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Biomedical subjects

D Schwartz

Publications and source records attributed to D Schwartz.

At least 271 records · Page 15Linked to original sources
PubMed1986

Origin of multiple "primary" colon carcinomas. A retrospective flow cytometric study.

Multiple, synchronous, apparently primary carcinomas of the colon are a relatively common occurrence. The DNA ploidy in 23 colon carcinomas from 10 patients was determined to see if this parameter supported common or independent origins for such synchronous lesions. Paraffin blocks of each tumor were prepared for flow cytometry, then analyzed for nuclear DNA content. In 3 of the 10 cases, the tumors within each colon differed with respect to DNA ploidy; in four cases all tumors were diploid; and in three cases both (all) tumors within each colon had identical aneuploid DNA indices. Tumors from the same colon with identical DNA histograms often had dissimilar histology. The replicate aneuploid DNA indices strongly suggest a common origin for the multiple tumors within these colons; tumors in the other groups are compatible with either single or multiple origins. These findings suggest that multiple "primary" colon carcinomas may, in some cases, arise as translumenal metastases from an initial single lesion.

Adenocarcinoma↗
PubMed1986

Atriopeptin release in conditions of altered salt and water balance in the rat.

Manipulations of salt and water intake influenced the atriopeptin content in the atria and plasma of rats. Plasma levels of atriopeptin varied in proportion with dietary salt intake. In contrast, cardiac levels of atriopeptin varied inversely with the amount of salt in the diet. Acute stimulation of atriopeptin release can be produced by treatments which elevate atrial pressure, including atrial stretch, volume overloading, water immersion, and vasoconstrictor agents. Vasopressin-stimulated atriopeptin release preferentially depleted right atrial stores. In spite of the initial differences in cardiac stores of atriopeptin in the rats on different diets, there were no major differences in the amount of atriopeptin released in response to vasopressin stimulation. These data suggest that there is a functional excess of cardiac atriopeptin stores. We also examined the atrial and plasma atriopeptin content in the Dahl salt-sensitive and resistant rats to determine whether the development of hypertension in the Dahl sensitive rats is associated with abnormalities in basal or stimulated levels of atriopeptin. The effects of dietary salt intake on basal and stimulated atriopeptin levels in both the Dahl sensitive and resistant rats were similar to those observed in normal rats, suggesting that abnormalities in atriopeptin content do not contribute to the etiology of hypertension in the Dahl salt-sensitive rat.

Animals↗
PubMed1986

Flow cytometric analysis of deparaffinized nuclei in urinary bladder carcinoma. Comparison with cytogenetic analysis.

Both cytogenetic analysis and flow cytometry (FCM) have prognostic efficacy in the analysis of transitional cell carcinoma (TCC) of urinary bladder. To correlate results of the two methods, we studied a unique group of patients whose tumors had undergone prospective conventional cytogenetic analysis. Paraffin blocks of these tumors were processed for FMC, then analyzed for nuclear DNA content. Of the 34 tumors processed, 30 (88%) yielded interpretable DNA histograms. In 26 (87%) of these, there was good correlation between the two methods with respect to the presence or absence of a hyperdiploid cell line. Discrepancies may have resulted from sampling error or from interpretation of a tetraploid peak as a prominent G2M region. Retrospective FCM analysis of paraffinized TCC tissue correlates well with conventional, prospective cytogenetic analysis and is applicable to the majority of urinary bladder transitional cell carcinomas.

Adult↗
PubMed1986

Massive hemorrhage into a periappendiceal abscess: case report.

A case of significant hemorrhage into an ileal wall periappendiceal abscess in a 62-year-old man is described. Pathologic correlation of an unusual collection of contrast seen at the distal end of a branch of the ileocolic artery during angiography is discussed and illustrated.

Abscess↗
PubMed1986

Macronutrient selection by foraging rats.

Rats were studied in a laboratory simulation of foraging for separate sources of carbohydrate, fat, and protein. Fixed ratios of bar-presses were required to search for a cue signalling the availability of a meal and to procure each meal. In the first phase, the costs of procuring all three foods were raised equally for three rats. Meal frequency declined and meal size increased for all three foods. Protein opportunities were accepted more frequently than those for other foods, and the proportion of calories taken from protein remained low and constant. Two rats were studied in the remaining three phases. When protein meal cost was raised while the costs of energy foods were low, protein intake was gradually reduced and at the highest cost was dropped from the diet. There were individual differences in the preferred source of energy calories; when each animal's preferred energy source was made more costly, these preferences persisted over the range of costs studied in one rat, but shifted abruptly in the other rat. Finally, when search costs were raised, the animals became less selective in accepting meal opportunities and composing their diets. These results suggest that diet selection in the rat is flexible and responsive to changes in the costs of acquiring food. This ability is consistent with the foraging behaviors required by omnivorous generalized feeders.

Animals↗
PubMed1986

Space Station gas-grain simulation facility: application to exobiology.

The Space Station provides an environment in which the forces required to suspend particles during an experiment can be reduced by as much as six orders of magnitude. This reduction in levitation force enables us to perform many new experiments in a variety of disciplines. We have grouped these experiments into two categories: 1) those involving an individual particle or the interaction between a few particles and 2) those involving clouds in particles. We consider only particle experiments at this stage because cloud experiments suffer from electrostatic interactions and levitation-forced coalescence therefore requiring considerably more space, mass and crew interaction. The displacement of a particle resulting from g-jitter for ballistic, Knudsen and Stokes flow regimes is considered in detail and the radiation, acoustic, electrostatic and electromagnetic levitation mechanisms to control this motion are reviewed. We have selected the simulation of organic haze production ion Titan as an example experiment for detailed study. The objective of this experiment is to simulate the photolysis of methane and the subsequent formation of the organic haze particles in the upper atmosphere of Titan.

Aerosols↗
PubMed1986

Lower sperm characteristics in 36 brothers of infertile men, compared with 545 controls.

Among the men who volunteered to become semen donors for artificial insemination at the sperm bank of Centre d'Etude et de Conservation du Sperme Humain, Paris-Bicêtre, some were brothers of the infertile men of couples entering the Artificial Insemination with Donor program. Their sperm characteristics, compared with those of other donor candidates, are clearly lower. The difference is significant for count (78.0 versus 102.8, P less than 0.05) and very significant for the percentage of motile spermatozoa (61.5 versus 66.9, P less than 0.01) and for the percentage of normal forms (51.8 versus 62.7, P less than 0.00001). The differences are even more pronounced when the brothers of azoospermic men are considered. The possibility that some cases of infertility could have a genetic origin is discussed.

Adult↗
PubMed1986

Importance of continued activation of thrombin reflected by fibrinopeptide A to the efficacy of thrombolysis.

Factors responsible for initial success or failure of coronary thrombolysis and persistent recanalization or early reocclusion have not been thoroughly elucidated. Both adequate initial clot lysis and preclusion of rethrombosis are required. Failure may reflect clot lysis followed immediately or somewhat later by rethrombosis. To determine whether differences in the intensity and persistence of the activation of thrombin are determinants of success or failure of recanalization, plasma fibrinopeptide A, a fibrinogen product liberated by thrombin, was serially assayed in 19 patients treated with intravenous streptokinase. In patients exhibiting recanalization (n = 9), plasma fibrinopeptide A decreased after administration of streptokinase but before administration of heparin. In patients without initially apparent recanalization, fibrinopeptide A increased, suggesting ongoing thrombosis, and subsequently decreased promptly after heparin. In patients with initial recanalization followed by overt reocclusion the pattern was different. Despite recanalization, fibrinopeptide A continued to rise markedly. Elevations persisted despite administration of heparin. Thus, inhibition of activation of thrombin is associated with successful recanalization. Conversely, persistent activation of thrombin may be a predisposing factor to both apparent initial failure of recanalization and overt early reocclusion.

Coronary Disease↗
PubMed1986

In-vitro fertilization and embryo transfer: a collaborative study of 1163 pregnancies on the incidence and risk factors of ectopic pregnancies.

In a multi-centric study undertaken on 1163 pregnancies obtained by in-vitro fertilization, a 5% risk of ectopic pregnancies was observed. This figure is certainly higher than that admitted for natural reproduction. After simultaneous adjusting for all variables in our data by means of a multiple logistic regression technique, two factors have specific influence: the therapeutic use of clomiphene citrate which increased the rate of ectopic pregnancies from 3 to 6% and the number of patent Fallopian tubes with a change in ectopic pregnancies rate from 3 or 4% (with 0 or 2 patent tubes) to 13% (with one patent tube). These results suggest various physiologic hypotheses as well as therapeutic considerations.

Clomiphene↗
PubMed1986

Within-subject variability of the percentage of morphologically abnormal spermatozoa among fertile men: biological and measurement components.

Two groups of men were studied to determine how much an individual's spermatozoal morphology varies and which part of the variability is due to biological and to measurement variation. A first group of ten subjects each provided five ejaculates; the other group of four subjects each provided one ejaculate, from each of which five smears were prepared, and evaluated twice. The slides were examined in random order and blindly by the same experienced technician. The total within-subject variability of the percentage of abnormal forms was large (SD = 8.8%), as was the component of this variability due to biologic fluctuation (SD = 5.8%). The distribution of the various abnormalities also varied greatly from one ejaculate to another. The results indicate that more work is needed to determine why biological variation exists, and that several ejaculates (three if possible, two at minimum) are needed for an accurate evaluation of spermatozoal morphology, whereas the examination of greater than 100 spermatozoa/ejaculate is not advantageous.

Fertility↗
PubMed1986

Synthesis of globulins in maize embryos.

The two major components of the globulin fraction in Zea mays embryos are specified by the Prot gene. Pulse-chase analysis of protein synthesis in cultured, immature embryos indicates that the smaller Prot-specific polypeptide, PROT, is derived from the larger polypeptide, PROT'. These experiments also demonstrate that PROT' is derived from a short-lived precursor polypeptide, prePROT'. The primary Prot-specific translation product, as detected by in vitro translation of immature embryo RNA, is of a lower apparent molecular weight than pre-PROT', suggesting the involvement of co- and/or post-translational modification in the production of prePROT'.

Journal Article↗
PubMed1986

Hispanic adolescent fertility.

Knowledge regarding the fertility of Hispanic adolescents in the US is quite limited. This paper discusses the fertility of these adolescents and summarizes what is known about sexuality, contraception, pregnancy, and childbearing among male and female Hispanics of various countries of origin. As a group, Hispanic adolescents have birth rates that fall between those of non-Hispanic whites and blacks, but there is considerable within-group variation in Hispanic fertility. More research is needed concerning the correlates of these rates with factors such as age, marital status, socioeconomic level, or generational status in the US.

Adolescent↗
PubMed1986

Invasive pneumococcal infection in Israel. Review of 90 cases.

90 cases of invasive pneumococcal infection hospitalized during the period 1975-1984 were reviewed. The organism was recovered from blood, cerebrospinal fluid or other normally sterile body fluids. 40 of the patients were adults, most of whom had pneumonia, and 50 were children who had pneumonia, primary bacteremia or meningitis. 90% of the adults and 14% of the children had underlying conditions. Nosocomial infection was remarkably more common among adults (25%), than among children (2%). Mortality was similar to that reported by others: 37% for adults and 10% for children. The most important predictive factors for fatal outcome were: old age (greater than 80), meningeal infection, presence of malignancy or chronic lung disease, and failure to mount leucocytosis. 13% of the strains were moderately resistant to penicillin.

Adolescent↗
PubMed1986

Atriopeptins: circulating volume regulatory hormones with potential therapeutic role in chronic renal failure.

Sprague-Dawley rats given bolus intravenous injections of vasoconstrictors, including 1-deamino-Arg8-vasopressin (dAVP), demonstrated remarkable increases in plasma immunoreactivity (APir) to atriopeptin (AP). These elevations were accompanied by increases in systemic blood pressure, right atrial pressure and urinary volume excretion. Fractionated plasma APir peaks obtained by stimulation with dAVP were identified as primarily AP 28, with a smaller amount of AP 24, suggesting that AP 28 is the predominant circulating atrial peptide. Rats with reduced renal mass have increased single-nephron glomerular filtration rates (GFR). Despite these increases, AP 24 stimulated a marked increase in total GFR and promoted a profound natriuresis and diuresis. Atriopeptin 24 may therefore have potential as a therapeutic tool in the management of volume overload in chronic renal failure.

Animals↗
PubMed1986

Atriopeptins in fluid and electrolyte homeostasis.

Atriopeptins are biologically active peptides with potent natriuretic, diuretic, and vasorelaxant activities. Manipulation of an animal's salt and water intake influences the synthesis, storage, and release of atriopeptin. In addition to its direct effects on fluid and electrolyte balance, atriopeptin influences other volume regulatory hormones, including renin, aldosterone, and vasopressin. Atriopeptin, by its direct actions and its effects on hormone systems, provides a means for delicate hormonal control of fluid and electrolyte homeostasis.

Animals↗
PubMed1986

Atriopeptin turnover: quantitative relationship between in vivo changes in plasma levels and atrial content.

Administration of the 1-deamino-arginine8 vasopressin caused a decrease in right, but not left, atrial levels of atriopeptin (AP) in chloral hydrate-anesthetized rats. The amount of exogenous AP required to match the 1-deamino-arginine8 vasopressin-stimulated plasma levels of AP was equivalent to the decrease in AP content of the right atrium, suggesting that resynthesis of AP did not occur within the 60 min after 1-deamino-arginine8 vasopressin stimulation. The correlation between increased plasma levels and decreased atrial content was also observed in bilaterally nephrectomized rats, suggesting that the kidney is not a major site of degradation of AP in vivo. This finding was confirmed by the comparison of the half-life of exogenous AP in normal (T1/2 = 31 sec) and nephrectomized (T1/2 = 64 sec) animals. Plasma immunoreactivity of the N-terminal fragment of the prohormone (which is also released after cleavage of the precursor peptide) increased 35-fold by 24 hr after nephrectomy in comparison with a 5-fold increase in AP. Half-life studies of the N-terminal fragment suggest that the kidney is the major site of degradation of this molecule. This study demonstrated the different kinetics and renal metabolism of the AP and N-terminal portions of the prohormone.

Animals↗
PubMed1986

Prenatal diagnosis of a congenital mesoblastic nephroma. A case report.

Fetal urinary tract malformations are diagnosed frequently with ultrasonography. There are many published papers on in utero detection of fetal cystic abnormalities. In this case the prenatal diagnosis of a solid kidney mass was made, and histopathologic examination after surgical resection revealed congenital mesoblastic nephroma.

Adult↗