Excretion of non-conjugated androstenedione and testosterone in human urine.

A method for the measurement of unconjugated testosterone and androstenedione in human urine is described. The method uses chromatographic separation followed by radioimmunoassay and has been examined for reliability. The mean 24-hour excretion of androstenedione by adult male subjects was 2.5 mug and of testosterone was 0.8 mug. For women, the mean excretion was 2.9 mug of androstenedione and 0.25 mug of testosterone. In pregnancy, androstenedione excretion was occasionally elevated above the normal range, but testosterone excretion was quite commonly increased. Some hirsute subjects exhibited an increase in androstenedione excretion, which was decreased by administration of dexamethasone. The results suggest that the amount of unconjugated testosterone in urine is not a direct reflection of the plasma free testosterone, but urinary androstenedione may be a useful reflection of plasma androstenedione levels.     

Acrylonitrile inhalation in rats: II. Excretion of thioethers and thiocyanate in urine

In male Wistar rats, the inhalation exposure to acrylonitrile (AN), 271 mg X m-3, 8 hours a day, 5 days a week, did not affect protein sulfhydryl concentration in liver and blood and decreased glutathione concentration in the liver, but not in the brain at the end of the fifth exposure. The urinary excretion of the main AN metabolites, thioethers (AN-mercapturic acids) and thiocyanate was proportional to the inhaled AN concentration (57, 125, 271 mg X m-3, respectively) in a single exposure for 12 hours, and their mutual ratio was greatly different from that after injection of AN. The results revealed that the urinary excretion of thioethers is a very sensitive and dose-related indicator of exposure to AN and extrapolation of the results indicates that the exposure to AN concentration below 10 mg X m-3 could thus be demonstrated.     

Excretion of corticosteroid metabolites in urine and faeces of rats.

Stress enhances the production of corticosteroids by the adrenal cortex, resulting in the increased excretion of their metabolites in urine and faeces. An intraperitoneal injection of radioactive corticosterone was applied to adult, male Sprague-Dawley rats to monitor the route and delay of excreted metabolites in urine and faeces. Peak concentrations appeared in urine after 3.2 +/- 1.9 h and in faeces after 16.7 +/- 4.3 h. Altogether about 20% of the recovered metabolites were found in urine and about 80% in faeces. Using high-performance liquid chromatography (HPLC), several peaks of radioactive metabolites were found. Some metabolites were detected by enzyme immunoassay (EIA) using two different antibodies (corticosterone, 11beta-OH-aetiocholanolone). There was a marked diurnal variation with low levels of faecal corticosterone metabolites in the evening and higher values in the morning. This diurnal variation was influenced neither by the intraperitoneal injection of isotonic saline nor by ACTH. However, the administration of dexamethasone eliminated the morning peak for 2 days.     

Oxygen levels in the gut lumens of herbivorous insects

Oxygen levels were measured in the foregut and midgut lumens of ten species of caterpillars and three species of grasshoppers. In most species, the foregut was nearly anoxic, with oxygen levels ranging from 0 to 2.5 mm Hg. However, two caterpillar species with large foreguts (Malacosoma disstria and Lymantria dispar) had elevated oxygen levels (27.9 and 32.1 mm Hg) in this region when they were fed artificial diet. In all of the species surveyed, the anterior and posterior midgut were nearly anoxic, with oxygen levels ranging from 0 to 7.3 mm Hg. Oxygen levels in the midgut lumen of Helicoverpa zea did not differ when caterpillars were fed artificial diet or tomato foliage, suggesting that the insect is capable of reducing the level of ingested oxygen in its gut. An examination of the radial microgradient of oxygen in the gut lumen demonstrated that the midgut epithelium is not a sink for ingested oxygen. However, the midgut contents of larvae fed artificial diet were capable of depleting oxygen. This capacity was reduced by boiling, suggesting that the nearly anoxic state of the midgut lumen in some insects is maintained by endogenous chemical processes. We conclude that low oxygen levels in the gut lumens of most herbivorous insects may greatly reduce the rates of oxidation of ingested plant compounds by oxygen-dependent reactions.     

Measurements on the kidneys and vasa recta of various mammals in relation to urine concentrating capacity.

Maximum urine-concentrating capacity (UCC) differs widely among mammals of different species, being very high in some desert species (e.g. kangaroo rats) and very low in freshwater acquatic species (e.g. beaver). In this study, kidneys of 21 species of mammals from widely different habitats were studied in histological sections to determine whether differences in UCC can be attributed to differences in kidney structure. Parameters studied included the ratio of medullary to cortical thickness, the proportional subdivision of the medulla into inner and outer zones, and the dimensions of the vasa recta expressed in terms of the total area and the number of lumens within the vascular bundles. Determinations were made at a level where the size of individual vasa recta bundles has reached a constant maximum size, i.e. in the distal half of the outer zone. A positive correlation was found between the UCC and the ratio of medullary length to cortical thickness. No clear correlation existed between the proportion of the medullary length comprised of outer or inner zones and the UCC, although a trend to higher UCC in animals with relatively longer inner zones was apparent. Thus, it appears that the relative length of the entire medullary region is a major factor determining UCC, but the length of individual medullary zones is of lesser importance. A correlation was also found between the density of vasa recta per cubic millimeter of medullary tissue (the number of lumens regardless of identify in bundles, based on the number counted at the level sampled) and the UCC of the species. Data reported here support the view that UCC can be correlated with two parameters of kidney structure - the length of medulla relative to that of cortex and the density of vasa recta within the outer zone. It is proposed that the anatomical characteristics of the vascular supply to the medulla - that is, the vasa recta - are equally as important for the concentration of urine as is the primary mechanism determined by the characteristics of the loop of Henle and collecting ducts.     

Muscular connections between the gut and thoracic exoskeleton in some orthopteroid insects

Muscle and connective tissue strands linking the prothoracic cuticle to the posterior foregut and anterior midgut are described for 17 species of orthopteroid insects: Dinocras cephalotes (Plecoptera); Forficula aurkularia (Dermaptera); Acheta domesticus, Gryllus bimaculatus, Brachytrupes sp. and Phaeophyllacris spectrum (Gryllidae); Schizodactylus monstrosus (Schizodactylidae); Hemideina crassidens (Stenopelmatidae); Ephippiger ephippiger, Tettigonia viridissima, Conocephalus dorsalis and Pholidoptera griseoaptera (Tetligoniidae); Schislocerca gregaria, Omocestus viridulus and Chorthippus brunneus (Acrididae), and Carausms morosus (Phasmida). Of the 18 species examined, only the Gryllotalpa sp. (Gryllotalpidae) lacked extrinsic strands to the post-cephalic gut. The arrangement of the strands in the various species is compared, and the possible evolution and function of the strands are briefly discussed.     

A mathematical model of the urine concentrating mechanism in the rat renal medulla. I. Formulation and base-case results

A new, region-based mathematical model of the urine concentrating mechanism of the rat renal medulla was used to investigate the significance of transport and structural properties revealed in anatomic studies. The model simulates preferential interactions among tubules and vessels by representing concentric regions that are centered on a vascular bundle in the outer medulla (OM) and on a collecting duct cluster in the inner medulla (IM). Particularly noteworthy features of this model include highly urea-permeable and water-impermeable segments of the long descending limbs and highly urea-permeable ascending thin limbs. Indeed, this is the first detailed mathematical model of the rat urine concentrating mechanism that represents high long-loop urea permeabilities and that produces a substantial axial osmolality gradient in the IM. That axial osmolality gradient is attributable to the increasing urea concentration gradient. The model equations, which are based on conservation of solutes and water and on standard expressions for transmural transport, were solved to steady state. Model simulations predict that the interstitial NaCl and urea concentrations in adjoining regions differ substantially in the OM but not in the IM. In the OM, active NaCl transport from thick ascending limbs, at rates inferred from the physiological literature, resulted in a concentrating effect such that the intratubular fluid osmolality of the collecting duct increases ~2.5 times along the OM. As a result of the separation of urea from NaCl and the subsequent mixing of that urea and NaCl in the interstitium and vasculature of the IM, collecting duct fluid osmolality further increases by a factor of ~1.55 along the IM.     

Activity of gut invertase in phytophagous, saprophagous and carnivorous insects

The effect of hydrogen-ion concentration, temperature, substrate concentration, enzyme concentration and incubation period on invertase activity of Dactylosternum hydrophilioides, Catharsius molossus and Pheropsophus occipitalis has been studied. The optimum invertase activity was observed at pH 6.5, 6.8 and 6.0 and at temperatures 35, 38 and 37 degrees C in D. hydrophiliodes, C. molossus and P. occipitalis, respectively. With the increase in substrate (sucrose) concentration, an increase in invertase activity was recorded. For invertase activity estimation, 4% sucrose concentration was found suitable in these insects where an increase in enzyme concentration increases the invertase activity. The invertase activity also increases with lengthening of the incubation period but after some time it remains constant in the phytophagous, saprophagous and carnivorous insects. The activity of invertase in phytophagous, saprophagous and carnivorous insects shows their independent nature as regards the pH and temperature.     

Cold survival in freeze-intolerant insects: the structure and function of beta-helical antifreeze proteins.

Antifreeze proteins (AFPs) designate a class of proteins that are able to bind to and inhibit the growth of macromolecular ice. These proteins have been characterized from a variety of organisms. Recently, the structures of AFPs from the spruce budworm (Choristoneura fumiferana) and the yellow mealworm (Tenebrio molitor) have been determined by NMR and X-ray crystallography. Despite nonhomologous sequences, both proteins were shown to consist of beta-helices. We review the structures and dynamics data of these two insect AFPs to bring insight into the structure-function relationship and explore their beta-helical architecture. For the spruce budworm protein, the fold is a left-handed beta-helix with 15 residues per coil. The Tenebrio molitor protein consists of a right-handed beta-helix with 12 residues per coil. Mutagenesis and structural studies show that the insect AFPs present a highly rigid array of threonine residues and bound water molecules that can effectively mimic the ice lattice. Comparisons of the newly determined ryegrass and carrot AFP sequences have led to models suggesting that they might also consist of beta-helices, and indicate that the beta-helix might be used as an AFP structural motif in nonfish organisms.     

Role of structural organization in the urine concentrating mechanism of an avian kidney

The organization of tubules and blood vessels in the quail medullary cone is highly structured. This structural organization may result in preferential interactions among tubules and vessels, interactions that may enhance urine concentrating capability. In this study, we formulate a model framework for the urine concentrating mechanism of the quail kidney. The model simulates preferential interactions among renal tubules by representing two concentric cores and by specifying the fractions of tubules assigned to each of the concentric cores. The model equations are based on standard expressions for transmural transport and on solute and water conservation. Model results suggest that the preferential interactions among tubules enhance the urine concentration capacity of short medullary cones by reducing the diluting effect of the descending limbs on the region of the interstitium where the collecting ducts are located; however, the effects on longer cones are unclear.     

Comparative bacterial survey in the gut of lepidopteran insects with different bionetwork

Insect gut is an untapped reservoir persist numerous unidentified gene responsible for the digestion of complex food material into a simpler nutrients, this activity of gut was enhanced by the microbial interaction. Insect gut-microbe interaction encodes beneficial activity to its host in several aspects, to illuminate the tactic of the interaction this study was framed and worked out in two insect species such as Spodoptera litura and Bombyx mori. The present study surveyed the comparative diversity of microbial population in the gut of a field pest Spodoptera litura and domesticated insect silkworm Bombyx mori at their active feeding larval stage. Both culture dependent and culture independent approaches exposed the dominance of Enterobacteriacae family and with majority of proteobacteria and firmicutes residing in the gut of both Spodoptera litura and Bombyx mori. Especially, the Enterococcus mundtii is a predominant affiliate in both processes of both insects.     

昆虫温度感受器的结构和功能

昆虫中拥有各种不同类型的温度感受器,有的种类还能感知红外辐射。介绍了不同类群中温度感受器,包括红外感受器的类型和功能,描述了各种感受器结构,特别是电子显微镜下超微结构的特点。     

Melanin concentrating hormone. III. Melanin concentrating hormone (MCH): the message sequence

Melanin concentrating hormone (MCH) is a heptadecapeptide synthesized by the hypothalamus and secreted by the neurohypophysis of the teleost pituitary gland. MCH stimulates melanosome aggregation within teleost melanocytes but also exhibits MSH-like (melanosome dispersing) activity on tetrapod (frog and lizard) melanocytes. We have synthesized a number of MCH analogues to determine the essential features of the primary structure necessary to stimulate either melanosome aggregation or dispersion in fish or tetrapod melanocytes, respectively. An analysis of the potencies and actions of these analogues on vertebrate melanocytes is provided and demonstrates that the two activities have different structural requirements.