Biomedical subjects

S L Jacobson

Publications and source records attributed to S L Jacobson.

21 records · Page 2Linked to original sources

PubMed1970

Response properties of a sensory hair excised from Venus's flytrap.

Multicellular sensory hairs were excised from the leaf of Venus's flytrap, and the sensory cells were identified by a destructive dissection technique. The sensory layer includes a radially symmetrical rosette of 20-30 apparently identical cells, and the sensory cells are organized in a plane normal to the long axis of the sensory hair. The sensory cells were probed with intracellular glass electrodes. The resting membrane potential was about -80 mv, and the response to a mechanical stimulus consisted of a graded response and an "action potential." The action potential appears to be similar to the action potential which propagates over the surface of the leaf. In the absence of stimulation, the upper and lower membranes of a single sensory cell behave in an electrically symmetrical fashion. Upon stimulation, however, the upper and lower membranes become electrically asymmetrical. Limiting values for the response asymmetry were calculated on the hypothesis of an electrical model consistent with the histology of the sensory cells.

Action Potentials↗

PubMed1965

Receptor response in Venus's fly-trap.

The insect-trapping movement of the plant Dionaea muscipula (Venus's fly-trap) is mediated by the stimulation of mechanosensory hairs located on the surface of the trap. It is known that stimulation of the hairs is followed by action potentials which are propagated over the surface of the trap. It has been reported that action potentials always precede trap closure. The occurrence of non-propagated receptor potentials is reported here. Receptor potentials always precede the action potentials. The receptor potential appears to couple the mechanical stimulation step to the action potential step of the preying sequence. Receptor potentials elicited by mechanical stimulation of a sensory hair were measured by using the hair as an integral part of the current-measuring path. The tip of the hair was cut off exposing the medullary tissue; this provided a natural extension of the measuring electrode into the receptor region at the base of the hair. A measuring pipette electrode was slipped over the cut tip of the hair. Positive and negative receptor potentials were measured. Evidence is presented which supports the hypothesis that the positive and negative receptor potentials originate from independent sources. An analysis is made of (a) the relation of the parameters of mechanical stimuli to the magnitude of the receptor potential, and (b) the relation of the receptor potentials to the action potential. The hypothesis that the positive receptor potential is the generator of the action potential is consistent with these data.

Electrophysiology↗

PubMedDate not supplied

Localization of fibrillin-1 in the human term placenta.

OBJECTIVE: We determined the level of message for fibrillin-1, a single-stranded glycoprotein found in the elastic microfibrils of the extracellular matrix, in human placenta compared with other adult human tissues and localized the protein in the term human placenta. METHODS: Northern blot analysis using a cDNA specific for fibrillin-1 was used to compare message levels in several adult human tissues and placenta. Immunohistochemical staining, using a monoclonal antibody to human fibrillin-1, was used to visualize the site of fibrillin-1 in term human placenta. RESULTS: Larger amounts of message for fibrillin-1 were present in placenta than in any of the other tissues tested. Staining for fibrillin-1 was present in the villous stroma but not in the basement membranes, trophoblast cells, or in blood vessels of stem, mature intermediate, or terminal villi. CONCLUSIONS: Fibrillin-1 is distributed extensively in the villous stroma of the term human placenta and may contribute elastic properties to the placenta and basal plate required for an active uterus.

Adult↗