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Biomedical subjects

K E Ross

Publications and source records attributed to K E Ross.

8 recordsLinked to original sources
PubMed2001

A 48-h larval development toxicity test using the marine polychaete Galeolaria caespitosa Lamarck (Fam. Serpulidae).

Assessing the risk of effluents and other anthropogenic inputs to the receiving environment is ultimately best done on a site-specific basis, which often requires toxicity tests using organisms relevant to that environment. Additionally, the test species or life stage needs to be available for a reasonable portion of the year to allow temporal fluctuations to be assessed. A 48-h larval development toxicity test using the marine polychaete Galeolaria caespitosa was developed. This test was developed as G. caespitosa releases viable gametes year-round, and the test species is environmentally relevant to the marine system receiving the liquid effluent being evaluated. Toxicity tests were conducted using G. caespitosa from different locations and evaluating the gamete response to copper. All population responses were comparable, with EC50 values ranging from 16 to 40 microg/L copper (as CuCl2, x 2H2O). Toxicity tests were also conducted using G. caespitosa gametes with an effluent produced by a lead smelting operation. The response of the G. caespitosa test with this effluent was compared with three other test methods using two microalgal species, Isochrysis sp. and Nitzschia closterium, and gametes from the mussel Mytilus edulis. The G. caespitosa larval development toxicity test was the most sensitive test to the effluent, with EC50 values ranging from 1-23% effluent, while it ranked second in sensitivity to copper. This test could be applied to other common serpulids worldwide.

Animals↗
PubMed2000

Activating phosphorylation of the Saccharomyces cerevisiae cyclin-dependent kinase, cdc28p, precedes cyclin binding.

Eukaryotic cell cycle progression is controlled by a family of protein kinases known as cyclin-dependent kinases (Cdks). Two steps are essential for Cdk activation: binding of a cyclin and phosphorylation on a conserved threonine residue by the Cdk-activating kinase (CAK). We have studied the interplay between these regulatory mechanisms during the activation of the major Saccharomyces cerevisiae Cdk, Cdc28p. We found that the majority of Cdc28p was phosphorylated on its activating threonine (Thr-169) throughout the cell cycle. The extent of Thr-169 phosphorylation was similar for monomeric Cdc28p and Cdc28p bound to cyclin. By varying the order of the addition of cyclin and Cak1p, we determined that Cdc28p was activated most efficiently when it was phosphorylated before cyclin binding. Furthermore, we found that a Cdc28p(T169A) mutant, which cannot be phosphorylated, bound cyclin less well than wild-type Cdc28p in vivo. These results suggest that unphosphorylated Cdc28p may be unable to bind tightly to cyclin. We propose that Cdc28p is normally phosphorylated by Cak1p before it binds cyclin. This activation pathway contrasts with that in higher eukaryotes, in which cyclin binding appears to precede activating phosphorylation.

Antibody Specificity↗
PubMed1999

Dephosphorylation of cyclin-dependent kinases by type 2C protein phosphatases.

Activating phosphorylation of cyclin-dependent protein kinases (CDKs) is necessary for their kinase activity and cell cycle progression. This phosphorylation is carried out by the Cdk-activating kinase (CAK); in contrast, little is known about the corresponding protein phosphatase. We show that type 2C protein phosphatases (PP2Cs) are responsible for this dephosphorylation of Cdc28p, the major budding yeast CDK. Two yeast PP2Cs, Ptc2p and Ptc3p, display Cdc28p phosphatase activity in vitro and in vivo, and account for approximately 90% of Cdc28p phosphatase activity in yeast extracts. Overexpression of PTC2 or PTC3 results in synthetic lethality in strains temperature-sensitive for yeast CAK1, and disruptions of PTC2 and PTC3 suppress the growth defect of a cak1 mutant. Furthermore, PP2C-like enzymes are the predominant phosphatases toward human Cdk2 in HeLa cell extracts, indicating that the substrate specificity of PP2Cs toward CDKs is evolutionarily conserved.

CDC28 Protein Kinase, S cerevisiae↗
PubMed1999

An introductory therapeutic modality for restoring implants and natural teeth using conus crowns: a 5-year case report.

The advent of cylindric titanium implants and the prevalence of periodontal disease have necessitated a restoration that facilitates the performance of oral physiotherapy. The use of the conical crown as a metallic covering over natural teeth and implants--with a suprastructure that is retained through a specific degree of convergence without cement or screws--allows access for enhanced oral hygiene practices, while providing for esthetic and functional goals.

Crowns↗
PubMed1996

Immunolocalization of ion transport proteins in human autosomal dominant polycystic kidney epithelial cells.

The kidneys of patients with autosomal dominant polycystic kidney disease become massively enlarged due to the progressive expansion of myriad fluid-filled cysts. The epithelial cells that line the cyst walls are responsible for secreting the cyst fluid, but the mechanism through which this secretion occurs is not well established. Recent studies suggest that renal cyst epithelial cells actively secrete Cl across their apical membranes, which in turn drives the transepithelial movement of Na and water. The characteristics of this secretory flux suggest that it is dependent upon the participation of an apical cystic fibrosis transmembrane conductance regulator (CFTR)-like Cl channel and basolateral Na,K-ATPase. To test this hypothesis, we have immunolocalized the CFTR and Na,K-ATPase proteins in intact cysts and in cyst epithelial cells cultured in vitro on permeable filter supports. In both settings, cyst epithelial cells were found to possess Na,K-ATPase exclusively at their basolateral surfaces; apical labeling was not detected. The CFTR protein was present at the apical surfaces of cyst epithelial cells that had been stimulated to secrete through incubation in forskolin. CFTR was detected in intracellular structures in cultured cyst epithelial cells that had not received the forskolin treatment. These results demonstrate that the renal epithelial cells that line cysts in autosomal dominant polycystic kidney disease express transport systems with the appropriate polarity to mediate active Cl and fluid secretion.

Antibodies, Monoclonal↗
PubMed1980

The obese child: observations in the gymnasium of the Adelaide Children's Hospital.

This study reviews 107 obese children who were referred to the gymnasium of the Adelaide Children's Hospital. The majority had multiple handicaps. The treatment involved physical activities in small groups associated with counselling of parents (both individually and in groups) by social workers, dietitians, and doctors. A significant number of children were helped by the programme, showing not only a reduction in weight but also improvement in behaviour and attitude. Some children exhibited a hypoactive form of minimal cerebral dysfunction, which is postulated as a new risk factor in the development of childhood obesity. The importance of prevention is emphasized.

Adolescent↗
PubMed1978

The clumsy child: observations in cases referred to the gymnasium of the Adelaide Children's Hospital over a three-year period.

Group treatment of clumsy children is one part of a multidisciplinary management programme which is provided at The Adelaide Children's Hospital for children who have multiple handicaps. This study reviews 176 children who were referred for treatment. Clumsiness was the most common reason for referral. Not all children benefited from group treatment, and those who had significant degrees of mental retardation, or mild spasticity worsening on effort, needed individual handling. Movement training aims mainly to reduce physical clumsiness, and it is hoped that certain nonspecific benefits may result. The greatest improvement occurred in the ability to mix with others. Group counselling of parents, with a social worker as leader, is considered to have played an essential part in the management of these children's problems.

Adolescent↗