Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS) Research Network, a unique collaborative effort to conceive and implement a research design intended to examine HIV pathogenesis, pubertal hormonal variation, and the effects of sexually transmitted disease comorbidity in HIV-infected youth to improve their health care. METHODS: This multidisciplinary team has drawn on basic science and clinical experience to produce a study design with relevant and feasible study aims and testable hypotheses. Particular attention has been paid to centralized training and quality control practices. Standardized measurements include direct and computer interviews, physical examination, laboratory analysis, and medical chart abstraction. The protocol has been approved by local institutional review boards. RESULTS: A highly standardized and quality control monitored protocol has been implemented at 16 sites throughout the United States collecting historical, observational, and laboratory data in a group of HIV-infected adolescents and HIV-negative controls. Preliminary data collected on subjects are consistent with published reports of the sociodemographic and clinical characteristics of the HIV epidemic in sexually active youth, thus supporting the integrity of the protocol development process. The study population is, for the most part, in older adolescence, predominantly minority and female, and with publicly financed or no health insurance. CONCLUSIONS: The REACH Project is positioned to address questions about the clinical course, immunologic profile, and viral dynamics in HIV-positive youth, and thus is able to inform drug development and management strategies for this understudied population.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Two-color green fluorescent protein time-lapse imaging.

The Aequorea victoria green fluorescent protein (GFP) is widely recognized as a powerful tool in cell biology, serving as a vital reporter for monitoring localization and dynamics of intracellular proteins and organelles over time. GFP variants with shifted spectral characteristics have been described and offer enormous potential for double-labeling experiments and protein-protein interaction studies. However, most GFP variant combinations are not suitable for double-label, time-lapse imaging experiments because of either extremely rapid photobleaching of blue-shifted GFP variants or crossover of their excitation and emission spectra, which must then be computer corrected. Here, we describe the successful use of two photostable spectral GFP variants, W7 and 10C, in dual-color, time-lapse imaging of fusion proteins in living cells using either wide-field or confocal microscopy. W7 and 10C were highly photostable during repetitive long-term imaging and were cleanly separated by their different excitation spectra alone with negligible crossover of fluorescence. We present time-lapse image sequences of COS-7 cells co-expressing both a marker of the Golgi complex (galactosyl transferase) fused to W7 and a marker of the nuclear envelope (lamin-B receptor) fused to 10C. To our knowledge, these image sequences provide the first simultaneous visualization of Golgi and nuclear envelope membranes in living cells.

Animals↗
PubMed1997

Nuclear membrane dynamics and reassembly in living cells: targeting of an inner nuclear membrane protein in interphase and mitosis.

The mechanisms of localization and retention of membrane proteins in the inner nuclear membrane and the fate of this membrane system during mitosis were studied in living cells using the inner nuclear membrane protein, lamin B receptor, fused to green fluorescent protein (LBR-GFP). Photobleaching techniques revealed the majority of LBR-GFP to be completely immobilized in the nuclear envelope (NE) of interphase cells, suggesting a tight binding to heterochromatin and/or lamins. A subpopulation of LBR-GFP within ER membranes, by contrast, was entirely mobile and diffused rapidly and freely (D = 0. 41 +/- 0.1 microm2/s). High resolution confocal time-lapse imaging in mitotic cells revealed LBR-GFP redistributing into the interconnected ER membrane system in prometaphase, exhibiting the same high mobility and diffusion constant as observed in interphase ER membranes. LBR-GFP rapidly diffused across the cell within the membrane network defined by the ER, suggesting the integrity of the ER was maintained in mitosis, with little or no fragmentation and vesiculation. At the end of mitosis, nuclear membrane reformation coincided with immobilization of LBR-GFP in ER elements at contact sites with chromatin. LBR-GFP-containing ER membranes then wrapped around chromatin over the course of 2-3 min, quickly and efficiently compartmentalizing nuclear material. Expansion of the NE followed over the course of 30-80 min. Thus, selective changes in lateral mobility of LBR-GFP within the ER/NE membrane system form the basis for its localization to the inner nuclear membrane during interphase. Such changes, rather than vesiculation mechanisms, also underlie the redistribution of this molecule during NE disassembly and reformation in mitosis.

Animals↗
PubMed1997

The transmembrane domain of a carboxyl-terminal anchored protein determines localization to the endoplasmic reticulum.

UBC6 is a C-terminal membrane-anchored (type IV) protein, native to Saccharomyces cerevisiae, where it is found in the endoplasmic reticulum. When expressed in mammalian cells, this novel ubiquitin-conjugating enzyme also localizes to the endoplasmic reticulum. UBC6 lacks a lumenal domain and contains no known endoplasmic reticulum retention signals. Analysis of chimeric proteins in which the cytosolic domain of UBC is linked to a heterologous transmembrane domain, or in which the UBC6 transmembrane domain is appended to an unrelated soluble protein, led to the determination that the transmembrane domain of UBC6 plays a dominant role in its compartmental localization. The basis for the transmembrane domain-mediated subcellular targeting of UBC6 was evaluated by lengthening the wild type UBC6 hydrophobic segment from 17 to 21 amino acids, which resulted in re-targeting to the Golgi complex. A further increase in length to 26 amino acids allowed this modified protein to traverse the secretory pathway and gain expression at the plasma membrane. These findings are consistent with models in which, in the absence of dominant cytosolic or lumenal targeting determinants, proteins may be sorted within the secretory pathway based on interactions between their transmembrane domains and the surrounding lipid bilayer.

Amino Acid Sequence↗
PubMed1995

Cloning and electrophysiological analysis of KST1, an inward rectifying K+ channel expressed in potato guard cells.

Potassium uptake by guard cells represents part of the osmotic motor which drives stomatal opening. Patch-clamp measurements have identified inward rectifying K+ channels capable of mediating K+ uptake in guard cells and various other plant cell types. Here we report the molecular cloning and characterization of a voltage-dependent K+ channel (KST1) from potato (Solanum tuberosum L.) guard cells. In situ hybridization shows expression of kst1 in guard cells. Two-electrode voltage-clamp and patch-clamp studies of the gene product after cRNA injection into Xenopus oocytes identified KST1 as a slowly activating, voltage-dependent, inward rectifying K+ channel. The single channel current voltage curve was linear in the range -160 to +20 mV, with a deduced single channel conductance of 7 pS in symmetrical 100 mM K+. This channel type, modulated by pH changes within the physiological range, required ATP for activation. In line with the properties of a K(+)-selective channel, KST1 was permeable to K+, Rb+ and NH4+ and excluded Na+ and Li+. Cs+ at submillimolar concentrations blocked the channel in a voltage-dependent manner. Related studies on potato guard cell protoplasts confirmed the biophysical characteristics of the kst1 gene product (KST1) in the heterologous expression system. Therefore, KST1 represents a major K+ uptake channel in potato guard cells.

Amino Acid Sequence↗
PubMed1982

Infertility and depression.

This is a preliminary report of an ongoing study of the relationship between unexplained infertility and depressive illness conducted by a team of two specialists: a gynecologist and a psychiatrist. Over a 3-year period, 16 cases of unexplained infertility and depressive illness were treated by the team. Nine of the cases received psychiatric treatment, consisting of pharmacotherapy with Amitriptyline and a limited number of psychotherapy sessions. The other seven cases terminated with the psychiatrist after the psychiatric evaluation. Three of the cases that received the psychiatric treatment became pregnant. Follow-up at the end of the 3-year period revealed that none of the 13 others (psychiatrically treated and untreated) had become pregnant. These preliminary data suggest that in cases of depression preceding the onset of unexplained infertility psychiatric treatment as described above increases reproductive capacity.

Adult↗
PubMed1980

A lithium clinic in a community mental health center.

A community mental health center established a group lithium clinic to introduce a medical model of treatment for manic-depressive patients and to reduce staff time in caring for these patients. Clinical maintenance consisted of a monthly group meeting with a psychiatrist and a social worker; the social worker led general discussions on symptomatology, the toxic side-effects of lithium, and the importance of medication compliance, while the psychiatrist reviewed the effectiveness of the pharmacotherapy with each patient individually. Drug compliance was good, and patients seemed pleased to discuss their problems with others having similar diagnoses. Most patients ended or reduced visits to their therapists, and staff time spent on lithium-taking patients was greatly reduced.

Adult↗