«Neuropeptide receptors have undergone the same process of discovery and characterization that receptors for other neurotransmitters have enjoyed. The process begins with the pharmacological characterization of the receptor's physicochemical binding...» Document abstract
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SummaryNeuropeptide receptors have undergone the same process of discovery and characterization that receptors for other neurotransmitters have enjoyed. The process begins with the pharmacological characterization of the receptor's physicochemical binding properties by assessing the affinity of various metabolically derived and synthetic peptide fragments, and the native molecule, for the receptor binding site found in membrane preparations. Peptide receptor locations are mapped with radioactive or fluorescent tags that are inserted into peptide molecules, which often contain substituted amino acids at the most vulnerable peptidase cleavage sites. Previously, once the peptide receptor was characterized pharmacologically, it was usually purified from some relatively enriched biological tissue source or brain region by affinity column chromatography. After it had been purified, binding parameters and activity were recharacterized for the reconstituted purified receptor protein and structural information obtained by X-ray crystallography. This process was closely followed in the purification of the neurotensin-neuromedin N receptor.
Table of Contents- The neurotensin receptor was first characterized by photoaffinity labeling and cross-linking of radioiodinated ligands, which resulted in two labeled subunits of about 49 Kd and 51 Kd from rat brain synaptosomes.
- The much more powerful tools of molecular biology have been utilized more recently.
- Neuropeptide receptors have been associated with just about every type of second messenger signal transduction system that has been identified.
- Peptides are degraded to smaller fragments, and eventually to single amino acids, by specific enzymes termed peptidases.
- The metabolism of TRH has been investigated fairly completely, principally because of the limited number of fragments that can be generated from a tripeptide.
- The peptides involved in neuroendocrine regulation have cell bodies residing in the hypothalamus that receive feedback from all levels of the endocrine axes.
- Regional differences in CRF receptor regulation by corticosterone have also been reported, which have been shown to partly result from differential glycosylation of the CRF receptor.
- Alzheimer's Disease Dementia of the Alzheimer's Type represents up to two thirds of the demented population encountered in clinical practice, and over half of the nursing home beds in the United States are currently occupied by such patients.
- The CRF-containing interneurons of the cortex are also consistently depleted in Alzheimer's disease. As with SRIF, subcortical areas containing CRF neurons may be spared, but unlike SRIF, CRF receptors are increased in number (up-regulated) with no change in affinity.
- Corticotropin-Releasing Factor After a search spanning nearly three decades, CRF was isolated and characterized in 1981 as a 41-amino acid peptide.
- A series of studies have demonstrated significant elevations of CRF concentrations in the CSF of drug-free patients with major depression or following suicide.
- Like many other neuropeptide transmitters, central administration of SRIF produces a variety of behavioral and physiological effects.
- Decreased neurotensin concentrations in CSF have been reported in several populations of patients with schizophrenia when compared to controls or patients with other psychiatric disorders.
«The past several decades have witnessed a veritable explosion of knowledge about the central nervous system (CNS), and in no area has this been as impressive as in peptide neurobiology. Numerous peptide neurotransmitter candidates have been...» Document abstract
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SummaryThe past several decades have witnessed a veritable explosion of knowledge about the central nervous system (CNS), and in no area has this been as impressive as in peptide neurobiology. Numerous peptide neurotransmitter candidates have been identified and characterized, their CNS distributions mapped, and their genes cloned. The tenet “one neuron-one transmitter” erroneously attributed to Dale has been convincingly refuted with numerous demonstrations of neurons containing multiple peptides or combinations of peptide and nonpeptide neurotransmitters. Additionally, since the early 1980s there has been an embarrassment of riches in the form of knowledge about neurotransmitter receptor diversity, diversity of receptor-effector coupling, and neurotransmitter transporters. These discoveries have not yet been fully integrated into what is known about normal or aberrant CNS function, although dysfunction at virtually any level could conceivably lead to neuropsychiatric deficits.
Table of Contents- By definition, a neuropeptide is a chain of two or more amino acids linked by peptide bonds, and differs from other proteins only in the length of the amino acid chain.
- Many of the known behavioral effects of neuropeptides are observed only after their direct injection into the CNS because most peptides do not penetrate the blood-brain barrier in amounts sufficient to produce effects before being inactivated by serum and tissue enzymes that degrade them.
- The tertiary structure for recognition is also used by the immune system for the production of specific antibodies, as well as by biological receptors.
- Neuropeptides are found throughout the CNS, as well as in various peripheral organs, such as the gastrointestinal tract, pancreas, and adrenal glands.
- In the cortex of rats SRIF is found in some of the large stellate-shaped neurons and in abundance among the fusiform-shaped, nonpyramidal neurons of layers II to V, and particularly in layer V of the sensory cortex.
- Through the use of retrograde tracing methods and dual staining techniques, several pathways for certain peptides have now been delineated.
- Some of the noradrenergic locus ceruleus neurons, in turn, project to the hypothalamic paraventricular nucleus where their input increases CRF synthesis and release.
- The neurotensin-neuromedin N gene was originally cloned from canine ileal mucosa, and complementary deoxyribonucleic acid (cDNA) probes constructed against this form were used to clone the rat gene.
«Common: Eastern White Pine
Scientific: Pinus strobus
Derivation of name: Latin name for pine from Greek "pitus" / incense-bearing or a gum-yielding tree (pitchy) or [sic] Greek "strobus" (cone) [1]
Also known as: white pine, northern white...» Document abstract
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SummaryCommon: Eastern White Pine
Scientific: Pinus strobus
Derivation of name: Latin name for pine from Greek "pitus" / incense-bearing or a gum-yielding tree (pitchy) or [sic] Greek "strobus" (cone) [1]
Also known as: white pine, northern white pine, northern pine, ship-mast pine, soft pine, pin blanc, and Weymouth pine [2]
Table of Contents- Family Pinacea
- More detail of Subgenus Strobus
- Close relatives
- How to identify White Pine
- Place/Habitat
- Conservation Status
- Associated Animals
- Mycorrhizae
- Folk-Medicinal Properties
- Economic Importance
- Evolutionary History
- Biggest white pine on record
«Mites make up the largest group in the class Arachnida. Most are small arthropods, and many are barely visible. Mites have two body regions, a small cephalothorax and a larger, unsegmented abdomen. The cephalothorax and abdomen are broadly joined,...» Document abstract
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SummaryMites make up the largest group in the class Arachnida. Most are small arthropods, and many are barely visible. Mites have two body regions, a small cephalothorax and a larger, unsegmented abdomen. The cephalothorax and abdomen are broadly joined, giving most mites an oblong to globular appearance. Newly hatched larvae have three pairs of legs, and larvae acquire a fourth pair after the first molt. Mites are highly diverse. Some are parasitic, with both vertebrates and invertebrates serving as hosts; some are scavengers, some feed on plants, and many are free living and predaceous. Although most species are oviparous, some are ovoviviparous, and a few are viviparous. They occur worldwide and frequently in great numbers. Mites have been associated with disease transmission, allergies, and dermatologic manifestations. Of the approximately 35,000 species, about 50 are known to cause human skin lesions, and most of the cutaneous lesions are caused by mites feeding or burrowing in the skin. Since children and adults of all races are susceptible to these ubiquitous arthropods, they are responsible for considerable morbidity. The mites of medical importance are some of the sarcoptic mites, some of the trombiculid mites, a number of other acariform mites that infest organic substances such as grains and produce, and the gamasid mites that are vectors of several rickettsial and viral diseases. Dermatologic manifestations of mite bites may be seasonal, as with the trombiculids; individual cases or outbreaks of varying magnitude may be related to contact with mites that infest animals or various foods. Epidemics may occur, as is presently the case with scabies.
Table of Contents- The human scabies mite is Sarcoptes scabiei var. hominis, an obligate human parasite that completes its entire life cycle in and on the epidermis of humans.
- Severe nocturnal pruritus is the hall-mark of scabies. Itching also may be provoked by any sudden warming of the body and generally does not involve the face.
- Diagnosis is based on the combination of nocturnal pruritus and cutaneous findings and is confirmed by microscopic examination of burrow contents.
- A number of topical treatments are available. In most cases a single overnight application of 5% permethrin cream (Elimite) is curative.
- Control of scabies outbreaks in nursing homes and similar epidemic situations can be almost insurmountable because of the number of patients and contacts that must be treated simultaneously.
- Humans develop itchy papules, often with some urtication, and scratching may give rise to varying degrees of secondary infection.
- Treatment is symptomatic and consists of topical antipruritic agents, corticosteroids, systemic antihistamines, and occasionally, pulse therapy with systemic corticosteroids.
«Lice are small wingless insects that are ectoparasites of mammals. They are mostly host specific, and two species are human parasites: Pthirus pubis (pubic louse) and Pediculus humanus, with two varieties, P. h. capitis (head louse) and P. h....» Document abstract
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SummaryLice are small wingless insects that are ectoparasites of mammals. They are mostly host specific, and two species are human parasites: Pthirus pubis (pubic louse) and Pediculus humanus, with two varieties, P. h. capitis (head louse) and P. h. corporis (body louse). They are obligatory parasites, subsisting on blood from the host, and have mouthparts modified for piercing and sucking. The mouthparts are drawn into the head of the louse when not in use.
The adult head louse is about 2 to 4 mm long with an elongated body that is flattened dorsoventrally. The head is only slightly narrower than the thorax. The three pairs of legs are about equal in length and possess delicate hooks at the distal extremities. The entire life is spent on the host's body. The eggs (nits) are deposited on hair shafts, generally one nit to a shaft. The nits hatch in about 1 week, and the freshly hatched larvae, which must feed within 24 hours of hatching or die, mature in about 15 to 16 days. The adult female lives for approximately 1 month and may deposit more than 100 eggs during her reproductive life. Body lice are slightly larger than head lice but are similar in appearance with a similar life cycle, although the nits are deposited on fibers of clothing. Head lice and body lice interbreed.
The adult head louse is about 2 to 4 mm long with an elongated body that is flattened dorsoventrally. The head is only slightly narrower than the thorax. The three pairs of legs are about equal in length and possess delicate hooks at the distal extremities. The entire life is spent on the host's body. The eggs (nits) are deposited on hair shafts, generally one nit to a shaft. The nits hatch in about 1 week, and the freshly hatched larvae, which must feed within 24 hours of hatching or die, mature in about 15 to 16 days. The adult female lives for approximately 1 month and may deposit more than 100 eggs during her reproductive life. Body lice are slightly larger than head lice but are similar in appearance with a similar life cycle, although the nits are deposited on fibers of clothing. Head lice and body lice interbreed.
Table of Contents- The adult head louse is about 2 to 4 mm long with an elongated body that is flattened dorsoventrally
- Lice are found wherever people are found. Able to exist only briefly away from the human body, lice are spread by close personal contact and by sharing of clothing and bedding.
- The head louse localizes on the scalp and rarely on other hairy areas of the body.
- The body louse lives chiefly in the seams of clothing and is rarely seen on the skin.
- Treatment of all types of lice strives to eradicate lice and nits and prevent reinfestation.
- Body lice may be treated with the same medications, but parasites and nits are not generally found on the skin.
«By far the most important venomous insects are members of the order Hymenoptera, including bees, wasps, and ants. They vary in size from minute to large (up to 60 mm in body length). The abdomen and thorax are connected by a slender pedicle that may...» Document abstract
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SummaryBy far the most important venomous insects are members of the order Hymenoptera, including bees, wasps, and ants. They vary in size from minute to large (up to 60 mm in body length). The abdomen and thorax are connected by a slender pedicle that may be quite long in certain wasps and ants. Bees and most wasps are winged as adults; ants are wingless, except for sexually mature adults during part of the life cycle. Mouthparts are adapted for chewing but in some species are modified for sucking. The life cycle includes egg, larva, and pupa stages before emergence of adults. Immature stages may be protected and provided with food by the adult. Both animal and plant foods are used. Many species are parasitic on other arthropods. All ants and many species of bees and wasps are social insects. Colonies range in size from a few dozen individuals to many thousands. In cold climates, most individuals die in autumn, leaving the fertilized females to winter over and found new colonies in the spring.
Table of Contents- The honeybee (Apis mellifera) is one of the few domesticated insects and is maintained in hives in many countries.
- The first escapes from hives occurred in the state of São Paulo in 1957, and the "Brazilian killer bees," or "Africanized bees," have spread widely.
- Bumblebees (Bombus and related genera) are a largely holarctic group often found in quite cold environments.
- Solitary wasps are predators, feeding largely on other insects and spiders.
- Ants are social insects, worldwide in distribution over a wide range of habitats. Many ants sting, and others have repugnant secretions.
- Multiple stings often result from disturbance of a nest, as the first insects encountered release alarm pheromones that incite aggressive behavior in other members of the colony.
- Intense pain after stings by hornets and other social wasps is largely caused by serotonin and acetylcholine, which constitute 1% to 5% of dry venom weight.
- Ant venoms show great variation. Those of more primitive ants (subfamilies Ponerinae, Myrmicinae, and Dorylinae) resemble venoms of social wasps, containing kininlike peptides, enzymes, and unidentified proteins.
«Insects of the order Lepidoptera typically cause human envenomation, but effects generally are less serious than with hymenopterans. Injury usually follows contact with caterpillars, occurring less frequently with the cocoon or adult stage. The...» Document abstract
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SummaryInsects of the order Lepidoptera typically cause human envenomation, but effects generally are less serious than with hymenopterans. Injury usually follows contact with caterpillars, occurring less frequently with the cocoon or adult stage. The larval lepidopteran (caterpillar) is usually free living, is moderately active, and feeds on plants, although a few are parasites of insect nests or eat food of animal origin. The pupal stage may be free or encased in a silk cocoon. Wintering over in cold climates is usually in the pupal stage. Adults (butterflies and moths) have wings with microscopic chitinous scales. They primarily feed on nectar and other plant juices, but some eat semiliquid mammalian feces and urine. The adult provides no care or protection of immature stages. No social organization exists, although larvae and adults of some species assemble in large aggregations.
Table of Contents- Venomous species occur in about 16 families of Lepidoptera, with no general rules for recognition.
- This hairy, flat, and ovoid caterpillar reaches a length of 30 to 35 mm and feeds on shade trees, including elm, oak, and sycamore.
- Caterpillar envenomation usually occurs when living insects are touched as they cling to vegetation or drop onto bare skin.
- The second syndrome is associated with caterpillars with a less highly developed venom apparatus (e.g., Lymantria, Euproctis, Thaumetopoea).
- Trees on which caterpillars feed may be sprayed with appropriate insecticides to control species such as the puss caterpillar.
«Insects of the order Diptera are characterized by one pair of wings. The second pair is usually modified to form a pair of drumsticklike structures known as halteres. A typical life cycle consists of eggs, limbless larvae, pupae, and winged adults,...» Document abstract
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SummaryInsects of the order Diptera are characterized by one pair of wings. The second pair is usually modified to form a pair of drumsticklike structures known as halteres. A typical life cycle consists of eggs, limbless larvae, pupae, and winged adults, but numerous variations exist. Mouthparts are of the sucking type. Females of many species, although free living, take blood or other tissue fluids from vertebrates, injecting salivary secretions that are not intrinsically toxic but are potent sensitizing agents for most humans. Larvae of some Diptera are human parasites. Other adult Diptera feed indiscriminately on feces and human foodstuffs. These habits make them by far the most important arthropod vectors of human disease.
Table of Contents- Most of these insects are cosmopolitan in distribution, except tsetse flies, which are restricted to Africa, and tropical and subtropical sand flies.
- Carbon dioxide, body heat, and sweat gland secretions, especially apocrine, are attractants for mosquitoes; certain skin lipids are repellent.
- Treatment of mosquito bites consists of local application of antipruritic lotions or creams.
- Bites are immediately painful and result in raised, red, and pruritic lesions that persist from a few hours to a week or more.
- Blackfly bites are more common on the upper half of the body.
- Horseflies and deerflies are medium to large (10 to 25 mm body length) stocky flies whose large eyes often are brightly colored.
- The term myiasis for parasitism by fly larvae was introduced into the medical literature in 1840, although the condition has been observed since antiquity.
- Another form of migratory myiasis is caused by larvae of Gastrophilus, which normally are gastrointestinal or nasal parasites of horses.
«Scorpion envenomation can result in distinct clinical syndromes. Most scorpion species' stings cause only local pain and inflammation that respond well to minimal supportive therapy and wound care. These scorpions pose no significant management...» Document abstract
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SummaryScorpion envenomation can result in distinct clinical syndromes. Most scorpion species' stings cause only local pain and inflammation that respond well to minimal supportive therapy and wound care. These scorpions pose no significant management issues and, with few exceptions, are not discussed here in further detail. The truly dangerous scorpions of the world, typified by Tityus species in the Caribbean region and in South America, Androctonus species and Buthus occitanus in North Africa, Leiurus quinquestriatus in the Near East, and Mesobuthus tamulus in India, cause an "autonomic storm" with prominent cardiopulmonary effects. A third clinical syndrome occurs from stings of Centruroides species in the southwestern United States and Mexico and from Parabuthus species in southern Africa. These produce prominent neurologic effects associated with excess cholinergic tone. Children are typically more severely affected than adults and often require prompt medical management to avoid morbidity and mortality. The ideal treatment of scorpion envenomation remains controversial, primarily because controlled clinical trials are lacking. Although anecdotal experience and comparisons of historic cohorts demonstrate a benefit from aggressive symptomatic and supportive care, the proper use of antivenins has not been fully resolved.
Table of Contents- INTRODUCTION
- TAXONOMY AND ANATOMY
- VENOM
- PREVENTION
«North America is unique in that it is home not only to venomous snakes, but also to the world's only known venomous lizards. Fortunately, bites by venomous reptiles in North America are relatively uncommon, although precise statistics are not...» Document abstract
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SummaryNorth America is unique in that it is home not only to venomous snakes, but also to the world's only known venomous lizards. Fortunately, bites by venomous reptiles in North America are relatively uncommon, although precise statistics are not available. The only systematic attempt to evaluate the incidence of venomous snakebite in the United States was done in the late 1960s by Dr. Henry Parrish. He estimated that there were approximately 7000 bites by venomous snakes, of which approximately 15 ended in death. The incidence of venomous snakebite may have changed significantly since Parrish's study, but given that snakebite is not a reportable "disease," no mechanism exists for obtaining reliable data. The incidence of snakebite in Canada is lower than that in the United States because fewer snakes species are found farther north up the continent. In Mexico, however, snakebite takes on increasing medical importance because this country has more venomous snake species than any other nation in the New World. As many as 150 deaths may be caused by snakebite in Mexico each year.
Table of Contents- Establishing credible estimates of the incidence of venomous lizard bites is even more difficult than for snakes
- Snake venoms are highly complex mixtures of enzymes, low-molecular-weight polypeptides, glycoproteins, minerals, and other unidentified substances.
- Rattlesnakes are the most widespread of pit vipers, found throughout most of North America.
- The only two known species of venomous lizards in the world are found in North America and belong to the genus Heloderma.
- With the growing popularity of herpetoculture in the United States, bites by captive venomous reptiles have increased.
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