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Biomedical subjects

M C Gregory

Publications and source records attributed to M C Gregory.

At least 19 recordsLinked to original sources

Expression of mRNA for type IV collagen alpha1, alpha5 and alpha6 chains by cultured dermal fibroblasts from patients with X-linked Alport syndrome.

COL4A5 mutations causing X-linked Alport syndrome (XLAS) are frequently associated with absence of the alpha3, alpha4,alpha5 and alpha6 chains of type IV collagen from basement membranes and increased amounts of the alpha1(IV) and alpha2(IV) chains in glomerular basement membrane. Although many COL4A5 mutations have been described in XLAS, the mechanisms by which these mutations influence the basement membrane appearance of chains other than alpha5(IV) remain poorly understood. In this study, we used dermal fibroblasts from eight normal individuals and nine males with XLAS to test the hypotheses that COL4A5 mutations increase transcription of COL4A1 and suppress transcription of COL4A6. Ribonuclease protection assays revealed that alpha1(IV), alpha5(IV) and alpha6(IV) transcripts were expressed in cultures of dermal fibroblasts. The mRNA levels for alpha1(IV) in eight of nine patients with XLAS were not increased compared to controls; one patient with a large COL4A5 deletion showed significant elevation of alpha1(IV) mRNA levels. No differences in steady-state mRNA levels for alpha6(IV) were found when XLAS fibroblasts were compared with controls, even though little or no alpha6(IV) protein was detectable at the dermal-epidermal junction by immunofluorescence study. This finding suggests that post-transcriptional events account for the absence of alpha6(IV) in the Alport dermal-epidermal junction.

Adolescent

Common ancestry of three Ashkenazi-American families with Alport syndrome and COL4A5 R1677Q.

Mutations in the basement membrane collagen gene COL4A5 cause the progressive renal glomerular nephropathy and typical hearing loss that occur in X-linked Alport syndrome. Nearly all cases involve distinct mutations, as expected for an X-linked disease that significantly reduces the fitness of affected males. A few exceptional COL4A5 mutations appear to be associated with a reduced disease severity and may account for a significant proportion of late-onset Alport syndrome in populations where a founder effect has occurred. The novel mutation reported here, COL4A5 arg1677gln, has been detected in three independently ascertained Ashkenazi-American families, causes a relatively mild form of nephritis with typical onset in the fourth or fifth decade, and may be involved in the etiology of a large proportion of adult-onset hereditary nephritis in Ashkenazi Jews.

Adult

A mutation causing Alport syndrome with tardive hearing loss is common in the western United States.

Mutations in the COL4A5 gene, located at Xq22, cause Alport syndrome (AS), a nephritis characterized by progressive deterioration of the glomerular basement membrane and usually associated with progressive hearing loss. We have identified a novel mutation, L1649R, present in 9 of 121 independently ascertained families. Affected males shared the same haplotype of eight polymorphic markers tightly linked to COL4A5, indicating common ancestry. Genealogical studies place the birth of this ancestor >200 years ago. The L1649R mutation is a relatively common cause of Alport syndrome in the western United States, in part because of the rapid growth and migratory expansion of mid-nineteenth-century pioneer populations carrying the gene. L1649R affects a highly conserved residue in the NC1 domain, which is involved in key inter- and intramolecular interactions, but results in a relatively mild disease phenotype. Renal failure in an L1649R male typically occurs in the 4th or 5th decade and precedes the onset of significant hearing loss by approximately 10 years.

Adolescent

Cost of hypertension treatment.

A retrospective analysis was conducted of the cost of hypertension care at one internal medicine clinic, looking at the cost of office visits, laboratory tests, and medications. Cost of hypertension care was $947 the first year of treatment, $575 the second year, and $420 per year thereafter. Drug costs were the major determinant of cost of care, comprising 80% of the total cost of treatment after the first year of therapy.

Adult

Stress in bone adjacent to dental implants.

Finite element analysis (FEA) was employed to assess patterns of stress in bone adjacent to an implant after application of loads through an attached distal extension cantilever. Under all loading conditions, the highest stresses occurred at the distal cervical bone margin adjacent to the cantilever. In clinical studies, this is not consistently the site of the greatest bone changes seen radiographically. This suggests that extrapolation of FEA studies to clinical implantology should be approached with caution until further data become available on both mechanical properties of bone and patterns of bone remodelling induced by defined functional stresses in mandible and maxillae.

Bone Remodeling

Alport syndrome: clinical update.

This review of the literature on Alport syndrome (AS) places emphasis on genetic and clinical issues related to the sensorineural hearing loss in type III and type IV X-linked AS. The review covers prevalence, medical issues, genetic issues, audiologic findings, vestibular findings, the pathophysiology of hearing loss in type III AS, age- and phenotype-specific normative data and concludes with a discussion regarding future auditory-genetic research with AS.

Auditory Threshold

Hearing loss.

Explore the source record for details and available documents.

Genetic Counseling

Percutaneous native renal biopsy: comparison of a 1.2-mm spring-driven system with a traditional 2-mm hand-driven system.

Over the last few years spring-driven mechanical biopsy guns have been introduced for performing renal biopsies. There has been little research done comparing these guns with traditional hand-driven needles in performing biopsies of native kidneys. We wished to compare our experience with the two needle types. We studied retrospectively the results and complication rates of 155 native kidney biopsies. Sixty-nine were performed with hand-driven 14-gauge needles and eighty-six with 18-gauge, spring-driven biopsy guns. Sufficient tissue for diagnosis was obtained in 96% of cases in the hand-driven group compared with 99% in the biopsy gun group (P = NS). Complications occurred in six cases in the hand-driven group compared with one case in the biopsy gun group (P = 0.02). As expected, the reported number of glomeruli per core in the 14-gauge cores was greater than in the 18-gauge cores (16.5 v 6.2, P < 0.01). This was partially offset by the greater number of passes made with the smaller needle. We conclude that similar results can be expected from both biopsy methods, with a possible slight decrease in complications using biopsy guns with smaller needle diameters.

Adolescent

Mutations in the codon for a conserved arginine-1563 in the COL4A5 collagen gene in Alport syndrome.

We have screened 110 unrelated Alport syndrome kindreds for mutations in the exon 48 region of the COL4A5 collagen gene. Denaturing gradient gel electrophoresis (DGGE) of the PCR-amplified region of exon 48 revealed sequence variants in DNA from affected males and carriers of three unrelated kindreds. All three kindreds have classical Alport syndrome of the juvenile type. DNA-sequencing analyses demonstrated two different single base changes in the codon for arginine-1563 located in exon 48. In Utah kindred 2103, there was a substitution of C by T resulting in the change of the CGA codon for arginine to the translation stop codon TGA. In Utah kindred 2123 and in the Danish kindred A13, there was a C-->T mutation in the noncoding strand changing the same codon to CAA for glutamine. Both mutations were confirmed by allele-specific hybridization on PCR-amplified DNA from other family members.

Adult

X-linked nephrogenic diabetes insipidus mutations in North America and the Hopewell hypothesis.

In X-linked nephrogenic diabetes insipidus (NDI) the urine of male patients is not concentrated after the administration of the antidiuretic hormone arginine-vasopressin. This disease is due to mutations in the V2 receptor gene that maps to chromosome region Xq28. In 1969, Bode and Crawford suggested that most NDI patients in North America shared common ancestors of Ulster Scot immigrants who arrived in Halifax in 1761 on the ship Hopewell. A link between this family and a large Utah kindred was also suggested. DNA was obtained from 17 affected male patients from the "Hopewell" kindred and from four additional families from Nova Scotia and New Brunswick who shared the same Xq28 NDI haplotype. The Utah kindred and two families (Q2, Q3) from Quebec were also studied. The "Hopewell" mutation, W71X, is a single base substitution (G-->A) that changes codon 71 from TGG (tryptophan) to TGA (stop). The W71X mutation was found in affected members of the Hopewell and of the four satellite families. The W71X mutation is the cause of X-linked NDI for the largest number of related male patients living in North America. Other families (Utah, Q2 and Q3) that are historically and ethnically unrelated bear other mutations in the V2 receptor gene.

Amino Acid Sequence

A prospective study on treatment of hypercholesterolemia with lovastatin in renal transplant patients receiving cyclosporine.

Hypercholesterolemia occurs commonly in renal transplant recipients and may contribute to the high cardiovascular morbidity and mortality in these patients. Although an effective hypolipidemic agent, lovastatin has been associated with rhabdomyolysis and acute renal failure in patients on cyclosporin A (CsA). In this study, lovastatin was administered at 10 mg/day for 8 wk followed by 20 mg/day for 12 wk to six renal transplant recipients who were receiving CsA concomitantly. The 10-mg/day dose was effective, but an additional lipid-lowering effect was seen with the 20-mg/day dose. Both serum total cholesterol and low-density lipoprotein cholesterol levels decreased by 27% at the end of the 20 wk of lovastatin administration. Serum high-density lipoprotein cholesterol and triglyceride levels remained unchanged. No significant clinical or laboratory adverse effects were observed, including muscular symptoms, ophthalmologic abnormalities, or alterations in serum creatine kinase, urea nitrogen, creatinine, transaminases, and CsA levels. Peak and trough plasma concentrations of active lovastatin were comparable to those reported in normal subjects receiving a higher lovastatin dose without CsA. It was concluded that the administration of low-dose (10 to 20 mg/day) lovastatin to renal transplant recipients receiving concomitant CsA can be safe and effective in lowering serum cholesterol.

Adult

Family support, physical impairment, and adherence in hemodialysis: an investigation of main and buffering effects.

Patient noncompliance is a pervasive problem among end-stage renal disease (ESRD) patients. Previous studies have implicated social support as an important correlate of adherence behavior in other chronic illness groups, but little research has examined this relationship in a hemodialysis population. The present study examined the main and interactive effects of social support in the family and illness-related physical impairment with regard to patient compliance in a sample of 78 hemodialysis patients. Results indicated that patients holding perceptions of a more supportive family environment exhibited significantly more favorable adherence to fluid-intake restrictions than did patients reporting less family support. Family support was not associated with adherence to dietary restrictions. The effect of family support on fluid-intake adherence was not moderated by level of physical impairment. This pattern suggests that the influence of support on adherence is more attributable to a main or direct effect, as opposed to a buffering process in the face of increased physical impairment.

Activities of Daily Living

Experience with the Astra dental implant system.

The Astra Dental Implant System appears to be a relatively successful and economical method of osseointegration. This article lists its clinical components, explains how the system is fitted and discusses the preliminary results.

Aged

Evaluation of labetalol in elderly patients with essential hypertension.

Labetalol was evaluated in a multicenter, placebo-controlled study of elderly patients (greater than or equal to 60 years) with mild to moderate essential hypertension. After a placebo-washout period, doses were titrated from 100 mg BID to a maximum of 400 mg BID over a 6-week period. Once blood pressure control (standing diastolic blood pressure [SDBP] less than 90 mm Hg and greater than or equal to 10 mm Hg reduction from baseline) was achieved or the maximum allowable dosage had been given, the dosage remained the same until the end of the study. The titration phase was followed by a 4-week maintenance period. Blood pressure control was achieved in 37/54 (69%) of the patients who were treated with labetalol compared with 21/58 (36%) of the patients who received placebo (P less than .001). Twenty-nine (78%) of those controlled on labetalol responded to doses of 200 mg or less BID, and there was no significant difference between groups with respect to orthostatic blood pressure changes. Adverse experiences were generally mild and occurred with similar frequency in the labetalol and placebo groups; six patients who received labetalol and five who received placebo withdrew from the study due to adverse experiences, but in only one case (labetalol) was the adverse experience considered drug-related. In summary, labetalol effectively and safely lowered diastolic blood pressure in the elderly without producing significant orthostatic changes.

Aged