VGF: an inducible gene product, precursor of a diverse array of neuro-endocrine peptides and tissue-specific disease biomarkers.

The vgf gene (non-acronymic) is induced in vivo by neurotrophins including Nerve Growth Factor (NGF), Brain Derived Growth Factor (BDNF) and Glial Derived Growth Factor (GDNF), by synaptic activity and by homeostatic and other stimuli. Post-translational processing of a single VGF precursor gives raise to a varied multiplicity of neuro-endocrine peptides, some of which are secreted upon stimulation both in vitro and in vivo. Several VGF peptides, accounting for ∼20% of the VGF precursor sequence, have shown biological roles including regulation of food intake, energy balance, reproductive and homeostatic mechanisms, synaptic strengthening, long-term potentiation (LTP) and anti-depressant activity.

Embedding media for cryomicrotomy: an applicative reappraisal.

We reassess here the formulation of cryoembedding media in connection with recent developments in commercial cryomicrotomes. Water-based solutions of polyvinyl alcohols were our starting media, and each of 2 different polymers (56-98, MW approximately 195000; and 6-98, MW approximately 47000) showed a critical concentration for optimum sectioning. At higher or lower polymer concentrations, wrinkles and folds became apparent in tissue areas of sections, or in the sectioned embedding medium areas between tissues, respectively.

Equipment testing and tuning: the cold-knife cryomicrotome microm HM-560.

A major innovative feature of the Microm HM-560 cryomicrotome is the independent control of specimen and knife temperatures. We used such equipment with a variety of tissues, and fixation and freezing procedures. High-quality sectioning was reproducibly obtained using 1) a low temperature setting for the sectioning blade ("cold knife," about -33 degrees C); 2) a comparatively high temperature for the specimen; and 3) a suitable mounting medium, which would remain solid up to about 0 degrees C.