Search PubMed⌕ Search

Biomedical subjects

J R Brown

Publications and source records attributed to J R Brown.

At least 73 records · Page 4Linked to original sources
PubMed1997

Archaea and the prokaryote-to-eukaryote transition.

Since the late 1970s, determining the phylogenetic relationships among the contemporary domains of life, the Archaea (archaebacteria), Bacteria (eubacteria), and Eucarya (eukaryotes), has been central to the study of early cellular evolution. The two salient issues surrounding the universal tree of life are whether all three domains are monophyletic (i.e., all equivalent in taxanomic rank) and where the root of the universal tree lies. Evaluation of the status of the Archaea has become key to answering these questions. This review considers our cumulative knowledge about the Archaea in relationship to the Bacteria and Eucarya. Particular attention is paid to the recent use of molecular phylogenetic approaches to reconstructing the tree of life. In this regard, the phylogenetic analyses of more than 60 proteins are reviewed and presented in the context of their participation in major biochemical pathways. Although many gene trees are incongruent, the majority do suggest a sisterhood between Archaea and Eucarya. Altering this general pattern of gene evolution are two kinds of potential interdomain gene transferrals. One horizontal gene exchange might have involved the gram-positive Bacteria and the Archaea, while the other might have occurred between proteobacteria and eukaryotes and might have been mediated by endosymbiosis.

Archaea↗
PubMed1997

A spray management valve for hand-compression sprayers.

The commercially available spray management valve provided consistent flow rates when used with hand-compression sprayer systems. The 15-psi spray management valve maintained a constant flow rate of 180, 150, and 155 ml/min in combination with a fine 45 degrees flat fan nozzle and Hudson. B&G, and Chapin hand-compression sprayers, respectively. The 30-psi spray management valve maintained a constant flow rate and adequate spray-on time when combined with the coarse flat fan nozzle for each of the 3 hand-compression sprayers tested.

Mosquito Control↗
PubMed1997

An electrostatic backpack sprayer: potential for mosquito control.

A Southwest Electrostatic Sprayers, Inc., nozzle was configured to a Hudson PortaPak backpack. A test was run to compare deposition of BVA no. 13 oil by the electrostatic nozzle to a standard nonelectrostatic nozzle as collected by Teflon slides. Results indicate that 100% greater deposition occurred with the electrostatic nozzle.

Mosquito Control↗
PubMed1997

Field trial efficacy of two formulations of Permanone against Culex quinquefasciatus and Anopheles quadrimaculatus.

Tests were conducted during the summer of 1996 to evaluate the effectiveness of different formulations of permethrin, Permanone 31-66 and Aquareslin, against Anopheles quadrimaculatus and Culex quinquefasciatus. Tests of both formulations were conducted at rates of 2.019 and 3.926 g AI/h with each formulation/rate replicated 3 times. Results indicate significantly greater control of both pest species at the higher application rate for both formulations. The high rate of Permanone 31-66 proved more effective than that of Aquareslin. Exposure at the low rate for both formulations provided inadequate adult control that was particularly pronounced against Cx. quinquefasciatus. Regardless, negligible recovery of exposed adults was observed at any formulations/rate. No significant differences in mortality were noted for any formulation/rate relative to distance downwind. However, volume median diameter and droplets/cm2 were significantly affected by distance downwind. Furthermore, volume median diameter and droplets/cm2 were both determined to significantly affect mortality in both mosquito species (P < or = 0.05). Overall, results indicate that Permanone 31-66 and Aquareslin applied at a rate of 3.926 g AI/h were effective.

Animals↗
PubMed1996

A defect in nurturing in mice lacking the immediate early gene fosB.

Although expression of the Fos family of transcription factors is induced by environmental stimuli that trigger adaptive neuronal response, evidence that Fos family members mediate these responses is lacking. To address this issue, mice were generated with an inactivating mutation in the fosB gene. fosB mutant mice are profoundly deficient in their ability to nurture young animals but are normal with respect to other cognitive and sensory functions. The nurturing defect is likely due to the absence of FosB in the preoptic area, a region of the hypothalamus that is critical for nurturing. These observations suggest that a transcription factor controls a complex behavior by regulating a specific neuronal circuit and indicate that nurturing in mammals has a genetic component.

Animals↗
PubMed1996

Polycyclic aromatic hydrocarbons in central London air during 1991 and 1992.

The results of monitoring for 18 polycyclic aromatic hydrocarbons (PAH) at Exhibition Road, London, UK during the period from January 1991 to September 1992 are presented. Although both particulate and gaseous PAH were analysed, the results are expressed as total PAH. The PAH measurements are complemented by the simultaneous monitoring of a range of air quality variables. These parameters have been subjected to correlation analysis and the dependence on motor vehicle emissions for many of the PAH species is inferred. The majority of the PAH displayed higher annual mean concentrations during 1991 than previous measurements taken at the same site in 1987. The impact of motor vehicle emission legislation, the increased use of unleaded petrol and the rise in the use of diesel powered motor vehicles are all discussed in the context of the presented results. A pollution event during December 1991 caused significantly increased PAH concentrations. A comparison with PAH data from another site in London indicates good agreement between the two sets of data.

Air Pollutants↗
PubMed1996

The role of vascular endothelial growth factor in a murine chronic granulomatous tissue air pouch model of angiogenesis.

Chronic granulomatous inflammation may be considered an angiogenic-dependent process. Recently it has been demonstrated that vascular endothelial growth factor (VEGF) or vascular permeability factor is essential for tumour angiogenesis. Its role in inflammation-mediated angiogenesis has yet to be determined. In this study, the murine chronic granulomatous air pouch model was used to investigate the role of VEGF in angiogenesis. Animals were treated twice weekly with 10 micrograms per animal of neutralizing antibody to rh VEGF and the vascularity and granuloma dry weight were assessed after 7 days. This resulted in significant suppression of both angiogenesis and granuloma dry weight. Western blot analysis demonstrated the presence of VEGF; the levels of protein paralleled the angiogenic response. These results demonstrate for the first time that VEGF may be an important regulator of angiogenesis in inflammation.

Air↗
PubMed1996

Length variation, heteroplasmy and sequence divergence in the mitochondrial DNA of four species of sturgeon (Acipenser).

The extent of mtDNA length variation and heteroplasmy as well as DNA sequences of the control region and two tRNA genes were determined for four North American sturgeon species: Acipenser transmontanus, A. medirostris, A. fulvescens and A. oxyrhnychus. Across the Continental Divide, a division in the occurrence of length variation and heteroplasmy was observed that was concordant with species biogeography as well as with phylogenies inferred from restriction fragment length polymorphisms (RFLP) of whole mtDNA and pairwise comparisons of unique sequences of the control region. In all species, mtDNA length variation was due to repeated arrays of 78-82-bp sequences each containing a D-loop strand synthesis termination associated sequence (TAS). Individual repeats showed greater sequence conservation within individuals and species rather than between species, which is suggestive of concerted evolution. Differences in the frequencies of multiple copy genomes and heteroplasmy among the four species may be ascribed to differences in the rates of recurrent mutation. A mechanism that may offset the high rate of mutation for increased copy number is suggested on the basis that an increase in the number of functional TAS motifs might reduce the frequency of successfully initiated H-strand replications.

Animals↗
PubMed1996

Natural cycle in-vitro fertilization with embryo cryopreservation prior to chemotherapy for carcinoma of the breast.

Chemotherapeutic treatment for malignant disease may cause infertility secondary to gonadal failure. In-vitro fertilization (IVF) with embryo cryopreservation prior to chemotherapy has been described as a means of preserving future fertility potential. However, the supraphysiological levels of sex steroids that result from ovarian stimulation for IVF may, at least theoretically, stimulate growth of malignant cells in a patient with a hormonally sensitive tumour such as carcinoma of the breast. This report describes a patient with carcinoma of the breast who underwent IVF in the natural cycle prior to embarking on a course of combination chemotherapy. Of three oocytes retrieved, two fertilized and were cryopreserved. This case represents a novel application of IVF with embryo cryopreservation in the natural cycle. Although embryo thawing and transfer have not yet been attempted, the patient has already benefitted psychologically from having the opportunity to assume an element of control over her reproductive future. Should pregnancy occur, this would be the first report of human pregnancy from cryopreserved embryos obtained in a natural cycle.

Adult↗
PubMed1996

Characterization of reproductive hormonal dynamics in the perimenopause.

Medical therapy for women in the perimenopausal period is controversial, in part due to varying degrees of ovarian hormone secretion characteristic of this time of life. To extend our understanding of the reproductive endocrine milieu of perimenopausal women, we studied 6 cycling women, aged 47 yr and older, for 6 months with daily collections of first morning voided urine. Five additional older reproductive aged (43-47 yr old) women were studied with daily urine and serum sampling for a single menstrual cycle; their urinary hormone data were combined with the former group for menstrual cycle comparisons. Urine was assayed for LH, FSH, estrone conjugates, and pregnanediol glucuronide and normalized for creatinine (Cr). Eleven midreproductive aged (19-38 yr old) normally cycling women, 5 women with well defined premature ovarian failure, and 5 women aged 54 yr and older who were at least 1 yr postmenopausal were used for comparison. Perimenopausal women had shorter follicular phases (11 +/- 2 days vs. 14 +/- 1 days; P = 0.031) and, hence, shorter menstrual cycles than midreproductive aged controls. FSH excretion in perimenopausal women was greater than that in younger women (range of means, 4-32 vs 3-7 IU/g Cr; P = 0.0005). LH secretion was overall greater than that in younger normal subjects (range of means, 1.4-6.8 vs. 1.1-4.2 IU/g Cr; P < 0.026). Overall mean estrone conjugate excretion was greater in the perimenopausal women compared to that in the younger women [76.9 ng/mg Cr (range, 13.1-135) vs. 40.7 ng/mg Cr (range, 22.8-60.3); P = 0.023] and was similarly elevated in both follicular and luteal phases. Luteal phase pregnanediol excretion was diminished in the perimenopausal women compared to that in younger normal subjects (range for integrated pregnanediol, 1.0-8.4 vs. 1.6-12.7 microg/mg Cr/luteal phase; P = 0.015). Compared to postmenopausal women, perimenopausal women had more overall estrone excretion (2.5-6.2 ng/mg Cr in postmenopausal women; P = 0.02) and lower mean FSH (range of means for postmenopause, 24-85 IU/g Cr; P = 0.017) and LH (range for postmenopause, 4.3-14.8 IU/g Cr; P = 0.041). Compared to women with premature menopause, perimenopausal women again had lower FSH (range of means for premature menopause, 36-82 IU/g Cr; P = 0.0022), lower LH (range of means for premature menopause, 5.5-23.8 IU/g Cr; P = 0.0092), borderline higher mean estrone conjugates (range of means for premature menopause, 4-44 ng/mg Cr; P = 0.064), and far longer periods of ovarian activity (one to two cycles in prematurely menopausal women vs. three to six cycles in perimenopausal women). We conclude that altered ovarian function in the perimenopause can be observed as early as age 43 yr and include hyperestrogenism, hypergonadotropism, and decreased luteal phase progesterone excretion. These hormonal alterations may well be responsible for the increased gynecological morbidity that characterizes this period of life.

Adult↗
PubMed1996

Continuities in emotion understanding from three to six years.

As part of a longitudinal study, 47 children who were tested on their understanding of basic emotions when they were 3 years old were tested again at 6 on their understanding of conflicting emotions. Significant stability in individual differences was found over this 3-year period. Antecedents to emotion understanding at 3 continued to be significantly related to children's understanding at 6, including participation in discourse about causality, positive interaction with older siblings, and language ability. Girls outperformed boys, and there was a suggestion that the girls' understanding of emotions was more closely associated than the boys' with the quality of their sibling relationships. Children's concurrent reports of negative experiences at home and at school were related to their sensitivity to the experience of ambivalent emotions. The results are discussed with respect to the social origins and implications of this core aspect of children's social-cognitive development.

Child↗
PubMed1996

Why talk about mental states? The significance of children's conversations with friends, siblings, and mothers.

Natural language data from 38 47-month-olds recorded at home in unstructured observations were analyzed and comparisons made of characteristics of mental state term use in child-friend, child-sibling, and child-mother dyads. Significantly more references to mental states were made by the children in conversations with siblings and friends than with mothers. Frequent use of mental state terms by both partners was related to cooperative interaction in both child-friend and child-sibling dyads and several associations were found with measures of language fluency, gender, and maternal education, although these varied across the 2 dyads. Children's use of mental state terms in conversations with siblings and friends was correlated with their performance on two false belief measures. Results highlight the importance of extending investigations into the social implications of the development of children's "theories of mind."

Child↗
PubMed1996

Geographic and temporal patterns of recurrent intentional injury in south-central Los Angeles.

To better understand geographic and temporal patterns of recurrent intentional injury, 285 consecutive trauma patients were evaluated prospectively. Fifteen were excluded because of immediate death or severe brain injury. The remaining 270 patients were interviewed. Of these, 59 (22%) had been treated in a hospital for a total of 75 previous episodes of intentional trauma (mean: 1.3 episodes/patient). In 66 of the 75 episodes, the patient recalled where treatment had been received (88%). Twenty-eight (42%) of the 66 episodes had been treated at King/Drew Medical Center (KDMC), 36 (55%) had been treated at a hospital within a 3-mile radius of KDMC, 48 (73%) within an 8-mile radius, and 63 (95%) within a 10-mile radius. Sixty-five percent of the episodes occurred 5 years or less prior to the current injury (range: 11 days to 30 years; mean: 4.9 years). Patients currently admitted for intentional injury were more likely to have had intentional injury previously than those with unintentional injury (27% versus 12%). Based on these findings, we conclude that intentional trauma patients in our community remain in a defined geographic region and that there is a definable high-risk period for recurrent intentional injury. These conclusions should enhance the development of a framework on which future violence prevention programs can be designed.

Adolescent↗
PubMed1995

Root of the universal tree of life based on ancient aminoacyl-tRNA synthetase gene duplications.

Universal trees based on sequences of single gene homologs cannot be rooted. Iwabe et al. [Iwabe, N., Kuma, K.-I., Hasegawa, M., Osawa, S. & Miyata, T. (1989) Proc. Natl. Acad. Sci. USA 86, 9355-9359] circumvented this problem by using ancient gene duplications that predated the last common ancestor of all living things. Their separate, reciprocally rooted gene trees for elongation factors and ATPase subunits showed Bacteria (eubacteria) as branching first from the universal tree with Archaea (archaebacteria) and Eucarya (eukaryotes) as sister groups. Given its topical importance to evolutionary biology and concerns about the appropriateness of the ATPase data set, an evaluation of the universal tree root using other ancient gene duplications is essential. In this study, we derive a rooting for the universal tree using aminoacyl-tRNA synthetase genes, an extensive multigene family whose divergence likely preceded that of prokaryotes and eukaryotes. An approximately 1600-bp conserved region was sequenced from the isoleucyl-tRNA synthetases of several species representing deep evolutionary branches of eukaryotes (Nosema locustae), Bacteria (Aquifex pyrophilus and Thermotoga maritima) and Archaea (Pyrococcus furiosus and Sulfolobus acidocaldarius). In addition, a new valyl-tRNA synthetase was characterized from the protist Trichomonas vaginalis. Different phylogenetic methods were used to generate trees of isoleucyl-tRNA synthetases rooted by valyl- and leucyl-tRNA synthetases. All isoleucyl-tRNA synthetase trees showed Archaea and Eucarya as sister groups, providing strong confirmation for the universal tree rooting reported by Iwabe et al. As well, there was strong support for the monophyly (sensu Hennig) of Archaea. The valyl-tRNA synthetase gene from Tr. vaginalis clustered with other eukaryotic ValRS genes, which may have been transferred from the mitochondrial genome to the nuclear genome, suggesting that this amitochondrial trichomonad once harbored an endosymbiotic bacterium.

Amino Acid Sequence↗
PubMed1995

Changes in casein composition of goats' milk during the course of lactation: physiological inferences and technological implications.

Five British Saanen goats were milk sampled during the first 39 weeks of lactation to determine changes in casein composition. Caseins were separated by anion- and cation-exchange FPLC to determine the relative amounts of the individual caseins. Acid, alkaline and SDS-PAGE were used to determine possible genetic polymorphisms and observe any lactational changes. Total casein nitrogen was determined using a micro-Kjeldahl method and this allowed the concentrations of individual caseins to be calculated. The milk of one animal, which had the deduced genotype alpha s1-CnAB, showed higher concentrations of both total and alpha s1-casein. The remainder of the group were either heterozygous alpha s1-CnBE or, more probably, homozygous alpha s1-CnE and produced milk of a generally lower protein concentration. Both FPLC and PAGE results showed that the relative amounts and concentrations of alpha s2-casein decreased with stage of lactation, consistent with its susceptibility to proteolysis. The relative amounts of the breakdown products of plasmin attack on beta-casein, gamma-caseins, were highly negatively correlated with milk yield (r = -0.942, P < 0.001) in the declining phase of lactation, reflecting the gradual involution of the gland at this time. The relative amount of kappa-casein increased by approximately 50% after peak lactation and its concentration almost doubled near the end of lactation. These compositional changes may alter the processing qualities of goats' milk in relation to cheese production.

Animals↗
PubMed1995

Diminished function of the somatotropic axis in older reproductive-aged women.

Circulating GH and insulin-like growth factor-I (IGF-I) levels in adults generally fall with age. Studies in aging women have rarely controlled for menstrual cycle stage or status or body mass index. We hypothesized that GH and IGF-I levels in reproductive-aged women fall with age despite the stimulatory effects of endogenous estradiol (E2). Eight older reproductive-aged women (aged 42-46 yr) with regular menses, of normal weight, and in good health were compared to a group of eight young control subjects (aged 19-34 yr). Daytime frequent blood sampling was performed in the early follicular phase of the menstrual cycle to characterize pulsatile GH and LH concentrations. Pooled samples were also analyzed for IGF-I, E2, progesterone, and FSH levels. Older reproductive-aged women had lower 12-h integrated daytime GH concentrations (mean +/- SE, 171 +/- 35 vs. 427 +/- 130 micrograms min/L; P = 0.036) than younger controls and a strong trend for lower IGF-I levels (22.7 +/- 2.1 vs. 31.3 +/- 3.5 nmol/L; P = 0.055) than younger controls despite having higher circulating E2 on the day of sampling (368 +/- 51 vs. 167 +/- 20 pmol/L; P = 0.002). We conclude that older reproductive-aged women have lower daytime GH concentrations than younger controls despite having higher E2 levels on the day of sampling and overall normal gonadal hormone parameters.

Adult↗