Biomedical subjects

N Melamed

Publications and source records attributed to N Melamed.

4 recordsLinked to original sources

PubMed1993

Visualization of synaptic structure and function with confocal microscopy: calcium fluctuations and oscillations.

This article summarizes the basic principles of confocal microscopy and how they can be employed to visualize synaptic structure and function. Optical 'sectioning' of living cells allows the examination of a large number of biological processes at different subcellular localities. Different fluorescent markers enable the study of processes in the extracellular, intracellular and membrane domains of the nerve cell. The excellent spatial resolution of confocal microscopy permits to study the changes in intracellular calcium concentration in single synaptic boutons, without a substantial interference from supporting cells. Intracellular calcium concentration shows coordinated fluctuations in space and periodic oscillations. Periodic oscillations can serve as time keeping devices in nerve terminals. Oscillations were previously observed also in the process of transmitter release. We speculate therefore that these calcium oscillations may be of significance, if the quantal transmitter release is governed by a sequence of calcium dependent steps, which have a different affinity for calcium.

Animals↗

PubMed1993

Confocal microscopy reveals coordinated calcium fluctuations and oscillations in synaptic boutons.

Calcium ions are one of the main factors regulating quantal transmitter release and thus synaptic transmission in the nervous system. Using confocal microscopy, fluorescent imaging with the calcium indicator Rhod-2, and time series analysis, we show that the levels of calcium ions inside single synaptic boutons of the lizard neuromuscular junction are not constant at rest, but undergo coordinated fluctuations in the space domain, which cover a large fraction of the synaptic bouton. Furthermore, oscillations in intracellular calcium were frequently observed in the time domain. Control experiments showed no coordinated fluctuations or oscillations at locations outside the synaptic boutons. Edge detection analysis showed that the coordinated fluctuations and oscillations were not due to movement artifacts. No coordinated fluctuations and oscillations were seen when similar measurements and analyses were performed on artificial fluorescent beads. A variance analysis was performed on artificial fluorescent beads and on synaptic boutons. The variance of the fluorescent signal at the synaptic boutons was larger than the variance in artificial beads with the same mean fluorescence. This extra variance was greatly reduced when the extracellular calcium concentration was decreased from 2.0 mM to 0.4 mM. We conclude that the coordinated fluctuations and oscillations in the calcium-induced fluorescence at the synaptic boutons are genuine biological phenomena and may be of significance in the regulation of transmitter release.

Animals↗

PubMed1984

Cerebellar hemorrhage. A review and reappraisal of benign cases.

We reviewed 17 cases of cerebellar hemorrhage that occurred in our institutions over a five-year period. Nine of these patients had a benign immediate outcome, recovering without surgery. One patient died four weeks later of septicemia. We reviewed the clinical and radiological features of benign cases from our institutions and from the literature. Our results indicate that there is no single determinant that will confidently predict such a benign outcome in a given patient. The size of the hemorrhage, its location, and the level of consciousness of the patient had no consistent bearing on outcome. However, marked hydrocephalus or deteriorating level of consciousness indicated a poor prognosis, irrespective of the choice of therapy. Benign outcomes were not confined only to those who were alert or had small laterally placed hemorrhages. We were able to identify unequivocal hypertension, preceding the hemorrhage, in only four of our 17 patients.

Adult↗

PubMedDate not supplied

Confocal microscopy of the lizard motor nerve terminals.

Confocal imaging was performed on the ceratomandibularis nerve muscle preparation of the lizard Anolis carolinensis, using 4-Di-2-ASP as a fluorescent probe. The imaging system consisted of a Sarastro Phoibos 1000 (Molecular Dynamics) scanning system and a Zeiss Universal microscope. The data were analyzed using the VANIS set of programs on a Silicon Graphics Personal Iris computer. A three dimensional reconstruction of the nerve terminals was performed using look-through and depth-coded projections. The volume of the nerve terminal was estimated in 15 neuromuscular junctions and found to be 84,835 microns 3 (+/- 8558 SEM). The largest diameter in each one of the 178 individual boutons was estimated from the look-through projections of 17 nerve terminals in 9 preparations. It was found to be 4.71 microns (+/- 0.08 SEM). The diameter perpendicular to the largest diameter in the same projection at 0 degrees was 3.3 microns (+/- 0.054 SEM). Thus it seems that the synaptic boutons of the ceratomandibularis are suitable for combined optical and electrophysiological recordings.

Animals↗