Thermal unfolding of ribonuclease A in phosphate at neutral pH: deviations from the two-state model.

The thermal denaturation of ribonuclease A (RNase A) in the presence of phosphate at neutral pH was studied by differential scanning calorimetry (DSC) and a combination of optical spectroscopic techniques to probe the existence of intermediate states. Fourier transform infrared (FTIR) spectra of the amide I' band and far-uv circular dichroism (CD) spectra were used to monitor changes in the secondary structure. Changes in the tertiary structure were monitored by near-uv CD. Spectral bandshape changes with change in temperature were analyzed using factor analysis. The global unfolding curves obtained from DSC confirmed that structural changes occur in the molecule before the main thermal denaturation transition. The analysis of the far-uv CD and FTIR spectra showed that these lower temperature-induced modifications occur in the secondary structure. No pretransition changes in the tertiary structure (near-uv CD) were observed. The initial changes observed in far-uv CD were attributed to the fraying of the helical segments, which would explain the loss of spectral intensity with almost no modification of spectral bandshape. Separate analyses of different regions of the FTIR amide I' band indicate that, in addition to alpha-helix, part of the pretransitional change also occurs in the beta-strands.

The effect of diapulse therapy on the healing of decubitus ulcer.

The effect of pulsed high peak power electromagnetic field (Diapulse) on treatment of pressure ulcers is under investigation. 20 elderly patients, aged from 60 to 84, hospitalized with chronic conditions and bearing long-standing pressure ulcers, are subjected to Diapulse sessions (1-2 daily), parallel to conventional treatment. 5 patients undergo conventional therapy, serving as control and 5 others follow conventional+placebo Diapulse treatment. All patients were daily monitored, concerning their clinical status and ulcers' healing. After a maximum 2-weeks treatment, bulge healing rate was, as follows: 85% excellent and 15% very good healing under Diapulse therapy; in the placebo group, 80% patients show no improvement and 20% poor improvement; in the control group, 60% patients show no improvement and 40% poor improvement of ulcers. This investigation strongly advises for Diapulse treatment as a modern, uninvasive therapy of great efficiency and low social costs in resolving a serious, widespread medical problem.

Circadian rhythm of TSH in adult onset non-insulin dependent (type II) diabetics with altered thyroid state.

Twenty adult onset non-insulin dependent (Type II) diabetic patients and twenty non-diabetic subjects matched for sex, age, height and weight were studied. The diabetes was controlled by diet only in 10 patients and by oral hypoglycemic agents in 10. All patients were diurnally active and rested at night. Blood was sampled at 4-hour intervals over a 24-hour span (6 samples). TSH, total T3 and total T4 were determined by radioimmunoassay. The circadian rhythm in TSH was statistically significant by cosinor analysis and was comparable in all rhythm parameters in diabetics and non-diabetics. The rhythms of total T3 and T4 also seem to persist with comparable timing although the small number of subjects did not allow rhythm detection at the 5 per cent level in all groups. The circadian mean of the total T3 plasma concentration in the diabetics, however, was statistically significantly lower than the usual range of this laboratory and the total T4 was elevated but within the usual range. The changes in total T3 and T4 were most pronounced in the patients on oral hypoglycemic agents. This study indicates persistence of a circadian rhythm in TSH (and presumably also in the plasma concentrations of total T3 and T4) in non-insulin dependent diabetic patients in spite of a lowered circadian mean concentration of total T3 and a slightly but statistically significantly higher total T4 than in the matched non-diabetic subjects. The altered thyroidal state in the diabetic patients thus does not interfere with the circadian periodic secretion of TSH.

Circadian variations in plasma immunoreactive insulin (IRI) and C-peptide concentrations in adult onset (type II) diabetes mellitus.

Plasma immunoreactive insulin (IRI), C-peptide and serum glucose concentrations were determined in 19 adult onset non-insulin dependent (type II) diabetics, in one adult onset diabetic on insulin and in 20 non-diabetic subjects matched for sex, age, weight and height. The subjects lived on a schedule of diurnal activity and nocturnal rest (21:00 to 06:00) at Berceni Clinical Hospital, Bucharest, Romania and ate three meals at 08:30, 13:00 and 18:30 and a snack at 10:00 (carbohydrate content: 50 gm, 65 gm, 60 gm and 25 gm respectively). Nine of the diabetic patients were on oral hypoglycemic agents (tolbutamide or meguan), the others were controlled by diet only. Blood was sampled beginning at 08:00 at 4 hourly intervals over a 24-hour span. The circadian variations of IRI, C-peptide and serum glucose were analysed by population mean cosinor. The non-insulin dependent diabetic subjects as a group and the matched non-diabetic subjects showed under the conditions of this study circadian variations in serum glucose, plasma IRI and C-peptide which were identical in timing (acrophase) and amplitude and with the exception of the much higher serum glucose concentrations in the diabetics, not significantly different in the circadian mean concentration (or mesor). The diabetics on oral hypoglycemic agents if investigated separately showed in spite of identical serum glucose concentration a statistically significantly lower circadian mean IRI and C-peptide concentration than either non-diabetic subjects or the diabetics treated by diet only. Acrophase and relative amplitude remained unchanged. Adult onset non-insulin dependent (type II) diabetics maintained on diet only show the same circadian variations in plasma IRI and C-peptide as non-diabetic matched for sex, age, height and weight. The adult onset diabetic on insulin showed an extremely high serum glucose concentration which varied in its timing over the 24-hr span similar to the other subjects. His plasma IRI concentration was about ten times that of the non-diabetic or other diabetic subjects in this study. There was no statistically recognizable circadian variation of IRI. In contrast C-peptide was found at the same concentration as found in the other two groups and showed in all rhythm parameters an identical circadian variation. The circadian acrophase of plasma IRI and C-peptide concentrations in adult onset diabetics and the non-diabetics is the same.(ABSTRACT TRUNCATED AT 400 WORDS)

Circadian and circannual variations in plasma immunoreactive insulin (IRI) and C-peptide concentrations in elderly subjects.

Groups of 49-51 elderly men and women 77 +/- 8 years of age, institutionalized at the Berceni Clinical Hospital, Bucharest, Romania, were studied over a 24 hour span in spring, summer, fall and winter. All subjects followed a diurnal activity pattern with rest at night and ate three meals per day with breakfast at about 08:30, lunch at about 13:00, dinner at 18:30. The meals were similar, although not identical for all subjects during all seasons. On each day of sampling, blood was collected at four hourly intervals over a 24 hrs span. Immunoreactive insulin (IRI) and C-peptide were determined in plasma and glucose (during fall and winter only) in serum. Circadian variations of all three parameters were found and the rhythm parameters were determined statistically by cosinor analysis. The acrophases of the circadian rhythm of IRI and C-peptide were the same during all four seasons. The circadian acrophase of plasma IRI and C-peptide precedes that of serum glucose. The circadian mean concentrations of IRI and C-peptide show a circannual variation with higher values in winter and fall than in spring and summer for plasma insulin and with higher values for summer and fall than in spring for C-peptide. Sex differences in IRI and C-peptide concentrations with higher values in men are manifested during certain circadian and circannual stages but not during others.