Encapsulation of bovine serum albumin in poly(lactide-co-glycolide) microspheres by the solid-in-oil-in-water technique

Non-aqueous protocols to encapsulate pharmaceutical proteins into biocompatible polymers have gained much attention because they allow for the minimization of procedure-induced protein structural perturbations. The aim of this study was to determine if these advantages could be extended to a semi-aqueous encapsulation procedure, namely the solid-in-oil-in-water (s/o/w) technique. The model protein bovine serum albumin (BSA) was encapsulated into poly(lactide-co-glycolide) (PLG) microspheres by first suspending lyophilized BSA in methylene chloride containing PLG, followed by emulsification in a 1% aqueous solution of poly(vinyl alcohol). By variation of critical encapsulation parameters (homogenization intensity, BSA:PLG ratio, emulsifier concentration, ratio of organic to aqueous phase) an encapsulation efficiency of > 90% was achieved. The microspheres obtained showed an initial burst release of < 20%, a sustained release over a period of about 19 days, and a cumulative release of at least 90% of the encapsulated BSA. Different release profiles were observed when using different encapsulation protocols. These differences were related to differences in the microsphere erosion observed using scanning electron microscopy. Release of BSA was mainly due to simple diffusion or to both diffusion and microsphere erosion. Fourier-transform infrared studies were conducted to investigate the secondary structure of BSA during the encapsulation. Quantification of the alpha-helix and beta-sheet content as well as of overall structural changes showed that the secondary structure of encapsulated BSA was not more perturbed than in the lyophilized powder used initially. Thus, the encapsulation procedure did not cause detrimental structural perturbations in BSA. In summary, the results demonstrate that the s/o/w technique is an excellent alternative to the water-in-oil-in-water technique, which is still mainly used in the encapsulation of proteins in PLG microspheres.

Development of a monoclonal antibody specific to a recombinant envelope protein from dengue virus type 4 expressed in Pichia pastoris

A mouse monoclonal antibody (MAb, 4B6) was able to recognize dengue virus type 4 envelope (E) protein both as a recombinant protein in Pichia pastoris and when it was present in infected brains of suckling mice. 4B6 was characterized by enzyme-linked immunoadsorbent assay (ELISA), hemaglutination inhibition, neutralization, and immunoblot. The MAb was isotyped as IgG2a. It was serotype 4 specific and it inhibited hemaglutination and neutralized homologous virus. It did not enhance infection of P338D1 cells by dengue type 4 virus strain H-241 strain. This MAb was reactive with recombinant E protein and dengue 4 virus, as revealed by Western blot. In vivo, MAb 4B6 conferred passive protection in mice challenged with homologous virus. Currently, this MAb is being used to purify recombinant E protein for further studies.

Virulent strains of Salmonella enteritidis disrupt the epithelial barrier of Caco-2 and HEp-2 cells

To confirm the existence in nature of Salmonella enteritidis strains of different degrees of virulence and to elucidate the mechanisms underlying the effects of such strains on the epithelial barrier function, the consequences of infection of Caco-2 cells and HEp-2 cells with 15 S. enteritidis strains in a chicken infection model were examined. The more virulent strains of S. enteritidis, which are biofilm producers in adherence test medium, were able to disrupt HEp-2 and Caco-2 monolayers, as shown by transmonolayer electrical resistance and lactate dehydrogenase activity. In contrast, the low-virulence strains of S. enteritidis, which do not produce biofilms in adherence test medium, had no effect on the same cells. An avirulent rough mutant of Salmonella minnesota exhibited a pattern of behaviour similar to that of the low virulence strains of S. enteritidis, whilst a clinical Salmonella typhi strain caused rapid injury to the monolayers. The effect of supernatants of Salmonella cultures in adherence test medium on the integrity of Caco-2 cell monolayers indicated that the high-virulence S. enteritidis strains, but not the low-virulence strains, release a soluble factor when incubated under optimum biofilm-forming conditions, which enables the disruption of the integrity of Caco-2 monolayers.

How partial nitrification could improve reclaimed wastewater transport in long pipes

Reclaimed wastewater transport is studied in a concrete-lined cast iron pipe, where a nitrification-denitrification process occurs. The pipe is part of the Reuse System of Reclaimed Wastewater of South Tenerife (Spain), 0.6 m in diameter and 61 km long. In order to improve wastewater quality, at 10 km from the inlet there is injection of fresh water saturated in dissolved oxygen (DO), after which a fast nitrification process usually appears (less than two hours of space time). The amount of oxidized nitrogen compounds produced varies between 0.8 and 4.4 mg/l NOx(-)-N. When DO has disappeared, a denitrification process begins. The removal of nitrite is complete at the end of the pipe, whereas the nitrate does not disappear completely, leaving a concentration of about 0.4-0.5 mg/l. For a COD/NOx(-)-N ratio higher than 5, a first order nitrification rate in NOx(-)-N has resulted, with the constant k20 = 0.079 h-1, for a NOx(-)-N concentration range of 0.8-4.4 mg/l. Finally the following temperature dependency for the first order denitrification rate constant has been found: k = k20 x 1 x 15T-20. Although nitrogen could be used as nutrient in the agricultural reuse, its removal from reclaimed wastewater could be useful in order to diminish the chlorine needs for reclaimed wastewater disinfection.

Cloning and functional analysis of a family of nuclear matrix transcription factors (NP/NMP4) that regulate type I collagen expression in osteoblasts

Collagen expression is coupled to cell structure in connective tissue. We propose that nuclear matrix architectural transcription factors link cell shape with collagen promoter geometry and activity. We previously indicated that nuclear matrix proteins (NP/NMP4) interact with the rat type I collagen alpha1(I) polypeptide chain (COL1A1) promoter at two poly(dT) sequences (sites A and B) and bend the DNA. Here, our objective was to determine whether NP/NMP4-COL1A1 binding influences promoter activity and to clone NP/NMP4. Promoter-reporter constructs containing 3.5 kilobases (kb) of COL1A1 5' flanking sequence were fused to a reporter gene. Mutation of site A or site B increased promoter activity in rat UMR-106 osteoblast-like cells. Several full-length complementary DNAs (cDNAs) were isolated from an expression library using site B as a probe. These clones expressed proteins with molecular weights and COLIA1 binding activity similar to NP/NMP4. Antibodies to these proteins disrupted native NP/NMP4-COL1A1 binding activity. Overexpression of specific clones in UMR-106 cells repressed COL1A1 promoter activity. The isolated cDNAs encode isoforms of Cys2His2 zinc finger proteins that contain an AT-hook, a motif found in architectural transcription factors. Some of these isoforms recently have been identified as Cas-interacting zinc finger proteins (CIZ) that localize to fibroblast focal adhesions and enhance metalloproteinase gene expression. We observed NP/NMP4/CIZ expression in osteocytes, osteoblasts, and chondrocytes in rat bone. We conclude that NP/NMP4/CIZ is a novel family of nuclear matrix transcription factors that may be part of a general mechanical pathway that couples cell structure and function during extracellular matrix remodeling.

Daily assessment of severity of illness and mortality prediction for individual patients

OBJECTIVE

To refine the prognosis of critically ill patients using a statistical model that incorporates the daily probabilities of hospital mortality during the first week of stay in the intensive care unit (ICU).

DESIGN

Prospective inception cohort.

SETTING

Fifteen adult medical and surgical ICUs in Spain.

PATIENTS

A total of 1,441 patients aged > or =18 yrs who were consecutively admitted from April 1, 1995, through July 31, 1995.

INTERVENTIONS

Prospective data collection during the stay of the patient in the ICU. Data collected included vital status at hospital discharge as well as all variables necessary for computing the Mortality Probability Models II system at admission and during the first 7 days of stay in the ICU.

MEASUREMENTS AND MAIN RESULTS

Four logistic regression models were obtained. These models contained survival status at hospital discharge as a dependent variable and the following explanatory variables: (model 1) only the probability of dying at admission; (model 2) only the probability of dying during the current day; (model 3) the probability of dying at admission and during the current day; and (model 4) the probabilities of dying at admission and during the previous and current days. Models were evaluated using the Hosmer-Lemeshow statistic and the area under the receiver operating characteristic curve. For survivor and nonsurvivor patients, mortality probabilities obtained using the aforementioned models were compared using linear regression and the paired Student's t-test. Although severity at admission was a statistically significant variable, models 2 and 3 produced almost the same probabilities of hospital mortality, as shown with the linear regression and paired Student's t-test results.

CONCLUSIONS

To have an accurate measurement of the prognosis, it is necessary to update the severity measure. The best estimate of hospital mortality was the probability of death on the current day. Severity at admission and at previous days did not improve the assessment of prognosis.

Inhomogeneous integral equation approach to pair and triple correlations in a glass-forming simple liquid

A simple model of glass-forming liquid modeled via Dzugutov's pair potential is studied by means of the triplet hypernetted chain approximation as formulated by Attard [P. Attard, J. Chem. Phys. 93, 7301 (1990)]. This system, which is known to be mostly dominated by microscopic icosahedral ordering, eludes a correct description in terms of classical two-body integral equation theories. However, it is found here that the simple hypernetted chain approximation when applied at the three-particle level can yield a correct semiquantitative description of both the pair and triplet structure of the supercooled state, capturing features which escape more sophisticated closures implemented on the two-particle level.

Prevalence and viral persistence of TT virus in patients on hemodialysis

The aim of this study was toevaluate the prevalence of TT virus (TTV) in 107 hemodialysis patients and 100 healthy individuals. Sixteen percent of hemodialysis patients and 2% of the control population were TTV positive (P<0.001). Sex, time on dialysis, transfusions, and alanine aminotransferase levels were not related to the presence of TTV DNA. TTV was more frequent in patients 50 to 70 (12/51) years of age and persisted in the serum of six of nine patients 8 months later. TTV was found in peripheral blood mononuclear cells of all patients with chronic infection, and sequence variation was noted in the peripheral blood mononuclear cells of two patients. No relationship between TTV infection and hepatitis was observed. Viral persistence and nonparenteral transmission may be possible in patients on hemodialysis.

Epidemiologic studies on Dengue in Santiago de Cuba, 1997

A small, isolated outbreak of dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) due to dengue virus type 2 (DEN-2) was documented in Santiago de Cuba on the island of Cuba beginning in January 1997. There were 205 DHF/DSS cases, all in persons older than age 15 years. All but three had evidence of a prior dengue infection, with the only known opportunity being the islandwide dengue virus type 1 (DEN-1) epidemic of 1977-1979. Virtually complete clinical and laboratory surveillance of overt disease was achieved. From December 1997 to January 1998, a random, age-stratified serum sample was obtained from 1,151 persons in 40 residential clusters in Santiago. Sera were tested for DEN-1 and DEN-2 neutralizing antibodies. The prevalence of DEN-2 antibodies in children age 15 years and under, born after the 1981 DEN-2 epidemic, was taken as the 1997 DEN-2 infection rate. This was adjusted slightly to accommodate observed cases, resulting in an estimated infection rate of 4.3%. Dengue fever and DHF/DSS attack rates were calculated from estimated total primary and secondary DEN-2 infections. Only 3% of 13,116 primary infections were overt. The DHF/DSS attack rate for adults of all ages was 420 per 10,000 secondary DEN-2 infections.

Human chorionic gonadotropin and intravaginal natural progesterone are equally effective for luteal phase support in IVF

This prospective randomized study compared human chorionic gonadotropin (hCG) and micronized transvaginal progesterone for luteal support in 310 in vitro fertilization (IVF) patients treated with leuprolide acetate and gonadotropins in a long protocol, and showing normal ovarian response. Both treatment groups were homogeneous for age, BMI, stimulation treatment and ovarian response. Pregnancy rates per embryo transfer were not significantly different (33.1% for the hCG group versus 38.7% for the progesterone group). For IVF patients with a normal response to stimulation under pituitary suppression, the use of hCG or progesterone for luteal support does not seem to have any effect on pregnancy rate. The choice of luteal treatment must balance medical hazard and patient convenience, as both therapeutic regimens seem equally effective.

The relationship between glycogen synthesis, biofilm formation and virulence in salmonella enteritidis

Salmonella enteritidis accumulated large quantities of intracellular polysaccharide when grown in unrestricted nutrient conditions. Dense, abundant cytoplasmic granules were observed by electron microscopy in sections stained by the periodic acid-chlorite technique, indicating that the polysaccharide was of the glycogen type. When biofilm-producing S. enteritidis was pre-incubated in media containing increasing levels of glucose concentration, the levels of both cytoplasmic glycogen and biofilm rose correlatively to a point where a ceiling effect was observed. Studies carried out with activators and inhibitors of glycogen biosynthesis confirmed that biofilm was formed from glycogen cell stores. On the other hand, the virulence of the biofilm-producing strain in infected chickens increased proportionally to the amount of stored glycogen, suggesting a possible role of the glycogen depot in the virulence of S. enteritidis.

Human Dengue antibodies against structural and nonstructural proteins

Antibodies against dengue virus type 2 and 4 proteins in acute-phase sera of 10 primary and 10 secondary dengue fever and dengue hemorrhagic fever patients were studied by Western blotting. In the first group the immune response was barely detectable, while in the second group more proteins were detected, with a very strong reaction. Anti-NS1 and -NS3 antibodies were detected mainly in secondary cases. Anti-E, -NS3, and -NS5 antibodies were detected in a high number of cases. The possibility of implementing early diagnostic assays for antigen detection is suggested.

Comparison of rapid centrifugation assay with conventional tissue culture method for isolation of dengue 2 virus in C6/36-HT cells

A rapid centrifugation assay was compared with conventional tube cell culture for dengue virus isolation in both sera and autopsy samples from dengue and dengue hemorrhagic fever/dengue shock syndrome fatal cases. The rapid centrifugation assay allowed isolation of virus from 16.6% more samples than the conventional method, and it shortened the time for dengue virus detection. Finally, it allowed the isolation of dengue 2 virus in 42.8% of tissue samples from five fatal cases. Our results suggest that the rapid centrifugation assay may be useful for detection of dengue virus in clinical specimens.

Enzyme-linked immunosorbent assay with a Salmonella enteritidis antigen for differentiating infected from vaccinated poultry

The specificity and sensitivity of indirect ELISA, based on the use of four different antigenic extracts obtained from a clinical isolate of Salmonella enteritidis, were compared with those obtained with the gm-flagellin based ELISA (IDEXX). A total of 116 serum samples from salmonellae free, naturally infected and vaccinated hens were studied. The results showed that the indirect ELISA, based on lipopolysaccharide (LPS), O-polysaccharide (PS) or membrane sediment (SD) antigens, enable the identification of a greater number of infected birds and discriminated field antibody responses from vaccinal ones better than the commercial IDEXX test. The indirect ELISA that used a O-polysaccharide rich fraction (PS) proved to be the most specific and sensitive test, suggesting that this indirect ELISA could be used to confirm IDEXX results, especially when the differentiation between vaccinated and infected poultry is required.

[Biological behavior of 3 strains of the dengue-2 virus in 2 cell lines of mosquitoes]

Strains A-15 (isolated in Cuba, 1981), Jamaica (isolated in Jamaica, 1981) and Nueva Guinea "C" (standard) from dengue-2 virus were compared according to the time of appearance of the cytopathic effect (CPE), to the time of appearance of specific fluorescence and to the kynetics of viral multiplication on being innoculated in the cell lines AP-61 (Aedes pseudoscutellaris) and C6/36 HT (Aedes albopictus). The results showed that the CPE of highest intensity and earliest appearance was for A-15, followed by Jamaica and Nueva Guinea "C" (NGC). AP-61 seems to favor the CPE of Jamaica with respect to that of the same strain in C6/36 HT. The fluorescence was earlier for Jamaica and A-15 and more intensive for the latter, whereas NGC manifested late. This behaviour was similar in the 2 cellular systems. The greatest titres during the kinetics of viral multiplication were obtained from A-15 in both lines, although in AP-61 they tend to be equal from the 4th day on. The strain A-15 showed a particular behaviour of these biological properties on comparing them with the other strains under study, which may be related to changes found in its neucleotide sequence.

Performance of the Mortality Probability Models in assessing severity of illness during the first week in the intensive care unit

OBJECTIVE

To extend the Mortality Probability Models (MPM) II severity system to time periods between 4 and 7 days after admission to the intensive care unit (ICU).

DESIGN

Prospective inception cohort.

SETTING

Fifteen adult medical and surgical ICUs in Spain.

PATIENTS

A total of 1,441 patients aged > or =18 yrs consecutively admitted from April 1, 1995 through July 31, 1995.

INTERVENTIONS

Prospective data collection during the stay of the patient in the ICU. Data collected included demographic information, length-of-stay and vital status at both ICU and hospital discharge, as well as all variables necessary for computing the MPM II system at admission and during the first 7 days of stay in the ICU MEASUREMENTS AND MAIN RESULTS: Calibration and discrimination of the four existing MPM II models (MPM0, MPM24, MPM48, and MPM72) were assessed in the study database. The MPM II system overestimated the mortality of patients with probabilities of death > or =0.4. The MPM24 model was customized. Models for time periods between 48 hrs and 7 days (MPM48 to MPMd7) were obtained using the same strategy that was used to develop the original MPM48 and the MPM72 models. The variable coefficients of the MPM24 model were kept fixed and the constant terms of the MPM48 to MPMd7 models were estimated by logistic regression. The constant term stabilized after the fourth day of admission and it was similar to the constant term of the MPM72 model. The customized MPM72 performed very well for days 4 to 7 after admission to the ICU.

CONCLUSIONS

If the patient's condition stays the same day after day, the probability of dying in the hospital increases until 72 hrs, and then stabilizes. A severity measure that performs well at 72 hrs can be a useful tool for measuring severity at later time periods.

Persistence of well-defined collective excitations in a molten transition metal

Well-defined microscopic collective excitations are found in liquid Ni at 1763 K by means of inelastic neutron scattering. Such excitations are supported by the liquid despite an anharmonic character of its thermodynamic functions. Consideration of the detailed shape of the interionic pair potential provides a way to understand why atomic motions at microscopic scales behave in a way much closer to the alkali metals than to the liquefied rare gases.

[Economic and social impact of the National Tuberculosis Control Program (NTCP) on the Cuban population]

Tuberculosis (TB) control strategies provide one of the greatest cost/effectiveness results. To assess the impact of the national TB control program on the Cuban population, the time series of new TB cases and death reports, potential years of life lost, and the numbers of beds for TB case hospitalization in the entire country during 1964-91 and 1992-96 were described by common simple calculation on the basis of estimated expected values. The reduction in new TB cases and deaths, potential years of life saved, and savings in expenditures for treatment, hospitalization, and unemployment compensation were estimated. From 1965 to 1991 new case reports were reduced by 94.6% (4% per year); 86,500 cases were avoided; 166,439 potential years of life were saved; 2,831,625 million pesos were saved on tuberculostatic drugs; 82.7 million pesos were saved on unemployment compensation under the social security system for workers with active TB. Estimated savings totaled 494,919,631.3 pesos. Nationwide intervention for TB control produced an important impact on the basis of the sociopolitical status making it possible to approach complete elimination of the disease in the future.