Peroxidase-antiperoxidase Procedure Research Articles

Comparison of Peroxidase‐Anti‐Peroxidase and Avidin‐Biotin‐Peroxidase Complex (ABC) Immunohistochemical Staining Procedures for Tryptophan Hydroxylase in Rat Brain

The neurotransmitter serotonin (5‐hydroxytryptamine; 5‐HT) plays a key role in sleep, feeding behavior, motor activity and, importantly, mood and the mechanism of action of antidepressant drugs. Immunohistochemistry for tryptophan hydroxylase (TpOH), the synthetic enzyme for 5‐HT, can be used to identify 5‐HT neurons in the central nervous system. As part of a project examining 5‐HT in brain function in the rat, we compared 2 indirect methods of visualizing primary antibodies against TpOH, a peroxidase‐anti‐peroxidase (PAP) method and the more sensitive avidin‐biotin‐peroxidase (ABC) procedure.A cryostat microtome was used to cut 40 micron sections from brains from rats transcardially perfused with 0.9% saline and 4% p‐formaldehyde in 0.1 M phosphate buffer (PB). Brains were post‐fixed 24 h in p‐formaldehyde and cryoprotected in 20% sucrose in 0.1 M PB. Sections were washed in phosphate‐buffered saline (PBS) before and between all steps. Tissues were treated with 0.4% H2O2 in methanol for 20 min to quench endogenous peroxidase activity and 1% sodium borohydride in 0.1 M PB for 30 min to enhance permeability of the tissue and improve staining quality. Sections were then treated with 1% normal donkey (PAP method) or horse (ABC method) serum in PBS with 0.2% Triton X‐100 detergent for 1 h and then 0.8% bovine serum albumin in PBS for 40 min. Tissues were incubated for 48 h in mouse monoclonal anti‐TpOH antibody (Sigma, 1:1000) in PBS with 0.3% Triton X‐100 and serum. Some sections were incubated without the primary antibody (omit negative controls). For the PAP protocol, tissues were treated with donkey anti‐mouse antibody (Jackson; 1:100) and then mouse PAP (Jackson; 1:400), both in PBS with 0.3% Triton X‐100 for 1 h. For the ABC protocol, tissues were treated with biotinylated horse anti‐mouse antibody and then avidin‐biotin‐peroxidase complex (Vector Elite kit), both in PBS with 0.3% Triton X‐100 and serum for 1 h. All sections were reacted with 0.0005% diaminobenzidine with 0.0001% H2O2 for 45 – 120 sec and mounted on gelatin‐coated slides that were coverslipped with DPX. Stained and negative control sections from both methods were examined using standard light microscopy.Staining using the PAP method was faint, homogenous and only slightly darker than negative controls. Individual neurons could not be identified. Increasing concentrations (1:500, 1:250, 1:100) of anti‐TpOH antibody had no effect on specific labeling but slightly increased background staining. This was surprising because the exact same reagents and PAP procedure has produced outstanding staining of tyrosine hydroxylase in brainstem catecholamine neurons (e.g., Muma et al., Exp. Neurology, 168:135–143, 2001). In contrast, labeling of TpOH using the ABC method was excellent. TpOH immunoreactivity was highly visible in the somata and primary dendrites of neurons in the dorsal and median raphe nuclei. These results add to and amplify the enhanced staining quality of the ABC procedure over the PAP method in formaldehyde‐fixed rat brain sections.Support or Funding InformationSupported by the School of Biological Sciences and the Department of Psychology, Illinois State University.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Immunohistomorphometric Features of ACTH Cells in Juvenile Rats after Treatment with Estradiol or Human Chorionic Gonadotropin

Immunohistomorphometric Features of ACTH Cells in Juvenile Rats after Treatment with Estradiol or Human Chorionic GonadotropinEstradiol and human chorionic gonadotropin (hCG) are very important in controlling the secretory activity of hormone producing cells in the female rat pituitary glands. The aim of the present study was to examine the morphometric parameters of immunohistochemically labeled ACTH cells in juvenile (16th day) female rat pituitaries after treatment with five doses of estradiol dipropionate (EDP) and two doses of hCG during the neonatal period of life. The controls were treated on the same schedule with an equivalent volume of vehicle. All animals were sacrificed 24 h after the last treatment. ACTH-producing cells were studied using the peroxidase-antiperoxidase immunohistochemical procedure. The absolute and relative pituitary weights were increased (p<0.05) only in the EDP treated group by 120.0% and by 121.1% respectively, in comparison with the controls. In this group, the volume of ACTH cells, volume of their nuclei and volume density were significantly decreased (p<0.05) by 6.4%, 33.3% and 46.2% respectively, compared to the corresponding controls. After treatment with hCG, there were no significant (p>0.05) changes neither in the volume of ACTH cells nor in the volume of their nuclei, in comparison with the controls. On the basis of the results obtained in our study, it can be concluded that EDP, injected into female rats during the neonatal period of life, has an inhibitory effect on the immunohistomorphometric parameters of ACTH cells, but such an effect is not clearly expressed after treatment with hCG.

Genitourinary changes in hamsters infected and reinfected with Trypanosoma cruzi.

Authors describe genitourinary changes in male hamsters infected and reinfected with Trypanosoma cruzi. Changes in genital organs have been described in human and in experimental chagasic infection. Genital dysfunctions in chronic chagasic patients affect ejaculation, libido and sexual potency, and testis biopsies may show arrested maturation of germ cells, oligozoospermia and azoospermia. Sixty-five male hamsters were inoculated and reinoculated with 2x10 trypomastigotes of T. cruzi VIC strain, and 22 non-infected animals constituted the control group. Animals were necropsied and fragments from testis, epididymis, seminal vesicle and bladder were collected and stained with hematoxylin-eosin. Peroxidase anti-peroxidase procedure was utilized to detect tissue parasitism. T. cruzi nests were found in testis, epididymis and seminal vesicle of these hamsters. Such parasitism plays a role in the origin of genital lesions observed in humans and laboratory animals during chronic chagasic infection.

Ultrastructural organization of GABA-like immunoreactive profiles in the weaver substantia nigra.

GABA-like immunoreactivity (GABA-LI) in the substantia nigra pars compacta (SNc) of mutant weaver mice was investigated at the electron microscope level. Eight-week-old homozygous mutant weaver mice, paired with wildtype littermates as controls, were perfused with a buffered paraformadehyde/acrolein solution. Sections containing the SN were immunocytochemically reacted with an antiserum to GABA using the peroxidase-antiperoxidase (PAP) procedure. Ultrastructural examination revealed that profiles of GABA-LI dendrites were decreased in number while profiles of labeled axonal processes were increased. In addition, there were an increased number of GABA-LI terminals in contact with similarly labeled GABA-LI dendrites. Double-labeling experiments using the antibodies to GABA and dopamine D(2) receptors showed that a small number of GABA-LI profiles exhibited D(2)-like immunoreactivity in both controls and weavers. These results suggest that the GABA-LI synaptic connections are altered as a result of the loss of DA neurons in the SNc of the weaver mice.

Effects of multiple somatostatin treatment on rat gonadotrophic cells and ovaries.

The effect of multiple somatostatin (SRIH-14) treatment on the pituitary gonadotrophs, follicle stimulating harmone (FSH) and luteinizing harmone (LH), and ovaries of adult female Wistar rats was examined. Females received two 20 microg/100 g body wt. doses daily subcutaneously, for five consecutive days. FSH and LH cells were studied using a peroxidase-antiperoxidase immunocytochemical procedure. Morphometry and stereology were used to evaluate changes in the number per unit area (mm2), cell volume and volume densities of LH- and FSH-immunoreactive cells. Ovaries were analysed by simple point counting of follicles and corpora lutea. Follicles were divided by size according to the classification of Gaytán and Osman. Morphometric and stereological analysis of the pituitary showed that the number, volume and the volume density of FSH- and LH-immunoreactive cells were decreased after multiple SRIH-14 treatment, particularly in the latter. In the ovary, SRIH-14 induced decreases in the number of healthy follicles in all phases of folliculogenesis and corpora lutea, but the large antral follicle stage was most affected. The number of atretic follicles was increased. It can be concluded that multiple SRIH-14 treatment markedly inhibited LH cells, but affected FSH cells as well. In the ovary, SRIH- 14 acted by inhibiting folliculogenesis and enhancing atretic processes.

Effect of centrally administered somatostatin on pituitary thyrotropes in male rats.

The effects of intracerebroventricularly administered somatostatin (SRIH-14 or -28) on growth and function of pituitary thyrotropes (TSH-cells) were examined in adult male Wistar rats. The animals were implanted with an intracerebroventricular cannula and after a recovery period, administered three 1 microg doses of SRIH-14 or -28 dissolved in 5 microl saline every second day. Controls were treated in the same way with the same volume of saline only. TSH-producing cells were studied using the peroxidase-antiperoxidase immunohistochemical procedure. Blood samples were collected for hormone (TSH) analyses 5 days after the last injection. Both SRIH-treatments significantly decreased (p < 0.05) all morphometric parameters obtained for TSH-cells in comparison with controls. The volume of TSH-cells decreased by 27%, nuclei by 44% and volume density by 33% in animals treated with SRIH-14. In animals treated with SRIH-28, these parameters were also significantly decreased (p < 0.05) (22%, 31%, and 25% respectively) compared to control rats. Serum concentrations of TSH were significantly decreased (p < 0.05) by 15% in SRIH-14- and by 12% in SRIH-28-treated animals in comparison with the controls. These observations suggest that centrally administered SRIH- 14 or -28 is specifically involved in the control of growth and secretory activity of TSH cells.

Neuroendocrine cells in the female urogenital tract of the pig, and their immunohistochemical characterization.

A systematic search for neuroendocrine (NE) cells in the urogenital organs of the pig was carried out by means of Linder's argyrophil method and immunohistochemical techniques. The occurrence, distribution and immunohistochemical character of NE cells (paraneurons) were studied in the vaginal vestibulum, vagina, uterus, oviduct, ovary, urethra, urinary bladder and ureter. In the vestibular glands paraneurons were found to be the most numerous, while a moderate number of these cells occurred in the uterine horn and in the urethra. A distinctly smaller number of paraneurons was present in the oviduct and only occasional NE cells were observed in the urinary bladder. Immunohistochemistry was performed by using the peroxidase-antiperoxidase procedure. Different subpopulations of paraneurons were distinguishable. Chromogranin A-positive paraneurons were found in the vestibular glands, uterine horns, oviducts, urethra and urinary bladder. Somatostatin positivity was observed in NE cells of the vestibular gland, uterine horn, oviduct and urethra. The subpopulation of serotonin-positive paraneurons was present in the vestibular gland and urethra. Bombesin, vasoactive intestinal polypeptide, cholecystokinin, substance P, nitric oxide synthase, beta-endorphin, insulin, adrenocorticotropic hormone, oxytocin and thyroid-stimulating hormone antibodies gave negative reactions in the studied NE cells.

Immunohistochemical detection of substance P and vasoactive intestinal peptide fibres in the auricular lymph nodes of sensitized guinea pigs and mice

The presence of substance P (SP) and vasoactive intestinal peptide (VIP) in auricular lymph nodes of normal and sensitized guinea pigs and mice has been investigated using polyclonal antibodies directed against these neurotransmitters and the unlabelled peroxidase-antiperoxidase procedure. Positive immunoreactivity could be observed only in draining lymph nodes of sensitized animals. SP-immunoreactivity was found in mice and guinea pigs but a VIP-positive reaction only in mice. The immunopositive sites were always associated with blood vessels. The present study suggests that the neurotransmitters SP and VIP are involved in mechanisms of sensitization taking place in secondary lymphoid organs.

Immunohistochemical distribution of basement membrane type IV collagen and laminin in synovial sarcoma.

To investigate the distribution of basement membrane components type IV collagen and laminin in synovial sarcomas. Paraffin sections from synovial sarcomas were studied by the peroxidase-antiperoxidase procedure using specific antibodies to type IV collagen and laminin. Type IV collagen and laminin immunoreactivity was confined around epithelial areas in biphasic tumors. Several interruptions and discontinuities of the linear basement membrane profile were seen in sites of transition between mesenchymal and epithelial tissue. Moreover, a spot-like immunoreactivity was often observed in the spindle cell component of biphasic tumors. Monophasic tumors were either negative or showed a pericellular staining for both type IV collagen and laminin. The distribution of basement membrane components is clearly related to the formation of epithelial elements in biphasic synovial sarcoma. The spot-like immunoreactivity of the spindle cell component, and the basement membrane interruptions at the boundary between mesenchymal and epithelial tissue, are both consistent with early basement membrane formation by developing epithelium. These findings support the concept that synovial sarcomas are basically soft tissue carcinosarcomas and that the epithelial component of the tumors develops by conversion of mesenchyme to epithelium.

Distribution of glutamate-like and glutamine-like immunoreactivities in the rat organ of Corti: a light microscopic and semiquantitative electron microscopic analysis with a note on the localization of aspartate.

The light- and electron microscopic localization of glutamate and glutamine in the rat organ of Corti was studied by means of antisera raised against the respective amino acids coupled to carrier proteins. The light microscopic analysis was performed in semithin sections treated according to the peroxidase-antiperoxidase procedure. The two amino acids were visualized in the same ultrathin sections by use of postembedding immunocytochemistry with two different gold particle sizes. The distribution of aspartate-like immunoreactivity was also recorded, but only at the light microscopic level. In the hair cells, the level of glutamate-like immunoreactivity was higher than that in supporting cells but lower than that in the presumed glutamatergic terminals of cerebellar parallel and mossy fibres. The latter types of terminal were sampled from ultrathin sections that had been incubated under the same conditions as the cochlear sections. Within the hair cells, gold particles signalling glutamate were enriched on mitochondria but not on clusters of synaptic vesicles. Glutamine-like immunoreactivity was present in hair cells as well as supporting cells. The glutamate/glutamine ratio, expressed as the ratio between the respective gold particle densities, was considerably lower for hair cells compared with the cerebellar excitatory terminals. No consistent difference was found between outer and inner hair cells in relation to the levels and subcellular distribution of glutamate and glutamine immunoreactivities. Aspartate-like immunoreactivity was accumulated in outer hair cells, with some labelling also of border cells and Böttcher cells. While the present study confirmed the presence of glutamate in hair cells and demonstrated that these cells are also endowed with the important glutamate precursor glutamine, it revealed notable differences between hair cells and presumed glutamatergic terminals in the CNS. These could reflect differences in the synthesis and compartmentation of transmitter glutamate. Methodological factors could also contribute. Alternatively, the differences could be interpreted to suggest that the hair cell transmitter is not glutamate, but a similar compound. Aspartate could be a candidate in the case of the outer hair cells.

Quantitative immunohistologic study of lip biopsies evaluation of diagnostic and prognostic value in Sjögren's syndrome

In a group of 45 patients with Sjögren's syndrome (SS) and 80 controls the high specificity (95%) and sensitivity (100%) of a recently proposed bivariate quantitative immunohistologic (QIH) criterion for SS, based on percentages of IgA and IgG-containing plasma cells in labial salivary gland (LSG) tissue, was confirmed. The best univariate QIH criterion for discrimination between LSG biopsies of SS patients and controls appeared to be based on the percentage of IgA containing plasma cells, and had a specificity of 99% and a sensitivity of 96%. A criterion based only on the percentages of IgM-containing plasma cells, proposed in another recent study, resulted in a high number (31%) of false negatives. Interobserver reproducibility of QIH diagnoses was excellent. Moreover it was demonstrated that accuracy, precision and the interobserver reproducibility of plasma cell counting depends on the choice of tissue fixation and immunohistologic staining procedure. The combination of formol sublimate fixation and peroxidase anti-peroxidase procedure appeared to be the best combination for QIH examination. Furthermore, in 2 SS patients systemic monoclonal IgM/kappa gammopathy was preceded by high predominance of IgM and kappa containing plasma cells in the plasma cellular infiltrate of the LSG tissue.

Calcitonin gene-related peptide in rat spinal cord motoneurons: Subcellular distribution and changes induced by axotomy

Using light and electron microscopy, a study has been made of the changes of calcitonin gene-related peptide-like immunoreactivity in rat lumbar spinal cord motoneurons during cell body response to sciatic nerve injury. At light microscopy level, calcitonin gene-related peptide-like immunoreactivity was evaluated using an indirect immunofluorescence technique combined with Fast Blue retrograde tracing and a peroxidase-antiperoxidase procedure. The calcitonin gene-related peptide changes to sciatic nerve transection and crushing were compared. Calcitonin gene-related peptide-like immunoreactivity was transiently increased after the peripheral nerve lesion, but the response was sustained for a longer period when the peripheral nerve was transected and nerve regeneration prevented. The first changes in calcitonin gene-related peptide-like immunoreactivity were detected four days after nerve crush or transection. In animal spinal cords to which nerve crush had been applied, the maximal enhancement of immunoreactivity was found 11 days after lesion. This was followed by a gradual decline, normal levels being attained 45 days after nerve crushing. When the nerve was transected, the response was similar, but the maximal calcitonin gene-related peptide-like immunoreactivity was maintained over a period of between 11 and 30 days. As with crushing, an important decrease was observed after 45 days. The ultrastructural compartmentation of calcitonin gene-related peptide-like immunoreactivity was studied using either peroxidase-antiperoxidase method or immunogold labelling. Calcitonin gene-related peptide-like immuno-reactivity was located in restricted sacs of the Golgi complex, multivesicular bodies, small vesicles and tubulo-vesicular structures. Large, strongly labelled vesicles resembling secretory granules were also observed in neuronal bodies. Our results reveal that the increase of calcitonin gene-related peptide in motoneurons is a relevant change the cell body undergoes in response to peripheral injury. The ultrastructural location of the peptide distribution suggests specific compartmentation on tubulo-vesicular structures connected with the Golgi complex which form a network in the neuronal cytoplasm. The distribution pattern observed may be related to the sorting and delivery of calcitonin gene-related peptide to secretory vesicles.

Ultrastructural single‐ and double‐label immunohistochemical studies of substance P‐containing terminals and dopaminergic neurons in the substantia nigra in pigeons

The vast majority of striatonigral projection neurons in pigeons contain substance P (SP), and the vast majority of SP-containing fibers terminating in the substantia nigra arise from neurons in the striatum. To help clarify the role of striatonigral projection neurons, we conducted electron microscopic single- and double-label immunohistochemical studies of SP+ terminals and/or dopaminergic neurons (labeled with either anti-dopamine, DA, or anti-tyrosine hydroxylase, TH) in pigeons to determine: (1) the synaptic organization of SP+ terminals, (2) the synaptic organization of TH+ perikarya and/or dendrites, and (3) the synaptic relationship between SP+ terminals and TH+ neurons in the substantia nigra. Tissue single-labeled for SP revealed numerous SP+ terminals contacting thin unlabeled dendrites in the substantia nigra, but few SP+ terminals were observed contacting perikarya or large-diameter dendrites. SP+ terminals contained round, densely packed, clear vesicles, and often contained one or more dense-core vesicles. Synaptic junctions between SP+ terminals and their targets were more often symmetric (86%) than asymmetric. In tissue single-labeled for DA, we observed few terminals contacting DA+ perikarya, whereas terminals contacting DA+ dendrites were more abundant. Terminals contacting DA+ structures comprised at least four different morphologically distinct types based on the morphology of the clear synaptic vesicles and the type of synaptic junction. One type of terminal contained round clear vesicles and made symmetric synapses, and thus resembled the predominant type of SP+ terminal. The second type contained round clear vesicles and made asymmetric synapses, the third type contained medium-size pleomorphic clear vesicles and made symmetric synapses, and the fourth type contained small pleomorphic clear vesicles and made symmetric synapses. The presence of contacts between SP+ terminals and dopaminergic dendrites in the substantia nigra was directly demonstrated in tissue double-labeled for SP (by the peroxidase-antiperoxidase procedure, or PAP, with diaminobenzidine) and TH (by either the silver-intensified immunogold procedure or the PAP procedure with benzidine dihydrochloride). SP+ terminals commonly contacted thin TH+ dendrites in the substantia nigra, but few SP+ terminals contacted large-diameter TH+ dendrites or perikarya. Synapses between SP+ terminals and TH+ neurons were always symmetric. TH+ dendrites also were contacted by terminals not labeled for SP, which were more abundant than were SP+ terminals. Non-TH+ neurons were also contacted by both SP+ terminals and non-SP+ terminals.(ABSTRACT TRUNCATED AT 400 WORDS)

Evaluation of a New Chemiluminometric Immunoassay, Magic Lite Chlamydia, for Detecting Chlamydia trachomatis Antigen from Urogenital Specimens

The chemiluminometric sandwich immunoassay, Magic Lite Chlamydia by Ciba Corning (Medfield, MA), using one Chlamydia trachomatis-specific monoclonal antibody conjugated with acridinium ester and one polyclonal immobilized to magnetic particles, was compared to cell culture in 291 urogenital specimens from 92 men and 102 women tested both in the cervix and urethra. The proportion of patients with positive culture results ranged from 11.8% among the women to 15% among the men, using microculture plates and peroxidase-antiperoxidase staining procedure with genus-specific monoclonal antibody (Orthodiagnostics, Raritan, NJ). The chemiluminometric method for detecting Chlamydia trachomatis antigen showed an overall sensitivity of 72.4%, specificity of 97.7%, positive predictive value of 77.7%, and negative predictive value of 96.9%. A higher sensitivity of Magic Lite was found in clinical specimens yielding more than 10 inclusions by well in cell culture. The newly developed chemiluminometric test, easy to perform, had the same limits in terms of sensitivity and positive predictive value than the other widely-used existing tests for detecting Chlamydia trachomatis antigen from urogenital specimens.

Distribution of glutamine-like immunoreactivity in the cerebellum of rat and baboon (Papio anubis) with reference to the issue of metabolic compartmentation

The cellular and subcellular localization of glutamine, a major glutamate precursor, was studied by means of an antiserum raised against glutaraldehyde-fixed glutamine. Ultrathin sections from the cerebellar cortex of rat and baboon (Papio anubis) were incubated sequentially in the primary antiserum and in a secondary antibody coupled to colloidal gold particles. The labelling intensity was quantified by computer-aided calculation of gold particle densities. High levels of immunoreactivity occurred in glial cells (Bergmann fibres, astrocytes, and oligodendrocytes), intermediate levels in cell bodies and processes of granule cells, and low levels in terminals of presumed GABAergic or glutamatergic fibres (terminals of basket and Golgi cells, and of parallel, mossy, and climbing fibres). The labelling intensity of Purkinje cells showed some variation, but never exceeded that in glial cells. Within the nerve fibre terminals, the glutamine-like immunoreactivity showed some preference for mitochondria, but was otherwise evenly distributed. The predominant glial localization of glutamine was also obvious in light microscopic preparations processed according to the postembedding peroxidase-antiperoxidase procedure. Gold particle densities over different types of profile in glutamine immunolabeled sections were compared with particle densities over the corresponding types of profiles in neighbouring sections labelled with an antiserum to glutaraldehyde-fixed glutamate. The glutamate/glutamine ratio, expressed arbitrarily by the ratio between the respective gold particle densities, varied by a factor of about 6, with the highest ratio in the putative glutamatergic mossy and parallel fibre terminals, and the lowest ratio in glial elements. The remaining tissue components displayed intermediate ratios. The present study provides direct morphological evidence for the existence in the brain of distinct compartments with differing glutamate/glutamine ratios.

Immunohistochemical Localization of Basic Fibroblast Growth Factor in Ependymal Cells of the Rat Lateral and Third Ventricles

The presence of basic fibroblast growth factor (bFGF) in the third and the lateral ventricular ependyma of the rat has been investigated under the light microscope using a polyclonal antibody against bFGF, through the unlabelled peroxidase-antiperoxidase procedure; bFGF-immunoreactivity (bFGF-IR) is observed in the entire ependymal cell layer of ventricles. Also ependymal tanycytes within the inferior portion of the wall and floor of the third ventricle show bFGF-IR. Tanycytic processes are in close contact with hypothalamic capillaries. The present study strongly suggests that brain ependymal bFGF plays unidentified roles unrelated to its angiogenic or mitogenic capacities.

GABA neurons in the rat suprachiasmatic nucleus: Involvement in chemospecific synaptic circuitry and evidence for GAD-peptide colocalization

Dual labelling methods were employed for the electron microscopic detection of glutamate decarboxylase (GAD) immunoreactivity, together with vasoactive intestinal peptide (VIP) or neuropeptide Y (NPY) immunoreactivity in the suprachiasmatic nucleus (SCN) of colchicine pretreated and untreated rats. These methods involved the combined use of diaminobenzidine and benzidine dihydrochloride as distinct chromogens to visualize peroxidase-anti-peroxidase (PAP) immunostaining, and a combination of the PAP procedure with a radioimmunocytochemical method employing 125I-labelled secondary antisera. We were thereby able to demonstrate that gamma-aminobutyric acid (GABA) terminals provide an important afferent synaptic input to VIP neurons. Some of these VIP-immunoreactive neurons also exhibited GAD immunoreactivity. Examples of direct appositions between GABA and NPY terminals, and of a convergence of the two types of terminals on to the same postsynaptic targets, were frequently encountered. NPY/GAD colocalization within a few axonal varicosities was also demonstrated. These data provide additional information concerning chemospecific neuronal interactions that could be of functional importance in the regulation of circadian rhythmicity at the level of the SCN.

Distribution of aromatase in the brain of the Japanese quail, ring dove, and zebra finch: An immunocytochemical study

An immunocytochemical peroxidase-antiperoxidase procedure using a purified polyclonal antibody raised against human placental aromatase was used to localize aromatase-containing cells in the brain of three avian species: the Japanese quail, the ring dove, and the zebra finch. In quail and dove, immunoreactive cells were found only in the preoptic area and hypothalamus, with a high density of positive cells being present in the medial preoptic area, in the septal area above the anterior commissure, in the ventromedial nucleus of the hypothalamus, and in rostral part of the infundibulum. Immunoreactivity was weaker in zebra finches, and no signal could therefore be detected in the ventromedial and tuberal hypothalamus. The positive material was localized in the perikarya and in adjacent cytoplasmic processes, including the full length of axons always leaving a clear unstained cell nucleus. These features could be observed in more detail on sections cut from perfused brains and stained with an alkaline phosphatase procedure. The distribution of aromatase immunoreactivity was similar in the three species although minor differences were observed in the preoptic area. The localization of labelled neurons coincided with the distribution of aromatase activity as studied by in vitro radioenzyme assays on brain nuclei dissected by the Palkovits punch method. There was one striking exception to this rule: no immunoreactivity was detected in the zebra finch telencephalon, while assays had shown the presence of an active enzyme in several nuclei such as the robustus archistriatalis, the hyperstriatum ventrale pars caudale, and the hippocampus and area parahippocampalis. The origins of this discrepancy and the functional role of the aromatase observed in the axons are discussed.

Age‐related immunohistochemical studies of A and D cells in pancreatic islets of C57BL/6J mice

Sections of pancreatic islets from C57BL/6J mice aged 3, 14, and 24 months, consisting of islets derived from the dorsal primordium (DPI) and from the ventral primordium (VPI), were immunostained using the peroxidase-antiperoxidase (PAP) procedure for localization of glucagon (A cells) and somatostatin (D cells). The density (A or D cell area/islet area) of immunopositive cells were determined using computer-assisted image analysis. The density of A cells was significantly less in VPI of 14- and 24-month-old mice compared to 3-month-old mice. The density of A cells in 24 month DPI was less than 3 month DPI but no different from 14 month DPI. The mean area (microns 2) of A cells (only in DPI) was significantly less at 24 months compared to the 3 and 14 month groups. There were no differences in somatostatin staining when comparing the three age groups, although at all ages the density of D cells was always greater in the DPI. In conclusion, the major difference between the young and older mice was a deficiency of glucagon-stained cells in older mice. These results might be important in explaining improved glucose tolerance in aged C57BL/6J mice.

Immunocytochemical localization of aromatase in the brain

An immunocytochemical peroxidase-antiperoxidase procedure using a purified polyclonal antibody raised against human placental aromatase was used to localize aromatase-containing cells in the Japanese quail brain. Immunoreactive cells were found only in the preoptic area and hypothalamus, with a high density of positive cells being present in the sexually dimorphic medial preoptic nucleus, in the ventromedial nucleus of the hypothalamus and in the infundibulum. The positive material was localized in the perikarya and in adjacent cytoplasmic processes. Aromatase-containing cells were a specific marker for the sexually dimorphic preoptic nucleus. Treatment with testosterone produced a 6-fold increase in the aromatase activity of the preoptic area and a 4-fold increase in the number of immunoreactive cells in the medial preoptic nucleus. Thus, the increase in aromatase activity observed after testosterone administration is caused by a change by a change in enzyme concentration