Biomedical subjects

A M Baker

Publications and source records attributed to A M Baker.

At least 19 recordsLinked to original sources

PubMed2006

Biogeographic history of an Australian freshwater shrimp, Paratya australiensis (Atyidae): the role life history transition in phylogeographic diversification.

The widespread distribution of the freshwater shrimp Paratya australiensis in eastern Australia suggests that populations of this species have been connected in the past. Amphidromy is ancestral in these shrimps, although many extant populations are known to be restricted to freshwater habitats. In this study, we used a fragment of the cytochrome c oxidase I mitochondrial DNA (mtDNA) gene to examine diversity within P. australiensis and to assess the relative importance of amphidromy in its evolutionary history. We hypothesized that if transitions from an amphidromous to a freshwater life history were important, then we would find a number of divergent lineages restricted to single or groups of nearby drainages. Alternatively, if amphidromy was maintained within the species historically, we expected to find lineages distributed over many drainages. We assumed that the only way for divergence to occur within amphidromous lineages was if dispersal was limited to between nearby estuaries, which, during arid periods in the earth's history, became isolated from one another. We found nine highly divergent mtDNA lineages, estimated to have diverged from one another in the late Miocene/early Pliocene, when the climate was more arid than at present. Despite this, the geographic distribution of lineages and haplotypes within lineages did not support the notion of a stepping-stone model of dispersal between estuaries. We conclude that the extensive divergence has most likely arisen through a number of independent amphidromy-freshwater life history transitions, rather than via historical isolation of amphidromy populations. We also found evidence for extensive movement between coastal and inland drainages, supporting the notion that secondary contact between lineages may have occurred as a result of drainage rearrangements. Finally, our data indicate that P. australiensis is likely a complex of cryptic species, some of which are widely distributed, and others geographically restricted.

Animal Migration↗

PubMed2005

Central penetration and stability of N-terminal tripeptide of insulin-like growth factor-I, glycine-proline-glutamate in adult rat.

Insulin-like growth factor-I is a neurotrophic factor and can prevent neurons from ischemic brain injury. However, the large molecular weight and metabolic effects can be problematic in its central delivery. Glycine-proline-glutamate (GPE) is the N-terminal tripeptide of insulin-like growth factor-I, which is naturally cleaved in the plasma and brain tissues. GPE reduces neuronal loss from hypoxic-ischemic brain injury following central administration. Central penetration and the stability of GPE in the plasma and central nervous system were examined in rats using radioimmunoassay and HPLC. GPE was rapidly metabolised in the plasma (8 min) after intraperitoneal administration. Despite having a short half-life in plasma, GPE was detected in the cerebrospinal fluid up to 40 min after intraperitoneal administration. With present of peptidase inhibitors, GPE existed in the brain tissue up to 3 h after intracerebroventricular administration, suggesting a role for peptolysis in its stability. The endopeptidase inhibitors 4- (2-aminoethyl) benzenesulfonyl fluoride hydrochloride (AEBSF) reduced GPE metabolism in the brain tissue while acid peptidase inhibitor pepstatin-A decreased GPE metabolism in the plasma. GPE reduced neuronal loss in the CA1-2 sub-region of the hippocampus given (intraperitoneally) after 30 min of hypoxic-ischemic injury in adult rats, further suggested the effectiveness of GPE central uptake. These results indicated that GPE crosses the blood-CSF and the functional CSF-brain barriers. The longer half-life of GPE in the CNS may be due to its unique enzymatic stability.

Animals↗

PubMed2004

Mitochondrial DNA signatures of restricted gene flow within divergent lineages of an atyid shrimp (Paratya australiensis).

We measured spatial genetic structure within three previously described mitochondrial lineages of the atyid shrimp, Paratya australiensis, occurring in upland streams of two major catchments within the Sydney Water Supply Catchment, New South Wales, Australia. In all three lineages, there was significant spatial structuring of genetic variation between catchments. In two lineages, recurrent but restricted maternal gene flow has apparently predominated in shaping within-catchment genetic structure, although this framework may be overlaid with episodic contiguous/long-distance expansion events. In the third lineage, there was no evidence of spatial genetic structuring within one of the catchments, because one haplotype was both common and widespread throughout the sampled area. High-frequency haplotypes were also shared among subcatchments in the other two lineages, and we discuss both historical and contemporary processes that may have left these genetic signatures. Our results are generally concordant with previous reports of significant population structuring in P. australiensis, occurring in upland river reaches elsewhere in eastern Australia. We propose that restricted dispersal and gene flow among upland populations of P. australiensis is linked to dramatic architectural structuring within and among mountain streams.

Analysis of Variance↗

PubMed2003

Patterns of spatial genetic structuring in a hydropsychid caddisfly (Cheumatopsyche sp. AV1) from southeastern Australia.

We assessed levels of mitochondrial genetic spatial structuring in the hydropsychid caddisfly Cheumatopsyche sp. AV1 in southeastern New South Wales, Australia. No significant spatial structuring was detected within or between catchments using analysis of molecular variance, and nested clade contingency analysis suggested no strong relationship between haplotypes and geographical location, at any clade level. However, tests for association among haplotypes incorporating geographical distance in the nested clade analysis, revealed patterns of historical range expansion and recent restricted gene flow. Most likely, population fragmentation preceded range expansion, although subsequent recontact and gene flow among the previously sundered populations has apparently obscured the geographical signature of the former fragmentation. Taken together, our analyses suggest that a number of populations fragmented during the Pleistocene evolved in isolation for a time and subsequently expanded into secondary contact. Since expansion, there has apparently been substantial (albeit somewhat restricted) dispersal and gene flow of adult female Cheumatopsyche sp. AV1, throughout the study area.

Analysis of Variance↗

PubMed2001

A Web-based diabetes care management support system.

BACKGROUND: Because of the often asymptomatic nature of diabetes and the long period between sustained hyperglycemia and observable complications, appropriate diabetes care relies on a long-term program of secondary prevention. Yet routine monitoring and screening among patients with diabetes is less than optimal. To support the provision of routine care to patients with diabetes, the Center for Health Services Research, Henry Ford Health System (Detroit), developed a Web-based Diabetes Care Management Support System (DCMSS). A nonrandomized, longitudinal study was conducted (January 1, 1998-October 31, 1999) with 13,325 health maintenance organization patients with diabetes who were aligned to 190 primary care providers practicing in 31 primary care clinics. RESULTS: Three DCMSS features--clinical practice guidelines, patient registries, and performance reports--were made available via a corporate intranet within an existing electronic medical record. The effect of DCMSS usage frequency was evaluated on the likelihood of a patient's receipt of glycated hemoglobin testing, lipid profile testing, and retinal examinations. Logistic regression models controlling for patient sociodemographic and clinical characteristics, and the testing history of the patient, the primary care physician, and the primary care clinic, were fit using generalized estimating equation methods. The more often a physician used DCMSS, the more likely his or her patients were to receive lipid profile testing (OR [odds ratio] = 1.01, 95% CI [confidence interval] = 1.01-1.02). Compared with patients of physicians who never used the system, patients of physicians who initiated 12 sessions were an estimated 19% more likely (95% CI = 7%-33%) to receive lipid profile testing. The analyses also suggested that the likelihood of a patient receiving a retinal exam was associated with system usage (OR = 1.01, 95% CI = 1.01-1.01). No relationship was found between system use and glycated hemoglobin testing. CONCLUSIONS: Computerized systems of clinical practice guidelines, patient registries, and performance feedback may help improve the rate of routine testing among patients with diabetes.

Adult↗

PubMed2001

A novel hunting accident. Discharge of a firearm by a hunting dog.

The authors report the case of a 21-year-old man who was killed while duck hunting when a shotgun accidentally discharged, shooting him in the head. The loaded weapon, which had been lying on the ground with the safety off and the muzzle pointed toward a river a few feet away, discharged when a hunting dog stepped on the trigger. Scene investigation confirmed that the victim had been standing in the river, planting decoys, with his head approximately level with the adjacent bank. Autopsy examination and ballistic testing confirmed a range of fire consistent with the witness' statements. Examination of the weapon in question documented a light trigger pull but no mechanical defects. The authors review the epidemiology and causality of hunting accidents and discuss the various safety rules that were violated in this highly unusual case. The importance of a complete death investigation, including autopsy, when dealing with a firearm death is emphasized.

Accidents↗

PubMed2001

Polyclonal systemic immunoblast proliferation: an unusual hematologic entity presenting as a medical examiner case.

A 43-year-old woman who was receiving oral antibiotics for several days for a superficial foot infection developed a persistent rash, fever, and lymphadenopathy, despite discontinuation of the antibiotic and administration of steroids for a presumed drug reaction. Hours after a subsequent visit to the emergency room for worsening symptoms, she died at home. At autopsy, there was a florid, systemic proliferation of polyclonal plasma cells and immunoblasts infiltrating nearly every organ and tissue of the body, most notably the lymph nodes and spleen. The polyclonal nature of the process was confirmed by immunofixation electrophoresis and immunohistochemistry. Cases of fatal polyclonal systemic immunoblast proliferations are extremely rare, and the trigger for such proliferations is not always known. We review the literature on this unusual entity and discuss the clinical and pathologic findings.

Adult↗

PubMed2000

EAE susceptibility in FVB mice.

The in vivo study of immunologic mechanisms in experimental allergic encephalomyelitis (EAE) requires, in some instances, the use of transgenic mice. As FVB mice represent a strain whose fertilized ova possess a relatively large pronucleus, this is a preferred strain in which to generate mice that are transgenic for a variety of genes. An important issue, then, is whether the FVB background supports the development of EAE. We report here that relapsing EAE is easily and reproducibly induced in FVB mice with whole myelin basic protein in complete Freund's adjuvant.

Animals↗

PubMed2000

Evolution and maintenance of stigma-height dimorphism in Narcissus. I. Floral variation and style-morph ratios.

An unusual stylar dimorphism occurs in Narcissus, a plant genus of insect-pollinated Mediterranean geophytes. To determine the characteristics of the sexual polymorphism, we investigated floral variation in 46 populations of N. assoanus (section Jonquillae) and 21 populations of N. dubius (section Tazettae) in SW France. Flowers possess two stamen levels in each morph that occupy slightly different positions within the floral tube. In long-styled plants (L-morph), the stigma is located within or slightly above the upper-level stamens, whereas in short-styled plants (S-morph) the stigma is placed well below the lower-level stamens. The stigma-height dimorphism is distinct from heterostyly because the reciprocity of stigma and anther positions in the two style morphs is only weakly developed and there are no differences between the style morphs in pollen size or production. In both species, mean stigma-anther separation is much greater in the S-morph than the L-morph. In N. assoanus, population style-morph ratios vary from isoplethy (1L:1S) to L-biased, whereas in N. dubius they are usually strongly L-biased or occasionally contain only the L-morph. Populations fixed for the S-morph, or with S-biased morph ratios, were not observed. In N. assoanus, style-morph ratios were associated with population size: large continuous populations always exhibited 1:1 morph ratios, whereas smaller, fragmented populations were often L-biased. This pattern was not evident in N. dubius. We argue that biased style-morph ratios largely result from morph-specific differences in assortative mating.

Biological Evolution↗

PubMed2000

Evolution and maintenance of stigma-height dimorphism in Narcissus. II. Fitness comparisons between style morphs.

Populations of the insect-pollinated geophytes Narcissus assoanus and N. dubius (Amaryllidaceae) are commonly dimorphic for stigma height. An extensive survey of populations of the two species in SW France revealed a wide range of style-morph frequencies, particularly populations with significantly more long-styled than short-styled plants. Here we employ experimental and theoretical approaches to investigate potential selective mechanisms governing the variation in style-morph frequencies. Controlled pollination of both species demonstrated that N. assoanus is moderately self-sterile whereas N. dubius is highly self-compatible. Both intra- and intermorph crosses of N. assoanus were equally fertile, indicating that the species does not exhibit heteromorphic incompatibility. Estimates of female fertility (fruit- and seed-set) and multilocus estimates of outcrossing using allozyme markers provided no evidence of morph-specific differences in maternal components of reproductive success in natural populations of the two species. This result suggested that differences between the morphs in male fertility may be largely responsible for the observed morph-ratio variation. To investigate this hypothesis we developed a mating model that incorporates the genetics of stigma-height dimorphism and contrasting rates of assortative and disassortative mating in the style morphs. Simulation results demonstrated that stigma-height dimorphism will always be maintained when levels of disassortative mating are greater than assortative mating, and that the observed L-biased populations in Narcissus spp. probably result from greater levels of assortative mating in this morph in comparison with the S-morph.

Biological Evolution↗

PubMed2000

Population genetic structure of Australian magpies: evidence for regional differences in juvenile dispersal behaviour.

Territorial group size in Australian magpies (Gymnorhina tibicen) ranges from monogamous pairs to groups of more than 20 individuals. It has been hypothesized that large territorial groups result from the retention of juveniles after a breeding effort. If this is true, local populations consisting of large groups are likely to exhibit the most genetic structure, because over time similar genotypes will tend to be confined to limited areas if juveniles are predominantly philopatric. The objective of the present study was to test this hypothesis using allozyme and mitochondrial DNA data to provide indirect estimates of regional gene flow (derived from hierarchical population subdivision analyses). These data were used in combination with estimates of group size to infer patterns of dispersal among magpie populations across mainland Australia. Territorial groups were significantly larger in the south-west compared to three eastern regions. Although inferred levels of gene flow were substantial for all four regions, a striking pattern emerged from both sets of genetic data: more differentiation was evident among populations in the south-western region than in any eastern region. We conclude that levels of juvenile dispersal influence group size in G. tibicen, because in the south-western region where groups were largest, populations were most genetically differentiated. Our results suggest that contrasting population genetic structures may develop within a single species as a result of differences in social system.

Animals↗

PubMed2000

Trophoblastic microemboli as a marker for preeclampsia-eclampsia in sudden unexpected maternal death: a case report and review of the literature.

The authors report the case of a 25-year-old white woman at 7 months' gestation who died suddenly and unexpectedly at home. Anatomic findings at autopsy included a tongue contusion, glomerulonephritis, changes indicative of systemic hypertension, and trophoblastic microemboli in the lungs. Review of the prenatal care record disclosed 3+ proteinuria 2 days before death. The features of the postmortem examination were consistent with clinically undiagnosed preeclampsia-eclampsia and glomerulonephritis. The authors discuss the rarity of fatal preeclampsia-eclampsia, the contribution of concomitant glomerulonephritis, and the significance of trophoblastic microemboli in the lungs.

Adult↗

PubMed2000

The distribution of costs of care in mechanically ventilated patients with chronic obstructive pulmonary disease.

OBJECTIVES: To delineate the costs of care of patients with Chronic Obstructive Pulmonary Disease (COPD) and respiratory failure and to compare them with those of other mechanically ventilated patients. DESIGN: A post hoc analysis of a prospective investigation. SETTING: Medical and coronary intensive care units (ICUs) of an 804-bed, university-based hospital. PATIENTS: A total of 300 mechanically ventilated patients, 44 with COPD and 256 others, were included. MEASUREMENTS AND MAIN RESULTS: Despite similar lengths of ICU stay (9 days) and mechanical ventilation (5.5 days COPD vs. 5 days other, p = .11), ICU respiratory care costs for patients with COPD were $2,422 ($1,157-$6,110) [median U.S. dollars (interquartile range)] vs. $1,580 ($738-$3,322) for the others (p = .01). Ventilator costs for COPD patients were $1,795 ($943-$5,782) vs. $1,574 ($613-$3,112) (p = .12). Total hospitalization respiratory care costs for COPD patients were higher, $4,064 ($2,422-$9,572) vs. $2,342 ($1,186-$4,591), (p = .0001), and 74.4% of the median difference in cost between COPD patients and others was accounted for by spontaneous nebulizers (p = .001), metered dose inhalers (p = .01), and pulse oximetry (p = .02). By using multiple linear regression analyses, we found that COPD remained associated with higher respiratory costs (p<.05). Respiratory Care was the third largest category of hospital costs after beds (27%) and pharmacy expenses (25%), and it comprised approximately 14% of total cost. Total hospital costs were large for both groups, but did not differ between COPD and the others [$24,217 ($16,211-$58,834) vs. $27,672 ($15,692-$53,766), respectively (p = .96)]. Linear regression analyses showed that only Acute Lung Injury score was significantly related to total ICU and hospital costs of care (p<.05). CONCLUSIONS: Costs of ICU and non-ICU respiratory care for patients with COPD are higher than costs of care for other mechanically ventilated patients. Although the increased cost of bronchodilators and oximetry in these patients may serve as target areas for reductions in respiratory care costs, it may also be true that these modalities of therapy and management are necessary and need to be used with even greater intensity to achieve better outcomes. The predominant contributions of bed and pharmacy costs in all of our patients with respiratory failure support research efforts addressing these aspects of care.

Aged↗

PubMed2000

United States Army Rangers in Somalia: an analysis of combat casualties on an urban battlefield.

BACKGROUND: This study was undertaken to determined the differences in injury patterns between soldiers equipped with modern body armor in an urban environment compared with the soldiers of the Vietnam War. METHODS: From July 1998 to March 1999, data were collected for a retrospective analysis on all combat casualties sustained by United States military forces in Mogadishu, Somalia, on October 3 and 4, 1993. This was the largest and most recent urban battle involving United States ground forces since the Vietnam War. RESULTS: There were 125 combat casualties. Casualty distribution was similar to that of Vietnam; 11% died on the battlefield, 3% died after reaching a medical facility, 47% were evacuated, and 39% returned to duty. The incidence of bullet wounds in Somalia was higher than in Vietnam (55% vs. 30%), whereas there were fewer fragment injuries (31% vs. 48%). Blunt injury (12%) and burns (2%) caused the remaining injuries in Somalia. Fatal penetrating injuries in Somalia compared with Vietnam included wounds to the head and face (36% vs. 35%), neck (7% vs. 8%), thorax (14% vs. 39%), abdomen (14% vs. 7%), thoracoabdominal (7% vs. 2%), pelvis (14% vs. 2%), and extremities (7% vs. 7%). No missiles penetrated the solid armor plate protecting the combatants' anterior chests and upper abdomens. Most fatal penetrating injuries were caused by missiles entering through areas not protected by body armor, such as the face, neck, pelvis, and groin. Three patients with penetrating abdominal wounds died from exsanguination, and two of these three died after damage-control procedures. CONCLUSION: The incidence of fatal head wounds was similar to that in Vietnam in spite of modern Kevlar helmets. Body armor reduced the number of fatal penetrating chest injuries. Penetrating wounds to the unprotected face, groin, and pelvis caused significant mortality. These data may be used to design improved body armor.

Adult↗

PubMed1999

Engineered mutants in the switch II loop of Ran define the contribution made by key residues to the interaction with nuclear transport factor 2 (NTF2) and the role of this interaction in nuclear protein import.

Nuclear protein import requires a precisely choreographed series of interactions between nuclear pore components and soluble factors such as importin-beta, Ran, and nuclear transport factor 2 (NTF2). We used the crystal structure of the GDPRan-NTF2 complex to design mutants in the switch II loop of Ran to probe the contribution of Lys71, Phe72 and Arg76 to this interaction. X-ray crystallography showed that the F72Y, F72W and R76E mutations did not introduce major structural changes into the mutant Ran. The GDP-bound form of the switch II mutants showed no detectable binding to NTF2, providing direct evidence that salt bridges involving Lys71 and Arg76 and burying Phe72 are all crucial for the interaction between Ran and NTF2. Nuclear protein accumulation in digitonin-permeabilzed cells was impaired with Ran mutants deficient in NTF2 binding, confirming that the NTF2-Ran interaction is required for efficient transport. We used mutants of the yeast Ran homologue Gsp1p to investigate the effect of the F72Y and R76E mutations in vivo. Although neither mutant was viable when integrated into the genome as a single copy, yeast mildly overexpressing the Gsp1p mutant corresponding Ran F72Y on a centromeric plasmid were viable, confirming that this mutant retained the essential properties of wild-type Ran. However, yeast expressing the Gsp1p mutant corresponding to R76E to comparable levels were not viable, although strains overexpressing the mutant to higher levels using an episomal 2micrometers plasmid were viable, indicating that the R76E mutation may also have interfered with other interactions made by Gsp1p.

Animals↗

PubMed1999

The prognostic significance of passing a daily screen of weaning parameters.

OBJECTIVE: While "weaning parameters" are commonly used to guide removal of mechanical ventilation devices, little information exists concerning their prognostic value. We evaluated whether passing weaning parameters was associated with survival. DESIGN: A prospectively followed cohort of mechanically ventilated patients. SETTING: Medical and coronary adult intensive care units of an 806-bed medical center. PATIENTS: 300 consecutively enrolled mechanically ventilated patients. MEASUREMENTS AND RESULTS: 216 patients who passed a daily screen of weaning parameters were more likely to be extubated successfully (87 vs 30%, p = 0.0001), less likely to require ventilation for > 21 days (3 vs 30%, p = 0.0001), and had a higher survival to hospital discharge (74 vs 29%, p = 0.0001) than 84 patients who never passed the screen. The overall accuracy of the daily screen for predicting successful extubation and in-hospital survival was 82 and 73%, respectively. Multivariate proportional hazards analysis of time until hospital death confirmed the beneficial effect of passing the daily screen (p = 0.01) and of duration of mechanical ventilation (p = 0.001) even after adjustment for differences in severity of illness, age, race, gender, diagnosis, and treatment assignment. While liberation from mechanical ventilation was predictive of survival at any time during the hospital stay (p = 0.001), the prognostic significance of the daily screen for hospital survival was related to how early after intubation it was passed. The difference in survival between patients who had passed and those who had not passed the daily screen was significant for 1 1/2 weeks postintubation but progressively decreased over time. The average time to extubation after passing the daily screen increased from 3 days (range 0 to 56), for those passing within 5 days of intubation, to 8 days (0 to 35), for those passing after 10 days of intubation (r = 0.26, p = 0.001). CONCLUSIONS: Passing a daily screen of weaning parameters is an independent predictor of successful extubation and survival, but its prognostic value decreases over time. Time spent on mechanical ventilation after passing the daily screen presents an important opportunity to optimize liberation from the ventilator.

Adult↗

PubMed1999

Venous air embolism from central venous catheterization: a need for increased physician awareness.

OBJECTIVES: To report a series of patients with clinically diagnosed venous air embolism (VAE) and major sequelae as a complication of the use of central venous catheters (CVCs), to survey health care professionals' practices regarding CVCs, and to implement an educational intervention for optimizing approaches to CVC insertion and removal. SETTING: Tertiary care, university-based 806-bed medical center. INTERVENTIONS: We surveyed 140 physicians and 53 critical care nurses to appraise their awareness of the proper management and complications of CVCs. We then designed, delivered, and measured the effects of a multidisciplinary educational intervention given to 106 incoming house officers. MEASUREMENTS AND MAIN RESULTS: Although most physicians (127, 91%) chose the Trendelenburg position for CVC insertion, only 42 physicians (30%) reported concern for VAE. On CVC removal, only 36 physicians (26%) cited concern for VAE. Some physicians (13, 9%) reported elevating the head of the bed during CVC removal, possibly increasing the risk of VAE. Awareness of VAE or its prevention did not correlate with the level of physician training, experience, or specialty. After the educational intervention, concern for and awareness of proper methods of prevention of VAE improved (p < .001). At 6-month follow-up, reported use of the Trendelenburg position continued, but concern cited for VAE had returned to baseline. CONCLUSIONS: There is inadequate awareness of VAE as a complication of CVC use. Focused instruction can improve appreciation of this potentially fatal complication and knowledge of its prevention, but the effect declines rapidly. To achieve a more sustained improvement, a more intensive, hands-on, periodic educational program will likely be necessary, as well as reinforcement through enhanced supervision of CVC insertion and removal practices.

Academic Medical Centers↗

PubMed1998

A military-civilian resource-sharing agreement.

A first-of-its-kind resource-sharing agreement between the US Department of Defense and a civilian hospital was undertaken with resounding success. This article discusses how Sacred Heart Medical Center, Spokane, Wash, and the 92nd Medical Group at Fairchild Air Force Base, Spokane, Wash, developed the project and accomplished the integration, which continues to benefit each organization.

Hospital Planning↗