Biomedical subjects

B J Davis

Publications and source records attributed to B J Davis.

At least 109 records · Page 6Linked to original sources

PubMed1987

Pseudoepidemic of aspergillosis after development of pulmonary infiltrates in a group of bone marrow transplant patients.

During February and March 1985, seven patients in the pediatric bone marrow transplant unit (PBMTU) of a 350-bed cancer hospital developed pulmonary infiltrates. Five of the patients had Aspergillus spp. isolated from the respiratory tract, and two of these patients had histologic evidence of aspergillosis. Between 26 February and 22 April, Aspergillus spp. were isolated in a total of 70 cultures from 39 hospitalized patients. Of the 70 cultures, 14 (group 1) were from respiratory specimens of PBMTU patients with pulmonary infiltrates and were submitted to the laboratory intermittently over the 56-day period. However, of the other 56 Aspergillus-positive cultures (group 2), 41 (73%) were submitted on six days during this period (P less than 0.001, chi-square goodness of fit), including 8 blood cultures submitted on one day. When Aspergillus sp. was recovered from group 1 cultures early during this period, the isolates were stored in the culture-processing room. Aspergillus isolates were not handled in a biological safety cabinet, and blood cultures were done by using a system which requires opening of an evacuated bottle to room air. The presence of stored Aspergillus isolates was associated with a markedly elevated concentration of airborne fungi in the culture-processing room. After removal of the stored Aspergillus isolates from the culture-processing room, the concentration of airborne fungi returned to background level and there were no further Aspergillus-positive cultures. These findings suggested that group 2 cultures had been contaminated by stored Aspergillus isolates. No evidence for a common source of infection was found in the PBMTU patients with pulmonary infiltrates.

Air Microbiology↗

PubMed1987

Counseling medical and dental patients about cigarette smoking: the impact of nicotine gum and chart reminders.

To investigate methods for improving and expanding the counseling of smokers by physicians and dentists, we assigned 112 physicians and 50 dentists (in separate studies) to one of the following conditions: the control or advice-only group received a one-hour lecture on the consequences and management of smoking and a booklet detailing a four-step protocol for counseling patients about smoking; three other groups received, in addition, either, protocol reminder stickers placed on their patients' charts; nicotine gum made freely available to their patients; or both chart reminders and nicotine gum. Exit interviews of 1,091 medical and 647 dental patients indicated that the presence of chart reminders and/or the availability of nicotine gum increased the time spent counseling and altered the nature of the smoking cessation counseling provided by both physicians and dentists.

Adolescent↗

PubMed1986

Functional properties of hemoglobins from deep-sea fish: correlations with depth distribution and presence of a swimbladder.

The ligand binding properties of the hemoglobins of several deep-sea, bottom-living fish have been examined. These include five species of rattails (Macrouridae) and Antimora rostrata, all of which possess swimbladders, and two unrelated species without swimbladders, Bathysaurus mollis and Alepocephalus sp. All of the hemolysates of these fish exhibited the Root effect with a minimum ligand affinity at about pH 6 in the presence of organic phosphate. Under these conditions the hemolysates from fish which possess swimbladders exhibit two roughly equal populations of heme groups with markedly different ligand affinities. For the deeper-dwelling species the affinities for carbon monoxide differ by some 500-fold, the low-affinity population having a p50(CO) of 100 mmHg at 15 degrees C. This very low affinity is associated with a second-order rate constant for CO combination of the order of 10(3) M-1 X s-1. Those species without swimbladders have hemoglobins which do not have such heterogeneous binding sites, suggesting a relationship between these very-low-affinity heme groups and the pumping of oxygen into a swimbladder at high hydrostatic pressures.

Air Sacs↗

PubMed1986

Localization of vasopressin-neurophysin and norepinephrine in the supraoptic nucleus of spontaneously hypertensive rats.

Histological analysis of the catecholaminergic innervation of vasopressin neurons in the supraoptic nucleus (SON) was performed using catecholamine histofluorescence and immunocytochemistry of vasopressin specific neurophysin (VP-NP) in order to determine if spontaneously hypertensive rats (SHR) demonstrate alterations in the relationship between these two types of chemically defined neurons. Chronically hypertensive SHRs showed an increased density of catecholamine fluorescence particularly in the dorsal part of the SON in comparison to age-matched, normotensive, Wistar-Kyoto (WKY) rats, but not in comparison to age-matched Wistar rats. In addition, there was an increase in the area of distribution of VP-NP immunopositive neurons such that they extended into the dorsal portion of the nucleus in the SHR compared to the WKY. Comparator bridge analysis of immunocytochemical staining and catecholamine histofluorescence revealed a precise overlap of the two patterns in SHR. Thus, the more extensive distribution of catecholamine fluorescence in the dorsal SON in the SHR compared to WKY paralleled the more extensive distribution of VP neurons in this region. Quantitative analysis of the relative percentage of SON neurons which were VP-NP positive indicated that the increased representation of VP-NP positive neurons in the dorsal portion of the nucleus reflected a greater distribution of the VP-NP cell population throughout the SON rather than an increase in the number of VP-NP neurons in the SHR. In young SHRs (5 weeks old) the catecholamine fluorescence pattern in the SON was considerably smaller than that observed in older SHRs. This low density pattern, however, was comparable to that observed in young WKYs. Thus, the catecholamine fluorescence in the SON apparently increases in the SHR in parallel with the development of the hypertension. This observation and the finding of comparable catecholamine fluorescence in Wistars and SHRs suggest that the altered catecholamine innervation of VP neurons observed in chronically hypertensive SHRs is not causal to the hypertension but may reflect a response to the elevated blood pressure. A marked increase in the catecholamine innervation of cerebral arteries was also noted.

Age Factors↗

PubMed1986

A cryoprotection method that facilitates cutting frozen sections of whole monkey brains for histological and histochemical processing without freezing artifact.

Cutting frozen sections of large (greater than 60 cc) blocks of monkey brain using the conventional procedures of infiltration with 30% sucrose as a cryoprotectant before freezing with pulverized dry ice often produces unacceptable levels of freezing artifact (FA) caused by displacement of tissue by ice crystals. Experiments investigating FA utilized perfusion-fixed brains from 46 monkeys and spanned combinations of cryoprotectants (glycerol, sucrose), freezing methods (dry ice or -75 degrees C isopentane), and fixatives (10% formalin, Karnovsky's or Timm's). The effects were evaluated by rating of FA severity in frozen sections of whole monkey brains. Minor FA appears as enlarged capillaries, more serious FA as large vacuoles, and both first appear midway between the periphery and center of the block. Stronger fixatives increased the severity of freezing artifact. The best method for eliminating FA was graded infiltration with up to 20% glycerol and 2% DMSO (in buffer or fixative), followed by rapid freezing in -75 degrees C isopentane. Although using a glycerol-DMSO infiltration before conventional freezing with pulverized dry ice or using conventional sucrose infiltration before freezing in isopentane gave better results than sucrose infiltration and dry-ice freezing, only the combination of glycerol-DMSO infiltration and freezing in isopentane produced consistently excellent results and virtually eliminated freezing artifact. To determine the effect of freezing with dry ice or isopentane on the rate of cooling in large blocks of CNS tissue, thermocouples were embedded in an 80-cc block of albumin-gelatin and frozen with the two methods. The rate of cooling (-3.5 degrees C/min) was twice as fast using isopentane.

Animals↗

PubMed1985

Nosocomial Legionnaires' disease. Epidemiologic demonstration of cooling towers as a source.

Investigation of a recent outbreak of nosocomial legionnaires' disease--initially thought to be due to the documented presence of Legionella pneumophila in the hospital potable water--showed that aerosols from one or more cooling towers were the actual source of infection. From June 27 to Aug 25, 1983, nosocomial legionnaires' disease developed in 15 persons at a hospital in Rhode Island. Twelve (80%) of 15 case-patients occupied rooms in building 1, unit B, compared with eight (28%) of 29 control patients (odds ratio = 10.8; 95% confidence interval = 1.4 to 85.6). Subsequent investigation demonstrated that water in a cooling tower located 100 ft upwind of unit B was heavily contaminated with L pneumophila, serogroup 1, subgroup 1, 2, 4, 5. The same strain was isolated from nine of the patients and from the make-up water for the tower. Active surveillance during the ten months following decontamination of the cooling tower identified no additional cases of nosocomial legionnaires' disease, although the hospital potable water had not been treated. While recommendations have been made for controlling nosocomial legionnaires' disease by heating or hyperchlorination of hospital potable water, this outbreak demonstrates the importance of an adequate epidemiologic-environmental investigation in choosing the appropriate control strategy.

Adult↗

PubMed1985

Effects of substantia nigra lesions on the volumes of A, B, and D cells and the content of insulin and glucagon in the rat pancreas.

The effects of substantia nigra lesions on the volume densities of islet cells and on the content of insulin and glucagon in the pancreas were examined using five groups of age-matched, Sprague-Dawley rats. Two groups received bilateral substantia nigra lesions using intrathecal injections of either a low (6 micrograms/hemisphere) or a high (12 micrograms/hemisphere) dose of 6-hydroxydopamine. Rats given sham lesions served as controls for the effects of the neurotoxic drug. These three groups, plus a fourth consisting of unoperated controls, were provided with a high-fat diet to minimize lesion-induced alterations of food intake and body weight. Eleven weeks after lesion placement, tissue was collected from all animals for the assessment of islet cell volume densities and the pancreatic content of insulin and glucagon. Plasma samples also were obtained to determine the levels of glucose, insulin, and glucagon. Data from those animals were compared with that obtained from a fifth group, termed "pre-lesion controls", sacrificed at the beginning of the experiment. Linear-scan morphometry documented an increase of B-cell volume density in the pancreas of non-lesioned rats over the 11-week period (p less than 0.05). However, the volume density of B cells in the pancreas of lesioned animals did not increase compared with that of pre-lesion controls. In terms of A or D cells, no significant differences of volume density were found between the five groups. Compared with that of the pre-lesion controls, pancreatic insulin and glucagon content increased in the lesioned and neurally-intact animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

The electronic pantograph: amplifier couples microscope stage to X-Y plotter.

A system is described that allows the X-Y movement of a microscope stage to be coupled to the movement of the pen of a X-Y plotter. Linear potentiometers are displaced by any X- or Y-axis movement of the microscope's stage and are connected to a DC amplifier which provides a varying DC voltage to the inputs of a X-Y plotter. The pen of the X-Y plotter becomes yoked to the movement of the stage and it is possible to draw or count the image that is being viewed at magnifications which are independent of those used for observation. The coupling DC amplifier provides a DC offset voltage at all gain settings of the pantograph which is sufficient to reposition the pen of the X-Y plotter in the center of the plotter's platen, regardless of the location of the specimen on the microscope slide. The electronic pantograph overcomes the limitations of a camera lucida, and is well suited for analyzing connectional neuroanatomical material with bright- and darkfield, polarized light or florescent illumination at a reasonable price and without the complexity and hardware requirements of a computerized system.

Animals↗

PubMed1985

Whirlpool operation and the prevention of infection.

Disease outbreaks involving public whirlpools have been reported frequently since their use has become popular in recent years. Because public whirlpools are often used by persons who have only transient contact, infections resulting from their use are difficult to identify, and published reports probably represent only a small portion of a larger public health problem. Most published outbreaks have reported Pseudomonas aeruginosa contamination of the whirlpool as a result of failure to operate the pool according to recommended practices. Maintaining the microbiologic quality of whirlpool water and preventing infection absolutely require regular operation and maintenance, including monitoring and record keeping by qualified personnel.

Bacterial Infections↗

PubMed1985

Factors associated with Pseudomonas pickettii intrinsic contamination of commercial respiratory therapy solutions marketed as sterile.

Laboratory investigations were conducted to study the growth dynamics of Pseudomonas pickettii in commercial 0.9% sodium chloride solution under various environmental conditions and to determine the retention of these organisms after challenge through a 0.2-micron cartridge filter system. Low numbers of P. pickettii (1 to 10 CFU/ml of test solution) inoculated into commercial vials containing 5 ml of 0.9% sodium chloride solution and 500-ml volumes of 0.9% sodium chloride solution were shown to proliferate over a 168-h incubation period. These organisms demonstrated growth over a wide range of temperatures (15 to 42 degrees C) in this salt solution, and survival studies at 50, 55, and 60 degrees C indicated that this strain was not unusually resistant to heat (with the times required at a given temperature to reduce the surviving microbial population 10-fold [D-values] being 26.0, 1.9, and 0.7 min, respectively). A challenge test demonstrated that P. pickettii organisms were not completely retained by a 0.2-micron cartridge filter. The number of organisms detected increased from 1 CFU/liter of effluent at 1 to 2 min to a maximum of 176 CFU/liter at 4 to 5 min. Our results indicate that P. pickettii can penetrate a 0.2-micron filtration system and that the passage of organisms and subsequent microbial growth in the filter effluent probably are the mechanisms by which these organisms were recovered from "sterile" commercial 0.9% sodium chloride solution.

Drug Contamination↗

PubMed1985

Mechanism of cross-contamination of blood culture bottles in outbreaks of pseudobacteremia associated with nonsterile blood collection tubes.

Several studies have identified nonsterile blood collection tubes as the reservoir for contaminating microorganisms in outbreaks of pseudobacteremia. Microorganisms are thought to be transferred from the nonsterile tubes to the blood culture tubes when blood is drawn for cultures, but the validity of this hypothesis has not previously been tested. We recently investigated an outbreak of Ewingella americana pseudobacteremia in which an epidemiological association was found between pseudobacteremia and the practice of drawing blood for culturing at the same time that blood for coagulation studies is drawn. The nonsterile coagulation tubes, prepared in the hospital, were contaminated with E. americana. We studied three different procedures that personnel reported using to inoculate blood culture tubes after dispensing blood into the coagulation tubes. Although the failure to change or remove the needle before inoculating the blood culture tubes resulted in the highest percentage of cross-contamination, we found that all the techniques we simulated carried some risk of cross-contamination when coagulation tubes were filled first.

Blood↗

PubMed1985

Nosocomial Pseudomonas pickettii colonization associated with a contaminated respiratory therapy solution in a special care nursery.

Pseudomonas pickettii caused respiratory tract colonization in five infants in the special care nursery of a Chicago hospital. All organisms had the same antimicrobial susceptibilities. Endotracheal suctioning with saline from 5-ml unit-dose vials was identified by epidemiologic investigation as a risk factor for colonization. The vials of saline were contaminated with a strain of P. pickettii having the same antimicrobial susceptibility pattern as the isolates from patients. As part of an investigation of the manufacturing plant where the saline solution was produced, P. pickettii was recovered from deionized water used to make the product and from several sites in the processing line. Bypassing of a 180 degrees F (ca. 82 degrees C) water-holding tank appeared to be temporally related to product contamination. The ability of P. pickettii to survive and grow in this solution has been demonstrated in the laboratory. This outbreak demonstrates that, despite pertinent Food and Drug Administration regulations and company programs for identifying such contamination, intrinsically contaminated solutions can occasionally reach the bedside of the patient.

Cross Infection↗

PubMed1985

Altered catecholamine innervation of the supraoptic nucleus in the nephrogenic diabetes insipidus mouse.

Fluorescence histochemical and immunocytochemical techniques were used to investigate morphologic correlates of the relationship between catecholamine varicosities and vasopressin-containing perikarya in an animal model of vasopressin excess, the nephrogenic diabetes insipidus mouse. Our results show hypertrophy and increased immunoreactivity in vasopressin neurons in these mice were accompanied by a marked increase in the density and to some extent the fluorescence intensity of catecholamine varicosities within the supraoptic nucleus. These results further support the concept of functional interactions between catecholamine and vasopressin neurons and raise the possibility that the target neuron, or one of its products, perhaps vasopressin, either exerts a trophic influence on the catecholamine innervation pattern of the supraoptic nucleus or enhances catecholamine content in existing fibers and terminals.

Animals↗

PubMed1984

Substance P and catecholaminergic expression in neurons of the hamster main olfactory bulb.

A coordinated series of immunohistochemical and biochemical analyses have been conducted in the hamster to examine the dependence of substance P and tyrosine hydroxylase (TH) expression by second-order olfactory neurons, and the level of dopamine in the main olfactory bulb (MOB), on the integrity of carnosine- and olfactory marker protein (OMP)-containing primary afferent neurons. Substance P-like immunoreactivity (SPLI) is localized in external tufted cells and centrifugal afferents of the MOB; TH immunoreactivity has a wider distribution, in external tufted, middle tufted, periglomerular, and deep short-axon cells as well as in centrifugal afferents. To characterize the SPLI, this material was isolated by guanidine-HCl extraction and passage over a C18 SEP-PAK. The SPLI coelutes on HPLC with authentic substance P and, following oxidation, coelutes with substance P sulfoxide. It is sensitive to alpha-chymotrypsin and is resistant to trypsin. Thus, the SPLI in the MOB behaves as authentic substance P. Intranasal irrigation with 0.17 M ZnSO4 results in peripheral deafferentiation of the MOB for up to 8 months as evidenced by a persistent loss of OMP immunoreactivity and shrinkage of the olfactory nerve layer and glomeruli. By these criteria, the vomeronasal inputs to the accessory olfactory bulb are not destroyed and the spared vomeronasal receptor neurons do not innervate the vacated peripheral projection field in the MOB. The loss of peripheral inputs to the MOB is accompanied by marked and parallel reductions in the incidences of SPLI- and TH-positive second-order neurons despite an increase in the density of neuronal somata in the glomerular layer. Biochemical quantifications following peripheral deafferentation also demonstrate significant decreases of both substance P and dopamine, together with the expected decrease of carnosine. In contrast, the SPLI and the TH and serotoninlike immunoreactivities in centrifugal afferents as well as the TH immunoreactivity in deep interneurons do not appear to be reduced, and the MOB content of norepinephrine in centrifugal afferents is unaffected. These results collectively indicate that the loss of inputs from the primary olfactory receptor neurons can reduce the levels of at least two different, putatively neuroactive compounds (substance P and dopamine) in at least three classes of second-order neurons (external tufted, middle tufted, and periglomerular cells). The control of central neuron phenotype by the peripheral olfactory neurons thus appears to be a phenomenon of broad influence. It may play a role in processing chemosensory information as well as offering a system in which to study neuronal plasticit

Animals↗

PubMed1984

Alterations of pancreatic islet size and growth following substantia nigra lesions in the rat.

Lesions of certain autonomic centers in the brain are known to alter feeding behavior, body weight, and influence the morphology and function of the pancreatic islets. Because marked reductions of food intake and body weight have been reported following damage to the substantia nigra (SN), we investigated the role of this brain area as a potential regulator of the endocrine pancreas. Rats were given bilateral SN lesions using the neurotoxin 6-hydroxydopamine (6-OHDA) at a dose of either 6 or 12 micrograms/hemisphere. Animals given sham lesions served as controls. Both the control and experimental rats were placed on a high-fat diet to minimize lesion-induced reductions of food intake and body weight. Eleven weeks following lesion placement, pancreatic tissues were collected and islet size and volume density were determined using point-counting stereological analyses. At the time of tissue collection, the body weights of control and experimental rats were comparable. Rats with SN lesions exhibited a reduction of pancreatic islet size and volume density, when compared with that of sham-lesioned controls. Moreover, the islets of SN-lesioned rats were comparable in size and volume density to that of younger animals. Hence, these observations suggest that damage to the SN produces an overall impairment of islet growth independently of changes in body weight.

Animals↗

PubMed1984

Intrinsic bacterial contamination of a commercial iodophor solution: investigation of the implicated manufacturing plant.

After an outbreak of peritoneal infections attributed to intrinsic contamination of a poloxamer-iodine solution with Pseudomonas aeruginosa, the manufacturer of the contaminated solution permitted investigation and sampling of materials within the plant. Pseudomonas spp. were recovered from two different unopened lots of solution and from numerous water samples obtained at the plant. The isolates from water identical to those of an isolate recovered from Prepodyne solution (West-Agro Chemical Co., Inc., Westwood, Kans., manufactured for AMSCO Medical Products Div., Erie, Pa.) manufactured 1 month earlier at the same plant. P. aeruginosa was not recovered from incoming city water. P. aeruginosa was recovered from sterile water and poloxamer-iodine after 48 h of incubation in a plant polyvinyl chloride pipe. Scanning electron micrographs of polyvinyl chloride pipe used in the plant showed massive concentrations of rod-shaped and coccobacillary cells apparently embedded in interior deposits of the pipe. Manufacturers of iodophors should be aware that pipes or other surfaces colonized with bacteria may be a source of contamination of their products.

Journal Article↗

PubMed1984

Investigations into the survival of Pseudomonas aeruginosa in poloxamer-iodine.

Laboratory investigations were conducted to study potential mechanisms for prolonged survival of Pseudomonas aeruginosa in poloxamer-iodine (PxI). P. aeruginosa organisms isolated from PxI and adapted for growth in distilled water or found as part of a mixed microbial population from water in a manufacturing plant did not survive more than 15 s after challenge in stock PxI solution. Batches of PxI were compounded in the laboratory to determine the survival and growth of P. aeruginosa during the various stages of preparation. No P. aeruginosa organisms were recovered from the finished product at 1 min after the addition of iodine-iodide. However, we found P. aeruginosa in PxI 48 h after adding sterile PxI to the inside of a naturally contaminated polyvinyl chloride water distribution pipe. These organisms (10(4) CFU/ml) survived for as long as 98 days in contaminated stock PxI after it was removed from the polyvinyl chloride pipe. Both decreasing the free iodine level through addition of potassium iodide and increasing the free iodine level through dilution of the product resulted in an increased length of survival of P. aeruginosa in contaminated PxI solution. Comparative survival studies with pipes of different composition revealed that other materials may exert an effect similar to polyvinyl chloride. We concluded that polyvinyl chloride and perhaps other materials may play an important role in the survival of P. aeruginosa in iodophors and may be one source of resistant microbial populations when used in manufacturing plants which produce these antimicrobial solutions.

Drug Combinations↗

PubMed1983

Memory and the septo-hippocampal cholinergic system in the rat.

This study examined the effects of intrahippocampal injections of scopolamine (a muscarinic antagonist drug) on performance of a working-memory task (contingently reinforced T-maze alternation) and a reference-memory task (visual discrimination) by the same rats in the same maze. Rats in the first shipment were trained in delayed alternation, received bilateral implantation of cannulae aimed at the CA 3 field of the dorsal hippocampus, and were tested for retention with 1 microliter microinjections of scopolamine (35 micrograms) and saline on alternate days. These rats were then trained on visual discrimination and tested alternately under scopolamine or saline as described above. It was found that scopolamine impaired performance of delayed alternation to a greater extent than performance of visual discrimination. Data from rats in the second shipment replicated this finding, with the order of the tasks reversed, and, additionally, showed that delayed alternation, but not visual discrimination, was impaired at a dose of 12 micrograms/microliter. A dose of 4 micrograms/microliter had no effect on either task. It is concluded that performance of a working-memory task is significantly more sensitive to disruption of cholinergic mechanisms in the hippocampus than performance of a reference-memory task.

Animals↗