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Biomedical subjects

J Beard

Publications and source records attributed to J Beard.

At least 55 records · Page 3Linked to original sources
PubMed1995

Structure-reactivity relationships for beta-galactosidase (Escherichia coli, lac Z). 2. Reactions of the galactosyl-enzyme intermediate with alcohols and azide ion.

Velocities for the synthesis of beta-D-galactopyranosyl derivatives by transfer of the galactosyl group from beta-galactosidase to seven alkyl alcohols, glucose, and azide ion have been determined as the difference in the velocities for beta-galactosidase-catalyzed cleavage of 4-nitrophenyl beta-D-galactopyranoside to give 4-nitrophenoxide anion (v PNP) and hydrolysis of this compound to give D-galactose (v Gal). Rate constant ratios kROH/ks (M-1) for partitioning of the galactosylated enzyme between reaction with alkyl alcohols and solvent determined by this method are in good agreement with values of kROH/ks (M-1) determined by analysis of alcohol inhibition of enzyme-catalyzed hydrolysis of the corresponding alkyl beta-D-galactopyranosides. Absolute rate constants kROH (M-1 s-1) for reaction of alkyl alcohols with the galactosylated enzyme intermediate were calculated from the corresponding rate constant ratio kROH/ks (M-1) and ks = 710 s-1. A Brønsted parameter of (beta nuc) ROH = -0.19 +/- 0.10 was determined from the second-order rate constants for the reactions of alcohols with the galactosylated enzyme. The large difference between (beta 1g)kcat/Km = -0.75 +/- 0.14 for cleavage of alkyl beta-D-galactopyranosides to form the galactosylated enzyme and (beta nuc)ROH = -0.19 for the reverse synthesis reaction requires that the equilibrium constants for galactosyl group transfer from alkyl beta-D-galactopyranosides to the enzyme increase sharply with decreasing pKa of the alkyl alcohol leaving group. These data give beta eq = -0.56 +/- 0.05 for the reaction of alkyl beta-D-galactopyranosides with ethanol to form ethyl beta-D-galactopyranoside and alkyl alcohol. Several effects that lead to this increased ease of cleavage of alkyl beta-D-galactopyranosides with decreasing basicity of the alkoxy group are discussed. A second-order rate constant of kGlc = 1.2 x 10(4) M-1 s-1 was determined for reaction of glucose with the galactosylated enzyme. The relatively low reactivity of glucose is surprising, because an earlier observation that the galactosylated enzyme complex generated by the cleavage of lactose undergoes release of glucose and synthesis of allolactose at nearly equal rates suggests that the binding of glucose to the galactosylated enzyme should be partly irreversible and that it takes place near the encounter-controlled limit. The data suggest a significant stabilization of nonproductive complexes formed by binding of glucose to the galactosylated enzyme. beta-Galactosidase catalyzes the hydrolysis of beta-D-galactopyranosyl azide, but not the synthesis of this compound by reaction of azide ion with the galactosylated enzyme.(ABSTRACT TRUNCATED AT 400 WORDS)

Alcohols↗
PubMed1995

A case of paternal uniparental disomy for chromosome 11.

We report a case of paternal uniparental disomy for chromosome 11 that presented as severe intrauterine growth retardation. Autopsy following intrauterine death also revealed aberrant intestinal rotation and hypospadias. Chromosome analysis of direct preparations from placental biopsy showed an abnormal 47,XY,+11 karyotype. Analysis of long-term cultures from the placenta revealed 46,XY/47,XY,+11 mosaicism. Fluorescence in situ hybridization (FISH) studies on interphase nuclei confirmed trisomy 11 in multiple placental sites but detected only disomic cells in fetal skin. Investigation using microsatellite polymorphisms demonstrated paternal isodisomy at loci D11S909, D11S956, and D11S488, and paternal heterodisomy at locus D11S928.

Adult↗
PubMed1995

Minimum doses of ultraviolet radiation required to induce murine skin edema and immunosuppression are different and depend on the ultraviolet emission spectrum of the source.

Many photo immunological studies have used UV radiation sources that emit nonsolar UV spectral energy and UV doses based on nonimmunological endpoints, e.g. erythema and skin edema. Interpretation of these data has led to misunderstanding when extrapolated to hypothetical effects in humans exposed to solar UV. The purpose of this study was to: (1) establish UV dose response relationships for murine skin edema and immunosuppression, and (2) determine how different UV spectra affect these relationships. Back skin and ear minimum edema doses (MEdD) for Kodacel-filtered FS20 sunlamp UV (290-400 nm) were greater than two-fold higher than those for unfiltered FS20 sunlamp UV (250-400 nm). Xenon are solar simulator UV (295-400 nm) MEdD were > 10-fold higher than those for unfiltered sunlamp UV. Back skin and ear MEdD differed two- to five-fold between C3H/HeN, SWR/J and HRA/Skh-1 mice. The minimum immunosuppression doses (MISD) in C3H mice showed similar UV source spectrum dependence. The solar simulator UV MISD was 5.4- and 1.5-fold higher than for unfiltered and Kodacel-filtered sunlamp UV MISD, respectively. Furthermore, MISD were from 3- to 50-fold higher than the MEdD for the three UV sources. The UV bioeffectiveness spectra indicated that UVC energy (250-290 nm) contributed 12% and 18%, respectively, of the total skin edema and immunosuppression UV energy. These data demonstrate the variability in UV sensitivity among mouse strains, the significant differences between murine MEdD and MISD and how these differences are influenced by nonsolar regions (below 295 nm) of the UV spectrum.

Animals↗
PubMed1995

Exposure to pesticides in ambient air.

Ambient air was monitored for pesticides at four sites in Coffs Harbour, a coastal town (population about 50,000) surrounded by banana plantations. Air was sampled continuously for five consecutive months during the peak agricultural spraying period using vacuum pumps set to sample one litre per minute through ORBO-42 absorption tubes. Six pesticides were detected: three organochlorines and three organophosphates. The most commonly detected pesticide (14 per cent of all samples) was chlorpyrifos (maximum detected level 208.0 ng/m3, mean 3.6 ng/m3). Heptachlor was detected in 7.1 per cent of all samples (maximum detected level 133 ng/m3, mean 2.7 ng/m3). Other pesticides were only rarely detected. The only pesticide applied by air in the district (propiconazole) was not detected. If international health guidelines are used as a yardstick, these levels of exposure appear unlikely to present an appreciable health risk. Chlorpyrifos detection was associated with low wind speed (P = 0.012) and high temperature (P = 0.015), and detection at one site was associated with detection at another (P < 0.001). Chlorpyrifos detection was also associated with domestic applications within the town area as reported by pesticide applicators (P = 0.045). Peak agricultural use of chlorpyrifos did not coincide with peak detection periods. None of the detected organochlorines is registered for agricultural use, although at the time, heptachlor was permitted for use as a domestic termiticide. Even in a semirural town with nearby widespread use of agricultural chemicals, community exposures to pesticides in ambient air may largely relate to their nonagricultural use.

Agriculture↗
PubMed1994

[Effects of maternal age in the neonate health status: Chilean evidence].

PURPOSE: The purpose of this study was to compare the pregnancy outcome and the growth and development of infants of adolescent and older mothers in a Latin American setting in which young mothers received aggressive prenatal care, and in which breast feeding behavior of all women was strongly encouraged and recorded. Our hypothesis was that the generally higher rates of low birth weight and neonatal complications among infants of Chilean adolescents would be eliminated by an aggressive protocol of prenatal care. METHODS: Data on prenatal care, gestation, birth and infant growth and development were extracted retrospectively from the medical records of 200 low socioeconomic status para I patients, all of whom received care by the same hospital team. The sample included 50 women ages 14-16, 50 women 17-19, and 100 women 20-24.

Adolescent↗
PubMed1993

The management of stroke during intraarterial thrombolysis.

Intraarterial thrombolytic therapy is being increasingly used in the treatment of acute limb ischaemia. When strokes occur during thrombolytic therapy treatment is usually stopped because of the suspicion of cerebral haemorrhage. If the stroke is not haemorrhagic then stopping the treatment jeopardizes the ischaemic limb. If the stroke is proven to be non-haemorrhagic on computed tomography (CT) then the thrombolytic therapy should be recommenced. We present three case histories of patients who suffered a stroke during thrombolytic therapy over a 30-month period, in whom CT confirmed non-haemorrhagic stroke and we suggest that managing the ischaemic limb with anticoagulant and thrombolytic therapy can be safe in the early period following the stroke. We also discuss the probable aetiology of the strokes and whether cardiac echocardiography should be performed in these patients.

Adult↗
PubMed1993

The ultraviolet C energy emitted from FS lamps contributes significantly to the induction of human erythema and murine ear edema.

FS ultraviolet (UV) lamps are used extensively to study the biological effects of ultraviolet radiation. Using published data, we investigated the relative contributions of the UVC (250-289 nm), UVB (290-319 nm), and UVA (320-400 nm) portions of the FS lamp emission spectrum to the induction of human erythema and murine ear edema. Many investigators contend that the biological activity of the spectrum emitted from these lamps resides primarily in the UVB region, based on the proportions of the power emission spectrum in this region (53.6%) versus the small relative contribution of UVC (3.2%) and the low biological activity of UVA (43.2%). However, if the biological effectiveness spectrum of FS lamps is calculated by multiplying the power spectrum with different action spectra, the biological effects of UVC are readily observed. For example, 10.4% of the murine ear edema activity and 11.1% (Parrish) or 16.7% (McKinlay-Diffey) of the human erythemal activity is due to the energy emitted in the UVC region. Experimental determination of human erythema and murine ear edema demonstrated that, for an equal amount of energy delivered, radiation from the unfiltered lamps was more potent in causing these responses than radiation from filtered lamps, and the ratio of effectiveness could be predicted by the effectiveness spectra. Thus, the contribution of UVC emitted from FS lamps to biological effectiveness spectra should not be ignored.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Developing a comprehensive maltreatment intervention program.

The dental health care professional must understand that every individual cannot be saved from maltreatment, but the task is not futile. Suspicion must be investigated. The responsibility for investigating reports of suspected maltreatment lies at the state level. Every state has established a protective service reporting agency. Begin by determining the names and addresses of the protective agencies in your area and the procedure for reporting suspected cases of maltreatment. Determine the most effective and thorough means of gathering current and relevant information on the detection and proper evaluation of maltreatment. Consider the knowledge and training that dental personnel need to make an intervention program successful. Decide now dental staff should proceed and what timetable should be set for the implementation of an intervention. Dental health care providers must be a part of coordinated effort involving all groups concerned with the welfare of the aged and the young. Be proactive not reactive. Additional information may be obtained from the ADA's Council on Dental Practice at 1-800-621-8099, ext. 2895; the National Center on Child Abuse and Neglect, Department of Health & Human Services, P.O. Box 1182, Washington, D.C. 20013 (703) 821-2986; or the National Committee for the Prevention of Child Abuse 111 E. Wacker Drive, Suite 510, Chicago, IL 60601. Reporting agencies include: local department of public welfare; local police department; state departments of public welfare; state department of health & human services; national child abuse hotline, toll free (1-800-422-4453).

Adult↗
PubMed1991

A model for the assessment of students' physician-patient interaction skills on the surgical clerkship.

Physician-patient interaction skills are predominantly taught by successful role modeling but are rarely evaluated formally and systematically. This study describes a new model for the assessment of student physician-patient interaction skills and reports results of use in 78 third-year medical students on clerkships at two institutions. A single nurse instructor at each institution evaluated these skills using an 18-item checklist during student performance of wound care and dressing changes. Students were focused on the evaluation of their technical skills and were unaware of the evaluation of their interaction skills. Immediate feedback on performance was provided. The mean percentage score for the interaction skills was 35%, and no improvement was noted with greater clinical experience (later rotations). We conclude that there is a striking deficiency in physician-patient interaction skills among third-year students. The model described is effective for both evaluation and feedback.

Clinical Clerkship↗
PubMed1991

Primary thrombocythaemia in pregnancy.

Nine pregnancies in six patients with primary thrombocythaemia are reported. Eight pregnancies resulted in the delivery of normal infants. One pregnancy ended in spontaneous abortion at 7 weeks gestation. One pregnancy was complicated by superficial thrombophlebitis and a postpartum haemorrhage. We suggest that pregnancy in patients with primary thrombocythaemia can have a favourable outcome, but requires close monitoring. Administration of aspirin during pregnancy may be of benefit.

Abortion, Incomplete↗
PubMed1990

Abdominocervical (transhiatal) oesophagectomy in the management of oesophageal carcinoma.

Fifty-four patients have undergone abdominocervical oesophagectomy for oesophageal carcinoma as an alternative to a conventional transthoracic approach. Their median age was 69 years, with a range of 38-90 years, and 39 per cent of patients had chronic cardiorespiratory disease. Lymph node metastases were found in 80 per cent of patients and transmural tumour spread in 91 per cent. Median duration of operation was 2.2 h (range 1.75-6.0 h), and median transfusion requirement was 2.5 units (range 0-8 units). Respiratory complications were common (41 per cent) and caused all six postoperative deaths (11 per cent). Other complications were atrial fibrillation (26 per cent), transient recurrent laryngeal nerve palsy (11 per cent), cardiac failure (2 per cent), stroke (2 per cent), subphrenic abscess (2 per cent) and empyema (2 per cent). There were two anastomotic leaks (4 per cent), clinically manifest as temporary salivary fistulae. There have been 32 deaths from recurrent carcinoma, with a median duration of survival of 14 months (range 4-53 months). Fifteen patients are still alive, with a median survival of 16.5 months (range 3-49 months); the current 3-year survival rate is 10 per cent. All patients resumed normal swallowing after operation, but 11 of them developed anastomotic strictures requiring a median of three dilatations. Avoidance of formal thoracotomy by the abdominocervical approach may allow more rapid oesophagectomy without increasing the risk of postoperative death and gives a quality of palliation at least equivalent to that of conventional transthoracic oesophageal excision.

Adenocarcinoma↗
PubMed1989

Evidence for thyroid hormone deficiency in iron-deficient anemic rats.

Iron-deficient anemic rats have previously been shown to have low plasma levels of thyroid hormone and a poor plasma thyroid hormone response to acute cold exposure. As an initial exploration, we examined thyroid hormone metabolism during iron deficiency in age-matched rats from three aspects: 1) plasma TSH (thyrotropin, thyroid stimulating hormone), T4 (thyroxine) and T3 (triiodothyronine) responses to graded doses of exogenous TRH (thyrotropin releasing hormone), 2) plasma T3 kinetics, and 3) rates of hepatic T3 production. Iron-deficient anemic rats had lower basal TSH values and blunted TSH responses to intravenous TRH injection at three different doses (10, 25 and 50 ng TRH/100 g body wt). Iron-deficient anemic rats also had a significant decrease in plasma T3 turnover (42 vs. 88 ng/h in controls), and significantly lower hepatic T4-5'-deiodinase activities than controls [26 vs. 44.0 ng T3/(mg protein.20 min)]. Thus, decreased rates of T3 production in iron-deficient anemic rats, as documented by turnover studies, may be related to decreased deiodinase activity and reduced peripheral formation of T3. The dampened TSH responses to TRH further facilitate or perpetuate this T3 deficiency. We propose that this abnormal thyroid state is partially responsible for impaired thermogenesis in iron-deficiency anemia.

Anemia, Hypochromic↗