The genome of the model beetle and pest Tribolium castaneum

Tribolium castaneum is a member of the most species-rich eukaryotic order, a powerful model organism for the study of generalized insect development, and an important pest of stored agricultural products. We describe its genome sequence here. This omnivorous beetle has evolved the ability to interact with a diverse chemical environment, as shown by large expansions in odorant and gustatory receptors, as well as P450 and other detoxification enzymes. Development in Tribolium is more representative of other insects than is Drosophila, a fact reflected in gene content and function. For example, Tribolium has retained more ancestral genes involved in cell-cell communication than Drosophila, some being expressed in the growth zone crucial for axial elongation in short-germ development. Systemic RNA interference in T. castaneum functions differently from that in Caenorhabditis elegans, but nevertheless offers similar power for the elucidation of gene function and identification of targets for selective insect control.

Responses to hypoxia and hypercapnia in infants of substance-abusing mothers

Because infants of substance-abusing mothers (ISAM) have an increased risk of sudden infant death syndrome and have abnormal sleeping ventilatory patterns, we studied the effects of mild hypoxia during quiet sleep on ventilatory pattern, heart rate, and arousal in 23 healthy ISAM (mean +/- SEM: 9.0 +/- 0.49 weeks of age) and 15 healthy, similarly aged, control infants. Hypercapnic challenges were performed in six ISAM and eight control subjects. Hypoxic arousal responses were elicited by rapidly decreasing inspired oxygen tension to 80 mm Hg for 3 minutes or until arousal occurred. Failure to arouse to hypoxia occurred in the majority of infants in both groups. All infants had a fall in end-tidal carbon dioxide tension during hypoxia, suggesting that each had a hypoxic ventilatory response. However, the fall in end-tidal carbon dioxide tension was significantly less in the ISAM (mean +/- SEM: -4.0 +/- 0.3 vs -8.0 +/- 1.0 mm Hg), suggesting blunted ventilatory responses to hypoxia. Periodic breathing occurred during 9.5% of hypoxic challenges in control infants compared with 37% in ISAM (p = 0.056). Heart rates were significantly higher in the ISAM before, during, and after hypoxic challenges. Hypercapnic challenges (inspired carbon dioxide tension of 60 mm Hg for a maximum of 3 minutes) resulted in arousal in all infants; however, ISAM required a significantly longer exposure to hypercapnia before arousal (mean +/- SEM; 116 +/- 7.8 vs 79 +/- 13.9 seconds; p < 0.02). We conclude that ISAM have an impaired repertoire of protective responses to hypoxia and hypercapnia during sleep, and that this may play a role in their increased risk for sudden infant death syndrome.

Elevated plasma norepinephrine levels in infants of substance-abusing mothers

Infants of substance-abusing mothers (ISAM) have significant growth and neurodevelopmental abnormalities. The origin of these abnormalities is unknown. We postulated that ISAM have increased sympathetic nervous system tone and altered catecholamine levels. Therefore, we measured plasma norepinephrine, epinephrine, and dopamine levels and the number and receptor affinity of beta-adrenoreceptor binding sites on lymphocytes and alpha-adrenoreceptor binding sites on thrombocytes in 22 otherwise healthy ISAM (age, 2.1 +/- 0.5 months; mean +/- SD) and 15 healthy controls (age, 2.5 +/- 0.8 months). Norepinephrine levels in venous blood were 1.8-fold higher in ISAM than in control infants (6.30 +/- 3.85 nmol/L vs 3.55 +/- 2.45 nmol/L). There were no differences in plasma epinephrine or dopamine levels. There were no differences in the number of binding sites or receptor affinity for beta- and alpha-adrenoreceptors. We conclude that ISAM have elevated circulating norepinephrine levels compared with controls. We speculate that this is associated with increased sympathetic nervous system tone in ISAM and that the absence of adrenoreceptor down-regulation may create catecholamine suprasensitivity.

What happens to babies exposed to phencyclidine (PCP) in utero?

Fifty-seven infants exposed to phencyclidine (PCP) in utero were followed for the first year of life. Thirty-six (65%) of the 55 for whom birth records were available manifested symptoms of neonatal narcotic withdrawal syndrome, including 16 (52%) of those whose mothers denied opiate abuse during pregnancy. Temperament problems were noted in 47% of the babies and sleep problems in 14%. The majority of infants grew normally, but a larger than expected number started out small and remained small. Testing using the Bayley Scales of Infant Development at age one year revealed a mental development index (mean +/- SD) of 94 +/- 10 and a psychomotor development index of 98 +/- 10. Attachment behavior was abnormal in 17%. Most infants were cared for by their natural mother. Further studies are needed to determine later effects of in utero PCP exposure, as well as effects on the infants being raised by women who have used PCP. Phencyclidine toxicity needs to be considered when evaluating babies with signs of neonatal narcotic withdrawal syndrome.

Abnormal sleeping ventilatory pattern in infants of substance-abusing mothers

Infants born to opiate-abusing mothers have a decreased ventilatory response to carbon dioxide and a five to ten times increased risk of sudden infant death syndrome (SIDS). These abnormalities of ventilatory control may be associated with abnormal sleeping ventilatory patterns. Therefore, 28 overnight pneumograms (respiratory pattern recording and electrocardiogram) were obtained from 27 infants of substance-abusing mothers (ISAM) (five opiate, seven phencyclidine hydrochloride, three cocaine, and 12 polydrug abusers) and compared with pneumograms from 43 control infants. Pneumograms were quantitated for total sleep time, greatest duration of apnea, total duration of apnea greater than or equal to 6 s, periodic breathing, and mean heart and respiratory rates. The ISAM had a longer total sleep time, greater durations of apnea, a higher total duration of apneas greater than or equal to 6 s, more periodic breathing, a higher mean respiratory rate, and a lower mean heart rate. Thirty-two percent of pneumograms from ISAM were abnormal compared with 9.3% of the control pneumograms. We conclude that ISAM have abnormal sleeping ventilatory patterns that may be related to their increased SIDS risk.

Differences between dropouts and active participants in a pediatric clinic for substance abuse mothers

We compared the maternal and birth characteristics of 87 first-year dropouts with 103 active participants of a pediatric clinic which provides long-term follow-up care to offspring exposed in utero to substance abuse mothers. The age, ethnicity, and marital status of the mother; the type of drug used during pregnancy; and the length, gender, number, and type of addiction problems of the newborn were not significantly different between the two groups. However, the dropouts differed significantly from the active participants in many other aspects. More dropout mothers received no prenatal care and did not have children at home at the time of the present birth. More of them were smokers; had gonorrhea, heart, and kidney problems; and had infections complicating their pregnancy. The dropout newborns were found to have lower birthweight and shorter gestation. These clinical parameters defined a suboptimal group of mothers and children requiring more attention and care. The findings also alert investigators of long-term follow-up studies to be aware of basic differences between nonparticipants and participants.