ABSTRACT
Different from conventional synthetic polymers, polypeptides exhibit a distinguishing characteristic of adopting specific secondary structures, including random coils, α-helixes, and ß-sheets. The conformation determines the rigidity and solubility of polypeptide chains, which further direct the self-assembly and morphology of the nanostructures. We studied the effect of distinct secondary structures on the self-assembly behavior of polytyrosine (PTyr)-derived amphiphilic copolymers. Two block copolymers of enantiopure poly(ethylene glycol)-b-poly(l-tyrosine) (PEG-b-P(l-Tyr)) and racemic poly(ethylene glycol)-b-poly(dl-tyrosine) (PEG-b-P(dl-Tyr)) were synthesized through the ring-opening polymerization of l-tyrosine N-thiocarboxyanhydride (l-Tyr-NTA) and dl-tyrosine N-thiocarboxyanhydride (dl-Tyr-NTA), respectively, by using poly(ethylene glycol) amine as the initiator. PEG44-b-P(l-Tyr)10 adopts a ß-sheet conformation and self-assembles into rectangular nanosheets in aqueous solutions, while PEG44-b-P(dl-Tyr)9 is primarily in a random coil conformation with a tiny content of ß-sheet structures, which self-assembles into sheaf-like nanofibrils. A pH increase results in the ionization of phenolic hydroxyl groups, which decreases the ß-sheet content and increases the random coil content of the PTyr segments. Accordingly, PEG44-b-P(l-Tyr)10 and PEG44-b-P(dl-Tyr)9 self-assemble to form slender nanobelts and twisted nanoribbons, respectively, in alkaline aqueous solutions. The secondary structure-driven self-assembly of PTyr-derived copolymers is promising to construct filamentous nanostructures, which have potential for applications in controlled drug release.
ABSTRACT
Onabotulinum toxin has been used to treat a variety of headaches. We report a case of a 29-year-old woman who developed temporary and reversible atrophy of corrugator supercilii muscle after onabotulinum toxin (Botox, Allergan, Irvine, CA, USA) injection. To our best knowledge this has not been described in the literature before.
Subject(s)
Botulinum Toxins, Type A/adverse effects , Facial Muscles/pathology , Neuromuscular Agents/adverse effects , Adult , Atrophy/chemically induced , Female , Headache/drug therapy , Humans , Pain MeasurementABSTRACT
Acupuncture, traditional Chinese needle therapy, has become widely used for the relief of headache. The history of the practice of acupuncture in the United States and the theoretical framework for acupuncture in Chinese medicine are reviewed. The basic scientific background and clinical application of acupuncture in the headache management are discussed.
Subject(s)
Acupuncture Therapy , Headache Disorders/therapy , Acupuncture Therapy/history , Analgesia/methods , Contraindications , Evidence-Based Medicine , History, 18th Century , History, 19th Century , History, 20th Century , History, Ancient , Humans , Medicine, Chinese Traditional , Models, TheoreticalABSTRACT
The first International Headache Society classification defined tension-type headaches (TTHs) by itemising those characteristics of migraines TTHs did not possess [1]. As a result, TTHs, both episodic and chronic, remain the most nonspecific of all the commonly observed primary headaches. Until recently, there has been little impetus on the part of the pharmaceutical industry to investigate TTHs; many of the potentially useful drugs are now generic and unprofitable. In addition, few investigators have pursued the study of TTHs in lieu of its more glamorous neighbour, migraine. As a result, there are few well-designed studies on the pharmacotherapy of TTHs. The few studies that exist support the use of age-old standard drug classes, the tricyclic antidepressants and the NSAIDs. New research is now emerging that points to the potential utility of botulinum toxin type A, NMDA-receptor antagonists including Mg(2+) and nitric oxide synthase inhibitors. More scientifically rigorous clinical studies are needed.
