Search PubMed⌕ Search

Biomedical subjects

J Hewitt

Publications and source records attributed to J Hewitt.

At least 145 records · Page 8Linked to original sources
PubMed1980

Umbilical blood flow response to embolization of the uterine circulation.

The uterine and umbilical blood flow response to uteroplacental insufficiency, produced by microsphere embolization of the uteroplacental circulation, was examined by means of electromagnetic flow transducers in 12 pregnant ewes. No acute changes were observed in either circulation immediately after embolization of the uterine vasculature. Significant morphometric fetal growth retardation, in terms of weight, length, and ponderal index, was not associated with early changes in fetal pH, PO2, or PCO2. However, the incremental increases in both flows that were observed in control animals did not occur either during or after embolization because of an increase in vascular resistance. During and after embolization the incremental increase in uterine blood flow was blunted or decreased in most, but not all, animals. A rapid, progressive, and persistent decrease in umbilical flow occurred in the growth-retarded group. The significance of these findings relative to intrauterine growth is discussed.

Animals↗
PubMed1980

[Urticaria-oike follicular mucinosis (author's transl)].

Attention is drawn to a new clinical and pathological syndrome, part of the follicular mucinosis group, which is a cyclic, urticarial rash, of the head and neck, occurring in man, without follicular plugging and alopecia, and of benign course. 10 cases are presented here. All patients are middle aged men. Rash is pruritic and recurrent. Clinical aspects and histological findings are described.

Adult↗
PubMed1979

Antigen-specific suppressor factors produced by T cell hybridomas for delayed-type hypersensitivity.

This study describes the generation of T hybridoma lines which secret factors specifically suppressing delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC). AKR strain-derived T lymphoma BW 5147 cells were fused with spleen cells from mice primed with SRBC and containing antigen-specific T suppressor cells for DTH. Supernants from the derived hybridomas were tested for suppression of either expression of induction of DTH to SRBC. Six lines produced specific suppressor activity for the expression of DTH; 4 lines produced suppressor activity for the induction of DTH of which only one line was antigen-specific. These lines were passaged in normal AKR mice, and the serum obtained had activity up to 10(-4) dilution. The factor was effective across the H-2 barrier.

Animals↗
PubMed1979

Organization of the rosy locus in Drosophila melanogaster: further evidence in support of a cis-acting control element adjacent to the xanthine dehydrogenase structural element.

The present report summarizes our recent progress in the genetic dissection of an elementary genetic unit in a higher organism, the rosy locus (ry:3--52.0) in Drosophila melanogaster. Pursuing the hypothesis that the rosy locus includes a noncoding control region, as well as a structural element coding for the xanthine dehydrogenase (XDH) peptide, experiments are described that characterize and map a rosy locus variant associated with much lower than normal levels of XDH activity. Experiments are described that fail to relate this phenotype to alteration in the structure of the XDH peptide, but clearly associate this character with variation in number of molecules of XDH per fly. Large-scale fine-structure recombination experiments locate the genetic basis for this variation in the number of molecules of XDH per fly to a site immediately to the left of the XDH structural element within a region previously designated as the XDH control element. Moreover, experiments clearly separate this "underproducer" variant site from a previously described "overproducer" site within the control region. Examination of enzyme activity in electrophoretic gels of appropriate heterozygous genotypes demonstrates the cis-acting nature of this variation in the number of molecules of XDH. A revision of the map of the rosy locus, structural and control elements is presented in the light of the additional mapping data now available.

Crosses, Genetic↗
PubMed1979

[Knowledge of Solomon's epidermal nevus syndrome (author's transl)].

Solomon's epidermal nevus syndrome is a questionable entity, because of its clinical heterogeneity. Four cases are presented in this paper, with emphasis on the complex relationship between variable types of epidermal nevi and diverse kinds of associated nervous, ocular and bone abnormalities. Nevertheless, it is of practical interest to know the frequency and the variability of these ectodermal and mesodermal associated defects; whatever the epidermal nevus, a careful examination must be carried out, in search of ocular, nervous, bone and renal signs, and, less frequently, but more often than in other children, these patients seem to be exposed to visceral malignancies.

Adolescent↗
PubMed1978

Anxiety and classroom examination performance.

Studied classroom examination performance over the course of an entire semester as a function of (a) students' anxiety level (high, medium, low); (b) difficulty level of exam question (more vs. less difficult); (c) type of exam question (rote memory vs. generalization); (d) sex of S; and (e) intelligence level of S. As expected, there was a strong main effect of anxiety and a significant interaction between anxiety and item difficulty. The latter was consistent with the Hull-Spence formulation of learning and performance--as the habit strength of incorrect responses increases (i.e., as the items become more difficult), the superiority of low over high anxious Ss also should increase. When item difficulty was held constant, anxiety did not interact with type of exam question.

Achievement↗
PubMed1978

Structure analysis of small proteins by electron microscopy: valinomycin, bacitracin and low molecular weight cell growth stimulators.

Dark field electron microscopy was combined with optical filtering to study at high resolution the structure of the cyclopeptide antibiotics, bacitracin and valinomycin, and two proteins of unknown structure, LMW-CSA N and B, low molecular weight granulocyte colony stimulating activity isolated from medium conditioned with normal or leukemic leukocytes. For bacitracin and valinomycin the images faithfully represented the known structural features at a resolution of 0.5 nm or better, depicting a two-ring structure for bacitracin, as well as the position of the potassium ion in valinomycin. Both proteins of unknown structrue had at least one cyclic peptide portion. LMW-CSA N had a size of 2.0 nm, LMW-CSA B of 2.4 nm. A potential site of the calcium ionophoric activity in the latter protein was found to be in the larger of the two ring portions constituting the molecule.

Bacitracin↗
PubMed1978

[Menkes' disease (new skin and hair ultrastructural abnormalities) (author's transl)].

The authors report the sixth case of Menkes' kinky hair disease. This boy has been observed for as long as 16 months, and he his still alive at the time of publication. This genetic, X linked disorder of copper metabolism is always fatal in childhood. Diagnosis is evoked when is noted the conjunction of progressive cerebral degeneration, seizures, with pili torti and monilethrix. It can be asserted with the very low copper and cerulo-plasmin blood levels. Recognition of the disease in utero might be possible. New findings in skin' electron microscopy and hair' scanning electron microscopy are reported here. And two RX scanner of the brain have been performed.

Brain Diseases, Metabolic↗
PubMed1977

An investigation of mistranslation in vivo induced by streptomycin by an examination of the susceptibility of abnormal proteins to degradation.

Proteolysis rates in vivo were measured in Escherichia coli cultures during treatment with dihydrostreptomycin and under various other conditions. Dihydrostreptomycin treatment caused an increase in the proteolysis rate, compared to untreated controls. The proteolytic system in vivo responsible for the elevated proteolysis in the early stages of dihydrostreptomycin treatment, or that during canavanine and puromycin treatment, were not inhibited by addition of phenylmethanesulphonyl fluoride. This agent did inhibit proteolysis rates in cultures whose growth was inhibited by starvation, or had been completely stopped by dihydrostreptomycin. It seems, therefore, that the extremely high proteolysis rates in cultures at this stage of dihydrostreptomycin treatment were due to the action of two protease systems: the one concerned with the breakdown of abnormal proteins, and the other concerned with normal protein turnover and active during a non-specific decline of growth. The proteolytic rate at complete growth inhibition brought about by dihydrostreptomycin was intermediate between those induced by canavanine and puromycin at the same stage of treatment. This indicated a similar hierarchy in the extent and nature of abnormality in the proteins synthesized under these conditions. The relationship between the abnormality of proteins induced by dihydrostreptomycin and the importance of this in the antibiotic mechanism is discussed.

Bacterial Proteins↗
PubMed1977

Signal to noise enhancement in dark field electron micrographs of vasopressin: filtering of arrays of images in reciprocal space.

A technique for filtering arrays of images of dispersed molecules is presented which takes advantage of the crystallographic properties of regular arrays and the rapidity of optical treatment. A filter in reciprocal space consisting of perforations in a square or rectangular lattice, as determined by the image arrrangement, reduces noise and averages the images simultaneously by transmitting only regularly recurring image structure. The filter is universal for all image contents and introduces no additional biases. The signal to noise improvement approaches square root N for N independent images of the same molecule in the same configuration. The procedure which is simple, rapid and inexpensive, is demonstrated with the aid of dark field electron micrographs of the protein vasopressin and combined with iodination of that molecule to elucidate its structure.

Crystallography↗
PubMed1977

[Cutaneous manifestations of angio-immunoblastic lymphadenopathy].

The authors report four cases of angio-immunoblastic lymphadenopathy, presenting with cutaneous lesions: these have a tumoral presentation in two cases while in the other two, the polymorphic aspect of the cutaneous lesions is reminiscent of a toxidermic eruption. In contrast to the relative clinical polymorphism, the pathological findings are monomorphic, i.e., in all cases, there was a vascular proliferation together with a more or less dense cellular infiltrate consisting of cells indistinguishable from those involving the abnormal lymph nodes.

Female↗
PubMed1977

[Lymphomatoid granulomatosis: cyclic nodular lymphomatoid panniculitis with immunologic deficiency].

The case of a 66 years old woman having presented an unusual cyclic dermatosis of 11 months duration is reported. The cutaneous elements were successively located in a subcutaneous, dermal and epidermal situation, and presented a spontaneous healing with sometimes deep retractive residual scars after an ulceration or not. Pathologically, the lesions consisted in dense mononuclear infiltrates and vascular lesions. This disease was associated with an immuno-deficiency state characterized by extremely low levels of circulating IgM. This deficit was found to be persistant as it was still present two years later. However during this lapse of observation no cutaneous lesions recurred. The possible connexions of such a case with those of lymphomatous granulomatosis are discussed. In the absence of pulmonary lesion in the case reported here, no identification to the syndrome isolated by Liebow seems permitted. The authors offer a new denomination for this unusual entity.

Aged↗