Human enamel dissolution in citric acid as a function of pH in the range 2.30< or =pH< or =6.30--a nanoindentation study

The objective of this study was to investigate the dissolution of human enamel in citric acid solutions over a wide range of pH. The in vitro conditions are considered to be relevant to soft drink-induced enamel erosion. Nanoindentation was used to investigate changes in the nanomechanical properties of polished enamel surfaces after exposure to citric acid solutions. Solutions used had 38.1 mmol l-1 citric acid and pH greater than 2.3 but less than 6.3 (2.30 < or = pH < or = 6.30). Samples were exposed to rapidly stirred, constant composition solutions for 120 s. Statistically significant changes in enamel hardness and reduced elastic modulus were observed after exposure to all solutions. There was an approximately linear dependence of enamel hardness on solution pH for 2.90 < or = pH < or = 6.30. Below pH 2.90, enamel is thought to have reached the lowest possible hardness value. The reduction in enamel dissolution caused by an increase in pH of a soft drink is likely to be small. Product modification to reduce the erosive potential of drinks may require additional methods such as addition of calcium salts.     

Sustained CD4+ T cell response after virologic failure of protease inhibitor-based regimens in patients with human immunodeficiency virus infection

The relationship between plasma human immunodeficiency virus (HIV) RNA levels and peripheral CD4+ T cell counts was examined in 380 HIV-infected adults receiving long-term protease inhibitor therapy. Patients experiencing virologic failure (persistent HIV RNA >500 copies RNA/mL) generally had CD4+ T cell counts that remained greater than pretherapy baseline levels, at least through 96 weeks of follow-up. The CD4+ T cell response was directly and independently related to degree of viral suppression below the pretreatment baseline. For any given HIV RNA level measured 12 weeks after virologic failure, subsequent CD4+ T cell decline was slower in patients receiving a protease inhibitor-based regimen than in a historical control group of untreated patients. These observations suggest that transient or partial declines in plasma HIV RNA levels can have sustained effects on CD4+ T cell levels.     

Chemiluminescence by polymorphonuclear leukocytes from patients with active bacterial infection

Polymorphonuclear leukocytes of 18 patients during 19 episodes of active bacterial infection produced increased chemiluminescence (mean +/- standard error [SE], 56.3 +/- 4.4 X 10(3) cpm) when the production was compared to that of 29 uninfected controls (35.3 +/- 2.4 X 10(3) cpm; P less than 0.01). Chemiluminescence production remained increased with persistent infection but fell to the levels of controls with appropriate therapy. Phagocytic uptake as determined with radiolabeled bacteria was increased, and chemotactic responsiveness was markedly enhanced in the patients (mean index +/- SE, 260 +/- 51) when these responses were compared with those of controls (77 +/- 18). Chemiluminescence and chemotactic activity correlated in the patients with bacterial infection (r = 0.76), but one function did not appear to depend upon the intactness of the other. The ratio of cyclic guanosine 3',5'-phosphate to cyclic adenosine 3',5'-hosphate in the polymorphonuclear leukocytes of patients with infections (mean +/- SE, 0.102 +/- 0.0008) was also significantly higher than in controls (0.067 +/- 0.007). These data indicate that the polymorphonuclear leukocytes of the majority of patients with active bacterial infection are in an activated state both functionally and metabolically.     

Occupational lead poisoning in the United States: clinical and biochemical findings related to blood lead levels

Dose-response relationships between blood lead levels and toxic effects have been evaluated in 160 lead workers in two smelters and a chemicals plant. Blood lead levels ranged from 0.77 to 13.51 mumol/litre (16-280 microgram/dl). Clinical evidence of toxic exposure was found in 70 workers (44%), including colic in 33, wrist or ankle extensor muscle weakness in 12, anaemia (Hgb less than 8.69 mumol/litre (Hb/4) or 14.0 gm/dl) in 27, elevated blood urea nitrogen (greater than or equal to 7.14 mmol/litre or 20 mg/dl) in 28, and possible encephalopathy in two. No toxicity was detected at blood lead levels below 1.93 mumol/litre (40 microgram/dl). However, 13% of workers with blood lead levels of 1.93 to 3.81 mumol/litre (40-79 microgram/dl) had extensor muscle weakness or gastrointestinal symptoms. Anaemia was found in 5% of workers with lead levels of 1.93-2.85 mumol/litre (40-59 microgram/dl), in 14% with levels of 2.90 to 3.81 mumol/litre (60-79 microgram/dl), and in 36% with levels greater than or equal to 3.86 mumol/litre (80 microgram/dl). Elevated blood urea nitrogen occurred in long-term lead workers. All but three workers with increased blood urea nitrogen had at least four years occupational lead exposure, and nine had received oral chelation; eight of this group had reduced creatinine clearance, and eight had decreased renal concentrating ability. These data support the establishment of a permissible biological limit for blood lead at a level between 1.93 and 2.90 mumol/litre (40-60 microgram/dl).     

Valproic acid and plasma levels of phenytoin.

Eight patients were treated concurrently with a constant dose of phenytoin and valproic acid for 1 year. During initial therapy with valproic acid, total plasma phenytoin levels decreased. The interaction was transient and was not observed at the end of 1 year. Total plasma phenytoin levels returned to pre-valproic-acid levels in seven patients.     

Tuberous sclerosis complex and renal angiomyolipoma. Collective review.

Numerous case reports of renal angiomyolipoma with or without tuberous sclerosis continue to be published with increasing frequency in the urologic literature. The need for a comprehensive and updated review of the subject is timely. A collective pathologic, clinical, and radiologic review of the subjects of tuberous sclerosis complex and renal angiomyolipoma is presented; and a plan for the urologic management is discussed.     

A prospective trial that demonstrates that dalteparin requirements increase in pregnancy to maintain therapeutic levels of anticoagulation

OBJECTIVE: The purpose of this study was to determine whether standard therapeutic doses of dalteparin maintain peak therapeutic levels of anticoagulation during pregnancy. STUDY DESIGN: This was a prospective trial in which 13 pregnancies that required therapeutic anticoagulation were treated with dalteparin 100 U/kg every 12 hours; peak and trough (predose) low molecular weight heparin (anti-Xa activity) levels were monitored every 2 weeks. Dosage adjustments were made to maintain peak anti-Xa activity between 0.5 and 1.0 IU/ml. Bone density and bone turnover markers were measured. RESULTS: A total of 250 peak and trough low-molecular-weight heparin (LMWH) levels were obtained. Eighty-five percent of pregnancies (11/13) required an upward dosage adjustment. Trough levels were in the therapeutic range only 9% of the time, despite the maintenance of therapeutic peak levels. Bone resorption markers and density were unchanged in singleton pregnancies. CONCLUSION: Dalteparin dosing, based on weight alone, every 12 hours is inadequate to maintain most pregnant women in the therapeutic range throughout pregnancy as measured by anti-Xa activity. Trough levels are rarely in the therapeutic range, despite maintenance of therapeutic peak levels. These notable changes in low molecular weight heparin peak may explain reported failures in pregnancy.     

Promoting participation in cardiac rehabilitation: patient choices and experiences

BACKGROUND: Cardiac rehabilitation can be an effective means for the secondary prevention of coronary heart disease, but a majority of eligible individuals fail to attend or drop out prematurely. Little research has examined patients' decisions about attendance. AIMS: This paper reports a study examining patients' beliefs and decision-making about cardiac rehabilitation attendance. METHODS: A purposive sample of patients from a mixed urban-rural region of Scotland was studied in 2001 using focus groups. Those who were eligible for a standardized 12-week cardiac rehabilitation programme were compared, with separate focus groups held for individuals with high attendance (>60% attendance; n = 27), high rates of attrition (<60% attendance; n = 9) and non-attendance (0% attendance; n = 8). A total of 44 patients (33 men; 11 women) took part in eight focus groups. RESULTS: Participants from all groups held sophisticated and cohesive frameworks of beliefs that influenced their attendance decisions. These beliefs related to the self, coronary heart disease, cardiac rehabilitation, other attending patients, and health professionals' knowledge base. An enduring embarrassment about group or public exercise also influenced attendance. Those who attended reported increased faith in their bodies, a heightened sense of fitness and a willingness to support new patients who attended. CONCLUSIONS: Reassurance to ease exercise embarrassment should be given before and during the early stages of programmes, and this could be provided by existing patients. Strategies to promote inclusion should address the inhibiting factors identified in the study, and should present cardiac rehabilitation as a comprehensive programme of activities likely to be of benefit to the individual irrespective of personal characteristics, such as age, sex or exercise capacity.