Changes in respiratory effort sensation over time are linked to the frequency content of diaphragm electrical activity

This study evaluated whether respiratory effort sensation (RES) changes over time when breathing is performed with constant contraction pattern, fixed diaphragm activation, and maintained pressure generation. Another aim was to assess whether there was any association between RES and the power spectrum center frequency of the diaphragm (CFdi) electrical activity. Six healthy subjects performed two 10-min periods targeting diaphragm electrical activation (EAdi) to 40% of maximum using (1) expulsive or Mueller maneuvers at FRC generating a mean transdiaphragmatic (Pdi) pressure of 55.0 +/- 22.7 cm H(2)O (+/- SD) and (2) inspiration to 71.2 +/- 14.1% of inspiratory capacity (IC) generating a Pdi of 21.4 +/- 5.2 cm H(2)O. The Pdi did not decrease over time during either maneuver. During both periods RES increased (p < 0.001) and CFdi decreased (p < 0.001) over time with higher Pdi levels producing larger decreases in CFdi (p = 0.003) and greater increases in RES (p = 0.008). Changes in CFdi and RES were related, and identical slopes were obtained during the two maneuvers. In conclusion, while breathing with a fixed pattern, constant diaphragm activation, and maintained pressure generation, RES increases over time and is associated with CFdi independent of the level of diaphragm pressure generated.

Alteration of the vascular supply in the rabbit ciliary body by transscleral diode laser cyclophotocoagulation

BACKGROUND

Besides the direct destruction of the non-pigmented ciliary epithelium by cyclodestructive procedures, further mechanisms are responsible for the decrease of intraocular pressure. This study evaluates the alteration of the ciliary body vascularization by contact transscleral diode laser cyclophotocoagulation in rabbit eyes.

METHODS

Pigmented chinchilla bastard rabbits were used. Preliminary experiments were conducted to determine the parameters for diode laser cyclophotocoagulation of the pars plana or pars plicata. Then, treatment of the pars plicata (three rabbits) or pars plana (three rabbits) was performed in the right eye of six rabbits. After 2, 6 and 12 weeks histologic and transmission electron microscopic studies were performed. Furthermore, three rabbits received pars plicata cyclophotocoagulation of the right and pars plana cyclophotocoagulation of the left eye. After 2, 6 and 12 weeks, vascular casts of the ciliary body were investigated by scanning electron microscopy.

RESULTS

Histologic and transmission electron microscopic studies showed a marked coagulation necrosis with subsequent ciliary body atrophy, destruction of the ciliary epithelium, pigment dispersion in the ciliary body stroma and peripheral anterior synechiae. Examination of vascular casts of the ciliary body revealed a marked rarefication of the capillary network within the treated areas of the ciliary body in all eyes and at every time of investigation. Anterior to the laser burns the capillary network was not markedly affected in the eyes with cyclophotocoagulation of the pars plana. After 3 months short vessel sprouts were seen, but regeneration was mostly incomplete.

CONCLUSIONS

The vascular casting technique is an excellent method for the investigation of changes in ciliary body vascularization after cyclodestruction. This study is the first to demonstrate a marked rarefication of the ciliary body vascularization after diode laser cyclophotocoagulation using vascular casts. The results suggest that alteration of vascularization probably acts as a strong synergistic mechanism in the decrease of intraocular pressure after cyclophotocoagulation of the pars plicata.

Hg3AsE4X (E = S, Se; X = Cl, Br, I), a family of isotypic compounds with an acentric, layered structure

Four isotypic compounds Hg3AsS4Cl, Hg3AsS4Br, Hg3AsSe4Br, and Hg3AsSe4I were synthesized in the quaternary system mercury/arsenic/chalcogen/halogen by vapor transport reactions from As, Hg(II) halide, Hg(II) chalcogenide, and elemental chalcogen at temperatures between 250 and 310 degrees C. Their structures were solved by single-crystal X-ray diffraction analyses. The compounds crystallize in the hexagonal system with the acentric space group P63mc and the following lattice parameters: a = 7.431(5) A, c = 9.003(8) A for Hg3AsS4Cl, a = 7.430(5) A, c = 9.364(5) A for Hg3AsS4Br, a = 7.707(8) A, c = 9.47(2) A for Hg3AsSe4Br, and a = 7.6902(7) A, c = 9.968(1) A for Hg3AsSe4I, and Z = 2. All compounds are air-stable and form hexagonal prismatic crystals. The colors vary from yellow (Hg3AsS4Cl) to red (Hg3AsSe4I). The structures consist of infinity 2[Hg3AsE4]+ polycationic layers built of six-membered Hg3E3 and Hg2AsE3 rings in chair and boat conformations. Alternatively, the structure of the layers can be described as composed of [AsE3]3- and [Hg3E]4+ ions both forming regular trigonal pyramids. The halide ions are intercalated between the layers and have only weak bonds to the mercury atoms. The acentricity of the structures was confirmed through SHG measurements using IR laser radiation (lambda = 1064 nm).

Characterization of osteoclast precursors in human blood

Osteoclast precursors (OCPs) circulate in the mononuclear fraction of peripheral blood (PB), but their abundance and surface characteristics are unknown. Previous studies suggest that the receptor activator for NF-kappaB (RANK) on cytokine-treated OCPs in mouse bone marrow interacts with osteoprotegerin ligand (OPGL/TRANCE/RANKL/ODF) to initiate osteoclast differentiation. Hence, we used a fluorescent form of human OPGL (Hu-OPGL-F) to identify possible RANK-expressing OCPs in untreated peripheral blood mononuclear cells (PBMCs) using fluorescence-activated cell sorting analysis. Monocytes [CD14-phycoerythrin (PE) antibody (Ab) positive (+) cells, 10-15% of PBMCs] all (98-100%) co-labelled with Hu-OPGL-F (n > 18). T lymphocytes (CD3-PE Ab+ cells, 66% of PBMCs) did not bind Hu-OPGL-F; however, B cells (CD19-PE Ab+ cells, 9% of PBMCs) were also positive for Hu-OPGL-F. All Hu-OPGL-F+ monocytes also co-labelled with CD33, CD61, CD11b, CD38, CD45 and CD54 Abs, but not CD34 or CD56 Abs. Hu-OPGL-F binding was dose dependent and competed with excess Hu-OPGL. When Hu-OPGL-F+, CD14-PE Ab+, CD33-PE Ab+, Hu-OPGL-F+/CD14-PE Ab+ or Hu-OPGL-F+/CD33-PE Ab+ cells were cultured with OPGL (20 ng/ml) and colony-stimulating factor (CSF)-1 (25 ng/ml), OC-like cells readily developed. Thus, all freshly isolated monocytes demonstrate displaceable Hu-OPGL-F binding, suggesting the presence of RANK on OCPs in PB; also, OCPs within a purified PB monocyte population form osteoclast-like cells in the complete absence of other cell types in OPGL and CSF-1 containing medium.

Glutathione S-transferase and drug sensitivity in malignant glioma

Malignant gliomas are largely resistant to current approaches of adjuvant chemotherapy. Gluthatione S-transferases (GST) have been attributed a role in the resistance of cancer cells, e.g., to nitrosoureas. Here, we assessed the expression levels of GST-pi and GST-mu RNA and protein as well as total GST activity in a panel of 12 human glioma cell lines and correlated these data with p53 status, BCL-2 family protein expression and drug sensitivity in these cells. Neither GST protein levels nor GST activity correlated with genetic or functional p53 status or with the expression of various BCL-2 family proteins. No evidence for GST-mediated protection from chemotherapeutic drugs became apparent. In contrast, high levels of GST-pi protein, probably the major source of GST activity in glioma cells, and of total GST activity correlated with enhanced sensitivity to vincristine-induced clonogenic cell death. Expression of GST-pi in human glioblastomas in vivo was confirmed by immunohistochemistry. Neither total, nor cytoplasmic or nuclear, GST-pi immunoreactivity correlated with the response to adjuvant radiotherapy or radiochemotherapy. A comparative analysis of primary and recurrent tumors showed that GST expression was not enhanced by radiochemotherapy in vivo. We conclude that GST does not account for the differential chemosensitivity of glioma cell lines in vitro and does not accumulate in glioma subpopulations that form recurrent tumors after radiochemotherapy in vivo.

Expiratory muscle pressure and breathing mechanics in chronic obstructive pulmonary disease

Expiratory muscle recruitment is common in stable chronic obstructive pulmonary disease (COPD) patients. Due to airway obstruction, there is little reason to believe that active expiration in COPD would be mechanically effective in lowering operating lung volume. The physiological significance of expiratory muscle recruitment in COPD, therefore, remains unknown. The purpose of this study was to assess, in COPD patients breathing at rest, the effect of expiratory muscle contraction on force generating ability of the diaphragm. The force generating ability of the diaphragm was evaluated from its pressure swing (Pdi) for a given diaphragm electrical activity (Edi), where Edi was normalized as % of its maximal value (Pdi/Edi/Edi,max). Phasic expiratory muscle contraction was measured as the total expiratory rise in gastric pressure (Pga,exp.rise). Nineteen seated patients with moderate to severe COPD, participated in the study and 10 exhibited phasic rise in Pga during expiration with a mean Pga,exp.rise of 1.91+/-0.89 cmH2O. The patients were thus divided into passive expiration (PE) and active expiration (AE) groups. There was no significant difference in various lung function and breathing pattern parameters between the two groups. Pdi/Edi/Edi,max was 0.63+/-0.07 and 0.54+/-0.07 cmH2O/% in PE and AE groups, respectively, and was not significantly different between each other. Compared with PE group, AE group not only recruited expiratory muscles, but also preferentially recruited inspiratory rib cage muscles and derecruited the diaphragm. The results do not support a significant improvement of the force-generating ability of the diaphragm by phasic contraction of expiratory muscles at rest in chronic obstructive pulmonary disease patients.

Endotoxin in pooled pericardial blood contributes to the systemic inflammatory response during cardiac surgery

Although endotoxin has been implicated as an important contributor to the systemic inflammatory response (SIR) during cardiopulmonary bypass (CPB), its source remains unclear. While gut translocation has traditionally been perceived as the primary source of endotoxemia, accumulation of endotoxin in pooled pericardial blood may represent an additional source of endotoxin that is continually reinfused into the CPB circuit. Eighteen patients undergoing primary coronary revascularization procedures were prospectively evaluated. Shed blood pooled in the pericardial space was returned to the CPB circuit through cardiotomy suction catheters at 45 min after placement of the aortic cross-clamp. Simultaneous samples of pooled pericardial and peripheral arterial blood were obtained and analyzed by a limulus amebocyte lysate assay for the determination of endotoxin concentration, and an enzyme-linked immunosorbent assay for tumor necrosis factor (TNF-alpha) levels. Significant elevations in endotoxin were demonstrated in pooled pericardial blood samples compared with arterial blood (3.5 +/- 0.5 vs 0.8 +/- 0.2 pg/ml; p < 0.05). TNF-alpha levels were below the limits of detection in both samples. These data implicate pooled pericardial blood as an important primary source of endotoxin that, when continually reinfused throughout CPB, may contribute to the overall SIR. Because endotoxemia has been identified as an important predictor of adverse outcomes following cardiac surgery, removal of endotoxin antigen in shed pericardial blood, prior to its reinfusion into the CPB circuit, may provide a directed means to improve perioperative outcome without compromising established blood conservation techniques.

Examination of the human prion protein-like gene doppel for genetic susceptibility to sporadic and variant Creutzfeldt-Jakob disease

A novel human gene named Doppel (DPL) that has homology to the prion protein gene (PRNP) has recently been identified on chromosome 20p. By automated sequencing we have found a common (M174T, 48%) and an uncommon coding polymorphism. The polymorphic frequency of the M174T allele was examined in cases of variant and sporadic Creutzfeldt-Jakob Disease and compared with the frequency in the normal UK population. In sharp distinction to the M129V polymorphism of PRNP we have not found any evidence of disease association nor is there any association with age of onset, disease duration, or prion protein (PrP(Sc)) strain type.

Asthma severity, recommended changes of inhaled therapy and exhaled nitric oxide in children: a prospective, blinded trial

Orally exhaled nitric oxide (ENO) correlates with several variables of airway inflammation and might be useful to direct asthma therapy. If this is true, ENO should correlate with disease severity and the therapeutic decisions made. - In 74 children with allergic asthma (age 9.7 years, range 4-16) disease severity was determined by history, clinical symptoms, and lung function and inhaled therapy was adjusted according to the NIH criteria. ENO was also measured, but the patients, their parents and the physicians who made the therapeutic decision were left unaware of the results. 31 healthy children served as controls. ENO was higher in asthmatics than in controls, but did not differ with asthma severity. ENO was weakly correlated with the changes in asthma therapy recommended (r = 0.303, P = 0.009). ENO values above normal (> 13 ppb) had a sensitivity of 0.67 and a specificity of 0.65 to predict a step up in therapy. Due to the non-normal distribution of ENO there was a substantial overlap between the different groups. The lack of correlation with disease severity and the weak prediction of physician recommended inhaled therapy, suggest that ENO may be of some value to guide asthma therapy. Studies using ENO to direct therapy are necessary for a definite answer.

The effect of CVVHD and endotoxin on the oxidative burst, adhesion molecules and distribution in tissues of granulocytes

OBJECTIVE

Extracorporeal circulation, such as cardiopulmonary bypass and haemodialysis, has been associated with an activation of the immune system, especially the granulocytes. Continuous veno-venous haemodiafiltration (CVVHD) is used in critically ill septic patients. During CVVHD cytokines are excreted in the ultrafiltrate. But when the membranes used in CVVHD are cultured with granulocytes, the granulocytes are slightly activated. This effect is potentiated by endotoxin. We therefore, in vivo, compared the effect on granulocyte activation of CVVHD with an endotoxin group and a control group.

METHODS

Thirty-one pigs were anaesthetized and mechanically ventilated. In ten pigs CVVHD was performed. Eleven pigs received an infusion of Escherichia coli endotoxin 30 mu/kg(-1) and ten pigs served as a control group. The adhesion molecules CD18 and CD62L were measured using monoclonal antibodies. The oxidative burst activity was assayed as superoxide dismutase-inhibitory reduction of cytochrome c. The number of granulocytes in peripheral blood and in the lungs and liver were counted.

RESULTS

The infusion of endotoxin was followed by granulocytopenia, reduced oxidative burst activity, increased expression of CD18 and decreased expression of CD62L on granulocytes. Accumulation of granulocytes in liver and lung tissue was also noted in this group. CVVHD was only associated with a non-significant decrease in CD62L expression on granulocytes. It did not affect any of the other measured immunological parameters.

CONCLUSION

In contrast to endotoxin-induced sepsis, the granulocytes were not activated during CVVHD.

Leukocyte-endothelium interactions in pial venules during the early and late reperfusion period after global cerebral ischemia in gerbils

The contribution of leukocytes to secondary brain damage after cerebral ischemia is still under discussion. The purpose of the present study was to examine the pial microcirculation after global cerebral ischemia while focusing on leukocyte-endothelium interactions during the early and late reperfusion period of up to 4 days. A closed cranial window technique that leaves the dura mater intact was used. Global cerebral ischemia of 15 minutes' duration was induced in male Mongolian gerbils (n = 91). Pial microcirculation was observed by intravital fluorescence microscopy. Leukocyte-endothelium interactions (LEIs) in pial venules, vessel diameters, capillary density, and regional microvascular blood flow measured by laser Doppler flowmetry were quantified during 3 hours of reperfusion and in intervals up to 4 days after ischemia. Within 3 hours of reperfusion, the number of leukocytes (cells/100 microm x minute) rolling along or adhering to the venular endothelium increased from 0.1 +/- 0.2 to 28.4 +/- 17.4 (P < 0.01 vs. control) and from 0.2 +/- 0.2 to 4.0 +/- 3.8 (P < 0.05), respectively. There was no capillary plugging by leukocytes; capillary density remained unchanged. In the late reperfusion period, at 7 hours after ischemia, LEIs had returned to baseline values. Furthermore, from 12 hours to 4 days after ischemia, no LEIs were observed. Changes in regional microvascular blood flow did not correlate with LEIs. Global cerebral ischemia of 15 minutes' duration induces transient LEIs that reach a maximum within 3 hours of reperfusion and return to baseline at 7 hours after ischemia. LEIs are not related to changes in microvascular perfusion, which suggests mainly that the expression of adhesion receptors is necessary to induce LEIs rather than rheologic factors. It seems unlikely that this short-lasting activation of leukocytes can play a role in the development of secondary brain damage.

Alzheimer's disease due to an intronic presenilin-1 (PSEN1 intron 4) mutation: A clinicopathological study

We describe 21 affected individuals from a kindred with early-onset autosomal dominant familial Alzheimer's disease caused by an intronic presenilin-1 mutation (in intron 4). Mean age at onset of symptoms was 37.4 years [95% confidence interval (CI): 36.6-38.2 years], mean age at death was 44.7 years (95% CI: 43.1-46.3 years) and mean duration of illness was 7.3 years (95% CI: 5.9-8.7 years). Myoclonus and seizures were prominent features of this pedigree. In the four cases for whom neuropsychometric data were available, verbal memory impairment preceded visual memory deficits; naming was relatively preserved until late in the disease. One of these four cases underwent serial volumetric MRI scans demonstrating in vivo brain tissue loss of 3.9% (38.9 ml, annualized rate of atrophy: 1. 7%) over 22 months of follow-up. The four individuals who had necropsies demonstrated the neuropathological hallmarks of Alzheimer's disease. Apolipoprotein E (APOE) status was assessed in five individuals: the case with the youngest age at onset at 33 years of age was found to be homozygous epsilon4/epsilon4, > 1 SD below the mean age of onset for those of known APOE genotype (36.4 +/- 2.3 years, mean +/- SD), and > 2 SDs below the mean age of onset for the pedigree as a whole (37.4 +/- 1.7 years, mean +/- SD). APOE genotype may therefore modulate age at onset in this pedigree.

Influence of IGF-I and cell density on MDR1 expression in the T-lymphoblastoid cell line CCRF-CEM

The debate about a direct or indirect effect of GH and IGF-I on the recurrence of malignancy, especially in the case of rhGH therapy in patients with leukemia, is still going on. Recent studies suggested that IGF-I plays a role in drug resistance during anticancer therapy. This resistance to diverse cytotoxic drugs, named multidrug-resistance (MDR), is mainly due to high levels of P-glycoprotein (P-gp). The gene encoding this membrane-associated transporter protein was named MDR1, and increased levels of P-gp are linked to enhanced MDR1 mRNA expression. Our aim was to investigate a possible effect of rhIGF-I on MDR1 gene expression in vitro. We cultured the T-lymphoblastoid cell line CCRF-CEM with different rhIGF-I concentrations (0, 5, 20 and 50 ng/ml) in serum-free medium for 3 days. CCRF-CEM cells are drug-sensitive and express MDR1 at low levels. MDR1 mRNA expression was measured by semiquantitative RT-PCR using a competitive assay with a heterologous DNA construct. In addition, GAPDH mRNA was amplified as an internal control for RNA integrity. P-gp activity was determined by a flow cytometric assay measuring rhodamine 123 accumulation. Furthermore, cell proliferation was monitored in all experiments. Our data do not support an effect of rhIGF-I on MDR1 mRNA expression, P-gp activity or cell proliferation in the CCRF-CEM cell line. MDR1 mRNA levels were inversely correlated to cell density with high significance (p < 0.0001). In conclusion, multidrug resistance linked to P-gp is not induced by IGF-I in CCRF-CEM cells. At high density, CCRF-CEM cells downregulate MDR1 gene expression. Our experimental model provides a very useful tool for monitoring the influence of growth factors on multidrug resistance in vitro.

Vaccination against hepatitis B: current challenges for Asian countries and future directions

AIMS

To review the current status of hepatitis B immunization programmes as well as future issues concerning hepatitis B immunization in Asian countries.

METHODS

Pertinent literature was identified via in-house and MEDLINE (1980-99) searches and references cited in published articles. Articles within the Proceedings of the IX Triennial International Symposium on Viral Hepatitis and Liver Disease provided valuable state-of-the-art resource data.

RESULTS

Chronic hepatitis B infection is responsible for 75-90% of primary hepatocellular carcinoma, one of the 10 most common cancers worldwide. Hepatitis B and its chronic sequelae can potentially be eradicated through vaccines that have been shown to be 95-99% efficacious in preventing development of the disease or the carrier state in immunized infants. Approximately 75% of the world's hepatitis B carriers live in Asian countries wherein wide variations in immunization strategies exist. Vaccination programmes in hyperendemic Asian countries have elicited decreases in the incidence of acute and chronic infections as well as a decrease in chronic carriers in the unvaccinated population. Decreases in the incidence of hepatocellular carcinoma have been recorded in Taiwan and Singapore after at least 10 years of universal hepatitis B immunization programmes.

CONCLUSIONS

In Asian countries currently without nationwide hepatitis B programmes, utilization of the existing vaccination infrastructure for administration of other World Health Organization Expanded Programme on Immunization vaccines will provide the most economical and efficient means of administration of the hepatitis B vaccine.

Characterization of lineage-specific chimaerism in patients with acute leukaemia and myelodysplastic syndrome after allogeneic stem cell transplantation before and after relapse

Recently, we have shown that patients with acute leukaemias and myelodysplastic syndromes (MDS), who showed increasing mixed chimaerism (MC) upon serial PCR analysis after transplant, have a significantly increased risk of relapse. To determine whether the increasing MC in these patients is caused by the reappearance of normal recipient haematopoiesis or by the reoccurrence of malignant cells, we purified different leucocyte subpopulations and analysed these subfractions with regard to their donor-recipient ratio by a PCR-based method for the analysis of minisatellite DNA regions. In 14 patients [eight acute lymphoblastic leukaemia (ALL), three acute myelogenous leukaemia (AML) and three MDS] subfractions were analysed when increasing MC was first noted upon serial analysis of the peripheral blood. In seven of these 14 patients (four ALL, two AML and one MDS), subfractions were characterized at the time of frank haematological relapse. In all 14 patients investigated with increasing MC, recipient cells were detected in different mononuclear cell subpopulations. In patients characterized during frank relapse, two distinct distribution patterns were found. Patients who relapsed before day +300 (one ALL, two AML and one MDS) showed recipient-derived (normal) cells in addition to blast populations in different mononuclear subsets as well as granulocytes. In patients with acute leukaemias who relapsed after day +300 (two ALL and one AML), only leukaemic cells were found that were of recipient origin, whereas all other haematopoietic cell lines were donor derived. These data show that persistent MC in the early post-transplant period is caused predominantly by normal recipient haematopoietic cells. This finding further supports the hypothesis that a state of mixed haematopoietic chimaerism may reduce the clinical graft-versus-leukaemia (GVL) effect of alloreactive donor-derived effector cells in patients with acute leukaemias and MDS, and thus facilitate the proliferation of residual malignant cells that may have survived the preparative regimen.

The role of mounts and intromissions in triggering ejaculation in rats

Eight male rats copulated with an estrus female with an open vagina (NF) and an estrus female with the vagina covered by adhesive tape (CF). Experimental sessions were composed of two phases. During Phase 1 the males copulated with NF or with CF females until 4 intromissions or 4 mount bouts were displayed respectively. In Phase 2 the males copulated alternately with NF or CF according to three schedules: (1) a sequence two mount bouts with a CF female followed by one intromission, (2) a sequence one intromission followed by two mount bouts with a CF female, and (3) a sequence one intromission followed by four mount bouts with a CF female. All of these sequences were repeated until ejaculation. Ejaculation occurred in 95.8% of cases within one minute after the last intromission during copulation with the CF female. The results of this study indicate that: (1) the number of intromissions displayed during Phase 2 does not depend on the character of the copulatory behaviour displayed during Phase 1, (2) at least two intromissions are displayed before ejaculation, and (3) the tactile stimulation of the glans of penis plays a crucial role in the ejaculatory seminal reflex.

A small 2'-OH- and base-dependent recognition element downstream of the initiation site in the RNA encapsidation signal is essential for hepatitis B virus replication initiation

Hepatitis B viruses replicate through reverse transcription of an RNA intermediate. In contrast to retroviral reverse transcriptases, their replication enzyme, P protein, does not use a nucleic acid primer but initiates DNA synthesis de novo from within an RNA stem-loop structure called epsilon. A short DNA oligonucleotide is copied from epsilon and covalently attached to P protein, and then synthesis is arrested. The information for initiation site selection and synthesis arrest must be contained in the structure of the P protein/epsilon complex. Because P protein activity depends on cellular chaperones this complex can as yet only be generated by in vitro translation of duck hepatitis B virus P protein in rabbit reticulocyte lysate; functional interaction with its cognate RNA element Depsilon can be monitored by the covalent labeling of P protein during primer synthesis. Combining this in vitro priming reaction and a set of chimeric RNA-DNA Depsilon analogues, we found that only five ribose residues in the 57-nucleotide stem-loop were sufficient to provide a functional template; these are a single residue in the template region and the two base pairs at the tip of the lower stem. The base identities in the very same region are essential as well. The presence of this 2'-OH- and base-dependent determinant shortly downstream of the initiation site suggests a mechanism that can account for both initiation site selection and programmed primer synthesis arrest.

Phase I study of subcutaneously administered recombinant human interleukin 12 in patients with advanced renal cell cancer

A phase I study was conducted to characterize the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacokinetics of a single dose followed by three times weekly s.c. injections of recombinant human interleukin 12 (rHuIL-12). The study encompassed 28 patients with advanced renal cell carcinoma. rHuIL-12 was administered on day 1, followed by an observation period of 7 days. Starting on day 8, repeated s.c. injections were administered 3 times a week for 2 weeks. The MTD of the initial injection was evaluated at dose levels of 0.1, 0.5, and 1.0 microg/kg. DLT was observed at 1.0 microg/kg and consisted of fever, perivasculitis of the skin, and leukopenia. The MTD of the subsequent repeated injections after 1 week of rest was studied at dose levels 0.5, 1.0, and 1.25 microg/kg. DLT at 1.25 microg/kg comprised deterioration of performance status, fever, vomiting, mental depression, and leukopenia. Other notable toxicities were oral mucositis and elevation of hepatic enzymes. Fever, leukopenia, and elevation of hepatic enzymes were more severe after the initial injection than after repeated injections at the same dose level. At dose level 0.5 microg/kg, the mean area under the plasma concentration-time curve decreased from 7.4 ng/h/ml after the first injection to 3.3 ng x h/ml (P = 0.034) after repeated administrations, and at dose level 1.0 microg/kg, it ranged from 31.8 ng/h/ml to 6.0 ng x h/ml (P = 0.041). One patient had a partial response and seven had stable disease. The MTD of a single s.c. injection of rHuIL-12 was 0.5 microg/kg, and the MTD of three subsequent administrations per week was 1.0 microg/kg. In comparison with a single administration, the three times weekly administrations at the same dose level was accompanied with a milder pattern of side effects and a reduction of the area under the plasma concentration-time curve.

Surfactant lipid uptake and metabolism by neonatal and adult type II pneumocytes

Animal experiments suggest developmental changes in surfactant homeostasis. The uptake and metabolism of [(3)H]dipalmitoylphosphatidylcholine-labeled liposomes with a surfactant-like composition were evaluated in type II cells isolated from rats of different postnatal ages. The early part of the uptake process (0-60 min) was more rapid and reached higher levels in cells from 2-day-old rats than in those from 7-day-old, 14-day-old, or adult rats. Temperature independence of this initial phase, differences in response to trypsin-EDTA or neuraminidase treatment, and the dependency of increased neonatal uptake on the presence of phosphatidylglycerol in liposomes suggested binding as a major mechanism of cell-lipid interaction. Although a two to three times larger amount of lipid was associated with neonatal cells, the metabolism of phosphatidylcholine, indicated by a decrease in label in phosphatidylcholine and an accompanying increase in sphingomyelin, was significantly smaller in 2-day-old than in adult cells. These studies support the hypothesis that neonatal and adult cells may have differences in the interaction with alveolar phospholipids and in the metabolism of phosphatidylcholine.

The interaction of phosphatidylcholine with alveolar type II pneumocytes is dependent on its physical state

Dipalmitoylphosphatidylcholine, the principal phospholipid component of surfactant, inhibits agonist stimulated surfactant secretion whereas dioleoylphosphatidylcholine does not. As knowledge of the type of interaction of phosphatidylcholines is important for the detailed analysis of surfactant homeostasis, this was examined in isolated rat type II pneumocytes in primary culture. Solid state [3H]-dipalmitoylphosphatidylcholine liposomes associated with the cells rapidly. No effect of blockade of endocytosis on the cellular association was observed, whereas that of the fluid phase marker [14C]-sucrose was reduced. No evidence for the fusion of the dipalmitoylphosphatidylcholine liposomes or for phospholipid exchange with the cells was detected, suggesting that the cells primarily bound the dipalmitoylphosphatidylcholine liposomes. Although a "specific" site with a saturable binding capacity (20 nmol dipalmitoylphosphatidylcholine/mg protein, KD 25 microM) was demonstrated, the interaction did not exhibit all the characteristics of a typical pharmacological receptor. The preincubation with nonlabeled dipalmitoylphosphatidylcholine almost completely inhibited binding to the cells. In accordance with their effects on stimulated surfactant secretion, various other phosphatidylcholine liposomes inhibited binding that was very much dependent on their physical state, as only those in a solid state were inhibitory by more than 50%. These results support the view that the binding of dipalmitoylphosphatidylcholine may be involved in the feedback regulation of surfactant secretion in type II pneumocytes and that these processes are dependent on the physical state of the interacting liposomes.

Nursing assessment of patient readiness for ambulation after cardiac catheterization

Although nurses routinely perform activities that prevent or detect vascular complications following a cardiac catheterization, determining patient readiness for ambulation has received minimal research attention. Educating nurses to determine patient readiness for ambulation is a safe and effective way to promote patient comfort.