Autonomic stimulation of short circuit current in swine trachea

Autonomic stimulation of ionic fluxes was studied in tracheal epithelium of weanling swine by measuring short circuit current (ISC) in an Ussing chamber. Basal currents were predominantly secretory since 0.1 mM diphenylamine 2-carboxylic acid (DPC) reduced currents by twice as much as did 10 microM amiloride. Both acetylcholine (ACh) and isoproterenol (ISO) produced a sustained increase in ISC, with the EC50 for ISO being 149 nM and for ACh being 500 nM. In both cases, the induced currents were predominantly secretory since 10 microM amiloride had little effect on either agonist-induced delta ISC whereas DPC inhibited the ISO- and ACh-induced delta ISC's by 30% and 47% respectively. However, responses to ACh and ISO could be distinguished on three grounds. [1] An anatomic gradient existed with smaller responses to agonists being observed towards the distal trachea. The ISO-induced currents showed a steeper gradient than the ACh-induced currents. [2] In single tissue samples, the size of the ISO-induced delta ISC was not correlated with the size of the ACh-induced delta ISC. [3] The magnitude of the delta ISC induced by ACh was unaffected by a concomitant stimulation of ISC by ISO. Thus, ACh-induced secretion was independent of ISO-induced secretion, and likely occurred in different cell types.     

Presentation of Sporothrix schenkii in pulmonary cytology specimens

Macrophages containing small ovoid intracytoplasmic yeast cells, surrounded by a slight "halo," were observed in Papanicolaou-stained smears of sputum submitted for cytologic examination from two patients with culture-confirmed pulmonary sporotrichosis. The cytologic findings are presented and discussed in relation to other pulmonary fungal infections and the appropriate stains to be used for their cytologic detection. The clinical symptoms of pulmonary sporotrichosis are nonspecific and may mimic those of tuberculosis or other diseases; the causative organism, Sporothrix schenkii, may remain undetected by routine microbiologic procedures unless there is cause to suspect the diagnosis. Sporotrichosis should be considered in the differential diagnosis when small ovoid intracellular yeast cells (2 microns to 4 microns in length) with an apparent "halo" are observed within macrophages in pulmonary cytology specimens; the recognition of these findings may aid in the diagnosis of this relatively rare disease.     

Hopping frequency in humans: a test of how springs set stride frequency in bouncing gaits.

The storage and recovery of elastic energy in muscle-tendon springs is important in running, hopping, trotting, and galloping. We hypothesized that animals select the stride frequency at which they behave most like simple spring-mass systems. If higher or lower frequencies are used, they will not behave like simple spring-mass systems, and the storage and recovery of elastic energy will be reduced. We tested the hypothesis by having humans hop forward on a treadmill over a range of speeds and hop in place over a range of frequencies. The body was modeled as a simple spring-mass system, and the properties of the spring were measured by use of a force platform. Our subjects used nearly the same frequency (the "preferred frequency," 2.2 hops/s) when they hopped forward on a treadmill and when they hopped in place. At this frequency, the body behaved like a simple spring-mass system. Contrary to our predictions, it also behaved like a simple spring-mass system when the subjects hopped at higher frequencies, up to the maximum they could achieve. However, at the higher frequencies, the time available to apply force to the ground (the ground contact time) was shorter, perhaps resulting in a higher cost of generating muscular force. At frequencies below the preferred frequency, as predicted by the hypothesis, the body did not behave in a springlike manner, and it appeared likely that the storage and recovery of elastic energy was reduced. The combination of springlike behavior and a long ground contact time at the preferred frequency should minimize the cost of generating muscular force.     

Uterine growth responses of the mature castrate rat to estradiol-17B

To examine estrogen-stimulated uterine growth we have monitored changes in uterine DNA synthesis, ornithine decarboxylase (ODC) activity and protein content as well as luminal epithelial (LE) cell mitotic index and ultrastructural changes. We have utilized this model to examine castrate mature rat uterine growth as a function of time between 18 and 40 hours following a single injection of 25.0 ug of estradiol-17B. LE cell mitotic index and protein content increases were maximally elevated as early as 18 hours postinjection while uterine ODC activity was maximal at 28 hours; uterine DNA synthesis increases continued throughout the experiment. In addition, the infusion of either 1 or 2 ug E2 plus progesterone over a 24 hour period, stimulated elevated ODC activity under both treatment regimens and LE cell mitotic index which was inversely related to E2 dose.     

Multiple types of voltage-dependent Ca2+-activated K+ channels of large conductance in rat brain synaptosomal membranes

K+-selective ion channels from a mammalian brain synaptosomal membrane preparation were inserted into planar phospholipid bilayers on the tips of patch-clamp pipettes, and single-channel currents were measured. Multiple distinct classes of K+ channels were observed. We have characterized and described the properties of several types of voltage-dependent, Ca2+-activated K+ channels of large single-channel conductance (greater than 50 pS in symmetrical KCl solutions). One class of channels (Type I) has a 200-250-pS single-channel conductance. It is activated by internal calcium concentrations greater than 10(-7) M, and its probability of opening is increased by membrane depolarization. This channel is blocked by 1-3 mM internal concentrations of tetraethylammonium (TEA). These channels are similar to the BK channel described in a variety of tissues. A second novel group of voltage-dependent, Ca2+-activated K+ channels was also studied. These channels were more sensitive to internal calcium, but less sensitive to voltage than the large (Type I) channel. These channels were minimally affected by internal TEA concentrations of 10 mM, but were blocked by a 50 mM concentration. In this class of channels we found a wide range of relatively large unitary channel conductances (65-140 pS). Within this group we have characterized two types (75-80 pS and 120-125 pS) that also differ in gating kinetics. The various types of voltage-dependent, Ca2+-activated K+ channels described here were blocked by charybdotoxin added to the external side of the channel. The activity of these channels was increased by exposure to nanomolar concentrations of the catalytic subunit of cAMP-dependent protein kinase. These results indicate that voltage-dependent, charybdotoxin-sensitive Ca2+-activated K+ channels comprise a class of related, but distinguishable channel types. Although the Ca2+-activated (Type I and II) K+ channels can be distinguished by their single-channel properties, both could contribute to the voltage-dependent Ca2+-activated macroscopic K+ current (IC) that has been observed in several neuronal somata preparations, as well as in other cells. Some of the properties reported here may serve to distinguish which type contributes in each case. A third class of smaller (40-50 pS) channels was also studied. These channels were independent of calcium over the concentration range examined (10(-7)-10(-3) M), and were also independent of voltage over the range of pipette potentials of -60 to +60 mV.(ABSTRACT TRUNCATED AT 400 WORDS)     

Chloroplast gene for Mr 32000 polypeptide of photosystem II in Euglena gracilis is interrupted by four introns with conserved boundary sequences

The gene for the Mr 32000 herbicide binding polypeptide of photosystem II has previously been mapped to the 5 kbp EcoRI fragment Eco I of Euglena gracilis chloroplast DNA. The nucleotide sequence of 3324 bp of Eco I, containing the psbA locus, has been determined. This locus encodes a polypeptide of 345 amino acids which is co-linear with, and has 86% derived amino acid sequence homology to sequences derived from four higher plants chloroplast psbA loci. The Euglena psbA gene contains four introns of size 435, 443, 434, and 617 bp. The four introns have conserved boundary sequences of the type previously described in the Euglena chloroplast gene (rbcL) for the large subunit of ribulose-1,5-bisphosphate carboxylase (Koller et al., Cell 36, 545-553, 1984).     

Historical changes in juvenile southern bluefin tuna Thunnus maccoyii growth rates based on otolith measurements

Suspected historic changes in juvenile southern bluefin tuna Thunnus maccoyii growth rates were investigated using otolith increment width data. Four hundred and ninety otoliths were selected from fish estimated to be between 1 and 41 years-old. The distance between the first five annuli were measured on the otoliths, giving estimates of otolith growth for age classes 1+ to 4+ years for fish spawned from the early 1960s to mid 1990s. The data showed that growth rates of juveniles (age 1+ and 2+ years) started to increase at around 1979–1980, and that growth continued to increase throughout the 1980s and early 1990s. Lee's phenomenon was not observed in the data. Correlation tests did not reveal clear relationships between annual otolith growth and regional environmental variables such as sea surface temperature or Southern Oscillation Index. The increase in otolith growth, however, was consistent with juvenile growth estimates obtained from other sources, and correlated with large-scale trends in population size and environmental conditions.