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M Dalton

Publications and source records attributed to M Dalton.

At least 37 records · Page 2Linked to original sources
PubMed1998

Cloning and expression of the ApaLI, NspI, NspHI, SacI, ScaI, and SapI restriction-modification systems in Escherichia coli.

The genes encoding the ApaLI (5'-GTGCAC-3'), NspI (5'-RCATGY-3'), NspHI (5'-RCATGY-3'), SacI (5'-GAGCTC-3'), SapI (5'-GCTCTTCN1-3', 5'-N4GAAGAGC-3') and ScaI (5'-AGTACT-3') restriction-modification systems have been cloned in E. coli. Amino acid sequence comparison of M.ApaLI, M.NspI, M.NspHI, and M.SacI with known methylases indicated that they contain the ten conserved motifs characteristic of C5 cytosine methylases. NspI and NspHI restriction-modification systems are highly homologous in amino acid sequence. The C-termini of the NspI and NlaIII (5'-CATG-3') restriction endonucleases share significant similarity. 5mC modification of the internal C in a SacI site renders it resistant to SacI digestion. External 5mC modification of a SacI site has no effect on SacI digestion. N4mC modification of the second base in the sequence 5'-GCTCTTC-3' blocks SapI digestion. N4mC modification of the other cytosines in the SapI site does not affect SapI digestion. N4mC modification of ScaI site blocks ScaI digetion. A DNA invertase homolog was found adjacent to the ApaLI restriction-modification system. A DNA transposase subunit homolog was found upstream of the SapI restriction endonuclease gene.

Amino Acid Sequence↗
PubMed1998

Adrenocortical response and regional T-lymphocyte activation patterns following minimally invasive surgery in a rat model.

BACKGROUND: Laparoscopic surgery is associated with less tissue trauma and postoperative pain as well as a more rapid recovery than open surgery. We hypothesized that these factors may result in less immune impairment following laparoscopic surgery. METHODS: We measured mitogen-induced surface interleukin-2 receptor (IL2R) expression and lymphocyte proliferation in CD4+ and CD8+ T-lymphocytes as well as serum corticosterone levels in rats 24 h following open (OP) and laparoscopic (LAP) fundoplication. RESULTS: Serum corticosterone levels were lower in LAP vs OP rats (p = 0.02). CD4+ IL2R expression was higher in the blood, but not in the spleen, in LAP vs OP animals (p = 0.02). CD8+ IL2R expression was similar in both groups. Mitogen-induced lymphocyte proliferation was no different in the blood but decreased in the spleen in LAP vs OP rats (p = 0.03). CONCLUSIONS: Compared to open surgery, laparoscopic fundoplication in the rat results in lower adrenocortical hormone levels and better-preserved T-helper-cell activation in the blood. Lymphocyte proliferation is suppressed in the spleen 24 h after laparoscopic surgery. Minimally invasive surgery may better preserve cell-mediated immunity in the early postoperative period.

Animals↗
PubMed1997

The optimum pneumoperitoneum pressure for laparoscopic surgery in the rat model. A detailed cardiorespiratory study.

BACKGROUND: There is increasing interest in the rat model of laparoscopic surgery. This study evaluates the cardiorespiratory effects of increasing CO2 pneumoperitoneum (PP) in the rat. METHODS: Nine Sprague-Dawley rats were subjected to CO2 PP at pressures of 2, 5, 10, and 15 mmHg or control (no PP) under anesthesia. Catheters were placed in the femoral artery and the jugular vein to measure heart rate (HR), blood pressure (MAP), and arterial pH, PCO2, PO2, and HCO3. A thermistor probe in the aortic arch measured cardiac output (CO) and blood temperature (BT). RESULTS: CO2 PP had no effect on CO, MAP, or BT at any pressure. CO2 PP greater than 5 mmHg caused significant bradycardia and CO2 PP greater than 10 mmHg caused significant respiratory acidosis. CONCLUSIONS: CO2 PP pressures above 10 mmHg in rat should be avoided when performing laparoscopic surgery in the rat model.

Analysis of Variance↗
PubMed1996

Embryonic lineage of vascular smooth muscle cells determines responses to collagen matrices and integrin receptor expression.

Developmental studies have demonstrated that the vascular smooth muscle cells (VSMC) present within the elastic arteries are differentiated from two definitive origins, the neural crest and the mesoderm. Cells from these distinct progenitors differ in their ability to determine long-range spatial order of the extracellular matrix, in proliferative responses, and in the expression of critical proteins. The present study utilizes collagen gel contraction assays and the analysis of integrin receptor subunit expression to evaluate cell-matrix interactions. In the presence of serum and transforming growth factor-beta 1 (TGF) or TGF-beta 1 alone, VSMC isolated from the abdominal aorta (AA-VSMC) were found to contract collagen matrices to a significantly greater extent than VSMC from the thoracic aorta (TA-VSMC). However, in TA-VSMC, beta 1 integrin and gel contraction were stimulated only in the presence of serum factors. Metabolic labeling and immunoprecipitation of integrin subunits revealed that TGF-beta 1 induced beta 1 and alpha 5 integrin subunits in AA-VSMC four-and ninefold, respectively. AA-VSMC gel contraction stimulated by serum and TGF-beta 1 alone was inhibited with anti-beta 1 integrin antibody by 70 and 100%, respectively. However, the beta 1 integrin-specific antibody inhibited serum-induced TA-VSMC gel contraction by 25%. The data suggest that vascular smooth muscle cell ontogeny is an important determinant of cell function, phenotype, and response to growth factors such as TGF-beta 1.

Animals↗
PubMed1996

Direct regulation of ZAP-70 by SHP-1 in T cell antigen receptor signaling.

The threshold at which antigen triggers lymphocyte activation is set by the enzymes that regulate tyrosine phosphorylation. Upon T cell activation, the protein tyrosine phosphatase SHP-1 was found to bind to the protein tyrosine kinase ZAP-70. This interaction resulted in an increase in SHP-1 phosphatase activity and a decrease in ZAP-70 kinase activity. Expression of a dominant negative mutant of SHP-1 in T cells increased the sensitivity of the antigen receptor. Thus, SHP-1 functions as a negative regulator of the T cell antigen receptor and in setting the threshold of activation.

Animals↗
PubMed1996

Determination of cardiorespiratory function and the optimum anesthetic regimen during laparoscopic surgery in the rat model.

BACKGROUND: The rat is increasingly being used in laparoscopic research yet the hemodynamic and respiratory effects of CO2 pneumoperitoneum have not been studied in this model. METHODS: Five Lewis rats were anesthetized with inhaled isoflurane (1.4-2.0%) and a 50% O2/50% N2O mixture by mask (ISO). Another five rats were anesthetized with 1 ml/kg intraperitoneal sodium pentobarbital (PB) and given 100% O2 by mask. Catheters were placed in the femoral artery and the right jugular vein and a thermistor probe was placed in the aortic arch. Heart rate (HR), blood pressure (MAP), cardiac index (CI), arterial pH, and PCO2 were measured at baseline and following 10, 20, and 30 min of 2 mmHg CO2 pneumoperitoneum. RESULTS: CO2 pneumoperitoneum had no effect on HR, MAP, CI, pH, or PCO2 in either the ISO or PB anesthetic groups. Comparing the two anesthetic groups, PB demonstrated a significantly higher MAP at all time points, a significantly higher PCO2 at baseline, and 10 min of pneumoperitoneum, a significantly lower pH at baseline, 10, and 30 minutes of pneumoperitoneum, and a significantly longer induction time (31 vs. 6 min). There was no difference in HR or CI between the two anesthetics. CONCLUSION: Low-pressure CO2 pneumoperitoneum up to 30 min in the spontaneously breathing rat does not significantly affect HR, MAP, CI, pH, or PCO2. Inhalational isoflurance/N2O anesthesia produces less hypertension and respiratory acidosis than intraperitoneal pentobarbital during pneumoperitoneum in the rat.

Anesthesia, Inhalation↗
PubMed1996

Egg-sharing in assisted conception: ethical and practical considerations.

The present acute shortage of eggs for donation cannot be overcome unless adequate guidelines are set to alleviate the anxieties regarding payments, in cash or kind, to donors. The current Human Fertilisation and Embryology Authority (HFEA) guidelines do not allow direct payment to donors but accept the provision of lower cost or free in vitro fertilization (IVF) treatment to women in recognition of oocyte donation to anonymous recipients. Egg-sharing achieved in this way enables two infertile couples to benefit from a single surgical procedure. However, the practical guidelines related to this approach are ill-defined at the present time leading to some justifiable uncertainty. A pilot study was therefore undertaken in order to establish the place of egg-sharing in an assisted conception programme. The current HFEA guidelines on medical screening of patients, counselling, age and rigid anonymity between the donor and recipient were followed. The study involved 55 women (25 donors and 30 recipients) in 73 treatment cycles involving fresh and frozen-thawed embryos. Donors were previous IVF patients who, regardless of their ability to pay, shared their eggs equally with matched anonymous recipients. They paid only for their consultations and tests right up to the point of being matched with a recipient. The sole recipient paid the cost applicable in egg donation of a single egg collection, although both received embryo transfers. The results indicate that although the recipients were older than the donors (41.4 +/- 0.9 versus 31.6 +/- 0.5 years), and there was no difference in the mean number of eggs allocated, the percentage fertilization rates, or the mean number of embryos transferred, there were more births per patient amongst recipients than amongst donors (30 versus 20%). We conclude that providing the donors are selected carefully, this scheme whereby a sub-fertile donor helps a sub-fertile recipient is a very constructive way of solving the problem of the shortage of eggs for donation. There are also the advantages of including a group of women who would otherwise be denied treatment. Problems related to 'patient coercion' can, in our view, be fully overcome by the application of strict common-sense safeguards. The ideal of pure altruism is not without its medical and moral risk. The success of egg-sharing depends on shared interests and a degree of altruism between the donor, the recipient and the centre. The current HFEA guidelines should be applauded for enabling a highly effective concept of mutual help to develop.

Adult↗
PubMed1996

Distinct tyrosine phosphorylation sites in ZAP-70 mediate activation and negative regulation of antigen receptor function.

Biochemical and genetic evidence has implicated two families of protein tyrosine kinases (PTKs), the Src- and Syk-PTKs, in T- and B-cell antigen receptor signaling. ZAP-70 is a member of the Syk-PTKs that associates with the T-cell antigen receptor and undergoes tyrosine phosphorylation following receptor activation. Three tyrosine residues, Tyr-292, -492, and -493, have been identified as sites of phosphorylation following T-cell antigen receptor engagement. Utilizing ZAP-70- and Syk-deficient lymphocytes (Syk-DT40 cells), we provide biochemical and functional evidence that heterologous trans-phosphorylation of Tyr-493 by a Src-PTK is required for antigen receptor-mediated activation of both the calcium and ras pathways. In contrast, cells expressing mutations at Tyr-292 or -492 demonstrate hyperactive T- and B-cell antigen receptor phenotypes. Thus, phosphorylation of ZAP-70 mediates both activation and inactivation of antigen receptor signaling.

Amino Acid Sequence↗
PubMed1996

Zebrafish translation elongation factor EF1 alpha mRNA: sequence and secondary structures.

We have determined the complete sequence of the translation elongation factor EF1 subunit alpha (EF1 alpha) mRNA of zebrafish, and the 3'-untranslated sequence of EF1 alpha mRNA of halibut. The 5'-untranslated leader sequence of the EF1 alpha mRNA starts with a polypyrimidine tract. This feature is shared with the mRNAs for ribosomal proteins, where it affects the utilization of mRNA by ribosomes. However, the secondary structures of these leader sequences may differ. 5'-Polypyrimidine tracts of vertebrate EF1 alpha mRNAs participate in the formation of stable stem-loop structures, whereas those of 15 randomly chosen mRNAs for ribosomal proteins do not. This difference may provide a basis for differential control of translation for the two classes of mRNA. The 3'-untranslated sequences of vertebrate EF1 alpha mRNA have diverged little during evolution. Analyses of sequence and putative secondary structures suggest that both sequence-specific interactions and secondary structures may have contributed to sequence conservation.

Amino Acid Sequence↗
PubMed1995

Activation of ZAP-70 kinase activity by phosphorylation of tyrosine 493 is required for lymphocyte antigen receptor function.

ZAP-70 is a protein tyrosine kinase (PTK) required for T-cell development and T-cell antigen receptor (TCR) function. ZAP-70 is associated with the phosphorylated antigen receptor and undergoes tyrosine phosphorylation following receptor activation. We demonstrate here that tyrosine phosphorylation of ZAP-70 results in an increase in its catalytic activity and that this activation is mediated by the phosphorylation of tyrosine residue 493 by the src family of PTKs. The activity of baculoviral expressed ZAP-70 was up-regulated 10-fold when ZAP-70 was co-infected and phosphorylated by the src family PTK, lck. Mutation of Y493 alone abrogated the ability of ZAP-70 to be activated by lck. Moreover, we demonstrate that phosphorylation of Y493 and activation of ZAP-70 is required for antigen receptor-mediated induction of interleukin-2 (IL-2) secretion in lymphocytes.

Amino Acid Sequence↗
PubMed1994

An antibody which specifically recognizes prelamin A but not mature lamin A: application to detection of blocks in farnesylation-dependent protein processing.

A polyclonal antibody [anti-prelamin A antibody (alpha-PA)] has been obtained against the peptide LLGNSSPRTQSPQN which is proteolytically removed during the farnesylation-dependent processing of prelamin A to mature lamin A. We tested the ability of this antibody to detect inhibition of farnesylation-dependent protein processing of prelamin A. The alpha-PA antibody was shown to immunoprecipitate prelamin A from lovastatin-treated HeLa cells but not mature lamin A from untreated cells. Further studies were performed after antigen-affinity chromatographic purification of the antibody. Western blotting of lovastatin-treated HeLa cell extract demonstrated that the purified alpha-PA antibody recognizes prelamin A. Furthermore, this signal could be competed away by incubation with the peptide. Indirect immunofluorescence helped detect nuclear accumulation of the antigen in response to treatment of HeLa cells with lovastatin or in Chinese hamster ovary K1 cells transiently transfected with a prelamin A mutant blocked in farnesylation. This antibody should be useful for screening compounds that may block any of the three common steps in the farnesylation-dependent processing of proteins (farnesylation, endoproteolysis, and carboxymethylation) since it appears that prelamin A undergoes all of these reactions prior to removal of the antigenic peptide. Inhibitors of these reactions have been proposed as potential anticancer drugs, since they would be expected to block the biological activity of oncogenic p21ras proteins. Since such screening would be performed most efficiently by enzyme-linked immunosorbent assays, we can detect the accumulation of prelamin A after treatment with lovastatin by performing this procedure as well. Application of alpha-PA in an enzyme-linked immunosorbent assay, which demonstrates the activity of a peptidomimetic farnesyltransferase inhibitor, supports the use of this antibody in large scale screening for inhibitors of farnesylation-dependent protein processing.

Amino Acid Sequence↗
PubMed1994

Nutrition education in Missouri schools.

This survey examined the status of nutrition education in Missouri schools, profiled teacher preparation in nutrition, and identified teacher preferences for additional nutrition education resources. Questionnaires were mailed to a systematic sample of 1,664 teachers representing different grade levels K-12 and subject areas including biological science, health, home economics, and physical education. Responses from 793 teachers indicated most integrated nutrition into other subjects such as health and science. Almost all taught the concept of food groups. Teachers expressed a need for materials on a range of concepts and preferred the videotape format. About one-third of elementary teachers reported completing a college-level nutrition course: 70% of secondary teachers had completed such a course. Results indicate the need for materials to integrate nutrition into various subjects and encourage teaching on concepts beyond the food groups.

Curriculum↗
PubMed1994

Hypertonic saline challenge in an epidemiologic survey of asthma in children.

To evaluate sensitivity and specificity of a 4.5% hypertonic saline challenge for a diagnosis of asthma, we studied 393 schoolchildren (13 to 15 yr of age) with "current wheeze," "former wheeze," and without history of wheeze in a community-based, cross-sectional survey. These children were selected from 2.836 schoolchildren in 26 schools in greater Melbourne, Australia who completed a self-administered questionnaire on respiratory symptoms, allergic rhinitis, and eczema. Three hundred eighty-two of 393 children successfully completed a 4.5% hypertonic saline challenge with increasing inhalation periods, and 365 of 393 performed a 6-min standardized, free running exercise challenge. The prevalence of bronchial hyperresponsiveness to hypertonic saline was 20.4%. Sensitivity and specificity for the hypertonic saline challenge to identify children with "current wheeze" were 47% and 92% respectively and for the exercise challenge, 46% and 88%. The agreement of response to hypertonic saline and to exercise was only moderate (kappa = 0.43). Factors associated with increased response to hypertonic saline in a multivariate logistic regression model were a history of "current wheeze," hay fever, response to the exercise challenge, female sex, and a lower baseline predicted FEV1. These results suggest that a 4.5% hypertonic saline challenge shows sensitivity and specificity similar to a standardized exercise challenge and pharmacologic challenges and a higher sensitivity than cold air hyperventilation and distilled water to identify asthma in children in a field study. Measurement of responsiveness to hypertonic saline may be of value as an objective marker of asthma to compare prevalence studies of bronchial hyperresponsiveness and of asthma over time and between countries.

Adolescent↗
PubMed1994

The processing pathway of prelamin A.

The conversion of mammalian prelamin A to mature lamin A proceeds through the removal of 18 amino acids from the carboxyl terminus. The initial step in this processing is the isoprenylation of a CAAX box cysteine. This proteolytic event is distinctive for prelamin A among the known prenylated mammalian proteins. Since the carboxyl terminus of prelamin A is removed during maturation, it is not obvious that this protein would undergo the two reactions subsequent to prenylation observed in other CAAX box proteins--the endoproteolytic removal of the carboxyl-terminal 3 amino acids and the subsequent methylation of the now carboxyl-terminal cysteine. To characterize the maturation of prelamin A further, we have developed a CHO-K1 cell line that possesses a dexamethasone-inducible human prelamin A against a genetic background of high mevalonate uptake. Utilizing this cell line in association with antibodies specific to the transgenic prelamin A, we have been able to demonstrate directly in vivo that prelamin A undergoes farnesylation and carboxymethylation prior to conversion to lamin A, as is the case for other prenylated proteins. We have demonstrated previously that in the absence of isoprenylation, conversion of prelamin A to lamin A is blocked, but that unprocessed prelamin A is transported to the nucleus where it can still undergo maturation. Consistent with the implications of these prior studies, we now demonstrate the presence of both subunits of farnesyl-protein transferase in the nucleus.

Amino Acid Sequence↗