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Floral development and the formation of unisexual spikelets in the Andropogoneae (Poaceae).

We investigated spikelet development in four distantly related species of the grass tribe Andropogoneae to determine whether spikelet development and the formation of unisexual florets are uniform throughout the tribe. We studied development in Bothriochloa bladhii, Coelorachis aurita, Heteropogon contortus, and Hyparrhenia hirta, and compared these with Panicum, a member of the sister tribe Paniceae. Many aspects of spikelet development in the species we have studied correlate with what is already known for Tripsacum and maize (both Andropogoneae), despite variation in how unisexual florets are distributed on the plant. The formation of unisexual spikelets is also uniform. All florets initiate both pistil and stamen primordia. In florets destined to be male, cell death occurs in the subepidermal layers of the gynoecium after the formation of a gynoecial ridge. In florets destined to be female, there is no apparent cell death in the stamens, but growth ceases after anther formation. The similarity in spikelet development and the formation of unisexual florets point to a common genetic mechanism for sex determination throughout the Andropogoneae and possibly the entire Panicoideae. Use of a cell death pathway to cause gynoecial abortion may be the basis of one morphological character that defines the subfamily.

Journal Article↗

Principal cells of the vas deferens are involved in water transport and steroid synthesis in the adult rat.

Principal cells show marked structural differences in the proximal, middle, and distal regions of the vas deferens, reflective of diverse functional activities. In the present study, we performed electron microscopy to examine the structural features of principal cells using glutaraldehyde-fixed, Epon-embedded material, while functional parameters were examined using light microscopic immunocytochemistry on Bouin-fixed, paraffin-embedded material. In the proximal region, the cuboidal principal cells resembled those of the cauda epididymidis, but few clear cells and occasional narrow cells were present. In the middle region, principal cells often contained blebs of their apical cytoplasm containing vesicular and tubular profiles. These blebs extended far from the cell surface and appeared to be liberated into the lumen, suggesting an apocrine type of secretion. In the distal region, dilated intercellular spaces containing numerous membranous profiles of different shapes and sizes were noted between adjacent principal cells and overlying basal cells. The use of an anti-aquaporin-1 antibody revealed an intense reaction over the endothelial cells of numerous vascular channels in the lamina propria. Taken together, these observations suggested water transport from the lumen of the vas deferens via the dilated spaces to underlying vascular channels, the function of which may be to concentrate sperm. The infranuclear cytoplasm of principal cells of this region showed whorls of smooth endoplasmic reticulum (sER). Large intracytoplasmic cavities were found within the sER aggregates, and these contained membranous profiles that appeared to peel off from the surrounding sER elements. Various images of such cavities closely juxtaposed to the lateral plasma membrane suggested that the membranous profiles of the intercellular spaces were derived from them. Use of anti-3beta-hydroxysteroid dehydrogenase antibody revealed an intense reaction over principal cells of the vas deferens, as well as over the blebs in the lumen of the vas deferens, which is indicative of the steroid synthesis performed by these cells. The release of sER membranous profiles into the dilated spaces and the presence of blebs in the lumen may represent a means of transporting steroids that are destined for different sites out of the principal cells. Steroids in the blebs would be ultimately destined for utilization by luminal sperm, while those steroids in the dilated spaces are designed for utilization by muscle layers of the lamina propria. In summary, principal cells of the vas deferens appear to be involved in synthesis and secretion of steroids and in eliminating water from the lumen of the vas deferens.

3-Hydroxysteroid Dehydrogenases↗

Glutamate acting at NMDA receptors stimulates embryonic cortical neuronal migration.

During cortical development, embryonic neurons migrate from germinal zones near the ventricle into the cortical plate, where they organize into layers. Mechanisms that direct neuronal migration may include molecules that act as chemoattractants. In rats, GABA, which localizes near the target destination for migrating cortical neurons, stimulates embryonic neuronal migration in vitro. In mice, glutamate is highly localized near the target destinations for migrating cortical neurons. Glutamate-induced migration of murine embryonic cortical cells was evaluated in cell dissociates and cortical slice cultures. In dissociates, the chemotropic effects of glutamate were 10-fold greater than the effects of GABA, demonstrating that for murine cortical cells, glutamate is a more potent chemoattractant than GABA. Thus, cortical chemoattractants appear to differ between species. Micromolar glutamate stimulated neuronal chemotaxis that was mimicked by microM NMDA but not by other ionotropic glutamate receptor agonists (AMPA, kainate, quisqualate). Responding cells were primarily derived from immature cortical regions [ventricular zone (vz)/subventricular zone (svz)]. Bromodeoxyuridine (BrdU) pulse labeling of cortical slices cultured in NMDA antagonists (microM MK801 or APV) revealed that antagonist exposure blocked the migration of BrdU-positive cells from the vz/svz into the cortical plate. PCR confirmed the presence of NMDA receptor expression in vz/svz cells, whereas electrophysiology and Ca2+ imaging demonstrated that vz/svz cells exhibited physiological responses to NMDA. These studies indicate that, in mice, glutamate may serve as a chemoattractant for neurons in the developing cortex, signaling cells to migrate into the cortical plate via NMDA receptor activation.

Animals↗

Special Education.

HEMOPOIETIC FACTORS AND BLOOD CELL PROLIFERATION AND DIFFERENTIATION: Blood cells are generally classified into three cell lineages: erythrocytes, granulocytes and megakaryocytes. In the bone marrow, pluripotent stem cells differentiate into either the lymphoid stem cell line, where they are further induced to differentiate into B- or T-derived lymphocytes, or the myeloid stem cell (CFU-GEMM) line, where they are further induced to become erythrocytes, granulocytes (neutrophils, eosinophils or basophils), macrophages or megakaryocytes (platelets). Proliferation and differentiation of blood cells in the bone marrow are regulated by hemopoietic factors. Hemopoietic factors include those that are continuously produced, such as EPO, G-CSF and thrombopoietin (TPO), and those that are produced on demand in response to inflammation and infection, such as IL-3, IL-11 and GM-CSF. In recent years the genes for hemopoietic factors which regulate erythrocytes and granulocytes have been cloned using the techniques of genetic engineering. In 1994 the gene for TPO was cloned. TPO acts specifically on megakaryocytes. PROLIFERATION AND DIFFERENTIATION OF ERYTHROCYTIC CELLS: The earliest cells destined to become erythrocytes which differentiate from the myeloid stem cells (CFU-GEMM) are early phase erythroblast progenitor cells called BFU-E cells. After the BFU-E cells have undergone several divisions, they differentiate into late phase erythroblast progenitor cells called CFU-E cells. After passing through the proerythroblast stage, the CFU-E cells become erythroblasts. Erythroblasts can be confirmed by light microscope as belonging to the erythroid cell line. Erythroblasts mature and become enucleated reticulocytes, which are then released from the bone marrow into the blood, thus becoming mature erythrocytes. Proliferation and differentiation of the erythroid progenitor cells are regulated by erythropoietin (EPO), which is primarily produced by the kidneys. In 1985 genomic DNA and cDNA for human EPO were cloned, and it was learned that the mature protein is a glycoprotein consisting of 165 amino acids and having a molecular weight of about 30,000. There is powerful evidence to suggest that EPO is produced by peritubular cells of the renal cortex. When the hematocrit drops for some reason and hypoxia occurs, the number of EPO-producing cells increases and EPO production rises in the kidneys. CFU-E cells are the main target cells for EPO. EPO receptors are expressed along the lineage from BFU-E cells to proerythroblasts, with peak expression found in CFU-E cells. The EPO receptor, which was cloned in 1989, belongs to the cytokine receptor family, transduces the EPO signal to the interior of the cell, and brings about the proliferation and differentiation of CFU-E cells. PROLIFERATION AND DIFFERENTIATION OF GRANULOCYTIC CELLS: The earliest cells destined to become neutrophils and macrophages which differentiate from the pluripotent stem cells are called granulocyte-macrophage progenitor (CFU-GM) cells. The CFU-GM cells are affected by colony-stimulating factors and become either CFU-G or CFU-M cells. Ultimately, they differentiate into mature neutrophils or macrophages. The main factor stimulating the proliferation and differentiation of neutrophils is the granulocyte colony-stimulating factor (G-CSF). CFU-GM cells are stimulated by G-CSF in the bone marrow, pass through the CFU-G stage, and become myeloblasts, which are the most primitive neutrophils that can be morphologically distinguished. Myeloblasts continue to divide and differentiate, and they mature into neutrophils, which then lose their ability to divide. Mature neutrophils are not immediately released into the blood, but rather are stored within the bone marrow. Neutrophils that have been released into the blood reside in the marginal granulocyte pool or the circulating granulocyte pool, and they later egress into tissues. G-CSF is produced by cells such as monocytes, macrophages and bone marrow stromal cells, and its action is almost entirely selective for the proliferation of neutrophils. The cDNA for G-CSF was cloned in 1986, and it was learned that the mature protein is a glycoprotein consisting of 174 amino acids and having a molecular weight of about 20,000. When G-CSF is administered to a patient it causes the release of mature neutrophils from the marrow into the peripheral blood. G-CSF also enhances neutrophil function in the presence of bacterial products, and it acts on mature neutrophils to enhance cellular motility, the production of bioactive oxygen, and microbicidal activity. The cDNA for the G-CSF receptor was cloned in 1990, and its receptor belongs to the cytokine receptor family. The human G-CSF receptor consists of 813 amino acids and has an approximate molecular weight of 100,000 to 130,000. The G-CSF receptor signal is mediated by the JAK-1 and JAK-2 tyrosine kinases.

Journal Article↗

Markers of lymphocyte homing distinguish CD4 T cell subsets that turn over in response to HIV-1 infection in humans.

In HIV-1 infection, the abrupt rise in CD4 T cells after effective antiretroviral therapy has been viewed as a measure of HIV-1-related CD4 T cell turnover in the steady state. The early (2-4 wk) response is reportedly dominated by CD4 T cells with a memory (CD45RO) phenotype. It is controversial whether the measurement of steady-state kinetics identifies cells that otherwise would have been recruited into a short-lived, virus-producing pool or reflects lymphoid redistribution/sequestration. We performed detailed phenotypic and kinetic analysis of CD4 T cell subsets in 14 patients. Turnover occurs in memory (CD45RO) as well as naive (CD45RA) cells, if the latter are present at baseline. Most of the turnover occurs in those memory (CD45RO) and naive (CD45RA) cells that are programmed for recirculation through lymphoid organs (CD62L+ and CD44low), whereas very little turnover occurs in memory cells (CD45RO) destined for recirculation from blood to tissue (CD62L- and CD44high). Turnover occurs in both activated (CD25+ and HLA-DR+) and nonactivated populations, although it is restricted to CD38-positive cells, indicating that turnover does not measure cells that are already infected. More likely, turnover occurs in cells that replace infected cells or are on their way to becoming infected. Taken together, markers of lymphocyte trafficking better describe cell turnover related to virus replication than do naive and memory markers per se, and lymph organs, not tissue-destined cells or peripheral blood cells, appear to be the important site of virus replication and CD4 T cell turnover, destruction, and redistribution.

ADP-ribosyl Cyclase↗

[Factors predicting return home of hospitalized aged patients].

BACKGROUND: The identification of predictors of return home and nursing home placement in elderly patients, at the moment of admission to a Geriatric Convalescence Unit, may allow to make a discharge planning for these patients, and also may improve efficiency in the unit. PATIENTS AND METHODS: A number of 445 patients over 65 years were consecutively admitted to the unit. Analyzed variables at admission were; age, sex, diagnostic, comorbidity, functional status prior to admission, degree of independence in activities of daily living (Barthel index), cognitive function (Folstein Mini-Mental) and social support (modified version of social-familiar evaluation scale of Gijón). All these variables were used in two models of logistic regression analysis: 1 [symbol: see text] (dependent variable: return home after discharge versus other destinations), and 2 [symbol: see text] (dependent variable: nursing home placement on discharge versus other destinations). RESULTS: The variables significatively associated with greater probability of at home discharge were: moderate dependency for activities of daily living (Barthel index = 31-59), odds ratio (OR) = 2.46 (95% confidence interval: 1.43-4.22); mild dependency (Barthel index > or = 60), OR = 3.67 (1.96-6.87); normal cognitive function (Mini-Mental > or = 21), OR = 3.14 (1.76-5.60), and a favourable social support (social-familiar scale < 12), OR = 7.33 (3.18-16.91). The only variable significatively associated with the probability of nursing home placement after discharge was an impaired social function (social-familiar scale > or = 12), OR = 4.53 (2.25-9.12). CONCLUSIONS: Probability of return home after discharge is associated with functional status, cognitive function and social support. Definitively nursing home placement was only related with de degree of familiar support.

Activities of Daily Living↗

From austerity to prosperity? Migration and child poverty among mainland and island Puerto Ricans.

Analyses of migrants' economic circumstances typically use the native-born in the destination as a comparison group. We use the 1990 Census Public Use Microdata Samples for the United States and Puerto Rico to demonstrate the benefits of a comparative approach that includes data from both the origin and the destination. Specifically, the primary objective is to determine how and why the risk of child poverty is associated with migration from Puerto Rico to the United States. The results show that migration reduces the risk of child poverty, partly because better jobs are available on the mainland. Employment, human capital, family structure, and public assistance cannot completely explain observed differences. The results also show that the economic benefits of migration continue for the native-born on the mainland and that return migration to Puerto Rico is associated with impoverishment.

Adolescent↗

Deleted in colorectal cancer (DCC) regulates the migration of luteinizing hormone-releasing hormone neurons to the basal forebrain.

Luteinizing hormone-releasing hormone (LHRH) neurons migrate from the vomeronasal organ (VNO) to the forebrain in all mammals studied. In mice, most LHRH neuron migration is dependent on axons that originate in the VNO but bypass the olfactory bulb and project into the basal forebrain. Thus, cues that regulate the trajectories of these vomeronasal axons are candidates for determining the destination of LHRH neurons. Using in situ hybridization techniques, we examined the expression of Deleted in colorectal cancer (DCC), a vertebrate receptor for the guidance molecule netrin-1, during development of the olfactory system. DCC is expressed by cells in the olfactory epithelium (OE) and VNO, and in cells migrating from the OE and VNO from embryonic day 11 (E11) to E14. Some DCC(+) cells on vomeronasal axons in the nose also express LHRH. However, DCC expression is downregulated beginning at E12, so few if any LHRH neurons in the forebrain also express DCC. In rat, DCC is expressed on TAG-1(+) axons that guide migrating LHRH neurons. We therefore examined LHRH neuron migration in DCC(-/-) mice and found that trajectories of the caudal vomeronasal nerve and positions of LHRH neurons are abnormal. Fewer than the normal number of LHRH neurons are found in the basal forebrain, and many LHRH neurons are displaced into the cerebral cortex of DCC(-/-) mice. These results are consistent with the idea that DCC regulates the trajectories of a subset of vomeronasal axons that guide the migration of LHRH neurons. Loss of DCC function results in the migration of many LHRH neurons to inappropriate destinations.

Animals↗

Influence of different transitional restorations on the fracture resistance of premolar teeth.

Controversy exists over the most favorable material and type of restoration to be used to transitionally restore teeth destined to be crowned. This in vitro study uses fracture resistance testing to compare eight different transitional restorations in maxillary premolars. Ninety sound maxillary premolars were randomly selected and allocated to nine groups, each comprising 10 teeth. One group remained unrestored and was used as the control. Teeth in the remaining groups were prepared to a standard cavity form using: a copy milling process removing the palatal cusp. Restorations were placed using amalgam with dentin pins and cavity varnish; amalgam with an amalgam bonding agent; resin composite with dentin pins and a dentin bonding agent; resin composite with a dentin bonding agent only; resin-modified glass ionomer with dentin pins; resin-modified glass ionomer cement alone and cermet with dentin pins and cermet alone. Each restored tooth was then subjected to axial loading via a bar contacting the buccal and restored palatal cusps until failure of the restored tooth occurred. The mean load-to-fracture values were statistically compared and the modes of failure recorded. It was found that the choice of restorative material and type of restoration had little effect on the fracture resistance of the restored tooth with the exception of those teeth restored with reinforced glass ionomer cement alone, which exhibited a significantly lower resistance to fracture than the other restored teeth. However, the choice of restorative material/technique did influence the mode of failure. Failure in teeth restored with resin-modified glass ionomer cement alone produced the least damage to the remaining tooth tissue when failure occurred. Consequently, this material may offer the most favorable range of properties for the transitional restoration of extensively broken-down maxillary premolar teeth destined to be crowned. Furthermore, the findings of this study fail to support the use of dentin pins in the placement of bonded build-up restorations.

Analysis of Variance↗

Guidelines for malaria prevention in travellers from the United Kingdom for 2001.

These guidelines on malaria prevention are designed to aid health care workers who advise travellers, particularly those who will be overseas for less than a year. The present, and any future, revisions are the responsibility of the Advisory Committee on Malaria Prevention in UK travellers (ACMP; membership given at the end of the Guidelines). This has replaced the consensus meetings which produced earlier versions from 1980 to the the 1997 version. The guidelines are in three parts. The first part is a summary that emphasises modifications to the advice given in the last set of guidelines, published in 1997. The second part discusses the issues addressed in formulating the guidelines. Oversimplified lists of recommendations by country can be misleading. The second part also addresses the health care worker's consultation with prospective travellers. Doctors, practice nurses and pharmacists are asked to read this section to ensure that due attention is paid to the traveller's history and destination. The third part gives specific recommendations for travellers to specific destinations and some details of individual drugs. Fuller information on some drugs now less used was given in earlier versions of the guidelines. These guidelines reflect experienced professional opinion. Data are inadequate for unequivocal views to be given on several issues, but all available evidence has been taken into consideration. There is often a range of acceptable options, but to meet the requests of general practitioners the guidelines aim to give one recommended option and state the alternatives, suggesting when and how different regimens can be used to good effect. However, there are now several options for effective prophylaxis of highly chloroquine-resistant falciparum malaria, and the choice between them will depend on details of the journey and individual preferences. Decisions on the terms under which different drugs are licensed for use are the responsibility of the Licensing Authority, advised by the Committee on Safety of Medicines and not of the ACMP. The guidelines should therefore be read as a supplement to and not as a substitute for the relevant data sheets. In concept and practice, chemoprophylaxis lies somewhere between vaccinations (for which people expect governments to lay down schedules) and treatment of ill people (which is determined by individual clinical need and choice). The risks of malaria need to be balanced against the risks of the preventive measures, on the basis of the data available. Travellers may ask for an explanation of these risks and doctors and practice nurses need to be well informed and able to present this information to travellers. The second part of these guidelines may also be of use to prospective travellers who wish to read about the options themselves. All readers are recommended to read part two in its entirety to get a balanced picture.

Antimalarials↗

Syncytial units isolated from early human placentas.

This morphological study demonstrates that during the early phases of pregnancy, in the syncytium there are individual multinucleated units joined to one another by junctional complexes which probably are destined to flow together with the main syncytium by membrane breakdown. Normal human placentas from 6th to 12th week of pregnancy, derived from voluntary abortions, have been utilized. According to the method described by Tedde et al. (1991), clusters of villi have been isolated, washed in saline and subjected to a treatment with a 0.3% trypsin solution that caused the detachment of numerous cellular elements from the surface of the free villi. Such isolated elements have been subjected to centrifugation and separation in Percoll gradients. Then multinucleated syncytial units have been collected, attached to slides by cytocentrifugation, stained with toluidine blue, observed at the light microscope and utilized to count their nuclei: about 600 elements from different weeks of pregnancy have been considered and the results have been submitted to statistical analysis. The svncytial units are multinucleated and can often be different from one another, particularly in regard to the characteristics and the number of the nuclei. The evaluation of the number of nuclei contained in different syncytial elements shows that nuclei are less numerous in the early phases (6-8 weeks) and increase in number towards the end of the first trimester in a statistic significant way. In conclusion, the present study could confirm the existence of single syncytial units, joined to constitute the syncytial layer, probably destined to a complete fusion in the main syncytium and likely in functional relationship with the underlying Langhans cells.

Cell Nucleus↗

Neocortical cell migration: GABAergic neurons and cells in layers I and VI move in a cyclin-dependent kinase 5-independent manner.

The adult mammalian cerebral cortex arises from a complex series of neuronal migrations. The primitive layer known as the preplate is split into an outer marginal zone and an inner subplate by invading cortical plate neurons in an "inside-out" pattern of layering with respect to time of neuronal origin. In cyclin-dependent kinase 5 (Cdk5)-deficient mice (cdk5(-/-)), the earliest born cortical neurons split the preplate, but later born neurons arrest below the subplate, resulting in an ectopic "outside-in" layer of neurons normally destined for layers II-V. We have pursued this analysis in cdk5(-/-) <--> wild-type chimeric mice coupled with experiments in cell culture. In vitro migration assays show no difference in migrational ability between embryonic cdk5(-/-) and wild-type neurons. In cdk5(-/-) chimeras, layers I and VI are made up of both mutant and wild-type genotype neurons, whereas layers II-V contain predominantly wild-type cells. In addition, a thin layer of neurons is found below layer VI, made up of cdk5(-/-) cells; bromodeoxyuridine labeling suggests that these neurons were destined for layers II-V. Scattered cdk5(-/-) cells are found throughout layers II-V, but these neurons are always found to be GABAergic. The findings suggest that Cdk5 is not required for migration of either the deepest cortical plate neurons or the GABAergic neurons from the ganglionic eminences. The migration of layer II-V pyramidal neurons, however, is intrinsically blocked by Cdk5 deficiency, thus suggesting that different neuronal cell types use distinct mechanisms of migration.

Animals↗

Combined orthogeriatric care in the management of hip fractures: a prospective study.

AIMS: To evaluate the efficacy of combined care between orthopaedic surgeons and geriatricians in the management of patients with fractured necks of femur. PATIENTS AND METHODS: A prospective study of the admissions to a district general hospital with hip fractures was carried out over a 5-year period. In the years 1992-1994, medical problems in this patient group were managed by a consultation-only service. At the end of 1994, a consultant geriatrician was appointed to manage these patients jointly with the orthopaedic surgeons, and the study was then carried through until the end of 1996. Information about the patients from admission to discharge or death was gathered prospectively using a proforma for the 3 years prior to orthogeriatric care, and the 2 years after. Main outcome measures were mortality, length of stay and discharge destination. These were compared for the two periods--pre- and post-orthogeriatric care. RESULTS: No significant differences were noted in mortality, length of stay or discharge destination. CONCLUSIONS: Combined orthogeriatric care according to our model did not have an impact on our chosen outcome measures.

Aged↗

Migration patterns in India.

"The chief objective of the present paper is to comprehend the broad spatial patterns of internal migrations in India." Aspects considered include data constraints, the magnitude of internal migration, interstate migration, migration to rural and to urban destinations, spatial patterns, and areas of origin and destination.

Asia↗

The causes of international labor migrations--a demand-determined approach.

The author first studies the reasons why people migrate using a neoclassical approach concerning income differentials. He tests this approach empirically and demonstrates its limits. A demand-determination approach based on human capital theory is then outlined to overcome these limits and to take into account restrictive immigration controls. Migration from Italy, Spain, Greece, Portugal, and Turkey to the European Community destination countries is examined. It is concluded that "the demand for immigrants in the destination country is the decisive condition for the phenomenon of international labor migration, and the supply of migration-willing workers is only a necessary condition."

Asia↗

Cohort size effects and migration.

"This article explores whether changes in the size of [U.S.] cohorts entering the labor force affect the propensity to migrate and the socioeconomic circumstances of migrants at destination. The flow of young in-migrants to large SMSAs declined during the 1965-76 period, but the relative socioeconomic standing of migrants at destination was unaffected by either cohort size or regional differentials in economic growth. It is suggested that a significant reduction in the volume of migration among members of the baby boom cohort was the primary adjustment mechanism, hence reducing the need for degrading the opportunities available to migrants."

Americas↗

[The typology of migration: developing an alternative concept].

Alternative ways to improve the definitions used in migration studies in Indonesia are explored using data from recent migration surveys carried out at Gadjah Mada University. They involve treating migration as a continuing process rather than an isolated move. "By introducing the variable of intention to remain at the destination and the length of migrants' stay in the destination, a fourfold typology of migrant type can be created: circular migrants, migrants who intend to remain circular, migrants who intend to be permanent and permanent migrants." (SUMMARY IN ENG)

Asia↗