Allele-Specific Mutation Genotyping with Mismatches in Primer Design

Genotyping technologies for single nucleotide polymorphisms (SNPs) and other mutation types have evolved to become essential tools in various fields. Although high-throughput genotyping technologies occupy a key position in handling large amounts of SNP data, simple, low-cost, and conventional genotyping technologies remain in demand. Allele-specific (AS) polymerase chain reaction (PCR) and its related improved methods can effectively identify target SNPs and allele types using AS primers that introduce instability through mismatched bases at and around the SNP site. In this chapter, we present what is known from the literature on primer design with mismatches for AS-PCR and describe three cases of mutation detection (SNPs and insertions/deletions) associated with functional genes of crop species, which could be useful to guide future AS-PCR experiments.

Long-term persisting hybrid swarm and geographic difference in hybridization pattern: genetic consequences of secondary contact between two Vincetoxicum species (Apocynaceae-Asclepiadoideae)

BACKGROUND

During glacial periods, glacial advances caused temperate plant extirpation or retreat into localized warmer areas, and subsequent postglacial glacial retreats resulted in range expansions, which facilitated secondary contact of previously allopatric isolated lineages. The evolutionary outcomes of secondary contact, including hybrid zones, dynamic hybrid swarm, and resultant hybrid speciation, depends on the strengths of reproductive barriers that have arisen through epistatic and pleiotropic effects during allopatric isolation. The aim of this study was to demonstrate refugia isolation and subsequent secondary contact between two perennial Asclepioid species and to assess the genetic consequences of the secondary contact. We modeled the range shift of two ecologically distinct Vincetoxicum species using the species distribution model (SDM) and assessed the genetic consequences of secondary contact by combining morphological and genetic approaches. We performed morphometric analysis (592 individuals) and examined 10 nuclear microsatellites (671 individuals) in V. atratum, V. japonicum, and putative hybrid populations.

RESULTS

Multivariate analysis, model-based Bayesian analysis, and non-model-based discriminant analysis of principal components confirmed the hybridization between V. atratum and V. japonicum. High pollen fertility and a lack of linkage disequilibrium suggested that the hybrid populations may be self-sustaining and have persisted since V. atratum and V. japonicum came into contact during the post-glacial period. Moreover, our findings show that the pattern of hybridization between V. atratum and V. japonicum is unidirectional and differs among populations. Geographically-isolated hybrid populations exist as genetically distinct hybrid swarms that consist of V. atratum-like genotypes, V. japonicum-like genotypes, or admixed genotypes. In addition, Bayesian-based clustering analysis and coalescent-based estimates of long-term gene flow showed patterns of introgressive hybridization in three morphologically 'pure' V. japonicum populations.

CONCLUSION

In this study, we demonstrated that climatic oscillations during the Quaternary period likely led to species range shift and subsequently secondary contact. Hybrid populations may be self-sustaining and have persisted since V. atratum and V. japonicum came into contact during the post-glacial period. Pattern of hybridization between V. atratum and V. japonicum is unidirectional and differs among populations. We concluded that these differences in the genetic consequences of secondary contact are caused by historical colonization processes and/or natural selection.

Antiemetic efficacy of combined aprepitant and dexamethasone in patients at high-risk of postoperative nausea and vomiting from epidural fentanyl analgesia

BACKGROUND

Postoperative opioid analgesia increases the incidence of postoperative nausea and vomiting (PONV). We investigated whether a combination of the neurokinin-1 antagonist aprepitant and dexamethasone decreases PONV incidence compared with dexamethasone alone in high-risk patients receiving continuous epidural fentanyl.

METHODS

Sixty nonsmoking female patients scheduled for elective knee osteoarthritis surgery were randomly allocated to receive oral aprepitant 80 mg (aprepitant+dexamethasone group, N.=30) 2 h before anesthesia induction or no oral aprepitant (dexamethasone group, N.=30). All patients received intravenous dexamethasone 8 mg immediately before anesthesia induction. Anesthesia was maintained with remifentanil and sevoflurane. Continuous infusion of epidural analgesia, including fentanyl, was provided during and after surgery. We assessed complete response (no PONV and no rescue antiemetic use), incidence of nausea and vomiting, nausea severity scale, vomiting frequency, rescue antiemetic use, and postoperative pain at 2 and 24 h after surgery.

RESULTS

The cumulative incidence of vomiting at 24 h was 3% in the aprepitant+dexamethasone group and 27% in the dexamethasone group (P=0.011). The incidence and frequency of vomiting in the late postoperative period was also significantly lower in the aprepitant+dexamethasone group than in the dexamethasone group. However, there were no significant group differences in the proportion of patients who experienced a complete response, the incidence and severity of nausea, and rescue antiemetic use at 24 h.

CONCLUSION

The combination of aprepitant and dexamethasone was more effective in preventing postoperative vomiting compared with dexamethasone alone in patients at high-risk of PONV from continuous epidural fentanyl analgesia.

[Severe lightning pain during spinal anesthesia in a patient with diabetic neuropathy]

A 71-year-old woman with diabetic neuropathy who had undergone amputation of the right lower leg for diabetic gangrene 4 years previously, experienced severe lightning pain in both legs during spinal anesthesia. She was scheduled for skin grafting for a burn ulcer on her left foot. Her preoperative physical examination revealed hypesthesia in both legs due to diabetic neuropathy. Spinal anesthesia was performed with a combined spinal-epidural needle at the L 4-5 interspace using 2.0 ml of 0.3% hyperbaric dibucaine in the left lateral position. The region of hypesthesia was spread below Th 4. Ten minutes later, she complained of severe lightning pain in both legs and midazolam 1 mg was administered intravenously against agitation. The severe lightning pain diminished after the administration of pentazocine 7.5 mg intravenously in the recovery room. There was no worsening of neurological findings 5 hours later when the effect of spinal anesthesia disappeared. This clinical picture seems to be different from that of reported cases of phantom limb pain during spinal anesthesia in which severe lightning pain occurred in both legs. This case suggests that patients with diabetic neuropathy might develop severe lightning pain during spinal anesthesia using dibucaine.

[Effects of pentobarbital on coronary and cerebral circulation and metabolism in dogs subjected to hemorrhage]

Mongrel dogs were divided into a neuroleptanesthesia group (n = 10) and a pentobarbital group (neuroleptanesthesia plus pentobarbital; n = 10). The dogs were subjected to stepwise hemorrhage increasing from 30 to 40 and 50 ml.kg-1. In the neuroleptanesthesia group, mean arterial pressure, and cerebral and coronary blood flow decreased. Furthermore the oxygen and hydrogen ion balance in both the brain and the myocardium was aggravated, even at 30 ml.kg-1 of hemorrhage. Compared to the neuroleptanesthesia group, mean arterial pressure, and cerebral and coronary blood flow showed a greater decrease, cerebral oxygen consumption was lower, and the brain and myocardial metabolism worsened similarly at equivalent hemorrhage in the pentobarbital group. These results suggest that pentobarbital in combination with neuroleptanesthesia reduces cerebral oxygen consumption, but does not improve cerebral metabolism in the state of acute hemorrhage due to simultaneous induction of severe circulatory depression.

[Effects of deep halothane and isoflurane anesthesia on cerebral as well as coronary metabolism]

Mongrel dogs were subjected to halothane or isoflurane to examine the relationship between systolic blood pressure and cerebral as well as myocardial metabolism. The oxygen and hydrogen ion balances in the brain were not disturbed in either group to the systolic blood pressure level of 70 mmHg and were well maintained in the isoflurane group below this level. The myocardial oxygen balance was not aggravated in either group, whereas, the myocardial hydrogen ion balance was disturbed in the halothane group at the systolic blood pressure level between 70 mmHg and 50 mmHg though it was preserved in the isoflurane group. These findings demonstrate that the systolic blood pressure not disturbing oxygen and hydrogen ion balances in the brain and myocardium is 70 mmHg during halothane or isoflurane anesthesia, while isoflurane anesthesia becomes advantageous at the systolic blood pressures below this level. While the myocardial metabolism is less affected by lowering of blood pressures than the cerebral metabolism, it seems important to secure cardiac functions to maintain metabolism in both organs.