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Biomedical subjects

S A Wolf

Publications and source records attributed to S A Wolf.

At least 19 recordsLinked to original sources
PubMed2001

Spintronics: a spin-based electronics vision for the future.

This review describes a new paradigm of electronics based on the spin degree of freedom of the electron. Either adding the spin degree of freedom to conventional charge-based electronic devices or using the spin alone has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and detection of spin polarization as well as spin-polarized currents. Recent advances in new materials engineering hold the promise of realizing spintronic devices in the near future. We review the current state of the spin-based devices, efforts in new materials fabrication, issues in spin transport, and optical spin manipulation.

Journal Article↗
PubMed2001

Th2 cells support intrinsic anti-inflammatory properties of the brain.

In experimental autoimmune encephalomyelitis (EAE), Th1 cells are responsible for disease induction while Th2 cells can be protective. To address the mechanisms of this differential behavior, we utilized organotypic murine entorhinal-hippocampal slice cultures to analyze interactions between myelin basic protein-specific Th1 and Th2 cells with microglial cells. While both Th1 and Th2 cells induced CD40 expression, only Th1 cells induced intercellular adhesion molecule-1 (ICAM-1) expression on microglia. Moreover, Th2 cells prevented or even reversed Th1-induced ICAM-1 upregulation. Evidently, Th2 cells could diminish Th1-induced inflammatory reactions and actively support the resting state of microglia, which could be one mechanism of Th2-mediated remission of neuroinflammation during EAE.

Animals↗
PubMed2001

Differential expression of costimulatory molecules B7-1 and B7-2 on microglial cells induced by Th1 and Th2 cells in organotypic brain tissue.

Autoreactive T-cells are involved in demyelination, neurodegeneration, and the recruitment of peripheral macrophages and nonspecific activated T-cells in autoimmune diseases such as multiple sclerosis (MS). The ligation of costimulatory B7 molecules on microglia with CD28/CTLA-4 on T-cells is thought to be crucial to the onset and course of MS and its rodent model experimental autoimmune encephalomyelitis (EAE). It is currently unclear as to how far the nature of infiltrating T-cells has an impact on the expression of the B7 molecules on microglia, the resident antigen-presenting cells (APCs) of the brain. We studied the expression of B7-1 and B7-2 on microglia after encounter with preactivated Th1 and Th2 cells from transgenic mice whose T-cells express a receptor (TCR) either specific to myelin basic protein (MBP) or ovalbumin (OVA) using murine organotypic entorhinal-hippocampal slice cultures (OEHSC). Our main finding was that Th1 cells downregulate the constitutive expression of B7-2 and induce B7-1 expression while Th2 cells do not induce this B7-1 upregulation. The main difference between MBP- and OVA-specific cells was seen in experiments were Th1 cells had direct contact to APCs but not to brain tissue. In contrast to MBP-specific Th1 cells, OVA-specific Th1 cells required the addition of antigen to upregulate B7-1 and downregulate B7-2. When the cells were allowed to have contact to brain tissue, no difference was seen in the pattern of B7 regulation between OVA- and MBP-specific T-cells. Our data suggest that T-cells are able to modulate B7 expression on microglial cells in the brain independent of antigen presentation through TCR/MHC-II ligation but presumably by soluble mediators.

Animals↗
PubMed1995

The efficacy of laparoscopic examination of the internal inguinal ring in children.

The ability of physicians to identify a patent processus vaginalis by laparoscopic examination of the internal ring is now well established, but the efficacy on patient outcome is not. The authors reviewed their experience to determine the effect of diagnostic laparoscopy of the internal ring on the management of children with inguinal hernias. The records of 150 children who underwent inguinal surgery were reviewed--75 before (group 1) and 75 after (group 2) pediatric laparoscopy was introduced into the authors' practice. The children in group 1 were selected for unilateral or bilateral surgery based on history, age, sex, side of presentation, and parental preference. For group 2, laparoscopy was an additional option offered to appropriate patients. Laparoscopy was performed in 43 group 2 patients, using an infraumbilical site. The minimum follow-up period was 2 years for group 1 and 1 year for group 2. The mean ages for groups 1 and 2 were 41.2 and 39.7 months, respectively. There were 61 boys and 14 girls in each group. The percentages of right (R), left (L), and bilateral (B) findings, based on clinical observation, were 56.0 (R), 29.3 (L), and 14.7 (B) for group 1, and 58.7 (R), 26.6 (L), and 14.7 (B) for group 2. The incidence of bilateral surgical exploration was similar for the two groups (group 1, 58.6%; group 2, 61.3%). The addition of laparoscopy significantly lowered the incidence of negative explorations (group 1, 16.0%; group 2, 2.6%; P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Laparoscopic incidence of contralateral patent processus vaginalis in boys with clinical unilateral inguinal hernias.

In 38 boys with clinical unilateral inguinal hernias (CUIH), the contralateral processus vaginalis was examined laparoscopically before surgical manipulation at the time of elective inguinal herniorrhaphy. General anesthesia was used in each case, and a 30 degrees, 2.7-mm laparoscopic was introduced using standard techniques. Positive laparoscope findings prompted surgical exploration. The age range was 2 to 134 months. Twenty-four had a right CUIH, and 14 had a left CUIH. Overall, the contralateral processus vaginalis was patent in 52.6%, with 58.3% and 42.8% patency on the nonclinical left and right sides, respectively. In boys under 2 years of age, 50% of those with a right CUIH had a contralateral patent processus vaginalis, as did 60% of those with a left CUIH. In two of these 38 patients in whom there was no clinically proven hernia, the only patent processus vaginalis was on the side opposite the one with a clinical history. Laparoscopic examination of the internal inguinal ring provided accurate information useful in determining the need for contralateral inguinal exploration in these 38 children.

Child↗
PubMed1988

Regulation of insulin receptors in the human ovary: in vitro studies.

The association between insulin resistance and ovarian hyperstimulation has led to a hypothesis that insulin stimulates ovarian steroidogenesis. This possible effect of insulin on the ovary could be mediated by either the insulin receptor or the type I insulin-like growth factor (IGF) receptor, both of which have been described in the human ovary. We examined the in vitro regulation of insulin receptors by LH, FSH, multiplication-stimulating activity (MSA), and insulin in ovarian stromal fragments from 24 women. [125I]Insulin binding was measured in the presence and absence of increasing concentrations of insulin, IGF-I, LH, and FSH. Neither LH nor FSH competed with [125I]insulin for binding sites, but preincubation with LH or FSH reduced [125I]insulin binding by 19-38%. Preincubation with MSA reduced [125I]insulin binding by 34-48%. The affinity of the insulin receptors, determined by Scatchard analysis, did not change (Ka = 3.3 X 10(8) mol-1). A concentration of 10 ng/mL insulin in the preincubation medium reduced [125I]insulin binding by 40%, whereas an insulin concentration of 50 or 500 ng/mL completely obliterated specific [125I]insulin binding. [125I]Insulin binding fully recovered, however, 4 h after termination of tissue exposure to insulin. The specificity of [125I] insulin binding was confirmed by studies with IGF-I. We conclude that of the hormones examined, insulin is the most potent regulator of human ovarian insulin receptors in vitro. Down-regulation of insulin receptors by insulin was reversed within 4 h after withdrawal of insulin. MSA, FSH, and LH also down-regulated the number of human ovarian insulin receptors in vitro, but were less potent. These phenomena, if also present in vivo, could be important factors in the regulation of ovarian function by insulin in normal and pathological states.

Adult↗
PubMed1986

Endocrine disorders of the pancreas and adrenal cortex in pediatric patients.

Hyperinsulinemia, a common cause of persistent hypoglycemia in infants and children, can result in permanent damage to the central nervous system. Thus, early diagnosis and treatment are important. The typical clinical manifestation of hyperinsulinemic hypoglycemia is symptomatic hypoglycemia that responds poorly to medical therapy. Affected infants may have tremors, jitteriness, apnea, cyanosis, or seizures. If initial medical therapy (frequent feedings, large amounts of intravenously administered glucose, diazoxide, and glucocorticoids) fails to stabilize plasma glucose levels, subtotal pancreatectomy is indicated. This surgical intervention does not completely correct the hypoglycemia in all patients, but it effectively reduces the severity of the condition. Surgical treatment of pediatric patients with Cushing's syndrome or aldosteronoma has also been effective. In our experience, survival of patients with adrenocortical adenomas has been 100%, whereas only five of nine children with adrenocortical carcinomas survived, and four of the five were younger than 10 years of age.

Adrenal Cortex Neoplasms↗
PubMed1986

The microvascular response of the neonatal mesentery to hypertonic feedings.

Using intravital microscopy we studied the responses of the jejunal and ileal mesenteric microcirculation to hypertonic meals in neonatal piglets. Test meals were infused through a cannulated segment of proximal jejunum. The intestinal segments were observed under conditions of controlled temperature and humidity, and the velocity of red blood cells through mesenteric arterioles was measured and blood flow calculated. Jejunal flow was not altered from baseline by saline or hypertonic mannitol infusion, while significant increases in flow were observed during hypertonic glucose infusion (3.8 X 10(-6) versus 10.7 X 10(-6) ml/s, p less than 0.01). Jejunal glucose infusion did not cause shunting from the ileal microcirculatory bed. We conclude that the infusion of hypertonic glucose causes an increase in jejunal blood flow, but does not result in a change in ileal flow. The increase in flow is a local phenomenon related to glucose absorption in neonatal piglets.

Animals↗
PubMed1983

Intestinal osmoregulation of single component meals in neonatal piglets.

The ability of the neonatal stomach and duodenum to modify the osmolality of hypotonic and hypertonic meals containing a single nutrient was studied in 3- to 5-day-old piglets. Test meals were administered through a gastrostomy and samples of gastric content and all proximal jejunal effluent were collected every 30 minutes for 2 hours. Hypotonic meals (149 mosm/L) and hypertonic meals (497 mosm/L) of glucose, crystalline amino acids, or lipids were used. Results were similar after all meals. There were significant changes in intragastric osmolality at each postprandial time period. However, osmolality never returned to basal levels. During duodenal transit there were further increases in osmolality after hypotonic meals and decreases after hypertonic meals but isotonic levels were never achieved. As a result, chyme of widely divergent osmolality entered the jejunum until late in the observation periods. Influx of sodium, potassium, and chloride were similar after all meals and were independent of original meal osmolality. These data indicate that, in awake, unstressed neonatal piglets, the stomach and duodenum are capable of effective but incomplete osmoregulation of hypotonic and hypertonic single component meals.

Animals↗
PubMed1983

Duodenal osmoregulation after total parenteral nutrition in neonatal piglets.

The physiologic effects of intestinal rest on the efficiency of gastroduodenal osmoregulation of hypertonic and hypotonic carbohydrate meals were studied in neonatal piglets 3 to 5 days old. Sixteen piglets underwent laparotomy, gastrostomy, and end jejunostomy just distal to the ligament of Treitz. Sixteen littermates had insertion of a central venous catheter and received 2 weeks of total parenteral nutrition (TPN) before laparotomy, gastrostomy, and end jejunostomy. Experiments were performed 2 days after laparotomy in all groups. Each piglet received intragastric infusions of two test meals (25 ml/kg), half the pigs receiving glucose (494 +/- 11, 147 +/- 3 mOsm/L) and half mannitol (493 +/- 11, 150 +/- 4 mOsm/L) (SD). Gastric samples and jejunal effluent were collected every 30 minutes for 2 hours. TPN did not influence duodenal osmoregulation. Significant changes in osmolality occurred during duodenal transit after all meals, and these changes were similar for all groups. However, jejunal osmolality did not approach basal levels until late in the observation period. These results demonstrate significant but incomplete intraduodenal osmoregulation of carbohydrate meals in neonatal piglets that is unaffected by 2 weeks of intestinal rest.

Animals↗
PubMed1980

Cystic adenomatoid dysplasia of the lung.

Cystic adenomatoid dysplasia of the lung is an unusual lesion, only 142 cases having been reported in the English literature by 1979. This review describes 32 additional previously unreported patients treated at our institution. The male:female ratio was 1.4:1 and lesions were equally distributed in both lungs. The age range at presentation was 1 day-14 yr. This large experience identifies two distinct modes of presentation. Ten patients presented as newborns with acute progressive respiratory distress secondary to mediastinal displacement and pulmonary compression as a result of the expanding cystic lesion. This group of patients ranged from 1 to 28 days with a mean of 9.4 days of age. Of the remaining patients, varying from 2 mo to 14 yr, half were under 1 yr. The presentation in this group was generally different. Unresolving pulmonary infiltrate (5) or recurrent respiratory infection localized to the same portion of the lung (7) prompted the diagnosis of a pulmonary developmental abnormality. Three children in this group had failure to thrive. Progressive dyspnea was not a characteristic finding. Specific lobar or segmental resection effectively eradicated the disease process. All of the last 30 patients resected have survived without unusual sequelae. Cystic adenomatoid dysplasia should be considered in the differential diagnosis of progressive respiratory disease in the neonate or of recurrent or persistent pneumonic processes in the same segment of the lung in the older child.

Adolescent↗
PubMed1979

Effect of proximal gastric vagotomy and truncal vagotomy and pyloroplasty on gastric functions and growth in puppies after massive small bowel resection.

The effects of truncal vagotomy and pyloroplasty and proximal gastric vagotomy on gastric acid hypersecretion, hypergastrinemia, and growth after massive bowel resection were studied in beagle puppies. In puppies with 80% enterectomy, neither type of vagotomy alters significantly the postprandial hypersecretion of acid from the Heidenhain pouch or the concentration of serum gastrin. Proximal gastric vagotomy tended to decrease the hypersecretion more than did truncal vagotomy. In beagle puppies undergoing 70% small bowel resection, growth was significantly decreased but survival was not impaired. Neither proximal gastric vagotomy nor truncal vagotomy and pyloroplasty reversed completely the impaired growth produced by massive resection. Proximal gastric vagotomy caused a small improvements in growth, while truncal vagotomy and pyloroplasty resulted in a slight decrease in growth. It remains possible that proximal gastric vagotomy could be of value in the management of growing infants with hypersecretion of acid due to short bowel syndrome.

Animals↗
PubMed1979

The continent ileostomy: a viable alternative.

The continent ileostomy is one of the alternative techniques in managing patients who require a proctocolectomy. Although previously plagued with up to 30% revisions, the continent ileostomy appears to contribute significantly to the social and psychologic well-being of these patients. Our experience suggests that improved surgical techniques make this procedure a safe and favorable alternative to the traditional Brooke ileostomy.

Adolescent↗
PubMed1977

Increased meal-stimulated gastric acid secretion and serum gastrin after extensive small bowel resection in puppies.

In six beagle puppies provided with vagally denervated pouches of the oxyntic gland area, the effects of massive resection of the small intestine on acid secretion and serum gastrin induced by feeding were studied. The enterectomies produced significant postprandial hypersecretion of acid and hypergastrinemia. A linear correlation existed between the increased acid output and serum gastrin level.

Adult↗