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Biomedical subjects

P Birch

Publications and source records attributed to P Birch.

33 records · Page 2Linked to original sources
PubMed1994

Oncoprotein immunoreactivity in human pituitary tumours.

OBJECTIVE AND DESIGN: The immediate early gene locus AP-1, incorporating the cellular oncogenes c-fos and c-jun (and their oncoprotein products Fos and Jun respectively) play a key role in regulating cell growth and differentiation. The myc-gene is also known to promote cell growth. In order to investigate the possible role of these oncogenes in human pituitary adenomas, Fos, Jun and Myc oncoprotein immunoreactivities were assessed in surgically resected pituitary adenomas in relation to in-vivo characteristics (hormone secretion, size and invasiveness) and an in-vitro index of cell proliferation (Ki-67 immunoreactivity). Thirty-three human pituitary adenomas and 16 normal pituitary glands were examined. MEASUREMENTS: Oncoprotein immunoreactivity was recorded as present (+) or absent (-), and Ki-67 labelling indices were scored quantitatively. Tumour size was scored from CT scan appearances and radiographic evidence of bone erosion was noted. RESULTS: Oncoprotein immunoreactivity was present in a total of 32/33 cases. Myc immunoreactivity was restricted to the only ACTH-secreting tumour in the series (1/33). Ki-67 immunoreactivity was present in 24/32 cases and labelling indices varied from 0.1 to 3.2%. CONCLUSIONS: Oncoprotein immunoreactivity did not correlate with hormonal profile, bone erosion or the size of the proliferating compartment estimated by Ki-67 labelling indices. Although oncoprotein expression is common in human pituitary adenomas, its significance remains to be elucidated.

Adenoma↗
PubMed1994

Phanerochaete chrysosporium and its natural substrate.

We seek to define more fully how Phanerochaete chrysosporium degrades its natural substrate, lignocellulose. This contribution concerns several relevant topics. Mineralisation of [14C]DHP, as a model for lignin degradation, showed that a set of genetically defined meiotically derived products of strain ME446 differed in their degradative ability and also that, under optimum conditions for mineralisation, extracellular lignin peroxidase activity was absent. Xylanolytic and xylosidase/beta(1-->3) glucanase activities are also described. The complexity of the CBHI gene family is described and differential splicing of a CBHI gene transcript is proposed. In contrast to the multiplicity of CHBI genes there is a single CBHII gene. PCR methods were developed to analyse differential gene expression on different substrates. We have also developed a transformation system involving a reporter construct for the analysis of CBHI promoter function.

Basidiomycota↗
PubMed1994

Interactions at the alpha 1 beta 1 interface in hemoglobin: a single amino acid change affects dimer ratio in transgenic mice expressing human hemoglobin.

The erythrocytes of transgenic mice expressing human hemoglobin contain mouse, human, and two hybrid hemoglobins. These hybrids include a predominant one, the human-alpha/mouse-beta and one found at lower levels, the human-beta/mouse-alpha. We used molecular modeling-aided hydropathic analysis of the globin alpha 1 beta 1 interface to identify a residue partly or wholly responsible for this distribution. Hemoglobin containing a single amino acid change [beta 112(G14)Cys-->Val] was expressed in transgenic mice. The hybrid ratio was reversed in transgenic mice expressing this mutated human hemoglobin as compared to the control transgenic mice expressing native human hemoglobin. These results demonstrate the importance of subunit assembly in the expression of hybrids in transgenic animals and may lead to successful design approaches for optimal expression of hemoglobin in larger animals such as the pig.

Amino Acid Sequence↗
PubMed1993

National Neurofibromatosis Foundation International Database.

The National Neurofibromatosis Foundation International Database is a system for collecting comprehensive information on the clinical manifestations and natural history of neurofibromatosis. Data are entered into personal computers at participating centres and are pooled at the Central Database and coordinating centre in Vancouver, Canada. The system includes special mechanisms to assure consistency among centres and to maintain patient confidentiality. The database is designed to foster collaborative clinical and molecular genetic research in many aspects of neurofibromatosis.

Canada↗
PubMed1993

A microplate system for ABO and Rh(D) blood grouping.

A microplate system for performing ABO and Rh(D) blood group determinations with a Kemble Kemtek 1000SP liquid handling processor, an Anthos 2001 microplate reader, an IBM Personal System 2 microcomputer, and Sanguin Forma software is described. The performance of this Kemble/Anthos/IBM/Sanguin microplate system for ABO and D grouping was evaluated by testing 10,042 routine blood donor samples in parallel with the forward-grouping channels of a Technicon AutoAnalyzer blood grouping system. Manual techniques were used to perform ABO reverse groupings and to resolve all ABO forward- and reverse-grouping discrepancies. D-negative test results were investigated and confirmed manually by the indirect antiglobulin test. Of the 10,042 samples tested, 97.3 percent were grouped correctly. There were 266 samples whose results were flagged as no type determined, of which 124 were ABO tests and 142 were Rh tests. In addition, 30 weak D samples missed by both automated systems were detected by manual indirect antiglobulin test. The system is flexible and easy to maintain and operate.

ABO Blood-Group System↗
PubMed1993

Carbamazepine poisoning in children.

Carbamazepine poisoning in children remains a significant problem for the emergency physician. We report 16 cases of toxicity at British Columbia Children's Hospital and discuss presenting symptoms, treatment, and hospital course. Pharmacology, drug interactions, resulting in carbamazepine toxicity, and treatment guidelines are summarized.

Adolescent↗
PubMed1992

Six amino acids determine the sequence-specific DNA binding and replication specificity of the initiator proteins of the pT181 family.

The replication of pT181 and related plasmids of Staphylococcus aureus proceeds by a rolling circle mechanisms. The initiator proteins encoded by the plasmids of the pT181 family have sequence-specific DNA binding and topoisomerase activities. These proteins nick one strand of the DNA at the origin of replication. The free 3'-hydroxyl end at the nick is then used as a primer for the replication of the leading strand of the DNA. Although these initiator proteins are highly homologous, they show specificity in DNA binding and replication for their cognate DNAs. In this study, we have generated hybrid initiator proteins and studied their various biochemical activities in vitro. Our results show that 6 amino acids are sufficient to determine the DNA binding and replication specificities of such initiator proteins.

Amino Acid Sequence↗
PubMed1992

Uncoupling of the DNA topoisomerase and replication activities of an initiator protein.

The replication initiator proteins encoded by the pT181 and related plasmids have sequence-specific DNA binding and topoisomerase activities. These proteins create a site-specific nick in one strand of the DNA at the origin of replication that serves as a primer for the initiation of replication. To define the regions of the pT181-encoded initiator protein, RepC, that are involved in its DNA binding, topoisomerase, and replication activities, we have carried out site-directed mutagenesis of the repC gene. Analysis of mutant RepC proteins in vitro and in vivo has identified the amino acids that are critical for its various biochemical activities. The DNA binding domain of RepC was found to be located near its C-terminal region and was different from the domain involved in its sequence-specific topoisomerase activity. These studies also showed that the DNA topoisomerase activity of the initiator protein can be uncoupled from its tight noncovalent DNA binding and replication activities.

Bacterial Proteins↗
PubMed1992

Replication of single-stranded plasmid pT181 DNA in vitro.

Plasmid pT181 is a 4437-base-pair, multicopy plasmid of Staphylococcus aureus that encodes tetracycline resistance. The replication of the leading strand of pT181 DNA initiates by covalent extension of a site-specific nick generated by the initiator protein at the origin of replication and proceeds by an asymmetric rolling circle mechanism. The origin of the leading strand synthesis also serves as the site for termination of replication. Replication of pT181 DNA in vivo and in vitro has been shown to generate a single-stranded intermediate that corresponds to the leading strand of the DNA. In vivo results have suggested that a palindromic sequence, palA, located near the leading strand termination site acts as the lagging strand origin. In this paper we report the development and characterization of an in vitro system for the replication of single-stranded pT181 DNA. Synthesis of the lagging strand of pT181 proceeded in the absence of the leading strand synthesis and did not require the pT181-encoded initiator protein, RepC. The replication of the lagging strand required RNA polymerase-dependent synthesis of an RNA primer. Replication of single-stranded pT181 DNA was found to be greatly stimulated in the presence of the palA sequence. We also show that palA acts as the lagging strand origin and that DNA synthesis initiates within this region.

Cell-Free System↗
PubMed1990

Specificity of RepC protein in plasmid pT181 DNA replication.

The plasmid pT181 of Staphylococcus aureus consists of 4437 base pairs and encodes resistance to tetracycline. Initiation of pT181 DNA replication specifically requires the plasmid-encoded initiator protein, RepC. The initiator protein binds specifically to a 32-base pair sequence within the pT181 origin of replication. RepC protein also has a nicking-closing activity that is specific for the pT181 origin. Replication of pT181 initiates by covalent extension of the nick and proceeds by a rolling circle mechanism. Two other small, multicopy plasmids pC221 and pS194 belong to the pT181 family and have common structural organization and replication properties. The replication proteins and replication origins of these plasmids have extensive sequence homologies, although they belong to different incompatibility groups. In spite of this homology, the replication proteins and replication origins of these three plasmids do not show any cross-reactivity in vivo. We have carried out a series of in vitro experiments to determine the specificity of pT181-encoded initiator protein, RepC. DNA binding experiments showed that although the binding of RepC to the pT181 origin was very efficient, little or no binding was seen with pC221 and pS194 origins. The nicking-closing activity of RepC was found to be equally efficient with the pC221 and pS194 plasmids. The plasmids pC221 and pS194 replicated efficiently in a RepC-dependent in vitro system. However, replication of these plasmids was greatly reduced in the presence of a competing pT181 origin. The results presented here suggest that nicking-closing by RepC at the origin is not sufficient for maximal replication and that tight binding of RepC to the origin plays an important role in the initiation of DNA replication.

Bacterial Proteins↗
PubMed1988

The effect of zeolite on the toxicity of lead to fungi.

In order to determine whether clinoptilolite, a naturally occurring zeolite, had any ameliorative effect on lead (Pb) toxicity to fungi, a series of growth experiments were performed. Three fungi, Aspergillus niger, Botrytis cinerea, and Fusarium culmorum, were grown on appropriately amended solid agar media, and their linear extension rates determined. B. cinerea was 25% inhibited, as compared to a control, at 100 mg dm(-3) Pb, and completely inhibited at 1000 mg dm(-3) Pb. F. culmorum was completely inhibited, and A. niger 97% inhibited at 1000 mg dm(-3) Pb. The addition of 3% clinoptilolite partially removed this inhibition in the case of A. niger and B. cinerea and almost completely removed it for F. culmorum. At a constant 500 mg dm(-3) Pb, increasing concentrations of clinoptilolite increased the linear extension rate of F. culmorum and B. cinerea, close to the rates achieved by the untreated controls. A. niger was not inhibited markedly at this Pb concentration. The evidence suggests that the Pb is adsorbed by the clinoptilolite which reduces the availability, and hence toxicity, of the metal to the fungi.

Journal Article↗
PubMedDate not supplied

The relationship between perceived dysfunctional family-of-origin rules and intimacy in young adult dating relationships.

This study examined the relationship between perceived dysfunctional family-of-origin rules and intimacy in single young adult dating relationships. A sample of 754 single, Caucasian-American young adults completed measures of perceived dysfunctional family-of-origin rules and emotional, intellectual, and sexual intimacy in dating relationships. When controlling for the effects of gender and age, results showed that perceived dysfunctional family-of-origin rules had a negative impact on the perceived expression and experience of these three kinds of intimacy in dating relationships. Implications for relationship therapy are discussed.

Adult↗