On the presence and mechanism of formation of heavy molecular weight aggregates in human normal and cataractous lenses

It has been suggested that the presence of high molecular weight protein aggregates in the lens can lead to light scattering and a consequent loss of transparency. We have measured the concentration of aggregates having a molecular weight greater than approximately 150 × 10⁶ g/mole present in the soluble fraction of both aging normal and cataractous human lenses. This protein population is approximately 5% of the total soluble protein in lenses up to age 75 and increases to 10–15% in lenses aged greater than 75 years and in cataracts. The amino acid composition of the heavy molecular weight soluble aggregates of normal lenses is different in leucine content from alpha, beta and gamma crystallins and different in tyrosine content from beta and gamma crystallins. The aggregates from cataractous lenses show a greater increase in leucine and greater decrease in tyrosine. An unidentified component is present in the cataractous aggregates. Furthermore, calcium, an ion which increases in concentration in cataractogenesis, induces alpha crystallin to aggregate and induces the heavy molecular weight fraction to aggregate. This aggregation is irreversible by dialysis or chelation.     

Antioxidant activity of isoflavones and biflavones isolated from Godoya antioquiensis

Two biflavones, ochnaflavone (1) and 2",3"-dihydroochnaflavone (2), and two isoflavones, 5,7,4'-trihydroxy-3',5'-dimethoxyisoflavone (piscigenin) (3) and 5,4'-dihydroxy-7,3',5'-trimethoxyisoflavone (4), a new natural compound, were isolated from the leaves of Godoya antioquiensis (Ochnaceae). Their structures were determined on the basis of spectral data and by comparison with data reported in the literature. The isolated compounds were evaluated for their radical scavenging activity using the NBT (nitrobluetetrazolium)/hypoxanthine superoxide and the .OH/luminol chemiluminescence methods. The isolated isoflavones were found to exhibit a strong hydroxyl radical scavenging activity and a moderate inhibition of the superoxide anion, whereas the two biflavones were inactive in the superoxide anion assay and showed a low hydroxyl radical scavenging activity.     

Analysis of ultradian sleep rhythms in rats, using stage transition functions

To analyse intrinsic sleep rhythms, transition probability functions were calculated from rat hypnograms. The method can be regarded as a generalization of Globus' binary autocorrelation analysis of sleep periodicity. It is useful for studying the construction of sleep cycles. The main advantage of the method is its insensitivity to random disturbances.     

A Simple Test for Detecting Disorders of Thromboplastin Generation

Observation of the dynamics of thromboplastin generation is still one of the best methods of controlling the early phase of blood coagulation. The original thromboplastin generation test and its modifications are too complicated to gain universal acceptance in practice. The authors have simplified the whole blood thromboplastin generation test, and describe the experience obtained by its critical analysis. The test has been subjected to control of its parameters and the results are compared with those obtained by other tests. The test is highly sensitive and has been used successfully in establishing the diagnoses of various coagulation disorders, including the detection and observation of haemophilia and other early-stage clotting disorders. The test may be carried out in any laboratory as it is simple and requires no specific reagents or equipment.     

Headache: diagnosis and treatment

Headache is the most common reason why patients visit a neurologist. Approximately 70% of the population suffer from headache. The symptoms in this condition are rather simple and a well-controlled therapy is mostly available, but there are still frequent failures in the diagnosis and therapy of headaches. Failures in the treatment are caused mainly by the fact the doctors are not able to set the appropriate diagnosis. It is recommended that patients with persisting headache should turn to headache centers. The therapy should be determined by the frequency and duration of the headache, its severity, the accompanying symptoms and preceding therapeutic history. This survey may be of assistance on the state-of-the-art diagnostics and therapy of headaches in neurological practice.     

Comparing outcomes in renal replacement therapy: how should we correct for case mix?

The need to evaluate the effectiveness of clinical practice to justify expensive therapy in the face of financial constraints in all areas of health care delivery makes it necessary to identify groups of patients who are likely to benefit most from treatment. Various risk stratification methods have been used for analyzing survival probabilities for patients receiving renal replacement therapy. Complicated risk stratification methods produce large numbers of risk groups of small sizes, which makes comparison between individual centers difficult. We compared three simple methods of risk stratification, that divided patients into low-, medium-, and high-risk groups, in a cohort of 1,407 patients who commenced renal replacement therapy in five European countries during a 7-year period. Method 1 considered age (>55 years) and diabetes alone; method 2 used a higher age limit (>70 years) and comorbid illnesses, including those other than diabetes; and method 3 used only the number of comorbidities (none, 1, or > or =2) for stratification. Kaplan-Meier survival curves were constructed for comparison between risk groups and Cox's regression model used to assess strength of relationship with mortality. Although patient survival was significantly different between the low-, medium-, and high-risk groups using all three methods, Cox's regression analysis showed that method 2 provided the greatest discrimination between risk groups. In predicting mortality, method 2 (based on comorbidities and age) showed the highest sensitivity and specificity (84% and 80%, respectively) compared with method 1 (80% and 74%) and method 3 (64% and 82%). Validation of this approach in other populations in a prospective study is required before this method, which takes into account the influences of both age and comorbidity for risk stratification, can be used for comparing survival data and for presenting results of renal replacement therapy.