Reduced sperm count and normal fertility in male mice with targeted disruption of the ADP-ribosylation factor-like 4 (Arl4) gene.

The ADP-ribosylation factor-like protein 4 (ARL4) is a 22-kDa GTP-binding protein which is abundant in testes of pubertal and adult rodents but absent in testes from prepubertal animals. During testis development, ARL4 expression starts at day 16 when the spermatogenesis proceeds to the late pachytene. In the adult testis, the ARL4 protein was detected in pre- and postmeiotic cells, spermatocytes, and spermatides, but not in spermatogonia and mature spermatozoa. Mouse Arl4-null mutants generated by targeted disruption of the Arl4 gene were viable and grew normally; male as well as female Arl4(-/-) mice were fertile. However, inactivation of the Arl4 gene resulted in a significant reduction of testis weight and sperm count by 30 and 60%, respectively, without reduction of litter size or frequency. It is suggested that the disruption of Arl4 produces a moderate retardation of germ cell development, possibly at the stage of meiosis.

Monitoring paracetamol metabolism after single and repeated administration in pediatric patients with neoplastic diseases.

INTRODUCTION: Paracetamol (PCM) is frequently used in pediatric patients with neoplastic disease. It is metabolized mainly by conjugation, but at therapeutic concentrations, a small fraction of the drug undergoes oxidative metabolism via cytochrome P450 forming the hepatotoxic intermediate N-acetyl-p-benzo-quinone-imine (NAPQI) which is usually conjugated with glutathione and excreted as paracetamol mercapturate and paracetamol cysteine. OBJECTIVE: The aim of this monitoring study was to evaluate PCM metabolism with minimal intervention during routine treatment with single and repeated administration in patients undergoing antineoplastic therapy. METHOD: A total of 107 urine samples collected 4-12 h after PCM administration from 29 children undergoing antineoplastic treatment, and 10 children without antineoplastic treatment were analyzed for PCM, PCM glucuronide (PCM-G), PCM sulfate (PCM-S), PCM mercapturate (PCM-M) and PCM cysteine (PCM-C). RESULTS: The median (range) percentages for metabolites in urine were: a) in children with and without chemotherapy after the first administration: PCM: 0 (0-100) and 4 (0-11)%, PCM-G: 55 (0-88) and 51 (18 - 68)%, PCM-S: 30 (0-73) and 32 (22-57)%, PCM-(M+C): 13 (0-52) and 9 (0-24)%, respectively; b) after repeated administration in children with chemotherapy: PCM: 0 (0-51)%, PCM-G: 42 (7-100)%, PCM-S: 28 (0-70)%, PCM-(M+C): 24 (0-66)%. CONCLUSION: The pattern of PCM excretion in children undergoing antineoplastic treatment regimens is highly variable. Repeated administration is associated with a significant increase in the products of oxidative metabolism. This might indicate an increase in metabolism via the hepatotoxic NAPQI.

ADP-ribosylation factor (ARF)-like 4, 6, and 7 represent a subgroup of the ARF family characterization by rapid nucleotide exchange and a nuclear localization signal.

The novel ARF-like GTPase ARL7 is a close relative of ARL4 and ARL6 (71% and 59%) identical amino acids). A striking characteristic of these GTPases is their basic C-terminus which, when fused to the C-terminus of green fluorescent protein (GFP), targets the constructs to the nucleus of transfected COS-7 cells. Full length ARL4 was detected in both nuclear and extranuclear compartments, whereas a construct of ARL4 lacking its C-terminus was excluded from the nucleus. Nucleotide exchange rates of recombinant ARL4, ARL6 and ARL7 were similar and appeared considerably higher than those of other members of the ARF family (ARF1, ARP). It is concluded that ARL4, ARL6 and ARL7 form a subgroup within the ARF family with similar, possibly nuclear, function.

[3-hydroxy-3-methylglutaraciduria (case report of a female Turkish sisters with 3-hydroxy-3- methylglutaryl-Coenzyme A lyase deficiency]. / 3-Hydroxy-3-methylglutaracidurie (Fallbeschreibung eines weiblichen türkischen Geschwisterpaares mit 3-Hydroxy-3-methylglutaryl-Coenzym A Lyase Mangel).

3-Hydroxy-3-methylglutaric aciduria is a rare inborn error of metabolism, caused by reduced enzyme activity of the intramitochondrial 3-hydroxy-3-methylglutaryl-CoA lyase. We describe two turkish sisters with this disease. In the older sister clinical symptoms with lethargy, convulsions, metabolic acidosis, hypoglycemia and hyperammonemia lead to the diagnosis. The younger sister was diagnosed prenatally. The clinical course of our patients is compared with those reported in the literature with respect to clinical symptoms, differential diagnosis and therapeutic regimens.

The ADP-ribosylation factor (ARF)-related GTPase ARF-related protein binds to the ARF-specific guanine nucleotide exchange factor cytohesin and inhibits the ARF-dependent activation of phospholipase D.

ADP-ribosylation factor-related protein (ARP) is a membrane-associated GTPase with remote similarity to the family of ADP-ribosylation factors (ARF). In a yeast two-hybrid screen designed to identify proteins interacting with ARP, we isolated a partial cDNA of the ARF-specific guanine nucleotide exchange factor mSec7-1/cytohesin encoding its N terminus and most of the Sec7 domain (codons 1-200). ARP and ARP-Q79L (GTPase-negative ARP) exhibited a higher affinity to mSec7-1-(1-200) than ARP-T31N (nucleotide exchange-defective ARP) in the two-hybrid assay. Similarly, full-length [35S]mSec7-1/cytohesin was specifically adsorbed to glutathione-Sepharose loaded with glutathione S-transferase (GST)-ARP-Q79L, GST-ARP, or GST-ARP-T31N, the latter exhibiting the lowest binding affinity. Overexpression of ARP-Q79L, but not of ARP-T31N, in COS-7 cells reduced the fluorescence from co-expressed green fluorescent protein fused with mSec7-1/cytohesin or mSec7-2/ARNO in plasma membranes as detected by deconvolution microscopy. Recombinant ARP and ARP-Q79L, but not ARP-T31N, inhibited the phospholipase D (PLD) activity stimulated by mSec7-2/ARNO and ARF in a system of isolated membranes. Furthermore, transfection of HEK-293 cells with ARP or ARP-Q79L, but not ARP-T31N, inhibited the muscarinic acetylcholine receptor-3 induced PLD stimulation and translocation of ARF from cytosol to membranes. These data suggest that the GTP-bound form of ARP specifically binds mSec7-1/cytohesin, and that ARP may be involved in a pathway inhibiting the ARF-controlled activity of PLD.