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Biomedical subjects

T Wang

Publications and source records attributed to T Wang.

At least 307 records · Page 17Linked to original sources
PubMed1999

L-arginine, prostaglandin, and white cell filtration equally improve myocardial protection in stressed neonatal hearts.

OBJECTIVES: L-Arginine may improve cardioplegic protection by increasing nitric oxide production. However, L-arginine may also be detrimental because it generates the free radical peroxynitrite. It would, therefore, be advantageous if the benefits of L-arginine could be achieved by another means. METHODS: Twenty neonatal piglets underwent 60 minutes of ventilator hypoxia (inspired oxygen fraction 8%-10%) followed by 20 minutes of ischemia on cardiopulmonary bypass (stress) and were then protected for 70 minutes with multiple doses of blood cardioplegic solution. In 5 piglets (group 1), the cardioplegic solution was not modified; in 5 (group 2), low-dose L-arginine (4 mmol/L) was added; in 5 (group 3), prostaglandin E(1) (alprostadil, 4 microgram/L) was added; and in 5 (group 4), the cardioplegic solution was passed through a leukodepleting filter. Myocardial function was assessed by pressure volume loops and expressed as percentage of control, and coronary vascular resistance was measured with each cardioplegic infusion. RESULTS: Unmodified blood cardioplegic solution (group 1) was unable to protect the severely stressed myocardium, resulting in depressed systolic function (39% +/- 1%) and preload recruitable stroke work (40% +/- 1%), increased diastolic stiffness (239% +/- 3%), and high conjugated diene production, myeloperoxidase activity, and coronary vascular resistance. In contrast, cardioplegic solutions modified with L-arginine, prostaglandin E(1), or leukodepletion, resuscitated the stressed myocardium, resulting in complete return of systolic function (100% vs 101% vs 101%; P <.001 vs group 1) and preload recruitable stroke work (100% vs 101% vs 101%; P <.001 vs group 1), minimal increase in diastolic stiffness (160% vs 162% vs 160%; P <. 001 vs group 1), and lowered conjugated diene production, myeloperoxidase activity, and coronary vascular resistance (P <.001 vs group 1 for each). CONCLUSIONS: (1) Unmodified blood cardioplegic solution is unable to protect the severely stressed myocardium. (2) L-Arginine, prostaglandin E(1), and leukocyte filtration all improve myocardial protection equally and appear to work by limiting a white blood cell-mediated injury. This reduces oxygen-derived free radical formation, maintains vascular function, and restores functional recovery. Since L-arginine may be detrimental, surgeons should consider using prostaglandin E(1) and/or a leukocyte filter instead.

Alprostadil↗
PubMed1999

Effects of intracerebroventricularly administered leptin on protein selection in the rat.

The effect of centrally administered rat leptin on selection of 5 and 30% protein diets was investigated in male Sprague-Dawley rats with indwelling i.c.v. cannulas. Leptin (0 vs 2.5 microg/day) was administered for 4 consecutive days, followed by an 8-day withdrawal period. Total intake was reduced to approximately 50% of that in the vehicle injected group during each day following leptin administration. Intake of both the 5 and 30% diets was reduced. Vehicle-treated rats selected a 13-15% CP diet. Diet selection in leptin-treated rats was not different during the first day, but on Days 2-4, leptin-treated rats selected a 10% CP diet. Intake began to normalize within 24-48 h after the last treatment, and was not different by Day 3 of the withdrawal period. Body weight was reduced by leptin treatment, and despite the normalization of food intake, did not recover during the withdrawal period. Rats were sacrificed at the end of the 8-day withdrawal period. Despite the reduction in body and carcass weights, liver, kidney, heart, and soleus muscle weights were not different between control and leptin-treated groups when expressed on an absolute or relative basis. However, epididymal and retroperitoneal fat pad weights were still reduced 56 and 78%, respectively, in rats that had been previously treated with leptin for 4 days and then not treated for 8 days. In addition, circulating T3 levels remained elevated in rats that had been treated with leptin. Centrally administered leptin has little effect on muscle mass, but had potent effects on intake of nonobese rats and a sustained effect on adipose tissue mass, thyroid hormone status, and body weight after withdrawal. Results from rats selecting between diets varying in protein content suggest that leptin may cause avoidance of protein.

Animals↗
PubMed1999

High serum hyaluronan indicates poor survival in renal replacement therapy.

Atherosclerotic cardiovascular disease (CVD), malnutrition, and inflammation are common clinical features of chronic renal failure and are associated with increased mortality. Elevated levels of C-reactive protein (CRP) and cytokines are commonly observed in dialysis patients and have been shown to predict mortality. Serum hyaluronan previously has been used as a marker of an inflammatory reaction, irrespective of its cause. We have determined serum levels of albumin and hyaluronan, as well as the prevalence of malnutrition (subjective global assessment, 2 to 4), inflammation (CRP >/= 10 mg/L), and overt CVD in a cohort of 97 predialysis patients (52 +/- 13 years). Moreover, we determined the outcome of these patients 29 +/- 11 months after the basal measurement of hyaluronan. Serum levels of hyaluronan (median) were markedly elevated in predialysis patients with signs of malnutrition (127.1 v 50.5 ng/mL; P < 0.0001), inflammation (130.1 v 55.0 ng/mL; P < 0.0001) and CVD (118.8 v 56.0 ng/mL; P < 0.001). The levels of log hyaluronan correlated significantly to log CRP (R = 0.35; P < 0.001), serum albumin (R = -0.40; P < 0.0001), CVD (R = 0.36; P < 0.001), and age (R = 0.40; P < 0.0001), respectively. Survival analysis by the Cox regression model showed that elevated hyaluronan levels were, independent of CVD, CRP, and age, significantly related to an increased mortality rate. The current study showed that markedly elevated serum hyaluronan levels are found in predialysis patients with malnutrition, inflammation, and CVD and that serum hyaluronan is a risk predictor of poor survival in dialysis.

Biomarkers↗
PubMed1999

Determination of tungsten in bulk drug substance and intermediates by ICP-AES and ICP-MS.

A quick and sensitive method has been developed and validated for the determination of tungsten in bulk drug substance and intermediates using either Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) or Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Sample preparation is by direct dissolution with a 80:20 (v/v) concentrated nitric acid:deionized water mixture and avoids labor intensive and potentially hazardous digestion techniques. Excellent agreement was found between ICP-AES and ICP-MS results and between Merck results and Microwave Induced Plasma Mass Spectrometry (MIP-MS) results provided by an independent raw material vendor.

Mass Spectrometry↗
PubMed1999

One-stage pedicled omentum majus transplantation into thoracic cavity for treatment of chronic persistent empyema with or without bronchopleural fistula.

OBJECTIVE: Assessment of the present results of surgical treatment for chronic persistent empyema with or without bronchopleural fistula (BPF) using one-stage pedicled omentum majus transplantation into the thoracic cavity. METHODS: From November 1979 to December 1996, 50 patients with chronic persistent empyema were treated by pedicled omentum majus transplanted into the thoracic cavity. There were 35 men and 15 women, and the age range was 15-58 years. Empyema had been present for 0.5-18 years. Twenty-six of 35 cases with chronic tuberculous empyema and six of 15 cases with chronic bacterial empyema suffered from concomitant BPF (n = 32). In the latter, the most common organisms were Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. RESULTS: There were no perioperative deaths. Two cases had a significant air leak on the first postoperative day. One of them underwent rethoractomy 30 h after the initial operation to stop the fistula using intrathoracic omentum. Thoracic dead space disappeared in most of the operated cases and a sterilized dry cavity remained in some cases. CONCLUSIONS: One-stage pedicled omentum majus transposition is a safe and easy procedure for chronic persistent empyema and BPF, it breaks down residual or recurrent inflammatory foci mechanically and closes the BPF effectively with minimal deformity of the chest wall.

Adolescent↗
PubMed1999

The effect of isovolemic anaemia on blood O2 affinity and red cell triphosphate concentrations in the painted turtle (Chrysemys picta).

The blood oxygen affinity of vertebrates is regulated, in part, through changes in red cell phosphate levels and increased oxygen affinity during reductions in inspired oxygen and is a well-described and common feature. However, during anaemia, when oxygen delivery is compromised by a reduction in blood oxygen carrying capacity, a lowering of blood oxygen affinity will facilitate oxygen unloading in the tissues, while oxygen loading at the gas exchange organ is not impaired. The present study investigated the effects of artificially induced anaemia in vivo on the blood oxygen affinity and red cell nucleoside triphosphate (NTP) concentrations in the turtle, Chrysemys picta. Blood was obtained from conscious animals through an arterial catheter and oxygen equilibrium curves were determined using the Tucker method while NTP concentrations were analyzed spectrophotometrically. Before induction of anaemia haematocrit averaged 23% and P50 was 18.5 +/- 0.7 with a NTP/Hb of 0.20 +/- 0.01 (mmol/mmol). After the haematocrit had been reduced to approximately 10% by bleeding (48-96 h) (blood volume was maintained by re-infusion of plasma and Ringer) there were no effects on P50 or red cell NTP concentrations. Thus, in contrast to fish and mammals, turtles do not exhibit a change in blood oxygen affinity during anaemia.

Anemia↗
PubMed1999

Respiratory consequences of feeding in the snake Python molorus.

Snakes can ingest large meals and exhibit marked increases in metabolic rate during digestion. Because postprandial oxygen consumption in some snakes may surpass that attained during exercise, studies of digestion offers an alternative avenue to understand the cardio-respiratory responses to elevated metabolic rate in reptiles. The effects of feeding on metabolic rate, arterial oxygen levels, and arterial acid-base status in the snake Python molorus are described. Four snakes (180-250 g) were cannulated in the dorsal aorta and blood samples were obtained during 72 h following ingestion of a meal (rat pups) exceeding 20% of body weight. Oxygen consumption increased from a fasting value of 1.71 +/- 0.08 to 5.54 +/- 0.42 ml kg-1 min-1 at 48 h following feeding, and the respiratory gas exchange ratio increased from 0.67 +/- 0.02 to a maximum of 0.92 +/- 0.03 at 32 h. Plasma lactate was always less than 0.5 mM, so the postprandial increase in metabolic rate was met by aerobic respiration. In fasting animals, arterial PO2 was 66 +/- 4 mmHg and haemoglobin-O2 saturation was 92 +/- 3%; similar values were recorded during digestion, but haematocrit decreased from 15.8 +/- 1.0 to 9.8 +/- 0.8 due to repeated blood sampling. Plasma [HCO3-] increased from a fasting level of 19.3 +/- 0.8 to 25.8 +/- 1.0 mmol l-1 at 24 h after feeding. However, because arterial PCO2 increased from 21.1 +/- 0.5 to 27.9 +/- 1.4 mmHg, there was no significant change in arterial pH from the fasting value of 7.52 +/- 0.01. Acid-base status returned to pre-feeding levels at 72 h following feeding. The increased arterial PCO2 is most likely explained by a reduction in ventilation relative to metabolism, but we predict that lung PO2 does not decrease below 115 mmHg. Although ingestion of large meals is associated with large metabolic changes in pythons, the attendant changes in blood gases are relatively small. In particular, the small changes in plasma [HCO3-] and stable pH show that pythons respond very differently to digestion than alligators where very large alkaline tides have been observed. It is unclear why pythons and alligators differ in the magnitude of their responses, but given these interspecific differences it seems worthwhile to describe arterial blood gases during digestion in other species of ectothermic vertebrates.

Acid-Base Imbalance↗
PubMed1999

Control and interaction of the cardiovascular and respiratory systems in anuran amphibians.

In anuran amphibians, respiratory rhythm is generated within the central nervous system (CNS) and is modulated by chemo- and mechanoreceptors located in the vascular system and within the CNS. The site for central respiratory rhythmogenesis and the role of various neurotransmitters and neuromodulators is described. Ventilatory air flow is generated by a positive pressure, buccal force pump driven by efferent motor output from cranial nerves. The vagus (cranial nerve X) also controls heart rate and pulmocutaneous arterial resistance that, in turn, affect cardiac shunts within the undivided anuran ventricle; however, little is known about the control of central vagal motor outflow to the heart and pulmocutaneous artery. Anatomical evidence indicates a close proximity of the centers responsible for respiratory rhythmogenesis and the vagal motoneurons involved in cardiovascular regulation. Furthermore, anurans in which phasic feedback from chemo- and mechanoreceptors is prevented by artificial ventilation exhibit cardiorespiratory interactions that appear similar to those of conscious animals. These observations indicate interactions between respiratory and cardiovascular centers within the CNS. Thus, like mammals and other air-breathing vertebrates, the cardio-respiratory interactions in anurans result from both feedback and feed-forward mechanisms.

Animals↗
PubMed1999

Viscoelastic response of the rat loading model: implications for studies of strain-adaptive bone formation.

Studies of the adaptive skeletal response to mechanical loading require appropriate animal models. Two new approaches involve the nonsurgical application of loads to either the ulna or tibia of rats. Both of these approaches require the loading of bone through adjacent soft tissues, and thus the tissue viscoelasticity might affect the way load is transferred to the bone. The objective of this study was to characterize the mechanical strain in the rat tibia or ulna during applied loading at different frequencies. For the rat ulna model, loading was applied to the ulnae of four adult, female rats as a haversine waveform at frequencies of 1, 2, 5, 10, and 20 Hz and peak loads of 5, 10, 15, and 20 N. Mechanical strain was measured on the medial and lateral ulnar surfaces using single element strain gauges. For the rat tibia model, four-point bending loads were applied to the right tibiae of seven rats at frequencies of 0.5, 1, 2, 5, 10, and 20 Hz and peak loads of 30, 40, 50, and 60 N. Mechanical strain was measured on the lateral tibial surface at 5 mm proximal to the tibiofibular junction. We found that peak strains were linearly proportional to applied load, but decreased logarithmically as loading frequency was increased, indicating a significant viscoelastic effect in the soft tissues surrounding the ulnocarpal joint and in the soft tissues surrounding the tibia shaft. The viscoelastic response of the ulna and tibia tends to "filter out" high-frequency loading components and, as a result, the rat loading systems act as a low-pass filter. Consequently, any experiment designed to test the effect of loading frequency on bone formation in the rat ulna and tibia should employ progressively larger loads at higher loading frequencies to guarantee a consistent peak strain magnitude in the bone. The filtering effect of the ulna loading system is illustrated by an analysis of the strain waveforms from the recent study by Mosley and Lanyon (Bone 23:313-318; 1998) that was designed to evaluate the effect of strain rate on bone formation.

Adaptation, Physiological↗
PubMed1999

Selective beta1-adrenoceptor blockade enhances the activity of the stimulatory G-protein in human atrial myocardium.

1. Chronic selective beta1-adrenoceptor (beta1AR) blocker treatment enhances the sensitivity of beta2-adrenoceptor (beta2AR) in human heart (Hall et al., 1990; 1991). To clarify the mechanism of the cross-sensitization between beta1AR and beta2AR, we determined whether the stimulatory G-protein (G(s)alpha) function is increased in atria from beta1AR-blocker treated patients compared with non-beta-blocked patients, and investigated whether this change is caused by an alteration of post-translational modification of Gsalpha protein. 2. G(s)alpha function was determined by reconstitution of human atrial G(s)alpha into S49 cyc- cell membranes. In the reconstitution system, GTPgammaS stimulated cyclic AMP generation in a dose-dependent manner. Upon 10(-4) M GTPgammaS stimulation, G(s)alpha activity in the beta1AR-blocker, atenolol, treated group (78.2+/-10. 3 pmol cyclic AMP mg(-1) min(-1) 10(-3)) was 65% higher than that in non-beta-blocked patients (47.3+/-6.3 pmol cyclic AMP mg(-1) min(-1) 10(-3), n=15, P=0.02). 3. Isoelectric point (pI) valu G(s)alpha were measured by two dimensional gel electrophoresis (2D-E) and the amount of each isoform quantified by image analysis of a Western blot of the gel using specific antibody. Multiple isoforms of G(s)alpha were detected by 2D-E with different pI values. There were no significant differences between the groups of patients in either pI values or the proportions of the acidic isoforms of G(s)alpha to the main basic form (n=12, P>0.05). 4. The results suggest that chronic beta1AR-blockade enhances Gsalpha function in human atrium, and this may account in part for the hypersensitivity of beta2AR and other Gs-coupled receptors during beta1AR-blockade. The increased G(s)alpha function is unlikely to be caused directly by blockade of protein kinase A phosphorylation of G(s)alpha protein.

Adenylyl Cyclases↗
PubMed1999

Do ACE-inhibitors suppress tumour necrosis factor-alpha production in advanced chronic renal failure?

OBJECTIVES: The serum levels of the catabolic cytokine TNF-alpha are often raised in malnourished chronic heart failure patients as well as in chronic renal failure (CRF) patients. Angiotensin-converting enzyme (ACE) inhibitors are often used in these patients and may decrease TNF-alpha and IL-1beta levels in vitro and in vivo. The aim of this study was to find out whether CRF patients with ongoing ACE-inhibitor treatment have lower TNF-alpha levels. DESIGN: Cross-sectional study. SETTING: Tertiary Referral Center and University Hospital. SUBJECTS: Ninety-six predialysis patients (mean age 52 +/- 1 years) with advanced CRF (glomerular filtration rate 7 +/- 1 mL min-1). MAIN OUTCOME MEASURES: Plasma levels of TNF-alpha, subjective global assessment of nutritional status and data on ongoing antihypertensive treatment (ACE-inhibitors, beta blockers, calcium channel blockers and angiotensin II (AII) receptor blockers). RESULTS: Patients treated with ACE-inhibitors (n = 44) had significantly lower plasma TNF-alpha levels (18.5 +/- 1.2 vs. 26.6 +/- 2.2 pg mL-1; P < 0.01) and were less frequently malnourished, relative to 52 patients not treated with ACE-inhibitors. No significant difference in TNF-alpha levels were observed when comparing patients with or without treatment with beta, calcium channel, or AII receptor blockers, respectively. CONCLUSIONS: The present data suggest that the use of ACE-inhibitors is associated with lower plasma TNF-alpha and CRP levels as well as a lower prevalence of malnutrition in patients with advanced CRF. Further studies are needed to establish if there is a casual relationship between these findings and, if so, the molecular mechanism(s).

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1999

Hyaluronan decreases peritoneal fluid absorption: effect of molecular weight and concentration of hyaluronan.

BACKGROUND: We have recently shown that the addition of hyaluronan to peritoneal dialysis solution could decrease the peritoneal fluid absorption rate, possibly through decreasing peritoneal tissue hydraulic conductivity. The physical-chemical properties of hyaluronan were found to be both molecular weight and concentration dependent. In this study, we investigated the effects of different molecular weight as well as different concentrations of hyaluronan on the peritoneal fluid kinetics. METHODS: A four-hour dwell study was performed in 48 male Sprague-Dawley rats (6 rats in each group) with 131I albumin (RISA) as an intraperitoneal volume marker. Each rat was intraperitoneally injected with 25 ml of 1.36% glucose dialysate alone (control) or with 0.01% hyaluronan (HA) with different molecular weights [85,000 (HA85K group), 280,000 (HA280K group), 500,000 (HA500K group), and 4,000,000 (HA4M group) molecular wt] or with a different concentrations of hyaluronan [(molecular wt 500,000); 0.01% (0.01% HA group), 0.05% (0.05% HA group), 0.1% (0.1% HA group), and 0.5% (0.5% HA group) hyaluronan]. RESULTS: The peritoneal fluid absorption rate (as assessed by the RISA elimination rate, KE) was significantly decreased in the HA500K and H4M groups as well as in all the different concentration groups (with molecular wt 500,000) as compared with the control group, resulting in significantly higher net fluid removal in these groups (except for the H4M group) as compared with the control group. In the 0.5% HA group (but not in the other hyaluronan groups), the direct lymphatic absorption (KEB) was also significantly decreased. The transcapillary ultrafiltration rate (Qu) was significantly lower in the HA4M group as compared with the control group but significantly higher in the 0.05% HA (and tended to be higher in the 0.1% HA group) as compared with the other groups. No difference in Qu was found between the 0.5% HA group as compared with the control group, despite a more marked decrease in KE in this group as compared with the H4M group. There were no significant differences in KE, Qu, and net fluid removal between the HA85K and HA280K groups and the control group. CONCLUSIONS: Our results suggest that (a) the addition of hyaluronan to dialysate could decrease peritoneal fluid absorption and thus increase the net ultrafiltration; this effect appears to be both size dependent and concentration dependent. (b) High molecular weight fraction of hyaluronan may also decrease the transcapillary Qu by decreasing tissue hydraulic conductivity. (c) A higher concentration of hyaluronan in dialysate resulted in a more marked decrease in peritoneal fluid absorption (absorption to peritoneal tissues as well as direct lymphatic absorption), possibly through both decreasing tissue hydraulic conductivity and increasing fluid viscosity. (d) Decreasing tissue hydraulic conductivity by adding a high concentration of hyaluronan to dialysate does not decrease the transcapillary ultrafiltration, possibly because the osmotic effect of hyaluronan may counterbalance the decrease in transcapillary ultrafiltration because of the decrease in tissue hydraulic conductivity.

Absorption↗
PubMed1999

Strong association between malnutrition, inflammation, and atherosclerosis in chronic renal failure.

BACKGROUND: Atherosclerotic cardiovascular disease and malnutrition are widely recognized as leading causes of the increased morbidity and mortality observed in uremic patients. C-reactive protein (CRP), an acute-phase protein, is a predictor of cardiovascular mortality in nonrenal patient populations. In chronic renal failure (CRF), the prevalence of an acute-phase response has been associated with an increased mortality. METHODS: One hundred and nine predialysis patients (age 52 +/- 1 years) with terminal CRF (glomerular filtration rate 7 +/- 1 ml/min) were studied. By using noninvasive B-mode ultrasonography, the cross-sectional carotid intima-media area was calculated, and the presence or absence of carotid plaques was determined. Nutritional status was assessed by subjective global assessment (SGA), dual-energy x-ray absorptiometry (DXA), serum albumin, serum creatinine, serum urea, and 24-hour urine urea excretion. The presence of an inflammatory reaction was assessed by CRP, fibrinogen (N = 46), and tumor necrosis factor-alpha (TNF-alpha; N = 87). Lipid parameters, including Lp(a) and apo(a)-isoforms, as well as markers of oxidative stress (autoantibodies against oxidized low-density lipoprotein and vitamin E), were also determined. RESULTS: Compared with healthy controls, CRF patients had an increased mean carotid intima-media area (18.3 +/- 0.6 vs. 13.2 +/- 0.7 mm2, P < 0.0001) and a higher prevalence of carotid plaques (72 vs. 32%, P = 0.001). The prevalence of malnutrition (SGA 2 to 4) was 44%, and 32% of all patients had an acute-phase response (CRP > or = 10 mg/liter). Malnourished patients had higher CRP levels (23 +/- 3 vs. 13 +/- 2 mg/liter, P < 0.01), elevated calculated intima-media area (20.2 +/- 0.8 vs. 16.9 +/- 0.7 mm2, P < 0.01) and a higher prevalence of carotid plaques (90 vs. 60%, P < 0.0001) compared with well-nourished patients. During stepwise multivariate analysis adjusting for age and gender, vitamin E (P < 0.05) and CRP (P < 0.05) remained associated with an increased intima-media area. The presence of carotid plaques was significantly associated with age (P < 0.001), log oxidized low-density lipoprotein (oxLDL; P < 0.01), and small apo(a) isoform size (P < 0.05) in a multivariate logistic regression model. CONCLUSION: These results indicate that the rapidly developing atherosclerosis in advanced CRF appears to be caused by a synergism of different mechanisms, such as malnutrition, inflammation, oxidative stress, and genetic components. Apart from classic risk factors, low vitamin E levels and elevated CRP levels are associated with an increased intima-media area, whereas small molecular weight apo(a) isoforms and increased levels of oxLDL are associated with the presence of carotid plaques.

Absorptiometry, Photon↗
PubMed1999

High peritoneal residual volume decreases the efficiency of peritoneal dialysis.

BACKGROUND: Wide variation in peritoneal residual volume (PRV) is a common clinical observation. High PRV has been used in both continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis to minimize the time of a dry peritoneal cavity and to achieve better dialysis. However, the impact of PRV on peritoneal transport is not well established. In this study, we investigated the effect of PRV on peritoneal transport characteristics. METHODS: Peritoneal effluents were collected in 32 male Sprague-Dawley rats after a five-hour dwell with 1.36% glucose solution. Forty-eight hours later, a four hour dwell using 25 ml of 3.86% glucose solution and frequent dialysate and blood sampling was done in each rat with 125I-albumin as a volume marker. Before the infusion of the 3.86% glucose solution, 0 (control), 3, 6, or 12 ml (8 rats in each group) of autologous effluent (serving as PRV) was infused to the peritoneal cavity. RESULTS: After subtracting the PRV, the net ultrafiltration was significantly lower in the PRV groups as compared with the control group: 13.4 +/- 0.5, 12.0 +/- 1.0, 11.7 +/- 1.7, and 8.9 +/- 0.4 ml for 0, 3, 6, and 12 ml PRV groups, respectively (P < 0.001). The lower net ultrafiltration associated with higher PRV was due to (a) a significantly lower transcapillary ultrafiltration rate (Qu) caused by a lower osmotic gradient, and (b) a significantly higher peritoneal fluid absorption rate (KE) caused by an increased intraperitoneal hydrostatic pressure. No significant differences were found in the diffusive mass transport coefficient for small solutes (glucose, urea, sodium, and potassium) and total protein, although the dialysate over plasma concentration ratios values were higher in the high-PRV groups. The sodium removal was significantly lower in the PRV groups as compared with the control group (P < 0.01). CONCLUSION: Our results suggest that a high PRV may decrease net ultrafiltration through decreasing the Qu, which is caused by a decreased dialysate osmolality, and increasing the KE caused by an increased intraperitoneal hydrostatic pressure. The high volume of PRV also decreased the solute diffusion gradient and decreased peritoneal small solute clearances, particularly for sodium. Therefore, a high PRV may compromise the efficiency of dialysis with a glucose solution.

Animals↗
PubMed1999

Effect of powder substrate on the dissolution properties of methyclothiazide liquisolid compacts.

The effects of powder substrate composition on the in vitro release properties of methyclothiazide liquisolid compacts were evaluated. The dissolution patterns of this water-insoluble drug formulated in liquisolid tablets were also compared to those of commercial products. According to the new liquisolid technique, liquid medications such as solutions or suspensions of water-insoluble drugs in suitable nonvolatile liquid vehicles can be converted into acceptably flowing and readily compressible powders by a simple admixture with certain powder substrates, which are selected powders referred to as the carrier and coating materials. Enhanced release profiles may be exhibited by such systems due to the increased wetting properties and surface of drug available for dissolution. Liquisolid tablets of methyclothiazide containing a 5% w/w drug solution in polyethylene glycol 400 were prepared using powder substrates of different excipient ratios. The release rates of such products were assessed using the USP dissolution test and were compared to those of their commercial counterparts. It was observed that maximum drug dissolution rates can be exhibited by systems that have powder substrates with optimum carrier-to-coating ratios. In addition, liquisolid tablets displayed significantly enhanced dissolution profiles compared to those of marketed products.

Chemistry, Pharmaceutical↗
PubMed1999

Peritoneal clearance of leptin in CAPD patients: impact of local insulin administration.

INTRODUCTION: The ob gene product leptin is secreted by fat cells and the serum leptin levels reflects the body fat content. Markedly elevated serum leptin levels have been reported in patients with chronic renal failure. The aim of the present study was to assess if the dialysate leptin levels in peritoneal dialysate are similar to what can be expected from passive diffusion or if intraperitoneal synthesis of leptin may occur. METHODS: We studied 39 patients (20 males), mean age 54+/-12 years, who had been treated with peritoneal dialysis for 17+/-12 months. Ten of the patients were diabetics of which seven used intraperitoneal insulin. A 24-h collection of dialysate was performed and dialysate and fasting blood samples were analysed for leptin, albumin and beta2-microglobulin, and the peritoneal clearances (PCl) were calculated for these solutes. RESULTS: Serum leptin (mean 47+/-76, range 3-350 ng/ml) was related to body mass index (r=0.35, P<0.05). In multiple regression analysis, serum leptin also correlated to serum TNF-alpha. Although dialysate leptin levels correlated to serum leptin, they were higher than expected from the molecular weight of 16 kD. PCl of leptin was 1.3 ml/min (range 0.2-5.9 ml/min), which was 1.6 times higher than expected from the molecular weight of leptin and PCl for albumin and beta2-microglobulin, not taking the protein binding of leptin into account. A strong correlation was found between PCI for albumin and beta2-microglobulin (r = 0.68, P < 0.0001) but neither PCl albumin, nor PCl beta2-microglobulin correlated to PCI leptin. The PCl of leptin was markedly higher in diabetics using intraperitoneal insulin (n = 7) compared to the other 32 patients (2.6+/-2.0 vs 1.1+/-0.7 ml/min, P<0.05). CONCLUSION: Serum leptin is locally produced in the peritoneal cavity, and intraperitoneal insulin enhances local production of leptin.

Adult↗
PubMed1999

Pixelwise fusion for optimizing SNR in multiple-plate computed radiography imaging.

The computed radiography (CR) technique, also known as the storage phosphor imaging technique, has evolved to be a major candidate for large-scale implementation of digital radiography during the past decade. In order to obtain a reasonable spatial resolution, the storage phosphor plate used is generally limited in thickness. This leads to X rays being only partially absorbed by the detector. Useful information may be contained in the X rays transmitted through the detector. Multiple-plate imaging techniques may be used to capture and utilize the X rays more efficiently. In this paper, an image fusion method, based on the Rayleigh principle and the Karhunen-Loeve (K-L) transform, is presented for optimizing the signal-to-noise ratio (SNR) of the fused image on a pixel-by-pixel basis. Because the multiple-plate images contain the same structural information, the signal components of the images are highly correlated with one another. Thus, the K-L transform is applied to decompose each of the multiple-plate images into an eigen image (the estimated signal) and a residual image (the estimated noise). An average representation entropy measure is maximized for selecting the number of eigen components to be included in the signal estimation. An experimental study, using an anthropomorphic chest phantom, is presented to illustrate pixelwise fusion of multiple-plate images. Experimental results show that the SNR of the fused image was improved by 12-48%, depending upon the anatomical regions of interest in the image.

Computer Simulation↗