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Biomedical subjects

M Head

Publications and source records attributed to M Head.

At least 19 recordsLinked to original sources
PubMed2004

Standards for the assay of Creutzfeldt-Jakob disease specimens.

Assays for the agent of Creutzfeldt-Jakob disease (CJD) include measurement of infectivity in different animal systems, such as wild-type or transgenic mice, and detection of PrP(Sc) by different methods and formats. The various assays could be best calibrated against each other by use of uniform readily available materials, and samples of four human brains, two from sporadic CJD patients, one from a variant CJD patient and one from a non-CJD patient, have been prepared as 10% homogenates dispensed in 2000 vials each for this purpose. Results of in vitro methods, particularly immunoblot assays, were compared in the first collaborative study described here. While dilution end-points varied, the minimum detectable volume was surprisingly uniform for most assays and differences in technical procedure, other than the sample volume tested, had no detectable systematic effect. The two specimens from sporadic CJD cases contained both type 1 and type 2 prion proteins in approximately equal proportions. The materials have been given the status of reference reagents by the World Health Organization and are available for further study and assessment of other in vitro or in vivo assay procedures.

Brain Chemistry↗
PubMed2003

Neuronal and astrocytic responses involving the serotonergic system in human spongiform encephalopathies.

The relationships between the degree of cortical prion protein (PrP) deposition, tissue vacuolation and astrocytosis were studied in the frontal cortex of 27 cases of human spongiform encephalopathy, encompassing 13 cases of sporadic Creutzfeldt-Jakob disease (sCJD), four cases of familial CJD (fCJD) (one owing to E200K mutation, one owing to 144 bp insertion, one owing to P102L mutation and one owing to A117V mutation), five cases of iatrogenic CJD (iCJD) owing to growth hormone therapy and five cases of variant CJD (vCJD). The size and number of tryptophan hydroxylase (TPH) positive cells in the dorsal raphe were determined as an index of the function of the brain's serotonergic system. The amount of PrP deposited in frontal cortex in vCJD was significantly greater than that in both sCJD and iCJD, which did not differ significantly from each other. The extent of grey matter deposition of PrP correlated with that of white matter deposition. Deposition of PrP as plaques was greater in cases of sCJD bearing valine at codon 129 of PrP gene, especially when homozygous. However, all cases of vCJD displayed florid plaque formation yet these were homozygous for methionine at codon 129. Prion protein deposition as plaques was greater in cases of sCJD with 2A PrP isotype than those with 1 PrP isotype, similar to that seen in cases of vCJD all of which are 2B PrP isotype. There were no significant differences in the extent of astrocytosis between the different aetiological groups, in either grey or white matter, as visualized with glial fibrillary acidic protein (GFAP) or 5HT-2A receptor (5HT-2AR) immunostaining, although there was a strong correlation between the severity of 5HT-2AR and GFAP reactions within both grey and white matter. The extent of PrP deposition within the grey, but not white, matter correlated with the degree of astrocytosis for both GFAP and 5HT-2AR and the extent of tissue vacuolation in grey and white matter, although the latter did not correlate with degree of astrocytosis for either GFAP or 5HT-2AR. Astrocytes may be responding directly to the presence of PrP within the tissue, rather than the vacuolar damage to neurones. Although S100beta immunoreactivity was present in astrocytes in control cases, no S100beta staining was seen in astrocytes in either grey or white matter in most CJD cases. There were no differences in the number of TPH-positive cells between CJD and control cases, although the mean TPH-positive cell size was significantly greater, and cells were more intensely stained, in CJD compared to controls, suggesting a pathological overactivity of the brain's serotonergic system in CJD. This may result in excessive release of 5HT within the brain triggering increased 5HT-2AR expression within activated astrocytes leading to release and depletion of S100beta protein from such cells. The clinical symptoms of fluctuating attention and arousal could be mediated, at least in part, by such alterations in function of the serotonergic system.

Adult↗
PubMed2001

Refined structures of beta-ketoacyl-acyl carrier protein synthase III.

beta-Ketoacyl-acyl carrier protein synthase III (FabH) is a condensing enzyme that plays central roles in fatty acid biosynthesis. Three-dimensional structures of E. coli FabH in the presence and absence of ligands have been refined to 1.46 A resolution. The structures of improved accuracy revealed detailed interactions involved in ligand binding. These structures also provided new insights into the FabH mechanism, e.g. the possible role of a water or hydroxyl anion in Cys112 deprotonation. A structure of the apo enzyme uncovered large conformational changes in the active site, exemplified by the disordering of four essential loops (84-86, 146-152, 185-217 and 305-307) and the movement of catalytic residues (Cys112 and His244). The disordering of the loops leads to greater than 50 % reduction in the FabH dimer interface, suggesting a dynamic nature for an unusually large portion of the dimer interface. The existence of a large solvent-accessible channel in the dimer interface as well as two cis-peptides (cis-Pro88 and cis-Phe308) in two of the disordered loops may explain the observed structural instabilities.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗
PubMed1999

The effect of human lactoferrin on the MICs of doxycycline and rifampicin for Burkholderia cepacia and Pseudomonas aeruginosa strains.

The presence of lactoferrin at the concentration found in cystic fibrosis (CF) sputum (0.9 g/L) reduced MICs and MBCs of doxycycline for Burkholderia cepacia and Pseudomonas aeruginosa strains. MICs for B. cepacia fell by 32- to 64-fold, from highly resistant to clinically achievable values. Rifampicin MICs for B. cepacia strains were reduced by lactoferrin and for some strains MBCs were reduced. These findings suggest new therapeutic approaches to infections and question the relevance of standard sensitivity tests for CF pathogens. Addition of lactoferrin to media for the routine sensitivity testing of CF isolates might give more relevant results.

Anti-Bacterial Agents↗
PubMed1998

Application of magnetic field-induced heat shock protein 70 for presurgical cytoprotection.

To develop an alternative to hyperthermia for the induction of hsp70 for presurgical cytoprotection, we investigated the optimal exposure conditions for magnetic field induction of hsp70. Normal human breast cells (HTB124) were exposed to 60-Hz magnetic fields and hsp70 levels were measured following three different exposure conditions: continuous exposure up to 3 h, a single 20-min exposure, and a single 20-min exposure followed by repeated 20-min exposures at different field strengths. In cells exposed continuously for 3 h, hsp70 levels peaked (46%) within 20 min and returned to control levels by 2 h. Following a single 20-min exposure, the return of hsp70 levels to control values extended to more than 3 h. When cells underwent a 20-min exposure followed by repeated 20-min exposures (restimulation) with different field strengths, additional increases in hsp70 levels were induced: 31% at 1 h, 41% at 2 h, and 30% at 3 h.

Breast↗
PubMed1998

Magnetic field activation of protein-DNA binding.

The mechanisms involved in sensing, signaling, and coordinating changes resulting from magnetic field-induced stress show substantial similarities to those of heat shock, e.g., magnetic field-induced heat shock 70 gene (HSP70) expression involves heat shock factor (HSF) activation and heat shock element binding. However, an additional requirement for transactivation of HSP70 expression by magnetic fields is the binding of Myc protein, indicating that additional elements and/or pathways are involved in the induction of HSP70 expression by magnetic fields. To investigate the possible participation of additional genetic elements in magnetic field-induced HSP70 expression, we examined both magnetic field exposure and heat shock on protein-DNA binding of the transcription factors HSF, AP-1, AP-2, and SP-1 in four human cell lines. The binding sites for these transcription factors are present in the HSP70 promoter. AP-1 binding activity, normally not increased by heat shock, was increased by magnetic fields; heat shock induced an increase only in HSF binding. Although intersecting and converging signaling pathways could account for the multiplicity of elements involved in magnetic field-induced HSP70 transcription, direct interaction of magnetic fields with DNA is also a possible mechanism. Because magnetic fields penetrate the cell, they could well react with conducting electrons present in the stacked bases of the DNA.

Binding, Competitive↗
PubMed1998

Myc-mediated transactivation of HSP70 expression following exposure to magnetic fields.

We investigated c-myc protein-binding sites on the HSP70 promoter as modulators of the induction of HSP70 gene expression in response to magnetic field stimulation (8microT at 60Hz) and whether the presence of c-myc protein potentiates transactivation of HSP70 expression. A 320 base pair region in the HSP70 promoter (+1 to -320) was analyzed. This region contains two c-myc-protein binding sites with consensus sequences located at -230 and -160 nucleotide positions (relative to the transcription initiation site) and overlapping with the region reported for the regulation of HSP70 gene expression by c-myc protein. This promoter region is upstream of other regulatory sequences, including the heat shock element (HSE), AP-2, and serum response element (SRE). Transfectants containing both c-myc protein-binding sites, HSP-MYC A and HSP-MYC B, and exposed to magnetic fields showed a 3.0-fold increase in expression of CAT activity as compared with sham-exposed control transfectants. Transfectants containing one c-myc binding site, HSP-MYC A, and exposed to magnetic fields showed a 2.3-fold increase in CAT expression. Transfectants in which both HSP-MYC A and HSP-MYC B binding sites were deleted showed no magnetic field sensitivity; values were virtually identical with sham-exposed controls. If the c-myc expression vector was not co-transfected with the constructs containing myc-binding sites, there was no difference in the expression of CAT activity between magnetically stimulated and sham-exposed controls, although both responded to heat shock. These data suggest that endogenous elevated levels of myc protein contribute to the induction of HSP70 in response to magnetic field stimulation.

Electromagnetic Fields↗
PubMed1997

Electromagnetic field exposure induces rapid, transitory heat shock factor activation in human cells.

Stimulation of human promyelocytic HL60 cells by a 60Hz magnetic field at normal growth temperatures results in heat shock factor 1 activation and heat shock element binding, a sequence of events that mediates the stress-induced transcription of the stress gene HSP70 and increased synthesis of the stress response protein hsp70kD. Thus, the events mediating the electromagnetic field-stimulated stress response appear to be similar to those reported for other physiological stresses (e.g., hyperthermia, heavy metals, oxidative stress) and could well be the general mechanism of interaction of electromagnetic fields with cells.

Binding Sites↗
PubMed1996

Mechanism and computer simulation of immune complex formation, opsonization, and clearance.

A computer simulation of immune complex formation, opsonization, and clearance has been developed (ICMODEL) that uses equations describing the kinetics of known immunologic processes and an additional pathologic process of immune complex-mediated tissue damage and antigen production. ICMODEL was used to (1) compare simulated with reported immune response kinetics, (2) evaluate the relative stability of the immune system described by the simulation, and (3) determine the conditions required to produce high immune complex levels as found in patients with immune complex-mediated disease. ICMODEL simulated primary and secondary immune responses as well as short- and long-term immunity. ICMODEL also depicted a relatively stable immune response system. Under certain conditions, however, the system could be perturbed, resulting in an unstable response. For example, when the rate constant regulating Fc gamma-mediated phagocytosis was decreased and the rate constant regulating immune complex-mediated tissue damage/antigen production was increased, immune complex concentrations oscillated with time and increased exponentially. These data suggest that ICMODEL can be used to define the specific parameters that, when perturbed, will give rise to increased immune complex concentrations. As such, this model has direct implications for studies of immune complex-mediated disease in human patients.

Animals↗
PubMed1996

A two-year follow-up on the effects of a smoking ban in an inpatient psychiatric service.

The effects of prohibiting cigarette smoking on the behavior of patients on a 25-bed psychiatric inpatient unit were assessed immediately after implementation of a smoking ban and two years later. No major behavioral disruptions were observed after the ban. The number of calls for security assistance, physical assaults, instances of leather restraints and of seclusions, and discharges against medical advice did not increase significantly immediately after the restriction on smoking or two years later. Significantly more verbal assaults and prescribing of p.r.n. medications for anxiety occurred immediately after the ban but not two years later.

Adolescent↗
PubMed1996

Use of species-specific oligonucleotide probes to detect Mycoplasma gallisepticum, M. synoviae, and M. iowae PCR amplification products.

Three digoxigenin-labeled oligonucleotide probes, complementary to the variable region of the 16S ribosomal RNA (rRNA) gene of Mycoplasma gallisepticum, M. synoviae, and M. iowae were designed. The oligonucleotides were used in a dot blot hybridization assay. The target DNA is a 780-bp fragment of the 16S rRNA gene of avian mycoplasmas amplified by a single set of primers (multispecies polymerase chain reaction [PCR]). The oligonucleotide probes were specific for their corresponding PCR products at hybridization conditions of 56 C and 50% formamide. The detection limit of the dot blot hybridization assay was approximately 70, 50, and 30 colony-forming units for M. gallisepticum, M. synoviae, and M. iowae, respectively, per 4 microliters of PCR. In general, the oligonucleotide probe dot blotting assay was a more sensitive and effective method of detecting PCR products than detection by gel electrophoresis.

Animals↗
PubMed1995

Unsuspected subdural hematoma as a differential diagnosis in elderly patients.

Subdural hematomas are among the most common forms of intracranial hemorrhage encountered in clinical practice and are a surgically remediable cause of dementia. When the symptom presentation is subtle or diffuse, a subdural hematoma can be overlooked. This is especially true among elderly people who may exhibit unrelated, preexisting dementia or delirium. Particularly confusing is that such declines in intellectual capacity can also result from subdural hematoma. It is therefore essential that a thorough physical and neurologic assessment be done on all patients with cognitive deficiencies. This always includes brain imaging. Early recognition of a subdural hematoma is important, given its treatability and potential reversibility. We describe an elderly woman with new-onset cognitive deficit and gait dyspraxia. There was no evidence of trauma. Physical examination was otherwise unremarkable. Initially, she refused evaluation, but once a subdural hematoma was identified by a tomographic scan, a satisfactory outcome followed surgical intervention.

Aged↗
PubMed1994

Effects of age and genetic growth rate on the crystallin composition of the chick lens.

This two part study continues and extends our examination of the effects of age and of genetically determined intrinsic growth rate on the overall protein composition of chick lens epithelia, lens fiber masses and whole lenses. Water-soluble proteins were analyzed by SDS-polyacrylamide and 2-dimensional gel electrophoresis. First, detailed age-related changes in protein expression between day 4 of embryonic development and the 8-week adult stage are described for one normal chick strain. Secondly, comparisons are made between day-old post-hatch chicks of four different genotypes: two genetically unrelated chick strains with a high growth rate and propensity for hyperplasia of the lens epithelium and two unrelated slow-growing strains, both with normal lens morphology. We find that the beta/delta-crystallin ratio in lens epithelia and fiber masses is higher in both the slow- than in both the fast-growing strains. The data emphasizes the importance of quantitative and non-coordinate changes in crystallin polypeptide expression during lens growth and development, and implicates growth rate as a modifier of the pattern of crystallin expression.

Aging↗
PubMed1993

Purification of a novel glycosylated ferritin from horse heart.

We have previously shown that mRNA coding for ferritin L subunit is present on both cytosolic ribosomes and endoplasmic reticulum-bound ribosomes in rat heart tissue [Campbell et al. (1989) Arch Biochem Biophys 273:89-98]; from this we infer that heart tissue is capable of making a secreted ferritin. We now report the purification from horse heart, of a ferritin that specifically binds to Concanavalin A-Sepharose and is immunologically cross-reactive with antibodies raised against both horse cellular ferritin and horse serum ferritin. Where cellular ferritin is 10 nm in diameter and contains primarily 21-kDa subunits (as determined by gel exclusion chromatography and electron microscopy), the glycosylated heart ferritin is smaller with diameters of 3-5 nm. Antisera raised against serum ferritin cross-reacted with the glycosylated heart ferritin did but did not show significant cross-reactivity with cellular ferritin thus indicating that serum ferritin and glycosylated heart ferritin have antigenic determinants which may not be present on cellular ferritin. The glycosylated ferritin also differs from cellular ferritin in subunit composition, with subunits of 66, 60.5, 53.5, 43.5, and 29.5 kDa, as shown by SDS-PAGE and Western blot analysis. Interestingly, ferritin purified from horse serum contains subunits of similar size.

Animals↗
PubMed1985

The majority of independently transformed BHK cell clones share a single functional lesion which determines anchorage independence and influences tumorigenicity.

Expression of the anchorage-independent transformed phenotype in BHK 21/13 cells generally behaves as a recessive trait. When chemically induced and spontaneously arising transformants are fused to the nontransformed parent line, transformation is initially suppressed, reappearing after extended growth of the hybrids. In this paper, complementation for the expression of anchorage independence was sought among a large group of such transformants, all independently derived from BHK 21/13 cells. Tumorigenicity studies on selected hybrids and parental lines indicated that the in vitro trait of anchorage independence is an accurate indicator of in vivo neoplasia for these cells. Seventeen of the 18 clones tested did not complement one or more of three tester strains. This result indicates that anchorage independence arose in these clones as a result of lesions in the same genetic function and suggests that the final step in the progressive changes of carcinogenesis may frequently be restricted to lesions at a single locus.

Animals↗
PubMed1984

The effect of antiserum quality on strain specificity assessment of foot and mouth disease virus by the neutralization reaction.

The factors affecting the virus strain specificity of antibody to foot an mouth disease virus prepared by a variety of protocols in several species were evaluated by neutralization tests. The time at which the serum was taken, the antigen dose given, whether or not revaccination had occurred and the animal species in which the sera were prepared, did not appear to affect the strain specificity of serum prepared to inactivated antigens when measured in neutralization tests, probably because of the restricted nature of the antigenic site involved. However, variation was observed with convalescent animal sera or sera from animals which had received trypsin cleaved virus were used. For these reasons banks of reference antisera are prepared as pooled sera using one or two inoculations of inactivated antigen.

Animals↗
PubMed1984

Demonstration of neutralizing and non-neutralizing epitopes on the trypsin-sensitive site of foot-and-mouth disease virus.

The isolation of monoclonal antibodies directed against the trypsin-sensitive site on the 140S particle of foot-and-mouth disease virus (FMDV) has enabled the demonstration of at least three distinct epitopes within this site. Reaction with two of these resulted in neutralization of virus infectivity. None of the epitopes appeared to be present on the 12S particles, and one of the neutralizing epitopes was sensitive to even milder configurational changes of the particle.

Animals↗