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Biomedical subjects

J M Murray

Publications and source records attributed to J M Murray.

At least 91 records · Page 5Linked to original sources
PubMed1992

The vinculin/sarcomeric-alpha-actinin/alpha-actin nexus in cultured cardiac myocytes.

Experiments are described supporting the proposition that the assembly of stress fibers in non-muscle cells and the assembly of myofibrils in cardiac cells share conserved mechanisms. Double staining with a battery of labeled antibodies against membrane-associated proteins, myofibrillar proteins, and stress fiber proteins reveals the following: (a) dissociated, cultured cardiac myocytes reconstitute intercalated discs consisting of adherens junctions (AJs) and desmosomes at sites of cell-cell contact and sub-sarcolemmal adhesion plaques (SAPs) at sites of cell-substrate contact; (b) each AJ or SAP associates proximally with a striated myofibril, and conversely every striated myofibril is capped at either end by an AJ or a SAP; (C) the invariant association between a given myofibril and its SAP is especially prominent at the earliest stages of myofibrillogenesis; nascent myofibrils are capped by oppositely oriented SAPs; (d) the insertion of nascent myofibrils into AJs or into SAPs invariably involves vinculin, alpha-actin, and sarcomeric alpha-actinin (s-alpha-actinin); (e) AJs are positive for A-CAM but negative for talin and integrin; SAPs lack A-CAM but are positive for talin and integrin; (f) in cardiac cells all alpha-actinin-containing structures invariably are positive for the sarcomeric isoform, alpha-actin and related sarcomeric proteins; they lack non-s-alpha-actinin, gamma-actin, and caldesmon; (g) in fibroblasts all alpha-actinin-containing structures are positive for the non-sarcomeric isoform, gamma-actin, and related non-sarcomeric proteins, including caldesmon; and (h) myocytes differ from all other types of adherent cultured cells in that they do not assemble authentic stress fibers; instead they assemble stress fiber-like structures of linearly aligned I-Z-I-like complexes consisting exclusively of sarcomeric proteins.

Actinin↗
PubMed1992

Indocyanine green clearance and hepatic function during and after prolonged anaesthesia: comparison of halothane with isoflurane.

Specific biochemical and physiological tests of liver function were used to assess 20 consecutive patients undergoing prolonged head and neck surgery with halothane or isoflurane anaesthesia. Hepatic function was assessed by measurement of serum concentrations of total bilirubin and albumin, and plasma activity of pseudocholinesterase, gamma-glutamyl transferase (GGT), aspartate transaminase (AST), alkaline phosphatase (ALP) and hepatic glutathione S-transferase. Plasma clearance of indocyanine green was used as an estimate of hepatic blood flow. No major differences were observed in serum concentrations of GGT, ALP, bilirubin, albumin or pseudocholinesterase. Serum AST activity in those patients receiving halothane was increased at 24 h and at 48 h compared with those who received isoflurane (not statistically significant). Glutathione S-transferase activity was increased significantly in the halothane group throughout the period of study, compared with those who received isoflurane. Similarly, there was a significant difference between the two groups as measured by plasma clearance of indocyanine green: in the halothane group there was a slower disappearance rate of the dye from plasma at specific times than in the patients who received isoflurane. Our data support the use of isoflurane rather than halothane for prolonged anaesthesia.

Adult↗
PubMed1992

Hepatic function and indocyanine green clearance during and after prolonged anaesthesia with propofol.

We have studied the effects of propofol on hepatic function and clearance of indocyanine green (ICG) in 13 consecutive patients undergoing prolonged plastic and reconstructive surgery. Hepatic function was assessed using serum concentrations of liver-specific glutathione-S-transferase (GST). There were no significant changes in GST activity or plasma clearance of ICG throughout the study.

Adult↗
PubMed1992

Plasma fluoride concentrations during and after prolonged anesthesia: a comparison of halothane and isoflurane.

Serum inorganic fluoride concentrations were studied in 19 adult patients undergoing prolonged head and neck surgery with either halothane or isoflurane anesthesia (mean 19.5 and 19.2 MAC-hours, respectively). In the group of nine patients anesthetized with isoflurane, plasma inorganic fluoride increased from a mean concentration of 3.5 mumols/L (baseline) to a peak of 43.2 mumols/L. Forty percent of the patients in the isoflurane group had peak plasma inorganic fluoride concentrations of more than 50 mumol/L. In the group that received halothane, plasma inorganic fluoride concentrations increased from a mean of 3.8 mumols/L to a peak of 12.6 mumols/L. Despite similar exposures to both anesthetics, the differences in serum inorganic fluoride concentrations between the two groups were significant at 10, 24, and 48 h after induction of anesthesia (P = 0.035, P = 0.003, and P = 0.003, respectively). Serum electrolyte, urea, and creatinine concentrations and urine output rates during and after surgery were similar in both groups. We conclude that, after anesthesia of up to 20 MAC-hours, metabolism of isoflurane to inorganic fluoride may be of a greater magnitude than has previously been realized. Although no clinical or biochemical evidence was found to suggest postoperative renal dysfunction, we recommend caution using isoflurane when prolonged anesthesia and surgery are planned.

Adult↗
PubMed1992

Tubulin in bovine retinal rod outer segments.

Bovine rod outer segment (ROS) preparations contain a major 58 kDa protein doublet that was identified by immunoblot as tubulin. Quantification by gel densitometry showed that the total amount of tubulin was 5- to 10-fold higher than that attributable to the rod axoneme, suggesting additional role(s) for tubulin in photoreceptor cells. Approximately 20% of this nonaxonemal tubulin (15% of total tubulin) is tightly associated with outer segment membranes. This fraction remains membrane-associated after extensive low- or high-salt washing, requiring detergents or protein denaturants for release from ROS membranes. Unlike ROS soluble tubulin it associates tightly with liposomes upon detergent solubilization and reconstitution. The ROS membrane-associated tubulin is highly enriched in isolated ROS plasma membrane fractions compared to the total outer segment membrane pool and can be localized to the plasma membrane but not to disks by immunofluorescent staining, suggesting a possible role in the structure or electrophysiology of the rod outer segment plasma membrane.

Animals↗
PubMed1992

Flexor to extensor tendon transfer for curly toes. 43 children reviewed after 8 (1-25) years.

43 children treated by flexor-to-extensor transfer for a total of 130 curly toes were retrospectively reviewed after a mean period of 8 years. According to an objective scoring system, 37 patients had a satisfactory result and 6 patients had a poor result of one or more toes. We now recommend that children with mild to moderate curly toes should be observed until the age of 6 years, by which time the majority will have had spontaneous correction. The remaining patients should be operated on at that stage because children operated on later had poor results. Attention should be paid to the surgical technique because the long flexor tendons are often bipartite.

Adolescent↗
PubMed1992

Neuropathology in depth: the role of confocal microscopy.

This review surveys the rapidly increasing applications of confocal microscopy in neuropathology and related areas of experimental neurology. The ability of this new instrument to "optically section" thick samples has opened up to microscopic examination a wide range of previously difficult specimens. The basic operating principle, trading field of view for axial resolution, is illustrated with a simple schematic comparison of conventional and confocal microscopes. Images can be collected in several different modes, utilizing fluorescence, reflectance, or transmitted light. The majority of the applications in neuropathology to date have focused on immunocytochemical labeling with peroxidase or fluorescent markers. New methods of specimen preparation designed explicitly for the confocal microscope are just beginning to appear. The trend toward new techniques that fully exploit the superior performance of confocal microscopes is expected to accelerate, which will quickly establish the confocal microscope as a routine laboratory tool for the neuropathologist.

Animals↗
PubMed1991

Cloning and characterisation of the rad9 DNA repair gene from Schizosaccharomyces pombe.

The rad9.192 DNA repair mutant from the fission yeast, Schizosaccharomyces pombe, is sensitive to both UV and ionising radiation. The rad9 gene has been cloned by complementation of the gamma-ray sensitivity of the mutant cell line. A 4.3 kb HindIII fragment was found to confer resistance to both types of radiation. The region of complementation was further localised to a 2.6 kb HindIII-EcoRV fragment, which, by DNA sequence analysis, was found to contain sequences capable of coding for a 427 amino acid protein, if three introns were postulated to remove stop codons. The introns were confirmed by sequence analysis of cDNA clones and PCR products derived from cDNA. The product of transcription is a 1.6 kb mRNA of low abundance. The putative rad9 protein shows no homology to any published sequence. A truncated protein is capable of complementing the radiation sensitivity of the rad9.192 mutant. Deletion of the gene is not lethal and the null allele has a similar phenotype to the rad9.192 mutant.

Amino Acid Sequence↗
PubMed1991

Epitopes located in spatially separate domains of each neurofilament subunit are present in Parkinson's disease Lewy bodies.

Subcortical Lewy bodies are the pathological hallmark of idiopathic Parkinson's disease. This study sought to determine the extent to which each neurofilament subunit [low (NF-L), mid (NF-M), or high (NF-H)] was present in Lewy bodies by using light, confocal, and electron microscopy. A battery of 37 antineurofilament antibodies, characterized as to subunit specificity, epitope domain, and phosphorylation status, was employed to probe substantia nigra Lewy bodies from 15 Parkinson's disease cases. All 37 antibodies labelled Lewy bodies. The epitopes recognized by these antibodies included those in the NF-L rod and tail domains; the NF-M head, rod, and tail domains, as well as epitopes within, and flanking, the multiphosphorylation repeat site; and the NF-H rod domain and multiphosphorylation repeat sites. With these probes, nearly the entire length of each subunit could be demonstrated in Lewy bodies. However, the staining pattern of the Lewy bodies suggested that the tail domains of NF-M and NF-H were present in the periphery of the Lewy body core and in the Lewy body corona, but they appeared to be altered or missing in the center of the Lewy body core. In contrast, the head domain of NF-M, the tail domain of NF-L, and the rod domains of all three subunits are present throughout the Lewy body. These results strongly suggest that the entire extent of each neurofilament subunit is found in Lewy bodies but that the neurofilament subunits may be altered during the processing of these filaments into Lewy bodies.

Aged↗
PubMed1991

Rod and cone specific domains in the interphotoreceptor matrix.

The insoluble matrix domain of the interphotoreceptor matrix (IPM) from normal dog, cat, and mouse retinae were characterized using lectin cytochemistry. The lectins WGA (wheat germ agglutinin) and PNA (peanut agglutinin) were used to label interphotoreceptor matrix microdomains in cryosections of retinal tissue and in extracted insoluble matrix. Retinal cryosections and extracted matrix were examined by epifluorescence microscopy and scanning confocal laser microscopy, the latter allowed for the removal of all background fluorescence and gave increased resolution. The insoluble matrix was extracted as a continuous sheet that was comprised of two photoreceptor-specific matrix domains distinguished both by the size of the domains, and by differential binding of WGA and PNA lectins. Each domain encloses a photoreceptor inner and outer segment. Individual rod-associated domains were connected into a hexagonal lattice and this pattern was regularly interrupted by the larger cone-associated domains which have 8-10 surrounding rod domains. The PNA lectin primarily labeled the cone-associated matrix with faint binding to the rod matrix; the WGA lectin labeled both the rod- and cone-associated matrix.

Animals↗
PubMed1991

Substrate specificity of the dsRNA unwinding/modifying activity.

Double-stranded RNA (dsRNA) unwinding/modifying activity, which is present in a wide range of eukaryotic cells, has been previously shown to convert up to 50% of adenosine residues to inosines within intermolecular dsRNA. In the present study, we report that this activity also modifies, though slightly less efficiently, intramolecular double-stranded regions of synthetic RNAs. Our results widen the range of the possible biological substrates for the activity since many stem and loop type RNA secondary structures (intramolecular dsRNA), present in eukaryotic as well as viral transcripts, can potentially serve as substrates. In addition, we have found that the dsRNA unwinding/modifying activity requires a double-stranded region of at least 15-20 base pairs (bp) for substrate recognition. Furthermore, modification efficiency was found to be critically dependent on the length of the double-stranded region; as the size decreased below 100 bp, it dropped precipitously. Our results suggest that efficient modification may occur only with relatively long (greater than 100 bp) dsRNA, perhaps because multiple copies of the enzyme must be bound.

Base Sequence↗
PubMed1991

Structure of flagellar microtubules.

There is a widely perceived and growing need for a reliable high-resolution three-dimensional structural model of MT. One contributor to this need has been the enormous burst of new information from molecular biological manipulations of tubulin primary sequence and pattern of expression in cells. A second contributor has been the astounding progress in defining the MT-dynein motors of cytoplasmic motility. To interpret this new information in terms of MT assembly and function, we simply must have the structure of tubulin to atomic resolution and know the arrangement of tubulin in MT to an accuracy of better than 1 nm. The best experimental system for understanding the structural basis of MT-dependent motility is the eukaryotic flagellum. Therefore, the MT whose structure we need to know first is the flagellar doublet MT. The most generally accepted specific model for flagellar MT structure was proposed by Amos and Klug in 1974. The impact of their model has been enormous. It has provided the structural framework for thinking about MT function and has influenced the interpretation of a vast body of experimental observation over the intervening 15 years. As a first approximation to the structure of the native MT, in flagellar doublets and cytoplasmic singlets, it has served superbly. Now, we face an accumulation of new information on the nature of the intersubunit bond gleaned from assembly reactions of tubulin, on the nature and probable structure of nontubulin components of flagellar MT, and on the appearance of MT in their native hydrated state. We are compelled by this new evidence to look for the next approximation to the three-dimensional structure of the flagellar doublet MT. This second generation model is not yet formulated in sufficient detail to serve as a replacement for the Amos and Klug model. What we can say at this point is that the new model will be much more complex than the old one, having only axial periodicity in both A and B subfibers rather than full helical symmetry. The model must include at least one tektin filament at the medial (in the flagellum) A-B junction, and perhaps another in a location yet to be determined. It may also include other nontubulin components. The axial period of the MT itself, free of attached cross-bridging structure from the flagellum, must be at least 32.8 nm.(ABSTRACT TRUNCATED AT 400 WORDS)

Flagella↗
PubMed1990

An analysis of the properties of monoclonal antibodies directed to epitopes on influenza virus hemagglutinin.

Monoclonal antibodies (MAbs) specific for the hemagglutinin (HA) of the H3 subtype of influenza A virus were grouped according to their inability to bind to particular MAb-selected neutralization escape mutants of the virus having an amino acid substitution in one of the five postulated antigenic sites on the molecule. Additional residues critical to the binding of the MAbs were deduced from their patterns of reactivity with a panel of field strains and receptor mutants of the H3 subtype. The relationship of these residues to the actual epitopes recognized by the MAbs was inferred from their location on the three-dimensional structure of the HA molecule. In this way it was generally possible to identify a number of residues that are critical to the integrity of the epitope recognized by each of the MAbs examined. It was found that: (1) Several of these epitopes appear to be discontinuous and some may depend on residues contributed by more than one monomer. For example, residue 205, in the interface between monomers of the HA, was found to affect the integrity of the epitopes for several MAbs, possibly by stabilizing the conformation of residues around the receptor-binding pocket and/or in site B on the adjacent monomer. The activity of these particular MAbs was greatly decreased if the virus was exposed to pH 5. (2) All the MAbs tested neutralized viral infectivity and inhibited hemagglutination, although the single MAb directed to site C, which is the most distant from the receptor-binding site, was the least efficient. (3) Hemagglutination inhibition, and particularly neutralization tests, were more discriminating than ELISA in discerning subtle differences between the corresponding epitopes recognized by MAbs on different field strains. (4) Efficiency of neutralization of infectivity did not correlate consistently with hemagglutination inhibiting efficiency; MAbs postulated to bind to epitopes close to the receptor-binding pocket were very efficient at inhibiting hemagglutination, whereas neutralization efficiency tended to be more influenced by the affinity of binding of the MAb. (5) A MAb binding to any particular epitope could affect the binding of a second MAb directed to an epitope within the same or even a different antigenic site. The observed effect was most commonly inhibition of binding, which was not always reciprocal; enhancement of binding was also observed with certain combinations of MAbs. The relative affinity of the MAbs, in addition to steric constraints, were shown to be important factors in the ability to compete for interaction with HA.

Amino Acid Sequence↗
PubMed1990

Three-dimensional structure of frozen-hydrated paracrystals of myosin rod.

Myosin rod, the tail fragment of myosin, aggregates into various structures at physiological ionic strength. One form, the type II paracrystal, a thin, ribbon-like species, has recently been studied using conventional electron microscopy and was shown to possess two-dimensional order and, further, is likely to be useful in the investigation of the arrangement of myosin molecules in the backbone of the vertebrate muscle thick filament (Ward & Bennett, 1989). We have now examined this aggregate in the frozen-hydrated state by cryo-electron microscopy. Image analysis indicated that the projected structure has the same p12, plane group symmetry as seen after negative staining. A three-dimensional map, calculated from projections, indicated that the structure comprises a bilayer arrangement of strands of grouped rod molecules, with the strands parallel in each layer. The layers themselves are related by screw symmetry. Strands in adjacent layers have opposing polarity with their long axes at an angle of 32 degree to each other. Protein density measurements, carried out on unstained specimens using electron energy-loss spectroscopy, showed that the 44 X 13 X 13 nm unit cell is composed of 40% protein. The density measurements indicated that 9-12 rod molecules pass through each strand. Modelling rod molecules with 43 nm parallel overlaps in a body-centered tetragonal lattice produced a strand that compared favorably with the reconstructed strand. The size and content of these strands suggests that they are analogous to subfilaments observed in the vertebrate myosin thick filament.

Animals↗
PubMed1990

Some optimal control problems in cancer chemotherapy with a toxicity limit.

We investigate some models of a cancer chemotherapy problem where the normal cell population must be maintained above a lower limit and a measure of the total drug use is bounded as a limit of toxicity. Three sets of objective functions are analyzed, and some numerical solutions are provided for the last case. In all cases the structure of the optimal solution is similar, including a bolus application of drug followed later by continuous infusion.

Antineoplastic Agents↗
PubMed1990

Optimal control for a cancer chemotherapy problem with general growth and loss functions.

We investigate a model of a cancer chemotherapy problem where the aim is to minimize the tumor burden at the end of the treatment period while maintaining a normal cell population above a lower level as a limit of toxicity. The analysis is performed for general classes of growth and loss functions. The optimal drug dose is maximum initially so that the normal cell population is driven down to its lower level, and then the drug level is chosen to maintain the normal cell population there until the end of treatment. During treatment the number of tumor cells is always decreasing.

Antineoplastic Agents↗
PubMed1990

Facial growth in males 16 to 20 years of age.

Postpubertal craniofacial skeletal and dental changes were examined from lateral cephalograms taken when subjects were 16, 18, and 20 years of age. The sample consisted of males with no previous orthodontic treatment who had Class I skeletal and dental characteristics. Mandibular growth was found to be statistically significant for the age periods of 16 to 18 years and 18 to 20 years. Growth from 16 to 18 years was greater than that from 18 to 20 years. Maxillary and mandibular growth were highly correlated at each age period. However, overall mandibular growth was approximately twice that of overall maxillary growth. Mandibular growth was found to involve an upward and forward rotation, a result of posterior vertical growth exceeding anterior vertical growth. Lower incisors were found to tip lingually with increasing age. Incremental changes in mandibular cephalometric measurements were found to be equivalent when measured from either articulare or condylion, indicating the interchangeability of the landmarks for growth estimates.

Adolescent↗