Beta-galactosidase detection as an indicator of endogenous PTHrP in cartilage.

Genetically altered mice are an important tool for biomedical research. Several transgenic mice have been created in which activation of the transgene results in production of beta-galactosidase that can be detected by histological means. While preservation and subsequent visualization of enzyme activity in soft tissues can be complicated, it is particularly difficult in bone specimens, especially those that have been decalcified. For these studies, we examined the bones of parathyroid hormone-related peptide (PTHrP) knock-in mice in which expression of PTHrP resulted in beta-galactosidase production. During the past decade, several studies have demonstrated the importance of PTHrP in bone. Thus, it is important to preserve and detect beta-galactosidase enzymatic activity in bone for these studies. We demonstrate here that beta-galactosidase was visualized better in slides with bone sections taken from PTHrP knock-in mice when bones were frozen and sectioned compared to bones that were embedded in plastic and sectioned using a microtome. Importantly, we were able to visualize beta-galactosidase in plastic embedded bones when specimens were fixed, stained (X-gal), embedded in plastic, and then sectioned rather than being fixed, embedded in plastic, sectioned, then stained.

Use of neostigmine to relieve a suspected colonic pseudoobstruction in pregnancy.

Neostigmine is a treatment option for colonic pseudoobstruction. However, experience in using neostigmine for this indication in pregnant women is limited. We present a case of a woman with an estimated fetal gestational age of 34 weeks presented with what was believed to be a pseudoobstruction and when conservative management failed, neostigmine was administered with no adverse side effects. Ultimately, the patient was found to have a mechanical obstruction and we discuss the challenges in making this diagnosis in pregnancy. Neostigmine may be a viable alternative to colonoscopy in pregnant women for whom mechanical obstruction is properly excluded.

Effects of long-term fixation on histological quality of undecalcified murine bones embedded in methylmethacrylate.

While long-term fixation and storage of specimens is common and useful for many research projects, it is particularly important for space flight investigations where samples may not be returned to Earth for several months (International Space Station) or years (manned mission to Mars). We examined two critical challenges of space flight experimentation: the effect of long-term fixation on the quality of mouse bone preservation and the preservation of antigens and enzymes for both histochemical and immunohistochemical analyses, and how the animal/sample processing affects the preservation. We show that long-term fixation minimally affects standard histological staining, but that enzyme histochemistry and immunolabeling are greatly compromised. Further, we demonstrate that whole animal preservation is not as suitable as whole leg or stripped leg preservation for long-term fixation and all histological analyses. Overall, we recommend whole leg processing for long-term storage of bone specimens in fixative prior to embedding in plastic for histological examination.

HistoChoice as an alternative to formalin fixation of undecalcified bone specimens.

We compared histochemical and immunohistochemical staining as well as fluorochrome labeling in murine bone specimens that were fixed with 10% neutral buffered formalin to those fixed with HistoChoice. We showed that sections from undecalcified tibiae fixed for 4 h in HistoChoice resulted in enhanced toluidine blue and Von Kossa histochemical staining compared to formalin fixation. HistoChoice produced comparable or improved staining for alkaline phosphatase. Acid phosphatase localization was better in formalin fixed specimens, but osteoclasts were visualized more easily in HistoChoice fixed specimens. As expected, immunohistochemical labeling was antibody dependent; some antibodies labeled better in HistoChoice fixed specimens while others were better in formalin fixed specimens. Toluidine blue, Von Kossa, and alkaline phosphatase staining of sections fixed for 12 h produced sections that were similar to 4 h fixed sections. Fixation for 12 h preserved acid phosphatase activity better. Increasing fixation to 12 h affected immunolocalization differentially. Bone sialoprotein labeling in HistoChoice fixed specimens was comparable to formalin fixed samples. On the other hand, after 12 h formalin fixation, osteocalcin labeling was comparable to HistoChoice. For most histochemical applications, fixing murine bone specimens for 4 h with HistoChoice yielded superior staining compared to formalin fixation. If immunohistochemical localization is desired, however, individual antibodies must be tested to determine which fixation process retains antigenicity better. In addition, there was no detectable difference in the intensity of fluorochrome labeling using either fixative. Finally, fixation duration did not alter the intensity of labeling.

Osteogenic protein-1 overcomes the inhibitory effect of nicotine on posterolateral lumbar fusion.

STUDY DESIGN: An established rabbit posterolateral lumbar fusion model was used to evaluate the ability of osteogenic protein-1 to overcome the inhibitory effect of nicotine. OBJECTIVE: To determine whether osteogenic protein-1 should be considered as a bone graft alternative for the patient who smokes. SUMMARY OF BACKGROUND DATA: Smoking interferes with the success of posterolateral lumbar fusion. This inhibitory effect has been attributed to nicotine and confirmed in a New Zealand white rabbit model. Osteoinductive protein-1 has been shown to induce posterolateral spine fusion reliably in the rabbit model. The effectiveness with which osteogenic protein-1 induces fusion in the presence of nicotine has not been studied previously. METHODS: Single-level posterolateral intertransverse process fusions were performed at L5-L6 in 18 New Zealand white rabbits. Either autograft or osteogenic protein-1 was used as grafting material. Nicotine was administered via subcutaneous mini-osmotic pumps. The animals were killed 5 weeks after surgery, and the resulting fusion masses were studied. RESULTS: Three rabbits (17%) were excluded because of complications. By manual palpation, two of the eight nicotine-exposed autograft rabbits (25%) and all of the nicotine-exposed osteogenic protein-1 rabbits (100%) were found to be fused. These results correlated well with those obtained from biomechanical testing. Histologically, the fusion zones of the nicotine-exposed autograft rabbits were distinctly less mature than the fusion masses of the nicotine-exposed osteogenic protein-1 rabbits. CONCLUSION: Osteoinductive protein-1 was able to overcome the inhibitory effects of nicotine in a rabbit posterolateral spine fusion model, and to induce bony fusion reliably at 5 weeks.

2000 Young Investigator Research Award winner. Evaluation of OP-1 as a graft substitute for intertransverse process lumbar fusion.

STUDY DESIGN: An established rabbit intertransverse process lumbar fusion model was used to evaluate osteogenic protein (OP)-1 as a potential graft substitute. OBJECTIVES: To determine whether OP-1 is effective in producing intertransverse process lumbar fusion in a rabbit model. SUMMARY OF BACKGROUND DATA: Autogenous iliac crest bone is the gold standard in grafting material for inducing intertransverse process fusion. However, bone graft substitutes are being considered as supplementary or alternative means to achieve such fusion with less morbidity. Relatively little research has been undertaken to investigate the efficacy of OP-1 in this role. METHODS: Single-level intertransverse process lumbar fusions were performed at L5-L6 of 31 New Zealand White rabbits. These were divided into three study groups: autograft, carrier alone, and carrier with OP-1. The animals were killed 5 weeks after surgery. Resultant fusion masses were evaluated by manual palpation, radiography, biomechanical multidirectional flexibility testing, and histology. RESULTS: Seven rabbits (23%) were excluded because of complications. Of the remaining 24 rabbits, 5 (63%) of the 8 in the autograft group had fusion detected by manual palpation, none (0%) of the 8 in the carrier-alone group had fusion, and all 8 (100%) in the OP-1 group had fusion. Radiographs were 55% sensitive and 92% specific for determining fusion. Biomechanical testing results correlated well with those of manual palpation. Histologically, autograft specimens were predominantly fibrocartilage, OP-1 specimens were predominantly maturing bone, and carrier-alone specimens did not show significant bone formation. CONCLUSIONS: OP-1 was found to reliably induce solid intertransverse process fusion in a rabbit model at 5 weeks.

Effects of calcitonin gene-related peptide on bone turnover in ovariectomized rats.

Calcitonin gene-related peptide (CGRP) is a neuropeptide abundantly concentrated in sensory nerve endings innervating bone metaphysis and periosteum, which indicates that it plays a local role in bone metabolism. CGRP-alpha and -beta share structural and functional homology with calcitonin (CT) and have been shown to inhibit bone resorption in vitro and to induce hypocalcemia in vivo. We recently reported that CGRP stimulates the production of the growth factor insulin-like growth factor-I and inhibits that of the cytokine tumor necrosis factor-alpha by osteoblasts, suggesting that CGRP may control bone cell activity. To investigate this possibility, we used ovariectomized (ovx) rats as a high bone turnover model and compared the effects of CGRP to those of CT. ovx young female rats were injected daily starting the day after surgery with either phosphate-buffered saline, CGRP-alpha (1.15 mg/kg per day), or CT (3 micrograms/kg per day) for 28 days. Ovariectomy induced an increase in bone turnover associated with a 60% loss in trabecular bone volume of the proximal tibia. CGRP inhibited bone resorption but not bone formation, and was nevertheless less efficient than CT in preventing bone loss, since CGRP-treated rats had a loss of 46% of cancellous bone, whereas CT-treated rats had a loss of 21%. This suggests that CGRP is either less potent than CT at inhibiting bone resorption or else very rapidly degraded. These data indicate that CGRP can control bone cells through a mechanism that is in part different from that of CT, and further suggest that CGRP may play a local role in bone metabolism.

Use of the pulmonary artery catheter in severe preeclampsia: a review.

The use of a balloon-tipped, flow-directed pulmonary artery catheter in critically ill and surgical patients has become commonplace in the United States since its introduction into clinical medicine in 1970. The capability of acquiring continuous hemodynamic and, more recently, oxygen transport data, has led to an enhanced understanding of pathophysiologic processes in disease states and to an improved ability to guide therapeutic decision making. The purpose of this paper is to review experience with the pulmonary artery catheter in subsets of women with severe preeclampsia.

Base deficit and oxygen transport in severe preeclampsia.

OBJECTIVE: To evaluate the relationship of anaerobic metabolism, as reflected by the calculated base deficit, with oxygen transport and left ventricular function in women with severe preeclampsia. METHODS: Forty women with singleton pregnancies and severe preeclampsia who met prescribed criteria for invasive hemodynamic monitoring had arterial blood gas and hemodynamic values obtained immediately after placement of a pulmonary artery catheter. Oxygen transport indices were stratified according to the admission base deficit. RESULTS: Linear regression analysis demonstrated a strong negative correlation between the calculated base deficit and the oxygen delivery index (r = -0.64), cardiac index (r = -0.62), and left ventricular stroke work index (r = -0.58). A baseline maternal base deficit exceeding -8.0 mEq/L consistently predicted fetal acidosis, fetal death, and maternal end-organ ischemic injury. CONCLUSION: The calculated base deficit reliably reflects maternal oxygen transport dynamics and identifies patients at risk for end-organ injury. Ventricular contractility and oxygen delivery decline with mounting oxygen debt.

Adult respiratory distress in pregnancy: critical care issues.

Adult respiratory distress syndrome (ARDS) is a complex disease process involving noncardiogenic pulmonary edema, central hypovolemia, widespread atelectasis, and, in the final stages, an inability to perfuse end organs. Uteroplacental perfusion is usually compromised in such situations, which may be catastrophic, depending on the amount of fetal oxygen reserve. ARDS is often preceded by sepsis and frequently ends in maternal death, despite aggressive intervention. Inflammatory responses, complement activation, and prostaglandins have been implicated as probable mediators of both sepsis and ARDS. Invasive hemodynamic monitoring and mechanical ventilation are usually warranted to provide detailed assessment and support. However, when a critical illness affects the family unit, emotional and spiritual issues must receive significant attention to provide holistic care.

Critical care obstetrics: experts' round table discussion.

A panel of leading experts in critical care obstetric (CCOB) nursing met to discuss the specialty and its future, the impact of changes in the health care system, educational opportunities to learn and update CCOB nursing, formation and use of standards for the specialty, patient placement (dedicated obstetric intensive care units [OB ICU], labor and delivery intensive care units [L & D ICU], regular intensive care units [ICU]), patient populations, and interactions and working relationships with the physicians who care for CCOB patients (perinatologists, obstetricians, internists, obstetric medicine specialists, anesthesiologists, other subspecialists). The topics for discussion were chosen by Carol J. Harvey, RNC, MS, who acted as moderator and Mary Ellen Burke, RN, MS, coordinated the publication of the discussion.

Critical care obstetrics: the role of advanced practice nursing.

The role of the advanced practice nurse in the specialty of critical care obstetric nursing is emerging to meet the dynamic needs of health care under reform. Advanced practice components, including case management, research utilization, collaborative consultation, and advanced educational preparation, give light to a new model of caregiver. This article details the educational preparation and specific roles of the advanced practice nurse in the specialty of critical care obstetrics.

Mice transgenic for HTLV-I LTR-tax exhibit tax expression in bone, skeletal alterations, and high bone turnover.

HTLV-I infection can result in adult T cell leukemia with accompanying hypercalcemia and increased bone resorption. A viral etiology has also been invoked for Paget's disease, a disease of high bone turnover. Delineation of pathogenetic mechanisms of viral-associated bone diseases has been impeded by the complexity of viral and host factors. In order to consider the relationship of HTLV-I infection to skeletal changes we have evaluated the role of a single viral gene in mice transgenic for HTLV-I tax under the control of the viral promoter. Tax mice exhibited severe skeletal abnormalities characterized by high bone turnover, increases in osteoblast and osteoclast numbers and activity, and myelofibrosis. These changes were apparent as early as two months of age. Tax mRNA and protein were highly expressed in bone but not in bone marrow nor in any other tissues except, as previously reported, salivary gland and neurofibromas when they did develop. Within bone, tax protein was detected in only two cell types, mature osteoclasts and spindle-shaped cells within the endosteal myelofibrosis. These observations suggest that local expression of the tax gene, which encodes a viral regulatory protein known to influence host gene expression, can induce within the bone environment marked changes in bone cell activity, resulting in profound skeletal alterations.

Osteocalcin and its message: relationship to bone histology in magnesium-deprived rats.

These studies examine effects of brief Mg deprivation on bone histomorphometry and on secretion and synthesis of the specific osteoblast product, osteocalcin. Osteocalcin mRNA was determined in calvaria-derived cells and was correlated to circulating concentrations of the protein after 8 days of Mg deprivation. Circulating osteocalcin was decreased in Mg-deprived rats when compared with pair-fed normal rats after 8 days of Mg deprivation, with no significant changes in calcium or 1,25-dihydroxyvitamin D [1,25(OH)2D]. Serial sampling demonstrated a difference in osteocalcin levels by 2 days of Mg deprivation, before any changes in circulating calcium or parathyroid hormone were present. Although circulating osteocalcin is decreased in Mg-deprived animals, levels can be stimulated with 1,25(OH)2D3. Osteocalcin mRNA is reduced after Mg deprivation, suggesting that low circulating levels are due, at least in part, to reduced osteocalcin synthesis. Mg-deprived rats had diminished bone volume and abnormal histological features consistent with disorganized and chaotic bone remodeling. These findings indicate that low-Mg intake during growth can alter the quality and quantity of bone and suggest that Mg deprivation may contribute to the development of osteoporosis.

Principles in hemodynamic assessment.

Use of invasive hemodynamic monitoring provides more thorough assessment of hemodynamic function and may reveal abnormal data before the development of adverse clinical signs and symptoms. The obstetric nurse caring for critically ill patients is responsible for understanding the principles associated with hemodynamic monitoring and interpretation of data to better plan and implement nursing care.

Mechanical ventilation during pregnancy.

Mechanical ventilatory support is a significant component in the delivery of critical care. With increasing frequency, obstetric critical care nurses face the challenge of caring for women who require mechanical ventilation during pregnancy. It is important that those caring for such patients understand fundamental principles of mechanical ventilation, associated complications, and specific nursing care measures.

Trauma during pregnancy.

The active roles assumed by most pregnant women today put them at risk for vehicular accidents, falls, industrial accidents, violence, and other injuries. Trauma during pregnancy increases the maternal and fetal mortality and morbidity risks. Knowledge of the physiology of pregnancy is essential to establishing priorities and providing optimum care for the woman and fetus. Assessments and care from trauma and obstetric perspectives are essential; however, treatment priorities for the pregnant trauma patient are the primary consideration and are identical to those for nonpregnant trauma patients. Pregnancy does not limit or restrict any resuscitative, diagnostic, or pharmacologic treatment indicated after trauma. Fetal survival is dependent on maternal survival, so the woman must receive immediate intervention and condition stabilization for optimum fetal outcome.

The influence of ibuprofen on fracture repair: biomechanical, biochemical, histologic, and histomorphometric parameters in rats.

Ibuprofen is a widely used cyclo-oxygenase inhibitor in clinical practice. It has been demonstrated by others to have an inhibitory effect on fracture repair in animals. In the present study, we were unable to demonstrate any significant alterations in fracture biomechanics as measured by torsion testing and fracture stage in mature Sprague-Dawley rats treated with 30 mg/kg/day oral dose of ibuprofen, starting 3 days following fracture, over a 12-week time interval. Fracture histology and serum osteocalcin levels were no different in treated animals than control animals. Furthermore, histomorphometric parameters of bone remodeling, including bone volume and bone formation rate in the intact tail vertebrae of these animals with unilateral femur fractures, were no different between treated and control animals.

Perinatal asphyxia: surveillance of the high-risk fetus.

Methods of testing to identify the fetus at risk for developing perinatal asphyxia continue to be developed and refined. The perinatal nurse needs to be knowledgeable of each test's purpose, capabilities, limitations, and clinical issues. Appropriate nursing interventions based on this knowledge facilitates the testing process and promotes the goal of improved perinatal outcome.