Dogmas and controversies in the handling of nitrogenous wastes: ammonia tolerance in the oriental weatherloach Misgurnus anguillicaudatus

The oriental weatherloach Misgurnus anguillicaudatus is an extremely ammonia-tolerant fish. Many ammonia-protection mechanisms have been reported in this fish. Six strategies used by this fish to deal with the problem of excess ammonia are described. The fish can (1) reduce ammonia production through reduction in protein and/or amino acid catabolism; (2) reduce ammonia production and obtain energy through partial amino acid catabolism leading to alanine formation; (3) detoxify ammonia to glutamine; (4) tolerate very high ammonia levels in its tissues; (5) get rid of ammonia as NH(3) gas and, probably, (6) possesses background K(+) channels that are impermeable to NH(4)(+). The effects of extracellular ammonia on the contraction performance of the heart from this fish were found to be the same as in rainbow trout, an ammonia-sensitive fish. It suggests that the hearts of most, if not all, fish species are protected against ammonia. MK-801, an NMDA receptor blocker, was found to have a protective effect against ammonia intoxication in the oriental weatherloach, which suggests that the NMDA receptor, as in mammals, is involved in ammonia toxicity.

Human lactoferrin in the milk of transgenic mice increases intestinal growth in ten-day-old suckling neonates

Regulatory roles and a signaling receptor have been proposed for the milk protein lactoferrin (Lf), but none has been definitively characterized. Nichols and colleagues (1987) observed that human lactoferrin (hLf) stimulated thymidine incorporation into the DNA of rat intestinal crypt cells. We tested the hypothesis that chronic Lf administration stimulates intestinal growth by studying neonatal mice suckling transgenic dams secreting about 12 mg/mL hLf in their milk. Specifically, nontransgenic litters were adjusted to eight pups each and cross-fostered to transgenic dams. Controls were pups suckling nontransgenic dams of the same strain. On day 10 postpartum pups were weighed, sacrificed, and the small intestines were weighed, measured, and stored for later determination of enzyme activities. The results indicate that intestinal growth was increased in neonates suckling transgenic dams. The weight of the small intestine was increased about 27% when the pups received milk containing hLf. Intestinal length only increased about 6.5% suggesting that Lf in milk enhanced mucosal growth. The ratio of maltase to lactase in the duodenal segment of the small intestine, an indicator of maturation, was also significantly increased in the pups suckling transgenic milks. Our results imply that chronic oral consumption of human Lf promotes the growth and maturation of the intestinal mucosa, and suggest a possible therapeutic role for the agent in premature infants as well as in patients with bowel damage.

Genetic analysis of mosaicism in 53 women with Turner syndrome

Mosaicism involving the sex chromosomes is a common finding in women with Turner syndrome (TS). It is especially important to detect Y-chromosomal material, since this is a risk factor for the development of gonadoblastoma. Recent studies have also indicated that the frequency of 45,X cells may be used to predict prognosis. As part of an ongoing multi-disciplinary study, we have examined the extent of Y-chromosomal material and sex chromosomal mosaicism and its tissue specificity in 53 women with TS. The results of lymphocyte karyotyping were compared with the use of interphase X/Y fluorescence in situ hybridisation (FISH) analysis of lymphocytes and buccal mucosal cells. As could be expected, an extended FISH analysis detected more Y-chromosomal material than karyotyping (in 15% vs. 11% of the women, respectively) and also detected more X-chromosomal mosaicism among the TS women (in 70% vs. 45 % of the women, respectively). In half of the women, tissue-specific differences between lymphocytes and buccal mucosal cells were found. Based on these results, we suggest the use of X/Y interphase FISH as a complement to karyotyping in order to obtain a more complete knowledge of the chromosome constitution of each individual with TS.

The theater of birth: scenes from women's scripts

An analogy between theater and birth is drawn from analyses of women's birth stories to describe birth from a fresh perspective. Birth and theater are compared using the theatrical production elements: setting, casting, props, set, behind the scenes, script, and roles. Selected examples from women's birth stories highlight each element. Nurses' roles are significant during labor and birth, but nurses' abilities to fulfill these roles are threatened. This analogy promotes rethinking of nursing actions in the theater of birth. Implications for clinical practice are provided, including altering the birth environment, offering choices, and maintaining the woman's role as star.

Risk factors for childhood asthma in Costa Rica

BACKGROUND

Little is known about factors determining the pathogenesis and severity of asthma in Latin American countries. Costa Rica, one of the most prosperous Latin American nations, has a very high asthma prevalence.

OBJECTIVE

To examine the relation between potential risk factors and childhood asthma in Costa Rica.

METHODS

Cross-sectional study of 214 schoolchildren aged 10 to 13 years participating in phase II of the International Study of Asthma and Allergies in Childhood.

RESULTS

After adjustment for age, gender, area of residence, maternal smoking during pregnancy, and airway responsiveness to hypertonic saline solution, sensitization to house dust mites was associated with asthma (odds ratio [OR], 2.2; 95% confidence interval [CI], 1.1 to 4.4; p = 0.02). In the multivariate analysis, parental education no higher than high school (OR, 3.0; 95% CI, 1.4 to 6.4; p < 0.01) and parental history of asthma (OR, 2.6; 95% CI, 1.3 to 5.2; p < 0.01) were also independent predictors of childhood asthma.

CONCLUSIONS

Sensitization to house dust mites, low parental education, and parental history of asthma are associated with asthma in Costa Rica.

Nurse-midwives' knowledge and promotion of lactational amenorrhea and other natural family-planning methods for child spacing

The purpose of this study was to describe and assess certified nurse-midwives' (CNMs) knowledge and promotion of two modalities for child spacing, natural family-planning (NFP) and the lactational amenorrhea method (LAM). One thousand two hundred CNMs were randomly selected from a national membership list and mailed a 24-item questionnaire on NFP and LAM. Of the 514 respondents (42.8% return rate), 450 (87.5%) were currently practicing as CNMs. Respondents had an average age of 46 years, with an average of 10 years of practice. CNMs ranked NFP as the ninth most used and the eighth most effective family-planning method in their practice, with an average perceived method-effectiveness of 88% and use-effectiveness of 70%. Although most respondents felt somewhat prepared during their education program to provide NFP, only 22% would offer NFP as a family-planning option for child spacing.

Testicular ultrasonography and extended chromosome analysis in men with nonmosaic Klinefelter syndrome: a prospective study of possible predictive factors for successful sperm recovery

OBJECTIVE

To investigate whether extended chromosome analysis or testicular sonography, including flow Doppler imaging, before diagnostic testicular sperm extraction have predictive value for successful sperm retrieval in men with nonmosaic Klinefelter syndrome.

DESIGN

Prospective clinical study.

SETTING

IVF clinic and genetics laboratory at a university hospital.

PATIENT(S)

Nineteen patients with nonmosaic Klinefelter syndrome and azoospermia.

INTERVENTION(S)

Collection of blood samples; histopathologic examination of testicular tissue; fluorescence in situ hybridization; sonography, including Doppler imaging; and testicular sperm extraction.

MAIN OUTCOME MEASURE(S)

Testicular volume, serum FSH and serum testosterone levels, percentage of normal XY cells, ultrasound echogenicity, intratesticular blood flow resistance, and sperm recovery.

RESULT(S)

Testicular volume and levels of serum FSH and serum testosterone levels did not differ significantly. No differences in testicular echogenicity or intratesticular blood flow resistance were found between 47,XXY men in whom sperm recovery was successful and those in whom sperm recovery failed. Significant differences were seen between all patients with the Klinefelter syndrome and controls with normal sperm values. Fluorescence in situ hybridization of peripheral lymphocytes and buccal tissue showed no correlation between frequency of normal 46,XY cells and testicular spermatogenesis.

CONCLUSION(S)

In azoospermic men with the Klinefelter syndrome, histopathologic findings seem to be predictive for successful sperm recovery. Infertility work-up, including diagnostic testicular sperm recovery, is recommended, and, if possible, viable sperm should be cryopreserved.

A lipoprotein-containing particle is transferred from the serum across the mammary epithelium into the milk of lactating mice

To investigate the role of low-density lipoprotein (LDL) in the delivery of cholesterol to the mammary gland during pregnancy and lactation, we examined the distribution of radioactivity from (125)I-tyramine cellobiose-LDL injected into the tail vein of female mice at various stages of the reproductive cycle. Changes in the proportion of isotope taken up by the mammary gland largely reflected the increased weight of the gland in pregnancy and lactation. In addition, during lactation, radioactivity was found in the milk and was associated with a protein of the molecular weight of apoB-100. Quantitatively similar results were obtained with mice homozygous for disruption of the LDL receptor gene (LDLR null). Analysis of endogenous lipoproteins showed that the milk lipoprotein particles were denser than the corresponding serum lipoproteins and largely depleted of triglyceride and cholesterol. Using fluorescence microscopy we visualize the sorting of apoB protein from the LDL lipid phase at the basal surface of the mammary epithelial cell of both wild-type and LDLR-null mice. Our findings provide evidence that the mammary epithelium of the lactating mouse is able to take up LDL from the plasma by a non-LDLR-mediated process. An apoB-containing particle from which the cholesterol has been removed is transferred into milk.

Access to palliative care and hospice in nursing homes

Nursing homes are the site of death for many elderly patients with incurable chronic illness, yet dying nursing home residents have limited access to palliative care and hospice. The probability that a nursing home will be the site of death increased from 18.7% in 1986 to 20.0% by 1993. Dying residents experience high rates of untreated pain and other symptoms. They and their family members are isolated from social and spiritual support. Hospice improves end-of-life care for dying nursing home residents by improving pain control, reducing hospitalization, and reducing use of tube feeding, but it is rarely used. For example, in 1997 only 13% of hospice enrollees were in nursing homes while 87% were in private homes, and 70% of nursing homes had no hospice patients. Hospice use varies by region, and rates of use are associated with nursing home administrators' attitudes toward hospice and contractual obligations. Current health policy discourages use of palliative care and hospice for dying nursing home residents. Quality standards and reimbursement rules provide incentives for restorative care and technologically intensive treatments rather than labor-intensive palliative care. Reimbursement incentives, contractual requirements, and concerns about health care fraud also limit its use. Changes in health policy, quality standards, and reimbursement incentives are essential to improve access to palliative care and hospice for dying nursing home residents. JAMA. 2000;284:2489-2494.

Evaluation of online course discussions. Faculty facilitation of active student learning

Graduate nursing faculty evaluated their initial experiences with online course discussions after making the transition from traditional use of weekly face-to-face classroom discussions to primarily computer-based interactions with students at distant sites. The online discussion data were analyzed qualitatively. The ways the faculty member communicated to facilitate active student involvement in the online discussions were coded. Six categories were identified that describe the ways the faculty member communicated to facilitate active student involvement in online discussions: assist with navigation, explain expectations, clarify faculty role, stimulate critical thinking, share expertise, and provide encouragement. Examples of each were provided to demonstrate ways faculty promoted student learning in online discussions.

Cloning and characterisation of polymorphic heterochromatic segments of Brachycome dichromosomatica

After selective enrichment and differential hybridisation of Cot-1 DNA fractions of plants with and without polymorphic heterochromatic segments, a repetitive sequence (called Bds1) specific to the polymorphic chromosome segments of Brachycome dichromosomatica (Brachyscome dichromosomatica) was isolated. A single repeat unit of Bds1 is 92 bp long and is organised in tandem arrays at three different polymorphic segment sites on the chromosomes of cytodeme A2. Although all three sites showed extensive polymorphism between plants, the karyotypes of all analysed mitotic root cells were stable within a single plant. Electron microscopy revealed heavily condensed chromatin structures at the most obvious polymorphic site. The mechanisms that generate and maintain the observed chromosome structure polymorphisms are discussed.

The effect of serum iron concentration on iron secretion into mouse milk

1. The concentration of iron in mouse milk is approximately 3 times that of the serum. Although there is clear evidence for the presence of the transferrin receptor in the rodent mammary gland, the precise mechanisms of iron transfer into milk are not known. 2. Milk iron was linearly related to the serum iron:transferrin ratio in lactating mice whose serum iron ranged from 8 to 66 microM. 3. Increasing the iron binding capacity of the milk by 340 microM by targeting the lactoferrin transgene to the mammary gland did not alter the relation between milk iron and the serum iron:transferrin ratio. 4. The steady-state distribution ratio of 125I-transferrin between plasma and milk was about 0.2, indicating that transcytosed transferrin contributed a maximum of 6% of the milk iron. 5. Fluorescently labelled transferrin incubated with the in situ gland localized mainly near the basal surface of the mammary alveolar cells. 6. These experiments provide evidence that the initial and rate-limiting step in the transfer of iron into milk is binding to a basal transferrin receptor. 7. A theoretical model of the relation between milk and serum iron suggests that the affinity of apotransferrin for the basal recycling system may be higher than observed in many other cell types.

Lactogenic hormones regulate xanthine oxidoreductase and beta-casein levels in mammary epithelial cells by distinct mechanisms

Xanthine oxidoreductase (XOR) is a prominent component of the milk lipid globule, whose concentration is selectively increased in mammary epithelial cells during the transition from pregnancy to lactation. To understand how XOR expression is controlled in the mammary gland, we investigated its properties and regulation by lactogenic hormones in cultured HC11 mammary epithelial cells. XOR was purified as the NAD(+)-dependent dehydrogenase by benzamidine-Sepharose chromatography and was shown to be intact and to have biochemical properties similar to those of enzyme from other sources. Treating confluent HC11 cells with prolactin and cortisol produced a progressive, four- to fivefold, increase in XOR activity, while XOR activity in control cells remained constant. Elevated cellular XOR activity was correlated with increased XOR protein and was due to both increased synthesis and decreased degradation of XOR. Prolactin and cortisol increased XOR protein and mRNA in the presence of epidermal growth factor, which blocked the stimulation of beta-casein synthesis by these hormones. Further, hormonal stimulation of XOR was inhibited by genistein (a protein tyrosine kinase inhibitor) and by PD 98059 (a specific inhibitor of the MAP kinase cascade). These findings indicate that lactogenic hormones stimulate XOR and beta-casein expression via distinct pathways and suggest that a MAP kinase pathway mediates their effects on XOR. Our results provide evidence that lactogenic hormones regulate milk protein synthesis by multiple signaling pathways.

Cholesterol, but not cigarette smoke, decreases rabbit carotid artery relaxation

The purpose of this study was to determine the physiologic effects of cigarette smoke exposure and dietary cholesterol on the availability of nitric oxide in carotid vascular rings. New Zealand white rabbits were placed in an airflow chamber for 3 hr/day over an 8-week period and were exposed to smoke from 600 cigarettes/per day added to the chamber inflow by a robotic smoke generator. New Zealand white rabbits, made hypercholesterolemic, and one group fed a normal diet, were similarly placed in the chamber without exposure to cigarette smoke. In those exposed groups, serum cotinine and cholesterol levels were consistently elevated. After the 8-week period, the carotid arteries were harvested. The vessels were cut into 3-mm rings which were suspended from pressure transducers. The rings were contracted with potassium chloride (KCl) to determine vessel integrity. One ring from each carotid was maximally contracted with 1 x 10(-3) molar norepinephrine (NE) while the experimental ring was contracted to 50% of maximum. Relaxation of the rings was achieved by adding incremental doses of acetylcholine. Our results showed that endothelial dysfunction, as measured by acetylcholine-mediated vasorelaxation, occurs in the rabbit carotid artery when exposed to high dietary cholesterol. Cigarette exposure alone in this particular vessel did not result in significant alteration in acetylcholine-mediated vasorelaxation.

Midwifery triage and management of trauma and second/third trimester bleeding

Trauma affects approximately 8% of all pregnancies, and bleeding affects nearly 5% of gestations. These two conditions are potentially life-threatening and require immediate management by the midwife. Trauma in pregnancy is commonly caused by motor vehicle accidents, falls, and assault. Although abruption resulting from trauma is a rare occurrence, injury caused by domestic violence, is associated with the greatest risk of obstetric complications. Bleeding in pregnancy has a number of etiologies. Midwives are well-prepared to safely and competently make a differential diagnosis of bleeding in the second and third trimesters. A sequence for midwifery triage of clients who present to the emergency room/triage area for trauma and bleeding is presented. Considerations for stabilization, history, physical examinations, diagnostic testing, initial management, and follow-up are described. Practical considerations for midwifery services incorporating provisions for triage into their caseloads are also provided.

Genome structure and evolution in the allohexaploid weed Avena fatua L. (Poaceae)

Allohexaploid wild oat, Avena fatua L. (Poaceae; 2n = 6x = 42), is one of the world's worst weeds, yet unlike some of the other Avena hexaploids, its genomic structure has been relatively little researched. Consequently, in situ hybridisation was carried out on one accession of A. fatua using an 18S-25S ribosomal DNA (rDNA) sequence and genomic DNA fromA. strigosa (AA-genome diploid) and A. clauda (CC-genome diploid) as probes. Comparing these results with those for other hexaploids studied previously: (i) confirmed that the genomic composition of A. fatua was similar to the other hexaploid Avena taxa (i.e., AACCDD), (ii) identified major sites of rDNA on three pairs of A/D-genome chromosomes, in common with other Avena hexaploids, and (iii) revealed eight chromosome pairs carrying intergenomic translocations between the A/D- and C-genomes in the accession studied. Based on karyotype structure, the identity of some of these recombinant chromosomes was proposed, and this showed that some of these could be divided into two types, (i) those common to all hexaploid Avena species analysed (3 translocations) and (ii) one translocation in this A. fatua accession not previously observed in reports on other hexaploid Avena species. If this translocation is found to be unique to A. fatua, then this information, combined with more traditional morphological data, will add support to the view that A. fatua is genetically distinct from other hexaploid Avena species and thus should retain its full specific status.Key words: wild oats, Avena, genomic in situ hybridisation (GISH), intergenomic translocations, ribosomal DNA.

Genome structure and evolution in the allohexaploid weed Avena fatua L. (Poaceae)

Allohexaploid wild oat, Avena fatua L. (Poaceae; 2n = 6x = 42), is one of the world's worst weeds, yet unlike some of the other Avena hexaploids, its genomic structure has been relatively little researched. Consequently, in situ hybridisation was carried out on one accession of A. fatua using an 18S-25S ribosomal DNA (rDNA) sequence and genomic DNA from A. strigosa (AA-genome diploid) and A. clauda (CC-genome diploid) as probes. Comparing these results with those for other hexaploids studied previously: (i) confirmed that the genomic composition of A. fatua was similar to the other hexaploid Avena taxa (i.e., AACCDD), (ii) identified major sites of rDNA on three pairs of A/D-genome chromosomes, in common with other Avena hexaploids, and (iii) revealed eight chromosome pairs carrying intergenomic translocations between the A/D- and C-genomes in the accession studied. Based on karyotype structure, the identity of some of these recombinant chromosomes was proposed, and this showed that some of these could be divided into two types, (i) those common to all hexaploid Avena species analysed (3 translocations) and (ii) one translocation in this A. fatua accession not previously observed in reports on other hexaploid Avena species. If this translocation is found to be unique to A. fatua, then this information, combined with more traditional morphological data, will add support to the view that A. fatua is genetically distinct from other hexaploid Avena species and thus should retain its full specific status.

Identification of a channel catfish, Ictalurus punctatus (Rafinesque), leukocyte-specific leucine zipper protein

Five clones isolated from a channel catfish cDNA library were each reactive with monoclonal antibodies (mAbs) C3-1 and 51A only. The size of the cDNA inserts from C3-1 and 51A positive clones was 2.5 Kb and identical based on sequence analysis. Monoclonal antibodies C3-1 and 51A specifically reacted with the expressed product of the 2.5 Kb cDNA clone. The complete DNA sequence indicated that the 2.5 Kb cDNA encoded an approximately 50 Kd protein molecule consisting of 445 amino acids. Sequence analysis showed that this putative protein was a potential leucine-zipper DNA binding protein. Comparison of the deduced amino acid sequence demonstrated homology (14.6 to 19.5%) throughout the sequence of the catfish protein with a group of cytoplasmic-leucine zipper containing proteins of humans; paraneoplastic cellebellar degeneration related (cdr) antigen 2 and 3 with 39.8 to 56.3% homology in the leucine-zipper motif (amino acids 52 through 175 in the catfish protein). This protein was detected in nuclear extracts. cytoplasmic membrane preparations and cytosolic extracts of neutrophils and lymphocytes when reacted with mAbs C3-1 and 51A in an ELISA. However, the intensity of the reactions was dependent upon the cell type and cellular component. The putative cdr protein was not detected with any appreciable intensity in preparations from other cell types. This finding strongly suggests that this protein is expressed in a leukocyte-specific manner and is unique among the cdr group in that it is being expressed in a site that is not immune privileged.

Second-stage positioning in nurse-midwifery practices. Part 2: Factors affecting use

This, the second of a two-part article, describes the findings of a national survey of practicing certified nurse-midwives (CNMs) regarding factors that affect the use of eight second-stage maternal positions. Lower CNM self-reported autonomy scores were associated with the use of the lithotomy and dorsal supine positions; maternal preference and higher CNM self-reported autonomy scores were associated with the use of the nonlithotomy positions. The use of nonlithotomy positions is one nontechnologic way to enhance the normal process of birth.

Second-stage positioning in nurse-midwifery practices. Part 1: Position use and preferences

A national survey of 800 certified nurse-midwives (CNMs) in active clinical practice was conducted from April through June 1994. The purpose of the survey was to study the extent to which eight operationally defined positions were used by CNM-attended women during the second stage of labor and factors that affected their use. This, the first of a two-part article, describes the positions used as well as the CNMs' preferences for the eight second-stage positions. The most frequently used second-stage position was sitting; the lithotomy position was rarely used by the CNMs. The survey findings reflect the preferences of birthing women.

A model for the future. Certified nurse-midwives replace residents and house staff in hospitals

In one model of the future, certified nurse-midwives (CNMs) replace most obstetric residents and house staff in hospitals. This model offers numerous benefits, such as cost containment and quality outcomes. Furthermore, its application could open opportunities for educating CNMs and residents in a truly collaborative model in an educational setting and begin to balance the ratio of physicians to CNMs in the care of low-risk populations. This model was used with some success in the late 1980s to early 1990s at an inner-city Midwestern medical center. By definition, CNMs are educated in the two disciplines of nursing and midwifery and possess evidence of certification according to the requirements of the American College of Nurse Midwives (ACNM, 1978). Nurse-midwifery practice is the independent management of care of normal newborns and women, antepartally, intrapartally, postpartally, and/or gynecologically. Certified Nurse Midwifery practice occurs within a health care system that provides for medical consultation, collaborative management, and referral (ACNM, 1978). Physician and CNM roles differ. Certified nurse-midwives focus on supporting the process of normal birth, whereas physicians focus more on the management of complications. There are data that suggest that CNM outcomes are equivalent to those of physicians (American Nurses Association, 1992; Thompson, 1986; Wilson, 1989); that CNM costs are less than those of physicians (Bell & Mills, 1989; Cherry & Foster, 1982; Gravely & Littlefield, 1992; Rooks, 1986); and that the cost of educating CNMs is much less than the cost of educating physicians (Safriet, 1992). Within an environment of health care reform and cost containment, CNMs can replace residents and house staff in hospitals in the care of low-risk clients and work in consultation with physicians for the care of high-risk clients. This article compares medical education and nurse-midwifery education, reviews nurse-midwifery outcome data, and discusses the pros and cons of a practice model for the future.

The importance of cellular environment to function of the CD44 matrix receptor

Much has been learned recently by experimental manipulation of the structure of CD44 and assessment of the resulting functions. However, even greater structural variation is naturally introduced by CD44-bearing cells. A structural model is now available for the portion of CD44 that recognizes hyaluronan, but it is clear that all domains of the molecule influence CD44 functions.