Archives of medical research最新文献

Background: Double- and single-strand DNA breaks (DSBs and SSBs, respectively) in spermatozoa, which emerge from intrinsic and extrinsic degenerative processes, are likely related to the underlying male pathology.

Aim: To determine whether the incidence of DSBs in the human ejaculate is a consistent predictor of whole sperm DNA fragmentation (W-SDF = SSBs + DSBs).

Methods: A correlation between the proportion of spermatozoa that showed whole W-SDF and those displaying only DSBs in DNA. Two patient cohorts were established: W-SDF ≤30% (low SDF; n = 153) and W-SDF ≥30% (high SDF; n = 222).

Results: An increasing level of W-SDF is associated with an increased incidence of DSBs in the ejaculate. When data from both the low and high W-SDF groups were combined, a linear relationship was observed, with DSBs increasing by 0.799 units for each unit increase in W-SDF. However, when the cohorts were analyzed separately, the relationships differed. In the low SDF group, DSBs increased linearly by 0.559 units for each unit increase in W-SDF. In the high SDF group, DSBs increased exponentially by 0.602 units per unit of W-SDF. Furthermore, the data dispersion between the two variables was significantly different between the cohorts, with the high SDF group showing 0.8 times greater variability than the low SDF group.

Conclusions: While the presence of DSBs in sperm is correlated with the W-SDF present in raw semen samples, the biological mechanisms responsible for DSBs are expressed in different proportions and/or at different levels in ejaculates with higher levels of DNA damage.

Background: Aging can lead to a decline in motor control. While age-related motor impairments have been documented, the underlying changes in cortico-cortical interactions remain poorly understood.

Methods: We took advantage of the high temporal resolution of dual-site transcranial magnetic stimulation (dsTMS) to investigate how communication between higher-order rostral premotor regions and the primary motor cortex (M1) influences motor control in young and elderly adults. We assessed the dynamics of connectivity from the inferior frontal gyrus (IFG) or pre-supplementary motor area (preSMA) to M1, by testing how conditioning of the IFG/preSMA affected the amplitude of motor evoked potentials (MEPs) induced by M1 stimulation at different temporal intervals. Moreover, we explored how age-related changes in premotor-M1 interactions relate to motor performance.

Results: Our results show that both young and elderly adults had excitatory IFG-M1 and preSMA-M1 interactions, but the two groups' timing and strength differed. In young adults, IFG-M1 interactions were early and time-specific (8 ms), whereas in older individuals, they were delayed and more prolonged (12-16 ms). PreSMA-M1 interactions emerged early (6 ms) and peaked at 10-12 ms in young individuals but were attenuated in older individuals. Critically, a connectivity profile of the IFG-M1 circuit like that of the young cohort predicted better dexterity in older individuals, while preserved preSMA-M1 interactions predicted greater strength, suggesting that age-related motor decline is associated with specific changes in premotor-motor networks.

Conclusions: Preserving youthful motor network connectivity in older individuals is related to maintaining motor performance and providing information for interventions targeting aging effects on behavior.