Search PubMed⌕ Search

Biomedical subjects

C A Stevens

Publications and source records attributed to C A Stevens.

At least 37 records · Page 2Linked to original sources
PubMed1992

Enhanced superoxide production by alveolar macrophages and air-space cells, airway inflammation, and alveolar macrophage density changes after segmental antigen bronchoprovocation in allergic subjects.

Airway inflammation is a principal determinant of airway responsiveness and function in asthma and allergic diseases. Alveolar macrophages (AM) may contribute to inflammation in multiple ways, including release of reactive oxygen species such as superoxide (SO) anion. We hypothesized that SO production by AM increases after segmental bronchoprovocation (SBP) with relevant antigen and contributes to airway injury. Eight ragweed-sensitive subjects with allergic rhinitis were studied by bronchoalveolar lavage and ragweed SBP to determine the SO production and characteristics of cells recruited after antigen challenge. No significant changes in cell numbers or total protein concentration were observed immediately after antigen challenge. Purification (to greater than 94%) of AM on discontinuous gradients of Percoll revealed significantly increased spontaneous and opsonized-zymosan-driven SO production immediately after antigen challenge. Forty-eight hours later, total air-space cells, AM, eosinophils, and total protein concentration were significantly increased in relationship to antigen dose given. Furthermore, both unfractionated air-space cells and purified AM obtained 48 h after antigen challenge released increased amounts of SO anion in response to activator compared with either cells obtained immediately after SBP or those obtained 48 h after saline challenge. In addition, significant increases in high density AM were also seen 48 h after antigen challenge. These data suggest that AM activation occurs immediately after antigen challenge, and that the late airway response to antigen is characterized by the appearance of high density AM, which have potentiated SO release. The increased oxidative burden thereby produced may contribute to increased airway injury.

Adult↗
PubMed1992

Craniofacial malformations and their syndromes. An overview for the speech and hearing practitioner.

Congenital malformations of the craniofacial region represent an important class of human developmental disorders. Abnormalities of speech and hearing frequently occur in this vast array of conditions. Knowledge of the diagnostic criteria, genetics, and natural history of these conditions is important for audiologists and speech-language pathologists because of their close involvement with the children and families in their care-providing role. Awareness of the important distinction between individuals with isolated defects vs. individuals who have their facial defect as part of a syndrome is important in diagnosis and management. Referral for genetic counseling is always indicated in families who have questions about these issues. The dysmorphologist, genetics professional, and speech-language pathologists are among those who play key roles in the care of persons with these disorders.

Craniofacial Dysostosis↗
PubMed1991

Tracheomalacia in Hallermann-Streiff syndrome.

We report on a white boy with Hallermann-Streiff syndrome (HSS) who also had tracheomalacia. Chronic respiratory insufficiency led to biventricular failure and death at age 6 months. There have been no previously reported cases of Hallermann-Streiff syndrome with documented tracheomalacia. However, there may be cases in which tracheomalacia may have been present, but not diagnosed. The literature contains 6 HSS cases with severe respiratory symptoms. Tracheomalacia should be considered in a patient with HSS who presents with an unusual cry, stridor, choking, or apnea. With the availability of surgery and supportive treatment, early diagnosis of tracheomalacia in these patients may prevent death and secondary neurologic insult from acute hypoxia.

Cartilage Diseases↗
PubMed1991

Modulation of superoxide production of alveolar macrophages and peripheral blood mononuclear cells by beta-agonists and theophylline.

Reactive oxygen species, including superoxide anion, have attracted increasing attention for their possible role in promoting inflammation in a variety of pulmonary diseases including asthma. However, reactive oxygen species metabolism of phagocytic cells may be substantially modified by therapeutic agents used for asthma. Peripheral blood mononuclear cells and alveolar macrophages from 15 normal subjects, and blood mononuclear cells from an additional 17 normal subjects, were studied to assess the effects of beta-receptor agonists and theophylline on phagocytic cell superoxide release. Isoproterenol produced a biphasic effect on spontaneous and phorbol ester stimulated alveolar macrophage and mononuclear cell superoxide production, augmenting release at 10(-5)M, and inhibiting release at 10(-4)M. These effects on spontaneous function in mononuclear cells were inhibited by 10(-5)M propranolol. Under conditions of phorbol ester-stimulation the enhancing effect of 10(-5)M isoproterenol on blood mononuclear cells was blocked by propranolol, but the inhibitory effect of 10(-4)M isoproterenol was not. Albuterol at equimolar concentrations with isoproterenol was not associated with altered spontaneous or stimulated superoxide release by alveolar macrophages or mononuclear cells. Further, spontaneous superoxide release by alveolar macrophages and mononuclear cells was significantly reduced by therapeutically achievable concentrations of theophylline (greater than 5 micrograms/ml). We conclude that the medication history must be controlled in studies of cell function in asthma, and that albuterol may be preferable to isoproterenol as a premedication for bronchoscopy when superoxide production of airspace cells is studied.

Adrenergic beta-Agonists↗
PubMed1991

Innovations in human genetics education. Medical student elective in clinical genetics.

The fourth-year medical student elective in clinical genetics has been enhanced by the addition of a problem-solving project. The assignment requires students to pose and answer a practical question about a professionally relevant genetic problem. Exemplary questions and the details of the exercise are given. Six of 10 students choosing an elective in clinical genetics have undertaken the project. Their feedback suggests that the requirements of decision making, library research, discussion with consultants, and medical writing in a limited time period are beneficial additions to the standard elective.

Curriculum↗
PubMed1990

Rubinstein-Taybi syndrome: a natural history study.

In order to examine several aspects related to the natural history of the Rubinstein-Taybi syndrome, we performed a questionnaire study of 50 patients who had been diagnosed with the condition. The cases were ascertained through a national parent support group and all of the individuals had been reared at home. The most frequent problems encountered were inadequate weight gain in infancy, eye problems, dental abnormalities, congenital heart defects, urinary tract problems, and severe constipation. These medical disorders and others resulted in approximately 10 times the average number of hospitalizations and surgeries as the general population of children. None of the 91 sibs of our study group were affected with the condition. Thirty-seven patients had undergone psychological testing with an average IQ of 51 and a range of 30 to 79. Timing for the attainment of various developmental stages was also determined. Individuals with Rubinstein-Taybi syndrome were found to have particular difficulty with expressive speech skills. Indexes for maladaptive behavior were calculated showing that approximately 10% of patients had significant behavior problems.

Abnormalities, Multiple↗
PubMed1990

Growth in the Rubinstein-Taybi syndrome.

In order to derive standard curves for height, weight, head circumference (OFC), weight-for-height, and height velocity, we obtained serial measurements in 95 patients with the Rubinstein-Taybi syndrome. Fifty individuals were part of an American study and 45 were ascertained in the Netherlands. Prenatal growth appears to be normal in the Rubinstein-Taybi syndrome, but height, weight, and OFC rapidly fall below the 5th centile in the first few months of life. Height velocity is somewhat below the mean but within the normal range except for the lack of a pubertal growth spurt. This phenomenon probably contributes to the short stature which is seen in these patients. Males are overweight for height during childhood while females are overweight during adolescence. The average OFC in males is smaller than in females. In general only a minority of adult patients are microcephalic.

Abnormalities, Multiple↗
PubMed1990

Etiology and recurrence risk in Rubinstein-Taybi syndrome.

Epidemiologic data on 45 patients with Rubinstein-Taybi syndrome from the Netherlands and 50 patients from the USA are compared with data from 407 patients reported in the literature. The 502 probands had a total of 708 sibs, including one probable recurrence. In 12 of 13 proven or possible monozygotic twins both children were affected. Two patients have reproduced with one affected and 2 normal offspring. The empiric recurrence risk figure for sibs is 0.1%. The recurrence risk for offspring of affected individuals could be as high as 50%. The cause of the syndrome remains unknown. There were no clues for autosomal recessive or X-linked inheritance, nor for a teratogenic cause. No consistent chromosome anomaly was found. An autosomal dominant mutation, either as submicroscopic chromosome deletion or duplication, or a point mutation seems the most likely explanation.

Abnormalities, Multiple↗
PubMed1990

Di George anomaly and velocardiofacial syndrome.

The velocardiofacial syndrome is an autosomal dominant disorder characterized by cleft palate, cardiac anomalies, characteristic facies, and learning disabilities. The Di George anomaly involves developmental defects of the third and fourth pharyngeal pouches, resulting in thymic and parathyroid hypoplasia and cardiac defects. The cases of individuals in two families help substantiate the notion that the Di George anomaly occurs as a feature of the velocardiofacial syndrome. The proband in family 1 was a male infant with persistent hypocalcemia and cardiac defects consisting of truncus arteriosus, atrial septal defect, ventricular septal defect, and abnormal aortic arch vessels. Autopsy revealed absence of thymic and parathyroid tissue, and the Di George anomaly was diagnosed. His father had a submucous cleft palate, T cell dysfunction, and facial features consistent with the velocardiofacial syndrome. This is the third case of male-to-male transmission of velocardiofacial syndrome. The proband of family 2 was a 4-year-old girl with developmental delay, persistent neonatal hypocalcemia, ventricular septal defect, T cell dysfunction, and facial features of the velocardiofacial syndrome. The Di George anomaly has been reported to occur in at least 18 different disorders. The observation that the Di George anomaly is a component manifestation of the velocardiofacial syndrome in these two families provides further evidence that the Di George anomaly is not a distinct syndrome of a single origin but rather a heterogeneous developmental field defect. It is proposed that all previously reported cases of autosomal dominant Di George anomaly are examples of the velocardiofacial syndrome.

Adult↗
PubMed1988

Report of two cases of distal deletion of the long arm of chromosome 6.

We report on two patients with distal deletions of 6q. In one case a de novo translocation between chromosomes 6 and 7 resulted in del(6q25----6qter). The other case had a de novo deletion, also from 6q25 to 6qter. There have been eight previous reports of distal deletions of 6q. These patients have developmental retardation, microcephaly, craniofacial anomalies, various types of congenital heart defects, and anomalies of hands and feet. The facial similarities of our two patients and those in six published photographs are subtle and may represent an emerging phenotype.

Abnormalities, Multiple↗
PubMed1988

Development of human palmar and digital flexion creases.

To determine the timing of the development of the various palmar and digital creases, we examined the hands of 100 human fetuses obtained after therapeutic abortion. The fetuses ranged in age from 7 to 19 fetal weeks, with age being established by menstrual period dates and ultrasound examination before termination. Our observations show that palmar and digital creases develop between 8 and 13 fetal weeks. Digital creases are well defined by 10 weeks; palmar creases are consistently seen by 13 weeks of gestation. The volar pads are present from 8 to 14 fetal weeks. A hand malformation or specific insult that occurs before the time of crease development and that alters the form or function of the fetal hand can cause secondary alterations increase patterns of the hand.

Dermatoglyphics↗
PubMed1988

The telecanthus-hypospadias syndrome.

The telecanthus-hypospadias (BBB) syndrome is characterised by widely spaced inner ocular canthi and hypospadias of variable degree. Heterozygous females have telecanthus. We have summarised the historical and phenotypic findings of 21 patients in seven previous publications. We have also had the opportunity to evaluate personally 12 families with a total of 18 affected males. The most frequent anomalies in patients previously reported are telecanthus 21/21, hypospadias 19/21, cleft lip/palate or uvula 7/21, high, broad nasal bridge 15/15, cranial abnormality 6/21, congenital heart defect 5/21, cryptorchidism 9/21, and mental retardation 11/17. In our series, the most frequent anomalies include telecanthus 18/18, hypospadias 18/18, cleft lip/palate or uvula 8/18, high, broad nasal bridge 10/11, cranial abnormality 12/18, congenital heart defect 3/18, upper urinary tract anomaly 4/9, and mental retardation 10/12. There is also an increased incidence of like-sex twinning, 11/18 in our families. This syndrome must be more common than reflected in published reports. Based upon the observation that males are much more severely affected than females and the lack of male to male transmission, it appears that this condition is most likely to be inherited in an X linked fashion. Further elucidation of the phenotype and documentation of the inheritance is needed. The distinction between the telecanthus-hypospadias syndrome and the G syndrome also needs further clarification.

Abnormalities, Multiple↗
PubMed1987

Cholestyramine treatment in early life. Immediate and delayed effects on arterial cholesteryl ester metabolizing enzymes in the rabbit.

Feeding of cholestyramine-enriched diet to weaned normocholesterolemic rabbits resulted in: lowering of plasma cholesterol and distinctly decreased activity of aortic acyl-CoA cholesterol acyl transferase with no changes in aortic acid and neutral cholesteryl esterase activity. At 9 weeks after cessation of cholestyramine treatment enhanced activity of both aortic esterases were noted despite normalization of plasma cholesterol. No evidence for the presence of plasma factor influencing esterases activity was found in lipoprotein-free serum from cholestyramine-treated animals. These studies show that cholestyramine treatment in early life causes immediate and delayed changes in rabbit arterial cholesteryl ester metabolizing enzymes.

Animals↗
PubMed1987

Production of Microbial Biomass Protein from Potato Processing Wastes by Cephalosporium eichhorniae.

The use of Cephalosporium eichhorniae 152 (ATCC 38255) (reclassified as Acremonium alabamense; see Addendum in Proof), a thermophilic, acidophilic, amylolytic fungus, for the conversion of potato processing wastes into microbial protein for use as animal feed was studied. The fungus was not inhibited by alpha-solanine or beta-2-chaconine, antimicrobial compounds in potatoes, or by morpholine or cyclohexylamine (additives to steam used in the peeling process) at levels likely to be encountered in this substrate. Mixed effluent from holding tanks at a potato-processing plant contained about 10 bacteria per ml and inhibited fungal growth. The fungus grew well on fresh potato wastes containing up to 5% total carbohydrate and utilized both starch and protein at 45 degrees C and pH 3.75. On potato homogenate medium containing 2% carbohydrate (about 14% fresh potato) supplemented with monoammonium phosphate (0.506 g/liter) and ferric iron (0.1 g/liter), with pH control (at 3.75) and additional nitrogen supplied by the automatic addition of ammonium hydroxide, typical yields were 0.61 g (dry weight) of product and 0.3 g of crude protein per g of carbohydrate supplied. An aerobic, spore-forming bacterium, related to Bacillus brevis, commonly contaminated nonsterilized batch cultures but was destroyed by heating for 15 min at 100 degrees C.

Journal Article↗
PubMed1985

Alcohol and fatty acid stimulation of neurotensin release from rat small intestine.

We have previously reported that neurotensin (NT) is released from the small intestine and elevated in the hepatic-portal circulation in response to the perfusion of the small intestine with a micellar solution of oleic acid. In order to determine the minimum acyl chain length and whether the presence of a carboxylic acid is necessary for the stimulation of NT release, the small intestine of anesthetized rats was perfused with test solutions of fatty acids of 2-, 4-, 8-, or 18-carbons or fatty alcohols of 2-, 4-, or 8-carbons at a concentration of 1 mM prepared in 2.4 mM taurodeoxycholate in 0.9% NaCl. Blood samples, collected from the superior mesenteric vein immediately before the start of the test perfusion and at 15-min intervals thereafter, were extracted immediately and radioimmunoassayed for NT-like immunoreactivity (NTLI) with a C-terminal-directed antiserum. Perfusions of fatty acids with 4 or more carbons and alcohols of 2 or more carbons resulted in a significant elevation (P less than 0.05) in plasma levels of NTLI above the values obtained before the onset of perfusion. Perfusions with ethanol resulted in a value of 4.3 +/- 0.03 mg/dl (SEM) in blood from the superior mesenteric vein while there was no increase in ethanol levels in the peripheral circulation. Perfusion with taurodeoxycholate and 0.9% NaCl alone had no significant effect on plasma levels of the NTLI. In order to characterize the chemical nature of the elevated NTLI, plasma samples from animals perfused with test solution were collected, extracted, pooled, and subjected to HPLC. NT and its N-terminal metabolite, NT(1-8), were quantitated. NT was defined as material having the same retention time as synthetic NT standard and having comparable measurements using N- and C-terminal-directed antisera. Perfusions of fatty acids of four or more carbons and alcohols of two or more carbons resulted in a 2- to 4-fold increase of both NT and NT(1-8) levels in plasma. It is particularly interesting that perfusion with ethanol (2-carbons) causes an elevation in plasma NT, because perfusion with acetic acid (2-carbons) does not increase NTLI. The fact that perfusion of ethanol is effective in releasing intestinal NT suggests that NT may mediate some of the biological effects observed after the consumption of alcohol.

Acetates↗
PubMed1983

An apparent lack of HLA restriction in the stimulation of granulocyte-macrophage colony formation from normal human null cells by helper T lymphocytes.

Haemopoietic progenitor cells capable of producing granulocyte-macrophage (GM) colonies have been demonstrated in the 'null' lymphocyte population of normal peripheral blood. The helper and suppressor roles of different T cell subpopulations have been implicated in the regulation of granulopoiesis in disease as well as in normal individuals. However, it is not certain whether such interactions between T cells and progenitor cells are HLA-restricted. We undertook further investigation of the effect of T cell subpopulations (TG and TnonG) on GM colony formation in vitro. In particular, we studied the possibility of HLA restriction in this process. Our results demonstrate that the enhancement of GM colony growth by T lymphocytes is not restricted by HLA compatibility between T cells and null cells, that such stimulation is radio-sensitive and that it is provided by the TnonG cell subpopulation.

Adult↗