The recombinant 23-kDa N-terminal fragment of bactericidal/permeability-increasing protein (rBPI23) decreases Escherichia coli-induced mortality and organ injury during immunosuppression-related neutropenia.

Cyclophosphamide-induced neutropenia exacerbates septic shock and multiple organ injury in conscious rats during Escherichia coli (EC) bacteremia despite antibiotics and fluid administration. We hypothesized that such shock and inflammatory organ injury would be mitigated by rBPI23's microbicidal activity and/or binding of EC endotoxins. Four days after 100 mg cyclophosphamide/kg, catheterized rats with < 300 PMNs/microL were pretreated with rBPI23 or the irrelevant 22 kDa protein thaumatin [3.3-6.6 mg/kg, i.v. in 0.9% NaCl (NS)] 5 min before graded i.v. infection with 5 x 10(9) or 1 x 10(10) cfu of EC serotype 055:B5 ending at t = 0. Posttreatment with each protein continued (3.3-6.6 mg/kg in 1 mL NS/h) through 8 h, in addition to penicillin plus amikacin sulfate at t = 1.5 and 8 h. Arterial samples were obtained before pretreatment and at t = 1.5, 4.5, 8, and 24 h when animals were necropsied. One of eight thaumatin + 5 x 10(9) EC rats and none of six thaumatin + 10(10) EC rats survived 24 h. In contrast, rBPI23 significantly reduced mortality after either inoculum, improved bacterial clearance, and led to renormalization of early EC-induced hypotension, hypothermia, tachypnea, hyperoxemia, and hypocarbia. Compared with thaumatin, however, rBPI23 did not reduce circulating endotoxin or bioactive and antigenic tumor necrosis factor-alpha. Sepsis-induced severe neutropenia (< 50 PMNs/microL) evident in all EC rats by t = 1.5 h was reversed with rBPI23 by t = 8 h, but thrombocytopenia (< 5 x 10(4) platelets/microL) evident in all groups by t = 4.5 h was not altered.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute lung injury during bacterial or fungal sepsis.

We compared physiological and ultrastructural indices of acute lung injury (ALI) during septic shock caused by taxonomically diverse pathogens to distinguish ALI due to endogenous inflammatory mediators vs. microbial exotoxins or other factors. Conscious rats were infected i.v. with gram-negative Escherichia coli (EC, serotype 055:B5), exotoxin-C producing gram-positive Staphylococcus aureus (SA), or yeast-phase Candida albicans (CA, a clinical isolate). Viable inocula of 10(10) EC, 10(10) SA, or 10(9) CA caused lethal shock in < 24 h, but distinct types of ALI were noted after bacteria vs. fungi. Within 0.5 h of EC infection, leukocytes marginated in the lung vasculature; by death at 6-14 h, animals were hyperoxemic but not acidemic, and showed slight interstitial edema with increased wet/dry weight ratios (W/D = 5.22 +/- 0.10, mean +/- SE, vs. 4.86 +/- 0.07 in controls, P < 0.05). Similarly mild ALI occurred after 10(10) SA. In contrast, within 0.5 h of CA infection, yeast were visible within lung intravascular leukocytes. By death at 6-12 h, CA animals showed hyperoxic acidemia and moderate ALI with capillary obstruction, interstitial hemorrhage, and elevated lung W/D (5.52 +/- 0.13, P < 0.01 vs. controls) associated with yeast-mycelial transformation. Prior neutropenia accelerated mortality and worsened ALI after CA, with hypoxemic acidemia, increased lung W/D (7.23 +/- 0.34, P < 0.05 vs. other groups), capillary occlusion, perivascular and alveolar hemorrhage, and septal disruption by mycelia. Bacteremia induced large increases in serum tumor necrosis factor-alpha (TNF) and interleukin-1 alpha within 1.5 h, but these cytokines remained low in CA animals, even at death. Neither survival nor ALI after EC or CA was altered by pentoxifylline, which attentuated TNF production, or by cyclooxygenase inhibition with ibuprofen. Thus, overall ALI severity correlated with physiological indices of pulmonary function, but ultrastructural changes correlated better with pathogen type than circulating cytokine or eicosanoid mediators. Whereas lethal bacteremia induced early cytokinemia and mild ALI with or without bacterial exotoxins, moderate ALI apparently was mediated by fungal exotoxins during lethal candidemia, which worsened during neutropenia due to enhanced mycelial proliferation.

Lung mechanics, cellularity, and surfactant after prenatal starvation in guinea pigs.

Prenatal starvation in the guinea pig causes reduced pulmonary diffusing capacity and retarded alveolarization among neonates. To study the impact of such starvation on biochemical and mechanical properties of the neonatal lung, pregnant guinea pigs were fed ad libitum throughout gestation or starved with 50% rations during their last trimester. Neonatal body weight was 35% less due to starvation, and dry lung weight, DNA, and protein contents were decreased 26, 36, and 31%, respectively (P less than 0.001 for all). Hematological data indicated no anemia, hypoproteinemia, or altered glucocorticoid levels due to starvation. Total surfactant phospholipids in these neonates were reduced 61% in lavage and 35% in the neonatal lung tissue, although surfactant compositions were similar to controls. Specific lung compliance in the air-filled lungs was not altered, but the saline-filled lungs were more distensible over deflation pressures of 9-18 cmH2O (transpulmonary). Although starvation retarded both lung cellularity and surfactant, only that portion of lung elastic recoil attributable to tissue forces was affected.

TNF-alpha and cyclooxygenase metabolites do not modulate C. albicans septic shock with disseminated candidiasis.

We analyzed differences in host regulation of tumor necrosis factor-alpha (TNF-alpha) production and pathophysiological responses in conscious rats after infection with two strains of pathogenic Candida albicans spp. (CA-1 and CA-2) compared with Escherichia coli serotype 055:B5 (EC). The hypothesis was tested that, in contrast to EC, hypotension, organ injury, and mortality after candidemia are not obligatorily dependent on TNF-alpha or TNF-alpha-induced cyclooxygenase pathway metabolites. Dose, viability, and strain-specific dependencies were established after intravenous 10(6) or 10(9) viable CA, as well as heat-killed (HK) or Formalin-inactivated (FI) CA blastospores, compared with live EC at the 24-h LD25 [10(9) colony-forming units (CFU)] and LD100 (10(10) CFU). Shock without endotoxemia developed 4-8 h after 10(9) live CA-1 or CA-2 (LD100 at 24 h) with disseminated yeast-mycelial transformation and increased microvascular permeability in multiple organs but not after HK or FI CA-1. Peak serum TNF-alpha after an LD100 of CA-1 or CA-2 was < 3% of LD25 EC values and was < 1% of peak values during lethal bacteremia. Similar pathogen-specific differences were found in liver- and lung-associated TNF. Production of functionally inactive TNF-alpha during candidemia was excluded by enzyme-linked immunosorbent assay and sodium dodecyl sulfate-polyacrylamide gel electrophoresis with Western blotting. Passive immunization against TNF-alpha 2 h before microbial challenge was not protective against CA but prevented otherwise lethal EC sepsis. Cyclooxygenase inhibition also failed to attenuate candidemic shock. We conclude that the magnitude and kinetics of TNF-alpha production and TNF-alpha-dependent immunophysiological responses are differentially regulated after lethal fungal vs. gram-negative bacterial infection. Thus TNF-alpha is not a pivotal mediator of the acute Candida septic shock syndrome with disseminated candidiasis.

A recombinant tumor necrosis factor-alpha p80 receptor:Fc fusion protein decreases circulating bioactive tumor necrosis factor-alpha but not lung injury or mortality during immunosuppression-related gram-negative bacteremia.

PURPOSE: During gram-negative bacteremia (GNB), tumor necrosis factor-alpha (TNF-alpha) is a critical early mediator of host defense, whose overexpression can initiate acute lung injury, multiple organ failure, and death. In this study we evaluated the ability of a chimeric fusion protein containing two extracellular domains of the human p80 TNF-alpha receptor and the Fc region of human IgG1 (TNFR:Fc) to reduce circulating TNF-alpha, and to ameliorate organ injury and improve survival in a rodent model of GNB during immunosuppression-related neutropenia. MATERIALS AND METHODS: Conscious catheterized male rats (n = 37) with stable cyclophosphamide-induced neutropenia were infected intravenously (i.v.) with 5 x 10(9) live Escherichia coli (EC, serotype O55:B5) ending at t = 0. All animals received antibiotics (penicillin/ amikacin sulfate) at t = 0.5 and t = 8 hours, and 0.9% sodium chloride (normal saline solution (NS), 1 mL/h) from t = 0 to 8 hours. Subgroups were post-treated at t = 0.5 hours with a 1.0 mL i.v. dose of TNFR:Fc (60, 600, or 1,200 micrograms; Immunex), 600 micrograms of human IgG1-kappa or IgG1-lambda (Sigma), or NS alone (controls). A separate TNFR:Fc pretreatment subgroup received 600 micrograms/rat of the fusion protein 5 minutes before starting EC infusion. Hemodynamics were monitored continuously through t = 24 hours, and arterial samples were collected at baseline and at t = 1.5, 4.5, 8, and 24 hours after EC were analyzed for blood gases, quantitative culture, serum endotoxin, bioactive and antigenic TNF-alpha, and formed elements. Postmortem tissues were examined for histopathologic changes. RESULTS: Compared with antibiotic-treated and fluid-supported controls, TNFR:Fc dose-dependently reduced bioactive but not antigenic TNF-alpha without altering bacterial clearance, serum endotoxin, or 24-hour survival. Of note, 600 micrograms of IgG1-kappa or IgG1-lambda attenuated peak bioactive TNF-alpha to a similar degree as 1,200 micrograms TNFR:Fc, and also significantly reduced serum endotoxin levels. Nevertheless, by t = 8 hours all bacteremic rats were hypothermic with tachypnea-related hypocarbia and hyperoxemia and were thrombocytopenic. At death, all subgroups showed similar hepatic glycogen depletion and pulmonary congestion with perivascular edema and alveolar hemorrhage. CONCLUSIONS: Although TNFR:Fc and its idiotypic control IgG1 reduced circulating bioactive TNF-alpha, neither treatment prevented progression of lethal shock with attendant organ injury in this conscious, antibiotic-treated and fluid-resuscitated model of immunosuppression-related GNB.

Interaction of prenatal starvation and dexamethasone treatment on lung development in newborn guinea pigs.

Prenatal starvation causes pulmonary hypoplasia, retarded alveolarization, and reduced surfactant production in newborn guinea pigs. This study examined the potential benefit of simultaneous transplacental dexamethasone, which accelerates fetal lung maturation in other species. Pregnant guinea pigs were placed in 1 of 4 groups: Control (C), fed ad libitum until term (67 days) and given daily saline injections from Day 55 of gestation until term; Dexamethasone (D), fed as Group C but given daily injections of 2.0 mg dexamethasone/kg BW from Day 55 until term; Starved (S), given 50% rations from Day 45 until term and injected as Group C; Starved + Dexamethasone (SD), fed as Group S and injected as Group D. Controls and Group D did not differ in body or lung weight, DNA, protein, or lung volume (VL), but Group D lungs contained more lavageable and tissue surfactant, total alveolar surface area (Sa), and membrane diffusing capacity (DmO2) because of increased alveolar surface density. The S neonates weighed 38% less than controls, with proportional reductions in lung weight, DNA, protein, lavage and tissue phospholipids, VL, Sa septal tissue, capillary surface area (Sc), and DmO2. Compared with these S neonates, the SD neonates did not differ for BW, lung weight, DNA, protein, phospholipids, or VL, but their lungs contained significantly more Sa, Sc, epithelial and endothelial tissue volumes, and a higher alveolar surface density. These differences resulted in an average DmO2 for SD neonates that was indistinguishable from that of controls, and correlated with greater viability among the smallest SD animals compared with those in Group S.(ABSTRACT TRUNCATED AT 250 WORDS)

Perinatal age determines the severity of retarded lung development induced by starvation.

Susceptibility of the lung to caloric restriction is age-dependent, with more permanent damage occurring during the phases of growth and differentiation. Because the guinea pig is born with more well-developed alveoli than are other rodents, the postnatal lung of this species may better resist alveolar hypoplasia than the prenatal lung. Control animals were raised from sows provided food ad libitum during and after normal gestations (66 to 68 days). Starvation groups received 50% rations of control food intakes during 1 of three 21-day periods: prenatal starvation, with sows rationed during their last trimester (Day 45 to term); neonatal starvation, with nursing sows rationed during the 21 days postpartum before weaning; weanling starvation, with animals starved from 21 to 42 days postpartum. Lungs were fixed in situ with glutaraldehyde and analyzed for pulmonary morphometrics. At the end of starvation and before refeeding, lungs of prenatal and weanling starvation groups were significantly reduced for tissue volumes, alveolar and capillary surface areas, and pulmonary diffusing capacity. Recovery with feeding was complete for most parameters in the starved weanlings by maturity, but animals starved prenatally showed residual starvation effects as adults. The neonatally starved animals showed minimal effects of starvation on lung dimensions, both acutely and as adults. Morphologically, the lungs of some prenatally starved neonates were apparently retarded, at least to the saccular phase, and correlated with significant increases in the number of stillborn litters and in neonatal mortality within hours of parturition.

Pulmonary design in a microchiropteran bat (Pipistrellus subflavus) during hibernation.

The Eastern pipistrelle (Pipistrellus subflavus) is typical of exceptionally small bats capable of a 30-fold range in aerobic metabolism as they arouse from hypothermia and sustain foraging flight. This report describes their basic lung structure and the extent to which this organ is protected from protein depletion during hibernation. Bats were collected at the beginning (Fall), middle (Winter), and end (Spring) of hibernation from a permanent overwintering cave, and analyzed within several days of capture. Regardless of whether bats were examined in the Fall (average body weight = 6.22 g) or in the Spring (4.58 g) no significant differences existed for total lung volume (237 microliter), alveolar surface area (338 cm2), harmonic mean septal thickness, tau ht (0.221 micron), or membrane diffusing capacity (4.13 microliter O2/sec/mbar). These parameters exceed predictions based on body weights for either season, and resemble published data for another highly active mammalian group, the insectivorous shrews. Both tau ht and the minimal septal thickness of 0.083 micron approach the anatomical limits for thinning of alveolar septa without loss of epithelial continuity. Although both the heart and lungs lost 13% of their fresh weights during hibernation, compared to 25% for the liver, the lung contents of DNA (0.14 mg) and blood-free protein (7.38 mg) were not altered significantly. These small bats possess lungs which are well suited for the high aerobic cost of flight. Those lungs are resistant to hibernation-induced proteolysis, and also resistant to the deterioration of alveolar membranes which occurs in nonhibernators subjected to starvation-induced weight losses of similar magnitude.

Starvation-induced organ hypoplasia in prenatal and postnatal guinea pigs.

The severity and permanence of growth retardation was measured in guinea pigs starved for 3 weeks with a 50% ration in late gestation (prenatal), at birth (neonatal), or at weaning. Acute and chronic effects were assessed as body mass, skeletal length, hematology, and the weight, DNA and protein contents of the hearts, the lungs, and the livers of the starved and refed animals. Organ hypoplasia was most pronounced in the prenatally starved group, and was associated with numerous stillbirths. Among survivors, catch-up growth was eventually complete. Prenatal starvation of this species provides a reproducible model of human intrauterine growth retardation, particularly of the pulmonary system.

Respiratory adaptations in burrowing pocket gophers from sea level and high altitude.

To examine the adaptations to low O2 and high CO2 among fossorial and nonfossorial rodents, hematological parameters were determined for laboratory rats, the valley pocket gopher (Thomomys bottae) from 250 m, and the mountain pocket gopher (T. umbrinus melanotis) from 3150 m. Hematocrit, hemoglobin concentration, and O2 capacity were higher in pocket gophers than in rats. Blood PO2 at 50% saturation and pH 7.4 was 33 mmHg for both gophers and 39 mmHg for rats. Bohr factors for all three rodents were similar (-0.55 to -0.61) but buffer value, delta log PCO2/delta pH, was -2.54 for T. umbrinus, -1.97 for T. bottae, and -0.98 for Rattus. Concentrations of total acid-soluble phosphates were 50-75% higher in gophers than in rats, while bicarbonate values were within the normal mammalian range. All three rodents had similar myoglobin concentrations in cardiac muscle. Myoglobin concentrations were significantly higher in skeletal muscles (diaphragm, gastrocnemius) of T. umbrinus when compared to T. bottae, and significantly higher in both gophers when compared to rats. These differences may constitute important adaptations to the hypoxia and hypercapnia in burrows; certain of these factors in pocket gophers respond to the additional stress of high altitude hypoxia.

The scaling of maximal oxygen consumption and pulmonary dimensions in small mammals.

This report has reexamined the relationship between standard and maximal rates of oxygen consumption (VO2std and VO2max) and pulmonary surface area in mammals whose weights extend over the lower half of the total log weight range in mammals. For combined groups of wild and laboratory animals with body weights of 2--3700 g, the following equations pertain: VO2std (ml . min-1) = 0.0602 . W0.727; VO2std, or the factorial aerobic scope, is nearly constant over this weight range at approximately 6.6 (range 5.8--7.1). In view of this finding, earlier studies relating SA or pulmonary diffusion capacity to VO2std are still appropriate models for pulmonary constraints on metabolic rate. The data summarized here suggest that, at least for wild species of mammals, pulmonary diffusion capacity may limit VO2max.

Electrophoretic characterization of the hemoglobins in pocket gophers of the genus Thomomys.

1. Hemoglobin phenotypes have been determined for closely related pocket gopher subspecies in the genus Thomomys from sea level and high altitude. 2. A single hemoglobin band was demonstrated for each gopher population with cellulose acetate membrane electrophoresis, with a mobility of 73% relative to human Hb-A. 3. Using polyacrylamide gel electrophoresis, a major Hb component (94% of the total Hb) showed a relative mobility of 68-69%; the minor Hb component showed a relative mobility of 74-75%. 4. The electrophoretic and physiological similarities of the gopher hemoglobins have persisted despite extreme differences in ambient PO2 in the habitats of each subspecies.

Prenatal starvation retards development of the ventilatory response to hypoxia in newborn guinea pigs.

Prenatal starvation causes pulmonary hypoplasia in newborn guinea pigs, and is associated with postnatal cyanosis, hypothermia, and respiratory failure. To determine the effects of such starvation on ventilation, neonates from litters either fed ad libitum throughout gestation (control) or given 50% rations in the last trimester of pregnancy (starved) were studied at 29 degrees C by plethysmography in 21, 11, and 5% O2. After 15 min (steady-state) in 11% and then 5% O2, 13 of 14 controls (mean = 95 g) sustained increases in weight-specific minute ventilation of 46 and 75% compared to values in air (p less than 0.01), due to increases in respiratory frequency. Seven of 11 starved neonates (mean = 76 g) also sustained increases in respiratory frequency and weight-specific minute ventilation in 11 and 5% O2 similar in magnitude to those of the normal controls, although at higher weight-specific tidal volumes. One abnormal control (85 g) and four starved neonates (mean = 70 g) hyperventilated in air, did not respond to 11% O2, and then hypoventilated in 5% O2 due to a reduced weight-specific tidal volume. Neonates with normal ventilatory patterns did not alter weight-specific minute ventilation in 100% O2 and did not show a biphasic response in acute (1-5 min) exposures to moderate hypoxia, as noted for newborn of other species. Thus, hypoxia identified those starved neonates in which pulmonary immaturity or other starvation-induced pathologies necessitated a maximal ventilatory effect in air. The sustainable hyperventilation among normal guinea pigs during hypoxia emphasizes the precocial development in this species at birth, which may be compromised by intrauterine starvation.

The yeast to hyphal transition following hematogenous candidiasis induces shock and organ injury independent of circulating tumor necrosis factor-alpha.

OBJECTIVES: Dimorphic Candida albicans spp. increasingly cause lethal septic shock and disseminated infection in the critically ill. Following candidemia, production of specific fungal exotoxins coincident with the yeast to hyphal phenotypic transition is believed to be important in the pathogenesis of Candida septic shock. However, overexpression of the pleiotropic cytokine tumor necrosis factor (TNF)-alpha by the host following hyphal germination is also thought to be a mechanism of Candida-related cardiopulmonary dysfunction, as well as of bacteremic shock. In this study, we hypothesized that increases in circulating TNF-alpha coinciding with the yeast to hyphal transition modulate the onset and progression of shock with multiple organ injury early after hematogenous candidiasis. DESIGN: Prospective, controlled laboratory animal study. SETTING: University hospital animal research facility. SUBJECTS: Pathogen-free, male Sprague-Dawley rats (n = 26). INTERVENTIONS: Conscious, antibiotic-treated animals with chronic indwelling carotid arterial and jugular venous catheters were intravenously infected with 10(9) viable blastoconidia of the C. albicans clinical pathogen, CA-MEN (n = 10), over 30 mins and ending at t = 0 hr, compared with an equivalent inoculum of its viable agerminative mutant, CA-MM2002 n = 11), or an intravenous infusion of 0.9% sodium chloride (n = 5). MEASUREMENTS AND MAIN RESULTS: Mean arterial pressure (MAP), pulse rate, respiratory frequency, rectal temperature, acid-base status, quantitative blood cultures, circulating alanine aminotransferase (ALT), and bioactive TNF-alpha were serially measured in all three groups over 24 hrs or until death. Organ cultures, wet/dry weight ratios, and histopathologic changes in the lungs, heart, liver, and kidneys were determined in Candida-infected and 0.9% sodium chloride (normal saline)-infused subgroups at 6 and 24 hrs. Animals hematogenously infected with the C. albicans clinical isolate developed lethal nonendotoxemic shock in < or = 6 hrs (MAP 49 +/- 7 mm Hg [SEM]; p < .05 vs. t = 0 hr), and at death (7.0 +/- 0.3 hrs) were acidotic, hypocapnic, and hypothermic (rectal temperature 33.2 +/- 0.7 degrees C). Despite similar peak concentrations of circulating fungal colony-forming units (cfu) and kinetics of vascular clearance in both Candida-infected groups, survival and MAP in rats challenged with the agerminative C. albicans mutant were unchanged for > 8 hrs, as were pH, Pco2, and rectal temperature. No germination of the agerminative fungal strain occurred in vivo over 6 hrs. Serum TNF was nearly undetectable at t = 0 hr in all three groups. Although shock developed soon after fungemia with the C. albicans clinical isolate, TNF-alpha concentrations did not increase above normal saline values in either candidemic group at t = 1.5, 4.5, or 6 hrs (17 +/- 7 vs. 14 +/- 1 U/mL in the parent C. albicans organism vs. its agerminative mutant at t = 6 hrs). Greater numbers of agerminative C. albicans than its dimorphic parent strain were recovered from the lungs (5.41 +/- 1.0 vs. 2.02 +/- 0.38 x 10(7) cfu/g, respectively; p < .05) and kidneys (p < .01). By 24 hrs, modest germination of the mutant Candida strain was observed in the tissues. However, lung wet/dry ratios, intrapulmonary hyphal proliferation, and alveolar hemorrhage were all greater after infection with the parent fungal isolate. Likewise, myocardial necrosis and hepatic glycogen depletion with vacuolization were more severe after infection with the C. albicans clinical isolate vs. candidemia with its agerminative mutant, although serum ALT values did not differ between these groups. CONCLUSIONS: Lethal C. albicans sepsis with lung injury and multiple organ damage are temporally associated with the in vivo yeast to hyphal transition in this model. However, this candidemic septic shock syndrome is modulated by circulating fungal virulence factors or host mediators other than TNF-alpha, a cytokine considered essen

Surfactant content and type II cell development in fetal guinea pig lungs during prenatal starvation.

Prenatal caloric restriction in guinea pigs causes intrauterine growth retardation and reduced neonatal viability and surfactant phospholipid (PL). We report here fetal surfactant levels in this model, and correlate total lung PL with ultrastructural maturation of surfactant type II cells and lamellar bodies (LB). Pregnant guinea pigs were fed ad libitum throughout their 68-d gestation (control), or fed 50% rations from d 45 until term (starved). Fetal lungs were examined at d 55, 60, and 65 for PL content and composition, including disaturated phosphatidylcholine (DPC), and compared with neonates for both groups. Lung lobes were analyzed ultrastructurally in d 65 fetuses for the numerical, volume, and surface densities of type II cells and the volume densities of LB. Prenatal starvation caused significant intrauterine growth retardation at all ages; body and dry lung weights were reduced on d 65 by 26 and 23%, respectively. By d 55 and thereafter, starvation decreased total lung PL by 43-45% but did not alter PL composition. On d 65, the total lung volumes and relative numbers, surface densities, and volumes of type II cells in tissue and the relative volumes of LB within type II cells did not differ by caloric regimen. Thus, starved and control fetuses had similar total volumes of LB per lung (13-15 microL), although starved animals had significantly less lung DPC. Although the total volume of LB per lung correlated well with total lung DPC from d 55 through birth in controls, starvation led to a significant departure from this relationship.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of alveolar septa and cellular maturation within the perinatal lung.

To quantitate fetal lung cellularity and regional variation in alveolar maturation, guinea pig lungs were studied at 55, 60, and 65 d of gestation or within 2 h of birth (term = 68 d), and the data were analyzed for intralobar, interlobar, and age-group differences. Nine blocks from each left cranial and caudal lobe were all measured for volume, numerical, and surface densities in tissue (Vv(i,t), Nv(i,t), and Sv(i,t], and total volumes, numbers, and surface areas per lung (V, N, and S) of type I and type II epithelia, presumptive progenitor epithelium (cuboidal cells lacking lamellar bodies [LB]), interstitium, and endothelium. Total fixed lung volume, VL, increased 3-fold from day 55 through birth. At each age, there were no consistent intralobar or interlobar differences in Vv(i,t), Nv(i,t), or Sv(i,t) for any cell type. Within a septal tissue volume of 580 to 670 microliters at all ages, the N and V of type I cells did not vary with age, although their S increased from 1,240 cm2 at day 55 to 3,967 cm2 at birth. The N of morphologic type II cells per lung increased 7-fold from day 55 to day 60 and was constant thereafter, while the N of cuboidal cells decreased proportionally; type II cells contained only 4.8% (vol/vol) of LB at 55 d compared to 18.0% at birth. The N and V of interstitium did not vary by age. While endothelial V was constant over these ages, endothelial S increased from 897 cm2 to 3,398 cm2, and the V of capillary blood and the V of alveolar airspace each increased 4-fold.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural analysis of regional type II cell development within fetal and neonatal lungs.

Type II cells within guinea pig lungs were studied beginning when lamellar bodies (LB) were first identifiable, to determine the pattern of their ultrastructural maturation through parturition and to search for regional differences suggested for other species in their numbers or maturity within the same lung. Fetuses were examined at gestational ages of 55, 60, and 65 days, as were newborn within 2 h of birth at 68 days. The stratified sampling system divided left lungs into nine blocks from each cranial and caudal lobe for electron-microscopic morphometry. Type II cells were compared among blocks within lobes, between lobes within age groups, and among ages for volume densities [VV(ep2, t)], numerical densities [NV(ep2, t)], and surface densities [SV(ep2, t)] per block; total tissue volumes [V(ep2)], numbers [N(ep2)], and cumulative surface areas [S(ep2)] per lung; and the VV(lb, ep2) and V(lb) of their LB. Within lobes, there were no significant differences among blocks for any parameter. Within age groups, significant interlobar differences were limited only to NV(ep2, t) (cranial greater than caudal at day 55, P less than 0.001). In age-by-age comparisons, the V(ep2), NV(ep2), and S(ep2) each increased dramatically from day 55 to 60 (P less than 0.001) but then remained unchanged through parturition. However, both VV(lb, ep2) and V(lb) increased linearly with fetal age (day 55 less than 60 less than 65 less than newborn), with VV(lb, ep2) achieving 18% type II cell volume in the postpartum group.(ABSTRACT TRUNCATED AT 250 WORDS)

Advanced pulmonary development in newborn guinea pigs (Cavia porcellus).

Morphological and morphometric evidence is presented to support the hypothesis that lung growth is advanced in mammals born at a relatively mature stage. The lungs from fetal and postnatal guinea pigs ranging in age from gestational age 56 days (normal gestation is 68 days in this species) through 16 days postpartum were fixed in situ by intratracheal glutaraldehyde. Morphometry included measurements of lung volume (VL), tissue and air-space volumes, fraction of respiratory parenchyma, alveolar (SA) and capillary (SC) surface areas, and the arithmetic mean thickness of the tissue barrier (tau t). VL, SA, and SC all increased monoexponentially versus body weight (W) from birth to adulthood; the lungs appeared to be in the equilibrated growth phase, with no postnatal period of pronounced tissue proliferation as reported in the newborn rat and mouse. The prepartum value of tau t was 1.96 micrometers; this value decreased by parturition of 1.27 micrometers and did not change significantly with additional age. At the light-microscopical level, respiratory bronchioles could be visualized giving rise to alveolar ducts by a gestational age of 58 days (10 days preterm) with well-developed alveolar septal partitioning evident. Structures resembling the primitive pre-alveolar saccules of newborn rats were never seen in even the youngest fetal animals. Elastin fibers were also evident at this age, both in bronchiolar and duct walls, as well as in alveolar septa. Using electron microscopy, the air-blood barrier appeared mature by a gestational age of 61 days and thereafter, double capillary layers were only rarely seen in septal walls.

Lung morphometry in guinea pigs acclimated to cold during growth.

Weanling male guinea pigs, Cavia porcellus [initial weight (W) = 200-250 g], were chronically acclimated to 5 degrees C for 2-18 wk before they were killed. Controls were raised at 22 degrees C. Food and water were given ad lib., and growth was the same in both groups. Under pentobarbital anesthesia (30 mg/kg), lungs were fixed by tracheal instillation of glutaraldehyde and processed for electron microscopy. Lung volume (VL, ml) was measured by displacement; alveolar and capillary surface areas (SA and Sc, m2) were determined morphometrically. Regressions of lung variables vs. W at 22 degrees C (range of W = 89-1,274 g) were as follows: VL = 0.175 W0.676, SA = 0.0097 W0.759, and Sc = 0.0055 W0.825; for 5 degrees C animals (range of W = 239-1,074 g): VL = 0.384 W0.584, SA = 0.0334 W0.594, and Sc = 0.032 W0.562. The total arithmetic mean thickness of lung tissue did not vary with W, and averaged 1.39 microns at 22 degrees C and 1.41 microns at 5 degrees C. VL, SA, and Sc are significantly greater in 5 degrees C guinea pigs than in 22 degrees C animals when W = 300-600 g, but are indistinguishable between groups when W > 700 g. Chronic increases in oxygen consumption, which occur with prolonged exposure to cold, result in accelerated lung development in immature guinea pigs toward normal adult dimensions.

Lung morphometry in guinea pigs acclimated to hypoxia during growth.

The effect of chronic hypoxic exposure on lung development has been assessed in growing guinea pigs (Cavia porcellus). Weanling males of initial W = 229 g were acclimated to a PO2 of 80 Torr for 2-14 weeks before sacrifice (range of W = 244-965 g). Growth was the same in hypoxic animals as in controls maintained at a PO2 of 133 Torr (range of W in controls = 89-1274 g). Lungs were fixed by tracheal instillation of glutaraldehyde and examined morphometrically with the electron microscope. Within 3 weeks of exposure, lung volume (VL) and alveolar surface area (Sa) were significantly increased by 32% and 27% respectively in the hypoxia acclimated animals compared to controls of similar W. However, these differences were progressively reduced with increasing time of exposure, and mean values of VL and Sa were not different between groups when W greater than 900 g. Chronic hypoxia accelerated lung development towards normal adult dimensions to a degree remarkably similar to that reported in cold acclimated guinea pigs. These findings are compatable with the theory of adaptive lung growth mediated by increased pulmonary blood flow, and suggest anatomical limitations to such growth related to an animal's age.