Regeneration of three-disulfide mutants of bovine pancreatic ribonuclease A missing the 65-72 disulfide bond: characterization of a minor folding pathway of ribonuclease A and kinetic roles of Cys65 and Cys72

The oxidative regeneration pathways of two three-disulfide mutants of bovine pancreatic ribonuclease A (RNase A) missing the 65-72 disulfide bond, [C65S,C72S] and [C65A,C72A], have been studied by using oxidized dithiothreitol (DTTox) as an oxidizing agent and 2-aminoethylmethanethiosulfonate (AEMTS) as a thiol-blocking agent at 25 degrees C and pH 8.0. These mutants are analogues of the des-[65-72] intermediate, which is one of the two major three-disulfide intermediates that follow after the transition states in the regeneration pathways of wild-type RNase A [Rothwarf, D. M., Li, Y.-J., and Scheraga, H. A. (1998) Biochemistry 37, 3760-3766, 3767-3776.]. Both mutants folded through the same pathway but at a rate lower than that of the wild-type protein. The major rate-determining step in the regeneration of these mutants was determined to be the oxidation from the two-disulfide intermediates (2S) to the post-transition-state three-disulfide intermediate (3S*), suggesting the existence of a minor oxidation pathway (2S --> 3S*, where 3S* is des-[65-72]) in the regeneration of the wild-type protein, in addition to one of the two major disulfide-rearrangement pathways (3S --> des-[65-72]). The regeneration intermediates of these mutants (R, 1S, 2S, and 3S) participate in a steady state with a kinetic behavior resembling that of the wild-type protein. However, the apparent equilibrium constants () in the steady state, averaged with statistical factors for these mutants, are significantly smaller than those for the wild-type protein, indicating that the intermediates in the regeneration of the mutants are relatively less stable by 0.32 kcal/mol. This difference is due to the decrease in the average rate constants for intramolecular disulfide-bond formation () for the mutant proteins. Loop entropy calculations indicate that the increase in the average length of all possible disulfide loops of the mutants due to the replacement of Cys65 and Cys72 is not sufficient to account for the observed reduction of the values of for the mutants. Therefore, it is the removal of energetic factors (arising from the loss of the 65-72 disulfide loop) that leads to deceleration of the regeneration of the mutant proteins. The formation of the 65-72 disulfide loop in the regeneration of wild-type RNase A appears to facilitate the subsequent folding events.     

Colour Doppler hysterosalpingosonography: a simple and potentially useful method to evaluate fallopian tubal patency

The functional state of the amacrine cells which contain enkephalin-, neurotensin- and somatostatin-like immunoreactivity of the chicken retina was monitored by measuring the rate of change in the levels of [Leu]enkephalin-like immunoreactivity in the retina. Dark-adapted birds were exposed to lights of different intensities for 12 h. At light levels of < or = 0.03 microW/cm2, the ENSLI amacrine cells were highly active but, by 0.08 microW/cm2, they reached a state of maximum inactivation. Thus, the ENSLI amacrine cells act as flip-flop devices, inactivated by critical levels of light, which correspond to those which inactivate pineal melatonin synthesis. They may, therefore, be involved in retinal pathways which signal the difference between day and night.     

Passive and active intracranial translocation of osteosynthesis plates in adolescent minipigs

On the basis of the clinical and experimental proof that intracranial translocation of osteosynthesis plates occurs in infants after fixation on frontal bone, we conducted an animal study on four adolescent G?ttingen minipigs. Our aim was to study the effects on intracranial translocation of two different types of osteosynthesis plates by comparing the plate-bone interface on the intact frontal bone treated with a multiple-point contact plate versus a conventional smooth one, paying special emphasis to the periosteum. Within a few weeks of implantation, osseous regeneration products surrounded the plate. Total invagination of plates with initial intracranial translocation occurred 12 to 16 weeks postimplantation, regardless of plate design. In epiperiosteal fixation, intracranial translocation was delayed. The results revealed two mechanisms at play here: cranial growth-related passive intracranial translocation, which occurs regardless of plate design, and plate-dependent active intracranial translocation. In conclusion, we recommend that all metal osteosynthesis materials implanted in the infant cranium be removed as early as possible (within 3 months).     

The effect of sulphasalazine on neutrophil superoxide generation in rheumatoid arthritis

Sensorineural hearing loss related to autoimmune disease is a well-recognized condition, although the exact pathophysiologic mechanisms remain unclear. One current theory postulates immune complex-induced interference with blood-labyrinth barrier integrity in the stria vascularis. The C3H/lpr autoimmune mouse was chosen to study the permeability of capillaries in the stria vascularis because this mouse model has demonstrated abnormalities of the stria vascularis and shifts in the auditory brain stem response threshold during active disease. C3H/lpr mice with active disease were compared with younger mice without disease, as well as age-matched C3H/HeJ control mice. The mice were injected with the tracer ferritin and examined by transmission electron microscopy to evaluate the integrity of the capillary tight junctions in the stria vascularis. Four of five mice with active disease were noted to have extensive leakage of ferritin into the perivascular tissues. Neither the young, disease-free autoimmune mice nor the nonautoimmune control mice demonstrated vessel leakage. Thickening of the basement membrane was also noted in the diseased animals. The results imply that active disease leads to a breakdown in the blood-endolymph barrier, which could underlie the hearing loss accompanying autoimmune and other immune diseases.     

Circulating leptin has saturable transport into intrathecal space in humans

BACKGROUND: Leptin is an adipocyte-derived hormone that is thought to provide a negative feedback signal to control body fat mass by interacting with its hypothalamic receptor. The present study was undertaken to examine the uptake of leptin in cerebrospinal fluid (CSF) space in humans and whether the transport of leptin into CSF space is an active phenomenon or due to free access through the blood-CSF barrier. METHODS: We determined serum and CSF leptin concentrations by radioimmunoassay in 17 men [42 +/- 4 years, mean +/- SE; body mass index (BMI) 27.3 +/- 1.8 kg m-2] and 22 women (40 +/- 3 years, BMI 25.1 +/- 1.0 kg m-2). The function of the blood-CSF barrier was evaluated by determining the CSF/serum albumin ratio. RESULTS: Serum leptin concentration was lower in male (5.8 +/- 1.6 microgram L-1) than in female subjects (13.1 +/- 1.7 microgram L-1, P = 0. 001), whereas the concentrations of leptin in CSF were virtually identical in male (0.34 +/- 0.03 microgram L-1) and female (0.36 +/- 0. 03 microgram L-1) subjects. Serum leptin was correlated positively with BMI both in men (r = 0.89, P < 0.01, n = 10) and in women (r = 0.61, P < 0.05, n = 14), whereas no correlation between CSF leptin concentration and BMI was found in either group. The CSF/serum leptin ratio correlated negatively with serum leptin concentration both in men (r = -0.93, P < 0.001) and in women (r = -0.77, P < 0. 001) and with BMI both in men (r = -0.75, P = 0.02, n = 10) and in women (r = -0.64, P < 0.02, n = 14). The CSF/serum albumin ratio was not correlated with the CSF/serum leptin ratio in either group. CSF leptin concentrations and the CSF/serum leptin ratio were virtually identical in subjects with impaired and normal blood-CSF barrier function. CONCLUSION: Thus, our data support the presence of a saturable and active transporter of leptin from circulation into intrathecal space.     

The treatment of severe hypertension with trandolapril, verapamil, and hydrochlorothiazide. Trandolapril/Verapamil Multicenter Study Group

A multiple drug regimen consisting of trandolapril, verapamil and hydrochlorothiazide (HCTZ) were sequentially added in an open-label evaluation of patients with severe hypertension. Ninety patients (58 white and 32 black patients) were titrated on one or more drugs and followed for a 19-week maintenance period. Statistically significant (P = 0.001) mean (+/-s.d.) decreases in supine diastolic blood pressure (DBP) were 9.0 (+/-9.3) mm Hg for trandolapril, 13.9 (+/-11.0) mm Hg for the trandolapril + verapamil (TV) combination, and 19.0 (+/-12.3) mm Hg when hydrochlorothiazide was added to the combination. The decrease in BP observed on TV combination therapy plus HCTZ was significantly (P = 0.001) greater than the decrease observed for the TV combination, which was significantly (P = 0.001) greater than the decrease observed for trandolapril monotherapy. Clinical responder rates were 44.8%, 56% and 77.7% for trandolapril monotherapy, trandolapril + verapamil combination therapy and triple therapy, respectively. Black and white patients had similar response rates, but black patients appeared to benefit more from the addition of HCTZ; 20% of black patients achieved a post-treatment supine DBP <90 mm Hg compared to 12.8% of white patients. This study demonstrates that the addition of verapamil to trandolapril has an additive effect on BP that is maintained throughout the day.