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Biomedical subjects

J Halliday

Publications and source records attributed to J Halliday.

At least 55 records · Page 3Linked to original sources
PubMed1993

Limb deficiencies, chorion villus sampling, and advanced maternal age.

Record linkage between a prenatal diagnosis register and a congenital malformation register in the state of Victoria, Australia, has enabled further evaluation of the suggested association between limb deficiencies and early chorion villus sampling (CVS). We found 3 anomalies in this category after later CVS (i.e., 9 weeks and beyond), but our data suggest that advanced maternal age may be a risk factor for both terminal and all limb deficiencies. The data from Victoria are tabulated with data obtained from other registers. Different birth prevalence figures are obtained by different registers, therefore limiting comparisons between registers.

Adult↗
PubMed1993

Absorbed aluminium is found with two cytosolic protein fractions, other than ferritin, in the rat duodenum.

After in vivo perfusion of the upper intestine of the rat with a range of concentrations of aluminium chloride, entry of the metal into the portal system was only detected when the perfusate exceeded 400 mumol/l, suggesting a mucosal block. Using gel filtration of a mucosal cytosol extract, two consistently appearing aluminium peaks were identified which may represent aluminium binding proteins. Both were heat stable at 60 degrees C and had molecular sizes of about 700 (kilo daltons) (kD) and 17 kD respectively. The larger molecule was distinct from ferritin. Neither molecule associated with 59Fe nor 45Ca. It is suggested that the aluminium peaks are relatively specific aluminium binding proteins that have a scavenging role, reducing entry of the metal from the intestinal contents into the portal blood.

Aluminum↗
PubMed1993

Significant changes in gastrointestinal tract parasitic infections in children of St. Kitts over the 9-year period 1982-1991.

When 239 (1982) and 361 (1991) five- and nine-year-old children in St. Kitts were assessed for the presence of parasitic infections, there were significant reductions in the prevalence of trichuriasis from 83% to 58%, of ascariasis from 24% to 8.6% and of giardiasis from 15% to 9.4%. Anthelminthic use, which appeared to be the most important responsible intervention tool, remained roughly at the same level at 59-51%. However, the types of anthelminthics used changed over the period. Piperazine citrate, which was used by 66% in 1982, only had 35% usage in 1991. Albendazole which was not used at all in 1982 was taken by 32% of the children in 1991 and at the same time use of laevo-tetramisole increased by 20% from 14%. Suggestions are made for an island-wide mass intervention programme to manage parasitic infections.

Anthelmintics↗
PubMed1992

Physical and genetic mapping of the telomeric major histocompatibility complex region in man and relevance to the primary hemochromatosis gene (HFE).

We performed pulsed-field gel electrophoresis (PFGE) on genomic DNA from a radiation hybrid (RH) cell line and constructed a high-resolution physical map of the major histocompatibility complex class I region in 6p21.3, where the gene for primary hemochromatosis (HFE) is believed to be located. Due to the intact microsegment of hemizygous human genomic DNA preserved in the RH cell line, simplified and distinct restriction fragment banding patterns were generated. Using the RH cell line, we were able to extend the physical map of the HLA class I region to about 3000 kb, order the known HLA class I genes from centromere to telomere: HLA-B, -C, -E, (-A, -H, -G), and -F, and orient the HLA-F gene along the chromosome. The proximity of HLA-F to HLA-A was confirmed by linkage and linkage disequilibrium analysis. This study shows that RH cell lines can be useful for constructing long-range physical maps in specific regions of the human genome with PFGE. Physical and genetic mapping studies of this region are consistent with a localization of the HFE gene proximal or distal to HLA-A.

Animals↗
PubMed1992

Cell-mediated immune response after vasectomy in rats.

This study investigated the development of a cell-mediated immune response after vasectomy in Swiss Albino rats, by comparing the development of the thymus-dependent lymphoid tissue of the regional testicular lymph node and the spleen in vasectomized and in sham-operated control animals. Frozen sections were used and thymus-dependent regions were stained by immunocytochemistry. After vasectomy, the areas occupied by the paracortex in the lymph node sections showed a significant increase in size; the thymus-dependent regions of the spleen, in contrast, showed no change. The regional lymph node, rather than the spleen, seems to be important in cell-mediated and humoral immune responses to vasectomy.

Animals↗
PubMed1989

Activation of sodium channels is not essential for endothelin induced vasoconstriction.

The role of sodium and calcium ions in the vasoconstrictor response of isolated rat aorta and protal vein to synthetically prepared endothelin is investigated. Contractile responses to endothelin, unlike those induced by the sodium channel activator veratridine, are unaffected by tetrodotoxin or by the removal of sodium chloride from the solution bathing the tissue. The responses are the same whether sodium chloride is replaced iso-osmotically with either sucrose or potassium chloride. The endothelin responses in all media are entirely dependent on the presence of extracellular calcium, and can be blocked by 1 microM nitrendipine. These findings offer no support to the idea that voltage activated sodium channels are the primary site of action of endothelin as suggested by sequence homologies to scorpion alpha-toxins, but are entirely consistent with the possibility that the site of action of endothelin is closely coupled to the calcium channel (Yanagisawa et al, 1988).

Animals↗
PubMed1989

Ionic requirements of the endothelin response in aorta and portal vein.

The vasoconstrictor responses of isolated rat portal vein and aorta to synthetically prepared endothelin are investigated. Both preparations respond to 10(-9) M levels of the peptide although the aortic response is more sustained than that of the portal vein. Endothelin-evoked contractions, unlike those evoked by scorpion alpha-toxins (which are homologous to endothelin) or by veratridine, are insensitive to tetrodotoxin or to the removal of sodium ions from the tissue-bathing medium. Contractile responses to endothelin may still be observed in high-potassium depolarizing medium and are not dependent on the presence of extracellular chloride; however, the responses are dependent on the presence of extracellular calcium and are blocked by nitrendipine, nifedipine, or nickel. Endothelin-evoked uptake of 45Ca into aortic tissue is also independent of extracellular sodium or potassium and is blocked by nifedipine. These data strongly suggest that endothelin acts at a site closely coupled to the calcium channel and that depolarization by sodium influx through voltage-dependent channels is not involved in endothelin-induced vasoconstriction.

Animals↗
PubMed1987

Phenotypic variation in male-transmitted fragile X: genetic inferences.

Three families with confirmed and one family with suspected male transmission of the fragile X are presented, with psychological and physical assessment of all available members. The psychological tests used were the Peabody Picture Vocabulary test and Block Design which measured verbal and non-verbal abilities, respectively. Physical status was assessed by recording dysmorphic features and by anthropometric measurements. This study demonstrated that there are appreciable differences in mental and physical status within sibships of daughters of male carriers, as well as recognizable physical alterations and intellectual impairment in the transmitting males. These findings contradict the concept that there are two distinct categories of fragile X carriers: phenotypically normal as opposed to affected. They suggest instead that the defect may be graded and emphasize the importance of intellectual deficits and physical alterations in defining the fragile X phenotype, both in low-penetrant males and female heterozygotes.

Child↗
PubMed1986

X linked hydrocephalus: a survey of a 20 year period in Victoria, Australia.

This study ascertained 164 males with non-communicating hydrocephalus in live or stillborn patients in Victoria. Australia in 1962 to 1982, after excluding those cases secondary to brain malformations other than aqueduct stenosis. Ascertainment was considered near complete, especially for the period since 1974, but details of the aqueduct pathology were inadequate in half the cases. A total of 91 families was seen to record detailed family information. The overall incidence of primary non-communicating hydrocephalus was estimated to be 0.6 +/- 0.2 per 1000 live and stillbirths, with three-fifths of the cases male. Twelve patients were classified as having definite X linked hydrocephalus and 13 others as probable cases of this condition. Deformities of the thumbs (generally adduction deformity) were present in nearly half of these cases. The pyramids were absent from sections of the medulla whenever these were available. Four of five survivors had signs suggesting pyramidal tract lesions, compared to four of 25 surviving non-X linked cases. The intellectual outcome was notably poorer in the X linked cases. Poor school performance was also described in five of 19 mothers of X linked cases but in only one of 64 mothers of the remaining cases. Familial recurrence in the whole group of patients was almost confined to the X linked families. The exceptions were two families in whom autosomal recessive inheritance is possible. It is important to remember X linked hydrocephalus in genetic counselling. Examination of the thumbs, search for clinical signs of pyramidal tract lesions, and anatomical examination of the pyramids in medullary sections are all important, along with careful questioning for a history of affected maternal relatives. The presence of any of these features is grounds for counseling on the basis of X linked inheritance. An empirical figure was derived to use when counseling about a male with non-communicating hydrocephalus in whom there is no adequate information about the thumbs or the pyramids: a 4% recurrence risk in male sibs and 2% in females.

Australia↗
PubMed1982

Dilution of liquid Rhizobium cultures to increase production capacity of inoculant plants.

Experiments were undertaken to test whether peat-based legume seed inoculants, which are prepared with liquid cultures that have been deliberately diluted, can attain and sustain acceptable numbers of viable rhizobia. Liquid cultures of Rhizobium japonicum and Rhizobium phaseoli were diluted to give 10, 10, or 10 cells per ml, using either deionized water, quarter-strength yeast-mannitol broth, yeast-sucrose broth, or yeast-water. The variously diluted cultures were incorporated into gamma-irradiated peat, and the numbers of viable rhizobia were determined at intervals. In all of the inoculant formulations, the numbers of rhizobia reached similarly high ceiling values by 1 week after incorporation, irrespective not only of the number of cells added initially but also of the nature of the diluent. During week 1 of growth, similar multiplication patterns of the diluted liquid cultures were observed in two different peats. Numbers of rhizobia surviving in the various inoculant formulations were not markedly different after 6 months of storage at 28 degrees C. The method of inoculant preparation did not affect the nitrogen fixation effectiveness of the Rhizobium strains.

Journal Article↗
PubMed1980

Removal of sialic acid from cardiac sarcolemma does not affect contractile function in electrically stimulated guinea pig left atria.

Calcium is essential for the maintenance of contraction in the heart, and it has been suggested that the glycoprotein matrix on the external surface of cardiac cells is a critical factor in the supply of 'activator' calcium to the beating heart. Sialic acid residues are important calcium-binding sites in the matrix and treatment with neuraminidase, an enzyme which cleaves sialic acid from oligosaccharide chains, has been reported to abolish spontaneous contraction in cultured heart cells, without causing general breakdown in the plasma membrane. However, we report here that in intact, electrically stimulated guinea pig atrial preparations, neuraminidase treatment produces no significant changes in resting tension or force of contraction. It is also without effect on the response to calcium removal and replacement, and inotropic or toxic concentrations of cardiac glycosides. In these experiments, up to 79% of the total tissue sialic acid was removed, and electron microscopy studies showed that this removal was accompanied by marked reduction of lanthanum binding to the sarcolemma. We therefore conclude that the calcium-binding sialic acid residues in the external matrix of the cardiac cells are of little importance in the maintenance of contractile function in these intact atrial preparations.

Animals↗
PubMed1980

Enhancement of the toxic effects of veratrine on guinea-pig atrium by threshold inotropic doses of ouabain.

Isolated atria of guinea-pigs were treated with veratrine until the initial signs of toxicity were seen. Ouabain was then added cumulatively, starting with a threshold inotropic concentration, 50 nM, until the tissue became dysrhythmic. It was found that a concentration of ouabain which by itself gave a positive inotropic effect of only 3%, significantly enhanced the toxicity of veratrine. Veratrine had no effect on the (Na+ + K+)-adenosine triphosphatase ((Na+ + K+)-ATPase) enzyme isolated from guinea-pig ventricle. The conclusion drawn is that at threshold inotropic concentrations of ouabain it is likely that the (Na+ + K+)-ATPase is inhibited rather than stimulated.

Animals↗