Slow Leak Research Articles

Pressure-regulating ear plug

A pressure regulating ear plug for regulating the rate of change of pressure inside an ear to minimize the pressure differential between the middle ear and a volume of the external ear cavity adjacent the ear drum is made of an ear plug adapted to fit tightly within the external ear cavity with no or minimal air leakage, and disposed within the ear plug is a pressure regulator with a slow leak rate. The pressure regulator is preferably made of a porous ceramic material.

Simulation of Isothermal and Adiabatic Leak Processes of Zeotropic Refrigerant Mixtures

Nonflammable zeotropic mixtures of flammable and nonflammable refrigerants are possible alternative refrigerants for use in domestic heat pumps and air conditioners. Refrigerant leakage from such a system is of paramount concern since it is possible that a mixture composition will shift to a flammable range. This paper presents simulations of leak processes of zeotropic refrigerant mixtures. Idealized cases of isothermal and adiabatic leak processes are considered in this study as representations of slow and fast leaks, respectively. Results of simulations are presented for a selected composition of binary and ternary refrigerant mixtures; R-32/134a and R-32/125/134a. Mass fraction changes of the mixtures are presented with respect to the percentage leak of the original charge. In the isothermal leak process, the fraction of the more volatile refrigerant in both vapor and liquid phases decreases for either a vapor or a liquid leak. The mass fraction changes at a low initial temperature are greater than those at a high initial temperature. During the adiabatic leak process, the vapor mass fraction of the more volatile component increases, while the liquid mass fraction of that component decreases for both vapor and liquid leak processes.

Tc-99m MAG3 as an Alternative to Tc-99m DTP A and I-131 Hippuran for Renal Transplant Evaluation

This study investigated the new radiopharmaceutical, Tc-99m mercaptoacetyltriglycine (MAG3), as a possible alternative to Tc-99m DTPA and I-131 Hippuran for renal transplant evaluation. Tc-99m MAG3 and I-131 Hippuran were used sequentially in 19 consecutive patient studies and compared qualitatively and quantitatively. Serum creatinine values ranged from 1.6 mg/dL to 10.3 mg/dL (mean, 5.4 mg/dL). The Tc-99m MAG3 images and time-activity curves were of superior quality (3+) compared to I-131 Hippuran (1-2+). Quantitative analysis of the time to peak activity (Tmax) demonstrated a high correlation and no significant difference for Tc-99m MAG3 (mean, 11.4 min) compared to I-131 Hippuran (mean, 11.2 min). The percentage of peak activity retained at 20 minutes (T20) also showed a high correlation between the two agents; however, Tc-MAG3 showed a significantly slower clearance (T20 mean, 77%) than I-131 Hippuran (mean, 71%). Flow images were judged to be of good quality; however, the first-pass time-activity curves were often different from that seen with Tc-99m DTPA. Interpretation of delayed Tc-99m MAG3 images, for example to diagnose a slow urinary leak, were sometimes complicated by bowel clearance. In conclusion, Tc-99m MAG3 is superior to I-131 Hippuran for evaluation of renal transplant function. Tc-99m is the agent of choice for evaluation of renal transplant blood flow and function.

Philosophy as I remember it: Locke

Locke was an English appearancist. An appearancist is one who believes that it is more important to look good than to be good because things are nothing but what they appear to be. The truth of an idea, like the beauty of a person, is only skin deep, superficial, and therefore, one never needs to go below the surface to get at it. Locke hoarded his ideas; he saved all of them, even those that were spent. He continuously inflated those that others devalued and therefore eventually placed infinite value on those that were worth nothing. He believed that all of us were born with completely blank minds and that they got filled by experience. His, however, had a slow leak. He argued that our senses pick up everything they come in contact with-that they see, hear, taste, feel, smell, or write about. Ideas, he said, arise from reflecting on all the junk that the senses collected. Whenever an idea came up, Locke put it down, usually on paper (Fig. 1). This was quite easy because none of them had a leg to stand on.

Delay in vesicle fusion revealed by electrochemical monitoring of single secretory events in adrenal chromaffin cells.

In synapses, a rise in presynaptic intracellular calcium leads to secretory vesicle fusion in less than a millisecond, as indicated by the short delay from excitation to postsynaptic signal. In nonsynaptic secretory cells, studies at high time resolution have been limited by the lack of a detector as fast and sensitive as the postsynaptic membrane. Electrochemical methods may be sensitive enough to detect catecholamines released from single vesicles. Here, we show that under voltage-clamp conditions, stochastically occurring signals can be recorded from adrenal chromaffin cells using a carbon-fibre electrode as an electrochemical detector. These signals obey statistics characteristic for quantal release; however, in contrast to neuronal transmitter release, secretion occurs with a significant delay after short step depolarizations. Furthermore, we identify a pedestal or 'foot' at the onset of unitary events which may represent the slow leak of catecholamine molecules out of a narrow 'fusion pore' before the pore dilates for complete exocytosis.

Designing a slow leak

Designing a slow leak

EFFECT OF ENALAPRIL ON HANDLING OF A SODIUM CHLORIDE LOAD BY GENETICALLY HYPERTENSIVE AND NORMOTENSIVE RATS

1. Enalapril was given in the drinking water (300 mg/L) for 4.5 days to normotensive (N) and genetically hypertensive (GH) rats on zero sodium intake. An intraperitoneal NaCl load was given 12 h after enalapril was started. 2. Enalapril did not increase the maximum rate of sodium excretion, but caused the rats to excrete more than the load in the first 24 h and then to have a slow fall in body sodium while on a sodium-free diet. 3. In terms of the Strauss et al. (1958) concept of body sodium, enalapril appears to lower the basal level. However, in addition it causes a slow leak of sodium which becomes apparent when sodium intake is very low.

Intracellular pH regulation in resting and contracting segments of rat mesenteric resistance vessels.

1. The pH-sensitive dye 2',7'-bis-(2-carboxyethyl)-5 (and -6)-carboxyfluorescein (BCECF) was used to measure intracellular pH (pHi) in segments of rat resistance vessels (internal diameter about 200 microns) with the vessels mounted in a myograph for simultaneous measurements of isometric contraction. 2. BCECF loaded slowly into the vessels over 1 h and did not affect the maximal contractility of the vessels. There was a loss of dye with time which, however, was very slow when the segments were only excited for 2 s/min, suggesting that the loss was mainly due to dye bleaching with only a very slow leak. 3. The ratio of the emissions (at 540 nm) with excitation at 495 and 450 nm was calibrated in terms of pH using the K+-H+ ionophore nigericin. This calibration gave a pHi value of 7.15 +/- 0.02 (n = 20), suggesting that hydrogen ions are not in electrochemical equilibrium in these vascular smooth muscles which have a membrane potential of about -60 mV. 4. Addition of 10 mM-NH4Cl caused a transient alkalinization and wash-out of 10 mM-NH4Cl a transient acidification. Increasing CO2 with maintained bicarbonate caused a rapid acidification followed by an incomplete recovery. Removal of CO2 and bicarbonate (HEPES-buffered solution) with constant extracellular pH caused a transient alkalinization but steady-state pHi was not significantly altered. 5. In bicarbonate-free buffer the Na+-H+ exchange blocker 5-(N-ethyl-N-isopropyl) amiloride (EIPA) and sodium-free conditions caused a slow acidification. In bicarbonate buffer (PSS) EIPA had no detectable effect after 10 min but the anion exchange blocker diisothio-cyanatostilbenedisulphonic acid (DIDS) caused a small acidification over that time course. 6. The rate of recovery after an acid load was about 50% lower in HEPES buffer compared to PSS and it was inhibited by EIPA. In PSS amiloride and EIPA each had a small inhibitory effect on the pH recovery after an acid load. DIDS also inhibited the recovery from an acid load in PSS and this effect was additive to that of EIPA. DIDS and EIPA also had additive inhibitory effects on the 22Na+ influx stimulated by the acid loading, while in HEPES buffer DIDS had no effect on either pH recovery or 22Na+ influx. These results suggest that a Na+-H+ exchange and an influx of bicarbonate coupled to sodium influx are of importance for pHi control in these vessels.(ABSTRACT TRUNCATED AT 400 WORDS)

Kainic acid inhibits the synaptosomal plasma membrane glutamate carrier and allows glutamate leakage from the cytoplasm but does not affect glutamate exocytosis.

Kainate inhibits the exchange of D-aspartate into guinea-pig cerebrocortical synaptosomes. Kainate inhibits the Ca2+-independent efflux of endogenous glutamate in the presence of a trapping system for the released amino acid but potentiates a Ca2+-independent net efflux of endogenous and labelled glutamate and aspartate in the absence of the trap. Dihydrokainate has a similar effect. No discrepancy is seen between the release of endogenous and exogenously accumulated amino acid. These results are consistent with the presence of a slow leak of glutamate or aspartate from the cytoplasm independent of the kainate-sensitive Na+-cotransport pathway. In the presence of the trap, glutamate effluxes by both pathways, whereas in the absence of the trap, the Na+-cotransport pathway opposes the leak. Neither in the presence or absence of the glutamate trap does kainate induce, inhibit, or otherwise affect the Ca2+-dependent release of endogenous glutamate. The results enable many of the apparent complexities in the presynaptic actions of kainate to be resolved.

Effect of Ca2+ channel blockers on passive calcium influx into resealed human red blood cell ghosts.

Red blood cells exhibit a slow but measurable inward leak of calcium (approx. 50 μmoles per hour per litre cells), which is easily compensated by an active Ca2+ efflux fueled by a powerful plasma membrane calcium pump (Lew et al., 1982). While there is considerable information on the calcium pump mechanism at the molecular level, mostly derived from the study of the coupled Ca2+ -ATPase activity in the isolated plasma membrane (see Schatzmann, 1982), the nature of the passive Ca2+ influx mechanism, is not well understood. It is generally agreed that passive Ca2+ uptake into intact human erythrocytes occurs by a carrier-mediated passive diffusion mechanism (Ferreira and Lew, 1977; Varecka and Carafoli, 1982; Gardos et al., 1980). The influx may occur through a protein channel, as it is inhibited by various sulphydryl agents and divalent cations (Varecka et al., 1986) and other Ca channel blockers (Locher et al., 1984). The Ca2+ influx mechanism appears to proceed by the discharge of the transmembrane K+ gradient (Varecka and Carafoli, 1982), but it does not appear to be entirely the result of hyperpolarization induced by activation of the Ca2+ -activated K+ channel (Varecka et al., 1986). By contrast to the low passive Ca2+ permeability of intact erythrocytes, resealed erythrocyte “ghosts” produced by hypotonic lysis of red cells show a considerably enhanced calcium permeability (Lew and Ferreira, 1977; Porzig, 1972). Because of the high haemoglobin content of red cells, photochromic calcium dyes cannot be readily used to study Ca2+ uptake in intact cells, but such methods have been used to study passive Ca2+ uptake into resealed white erythrocyte ghosts (Yingst and Hoffman, 1978). In the present study we have examined the effects of Ca2+ channel blockers and K on the passive uptake of Ca2+ into resealed ghosts and compared the properties of the Ca influx mechanism to those in intact cells.

Reliability of AMS M700 inflatable penile prosthesis

Two hundred ninety patients have been followed up for at least one year or longer after implantation of the AMS M700 inflatable penile prosthesis. One hundred twenty-seven males have been followed up for two years or longer. Eighty-six impotent men had a follow-up of eighteen months or longer. The remaining 77 patients were studied for at least twelve months or longer. There have been 3 mechanical failures of cylinders implanted secondary to nonabsorbable surgical sutures remaining from previous prosthetic surgery. There were no reservoir or pump malfunctions. Eight patients had a slow leak from the nonkinking tubing. Since a revision of the manufacturing process of the nonkinking tubing in September, 1983, there have been no further leaks. Life table analysis for survival in this group of patients showed a probability of survival at three years of 97.9 per cent. The satisfaction rate among patients is greater than 90 per cent.

Post-mastectomy breast reconstruction using the inflatable tissue expander.

Breast reconstruction following mastectomy has previously relied on the insertion of a silicone gel implant or the use of a myocutaneous flap. We report the use of an innovation, the inflatable tissue expander, for both immediate and delayed breast reconstruction in 26 patients where soft tissue cover was inadequate to permit the use of the silicone implant. By serial inflation of the tissue expander with saline, sufficient tissue cover was achieved for a second operative placement of a silicone prosthesis of appropriate volume to match the normal breast. To date, 10 patients undergoing delayed reconstruction and 5 of 16 patients with immediate reconstruction have had their final prosthesis inserted, while 3 women are satisfied with the result of the expandable implant and desire no further surgery. Only two technical complications have arisen with loss of the expander in one patient who had had recent radiotherapy and in another the tissue expander was placed much too high on the chest wall. Mechanical failure occurred in three cases where disruption of the seam led to sudden deflation in two and a slow leak from the injection port developed in one. One patient also attempted self-inflation leading to deflation of the tissue expander. The cosmetic results were subjectively and objectively very good with capsular distortion present in only one case. We feel that the inflatable tissue expander is simple and safe to use, may be used for immediate reconstruction without compromising the ablative surgery and should be a choice available to general surgeons for providing safe and cosmetically acceptable reconstructive surgery.

2073∼2273 K におけるNb-C-O固溶体の熱力学的研究

The carbothermic reduction-electron beam melting combination method has made it possible to produce the pure niobium metal. In the present investigation, the relationship between the pressure, the temperature and the concentration of carbon and oxygen in the Nb-C-O solid solutions has been determined as the base for the carbothermic reduction of niobium in vacuum.The niobium metal with arbitrary contents of carbon and oxygen was equilibrated with the CO-CO2 gas mixture of the CO2 content below 1000 ppm, at 2073∼2273 K and the reduced pressure. The reduced pressure from 0.13 to 13 Pa was realized in a vacuum furnace with a tantalum heating element by balancing the introducing rate of gas through a slow leak valve with the evacuating rate by a diffusion pump.The thermodynamic equilibrium between the Nb-C-O solid solution and the CO-CO2 gas mixture can be described by the following equations:(This article is not displayable. Please see full text pdf.) The total pressure must be reduced even at the temperature as high as 2273 K and the CO2 concentration must be very small for the Nb-C-O solid solution to be stable, so that the reaction (1) is predominant and the reaction (2) may be negligible. The following expression relating the pressure, the temperature and the concentration of carbon and oxygen in niobium has been derived:(This article is not displayable. Please see full text pdf.) \ oindentwhere PCO is the pressure in Pa, CC and CO the atomic percents of carbon and oxygen and T the absolute temperature.

Recurrent Meningococcal Meningitis With Occult CSF Leak

Recurrent meningococcal meningitis was associated with a slow CSF leak in a 24-year-old man. Unique features of the case included isolation of meningococcal group 29E. We speculate that an association exists between subclinical CSF leaks and sporadic cases of meningitis.

Recurrent meningococcal meningitis with occult CSF leak

Recurrent meningococcal meningitis was associated with a slow CSF leak in a 24-year-old man. Unique features of the case included isolation of meningococcal group 29E. We speculate that an association exists between subclinical CSF leaks and sporadic cases of meningitis.

Effects and distribution of acute fat embolism in spontaneously breathing dogs using radioactive carbon triolein

The acute effects of a triolein infusion in dogs were secondary to the mechanical effects of this neutral fat which was distributed in the pulmonary and systemic vascular tree of all organs without inflammatory change. Hypoxia developed immediately and became progressively worse as the infusion was continued. Pulmonary hypertension developed during the fat infusion without pneumonia, congestive heart failure or pulmonary edema. There was a slow leak of 14C triolein into the systemic circulation rather than a rapid shower, and this radioactive fat was recirculated between the pulmonary and systemic vasculature. Seventy-six per cent of the 14C triolein was retained in the lungs. Terminally, the dogs had a respiratory arrest without cardiac decompensation, cardiac arrest or pulmonary edema; cerebral fat embolism in addition to severe hypoxia appears to be the cause.

Perilymph fistula: A cause of auditory, vestibular, neurological and psychiatric disorder

It is suggested that damage by mild trauma, viruses or bone disease to the otic capsule or to the membranes between the cochlea and the middle ear is common, and involved in many syndromes of obscure etiology. The clinical perilymph fistula (PF) syndrome can consist of any combination of the following: tinnitus, deafness, phonophobia, vertigo, ataxia, otalgia, facial palsy, headache, diplopia, blackouts, psychological distress. The following testable hypotheses are proposed: otitis media is due to perilymph in the middle ear, with secondary changes resulting from infection or inflammation: otosclerosis results from a slow leak in the presence of enzymes promoting bone growth: Meniere's syndrome follows reduced perilymph support for the endolymphatic system: Bell's palsy results from a perilymph provoked oedema in the bony facial nerve canal: PFs may be responsible for progressive rubella deafness, and for some cases of migraine, epilepsy, anxiety neurosis and hysteria: psychiatric sequelae of the PF syndrome predominate in the post-concussional syndrome and infantile autism: organisms can pass from the throat into the spinal fluid, causing meningitis or encephalitis. The tinnitus and vertigo are caused by random labyrinthine fluid movements, the headache and diplopia by reduced spinal fluid pressure.

Application of Ground‐Water Flow Theory to a Subsurface Oil Spilla

ABSTRACTFuel oil, underlying approximately four acres, was discovered floating on the water table beneath oil products' storage tanks. The oil, of unknown origin, originally was observed discharging to a river adjacent to the storage tank area from an abandoned clay tile. Approximately 35,000 gallons (132,500 liters) of oil were intercepted and contained prior to the field investigation by borings.Hantush's (1968) theory for the formation of a fresh‐water lens in an unconfined saline aquifer was used to examine the decay of an oil lens resulting from a catastrophic oil spill at the site. The theory indicated that too much time had elapsed from the first detection of oil at the surface to the collection of subsurface information to make it feasible to speculate on the precise nature of the spill event–catastrophic or a slow leak. Application of the theory and consideration of the ground‐water hydrology of the site did make it possible to identify the probable source area of the spill. Analysis of the flow system also assisted in the selection of the appropriate collection system to clean‐up the spill.Subsequent to the boring program, an electrical resistivity survey was conducted to test the feasibility of delineating the extent of the subsurface oil by this method. Only modest success was achieved, apparently because of the thinness of the oil‐bearing zone.

Rectal bleeding.

BLOOD loss from the anus (rectal bleeding) is one of the more common manifestations of gastrointestinal disease, and a sign that nearly everyone observes during a lifetime. It may take the form of a massive exsanguinating hemorrhage, with all its attendant sequelae, or a slow leak of red cells from the gut, which can only be detected by chemical analysis. The implications of rectal bleeding are equally diverse, ranging from a nuisance stain on the undergarments to death from cardiovascular disturbances that accompany acute depletion of circulating blood volume. For the most part, however, blood loss from the rectum is . . .

Slow Arterial Leak Consequent to Unrecognized Arterial Laceration

The final outcome in the cases reported here clearly emphasizes the importance of early diagnosis. In three of the five cases, amputation was required because the condition was not recognized in time. Pain and tumescence in a previously injured extremity and sometimes fever, mimicking sepsis, should alert the surgeon to the possibility of a slow arterial leak, even when the peripheral circulation is normal and there is no bruit or pathological pulsation. Arteriography should be performed whenever the diagnosis of slow arterial leak is considered.