Biomedical subjects

M B Jones

Publications and source records attributed to M B Jones.

At least 37 records · Page 2Linked to original sources

PubMed2000

Ionic currents in cardiac myocytes of squid, Alloteuthis subulata.

This paper provides the first study of voltage-sensitive membrane currents present in heart myocytes from cephalopods. Whole cell patch clamp recordings have revealed six different ionic currents in myocytes freshly dissociated from squid cardiac tissues (branchial and systemic hearts). Three types of outward potassium currents were identified: first, a transient outward voltage-activated A-current (IA), blocked by 4-aminopyridine, and inactivated by holding the cells at a potential of -40 mV; second, an outward, voltage-activated, delayed rectifier current with a sustained time course (IK); and third, an outward, calcium-dependent, potassium current (IK(Ca)) sensitive to Co2+ and apamin, and with the characteristic N-shaped current voltage relationship. Three inward voltage-activated currents were also identified. First, a rapidly activating and inactivating, sodium current (INa), blocked by tetrodotoxin, inactivated at holding potentials more positive than -40 mV, and abolished when external sodium was replaced by choline. Second, an L-type calcium current (ICa,L) with a sustained time course, suppressed by nifedipine or Co2+, and enhanced by substituting Ca2+ for Ba2+ in the external medium. The third inward current was also carried by calcium ions, but could be distinguished from the L-type current by differences in its voltage dependence. It also had a more transient time course, was activated at more negative potentials, and resembled the previously described low-voltage-activated, T-type calcium current.

4-Aminopyridine↗

PubMed2000

Comparative field water relations of three Mediterranean shrub species co-occurring at a natural CO(2) vent.

Annual variations in the water relations and stomatal response of Erica arborea, Myrtus communis and Juniperus communis occurring at a natural CO(2) vent were analysed under Mediterranean field conditions. A distinct gradient of CO(2)concentration ([CO(2)]) exists between two sites near a natural CO(2)-emitting vent, with higher [CO(2)] (700 micromol mol(-1)) in the proximity of the CO(2) spring. Plants at the CO(2) spring site have been growing for generations at elevated [CO(2)]. At both sites, maximum leaf conductance was related to predawn shoot water potential. The effects of water deficits during the summer drought were severe. Leaf conductance and water potential recovered after major rainfalls in September to predrought values. Strong relationships between leaf conductance, predawn water potential, and leaf-specific hydraulic resistance are consistent with the role of stomata in regulating plant water status. Considerable between-species variation in sensitivity of water potentials and stomatal characters to elevated [CO(2)] were observed. Common to all the shrubs were a reduction in leaf conductance and an increase in water potentials in response to elevated [CO(2)]. Elevated [CO(2)] decreased the sensitivity of leaf conductance to vapour pressure deficit. Morphological characters (including stomatal density and degree of sclerophylly) showed site-dependent variations, but degree and sign of such changes varied with the species and/or the season. Measurements of discrimination against (13)C provided evidence for long-term decreases of water use efficiency in CO(2) spring plants. Analysis of C isotope composition suggested that a downward adjustment of photosynthetic capacity may have occurred under elevated [CO(2)]. Elevated [CO(2)] effects on water relations and leaf morphology persisted in the long term, but the three shrubs growing in the same environment showed species-specific responses.

Carbon Dioxide↗

PubMed2000

The familial aggregation of the lesser variant in biological and nonbiological relatives of PDD probands: a family history study.

OBJECTIVE: To determine the risk of the lesser variant (or PDD-like traits) in the biological and nonbiological second- and third-degree relatives of PDD probands using a screening questionnaire and to investigate the extent to which the risk of the lesser variant differs according to various characteristics of the proband. METHOD: The sample consists of a series of 34 nuclear families with 2 affected PDD children (multiplex, MPX), 44 families with a single PDD child (simplex, SPX), and 14 families who adopted a PDD child. Data on characteristics of the lesser variant in 1362 biological and 337 nonbiological second- and third-degree relatives were collected from parents by telephone interview and from several maternal and paternal relatives by questionnaire. RESULTS: All components of the lesser variant were more common in biological relatives (BR) than nonbiological relatives (NBR), confirming the familial aggregation of the traits. Proband characteristics associated with an increased risk of the lesser variant in relatives were a higher level of functioning and coming from a MPX family. CONCLUSIONS: These findings on the familial aggregation of the lesser variant suggest that the genes for PDD also confer susceptibility to the lesser variant and that PDD may be a genetically heterogeneous disorder.

Adolescent↗

PubMed2000

Isoperformance and personnel decisions.

Isoperformance curves are contour lines or surfaces that trace all combinations of two or more determinants that suffice to produce a specified level of performance hence the term isoperformance. When the determinants are aptitude and training time or time on the job, an isoperformance curve allows one to identify individuals who have sufficient aptitude for the work that they can be expected to reach a specified standard of performance in a specified length of time. This paper discusses isoperformance in the personnel selection and classification literature and then develops and illustrates the uses of isoperformance curves in personnel decisions. The idea of aptitude sensitivity is introduced, and the relationship between this idea and predictive validity is explained. The paper also indicates how isoperformance can be used to detail trade-offs among training time, the minimum qualifying score, attrition rate, quotas, and the specified level of criterion performance, Isoperformance finds direct application in the multiple-job assignment problem, exemplified by the choice of which recruit to send to which training school in the military services.

Aptitude↗

PubMed1999

Serum lysozyme activity can differentiate infection from rejection in organ transplant recipients.

BACKGROUND: The presentation of infection in immunocompromised patients can be subtle. Patients often undergo extensive testing and empiric treatment for rejection and infection while awaiting the results of the biopsy and culture results. Delay in diagnosis of either entity can result in a worse clinical outcome. Lysozyme activity has been found to be both a sensitive and a specific marker for infection in laboratory animals and trauma patients. Our goal was to determine whether lysozyme activity could serve as a reliable marker for infection in immunocompromised organ transplant recipients. METHODS: Transplant recipients from three clinical categories were enrolled in this study. Group 1 (n = 16) were patients hospitalized for sepsis (culture-positive), and Group 2 (n = 13) for biopsy-proven rejection. Group 3 (n = 51) were recipients who had routine blood sampling in the clinic. In Groups 1 and 2, blood was collected within 24 h of hospital admission and centrifuged, and serum samples were stored at 80 degrees C until processing. Lysozyme activity was assayed by turbidimetric measurement on a sample of a standard suspension (0.15 mg/ml) of Micrococcus lysodeikticus in buffer using a spectrophotometer to read the optical density at 450 nm. The lysozyme activity level was then determined by the measuring activity at 1 min subtracted from activity at 4 min. White blood cell count was determined by using a flow cytometer. Statistical comparisons between groups were made using paired Student's t test. RESULTS: Serum lysozyme was found to be significantly elevated in Group 1; the mean level of activity was 60.1 +/- 13 (P < 0.05) compared to the level of activity in Group 2, mean 41.1 +/- 11, and Group 3, mean 40.8 +/- 13. A level of 45 units of activity/ml of serum or above indicated infection and not rejection in the patients admitted to the hospital. CONCLUSIONS: These findings indicate that the lysozyme activity assay appears to be useful in differentiating infection from rejection in transplant recipients.

Adolescent↗

PubMed1999

Instability of the G-protein beta5 subunit in detergent.

Heterotrimeric guanine nucleotide-binding proteins are important mediators in signal transduction and function by transmitting information from membrane-bound receptors to effectors. Because these proteins are membrane bound and contain covalent lipid modifications, detergents are required for solubilization and purification. It was discovered that the interaction between the beta5 subunit and the gamma2 subunit was disrupted in two detergents, cholate and Chaps (3-[(3-cholamidopropyl) dimethylammonio]-1-propansulfonate). A beta5gamma2 column was constructed in which recombinant betagamma dimers were immobilized on a FLAG antibody column via a hexahistidine-FLAG-tagged gamma2 subunit, gamma2HF. Greater than 95% of the beta5 subunit was specifically eluted from the immobilized gamma2HF subunit using a cholate gradient from 0.05 to 1.0% and greater than 40% of the beta5 subunit was eluted using a Chaps gradient from 0.05 to 1.0%. In contrast, the beta1, beta2, and beta3 subunits remained bound to the gamma2HF subunit in all concentrations of Chaps and cholate. Genapol C-100, Triton X-100, and polyoxyethylene-10-lauryl ether did not interfere with any of the four beta subunits' ability to interact with the gamma2 subunit. These data suggest that the beta5 subunit is not stable in bile acid or Chaps-type detergents (i.e., Chapso, glycocholate, deoxycholate). Therefore, alternative detergents should be used to extract dimers containing the beta5 subunit.

Baculoviridae↗

PubMed1999

Effects of misclassification on estimates of relative risk in family history studies.

Two types of misclassification that commonly occur in family-genetic studies are distinguished: 1) nondifferential misclassification, in which the probability of error as to phenotype (presence or absence of psychiatric disorder) does not depend on exposure status (being kin to a case or control proband) and 2) differential misclassification, in which it does. Nondifferential misclassification of phenotype reduces the observed relative risk towards the null value, sometimes quite dramatically. Differential misclassification can bias the observed relative risk in either direction, depending on the different values of sensitivity and specificity among relatives of cases and controls. The impact of these biases on genetic-epidemiologic studies is reviewed and discussed. In particular, the ability to detect major gene effects from the pattern of relative risks in first-, second-, and third-degree relatives can be severely compromised. Although there are some methods available to correct the effects of nondifferential misclassification, a major priority for family history studies is to minimize differential misclassification.

Bias↗

PubMed1999

Experience with procedural sedation in a pediatric burn center.

BACKGROUND: Burn care requires daily debridement, dressing changes, and assessment regarding the need for skin grafting. These procedures are painful and may require an operating room environment. METHODS: The authors reviewed their experience with 912 consecutive procedural sedations (PS) in 220 pediatric burn patients over a 2-year period to identify what influence PS had on patient care. Median patient age was 32 months, and body surface area burn was 7.2%+/-6%. Pharmacological techniques included oral and intravenous medications and N2O. The authors included all sedations given in the burn treatment area and excluded all treatments given in the intensive care unit or emergency unit. RESULTS: PS allowed for early aggressive wound debridement, virtually eliminated the need for operating room debridement (used in only 22 patients), and eliminated patient discomfort and fear often associated with subsequent debridements. Burn wound-related complications occurred in 54 patients and included wound infection (n = 18), graft loss (n = 9), and pneumonia (n = 4). The incidence of PS complications was 7% with the most common problems including decreased arterial saturation (n = 41), emesis (n = 11), and agitation (n = 8). No patient required intubation or transfer to an intensive care unit bed. The average length of stay (LOS) for all patients was 8.7+/-6.2 days, and 6.2+/-3.8 days in the 200 patients not admitted to the intensive care unit. This compares favorably with the 9.5-day LOS of patients treated in 1990. CONCLUSIONS: PS in burn patients allows for early aggressive debridement, decreases the use of the operating room for debridement, and a decrease in length of stay when compared with our previous burn patients. PS has a modest risk of complications, enhances the family's cooperation and satisfaction with health care provided, and should be an integral part of burn care in children.

Adolescent↗

PubMed1999

Familial factors influence level of functioning in pervasive developmental disorder.

OBJECTIVE: To determine whether siblings with pervasive developmental disorders (PDD) tend to have the same type and number of PDD symptoms or a similar level of functioning. METHOD: The familial correlations for PDD subtype, symptom totals, adaptive behaviors, and nonverbal IQ were calculated for 94 children with PDD from 46 families. RESULTS: On variables measuring PDD symptoms, only impairments in nonverbal communication and verbal/nonverbal status tended to run true within families. There was no familial aggregation of PDD subtype. In contrast, measures of nonverbal IQ and adaptive behaviors in socialization and communication showed a moderate degree of familial resemblance. The degree of familial resemblance did not change if the analysis was restricted only to those families in which both affected children met criteria for autism. CONCLUSION: Insofar as the familial resemblance seen in PDD is due to genetic factors, these data provide some evidence that higher- and lower-functioning PDD children may arise from separate genetic mechanisms. Current gene-mapping studies of PDD may need to take this evidence of genetic heterogeneity into account.

Activities of Daily Living↗

PubMed1998

Uptake and depuration of 63Ni by Mytilus edulis.

The uptake and depuration of Ni (as radioisotope 63Ni) by Mytilus edulis (Mollusca: Bivalvia) has been investigated in a laboratory mesocosm. Nickel was reversibly held on low energy surface sites of estuarine suspended particulate matter (SPM), with a partition coefficient of the order 10(3) ml g-1, resulting in approximately 80% of radioisotopic Ni being in the dissolved phase. Mussels were fed a diet of radio-labelled estuarine SPM for 30 h in a flow-through exposure period and for a further 24 h in a static exposure period. Following exposure, the mussels were allowed to depurate in particle-free seawater. Pseudofaeces and faeces were collected throughout the experiment and tissues were dissected after 48 h of depuration. The 63Ni activity in the faeces was approximately 50% of that in the feedstock SPM, while the activity in the tissues was 2-29% of SPM activity. Tissue-specific accumulation occurred in the order viscera > byssus > mantle > adductor muscle > gill > foot. The results are discussed in the context of the bioavailability of Ni to mussels.

Animals↗

PubMed1998

Genetics of autism: overview and new directions.

Genetic epidemiology is the study of inherited factors involved in the etiology of a disease or disorder and uses the methods of both medical genetics and clinical epidemiology. In general, genetic epidemiology tries to answer the following four questions: Is the disorder inherited; What phenotype is inherited; How is it inherited or what is the mode of transmission; and What is the nature of the genetic mutation, if any, that gives rise to the disorder? The hope is that by identifying the gene or genes involved in pathophysiology, a much better understanding of the steps from gene product to phenotype will be possible, leading to improvements in diagnosis, an opportunity for thoughtful family planning, and perhaps, most important, to the development of treatments based on an understanding of the biochemistry of the disorder. We review the current knowledge of the genetic epidemiology of autism and the other pervasive developmental disorders (PDDs) and highlight promising new directions. There seems to be widespread agreement that the PDDs are caused, at least in part, by genetic factors. There is also some agreement on the phenotypic boundaries associated with these same genetic factors. However, many points of uncertainty remain, and several methodologic issues need to be resolved before further progress in mapping susceptibility genes is possible. We do not specifically review molecular studies, medical conditions associated with autism, or the broader autism phenotype, as these topics are covered in other papers in this special issue.

Autistic Disorder↗

PubMed1998

Reliability and accuracy of differentiating pervasive developmental disorder subtypes.

OBJECTIVE: To evaluate the ability of the DSM-IV criteria for the pervasive developmental disorders (PDD) to reliably and accurately differentiate PDD subtypes. METHOD: The sample consisted of 143 children with various types of developmental disabilities. A diagnosis of PDD and PDD subtype was made by one clinician using information obtained from the Autism Diagnostic Interview-Revised and the Autism Diagnostic Observation Schedule. The raw data from the Autism Diagnostic Interview-Revised, clinical notes (excluding diagnostic opinion), Autism Diagnostic Observation Schedule, IQ, and other available data were independently assessed by three experienced raters, each of whom then made a separate, blind diagnosis. If there was any disagreement, a consensus best-estimate (CBE) diagnosis was made after discussion. To assess reliability, the agreement between the three raters was calculated using k. Accuracy was assessed by calculating the agreement between the clinician's diagnosis and the CBE and by calculating the error rates associated with the three raters using latent class analysis. RESULTS: The current DSM-IV criteria show good to excellent reliability for the diagnosis of PDD, Asperger's disorder (AsD), and autism, but they show poor reliability for the diagnosis of atypical autism. The clinician (compared to the CBE) had little difficulty differentiating PDD from non-PDD children and autism from AsD but had more difficulty identifying children with atypical autism. The latent class analysis also showed that the average error rates of the three raters for a differentiation of atypical autism from autism were unacceptably high. CONCLUSIONS: Although the psychometric properties of the current DSM-IV criteria for autism and AsD appear quite acceptable, there is likely to be a high rate of misclassification of children given a diagnosis of atypical autism.

Adolescent↗

PubMed1998

HSP70 expression in the CNS in response to exercise and heat stress in rats.

We have previously documented the regional distribution of 70-kDa heat shock protein (HSP70) in brains of rats made hyperthermic by brief exposure to high-powered microwaves (HPM; 2.06 GHz). We now compare HSP70 expression induced by HPM exposure to that induced by exertional and/or environmental heat stress. Rats were chronically implanted with a temperature probe guide in the hypothalamic region of the brain (Tbr). After recovery, the following treatment groups were examined: HPM; sham exposed; treadmill exercise at room temperature (24 degreesC; Ex-1); treadmill exercise in a warm environment (34 degreesC; Ex-2); and sedentary groups (Sed-1 and Sed-2), in which ambient temperature was adjusted so that the Tbr mimicked the Tbr in the corresponding exercise groups. Significant HSP70 expression occurred only in the hyperthermic (Ex-2, Sed-2, and HPM) groups. The pattern of HSP70 expression was similar among Ex-2 and Sed-2 rats but differed from that in HPM rats. We conclude that 1) the pattern of HSP70 expression differs between HPM and nonmicrowave heating, and 2) exercise alone was not sufficient to induce central HSP70 expression.

Animals↗

PubMed1998

Effects of alcohol on perceptual speed.

In moderate to heavy doses, alcohol adversely affects performance on many tasks, and perceptual speed is a component in most performance tasks. Nevertheless, studies of alcohol's effects on perceptual speed have been largely limited to critical flicker frequency and backward masking. The present study extends these limits. 16 men and 12 women were administered four temporal-factors tests before and after the ingestion of alcohol. The four tests were Simultaneity, Apparent Movement, Bistable Stroboscopic Motion, and Backward Masking. At the first postalcohol testing (mean BAC = 0.111), all four tests showed pre-posttest changes indicating slowed perceptual speed. Perceptual speed was still slowed when BAC decreased to .096. When mean BAC decreased to .076, however, only Simultaneity and Backward Masking were still significantly slowed. At moderate BACs and possibly at lower ones, the effects of alcohol on task performance appear to be mediated in part by slowed perceptual speed.

Adult↗

PubMed1998

Birth order and male homosexuality: extension of Slater's index.

Homosexual men tend to be later-born children. Slater's index, the ratio of older sibs to all sibs, is consistently higher for male homosexuals than for comparable heterosexuals. According to some explanations of this tendency, homosexual men are later born with respect to their brothers and later born with respect to their sisters only secondarily and less strongly. We show that if sisters have no direct bearing on a brother's sexual orientation and brothers do, then [formula: see text] On the other hand, if sisters have the same bearing on a brother's sexual orientation as male sibs do, then [formula: see text] These ratios are calculated and compared in nine samples of homosexual men and nine corresponding samples of control heterosexuals. The first equation holds for homosexual men, and the second equation holds for heterosexual men. The late birth order of homosexual men is sex specific. What matters is a boy's birth order relative to his brothers only. This effect may have its origins in an immune reaction or in behavioral contagion.

Analysis of Variance↗

PubMed1997

A randomized, double-blind study of the effect of olestra on disease activity in patients with quiescent inflammatory bowel disease. Olestra in IBD Study Group.

PURPOSE: To determine the effects of olestra, a zero-calorie fat substitute that is neither digested nor absorbed, on the well-being and disease state of persons with chronic inflammatory bowel disease (IBD) in remission. PATIENTS AND METHODS: Eighty-nine patients with mild to moderate ulcerative colitis (n = 43) or Crohn's disease (n = 46) in remission, with a history of disease of 2 years or longer, were enrolled in this prospective study from nine private practices, three university-based medical centers, and one Veterans Administration medical center in the United States. Forty-four patients were randomly assigned to receive olestra and 45 to receive triglycerides in chips or cookies daily for 4 weeks. At Week 4, patients were classified as in remission, worsened, or relapsed according to an investigator's global assessment based on sigmoidoscopy (for ulcerative colitis) or the Crohn's disease activity index, laboratory findings, and clinical course. RESULTS: At Week 4, the olestra and triglyceride groups did not differ significantly with respect to the percentages of patients who relapsed (P = 0.494; difference = 2.4%; upper 95% CL = 8.8%) or with respect to the percentages of patients who experienced any worsening of their symptoms (P = 0.630; difference = 0.2%; upper 95% CL = 13.3%). Of evaluable patients, 90% (37 of 41) given olestra remained in remission with no worsening, compared with 90% (38 of 42) given triglycerides. Gastrointestinal symptoms were comparable between the treatment groups, and there were no treatment-related laboratory abnormalities. Six patients were excluded from analysis for reasons unrelated to treatment. CONCLUSION: Olestra did not affect the activity of quiescent mild to moderate IBD.

Abdominal Pain↗

PubMed1997

Olestra's effect on the status of vitamins A, D and E in the pig can be offset by increasing dietary levels of these vitamins.

Groups of weanling pigs (5 castrated males, 5 females per group) were fed purified diets containing the NRC's requirements for nutrients and 0, 1.1, 4.4 or 7.7% olestra for 12 wk. Graded concentrations of vitamins A, D2 and E were added at each olestra concentration. The primary purpose of the study was to establish relationships between dietary concentration of olestra and the amounts of vitamins A, D2 and E needed to restore tissue concentrations of these vitamins to control concentrations. A secondary purpose was to confirm that olestra does not affect the status of vitamin K or water-soluble nutrients. Liver concentrations of vitamins A, E and B12, iron and zinc and bone concentrations of ash, zinc, calcium and phosphorus, were measured in a group of pigs killed at the start of the study and in all pigs killed at wk 12. Growth, feed efficiency, hematology, clinical chemistry, blood concentrations of retinol, alpha-tocopherol, 25-hydroxyergocalciferol, 25-hydroxycholecalciferol, 1,25-dihydroxyvitamin D, folate, iron, total iron-binding capacity, zinc and calcium and adipose concentration of vitamin E were measured at 4-wk intervals. Prothrombin time was measured weekly for the control and 7.7% olestra groups, monthly for others. Relationships derived from measured tissue concentrations of vitamins A and E showed that constant amounts of the vitamins were required per unit mass of olestra in the diet to restore tissue concentrations to control values. Such a relationship could not be determined for vitamin D because exposure of the pigs to UV light resulted in an apparent interaction between vitamin D2 and vitamin D3. Olestra did not affect growth, digestible feed efficiency, vitamin K status or the status of the water-soluble micronutrients, in agreement with other studies in the pig.

Animals↗

PubMed1997

Nutritional status of pigs fed olestra with and without increased dietary levels of vitamins A and E in long-term studies.

In a 26-wk study, five groups (n = 10) of domestic pigs were fed 0.25, 0.5, 1.1, 3.3 or 5.5% olestra; three groups were fed 0.25% with graded levels of vitamins A and E; and one group was fed 5.5% with added vitamins A and E and exposed to UV light. In a 39-wk study, two groups (n = 10) were fed 0.25% olestra with or without added vitamins A and E. In each study, a control group was fed basal diet with no olestra, and a group was killed at d 0 for base-line nutrient measurements. The diets provided the NRC's requirements of micronutrients for 5- to 10-kg pigs, with the following two exceptions: vitamin D was provided at twice the requirement in the 26-wk study and vitamin K was provided at 20% of the requirement in the 39-wk study. One purpose of the studies was to determine the amounts of vitamins A and E required to restore tissue concentrations of those vitamins to control concentrations. A second purpose was to determine the effects of olestra on the status of vitamins A, D, E, K and B12, and folate, iron, calcium and zinc when pigs eat olestra at intakes similar to estimated human intake for a period covering major growth and developmental phases, including sexual maturation. Olestra reduced tissue concentrations of vitamins A, D and E but did not affect prothrombin time or the status of the water-soluble nutrients. The amount of vitamin A required to restore liver concentration to control concentration was 93 microg retinyl palmitate/g olestra. Restoration levels for serum and liver concentrations of vitamin E were 2.2 and 2.1 mg d-alpha-tocopheryl acetate/g olestra. Olestra did not affect growth or digestible feed efficiency in either study, indicating that the absorption and utilization of macronutrients were unaffected. There were no antemortem observations or changes in clinical chemistry or hematology that would indicate an adverse effect of olestra.

25-Hydroxyvitamin D 2↗