Stimulation-dependent alterations in peroxidase uptake at lobster neuromuscular junctions.

The uptake of cytochemically demonstrable horseradish peroxidase into small vesicles within nerve endings in lobster stretcher muscles can be enhanced by electrical stimulation of transmitter release by the endings. This is observed particularly if stimulation is interrupted periodically and the nerves

Plasma membrane: substructural changes correlated with electrical resistance and pinocytosis.

Inducers of pinocytosis in amoeba cause as much as a 50-fold decrease in the electrical resistance of the plasma membrane prior to the formation of the typical tunnels and vacuoles. In this state the thickness of the electron-transparent core or lamella of the unit membrane is at least twice as thick as that of the control. The changes in structure and resistance as well as the induction of pinocytosis are dependent on the initial external concentration of calcium. These changes are rapidly reversed when the concentration of calcium in the external medium is increased.

Synthetic peptides form ion channels in artificial lipid bilayer membranes.

Ion permeability of cell membranes is considered to be mediated by ion channels. The synthesis and testing of four peptides having the sequence (Leu-Ser-Leu-Gly)n and expected to form beta126,6-helical ion channels in lipid bilayer membranes is reported. The two peptides capable of forming helices four turns in length have been demonstrated to form ion channels in an artificial lipid bilayer membrane system. The ion selectivity of the channels is consistent with the predicted beta12-helical model in which ions traversing the channel are coordinated by serine hydroxyl groups arrayed in the interior of the channel.

Osmometrically determined characteristics of the cell membrane of squid and lobster giant axons.

Lobster and squid giant nerve fibers respond differently when subjected to osmotic challenges. The axons proper, as distinct from the total (fiber) complex formed by the axon and connective sheath, both behave as "fast" osmometers for changes in the concentration of NaCl, but the maximum degree of swelling in hyposmotic media is by about 60% in lobster and only by 20% in squid. The relative volume intercepts of the van't Hoff relation are about 0.2 for lobster and 0.4 for squid. The sheaths of both axons undergo only small, apparently passive changes in volume. Lobster axons are permeable to Cl, but squid axons are impermeable to this anion. Lobster axons are also permeable to glycerol. The implications of the data as to the nature of volume regulation of cells are discussed.

Potassium measurements in the extracellular spaces of normal and failing cat myocardium.

After periods of quiescence, papillary muscles and trabeculae from normal and hypertrophied-failing cat hearts were subjected to ionic stress induced by stimulation (drive) at different frequencies. Patterns of change in extracellular potassium concentration were measured using ion-selective microelectrodes and were shown to be significantly different in certain key parameters. In both types of tissue, extracellular potassium activity initially increased from the level in the bathing medium, reached a peak, and then returned toward the original levels. However, the time for this to occur was significantly longer in the hypertrophied-failing muscles than in the normal controls. Also, after more than 5 min of drive, the potassium activity in the extracellular spaces was significantly higher in the hypertrophied-failing tissue than in the normal tissue. The results of these experiments indicate that there may be quantitative differences between normal and hypertrophied-failing cardiac muscles with regard to the regulation of ionic balance.

Surgery for endometriosis-associated infertility: do we exaggerate the magnitude of effect?

OBJECTIVE: Surgery remains the mainstay in the diagnosis and management of endometriosis. The number of surgeries performed for endometriosis worldwide is ever increasing, however do we have evidence for improvement of infertility after the surgery and do we exaggerate the magnitude of effect of surgery when we counsel our patients? The management of patients who failed the surgery could be by repeat surgery or assisted reproduction. What evidence do we have for patients who fail assisted reproduction and what is their best chance for achieving pregnancy? MATERIAL AND METHODS: In this study we reviewed the evidence-based practice pertaining to the outcome of surgery assisted infertility associated with endometriosis. Manuscripts published in PubMed and Science Direct as well as the bibliography cited in these articles were reviewed. Patients with peritoneal endometriosis with mild and severe disease were addressed separately. Patients who failed the primary surgery and managed by repeat or assisted reproduction technology were also evaluated. Patients who failed assisted reproduction and managed by surgery were also studied to determine of the best course of action. RESULTS: In patients with minimal and mild pelvic endometriosis, excision or ablation of the peritoneal endometriosis increases the pregnancy rate. In women with severe endometriosis, controlled trials suggested an improvement of pregnancy rate. In women with ovarian endometrioma 4 cm or larger ovarian cystectomy increases the pregnancy rate, decreases the recurrence rate, but is associated with decrease in ovarian reserve. In patients who have failed the primary surgery, assisted reproduction appears to be significantly more effective than repeat surgery. In patients who failed assisted reproduction, the management remains to be extremely controversial. Surgery in expert hands might result in significant improvement in pregnancy rate. CONCLUSION: In women with minimal and mild endometriosis, surgical excision or ablation of endometriosis is recommended as first line with doubling the pregnancy rate. In patients with moderate and severe endometriosis surgical excision also is recommended as first line. In patients who failed to conceive spontaneously after surgery, assisted reproduction is more effective than repeat surgery. Following surgery, the ovarian reserve may be reduced as determined by Anti Mullerian Hormone. The antral follicle count is not significantly reduced. In women with large endometriomas > 4 cm the ovarian endometrioma should be removed. In women who have failed assisted reproduction, further management remains controversial in the present time.

Cyclospora cayetanensis infections in Haiti: a common occurrence in the absence of watery diarrhea.

Stool samples from a population-based cohort of mothers and children living in Leogane, Haiti were tested for Cyclospora cayetanensis from January 1997 through January 1998. Data on gastrointestinal symptoms were also collected. During the winter months of January to March, the infection was detected in 15-20% of the persons sampled. Most infections did not appear to be causing diarrhea and most infected persons had few oocysts detectable in concentrates of stool. The infection appears to have marked seasonality, with highest rates during the driest and coolest time of the year. It may be that in this tropical setting, high summer temperature is the critical environmental factor that influences the seasonality of infection. This study demonstrates that Cyclospora infections in Haiti are common in the general population.

A community-based trial for the control of lymphatic filariasis and iodine deficiency using salt fortified with diethylcarbamazine and iodine.

To evaluate the effectiveness of salt fortified with diethylcarbamazine (DEC) and iodine for elimination of Bancroftian filariasis and iodine deficiency, all consenting residents of Miton, Haiti (n = 1,932) were given salt fortified with 0.25% diethylcarbamazine and 25 ppm of iodine for one year. Wuchereria bancrofti microfilaria prevalence and intensity, antigenemia, and urinary iodine were measured before and one year after salt distribution began. To measure the effect of DEC-fortified salt on adult worm motility, 15 microfilaria-positive men were examined by ultrasound of the scrotal area. Entomologic surveys were conducted to determine the proportion of W. bancrofti-infected Culex quinquefasciatus. After one year of treatment, the prevalence and intensity of microfilaremia were both reduced by more than 95%, while antigenemia levels were reduced by 60%. The motility of adult worms, as detected by ultrasound, was decreased, but not significantly, by DEC-fortified salt. The proportion of vector mosquitoes carrying infective stage larvae decreased significantly from 2.3% in the nine months before the intervention to 0.2% in the last three-month follow-up period. Iodine deficiency, which had been moderate to severe, was eliminated after one year of iodized salt consumption. The DEC-fortified salt was well accepted by the community and reduced microfilaremia and transmission to low levels in the absence of reported side effects. Based on these results, salt cofortified with DEC and iodine should be considered as a concurrent intervention for lymphatic filariasis and iodine deficiency elimination programs.

Tryptamine enhancement of neurotransmitter release under conditions that normally depress calcium influx.

Neurotransmitter release, resulting in excitatory and inhibitory junction potentials (E- and IJPs) is normally mediated by an influx of calcium ions into nerve terminals following depolarization. At a lobster neuromuscular junction, tryptamine is shown to greatly enhance the amplitude and duration of evoked E- and IJPs in low Ca2+-high Mg2+ media that depress Ca2+ influx. This suggests that in the presence of tryptamine, intracellular Ca2+ sources may support evoked, phasic neurotransmitter release.

The effects of tryptamine on transmitter release at a lobster neuromuscular junction.

Electrophysiological techniques were employed to characterize the effects of tryptamine at excitatory and inhibitory neuromuscular junctions of the stretcher muscle in the carpopodite of lobster walking limbs. Tryptamine was found to have a concentration dependent, biphasic effect on excitatory junction potential (EJP) amplitude. At concentrations of 0.01-0.5 mM tryptamine increased the amplitude of evoked EJPs, but at higher concentrations (greater than 0.5 mM) the amplitude was decreased by this amine. The high concentrations also decreased the amplitude of inhibitory junction potentials (IJPs) and reduced the frequency of miniature excitatory junction potentials (MEJPs). When a preparation in which the EJPs had been depressed by tryptamine was washed with the control, artificial sea water solution, the EJPs were increased to an amplitude greater than that of the pre-tryptamine control. Current-voltage relationship studies showed that tryptamine did not affect the effective resistance of the muscle fiber membrane. Tryptamine had no effect on the amplitude of excitatory responses evoked by the iontophoretic application of glutamate. Concentrations of tryptamine ranging to 10.0 mM affected neither the conduction velocity in meropodite or that of giant central nervous system (CNS) axons. We conclude that tryptamine affects synaptic transmission pre-synaptically by influencing the transmitter release process. Mass spectrometric analysis showed tryptamine to be an endogenous substance in the lobster; but the concentrations were low in the tissues analyzed. The highest concentration (approximately 0.3 nmol/g wet tissue) was in the subesophageal ganglion. Tryptamine was not detected in the meropodite nerves or carpopodite muscles.

Oximes: 'enzymatic' slow channel antagonists in canine cardiac purkinje fibers?

In mammalian cardiac muscle voltage-dependent activation of slow channels, e.g., the slow inward current channel, may be possible only when the channels are phosphorylated. We examined the electrophysiological actions of oximes, mile nucleophilic agents which show 'phosphatase-like' activity in isolated enzyme systems, to assess their actions on slow channels in cardiac Purkinje fibers. Diacetyl monoxime (DAM) and pyridine-2-aldoxime (NorPAM) produced a marked, reversible and concentration-dependent reduction in the action potential (AP) plateau duration and abolished spontaneous phase 4 depolarization, but produced only minimal effects on resting potential, dV/dt max, action potential amplitude, duration of phase 3, or membrane resistance. Slow response action potentials evoked in the presence of elevated potassium plus isoproterenol or in Na-free solution were abolished by DAM. The effects of DAM on the AP plateau were antagonized by epinephrine, but an increase in Ca was relatively ineffective. The results suggest that oximes may act as surrogate phosphatases to remove phosphate groups which regulate the availability of slow current channels for voltage-dependent activation.

Survey for Cyclospora cayetanensis in domestic animals in an endemic area in Haiti.

From January 1997 through July 1998, we examined stool samples from 327 domestic animals, including pigs, cattle, horses, goats, dogs, cats, guinea pigs, chicken, ducks, turkeys, and pigeons in Leogane, Haiti, for the presence of Cyclospora cayetanensis infection. No coccidian oocysts morphologically compatible with C. cayetanensis were detected in any of the animal samples, despite their living in, or near, households with infected individuals. These results suggest that domestic animals are not reservoir hosts for C. cayetanensis and that in this endemic area, humans are the only natural host for this parasite.