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Biomedical subjects

D Tucker

Publications and source records attributed to D Tucker.

At least 19 recordsLinked to original sources
PubMed1997

Associative learning by locusts: pairing of visual cues with consumption of protein and carbohydrate

We investigated whether fifth instar African migratory locusts, Locusta migratoria could learn to associate visual cues with the macronutrient content of synthetic foods. During a 48-h training period, the insects had ad libitum access to two synthetic foods which were identical in all respects except that one lacked protein and the other lacked digestible carbohydrate. One food was placed at the end of a transparent Perspex cylinder which had been tinted green, and the other at the end of a yellow-tinted cylinder which was similar in all other respects. To obtain a balanced diet, the insects were thus forced to ingest the two macronutrients in visually different environments. Following this training period, they were then made selectively deficient in either protein or carbohydrate, before being tested for their tendency to enter, and the depth of entry into, yellow- or green-tinted cylinders that did not contain food. Locusts entered significantly more frequently the colour of cylinder that had previously been paired with the deficient nutrient (henceforth termed the 'training colour'). This was true irrespective of whether the nutrient was protein or carbohydrate, and whether the training colour was green or yellow. There was no effect of training on the average depth of entry into the cylinders. However, protein-deprived locusts penetrated significantly more deeply than carbohydrate-deprived locusts into both green and yellow cylinders, irrespective of the training colour. A separate experiment demonstrated that naive locusts entered more frequently into the yellow than the green side-arm, but there was no influence of colour on the depth of entry by naive locusts.Copyright 1997 The Association for the Study of Animal BehaviourCopyright 1997The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1997

Sydenham's chorea.

Sydenham's chorea (SC) is a disorder of the central nervous system (CNS) characterized by sudden, involuntary, arrhythmic, clonic, and purposeless movements. SC appears to provide a model for understanding various neuropsychiatric dysfunctions. Its relationship with attentional deficits, obsessive-compulsive symptoms (OCS) as well as movement disorders provides support for the hypothesis of the involvement of the corticostriatal loops in the pathophysiology of the disorder.

Autoimmune Diseases↗
PubMed1997

Morphological and morphometric characterisation of Onuf's nucleus in the spinal cord in man.

In the absence of a systematic morphometric study of Onuf's nucleus in man, this investigation defines the limits of variation of segmental position and the range of length and volume of Onuf's nucleus in 6 normal humans displaying no neurological disease (2 males, 4 females). Serial section reconstruction methods in conjunction with the disector method provided information on the numbers, sizes and shapes of the constituent motor neurons of Onuf's nucleus. In contrast to previous descriptions, the cranial origin of Onuf's nucleus occurred in rostral S1 in 50% of subjects, and midcaudal S1 in the remaining subjects. Onuf's nucleus varied in length between 4 and 7 mm, and was 0.2-0.37 mm3 in volume. Differences in length or volume between males or females, or between the left and right side of the cord were not statistically significant. Neurons in Onuf's nucleus varied in diameter between 10 microns and 60 microns (mean 26 microns) and their mean number was 625 +/- 137. A higher density of neurons occurred at the cranial and caudal ends of the nucleus relative to the middle. While 37% of neurons were approximately spherical (shape index approximately 1), 44% were ellipsoid and 19% fusiform (shape indices varying between 0.26 and 0.8). These findings are compared with previous studies of Onuf's nucleus in man and animals. The results form a basis for further studies on Onuf's nucleus in normality and neurodegenerative diseases.

Aged↗
PubMed1997

Relationship of diastolic blood pressure with cyclic GMP excretion among young adults (the CARDIA Study): influence of a family history of hypertension. Coronary Artery Risk Development in Young Adults.

BACKGROUND: Guanosine 3':5'-cyclic monophosphate (cGMP) is the second messenger of nitric oxide and atrial natriuretic factor, and mediates local vasodilatation. These vasodilatory factors are important in blood pressure regulation and possibly in the etiology of hypertension. Urinary cGMP levels among normotensive young adults have not previously been studied. SUBJECTS: A subset of normotensive participants from the CARDIA study (n = 563), aged 23-35 years, was studied. The sample was approximately balanced for sex and race (black/white). METHODS: Twenty-four-hour urinary cGMP levels were measured using an enzyme immunoassay; levels were adjusted for creatinine excretion. The blood pressure, smoking status, and risk factors for hypertension [including a family history of hypertension (FHH), the body mass index, education, alcohol intake, and sodium excretion] were also measured. RESULTS: Women excreted more cGMP than did men, and blacks excreted more cGMP than did whites (both P < 0.0001). Excretion of cGMP was also greater among smokers (P < 0.001) and those with an FHH (P = 0.05), and was related directly and independently to sodium excretion (P < 0.02). The diastolic blood pressure (DBP) was related inversely to the excretion of cGMP among individuals without an FHH (r = -0.36, P < 0.001), but not among individuals with an FHH. In multiple regression analysis, the excretion of cGMP remained related significantly to the DBP and accounted for more variance in DBP than did any other variable among those without an FHH (delta R2 = 0.08, P < 0.001). CONCLUSIONS: Urinary cGMP excretion is related inversely and independently to the DBP among those without an FHH but not among those with an FHH, suggesting that cGMP-related vasodilatation is impaired in those with an FHH. Sex differences in urinary excretion of cGMP are consistent with results from studies showing that estrogen increases the endothelial production of nitric oxide.

Adult↗
PubMed1997

Indicators of delayed maturation of rat heart treated prenatally with dexamethasone.

We investigated the effects of prenatal dexamethasone treatment on indicators of cardiac maturation: heart weight/body weight ratios, myosin heavy chain (MHC) expression, cell proliferation, and extracellular matrix. We administered dexamethasone, a synthetic glucocorticoid (approximately 48 microg/d, 3-wk slow release pellets), to pregnant rats (n = 8) beginning at 17 d postconception. Control dams were unmanipulated (n = 8). After approximately 4-5 d of dexamethasone exposure, hearts were collected from neonatal rats (12-24 h after birth). The prenatal dexamethasone treatment produced smaller pups with larger heart/body weight ratios, accompanied by a higher proliferative index and a reduction in extracellular matrix in the ventricles (with lowest values in the septal region) compared with control pups. We also report that, although there were no sex differences in body mass or heart and heart/body weight ratios, females had a greater proportion of cells synthesizing DNA in the heart. In addition, ventricles of male pups treated with dexamethasone contained lower levels of alpha-MHC mRNA, as reflected in a sex by treatment interaction. The changes in each parameter are consistent with delayed maturation. Our findings suggest that exposure to excess glucocorticoids in utero can affect cardiac development in potentially detrimental ways and that assessment of cardiac function should be closely monitored when such circumstances arise.

Animals↗
PubMed1997

Aural rehabilitation and graduate audiology programs.

The quantity and quality of aural rehabilitation training that audiology graduate students receive versus the current services available to those students regarding work with the hearing impaired, cochlear implant recipients, patients with vestibular disorders, patients with central auditory processing disorders, and patients suffering from tinnitus were examined. Forty ASHA-accredited colleges and universities were contacted by telephone and audiology faculty members were surveyed. The results of the survey may provide valuable information for identifying and addressing shortfalls in aural rehabilitation programs.

American Speech-Language-Hearing Association↗
PubMed1996

Morphologic changes following in vitro CO2 laser treatment of calculus-ladened root surfaces.

BACKGROUND AND OBJECTIVE: The purpose of this study was to compare morphologic changes following C02 laser or manual curette treatment of calculus-ladened tooth root surfaces. STUDY DESIGN/MATERIALS AND METHODS: Laser treatment consisted of repeated single passes with a 6 Watt focused beam at 20 pulses per second, a pulse length of 0.01 second, and a manufacturer's laser efficiency rating of 86% (i.e., the amount of total power delivered through the aperture). The rate of beam passage over the target surface was controlled at 4 mm/second using an 0.8 mm diameter tip. The calculated energy density was 240 J/cm2 for each pass of the beam. Scaled and root planed surfaces were treated with a standardized force of 600 grams using new curettes. Specimens were evaluated by scanning electron microscopy. RESULTS: Laser-induced surface changes included charring, meltdown and resolidification of calculus mineral, and ablation of microbial plaque. Laser-treated specimens also exhibited residual calculus and microbial plaque deposits in areas directly adjacent to the beam path. Scaled and root planed surfaces featured smooth and/or scale like smear layers and islands of residual calculus and microbial plaque. CONCLUSIONS: The rough surface topography resulting from laser treatment and residual calculus and microbial plaque deposits indicates that C02 laser treatment of exposed root surfaces is, at best, an adjunct to traditional methods of therapy.

Dental Calculus↗
PubMed1996

Genetic transformation, recovery, and characterization of fertile soybean transgenic for a synthetic Bacillus thuringiensis cryIAc gene.

Somatic embryos of jack, a Glycine max (L.) Merrill cultivar, were transformed using microprojectile bombardment with a synthetic Bacillus thuringiensis insecticidal crystal protein gene (Bt cryIAc) driven by the 35S promoter and linked to the HPH gene. Approximately 10 g of tissue was bombarded, and three transgenic lines were selected on hygromycin-containing media and converted into plants. The recovered lines contained the HPH gene, but the Bt gene was lost in one line. The plasmid was rearranged in the second line, and the third line had two copies, one of which was rear-ranged. The CryIAc protein accumulated up to 46 ng mg-1 extractable protein. In detached-leaf bioassays, plants with an intact copy of the Bt gene, and to a lesser extent those with the rearranged copy, were protected from damage from corn earworm (Helicoverpa zea), soybean looper (Pseudoplusia includens), tobacco budworm (Heliothis virescens), and velvetbean caterpillar (Anticarsia gemmatalis). Corn earworm produced less than 3% defoliation on transgenic plants, compared with 20% on the lepidopteran-resistant breeding line GatIR81-296, and more than 40% on susceptible cultivars. Unlike previous reports of soybean transformation using this technique, all plants were fertile. To our knowledge, this is the first report of a soybean transgenic for a highly expressed insecticidal gene.

Animals↗
PubMed1995

Transcription of interferon-alpha 2 alleles from virus-induced human leucocytes and lymphoblastoid cells of African origin.

It has been previously shown that the genomic DNA of both the lymphoblastoid cell line (Namalwa) and certain human donors (of African origin) contain sequences corresponding to two allelic variants, b and c, of the interferon-alpha 2 gene (IFNA2). Little is known however about the relative expression of these two alleles in heterozygous cells. We have therefore examined the transcription of allelic variants of the human IFNA2 locus by both normal human leucocytes (from a heterozygous donor) and Namalwa cells. Analysis of cDNA clones identified sequences of both allelic variants, IFNA2b and c, indicating active transcription by both cell types. Analysis of tryptic and peptic peptides derived from purified IFN-alpha 2 also demonstrated both IFN-alpha 2b and IFN-alpha 2c proteins. Populations of virus induced heterozygous cells can therefore effectively transcribe and secrete both forms of IFN-alpha 2 simultaneously, with no apparent restrictions on expression of either allele.

Alleles↗
PubMed1995

Detection of rare allelic variants of the interferon-alpha 2 gene in human genomic DNA.

We have analyzed human donor DNA for the presence of sequences corresponding to allelic variants of the IFN-alpha 2 locus. Using both restriction enzyme digestion of PCR-amplified fragments and sequence analysis of these fragments, we have identified the three reported allelic variants, IFN-alpha 2a, IFN-alpha 2b, and IFN-alpha 2c, in genomic DNA derived from donors of African or Afro-Caribbean origin. This is the first report of the IFN-alpha 2a and IFN-alpha 2c alleles occurring in human donor DNA and supports the view that these are variants of the predominant IFN-alpha 2b allele rather than arising from mutations occurring in cultured cells.

Alleles↗
PubMed1995

Immigrant families coping with schizophrenia. Behavioral family intervention v. case management with a low-income Spanish-speaking population.

BACKGROUND: This investigation compared the effectiveness and cross-cultural applicability of behavioural family management (BFM) and standard case management in preventing exacerbation of symptoms and relapse in schizophrenia. METHOD: Forty low-income Spanish-speaking people with a diagnosis of schizophrenia were randomly assigned to receive standard case management or behavioural family management after stabilisation with neuroleptic medication. RESULTS: Survival analyses indicated that among the less acculturated patients BFM was significantly related to greater risk of exacerbation of symptoms. Among the more acculturated patients, risk of exacerbation could be predicted by medication compliance but not by type of intervention. In analyses of symptom severity and functional status at 1-year follow-up, the level of patient acculturation was found to be significantly related to various measures of treatment outcome. CONCLUSION: Sociocultural factors affect responses to different types of intervention. The results did not support earlier findings of a beneficial effect of BFM when applied to a socioculturally diverse population.

Acculturation↗
PubMed1994

Inhibition of pancreatic proglucagon gene expression in mice bearing subcutaneous endocrine tumors.

The proglucagon-derived peptides (PGDPs) play key roles in the regulation of carbohydrate metabolism and insulin secretion, yet the factors important for the regulation of proglucagon gene expression remain poorly understood. Recent experiments demonstrated that nude mice carrying subcutaneous proglucagon-SV40 T antigen tumors contained markedly reduced levels of the pancreatic PGDPs. To determine if elevated circulating levels of the PGDPs are consistently associated with inhibition of endogenous pancreatic proglucagon gene expression, we have now studied islet hormone gene expression in mice bearing three different endocrine tumors (InR1-G9, RIN1056A, and STC-1) that express the proglucagon gene. All tumors synthesized large amounts of the PGDPs. Plasma levels of the PGDPs were elevated in all tumor-bearing mice (8- to 22-fold greater than controls, P < 0.001), and this was associated with marked inhibition of mouse pancreatic proglucagon gene expression. The levels of pancreatic PGDPs were also significantly lower in tumor-bearing mice compared with controls (71 +/- 4, 38 +/- 6, and 18 +/- 2% of controls for InR1-G9-, RIN1056A-, and STC-1-bearing mice, respectively, P < 0.05-0.001). This inhibition of proglucagon gene expression was highly specific, in that no consistent change in pancreatic insulin or somatostatin gene expression was detected. Examination of proglucagon posttranslational processing in the tumors demonstrated that proglucagon was processed differently in each tumor to yield a unique profile of PGDPs. These observations demonstrate that elevated circulating levels of the PGDPs are associated with reduction in islet size and inhibition of proglucagon gene expression and PGDP synthesis in the pancreatic A cell.

Animals↗
PubMed1993

Results of intensive therapy in childhood acute myeloid leukemia, incorporating high-dose melphalan and autologous bone marrow transplantation in first complete remission.

Childhood acute myeloid leukemia (AML) has a poor prognosis with standard chemotherapy. Allogeneic bone marrow transplantation (BMT) in remission improves the outlook only for the one third of patients with sibling donors. Autologous BMT with a lower morbidity and mortality is available to all. In this study, maximum cytoreduction was achieved by intensive early chemotherapy. Final intensification, with autologous BMT was offered to all those remaining in first complete remission (CR). Patients received two induction and two consolidation courses of intensively scheduled chemotherapy. Cytoreduction was assessed on day 14 and remission was assessed after courses 2 and 4. Bone marrow was harvested after recovery from the second consolidation course or after the first maintenance course and separated on a discontinuous percoll gradient before cryopreservation. Twenty-eight of 31 consecutively enrolled patients achieved CR. Three relapsed early and, of the 25 eligible, 24 underwent autologous BMT. Twenty-three patients received high-dose melphalan and 1 received busulphan and cyclophosphamide before autologous BMT at a median of 113 days (range, 86 to 301) after initial CR. Trilineage engraftment occurred in all. Neutrophil recovery to greater than 0.5 x 10(9)/L occurred at a median of 46 days (range, 13 to 92) after autologous BMT. Platelet recovery was delayed, with a median time to achieve greater than 20 x 10(9)/L of 42 days (range, 18 to 215). With a minimum follow up of 25 months following autologous BMT only 3 children have relapsed. The 5-year event-free survival rate (EFS) from diagnosis is 68% (95% confidence interval, 46% to 90%). Five-year EFS following autologous BMT is 87% (95% confidence interval, 67% to 100%). Autologous BMT with high-dose melphalan administration after intensive chemotherapy has produced EFS equivalent to allogeneic BMT and is associated with a strikingly low relapse rate. High-dose melphalan appears to be a valuable agent for conditioning therapy in AML.

Acute Disease↗
PubMed1993

Characterization of stroma-adherent colony-forming cells: a clonogenic assay for early hemopoietic cells?

Hemopoietic cells that adhered to preformed selected marrow stromal cell layers were characterized on the basis of progenitor cell production capacity, colony-formation kinetics and forward light scatter (FLS) properties. It was shown that early hemopoietic cells attached to the stromal layers within 2 hours of incubation, and were responsible for the initial production of the more differentiated granulocyte-macrophage colony-forming cells (day 14 GM-CFC) in long-term cultures (LTC). In a clonogenic assay system, hemopoietic cells that adhere to stromal layers can be detected by the formation of small colonies of blast-like cells and are designated as stroma-adherent CFC. Cell fractionation on the basis of FLS and counting colonies on days 5, 14 and 21 revealed that there was a succession of colony formation, indicating that the stroma-adherent CFC consisted of subpopulations with different lag-phases before initiation of proliferation. Day 5, day 14 and day 21 stroma-adherent CFC were shown to have a high, intermediate and low FLS, respectively. The cells that produced GM-CFC by day 21 showed FLS properties similar to those of day 21 stroma-adherent CFC, suggesting a correlation between day 21 stroma-adherent CFC and CFC-producing cells in LTC. The CFC present on day 21 required the synergistic action of GM-CSF+IL-3 + stem cell factor (SCF) for optimal proliferation. The prolonged lag-phase, the low FLS and the multifactor-responsive progeny are properties similar to those reported for other early cells, and it is proposed that day 21 stroma-adherent CFC represent an early hemopoietic cell type whereas day 5 stroma-adherent CFC represent a more mature stage of differentiation.

Bone Marrow↗
PubMed1992

Enhancement of chest images by automatic adaptive spatial filtering.

Postprocessing of the image data is an exciting capability of digital radiography that may improve diagnostic performance. We present a new algorithm that selectively enhances edges and contrast in both lungs and mediastinum while minimally amplifying noise in chest images. Using different size kernels, two smoothed images are generated from the original chest image. The two regions of interest (lungs and mediastinum) are identified based on the distribution of pixel values in the image. A modified nonlinear unsharp mask subtraction technique is then applied. The resulting image has enhanced high- and middle-frequency information in the mediastinum without distorting lung parenchyma or significantly enhancing noise. We consider that the technique employed in this study could be suitable for routine use although its true effectiveness in improving diagnostic accuracy awaits observer-performance evaluation that is currently under way.

Adult↗
PubMed1992

The endodontic microflora revisited.

The microbial flora of 35 dental root canals were examined, taking care to maintain the viability of obligate anaerobes which accounted for 45% of total isolations, while streptococcal species accounted for 24% of the total species isolated. Individual root canals yielded a maximum of eight bacterial species. A total of 40 different species was isolated of which the most prevalent were the facultative anaerobe Streptococcus sanguis and the obligate anaerobe, Peptostreptococcus micros (both in 23% of root canals), followed by Eubacterium aerofaciens and the 'Streptococcus milleri group' (both 17%) then Prevotella melaninogenica (formerly Bacteroides melaninogenicus), Enterococcus faecalis and Prevotella oralis (formerly Bacteroides oralis), which were each isolated from 14% of root canals. Highly significant associations were discovered between four pairs of species, viz P. melaninogenica with P. micros, P. melaninogenica with P. oralis, Prevotella corporis with Streptococcus morbillorum and Actinomyces odontolyticus with E. faecalis.

Dental Pulp Cavity↗