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Biomedical subjects

S Rhodes

Publications and source records attributed to S Rhodes.

30 records · Page 2Linked to original sources
PubMed1994

Increased collagen synthesis and decreased collagen degradation in right ventricular hypertrophy induced by pressure overload.

OBJECTIVE: The aim was to examine the effect of pressure overload in rabbits on ventricular collagen metabolism and procollagen gene expression. METHODS: Right ventricular hypertrophy was induced by banding the pulmonary artery such that the diameter of the vessel was reduced by 50%, and animals killed in groups after two and 14 days. Collagen synthesis and degradation of newly synthesised collagen were assessed following a single intravenous injection of 3H-proline with a flooding dose of non-radioactive proline, given 3 h before the animals were killed. Northern and slot blot analyses were performed to measure procollagen alpha 1(I) mRNA. RESULTS: The fractional collagen synthesis rate increased sixfold in the right ventricle only 2 d after pulmonary artery banding (p < 0.001), then fell to just over double the control value by 14 d (p < 0.05 from control). The proportion of newly synthesised collagen degraded decreased from 50.7(SD 12.8)% to 26.8(15.8)% in 2 d (p < 0.05) and remained at this level. The procollagen alpha 1(I) mRNA level increased by more than fourfold in the right ventricle 2 d after the onset of pressure overload, and was less than three times control levels at 14 d. CONCLUSIONS: The development of right ventricular hypertrophy is associated with a rapid increase in collagen production, with regulation at multiple sites in the biosynthetic pathway. This regulation occurs at both transcriptional and post translational levels.

Animals↗
PubMed1993

Injuries to workers in a swine confinement facility.

Animal confinement facilities are used to increase efficiency by capitalizing from economy of scale. Investigations of the major health effects of these facilities usually focus on the respiratory symptoms of their workers. We hypothesized that injury may also be a significant health issue for workers. We studied the incidence and patterns of injury during a 3-year period in a large, midwestern swine confinement facility.

Accidents, Occupational↗
PubMed1992

Ophthalmic day case surgery: the role of a dedicated day case unit.

A study was undertaken to examine all cases admitted to a new ophthalmic surgical day case unit during its first six months of operation. This paper describes the experience gained in establishing the unit, including operational management, and outlines the factors contributing to the unit's success. A quarter of the patients usually admitted as inpatients have been treated in the day unit, and day case surgery rarely results in unplanned inpatient admission, or subsequent readmission. Provided strict admission criteria are followed, the results show that this facility can accommodate a wide range of common ophthalmological procedures, and that general anaesthesia is compatible with day case management.

Ambulatory Surgical Procedures↗
PubMed1992

Amniotic fluid and plasma glycine/valine ratios in substrate deprived growth retarded fetal rats.

Characteristic profiles of the free amino acid concentration in umbilical cord blood of growth retarded newborns have been observed. We hypothesized that the amniotic fluid of growth retarded fetal rats would show an increase in the ratio between glycine and valine which would parallel the pattern observed in the cord blood of growth retarded neonates, thus providing an index for the antepartum identification of the substrate deprived growth retarded fetus. Six test and 6 control dams were tested. Four fetuses per dam, matched for uterine location were examined. Test animals were fasted for 72 hours. Sampling was performed on day 21 under anaesthesia. Fetal size was significantly reduced (P < 0.0001) in the test group. [T = 2.68 gs. +/- 0.28 vs. C = 3.67 gs. +/- 0.25]. Fetal plasma concentrations of glycine showed an increase in test animals (P < 0.01) while valine showed a significant reduction (P < 0.0001). Glycine (pm/microliters) T = 308 +/- 64 vs. C = 269 +/- 47, valine (pm/microliters) T = 424 +/- 79 vs. C = 671 +/- 218]. Amniotic fluid concentrations for both glycine and valine were significantly decreased (P < 0.0001) in test animals. [Glycine (pm/microliters) T = 710 +/- 124 vs. C = 931 +/- 178; valine (pm/microliters) T = 845 +/- 169 vs. C = 1,339 +/- 234]. The glycine/valine ratio was significantly increased (P < 0.01) in both fetal plasma and amniotic fluid in test animals [Plasma T = 0.74 +/- 0.18 vs. C = 0.43 +/- 0.13. Amniotic fluid T = 0.85 +/- 0.08 vs. C = 0.69 +/- 0.09]. Consistent with our hypothesis, the amniotic fluid concentrations generally parallel the observations made in the plasma. This finding could enhance the antepartum identification of the substrate deprived growth retarded fetus.

Amniotic Fluid↗
PubMed1991

Use of the Glu-Glu-Phe C-terminal epitope for rapid purification of the catalytic domain of normal and mutant ras GTPase-activating proteins.

The C-terminal catalytic domain (residues 704-1047) of the human ras GTPase-activating protein (GAP) has been engineered so as to incorporate the tripeptide, Glu-Glu-Phe, at its C terminus. This motif is recognized by the commercially available YL1/2 monoclonal antibody to alpha-tubulin and has previously been used for the immunoaffinity purification of HIV enzymes engineered to contain this epitope (Stammers, D. K., Tisdale, M., Court, S., Parmar, V., Bradley, C., and Ross, C. K. (1991) FEBS Lett. 283, 298-302). The engineered GAP catalytic domain (GAP-344) was obtained in high yield and purity from Escherichia coli extracts by means of a single affinity column of immobilized YL1/2, eluted under mild conditions with the dipeptide, Asp-Phe. The protein had similar activity to that previously described for full-length GAP, suggesting that the addition of the epitope did not grossly affect the activity. R903K and L902I mutants of GAP-344 were constructed, and the immunoaffinity purification procedure allowed their rapid characterization. The R903K mutant had less than 3% the activity of the normal protein, whereas the L902I substitution had less than 0.5% of normal activity, suggesting an important role for Leu-902 and Arg-903, residues absolutely conserved among GAP-related proteins. This work exemplifies the general utility of the C-terminal Glu-Glu-Phe motif for the rapid purification of proteins whose function is not altered by C-terminal modification.

Amino Acid Sequence↗
PubMed1991

Characterization of recombinant human Kirsten-ras (4B) p21 produced at high levels in Escherichia coli and insect baculovirus expression systems.

Kirsten-ras is the oncogene most frequently activated in human tumors. Studies of its biological function have been limited by the nonavailability of significant amounts of the major protein product, Kirsten-ras (4B) p21. When expressed in Escherichia coli K12, the recombinant protein was rapidly cleaved upon cell lysis in the lysine-rich C terminus region, probably by the ompT protease. However, soluble full-length protein was obtained when the Kirsten-ras gene was expressed in an E. coli strain lacking the ompT gene, and also in a baculovirus/insect cell expression system. Additionally, the baculovirus/insect cell system produced about half of the Kirsten-ras protein in a membrane-associated form, which was post-translationally modified by polyisoprenylation and carboxyl-methylation. A C-terminally truncated form (residues 1-166) was also expressed at high levels in E. coli for x-ray crystallographic studies. The kinetics of GDP release and of GTP hydrolysis of the purified proteins are similar to those of the corresponding Harvey-ras proteins, though there are small differences in the relative affinities for GDP and GTP. Biological activity of full-length Kirsten Val-12 p21 was demonstrated by microinjection into Swiss 3T3 cells, resulting in morphological transformation, with a lower potency than that of Harvey Val-12 protein.

Animals↗
PubMed1991

Daycase cataract surgery.

The increasing demand for cataract surgery, combined with limited resources, has created renewed interest in daycase admission. We have audited the results of all daycase and inpatient cataract surgery in a large unit over a six-month period to determine the factors influencing daycase admission and surgical outcome; 34% of cataract patients were admitted as daycases in the study period. Neither distance travelled by the patient nor age appear to influence daycase admission. However, the differing policies of the individual consultant surgeons resulted in a wide variation in the number of operations performed on a daycase basis by each firm. The rate of preoperative complications was unaffected by daycase admission, by the grade of surgeon operating, or by the type of anaesthetic employed. Only 2.1% of daycase admissions resulted in unplanned inpatient admission on the day of surgery, with another 2.1% being readmitted within six months of surgery. Late cancellation of surgery was much lower for daycases (0.4%) than for inpatients (5.1%).

Aged↗
PubMed1989

Expression and characterization of the Ha-ras p21 protein produced at high levels in the insect/baculovirus system.

Normal and mutated cDNAs of Ha-ras have each been cloned into a standard (pAc373) and a novel (p36C) baculovirus transfer vector and introduced via homologous recombination into the genome of Autographa californica nuclear polyhedrosis virus immediately downstream of the polyhedrin promoter. Spodoptera frugiperda cells infected with recombinant virus containing the normal Ha-ras gene express very high levels of ras p21 protein (approximately 20% of total cell protein), whereas the mutant protein was expressed at considerably lower levels. Molecular analysis showed that this was most likely due to a post-transcriptional event. The expression vector p36C produced considerably higher levels of recombinant p21 compared to the more commonly used pAc373. The majority of the normal ras p21 protein is soluble, cytoplasmic, and appears to be nonacylated. However, about 10% of the p21 associates with the membrane fraction of infected cells and migrates as a slightly faster band on gels. Furthermore, this band is sensitive to hydroxylamine treatment and shows specific incorporation of [3H]palmitate, strongly suggesting that it is the palmitoylated form of p21, which is the biologically active form of the protein. Both the soluble and membrane-associated p21 have been purified to homogeneity under nondenaturing conditions, the latter in the presence of detergents. The isolation of native palmitoylated p21 has not been reported previously. The difference in hydrophobicity between these two proteins has been demonstrated by Triton X-114 partitioning. The use of the insect/baculovirus expression system to express relatively high levels (20 mg/liter) of palmitoylated p21 should aid experiments to resolve the structural and functional properties of this molecule.

Amino Acid Sequence↗
PubMed1988

Purification and characterization of [acyl-carrier-protein] acetyltransferase from Escherichia coli.

A multi-step procedure has been developed for the purification of [acyl-carrier-protein] acetyltransferase from Escherichia coli, which allows the production of small amounts of homogeneous enzyme. The subunit Mr was estimated to be 29,000 and the native Mr was estimated to be 61,000, suggesting a homodimeric structure. The catalytic properties of the enzyme are consistent with a Bi Bi Ping Pong mechanism and the existence of an acetyl-enzyme intermediate in the catalytic cycle. The enzyme was inhibited by N-ethylmaleimide and more slowly by iodoacetamide in reactions protected by the substrate, acetyl-CoA. However, the enzyme was apparently only weakly inhibited by the thiol-specific reagent methyl methanethiosulphonate. The nature of the acetyl-enzyme intermediate is discussed in relationship to that found in other similar enzymes from E. coli, yeast and vertebrates.

Acetyltransferases↗