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M J Jaffe

Publications and source records attributed to M J Jaffe.

50 records · Page 3Linked to original sources
PubMed1973

Cholinesterases from plant tissues: I. Purification and characterization of a cholinesterase from mung bean roots.

A cholinesterase was purified 36-fold from mung bean (Phaseolus aureus) roots by a combination of differential extraction media and gel filtration. The enzyme could be effectively extracted only by high salt concentration, indicating that it is probably membrane-bound. Methods used for assaying animal cholinesterases were tested, two of which were adapted for use with the bean cholinesterase. The bean enzyme hydrolyzed choline and noncholine esters but showed its highest affinity for acetylcholine and acetylthiocholine. The pH optimum was 8.5 for acetylthiocholine and 8.7 for acetylcholine. The Michaelis constants were 72 and 84 mum for acetylcholine and acetylthiocholine, respectively. The cholinesterase was relatively insensitive to eserine (half-maximum inhibition at 0.42 mm) but showed high sensitivity to neostigmine (half-maximum inhibition at 0.6 mum). Other animal cholinesterase inhibitors were also found to inhibit the bean enzyme but most of them at higher concentrations than are generally encountered. Choline stimulated enzymatic activity. The molecular weight of the cholinesterase was estimated to be greater than 200,000, but at least one smaller form was observed. It is suggested that the large form of cholinesterase is converted to the smaller form by proteolysis.

Journal Article↗
PubMed1973

Cholinesterases from Plant Tissues: II. Inhibition of Bean Cholinesterase by 2-Isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine Carboxylate Methyl Chloride (AMO-1618).

2-Isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine carboxylate methyl chloride (AMO-1618) inhibits the activity of a cholinesterase isolated from mung bean (Phaseolus aureus) roots at concentrations comparable to those which retard growth and inhibit development of secondary roots of bean seedlings. Fifty per cent inhibition of the cholinesterase activity occurred at 0.21 mm. Inhibition of the cholinesterase is non-competitive and irreversible. The growth retardant seems to be a specific cholinesterase inhibitor since it has no effect on non-choline esterases.

Journal Article↗
PubMed1972

Rapid Respiratory Changes Due to Red Light or Acetylcholine during the Early Events of Phytochrome-mediated Photomorphogenesis.

Two millimeter long secondary root tips of etiolated mung bean (Phaseolus aureus) plants were given 4 minute consecutive treatments of darkness, red light, far red light, and acetylcholine during darkness. We studied the effects of these treatments on exogenous (H(+)) changes, ATP utilization, O(2) uptake, P(1) levels, and ATPase activity. Red light and acetylcholine increased the level of P(1), O(2) uptake, and exogenous H(+), but decreased ATP concentrations. Darkness and far red light caused the amount of ATP to increase and decreased the O(2) uptake and P(1) level. O(2) uptake of both excised root tips and isolated mitochondria was promoted by acetylcholine levels of the same order of magnitude that promoted the other photomimetic phenomena. ADP-O ratios indicated that acetylcholine did not cause an appreciable decrease in ATP synthesis. The total ATPase activity remained constant throughout all treatments. Ouabain caused no adhesion to negatively charged glass in the dark, while the inhibitors valinomycin, atractyloside, digitoxin, gramicidin, and oligomycin caused immediate adhesion. All of the inhibitors prevented release from the glass. In red light ouabain increased adhesion, whereas the other inhibitors caused caused immediate and complete adhesion.These data seem to imply that one of the functions of the phytochrome-mediated response to red light in roots, regulated by acetylcholine, is to cause the rapid utilization of ATP pools; far red light appears to inhibit this utilization.

Journal Article↗
PubMed1972

Migration of Calcium and Its Role in the Regulation of Seismonasty in the Motor Cell of Mimosa pudica L.

Volume and conformational changes of the contractile tannin vacuoles of the abaxial motor cells of the primary pulvinus of Mimosa pudica L. parallel the seismonastic leaf movement. Since such changes in cells and organelles of animal systems are often regulated by calcium, we studied Ca(2+) movement in the motor cells and tissue. By fixation with Lillie's neutral buffered formalin, followed by staining with alizarin red sulfate (ARS), calcium was localized in the tannin vacuoles of the motor cells of the primary pulvinus. After treatment with ethylenediaminetetraacetate, 8-hydroxyquinoline, and several other calcium-complexing or extracting agents, the color reaction due to alizarin red sulfonate was no longer present. By using an analytical method, it was shown that the effluent from stimulated pulvini has significantly more Ca(2+) than that from unstimulated controls. Ten millimolar LaCl(3) inhibits recovery of the tannin vacuole in vivo in 10 mm CaCl(2) or in distilled water. Quantitative data obtained by microspectrophotometry demonstrated calcium migration during the bending movement of the primary pulvinus. In the adaxial motor cells a small amount of calcium migrates from the tannin vacuole, and calcium on the cell wall moves to the central vacuole. In the abaxial half, a large amount of calcium from the tannin vacuole moves to the central vacuole of the motor cell. It is probable that the calcium binds to the microfibrillar contents of the central vacuole. These observations support the contention that Ca(2+) migrates between the surface of the tannin vacuole and the inside of the central vacuole. The recovery and maintenance of the tannin vacuole in the spherical form may play a role in maintaining turgor in the motor cells of the abaxial half of the primary pulvinus of Mimosa.

Journal Article↗
PubMed1970

Physiological Studies on Pea Tendrils: VI. The Characteristics of Sensory Perception and Transduction.

Tendrils may be said to possess a sense of touch, and the direction and amplitude of the coiling response can be used to define the characteristics of this sense. These characteristics are, first, that the tendril will coil only in response to ventral mechanical stimulation, that this coiling can be inhibited by subsequent dorsally presented stimulation, and that dorsal stimulation alone causes no coiling. This phenomenon seems to be due to some asymmetry in the response system. Second, the nature of the response is always determined by the location (i.e., dorsal or ventral) of the last stimulation the tendril experienced. Third, the ability of dorsally presented stimulation to reverse ventrally stimulated coiling is gradually lost. Complete escape from reversibility is attained if the interval between ventral and dorsal stimulation reaches 9 minutes. Fourth, the magnitude of response is determined by both the number and the frequency of the stimuli. Both ventrally stimulated coiling and dorsally stimulated inhibition of coiling can be temporarily stopped by a 9-minute cold break at 10 C, given immediately after stimulation. As soon as the tendrils are restored to room temperature, they proceed to respond to the stimulus.The pulling ability of the tendrils generated by contact coiling, as measured by an electronic monitoring system, is of the order of 6 milligrams per minute. Whenever these two factors have been compared, pulling weight parallels contact coiling, regardless of treatment.The relationship between the stimulus and the response appears to follow rules very similar to those followed by various sensory response systems in animals. It is therefore proposed that many of these systems may have functional characteristics in common.

Journal Article↗
PubMed1970

Physiological Studies on Pea Tendrils: VII. Evaluation of a Technique for the Asymmetrical Application of Ethylene.

A technique has been devised for the asymmetrical application of ethylene to specific surfaces of plant tissue. 2-Chloroethylphosphonic acid (CEPA) was dissolved in a phosphate buffer (pH 6.5) containing Tween-20 or dimethylsulfoxide as adjuvant. Ethylene evolution from tendrils of Pisum sativum cv. Alaska was greater during coiling than when they were at rest; and via topical application to the ventral surface, CEPA was able to stimulate contact coiling. Within 1 day of application of CEPA, the tendrils showed symptoms of senescence. It is concluded that ethylene participates in the control of contact coiling stimulated by touch, and it is suggested that this control may be exerted via permeability changes in the membranes of the motor cells.

Journal Article↗
PubMed1970

Evidence for the regulation of phytochrome-mediated processes in bean roots by the neurohumor, acetylcholine.

Using pharmacological and chromatographic techniques, it was shown that acetylcholine was present in all organs of both light- and dark-grown mung bean seedings (Phaseolus aureus). The highest concentrations were found in tissues containing active growing points: buds and secondary roots. Within 4 minutes, red light caused an increase in the efflux of acetylcholine from secondary root tips as well as a significant increase in the endogenous titer. Four minutes of subsequent far red light reduced the latter to a level comparable to that in the dark.Acetylcholine, given for 4 minutes in the dark, was able to substitute for red light in reducing the formation of secondary roots, inducing increased H(+) efflux, and causing the root tips to adhere to a negatively charged glass surface. Acetylcholine-esterase and atropine inhibited the latter phenomenon, whereas eserine inhibited the far red-induced release from glass. THESE AND OTHER DATA SUPPORT THE CONCLUSION THAT ACETYLCHOLINE FUNCTIONS IN MUNG BEAN ROOTS AS IT DOES IN ANIMAL SYSTEMS: by mediating changes in ion flux across cell membranes. It also seems probable that acetylcholine acts as a local hormone which regulates these phytochrome-mediated phenomena.

Journal Article↗
PubMed1968

Phytochrome-mediated bioelectric potentials in mung bean seedlings.

Excised root tips from dark-grown mung bean seedlings (Phaseolus aureus) that adhere to a negatively charged glass surface when irradiated with red light and release when irradiated by far-red light develop a positive bioelectric potential (about 1.0 millivolt) at the tip in red light and a negative bioelectric potential in far-red light. The sign of the bioelectric potential was repeatedly photo-reversible, and the adhesion and release kinetics were similar to those of the development of the bioelectric potentials. Photoconversion of the phytochrome holochrome perhaps changes permeability characteristics of the cell membrane, resulting in an induced localized electrochemical gradient manifested as a bioelectric potential. This supports the view that phytochrome in situ is membrane bound.

Evoked Potentials↗
PubMed1968

Physiological studies on pea tendrils. V. Membrane changes and water movement associated with contact coiling.

The coiling of excised pea tendrils in response to mechanical stimulation is accompanied by an increased efflux from their cut bases of electrolytes and label from previously absorbed (14)C-acetate and (14)C-sucrose. The major excreted cation is H(+); H(+) loss is potentiated by pretreatment with benzoic acid, which also leaves the tendrils during coiling.Label from previously absorbed tritiated water is excreted during coiling, mainly from the ventral side of the tendril, which contracts in the initial phase of coiling. Such label does not pass from the ventral to the dorsal side. Similarities between this and other rapidly moving systems in plants are surveyed and a hypothesis to explain turgor movements is advanced.

Journal Article↗
PubMed1967

Physiological Studies on Pea Tendrils. IV. Flavonoids and Contact Coiling.

Pea tendrils contain high concentrations of flavonoids, mainly quercetin-triglucosyl-p-coumarate (QGC). QGC is most abundant near the highly responsive apex of the tendril, and least abundant at the base. After mechanical stimulation, and during coiling of the tendril, the QGC titer drops to about 30% of its original value. The kinetics of flavonoid disappearance are significantly correlated with the kinetics of coiling.Aqueous extracts of unstimulated pea tendrils or 10 mum QGC inhibit contact coiling of excised tendrils. Extracts of coiled tendrils do not. The evidence indicates a possible regulatory role for flavonoids in contact coiling.

Journal Article↗
PubMed1966

Physiological studies on pea tendrils. I. Growth and coiling following mechanical stimulation.

Unbranched tendrils arising from the fifth node of light grown Alaska pea plants were found to reach maturity at the age of 10 days. Such tendrils, when stroked, coiled rapidly. They remained maximally irritable for at least 3 days.Coiling was separable into 2 components, curvature (measured in degrees) and elongation. Coiling reached a maximum from one-half to 3 hours after tactile stimulation. This maximum is followed by a decrease, then by a further increase up to 48 hours.The optimum temperature range for curvature was 16 to 30 degrees after 2 hours and 16 to 20 degrees after 20 hours. Curvature was minimal and elongation optimal at a pH of 6.6. Both curvature and elongation were greater in white light than in darkness.Severing the dorsal vascular bundles decreased coiling, whereas severing the ventral bundles had no effect. Amputation of the tip of an excised tendril increased curvature but decreased elongation. In some cases, coiling of tendrils in situ was followed by curvature of the subjacent stem.Various growth substances produce effects on elongation and curvature of tendrils in vitro, in light and dark. CCC and GA decrease curvature in the light and increase curvature in the dark and elongation in the light and in the dark. Kinetin decreases curvature in the light, increases it slightly in the dark and has no effect on elongation. IAA increases elongation in the light and in the dark at concentrations above 10(-6)m. At lower concentrations, curvature was increased in the light and decreased in the dark.These data are discussed with a view towards explaining the coiling event.

Journal Article↗
PubMed1966

Physiological Studies on Pea Tendrils. II. The Role of Light and ATP in Contact Coiling.

Excised pea (Pisum sativum L.) tendrils incubated in the light coil more than those incubated in the dark. This light effect, which displays spectral responses characteristic of chlorophyll-mediated mechanisms, is increased by at least 8 hours of prior dark incubation of plants from which the tendrils were derived. Considerable evidence indicates a major role of ATP in coiling. For example, inhibitors of ATP production decrease contact coiling. Exogenous ATP increases curvature in the dark, whereas exogenous adenosine, AMP and ADP are practically without effect. The ATP effect can be reversed by the addition of sucrose to the bathing solution. Tendrils of plants placed in the dark overnight have lower ATP levels than those held in the light. One half hour after stimulation, the endogenous ATP level of tendrils on plants kept in the light decreased fourfold. In the same period, the endogenous inorganic phosphate level increased markedly, indicating high adenosine triphosphatase activity.Curvature is proportional to the logarithm of the molarity of applied ATP between 10(-4) and 10(-2)m, whereas elongation responds only to the higher dosages. It is inferred that endogenous ATP is involved as an energy source in coiling, especially in the initial phase, which involves contraction of the tendril. The existence of a higher plant analog of actomyosin, suggested by others, is supported.

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