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Biomedical subjects

D R Johnson

Publications and source records attributed to D R Johnson.

At least 217 records · Page 12Linked to original sources

Divorce and marital instability over the life course.

"This study uses a [U.S.] national sample of married persons under age 55, interviewed in 1980 and again in 1983, to estimate why divorce and marital instability vary by age and duration of marriage. Results indicate that the accumulation of assets substantially reduces the propensity to divorce. We also find that several important correlates of divorce and instability (age at marriage, health, social integration, and income) interact with age and duration. In general, these factors seem to operate almost exclusively among young people and young marriages."

Age Factors↗

The clonal model of vertebral column development: a reinvestigation of vertebral shape using Fourier analysis.

Little work has been done on the skeletal system of allophenic mice (chimaeras). In this paper we re-examine the evidence presented for the clonal theory of vertebral development using quantitative methods which take account of variation. We conclude that the clonal theory is either an overly simplistic approximation of the real situation, or that the evidence so far given in its support is unsubstantiated.

Animals↗

Lactose synthase: effect of alpha-lactalbumin on substrate activity of N-acylglucosamines.

N-Acetyl-, N-propionyl-, N-butyryl- and N-valerylglucosamines were synthesized as topographical probes to localize further the interaction site of alpha-lactalbumin on galactosyltransferase. All these compounds were found to be substrates for galactosyltransferase with Km values in the millimolar range. In the presence of alpha-lactalbumin, the Michaelis-Menten constants were diminished. However, the effect on the initial rates of these reactions varied. Thus, at low N-acylglucosamine concentrations, alpha-lactalbumin activated the enzyme activity, but at high concentrations, alpha-lactalbumin became inhibitory. This mixed-type inhibition kinetics indicated that a quaternary complex between galactosyltransferase, alpha-lactalbumin, Mn2+-UDPgalactose and N-acylglucosamine existed during the catalytic process. The ability of these N-acylglucosamine substrates to bind to lactose synthase complex was further substantiated by the physical association of galactosyltransferase onto the solid-bound alpha-lactalbumin in the presence of any one of these compounds. The data revealed that the presence of the N-acyl group up to five carbons in length did not interfere with the interaction between alpha-lactalbumin and galactosyltransferase, suggesting that alpha-lactalbumin was not bound in the vicinity of the C-2 region of the monosaccharide site. The inhibitory effect of alpha-lactalbumin on N-acyllactosamine formation is probably a consequence of conformational changes of galactosyltransferase.

Animals↗

Origin and specificity of autoreactive T cells in antigen-induced populations.

We have characterized the major histocompatibility complex (MHC) specificity of autoreactive T cell clones arising from diverse donors after immunization with different antigens. The MHC fine specificity of autoreactive T cells for unique F1 hybrid determinants of BALB.K X BALB.B F1, and for the mutant I-Ab determinants of the B6.C-H-2bm12 (bm 12) strain is similar to that previously described for antigen-specific T cells. We find, furthermore, that the MHC specificity of autoreactive T cell clones selected from primed populations grown in the absence of Con A-stimulated supernatant factors reflects the predominant MHC restriction specificity of T cells specific for the immunogen. Thus, I-E subregion-specific autoreactive T cells are detected at a much higher frequency after immunization with the I-E-restricted antigen, GL (terpolymer of glutamic acid, lysine, and phenylalanine), than with the predominantly I-A-restricted antigen, keyhole limpet hemocyanin (KLH). These experiments strongly suggest that some autoreactive T cells are derived from antigen-stimulated precursors. This result contrasts with that obtained when autoreactive T cells are selected in bulk cultures, or in the presence of exogenous T cell factors. We conclude that, under optimal conditions, most autoreactive T cells are recruited from a relatively stable pool of predominantly I-A-specific precursors. Autoreactive precursors in this pool might themselves derive from previous antigenic stimulation, or be of independent origin.

Animals↗

Role of iron in jejunal uptake of cadmium in the newborn rat.

There is evidence that suckling animals and children have a greater capacity for intestinal transport of both essential and nonessential metals than do adults of the species. It has also been observed in experiments using adult animals that the intestinal transport of iron and the nonessential metal cadmium interact with one another. In the study reported here, the influence of tissue iron status on jejunal uptake of cadmium was investigated in suckling, adolescent, and young adult rats using an in situ incubation technique. In the presence of 0.4 mM FeSO4, intestinal uptake of cadmium was significantly decreased in 14-d-old pups. Access to an iron-deficient diet reduced tissue iron levels in 28- and 42-d-old but not in 14-d-old rats. Intestinal uptake of cadmium was significantly greater in 28- and 42-d-old rats placed on the iron-deficient diet but did not change in 14-d-old rats compared to controls. In suckling rats injected with iron dextran over a six-d period, a significant decrease in intestinal uptake of both cadmium and iron was observed compared to controls. The results of the present study suggest that intestinal cadmium transport in the suckling, as well as the adolescent and young adult rat, interacts with, at least in part, the pathway responsible for iron transport.

Aging↗

Renal cortical mercury distribution following dithiothreitol administration.

Previous studies from this laboratory have indicated that dithiothreitol (DTT) administration (31 mg DTT/kg, i.p.) 1 h after mercuric chloride injection (3 mg/kg, i.v.) results in partial reversal of Hg-induced renal toxicity without altering total renal mercury deposition. Studies were performed, therefore, to determine if DTT administration altered the renal delivery, excretion, and/or, in particular, subcellular distribution of mercury in a way that may explain the observed phenomenon. Analysis of mercury partitioning between red cells and plasma revealed no difference in relative distribution when Hg- or Hg + DTT-treated groups were compared. However, absolute mercury concentration in both whole blood and plasma of Hg + DTT-treated rats was significantly higher than in the Hg-treated group. Total urinary excretion of mercury was significantly less in Hg + DTT-treated rats than in rats treated with mercury alone. The subcellular distribution of mercury in the particulate and supernatant fractions of renal cortical homogenates from Hg-treated and Hg + DTT-treated rats was similar. Fractionation of the supernatant on G-75 Sephadex gel revealed no difference in the protein profiles between the Hg- and Hg + DTT-treated groups. It is concluded that DTT administration ameliorates the nephrotoxic effect of prior mercury injection by a more subtle mechanism than redistribution of renal cortical mercury.

Animals↗

Measurement of biological shape: a general method applied to mouse vertebrae.

A method is described for recording and analysing the projected shape of mouse vertebrae. The image of the shape is captured by a television camera, cleaned, digitized and subjected to mathematical analysis. A visual representation is obtained by reconstructing the shape in polar coordinates about its centre of area. Further statistical analysis of the whole shape is performed after a Fourier transform. This allows the shape to be represented by and reconstructed from 15 numbers. The method does not rely on homologous points or expert opinion and allows mean shapes to be constructed. It successfully distinguished between 92% of the test data, T1 and T2 vertebrae from two strains of mice.

Animals↗

Cell kinetics of growth cartilage of achondroplastic (cn) mice.

Mice homozygous for the recessive gene achondroplasia (cn) aged 16 and 17 days and some homozygotes aged 22-34 days have disruptions in the growth of the proximal tibial growth plate which are due solely to reduced hypertrophic cell height. A second class of homozygote, distinguishable at 22 days, has a greater disruption due to much reduced hypertrophic cell height, reduced labelling index and reduction of the number of cells in the effective proliferative zone.

Achondroplasia↗

Cell kinetics of growth cartilage in spondylo-metaphyseal chondrodysplasia (smc) mice.

The gene for spondylo-metaphyseal chondrodysplasia (smc) in the mouse disrupts the formation of growth plate cartilage. No cartilage columns are found in the head of the tibia and secondary centres of ossification appear very late. The number of cells labelled with tritiated thymidine is sharply reduced at 16, 18 and 21 days of age but hypertrophic cell height is normal. Cells taking up label are found scattered throughout the large cartilaginous epiphyses.

Animals↗

Toxicology screening in the emergency department: ethanol, barbiturates, and salicylates.

A review of 737 limited toxicological screens performed in a municipal teaching hospital over one calendar year was conducted to determine the value of performing analyses for ethanol, salicylates, and barbiturates. Less than 5% of salicylate determinations and less than 2% of barbiturate tests yielded positive results. On the other hand, ethanol was present in over 70% of cases. The low number of positive results and the cost do not justify analyzing for salicylates or barbiturates unless their presence is suspected. Ethanol determinations should be limited to patients without an obviously consistent clinical presentation. Selective use of these tests in the emergency department is called for.

Alcoholic Intoxication↗

Representation of the internal world in catatonic schizophrenia.

Catatonia, which until 1874 was called atonic melancholia, has remained a relative mystery despite many advances in the understanding of schizophrenia. Its typical symptoms are certainly distinctive: a motionless stupor, bizarre posturing, waxen flexibility, religious delusions, stereotyped movements, negativism, loss of will, confusion, and recurrent frenzy (Kahlbaum 1874). The processes which motivate this particular derailment of self and body have been sought in various organic etiologies, with little success. Arieti (1974) proposes several reasons for the paucity of case studies of the treatment of catatonic schizophrenia. First, catatonic schizophrenia has been declining in occurrence. Second, the symptoms themselves, such as mutism and excitement, make verbal therapy extremely difficult. Finally, catatonics often have no memory of their psychotic experiences. Psychotherapists have therefore had to rely on highly personal intuitions of their patients' crisis-in-being. Despite therapists' attention to nonverbal behavior, mutism and stupor are particularly effective hindrances to communication in psychotherapy. Psychotherapy is often not begun until the patient's symptoms ameliorate through chemotherapy and milieu support. The centrality of the verbal medium of communication in psychotherapy suggests that other approaches, using nonverbal media, may be indicated in the study of catatonia. This paper describes a treatment of a catatonic schizophrenic man which utilized movement and drama therapy. These methods were successful in evoking representations of the patient's inner life.

Adolescent↗