Delivery of the second twin.

OBJECTIVE: To determine the likelihood of cesarean for the second twin after vaginal delivery of the first and the risk of vaginal delivery. METHOD: A retrospective analysis of twin deliveries was performed on 10,365 live born twin pairs (20,730 births), using birth certificate data from the State of Illinois from 1997 through 2000. RESULT: The incidence of cesarean for the second twin after vaginal delivery of the first was 10.1%. The greatest incidence of failed vaginal delivery of the second twin was in the vertex/non-vertex group. Five-minute Apgar scores <4 were significantly more frequent in vaginally delivered twins <2000 g compared to those delivered via cesarean (p<0.001). CONCLUSION: Twin presentation type is predictive of the likelihood of a failed vaginal delivery of the second twin. Cesarean appears to significantly reduce the incidence of Apgars <4 for neonates <2000 g.

Mode of delivery and risk of respiratory diseases in newborns.

OBJECTIVE: To determine whether there is an increased incidence of persistent pulmonary hypertension in neonates delivered by cesarean, with or without labor, compared with those delivered vaginally. METHODS: We did a computerized retrospective review of 29,669 consecutive deliveries over 7 years (1992-1999). The incidences of persistent pulmonary hypertension of the newborn, transient tachypnea of the newborn, and respiratory distress syndrome (RDS) were tabulated for each delivery mode. Cases of persistent pulmonary hypertension were reviewed individually to determine delivery method and whether labor had occurred. The three groups defined were all cesarean deliveries, all elective cesareans, and all vaginal deliveries. RESULTS: Among 4301 cesareans done, 17 neonates had persistent pulmonary hypertension (four per 1000 live births). Among 1889 elective cesarean deliveries, seven neonates had persistent pulmonary hypertension (3.7 per 1000 live births). Among 21,017 vaginal deliveries, 17 neonates had persistent pulmonary hypertension (0.8 per 1000 live births). chi2 analysis showed an odds ratio 4.6 and P <.001 for comparison of elective cesarean and vaginal delivery for that outcome. CONCLUSION: The incidence of persistent pulmonary hypertension of the newborn was approximately 0.37% among neonates delivered by elective cesarean, almost fivefold higher than those delivered vaginally. The findings have implications for informed consent before cesarean and increased surveillance of neonates after cesarean.

Bone tissue engineering in a rotating bioreactor using a microcarrier matrix system.

A novel approach was utilized to grow in vitro mineralized bone tissue using lighter-than-water, polymeric scaffolds in a high aspect ratio rotating bioreactor. We have adapted polymer microencapsulation methods for the formation of hollow, lighter-than-water microcarriers of degradable poly(lactic-co-glycolic acid). Scaffolds were fabricated by sintering together lighter-than-water microcarriers from 500 to 860 microm in diameter to create a fully interconnected, three-dimensional network with an average pore size of 187 microm and aggregate density of 0.65 g/mL. Motion in the rotating bioreactor was characterized by numerical simulation and by direct measurement using an in situ particle tracking system. Scaffold constructs established a near circular trajectory in the fluid medium with a terminal velocity of 98 mm/s while avoiding collision with the bioreactor wall. Preliminary cell culture studies on these scaffolds show that osteoblast-like cells readily attached to microcarrier scaffolds using controlled seeding conditions with an average cell density of 6.5 x 10(4) cells/cm(2). The maximum shear stress imparted to attached cells was estimated to be 3.9 dynes/cm(2). In addition, cells cultured in vitro on these lighter-than-water scaffolds retained their osteoblastic phenotype and showed significant increases in alkaline phosphatase expression and alizarin red staining by day 7 as compared with statically cultured controls.

Numerical model and experimental validation of microcarrier motion in a rotating bioreactor.

The equations of motion for microcarriers in a rotating bioreactor have been formulated and trajectories obtained using numerical techniques. An imaging system was built to validate the results by direct observation of microcarrier trajectories in the rotating frame of reference. The microcarrier motion observed by this imaging system was in excellent agreement with the numerical predictions of that motion. In the rotating frame of reference, microcarriers with density greater than the surrounding fluid medium followed a circular motion relative to the culture medium combined with a persistent migration and eventual collision with the outer wall of the reactor. However, for microcarrier density less the fluid medium, their circular motion migrated toward the central region of the reactor. When multiple microcarrier beads that are lighter than water are inserted into the reactor, the centrally directed migration results in the formation of clusters that are stabilized by tissue bridges formed by osteoblasts seeded onto the microcarriers. This system offers unique opportunities to monitor tissue synthesis on microcarriers using real-time optical techniques and to optimize the bioreactor operating conditions for exploiting this technology to study early bone tissue synthesis in vitro.

Extraocular mesenchyme patterns the optic vesicle during early eye development in the embryonic chick.

The vertebrate eye develops from the neuroepithelium of the ventral forebrain by the evagination and formation of the optic vesicle. Classical embryological studies have shown that the surrounding extraocular tissues - the surface ectoderm and extraocular mesenchyme - are necessary for normal eye growth and differentiation. We have used explant cultures of chick optic vesicles to study the regulation of retinal pigmented epithelium (RPE) patterning and differentiation during early eye development. Our results show that extraocular mesenchyme is required for the induction and maintenance of expression of the RPE-specific genes Mitf and Wnt13 and the melanosomal matrix protein MMP115. In the absence of extraocular tissues, RPE development did not occur. Replacement of the extraocular mesenchyme with cranial mesenchyme, but not lateral plate mesoderm, could rescue expression of the RPE-marker Mitf. In addition to activating expression of RPE-specific genes, the extraocular mesenchyme inhibits the expression of the neural retina-specific transcription factor Chx10 and downregulates the eye-specific transcription factors Pax6 and Optx2. The TGF(&bgr;) family member activin can substitute for the extraocular mesenchyme by promoting expression of the RPE-specific genes and downregulating expression of the neural retina-specific markers. These data indicate that extraocular mesenchyme, and possibly an activin-like signal, pattern the domains of the optic vesicle into RPE and neural retina.

Soluble factors and the development of rod photoreceptors.

Photoreceptors are the most abundant cell type in the vertebrate neural retina. Like the other retinal neurons and the Müller glia, they arise from a population of precursor cells that are multipotent and intrinsic to the retina. Approximately 10 years ago, several studies demonstrated that retinal precursor cells (RPCs) are competent to respond to environmental factors that promote cell type determination and differentiation. Since those studies, significant effort has been directed at identifying the molecular nature of these environmental signals and understanding the precise mechanisms they employ to drive RPCs towards the different retinal fates. In this review, we describe the recent progress toward understanding how environmental factors influence the development of vertebrate rod photoreceptors.

p27(Kip1) regulates cell cycle withdrawal of late multipotent progenitor cells in the mammalian retina.

The cyclin-dependent kinase inhibitor protein, p27(Kip1), is necessary for the timing of cell cycle withdrawal that precedes terminal differentiation in oligodendrocytes of the optic nerve. Although p27(Kip1) is widely expressed in the developing central nervous system, it is not known whether this protein has a similar role in neuronal differentiation. To address this issue, we have examined the expression and function of p27(Kip1) in the developing retina, a well-characterized part of the central nervous system. p27(Kip1) is expressed in a pattern coincident with the onset of differentiation of most retinal cell types. In vitro analyses show that p27(Kip1) accumulation in retinal cells correlates with cell cycle withdrawal and differentiation, and when overexpressed, p27(Kip1) inhibits proliferation of the progenitor cells. Furthermore, the histogenesis of photoreceptors and Müller glia is extended in the retina of p27(Kip1)-deficient mice. Finally, we examined the adult retinal dysplasia in p27(Kip1)-deficient mice with cell-type-specific markers. Contrary to previous suggestions that the dysplasia is caused by excess production of photoreceptors, we suggest that the dysplasia is due to the displacement of reactive Müller glia into the layer of photoreceptor outer segments. These results demonstrate that p27(Kip1) is part of the molecular mechanism that controls the decision of multipotent central nervous system progenitors to withdraw from the cell cycle. Second, postmitotic Müller glia have a novel and intrinsic requirement for p27(Kip1) in maintaining their differentiated state.

Heparin/endothelial cell growth supplement regulates matrix gene expression and prolongs life span of vascular smooth muscle cells through modulation of interleukin-1.

Vascular smooth muscle cells produce and respond to interleukin-1, a cytokine which modifies inflammation-associated vascular activities including the synthesis of extracellular matrix proteins. We have established vascular smooth muscle cells culture conditions in which heparin, in the presence of endothelial cell growth supplement, promotes cell proliferation and inhibits interleukin-1 and matrix protein expression. To test whether interleukin-1 mediates growth and matrix modulation by heparin/endothelial cell growth supplement, vascular smooth muscle cells were transfected with an Epstein-Barr virus-derived expression vector designed to express interleukin-1 antisense transcripts. RNase protection and ELISA assays demonstrated a complete block of interleukin-1 transcription and protein synthesis. Northern blot analysis also showed that interleukin-1 antisense decreased the expression of matrix genes such as type I collagen, fibronectin, and decorin similar to downregulation after heparin/endothelial cell growth supplement treatment. In contrast, the expression of versican was not affected, indicating a selective suppression of matrix proteins. In addition, interleukin-1 antisense significantly prolonged the life span of vascular smooth muscle cells in culture. Our data suggest that heparin/endothelial cell growth supplement induces matrix remodeling and controls growth and senescence of vascular smooth muscle cells through down-regulation of interleukin-1.

Intrapartum antibiotic prophylaxis increases the incidence of gram-negative neonatal sepsis.

OBJECTIVE: To investigate the influence of the increased use of intrapartum chemoprophylaxis on the incidence of vertically transmitted neonatal sepsis. METHODS: Multiple institutional databases were queried for the number of cases in which intrapartum antibiotics were used, the obstetric risk factors that were present, and the number of resultant cases of neonatal sepsis that occurred for deliveries from 1992 through 1997. Intrapartum antibiotic use was compared between the first and fourth quarter of 1997. Comparisons were made between the years 1992-1996 and 1997 for the incidence of the various pathogens causing neonatal sepsis; group B streptococcus (GBS), gram-negative sepsis, and others. RESULTS: We found a significant increase in intrapartum chemoprophylaxis between the first and fourth quarters of 1997 corresponding to the increased physician awareness of published guidelines. As expected, the incidence of neonatal GBS sepsis was drastically reduced (from 1.7/1000 live births to 0 in 3730 births, P = 0.02). Unfortunately, there was a concomitant increase in the incidence of gram-negative sepsis (0.29/1000 vs. 1.3/1000, P = .02). The overall incidence of neonatal sepsis remained unchanged (2.7/1000 vs. 2.1/1000, P = .69). CONCLUSIONS: Published guidelines have encouraged physicians to increase the use of intrapartum chemoprophylaxis to reduce vertical transmission of GBS. This study confirms the efficacy of this approach. Unfortunately, this reduction comes at the cost of increasing the incidence of ampicillin-resistant gram-negative neonatal sepsis with a resultant increased mortality. These data provide compelling evidence that the policy of providing ampicillin chemoprophylaxis in selected patients needs to be reconsidered.

Pediatrician attendance at cesarean delivery: necessary or not?

OBJECTIVE: To determine whether it is necessary for a pediatrician to attend all cesarean deliveries. METHODS: We analyzed a database of 17,867 consecutive deliveries to determine the rates of low Apgar scores in the following three groups of patients: those with vaginal delivery, cesarean delivery using regional anesthesia without fetal indication, and cesarean delivery for fetal indications or using general anesthesia. RESULTS: There was a significantly higher rate of low Apgar scores in the fetal indications or general anesthesia group when compared with vaginal deliveries. Specifically, 35 (5.8%) of 596 cesareans for fetal heart rate abnormality or using general anesthesia had 1-minute Apgars under 4 in contrast to 115 of 10,270 (1.1%) of vaginal deliveries. There was no significantly increased risk for low Apgar scores in the group of cesareans using regional anesthesia for nonfetal indications (33 of 2057, 1.6%). Results were similar for Apgar scores under 7 at 5 minutes. CONCLUSION: Because there is no higher incidence of low Apgar scores in cesarean deliveries using regional anesthesia for nonfetal indications compared with vaginal deliveries, there is no convincing need for pediatrician attendance at such deliveries.

The nuclear receptor transcription factor, retinoid-related orphan receptor beta, regulates retinal progenitor proliferation.

We examined the role of retinoid-related orphan receptor (ROR)beta, a member of the nuclear receptor family of transcription factors, in retinal neurogenesis. In situ hybridization studies showed that RORbeta is expressed in retinal progenitor cells in the embryonic rat retina. Further studies demonstrated that RORbeta colocalizes with Chx10, a transcription factor thought to influence retinal progenitor proliferation (Burmeister, M., Novak, J., Liang, M-Y., Basu, S., Ploder, L., Hawes, N.L. Vidgen, D., Hoover, F., Goldman, D. , Kalnins, V.I., Roderick, T.H., Taylor, B.A., Hankin, M.H. and McInnes, R.R., 1996. Ocular retardation mouse caused by Chx10 homeobox null allele: impaired retinal progenitor proliferation and bipolar cell differentiation. Nature Genetics 12, 376-383). Northern analysis reveals that RORbeta expression is dramatically decreased in the ocular retardationJ mutant, which possesses a defect in the Chx10 gene. Overexpression of RORbeta in retinal progenitors by biolistic transfection results in an increase in the number of large cell clones. These data support a role for RORbeta in regulating retinal progenitor proliferation, possibly via the Chx10 gene.

Chronic vaginal candidiasis responsive to biotin therapy in a carrier of biotinidase deficiency.

BACKGROUND: Many patients experience recurrent or persistent episodes of vaginal candidiasis. Some of these women might be carriers of an inborn error of biotin metabolism (either biotinidase deficiency or holocarboxylase synthetase activity). These women might benefit from administration of pharmacologic amounts of biotin. CASE: A 38-year-old gravida 2, para 2 carrier of biotinidase deficiency presented with a 14-month history of persistent vaginal candidiasis, despite appropriate therapy. After 3 months of pharmacologic doses of biotin, her symptoms resolved completely. CONCLUSION: Given that 1 in every 123 individuals is predicted to be a carrier of biotinidase deficiency, there might be other women with chronic vaginal candidiasis who will respond to biotin administration.

Multipotential stem cells and progenitors in the vertebrate retina.

The vertebrate retina is derived from paired evaginations from the neural tube in embryonic development and is initially produced by progenitor cells similar to those that generate the neurons and glia of other areas of the central nervous system. In some amphibians and fish, the retina continues to grow along with the eye throughout the life of the animal. The new retinal cells are added at the ciliary margin of the eye from the mitotic activity of neural/glial stem cells in a region known as the germinal zone and are seamlessly incorporated into the existing retinal circuitry. Little is known about the cell or molecular biology of these stem cells; however, studies of retinal progenitor cells in chick and mammalian embryos have led to the identification of several factors that control their proliferation. Moreover, studies of retinal regeneration have shown that retinal stem cells can also be derived from two or perhaps three additional sources after retinal damage: (a) the retinal pigmented epithelium (RPE) in amphibians and embryonic chicks and mammals; (b) a specialized rod progenitor in fish; and (c) the Müller glial cells. While there is currently no evidence for a neural/glial stem cell in the adult mammalian retina, and the retina of the mature mammal does not show regenerative capacity after damage, there is a possibility for the reinitiation of stem cell potential at the peripheral retinal margin, from the RPE or from the Müller glial cells. The application of information derived from the studies of retinal progenitor cells in developing organisms should soon provide a test of these possibilities.

Intrapartum management relating to the risk of perinatal transmission of group B streptococcus.

OBJECTIVE: To review the incidence of neonatal group B streptococcal (GBS) sepsis and its associated risk factors in our obstetrical population. METHODS: A computerized perinatal database of over 17,000 births (from 1992 to 1996) was queried for the incidence of neonatal GBS sepsis. A more detailed review of 895 births (from the first quarter of 1997) was undertaken to identify the incidence of risk factors known to be associated with neonatal GBS sepsis. RESULTS: In our institution, 30 cases of neonatal early-onset GBS sepsis were identified in over 17,000 births (or 1.7/1,000 deliveries). Risk factors were identified in 17 of those cases (56%). There were two neonatal fatalities. Chemoprophylaxis was provided in 15% of the total deliveries. CONCLUSIONS: In spite of the lack of a uniform policy for identifying patients suitable for GBS chemoprophylaxis, we found only a 43% incidence of neonatal GBS sepsis occurring without risk factors present. Identification of antepartum or intrapartum risk factors in our series, therefore, would have identified the majority of cases resulting in neonatal GBS sepsis, which may have benefited from intrapartum therapy. Some negative potential consequences of chemoprophylaxis are discussed, raising questions regarding the recent recommendations of the Centers for Disease Control and Prevention.