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Biomedical subjects

D Holland

Publications and source records attributed to D Holland.

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

Geometrical properties and torsional fatigue life of a tibial interlocking intramedullary nail segment.

OBJECTIVES: The first goal was to present details of a methodology for selecting the cross-sectional geometry and associated dimensions for a tibial interlocking intramedullary (i.m.) nail segment, given a set of candidate geometries. The second goal was to study the effect of four variables on the torsional fatigue life of specimens that constitute a segment of a tibial i.m. nail. METHODS: For the cross-sectional geometry study, the geometric element modeling and analysis method was used to obtain the areas (A) and moments of inertia (I and J) of each of the cross-sectional geometries in the set considered. In the fatigue tests, a specimen was subjected to a load at the end of a lever arm, through an actuator, at a fixed frequency. RESULTS: On the basis of the values of the A, I, and J and consideration of compatibility with the biological envelope, the hourglass cross-section geometry was selected as the best compromise. The cannulation, fillet radius, and main radius of this hourglass were determined to be 3.96, 1.02, and 4.06 millimeters, respectively. Fatigue test specimens fabricated from Ti-6Al-4V and having three sets of additional characteristics performed equally well as those fabricated from 316L stainless steel. These sets of characteristics are hourglass cross-section and mill annealed only; hourglass cross-section and mill annealed, followed by machining and anodization to give a gray coating; and cloverleaf cross-section and mill annealed, followed by machining and anodization to give a gray coating. CONCLUSION: Tibial IM nails with hourglass cross-sectional shape and fabricated of Ti-6Al-4V or Ti-13Nb-13Zr alloy, having appropriate mechanical, thermal, and surface treatments, may be competitive with the current "gold standard" (namely cloverleaf cross-section and fabricated of 316L stainless steel in the cold-worked state).

Bone Nails↗
PubMed1998

Herpes simplex type 2 infection in a cohort aged 21 years.

OBJECTIVES: To measure the prevalence of HSV-2 antibodies in a birth cohort of 21 year old New Zealanders from whom detailed sexual histories had been obtained, and to assess the potential for HSV-2 serology in characterising a young adult population's risk for sexually transmitted diseases (STD). METHODS: Sera from 784 cohort members were tested using an indirect IgG enzyme linked immunoassay specific to the HSV-2 glycoprotein G. Positive results were confirmed by western blot. RESULTS: In all, 27 subjects were seropositive for HSV-2 (3.4%), only seven of whom gave a history of genital herpes (26%). Risk among females increased with lifetime number of partners, while risk for males increased with having a first partner who was aged 16 years or under. CONCLUSIONS: The seroprevalence of HSV-2 infection in this cohort was low, but similar to that seen in several other populations in this age group. HSV-2 seropositivity did not appear to be a sensitive marker for high risk sexual activity in this young population. This may be because a critical mass of HSV-2 carriers has not accumulated among potential partners by age 21 years.

Adult↗
PubMed1997

Induction of a Citrus gene highly homologous to plant and yeast thi genes involved in thiamine biosynthesis during natural and ethylene-induced fruit maturation.

Maturing citrus fruit undergo pigment changes which can be enhanced by exogenous ethylene. In order to identify genes induced by ethylene in citrus fruit peel, we cloned the gene c-thi1. mRNA corresponding to c-thi1 increased gradually in the peel during natural fruit maturation and in response to ethylene. GA3 pretreatment reduced the inductive effect of ethylene. Levels of c-thi1 increased also in juice sacs but the effect of ethylene was much less prominent. c-thi1 is homologous to yeast and plant genes encoding for an enzyme belonging to the pathway of thiamine biosynthesis. The data suggest that thiamine is involved in citrus fruit maturation.

Adenine↗
PubMed1997

Fertility and reproductive choice in women with HIV-1 infection.

OBJECTIVE: To measure fertility and birth rates and to describe the reproductive histories of women diagnosed with HIV-1 infection in Australia. METHODS: The medical records of 294 women with HIV-1 infection in four states of Australia were reviewed. Expected fertility and birth rates were calculated using national statistics. RESULTS: In the study population, 152 (52%) women had at least one pregnancy prior or subsequent to HIV-1 diagnosis. At maternal HIV-1 diagnosis, 71 (24%) women had a total of 106 children aged under 15 years. During the study period, 246 women were aged 15, 44 years and 58 (23%) of these became pregnant after HIV-1 diagnosis. Women whose exposure to HIV-1 was injecting drug use were twice as likely to become pregnant and more likely to have multiple pregnancies than women who did not report injecting drug use. The annual general fertility rate was 30 per 10,000 compared with 63 per 10,000 for the Australian female population aged 15-44 years, and the birth rate in women with HIV-1 infection was one-half that of the general female population. Of pregnancies confirmed after HIV-1 diagnosis, 47% were voluntarily terminated, a rate more than double that of the general population. All multiple terminations were among women whose exposure to HIV-1 was injecting drug use. CONCLUSIONS: Fertility and birth rates among women with HIV-1 infection are lower than the general population and the rate of termination higher. The results of this study provide a basis for the management of women with HIV-1 infection who are considering pregnancy.

Adolescent↗
PubMed1997

Psychomotor agitation following gabapentin use in brain injury.

Gabapentin, an anticonvulsant structurally related to gamma-aminobutyric acid (GABA) was recently reported to be effective in pain associated with reflex sympathetic dystrophy (RSD) and in pain associated with neuropathy. Yet, to our knowledge, the use of gabapentin for neuropathic pain in the presence of cognitive impairment has not been reported. In this report, we describe two patients (one with a traumatic brain injury, one with a putative acquired brain injury) who presented to a neurorehabilitation unit complaining of pain that was diagnosed as neurologically mediated. Within one week of receiving a daily 900 mg dose of gabapentin, both patients complained of heightened anxiety and restlessness. Correspondingly, each reported a diminution of psychological symptoms within 48 hours of gabapentin cessation. These two cases suggest that gabapentin may cause agitation in cognitive impaired patients. Physicians treating brain-injured patients and prescribing gabapentin for neuropathic pain may wish to closely monitor patients for similar signs of restlessness or anxiety.

Acetates↗
PubMed1997

Investigation of the mechanism of action of 2% fusidic acid lotion in the treatment of acne vulgaris.

We describe the results of a single-centre, double-blind, vehicle-controlled, parallel group study on the quantitative effects of 2% fusidic acid lotion (Fucidin lotion) in facial acne vulgaris. The trial was completed by 52 patients aged 15-25 years with mild to moderate acne who had been randomized to either Fucidin Lotion (n = 25) or its base (n = 27). Primary outcome measures included colony counts of Propionibacterium acnes and micrococcaceae and measurements of skin surface lipid free fatty acids and sebum excretion rate. Clinical assessment was based on the acne grade, count of inflamed and non-inflamed lesions and evidence of a primary irritant dermatitis. There was a variable but gradual reduction in lesion counts with the maximum improvement at 12 weeks for inflamed lesions, where the reduction was 19.9% for fusidic acid and 24.7% for the placebo. The non-inflamed lesions decreased by 10.8% in the fusidic acid group and increased by 15.9% in the placebo group; this difference was not statistically significant. Although the fusidic acid reduced the micrococcaceae count by 1 log cycle, inferring adequate compliance, there was no reduction in the counts of P. acnes, surface free fatty acids or sebum excretion rate. This study has failed to explain the mechanism of action of topical fusidic acid.

Acne Vulgaris↗
PubMed1996

Non random usage of T cell receptor alpha gene expression in atopy using anchored PCR.

The T cell receptor (TCR) alpha beta heterodimer recognises antigenic peptide fragments presented by Class II MHC. This interaction initiates T cell activation and cytokine release with subsequent recruitment of inflammatory cells. Previous work from our group suggests a qualitative difference in variable alpha gene expression in atopy as compared to non atopic controls. In this study we examine TCR alpha repertoire using anchored PCR to provide a quantitative assessment of the V alpha and J alpha repertoire. One atopic (DRB1*0701,DRB1*15: DRB4*0101, DRB5*01: DQB1* 0303, DQB1*601/2) and one non-atopic (DRB1*0701,DRB1*03011/2: DRB4*01, DRB3*0x: DQB1* 0303, DQB1*0201/2) control were studied. Variable gene usage was markedly limited in the atopic individual. V alpha 1, 3, 8 accounted for 60% and J alpha 12, 31 30% of the gene usage. There was evidence of preferential V alpha-J alpha gene pairing and clonal expansion. We conclude that there is a marked non random TCR alpha gene distribution in atopy using both V alpha family and anchored PCR. This may be due in part to antigen driven clonal expansion.

Gene Expression↗
PubMed1996

Characterization of echovirus 22 variants.

Ten presumptive enterovirus isolates which could not be neutralized by type specific antisera to any prototype enterovirus were related to echovirus 22 using molecular, biologic and serologic methods. Viral protein fingerprinting and PCR first suggested that these strains were variants of echovirus 22. Three of the strains were echovirus 22 prime strains, i.e., antiserum made to the variant strain neutralized the variant and the prototype strain. The other strains were neutralized by antiserum to the prime strains. Unlike typical enteroviruses, echovirus 22 and 23 prototype viruses and 7 of the 10 variants were heat stable at 50 degrees C in H2O for 1 h.

Animals↗
PubMed1996

Establishment of an Agrobacterium-mediated transformation system for grape (Vitis vinifera L.): the role of antioxidants during grape-Agrobacterium interactions.

Very short exposures of embryogenic calli of Vitis vinifera cv. Superior Seedless grape plants to diluted cultures of Agrobacterium resulted in plant tissue necrosis and subsequent cell death. Antibiotics used for Agrobacterium elimination or as plant selectable markers were not responsible for this necrotic response. Rather, cell death seemed to be oxygen-dependent and correlated with elevated levels of peroxides. Therefore, we studied the effects on necrosis of various combinations of antioxidants during and after grape-Agrobacterium cocultivation. The combination of polyvinylpolypyrrolidone and dithiothreitol was found to improve plant viability. Tissue necrosis was completely inhibited by these antioxidants while Agrobacterium virulence was not effected. These treatments enabled the recovery of stable transgenic grape plants resistant to hygromycin.

Antioxidants↗
PubMed1996

The effect of hypertonic sodium bicarbonate on QRS duration in rats poisoned with chloroquine.

OBJECTIVE: To determine efficacy of hypertonic sodium bicarbonate in narrowing QRS prolongation produced by chloroquine. DESIGN: Randomized, controlled animal experiment using an accepted rat model of sodium channel blockade. METHODS: Hypotension and widening of QRS complexes (lead II) of the ECG were produced in 16 rats by administration of a total of 87 mg/kg chloroquine intravenously over 20 minutes. Eight rats were treated with 6 mL/kg 1 M sodium bicarbonate intravenously over two minutes beginning ten minutes into the chloroquine infusion. Serial measurements of QRS duration and systolic blood pressure were obtained for 30 minutes. RESULTS: QRS intervals narrowed more rapidly in animals receiving sodium bicarbonate (p = .045), although the difference in mean rate of narrowing between groups was modest at only .23 msec/min. Because of large variances, no statistically significant differences could be demonstrated in systolic blood pressure. CONCLUSIONS: Hypertonic sodium bicarbonate partially reversed sodium channel blockade and resultant QRS interval prolongation produced by chloroquine in rats. These data should be interpreted with caution, given the need to extrapolate to humans and the modest effect of sodium bicarbonate on QRS narrowing.

Amebicides↗
PubMed1995

Induction of a gene encoding an oleosin homologue in cultured citrus cells exposed to salt stress.

A cDNA clone (C3) with high homology to plant oleosins was isolated from citrus cultured cells. The 827-bp cDNA insert has an open reading frame of 144 amino-acid residues. The central hydrophobic domain of the protein is nearly identical to oleosins from Brassica napus and maize, and the C-terminal hydrophilic region following the hydrophobic domain is also highly conserved. The steady-state level of mRNA hybridizing to C3 was significantly increased upon exposure of citrus cells to 0.2 M NaCl. A lower level of transcript was found in seeds, but none could be detected in any other vegetative tissue (leaves, roots or fruit) even in the presence of salt under the conditions used. The induction of the oleosin homologue in citrus cells by salt does not depend on the developmental stage of the cells.

Amino Acid Sequence↗
PubMed1995

A stress-associated citrus protein is a distinct plant phospholipid hydroperoxide glutathione peroxidase.

A protein whose level is markedly increased upon exposure of cultured citrus cells and whole plants to NaCl, was shown to specifically catalyze the reduction of phosphatidylcholine hydroperoxide in the presence of glutathione. This enzymatic activity was shown to be independent of a similar activity exhibited by glutathione S-transferase in plants. This finding corroborates the significant homology (52%) accounted between the deduced amino acid sequence of the gene encoding for this protein and that of mammalian phospholipid hydroperoxide glutathione peroxidases. While the mammalian enzyme is known and well investigated, this study establishes the presence of this key protein also in plants.

Cells, Cultured↗
PubMed1995

Drought, heat and salt stress induce the expression of a citrus homologue of an atypical late-embryogenesis Lea5 gene.

In a search for genes that are induced in citrus cell suspension in response to salt stress, a cDNA clone with high homology to cotton Lea5 gene was isolated. Data base analysis of the protein deduced from the nucleotide sequence indicates that, like in cotton, the protein from citrus contains regions with significant hydropathic character. The gene, designated C-Lea5, is expressed in citrus leaves as well as cell suspension. The steady-state level of C-Lea5 is increased in cell suspension that is grown in the presence of 0.2 M NaCl. This phenomenon is also observed in leaves of citrus plants irrigated with NaCl and in citrus seedlings which are exposed to drought and heat stress. We suggest that the osmotic stress resulted from elevated level of salt is responsible for the increase in the level of C-Lea5.

Amino Acid Sequence↗
PubMed1995

Magic-angle spinning nuclear magnetic resonance study of the structure of some PbO-Al2O3-P2O5 glasses.

Some PbO-Al2O3-P2O5 glasses have been investigated using 31P and 27Al magic-angle spinning nuclear magnetic resonance. The observed spectra could be divided into two groups. In the first, Al(IV), Al(V) and Al(VI) are observed, the 31P linewidths are large and the chemical shift range (-30 to -36 ppm) is typical of network phosphate. In the second group, only Al(VI) is observed, the 31P linewidths are much narrower and the shifts are less negative (-18 to -28 ppm).

Aluminum Oxide↗
PubMed1994

Reagents for the preparation of two oligonucleotides per synthesis (TOPS).

In order to increase the efficiency of use of automated DNA synthesizers (i.e. the number of oligomers prepared per day), we have devised and prepared novel phosphoramidite reagents that contain a linking group which, while stable under the normal synthesis conditions, is cleaved under basic conditions. When one of these linkers is introduced at the desired position in the synthesis of an oligonucleotide, subsequent detritylation enables the synthesis of a second oligonucleotides sequence upon the first. During deprotection of the oligonucleotide with ammonium hydroxide, the chain is cleaved at either side of the points of introduction of the novel reagent, generating two oligonucleotides free in solution. These reagents are of particular use in applications where oligomers are used in pairs (such as PCR, chemical synthesis of genes etc.) and means that an automated synthesis facility can be used more efficiently, without the need for operator intervention, after the working day is over.

Amides↗
PubMed1994

(-)-Deprenyl alters the survival of adult murine facial motoneurons after axotomy: increases in vulnerable C57BL strain but decreases in motor neuron degeneration mutants.

The effect of (-)-deprenyl on the survival of axotomized adult murine facial motoneurons was investigated. Previously, (-)-deprenyl was shown to increase the number of rat facial motoneurons (FMns) surviving after axotomy at postnatal day 14, apparently by compensating for the loss of muscle-derived trophic factor. In the present study, three different strains of adult mice--A/J, C57BL/6J, and a congenic substrain of the C57BL/6J mice, the C57BL/Mnd mutants--underwent unilateral facial nerve transection. FMns were counted from serial sections taken through the entire length of the facial nuclei ipsilateral and contralateral to the facial nerve transections in animals sacrificed 21 days after axotomy. Subgroups of C57BL/6J and Mnd mutants were treated with either saline or 1.0 mg/kg (-)-deprenyl for 21 days. Another subgroup of Mnd mutants were treated with the metabolites of (-)-deprenyl, a mixture of (-)-amphetamine and (-)-methamphetamine, at a dosage equimolar to 1.0 mg/kg (-)-deprenyl. The number of surviving facial motoneurons in the A/J strain was 90% of unlesioned, control values which supports previous findings that adult FMns receive adequate trophic support and thus can survive loss of muscle-derived trophic support. In the C57BL/6J strain, the facial motoneuron survival was 35% and (-)-deprenyl increased the survival to 50.5%. Mnd mutants showed 62.4% survival; however, (-)-deprenyl decreased the number of motoneurons to 54.9% and amphetamine and methamphetamine treatment further decreased the motoneuron survival to 41.1%. These findings show that FMns in the Mnd mutants and their parental strain, C57BL/6J mice, show greater vulnerability to axotomy as compared to other adult strains of mice. The vulnerability is similar to that found in early postnatal life. (-)-Deprenyl increases the survival of the axotomized C57BL/6J FMns but its major metabolites, (-)-methamphetamine and (-)-amphetamine, further decrease FMn survival in the C57BL/Mnd mutants, possibly due to the induction of neurotoxic proteins causing programmed neuronal death. The efficacy of (-)-deprenyl in increasing the survival of damaged neurons would be expected to decrease as dosage increased above the dosage sufficient to induce maximum neuronal rescue (approximately 0.01 mg/kg) but would decrease as the dosage exceeded that necessary to produce toxic concentrations of the metabolites of (-)-deprenyl (1.0 mg/kg in this study).

Amphetamine↗