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Biomedical subjects

M L Edwards

Publications and source records attributed to M L Edwards.

At least 19 recordsLinked to original sources
PubMed2003

Alignment of trans-tibial prostheses based on roll-over shape principles.

The authors examined the roll-over shape alignment hypothesis, which states that prosthetic feet are aligned by matching their roll-over shapes with an "ideal" shape. The "ideal" shape was considered to be the roll-over shape of the able-bodied foot-ankle system. An alignment algorithm and computational alignment system were developed to set trans-tibial alignments based on this hypothesis. Three prosthetic feet with considerably different roll-over shapes were either aligned using the alignment system or not aligned (i.e. used previous foot's alignment), and then were aligned by a team of prosthetists. No significant differences were found between roll-over shapes aligned by the computational alignment system and those based on standard clinical techniques (p = 0.944). Significant differences were found between the "no alignment" shapes and the prosthetist alignment shapes (p = 0.006), and between the "no alignment" shapes and the computational alignment system shapes (p = 0.024). The results of the experiment support the hypothesis that the goal of alignment is to match the prosthetic foot's roll-over shape, as closely as possible, with an "ideal" shape. The hypothesis is also supported by its ability to explain the results of previous studies. Using an "ideal" roll-over shape or surface as a goal for prosthetic alignment could lead to a priori alignment, eliminating the need for alignment hardware in some cases. Being able to build the alignment into a prosthesis without special hardware could be beneficial in low-income countries and in the fabrication of lightweight prostheses for the elderly.

Adult↗
PubMed2000

Below knee prosthetic socket designs and suspension systems.

The prosthetic socket must act as a customized connection between the residual limb's surrounding tissues and the prosthetic components. The socket must be designed to control weight bearing, suspension, and ambulation stability. When making a below-the-knee socket, the prosthetist attempts to maximize loading and minimize displacements, such as vertical, transverse, or rotational. This article discusses the engineering designs or shapes of the two basic forms of below-the-knee prosthetic sockets used today.

Artificial Limbs↗
PubMed1994

The status of implant training in oral and maxillofacial surgery residency programs.

PURPOSE: The results of a survey concerning the status of oral and maxillofacial surgery resident training in oral implantology are discussed. RESULTS: The results demonstrate that oral and maxillofacial surgery residents are exposed to a variety of implant types and systems, with most implant surgery being performed in association with intravenous sedation. The number of implants placed by each resident during training varied greatly. CONCLUSION: Most program directors believe that the implantology training of oral and maxillofacial surgery residents is superior or comparable to that of periodontal graduate students. However, this survey suggests that certain aspects of residency training in implantology, such as the performance of sinus lift procedures and participation in implant research, may require more emphasis.

Clinical Competence↗
PubMed1993

The identification, cloning, and sequence analysis of the coat protein coding region of a birch isolate (I2) of cherry leaf roll nepovirus.

The coat protein gene of RNA-2 of cherry leaf roll nepovirus (CLRV) birch isolate I2 was cloned, identified, and sequenced. Transcripts derived from cDNA to the coat protein gene made a polypeptide of M(r) 51.5 k when translated in vitro. The predicted amino acid sequence of the coat protein showed little identity with nepoviruses having small RNA-2s. It did, however, have 27% sequence identity with the coat protein of tomato ringspot nepovirus which, like CLRV, has a relatively large RNA-2.

Amino Acid Sequence↗
PubMed1993

The emerging phonological system of an autistic child.

This case report provides a detailed phonological investigation of the speech of an 8-year-old autistic boy. Three approaches were used for elicitation of speech: delayed imitation, object naming, and a connected speech sample. Phonetic inventory analysis revealed that stops, nasals, and glides were generally present, whereas fricatives, affricates, and the liquid /r/ were absent. There were also positional restrictions on the use of specific sounds. This information, together with a phonological process analysis, revealed: (a) the existence of several phonological processes that are common in normal development; (b) the persistence of several phonological processes, e.g., velar fronting, beyond the expected age; (c) the occurrence of some unusual sound changes, e.g., extensive glottal replacement and segment coalescence; (d) evidence of "chronological mismatch" (Grunwell, 1981); and (e) restricted use of contrasts (Ingram, 1976). The subject's use of phonological processes resulted in extensive homonymy, which, together with process interactions and the use of jargon, resulted in severely reduced intelligibility. This child appeared to be acquiring his phonological system in at least a partly unique way, showing some typical patterns as well as some patterns that rarely appear in normally developing children.

Articulation Disorders↗
PubMed1993

Lexical acquisition and acquisition of initial voiceless stops.

The interaction between lexical acquisition and acquisition of initial voiceless stops was studied in two normally developing children, aged 1;9 and 1;10, by acoustically examining the token-by-token accuracy of initial voiceless stop targets in different lexical items. Production accuracy was also examined as it related to the frequency of usage of different words, as well as the time when they entered the children's lexicons. Fewer than half of the words in the children's lexicons had tokens representing the emergence of accurate voiceless stop production prior to the session at which the voicing contrast was achieved. These words were primarily 'old' words that had been in the children's lexicons from the beginning of data collection, as opposed to 'new' words, first produced in later recording sessions. Findings are discussed in reference to the 'lexical diffusion' model of sound change and within the framework of nonlinear underspecification theory.

Female↗
PubMed1993

Coexistence of stuttering and disordered phonology in young children.

The purpose of the present study was to assess differences in stuttering, phonological, and diadochokinetic behaviors in young children who exhibit both stuttering and disordered phonology and children who exhibit only one of the disorders. Subjects were 21 male children (aged 4 to 6 years), representing three groups of seven children each: (a) stuttering and normal phonological abilities (S+NP), (b) stuttering and disordered phonology (S+DP), and (c) normal fluency and disordered phonology (NF+DP). Stuttering behavior was assessed during a 30-minute conversational speech task; phonological behavior was assessed during a 162 item picture-naming task; and diadochokinetic abilities were assessed during bi- and multisyllable productions. Results indicated that the S+DP group produced significantly more sound prolongations and significantly fewer iterations per whole-word repetition than the S+NP group. However, there were no differences between the two groups in other stuttering indices. Moreover, no differences were noted between the S+DP and NF+DP groups in phonological behavior. Diadochokinetic rates did not differ among the three groups. The possibility of two types of stuttering, one occurring with and one without disordered phonology, is discussed.

Articulation Disorders↗
PubMed1993

Biochemical changes associated with the symptomatic human intervertebral disk.

Significant changes in disk biochemistry were evident in the nuclei pulposi of 25 symptomatic disks that demonstrated abnormal diskography. Compared with the results from ten normal disk from young subjects (mean age, ten years) and from ten asymptomatic disks from adult patients (mean age, 33 years), the symptomatic disks demonstrated significantly greater collagen content than the young and asymptomatic adult subjects, respectively. Significantly fewer total glycosaminoglycans (GAGs) and significantly less water content were also evident for the diseased disks. The mean pH of the nucleus pulposus from 23 patients was also significantly reduced for the symptomatic disks as compared with the mean pH measured for four asymptomatic adult subjects. Although significantly fewer total GAGs were observed for the symptomatic disks, there were no significant differences in the percent composition of hyaluronic acid (HA), chondroitin sulfate (CS), or keratan sulfate (KS) among the normal and symptomatic disks. Significant changes in disk biochemistry are associated with the symptomatic disk, and these changes could contribute to the development of the painful disk syndrome.

Adult↗
PubMed1992

Fibrillar collagen-biphasic calcium phosphate composite as a bone graft substitute for spinal fusion.

The osteoconductive capacity of fibrillar collagen-biphasic calcium phosphate composition was compared to autogenous bone in a canine spinal fusion model. All animals underwent a standard intervertebral body fusion (L2-L4) with rigid internal fixation and received either autogenous bone alone or a mixture of the ceramic and autogenous bone (3:1) as the graft material. Animals were followed for 12 months and the quality of fusion in each animal assessed by biomechanical testing and histological analysis. The fused L2-L4 segment of each dog was embedded in bone cement and mounted in a specially designed mechanical tester for testing in flexion, extension, and side bending. Overall, the mean rigidity of the fusion mass was not significantly different between the two groups [10.5 +/- 4.1 (SD) for autogenous bone vs. 11.3 +/- 1.7 for the ceramic plus autogenous bone, p greater than 0.05]. Similar findings were obtained for mean bending moment, compressive load, angular deformation, and energy absorbed for the two groups. Histological analysis was performed on transverse nondecalcified specimens. Quantitation of bone ingrowth using back-scattered electron imaging disclosed no significant differences in the amount of new bone formed at the graft site between autogenous bone and the ceramic plus autogenous bone recipients (23.4 +/- 10% vs. 25.8 +/- 8.8%) when correction for the autogenous bone volumes was performed. Light microscopic analysis of toluidine blue-stained transverse sections demonstrated new bone growth around and through the ceramic bone graft material. These results suggest that use of a collagen-biphasic calcium phosphate ceramic and autogenous bone mixture (3:1) provides a suitable osteoconductive alternative to the use of autogenous bone and results in the formation of a mechanically competent fusion mass not significantly different from that obtained with autogenous bone alone.

Animals↗
PubMed1992

Antiretroviral activity of mechanism-based irreversible inhibitors of S-adenosylhomocysteine hydrolase.

S-Adenosylhomocysteine hydrolase (AdoHcy-nase) is a key enzyme in transmethylation reactions. The objective of the present study was to examine the potential antiretroviral activities of novel mechanism-based irreversible AdoHcy-nase inhibitors. (Z)-4',5'-didehydro-5'-deoxy-5'-fluoroadenosine (ZDDFA), (E)-4',5'-didehydro-5'-deoxy-5'-fluoroadenosine (EDDFA), (Z)-4',5'-didehydro-5'-deoxy-5'-chloroadenosine (ZDDCA) and 5'-deoxy-5'-acetylenic adenosine (DAA) inhibited AdoHcy-nase activity with Ki values of 0.55, 1.04, greater than 10.0 and 3.30 microM, respectively. These four compounds were tested for antiviral activity in vitro against Moloney leukemia virus (MoLV) in the XC-plaque assay. MoLV replication in murine fibroblasts (SC-1) was inhibited by ZDDFA, EDDFA and DAA with IC50 values of 0.05, 0.25 and 3.30 micrograms/ml, respectively. ZDDCA did not inhibit MoLV infection at the concentrations tested. Antiviral activity correlated with the ability of the individual compounds to maintain sustained elevations in intracellular S-adenosylhomocysteine (AdoHcy) concentrations in the SC-1 cells. ZDDFA, the most potent inhibitor of AdoHcy-nase and MoLV was also the most active in maintaining sustained elevations in intracellular AdoHcy levels. The antiviral activity of ZDDFA was also examined in murine C3H1OT1/2 fibroblasts which constitutively produce MoLV. Pretreatment with ZDDFA (1.0 microgram/ml) for 24 hr inhibited virus production by 88%. Similar to the SC-1 cells, and concomitant with enzyme inhibition, there was a 300-fold increase in AdoHcy levels in ZDDFA (1.0 microgram/ml) treated C3H1OT1/2 cells. Incorporation of a [3H]methyl group from tritiated S-adenosylmethionine into total RNA in C3H1OT1/2 cells was inhibited by ZDDFA without affecting cell viability. These results suggest that mechanism-based inhibitors of AdoHcy-nase, such as ZDDFA, may have potential as antiretroviral agents.

Adenosine↗
PubMed1992

Partial nucleotide sequence of poplar mosaic virus RNA confirms its classification as a carlavirus.

The nucleotide sequence of the 3'-proximal 1328 nucleotides of poplar mosaic virus (PMV) was determined and shown to contain two large open reading frames (ORFs). The ORF nearer to the 3' terminus of the RNA is capable of encoding a polypeptide of 14K with a 'zinc-finger' motif, and is homologous to sequences in corresponding positions in five other carlaviruses. The other ORF encodes a protein of 36K which includes two sequences of amino acids identified in tryptic digests as virion capsid protein, and has amino acid sequences in common with both carlaviruses and potexviruses.

Amino Acid Sequence↗
PubMed1992

The nucleotide sequence of RNA-2 of raspberry ringspot nepovirus.

The nucleotide sequence of raspberry ringspot nepovirus (RRV) RNA-2 consists of 3928 nucleotides and a poly(A) tract at the 3' end. RNA-2 contains one open reading frame which encodes a polypeptide of M(r) 123508 (123K). Edman degradation located the N terminus of the coat protein 514 residues from the C-terminal end of the 123K protein, which suggests that the coat protein is released from the polyprotein by cleavage of a C-A bond. The RRV coat protein has some sequence similarities with the coat proteins of other nepoviruses, but is no more like any one nepovirus than another. In contrast, the portion of the 123K protein to the N-terminal side of the coat protein is similar in sequence to the corresponding parts of the polyproteins of tomato black ring and grapevine chrome mosaic nepoviruses, though not to those of other nepoviruses.

Amino Acid Sequence↗
PubMed1991

Effects of polyamine analogs on the extent and fidelity of in vitro polypeptide synthesis.

A series of polyamine analogs has been examined for their ability to support protein synthesis in an in vitro rabbit reticulocyte translation system. Diamines were found to stimulate protein synthesis to the greatest extent (8-12 fold). Triamines, tetraamines and pentaamines only stimulated 2-4 fold under these conditions although much lower concentrations were required. At elevated temperatures (45 degrees C), diamines were somewhat more active than at lower temperature but activity of longer chain polyamines was elevated very significantly. Polyamines with terminal benzyl or smaller alkyl groups had diminished activity. It is concluded that both charge and charge distribution determine the ability of polyamines to stimulate translation. Fidelity studies identified two classes of polyamines: those which are able to lower the optimal Mg2+ concentration required for amino acid misincorporation while not affecting extent of misincorporation relative to Mg2+ alone, and those which are sparing for Mg2+ and also stimulate extent of misincorporation.

Animals↗
PubMed1991

Participation of T-lymphocytes in the curative effect of a novel synthetic polyamine analogue, N,N'-bis[3-(ethylamino)propyl]-1,7-heptanediamine, against L1210 leukemia in vivo.

We have recently established that combination therapy with N,N'-bis[3-(ethylamino)propyl]-1,7-heptanediamine (BEPH), a synthetic polyamine analogue, and N,N'-bis-2,3-butadieneyl-putrescine, a polyamine oxidase inhibitor, eradicated L1210 leukemia in mice and induced resistance to a subsequent L1210 challenge. We now demonstrate that BEPH treatment alone, given on a more frequent schedule (5 mg/kg, day 3, 4, 5) or at a higher dose (10 mg/kg, day 3, 4), cures 100% of L1210 leukemic mice. These treated animals were subsequently immune to a second challenge with L1210 tumor cells. However, mice cured with BEPH did not reject P388 leukemic cells, although their mean survival time was slightly prolonged. In an in vivo tumor neutralization assay, splenocytes from cured mice and L1210 cells were injected into naive mice; 80% did not develop L1210 leukemia. Coculturing lymphocytes from cured mice with L1210 cells in vitro generated a potent tumor-specific cytolytic response against L1210 target cells, whereas lymphocytes from naive mice did not generate any significant cytolytic activity. Both the in vitro and in vivo activities were completely eliminated by pretreating the splenic lymphocyte population with anti-Thy-1.2 monoclonal antibodies and complement, indicating T-cells as the effector population. In T-cell-deficient nude mice BEPH treatment was not curative, increasing survival time by approximately 2-fold. We conclude from these studies that T-cell-mediated immunity plays a pivotal role in the mechanism by which synthetic polyamine analogues, such as BEPH, prevent neoplastic growth.

Animals↗
PubMed1991

The effects of photoperiod and different dosages of melatonin on metamorphic rate and weight gain in Xenopus laevis tadpoles.

This study examined the effects of photoperiod and three different dosages of melatonin on the rate of metamorphosis and weight gain in Xenopus laevis. Exposure of larvae to 23L:1D resulted in lower mean body weight and a retarded metamorphic rate in comparison to larvae exposed to 1L:23D. Larvae reared in either photoperiod and treated with exogenous melatonin demonstrated a dose-dependent suppression of weight attained, with short photoperiod larvae showing a more dramatic effect. Analysis of growth patterns indicate that photoperiod and exogenous melatonin have a greater effect on weights prior to Nieuwkoop and Faber stage 56 in the development of Xenopus. Larvae exposed to 1L:23D and exogenous melatonin metamorphosed at an accelerated rate when compared to larvae exposed to 23L:1D and the same dosages of melatonin. In both photoperiod regimens an exogenous melatonin concentration of 45 micrograms/100 ml resulted in an accelerated metamorphic rate, whereas 225 and 450 micrograms/100 ml retarded metamorphic rate of larvae in comparison to controls.

Animals↗
PubMed1991

Antimalarial polyamine analogues.

A series of novel tetraamines of the general formula RNH(CH2)xNH(CH2)yNH(CH2)xNHR was synthesized and examined for activity against growth of Plasmodium falciparum in vitro. Within the series, dibenzyl analogues (R = benzyl) were found to be the most effective growth inhibitors, with IC50 values of about 10(-6) M. Further modifications of the tetraamine provided the optimum chain length for antimalarial activity of y = 7, x = 3. Compound 8 (MDL 27,695) with the structure y = 7, x = 3, R = benzyl, in combination with the ornithine decarboxylase inhibitor alpha-(difluoromethyl)ornithine, resulted in radical cures when tested against experimental Plasmodium berghei infections in mice. The structure-activity relationships of the series are discussed.

Animals↗