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Biomedical subjects

M R Stevens

Publications and source records attributed to M R Stevens.

At least 19 recordsLinked to original sources
PubMed2006

Construction of a quinoa (Chenopodium quinoa Willd.) BAC library and its use in identifying genes encoding seed storage proteins.

Quinoa (Chenopodium quinoa Willd.) is adapted to the harsh environments of the Andean Altiplano region. Its seeds have a well-balanced amino acid composition and exceptionally high protein content with respect to human nutrition. Quinoa grain is a staple in the diet of some of the most impoverished people in the world. The plant is an allotetraploid displaying disomic inheritance (2n=4x=36) with a di-haploid genome of 967 Mbp (megabase pair), or 2C=2.01 pg. We constructed two quinoa BAC libraries using BamHI (26,880 clones) and EcoRI (48,000 clones) restriction endonucleases. Cloned inserts in the BamHI library average 113 kb (kilobase) with approximately 2% of the clones lacking inserts, whereas cloned inserts in the EcoRI library average 130 kb and approximately 1% lack inserts. Three plastid genes used as probes of high-density arrayed blots of 73,728 BACs identified approximately 2.8% of the clones as containing plastid DNA inserts. We estimate that the combined quinoa libraries represent at least 9.0 di-haploid nuclear genome equivalents. An average of 12.2 positive clones per probe were identified with 13 quinoa single-copy ESTs as probes of the high-density arrayed blots, suggesting that the estimate of 9.0x coverage of the genome is conservative. Utility of the BAC libraries for gene identification was demonstrated by probing the library with a partial sequence of the 11S globulin seed storage protein gene and identifying multiple positive clones. The presence of the 11S globulin gene in four of the clones was verified by direct comparison with quinoa genomic DNA on a Southern blot. Besides serving as a useful tool for gene identification, the quinoa BAC libraries will be an important resource for physical mapping of the quinoa genome.

Cell Nucleus↗
PubMed2006

An algorithm for analyzing linkages affected by heterozygous translocations: QuadMap.

Heterozygous chromosome rearrangements such as reciprocal translocations are most accurately displayed as two-dimensional linkage maps. Standard linkage mapping software packages, such as MapMaker, generate only one-dimensional maps and so reciprocal translocations appear as clusters of markers, even though they originate from two nonhomologous chromosomes. To more accurately map these regions, researchers have developed statistical methods that use the variance in map distance to distinguish among the four segments (two translocation, two interstitial) of the translocation. In this study, we describe modifications to one of these protocols, that proposed by Livingstone et al. (2000). We also introduce QuadMap, a new software application for dissecting heterozygous translocation-affected linkage maps.

Algorithms↗
PubMed2006

Molecular and cytological characterization of ribosomal RNA genes in Chenopodium quinoa and Chenopodium berlandieri.

The nucleolus organizer region (NOR) and 5S ribosomal RNA (rRNA) genes are valuable as chromosome landmarks and in evolutionary studies. The NOR intergenic spacers (IGS) and 5S rRNA nontranscribed spacers (NTS) were PCR-amplified and sequenced from 5 cultivars of the Andean grain crop quinoa (Chenopodium quinoa Willd., 2n = 4x = 36) and a related wild ancestor (C. berlandieri Moq. subsp. zschackei (Murr) A. Zobel, 2n = 4x = 36). Length heterogeneity observed in the IGS resulted from copy number difference in subrepeat elements, small re arrangements, and species-specific indels, though the general sequence composition of the 2 species was highly similar. Fifteen of the 41 sequence polymorphisms identified among the C. quinoa lines were synapomorphic and clearly differentiated the highland and lowland ecotypes. Analysis of the NTS sequences revealed 2 basic NTS sequence classes that likely originated from the 2 allopolyploid subgenomes of C. quinoa. Fluorescence in situ hybridization (FISH) analysis showed that C. quinoa possesses an interstitial and a terminal pair of 5S rRNA loci and only 1 pair of NOR, suggesting a reduction in the number of rRNA loci during the evolution of this species. C. berlandieri exhibited variation in both NOR and 5S rRNA loci without changes in ploidy.

Base Sequence↗
PubMed2004

A genetic linkage map of quinoa ( Chenopodium quinoa) based on AFLP, RAPD, and SSR markers.

Quinoa ( Chenopodium quinoa Willd.) is an important seed crop for human consumption in the Andean region of South America. It is the primary staple in areas too arid or saline for the major cereal crops. The objective of this project was to build the first genetic linkage map of quinoa. Selection of the mapping population was based on a preliminary genetic similarity analysis of four potential mapping parents. Breeding lines 'Ku-2' and '0654', a Chilean lowland type and a Peruvian Altiplano type, respectively, showed a low similarity coefficient of 0.31 and were selected to form an F(2) mapping population. The genetic map is based on 80 F(2) individuals from this population and consists of 230 amplified length polymorphism (AFLP), 19 simple-sequence repeat (SSR), and six randomly amplified polymorphic DNA markers. The map spans 1,020 cM and contains 35 linkage groups with an average marker density of 4.0 cM per marker. Clustering of AFLP markers was not observed. Additionally, we report the primer sequences and map locations for 19 SSR markers that will be valuable tools for future quinoa genome analysis. This map provides a key starting point for genetic dissection of agronomically important characteristics of quinoa, including seed saponin content, grain yield, maturity, and resistance to disease, frost, and drought. Current efforts are geared towards the generation of more than 200 mapped SSR markers and the development of several recombinant-inbred mapping populations.

Base Sequence↗
PubMed2003

Genetic mapping and QTL analysis of horticultural traits in cucumber ( Cucumis sativus L.) using recombinant inbred lines.

A set of 171 recombinant inbred lines (RIL) were developed from a narrow cross in cucumber ( Cucumis sativus L.; 2n = 2 x = 14) using the determinate ( de), gynoecious ( F), standard-sized leaf line G421 and the indeterminate, monoecious, little-leaf ( ll) line H-19. A 131-point genetic map was constructed using these RILs and 216 F(2) individuals to include 14 SSRs, 24 SCARs, 27 AFLPs, 62 RAPDs, 1 SNP, and three economically important morphological [ F (gynoecy), de (determinate habit), ll (little leaf)] markers. Seven linkage groups spanned 706 cM with a mean marker interval of 5.6 cM. The location of F and de was defined by genetic linkage and quantitative trait locus (QTL) analysis to be associated with SSR loci CSWCT28 and CSWCTT14 at 5.0 cM and 0.8 cM, respectively. RIL-based QTL analysis of the number of lateral branches in three environments revealed four location-independent factors that cumulatively explained 42% of the observed phenotypic variation. QTLs conditioning lateral branching (mlb1.1), fruit length/diameter ratio (ldr1.2) and sex expression (sex1.2) were associated with de. Sex expression was influenced by three genomic regions corresponding to F and de both on linkage Group 1, and a third locus (sex6.1) on linkage Group 6. QTLs conditioning the number of fruit per plant (fpl1.2), the number of lateral branches (mlb1.4) and fruit length/diameter ratio (ldr1.3) were associated with ll. The potential value of these marker-trait associations (i.e., yield components) for plant improvement is portended by the relatively high LOD scores (2.6 to 13.0) and associated R(2) values (1.5% to 32.4%) that are affiliated with comparatively few genetic factors (perhaps 3 to 10).

Chromosome Mapping↗
PubMed2002

The GAIN (Geriatric Anorexia Nutrition) registry: the impact of appetite and weight on mortality in a long-term care population.

PURPOSE: To investigate nursing home residents at high nutritional risk to determine: 1) which baseline nutrition or health status indicators correlated with subsequent weight gain or appetite improvement; and, 2) whether a continued weight loss correlated with higher mortality. METHODS: At study entry, nutritional, health status, and demographic data were extracted from the nursing home chart or the MDS. Each subject was tracked for 6 months with survival, weight gain of 5%, and appetite improvement the primary outcome measures. RESULTS: During the 6-month study, younger age was the strongest correlate of appetite improvement. The odds of gaining weight were negatively correlated with BMI, age, and feeding dependency. Subjects who were receiving appetite stimulants (orexigenics) at study entry had a 70% greater probability of gaining weight than those who were not. A weight loss during the 6-month period was associated with a nearly two-fold increase in the likelihood of dying (adjusted RR: 1.95, 95% CI 1.43 to 2.66). CONCLUSION: The course of nutritional problems within nursing homes is highly variable. Continued weight loss, however, appears to have ominous implications for mortality. Younger residents who are not dependent on others for feeding assistance, and who receive orexigenics tend to experience weight gain.

Age Factors↗
PubMed2001

The correlation of cytokine levels with body weight after megestrol acetate treatment in geriatric patients.

BACKGROUND: Cachexia is associated with elevated levels of cytokines in cancer and human immunodeficiency virus patients. Studies in cancer and acquired immunodeficiency syndrome patients showed that treatment with megestrol acetate (MA) is associated with improvement in appetite and weight gain. Reduction in the levels of cytokines is associated with weight gain in laboratory animals with cancer. This study evaluates the correlation between changes in cytokine (or their receptor) levels and weight following MA treatment in geriatric weight-loss patients. METHODS: Veterans Administration Medical Center nursing home patients (N = 69) with a weight loss of > or =5% of usual body weight over the past 3 months or body weight 20% below their ideal body weight participated in a 12-week, randomized, double-blind, placebo-controlled trial, with an additional 13-week follow-up period. Patients were randomly assigned to receive a placebo or MA oral suspension of 800 mg/d for 12 weeks. Levels of the following cytokines (or their receptors) were measured at baseline and after 12 weeks of treatment: tumor necrosis factor soluble receptor (TNFR) subunits. TNFR-p55 and TNFR-p75: interleukin 6 (IL-6); and the soluble interleukin-2 receptor (sIL-2R). The subjects' weight and body composition were measured at the start of the study. Weight and mortality were followed up for another 13 weeks after discontinuing the MA study drug. RESULTS: Elevated levels of IL-6 in almost all geriatric cachexic patients, compared with normal volunteers (mean, <4.6 pg/ml). were noted at baseline. At 12 weeks after the study drug treatment, there was a decrease in cytokine levels (or their receptors) in the MA group (mean change in IL-6, 3.63+/-6.62 pg/ml; TNFR-p55, -0.06+/-0.11 ng/ml; TNFR-p75. -0.01+/-0.29 ng/ml; and sIL-2R, 0.08+/-0.07 ng/ml) and the placebo group (mean change in IL-6, -2.08+/-3.92 pg/ml; TNFR-p55, -0.02+/-0.08 ng/ml; TNFR-p75, -0.20+/-0.18 ng/ml; and sIL-2R, 0.02+/-0.03 ng/ml). Although the change in cytokine levels was not statistically significant between the two groups, significant negative correlation (p < .05) was found. For example, increased weight correlated with decreased sIL-2R levels (r = .36) and TNFR-p75 (r = -.31; fat-free mass (FFM) gain and reduction of sIL-2R (r = -.39), TNFR-p75 (r = -.30). There was a significant correlation between weight gain and reduction of TNFR-p75 (r = .54), TNFR-p55 (r- = .47), and sIL-2R (r = -.53); FFM gain and reduction of sIL-2R (r = -.59), TNFR-p75 (r = -.41), TNFR-p55 (r = -.42); and fat gain and reduction of TNFR-p75 (r = -.41) in the MA group (p < .05), but not in the placebo group. CONCLUSIONS: Although there was no significant change in cytokine levels between the two groups, the reduction in cytokine levels after MA treatment correlated with improvement in weight, fat mass, and FFM at 12 weeks.

Aged↗
PubMed2001

[Use of autogenous cranial bone grafts for orbital floor reconstruction].

OBJECTIVE: To evaluate the effects of autogenous calvarial bone grafts on treatment of the patients with defect of orbital floor from facial trauma. METHODS: During a 5-year period from April 1994 to April 1999, 34 patients ranging in age from 16 to 68 years (twenty males and fourteen females), who presented with orbital floor defects associated with other facial fractures were reconstructed by autogenous calvarial bone grafts. The surgical approach to the orbital floor involved a transconjunctival incision in 31 patients and a subciliary incision in 3 patients. After the orbital floor exploration, the bone graft was harvested through the coronal incision in 29 patients and the parietotemporal region incision in 5 patients. The bone graft was then fashioned to the appropriate size and configuration and fixed to the stable bone of the orbital floor with microplates or screws. RESULTS: The surgical incisions healed well with a minimal scar. There were no infection, extrusion or other complications associated with autogenous calvarial bone graft. There were no cases of optic neuropathy, diplopia and enophthalmos. There was no morbidity in donor sites. One patient had slight ectropion, which lasted three months and became inconspicuous in six months. 8 cases with hypoesthesia of the infraorbital region returned the sensory function within 6 months. 6 patients with enophthalmos were partly corrected. The follow-up period ranged from 6 months to 5 years. CONCLUSION: The orbital floor defects should be managed by early exploration to avoid later complications. The sequel, such as enophthalmos and dystopia or diplopia are much more difficult to correct after bony union. A vast array of autogenous and alloplastic materials have been used to reconstruct the defect of orbital floor. Autogenous bone graft reduces the risk of infection and extrusion. Cranial bone graft produces less donor site morbidity compared with other sites, non-visible scar as the incision is placed within the hair-bearing skin and the conjunctiva. The membranous bone from the skull has been shown to undergo less resorption and greater graft volume survival as compared to endochondral bone of the iliac crest or rib. Skull bone is an ideal source of bone graft in orbital reconstruction.

Adolescent↗
PubMed2000

Improvement in quality-of-life measures and stimulation of weight gain after treatment with megestrol acetate oral suspension in geriatric cachexia: results of a double-blind, placebo-controlled study.

BACKGROUND: Weight loss among older patients is a severe problem, associated with an increased incidence of infections, decubiti, and death. Megestrol acetate (MA) causes weight gain in cachectic cancer and AIDS patients, but its effects in older cachectic patients are unknown. OBJECTIVE: To compare the effects of MA oral suspension (O.S.), 800 mg/day, versus placebo on weight in geriatric nursing home patients with weight loss or low body weight. DESIGN: Twelve-week, randomized, double-blind, placebo-controlled trial with a 13-week follow-up period. SETTING: Veterans Administration Medical Center (VMAC) nursing home. PATIENTS: Nursing home patients with weight loss of > or =5% of usual body weight over the past 3 months, or body weight 20% below their ideal body weight. INTERVENTIONS: Patients were randomly assigned to receive placebo or MA 800 mg/day for 12 weeks and were then followed for 13 weeks off treatment. MEASUREMENTS: Primary outcome was measured by weight and appetite change. Secondary outcome measures included sense of well-being, enjoyment of life, change in depression scale, laboratory nutrition parameters, energy intake counts, body composition, and adverse events. RESULTS: At 12 weeks there were no significant differences in weight gain between treatment groups, whereas MA-treated patients reported significantly greater improvement in appetite, enjoyment of life, and well-being. Body composition was not statistically different between the two groups. At Week 25 (3 months after treatment), 61.9% of MA-treated patients had gained > or =1.82 kg (4 lbs) compared to 21.7% of placebo patients. CONCLUSIONS: In geriatric patients with weight loss or low body weight MA improves appetite and well-being after 12 weeks of treatment. During the 3 months of MA treatment, there was no statistically significant weight gain (> or =4 lbs). Three months after treatment, weight gain (> or =4 lbs) was significantly increased in MA-treated patients.

Administration, Oral↗
PubMed2000

Quality of life and stimulation of weight gain after treatment with megestrol acetate: correlation between cytokine levels and nutritional status, appetite in geriatric patients with wasting syndrome.

BACKGROUND: The geriatric wasting syndrome (GWS) has been associated with proinflammatory cytokines, depression and progressive decline in quality of life (QOL). The objective of this study was to evaluate the correlation between the changes in cytokine levels and appetite, nutritional markers, and QOL in geriatric patients with GWS following a randomized clinical trial of megestrol acetate (MA) versus placebo. METHODS: This was a prospective, double-blind, placebo-controlled trial. We evaluated 69 predominantly male (3 females) nursing home residents with weight loss of > or =5% of their usual body weight over the past three months or body weight 20% below their ideal body weight. Patients were randomly assigned to receive either placebo or megestrol acetate (MA) oral suspension (O.S.) 800 mg/day for 12 weeks and were then followed for 13 weeks off treatment. Data on appetite, weight, nutritional status, QOL and cytokine levels were collected at baseline and week 12. The correlation between appetite, weight, nutritional status, sense of well being and cytokine level changes in response to MA treatment was examined at week 12. RESULTS: Appetite, sense of well being, and QOL assessed by an "enjoyment list" significantly improved in the MA arm. Rising prealbumin showed a negative correlation with decreasing IL-6 (r = -0.51), TNFR-p 55 (r = -0.49) and sIL-2R (r = -0.38). There was also an improvement in prealbumin and a decrease in IL-6 and TNFR-p55 in the MA-arm (p < 0.01). A correlation between a decrease in the IL-6 levels and improvement in depression (r = 0.50) was seen in the MA arm as well. Improvement in appetite positively correlated with increased enjoyment of life (r = -0.41), less depression (r = -0.34), improved sense of well being (r = 0.36), prealbumin gain (r = 0.30), and weight gain (r = 0.38) by 12 weeks. Also, improvement in appetite positively correlated with improvement in nutritional parameters such as prealbumin, albumin, fat free mass and weight in the MA arm. CONCLUSIONS: In a geriatric nursing home population with weight loss, reduction in cytokine levels after MA treatment correlates with improvement in appetite, prealbumin, albumin, and improvement in quality of life.

Aged↗
PubMed1999

Hydroxyapatite cement in craniofacial trauma surgery: indications and early experience.

BACKGROUND AND OBJECTIVES: Reconstruction of the nonstress-bearing portions of the craniofacial skeleton has recently utilized several alloplastic compounds. One such recent compound is hydroxyapatite cement (HAC)--a calcium-phosphate-based product. Its chemical structure consists primarily of calcium phosphate, as does human bone, and this similarity in the mineral structure renders it biocompatible. METHODS AND MATERIALS: Based on clinical indications for HAC, the authors have classified acquired craniofacial defects into four types. This article presents 5 clinical cases with craniofacial fractures, sustained in various accidents, in which hydroxyapatite cement was used to prevent cranial deformities or to reinstate contour. RESULTS AND/OR CONCLUSIONS: Complications were encountered in some of these cases, but all patients healed without any secondary complications. While the short-term experience using hydroxyapatite cement in craniofacial trauma surgery has been favorable, long-term studies in humans are required to validate the safety and efficacy of this product.

Adolescent↗
PubMed1998

The use of osseointegrated implants in craniofacial trauma.

The objective in treating patients with injuries sustained in craniofacial trauma is to reinstate preinjury facial projection and function. The capability of providing spatially related facial reconstruction is predicated on basic craniofacial surgical principles, generally accepted as the standard of care. These principles include early surgical intervention, immediate bone grafting, and the use of internal rigid fixation. The introduction of osseointegrated dental implants has significantly improved the overall reconstruction of patients with cranio-maxillofacial injuries, including soft tissue repair and cosmetic surgery. The purpose of this article is to review the utilization of dental implants in the context of maxillofacial trauma, using three cases to document the clinical procedure.

Adolescent↗
PubMed1997

Comparison of ceftriaxone with penicillin for antibiotic prophylaxis for compound mandible fractures.

PURPOSE: The purpose of the study was to compare the efficacy and cost of two antibiotic regimens for prophylaxis of compound mandible fractures: 1 gm/day ceftriaxone and 2 million U penicillin G every 4 hours. DESIGN: A prospective study of 90 patients with compound mandible fractures was performed. The patients were randomized to the two antibiotic regimens. The surgical procedures were performed by oral/maxillofacial surgery residents at a large urban training center. Standard treatment consisted of open reduction with either bone plates or wires, with all patients receiving 6 weeks of maxillomandibular fixation. The patients were monitored at 2-week intervals for 8 weeks by two of the authors, who were blinded to which antibiotic regimen the patient was assigned. RESULTS: Two patients in each group had postoperative infections within the first 2 weeks of treatment. The infections resolved with local wound care, removal of internal fixation devices, and oral antibiotics. After resolution of the infection each patient had a malunion, which was managed without additional complications. The cost difference between the two treatment regimens was approximately $350 per day. CONCLUSION: Ceftriaxone was noted to be an efficacious and cost-effective treatment alternative to penicillin G for compound mandible fracture antibiotic prophylaxis.

Adolescent↗
PubMed1996

Primary surgical repair of traumatic lacerations of the lacrimal canaliculi.

Injuries of the lacrimal system are occasionally associated with maxillofacial trauma. Detailed knowledge of the anatomy of the lacrimal apparatus is essential for optimal treatment of these injuries. The pertinent anatomy is reviewed. Techniques for the diagnoses and repair of lacrimal injuries specific to the canaliculi are presented and discussed with emphasis on early detection and intervention.

Anastomosis, Surgical↗
PubMed1996

The traumatic saddle nose deformity: etiology and treatment.

The saddle nose resembles a saddle, i.e., with a concave, often flattened dorsum and an apparent cephalic rotation of the nasal tip. The concavity may be present in the osseous or cartilaginous dorsum, or both. The saddle nose deformity can be divided into congenital, postinfection, postsurgical, and traumatic types. Congenital saddle nose deformity is rare, often accompanying midfacial deficiency malformation syndromes. The advent of antimicrobial therapy has helped restrict the incidence of syphilitic or leprotic saddle nose to the nonindustrialized nations. Postsurgical saddle nose deformity occurs most often as a result of the overzealous septorhinoplasty. The most common type of saddle nose deformity may be traumatic. The authors use Kazanjian and Converse's characterization of the true saddle nose as one in which the bony and/or cartilaginous portions are depressed and the projection of the nose is generally preserved. This article describes the saddle nose deformity and its etiology and proposes a management technique with minimal complications.

Adolescent↗
PubMed1995

Comparison of the effects of growth hormone, insulin-like growth factor-I and fetal calf serum on mouse molar odontogenesis in vitro.

The effects of growth hormone, its mediator insulin-like growth factor-I (IGF-I), and fetal calf serum on odontogenesis were compared to those of serum-free medium. Explanted, 16-day, fetal mouse first molar tooth germs in early bell stage were grown on semisolid, serum-free medium supplemented with ascorbic and retinoic acids. Recombinant human growth hormone at 50 or 100 ng/ml, IGF-I at 100 or 200 ng/ml, or fatal calf serum at 20% concentration were added to the media. Volumetric changes in serial sections of six tooth germs per treatment over 3 days of treatment (4, 5, 6 days in vitro) were compared by digitized morphometry. Mitotic indices were also compared and the cell densities of the dental papillae recorded. Qualitative ratings of differentiation were ascribed to each tooth germ by light microscopy. Differences in volume, mitotic activity and cell densities were found. The growth hormone-treated tooth germs were not larger than the serum-free ones but had increased mitotic indices and higher cell densities in the dental papillae. IGF-I-treated tooth germs had larger volumes than with all other treatments, e.g. germs treated with 200 ng/ml of IGF-I, after 6 days in culture, were significantly larger than with all other treatments (p<0.01-<0.001). Whilst IGF-I-treated germs displayed the greatest extent of differentiation, growth hormone-treated germs also showed advanced differentiation compared to those on serum-free medium. These results suggest that growth hormone and IGF-I are involved in odontogenesis of murine teeth in vitro by affecting mitotic activity, tissue volume and cell differentiation. In conjunction with previous immunohistochemical studies that show expression of growth hormone receptor and IGF-I in developing teeth, these results provide evidence that both growth hormones and its mediator play a part in odontogenesis.

Animals↗