Inhibition of [3H]thymidine incorporation into DNA of rat regenerating liver by 2',2'-difluorodeoxycytidine coupled to lactosaminated poly-L-lysine

The expression of asialoglycoprotein receptor (ASGP-R) on human hepatocarcinoma cells might be exploited to reduce the extrahepatic toxicity of DNA synthesis inhibitors by their conjugation with galactosyl- terminating peptides. We conjugated 2',2'-difluorodeoxycytidine (dFdC), an inhibitor of DNA synthesis active on solid tumors, with lactosaminated poly-L-lysine (L-poly(LYS)). In experiments in vitro, L-poly(LYS)-dFdC inhibited proliferation of Hep G2 cells, a human hepatocarcinoma cell line which maintains the ASGP-R. Inhibition was rescued by asialofetuin. To study the pharmacological action of the conjugate in vivo, we used rats 18-24 hr after 2/3 hepatectomy and observed that regenerating hepatocytes expressed ASGP-R on their surface and internalized L-poly(LYS)-dFdC. Conjugate uptake by bone marrow, spleen, and intestine was negligible. We also found that L-poly(LYS)-dFdC inhibited [3H]thymidine incorporation into DNA of regenerating liver. These results indicated that hepatectomized rats were a suitable animal model to study the pharmacological action, on DNA-synthesizing hepatocytes, of conjugates binding to ASGP-R and carrying inhibitors of DNA synthesis. L-poly(LYS)-dFdC also inhibited [3H]thymidine incorporation in bone marrow, spleen, and intestine. Evidence was obtained that inhibition of DNA synthesis in extrahepatic tissues was a consequence of drug release from hepatocytes into blood-stream after the bond with the carrier has been broken down within liver cells. Possible ways of reducing the exit of dFdC from liver cells, thereby obtaining an inhibition of DNA synthesis restricted to dividing hepatocytes, were discussed.     

psi(SO2NH) transition state isosteres of peptides. Synthesis and bioactivity of sulfonamido pseudopeptides related to carnosine

This paper reports the synthesis of tauryl dipeptides related to carnosine. In particular H-Tau-His-OH (5), H-Tau-His(pi-Me)-OH (6) and H-Tau-His(tau-Me)-OH (9) are described. The enzyme carnosinase has been isolated from pig kidney and after purification has been used to test the stability and the inhibitory activity of the three new analogues. H-Tau-His-OH (5) and H-Tau-His(tau-Me)-OH (9) were found to possess weak inhibitory properties towards carnosinase, while H-Tau-His(pi-Me)-OH (6) proved to be devoid of any significant activity. All the three sulfonamido pseudopeptides 5, 6 and 9 show stability to carnosinase activity.     

Chlorpyrifos-induced delayed polyneuropathy

Chlorpyrifos [0,0-diethyl 0-(3,5,6-trichloro-pyridyl) phosphorothioate] caused delayed polyneuropathy in man. Contrary to previous studies, we report here that it also causes delayed polyneuropathy in the hen, the animal model for this toxicity. The minimal neuropathic dose was 60–90 mg/kg p.o., corresponding to 4–6 times the estimated LD₅₀. Consequently, pralidoxime (2-PAM) in conjunction with atropine was necessary to reverse acetylcholinesterase (AChE) inhibition and cholinergic toxicity in hens given high enough doses of chlorpyrifos to cause neuropathy. Chlorpyrifos was slowly absorbed after single oral doses and the threshold of inhibition (>70%) of neuropathy target esterase (NTE), the putative target for delayed neuropathy, was reached within 5–6 days. High AChE inhibition (>90%), however, was measured within hours after dosing because of the higher potency of chlorpyrifos to inhibit this enzyme. In vitro studies showed that chlorpyrifos-oxon, the active metabolite of chlorpyrifos, was 10–20 times more active against AChE than against NTE, confirming the clinical observation. No differences were seen between human and hen enzymes in this respect. Hen and human brain homogenates contain A-esterases which hydrolysed chlorpyrifos to about the same extent in both species. In conclusion, chlorpyrifos causes delayed polyneuropathy in the hen, as was reported in man. The reasons for previous negative data in the hen are probably due to the relatively lower doses which were used. Judging from in vitro studies with hen and human enzymes, there are no differences in the two species as far as their relative sensitivity to delayed polyneuropathy. It is likely that delayed polyneuropathy would develop in both species only after severe cholinergic toxicity requiring aggressive antidotal treatment.Part of this work was presented at the 25th Annual Meeting of the Society of Toxicology held in New Orleans, LA, USA, March 1986, at the International Symposium on Biochemical and Cellular Indices of Toxicity in Occupational and Environmental Medicine held in Milan, Italy, June 1986, and at the 9th Meeting of the Peripheral Nerve Study Group, Praglia (PD), Italy, August – September, 1989     

Bulbectomy Enhances Neurogenesis and Cell Turnover of Primary Olfactory Neurons But Does Not Abolish Carnosine Expression

Primary olfactory neurons located in the olfactory neuroepithelium project to the ipsilateral olfactory bulb and undergo a continuous process of neurogenesis and differentiation. We describe, in the adult rat, the kinetics of proliferation, differentiation and survival of primary olfactory neurons either in the presence or absence of their target, the olfactory bulb. The experimental design included unilateral bulbectomy, coupled with a single bromodeoxyuridine pulse 35 days after surgery. The rate of proliferation and survival of olfactory neurons was then examined by immunohistochemistry for bromodeoxyuridine, and the differentiation status by in situ hybridization for calmodulin messenger RNA in immature and mature olfactory neurons and immunohistochemistry for the dipeptide carnosine in mature olfactory neurons. We show that primary olfactory neurons can synthesize carnosine in the absence of the olfactory bulb. However, the number of carnosine-immunopositive neurons in the absence of their target is dramatically reduced to less than one-fourth, whereas the number of olfactory neurons expressing calmodulin messenger RNA is only slightly reduced. The numeric reduction of camosine-positive neurons in the target-deprived neuroepithelium is correlated with a dramatic reduction in the survival rate of olfactory neurons, since newly generated olfactory neurons are completely lost 35 days after the bromodeoxyuridine pulse. In contrast, in the normal olfactory neuroepithelium almost one-third of newly generated olfactory neurons survive 35 days after the bromodeoxyuridine pulse. On the whole, these data indicate that most of the primary olfactory neurons have a short lifespan but that once they have connected with the olfactory bulb they may persist longer, and suggest that throughout adulthood olfactory neurons are overproduced, differentiate independently from their target, and then undergo a process of target-induced neuronal selection.     

Acquired hyperoxaluria and haematuria in children

Two children with extensive ileal resection are reported. They developed gross haematuria of non-glomerular origin, without stones or nephrocalcinosis. Previous reports indicate that acquired hyperoxaluria is common in children with a variety of intestinal disorders. Our patients had hyperoxaluria. We think that hyperoxaluria may be the cause of haematuria through a pathogenetic mechanism similar to the one ascribed to haematuria secondary to hypercalciuria and hyperuricosuria.     

Simultaneous recording of pattern electroretinogram (PERG) and visual evoked potential (VEP) in multiple sclerosis

We studied 18 multiple sclerosis (MS) patients affected by retrobulbar neuritis (RBN). The patients were subdivided into two groups. Group 1: 14 patients with RBN. Group 2: 4 patients with optic atrophy. An ophthalmological examination (visual acuity, fundus oculi, visual field) was carried out in all the patients. A simultaneous visual evoked potential (VEP) and pattern electroretinogram (PERG) recording at two spatial frequencies (45' and 15') was performed. All the data obtained in Group 1 were compared (Student T-Test) with those of a control group of normal subjects matched for age and sex. Group 1. VEP: a comparison of the data in MS patients affected by RBN with the control group revealed a statistically significant P100 latency delay with both spatial frequencies (P less than 0.001). PERG: no "b" wave latency change at 45' and 15' spatial frequencies were seen. A "b" wave amplitude reduction was observed; this reduction reached significant values at 45' (P less than 0.001). Group 2. In optic atrophies the PERG was absent in 4 eyes at 45' and in 5 eyes at 15'.     

Binocular Interactions in the Lateral Suprasylvian Visual Area of Strabismic Cats Following Section of the Corpus Callosum

Visually responsive neurons have been recorded in the lateral suprasylvian area (LSA) of cats raised with either a convergent or a divergent strabismus. In contrast to areas 17 and 18, where many studies have documented a profound loss of binocularly activated neurons following early strabismus, in the LSA the majority of cells could still be binocularly driven. Acute or chronic section of the splenium of the corpus callosum reduced but did not abolish binocularity in the LSA. We propose that the widespread callosal connections, the large size of the receptive fields and the peculiar internal circuitry of the LSA all concur in permitting the maintenance of binocular coding in spite of early misalignment of the eyes.     

Different biological properties of paired HIV-1 isolates from peripheral blood mononuclear cells and cerebrospinal fluid.

Seven paired HIV-1 isolates from peripheral blood mononuclear cells (PMCs) and cerebrospinal fluid (CSF) of infected subjects at various stages of the disease were studied for their capacity to replicate in continuous cell lines (Molt-3 and U-937 cells) and to induce cytopathic effects "in vitro". Obtained results indicate that paired HIV-1 isolates from PMCs and CSF of the same patient can differ in their replicative activity "in vitro", suggesting that, at least in some cases, CSF isolates may represent a distinct subtype of HIV-1.     

Effects of sympathectomy on the in vivo α and β-responses of the parotid gland

Summary Salivary secretion in response to noradrenaline and isoprenaline was measured in innervated and chronically sympathectomized parotid glands of the rat. In innervated glands, the responses to isoprenaline lasted longer than those to noradrenaline. Chronic sympathetic denervation enhanced the responses to both noradrenaline and isoprenaline. The magnitude of the supersensitivity to isoprenaline was related to the dose and the time at which the responses were analyzed. Supersensitivity was greater for the initial than for the total secretion elicited by isoprenaline. Propranolol (1 mg/kg) and phenolamine (5 mg/kg) were used in order to determine the relative participation of and -adrenoceptors in the enhanced responses to isoprenaline. The results suggest that postjunctional supersensitivity for the secretory responses of this organ to isoprenaline is mainly mediated through -adrenoceptors of the secretory cells and -adrenoceptors of the myoepithelial cells.