Dipygus is a severe congenital deformity where the body axis forks left and right partway along the torso with the posterior end (pelvis and legs) duplicated. Myrtle Corbin was a dipygus; she married and had five children. In human cases, the inner two of the four hindquarters develop much smaller than normal. This is a type of "teras catadidymum" ("monster twinned below"). Another sort of deformity with extra legs can happen from a degenerated conjoined twin, as may have happened with Frank Lentini with his third leg. Signs
Dipygus manifests as duplicated lower limbs and could include additional organs or bodily structures. Causes
Dipygus is caused by genetic, environmental, or teratogenic factors. It occurs early in intrauterine life. == References ==
Addiction is a component of a substance use disorder and represents the most severe form of the disorder.Overexpression of the gene transcription factor ΔFosB in the nucleus accumbens plays a crucial role in the development of an addiction to opioids and other addictive drugs by sensitizing drug reward and amplifying compulsive drug-seeking behavior. Like other addictive drugs, overuse of opioids leads to increased ΔFosB expression in the nucleus accumbens. Opioids affect dopamine neurotransmission in the nucleus accumbens via the disinhibition of dopaminergic pathways as a result of inhibiting the GABA-based projections to the ventral tegmental area (VTA) from the rostromedial tegmental nucleus (RMTg), which negatively modulate dopamine neurotransmission. In other words, opioids inhibit the projections from the RMTg to the VTA, which in turn disinhibits the dopaminergic pathways that project from the VTA to the nucleus accumbens and elsewhere in the brain.The differences in the genetic regions encoding the dopamine receptors for each individual may help to elucidate part of the risk for opioid addiction and general substance abuse. Studies of the D2 Dopamine Receptor, in particular, have shown some promising results. One specific SNP is at the TaqI RFLP (rs1800497). In a study of 530 Han Chinese heroin-addicted individuals from a Methadone Maintenance Treatment Program, those with the specific genetic variation showed higher mean heroin consumption by around double those without the SNP. This study showed a p-value of .003 and along with several other works, this helps to show the contribution of dopamine receptors to substance addiction and more specifically, to opioid abuse.