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Biomedical subjects

J Adam

Publications and source records attributed to J Adam.

At least 37 records · Page 2Linked to original sources
PubMed1997

Maintenance of neuroepithelial progenitor cells by Delta-Notch signalling in the embryonic chick retina.

BACKGROUND: Neurons of the vertebrate central nervous system (CNS) are generated sequentially over a prolonged period from dividing neuroepithelial progenitor cells. Some cells in the progenitor cell population continue to proliferate while others stop dividing and differentiate as neurons. The mechanism that maintains the balance between these two behaviours is not known, although previous work has implicated Delta-Notch signalling in the process. RESULTS: In normal development, the proliferative layer of the neuroepithelium includes both nascent neurons that transiently express Delta-1 (Dl1), and progenitor cells that do not. Using retrovirus-mediated gene misexpression in the embryonic chick retina, we show that where progenitor cells are exposed to Dl1 signalling, they are prevented from embarking on neuronal differentiation. A converse effect is seen in cells expressing a dominant-negative form of Dl1, Dl1(dn), which we show renders expressing cells deaf to inhibitory signals from their neighbours. In a multicellular patch of neuroepithelium expressing Dl1(dn), essentially all progenitors stop dividing and differentiate prematurely as neurons, which can be of diverse types. Thus, Delta-Notch signalling controls a cell's choice between remaining as a progenitor and differentiating as a neuron. CONCLUSIONS: Nascent retinal neurons, by expressing Dl1, deliver lateral inhibition to neighbouring progenitors; this signal is essential to prevent progenitors from entering the neuronal differentiation pathway. Lateral inhibition serves the key function of maintaining a balanced mixture of dividing progenitors and differentiating progeny. We propose that the same mechanism operates throughout the vertebrate CNS, enabling large numbers of neurons to be produced sequentially and adopt different characters in response to a variety of signals. A similar mechanism of lateral inhibition, mediated by Delta and Notch proteins, may regulate stem-cell function in other tissues.

Animals↗
PubMed1995

Expression of a Delta homologue in prospective neurons in the chick.

The product of the Delta gene, acting as ligand, and that of the Notch gene, acting as receptor, are key components in a lateral-inhibition signalling pathway that regulates the detailed patterning of many different tissues in Drosophila. During neurogenesis in particular, neural precursors, by expressing Delta, inhibit neighbouring Notch-expressing cells from becoming committed to a neural fate. Vertebrates are known to have several Notch genes, but their functions are unclear and their ligands hitherto unidentified. Here we identify and describe a chick Delta homologue, C-Delta-1. We show that C-Delta-1 is expressed in prospective neurons during neurogenesis, as new cells are being born and their fates decided. Our data from the chick, combined with parallel evidence from Xenopus, suggest that both the Delta/Notch signalling mechanism and its role in neurogenesis have been conserved in vertebrates.

Amino Acid Sequence↗
PubMed1993

[The effect of middle-molecular ninhydrin-positive substances isolated from the rat myocardium on rat serum arylamidase activity after administration of ethanol].

Protein-free extract from the myocardium of control rats and the majority of its fractions were found to stimulate arylamidase activity. Ethanol administration to rats for 1, 3 or 7 weeks increased the amount of fractions which displayed an inhibitory effect. The observed changes were probably due to enhanced protein degradation and/or to decreased amino acid incorporation into proteins following ethanol administration. (Tab. 4, Fig. 2, Ref. 19.).

Aminopeptidases↗
PubMed1993

[The effect of ethanol on the occurrence of peptides with antibacterial effects in the rat myocardium]].

The effect of 7% ethanol on the peptide content in the myocardium was studied during prolonged exposition. The protein-free extract from the myocardium of controls as well as experimental groups following 1-8 weeks ethanol administration contained peptides with antibacterial activity. Long-term ethanol administration resulted in changes in physico-chemical properties of peptides both compared with controls and also among the experimental groups mutually. The changes were manifested by differences in the elution profiles following gel chromatography and RF values after electrophoresis or by different amino acid composition. The results are compared with the influence of peptides on the growth of bacterial cultures S. aureus. Ethanol administration induced diminution of the diameter of the inhibitory zones. This effect was most marked in the group fed with ethanol for 3 and 8 weeks. (Fig. 5, Ref. 17.)

Amino Acids↗
PubMed1992

Effects of discrimination training on responding during a compound conditioned stimulus.

Four experiments examined responding in the presence of a triple-element compound ABC after discrimination training in which 2 compounds, AB and BC, signaled the delivery of food and 1 element alone, B, signaled the absence of food. In Experiments 1 and 2, using rats, responding during ABC was more vigorous than in a control group for which A and C but not B had been individually paired with food. This finding was replicated in Experiment 3, which used pigeons, and in Experiment 4, where all 3 stimuli of the control condition were individually paired with food. The results are more consistent with a configural than with an elemental theory of learning.

Animals↗
PubMed1992

The survival game.

This paper describes a flexible and enjoyable learning game and summarizes our experiences of using it (including the medical students' own evaluation of the game). The description is sufficiently detailed to encourage readers to reproduce and adapt the game to fit their own requirements.

England↗
PubMed1991

Testing various methods of introducing health charts into medical records in family medicine units.

OBJECTIVE: To test three methods of introducing health charts into the medical records of six family medicine units. DESIGN: Quasi-experiment. PARTICIPANTS: The staff physicians and family medicine residents in all six units and the nurses in two units. INTERVENTIONS: Group 1 (minimal intervention): health charts, a user's guide and one training session. Group 2 (intermediate intervention): same intervention as for group 1 plus two feedback sessions at 3 and 6 months. Group 3 (maximum intervention): same intervention as for group 2 plus promotion of the team concept (nurses were included). The intervention phase lasted from September 1987 to August 1988. OUTCOME MEASURES: The frequency with which the health charts were used, the item scores of each preventive care activity and the overall unit scores. Data were gathered through chart audits at baseline and at the end of the intervention phase. RESULTS: The frequency with which the health charts were used varied from 3.9% to 26.9%. The greatest increases in item scores were observed in the use of mammography (20.0%), counselling on lifestyle (19.4%) and breast examination (17.2%). Although the overall improvement in the unit scores was statistically significant (p less than 0.05) the hypothesis of an increasing gradient of effect across the three intervention groups could not be tested because of the variation in scores across the units. CONCLUSION: Health charts and other similar tools are useful; however, they are not sufficient to change practice behaviours. The support of a "champion" on the health care team might well be a determining factor of success for the delivery of preventive services in primary care practice.

Adult↗
PubMed1991

DNA methylation changes in the IL-1 (2F) chromosomal region of some radiation-induced acute myeloid leukaemias carrying chromosome 2 rearrangements.

Acute myeloid leukaemias (AML) arising in irradiated CBA/H mice frequently have breakpoints in the F region of chromosome 2. The closely linked cytokine genes interleukin (IL)-1 alpha and beta map to this region, and the beta gene is deregulated in some AMLs. Using pulsed-field gel electrophoresis techniques, we show here that an 800 kb 2F region encoding IL-1 alpha and beta is not obviously rearranged in six leukaemias carrying chromosome 2 abnormalities. However, changes in IL-1 region DNA methylation in three leukaemias may be consistent with loss of hypermethylated sequences from one chromosome copy. These possible 2F region losses are discussed in relation to genomic imprinting and its potential role in murine myeloid leukaemogenesis.

Acute Disease↗
PubMed1991

Peritonitis rates for CAPD patients using the SCD 210 (Inpersol sterile connecting device): a Canadian survey.

A retrospective study was conducted in 20 Canadian hospitals to assess peritonitis rates of CAPD patients utilizing the SCD 210 patient assist device during a 30 month study period. A total of 175 patients having a cumulative SCD experience of 1,494 patient months were included in the survey. Sixty-eight patients experienced 116 episodes of peritonitis, i.e., one episode every 12.9 patient months (pt mo). Patients that had used the SCD for their entire CAPD experience had a significantly lower peritonitis rate (1/15.2 pt mo) compared to patients who had used other CAPD systems (1/10.1 pt mo). Peritonitis rates for diabetic study patients or patients with impaired vision and/or dexterity were not significantly greater than non-diabetic or non-impaired study patients. Staphylococcus epidermidis and Staphylococcus aureus were the most frequent causative microorganisms, accounting for 27.7% and 16.0% of peritonitis episodes caused by single organisms, respectively. The proportion of peritonitis caused by skin commensals was consistent across all study patients, regardless of impairment of vision and/or dexterity. The study results demonstrate the successful application of this patient assist device in a CAPD population that consisted of a large proportion of high risk patients.

Bacteria↗
PubMed1990

The IL-1 alpha and beta genes are closely linked (less than 70 kb) on mouse chromosome 2.

The murine IL-1 alpha and IL-1 beta genes encode structurally and evolutionarily related cytokines that exert a regulatory role in numerous physiological processes including hemopoiesis. Previous studies have shown these genes to be closely linked in the F region of mouse chromosome 2. Here we show, using pulsed-field gel electrophoresis, that the IL-1 alpha and beta genes of the CBA/H mouse are very closely linked and contained within a SmaI genomic fragment of approximately 70 kb. From conventional and PFGE analyses we suggest that IL-1 beta lies 5' to IL-1 alpha and that the two genes are in the same orientation and separated by approximately 50 kb. The apparent clustering of such hemopoietic genes is discussed in relation to evolutionary tandem gene duplication and possible associations with chromosomal fragile sites and leukemogenesis.

Animals↗
PubMed1990

Complications of microwave hyperthermia treatment of psoriasis.

Three healthy men with psoriatic plaques unresponsive to tar, anthralin, and UVB were treated with 2450 MHz microwave heating for 30 minutes at 42 degrees C. Two patients had plaques over bony prominences. Pain developed in both patients, and one had a hypotensive episode during the first treatment. The third patient, whose plaque was greater than 2 cm and was not located over a bony prominence, completed the 5 weeks of biweekly treatments with complete resolution of the plaque and no complications.

Adult↗
PubMed1990

Predicting arterial oxygenation during one-lung ventilation with continuous positive airway pressure to the nonventilated lung.

Forty patients undergoing elective thoracotomy were studied to assess the possibility of predicting PaO2 during one-lung ventilation (OLV) when continuous positive airway pressure (CPAP) was applied to the nondependent lung. The first 20 patients were studied retrospectively and the three most significant independent variables that correlated with PaO2 during OLV with CPAP were: side of operation (P = 0.04), FEV1/FVC ratio (P = 0.01), and the intraoperative PaO2 during two-lung ventilation (P = 0.0002). By the method of multiple linear regression, these three variables were used to construct a predictive equation for PaO2 during OLV with CPAP. The second 20 patients were studied prospectively and the predicted PaO2 correlated significantly with the observed PaO2 during OLV with CPAP (r = 0.86, P less than 0.001). Therefore, it is concluded that the PaO2 during OLV with CPAP can be predicted using routinely available data.

Aged↗