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Biomedical subjects

R David

Publications and source records attributed to R David.

At least 37 records · Page 2Linked to original sources
PubMed2000

Ongoing clinical assessment of the safety profile and efficacy of brimonidine compared with timolol: year-three results. Brimonidine Study Group II.

OBJECTIVE: We compared the safety profile and efficacy of brimonidine 0.2% BID with those of timolol 0.5% BID over 3 years in patients with ocular hypertension and glaucoma. METHODS: Ninety-four eligible patients from an ongoing multicenter, interventional, double-masked clinical trial were followed through year 3, 48 receiving brimonidine 0.2% and 46 receiving timolol 0.5%. Study visits occurred at months 24, 27, 30, 33, and 36. The primary efficacy variable was mean reduction from baseline intraocular pressure (IOP) at trough. Visual acuity, visual fields, and safety variables (adverse events, ocular symptoms, heart rate, blood pressure, and laboratory test results) were monitored throughout the study. RESULTS: The 2 treatment groups were well matched, with no significant differences in demographic or clinical characteristics. Both drug regimens caused significant mean reductions from baseline IOP at trough during year 3 (P < 0.001), with no significant differences between groups at any study visit. The overall mean reduction from baseline IOP at trough was 5.02 mm Hg with brimonidine and 5.57 mm Hg with timolol (P = 0.383). Brimonidine caused reductions in IOP at trough that were equivalent to those with timolol at months 30 and 36 (within the 95% CI). Visual fields were unchanged or improved in 95% of patients in both treatment groups. Both drug regimens appeared to be safe and were well tolerated. Ocular allergy occurred in 2 brimonidine-treated patients (4.2%). There were no statistically significant differences in adverse-event reports and no clinically significant effects on any ocular or systemic safety variable in either group. CONCLUSIONS: Brimonidine 0.2% BID continues to appear to be safe, well tolerated, and effective in the long-term management of ocular hypertension and glaucoma. Over 3 years, it provided sustained IOP-lowering efficacy and visual-field preservation equal to those with timolol 0.5% BID.

Adrenergic alpha-Agonists↗
PubMed2000

Xenopus cadherin-6 is expressed in the central and peripheral nervous system and in neurogenic placodes.

We have cloned the cDNAs encoding the two Xenopus laevis cadherin-6 pseudoalleles (Xcad-6 and Xcad-6'), which belong to the classical type II cadherin subfamily. During embryogenesis, Xcad-6 expression starts at early neurula and increases dramatically until tadpole stages. Whole-mount in situ hybridization revealed that the transcripts are localized in the developing brain and eye. However, most prominent expression was found in the peripheral nervous system, including a major proportion of lateral line structures. Our results implicate an important contribution of cadherin-6 to the formation of placode derived nerves in Xenopus, an observation which has not been described for other species.

Amino Acid Sequence↗
PubMed2000

Immunohistochemical evaluation of estrogen and progesterone receptors in adenoid cystic carcinoma of salivary gland origin.

Adenoid cystic carcinoma (ACC) is a malignant tumor of salivary gland origin, which is characterized by a high rate of local recurrence and distant metastasis even after aggressive surgical treatment. In several studies using various immunohistochemical techniques, estrogen and progesterone receptor (ER and PgR) proteins in salivary gland ACC have been identified and the possible use of endocrine therapy as a treatment modality suggested. On this basis, 27 samples of formalin-fixed paraffin-embedded salivary gland ACC were immunohistochemically evaluated for the presence of ER and PgR. ER was not detected in any of the tumors and PgR was identified in only two cases. Thus, application of hormone therapy to salivary gland ACC is not supported by the results of the present study.

Adult↗
PubMed2000

Phenotype and phenocopy: the relationship between genotype and clinical phenotype in a single large family with multiple endocrine neoplasia type 1 (MEN 1).

BACKGROUND: The majority of reports describing the natural history and prognosis of multiple endocrine neoplasia type 1 (MEN 1) utilize phenotypic rather than molecular genetic criteria to establish a diagnosis of MEN 1. OBJECTIVES AND PATIENTS: We sought to determine the spectrum of endocrine abnormality amongst 152 members (64 gene carriers and 88 noncarriers) of a large MEN 1 family in whom a determination of MEN 1 status had previously been made by phenotype screening. The predictive utility of both clinical and molecular screening techniques are described. RESULTS: A novel IVS2-3 (C-G) MEN1 mutation was identified in affected members of this family. Seven (10%) of 71 individuals satisfying clinical diagnostic criteria for MEN 1 were found to be genetically negative (excluded by mutation analysis and haplotyping) for MEN 1. These cases of MEN 1 phenocopy comprised four cases of primary hyperparathyroidism, two 'nonsecretory' pituitary adenoma and one case of coincident prolactinoma and hyperparathyroidism. Three of the patients with hyperparathyroidism had previously required parathyroidectomy and each had achieved normocalcaemia following parathyroid resection. Predictive genetic testing prospectively identified three children with the MEN 1 genotype. Serum calcium was normal at the time of their initial molecular genetic diagnosis. In each case hyperparathyroidism subsequently developed during adolescence. CONCLUSION: Multiple endocrine neoplasia type 1 phenocopy is an important differential diagnosis in patients exhibiting an multiple endocrine neoplasia type 1 phenotype. This is a relevant consideration, particularly when the diagnosis of multiple endocrine neoplasia type 1 is made using sensitive, but nonspecific, criteria such as mild hyperparathyroidism, pituitary micoadenoma, and hyperprolactinaemia. Confirmatory genetic testing should be undertaken to confirm clinical diagnoses of multiple endocrine neoplasia type 1.

Adult↗
PubMed2000

Pressure changes during reaming with different parameters and reamer designs.

Reaming increases intramedullary pressure and can cause fat intravasation. This study investigated the influence of reaming parameters on pressure changes using the AO, Gray, and Howmedica reamers. Silicone cylindrical shells with 10-, 11-, 16-, 19-, and 20-mm inner diameters were filled with a 1:2 ratio of paraffin and petroleum jelly. The 10- and 11-mm shells were reamed using a 9-mm reamer, the 16-mm shells with a 14-mm reamer, and the 19- and 20-mm shells with an 18-mm reamer. Each experiment was performed seven times while singularly varying driving speeds of 15, 30, and 50 mm per second, with a revolution rate of 150, 250, and 500 revolutions per minute. Using stepwise linear regression analysis, driving speed was the most significant parameter. The lowest pressure increases occurred at the lowest driving speed and the highest revolution rate in all cylinders. The model used for this study did not take into consideration the interaction between the cortical shell and reamer head. The results of this study suggest that reaming should be done at a low driving speed and a high revolution rate using a small cored reamer head, especially during the first reaming steps.

Embolism, Fat↗
PubMed2000

Vitamin D deficiency and secondary hyperparathyroidism: clinical and biochemical associations in older non-institutionalised Southern Tasmanians.

AIM: To determine the prevalence and associations of vitamin D (25-OHD) deficiency in a sample of older Tasmanian subjects. METHODS: A cross-sectional survey of: 109 patients with a mean age of 79 years (range 60-101 years) consecutively admitted to a short stay geriatric rehabilitation ward; 52 community dwelling subjects with a mean age of 75 years (range 64-88 years). Subjects answered a questionnaire, had anthropometric measurements and underwent venepuncture. RESULTS: The main outcome measure was 25 hydroxy vitamin D (25-OHD) level with deficiency defined as <28 nmol/L. Vitamin D deficiency was found in 67% and secondary hyperparathyroidism in 49% of the hospitalised group. Vitamin D deficiency was also found in 17% of the community group, in particular one in three residents of Independent Living Units was deficient. Subjects who were deficient were older (80 years vs 76 years [p<0.001]), had lower body mass index (23.7 kg/m2 vs 25.9 kg/m2 [p<0.001]) and had a lower serum albumin (35 gm/L vs 39 gm/L [p<0.001]). Deficient subjects had poorer physical functional status (p=0.02) and lower activity levels (p<0.001) and reported less habitual sun exposure (p<0.001). Biochemical measures such as parathyroid hormone, alkaline phosphatase and calcium were weakly predictive of vitamin D levels. By stepwise multiple regression analysis, the only significant predictors of vitamin D levels were the Frenchay Activity Index, albumin and calcium. CONCLUSION: Vitamin D deficiency and secondary hyperparathyroidism is common in community living older people who are hospitalised in Southern Tasmania and is associated with increasing age, poor physical function and activity and low reported sun exposure.

Activities of Daily Living↗
PubMed2000

Automatic classification of protein sequences into structure/function groups via parallel cascade identification: a feasibility study.

A recent paper introduced the approach of using nonlinear system identification as a means for automatically classifying protein sequences into their structure/function families. The particular technique utilized, known as parallel cascade identification (PCI), could train classifiers on a very limited set of exemplars from the protein families to be distinguished and still achieve impressively good two-way classifications. For the nonlinear system classifiers to have numerical inputs, each amino acid in the protein was mapped into a corresponding hydrophobicity value, and the resulting hydrophobicity profile was used in place of the primary amino acid sequence. While the ensuing classification accuracy was gratifying, the use of (Rose scale) hydrophobicity values had some disadvantages. These included representing multiple amino acids by the same value, weighting some amino acids more heavily than others, and covering a narrow numerical range, resulting in a poor input for system identification. This paper introduces binary and multilevel sequence codes to represent amino acids, for use in protein classification. The new binary and multilevel sequences, which are still able to encode information such as hydrophobicity, polarity, and charge, avoid the above disadvantages and increase classification accuracy. Indeed, over a much larger test set than in the original study, parallel cascade models using numerical profiles constructed with the new codes achieved slightly higher two-way classification rates than did hidden Markov models (HMMs) using the primary amino acid sequences, and combining PCI and HMM approaches increased accuracy.

Algorithms↗
PubMed2000

Isolated extramedullary plasmacytoma of the true vocal fold.

We report a rare case of isolated extramedullary plasmacytoma (EMP) of the right true vocal fold in a 38-year-old male with a one-year history of hoarseness. Immunohistochemical staining of plasma cells in the tumour, showed over 90 per cent of them to be positive for kappa light chains. After two attempts at local surgical excision and recurrence within 10 months, the tumour was irradiated. Only seven reported cases of isolated EMP of the true vocal fold are reported in the literature. The therapeutic options are discussed.

Adult↗
PubMed2000

Increased 5alpha-reductase and normal 11beta-hydroxysteroid dehydrogenase metabolism of C19 and C21 steroids in a young population with polycystic ovarian syndrome.

OBJECTIVE: To test the hypothesis that 5alpha-reductase (5alphaR) and 11beta-hydroxysteroid dehydrogenase (11beta-HSD) activity are increased in adolescent and young-adult women with PCOS and that an altered regulation of the hypothalamic-pituitary-adrenal (HPA) axis occurred in these subjects. DESIGN: Prospective non-randomized study in an academic research environment. PATIENTS: Eleven women, aged 14 to 25 years, were studied who were at least one year post-menarche and who had a diagnosis of PCOS based on a history of oligomenorrhea and elevated total and or free serum testosterone. INTERVENTION: 24-Hour urinary metabolites were assessed in nine subjects and five underwent stimulation with ovine corticotropin releasing factor (oCRF). OUTCOME MEASURES: C19 and C21 steroid urinary metabolite 5-alpha/5-beta pairs, 11-oxo/11-hydroxy products and the ratio of the total 5-alpha/5-beta reduced and 11-oxo/11-hydroxy products were compared to values in control women. Urinary cortisol (F) (sum of conjugated and free, and free F) and total F metabolites (the sum of THE, THF, 5alpha-THF, cortolones, and cortols) were determined. A 1 microg/kg oCRF stimulation test was performed with timed samples determined for plasma ACTH and serum F levels. RESULT: The 24-hour total and free urinary F were not different from control. However, the total F metabolites were markedly elevated (7922+/-2666 vs 5418+/-1549 microg/24 h, p<0.01). A marked increase in the total 5-alpha reduced C19 and C21 metabolites was observed in the PCOS population vs control (5084+/-1977 vs 2681+/-1188 microg/24 h, p<0.01). The total urinary 11-oxo/11-hydroxy metabolite ratio was not different, p=0.23. The basal values and response of both ACTH and F to oCRF stimulation were not different from those of controls. CONCLUSION: There is a marked increase in 5alphaR metabolism of both C19 and C21 steroids in younger women with PCOS.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗
PubMed2000

3D-1D threading methods for protein fold recognition.

The threading approach to protein fold recognition attempts to evaluate how well a query sequence fits into an already-solved fold. 3D-1D threaders rely on matching 1-dimensional strings of 3-dimensional information predicted from the query sequence with corresponding features of the target structure. In many cases this is combined with a sequence comparison. The combination of sequence and structure information has been shown to improve the accuracy of fold recognition, relative to the exclusive use of sequence or structure. In this paper, we review progress made since the introduction of threading methods a decade ago, highlighting recent advances. We focus on two emerging methods that are unconventional 3D-1D threaders: proximity correlation matrices and parallel cascade identification.

Animals↗
PubMed2000

Osteoid osteoma: resection with CT guidance.

BACKGROUND: Osteoid osteoma is a benign bone lesion characterized by nocturnal pain mostly, which may be relieved by non-steroidal prostaglandin inhibitors. Treatment by complete resection of the nidus immediately relieves the pain. Intraoperative location of the nidus may be difficult, and extensive bone resection may be necessary to ensure complete excision. Few studies have described resection of osteoid osteoma under CT guidance, and little attention has been given to lesions near the neurovascular bundle. OBJECTIVE: To report our results of osteoid osteoma resection under CT guidance, with specific attention to lesions lying near the neural structure. METHODS: Nine patients with suspected osteoid osteoma underwent resection with a 6.8 mm core drill under CT guidance. RESULTS: Histologic confirmation was obtained in seven patients, while in two there was no evidence of the nidus in the excised bone material. All nine reported complete pain relief immediately after the surgery. Postoperative CT scan showed complete removal of the osteoid osteoma. CONCLUSIONS: Removal of osteoid osteoma under CT guidance is simple, safe and allows complete removal of the nidus with low morbidity.

Adolescent↗
PubMed2000

[Streptococcus pneumoniae--an infectious agent in coxitis].

Based on their own observation the authors describe pneumococcal coxitis in a young man. With regard to the atypical clinical picture of the disease the authors draw attention to the necessity to consider in the differential diagnosis of pain in the inguinal and coxal area also infectious arthritis. This concerns in the first place physicians in the first line of contact.

Adult↗
PubMed1999

Osteoporosis in multiple endocrine neoplasia type 1: severity, clinical significance, relationship to primary hyperparathyroidism, and response to parathyroidectomy.

BACKGROUND: Sporadic primary hyperparathyroidism (PHPT) occurs most frequently in postmenopausal women. Multiple endocrine neoplasia type 1 (MEN 1) is an autosomal-dominant disease in which mild to moderate PHPT develops in most gene carriers by 20 years of age. Primary hyperparathyroidism associated with MEN 1 is typically recurrent, despite initially successful subtotal parathyroidectomy. Osteoporosis is considered a complication of sporadic PHPT and an indication for parathyroidectomy. In the setting of MEN 1, however, the relationship of bone mass to PHPT, fracture risk, and parathyroidectomy is unknown. HYPOTHESIS: Parathyroidectomy improves bone mineral density for patients with primary hyperparathyroidism in the setting of MEN 1. DESIGN: Case series. SETTING: Tertiary referral center. PATIENTS: Twenty-nine women with MEN 1 belonging to a single family with a history of MEN 1. INTERVENTIONS: Parathyroidectomy. MAIN OUTCOME MEASURES: Bone mineral density (BMD) and history of skeletal fracture. RESULTS: Osteopenia and osteoporosis were diagnosed in 41% and 45% of patients, respectively. Forty-four percent of patients with uncontrolled PHPT had severe osteopenia (T score, <-2.0) by 35 years of age. Reduction in BMD was greatest at the femoral neck. Reduced BMD was associated with an increased likelihood of skeletal fracture (P = .05). Patients with uncontrolled PHPT had lower femoral neck and lumbar spine BMDs than those in whom PHPT was controlled by parathyroidectomy (P = .005 and .02, respectively). Successful parathyroidectomy improved femoral neck and lumbar spine BMDs by a mean +/- SEM of 5.2% +/- 2.5% and 3.2% +/- 2.9%, respectively. CONCLUSIONS: Osteoporosis is a frequent and early complication of PHPT in MEN 1. Despite difficulty in achieving a cure of PHPT in MEN 1, parathyroidectomy has an important role in the optimization of BMD for patients with MEN 1.

Adult↗
PubMed1999

A neural explanation of fetal heart rate patterns: A test of the polyvagal theory.

The current study applies a neurophysiological model based on the Polyvagal Theory (Porges, 1995) to interpret fetal heart rate patterns. Beat-to-beat heart rate data from 7 fetuses monitored during the first and second stages of labor were analyzed. Transitory heart rate accelerations and reduced beat-to-beat variability reliably preceded heart rate decelerations. The data are interpreted within the context of the Polyvagal Theory, which provides a plausible explanation of the neurophysiological mechanisms that mediate fetal heart rate decelerations. Specifically, it is proposed that both the transitory heart rate accelerations and the depression of the respiratory rhythm in the beat-to-beat heart rate pattern reflect a withdrawal of the vagal tone determined by myelinated vagal pathways originating in the nucleus ambiguus. Functionally, withdrawal of vagal tone originating in the nucleus ambiguus results in the cardiac pacemaker becoming vulnerable to sympathetic influences and to the more-primitive unmyelinated vagal pathways originating in the dorsal motor nucleus of the vagus, which may contribute to clinically relevant bradycardia.

Arrhythmia, Sinus↗
PubMed1998

Enteropancreatic malignancy associated with multiple endocrine neoplasia type 1: risk factors and pathogenesis.

BACKGROUND: Enteropancreatic malignancy is an important cause of morbidity and mortality associated with multiple endocrine neoplasia type 1 (MEN 1). However, the risk factors and mechanisms of the tumorigenesis of this malignancy are poorly understood. METHODS: The authors conducted a retrospective study of factors associated with the development of malignant enteropancreatic tumor in 69 patients with MEN 1 belonging to a single family. RESULTS: Metastatic enteropancreatic tumor and gastrinoma were identified in 20% and 36% of patients, respectively. Compared with MEN 1 patients who did not have an immediate family history of enteropancreatic malignancy, MEN 1 patients with a first-degree relative affected by enteropancreatic malignancy had an increased risk of developing disseminated tumor (odds ratio, 3.7; P < 0.05). In addition, hypergastrinemia and advanced age were both associated with a significant increase in the risk of enteropancreatic malignancy. Elevated serum glycoprotein alpha subunit levels were associated with enterochromaffin-like cell hyperplasia, gastric carcinoid formation, and disseminated enteropancreatic tumor in hypergastrinemic patients (P < 0.05). CONCLUSIONS: Disease modifier factors act in concert with the MEN 1 gene to modulate the development of enteropancreatic neoplasia. It is possible to identify MEN 1 patients at high risk for developing aggressive enteropancreatic tumors. Heritable disease modifier factor(s) affecting enteropancreatic malignancy appear to reside at loci distinct from that of the MEN 1 gene.

Adenoma↗
PubMed1998

The outcome of subtotal parathyroidectomy for the treatment of hyperparathyroidism in multiple endocrine neoplasia type 1.

BACKGROUND: The efficacy of subtotal parathyroidectomy for the treatment of hyperparathyroidism in multiple endocrine neoplasia type 1 (MEN 1) is unclear. The long-term outcome and optimal timing of operation remain controversial. OBJECTIVE: To determine the long-term outcome of parathyroidectomy for primary hyperparathyroidism in the presence of MEN 1. DESIGN: Case series and retrospective analysis. SETTING: Tertiary referral center. PATIENTS: Patients with MEN 1 from 2 families. INTERVENTIONS: Subtotal parathyroidectomy, ie, resection of 3 1/2 parathyroid glands from each patient. MAIN OUTCOME MEASURES: Recurrence of hyperparathyroidism. RESULTS: Thirty-seven patients underwent subtotal parathyroidectomy. Overall, persistent postoperative hypoparathyroidism developed in 24%, normocalcemia was maintained in 46%, and hyperparathyroidism recurred in 30%. However, after adjustment for the duration of follow-up (by using the Kaplan-Meier method), the cumulative recurrence rates for hyperparathyroidism were 15% at 2 years, 23% at 4 years, 55% at 8 years, and 67% after 8 years. Early recurrence of hyperparathyroidism (within 5 years of operation) was less likely to develop in patients in whom ionized calcium levels of 1.00 mmol/L (4.00 mg/dL) or less were achieved during the perioperative period than in patients in whom this degree of hypocalcemia failed to develop (P=.01). CONCLUSIONS: While relatively long periods of disease remission are possible after subtotal parathyroidectomy, our results indicate that recurrent hyperparathyroidism eventually develops in most patients with MEN 1.

Adult↗
PubMed1998

Anteroposterior patterning and organogenesis of Xenopus laevis require a correct dose of germ cell nuclear factor (xGCNF).

The germ cell nuclear factor of Xenopus laevis (xGCNF; NR6A1) is a nuclear orphan receptor that is predominantly expressed during neurula and late tailbud stages. As a strategy to analyze the role of xGCNF in embryogenesis, we have induced a gain of function by overexpression of full-length (fl) GCNF and a functional inhibition by a dominant-negative (dn) GCNF. Early events of embryogenesis including gastrulation and neurulation were not affected and the expression of several early mesodermal markers was normal. Yet specific defects were observed upon organogenesis. Ectopic posterior overexpression of the full-length xGCNF caused posterior defects and disturbed somite formation. In contrast, expression of dnGCNF interfered with differentiation of the neural tube and affected the differentiation of anterior structures, including the cement gland and the eyes. Embryos affected by dnGCNF were rescued by coexpression of flGCNF. After expression of dnGCNF, mRNA encoding the the retinoic acid receptor xRAR gamma 2 was selectively suppressed anteriorly. From the distinct phenotypes obtained, we conclude that GCNF has an essential function in anteroposterior differentiation during organogenesis.

Animals↗