freeze-thaw cycle is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2025-09-24. Numbers and descriptions here follow the published literature rather than marketing material.
Early research on PT-141 grew out of work on melanotan II, a related cyclic peptide studied for pigmentation. Investigators observed that centrally acting melanocortin agonists also influenced sexual behaviour in animal models, and the programme shifted toward that endpoint. A nasal formulation was evaluated in clinical trials but showed inconsistent absorption, and later studies used subcutaneous administration instead. Regulatory approval in the United States followed in 2019 for a defined population of premenopausal women with acquired, generalised hypoactive sexual desire disorder. That approval was specific to that group rather than a broad indication.
Bremelanotide acts as a non-selective agonist at melanocortin receptors, with reported activity at MC1R, MC3R, MC4R and MC5R. The proposed basis for its central effects is activation of MC4R populations in the hypothalamus, a region associated with appetite and reproductive signalling. Because the peptide carries a net positive charge and polar side chains, it does not cross biological membranes freely, which is one reason oral administration is not the standard route. Effects generally appear within an hour of parenteral administration and are described as centrally mediated rather than peripheral.
Bremelanotide, developed under the code PT-141, is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone. Its structure is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, with a lactam bridge joining the aspartate and lysine side chains. The molecule has the formula C50H68N14O10 and a monoisotopic mass near 1025 daltons. It is commonly prepared as the acetate salt and appears as a white to off-white lyophilised powder in solid form. The free acid is the pharmacologically relevant species, while the counter-ion improves handling and dissolution.
Published studies differ in design, population and endpoint definition, so results are not always directly comparable across reports. Some trials used patient-reported measures of desire and distress, while others tracked physiological or behavioural outcomes. Questions that remain open include the durability of effects beyond short follow-up periods, the frequency of transient blood pressure elevation observed after administration, and whether a subtype-selective analogue could separate central effects from pigmentation-related activity. These points are usually framed as unresolved rather than settled in review literature.
Routine characterisation of bremelanotide relies on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nm, where the peptide backbone absorbs. Mass spectrometry, typically in tandem mode with electrospray ionisation, confirms identity and supports quantification in biological matrices. Additional checks include amino acid analysis, peptide mapping after enzymatic digestion, and confirmation of the lactam bridge, since incomplete cyclisation produces a mass-shifted by-product. Purity values above 95 percent are common in reference-grade material, though reports vary in how strictly related substances are resolved from the parent peak.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Cyclic heptapeptide | Synthetic analogue of alpha-MSH |
| Molecular formula | C50H68N14O10 | Acetate salt form commonly reported |
| Molecular mass | ~1025 Da | Monoisotopic value near 1025.2 |
| Key structural motif | Lactam bridge | Asp side chain to Lys side chain |
| Solid appearance | White to off-white powder | Lyophilised and hygroscopic |
Whether the behavioral effect originates centrally, peripherally, or through both remains an active question. Animal experiments using receptor antagonists and site-specific injections point toward hypothalamic melanocortin circuits as a key locus, but translating those findings to humans is not straightforward. Blood pressure changes observed in trials suggest a vascular component that may be peripherally mediated. The relationship between receptor occupancy and reported effect has not been mapped in humans, and no validated biomarker predicts response. This gap makes it difficult to explain individual variability on pharmacological grounds alone.
Bremelanotide acts as an agonist at melanocortin receptors, a family of five G-protein-coupled receptors labeled MC1 through MC5. Binding studies indicate activity at several of these subtypes rather than strict selectivity for one. Signalling proceeds mainly through Gs-mediated activation of adenylyl cyclase, raising intracellular cyclic AMP. The MC4 receptor, expressed in hypothalamic and limbic circuits, is widely regarded as the subtype most relevant to sexual response. Because the molecule is not subtype-selective, effects at other melanocortin receptors are expected and are used to explain some observed side effects.
Across literature and commercial listings, the substance appears under several names, including bremelanotide, PT-141, and various brand designations. A CAS registry number provides a unique identifier for the compound, aiding retrieval from chemical databases. Synonym lists may also contain early development codes and descriptive chemical names. When consulting sources, researchers need to confirm that the cited names refer to the same molecular structure to avoid confusion. Naming consistency matters especially when comparing analytical data across publications.
PT-141 is a synthetic cyclic heptapeptide whose development code is bremelanotide. It belongs to the class of melanocortin receptor agonists and acts by mimicking endogenous peptide hormones. The compound originated from research on melanotan II, where investigators exploring derivatives found distinct pharmacological features. Unlike the parent compound, PT-141 showed effects on pathways related to sexual desire and function in early studies, prompting its development as a separate candidate. Its molecular design aimed to separate receptor activity from pigmentary effects.
The molecular backbone consists of seven amino acid residues joined into a ring through a disulfide bridge. This cyclic conformation is critical for receptor binding. The sequence includes an acetylated N-terminus and an amidated C-terminus, modifications that improve resistance to enzymatic breakdown. One residue is in the D-configuration, a feature that further stabilizes the peptide against protease activity. Together, the ring structure and specific stereochemistry determine selectivity among melanocortin receptor subtypes.
From a pharmacokinetic standpoint, the peptide is usually delivered by injection because oral bioavailability is very low; proteases in the digestive tract degrade it rapidly. After subcutaneous administration, plasma concentrations reach a peak within roughly one hour. Its elimination half-life is relatively short, with most reports placing it in the range of a few hours. Nasal formulations have also been examined, though absorption varies widely between individuals. Metabolism proceeds mainly through peptidase cleavage, and the resulting products are excreted by the kidneys.
PT-141 initiates cellular signaling by binding to specific subtypes within the melanocortin receptor family. These receptors belong to the G protein-coupled receptor superfamily, and activation raises intracellular cyclic adenosine monophosphate levels. This cascade ultimately influences neuronal circuits in the central nervous system that are associated with sexual desire and arousal. Research indicates the compound's action concentrates in hypothalamic regions rather than peripheral tissues, which helps explain some observed pharmacological features. The selectivity of receptor binding underlies its functional differences.
Compared with the related compound melanotan II, PT-141 shows markedly weaker activation of receptors tied to pigmentation. This difference stems from subtle structural variations that alter affinity distribution across receptor subtypes. Investigators propose that such selectivity produces a different side effect profile in specific applications. However, downstream consequences of prolonged receptor activation remain uncertain in the literature. Published studies do not fully agree on the duration of signaling pathway activity and the mechanisms of desensitization.
Identity and purity are established with orthogonal methods rather than a single test. Reverse-phase high-performance liquid chromatography with ultraviolet detection gives a purity figure by area normalization, while mass spectrometry confirms the expected molecular ion. Amino acid analysis or peptide mapping can detect sequence errors that a mass value alone would miss, and residual counterion content is sometimes measured separately. Common impurities include truncated sequences, oxidized residues, and deamidated products; reporting them individually is more informative than a single composite purity number.
Lyophilized peptide arrives as a white to off-white cake or powder and is normally held at minus twenty degrees Celsius or colder for extended periods. Short-term bench work at ambient temperature is tolerable for minutes, not hours, because the solid is hygroscopic and picks up moisture that promotes hydrolysis. Vials should stay in a desiccator or a sealed bag with desiccant, protected from light, since aromatic residues in the sequence are susceptible to photo-oxidation. Inventory records that note arrival date and storage location reduce the chance of using degraded material.
Reconstitution is usually performed with sterile water or a dilute acetic acid solution, and the choice of solvent affects both dissolution speed and final pH. Complete dissolution should be confirmed by visual inspection before any aliquot is taken, since undissolved particles can concentrate in the sampling volume. Repeated freeze-thaw cycles are the most common cause of gradual loss of purity, so dividing a stock into single-use aliquots at the first opportunity is standard practice. Working solutions kept refrigerated are generally used within days rather than weeks.
=== Juvenile breast hypertrophy === When gigantomastia occurs in pubescent females, the medical condition is known as juvenile macromastia or juvenile gigantomastia and sometimes as virginal breast hypertrophy or virginal mammary hypertrophy although the term virginal is now considered misleading and outdated. Along with the excessive breast size, other symptoms include red, itchy lesions and pain in the breasts. A diagnosis is made when an adolescent's breasts grow rapidly and achieve great weight, usually soon after their first menstrual period. Some doctors suggest that the rapid breast development occurs before the onset of menstruation. Some adolescents with juvenile breast hypertrophy experience breast growth at a steady rate for several years, after which the breasts rapidly develop exceeding normal growth. Some adolescent females experience minimal or negligible breast growth until their breasts suddenly grow very rapidly in a short period of time. This may cause considerable physical discomfort. Individuals with JBH often experience an excessive growth of their nipples as well. In severe cases of JBH, clitoromegaly occurs. At the onset of puberty, some females who have experienced little or no breast development can reportedly reach three or more cup sizes within a few days (see below). As of 1992, 70 cases of juvenile breast hypertrophy had been reported.
In the study of geochemistry, biogenic substances can be isolated from fossils and sediments through a process of scraping and crushing the target rock sample, then washing with 40% hydrofluoric acid, water, and benzene/methanol in the ratio 3:1. Following this, the rock pieces are ground and centrifuged to produce a residue. Chemical compounds are then derived through various chromatography and mass spectrometry separations. However, extraction should be accompanied by rigorous precautions to ensure there is no amino acid contaminants from fingerprints, or silicone contaminants from other analytical treatment methods.
2 October A U.S. Navy C-2A Greyhound crashed into the Gulf of Tonkin on a flight from Naval Air Station Cubi Point to the aircraft carrier USS Constellation killing all 27 on board. Hanna E. Crews a Donut Dolly died of head injuries after a vehicle accident near Bien Hoa, becoming the first of three Donut Dollies to die in the war.
== Awards and recognition == Metropolis was awarded the Diagnostic Services Company of the Year by Frost & Sullivan in 2010. In 2014, it was awarded India's Most Promising Brand by the World Consulting and Research Corporation, which was evaluated by Ernst & Young. In 2018 and 2017, MD of Metropolis, Ameera Shah was ranked 36th and 46th respectively, in "India's Most Powerful Women in Business" by Fortune India Magazine. in 2015, Shah was awarded as one of the Asia's Power Business Women by Forbes.
Randomized controlled trials have found that higher dosages of CPA (e.g., 20 mg/day or 100 mg/day) added cyclically to a birth control pill containing ethinylestradiol and 2 mg/day CPA were no more effective or only marginally more effective in the treatment of severe hirsutism in women than the birth control pill alone. Maintenance therapy with lower doses of CPA, such as 25 mg/day, has been found to be effective in preventing relapse of symptoms of hirsutism. CPA has typically been combined with ethinylestradiol, but it can alternatively be used in combination with hormone replacement therapy dosages of estradiol instead. CPA at a dosage of 50 mg/day in combination with 100 μg/day transdermal estradiol patches has been found to be effective in the treatment of hirsutism similarly to the combination of CPA with ethinylestradiol. The efficacy of the combination of an estrogen and CPA in the treatment of hirsutism in women appears to be due to marked suppression of total and free androgen levels as well as additional blockade of the androgen receptor.
Sources: en.wikipedia.org
== Side effects == Side effects of fentanyl analogs are similar to those of fentanyl itself, which include itching, nausea, and potentially serious respiratory depression, which can be life-threatening. Fentanyl analogs have killed hundreds of people throughout Europe and the former Soviet republics since the most recent resurgence in use began in Estonia in the early 2000s, and novel derivatives continue to appear. A new wave of fentanyl analogues and associated deaths began in around 2014 in the US, and have continued to grow in prevalence; especially since 2016 these drugs have been responsible for hundreds of overdose deaths every week.
== Evolutionary origins == Synovial joints have been found in the earliest jawed vertebrates (gnathostomes) 400 million years ago during the Silurian and Devonian. This finding overturns an earlier view that these joints first evolved in early tetrapods for terrestrial locomotion. Comparative studies find that synovial joints are present in all major groups of jawed vertebrates, including cartilaginous fishes (sharks, skates, and rays), bony fishes, and tetrapods. They are, however, absent in jawless vertebrates such as lampreys and hagfish. Cartilaginous fishes have true synovial joints with clear synovial cavities, articular cartilage lined by flattened chondrocytes, and express key developmental signaling molecules including growth differentiation factor-5 (Gdf5) and β-catenin, and require muscle contraction for proper joint cavitation. In contrast, cyclostomes have joints filled with tissue rather than fluid-filled cavities, with proteoglycans uniformly distributed across cartilages. Fossil evidence finds jawless osteostracans had pectoral fin connections filled with canals incompatible with fluid-filled joint cavities, while early jawed placoderms have reciprocally articulating surfaces separated by joint cavities. Synovial joints, it has been suggested, arose due to the high mechanical loads associated with predation and feeding and, as a result, allowed for the evolution of the complex skeletons of modern jawed vertebrates.
In SN 12.59 and its counterpart SA 284, there is a chain that starts by saying that for someone who "abides in seeing [the Chinese has grasping at] the flavour in enfettering dharmas (saññojaniyesu dhammesu), there comes the appearance (avakkanti) of consciousness." There then follows the standard list. Then it states that if someone abides by seeing the danger (adinavanupassino) in the dharmas (the Chinese has seeing impermanence), there is no appearance of consciousness (Chinese has mind). SN 12.65 and 67 (and SA 287 and 288) begin the chain with both consciousness and name and form conditioning each other in a cyclical relationship. It also states that "consciousness turns back, it goes no further than name and form." SN 12.67 also contains a chain with consciousness and name and form being in a reciprocal relationship. In this sutta, Sariputta states that this relationship is like two sheaves of reeds leaning on each other for support (the parallel at SA 288 has three sheaves instead).
=== Italy === The 2013 Italian general election led to a major change in the country's political landscape, as the traditional center-right and center-left parties were challenged by the new Five Star Movement, a populist party led by comedian Beppe Grillo. None of the three main alliances – the centre-right led by Silvio Berlusconi, the centre-left led by Pier Luigi Bersani and the Five Star Movement – won an outright majority in Parliament. After a failed attempt to form a government by Bersani, then-secretary of the Democratic Party (PD), and Giorgio Napolitano's re-election as President, Enrico Letta, Bersani's deputy, received the task of forming a grand coalition government. The Letta Cabinet consisted of the PD, Berlusconi's The People of Freedom (PdL), Civic Choice (SC), the Union of the Centre (UdC) and others. Following the election of Matteo Renzi as Secretary of the PD in December 2013, there were persistent tensions culminating in Letta's resignation as prime minister in February 2014. Subsequently, Renzi formed a government based on the same coalition (including the NCD), but in a new fashion. The new prime minister had a strong mandate from his party and was reinforced by the PD's strong showing in the 2014 European Parliament election and the election of Sergio Mattarella, a fellow Democrat, as president in 2015.
=== Assumptions === The mathematics of radioactive decay depend on a key assumption that a nucleus of a radionuclide has no "memory" or way of translating its history into its present behavior. A nucleus does not "age" with the passage of time. Thus, the probability of its breaking down does not increase with time but stays constant, no matter how long the nucleus has existed. This constant probability may differ greatly between one type of nucleus and another, leading to the many different observed decay rates. However, whatever the probability is, it does not change over time. This is in marked contrast to complex objects that do show aging, such as automobiles and humans. These aging systems do have a chance of breakdown per unit of time that increases from the moment they begin their existence. Aggregate processes, like the radioactive decay of a lump of atoms, for which the single-event probability of realization is very small but in which the number of time-slices is so large that there is nevertheless a reasonable rate of events, are modelled by the Poisson distribution, which is discrete. Radioactive decay and nuclear particle reactions are two examples of such aggregate processes. The mathematics of Poisson processes reduce to the law of exponential decay, which describes the statistical behaviour of a large number of nuclei, rather than one individual nucleus.
Sources: en.wikipedia.org
=== Production of ethanolamines === In the industry, ethanolamines (mono-, di-, and triethanolamines) are produced by reacting ammonia and ethylene oxide in anhydrous medium at a temperature of 40–70 °C (100–160 °F) and pressure of 1.5–3.5 MPa (220–510 psi) MPa:
Bernice Rubens, novelist Miri Rubin (born 1956), historian and Professor of Medieval and Early Modern History at Queen Mary University of London and author of over ten scholarly academic texts and monographs on religion and the Middle Ages; educated at the Hebrew University of Jerusalem and the University of Cambridge; Rubin writes about social and religious history of Europe between 1100 and 1500, concentrating on interactions between public rituals, power, and community life. Oliver Sacks (9 July 1933 – 30 August 2015), neurologist, naturalist, historian of science, and writer of over twenty books, screenplays and scholarly articles, amongst them, 1973 book Awakenings, which was adapted into an Academy Award-nominated feature film in 1990, starring Robin Williams and Robert De Niro. Nina Salaman, (n15 July 1877 – 22 February 1925) was a British Jewish poet, translator, and social activist. Aside from her original poetry, she is best known for her English translations of medieval Hebrew verse—especially of the poems of Judah Halevi—which she began publishing at the age of 16. Maurice Samuel (1895 – 1972), author of the book You Gentiles, which is controversial for its portrayal of Jews and Gentiles as fundamentally distinct and incompatible civilisations. Samuel's depiction of enduring cultural and psychological differences between the two groups has been described by some critics as implying a form of Jewish supremacy and civilisational separatism.
=== Surgery === Aggressive wound debridement should be performed as soon as the diagnosis is made. The affected area may need to be debrided several times, usually once every 12–36 hours. Large sections of tissue and muscle may need to be removed to prevent the infection from spreading. Amputation may be needed if the infection is too severe. En bloc debridement (EBd) is most commonly employed in treating NSTIs. This involves cutting away the skin overlying all diseased areas at the cost of increased scar formation and potential decreased quality of life post-operatively. More recently, skin-sparing debridement (SSd) has gained traction, as it resects the underlying tissue and sources of infection while preserving skin that is not overtly necrotic. However, more studies are needed to examine whether SSd actually accelerates the healing process after surgery.
SASP induces an unfolded protein response in the endoplasmic reticulum because of an accumulation of unfolded proteins, resulting in proteotoxic impairment of cell function. SASP cytokines can result in an inflamed stem cell niche, leading to stem cell exhaustion and impaired stem cell function. The pro-inflammatory environment generated by SASP factors accelerates the breakdown of extracellular matrix thereby worsening intervertebral disc degeneration (IVDD). AMPK/p53 senescence produces a completely different SASP than IL-1 (p16INK4a) senescence, which is primarily responsible for IVDD. In IVDD, SASP is secreted by nucleus pulposus and annulus fibrosus cells, resulting in extracellular matrix degradation and extracellular inflammation. Senomorphics, but not senolytics have been found to alleviate symptoms without eliminating senescent cells. SASP can either promote or inhibit cancer, depending on the SASP composition, notably including p53 status. Despite the fact that cellular senescence likely evolved as a means of protecting against cancer early in life, SASP promotes the development of late-life cancers. Cancer invasiveness is promoted primarily through the actions of the SASP factors metalloproteinase, chemokine, interleukin 6 (IL-6), and interleukin 8 (IL-8). In fact, SASP from senescent cells is associated with many aging-associated diseases, including not only cancer, but atherosclerosis and osteoarthritis. For this reason, senolytic therapy has been proposed as a generalized treatment for these and many other diseases.
== Related conditions == Disorders that are clinically similar are konzo and Lytico-bodig disease. Konzo means "tied legs" in the Yaka language, and is common in some African people in central and eastern parts of the continent who are consuming diets poor in protein. The possible molecule causing this problem is thiocyanate, which stimulates AMPA receptors.
Sources: en.wikipedia.org
PT-141 was the development code used for bremelanotide during its preclinical and early clinical programme. The peptide is now generally referred to by its international nonproprietary name.
The two compounds share the same cyclic core and are both non-selective melanocortin agonists. They differ chiefly at the C-terminus, where bremelanotide carries a free carboxylic acid and melanotan II a terminal amide.
Receptor binding profiles are well characterised in vitro, but the downstream pathway linking MC4R activation to behavioural effects is not fully mapped. Several intermediate neural circuits have been proposed without definitive confirmation.
The peptide is polar and charged, and reversed-phase chromatography with acidic mobile phases resolves it well from related substances. Ultraviolet detection near 214 nm gives adequate sensitivity without derivatisation.