Ultrastructural cytochemistry of biogenic amines in nervous tissue: methodologic improvements

A new fixation method has been developed for localizing biogenic amines in nervous tissue. The method is a modification of the chromaffin reaction in which all fixation steps are buffered with mixtures of sodium chromate and potassium dichromate. In this way the fixation and cytochemical reaction are carried out almost simultaneously. Using the rat vas deferens as a model tissue, it was found that the preservation of electron dense (chromaffin) cores in the vesicles of adrenergic nerve terminals depended on several factors: a short primary fixation using low concentrations of aldehydes, the presence of the chromate/dichromate buffer during all fixation steps and, finally, a long incubation period in a slightly acidic (pH 6.0) solution of this buffer before postfixation in osmium tetroxide. Using this method it was possible to identify not only small and large dense-cored vesicles as storage sites for amines but also a tubular reticulum (neuronal endoplasmic reticulum), the latter especially in nerve terminals of mesenteric arteries and iris. Biogenic amines were also visualized in sympathetic ganglion cells and in the central nervous system e.g., supraependymal nerve terminals, tissues that up to now proved the most difficult in terms of amine localization. In all the tissues examined the cytochemical reaction was highly selective and present in well preserved tissue, which is a significant advance over previously available techniques. It therefore offers new opportunities for further studies on the role of biogenic amines as neurotransmitters.

Characteristic multiorgan pathology of cystic fibrosis in a long-living cystic fibrosis transmembrane regulator knockout murine model

The lack of an appropriate animal model with multiorgan pathology characteristic of the human form of cystic fibrosis has hampered our understanding of the pathobiology of the disease. We evaluated multiple organs of congenic C57BL/6J cystic fibrosis transmembrane regulator (Cftr)(-/-) and Cftr(+/+) mice maintained from weaning on a liquid diet then sacrificed between 1 and 24 months of age. The lungs of the Cftr(-/-) animals showed patchy alveolar overdistention, interstitial thickening, and fibrosis, with progression up to 6 months of age. The proximal and distal airway surface was encased with mucus-like material but lacked overt evidence of chronic bacterial infections or inflammation. All Cftr(-/-) animals showed progressive liver disease, with hepatosteatosis, focal cholangitis, inspissated secretions, and bile duct proliferation; after 1 year of age there was progression to focal biliary cirrhosis. The intercalated, intralobular and interlobular ducts and acinar lumina of the exocrine pancreas, the parotid and submaxillary glands of the Cftr(-/-) animals were dilated and filled with inspissated material, as well as mild inflammation and acinar cell drop out. Quantitative measurements of the pancreas showed significant acinar atrophy and increased acinar volume in comparison with age-matched Cftr(+/+) littermates. The ileal lumen and crypts were filled with adherent fibrillar material. After 3 months of age the vas deferens of the Cftr(-/-) animals could not be identified. None of the aforementioned pathological changes were observed in the Cftr(+/+) littermates fed the same liquid diet. We show, for the first time, that long-lived C578L/6J Cftr(-/-) mice develop manifestations of cystic fibrosis-like disease in all pathologically affected organs in the human form of cystic fibrosis.

Nature's ingenuity: bypassing the classical secretory route via apocrine secretion

Although it has been suggested that epithelial cells of the male reproductive system are involved in apocrine secretion, this method of secretion is not fully understood. In the present study, apocrine secretion was investigated in epithelial principal cells lining the epididymis and vas deferens (VD) of adult mice. The tissues were fixed by cardiac vascular perfusion with glutaraldehyde for routine electron microscope (EM) analysis and Bouin's fixative for light microscope (LM) immunocytochemistry to access functional roles. In the epididymis and VD, the apex of principal cells revealed protrusions of cytoplasm referred to as apical blebs (ABs). The latter contained solely numerous free ribosomes, 20 nm vesicles and few ER cisternae, suggesting segregation of their contents. While some ABs displayed wide areas of contact with the apical principal cell cytoplasm, others showed thin stalk-like attachment points as well as fissures at the junction of the two areas. Together with images of ABs and their contents deep in the lumen, it is suggested that ABs detach from principal cells whereupon they breakdown to release their contents therein. As ABs of the epididymis were immunoreactive for glutathione-S-transferases (GSTs) and ubiquitin, it is proposed that these proteins are synthesized on free ribosomes in ABs and that apocrine secretion represents the manner whereby they enter the lumen to effectively protect sperm from free radical injury and ubiquitinate proteins for degradation, respectively. ABs of the VD were immunoreactive for 3beta-HSD, suggesting that they are also capable of synthesis of steroids with their release via apocrine secretion. Taken together the data provide evidence for apocrine secretion in the adult mouse epididymis and VD that could play important roles in relation to sperm maturation, protection and viability.

Inhibition by nucleotides acting at presynaptic P2-receptors of sympathetic neuro-effector transmission in the mouse isolated vas deferens

Effects of nucleotides and nucleosides on smooth muscle tension and the release of previously stored [3H]-noradrenaline were studied in the mouse isolated vas deferens. The tissue was stimulated twice by 20 electrical field pulses delivered at 2 Hz (S1, S2). alpha,beta-Methylene-ATP, ATP gamma S, ATP and UTP elicited contraction, with potency decreasing in that order; there was no contractile response to adenosine (up to 100 mumol/l) and uridine (up to 1 mmol/l). The electrically evoked overflow of tritium was reduced by the drugs in the following order of potency: ATP gamma S greater than ATP = adenosine greater than UTP; alpha,beta-methylene-ATP (up to 10 mumol/l) and uridine (up to 1 mmol/l) did not significantly change the evoked overflow. 8-(p-Sulphophenyl)theophylline did not alter the contractile responses to the nucleotides; it prevented the overflow-inhibiting effect of adenosine and reduced that of UTP; the overflow-inhibiting effects of ATP and ATP gamma S were not significantly attenuated. After prolonged exposure to alpha,beta-methylene-ATP, all contractile nucleotide effects were abolished; in contrast, the depression by adenosine and the nucleotides of the evoked overflow of tritium persisted. None of the effects was changed by indometacin, yohimbine or reactive blue 2. It is concluded that ATP, ATP gamma S, alpha,beta-methylene-ATP and UTP produce contraction of the vas deferens by activation of P2x-receptors. Moreover, the nucleotides inhibit per se the release of [3H]-noradrenaline (and presumably the co-transmitter mixture of noradrenaline and ATP); the effect of ATP is not, or only to a small extent, due to breakdown to adenosine. The presynaptic site of action of the purine nucleotides is a P2-receptor which differs from the P2x-receptor and may be a reactive blue 2-resistant "P2y-like" receptor.

Contractile properties and proteins of smooth muscles of a calponin knockout mouse

The role of h1-calponin in regulating the contractile properties of smooth muscle was investigated in bladder and vas deferens of mice carrying a targeted mutation in both alleles designed to inactivate the basic calponin gene. These calponin knockout (KO) mice displayed no detectable h1-calponin in their smooth muscles. The amplitudes of Ca2+ sensitization, force and Ca2+ sensitivity were not significantly different in permeabilized smooth muscle of KO compared with wild-type (WT) mice, nor were the delays in onset and half-times of Ca2+ sensitization, initiated by flash photolysis of caged GTPgammaS, different. The unloaded shortening velocity (Vus) of thiophosphorylated fibres was significantly (P<0.05) faster in the smooth muscle of KO than WT animals, but could be slowed by exogenous calponin to approximate WT levels; the concentration dependence of exogenous calponin slowing of Vus was proportional to its actomyosin binding in situ. Actin expression was reduced by 25-50%, relative to that of myosin heavy chain, in smooth muscle of KO mice, without any change in the relative distribution of the actin isoforms. We conclude that the faster Vus of smooth muscle of the KO mouse is consistent with, but does not prove without further study, physiological regulation of the crossbridge cycle by calponin. Our results show no detectable role of calponin in the signal transduction of the Ca2+-sensitization pathways in smooth muscle.

Characterization of alpha 1 D-adrenoceptor subtype in rat myocardium, aorta and other tissues

1. This study was done to characterize the functional role of alpha 1D-adrenoceptors in rat myocardium, aorta, spleen, vas deferens and prostate by use of the selective antagonist BMY 7378. 2. BMY 7378 inhibited [3H]-prazosin binding to aortic membranes with a potency (pKi 9.8 +/- 0.40) approximately 100 fold higher than in right ventricular membranes (pKi 7.47 +/- 0.11) and approximately 1,000 fold higher than that in plasma membranes of the prostate (pKi 6.62 +/- 0.39), vas deferens (pKi 6.67 +/- 0.15), salivary gland (pKi 6.46 +/- 0.38) and liver (6.58 +/- 0.06). 3. BMY 7378 antagonized the positive inotropic effects of phenylephrine (in the presence of 1 microM propranolol) on right ventricles (pA2 7.0 +/- 0.11), left atria (pKB 7.04 +/- 0.18) and papillary muscles (pKB 6.9 +/- 0.1) and inhibited phenylephrine-induced increase in inositol phosphates. 4. BMY 7378 was approximately 100 fold more potent as an antagonist of phenylephrine on aortic strips (pA2 9.0 +/- 0.13) than on vas deferens (pKB 7.17 +/- 0.08) and spleen (pKB 7.16 +/- 0.21); it was ineffective on the prostate. 5. Chloroethylclonidine suppressed the maximal effects of phenylephrine on spleen; 5-methylurapidil antagonized the effects of phenylephrine on aortic strips (pA2 7.98 +/- 0.08), vas deferens (pKB 8.89 +/- 0.07) and prostate (pKB 8.85 +/- 0.21). 6. BMY 7378 caused a dose (0.1-100 nmol kg-1)-dependent decrease in mean blood pressure of urethane-anaesthetized rats and its hypotensive efficacy was equal to that of hexamethonium. 7. The data suggest that alpha 1D-adrenoceptors play a significant role in rat aorta, a minor role in the heart, vas deferens and spleen and virtually no role in the prostate.

Noninvasive measurement of hydrogen and potassium ion flux from single cells and epithelial structures

This review introduces new developments in a technique for measuring the movement of ions across the plasma membrane. With the use of a self-referencing ion-selective (Seris) probe, transport mechanisms can be studied on a variety of preparations ranging from tissues to single cells. In this paper we illustrate this versatility with examples from the vas deferens and inner ear epithelium to large and small single cells represented by mouse single-cell embryos and rat microglia. Potassium and hydrogen ion fluxes are studied and pharmacological manipulation of the signals are reported. The strengths of the self-referencing technique are reviewed with regard to biological applications, and the expansion of self-referencing probes to include electrochemical and enzyme-based sensors is discussed.

Investigation of the actions of PPADS, a novel P2x-purinoceptor antagonist, in the guinea-pig isolated vas deferens

1. Pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) was investigated for its ability to act as an antagonist at P2x-purinoceptors which mediate neurogenic excitatory junction potentials (e.j.ps) and contractions in the guinea-pig isolated vas deferens. 2. PPADS (10(-7) M) caused a small potentiation of the phasic, predominantly purinergic component of contractions evoked by symapthetic nerve stimulation, but higher concentrations of PPADS (3 x 10(-6)-3 x 10(-5) M) elicited a substantial and significant concentration-dependent inhibition. In contrast, over the same concentration-range, PPADS had no effect on the tonic, predominantly noradrenergic phase. 3 PPADS (3 x 10(-5) M) also inhibited contractile responses to exogenous alpha,beta-methyleneATP (10(-8)-10(-3)M), a P2x-purinoceptor agonist, without affecting the responses to exogenous noradrenaline (10(-8)-10(-3) M), carbachol (10(-5) M) or histamine (10(-4) M). 4. PPADS (10(-7)-3 x 10(-5) M) produced a concentration-dependent reduction in e.j.p. magnitude and resting membrane potential. The maximum effect was seen at 10(-5) M PPADS, which reduced e.j.p. magnitude from 13.7 +/- 0.6 mV (n = 12) to 1.8 +/- 0.7 mV (n = 12) and membrane potential from -64.8 +/- 0.6 mV (n = 51) to -55.0 +/- 1.8 mV (n = 12). 5. The PPADS-induced depolarization was not inhibited by the P2x-purinoceptor antagonist, suramin (10(-4) M). This indicates that the depolarization was not due to an agonist action of PPADS at P2x-purinoceptors. 6. The results support the proposal that PPADS is a selective antagonist at P2x purinoceptors as opposed to non-P2-purinoceptors in the guinea-pig vas deferens, but its ability to cause membrane depolarization independently of P2x-purinoceptors and also, at a low concentration, to potentiate the phasic component of the neurogenic contraction indicates that it has other actions.

Light and electron microscope demonstration of VIP- and enkephalin-immunoreactive nerves in the human male genitourinary tract

Vasoactive intestinal polypeptide (VIP) and enkephalins were demonstrated in the nerves of the human male urogenital tract by light and electron microscope immunohistochemical techniques. Nerves containing immunoreactivity to VIP were more numerous than enkephalin-immunoreactive nerves. Both VIP- and enkephalin-immunoreactive nerves were detected in the vas deferens, prostate, seminal vesicles, and urinary bladder. In the kidney, testis, and epididymis no immunoreactive nerves could be demonstrated. By electron microscope both types of immunoreactivities were localized to the large granular vesicles of nerve terminals. VIP-immunoreactive nerves were mostly found subepithelially, whereas enkephalin-immunoreactive nerves were mainly related to smooth muscle cells. The possible functions of these peptide-containing nerves are discussed.

Localization of ryanodine receptors in smooth muscle

The ryanodine receptor (RyR) in aortic and vas deferens smooth muscle was localized using immunofluorescence confocal microscopy and immunoelectron microscopy. Indirect immunofluorescent labeling of aortic smooth muscle with anti-RyR antibodies showed a patchy network-like staining pattern throughout the cell cytoplasm, excluding nuclei, in aortic smooth muscle and localized predominantly to the cell periphery in the vas deferens. This distribution is consistent with that of the sarcoplasmic reticulum (SR) network, as demonstrated by electron micrographs of osmium ferrocyanide-stained SR in the two smooth muscles. Immunoelectron microscopy of vas deferens smooth muscle showed anti-RyR antibodies localized to both the sparse central and predominant peripheral SR elements. We conclude that RyR-Ca2+-release channels are present in both the peripheral and central SR in aortic and vas deferens smooth muscle. This distribution is consistent with the possibility that both regions are release sites, as indicated by results of electron probe analysis, which show a decrease in the Ca2+ content of both peripheral and internal SR in stimulated smooth muscles. The complex distribution of inositol 1,4,5-trisphosphate and ryanodine receptors (present study) is compatible with their proposed roles as agonist-induced Ca2+-release channels and origins of Ca2+ sparks, Ca2+ oscillations, and Ca2+ waves.

New views of smooth muscle structure using freezing, deep-etching and rotary shadowing

Freezing, deep-etching and rotary shadowing techniques have been applied to study smooth muscle ultrastructure. The results show some new aspects of intracellular and extracellular connections, interior views of the sarcoplasmic reticulum showing a luminal content, coated pits and vesicles, contractile filaments and other organelles in smooth muscle.

P2-purinoceptor antagonists discriminate three contraction-mediating receptors for ATP in rat vas deferens

The sites of action at which ATP elicits contraction of the rat vas deferens were studied by means of the P2-purinoceptor antagonists pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (iso-PPADS), suramin and reactive blue 2. Increasing concentrations of iso-PPADS (up to 1 mM), suramin (up to 1 mM) and reactive blue 2 (up to 320 microM) reduced and eventually abolished contractions elicited by the P2x-purinoceptor-selective agonist alpha,beta-methylene ATP 3 microM with IC50 values of 2.1, 10.1 and 27.0 microM, respectively. In contrast, iso-PPADS and suramin caused only a partial inhibition of contractions elicited by ATP 1 mM, maximal reduction by about 40%, IC50 values 1.3 and 5.0 microM, respectively; reactive blue 2 did not change ATP-induced contractions. In tissues exposed to iso-PPADS 320 microM throughout, increasing concentrations of reactive blue 2 or suramin decreased contractions elicited by ATP 1 mM, IC50 values 2.6 and 14.5 microM, respectively. In tissues exposed to suramin 320 microM throughout, increasing concentrations of iso-PPADS decreased contractions elicited by ATP 1 mM, IC50 37.9 microM, whereas reactive blue 2 slightly enhanced these contractions. In tissues exposed to reactive blue 2 100 microM throughout, increasing concentrations of iso-PPADS reduced contractions elicited by ATP 1 mM, IC50 26.6 microM, whereas suramin caused no change. Pre-exposure to alpha,beta-methylene ATP 1 microM to desensitize P2x-purinoceptors reduced the response to ATP 1 mM by 91% in otherwise untreated tissues, but did not reduce the response to ATP 1 mM in tissues exposed throughout to iso-PPADS 320 microM, suramin 320 microM or reactive blue 2 100 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

Different neuropeptide Y receptor subtypes in rat and rabbit vas deferens

Prejunctional neuropeptide Y (NPY) receptors that inhibit the contractions evoked in rat and rabbit vas deferens by field stimulation were investigated by using NPY, [Leu31,Pro34]NPY and the fragments, NPY-(13-36) and NPY-(18-36). NPY, and especially [Leu31,Pro34]NPY, were more potent agonists on the twitch response of the rabbit vas deferens. In contrast the NPY C-terminal fragments, NPY-(13-36) and NPY-(18-36), inhibited the twitch response at lower concentrations in the rat vas deferens. These results indicate that distinct NPY receptor subtypes mediate the biological effect in these two tissues. We suggest that prejunctional receptors in the rat vas deferens are of the Y2-subtype and those in rabbit vas deferens of the Y1-subtype.

P2X receptor immunoreactivity in the male genital organs of the rat

The distribution of ATP ionotropic P2X receptors in the genital organs of the male rat has been investigated with immunohistochemical techniques using specific antibodies to P2X1-7 receptors. In the excretory ducts of the testis (ductus epididymidis, vas deferens and its associated seminal vesicles), the major signals were seen with antibodies to P2X1 and P2X2 in the membranes of the smooth muscle layer, suggesting that these receptors are involved in the process of sperm transport and ejaculation. In the penis body, strong P2X1 and weaker P2X2 immunoreactivity was seen in the smooth muscle of blood vessels and the corpus cavernosum, suggesting a participation in the detumescence process. P2X5 immunoreactivity, a marker for differentiating cells in stratified squamous epithelia, was observed in the epithelia of the terminal urethra, the "horny spur" (spine-studded epithelium of the glans) and the inner surface of the prepuce. Antibodies to P2X3 reacted with nerve fibres in the adventitia of vas deferens, and the P2X6 receptor was localised in the basal lamina of the epithelium. In the prostate, there was immunostaining of the smooth muscle between the tubules with antibody for P2X1, but not with P2X2; P2X3 immunostaining of nerves and strong P2X7 immunostaining of the glandular epithelium of the prostate were also present.

Evidence for the coexistence and co-release of [Met]enkephalin and noradrenaline from sympathetic nerves of the bovine vas deferens

The localization and neurosecretion of methionine-enkephalin was studied in sympathetic nerves of the bovine vas deferens. Immunostaining showed methionine-enkephalin-like immunoreactivity in a network of varicose nerve fibres in the smooth muscle layers of the vas deferens. When vas deferens homogenates were subjected to differential and sucrose density gradient centrifugation, methionine-enkephalin was found to parallel the distribution of noradrenaline in the more dense region of the gradient, where "heavy" or large dense-cored vesicles are present. Electron microscopic immunochemistry confirmed this finding and showed methionine-enkephalin-like immunoreactivity in large dense-cored vesicles. The release of methionine-enkephalin upon electrical stimulation was studied in superfusion experiments. The methionine-enkephalin secretion was shown to be Ca2+-dependent and was inhibited by adding the adrenergic neuron blocking drug guanethidine to the superfusion medium. We conclude that in the bovine vas deferens methionine-enkephalin is only present in large dense-cored vesicles of adrenergic neurons and that the peptide is released from these vesicles together with noradrenaline by a Ca2+-dependent mechanism.

Region-specific inhibition of prostatic epithelial bud formation in the urogenital sinus of C57BL/6 mice exposed in utero to 2,3,7,8-tetrachlorodibenzo-p-dioxin

In utero 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure causes abnormal ventral, dorsolateral, and anterior prostate development in wild-type but not aryl hydrocarbon receptor (AhR) null mutant C57BL/6 mice. Experiments have now been conducted to test the hypothesis that TCDD causes an AhR-dependent inhibition of the earliest visible stage of prostate development, the formation of prostatic buds by urogenital sinus (UGS) epithelium. A novel method for viewing budding was developed that uses scanning electron microscopy of isolated UGS epithelium instead of three-dimensional reconstruction of serial histological sections of intact UGS. In the initial experiment, the time course for prostatic epithelial bud formation in vehicle- and TCDD-exposed wild-type C57BL/6J mice was determined. A single maternal dose of TCDD (5 mug/kg) on gestation day 13 delayed the appearance of dorsal, lateral, and anterior buds by about one day, reduced dorsolateral bud number, and prevented ventral buds from forming. No such effects were seen in TCDD-exposed AhR null mutant fetuses, while AhR null mutation, alone, had no detectable effect on budding. Treatment of wild-type dams with sufficient 5alpha-dihydrotestosterone (DHT) to masculinize female fetuses failed to protect against the inhibition of budding caused by TCDD. These results demonstrate that in utero TCDD exposure causes an AhR-dependent inhibition of prostatic epithelial bud formation commensurate with its inhibitory effects on ventral and dorsolateral prostate development, and that the inhibition of budding is not due to insufficient DHT. Inhibited bud formation appears to be the primary cause of abnormal prostate development in TCDD-exposed mice.

Melatonin receptors in peripheral tissues: a new area of melatonin research

Melatonin is synthesized and secreted by pineal gland, retina, harderian gland, lacrimal gland, and gut. It is a lipid-soluble molecule with ubiquitous distribution and multifarious functions. Thus, along with the better established sites of melatonin action, such as brain, retina, and pituitary, direct melatonin actions on other peripheral tissues should also be considered. The presence of melatonin receptors in peripheral tissues was rightfully hypothesized. Earlier studies on melatonin receptors had limited success. The advent of 2-[125I]iodomelatonin, a labelled melatonin agonist with a specific activity as high as 2,200 Ci/mmol, has allowed the studies of melatonin receptors with picomolar affinity and femtomolar density. Putative melatonin receptors demonstrated by autoradiography and/or radioreceptor assay in gut, kidney, lung, heart, vas deferens, and blood vessels are discussed.

Estrogen receptor in the ductuli efferentes, epididymis, and testis of rhesus and cynomolgus macaques

We obtained the testes, ductuli efferentes, and epididymides from adult rhesus and cynomolgus macaques and examined these tissues for estrogen receptors (ER) with immunocytochemistry (ICC) and a sucrose gradient assay. Both techniques employed monoclonal antibodies prepared against ER, and both showed that high concentrations of ER were present OFFy in the ductuli efferentes. Moreover, all specific staining was confined to the nuclei of the nonciliated, absorptive epithelial cells. The quantity of salt-extractable ER in the ductuli efferentes (834 +/- 161 [SEM] fmol/mg DNA [n = 8]) did not differ significantly from the amounts measured with the identical assay in oviducts and endometrium of estrogenized female macaques. Testes and epididymides of macaques had no specific staining by ICC and barely detectable amounts by biochemical analysis (7 +/- 4 [n = 3], 8 +/- 2 [n = 5], 33 +/- 16 [n = 3], and 6 +/- 3 [n = 8] fmol/mg DNA for testis and caput, corpus, and cauda epididymis, respectively). The functional significance of the high levels of ER in the ductuli efferentes of macaques remains to be determined.

Characterization of somatostatin receptors in guinea-pig isolated ileum, vas deferens and right atrium

1. Somatostatin14 (SS14) inhibits neurogenically mediated contractile responses in guinea-pig ileum and vas deferens and exerts a direct negative inotropic action in guinea-pig spontaneously beating right atrium. In this study, the receptors mediating these inhibitory effects have been characterized by comparing the potencies of several cyclic somatostatin analogues. 2. In the guinea-pig ileum, SS14, somatostatin28 (SS28), somatostatin25 (SS25) and several smaller cyclic somatostatin analogues including octreotide, angiopeptin and CGP 23996, inhibited neurogenically mediated contractile responses, each being of similar potency. 3. In contrast, in the guinea-pig vas deferens and right atrium, SS28 was about 30 times more potent than SS14. However, although angiopeptin was nearly as potent as SS14 as an agonist in the vas deferens, in guinea-pig atrium angiopeptin had low intrinsic activity and antagonized the negative inotropic action of both SS14 and SS28 (pKB values of 7.4 and 7.2, respectively). CGP 23996 was 2-7 times weaker than SS14 in guinea-pig vas deferens and atria. 4. Phosphoramidon (1 microM) and amastatin (10 microM) did not influence the potency of SS14 or SS28 in either the guinea-pig ileum or right atrium. In the guinea-pig vas deferens, phosphoramidon and amastatin did not affect the potency of SS28, but enhanced the potency of SS14 about 5 fold. Despite the presence of phosphoramidon and amastatin, SS28 was still more potent than SS14 in the vas deferens. 5. The putative somatostatin receptor blocking drug, cyclo(7-aminoheptanoyl Phe-D-Trp-Lys-Thr[Brl]) (CPP; 1 microM), did not antagonize the effects of either SS14 or SS28 in ileum, vas deferens or atrial preparations. 6. Somatostatin14 did not modify the contractile action of carbachol or alpha,beta-methylene ATP in the ileum and vas deferens respectively, suggesting that the site of the inhibitory effects on neurogenically mediated contractile responses in both preparations was pre-junctional. Consistent with this conclusion was the observation that the inhibitory effect of SS14 was markedly and inversely related to the external Ca2+concentration. The inhibitory effect of SS14 in guinea-pig atrium was only partly dependent on the external Ca2+ concentration.7. The somatostatin receptors mediating the inhibitory effect of SS14 in the ileum and vas deferens can be distinguished by the differential relative potencies of SS14 and SS28. In the former, SS14 and SS28 have similar potency whilst in the latter SS28 is much more potent. In this respect, the somatostatin receptor mediating negative inotropy in the guinea-pig right atrium appears similar to that identified in the vas deferens.8. We suggest that the somatostatin receptor mediating inhibition of neurogenic contraction in the ileum is similar to the recently cloned SSTR2 receptor. In contrast, the somatostatin receptor mediating negative inotropy in the atrium and inhibition of neurotransmission in the vas deferens appears similar to the SSTR4 receptor which recognises SS28 with higher affinity than SS14.

Scanning electron microscopic studies of tissue elastin components exposed by a KOH-collagenase or simple KOH digestion method

A KOH-collagenase or simple KOH digestion method was employed for scanning electron microscope (SEM) studies of elastin components in the rat thoracic aorta, mouse urinary bladder, and human ductus deferens. Immersion of the fixed tissues in 30% KOH solution for 8-10 min at 60 degrees C, with or without subsequent collagenase treatment, successfully removed collagen fibrils and basal laminae while leaving cellular and elastin elements unchanged at their original shapes and locations. The internal elastic lamina of the rat aorta appeared as a solid sheet formed by elastin fibrils 0.1-0.2 microns thick, while the medial elastic laminae were more fibrous because of the presence of numerous fine elastin fibers on their surface. Adventitial elastin fibers were of a cord-like shape complicatedly entangled among the adventitial fibroblasts. These fibers were seen as bundles of fibrils 0.1-0.2 microns thick. In the mouse urinary bladder, elastin formed a thin lace-like sheet just beneath the serosal covering of the peritoneum. This sheet was composed of small bundles of fine (0.1-0.2 microns thick) fibrils. The external connective tissue of the human ductus deferens was made up of a three-dimensional loose network of elastin fibers 0.1-1.5 microns thick. These fibers also appeared as bundles of the fine fibrils. These findings indicate that the present method is useful for SEM studies of elastin as well as cellular components in various tissues and organs. This study also maintains that elastin fibers and laminae are basically composed of unit fibrils of 0.1-0.2 microns thickness. As elastin components are arranged specific to individual organs and tissues, it is reasonable that these components are concerned in the characteristic mechanical properties of these tissues and organs.

Ultrastructural studies of spermatozoa and the epithelial lining of the epididymis and vas deferens in rats treated with gossypol

This study was undertaken to determine the effects at early time intervals of gossypol on sperm motility and on the ultrastructure of rat epididymal and vasal sperm and epididymal and vasal epithelium. Rats were treated by gavage with 20 or 30 mg/kg/day of gossypol for 7 weeks; control animals were unfed or received the vehicle alone. The results confirm and extend earlier observations demonstrating that epididymal sperm of gossypol-treated rats exhibit distinct ultrastructural changes under the experimental conditions employed. The severity and frequency of the degenerative changes appear to increase with dose and duration of treatment. Striking ultrastructural defects can be seen as early as 3 weeks after 20 mg/kg/day of gossypol. By the fifth week of either 20 or 30 mg/kg/day of gossypol, significant damage to virtually all sperm flagella is observed throughout the epididymal duct of all treated rats. The initial and predominant defect is degeneration of the midpiece mitochondria but additional flagellar defects are described in detail. Not surprisingly, caudal spermatozoa are totally immotile by the fifth week. The ultrastructure of the epididymal and vasal epithelium is not affected by gossypol.

Neurosecretory vesicles can be hybrids of synaptic vesicles and secretory granules

We have investigated the relationship of the so-called small dense core vesicle (SDCV), the major catecholamine-containing neurosecretory vesicle of sympathetic neurons, to synaptic vesicles containing classic neurotransmitters and secretory granules containing neuropeptides. SDCVs contain membrane proteins characteristic of synaptic vesicles such as synaptophysin and synaptoporin. However, SDCVs also contain membrane proteins characteristic of certain secretory granules like the vesicular monoamine transporter and the membrane-bound form of dopamine beta-hydroxylase. In neurites of sympathetic neurons, synaptophysin and dopamine beta-hydroxylase are found in distinct vesicles, consistent with their transport from the trans-Golgi network to the site of SDCV formation in constitutive secretory vesicles and secretory granules, respectively. Hence, SDCVs constitute a distinct type of neurosecretory vesicle that is a hybrid of the synaptic vesicle and the secretory granule membranes and that originates from the contribution of both the constitutive and the regulated pathway of protein secretion.