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Biomedical subjects

D York

Publications and source records attributed to D York.

At least 37 records · Page 2Linked to original sources
PubMed1998

A psychoeducational program for caregivers of the chronic mentally ill residing in community residencies.

The objective of this study was to develop a psychoeducational program for caregivers of the chronically mentally ill residing in community residencies. An evaluative component was added to determine how well the program was received by caregivers and what impact the program had on the residents. A total of 20 caregivers and 63 residents participated in the program. In general, the psychoeducational program was well received by the caregivers. They especially liked the mental health component and opportunity to meet and interact with other caregivers. There was a significant drop in hospital admissions following the program. There was also improvement in a number of quality of life activities such as trips to the local coffee shop and mall.

Aged↗
PubMed1997

DNA binding and phasing analyses of Tn5 transposase and a monomeric variant.

Both full-length Tn 5 transposase and a COOH-terminal truncated monomeric form of the protein,n369, have been shown to specifically bind end sequences at comparable affinities. In addition, both proteins distort the target sequence in a similar manner, as determined by a circular permutation assay. In this study,nEK54, a derivative ofn369 with a single amino acid substitution that significantly enhances binding activity, is used in further binding and bending studies along with full-length transposase. Phasing analysis has shown that distortion of the end sequences upon binding of full-length transposase and nEK54 protein is due in part to a protein-induced bend oriented towards the major groove. Because the center of transposase-induced bending maps to the extreme leftward end of the 19 bp consensus sequence, we examined the possibility that optimal protein binding requires additional upstream nucleotide contacts. Experiments presented here show that 9-10 nucleotides are needed upstream of +1 of the 19 bp sequence for efficient binding and this requirement can be met by either single-stranded or double-stranded DNA.

DNA Nucleotidyltransferases↗
PubMed1997

Enterostatin--a peptide regulating fat intake.

A high fat intake, together with an inability to match lipid oxidation to fat intake, has been found to be correlated with obesity in humans. This review describes our current understanding of enterostatin, a peptide that selectively reduces fat intake. Enterostatin is formed in the intestine by the cleavage of secreted pancreatic procolipase, the remaining colipase serving as an obligatory cofactor for pancreatic lipase during fat digestion. Enterostatin is also produced in the gastric mucosa and the mucosal epithelia of the small intestine. Procolipase gene transcription and enterostatin release into the gastrointestinal lumen are increased by high-fat diets. After feeding, enterostatin appears in the lymph and circulation. Enterostatin will selectively inhibit fat intake during normal feeding and in experimental paradigms that involve dietary choice. Its anorectic effect has been demonstrated in a number of species. Both peripheral and central sites of action have been proposed. The peripheral mechanism involves an afferent vagal signaling pathway to hypothalamic centers. The central responses are mediated through a pathway that includes both serotonergic and opioidergic components. Chronically, enterostatin reduces fat intake, bodyweight, and body fat. This response may involve multiple metabolic effects of enterostatin, which include a reduction of insulin secretion, an increase in sympathetic drive to brown adipose tissue, and the stimulation of adrenal corticosteroid secretion. A possible pathophysiological role is suggested by studies that have linked low enterostatin production and/or responsiveness to strains of rat that become obese and prefer dietary fat. Humans with obesity also exhibit a lower secretion of pancreatic procolipase after a test meal, compared with persons of normal weight.

Animals↗
PubMed1996

The Edge of Time: Dating Young Volcanic Ash Layers with the 40Ar-39Ar Laser Probe

Argon-40-argon-39 single-crystal dating of young (5000 to 30,000 years ago) volcanic ash layers erupted from the Mono Craters, California, shows that the method can yield meaningful ages in Holocene tephra. Because of ubiquitous xenocrystic contamination, the data do not form isochrons but plot in wedge-shaped regions on an argon isotopic diagram. The upper boundary of the region is an isochron matching the 14C-derived age of the eruption. Such contamination-related patterns may be common in dating young materials by the single-crystal method. Argon dating by this method can help refine the time scale of physical and biological evolution over the past 100,000 years.

Journal Article↗
PubMed1996

Purification and biochemical analyses of a monomeric form of Tn5 transposase.

The binding of transposase (Tnp) to the specific Tn5 end sequences is the first dedicated reaction during transposition. In this study, comparative DNA-binding analyses were performed using purified full-length Tnp and a C-terminal deletion variant (delta369) that lacks the putative dimerization domain. The shape of the binding curve of full-length Tnp is sigmoidal in contrast to the hyperbolic-shaped binding curve of delta369. This observation is consistent with previous observations as well as a rate of binding study presented here, which suggest that the full-length Tnp-end interaction, unlike that of the truncated protein, is a complex time-dependent reaction possibly involving a subunit exchange. Circular permutation assay results indicate that both proteins are capable of distorting the Tn5end sequences upon binding. Molecular weight determinations based on the migratory patterns of complexed DNA in polyacrylamide gels has shown that delta369 specifically binds the Tn5 end sequences as a monomer while full-length Tnp in complex represents a heterodimer.

DNA↗
PubMed1996

The organization of the outside end of transposon Tn5.

The end sequences of the IS50 insertion sequence are known as the outside end (OE) and inside end. These complex ends are related but nonidentical 19-bp sequences that serve as substrates for the activity of the Tn5 transposase. Besides providing the binding site of the transposase, the end sequences of a transposon contain additional types of information necessary for transposition. These additional properties include but are not limited to host protein interaction sites and sites that program synapsis and cleavage events. In order to delineate the properties of the IS50 ends,the base pairs involved in the transposase binding site have been defined. This has been approached through performing a variety of in vitro analyses: a ++hydroxyl radical missing-nucleoside interference experiment, a dimethyl sulfate interference experiment, and an examination of the relative binding affinities of single-site end substitutions. These approaches have led to the conclusion that the transposase binds to two nonsymmetrical regions of the OE, including positions 6 to 9 and 13 to 19. Proper binding occurs along one face of the helix, over two major and minor grooves, and appears to result in a significant bending of the DNA centered approximately 3 bp from the donor DNA-OE junction.

Base Sequence↗
PubMed1995

Buffer composition mediates a switch between cooperative and independent binding of an initiator protein to DNA.

The regulation of many biological processes, including DNA replication, is frequently achieved by protein-protein interactions, as well as protein-DNA interactions. Multiple protein-binding sites are often involved. For example, the replication of plasmid R6K involves binding of the initiator protein pi to seven 22-bp direct repeats (DR) in the gamma origin of replication (gamma ori). A mutant protein pi S87N has been isolated, that in Tris.borate buffer (TB) binds cooperatively to seven DR, whereas wild-type (wt) pi binds independently [Filutowicz et al., Nucleic Acids Res. 22 (1994) 4211-4215]. Surprisingly, we found that wt pi can also bind cooperatively when Tris.acetate (TA), Tris.succinate or Tris.glutamate buffers are used instead of TB. The cooperative binding of the wt pi protein was also observed in the TB buffer at high concentrations of Na2EDTA. These results suggest that pi may be able to assume two functionally distinct conformations as a result of either mutation or buffer composition. Moreover, we found that the mode of pi binding is determined not by the composition of the buffer in which the reaction was assembled, but by the composition of the electrophoresis buffer. We discuss the general implications of these findings.

Acetates↗
PubMed1994

Cooperative binding of initiator protein to replication origin conferred by single amino acid substitution.

The replication initiator protein pi of plasmid R6K binds seven 22 bp direct repeats (DR) in the gamma origin. The pi protein also binds to an inverted repeat (IR) in the operator of its own gene, pir, which lies outside the gamma origin sequences. A genetic system was devised to select for pi protein mutants which discriminate between IR and DR (York et al., Gene (Amst.) 116, 7-12, 1992; York and Filutowicz, J. Biol. Chem. 268, 21854-21861, 1993). From this selection the mutant pi S87N protein was isolated which is deficient in repressing the pir gene's expression because it cannot bind to IR at the pir gene operator. Remarkably, we discovered that pi S87N binds to DR cooperatively under conditions where wt pi binds independently. Moreover, the pi S87N is more active as a replication initiator in vivo when supplied at the same level as wt pi. Quantitative binding assays showed that both wt pi and pi S87N bind a DNA fragment containing a single DR unit with a similar affinity (Kd = 0.3 x 10(-12) M). Thus, cooperativity of pi S87N is most likely achieved through altered interactions between promoters bound at adjacent DR units.

Bacterial Proteins↗
PubMed1994

The dimerization domain of R6K plasmid replication initiator protein pi revealed by analysis of a truncated protein.

Replication of plasmid R6K is controlled by the homodimeric initiator protein pi, which binds to seven 22-bp direct repeats (iterons) in the gamma-origin. One of the genetically engineered pi variants (delta C164 pi) contains only the 164 N-terminal amino acids (aa) of the 305-aa pi molecule. This truncated pi polypeptide retains the ability to function as a specific inhibitor of R6K replication in vivo, though it neither drives replication, nor binds to iterons [Greener et al., Mol. Gen. Genet. 224 (1990) 24-32]. In order to define the region of pi responsible for dimerization, we have performed chemical crosslinking experiments with purified delta C164 pi and shown that this polypeptide is dimeric. We did not observe an exchange between protein monomers upon mixing of wild-type pi and delta C164 pi homodimers. However, heterodimers, as well as each type of homodimers, were formed when these polypeptides refolded after guanidine hydrochloride treatment. Thus, both dimerization and dimer stability are determined by the N-terminal domain of pi. We speculate that these properties might depend on the leucine zipper and RGD motifs that have been identified in the two regions of the N-terminal domain of pi.

Amino Acid Sequence↗
PubMed1994

Visual evoked responses as a monitor of intracranial pressure during hyperosmolar blood-brain barrier disruption.

Intracarotid mannitol (HBBBD = hyperosmotic BBB disruption) as a method of transiently increasing solute/drug delivery to brain parenchyma has been associated in animals with a 1-2% increase in brain water and an increase in cisternal ICP. To determine whether these changes are clinically significant, we investigated ICP changes associated with HBBBD in 33 patients with malignant brain tumor utilizing flash VERs in which the N2 latency correlates well with ICP (N2 > 80 ms linearly corresponds to ICP > 20 cm H2O). VERs were obtained prior to, 4 and 24 h after 114 HBBBD/chemotherapy procedures. Additionally, in 10 patients (37 HBBBDs), VER monitoring was performed during the procedure. In 112/150 (75%) HBBBDs, good barrier opening was obtained (radionuclide brain scan). Postoperative mean N2 latencies did not differ significantly from pre-HBBBD values (N2 = 86 +/- 3.3 pre, 90 +/- 3.0/4 h, 87 +/- 3.6/24 h); there was no significant difference in N2 latencies in those patients with good vs poor BBBD. In the 10 patients monitored during HBBBD, peak N2 latency = 94.9 +/- 1.6, however, was significantly above pre- and post-HBBBD values (p < 0.04). We conclude that flash VERs are a useful noninvasive measure of ICP, and that HBBBD is associated with mild transient increase in ICP which is not clinically detrimental.

Adolescent↗
PubMed1993

Autoregulation-deficient mutant of the plasmid R6K-encoded pi protein distinguishes between palindromic and nonpalindromic binding sites.

The autogenously regulated gene pir of Escherichia coli plasmid R6K encodes the replication protein pi. This protein binds to two sites in the operator region of the pir gene: a 22-base pair nonpalindromic sequence and a pair of palindromic 9-base pair sequences. These pi-binding sites are similar, suggesting that pi uses a single DNA-binding domain in recognizing them. We devised a plasmid system permitting isolation of mutants of the pi protein which are altered in autoregulation. A Ser87 to Asn substitution in one such mutant, designated pi 87, reduces the protein's ability to repress the pir gene promoter in vivo. DNase I protection and gel retardation assays were carried out with highly purified pi 87 protein. In these studies pi 87 exhibited altered binding to the palindromic but not to the nonpalindromic part of the operator of the pir gene. Chemical cross-linking and gel filtration analyses have shown that the dimerization properties of wild type pi and pi 87 proteins are similar in solution. We propose that the interaction of pi protein with the palindromic part of the pir operator is essential for autoregulation; we also propose that there is a fundamental difference in the mechanisms of pi protein recognition of palindromic and nonpalindromic sequences.

Amino Acid Sequence↗
PubMed1993

A comparison study of chest tube thoracostomy: air medical crew and in-hospital trauma service.

Chest tube thoracostomy (CTT) is not frequently performed by non-physician-staffed air medical crews (AMC) due to concern regarding safety, efficiency and training requirements. This study compared two groups of patients requiring CTT, one group with insertion performed by an AMC and the other by a physician trauma service (TS) in the emergency department on patient arrival. The CTT of 172 patients managed at a Level I trauma center between October 1988 and September 1990 were reviewed. Seventy-two patients were managed by the AMC and received CTT in a prehospital setting; the air medical personnel placed the chest tube cleanly in all cases. Chest tubes placed by AMC were removed within 48 hours of transport to minimize infection risk. One hundred patients requiring CTT in the hospital setting were randomly selected from the trauma registry during a similar time span. The study compared the patients' Injury Severity Scores (ISS), and trauma scores, any placement complications and the overall mortality. While the AMC often treated patients with higher acuity, as reflected by ISS and trauma scores and overall higher mortality, the rate of complications between CTT performed by AMC and TS was similar. Appropriately trained AMC can safely perform CTT without putting patients at increased risk.

Aircraft↗
PubMed1992

Translational options for the pir gene of plasmid R6K: multiple forms of the replication initiator protein pi.

The autogenously controlled pir gene of plasmid R6K was believed to encode a single polypeptide that plays multiple roles in the plasmid's biology. We have isolated an opal (op) mutant at the 18th codon of the pir coding frame which does not totally abolish translation of pir mRNA. In extracts of cells containing this mutation two translational products (35 kDa and 30.2 kDa) have been detected. We propose that the 35-kDa polypeptide produced by the pir18 op mutation contains Trp substituted for Arg18 as the result of an opal readthrough. Translation, which results in the 30.2-kDa polypeptide, originates downstream from the UGA stop signal created by the mutation. Moreover, we realize now that the 30.2-kDa polypeptide is also produced in cells containing a wild-type (wt) pir gene. The shorter variant of the pi protein lacks replication initiation and inhibition functions, as well as autorepressor activity in vivo. We also show that an in-frame fusion of seven N-terminal codons of the trpE gene with a pir gene lacking the first two codons produces two polypeptides which replace the 35-kDa pi protein and are of similar molecular weight. Thus, at least three options exist in the translation of the wt pir mRNA. Start codons are most likely at codon positions 1, 6 or 7, and 36 or 38. Each of these five AUG codons is preceded by a consensus ribosome-binding site (RBS).

Bacterial Proteins↗
PubMed1992

Cocaine abuse: an expanding healthcare problem for the 1990s.

Cocaine, the most addictive recreational drug available, has increased in popularity and widespread use in the past decade. Crack, a new form of cocaine that is smoked, is purer and more rapidly absorbed into the vascular system, greatly increasing the risk of overdose. Cocaine produces many physiologic effects on the body systems. This case report focuses on two cardiovascular responses related to cocaine use: cardiomyopathy and coronary vasospasm. Cocaine abusers may present with complaints of chest pain or other nonspecific symptoms that require diligent assessment skills to be recognized as cocaine-related. Therefore, it is essential that nurses be knowledgeable about the effects of cocaine and the symptoms of cocaine abuse.

Adult↗