Rebecca S. Hartley

Airflow and pressure during canary song: direct evidence for mini-breaths

SummaryMale canaries (Serinus canaria) produce songs of long duration compared to the normal respiratory cycle. Each phrase in a song contains repetitions of a particular song syllable, with repetition rates for different syllables ranging from 3 to 35 notes/s. We measured tracheal airflow and air sac pressure in order to investigate respiratory dynamics during song.Song syllables (11–280 ms) are always accompanied by expiratory tracheal airflow. The silent intervals (15–90 ms) between successive syllables are accompanied by inspiration, except for a few phrases where airflow ceases instead of reversing. Thus, the mini-breath respiratory pattern is used most often by the five birds studied and pulsatile expiration is used only occasionally.Songs and phrases accompanied by minibreaths were of longer duration than those accompanied by pulsatile expiration, presumably because the animals finite vital capacity is not a limiting factor when the volume of air expired for one note is replaced by inspiration prior to the next. Pulsatile expiration was used for only a few syllable types from one bird that were produced at higher repetition rates than syllables accompanied by mini-breaths. We suggest that male canaries switch to pulsatile expiration only when the syllable repetition rate is too high (greater than about 30 Hz) for them to achieve mini-breaths.Changes in syringeal configuration that may accompany song are discussed, based on the assumption that changes in the ratio of subsyringeal (air sac) pressure to tracheal flow rate reflect changes in syringeal resistance.

Skeletal muscle satellite cells appear during late chicken embryogenesis.

The emergence of avian satellite cells during development has been studied using markers that distinguish adult from fetal cells. Previous studies by us have shown that myogenic cultures from fetal (Embryonic Day 10) and adult 12-16 weeks) chicken pectoralis muscle (PM) each regulate expression of the embryonic isoform of fast myosin heavy chain (MHC) differently. In fetal cultures, embryonic MHC is coexpressed with a ventricular MHC in both myocytes (differentiated myoblasts) and myotubes. In contrast, myocytes and newly formed myotubes in adult cultures express ventricular but not embryonic MHC. In the current study, the appearance of myocytes and myotubes which express ventricular but not embryonic MHC was used to determine when adult myoblasts first emerge during avian development. By examining patterns of MHC expression in mass and clonal cultures prepared from embryonic and posthatch chicken skeletal muscle using double-label immunofluorescence with isoform-specific monoclonal antibodies, we show that a significant number of myocytes and myotubes which stain for ventricular but not embryonic MHC are first seen in cultures derived from PM during fetal development (Embryonic Day 18) and comprise the majority, if not all, of the myoblasts present at hatching and beyond. These results suggest that adult type myoblasts become dominant in late embryogenesis. We also show that satellite cell cultures derived from adult slow muscle give results similar to those of cultures derived from adult fast muscle. Cultures derived from Embryonic Day 10 hindlimb form myocytes and myotubes that coexpress ventricular and embryonic MHCs in a manner similar to cells of the Embryonic Day 10 PM. Thus, adult and fetal expression patterns of ventricular and embryonic MHCs are correlated with developmental age but not muscle fiber type.

Expiratory muscle activity during song production in the canary

Elaborate respiratory patterns accompany song production in male canaries (Serinus canaria). To learn how such patterns arise, electromyographic activity was measured in the expiratory muscles in the abdomen. Most song phrases are accompanied either by mini-breaths (when syllable repetition rates are 2 to 27/sec) or by pulsatile expiration (when syllable repetition rates are 30 to 38/sec). In both cases there is a one-to-one correspondence between bursts of expiratory muscle electrical activity and song syllables. Phrases with syllable repetition rates of 62-70/sec, which are rare, are accompanied by expiratory airflow that may be either pulsatile or continuous. The expiratory muscles are active throughout such phrases, suggesting that the muscles of the vocal organ, the syrinx, are responsible for producing separate notes. Thus, at rates up to 38/sec, the abdominal muscles of canaries contract briefly for the production of each song syllable.

Myoblasts from fetal and adult skeletal muscle regulate myosin expression differently

We compared the expression of myosin heavy chains in myogenic cultures prepared from fetal (embryonic Day 10) and adult (12-16 weeks) chicken pectoralis muscle using immunofluorescence with isoform-specific monoclonal antibodies. We found that the majority of fetal myocytes (differentiated myoblasts) and myotubes coexpressed ventricular and embryonic myosin heavy chains in culture. Also, when fetal cells were plated at a clonal density most clones coexpressed both ventricular and embryonic isoforms. In contrast, all adult myocytes and newly formed adult myotubes expressed just ventricular myosin, whether plated at mass or clonal densities. Within 12-24 hr of the onset of fusion, adult myotubes began to express embryonic myosin as well. Eventually, the majority of adult myotubes coexpressed both ventricular and embryonic myosin. The delay of embryonic myosin expression until after fusion was also seen in passaged adult myoblasts and in myoblasts isolated from regenerating adult muscle. The expression of embryonic myosin can be abolished by inhibiting fusion with EGTA in adult but not in fetal cultures. We conclude that both fetal and adult myotubes express ventricular and embryonic myosins but only fetal myocytes express the embryonic isoform prior to fusion. This difference in the regulation of embryonic myosin expression between fetal and adult myoblasts supports the hypothesis that these cells may represent two distinct populations of myogenic precursors.

Birth order and delivery interval: analysis of twin pair perinatal outcomes.

Objective. To determine whether second-born twins (B) have higher morbidity and mortality than first-born twins (A), using a paired analysis. Study design. We conducted a retrospective analysis of birth certificates and fetal and infant death certificates for 5138 twin pairs selected from those born in Washington State from 1989 to 2001. Twin A was vertex and delivered vaginally. Pairs were not size-discordant ( < 20%) and had no malformations. Matched-pair odds ratios were calculated. Results. Twin B had more fetal distress (OR = 6.0) and more low 5-min Apgar scores (OR = 2.1) than Twin A, except at short delivery intervals. Pairs had relatively high rates of combined vaginal plus cesarean deliveries at delivery intervals ⩾15 min. Conclusion. If prompt vaginal delivery of Twin B does not occur, the benefits of vaginal delivery for Twin A might not outweigh the risks of distress and low Apgar scores in Twin B and vaginal plus cesarean delivery for the mother.

Long-term maintenance of primary myogenic cultures on a reconstituted basement membrane.

SummaryWe describe a simple technique for maintaining highly contractile long-term chicken myogenic cultures on Matrigel, a gel composed of basement membrane components extracted from the Engelbreth-Holm-Swarm mouse tumor. Cultures grown on Matrigel consist of three-dimensional multilayers of cylindrical, contracting myotubes which endure for at least 60 d without myotube detachment. A Matrigel substrate increases the initial plating efficiency but does not effect cell proliferation. Large-scale differentiation in cultures maintained on Matrigel is delayed by 1 to 2 d, compared to cultures grown on gelatin-coated dishes. Long-term maintenance on Matrigel also results in increased expression of the neonatal and adult fast myosin heavy chain isoforms. Culturing of cells on a Matrigel substrate could thus facilitate the study of later events of in vitro myogenesis.

Morphogenesis of the Hair Follicle during the Ontogeny of Human Skin

Hair follicle development in the human foetus begins subsequent to epidermal stratification at 60 days estimated gestational age when clusters of basal cells form a hair germ. Hair germs bud into the dermis, elongate (hair pegs) and become surrounded by an accumulation of fibroblastic cells. Hair immunolabeling with anti-keratin antibodies suggests that the outer layer of follicle cells is derived from basal keratinocytes, whereas cells in the follicle core are continuous with intermediate cells. During the fourth month the follicle develops into a bulbous hair peg; bulges representing primordia of the apocrine gland, the sebaceous gland (intermediate) and the bulge (distal) form on its posterior aspect. , The tetminus infolds to form a concavity that encompasses cells of the dermal papilla. Matrix cells lining the roof of the bulb give rise to concentric layers of the inner root sheath and hair. These layers can be recognized morphologically and by labeling with several monoclonal antibodies. An intra-epidermal hair canal forms within the hair tract and the infundibulum of the follicle by keratinization identical to that of the interfollicular epidermis. Hairs grow into the hair canal and are exposed around 19–21 weeks by erosion of the roof of the hair canal at the skin surface.

Please exit safely: maternal and twin pair neonatal outcomes according to delivery mode when twin A is vertex().

Abstract Objective: To investigate maternal and infant outcomes associated with delivery mode for twins with a cephalic presenting twin. Methods: Linked birth certificate and ICD hospital discharge data were analyzed retrospectively for 5573 mothers and their respective twin pairs born live at 34–42 weeks’ gestation, with twin A vertex, in Washington State from 1997–2007. Relative risks (RR) and 95% confidence intervals of adverse maternal and twin pair outcomes were calculated for vaginal delivery or cesarean during labor in comparison to cesarean without labor. Results: Vaginal delivery or cesarean during labor was associated with significantly elevated rates of maternal hemorrhage (RR = 2.8 [2.2,3.7]), infection (RR = 2.2 [1.5,3.3]), twin pair birth injury (RR = 2.6 [1.2,5.4]) and low 5-min Apgar scores (RR = 1.4 [1.1,1.8]) and with significantly lower rates of ventilation among preterm twin pairs only (RR = 0.8 [0.7,0.9]). The lowest rate of combined poor short-term outcomes occurred in mothers and twin pairs delivered by cesarean without labor (23%) and the highest rates occurred in those with operative vaginal or cesarean during labor (39% and 34%, respectively). Among women in labor, 35% of nulliparas achieved spontaneous vaginal delivery of both twins compared to 63% of non-nulliparas. Conclusion: For nulliparous women who carry twins to term, planned cesarean may improve outcomes.