Cryptdins are antimicrobial peptides of the defensin family that are produced by intestinal Paneth cells. mRNAs encoding 17 cryptdin isoforms have been characterized from a cDNA library generated from a single jejunal crypt. Six cryptdin cDNAs correspond to known peptides, and the remainder predict 11 novel Paneth cell defensins. Most cryptdin cDNAs have .93% nucleotide sequence identity overall, except for cryptdin 4 and 5 cDNAs, whose respective mature peptide-encoding regions are only 74 and 78% identical to that of cryptdin 1. Cryptdin cDNAs differ at a small number of nucleotide positions: frequent substitutions were found in codons 38 and 52 of the propiece and in codons 68, 73, 76, 87, and 89 of the deduced peptides; cDNA clones with changes in codons 74, 83, and 88 were found, but there were fewer of these. The antimicrobial activities of cryptdins 1 to 6 were tested against Escherichia coli ML35 in two assays. In an agar diffusion assay, the potencies of cryptdins 1 to 3, 5, and 6 were approximately equivalent to that of rabbit neutrophil defensin NP-1 but cryptdin 4 was 30 times more active than NP-1. In a bactericidal assay system, cryptdins 1 and 3 to 6 were equally active at 10 ,ug/ml but cryptdin 2 and rabbit NP-1 were not active at this concentration. Since cryptdins 2 and 3 differ only at residue 10 (Thr and Lys, respectively), this amino acid appears to function in bactericidal interaction with E. coli. The demonstration that Paneth cells express a diverse population of microbicidal defensins further implicates cryptdins in restricting colonization or invasion of small intestinal epithelium by bacteria.

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Muscle weakness and aberrant responses to neuromuscular relaxants after burn injury are associated with upregulation of acetylcholine receptors (AChRs). Typically, these functional, pharmacological, and biochemical changes occur after denervation, in which transcriptionally mediated qualitative changes in AChRs and Na+ channels and of myogenic regulatory proteins MyoD and myogenin also occur. This study in rats, by an examination of changes in the above-enumerated proteins or their transcripts in the gastrocnemius muscle distant from the burn, verifies whether a denervation-like state exists after burns. Scatchard analysis of [3H]saxitoxin binding revealed no changes in the affinity (K(d)) and total number (B(max)) of Na+ channels between control and burn-injured animals at both 7 and 14 days after injury. The mRNA levels of the immature proteins, SkM2 of the Na+ channels and the gamma-subunits of AChRs, the increase of which is pathognomic of denervation, were assessed by Northern analysis and were unchanged. The transcripts of mature Na+ channels, SkM1, were significantly increased at day 14 after the burn (1.24 +/- 0.10 in burn-injured vs. 1.06 +/- 0.12 in sham animals, arbitrary units, P = 0.006). Although MyoD levels were increased in burn-injured animals at 14 days (0.21 +/- 0.02 vs. 0.15 +/- 0.07 arbitrary units, P = 0.05), myogenin levels were unaltered. The absence of changes in AChR transcripts, including alpha-, delta-, and gamma-subunits, indicates that the upregulation of AChR in burns is not transcriptionally mediated. The unaltered levels of transcripts of myogenin, SkM2 of Na+ channels and gamma-subunit of AChR, confirm that there is no denervation-like prejunctional (nerve-related) component to explain the muscle weakness or the upregulation of AChRs at sites distant from burns.

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ABSTRACT. The matrix adenine nucleotide pool size of rat liver mitochondria was low at birth (2.6-3.0 nmol ATP+ADP+AMP/mg mitochondrial protein). After parturition, the pool size was increased by 50-75% within 1 h, which was sufficient for full development of state 3 respiration rates. The adenine nucleotide pool size continued to increase to 100-150% of the value at birth by 2-3 h postnatal. The ATPIADP ratio in isolated mitochondria also increased postnatally, to about double the value at birth by 3 h. There were no matrix volume changes over this postnatal period, so the increased ATP+ADP+AMP pool size and the increased ATPIADP ratio together inferred an overall increase of about 5-fold in the matrix ATP concentration under aerobic conditions. The postnatal uptake of adenine nucleotides into mitochondria occurred at a slower rate in newborns that were hypoxic (11% Oz) and in newborns of diabetic mothers (diabetes induced on day 5 of gestation by streptozotocin injection). The normal increase in matrix ATP content is responsible for the rapid stimulation of pyruvate carboxylation (an ATP-requiring matrix reaction) and this in turn contributes to the rapid postnatal onset of gluconeogenesis. The results suggest that delayed adenine nucleotide uptake into liver mitochondria may retard initiation of gluconeogenesis in newborns experiencing hypoxia, as in respiratory distress or in newborns of diabetic mothers. We speculate that this mechanism contributes to the persistent hypoglycemia that is typical of these at-risk newborns. (Pediatr Res 21: 266-269,1987) Mitochondria isolated from full-term fetal rat liver are functionally well coupled, but the rate of oxidative phosphorylation (state 3 respiration) is very low (reviewed in Reference 1). Within 1 h after birth, the state 3 rate increases to adult values (2-4). This functional maturation depends on a rapid increase in the mitochondrial adenine nucleotide content (ATP+ADP+AMP) which occurs in the immediate postnatal period (2, 4-6) In addition to activating state 3 respiration the increased adenine nucleotide pool size may also stimulate metabolic pathways that have adenine nucleotide-dependent enzymes within the mitochondrial compartment (reviewed in Reference 1). One matrix enzyme subject to this kind of control is pyruvate carboxylase. In both the newborn rat and rabbit the sudden postnatal increase in the matrix ATP concentration enhances pyruvate carboxylation rates enabling the onset of gluconeogenesis and recovery from postnatal hypoglycemia (7-9). Thus, the accumulation of adenine nucleotides into the mitochondria appears to be important for metabolic adaptation to neonatal life (see Reference 1).Received May 13, 1986; accepted October 23, 1986. Correspondence and reprint requests Dr. June R. Aprille, Mitochondria1 Physiology Unit, Department of Biology, Tufts University, Medford, MA 02155.Supported by NIH Grants HD 16936 and NS 14936.There is considerable evidence that hormones and oxygenation are important controlling factors for the subcellular red...

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