Trace metals in estuarine sediments from the southwestern Spanish coast

The impact of river-transported metal pollution and industrial wastes on the metal distribution (Cr, Cu, Zn, Pb) in estuarine sediments was studied in the southwestern Spanish estuaries. Intertidal and subtidal surface sediments of the Tinto-Odiel Estuary are very highly polluted by heavy metals, with geoaccumulation indices up to 4 in the three sedimentary environments studied (channel, channel border and salt marsh). The single exception is the Punta Umbria channel, very protected from the point sources by salt marsh deposits and hydraulic processes. In the remaining two estuaries, pollution (Pb, Cu) was only significant near the harbour situated in the Piedras river mouth, whereas very low values were found in the Guadiana Estuary. In these last rivers, the enrichment factor increases from the channel to the salt marsh sediments.

Evidence that systemic gentamicin suppresses premature stop mutations in patients with cystic fibrosis

Here we report the effects of gentamicin treatment on cystic fibrosis transmembrane regulator (CFTR) production and function in CF airway cells and patients with CF with premature stop mutations. Using immunocytochemical and functional [6-methoxy-N- (3-sulfopropyl) quinolinium (SPQ)-based] techniques, ex vivo exposure of airway cells from stop mutation CF patients led to the identification of surface-localized CFTR in a dose-dependent fashion. Next, five patients with CF with stop mutations and five CF control subjects were treated with parenteral gentamicin for 1 wk, and underwent repeated in vivo measures of CFTR function (nasal potential difference [PD] measurements and sweat chloride [Cl(-)] testing). During the treatment period, the number of nasal PD readings in the direction of Cl(-) secretion was increased approximately 3-fold in the stop mutation patient group compared with controls (p < 0.001), and four of five stop mutation patients with CF had at least one reading during gentamicin treatment with a Cl(-) secretory response of more than -5 mV (hyperpolarized). A response of this magnitude was not seen in any of the CF control subjects (p < 0.05). In an independent series of experiments designed to test the ability of repeat nasal PDs to detect wild-type CFTR function, evidence of Cl(-) secretion was seen in 88% of control (non-CF) nasal PDs, and 71% were more than -5 mV hyperpolarized. Together, these results suggest that gentamicin treatment can suppress premature stop mutations in airway cells from patients with CF, and produce small increases in CFTR Cl(-) conductance (as measured by the nasal PD) in vivo.

Mathematical Modeling of Carbon Monoxide Exposures from Anesthetic Breakdown

Background

Carbon monoxide (CO) is produced by reaction of isoflurane, enflurane, and desflurane in desiccated carbon dioxide absorbents. The inspiratory CO concentration depends on the dryness and identity of the absorbent and anesthetic. The adaptation of existing mathematical models to a rebreathing circuit allows identification of patient factors that predispose to more severe exposures, as identified by carboxyhemoglobin concentration.

Methods

From our companion study, the authors used quantitative in vitro CO production data for 60 min at 7.5% desflurane or 1.5% isoflurane at 1 l/min fresh gas flow. The carboxyhemoglobin concentration was calculated by iteratively solving the Coburn Forster Kane equation modified for a rebreathing system that incorporates the removal of CO by patient absorption. Demonstrating good fit of predicted carboxyhemoglobin concentrations to published data from animal and human exposures validated the model. Carboxyhemoglobin concentrations were predicted for exposures of various severity, patients of different sizes, hematocrit, and fraction of inspired oxygen.

Results

The calculated carboxyhemoglobin concentrations closely predicted the experimental results of other investigators, thereby validating the model. These equations indicate the severity of CO poisoning is inversely related to the hemoglobin quantity of a subject. Fraction of inspired oxygen had the greatest effect in patients of small size with low hematocrit values, where equilibrium and not the rate of uptake determined carboxyhemoglobin concentrations.

Conclusion

This model predicts that patients with low hemoglobin quantities will have more severe CO exposures based on the attainment of a higher carboxyhemoglobin concentration. This includes patients of small size (pediatric population) and patients with anemia.

Physical Factors Affecting the Production of Carbon Monoxide from Anesthetic Breakdown

Background

Parameters determining carbon monoxide (CO) concentrations produced by anesthetic breakdown have not been adequately studied in clinical situations. The authors hypothesized that these data will identify modifiable risk factors.

Methods

Carbon monoxide concentrations were measured when partially desiccated barium hydroxide lime was reacted with isoflurane (1.5%) and desflurane (7.5%) in a Draeger Narkomed 2 anesthesia machine with a latex breathing bag substituting for a patient. Additional experiments determined the effects of carbon dioxide (0 or 350 ml/min), fresh gas flow rates (1 or 4 l/min), minute ventilation (6 or 18 l/min), or absorbent quantity (1 or 2 canisters). End-tidal anesthetic concentrations were adjusted according to a monochromatic infrared monitor.

Results

Desflurane produced approximately 20 times more CO than isoflurane when completely dried absorbents were used. Peak CO concentrations approached 100,000 ppm with desflurane. Traces of water remaining after a 66-h drying time (one weekend) markedly reduced the generation of CO compared with 2 weeks of drying. Reducing the quantity of desiccated absorbent by 50% reduced the total CO production by 40% in the first hour. Increasing the fresh gas flow rate from 1 to 4 l/min increased CO production by 67% in the first hour but simultaneously decreased average inspiratory concentrations by 53%. Carbon dioxide decreased CO production by 12% in completely desiccated absorbents.

Conclusion

Anesthetic identity, fresh gas flow rates, absorbent quantity, and water content are the most important factors determining patient exposures. Minute ventilation and carbon dioxide production by the patient are relatively unimportant.

Mechanisms for cholesterol homeostasis in rat jejunal mucosa: effects of cholesterol, sitosterol, and lovastatin

The effects of feeding cholesterol, sitosterol, and lovastatin on cholesterol absorption, biosynthesis, esterification, and LDL receptor function were examined in the rat jejunal mucosa. Cholesterol absorption was measured by the dual-isotope plasma ratio method; the rate-limiting enzyme of cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, was measured as total and expressed enzyme activities (in the absence and presence of a phosphatase inhibitor, NaF, respectively); mucosal total and esterified cholesterol concentrations were determined by gas-liquid chromatography; LDL receptor function was assayed as receptor-mediated binding of (125)I-labeled LDL to mucosal membranes. Feeding 2% sitosterol or 0.04% lovastatin for 1 week significantly (P < 0.01) decreased the amounts of cholesterol absorbed per day (-85% and -63%, respectively). In contrast, feeding 2% cholesterol for 1 week increased the amounts of absorbed cholesterol 27-fold, even though the percent absorption significantly decreased. With all three treatments, there was a coordinate regulation of total HMG-CoA reductase activity and receptor-mediated LDL binding. Cholesterol feeding downregulated both total jejunal HMG-CoA reductase activity (P < 0.05) and receptor-mediated LDL binding (P < 0.01), whereas lovastatin- and sitosterol-supplemented diets significantly upregulated both of these parameters. In the control, cholesterol-fed, and sitosterol-fed animals, about half of the total jejunal HMG-CoA reductase activity was expressed (in functional dephosphorylated form). However, in the lovastatin-treated rats with 4-fold stimulation of HMG-CoA reductase, only 23% of the total enzyme activity was expressed. Changes in total HMG-CoA reductase activity and receptor-mediated LDL binding in all tested groups occurred with no change in total concentrations of mucosal cholesterol, and only cholesterol-fed animals had increased mucosal esterified cholesterol concentrations. Thus, in response to various fluxes of dietary or newly formed cholesterol, HMG-CoA reductase and receptor-mediated LDL binding are coordinately regulated to maintain constant cellular cholesterol concentrations in the jejunum.

The role of oxidative stress in the toxicity induced by amyloid beta-peptide in Alzheimer's disease

One of the theories involved in the etiology of Alzheimer's disease (AD) is the oxidative stress hypothesis. The amyloid beta-peptide (A beta), a hallmark in the pathogenesis of AD and the main component of senile plaques, generates free radicals in a metal-catalyzed reaction inducing neuronal cell death by a reactive oxygen species mediated process which damage neuronal membrane lipids, proteins and nucleic acids. Therefore, the interest in the protective role of different antioxidants in AD such as vitamin E, melatonin and estrogens is growing up. In this review we summarize data that support the involvement of oxidative stress as an active factor in A beta-mediated neuropathology, by triggering or facilitating neurodegeneration, through a wide range of molecular events that disturb neuronal cell homeostasis.

The SM19 gene, required for duplication of basal bodies in Paramecium, encodes a novel tubulin, eta-tubulin

The discovery of delta-tubulin, the fourth member of the tubulin superfamily, in Chlamydomonas [1] has led to the identification in the genomes of vertebrates and protozoa of putative delta homologues and of additional tubulins, epsilon and zeta [2-4]. These discoveries raise questions concerning the functions of these novel tubulins, their interactions with microtubule arrays and microtubule-organising centres, and their evolutionary status. The sm19-1 mutation of Paramecium specifically inhibits basal body duplication [5] and causes delocalisation of gamma-tubulin, which is also required for basal body duplication [6]. We have cloned the SM19 gene by functional complementation and found that it encodes another new member of the tubulin superfamily. SM19p, provisionally called eta-tubulin (eta-tubulin), shows low sequence identity with the tubulins previously identified in Paramecium, namely, alpha [7], beta [8], gamma [6], delta (this work) and epsilon (P. Dupuis-Williams, personal communication). Phylogenetic analysis indicated that SM19p is not consistently grouped with any phylogenetic entity.

Cyclosporin A targets involved in protection against glutamate excitotoxicity

The toxicity of glutamate in neuronal cultures has been attributed in part to a mitochondrial dysfunction involving the permeability transition pore. The participation of the permeability transition pore in this process has been pharmacologically demonstrated by the use of cyclosporin A, which inhibits pore opening by interaction with mitochondrial cyclophilin and, thus, prevents cell death and upstream events. Since cyclosporin A also acts on calcineurin, we have investigated which of the targets of cyclosporin A was responsible for the inhibition of glutamate-excitotoxicity in cerebrocortical primary neuronal cultures. Reactive oxygen species production and early (30 min to 2 h) drop in ATP levels are initial events in glutamate excitotoxicity taking place before neuronal death. Cyclosporin A did not inhibit reactive oxygen species production, but reduced the drop in ATP levels and subsequent neuronal death. However, cyclosporin derivatives that do not bind to calcineurin had smaller effect on survival than cyclosporin A, (regardless of whether they were able to bind cyclophilin), indicating that cyclosporin A protects against glutamate toxicity also through calcineurin-related mechanisms. Consistent with this view, ATP loss appears to result from nitric oxide synthase (NOS) activation (including calcineurin-dependent dephosphorylation) and nitric oxide (NO)/peroxinitrite-dependent increase in poly (ADP-ribose) polymerase activity, since it was reduced by inhibitors of these activities. Collectively, these results suggest that cyclosporin A exerts its protective effects through calcineurin-dependent and independent mechanisms.

Low cleavage activity of 15,15'dioxygenase to convert beta-carotene to retinal in cattle compared with goats, is associated with the yellow pigmentation of adipose tissue

Two experiments (one with twelve heifers and the other with 14 goats) were designed to evaluate the effect of increasing dietary beta-carotene concentration on the activity of the cleaving enzyme 15,15' beta-carotene dioxygenase and the concentration of beta-carotene and retinol in selected tissues. The experiments lasted 120 days. During the first 90 days animals were offered a beta-carotene unsupplemented diet. In the following 30 days, they were distributed to one of three treatments: 0, 5.5 or 352 mg of beta-carotene/kg of dry matter intake. All animals were slaughtered at the end. In heifers the concentration of beta-carotene in plasma, reflected the level of beta-carotene fed. Goats had detectable levels of beta-carotene only on day 10 of supplementation. In the liver, beta-carotene concentrations were highest with the 352 dose in both species. Heifers had the highest concentration of beta-carotene in the adipose tissue. In bovines, no interaction between beta-carotene treatment and intestinal sampling site was found (P > 0.2) for the activity of 15,15 dioxygenase. Across beta-carotene levels, results of the enzyme assay were: 0.19, 0.32 and 0.45 nmol retinal/(mg S-9 protein/h) (P < 0.01) for 0, 5.5 and 352 mg beta-carotene.kg dry matter intake -1.d-1, respectively; across intestinal sampling sites results of the enzyme assay were 0.45, 0.43 and 0.08 nmol retinal/(mg S-9 protein/h) (P < 0.01) for duodenum, jejunum and ileum, respectively. Caprine data showed an interaction between beta-carotene treatment and intestinal sampling site (P < 0.05) for the activity of 15,15 dioxygenase. The results for treatment 0 were: 1.4, 1.4 and 0; for treatment 5.5: 1.41, 1.42 and 0.13; and for treatment 352: 1.46, 1.99 and 0.48 nmol retinal/mg S-9 protein/h for duodenum, jejunum and ileum, respectively. The lower levels of duodenal and jejunal 15,15'dioxygenase activity in cattle compared with goats, may explain the greater pigmentation of adipose tissue in the former ruminant specie.

Chromosome diversity of the genus Aotus from Colombia

Description of six Colombian karyomorphs is completed through an extensive cytogenetic characterization of 35 Aotus (owl monkeys) specimens. The description of a new karyomorph for Colombian Aotus by chromosome on Q, G, R, and C, sequential banding is included. Pairs of karyomorphs 2 and 3 and 6 and 9 with 2n of 54, and 50, respectively, as well as karyomorphs 7 and 8 with 46 and 58 chromosomes were strongly suspected to represent different species on the grounds of large karyotypic differences. A proposal for a chromosome nomenclature of Aotus karyomorphs that aims to clarify Aotus taxonomy is presented which achieves a precise correspondence of different banding patterns, based on Q, G, R, and C sequential banding and chromosome measurements. Although our contribution is not a universal nomenclature system, unique criteria for chromosome denomination within Aotus karyomorphs are established. Previous systems of chromosome nomenclature have not successfully addressed the nomenclature of chromosomes of the same karyotype.

Non-heart-beating donors from the streets: an increasing donor pool source

BACKGROUND

Non-heart-beating donors have become a source for organ donation, especially kidneys. The emergency room and the critical care unit are the two sources for this kind of donor. Three years ago, our hospital began a policy of obtaining organs and tissues successfully from subjects who died in the streets.

METHODS

We consider as potential organ donors people who die out-of-hospital, are less than 50 years old, with less than 15 min of asystolia without cardiac massage, with a known etiology of death, and without general contraindications for donating. After death diagnosis, the cadaver is taken to the hospital where an emergency room doctor certifies the death. Afterward, the cadaver is transferred to the operating room where a cardiopulmonary bypass is performed to preserve the organs while the legal aspects of donation go on.

RESULTS

Up to now, 111 cadavers have been taken as non-heart-beating donors; 53 of them have been actual donors. The average time before arrival to the hospital was 68+/-2.64 min, and the average interval between cardiac arrest and the beginning of cardiopulmonary bypass was 111.33+/-7.09 min. We have obtained 105 kidneys, 12 livers, 84 corneas, and 31 pancreata for islets isolation as well as 49 long bones. Seventy-two kidneys were transplanted, with a probability of survival of 83% at 36 months.

CONCLUSIONS

Our experience indicates that it is possible to obtain organs for transplant from donors who die in the streets and are brought to the hospital under strict selection criteria.

Patient dose from barium procedures

The objective of this work was to estimate patient doses (dose-area product, organ dose, effective dose and entrance surface dose) for barium procedures. A total of 175 procedures, in 175 patients, for five different examination categories was analysed. Dose-area product was determined using a transmission ionization chamber. Organ dose and effective dose were assessed using a knowledge of the examination and the software. For all patients, the contribution of fluoroscopy to the total dose was greater than that from radiography. Dose-area product from double contrast barium enema, enteroclysis and intestinal tract procedures was higher than that obtained for the other procedures. The average effective dose was 1.04 mSv and 13.99 mSv for oesophageal tract and enteroclysis examinations, respectively. Entrance surface dose in the oesophageal tract was 16 mGy, 10 times lower than for the other four procedures. Patient dose reduction in barium procedures may be achieved by improved training of resident radiologists, senior radiologists and other specialists in radiation protection.

Genetic evidence for a role of centrin-associated proteins in the organization and dynamics of the infraciliary lattice in Paramecium

Within the superfamily of "EF-hand Ca2+-modulated proteins," centrins constitute a family of cytoskeletal proteins that are highly conserved from lower eukaryotes to man. Their cytoskeletal specialization is manifest in their capacity to form filamentous contractile arrays of various shapes and functions and by their association with microtubule organizing centres (MTOCs). While the latter property has been conserved throughout the evolution of eukaryotes, centrin-based contractile structures are only found in protists where they form arrays of widely diverse organization and function. In the ciliate Paramecium tetraurelia, three centrin genes have been characterized, which may be part of a larger centrin gene family [Madeddu et al., 1996: Eur J. Biochem. 238:121-128]. The products of these genes were originally identified as components of the infraciliary lattice, a contractile cytoskeletal network [Garreau de Loubresse et al., 1991: Biol. Cell 71:217-225]. We show here that centrins are localized not only in this lattice but also in basal bodies and in the cord, a filamentous structure associated with the oral apparatus. We demonstrate that in the infraciliary lattice, but not in basal bodies, centrins are associated with high-molecular-weight proteins (ca. 350 kD). Their role in the biogenesis of the infraciliary lattice is documented by cytological and biochemical properties of the mutant "démaillé" (dem1) characterized by altered centrin-associated proteins and abnormal organization and dynamics of the infraciliary lattice.

Assessing the effectiveness of direct digital radiography barrier sheaths and finger cots

BACKGROUND

Effective cross-contamination prevention is critical for direct digital radiography, or DDR, sensors, which are not sterilizable; however, current manufacturers' recommendations for standard precautions are limited to the use of plastic barrier sheaths, which are commonly known to tear or leak. The authors sought to determine the incidence of digital radiography barrier-sheath leakage, with and without additional latex finger cot protection, as measured by a water pressure test.

METHODS

Four hundred plastic barrier sheaths were randomly assigned to four groups based on intraoral radiograph positioning device use and supplemental barrier protection with a latex finger cot. Sheaths were carefully placed to cover DDR sensors for a single intraoral use, gently removed from the sensors and tested for leakage through a water pressure technique.

RESULTS

Perforations occurred in 44 to 51 percent of plastic sheaths after a single radiographic exposure. However, only up to 6 percent of the plastic sheaths that were covered by a latex finger cot leaked during the water pressure test.

CONCLUSIONS

At least 44 percent of the plastic barrier sheaths leaked after a single intraoral radiographic exposure. Use of a latex finger cot over the plastic sheath significantly reduced leakage to no more than 6 percent.

CLINICAL IMPLICATIONS

Latex finger cots used in conjunction with the standard plastic sheaths that cover DDR sensors may more effectively prevent cross-contamination than do plastic sheaths alone. Dentists who use DDR sensors during highly invasive dental procedures such as dental implant surgery are encouraged to consider supplemental barrier protection for these delicate, expensive and nonsterilizable sensors to prevent patient cross-contamination.

Sex differences in perceptions of romantic acts in Portuguese adolescents

The study was done to examine sex differences in the importance attributed to romantic acts by adolescents. On a 15-item Romantic Acts questionnaire of Neto participants rated the importance of each act. Four factors of Offerings, Physical Intimacy, Altruistic Behavior, and Sexual Behavior were found. The 108 girls judged physical intimacy as more important than the 79 boys.

Transpyloric enteral nutrition reduces the complication rate and cost in the critically ill child

BACKGROUND

Studies in adults have shown that transpyloric enteral nutrition (TEN) is useful in certain patients who cannot tolerate oral or gastric feeding. This study was conducted to compare TEN with parenteral nutrition (PN) in critically ill pediatric patients.

METHODS

A retrospective descriptive study conducted in the pediatric intensive care unit of a tertiary pediatric referral center. All patients in the pediatric intensive care unit (PICU) receiving PN and/or TEN from January 1993 through December 1996 were included in the study.

RESULTS

Two hundred forty patients (14.6% of all patients admitted to the PICU) received PN and/or TEN (168 exclusively PN, 21 exclusively TEN, and 51 a combined regimen). The number of patients receiving PN and duration of PN declined significantly from 1993 (65 patients, 703 days) through 1996 (48 patients, 395 days). This was mirrored by the increase in the number of patients receiving TEN and duration of TEN. The incidence of complications (hyperglycemia, hypertriglyceridemia, and cholestasis) was higher in the PN group. There was no difference in the incidence of hospital-acquired infection or mortality between the two groups. The cost of TEN was lower than that of PN, with an estimated annual saving of $5,422.

CONCLUSIONS

Transpyloric enteral nutrition is a suitable method of nutritional support for critically ill pediatric patients. It has fewer complications and a lower cost than PN.

Beta,gamma-methylene ATP but not alpha,beta-methylene ATP mimics the inhibitory effect of ATP on ventricular automaticity

The effects of alpha,beta- and beta,gamma-methylene ATP on ventricular automaticity induced by local injury in the right ventricle of rats pretreated with reserpine, were investigated and compared with the effects of ATP and adenosine. Beta,gamma-methylene ATP but not alpha,beta-methylene ATP mimicked the inhibitory effect of both ATP and adenosine on the spontaneous automaticity In low concentrations, adenosine was more effective than ATP. Alpha,beta-methylene ATP caused little or no effect on ventricular automaticity. The results suggest that the effect of ATP might depend on its hydrolysis into AMP/adenosine.

Stochastic risk estimate for barium radiological examinations in Malaga (Spain)

The aim of this research work has been the estimation of the stochastic risk for five barium examinations. The sample was the population attending the Radiological Service of the 'Nuestra Señora de la Victoria' University Hospital, who had been treated with some barium examinations, set in five different groups: oesophagus tract, oesophagus-gastric-duodenal tract, intestinal tract, enteroclysis and double enema. To estimate the stochastic risk, it is necessary to know the organ dose. This can be calculated from the dose-area product which allows us to determine the effective dose using software. The dose-area product is the most suitable quantity to measure in these types of examination. We have evaluated the contribution that each procedure provides to the genetically significant dose, somatically significant dose, collective effective dose, annual effective dose 'per capita' and detriment, which are useful for assessing the population risk of cancer or hereditary effects after x-ray exposure. The contribution to the genetically significant dose is 6.7 microGy, to the somatically significant dose 8.82 mSv-yr, 16.07 person-Sv for the collective effective dose, 0.03 mSv for the 'per capita' annual effective dose and the annual aggregated detriment is 0.33.

In vivo regulation by glutathione of methionine adenosyltransferase S-nitrosylation in rat liver

BACKGROUND/AIMS

Ethanol consumption and pathological conditions such as cirrhosis lead to a reduction of hepatic glutathione. Hepatic methionine adenosyltransferase, the enzyme that synthesizes S-adenosylmethionine, the major methylating agent, is regulated in vivo by glutathione levels. We have previously shown that nitric oxide inactivates methionine adenosyltransferase in vivo by S-nitrosylation. In this study, we aimed to investigate the regulation by glutathione of methionine adenosyltransferase S-nitrosylation in rat liver.

METHODS

Rat hepatocytes and whole animals were treated with buthionine sulfoximine, an inhibitor of glutathione synthesis, and methionine adenosyltransferase S-nitrosylation and activity were determined.

RESULTS

In hepatocytes, buthionine sulfoximine led to the S-nitrosylation and inactivation of methionine adenosyltransferase. Restoring glutathione levels in hepatocytes treated with buthionine sulfoximine, by the addition of glutathione monoethyl ester, a permeable derivative of glutathione, led to the denitrosylation and reactivation of methionine adenosyltransferase. In whole animals, buthionine sulfoximine led also to methionine adenosyltransferase S-nitrosylation and inactivation. S-Nitrosylation and inactivation of methionine adenosyltransferase induced by buthionine sulfoximine in whole animals was prevented by glutathione monoethyl ester.

CONCLUSIONS

These results indicate that in vivo hepatic methionine adenosyltransferase exists in two forms in equilibrium, nitrosylated (inactive) and denitrosylated (active), which are regulated by both the cellular levels of nitric oxide and glutathione.

Role of antioxidants in the survival of normal and vitiliginous avian melanocytes

Mutant feather melanocytes from Barred Plymouth Rock (BPR) and White Leghorn (WL) chickens are currently being used as avian models of vitiligo. Feather melanocytes in BPR and WL chickens die prematurely in vivo due to low (50-66%) antioxidant glutathione and superoxide dismutase levels when compared to the wild type Jungle Fowl (JF) melanocytes. Excess superoxide anions, generated by xanthine:xanthine oxidase (X:XO), caused a 15-20% increase in mortality after 1 and 2 hrs. in all three genotypes of in vitro melanocytes as compared to control values that received no X:XO. Overall, the JF wild type melanocytes had the lowest mortality rate, WL melanocytes had the highest mortality rate and the BPR melanocytes had an intermediate mortality rate. Superoxide anion and hydroxyl radical production in the WL feather were double the production in the JF wild type feather. The production of reactive oxygen species in BPR was intermediate to the other two genotypes. In an effort to mimic the low antioxidant levels of the BPR and WL feathers in the JF feather, JF in vitro feather melanocytes were treated with buthionine sulfoximine (BSO), a glutathione synthesis inhibitor. With BSO added to the medium, the JF mortality rates increased by 20-25%, reaching the mortality levels of the mutant BPR melanocytes. The addition of iron to the JF melanocyte X:XO medium increased their mortality rate by 20%, probably via the Fenton reaction. Thus, antioxidants play an extremely important role in both the viability of normal avian melanocytes and the premature death of the vitiliginous avian melanocytes. A working hypothesis, supported in part by the current results, is that the premature death of the mutant melanocytes could be precipitated in the poorly vascularized feather by low antioxidant protection due to both low turnover of tissue fluids which contain SOD and to genetically determined low levels of internal antioxidant protection in these melanocytes. This same mechanistic hypothesis could apply as "a" cause of premature melanocyte cell death in human vitiligo wherein the vitiliginous melanocytes may have a genetic defect in their antioxidant protection system and blood flow to an area may be restricted.

Efficacy of ampicillin plus ceftriaxone in treatment of experimental endocarditis due to Enterococcus faecalis strains highly resistant to aminoglycosides

The purpose of this work was to evaluate the in vitro possibilities of ampicillin-ceftriaxone combinations for 10 Enterococcus faecalis strains with high-level resistance to aminoglycosides (HLRAg) and to assess the efficacy of ampicillin plus ceftriaxone, both administered with humanlike pharmacokinetics, for the treatment of experimental endocarditis due to HLRAg E. faecalis. A reduction of 1 to 4 dilutions in MICs of ampicillin was obtained when ampicillin was combined with a fixed subinhibitory ceftriaxone concentration of 4 micrograms/ml. This potentiating effect was also observed by the double disk method with all 10 strains. Time-kill studies performed with 1 and 2 micrograms of ampicillin alone per ml or in combination with 5, 10, 20, 40, and 60 micrograms of ceftriaxone per ml showed a > or = 2 log10 reduction in CFU per milliliter with respect to ampicillin alone and to the initial inoculum for all 10 E. faecalis strains studied. This effect was obtained for seven strains with the combination of 2 micrograms of ampicillin per ml plus 10 micrograms of ceftriaxone per ml and for six strains with 5 micrograms of ceftriaxone per ml. Animals with catheter-induced endocarditis were infected intravenously with 10(8) CFU of E. faecalis V48 or 10(5) CFU of E. faecalis V45 and were treated for 3 days with humanlike pharmacokinetics of 2 g of ampicillin every 4 h, alone or combined with 2 g of ceftriaxone every 12 h. The levels in serum and the pharmacokinetic parameters of the humanlike pharmacokinetics of ampicillin or ceftriaxone in rabbits were similar to those found in humans treated with 2 g of ampicillin or ceftriaxone intravenously. Results of the therapy for experimental endocarditis caused by E. faecalis V48 or V45 showed that the residual bacterial titers in aortic valve vegetations were significantly lower in the animals treated with the combinations of ampicillin plus ceftriaxone than in those treated with ampicillin alone (P < 0.001). The combination of ampicillin and ceftriaxone showed in vitro and in vivo synergism against HLRAg E. faecalis.