Writing the Manuscript: Discussion

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Writing the Manuscript Discussion Introduction

• APS Professional Skills Course
• Writing and Reviewing for Scientific Journals

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Discussion Introduction Sections

• Focus on how your story fits into broader picture
• Require considerable thought
• Dont just report on what you did
• Relate your work to that of others

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Discussion

• Write after Results Section
• Synthesize your results
• Describe their relevance
• Look at the literature critically
• Use an outline for structure

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Discussion

• State the answer to the question you asked at the
  beginning of the discussion
• Follow up with supporting evidence
• Explain your answer
• Discuss the most important conclusions first
• Write in present tense

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Example State the answer to the studys question
at the beginning

• Discussion -- Major findings of this study are
  that augmented contraction to serotonin of the
  basilar artery after SAH was strongly inhibited
  by fasudil, a Rho kinase inhibitor, and that
  phosphorylation of MYPT-1 after serotonin was
  greater in SAH than in control animals. These
  results suggest that enhancement of activation of
  Rho kinase contributes to augmentation of
  contraction to serotonin in the basilar artery
  after SAH.
• From Y Watanabe, et al. Activation of
  Rho-associated kinase during augmented
  contraction of the basilar artery to serotonin
  after subarachnoid hemorrhage. Am J Physiol Heart
  Circ Physiol 288 H2653-H2658, 2005.

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Example Follow up with supporting evidence

• In this study, serotonin-induced contraction
  was abolished by fasudil in control rabbits,
  suggesting a major role of Rho kinase in
  serotonin-induced contraction in the basilar
  artery of rabbits.
• In addition, augmented contraction to serotonin
  after SAH was strongly inhibited by fasudil. In
  contrast to serotonin-induced contraction,
  histamine-induced contraction did not increase
  after SAH and was not inhibited by fasudil. Thus,
  Rho kinase has a critical role in augmentation
  of contraction of the basilar artery to serotonin
  after SAH.

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Example Explain your answer

• Upregulation of the serotonin 1B receptor on
  smooth muscle cells after SAH may contribute to
  enhanced activation of Rho kinase (2).
• Endothelium-derived nitric oxide (NO) may
  inhibit the RhoA/Rho kinase pathway in smooth
  muscle (31). Thus, if NO-mediated signaling in
  the basilar artery is impaired after SAH, Rho
  kinase may be activated. There is evidence for
  impairment of the NO/cGMP pathway in the basilar
  artery after SAH (30). Because serotonin may
  release NO from the endothelium in the basilar
  artery of normal rabbits (25), reduced
  bioavailability of endothelium-derived NO after
  SAH may contribute to enhanced activation of Rho
  kinase and augmented contraction induced by
  serotonin.

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Example Discuss the most important conclusions
first

• We observed that phosphorylation of MYPT-1
  induced by serotonin was enhanced in basilar
  arteries from SAH animals. A similar finding has
  been demonstrated in a model of coronary
  vasospasm (7). These findings support the
  hypothesis, based on effects of inhibitors of Rho
  kinase on vasomotor responses, that enhanced
  activation of Rho kinase contributes to augmented
  contraction to serotonin.

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Discuss Your Findings

• Discuss results, but do not repeat them
• Link hypothesis to results to conclusions
• Describe results in terms of their wider
  significance
• Allow for justified speculation
• Avoid undue speculation
• Make only well-justified claims of primacy
• Avoid personal communication citations
• Use headings only if necessary

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Example Link hypothesis from introduction to
conclusions

• These findings support the hypothesis, based on
  effects of inhibitors of Rho kinase on vasomotor
  responses, that enhanced activation of Rho kinase
  contributes to augmented contraction to
  serotonin.

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Example Discuss wider significance of results

• Example 1 Contraction of cerebral arteries to
  other vaso-constrictors, including norepinephrine
  and PGF2?, is also augmented after SAH in rabbits
  (11, 34). Contraction of vascular smooth muscle
  induced by these agonists may involve activation
  of the RhoA/Rho kinase pathway (6, 22). Thus, we
  speculate that subcellular mechanisms that
  enhance activation of Rho kinase may act as a
  common pathway for augmentation of contraction of
  cerebral arteries to various agonists after SAH.
• Example 2 We observed, however, that
  phosphorylation at Thr853 was significantly
  increased after application of serotonin in the
  basilar artery of SAH animals. The mechanism of
  lack of an increase in phosphorylation at Thr696
  is not clear. We speculate that the difference in
  pattern of phosphorylation of MYPT-1 may be
  related to differences in blood vessels and/or
  vasoconstrictor agonists.

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Example Limitations of the Study

• We have considered the possibility that fasudil
  may affect the endothelium during
  serotonin-induced contraction. The role of
  endothelial Rho kinase in regulation of smooth
  muscle contraction is not clear. Rho kinase
  downregulates activity of endothelial NO synthase
  (eNOS) (13). It is not clear, however, whether
  inhibition of Rho kinase increases eNOS activity
  and alters vascular reactivity. In addition,
  inhibition of Rho kinase may negatively regulate
  agonist-induced activation of eNOS, because the
  RhoA/Rho kinase pathway may contribute to
  agonist-induced elevation of intracellular Ca2
  concentration in endothelial cells (37).

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Introduction

• Two main purposes
• Get reader interested in the topic
• Prepare reader to understand the paper
• What is the question being asked?
• Where did the question come from?
• Why are you asking that question?

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Writing a Concise Introduction

• Keep it short
• Brief review of pertinent literature
• Place your study in historical context
• Provide a general description of field
• Statement of the hypothesis and/or research
  question(s)
• State animal or material used in study
• No data summary

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Example Get the reader interested

• Women, primarily young women, have a greater
  incidence of orthostatic intolerance than men
  (10, 33), and this difference is especially
  dramatic after spaceflight (9, 45) or bed rest
  (6), in which hypovolemia and "cardiovascular
  deconditioning" occur. However, the underlying
  mechanisms remain unclear. It is likely that
  certain gender-specific factors such as
  differences in some hormonal levels, which may
  affect the neurohumoral regulation of arterial
  pressure, or physical characteristics such as a
  smaller and less "distensible" heart (10) may
  influence orthostatic blood pressure (BP)
  control.
• From Q. Fu, et al. Effects of gender and
  hypovolemia on sympathetic neural responses to
  orthostatic stress. Am J Physiol Regul Integr
  Comp Physiol 289 R109-R116, 2005.

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Example Review of literature to place study in
historical context

• Results regarding gender differences in
  sympathetic neural responsiveness to orthostatic
  challenges are few but controversial. Similar
  (10, 12) or attenuated (1, 3, 45) adrenergic
  responses during orthostatic stress have been
  reported in healthy women compared with men.
  There is only one study showing lower muscle
  sympathetic nerve activity (MSNA) responses, when
  expressed as average amplitude per burst, in
  healthy young women vs. men during a graded
  head-up tilt (HUT). However, both MSNA burst
  frequency (bursts per minute) and burst incidence
  (bursts per 100 heartbeats) were not different
  between the genders moreover, peripheral
  vascular resistance responses did not differ
  between men and women in this study (35). Thus,
  evidence for the conclusion that women have a
  lower sympathetic neural response than men is not
  definitive.

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Example What question is being asked?Statement
of the hypothesis

• The present study was performed to test the
  hypothesis that women have blunted vasomotor
  sympathetic responses to orthostatic stress
  compared with men, which may be elicited under
  hypovolemic conditions.
• To accomplish this objective, we measured MSNA,
  plasma catecholamines, and hemodynamics in
  healthy young women and men in the supine
  position and during acute 60 HUT under both
  normovolemic and hypovolemic conditions and
  compared the responses between the genders.
  Additionally, to determine the maximal
  orthostatic tolerance, progressive lower body
  negative pressure (LBNP) to presyncope was
  applied in all subjects under both conditions.

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Additional Sections

• Acknowledgements
• References
• Appendices

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Acknowledgements

• Intellectual contributions
• Technical contributions
• Financial contributions
• Grants
• Awards
• Conflicts of interest?

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References

• Cite only most valid relevant references
• Limit the number of references
• Check journal policy
• Avoid excessive self-citation
• Check all citations for accuracy
• Finalize using software package
• Format correctly for journal selected

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Appendices

• Optional part of manuscript
• Contains additional material not essential to
  understanding of the main paper
• Uses
• Mathematical models
• Supplemental data
• Computer programs
• Diagrams of apparatus

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Experience Issues

• How important is this work?
• Self-assured and competent writing
• Claiming conclusions
• Specificity of conclusions due to study
  limitations
• Conciseness in writing