Probiotic Lactobacillus fermentum UCO-979C biofilm formation on AGS and Caco-2 cells and Helicobacter pylori inhibition.

The ability of the human isolate Lactobacillus fermentum UCO-979C to form biofilm and synthesize exopolysaccharide on abiotic and biotic models is described. These properties were compared with the well-known Lactobacillus casei Shirota to better understand their anti-Helicobacter pylori probiotic activities. The two strains of lactobacilli synthesized exopolysaccharide as detected by the Dubois method and formed biofilm on abiotic and biotic surfaces visualized by crystal violet staining and scanning electron microscopy. Concomitantly, these strains inhibited H. pylori urease activity by up to 80.4% (strain UCO-979C) and 66.8% (strain Shirota) in gastric adenocarcinoma (AGS) cells, but the two species showed equal levels of inhibition (~84%) in colorectal adenocarcinoma (Caco-2) cells. The results suggest that L. fermentum UCO-979C has probiotic potential against H. pylori infections. However, further analyses are needed to explain the increased activity observed against the pathogen in AGS cells as compared to L. casei Shirota.

Bacterial eye infections associated with sexual transmission infections: A review.

The objective of this work was to collect updated information on Treponema pallidum, Chlamydia trachomatis and Neisseria gonorrhoeae, causing sexually transmitted infections (STIs) and etiological agents of eye infections, to provide relevant information on this public health problem. For this, a bibliographic review was carried out using different electronic databases such as: PubMed central, google academic, Lilacs, Scopus, Science Direct and Scielo, between March 2009 and August 2019. According to the WHO, more than a million people a day contract a sexually transmitted infection. For T. pallidum, a global prevalence of 0.5% is estimated for both men and women. It is a causative agent of syphilis and ocular syphilis, which manifests as uveitis. Overall, a prevalence of 2.8% in men and 3.8% in women for C. trachomatis is estimated. It is associated with oculo-genital disease, which includes STIs, inclusion conjunctivitis in adults and neonatal ophthalmia. Among its complications is trachoma, which is the leading cause of infectious blindness worldwide. Regarding N. gonorrhoeae, it has a global selection of 0.9% and 0.7% in women and men, respectively. It manifests with gonococcal conjunctivitis and neonatal ophthalmia. We can conclude that the information that relates T. pallidum, C. trachomatis and N. gonorrhoeae with their ocular compromise problems is insufficient, and even more so if we seek to find them related to each other, which makes it difficult to access data of clinical utility for visual health.

Perinatal cardiopulmonary adaptation to the thin air of the Alto Andino by a native Altiplano dweller, the llama.

Most mammals have a poor tolerance to hypoxia, and prolonged O2 restriction can lead to organ injury, particularly during fetal and early postnatal life. Nevertheless, the llama (Lama Glama) has evolved efficient mechanisms to adapt to acute and chronic perinatal hypoxia. One striking adaptation is the marked peripheral vasoconstriction measured in the llama fetus in response to acute hypoxia, which allows efficient redistribution of cardiac output toward the fetal heart and adrenal glands. This strong peripheral vasoconstrictor tone is triggered by a carotid body reflex and critically depends on α-adrenergic signaling. A second adaptation is the ability of the llama fetus to protect its brain against hypoxic damage. During hypoxia, in the llama fetus there is no significant increase in brain blood flow. Instead, there is a fall in brain O2 consumption and temperature, together with a decrease of Na+-K+-ATPase activity and Na+ channels expression, protecting against seizures and neuronal death. Finally, the newborn llama does not develop pulmonary hypertension in response to chronic hypoxia. In addition to maintaining basal pulmonary arterial pressure at normal levels the pulmonary arterial pressor response to acute hypoxia is lower in highland than in lowland llamas. The protection against hypoxic pulmonary arterial hypertension and pulmonary contractile hyperreactivity is partly due to increased hemoxygenase-carbon monoxide signaling and decreased Ca2+ sensitization in the newborn llama pulmonary vasculature. These three striking physiological adaptations of the llama allow this species to live and thrive under the chronic influence of the hypobaric hypoxia of life at high altitude.

Chemoreflex contribution to adrenocortical function during acute hypoxemia in the llama fetus at 0.6 to 0.7 of gestation.

This study tested the hypothesis that the fetal llama, a species adapted to the chronic hypoxia of life at high altitude, demonstrates a potent carotid chemoreflex influence on adrenocortical responses during acute hypoxemia. Plasma ACTH and cortisol concentrations, and mesencephalic and adrenal blood flows were measured during a 1-h period of acute hypoxemia in six intact and four carotid sinus-denervated llama fetuses at 0.6-0.7 of gestation. Fetal PaO2 was reduced from approximately 23 to about 14 mm Hg in both intact and carotid-denervated groups during acute hypoxemia. During hypoxemia, fetal plasma ACTH, adrenal blood flow, and, therefore, delivery of ACTH to the adrenals increased to similar extents in both intact and carotid-denervated fetal llamas. Despite this, the increase in plasma cortisol in hypoxemia in intact fetuses was absent in carotid-denervated fetuses. In addition, the increase in delivery of cortisol to the mesencephalon calculated in intact fetuses during hypoxemia did not occur in the carotid-denervated group. These data suggest that the integrity of the carotid chemoreceptors is indispensable to cortisol release during acute hypoxemia in the llama fetus, even at 0.6-0.7 of gestation.

Renal function in the chronically cannulated fetal llama: comparison with studies in the ovine fetus.

Samples of maternal and fetal plasma, fetal urine, and amniotic fluid were collected from 8 chronically cannulated pregnant llamas, in the last third of gestation. The samples were obtained for up to 18 days post-surgery. Osmolality, sodium (Na), potassium (K), chloride (Cl), and urea were measured on 40 samples collected on days 1, 2, 3, 4-5, 6-7, 8-9, and 10-19. The osmolalities of maternal and fetal plasma, fetal urine and amniotic fluid, averaged over these 7 time periods, were, respectively, 312 +/- 2, 311 +/- 1, 484 +/- 14, and 317 +/- 1 mosmol kg-1. Values are given as mean +/- s.e. The major differences from fetal fluid values in the ovine fetus (from previously published values) were the higher osmolality and urea concentration of llama fetal urine. Urine flow rate measured in 6 fetuses, 4.5-6.5 kg body weight, was 5.8 +/- 0.4 mliter h-1; urea clearance rate was 55.5 +/- 11.8 mliter h-1. Glomerular filtration rate (GFR), measured with 51Cr-EDTA in 5 fetuses on 1-4 occasions, was 111.4 +/- 23.3 mliter h-1. Fractional reabsorptions (FR) of Na, K and Cl were 97.9 +/- 1, 75.9 +/- 13.5 and 97.7 +/- 0.4% respectively. The GFR (25 mliter kg-1 h-1) and urine flow rate (1 mL kg-1 h-1) were less than half and about one-tenth the respective values in ovine fetuses. As Na reabsorption is the major oxygen-consuming activity of the kidney, the llama fetal kidney requires only half the oxygen needed by the ovine fetal kidney to reabsorb the filtered sodium load. The reason for the formation of hypertonic, rather than hypotonic, urine in the fetal llama may be due to both greater morphological maturity of the kidney and the excretion of as yet unidentified osmotically active organic substances.

Cardiovascular responses to arginine vasopressin blockade during acute hypoxemia in the llama fetus.

The fetal llama has a marked increase in the peripheral vascular resistance and no augmentation of brain blood flow during hypoxemia. In spite of the substantial plasma arginine-vasopressin (AVP) increase during hypoxemia, up to 8 times greater than in fetal sheep, there are no changes of carotid and femoral blood flows during hypoxemia with a V1 receptor blockade, as is seen in the fetal sheep. The aim of this study was to assess the role of AVP function in mediating the combined ventricular output and organ blood flow in the hypoxemic llama fetus. Six fetal llamas at 0.65 of gestation were instrumented under general anesthesia, and cardiorespiratory responses and blood flows determined under normoxemic and hypoxemic conditions. The AVP effect was determined using a V1 antagonist during normoxemic and hypoxemic conditions. Organ blood flows were measured with the radioactive microsphere technique. No significant differences in organ blood flow or in their vascular resistances were seen between the control and treated fetuses during hypoxemia. We conclude that V1 blockade did not have any important role in the cardiovascular response to acute hypoxemia in the llama fetus, in contrast with lowland fetuses. AVP may be playing a role in other regions, possibly in kidney or lung, during hypoxemia.

Low-dose inhaled carbon monoxide reduces pulmonary vascular resistance during acute hypoxemia in adult sheep.

Carbon monoxide (CO) is produced by the action of the heme oxygenase (HO) complex through the oxidation of heme. CO, like nitric oxide (NO), is a molecular gas that among other actions stimulates guanylyl cyclase and increases cGMP levels in smooth muscle cells, regulating the vascular tone. Acute hypoxia generates pulmonary hypertension and increases the expression of inducible HO isoform (HO-1) in the vascular endothelium. Inhaled NO causes a potent pulmonary vasodilation. We hypothesized that inhaled CO might produce similar actions as NO on pulmonary vascular resistance (PVR). To test our contention, we studied the effects of inhaled CO (40 ppm) in the augmented PVR observed during hypoxemia. Five chronically instrumented German Merino sheep were submitted to a protocol consisting of 20 min of normoxemia (N), 20 min of isocapnic hypoxemia (H20), 20 min of isocapnic hypoxemia plus CO 40 ppm (H40), and 20 min of recovery (R). In the control protocol, we did not administer inhaled CO. Arterial gases and pH, percentage of carboxyhemoglobin (COHb), systemic and pulmonary arterial pressure, systemic and pulmonary vascular resistance, and cardiac output were measured during each period. During H20 period, there was a significant increase in cardiac output and PVR in sheep submitted to both protocols. The sheep treated with inhaled CO (H40 + CO) showed a modest but significant decrease (16%) in the elevated PVR. Our data indicate that inhaled CO decreases pulmonary vascular resistance associated with acute hypoxemia in adult sheep.

IL-2 receptor blockers in liver transplantation: initial experience with daclizumab in Chile.

UNLABELLED: Monoclonal antibodies against the interleukin 2 receptor have been developed in an effort to decrease rejection rates and spare calcineurin inhibitors when renal dysfunction occurs after transplant. While success has been reported in kidney transplantation, its effectiveness in liver transplantation is less clear. METHODS: This prospective nonrandomized study including adult patients was performed between October 2000 and April 2003. Two groups of immunosuppressive regimens were compared: group A received 2 g of methylprednisolone intraoperatively followed by a rapid reduction with intention to withdraw by month 4, continuing on Neoral monotherapy. Cellcept was also given for 2 months in the absence or for up to 4 months in the presence of rejection. Group B received the same immunosuppressive regimen but, in addition, daclizumab 1 to 1.5 mg/kg on day 1 and day 5 posttransplant. Rejection diagnosis is made on histology basis. Protocol biopsies were performed in all the patients on day 7 and if indicated by biochemistry thereafter. RESULTS: Both groups were similar in terms of preoperative CHILD score, serum creatinine, incidence of status I, donor and recipient age and ischemia times. The mean follow-up time was 20 months for Group B (n = 24) and 7 months for Group A (n = 10). The 1-month and 1-year rejection rates are 29.1% and 41% in Group A versus 20% and 30% in group B. Rejection severity was similar between both groups. One-year patient and graft survival rates were 96% and 92% in group A and 100% for both in Group B. CONCLUSIONS: In this series, daclizumab induction therapy seems to display a trend toward a lower rejection rate without increasing infectious complications nor affecting graft survival rates.

Transcystic cholangiogram access via rubber band with early withdrawal after liver transplantation: a safe technique.

OBJECTIVE: Since different techniques have been described for cholangiogram access after liver transplantation, we compared two different methods for patients with duct-to-duct biliary anastomoses. METHODS: Adult liver transplant patients from program inception in 1993 to May 2003 in whom a duct-to-duct biliary anastomosis with a T-tube choledochostomy were compared with those having a transcystic duct catheter using a rubber band. We excluded 10 patients in which a different technique was used or graft or patient survived less than 21 days. Group A (n = 28,) had a number 10 T-tube exteriorized through the recipient main bile duct; and group B (n = 33) a number 5 Bard ureteral stent tied to the cystic stump with reabsorbable suture and secured with a hemorrhoidal rubber ligature. RESULTS: The biliary complication rate was lower among the transcystic catheter group (9.1%, 3/33) compared to the T-tube group (35.7%, 10/28). Postcatheter withdrawal peritonitis was present in two patients in the T-tube group, one of whom required emergency laparotomy. A satisfactory postoperative cholangiogram was obtained in both groups. The transcystic catheter was withdrawn on average at 29 days, compared to 136 days in the T-tube group. CONCLUSIONS: Both techniques are equally effective in obtaining a satisfactory postoperative cholangiogram. However, the transcystic catheter technique allows a significantly earlier withdrawal with fewer complications compared to the T-tube technique.

Predictive models in cirrhosis: correlation with the final results and costs of liver transplantation in Chile.

Medical scores for predicting survival are essential to stratify patients with end-stage liver disease (ESLD) for prioritization for liver transplantation (OLT). Recently the UNOS has adopted the Mayo Model for End-stage Liver Disease (MELD) score as the basis for liver allocation in the United States. We retrospectively evaluated and assessed the prognostic impact, the length of stay (LOS), and hospital charges for OLT using two severity scores (Child-Turcotte-Pugh [CTP] versus MELD) to stratify cirrhotic patients before OLT. Twenty-six consecutive adult cirrhotic patients (11 women, mean age 46 years) underwent LT between 2000 and 2002. The main causes for transplantation were alcohol and primary biliary cirrhosis. The mean CTP and MELD scores at the moment of listing for OLT were 8.9 and 16.3 points, respectively. The best discriminative values with prognostic impact in terms of outcome and costs of OLT were a Child Pugh score >/=11 points or a MELD score >/=20 points. Patients in these strata showed a significant increase in LOS in the hospital (from a mean of 12 to 22 days) and intensive care stay (from a mean of 4 to 14 days) post-OLT when compared with patients with a lower CTP or MELD score (P <.05). There was also a trend toward higher hospital charges (P =.06). Organ allocation by MELD score will probably adversely affect the LOS and hospital charges of patients being transplanted due to ESLD.

Clinical characterization and survival of adult patients awaiting liver transplantation in Chile.

Liver transplantation has become widely used for patients with decompensated disease. Because of the shortage of donors, each year more patients die on the waiting list. Our aim was to characterize and evaluate the final outcomes of all listed candidates for liver transplantation during a 34-month period. We retrospectively evaluated all adults listed between January 2000 and November 2002. Sixty-three patients (37 women, mean age 45.8 years) were listed: 48 due to chronic liver disease and 15 for a highly urgent transplantation due to acute liver failure. The main etiology of chronic disease was alcoholic (22%) or primary biliary cirrhosis (17%). Of 52 chronic patients, 26 (50%) were transplanted with a mean waiting time of 168 days. Among the others, 8 died (15%) while awaiting transplantation, 3 (5%) were removed from the list, and 15 patients still await transplantation (28%). Among acute liver failure patients, the main etiologies were autoimmune (25%) and medication induced (25%). Of 15 acute patients, 6 (37.5%) have been transplanted at a mean waiting time of 6.8 days with 100% survival posttransplantation. In this cohort, 6 patients (37.5%) died while awaiting liver transplantation, and 4 (25%) survived with medical support. In conclusion, the severity of liver disease and death rate among our waiting list was similar to that observed in developed countries. It seems reasonable to review our current allocation system based on waiting time on the list. We will have to decide whether to transplant sicker patients or those with hepatocarcinoma (as in the United States recently with the MELD system), thereby possibly decreasing the mortality rate on the waiting list at the expense of higher costs and more difficult postoperative care or to just keep our current policy.

Rapid steroid taper and neoral monotherapy in liver transplantation in Chile: a step in the right direction?

UNLABELLED: Diabetes, hypercholesterolemia, hypertension, obesity, osteopenia, and increased risk of viral recurrence are among the complications associated with posttransplant steroid use. Steroid withdrawal or rapid taper has been reported to be safe. The aim of this study was to compare the rejection incidence and severity among patients treated with two different steroid taper strategies. METHODS: This retrospective study included all the adult liver transplant recipients since the program's inception from 1993 to January 2002. The minimum follow-up was 1 year. Exclusions included patients receiving an immunosupressive regimen other than mycophenolate mofetil, steroids, and Neoral, or suffering an autoimmune etiology, or displaying patient or graft survival less than 1 year. The incidence and severity of rejection episodes were compared between the two groups of steroid taper protocols: group A received methylprednisolone (1 g) intraoperatively with a slow taper to 10 mg prednisone per day at 1 year. Group B received methylprednisolone (2 g) intraoperatively followed by a rapid reduction with intention to withdraw by month 4, continuing on Neoral monotherapy. Rejection diagnosis was made on histological bases. RESULTS: One-month and 1-year rejection rates were 47% and 53%, respectively, among the rapid taper group with Neoral monotherapy, which was similar to 60% and 64%, respectively, in the slow taper group. Rejection severity was also comparable between the two groups. CONCLUSIONS: Patients treated with a rapid steroid taper protocol followed by Neoral monotherapy or a slow taper protocol showed similar acute rejection incidences and severities. Their survival rates were also comparable. Further study is necessary to evaluate the impact of rapid steroid taper to prevent the complications of steroid use.

A decade of adult liver transplantation in a single center in Chile.

INTRODUCTION: Since the early days, liver transplantation (OLT) has conquered several barriers worldwide to become a proven therapy. We assessed the evolution of our adult liver transplant program. METHODS: We studied all adult patients who underwent OLT since the inception from November 1993 through May 2003. Donor data, recipient pretransplantation evaluation, surgical technique, results, and costs were examined over our evolution, stratifying 3 groups over time, based on the number of adult OLT per year. RESULTS: Between November 1993 and May 2003, 70 OLT were performed in 64 patients older than 15 years of age. Preoperative Child score, preoperative creatinine level, donor and recipient age, and proportion of emergencies were similar in the 3 groups. Over time, the predominant surgical technique was the piggyback technique (97% of OLT) with a decrease in the use of bypass from 63% to 5% during the last time period. Over the 10 years of our program's existence, warm ischemia time has been reduced to less than 1 hour, whereas cold ischemia time has remained constant at around 5 hours. Biliary and vascular complications decreased over time to around 10%. The mean length of hospital stay (LOS) decreased to 12 days (excluding emergencies). Since inception, our 1-year patient survival rate average is 91%; however, in just the last 3 years of our program (2000 through 2003), the 1-year patient survival rate is 97%. CONCLUSIONS: In summary, our surgical technique has evolved toward piggyback use without veno-venous bypass with a significant decrease in warm ischemia times. As expected, our results have improved over time and our LOS and costs have decreased. Finally, our current results are similar to the best ones reported in the medical literature today.

Air pollution in tropical areas.

Air pollution problems in three different tropical areas are presented. The levels of various atmospheric contaminants (i.e. SO4) indicate that the operation of a large petroleum refinery affects a substantial portion of the island of Curacao. A significant fraction of the suspended particles in Curacao are due to non-traditional open source emissions aided by the predominantly high wind speeds. Particulate missions from the industrial complex in Guayana, Venezuela, noticeably affect the surrounding savannah. The constant direction of the Trade Winds is an important factor in the high long-term average particulate levels down-wind of the complex. A serious atmospheric contamination problem (i.e. TSP) exists in The Valley of Caracas. The high emission, principally due to the circulation of vehicles, exceed the average dispersion capacity of the atmosphere.

Liver transplantation results for hepatocellular carcinoma in Chile.

UNLABELLED: Hepatocellular carcinoma (HCC) is the most common malignant tumor of the liver. Liver transplantation is the best treatment for HCC; it improves survival, cures cirrhosis, and abolishes local recurrence. We describe the outcomes of patients with HCC who underwent liver transplantation in two liver transplantation centers in Chile. METHODS: This study is a clinical series elaborated from the liver transplantation database of Pontificia Universidad Católica and Clínica Alemana between 1993 and 2009. The survival of patients was calculated using the Kaplan-Meier survival analysis. The significant alpha level was defined as <.05. RESULTS: From 250 liver transplantations performed in this period, 29 were due to HCC. At the end of the study, 25 patients (86%) were alive. The mean recurrence-free survival was 30 months (range 5 months to 8 years). The 5-year survival for patients transplanted for HCC was >80%; however, the 5-year overall survival of patients who exceeded the Milan criteria in the explants was 66%. There was no difference in overall survival between patients transplanted for HCC versus other diagnosis (P = .548). CONCLUSION: This series confirmed that liver transplantation is a good treatment for patients with HCC within the Milan criteria.

Bridge therapy in hepatocellular carcinoma before liver transplantation: the experience of two Chilean centers.

BACKGROUND: Orthotopic liver transplantation (OLT) is currently an established therapy for small, early-stage hepatocellular carcinoma (HCC) within the Milan criteria. Long waiting times due to the shortage of donor organs can result in tumor progression and drop-out from OLT candidacy. Therefore a wide variety of procedures are necessary before OLT. The aim of this retrospective study was to review our experience in relation to bridge therapy prior to OLT for HCC. METHODS: This was a retrospective database review of all of the patient who underwent transplantation in our institutions between January 1993 and June 2009. We analyzed patients with a diagnosis of HCC in the explant. RESULTS: Among 29 patients, including 12 who were diagnosed by the explant and 17 prior to transplantation, 88% underwent bridge therapy during a mean waiting time to OLT of 12 months. Among the 23 procedures, namely 1.5 procedures per patient, included most frequently chemoembolization (48%), alcohol ablation (30%), radiofrequency ablation (13%), and surgery (9%). Thirty-three percent of the explants contained lesions within the Milan criteria. In our series the 5-year survival rate for patients transplanted for HCC was 86%; in the bridge therapy group, it was 73%. CONCLUSIONS: The incidence of patients who underwent bridge therapy (52%) was similar to other reported experiences, but the fulfillment of Milan criteria in the explants was lower. Among the bridge therapy group, the survival was slightly lower, probably because this group displayed more advanced disease.

Cardiorespiratory responses to acute hypoxemia in the chronically catheterized fetal llama at 0.7-0.9 of gestation.

The adult llama (Lama glama) has several compensatory mechanisms that allow it to successfully survive at high altitude. Llama fetuses at 0.6-0.7 of gestation, and near-term llama fetuses studied close to surgery, did not increase cerebral blood flow and decreased cerebral oxygen delivery during acute hypoxemia. It is not known whether these responses were the result of immaturity or surgical stress. The aim of this study was to determine whether the lack of increase in cerebral blood flow and the decrease in cerebral oxygen delivery during hypoxemia in the fetal llama is characteristic of this high-altitude species near term, and under nonstressed conditions. We chronically catheterized 7 llamas and their fetuses near to term, at 0.7-0.9 of gestation. Fetal cardiac output, cerebral and regional blood flows, systemic blood pressure, heart rate, pH, and blood gases, organ vascular resistances and organ oxygen deliveries were determined at least 4 days after surgery, both during the basal state and after 1 hr of acute fetal hypoxemia. During hypoxemia the llama fetus did not increase cerebral blood flow and markedly decreased its cerebral oxygen delivery. There was also a marked decrease in kidney blood flow and oxygen delivery. These results indicate that, in contrast to fetuses of lowland species, the fetal llama does not increase the cerebral blood flow during hypoxemia, suggesting specific cellular mechanisms to preserve brain integrity during oxygen limitation.

Nitric oxide synthase activity in brain tissues from llama fetuses submitted to hypoxemia.

The fetal llama (Lama glama; a species adapted to live in chronic hypoxia in the highlands of the Andes) did not increase cerebral blood flow and reduce the brain oxygen uptake during hypoxemia. Although nitric oxide (NO) is a normal mediator in the regulation of vascular tone and synaptic transmission, NO overproduction by hypoxemia could produce neuronal damage. We hypothesized that nitric oxide synthase (NOS) activity is either maintained or reduced in the central nervous system of the llama fetuses submitted to chronic hypoxemia. Approximately 85% of the Ca(2+)-dependent NOS activity was soluble, at least 12% was associated with the mitochondrial fraction, and less than 5% remains associated with microsomes. To understand the role of NO in chronic hypoxemia, we determined the effect of 24-h hypoxemia on NOS activity in the central nervous system. No changes in activity or the subcellular distribution of NOS activity in brain tissues after hypoxemia were found. We proposed that the lack of changes in NOS activity in the llama under hypoxemia could be a cytoprotective mechanism inherent to the llama, against possible toxic effects of NO.

Adrenergic and vasopressinergic contributions to the cardiovascular response to acute hypoxaemia in the llama fetus.

1. The effects of fetal intravenous treatment with phentolamine or a vasopressinergic V1-receptor antagonist on the fetal cardiovascular responses to acute hypoxaemia in the llama were investigated. 2. Six llama fetuses were surgically prepared between 60 and 70 % of gestation under general halothane anaesthesia with vascular catheters and transit-time ultrasonic flow probes around a carotid artery and a femoral artery. At least 4 days after surgery all fetuses were subjected to a 3 h experiment: 1 h of normoxia, 1 h of hypoxaemia and 1 h of recovery while on slow i.v. infusion with saline. On separate days this experiment was repeated with fetal i.v. treatment with either phentolamine or a V1-receptor antagonist dissolved in saline. 3. During saline infusion all llama fetuses responded to acute hypoxaemia with intense femoral vasoconstriction. Phentolamine during normoxia produced hypotension, tachycardia and vasodilatation in both the carotid and the femoral circulations. During hypoxaemia, fetuses treated with phentolamine did not elicit the pronounced femoral vasoconstriction and all died within 20 min of the onset of hypoxaemia. A V1-receptor antagonist produced a femoral vasodilatation during normoxia but did not affect the fetal cardiovascular responses to acute hypoxaemia. 4. In conclusion, alpha-adrenergic and V1-vasopressinergic mechanisms contribute to a basal vasoconstrictor tone in the femoral circulation in the llama fetus. The enhanced femoral vasoconstriction during acute hypoxaemia in the llama fetus is not mediated by stimulation of V1-vasopressin receptors, but is dependent on alpha-adrenergic receptor stimulation. Such alpha-adrenergic efferent mechanisms are indispensable to fetal survival during hypoxaemia in the llama since their abolition leads to cardiovascular collapse and death.

Chemoreflex and endocrine components of cardiovascular responses to acute hypoxemia in the llama fetus.

We tested the hypothesis that the llama fetus has a blunted cardiovascular chemoreflex response to hypoxemia by investigating the effects of acute hypoxemia on perfusion pressure, heart rate, and the distribution of the combined ventricular output in 10 chronically instrumented fetal llamas at 0.6-0.7 gestation. Four llama fetuses had the carotid sinus nerves sectioned. In the intact fetuses, there was a marked bradycardia, an increase in perfusion pressure, and a pronounced peripheral vasoconstriction during hypoxemia. These cardiovascular responses during hypoxemia in intact fetuses were accompanied by a pronounced increase in plasma vasopressin, but not in plasma angiotensin II concentrations. Carotid denervation prevented the bradycardia at the onset of hypoxemia, but it did not affect the intense vasoconstriction during hypoxemia. Plasma vasopressin and angiotensin II levels were not measured in carotid-denervated fetuses. Our results do not support the hypothesis that the carotid chemoreflex during hypoxemia is blunted in the llama fetus. However, they emphasize that other mechanisms, such as increased vasopressin concentrations, operate to produce an intense vasoconstriction in hypoxemia. This intense vasoconstriction in the llama fetus during hypoxemia may reflect the influence of chronic exposure to the hypoxia of high altitude on the magnitude and gain of fetal cardiovascular responses to a superimposed acute episode of hypoxemia.