Writing the Manuscript: Discussion & Introduction

APS Professional Skills Course:

Writing and Reviewing for Scientific Journals

Discussion & Introduction Sections

• Focus on how your story fits into broader picture

• Require considerable thought

– Don’t just report on what you did

– Relate your work to that of others

Discussion

• Write after Results Section

• Synthesize your results

• Describe their relevance

• Look at the literature critically

• Use an outline for structure

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

Example: State the answer to the study’s 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.

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.”

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.”

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.”

“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

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.”

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.”

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).”

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?

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

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.

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.”

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.”

Additional Sections

• Acknowledgements

• References

• Appendices

Acknowledgements

• Intellectual contributions

• Technical contributions

• Financial contributions

– Grants

– Awards

• Conflicts of interest?

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

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

Experience Issues

• How important is this work?

• Self-assured and competent writing

• Claiming conclusions

• Specificity of conclusions due to study limitations

• Conciseness in writing