Decrease in skin collagen glycation with improved glycemic control in patients with insulin-dependent diabetes mellitus.

Glycation, oxidation, and nonenzymatic browning of protein have all been implicated in the development of diabetic complications. The initial product of glycation of protein, fructoselysine (FL), undergoes further reactions, yielding a complex mixture of browning products, including the fluorescent lysine-arginine cross-link, pentosidine. Alternatively, FL may be cleaved oxidatively to form N(epsilon)-(carboxymethyl)lysine (CML), while glycated hydroxylysine, an amino-acid unique to collagen, may yield N(epsilon)-(carboxymethyl)hydroxylysine (CMhL). We have measured FL, pentosidine, fluorescence (excitation = 328 nm, emission = 378 nm), CML, and CMhL in insoluble skin collagen from 14 insulin-dependent diabetic patients before and after a 4-mo period of intensive therapy to improve glycemic control. Mean home blood glucose fell from 8.7 +/- 2.5 (mean +/- 1 SD) to 6.8 +/- 1.4 mM (P less than 0.005), and mean glycated hemoglobin (HbA1) from 11.6 +/- 2.3% to 8.3 +/- 1.1% (P less than 0.001). These changes were accompanied by a significant decrease in glycation of skin collagen, from 13.2 +/- 4.3 to 10.6 +/- 2.3 mmol FL/mol lysine (P less than 0.002). However, levels of browning and oxidation products (pentosidine, CML, and CMhL) and fluorescence were unchanged. These results show that the glycation of long-lived proteins can be decreased by improved glycemic control, but suggest that once cumulative damage to collagen by browning and oxidation reactions has occurred, it may not be readily reversed. Thus, in diabetic patients, institution and maintenance of good glycemic control at any time could potentially limit the extent of subsequent long-term damage to proteins by glycation and oxidation reactions.     

Peer coaching: the next step in staff development

A common problem in continuing nursing education and staff development is the transfer of learning to clinical practice. Peer coaching offers a solution to this problem. Initiated by educators, peer coaching has been researched in educational settings and found to be effective in facilitating the transfer of newly acquired knowledge and skill into classroom teaching strategies. This article describes the background, components, process, characteristics, and benefits of peer coaching. A specific example of using peer coaching to teach clinical breast examination skills is used to illustrate the application of peer coaching to the staff development of healthcare professionals. Peer coaching is the next step in nursing staff development.     

Further observations upon gastric function in rats after prolonged administration of an anticholinergic drug,propantheline bromide

Gastric function was assessed in Wistar rats which received propantheline bromide by daily injection for 20 weeks. The results were compared with those from two control groups, one of which was injected daily with saline for 20 weeks. Gastric acid secretion, as measured by test meal and after ligation of the pylorus, was similar in all three groups. Acid secretion, as measured by test meal with pentagastrin 100 µg/kg body weight, gastric emptying, and fundic mucosal volume, expressed in terms of body weight, were all significantly increased in rats given propantheline. Only those measurements of acid secretion obtained by test meal with pentagastrin showed a significant correlation with fundic mucosal volume. Hence, since this method provides the most accurate indication of secretory capacity, it is concluded that the prolonged parenteral administration of propantheline may lead to an increase in parietal cell mass and its correlate, maximal secretory capacity. The mechanism by which these changes are produced is obscure.The author is grateful to Mr. Howard Ireson for his expert technical assistance, and to Mr. Ralph Marshall, Department of Medical Illustration, Cardiff Royal Infirmary, for the photography employed.Propantheline bromide (Pro-Banthine) was generously supplied by G. D. Searle and Co., Ltd.     

High energy phosphate stores and lactate levels in different layers of the canine left ventricle during reactive hyperemia.

To study postischemic recovery of myocardial energy metabolism in relation to the reactive hyperemic response, the tissue levels of creatine phosphate (CP), adenosine triphosphate (ATP), and lactate were estimated in the outer, middle, and inner layers of the left ventricle before, during, and at several times after a 20-second bilateral coronary arterial occlusion in the open-chest dog. The reactive hyperemic response was characterized by monitoring blood flow in the cannulated coronary sinus in a separate group of dogs. Substantial changes in myocardial CP and lactate, but not ATP, were produced by the occlusion and reciprocal transmural gradients in CP and lactate occurred such that CP was lowest and lactate was highest in the inner layer. Recovery of high energy phosphate stores (CP + ATP) occurred long before blood flow returned to the preocclusion level, this being achieved in two of the three layers after completion of only 29% of the reactive hyperemic response when the blood flow debt repayment was 151%. Lactate returned to control levels during the response, but recovery times in the different layers were delayed compared to those for the high energy phosphate stores. A transmural lactate gradient was maintained as the regional levels declined, and recovery times were different for each of the three layers, being longest in the inner layer. The results suggest that during the reactive hyperemic response (1) kinetically different processes are involved in the repletion of energy stores and the removal of anaerobically produced metabolites, and (2) metabolic vasodilation of coronary vessels probably is more pronounced and sustained longer in the inner than in the outer ventricular layer.     

Regression of significant tricuspid regurgitation after mitral balloon valvotomy for severe mitral stenosis

Background

Significant tricuspid regurgitation (TR) is occasionally associated with severe mitral stenosis and has an adverse impact on morbidity and mortality in patients undergoing mitral valve surgery. However, the effect of successful mitral balloon valvotomy (MBV) on significant TR is not fully elucidated. The aim of this study was to investigate TR after MBV in patients with severe mitral stenosis.

Methods

We analyzed the data of 53 patients with significant TR (grade ≥2, on a 1 to 3 scale) from the mitral balloon valvotomy database at our hospital. Patients were evaluated by Doppler echocardiography before valvotomy and at follow-up 1 to 13 years after MBV. Patients were divided into group A (27 patients), in whom TR regressed by ≥1 scale, and group B (26 patients), in whom TR did not regress.

Results

The Doppler-determined pulmonary artery systolic pressure was initially higher and decreased at follow-up more in group A (from 70.7 ± 23.8 to 36.5 ± 8.3 mm Hg; P < .0001) than in group B (from 48.7 ± 17.8 to 41.6 ± 13.1 mm Hg; P = NS). Compared with patients in group B, patients in group A were younger (25 ±10 vs 35 ± 11 years; P < .005), had higher prevalence of functional TR (85% vs 8%; P < .0001), and had lower incidence of atrial fibrillation (7% vs 38%; P < .005). Significant decrease in right ventricular end-diastolic dimension after MBV was noted in group A but not in group B. The mitral valve area at late follow-up was larger in group A than in group B (1.8 ± 0.3 vs 1.6 ± 0.3 cm²; P < .05).

Conclusions

Regression of significant TR after successful MBV in patients with severe mitral stenosis was observed in patients who had severe pulmonary hypertension. This improvement in TR occurred even in the presence of organic tricuspid valve disease.     

The influence of type 2 diabetes on fibrin structure and function

Aims/hypothesis The precise mechanisms underlying the increased risk of cardiovascular disease (CVD) in type 2 diabetes are unclear. Fibrin clot structure has been related to CVD risk in the general population. We therefore assessed this in type 2 diabetic patients as a potential mechanism whereby diabetes influences CVD risk.Methods Fibrin clots were formed from fibrinogen purified from 150 subjects with type 2 diabetes and varying degrees of glycaemic control (assessed by HbA₁c), and from 50 matched control subjects. Clot structure was assessed by turbidity, permeation and confocal microscopy. The specific effect of glucose itself was assessed by analysing the structure of clots formed from purified fibrinogen in the presence of increasing concentrations of the sugar.Results Clots formed by fibrinogen purified from type 2 diabetic subjects had a denser, less porous structure than those from control subjects. The structural changes found were related to the individuals glycaemic control; HbA₁c correlated negatively with permeation coefficient (K_s) values (indicates clot pore size) (r=–0.57, p<0.0001) and positively with maximum absorbance (indicator of fibre size) (r=0.33, p<0.0001), branch point number (r=0.78, p<0.0001) and fibre density (r=0.63, p<0.0001). The ambient glucose level influenced clot structure; hypo- (<5 mmol) and hyperglycaemia (10 mmol/l) were both associated with a reduction in K_s values and maximum absorbance, and with increased fibre density and branch point number within clots.Conclusions/interpretation The structural differences found to occur in type 2 diabetes and in association with hypo- and hyperglycaemia may confer increased resistance to fibrinolysis, and in consequence contribute to the increase in CVD risk in diabetic patients.     

A candidate vaccine for hepatitis B containing the complete viral surface protein

The entire surface protein of hepatitis B virus serotype ayw containing the preS (preS1+preS2) and S domains has been expressed in the yeast Saccharomyces cerevisiae. Yeast containing a recombinant plasmid utilizing a constitutive promoter did not express this gene successfully due to the toxicity of the protein. A plasmid using a regulatable promoter directed expression which initiated late in the exponential phase of growth and resulted in the accumulation of high intracellular levels of the complete surface protein. The purified polypeptide aggregates into a form which, although not comprised of typical 20 nm particles, displays antigenic determinants encoded by the preS1, preS2 and S domains. Immunization of rabbits elicited the formation of antibodies directed against all three domains. This candidate vaccine will be useful for studying the contributions to viral immunity of the host response to the preS1 and preS2 domains.     

Is this bone infected or not? Differentiating neuro-osteoarthropathy from osteomyelitis in the diabetic foot

Osteomyelitis (bone infection) and neuro-osteoarthropathy (Charcot arthropathy) are limb-threatening complications of diabetic neuropathy with very different therapies. Distinguishing between them may be difficult, but it is important. In Charcot arthropathy, noninfectious soft tissue inflammation accompanies rapidly progressive destruction, first of joints, then of bone. This occurs in a well-vascularized and severely neuropathic, but nonulcerated, foot. In osteomyelitis, chronic soft tissue ulceration precedes infection of bone, which may be physically exposed. Magnetic resonance imaging and bone biopsy are the preferred diagnostic tests, provided adequate technical and interpretive skills are available.     

Functional profiling of a human cytomegalovirus genome

Human cytomegalovirus (HCMV), a ubiquitous herpesvirus, causes a lifelong subclinical infection in healthy adults but leads to significant morbidity and mortality in neonates and immunocompromised individuals. Its ability to grow in different cell types is responsible for HCMV-associated diseases, including mental retardation and retinitis, and vascular disorders. To globally assess viral gene function for replication in cells, we determined the genomic sequence of a bacterial artificial chromosome (BAC)-based clone of HCMV Towne strain and used this information to delete each of its 162 unique ORFs and generate a collection of viral mutants. The growth of these mutants in different cultured cells was examined to systematically investigate the necessity of each ORF for replication. Our results showed that 45 ORFs are essential for viral replication in fibroblasts and 117 are nonessential. Some genes were found to be required for viral replication in retinal pigment epithelial cells and microvascular endothelial cells, but not in fibroblasts, indicating their role as tropism factors. Interestingly, several viral mutants grew 10- to 500-fold better than the parental strain in different cell types, suggesting that the deleted ORFs encode replication temperance or repressing functions. Thus, HCMV encodes supportive and suppressive growth regulators for optimizing its replication in human fibroblasts, epithelial, and endothelial cells. Suppression of viral replication by virus-encoded temperance factors represents a novel mechanism for regulating the growth of an animal virus, and may contribute to HCMV's optimal infection of different tissues and successful proliferation among the human population.     

Altered immunoreactivity of thyroglobulin in thyroid disease

We prepared 3 samples of 19S thyroglobulin (Tg), 1 from a patient with Graves' disease, another from a patient with nontoxic goiter, and the third from a pool of Tg from normal subjects, and used each Tg preparation to produce a polyvalent antiserum in rabbits. The 3 antisera were similar to each other in their reactivity with thyroid Tg samples from 25 patients with various thyroid disorders and from 10 normal subjects. However, the immunoreactivity of the 35 individual Tg samples varied considerably. Decreased reactivity was associated with proteolysis during Tg preparation, iodination in vitro with 20 or more atoms of iodine/molecule Tg, the 27S species of Tg, Tg from 3 patients with thyroid cancer, and Tg from several patients with Graves' disease. The antiserum to Graves' Tg contained some antibodies that did not bind normal Tg on an affinity column, and these antibodies reacted more with Tg from patients with Graves' disease than with Tg from normal subjects or patients with nontoxic goiters. Thus, Tg from patients with Graves' disease may contain antigenic sites that are not present or exposed in Tgs from other subjects. We conclude that thyroid Tgs from patients with Graves' disease and from those with thyroid cancer may be different in structure from the Tgs of normal subjects. This conclusion is important to an understanding of Tg structure in thyroid disease and to the use of thyroid Tg for preparation of antisera and standards for measuring serum Tg concentrations.