Biomedical subjects

R Clausen

Publications and source records attributed to R Clausen.

12 recordsLinked to original sources

PubMed2002

The (ProB27, ThrB28) human insulin analogue is more potent and more rapidly absorbed from subcutis than human insulin.

OBJECTIVE: To test the physiological properties of human insulin in which the amino acids Thr (B27) and Pro (B28) are interchanged (PT insulin). This was hypothesised to prevent dimerisation and accelerate the absorption from s.c. tissue without altering the affinity for the insulin receptor. DESIGN: PT insulin was expressed in Pichia pastoris and processed in vitro. The purified compound was used for physiological investigations. METHODS: Receptor binding activity to insulin and IGF receptors was evaluated in a competition assay using iodinated PT insulin and recombinant receptors while growth induction properties were evaluated by thymidine incorporation. Absorption kinetics from pig subcutis was investigated by measuring the disappearance of iodinated PT insulin. The potency was evaluated by measuring the blood glucose lowering activity in mice. RESULTS: The absorption of PT insulin was accelerated compared with human insulin, although still slower than Asp (B28) insulin. Human and PT insulin had similar affinities for the human insulin receptor (K(d)=3.6 x 10(-12) vs 5.2 x 10(-12) mol/l) while the affinity for the IGF receptor was four times higher for PT insulin than for human insulin (K(d)=3.4 x 10(-8) vs 1.3 x 10(-7) mol/l). This resulted in a slightly higher DNA synthesis when assayed in intermediary insulin concentrations. The blood glucose lowering effect in mice exceeded the effect of human insulin (integral 0-60 min: 61.4+/-7 vs 30+/-4, n=6, P=0.046). CONCLUSIONS: PT insulin is absorbed faster and is more potent than human insulin. Although PT insulin stimulates growth more than human insulin, this will not prevent its use in the clinic, but the main interest will probably focus on investigations to clarify the paradox of full biological activity in connection with the recently described lack of structure in the B-chain.

Absorption↗

PubMed2001

Flexibility and bioactivity of insulin: an NMR investigation of the solution structure and folding of an unusually flexible human insulin mutant with increased biological activity.

The structure and folding of a novel human insulin mutant, [Thr(B27) --> Pro, Pro(B28) --> Thr]insulin (PT insulin), in aqueous solution and in mixtures of water and 2,2,2-trifluoroethanol (TFE) have been studied by NMR spectroscopy. It was found that PT insulin has a highly flexible structure in pure water and is present in at least two different conformations, although with an overall tertiary structure similar to that of native insulin. Furthermore, the native helical structures are poorly defined. Surprisingly, the mutant has a biological activity about 50% higher than native insulin. In contrast, in TFE/water solution the mutant reveals a propensity of forming a well-defined structure at the secondary structure level, similar to monomeric native insulin. Thus, as shown by a detailed determination of the structure from 208 distance restraints and 52 torsion angle restraints by distance geometry, simulated annealing, and restrained energy minimization, the native insulin helices (A2-A7, A13-A19, and B10-B19) as well as the beta-turn (B20-B23) are formed in 35% TFE. However, the amount of tertiary structure is decreased significantly in TFE/water solution. The obtained results suggest that only an overall tertiary fold, as observed for PT insulin in pure water, is necessary for expressing the biological activity of insulin, as long as the molecule is flexible and retains the propensity to form the secondary structure required for its receptor binding. In contrast, a compact secondary structure, as found for native insulin in solution, is unnecessary for the biological activity. A model for the receptor binding of insulin is suggested that relates the increased bioactivity to the enhanced flexibility of the mutant.

Amino Acid Sequence↗

PubMed2001

Measuring and improving patients' and families' perceptions of care in a system of pediatric hospitals.

BACKGROUND: Shriners Hospitals for Children (SHC) is a network of 22 pediatric specialty hospitals that provide medical care free of charge to children up to 18 years of age and that serve as referral centers for children with complex orthopedic and burn problems. In 1998 the SHC system began using The Picker Institute's Patient and Family Perception of Care inpatient survey throughout its hospitals. SYSTEMWIDE IMPLEMENTATION: A broad-based implementation plan was developed to promote acceptance of the perception of care topic and provide education on performance improvement. In 1999 a work group was formed to prioritize areas for improvement, survey benchmark hospitals, and identify best practices in benchmark hospitals. This work group first focused on the dimensions of Partnership Between Families and Clinicians and Information and Education to the Child. In May 1999 the work group began the task of identifying best practices in these two priority dimensions from the SHC benchmark hospitals. Surveys were submitted to those hospitals, asking what they perceived as being the reasons they scored well in those areas. The results of these surveys were used to identify key practices in these benchmark hospitals that are of significant importance in patient and family perceptions of quality care. NEXT STEPS: The challenge is to facilitate cross-facility interactions to understand and adopt best practices. Focus groups will be conducted to further delineate the dimensions with higher problem scores. The SHC system plans to expand the patient surveys to outpatients, to allow for the evaluation of the full complement of hospital patients.

Burn Units↗

PubMed1991

An immunochemical quantitative analysis of the protein pattern in physiologic and pathologic vitreous.

Biochemical changes in the vitreous in different vitreoretinal disorders have not yet been thoroughly studied. Using enzyme-linked immunosorbent analysis (ELISA), we established mean values and 95% confidence intervals for six proteins of physiologic human vitreous: albumin (293 +/- 18 mg/l), transferrin (73.7 +/- 6.6 mg/l), immunoglobulin G (IgG), (33.5 +/- 3 mg/l), alpha 1-antitrypsin (14.1 +/- 2.9 mg/l), alpha 1-acid glycoprotein (4 +/- 0.7 mg/l), and lactoferrin (less than 50 micrograms/l). These six proteins were also determined in vitreous aspirates from patients with idiopathic proliferative vitreoretinopathy (n = 10), traumatic proliferative vitreoretinopathy (n = 10), and proliferative diabetic retinopathy (n = 15). The pattern of protein levels varied widely within each of the disorders. An analysis of absolute protein levels showed significant differences in total protein and alpha 1-antitrypsin levels between controls and pathologic vitreous samples. We observed differences in transferrin between controls and proliferative diabetic retinopathy (PDR), and differences in alpha 1-acid glycoprotein between controls and both types of proliferative vitreoretinopathy (PVR). The single disorders themselves could not be differentiated by any of the proteins. When the relative contribution of single proteins to total vitreal protein was compared, albumin was lower in all three disorders than in controls. Transferrin was lower in traumatic PVR than in controls, in PDR, or in idiopathic PVR. Our results indicate that the three vitreoretinal disorders studied are characterized by a breakdown of blood-ocular barriers.

Albumins↗

PubMed1990

Immunoglobulin G, complement factor C3 and lymphocytes in proliferative intraocular disorders.

This study examines a possible immunological contribution to the development of proliferative intraocular disorders (PID) with traction retinal detachment. We analysed 24 periretinal membranes and 35 vitreous aspirates from patients with idiopathic proliferative vitreoretinopathy (PVR), traumatic PVR, and proliferative diabetic retinopathy (PDR). Lymphocytes and complement factor C3 deposits could not be detected in any of the membrane specimens. IgG was present in all but one of the PVR membranes but in less than half of the PDR specimens and there to a lesser extent. The IgG immunoreactivity was not collocalized with macrophages but instead located to the extracellular matrix. The intravitreal levels of IgG (ELISA) and protein were elevated in PID but the range of these biochemical changes was so wide that there were no significant differences of the IgG levels between the single types of PID. Using electrophoresis and Western blotting, C3 was detected in normal and pathologic vitreous but smaller C3 fragments indicative of C3 breakdown were only found in PID.

Blotting, Western↗

PubMed1990

Iron-binding proteins in the human vitreous: lactoferrin and transferrin in health and in proliferative intraocular disorders.

Transferrin, recently detected in preretinal membranes, may contribute to cell proliferation by iron donation for mitosis. We have investigated whether lactoferrin, the second iron-binding protein of the human vitreous, could play a similar role in proliferative intraocular disorders (PID). Using immunochemistry, however, we could not label lactoferrin in surgically obtained membrane specimens from patients with idiopathic proliferative vitreoretinopathy (PVR), traumatic PVR, and proliferative diabetic retinopathy (n = 15). The amounts of both proteins in normal human vitreous, as measured by enzyme-linked immunosorbent assay, were 73.7 +/- 6.6 mg/l for transferrin but below 50 micrograms/l for lactoferrin. Transferrin was also determined in 35 vitreous aspirates from patients with PID. The highest levels were found in idiopathic PVR (846 +/- 256 mg/l), followed by proliferative diabetic retinopathy (405 +/- 121) and traumatic PVR (197 +/- 83 mg/l). A statistically significant difference between the three types of PID and physiologic vitreous, respectively, was not observed. The total vitreal protein, however, was significantly elevated in all three groups of PID.

Cell Membrane↗

PubMed1990

[Quantitative determination of 5 vitreal proteins in the normal vitreous body and proliferative retinal diseases].

While progress in vitreoretinal surgery has been very rapid in recent years, our understanding of the biochemistry of normal and pathological vitreous is still limited. Therefore, we developed non-competitive ELISA techniques for the quantification of five vitreal proteins which, together with vitreal collagen (300 mg/l), account for more than 70% of the total vitreal protein. Physiological levels of the individual proteins were determined as follows: albumin 293 +/- 18 mg/l, IgG 34 +/- 3 mg/l, transferrin 74 +/- 7 mg/l, alpha 1-antitrypsin 14 +/- 3 mg/l, alpha 1-acid glycoprotein 4 +/- 0.7 mg/l. Mean values for these proteins were also obtained in vitreous aspirates from patients with traumatic proliferative vitreoretinopathy (PVR) (n = 10), idiopathic PVR (n = 10) and proliferative diabetic retinopathy (PDR) (n = 15). Significant differences were found for total vitreal protein and alpha 1-antitrypsin between the control groups and the three vitreoretinal disorders, between the PDR and control group for transferrin, and between both types of PVR and controls for alpha 1-acid glycoprotein. Given the high plasma levels of the individual proteins quantified in this study and the uniform rise in total vitreal protein, a disturbancee of blood-retinal and blood-vitreal barriers seems to be an essential features of proliferative intraocular disorders. No disease-specific change in the protein pattern could be detected for the three disorders examined.

Blood Proteins↗

PubMed1984