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Michmerhuizen NL, Owen JH, Heft Neal ME, Mann JE, Leonard E, Wang J, Zhai J, Jiang H, McHugh JB, Brenner JC, Prince MEP. Rationale for the advancement of PI3K pathway inhibitors for personalized chordoma therapy. J Neurooncol 2020; 147:25-35. [PMID: 32067197 DOI: 10.1007/s11060-020-03418-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 01/30/2020] [Indexed: 11/26/2022]
Abstract
PURPOSE Chordomas are rare and serious tumors with few effective treatments outside of aggressive surgery and radiation. Targeted therapies may present a more effective option for a subset of patients with lesions possessing certain genetic biomarkers. METHODS A small molecule inhibitor library was tested in patient-derived UM-Chor1 cells to identify targeted therapies with potential efficacy. Targeted exome sequencing of UM-Chor1 and UM-Chor2 cells was performed to investigate genetic aberrations in relevant pathways. Chordoma cell lines were treated with inhibitors of the phosphotidylinositol 3-kinase (PI3K), epidermal growth factor receptor (EGFR), and cyclin dependent kinase (CDK) pathways, and responses were determined using resazurin cell viability assays, Annexin V apoptosis assays, and western blotting. Pan-PI3K inhibitor BKM120 was also tested in five chordoma xenograft models. RESULTS Unbiased small molecule profiling nominated PI3K-AKT-mTOR pathway inhibitors as a promising therapy in chordoma, and genetic analyses of UM-Chor1 and UM-Chor2 cell lines revealed aberrations in PTEN, EGFR, and CDKN2A. Treatment of UM-Chor1 and UM-Chor2 with targeted PI3K, EGFR, and CDK inhibitors inhibited growth and proliferation and induced apoptosis more robustly than imatinib, a currently used chordoma therapy. Furthermore, BKM120 significantly inhibited tumor growth in a subset of the xenograft models tested. CONCLUSION Targeted therapies, especially those inhibiting PI3K, display promising effects in multiple chordoma cell line and xenograft models. Nevertheless, the limited effects of PI3K, EGFR, and CDK targeting agents in other models reveal the presence of resistance mechanisms, which motivates future research to both identify biomarkers of response and develop combination therapies.
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Affiliation(s)
- N L Michmerhuizen
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, 1150 E. Medical Center Dr., 9301B MSRB3, Ann Arbor, MI, 48109-0602, USA
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - J H Owen
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, 1150 E. Medical Center Dr., 9301B MSRB3, Ann Arbor, MI, 48109-0602, USA
| | - M E Heft Neal
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, 1150 E. Medical Center Dr., 9301B MSRB3, Ann Arbor, MI, 48109-0602, USA
| | - J E Mann
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, 1150 E. Medical Center Dr., 9301B MSRB3, Ann Arbor, MI, 48109-0602, USA
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - E Leonard
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, 1150 E. Medical Center Dr., 9301B MSRB3, Ann Arbor, MI, 48109-0602, USA
| | - J Wang
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, 1150 E. Medical Center Dr., 9301B MSRB3, Ann Arbor, MI, 48109-0602, USA
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - J Zhai
- Department of Biostatistics, University of Michigan School of Public Health, Ann Arbor, MI, USA
| | - H Jiang
- Department of Biostatistics, University of Michigan School of Public Health, Ann Arbor, MI, USA
- Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI, USA
| | - J B McHugh
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, USA
- Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI, USA
| | - J C Brenner
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, 1150 E. Medical Center Dr., 9301B MSRB3, Ann Arbor, MI, 48109-0602, USA.
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA.
- Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI, USA.
| | - M E P Prince
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, 1150 E. Medical Center Dr., 9301B MSRB3, Ann Arbor, MI, 48109-0602, USA
- Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI, USA
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Abstract
Unresectable recurrent or metastatic head and neck cancer is an incurable disease with survival of approximately 12 months. Head and neck tumors exhibit numerous derangements in the tumor microenvironment that aid in immune evasion and may serve as targets for future therapies. Pembrolizumab is now approved as a first line therapy. Despite the promise of currently approved immunotherapies there continues to be low response rates and additional strategies are needed. Here, alterations in the immune microenvironment and current therapeutic strategies are reviewed with a focus on novel immunologic approaches.
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Affiliation(s)
- M E Heft Neal
- Department of Otolaryngology Head and Neck Surgery, University of Michigan, Ann Arbor, MI
| | - C T Haring
- Department of Otolaryngology Head and Neck Surgery, University of Michigan, Ann Arbor, MI
| | - J E Mann
- Department of Otolaryngology Head and Neck Surgery, University of Michigan, Ann Arbor, MI
| | - J C Brenner
- Department of Otolaryngology Head and Neck Surgery, University of Michigan, Ann Arbor, MI.,Department of Pharmacology, University of Michigan.,Rogel Cancer Center, University of Michigan
| | - M E Spector
- Department of Otolaryngology Head and Neck Surgery, University of Michigan, Ann Arbor, MI
| | - P L Swiecicki
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan Medical School, Ann Arbor, Michigan
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Mann JE, Hoesli R, Michmerhuizen NL, Devenport SN, Ludwig ML, Vandenberg TR, Matovina C, Jawad N, Mierzwa M, Shuman AG, Spector ME, Brenner JC. Surveilling the Potential for Precision Medicine-driven PD-1/PD-L1-targeted Therapy in HNSCC. J Cancer 2017; 8:332-344. [PMID: 28261333 PMCID: PMC5332883 DOI: 10.7150/jca.17547] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 11/14/2016] [Indexed: 12/20/2022] Open
Abstract
Immunotherapy is becoming an accepted treatment modality for many patients with cancer and is now approved for use in platinum-refractory recurrent or metastatic head and neck squamous cell carcinoma (HNSCC). Despite these successes, a minority of patients with HNSCC receiving immunotherapy respond to treatment, and few undergo a complete response. Thus, there is a critical need to identify mechanisms regulating immune checkpoints in HNSCC such that one can predict who will benefit, and so novel combination strategies can be developed for non-responders. Here, we review the immunotherapy and molecular genetics literature to describe what is known about immune checkpoints in common genetic subsets of HNSCC. We highlight several highly recurrent genetic lesions that may serve as biomarkers or targets for combination immunotherapy in HNSCC.
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Affiliation(s)
- J E Mann
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, Ann Arbor, MI.; Department of Pathology, University of Michigan Medical School, Ann Arbor, MI
| | - R Hoesli
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, Ann Arbor, MI
| | - N L Michmerhuizen
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, Ann Arbor, MI.; Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI
| | - S N Devenport
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, Ann Arbor, MI.; Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI
| | - M L Ludwig
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, Ann Arbor, MI.; Program in Cellular and Molecular Biology, University of Michigan Medical School, Ann Arbor, MI
| | - T R Vandenberg
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, Ann Arbor, MI
| | - C Matovina
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, Ann Arbor, MI
| | - N Jawad
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, Ann Arbor, MI
| | - M Mierzwa
- Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, MI.; Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI
| | - A G Shuman
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, Ann Arbor, MI.; Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI
| | - M E Spector
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, Ann Arbor, MI.; Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI
| | - J C Brenner
- Department of Otolaryngology - Head and Neck Surgery, University of Michigan Medical School, Ann Arbor, MI.; Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI
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Mann JE, Brashears MM. Contribution of humidity to the lethality of surface-attached heat-resistant Salmonella during the thermal processing of cooked ready-to-eat roast beef. J Food Prot 2007; 70:762-5. [PMID: 17388073 DOI: 10.4315/0362-028x-70.3.762] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
To provide meat processors with data to assess the safety of cooked ready-to-eat roast beef production parameters, a study was conducted to determine the contribution of humidity to the lethality of salmonellae during thermal processing. Destruction of Salmonella during thermal processing at different levels of humidity and a constant cooking temperature of 82.2 degrees C was examined. Raw beef top round roasts purchased from a commercial supplier were inoculated with a seven-strain cocktail of heat-shocked Salmonella. Inoculated roasts were thermally processed to an internal temperature of 62.8 degrees C at 0 to 90% humidity. Salmonella counts were determined utilizing the thin agar layer method on xylose-lysine-desoxychlolate agar to facilitate the enumeration of injured cells. Significant differences (P < 0.05) in Salmonella counts were observed between roasts processed at 30% humidity and those processed at 15% humidity or lower. Salmonella reductions were less than the regulatory performance standard of 6.5 log units at a humidity of < 30%. These results indicate that cooked ready-to-eat roast beef can be safely processed under conditions outside of the U.S. Department of Agriculture (USDA) Food Safety and Inspection Service "safe harbor" guidelines. However, the results also indicate that one of these current safe harbor guidelines for the production of cooked ready-to-eat roast beef (> or = 62.8 degrees C product internal temperature with humidity introduced for > or = 50% of the cooking cycle) could result in a finished product that does not meet USDA performance standards. This specific guideline should be clarified with a minimum relative humidity requirement to ensure the production of a safe product.
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Affiliation(s)
- J E Mann
- Department of Animal and Food Sciences, Texas Tech University, Box 42141, Lubbock, Texas 79409, USA
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Mann JE, Brashears MM. Validation of time and temperature values as critical limits for the control of Escherichia coli O157:H7 during the production of fresh ground beef. J Food Prot 2006; 69:1978-82. [PMID: 16924927 DOI: 10.4315/0362-028x-69.8.1978] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In order to provide beef processors with valuable data to validate critical limits set for temperature during grinding, a study was conducted to determine Escherichia coli o157:H7 growth at various temperatures in raw ground beef. Fresh ground beef samples were inoculated with a cocktail mixture of streptomycin-resistant E. coli O157:H7 to facilitate recovery in the presence of background flora. Samples were held at 4.4, 7.2, and 10 degrees C, and at room temperature (22.2 to 23.3 degrees C) to mimic typical processing and holding temperatures observed in meat processing environments. E. coli O157:H7 counts were determined by direct plating onto tryptic soy agar with streptomycin (1,000 microg/ml), at 2-h intervals over 12 h for samples held at room temperature. Samples held under refrigeration temperatures were sampled at 4, 8, 12, 24, 48, and 72 h. Less than one log of E. coli O157:H7 growth was observed at 48 h for samples held at 10 degrees C. Samples held at 4.4 and 7.2 degrees C showed less than one log of E. coli O157:H7 growth at 72 h. Samples held at room temperature showed no significant increase in E. coli O157:H7 counts for the first 6 h, but increased significantly afterwards. These results illustrate that meat processors can utilize a variety of time and temperature combinations as critical limits in their hazard analysis critical control point plans to minimize E. coli O157:H7 growth during the production and storage of ground beef.
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Affiliation(s)
- J E Mann
- Department of Animal and Food Sciences, Texas Tech University, Box 42141, Lubbock, Texas 79409, USA
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Smith L, Mann JE, Harris K, Miller MF, Brashears MM. Reduction of Escherichia coli O157:H7 and Salmonella in ground beef using lactic acid bacteria and the impact on sensory properties. J Food Prot 2005; 68:1587-92. [PMID: 21132964 DOI: 10.4315/0362-028x-68.8.1587] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Studies were conducted to determine whether four strains of lactic acid bacteria (LAB) inhibited Escherichia coli O157: H7 and Salmonella in ground beef at 5 degrees C and whether these bacteria had an impact on the sensory properties of the beef. The LAB consisted of frozen concentrated cultures of four Lactobacillus strains, and a cocktail mixture of streptomycin-resistant E. coli O157:H7 and Salmonella were used as pathogens. Individual LAB isolates at 10(7) CFU/ml were added to tryptic soy broth containing a pathogen concentration of 10(5) CFU/ml. Samples were stored at 5 degrees C, and pathogen populations were determined on days 0, 4, 8, and 12. After 4 days of storage, there were significant differences in numbers of both pathogens exposed to LAB isolates NP 35 and NP 3. After 8 and 12 days of storage, all LAB reduced populations of both pathogens by an average of 3 to 5 log cycles. A second study was conducted in vacuum-packaged fresh ground beef. The individual LAB isolates resulted in an average difference of 1.5 log cycles of E. coli O157:H7 after 12 days of storage, and Salmonella populations were reduced by an average of 3 log cycles. Following this study, a mixed concentrated culture was prepared from all four LAB and added to ground beef inoculated with pathogen at 10(8) CFU/g. After 3 days of storage, the mixed culture resulted in a 2.0-log reduction in E. coli O157:H7 compared with the control, whereas after 5 days of storage, a 3-log reduction was noted. Salmonella was reduced to nondetectable levels after day 5. Sensory studies on noninoculated samples that contained LAB indicated that there were no adverse effects of LAB on the sensory properties of the ground beef. This study indicates that adding LAB to raw ground beef stored at refrigeration temperatures may be an important intervention for controlling foodborne pathogens.
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Affiliation(s)
- L Smith
- Department Animal and Food Sciences, Texas Tech University, Box 42141, Lubbock, Texas 79409, USA
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7
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Mann JE, Smith L, Brashears MM. Validation of time and temperature values as critical limits for Salmonella and background flora growth during the production of fresh ground and boneless pork products. J Food Prot 2004; 67:1389-93. [PMID: 15270491 DOI: 10.4315/0362-028x-67.7.1389] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
To provide pork processors with valuable data to validate the critical limits set for temperature during pork fabrication and grinding, a study was conducted to determine the growth of Salmonella serotypes and background flora at various temperatures. Growth of Salmonella Typhimurium and Salmonella Enteritidis and of background flora was monitored in ground pork and boneless pork chops held at various temperatures to determine growth patterns. Case-ready modified atmosphere packaged ground pork and fresh whole pork loins were obtained locally. Boneless chops and ground pork were inoculated with a cocktail mixture of streptomycin-resistant Salmonella to facilitate recovery in the presence of background flora. Samples were held at 4.4, 7.2C, and 10 degrees C and at room temperature (22.2 to 23.3 degrees C) to mimic typical processing and holding temperatures observed in pork processing environments. Salmonella counts were determined at regular intervals over 12 and 72 h for both room and refrigeration temperatures. No significant growth of Salmonella (P < 0.05) was observed in boneless pork chops held at refrigeration temperatures. However, Salmonella in boneless pork chops held at room temperature had grown significantly by 8 h. Salmonella grew at faster rates in ground pork. Significant growth was observed at 6, 24. and 72 h when samples were held at room temperature, 10 degrees C, and 7.2 degrees C, respectively. No significant growth was observed at 4.4 degrees C. Background flora in ground pork samples increased significantly after 10 h at room temperature and after 12 h for samples held at 10 and 7.2 degrees C. Background flora in samples held at refrigeration temperatures did not increase until 72 h. Background flora in the boneless chops increased significantly after 6 h at room temperature and after 24 h when held at 10 and 4.4 degrees C. These results illustrate that meat processors can utilize a variety of time and temperature combinations as critical limits to minimize Salmonella growth during production and storage of raw pork products.
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Affiliation(s)
- J E Mann
- Department of Animal and Food Sciences, Texas Tech University, Box 42141, Lubbock, Texas 79409, USA
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Brashears MM, Galyean ML, Loneragan GH, Mann JE, Killinger-Mann K. Prevalence of Escherichia coli O157:H7 and performance by beef feedlot cattle given Lactobacillus direct-fed microbials. J Food Prot 2003; 66:748-54. [PMID: 12747680 DOI: 10.4315/0362-028x-66.5.748] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Fecal shedding of Escherichia coli O157:H7, the prevalence of Escherichia coli O157:H7 in pens and on carcasses and hides, and cattle performance as a result of daily dietary supplementation with Lactobacillus-based direct-fed microbials (DFMs) were evaluated in a feeding trial involving 180 beef steers. Steers were evaluated for shedding of E. coli O157:H7 by an immunomagnetic separation technique on arrival at the feedlot, just before treatment with the DFMs, and every 14 days thereafter until slaughter. Composite pen fecal samples were collected every 14 days (alternating weeks with animal testing), and prevalence on hides and carcasses at slaughter was also evaluated. Feedlot performance (body weight gain and feed intake) was measured for the period during which the DFMs were fed. Gain efficiency was calculated as the ratio of weight gain to feed intake. Lactobacillus acidophilus NPC 747 decreased (P < 0.01) the shedding of E. coli O157:H7 in the feces of individual cattle during the feeding period. E. coli O157:H7 was approximately twice as likely to be detected in control animal samples as in samples from animals receiving L. acidophilus NPC 747. In addition, DFM supplementation decreased (P < 0.05) the number of E. coli O157:H7-positive hide samples at harvest and the number of pens testing positive for the pathogen. Body weight gains (on a live or carcass basis) and feed intakes during the DFM supplementation period did not differ among treatments. Gain efficiencies on a live-weight basis did not differ among treatments, but carcass-based gain/feed ratios tended (P < 0.06) to be better for animals receiving the two DFM treatments than for control animals. The results of this study suggest that the feeding of a Lactobacillus-based DFM to cattle will decrease, but not eliminate, fecal shedding of E. coli O157:H7, as well as contamination on hides, without detrimental effects on performance.
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Affiliation(s)
- M M Brashears
- Department of Animal and Food Sciences, Texas Tech University, Lubbock, Texas 79409, USA.
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Abstract
Some landslides move imperceptibly downslope, whereas others accelerate catastrophically. Experimental landslides triggered by rising pore water pressure moved at sharply contrasting rates due to small differences in initial porosity. Wet sandy soil with porosity of about 0.5 contracted during slope failure, partially liquefied, and accelerated within 1 second to speeds over 1 meter per second. The same soil with porosity of about 0.4 dilated during failure and slipped episodically at rates averaging 0.002 meter per second. Repeated slip episodes were induced by gradually rising pore water pressure and were arrested by pore dilation and attendant pore pressure decline.
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Affiliation(s)
- R M Iverson
- U.S. Geological Survey, 5400 MacArthur Boulevard, Vancouver, WA 98661, USA
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Mann JE. Obligations of the health care community in organ procurement. Transplant Proc 1990; 22:1012-3. [PMID: 2349645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- J E Mann
- H.O.P.E. Program, Southern Alberta, Foothills Hospital, Calgary, Canada
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Sperelakis N, Marschall RA, Mann JE. Propagation down a chain of excitable cells by electric field interactions in the junctional clefts: effect of variation in extracellular resistances, including a "sucrose gap" simulation. IEEE Trans Biomed Eng 1983; 30:658-64. [PMID: 6654372 DOI: 10.1109/tbme.1983.325068] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Mann JE, Sperelakis N, Ruffner JA. Alteration in sodium channel gate kinetics of the Hodgkin-Huxley equations applied to an electric field model for interaction between excitable cells. IEEE Trans Biomed Eng 1981; 28:655-61. [PMID: 6274786 DOI: 10.1109/tbme.1981.324756] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Ruffner JA, Sperelakis N, Mann JE. Application of the Hodgkin--Huxley equations to an electric field model for interaction between excitable cells. J Theor Biol 1980; 87:129-52. [PMID: 7206743 DOI: 10.1016/0022-5193(80)90224-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Abstract
The human body was modeled by numerical procedures to determine the thermal response under varied electromagnetic (EM) exposures. The basic approach taken was to modify the heat transfer equations for man in air to account for thermal loading due to the energy absorbed from the EM field. The human body was represented in an EM model by a large number of small cubical cells of tissue, and the energy density was determined for each cell. This information was then analyzed by a thermal response model consisting of a series of two-dimensional transient conduction equations with internal heat generation due to metabolism, internal convective heat transfer due to blood flow, external interaction by convection and radiation, and cooling of the skin by sweating and evaporation. This model simulated the human body by a series of cylindrical segments. The local temperature of 61 discrete locations as well as the thermoregulatory responses of vasodilatation and sweating were computed for a number of EM field intensities and two frequencies, one near whole-body resonance.
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Mann JE, Sperelakis N. Further development of a model for electrical transmission between myocardial cells not connected by low-resistance pathways. J Electrocardiol 1979; 12:23-33. [PMID: 422916 DOI: 10.1016/s0022-0736(79)80041-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
We previously described a model for the electrical transfer of excitation from one cell to the next which utilized the electric field generated in the cleft between the cells. This model was analyzed only for the steady-state condition. In the present paper, we calculate the effects of membrane capacitance on the transmission of an action potential between two adjacent cardiac cells; the junction between cells was composed of two high-resistance excitable membranes separated by a narrow cleft. The parameters varied for this study included the threshold potential and capacitance of the junctional membranes. The calculations indicate that it is somewhat easier to achieve transmission when capacitive effects are included. Thus, the electric field model provides an alternative means of cell-to-cell propagation between myocardial cells which is electrical in nature but does not require the presence of low-resistance connections between cells.
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Mann JE, Foley E, Sperelakis N. Resistance and potential profiles in the cleft between two myocardial cells: electrical analog and computer simulations. J Theor Biol 1977; 68:1-15. [PMID: 916699 DOI: 10.1016/0022-5193(77)90223-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Abstract
Suppose that A1, A2, · ··, An are disjoint subarcs of a rectifiable arc A ⊆ Rk. The location and length of each subarc are assumed to be continuous random variables. An expression for the expected fraction of A covered by subarcs each of length greater than τ ≧ 0 is obtained and applied to two conceptually distinct problems associated with light penetration of an absorbing medium.
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MacDonald RL, Hsu D, Mann JE, Sperelakis N. An analysis of the problem of K-+ accumulation in the intercalated disk clefts of cardiac muscle. J Theor Biol 1975; 51:455-73. [PMID: 1142797 DOI: 10.1016/0022-5193(75)90074-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Macdonald RL, Mann JE, Sperelakis N. Derivation of general equations describing tracer diffusion in any two-compartment tissue with application to ionic diffusion in cylindrical muscle bundles. J Theor Biol 1974; 45:107-30. [PMID: 4836883 DOI: 10.1016/0022-5193(74)90046-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Abstract
A maximum growth rate with doubling time of 18 hr at 18 C could be maintained. Continuous cultures at about half maximum growth rate provided cells for study of pigments and photosynthesis. The light intensity curve of photosynthesis had no unusual features and showed light-saturated rates of 30-35 μl O2 /mrn(3) -hr at 18 C. Pigment analysis showed chlorophylls a and c (a/c ratio = 4), fucoxanthin, β-carotene, and diadinoxanthin. Growth under red light (±660 mμ) altered pigments only by decrease in chlorophyll c to about one-half the content obtained under clear tungsten lamps. The large and anomalous spectral shift in fucoxanthin following organic solvent extraction runs confirmed, but efforts to isolate a native fucoxanthin were unsuccessful. Spectral analysis of acetone extracts and sonicated cell preparations allowed estimate of fractional absorption by each component pigment. The analysis shows that chlorophyll a and fucoxanthin are the principal light absorbing pigments and that absorption by other carotenoids is very small.
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Affiliation(s)
- J E Mann
- Departments of Botany and Zoology, The University of Texas, Austin, Texas 78712
| | - J Myers
- Departments of Botany and Zoology, The University of Texas, Austin, Texas 78712
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Abstract
Enhancement phenomena in photosynthesis of the diatom Phaeodactylum tricornutum Lewin were studied by means of a Haxo oxygen electrode and 2 monochromatic light beams. It was necessary to correct for a minor non-linearity in rate oxygen evolution vs. intensity similar to that reported for Chlorella. Action spectra on complementary backgrounds and derived enhancement spectra were compared to in vivo absorption spectra in identifying the character of pigment systems 1 and 2. Fucoxanthin, chlorophyll c, and chlorophyll a-670 are clearly assignable to pigment system 2 which absorbs in excess at wavelengths 400 to 678 mmu. Chlorophyll a-1 (and a portion of the fucoxanthin) are assignable to pigment system 1 which absorbs in excess at wavelengths 678 to 750 mmu. Enhancement values were generally lower than those observed in Chlorella or Anacystis and lead to conclusion that diatom pigmentation provides an effective light harvesting apparatus.
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Affiliation(s)
- J E Mann
- Department of Botany, The University of Texas, Austin, Texas 78712
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