Biomedical subjects

L Lifshitz

Publications and source records attributed to L Lifshitz.

4 recordsLinked to original sources

PubMed2001

Insulin action on GLUT4 traffic visualized in single 3T3-l1 adipocytes by using ultra-fast microscopy.

A novel imaging technology, high-speed microscopy, has been used to visualize the process of GLUT4 translocation in response to insulin in single 3T3-L1 adipocytes. A key advantage of this technology is that it requires extremely low light exposure times, allowing the quasi-continuous capture of information over 20-30 min without photobleaching or photodamage. The half-time for the accumulation of GLUT4-eGFP (enhanced green fluorescent protein) at the plasma membrane in a single cell was found to be of 5-7 min at 37 degrees C. This half-time is substantially longer than that of exocytic vesicle fusion in neuroendocrine cells, suggesting that additional regulatory mechanisms are involved in the stimulation of GLUT4 translocation by insulin. Analysis of four-dimensional images (3-D over time) revealed that, in response to insulin, GLUT4-eGFP-enriched vesicles rapidly travel from the juxtanuclear region to the plasma membrane. In nontransfected adipocytes, impairment of microtubule and actin filament function inhibited insulin-stimulated glucose transport by 70 and 50%, respectively. When both filament systems were impaired insulin-stimulated glucose transport was completely inhibited. Taken together, the data suggest that the regulation of long-range motility of GLUT4-containing vesicles through the interaction with microtubule- and actin-based cytoskeletal networks plays an important role in the overall effect of insulin on GLUT4 translocation.

3T3 Cells↗

PubMed1997

Quantitative digital analysis of diffuse and concentrated nuclear distributions of nascent transcripts, SC35 and poly(A).

Digital imaging microscopy was used to analyze the spatial distribution and levels of newly synthesized RNA in relation to steady-state poly(A) RNA and to the splicing factor SC35. Transcription was monitored over time after microinjection of BrUTP and was detected using antibodies. Poly(A) RNA was detected with probes directly conjugated to fluorochromes, allowing direct detection of the hybrids. Objective methods were used to determine genuine signal. A defined threshold level to separate signal from noise was established for each nucleus. The nucleolus was used to determine poly(A) and SC35 background and the juxtanuclear cytoplasm was used for the BrUTP background. The remaining signal was segmented into high (concentrated) and low (diffuse) levels. Surprisingly, for all probes examined, most of the signal was not in concentrated areas, but rather was diffusely spread throughout the nucleoplasm. A minority (20-30%) of the SC35 signal was in concentrated areas ("speckles") and the rest was dispersed throughout the nucleoplasm. In addition, the concentrated areas had a mean intensity only twice the average. The amount and significance of the colocalization of the diffuse, or concentrated, areas of SC35 [or poly(A)] with BrUTP incorporation were analyzed. The image from one probe was translated with respect to the other in three dimensions to compare colocalization with random alignments. Both poly(A) and SC35 were found to have low colocalization with the total BrU signal. Sites of transcription were determined using an algorithm to find maxima of BrUTP signal within clusters. From 849 to as many as 3888 sites per nucleus were detected. A rim of hybridization to poly(A) coinciding with the nuclear envelope was eliminated by actinomycin treatment, suggesting that these transcripts were exiting from the nucleus. These results emphasize the importance of utilizing the full dynamic range of the image before drawing conclusions as to the distribution of nuclear components.

Algorithms↗

PubMed1992

Primary lymphoplasmacytoma of the conjunctiva.

We report the case of an 80-year-old patient with isolated lymphoplasmacytoma of the conjunctiva. Only five other such cases have been previously reported in the literature. In all six patients, the disease remained limited and no sign of systemic disease could be found after prolonged follow-up. As isolated plasmacytoma of the conjunctiva seems to be benign, treatment of such tumours should be conservative.

Aged↗

PubMedDate not supplied

Quantitative digital fluorography. Computer vs. human estimation of vascular stenoses.

Digital subtracted images of iodinated rods, incorporating accurately measured areas of eccentric stenosis were obtained. The average subjective estimations of fractional area reduction (211 readings each) by three experienced angiographers were compared with values obtained using an interactive computer algorithm using the densitometric data. Results were analyzed to identify major influences on accuracy, including iodine concentration, vessel width, absolute severity of the stenosis, and vessel orientation. While no single factor appeared to seriously affect human accuracy, computer readings were significantly influenced by the tilt of the vessel in relation to the x-ray beam. Various potential sources of error including beam hardening, stenosis geometry, and scattering are discussed and appropriate algorithm corrections suggested. The importance of the availability of a reliable and accurate method to quantify vascular stenosis and volume of stenotic material is stressed.

Absorptiometry, Photon↗