Two-step hot isostatic pressing densification achieved non-porous fully-densified wood with enhanced physical and mechanical properties

A new two-step densification method for wooden materials entitled hot isostatic pressing (HIP) is proposed. This method has the advantage over previous densification methods that can achieved almost the full densification of wood, reaching values up to 1.47 kg/m3, which exceeds any value ever reported for a hardwood species. Furthermore, it can preserve about 35% of the original volume, in comparison to other methods which typically can preserve only 20% of the volume. Although not tested in this investigation, in principle, the HIP method should be capable of densifying any shape of wood including circular and tubular cross sections because the main densification mechanism is based on gas pressure that is equally exerted in the entire surface, rather than localized mechanical compression, which can only be effective with rectangular cross sections. In the first stage of the two-step proposed method, the compressive strength of the anatomical wood structure is reduced by delignification, and, in the second, a full densification is achieved by hot isostatic pressing under argon atmosphere. Three tropical hardwood species with distinct anatomical characteristics and properties were used to test the method. The HIP-densified wood's microstructural, chemical, physical, and mechanical properties were assessed. Apart from the high densification values and volume preservation, the results indicate that proposed method was effective for all the tested species, showing homogenous density patterns, stable densification without noticeable shape recovery, and enhanced mechanical properties. Future research should test the HIP method in softwoods and consider the ring orientation in order to enhance the control of the densified geometry.

Characterization of polycaprolactone/rGO nanocomposite scaffolds obtained by electrospinning

The incorporation of nanoparticles inside polymeric matrices has led to the development of multifunctional composites necessary to repair human tissues. The addition of nanoparticles may improve the properties of the composite materials such as surface area, mechanical properties, flexibility, hydrophilicity, electrical conductivity, etc. These properties can help in cellular growth, proliferation and/or differentiation. In this work, scaffolds of polycaprolactone (PCL) and reduced graphite oxide (rGO) were built by electrospinning technique. The ratios of rGO/PCL employed were 0.25, 0.5, 0.75 and 1 wt%. Two different voltage setup (10 and 15 kV) and distance of 10 cm were used for electrospinning. Thermal, mechanical, morphological, electrical, porosity and absorption water tests were made to the scaffolds. Samples electrospun at 10 kV with rGO showed improvement in mechanical properties with an increase of 190% of Young's Modulus in comparison with sample without rGO. Furthermore, samples electrospun at 15 kV showed an important deterioration with the addition of rGO but had an increase in the electrical conductivity and porosity. Overall, the addition of 0.75 and 1 wt% of rGO led to a detriment on properties due to formation of aggregates. The voltage on the electrospinning process plays a very important role in the final properties of the nanocomposites scaffolds of PCL-rGO.

Semen quality before cryopreservation and after thawing in 543 patients with testicular cancer

OBJECTIVE

The main objective of this study was to assess semen characteristics of patients with testicular cancer before cryopreservation and after thawing, to evaluate the consequences of this technique on sperm quality in patients with testicular cancer.

METHODS

Five hundred eighty-nine samples from 543 patients with testicular cancer were cryopreserved between 1995 and 2015, one aliquot per patient was used for a thawing test to assess the impact of cryopreservation on sperm motility; semen analysis was performed before cryo preservation and after thawing, the result interpretation was carried out using the 2010 World Health Organization (WHO) Laboratory Manual, and consent forms were signed by the patients for freezing and when sperm was used for reproductive purposes.

RESULTS

Hypospermia was observed in 28.7% of samples, the median sperm concentration was 18 million/mL with 35% oligozoospermia; twenty-two patients (4.1%) had azoospermia and 12.7% had severe oligozoospermia, the median sperm count was 31.3 million and 261 semen samples (44.3%) were normal in all parameters according to the WHO; total motile sperm count before cryopreservation and after thawing was 12 (0-412.2) and 7 (0-303.9) million sperm, respectively (p < 0.00001, 95% CI 5.48-14.91), which represents a 32% reduction; concerning the utilization of cryopreserved semen samples, only twelve patients (2.2%) used their frozen sperm for reproductive purposes.

CONCLUSIONS

An impairment in semen quality was found in almost half of the samples from patients with testicular cancer, only few patients had azoospermia or severe oligozoospermia; sperm cryopreservation significantly reduces sperm motility and total motile sperm count and very few patients use their frozen sperm for reproductive purposes.

[Association between hospital admissions due to affective disorders and solar activity. Analysis of 16 years]

BACKGROUND

Exposure to solar activity may be associated with incidence of depressive and manic disorders.

AIM

To assess the link between solar activity and appearance of affective disorders.

MATERIAL AND METHODS

We examined 1862 clinical records of a psychiatric clinic located in Santiago, Chile. Patients with major depression and manic disorders were included in the study, only when they were admitted at the clinic for the first time. Solar activity was calculated using the Wolf number, which is given by the formula R = K(10g+f), where "g" stands for the groups of sunspots and "f" is the total number of sunspots. We examined the correlation between annual incidence of hospital admissions and average Wolf numbers for the period 1990-2005, which corresponds to approximately one and half solar cycles of 16 years.

RESULTS

A total of 450 medical records corresponding to 299 patients (199 women) with depressive symptoms and 151 patients (73 women) with mania, were analyzed. There was a higher number of admissions for depression during the years with lower solar activity. Admissions due to mania tended to increase in the years with high solar activity. There was a negative correlation between the number of hospital admissions due to depression and solar activity (Spearman r = -0.812, p < 0.01). The association between the latter parameter and admissions due to mania did not reach statistical significance.

CONCLUSIONS

There is a significant negative association between the rate of hospital admissions due to depressive disorders and solar activity.

Current status of human rabies transmitted by dogs in Latin America

Latin American countries made the political decision to eliminate human rabies transmitted by dogs by the year 2005. The purpose of the current study is to evaluate to what extent this goal has been reached. The epidemiological situation and control measures were analyzed and broken down within the countries by georeferencing. The 27 human cases reported in 2003 occurred in some 0.2% of the second-level geopolitical units (municipalities or counties) in the region, suggesting that the disease is a local problem. Several areas within the countries reported no more transmission of rabies in dogs. Nearly 1 million people potentially exposed to rabies received treatment. On average, 34,383 inhabitants per health post receive anti-rabies treatment (range: 4,300-148,043). Nearly 42 million dogs are vaccinated annually. Surveillance is considered fair according to the epidemiological criteria adopted by the study. Samples sent for rabies testing represent 0.05% of the estimated canine population (range: 0.001 to 0.2%). The countries are quite close to achieving the goal.

Peginterferon alfa-2a (40KD) (PEGASYS) plus ribavirin (COPEGUS) in retreatment of chronic hepatitis C patients, nonresponders and relapsers to previous conventional interferon plus ribavirin therapy

Peginterferon alfa plus ribavirin is currently the treatment of choice for chronic hepatitis C. Peginterferon alfa-2a (40KD) plus ribavirin has given an overall sustained virological response of 18% in F3/F4 previous nonresponder US patients. We evaluated the effectiveness of peginterferon alfa-2a (40KD) plus ribavirin in Brazilian patients who were relapsers or nonresponders to previous interferon-based therapy. One-hundred-thirty-four patients with biopsy-proven chronic hepatitis C, HCV RNA positive, elevated ALT and who were either relapsers (n=37) or nonresponders (n=97) to at least 24 weeks of conventional interferon/ribavirin therapy were retreated with peginterferon alfa-2a (40KD) 180mg/qw and ribavirin 800 mg bid for 48 weeks. Efficacy was assessed as virological response (defined as undetectable HCV RNA) at the end of treatment (EoT) and at the end of follow-up (SVR - Sustained Virological Response). Safety assessments consisted of clinical and laboratory evaluations. In the patient sample, 72% were genotype 1 and 34% were cirrhotic. In an intention-to-treat analysis, relapser patients showed 78% EoT response and 51% SVR. Nonresponders showed 57% EoT response and 26% SVR. Positive predictive factors of SVR were non-1 genotype and relapser state. Six percent of the patients interrupted treatment because of adverse events and 45% had dose reduction (mainly associated with leucopenia and anemia). Brazilian patient relapsers and nonresponders to conventional interferon and ribavirin treatment can achieve a sustained virological response when retreated with peginterferon alfa-2a (40KD) and ribavirin. The safety profile is similar to that of naive patients.

Overview of rabies in the Americas

Between 1993 and 2002, the number of human and canine rabies cases in the Americas Region fell by approximately 80%. There were 39 human cases in 2002, 63% of them transmitted by dogs. Furthermore, human rabies transmitted by wildlife, mostly by bats is a risk to inhabitants in many countries in the Region. The objective of this study is to describe this epidemiological situation based in the information received from the countries of the Americas Region in Regional Rabies Surveillance System in the Americas (SIRVERA) administrated by the Pan American Health Organization. This sharp reduction is attributable mainly to the control measures implemented by the countries of the Region, such as the mass vaccination of dogs and prophylactic treatment for people who have been exposed.

Thrombin is present in the lungs of patients with primary extremity osteosarcoma and pulmonary metastases

Osteosarcoma is a rare cancer, which metastasizes to the lung in up to 80% of cases. Thrombin is involved in metastasis and is present in the lungs of patients with pulmonary metastases (PM). To identify its role in PM and osteosarcoma, we measured thrombin levels in the bronchoalveolar lavage fluid (BALF) of 15 patients. BALF was collected at different stages of the disease and correlated with the diagnosis of PM. We also assessed fibrinogen overexpression in the tumors. We found that 11/15 (73%) patients with high thrombin levels in the lungs developed PM within the first 12 months from primary surgery. The median thrombin concentration in the BALF of these patients increased up to 8x10(-9) M (range, 3x10(-9)M-15x10(-9)M), which represents a more than 100-fold increase compared to patients without PM (p<0.0001). Eight of 15 (53%) primary and 11/15 (73%) metastatic samples showed fibrinogen overexpression. A significant difference between high thrombin levels, fibrinogen overexpression and PM was found compared to patients without PM (p=0.00073 and p=0.025). These results show that thrombin levels are increased in the lungs of patients with primary osteosarcoma and a high risk of developing PM. They suggest that thrombin may be involved in the development of PM.

Ki-67: a proliferative marker that may predict pulmonary metastases and mortality of primary osteosarcoma

Alterations in Ki-67 activity have been associated with tumor progression and poor outcome in cancer patients. This study was undertaken to identify the potential of this proliferative marker as a predictor of pulmonary metastases (PM) and mortality in osteosarcoma patients. In 38 patients with tissue available for immunohistochemical analysis, overexpression of Ki-67 was assessed. Chi-square and log rank tests were used to determine differences between proportions of the marker with PM and mortality and survival distributions respectively. P values equal or less than .05 were considered statistically significant. The median follow up of this case series was 28 months. Eighteen (47.4%) of 38 patients developed PM, and 17 (44%) overexpressed Ki-67. We found a high frequency of PM (15 of 17) among those cases that overexpressed Ki-67. This relationship was significant (P = .000006) when compared to the rest of the group. We also found a statistically significant correlation between patients with positive and negative Ki-67 scores and higher and lower mortality (P = .000962). These findings suggest that Ki-67 overexpression could be used as a prognostic molecular marker for the development of PM in osteosarcoma patients.

Evidence that thrombin present in lungs of patients with pulmonary metastasis may contribute to the development of the disease

Early cellular events in the lung which may lead to the development of pulmonary metastases (PM) are still poorly understood. Thrombin, a key component of the coagulation cascade, may be involved in the development of PM as it has been shown to be an enhancer of platelet-tumor interaction in vitro and metastasis in vivo, and because it has been found in high levels in lungs from patients with PM. In this study, we assessed the potential role of thrombin in promoting PM by inducing an enhancement of tumor cell adhesion to platelets and tumor cell chemoinvasion and proliferation. We used bronchoalveolar lavage fluid (BALF) from 20 patients with PM. Results were compared with those from healthy controls. We found an enhancement of adhesion of PM-BALF-treated tumor cells to untreated platelets. BALF from patients with PM significantly increased chemoinvasion and proliferation in three human tumor cell lines. These activities were attenuated significantly by a thrombin inhibitor: hirudin. These results indicate that the thrombin present in the lungs of patients with PM is, at least in part, responsible for their adhesive, invasive and mitogenic activity on three different tumor cell lines. They also suggest that thrombin may be involved in the development of PM.

Effects of short-term zinc supplementation on cellular immunity, respiratory symptoms, and growth of malnourished Equadorian children

OBJECTIVE

To assess the effect of zinc supplementation on respiratory tract disease, immunity and growth in malnourished children.

DESIGN

A randomized double-blind placebo-controlled trial.

SETTING

A day-care center in Quito, Ecuador.

SUBJECTS

Fifty children (12-59 months old) recruited by height-for-age and weight-for-age deficit.

INTERVENTIONS

Twenty-five children (supplemented, S group) received 10 mg/day of zinc as zinc sulfate, and 25 (nonsupplemented, NS group) received a placebo during 60 days. All were also observed during a 60-day postsupplementation period. Two children of the S group dropped out. Daily the clinical presence of cough, respiratory tract secretions, and fever, was recorded. On days 0,60 and 120, the cutaneous delayed-type hypersensitivity (DTH) to multiple antigens, and anthropometric parameters were assessed. On days 0 and 60 serum zinc levels were also measured.

RESULTS

On day 60, DTH was significantly larger (20.8 +/- 7.1 vs 16.1 +/- 9.7 mm), and serum zinc levels were significantly higher (118.6 +/- 47.1 vs 83.1 +/- 24.5 micrograms/dl) in the S group than in the NS group (P <0.05 for each). The incidence of fever [relative risk (RR): 0.30, c.i. = 0.08- 0.95, P =0.02], cough (RR): 0.52, c.i. = 0.32-0.84, P = 0.004) and upper respiratory tract secretions (RR):0.72, c.i. = 0.59-0.88, P = 0.001) was lower in the S group than in the NS group at day 60. At the end of the postsupplementation observation period (day 120), the incidence of fever and upper respiratory tract secretions was the same in both the S and NS groups. The incidence of cough was higher at day 120 in the S group than in the NS group (RR): 2.28, c.i. = 1.37-3.83, P = 0.001).

CONCLUSIONS

This study supports a role for zinc in immunity, and immunity to respiratory infections, while pointing out the need for larger studies.

Effect of hydralazine on vascular mechanics in a canine lobar preparation of pulmonary embolism

We studied the effect of hydralazine (H) on pulmonary vascular mechanics in an isolated, in situ, canine lobe model of normal and increased pulmonary vascular resistance (Rp) produced by Gelfoam embolization (GE). Pulmonary pressure-flow (P-Q) curves from 24 lobes were obtained at baseline and after each intervention. Hemodynamic parameters for analysis included: the mean critical closing pressure (Ppai), vascular conductance (1/Rp), lobar flow (QL), and the pulmonary inflow pressure (Ppa) at different levels (50, 100, 200, 400, and 600 ml/min) of a fixed flow. After the preparation was stabilized, the 24 lobes were classified into 2 groups. For group 1 (n = 8) we studied the effect of H on the normal pulmonary vasculature. In group 2 (n = 16) we studied the effect of GE. Following GE, this group was further divided in half. For group 2A (n = 8) we followed the natural history of GE with measurements at 15 and 60 min. For group 2B (n = 8) measurements were done 15 min after GE and repeated again 15 min after the infusion of H. For group 1 lobes, H promoted a significant decrease (p less than 0.001) in Ppa at fixed flows of 200, 400, and 600 ml/min compared to baseline, with no change in Ppa for flows below 100 ml/min. QL and 1/Rp increased (p less than 0.01), and there was not any significant change in Ppai. In group 2A lobes, GE produced an increase in Ppa at all levels of flow (p less than 0.01), QL and 1/Rp decreased (p less than 0.05), and there was an increase in Ppai (p less than 0.05). These changes remained stable over the 60 min of observation. For group 2B lobes, GE produced the same hemodynamic changes as in group 2A, and the infusion of H caused a decrease in Ppa at flows between 100 and 300 ml/min. (p less than 0.01) with no change in Ppa at flows below 100 ml/min. QL and 1/Rp increased (p less than 0.01) and Ppai did not change compared to 15 min after GE. We conclude that in the normal canine pulmonary vasculature as well as in the model of GE, H decreased Rp and did not affect mean critical closing pressure, all of which may be explained by an increase in vascular conductance due to an increase in vascular distensibility.

Left ventricular contractility is depressed in IgE-mediated anaphylactic shock in dogs

To determine whether myocardial dysfunction contributes to vascular collapse in anaphylactic shock, we examined left ventricular (LV) contractility, coronary blood flow, and myocardial lactate metabolism during antigen challenge in eight dogs that were sensitized to ragweed pollen extract (anaphylaxis group). Findings in the anaphylaxis group were contrasted to those in another group of dogs in which mean blood pressure was decreased to the same extent by arteriolar vasodilation with nitroprusside. The animals were examined under nonhypoxic conditions while anesthetized and ventilated. LV mechanics were examined with subendocardial crystals placed primarily along the anterior-posterior minor axis of the LV. During antigen challenge, a depression in LV contractility was observed in the anaphylaxis group as assessed by fractional dimensional shortening, stroke volume, and the slope of the end-systolic pressure-dimension relationship. During anaphylaxis, moreover, coronary vasodilation rather than coronary vasoconstriction was observed, and evidence of myocardial ischemia as assessed by altered myocardial lactate metabolism was not found. Our results indicate that depressed LV contractility occurs in anaphylactic shock. The results further suggest that the mechanism may be due to a direct effect of mediators of anaphylaxis on the myocardium to produce systolic dysfunction.

hemofiltration reverses left ventricular dysfunction during sepsis in dogs

Depressed left ventricular (LV) contractility in sepsis has been ascribed to the presence of circulating cardiodepressant substance (filterable cardiodepressant factor in sepsis [FCS]); however, this finding is controversial. The authors hypothesized that if a decrease in LV contractility indeed occurred due to a circulating depressant substance, then removal of this substance by hemofiltration would reverse by dysfunction. In this study, LV mechanics were examined before and after hemofiltration in anesthetized dogs during continuous intravenous infusion of live Escherichia coli. Left ventricular anterior-posterior and apex-base dimensions were measured by subendocardial ultrasonic crystal transducers implanted 4 weeks before the experiments. Left ventricular contractility was determined from the end-systolic pressure-dimension relationship. The slope of this relationship (Emax) is an index of contractility. After 4 h of sepsis, Emax was reduced by one half. Hemofiltration resulted in a return of Emax to control values. The FCS activity in the plasma was also assessed by the percent reduction in isometric contraction of electrically stimulated, isolated right ventricular trabeculae obtained from nonseptic dogs. The FCS activity reached a peak 4 h after sepsis and was reduced after 2 h of hemofiltration. The results show that during experimental sepsis, a circulating substance of less than 30,000 d produces a decrease in LV contractility and that this LV dysfunction may be improved by hemofiltration.

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone is an active transplacental carcinogen in Syrian golden hamsters

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent carcinogen in adult laboratory rodents. Our previous studies have shown that NNK crosses the placenta in pregnant hamsters and is metabolized into DNA-methylating and clastogenic intermediates by fetal respiratory tract tissues. Based on these findings, we have tested the transplacental carcinogenicity of NNK in this species. Groups of pregnant hamsters were given s.c. injections of single or multiple doses of NNK (cumulative dose range, 50-300 mg/kg) on day 15 (last day of gestation) or on days 13, 14, and 15 of gestation. Within 1 year after treatment, up to 70% of the offspring developed tumors in various organs, including respiratory tract, nasal cavity, adrenal glands, pancreas, and liver. No tumors were found in the control hamsters treated with the vehicle (trioctanoin) alone. The overall tumor incidence was proportional to the cumulative dose. Females had a generally higher tumor incidence than males.

[The effect of gelfoam embolism in vascular conduction and critical pressure in the isolated canine lobe]

Pulmonary pressure-flow curves, hemodynamic and blood gas parameters in West's zone II condition were obtained in nine isolated in situ left lower lobes (LLL) before (condition A), and after 15, 30 and 60 minutes of lobar gelfoam embolization (GE) (condition B) in order to know the natural history of this model. After GE a decrease in PaO2 and lobar O2 were noticed (p less than 0.05). Vascular conductance (p less than 0.001) and lobar blood flow decreased (p less than 0.05), accompanied by a significant increase in the inflow (p less than 0.01) and in the mean closing pressures (p less than 0.01). These parameters did not change during the time of observation at condition B. Nor the cardiac output or the minimal closing pressure changed in relation to condition A. LLL angiographic findings showed evidence of arterial occlusion and the pattern of obstruction was not homogeneous. Lobes histology showed occluded arteries of more than 300 micrometers of diameter. We concluded that in this canine model of increased pulmonary vascular resistance, pulmonary vascular conductance and mean closing pressure change, remain stable during 60 minutes after GE allowing us to know the natural history of the preparation. Condition than allow to perform and evaluate other interventions on lung vascular mechanics in the experimental setting of pulmonary embolization.

Pathobiology of lung tumors induced in hamsters by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and the modulating effect of hyperoxia

Neuroendocrine lung cancer is among the most common types of lung cancers in smokers. We have recently shown that exposure of hamsters to N-nitrosodiethylamine and hyperoxia causes a high incidence of this tumor type. In this study, we show that the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone also causes neuroendocrine lung tumors in hyperoxic hamsters. Animals maintained in ambient air while being treated with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone developed pulmonary adenomas composed of Clara cells and alveolar type II cells. Pathogenesis experiments provide evidence for the tumors caused by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in ambient air being derived from Clara cells. In the hyperoxic hamsters, the neuroendocrine carcinogenesis appears to involve two stages: (a) transformation of focal alveolar type II cells into neuroendocrine cells and (b) development of neuroendocrine lung tumors from such foci.

Successful chemotherapy of experimental neuroendocrine lung tumors in hamsters with an antagonist of Ca2+/calmodulin

The chemotherapeutic effect of B859-35, the (-)-enantiomer of dihydropyrine 3-methyl-5-3-(4,4-diphenyl-1-piperidinyl)-propyl-1,4-dihydro-2,6-dimethy l-4- (3-nitrophenyl)-pyridine-3,5-dicarboxylate-hydrochloride (niguldipine), was tested on tumors induced in Syrian golden hamsters by N-nitrosodiethylamine (DEN). Peripheral pulmonary adenomas/adenocarcinomas were induced in hamsters maintained under ambient air conditions by multiple s.c. injections of DEN for 20 weeks. We have reproducibly shown that within this time interval lung adenomas develop in a significant number of the animals. The carcinogen treatment was discontinued at this point and one group of these hamsters was given B859-35 intragastrically 5 days/week for 20 weeks while the second group of such tumor-bearing hamsters were kept for an identical time interval without further treatment. Neuroendocrine lung tumors were induced in hamsters maintained in an atmosphere of 60% O2 by multiple s.c. injections of DEN for 8 weeks. We have reproducibly shown that within this short time interval neuroendocrine lung tumors develop in a significant number of the animals. The carcinogen treatment was discontinued at this point and the animals were returned to ambient air conditions. One group of these tumor-bearing hamsters was then given B859-35 intragastrically 5 days/week for 20 weeks while a second group of these hamsters was kept untreated for an identical time interval. A control group was given s.c. injections of saline for 20 weeks under ambient air conditions. A dramatic and selective anticarcinogenic effect of B859-35 was observed on the neuroendocrine lung tumors and nasal cavity tumors induced by DEN/hyperoxia while tumors of larynx/trachea were not affected. B859-35 had no effect on peripheral adenomas/adenocarcinomas, nasal cavity tumors, papillary polyps of larynx/trachea, or liver tumors induced by DEN under ambient air conditions.

[Effects of venous segment pressure on the critical closure pressure, in the isolated lung lobe from dogs in situ]

In an isolated in situ canine left lower lobe preparation we studied the influence of the distal vascular compartment or venous pressure (PV) on the pressure of arterial vascular segment at zero flow or minimal critical closing pressure (MCCP), while alveolar pressure was held constant and below MCCP. The MCCP-PV curve showed an independent segment when PV was less than 8 mmHg. Above this value (that we define as PV), an slope of 1.08 was found. Our findings indicate that MCCP is not MCCP if PV greater than 8 mmHg (it is MCCP). Because MCCP is higher than alveolar pressure, MCCP must be the back pressure for flow. This finding is not in disagreement with the new concept regarding that MCCP is the back pressure for flow and not alveolar pressure in West's zone II condition.

[Effects of the chest wall and air volume on the perivascular pressure of the arterial segment. Study of the isolated canine lobule]

Ten isolated in situ canine left lower lobes (LLL) were studied in West zone II condition. In four dogs (group I) the chest wall surrounding the LLL was surgically removed, in the remaining dogs (group II) this procedure was not done. After basal parameters were obtained, minimal critical pressure (MCCP) was recorded and the influence of increasing alveolar pressure (PA) from o to 20 mmHg was noted. For group I lobes, PA value did not influence MCCP measurements, thus an independent relation between the pressures was found (delta MCCP/delta PA = 0). For group II lobes, when PA less than 6.8 +/- 2.1 mmHg also a delta MCCP/delta PA +/- was noted. Above this PA (PA1) a slope of 0.25 +/- 0.04 was documented for the delta MCCP/delta PA relationship. On the basis of our findings we conclude that MCCP is independent form PA. However if this relationship is studied in the isolated in situ LLL, at open chest with the condition of integrity of the chest wall when PA1 is applied the changes in MCCP are the result of the effect of lung inflation on the chest wall resulting in changes of the extravascular compliance (of the arterial segment) and is not due to a direct influence of PA on MCCP.