Ischemic preconditioning negatively regulates plenty of SH3s-mixed lineage kinase 3-Rac1 complex and c-Jun N-terminal kinase 3 signaling via activation of Akt

Activation of Akt/protein kinase B has been recently reported to play an important role in ischemic tolerance. We here demonstrate that the decreased protein expression and phosphorylation of phosphatase and tensin homolog deleted from chromosome 10 (PTEN) underlie the increased Akt-Ser-473 phosphorylation in the hippocampal CA1 subfield in ischemic preconditioning (IPC). Co-immunoprecipitation analysis reveals that Akt physically interacts with Rac1, a small Rho family GTPase required for mixed lineage kinase 3 (MLK3) autophosphorylation, and both this interaction and Rac1-Ser-71 phosphorylation induced by Akt are promoted in preconditioned rats. In addition, we show that Akt activation results in the disassembly of the plenty of SH3s (POSH)-MLK3-Rac1 signaling complex and down-regulation of the activation of MLK3/c-Jun N-terminal kinase (JNK) pathway. Akt activation results in decreased serine phosphorylation of 14-3-3, a cytoplasmic anchor of Bax, and prevents ischemia-induced mitochondrial translocation of Bax, release of cytochrome c, and activation of caspase-3. The expression of Fas ligand is also decreased in the CA1 region. Akt activation protects against apoptotic neuronal death as shown in TUNEL staining following IPC. Intracerebral infusion of LY294002 before IPC reverses the increase in Akt phosphorylation and the decrease in JNK signaling activation, as well as the neuroprotective action of IPC. Our results suggest that activation of pro-apoptotic MLK3/JNK3 cascade can be suppressed through activating anti-apoptotic phosphoinositide 3-kinase/Akt pathway induced by a sublethal ischemic insult, which provides a functional link between Akt and the JNK family of stress-activated kinases in ischemic tolerance.

Prevention and treatment of experimental autoimmune encephalomyelitis with recombinant adeno-associated virus-mediated α-melanocyte-stimulating hormone-transduced PLP139-151-specific T cells

The aim of this study was to investigate the immunomodulatory effects and mechanism of action of alpha-melanocyte-stimulating hormone (alpha-MSH) gene modified proteolipid protein (PLP) 139-151-specific T cells (T(PLP-alpha-MSH)) in the SJL mouse model of experimental autoimmune encephalomyelitis (EAE). PLP139-151-specific T cells (T(PLP) cells) were transduced with a recombinant adeno-associated virus 2 (rAAV2) encoding alpha-MSH. After activation with PLP139-151 in vitro, T(PLP-alpha-MSH) cells secreted high levels of alpha-MSH and also demonstrated an altered Th1-like cytokine pattern as well as a high frequency of CD4(+)CD25(+)Treg cells. Transfer studies showed that T(PLP-alpha-MSH) cells could suppress the induction of adoptive transfer EAE. More importantly, our studies demonstrated that T(PLP-alpha-MSH) cells had preventive and therapeutic effect on active relapse-remitting EAE (REAE) in an antigen-inducible manner. Suppression of REAE by T(PLP-alpha-MSH) cells was associated with a general reduction of inflammatory central nervous system (CNS) infiltrates, a pronounced decrease in Th1 cytokines and chemokines expression and an increase in Th2 cytokines. These data strongly suggested that local delivery of alpha-MSH by rAAV2-mediated alpha-MSH-transduced PLP139-151-specific T cells (T(PLP-alpha-MSH)) would be a desirable new approach to the treatment of autoimmune disease in the CNS.

Erythroid differentiation denucleation factors (EDDFs) function as intrinsic, post-erythropoietin regulators for mammalian erythroid terminal differentiation

Regulatory factors other than erythropoietin (Epo) dependence, that control mammalian erythroid terminal differentiation, are currently uncertain. Here we report the existence of erythroid differentiation factors in erythroid cytoplasm. Purification of these factors from cultured Friend virus anaemia (FVA)-infected mouse splenic erythroblasts was carried out using isoelectrophoresis and high performance of liquid chromatography techniques. We have identified intracellular erythroid differentiation denucleation factors (EDDFs) that were able to mediate the events of post-Epo-dependent erythroblast terminal differentiation. Purified EDDF proteins bound specifically to the enhancer HS2 sequence of the globin gene activated the expression of haemoglobin in mouse erythroleukaemia and K562 erythroleukaemic cells and promoted them to differentiate into mature erythrocytes. EDDF proteins began to emerge at the pro-early erythroblast stages upon exposure to Epo in culture, and increased dramatically in early erythroblast stage. The dynamic of EDDF expression and its action on the key events of erythroblast differentiation and denucleation appeared to be closely consistent with its spatiotemporal distribution. These results suggest that EDDFs are the critical intracellular regulatory factors that may act as the successive regulators to Epo, responsible for the final stages of erythroid terminal differentiation.

Assessment of Canadian provincial expenditures in depressed patients treated with venlafaxine XR versus SSRIs: the APEX Study

OBJECTIVE

Empirical studies of antidepressant cost-effectiveness suggest that the use of venlafaxine may be no more costly than selective serotonin reuptake inhibitors (SSRIs) in the treatment of depression. The objectives of this study were to identify patients' characteristics and factors associated with the choice of antidepressant and to assess differences in persistence, healthcare utilization and direct medical costs associated with venlafaxine and SSRIs pharmacotherapy.

RESEARCH DESIGN AND METHODS

We examined demographic and clinical characteristics of patients (n = 17 144) who received both a diagnosis of depression and a prescription for venlafaxine or an SSRI between 1996 and 2004 using the Quebec health administrative databases. Logistic regression models were used to identify factors independently associated with the choice of antidepressant. Persistence to treatment and overall direct medical costs during 12 months after initiation of therapy were assessed using Cox proportional hazard and GLM models, respectively.

RESULTS

Age, sex, provider specialty, and prior 12-month healthcare utilization significantly influenced initial antidepressant choice. Fewer venlafaxine-treated patients discontinued their initial therapy relative to SSRIs' (persistence to initial treatment: 38.4% vs. 29.4% and 24.4% vs. 15.8% at 6 and 12 months, respectively; p < 0.0001), and they were less likely to require treatment switching. Overall 12-month direct medical costs for SSRI- and venlafaxine-treated patients were Can$2759 and Can$2604, respectively. Patients treated with SSRIs had significantly higher expenditures in a univariate analysis (cost ratio: 1.06 [95% CI: 1.02, 1.10]). However, after controlling for potential confounding factors such as patients' characteristics, prior healthcare utilization, and comorbid conditions in multivariate analyses, the overall expenditures were similar in both groups (cost ratio: 1.03 [95% CI: 0.99, 1.07]).

CONCLUSIONS

Direct medical costs were generally similar among patients with depression treated with venlafaxine and SSRIs. In a 'real world' setting, the higher acquisition cost of venlafaxine is offset by savings due to fewer hospitalizations and fewer outpatient medical visits. Differences in treatment persistence may also, in part, explain the observed differences in average direct medical costs between venlafaxine and SSRIs.

273 OPTIMIZATION OF PROTOCOLS FOR ACTIVATION OF GOAT OOCYTES WITH IONOMYCIN IN COMBINATION WITH 6-DIMETHYLAMINOPURINE

The protocol of ionomycin in combination with 6-dimethylaminopurine (6-DMAP) is commonly used for activation of oocytes and reconstructed embryos of different species. Since numerous abnormalities and impaired development have been observed when oocytes are activated with 6-DMAP, this protocol needs optimization. Effects of concentration and treatment duration of both drugs on activation kinetics and parthenogenetic development of goat oocytes were examined in this study. When goat oocytes matured in vitro in TCM-199 were treated with 5 M ionomycin in PBS for different periods before exposure to 6-DMAP in CR1aa, the activation rate obtained with ionomycin treatment for 1 min (95.2%) was significantly (P < 0.05, Duncan multiple comparison test) higher than with ionomycin treatments for 3, 5, 7, or 9 min. When oocytes were treated with different concentrations of ionomycin for 1 min before exposure to 6-DMAP, activation rates obtained with 0.625, 1.25, 2.5, 5, 10, and 20 M ionomycin (87–95%) did not differ significantly but were significantly higher than that achieved with 0.3125 M ionomycin. Progressive reduction of time for 6-DMAP exposure showed that the duration of 6-DMAP treatment can be reduced to 1 h from the 2nd up to the 4th hour after ionomycin treatment, to produce activation rates greater than 85%. When oocytes were treated with different concentrations of 6-DMAP for the 3rd hour (atotal of 1 h, 3 h after the exposure to ionomycin), activation rates with 4 and 2 mM 6-DMAP (>90%) were significantly higher than those with 1and 0.5 mM. Therefore, the best protocol for goat oocyte activation would be a 1-min exposure to 2.5 M ionomycin followed by 2 mM 6-DMAP treatment for the 3rd hour. When oocytes matured in vitro for different times were stimulated with the best protocol, activation rates of the 27-, 30-, and 33-h oocytes (85, 85, and 91%) were significantly higher than those of the 24-, 26-, and 39-h oocytes. When activated oocytes were co-cultured in CR1aa with cumulus cell monolayers, the highest rates of cleavage (92%) and morulae/blastocysts (23%) were obtained with oocytes activated by the best protocol, and any increase in the intensity of ionomycin treatment and in the duration of 6-DMAP exposure impaired the development of the parthenotes. During anaphase II, chromosomes (the dyads) did not separate into two units in oocytes that were activated by long exposure to 6-DMAP, but they did in oocytes that were activated by short or no exposure to 6-DMAP; as a result, only one pronucleus developed in most of the former but two pronuclei were formed in most of the latter cases. Laser scanning confocal microscopy showed that microtubules also behaved differently in these two groups of activated oocytes. It is therefore concluded that to obtain better activation and development, goat oocytes matured in vitro for 27–33 h should be used, and these should be activated by a 1-min exposure to 2.5 M ionomycin followed by 2 mM 6-DMAP treatment for the 3rd hour. This study was supported by the “973” Project of China Sci. Technol. Ministry (No. G200016108).

Auxiliary liver-heart transplantation in the rat: a new microsurgical model inducing tolerance

OBJECTIVE

To establish a model of immunological tolerance induced by simultaneous auxiliary liver transplantation and heterotopic heart transplantations using PVG and DA rats as donors and recipients respectively, to provide a new method for the research of liver transplantation.

METHODS

The recipient's whole portal vein blood was transfered to the auxiliary liver allograft. The donor's heart was transplanted to the recipient's abdominal cavity by end-to-side anastomosis of the donor aorta and pulmonary artery to the recipient aorta and vena cava, respectively.

RESULTS

In the syngeneic control group and the test group the recipient rats and their transplanted hearts both survived more than 100 days, while the hearts of alloheart control group only survived 6 days. The weight of the liver graft increased slowly.

CONCLUSIONS

In the presence of recipient liver, the auxiliary liver graft functioned well to induce tolerance. At 100 days, the auxiliary liver graft had increased in volume and weight with maintenance of its tolerance-inducing effects.

Analysis of intra-operative bleeding and recurrence of juvenile nasopharyngeal angiofibromas

The purpose of this study is to present our experience with 34 patients diagnosed with juvenile nasopharyngeal angiofibromas and treated in the Chinese PLA General Hospital between 1986 and 1999, and to examine the factors influencing intra-operative bleeding and tumour recurrence. The age of the patient, the duration of symptoms and tumour stage were related to the amount of intra-operative bleeding. The tumours were totally resected in 30 patients and recurred in five patients (16.7%), with a mean follow-up time of 77 months. The mean time to tumour recurrence after operation was 3.2 months (1-6 months). The incidence of recurrence had no correlation with the age of the patient, duration of symptoms, peri-operative treatment or surgical approaches (P > 0.05); but strongly correlated with tumour stage (P < 0.05).

Inherited prion disease caused by the V210I mutation: transmission to transgenic mice

OBJECTIVE

To describe the clinical and neuropathologic profile and determine the strain characteristics of familial Creutzfeldt-Jakob disease (fCJD) caused by a point mutation of the PRNP gene at codon 210 that results in a valine-to-isoleucine substitution in the prion protein (PrP).

METHODS

The clinicopathologic features of four individuals from the United States who died of fCJD(V210I) were compared. Transgenic (Tg) mice expressing a chimeric human-mouse PrP transgene were inoculated with brain extracts from three fCJD(V210I) cases, sporadic CJD (sCJD), fCJD(E200K), and fatal familial insomnia (FFI), to compare prion strain characteristics.

RESULTS

The clinicopathologic profile of fCJD(V210I) was variable among cases but shared similarities with sCJD. The pattern of PrP(Sc) deposition in the brains of Tg mice was similar to that caused by sCJD but different from that associated with fCJD(E200K) or FFI.

CONCLUSIONS

Each of these prion diseases is characterized by a rapidly progressive dementia with myoclonus, periodic complexes on EEG, and spongiform change without PrP plaque deposition in the brain. The occurrence of a different PrP(Sc) phenotype with each PRNP mutation argues that each respective amino acid sequence substitution produces a different prion strain.

[Study on vibration mode of different phonatory source and compensation after partial laryngectomy]

OBJECTIVE

To investigate the nature of pathological voice production and compensatory mechanism after partial laryngectomy.

METHODS

Vocal function of 93 cases following partial laryngectomy (28 cases of horizontal partial laryngectomy, 35 vertical partial laryngectomy, 30 horizontal-vertical partial laryngectomy) were examined by acoustic analysis, aerodynamic analysis and videostroboscopic examination.

RESULTS

Horizontal supraglottic laryngectomy(HL) resulted in slight dysphonia after operation. The cover of vocal fold was hypertrophic and edematous. Mucosa wave was increased. Acoustic analysis showed significant difference between normal and horizontal laryngectomy groups(P < 0.05). Vertical laryngectomy(VL) resulted in moderate-severe dysphonia. Acoustic analysis was significantly worse in VL than in normal group(P < 0.01). The nonglottic phonatory source was the contralateral ventricular fold or contralateral vestibular mucosa (arytenoid mucosa, root mucosa of glottis) to approximate the reconstructed flap. It was noted that contralateral vocal fold did not participate in vibration. Horizontal-vertical partial laryngectomy (HVL) resulted in moderate-severe dysphonia. Acoustic analysis of HVL was significantly worse than that of normal phonation(P < 0.01). The site of compensatory mucosa vibration upon phonation was the contralateral vocal fold or contralateral hypertrophic arytenoid mucosa. The thinner the flap, the better the vocal quality was. Vocal quality of VL was worse than that of HVL in regard to shimmer, jitter, normalized noise energy, maximal phonation time and harmonic-noise ratio, but there was no significant difference between them.

CONCLUSIONS

Partial laryngectomy has different vibrating compensatory modes: Voice function of horizontal partial laryngectomy was the best as it preserved the normal vibration mode; vertical partial laryngectomy was the worst with the nonglottic vibrating source of reconstructed flap-ventricular fold. The reconstructed flap, ventricular fold, mucosa of epiglottis and arytenoid take predominantly part in neoglottal vibration. The situation, volume and pliability characteristic of reconstructed flap was also important to vocal quality.

[Rat hearing loss and hearing organs mitochondrial DNA4834 deletions associated with hypercholesteremia]

OBJECTIVE

To determine whether or not the rat hypercholesteremia contributes to hearing organs mtDNA4834 deletion and involves in the development of hearing loss.

METHODS

The rat hypercholesteremia model (n = 38) was established by feeding with high cholesterol diet and the control group (n = 22) with common diet for 6 months. The rats were tested for auditory sensitivity using auditory brainstem response (ABR). Twenty-one left cochleae and 27 left cochlear nuclei from experimental group and 10 left cochleae and 13 left cochlear nuclei from control group were harvested. The total DNA of them was extracted. mtDNA was amplified by nest PCR to examine the presence of mtDNA4834 deletion.

RESULTS

Our result showed: (1) There is a significant increase in serum cholesterol level and ABR threshold in the experimental group. (2) The mitochondrially-encoded tRNA and ND1 segments were amplified from all samples, as well as mtDNA4834 deletions. (3) The incidence of mtDNA4834 deletions in hearing organs of hypercholesteremia rats was significantly higher than that of the control group (P < 0.05).

CONCLUSION

Extended hypercholesteremia can induce hearing loss, and mtDNA4834 deletion in hearing organs may be one of the pathogenic mechanisms.

Huntington disease phenocopy is a familial prion disease

Huntington disease (HD) is a common autosomal dominant neurodegenerative disease with early adult-onset motor abnormalities and dementia. Many studies of HD show that huntingtin (CAG)n repeat-expansion length is a sensitive and specific marker for HD. However, there are a significant number of examples of HD in the absence of a huntingtin (CAG)n expansion, suggesting that mutations in other genes can provoke HD-like disorders. The identification of genes responsible for these "phenocopies" may greatly improve the reliability of genetic screens for HD and may provide further insight into neurodegenerative disease. We have examined an HD phenocopy pedigree with linkage to chromosome 20p12 for mutations in the prion protein (PrP) gene (PRNP). This reveals that affected individuals are heterozygous for a 192-nucleotide (nt) insertion within the PrP coding region, which encodes an expanded PrP with eight extra octapeptide repeats. This reveals that this HD phenocopy is, in fact, a familial prion disease and that PrP repeat-expansion mutations can provoke an HD "genocopy." PrP repeat expansions are well characterized and provoke early-onset, slowly progressive atypical prion diseases with an autosomal dominant pattern of inheritance and a remarkable range of clinical features, many of which overlap with those of HD. This observation raises the possibility that an unknown number of HD phenocopies are, in fact, familial prion diseases and argues that clinicians should consider screening for PrP mutations in individuals with HD-like diseases in which the characteristic HD (CAG)n repeat expansions are absent.

[Sequence analysis of mtDNA 12S rRNA, tRNA(Leu(UUR)),tRNA(Ser(UCN))and 16S rRNA gene of 12 nonsyndromic inherited deafness pedigrees]

OBJECTIVE

To detect the relationship of mtDNA mutation with inherited deafness and the reason for pedigree's hypersensitivity to ototoxicity of aminoglycoside antibiotics(AmAn).

METHODS

Pedigree investigations were conducted. The blood samples were obtained from 12 pedigrees, and DNA was extracted from the isolated leukocytes. After that, mtDNA fragments were amplified by PCR. The 1555(G), 3243(G) and 7445(G) mutations were detected by Alw 26 I, Apa I and Xba I restriction endonuclease digestion respectively, and then sequencing of 12S rRNA, tRNA(Leu(UUR)), tRNA(Ser(UCN))and 16S rRNA gene was performed.

RESULTS

Restriction endonuclease digestion and sequence analysis showed that all the pedigrees carried mtDNA mutation, among them, 10 pedigrees carried 1555(G) mutation; 2 pedigrees, 7445(G) mutation; no pedigree was found to harbor the 3243(G) mutation. Sequence analysis of 16S rRNA gene showed that the mutations are 2230(G), 2230(AG), 2243(AG), 2230(AA).

CONCLUSION

The pedigrees that carried 1555(G) or 7445(G) mutation showed hereditary or congenital hearing loss. The 1555(G) or 7445(G) mutation in association with 16S rRNA gene mutation led to pedigree's hypersensitivity to AmAn ototoxicity.

[Clinical study of juvenile-onset recurrent respiratory papillomatosis]

OBJECTIVE

To study the clinical behavior of juvenile-onset recurrent respiratory papillomatosis in order to find some factors correlated to the development of this disease, and to sum up the significance and experience of CO2 laser surgery.

METHOD

Sixty patients with juvenile-onset recurrent respiratory papillomatosis from September 1995 to December 1998 were retrospectively analyzed.

RESULTS

The age of onset in 50 cases (83.3%) was below 4 years, and the peak-age was 2 years. The rates of recurrence were 72.0% and 45.7% (chi 2 = 4.71, P < 0.05) below and over 2 years, respectively. The rates of aggressive disease were 88.0% and 54.3% (chi 2 = 7.66, P < 0.01) below and over 2 years, respectively. The predominant sites of the disease were the vocal cords, the false vocal cords, the laryngeal ventricle, the laryngeal surface of the epiglottis and the subglottic region. Tracheostomy induced the development of tracheal papilloma, therefore should be avoided as possible. Laryngeal papilloma might be divided into four types on the basis of the growth manner and surface form corresponding to clinical behaviors. Five patients were followed-up for 1.5 years without recurrence, 18 patients had fewer recurrences following treatment, 33 patients were under treatment, and 3 patients died. Nineteen patients lost follow-up. The major complications included laryngeal and tracheal stenosis.

CONCLUSION

Clinical behaviors of juvenile-onset recurrent respiratory papillomatosis were relevant to the age, growth form and tracheotomy. CO2 laser was an ideal instrument for ablation of the laryngeal papillomas with the following advantages: simple management, less bleeding, preservation of laryngeal structure and avoidance of tracheostomy.

Confinement effect on dipole-dipole interactions in nanofluids

Intermolecular dipole-dipole interactions were once thought to average to zero in gases and liquids as a result of rapid molecular motion that leads to sharp nuclear magnetic resonance lines. Recent papers have shown that small residual couplings survive the motional averaging if the magnetization is nonuniform or nonspherical. Here, we show that a much larger, qualitatively different intermolecular dipolar interaction remains in nanogases and nanoliquids as an effect of confinement. The dipolar coupling that characterizes such interactions is identical for all spin pairs and depends on the shape, orientation (with respect to the external magnetic field), and volume of the gas/liquid container. This nanoscale effect is useful in the determination of nanostructures and could have unique applications in the exploration of quantum space.

[The infiltration and activation stage of eosinophils in nasal polyps]

OBJECTIVE

To assess the infiltration and activation of eosinophils in nasal polyps.

METHOD

Nasal polyps from sixteen patients were investigated. The samples were stained with Chromotrope 2R histochemical and ABC immunohistochemical methods.

RESULT

The majority of eosinophils in nasal polyps were activated, and there were no significant differences in the numbers of total eosinophils (Chromotrope 2R positive cells) and activated eosinophils (EG2 positive cells) between allergic and nonallergic patients.

CONCLUSION

Eosinophilia is a prominent histologic feature of nasal polyps which indicates that the activated eosinophils may play vital role in the pathogenesis of nasal polyps.

[Roles of CD43, CD20 and local IgE in the pathogenesis of nasal polyps]

OBJECTIVE

To estimate the roles of CD43, CD20 and total IgE in the pathogenesis of nasal polyps.

METHOD

Twenty-six cases of nasal polyps and 20 cases of mucosa of middle turbinates were used in present study.

RESULTS

The number of CD43+ cells, CD20+ cells and plasma cells in nasal polyps were significantly more than that in middle turbinates (P < 0.01). The positive rate of local IgE+ cells in nasal polyps was significantly higher than in middle turbinate (P < 0.01).

CONCLUSION

There were active cellular immunity and humoral immunity in nasal polyps. Local allergy may play a role in the pathogenesis of nasal polyps.

[Observation of nasal mucosal cilia ultrastructure of Kartagener's syndrome]

OBJECTIVE

To report the ultrastructure of nasal mucosal cilia of Kartagener's syndrome and the operative results of 2 cases.

METHODS

Both two cases were underwent endoscopic sinus surgery. Transmission and scanning electron microscopic examinations of nasal mucosa for case 1 were performed.

RESULTS

All 2 cases presented situs inversus, chronic paranasal sinusitis and bronchiectasis. The electron microscopic examination showed that the shape of nasal cilia and "9 + 2" structure were normal, but the lack of inner dynein arm of cilia and confused arrangement of central pair of microtubules were confirmed. The recurrent of nasal polyps after 1-year follow-up was observed in case 1.

CONCLUSIONS

The disturbance of mucociliary clearance due to congenital ciliary structure defect might be the cause of chronic sinusitis and polyps, which might be one of reasons for poor prognosis after operation and we should pay more close attention.

[Studies on the chemical constituents from Tribulus terrestris]

AIM

To investigate the chemical constituents of the fruit of Tribulus terrestris J..

METHODS

Various chromatographic techniques were used to separate the chemical constituents. ESIMS, IR, 1HNMR, 13CNMR and HMBC were used to determine the structures of the isolated constituents.

RESULTS

Two new compounds were isolated from the fruits of Tribulus terrestris J. and were identified as neohecogenin-3-O-beta-D-glucopyranosyl (1-->2)-beta-D-glucopyranosyl (1-->4)-beta-D-galactopyranoside (I); neohecogenin-3-O-beta-D-glucopyranosyl (1-->4)-beta-D-galactopyranoside (II).

CONCLUSION

Compounds I and II are new steroidal saponins.

New method to calculate the N2 evolution from mixed venous blood during the N2 washout

To model the normalized phase III slope (Sn) from N2 expirograms of the multibreath N2 washout is a challenge to researchers. Experimental measurements show that Sn increases with the number of breaths. Previously, we predicted Sn by setting the concentration (atm) of mixed venous blood (Fbi,N2) to a constant value of 0.3 after the fifth breath to calculate the amount of N2 transferred from the blood to the alveoli. As a consequence, the predicted curve of the Sn values showed a maximum before the quasi-steady state was reached. In this paper, we present a way of calculating the amount of N2 transferred from the blood to the alveoli by setting Fbi,N2 in the following way: In the first six breaths Fbi,N2 is kept constant at the initial value of 0.8 because circulation time needs at least 30 s to alter it. Thereafter, a single exponential function with respect the number of breaths is used: Fbi = 0.8 exp[0.112(6-n)], in which n is the breath number. The predicted Sn values were compared with experimental data from the literature. The assumption of an exponential decay in the N2 evolved from mixed venous blood is important in determining the shape of the Sn curve but new experimental data are needed to determine the validity of the model. We concluded that this new approach to calculate the N2 evolution from the blood is more meaningful physiologically.