Mouse erythrocytes as carriers for coencapsulated alcohol and aldehyde dehydrogenase obtained by electroporation in vivo survival rate in circulation, organ distribution and ethanol degradation

Alcohol dehydrogenase and aldehyde dehydrogenase (ADH and ALDH) have been coencapsulated into mouse erythrocytes by an electroporation technique. The optimal conditions were achieved as follows: 420 V, four pulses of 1 ms every 15 min. at 37 degrees C, completed by resealing: 1 h at 37 degrees C. An encapsulation yield ranging from 11-12% was obtained for ADH+ALDH-loaded erythrocytes. Carrier cell recovery was 52%. Electroporated-RBCs observed under Scanning electron microscopy exhibited a tendency toward invaginated sphero-stomatocytes. These invaginations were not found in electroporated/resealed RBCs. The intravenous administration of 51Cr-RBCs manifested a bimodal pharmacokinetic profile: an initial phase (t1/2alpha) with a rapid decrease of plasma 51Cr-RBCs followed by a slow and prolonged elimination phase (t1/2beta). The values corresponding to in vivo survival rate during the elimination phase indicated that the survival rate of 51Cr-electroporated loaded-RBCs was slightly lower (t1/2beta, 4.5 days) than 51Cr-native RBCs (t1/2beta, 5.3 days). The mean clearance values from blood of electroporated 51Cr-RBCs (unloaded and loaded) were higher (0.51 %51Cr/day and 0.54 %51Cr/day, respectively) than the obtained for native 51Cr-RBCs (0.18 %51Cr/day). The target organs for electroporated RBCs proved to be the same as for native RBCs. However, electroporated RBCs showed highest accumulation in liver, spleen and lung, since they were promptly recognized by the reticuloendothelium system. Mice induced to the state of acute ethanol intoxication and treated with ADH+ALDH-RBCs clearly showed a lower level of ethanol concentration in plasma (less than 43% ethanol) than the intoxicated mice treated with native RBCs. En consequence the clearance values of ethanol from blood in intoxicated mice treated with ADH+ALDH-RBCs (0.39 ml/min) were higher than the treated with native RBCs (0.20 ml/min). The results obtained suggest that ADH+ALDH-loaded erythrocytes could be used as a potential carrier system for in vivo removal of high levels of ethanol from blood caused by excessive alcohol consumption.

In vitro and in vivo study of glutamate dehydrogenase encapsulated into mouse erythrocytes by a hypotonic dialysis procedure

Glutamate dehydrogenase (GDH) has been encapsulated into mouse erythrocytes by a hypotonic dialysis/isotonic resealing method. Although a low GDH entrapment yield was achieved (3.8%), this percentage appeared sufficient enough to metabolize high quantities of ammonia. Carrier cell recovery yield was 56%. Due to the decrease in cell volume and haemoglobin content, constant mean cell haemoglobin concentration (MCHC) values were obtained. The osmotic fragility curves (OFC) indicated that dialyzed/resealed-RBCs are more resistant to hypotonic haemolysis than native-RBCs. The successful in vitro ammonia degradation by GDH-RBCs was reflected in its total disappearance from the incubation medium at around 48 h. In contrast, initial ammonia levels were not affected during the incubation in the presence of native-RBCs and remained constant. Two different methods were used for the preparation of hyperammonaemic mice model. Since the intraperitoneal (i.p.) administration of ammonium acetate produced high ammonia levels that lasted only a few minutes, the i.p. administration of urease was chosen, given that it generated elevated ammonia levels for longer periods of time. Hyperammonaemic mice quickly removed high levels of circulating ammonia in the presence of GDH-RBCs, whereas in the presence of native-RBCs ammonia was slowly metabolized. These results suggest that loaded GDH-erythrocytes can be used as a potential carrier systems for the in vivo removal of high levels of ammonia from blood.

In vivo survival of selected murine carrier red blood cells after separation by density gradients or aqueous polymer two-phase systems

In order to explore possibilities of using erythrocytes as carrier systems for delivery of pharmacological agents, we have studied the in vivo survival of murine carrier red blood cell populations enriched in young or old cells. Hypotonic-isotonic dialysis has been used to modify the cells as carrier systems and Percoll/albumin density gradients or counter-current distribution in aqueous polymer two-phase systems to separate them according to age. Hypotonic-isotonic dialysis produces a decrease in the red blood cell populations in vivo survival rate (from 9.5 to 7.8 days). Among the cells modified as carriers, the enriched young red blood cell populations show a higher in vivo survival (half-life 6.5-7.4 days) than populations made up of predominantly old red blood cells (half-life 4.7-6.2 days). Half-life of young or old circulating red blood cells was approximately one day longer when these cells were separated by counter-current distribution rather than by Percoll density gradients. Based on these results, hypotonic-isotonic dialysis of whole and enriched young or old red blood cell populations, with higher or lower survival rates, can be considered as a useful tool for modification of these cells as carriers. The final outcome of such changes can be translated into better control of plasma drug delivery during therapy.

[Retrospective study of complications of surgery for laryngeal cancer]

Surgery, alone or in combination with other therapeutic measures, is one of the main approaches to curing laryngeal cancer. The risk of complications is implicit in any surgical procedure. We describe our experience with general and local complications in surgery for laryngeal cancer and examine their relation to tumor extension and surgical technique. A review was made of a series of 431 patients who underwent surgery for laryngeal cancer over a 10-year period (1982-1991). Twenty-two patients (5.1%) had systemic complications, including upper gastrointestinal hemorrhage (n = 5), massive cervical hemorrhage (n = 5), and four renal failure. Minor complications were recorded in 77 cases (17.8%), predominantly pharyngocutaneous salivary fistula, which developed in 55 patients (13.8%). The incidence of local complications was significantly greater in patients with extensive local spread (T4). There were no differences among patients with regional spread. The surgical technique and type of pharyngoesophageal reconstruction played no role in the development of complications. Preoperative radiotherapy did not influence on the development of salivary fistulas.

[Oncologic surgery of the larynx after failure of radiotherapy]

The treatment of early-stage laryngeal cancer using either partial surgical techniques or irradiation still is controversial. The performance of rescue surgical procedures after irradiation is related to increased postsurgical complications and lower survival rates. We made a retrospective study of 73 patients who underwent rescue surgery after failure of radiotherapy in our department in the last 10 years. A statistical analysis was made of the complications and survival rate of these patients in accordance with tumor location and clinicopathological stage compared with patients who underwent surgery alone (n = 435). More rescue surgery was performed for glottic carcinomas (52/73) than for supraglottic carcinomas (21/73). No significant differences were found in the complication rate (23.6%) compared with the control group (19.6%). There was a significant reduction in survival in patients who underwent previous irradiation of supraglottic tumors compared with glottic tumors and the control group. In view of these results, we conclude that irradiation is not a good option as an initial treatment for supraglottic tumors and that the procedure of choice should be surgical.

In vitro study of alcohol dehydrogenase and acetaldehyde dehydrogenase encapsulated into human erythrocytes by an electroporation procedure

The optimal conditions for electroporated/resealed loading of alcohol dehydrogenase (ADH) and/or acetaldehyde dehydrogenase (ALDH) into human erythrocytes were established prior to the study, with the following characteristics: 300 V, 1 ms pulse time, eight pulses every 15 min and 1 h resealing at 37 degreesC. High encapsulation yield and carrier cell recoveries were achieved. Cell volumes increase while hemoglobin contents decrease; in consequence a decrease in cell hemoglobin concentration was observed. A lower hypotonic resistance of loading erythrocytes (throughout osmotic fragility curves) and unaltered oxygen transport capability (as given by oxygen equilibrium curves) were observed. The stability against time (up to 168 h-7 days) of encapsulated individual enzymes, either ADH- or ALDH-red blood cells (RBCs), was studied at 4 degreesC and 37 degreesC, in comparison with that of free enzyme solutions. Both enzymes were released from carrier RBCs to the incubation medium. The stability of carrier RBCs was studied under similar conditions. Non-significant variations in hematological parameters were observed. However, the hemoglobin derivative forms showed modifications. The continuous degradation of ethanol by ADH-RBCs and coencapsulated ADH- and ALDH-RBCs, as a function of time (up to 70 h) suggests the use of these carrier RBCs as agents for complete metabolization of ethanol. The mentioned properties bare the possibility of using ADH and ALDH as carrier systems in in vivo situations.

A comparative study by a single chromatographic procedure of glycolytic regulatory kinase isozymes in rat erythroid cells as a function of differentiation-maturation process

The isozymes of three glycolytic regulatory kinases: hexokinase, phosphofructokinase and pyruvate kinase are fractionated by a single ion exchange chromatographic procedure on DEAE-cellulose. Enriched-erythroblast bone marrow cells showed two heterogeneous peaks, each consisting of two overlapping peaks: one major and one minor peak, but only two isozymes were observed in reticulocytes and erythrocytes. Phosphofructokinase showed multiple isozymic forms in the three cell populations, but while in erythroblasts the main one eluted in the last fractions, in reticulocytes and erythrocytes it eluted in the early fractions. Pyruvate kinase showed a main early activity peak with a shoulder in erythroblasts, reticulocytes and erythrocytes but the response to the allosteric effectors (fructose-1,6-bisphosphate and ATP) suggests the presence of different pyruvate kinase isozymes in reticulocytes and erythrocytes.

Surface and metabolic properties of microcytic and macrocytic human anaemic red blood cells detected in polymer aqueous two-phase systems

Microcytic and macrocytic red blood cells from anaemic patients have been fractionated as a function of cell surface properties by the countercurrent distribution technique using charge-sensitive dextran/poly(ethylene glycol) aqueous two-phase systems. As deduced from the fractionation profiles, microcytic cells constitute a heterogeneous cell population with decreased surface charge properties while. macrocytic cells constitute a homogeneous cell population with behaviour similar to that of the control red blood cells. The specific activity of pyruvate kinase, an age-dependent enzyme, did not change along microcytic red blood cells fractionation profiles, suggesting that such cells have altered ageing properties. However, pyruvate kinase specific activity decreases from the left- to the right-hand side of the fractionation profile of macrocytic red blood cells, indicating that these cells follow the normal ageing process. Bisphosphoglycerate mutase specific activity did not change along the fractionation profile of any cell population under study, thus providing 2,3-bisphosphoglycerate during the life-span of the red blood cells from anaemic patients.

Chondrosarcoma of the temporal bone and otosclerosis

Chondrosarcoma constitutes 6% of all primary bone tumors and 11% of malignant primary bone tumors. Nevertheless, in a review of the tumor registry of the University of Michigan covering a period of 50 years, there were only 3 cases involving the temporal bone. A case of a woman with a chondrosarcoma of the temporal bone that was partially resected by means of an infratemporal approach at the skull base is presented. This patient had previously undergone surgical treatment for otosclerosis of the other ear. Several considerations regarding survival factors in this type of tumor are dealt with in terms of the histological features, therapeutic options and anatomic location. The possibility that this lesion may originate from the persistence of the cartilaginous inclusions that some authors consider to be involved in the origin of otosclerosis is discussed.

[Protocol for the endoscopic sinus surgery: comparative analysis of 200 cases]

A preliminary analysis was published in 1993 of 100 cases of endoscopic sinus surgery (ESS) carried out in our service following a protocol that included sinusitis, nasal polyps, and other endoscopic nasal procedures. Another 100 cases of ESS were analyzed for the present study and compared with the 1993 group. Comparative analysis showed improved results in the second series, with fewer minor complications and no major complications. These findings confirm the general opinion that endoscopic sinus surgery requires an adequate training period before optimal results are obtained.

Oxygenation capacity of hypotonized and crosslinked rat erythrocytes

Rat erythrocytes subjected to hypotonic-isotonic dialysis, or crosslinking with bifunctional reagents (glutaraldehyde and dimethyl suberimidate hydrochloride) show a high percentage of methemoglobin and decreased oxyhemoglobin content which implies a low oxygen carrying capacity. Such modified cells maintain reversible oxygen binding properties although, they present a high hemoglobin oxygen affinity (low P50) and a diminished cooperativity in binding oxygen to hemoglobin (low n). These results suggest a reduced capacity of liberating oxygen to tissues under low PO2. Changes produced in erythrocytes can not be restored even in the presence of energy (ATP), reduced glutathione and 2,3-bisphosphoglyceric acid during the dialysis process or after crosslinking/permeabilizing treatment.

Osteoma of the promontory: a case report

Osteomas of the middle ear are rare lesions. We report the case of a 20-year-old male with osteoma originating from the promontory coincident with tympanic membrane perforation. Histopathological diagnosis was performed by means of a superficial curettage during surgery, to avoid a cochlear fenestration. Postoperative closure of the air-bone gap after myringoplasty confirmed the presumed asymptomatic nature of these lesions.

[Synthetic implants in the reconstruction of the ossicular chain]

Experience has revealed a higher rate of functional failure of biocompatible prostheses used in the surgical reconstruction of the middle ear than was reported initially. The cause of these failures was analyzed in a retrospective study of 135 patients who underwent middle ear reconstructive procedures: 47 of them involved implantation of plastic prostheses. Proplast or Plastipore, and had a sufficient follow-up. We evaluated the prosthetic material and middle-ear conditions for which they were implanted.

Erythrocytes as carriers for recombinant human erythropoietin

PURPOSE

The aim of this work was to encapsulate recombinant human erythropoietin (rHuEpo) in human and mouse red blood cells (RBCs) to improve the stability of encapsulated rHuEpo.

METHODS

The encapsulation of rHuEpo was achieved by an hypotonic dialysis-isotonic resealing procedure. A radioimmunoassay method was used for the estimation of rHuEpo. The hypoosmotic resistance of carrier erytrhocytes was studied by osmotic fragility measurements. Cell morphology was observed under scanning electron microscopy. Encapsulated rHuEpo was identified by an immunogold labeling assay.

RESULTS

Encapsulation yields were 22% for human RBCs and 14% for mouse RBCs. Cell recovery was around 70%. Carrier-RBCs exhibited a tendency to spherocytic morphology, and showed the typical higher hypoosmotic resistance than normal RBCs. The presence of rHuEpo inside carrier RBCs was identified. The stability of encapsulated rHuEpo seems to be related to the experimental conditions used during the encapsulation procedure. An increase with time of released rHuEpo was observed in carrier-RBC suspensions.

CONCLUSIONS

The encapsulation of rHuEpo in RBCs has been achieved for the first time. These carrier RBC-preparations may serve as an alternative sustained cell delivery system for the in vivo administration of rHuEpo.

The influence of enzyme concentration on the encapsulation of glutamate dehydrogenase and alcohol dehydrogenase in red blood cells

Glutamate dehydrogenase (GDH) and alcohol dehydrogenase (ADH) have been encapsulated in sheep and human red blood cells (RBCs) by a hypotonic dialysis/isotonic resealing procedure. At a fixed enzyme level in the dialysis bag (100 units/ml of RBCs), a significant encapsulation yield was observed for ADH, both in human (17.2%) and sheep (47.9%) RBCs, whereas a very low entrapment of GDH was achieved (1-3%) in either species. Carrier cell recovery was 61-65% in humans and 30-34% in sheep. Because of the aggregation of GDH to large polymers at protein levels above 1 mg/ml, the yield of encapsulation and the specific activity in human carrier RBCs were compared at different enzyme concentrations. While entrapment was not affected by differences in ADH up to 13,000 units/ml of RBCs (38 mg/ml), the yield of GDH encapsulation significantly decreased as the enzyme level increased up to 750 units/ml of RBCs (15 mg/ml), thus demonstrating the importance of protein concentration in the encapsulation process for those enzymes that tend to aggregate.

Surface properties of crosslinked erythrocytes as studied by counter-current distribution in aqueous polymer two-phase systems

The bifunctional imidoester dimethyl suberimidate hydrochloride can stabilize rat red blood cells (RBCs) by membrane protein crosslinking, and in that way they can be used as carrier systems for exogenous substances. Counter-current distribution fractionation in charge-sensitive dextran-polyethyleneglycol two-phase systems has been used to detect slight changes in surface charge in stabilized cells. A decrease in the surface charge of crosslinked RBCs and an apparent masking of the age-related cell surface properties have been found to result from the protein crosslinking. Digitonin treatment used to permeabilize crosslinked RBCs produces a significant decrease of the cell surface charge while the age-related surface properties do not seem to be modified by the treatment.

[Endoscopic approach of antrochoanal polyps]

Antrochoanal polyps represent a particular pathology among nasosinusal polyposis. Since KILLIAN'S first report in 1906, several pathogenic mechanisms and surgical techniques have been described. Surgical removal of an antrochoanal polyp by the classic Caldwell-Luc approach has been reviewed since the beginning of the use of nasosinusal functional endoscopic surgery. We present 12 cases of antrochoanal polyps removed by this technique in our hospital, during the last three years, analyzing the results and complications of this endoscopic approach. We conclude that functional endoscopic surgery of the sinus for removal of antrochoanal polyps, is a recommendable surgical technique due to its efficiency and low morbidity.

[Acquired stenosis of the nasopharynx]

A case of scarring stenosis of the nasopharynx occurring in the fifth decade without previous medical history is presented. Transpalatal resection with a prolonged stent, produced patent nasal cavities, but the different studies performed did not establish the etiological diagnosis. A final stage of rhinoscleroma was suspected.

Density gradient separation of L-asparaginase-loaded human erythrocytes

L-Asparaginase has been encapsulated in human red blood cells using a hypotonic dialysis process. Erythrocytes loaded with L-Asparaginase were separated into eight fractions using a discontinuous Percoll density gradient. A minor cell subpopulation of low density cells and a major subpopulation of denser erythrocytes was obtained after hypotonic dialysis treatment, in both the absence or presence of L-Asparaginase. The encapsulated L-Asparaginase activity per resealed erythrocyte was higher in low-density cells and decreased progressively with increasing in cellular density.

Biochemical characterization of human erythrocytes fractionated by counter-current distribution in aqueous polymer two-phase systems

The fractionation of normal human erythrocytes by counter-current distribution (CCD) in charge-sensitive dextran-polyethylene glycol two-phase systems was confirmed and extended to red blood cells from heterozygous beta-thalassaemic patients. The differences between the distribution profiles of normal (homogeneous) and abnormal (heterogeneous) red blood cells reflect their different surface-charge properties. As suggested by the decline of membrane sialic acid released after neuraminidase treatment and the specific activities of two age-dependent enzymes (membrane acetylcholinesterase and intracellular pyruvate kinase) in the distribution profiles (from the left- to the right-hand side fractions), the fractionation seems to be according to red blood cell age. A constancy of the 2,3-bisphosphoglycerate level was observed in ageing red blood cells.

Surface properties of crosslinked and crosslinked-permeabilized erythrocytes as studied by partitioning in aqueous polymer two-phase systems

Non-charge- and charge-sensitive dextran/polyethyleneglycol two-phase systems have been used to study the surface properties of red blood cells stabilized by crosslinking with dimethyl suberimidate and permeabilized with digitonin. While crosslinked red blood cells show similar hydrophobic- and charge-related surface properties as control cells, the digitonin treatment changes their surface properties. The changes in hydrophobicity are related to the cell total lipid and cholesterol content while the changes in the charge are related to the sialic acid released by neuraminidase.

Properties of hypotonized, crosslinked and crosslinked- permeabilized rat erythrocytes as potential carrier systems

The osmotic fragility curves of isotonic rat RBCs, studied at pH 8 to avoid the Hb insolubility, are similar to those in humans at pH 7.4. Hypotonized rat RBCs, either directly or dialysed (0-24 h), are more hemolysis-resistant than isotonic rat RBCs. The discocyte-stomatocyte-spherocyte transformation can be observed with scanning electron microscopy. Protein crosslinking with dimethyl suberimidate can stabilize RBCs. The crosslinking level (60%), the cellular yield (80%), the mechanical and hemolytic resistance and the protective effect of enzyme activities, were studied in crosslinked or crosslinked- permeabilized RBCs after digitonin treatment. The normal discocytic shape of RBCs under scanning electron microscopy becomes stomatocytic in crosslinked and crosslinked- permeabilized RBCs with an erosioned surface.

Changes in glycolytic enzyme activities in aging erythrocytes fractionated by counter-current distribution in aqueous polymer two-phase systems

Human and rat erythrocytes were fractionated by counter-current distribution in charge-sensitive dextran/poly(ethylene glycol) two-phase systems. The specific activities of the key glycolytic enzymes (hexokinase, phosphofructokinase and pyruvate kinase) declined along the distribution profiles, although the relative positions of the activity profiles were reversed in the two species. These enzymes maintained their normal response to specific regulatory effectors in all cell fractions. No variations were observed for phosphoglycerate kinase and bisphosphoglycerate mutase activities. Some correlations between enzyme activities (pyruvate kinase/hexokinase, pyruvate kinase/phosphofructokinase, pyruvate kinase/pyruvate kinase plus phosphoglycerate kinase, pyruvate kinase/bisphosphoglycerate mutase and phosphoglycerate kinase/bisphosphoglycerate mutase ratios) were studied in whole erythrocyte populations as well as in cell fractions. These results strongly support the fractionation of human erythrocytes according to cell age, as occurs with rat erythrocytes.

Comparison of the PREMIER cryptococcal antigen enzyme immunoassay and the latex agglutination assay for detection of cryptococcal antigens

A new enzyme immunoassay (EIA), PREMIER Cryptococcal Antigen, was compared with latex agglutination (LA) for the detection and quantitation of circulating capsular polysaccharide antigen from Cryptococcus neoformans. The clinical evaluation of PREMIER EIA as a screening assay, including 475 specimens with 120 LA and EIA positives, resulted in 99% sensitivity and 97% specificity. The clinical specimens included sera and cerebrospinal fluids as well as 10 rheumatoid factor-positive and 20 anti-nuclear antibody-positive serum samples. This monoclonal antibody-based assay detects serotypes A to D at 0.63, 0.63, 7.8, and 62 ng/ml, respectively. With three different known positive specimens, the assay was found to yield coefficients of variation of 2 to 12% for intra- and interassay comparisons of precision and reproducibility. The primary use for semiquantitative values derived with the LA or EIA is to follow the course of disease and monitor drug therapies. The present data suggest that the PREMIER EIA will be a valuable method for this purpose. We conclude that the PREMIER Cryptococcal Antigen EIA provides a rapid, convenient, and reliable antigen detection method for screening and semiquantitative determination of antigen levels.

Fractionation in two-phase systems of red cells during rat development: changes in pyruvate kinase and bisphosphoglycerate mutase activities in relation to red cell switching

An inverse relationship between 2,3-bisphosphoglycerate levels and the ratio calculated from pyruvate kinase and bisphosphoglycerate mutase activities has been observed in red populations of rats during animal development. Counter-current distribution in aqueous two-phase systems of these cells populations shows a displacement of distribution profiles towards the high-numbered cavities of the rotor as animal ages. Heterogeneity of cells after distribution is only observed during the switching process from fetal to adult red cells taking place along the postnatal stage of development. Values for the pyruvate kinase/bisphosphoglycerate mutase ratio in these fractions suggest the separation of fetal (liver) from adult (bone marrow) red cells.