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Biomedical subjects

S Jordan

Publications and source records attributed to S Jordan.

At least 127 records · Page 7Linked to original sources
PubMed1987

Accuracy of temporomandibular joint space measurements using corrected hypocycloidal tomography.

This study underscores the importance of obtaining radiographs in a tomographic plane bisecting the long axis of the condyle. The accuracy of joint relationships and clarity of the images produced using the horizontally and vertically corrected techniques were significantly greater than when both standard or only horizontally corrected techniques were used in the cases examined. Correlative clinical studies are recommended to be studied.

Humans↗
PubMed1987

Polychlorinated biphenyls and related compound interactions with specific binding sites for thyroxine in rat liver nuclear extracts.

Thyroid hormone analogues, polychlorinated biphenyls (PCBs), and their derivatives were shown to bind specifically to thyroxine-specific binding sites in rat liver nuclear extracts. The structure-binding relationship for thyroxine binding prealbumin was qualitatively similar to that for the nuclear receptor. In general for both binding proteins, increased binding affinity was seen for the more linear and in some cases rectangular shaped (as opposed to the angular shaped thyroid hormones) chlorinated aromatic hydrocarbons with chlorine concentrated in lateral positions (3,3',5,5'-substitution on biphenyl nucleus). However two groups of compounds showed distinct quantitative differences. The relatively less polar and more lipophilic nonhydroxylated PCBs bound the nuclear receptor with significantly lower affinities while two compounds that are structurally related by the potential for equilibrium interconversion to a rigid planar structure bound with significantly higher affinities. This latter class of compounds represents soluble dioxin (TCDD) approximate isosteres and has an extended (polarizable) pi-system brought about by a planar structure (or conversion to the same) and lateral halogenation. These structure requirements are maximally expressed in 3,3',5,5'-tetrachlorodiphenoquinone (TCDQ), which shows a remarkably high affinity (Ka = 1.84 X 10(11) M-1) for the nuclear receptor. Thus, the nuclear receptor shows the expected structural specificity and sensitivity for possible involvement in the high toxicity of these classes of compounds. The physiological significance of these binding results is supported by the dose-dependent regulation (increase) of the thyroxine nuclear receptor number by dioxin, although the mechanism responsible for this increase is not clear. The nuclear binding component was further analyzed by sucrose density gradient centrifugation and was found to have a sedimentation coefficient of 4.3 S under high salt conditions. A crude estimate of the molecular weight (45,200) was obtained from a linear plot of standard globular protein fraction number (sedimentation coefficient) vs. log molecular weight. Although direct evidence is not provided, the thyroxine nuclear receptor may cooperate with a second receptor in binding the TCDQ type ligand or exists as a multimeric species with binding properties of both prealbumin and the dioxin (or Ah) receptor.

Animals↗
PubMed1987

Somatosensory evoked potentials in the assessment of thoracic outlet compression syndrome.

To evaluate the assessment of thoracic outlet compression syndrome (TOS) by objective methods, we prospectively studied a group of 80 consecutive patients with disabling TOS who had been selected for surgical therapy. Comprehensive pre- and postoperative neurophysiologic tests were used and included electromyography, nerve conduction times, F wave determination, and somatosensory evoked potentials (SEPs) of median and ulnar nerves in neutral and stressed positions. Measurements were made of Erb's point peak (N9), cervical peak (P/N13), and cortical complex (N18-P22). Amplitude ratios were calculated for each side, and interpeak latencies were measured for N9-P/N13, P/N13-N18, and N9-N18. SEP results were abnormal on the affected side in 59 of 80 patients (74%); ulnar peak amplitudes were either less than 33% of median, reduced by more than 50% in the stressed position, or reduced by more than 50% when compared with the contralateral side. Of 64 patients studied pre- and postoperatively with SEP, 40 of 47 abnormal tests showed improvement, with 30 of these returning to normal values in the early postoperative period. Excellent clinical correlation was evident in 43 of these 47 patients (92%) who had pre- and postoperative tests; with relief of symptoms reflected in improved SEP, or continued symptoms explained by evidence of persistent or residual nerve dysfunction. The present methodology and criteria for test interpretation demonstrate that SEP can document the neurocompressive component of TOS and provide an objective assessment of pre- and postoperative clinical observations.

Action Potentials↗
PubMed1987

Pentobarbital-like discriminative stimulus properties of halothane, 1,1,1-trichloroethane, isoamyl nitrite, flurothyl and oxazepam in mice.

Volatile inhalants represent a diverse group of chemicals which pose a public health problem because of their abuse potential and neurobehavioral toxicity. Although relatively little is known about their pharmacology, they share certain pharmacological properties with classic central nervous system depressants. Drug discrimination procedures were used to compare the effects produced by pentobarbital (PB), oxazepam and several inhalants. Mice were trained to discriminate PB from saline injections in a two-lever operant task. Stimulus generalization was examined after 20-min inhalation exposures to halothane (500-8000 ppm), 1,1,1-trichloroethane (500-12000 ppm), isoamyl nitrite (150-1050 ppm), flurothyl (562-1300 ppm) and injections of oxazepam (0.1-20 mg/kg). Halothane, 1,1,1-trichloroethane and oxazepam produced discriminative stimulus effects similar to those produced by PB. Isoamyl nitrite and flurothyl, while decreasing rates of responding, were not consistently generalized from PB. Differences are apparent in the PB-like discriminative effects of inhalants. Toluene, as shown in a previous study, as well as halothane and 1,1,1-trichloroethane have PB-like discriminative effects which are also shared by oxazepam and may be another common effect of central nervous system depressants. Other chemicals, like isoamyl nitrite and flurothyl, are representative of qualitatively different classes of behaviorally active inhalants.

Administration, Inhalation↗
PubMed1986

Factors affecting pregnancy rates in a donor insemination program using frozen semen.

The results of therapy of 226 women receiving frozen and fresh donor semen are reported. Overall, 45.6% of patients conceived with a monthly fecundability of 0.102. The effect of a variety of factors on fertility rates was analyzed in life-table analysis of 1000 cycles. Optimal pregnancy rates were obtained in couples with azoospermia (0.17) or no female infertility factors (0.2). Patients with ovulatory dysfunction treated with clomiphene also had optimal pregnancy rates (0.17 per cycle). Endometriosis reduced fecundability significantly (0.04 per cycle). There was no significant difference in pregnancy rates per cycle between fresh (0.12) and frozen (0.09) semen. Acceptable pregnancy rates were obtained with frozen semen therapy and in patients with treated ovulatory dysfunction.

Clomiphene↗
PubMed1985

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) as a potent and persistent thyroxine agonist: a mechanistic model for toxicity based on molecular reactivity.

TCDD and thyroxine have common molecular reactivity properties which enable them to present a planar face and lateral halogens in interactions with proteins. These molecular properties are consistent with the structure-toxicity relationship for TCDD and related compounds. Biological evidence is discussed including preliminary studies on the effects of TCDD exposure on tadpole growth and development which is consistent with the possible thyroxine-like activity of TCDD. The work suggests the possibility that toxicity is at least in part the expression of potent and persistent thyroid hormone activity (responses induced by TCDD which qualitatively correspond to those mediated by thyroid hormones). A mechanism for toxicity is proposed which involves receptor proteins; the planar aromatic system controls binding to cytosolic proteins and halogen substituents regulate binding to nuclear proteins. This simple model based on molecular reactivity sheds light on the diversified effects of TCDD and related compound toxicity and on certain thyroid hormone action. The model also permits predictions to be made with regard to the toxicity and thyroid hormone activity of untested compounds. In addition, the model suggests a general mechanism for hormone action based on metabolically regulated differential and cooperative protein receptor binding events in cellular compartments which can explain agonism, antagonism and potentiation within the framework of receptor occupancy theory.

Animals↗
PubMed1984

Embryonic/fetal growth following suckling-induced delay of implantation.

In rats fertilized during the first or second day post partum (second consecutive pregnancy), suckling induces delay of implantation for 8 to 22 days. However, pregnancy is prolonged for only 3 to 17 days because accelerated embryonic and early fetal growth makes up 4 to 5 days of the implantation delay. After implantation, embryonic/fetal growth is accomplished within 11 to 12 days for a second consecutive pregnancy, whereas 16 days are required for first or second-spaced pregnancies. After weaning, increased function of the intestinal tract and liver is not needed anymore for mammary milk synthesis, and abundant nutrients can be shifted to the uteroplacental unit for rapid embryonic/fetal growth. Because the exponential curves for fetal growth are similar for first, second consecutive, and second-spaced pregnancies, it seems that, besides an increased supply of nutrients, an as yet unidentified maternal or a placentofetal factor(s) may play a role for embryonic/fetal growth.

Animals↗
PubMed1984

Induction of tolerance to factor VIII in a child with a high-titer inhibitor: in vitro and in vivo observations.

High dose factor VIII concentrate was infused over 12 months in a 3-year-old child with hemophilia A and a high-titer inhibitor. This regimen was successful in producing clinical tolerance to the factor VIII and was associated with a fall of inhibitor titer from 85 BU to less than 1 BU. Subsequently, a rise in inhibitor to peak at 3.5 BU correlated with a decrease in infusion dose. In vitro studies using a microdroplet assay for immunoglobulin synthesis in the presence of varying concentrations of factor VIII was carried out prior to the clinical trial. This system indicated that the patient's peripheral blood mononuclear cells were stimulated to release IgG by 0.01 U/ml factor VIII coagulant activity and inhibited at 0.9 U/ml FVIIIc. Lymphocyte subsets were monitored during the course of therapy. The ratio of Leu-3a+/Leu-2a+ (helper/suppressor) varied considerably, fluctuating between a peak of 4.4 and low point of 0.6, with the initial pretrial ratio being 1.2.

Antibodies↗
PubMed1984

Heart surgery in infants: a preliminary assessment of maternal adaptation.

The present investigation was undertaken to determine the effects on the mother of having a child undergo heart surgery. Three groups of subjects were recruited and included mothers of infants undergoing heart surgery (Heart Surgery group), mothers of infants admitted on an emergency basis for nonsurgical/nonterminal illness (Inpatient Control), and mothers of infants visiting the pediatrician for well baby checks (Outpatient Control). Data were collected at three times: PRE, the day of admission; POST, the 7th day of admission or day of discharge (whichever came first); and FOLLOW-UP, 2 months after discharge. Relative to the other two groups, a differential attrition rate was evidenced in the Inpatient Control group and this finding is discussed. Given the attrition rate, analyses after PRE involved the Heart Surgery and Outpatient Control. Findings indicate that, relative to the Outpatient Control group, the Heart Surgery group reported greater distress at FOLLOW-UP than at any other time. The distress that was reported involved disruption in the family environment. Results of the analyses are discussed as consistent with posttraumatic stress theory.

Cardiac Surgical Procedures↗
PubMed1983

Polar metabolites of di-(2-ethylhexyl)phthalate in the rat.

Di-(2-ethylhexyl)phthalate (DEHP) is an important industrial chemical widely used as a plasticizer for vinyl and other plastics. DEHP is extensively metabolized by mammals, different species showing dramatic differences in metabolite distributions. Previous studies of the metabolism in rats led to the suggestion that the enzymatic processes normally associated with omega-, omega-1, alpha-, and beta-oxidation of fatty acids could account for the known metabolites of DEHP found in the urine. Several additional metabolites of DEHP have been identified in the present study. Their formation requires that the initial hydroxylation process be less specific than fatty acid omega- and omega-1 oxidation are thought to be. Furthermore, it is necessary to postulate either that the aliphatic chain of mono-(2-ethylhexyl)phthalate can be oxidized at two sites simultaneously, or that oxidation products can be recycled for a second hydroxylation prior to excretion.

Animals↗
PubMed1982

The relationship between metabolism of 2,3,4,5,3',4',5'-heptachlorobiphenyl and its ability to induce both cytochromes P-448 and P-450.

Male CD rats received i.p. injections of 2,3,4,5,3',4',5'-heptachlorobiphenyl (7CB) under conditions resulting in induction of both benzphetamine demethylase (cytochrome P-450-dependent) and ethoxyresorufin deethylase (cytochrome P-448-dependent) activities. To test the possibility that one class of induction (P-450) was due to the parent compound and the other (P-448) to a metabolite, liver, adipose, bile, urine and feces were analyzed for the presence of 3,4,5,3',4',5'-hexachlorobiphenyl (6CB) (the major photolysis product of 7CB) and/or 3-hydroxy-3,4,5,3',4',5'-hexachlorobiphenyl (OH-6CB), another known P-448 inducer. To allow for the possibility that 6CB might be a transient intermediate. The results supported the hypothesis that 7CB is a true 'mixed inducer', nor requiring metabolic alteration for its dual activity.

Adipose Tissue↗
PubMed1982

Pharmacokinetics, interactions with macromolecules and species differences in metabolism of DEHP.

The recent long-term carcinogenesis bioassay of di(2-ethylhexyl) phthalate (DEHP) in rats and mice reported by the National Toxicology Program was the first such bioassay to implicate DEHP as a hepatocarcinogen. At the levels of DEHP fed (up to 1.2% of the diet for two years), the livers of the rats would have been exposed to unhydrolyzed diester; this would not have been the case at lower dosages. Extrapolation to lower dosages is therefore questionable. We do not have sufficient pharmacokinetic data in mice to evaluate the dose relationships as yet. Rodents differ conspicuously from primates in their manner of metabolizing DEHP, both in terms of the demand made on the oxidation potential of the liver and in the chemical properties of the major metabolites. The relevance of these differences must be determined before rodent species can be considered models for the effects of DEHP in humans. Radioactivity from carbonyl-labeled DEHP did not associate with purified protein, RNA or DNA from rat liver in vivo. Label from 2-ethyl-(1-14C)-hexyl-labeled DEHP or mono(2-ethylhexyl) phthalate (MEHP) did appear to associate strongly with purified DNA, but label from free 14C-labeled 2-ethylhexanol did not. The apparent binding from DEHP and MEHP was not exchangeable, but was not proven to be covalent. This phenomenon needs additional study.

Absorption↗
PubMed1982

Urinary tract infection in women visiting rural primary care practices.

In order to estimate the proportion of women who have urinary tract infection, 23 rural primary care private practices agreed to obtain information according to a standard protocol on women over 12 years of age with urinary tract symptoms. Women excluded were those with vaginitis, chronic urinary tract infection, or concurrent confounding diagnoses. The results of the study on 213 women showed that the proportion of ambulatory women with urinary symptoms diagnosed as having urinary tract infection ranged from 31 percent to 71 percent, depending on the diagnostic criteria used. The type of urinary symptoms experienced by the women were not sensitive for cultures of 10(5) or more organisms per milliliter.

Adolescent↗
PubMed1981

Autolymphocytotoxic antibodies in patients on dialysis awaiting renal transplantation.

Two-hundred eighty sera from 78 dialysis patients were examined for autolymphocytotoxic antibodies (ALCAs). Thirty-five (12%) sera in 18 (23%) patients had ALCAs. Eight patients had ALCAs in multiple sera. Two patients had ALCAs against both T and B lymphocytes, 2 against T lymphocytes, and 14 against B lymphocytes. In those sera with ALCAs against both B and T lymphocytes, broad thermal reactivity was present. In sera with ALCAs against only B lymphocytes, the majority were reactive at 5 C. Sixteen (89%) patients with ALCAs had some form of glomerulonephritis; five had rapidly progressive glomerulonephritis (RPGN) and three had systemic lupus erythematosis (SLE). Nine of 10 sera with a positive crossmatch against B lymphocytes from a renal transplant donor did not have ALCAs against autologous B lymphocytes; three sera with ALCAs against B lymphocytes and two with ALCAs against T lymphocytes had negative crossmatches against transplant donor lymphocytes. Positive crossmatches against donor B and T lymphocytes attributable solely to ALCAs were therefore uncommon in our patients. Nevertheless, patients at risk to develop ALCA, including those with SLE and RPGN, should be identified and their sera tested for ALCAs. Once identified, studies can be carried out to distinguish a positive crossmatch attributable to ALCAs from that attributable to HLA alloantibody.

Adolescent↗
PubMed1978

Some clinical interpretations of the Haptic Intelligence Scale for adult blind.

The structure of the over-all test and subtest designs of the Haptic Intelligence Scale for Adult Blind fosters inferences that what is being measured is the same, or similar to, the Performance subscales of the WAIS. The implied assumption that, while the task is similar, performance without seeing may not be interpreted differently is questioned. Theoretical notions, in part, derived from the Dutch psychologist, Révész, are employed to interpret what is being assessed in terms of non-visual sensory input, resultant differences in modes of recognition and structuring of the stimulus, and tasks involved. Analysis is done on two levels: (a) The over-all test results as a measure of non-verbal cognitive adaptation to and ability to employ touch and movement in a variety of tasks; and (b) the subtests as to mental functions involved, the clinical cues that can be derived from performance of the tasks, and instances of marked differences in scores earned on one subtest relative to other subtests.

Blindness↗