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Dr. Mark  Sendar  Md image

Dr. Mark Sendar Md

3732 Strata Dr
Carlsbad CA 92010
760 920-0559
Medical School: Other - Unknown
Accepts Medicare: No
Participates In eRX: No
Participates In PQRS: No
Participates In EHR: No
License #: C43303
NPI: 1649375528
Taxonomy Codes:
207Q00000X

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Publications

The role of nitrogen and phosphorus in regulating Phormidium sp. (Cyanobacteria) growth and anatoxin production. - FEMS microbiology ecology
Benthic proliferations of the cyanobacteria Phormidium can cover many kilometres of riverbed. Phormidium can produce neurotoxic anatoxins and ingestion of benthic mats has resulted in numerous animal poisonings in the last decade. Despite this, there is a poor understanding of the environmental factors regulating growth and anatoxin production. In this study the effects of nitrogen and phosphorus on the growth of two Phormidium strains (anatoxin-producing and non-anatoxin-producing) were examined in batch monocultures. Cell concentrations were significantly reduced under reduced nitrogen (ca. <0.100 mM), and phosphorus conditions (ca. <0.003 mM). Cell concentrations and maximum growth rates were higher for the non-anatoxin-producing strain in all treatments, suggesting there may be an energetic cost to toxin production. Cellular anatoxin concentrations were lowest (169 fg cell(-1)) under the high-nitrogen and high-phosphorus treatment. This supports the growth-differentiation balance hypothesis that suggests actively dividing and expanding cells are less likely to produce secondary-metabolites. Anatoxin quota was highest (>407 fg cell(-1)) in the reduced phosphorus treatments, possibly suggesting it is produced as a stress response to growth limiting conditions. In all treatments there was a 4-5 fold increase in anatoxin quota in the lag growth phase, possibly indicating it may provide a physiological benefit during initial substrate colonisation.© FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Validating lipid force fields against experimental data: Progress, challenges and perspectives. - Biochimica et biophysica acta
Biological membranes display a great diversity in lipid composition and lateral structure that is crucial in a variety of cellular functions. Simulations of membranes have contributed significantly to the understanding of the properties, functions and behaviour of membranes and membrane-protein assemblies. This success relies on the ability of the force field used to describe lipid-lipid and lipid-environment interactions accurately, reproducibly and realistically. In this review, we present some recent progress in lipid force-field development and validation strategies. In particular, we highlight how a range of properties obtained from various experimental techniques on lipid bilayers and membranes, can be used to assess the quality of a force field. We discuss the limitations and assumptions that are inherent to both computational and experimental approaches and how these can influence the comparison between simulations and experimental data. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov.Copyright © 2016. Published by Elsevier B.V.
Membrane-binding properties of gating modifier and pore-blocking toxins: Membrane interaction is not a prerequisite for modification of channel gating. - Biochimica et biophysica acta
Many venom peptides are potent and selective inhibitors of voltage-gated ion channels, including channels that are validated therapeutic targets for treatment of a wide range of human diseases. However, the development of novel venom-peptide-based therapeutics requires an understanding of their mechanism of action. In the case of voltage-gated ion channels, venom peptides act either as pore blockers that bind to the extracellular side of the channel pore or gating modifiers that bind to one or more of the membrane-embedded voltage sensor domains. In the case of gating modifiers, it has been debated whether the peptide must partition in to the membrane to reach its binding site. In this study, we used surface plasmon resonance, fluorescence spectroscopy and molecular dynamics to directly compare the lipid-binding properties of two gating modifiers (μ-TRTX-Hd1a and ProTx-I) and two pore blockers (ShK and KIIIA). Only ProTx-I was found to bind to model membranes. Our results provide further evidence that the ability to insert into the lipid bilayer is not a requirement to be a gating modifier. In addition, we characterised the surface of ProTx-I that mediates its interaction with neutral and anionic phospholipid membranes and show that it preferentially interacts with anionic lipids.Copyright © 2016. Published by Elsevier B.V.
A Vector with a Single Promoter for In Vitro Transcription and Mammalian Cell Expression of CRISPR gRNAs. - PloS one
The genomes of more than 50 organisms have now been manipulated due to rapid advancement of gene editing technology. One way to perform gene editing in the mouse using the CRISPR/CAS system, guide RNA (gRNA) and CAS9 mRNA transcribed in vitro are microinjected into fertilized eggs that are then allowed to develop to term. As a rule, gRNAs are tested first in tissue culture cells and the one with the highest locus-specific cleavage activity is chosen for microinjection. For cell transfections, gRNAs are typically expressed using the human U6 promoter (hU6). However, gRNAs for microinjection into zygotes are obtained by in vitro transcription from a T7 bacteriophage promoter in a separate plasmid vector. Here, we describe the design and construction of a combined U6T7 hybrid promoter from which the same gRNA sequence can be expressed. An expression vector containing such a hybrid promoter can now be used to generate gRNA for testing in mammalian cells as well as for microinjection purposes. The gRNAs expressed and transcribed from this vector are found to be functional in cells as well as in mice.
Comparison of Particle-Associated Bacteria from a Drinking Water Treatment Plant and Distribution Reservoirs with Different Water Sources. - Scientific reports
This study assessed the characteristics of and changes in the suspended particles and the associated bacteria in an unchlorinated drinking water distribution system and its reservoirs with different water sources. The results show that particle-associated bacteria (PAB) were present at a level of 0.8-4.5 × 10(3) cells ml(-1) with a biological activity of 0.01-0.04 ng l(-1) ATP. Different PAB communities in the waters produced from different sources were revealed by a 16S rRNA-based pyrosequencing analysis. The quantified biomass underestimation due to the multiple cells attached per particle was ≥ 85%. The distribution of the biologically stable water increased the number of cells per particle (from 48 to 90) but had minor effects on the PAB community. Significant changes were observed at the mixing reservoir. Our results show the characteristics of and changes in suspended PAB during distribution, and highlight the significance of suspended PAB in the distribution system, because suspended PAB can lead to a considerable underestimation of biomass, and because they exist as biofilm, which has a greater mobility than pipe-wall biofilm and therefore presents a greater risk, given the higher probability that it will reach the customers' taps and be ingested.
How Reliable are Patient-Reported Rehospitalizations? Implications for the Design of Future Practical Clinical Studies. - Journal of the American Heart Association
Longitudinal clinical investigations often rely on patient reports to screen for postdischarge adverse outcomes events, yet few studies have examined the accuracy of such patient reports.Patients with acute myocardial infarction (MI) in the TRANSLATE-ACS study were asked during structured interviews at 6 weeks, 6 months, and 12 months postdischarge to report any rehospitalizations. The accuracy of patient-reported rehospitalizations within 1 year of postdischarge was determined using claims-based medical bill validation as the reference standard. The cumulative incidence of rehospitalizations was compared when identified by patient report versus medical bills. Patients were categorized by the accuracy in reporting events (accurate, under-, or over- reporters) and characteristics were compared between groups. Among 10 643 MI patients, 4565 (43%) reported 7734 rehospitalizations. The sensitivity and positive predictive value of patient-reported rehospitalizations were low at 67% and 59%, respectively. A higher cumulative incidence of rehospitalization was observed when identified by patient report versus medical bills (43% vs 37%; P<0.001). Overall, 18% of patients over-reported and 10% under-reported the number of hospitalizations. Compared with accurate reporters, under-reporters were more likely to be older, female, African American, unemployed, or a non-high-school graduate, and had greater prevalence of clinical comorbidities such as diabetes and past cardiovascular disease.The accuracy of patient-reported rehospitalizations was low with patients both under- and over-reporting events. Longitudinal clinical research studies need additional mechanisms beyond patient report to accurately identify rehospitalization events.URL: https://clinicaltrials.gov. Unique identifier: NCT01088503.© 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.
Renal artery sympathetic denervation: observations from the UK experience. - Clinical research in cardiology : official journal of the German Cardiac Society
Renal denervation (RDN) may lower blood pressure (BP); however, it is unclear whether medication changes may be confounding results. Furthermore, limited data exist on pattern of ambulatory blood pressure (ABP) response-particularly in those prescribed aldosterone antagonists at the time of RDN.We examined all patients treated with RDN for treatment-resistant hypertension in 18 UK centres.Results from 253 patients treated with five technologies are shown. Pre-procedural mean office BP (OBP) was 185/102 mmHg (SD 26/19; n = 253) and mean daytime ABP was 170/98 mmHg (SD 22/16; n = 186). Median number of antihypertensive drugs was 5.0: 96 % ACEi/ARB; 86 % thiazide/loop diuretic and 55 % aldosterone antagonist. OBP, available in 90 % at 11 months follow-up, was 163/93 mmHg (reduction of 22/9 mmHg). ABP, available in 70 % at 8.5 months follow-up, was 158/91 mmHg (fall of 12/7 mmHg). Mean drug changes post RDN were: 0.36 drugs added, 0.91 withdrawn. Dose changes appeared neutral. Quartile analysis by starting ABP showed mean reductions in systolic ABP after RDN of: 0.4; 6.5; 14.5 and 22.1 mmHg, respectively (p < 0.001 for trend). Use of aldosterone antagonist did not predict response (p > 0.2).In 253 patients treated with RDN, office BP fell by 22/9 mmHg. Ambulatory BP fell by 12/7 mmHg, though little response was seen in the lowermost quartile of starting blood pressure. Fall in BP was not explained by medication changes and aldosterone antagonist use did not affect response.
Peripheral Edema, Central Venous Pressure, and Risk of AKI in Critical Illness. - Clinical journal of the American Society of Nephrology : CJASN
Although venous congestion has been linked to renal dysfunction in heart failure, its significance in a broader context has not been investigated.Using an inception cohort of 12,778 critically ill adult patients admitted to an urban tertiary medical center between 2001 and 2008, we examined whether the presence of peripheral edema on admission physical examination was associated with an increased risk of AKI within the first 7 days of critical illness. In addition, in those with admission central venous pressure (CVP) measurements, we examined the association of CVPs with subsequent AKI. AKI was defined using the Kidney Disease Improving Global Outcomes criteria.Of the 18% (n=2338) of patients with peripheral edema on admission, 27% (n=631) developed AKI, compared with 16% (n=1713) of those without peripheral edema. In a model that included adjustment for comorbidities, severity of illness, and the presence of pulmonary edema, peripheral edema was associated with a 30% higher risk of AKI (95% confidence interval [95% CI], 1.15 to 1.46; P<0.001), whereas pulmonary edema was not significantly related to risk. Peripheral edema was also associated with a 13% higher adjusted risk of a higher AKI stage (95% CI, 1.07 to 1.20; P<0.001). Furthermore, levels of trace, 1+, 2+, and 3+ edema were associated with 34% (95% CI, 1.10 to 1.65), 17% (95% CI, 0.96 to 1.14), 47% (95% CI, 1.18 to 1.83), and 57% (95% CI, 1.07 to 2.31) higher adjusted risk of AKI, respectively, compared with edema-free patients. In the 4761 patients with admission CVP measurements, each 1 cm H2O higher CVP was associated with a 2% higher adjusted risk of AKI (95% CI, 1.00 to 1.03; P=0.02).Venous congestion, as manifested as either peripheral edema or increased CVP, is directly associated with AKI in critically ill patients. Whether treatment of venous congestion with diuretics can modify this risk will require further study.Copyright © 2016 by the American Society of Nephrology.
Growth in spending on substance use disorder treatment services for the privately insured population. - Drug and alcohol dependence
Approximately 8% of individuals with private health insurance in the United States have substance use disorders (SUDs), but in 2009 only 0.4% of all private insurance spending was on SUDs. The objective of this study was to determine if changes that occurred between 2009 and 2012 - such as more generous SUD benefits, an epidemic of opioid use disorders, and slow recovery from a recession - were associated with greater use of SUD treatment.Data were from the 2004-2012 Truven Health Analytics MarketScan(®) Commercial Claims and Encounters Database. This database is representative of individuals with private insurance in the United States. Per enrollee use of and spending on SUD treatment was determined and compared with spending on all health care services. Trends were examined for inpatient care, outpatient care, and prescription medications.During the 2009-2012 time period, use of and spending on SUD services increased compared with all diagnoses. Two-thirds of the increase was driven by higher growth rates in outpatient use and prices. Despite the high growth rates, SUD treatment penetration rates remained low. As of 2012, only 0.6% of individuals with private insurance used SUD outpatient services, 0.2% filled SUD medication prescriptions, and 0.1% used inpatient SUD services. In 2012, SUD services accounted for less than 0.7% of all private insurance spending.Despite recent coverage improvements, individuals with private health insurance still may not receive adequate levels of treatment for SUDs, as evidenced by the small proportion of individuals who access treatment.Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
The SGLT2 inhibitor empagliflozin improves insulin sensitivity in db/db mice both as monotherapy and in combination with linagliptin. - Metabolism: clinical and experimental
Combining different drug classes to improve glycemic control is one treatment strategy for type 2 diabetes. The effects on insulin sensitivity of long-term treatment with the sodium glucose co-transporter 2 (SGLT2) inhibitor empagliflozin alone or co-administered with the dipeptidyl peptidase-4 inhibitor linagliptin (both approved antidiabetes drugs) were investigated in mice using euglycemic-hyperinsulinemic clamps.db/db mice (n=15/group) were treated for 8weeks with 10mg/kg/day empagliflozin monotherapy, 10mg/kg/day empagliflozin plus 3mg/kg/day linagliptin combination therapy, or 3mg/kg/day linagliptin monotherapy. At the end of the study, euglycemic-hyperinsulinemic clamp studies were performed 4days after the last dose of treatment.HbA1c and 2-hour fasting glucose concentrations were improved with empagliflozin monotherapy and combination therapy compared with vehicle and linagliptin monotherapy. During the clamp, glucose disposal rates increased and hepatic glucose production decreased with empagliflozin monotherapy and combination therapy compared with vehicle and linagliptin monotherapy. Glucose uptake in liver and kidney was higher with empagliflozin monotherapy and combination therapy compared with vehicle; glucose uptake into both muscle and adipose tissue was only affected by linagliptin treatment. Empagliflozin and combination therapy altered the expression of genes involved in the inflammatory response, fatty acid synthesis and oxidation.These findings suggest that the insulin-sensitizing effects of SGLT2 inhibition contribute to improvements in glycemic control in insulin-resistant states.Copyright © 2015 Elsevier Inc. All rights reserved.

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