The impact of the implementation of physician assistants in inpatient care: A multicenter matched-controlled study.

Background: Medical care for admitted patients in hospitals is increasingly reallocated to physician assistants (PAs). There is limited evidence about the consequences for the quality and safety of care. This study aimed to determine the effects of substitution of inpatient care from medical doctors (MDs) to PAs on patients' length of stay (LOS), quality and safety of care, and patient experiences with the provided care.

Evolutionary development of three gonadotropin-releasing hormone (GnRH) systems in vertebrates.

Gonadotropin-releasing hormone (GnRH) is the neuropeptide that links the brain to the reproductive system. Most vertebrate species express two forms of GnRH, which differ in amino acid sequence, localization, distribution, and embryological origin. The GnRH system in the ventral forebrain produces a species-specific GnRH form and projects toward the gonadotropic cell in the pituitary.

Development of three distinct GnRH neuron populations expressing two different GnRH forms in the brain of the African catfish (Clarias gariepinus).

The early development of both the catfish gonadotropin-releasing hormone (cfGnRH)- and the chicken GnRH-II (cGnRH-II) system was investigated in African catfish by immunocytochemistry by using antibodies against the GnRH-associated peptide (GAP) of the respective preprohormones. Weakly cfGnRH-immunoreactive (ir) neurons and fibers were present at 2 weeks after hatching (ph) but only in the ventral telencephalon and pituitary. Two weeks later, cfGnRH fibers and neurons were also observed in more rostral and in more caudal brain areas, mainly in the preoptic area and hypothalamus.

Gonadal steroids and the maturation of the species-specific gonadotropin-releasing hormone system in brain and pituitary of the male African catfish (Clarias gariepinus).

The effect of testosterone (T), 11-ketotestosterone (KT) and estradiol (E(2)) on the development of the catfish gonadotropin-releasing hormone system (cfGnRH) of male African catfish (Clarias gariepinus), at the onset of puberty [between 10 and 12 weeks post hatching (ph)] was investigated. The cfGnRH neurons, located in the ventral forebrain, were visualized by immunofluorescence and their numbers were determined and the amounts of cfGnRH-associated peptide (cfGAP) in the pituitary were measured by RIA. Steroid treatments did not significantly alter the numbers of immunoreactive GnRH neurons.

Gonadotropin-releasing hormone fibers innervate the pituitary of the male African catfish (Clarias gariepinus) during puberty.

The development of the catfish gonadotropin-releasing hormone (cfGnRH) fiber network in the pituitary of male African catfish (Clarias gariepinus) was investigated in relation to puberty. Double immunolabeling studied by confocal laser scanning microscopy revealed a concomitant development of gonadotropes and of pituitary cfGnRH innervation during the first wave of spermatogenesis. Catfish GnRH-immunoreactive fibers in the proximal pars distalis (PPD) of the pituitary were initially observed at the age of 10 weeks (onset of spermatogonial proliferation) and gradually reached the adult pattern at the age of 20 weeks (spermatozoa present in the testis).

Testosterone accelerates the development of the catfish GnRH system in the brain of immature African catfish (Clarias gariepinus).

The effects of two endogenous steroids on the maturation of the catfish GnRH and the chicken GnRH-II system in the African catfish were investigated. Immature fish (2 weeks of age, which is before sexual differentiation; thus male and female genotypes present) were fed with food pellets containing either testosterone (T), 11beta-hydroxyandrostenedione (OHA) or no steroid (control). After 2 and 4 weeks of treatment, the effects on the two GnRH systems were investigated immunocytochemically, using specific antibodies against the respective GnRH-associated peptides.

Modulation of testicular androgen production in adolescent African catfish (Clarias gariepinus).

At 6 months of age the first spermatozoa appear in the testes of the African catfish considered to be adolescent, since the development to adulthood (12 months of age) is accompanied by further morphological and functional differentiation of Leydig cells. There are increasing plasma levels of 11-ketotestosterone (11-KT) and an increasing responsiveness to luteinizing hormone (LH) of testicular androgen secretion in vitro. Whether treatment of adolescent males with key hormones of the brain-pituitary-gonad axis [gonadotropin-releasing hormone (GnRH), LH, and 11-KT] affects the testicular steroidogenic response to a challenge with LH in vitro 7 days later has been investigated.

Pituitary gonadotrophs are strongly activated at the beginning of spermatogenesis in African catfish, Clarias gariepinus.

Pituitary gonadotrophs were studied in male African catfish between 1 and 37 wk of age using antisera against the LH subunits for immunohistological and radioimmunological purposes, and cRNA probes for in situ hybridization. Immunoreactive material was already detectable at the earliest age examined. In juveniles, the signal for the common glycoprotein alpha subunit (GP alpha) was stronger than that for the LH beta subunit.

Preferential release of newly synthesized, exportable neuropeptides by insect neuroendocrine cells and the effect of ageing of secretory granules.

The release of newly synthesized neuropeptides was studied in an in vitro system using the adipokinetic hormone (AKH)-producing cells of an insect (Locusta migratoria) as a model system. Tritiated phenylalanine incorporated into three hormonal neuropeptides, AKH I, II and III, was used to distinguish newly synthesized hormones from older, preexisting ones. After pulse-chase labeling experiments of varying duration, the secretion of AKHs by the AKH cells was stimulated.

Testicular responsiveness to gonadotropic hormonein vitro and Leydig and Sertoli cell ultrastructure during pubertal development of male African catfish (Clarias gariepinus).

The gonadotropin (GTH)-stimulated testicular androgen secretionin vitro and the ultrastructure of Leydig and Sertoli cells was studied during the pubertal development in male African catfish. Testicular weight increased from less than 1 mg in the ninth week of age to nearly 600 mg in the 28th week. Immature testes (stage I: spermatogonia) were highly sensitive to GTH and secreted very high amounts of androgens per mg of tissue.

Expression and distribution of two gonadotropin-releasing hormones in the catfish brain.

The expression of prepro-catfish GnRH mRNA and prepro-chicken GnRH-II mRNA was investigated by means of in situ hybridization. The differential distribution of cells expressing the respective mRNAs was compared with the distribution of cells immunoreactive for (1) catfish (cf) GnRH and chicken (c) GnRH-II and (2) both GnRH-associated peptides (GAPs). It was found that the prepro-cfGnRH mRNA expressing cells were located in the ventral forebrain, with a similar distribution of the cfGnRH- and cfGAP-immunoreactive perikarya.

The adipokinetic cells in the corpus cardiacum of Locusta migratoria preferentially release young secretory granules.

The influence of flight activity on the release of secretory granules from the adipokinetic cells in the corpus cardiacum of Locusta migratoria was studied. Two labeling methods, an enzymatical and a radioactive one, were used to label young, newly synthesized secretory granules and so distinguish them from older, preexisting granules. Both methods demonstrated that the ratio between the numbers of labeled and unlabeled secretory granules was lower in flight-stimulated adipokinetic cells than in unstimulated cells.

Pubertal development of male African catfish (Clarias gariepinus). Pituitary ultrastructure and responsiveness to gonadotropin-releasing hormone.

Pubertal development was studied in male African catfish by immunocytochemical examination of pituitary gonadotrophs and by monitoring the responsiveness of gonadotropin (GTH) secretion to salmon GnRH analogue (sGnRHa) in vitro. Experiments were carried out with fish from 9 to 28 wk of age. Fish were assigned to four groups, according to the stage of spermatogenesis: I, spermatogonia alone; II, spermatogonia and spermatocytes; III, spermatogonia, spermatocytes, and spermatids; IV, all germ cell stages, including spermatozoa.

Two gonadotropin-releasing hormones in the African catfish, Clarias gariepinus: localization, pituitary receptor binding, and gonadotropin release activity.

Two GnRH peptides have recently been identified in brain extracts of the African catfish, chicken-II GnRH ([His5,Trp7,Tyr8]GnRH, cGnRH-II) and catfish GnRH ([His5,Asn8]GnRH, cfGnRH). Using three experimental approaches, we investigated whether both peptides are involved in the regulation of pituitary gonadotropin secretion. First, the presence of cfGnRH and cGnRH-II in the pituitary was studied by biochemical and immunocytochemical techniques, as GnRH reaches the pituitary via axonal transport in teleost fish.

Gonadotropin-releasing hormones, including a novel form, in snook Centropomus undecimalis, in comparison with forms in black sea bass Centropristis striata.

The molecular forms of gonadotropin-releasing hormone (GnRH) in brain-pituitary extracts were determined for snook Centropomus undecimalis and black sea bass Centropristis striata. The extracts were analyzed in both isocratic and gradient high performance liquid chromatography (HPLC) programs. Eluted fractions were tested in radioimmunoassays with 4 different antisera made against 3 distinct GnRH peptides.

GTH-cells in the pituitary of the African catfish, Clarias gariepinus, during gonadal maturation: an immuno-electron microscopical study.

In an ultrastructural immunocytochemical study we investigated the development of the gonadotropic cells in the pituitary of two to six months old male African catfish in relation to testicular development. In this period, pituitary and testicular tissue samples were collected on five occasions (groups I-V). Blood samples could only be taken from the fish in groups III-V.

Maturational gonadotropin from the African catfish, Clarias gariepinus: purification, characterization, localization, and biological activity.

A gonadotropic hormone of the African catfish, Clarias gariepinus, was was purified and chemically characterized. Its biological activity was tested and its localization in the gonadotropic cells of the pituitary demonstrated. An ethanolic extract of 500 pituitaries of adult male and female African catfish was subjected to ion-exchange chromatography on DE-52.

Distribution of catecholaminergic and serotoninergic systems in forebrain and midbrain of the newt, Triturus alpestris (Urodela).

Mapping of monoaminergic systems in the brain of the newt Triturus alpestris was achieved with antisera against (1) thyrosine hydroxylase (TH), (2) formaldehyde-conjugated dopamine (DA), and (3) formaldehyde-conjugated serotonin (5-HT). In the telencephalon, the striatum was densely innervated by a large number of 5-HT-, DA- and TH-immunoreactive (IR) fibers; IR fibers were more scattered in the amygdala, the medial and lateral forebrain bundles, and the anterior commissure. In the anterior and medial diencephalon, TH-IR perikarya contacting the cerebrospinal fluid (CSF-C perikarya) were located in the preoptic recess organ (PRO), the organum vasculosum laminae terminalis and the suprachiasmatic nucleus.

Application of cryosubstitution in neurohormone- and neurotransmitter-immunocytochemistry.

Pituitaries of the African catfish, Clarias gariepinus, were prefixed in aldehyde fixatives, frozen in liquid propane and submitted to a cryosubstitution procedure. Ultrathin sections of the Lowicryl HM20-embedded tissue were treated with primary antisera raised in rabbits to gonadotropin releasing hormone (GnRH), vasopressin or gamma amino butyric acid (GABA) respectively. Binding of the primary antisera was visualized with goat anti-rabbit (GAR) labeled with gold.

Distribution of serotonin- and dopamine-immunoreactivity in the brain of the teleost Clarias gariepinus.

The distribution of serotonergic and dopaminergic cell bodies and varicose fibres in the brain of the teleost Clarias gariepinus was studied immunohistochemically using antisera against formaldehyde-conjugated serotonin and dopamine. Many serotonergic and dopaminergic fibres innervated the areas dorsalis telencephali pars medialis and pars lateralis dorsalis, as well as the area ventralis telencephali pars ventralis. In the diencephalon, a large number of serotonergic and some dopaminergic fibres were found in the preoptic nucleus, innervating the cells of this nucleus.

Topographical relationships between catecholamine- and neuropeptide-containing fibers in the median eminence of the newt, Triturus alpestris. An ultrastructural immunocytochemical study.

Dopaminergic and peptidergic nerve fibers were simultaneously demonstrated with a double-labeling technique at the ultrastructural level. The first antibody, raised against tyrosine hydroxylase, was applied during the preembedding phase and visualized with the peroxidase method. The second antibody, raised against one of the peptides met-enkephalin, somatostatin or gonadotropin-releasing hormone (GnRH), was applied to the ultrathin sections and visualized with gold-labeled goat anti-rabbit IgG.

Ultrastructural localization of calcium and Ca(2+)-ATPase activity in gonadotropes and stellate cells of the catfish pituitary.

In the pituitary of the African catfish, Clarias gariepinus, calcium precipitates were ultrastructurally visualized with the oxalate-pyroantimonate procedure (OPP). The presence of calcium in these precipitates was validated with several methods, including "Electron Energy Loss Spectrometry" (EELS). In the OPP-treated tissue calcium precipitates were seen in a) non-secretory stellate cells and b) gonadotropic (GTH-) cells.

Pituitary steroids in two teleost species: immunohistological and biochemical studies.

Antisera raised against steroid hormones [estradiol-17 beta (E2), testosterone (T), 11 beta-hydroxyandrostenedione (OHA)] were used to localize immunoreactive material in fixed and paraffin-embedded pituitaries of the African catfish and the rainbow trout. Organic extracts of pituitary homogenates were analyzed for steroid hormones by radioimmunoassay and gas chromatography-mass spectrometry (E2 in female catfish only). With the exception of an E2-positive cell type in the catfish neurointermediate lobe, steroid immunoreactivity was found to be restricted to the cytoplasm of adenohypophyseal cells, which were also labeled after incubation with catfish alpha,beta-gonadotropin and salmon gonadotropin antisera, respectively.

Effects of castration on pituitary gonadotropic cells of the male three-spined stickleback, Gasterosteus aculeatus L., under long photoperiod in winter: indications for a positive feedback.

Male three-spined sticklebacks caught in winter were castrated or sham-operated and subsequently kept under long photoperiod at about 20 degrees for a month. With this treatment the sham-operated fish attained breeding condition. The gonadotropic cells of the sham-operated fish contained significantly more dilated endoplasmic reticulum and fewer granules than those of the castrated fish, indicating a higher secretory activity of the gonadotrops in the sham-operated fish.

Immunocytochemical evidence for peptidergic (GnRH) and dopaminergic innervation of the gonadotropic cells in the pituitary of the African catfish, Clarias gariepinus.

The proximal pars distalis (PPD) of the pituitary of the African catfish, Clarias gariepinus, was studied with immunocytochemical methods at the ultrastructural level. Anti-serum raised against synthetic mammalian luteinizing hormone-releasing hormone (LHRH) was applied on Lowicryl-embedded pituitaries and the antigenic sites were visualized with protein A-gold. In nerve fibers contacting the gonadotropic cells, granulated vesicles with a diameter of 90-120 nm were labeled after this procedure, whereas the glandular cells were not labeled.