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Biomedical subjects

J Griffith

Publications and source records attributed to J Griffith.

At least 91 records · Page 5Linked to original sources
PubMed1995

p53 and its 14 kDa C-terminal domain recognize primary DNA damage in the form of insertion/deletion mismatches.

Insertion/deletion (IDL) mismatches in DNA are lesions consisting of extra bases on one strand. Here, the binding of p53 and its 14 kDa C-terminal domain to DNAs containing one or three 3-cytosine IDL mismatches was examined. Electron microscopy showed that both p53 forms bound predominantly as tetramers at the lesions while single-stranded binding proteins did not bind. Gel retardation assays showed that p53 formed highly stable complexes when the DNA contained the IDL mismatches, but only unstable complexes when the DNA lacked lesions (but did contain free ends). The highly stable complexes had a half-life of > 2 hr, suggesting that upon encountering lesions, p53 may recruit other proteins to the site, providing a signal for DNA damage.

Base Composition↗
PubMed1995

A high-resolution map of the chromosomal region surrounding the nude gene.

The nude mutation produces the apparently disparate phenotypes of hairlessness and congenital thymic aplasia. These pleiotropic defects are the result of a single, autosomal recessive mutation that was previously mapped to a 9-cM region of murine chromosome 11 bounded by loci encoding the acetylcholine receptor beta subunit and myeloperoxidase. In this study, exclusion mapping of a panel of congenic nude strains was used to place the nude locus between the microsatellite loci D11Nds1 and D11Mit8. The relative distance from nude to each of these loci was determined by analyzing a large segregating cross. Thus, nude lies 1.4 cM distal to D11Nds1 and is 0.5 cM proximal to D11Mit8. Mice that carried recombinational breakpoints between D11Nds1 and D11Mit8 were further analyzed at the loci Evi-2 and D11Mit34, which placed nu 0.2 cM proximal to these markers. D11Nds1 and Evi-2/D11Mit34 thus define the new proximal and distal boundaries, respectively, for the nu interval. We also report the typing of the above microsatellite markers in the AKXD, AKXL, BXD, CXB, and BXH recombinant inbred strains, which confirmed the relative order and separation of loci in this region.

Animals↗
PubMed1995

Expanded CTG triplet blocks from the myotonic dystrophy gene create the strongest known natural nucleosome positioning elements.

Expanded blocks of repeating nucleotide triplets have been found in or near genes associated with several human diseases. In the case of myotonic dystrophy, a block of repeating CTG trinucleotides is located downstream of the gene, and expansions of this block to repeats of n = 100 or more are frequently found in afflicted individuals. Using electron microscopy, we recently demonstrated that these blocks form unusually stable nucleosomes. Here, competitive nucleosome reconstitution was employed to measure the energetics of nucleosome formation over CTG repeat blocks of n = 75 and n = 130. These values were compared to the Xenopus borealis somatic 5S RNA gene, previously one of the strongest known natural nucleosome positioning elements. It is shown that DNA fragments containing 75 and 130 CTG repeats are 6 and 9 times stronger in nucleosome formation, respectively, than the 5S RNA gene. These findings suggest that expanded CTG blocks may profoundly alter local chromatin structure.

Animals↗
PubMed1995

Do prehospital trauma center triage criteria identify major trauma victims?

OBJECTIVE: To evaluate anatomic, physiologic, and mechanism-of-injury prehospital triage criteria as well as the subjective criterion of provider "gut feeling." DESIGN: Prospective analysis. SETTING: A state without a trauma system or official trauma center designation. PATIENTS: Patients treated by emergency medical services personnel statewide over a 1-year period who were injured and met at least one prehospital triage criterion for treatment at a trauma center. MAIN OUTCOME MEASURES: Outcome was analyzed for injury severity using the Injury Severity Score and mortality rates. A major trauma victim (MTV) was defined as a patient having an Injury Severity Score of 16 or greater. The yield of MTV and mortality associated with each criterion was determined. RESULTS: Of 5028 patients entered into the study, 3006 exhibited a singular entry criterion. Triage criteria tended to stratify into high-, intermediate-, and low-yield groups for MTV identification. Physiologic criteria were high yield and anatomic criteria were intermediate yield. Provider gut feeling alone was a low-yield criterion but served to enhance the yield of mechanism of injury criteria when the two criteria were applied in the same patient. CONCLUSIONS: A limited set of high-yield prehospital criteria are acceptable indicators of MTV. Isolated low- and intermediate-yield criteria may not be useful for initiating trauma center triage or full activation of hospital trauma teams.

Adolescent↗
PubMed1995

What is the basis of sequence-directed curvature in DNAs containing A tracts?

A variety of solution and gel experiments show that DNAs containing tracts of 4-8 A's repeated in phase with the helix repeat are curved. Several independent analyses of these experiments argue that curvature resides in the A tracts themselves. In x-ray crystallographic studies of several DNAs containing A tracts, however, the A tracts are uncurved, leading to models in which curvature resides in the non-A tracts. This "curved general sequence model" has several problems, in our view. We review those, and we describe recent experiments that show that the dehydrating agents commonly used in x-ray crystallography markedly reduce curvature in gels and in solution, calling into question the ability of crystallography to determine the structural basis of DNA curvature. Finally, we discuss the critical role of hydration in curved DNAs and suggest new experiments that we hope could finally determine exactly which sequences are responsible for curvature.

Adenine↗
PubMed1995

Effects of sound intensity on a midlatency evoked response to repeated auditory stimuli in schizophrenic and normal subjects.

Inhibitory gating of response to repeated stimuli is demonstrated by several event-related potentials, including the auditory P50 wave. The present study examined the effects of variation in sound intensity on this phenomenon in schizophrenics and normal subjects. Paired clicks, 500 ms apart, were presented 50 dB above threshold to 10 normal subjects and 10 schizophrenics. The normal subjects demonstrated significantly more decrement of response to the second stimulus than did the schizophrenics. When the sounds were noticeably louder(70 dB above threshold), no such difference was observed. Rather, both groups had similarly diminished gating of response. A significant difference between schizophrenics and normal subjects was also observed when the sounds were 30 dB above threshold, but the difference was smaller than that at 50 dB. At any stimulus intensity, concomitant eye movements led to loss of gating of P50 in the normal subjects.

Acoustic Stimulation↗
PubMed1995

Further evidence of a dose-response threshold for haloperidol in psychosis.

OBJECTIVE: The authors' goal was to determine whether higher doses of haloperidol improve antipsychotic response. METHOD: During a 2-week, double-blind, randomized fixed-dose study, 24 psychotic patients were given 4, 10, or 40 mg/day of haloperidol. RESULTS: No clinically relevant difference between groups in favor of the higher antipsychotic doses could be detected. CONCLUSIONS: Doses of 4 mg/day of haloperidol appear to be as effective as higher doses in the treatment of psychosis.

Adult↗
PubMed1995

Organized chaos? Computed tomographic evaluation of the neuropathic diabetic foot.

Accurate radiographic evaluation of diabetic neuroarthropathy is increasingly difficult as the disease becomes more florid. 22 patients with a known diabetic neuroarthropathy of one or both feet were prospectively examined by computed tomography (CT) in the axial and coronal planes. Bilateral changes of a neuroarthropathy were present in 75% of cases. Distinct patterns of disease were seen and categorized into five types in order of increasing severity. Changes at the medial tarsometatarsal joints and adjacent intercuneiform joints were seen in all affected feet. More extensive disease involved the medial arch more commonly than the lateral. Fractures of the tarsal bones were found in 32% of cases and were associated with neuroarthropathic changes in adjacent joints. Calcaneal fractures were seen in four feet. A Lisfranc fracture-dislocation was present in 41% of cases and a bilateral in only 21%. A single CT examination of the foot, while an accurate method of demonstrating the extent of the disease, is an insensitive indicator of disease activity.

Adult↗
PubMed1995

Human tissue monitoring and specimen banking: opportunities for exposure assessment, risk assessment, and epidemiologic research.

A symposium on Human Tissue Monitoring and Specimen Banking: Opportunities for Exposure Assessment, Risk Assessment, and Epidemiologic Research was held from 30 March to 1 April 1993 in Research Triangle Park, North Carolina. There were 117 registered participants from 18 states and 5 foreign countries. The first 2 days featured 21 invited speakers from the U.S. Environmental Protection Agency, the Centers for Disease Control and Prevention, the National Institute of Environmental Health Sciences, various other government agencies, and universities in the United States, Canada, Germany, and Norway. The speakers provided a state-of-the-art overview of human exposure assessment techniques (especially applications of biological markers) and their relevance to human tissue specimen banking. Issues relevant to large-scale specimen banking were discussed, including program design, sample design, data collection, tissue collection, and ethical ramifications. The final group of presentations concerned practical experiences of major specimen banking and human tissue monitoring programs in the United States and Europe. The symposium addressed the utility and research opportunities afforded by specimen banking programs for future research needs in the areas of human exposure assessment, risk assessment, and environmental epidemiology. The third day of the symposium consisted of a small workshop convened to discuss and develop recommendations to the U.S. Environmental Protection Agency regarding applications and utility of large-scale specimen banking, biological monitoring, and biological markers for risk assessment activities.

Biomarkers↗
PubMed1995

The role of specimen banking in risk assessment.

The risk assessment process is described with a focus on the hazard identification and dose-response components. Many of the scientific questions and uncertainties associated with these components are discussed, and the role for biomarkers and specimen banking in supporting these activities are assessed. Under hazard identification, the use of biomarkers in defining and predicting a) biologically adverse events; b) the progression of those events towards disease; and c) the potential for reversibility are explored. Biomarker applications to address high-to-low dose extrapolation and interindividual variability are covered under dose-response assessment. Several potential applications for specimen banking are proposed.

Biomarkers↗
PubMed1994

Binding of mismatched microsatellite DNA sequences by the human MSH2 protein.

Alteration of the human mismatch repair gene hMSH2 has been linked to the microsatellite DNA instability found in hereditary nonpolyposis colon cancer and several sporadic cancers. This microsatellite DNA instability is thought to arise from defective repair of DNA replication errors that create insertion-deletion loop-type (IDL) mismatched nucleotides. Here, it is shown that purified hMSH2 protein efficiently and specifically binds DNA containing IDL mismatches of up to 14 nucleotides. These results support a direct role for hMSH2 in mutation avoidance and microsatellite stability in human cells.

Base Composition↗
PubMed1994

A fast random cost algorithm for physical mapping.

Ordering clones from a genomic library into physical maps of whole chromosomes presents a central computational/statistical problem in genetics. Here we present a physical mapping algorithm for creating ordered genomic libraries or contig maps by using a random cost approach [Berg, A. (1993) Nature (London) 361, 708-710]. This random cost algorithm is 5-10 times faster than existing physical mapping algorithms and has optimization performance comparable to existing procedures. The speedup in the algorithm makes practical the widespread use of bootstrap resampling to assess the statistical reliability of links in the physical map as well as the use of more elaborate physical mapping criteria to improve map quality. The random cost algorithm is illustrated by its application in assembling a physical map of chromosome IV from the filamentous fungus Aspergillus nidulans.

Aspergillus nidulans↗
PubMed1994

The latch region of calcineurin B is involved in both immunosuppressant-immunophilin complex docking and phosphatase activation.

The immunosuppressants cyclosporin A and FK506, when complexed with their intracellular receptors, prevent T cell activation by directly binding to the phosphatase calcineurin. We have used molecular modeling and mutagenesis to identify sites on calcineurin important for this interaction. We have created calcineurins that are resistant to both cyclosporin A and FK506 by mutating specific residues in CnB, a calcium-binding protein that regulates the catalytic subunit, CnA. Significantly, on a model of CnB, these mutations map to the latch region, an element of tertiary structure that forms when CnB binds CnA. In addition, we show that this latch region plays an important role in activating the catalytic subunit CnA. These results suggest a molecular mechanism for suppression of calcineurin by cyclosporin A and FK506 involving their binding to the same region of CnB used for allosterically activating CnA.

Amino Acid Isomerases↗
PubMed1994

Flow linear dichroism and electron microscopic analysis of protein-DNA complexes of a mutant UvrB protein that binds to but cannot kink DNA.

(A)BC excinuclease of Escherichia coli is the enzymatic activity resulting from sequential and partially overlapping actions of UvrA, UvrB, and UvrC protein. UvrA is a molecular matchmaker which promotes the formation of a stable UvrB-damaged DNA complex in which the DNA is kinked by about 130 degrees. The UvrB-DNA complex is then recognized by UvrC and two incisions are made in the DNA by the joint actions of UvrC and UvrB. A mutant of UvrB (D478A) can be loaded onto the DNA but it does not interact with UvrC to cause a nick 3' to the lesion. Based on the lack of a DNase-I-hypersensitive site in the footprint of the mutant, it was proposed that the lack of incision was due to the inability of the mutant UvrB to kink the DNA. In the current study we have investigated the interaction of the mutant UvrB with DNA using two biophysical methods, flow linear dichroism and electron microscopy. Both methods reveal that the mutant UvrB is unable to bend DNA.

Adenosine Triphosphatases↗
PubMed1994

Electron microscopic studies of the interaction between a Bacillus subtilis alpha/beta-type small, acid-soluble spore protein with DNA: protein binding is cooperative, stiffens the DNA, and induces negative supercoiling.

DNA within spores of Bacillus subtilis is complexed with a group of alpha/beta-type small acid-soluble spore proteins (alpha/beta-type SASPs), which have almost identical primary sequences and DNA binding properties. Here electron microscopic and cyclization studies were carried out on alpha/beta-type SASP-DNA complexes. When an alpha/beta-type SASP was incubated with linear DNA, the protein bound cooperatively, forming a helical coating 6.6 +/- 0.4 nm wide with a 2.9 +/- 0.3 nm periodicity. alpha/beta-Type SASP binding to an 890-bp DNA was weakest at an (A+T)-rich region that was highly bent, but binding eliminated the bending. alpha/beta-Type SASP binding did not alter the rise per bp in DNA but greatly increased the DNA stiffness as measured by both electron microscopic and cyclization assays. Addition of alpha/beta-type SASPs to negatively supertwisted DNA led to protein binding without significant alteration of the plectonemically interwound appearance of the DNA. Addition of alpha/beta-type SASPs to relaxed or nicked circular DNA led to molecules that by electron microscopy appeared similar to supertwisted DNA. The introduction of negative supertwists in nicked circular DNA by alpha/beta-type SASPs was confirmed by ligation of these molecules followed by topoisomer analyses using agarose gel electrophoresis.

Bacillus subtilis↗
PubMed1994

MRI of eosinophilic granuloma.

The imaging studies of nine histologically proven eosinophilic granulomas were reviewed. Radiographs and MRI studies were performed on all patients, with eight patients being examined by bone scintigraphy and six by CT. Matrix calcification, not evident on radiography, was demonstrated in two cases by CT. MRI proved superior to both the radiographs and CT in defining the medullary extent of the lesion and the surrounding soft tissue changes. In eight of nine cases, on STIR sequences, an endosteal rim of low signal intensity surrounding the main lesion was present and may be an early feature of healing. The degree of peritumoral oedema accompanying eosinophilic granuloma was less extensive than that seen in either Ewing's sarcoma or osteomyelitis. The presence of both a low signal endosteal rim and limited peritumoural oedema on STIR sequences may be a useful indicator to the diagnosis of underlying eosinophilic granuloma.

Adolescent↗