Long-term weight development after esophagectomy for cancer-comparison between open Ivor-Lewis and minimally invasive surgical approaches

Esophagectomy is an extensive procedure with severe postoperative effects. It can be assumed that the greater the trauma, the longer the nutritional recovery. This retrospective observational single-center cohort study compared weight development after esophagectomy with open and minimally invasive techniques. Three groups were compared in this study, one representing the first 41 patients who underwent the minimally invasive McKeown esophagectomy (MIMK). The second group included the first 84 consecutive patients operated with the minimally invasive Ivor-Lewis esophagectomy (MIIL). The third group comprised 100 consecutive patients operated with open thoracoabdominal Ivor-Lewis esophagectomy (IL). Virtually all patients submitted to a minimally invasive esophagectomy (MIE) and the majority with an IL had a jejunal catheter inserted during operation for postoperative enteral feeding. All together 225 patients were included in this study. The mean weight loss during the first year was 13.1% (±4.1), 11.2% (±6.1), and 9.6% (±7.5) in the IL, MIIL, and MIMK group, respectively (P = 0.85 and P = 0.95, respectively). The median duration of postoperative enteral nutrition support varied substantially within the groups and was 23.5 days in the IL group (range: 0-2033 days), 54.5 days in those having an MIIL (range: 0-308 days; P ≤ 0.001) and 57.0 days among patients in the MIMK group (range: 0-538 days; P ≤ 0.022). There was no difference in the risk of losing at least 10% of the preoperative weight at 3 or 6 months postoperatively between the groups. However, in patients who suffered severe complications (Clavien-Dindo score ≥ IIIb) after MIIL, there was a nonsignificant trend toward a lower risk of a 10% or greater weight loss, 3 months postoperatively. In conclusion, the greater surgical trauma associated with the traditional open esophagectomy was not followed by more severe weight loss, or other signs of poorer nutritional recovery, when compared to minimal invasive surgical techniques.

Relief of dysphagia during neoadjuvant treatment for cancer of the esophagus or gastroesophageal junction

Dysphagia is the main symptom of cancer of the esophagus and gastroesophageal junction and causing nutritional problems and weight loss, often counteracted by insertion of self-expandable metal stents or nutrition via an enteral route. Clinical observations indicate that neoadjuvant therapy may effectively and promptly alleviate dysphagia, making such nutrition supportive interventions redundant before surgical resection. The objective of the current study was to carefully study the effects of induction neoadjuvant therapy on dysphagia and its subsequent course and thereby investigate the actual need for alimentary gateways for nutritional support. Thirty-five consecutive patients scheduled for neoadjuvant therapy were recruited and assessed regarding dysphagia and appetite at baseline, after the first cycle of preoperative treatment with either chemotherapy alone or with chemoradiotherapy and before surgery. Platinum-based therapy in combination with 5-fluorouracil was administered intravenously days 1-5 every 3 weeks and consisted of three treatments. Patients receiving combined chemoradiotherapy started radiotherapy on day one of second chemotherapy cycle. They received fractions of 2 Gy/day each up to a total dose of 40 Gy. Watson and Ogilvie dysphagia scores were used to assess dysphagia, while appetite was assessed by the Edmonton Assessment System Visual analogue scale-appetite questionnaire. Patients were evaluated at regular outpatient clinic visits or by telephone. The histological tumor response in the surgical specimen was assessed using the Chirieac scale. Ten patients scheduled for neoadjuvant chemotherapy and 25 patients scheduled for chemoradiotherapy were included in the analysis. There was a significant improvement in dysphagia in both treatment groups, according to both scales, already from baseline to the completion of the first chemotherapy cycle which remained to the end of the neoadjuvant treatment (P < 0.001). Appetite also improved after the first chemotherapy cycle (P = 0.03). Body weight did not change during any type of neoadjuvant therapy. We were unable to demonstrate any association between relief of dysphagia and the degree of histological response to neoadjuvant therapy in the surgical specimen. The present study shows that a platin - 5FU-based neoadjuvant chemotherapy, with or without concomitant radiotherapy, effectively and promptly relieves dysphagia in patients presenting with cancers of the esophagus or gastroesophageal junction already after the first cycle.

Pen and Pal are nucleotide-sugar dehydratases that convert UDP-GlcNAc to UDP-6-deoxy-D-GlcNAc-5,6-ene and then to UDP-4-keto-6-deoxy-L-AltNAc for CMP-pseudaminic acid synthesis in Bacillus thuringiensis

CMP-pseudaminic acid is a precursor required for the O-glycosylation of flagellin in some pathogenic Gram-negative bacteria, a process known to be critical in bacterial motility and infection. However, little is known about flagellin glycosylation in Gram-positive bacteria. Here, we identified and functionally characterized an operon, named Bti_pse, in Bacillus thuringiensis israelensis ATCC 35646, which encodes seven different enzymes that together convert UDP-GlcNAc to CMP-pseudaminic acid. In contrast, Gram-negative bacteria complete this reaction with six enzymes. The first enzyme, which we named Pen, converts UDP-d-GlcNAc to an uncommon UDP-sugar, UDP-6-deoxy-D-GlcNAc-5,6-ene. Pen contains strongly bound NADP(+) and has distinct UDP-GlcNAc 4-oxidase, 5,6-dehydratase, and 4-reductase activities. The second enzyme, which we named Pal, converts UDP-6-deoxy-D-GlcNAc-5,6-ene to UDP-4-keto-6-deoxy-L-AltNAc. Pal is NAD(+)-dependent and has distinct UDP-6-deoxy-d-GlcNAc-5,6-ene 4-oxidase, 5,6-reductase, and 5-epimerase activities. We also show here using NMR spectroscopy and mass spectrometry that in B. thuringiensis, the enzymatic product of Pen and Pal, UDP-4-keto-6-deoxy-L-AltNAc, is converted to CMP-pseudaminic acid by the sequential activities of a C4″-transaminase (Pam), a 4-N-acetyltransferase (Pdi), a UDP-hydrolase (Phy), an enzyme (Ppa) that adds phosphoenolpyruvate to form pseudaminic acid, and finally a cytidylyltransferase that condenses CTP to generate CMP-pseudaminic acid. Knowledge of the distinct dehydratase-like enzymes Pen and Pal and their role in CMP-pseudaminic acid biosynthesis in Gram-positive bacteria provides a foundation to investigate the role of pseudaminic acid and flagellin glycosylation in Bacillus and their involvement in bacterial motility and pathogenicity.

The biosynthesis of UDP-d-FucNAc-4N-(2)-oxoglutarate (UDP-Yelosamine) in Bacillus cereus ATCC 14579: Pat and Pyl, an aminotransferase and an ATP-dependent Grasp protein that ligates 2-oxoglutarate to UDP-4-amino-sugars

Surface glycan switching is often observed when micro-organisms transition between different biotic and abiotic niches, including biofilms, although the advantages of this switching to the organism are not well understood. Bacillus cereus grown in a biofilm-inducing medium has been shown to synthesize an unusual cell wall polysaccharide composed of the repeating subunit →6)Gal(α1-2)(2-R-hydroxyglutar-5-ylamido)Fuc2NAc4N(α1-6)GlcNAc(β1→, where galactose is linked to the hydroxyglutarate moiety of FucNAc-4-amido-(2)-hydroxyglutarate. The molecular mechanism involved in attaching 2-hydroxyglutarate to 4-amino-FucNAc has not been determined. Here, we show two genes in B. cereus ATCC 14579 encoding enzymes involved in the synthesis of UDP-FucNAc-4-amido-(2)-oxoglutarate (UDP-Yelosamine), a modified UDP-sugar not previously reported to exist. Using mass spectrometry and real time NMR spectroscopy, we show that Bc5273 encodes a C4″-aminotransferase (herein referred to as Pat) that, in the presence of pyridoxal phosphate, transfers the primary amino group of l-Glu to C-4″ of UDP-4-keto-6-deoxy-d-GlcNAc to form UDP-4-amino-FucNAc and 2-oxoglutarate. Pat also converts 4-keto-xylose, 4-keto-glucose, and 4-keto-2-acetamido-altrose to their corresponding UDP-4-amino-sugars. Bc5272 encodes a carboxylate-amine ligase (herein referred as Pyl) that, in the presence of ATP and Mg(II), adds 2-oxoglutarate to the 4-amino moiety of UDP-4-amino-FucNAc to form UDP-Yelosamine and ADP. Pyl is also able to ligate 2-oxoglutarate to other 4-amino-sugar derivatives to form UDP-Yelose, UDP-Solosamine, and UDP-Aravonose. Characterizing the metabolic pathways involved in the formation of modified nucleotide sugars provides a basis for understanding some of the mechanisms used by bacteria to modify or alter their cell surface polysaccharides in response to changing growth and environmental challenges.

Orphan nuclear receptor Nurr1 is essential for Ret expression in midbrain dopamine neurons and in the brain stem

The orphan nuclear receptor Nurr1 is essential for development of midbrain dopamine (DA) cells. In Nurr1-deficient mice, DA precursor cells fail to migrate normally, are unable to innervate target areas, and only transiently express DA cell marker genes. In the search for Nurr1-regulated genes that might explain this developmental phenotype, we found that expression of the receptor tyrosine kinase Ret is deregulated in these cells of Nurr1-deficient embryos. In addition, our analyses establish Nurr1 as an early marker for the dorsal motor nucleus (DMN) of the vagus nerve. Interestingly, Ret expression is absent also in these cells in Nurr1-targeted mice. Neuronal innervation of vagus nerve target areas appeared normal apart from a subtle disorganization of the DMN-derived nerve fibers. In conclusion, regulation of Ret by Nurr1 in midbrain DA neurons and in the DMN has implications for both embryonal development and adult physiology in which signaling by neurotrophic factors plays important roles.

Different levels of repressor activity assign redundant and specific roles to Nkx6 genes in motor neuron and interneuron specification

Specification of neuronal fate in the vertebrate central nervous system depends on the profile of transcription factor expression by neural progenitor cells, but the precise roles of such factors in neurogenesis remain poorly characterized. Two closely related transcriptional repressors, Nkx6.2 and Nkx6.1, are expressed by progenitors in overlapping domains of the ventral spinal cord. We provide genetic evidence that differences in the level of repressor activity of these homeodomain proteins underlies the diversification of interneuron subtypes, and provides a fail-safe mechanism during motor neuron generation. A reduction in Nkx6 activity further permits V0 neurons to be generated from progenitors that lack homeodomain proteins normally required for their generation, providing direct evidence for a model in which progenitor homeodomain proteins direct specific cell fates by actively suppressing the expression of transcription factors that direct alternative fates.

An investigation of environmental racism claims: testing environmental management approaches with a geographic information system

The purpose of this research was to explore the concept of an environmental racism claim through the use of several environmental management tools. The EPAs Toxics Release Inventory, Cumulative Exposure Project, and the Los Angeles County Department of Health Services' Hot Zone Census Tract Assessment were combined with racial and socioeconomic data to test claims that minorities in South Central Los Angeles are disproportionately exposed to environmental lead. Multivariate analysis indicated that race is strongly associated with the number of cases of elevated blood lead levels in South Central, irrespective of poverty status. Proximity to point sources, a common focal point for studies of environmental racism, was not a contributing factor to health outcomes. Proximity to transportation corridors was consistently the strongest indicator of environmental lead exposure, while median home values were significantly and positively related to elevated blood lead levels. Implications for environmental justice advocates and social and environmental scientists are discussed.

Groucho-mediated transcriptional repression establishes progenitor cell pattern and neuronal fate in the ventral neural tube

The pattern of neuronal specification in the ventral neural tube is controlled by homeodomain transcription factors expressed by neural progenitor cells, but no general logic has emerged to explain how these proteins determine neuronal fate. We show that most of these homeodomain proteins possess a conserved eh1 motif that mediates the recruitment of Gro/TLE corepressors. The eh1 motif underlies the function of these proteins as repressors during neural patterning in vivo. Inhibition of Gro/TLE-mediated repression in vivo results in a deregulation of cell pattern in the neural tube. These results imply that the pattern of neurogenesis in the neural tube is achieved through the spatially controlled repression of transcriptional repressors-a derepression strategy of neuronal fate specification.

Specification of neuronal fates in the ventral neural tube

The generation of distinct classes of neurons at defined positions is a fundamental step in the development of the vertebrate central nervous system. Recent work has begun to reveal the extracellular signals and transcriptional mediators that direct the pattern of generation of distinct neuronal subtypes in the neural tube. This work has provided a framework to understand the patterning of the ventral neural tube and is permitting molecular analyses of the assembly of functional neuronal circuits.

Ventral neural patterning by Nkx homeobox genes: Nkx6.1 controls somatic motor neuron and ventral interneuron fates

There is growing evidence that sonic hedgehog (Shh) signaling regulates ventral neuronal fate in the vertebrate central nervous system through Nkx-class homeodomain proteins. We have examined the patterns of neurogenesis in mice carrying a targeted mutation in Nkx6.1. These mutants show a dorsal-to-ventral switch in the identity of progenitors and in the fate of postmitotic neurons. At many axial levels there is a complete block in the generation of V2 interneurons and motor neurons and a compensatory ventral expansion in the domain of generation of V1 neurons, demonstrating the essential functions of Nkx6.1 in regional patterning and neuronal fate determination.

A homeodomain protein code specifies progenitor cell identity and neuronal fate in the ventral neural tube

Distinct classes of neurons are generated at defined positions in the ventral neural tube in response to a gradient of Sonic Hedgehog (Shh) activity. A set of homeodomain transcription factors expressed by neural progenitors act as intermediaries in Shh-dependent neural patterning. These homeodomain factors fall into two classes: class I proteins are repressed by Shh and class II proteins require Shh signaling for their expression. The profile of class I and class II protein expression defines five progenitor domains, each of which generates a distinct class of postmitotic neurons. Cross-repressive interactions between class I and class II proteins appear to refine and maintain these progenitor domains. The combinatorial expression of three of these proteins--Nkx6.1, Nkx2.2, and Irx3--specifies the identity of three classes of neurons generated in the ventral third of the neural tube.

Cloning and DNA-binding properties of the rat pancreatic beta-cell-specific factor Nkx6.1

The homeodomain (HD) protein Nkx6.1 is the most beta-cell-specific transcription factor known in the pancreas and its function is critical for the formation of the insulin-producing beta-cells. However, the target genes, DNA-binding site, and transcriptional properties of Nkx6.1 are unknown. Using in vitro binding site selection we have identified the DNA sequence of the Nkx6.1 binding site to be TTAATTG/A. A reporter plasmid containing four copies of this sequence is activated by an Nkx6.1HD/VP16 fusion construct. Full-length Nkx6.1 fails to activate this reporter plasmid in spite of robust interaction with the binding site in vitro. Stable expression of Nkx6.1 in the glucagon-producing alpha-cell-like MSL-G-AN cells induces expression of the endogenous insulin gene in a subset of the cell population. The expression of other known beta-cell-specific factors such as Pax4, Pax6, Pdx1, GLUT2 and GLP1-R is unchanged by the introduction of Nkx6.1.

The specification of neuronal identity by graded Sonic Hedgehog signalling

During the development of vertebrate nervous system, distinct classes of motor neurons and interneurons are generated at distinct dorsoventral positions in the ventral neural tube. The differentiation of these neuronal subtypes is directed by the secreted protein Sonic Hedgehog (Shh). Shh acts in a graded manner to establish different neural progenitor cell populations, defined by the expression of homeodomain transcription factors. These factors are critical for the interpretation of graded Shh signalling and act initially both to refine progenitor domain boundaries and to maintain their integrity. Subsequently, these factors direct the expression of genes that confer neuronal subtype identity to post-mitotic neurons.

Homeobox gene Nkx2.2 and specification of neuronal identity by graded Sonic hedgehog signalling

During vertebrate development, the specification of distinct cell types is thought to be controlled by inductive signals acting at different concentration thresholds. The degree of receptor activation in response to these signals is a known determinant of cell fate, but the later steps at which graded signals are converted into all-or-none distinctions in cell identity remain poorly resolved. In the ventral neural tube, motor neuron and interneuron generation depends on the graded activity of the signalling protein Sonic hedgehog (Shh). These neuronal subtypes derive from distinct progenitor cell populations that express the homeodomain proteins Nkx2.2 or Pax6 in response to graded Shh signalling. In mice lacking Pax6, progenitor cells generate neurons characteristic of exposure to greater Shh activity. However, Nkx2.2 expression expands dosally in Pax6 mutants, raising the possibility that Pax6 controls neuronal pattern indirectly. Here we provide evidence that Nkx2.2 has a primary role in ventral neuronal patterning. In Nkx2.2 mutants, Pax6 expression is unchanged but cells undergo a ventral-to-dorsal transformation in fate and generate motor neurons rather than interneurons. Thus, Nkx2.2 has an essential role in interpreting graded Shh signals and selecting neuronal identity.

Integrated FGF and BMP signaling controls the progression of progenitor cell differentiation and the emergence of pattern in the embryonic anterior pituitary

The mechanisms by which inductive signals control the identity, proliferation and timing of differentiation of progenitor cells in establishing spatial pattern in developing vertebrate tissues remain poorly understood. We have addressed this issue in the embryonic anterior pituitary, an organ in which distinct hormone cell types are generated in a precise temporal and spatial order from an apparently homogenous ectodermal primordium. We provide evidence that in this tissue the coordinate control of progenitor cell identity, proliferation and differentiation is imposed by spatial and temporal restrictions in FGF- and BMP-mediated signals. These signals derive from adjacent neural and mesenchymal signaling centers: the infundibulum and ventral juxtapituitary mesenchyme. The infundibulum appears to have a dual signaling function, serving initially as a source of BMP4 and subsequently of FGF8. The ventral juxtapituitary mesenchyme appears to serve as a later source of BMP2 and BMP7. In vitro, FGFs promote the proliferation of progenitor cells, prevent their exit from the cell cycle and contribute to the specification of progenitor cell identity. BMPs, in contrast, have no apparent effect on cell proliferation but instead appear to act with FGFs to control the initial selection of thyrotroph and corticotroph progenitor identity.

Pax6 controls progenitor cell identity and neuronal fate in response to graded Shh signaling

Distinct classes of motor neurons and ventral interneurons are generated by the graded signaling activity of Sonic hedgehog (Shh). Shh controls neuronal fate by establishing different progenitor cell populations in the ventral neural tube that are defined by the expression of Pax6 and Nkx2.2. Pax6 establishes distinct ventral progenitor cell populations and controls the identity of motor neurons and ventral interneurons, mediating graded Shh signaling in the ventral spinal cord and hindbrain.

Two critical periods of Sonic Hedgehog signaling required for the specification of motor neuron identity

Antibodies that block Sonic Hedgehog (SHH) signaling have been used to show that SHH activity is required for the induction of floor plate differentiation by the notochord and independently for the induction of motor neurons by both the notochord and midline neural cells. Motor neuron generation depends on two critical periods of SHH signaling: an early period during which naive neural plate cells are converted into ventralized progenitors and a late period that extends well into S phase of the final progenitor cell division, during which SHH drives the differentiation of ventralized progenitors into motor neurons. The ambient SHH concentration during the late period determines whether ventralized progenitors differentiate into motor neurons or interneurons, thus defining the pattern of neuronal cell types generated in the neural tube.

Sonic hedgehog: a common signal for ventral patterning along the rostrocaudal axis of the neural tube

The vertebrate hedgehog-related gene, sonic hedgehog, is expressed in ventral domains along the entire rostrocaudal length of the neural tube, including the forebrain. Shh induces the differentiation of ventral neuronal cell types in explants derived from prospective forebrain regions of the neural plate. Neurons induced in explants derived from diencephalic and telencephalic levels of the neural plate express the LIM homeodomain protein Islet-1, but these neurons possess distinct identities that match those of the ventral neurons normally generated in these two subdivisions of the forebrain. These results, together with other studies of neuronal differentiation at caudal levels of the neural tube, suggest that a single inducing molecule, Shh, mediates the induction of distinct ventral neuronal cell types along the entire rostrocaudal extent of the embryonic central nervous system.

Sonic hedgehog induces the differentiation of ventral forebrain neurons: a common signal for ventral patterning within the neural tube

The vertebrate hedgehog-related gene Sonic hedgehog (Shh) is expressed in ventral domains along the entire rostrocaudal length of the neural tube, including the forebrain. We show here that SHH induces the differentiation of ventral neuronal cell types in explants derived from prospective forebrain regions of the neural plate. Neurons induced in explants derived from both diencephalic and telencephalic levels of the neural plate express the LIM homeodomain protein Isl-1, and these neurons possess distinct identities that match those of the ventral neurons generated in these two subdivisions of the forebrain in vivo. A single inducing molecule, SHH, therefore appears to mediate the induction of distinct ventral neuronal cell types along the entire rostrocaudal extent of the embryonic central nervous system.

Depressive symptomatology in women and residential proximity to high-voltage transmission lines

A number of epidemiologic studies indicate an association between depression and proximity to high-voltage transmission lines. These studies have been criticized, however, for using surrogate measures of electromagnetic fields and unstandardized measures of depression. In an effort to overcome these limitations, the authors administered the Center for Epidemiological Studies Depression scale (CES-D) in 1992 to 152 women in Orange County, California, who lived either adjacent to a transmission line or one block away. The results indicated that the average magnetic field level is 4.86 mG at the front door of homes adjacent to transmission lines and 0.68 mG at the front door of homes one block away. There was no significant difference in CES-D scores between the groups when demographic variables were controlled for. The homogeneity of the study population may limit the generalizability of findings.

Early stages of motor neuron differentiation revealed by expression of homeobox gene Islet-1

Motor neurons in the embryonic chick spinal cord express a homeobox gene, Islet-1, soon after their final mitotic division and before the appearance of other differentiated motor neuron properties. The expression of Islet-1 by neural cells is regulated by inductive signals from the floor plate and notochord. These results establish Islet-1 as the earliest marker of developing motor neurons. The molecular nature of the Islet-1 protein suggests that it may be involved in the establishment of motor neuron fate.

The homeodomain LIM protein Isl-1 is expressed in subsets of neurons and endocrine cells in the adult rat

We have used immunocytochemical methods to localize the homeodomain LIM protein Isl-1 in the adult rat. Isl-1 immunoreactivity is expressed in polypeptide hormone-producing cells of the endocrine system, in neurons of the peripheral nervous system, and in a subset of brain nuclei. Isl-1 is also expressed in a subset of motoneurons in the spinal cord and brain stem, but not in regions of the central nervous system involved in sensory function or in neocortical areas. The pattern of expression of Isl-1 suggests that this gene may be involved in the specification and maintenance of differentiated phenotypical properties of these cells.

Structure-function studies of the SERPIN plasminogen activator inhibitor type 1. Analysis of chimeric strained loop mutants

Three chimeric mutants of plasminogen activator inhibitor 1 (PAI-1) have been constructed where the strained loop of wild type PAI-1 (wtPAI-1) has been replaced with a 19-amino acid region from either plasminogen activator inhibitor 2 (PAI-2), antithrombin III, or with an artificial serine protease inhibitor superfamily consensus strained loop. The inhibitors were expressed in Escherichia coli, and the purified proteins had specific activities toward urokinase-type plasminogen activator (uPA) or the single- and two-chain forms of tissue type plasminogen activator (tPA) that were similar to wtPAI-1. Experiments suggest that the strained loop of PAI-1 is not responsible for the transition between the latent and the active conformations or for binding to vitronectin. Second-order rate constants for the interactions with uPA and single- or two-chain tPA were similar to those of wtPAI-1. Values range from a low of 1.8 x 10(5) M-1 s-1 for the interaction of the PAI-2 chimera with single-chain tPA to a high value of 1.6 x 10(7) M-1 s-1 for the consensus mutant with two-chain tPA. This former value is 200 times higher than the reported rate constant for the interaction between PAI-2 and single-chain tPA, suggesting that structures outside of the strained loop are responsible for the major differences in specificity between PAI-1 and PAI-2.

Effect of dose on serum pharmacokinetics of intravenous ciprofloxacin with identification and characterization of extravascular compartments using noncompartmental and compartmental pharmacokinetic models

The effect of dose on the pharmacokinetics of ciprofloxacin in serum and urine following single intravenous doses of 100, 150, and 200 mg was studied in nine healthy volunteers. Mean peak levels in serum were 1.4, 2.0, and 3.2 mg/liter for the 100-, 150-, and 200-mg doses, respectively. The data on concentrations in serum were best described by a three-compartment pharmacokinetic model. The terminal half-life (from noncompartmental analysis) averaged between 4.2 and 4.6 h. Average urinary recovery ranged between 45.8 and 48.1%. The average renal clearance of ciprofloxacin was 2.9- to 3.4-fold greater than the measured creatinine clearance. Total serum and renal clearances decreased with increasing dose; however, this was not statistically significant (P greater than 0.05; repeated-measures analysis of variance). Ciprofloxacin was well tolerated by all subjects. In this dose range, ciprofloxacin pharmacokinetics are independent of dose.

Pharmacokinetics and pharmacodynamics of intravenous ciprofloxacin. Studies in vivo and in an in vitro dynamic model

The pharmacokinetics and pharmacodynamics of a 200-mg intravenous dose of ciprofloxacin were studied in normal volunteers and in an in vitro dynamic model that exposes bacteria to changing concentrations of the drug in a neutropenic setting. Peak ciprofloxacin concentrations in vivo averaged 3.2 micrograms/ml. The terminal serum elimination half-life averaged 4.2 hours. The volume of distribution of ciprofloxacin was large and consistent with extensive extravascular distribution. Slightly less than half of the dose was recovered unchanged in urine by 48 hours after infusion. The median serum bactericidal titer against a strain of Escherichia coli was 1:16 or more for at least six hours after infusion, but was only 1:2 against a strain of Pseudomonas aeruginosa immediately after the end of the infusion. Pharmacodynamic studies in the in vitro model with a simulated regimen of 200 mg administered intravenously every 12 hours demonstrated rapid and complete killing of this strain of E. coli following the first 200-mg "dose." For the strain of P. aeruginosa, an initial bactericidal effect was observed due to the eradication of susceptible subpopulations of bacteria; however, regrowth of resistant organisms was observed. These data suggest that a regimen of 200 mg administered intravenously every 12 hours results in rapid killing of susceptible bacteria. Higher doses or combination therapy may be required to prevent the emergence of resistant P. aeruginosa in this model and in the setting of neutropenia.

Stability of trimethoprim-sulfamethoxazole injection in two infusion fluids

The concentrations over time of trimethoprim (TMP) and sulfamethoxazole (SMZ) in solution after preparations of admixtures of TMP-SMZ in 5% dextrose injection (D5W) and in 0.9% sodium chloride injection (NS) were measured. Admixtures (50 ml) containing three TMP concentrations (0.64 mg/ml, 1.6 mg/ml, and 3.2 mg/ml) and three SMZ concentrations (3.2 mg/ml, 8.0 mg/ml, and 16 mg/ml) were prepared in D5W or NS, representing 1:25 v/v, 1:10 v/v, and 1:5 v/v dilutions of TMP-SMZ injection, respectively. Aliquots of each admixture were obtained immediately upon dilution and after 0.5, 1, 2, 4, 8, and 24 hours. The aliquots were filtered and assayed for TMP and SMZ by high-pressure liquid chromatography. Each mixture was inspected visually for any changes in clarity or color, and the pH of each admixture was measured over time. The concentration of SMZ in all admixtures remained constant over 24-hour study period. The TMP concentration did not change significantly (less than 10% of initial concentration) after 1:25 v/v dilutions in either D5W or NS for up to four hours. With a dilution of 1:10 v/vv D5W TMP was stable at D5W for up to two hours. TMP precipitated rapidly in dilutions of 1:5 v/v in either D5W or NS. The pH of the admixtures ranged from 9.39 to 10.10. D5W is the preferred diluent for TMP-SMZ injection if a dilution ratio of 1:10 v/v is desired. Either D5W or NS may be used if a dilution ratio of 1:25 v/v is desired.