Search PubMed⌕ Search

Biomedical subjects

J Watts

Publications and source records attributed to J Watts.

At least 19 recordsLinked to original sources
PubMed1992

Tyrosyl phosphorylation and activation of MAP kinases by p56lck.

T cell signaling via the CD4 surface antigen is mediated by the associated tyrosyl protein kinase p56lck. The 42-kilodalton mitogen-activated protein (MAP) kinase (p42mapk) was tyrosyl-phosphorylated and activated after treatment of the murine T lymphoma cell line 171CD4+, which expresses CD4, with antibody to CD3. Treatment of the CD4-deficient cell line 171 with the same antibody did not result in phosphorylation or activation of p42mapk. Purified p56lck both tyrosyl-phosphorylated and stimulated the seryl-threonyl phosphotransferase activity of purified p44mpk, a MAP kinase isoform from sea star oocytes. A synthetic peptide modeled after the putative regulatory phosphorylation site in murine p42mapk (Tyr185) was phosphorylated by p56lck with a similar Vmax, but a fivefold lower Michaelis constant (Km) than a peptide containing the Tyr394 autophosphorylation site from p56lck. MAP kinases may participate in protein kinase cascades that link Src family protein-tyrosyl kinases to seryl-threonyl kinases such as those encoded by rsk and raf, which are putative substrates of MAP kinases.

Amino Acid Sequence↗
PubMed1992

Mutational analysis of the coat protein gene of potato virus X: effects on virion morphology and viral pathogenicity.

The role of the coat protein of potato virus X (PVX) was investigated by site-directed mutation of the coat protein gene. Mutant viruses with in-frame deletions in the 5' end of the coat protein gene were capable of systemically infecting plants, but produced virions with atypical morphology. Viruses with a frameshift mutation near the 5' end or with deletions in the central part of the coat protein gene failed to accumulate at detectable levels, even in the inoculated leaf. In protoplasts, mutants that infected systemically either had a wild-type phenotype or showed a small reduction in accumulation of genomic RNA. The other mutants, which did not accumulate in the inoculated leaf, were unaffected in genomic RNA accumulation 8 hr postinoculation, but at 16 hr and later they accumulated less genomic RNA than wild-type virus. None of the mutations had an effect on accumulation of negative-strand RNA. The data indicate that efficient accumulation and spread of PVX, even in the inoculated leaf, requires coat protein production and encapsidation of the viral RNA.

Amino Acid Sequence↗
PubMed1991

A controlled trial of synthetic surfactant in infants weighing 1250 g or more with respiratory distress syndrome. The American Exosurf Neonatal Study Group I, and the Canadian Exosurf Neonatal Study Group.

BACKGROUND: Surfactant-replacement therapy is now recognized as a life-saving and safe intervention in small premature infants, but there is little evidence concerning its risks and benefits in larger premature infants. METHODS: We conducted a placebo-controlled, blinded trial in 1237 infants with respiratory distress who were enrolled at 23 hospitals in the United States and 13 hospitals in Canada. At entry all the infants weighed at least 1250 g, were receiving mechanical ventilation, and had a ratio of arterial to alveolar oxygen tension below 0.22. The initial dose of either the synthetic surfactant (Exosurf, 5 ml per kilogram of body weight) or air (the placebo) was administered less than 24 hours after birth, with a second dose given 12 hours later. A total of 614 infants were assigned to receive surfactant, and 623 to receive placebo. RESULTS: Fewer infants in the surfactant group than in the placebo group died before 28 days of age or survived at 28 days with bronchopulmonary dysplasia (7 percent vs. 12 percent, P = 0.002). In the first 28 days of life, there were fewer deaths due to respiratory distress syndrome in the surfactant group (1 percent vs. 3 percent, P = 0.043), lower overall neonatal mortality (4 percent vs. 7 percent, P = 0.04), and a lower incidence of bronchopulmonary dysplasia (3 percent vs. 6 percent, P = 0.008). There was also a significantly lower incidence of pulmonary air leaks, intraventricular hemorrhage, patent ductus arteriosus, seizures, hypotension, and pulmonary hypertension in the surfactant group. The infants treated with surfactant were weaned from oxygen and mechanical ventilation significantly sooner than those given placebo, and they less often required high-frequency ventilation or extracorporeal membrane oxygenation. The primary side effect observed more frequently among the infants who received surfactant treatment was pulmonary hemorrhage (six infants vs. one infant, P = 0.055). CONCLUSIONS: In infants weighing at least 1250 g at birth who have respiratory distress syndrome, treatment with two doses of synthetic surfactant improves survival and reduces perinatal morbidity.

Birth Weight↗
PubMed1991

Automated nonisotopic assay for protein-tyrosine kinase and protein-tyrosine phosphatase activities.

A sensitive, automated, and nonisotopic assay for protein-tyrosine kinases and phosphatases has been developed. The assay uses commercially available antiphosphotyrosine monoclonal antibodies and the recently developed particle concentration immunofluorescence immunoassay technology. The assay is specific for phosphotyrosine residues, can be performed faster, and is at least 100-fold more sensitive than the current standard filter type radioassay. Myelin basic protein and a synthetic peptide corresponding to the autophosphorylation site of p56lck performed equally well in the detection of p56lck kinase activity. Myelin basic protein phosphorylated on tyrosine residues by p56lck was successfully used as substrate in the detection of phosphatase activity and vanadate or molybdate were shown to inhibit the phosphatase activity. The assay is particularly useful for the rapid detection of enzyme activities in column fractions from biochemical procedures steps and also for screening of large numbers of potential inhibitors or activators of protein-tyrosine kinases and phosphatases.

Antibodies, Monoclonal↗
PubMed1991

Mutational analysis of complementary-sense genes of African cassava mosaic virus DNA A.

We have investigated the ability of African cassava mosaic virus DNA A mutants, containing disrupted complementary-sense genes, to infect Nicotiana benthamiana and to replicate in Nicotiana tabacum protoplasts. Three overlapping open reading frames (ORFs) with the capacity to encode proteins with an Mr greater than 10K (AC1, AC2 and AC3) are highly conserved between geminiviruses that infect dicotyledonous plants and one (AC4) is less well conserved. Of these, only AC1 is a prerequisite for DNA replication; disruption of this ORF rendered the DNA noninfectious in plants and prevented DNA replication in protoplasts. Disruption of ORF AC2 prevented plant infection but mutants were capable of autonomous replication and replicated DNA B in trans in protoplasts to produce DNA forms that comigrated with wild-type virus DNAs. The AC2 mutant phenotype suggests that the product of this ORF is involved in virus spread within the plant. Mutants in which ORF AC3 had been disrupted retained the ability to replicate and to infect plants systemically although symptom development was delayed and attenuated, and mutant DNA accumulated to much lower levels (10 to 20%) in comparison with wild-type infection. Typical geminate virus particles were observed in extracts of plants infected with ORF AC3 mutants indicating that this gene is not essential for coat protein synthesis or virus assembly but possibly acts by modulating virus levels in infected tissues. Disruption of ORF AC4 had no effect on infectivity or symptom development suggesting that this ORF is maintained only because it overlaps the highly conserved ORF AC1.

DNA Mutational Analysis↗
PubMed1991

Peri-operative colonoscopy detects synchronous tumours in patients with colorectal cancers.

The aim of this study was to assess the value of colonoscopy as a peri-operative investigation in patients treated for colorectal cancer by surgical excision. Patients (134 male, 83 female) undergoing curative resection for colorectal carcinoma between August 1984 and January 1989 had colonoscopy within 3 months of surgery. Eleven patients (5%) had a synchronous cancer, which was diagnosed by colonoscopy in eight. In six of these eight, the diagnosis was made after surgery and 3 patients needed a second colectomy. However, in 3 patients the synchronous cancer was removed endoscopically without the need for further surgical resection. Most synchronous cancers had an earlier pathological stage than the index tumour. The rate of synchronous cancers was higher in patients with synchronous benign polyps (16%) than in those without polyps (3%). Colonoscopy is clearly justified as a peri-operative investigation in all patients undergoing potentially curative resection of colorectal cancer. If possible, the examination should be carried out prior to surgery, to guide the extent of resection.

Adult↗
PubMed1991

Thyroid hormone increases muscle/fat glucose transporter gene expression in rat skeletal muscle.

The enhancement of metabolic rate by thyroid hormone in target tissues is accompanied by increased glucose utilization, which in skeletal muscle and many other tissues is regulated at the level of membrane transport. To elucidate the role of thyroid hormone as a regulator of glucose transport in skeletal muscle, we have examined its effects on the expression of the muscle/fat (insulin-regulatable) glucose transporter, a distinct glucose transporter isotype whose expression is limited to insulin-sensitive tissues and which appears to be the major glucose transport protein in skeletal muscle. Treatment of hypothyroid rats with L-T3 (T3; 100 micrograms/100 g BW.day for 6 days) increased the abundance of the muscle/fat glucose transporter protein in crude membranes from hindlimb muscle, assessed by immunoblotting, to 145 +/- 8% of the control value in animals fasted for 17-20 h before death and to 159 +/- 16% of the control value in animals fed ad libitum (mean +/- SE). In purified plasma membranes, this effect of thyroid hormone was greater (208 +/- 23% and 219 +/- 13% of control in fasted and fed animals, respectively). Similar increases were found in an intracellular membrane fraction. Levels of muscle/fat glucose transporter mRNA were also increased in hindlimb muscle from the T3-treated rats, to 261 +/- 17% and 316 +/- 23% of control values in fasted and fed animals, respectively. In contrast, the erythroid glucose transporter protein and its mRNA, which are only weakly expressed in skeletal muscle but strongly expressed in brain, were not substantially increased by T3 treatment in either tissue. In experiments comparing hypothyroid, euthyroid, and chronically T4-treated animals, muscle/fat glucose transporter protein and mRNA abundance in skeletal muscle were also found to be dependent on thyroid status. Thyroid hormone may, thus, be an important regulator of the muscle/fat glucose transporter in skeletal muscle.

Adipose Tissue↗
PubMed1991

Evaluation of graduating neonatal nurse practitioners.

To compare the knowledge and problem-solving, communication, and clinical skills of graduating neonatal nurse practitioners (NNPs) and pediatric residents, a cohort study was conducted in a 33-bed tertiary-level neonatal intensive care unit in a 400-bed teaching hospital affiliated with a faculty of health sciences. Participants were all (n = 10) NNP graduates from the first 3 years of the educational program and 13 (87%) of 15 second-year pediatric residents. One hundred multiple-choice questions and 20 radiographic slides were used to test knowledge; a semistructured oral examination tested problem-solving skills; three simulated interactions with parents tested communication skills; and seven simulated procedures tested clinical skills. Graduating NNPs scored similarly to the pediatric residents on the multiple-choice questions (difference -3.4%; 95% confidence interval [CI] around difference -9.7, 2.9), radiographs (difference -1.4%; 95% CI -11.5, 8.7), oral examination (difference 2.8%; 95% CI -11.1, 16.7), communication skills (simulated parents assessment: difference 0.8%; 95% CI -4.2, 5.7; expert observer assessment: difference 5.8%; 95% CI -2.8, 14.3), and clinical skills (difference 7.4%; 95% CI -5.5, 20.2). The NNPs about to graduate from their educational program showed knowledge and problem-solving, communication, and clinical skills equivalent to those of second-year pediatric residents and are thus likely to deliver comparable care in the clinical setting. The results support the adoption of the NNP role.

Clinical Competence↗
PubMed1990

Stimulation of glucose transport by thyroid hormone in ARL 15 cells: increased abundance of glucose transporter protein and messenger ribonucleic acid.

We have studied regulation of the glucose transporter by thyroid hormone in ARL 15 cells, a thyroid hormone-responsive cell line derived from rat liver, T3 treatment (5 x 10(-8) M for 48 h) of confluent cell monolayers grown in thyroid hormone-deficient medium increased the rate of uptake of [3H] 2-deoxyglucose by 2.3 +/- 0.2-fold; this effect was half-maximal at a T3 concentration of 5 nM. The uptake of the nonmetabolizable hexose [3H]3-O-methylglucose was comparably increased, confirming a stimulation of glucose transport by thyroid hormone in these cells. In addition to enhancing glucose transporter activity, T3 increased the utilization of medium glucose to a similar degree. To elucidate the mechanism of the stimulation of glucose transport by T3, the number of glucose transporter units in crude membrane preparations was quantitated by measuring the glucose-inhibitable binding of [3H]cytochalasin-B. The Kd for specific (glucose-inhibitable) binding of [3H]cytochalasin-B was 50-60 nM, a value typical for nonhepatic glucose transporters. T3 treatment caused an increase in the glucose-inhibitable binding of this ligand that was similar in magnitude to the stimulation of [3H]2-deoxyglucose uptake (2.5 +/- 0.6-fold). Northern blot analysis of total cellular RNA using a cDNA probe for the rat brain glucose transporter showed a strong 2.9-kilobase hybridization signal after stringent washing, indicating that ARL 15 cells express the specific mRNA for this type of glucose transporter. T3 treatment increased the abundance of this mRNA by 2.3 +/- 0.2-fold. It is concluded that thyroid hormone stimulates glucose transport in ARL 15 cells, which express the brain type of glucose transporter. This effect is attributable at least in part, if not entirely, to an increase in the level of glucose transporter mRNA and an accompanying increase in the number of glucose transporter units. These findings suggest that thyroid hormone may be an important regulator of glucose transporter gene expression.

Animals↗
PubMed1989

Squint.

The most important squints to diagnose are the concomitant squints of childhood as they can lead to amblyopia, which is irreversible after the age of ten years. Familiarity with the cover test is desirable, and early referral for treatment essential.

Humans↗
PubMed1989

Medical staffing in Ontario neonatal intensive care units.

Advances in technology have improved the survival rates of infants of low birth weight. Increasing service commitments together with cutbacks in Canadian training positions have caused concerns about medical staffing in neonatal intensive care units (NICUs) in Ontario. To determine whether an imbalance exists between the supply of medical personnel and the demand for health care services, in July 1985 we surveyed the medical directors, head nurses and staff physicians of nine tertiary level NICUs and the directors of five postgraduate pediatric residency programs. On the basis of current guidelines recommending an ideal neonatologist:patient ratio of 1:6 (assuming an adequate number of support personnel) most of the NICUs were understaffed. Concern about the heavy work pattern and resulting lifestyle implications has made Canadian graduates reluctant to enter this subspecialty. We propose strategies to correct staffing shortages in the context of rapidly increasing workloads resulting from a continuing cutback of pediatric residency positions and restrictions on immigration of foreign trainees.

Health Services Needs and Demand↗
PubMed1989

Randomized trial using piperacillin versus ampicillin and amikacin for treatment of premature neonates with risk factors for sepsis.

Premature infants with risk factors for early onset sepsis who were less than seven days of age were blindly randomized to receive either piperacillin and placebo (200 infants) or ampicillin and amikacin (196 infants). One of 30 treated infants developed positive blood cultures. The overall mortality in the two groups was 8.5% for piperacillin/placebo and 13.8% for ampicillin/amikacin (p = 0.11). Serum creatinine elevation above 100 mumol/l (1.131 mg/dl) during treatment was similar in the two groups. The effectiveness of piperacillin/placebo is similar to that of ampicillin/amikacin for empiric treatment of premature newborns with risk factors for early onset sepsis.

Amikacin↗
PubMed1989

The coat protein of beet curly top virus is essential for infectivity.

We have applied the procedure of Agrobacterium-mediated inoculation to develop a simple, efficient, and reproducible assay for the infectivity of the leafhopper-transmitted geminivirus, beet curly top virus (BCTV). This assay system was used to show that a coat protein mutant of BCTV is not infectious, but could be complemented by coagroinoculation with a second mutant bearing a lethal mutation in the complementary-sense open reading frame, C1. Furthermore, the coat protein mutant retained the ability to replicate and to produce both ssDNA and dsDNA when electroporated into Nicotiana tabacum protoplasts. We conclude that the coat protein of BCTV is essential for spread of the virus. The results are discussed in the light of results with coat protein mutants of other geminiviruses.

Blotting, Southern↗
PubMed1989

Size reversion of African cassava mosaic virus coat protein gene deletion mutants during infection of Nicotiana benthamiana.

Mutants of African cassava mosaic virus containing extensive deletions across the coat protein gene that remove up to one-third of the genomic component have been constructed and shown to be infectious when mechanically inoculated onto Nicotiana benthamiana by leaf abrasion. Using N. tabacum protoplasts we demonstrate that mutant pCLV.CP delta 11, containing a 712 bp deletion, is competent for replication in its deleted form. However, systemic spread of pCLV. CP delta 11 and other deletion mutants is associated with reversion of DNA 1 to a size comparable to that of the native genomic component. This contrasts with the behaviour of coat protein mutants of the closely related geminivirus tomato golden mosaic virus which maintain their deletions during spread. Appraisal of the different inoculation procedures used to introduce the mutants into plants suggests the imposition of a stringent size requirement for localized cell-to-cell spread which is relaxed for long distance spread through the vascular system.

Base Sequence↗
PubMed1989

Corneal amyloidosis.

A 54-year-old man presented with a corneal lesion which on excision biopsy was found to be composed of amyloid. This material was presumably laid down in response to chronic irritation from the scarred lid and thus represents an example of secondary localised amyloidosis.

Amyloidosis↗