UNC-73 activates the Rac GTPase and is required for cell and growth cone migrations in C. elegans.

unc-73 is required for cell migrations and axon guidance in C. elegans and encodes overlapping isoforms of 283 and 189 kDa that are closely related to the vertebrate Trio and Kalirin proteins, respectively. UNC-73A contains, in order, eight spectrin-like repeats, a Dbl/Pleckstrin homology (DH/PH) element, an SH3-like domain, a second DH/PH element, an immunoglobulin domain, and a fibronectin type III domain. UNC-73B terminates just downstream of the SH3-like domain. The first DH/PH element specifically activates the Rac GTPase in vitro and stimulates actin polymerization when expressed in Rat2 cells. Both functions are eliminated by introducing the S1216F mutation of unc-73(rh40) into this DH domain. Our results suggest that UNC-73 acts cell autonomously in a protein complex to regulate actin dynamics during cell and growth cone migrations.

Cloning by insertional mutagenesis of a cDNA encoding Caenorhabditis elegans kinesin heavy chain.

An additional genetic locus in Caenorhabditis elegans, unc-116, was identified in a screen for mutations resulting in defective locomotion. unc-116 was cloned by use of a transposon insertion mutant and the physical and genetic map of the genome. The cDNA sequence predicts an 815-amino acid protein. Based upon sequence comparison and secondary structure predictions, unc-116 encodes all three domains of the kinesin heavy chain: the motor, stalk, and tail. While the motor and tail domains have a high degree of identity to the equivalent domains of cloned kinesin heavy chains, the rodII domain of the stalk is significantly shorter than those previously reported and is not predicted to form a coiled-coil alpha-helix. Analysis of mutational defects in two C. elegans genes encoding anterograde motor molecules, unc-116 and unc-104, should provide insight into the in vivo functions of these members of the kinesin heavy chain superfamily.

C-fos expression in the pons and medulla of the cat during carbachol-induced active sleep.

Microinjection of carbachol into the rostral pontine tegmentum of the cat induces a state that is comparable to naturally occurring active (REM, rapid eye movement) sleep. We sought to determine, during this pharmacologically induced behavioral state, which we refer to as active sleep-carbachol, the distribution of activated neuron within the pons and medulla using c-fos immunocytochemistry as a functional marker. Compared with control cats, which were injected with saline, active sleep-carbachol cats exhibited higher numbers of c-fos-expressing neurons in (1) the medial and portions of the lateral reticular formation of the pons and medulla, (2) nuclei in the dorsolateral rostral pons, (3) various raphe nuclei, including the dorsal, central superior, magnus, pallidus, and obscurus, (4) the medial and lateral vestibular, prepositus hypoglossi, and intercalatus nuclei, and (5) the abducens nuclei. On the other hand, the mean number of c-fos-expressing neurons found in the masseter, facial, and hypoglossal nuclei was lower in carbachol-injected than in control cats. The data indicate that c-fos expression can be employed as a marker of state-dependent neuronal activity. The specific sites in which there were greater numbers of c-fos-expressing neurons during active sleep-carbachol are discussed in relation to the state of active sleep, as well as the functional role that these sites play in generating the various physiological patterns of activity that occur during this state.

[Treatment of diarrheic disease at home. Comparison of 2 forms of oral solutions: liquid and concentrated in small bags]. / Tratamiento de la enfermedad diarreica en el hogar. Comparación de dos presentaciones de suero oral: líquida y concentrada en sobres.

One hundred children, ranging in ages from a month to a year, with acute diarrhea who were treated at home following the basic standard recommendations, were studied. In order to prevent dehydration, half of the children were given oral solution (OS) containing the concentrated official formula in packets (group A), and the remaining half was given a commercially prepared ready-to-use OS (group B). During the treatment period, two house calls were made and the third day the patient was asked to come in for a check-up at the hospital. The clinical and socioeconomic characteristics were similar in both groups. The majority of parents made some reference to the "salty" taste of their OS, while only a few thought it has a sweet taste. In Group B, there were greater numbers of relatives who did not wash their hands before administering the OS and did it through bottles. A reminder was given on suggestive signs of dehydration expected, during the second home visit, although they were few. In both groups the average amount of OS administered was greater than 40 mL/kg/24 hours. The majority of the patients gained weight during the treatment. Four patients showed signs of slight dehydration (three from group A and one from group B). The OS's bacteriologic examination was positive for enteropathogens in 16% of the samples from group A and in 5% from group B. The average time the diarrhea continued was similar for both groups. Sodium concentration ranged from 60 to 120, potassium from 15 to 30 mmol/L, in 85% of those cases in group A and 98% in group B.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiology of ethanol on central neurons.

With respect to the theme of this volume, the results of our recent studies on three neuronal model systems point to several relevant conclusions: ethanol may interact electrophysiologically with certain anesthetics such as urethane; ethanol can selectively enhance responses to certain neurotransmitters; resting membrane properties of individual neurons show a wide range of sensitivities to ethanol and are generally fairly insensitive; the synapse--independent of specific transmitters--seems most sensitive to ethanol. As regards the first point, it has long been known that ethanol and anesthetics have features in common, including the ability to alter the lipid components of biological membranes (see R. A. Harris et al., L. L. M. van Deenen et al., M. J. Hudspith et al., E. Rubin et al., and C. C. Cunningham & P. I. Spach in this volume), so interactions between the two are not unexpected. However, our electrophysiological findings suggest great caution and appropriate controls be used in in-vivo studies of anesthetized animals, as the interactions derived may actually reverse the usual effect of ethanol. The enhancement of responses to ACh and SS (second point) might be assumed to arise postsynaptically in the target cells recorded and are seen with low, intoxicating doses of ethanol. Whether this potentiation involves enhancement of specific agonist binding to the receptor or facilitation of the function of the ionic channel linked to the receptor remains to be determined. It is not hard to imagine that ethanol could perturb membrane properties near receptors, to alter their conformation and ligand binding, or perhaps even uncover hidden receptors. The relative insensitivity of the resting membrane properties (third point) may suggest that membrane channels responsible for these functions (e.g., 'leak' channels for Na+ and K+ ions) do not usually interact with the lipid components affected by ethanol, at least at low, 'intoxicating' ethanol concentrations. Finally, the reduction of synaptic potentials by ethanol may indicate a presynaptic locus of action, as the response to the transmitter for at least one of these synaptic potentials (GABA) was not altered. These data would seem to indicate that synaptic release of the transmitter is reduced by ethanol, at least in the hippocampal slice. The high sensitivity of this presynaptic element for ethanol could indicate that the machinery for synaptic release, such as conductances for calcium entry (see REF. 39) or the action of second messenger systems (e.g., those leading to synapsin phosphorylation) are particularly sensitive to ethanol.(ABSTRACT TRUNCATED AT 400 WORDS)

Somatostatin selectively enhances acetylcholine-induced excitations in rat hippocampus and cortex.

The neuronal effects of somatostatin-14 (SS-14) and its influence on responses to acetylcholine (AcCho) were studied in vivo in the rat parietal cortex and dorsal hippocampus, using single-unit recording and microiontophoresis. SS-14 inhibited spontaneous firing of nearly all cells tested, while AcCho facilitated their firing. In contrast to its direct slowing effect, sustained iontophoretic application of SS-14 enhanced AcCho-induced excitations in 78% of all cells tested. This AcCho-enhancing effect of SS-14 was dose dependent. SS-14 did not enhance the responsiveness to pulses of the excitatory amino acid glutamate. Neurons tonically driven by iontophoretic currents of AcCho responded to concurrent pulses of SS-14 with an increase in firing. Thus, iontophoretic application of SS-14 can produce qualitatively different effects on the spontaneous activity of its target cells depending on the simultaneous effects of other chemical messengers. These condition-dependent interactions may explain the diverse neuronal effects of SS-14 reported in the literature.

Systemic ethanol: selective enhancement of responses to acetylcholine and somatostatin in hippocampus.

In rat hippocampal pyramidal cells tested in situ by iontophoresis of several neurotransmitters, ethanol significantly enhanced excitatory responses to acetylcholine and inhibitory responses to somatostatin-14 but had no statistically significant effect on excitatory responses to glutamate or inhibitory responses to gamma-aminobutyric acid or, in preliminary tests, to norepinephrine or serotonin. The effects of ethanol on responses to acetylcholine and somatostatin-14 may provide insight into synaptic mechanisms underlying the behavioral consequences of ethanol intoxication.

Substance P-like immunoreactivity is present in the central nervous system of Limulus polyphemus.

The distribution of substance P-like immunoreactivity (substance P-li) in the central nervous system of Limulus polyphemus was studied by using indirect immunocytochemical techniques. Six bilaterally symmetrical pairs of cell clusters in the circumesophageal connectives and the subesophageal mass contain substance P-li. Two of those pairs are the source of a system of efferent fibers that is involved in the expression of circadian rhythms of photosensitivity by the lateral eye. Substance P-li-containing cells were also observed scattered along the length of the circumesophageal connectives, which contain abundant stained fibers and some terminals. Substance P-li fibers leave through the ventral and dorsal nerves of the posterior circumesophageal ring. The neuropil of the subesophageal mass contains an abundance of stained terminals. Immunoreactive fibers can be seen throughout the length of the two longitudinal connectives of the ventral cord, in discrete fiber tracts in the lateral edges of the interganglionic connectives, and in the dorsal and ventral nerves of abdominal ganglia 1-4. Each of these ganglia contains three pairs of substance P-immunoreactive cell body clusters: an anterolateral, a medial longitudinal, and a medial posterior cluster. Substance P-li fibers entering through the ventral (posterior) nerves form very distinctive fascicles in each side of the ganglia, giving off fibers throughout their length. The neuropil is filled with immunoreactive terminals distributed homogeneously. The anterolateral clusters of the abdominal ganglia may be involved in cardioregulation. The six pairs of clusters in the posterior circumesophageal ring, and perhaps some of those in the abdominal ganglia, are believed to constitute a neurosecretory system, projecting to multiple targets throughout the organism. This system is postulated to modulate various sensory inputs and motor activity, and could be driven by a circadian clock, as well as by other systems responsible for integrated organismic responses.

Neuropeptide modulation of photosensitivity. I. Presence, distribution, and characterization of a substance P-like peptide in the lateral eye of Limulus.

The lateral eye of Limulus is innervated by an efferent system of fibers containing a substance P-like peptide. They were detected and their distribution was studied using indirect immunocytochemical techniques and monoclonal and serum antibodies. These thin, efferent fibers travel up the optic nerve, cross the lateral plexus, and branch out profusely when reaching the ommatidial layer. Innervation is extended to more than one component of the ommatidia, including the pigment, retinular, and eccentric cells. Immunoreactive staining could be abolished by absorbing the antisera with as little as 1 microM synthetic substance P. The efferent character of the fibers was established by means of ligation experiments, a technique also used to determine their origin in the circumesophageal connectives. Radioimmunoassay with two different C-terminal serum antibodies confirmed the presence of substance P-like material in the eye in the amounts of 61.44 pg/micrograms of protein, or up to 18 ng/eye. Gel filtration chromatography of crude extracts of the lateral eye, followed by radioimmunoassay, revealed an elution pattern extremely similar but not identical to that of synthetic substance P. These results show that a system of efferent fibers containing a substance P-like peptide originates in cells in the circumesophageal ring and innervates the ommatidia of the lateral eye. Their distribution and origin suggest an involvement in the modulation of photosensitivity, as part of a larger, generalized, level-setting regulator that is driven by a circadian clock but can also be activated by other systems.

Neuropeptide modulation of photosensitivity. II. Physiological and anatomical effects of substance P on the lateral eye of Limulus.

A system of efferent substance P-like immunoreactive fibers innervates the ommatidia of the Limulus lateral eye. Thus, we tested the physiological effects of substance P on the lateral eye by measuring the electroretinogram, a population potential reflecting the photoreceptors' response to light, under different experimental conditions. Substance P had no direct effect on the photoreceptors, but it induced an increase in their responsiveness to test flashes of light. The latency, magnitude, and duration of this reversible modulatory effect was dose-dependent. The lateral eye displays an endogenous circadian rhythm in its responsiveness to light. Application of exogenous substance P in the daytime causes an immediate rise as well as an increase in the nocturnal peak, while injection of one of its antagonists (D-Pro2, D-Phe7, D-Trp9 substance P) in the afternoon retards the normal rise in sensitivity and reduces the nighttime levels. Passive incubation with substance P antibodies at midnight caused a drop to diurnal levels of photosensitivity. Short-term changes in photosensitivity, similar in their nature to the substance P-induced ones, were caused by arousing the subjects. Arousal had an effect on the ongoing circadian rhythm similar to that of substance P application. Thus, the substance P efferent system may regulate neural responsiveness in both a short-term, environmentally induced manner, as well as for level setting in a circadian fashion. The mechanism for substance P-induced increases in photosensitivity involves changes in ommatidial structure: contraction of distal pigment cells, resulting in an increased aperture, and contraction of the retinular cells and rhabdom, resulting in a wider diameter of the latter. These structural modifications result in a greater angle of acceptance and increased light quantum catch.