Swelling-induced anion and cation conductances in human epididymal cells

1. Activation of both anion and cation conductances was observed in primary cultured human epididymal cells during osmotic swelling under the patch-clamp whole-cell configuration. The swelling-induced anion conductance was 25.66 +/- 4.70 nS and the cation conductance was 7.35 +/- 1.40 nS. The permeability ratio of K+ to Cl- (PK/PCl) was calculated to be 0.40. Known anion or cation channel blockers could inhibit both conductances simultaneously. 2. When the major permeant ion species in the pipette and bath solution was Cl-, the mean conductance was found to be 17.06 +/- 1.8 nS, significantly smaller than that obtained in the presence of intracellular K+, 25.66 +/- 4.70 nS (P < 0.05). No significant current activation was observed when solutions containing only K+ as the permeant ion were used. 3. When the anionic amino acids glutamate and aspartate were used to replace extracellular Cl-, the permeability ratios were calculated to be PGlut/PCl = 0.20 and PAsp/PCl = 0.17. 4. The cation conductance was found to be non-selective since its permeability to other cations such as Na+ and choline, an organic compound highly concentrated in epididymal fluid, was similar to that of K+. 5. Regulatory volume decrease (RVD) was observed after initial osmotic swelling; this could be inhibited by either anion or cation channel blockers. 6. The results of this study suggest that both anion and cation conductances are activated during cellular swelling, and indicate the existence of an interdependent relationship between the swelling-induced cation and anion conductances. Both swelling-induced cation and anion conductances are involved in the volume regulatory process and may be responsible for transporting amino acids or organic compounds in human epididymal cells.

The effect of [Arg8]vasopressin on electrogenic chloride secretion in cultured rat epididymal epithelia

Primary cultured rat efferent ductal epithelia and cauda epididymal epithelial were mounted in Ussing chambers to study the effect of arginine vasopressin (AVP) on chloride secretion in the male excurrent duct. The regional differences in the signal transduction pathways involved were also investigated. In both the efferent duct and the cauda epididymidis, basolateral addition of AVP resulted in a dose-dependent increase in the short-circuit current (Isc), which was mediated via V1 receptor. Replacement of ambient Cl- with gluconate or pretreatment of a Cl- channel blocker, diphenylamine-2-carboxylate (apical, 1 mM), completely abolished the response, whereas addition of amiloride had no effect on the Isc. Pretreating the epithelia of the efferent duct with indomethacin (apical, 5 microM) or forskolin (basolateral, 1 microM), but not thapsigargin (apical, 1 microM) or trifluoperazine (apical, 20 microM), significantly inhibited the AVP response (P < 0.001). By comparison, pretreating the epithelia of the cauda epididymidis with any of the four agents significantly reduced the AVP-evoked response. These results suggested that the stimulation of chloride secretion by AVP in the efferent duct and the cauda epididymidis is mediated by prostaglandin synthesis and involves adenosine 3',5'-cyclic monophosphate (cAMP) as a second messenger. In the cauda epididymidis, calcium, in addition to cAMP, may play a role in mediating the AVP-induced response.

A role for annexin IV in epithelial cell function. Inhibition of calcium-activated chloride conductance

The cellular function of annexin IV was evaluated by correlating tissue expression, cellular localization, and whole-cell electrophysiology. Immunolocalization and biochemical data demonstrate that annexin IV is concentrated along the apical membranes of many epithelia. Introduction of purified exogenous annexin IV into colonic T84 cells through a patch pipette specifically prevented Ca(2+)-dependent Cl- current activation. Affinity-purified antibody against annexin IV applied in the same manner enhanced the activation. Reduction of the endogenous level of annexin IV with a derivatized oligodeoxynucleotide antisense to annexin IV mRNA lowered the threshold for the Ca(2+)-induced current response, mimicking the enhancement of current activation exerted by anti-annexin IV antibody. The inhibitory effect of annexin IV on Ca(2+)-dependent Cl- conductance represents a novel mechanism by which Ca(2+)-binding proteins modulate membrane channel activity.

Adrenaline-regulated Cl- transport in cultured single rat epididymal cells measured by an entrapped Cl-(-)sensitive fluorophore

1. Isolated cells from primary cultures of rat epididymal epithelial cells were employed for the study of adrenaline-stimulated Cl- transport using a Cl-(-)sensitive fluorophore 6-methoxy-N-(3-sulphopropyl) quinolinium (SPQ). SPQ was loaded into the cells by the hypotonic shock method. 2. The resting intracellular Cl- concentration, estimated in the presence of nigericin and tributyltin in high-K+ solution, was 62.3 +/- 0.2 mM. This value was not altered in the presence of 1 microM adrenaline. When extracellular Cl- was replaced by NO3-, an increase in fluorescence corresponding to a decrease in intracellular Cl- was observed. The initial outward Cl- movement was estimated to be 0.54 +/- 0.08 mM s-1. This value was increased by incubating the cells with adrenaline. The stimulatory effect of adrenaline was reduced by 1 mM DPC. 3. Addition of Cl- to cells previously depleted of Cl- caused an instantaneous decrease in fluorescence due to the entry of Cl-. The initial rate of Cl- entry was -0.62 +/- 0.13 mM s-1. Adrenaline increased the rate of entry to -2.13 +/- 0.08 mM s-1. The adrenaline-stimulated rate of entry was reduced by DPC or frusemide (0.5 mM) and was completely blocked in the presence of both agents. 4. In Na(+)-free solution, the adrenaline-stimulated rise of rate of Cl- entry was reduced in the presence of DPC. Frusemide had no effect on the entry rate. 5. The stimulatory effect of adrenaline were abolished by propranolol (5 microM) but not by phentolamine (5 microM). Conversely, isoprenaline (1 microM) and forskolin (1 microM) mimicked the effects of adrenaline.(ABSTRACT TRUNCATED AT 250 WORDS)

Selection of targeted biological modifiers from a bacteriophage library of random peptides. The identification of novel calmodulin regulatory peptides

The interaction of short amino acid sequences is the basis of molecular recognition and biological regulation in many cellular systems. Libraries of random peptides provide an approach to identify peptides that can be used to modulate, in a targeted fashion, the function of specific gene products. We have used a library of random peptides designed and constructed in the M13 bacteriophage to select calcium-dependent calmodulin binding-peptides. Twenty-eight independent sequences were obtained; all contained a tryptophan within the fifteen-amino acid insert. In 11 sequences, the tryptophan was located in the first possible variable position of the inserted sequence and was followed by a proline. The tryptophan-proline combination was also present in six additional isolates but at various other positions within the peptide insert. Synthetic peptides, representative of the calmodulin binding sequences, bound to calmodulin in a calcium-dependent fashion, competed with known calmodulin inhibitors and, when introduced via a patch pipette, inhibited calcium-activated chloride conductance of the colonic epithelial cell line, T84. This report demonstrates the utility of identifying modifiers of biological function and should prove to be a valuable approach in understanding the cellular role of proteins of unknown function.

Differences between nursing home admissions and residents

The use of a cross-sectional sample of nursing home residents rather than a sample of admissions to estimate admission characteristics carries a potential bias. The purpose of this study was to fill this void by comparing abstracted records data for an admissions cohort (n = 1,118) and a residents cohort (n = 830) residing in the same nursing homes. Compared to residents, admissions were significantly more dependent in their ability to get around and to dress themselves, received more clinical services, and had a higher rate of medication use. Over a 12-month period, admissions had a fivefold greater likelihood of being discharged to community, but about the same mortality rate as residents. Within both groups, those discharged to the community as well as those who died had expenditures that were almost twice as high as those of their counterparts who remained alive in the nursing home.

Characterization of a swelling-induced chloride conductance in cultured rat epididymal cells

Swelling-induced Cl- conductance in cultured rat epididymal cells was characterized using whole cell patch-clamp techniques. Activation of whole cell current with an outwardly rectifying current-potential relationship was observed in cells exposed to hyposmotic solutions. This current was determined, from the observed current-reversal potentials at different Cl- concentrations, to be Cl- selective. The anion selectivity sequence of the swelling-induced Cl- conductance was I- approximately NO3- approximately Br- > Cl- > 2-(N-morpholino)ethanesulfonic acid. The swelling-induced Cl- conductance was reversibly inhibited by different Cl- channel blockers. Unlike diphenylamine-2-carboxylate or 5-nitro-2-(3-phenylpropylamino)-benzoate, which showed voltage-independent blockade, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid showed a marked voltage-dependent blockade of the volume-sensitive Cl- current, with a greater effect at depolarizing voltages. The swelling-induced Cl- conductance appeared to be different from the Ca(2+)- or adenosine 3',5'-cyclic monophosphate-activated Cl- conductances on the basis of the following observations: 1) swelling-induced current activation was seen even in the presence of kinase inhibitor (H-8) or absence of external free Ca2+, and 2) further increase in current activation could be produced by swelling after Ca(2+)- or adenosine 3',5'-cyclic monophosphate-induced current activation. The swelling-induced Cl- conductance may be involved in regulating epithelial cell volume as well as serving other important epididymal functions such as facilitating transepithelial secretion of organic compounds.

Effect of intravenous clonidine on prevention of postepidural shivering

The effects of intravenous clonidine, a central adrenergic alpha-2 agonist, on the incidence of shivering and hemodynamic changes after epidural anesthesia were assessed in patients undergoing extracorporeal shock wave lithotripsy (ESWL). Forty ASA class I or II patients were randomly assigned in a double-blind manner to one of two groups. Twenty patients received intravenous clonidine 150 micrograms/10 ml (clonidine group) and twenty patients received normal saline (control group) at 20 min before epidural administration of 1.5% lidocaine. Shivering was determined objectively by observing involuntary muscle activity. Arterial blood pressure, heart rate, respiratory rate and oxygen saturation were measured at 5-min intervals during the first 50 minutes following IV pretreatment. There was significant difference between clonidine and control groups in the incidence of shivering (5% vs. 55%, p = 0.002). Shivering began at an average of 16.8 +/- 9 min (range: 5-30 min) in control group and only one patient shivered at 18 min in clonidine group. The mean sensory level was T7 in both groups. There were no differences between the two groups in mean arterial pressure and respiratory rate, though there was a trend in reduction of MAP in clonidine group. Heart rate and oxygen saturation decreased slightly in clonidine group. The main adverse effect of clonidine pretreatment was drowsiness. In conclusion, intravenous clonidine 150 micrograms was effective in preventing shivering with minor hemodynamic changes in patients receiving epidural anesthesia.

Lumbar extradural morphine and caudal extradural morphine for postoperative analgesia and their adverse effects

The efficacy of morphine by either lumbar extradural route or caudal extradural route and their adverse effects for postoperative analgesia were studied by comparing with the control group without morphine administration. 105 patients, 79 males and 26 females, aged 18 to 70 years, scheduled for hemorrhoidectomy surgery were selected. They were randomly assigned into three groups, i.e group I: without morphine use as control group (n = 35), group II: lumbar extradural morphine group (n = 35) and group III: caudal extradural morphine group (n = 35). Patients in group I received general anesthesia by face mask after induction by intravenous anesthetics and maintained with potent halogenated inhalation agents (isoflurane) through face mask. Patients in group II received lumbar extradural blockade through the L4-L5 intervertebral space, and those in group III received caudal extradural blockade through the sacrococcygeal junction (sacral hiatus) for intraoperative anesthesia and analgesia. Drugs included 0.5% bupivacaine 10ml + 2% xylocaine 10ml + 2mg morphine HCl + 0.1mg epinephrine were given either into the lumbar extradural space or into the caudal extradural space. No more narcotic has been given throughout the whole intraoperative course. All of these patients were followed up 24 hours later after the end of anesthesia. There were 11 patients (31.4%) in the control group, 26 patients (74.3%) in the lumbar extradural morphine group, and 25 patients (71.4%) in the caudal extradural morphine group who did not need additional narcotic for pain relief for more than 24 hours postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Endotracheal lidocaine instillation in pediatric anesthesia

The purpose of this study is to evaluate the effectiveness of lidocaine administered via the endotracheal tube in suppressing cough reflex during anesthetic recovery in children. Fifty ASA class I-II children, aged from 1-5 years old undergoing elective abdominal or urogenital surgery were randomly assigned into two groups. 2% lidocaine 1.5 mg/kg (1ml = 20mg) was administered in group B while normal saline (N/S) 0.1 ml/kg was used in group A (control group). Either one of the agents was instilled into the endotracheal tube right before the end of operation. Airway responses and other associated phenomena were recorded during the recovery period. Recovery condition was categorized into a two-grade categories, namely "good", and "poor" to denote the quality of recovery. Recovery conditions differ significantly between the control group and the experimental group. In group A, 3 patients were classified as the "good" grade but 22 patients were categorized in the "poor" grade. Group B (lidocaine 1.5 mg/kg) has a much better recovery condition than the control group, there were 19 in the "good" grade and only 6 in the "poor" grade. The experimental group treated with 2% lidocaine presented a significantly better recovery than the control group. This effective suppression of the cough reflex might be due to the local anesthetic effect exerted by lidocaine. For the sake of safety all patients were closely followed up at the post anesthesia room until the return of consciousness and laryngeal reflexes. In conclusion, we found that 2% lidocaine 1.5 mg/kg given intratracheally via the endotracheal tube could attenuate cough response during recovery in pediatric anesthesia.

Chloride-dependent cation conductance activated during cellular shrinkage

A chloride (Cl-)-dependent, nonselective cation conductance was activated during cellular shrinkage and inhibited during cellular swelling or by extracellular gadolinium. The shrinking-induced, nonselective cation conductance and the swelling-induced anion conductance appear to function in the regulation of cell volume in airway epithelia. The shrinking-induced cation conductance had an unusual dependence on Cl-: partial replacement of extracellular Cl- with aspartate reduced the magnitude of the shrinking-enhanced current without accompanying changes in the reversal potential. The Cl- dependence of the nonselective cation conductance could provide a mechanism that tightly regulates Cl- secretion and sodium reabsorption in cells under osmotic stress.

Alternate pathways for chloride conductance activation in normal and cystic fibrosis airway epithelial cells

Using whole cell patch-clamp and perforated patch recording techniques on human cystic fibrosis (CF) and non-CF airway epithelial cells, we sought to determine whether a single Cl- conductance (GCl) could be modulated via different regulatory pathways or whether multiple conductances could be identified. Cl- current in both CF and non-CF cells was activated by cellular swelling as well as by an elevation in intracellular calcium ([Ca2+]i). While the adenosine 3',5'-cyclic monophosphate (cAMP)-activated GCl was absent in CF cells, its activation in non-CF cells was only observed in the perforated patch configuration at lower temperatures (24 degrees C) or infrequently in the whole cell configuration at elevated temperatures (33 degrees C). Currents activated by all three regulatory pathways were sensitive to the Cl- channel blocker 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). Further increases in current activation could be produced by cellular swelling after maximal Ca2+ or cAMP-induced current activation. Intracellular application of a peptide inhibitor of Ca(2+)-calmodulin-dependent protein kinase selectively blocked the Ca(2+)-dependent current activation while leaving the swelling-induced current increase intact. These results are consistent with the presence of multiple anion conductances in both CF and non-CF airway cells. The heterogeneity of the responses to the three regulatory stimuli, however, prevented the correlation of a specific anion conductance with a separate modulatory pathway based on characteristic voltage-dependent kinetics and conductance.

Antibody against a cystic fibrosis transmembrane conductance regulator-derived synthetic peptide inhibits anion currents in human colonic cell line T84

The cystic fibrosis (CF) phenotype is characterized by a regulatory defect in Cl- permeability in epithelia. A gene (250,000 base pairs) that is associated with this autosomal genetic disorder has been identified. To determine the cellular function of the recently cloned gene product, the cystic fibrosis transmembrane conductance regulator (CFTR), we have produced antibody against a synthetic peptide deduced from the CFTR cDNA sequence corresponding to positions 505-511. This site includes phenylalanine 508, the deletion of which is the most commonly expressed mutation in CF. We sought to determine whether the anti-CFTR505-511 peptide antibody could modulate the activation of the volume-sensitive, Ca(2+)-dependent, as well as the cAMP-dependent Cl- conductances present in the Cl(-)-secreting human colonic T84 cell line. Affinity-purified anti-CFTR505-511 antibody was introduced into the cytoplasm of individual T84 cells and its function studied using the whole-cell patch-clamp technique. Although cAMP-dependent Cl- current activation was inhibited in cells perfused with the anti-CFTR505-511 peptide antibody, Ca(2+)-dependent anion current activation remained unaffected. Chloride current activation, which accompanies cellular swelling, was partially attenuated in anti-CFTR505-511 antibody-loaded cells as compared with control cells perfused with either saline or irrelevant antibody. These results further support a role for CFTR in anion transport in epithelial cells and suggest its possible involvement in a number of anion transport pathways in chloride secretory epithelia.

In vivo oximetry using a nitroxide-liposome system

Liposomes containing the deuterated, charged, aqueous soluble nitroxide 4-trimethyl-ammonium-2,2,6,6-tetramethylpiperidine-d16-1-oxyl (d-Cat1) were used as probes to measure oxygen concentrations in vivo. Following intramuscular or intraperitoneal injection of the liposome suspension. ICR mice were placed over the surface probe of a low frequency (1.1 GHz) electron paramagnetic resonance (EPR) spectrometer. The linewidth of the deuterated nitroxide is sensitive to changes in the dissolved oxygen concentration: this parameter was calibrated separately so that linewidths measured in the injected mice could be converted into oxygen tensions. This technique detected substantial changes in pO2 as the oxygen content of the breathing gas was changed from 21 to 85 to 0%. Intravenous injection of the liposomes also is possible, and the liposomes accumulate in the liver and spleen, where detectable, oxygen-sensitive EPR signals can be measured.

Comparison of inguinal nerve block and intravenous fentanyl in relieving postinguinal herniorrhaphy pain for pediatric outpatients

The purpose of this study was to compare the effects of ilioinguinal/iliohypogastric (IG/IH) nerve block and intravenous fentanyl for pain control following inguinal herniorrhaphy in pediatric outpatients. Seventy-five ASA physical status I and II children (aged 1 to 10 yr) with unilateral inguinal herniorrhaphy under general anesthesia were randomly divided into three groups. Group A received IG/IH nerve block, using 0.25% bupivacaine (1 mg/kg) immediately after induction. Group B received intravenous fentanyl (1 microgram/kg) immediately after induction. Group C received only general anesthesia as control. At postanesthetic care unit (PACU), we recorded the degree of pain/or discomfort at 5, 15, 30, 45 and 60 min using modified Hannallah's scoring system after the patient was fully awake. The degree of recovery was also evaluated using Steward's scoring system. After discharge, the parents were interrogated about the condition of child within 24 h by telephone. Follow-up items raised included vomiting, drowsiness, pain and shivering. Our results showed that children in both study groups had lower pain score than those in the control group, and in the fentanyl group children had lower pain score than in the nerve block group during the first 30 min at PACU. The recovery time was also longer in the fentanyl group. There was no significant difference among the three groups regarding the raised items over telephone interrogation. In sum, inguinal nerve block was effective for postoperative pain relief in children undergoing inguinal herniorraphy. We also suggested that small dose of intravenous fentanyl would serve as an easy, simple and effective means for relieving postinguinal herniorrhaphy pain during the first 30 min of the initial postoperative period.

Low concentration of caudal bupivacaine for postoperative analgesia in elective pediatric surgery

This report summarizes [corrected] our experiences in 0.125% bupivacaine caudal analgesia in 70 pediatric patients with age ranging from 3 months to 7 years undergoing routine surgical procedures including herniorrhaphies, orchiopexies, and circumcision. The local anesthetic chosen was 0.125% bupivacaine with epinephrine (1:200,000) being added and the dosage administered [corrected] varied from 0.5-1.0 ml/kg depending upon the sites of the surgical procedures. In the recovery room, patients were observed and accessed using the modified Hannallah's pain/discomfort scoring system. Patients who achieved a score of four or more during a 30 min observation period were given codeine 1 mg/kg intramuscularly and the blocks were rated as uneffective. Our result was that 0.125% bupivacaine caudal analgesia was effective. The rate of success was 79%. The duration of analgesia was 4-8 hours. No delay or difficulty in urination was found. Most of the patients could move their lower extremities but could not bear their weight. Telephone follow-up failed to reveal any analgesia-related complication.

Effects of HMOs on the creation of competitive markets for hospital services

Why do health maintenance organizations (HMOs) use particular hospitals, and do they concentrate patients in hospitals where they obtain low prices? We answered these questions with a study of six HMOs in four large metropolitan areas in 1986. A two-part model was estimated for the probability that a hospital would be used and the demand for general inpatient admissions at hospitals that were used. Four staff-network plans in our study do shop for hospital services on the basis of price more than was generally believed. However, two independent practice association (IPAs) plans use more hospitals in the community and do not concentrate patients effectively at hospitals that offer the lowest prices.

Health insurance coverage of Minnesota farm families

This study of 1,482 farm families assesses the extent and cost of health insurance coverage among Minnesota farm families and finds that these families are buying less insurance coverage than urban families, while paying a higher proportion of their income for these premiums. More than three-fourths of the farm families surveyed buy their health insurance plan themselves and pay for it out of pocket. Their plans, on average, are slightly less expensive than employer-provided plans in urban areas, but they provide much less coverage and have more copayments and deductibles. Unlike their urban counterparts, who often choose health plans for convenience of location or freedom to choose physicians, farmers generally choose plans on the basis of costs and services provided. About 7 percent of farm families are without insurance, and many others are underinsured because they cannot afford to purchase an adequate plan.

Contracts between hospitals and health maintenance organizations

This article describes the contractual relations that are emerging between health maintenance organizations (HMOs) and hospitals. Six HMOs in four large metropolitan areas provided information on 102 hospital contracts. The authors found that the HMOs are becoming more aggressive in placing hospitals in competition with each other for HMO patients. Staff and network HMOs are able to obtain a higher concentration of patients and substantially larger discounts for inpatient services than are individual practice association (IPA) plans in this study.

Potential of albumin labeled with nitroxides as a contrast agent for magnetic resonance imaging and spectroscopy

The biological and physical properties of albumin and nitroxides make them attractive candidates as special purpose MRI contrast agents which could be used to study the intravascular compartment or specific targets in tissues. In this study, albumin-nitroxide complexes were prepared by reduction and alkylation of the disulfide bonds of the protein and characterized by electron spin resonance and ultraviolet absorption spectroscopy. An average of six nitroxides were bound covalently to each molecule of human serum albumin. The water proton relaxivity of the protein-bound nitroxide (at 20 MHz and 37 degrees C) was 4-fold greater than that of the free nitroxide. The digestion of the nitroxide-albumin complexes by cells or by trypsin decreased the relaxivity of the nitroxide-protein complex. The rate of reduction of albumin-bound nitroxide by cells was much slower than that of the free nitroxide but still was oxygen-sensitive (2-3-fold increase in the rate of reduction in the absence of oxygen).

[Intraoperative anaphylactic shock--report of two cases]

Allergic reactions are often unpredictable, sudden in onset and may be potentially lethal. Clinical manifestations are confined to skin (rash, urticaria, angioedema), respiratory tract (laryngeal edema, bronchospasm) and cardiovascular system (hypotension, bradycardia, dysrhythymia). Because cardiovascular collapse is the most common life-threatening clinical feature, immediate and proper treatment is necessary. We have experienced two cases of intraoperative anaphylatic shock between September 1988 and April 1989. The precipitating factors were of nonanesthetic origin (case 1 was probably due to cephalothin and case 2 was due to dextran 40). Both cases manifestated with hypotension, bradycardia, cutaneous rash and urticaria. Recovery was smooth and without sequela after volume expansion and sympathomimetic drug. We discuss these two cases with a brief review.

Oximetry in cells and tissues using a nitroxide-liposome system

In order to avoid the complication of reduction of nitroxides in biological media during oxygen measurements, liposomes containing a water-soluble nitroxide, 2,2,6,6-tetramethyl-piperidine-N-oxyl-4-trimethylammonium (Cat1), were used in studies of oxygen consumption by thymus-bone-marrow cells. The superhyperfine structure of Cat1 contained in liposomes was found to be sensitive to oxygen concentration in a fashion similar to that of free Cat1. Measurements of cellular respiration using Cat1 contained in liposomes agreed well with the results obtained using free Cat1. Using this nitroxide-liposome system, the respiration of liver slices was measured successfully, whereas such measurements using free cat1 were complicated by rapid reduction of the nitroxide. This nitroxide-liposome system also could be used in conjunction with a membrane permeable nitroxide and an extracellular broadening agent to measure intracellular and extracellular oxygen concentrations simultaneously.

Bone marrow uptake of liposome-entrapped spin label after liver blockade with empty liposomes

Using an ESR spectrometer, we studied the time course of the uptake of the liposome-entrapped spin label 2,2,6,6-tetramethylpiperidine-N-oxyl-4-trimethylammonium in liver, spleen, and bone marrow following reticuloendothelial liver blockade. Our results show that suppression of the phagocytic activity of the liver increases the delivery of liposomes to the spleen and bone marrow without substantially altering uptake by the liver.

Rapid assessment of liposomal stability in blood by an aqueous nitroxide spin label

An electron spin resonance method using an aqueous nitroxide spin label, 2,2,6,-tetramethyl-piperidine-N-oxyl-4-trimethyl-ammonium, for rapid assessment of liposome stability in blood is presented. The retention of the nitroxide in liposomes is measured by its electron spin resonance signal intensity, a procedure which does not require separation of the sample from the blood. Any nitroxide that is released from the liposomes is reduced by external ascorbic acid which is added to the sample. The method permits kinetic studies on the integrity of liposomes in the presence of destabilizing factors such as detergent, blood, or alteration in temperature.