Physical activity in adults with and without rheumatoid arthritis: cross-sectional results from the Survey of Health, Ageing and Retirement in Europe (SHARE)

OBJECTIVE

Studies examining habitual physical activity levels and patterns in adults with rheumatoid arthritis (RA) using raw data from modern accelerometers are lacking. We aimed (i) to examine physical activity levels and patterns in adults with RA in their familiar environment, and (ii) to investigate whether physical activity levels differ throughout the day.

METHOD

Data were taken from Wave 8 of the Survey of Health, Ageing and Retirement in Europe, including N = 607 men and women who wore a triaxial accelerometer and had adequate information for RA and accelerometry data summarized as Euclidean norm minus one (ENMO, mg). Growth-curve models and simple contrast analysis were used to examine the effect of RA on daily patterns of physical activity levels, including mean total ENMO in mg, mean minutes of light-intensity physical activity (ENMO values ≥ 25 mg and ≤ 75 mg), and moderate-to-vigorous-intensity physical activity (ENMO values > 75 mg).

RESULTS

Total physical activity averaged throughout the day was 25.0 and 28.6 mg for respondents with and without RA, respectively. Respondents with RA spent more time in light-intensity physical activity throughout the day (p < 0.001), but less time in moderate-to-vigorous-intensity physical activity between 4 am and 11 pm (p < 0.001) than respondents without RA.

CONCLUSION

Adults with RA were less physically active than adults without RA. However, there were no diurnal differences in physical activity.

Changes in physical activity and the association between pain and physical activity - a longitudinal analysis of 17,454 patients with knee or hip osteoarthritis from the GLA:D® registry

OBJECTIVE

Investigate change in physical activity following an 8-week education and exercise therapy program for patients with knee/hip osteoarthritis, focusing on those with low physical activity level. Furthermore, to evaluate associations between changes in pain intensity and physical activity.

METHOD

Data from the Good Life with osteoArthritis in Denmark (GLA:D®) registry, at baseline, immediately after completion, and 12 months after entering the program was used. Measures of interest were UCLA activity scale (1-10) and Visual Analog Scale for pain intensity (0-100 mm). Changes in physical activity levels (low 1-4, moderate 5-6, and high 7-10) over three time points were investigated. Asymmetric fixed effects regression models were used to evaluate the association between clinically relevant change in pain (≥15 mm) and change in physical activity level from baseline to 12 months.

RESULTS

37% with low activity level at baseline (n = 4,836) and 69% of all patients (n = 17,454) reached or maintained at least a moderate physical activity level at follow-ups. Surprisingly, both an improvement (β = 1.44, P < 0.001) and a worsening (β = 1.18, P < 0.001) in pain intensity was associated with increased physical activity in low activity patients. For all patients a similar trend was observed (β = 0.51, P < 0.001 and β = 0.11, P = 0.215, respectively).

CONCLUSION

In low active knee or hip OA patients, a third of patients participating in an education and exercise therapy program reached and maintained at least a moderate physical activity level for 1 year. The improvement in physical activity was not dependent on pain reduction.

Individualized predictions of changes in knee pain, quality of life and walking speed following patient education and exercise therapy in patients with knee osteoarthritis - a prognostic model study

OBJECTIVE

To facilitate shared decision-making for patients with knee osteoarthritis (OA), we aimed at building clinically applicable models to predict the individual change in pain intensity (VAS scale 0-100), knee-related quality of life (QoL) (KOOS QoL score 0-100) and walking speed (m/sec) immediately following two educational and 12 supervised exercise therapy sessions.

METHODS

We used data from patients with knee OA from the 'Good Life with osteoArthritis in Denmark' (GLA:D®) registry (n = 6,767). From 51 patient characteristics, we selected the best performing variables to predict the outcomes via random forest regression. We evaluated model performance via R². Lastly, we validated and compared our models with the average improvements via the mean differences in an independent validation data set from the GLA:D® registry (n = 2,896) collected 1 year later than the data used to build the models.

RESULTS

Validating our models including the best performing variables yielded R²s of 0.34 for pain intensity, 0.18 for knee-related QoL, and 0.07 for walking speed. The absolute mean differences between model predictions and the true outcomes were 14.65 mm, 10.32 points, and 0.14 m/s, respectively, and similar to the absolute mean differences of 17.64, 11.28 and 0.14 observed when we subtracted the average improvements from the true outcomes.

CONCLUSION

Despite including 51 potential predictors, we were unable to predict changes in individuals' pain intensity, knee-related QoL and walking speed with clinically relevant greater precision than the respective group average outcomes. Therefore, average prediction values can be used to inform patients about expected outcomes.

Abstract P4-08-12: Gene Expression Profiling of Formalin-Fixed, Paraffin-Embedded (FFPE) Breast Cancer Samples and Analysis of Intrinsic Subtypes

Background: The advent of microarray technology has enabled robust, high throughput analysis of breast cancer (BC) transcriptomes. Indeed, molecular classification of BC has been revolutionized by the advent of Gene Expression Profiling (GEP). FFPE tumor samples have presented a technical challenge for GEP studies due to degradation of extracted RNA. Newer technologies have overcome this challenge, and have lead to generation of quality GEP data and thus, new insights using archived tissues. Of particular interest to our group has been application of these techniques to the study of triple negative breast cancer (TNBC). TNBC is a BC sub-type characterized by a lack of erbB2 gene amplification and estrogen and progesterone receptor expression. This clinically-defined BC sub-type carries a poor prognosis, is insensitive to hormonal or HER-2 targeted therapies, and displays different incidences among ethnic groups. A better understanding of the genetic and molecular mechanisms underlying TNBC is critical to improving clinic outcomes and developing tailorized therapies.

Study Objective: We demonstrate utility of FFPE BC samples in obtaining consistent, reproducible GEP data, and apply this technology to validate the ability to identify intrinsic BC subtypes in unselected specimens, as well to identify differentially expressed genes in TNBC.

Methods: RNA isolation and labelled cDNA preparation were performed from freshly cut FFPE sections. Samples were hybridized to a breast cancer focused gene expression array (Breast Cancer DSA Research Tool, Almac Diagnostics Inc). DSA chip quality was assessed on parameters selected automatically from GCOS report files per chip using MATLAB script based web application developed by Almac. Data pre-processing used the Resolver Error Model. All parameters including Raw Q, Background, Scaling Factor and all controls met quality criteria set by Affymetrix and Almac Dx SOPs. Hybridization results were assessed with Principal Component Analysis and Cluster Analysis in a Rosetta Resolver Gene Expression Data Analysis System to identify potential outliers, contamination, or intra-tumor heterogeneity. In total, 47 FFPE breast cancer samples covering a range of hormonal receptor status and sub-types were profiled, as were 28 TNBC FFPE tumor samples.

Results: Cluster analysis demonstrated that the Almac Breast Cancer DSA was able to clearly separate the 47 tumor samples of the mixed subtype group into the previously described intrinsic subgroups. Moreover, the DSA array contains 167 probesets which correspond to the 40 of the PAM-50 gene set used as a subtype predictor (Parker et al 2009). Analysis of the TNBC samples using the 167 probeset (based on mean intensity for probes representing each of the 40 genes) showed 100% consistency with published results demonstrating a basal-like gene expression signature. Summary: We have shown that our study methodology used can reliably measure gene expression in FFPE BC samples, and that the Breast Cancer DSA can be used to evaluate intrinsic subtypes of BC specimens. Analysis of the TNBC cases showed complete concordance between the PAM-50 gene set and the corresponding genes in the DSA. These study results are being validated in a larger data set.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-08-12.

Gene Expression Profiling of Formalin-Fixed, Pariffin-Embedded (FFPE) Tissues from Triple-Negative (TN) Breast Cancer (BC) Patients

Background: FFPE tumor samples present a technical challenge for gene expression profiling studies. Newer technologies are resulting in quality data and new insights from these archived tissues. TNBC is a sub-type of BC characterized by a lack of erbB2 gene amplification and estrogen and progesterone receptor expression. This clinically-defined BC sub-type carries a poor prognosis, is insensitive to hormonal or HER-2 targeted therapeutic agents, and has different incidence among ethnic groups. A better understanding of the genetic and molecular mechanisms underlying TNBC is critical to improving clinic outcomes and developing individualized therapies.Study Objective: We demonstrate the utility of FFPE samples in obtaining consistent, reproducible data from gene expression arrays, and apply this technology to the identification of differentially expressed genes between TNBC and normal breast tissue that are common or unique among selected ethnic groups.Methods: RNA isolation and labeled cDNA preparation from freshly cut FFPE blocks (marked by a pathologist as to normal vs. tumor tissue) was performed using the NuGEN™ WT-Ovation™ FFPE RNA Amplification System. Hybridization of tumor and normal cDNAs occurred to a breast cancer focused gene expression array (Breast Cancer DSA Research Tool, Almac Diagnostics Inc). Each patient' sample served as it's own control (tumor vs. normal). In total, 75 FFPE samples were profiled. The quality of each DSA chip was assessed on parameters selected automatically from GCOS report files per chip using MATLAB script based web application developed by Almac Dx. Data pre-processing used the Resolver Error Model. All parameters including Raw Q, Background, Scaling Factor and all controls met quality criteria set by Affymetrix and Almac Dx SOPs. Hybridization results were assessed using Principal Component Analysis and Clustering Analysis in Rosetta Resolver Gene Expression Data Analysis System 7.1 to identify potential outliers, contamination, or intra-tumor heterogeneity.Results: A Sign Agreement Matrix of FFPE and fresh frozen tissue samples during validation of the Breast Cancer DSA demonstrated that 98% of the probesets showed the same direction of fold change [p Spearman(FC)=0.84]. The FFPE samples had an average present call ∼ 43%, and more than 90% of the FFPE samples had present call rates greater than 25%. QC analysis demonstrated that the Almac Breast Cancer DSA was able to clearly and consistently separate tumor samples from normal in FFPE tissues and to identify samples of quality or integrity issues. Application of this methodology to analyses of differentially expressed transcripts between cancer and normal tissue samples across ethnicities in the TNBC samples, detected 1350 differentially expressed genes in the African-American group, 1220 genes in the Caucasian group and 1226 genes in the White Hispanic group. We also observed certain subtle ethnic-specific expression patterns across these three ethnic groups.Summary: The above-described methodology can be used to reliably measure gene expression in FFPE breast samples. Our study results are being validated in a larger data set.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6125.

Distinct multiethnic genome-wide alterations in breast cancer using paraffin embedded samples: preliminary analysis

Abstract #2024

Background and Rational: Ethnic-specific disparities in breast cancer (BC) stage of presentation and survival rates are well documented. To further investigate possible ethnic-specific genetic contributions to these disparities, we are completing gene expression profiling studies in a multi-ethnic cohort consisting of thirty “Triple Negative” BC patients [10 each African-American (AA), Hispanic (His) and non-Hispanic white (Cauc) women] matched for age of diagnosis and hormone receptor status. The overall study aim is an increased understanding of the biological basis of ethnic-specific BC disparities, leading ultimately to individualized, ethnic-specific diagnostic and therapeutic approaches. Two immediate study goals are to demonstrate the utility of FFPE samples in obtaining consistent, reproducible data from gene expression arrays, and secondly, to identify differentially expressed genes between tumor and normal tissue that are common or unique among the three ethnic groups. Methods: Pathology specimens were freshly cut from FFPE blocks and marked by a pathologist as to normal vs. tumor tissue. RNA isolation, labeled cDNA preparation, and hybridization of tumor and normal cDNAs to a breast cancer focused gene expression microarray (Breast Cancer DSA Research Tool) was performed by Almac Diagnostics. Each patient was self-matched (tumor vs. normal tissue) for gene expression studies. Results: Using 36 matched tumor and normal FFPE samples from 18 patients, approximately 17516 transcripts were detected on the Breast Cancer DSA with intensity significantly greater than background. For normal and tumor tissue samples, 9399 and 10,296 transcripts respectively, were detected in all three ethnic groups. Importantly, a subset of transcripts (hundreds to one thousand) was detected in only one or two ethnic groups. Using two-way ANOVA (disease state and ethnicity), a subset of 6479 transcripts was identified with p-value less than 0.01 in the statistical test and was selected and further used in data quality control. Data QC indicated that patient samples clustered well with respect to both ethnicity and normal versus tumor tissue. Additional analytical methods included K-means 2-Dimensional clustering and Principal Component Analysis. From these analyses, we identified ethnic-specific expression patterns in the matched normal and tumor tissue samples. We are completing these studies by increasing sample size and matching for stage of diagnosis, mapping clusters of differentially-expressed genes in pathway analysis, and validation by real-time PCR. In the longer term, DNA copy number variation (CNV) and chromosomal alterations will be investigated by high density arrays. Summary: These preliminary analyses shows that high quality gene expression data can be generated from FFPE samples, and that ethnic specific gene expression differences can be detected in tumor and matched normal breast tissue samples across ethnic groups.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2024.

Practice parameter: corticosteroid treatment of Duchenne dystrophy: report of the Quality Standards Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society

BACKGROUND

The Quality Standards Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society develop practice parameters as strategies for patient management based on analysis of evidence.

OBJECTIVE

To review available evidence on corticosteroid treatment of boys with Duchenne dystrophy.

METHODS

Relevant literature was reviewed, abstracted, and classified. Recommendations were based on a four-tiered scheme of evidence classification, and areas for future research are defined.

RESULTS

Seven class I studies and numerous less rigorous trials all demonstrated that corticosteroid treatment for 6 months with prednisone (0.75 or 1.5 mg/kg/day) increased muscle strength, performance, and pulmonary function and significantly slowed the progression of weakness. Two class I trials examined the effect of lower dosage of prednisone (0.30 and 0.35 mg/kg/day), demonstrated lesser but similar benefits, and showed a lower frequency of side effects (e.g., weight gain). The only significant side effects in all class I trials were weight gain and development of a cushingoid facial appearance. One longer-term trial of daily prednisone (0.3 to 0.7 mg/kg/day), a class III study, showed prolongation of functional ability and slower progression of weakness in patients during 3 years of treatment. One class IV, open trial of alternate-day prednisone (2 mg/kg for 2 months, then two-thirds dose every other day) extended ambulation by approximately 2 years in treated compared with untreated patients. Deflazacort, a corticosteroid similar in structure to prednisone, produced similar improvement in muscle strength and function with a similar side effect profile.

CONCLUSIONS

Prednisone has been demonstrated to have a beneficial effect on muscle strength and function in boys with Duchenne dystrophy and should be offered (at a dose of 0.75 mg/kg/day) as treatment. If side effects require a decrease in prednisone, tapering to dosages as low as 0.3 mg/kg/day gives less robust but significant improvement. Deflazacort (0.9 mg/kg/day) can also be used for the treatment of Duchenne dystrophy in countries in which it is available. Benefits and side effects of corticosteroid therapy need to be monitored. The offer of treatment with corticosteroids should include a balanced discussion of potential risks.

The UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase gene is mutated in recessive hereditary inclusion body myopathy

Hereditary inclusion body myopathy (HIBM; OMIM 600737) is a unique group of neuromuscular disorders characterized by adult onset, slowly progressive distal and proximal weakness and a typical muscle pathology including rimmed vacuoles and filamentous inclusions. The autosomal recessive form described in Jews of Persian descent is the HIBM prototype. This myopathy affects mainly leg muscles, but with an unusual distribution that spares the quadriceps. This particular pattern of weakness distribution, termed quadriceps-sparing myopathy (QSM), was later found in Jews originating from other Middle Eastern countries as well as in non-Jews. We previously localized the gene causing HIBM in Middle Eastern Jews on chromosome 9p12-13 (ref. 5) within a genomic interval of about 700 kb (ref. 6). Haplotype analysis around the HIBM gene region of 104 affected people from 47 Middle Eastern families indicates one unique ancestral founder chromosome in this community. By contrast, single non-Jewish families from India, Georgia (USA) and the Bahamas, with QSM and linkage to the same 9p12-13 region, show three distinct haplotypes. After excluding other potential candidate genes, we eventually identified mutations in the UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE) gene in the HIBM families: all patients from Middle Eastern descent shared a single homozygous missense mutation, whereas distinct compound heterozygotes were identified in affected individuals of families of other ethnic origins. Our findings indicate that GNE is the gene responsible for recessive HIBM.

US-guided fine needle aspiration versus coarse needle biopsy of thyroid nodules

OBJECTIVE

The aim of this study was retrospectively to evaluate ultrasound (US) guided fine-needle aspiration (FNA), in combination with US-guided coarse-needle biopsies, (CNB) from solitary or dominant thyroid nodules routinely performed during a 2 year period.

METHODS

Seventy seven patients were biopsied using US-guided FNA and CNB. FNA was performed using a 21-Gauge needle and CNB using a 18-Gauge single action spring-activated needle biopsy system. The biopsies were performed with local anaesthesia. The Department of Pathology routinely examined the biopsy specimens. The retrieval rate in obtaining material for diagnostic evaluation was FNA (97%), CNB (88%), FNA and CNB (100%).

RESULTS

In all, 41 of the 77 patients underwent neck-surgery. The surgical specimens were used to determine the results of diagnosing neoplasia. The accuracy, sensitivity and specificity for FNA were 80, 83, and 77%. For CNB 86, 78, and 94%. For both FNA and CNB 80, 89 and 73%. The diagnostic value of the two methods showed no significant difference (P < 0.05). CNB revealed contrary to FNA, however, one additional cancer. Also a higher number of false positive findings was noticed using FNA. No serious complications were registered. Adequate biopsies were obtained in all the patients using the combination of US-guided FNA and CNB. No patient underwent rebiopsy.

CONCLUSIONS

The study demonstrated that neither US-guided CNB nor the combination of US-guided FNA and CNB were superior to US-guided FNA. US-guided CNB is only recommended in few selected patients.

Analysis of CpG C-to-T mutations in neurofibromatosis type 1. Mutations in brief no. 129. Online

Neurofibromatosis type 1 (NF1) is a dominant disorder caused by mutations in the NF1 gene; approximately 100 NF1 gene mutations have been published. The CpG C-to-T transition is a frequent mutation mechanism in genetic disorders. To estimate its frequency in NF1, we employed a PCR-restriction digestion method to examine 17 CpGs in 65 patients, and also screened for a CpG nonsense transition (R1947X) that occurs in 1-2% of patients. The analysis revealed disease-related CpG C-to-T transitions (including a nonsense mutation that may be as frequent as R1947X) as well as a benign variant and another mutation at a CpG. Four patients showed CpG mutations in analysis of 18 sites (17 surveyed by restriction digest, plus the R1947X assay), including three C-to-T transitions and one C-to-G transversion. These 18 sites represent one-fifth of the 91 CpGs at which a C-to-T transition would result in a nonsense or nonconservative missense mutation. Thus, it is feasible that the CpG mutation rate at NF1 might be similar to that seen in other disorders with a high mutation rate, and that recurrent NF1 mutations may frequently reside at CpG sites.

Changes in cardiac muscle mass and function in hemodialysis patients during growth hormone treatment

BACKGROUND

Adult patients with chronic renal failure (CRF) often show symptoms as fatigue, wasting, and reduced working capacity with concomitant findings of reduced cardiac performance and muscle mass. This state may in part be caused by an imbalance in the somatostatin/somatomedine axis resulting in increased catabolism. During an attempt to correct this catabolic state by administration of exogenous growth hormone, cardiac muscle mass and performance were studied.

METHODS

In a double-blind, placebo-controlled 6-month study comprising 20 adult enfeebled hemodialysis patients, 9 patients were treated with a single daily subcutaneous injection of recombinant human growth hormone (rhGH) 4 IU/m2 and 11 with placebo injections. Left ventricular muscle mass (LVM) and ejection fraction (EF) were evaluated by echocardiography and the maximal working capacity (MWC) was measured by a bicycle exercise test performed before and after the treatment period. Supplementary electrocardiography (ECG) was performed before and after 6-month treatment.

RESULTS

Median LVM increased significantly from 172 to 220 g (p = 0.03) in the rhGH-treated group, while an insignificant decrease was observed in the placebo group from 281 to 200 g (p = 0.3). The EF showed no significant changes in the two groups. MWC showed a slight, insignificant decrease in both groups. From ECG no significant ST deviations were found and no significant changes regarding B-Hb, blood pressure or pulse were observed in the two groups. Irregular heart rhythm aggravated in one patient during the first month of treatment with rhGH, but was overcome by a -blocking agent.

CONCLUSION

The treatment with rhGH of adult chronic hemodialysis patients for 6 months increased the left ventricular mass significantly, but without any effect on ejection fraction or maximal working capacity. No electrocardiographic signs of ischemia were associated with the increasing muscle mass and only one patient developed symptoms that might relate to ischemia. No changes in B-Hb, blood pressure or pulse were observed during the treatment period.

Germline mutations in NF1 patients with malignancies

We have analyzed 98.5% of the coding region of the NF1 gene at the cDNA level in seven NF1 patients who developed malignant peripheral nerve sheath tumors. Seven germline mutations were detected in six individuals: a 6-bp in-frame deletion in exon 28, a splice acceptor mutation in intron 31 resulting in a premature stop of translation, a missense mutation in exon 38, and three total NF1 gene deletions. In one of the patients with a total NF1 gene deletion, a missense mutation in exon 16 on the other NF1 allele was detected. These data indicate that NF1 patients developing malignant neoplasms can have any type of NF1 germline mutation such as a total gene deletion, a frameshift mutation, an in-frame deletion, or a missense mutation. We conclude that in our series no specific type of NF1 germline mutation was found in NF1 individuals with malignancies, but that large NF1 gene deletions were more frequently found in this group than reported for the general population of NF1 individuals. Genes Chromosomes Cancer 26:376-380, 1999.

Homozygosity mapping to the USH2A locus in two isolated populations

Usher syndrome is a group of autosomal recessive disorders characterised by progressive visual loss from retinitis pigmentosa and moderate to severe sensorineural hearing loss. Usher syndrome is estimated to account for 6-10% of all congenital sensorineural hearing loss. A gene locus in Usher type II (USH2) families has been assigned to a small region on chromosome 1q41 called the UHS2A locus. We have investigated two families with Usher syndrome from different isolated populations. One family is a Norwegian Saami family and the second family is from the Cayman Islands. They both come from relatively isolated populations and are inbred families suitable for linkage analysis. A lod score of 3.09 and 7.65 at zero recombination was reached respectively in the two families with two point linkage analysis to the USH2A locus on 1q41. Additional homozygosity mapping of the affected subjects concluded with a candidate region of 6.1 Mb. This region spans the previously published candidate region in USH2A. Our study emphasises that the mapped gene for USH2 is also involved in patients from other populations and will have implications for future mutation analysis once the USH2A gene is cloned.

Clinical and biochemical phenotype of familial anterior hypopituitarism from mutation of the PROP1 gene

We have investigated the largest family with PROP1 deficiency reported to date. Eight patients, aged 17-40 yr, in two sibships with possibly related mothers but no parental consanguinity were 109-137 cm in height (-8.8 to [minus]5.9 SD score) and sexually immature. None had received hormonal therapy. Affected individuals had similarities to and significant differences from patients with insulin-like growth factor I (IGF-I) deficiency due to GH receptor deficiency (GHRD) and normal thyroid function and sexual maturation. The differences from patients with GHRD include normal hand and foot length in seven of eight, normal arm span with relatively long legs, and persistence of extremely low levels of IGF-I into adulthood; similarities include the degree of growth failure, frequent but not uniform increased body weight for height or body mass index, and the presence of limited elbow extensibility and blue scleras in six of eight. Three patients had markedly increased sella turcica area for height age and bone age, determined from lateral skull films. The degree of sellar enlargement is variable in these two sibships. Serum GH concentrations were 0.1 ng/mL or less after clonidine ingestion. Other results were: IGF-I, 3-11 ng/mL (normal, 114-492); IGF-II, 185-299 ng/mL (normal, 358-854); IGF-binding protein-1 (IGFBP-1), 12-200 ng/mL (normal, 13-73); IGFBP-2, 60-384 ng/mL (normal, 55-480); and IGFBP-3, 400-600 ng/mL (normal, 2000-4000). The very low IGF-I and normal IGFBP-1 and -2 levels differ from findings in adults with GHRD. The GH-binding protein concentration was 58-799 pmol/L, with two patients above the normal range of 66-306. LH and FSH levels were very low, with no sex differences between serum levels of estradiol (3-6 pg/mL) and testosterone (3-10 ng/dL). PRL levels all were below normal. Serum concentrations of cortisol were normal. Serum T4 levels were uniformly low (<0.2-0.5; normal, 0.8-2.7 ng/dL), free T3 values were less than normal in seven of eight subjects, and total T3 concentrations were below normal in five of eight, but TSH levels were normal (0.58-2.18; normal, 0.4-4.2 mU/L). DNA specimens from affected individuals in each sibship were homozygous for a 2-bp deletion in exon 2 of the PROPI (Prophet of Pit-I) gene, which causes a shift of reading frames and results in a translational stop signal at codon 109. The mutant protein, when expressed in vivo lacks DNA-binding and transcriptional activation functions. The consequences of the PROPI abnormality in this and other kindreds include gonadotropin deficiency as well as the expected deficiencies in products of Pit-I-dependent somatotrophs, lactotrophs, and thyrotrophs. The severity of the hormone deficiency phenotype is compatible with the complete loss of PROP1 activity.

Growth hormone receptor mutations in children with idiopathic short stature

Homozygous or compound heterozygous mutations in the GH receptor (GHR) gene result in GH insensitivity syndrome. Previous reports have shown that some heterozygous mutations may induce a partial insensitivity to GH, but others appear to have limited effect on growth. To investigate further these observations, we analyzed the GHR gene in 17 subjects with idiopathic short stature (ISS). All subjects had a height 2 SD or more below the mean and/or abnormal growth velocity. In addition, serum GH levels were 10 ng/mL or more and insulin-like growth factor I levels were normal or low. A novel heterozygous mutation resulting in a valine to isoleucine change (V144I) in exon 6 in the extracellular domain was found in one subject. His mother and one brother had significant short stature and also had the identical mutation. Affected family members also had a polymorphism in exon 6 of the GHR gene, which has been present in other subjects who had short stature and heterozygous mutations of the GHR gene. The other subjects with ISS had normal GHR genes. However, eight subjects had neutral polymorphisms distributed throughout the GHR locus. Accumulating evidence suggests that GHR gene mutations account for up to 5% of all ISS patients. These mutations should be considered when other causes of short stature have been eliminated.

Clinical, serologic, and immunogenetic features of familial idiopathic inflammatory myopathy

OBJECTIVE

To describe the clinical, serologic, and immunogenetic features of familial idiopathic inflammatory myopathy (IIM) and to compare these with the features of sporadic IIM.

METHODS

Clinical signs and symptoms, autoantibodies, HLA-DRB1 and DQA1 alleles, and GM/KM phenotypes were compared among 36 affected and 28 unaffected members of 16 unrelated families in which 2 or more blood relatives developed an IIM. In addition, findings in patients with familial IIM were compared with those in 181 patients with sporadic IIM. The families included 3 pairs of monozygotic twins with juvenile dermatomyositis, 11 families with other siblings or relatives with polymyositis or dermatomyositis, and 2 families with inclusion body myositis.

RESULTS

The clinical features of familial IIM were similar to those of sporadic IIM, although the frequency of myositis-specific autoantibodies was lower in familial than in sporadic IIM. DRB1*0301 was a common genetic risk factor for familial and sporadic IIM, but contributed less to the genetic risk of familial IIM (etiologic fraction 0.35 versus 0.51 in sporadic IIM). Homozygosity at the HLA-DQA1 locus was found to be a genetic risk factor unique to familial IIM (57% versus 24% of controls; odds ratio 4.2, corrected P = 0.002).

CONCLUSION

These findings emphasize that 1) familial muscle weakness is not always due to inherited metabolic defects or dystrophies, but may be the result of the development of IIM in several members of the same family, and 2) multiple genetic factors are likely important in the etiology and disease expression of familial IIM, as is also the case for sporadic myositis, but DQA1 homozygosity is a distinct risk factor for familial IIM.

Clinical, biochemical, and molecular investigations of a genetic isolate of growth hormone insensitivity (Laron's syndrome)

We have characterized the GH receptor mutation that is responsible for extreme short stature and GH insensitivity in a Bahamian genetic isolate. Heights of affected individuals ranged from -4.0 to -6.3 SD. Like others with Laron's syndrome, they had normal to high serum GH concentrations and low serum insulin-like growth factor I concentrations. Circulating levels of GH-binding protein activity were below limits of detection. Amplification of exons 2-7 and screening with single strand conformational polymorphism analysis located an abnormality in exon 7. Sequencing identified homozygosity for a C to T transition in the third position of codon 236. Reverse transcription and PCR amplification of complementary DNA from lymphocytes showed that this same sense mutation generated a new splice donor site 63 bp 5' to the normal exon 7 splice site. This novel site was used to the exclusion of the normal site in homozygotes. Both normal and variant messenger ribonucleic acid species were detected in heterozygotes. The predicted protein lacks 21 amino acids, including those defining the WS-like motif of the GH receptor extracellular domain. The high frequency of Laron's syndrome in this isolated island population probably reflects the introduction of the G236 splice mutation by a settler early in the 300-yr history of English settlement.

A gene for a severe lethal form of X-linked arthrogryposis (X-linked infantile spinal muscular atrophy) maps to human chromosome Xp11.3-q11.2

X-linked arthrogryposis Type I (X-linked infantile spinal muscular atrophy) is a rare disorder showing hypotonia, areflexia, and multiple congenital contractures (arthrogryposis) associated with loss of anterior horn cells and death in infancy. We have studied an X-linked arthrogryposis family using highly polymorphic microsatellite markers throughout the X chromosome. Meiotic breakpoint analysis (concordance analysis) based on shared regions of the founder X chromosome was successful in localizing the X-linked arthrogryposis gene to Xp11.3-q11.2. In this region, the highest two-point lod score was found with DXS991 (Zmax = 2.63, theta = 0.00). In multipoint linkage analysis covering the entire X chromosome, only the region defined by MAOB and DXS991 showed positive lod scores and all other regions showed negative lod scores. These data establish the first gene mapping assignment of an X-linked lethal form of human lower motor neuron disease.

Familial inclusion body myositis: evidence for autosomal dominant inheritance

We report a kindred manifesting clinical features and muscle biopsy findings of inclusion body myositis (IBM). In this family, multiple members were affected in two generations with direct male-to-male and female-to-male transmission. This is the first reported instance of autosomal dominant inheritance in IBM, which usually occurs sporadically or, rarely, may be transmitted as an autosomal recessive disorder.

242 breakpoints in the 200-kb deletion-prone P20 region of the DMD gene are widely spread

Using whole cosmids as probes, we have mapped 242 DMD/BMD deletion breakpoints located in the major deletion hot spot of the DMD gene. Of these, 113 breakpoints were mapped more precisely to individual restriction enzyme fragments in the distal 80 kb of the 170-kb intron 44. An additional 12 breakpoints are distributed over the entire region, with no significant local variation in frequency. Furthermore, deletion sizes vary and are not influenced by the positions of the breakpoints. This argues against a predominant role of one or a few specific sequences in causing frequent rearrangements. It suggests that structural characteristics or a more widespread recombinogenic sequence makes this region so susceptible to deletion. Our study revealed several RFLPs, one of which is a 300-bp insertion/deletion polymorphism. Abnormally migrating junction fragments are found in 81% of the precisely mapped deletions and are highly valuable in the diagnosis of carrier females.

Molecular and clinical correlations of deletions leading to Duchenne and Becker muscular dystrophies

Human DMD cDNA probes have been used to delineate possible deletions in 160 affected males. Approximately 56% of these individuals had detectable deletions, 29% of which mapped to a region centered around 500 kb from the 5' end of the gene whereas 69% mapped to a region located centrally 1,200 kb from the 5' end. We have observed no correlation between the extent of a deletion, its location, and clinical severity of the associated disease. For some cases with deletions in the two high-frequency deletion regions, the predicted effect upon translational reading frame of the resultant dystrophin mRNA did not correlate with the associated disease phenotype.

Prenatal diagnosis of Duchenne muscular dystrophy: prospective linkage analysis and retrospective dystrophin cDNA analysis

The accuracy of DNA-based prenatal diagnosis of Duchenne muscular dystrophy (DMD) was determined by study of 174 families. Only 60% of families had a living affected male, and 63% had history of a single affected male. Prenatal diagnosis was declined by 47% of mothers whose DNA studies predicted a carrier risk below 2%, and none have had affected sons. Fetal risk was estimated prospectively by linkage analysis using intragenic and flanking RFLPs and retrospectively using dystrophin cDNA analysis for families whose linkage estimates lacked precision. Diagnostic accuracy was determined by comparing predictions with 40 male pregnancy outcomes. On the basis of linkage analysis, we anticipated 3.2 DMD males and observed 3.0. Retrospective cDNA analysis identified deletions in 2 of these 3 males. The combined use of linkage and cDNA deletion analysis provided a highly accurate method for prenatal diagnosis of DMD.

Complementary DNA probes for the Duchenne muscular dystrophy locus demonstrate a previously undetectable deletion in a patient with dystrophic myopathy, glycerol kinase deficiency, and congenital adrenal hypoplasia

Genomic DNA from a patient with dystrophic myopathy, glycerol kinase deficiency, and congenital adrenal hypoplasia was investigated using cDNA probes for the Duchenne muscular dystrophy (DMD) locus. Genomic probes had not detected a deletion in this patient. Southern analysis of Hind III-digested genomic DNA from this patient identified a deletion when the three distal Hinc II DMD cDNA fragments were used as probes. The deletion began in the genomic region corresponding to the 1.05-kb Hinc II cDNA fragment and extended through the 3' end of the DMD gene. This represents a centromeric breakpoint that corresponds to a position approximately 10.2-10.6 kb from the 5' end of the 14-kb DMD cDNA. These investigations demonstrate the value of the DMD cDNA probes for improved diagnoses in patients with molecular lesions involving the DMD locus. Furthermore, this novel deletion involving the coding portion of the 3' end of the DMD gene assists in the ordering of exons in this region and will provide insight into the functional role of the carboxy terminus of the DMD gene product, dystrophin.

Regulation of human histone gene expression: transcriptional and posttranscriptional control in the coupling of histone messenger RNA stability with DNA replication

The extent to which transcriptional and posttranscriptional regulation contributes to the coupling of histone gene expression and DNA replication was examined during the cell cycle in synchronized HeLa S3 cells. Rates of transcription were determined in vitro in isolated nuclei. A 3-5-fold increase in cell cycle dependent histone gene transcription was observed in early S phase, prior to the peak of DNA synthesis. This result is consistent with a previous determination of histone mRNA synthesis in intact cells [Plumb, M., Stein, J., & Stein, G. (1983) Nucleic Acids Res. 11, 2391]. The transcription of these genes did not change appreciably after inhibition of DNA replication by hydroxyurea treatment, although Northern blot analysis indicated that cellular levels of histone mRNA decreased rapidly in the presence of the drug. Total cellular levels of histone mRNA closely parallel the rate of DNA synthesis as a function of cell cycle progression, reaching a maximal 20-fold increase as compared with non S phase levels. This DNA synthesis dependent accumulation of histone mRNA occurs predominantly in the cytoplasm and appears to be mediated primarily by control of histone mRNA stability. Changes in nuclear histone mRNA levels were less pronounced. These combined observations suggest that both transcriptional regulation and posttranscriptional regulation contribute toward control of the cell cycle dependent accumulation of histone mRNA during S phase, while the stability of histone mRNA throughout S phase and the selective turnover of histone mRNAs, either at the natural termination of S phase or following inhibition of DNA synthesis, are posttranscriptionally regulated.(ABSTRACT TRUNCATED AT 250 WORDS)

Tachyphylaxis of juxtaglomerular epithelioid cells to angiotensin II. Differences between the electrical membrane response and renin secretion

A study has been made of desensitization of the depolarizing response to angiotensin II of juxtaglomerular epithelioid and vascular smooth muscle cells in the mouse kidney afferent arteriole, of media cells from the mesenteric artery as well as of cultured smooth muscle and mesangial cells. In all cell types, desensitization to this effect of angiotensin II was observed. There was no cross-desensitization between angiotensin II and other depolarizing agonists. Hence, it is concluded that this desensitization is specific, i.e. of the tachyphylaxis type. Substances interfering with receptor recycling, such as chloroquine and monensin, did not block the recovery of the cells from desensitization after removal of the octapeptide. Desensitization to the action of angiotensin II was also observed with respect to its vasoconstrictor effect in the isolated perfused rat kidney. In contrast there was no desensitization of renin secretion in the isolated perfused rat kidney, nor in isolated hydronephrotic mouse tissue, nor in microdissected rat glomeruli.

[The biological effects of coordination compounds of transitional metals. 6. Effect of 4-methyl-2-aminopyridine-palladium chloride and cis-dichlorodiammine-platinum(II) on retroviruses and the virus-associated RNA polymerase of the influenza virus]

The effect on retroviruses of two transition metal complexes of known antiviral activity, 4-methyl-2-amino-pyridine-palladium-chloride (MAP) and cis-dichloro-diammine-platinum(II) (cis-DDP) has been investigated. The experiments included the evaluation of the action of compounds on virus particle-associated reverse transcriptase in exogenous assays, on virus propagation in persistently infected cell cultures and on virus infectivity in mice. In disrupted viruses and in the absence of excess protein, the reverse transcriptase was inhibited by MAP but not by cis-DDP. The same results were obtained when examining the activity of the virus-associated RNA polymerase of influenza virus A/WSN. Both compounds did not inhibit the replication of retroviruses in cell cultures, except at high dose levels which exerted toxic action on both cells and virus formation. The leukemogenicity of Rauscher murine leukemia virus was strongly inhibited when the virus had been incubated with MAP before inoculation. A similar treatment with cis-DDP did not influence viral leukemogenicity. Despite somewhat different results with both compounds tested, we conclude from the present results that the above mentioned compounds cannot be considered as antiretroviral drugs.

Renin release from different parts of rat afferent arterioles in vitro

A technique was designed to study renin release from superfused rat glomeruli with short attached arterioles (SAG), from single glomeruli with long attached arterioles (LAG), and from single afferent arterioles (AA). The preparations obtained by magnetic isolation and microdissection were superfused individually, and the renin release was measured by an ultramicroradioimmunoassay with a detection limit of 3 X 10(-9) Goldblatt units. The renin content of one SAG was about one-fifth of that contained in one AA. Isoprenaline (10(-5) M) did not change renin release from SAG, whereas renin release from AA and LAG increased threefold (P less than 0.01). A 30-mosmol/kg reduction in medium sodium chloride concentration increased renin release from SAG 50% (P less than 0.01). This challenge caused no change in renin release from AA. It is concluded that the isoprenaline-sensitive juxtaglomerular (JG) cells are located in the afferent arteriole only at some distance from the glomerulus, whereas those cells sensitive to sodium chloride are located within and/or close to the glomerulus.

Effects of adenosine on renin release from isolated rat glomeruli and kidney slices

Adenosine produced by the macula densa cells in response to changes in the tubular NaCl-concentration has been suggested to inhibit renin release in vivo. In order to test this suggestion we studied: incubated kidney cortical slices (KS) which contain both the macula densa and the entire afferent arteriole; superfused single microdissected glomeruli (LAG) without macula densa but with the afferent arteriole preserved; and superfused batches of selected glomeruli (SAG) containing only the juxtaglomerular cells closest to the glomerulus. For superfusion and incubation a bicarbonate Ringer solution was used. The specificity of the renin release process was validated by measuring adenylate kinase as a marker for cytoplasmatic leak. Adenosine (10 micrograms/ml) halved basal renin release from incubated KS as compared to controls (P less than 0.001, n = 8, 8). Renin release from LAG stimulated by calcium depletion was also inhibited (P less than 0.05, n = 8, 9) whereas basal release was not affected (n = 6, 12). No effect was detected neither on basal nor on calcium stimulated renin release from SAG. We conclude that adenosine inhibits renin release in vitro by a mechanism independent of a functioning nephron, and which involves only the JG-cells located in the afferent arteriole at some distance from the glomerulus.

Inhibition of DNA replication coordinately reduces cellular levels of core and H1 histone mRNAs: requirement for protein synthesis

Cellular levels of H1 and core histone mRNAs have been examined in exponentially growing HeLa S3 cells as a function of DNA synthesis inhibition under varying concentrations of three DNA synthesis inhibitors. Total cellular histone mRNAs were analyzed by Northern blot hybridization, and their relative abundance was shown to be stoichiometrically and temporally coupled to the rate of DNA synthesis. In the presence of cytosine arabinoside, hydroxyurea, or aphidicolin, a rapid, proportionate decrease of histone mRNA levels resulted in an apparent mRNA half-life of less than 10 min. Using inhibitors of transcription and translation, we show that transcription is not necessary for the coordinate decrease of histone mRNA levels that occurs when DNA synthesis is inhibited. When protein synthesis is inhibited by addition of cycloheximide, core and H1 histone mRNAs do not decrease in parallel with reduced rates of DNA synthesis but instead are stabilized and accumulate with time, thus uncoupling histone mRNA levels and DNA replication. These last observations suggest that protein synthesis, either of histones or of some unidentified regulatory molecules, is required for the stoichiometric turnover of H1 and core histone mRNAs coordinate with reduced rates of DNA synthesis.

Requirement of protein synthesis for the coupling of histone mRNA levels and DNA replication

H1 and core histone mRNA levels have been examined in the presence of protein synthesis inhibitors with different mechanisms of action. Total HeLa cell RNAs were analyzed by Northern Blot hybridization using cloned human histone genes as probes. Inhibition of DNA replication resulted in a rapid decline in histone mRNA levels. However, in the presence of cycloheximide or puromycin, H1 and core mRNAs did not decrease in parallel with DNA synthesis, but were stabilized and accumulated. Inhibition of DNA synthesis with hydroxyurea after the inhibition of protein synthesis did not lead to a decline in histone mRNA levels. These results suggest that synthesis of a protein(s)--perhaps a histone protein(s)--is required for the coordination of DNA synthesis and histone mRNA levels.

An oscillating intratubular pressure response to alterations in Henle loop flow in the rat kidney

We describe in gas anesthetized rats an oscillating intratubular pressure response, probably of vascular origin, sensitive to small physiological changes in fluid delivery to the distal tubule. The oscillation apparently indicates that an adjustment of vascular resistance is in operation, but at present it reveals neither the effector site (afferent and/or efferent arteriole) nor the effector mechanism (vasoconstriction and/or dilatation). The renin-angiotensin system seems to be involved in this phenomenon.

Isolated glomeruli in vitro: an approach to the macula-densa-mediated renin release

The introduction of an assay for adenylate kinase into the study of renin release from isolated glomeruli is a useful tool in determining the specificity of the release process. Interestingly, even the absolute values of AK activity yield information that might be of value in understanding the effects on net renin output in media of grossly unphysiological composition. In qualitative terms, though, the AK measurements provide evidence against an unspecific loss of cytoplasmatic proteins as the cause of increased release of renin after removal of calcium or sodium bicarbonate. This renin release must have come from a compartment other than the cytoplasma of the juxtaglomerular cells. The in vivo position of the juxtaglomerular cells remaining in the present preparation, situated at the polkissen only few microns from the only hypoosmotic area in the body, suggests that the extreme osmosensitivity of renin release from isolated glomeruli represents a physiologic phenomenon. Because urea and sodium chloride are the predominant solutes in the tubular fluid at the macula densa, available data from isolated glomeruli are consistent with a macula densa feedback mechanism if it is accepted that a decrease in tubular sodium chloride concentration (and osmolality) increases the release of renin.

Histone proteins in HeLa S3 cells are synthesized in a cell cycle stage specific manner

The synthesis of histone proteins in G1 and S phase HeLa S3 cells was examined by two-dimensional electrophoretic fractionation of nuclear and total cellular proteins. Newly synthesized histones were detected only in S phase cells. Histone messenger RNA sequences, as detected by hybridization with cloned human histone genes, were present in the cytoplasm of S phase but not G1 cells.

Tumor promoter-stimulated synthesis of Mason-:Pfizer monkey virus

The tumor promoter 12-0-tetradecanoyl-phorbol-14-acetate (TPA) increases by severalfold the synthesis of Mason-Pfizer monkey virus (MPMV), a type D retrovirus, when the virus is growing in human embryo kidney (HEK) cells. The effect is transient and paralleled by a striking morphological alteration of the cells. The optimal TPA concentration for stimulation is 5 ng. ml-1. Contrary to infected HEK cells, TPA induces at similar concentrations neither stimulation of MPMV synthesis nor altered morphology in persistently MPMV-infected cells of the continuous human tumor cell line A 204.

Renin release from isolated rat glomeruli: seasonal variations and effects of D600 on the response to calcium deprivation

1. The effects of calcium deprivation and D600 on the rate of renin release and seasonal variations in the response were studied on juxtaglomerular cells from a preparation of isolated rat glomeruli superfused in vitro. 2. Reduction of superfusate calcium concentration caused an increase in renin release, which was significantly higher during the summer (May-August) than during the rest of the year. 3. Addition of D600 (2 X 10(-4) M) to a calcium-free medium in the low responsive period caused a markedly increased renin release. In the high responsive period renin release increased more rapidly and to a higher level initially than observed in the control lines without D600. 4. It is suggested that the effect of calcium on renin release predominantly is mediated by changes in calcium bound to the plasma membrane of the juxtaglomerular cell. The sensitivity of this cell to changes in the extracellular calcium concentration seems to be regulated and varies with season, possibly due to regulation of the amount of calcium bound to the membrane.

Renin release from isolated rat glomeruli: effects of colchicine, vinca alkaloids, dimethylsulphoxide, and cytochalasins

1. Preparations of isolated glomeruli were superfused and the effects of colchicine, the vinca alkaloids, and the cytochalasins A, B, D, and E investigated on basal renin release and the response of the glomeruli to osmotic stress. 2. Colchicine (10(-3) M) had no effect, whereas vinblastine and vincristine (10(-5) M) caused a progressive increase in basal renin release from isolated glomeruli. 3. After 60 min exposure to either colchicine or the vinca alkaloids, the first renin release response to a hypoosmotic challenge (reduction in sucrose or sodium chloride concentration) was depressed while that of the second (after 120 min exposure) was enhanced. 4. Addition of 0.5% dimethylsulphoxide (DMSO) and each of the cytochalasins A, B, D, and E (5 micrograms/ml.) had no significant effect on basal renin release. 5. DMSO (0.5%) depressed the release response to the first 20 m-osmole/kg reduction in medium osmolality obtained by lowering the sucrose concentration. This effect had vanished at the time of the second 20 m-osmole stimulus (120 min). 6. The normal response to the first 30 m-osmole/kg reduction in NaCl concentration (and medium osmolality) was abolished by 0.5% DMSO. Rather, a depressed release compared to unstimulated control experiments was observed. The response to the second stimulus in the presence of DMSO was about half that of control experiments. 7. Following the first hypoosmotic stimulus (by lowering the concentrations of sucrose of NaCl) the cytochalasins A, B, D and E (5 micrograms/ml.) caused an increased release of renin which persisted throughout the length of the experiment. The cytochalasins used were equally potent in this respect. 8. The results are in agreement with previous findings, suggesting that renin release from the juxtaglomerular cells adhering to isolated glomeruli is mediated through a mechanism different from exocytosis.

Studies on the mechanism of renin release from isolated superfused rat glomeruli: effects of calcium, calcium ionophore and lanthanum

1. The effects of external medium calcium concentration, the ionophore A(23187) and lanthanum on the rate of renin release in vitro were studied with particular emphasis on results obtained from isolated superfused glomeruli of rat kidneys.2. The response to reduction in superfusate calcium concentration from 2 mM was a graded and reversible increase in the rate of renin release. An increase in release was detectable at 0.2 mM calcium; a threefold increase was found 36 min after a change from 2 mM calcium to calcium-free superfusate. A similar relative increase in release resulted from reductions from 0.1 mM to zero calcium, but the absolute amounts of renin released were greater in this latter series. Renin release from kidney cortical slices similarly increased in response to calcium-free incubation medium.3. The effects of A(23187) on renin release were modest. Changing from 2 mM calcium during control periods to calcium-free Ringer with A(23187) added caused an attenuated and more delayed increase in release than the change to calcium-free Ringer without ionophore. This difference in response was abolished when glomeruli were superfused with 0.1 mM calcium during the preceding 1 hr control period. There was no significant difference in renin release from glomeruli exposed to calcium-free EGTA-Ringer with and without A(23187) in the 2 mM calcium series; in the 0.1 mM calcium series the increase in release following a shift to calcium-free EGTA-containing superfusate with A(23187) added was significantly greater than in the absence of the ionophore.4. Addition of lanthanum (1 or 0.05 mM) to calcium-containing as well as calcium-free superfusate resulted in a significant depression of renin release. Subsequent removal of the lanthanum did not restore the rate of release unless EGTA was added; in the latter case a massive increase in renin release occurred resulting in a marked depletion of the remaining renin content of the glomeruli.5. It is concluded that calcium influences renin release by a direct action on the juxtaglomerular cells. The data support the previous suggestion that basal renin release is a function of active, calcium-dependent cell volume regulation - swelling causing an increase in the release; and further suggest that membrane-bound calcium has a direct effect on the cell membrane permeability to renin.6. The results exclude that calcium-stimulated exocytosis is responsible for basal renin release from the juxtaglomerular cells adhering to isolated glomeruli.

Studies on renin release from isolated superfused glomeruli: effects of temperature, urea, ouabain and ethacrynic acid

1. The effects of different energy substrates, of low temperature, of urea, and of ouabain and ethacrynic acid were studied on the rate of renin release from viable juxtaglomerular cells during superfusion of isolated rat glomeruli. 2. Neither lactate nor glutamate altered renin release rate from that observed using glucose as the sole energy substrate. Succinate 10 mM elevated release transiently but did not influence the release caused by reductions in osmolality through lowering sucrose concentration. 3. Peak renin release was more prolonged and returned more slowly to control following reductions in osmolality in phosphate-Ringer than in bicarbonate-Ringer. 4. At 37 degrees C, the peak of renin released induced by hypo-osmolality was smaller and delayed, and returned earlier to control than at 30 degrees C. Reduction in temperature from 30 to 4 degrees C resulted in a 32-fold increase in basal release rate. At 4 degrees C a 20 m-osmole/kg reduction in tonicity caused an additional 2-5-fold increase in release rate. 6. Increasing superfusate osmolality with urea did not affect basal renin release but 100 mM urea suppressed the releasing effect of a 15 mM reduction in NaCl concentration. 7. Ouabain (10(-4) M) caused a small (33 +/- 9%, P less than 0-025) transient increase in renin release. Ethacrynic acid (10(-3) M) provoked a progressive increase in release reaching 100 +/- 15% above control within 50 min. In the presence of both inhibitors the release provoked by hyposmolality was prolonged. 8. It is concluded that renin release in vitro is a function of actively regulated cell volume and it is proposed that a similar mechanism could underline both barorecptor and macula densa controls of renin secretion in vivo.