UHealth - University of Miami Health System

Nancy L. Brackett, Ph.D., H.C.L.D.

General Information

Nancy L. Brackett, Ph.D., H.C.L.D.


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  • English


  • Clinical Andrologist
  • Director, Male Fertility Research Program
  • Research Associate Professor

Clinical Interests

Male infertility

Research Interests

The research in my laboratory is focused on understanding and improving the impairments to male fertility which occur following spinal cord injury (SCI). Following SCI, most men, but not women, experience impaired fertility. Specifically, most men with SCI are anejaculatory, and some experience erectile dysfunction. Although their semen may be obtained by medically-assisted ejaculation procedures, in most cases, semen quality is impaired, specifically, sperm motility and viability are abnormally low, although sperm numbers tend to be normal.

Our research is focused on determining the cause of impaired semen quality in men with SCI. Our studies have shown that factors secondary to SCI are not responsible for impaired semen quality in men with SCI. For example, the condition is not due to scrotal thermoregulatory dysfunction, the method or frequency of ejaculation, the number of ensuing years post-injury, or hormonal alterations. Our recent evidence indicates that the problem is related to the seminal plasma. For example, seminal plasma of men with SCI inhibits sperm motility of able-bodied men. In addition, sperm motility is much higher in men with SCI before the sperm mix with seminal plasma. Substances within the seminal plasma are abnormal in men with SCI, including elevated reactive oxygen species, decreased prostate specific antigen (a marker of prostate function) and decreased fructose (a marker of seminal vesicle function). The semen of men with SCI contains an abnormally high number of non-spermatozoon cells, most of which are leukocytes. Our current research is investigating inflammatory factors, including semen cytokine levels, as contributors to the problem. Our ultimate goal is to develop therapies to normalize semen quality in men with SCI, so that chances of biological fatherhood are increased.

In addition to our investigation of the seminal plasma, we are studying methods to improve semen retrieval and semen processing for assisted conception procedures. Our research has shown that sperm motility is better when obtained by penile vibratory stimulation versus electroejaculation, and that semen of men with SCI should be processed quickly and at room temperature, in contrast to prolonged processing at body temperature typically used for semen from able-bodied men. In addition, we have shown that brown-colored semen is a common occurrence in men with SCI. The cause of the brown color is unknown, and does not harm sperm motility. Contrary to common belief, our research showed that repeated ejaculation does not necessarily eliminate the brown color. We are currently investigating whether oral administration of nifedipine impairs sperm function in men with SCI, and we are investigating methods to improve antegrade semen recovery during assisted ejaculation procedures.infertility in men with spinal cord injury

1: Zhu J, Brackett NL, Aballa TC, Lynne CM, Witt MW, Kort HI, Roudebush WE.
Free Full Text High Seminal Platelet-Activating Factor Acetylhydrolase Activity in Men with Spinal Cord Injuries.
J Androl. 2005 Dec 8; [Epub ahead of print]
PMID: 16339448 [PubMed - as supplied by publisher]

2: Cohen DR, Basu S, Randall JM, Aballa TC, Lynne CM, Brackett NL.
Free Full Text Sperm motility in men with spinal cord injuries is enhanced by inactivating cytokines in the seminal plasma.
J Androl. 2004 Nov-Dec;25(6):922-5.
PMID: 15477364 [PubMed - indexed for MEDLINE]

3: Basu S, Aballa TC, Ferrell SM, Lynne CM, Brackett NL.
Free Full Text Inflammatory cytokine concentrations are elevated in seminal plasma of men with spinal cord injuries.
J Androl. 2004 Mar-Apr;25(2):250-4.
PMID: 14760011 [PubMed - indexed for MEDLINE]

4: Randall JM, Evans DH, Bird VG, Aballa TC, Lynne CM, Brackett NL.
Abstract Leukocytospermia in spinal cord injured patients is not related to histological inflammatory changes in the prostate.
J Urol. 2003 Sep;170(3):897-900.
PMID: 12913725 [PubMed - indexed for MEDLINE]

5: Basu S, Lynne CM, Ruiz P, Aballa TC, Ferrell SM, Brackett NL.
Free Full Text Cytofluorographic identification of activated T-cell subpopulations in the semen of men with spinal cord injuries.
J Androl. 2002 Jul-Aug;23(4):551-6.
PMID: 12065463 [PubMed - indexed for MEDLINE]

6: Brackett NL, Ead DN, Aballa TC, Ferrell SM, Lynne CM.
Abstract Semen retrieval in men with spinal cord injury is improved by interrupting current delivery during electroejaculation.
J Urol. 2002 Jan;167(1):201-3.
PMID: 11743305 [PubMed - indexed for MEDLINE]

7: Bird VG, Brackett NL, Lynne CM, Aballa TC, Ferrell SM.
Abstract Reflexes and somatic responses as predictors of ejaculation by penile vibratory stimulation in men with spinal cord injury.
Spinal Cord. 2001 Oct;39(10):514-9.
PMID: 11641794 [PubMed - indexed for MEDLINE]

8: Brackett NL, Lynne CM.
Abstract The method of assisted ejaculation affects the outcome of semen quality studies in men with spinal cord injury: A review.
NeuroRehabilitation. 2000;15(2):89-100.
PMID: 11455086 [PubMed - as supplied by publisher]

9: Brackett NL, Lynne CM, Aballa TC, Ferrell SM.
Abstract Sperm motility from the vas deferens of spinal cord injured men is higher than from the ejaculate.
J Urol. 2000 Sep;164(3 Pt 1):712-5.
PMID: 10953131 [PubMed - indexed for MEDLINE]

10: Wieder JA, Brackett NL, Lynne CM, Green JT, Aballa TC.
Abstract Anesthetic block of the dorsal penile nerve inhibits vibratory-induced ejaculation in men with spinal cord injuries.
Urology. 2000 Jun;55(6):915-7.
PMID: 10840108 [PubMed - indexed for MEDLINE]

11: Brackett NL.
Free Full Text Penile vibratory stimulation for men with spinal cord injury.
Hum Reprod Update. 1999 Sep-Oct;5(5):551-2. No abstract available.
PMID: 10582793 [PubMed - indexed for MEDLINE]

12: Wieder JA, Lynne CM, Ferrell SM, Aballa TC, Brackett NL.
Abstract Brown-colored semen in men with spinal cord injury.
J Androl. 1999 Sep-Oct;20(5):594-600.
PMID: 10520571 [PubMed - indexed for MEDLINE]

13: Brackett NL.
Free Full Text Semen retrieval by penile vibratory stimulation in men with spinal cord injury.
Hum Reprod Update. 1999 May-Jun;5(3):216-22. Review.
PMID: 10438106 [PubMed - indexed for MEDLINE]

14: Lynne CM, Aballa TC, Wang TJ, Rittenhouse HG, Ferrell SM, Brackett NL.
Abstract Serum and semen prostate specific antigen concentrations are different in young spinal cord injured men compared to normal controls.
J Urol. 1999 Jul;162(1):89-91.
PMID: 10379747 [PubMed - indexed for MEDLINE]

15: Brackett NL, Ferrell SM, Aballa TC, Amador MJ, Lynne CM.
Abstract Semen quality in spinal cord injured men: does it progressively decline postinjury?
Arch Phys Med Rehabil. 1998 Jun;79(6):625-8.
PMID: 9630139 [PubMed - indexed for MEDLINE]

16: Brackett NL, Ferrell SM, Aballa TC, Amador MJ, Padron OF, Sonksen J, Lynne CM.
Abstract An analysis of 653 trials of penile vibratory stimulation in men with spinal cord injury.
J Urol. 1998 Jun;159(6):1931-4.
PMID: 9598490 [PubMed - indexed for MEDLINE]

17: Wang TJ, Rittenhouse HG, Wolfert RL, Lynne CM, Brackett NL.
Free Full Text PSA concentrations in seminal plasma.
Clin Chem. 1998 Apr;44(4):895-6. No abstract available.
PMID: 9554514 [PubMed - indexed for MEDLINE]

18: Brackett NL, Bloch WE, Lynne CM.
Abstract Predictors of necrospermia in men with spinal cord injury.
J Urol. 1998 Mar;159(3):844-7.
PMID: 9474165 [PubMed - indexed for MEDLINE]

19: Padron OF, Brackett NL, Sharma RK, Lynne CM, Thomas AJ Jr, Agarwal A.
Abstract Seminal reactive oxygen species and sperm motility and morphology in men with spinal cord injury.
Fertil Steril. 1997 Jun;67(6):1115-20.
PMID: 9176453 [PubMed - indexed for MEDLINE]

20: Brackett NL, Santa-Cruz C, Lynne CM.
Abstract Sperm from spinal cord injured men lose motility faster than sperm from normal men: the effect is exacerbated at body compared to room temperature.
J Urol. 1997 Jun;157(6):2150-3.
PMID: 9146604 [PubMed - indexed for MEDLINE]

21: Brackett NL, Padron OF, Lynne CM.
Abstract Semen quality of spinal cord injured men is better when obtained by vibratory stimulation versus electroejaculation.
J Urol. 1997 Jan;157(1):151-7.
PMID: 8976239 [PubMed - indexed for MEDLINE]

22: Brackett NL, Nash MS, Lynne CM.
Abstract Male fertility following spinal cord injury: facts and fiction.
Phys Ther. 1996 Nov;76(11):1221-31. Review.
PMID: 8911434 [PubMed - indexed for MEDLINE]

23: Brackett NL, Davi RC, Padron OF, Lynne CM.
Abstract Seminal plasma of spinal cord injured men inhibits sperm motility of normal men.
J Urol. 1996 May;155(5):1632-5.
PMID: 8627840 [PubMed - indexed for MEDLINE]

24: Brackett NL, Abae M, Padron OF, Lynne CM.
Abstract Treatment by assisted conception of severe male factor infertility due to spinal cord injury or other neurologic impairment.
J Assist Reprod Genet. 1995 Mar;12(3):210-6.
PMID: 8520188 [PubMed - indexed for MEDLINE]

25: Brackett NL, Lynne CM, Weizman MS, Bloch WE, Padron OF.
Abstract Scrotal and oral temperatures are not related to semen quality of serum gonadotropin levels in spinal cord-injured men.
J Androl. 1994 Nov-Dec;15(6):614-9.
PMID: 7721665 [PubMed - indexed for MEDLINE]

26: Padron OF, Brackett NL, Weizman MS, Lynne CM.
Abstract Semen of spinal cord injured men freezes reliably.
J Androl. 1994 May-Jun;15(3):266-9.
PMID: 7928669 [PubMed - indexed for MEDLINE]

27: Brackett NL, Lynne CM, Weizman MS, Bloch WE, Abae M.
Abstract Endocrine profiles and semen quality of spinal cord injured men.
J Urol. 1994 Jan;151(1):114-9.
PMID: 8254785 [PubMed - indexed for MEDLINE]

28: Brackett NL, Iuvone PM, Edwards DA.
Abstract Midbrain lesions, dopamine and male sexual behavior.
Behav Brain Res. 1986 May;20(2):231-40.
PMID: 3524604 [PubMed - indexed for MEDLINE]

29: Brackett NL, Edwards DA.
Abstract Medial preoptic connections with the midbrain tegmentum are essential for male sexual behavior.
Physiol Behav. 1984 Jan;32(1):79-84.
PMID: 6718539 [PubMed - indexed for MEDLINE]

30: Kuo JF, Andersson RG, Wise BC, Mackerlova L, Salomonsson I, Brackett NL, Katoh N, Shoji M, Wrenn RW.
Free in PMC Calcium-dependent protein kinase: widespread occurrence in various tissues and phyla of the animal kingdom and comparison of effects of phospholipid, calmodulin, and trifluoperazine.
Proc Natl Acad Sci U S A. 1980 Dec;77(12):7039-43.
PMID: 6938952 [PubMed - indexed for MEDLINE]

31: Kuo JF, Shoji M, Brackett NL, Helfman DM.
Abstract Effects of phosphodiesterase inhibitors, imidazole and phosphate on cyclic CMP phosphodiesterase are different from those on cyclic AMP and cyclic GMP phosphodiesterases.
J Cyclic Nucleotide Res. 1978 Dec;4(6):463-74.
PMID: 85641 [PubMed - indexed for MEDLINE]

32: Tse J, Brackett NL, Kuo JF.
Abstract Alterations in activities of cyclic nucleotide systems and in beta-adrenergic receptor-mediated activation of cyclic AMP-dependent protein kinase during progression and regression of isoproterenol-induced cardiac hypertrophy.
Biochim Biophys Acta. 1978 Sep 6;542(3):399-411.
PMID: 210840 [PubMed - indexed for MEDLINE]

33: Helfman DM, Brackett NL, Kuo JF.
Free in PMC Depression of cytidine 3':5'-cyclic monophosphate phosphodiesterase activity in developing tissues of guinea pigs.
Proc Natl Acad Sci U S A. 1978 Sep;75(9):4422-5.
PMID: 212750 [PubMed - indexed for MEDLINE]

34: Shoji M, Brackett NL, Kuo JF.
Abstract Cytidine 3',5'-monophosphate phosphodiesterase: decreased activity in the regenerating and developing liver.
Science. 1978 Sep 1;201(4358):826-8.
PMID: 210503 [PubMed - indexed for MEDLINE]

35: Shoji M, Brackett NL, Helfman DM, Morris HP, Kuo JF.
No abstract Decreased activity of cytidine 3':5'-monophosphate (cyclic CMP) phosphodiesterase in the fast-growing Morris hepatoma 3924A, but not in the slow-growing Morris hepatoma 9618A.
Biochem Biophys Res Commun. 1978 Aug 14;83(3):1140-6. No abstract available.
PMID: 213064 [PubMed - indexed for MEDLINE]

36: Shoji M, Brackett NL, Tse J, Shapira R, Kuo JF.
Free Full Text Molecular properties and mode of action of homogeneous preparation of stimulatory modulator of cyclic GMP-dependent protein kinase from the heart.
J Biol Chem. 1978 May 25;253(10):3427-34. No abstract available.
PMID: 206543 [PubMed - indexed for MEDLINE]

37: Kuo JF, Brackett NL, Shoji M, Tse J.
Free Full Text Cytidine 3':5'-monophosphate phosphodiesterase in mammalian tissues. Occurrence and biological involvement.
J Biol Chem. 1978 Apr 25;253(8):2518-21.
PMID: 204653 [PubMed - indexed for MEDLINE]

38: Kuo JF, Brackett NL, Stubbs JW, Shoji M, Helfman DM.
No abstract Involvements of cyclic nucleotide systems in enlarged mice lungs produced by butylated hydroxytoluene.
Biochem Pharmacol. 1978;27(12):1671-5. No abstract available.
PMID: 212077 [PubMed - indexed for MEDLINE]

39: Shoji M, Morris HP, Davis CW, Brackett NL, Kuo JF.
Abstract Modified cyclic nucleotide systems in Morris hepatoma 3924A favoring expression of cyclic GMP effect.
Biochim Biophys Acta. 1977 Dec 22;500(2):419-24.
PMID: 201299 [PubMed - indexed for MEDLINE]


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