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Biomedical subjects

H Gainer

Publications and source records attributed to H Gainer.

At least 163 records · Page 9Linked to original sources
PubMed1976

Evidence for the local synthesis of a transmitter enzyme (glutamic acid decarboxylase) in crayfish peripheral nerve.

The activities of three enzymes of neurotransmitter metabolism (choline acetyl-transferase, CAT; acetylcholinesterase, AChE; and glutamic acid decarboxylase, GAD) were studied in normal, transected, and organ cultured crayfish nerves. CAT (to a lesses extent AChE) was dramatically decreased in activity when the nerve was cut proximal to the nerve cell bodies. GAD activity was unaffected by such procedures. In organ cultured nerve, where both motor and sensory axons degenerated, the CAT and AChE activities were virtually absent, whereas GAD activity remained close to normal levels. Inhibition of protein synthesis in cultured nerve caused the GAD activity to decrease rapidly. In view of these data, and the well documented fact that motor axons survive axotomy whereas sensory axons do not, a hypothesis that GAD is synthesized in the peripheral nerve is presented.

Acetylcholinesterase↗
PubMed1976

Rapidly transported proteins in sensory, motor and sympathetic nerves of the isolated frog nervous system.

The synthesis and rapid axonal transport of [35S]methionine-labelled proteins has been studied using the isolated frog spinal cord and peripheral nervous system. Polyaerylamide gel electrophoresis in sodium dodecylsulfate of synthesized and transported proteins revealed similar labelling patterns of proteins transported in the sensory, motor and sympathetic systems. The relative labelling pattern of transported proteins which accumulated at ligatures in peripheral nerves was different from those obtained from ganglia or nerves and roots when they were incubated in labelled methionine. When compared with methionine-labelled protein profiles of rapid axonal transport in other species and systems, a common set of rapidly transported proteins emerges. The approximate molecular weights of these common proteins include (in 1000 daltons): 18,24-29, 34-36, 57, 65-68, 100 and 130. These proteins may represent fundamental macromolecules involved in the general maintenance of the function of nerve processes.

Animals↗
PubMed1976

Release of proteins from the inner surface of squid axon membrane labeled with tritiated N-ethylmaleimide.

Proteins in the inner surface of the squid axon membrane were labeled by intracellular perfusion of [3H]N-ethylmaleimide (NEM), which forms covalent bonds with free sulfhydryl groups. The excitability of the axon was unaffected by the [3H]NEM perfusion. After washout of the unbound label, the perfusate was monitored for the release of labeled proteins. Labeled proteins were released from the inner membrane surface by potassium depolarization of the axon only in the presence of external calcium ions. Replacement of the fluoride ion in the perfusion medium by various anions also caused labeled protein release. The order of effectiveness was SCN- greater than Br- greater than Cl- greater than F-. The extent of labeled protein release by the various anions was correlated with their effects on axonal excitability. The significance of these results is discussed.

Animals↗
PubMed1975

Molluscan gastrin: concentration and molecular forms.

Blood and gastrointestinal tissues of the sea hare Aplysia californica and the land snail Otala lactea contain immunoreactive gastrin in heterogeneous forms similar to those of mammals. The observation that blood concentrations in terms of porcine gastrin standard are comparable to those of pig, man, and dog suggests significant homology between the structures of molluscan and mammalian gastrins.

Animals↗
PubMed1975

Rapid transport of proteins in the sonic motor system of the toadfish.

A pure cholinergic, motor system of a marine fish has been utilized to study the kinetics and characteristics of proteins rapidly transported from the sonic motor nucleus to the musculature enveloping the swim bladder. Following microinjection of [3H]leucine, [3H]lysine, [35S]methionine, or [3H]fucose into the nucleus a wave of radioactivity was observed moving along the sonic motor nerves with an apparent rate of 96-120 mm/day. Analysis of the rapidly transported methionine-labeled protein using SDS gel electrophoresis revealed at least 9 major peaks of activity. Eight of these proteins were found to incorporate fucose, suggesting that most of the rapidly transported material consists of glycoproteins. These results are consistent with the previously suggested hypothesis relating the function of rapid transport to synaptic vesicles and the maintenance of pre-synaptic terminal membranes.

Air Sacs↗
PubMed1975

Low molecular weight specific proteins in identified molluscan neurons. I. Synthesis and storage.

Low molecular weight specific proteins in phenotypically distinct, identified neurons of Aplysia californica, have been detected using a high resolution acid-urea polyacrylamide gel system, and the molecular weight of these proteins labeled by in vitro incubation in [3H]leucine were determined by two different methods. The relative mobilities of these proteins on the acid-urea gel differed significantly, even though they appeared to co-electrophorese on SDS gelss. These identified neurons, and the specific proteins that they synthesize and store represent excellent model systems for the study of specific protein regulation in neurons.

Animals↗
PubMed1975

Low molecular weight specific proteins in identified molluscan neurons. II. Processing, turnover, and transport.

Three identified neurons (R14, R15, and L2-6) from Aplysia californica synthesize specific, low molecular weight proteins which are further processed or converted into smaller sized specific proteins. These specific proteins have differential turnover rates, and appear to be selectively transported out of the individual neuronal somata at different rates. The latter transport process can be blocked by colchicine, a well-known blocker of axonal transport. The relationship of these phenomena to the functional activity of the individual neurons is discussed.

Animals↗
PubMed1975

Studies on bursting pacemaker potential activity in molluscan neurons. I. Membrane properties and ionic contributions.

Bursting pacemaker potential (BPP) activity of identified molluscan neurons has been studied using cells from Aplysia and Otala. The results presented in this paper indicate that (1) a potassium conductance mediates the hyperpolarizing phase of the BPP; (2) the BPP amplitude is directly dependent on [Na+]0; (3) BPP activity requires the presence of divalent cations and is prevented by C02+ and La3+, but not D-600; (4) the apparent increase in membrane resistance during the depolarizing phase of the Bd can be accounted for by the movement of the membrane potential along the non-linear portion of the I-V curve; and (5) non-linear I-V relations and a minimal effective membrane resistance are pre-requisite to BPP generation. Coupled with recent observations on the presence of an inward current in these cells, the results suggest that the mechanisms underlying the BPP are similar to those proposed to describe the myocardial pacemaker potential: the hyperpolarizing phase is due to activation of a potassium conductance which slowly inactivates, resulting in a gradula deplorization until a voltage-dependent inward current is activated which then leads to an increasingly rapid deplorization and initiation of the burst of spikes. It would appear that Na+ may play the major role in carrying the inward current, although a secondary role for divalent cations cannot be discounted.

Action Potentials↗
PubMed1975

Studies on bursting pacemaker potential activity in molluscan neurons. II. Regulations by divalanet cations.

Identified cells in Aplysia (R15, R2, LPG) and cell 11 in Otala have been used to investigate the effects of divalent cations, temperature, pH and ouabain on neuronal activity. Divalent cations act primarily to regulate the appearance of bursting pacemaker potential (BPP) activity in these cells. These ions are necessary for B generation and will inhibit its appearance at high concentrations (Ca greater than Mg greater that greater than Sr). In addition, Ca is involved in the seasonal modulation of BPP activity in a neurosecretory cell in Otala. Monovalent cations play secondary roles as regulators of BPP activity by competing with divalent cations for the sites involved in the regulation of the (probable) monovalent conductances underlying BPPs. The effects of pH, temperature and ouabain on membrane properties and BPP activity are partly related to their interaction with divalent cations. The results described indicate important roles for divalent cations in the regulation of the expression of BPP activity and its underlying membrane properties both in different nerve cells and in the same cell during dormancy and activity of the snails.

Animals↗
PubMed1974

Peptide regulation of bursting pacemaker activity in a molluscan neurosecretory cell.

Vasopressin and related peptides (10(-9) to 10(-6) molar) induced bursting pacemaker potential activity and altered the current-voltage relations of the membrane in a specific molluscan neurosecretory cell. These effects long outlasted the period of application of the peptides. Sensitivity of the cell to these peptides was primarily localized on the axon hillock region. The observed effects do not resemble conductance changes evoked by conventional neurotransmitters, but rather suggest a membrane regulatory role for these peptides, and thus may be indicative of a new form of information transfer in the nervous system.

Acetylcholine↗