Cryptic species in a Neotropical parrot: genetic variation within the Amazona farinosa species complex and its conservation implications

The application of genetic approaches has enhanced the identification of cryptic species in a wide variety of taxa, often with immediate conservation implications. Here, we employed multilocus DNA analyses to assess genetic variation and its correspondence to taxonomy within the Mealy Amazon (Amazona farinosa), a parrot species found in Central and South America. DNA sequence data from four mitochondrial regions and two nuclear introns were used to infer relationships among all five named subspecies in this species complex. Two reciprocally monophyletic groups with strong nodal support were found; one comprised of the two Central American subspecies guatemalae and virenticeps and one including all three South American subspecies farinosa, chapmani, and inornata. Molecular characters diagnosed distinct Central American and South American lineages, with an estimated divergence time of 1.75–2.70 million years ago as inferred from cytochrome-b (3.5–5.4 % corrected distance). Our data support recognizing Central American and South American Mealy Amazons as separate species worthy of independent conservation management. Furthermore, our results suggest recognition of two separate management units within the South American clade, although further study is required. These findings have important conservation implications as Central American A. farinosa are under increased pressure from habitat destruction and collection for the pet trade, yet are listed as of Least Concern due to their current classification as subspecies’ subsumed within the species complex.     

Preserved autonomic function in amenorrheic athletes.

Reproductive hormones such as estradiol and progesterone are known to influence autonomic cardiovascular regulation. The purpose of this study was to determine whether amenorrheic athletes (AA) have impaired autonomic cardiovascular regulation compared with eumenorrheic athletes (EA). Thirty-five athletes were tested: 13 AA (19 +/- 1 yr), 13 EA (21 +/- 1 yr), and 9 EA (23 +/- 1 yr) on oral contraceptives (EA-OC). Multiple indexes of autonomic cardiovascular regulation were assessed: respiratory sinus arrhythmia (RSA), cardiovagal baroreflex sensitivity (BRS) via phase IV and phase II of the Valsalva maneuver, a spontaneous index of BRS, and the heart rate and blood pressure responses to orthostatic stress (20-min 60 degrees head-up tilt). RSA was not different among the groups. There were no group differences in the spontaneous index of BRS (AA = 30 +/- 6, EA = 24 +/- 3, EA-OC = 29 +/- 5 ms/mmHg) or in phase II (AA = 8 +/- 2, EA = 7 +/- 1, EA-OC = 8 +/- 1 ms/mmHg) of the Valsalva. There was a difference in BRS during phase IV (AA = 21 +/- 3, EA = 15 +/- 1, EA-OC = 26 +/- 6 ms/mmHg; ANOVA P = 0.04). Tukey's post hoc test indicated that BRS was greater in the EA-OC group compared with the EA group (P = 0.04). There were no differences in cardiovascular responses to orthostatic stress among the groups. In conclusion, AA do not display signs of impaired autonomic function and orthostatic responses compared with EA or EA-OC during the follicular phase of the menstrual cycle.     

Homeostatic Intrinsic Plasticity Is Functionally Altered in Fmr1 KO Cortical Neurons

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Buffer effects on EcoRV kinetics as measured by fluorescent staining and digital imaging of plasmid cleavage

We have developed a protocol to quantify polymer DNA cleavage which replaces the traditional radiolabeling and scintillation counting with fluorescent staining and digital imaging. This procedure offers high sensitivity, speed, and convenience, while avoiding waste and error associated with traditional 32P radiolabeling. This protocol was used to measure cleavage of pBR322 plasmid DNA by EcoRV, a type II restriction enzyme. EcoRV was found to exhibit an order of magnitude difference in binding in two apparently similar buffers used in previous investigations. To determine the origin of this effect, we measured reaction kinetics in buffers of different chemical nature and concentration: Tris, bis-Tris propane, Tes, Hepes, and cacodylate. We found that buffer concentration and identity had significant effects on EcoRV reaction velocity through large changes in specific binding and nonspecific binding (reflected in the Michaelis constant Km and the dissociation constant for nonspecific binding Kns). There were only small changes in Vmax. The source of the buffer effect is the protonated amines common to many pH buffers. These buffer cations likely act as counterions screening DNA phosphates, where both the protonated buffer structure and concentration affect enzyme binding strength. It appears that by choosing anionic buffers or zwitterionic buffers with a buried positive charge, buffer influence on the protein binding to DNA can be largely eliminated.     

Entropy and heat capacity of DNA melting from temperature dependence of single molecule stretching

When a single molecule of double-stranded DNA is stretched beyond its B-form contour length, the measured force shows a highly cooperative overstretching transition. We have measured the force at which this transition occurs as a function of temperature. To do this, single molecules of DNA were captured between two polystyrene beads in an optical tweezers apparatus. As the temperature of the solution surrounding a captured molecule was increased from 11 degrees C to 52 degrees C in 500 mM NaCl, the overstretching transition force decreased from 69 pN to 50 pN. This reduction is attributed to a decrease in the stability of the DNA double helix with increasing temperature. These results quantitatively agree with a model that asserts that DNA melting occurs during the overstretching transition. With this model, the data may be analyzed to obtain the change in the melting entropy DeltaS of DNA with temperature. The observed nonlinear temperature dependence of DeltaS is a result of the positive change in heat capacity of DNA upon melting, which we determine from our stretching measurements to be DeltaC(p) = 60 +/- 10 cal/mol K bp, in agreement with calorimetric measurements.     

Expression of polypeptide GalNAc-transferases in stratified epithelia and squamous cell carcinomas: immunohistological evaluation using monoclonal antibodies to three members of the GalNAc-transferase family

Mucin-type O-glycosylation is initiated by a large family of UDP- GalNAc: polypeptide N -acetyl-galactosaminyltransferases (GalNAc- transferases). Individual GalNAc-transferases appear to have different functions and Northern analysis indicates that they are differently expressed in different organs. This suggests that O-glycosylation may vary with the repertoire of GalNAc-transferases expressed in a given cell. In order to study the repertoire of GalNAc-transferases in situ in tissues and changes in tumors, we have generated a panel of monoclonal antibodies (MAbs) with well defined specificity for human GalNAc-T1, -T2, and -T3. Application of this panel of novel antibodies revealed that GalNAc- transferases are differentially expressed in different cell lines, in spermatozoa, and in oral mucosa and carcinomas. For example, GalNAc-T1 and -T2 but not -T3 were highly expressed in WI38 cells, and GalNAc-T3 but not GalNAc-T1 or -T2 was expressed in spermatozoa. The expression patterns in normal oral mucosa were found to vary with cell differentiation, and for GalNAc-T2 and -T3 this was reflected in oral squamous cell carcinomas. The expression pattern of GalNAc-T1 was on the other hand changed in tumors to either total loss or expression in cytological poorly differentiated tumor cells, where the normal undifferentiated cells lacked expression. These results demonstrate that the repertoire of GalNAc-transferases is different in different cell types and vary with cellular differentiation, and malignant transformation. The implication of this is not yet fully understood, but it suggests that specific changes in sites of O-glycosylation of proteins may occur as a result of changes in the repertoire of GalNAc-transferases.      

Motor development: activity matters after all

Developing spinal networks are constructed through the integration of local microcircuits and the ongoing incorporation of later-developing neurons. This process is dependent on neuronal activity prior to synaptogenesis.     

Roles of tidal and wind-generated currents in transporting white shrimp (Penaeus setiferus) postlarvae through a South Carolina (USA) inlet

The temporal and spatial abundance of postlarval Penaeus setiferuswas studied from plankton samples in oceanic and estuarine watersnear the North Edisto Inlet, South Carolina (USA), during threecruises in 1993 and 1994 (May 1993, August/September 1993 andJune 1994). Each covered a full cycle of neap-spring tides.On each cruise, bongo nets were towed at three stations acrossthe inlet throat on nightly flood tides. During the first twocruises, tows were made at surface and near-bottom depths inthe inlet, while sampling was confined to surface depths duringthe last cruise. Plankton tows were also made outside the inletalong transects extending in a cross-shelf direction and alongan arcuate transect around the inlet mouth. Stations along thearcuate transect were intensively sampled over a full tidalcycle during the last cruise. Extensive oceanographic and meteorologicalobservations were obtained from moored instrument arrays andshipboard sampling in order to relate fluctuations in tidal,lunar and wind phenomena to temporal changes in postlarval density.Densities of postlarvae were greater in the inlet throat thanat stations offshore. A significant interaction of postlarvaldensity among inlet stations and depth was noted in May. Forother cruises, no significant differences in density were notedamong stations across the inlet, but postlarvae were concentratedat the surface. The lack of a consistent horizontal salinitygradient and obvious pattern in water masses across the inletmay explain why postlarval densities did not consistently differlaterally in the inlet. Greater densities generally occurredduring the first quarter moon, although a clear relationshipof larval density to the spring-neap cycle was not observed.Highest mean densities of ingressing postlarvae in surface floodtide collections from the inlet were generally associated withdownwelling onshore winds which generate onshore flow near thesurface. The similarity between the time series curves of postlarvaldensity and the tidal component of currents just offshore ofthe inlet suggests that tidal transport may facilitate movementinto the estuary. Based on increased postlarval density at thesurface during early strong flood tides and a reduced densityat depth in the inlet, we hypothesize that postlarval P setiferusare utilizing selective tidal stream transport.