Incidence and pathophysiological changes in chronic two-kidney hypertension in the dog

Unilateral renal artery plication in dogs reduced renal blood flow by 80% and produced a sustained elevation in arterial pressure whereas plasma renin activity increased for only 4 days. Sodium was retained for 3 days after plication, but this response is similar to that after a sham operation. Of seven dogs studied chronically, elevated arterial pressure was sustained for 27 days or longer in six animals. In three dogs hypertension continued for 2 mo before collateral vessels developed and arterial pressure fell; ligation of these collaterals restored hypertension. Arterial pressure was unaffected by an infusion of [1-sarcosine, 8-alanine] angiotensin II in chronic hypertensive dogs on a normal sodium intake. This angiotensin antagonist lowered arterial pressure after sodium depletion, but became ineffective following rapid sodium repletion. Chronic hypertensive dogs showed normal responses to deoxycorticosterone acetate. These findings suggest that the renin-angiotensin system is not critically involved in maintenace of chronic two-kidney renovascular hypertension in the dog. The data also show that the homeostatic role played by the renin-angiotensin system in the maintenance of arterial pressure remained intact in chronic hypertension.     

The BsmI vitamin D receptor restriction fragment length polymorphism (bb) influences the effect of calcium intake on bone mineral density

Previous studies of the vitamin D receptor (VDR) polymorphisms and bone mineral density (BMD) have suggested that there may be differences in calcium absorption among groups of women with different VDR genotypes, and that the association may be stronger in younger women. To investigate the association between the VDR polymorphisms and BMD, this study was undertaken in the Framingham Study Cohort and a group of younger volunteers. Subjects from the Framingham Study (ages 69-90 years) included those who underwent BMD testing and who had genotyping for the VDR alleles (n = 328) using polymerase chain reaction methods and restriction fragment length polymorphisms with BsmI (B absence, b presence of cut site). A group of younger volunteer subjects (ages 18-68) also underwent BMD testing and VDR genotyping (n = 94). In Framingham Cohort subjects with the bb genotype, but not the Bb or BB genotypes, there were significant associations between calcium intake and BMD at five of six skeletal sites, such that BMD was 7-12% higher in those with dietary calcium intakes greater than 800 mg/day compared with those with intakes < 500 mg/day. The data also suggested that BMD was higher in persons with the bb genotype only in the group with calcium intakes above 800 mg/day. No significant differences were found in the Framingham Cohort for age-, sex-, and weight-adjusted BMD at any skeletal site between those with the BB genotype and those with the bb genotype regardless of 25-hydroxyvitamin D levels or country of origin. In the younger volunteers, BMD of the femoral neck was 5.4% higher (p < 0.05) in the bb genotype group compared with the BB group and 11% higher (p < 0.05) in males with the bb genotype compared with the BB group. There were no significant differences at the lumbar spine. In this study, the association between calcium intake and BMD appeared to be dependent upon VDR genotype. The findings of an association between dietary calcium intake and BMD only in the bb genotype group suggests that the VDR genotype may play a role in the absorption of dietary calcium. Studies that do not consider calcium intake may not detect associations between VDR genotype and BMD. In addition, the association between VDR alleles and BMD may become less evident in older subjects.     

Osteopontin in chronic puromycin aminonucleoside nephrosis

Increased expression of osteopontin (OPN) associated with interstitial monocyte infiltration has been demonstrated in the early phase of a variety of experimental renal diseases. Whether these changes occur in the chronic phase of progressive glomerular disease is unknown. Chronic puromycin aminonucleoside nephrosis (PAN) was induced in 16 rats by the injection of a single bolus of PA into the internal jugular vein, which results in a triphasic disease characterized by minimal glomerular change and marked proteinuria, peaking at about 10 to 14 d and subsiding by 28 d, followed by a quiescent 4-wk period of no or minimal proteinuria and then the development of progressive focal glomerulosclerosis (FGS) and increasing proteinuria. Fifteen rats injected similarly with normal saline served as controls. At 11 d after injection, PA rats demonstrated significantly greater urinary protein excretion (P = 0.0107), cortical tubular OPN expression (P = 0.0086), and intraglomerular (P = 0.0009) and interstitial (P = 0.0212) monocyte infiltration than did the controls. At 42 d, no significant differences between the two groups with respect to the above parameters were detected. At 98 d, PA rats had FGS and showed a definite trend to increased proteinuria, cortical tubular OPN, and intraglomerular monocyte infiltration. Although the cortical interstitial monocyte count was not elevated in PA rats compared with controls, there were significantly more monocytes around OPN-positive cortical tubules than around OPN-negative ones (P = 0.0011). Cortical tubular OPN expression correlated well with urinary protein excretion (r = 0.932, P < 0.0001), cortical tubular proliferating cell nuclear antigen (r = 0.796, P < 0.0001), and intraglomerular monocyte count (r = 0.552, P = 0.0013). The results are consistent with a monocyte chemoattractant role for OPN and suggest that OPN is upregulated in the chronic phase of PAN and that this increase in expression is a result of glomerular events.     

Value of transcranial Doppler indices in predicting raised ICP in infantile hydrocephalus. A study with review of the literature

Cerebral hemodynamic changes in infants with progressive hydrocephalus have been studied with the transcranial Doppler (TCD) technique. Several authors have referred to the correlation between the hemodynamic changes and increased intracranial pressure (ICP). Despite conflicting conclusions on the value of pulsatility index (PI) and resistance index (RI) measurements for monitoring infantile hydrocephalus, these pulsatility indices are the most commonly used for this purpose. Although clinical signs of raised ICP are highly variable and unreliable in infants, assumptions have been made in most of the studies about the presence of elevated ICP on the basis of the patient's clinical state. Few studies have reported on actual ICP values, however, and a direct relationship between ICP and TCD changes has never been adequately demonstrated. In the present study, this relationship was investigated in long-term simultaneous TCD/ICP measurements, in an attempt to develop a noninvasive method of monitoring the effect of ICP on intracranial hemodynamics. Two groups of data sets were established. Group I consisted of pre- and postoperative (shunt implantation) TCD/ICP measurements. Group II were long-term simultaneous TCD/ICP recordings showing significant ICP variations. In most of the postoperative measurements there was a decrease in the average PI and RI values. The correlation between PI or RI and ICP in the long-term simultaneous recordings, however, was generally poor. The risk of obtaining false positive or false negative PI or RI values in short-term measurements was also demonstrated. It can be concluded from our results, besides the wide range of reference values for the Doppler indices and extracranial influences upon them, that the present Doppler indices are inadequate for monitoring the complex intracranial dynamic responses in patients with raised ICP.     

Renaturation of formyltetrahydrofolate synthetase from urea and guanidinium chloride solutions

Formyltetrahydrofolate synthetase from Clostridium cylindrosporum and Clostridium acidi-urici was denatured in 6 M urea and 4 M guanidinium chloride. Viscometric, fluorimetric and ultracentrifugal measurements were used to determine that the protein is completely unfolded under these conditions. The polypeptide chains refold upon dilution of the denaturant-protein solutions to give final concentrations of 0.5 M urea or 0.1 M guanidinium chloride. In the presence of NH4+, but not in its absence, the refolded proteins associate to produce the catalytically active tetramer. Refolding and reassociation were followed by measuring changes in protein fluorescence and by determination of sedimentation constants. Under most conditions 80% of the enzymic activity is recovered.     

Functional analysis of the placenta-specific enhancer of the human glycoprotein hormone alpha subunit gene. Emergence of a new element

Placental expression of the alpha subunit gene of the human glycoprotein hormones requires a multicomponent enhancer composed of tandem cAMP-response elements and an adjacent upstream regulatory element. Based on recent studies indicating that the upstream regulatory element includes binding sites for more than one protein, we investigated how functional activity correlated with these binding sites. Through extensive replacement mutagenesis of the native promoter regulatory region, we provide the first functional map of the upstream regulatory element. Within this region, we find that distinct proteins interact with three overlapping binding sites. While each site is functionally significant, no single site is essential or displays clear dominance. This is surprising since one of the sites binds a placenta-specific protein that heretofore has been regarded as essential for activity of the human alpha subunit placenta-specific enhancer. Consequently, our refined functional map of the upstream regulatory element reveals a complex combinatorial code that directs expression of the human alpha subunit gene to placenta.