P2X(7) receptors are expressed during mouse nephrogenesis and in collecting duct cysts of the cpk/cpk mouse.

BACKGROUND: Purinergic receptors are cell-surface molecules that bind extracellular nucleotides, notably ATP. The P2X family includes seven nonselective ion channels with one member, P2X(7), implicated in cytolytic pore formation and cell death. MATERIALS AND METHODS: We sought P2X(7) expression in mouse nephrogenesis and cpk/cpk renal cyst growth, conditions in which both proliferation and apoptosis are prominent. RESULTS: P2X(7) immunolocalized to condensed metanephric mesenchyme: both proliferation and apoptosis were detected in this compartment, assessed by proliferating cell nuclear antigen expression and propidium iodide-stained pyknotic nuclei respectively. Later in nephrogenesis, P2X(7) was detected in collecting ducts, a pattern persisting to maturity. A mesenchymal to epithelial shift of P2X(7) expression was also documented in ureter development. In cpk/cpk kidneys, P2X(7)-expressing collecting duct cysts dominated histology from two weeks until four weeks after birth, when animals die from uremia. In polycystic kidneys pyknotic nuclei were rarely identified in P2X(7)-expressing epithelia, but were detected between cysts, consistent with a non-apoptotic role for P2X(7) in cyst enlargement. CONCLUSION: P2X(7) is expressed during normal nephrogenesis and in a model of congenital polycystic kidney disease. Further experiments are necessary to define possible functions of P2X(7) in these settings.     

Postnatal development of cholinergic neurons in the rat: I. Forebrain.

The postnatal development of cholinergic projection and local-circuit neurons in the rat forebrain was examined by use of choline acetyltransferase (ChAT) immunohistochemistry and acetylcholinesterase (AChE) histochemistry. Although regional nuances were apparent, a general trend emerged in which cholinergic projection neurons in the basal nuclear complex (i.e., medial septal nucleus, vertical and horizontal diagonal band nuclei, magnocellular preoptic field, substantia innominata, nucleus basalis, and nucleus of the ansa lenticularis) demonstrated ChAT-like immunoreactivity earlier in postnatal development than intrinsically organized cholinergic cells in the caudate-putamen nucleus and nucleus accumbens, although this disparity was less apparent for local circuit neurons in the olfactory tubercle and Islands of Calleja complex. Ontologic gradients of enzyme expression also existed in some regions. A lateral to medial progression of ChAT and AChE appearance was observed as a function of increasing postnatal age in the nucleus accumbens and rostral caudate-putamen nucleus. By comparison, a rostrocaudal gradient of expression of ChAT-like immunoreactivity was apparent within the basal nuclear complex. Moderate to intense ChAT positivity, for example, appeared first in the medial septal nucleus. Furthermore, compared to more caudal regions, a greater proportion of AChE-positive neurons in rostral aspects of the basal forebrain expressed ChAT immunoreactivity on postnatal day 1, a difference that was no longer present by postnatal day 5. Cholinergic neurons in all forebrain regions also underwent an initial stage of progressive soma and proximal-dendrite hypertrophy, which peaked during the third postnatal week, followed by a period of cell-body and dendritic shrinkage that persisted into the fifth postnatal week when adult configurations were reached. These soma and dendritic size increases and decreases were not correlated with the magnitude of postnatal ChAT expression, which increased progressively until adult levels were attained approximately by the third to fifth weeks after birth. Expression of AChE in putative cholinergic neurons appeared to precede that of ChAT, especially in the caudate-putamen complex. Staining intensity of AChE also incremented earlier than that of ChAT.     

Electrocardiographic findings in children with Lyme disease.

The incidence of cardiac involvement in Lyme disease (LD) has been estimated to be 4 to 10% in adults, with conduction and rhythm disturbances noted most frequently. To assess the frequency of electrocardiographic abnormalities in children with LD, we prospectively performed 12-lead electrocardiograms in 32 randomly selected children presenting with LD between May and September 1989. No patient had symptoms of cardiac involvement. Using defined diagnostic criteria, combining symptoms, signs, serology, and residence in or travel to an endemic area, 14 patients were classified as having definite LD and 10 were categorized as probable. The incidence of electrocardiographic abnormalities in the definite group was 29% (4/14), including two patients with 1 degree atrioventricular block, one with left axis deviation, and one with ventricular ectopy. Thirty percent (3/10) of the probable group had abnormal ECGs, including one with ST-T wave abnormalities, one with prominent sinus arrhythmia, sinus bradycardia, and wandering atrial pacemaker, and one with ectopic atrial bradycardia. No patient required cardiac therapy. The incidence of abnormal ECG findings in this group of children with either probable or definite LD was thus 29%, with 1 degree atrioventricular block noted most frequently. When the diagnosis of LD is highly suspected, an electrocardiogram may be a useful screening test for cardiac involvement.     

Effects of autologous mesothelial cell seeding on prostacyclin production within Dacron arterial prostheses

Canine abdominal aortas have been replaced with Dacron arterial prostheses to assess the effects of mesothelial cell seeding on graft prostacyclin and thromboxane A2 release. At both 2 weeks and 6 weeks after surgery, three seeded and two unseeded control grafts were examined for prostacyclin release. In addition, thromboxane release was assessed in one seeded and one unseeded graft. Sections of aorta and graft were removed and incubated in PBS containing either 10 microM calcium ionophore A23187 or 20 microM arachidonic acid. The incubation mixture was sub-sampled at 5 min intervals over a 20 min period to assess the progressive release of prostacyclin and thromboxane A2 using a radioimmunoassay for 6-keto-prostaglandin F1 alpha and thromboxane B2 respectively. In seeded grafts, 6-keto-prostaglandin F1 alpha release averaged 15 per cent compared with aorta at 2 weeks and 45 per cent compared with aorta at 6 weeks. By contrast, release from unseeded grafts was undetectable at 2 weeks; however, by 6 weeks there was some release amounting to 15 per cent compared with aorta. There was a statistically significant increase in the release of 6-keto-prostaglandin F1 alpha from mesothelial cell seeded grafts at 6 weeks compared with unseeded grafts (P less than 0.01). Thromboxane release from the graft sections was variable and unrelated to whether the grafts had been seeded or not. These preliminary results, showing that grafts seeded with autologous peritoneal mesothelial cells release more prostacyclin than unseeded grafts, further highlight the role of the mesothelial cell as an alternative to the endothelial cell for improving the patency of arterial Dacron prostheses in the early postoperative days.     

Reliability of data sources for poisoning deaths in Massachusetts.

The authors analyzed poisoning-related deaths in Massachusetts from 1986 and 1987 recorded in three datasets: poison center records, death certificate, and state medical examiner's office records. While 714 such deaths were found, 551 of these were prehospital deaths recorded within the medical examiner's office but not by the poison center. The poison center was not consulted in over 47% of the poisoning deaths occurring in Massachusetts hospitals. Conversely, 15% of deaths were reported to the poison center but were not found either in death certificate or medical examiner records. Concordance between all three datasets for recording the 163 poisoning-related hospital deaths was only 17%. The authors conclude that reliance on a single data source underestimates and potentially misrepresents both the numbers and types of poisoning deaths occurring in the state. They also believe the files of the medical examiner are an underappreciated, rich source of data concerning out-of-hospital deaths due to poisonings and intoxications. Their findings suggest that the regional poison center is an underused resource for the management of seriously poisoned patients. There is a need for a better working relationship between poison centers and area hospitals so that all serious intoxications and poisonings are reported to the poison center in a timely fashion.     

The application of x-ray diffraction and electron microscopy to the study of human peripheral nerve obtained by biopsy

Human peripheral nerves obtained by biopsy from patients suffering from neuromuscular disorders have been studied by x-ray diffraction and electron microscopy. Few abnormal diffraction patterns have yet been recorded and their significance is not yet established. Electron micrographs have revealed wide variations in the numbers of myelinated fibres included in the nerve trunks and have facilitated a detailed study of the Schwann cell-axon relationships in the large numbers of unmyelinated fibres always present. Some indications of demyelination have been encountered.     

A selective effect of naloxone on heterosynaptic C-fibre-mediated inhibitions in the rat dorsal horn

The effect of naloxone on C-primary afferent-mediated inhibitions of C-fibre-evoked activity in deep dorsal horn neurones has been examined in decerebrate-spinal rats. The same C-afferents that evoke activity in a given neurone can inhibit that C-evoked activity (homosynaptic inhibition), and C-afferent input can also inhibit the activity evoked in dorsal horn neurones by other C-afferents (heterosynaptic inhibition). Naloxone was found to selectively reverse heterosynaptic C-mediated inhibitions without affecting homosynaptic inhibitions. In several neurones the heterosynaptic inhibitions were completely abolished by naloxone. These results show that homo- and heterosynaptic C-mediated inhibitions operate by different mechanisms and that, at least in some neurones, endogenous opioids are likely to be the major inhibitory transmitters involved in producing the heterosynaptic inhibition of the activity evoked by one C-input by another C-input.     

The somatotopic organization of primary afferent terminals in the superficial laminae of the dorsal horn of the rat spinal cord

Transganglionic transport of wheatgerm agglutinin conjugated horse-radish peroxidase (WGA-HRP) was used to reveal the central distribution of terminals of primary afferent fibers from peripheral nerves innervating the hind leg of the rat. In separate experiments the sizes and locations of cutaneous peripheral receptive fields were determined by electrophysiological recording techniques for each of the nerves that had been labeled with WGA-HRP. By using digital image analysis, the sizes and positions of the peripheral receptive fields were correlated with the areas of superficial dorsal horn occupied by terminals of primary afferents from each of these receptive fields. Data were obtained from the posterior cutaneous nerve of the thigh, lateral sural, sural, saphenous, superficial peroneal, and tibial nerves. The subdivisions of the sciatic nerve, the sural, lateral sural, superficial peroneal, and tibial nerves each projected to a separate and distinct region of the superficial dorsal horn and collectively formed a "U"-shaped zone of terminal labeling extending from lumbar spinal segments L2 to the caudal portions of L5. The gap in the "U" extended from L2 to the L3-4 boundary and was occupied by terminals from the saphenous nerve. Collectively, all primary afferents supplying the hindlimb occupied the medial 3/4 of the superficial dorsal horn with terminals from the tibial nerve lying most medially and occupying the largest of all the terminal fields. Afferents from the superficial peroneal lay in a zone between the medially situated tibial zone and the more laterally placed sural zone. Afferents from the posterior cutaneous nerve were located most caudally and laterally. Terminal fields from the posterior cutaneous and saphenous nerves differed from the others in having split representations caused presumably by their proximity to the mid-axial line of the limb. Comparisons between the peripheral and the central representations of each nerve revealed that 1 mm2 of surface area of the superficial dorsal horn serves approximately 600-900 mm2 of hairy skin and roughly 300 mm2 of glabrous skin. The vast majority of terminal labeling observed in the dorsal horn was found in the marginal layer and substantia gelatinosa, suggesting that small diameter afferents have an orderly somatotopic arrangement in which each portion of the skin surface is innervated by afferent fibers that terminate in preferred localities within the dorsal horn.     

The effect of an inhibitor of adenylate cyclase on the development of pyrogen,prostaglandin and cyclic AMP fevers in the rabbit

Summary An exotoxin of Bacillus thuringiensis known to inhibit adenylate cyclase in vitro has been used to investigate the role of cyclic AMP in the pathogenesis of fever in the rabbit. Intra-hypothalamic microinjections of the exotoxin are non-pyrogenic and significantly attenuate the hyperthermia caused by intrahypothalamic microinjections of both bacterial pyrogen (endotoxin) and prostaglandin E₁. The hyperthermia produced by dibutyryl cyclic AMP is not affected by the exotoxin. These results support the idea that adenylate cyclase is activated during the development of fever in the rabbit.     

Metabolism and excretion of atorvastatin in rats and dogs.

Atorvastatin (AT) is a second-generation potent inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase, clinically approved for lowering plasma cholesterol. Using a mixture of [D(5)/D(0)] AT and/or [(14)C]AT, the metabolic fate and excretion of AT were examined in rats and dogs following single and multiple oral doses. Limited biliary recycling was examined in one dog after a single dose of AT. AT-derived metabolites in bile samples were identified by metabolite screening of the [D(5)/D(0)] AT molecular clusters using tandem mass spectrometry. Bile was a major route of [(14)C] drug-derived excretion, accounting for 73 and 33% of the oral dose in the rat and dog, respectively. The remaining radioactivity was recovered in the feces; only trace amounts were excreted in urine. Radioactive components identified in rat and dog bile were the para- and ortho-hydroxy metabolites, a glucuronide conjugate of ortho-hydroxy AT, and unchanged AT. Two minor radioactive components were identified as beta-oxidation products of AT with one confirmed as a beta-oxidized AT derivative. The reappearance of AT and major metabolites in bile from a dog administered a sample of its previously excreted bile indicated biliary recycling is an important component in AT metabolism. Multiple dose administration in rats did not alter biliary metabolic profiles. Rat and dog plasma profiles after multiple dose administration were similar and showed no additional metabolites not found in bile. Examination of rat and dog bile and plasma indicates that AT primarily undergoes oxidative metabolism.