Search PubMed⌕ Search

Biomedical subjects

R Douglas

Publications and source records attributed to R Douglas.

At least 55 records · Page 3Linked to original sources
PubMed1988

Surrogate testing for non-A, non-B hepatitis in Queensland, Australia: an ALT microtitre tray method for screening blood donors.

The estimation of plasma alanine aminotransferase (ALT) has been proposed as a surrogate test to identify potential non-A, non-B hepatitis carriers in blood donor populations. This report describes an ALT screening procedure which uses wells of microtitration trays as reactant vessels. The method utilizes a rate reading photometer, is economical and conveniently fits into the routine workflow. Within-batch and between-batch precision was 4.1% and 6.3% at enzyme concentrations of 49 IU/I. Results of testing 29,675 healthy blood donors gave values which ranged between 1.0 IU/I and 214 IU/I. A study of 762 donations showed a significant difference in mean ALT values between males and females (p less than 0.01). When a cut-off value of 46 IU/I was used, 2.5 percent of donations were considered unsuitable for transfusion. The medico-legal implications that may arise from the introduction of this screening test into the routine work flow are discussed.

Alanine Transaminase↗
PubMed1987

The crossed nigrostriatal projection decussates in the ventral tegmental decussation.

Horseradish peroxidase (HRP) tract-tracing techniques were used in 44 rats in order to establish the site of decussation of the crossed nigrostriatal projection. Somata in both the ipsilateral and the contralateral ventromedial mesencephalon were labelled after injection of HRP into the caudate nucleus. In agreement with previous studies, contralateral labelling constituted about 3% of the ipsilateral labelling. Midsagittal transection of the mesodiencephalic junction did not prevent the contralateral labelling. However, mid-sagittal transection of the ventral mesencephalon, or selective 6-hydroxydopamine (6-OHDA) lesions of the ventral tegmental decussation did prevent the contralateral labelling. Moreover, 6-OHDA lesions of the substantia nigra ipsilateral to the horseradish peroxidase injection also prevented contralateral labelling. We conclude that the crossed nigrostriatal projection decussates in the ventral tegmental decussation, and that this projection is susceptible to damage by standard 6-OHDA lesions located on the opposite side to the origin of the crossed pathway.

Animals↗
PubMed1987

Plasminogen activator inhibitor type 1 gene is located at region q21.3-q22 of chromosome 7 and genetically linked with cystic fibrosis.

The regional chromosomal location of the human gene for plasminogen activator inhibitor type 1 (PAI1) was determined by three independent methods of gene mapping. PAI1 was localized first to 7cen-q32 and then to 7q21.3-q22 by Southern blot hybridization analysis of a panel of human and mouse somatic cell hybrids with a PAI1 cDNA probe and in situ hybridization, respectively. We identified a frequent HindIII restriction fragment length polymorphism (RFLP) of the PAI1 gene with an information content of 0.369. In family studies using this polymorphism, genetic linkage was found between PAI1 and the loci for erythropoietin (EPO), paraoxonase (PON), the met protooncogene (MET), and cystic fibrosis (CF), all previously assigned to the middle part of the long arm of chromosome 7. The linkage with EPO was closest with an estimated genetic distance of 3 centimorgans, whereas that to CF was 20 centimorgans. A three-point genetic linkage analysis and data from previous studies showed that the most likely order of these loci is EPO, PAI1, PON, (MET, CF), with PAI1 being located centromeric to CF. The PAI1 RFLP may prove to be valuable in ordering genetic markers in the CF-linkage group and may also be valuable in genetic analysis of plasminogen activation-related diseases, such as certain thromboembolic disorders and cancer.

Chromosomes, Human, Pair 7↗
PubMed1986

Plasminogen activator inhibitor type-1: reactive center and amino-terminal heterogeneity determined by protein and cDNA sequencing.

Both the urokinase-type and tissue-type plasminogen activator can convert their approximately 54 kDa type-1 inhibitor (PAI-1) to an inactive form with a lower apparent molecular mass. We have determined the amino-terminal amino acid sequences of human native and converted PAI-1, and isolated PAI-1 cDNA and determined the nucleotide sequence in regions corresponding to the amino-terminus and the cleavage site. The data show that the conversion of the inhibitor consists of cleavage of an Arg-Met bond 33 residues from the carboxy-terminus, thus localizing the reactive center of the inhibitor to that position. In addition, a heterogeneity was found at the amino-terminus, with a Ser-Ala-Val-His-His form and a two-residue shorter form (Val-His-His-) occurring in approximately equal quantities.

Amino Acid Sequence↗
PubMed1985

Hemispheric disconnection and rotational behaviour.

Several studies have demonstrated the existence of crossed pathways interconnecting the bilateral extrapyramidal system. The present study has evaluated the role of the thalamus in the interhemispheric control of nigrostriatal function by observing the effect of midsagittal thalamic transection on amphetamine-induced rotation in rats. The effect of thalamic transection on net rotational asymmetry did not differ from the effects of sham operations. Also, the transection did not affect the rotational asymmetry induced by subsequent lesioning of the dominant hemisphere substantia nigra. The failure to affect the rotation asymmetry by the transection suggests either that the inter-hemispheric pathway does not control extrapyramidal asymmetry or that the crossing takes place outside the thalamus. In an additional group of rats, thalamic transection did not interrupt retrograde labeling of somata in the substantia nigra and ventral tegmental area by horseradish peroxidase injected in the contralateral caudate. Thus, the crossed nigrostriatal projection does not decussate via the thalamus. It is suggested that this pathway decussates in the ventral mesencephalon.

Amphetamine↗
PubMed1984

The reciprocating gait orthosis in myelomeningocele.

Seventeen patients with myelomeningocele were fitted with a device that reciprocally controls hip flexion and extension in an attempt to improve ambulatory ability. To evaluate the function of the reciprocating mechanism, the orthosis was tested in three configurations. With the reciprocating mechanism functioning at the hips, five of eight patients ambulated faster than in other configurations. With the mechanism released for free hip joint motion, five of eight patients ambulated slower or not at all. With the hip joints locked, six of eight patients ambulated more slowly than with the reciprocating mechanism functioning. Two were faster with a swing-through gait. However, 11 of 12 independent ambulators spontaneously chose the reciprocating gait pattern over the swing-through pattern. The reciprocating gait orthosis was used by patients with meningomyelocele from 18 months to 15 years of age. The device was most successful if strong hip flexors were present, although ambulation in a reciprocal pattern was possible for some with no active hip musculature. We believe that this orthosis is the most effective ambulatory aid for children handicapped by hip extensor weakness.

Adolescent↗
PubMed1984

Action spectrum of photomechanical cone contraction in the catfish retina.

The action spectrum for the photomechanical contraction of catfish single cones was found to fit the absorbance spectrum of the visual pigment they contain (determined by microspectrophotometry). This indicates that cone contraction is brought about by a direct effect of light on the cones themselves and not, as is the case for the epithelial pigment, by an indirect effect via the rods.

Animals↗
PubMed1983

A study of the errors produced when weak antibodies are tested by the indirect antiglobulin method.

An investigation is reported into the error rate of the indirect antiglobulin test when random, weakly reactive samples are tested. Tests were completed by the majority of laboratory staff in 2 transfusion services and 3 major general hospital blood banks, during their routine daily work. A significant level of technical difficulty was revealed, from 5.2 to 60.8% of positive tests being called negative, and from 5.7 to 32.3% of negative tests being called positive. Reproducibility of weakly reacting duplicates was generally poor, as was the allocation of score values to the agglutination reactions. The significance of these findings relative to the content of quality control surveys is discussed.

Blood Banks↗
PubMed1981

IgG antibodies to phosphorylcholine exhibit more diversity than their IgM counterparts.

An amino acid sequence analysis of the N-terminal immunoglobulin heavy and light chain variable regions (VH and VL) from 16 hybridoma proteins which bind phosphorylcholine as well as the complete sequence analysis of 9 of these VH regions is presented. There seem to be more VH regions participating in the phosphorylcholine response than can be encoded directly by germ-line VH gene segments. Moreover, the V regions from IgG antibodies are considerably more variable than those from their IgM counterparts. These observations raise the possibility that a somatic mechanism for V region diversification produces greater diversity in IgG than in IgM antibodies.

Amino Acid Sequence↗