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Biomedical subjects

D Nelson

Publications and source records attributed to D Nelson.

At least 127 records · Page 7Linked to original sources
PubMed1997

Prevalence of intestinal chlamydial infection in pigs in the midwest, as determined by immunoperoxidase staining.

OBJECTIVE: To determine prevalence of intestinal chlamydial infection in pigs and to compare prevalence of diarrhea in infected pigs with that in noninfected pigs to evaluate the importance of Chlamydia sp as causes of diarrhea in pigs. ANIMALS AND PROCEDURES: Intestines from 351 sick pigs submitted to 2 veterinary diagnostic laboratories and from 96 healthy pigs that were part of an Escherichia coli susceptibility study were examined by immunoperoxidase staining for chlamydial antigen. The proportion of Chlamydia-infected pigs in each group was calculated and compared. The proportion of Chlamydia-infected pigs with diarrhea was compared with the proportion of noninfected pigs with diarrhea. RESULTS: 15% of the sick and healthy pigs were infected with Chlamydia sp. Prevalence of diarrhea was equal between infected and noninfected pigs. Chlamydia sp were the third most common pathogens identified, and prevalence of chlamydial infection increased after 3 weeks of age. CONCLUSIONS AND CLINICAL RELEVANCE: Intestinal chlamydiosis is common in commercial pigs, but most, if not all, infections are subclinical Without collaborative evidence, simply identifying Chlamydia sp in feces or the intestinal tract of pigs with enteritis or diseases of other organ systems should not be considered proof that the organism caused the clinical signs of disease.

Animals↗
PubMed1996

Limitation of glycolysis by hexokinase in rat brain synaptosomes during intense ion pumping.

Incubation of rat brain synaptosomes under conditions of either increased energy utilization (addition of Na+ channel opener, veratridine, or ionophores, monensin and nigericin) or inhibition of oxidative phosphorylation (addition of rotenone), or a combination thereof, decreased [ATP], increased [ADP] and stimulated glycolysis. The rates of lactate generation were linear over a 15-min interval in the presence of rotenone alone but decreased in the other two conditions. During the first 5 min, the amount of lactate formed with veratridine, monensin or nigericin was as high or higher than with rotenone, but it was lower in the last 10 min. With a combination of one of the stimulators of ion movements and rotenone the rate of glycolysis was always markedly lower than with each compound added singly. The stimulated rates of lactate formation correlated positively with the synaptosomal content of [ATP]. After 15 min, [ATP] was 0.9-1.0 nmol/mg with rotenone, 0.5-0.9 nmol/mg with veratridine (or ionophores), and <0.3 nmol/mg with a combination of the two. Under the conditions used, calcium did not affect glycolytic activity directly. The Lineweaver-Burk plot of the rate of lactate formation against [ATP] yielded a straight line with a Km for ATP of about 0.1 mM, which is very similar to the Km for this nucleotide of brain hexokinase bound to mitochondria. In C6 cells glycolytic rate measured with a combination of an ionophore and rotenone was higher than with each of these compounds added singly while [ATP] never declined below about 9 nmol/mg prot. It is concluded that in synaptosomes, the high rate of energy utilization required for intense ion movement decreases [ATP] to a level that limits hexokinase activity kinetically. This may contribute to a reduction in the rate of glycolysis and hence energy production in brain hypoxia and ischemia.

Adenosine Diphosphate↗
PubMed1996

Situational feature recognition in schizophrenic outpatients.

Previous research has suggested that patients with schizophrenia are significantly better at identifying relatively concrete features that describe social situations (e.g., actions and roles) than more abstract features (e.g., rules and goals). Because participants in the earlier research were all inpatients, the results may have been confounded by various factors that are commensurate with a hospital stay. Thirty-one patients with DSM-III-R diagnoses of schizophrenia or schizoaffective disorder and 39 normal volunteers completed the Situational Feature Recognition Test to determine whether they also showed the differential deficit. Results showed that the outpatient group was, indeed, less symptomatic than the inpatient group; outpatients also showed better overall feature recognition than inpatients. Schizophrenic outpatients and normal volunteers are significantly better at identifying concrete features than abstract features. Additional analyses suggested that the differential deficit in outpatients is due, in part, to their disorder. Implications for the remediation of social functioning deficits are discussed.

Adult↗
PubMed1996

Attention and regional cerebral blood flow in posttraumatic stress disorder patients with substance abuse histories.

Performance on an attentional task was assessed in posttraumatic stress disorder patients with substance abuse histories (PTSD-SA). Positron emission tomography (PET) was used to measure concurrent regional cerebral blood flow (rCBF). Eight male PTSD-SA patients and eight normal subjects each received three serial PET scans with 15O-labeled water under the following conditions: (1) resting, (2) auditory continuous performance task (ACPT1), and (3) repeat auditory task (ACPT2). PTSD-SA patients made more errors of commission on the ACPT than normal subjects. Examination of right frontal and parietal cortex ACPT task substrates revealed decreased parietal blood flow in PTSD-SA, which may represent a pathophysiology for poor attentional task performance in PTSD-SA. Attentional problems may underlie other symptomatology in PTSD.

Adult↗
PubMed1996

Effect of ethnicity and age or menopause on the structure and geometry of iliac bone.

We measured indices of bone volume (cancellous, cortical) and bone surface (cancellous, endocortical, and intracortical) in intact full-thickness transiliac bone biopsies obtained from 144 healthy women aged 20-74 (35 black and 109 white, 62 premenopausal and 82 postmenopausal). The data were analyzed by two-way analysis of variance of the four groups defined by age/menopause and ethnicity and by linear regression of major variables on age. None of the interaction terms was significant, and none of the regression slopes on age differed between blacks and whites, indicating that the effects of ethnicity and of age/menopause were independent. Accordingly, the data were also analyzed separately for the effects of ethnicity (pre- and postmenopausal combined) and age/menopause (blacks and whites combined). The analyses led to the following conclusions. (1) Blacks have more cancellous and cortical bone than whites in the ilium; the difference was due to thicker trabeculae and thicker cortices with no difference in trabecular number or cortical porosity. (2) The magnitude of the black/white differences was the same throughout the age range covered by the study, indicating differences in peak adult values, not in rates of loss with age. (3) As the result of age/menopause, there were significant reductions in all indices of the amount and structure of bone except for trabecular thickness; the magnitude of the reductions was the same in blacks and whites. (4) Cancellous bone loss was mainly the result of the complete removal of some trabecular elements with increased separation between remaining elements. Cortical bone loss was due to thinning from the endocortical surface with a small but significant contribution from increased cortical porosity, due to an increased number of intracortical canals. These patterns of bone loss were the same in blacks and whites. (5) Although the percentage losses of bone with age/menopause were higher for cancellous than for cortical bone, the absolute amounts of bone lost were about the same for cortical as for cancellous bone. (6) The ratio of surface to tissue volume decreased with age/menopause in cancellous bone but increased in cortical bone; rates of bone loss would change in the same manner if the loss per unit of surface remained constant. (7) The total extent of bone surface in the ilium did not change with age/menopause, so that the surface/volume ratio for the entire bone increased; volumetric bone turnover would increase and bone age decrease if remodeling activity per unit of surface remained constant.

Adult↗
PubMed1996

Emergency echocardiography telemedicine: an efficient method to provide 24-hour consultative echocardiography.

OBJECTIVES: This study sought to assess the clinical utility of interpreting emergency echocardiograms after regular working hours through a telemedicine connection to on-call cardiologists. BACKGROUND: Physician interpretation of emergency echocardiograms is often delayed during weekends, evenings or night hours. This delay places undue responsibility on less qualified personnel to interpret echocardiograms of vital importance. METHODS: Digital quad-screen cine-loop format was transmitted over standard telephone lines. Clinical data and conventional and telemedicine interpretations were collected prospectively for 187 emergent or semiemergent tele-echocardiograms after regular working hours. RESULTS: Indications for the echocardiogram included assessment of left ventricular function, ischemia, pericardial effusion, valvular disease, heart donor status and arrhythmia. Three off-site echocardiographers received the standard echocardiogram and spectral, gray-scale and color flow Doppler images in cineloop format using a laptop computer. Laptop interpretation showed 19 technically limited studied, 153 abnormal studies and 54% with wall motion abnormalities. Overall mean agreement rate between telemedicine laptop interpretation and conventional workstation interpretation performed in blinded manner for serious disorders with classic echocardiographic findings (pulmonary hypertension, left ventricular thrombus, aortic dissection, severe valvular insufficiency and large pericardial effusion) was 99.0% (95% confidence interval [CI] 96% to 99%). For serious wall motion abnormalities, the agreement rate was 96.3% (95% CI 92% to 99%). The following mean times elapsed after completion of the echocardiogram: to laptop fax report, 2.14 (range 10 min to 8 h); to dictation of videotape, 11.74 h (p < 0.001); to transcription of videotape diction, 56.6 h (p < 0.0001). CONCLUSIONS: After-hours emergency echocardiography telemedicine using a laptop computer is more rapid than scheduled conventional interpretation from a videotape workstation, yet diagnostic accuracy is comparable.

Adolescent↗
PubMed1996

Symptomatology and energy intake during the menstrual cycle in smoking women.

This study extends our understanding of smoking behavior, withdrawal, and premenstrual symptomatology in smoking women, as well as energy intake as a function of cycle phase. Thirty-two women age 18 to 40 years, smoking ad lib, were followed for an average of two menstrual cycles with hormonal verification. Withdrawal and premenstrual symptomatology as well as energy intake were reported during the follicular (F), luteal (L), and late luteal (LL) cycle phases. Both premenstrual symptomatology and withdrawal symptomatology were higher during the LL phase. Subject response on measurements of craving, irritability, restlessness, increased appetite, and depressed mood tended to be higher in the LL phase. Energy intake did not vary as a function of cycle phase. Participants perceived that they smoked more and had increased appetite in the LL phase but related measurements did not confirm this. Premenstrual and withdrawal symptoms are highly correlated and one needs to be cautious in interpreting cycle effects on withdrawal. Overall symptomatology seems to be lower during the F phase, indicating that this may be a more opportune time for women to quit smoking.

Adolescent↗
PubMed1996

Neuronal metabolism of branched-chain amino acids: flux through the aminotransferase pathway in synaptosomes.

The metabolism of branched-chain amino acids (BCAAs) was studied in cortical synaptosomes. With [15N]leucine (1 mM) as precursor, the cumulative appearance of 15N in [15N]glutamate and [15N]aspartate was 0.2 nmol/min/mg of protein without supplemental alpha-ketoglutarate and 0.3 nmol/min/mg of protein in the presence of alpha-ketoglutarate (0.5 mM). The BCAA amino-transferase reaction also proceeded in the "reverse" direction [alpha-ketoisocaproate (KIC) + glutamate-->leucine + alpha-ketoglutarate]. This was documented by incubating synaptosomes with [15N]glutamate and measuring the formation of [15N]leucine. Without KIC in the medium, the rate of [15N]leucine production was 0.13 nmol/min/mg of protein. In the presence of 25 microM KIC the rate was 0.79 nmol/min/mg of protein and even greater (1.0 nmol/ min/mg of protein) in the presence of 500 microM KIC. The reamination of KIC was two- to threefold faster with [2-15N]glutamine as precursor compared with [15N]-glutamate. The ketoacid of valine, alpha-ketoisovalerate (KIV), was reaminated to [15N]valine at a rate comparable to that observed with respect to KIC. The BCAA transaminase mediated not only the bidrectional transfer of amino groups between leucine or valine and glutamate, but also the direct transfer of nitrogen between leucine and valine. This was ascertained in studies in which the incubation medium was supplemented with either [15N]leucine and KIV or [15N]valine and KIC (amino acids at 1 mM and ketoacids at 25 or 500 microM). The rate was faster in the direction of leucine formation at both the lower (6.1-fold) and higher (1.7-fold) KIC concentration. It is suggested that in synaptosomes the BCAA transaminase (a) functions predominantly in the direction of leucine formation and (b) maintains a constant ratio of BCAAs and ketoacids to one other.

Amino Acids, Branched-Chain↗
PubMed1996

Regulation of GABA level in rat brain synaptosomes: fluxes through enzymes of the GABA shunt and effects of glutamate, calcium, and ketone bodies.

Stable isotopes were used to measure both the rate of GABA formation by glutamic acid decarboxylase (GAD) and the rate of utilization by GABA-transaminase (GABA-T). The initial rate of GABA accumulation, determined with either [2-15N]glutamine or [2H5]glutamine as precursor, was 0.3-0.4 nmol/min/mg of protein. Addition of the calcium ionophore A23187 enhanced GAD activity, whereas changes in levels of inorganic phosphate and H+ were without influence. Flux through GABA-T (GABA--> glutamate), measured with [15N]GABA as precursor, was 0.82 nmol/min/mg of protein, whereas the reamination of succinic acid semialdehyde (reverse flux through GABA-T) was almost sixfold faster, 4.8 nmol/min/mg of protein. The rate of GABA metabolism via the tricarboxylic acid cycle was very slow, with the upper limit on flux being 0.03 nmol/min/mg of protein. Addition of either acetoacetate or beta-hydroxybutyrate raised the internal content of glutamate and reduced that of aspartate; the GABA concentration and the rate of its formation increased. It is concluded that in synaptosomes (a) GABA-T is a primary factor in regulating the turnover of GABA, (b) a major regulator of GAD activity is the concentration of internal calcium, (c) GAD in nerve endings may not be saturated with its substrate, glutamate, and the concentration of the latter is a determinant of flux through this pathway, and (d) levels of ketone bodies increase, and maintain at a higher value, the synaptosomal content of GABA, a phenomenon that may contribute to the beneficial effect of a ketogenic diet in the treatment of epilepsy.

4-Aminobutyrate Transaminase↗
PubMed1996

A seasonal staffing model.

The staffing of a nursing unit provides a unique challenge when that unit experiences significant seasonal fluctuations in census. Although overtime, perdiem, or agency personnel are staffing alternatives to meet seasonal fluctuations in census, they are costly alternatives that are not the most efficient use of human resources. The authors present a seasonal staffing model that reallocates employee work hours in a pattern that closely matches the seasonal work load trends of the department.

Cost Savings↗
PubMed1996

Function and medical comorbidity in south Texas nursing home residents: variations by ethnic group.

OBJECTIVE: To evaluate differences in functional status and burdens of medical conditions in Mexican American and non-Hispanic white nursing home residents. DESIGN AND SETTING: Cross-sectional survey of 17 nursing homes in south Texas. PARTICIPANTS: A total of 617 older nursing home residents, of whom 366 were Mexican American and 251 were non-Hispanic white. MEASURES: Activities of Daily Living (ADL) status abstracted from standard nurses notes and Burden of Disease abstracted from medical records. RESULTS: Mexican American residents had greater numbers of ADL dependencies and poorer overall ADL scores than non-Hispanic white residents. This poor functioning was not explained by age, gender, or marital or educational status. The average number of medical conditions was greater, and specific conditions, such as cerebrovascular disease, recent acute infections, diabetes, hypertension, and anemia, were more common in Mexican American residents compared with non-Hispanic white residents. In models relating function with medical conditions and ethnic group, ADL scores and dependencies were significantly related to bowel and bladder incontinence, cerebrovascular disease, dementia, recent infections, and skin decubiti, but not to ethnic group. CONCLUSION: Mexican American nursing home residents are more functionally dependent than non-Hispanic white residents. The difference in function is explained by a greater burden of medical conditions in the Mexican American residents.

Activities of Daily Living↗
PubMed1996

Does storage of sputum specimens adversely affect culture results?

It has been recommended that samples submitted for microbiological examination should be retained for 48 hours after issue of the final report. In order to ascertain whether reproducible results could be achieved following storage of sputum specimens, two laboratories each re-cultured 100 samples 48 hours after their report had been issued and a further laboratory re-cultured 100 samples 48 hours after receipt. Discordant results were obtained in only 5-25% of specimens, indicating that potential respiratory pathogens could survive storage.

Bacteriological Techniques↗
PubMed1996

A Medicaid mental health carveout program: the Massachusetts experience.

Private sector contracts with Medicaid mental health programs have the potential to help states offer quality improvements and cost savings for chronically mentally ill populations. A Massachusetts experience illustrates how state agencies, community providers, and a private, mental health management firm collaborated to reduce rising Medicaid mental health and substance abuse costs and improve access and quality of care for Medicaid recipients.

Cost Savings↗
PubMed1996

Synergy between lysosomotropic amines and cyclosporin A on human T cell responses to an exogenous protein antigen, tetanus toxoid.

Previously, it has been shown that the lysosomotropic amine, chloroquine, is effective in the prevention of graft-versus-host disease (GVHD) using murine models. Because chloroquine and hydroxychloroquine suppress MHC class II antigen presentation, their mechanism of action is different to other immune suppressant drugs (cyclosporin A) currently used to control GVHD. It is possible that the use of cyclosporin A and chloroquine in combination may have an additive or synergistic effect on T cell responses to antigens presented in the context of MHC class II. We investigated the effects of chloroquine or hydroxychloroquine in combination with cyclosporin A on human T cell responses in vitro to tetanus toxoid, an exogenous protein antigen dependent on MHC class II presentation for proliferative responses. We demonstrate that similar levels of chloroquine and hydroxychloroquine suppress human T cell responses to tetanus toxoid and that the use of either agent in combination with cyclosporin A results in synergistic suppression. Evaluation for a direct effect by the lysosomotropic amines on T cells, in the absence of antigen presenting cells, revealed that there was inhibition of T cell responses but only at high concentrations. No significant decrease or increase was seen in surface MHC II or invariant chain expression or in cytoplasmic invariant chain after exposure to chloroquine. Thus, lysosomotropic amines in combination with cyclosporin A are synergistic in suppression of T cell proliferation. Use of these agents in combination with cyclosporin A may improve control of graft-versus-host disease.

Adult↗
PubMed1995

Single-word auditory stimulation and regional cerebral blood flow as studied by SPECT.

Single photon emission computed tomography (SPECT) examined changes in regional cerebral blood flow (rCBF) induced by passive auditory single-word stimulation. A split-dose SPECT technique was used between resting and activated states, in which a smaller amount of ligand (99m technetium hexamethyl propyleneamine oxide, HMPAO) was given with the first scan, accompanied by a prolonged scan time. A larger amount of ligand was given with the second scan, accompanied by a shorter scan time. This split-dose SPECT technique has met with previous success for other activation tasks. The brain regions of interest (ROIs) in this study were selected from ROIs previously found to be activated by passive auditory single-word stimulation and not by non-word stimuli in positron emission tomography (PET) rCBF studies. This study thus tested the sensitivity of SPECT with HMPAO to detect brain activation with a stimulus previously demonstrated to elicit changes in rCBF with PET. However, no significant difference was detected between resting and activated states in this study. Thus, SPECT was not as sensitive as PET in this activation task. Since SPECT is a less costly and more widely available modality to study brain activation than PET, it is important to delineate its potential capacities to maximize the efficiency of future research in this field.

Adult↗
PubMed1995

Analysis of sevoflurane degradation products in vapor phase samples.

Sevoflurane degradation products were measured by GC-flame ionization detection in vapor phase samples using manual and automated injection methods. Sample handling techniques allowed the transfer and storage of samples for up to 72 h. Compound A, fluoromethyl 2,2-difluoro-1-(trifluoromethyl)vinyl ether, was the major vapor phase degradation product formed in simulated clinical conditions. Recoveries of 4-32 ppm (v/v) compound A concentrations using the manual method were in the range of 88-117% (n = 12, mean = 102%, R.S.D. = 9%).

Anesthetics↗