Showing papers by "University of Maryland, Baltimore published in 1968"

The Influence of H+ on the Membrane Potential and Ion Fluxes of Nitella

Abstract: The resting membrane potential of the Nitella cell is relatively insensitive to [K]o, but behaves like a hydrogen electrode. K+ and Cl- effluxes from the cell were measured continuously, while the membrane potential was changed either by means of a negative feedback circuit or by external pH changes. The experiments indicate that PK and PCl are independent of pH but are a function of membrane potential. Slope ion conductances, GK, GCl, and GNa were calculated from efflux measurements, and their sum was found to be negligible compared to membrane conductance. The possibility that a boundary potential change might be responsible for the membrane potential change was considered but was ruled out by the fact that the peak of the action potential remained at a constant level regardless of pH changes in the external solution. The conductance for H+ was estimated by measuring the membrane current change during an external pH change while the membrane potential was clamped at K+ equilibrium potential. In the range of external pH 5 to 6, H+ chord conductance was substantially equal to the membrane conductance. However, the [H]i measured by various methods was not such as would be predicted from the [H]o and the membrane potential using the Nernst equation. In artificial pond water containing DNP, the resting membrane potential decreased; this suggested that some energy-consuming mechanism maintains the membrane potential at the resting level. It is probable that there is a H+ extrusion mechanism in the Nitella cell, because the potential difference between the resting potential and the H+ equilibrium potential is always maintained notwithstanding a continuous H+ inward current which should result from the potential difference.

Influenza antibody in human respiratory secretions after subcutaneous or respiratory immunization with inactivated virus.

Abstract: STUDIES with human volunteers have shown that experimental infection with influenza virus is a better stimulus of antibody in respiratory secretions than is subcutaneous immunization with inactivated vaccine, although both procedures result in the production of similar concentrations of serum antibody1,2. The work reported here was undertaken to determine if administration of inactivated virus vaccine through the respiratory tract provokes a similar antibody response in respiratory secretions.

The dual effect of lithium ions on sodium efflux in skeletal muscle.

Abstract: Sartorius muscle cells from the frog were stored in a K-free Ringer solution at 3°C until their average sodium contents rose to around 23 mM/kg fiber (about 40 mM/liter fiber water). Such muscles, when placed in Ringer's solution containing 60 mM LiCl and 50 mM NaCl at 20°C, extruded 9.8 mM/kg of sodium and gained an equivalent quantity of lithium in a 2 hr period. The presence of 10-5 M strophanthidin in the 60 mM LiCl/50 mM NaCl Ringer solution prevented the net extrusion of sodium from the muscles. Lithium ions were found to enter muscles with a lowered internal sodium concentration at a rate about half that for entry into sodium-enriched muscles. When sodium-enriched muscles labeled with radioactive sodium ions were transferred from Ringer's solution to a sodium-free lithium-substituted Ringer solution, an increase in the rate of tracer sodium output was observed. When the lithium-substituted Ringer solution contained 10-5 M strophanthidin, a large decrease in the rate of tracer sodium output was observed upon transferring labeled sodium-enriched muscles from Ringer's solution to the sodium-free medium. It is concluded that lithium ions have a direct stimulating action on the sodium pump in skeletal muscle cells and that a significantly large external sodium-dependent component of sodium efflux is present in muscles with an elevated sodium content. In the sodium-rich muscles, about 23% of the total sodium efflux was due to strophanthidin-insensitive Na-for-Na interchange, about 67% being due to strophanthidin-sensitive sodium pumping.

Quantitative studies of superior cervical sympathetic ganglia in a variety of primates including man. I. The ratio of preganglionic fibers to ganglionic neurons

Abstract: Estimates of the number of ganglionic neurons of superior cervical sympathetic ganglia and the number of preganglionic axons in the trunks just caudal to these ganglia were obtained from a sample of primates that included: man, chimpanzee, baboon, stump-tailed macaque, rhesus monkey, and squirrel monkey. The number of ganglionic neurons ranged from 63,625 in a squirrel monkey ganglion to 1,041,652 neurons in a human ganglion. Estimates of the number of preganglionic fibers varied between 2,285 in a cervical sympathetic trunk of a squirrel monkey and 12,008 in a human specimen. The resulting ratios of preganglionic fibers to ganglionic neurons ranged from 1:28 in a squirrel monkey ganglion to 1:196 in a human ganglion. The data reported in this study reveal considerable variation in the ratio of pre- to post-ganglionic neurons, and as was noted in regard to the number of cells in the ganglion, the ratios of ganglionic to preganglionic neurons appear to increase as a function of body size. In contrast, the number of preganglionic fibers does not increase as strikingly with body size, but varies greatly in the same species. The resulting ratio between the two orders of neurons is, therefore, less predictable than the number of ganglionic neurons in any given ganglion.

Coupling and Selectivity of Sodium and Potassium Transport in Squid Giant Axons

Abstract: O u r purpose in this paper is to present some experimental findings that have a bear ing on the t ransport of sodium a nd potassium across the m e m b r a n e of the squid giant axon. As in a variety of cellular types that actively t ranspor t sodium ions, a marked drop in the efflux of sodium ions from squid g iant axons occurs when potassium ions are removed from the external solution (CaldweU et al., 1960). As both sodium exit and potassium entry are susceptible to inhibi t ion by appl icat ion of cyanide and other metabol ic inhibitors, the implicat ion is tha t some form of coupling exists between K influx and Na efltux. CaldweU et al. (1960) observed that inject ion of arginine phosphate into cyanide-poisoned axons restored the coupling between K entry and Na exit. I n the experiments described here, a n a t tempt was made to vary the inside concentra t ion of sodium ions in squid giant axons a nd the outside concentra t ion of potassium and potassium-like ions ( R b + and Cs +) in order to study the influence of such variat ions on the coupled t ransport of sodium a nd potassium ions.

A single channel or a dual channel mechanism for nerve excitation.

Abstract: Dear Sir: Narahashi and Haas (1968) and HiUe (1968) have suggested that data obtained when various pharmacological agents are applied to nerve make it likely that the channels in the axon membrane that carry Na and K are separate entities in contrast with the suggestion that there is a single channel (MuUius, 1959) that modifies its selectivity first in favor of Na and later in favor of K. My purpose is to examine the assumptions underlying the analysis that has been made and to show that the evidence for two channels is not at present compelling. The models to be considered are shown below.

Dynamic asymmetries in the squid axon membrane.

Abstract: In 1952 Hodgkin and Huxley were able to separate the m e m b r a n e currents which occur in response to step changes in membrane potential, upon voltage c lamping the squid giant axon, into two major current components : an initial transient component mainly carried under normal conditions by sodium ions and a delayed component mainly carried by potassium ions. Tetrodotoxin ( T T X ) specifically blocks the initial current mechanism when applied externally (Narahashi et al., 1964; N a k a m u r a et al., 1965). However, internal application of T T X at the same concent ra t ion does not block the sodium current. At higher internal concentrations, it becomes effective (Narahashi et al., 1966). O n the other hand, in the squid axon, te t rae thylammonium ion (TEA) blocks the delayed current when applied internally (Tasaki and Hagiwara, 1957; Armstrong and Binstock, 1965; Armstrong, 1966). Whereas cesium ion is able to block the delayed outward steady-state current when applied internally (Chandler and Meres, 1965; Adelman and Senft, 1966), cesium ion has no effect on this current when applied externally (Pickard et al., 1964). T h e object of this paper is to examine in some detail interactions among the five readily available group IA metal cations in contributing to a n d / o r inhibiting membrane conductances when the concentrations of these ions are varied externally.

Observations on the Biology and Behavior of the Evergreen Bagworm Moth, Thyridopteryx ephemeraeformis (Lepidoptera: Psychidae)

Abstract: Females of Thyridopteryx ephemeraeformis (Haworth) usually oviposited in their own pupal cases, where the eggs remained in diapause until the following spring. Larvae, after emerging from the pupal cases and the parental bags, passed through 7 stadia in the laboratory, in about 3 months, in bags which they constructed. Exuviae were not eaten, but fell out of the bags or were pushed out by the larvae themselves. Ability to construct bags was limited to a brief period following eclosion. Positive phototropism apparently was involved in the reversal by last-instar larvae of their position in the bags, turning their heads toward the posterior bag openings. The pupal period averaged 18 days. Males emerged as active, free-flying moths; females, with vestigal mouthparts and legs, small eyes, and no antennae or wings, remained in the bags and became merely egg-filled sacs. Some, which had failed as larvae to reverse their position, did so upon becoming adult. This was necessary because pupal cases were only about half as long as the bags, and the bags were crisscrossed internally with larval silk which prevented the pupae from slipping to the posterior ends where the adult female would be accessible to the males. Mating, at best, was a difficult and complicated process; some males died clinging to the bags of receptive females which they had been unable to inseminate. Despite a sex ratio of about 1:1, only about 14% of the females were fertilized in the laboratory-reared generation. However, in nature, all the 21 females of the parent generation collected at Norman, Oklahoma, had been fertilized. Unfertilized eggs remained in the maternal body and appeared viable even a month or more after the parent's death, but eventually they degenerated. Adult longevity was 1–2 days for males, 4–9 days (average 8 days) for females.

The biometry of an isotope displacement immunologic microassay

Abstract: Bioassay micro techniques have been used widely in determining the potency of insulin as well as for estimating the strength of many other biological substances. The development of micro bioassay methods which rely on the antigenic specificity of the biological substance being assayed is an encouraging recent development. Such immunoassay procedures, which are both reliable and practical, appear to provide a general method for the measurement of many biological substances. The present study is concerned with certain biometric aspects of isotope displacement immunoassays. General principles associated with such assays are presented, and the primary sources of variation are discussed. A nonlinear statistical model, based upon the assumption of univalent antigen and a single order of antibody combining sites, is developed. Procedures are outlined and numerically illustrated for inverse point and interval estimation for this model. Specific examples illustrating the procedure are drawn from the diabetes and insulin literature. This is done because the procedure was first developed for assaying minute quantities of insulin and is most widely used for this purpose. However, it should be noted that the method has been successful in many other applications as well.

Familial thyroxine-binding globulin deficiency.

Abstract: A 6-year-old boy who was clinically euthyroid was found to have a low PBI and no detectable TBG in the serum. Two brothers had absent TBG and four other relatives had low TBG. This suggests an autosomal pattern of inheritance of the gene concerned with TBG.

The effects of some ions on the membrane potential of the giant axon of Myxicola

Abstract: The effects of various ions on the resting membrane potential of the giant axons of Myxicola were determined. The mean resting potential in artificial sea water is 69 mv, inside negative. The membrane potential decreases with incresing external potassium concentrations, while changes in the sodium and chloride concentrations have little or no effect. For potassium concentrations greater than 50 mM/L the relation between membrane potential and concentration approximates that of a perfectly selective potassium electrode. The data for the whole range of concentrations examined can be well fitted by the equation: It was pointed out that the Myxicola giant axons can be studied under space voltage clamp and can be made available in the laboratory for 12 months out of the year. Myxicola then should become a very useful preparation for the study of membrane phenomena.

A Laboratory Study of Feeding Habits of Melanoplus differentialis in Maryland (Orthoptera: Acrididae)

Abstract: Among the food plants offered to the differential grasshopper, Melanoplus differentialis (Thomas), Taraxacum officinale proved to be preferred. However, unlike many other forbivorous acridids, this grasshopper can also develop and reproduce by feeding on Gramineae only, although individuals reared exclusively on this diet were small. In addition to their normal green plant food, M. differentialis also feeds on entirely dried-up plants, even in the presence of fresh plants—an adaptation for survival during the hot, dry part of the year. The feeding habits of this grasshopper were greatly influenced, among other ecological factors, by its own behavior toward light and temperature, in addition to the physical features and orientation of the food plants themselves. Consequently, the plants actually used as food in nature may be very different from those the insect prefers. The mandibles of this species are typically of the forbivorous type, while the maxillae resemble those of Tetrix, the moss feeders. The ventral digestive caeca are always longer than the dorsal, and the proportions of anterior and posterior lobes of the caeca vary in different age groups. Other morphological variations in this organ also were noted. The mid-gut of adult M. differentialis was heavily infested by gregarines, which were seen in various stages of development in the alimentary canal. No detectable influence on the host was noticed; the host-parasite relationship is obscure.

Restoration of a Potassium-requiring Sodium Pump in Squid Giant Axons Poisoned with CN and Depleted of Arginine

Abstract: MICROINJECTION of high energy phosphate compounds such as ATP and phosphoarginine (ArgP) into CN-poisoned squid giant axons restores sodium extrusion to normal levels1. Only the latter compound, however, also restores the “K-free effect”, that is to say, a 30–70 per cent drop in sodium efflux when the axon is transferred to potassium-free seawater2. Furthermore, treatments resulting in intracellular ArgP breakdown without ATP breakdown (namely, incipient CN poisoning or partial poisoning with 2,4-dinitrophenol) abolish the K-free effect. Caldwell et al.3 considered two possible explanations for this observation: either ArgP itself plays a part in Na–K coupling, or a high axoplasmic ATP/ADP ratio is required for the K-free effect to occur. Injected ArgP continuously regenerates ATP from ADP, maintaining a high ratio, whereas injected ATP rapidly breaks down to ADP, thus lowering the ratio.

Carcinogens 3,4-benzpyrene and 3-methylcholanthrene: induction of mitochondrial oxidative enzymes.

Abstract: Sections of liver from rats injected with 3,4-benzpyrene and 3-methylcholanthrene, when incubated in mediums specific for the histochemical demonstration of mitochondrial oxidative enzymes, show greater activity of several of these enzymes than do sections from control rats. This observation was confirmed by comparison of the staining of mitochondria isolated from the control and from "induced" rats. The fact that an inhibitor of protein synthesis, actinomycin D, effectively diminished the stimulation provided evidence that the stimulation of activity is due to an increase in enzyme synthesis, generally called induction.