Search PubMed⌕ Search

Biomedical subjects

B J Davis

Publications and source records attributed to B J Davis.

At least 91 records · Page 5Linked to original sources
PubMed1992

Nosocomial transmission of multidrug-resistant Mycobacterium tuberculosis. A risk to patients and health care workers.

OBJECTIVE: To determine the factors associated with the development of multidrug-resistant tuberculosis among patients at a New York City Hospital and to investigate possible nosocomial transmission. DESIGN: A retrospective case-control study and tuberculin skin test survey. PATIENTS: Twenty-three patients with tuberculosis whose isolates were resistant to at least isoniazid and rifampin (case patients) were compared with patients with tuberculosis whose isolates were susceptible to all agents tested (controls). Tuberculin skin test conversion rates were compared among health care workers assigned to wards where patients with tuberculosis were frequently or rarely admitted. SETTING: A large, teaching hospital in New York City. MEASUREMENTS: Mycobacterium tuberculosis isolates from case patients and controls were typed by restriction fragment length polymorphism analysis. RESULTS: Case patients were younger (median age, 34 compared with 42 years; P = 0.006), more likely to be seropositive for HIV (21 of 23 compared with 11 of 23 patients; odds ratio, 11.5; 95% CI, 1.9 to 117), and more likely to have had a previous hospital admission within 7 months before the onset of tuberculosis (19 of 23 compared with 5 of 23 patients; odds ratio, 17.1; CI, 3.3 to 97), particularly on one ward (12 of 23 compared with 0 of 23 patients; odds ratio, undefined; P = 0.002). Health care workers assigned to wards housing case patients were more likely to have tuberculin skin test conversions than were health care workers assigned to other wards (11 of 32 compared with 1 of 47 health care workers; P less than 0.001). Few (6 of 23) case patients were placed in acid-fast bacilli isolation, and no rooms tested had negative pressure. Of 16 available multidrug-resistant isolates obtained from case patients, 14 had identical banding patterns by restriction fragment length polymorphism analysis. In contrast, M. tuberculosis isolates from controls with drug-susceptible tuberculosis had patterns distinct from each other and from those of case patients. CONCLUSIONS: These data suggest nosocomial transmission of multidrug-resistant tuberculosis occurred from patient to patient and from patient to health care worker and underscore the need for effective acid-fast bacilli isolation facilities and adherence to published infection control guidelines in health care institutions.

Adult↗
PubMed1992

Aspergillus fumigatus sternal wound infections in patients undergoing open heart surgery.

During a 21-month period (July 1986-April 1988), six patients who underwent open heart surgery at Holston Valley Hospital and Medical Center in Kingsport, Tennessee, developed sternal would infections caused by Aspergillus fumigatus. All patients required sternectomy, reconstructive surgery, and long term amphotericin B therapy; no patient died. By univariate analysis, the following were significantly associated with A. fumigatus sternal would infection: chronic lung disease, a recent history of pneumonia, a greater mean number of admission diagnoses, and a particular surgeon. However, multivariate analysis identified chronic lung disease as the only independent risk factor and the best predictor of A. fumigatus sternal wound infections. No factors related to the surgical procedure or operating room personnel were associated with infection. A review of the characteristics of the patients undergoing open heart surgery showed that since 1985, there had been a trend for these patients at Holston Valley Hospital and Medical Center to be older and sicker, which may have contributed to the occurrence of infections never observed before. Despite an extensive investigation, no environmental source for A. fumigatus was identified. A. fumigatus, however, grew from the bronchial washing of one patient at the time the sternal wound infection was diagnosed, and a prospective study showed that the rate of A. fumigatus colonization among open heart surgery patients was the same as the rate of sternal wound infections caused by A. fumigatus. These data suggest that patients with chronic lung disease and respiratory colonization with A. fumigatus are at increased risk for A. fumigatus sternal wound infections after open heart surgery.

Aged↗
PubMed1992

Proteolysis at pressure and HPLC peptide mapping of M4-lactate dehydrogenase homologs from marine fishes living at different depths.

1. The effects at 10 degrees C of moderate hydrostatic pressure (136 atm) on trypsinolysis of muscle-type (M4) lactate dehydrogenase homologs (LDH, EC 1.1.1.27, L-lactate:NAD+ oxidoreductase) from shallow- and deep-occurring marine fishes were examined by mapping the partial digests by reverse phase HPLC. 2. Comparison of peptide maps of digests generated at 1 and 136 atm revealed that increased pressure did not expose new cleavage sites in homologs of any of the species; no new peptides were generated. 3. Increased pressure did alter the relative amounts of peptides produced. The net effect of increased pressure was to increase the amount of peptides generated in the shallow-occurring species. For deep-living species pressure did not alter the net amount of peptides produced compared to the 15 min atmospheric pressure samples, although the relative amounts of some of the peptides changed. Incubation at 136 atm for 30 min decreased the net amount of peptides produced. 4. It is suggested that the effects of pressure on trypsinolysis may result from slight conformational changes in the substrate proteins.

Adaptation, Physiological↗
PubMed1992

Complex maze performance in young and aged rats: response to glucose treatment and relationship to blood insulin and glucose.

In aged rats and humans, impaired glucose regulation has been correlated with poor memory performance, and glucose treatment can result in improved performance. We tested this glucose hypothesis with rats in a 14-unit T-maze that has provided robust evidence of age-related performance decline. Aged (24-25 month) and young (6-7 month) male F-344 rats were pretrained for one-way active avoidance before receiving complex maze training (4 daily trials over 5 days) with the contingency of moving through each of 5 segments to avoid footshock. Ten min before daily training, aged rats received either saline or glucose in doses of 10, 100, or 500 mg/kg IP, while young rats received saline. Significant (ps less than 0.05) age-related increases in errors, runtime, and shock duration were observed. Glucose treatment had no significant effect on the number of maze errors committed; however, performance variables such as runtime and shock duration appeared to be reduced in rats receiving glucose. About 4-6 weeks later, a sample of these rats was fasted overnight, injected IP with glucose (150 mg/kg), and bled at various postinjection intervals to obtain estimates of blood glucose and insulin levels. Significant correlations (ps less than 0.05) were observed between maze errors and baseline glucose levels, r(21) = -.62, and peak glucose response, r(19) = .49. However; within the aged group, significant correlations (ps less than 0.01) with maze errors emerged only for baseline glucose, r(13) = -.69, and peak insulin response, r(13) = -.65. Thus, regulation of insulin, but not glucose, appeared related to learning abilities among aged rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1992

Plasma concentrations of glucose, insulin, and percent glycosylated hemoglobin are unaltered by food restriction in rhesus and squirrel monkeys.

Plasma concentrations of glucose and percentage of glycosylated hemoglobin have been reported to be reduced in food-restricted rats when compared with ad libitum-fed controls (Masoro et al., 1989). A similar experiment in primates, in which we also measured plasma insulin, is reported in this article. Rhesus and squirrel monkeys were fed either ad libitum or 30% less than weight-matched controls for up to 36 months. No significant age or diet effects on plasma concentration of glucose, insulin, or percentage glycosylated hemoglobin were observed, except that glucose concentration decreased with age in ad libitum-fed rhesus monkeys. Moreover, no correlations between glucose levels and the percentage of glycosylated hemoglobin could be established within any group of animals. These results suggest possible differences in glucose-related metabolism in ad libitum and food-restricted primates as compared to observations made in rats.

Aging↗
PubMed1991

NADPH-diaphorase activity in the olfactory system of the hamster and rat.

A comparative analysis of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity in the olfactory bulb was conducted in the hamster and rat. The distribution and morphological features of NADPH-stained neurons were compared to those of glutamic acid decarboxylase-like (GAD-LI) and tyrosine hydroxylase-like (TH-LI) immunoreactive somata in order to relate NADPH-staining to neuronal classes with specific biochemical properties. Intense NADPH-staining was located in primary nerve fibers of the accessory and main olfactory systems, producing dense staining of individual glomeruli. The entire vomeronasal nerve and all glomeruli were stained in the accessory olfactory bulb, but olfactory nerve and glomerular staining were restricted to the dorsal half of the main olfactory bulb. The glomerular layer of the main olfactory bulb of both animals contained numerous small NADPH-stained neurons. The range of somal areas of these neurons was relatively narrow and averaged about 60 microns2 (ca. 8 x 11 microns). Most neurons possessed ovoid somata and monoglomerular intraglomerular dendrites. Previous Golgi studies indicate that such features characterize periglomerular cells. The somal areas of GAD-LI somata in the glomerular layer overlapped that of the NADPH-stained neurons, providing additional evidence that these neurons are probably periglomerular cells. The range of somal areas of TH-LI somata in the glomerular layer was broader and included both small and large neurons that usually possessed intraglomerular dendritic tufts. The smaller TH-LI somata corresponded in size to both the NADPH-stained and GAD-LI somata, suggesting an interrelationship among periglomerular cells, GAD-LI, TH-LI, and NADPH-diaphorase activity. The larger TH-LI somata were probably external tufted cells. In the external plexiform layer of the hamster, oriented NADPH-stained neurons were observed that possessed an intraglomerular dendrite. These neurons appeared to be middle tufted cells. Lightly stained and smaller neurons were occasionally seen in the mitral body and internal plexiform layers, corresponding in somal area and morphological features to those of type III granule cells. No internal tufted or mitral cells were stained. The largest NADPH-stained neurons were located in the inner half of the granule cell layer and were classified as Golgi cells. Their somata averaged 125 microns2 (ca. 10 x 17 microns). Many NADPH-stained neurons were observed in all subdivisions of the anterior olfactory nucleus, the anterior hippocampal rudiment, anterior and posterior levels of the piriform cortex, and the vertical and horizontal limbs of the diagonal band of Broca, all of which are known to provide centrifugal inputs to the olfactory bulb.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

The influence of anti-inflammatory therapy on bacterial clearance following intramammary Escherichia coli challenge in goats.

Coliform mastitis in dairy cattle frequently results in systemic disease with occasional deaths in association with endotoxic shock. Systemic anti-inflammatory therapy has been used to alter the course of endotoxic shock in severe cases. Use of anti-inflammatory therapy has been questioned on the basis that such treatment may compromise immune function and decrease clearance of bacteria from infected mammary glands. The purpose of this investigation was to determine whether anti-inflammatory therapy influenced bacterial clearance following intramammary challenge of lactating goats with Escherichia coli. Standardized quantities of a pathogenic coliform culture were infused through the teat canal into one half of the mammary gland in 18 goat does. The does were then randomly assigned to receive one of three intravenous treatments: saline (controls), one dose of steroid (dexamethasone), or two doses of a non-steroidal anti-inflammatory agent (flunixin meglumine). The clinical signs, milk production, complete blood counts, serum clinical chemistry values, milk bacterial cultures and milk somatic cell concentrations were monitored sequentially. Goats treated with anti-inflammatory agents exhibited some improvement in clinical response to challenge with E. coli (e.g. rectal temperature, degree of appetite suppression) as compared to saline controls. There were no significant differences between treatments in the degree of inflammation present in the mammary glands or supramammary lymph nodes examined at necropsy. The most important finding was that anti-inflammatory therapy did not adversely influence the clearance of E. coli from challenged glands.

Animals↗
PubMed1991

The ascending gustatory pathway: a Golgi analysis of the medial and lateral parabrachial complex in the adult hamster.

This study examined the somal areas, dendritic features and orientations of neurons within taste responsive regions of the parabrachial complex, including the "waist" area that spans the brachium conjunctivum. The data were compared with those of a Golgi study of the gustatory zone of the nucleus of the solitary tract. Both fusiform and multipolar neurons were identified. Fusiform neurons had elongated somata that average 205 microns2 (range: 128-281 microns2) and generally possessed bipolar primary dendrites. Multipolar neurons had a stellate appearance and somal areas that averaged 230 microns2 (range: 109-443 microns2). These multipolar neurons possessed significantly more primary dendrites than fusiform neurons (4.0 versus 2.9 primary dendrites). Fusiform neurons were uncommon in the medial and lateral regions of the parabrachial complex but predominated in the solitary nucleus. Parabrachial neurons were usually larger and possessed more complex higher-order dendritic arborizations than solitary neurons. Computer-generated three-dimensional rotational analyses failed to demonstrate the strong orientation specificity in parabrachial neurons that characterizes gustatory solitary neurons. These Golgi studies described for the first time the morphological features of pontine neurons that could possibly receive ascending gustatory projections, and the morphological differences between neurons that receive direct peripheral input from taste receptors and the pontine targets of such neurons.

Afferent Pathways↗
PubMed1991

Substance P immunoreactivity in the superficial laminae of the hamster olfactory bulb.

The direct application of colchicine to the hamster olfactory bulb has engendered the appearance of a broader distribution of substance P-like immunoreactivity (SP-LI) than has been previously reported. In the glomerular layer, both external tufted and periglomerular cells were strongly immunopositive. These two classes could be identified by somal size and the presence and branching pattern of intraglomerular dendrites. SP-LI neurons were also identified in the external plexiform layer and many were similar to middle tufted cells. These findings demonstrate that substance P expression is not uniquely associated with classes of projection neurons, but is also found in periglomerular cells, a class of inhibitory local circuit neurons.

Animals↗
PubMed1988

A Golgi analysis of the gustatory zone of the nucleus of the solitary tract in the adult hamster.

The somal shapes, dendritic features, and orientations of the neurons within the gustatory zone of the nucleus of the solitary tract were studied with the rapid Golgi method in the adult hamster. These Golgi studies complement previous quantitative morphometric analyses of the distributions of large and small neurons within the gustatory zone. Class 1 neurons are usually fusiform and possess long, relatively unbranched dendrites that often extend beyond the cytoarchitectonic boundaries of the gustatory zone. Class II neurons are multipolar and possess more dendrites that are significantly shorter than those of class I neurons. Both classes of neurons are spine poor. Computer-generated three-dimensional rotational analyses demonstrate that the dendritic arborizations of neurons of the gustatory zone are oriented preferentially in the horizontal plane. Dendrites extend in parallel or perpendicular to the solitary tract, the source of peripheral gustatory inputs, and appear to be positioned spatially to maximize synaptic interactions with these peripheral fibers. These Golgi studies also suggest that individual gustatory neurons may be influenced by incoming gustatory fibers that innervate separate populations of taste buds, a finding that is not predictable from the topographical organization of the gustatory zone.

Animals↗
PubMed1988

Tyrosine hydroxylase-like and dopamine beta-hydroxylase-like immunoreactivity in the gustatory zone of the nucleus of the solitary tract in the hamster: light- and electron-microscopic studies.

A quantitative electron-microscopic analysis has been conducted on the neurons within the gustatory zone of the nucleus of the solitary tract of the hamster. The most common group of neurons within the gustatory zone contains both large (X1) and small (X3) members that possess deeply invaginated nuclear profiles. These neurons have somal areas that average 113 micron2 (range 34-281 micron2) and a value of somal area/nuclear area that averages 2.2. Other large and small neurons that have non-invaginated nuclear profiles are also observed. The larger (X2) neurons average 151 micron2 (range 49-487 micron2) and have much cytoplasm and associated membranous organelles that is reflected in a mean value of somal area/nuclear area of 2.6. Members of the X2 group are the largest neurons in the gustatory zone. The smaller (X4) group contains the smallest neurons in the gustatory zone of the nucleus of the solitary tract, averages 50 micron2 (range 16-103 micron2), shows almost no perinuclear cytoplasm and has a mean value of somal area/nuclear area of only 1.5. These findings are consistent with and expand upon the results of similar studies at the light-microscopic level. This grouping has been used to explore the association of tyrosine hydroxylase-like and dopamine beta-hydroxylase-like immunoreactivities with specific populations of neurons that are known to be distributed across the various levels of the gustatory zone. At the light-microscopic level, numerous well-defined and intensely labelled tyrosine hydroxylase-like immunoreactive somata of various morphologies and sizes are observed. Quantification at the electron-microscopic level indicates that 10-15% of the neurons encountered in the dorsal and intermediate levels of the gustatory zone are immunoreactive. The ventral level of the gustatory zone contains few immunoreactive neurons. Tyrosine hydroxylase-like immunoreactive neurons possess either non-invaginated or invaginated nuclear profiles and their somal areas average 106 and 142 micron2, respectively. On the bases of size and ultrastructural features, these immunoreactive somata are assigned to the two groups (X1 and X2) of large neurons within the gustatory portion of the nucleus of the solitary tract. In general, small neurons are not immunoreactive. The distribution of dopamine beta-hydroxylase-like immunoreactivity has also been examined in adjacent sections in order to reveal the presence of any putative noradrenergic neurons in the gustatory zone.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Computer-generated rotation analyses reveal a key three-dimensional feature of the nucleus of the solitary tract.

The dendritic processes of neurons within the nucleus of the solitary tract are oriented in the horizontal plane and often extend unusually long distances along the long axis of the brainstem. This preferred orientation is not predictable from a knowledge of the cytoarchitectonic organization of their somata within the various subnuclei of the nucleus of the solitary tract. Incoming peripheral afferent fibers, their collaterals and end-terminal ramifications are also oriented in the horizontal plane and are in alignment with the dendrites of second order neurons. These features enable single neurons to be influenced by a variety of widely distributed inputs that are related to vital autonomic functions and ingestional behavior.

Animals↗
PubMed1988

Nosocomial Mycobacterium fortuitum colonization from a contaminated ice machine.

Between October 15 and November 18, 1985, 5 patients on a medical ward of the Albany VA Medical Center (Ward 8A) became colonized with Mycobacterium fortuitum. Because other patients in Ward 8A were at risk of developing disease with M. fortuitum, microbiologic surveillance to identify colonization in sputum was begun. By February 15, 1986, 30 colonized patients had been identified in this ward but none in another ward with a comparable patient population, which suggests a source unique to Ward 8A. Because water has been recognized as a source of opportunistic mycobacterial pathogens, we conducted a retrospective case-control study using a telephone survey questionnaire to examine a number of water exposures in 10 patients and 20 control subjects. Exposure to ice from the Ward 8A ice machine, but not to potable water, was associated with colonization with M. fortuitum. Large-volume water samples from a variety of sources were cultured for acid-fast bacilli. M. fortuitum was isolated only from the ice machine in Ward 8A. The ice machine was disconnected, and no additional patients became colonized. Although ice machines are infrequently implicated in nosocomial outbreaks, they represent a potential source for pathogens that survive or replicate in water.

Cross Infection↗
PubMed1987

Effects of lesions of hypothalamic catecholamines on blood pressure, fluid balance, vasopressin and renin in the rat.

Fluid balance, systolic blood pressure (BP) and serum vasopressin (VP) and renin activity (SRA) in the basal state and in response to blood volume depletion were examined in unanesthetized rats previously given intrathecal 6-hydroxydopamine (6-OHDA) to destroy catecholaminergic (CA) input to supraoptic nucleus (SON). Sham-operated rats, unoperated ad libitum hydrated rats and rats undergoing 4 days of water deprivation served as controls. The 6-OHDA lesion resulted in adipsia, a failure to conserve administered fluids and a decrease in systolic BP. Despite decreased blood volume secondary to dehydration, and decreased systolic BP, the 6-OHDA group failed to show the expected increase in serum VP. However, when blood volume was further decreased following intraperitoneal polyethylene glycol, lesioned rats showed robust VP and SRA responses. Thus, CA input to critical target areas in the hypothalamus may be necessary for maintenance of sensitivity to stimuli that normally elicit VP release. Decreased systolic BP following 6-OHDA lesions most likely results from dehydration coupled with inadequate VP responses.

Animals↗
PubMed1987

Construction activity: an independent risk factor for invasive aspergillosis and zygomycosis in patients with hematologic malignancy.

Between November 1982 and July 1984, five patients at a 110-bed pediatric hospital were diagnosed with invasive filamentous fungal infection; three had invasive aspergillosis (IA) and two had invasive zygomycosis (IZ). All five had underlying hematologic malignancy (HM). In a case-control study, these five HM patients (cases) were compared to 10 autopsied HM patients without evidence of aspergillosis or zygomycosis (controls). Cases and controls did not differ in underlying disease or in the degree of immunosuppression, as measured by duration of granulocytopenia and number of platelet transfusions. However, case-patients were more likely than controls to have been hospitalized during the construction of a hospital addition (p less than 0.02, Fisher's exact test [FET]). Four (80%) of five HM patients autopsied during the period of construction had IA or IZ compared with one (5%) of 21 autopsied before construction began (p = 0.001, FET). These findings suggest that, in a population of comparably immunosuppressed patients, construction activity may represent an independent risk factor for IA or IZ. Hospitals caring for such patients should take precautions which minimize exposure of these patients to construction or renovation activity.

Adolescent↗
PubMed1987

Ewingella americana: recurrent pseudobacteremia from a persistent environmental reservoir.

From September 1981 through April 1984, 20 patients at one hospital were identified with Ewingella americana pseudobacteremia. Case-control studies demonstrated an association between having a positive blood culture for E. americana and having blood for culture obtained simultaneously with blood obtained for coagulation studies (15 of 19 case patients versus 4 of 38 controls; P = 4.5 X 10(-7)). Review of blood-drawing procedures showed that blood for coagulation studies and culture was drawn with the same syringe, and coagulation tubes were filled before blood culture tubes. Some phlebotomists were not using new sterile needles to inoculate blood culture bottles. Collection tubes for coagulation studies were prepared in the hospital, and E. americana was isolated from all 52 unused coagulation tubes tested. Solutions prepared in the hospital may constitute a persistent inanimate environmental reservoir for this uncommon microorganism. Pseudobacteremia can result in unnecessary antimicrobial therapy for some patients, incurring the risks of adverse drug reactions, selection of drug-resistant bacteria, and increased health care costs.

Adolescent↗
PubMed1987

Plasmids of Ewingella americana: supplementary epidemiologic markers in an outbreak of pseudobacteremia.

During an outbreak of pseudobacteremia in a children's hospital, Ewingella americana was found in blood cultures from 20 patients. E. americana was inoculated into blood culture bottles at the time of specimen collection due to cross contamination from nonsterile, citrated blood collection tubes used for coagulation studies. Antimicrobial susceptibility testing and plasmid profiling were used to assess the association between patient isolates and isolates from unused blood collection tubes. All E. americana isolates had similar antibiograms (i.e., resistance only to cephalothin) when tested at 37 degrees C. However, when the same isolates were tested for antimicrobial susceptibility at 25 degrees C, a different antibiogram (i.e., resistance to chloramphenicol, ampicillin, and cephalothin) was found. The majority of these isolates also demonstrated a unique four-plasmid profile (130, 56, 4.6, and 3.1 megadaltons), and two of these plasmids (130 and 56 megadaltons) were characterized as temperature-sensitive plasmids. An epidemiologic link between outbreak-associated isolates obtained from different time periods in the outbreak was supported by evidence of a significant trend in the ability of the outbreak-associated isolates to reduce nitrate, together with the presence of the resistance antibiogram at 25 degrees C and the demonstration of the unique four-plasmid profile.

Adolescent↗