Impact of NO-synthase inhibition on renal hemodynamics in normotensive and hypertensive subjects

OBJECTIVE

To examine the acute effects of NO-synthase inhibition on renal hemodynamics in normotensive and hypertensive subjects.

METHODS

Changes of renal plasma flow (RPF) and glomerular filtration rate (GFR) in response to intravenous infusions of NG-monomethyl-l-arginine (l-NMMA) (3 mg/kg per 30 min) were measured in 32 normotensive and in 39 essential hypertensive patients by use of clearance technique.

RESULTS

l-NMMA significantly decreased RPF in normotensive and hypertensive individuals (P < 0.001), while GFR was preserved. Changes of renal hemodynamic parameters were similar in hypertensive and normotensive subjects (deltaRPF: -88 +/- 89 versus -81 +/- 105 ml/min, P = NS; deltaGFR 1.6 +/- 8.2 versus 4.3 +/- 8.9 ml/min, P = NS) Furthermore, l-NMMA increased mean arterial pressure (deltaMAP 5.3 +/- 6.3 versus 6.0 +/- 6.1 mmHg, P = NS) and decreased heart rate (deltaHR -5.8 +/- 3.9 versus -4.1 +/- 3.8 beats/min, P = NS) to a similar extent in both groups.

CONCLUSION

Basal NO synthesis of the renal vasculature is not impaired in patients with established essential hypertension.

Altered aldosterone response to salt intake and angiotensin II infusion in young normotensive men with parental history of arterial hypertension

OBJECTIVE

An increased sensitivity to angiotensin II (Ang II) has been observed in patients with established hypertension. In the current study we tested whether young normotensive subjects with positive family history of arterial hypertension exhibit an increased sensitivity to Ang II, thereby potentially contributing to the pathogenesis of essential hypertension in these subjects.

METHODS AND DESIGN

Normotensive young men (25 +/- 2 years) with positive family history (PFH) (n = 28) and negative family history (NFH) (n = 60) of arterial hypertension were investigated to study aldosterone response, and systemic and renal haemodynamic changes (p-aminohippurate- and inulin-clearance) to Ang II infusion (0.5 and 3.0 ng/min per kg). In addition, aldosterone response to salt loading (5 g/day for 1 week) was analysed.

RESULTS

Ambulatory blood pressure (ABP) (mean: 84 +/- 4 versus 83 +/- 4 mmHg; NS), body mass index (23.5 +/- 2.5 versus 24.1 +/- 2.4 kg/m(2); NS), and urinary sodium excretion (191 +/- 55 versus 170 +/- 73 mmol/24 h; NS) did not differ between PFH and NFH at baseline. Changes in BP, urinary sodium and potassium excretion were similar between PFH and NFH in response to salt loading. However, salt loading did not result in an adequate suppression of aldosterone in PFH compared with NFH (8 +/- 62 versus -32 +/- 39 pg/ml; P < 0.001). Baseline values and changes in mean arterial BP (NFH: +13.4 +/- 7.6; PFH: +14.4 +/- 5.3 mmHg; NS), renal plasma flow (NFH: - 113 +/- 68; PFH: - 122 +/- 64 ml/min; NS) and glomerular filtration rate (NFH: +5.0 +/- 5.3; PFH: +4.2 +/- 8.3 ml/min; NS) in response to Ang II (3.0 ng/min per kg) were similar between the two groups. In contrast, the increases in serum aldosterone (PFH: 63.6 +/- 70.1 versus NFH: 37.7 +/- 46.8 pg/ml; P < 0.05) and urinary potassium excretion (PFH: 0.05 +/- 0.1 versus NFH: -0.01 +/- 0.07 mmol/min; P < 0.05) 30 min after stopping Ang II infusion were more pronounced and prolonged in PFH than in NFH.

CONCLUSIONS

Our findings suggest that young normotensive subjects with parental history of arterial hypertension are characterized by an inadequate suppression of aldosterone production in response to salt loading and an exaggerated and prolonged hyper-responsiveness of aldosterone secretion in response to Ang II. This might contribute to the increased risk for the development of essential hypertension in subjects with positive family history of arterial hypertension.

HELLP syndrome in the 18th week of gestation in association with elevated angiotensin AT(1)-receptor autoantibodies

We present a 24-year-old woman with a twin pregnancy who was with a typical HELLP syndrome at the 18th week of pregnancy. One fetus was dead, while the other was severely growth retarded. Our patient had agonistic autoantibodies directed at the angiotensin AT(1)-receptor. Termination of the pregnancy proved necessary. This report is the first to our knowledge associating HELLP syndrome with angiotensin AT(1)-receptor antibodies. Since the antibodies may have a pathogenic significance, their removal could permit the prolongation of pregnancy in preeclamptic and HELLP syndrome patients.

Impaired sodium excretion during mental stress in mild essential hypertension

In hypertensive rats, environmental stress causes sodium retention by an exaggerated increase in renal sympathetic nerve activity, which is modulated by angiotensin II. We tested whether similar effects can be observed in humans. In 66 normotensive subjects (half of them with a family history of hypertension) and 36 subjects with mild essential hypertension, urinary sodium excretion and renal hemodynamics were examined at rest and during mental stress treated either with placebo or ACE inhibition in a double-blind, randomized, cross-over design. Despite a marked increase in glomerular filtration rate in response to mental stress (Deltaglomerular filtration rate, 4.3+/-7.7 mL/min in normotensives without versus 5.6+/-8.4 mL/min in normotensives with a family history versus 10.1+/-5.7 mL/min in patients with mild essential hypertension; P:<0.002), the increase in urinary sodium excretion was blunted in patients with mild essential hypertension (Deltaurinary sodium excretion, 0.12+/-0.17 mmol/min versus 0.10+/-0.14 mmol/min versus 0.05+/-0.14 mmol/min; P:<0.05). ACE inhibition corrected the natriuretic response to mental stress in subjects with mild essential hypertension (Deltaurinary sodium excretion, 0.05+/-0.14 mmol/min with placebo versus 0.13+/-0.19 mmol/min with ACE inhibition; P:<0.01); thus, after ACE inhibition, urinary sodium excretion increased similarly in all 3 groups. In conclusion, impaired sodium excretion occurs during mental stress in human essential hypertension but not in subjects with positive family history of hypertension. This abnormality in sodium handling during activation of the sympathetic nervous system appears to be mediated by angiotensin II.

Electronic compliance monitoring in resistant hypertension: the basis for rational therapeutic decisions

OBJECTIVE

Incomplete compliance is one of several possible causes of uncontrolled hypertension. Yet, non-compliance remains largely unrecognized and is falsely interpreted as treatment resistance, because it is difficult to confirm or exclude objectively. The goal of this study was to evaluate the potential benefits of electronic monitoring of drug compliance in the management of patients with resistant hypertension.

METHODS

Forty-one hypertensive patients resistant to a three-drug regimen (average blood pressure 156/ 106 +/- 23/11 mmHg, mean +/- SD) were studied prospectively. They were informed that for the next 2 months, their presently prescribed drugs would be provided in electronic monitors, without any change in treatment, so as to provide the treating physician with a measure of their compliance. Thereafter, patients were offered the possibility of prolonging the monitoring of compliance for another 2 month period, during which treatment was adapted if necessary.

RESULTS

Monitoring of compliance alone was associated with a significant improvement of blood pressure at 2 months (145/97 +/- 20/15 mmHg, P < 0.01). During monitoring, blood pressure was normalized (systolic < 140 mmHg or diastolic < 90 mmHg) in one-third of the patients and insufficient compliance was unmasked in another 20%. When analysed according to tertiles of compliance, patients with the lowest compliance exhibited significantly higher achieved diastolic blood pressures (P = 0.04). In 30 patients, compliance was monitored up to 4 months and drug therapy was adapted whenever necessary. In these patients, a further significant decrease in blood pressure was obtained (from 150/100 +/- 18/15 to 143/94 +/- 22/11 mmHg, P = 0.04/0.02).

CONCLUSIONS

These results suggest that objective monitoring of compliance using electronic devices may be a useful step in the management of patients with refractory hypertension, as it enables physicians to take rational decisions based on reliable and objective data of drug compliance and hence to improve blood pressure control.

Vascular reactivity in patients with preeclampsia and HELLP (hemolysis, elevated liver enzymes, and low platelet count) syndrome

OBJECTIVE

Early structural and functional changes in the systemic vasculature have been proposed to play a major pathogenetic role in preeclampsia and HELLP (hemolysis, elevated liver enzymes, and low platelet count) syndrome. The aim of the study was to determine vascular reactivity in patients with preeclampsia with and without HELLP syndrome with respect to those in healthy pregnant control subjects.

STUDY DESIGN

Forearm blood flow was measured by strain gauge plethysmography with the venous occlusion technique in 12 hypertensive patients with HELLP syndrome, in 8 patients with preeclampsia without HELLP syndrome, and in 8 healthy normotensive pregnant control subjects. To determine vascular reactivity the forearm blood flow was measured at baseline and after forearm occlusion for a period of 5 minutes (reactive hyperemia). The investigations were repeated 4 to 6 months post partum. Forearm vascular resistance was calculated as the ratio of mean arterial pressure to forearm blood flow.

RESULTS

Mean arterial pressure at rest was elevated in patients with preeclampsia (116 +/- 20 mm Hg) and in patients with HELLP syndrome (110 +/- 16 mm Hg) with respect to healthy pregnant control subjects (86 +/- 10 mm Hg; P <.05). Forearm blood flow at rest was not statistically different in patients with preeclampsia (5.1 +/- 2.6 mL/min per 100 mL) and with HELLP syndrome (4.7 +/- 1.5 mL/min per 100 mL) with respect to pregnant control subjects (5.9 +/- 3.1 mL/min per 100 mL); however, forearm vascular resistance at rest was elevated in patients with preeclampsia (25.9 +/- 9.5 units; P <.05) and in patients with HELLP syndrome(24.6 +/- 6.9 units; P <.05) with respect to healthy control subjects (17.0 +/- 6.1 units). During reactive hyperemia the peak forearm blood flow, which is an indicator of maximal vasodilatory capacity, was impaired in patients with preeclampsia (21.9 +/- 8.2 mL/min per 100 mL; P <.05) but not in patients with HELLP syndrome (37.4 +/- 17.5 mL/min per 100 mL) and healthy control subjects (44.9 +/- 15.0 mL/min per 100 mL). Consequently, minimum forearm vascular resistance was higher in women with preeclampsia (6.1 +/- 1.9 units) than in both women with HELLP syndrome (3.5 +/- 1.6 units) and the control subjects (2.8 +/- 2.4 units).

CONCLUSION

Despite similarly elevated forearm vascular resistances at rest in patients with HELLP syndrome and in patients with preeclampsia, forearm vascular resistance during reactive hyperemia did not differ significantly from that in healthy control subjects in the women with HELLP syndrome but was increased in women with preeclampsia. Vasodilatory reactivity thus is reduced in preeclampsia but not in HELLP syndrome, which suggests different alterations of the vasculature.

Functional gene testing of the Glu298Asp polymorphism of the endothelial NO synthase

OBJECTIVES

To test whether the Glu298Asp polymorphism of the endothelial nitric oxide synthase (eNOS) gene is of functional relevance in humans by altering endothelium-dependent vasodilation.

BACKGROUND

The Asp298 variant of the eNOS gene product has been associated with arterial hypertension, coronary artery disease and myocardial infarction. The pathogenetic mechanism has not yet been elucidated. Since endothelium-dependent vasodilation has been shown to be impaired in these disorders, we hypothesized that the Glu298Asp polymorphism of the eNOS gene influences endothelium-dependent vasodilation.

METHODS

In 80 patients with normal or elevated cholesterol, endothelium-dependent and -independent vasodilation was assessed. Forearm blood flow was measured by plethysmography in response to intra-arterial (i.a.) infusion of 12 and 48 microg/min acetylcholine and 3.2 and 12.8 microg/min nitroprusside, respectively. NG-monomethyl-L-arginine (L-NMMA) in doses of 4, 8 and 16 micromol/min was infused to test basal nitric oxide (NO) production and release. Genomic DNA was extracted from blood samples to determine the Glu298Asp polymorphism of the eNOS gene at position 1917 G/T after BanII restriction.

RESULTS

Baseline parameters (age, gender, blood pressure, body mass index, cholesterol level) were similar across the genotypes. Genotype frequencies did not deviate from the Hardy-Weinberg equilibrium. No differences in forearm blood flow to i.a. acetylcholine (average increase: + 554 +/- 371%), nitroprusside or L-NMMA infusion were found across the eNOS genotypes, neither for endothelium-dependent or endothelium-independent vasodilation, nor for basal NO production and release. Our sample size of n = 80 had a power of > 80% (beta = 0.20) with a P value < 0.05 (alpha = 0.05) to detect a 200% difference in forearm blood flow response to 48 microg/min acetylcholine.

CONCLUSIONS

At a power of 80%, we can exclude a relevant effect on endothelium-dependent vasodilation due to the eNOS Glu298Asp polymorphism. Thus, our functional genetic study does not suggest any biological effect of the eNOS Glu298Asp genotype on the cardiovascular system via an influence on endothelium-dependent vasodilation.

Sequences from the 5' flanking region of the epsilon-globin gene support the relationship of Callicebus with the pitheciins

The purpose of this study was to determine nucleotide sequences from the 5' flanking region of the epsilon-globin gene of selected platyrrhine primates and to analyze the data for phylogenetic information and estimated times of divergence. We report new sequence data for two species of New World monkeys, Callicebus torquatus and Pithecia irrorata. We analyzed these data in conjunction with homologous sequences from other primate species. The data support the hypothesis that the titi monkeys (Callicebus) and seed predators (Tribe Pitheciini) form a clade (Subfamily Pitheciinae), and also provide limited support for that subfamily being allied with the atelines. We also present estimated dates of divergence for the Callicebus and pitheciin lineages.

New Syntheses with Oils and Fats as Renewable Raw Materials for the Chemical Industry

Oils and fats are the most important renewable raw materials for the chemical industry. Hitherto, industrial oleochemistry has concentrated predominantly on the carboxy functionality of fatty acids but, more recently, modern synthetic methods have been applied extensively to fatty compounds for the selective functionalization of the alkyl chain. Radical, electrophilic, nucleophilic, and pericyclic as well as transition metal catalyzed additions to the C-C double bond of, for example, oleic acid as the prototype of a readily accessible, unsaturated fatty acid have led to a large number of novel fatty compounds from which interesting properties are expected. Functionalization of C-H bonds in the alkyl chain is also feasible with remarkable selectivity. Effective and highly versatile catalysts for the metathesis of esters of unsaturated fatty acids have been developed, which lead to new and interesting omega-unsaturated fatty acids. The epoxidation of unsaturated fatty acids has been developed extensively. Enzymatic reactions allow syntheses with high selectivity and yield of mono- and diglycerides and esters of carbohydrates with a variety of surfactant properties. Regio- and enantioselective microbial hydrations and hydroxylations widen the spectrum of selective reactions. Of considerable significance is that, with the use of gene technology, natural oils and fats have been improved significantly and will be improved still further, insofar as they show a more uniform and often unusual fatty acid spectrum. Numerous fatty acids are now available in a purity which makes them attractive for synthesis and as raw materials for the chemical industry.

Computer simulations of enantioselective ester hydrolyses catalyzed by Pseudomonas cepacia lipase

On the basis of the X-ray crystal structure of the lipase from Pseudomonas cepacia (PcL)-an enzyme representative for a whole family of Pseudomonas lipases (lipase PS, SAM-2, AK 10, and others with a high degree of homology with PcL)-a computational study was performed to rationalize both the enantioselectivity and substrate specificity (tolerance) displayed by this lipase in the enantioselective hydrolysis of racemic esters 1a-12a from various secondary aromatic alcohols. The major goal of this project was the development of a binding model for PcL which is able to rationalize the experimental findings to predict "a priori the enantioselective behavior of PcL toward a wider range of substrates. A two-step modeling procedure, namely, docking experiments followed by construction of tetrahedral intermediates, was used for the simulation of the involved enzyme-substrate recognition/hydrolysis processes. The study of the recognition process (docking experiments) led to unambiguous identification of the binding geometry for the two enantiomeric series of substrates, but did not suggest a definitive interpretation of the behavior of PcL. Taking into consideration the stereoelectronic requirements of the enzymatic hydrolysis reaction, both the enantioselectivity and tolerance of the enzyme were then explained through the study of the tetrahedral intermediates, in turn constructed from the calculated docking geometries of 1a-12a.

Plasma endothelin is increased in early essential hypertension

Local vascular generation of endothelin-1 (ET-1) may contribute to elevated peripheral resistance in hypertension. We tested the hypothesis that immunoreactive ET production in the forearm circulation is increased in early essential hypertensive subjects. Ten young, previously untreated male patients with mild essential hypertension and no signs of target organ damage were compared with matched normotensive subjects in an outpatient setting. Arterial and venous samples were obtained from indwelling catheters in the brachial artery and the medial cubital vein, respectively. Samples were collected at baseline and after induction of endothelium-dependent (acetylcholine) vasodilation. Immunoreactive ET (ET) was measured after column extraction by a sensitive radioimmunoassay employing a C-terminal ET-1 antibody with negligible cross-reaction to big-ET. Individual recovery rates were determined for each sample. Basal ET was significantly higher in hypertensive than in normotensive subjects, both in venous and arterial samples (P < .01). This difference was also present after correction for recovery (P < .01). There was no significant difference between venous and arterial ET concentrations. Local vasodilation did not change arterial or venous ET levels. In conclusion, plasma ET is increased in young, untreated, essential hypertensive subjects with no signs of target organ damage. The increased circulating immunoreactive ET may point to a role for the peptide early in the development of high blood pressure.

[The study of hydrolysis of new lipid-like substrates and trilaurin in monolayers catalyzed with the lipase from Pseudomonas fluorescens]

A simple method for determining the enzymic hydrolysis parameters of lipid-like substrates and trilaurin assembled in monolayers at the water-air interface was suggested. At a surface pressure of 10 mN/m, the initial rates of lipolysis were found to be proportional to the decrease in area of the substrate monolayer caused by the enzymic hydrolysis in a single-compartment Langmuir balance. The kinetic parameters for the hydrolysis of trilaurin and three 1,3-dilaurylpseudoglycerides acetylated in position 2 with an amino acid (phenylalanine, leucine, or valine) catalyzed with lipase from Pseudomonas fluorescens were determined. Unlike models of enzymic hydrolysis that neglect the thickness of the substrate monolayer, our method allows the determination of kinetic parameters in standard dimensions. The values of kcat for the synthetic pseudoglycerides were found to be significantly higher than that for trilaurin, while the values of Km(app) were close. This may be due to the presence of positively charged primary amino groups in the molecules of pseudoglycerides.

The place of Callimico goeldii in the Callitrichine phylogenetic tree: evidence from von Willebrand factor gene intron II sequences

Sequences of a 0.9-kb DNA segment spanning intron 11 of the von Willebrand Factor gene (vWF) were determined for 21 individuals of 19 primate species. The results of maximum parsimony and maximum likelihood analyses of these vWF sequences are congruent with previous molecular findings from other nonlinked nuclear genomic loci which divide the platyrrhine superfamily Ceboidea into three monophyletic families: Cebidae, Atelidae, and Pitheciidae. The vWF results strongly support the taxon Callitrichinae as a monophyletic subfamily within Cebidae. The four extant callitrichine genera constitute tribe Callitrichini, and the basal branchings within this tribe first separate out Saguinus (tamarins), next Leontopithecus (lion tamarins), and last the sister genera Callimico (Goeldi's monkeys) and Callithrix (marmosets). Callithrix divides into three subclades, with pygmy marmosets (C. pygmaea) as sister of the C. argentata species group and with the C. jacchus species group as their sister. Fossil and DNA evidence place the emergence of the callitrichine clade in the basal cebid radiation at about 20 Ma (million years ago) and the three basal branchings in the callitrichin radiation at about 13 to 11 Ma. In turn, the branchings separating the three subclades of Callithrix are placed at about 5 to 4 Ma.

Genetic diversity of two African and sixteen South American populations determined on the basis of six hypervariable loci

A total of 582 individuals (1,164 chromosomes) from two African, eight African-derived South American, five South American Amerindian, and three Brazilian urban populations were studied at four variable number of tandem repeat (VNTR) and two short tandem repeat (STR) hypervariable loci. These two sets of loci did not show distinct allele profiles, which might be expected if different processes promoted their molecular differentiation. The two African groups showed little difference between them, and their intrapopulational variation was similar to those obtained in the African-derived South American communities. The latter showed different degrees of interpopulation variability, despite the fact that they presented almost identical average degrees of non-African admixture. The F(ST) single locus estimates differed in the five sets of populations, probably due to genetic drift, indicating the need to consider population structure in the evaluation of their total variability. A high interpopulational diversity was found among Amerindian populations in relation to Brazilian African-derived isolated communities. This is probably a consequence of the differences in the patterns of gene flow and genetic drift that each of these semi-isolated groups experienced.

Molecular phylogeny of ateline new world monkeys (Platyrrhini, atelinae) based on gamma-globin gene sequences: evidence that brachyteles is the sister group of lagothrix

Nucleotide sequences, each spanning approximately 7 kb of the contiguous gamma1 and gamma2 globin genomic loci, were determined for seven species representing all extant genera (Ateles, Lagothrix, Brachyteles, and Alouatta) of the New World monkey subfamily Atelinae. After aligning these seven ateline sequences with outgroup sequences from several other primate (non-ateline) genera, they were analyzed by maximum parsimony, maximum likelihood, and neighbor-joining algorithms. All three analyzes estimated the same phylogenetic relationships: [Alouatta [Ateles (Brachyteles, Lagothrix)]]. Brachyteles and Lagothrix are sister-groups supported by 100% of bootstrap replications in the parsimony analyses. Ateles joins this clade, followed by the basal genus Alouatta; these joinings were strongly supported, again with 100% bootstrap values. This cladistic pattern for the four ateline genera is congruent with that obtained in previous studies utilizing epsilon-globin, IRBP, and G6PD nuclear genomic sequences as well as mitochondrial COII sequences. Because the number of aligned nucleotide positions is much larger in the present datasetoff than in any of these other datasets, much stronger support was obtained for the cladistic classification that divides subfamily Atelinae into tribes Alouattini (Alouatta) and Atelini, while the latter divides into subtribes Atelina (Ateles) and Brachytelina (Brachyteles and Lagothrix).

Electrophoretic polymorphisms and their taxonomic implications in Callitrichini (Primates, Platyrrhini)

Five hundred forty-three blood samples from 15 populations of the four genera of callitrichin primates were studied electrophoretically. Polymorphism and genetic distances were estimated for 20 loci, 13 of which were polymorphic. The lion tamarin (Leontopithecus) studied here exhibited the least variability for these loci, while the monospecific Cebuella showed the most. The genetic distances observed between Callithrix and Cebuella genera support previous evidence indicating a close taxonomic relationship between them. Genetic distance values obtained in this study also support the synonimyzation of the kuhli form with Callithrix jacchus penicillata.

Evaluation of nurses' errors associated in the preparation and administration of medication in a pediatric intensive care unit

The objectives of this study were to determine the frequency and the types of errors which occur regarding the preparation and the administration of medication and to identify the main causes of these errors in a pediatric intensive care unit (PICU) at the University Hospital in Lausanne (Switzerland). In this prospective study, based on the observation of nurses' activities, the data were collected over a period of 10 weeks. The error classification was based on the American Society of Hospital Pharmacy (ASHP) definitions. The frequency of errors was calculated as the sum of all noted errors divided by the total administered drugs, plus the sum of all omitted drugs, multiplied by 100. The sum of all given doses plus all omitted doses gives the 'total opportunity for errors'. This total was 275 and the total frequency of errors was 26.9%. The most frequent errors were wrong-time errors (32.4%), wrong-administration-technique errors (32.4%) and preparation errors (23.0%). In relation with other studies conducted under comparable conditions, a lesser number of omissions and wrong-time errors were observed. On the contrary, administration-technique and dose-preparation errors were more frequent at our hospital. A program of systematic assistance and survey by professional pharmacists could improve the quality of the preparation and administration of medication in the PICU.

Protein and hypervariable tandem repeat diversity in eight African-derived South American populations: inferred relationships do not coincide

We compared data from individuals living in 4 African Venezuelan and 4 African Brazilian communities for 11 protein loci (551 subjects) and 8 hypervariable tandem repeat polymorphisms (252 subjects). There is heterogeneity in diversity within and between the two sets of loci. On the other hand, African-derived Brazilians and Venezuelans do not present marked variability differences between themselves. Although the hypervariable loci show gene diversities that are about four times higher than those obtained from the protein data, they are not more discriminative at the interpopulation level (averages 6% and 4%, respectively). Interpopulation differences do not strictly parallel the geographic distances between the groups, and population relationships obtained from the protein data are not the same as those indicated by hypervariable tandem repeat polymorphisms. Caution is needed in establishing relationships considering just one level of the biological hierarchy.

Molecular genetics of spectral tuning in New World monkey color vision

Although most New World monkeys have only one X-linked photopigment locus, many species have three polymorphic alleles at the locus. The three alleles in the squirrel monkey and capuchin have spectral peaks near 562, 550, and 535 nm, respectively, and the three alleles in the marmoset and tamarin have spectral peaks near 562, 556, and 543 nm, respectively. To determine the amino acids responsible for the spectral sensitivity differences among these pigment variants, we sequenced all exons of the three alleles in each of these four species. From the deduced amino acid sequences and the spectral peak information and from previous studies of the spectral tuning of X-linked pigments in humans and New World monkeys, we estimated that the Ala --> Ser, Ile --> Phe, Gly --> Ser, Phe --> Tyr, and Ala --> Tyr substitutions at residue positions 180, 229, 233, 277, and 285, respectively, cause spectral shifts of about 5, -2, -1, 8, and 15 nm. On the other hand, the substitutions His --> Tyr, Met --> Val or Leu, and Ala --> Tyr at positions 116, 275, and 276, respectively, have no discernible spectral tuning effect, though residues 275 and 276 are inside the transmembrane domains. Many substitutions between Val and Ile or between Val and Ala have occurred in the transmembrane domains among the New World monkey pigment variants but apparently have no effect on spectral tuning. Our study suggests that, in addition to amino acid changes involving a hydroxyl group, large changes in residue size can also cause a spectral shift in a visual pigment.

Sequences of the primate epsilon-globin gene: implications for systematics of the marmosets and other New World primates

Sequences of the epsilon-globin gene were determined for five species of marmosets, along with approximately 2 kb of 5' flanking sequence. An analysis of these data, compared with those of other primates strongly supports the classification of Callithrix jacchus and C. geoffroyi into the jacchus group, and C. argentata and C. mauesi into the argentata group. The pygmy marmoset, formerly identified as Cebuella pygmaea joined strongly to the argentata group, indicating that without the pygmy marmoset the genus Callithrix would be paraphyletic. Our data support recent studies which indicate that C. pygmaea should be included in the genus Callithrix. Relationships among other primates were as indicated by previous studies of epsilon-globin sequences. Divergence times were estimated according to a local molecular clock. These calculations indicated the divergence of C. mauesi and C. argentata to be approximately 1.6-1.9 Myr (million years ago), and the most recent common ancestor of the marmosets to be between 4.5 and 4.7 Myr. The latter estimate corresponds well to the date of 4.6 Myr calculated from an independent data set.

Marmoset phylogenetics, conservation perspectives, and evolution of the mtDNA control region

Marmosets (genus Callithrix) are a diverse group of platyrrhine primates with 13-15 purported taxa, many of them considered endangered. Morphological analyses constitute most of the basis for recognition of these forms as distinct taxa. The purpose of this study was to provide a molecular view, based on mitochondrial control region sequences, of the evolutionary history of the marmosets, concomitant with a molecular phylogenetic perspective on species diversity within the group. An additional purpose was to provide the first comparative examination of a complete New World monkey control region sequence with those of other mammals. The phylogenetic analyses provide convincing support for a split between the Atlantic forest and Amazonian marmosets, with the inclusion of the pygmy marmoset (Cebuella pygmaea) at the base of the Amazonian clade. The earliest branch of the Atlantic forest group was C. aurita. In the Amazonian group, the analyses do not support the recognition of C. humeralifer and the recently described C mauesi as distinct taxa. They do, however, support a clear distinction between C. argentata and a strongly supported mixed clade of C. humeralifer and C. mauesi. In the Atlantic forest group, the phylogenetic tree suggests mixing between C. penicillata, C. kuhli, and possibly C. jacchus. Most of the sequence features characteristic of other mammal control regions were also evident in marmosets, with the exception that conserved sequence blocks (CSBs) 2 and 3 were not clearly identifiable. Tandem repeat units often associated with heteroplasmy in a variety of other mammals were not evident in the marmoset sequences.

Identification of pre-gamma-globin

A pre-gamma-globin species was identified by high performance liquid chromatography in platyrrhine primates. Although pre-gamma-globin has not been observed in human hemoglobin, its identification in platyrrhine hemoglobin was facilitated by the functional inactivation of one of the duplicated gamma-globin genes in platyrrhines, which simplified the high performance liquid chromatography elution pattern. Part, but not all, of the pre-gamma was glutathionyl gamma 2-globin, and matrix-assisted laser desorption/ionization mass spectrometry was used to demonstrate that the glutathionyl residue was located on cysteine 93. As this residue is invariant in primates, it is predicted that the formation of glutathionyl gamma-globin will be seen in all primate hemoglobins under appropriate conditions.