Oxytocinergic innervation of autonomic nuclei controlling penile erection in the rat

In the rat, spinal autonomic neurons controlling penile erection receive descending pathways that modulate their activity. The paraventricular nucleus of the hypothalamus contributes oxytocinergic fibers to the dorsal horn and preganglionic sympathetic and parasympathetic cell columns. We used retrograde tracing techniques with pseudorabies virus combined with immunohistochemistry against oxytocin and radioligand binding detection of oxytocinergic receptors to evidence the oxytocinergic innervation of thoracolumbar and lumbosacral spinal neurons controlling penile erection. Spinal neurons labelled with pseudo-rabies virus transsynaptically transported from the corpus cavernosum were present in the intermediolateral cell column and the dorsal gray commissure of the thoracolumbar and lumbosacral spinal cord. Confocal laser scanning microscopic observation of the same preparations revealed close appositions between oxytocinergic varicosities and pseudorabies virus-infected neurons, suggesting strongly the presence of synaptic contacts. Electron microscopy confirmed this hypothesis. Oxytocin binding sites were present in the superficial layers of the dorsal horn, the dorsal gray commissure and the intermediolateral cell column in both the thoracolumbar and lumbosacral segments. In rats, stimulation of the paraventricular nucleus induces penile erection, but the link between the nucleus and penile innervation remains unknown. Our findings support the hypothesis that oxytocin, released by descending paraventriculo-spinal pathways, activates proerectile spinal neurons.

In situ detection of lipid peroxidation by-products as markers of renal ischemia injuries in rat kidneys

PURPOSE

Lipid peroxidation is an autocatalytic mechanism leading to oxidative destruction of cellular membranes. In renal transplantation, this mechanism is triggered by ischemia/reperfusion and may be of relevance in graft failure.

MATERIALS AND METHODS

Using specific antibodies directed against malondialdehyde (MDA) and 4-hydroxynonenal (HNE) adducts, major aldehydic metabolites of lipid peroxidation, we investigated, in situ, by means of an immunohistochemical procedure, the occurrence of lipid peroxidation during different warm ischemic periods of 0, 15, 30, 45 and 60 minutes in rat kidneys prior to reperfusion. The same experiments included followup of the rats after nephrectomy and reperfusion for 10 days.

RESULTS

We observed superficial and deep cortex immunostaining with both antibodies against MDA and HNE after 30 minutes of warm ischemia. This immunostaining was observed in the absence of any histological lesions, as assessed by routine staining. After 45 and 60 minutes of warm ischemia, lipid peroxidation byproducts were detected both in the cortex and in the medulla, which is associated with 33% and 66% of rat deaths respectively.

CONCLUSIONS

This study confirms the involvement of the lipid peroxidation process in kidney damage during anoxia before reperfusion, and its extension to the whole organ. Lipid peroxidation byproducts were detectable in warm ischemic kidney, and the presence of medulla immunostaining was associated with the animals' death. Lipid peroxidation immunostaining might thus be useful as a sensitive tool to detect ischemic damage after warm ischemia prior to reperfusion, as well as in the decision to carry out kidney transplantation in humans.

[Organ procurement from cardiac arrest donors: outcome of kidney grafts and recommendations]

OBJECTIVES

To compare literature data with results obtained with organs procured from donors who died from cardiac arrest and to make proposals for this mode of organ procurement in France.

METHODS

Over the last 10 years, 10 organ donors (2%) among a series of 486 donors in a state of brain death, had died of cardiac arrest. The arrest were perfused with double-balloon catheters. The outcome of the subsequent kidney grafts was compared with data in the literature.

RESULTS

Fifteen of the 18 kidneys from cardiac arrest donors were functioning 1 month after implantation compared with 17 of the 20 kidneys from braindeath donors with beating hearts. The rate of acute tubular necrosis was 55% in the cardiac arrest kidneys and 40% in the beating-heart kidneys. Serum creatinine at 1 yeart was 145 +/- 69 mumol/l 17 +/- 29 mumol/l respectively.

DISCUSSION

These results and those reported in the literature demonstrate that kidney procurement from cardiac arrest donors is feasible. If intensive care and surgery units are well organized, this type of organ procurement could provide a larger number of organs for transplantation. Emergency teams must be available for preparing and transferring the organs.

Expression patterns of the JEM-1 gene in normal and tumor cells: ubiquity contrasting with a faint, but retinoid-induced, mRNA expression in promyelocytic NB4 cells

The JEM-1 gene, recently identified in acute promyelocytic leukemia (APL) cells, codes for a novel nuclear factor (Duprez et al Oncogene 1997; 14: 1563-1570). JEM-1 is kept silent in the APL cell line NB4, but up-regulated (3 kb transcript) during cell maturation. Here, we show that retinoic acid (RA)-induced JEM-1 expression is biphasic (peaks at 6 h and 48 h) and associated with the later stages of maturation. Retinoids, which cooperates with cAMP to induce maturation, also cooperates with cAMP to up-regulate JEM-1, either in maturation-responsive NB4 cells or in NB4-R1 resistant subclones. APL patients showed a low, yet variable, level of JEM-1 mRNA in bone marrow. RA treatment induced an increase in the level of JEM-1 mRNA, as detected by a semi-quantitative PCR. This increase can result from both gene up-regulation or replacement of leukemia cells by differentiated ones. Analysis of JEM-1 expression patterns in normal and tumor cells revealed that JEM-1 expression was ubiquitous. Cell lines derived from monocytic and erythroid leukemias, expressed low and high amounts of JEM-1 mRNA, respectively. Using a JEM cDNA probe, distinct profiles of expression and different transcript sizes (4 kb, 3 kb and 2 kb) were also identified in tumour and normal non-hematopoietic tissues, while interestingly only the 3kb transcript was up-regulated in NB4 cells. This work identifies JEM-1 as a novel ubiquitous gene whose expression is low in APL cells, but can be restored by RA treatment, concomitant with cell maturation.

Expression of alpha 1 adrenoceptor subtypes in rat corpus cavernosum

Norepinephrine mediates the antierectile role of the sympathetic nervous system. It binds to postsynaptic alpha 1 adrenoceptors present on smooth muscle fibers of the corpus cavernosum. Receptor cloning studies have evidenced three alpha 1 adrenoceptor subtypes: alpha 1A, alpha 1B and alpha 1D. We searched for the presence of these three alpha 1 adrenoceptor subtypes in the rat corpus cavernosum using in situ hybridization with specific oligonucleotide probes. Brain tissue was used as the reference of probes specificity. Autoradiographic films were studied with light illumination and computer-assisted densitometry using an image analyser. We provide evidence that the three alpha 1 adrenoceptor subtypes are expressed in the rat corpus cavernosum. These three subtypes appear to be more expressed in the trabecular smooth muscle fibers than in vascular smooth muscle fibers. Further experiments are needed to determine whether the proportion of alpha 1 adrenoceptor subtypes changes according to the etiology of erectile dysfunction. This morphological approach provides a basis for future pharmacological research of specific alpha 1 adrenoceptor subtypes blocking agents designed to treat erectile dysfunction.

[Von Hippel-Lindau disease and renal cancer: 10 years of genetic progress. GEFVHL (French-Speaking Study Group on von Hippel-Lindau disease)]

Von Hippel-Lindau (VHL) disease is a genetic disease predisposing to the development of various tumours (haemangioblastomas of the neuraxis and retina, tumours of the membranous labyrinth, renal clear cell carcinomas or cysts, phaeochromocytomas, pancreatic cysts or tumours, epididymal cystadenomas), affecting one in 36,000 people. Renal cancer constitutes one of the main causes of death. The VHL gene, situated at 3p25-26, is a tumour suppressor gene which plays a major role in regulation of VEGF transcription and expression. The germ cell mutation can be identified in 70% of patients. Somatic mutations of the VHL gene are also responsible for sporadic clear cell carcinomas. In the urological setting, any patient presenting with "sporadic" bilateral clear cell renal cancer or detected at an early age, or bilateral epididymal cystadenomas, should be investigated for the presence of VHL disease.

Combined arsenic and retinoic acid treatment enhances differentiation and apoptosis in arsenic-resistant NB4 cells

In the acute promyelocytic leukemia (APL) cell line NB4, as well as in APL patients' cells, arsenic trioxide (As2O3) leads to incomplete cell maturation, induction of apoptosis, as well as to the degradation of the oncogenic PML/RARalpha fusion protein. We have isolated an arsenic-resistant NB4 subline (NB4-AsR), which fails to undergo apoptosis, but maintains the partial differentiation response to this drug. When grown in the presence of As2O3, NB4-AsR cells degrade PML/RARalpha, slightly differentiate, and become more sensitive to serum deprivation-induced apoptosis. Similarly, in RA-resistant NB4-R1 cells, RA induced a significant PML/RARalpha degradation and yet failed to induce cell maturation. Thus, As2O3- or retinoic acid (RA)-induced PML/RARalpha degradation may be a prerequisite, but is not sufficient for the full differentiative/apoptotic response to these drugs. Strikingly, RA-triggered differentiation and apoptosis were greatly accelerated in As2O3-treated NB4-AsR cells. The synergism between these two agents in this setting could provide an experimental basis for combined or sequential RA/As2O3 therapies.

[Pachydermoperiostosis with extramedullary hematopoiesis without myelofibrosis]

BACKGROUND

In three previous reports of primary hypertrophic osteoarthropathy, an associated extramedullary hematopoiesis was related to myelofibrosis.

CASE REPORT

A 44-year-old male patient with primary hypertrophic osteoarthropathy diagnosed when he was 34-year-old was referred to our hospital with an abdominal mass fortuitously detected.

DISCUSSION

The present case is unique for the patient developed an extramedullary hematopoïesis without associated myelofibrosis. It suggests the possible intervention of growth factors common to the skin fibroblasts and the blood progenitor cells in the pathogenesis of primary osteoarthropathy.

[No relationship between tacrine cytotoxicity and its metabolisation by cytochrome P4501A2]

It has been suggested that tacrine (THA) induced hepatotoxicity was related to its metabolic pathway involving cytochrome P4501A2 (CYP1A2). Using a model of genetically modified cells we have demonstrated that THA induced a marked decrease in cell viability and a strong inhibition of RNA and protein synthesis. However, these cytotoxic effects did not differ in parental Chinese hamster V79 cells and variant cells expressing human or rat CYP1A2 as well in human HepG2 and Chang Liver cells despite their notable metabolism ability to metabolize THA to hydroxylated metabolites. These results strongly suggest that THA-induced cytotoxicity is not mediated by CYP1A2 indicating that THA could be toxic by direct inhibition at the ribosomial level.

Evidence of sympathetic fibers in the male rat pelvic nerve by gross anatomy, retrograde labeling and high resolution autoradiographic study

Several arguments exist in various animal species and man for the presence of a sympathetic component in the pelvic nerve, classically regarded as parasympathetic. We tested this hypothesis in the male rat. Nerve bundles issued from the sacral region of the paravertebral sympathetic chain and reaching the S1 spinal nerve were identified. Neurons in the sacral parasympathetic nucleus of the L6-S1 spinal cord and in the L2-S1 paravertebral sympathetic chain were retrogradely labeled from the pelvic nerve. Radioautography evidenced labeling of unmyelinated fibers in the pelvic nerve following in vitro incubation with 3H-noradrenaline. A population of sympathetic fibers issued from the lumbosacral sympathetic chain exists in the pelvic nerve of the male rat. This qualitative study provides a morphological basis to uncover the role of the sympathetic outflow present in the pelvic nerve.

Erectile response to hypothalamic stimulation in rats: role of peripheral nerves

The role of peripheral parasympathetic and sympathetic pathways was explored in erectile responses elicited by hypothalamic medial preoptic area (MPOA) stimulation in adult male anesthetized rats. Under control conditions, MPOA stimulation reliably elicited erectile responses evidenced by an increase of the intracavernous pressure-to-blood pressure ratio. The erectile response was abolished by 1) acute bilateral section of cavernous or pelvic nerves or cauda equina and 2) chronic lesions of pelvic nerves or cauda equina. Acute section of the hypogastric nerve did not significantly decrease the erectile response. The erectile response was significantly depressed after acute or chronic sections of the paravertebral sympathetic chain at the L4-L5 level or chemical sympathectomy with 6-hydroxydopamine. The decrease due to acute sympathetic chain lesion was reversed by bilateral ligation of the external iliac arteries. Accordingly MPOA stimulation elicits erectile responses via 1) activation of the parasympathetic outflow conveyed by the pelvic and cavernous nerves and 2) activation of neural fibers conveyed by the sympathetic pathways. We propose that sympathetic fibers running in the paravertebral sympathetic chain are responsible for vasoconstriction of nonpenile areas to divert blood to the penis, allowing the dramatic increase of penile arterial inflow required for erection.

MHC-dependent cytolysis of autologous tumor cells by lymphocytes infiltrating urothelial carcinomas

Tumor-infiltrating lymphocytes (TIL) were grown from 23 urothelial carcinomas. Phenotyping analysis showed that the TIL cultures were mainly CD3+. Although CD4+ and CD8+ T-cell sub-sets were grown in culture, CD4+ T-cell sub-sets predominated over CD8+ T cells. Immunohistochemical studies performed on 5 tumor specimens confirmed this observation, and indicated that CD4+ T cells surrounded the tumor islets, whereas CD8+ T lymphocytes were localized among the tumor cells. Five short-term carcinoma cell lines established from these urothelial tumors were used as target cells in cytolysis assays in order to investigate the functional anti-tumor activity of autologous TIL. TIL from 4/5 tumors were lytic and 3 TIL lines displayed MHC-class-I-dependent cytotoxicity directed against autologous tumor cells. CD4+ T-cell-depletion experiments performed on TIL line 07 confirmed that CD8+ MHC-class-I-dependent CTL were the predominant effectors. Finally, experiments performed on 6 allogeneic urothelial-cancer cell lines matched for HLA-class-I molecules showed that TIL07 exhibited selective lytic activity toward tumor 07. These data indicate that CD8+ MHC-class-I-dependent CTL present in urothelial carcinomas are functional and may participate in the anti-tumor immune response.

[Central nervous system control of erection]

Relaxation of arterial and cavernous smooth muscle fibers, leading to the filling of the sinusoidal spaces with blood, are the local mechanisms of erection. Smooth muscle relaxation results from activation of parasympathetic neural pathway and probably simultaneous inhibition of the sympathetic outflow. Reflexive erection elicited by recruitment of penile afferents conveyed by the dorsal penile nerve involves both autonomic and somatic efferents. This reflex is mediated at the spinal cord level and modulated by supraspinal influences. Serotonergic pathways originating in the raphe nuclei mediate inhibitory control on reflexive erection. Several hypothalamic areas such as the medial preoptic area and the paraventricular nucleus are the source of descending pathways and/or represent important integrating centers. Dopamine acting at the medial preoptic area level may regulate penile erection. Neuroendocrine regulation may vary depending on the context in which erection occurs, for example, coitus, in response to extrinsic or psychogenic stimuli, and rapid eye movement sleep.

[The peripheral pharmacology of erection]

The peripheral control of local mechanisms of erection and detumescence has now been more clearly elucidated. This knowledge has been acquired as a result of the recent development of pharmacological research designed to study the regulation of erectile smooth muscle tone. Smooth muscle fibres of the corpora cavernosa and arteries supplying the penis relax in response to a reduction of intracellular calcium. This relaxation allows both an increase of the blood flow to the penis and opening of sinusoid spaces. Cyclic nucleotides, cAMP and cGMP, are intracellular messengers of the mediators acting on smooth muscle fibres and regulating these intracellular calcium movements. Gap-junctions, greatly facilitating rapid ion exchanges between smooth muscle fibres, make erectile tissue a real functional syncytium. Nonadrenergic, noncholinergic neurotransmitters, mainly nitric oxide (NO), are synthesized by parasympathetic neurons present in cavernous nerves and act directly on smooth muscle fibres. NO increases the intracellular cGMP concentration. Other proerectile mediators, such as acetylcholine, CGRP or substance P, act via endothelial cells by promoting the synthesis and release of NO by these cells. In contrast, neurotransmitters of the sympathetic nervous system, norepinephrine and neuropeptide Y, and endothelin, secreted by endothelial tissues, induce contraction of cavernous smooth muscle fibres, thereby opposing erection. Oxygenation of the cavernous tissue is also an important factor in the regulation of local mechanisms of erection. Poor oxygenation prevents the synthesis of cGMP and predisposes to cavernous fibrosis due to increased synthesis of collagen via TGF beta. A better understanding of the peripheral pharmacology of erection opens the way to new pathophysiological and therapeutic prospects in the broad symptomatic context of erectile dysfunction.