Selection of the T-cell repertoire in transgenic mice expressing a transplantation antigen in distinct thymus subsets

Transgenic mice that expressed a transplantation antigen, H-2Kb, in an unusual tissue distribution have been developed. Gene-regulatory elements from the immunoglobulin heavy-chain locus (Emu enhancer and heavy chain promoter) were linked to the class I Kb gene and the construct microinjected into fertilized mouse eggs of a different haplotype. It was expected that such gene-regulatory elements would direct expression of the foreign class I molecules only to B and T lymphocytes. However, expression was also detected in a subset of thymus medullary epithelium. The Kb molecules expressed on this thymic subset were unable to positively select T cells for passage to the periphery. The mice were, however, tolerant of the cell types expressing the foreign Kb molecules and were also tolerant of Kb presented as skin grafts. These results suggest that not all components of thymic epithelium are involved in positive selection of T cells and that transplantation antigens expressed on non-dendritic cells can induce tolerance.

Growth response to enteral feeding by children with cerebral palsy

This study evaluated the growth of 51 children with cerebral palsy after the initiation of enteral tube feedings. The children were divided into three groups according to how soon after their central nervous system (CNS) insult they were started on enteral feedings. Group 1 consisted of 14 children who were within a year of their CNS insult; they were underweight for age, but had normal length as well as weight for length. Within 6 months of initiating enteral tube feedings, most children in this group had normalized their weights. Group 2 consisted of 27 children who were within 8 years of their CNS insult; they were stunted and were underweight for both their age and their length. Within 6 months of initiating enteral feeds, the group increased both weight and weight for length to near normal, but their gains in length reached a plateau at 90% of ideal for age. Group 3 consisted of 10 children who were more than 8 years after their CNS insult. This group was severely malnourished but had some improvement in their weight for age and for length but, length for age showed no significant change. We conclude that the earlier adequate nutritional management of children with severe cerebral palsy is initiated, the more readily the nutritional deficits will reverse.

Effects of bone matrix components on osteoclast differentiation

When implanted subcutaneously in rats, devitalized bone particles (BP) elicit the differentiation of osteoclastic cells. Those cells can be distinguished from foreign body giant cells that form in response to particulate plastics. Osteoclast features include resorption of the bone substrate, ruffled borders, calcitonin receptors, tartrate-resistant acid phosphatase activity, and modulation by bone active agents. To determine whether expression of these features depends on specific components of the matrix, we characterized the multinucleated cells that developed in response to osteocalcin-deficient BPs, particulate microcrystalline hydroxyapatite (HA), and HA containing 0.1% osteocalcin, collagen, or bovine serum albumin. Only those particles that contained mineral and osteocalcin were associated with osteoclastic cells. These studies support the hypothesis that osteocalcin may function as a matrix signal in the differentiation of osteoclasts.

Cloning genes for the biosynthesis of a macrolide antibiotic

Macrocin-O-methyltransferase (MacOMeTase) catalyzes the final enzymatic step in the biosynthesis of tylosin in Streptomyces fradiae. A 44-base mixed oligonucleotide probe containing only guanosine and cytidine in the third position of degenerate codons was synthesized based on the amino acid sequence of the amino terminus of MacOMeTase. Plaque blot hybridization to a bacteriophage lambda library and colony blot hybridization to a cosmid library of S. fradiae DNA identified recombinants that contained overlapping fragments of chromosomal DNA. The nucleotide sequence of the cloned DNA verified that the DNA contained the coding sequence for MacOMeTase. Recombinant plasmids transformed mutants blocked in tylosin biosynthesis and complemented tylF (the structural gene for MacOMeTase) and tyl mutations of eight other classes.

Cervical dilatation and prematurity revisited

Cervical examination between 26 and 30 weeks' gestation is described as a method for identifying women at risk for delivery before 34 weeks. Blinded cervical examinations were performed in 185 consecutive women, and 15 (8%) were found to have cervixes dilated 2 or 3 cm. The incidence of delivery before 34 weeks' gestation was 27% in such women compared with 2% in those whose cervixes were undilated or 1 cm. Other factors linked to cervical dilatation included parity and prior preterm delivery. However, parous women with cervical dilatation remained at increased risk for delivery before 34 weeks' gestation. We conclude that early third-trimester cervical examination may be an important adjunct in identifying women at risk for preterm delivery.

The relationship between abortion in the first pregnancy and development of pregnancy-induced hypertension in the subsequent pregnancy

The relation between pregnancy-induced hypertension and reproductive history was assessed in 29,484 women receiving obstetric care at Parkland Memorial Hospital. The incidence of pregnancy-induced hypertension was 25.4% in primigravid women, somewhat lower (22.3%) in women whose only previous pregnancy terminated in abortion, and much lower (10%) in women who carried two or more successive pregnancies to viability.

Simultaneous expression of early and late histone messenger RNAs in individual cells during development of the sea urchin embryo

The transition from early (E) to late (L) histone gene expression in developing sea urchin (Strongylocentrotus purpuratus) embryos was examined for H2B, H3, and H4 mRNAs by in situ hybridization of class-specific probes. Hybridization patterns indicate that the shift from E to L mRNAs occurs gradually and simultaneously in all blastomeres. Thus, during the transition the ratio of L to E mRNAs is similar in most cells. This suggests that no sudden changes in histone composition occur in individual cells which might be related to alterations in gene expression associated with differentiation of cell lineages. Around the midpoint of the transition, clusters of cells progressively appear which contain little, if any, E or L histone mRNA. This modulation of expression is coordinated for the three late genes examined because most individual cells contain either high or low levels of all three mRNAs. At blastula stage these clusters of unlabeled cells appear to be randomly distributed throughout the embryo. Subsequently the unlabeled regions expand and are found predominantly in aboral ectoderm as these cells cease to divide. Thus, the L/E histone mRNA ratio is not differentially regulated in diverse cell lineages, and the major differences in total histone mRNA content among individual cells may be related to cell cycle and/or the cessation of division.

Amebiasis presenting as rectal bleeding without diarrhea in childhood

A 6-year-old boy with no history of foreign travel had presented with rectal bleeding without diarrhea for 2 months. Despite negative stool cultures, a diagnosis of intestinal amebiasis was made by colonoscopy with tissue biopsy. In cases of persistent rectal bleeding, even without diarrhea, a diagnosis of amebiasis should be considered. When routine stool parasite examinations are negative, unsuspected amebiasis may be diagnosed by sigmoidoscopy or colonoscopy with tissue biopsy.

Plasma prostaglandins during the intravenous infusion of angiotensin II in pregnant women

The possible relation between prostaglandin production and the sensitivity of pregnant women with pregnancy-induced hypertension to the pressor effects of angiotensin II was investigated. Plasma prostaglandin levels were determined in four groups of women before, during, and after intravenous infusion of angiotensin II. Concentrations of the stable metabolites of prostaglandin E2, prostaglandin F2 alpha, and prostaglandin I2 (prostacyclin) were quantified by specific radioimmunoassays in the plasma of nonpregnant women, women pregnant in the late third trimester, and women pregnant in the late third trimester with either pregnancy-induced or chronic hypertension. Plasma prostaglandin concentrations did not change significantly during angiotensin II infusion in any of the four groups of women. Levels of the prostacyclin metabolite, however, were significantly higher in the hypertensive pregnant women than in the normotensive pregnant women.

Prostaglandin synthase inhibitory activity in plasma of women with dysmenorrhea

Prostaglandins have been implicated in the etiology of dysmenorrhea, and plasma levels of prostaglandin F metabolite are increased in women during dysmenorrhea episodes. We determined the prostaglandin synthase inhibitory activity of plasma obtained from the blood of women who experience moderate to severe dysmenorrhea. Blood was obtained at the onset of dysmenorrhea ("symptomatic") and during the late follicular phase of the ovarian cycle ("asymptomatic"). Prostaglandin synthase inhibitory activity in all samples was comparable to that previously found in adult women, and we found no difference in activity between the paired plasma samples, those obtained during symptomatic and asymptomatic times. Protein denaturation of the plasma by boiling also did not produce differences in prostaglandin synthase inhibition.

Decision making in professional associations

Processes for decision making by large groups such as professional associations have not adapted rapidly to the growing complexity of the situations those associations face. This paper describes a ten-step procedure which has enabled professional bodies to engage a large sample of their constituency in extensive planning exercises. These planning workshops addressed a wide range of complex issues, many of which were sensitive and threatening. The steps comprised identifying the problems, collating the agenda, analysis of the issues raised, deriving a structured sequence of tasks, pre-circulating papers, forming working groups, providing adequate time and facilities in a suitable setting for effective workshop activity, ensuring communication among groups within the workshop, managing the plenary reporting and consensus seeking, plus recording and circulating the report back to members. Groups worked cooperatively and constructively without evidence of intragroup competition, which reflects both the homogeneity of purpose within those professions and the effect of strong task structuring.

Pressor responsiveness to angiotensin II in hospitalized primigravid women with pregnancy-induced hypertension

Hospitalization of women with pregnancy-induced hypertension is beneficial in improving pregnancy outcome, but how it affects this physiologic process is not clear. In the present investigation, we evaluated pressor responsiveness to angiotensin II in 62 hospitalized women with pregnancy-induced hypertension. Although each of the women became normotensive, at least transiently, all remained sensitive to the pressor effects of angiotensin II. Thus, the beneficial effect of hospitalization on women with pregnancy-induced hypertension cannot be attributed to a decrease in the responsiveness to the action of angiotensin II.

A sensitive radioimmunoassay for 11-deoxy-13, 14-dihydro-15-keto-11, 16-cyclo-prostaglandin E2: application as an index of prostaglandin E2 biosynthesis during human pregnancy and parturition

A radioimmunoassay for 11-deoxy-13, 14-dihydro-15-keto-11, 16-cycloprostaglandin E2 (PGEM-II) is described. At pH 10.5, in the presence of albumin, 13, 14-dihydro-15-keto-prostaglandin E2 (PGEM-I) is transformed quantitatively into PGEM-II. Hence, after plasma samples are subjected to this transformation procedure, PGEM-II can be measured in such samples and be a true reflection of PGEM-I production and thereby prostaglandin E2 (PGE2) biosynthesis. The antiserum raised against PGEM-II is minimally cross-reactive with all prostaglandins tested (less than 0.01%). The mean least detectable mass of PGEM-II is 0.8 pg and the mean mass of added PGEM-II required to displace zero-point binding by 50% is 16.6 pg. The assay meets all the standard criteria for accuracy, reproducibility and parallelism. Concentrations of PGEM-II measured by this assay in peripheral plasma from men and nonpregnant women are similar to those reported for PGEM-I after measurements by gas chromatography - mass spectrometry. Plasma concentrations of PGEM-II in men were greater than in nonpregnant women. PGEM-II in increased concentration was found in early pregnancy although concentrations declined in the third trimester until labor when a significant increase was found. Concentrations of PGEM-II in umbilical venous plasma were significantly greater than those in maternal plasma.

Rhomboid flap dynamics

The rhomboid flap is a reliable, versatile, and widely used tool in head and neck surgery. Although its geometry is well described, the mechanics of the flap have not been scientifically investigated. For example, there is disagreement whether the maximum tension is located at the closure of the donor site or at the tip of the flap. An experimental model using piglets and stabilized force gauges has been developed to measure the distribution of tension in a standard Limberg flap (60 degrees rhomboid). Variables evaluated include the size of the rhomboid, the amount of undermining, and the position of the flap on the animal. Consistent measurements show tension at the closure of the donor site to represent the majority of tension around the flap (58% average); the size of the rhomboid and degree of undermining do not change relative tensions. A composite figure discloses the relationship of the initially outlined flap to the final result and quantifies the observable changes in the length of sides.

In search of criteria for the assessment of medical education

This paper describes results of a study to assess whether an undergraduate educational curriculum is 'relevant'. The people surveyed comprised 290 individuals involved in medical education or health service administration. They were asked to suggest five major criteria for judging whether a medical undergraduate programme is relevant or not and to say whether they felt current curricula meet these criteria. Of those sampled, 40% replied. An analysis of the data from respondents showed that medical school professors and senior administrators of health services in Australia have roughly similar expectations of the outcome of medical education. Both groups were concerned that graduates be conscious of health care requirements and costs, that they have adequate clinical skills, knowledge in medical school subjects and skill in interacting with patients and managing their continuing education. On the various dimensions examined there were frequently strong expressions of dissatisfaction with current achievements.

Creating critical consciousness in health: applications of Freire's philosophy and methods to the health care setting

Paulo Freire's philosophy of "education for critical consciousness" takes on special relevance within the context of the health care system. This dialogical approach to change, stressing action based on critical reflection by the people is seen here as importantly supplementing current efforts to deal with the "health care crisis" in the United States and many developing countries. Applications of the Freir approach in a health context of necessity involve the perception of health and medical care within the total oppressive structure of society. Viewed thusly, health "reform" cannot justifiably be envisioned except within the context of broader structural transformations. Two case studies are presented to illustrate the application of the Freire approach within a health context. Successful utilization of the methodology among peasants in rural Honduras and a relatively unsuccessful application among impoverished elderly residents of an urban United States ghetto are described and analyzed. Modifications of the approach to increase its usefulness in a variety of situational contexts are suggested. The potentials and limitations of this approach to radical change in the health field finally are described, along with lessons learned from initial work in the applications of conscientización to the health field.

Upper gastrointestinal bleeding in children and adolescents

This is a retrospective study of upper gastrointestinal hemorrhage in 68 children and adolescents who were less than 19 years old. In descending order of frequency, the five most common causes were duodenal ulcers, gastric ulcers, esophagitis, gastritis, and esophageal varices. There was male predominance in all diagnoses except gastric ulcers and gastritis. Signs and symptoms correlated poorly with the source of bleeding. Endoscopy was the most reliable method of identifying the bleeding site. Mortality correlated with the following: (1) initial hematocrit or hemoglobin level of less than 20% or less than 7 gm/100 ml, respectively, (2) transfusion requirements of greater than 85 ml/kg of blood without surgical intervention, (3) failure to identify the source of bleeding, (4) presence of a coagulation disorder, and (5) coexistence of another life-threatening disease.

Oral prostaglandin E2 for labor induction in high-risk pregnancy

Oral prostaglandin E2 (PGE2) was used alone or synergistically with intravenous oxytocin to induce labor in 84 women whose pregnancies were at high risk. A control group of 84 similar high-risk pregnancies where labor was induced with intravenous oxytocin alone was studied to compare the safety and efficacy of the two regimens. Oral PGE2 administration, combined with the synergistic effect of intravenous oxytocin, is safe for induction of labor in gravid women whose fetuses are at risk. Uterine polysystole, which is potentially dangerous, especially to the high-risk fetus, was not commonly encountered and only once was associated with transient fetal bradycardia. Uterine hypertonus was not encountered with PGE2; however, it did occur with oxytocin stimulation. Nausea and vomiting occurred in one third of the women treated with PGE2 but were well tolerated and required discontinuation of the drug in only one instance. There was no apparent advantage of using the combination PGE2 regimen in patients whose cervices were more favorable for induction of labor (Bishop score, 5 to 9). However, oral PGE2, used either alone or synergistically with oxytocin, appears twice as effective in inducing labor than was oxytocin alone in women in whom labor was considered to be "difficult to induce" (Bishop score, 0 to 4).

Further observations on the nature of pressor responsivity to angiotensin II in human pregnancy

The pressor dose of infused angiotensin II was determined before and after rapid volume expansion with 800 to 1075 ml of high-hematocrit blood. There was no remarkable change in sensitivity to infused angiotensin demonstrated except in two instances in which transient volume overload developed. The data support the hypothesis that increased angiotensin sensitivity observed in patients with pregnancy-induced hypertension is the consequence of increased vascular responsivity.

Learning by experience. A student residential workshop in hospital

A four-day residential workshop was conducted for students beginning their clinical studies at the St George Hospital in 1974. The aim of the workshop was that the students should understand the functioning of the hospital and feel comfortable as students in the hospital, so that they would learn their clinical skills more effectively in their subsequent years at the hospital. Each student lived in a hospital bed with an "illness" for two days, and spent another two days helping care for these "student patients" and exploring the hospital. Evaluation at the end of the workshop suggested that the objectives had been achieved.

Sites of formation of the serum proteins transferrin and hemopexin

Sites of synthesis of hemopexin and transferrin were determined by culturing various tissues of rabbits and monkeys in the presence of labeled amino acids. Labeling of the serum proteins was examined by means of autoradiographs of immunoelectrophoretic patterns as well as by precipitation in the test tubes employing immunospecific antisera. Good correlation was seen between the results obtained by the two different methods. The liver was found to be the only site of many tissues studied that synthesized hemopexin. Transferrin production was observed in the liver, submaxillary gland, lactating mammary gland, testis, and ovary.

What are you teaching and why?

What are Universities trying to produce by the end of the medical course? What is the purpose of our clinical education? It is easy enough to say that it is to produce "a good doctor", and perhaps we all know what that means although we might have differing interpretations of what constitutes a good doctor. Perhaps you know clearly what you mean when you graduate a good physiotherapist or a good speech therapist, but we have a lot of uncertainties about this, and about whether somebody who is reasonably good now will also be good in five years' or 10 years' time or even in one year's time when they are practising by themselves and not under our supervision.