Neuronal nitric oxide synthase and the autonomic innervation of the mouse lacrimal gland

PURPOSE

To determine the expression patterns of the vesicular acetylcholine transporter (VAChT), tyrosine hydroxylase (TH) and neuronal nitric oxide synthase (nNOS) in the pterygopalatine ganglion (PPG) and the exorbital lacrimal gland of normal mice.

METHODS

Mouse PPG and lacrimal glands were processed for single- and double-labeled indirect immunofluorescence studies. Slides were examined with conventional fluorescence microscopy and confocal laser scanning microscopy.

RESULTS

All the somata in the PPG expressed both VAChT and nNOS immunoreactivity (IR). The postganglionic axons within the ganglion showed less VAChT-immunoreactive intensity than that seen in the somata, whereas nNOS IR was almost undetectable. In the lacrimal gland, nNOS-positive nerve bundles and fibers were observed to be associated with tear-collecting ducts, blood vessels, and acini. Some nNOS-positive punctate elements appeared to be distributed among acini. Many nerve fibers were VAChT immunoreactive and a small number of fibers were TH immunoreactive in the gland. Most of the VAChT-positive fibers and some of the TH-positive nerves displayed nNOS IR.

CONCLUSIONS

The expression of nNOS in cells of the PPG and in lacrimal gland nerves suggests that NO may play a role in modulating tear production. The site of action may include the PPG, ducts, blood vessels, acini, nerve fibers, and myoepithelial cells within the gland. NO may modulate parasympathetic and/or sympathetic synaptic transmission or by acting directly on lacrimal gland components. The interaction between NO-ergic and the conventional autonomic input illustrates the complexity of the innervation pattern of the mouse lacrimal gland.

Lacrimal gland fluid secretion and lymphocytic infiltration in the NZB/W mouse model of Sjögren's syndrome

PURPOSE

The fluid secretory impairment of lacrimal and salivary glands in Sjögren's syndrome (SS) is thought to be related to the extent of lymphocytic infiltration (LI) and subsequent loss of glandular tissue. In this study, we examine the correlation between the extent of tear flow reduction and the extent of LI of lacrimal glands in the NZB/W mouse, a model of SS.

METHODS

We stimulated tear production by topical application of carbachol onto the gland while fluid was collected from the lacrimal duct. The lacrimal glands were removed after fluid collection for histology.

RESULTS

Fluid secretion in response to carbachol was less in the majority of young NZB/W females compared to C57 control animals and none of the glands showed LI. Fluid secretion was also impaired in the majority of old NZB/W females, and the extent of LI was highly variable. Some of the old SW females also showed blunted fluid secretory responses and some degree of focal LI. Young SW females showed no LI and most animals exhibited normal flow responses. Analysis of paired flow and LI measurements showed no correlation between LI and flow impairment in any of the groups or in the pooled data. Carbachol-stimulated protein secretion from lacrimal gland slices in vitro were similar in young and old SW and NZB/W mice.

CONCLUSIONS

These results suggest that LI alone is not sufficient to explain the secretory dysfunction in the NZB/W mouse model of Sjögren's syndrome.

New method for imaging innervation of the renal preglomerular vasculature. Alterations in hypertensive rats

OBJECTIVE

To develop a new method for viewing adrenergic innervation along renal preglomerular vessels; to assess nerve densities and vascular lesions along arcuate arteries (ArcA), arcuate arterial branches (ArcB), and interlobular arteries (ILA) in spontaneously hypertensive rats (SHR) and in angiotensin II (AngII) and in N(G)-nitro-L-arginine methyl ester (L-NAME) hypertensive rats.

METHODS

Preglomerular vasculatyres were isolated after HCl maceration and were immunostained against synaptophysin, a membrane protein of synaptic vesicles. Lesions were stained with Sudan black. Longitudinal nerve densities and relative frequencies of ArcA, ArcB, and ILA endowed with sudanophilic lesions were assessed separately.

RESULTS

Synaptophysin immunostaining revealed the vascular neural plexus. Nerves were adrenergic, as the plexus was destroyed by treatment with 6-hydroxy dopamine. Vascular lesions were not seen in SHR, and increased nerve density was observed along ArcA and ILA. In L-NAME- and AngII-hypertensive rats, vascular lesions affected predominantly ArcB and ILA, and nerve density was reduced by 12% and 28% (ArcA), 37% and 31% (ArcB), and by 55% and 34% (ILA), respectively, versus normotensive controls. Endothelin-1 receptor blockade did not affect AngII-induced hypertension but prevented both lesion development and reduction of density of the vascular neural plexus.

CONCLUSIONS

The method we have devised provides a direct en face view of the vascular adrenergic innervation of isolated preglomerular vasculature. Measurements in hypertensive rat models suggest a link between vascular lesions and reduction in nerve density in hypertension. Endothelin-1 likely plays a key role in mediation both vascular injury and altered vascular nerve density in hypertension.

Myocardial connexin43 expression in left ventricular hypertrophy resulting from aortic regurgitation

Intercellular conduction in the working myocardium of the mammalian heart is mediated by gap junctions composed of connexin43 or 45. Recently, it has been shown that myocardial connexin expression is malleable and may be altered with disease. To better understand myocardial conduction in left ventricular hypertrophy resulting from volume overload, we used indirect immunofluorescence microscopy to examine cardiac connexin43 expression in 10 New Zealand white rabbits with surgically induced aortic regurgitation (AR) and in 10 age-matched sham-operated controls. Animals were sacrificed at approximately 1 month or > or =2.5 years after operation. All AR animals developed eccentric hypertrophy; none evidenced heart failure. The heart-to-body weight ratios for the 1 month AR and control groups were 2.9+/-0.8 vs 1.8+/-0.2 g/kg (p < or = 0.01) while ratios for the > or =2.5 year AR and control groups were 2.4+/-0.3 vs 1.9+/-0.3 (p < or = 0.05). No significant differences in posterior wall thickness were found among any of the groups. Although the overall pattern of connexin43-like immunoreactivity was similar for all four groups, staining in the I month AR animals tended to be less than that of age-matched controls; staining was increased in the > or =2.5 year AR animals and was greater than control (p < 0.05), in which staining did not change with animal age. This disease duration-related increase differs from the long-term decrease in connexin43 expression associated with other forms of heart disease and suggests that alterations in connexin expression may play a role in the rhythm abnormalities commonly seen in AR.

Diminished neurogenic but not pharmacological erections in the 2- to 3-month experimentally diabetic F-344 rat

The rapid spread of locally restricted neural and hormonal signals among the vast array of largely inexcitable corporal smooth muscle cells is an absolute prerequisite to normal erectile function. And yet the mechanism(s) responsible for this phenomenon is not well understood. As a first step toward a more integrative understanding of erectile physiology and/or dysfunction, an 8- to 12-wk period of experimental diabetes was induced in 2-mo-old male Fischer 344 rats by either intraperitoneal streptozotocin (STZ) injection (35 mg/kg; n = 22) or subtotal pancreatectomy (n = 11). Fourteen age-matched control animals received injection of vehicle only while nine others served as sham-operated control animals. Eight STZ-diabetic animals received insulin replacement. Erectile function was assessed by evaluation of penile reflexes and monitoring of intracavernous pressure responses to both electrical stimulation of the cavernous nerve and intracorporal papaverine or nitroglycerin injection. Intracavernous pressure responses to neurostimulation were significantly attenuated in both STZ-diabetic and subtotal pancreatectomy animals compared with age-matched control animals (P < 0.05). Penile reflexes were also significantly diminished (P < 0.05). Regression analysis revealed that diabetes-related decreases in neurostimulated intracavernous pressure responses were strongly correlated with diminished synaptophysin immunoreactivity in the corpora (P < 0.001; r = 0.88). However, there were no detectable diabetes-related differences in pharmacological erections induced by intracavernous papaverine or nitroglycerin injection. Northern analysis revealed a marked diabetes-related increase in the amount of connexin 43 mRNA measured in frozen corporal tissue. Insulin replacement partially restored (attenuated the loss of) synaptophysin immunoreactivity and maintained neurostimulated intracavernous pressure responses to control levels while having no effect on penile reflexes. These observations may have important implications to the understanding of erectile physiology as well as the etiology of diabetes-related erectile dysfunction.

Cholinergic modulation of immunoglobulin secretion from avian plasma cells: the role of cyclic mononucleotides

The chicken Harderian (lacrimal) gland contains an abundance of plasma cells in the interstitium of the gland that secrete IgG, IgM, and IgA. In in vitro preparations of this gland, the cholinergic agonist carbachol causes a transient increase in the secretion rate of IgG above a basal level of secretion. We have investigated the effects of the cyclic mononucleotides cAMP and cGMP on this secretagogue response. Pretreatment with 20 microM forskolin or 1 mM dibutyryl cAMP abolished the carbachol-induced secretory response. When the gland was isolated in normal media and then treated with either forskolin or dibutyryl cAMP, there was no change in the baseline secretion rate. cGMP at either 10 microM or 1.0 mM did not affect the baseline secretion rate, nor did it have an effect on the carbachol response. We postulate that muscarinic receptor activation leads to a calcium influx that in turn leads to an increased secretion rate of IgG. The opposing effects of elevating cAMP and cGMP are discussed in the context of this model of cholinergic activation of avian plasma cells.

Cholinergic modulation of immunoglobulin secretion from avian plasma cells: the role of calcium

The existence of a functional connection between the nervous and immune systems has long been argued. To determine if such a link exists in the secretory immune system, we have examined the avian lacrimal gland (Harderian gland) which contains large numbers of plasma cells. We have shown that these plasma cells bind an antibody to muscarinic acetylcholine receptor and that carbachol, an acetylcholine agonist, increases the secretion rate of IgG by these cells above a constitutive baseline level. This neurotransmitter-dependent increase of immunoglobulin secretion requires an influx of Ca2+, whereas the constitutive baseline secretion is apparently less dependent on such a flux. Furthermore, the Ca2+ flux appears to be mediated by voltage-dependent calcium channels. These data support the hypothesis that plasma cells can respond to neurotransmitters and, in the case of acetylcholine, increase immunoglobulin secretion.

Maxi-K channels in plasma cells

Whole-cells, excised outside-in and outside-out membrane patches were employed to study the electrophysiological properties of plasma cells isolated from the Harderian (lacrimal) gland of chicken. The study revealed that the whole-cell currents are dominated by outward rectifying currents which display slow inactivation times of the order of seconds. Records from excised outside-in and outside-out patches consistently revealed one channel type, a maxi-K channel. These maxi-K channels were shown to be both voltage and calcium sensitive. The single channel conductance of the maxi-K channel, with KCl solutions on both sides of the patch, ranged from 200-265 pS (n = 26). Both whole-cell currents and single channel activity (outside-out) were reduced by the introduction of 10 mM TEA in the bath. The ease with which a large number of plasma cells can be isolated free of undifferentiated B-lymphocytes makes this preparation ideal for studying the relationship between the electrophysiological properties and immunoglobulin secretion in plasma cells.

Neuropeptides and the innervation of the avian lacrimal gland

The chicken Harderian gland, the major lacrimal gland, has two major cell populations: a cortical secretory epithelium and a medullary interstitial cell population of lymphoid cells. There is an extensive acetylcholinesterase (AChE) network throughout the gland, as well as catecholamine positive fibers among the interstitial cells. There are substance P-like (SPLI) and vasoactive intestinal polypeptide-like (VIPLI) immunoreactive fibers throughout the gland. These fibers are particularly dense and varicose among the interstitial cells. The adjacent pterygopalatine ganglion complex has neuronal somata that exhibit VIPLI and were AChE-positive. This ganglion complex also contains SPLI and catecholamine-positive fibers. In regions of the ganglion, the somata appear surrounded by SPLI varicosities. Surgical ablation of the ganglion eliminated or reduced the VIPLI, AChE and catecholamine staining in the gland. The SPLI was reduced only in some regions. Ablation of the superior cervical ganglion or severance of the radix autonomica resulted in the loss of catecholamine staining in the pterygopalatine ganglion and the gland. Severance of the ophthalmic or infraorbital nerves had no effect on the VIPLI or the SPLI staining pattern in the gland.

Vasoactive intestinal polypeptide and the innervation of the human lacrimal gland

Vasoactive intestinal polypeptide (VIP) is a biologically active neuropeptide found in both the peripheral and the central nervous systems. Previous studies have shown that VIP-like immunoreactive nerves are present in the uveal tissues of the human eye. The distribution of VIP-like immunoreactivity of the human lacrimal gland and sphenopalatine ganglion was studied. A lacy network of VIP-like immunoreactive nerve fibers was found in the lacrimal gland and was predominantly located along the basilar surface of the acinar epithelium and in the interstitial connective tissue of the gland. This pattern of innervation was nearly identical to the distribution of cholinesterase-positive fibers in human lacrimal glands. The VIP-like immunoreactive cell bodies were found throughout the sphenopalatine ganglion obtained at autopsy. The distribution of VIP-like immunoreactive nerves in the human lacrimal gland and sphenopalatine ganglion was generally similar to that described in mammalian and avian systems, although some differences were noted. Vasoactive intestinal polypeptide may represent an important cotransmitter or neuromodulator for the facial parasympathetic nerves that supply the eye and the lacrimal gland.

Iron-containing cells in the honey-bee (Apis mellifera). II. accumulation during development

The development of iron granules in honey-bee tissues was investigated using both anatomical and analytical methods. Iron granules are present only in the trophocytes of post-eclosion adults and have the same elemental composition as those in foraging adults. The granules increase in both size and number during ageing. Iron levels in developing worker honey-bees were measured by proton-induced X-ray emission spectroscopy. The rate of iron accumulation was directly related to iron levels in the diet, and the iron can be obtained from pollen and honey, both major food sources of the bee. In adults, the iron content of the fat body reached a maximum level (2.4 +/− 0.15 micrograms mg-1 tissue), regardless of the amount of iron available for ingestion. Maximal iron levels are reached at the time when honey-bee workers commence foraging behaviour, suggesting that iron granules may play a role in orientation. Alternatively, accumulation of iron in granules may be a method of maintaining iron homeostasis.

Iron-containing cells in the honey-bee (Apis mellifera). I. Adult morphology and physiology

Particulate iron was found within the trophocytes of the fat body of the adult honey-bee. These iron granules differed in their structure and composition from iron granules found in other biological systems. The granules had an average diameter of 0.32 +/− 0.07 micron and were composed of iron, calcium and phosphorus in a non-crystalline arrangement. The granules were apparently randomly distributed within the cytoplasm of the cells, and were not associated with any particular cellular organelle. Electron microscopy revealed the presence of cell junctions between the trophocytes. In tissues treated with colloidal lanthanum, 20-nm gaps were seen between the outer leaflets of the cells forming the cell junction. Physiological studies showed that these cells are electrically coupled, but the coupling ratio is low, as a result of extensive coupling to many cells.

Catecholamine-containing neurons and lymphoid cells in a lacrimal gland of the pigeon

The Harderian gland of birds, a major lacrimal gland, contains a large population of lymphoid cells that produce IgA, a significant component of tears. Using histochemical techniques, we have examined the innervation of the gland. There was an extensive acetylcholine-esterase positive fiber network throughout the gland. However, catecholamine positive fibers were seen mainly associated with peripheral blood vessels and the lymphoid cell population which contained autofluorescent plasma cells. Ultrastructural examination showed that vesicle filled nerve varicosities were often seen near plasma cells and that some of these varicosities reacted positively for catecholamines. These anatomical data suggest that the lymphoid cell population may be affected by the autonomic nervous system.

Conductance and dye permeability of a rectifying electrical synapse

Electrical synapses provide a basis for efficient signal transmission in a wide variety of nervous systems. These synapses are composed of specialized cell-to-cell contacts known as nexuses or gap junctions which mediate the direct transfer of ions and small molecules between adjacent cell interiors by way of intercellular channels embedded in the junctional membrane. The crayfish giant motor synapse (GMS) was the first cell-to-cell junction clearly demonstrated to operate by an electrical mechanism. Current applied to the presynaptic lateral giant (LG) axon or to the neurite of the postsynaptic giant flexor motoneurone (MoG) spreads passively through the synapse into the adjacent neurone. Each GMS behaves like an electrical rectifier: its conductance is high when LG is positive with respect to MoG, and decreases dramatically when the sign of the trans-synaptic voltage is reversed. We have now examined GMS conductance and dye permeability at thoracic and abdominal levels of the crayfish nerve cord. At both levels, values of GMS chord conductance fit a simple Boltzmann model in which the conductance of individual synaptic channels is assumed to be voltage dependent. Moreover, thoracic synapses display higher limiting conductances than do those at an abdominal level, apparently as a result of their larger size. We also find that synapses at both locations are permeable to the fluorescent dye Lucifer yellow, even in conditions where electrical conductance is low. These results provide a framework for understanding the operation and functional limits of rectifying electrical synapses, and illustrate that dye permeability can be associated even with their relatively low conductance condition.

Iron-Containing Cells in the Honey Bee ( Apis mellifera )

Honey bees are sensitive to earth strength magnetic fields and are reported to contain magnetite (Fe3O4) in their abdomens. We report bands of cells around each abdominal segment that contain numerous electron-opaque, iron-containing granules. The iron is principally in the form of hydrous iron oxides.

The shadow response of the cockroach periplaneta americana

We show that the "escape response" (running) of the cockroach Periplaneta americana is interrupted when the insect runs through a shadow. Shadows were cast by holding an opaque plastic sheet so that the cockroach ran beneath it. In control experiments, a similarly positioned clear plastic sheet was ineffective. Removal of the shadow stimulus allowed running to continue. The likelihood that cockroaches would resume running after removal of the shadow stimulus decreased with the time they were allowed to remain in shadow.

Length-tension relation in Limulus striated muscle

Laser diffraction techniques coupled with simultaneous tension measurements were used to determine the length-tension relation in intact, small (0.5-mm thick, 10-mm wide, 20-25-mm long) bundles of a Limulus (horseshoe crab) striated muscle, the telson levator muscle. This muscle differs from the model vertebrate systems in that the thick filaments are not of a constant length, but shorten from 4.9 to approximately 2.0 micrometers as the sarcomeres shorten from 7 to 3 micrometers. In the Limulus muscle, the length-tension relation plateaued to an average maximum tension of 0.34 N/mm2 at a sarcomere length of 6.5 micrometers (Lo) to 8.0 micrometers. In the sarcomere length range from 3.8 to 12.5 micrometers, the muscle developed 50% or more of the maximum tension. When the sarcomere lengths are normalized (expressed as L/Lo) and the Limulus data are compared to those from frog muscle, it is apparent that Limulus muscle develops tension over a relatively greater range of sarcomere lengths.

Changes in thick filament length in Limulus striated muscle

Here we describe the change in thick filament length in striated muscle of Limulus, the horseshoe crab. Long thick filaments (4.0 microns) are isolated from living, unstimulated Limulus striated muscle while those isolated from either electrically or K+-stimulated fibers are significantly shorter (3.1 microns) (P less than 0.001). Filaments isolated from muscle glycerinated at long sarcomere lengths are long (4.4 microns) while those isolated from muscle glycerinated at short sarcomere lengths are short (2.9 microns) and the difference is significant (P less than 0.001). Thin filaments are 2.4 microns in length. The shortening of thick filaments is related to the wide range of sarcomere lengths exhibited by Limulus telson striated muscle.

Paramyosin in invertebrate muscles. II. Content in relation to structure and function

By quantitative sodium dodecyl sulfate-polyacrylamide gel electrophoresis, paramyosin:myosin heavy chain molecular ratios were calculated for three molluscan muscles:Aequipecten striated adductor, Mercenaria opaque adductor, and Mytilus anterior byssus retractor; and four arthropodan muscles:Limulus telson, Homarus slow claw. Balanus scutal depressor, and Lethocerus air tube retractor. These ratios correlate positively with both thick filament dimensions and maximum active tension development in these tissues. The role of paramyosin in these muscles is discussed with respect to the following characteristics: force development, "catch," and extreme reversible changes in length.

The tiered retina of Dytiscus: a new type of compound eye

The retina of Dytiscus is tiered, with proximal and distal layers of receptors at different levels. Photoreceptor units of the proximal retina of the eye of Dytiscus have fields of view so wide that light entering by any facet is able to excite a receptor belonging virtually to any ommatidium in the light- or dark-adapted eye. Although the distal rhabdomeres may have small fields of view, the proximal retina is clearly not adapted for perception of form or movement. The sensitivity of proximal retinula units is compatible with the observations that light passing through many facets sums upon them and that their rhabdomeres are relatively large and jointly occupy the whole cross-sectional area of the eye. The lack of polarized light sensitivity of the proximal retinula units can be attributed to electrical coupling between cells with tubules oriented in different directions within each ommatidium.

Recording of electrical activity and movement from legs of walking crabs

Recordings of electrical activity were made from the leg muscles of walking crabs. In some, the movement of leg joints was monitored by means of a small transducer. Regular patterns of electrical activity appeared during walking. The motor axons of antagonistic muscles were frequently active in reciprocating bursts. In muscles innervated by two motor axons, "fast" and "slow", the latter axon was normally the more active. The inhibitory axons of certain muscles were apparently sometimes fired in a manner which could permit facilitation at the motor nerve endings without tension development in the muscle.