Response to hepatitis B virus vaccination in haemodialysis patients with and without hepatitis C infection

The aim of this study was to determine the efficacy of hepatitis B virus (HBV) vaccination and the response to vaccine in individuals on haemodialysis with and without HCV infection. From April 2000 to September 2003 all haemodialysis patients referred to the haemodialysis department in a Babol hospital received 4 microg vaccine intramuscularly at 0, 1, and 6 months. All were negative for HBV infection markers (HBcAb, HBsAg and HBsAb). Of 62 patients, 53 (85.5%) responded to vaccination and 26 (49.1%) were high responders. All individuals with HCV infection responded to vaccination. Duration of haemodialysis had no effect on response to vaccination.

Solid-state (207)Pb NMR studies of lead-group 16 and mixed transition-metal/lead-group 16 element-containing materials

(207)Pb solid-state NMR studies have been conducted on binary lead-group 16 and mixed transition-metal/lead group 16 materials, correlating the NMR chemical shifts of the materials with their structures. The experimental results show that the (207)Pb chemical shifts are strongly influenced by the local electronic structure. Data are reported for lead selenide, lead selenate, calcium plumbate, strontium plumbite, barium plumbite, lead borate, lead zirconate, lead tungstate, lead meta-tantalate, lead niobate, lead molybdate, lead meta-vanadate, lead sulfite, and lead sulfate.

Kinetics of NMR spin-lock polarization transfer in crystalline glycine and spin-lattice relaxation of amino acids

We report data determined from proton-carbon polarization-transfer kinetics at 23 degrees C for six common solid amino acids. Proton spin-lattice relaxation times in the rotating frame, T(1rhoH), for alpha-glycine, alanine, cysteine, leucine, isoleucine, and valine determined from the long-time decay of the carbon magnetization indicate that the presence of a mobile entity such as a methyl group shortens T(1rhoH) to a few milliseconds. Polarization transfer between protons and carbons in polycrystalline alpha-glycine is analyzed and compared to theoretical models, two of which account for the variation of polarization-transfer rate with orientation of the dipole-dipole vector in the magnetic field. A generalization of a model proposed by Mueller et al. (Phys. Rev. Lett. 32 (1974) 1402) reproduces the observed polarization transfer in alpha-glycine with reasonable accuracy, showing that the early time development reflects orientational variation of dipolar oscillations.

Twice-daily pre-mixed insulin rather than basal insulin therapy alone results in better overall glycaemic control in patients with Type 2 diabetes

AIMS

To compare the glycaemic control of an insulin lispro mixture (25% insulin lispro and 75% NPL) twice daily in combination with metformin to that of once-daily insulin glargine plus metformin in patients with Type 2 diabetes inadequately controlled with intermediate insulin, or insulin plus oral agent(s) combination therapy.

RESEARCH DESIGN AND METHODS

Ninety-seven patients were randomized in a multicentre, open-label, 32-week crossover study. Primary variables evaluated: haemoglobin A1c (A1c), 2-h post-prandial blood glucose (BG), hypoglycaemia rate (episodes/patient/30 days), incidence (% patients experiencing > or = 1 episode) of overall and nocturnal hypoglycaemia.

RESULTS

At endpoint, A1c was lower with the insulin lispro mixture plus metformin compared with glargine plus metformin (7.54% +/- 0.87% vs. 8.14% +/- 1.03%, P < 0.001). Change in A1c from baseline to endpoint was greater with the insulin lispro mixture plus metformin (-1.00% vs. -0.42%; P < 0.001). Two-hour post-prandial BG was lower after morning, midday, and evening meals (P < 0.001) during treatment with the insulin lispro mixture plus metformin. The fasting BG values were lower with glargine plus metformin (P = 0.007). Despite lower BG at 03.00 hours (P < 0.01), patients treated with the insulin lispro mixture plus metformin had a lower rate of nocturnal hypoglycaemia (0.14 +/- 0.49 vs. 0.34 +/- 0.85 episodes/patient/30 days; P = 0.002), although the overall hypoglycaemia rate was not different between treatments (0.61 +/- 1.41 vs. 0.44 +/- 1.07 episodes/patient/30 days; P = 0.477).

CONCLUSION

In patients with Type 2 diabetes and inadequate glucose control while on insulin or insulin and oral agent(s) combination therapy, treatment with a twice-daily insulin lispro mixture plus metformin, which targets both post-prandial and pre-meal BG, provided clinically significant improvements in A1c, significantly reduced post-prandial BG after each meal, and reduced nocturnal hypoglycaemia as compared with once-daily glargine plus metformin, a treatment that targets fasting BG.

Needles to promote ventricular blood into the ischemic myocardium applied in a rat heart transplant model: an acute observation [corrected]

Two needles were designed in order to revascularize an ischemic myocardium in the event of left coronary artery occlusion. This study was conducted by performing the Lee modified Fox-Montorsi heart-lung transplant on 25 San Diego Microsurgical Institute-bred Sprague Dawley rats that were subjected to left coronary artery ligation in each case. Of these 25 rats, a straight-porous (SP) needling procedure was applied to 9 heterotopically transplanted rat hearts, and a distinct horseshoe (HS)-shaped needle application was performed on the remaining 16 heterotopically transplanted rat hearts. This report represents an acute study on the efficiency of these two needles to transmit oxygen-rich blood from the left ventricle into the ischemic myocardium. Doppler readings for male vs. female transplants showed that the control peak (PK) and mean (MN) kHz values are on the average of 0.20 kHz higher in males than in females. However, control heart rate values in both sexes are approximately equal. Ligation of the left coronary artery caused a dramatic decrease of PK and MN kHz values in both sexes, while heart rate showed no significant decrease from the original control values in response to ischemia. Application of the SP needle showed only a slight return of PK and MN values in both sexes, but heart rate values increased to levels higher than the original control values. The HS needling procedure was able to recover approximately 80% of the control PK and MN kHz values in both sexes. Thus, these data indicate that the HS needle can successfully transmit left ventricular blood into the myocardium.

Observations of rat ovarian-splenic consecutive transplants

We examined the results after implantation of ovarian follicles by various modes in a total of 82 cases. One or five ovarian follicles were implanted into spleens in castrated female rats. In 20 cases among these, each five follicles were implanted into native and transplanted spleens after spleen transplantation (double implantation of the ovary). Through consecutive spleen transplantation, we observed the results beyond the rat's life span for a limited period. In many cases, we found a more aggressive form of malignant tumor, i.e., dysgerminoma. We present the results and discuss the modes of implantations and possible pathogenetic mechanisms of tumor formation.

Consecutive en-bloc liver (30%)-pancreas-duodenum-spleen-stomach transplant in Lewis rats

It is well-known that 30% of the remaining liver mass, following partial hepatectomy, regenerates to full original mass within 2 weeks in rats. In order to carry the transplanted rat liver to repeated transplantation, a technique of combining 30% of the liver with the pancreaticoduodenum and spleen transplantation is performed in this consecutive organ transplantation study. Our laboratory observed several 37-month-old transplanted rats by carrying through 2-3 generations, and histological disclosure were made. Because the partial liver transplants did not regenerate after the transplantation with other splanchnic organs, this technique is not so difficult though subsequent surgical maneuvers are needed and the liver histology proved entirely normal in every aspect when followed beyond the rat's life span of 24 months.

Metabolic effects of mealtime insulin lispro in comparison to glibenclamide in early type 2 diabetes

The efficacy and safety of the preprandial injection of insulin lispro was compared with the oral administration of glibenclamide in patients with early type 2 diabetes. In this open-label, multicenter study, 143 patients with a glucagon-stimulated increase in C-peptide of at least 0.4 nmol/L were randomized to receive preprandial insulin lispro (LP) or glibenclamide (GB) for 26 weeks. Seventy-five patients received LP (51 male/24 female; age 40 to 70 years, duration of diabetes 4.4 +/- 2.9 years) and 68 patients received GB (39 male/29 female; age 39 to 70 years; duration of diabetes 4.3 +/- 3.4 years). After 12 weeks, mean 90 minute blood glucose excursions were 0.9 +/- 1.0 mmol/L for LP and 1.8 +/- 1.2 mmol/L for GB (p < 0.0001). After 24 weeks, mean blood glucose excursions were 1.0 +/- 1.1 mmol/L for LP and 1.7 +/- 1.2 mmol/L for GB (p = 0.002). Body weight decreased slightly from 87.2 +/- 2.3 to 86.5 +/- 12.2 kg in the LP group and increased from 84.1 +/- 13.7 to 84.4 +/- 13.3 kg in the GB group. LP versus GB induced changes from baseline to endpoint in fasting C-peptide (nmol/L), proinsulin and insulin levels (pmol/L) were - 0.2 +/- 0.4 versus - 0.1 +/- 0.6 (p = 0.04), - 11.2 +/- 26.0 versus - 1.1 +/- 17.3 (p = 0.03), and - 27.8 +/- 147.4 versus + 32.6 +/- 286.2 (not significant), respectively. HbA 1c at baseline was 7.5 +/- 1.0 % for LP and 7.7 +/- 1.2 % for GB and did not change significantly in either group during the investigation. No significant difference was observed between the groups with respect to hypoglycemic episodes. Treatment with LP improved postprandial blood glucose control more than GB without increasing body weight or hypoglycemic episodes. In addition, use of LP was associated with a decrease in fasting C-peptide and proinsulin levels, suggesting a potential down regulation of endogenous insulin production and improved proinsulin processing efficiency.

Syngeneic consecutive rat spleen transplantation bearing infantile testis

Seventy-seven Lewis adult rats received autologous testicular implants in the spleen. These spleens were retransplanted in a consecutive transplant fashion as we described earlier. Some were observed as long as 26 to 27 months. Although earlier splenic-testicular transplants showed benign granulosa cell tumors, some of the long-term follow-ups showed a seminoma-like transformation.

The novel gene locus for agenesis of permanent teeth (He-Zhao deficiency) maps to chromosome 10q11.2

He-Zhao deficiency has been recently characterized with a distinct form of agenesis of permanent teeth that is different from other previously reported disorders of tooth agenesis. This inherited abnormality suggests that some gene(s) associated with the development of permanent teeth may mutate. In this study, we map the gene locus to chromosome 10q11.2. The DNA pooling method combined with two-point and multi-point linkage analysis has been successfully applied. The maximum LOD (Zmax) scores for two-point and multi-point analyses are 13.29 (on marker D10S196) at recombination fraction (theta) = 0 and 18.09 (between markers D10S1772 and D10S1766), respectively. Haplotype analysis confined the locus within an interval of 5.5 cM flanked by markers D10S604 and D10S568. This study has demonstrated a novel gene locus responsible for He-Zhao deficiency and provides a good likelihood for the discovery of one of the genes determining permanent tooth formation and development.

In vivo induction of hepatic p-glycoprotein by cyclosporine in the rat

The objective of the present study was to investigate the regulation of P-glycoprotein by cyclosporine, a known inhibitor of CYP3A, at different dosage levels and lengths of treatment. Rats were given various doses of cyclosporine through oral administration or subcutaneous injection. Each treatment group was studied for 28 days or 28 days followed by 14 days of olive oil vehicle dosing. In each group, rats administered vehicle alone served as the controls. At the end of the study, liver microsomes were prepared and hepatic P-glycoprotein levels were quantified by Western blot analysis. Significant induction of hepatic P-glycoprotein was found in rats given cyclosporine. Rats administered 30 mg/Kg/d orally and 15 mg/Kg/d subcutaneously showed an increase in hepatic P-glycoprotein by 93% (p = 0.0011) and 136% (p < 0.001), respectively. Low doses of cyclosporine also induced P-glycoprotein but not to a significant extent, indicating a dose-dependent effect. The pattern of induction of P-glycoprotein was not, however, dependent on the route of administration. Fourteen days after the discontinuation of cyclosporine treatment, P-glycoprotein levels returned to near the control values. As a drug efflux transporter, the induction of P-glycoprotein by cyclosporine may decrease the hepatic metabolism of P-glycoprotein substrates. Therefore this induction of hepatic P-glycoprotein and suppression of hepatic CYP3A may have a coordinate effect on the metabolism of cyclosporine. These data may help explain the large variability associated with cyclosporine absorption, metabolism, and circulating blood levels.

Effect of low dose cyclosporine and sirolimus on hepatic drug metabolism in the rat1

BACKGROUND

We examined the effect cyclosporine (CsA) and sirolimus (SRL) alone and in combination on hepatic cytochrome P450-mediated metabolism in rats.

METHODS

Rats were given 1 mg/kg of CsA or 0.4 mg/kg of SRL alone or in combination via constant intravenous infusion. Renal function was evaluated at the end of treatment. Blood samples were obtained to estimate CsA and SRL concentrations. Hepatic microsomes were prepared for immunoblotting and catalytic assays.

RESULTS

CsA alone did not alter serum creatinine levels. SRL given alone or in combination with CsA produced a significant increase in urine output without changes in fluid balance. Although CsA and SRL administered alone caused damage to renal proximal tubules, the two-drug combination dramatically increased the renal structural damage. CsA alone suppressed cytochrome P450 (CYP) 3A2 protein levels by 39% (P=0.012) and catalytic activity by 30% (P=0.042). SRL alone reduced catalytic activity by 38% (P=0.012). Combination therapy reduced both CYP3A2 levels by 55% (P<0.001) and catalytic activity by 55% (P=0.001). CYP2C11 protein expression or catalytic activity were not changed in any group. CYP2A1 protein expression and catalytic activity were both significantly reduced in rats given CsA or/and SRL. Steady-state CsA levels were increased during concurrent SRL dosing, however, SRL concentrations were not changed by CsA coadministration.

CONCLUSIONS

Concurrent SRL dosing increases CsA concentrations due to inhibition of hepatic CYP3A2 protein expression. Nephrotoxicity caused by combination therapy is due to CsA elevating levels of SRL or by SRL itself. Concurrent administration of CsA and SRL in transplant patients should be performed with caution.

[Loss of heterozygosity on chromosome 3 in sporadic colorectal carcinoma]

OBJECTIVE

To study the loss of heterozygosity (LOH) on chromosome 3 in sporadic colorectal carcinoma (SCRC) and to explore the possible CRC related genes or loci.

METHODS

LOH at 13 microsatellite loci spanning chromosome 3 were detected in 83 cases with SCRC.

RESULTS

At least two loci LOH on chromosome 3 were detected in 29 of 74 (39%) cases. In 27 of 74 (37%) cases at least one locus LOH was detected on 3p, and in 39 of 74 (53%) cases at least one of 9 loci had LOH on 3q. Of the 13 loci examined, D3S1300 (3p14.2) was identified as the locus with most frequent LOH. 3q LOH was found to occur in distal CRCs more often than those proximal. Tumors with 3p and/or D3S1300 LOH had a tendency of local invasion, and occurred more often in patients older than 50 years.

CONCLUSION

LOH on chromosome 3, dispersed with high frequency at several loci, was correlated with clinico-pathology of SCRC, indicating the existence of SCRC related genes on it. The discovery of D3S1300 locus with highly frequent LOH suggested that FHIT gene located in this region might act as a candidate tumor suppressor gene in the development of colorectal carcinoma.

[Clinical analysis of 68 patients with ruptured sinus of Valsalva aneurysm]

OBJECTIVE

To evaluate the clinical characteristics, diagnosis, treatment and prognosis of ruptured aneurysm of the sinus of Valsalva (ASV).

METHODS

Sixty-eight cases of ruptured ASV treated in our hospital from 1986 to 1998 were retrospectively analyzed.

RESULTS

The ratio of male to female was 1.8:1 in 68 patients (44 males, 24 females). The mean age was (29.5 +/- 10.7) years (8-60 years). The proportion of ruptured aneurysms originating from the right coronary and noncoronary sinus was 79.4% and 20.6% respectively. Sixty-seven point six percent of ASV ruptured into right ventricle and 32.3% into right atrium. The incidence of ventricular septal defect and aortic valve insufficiency was 48.5% and 20.6% respectively. The former only existed in those patients whose ASV originating from the right coronary sinus and rupturing into right ventricles. There was a significant correlation between sudden onset of symptoms and fistulating of ASV into right atrium and a significant difference as compared with those fistulating into right ventricle (P < 0.001). Diagnostic sensitivity and specificity of echocardiography in ruptured ASV was 97.1% and 100% respectively, but the rate of missing subarterial ventricular septal defect was 24.2%. Sixty-seven patients received operation, one died of pulmonary embolism six weeks after operation. Thirty-six patients were followed up, the mean follow-up period was 6.5 years (range 1 to 16 years). Two patients were reoperated for leak of ventricular septal defect and aortic regurgitation. The cardiac function of sixteen patients were found to be of NYHA class I, seventeen of class II and three of class III.

CONCLUSION

Echocardiography in combination with aortography is an accurate diagnostic method for ruptured ASV and the prognosis in majority of the patients operated in time is good.

Mechanisms of plant embryo development

1. Evolution in plants has favored both a simpler body plan with fewer cell types and the epigenetic flexibility to regenerate, via growth, dedifferentiation, and redifferentiation, to recover from environmental insults. It has become increasingly apparent that a plant cell uses external signals to differentiate and to maintain or to change the differentiated state. A cell-cell signaling and positional information strategy seems to be the predominant mechanism employed in plant development. 2. An axis can be initiated by physical/chemical forces such as light and ion current, requiring no new gene action. Random chemical fluctuations and physicochemical forces could explain the initiation of differences among cells of equal developmental potential. Amplification of chemical polarizing events may lead to biochemical differences, new gene expression, and finally shoot/root axis establishment. 3. Radial and axial patterning may be governed by a mechanism involving polar auxin transport. 4. Because the meristems and the three fundamental tissues formed during embryogenesis are renewed and extended throughout the life of the plant, with some exceptions, most genes expressed in the embryo are also expressed during postgermination development. 5. Embryogenic competence is acquired during reproductive development. While the zygote is determined for embryogenesis, the developing embryo and often the seedling remain embryogenic. Embryogenic potential declines during vegetative development. The embryogenic strength of a tissue is correlated with its developmental distance from the zygote.

[Soil P availability in larch rhizosphere]

Soil samples were collected from the rhizosphere and non-rhizosphere of larch(Larix gmelini) stand by exfoliation method, and the variation of P concentration was analyzed. The results show that there was no significant difference between total P concentrations in the rhizosphere and the non-rhizosphere soil, while the concentration of available P in rizhosphere soil was significantly higher than that in the non-rhizosphere soil. The concentrations of available P in rhizosphere 12 years old and 40 years old larch rhizosphered by 12.6% and 23.4% respectively, indicating that larch roots had the effect of mobilizing soil phosphorus. The components of inorganic P in rhizospheric soil were different from those in non-rhizospheric soil. The concentration of O-P was lower, and the concentrations of Al-P, Fe-P, Ca-P, NH4Cl-P were higher in the rhizosphere. The pH of rhizospheric soil was lower than that of non-rhizospheric soil, but no further acidification was observed. There was no close relationship between pH variation and available P concentration in larch rhizosphere.

Hoxa-9 represses transforming growth factor-beta-induced osteopontin gene transcription

Smad2 and Smad3 are downstream transforming growth factor-beta (TGF-beta) signaling molecules. Upon phosphorylation by its type I receptor, Smad2 or Smad3 forms a complex with Smad4 and translocates to the nucleus where the complex activates target gene transcription. In the present study, we report that Smad3 binds directly to the osteopontin (OPN) promoter and that Smad4 interacts with the Hox protein and displaces it from its cognate DNA binding site in response to TGF-beta stimulation. In gel shift assays, the glutathione S-transferase-Smad3 fusion protein was found to bind to a 50-base pair DNA element (-179 to -229) from the OPN promoter. Also, we found that both Hoxc-8 and Hoxa-9 bound to a Hox binding site adjacent to Smad3 binding sequence. Interestingly, Smad4, the common partner for both bone morphogenic protein and TGF-beta signaling pathways, inhibited the binding of Hox protein to DNA. FLAG-tagged Smad4 coimmunoprecipitated with HA-tagged Hoxa-9 from cotransfected COS-1 cells, demonstrating an interaction between Smad4 and Hoxa-9. Transfection studies showed that Hoxa-9 is a strong transcriptional repressor; it suppresses the transcription of the luciferase reporter gene driven by a 124-base pair OPN promoter fragment containing both Smad3 and Hox binding sites. Taken together, these data demonstrate a unique TGF-beta-induced transcription mechanism. Smad3 and Smad4 exhibit different functions in activation of OPN transcription. Smad3 binds directly to the OPN promoter as a sequence-specific activator, and Smad4 displaces the transcription repressor, Hoxa-9, by formation of Smad4/Hox complex as part of the transcription mechanism in response to TGF-beta stimulation.

Functional analysis of the mouse galactose-1-phosphate uridyl transferase (GALT)promoter

Galactose-1-phosphate uridyltransferase (GALT) is expressed in most tissues, but the near total absence of catalytic activity in humans with the disease galactosemia leads to specific organ dysfunction, the pathophysiology of which remains an enigma. To characterize the transcriptional regulation of the mouse GALT gene, we isolated and sequenced over 3 kb of a 5'-flanking sequence and functionally characterized the region using in vitro transient transfection and in transgenic mice. A minimal promoter of 145 bp was found to function in both HepG2 cells and NS20Y mouse neuroblastoma cells. The minimal promoter contains regions of homology to the corresponding rat and human GALT genes. In transgenic mice expressing a luciferase transgene under control of a 1.9-kb fragment of the mGALT promoter region, reporter activity was found in most tissues, with higher than expected reporter levels in neonatal brain. To determine if high galactose levels in tissues could induce promoter activity, we bred the mGALT:luciferase transgene into a line of mice in which the GALT gene function has been eliminated by homologous recombination. High tissue levels of galactose and metabolites did not induce reporter activity above background. The studies show that GALT transcriptional regulation is complex and not directly induced by substrate levels.

Unusual deregulation of cell cycle components in early and frank estrogen-induced renal neoplasias in the Syrian hamster

There is strong evidence that estrogens are involved in the etiology, promotion and progression of a variety of cancers, including the cancers of the breast and endometrium. The Syrian hamster estrogen-induced, estrogen-dependent renal neoplasm is a well-established animal model used to elucidate the cellular and molecular mechanisms involved in solely estrogen-induced carcinogenic processes. G(1) cell cycle progression was studied in estrogen-induced early renal tumor foci and in large kidney tumors of castrated male hamsters. Levels of cyclin D1, cyclin E and retinoblastoma (pRb) proteins were higher in these renal neoplasias than in adjacent uninvolved renal tissue and kidneys from untreated, age-matched animals. Of particular interest is the presence of a predominant 35 kDa cyclin E protein variant form in primary renal tumors. In addition, amounts of the phosphorylated forms of cyclin-dependent kinases (cdk) 2 and 4 were decreased, and both RNA and protein levels of p27(kip1) (p27), a cyclin-dependent kinase inhibitor, were markedly higher in early and frank renal tumors than in adjacent uninvolved renal tissue and kidneys of untreated, age-matched animals. These changes in cell cycle components coincided with a rise in renal tumor cell proliferation. Binding of the elevated p27 protein to cyclin E, cdk2 and cdk4, however, was not impaired, suggesting that this cell cycle suppressor protein is functional. In addition, cyclin D1-, cdk2-, cdk4- and cyclin E-associated kinase activities were also lower in these estrogen-induced renal neoplasms than in untreated, age-matched kidneys. Interestingly, when compared with untreated kidney tissue, early and frank renal neoplasms had less of the 62 kDa native form of E2F1 and contained a 57 kDa variant form. Thus we have characterized an unusual deregulation of the cell cycle during estrogen-induced renal tumorigenesis in Syrian hamsters which still allows for estrogen-driven kidney tumor cell proliferation and may contribute to the early genomic instability found.

[Utilization of insoluble phosphate by Larix gmelini seedlings under phosphorus starvation]

The utilization of insoluble phosphate by 2 years old larch(Larix gmelini) seedlings was studied in greenhouse. The seedlings were grown in sand and AlPO4 was supplied as a source of P. The results showed that larch seedlings could utilize some amount of AlPO4. Supplied with AlPO4 but not incubated with mycorrhizal-fungi, the seedlings could absorb 35.1% and 64.9% of the phosphorus uptake when supplied with soluble phosphate. The effects of various mycorrhizal-fungi on utilization of phosphate were different, i.e., the utilization rate of AlPO4 was higher when incubated with Suillus granulatus, but was similar to control when incubated with Suillus grevillei. The proportion of root/crown became higher under P-starvation, and larch seedlings could gain more P by enlarging their root growth.

Effect of simulated weightlessness on phase II drug metabolism in the rat

BACKGROUND

Exposure to weightlessness is known to alter physiological processes in humans and animals. As a result of these changes, hepatic drug metabolism may be altered as well. Indeed, short term simulated weightlessness in the rat has been shown to increase oxidative metabolism.

HYPOTHESIS

Simulated weightlessness will increase Phase II drug metabolism in the rat during short-term tail suspension.

METHODS

The tail-suspended rat model was used to simulate weightlessness. Rats were subjected to 1, 3, 7, or 10 d of tail-suspension in order to mimic the effect of exposure to a microgravity environment. One additional rat group was not suspended and served as a control. On the final day of the study, rats we administered a single intravenous bolus dose of acetaminophen 25 mg x kg(-1) through an implanted jugular catheter and serial blood samples were taken for 90 min. Serum acetaminophen concentrations were measured by high-performance liquid chromatography. Pharmacokinetic parameters were determined by using standard model independent methods.

RESULTS

The results show that simulated weightlessness in the rat has no effect on Phase II drug metabolism, using acetaminophen as a marker compound.

CONCLUSIONS

These data support the hypothesis that simulated weightlessness in the rat modulates oxidative metabolism, but not drug conjugation to glucuronide or sulfate metabolites. These data offer insight into the physiological changes and variability seen in hepatic metabolic profiles in humans and animals following actual spaceflight.