Specific fetometric formulas of ICC and BP for calculating the parturition date in the miniature breeds of canine.

The aim of this study was to derive the growth curves of the inner chorionic cavity and the biparietal distance in miniature dog breeds by ultrasonographic fetometry and present new specific formulas for prediction of parturition date. In this study, foetal biometry parameters were obtained using serial ultrasonographic examinations in 24 pregnant bitches of six different miniature breeds (≤5 kg). The mating time was unknown. Overall, 25 inner chorionic cavity diameter (ICC) and 22 biparietal diameter (BP) measurements were taken. The relationship between ICC or BP growth and days to parturition was analysed by linear regression. The results showed a significant relationship between days before delivery and ICC or BP. The equations derived from the growth curves can be used in practical prediction of parturition date in miniature dog breeds.

The effects of osaterone acetate on clinical signs and prostate volume in dogs with benign prostatic hyperplasia.

A clinical trial was performed to evaluate the therapeutic efficacy of osaterone acetate (OSA) in the treatment of benign prostatic hyperplasia (BPH) in dogs. Osaterone acetate (Ypozane, Virbac) was administered orally at a dose of 0.25 mg/kg body weight once a day for seven days to 23 dogs with BPH. During the 28-day trial, the dogs were monitored five times for their clinical signs and prostate volume. The OSA treatment promoted rapid reduction of clinical scores to 73.2% on day 7 and to 5.9% on day 28 (p⟨0.05). Osaterone acetate induced the complete clinical remission in approximately 83.0% of the dogs on day 28. The prostate volume regressed to 64.3% of the pretreatment volume after two weeks of the treatment (p⟨0.05) and to 54.7% at the end of the trial (p⟨0.05). In conclusion, OSA quickly reduced clinical signs and volume of the prostate glands in dogs with BPH.

CD4- and CD8-expressing cells found in the bovine and porcine anterior chamber of the eye.

The aim of the present study was to investigate whether the anterior chamber constitutes part of the normal migratory pathway of CD4+ and CD8+ lymphocytes in cattle and swine. The cells obtained from aqueous humor of cows and pigs were stained for CD4 and CD8 receptors, and subsequently analyzed with flow cytometry. The mean percentage of CD4+CD8-, CD4-CD8+ and CD4+CD8+ cells within the total lymphocyte population of the bovine anterior chamber was, respectively, 17.88, 12.64 and 27.26%. In turn, the mean values of these parameters in pigs were 1.77, 38.48 and 17.45, respectively. Among bovine and porcine CD4+CD8+ cells prevalent were those displaying CD4lowCD8low and CD4lowCD8high phenotypes, respectively. The results suggest that the anterior chamber in cattle and swine is an element in the normal migratory pathway of CD4+, CD8+ and CD4+CD8+ cells. Furthermore, the contribution of these subsets in the anterior chamber lymphocyte population can differ considerably between animal species.

Association of early protein intake and pre-peritoneal fat at five years of age: Follow-up of a randomized clinical trial.

BACKGROUND AND AIMS: The double-blind randomized European Childhood Obesity Project (CHOP) demonstrated that reduced protein content in infant formula leads to a lower body mass index (BMI) up to six years of age. Here we aimed at assessing pre-peritoneal fat, a marker of visceral fat, in children participating in the CHOP trial. METHODS AND RESULTS: Healthy term formula-fed infants in five European countries were randomized either to higher (n = 550) or lower (n = 540) protein formulas in the first year of life. Infants who were exclusively breastfed for at least three months (n = 588) were enrolled as an observational (non randomized) group. At age 5 years, subcutaneous fat (SC) and pre-peritoneal fat (PP) were measured by ultrasound in a subgroup of 275 children. The PP fat layer was thicker in the higher compared to the lower protein group (adjusted estimated difference: 0.058 cm, 95%CI 0.002; 0.115; p = 0.043), while SC fat was not different. Girls showed a thicker SC fat layer than boys. CONCLUSIONS: Higher protein intake in formula-fed infants appears to enhance pre-peritoneal fat tissue accumulation at the age of 5 years, but not of subcutaneous fat, which may trigger adverse metabolic and health consequences.

Detection of Pentatrichomonas hominis in dogs using real-time PCR.

Trichomonadidae family is a protozoan occurring in different animal species. It inhabits the gastrointestinal and urinary tracts. P. hominis is rarely found in faecal samples of dogs, and its identification and differentiation from other trichomonads by light microscopy are difficult. Methods of molecular biology are the most effective in this case, because they confirm the presence of the specific species in animal organisms, irrespective of the protozoan form. The aim of this study was to find P. hominis in selected dog kennels in North-Eastern Poland. Forty-one faecal samples of dogs from 7 dog kennels were examined. The occurrence of P. hominis in 5 faecal samples of dogs with no symptoms of diarrhoea was the first one to be confirmed in Poland.

Predicting the Parturition Date in Bitches of Different Body Weight by Ultrasonographic Measurements of Inner Chorionic Cavity Diameter and Biparietal Diameter.

Predicting the parturition date in dogs by taking ultrasonographic foetometry has opened interesting research areas of veterinary obstetrics. Recently developed calculation formulas of inner chorionic cavity diameter (ICC) and biparietal diameter (BP) are formulas by Luvoni and Grioni (2000). This study is one of the first reports referring to ICC and BP with the use of Luvoni and Grioni formulas for predicting the parturition time in dogs of different body weight in clinical practice conditions. The research material consists of 70 clinically healthy pregnant bitches of 27 breeds and cross-breeds. Bitches were divided into 4 groups according to their body weight. In each of the bitches, ultrasonographic examination of pregnancy was performed at least twice (ICC and BP measurements). Parturition dates for dogs with a body weight over 25 kg were calculated based on formulas intended for the group of medium dogs. It was caused by the lack of appropriate formulas for these groups of dogs. The predicting parturition dates were compared with the actual dates of delivery provided by the bitch owners. Generally, the results obtained in this study are very encouraging and similar or even better than those published by other authors using foetometric measurements. In our research, when comparing the effectiveness of predicting the delivery date based on foetometric formulas by Luvoni and Grioni (2000), it was proved that in all groups of dogs, even those over 25 kg, ICC and BP measurements at both accuracy levels were characterized similar reliability.

Bioserotypes and virulence markers of Y. enterocolitica strains isolated from roe deer (Capreolus capreolus) and red deer (Cervus elaphus).

Free-living animals are an important environmental reservoir of pathogens dangerous for other animal species and humans. One of those is Yersinia (Y.) enterocolitica, the causative agent of yersiniosis--foodborne, enzootic disease, significant for public health. The purpose of the study was to identify bioserotypes and virulence markers of Y enterocolitica strains isolated from roe deer (Capreolus capreolus) and red deer (Cervus elaphus) obtained during the 2010/2011 hunting season in north-eastern Poland. From among 48 rectal swabs obtained from 24 roe deer, two strains of Y enterocolitica from one animal were isolated. Although both belonged to biotype 1A they were identified as different serotypes. The strain obtained from cold culture (PSB) belonged to serotype 0:5, while the strain isolated from warm culture (ITC) was regarded as nonidentified (NI), what may suggest mixed infection in that animal. The presence of ystB gene, coding for YstB enterotoxin, directly related to Y enterocolitica pathogenicity was detected in both strains using triplex PCR. The effect of the examination of 32 swabs obtained from 16 red deer was the isolation of two Y enterocolitica strains from two different animals. Both belonged to biotype 1A with NI serotype, but were originated from different types of culture. They gave positive results in case of products of a size corresponding to the ystB gene. No amplicons corresponding to ail and ystA genes were found. Roe deer and red deer may carry and shed Y. enterocolitica, what seems to be important in aspect of an environmental reservoir of this pathogen. The Y enterocolitica strains isolated from wild ruminants had the amplicons of the ystB gene, what suggest they can be potential source of Y enterocolitica infection for humans.

Multidimensional Measurement of Attitudes Toward Consensual Non-Monogamy.

Despite increased interest in consensual non-monogamy (CNM), significant stigma remains against CNM. Consequently, there is a need for scales to assess attitudes toward CNM. In response to this need we developed the Multidimensional Attitudes toward CNM Scale (MACS). Items were developed in consultation with content experts and data were collected from two samples at two different Canadian Universities. Fit indices of exploratory (Sample A) and confirmatory (Sample B) factor analysis suggested a 16-item scale with three underlying factors: CNM is Dysfunctional, CNM is Immoral, and CNM is Healthy and Satisfying. Validity analyses, conducted using the combined sample (n = 806; 79% women; 67% heterosexual), demonstrated that participants with higher MACS total scores (i.e. more negative attitudes) were less likely to have ever been involved in a CNM relationship and were more likely to report monogamy as their ideal relationship style. Higher MACS scores were also associated with more negative attitudes toward bisexuality and toward women, and higher scores on measures of homophobia and jealousy. In contrast, individuals with higher scores on the CNM is Healthy subscale tended to score higher on measures of empathy. The MACS demonstrates strong psychometric properties and can assist in better understanding attitudes toward CNM relationships in research and clinical settings.

The application of circulating tumor cells detecting methods in veterinary oncology.

Cancers are one of the most common diseases affecting dogs. Many of them develop spontaneously and their biology and histopathology shows many similarities to human cancers. What more, it is proved that there are much more analogies in molecular mechanisms of cancer development between these two species. Human oncology is seeking more and more efficient methods for an early disease detection which results directly in the extended life expectancy of patients affected. One of the most modern trends in the diagnosis of cancer is to detect circulating tumor cells (CTC) in the blood of patients. It is known that these cells are responsible for the formation of metastases in distant organs what results in the patient death. Moreover, it's confirmed that CTC are already present in patients' bloodstream in the early stages of tumor development. There is no doubt that mechanism of metastasis development in dogs is identical and thus the CTC are also present in their bloodstream. Despite the intense researches there is still no optimal method of isolating cancer cells from the blood where they occur extremely rarely. The purpose of this study is to analyze the implications of the detection methods of tumor cells in the blood in veterinary oncology.

Vaginal aerobic bacteria of healthy bitches and those with fertility problems.

The most common problems in veterinary practice in bitches are bacterial infections of the reproductive tract associated with fertility problems. Research to determine the correlation between the health status of female dogs and bacterial flora of the genital tract has been ongoing for years, but the results obtained by different authors are often contradictory, and do not always concern breeding bitches. Our study identified the most common aerobic bacteria in the genital tract of numerous breeding bitches population. A total of 275 breeding dogs in anestrous phase of the estrous cycle were included in this study. 198 were qualified to the first group with no genital tract infections and no reproductive disorders. 68 bitches were qualified to the second group with complications such as: infertility, abortion, foetus resorptions and newborn mortality. The type of bacterial isolates was almost the same in the healthy bitches and the group with fertility problems. The most common bacteria obtained from the vaginal tract of the tested dogs were Streptococcus spp., Staphylococcus spp., Mycoplasma canis and Escherichia coli. There were no significant differences in bacterial prevalence in the group with reproductive problems versus healthy dogs; however, we found a statistically significant difference between both groups when the numbers of bacterial strains were compared. The number of one-strain bitches was statistically higher in the problematic group than in the non-problematic one. Bacterial culturing of vaginal swab specimens from breeding bitches without clinical signs of genital disease is of little value. Furthermore, it should always be preceded by an examination (clinical, cytological or vaginoscopy etc.). The request or requirement to perform vaginal cultures that is made by some breeders, while common, is not diagnostic for any pathologic condition and the results of these cultures should never be used to determine if antibiotic therapy is indicated.

Effectiveness of determining the parturition date in bitches using the ultrasonographic fetometry as compared to hormonal and cytological methods.

In clinical practice, the parturition date in bitches is calculated on the basis of the established ovulation date, using determination of the level of LH and P4. Additionally cytological examination of vaginal smears makes it possible to establish the onset of diestrus, from which the delivery occurs after about 57 days. The latest method used in bitches for this purpose is foetal biometry. Measurements of the inner chorionic cavity diameter (ICC) and biparietal diameter (BP) with formulas published by Luvoni and Grioni have been popularized and the most practically useful. In a group of six bitches the effectiveness obtained with the use of ICC was 66.67% with an accuracy of 1 day and 100% with an accuracy of 2 days. BP measurements gave better results, as the accuracy was respectively 83.33% and 100%. The effectiveness of predicting the delivery date on the base of method consisting in determining the LH surge was 66.67% with an accuracy of 1 day and 100% with an accuracy of 2 days. The best effectiveness was obtained while using the method based on P4 level determination (100% both with an accuracy of 1 day, as well as of 2 days). The lowest accuracy was obtained while using the cytological method. Generally, a comparison of the methods used for predicting the date of delivery in bitches confirms practical usefulness of fetometry. Its effectiveness was not lower than traditional methods used so far, while its advantage lies in the ease of performance and the long term of application during gestation. However, full confirmation of the practical usefulness of this method requires further research on a larger number of animals.

Obstetric and newborn parameters in the Maine Coon cats.

The aim of this study was to determine several obstetric and neonatal parameters in the Maine Coon breed. The birth data of Maine Coon breeding population were collected of 52 litters from different households using a questionnaire. Significant relationships between various outcomes and the relevant predictors were assessed by multiple linear regression or logistic regression, as appropriate. The overall mean gestation length was 65.5±1.32 days. Larger litter size was associated with shorter gestation lengths (p⟨0.01). Mean litter size was 5.3±2.3 kittens. The weight of kittens born alive (overall mean 119.6±18.4 g) increased with prolonged gestation lengths (p⟨0.01) and decreased with larger litter sizes (p⟨0.01). In the analyzed group of kittens, 12.5% were stillborn. The expulsion intervals varied widely. The duration of the first stage of labour was less than 2h in 82.9% of the cats. The interval between the birth of the first and the last kitten was less than 6h in 99.3% of the cats, and it exceeded 6 h in only 2 cats. The present results can be used to develop references values and reliable assistance protocol for assessing the parturition in the Maine Coon to protect the queen and reduce perinatal losses.

Pathogenic potential to humans of Shiga toxin-producing Escherichia coli isolated from wild boars in Poland.

The aim of the study was to investigate the presence of Shiga toxin-producing Escherichia coli (STEC) in the wild boar population of north-eastern Poland, and to evaluate the potential health risk associated with wild boars carrying STEC/AE-STEC strains. In Poland, the African Swine Fever (ASF) virus has been a growing problem in domestic pigs and wild boars, one of the main reservoirs of the virus, because of this hunters, veterinary practitioners and foresters thus face a greater risk of coming into contact with animals. Rectal swabs samples were obtained from 152 wild boars hunter-harvested in the 2017/2018 season (autumn-winter) in north-eastern Poland. The samples were enrichment in modified buffered peptone water. Polymerase chain reaction (PCR) assays were conducted to determine the virulence profile of stx1, stx2 and eae and aggR genes, identify subtypes of stx1 and stx2 genes, and perform O and H serotyping. STEC/AE-STEC virulence genes were detected in 43 isolates (28.29%): STEC in 17 isolates (11.18%) and AE-STEC in 26 isolates (17.11%), respectively. None of the tested isolates carried the aggR gene. The most dangerous AE-STEC virulence profile associated with HUS was found in 2 isolates (1.32%): stx1NS/stx2a/d/eae serotype ONT:H7 and stx2a/eae serotype O146:H7. Six of the 152 tested samples belonged to serogroup O157 (3.95%), including one AE-STEC isolate with virulence profile stx2g/eae and five EPEC isolates. The results of this study suggest that wild boars in north-eastern Poland can carry STEC/AE-STEC strains that are potentially pathogenic for humans. This is the first report documenting the virulence of STEC and AE-STEC isolates from wild boars in Poland.

Good and bad prognosis of alpha-1-antitrypsin deficiency in children: when to list for liver transplantation.

Alpha1-antitrypsin deficiency (alpha1-ATD) is a genetic disorder that may predispose to chronic liver disease. The clinical manifestations and prognosis of this disorder are variable. The aim of the study was to evaluate the clinical presentation and liver tests in two groups of children with alpha1-ATD: those with a good prognosis who survived long term with their native liver, and those with a bad one, requiring liver transplantation (OLT) or dying before OLT. We studied 59 children homozygous for alpha1-ATD admitted to our hospital with cholestasis or chronic hepatitis since infancy. Patients without liver transplantation were regarded to be the good prognosis group I (n=45). In contrast the 11 children who required liver transplantation and the three who died before OLT were the bad prognosis cohort (Group II, n=14). We analyzed the laboratory parameters of cholestasis, hepatitis, and liver insufficiency in both groups. In the group with a good prognosis, eight children still suffered from cholestasis at the ages of 9 to 14 years while nine had hepatitis at the ages of 9 to 14 years. We observed a temporarily increased international normalized ratio (1.2 to 1.5) in eight subjects at the ages of 1 month to 17 years, and slight hypoalbuminemia (30 to 35 mg/dL) in nine children at the ages of 1 month to 10 years. OLT was performed in 11 children at the ages of 10 to 17 years. Our center's experience suggested that in the PiZZ patients with portal hypertension, esophageal varices, or deterioration of hepatic function, liver transplantation should not be delayed.

Lipid, carbohydrate metabolism, and antioxidant status in children after liver transplantation.

Organ transplantation is a risk factor for atherogenesis that may be related to immunosuppressive therapy. Increased free radical generation may even aggravate atherogenesis. The aim of the study was to assess lipid metabolism in relation to risk factors for atherogenesis as well as carbohydrate metabolism and antioxidant status among children after liver transplantation. We studied 35 children at 3 to 5 years after liver transplant in whom the following parameters were assessed: total cholesterol; triglyceride; high-density lipoprotein cholesterol; low-density lipoprotein cholesterol (LDL-C); very low-density lipoprotein cholesterol; apolipoproteins B, AI, E, lipoprotein (a); vitamin E; glutathione; glucose; insulin; and glutathione peroxidase activity. Three subgroups of patients were assessed according to the immunosuppressive therapy: cyclosporine (CsA), tacrolimus (Tac), or mycophenolate mofetil (MMF) in combination with low-dose CsA or Tac. We observed differences among the subgroups only in total cholesterol (CsA: 131.6 to 285.6; Tac: 144.0 to 181.61; MMF: 132.1 to 181.2) and LDL-C (CsA: 79.4 to 126.9; Tac: 42.2 to 118.8; MMF: 74.2 to 117.3). Lipid metabolism was not significantly disturbed among children after liver transplantation, an observation that does not point to a high risk of atherogenesis. CsA seems to have the strongest untoward effect on cholesterol metabolism. Decreased GSH concentration after liver transplantation may be related to slightly impaired liver function, but GPx activity and vitamin E concentrations remained normal.

Liver Transplantation in Polish Children With α1-Antitrypsin Deficiency: A Single-Center Experience.

BACKGROUND: α1-Antitrypsin deficiency (ATD) is the most common genetic cause of liver injury in young children. Asymptomatic hepatitis is observed in most patients. However, the course of liver disease due to ATD is unpredictable, and some children develop liver cirrhosis. Liver transplantation (Ltx) dramatically improves their outcome and in some cases is required in the first years of life. The aim of the study was to evaluate the course of the disease in children with ATD treated with Ltx in a single center. METHODS: We retrospectively reviewed the clinical features (ascites, esophageal varices, esophageal bleeding) and laboratory parameters of liver function in children with ATD who were treated with Ltx. RESULTS: Twenty-two Ltxs were performed in 20 children (13 boys, 7 girls). Median age at transplantation was 12 years (range 0.5 to 17.1). Four children were transplanted in the first 2 years of life and 16 patients were over 7 years old. The indications for Ltx in younger children were progressive cholestasis with coagulopathy and ascites. In older patients, the indications were as follows: liver failure presenting with variceal bleeding in 7 patients, ascites in 5 patients, hypersplenism in all but 1 patient. In the group of children transplanted over 7 years old, the frequency of cholestasis decreased intermittently in the second year of life: 4 patients (25%) compared to 15 patients (94%) and 10 patients (63%) in the neonatal and pretransplant period, respectively. In the group of children transplanted earlier, cholestasis and hepatitis were maintained until Ltx. Of transplanted patients, 50% were malnourished at the transplantation, and 50% were followed for more than 10 years. Five-year post-transplant survival was 100% (n = 14), and 10-year survival was 90%. Two patients died as adults with biliary post-transplant complications and problems with compliance. CONCLUSIONS: Our experience suggests that transient normalization of liver parameters in some patients with ATD do not exclude the liver disease progression to cirrhosis and unfavorable outcome of liver disease in childhood. In our group of patients, median age at transplantation was high compared to other centers. The long-term prognosis in children after transplantation is very good, but early post-transplant complications and probable problems with compliance in young adults may lead to graft failure.

Challenges and opportunities in Pan-European collaboration for researchers from Central and Eastern Europe.

Ten Central and Eastern [NLG4] European countries have recently joined the European Union. This historical enlargement provided a good opportunity to discuss the challenges and opportunities in Pan-European Research Collaboration for researchers from Central/Eastern Europe. This paper summarises examples of productive research collaboration between East and West, current challenges [NLG5], and ideas on how to facilitate better collaboration. A short overview of training, mobility and career development opportunities, covered by the Marie Curie actions, is also presented.

The role of toll-like receptors 2 and 4 in the pathogenesis of feline pyometra.

Pyometra is the most common uterine disease in queens. To protect itself from infection, the female reproductive tract possesses several immune mechanisms that are based on germline-encoded pattern recognition receptors (toll-like receptors [TLRs]). The aim of our study was to examine endometrial immunolocalization of TLR2/4, study the influence of lipopolysaccharide (LPS) and tumor necrosis factor (TNF) α on messenger RNA expression of both receptors in pyometric queens, and compare these patterns between estrous cycling queens and those hormonally treated with medroxyprogesterone acetate (MPA). Thirty-six queens, ranging in age from 7 months to 11 years, were allocated into seven groups (anestrus, estrus, mid-diestrus and late diestrus, short-term and long-term hormonally treated queens, and pyometric queens). At the messenger RNA level, the real-time polymerase chain reaction was applied, whereas at the TLR2/4 protein level, the expression was tested by immunohistochemistry. In queens at estrus, gene expression of TLR2 was upregulated after stimulation of endometrial explants by TNF (P < 0.001) and by TNF together with the LPS (P < 0.01). Moreover, gene expression of TLR2 was significantly upregulated after stimulation by TNF (P < 0.001) and LPS (P < 0.01) explants derived from queens that had been long-term hormonally treated with MPA. Endometrial gene expression of TLR4 was significantly upregulated after incubation of explants with TNF (P < 0.001) in queens at estrus and with LPS (P < 0.05) in queens short-term hormonally treated with MPA. Immunolocalization reported that TLR2/4 receptors are mainly localized in the surface and glandular epithelia. These data show that short-term and especially long-term administration of progesterone derivatives impairs TLRs in the endometrial epithelium, presumably enabling pathogens to break through this first natural barrier and thereby increase the risk of pyometra development.

Deficiency of the expression of CD45RA isoform of CD45 common leukocyte antigen in CD4+ T lymphocytes in children with infantile cholestasis.

The immunological background of the pathological changes that appear in infantile cholestasis (infections, inflammatory process in the liver) is largely unknown. With the use of double color flow cytometry, we assessed the distribution of functionally different lymphocyte subpopulations in the peripheral blood of 29 infants with extra and intra-hepatic cholestasis (12 and 17 patients, respectively), aged from 1 to 8.6 months. Control group consisted of 15 age-matched, healthy infants. We examined: (1) the expression of CD3, CD4, CD8, CD19 lymphocyte surface receptors; and (2) the distribution of lymphocyte subsets with distinctive surface Ag characteristics of 'naive' (CD45RA+) and 'memory' (CD45RO+) cells in both CD4+ and CD8+ cell populations. The surface markers expression was evaluated in terms of percentage of positive cells and receptor density. The following changes in the expression of lymphocyte surface markers are described: (1) a decrease in the percentage of total CD3+, CD4+ cells but normal percentage of CD8+ cells and elevated proportion of CD19+ B cells; (2) a reduction of the proportion of 'naive' CD4+ lymphocytes but normal percentage of 'naive' CD8+ as well as 'memory' CD4+ and CD8+ cell subsets; (3) a decrease in density of CD3, CD4+, CD8 receptors, and D45RA isoform in a subset of 'naive' CD4+ cells. We conclude that deficiency of 'naive' CD4+ T cell subset which possess important effector and immunoregulatory functions, and low expression of certain lymphocyte receptors known to be engaged in T cell activation, possibly reflect a defect of cell mediated immunity that may account for viral and bacterial infections, often observed in infants with cholestasis.

Effect of flow direction on collateral ventilation in excised dog lung lobes.

We determined the effect of flow direction on the relationship between driving pressure and gas flow through a collaterally ventilating lung segment in excised cranial and caudal dog lung lobes. He, N2, and SF6 were passed through the lung segment distal to a catheter wedged in a peripheral airway. Gases were pushed through the segment by raising segment pressure (Ps) relative to airway opening pressure (Pao) and pulled from the segment by ventilating the lobe with the test gas, then lowering Ps relative to Pao. Driving pressures (Ps - Pao) between 0.25 and 2 cmH2O were evaluated at Pao values of 5, 10, and 15 cmH2O. Results were similar in cranial and caudal lobes. Flow increased as Ps - Pao increased and was greatest at Pao = 15 cmH2O for the least-dense gas (He). Although flow direction was not a significant first-order effect, there was significant interaction between volume, driving pressure, and flow direction. Dimensional analysis suggested that, although flow direction had no effect at Pao = 10 and 15 cmH2O, at Pao = 5 cmH2O, raising Ps relative to Pao increased the characteristic dimension of the flow pathways, and reducing Ps relative to Pao reduced the dimension. These data suggest that at large lobe volumes, airways (including collateral pathways) within the segment are maximally dilated and the stiffness of the parenchyma prevents any significant distortion when Ps is altered. At low lobe volumes, these pathways are affected by changes in transmural pressure due to the increased airway and parenchymal compliance.