Abstract 1686: TSC2 enhances antitumor immunity and potentiates PD-1 and CTLA-4 blockade

Tuberous sclerosis complex (TSC) is an incurable multisystem genetic disease characterized by mTORC1-hyperactive hamartomatous tumors of brain, kidney, and lung. TSC is caused by mutations in the two TSC1 or TSC2 tumor-suppressor genes. mTORC1 inhibitors lead to partial antitumor responses in TSC, with tumor regrowth upon treatment cessation. Understanding the interaction between T cells and tumor cells has led to the development of successful checkpoint blockade immunotherapy targeting PD-1, programmed cell death-ligand 1 (PD-L1), and CTLA-4. These therapies have proven to be highly effective in treating several malignancies, including non-small cell lung cancer (NSCLC), renal cell carcinoma (RCC), melanoma, bladder cancer and Hodgkin's lymphoma. It is currently unknown whether benign tumors, such as those arising in TSC, will also respond to checkpoint blockade therapy. Using multiparametric flow cytometry and immunohistochemistry of human angiomyolipomas and pulmonary LAM, we discovered that PD-1 is highly expressed on tumor-infiltrating T cells. Using immunocompetent preclinical models of TSC, we found that dual blockade of PD-1 and CTLA-4 inhibited the growth of TSC2-deficient tumors by 77% (p < 0.0001). This was associated with increased tumor-infiltrating CD8+ and CD4+ T cells and decreased Tregs, G-MDSCs and regulatory CD11b+ DCs. Strikingly, we discovered that complete regression of established tumors can be achieved in 37% of the mice using anti-PD-1 monotherapy and in 62% of the mice using combined anti-PD-1 and anti-CTLA-4 therapy. We also assessed a treatment regimen of rapamycin followed by PD-1 blockade and found that this sequential treatment delays regrowth of TSC2-deficient tumors. Furthermore, TSC2 re-expression in TSC2-deficient tumors promoted antitumor responses via increasing T cells and decreasing CD11b+Ly6G+Ly6Cmed G-MDSCs and CD11b+ DCs infiltration into tumors. Importantly, we found that the potency of dual PD-1 and CTLA-4 blockade is significantly enhanced by TSC2 re-expression. Our data indicate that PD-1 is upregulated on T cells in TSC-associated tumors and that dual blockade of PD-1 and CTLA-4 pathways is effective in delaying tumor growth and improving long-term survival, with long-term complete tumor responses. Therefore, PD-1 and/or CTLA-4 blockade may represent a promising dual immunotherapy for patients with TSC-associated tumors and women with the sporadic form of LAM. Our data may have relevance for the many sporadic human tumors with mTORC1 hyperactivation (~50% of all human malignancies) and also for other hamartomatous tumor syndromes such as neurofibromatosis. Furthermore, the specific role of intratumoral TSC2 in antitumor T cell responses that we discovered may help to elucidate the response to immunotherapy in sporadic human malignancies with mutations in the TSC genes, which include a subset of bladder cancer and renal cell carcinoma.

Citation Format: Heng-Jia Liu, Patrick Lizotte, Heng Du, Maria Speranza, Spencer Vaughan, Nicola Alesi, Kwok-Kin Wong, Gordon Freeman, Arlene Sharpe, Elizabeth Henske. TSC2 enhances antitumor immunity and potentiates PD-1 and CTLA-4 blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1686.

TSC2-deficient tumors have evidence of T cell exhaustion and respond to anti-PD-1/anti-CTLA-4 immunotherapy

Tuberous sclerosis complex (TSC) is an incurable multisystem disease characterized by mTORC1-hyperactive tumors. TSC1/2 mutations also occur in other neoplastic disorders, including lymphangioleiomyomatosis (LAM) and bladder cancer. Whether TSC-associated tumors will respond to immunotherapy is unknown. We report here that the programmed death 1 coinhibitory receptor (PD-1) is upregulated on T cells in renal angiomyolipomas (AML) and pulmonary lymphangioleiomyomatosis (LAM). In C57BL/6J mice injected with syngeneic TSC2-deficient cells, anti-PD-1 alone decreased 105K tumor growth by 67% (P < 0.0001); the combination of PD-1 and CTLA-4 blockade was even more effective in suppressing tumor growth. Anti-PD-1 induced complete rejection of TSC2-deficient 105K tumors in 37% of mice (P < 0.05). Double blockade of PD-1 and CTLA-4 induced rejection in 62% of mice (P < 0.01). TSC2 reexpression in TSC2-deficient TMKOC cells enhanced antitumor immunity by increasing T cell infiltration and production of IFN-γ/TNF-α by T cells, suggesting that TSC2 and mTORC1 play specific roles in the induction of antitumor immunity. Finally, 1 month of anti-PD-1 blockade reduced renal tumor burden by 53% (P < 0.01) in genetically engineered Tsc2+/- mice. Taken together, these data demonstrate for the first time to our knowledge that checkpoint blockade may have clinical efficacy for TSC and LAM, and possibly other benign tumor syndromes, potentially yielding complete and durable clinical responses.

Endocytosis regulates TDP-43 toxicity and turnover

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron degenerative disease. ALS-affected motor neurons exhibit aberrant localization of a nuclear RNA binding protein, TDP-43, into cytoplasmic aggregates, which contributes to pathology via unclear mechanisms. Here, we demonstrate that TDP-43 turnover and toxicity depend in part upon the endocytosis pathway. TDP-43 inhibits endocytosis, and co-localizes strongly with endocytic proteins, including in ALS patient tissue. Impairing endocytosis increases TDP-43 toxicity, aggregation, and protein levels, whereas enhancing endocytosis reverses these phenotypes. Locomotor dysfunction in a TDP-43 ALS fly model is also exacerbated and suppressed by impairment and enhancement of endocytic function, respectively. Thus, endocytosis dysfunction may be an underlying cause of ALS pathology.

Impaired turnover of TDP-43 by impaired autophagy or proteasomal function have been suggested to be the cause of TDP-43 accumulation, a hallmark of ALS. Here the authors demonstrate that endocytosis is also important for regulating TDP-43 turnover and toxicity.

Patient education videos for elective colorectal surgery: results of a randomized controlled trial

AIM

Recent advances in surgery have focused on peri-operative care and interventions to improve outcome following surgery. Psychological preparation has a positive impact on recovery and incorporates a range of strategies with dissemination of information as one of the key elements. Information can be given verbally, through printed information or through use of a video. Traditionally, reliance has been on the use of written material as an adjunct to patient education in clinic. The current study is a randomized trial on the use of video education in patients undergoing elective colorectal resection within an enhanced recovery programme.

METHOD

Sixty-five eligible patients undergoing elective colorectal surgery were identified and 61 were randomized between August 2010 and August 2011 to either video and information leaflets or information leaflets alone. A fast track protocol was established for all the patients. Clinicians in charge of postoperative recovery were blinded. Standard discharge criteria were employed for all patients.

RESULTS

Of 61 patients randomized, one dropped out and outcomes on 60 were analysed. There was no difference in baseline characteristics between the groups (age, P = 0.964; body mass index, P = 0.829). Twenty-eight (91%) patients in the video group had left sided resections while two (6%) had right sided resections. Nineteen (66%) in the non-video group had left sided resections while nine (31%) had right sided resections. One (3%) patient in the non-video group and one (3%) in the video group had a total colectomy. Fourteen (45%) patients in the video group and 12 (41%) in the non-video group had surgery completed laparoscopically. There was no difference in the primary (median hospital stay 5 vs 5 days; P = 0.239) or the secondary outcome measures (pain score on movement, P = 0.338; pain score at rest, P = 0.989; nausea score, P = 0.74; epidural use, P = 0.984; paracetamol use, P = 0.44; voltarol use, P = 0.506) between the groups.

CONCLUSION

Use of video education in the psychological preparation of patients undergoing elective colorectal surgery does not improve short-term outcomes.

Advance care planning in care homes for older people: an English perspective

Advance care planning (ACP) as a process of discussing and recording wishes for future care and treatment is increasingly being promoted and discussed in the UK, reflecting recent changes in legislation. This study describes current ACP practice in care homes for older people drawing on data from a questionnaire survey (n = 213) of, and interviews (n = 15) with, care home managers. Whilst consultation about general care is taking place in the majority of homes surveyed using both formal and informal processes, the number of residents that have completed any ACP processes varies. Managers face intrinsic and extrinsic challenges related to the ascertaining of, and the implementing of wishes as they address ACP in the care home context. Until these wider contextual factors are addressed it will be difficult for staff in care homes to effectively undertake and implement ACP in care homes.

An origin for short gamma-ray bursts unassociated with current star formation

Two short (< 2 s) gamma-ray bursts (GRBs) have recently been localized and fading afterglow counterparts detected. The combination of these two results left unclear the nature of the host galaxies of the bursts, because one was a star-forming dwarf, while the other was probably an elliptical galaxy. Here we report the X-ray localization of a short burst (GRB 050724) with unusual gamma-ray and X-ray properties. The X-ray afterglow lies off the centre of an elliptical galaxy at a redshift of z = 0.258 (ref. 5), coincident with the position determined by ground-based optical and radio observations. The low level of star formation typical for elliptical galaxies makes it unlikely that the burst originated in a supernova explosion. A supernova origin was also ruled out for GRB 050709 (refs 3, 31), even though that burst took place in a galaxy with current star formation. The isotropic energy for the short bursts is 2-3 orders of magnitude lower than that for the long bursts. Our results therefore suggest that an alternative source of bursts--the coalescence of binary systems of neutron stars or a neutron star-black hole pair--are the progenitors of short bursts.

Practical lessons from the management of an outbreak of small round structured virus (Norwalk-like virus) gastroenteritis

An outbreak of viral gastroenteritis caused illness in 92 people during October 2000. All the cases had an association with one hotel and 80% of cases identified had attended one of two buffet meals on 18th October 2000. Cohort analysis did not implicate any particular foodstuff in this outbreak. All bacteriological tests on food samples were negative. Small round structured virus (SRSV)/Norwalk-like virus (NLV) particles were seen by electron microscopy in 6 out of 27 stool samples submitted for analysis. This paper describes the outbreak and in particular the lessons learned from the management and control of it. These include practical points with regard to the outbreak control team, liaison with the microbiology laboratory, handling data, agreeing a case definition, and occupational health issues. All can be applied elsewhere by those responsible for managing outbreaks at a local level.

The extended tubulin superfamily

Although most eukaryotic cells can express multiple isotypes of αβ-tubulin, the significance of this diversity has not always been apparent. Recent data indicate that particular αβ-tubulin isotypes, both genome encoded and those derived by post-translational modification, can directly influence microtubule structure and function — thus validating ideas originally proposed in the multitubulin hypothesis over 25 years ago.

It has also become increasingly evident over the past year that some (but intriguingly not all) eukaryotes encode several other tubulin proteins, and to date five further members of the tubulin superfamily, γ, δ, ϵ, 𝛇 and η, have been identified. Although the role of γ-tubulin in the nucleation of microtubule assembly is now well established, far less is known about the functions of δ-, ϵ-, 𝛇- and η-tubulin. Recent work has expanded our knowledge of the functions and localisation of these newer members of the tubulin superfamily, and the emerging data suggesting a restricted evolutionary distribution of these `new' tubulin proteins, conforms to established knowledge of microtubule cell biology. On the basis of current evidence, we predict that δ-, ϵ-, 𝛇- and η-tubulin all have functions associated with the centriole or basal body of eukaryotic cells and organisms.

Assessing the subjective experience of being a participant in psychiatric research

OBJECTIVE

To address both clinical and ethical concerns in psychiatric research, the study assessed the subjective experience of being a participant in a feasibility study of outcome in long-term psychodynamic psychotherapy and psychoanalysis.

METHOD

A questionnaire assessing positive and negative reactions to three typical research methodologies (self-report questionnaires, structured diagnostic interviews, and tape-recording of sessions) was administered to 23 patient-therapist pairs.

RESULTS

Patients reported that questionnaires and interviews were slightly to moderately helpful in promoting self-realization and facilitating therapy, and not at all to slightly intrusive and disruptive. Adjustment to audiotaping of sessions was rapid (within two sessions). Therapists significantly overestimated the negative effects and underestimated the positive benefit patients reported from participating in research.

CONCLUSIONS

Traditional objections to research in dynamic psychotherapy on the grounds that patients experience research procedures as significantly intrusive and disruptive appear to be unfounded.

Determination of stable isotopic enrichment and concentration of glycerol in plasma via gas chromatography-mass spectrometry for the estimation of lipolysis in vivo

Measuring glycerol's rate of appearance into the plasma compartment provides an excellent estimation of whole-body lipolysis. The glycerol rate of appearance can be calculated by estimating the plasma dilution of continuously infused stable or radioactive isotopes of glycerol. Previously, determination of glycerol stable isotopic enrichment has required either chemical ionization gas chromatography-mass spectrometry (GC-MS) or electron impact ionization GC-MS in which a fragment containing only a portion of the glycerol molecule was measured. The present method uses tert.-butyldimethylsilyl (tBDMS) derivatization and electron impact ionization to measure a fragment including the entire glycerol molecule. The method determines concentration and enrichment of plasma glycerol in a simple, precise, and cost-efficient manner, providing a basis from which lipid homeostasis can be assessed.

The provision of occlusal splints in primary dental care

Occlusal splints (Michigan splints, night/bite guards or bite-raising appliances) can be an effective, inexpensive and reversible treatment for a wide range of dental problems.

OBJECTIVE

The aim of this study was to analyse retrospectively the provision of occlusal splint ('Michigan' type) in general dental practice, following a prescription by a restorative dental consultant.

METHOD

One hundred patients were recruited from consultant clinics in a department of conservative dentistry during 1995 and 1996. All patients were prescribed a maxillary, full-coverage, heat-cured, acrylic-resin splint (Michigan splint) as part of a treatment plan. An explanatory letter and questionnaire were sent to all patients and to their referring general dental practitioner in 1997 and 1998.

RESULTS

A response rate of 79% was achieved in obtaining completed questionnaires from both patients and general dental practitioners. Of respondents 43% (34/79) received an occlusal splint of some form. A small proportion of the respondents (16.5% [13/79]) received a Michigan splint as prescribed. Irrespective of the type of appliance provided, most patients (82% [28/34]) found them helpful. Of those who did not receive an occlusal splint, 38% (17/45) of patients felt financial implications deterred them from obtaining an appliance. Other common reasons for non-provision included: patients felt that symptoms had improved (18% [8/45]) and patients did not agree with treatment (18% [8/45]). The general dental practitioners had similar opinions to their patients.

DISCUSSION

These findings raise some serious doubts on the efficacy of consultant clinic advice in the prescription of occlusal splints in general dental practice. The financial and educational issues raised by this study will need to be addressed to improve service provision.

CONCLUSION

The results of this study indicate that 16.5% of patient respondents prescribed a Michigan splint at a consultant clinic received such an appliance in general dental practice.

Tooth wear treated with direct composite restorations at an increased vertical dimension: results at 30 months

STATEMENT OF PROBLEM

Severe tooth wear localized to the anterior maxillary or mandibular teeth with loss of interocclusal space is difficult to manage.

PURPOSE

This study evaluated the outcome of composite restorations placed at an increased vertical dimension of occlusion in such patients.

METHODS AND MATERIAL

Sixteen patients were restored with 104 restorations in 2 groups. In group A, Durafill composite and Scotchbond Multipurpose dentine adhesive system were used to place direct anterior restorations (N = 52). In group B, Herculite XRV composite and Optibond dentine bonding agent was used (N = 52). The restorations were placed at an increased vertical dimension of occlusion creating a posterior disclusion of 1 to 4 mm.

RESULTS

Clinical follow-up showed that the posterior occlusion remained satisfactorily restored after a mean duration of 4.6 months (range 1 to 11 months). Mean follow-up of 30 months has shown a combined success rate of 89.4% for both groups with 93 of the restorations remaining in service. Maintenance in group A was high with 33 failures, but low in group B with 6 failures. Patient satisfaction was reported as good.

CONCLUSION

Direct composite restorations may be a treatment option for localized anterior tooth wear.

Postoperative adjuvant radiotherapy and 5-fluorouracil chemotherapy for rectal carcinoma

Postoperative combined modality therapy with radiotherapy and 5-fluorouracil (5FU) chemotherapy is an effective adjuvant approach that reduces locoregional and distant metastatic disease in patients with high-risk rectal carcinoma. However, this approach results in a treatment regimen of at least 6 months' duration. The present prospective study investigates the integration of radiotherapy and 5FU chemotherapy in a protocol designed to minimize toxicity and reduce the overall treatment time. A total of 40 patients with TNM stage II or III disease received postoperative radiotherapy at four fractions per week with weekly 5FU bolus injections delivered on the fifth non-radiotherapy day. Patients also received systemic chemotherapy with leucovorin both before and after pelvic irradiation, with the total treatment duration extending for only 18 weeks. Patients were able to complete radiotherapy in 90% of cases, while the delivery of full-dose chemotherapy was achievable in the vast majority. The incidence of haematologic and gastrointestinal toxicities requiring the cessation of treatment was acceptable. With a median follow-up of 20.9 months among surviving patients, the estimated progression-free and overall survival at 2 years were 71% and 79%, respectively.

Silicone absorption of elastomeric closures--an accelerated study

There is a trend in the parenteral industry to move from the use of elastomeric closures which are washed, siliconized, dried and sterilized in-house at the pharmaceutical manufacturers' site to pre-prepared closures purchased from the closure supplier. This preparation can consist of washing to reduce particle-load and bioburden, siliconization, placement in ready-to-sterilize bags and may eventually extend to sterilization by steam autoclave or gamma irradiation. Since silicone oil lubrication is critical to the processability/machinability of closures, research was designed to investigate this phenomenon in closures prepared using the Westar RS (Ready-to-Sterilize) process. This paper presents the data gathered in a study of the characteristic of silicone absorption into elastomeric closures under accelerated conditions. Variables such as silicone viscosity, rubber formulation, effect of sterilization and others are considered.

The gentle touch

This research study, which, because of its small numbers should be regarded as more of a pilot study, investigated the effect that therapeutic touch may have on measurable physical signs of the subjects involved. It also looked at any change this complementary therapy may have made in health perception immediately following the experiment and 1 week later. The design is modelled on that of Quinn (1984), eminent researcher in the field of energy exchange. Therapeutic touch is a misnomer because physical touch is not necessary--it is the energy field that is touched.

A compact and noise free electrohydraulic total artificial heart

The ABIOMED total artificial heart (TAH) is designed for long-term tether-free use in patients with end-stage heart disease. Blood pumping is achieved through hydraulic fluid motion across flexing diaphragms. The hydraulic power is derived from a miniature centrifugal pump (50% efficiency). Flow directional change needed for alternate left and right filling and ejection is achieved with a rotary valve. With no mechanical contact with the flexing membrane, the wedge angle between the two pumps sandwiching the energy convertor can be easily optimized for anatomic fit. The blood pumps (80 ml strokes) are fitted with trileaflet polyetherurethane valves (24 mm). The TAH is implanted using twist-lock stepless quick connectors to the inflow cuffs and outflow grafts. Left-right flow balance is achieved with an atrial hydraulic shunt placed between the left cuff and inflow valve. Animal studies show that the TAH fits very well in Long Horn calves weighing 90 to 100 kg and can provide cardiac output in excess of 10 L/min. A cadaver (85 kg) study showed the TAH fits within the pericardial region.

Organizational factors affecting growth and decline in adult day-care programs: a comparative study

Data derived from a mailed questionnaire of adult day-care providers in Illinois and from the records of the Illinois Department on Aging for fiscal years 1984 and 1985 were analyzed to determine which factors affect growth or decline in the programs, measured in terms of number of clients served and units of service provided. Initial analysis revealed that all providers under contract with the state for less than 3 years were growing, and approximately one half of the older providers had similar changes. A separate regression analysis of the older adult day care providers indicated that growth tended to be positively associated with reports of good relationships with referral agents and resource support from umbrella organizations and the larger community, and negatively associated with longevity of the provider. These findings highlight the importance of supportive interorganizational relationships for program growth.

AIDS beliefs in young women: are they related to AIDS risk-reduction behavior?

Little is known about the relationship between AIDS beliefs and AIDS risk-reduction behavior, especially in young heterosexual adults. This study explores young women's beliefs and behavior regarding AIDS. The results of this exploratory study indicate that college women generally see AIDS as serious, do not see themselves as susceptible, and are uncertain if AIDS beliefs influence their contraceptive behavior. Higher susceptibility scores are consistently correlated with AIDS risk-reduction behavior, and women who believe that AIDS affects their contraceptive use are more likely to use condoms. Implications for practice and strategies to increase susceptibility in women at risk are discussed.

Development of an efficient electrohydraulic total artificial heart

The efficient use of space and energy is achieved in a new implantable total artificial heart (TAH). To fit the orthotopic thoracic space, toroidal blood pumps encircle an energy converter, consisting of a centrifugal hydraulic fluid pump and a rotary reversing valve. The new centrifugal pump produces cardiac outputs of 6 L/min, with an average hydraulic efficiency of 47%. Toroidal blood pumps encircling the pump deliver a 60 cc stroke with an 85% ejection fraction and have a predictable blood flow pattern with no stagnant regions. Components have been characterized in vitro, and blood contacting elements have been tested in vivo.

Autoreactive platelet antibody in post transfusion purpura

Post transfusion purpura in a DR3, DRw52 positive, PlA1 negative woman rapidly responded to high-dose intravenous gammaglobulin therapy. Using the platelet immunofluorescence test (PIFT) high titre IgG and IgM alloantibodies were detected in the patient's acute serum. These alloantibodies had PlA1 specificity and the patient's serum produced a broad, 100 kDa band on Western Blot with PlA1 positive platelets. Acute phase serum also contained an IgG antibody which reacted in the PIFT with the patient's own platelets, and PlA1 negative platelets. When tested by Western Blot with PlA1 negative and Glanzmann's Thrombasthenia platelets, the acute serum produced bands at 180 and 200 kDa. The autoreactive antibody was not detected once the platelet count returned to normal. These findings provide evidence for the hypothesis that the mechanism of autologous platelet destruction in PTP is autoimmune.

Occult gastric cancer manifested by progressive shortness of breath in a young adult

We have reported a case of occult, diffuse gastric cancer in a young adult with progressive shortness of breath and bilateral pulmonary interstitial infiltrates. Progressive shortness of breath may be the first or only manifestation of occult gastric cancer caused by either lymphangitic carcinomatosis or microscopic tumor emboli to the lungs. Widespread recognition of this syndrome, a high index of suspicion, and prompt lung biopsy are necessary to make the correct diagnosis. With progress in chemotherapy for malignant diseases, early diagnosis and specific treatment may improve the prognosis of this condition.

Intramucosal gastric carcinoma in a patient with familial polyposis coli

Upper gastrointestinal polyps commonly occur in patients with familial polyposis coli; but the occurrence of gastric carcinoma is very rare in this disorder. We report a case of intramucosal gastric carcinoma in a patient with familial polyposis coli and multiple gastrointestinal adenomatous polyps.

De novo carcinoma of the rectum: a case report

There is strong evidence in the literature to suggest that most of the colorectal carcinomas arise from adenomatous polyps. Yet, rare carcinomas may arise de novo and we are reporting such a case of intramucosal rectal carcinoma occurring in a 47-year-old healthy man.

'O'-antigens are essential virulence factors of Shigella sonnei and Shigella dysenteriae 1

A novel transposon mutagenesis system has been developed for Shigella. We have used it to isolate specific mutants of Shigella sonnei and Shigella dysenteriae 1 that fail to produce lipopolysaccharide 'O' side chains. The virulence of the mutants was evaluated in the Sereny test and in a HeLa cell invasion assay. All HO'-minus mutants failed to provoke a positive Sereny reaction but retained the ability to invade HeLa cells. This demonstrates that 'O' side chains are virulence factors of S. sonnei and S. dysenteriae 1. 'O'-minus mutants of S. sonnei which still contained the Form I plasmid were capable of invading HeLa cells whilst plasmid-minus mutants were not, demonstrating that this plasmid encodes properties other than 'O'-antigen production that are involved in virulence.

Invasive ability of Plesiomonas shigelloides

Five of 16 strains of Plesiomonas shigelloides freshly isolated from children with acute diarrhoea, exhibited invasiveness for HeLa cells comparable to that of Shigella sonnei. None of the five, however, gave a positive reaction in the Sereny test. Although three of the invasive strains shared antigens with Shigella, no correlation was observed between invasiveness and the possession of such antigens. Only one of the invasive strains produced a toxin detectable as causing rounding of HeLa cells, although others released a product which inhibited protein synthesis in HeLa cells but which failed to provoke any dramatic morphological change.

Theoretical and experimental analysis of the single-coil pulsed-NMR method for measuring fluid flow

A theoretical and experimental analysis of the application of pulsed proton nuclear magnetic resonance (NMR) to the measurement of fluid flow has been made. Calculations of the detector signal line shapes, S(t), for a single-coil NMR laboratory experiment, were performed using a computer to identify the optimum choice of flow signature. The theoretical model included the influence of coil-field shape, coil length, and effects of flow phase. High flow rates, typical of arterial blood flow, were simulated. Good correlation between theory and experiment was observed. The maximum amplitude of the slope of the signal [dS(t)/dt] was found to be the optimum flow signature. The line shape S(t) was found to depend on flow phase. Comparison between theory and experiment provided a better understanding of the potential of NMR for measuring fluid or blood flow.

Theoretical analysis of the two-coil method for measuring fluid flow using nuclear magnetic resonance

A theoretical study of the application of pulsed nuclear magnetic resonance (NMR) to the measurement of fluid flow has been made. Calculations of detector signal line shapes, for a two-coil NMR laboratory experiment, were performed using a computer to determine the appropriate choice of flow signature. Results of calculations are presented showing the sensitivity of the method to various experimental parameters. The position of the received peak signal, in time, was found to correlate directly with mean flow velocity. However, the shape of the received signal was observed to depend markedly upon the state of flow, i.e., laminar, turbulent (plug). Hence, accurate determinations of flow required a knowledge of flow type. The theoretical calculations provided a better understanding of the potential of NMR for measuring fluid or blood flow.