Transcription factor induction of vascular blood stem cell niches in vivo

The hematopoietic niche is a supportive microenvironment composed of distinct cell types, including specialized vascular endothelial cells that directly interact with hematopoietic stem and progenitor cells (HSPCs). The molecular factors that specify niche endothelial cells and orchestrate HSPC homeostasis remain largely unknown. Using multi-dimensional gene expression and chromatin accessibility analyses in zebrafish, we define a conserved gene expression signature and cis-regulatory landscape that are unique to sinusoidal endothelial cells in the HSPC niche. Using enhancer mutagenesis and transcription factor overexpression, we elucidate a transcriptional code that involves members of the Ets, Sox, and nuclear hormone receptor families and is sufficient to induce ectopic niche endothelial cells that associate with mesenchymal stromal cells and support the recruitment, maintenance, and division of HSPCs in vivo. These studies set forth an approach for generating synthetic HSPC niches, in vitro or in vivo, and for effective therapies to modulate the endogenous niche.

Generation of mouse-zebrafish hematopoietic tissue chimeric embryos for hematopoiesis and host-pathogen interaction studies

Xenografts of the hematopoietic system are extremely useful as disease models and for translational research. Zebrafish xenografts have been widely used to monitor blood cancer cell dissemination and homing due to the optical clarity of embryos and larvae, which allow unrestricted in vivo visualization of migratory events. Here, we have developed a xenotransplantation technique that transiently generates hundreds of hematopoietic tissue chimeric embryos by transplanting murine bone marrow cells into zebrafish blastulae. In contrast to previous methods, this procedure allows mammalian cell integration into the fish developmental hematopoietic program, which results in chimeric animals containing distinct phenotypes of murine blood cells in both circulation and the hematopoietic niche. Murine cells in chimeric animals express antigens related to (i) hematopoietic stem and progenitor cells, (ii) active cell proliferation and (iii) myeloid cell lineages. We verified the utility of this method by monitoring zebrafish chimeras during development using in vivo non-invasive imaging to show novel murine cell behaviors, such as homing to primitive and definitive hematopoietic tissues, dynamic hematopoietic cell and hematopoietic niche interactions, and response to bacterial infection. Overall, transplantation into the zebrafish blastula provides a useful method that simplifies the generation of numerous chimeric animals and expands the range of murine cell behaviors that can be studied in zebrafish chimeras. In addition, integration of murine cells into the host hematopoietic system during development suggests highly conserved molecular mechanisms of hematopoiesis between zebrafish and mammals.This article has an associated First Person interview with the first author of the paper.

Role of RFRP-3 in the development of cold stress-induced polycystic ovary phenotype in rats

RFamide-related peptide (RFRP-3) is a regulator of GnRH secretion from the brain, but it can also act in human ovary to influence steroidogenesis. We aimed to study the putative local role of RFRP-3 in the ovary and its potential participation in the development of a polycystic ovary phenotype induced by chronic sympathetic stress (cold stress). We used adult Sprague–Dawley rats divided into control and stressed groups. In both groups, we studied the effect of intraovarian exposure to RFRP-3 on follicular development and plasma ovarian steroid concentrations. We also tested the effect of RFRP-3 on ovarian steroid production in vitro. Chronic in vivo intraovarian exposure to RFRP-3 decreased basal testosterone concentrations and cold stress-induced progesterone production by the ovary. In vitro, RFRP-3 decreased hCG-induced ovarian progesterone and testosterone secretion. Immunohistochemistry and mRNA expression analysis showed a decrease in Rfrp and expression of its receptor in the ovary of stressed rats, a result which is in line with the increased testosterone levels found in stressed rats. In vivo application of RFRP-3 recovered the low levels of secondary and healthy antral follicles found in stressed rats. Taken together, our data indicate a previously unknown response of hypothalamic and ovarian RFRP-3 to chronic cold stress, influencing ovarian steroidogenesis and follicular dynamics. Thus, it is likely that RFRP-3 modulation in the ovary is a key component of development of the polycystic ovary phenotype.

CXCR1 remodels the vascular niche to promote hematopoietic stem and progenitor cell engraftment

Blaser et al. use live imaging of the zebrafish hematopoietic niche to show that cxcl8/cxcr1 signaling positively regulates HSPC engraftment by increasing HSPC-niche interactions, HSPC mitotic rate, niche size, and expression of cxcl12a in a niche-autonomous manner.

The microenvironment is an important regulator of hematopoietic stem and progenitor cell (HSPC) biology. Recent advances marking fluorescent HSPCs have allowed exquisite visualization of HSPCs in the caudal hematopoietic tissue (CHT) of the developing zebrafish. Here, we show that the chemokine cxcl8 and its receptor, cxcr1, are expressed by zebrafish endothelial cells, and we identify cxcl8/cxcr1 signaling as a positive regulator of HSPC colonization. Single-cell tracking experiments demonstrated that this is a result of increases in HSPC–endothelial cell “cuddling,” HSPC residency time within the CHT, and HSPC mitotic rate. Enhanced cxcl8/cxcr1 signaling was associated with an increase in the volume of the CHT and induction of cxcl12a expression. Finally, using parabiotic zebrafish, we show that cxcr1 acts HSPC nonautonomously to improve the efficiency of donor HSPC engraftment. This work identifies a mechanism by which the hematopoietic niche remodels to promote HSPC engraftment and suggests that cxcl8/cxcr1 signaling is a potential therapeutic target in patients undergoing hematopoietic stem cell transplantation.

Generation of Parabiotic Zebrafish Embryos by Surgical Fusion of Developing Blastulae

Surgical parabiosis of two animals of different genetic backgrounds creates a unique scenario to study cell-intrinsic versus cell-extrinsic roles for candidate genes of interest, migratory behaviors of cells, and secreted signals in distinct genetic settings. Because parabiotic animals share a common circulation, any blood or blood-borne factor from one animal will be exchanged with its partner and vice versa. Thus, cells and molecular factors derived from one genetic background can be studied in the context of a second genetic background. Parabiosis of adult mice has been  used extensively to research aging, cancer, diabetes, obesity, and brain development. More recently, parabiosis of zebrafish embryos has been used to study the developmental biology of hematopoiesis. In contrast to mice, the transparent nature of zebrafish embryos permits the direct visualization of cells in the parabiotic context, making it a uniquely powerful method for investigating fundamental cellular and molecular mechanisms. The utility of this technique, however, is limited by a steep learning curve for generating the parabiotic zebrafish embryos. This protocol provides a step-by-step method on how to surgically fuse the blastulae of two zebrafish embryos of different genetic backgrounds to investigate the role of candidate genes of interest. In addition, the parabiotic zebrafish embryos are tolerant to heat shock, making temporal control of gene expression possible. This method does not require a sophisticated set-up and has broad applications for studying cell migration, fate specification, and differentiation in vivo during embryonic development.

Loss of lysophosphatidic acid receptor LPA1 alters oligodendrocyte differentiation and myelination in the mouse cerebral cortex

Lysophosphatidic acid (LPA) is an intercellular signaling lipid that regulates multiple cellular functions, acting through specific G-protein coupled receptors (LPA(1-6)). Our previous studies using viable Malaga variant maLPA1-null mice demonstrated the requirement of the LPA1 receptor for normal proliferation, differentiation, and survival of the neuronal precursors. In the cerebral cortex LPA1 is expressed extensively in differentiating oligodendrocytes, in parallel with myelination. Although exogenous LPA-induced effects have been investigated in myelinating cells, the in vivo contribution of LPA1 to normal myelination remains to be demonstrated. This study identified a relevant in vivo role for LPA1 as a regulator of cortical myelination. Immunochemical analysis in adult maLPA1-null mice demonstrated a reduction in the steady-state levels of the myelin proteins MBP, PLP/DM20, and CNPase in the cerebral cortex. The myelin defects were confirmed using magnetic resonance spectroscopy and electron microscopy. Stereological analysis limited the defects to adult differentiating oligodendrocytes, without variation in the NG2+ precursor cells. Finally, a possible mechanism involving oligodendrocyte survival was demonstrated by the impaired intracellular transport of the PLP/DM20 myelin protein which was accompanied by cellular loss, suggesting stress-induced apoptosis. These findings describe a previously uncharacterized in vivo functional role for LPA1 in the regulation of oligodendrocyte differentiation and myelination in the CNS, underlining the importance of the maLPA1-null mouse as a model for the study of demyelinating diseases.

Neonatal exposure to estradiol valerate increases dopamine content in nigrostriatal pathway during adulthood in the rat

Research in programming has focused in the study of stimuli that affect sensitive periods of development such as prenatal and neonatal stage. We previously showed that exposure to estradiol valerate to female rats during the first 12 h of life increased catecholamine content in ventromedial-arcuatus hypothalamus of the adult rat. However, changes in others dopaminergic circuits have not been studied. The purpose of this work was to determine the neurotransmitters changes induced by neonatal estradiol valerate (0.1 mg/50 μl s. c. per rat) administration on nigrostriatal pathway of adult female rats. Sesame oil (50 μl s. c. per rat) was administered in a control parallel group. EV-1 adult rats presented effective markers of long-term estrogenization as decreased serum levels of progesterone and a reduction in the size of estrogen-sensitive organs. In the brain, neonatal estradiol valerate administration led to a significant increase in dopamine content in striatum, substantia nigra and ventral tegmental area. With respect to the contents of dopamine metabolites, only 3-methoxytyramine content increased in substantia nigra and ventral tegmental area. In addition, the content of noradrenaline increased only in striatum. Interestingly, estrogenized rats lacked locomotor activity induced by acute dose of amphetamine (1 mg/kg i. p.). Altogether, these results show that neonatal exposure to estradiol valerate permanently modified the content of monoamine neurotransmitters in nigrostriatal pathway and amphetamine-induced locomotor activity of adult female rats. This might imply that estrogenized rats could have changes in the expression of key proteins in dopaminergic regulation, as tyrosine hydroxylase and dopamine transporter.

Predicting mortality in hospitalized patients with 2009 H1N1 influenza pneumonia

BACKGROUND

Community-acquired pneumonia (CAP) severity scores can identify patients at low risk for mortality who may be suitable for ambulatory care. Here, we follow the clinical course of hospitalized patients with CAP due to 2009 H1N1 influenza.

OBJECTIVE

To evaluate the role of CAP severity scores as predictors of mortality.

METHODS

This was a secondary data analysis of patients hospitalized with CAP due to 2009 H1N1 influenza confirmed by reverse transcriptase polymerase chain reaction enrolled in the CAPO (Community-Acquired Pneumonia Organization) international cohort study. CAP severity scores PSI (Pneumonia Severity Index), CURB-65 (confusion, urea, respiratory rate, blood pressure, age ≥ 65 years) and CRB-65 (confusion, respiratory rate, blood pressure, age ≥ 65 years) were calculated. Actual and predicted mortality rates were compared. A total of 37 predictor variables were evaluated to define those associated with mortality.

RESULTS

Data from 250 patients with CAP due to 2009 H1N1 influenza were analyzed. Patients with low predicted mortality rates (0-1.5%) had actual mortality rates ranging from 2.6% to 17.5%. Obesity and wheezing were the only novel variables associated with mortality.

CONCLUSIONS

The decision to hospitalize a patient with CAP due to 2009 H1N1 influenza should not be based on current CAP severity scores, as they underestimate mortality rates in a significant number of patients. Patients with obesity or wheezing should be considered at an increased risk for mortality.

Influenza pneumonia: a comparison between seasonal influenza virus and the H1N1 pandemic

We compared clinical presentation, complications and outcome in patients with influenza A (H1N1) and seasonal influenza pneumonia. The group of patients with influenza A (H1N1) pneumonia consisted of 75 patients. 52 patients with pneumonia associated with seasonal influenza were included for comparison. Patients with pneumonia associated with novel H1N1 influenza were younger (mean age 39.7 yrs versus 69.6 yrs) and had fewer chronic comorbidities and less alcoholism. Infiltrates were more extensive and frequently interstitial. Respiratory failure was more frequent (those with an arterial oxygen tension/inspiratory oxygen fraction ratio <200 28% versus 12%, p = 0.042), leading to a higher rate of intensive care unit (ICU) admission and mechanical ventilation (29.3% versus 7.7% (p<0.0030) and 18.7% versus 2% (p<0.0045)). Mortality was twice as high in patients with novel H1N1 (12% versus 5.8%; p = 0.238), although this was not significant, and was attributable to pneumonia in most instances (77.8% versus 0%; p = 0.046). Younger age, fewer comorbidities, more extensive radiographic extension and more severe respiratory compromise, and ICU admissions are key features of the clinical presentation of patients with novel H1N1-associated pneumonia compared with seasonal influenza pneumonia.

A comparative study of age-related hearing loss in wild type and insulin-like growth factor I deficient mice

Insulin-like growth factor-I (IGF-I) belongs to the family of insulin-related peptides that fulfils a key role during the late development of the nervous system. Human IGF1 mutations cause profound deafness, poor growth and mental retardation. Accordingly, Igf1^−/− null mice are dwarfs that have low survival rates, cochlear alterations and severe sensorineural deafness. Presbycusis (age-related hearing loss) is a common disorder associated with aging that causes social and cognitive problems. Aging is also associated with a decrease in circulating IGF-I levels and this reduction has been related to cognitive and brain alterations, although there is no information as yet regarding the relationship between presbycusis and IGF-I biodisponibility. Here we present a longitudinal study of wild type Igf1^+/+ and null Igf1^−/− mice from 2 to 12 months of age comparing the temporal progression of several parameters: hearing, brain morphology, cochlear cytoarchitecture, insulin-related factors and IGF gene expression and IGF-I serum levels. Complementary invasive and non-invasive techniques were used, including auditory brainstem-evoked response (ABR) recordings and in vivo MRI brain imaging. Igf1^−/− null mice presented profound deafness at all the ages studied, without any obvious worsening of hearing parameters with aging. Igf1^+/+ wild type mice suffered significant age-related hearing loss, their auditory thresholds and peak I latencies augmenting as they aged, in parallel with a decrease in the circulating levels of IGF-I. Accordingly, there was an age-related spiral ganglion degeneration in wild type mice that was not evident in the Igf1 null mice. However, the Igf1^−/− null mice in turn developed a prematurely aged stria vascularis reminiscent of the diabetic strial phenotype. Our data indicate that IGF-I is required for the correct development and maintenance of hearing, supporting the idea that IGF-I-based therapies could contribute to prevent or ameliorate age-related hearing loss.

Characteristics of hospitalised patients with 2009 H1N1 influenza in Chile

As the pandemic of 2009 H1N1 influenza A virus progressed, more patients required hospitalisation. The objective of this study is to describe the characteristics and clinical course of hospitalised patients with 2009 H1N1 virus infection in Chile. This was a prospective, observational study of 100 consecutive hospitalised patients with RT-PCR-confirmed 2009 H1N1 influenza A, admitted to Puerto Montt General Hospital (Puerto Montt, Chile). Information was obtained regarding contact history, demographics, laboratory values and clinical course. The primary reason for hospitalisation was pneumonia, in 75% of patients. Rapid influenza A test was positive in 51% of patients. Prior exposure to 2009 H1N1 virus was documented in 21% of patients. Clinical failure, documented in 18% of cases, was characterised by respiratory failure and acute respiratory distress syndrome. Failure was more common in patients with obesity, tachypnoea, confusion and multilobar infiltrates. When evaluating a patient hospitalised with influenza-like illness, a negative rapid test for influenza A or negative contact with a suspected case should not alter physicians' considerations regarding the likelihood of 2009 H1N1 virus infection. Patients with 2009 H1N1 virus infection with obesity, tachypnoea, confusion and multilobar infiltrates should be closely monitored since they are at high risk for clinical failure.

Behavioral phenotype of maLPA1-null mice: increased anxiety-like behavior and spatial memory deficits

Lysophosphatidic acid (LPA) has emerged as a new regulatory molecule in the brain. Recently, some studies have shown a role for this molecule and its LPA(1) receptor in the regulation of plasticity and neurogenesis in the adult brain. However, no systematic studies have been conducted to investigate whether the LPA(1) receptor is involved in behavior. In this study, we studied the phenotype of maLPA(1)-null mice, which bear a targeted deletion at the lpa(1) locus, in a battery of tests examining neurologic performance, habituation in exploratory behavior in response to low and mild anxiety environments and spatial memory. MaLPA(1)-null mutants showed deficits in both olfaction and somesthesis, but not in retinal or auditory functions. Sensorimotor co-ordination was impaired only in the equilibrium and grasping reflexes. The mice also showed impairments in neuromuscular strength and analgesic response. No additional differences were observed in the rest of the tests used to study sensoriomotor orientation, limb reflexes and co-ordinated limb use. At behavioral level, maLPA(1)-null mice showed an impaired exploration in the open field and increased anxiety-like response when exposed to the elevated plus maze. Furthermore, the mice exhibit impaired spatial memory retention and reduced use of spatial strategies in the Morris water maze. We propose that the LPA(1) receptor may play a major role in both spatial memory and response to anxiety-like conditions.

RasGRF1 disruption causes retinal photoreception defects and associated transcriptomic alterations

RasGRF1 null mutant mice display impaired memory/learning and their hippocampus transcriptomic pattern includes a number of differentially expressed genes playing significant roles in sensory development and function. Odour avoidance and auditory brainstem response tests yielded normal results but electroretinographic analysis showed severe light perception impairment in the RasGRF1 knockouts. Whereas no structural alterations distinguished the retinas of wild-type and knockout mice, microarray transcriptional analysis identified at least 44 differentially expressed genes in the retinas of these Knockout animals. Among these, Crb1, Pttg1, Folh1 and Myo7a have been previously related to syndromes involving retina degeneration. Interestingly, over-expression of Folh1 would be expected to result in accumulation of its enzymatic product N-acetyl-aspartate, an event known to be linked to Canavan disease, a human cerebral degenerative syndrome often involving blindness and hearing loss. Consistently, in vivo brain nuclear magnetic resonance spectroscopy identified higher levels of N-acetyl-aspartate in our RasGRF1-/- mice and immunohistochemical analysis detected reduced levels of aspartoacylase, the enzyme which degrades N-acetyl-aspartate. These studies demonstrate for the first time the functional relevance of Ras signalling in mammalian photoreception and warrant further analysis of RasGRF1 Knockout mice as potential models to analyse molecular mechanisms underlying defective photoreception human diseases.

Evidence of a role for melatonin in fetal sheep physiology: direct actions of melatonin on fetal cerebral artery, brown adipose tissue and adrenal gland

Although the fetal pineal gland does not secrete melatonin, the fetus is exposed to melatonin of maternal origin. In the non-human primate fetus, melatonin acts as a trophic hormone for the adrenal gland, stimulating growth while restraining cortisol production. This latter physiological activity led us to hypothesize that melatonin may influence some fetal functions critical for neonatal adaptation to extrauterine life. To test this hypothesis we explored (i) the presence of G-protein-coupled melatonin binding sites and (ii) the direct modulatory effects of melatonin on noradrenaline (norepinephrine)-induced middle cerebral artery (MCA) contraction, brown adipose tissue (BAT) lypolysis and ACTH-induced adrenal cortisol production in fetal sheep. We found that melatonin directly inhibits the response to noradrenaline in the MCA and BAT, and also inhibits the response to ACTH in the adrenal gland. Melatonin inhibition was reversed by the melatonin antagonist luzindole only in the fetal adrenal. MCA, BAT and adrenal tissue displayed specific high-affinity melatonin binding sites coupled to G-protein (K(d) values: MCA 64 +/- 1 pm, BAT 98.44 +/- 2.12 pm and adrenal 4.123 +/- 3.22 pm). Melatonin binding was displaced by luzindole only in the adrenal gland, supporting the idea that action in the MCA and BAT is mediated by different melatonin receptors. These direct inhibitory responses to melatonin support a role for melatonin in fetal physiology, which we propose prevents major contraction of cerebral vessels, restrains cortisol release and restricts BAT lypolysis during fetal life.

Optimizing the stimuli to evoke the amplitude modulation following response (AMFR) in neonates

OBJECTIVE

The goal was to identify stimulus features that enhance the detection of the amplitude modulation following response (AMFR) in neonates. The features explored were (1) envelope type, sinusoidal versus a half-wave rectified sinusoid (transposed); (2) best modulation frequency; and (3) spectral content, i.e., tone versus band-pass noise.

DESIGN

Results are based on recordings from 149 babies (80 babies in the neonatal intensive care unit and 69 newborn infants). All had passed hearing screening based on the click-evoked ABR. Babies were not sedated. We used carrier frequencies of approximately 500, 1000, 2000, and 4000 Hz and modulation frequencies between approximately 25 and 98 Hz. For the noise stimuli, we used band-pass noise at center frequencies of 500, 1000, 2000, and 4000 Hz. All stimuli were presented through insert earphones delivered simultaneously to both ears, at intensities ranging from 20 to 70 dB SPL. Magnitude squared coherence, phase coherence, and spectral criteria were used to detect criterion AMFRs. We analyzed four measures: (1) percent of satisfied runs; (2) the amplitude of criterion AMFR; (3) time to detect a criterion AMFR; and (4) response strength (e.g., the value of the magnitude squared coherence when it reached criterion minus the critical value it had to exceed for that number of averages all divided by the critical value).

RESULTS

(1) The AMFRs evoked by transposed tones were larger and detected faster than those to sinusoidal amplitude modulated tones. Consequently, remaining protocols all used the transposed envelopes. (2) The range of effective modulation frequencies was broad (41 to 88 Hz) across carrier frequencies. (3) The AMFRs evoked by transposed noise were faster and more efficient than those to transposed tones.

CONCLUSIONS

In neonates, transposed tones are more effective than sinusoidal amplitude modulated tones in evoking the AMFR, modulation frequencies between 41 to 88 Hz are almost equally effective in evoking the AMFR, and band-pass noises are more effective in evoking the AMFR than tones. These three stimulus factors all add incrementally to the efficiency of evoking the AMFR. The short detection times indicate that the AMFR could be an effective tool for hearing screening.

Sensorineural hearing loss in insulin-like growth factor I-null mice: a new model of human deafness

It has been reported that mutations in the gene encoding human insulin-like growth factor-I (IGF-I) cause syndromic hearing loss. To study the precise role of IGF-I in auditory function and to hypothesize the possible morphological and electrophysiological changes that may occur in the human inner ear, we have analysed the auditory brainstem response in a mouse model of IGF-I deficiency. We show here that homozygous Igf-1(-/-) mice present an all-frequency involved bilateral sensorineural hearing loss. Igf-1(-/-) mice also present a delayed response to acoustic stimuli; this increases along the auditory pathway, indicating a contribution of the central nervous system to the hearing loss in Igf-1(-/-) mice. These results support the use of the Igf-1(-/-) mouse as a new model for the study of human syndromic deafness.

GRIP1 in GABAergic synapses

The glutamate receptor-interacting protein GRIP1 is present in glutamatergic synapses and interacts with the GluR2/3/4c subunits of the AMPA receptors. This interaction plays important roles in trafficking, synaptic targeting, and recycling of AMPA receptors as well as in the plasticity of glutamatergic synapses. Although GRIP1 has been shown to be present at GABAergic synapses in cultured neurons, the use of EM (electron microscopy) immunocytochemistry in the intact brain has failed to convincingly reveal the presence of GRIP1 in GABAergic synapses. Therefore, most studies on GRIP1 have focused on glutamatergic synapses. By using mild tissue fixation and embedding in EM, we show that in the intact brain the 7-PDZ domain GRIP1a/b is present not only in glutamatergic synapses but also in GABAergic synapses. In GABAergic synapses GRIP1a/b localizes both at the presynaptic terminals and postsynaptically, being frequently localized on the synaptic membranes or the synaptic junctional complex. Considerably higher density of GRIP1a/b is found in the presynaptic GABAergic terminals than in the glutamatergic terminals, while the density of GRIP1a/b in the postsynaptic complex is similar in both types of synapses. The results also show that the 7-PDZ and the shorter 4-PDZ domain splice forms of GRIP1 (GRIP1c 4-7) frequently colocalize with each other in individual GABAergic and glutamatergic synapses. The results suggest that GRIP1 splice forms might play important roles in brain GABAergic synapses.

Susceptibility and exposure biomarkers in people exposed to PAHs from diesel exhaust

Xenobiotic metabolizing enzymes, especially CYP1A1 and GSTM1, are involved in the activation and conjugation of PAHs and are controlled by polymorphic genes. PAHs released from diesel emissions in many cities of the world, especially in developing countries, contribute significantly to the toxic effects of airborne inhalable particles. We have evaluated the gene-environment interaction in Santiago of Chile, studying the contribution of CYP1A1 and GSTM1 polymorphisms on 1-OH-P urinary levels used as the PAHs exposure biomarker. The study was performed on 59 diesel exposed (38 diesel revision workers and 21 subjects working in an urban area as established street vendors) and 44 non-exposed subjects living in a rural area. The 1-OH-P urinary levels of the urban (P=0.043) and rural (P=0.040) populations showed, without considering the genotypes, significant differences between smokers and non-smokers, but no significant differences were found between smokers and non-smokers among the diesel plant workers (P=0.33). Non-smoking subjects of the diesel plants and the urban area showed similar 1-OHP levels (P=0.466) which were significantly higher than those of the subjects living in the rural area (P<0.05). When 1-OH-P levels were related with genotypes, an association was observed for the CYP1A1*2A genotype, so that the diesel-exposed workers carrying the CYP1A1*2A allele showed significantly higher 1-OH-P levels than the subjects from the rural area with the same genotype (P=0.008). On the other hand, there was no significant correlation between urinary 1-OH-P levels and GSTM1 null genotype, although higher levels of the urinary metabolite were found in individuals carrying the combined CYP1A1*2A and GSTM1 null genotype (P=0.055). These results may suggest an association between levels of the exposure biomarker 1-OH-P and presence of the CYP1A1*2A genotype, a potential genetic susceptibility biomarker which might be useful in identifying individuals at higher risk among people exposed to high PAH levels in diesel exhaust.

Prevalence of sexual dysfunction in a cohort of middle-aged women: influences of menopause and hormone replacement therapy

In order to determine the prevalence of sexual dysfunction (SD) and related risk factors in a cohort of middle-aged women the Laumann's test (DSM-IV) was passed to 534 healthy women between 40 and 64 years old (mean: 52.4+/-5.7) attending the Southern Metropolitan Health Service in Santiago de Chile. Of all the women, 82.8% were peri- or postmenopausal, 23% had received hormone replacement therapy (HRT) and 79.2% were sexually active. Among those who were sexually active a total of 51.3% presented SD. The prevalence of SD increased with age (from 22.2% in the 40-44-year age group to 66% in the 60-64-year age group). HRT users and healthy women presented a lower risk of SD (OR: 0.1 CI: 0.0-0.1 and OR: 0.6 CI: 0.3-0.9, respectively). The risk increased after the menopause (OR: 3.3 CI: 1.6-6.9) and with age older than 49 years (OR: 3.4 CI: 1.8-6.4), hysterectomy (OR: 3.7 CI: 1.3-10.6) and when male partners presented erectile dysfunction (OR: 3.2 CI: 1.2-8.6). In conclusion sexual dysfunction affects more than 51% of middle-aged women who are sexually active and increases with age. Ovarian function and HRT significantly influence sexual activity.

Bergmann glia GABA(A) receptors concentrate on the glial processes that wrap inhibitory synapses

We studied the cellular and subcellular distribution of GABA(A) receptors in the Bergmann glia and Purkinje cells in the molecular layer of the cerebellum by using electron microscopy postembedding immunogold techniques. Gold particles corresponding to alpha2 and gamma1 immunoreactivity were localized in Bergmann glia processes that wrapped Purkinje cell somata, dendritic shafts, and some dendritic spines. The gold particles were mainly located on the glial plasma membrane or intracellularly but near the plasma membrane. The density of gold particles corresponding to alpha2 and gamma1 GABA(A) receptor subunits was 4.3-fold higher in the glial processes wrapping Purkinje cell somata than in the glial processes wrapping Purkinje cell dendritic spines. Moreover, the Bergmann glia GABA(A) receptors were often located in close proximity to the type II GABAergic synapses made by the basket cell axons on Purkinje cell somata. These GABAergic synapses were enriched in neuronal GABA(A) receptors containing alpha1 and beta2/3 subunits. Unexpectedly, 2.8% of the Purkinje cell dendritic spines also showed immunoreactivity for the neuronal alpha1 or beta2/3 subunits, which were located on the spine in type I synapses or extrasynaptically. Double-labeling immunogold experiments showed that approximately 50% of the dendritic spines that were immunolabeled with the neuronal GABA(A) receptors were wrapped by Bergmann glia processes containing glial GABA(A) receptors. These results are consistent with a role of the Bergmann glial GABA(A) receptors in sensing GABAergic synaptic function.

First-trimester pregnancy loss and active Chlamydia trachomatis infection: correlation and ultrastructural evidence

The incidence of Chlamydia trachomatis (Ct) infection and the possible correlation between couples presenting with first-trimester spontaneous abortions and active Ct infection was assessed. Additionally, the ability of Ct to infect zona-free hamster oocytes was explored by incubating the oocytes with spermatozoa from infected patients. A total of 961 women and 750 men consulting our reproductive medicine centre were screened for Ct using direct immunofluorescence. The general incidence of Ct infection was 9.4% in females (90 of 961) and 13.9% in males (104 of 750). In women with spontaneous abortions the incidence of Ct was 21.0% (14 of 66) compared with 8.9% (23 of 59) for women without spontaneous abortions and term pregnancies (chi-square, P < 0.05). When both partners of the couples were considered (one or both partners infected), the incidence rose to 68.8% (22 of 32) (chi-square, P < 0.001). In vitro studies using electron microscopy demonstrated the presence of Ct on the surface of and inside the oocyte. These results indicate a correlation between an active Ct infection and spontaneous abortion. Electron microscopy studies suggested the possibility of direct oocyte infection by Ct. Two models are proposed for the pathogenesis of Ct-related early abortions: (i) direct zygote infection, and (ii) immune response to heat shock proteins expressed by the zygote and triggered by previous Ct infections.

Chlamydia trachomatis infection in male partners of infertile couples: incidence and sperm function

Chlamydia trachomatis infection is one of the most common sexually transmitted diseases. Its effect on male fertility, however, is still controversial. In this study, 284 male partners of infertile couples consulting the Center of Studies in Reproductive Biology (CEBRE) were analyzed. The incidence of C. trachomatis infection among male partners of infertile couples was 38.6%. There were no significant differences between infected and noninfected infertile men in any of the sperm parameters assessed (sperm concentration, motility and morphology). The results of the three bioassays developed to evaluate sperm physiology, namely spermatozoa-zona pellucida binding, acrosome reaction stimulated with human follicular fluid and zona-free hamster oocyte penetration, showed no differences between infected and noninfected men. Electron microscopy studies suggest that spermatozoa are active agents in the dissemination of the chlamydial infection; they could be acting as 'vehicles' for the pathogens. These, and other results, suggest that the possible effect of C. trachomatis on male fertility is not due to alterations in sperm 'quality' or function, but rather to the transmission of the disease to female partners, causing inflammatory processes and promoting the generation of antisperm antibodies.

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.

Colocalization of GABA and glycine in the ventral nucleus of the lateral lemniscus in rat: an in situ hybridization and semiquantitative immunocytochemical study

We have studied by in situ hybridization for GAD65 mRNA in thick sections and by semiquantitative postembedding immunocytochemistry in consecutive semithin sections, the expression of gamma-aminobutyric acid (GABA) and glycine in cell bodies and axosomatic puncta of the rat ventral nucleus of the lateral lemniscus (VNLL), a prominent monaural brainstem auditory structure. The in situ hybridization and the densitometric analysis of the immunostaining suggest that the rat VNLL contains two main populations of neurons. Approximately one-third of neurons are unstained with either technique and are presumably excitatory; their cell bodies are enveloped by a large number of glycine-immunoreactive puncta. Most if not all of the remaining two-thirds colocalize GABA and glycine and are assumed to be inhibitory. These two populations show a complementary distribution within the VNLL, with inhibitory neurons located mainly ventrally and excitatory neurons dorsally. In scatterplots of gray values measured from cell bodies, the double-labeled cells appear to form a single cluster in terms of their staining intensities for the two transmitter candidates. However, this cluster may have to be further subdivided because cells with extreme GABA/glycine ratios differ from those with average ratios with respect to location or size. The VNLL seems unique among auditory structures by its large number of neurons that colocalize GABA and glycine. Although the functional significance of this colocalization remains unknown, our results suggest that the VNLL exerts convergent excitatory and inhibitory influences over the inferior colliculus, which may underlie the timing processing in the auditory midbrain.

Depletion of substance P, neurokinin A and calcitonin gene-related peptide from the contralateral and ipsilateral caudal trigeminal nucleus following unilateral electrical stimulation of the trigeminal ganglion; a possible neurophysiological and neuroanatomical link to generalized head pain

Primary trigeminal neurons of the trigeminal ganglion (TG) innervate major parts of the face and head, including the dura. Electrical stimulation of the TG at specific parameters, can activate its nociceptive neurons and may serve as an experimental pain model. Markowitz [J. Neurosci. 7 (1987) 4129] reported that electrical stimulation of the trigeminal ganglion (TG) causes extravasation of plasma proteins from venules of the trigeminally innervated domain possibly due to the release of vasoactive substances. Neurogenic inflammation (vasodilatation, plasma protein extravasation, release of vasoactive peptides) in dura may serve as one of the possible pathomechanisms underlying vascular head pain [Moskowitz, Ann. Neurol. 16 (1984) 157]. We performed a unilateral electrical stimulation (7.5 Hz, 5 ms, 0.8-1.4 mA for 5 min) of the TG in rat, to induce a neurogenic inflammation in the peripheral trigeminal domain including the dura, looking for calcitonin gene related peptide (CGRP), substance P (SP) and neurokinin A (NKA) immunoreactivity (IR) in the caudal trigeminal nucleus (CTN) into which massive central trigeminal processes terminate. Here, we show patchy depletion(s) of CGRP-, SP- and NKA-IRs in the contralateral CTN of the rat in addition to their ipsilateral depletion. Such depletion is due to the release of these neuropeptides in the CTN leading to the activation of bilateral trigeminal nociceptive pathway. These data afford the possibility that under specific frequencies (which may roughly correlate to the intensity of the painful stimulus) and/or specific intensities (may correlate to specific areas of the peripheral trigeminal domain) of stimulation, activation of one side of the TG may activate bilateral trigeminal nociceptive pathway leading to the perception of an ill localized/generalized pain or headache rather than a unilateral one.

Prospective study of prognostic factors in community-acquired bacteremic pneumococcal disease in 5 countries

To define the influence of prognostic factors in patients with community-acquired pneumococcal bacteremia, a 2-year prospective study was performed in 5 centers in Canada, the United States, the United Kingdom, Spain, and Sweden. By multivariate analysis, the independent predictors of death among the 460 patients were age >65 years (odds ratio [OR], 2.2), living in a nursing home (OR, 2.8), presence of chronic pulmonary disease (OR, 2.5), high acute physiology score (OR for scores 9-14, 7.6; for scores 15-17, 22; and for scores >17, 41), and need for mechanical ventilation (OR, 4.4). Of patients with meningitis, 26% died. Of patients with pneumonia without meningitis, 19% of those with >/=2 lobes and 7% of those with only 1 lobe involved (P=.0016) died. The case-fatality rate differed significantly among the centers: 20% in the United States and Spain, 13% in the United Kingdom, 8% in Sweden, and 6% in Canada. Differences of disease severity and of frequencies and impact of underlying chronic conditions were factors of probable importance for different outcomes.

Community-acquired pneumonia in the elderly

The incidence of community-acquired pneumonia (CAP) in the elderly is higher compared to younger populations. In addition, pneumonia in the elderly is a life-threatening problem. As our demographics have changed, clinicians have developed a heightened interest in managing pneumonia in the elderly. The development of pneumonia in elderly patients differs from that in younger individuals due to a complex array of factors. (1) The organisms involved depend on the setting in which the pneumonia developed: either the nonhospitalized elderly patient with CAP or the institutionalized patient who develops nursing-home-acquired pneumonia. (2) Underlying comorbid conditions commonly exist in the elderly that affect the etiology and outcome of pneumonia. Overall, Streptococcus pneumoniae and Haemophilus influenzae are still the most common etiologies of pneumonia in the elderly. The true role of gram-negative bacilli remains unclear although these micro-organisms may be more common etiologic agents in nursing-home pneumonia. Some recent studies from Mediterranean areas have reported high rates of infection by Chlamydia pneumoniae, but the real role of this micro-organism has to be confirmed. Another important issue is that the presenting symptoms of pneumonia in the elderly can be subtle and sometimes difficult to recognize. Fever is frequently absent, and delirium or alteration of functional physical capacity may be the only manifestations. Mortality in the elderly with CAP is higher when compared to younger populations. However, this may be explained by the concomitant presence of comorbid conditions more than by age per se. This statement has to be kept in mind when considering hospital and, particularly, intensive care unit admissions. Finally, antibiotic pharmacokinetics in the elderly populations with CAP ought to be considered to avoid frequent side-effects and complications. Overall, antibiotic regimens in hospitalized elderly patients with CAP do not differ from other hospitalized CAP populations. An organized approach to assessing elderly patients with suspicion of pneumonia and an awareness of common pitfalls in the management of this pulmonary infection in this population are essential to improving outcomes.

Pulmonary complications in patients with haematological malignancies treated at a respiratory ICU

Patients with haematological malignancies developing severe pulmonary complications have a poor outcome, especially after bone-marrow transplantation (BMT). We studied the aetiology, the yield of different diagnostic tools, as well as the outcome and prognostic factors in the corresponding population admitted to our respiratory intensive care unit (RICU). Overall, 89 patients with haematological malignancies and pulmonary complications treated within a 10 yr period were included. The underlying malignancies were predominantly acute leukaemia and chronic myeloid leukaemia (66/89, 74%). Fifty-two of 89 (58%) patients were bone marrow recipients. An aetiological diagnosis could be obtained in 61/89 (69%) of cases. The aetiology was infectious in 37/89 (42%) and noninfectious in 24/89 (27%). Blood cultures and cytological examinations of bronchoalveolar lavage fluid were the diagnostic tools with the highest yield (13/43 (30%) and 13/45 (29%) positive results, respectively). Necropsy results were coincident with results obtained during the lifetime in 43% of cases with infectious and 60% with noninfectious aetiologies. Overall mortality was 70/89 (79%), and 47/52 (90%) in transplant recipients. The requirement of mechanical ventilation, BMT, and an interval <90 days of BMT prior to ICU admission were independent adverse prognostic factors. The outcome in this patient population was uniformly poor. It was worst in bone marrow recipients developing pulmonary complications <90 days after transplantation and requiring mechanical ventilation. Decisions about intensive care unit admission and mech-anical ventilation should seriously consider the dismal prognosis of these patients.

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.

Community-acquired pneumonia in the elderly. Clinical and nutritional aspects

Community-acquired pneumonia (CAP) in the elderly has a different clinical presentation than CAP in other age groups. Confusion, alteration of functional physical capacity, and decompensation of underlying illnesses may appear as unique manifestations. Malnutrition is also an associated feature of CAP in this population. We undertook a study to assess the clinical and nutritional aspects of CAP requiring hospitalization in elderly patients (over 65 yr of age). One hundred and one patients with pneumonia, consecutively admitted to a 1,000-bed teaching hospital over an 8-mo period, were studied (age: 78 +/- 8 yr, mean +/- SD). Nutritional aspects and the mental status of patients with pneumonia were compared with those of a control population (n = 101) matched for gender, age, and date of hospitalization. The main symptoms were dyspnea (n = 71), cough (n = 67), and fever (n = 64). The association of these symptoms with CAP was observed in only 32 patients. The most common associated conditions were cardiac disease (n = 38) and chronic obstructive pulmonary disease (COPD) (n = 30). Seventy-seven (76%) episodes of pneumonia were clinically classified as typical and 24 as atypical. There was no association between the type of isolated microorganism and the clinical presentation of CAP, except for pleuritic chest pain, which was more common in pneumonia episodes caused by classical microorganisms (p = 0.02). This was confirmed by a multivariate analysis (relative risk [RR] = 11; 95% confidence interval [CI]: 1.7 to 65; p = 0.0099). The prevalence of chronic dementia was similar in the pneumonia cohort (n = 25) and control group (n = 18) (p = 0.22). However, delirium or acute confusion were significantly more frequent in the pneumonia cohort than in controls (45 versus 29 episodes; p = 0.019). Only 16 patients with pneumonia were considered to be well nourished, as compared with 47 control patients (p = 0.001). Kwashiorkor-like malnutrition was the predominant type of malnutrition (n = 65; 70%) in the pneumonia patients as compared with the control patients (n = 31; 31%) (p = 0.001). The observed mortality was 26% (n = 26). Pleuritic chest pain is the only clinical symptom that can guide an empiric therapeutic strategy in CAP (typical versus atypical pneumonia). Both delirium and malnutrition were very common clinical manifestations of CAP in our study population.

Community-acquired pneumonia in the elderly: A multivariate analysis of risk and prognostic factors

To assess the risk and prognostic factors of community-acquired pneumonia occurring in the elderly (over age 65 yr) requiring hospitalization, two studies, case-control and cohort, were performed over an 8-mo period in a 1,000-bed university teaching hospital. We studied 101 patients with pneumonia (cases), age 78.5 +/- 7.9 yr (mean +/- SD). Each case was matched for sex, age (+/- 5 yr), and date of admission (+/- 2 d) with a control subject, without pneumonia during the preceding 3 yr, arriving at the emergency room. Etiologic diagnosis was obtained in 43 of 101 (42%) cases. The main microbial agents causing pneumonia were: Streptococcus pneumoniae (19 of 43, 44%), and Chlamydia pneumoniae (9 of 43, 21%). Gram-negative bacilli were uncommon (2 of 43, 5%). The multivariate analysis demonstrated that large-volume aspiration, and low serum albumin (< 30 mg/dl) were independent risk factors associated with the development of pneumonia. Crude mortality rate was 26% (26 of 101), while pneumonia-related mortality was 20% (20 of 101). The attributable mortality was 23% (odds ratio [OR]: 11.3; 95% confidence interval [CI]: 3.25 to 60.23; p < 0.0001). The multivariate analysis showed that patients had a worse prognosis if they were previously bedridden, had prior swallowing disorders, body temperature on admission was less than 37 degrees C, respiratory frequency was greater than 30/min or had three or more affected lobes on chest radiograph. Age by itself was not a significant factor related to prognosis. Among the significant risk factors, only nutritional status is probably amenable to medical intervention. The prognostic factors found in this study may help to identify, upon admission, those subjects at higher risk and who may require special observation.

Fetal and maternal blood oxygen affinity: a comparative study in llamas and sheep

We compared blood oxygen affinity (P50) and hemoglobin concentration among fetal and maternal llamas and sheep, as respective examples of species native to high and low altitudes. P50, hemoglobin concentration and blood oxygen content were determined at sea level in 16 pregnant llamas, 6 pregnant sheep and their respective fetuses. P50 was similar in fetal llamas and sheep, but maternal llamas had higher blood oxygen affinity than maternal sheep. As a consequence, the P50 difference between mother and fetus was less in llamas than in sheep. Fetal llamas had higher hemoglobin concentrations than fetal sheep. In contrast, the maternal hemoglobin concentrations were similar. The blood oxygen content was higher in fetal and maternal llamas than in fetal and maternal sheep. We conclude that the llama, a species native to the altiplano, has a higher blood oxygen content than the sheep, as determined in the fetus by a high hemoglobin concentration and in the mother by a low P50.

Sperm binding to the human zona pellucida after migration through human cervical mucus

During lactational amenorrhea a special type of cervical mucus, similar to that found during the luteal phase, is produced. This mucus, however, is able to support sperm migration. In the study described, the ability of spermatozoa to bind to the human zona pellucida (hZP) after migration through periovulatory and post-partum mucus was studied. Mucus was obtained from exclusively breastfeeding women in amenorrhea at 30, 60, 120 and 180 days post-partum. Periovulatory mucus samples from normally cycling women were used as a control. Flat capillary tubes were filled with BWW culture medium at the top and cervical mucus at the bottom. The tubes were immersed in a semen reservoir and the spermatozoa allowed to migrate through the mucus for 3 h into the culture media. Then the spermatozoa were coincubated with 3-4 hZP for 30 min and the number of bound spermatozoa per zona was counted. Periovulatory cervical mucus had an average Insler score of 14 +/- 0.5 as compared to 4.6 +/- 0.4 for post-partum mucus. Spermatozoa recovered from periovulatory mucus were always able to bind to the hZP in only 68 +/- 7% of the cases. Moreover, spermatozoa recovered from post-partum mucus bound to the ZP in lower numbers than did spermatozoa recovered fro periovulatory mucus (p < 0.03). These results suggest a greater ability of sperm-hZP binding after migration through periovulatory mucus and they also indicate that sperm binding to the ZP is possible even after sperm migration through a low quality mucus.

Prognostic factors influencing the outcome in pneumocystis carinii pneumonia in patients with AIDS

BACKGROUND

Studies attempting to identify the prognostic factors that influence the outcome of Pneumocystis carinii pneumonia (PCP) in patients with AIDS using a multivariate analysis are few. In order to identify those prognostic factors amenable to medical intervention, univariate and multivariate analyses were performed on 102 patients with AIDS suffering a first episode of PCP.

METHODS

One hundred and two consecutive patients with AIDS (51% drug abusers, 45% homosexuals, and 4% with other HIV risk factors) admitted to our institution between 1986 and 1989 whose respiratory infection was diagnosed by bronchoalveolar lavage were studied prospectively.

RESULTS

The overall mortality was 28%, rising to 79% in those patients who required mechanical ventilation. According to univariate analysis the following variables were related to a poor prognosis: age > 35 years; risk factor for HIV infection other than drug abuse; and AIDS diagnosis confirmed before 1988; PaO2 < 8 kPa at admission; severe acute respiratory failure on admission (PaO2/FIO2 < 20 kPa); mechanical ventilation; antibiotic therapy for PCP other than trimethoprim-sulphamethoxazole; multiple microbial pulmonary infection; serum lactate dehydrogenase (LDH) > 22.5 mukat/l on admission; serum albumin level < 30 g/l. Multivariate analysis showed that only mechanical ventilation was independently associated with a poor outcome.

CONCLUSIONS

The mortality of AIDS patients presenting with a first episode of PCP before 1990 was high (28%). The main prognostic factor associated with poor outcome was the requirement for mechanical ventilation due to severe acute respiratory failure.

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.

The retino-hypothalamic tract is involved in prolactin regulation in fetal sheep

To investigate the role of the retino-hypothalamic tract on fetal prolactin regulation, we examined the effect of ocular enucleation on fetal plasma prolactin. Eleven fetuses of Suffolk ewes were chronically catheterized during fall, and six of them were subjected to bilateral ocular enucleation. All ewes were kept at 12h:12h light:dark cycle (lights on at 0800 and off at 2000). The experiments were performed 5-9 days after surgery (GA control fetuses 125 +/- 1.5, optical enucleation 121.3 +/- 1.5 days). Blood samples were taken from fetuses hourly around the clock, and plasma prolactin and cortisol were measured by radioimmunoassay (RIA). Luteinizing hormone (LH) and Growth hormone (GH) were measured in pooled plasma samples from control and enucleated fetuses by RIA. Average plasma prolactin was 5-fold lower in enucleated than in control fetuses (9.6 +/- 0.5 and 54.2 +/- 3.3 ng/ml, SEM; P < 0.005). Both control and enucleated fetuses presented circadian rhythm of prolactin with acrophase between 1400 and 1830 h. An enucleated fetus was tested for response of prolactin to TRH. Prolactin increased as described in the literature. There was no change in plasma concentration of cortisol, LH or GH after ocular enucleation. Our data indicate that the optical pathway participates in prolactin regulation in the fetal sheep.

Effect of a melatonin implant on the circadian variation of plasma prolactin and rectal temperature in newborn sheep

Plasma prolactin and rectal temperature show a circadian rhythm in newborn sheep raised under continuous light. Melatonin lowers the concentration of plasma prolactin but it is not known if it affects its circadian rhythm. To detect whether melatonin acts on the circadian system we studied the effect of a subcutaneous melatonin implant in the circadian rhythms of prolactin and rectal temperature in newborn lambs raised under continuous light. We placed catheters in the pedal artery and vein in 9 newborn lambs (2-5 days of age). A subcutaneous melatonin implant was placed in 4 of the lambs at 9-12 days of age. Blood samples and rectal temperature measurements were obtained hourly for a period of 24 h, 11-15 days after the implant, at 20-27 days of age. To avoid interferences of heparin in our melatonin assay, serum melatonin concentration was measured before and during the implant in three additional newborns. Prolactin and melatonin were measured by RIA. Melatonin concentrations were 52.8 +/- 45.9 pg/ml (day) and 315.5 +/- 77.0 pg/ml (night) before treatment (SEM, P less than 0.001), and increased to 594.1 +/- 54.5 pg/ml after placing the implant (there was no difference in melatonin concentration between day and night during the time that the implant was in place). Melatonin had no effect on rectal temperature or its rhythm, but decreased basal plasma prolactin concentration (control: 97.5 +/- 11.3 ng/ml; treated: 25.1 +/- 2.4 ng/ml, P less than 0.001) and abolished the prolactin circadian rhythm, (Cosinor analysis): control: log prolactin (ng/ml) = 1.8 + 0.26 cos 15 (t - 11.16), p = 0.05; treated: log prolactin (ng/ml) = 1.2 + 0.14 cos 15 (t - 9.43), P = 0.36.

The circadian variation of prolactin in fetal sheep is affected by the seasons

Plasma PRL concentration shows a circadian variation in fetal and adult sheep. In the adult sheep the presence of this variation depends on the season. In this paper we investigated whether season affects the presence of the circadian variation of PRL in the fetal sheep. To that effect we measured plasma PRL concentration every 2 h for 24 h during summer, fall, and winter in three groups of fetal sheep whose gestational ages ranged from 125-133 days. Mean (+/- SEM) fetal plasma PRL concentrations were 352.8 +/- 65.0 ng/ml during summer (n = 6), 98.7 +/- 12.9 during fall (n = 8), and 10.5 +/- 2.6 during winter (n = 4). A 24-h variation of plasma PRL was detected during summer [PRL (ng/ml) = 352.8 + 85.2 cos 15 (t - 18.5); P = 0.007] and fall [PRL (ng/ml) = 98.7 + 26.6 cos 15 (t - 23.6); P = 0.041] but not during winter. The mesor and amplitude of the variation are higher in summer than in fall, and the acrophases differ by 5 h, taking place at dusk in summer and close to midnight in fall. These findings show that in fetal sheep, PRL responds to seasons in utero. The signal triggering this response is most likely photoperiod.

Fetal prolactin levels respond to a maternal melatonin implant

Seasonal PRL changes in adult sheep are controlled by photoperiod. The ability to detect photoperiod is mediated by the pineal gland through melatonin secretion. A rhythm in plasma melatonin has been described in fetal sheep. In this work we investigated whether the fetus responds to changes in circulating levels of melatonin. Fetal plasma PRL was measured every 2 h for 24 h, 7 days after the mother had received a sc Silastic implant containing approximately 1 g melatonin. Control fetuses received an empty implant. Melatonin is slowly released from implants, and it is known to cross the sheep placenta. Fetal plasma melatonin increased 10-fold after the implant. Plasma PRL in fetuses treated with melatonin was a third of that of control fetuses. Fetal plasma PRL concentrations were 56.6 +/- 5.7 ng/ml (mean +/- SE) in control and 18.1 +/- 2.7 ng/ml 7 days after the melatonin implant. We conclude from these data that the ability to respond to melatonin is present in sheep during fetal life.

Ontogeny of the circadian rhythm of cortisol in sheep

In this work we investigated the ontogeny of the rhythm of plasma cortisol in sheep. Plasma cortisol was measured by radioimmunoassay in blood samples obtained every 1 or 2 h, for periods of 24 or 48 h, in 13 fetal sheep (124-140 days of gestation; 130.6 +/- 1.5, mean +/- SE) and in 23 newborn (5-39 days of age). To this end, indwelling polyvinyl catheters were implanted into the femoral artery and vein in all animals. The presence of rhythm was determined by Cosinor Analysis. Newborns were separated into four groups. Group 1, newborns younger than 15 days of age (7.9 +/- 0.7 days), and Group 2, newborns older than 15 days of age (25.4 +/- 2.3), were raised under nyctohemeral conditions (12L:12D). Group 3, newborns younger than 15 days of age (11.4 +/- 0.9 days), and Group 4, newborns older than 15 days of age (22.0 +/- 1.2 days), were raised under constant light conditions. A 24-h rhythm of plasma cortisol (F) was observed in newborns over 15 days of age under both nyctohemeral: F (ng/ml) = 16.1 + 7.6 cos [15 (t-12.9)], (p = 0.01, n = 8) and constant light conditions: F (ng/ml) = 17.1 + 3.9 cos [15 (t-7.9)], (p = 0.02, n = 5). No rhythm was observed in fetal sheep or in newborn sheep younger than 15 days of age under nyctohemeral or constant light conditions.

Arginine vasopressin mediates cardiovascular responses to hypoxemia in fetal sheep

Acute hypoxemia results in hypertension, bradycardia, and cardiac output redistribution in fetal sheep. The blood flow redistribution is produced by differential changes in vascular resistance of various fetal organs. alpha-Adrenergic activity is one of the few vasoconstrictor mechanisms thus far identified in the hypoxemic fetal sheep. Arginine vasopressin (AVP) is a potent vasoconstrictor in adults. Since AVP administration to the normoxic fetus mimics some of the fetal cardiovascular responses to hypoxemia and fetal plasma AVP levels increase with hypoxemia, we examined the hypothesis that AVP modifies the fetal cardiovascular response to hypoxemia by changing the vascular resistance of some fetal vascular beds. To test this we determined fetal systemic arterial pressure and fetal cardiac output and its distribution during hypoxemia with and without the V1 AVP antagonist d(CH2)5-Tyr(Me)AVP. Fourteen fetal sheep (0.79-0.90 of gestation) were chronically catheterized. Five days after surgery fetal hypoxemia was induced by introducing a mixture of 95% N2-5% CO2 (10-20 l/min) into a maternal tracheal catheter. The hypoxemia was maintained for 40 min. Fetal heart rate, systemic arterial blood pressure, and combined ventricular output and its distribution (radiolabeled microspheres) were measured before hypoxemia, at 20 min of hypoxemia alone, and at 20 min of hypoxemia plus either AVP antagonist (n = 5) or NaCl 0.9% (n = 5, controls). Fetal hypertension and bradycardia were partially reversed after the AVP antagonist administration during hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of endogenous opioids in the cardiovascular responses to asphyxia in fetal sheep

Intravenous administration of the opioid receptor antagonist naloxone to asphyxiated fetal sheep increases the arterial blood pressure. We examined the hypothesis that endogenous opioids modify the cardiac output distribution during asphyxia due to changes in the vascular resistance of some fetal organs. Thirteen fetal sheep (0.8-0.9 of gestation) were chronically catheterized. Fetal asphyxia was induced by reducing the uterine blood flow with an inflatable occluder around the common internal iliac artery to approximately 50% of control for 40 min. Naloxone solution or the solvent alone was added for the last 20 min. Asphyxia caused hypertension, and the fetal arterial blood pressure further increased when asphyxiated fetuses received naloxone. Heart, brain, and adrenal blood flows increased due to the increase in blood pressure, with no changes in their vascular resistances. In contrast, kidney and carcass blood flows decreased, and their vascular resistances increased. We conclude that endogenous opioids inhibit the vasoconstriction of these vascular beds during fetal asphyxia.

Cardiorespiratory functions in the fetal llama

Factors which allow the adaptation of adult llamas to oxygen limitation include principally: low P50, small elliptical red cells with high hemoglobin concentration, high muscle myoglobin concentration, high capillary density and a more efficient O2 extraction at tissue levels. The fetal llama is known to have blood with a low P50 but it is not known whether it has further cardiorespiratory adaptations which could allow it to cope with a low oxygen milieu. To investigate this, we have measured fetal blood flow and blood oxygen content in 8 fetal llamas and compared the findings to similar measurements in 10 low altitude bred fetal sheep, during the last third of gestation. The llamas were born and raised at 4500 m. They were brought to Santiago (586 m) and were studied one week later. The results show that there was higher hemoglobin concentration and higher oxygen capacity in blood from the fetal llama compared to the fetal sheep. Fetal llama combined ventricular output and umbilical blood flow were less than one fourth of those found in fetal sheep. Regional blood flows and oxygen delivery to fetal tissues were in most cases less than half those found in the fetal sheep. Calculated vascular resistances in the fetal llama in almost all vascular beds are higher than those in fetal sheep. These studies suggest that basal fetal llama oxygen uptake is maintained due to an increased oxygen extraction by fetal llama tissues. This increased oxygen extraction may be the result of a high capillary density.(ABSTRACT TRUNCATED AT 250 WORDS)

Ontogeny of the circadian variation of plasma prolactin in sheep

The ontogeny of circadian rhythms is unknown. The newborn sheep has a circadian rhythm of temperature; to study the ontogeny of other rhythms, we examined the 24-h variation of plasma prolactin concentration in fetal and newborn sheep. To this effect, we measured plasma prolactin concentration in chronically catheterized fetuses (n = 7) and in newborn lambs raised under short day nycthemeral (12 light:12 dark, n = 13) or constant light conditions (n = 5). Indwelling catheters were implanted into the jugular vein and carotid artery of late gestation fetuses (0.9 gestation) and newborns (5-29 days old). Experiments were performed 4 or more days after surgery. Lambs were kept in a canvas sling and were fed cow's milk either by mouth or through a nasogastric catheter at established time intervals. Haematocrit, pH, and blood gases were measured before and after the experiments in all cases and remained within normal values. Lights were on and room temperature was maintained constant during the whole experiment. Samples were obtained every 1-2 h for 24 h in fetuses and newborn lambs under nycthemeral conditions and every hour for 48 h in newborn lambs kept under constant light. Plasma prolactin was measured by radioimmunoassay. The presence of a 24 h rhythm was determined by Cosinor analysis. Fetuses, aged 129 +/- 6 days (SD) n = 7, showed a variation in plasma prolactin concentration with a period of 24 h that fits the equation: plasma prolactin (ng ml-1) = 97.0 + 15.4 cos 15 (t-23.0), P = 0.035.(ABSTRACT TRUNCATED AT 250 WORDS)