Expression of the lux genes in Streptococcus pneumoniae modulates pilus expression and virulence

Bioluminescence has been harnessed for use in bacterial reporter systems and for in vivo imaging of infection in animal models. Strain Xen35, a bioluminescent derivative of Streptococcus pneumoniae serotype 4 strain TIGR4 was previously constructed for use for in vivo imaging of infections in animal models. We have shown that strain Xen35 is less virulent than its parent TIGR4 and that this is associated with the expression of the genes for bioluminescence. The expression of the luxA-E genes in the pneumococcus reduces virulence and down regulates the expression of the pneumococcal pilus.

Flavin Reductase Contributes to Pneumococcal Virulence by Protecting from Oxidative Stress and Mediating Adhesion and Elicits Protection Against Pneumococcal Challenge

Pneumococcal flavin reductase (FlaR) is known to be cell-wall associated and possess age dependent antigenicity in children. This study aimed at characterizing FlaR and elucidating its involvement in pneumococcal physiology and virulence. Bioinformatic analysis of FlaR sequence identified three-conserved cysteine residues, suggesting a transition metal-binding capacity. Recombinant FlaR (rFlaR) bound Fe²⁺ and exhibited FAD-dependent NADP-reductase activity, which increased in the presence of cysteine or excess Fe²⁺ and inhibited by divalent-chelating agents. flaR mutant was highly susceptible to H₂O₂ compared to its wild type (WT) and complemented strains, suggesting a role for FlaR in pneumococcal oxidative stress resistance. Additionally, flaR mutant demonstrated significantly decreased mice mortality following intraperitoneal infection. Interestingly, lack of FlaR did not affect the extent of phagocytosis by primary mouse peritoneal macrophages but reduced adhesion to A549 cells compared to the WT and complemented strains. Noteworthy are the findings that immunization with rFlaR elicited protection in mice against intraperitoneal lethal challenge and anti-FlaR antisera neutralized bacterial virulence. Taken together, FlaR's roles in pneumococcal physiology and virulence, combined with its lack of significant homology to human proteins, point towards rFlaR as a vaccine candidate.

Streptococcus pneumoniae and lytic antibiotic therapy: are we adding insult to injury during invasive pneumococcal disease and sepsis?

Streptococcus pneumoniae (S. pneumoniae), otherwise known as 'the pneumococcus', is a fascinating microbe that continues to pose a significant problem to public health. Currently there are no specific National Institute for Clinical Excellence (NICE) or British Thoracic Society (BTS) clinical guidelines referring to the treatment of invasive pneumococcal infection. NICE clinical guidelines suggest the use of lytic β-lactam antibiotic regimens for the management of community-acquired pneumonia and bacterial meningitis; infections for which S. pneumoniae is a likely causative organism. Lytic antibiotics have been shown to increase the release of pneumolysin (the highly inflammatory and damaging toxin of the pneumococcus), thus theoretically increasing host damage, which may lead to a decline of clinical outcomes in vulnerable patients. In light of this information, should the use of non-lytic antibiotics, such as quinolones, rifamycins and macrolides, be considered for the treatment of invasive pneumococcal disease?

A Serine-Threonine Kinase (StkP) Regulates Expression of the Pneumococcal Pilus and Modulates Bacterial Adherence to Human Epithelial and Endothelial Cells In Vitro

The pneumococcal serine threonine protein kinase (StkP) acts as a global regulator in the pneumococcus. Bacterial mutants deficient in StkP are less virulent in animal models of infection. The gene for this regulator is located adjacent to the gene for its cognate phosphatase in the pneumococcal genome. The phosphatase dephosphorylates proteins phosphorylated by StkP and has been shown to regulate a number of key pneumococcal virulence factors and to modulate adherence to eukaryotic cells. The role of StkP in adherence of pneumococci to human cells has not previously been reported. In this study we show StkP represses the pneumococcal pilus, a virulence factor known to be important for bacterial adhesion. In a serotype 4 strain regulation of the pilus by StkP modulates adherence to human brain microvascular endothelial cells (HBMEC) and human lung epithelial cells. This suggests that the pneumococcal pilus may play a role in adherence during infections such as meningitis and pneumonia. We show that regulation of the pilus occurs at the population level as StkP alters the number of pili-positive cells within a single culture. As far as we are aware this is the first gene identified outside of the pilus islet that regulates the biphasic expression of the pilus. These findings suggest StkPs role in cell division may be linked to regulation of expression of a cell surface adhesin.

Pneumococcus adapts to the sickle cell host

Children with sickle cell disease (SCD) have significantly increased risk of invasive pneumococcal disease. In this issue of Cell Host & Microbe, Carter et al. (2014) report that pneumococcal strains from SCD children have genetic mutations associated with the unique SCD environment, which need to be considered in developing new vaccines.

Resolving Salmonella infection reveals dynamic and persisting changes in murine bone marrow progenitor cell phenotype and function

The generation of immune cells from BM precursors is a carefully regulated process. This is essential to limit the potential for oncogenesis and autoimmunity yet protect against infection. How infection modulates this is unclear. Salmonella can colonize systemic sites including the BM and spleen. This resolving infection has multiple IFN-γ-mediated acute and chronic effects on BM progenitors, and during the first week of infection IFN-γ is produced by myeloid, NK, NKT, CD4(+) T cells, and some lineage-negative cells. After infection, the phenotype of BM progenitors rapidly but reversibly alters, with a peak ∼ 30-fold increase in Sca-1(hi) progenitors and a corresponding loss of Sca-1(lo/int) subsets. Most strikingly, the capacity of donor Sca-1(hi) cells to reconstitute an irradiated host is reduced; the longer donor mice are exposed to infection, and Sca-1(hi) c-kit(int) cells have an increased potential to generate B1a-like cells. Thus, Salmonella can have a prolonged influence on BM progenitor functionality not directly related to bacterial persistence. These results reflect changes observed in leucopoiesis during aging and suggest that BM functionality can be modulated by life-long, periodic exposure to infection. Better understanding of this process could offer novel therapeutic opportunities to modulate BM functionality and promote healthy aging.

Point of care testing provides an accurate measurement of creatinine, anion gap, and osmolal gap in ex-vivo whole blood samples with nitromethane

CONTEXT

Nitromethane interferes with Jaffé measurements of creatinine, potentially mimicking acute kidney injury.

OBJECTIVES

We determined the proportional contribution of nitromethane in blood samples to creatinine measured by the Jaffé colorimetric and the point-of-care (POC) reactions and determined whether the difference can reliably estimate the concentration of nitromethane. Additionally, we determined whether the presence of nitromethane interferes with anion/osmolal gaps and ascertained the stability of nitromethane in serum after 7 days.

METHODS

Nitromethane was added to whole blood from four healthy volunteers to achieve concentrations of 0, 0.25, 0.5, 1, and 2 mmol/L. The following tests were performed: creatinine (Jaffé and POC), electrolytes (associated with Jaffé and POC), osmolality and nitromethane concentration (gas chromatography [GC]). Remaining samples were refrigerated and reanalyzed using GC at 7 days. Anion and osmolal gaps were calculated. Proportional recovery and degradation of nitromethane were measured using GC. Data were analyzed for agreement with single-factor ANOVA (p = 0.05).

RESULTS

Mean creatinine for POC and Jaff methods were 0.93 vs. 0.76 mg/dL, respectively. Jaff creatinine concentrations increased linearly with increasing nitromethane concentrations (R(2) = 1, p = 0.01): measured creatinine (mg/dL) = 7.1*nitromethane (mmol/L) = 0.79. POC creatinine remained unchanged across the range of nitromethane concentrations (p = 0.99). Anion and osmolal gaps also remained unchanged. Nitromethane was reliably identified in all sample concentrations using GC on Day 0. Detection of 0.25 mmol/L nitromethane was not consistently recovered on Day 7. Nitromethane degradation was most pronounced at 2 mmol/L concentrations (81% recovery).

CONCLUSIONS

Nitromethane alters apparent concentration of creatinine using the Jaffé reaction in a linear fashion but not when using the POC reaction. Measured difference between Jaffé and POC creatinine may identify the presence and estimate concentration of nitromethane. Presence of nitromethane did not alter the anion or osmolal gap; thus it would not potentially interfere with the diagnosis of co-exposure to a toxic alcohol.

Dominant role of nucleotide substitution in the diversification of serotype 3 pneumococci over decades and during a single infection

Streptococcus pneumoniae of serotype 3 possess a mucoid capsule and cause disease associated with high mortality rates relative to other pneumococci. Phylogenetic analysis of a complete reference genome and 81 draft sequences from clonal complex 180, the predominant serotype 3 clone in much of the world, found most sampled isolates belonged to a clade affected by few diversifying recombinations. However, other isolates indicate significant genetic variation has accumulated over the clonal complex's entire history. Two closely related genomes, one from the blood and another from the cerebrospinal fluid, were obtained from a patient with meningitis. The pair differed in their behaviour in a mouse model of disease and in their susceptibility to antimicrobials, with at least some of these changes attributable to a mutation that up-regulated the patAB efflux pump. This indicates clinically important phenotypic variation can accumulate rapidly through small alterations to the genotype.

Monocytes regulate the mechanism of T-cell death by inducing Fas-mediated apoptosis during bacterial infection

Monocytes and T-cells are critical to the host response to acute bacterial infection but monocytes are primarily viewed as amplifying the inflammatory signal. The mechanisms of cell death regulating T-cell numbers at sites of infection are incompletely characterized. T-cell death in cultures of peripheral blood mononuclear cells (PBMC) showed 'classic' features of apoptosis following exposure to pneumococci. Conversely, purified CD3(+) T-cells cultured with pneumococci demonstrated necrosis with membrane permeabilization. The death of purified CD3(+) T-cells was not inhibited by necrostatin, but required the bacterial toxin pneumolysin. Apoptosis of CD3(+) T-cells in PBMC cultures required 'classical' CD14(+) monocytes, which enhanced T-cell activation. CD3(+) T-cell death was enhanced in HIV-seropositive individuals. Monocyte-mediated CD3(+) T-cell apoptotic death was Fas-dependent both in vitro and in vivo. In the early stages of the T-cell dependent host response to pneumococci reduced Fas ligand mediated T-cell apoptosis was associated with decreased bacterial clearance in the lung and increased bacteremia. In summary monocytes converted pathogen-associated necrosis into Fas-dependent apoptosis and regulated levels of activated T-cells at sites of acute bacterial infection. These changes were associated with enhanced bacterial clearance in the lung and reduced levels of invasive pneumococcal disease.

Contrast nephropathy following computed tomography angiography of the chest for pulmonary embolism in the emergency department

OBJECTIVE

To estimate the frequency of contrast nephropathy after computed tomography angiography (CTA) to rule out pulmonary embolism (PE) in the emergency department (ED) setting.

METHODS

We prospectively followed patients undergoing CTA for PE, while in the ED, for 45 days. Patients who refused follow-up or were receiving hemodialysis were excluded. Severe renal failure was defined as an increase in creatinine > or = 3.0 mg dL(-1) or a need for hemodialysis within the follow-up period. Patients were also followed for laboratory-defined contrast nephropathy, defined as an increase in creatinine of > 0.5 mg dL(-1) or > 25%, within seven days following CTA.

RESULTS

A total of 1224 patients were followed, and 354 [29%, 95% confidence interval (CI): 26-32%] patients had paired (preCTA and post-CTA) creatinine measurements. None developed renal failure (0/1224; 0%, CI: 0-0.3%). 44 patients developed laboratory-defined contrast nephropathy, corresponding to an overall frequency of 4% (44/1224; CI: 3-5%) and 12% (44/354; 95% CI: 9-16%) among those with paired creatinine measurements.

CONCLUSIONS

Following CTA for PE, the incidence of severe renal failure was very low, but the incidence of laboratory-defined contrast nephropathy (4% overall and 12% of those with paired measurements) was higher than expected.

Thyroid hormone export from cells: contribution of P-glycoprotein

Verapamil inhibits tri-iodothyronine (T3) efflux from several cell types, suggesting the involvement of multidrug resistance-associated (MDR) proteins in T3 transport. The direct involvement of P-glycoprotein (P-gp) has not, however, been investigated. We compared the transport of 125I-T3 in MDCKII cells that had been transfected with mdr1 cDNA (MDCKII-MDR) versus wild-type MDCKII cells (MDCKII), and examined the effect of conventional (verapamil and nitrendipine) and specific MDR inhibitors (VX 853 and VX 710) on 125I-T3 efflux. We confirmed by Western blotting the enhanced expression of P-gp in MDCKII-MDR cells. The calculated rate of 125I-T3 efflux from MDCKII-MDR cells (around 0.30/min) was increased twofold compared with MDCKII cells (around 0.15/min). Overall, cellular accumulation of 125I-T3 was reduced by 26% in MDCKII-MDR cells compared with MDCKII cells, probably reflecting enhanced export of T3 from MDCKII-MDR cells rather than reduced cellular uptake, as P-gp typically exports substances from cells. Verapamil lowered the rate of 125I-T3 efflux from both MDCKII and MDCKII-MDR cells by 42% and 66% respectively, while nitrendipine reduced 125I-T3 efflux rate by 36% and 48% respectively, suggesting that both substances inhibited other cellular T3 transporters in addition to P-gp. The specific MDR inhibitors VX 853 and VX 710 had no effect of 125I-T3 efflux rate from wild-type MDCKII cells but reduced 125I-T3 export in MDCKII-MDR cells by 50% and 53% respectively. These results have provided the first direct evidence that P-gp exports thyroid hormone from cells.

Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism

Overuse of the d-dimer to screen for possible pulmonary embolism (PE) can have negative consequences. This study derives and tests clinical criteria to justify not ordering a d-dimer. The test threshold was estimated at 1.8% using the method of Pauker and Kassirer. The PE rule-out criteria were derived from logistic regression analysis with stepwise backward elimination of 21 variables collected on 3148 emergency department patients evaluated for PE at 10 US hospitals. Eight variables were included in a block rule: Age < 50 years, pulse < 100 bpm, SaO(2) > 94%, no unilateral leg swelling, no hemoptysis, no recent trauma or surgery, no prior PE or DVT, no hormone use. The rule was then prospectively tested in a low-risk group (1427 patients from two hospitals initially tested for PE with a d-dimer) and a very low-risk group (convenience sample of 382 patients with chief complaint of dyspnea, PE not suspected). The prevalence of PE was 8% (95% confidence interval: 7-9%) in the low-risk group and 2% (1-4%) in the very low-risk group on longitudinal follow-up. Application of the rule in the low-risk and very low-risk populations yielded sensitivities of 96% and 100% and specificities of 27% and 15%, respectively. The prevalence of PE in those who met the rule criteria was 1.4% (0.5-3.0%) and 0% (0-6.2%), respectively. The derived eight-factor block rule reduced the pretest probability below the test threshold for d-dimer in two validation populations, but the rule's utility was limited by low specificity.

Preoperative core temperatures in elective surgical patients show an unexpected skewed distribution

PURPOSE

To document the preoperative core temperature of adult elective surgical patients.

METHODS

A prospective audit obtained sublingual temperatures from 446 adult elective surgical patients on arrival in the preoperative holding area.

RESULTS

Temperatures ranged from 35.7 degrees C to 37.8 degrees C with a mean of 36.5 degrees C (0.4 SD). The median was 36.4 degrees C and the mode was 36.1 degrees C. There was a skewed distribution with a clustering of values at the lower end of the range. All recordings were within the accepted normothermic range.

CONCLUSION

The asymmetric distribution we observed differs from previously published normothermia data which shows a symmetrical distribution of temperatures. This skewed distribution has not previously been documented and we interpret it as being due to the effect of preoperative cooling factors.

Sodium iodide symporter (NIS) gene expression in human placenta

The placenta must allow the passage of iodide from the maternal to the fetal circulation for synthesis of thyroxine by the fetal thyroid. The thyroid sodium iodide symporter (NIS) was cloned in 1996 and, although widely distributed among epithelial tissues, early studies failed to detect it in placenta. We demonstrated NIS mRNA in human placenta and in the human choriocarcinoma cell line, JAr. NIS protein was localized to trophoblasts, with a tendency to apical distribution, in sections of human placenta immunostained with a monoclonal antibody against hNIS. We conclude that NIS is expressed in placenta and may mediate placental iodide transport.

Different transporters for tri-iodothyronine (T(3)) and thyroxine (T(4)) in the human choriocarcinoma cell line, JAR

We investigated transport systems for tri-iodothyronine (T(3)) and thyroxine (T(4)) in the human choriocarcinoma cell line, JAR, using a range of structurally similar compounds to determine whether these thyroid hormones are transported by common or different mechanisms. Saturable T(3) but not saturable T(4) uptake was inhibited by a wide range of aromatic compounds (nitrendipine, nifedipine, verapamil, meclofenamic acid, mefenamic acid, diazepam, phenytoin). Nitrendipine and diazepam were the most effective inhibitors of saturable thyroid hormone uptake. Nitrendipine decreased the K(m) for T(4) uptake from a control value of around 500 nM to around 300 nM (n=6). In contrast, the K(m) for T(3) uptake was increased from a control value of around 300 nM to around 750 nM (n=4). Diazepam had similar effects. This divergent shift in affinity for the uptake of T(3) and T(4) suggested that separate uptake systems exist for these two thyroid hormones. This provides evidence for at least two transporters mediating uptake of T(3) and T(4) in JAR cells: a specific T(4) transporter that does not interact with T(3) or structurally similar compounds; and a shared iodothyronine transporter that interacts with T(3), T(4), nitrendipine and diazepam.

Lack of membrane transport of l-thyroxine sulphate in the human choriocarcinoma cell line, JAr

We examined uptake of l -thyroxine sulphate (T(4)S) and possible interactions between T(4)S and thyroxine (T(4)) uptake in the choriocarcinoma cell line JAr. Cells were incubated with 50 p m(125)I-T(4)S in the absence (total uptake) and in the presence (non-specific uptake) of 10 microm T(4)S. Cells were also incubated at 37 degrees C for 2 min with 50 p m(125)I-T(4)in the presence of an increasing amount of unlabelled T(4)(0-10 microm) or T(4)S (0-30 microm). There was negligible total uptake of(125)I-T(4)S (1.14+/-0. 05 fmol/mg cellular protein, mean+/-sem) and no specific uptake after 120 min incubation. Minor inhibition of(125)I-T(4)uptake by T(4)S could be explained entirely by a low level of residual T(4)(0. 2 per cent) in the T(4)S preparation. These findings indicate that T(4)S does not share the T(4)membrane transporter.

Comparison of mechanisms mediating uptake and efflux of thyroid hormones in the human choriocarcinoma cell line, JAR

We compared the specificities of transport mechanisms for uptake and efflux of thyroid hormones in cells of the human choriocarcinoma cell line, JAR, to determine whether triiodothyronine (T3), thyroxine (T4) and reverse T3 (rT3) are carried by the same transport mechanism. Uptake of 125I-T3, 125I-T4 and 125I-rT3 was saturable and stereospecific, but not specific for T3, T4 and rT3, as unlabelled L-stereoisomers of the thyroid hormones inhibited uptake of each of the radiolabelled hormones. Efflux of 125I-T3 was also saturable and stereospecific and was inhibited by T4 and rT3. Efflux of 125I-T4 or 125I-rT3 was, in contrast, not significantly inhibited by any of the unlabelled thyroid hormones tested. A range of compounds known to interfere with receptor-mediated thyroid hormone uptake in cells inhibited uptake of 125I-T3 and 125I-rT3, but not 125I-T4. We conclude that in JAR cells uptake and efflux of 125I-T3 are mediated by saturable and stereospecific membrane transport processes. In contrast, the uptake, but not the efflux, of 125I-T4 and 125I-rT3 is saturable and stereospecific, indicating that uptake and efflux of T4 and rT3 in JAR cells occur by different mechanisms. These results suggest that in JAR cells thyroid hormones may be transported by at least two types of transporters: a low affinity iodothyronine transporter (Michaelis constant, Km, around 1 microM) which interacts with T3, T4 and rT3, but not amino acids, and an amino acid transporter which takes up T3, but not T4 or rT3. Efflux of T4 and rT3 appears to occur by passive diffusion in these cells.

Uptake of L-triiodothyronine sulphate by human choriocarcinoma cell line, JAr

This study investigated uptake of triiodothyronine sulphate (T3S) and interactions between uptake of T3S and triiodothyronine (T3) using the human choriocarcinoma cell line (JAr) as a model of placental transport. Cells were incubated at 37 degrees C with 30 pM 125I-T3 for 2 min with unlabelled T3 (0-30 microM) or T3S (0-1 mM). Addition of an excess unlabelled T3 (30 microM) or T3S (1 mM) reduced the initial rate of 125I-T3 uptake by 69.3+/-3.6 per cent (P<0.0001) and 52.9+/-7.8 per cent (P<0.0001), respectively. The calculated Michaelis constant (Km) for T3 uptake was 0.378+/-0.133 microM (n = 3) with a corresponding maximum velocity (Vmax) of 15.4+/-6.9 pmol/min/mg protein. Uptake of 125I-T3 was inhibited in a dose-dependent way by the addition of unlabelled T3S (0-1 mM). The calculated inhibition constant (Ki) for the inhibition of 125I-T3 uptake by T3S was 121.8+/-35.2 microM (n = 6). Saturable uptake of 125I-T3S by JAr cells was negligible. The T3S preparation incubated with the cells contained about 0.1 per cent T3, sufficient to explain the apparent inhibition of 125I-T3 uptake by unlabelled T3S. These results suggest that, in contrast to T3 uptake in these cells, JAr cells do not have a saturable uptake mechanism for T3S, and that T3S does not interact with the T3 transporter in these cells.

Uptake of reverse T3 in the human choriocarcinoma cell line, JAr

The uptake and efflux of reverse triiodothyronine (rT3) in JAr cells were investigated. Uptake of 125I-rT3 was time dependent and reversible with a saturable component of around 70 per cent of total uptake after 30 min of incubation. Efflux was not saturable. Kinetic analysis of the initial specific uptake rates revealed an uptake process with a Michaelis constant of 3.04+/-0.53 microM (mean+/-SEM, n=15) and a corresponding maximum velocity of 9.65+/-2.49 pmol/min/mg protein (n=15). Uptake of rT3 was stereospecific, but not specific for rT3, as unlabelled L stereoisomers of thyroid hormone analogues were more effective as inhibitors of 125I-rT3 uptake than rT3. Unlabelled T3 and thyroxine (T4) (10 microM) reduced cellular uptake of 125I-rT3 by around 82 and 74 per cent, respectively. The calculated inhibition constants Ki were 1.23+/-0.29 microM (n=4) and 0.66+/-0.19 microM (n=4) for T3 and T4, respectively. Similarly, rT3 reduced cellular uptake of 125I-T3 and 125I-T4 by 34 and 23 per cent, respectively. The calculated inhibition constants Ki were 1.75+/-0.55 microM (n=8) and 1.08+/-0.36 microM (n=8) for the inhibition of 125I-T3 and 125I-T4 uptake, respectively. Reverse T3 inhibited efflux of 125I-T3 from the cells by around 20 per cent, but did not inhibit efflux of 125I-T4. These results suggest that uptake of rT3 in JAr cells may occur via a single, saturable membrane carrier, which also interacts with T3 and T4, while efflux of rT3 may occur by passive diffusion.

Caregiver burden: historical development

Within the last decade there has been a multitude of research related to the phenomenon of caregiver burden. Although the concept is relatively new in the literature, the responsibility and ultimately consequences of caring for another family member has existed for centuries. Often this responsibility lies with the female members of the family, but lately more husbands, sons, close family members, or friends have assumed the primary caregiver role. This article reviews the concept of caregiver burden from a historical perspective. Research related to the definition of the concept and its impact on women, men, and siblings and the effect of ethnicity, is discussed.

The relationship between lethality of attempted suicide and prior suicidal communications in a sample of residential youth

Some type of suicidal communication precedes 80% of attempted and completed suicides in adolescents. This study investigates the relationship between the number of suicidal communications prior to an attempt and the lethality of the attempt in a sample of adolescent youth residing in a residential treatment facility. The sample consisted of 46 youth who had a suicide attempt while in a large group home residential facility over a 9-year period. Results indicated that attempters who made fewer suicidal communications beforehand tended to use more lethal methods in their attempts. Attempters with two or more preceding suicidal communications had significantly lower lethality in their attempts than did those with fewer suicidal communications. Few differences emerged between the groups in regards to demographic or psychosocial variables.

Thyroid hormone efflux from placental tissue is not stimulated during cell volume regulation

The effects of cell swelling induced by hyposmotic shock on efflux of hybrid hormones and selected amino acids from human placental tissue were examined. Decreasing the osmolarity of external medium from 290 to 140 mOsm/kg stimulated release of taurine, tryptophan and glutamine from placental tissue fragments. The efflux rate constant for taurine increased from 0.0069 +/- 0.0012/min to 0.0646 +/- 0.0217/min (n = 6) (P < 0.001), for tryptophan from 0.016 +/- 0.0010/min to 0.0295 +/- 0.0016/min (n = 6) (P < 0.001), and for glutamine from 0.0267 +/- 0.0027/min to 0.0659 +/- 0.0043/min (n = 4) (P < 0.001). In contrast, hyposmotic challenge did not affect release of triiodothyronine, thyroxine and leucine. These results indicate that transport processes involved in the regulation of cellular volume are unlikely to facilitate efflux of thyroid hormones from placental tissue, and therefore are unlikely to mediate transfer of thyroid hormones across the placenta. In addition, it is unlikely that the transport system facilitating the release of amino acids from placental tissue during regulatory volume decrease is one of the known amino acid carriers.

Uptake of thyroxine in the human choriocarcinoma cell line JAR

We have studied the uptake of 125I-thyroxine (125I-T4) in the human choriocarcinoma cell line JAR. Uptake of 125I-T4 was time-dependent, stereospecific and reversible, with a saturable component of 33% after 120 min of incubation. Kinetic analysis of the initial specific uptake rates indicated the presence of a single uptake process with a Michaelis constant of 59.4 +/- 13.9 nM (n = 12) and maximum velocity of 0.29 +/- 0.06 pmol/min per mg protein. Uptake was dependent on intracellular energy as, in the presence of 2 nM potassium cyanide, saturable uptake was reduced to 60.6 +/- 8.5% (n = 4) of control uptake. Uptake was also temperature-dependent. Saturable 125I-T4 uptake after 60 min of incubation was 26.1 +/- 3.0% at 25 degrees C (n = 6) and 27.3 +/- 5.7% at 4 degrees C of control uptake at 37 degrees C. Ouabain did not inhibit 125I-T4 uptake indicating that the uptake was independent of the Na+ gradient across the cell membrane. Although T4 uptake was stereospecific, as D-T4 failed to inhibit 125I-L-T4 uptake, it was not specific for T4, as tri-iodothyronine (T3) and reverse T3 also inhibited 125I-T4 uptake. We conclude that JAR cells have a saturable, stereospecific and reversible membrane transport mechanism for T4 which is dependent on intracellular energy, but independent of the Na+ gradient across the cell membrane.

Exploring Widows' Experiences After the Suicide of Their Spouse

1. The widow of a spouse who committed suicide must cope with issues related to depression, anger, blame, guilt, and the stigma associated with suicide that makes recovery from this type of loss different for the survivors. 2. The predominant need of widows and widowers of suicide victims was to talk in an environment of acceptance and understanding, which could only be provided by other people who have had the same kind of experience. 3. There is no precise formula that exists to guide caregivers when assisting survivors of suicide victims, however suggestions include communicating with compassion; demonstrating care and concern; accepting the individual's grief; and offering and providing information.

Characterization of cell polarity and epithelial junctions in the choriocarcinoma cell line, JAR

In the placenta the trophoblast cell layer separates maternal and fetal circulations and is involved in the active transport of selected substances across this barrier. We have used the JAR choriocarcinoma cell line to study aspects of trophoblast membrane transport. To determine whether JAR cells could be used in studies of vectorial transepithelial transport it was necessary to determine whether these cells were polarized and assembled tight junctions. In the present study we investigated JAR cells using a range of markers for specific cell surface domains combined with confocal laser scanning microscopy. Freshly isolated cells initially formed a confluent epithelial monolayer with recruitment of a tight junction-associated protein, ZO-1, and a cell adhesion molecule, E-cadherin, to the surface at sites of cell-cell contact. They did not, however, display cell surface polarization, as NaK-ATPase was not segregated in the basolateral domain, and a differentiated apical cell surface was not assembled. The monolayer stage was also unstable, as continued proliferation resulted in the formation of multilayered aggregates where ZO-1 and E-cadherin were lost from the cell surface. These results suggest that the JAR cell line is unlikely to be a suitable model for studies of transepithelial transport in the placenta.

Interactions between transport of triiodothyronine and tryptophan in JAR cells

We studied the effect of a number of amino acids on uptake of L-triiodothyronine (T3) in the human choriocarcinoma cell line, JAR. Tryptophan inhibited saturable T3 uptake by about 57% without any significant effect on the non-saturable uptake. Michaelis constant (Km) for T3 uptake was 1.06 +/- 0.15 microM (n = 15) with the corresponding maximum velocity (Vmax) of 24.2 +/- 3.1 pmol/min/mg cellular protein. For tryptophan uptake the Km was 1.31 +/- 0.26 microM (n = 7) and Vmax was 166.4 +/- 35.7 pmol/min/mg protein. The kinetic parameters for both uptake processes were similar to those reported in normal placenta. Uptake of T3 was inhibited by tryptophan but not phenylalanine, but tryptophan uptake was inhibited both by T3 and phenylalanine. Inhibition of T3 uptake by tryptophan was dose dependent, with an inhibition constant (Ki) of 2.9 +/- 0.5 mM. Similarly, tryptophan uptake was inhibited by T3 and phenylalanine in a dose dependent way with Ki values of 4.9 +/- 0.5 microM and 15.6 +/- 4.8 microM respectively. Km for T3 uptake was significantly increased to 1.86 +/- 0.42 microM (n = 4) in the presence of 3 mM unlabelled tryptophan and, similarly, Km for tryptophan uptake was significantly increased to 9.91 +/- 2.57 microM (n = 3) in the presence of 5 microM unlabelled T3. Efflux of T3 was progressively inhibited by increasing concentrations of both ligands, i.e. was saturable. We conclude that there is mutual competitive inhibition between uptake systems for T3 and tryptophan in JAR cells, but the kinetic parameters of cross-inhibition of uptake by the substrates suggest that the carriers are distinct. T3 may be transported in JAR cells by at least two transport systems with differing substrate specificities. We also demonstrated the presence of a saturable membrane carrier mediating the efflux of T3 from the cells which was subject to trans-inhibition by T3 and tryptophan.

The insulin-like growth factor I generation test: resistance to growth hormone with aging and estrogen replacement therapy

Circulating IGF-I is primarily regulated by growth hormone, but other factors such as nutritional status may also influence IGF-I secretion. The effects of age, gender, and estrogen replacement on responsiveness of serum IGF-I to GH administration have not been directly studied. The high-affinity circulating GH-binding protein (GHBP) has the same structure as the extracellular domain of the GH receptor and may reflect the sensitivity to GH in humans. To examine these issues, we employed an IGF-I generation test in which a single dose of GH (0.1 mg/kg SQ) was administered to 31 healthy adults comprising five groups: young (20-29 years) males (YM), young females in the follicular phase of the menstrual cycle (YF), older (60-69 years) males (OM), older females not on estrogen replacement (OFN), and older females on oral estrogen replacement (OFE). Blood was sampled for IGF-I and GHBP over 72 hours following GH administration. OM had lower peak IGF-I levels (323 +/- 38 vs. 497 +/- 85 micrograms/l, p = 0.0015) and a lower IGF-I response to GH (delta IGF-I: 187 +/- 33 vs. 293 +/- 57 micrograms/l, p = 0.0085) than YM. OFE had lower basal IGF-I (63 +/- 11 vs. 133 +/- 19 micrograms/l, p = 0.0046), peak IGF-I (174 +/- 28 vs. 400 +/- 40 micrograms/l, p = 0.0015), and delta IGF-I (111 +/- 21 vs. 268 +/- 27 micrograms/l, p = 0.0085) than OFN. IGFBP-3 levels were unchanged 24 hours after GH administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Reflective peer journals: developing authentic nurses

Nursing education courses often require students to write about their learning experiences in a journal or a log book. Students write the journal/log and submit it to the instructor. The instructor reads, comments, and may or may not grade it. This paper is a reflection on the use and misuse of journals in nursing education from the viewpoints of students and instructors. Related literature is integrated into a dialogue with concepts that relate to nursing education. A theoretical framework, a format and guidelines for peer journals are presented, along with the rationale for having students keep peer journals rather than student/instructor logs.

Membrane transport of thyroid hormone in the human choriocarcinoma cell line, JAR

We studied uptake of L-triiodothyronine (T3) by the human choriocarcinoma cell line, JAR. Uptake was time dependent with a half-time of 56.2 +/- 7.2 min (mean +/- SEM, n = 4). A non-saturable component accounted for about 24% of total uptake. We found a single saturable uptake mechanism with a calculated Michaelis constant (Km) of 586 +/- 206 nM (n = 9) and a corresponding maximum velocity of 17.0 +/- 5.7 pmol/min per mg protein (n = 9), values similar to those we have described recently in cultured normal human trophoblast cells. Uptake was dependent on temperature and intracellular energy, being reduced at lower temperatures and in the presence of potassium cyanide. It was independent of the Na+ gradient across the cell membrane and the presence of Na+ in the external medium, but was affected by the cell membrane potential.

Uptake of L-tri-iodothyronine by human cultured trophoblast cells

We investigated the uptake of L-tri-iodothyronine (T3) by cultured human trophoblast cells. Uptake was time-dependent, initially linear and approaching equilibrium after 60 min with an approximate half-time of 13 +/- 4.5 min (mean +/- S.E.M., n = 4). It had a non-saturable component accounting for about 50% of total uptake. We demonstrated a single saturable T3 uptake mechanism with a calculated Michaelis constant (Km) of 755 +/- 145 nmol/l (n = 11-13) and a corresponding maximum velocity of 28.8 +/- 5.3 pmol/min per mg protein (n = 11-13). The Km value was similar to those reported in other tissues.

Determination of temelastine and a hydroxymethyl-pyridyl metabolite in biological fluid by high-performance liquid chromatography

A high-performance liquid chromatographic method for the analysis of temelastine (1) and 2-[4-(5-bromo-3-methylpyrid-2-yl)-butylamino]-5-[6-hydroxymethy lpyrid-3- ylmethyl]-pyrimidin-4(1H)-one (1-A) in biological fluid is presented. The method combines the previously reported extraction procedure and new chromatography conditions capable of resolving 1, 1-A, and structurally similar compounds formed by the oxidation of 1. The modified method has been used to measure concentrations of 1 and 1-A in biological fluids taken from the rat and dog, and to look for the presence of 1-A in humans following administration of 1.

Induction of cytochrome P-450 in cultured rat hepatocytes. The heterogeneous localization of specific isoenzymes using immunocytochemistry

Primary cultures of rat hepatocytes were exposed to phenobarbitone, clofibric acid, beta-naphthoflavone, isosafrole or dexamethasone for 3 days, and the induction of several cytochrome P-450 isoenzymes was demonstrated by increased catalytic activity, by Western blotting and by immunocytochemistry. The profiles of isoenzymes induced in vitro were compared with those induced in liver microsomes of rats dosed with the same agents. Clofibric acid, an agent which has not been thoroughly investigated previously, was shown to induce both in vivo and in vitro several P-450 isoenzymes normally inducible by phenobarbitone (PB1a, PB3a and PB3b) or steroids (PB2c). Immunocytochemical studies demonstrated that the inducible isoenzymes of cytochrome P-450 are not distributed evenly throughout the hepatocyte population, and increasing concentrations of phenobarbitone or beta-naphthoflavone in the medium results in an increasing proportion of 'induced' cells. However, whereas maximal concentrations of beta-naphthoflavone resulted in virtually all cells containing induced levels of MC1b, a maximal concentration of phenobarbitone resulted in only 30% of the cells containing induced levels of PB3a/PB3b. These results are discussed in relation to the heterogeneous distribution and induction of cytochrome P-450 in the intact liver.

The metabolism of mono-(2-ethylhexyl) phthalate (MEHP) and liver peroxisome proliferation in the hamster

This study has investigated the in vivo metabolism of mono-(2-ethylhexyl) phthalate (MEHP), the initial metabolite of di-(2-ethylhexyl) phthalate in mammals, and the hepatic peroxisome proliferation induced by this compound following multiple oral administration to hamsters. Hamsters received [14C]-MEHP, by gavage, at doses of 50 and 500 mg/kg body wt on each of three consecutive days. Urine was collected every 24 hours and metabolite profiles were determined using capillary gas-chromatography. Multiple high doses of MEHP (500 mg/kg) induced a change in the relative proportions of metabolites produced. As previously reported for the rat, metabolites derived from sequential omega- following by beta-oxidation were increased. This increase was correlated with a parallel 3-fold increase in peroxisomal beta-oxidation--a marker for peroxisome proliferation. Hamsters were less responsive than rats to peroxisome proliferation elicited by MEHP. In contrast to the rat, a large proportion of hamster omega-1 oxidation products of MEHP (metabolites 6 and 9, mono (2-ethylhexyl-5-oxohexyl) phthalate and mono (2-ethyl-5-hydroxyhexyl) phthalate, respectively) were found as their glucuronide conjugates. This metabolic species difference may relate to differences in sensitivity to MEHP as a peroxisome proliferator. The relationship between metabolite conjugation, peroxisome proliferation and production of omega-oxidation metabolites is discussed.

Peroxisome proliferation due to di(2-ethylhexyl) phthalate (DEHP): species differences and possible mechanisms

The exposure of cultured rat hepatocytes to mono(2-ethylhexyl)phthalate (MEHP) for 72 hr resulted in marked induction of peroxisomal enzyme activity (beta-oxidation; cyanide-insensitive palmitoyl CoA oxidase) and concomitant increases in the number of peroxisomes. Similar treatment of cultured guinea pig, marmoset, or human hepatocytes revealed little or no effect of MEHP. In order to eliminate possible confounding influences of biotransformation, the proximate peroxisome proliferator(s) derived from MEHP have been identified. Using cultured hepatocytes these agents were found to be metabolite VI [mono(2-ethyl-5-oxohexyl) phthalate] and metabolite IX [mono(2-ethyl-5-hydroxyhexyl) phthalate]. The addition of these "active" metabolites to cultured guinea pig, marmoset, or human hepatocytes again revealed little effect upon peroxisomes or related enzyme activities (peroxisomal beta-oxidation or microsomal lauric acid hydroxylation). These studies demonstrate a marked species difference in the response of hepatocytes to MEHP-elicited peroxisome proliferation. Preliminary studies have also suggested that peroxisome proliferation due to MEHP may be due to an initial biochemical lesion of fatty acid metabolism.

Identification of the proximate peroxisome proliferator(s) derived from di(2-ethylhexyl) phthalate

A primary rat hepatocyte culture system was utilized to determine the proximate peroxisome proliferator(s) derived from di(2-ethylhexyl) phthalate (DEHP). DEHP was administered to rats and the urinary metabolites were identified and isolated. The major metabolites were those resulting from initial omega- or omega - 1-carbon oxidation of the mono(2-ethylhexyl) phthalate (MEHP) moiety. These metabolites, together with MEHP and 2-ethylhexanol, were added to primary rat hepatocyte cultures and the effect on peroxisomal enzyme activity was determined. The omega-carbon oxidation products [mono(3-carboxy-2-ethylpropyl) phthalate (I) and mono(5-carboxy-2-ethylpentyl) phthalate (V)] and 2-ethylhexanol produced little or no effect on CN- -insensitive palmitoyl-CoA oxidation (a peroxisomal marker). MEHP and the omega - 1-carbon oxidation products [mono-(2-ethyl-5-oxohexyl) phthalate (VI) and mono(2-ethyl-5-hydroxyhexyl) phthalate (IX)] produced a large (7- to 11-fold) induction of peroxisomal enzyme activity. Similar structure-activity relationships were observed for the induction of cytochrome P-450-mediated lauric acid hydroxylase and increase in cellular coenzyme A content. This identification of the proximate proliferators will aid in the elucidation of the mechanism by which DEHP causes proliferation of peroxisomes in the rodent liver. Oral administration of MEHP (150 or 250 mg/kg) to male guinea pigs did not produce hepatic peroxisome proliferation. Addition of MEHP (0 to 0.5 mM) or one of the "active" proliferators in the rat (metabolite IX, 0 to 0.5 mM) to primary guinea pig hepatocyte cultures also failed to produce an induction of peroxisomal beta-oxidation. Possible reasons for this species difference are discussed.

The metabolism of di(2-ethylhexyl) phthalate (DEHP) and mono-(2-ethylhexyl) phthalate (MEHP) in rats: in vivo and in vitro dose and time dependency of metabolism

This study investigated the in vivo metabolism of di(2-ethylhexyl) phthalate (DEHP) and mono(2-ethylhexyl) phthalate (MEHP) in rats after multiple dosing, the metabolism of MEHP in primary rat hepatocyte cultures for periods of up to 3 days, and the biotransformation of some major metabolites of MEHP. Rats were orally administered [14C]DEHP or [14C]MEHP at doses of 50 and 500 mg/kg body wt for three consecutive days. Urine was collected at 24-hr intervals, and metabolite profiles were determined. After a single dose of either compound, urinary metabolite profiles were similar to those previously reported. However, after multiple administration of both DEHP and MEHP at 500 mg/kg, increases in omega-/beta-oxidation products [metabolites I and V, mono(3-carboxy-2-ethylpropyl) phthalate and mono(5-carboxy-2-ethylpentyl) phthalate, respectively] and decreases in omega - 1-oxidation products [metabolites VI and IX, mono(2-ethyl-5-oxohexyl) phthalate and mono(2-ethyl-5-hydroxyhexyl) phthalate, respectively] were seen. At the low dose of 50 mg/kg little or no alteration in urinary metabolite profiles was observed. At 500 mg/kg of MEHP a 4-fold stimulation of CN- -insensitive palmitoyl-CoA oxidation (a peroxisomal beta-oxidation marker) was seen after three consecutive daily doses. At the low dose of 50 mg/kg only a 1.8-fold increase was noted. Similar observations were made with rat hepatocyte cultures. MEHP at concentrations of 50 and 500 microM was extensively metabolized in the rat hepatocyte cultures. Similar metabolic profiles to those seen after in vivo administration of MEHP were observed. At the high (500 microM) concentration of MEHP, changes in the relative proportions of omega- and omega- 1-oxidized metabolites were seen. Over the 3-day experimental period, omega-/beta-oxidation products increased in a time-dependent manner at the expense of omega - 1-oxidation products. At a concentration of 500 microM MEHP, a 12-fold increase of CN- -insensitive palmitoyl CoA oxidation (a peroxisomal beta-oxidation marker) was observed. At the low concentration of MEHP (50 microM) only a 3-fold increase in CN- -insensitive palmitoyl-CoA oxidation was noted and little alteration in the metabolite profile of MEHP was observed with time. Biotransformation studies of the metabolites of MEHP confirmed the postulated metabolic pathways. Metabolites I and VI appeared to be endpoints of metabolism, while metabolite V was converted to metabolite I, and metabolite IX to metabolite VI. It was also possible to reduce the transformation of metabolite X [mono(2-ethyl-6-hydroxyhexyl) phthalate] to metabolite V.(ABSTRACT TRUNCATED AT 400 WORDS)

Factors influencing peroxisome proliferation in cultured rat hepatocytes

A primary rat hepatocyte culture system has been developed for the study of peroxisome proliferation. Maximal induction of peroxisomal activity requires supplementation of the culture medium with hydrocortisone. The addition of clofibric acid (0.01-1 mM), mono-(2-ethylhexyl)phthalate (0.01-0.5 mM) and trichloroacetic acid (0.1-5 mM) to cultured rat hepatocytes resulted in a time- and dose-related increase in CN- insensitive palmitoyl CoA oxidation (maximal increases: 27-, 15.5-, and 5-fold respectively) and mitochondrial alpha-glycerophosphate dehydrogenase activity (maximal increases: 7.3-, 5.8-, and 1.6-fold respectively). Electron microscopic examination revealed smooth endoplasmic reticulum proliferation and morphometric analysis indicated an increase in fractional peroxisomal volume of X 8 and X 4 for clofibric acid (1 mM) and trichloroacetic acid (2.5 mM), respectively. SDS-PAGE of cell homogenates revealed an intensified protein band of mol. wt. 76-78,000. The induction of peroxisomal beta-oxidation by clofibric acid was elevated from 9- to 12-fold by supplementation of the medium with L-carnitine (2 mM).