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1.
J Child Health Care ; : 13674935231185181, 2023 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-37406354

RESUMO

This systematic review summarises evidence regarding oral nutritional supplement (ONS) use in children with, or at risk of, faltering growth (FG). Ten randomised controlled trials (RCTs), compared changes in outcomes amongst children receiving ONS versus control were included. Overall, 1116 children (weighted mean (WM) age 5 years; n658 (59%) male) were recruited, of which 585 (52%) received ONS (WM intake contribution 412 kcal, 16.3 g protein, 395 ml) for 116 days (WM). ONS use was associated with significantly greater gains in weight (mean difference (MD) 0.4 kg, 95% CI [0.36, 0.44]) and height (MD 0.3 cm, 95% CI [0.03, 0.57]), likely related to improvements in nutritional intake. Mean compliance to prescribed dose was 98%. Data suggested an association between ONS use and reduced infections. Further research is warranted to establish ONS dosage and effects upon other outcomes. This review provides evidence to support use of ONS in the management of children with, or at risk of, FG.

2.
Ageing Res Rev ; 88: 101953, 2023 07.
Artigo em Inglês | MEDLINE | ID: mdl-37182743

RESUMO

The impact of oral nutritional supplements (ONS) on patients with complications (disease related morbidity) requires further exploration. This systematic review included 44 randomised controlled trials (RCT) (29 RCT surgical, 15 RCT medical patients) examining the effect of ONS in community settings on the incidence of complications (n = 716, mean age 67 years, range 35-87). ONS (mean intake 588 kcal/day, range 125-1750; protein 22 g/day, range 0-54; mean energy from protein 22 %, range 0-54) were prescribed for a mean 74 days, range 5-365. Most RCT (77 %) reported fewer complications in the ONS group versus control. Meta-analysis (39 RCT) showed ONS consumption reduced complications including infections, pressure ulcers, wound and fracture healing (OR 0.68, 95 % CI 0.59,0.79; p<0.001). Results showed reductions when ONS were used in hospital and community settings (OR 0.72, 95 % CI 0.59,0.87; p = 0.001) or just in the community (OR 0.65, 95 % CI 0.52, 0.80; p<0.001). Reductions in complications were only seen with high ONS adherence ≥ 80 % (OR 0.63, 95 % CI 0.48,0.83; p = 0.001) and ready-to-drink ONS (OR 0.69, 95 % CI 0.60,0.81; p<0.001). This systematic review and meta-analysis show community-based use of ONS in addition to the diet substantially reduces the incidence of complications. The diversity of ONS, patient populations and complication outcomes within the trials included in this review mean further research is warranted.


Assuntos
Suplementos Nutricionais , Desnutrição , Humanos , Idoso , Idoso de 80 Anos ou mais
3.
J Nutr Health Aging ; 24(3): 305-311, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32115612

RESUMO

OBJECTIVES: Malnutrition is a common and significant public health problem, especially for older adults, as the consequences are costly. National guidelines (NICE CG32/QS24) highlight the need to identify and manage malnutrition, the implementation of which was deemed "high impact to produce cost savings". The 'Malnutrition Pathway', endorsed by NICE and other professional bodies, is a practical evidence-based guide to help community healthcare professionals (HCP) to implement guidance on malnutrition management. Published evaluations of its use are needed. DESIGN: This service evaluation in older adults assessed the impact of implementing the 'Malnutrition Pathway' on health care use and costs, as well as the acceptability of the management strategies and effect on malnutrition risk. SETTING: 5 GP surgeries in Gloucestershire. PARTICIPANTS: 163 older adults (80±9 years) with a range of primary diagnoses, living in their own home, were screened using the Malnutrition Universal Screening Tool ('MUST') (n50 low risk (LR); n41 medium risk (MR); n72 high risk (HR)). All patients were managed according to risk (LR: no further management; MR: dietary advice (DA); and HR: DA plus two oral nutritional supplements (ONS) (1 serve 300kcal, 18g protein; 125ml). MEASUREMENTS: At each review (6weeks, 3 and 6 months), 'MUST' score, compliance and satisfaction to their management plan were recorded. Healthcare use was collected from GP records 6 months before and after implementation of the pathway. A simple cost analysis was completed. RESULTS: Implementing appropriate management of malnutrition led to significant reductions in hospital admissions (p=0.028), length of hospital stay (p=0.05), GP visits (p=0.007) and antibiotic prescriptions (p=0.05). Over 6 months, the costs to manage malnutrition (HCP time, ONS) were more than offset by the savings associated with these reductions in health care use (per patient savings of -£395.64 MR+HR; -£997.02 HR). The proportion of individuals at risk of malnutrition reduced over time, and patients reported being satisfied with the DA (97%) and ONS (96%), consuming 90% of their ONS prescription. CONCLUSION: Managing malnutrition significantly reduces healthcare use, with a positive budget impact, in older malnourished patients in primary care. This represents an opportunity to improve patient care with benefit on health care spend.


Assuntos
Desnutrição/diagnóstico , Desnutrição/economia , Programas de Rastreamento/métodos , Avaliação Nutricional , Idoso de 80 Anos ou mais , Feminino , Medicina Geral , Humanos , Masculino
4.
Ageing Res Rev ; 11(2): 278-96, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22212388

RESUMO

Disease-related malnutrition is common, detrimentally affecting the patient and healthcare economy. Although use of high protein oral nutritional supplements (ONS) has been recommended to counteract the catabolic effects of disease and to facilitate recovery from illness, there is a lack of systematically obtained evidence to support these recommendations. This systematic review involving 36 randomised controlled trials (RCT) (n=3790) (mean age 74 years; 83% of trials in patients >65 years) and a series of meta-analyses of high protein ONS (>20% energy from protein) demonstrated a range of effects across settings and patient groups in favour of the high protein ONS group. These included reduced complications (odds ratio (OR) 0.68 (95%CI 0.55-0.83), p<0.001, 10 RCT, n=1830); reduced readmissions to hospital (OR 0.59 (95%CI 0.41-0.84), p=0.004, 2 RCT, n=546); improved grip strength (1.76 kg (95%CI 0.36-3.17), p<0.014, 4 RCT, n=219); increased intake of protein (p<0.001) and energy (p<0.001) with little reduction in normal food intake and improvements in weight (p<0.001). There was inadequate information to compare standard ONS (<20% energy from protein) with high protein ONS (>20% energy from protein). The systematic review and meta-analysis provides evidence that high protein supplements produce clinical benefits, with economic implications.


Assuntos
Proteínas Alimentares/administração & dosagem , Suplementos Nutricionais , Nutrição Enteral , Desnutrição/terapia , Estado Nutricional , Administração Oral , Adulto , Idoso , Idoso de 80 Anos ou mais , Proteínas Alimentares/efeitos adversos , Proteínas Alimentares/metabolismo , Suplementos Nutricionais/efeitos adversos , Ingestão de Energia , Metabolismo Energético , Nutrição Enteral/efeitos adversos , Medicina Baseada em Evidências , Humanos , Desnutrição/complicações , Desnutrição/metabolismo , Desnutrição/fisiopatologia , Pessoa de Meia-Idade , Razão de Chances , Recuperação de Função Fisiológica , Medição de Risco , Fatores de Risco , Resultado do Tratamento
5.
J Pharm Pharmacol ; 43(2): 117-9, 1991 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-1672895

RESUMO

The in-vitro dissolution profiles of two carbamazepine formulations (Tegretol and a generic carbamazepine) have been assessed and the bioavailability of carbamazepine compared in 12 epileptic children at steady-state. Dissolution from the generic formulation (100 and 200 mg tablets) tended to be greater than for the proprietary tablets. However, the bioavailability and pharmacokinetics of carbamazepine when assessed at steady-state were similar for the two formulations. It appears, therefore, that the breakthrough seizures and higher incidence of neurological side-effects observed when children were given generic carbamazepine in place of the proprietary formulation cannot be accounted for by differences in bioavailability or pharmacokinetics.


Assuntos
Carbamazepina/farmacocinética , Epilepsia/tratamento farmacológico , Adolescente , Disponibilidade Biológica , Carbamazepina/análogos & derivados , Carbamazepina/sangue , Carbamazepina/metabolismo , Criança , Epilepsia/metabolismo , Feminino , Humanos , Masculino , Distribuição Aleatória , Equivalência Terapêutica
6.
Int J Radiat Biol ; 56(4): 493-501, 1989 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-2571661

RESUMO

The radiosensitivity of meiotic stem cells from photoregressed testes of the Syrian hamster was studied after in vivo irradiation with 2.67 Gy (1.77 Gy/min). The testes of Expt I animals were irradiated at the time of transfer from short days (11 weeks at 6L:18D (6 hours light: 18 hours) darkness) to long days (14L:10D) and sampled at weekly intervals between 5 and 10 weeks and at 15 weeks postirradiation. The Ext II animals received the same X-ray dose, 2, 4, 6, 8 weeks after the transfer to long days and were sampled 10 weeks postirradiation. In Expt I X-irradiation delayed the recovery of testis structure and function by 4 weeks. Animals in Expt II were homogeneous with regard to testicular weight, sperm count, tubule diameter and the level of pachytene, MI and MII damage. The incidence of structural chromosomal changes in primary spermatocytes at pachytene (synaptonemal complexes) and MI and MII was determined. In Exp I and II and data from X-irradiated testes (2.6 Gy) not exposed to short days (Control B, see Cawood and Breckon 1983), these cell types show a difference in sensitivity to the induction of structural damage. The lowest level of pachytene damage was in Expt II, and the ratio of the number of pachytene to MI cells showing structural change was 1.23:1 (P = 0.41), not significantly different from 1:1. In Expt I the pachytene, MI structural change ratio was 1.60:1 (P = 0.010), significantly different from 1:1. The control B ratio was 1.85:1 (P = 0.0037) which was significantly different from 1:1. The preliminary results indicate that testes fully regressed to the 'stem' cell level by exposure to short day length have a similar radiosensitivity to normal (non-regressed) testes. However, testes irradiated during the recovery phase from photoperiod-induced regression have increased sensitivity to radiation damage. The relative testis weight was reduced to a mean of 1.25 g by the sequential X-ray treatment--this may indicate that the effects of the X-rays (3 Gy) on a recovering photoregressed testis are independent of the time of the X-ray treatment during the recovery period. Recovery of tubule diameter is not perturbed and may be slightly increased, with an associated elevation of MI-MII activity--but a low spermatogonia count.(ABSTRACT TRUNCATED AT 400 WORDS)


Assuntos
Cricetinae/fisiologia , Mesocricetus/fisiologia , Espermatogênese/efeitos da radiação , Testículo/efeitos da radiação , Animais , Luz , Masculino , Meiose/efeitos da radiação , Tamanho do Órgão , Periodicidade , Estações do Ano , Espermatogônias/efeitos da radiação , Testículo/anatomia & histologia , Raios X
7.
Chromosoma ; 98(4): 301-6, 1989 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-2612290

RESUMO

Chromosome behaviour during meiosis in male Syrian hamsters heterozygous for one of three translocations was analysed as part of a study of the transmission of these structural changes. Synapsis was studied using preparations of synaptonemal complexes, and chiasmate associations and the results of anaphase I segregation were studied in air-dried preparations of metaphases I and II respectively. The main findings were: (i) that, at least in the two trivalent-forming translocations, there is no simple relationship between either the frequency or the extent of synapsis and chiasma formation between the chromosomes involved in the translocation; (ii) that the presence of a univalent in a substantial proportion of metaphase I cells does not necessarily lead to irregular segregation as judged by analysis of metaphase IIs; and (iii) conversely, that in translocation heterozygotes in which metaphase I contains the chromosomes involved in the translocation as a quadrivalent or as two bivalents, with no univalents or trivalents, unexpected numerical segregation can be found. The observations of meiotic chromosomes behaviour reported here show that it is not always possible to predict the effects of structural change, or to determine the basis of these effects, from an analysis of any stage of meiosis taken in isolation, or from an analysis of an apparently similar change.


Assuntos
Cromossomos/ultraestrutura , Translocação Genética , Animais , Bandeamento Cromossômico , Cricetinae , Cariotipagem , Masculino , Meiose , Mesocricetus , Metáfase , Recombinação Genética
8.
Clin Chem ; 35(9): 1832-7, 1989 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-2570651

RESUMO

Hypervariable tandem-repetitive minisatellite regions of human DNA can be used to generate individual-specific DNA fingerprints. Validation studies have demonstrated the reliability of the analysis, the mode of inheritance of the minisatellites, and the unparalleled degree of individual specificity. The uses of hypervariable probes in forensic biology, paternity testing, and the resolution of a wide range of problems in genetics, molecular biology, population biology, and medicine are illustrated.


Assuntos
Sondas de DNA , Técnicas Genéticas , Animais , Medicina Legal , Humanos , Polimorfismo de Fragmento de Restrição
9.
J Med Genet ; 26(5): 294-8, 1989 May.
Artigo em Inglês | MEDLINE | ID: mdl-2567354

RESUMO

We review the published reports on reproduction in cases of non-mosaic trisomy 21 (Down's syndrome) and present the first fully documented case of a non-mosaic male with Down's syndrome fathering a pregnancy, a fact which has important implications in the light of caring for these people in the community.


Assuntos
Síndrome de Down/genética , Fertilidade , Adulto , DNA/análise , Humanos , Masculino , Mosaicismo , Paternidade , Polimorfismo de Fragmento de Restrição
10.
Dev Med Child Neurol ; 28(6): 708-12, 1986 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-3817309

RESUMO

A study of bio-availability of three drug companies' brands of phenytoin preparations (50mg capsule/tablets) was undertaken on 30 children with tonic-clonic or complex partial seizures. Eight children were excluded because of non-compliance and three because of abnormally high serum levels. Phenytoin capsules (Parke Davis) and tablets (Boots) produced significantly higher serum-level profiles than phenytoin tablets (Evans). Seizure frequencies did not differ significantly with the three brands of phenytoin. Dissolution of the three preparations tested in vitro was different. As a result of this study the authors recommend that children remain on the same manufacturer's brand of phenytoin throughout their treatment.


Assuntos
Fenitoína/administração & dosagem , Adolescente , Disponibilidade Biológica , Cápsulas , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Fenitoína/metabolismo , Fenitoína/uso terapêutico , Convulsões/tratamento farmacológico , Solubilidade , Comprimidos
11.
Mutat Res ; 144(1): 19-21, 1985 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-3897841

RESUMO

The dose-response relationships of the induction of structural change in chromosomes after X-irradiation of spermatogonia have been determined from analyses of synaptonemal complexes in pachytene spermatocytes and from air-dried preparations of metaphase I. The dose-response curves were superficially the same shape, with a peak yield of cells containing a multivalent at 4 Gy, although only in the pachytene data was there any statistically significant hump. The pachytene preparations were much more sensitive, revealing nearly twice the proportion of cells containing multivalents than found at metaphase.


Assuntos
Cromossomos/efeitos da radiação , Espermatogônias/efeitos da radiação , Espermatozoides/efeitos da radiação , Animais , Aberrações Cromossômicas , Cricetinae , Técnicas Citológicas , Relação Dose-Resposta à Radiação , Masculino , Meiose/efeitos da radiação , Mesocricetus , Metáfase , Espermatócitos/efeitos da radiação
12.
J Reprod Fertil ; 75(1): 177-81, 1985 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-4032370

RESUMO

Male Syrian hamsters exposed to short photoperiods of 6 h light/day (6L:18D) show regression of the testes within 12 weeks. Chromosome preparations of the meiotic stages (pachytene, metaphase I (MI) and metaphase II (MII)), testicular weights relative to body weights, sperm counts, seminiferous tubule diameter and histological appearance were examined at intervals during regression and subsequent recovery in a long photoperiod (14L:10D). The fall of testicular weight was associated with the decrease in tubule diameter. Spermatogenesis and sperm count were reduced rapidly and finally ceased after 10 weeks in short days. The numbers of MI and MII cells relative to 100 pachytene cells progressively decreased during the short-day treatment, although the ratio of MI:MII stayed constant whenever there was meiotic activity (except in the first week of the recovery phase). This suggests that an increasing proportion of pachytene cells did not progress to MI with increased time in short days, but cells which did reach MI progressed to MII in the same proportions as in the control testes. Meiosis ceased after 10 weeks in short days. Recovery in the long days was marked by a peak in the number of MI and MII cells/100 pachytene cells soon after the return to long days. This preceded the return (to control values) of the sperm count by 10 weeks. Initial recovery in the first 3 weeks was very rapid in all the determined values.


Assuntos
Luz , Meiose/efeitos da radiação , Testículo/fisiologia , Animais , Cricetinae , Masculino , Mesocricetus , Tamanho do Órgão , Túbulos Seminíferos/anatomia & histologia , Túbulos Seminíferos/efeitos da radiação , Contagem de Espermatozoides , Testículo/anatomia & histologia , Testículo/efeitos da radiação , Fatores de Tempo
13.
Chromosoma ; 91(2): 164-6, 1985.
Artigo em Inglês | MEDLINE | ID: mdl-3987442

RESUMO

Untransformed Syrian hamster fibroblasts in exponential growth were exposed to a pulse of [3H]-thymidine for 5 min, followed immediately by bromodeoxyuridine, and serial samples were taken up to 16 h. Preparations were autoradiographed and stained for replication banding. No cell with replication bands was found without significant [3H]-thymidine uptake, although the extent of uptake varied between sub-phases of S. Thus there is no indication of a total cessation of synthesis at any period during S-phase.


Assuntos
Replicação do DNA , Interfase , Animais , Células Cultivadas , Cromossomos/metabolismo , Cricetinae , Fibroblastos , Mesocricetus , Replicon
14.
Mutat Res ; 122(2): 149-54, 1983 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-6656805

RESUMO

The incidence of multivalent formation has been compared in primary spermatocytes at pachytene, using synaptonemal complex preparations and at diakinesis/metaphase, using air-dried preparations, from testes of Syrian hamsters several weeks after exposure to an acute dose of X-rays. The pachytene preparations revealed nearly twice the number of multivalents found at diakinesis/metaphase I, and showed the ability to reveal types of structural alteration undetectable in conventional air-dried techniques.


Assuntos
Cromossomos/efeitos da radiação , Meiose/efeitos da radiação , Espermatogônias/efeitos da radiação , Espermatozoides/efeitos da radiação , Animais , Masculino , Camundongos , Espermatócitos/efeitos da radiação , Raios X
15.
J Theor Biol ; 100(4): 631-43, 1983 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-6876817

RESUMO

When the patterns of replicating chromosome bands of homologous chromosomes within a diploid cell during DNA synthesis phase are compared, the frequency of disparity (i.e. a band present on only one homologue) is less than expected on the basis of chance. This could be taken as implying some "link" between homologues which constrains their programmes of replication to keep in step. This paper develops a model showing that the observed disparities can be accommodated within a framework of homologue independence. Differences between cells in the time of appearance of bands lead in any sample to the summation of an infinitude of binomial distributions and hence to over-dispersion. The model fits observed data for bands replicating in euchromatic and heterochromatic chromosome regions obtained from Syrian hamster fibroblast cells growing in vitro.


Assuntos
Cromossomos , Replicação do DNA , Modelos Genéticos , Animais , Bandeamento Cromossômico , Cricetinae , Fibroblastos/fisiologia , Mesocricetus
16.
Cell Tissue Kinet ; 16(1): 51-7, 1983 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-6825156

RESUMO

Untransformed Syrian hamster fibroblasts in short-term culture were studied by means of [3H]thymidine autoradiography combined with differential staining after continuous exposure to bromodeoxyuridine. Fractions of 3H-labelled metaphases (FLM) and of differentially stained metaphases (FDM) were determined in sequential samples. The resulting FLM and FDM curves are in close agreement, in sequential samples. The resulting FLM and FDM curves are in close agreement, except at later sample times (10 hr onwards), when the FLM is greater than the FDM. This inefficiency on the part of the bromodeoxyuridine technique in the detection of cells in early S-phase leads to an underestimate of the average duration of S compared with that derived from autoradiography. Grain counts suggest that only a small proportion of total DNA synthesis is missed. FLM and FDM curves from both diploid and tetraploid cells are very similar. Despite the inefficiency in the detection of cells in early S phase, the bromodeoxyuridine technique has a number of useful features in studies of the cell cycle. It is possible to distinguish pre-S cells from G2 cells unambiguously, and cells in their first cycle can be distinguished from those in their second with a much greater efficiency than by autoradiography. The technique is consistent and has no problems from background or the consequent need for thresholds in scoring. As is demonstrated here, the two methods can be combined, the differential staining being little affected by the autoradiographic procedures.


Assuntos
Bromodesoxiuridina/farmacologia , Ciclo Celular , Replicação do DNA , Timidina/metabolismo , Animais , Autorradiografia , Células Cultivadas , Cricetinae , Replicação do DNA/efeitos dos fármacos , Fibroblastos/metabolismo , Cinética , Masculino , Mesocricetus , Pele/metabolismo , Trítio
17.
Chromosoma ; 84(4): 505-9, 1982.
Artigo em Inglês | MEDLINE | ID: mdl-7075351

RESUMO

From crosses within a 2n=43 line of Syrian hamsters (Mesocricetus auratus) lacking one derivative (der 11) of an 11;20 reciprocal translocation we have obtained homozygotes with only 42 chromosomes. These animals are homozygous deficient (nullisomic) for the centromere and short arm of chromosome 11 and for the bulk of the long arm of chromosome 20. -During cytogenetic studies, we investigated the frequency patterns of early-replicating bands in the surviving derivative (der 20) at two cytologically defined sub-phases of S using short-term fibroblast cultures. These patterns were compared with those observed in the component, untranslocated arms in normal 2n=44 cells at the same two sub-phases. -Very close agreement was found, indicating that neither the nullisomy, nor the new arm combination has interfered detectably with the pattern or programme of early band replication.


Assuntos
Aneuploidia , Cricetinae/genética , Replicação do DNA , Mesocricetus/genética , Animais , Células Cultivadas , Bandeamento Cromossômico , Cruzamentos Genéticos , Pele/citologia
18.
Chromosoma ; 83(5): 711-20, 1981.
Artigo em Inglês | MEDLINE | ID: mdl-7297246

RESUMO

The BrdU/Hoechst 33258/Giemsa method for sub-dividing S-phase in asynchronous cell populations has been re-evaluated and modified to give better definition and more even distribution of sub-phases. A reference pattern of early-replicating euchromatic bands is given for all chromosomes at Sk2 in primary cultures of skin fibroblasts. The overall band patterns at each sub-phase have allowed more objective definitions of "early" and "late" replication for these cells, and show that in both classes of chromatin light G-bands preceed dark G-bands. Asynchrony between homologous bands is observed at all stages of S, albeit with a variable frequency. The observed in vitro replication patterns and programme for the chromosomes of skin fibroblasts does not appear to be affected by the age or sex of the source.


Assuntos
Ciclo Celular , Cromossomos/ultraestrutura , Cricetinae/genética , Mesocricetus/genética , Animais , Células Cultivadas , Bandeamento Cromossômico , Cariotipagem , Masculino , Pele/ultraestrutura
19.
Chromosoma ; 84(3): 365-72, 1981.
Artigo em Inglês | MEDLINE | ID: mdl-7327050

RESUMO

The sub-division of S-phase in Syrian hamsters, on the basis of Brd/U/Hoechst 33258/Giemsa banding, has allowed a quantitative comparison of the replication of individual chromosome bands within defined subphases of S. This analysis has shown that in hamsters, as has been reported in humans, there are distinct patterns of early replication in vitro in the early X, the late X in fibroblasts, and the late X in lymphocytes. In addition, it has been possible to show that, although the pattern of replication of the late X in fibroblasts differs from that in lymphocytes, the time in S at which bands first appear on this chromosome is the same in the two cell types. No significant heterogeneity can be ascribed to differences between individuals, adult or embryonic sources, culture media, or time of exposure to BrdU. The absence of any detectable heterogeneity in the replication band frequencies in autosomal heterochromatic arms suggests that the cell-specific variability of the late-replicating X is a feature of facultative rather than constitutive heterochromatin.


Assuntos
Cricetinae/genética , Replicação do DNA , Variação Genética , Mesocricetus/genética , Cromossomos Sexuais , Cromossomo X , Animais , Bandeamento Cromossômico , Embrião de Mamíferos/ultraestrutura , Feminino , Linfócitos/ultraestrutura , Masculino , Pele/ultraestrutura
20.
Planta ; 146(5): 597-601, 1979 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24318333

RESUMO

Vacuoles formed by the invagination of the inner membrane of the nuclear envelope have been observed during meiotic prophase in a wide range of plants. In the angiosperm Lycopersicon their formation was found to coincide with the completion of synaptonemal complex formation, and this timing is analogous to that observed during this stage in the silkworm Bombyx. The implications of this activity in relation to the process of chromosome movement are discussed. In the gymnosperm Pinus, the heterosporous fern Marsilea and homosporous ferns Pteridium and Dryopteris the formation of nuclear vacuoles begins much earlier, coinciding with the condensation of chromatin during leptotene. They enlarge and become more elaborate as meiosis proceeds, and may eventually become detached from the nuclear envelope. It is therefore thought unlikely that theyfulfil functions connected with chromosome movement in the manner proposed for the silkworm and the tomato. During diplotene/diakinesis they contain electron-opaque granules and fibrils, and the possible origin and significance of this material is discussed.

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