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Biomedical subjects

K D Taylor

Publications and source records attributed to K D Taylor.

At least 19 recordsLinked to original sources
PubMed1992

Expression of ribosomal protein genes in mouse oocytes and early embryos.

The quantitative changes in the mRNAs for ribosomal proteins L7a, L18a, and S15 were assayed in slot hybridization experiments using labeled cRNA probes with total RNA from late growth-phase oocytes, ovulated eggs, and early embryos through the blastocyst stage. All three mRNAs showed a similar developmental pattern of prevalence, but their copy numbers per oocyte or embryo fluctuated according to developmental stage. There are on an average about 17,000 copies of each mRNA in the late growth-phase oocyte; this number drops to one-fifth to one-tenth in the ovulated egg and two-cell embryo but increases rapidly during cleavage to bout 25,000 in the eight-cell embryo and about 42,000 in the blastocyst. A comparison of the levels of these mRNAs with the reported rates of ribosomal protein synthesis (LaMarca and Wassarman, 1979) suggests that, in late growth-phase oocytes, ribosomal protein synthesis is regulated primarily at the translational level and is kept low by some factor limiting mRNA utilization. On the other hand, the high rate of ribosome biosynthesis during early embryogenesis from the two-cell stage onward appears to involve the coordinate activation and transcription of ribosomal RNA and ribosomal protein genes coupled with the immediate translational utilization of ribosomal protein mRNAs.

Animals↗
PubMed1992

Improved method for i.r. determination of the degree of N-acetylation of chitosan.

Three published i.r. absorption band ratios for determining the % N-acetylation of chitosan have been used to follow the rate of alkaline deacetylation of chitin. Only one, the A1655/A3450 ratio, gives the expected rate of deacetylation curve. Consideration of the various i.r. ratios has led to a new relationship, % N-acetylation = (A1655/A3450) x 115, where the absorbance of the amide I band at approximately 1655 cm-1 is determined using the baseline proposed previously. The values obtained using this proposed relationship agree closely with those obtained from dye adsorption measurements for chitosans having % N-acetylation values in the range 0-55%.

Acetylation↗
PubMed1991

Expression of the rig gene in mouse oocytes and early embryos.

A clone selected from a two-cell mouse embryo cDNA library has been sequenced and identified as rig cDNA. The rig gene codes for a highly conserved nuclear protein, which may have a general role in cell growth or replication (Shiga et al.: Proc Natl Acad Sci USA 87:3594, 1990). The quantitative changes in rig mRNA were studied in blot hybridization experiments with total RNA from oocytes and early embryos. The amount and relative abundance of rig mRNA change considerably during early development. There are about 1.6 x 10(4) rig mRNA molecules in a late growth-stage oocyte; this number is reduced to about one-tenth in the ovulated egg but increases about twenty-fold during cleavage through the blastocyst stage. In F9 embryonal carcinoma cells, the relative abundance of rig mRNA is similar to that in blastocysts (about 0.1% of the mRNA population), but it is about eight-fold higher in the mouse myeloma cell line MOPC-104E. The high level of rig mRNA in late growth-stage oocytes suggests that the rig gene product may be important for overall transcriptional activity rather than DNA replication and mitosis. Alternatively, the rig protein may be a storage product of oogenesis and have a role in the initiation of development.

Amino Acid Sequence↗
PubMed1991

Iron status in a group of long-stay mentally handicapped menstruating women: some dietary considerations.

As part of a longitudinal study aimed at assessing the dietary intakes and nutritional status of a group of long-stay mentally handicapped subjects, 15 women of menstruating age were considered for a substudy to assess the influence of intake levels of dietary iron, energy, tea, coffee and vitamin C on their iron status. The assessment comprised a week-long weighed dietary survey and the measurement of a number of haematological indices that included serum ferritin concentration. Information on duration of menses was also collected and included in the assessment. Two-fifths of the subjects assessed had a serum ferritin concentration less than 12 micrograms/l indicating iron deficiency, including one who was considered anaemic as suggested by a haemoglobin level less than 12 g/dl. Duration of menses showed a negative significant correlation with serum ferritin concentration. The mean iron intake in the group was 9.5 +/- 1.5 mg/day. Energy intakes were low and positively correlated with iron intake. Although serum ferritin showed no correlation with iron intake, it showed significant negative correlations with the daily and meal-time intakes of tea and a significant positive correlation with the meal-time intakes of vitamin C. The six iron-depleted subjects were assessed as a separate group (Group I) in comparison with the other nine subjects who had a serum ferritin concentration greater than 12 micrograms/l. The results of this assessment showed that, while there were no significant differences in duration of menses or the mean daily intakes of iron and energy between the two groups. Group I subjects had significantly higher daily and meal-time intakes of tea and significantly lower meal-time intakes of vitamin C compared to Group II subjects. The study provides some evidence suggestive of an association between the iron deficiency states observed and tea intake in adversely affecting iron status, particularly in the absence of adequate meal-time intakes of vitamin C. The findings from the study also suggest that long-stay mentally handicapped women of menstruating age, in addition to their handicap and dependency states which may often predispose them to a low dietary intake, are at particular risk of iron deficiency.

Adult↗
PubMed1991

Leptospires in Rattus spp. on Barbados.

Among 138 Rattus norvegicus and 98 R. rattus trapped on Barbados in 1964-65 and examined for evidence of leptospiral infection, seropositivity prevalence rates were similar (34 and 30%, respectively), but isolation/dark field microscopy rates were higher in R. norvegicus (27%) than R. rattus (15%). R. norvegicus carried mainly serogroup Icterohaemorrhagiae and R. rattus mainly serogroup Autumnalis. These two serogroups cause 90% of severe human leptospirosis on the island.

Animals↗
PubMed1990

Quantitative changes in cytoskeletal beta- and gamma-actin mRNAs and apparent absence of sarcomeric actin gene transcripts in early mouse embryos.

Actin is known to be synthesized both during oogenesis and in cleavage-stage embryos in mice. Cytoskeletal beta-actin appears to be the major component, followed by gamma-actin, but the synthesis of alpha-actin has also been inferred from protein electrophoretic patterns. We have studied the expression of cytoskeletal (beta- and gamma-) and sarcomeric (alpha-cardiac and alpha-skeletal) actin genes at the level of the individual mRNAs in blot hybridization experiments using isoform-specific RNA probes. The results show that there are about 2 x 10(4) beta-actin mRNA molecules in the fully grown oocyte; this number drops to about one-half in the egg and less than one-tenth in the late two-cell embryo but increases rapidly during cleavage to about 3 x 10(5) molecules in the late blastocyst. The amount of gamma-actin mRNA is similar to that of beta-actin in oocytes and eggs but only about 40% as much in late blastocysts, indicating a differential accumulation of these mRNAs during cleavage. The developmental pattern of beta- and gamma-actin mRNA provides a striking example of the transition from maternal to embryonic control that occurs at the two-cell stage and involves the elimination of most or all of the maternal actin mRNA. There was no detectable alpha-cardiac or alpha-skeletal mRNA (i.e., less than 1,000 molecules per embryo) at any stage from oocyte to late blastocyst, suggesting that the sarcomeric actin genes are silent during preimplantation development.

Actins↗
PubMed1990

Mercury battle.

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Alaska↗
PubMed1987

Amounts of mitochondrial DNA and abundance of some mitochondrial gene transcripts in early mouse embryos.

The contents of mitochondrial DNA (mtDNA) and the steady-state amounts of 12 and 16 S mitochondrial rRNAs and the mRNAs for cytochrome c oxidase subunits I and II (COI and COII) were determined in dot hybridization experiments with cloned mtDNA fragments as probes during development from the one-cell to the blastocyst stage. The mtDNA content remained constant during this period at about 2.13 pg or 119,000 mtDNA molecules per embryo, suggesting an absence of mtDNA replication. The amounts of mitochondrial rRNA and the mRNAs for COI and COII varied markedly depending on developmental stage. They remained low between the end of oocyte growth and the late two-cell stage but increased 25-50X during cleavage from two-cell to early blastocyst. In the early blastocyst, the number of mitochondrial mRNA molecules was estimated at 7.9 X 10(6) or about 23% of the total embryo poly(A)+ RNA. These results suggest that the mitochondrial genome is largely inactive in the egg and two-cell embryo but that a high rate of mitochondrial transcription is initiated during cleavage. The activation of the mitochondrial genome coincides with a pronounced structural and functional differentiation of the mitochondria.

Animals↗
PubMed1987

Patterns of mRNA prevalence and expression of B1 and B2 transcripts in early mouse embryos.

Considerable evidence indicates that the 2-cell stage is a critical period of mouse embryo development when a transition from maternal to zygotic genomic control takes place. The overall changes in the structure of the mRNA population as a result of this transition were explored using a random cDNA library of 69 clones derived from late 2-cell embryos. The prevalence of the cloned sequences was analysed by dot hybridization of the cDNA clones with labelled cDNA probes synthesized to poly(A)+ RNA from different stages of development from 1-cell through blastocyst. The number of copies of individual transcripts was quantitatively estimated by comparison to standard clones of known prevalence. About one half of the transcripts that gave a measurable reaction at the 2-cell and later stages were not represented detectably in egg RNA, suggesting that a large set of zygote-specific genes not included in the maternal gene set becomes transcriptionally active in the 2-cell embryo. Six of the cDNA clones represented B1 and B2 repeat sequences. As measured by hybridization with labelled cDNA, B1 and B2 transcripts were abundantly expressed throughout cleavage, being represented by about 10(5) to 10(6) copies per embryo. However, the developmental pattern of prevalence was different for the two transcripts suggesting that their expression is regulated independently. The results of this study corroborate previous evidence derived from protein synthetic patterns and in vitro translation experiments that a major qualitative shift in the mRNA population occurs in the 2-cell embryo.

Animals↗
PubMed1986

Mechanical support for the failing heart.

The National Heart, Lung, and Blood Institute (NHLBI) has sponsored considerable research directed toward basic studies on the etiology of heart disease and atherosclerosis. While progress has been very encouraging there are still significant numbers of patients with end-stage heart disease. NHLBI initiated goal-oriented research activities on the artificial heart based upon the recommendation of the National Heart Advisory Council in 1964. The major goal of the Artificial Heart Program was to develop devices which could be effectively used to rehabilitate patients with end-stage heart disease. This paper will describe the evolution and specific program goals of the Artificial Heart Program and provide a description of the left ventricular assist system (LVAS) and total artificial heart (TAH) research efforts. Specific attention will be directed toward defining device requirements, descriptions of the blood pump and energy converter, control system operation and energy transmission methods. A summary of experimental results and current development status will also be provided.

Assisted Circulation↗
PubMed1977

Noncontact detection of ocular pulse--correlation with carotid stenosis.

Differences in ocular pulses from both eyes are well known to be associated with pathology; correlation of ocular pulse amplitude with the degree of carotid stenosis is made by a new method. Detection of ocular pulse is done by noncontact air-propagated ultrasound. Experimental results with dogs show detection of 10 to 15% carotid stenosis. By this method, one can screen for potential stroke in its incipient stages.

Animals↗