physiology-lab-demonstration-glomerular-filtration-rate-in-a-rat

Physiology Lab Demonstration: Glomerular Filtration Rate in a Rat

Measurements of glomerular filtration rate (GFR), and the fractional excretion of sodium (Na) and potassium (K) are critical in assessing renal function ...

Thirst was induced by rapid i.v. infusion of hypertonic saline (0.51 M at 13.4 ml/min). Ten humans were neuroimaged by positron-emission tomography (PET) and four by functional MRI (fMRI). PET images were made 25 min after beginning infusion, when the sensation of thirst began to enter the stream of consciousness. The fMRI images were made when the maximum rate of increase of thirst occurred. The PET results showed regional cerebral blood flow changes similar to those delineated when thirst was maximal. These loci involved the phylogenetically ancient areas of the brain. fMRI showed activation in the anterior wall of the third ventricle, an area that is key in the genesis of thirst but is not an area revealed by PET imaging. Thus, this region plays as major a role in thirst for humans as for animals. Strong activations in the brain with fMRI included the anterior cingulate, parahippocampal gyrus, inferior and middle frontal gyri, insula, and cerebellum. When the subjects drank water to satiation, thirst declined immediately to baseline. A precipitate decline in intensity of activation signal occurred in the anterior cingulate area (Brodmann area 32) putatively related to consciousness of thirst. The intensity of activation in the anterior wall of the third ventricle was essentially unchanged, which is consistent with the fact that a significant time (15-20 min) would be needed before plasma Na concentration changed as a result of water absorption from the gut.

Neural correlates of the emergence of consciousness of thirst.

This study used positron-emission tomography to establish the patterns of brain activity involved in the isolated and concurrent experiences of thirst and pain. Ten subjects were scanned while experiencing pain evoked with noxious pressure, while experiencing thirst after the infusion of hypertonic saline, and while experiencing pain when thirsty. After the onset of thirst, noxious pressure evoked more intense sensations of pain. Noxious pressure did not change subjective ratings of thirst. Thirst caused activation in the anterior cingulate (Brodmann area 32) and the insula. Enhanced pain responses were associated with increased activity in cortical regions that are known to correlate with pain intensity, and also with unique activity in the pregenual anterior cingulate and ventral orbitofrontal cortex. These findings suggest a role for limbic and prefrontal cortices in the modulation of pain during the experience of thirst.

Unique, common, and interacting cortical correlates of thirst and pain.

Addition of up to 15.0 g/d salt to the diet of chimpanzees caused large rises in blood pressure, which reversed when the added salt was removed. Effects of more modest alterations to sodium intakes in chimpanzees, akin to current efforts to lower sodium intakes in the human population, are unknown.

Change in salt intake affects blood pressure of chimpanzees: implications for human populations.

Baboons (Papio hamadryas Sp.) develop features of the cardiometabolic syndrome and represent a clinically-relevant animal model in which to study the aetiology of the disorder. To further evaluate the baboon as a model for the study of the cardiometabolic syndrome, we developed a high sugar high fat diet and hypothesized that it could be used to induce adiposity gain and affect associated circulating biomarkers.

Eight week exposure to a high sugar high fat diet results in adiposity gain and alterations in metabolic biomarkers in baboons (Papio hamadryas sp.).

An inverse relationship between serum prostate specific antigen (PSA) levels and body mass index (BMI) has been reported in men but not in any animal model.

Serum prostate specific antigen changes in cynomolgus monkeys (Macaca fascicularis) on a high sugar high fat diet.

The metabolic syndrome is common in populations exposed to a typical Western diet. There is a lack of an animal model that mimics this condition.

A preliminary report on the feeding of cynomolgus monkeys (Macaca fascicularis) with a high-sugar high-fat diet for 33 weeks.

Androgen receptor [CAG](n) microsatellite has been linked to human diseases.

Androgen receptor CAG repeat polymorphism in males of six non-human primate species.

One challenge in understanding the polygenic disease of hypertension is elucidating the genes involved and defining responses to environmental factors. Many studies focus on animal models of hypertension; however, this does not necessarily extrapolate to humans. Current technology and cost limitations are prohibitive in fully evaluating hypertension within humans. Thus, we have designed a single-array platform that allows direct comparison of genes relevant to hypertension in animal models and non-human primates/human hypertension. The custom array is targeted to 328 genes known to be potentially related to blood pressure control. Studies compared gene expression in the kidney from normotensive rats and baboons. We found 74 genes expressed in both the rat and baboon kidney, 41 genes expressed in the rat kidney that were not detected in the baboon kidney and 34 genes expressed in the baboon kidney that were not detected in the rat kidney. To begin the evaluation of the array in a pathological condition, kidney gene expression was compared between the salt-sensitive deoxycorticosterone acetate (DOCA) rat model of hypertension and sham animals. Gene expression in the renal cortex and medulla from hypertensive DOCA compared with sham rats revealed three genes differentially expressed in the renal cortex: annexin A1 (up-regulated; relative intensity: 1.316 Â± 0.321 versus 2.312 Â± 0.283), glutamate-cysteine ligase (down-regulated; relative intensity: 3.738 Â± 0.174 versus 2.645 Â± 0.364) and glutathione-S transferase (down-regulated; relative intensity: 5.572 Â± 0.246 versus 4.215 Â± 0.411) and 21 genes differentially expressed in the renal medulla. Interestingly, few genes were differentially expressed in the kidney in the DOCA-salt model of hypertension; this may suggest that the complexity of hypertension may be the result of only a few gene-by-environment responsive events.

A custom rat and baboon hypertension gene array to compare experimental models.

Eine Herausforderung im Verst&auml;ndnis der Polygene Krankheit der Hypertonie ist die Gene beteiligt und Antworten zu Umweltfaktoren definieren elucidating. Viele Studien konzentrieren sich auf Tiermodellen f&uuml;r Hypertonie; Allerdings dies nicht notwendigerweise auf den Menschen extrapolieren. Aktuelle Kosten- und Einschr&auml;nkungen sind bei der Bewertung vollst&auml;ndig Hypertonie innerhalb Menschen unerschwinglich. Daher haben wir eine Einzel-Array-Plattform entwickelt, die direkten Vergleich von Genen f&uuml;r Bluthochdruck in Tiermodellen und nicht-menschlichen Primaten/Mensch Bluthochdruck erlaubt. Benutzerdefinierte Arrays zielt auf 328 Gene bekannt, um potenziell mit Blutdruck-Kontrolle in Zusammenhang stehen. Studien verglichen die Genexpression in der Niere aus normotensive Ratten und Paviane. Wir fanden 74 Gene ausgedr&uuml;ckt in der Ratte und Pavian-Niere, 41 Gene ausgedr&uuml;ckt in der Ratte-Niere, die nicht in der Pavian-Niere erkannt wurden und 34 Gene ausgedr&uuml;ckt in der Pavian-Niere, die nicht in der Ratte-Niere festgestellt wurden. Um die Bewertung des Arrays in einem pathologischen Zustand zu beginnen, wurde Niere Genexpression zwischen den Salz-Sensitive Deoxycorticosterone Acetat (DOCA) Rattenmodell f&uuml;r Bluthochdruck und Schein Tiere verglichen. Genexpression in der renalen Cortex und Medulla von Hypertensive DOCA Schein Ratten gegen&uuml;ber ergab drei Genen differenziell ausgedr&uuml;ckt in der renalen Kortex: annexin A1 (oben-geregelt; relative Intensit&auml;t: 1.316 &plusmn; 0.321 gegen&uuml;ber 2.312 &plusmn; 0,283), Glutamat-Cystein-Ligase (unten-geregelt; relative Intensit&auml;t: 3.738 &plusmn; 0,174 gegen&uuml;ber 2.645 &plusmn; 0,364) und Glutathion-S-Transferase (unten-geregelt; relative Intensit&auml;t: 5.572 &plusmn; 0.246 gegen&uuml;ber 4.215 &plusmn; 0.411) und 21 Gene differentiell in der renalen Medulla ausgedr&uuml;ckt. Interessanterweise wurden nur wenige Gene in der Niere im DOCA-Salz-Modell der Hypertonie differentiell ausgedr&uuml;ckt; Dies kann bedeuten, dass die Komplexit&auml;t der Hypertonie aus nur wenigen gen-durch-Umwelt reagieren Ereignisse ergeben kann.

Ein benutzerdefiniertes Ratte und Pavian Hypertonie gen Array, experimentelle Modelle zu vergleichen.

Naturally occurring type 2 diabetes has been found in a colony of baboons. Ongoing characterization of the baboon colony maintained at the Southwest National Primate Research Center has revealed a significant range of glucose sensitivity with some animals clearly diabetic.   Seven baboons, four with diabetes and three without diabetes, underwent histopathological investigation. Three diabetic animals were diagnosed using fasting blood glucose, hemoglobin A1C, and intravenous glucose tolerance test, and a fourth one was known to have hyperglycemia. One control baboon and three baboons with diabetes had microalbuminuria. On kidney biopsy, diabetic baboons had thickening of the glomerular basement membrane and mesangial matrix expansion compared to controls. Immunohistochemistry showed the diabetic animals had increased mesangial expression of cellular fibronectin ED-A. Two diabetic animals with microalbuminuria had evidence of mesangiolysis with the formation of an early nodule. One diabetic animal had a Kimmestiel-Wilson nodule. We conclude that the baboon represents a useful primate model of diabetes and nephropathy that resembles the nephropathy associated with type 2 diabetes in humans.

Renal histopathology of a baboon model with type 2 diabetes.

We established a model of chronic portal vein catheterization in an awake nonhuman primate to provide a comprehensive evaluation of the metabolic response to low-carbohydrate/high-fat (LCHF; 20% carbohydrate and 65% fat) and high-carbohydrate/low-fat (HCLF; 65% carbohydrate and 20% fat) meal ingestion. Each meal was given 1 wk apart to five young adult (7.8 ± 1.3 yr old) male baboons. A [U-¹³C]glucose tracer was added to the meal, and a [6,6-²H₂]glucose tracer was infused systemically to assess glucose kinetics. Plasma areas under the curve (AUCs) of glucose, insulin, and C-peptide in the femoral artery and of glucose and insulin in the portal vein were higher (P ≤ 0.05) after ingestion of the HCLF compared with the LCHF meal. Compared with the LCHF meal, the rate of appearance of ingested glucose into the portal vein and the systemic circulation was greater after the HCLF meal (P < 0.05). Endogenous glucose production decreased by ∼40% after ingestion of the HCLF meal but was not affected by the LCHF meal (P < 0.05). Portal vein blood flow increased (P < 0.001) to a similar extent after consumption of either meal. In conclusion, a LCHF diet causes minimal changes in the rate of glucose appearance in both portal and systemic circulations, does not affect the rate of endogenous glucose production, and causes minimal stimulation of C-peptide and insulin. These observations demonstrate that LCHF diets cause minimal perturbations in glucose homeostasis and pancreatic β-cell activity.

Metabolic response to high-carbohydrate and low-carbohydrate meals in a nonhuman primate model.

The baboon is an invaluable model for the study of human health and disease, including many complex diseases of the kidney. Although scientists have made great progress in developing this animal as a model for numerous areas of biomedical research, genomic resources for the baboon, such as a quality annotated genome, are still lacking. To this end, we characterized the baboon kidney transcriptome using high-throughput cDNA sequencing (RNA-Seq) to identify genes, gene variants, single nucleotide polymorphisms (SNPs), insertion-deletion polymorphisms (InDels), cellular functions, and key pathways in the baboon kidney to provide a genomic resource for the baboon. Analysis of our sequencing data revealed 45,499 high-confidence SNPs and 29,813 InDels comparing baboon cDNA sequences with the human hg18 reference assembly and identified 35,900 cDNAs in the baboon kidney, including 35,150 transcripts representing 15,369 genic genes that are novel for the baboon. Gene ontology analysis of our sequencing dataset also identified numerous biological functions and canonical pathways that were significant in the baboon kidney, including a large number of metabolic pathways that support known functions of the kidney. The results presented in this study catalogues the transcribed mRNAs, noncoding RNAs, and hypothetical proteins in the baboon kidney and establishes a genomic resource for scientists using the baboon as an experimental model.

The baboon kidney transcriptome: analysis of transcript sequence, splice variants, and abundance.

A major challenge for understanding susceptibility to common human diseases is determining genetic and environmental factors that influence mechanisms underlying variation in disease-related traits. The most common diseases afflicting the US population are complex diseases that develop as a result of defects in multiple genetically controlled systems in response to environmental challenges. Unraveling the etiology of these diseases is exceedingly difficult because of the many genetic and environmental factors involved. Studies of complex disease genetics in humans are challenging because it is not possible to control pedigree structure and often not practical to control environmental conditions over an extended period of time. Furthermore, access to tissues relevant to many diseases from healthy individuals is quite limited. The baboon is a well-established research model for the study of a wide array of common complex diseases, including dyslipidemia, hypertension, obesity, and osteoporosis. It is possible to acquire tissues from healthy, genetically characterized baboons that have been exposed to defined environmental stimuli. In this review, we describe the genetic and physiologic similarity of baboons with humans, the ability and usefulness of controlling environment and breeding, and current genetic and genomic resources. We discuss studies on genetics of heart disease, obesity, diabetes, metabolic syndrome, hypertension, osteoporosis, osteoarthritis, and intrauterine growth restriction using the baboon as a model for human disease. We also summarize new studies and resources under development, providing examples of potential translational studies for targeted interventions and therapies for human disease.

Baboons as a model to study genetics and epigenetics of human disease.

Lower body negative pressure (LBNP), a model of hemorrhage (Hem), shifts blood to the legs and elicits central hypovolemia. This study compared responses to LBNP and actual Hem in sedated baboons. Arterial pressure, pulse pressure (PP), central venous pressure (CVP), heart rate, stroke volume (SV), and +dP/dt were measured. Hem steps were 6.25%, 12.5%, 18.75%, and 25% of total estimated blood volume. Shed blood was returned, and 4 wk after Hem, the same animals were subjected to four LBNP levels which elicited equivalent changes in PP and CVP observed during Hem. Blood gases, hematocrit (Hct), hemoglobin (Hb), plasma renin activity (PRA), vasopressin (AVP), epinephrine (EPI), and norepinephrine (NE) were measured at baseline and maximum Hem or LBNP. LBNP levels matched with 6.25%, 12.5%, 18.75%, and 25% hemorrhage were -22 ± 6, -41 ± 7, -54 ± 10, and -71 ± 7 mmHg, respectively (mean ± SD). Hemodynamic responses to Hem and LBNP were similar. SV decreased linearly such that 25% Hem and matching LBNP caused a 50% reduction in SV. Hem caused a decrease in Hct, Hb, and central venous oxygen saturation (ScvO2). In contrast, LBNP increased Hct and Hb, while ScvO2 remained unchanged. Hem caused greater elevations in AVP and NE than LBNP, while PRA, EPI, and other hematologic indexes did not differ between studies. These results indicate that while LBNP does not elicit the same effect on blood cell loss as Hem, LBNP mimics the integrative cardiovascular response to Hem, and validates the use of LBNP as an experimental model of central hypovolemia associated with Hem.

Validation of lower body negative pressure as an experimental model of hemorrhage.

Trypanosoma cruzi, the causative agent of Chagas' disease, preferentially infects cardiac and digestive tissues. Baboons living in Texas (Papio hamadryas) and cynomolgus monkeys (Macaca fascicularis) have been reported to be infected naturally with T. cruzi. In this study, we retrospectively reviewed cases of animals that were diagnosed with lymphocytic myocarditis and used a polymerase chain reaction (PCR)-based method (S36/S35 primer set) to amplify T. cruzi DNA from archived frozen and formalin-fixed paraffin-embedded (FFPE) cardiac tissues. We show that the PCR method is applicable in archived frozen and FFPE tissues and the sensitivity is in the femtogram range. A positive correlation between PCR positivity and lymphocytic myocarditis in both baboons and cynomolgus monkeys is shown. We also show epicarditis as a common finding in animals infected with T. cruzi.

Correlation between presence of Trypanosoma cruzi DNA in heart tissue of baboons and cynomolgus monkeys, and lymphocytic myocarditis.

The function of prostate-specific antigen (PSA) is to liquefy the semen coagulum so that the released sperm can fuse with the ovum. Fifteen spliced variants of the PSA gene have been reported in humans, but little is known about alternative splicing in nonhuman primates. Positive selection has been reported in sex- and reproductive-related genes from sea urchins to Drosophila to humans; however, there are few studies of adaptive evolution of the PSA gene. Here, using polymerase chain reaction (PCR) product cloning and sequencing, we study PSA transcript variant heterogeneity in the prostates of chimpanzees (Pan troglodytes), cynomolgus monkeys (Macaca fascicularis), baboons (Papio hamadryas anubis), and African green monkeys (Chlorocebus aethiops). Six PSA variants were identified in the chimpanzee prostate, but only two variants were found in cynomolgus monkeys, baboons, and African green monkeys. In the chimpanzee the full-length transcript is expressed at the same magnitude as the transcripts that retain intron 3. We have found previously unidentified splice variants of the PSA gene, some of which might be linked to disease conditions. Selection on the PSA gene was studied in 11 primate species by computational methods using the sequences reported here for African green monkey, cynomolgus monkey, baboon, and chimpanzee and other sequences available in public databases. A codon-based analysis (dN/dS) of the PSA gene identified potential adaptive evolution at five residue sites (Arg45, Lys70, Gln144, Pro189, and Thr203).

Article	Year
Neural correlates of the emergence of consciousness of thirst. Proceedings of the National Academy of Sciences of the United States of America\| PubMed ID: 14657368	2003
Unique, common, and interacting cortical correlates of thirst and pain. Proceedings of the National Academy of Sciences of the United States of America\| PubMed ID: 16461454	2006
Change in salt intake affects blood pressure of chimpanzees: implications for human populations. Circulation\| PubMed ID: 17785625	2007
Eight week exposure to a high sugar high fat diet results in adiposity gain and alterations in metabolic biomarkers in baboons (Papio hamadryas sp.). Cardiovascular diabetology\| PubMed ID: 21034486	2010
Serum prostate specific antigen changes in cynomolgus monkeys (Macaca fascicularis) on a high sugar high fat diet. The Prostate\| PubMed ID: 21713965	2012
A preliminary report on the feeding of cynomolgus monkeys (Macaca fascicularis) with a high-sugar high-fat diet for 33 weeks. Journal of medical primatology\| PubMed ID: 21812784	2011
Androgen receptor CAG repeat polymorphism in males of six non-human primate species. Journal of medical primatology\| PubMed ID: 21978295	2012
A custom rat and baboon hypertension gene array to compare experimental models. Experimental biology and medicine (Maywood, N.J.)\| PubMed ID: 22228705	2012
Renal histopathology of a baboon model with type 2 diabetes. Toxicologic pathology\| PubMed ID: 22552392	2012
Metabolic response to high-carbohydrate and low-carbohydrate meals in a nonhuman primate model. American journal of physiology. Endocrinology and metabolism\| PubMed ID: 23269412	2013
The baboon kidney transcriptome: analysis of transcript sequence, splice variants, and abundance. PloS one\| PubMed ID: 23637735	2013
Baboons as a model to study genetics and epigenetics of human disease. ILAR journal / National Research Council, Institute of Laboratory Animal Resources\| PubMed ID: 24174436	2013
Validation of lower body negative pressure as an experimental model of hemorrhage. Journal of applied physiology (Bethesda, Md. : 1985)\| PubMed ID: 24356525	2014
Correlation between presence of Trypanosoma cruzi DNA in heart tissue of baboons and cynomolgus monkeys, and lymphocytic myocarditis. The American journal of tropical medicine and hygiene\| PubMed ID: 24567317	2014
Analysis of prostate-specific antigen transcripts in chimpanzees, cynomolgus monkeys, baboons, and African green monkeys. PloS one\| PubMed ID: 24732672	2014

Robert Shade

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