Lambert-Eaton Myasthenic Syndrome (LEMS) is a neuromuscular disorder characterized by muscle weakness in which the motor nerve has difficulty releasing enough neurotransmitter to cause muscle contraction. Through clinical trials, 3,4-diaminopyridine (DAP) has been shown to successfully treat LEMS by increasing muscle contraction and strength. However, the precise effect of DAP on synaptic facilitation (an increase in transmitter release seen during high frequency stimulation) is not well understood. Here a well described neuromuscular synaptic preparation and a selective neurotoxin is used to model LEMS. Using the cutaneous pectoris muscle of the leopard frog (Rana pipiens), the electrical response of muscle cells to various frequencies of synaptic stimuli was measured using intracellular recording methods. The amplitude of muscle cell response to the nerve stimuli was used as an assay of neurotransmitter release in both LEMS-like and control (low calcium) conditions. The data indicate that, as expected, DAP increases the amount of neurotransmitter released in both control and LEMS conditions, but decreases the degree of facilitation in both conditions. The preliminary results are not sufficient to determine whether DAP causes a higher level of facilitation in LEMS conditions than in the control (low calcium) conditions. The collected data are a foundation for the continued studies on the mechanism of action of DAP, and the functional arrangement of synaptic proteins in a model synapse.

The plant genus Saintpaulia (African violet) is endemic to a small area in northeastern Tanzania and has undergone a recent radiation producing species which are difficult to distinguish morphologically. Previous molecular work identified a group of eleven species of the ionantha complex that are indistinguishable using sequence analysis of the internal transcribed spacer (ITS) of the ribosomal DNA gene. Exon 2 of the chalcone synthase (CHS) gene was PCR amplified producing 21 sequences from Sa. ionantha and 11 sequences from four other Saintpaulia species. The genus Saintpaulia contains two CHS genes (SaCHSA and SaCHSD). SaCHSD was used to construct a gene tree of six species. The sequence analysis clearly distinguishes four of the five closely related species of the ionantha complex.

The naturally occurring auxin, indole-3-acetic acid (IAA), and IAA-amino acid conjugates were compared to the synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) for triggering somatic embryogenesis in carrot cells. Somatic embryos triggered by 2,4-D treatment may be a suitable model system for studying embryogenesis and embryo development. Use of 2,4-D avoids the challenges encountered with the use of IAA in tissue culture, but first it is essential to show that 2,4-D is an accurate substitute for the naturally occurring auxin. IAA or IAA-conjugates were substituted for the 2,4-D normally present in carrot cell culture medium. After 4 weeks the cells were transferred to medium without auxin. The cells were monitored to determine whether they formed somatic embryos exactly as cells do when taken off 2,4-D. Two of the conjugates tested exhibited the same effect on embryogenesis as 2,4-D. Embryos did not form in the presence of the auxin, but did form when the auxin was denied. With one conjugate or with IAA embryos formed in the presence of the auxin suggesting that auxin levels were too low to prevent embryo formation. With two other conjugates the cells apparently lost their ability to form embryos.