Optical frequency averaging of light

The use of averaging has long been known to reduce noise in statistically independent systems that exhibit similar levels of stochastic fluctuation. This concept of averaging is general and applies to a wide variety of physical and man-made phenomena such as particle motion, shot noise, atomic clock stability, measurement uncertainty reduction, and methods of signal processing. Despite its prevalence in use for reducing statistical uncertainty, such averaging techniques so far remain comparatively undeveloped for application to light. We demonstrate here a method for averaging the frequency uncertainty of identical laser systems as a means to narrow the spectral linewidth of the resulting radiation. We experimentally achieve a reduction of frequency fluctuations from 40 Hz to 28 Hz by averaging two separate laser systems each locked to a fiber resonator. Only a single seed laser is necessary here as acousto-optic modulation is used to enable independent control of the second path. This technique of frequency averaging provides an effective solution to overcome the linewidth constraints of a single laser alone, particularly when limited by fundamental noise sources such as thermal noise, irrespective of the spectral shape of noise.

Continuous real-time photoacoustic demodulation via field programmable gate array for dynamic imaging of zebrafish cardiac cycle

A four dimensional data set of the cardiac cycle of a zebrafish embryo was acquired using postacquisition synchronization of real time photoacoustic b-scans. Utilizing an off-axis photoacoustic microscopy (OA-PAM) setup, we have expanded upon our previous work with OA-PAM to develop a system that can sustain 100 kHz line rates while demodulating the bipolar photoacoustic signal in real-time. Real-time processing was accomplished by quadrature demodulation on a Field Programmable Gate Array (FPGA) in line with the signal digitizer. Simulated data acquisition verified the system is capable of real-time processing up to a line rate of 1 MHz. Galvanometer-scanning of the excitation laser inside the focus of the ultrasonic transducer enables real data acquisition of a 200 by 200 by 200 pixel, volumetric data set across a 2 millimeter field of view at a rate of 2.5 Hz.

A comparison of neonatal and adult multiorgan failure in a rat model

BACKGROUND/PURPOSE

To establish a neonatal animal model of multiorgan failure (MOF) for the histological study of the sequence and severity of neonatal MOF in comparison to a model of adult MOF.

METHODS

Neonatal and adult Sprague-Dawley rats received a single intraperitoneal injection of the inflammatory agent Zymosan. Rats were weighed; randomly killed on days 1 through 6; and heart, lung, liver, kidney, spleen, and ileocecum harvested for histological examination.

RESULTS

Neonatal animals receiving Zymosan showed a significant increase in total body weight not seen in adults. The sequence and severity of MOF-induced organ damage were strikingly different in adult and neonatal animals. Mild lung damage was seen as early as day 1 in adult rats receiving Zymosan. This progressed to moderate damage by day 2 and severe damage by day 6. Lungs of neonatal rats receiving Zymosan showed only mild damage by day 4, which had progressed no further by day 6. Mortality rate was not significantly different between adult and neonatal animals receiving Zymosan.

CONCLUSIONS

Zymosan can be used in a neonatal animal model to incite MOF. In the neonatal animal model of MOF there is (1) substantial early capillary leak as shown by increased body weight; (2) a unique progression of organ involvement-liver, kidney, lung compared with adult animals with MOF-lung, liver, kidney; and (3) relative sparing of the lung from injury. These findings are consistent with previous clinical observations of a difference in neonatal and adult MOF.

Is nasogastric tube decompression necessary after major abdominal surgery in children?

Nasogastric (NG) decompression has traditionally been used after major abdominal surgery in pediatric patients. This study was designed to determine if NG tubes could be routinely omitted in pediatric patients undergoing major abdominal procedures. Between January 1993 and December 1995, 83 patients had follow-up prospectively without NG decompression after a variety of major abdominal surgeries. NG tubes were inserted for persistent vomiting or abdominal distension. Exclusion criteria included bowel obstruction, intestinal atresia, and perforation of the stomach or duodenum. Ages ranged from 13 days to 22 years. Seventy-four patients (89%) were treated successfully without postoperative NG decompression. There were no cases of pneumonia, wound dehiscence, anastomotic leak, or delay in return of gastrointestinal function. Nine patients required NG tubes for persistent vomiting or abdominal distension. An anastomotic leak developed in one patient after endorectal pull-through. NG decompression is unnecessary after most major abdominal operations in pediatric patients. The endorectal pull-through may represent a group of patients that benefit from routine decompression.

Malrotation in the older child: surgical management, treatment, and outcome

Malrotation in the neonate is an anomaly for which there are clear indications for surgery. However, the management of the older patient with this entity is not well defined. At Arkansas Children's Hospital, we reviewed our patients who were older than two years of age with malrotation. Between 1978 and 1993, 22 cases ages 2-23 years were identified. The most common presenting symptoms were vomiting 15 (68%), colicky abdominal pain 12 (55%), and diarrhea 2 (9%). Other symptoms were hematemesis 1 (5%), and constipation 1 (5%). The duration of symptoms averaged 28 months, range 2-96 months. All diagnoses were made by upper gastrointestinal (UGI) series, except for one that was recognized during an exploratory laparotomy for an intestinal duplication. A Ladd's procedure with appendectomy was performed in all cases. A significant number of patients in our series (41%) were found to have either a volvulus or internal hernia at exploration that was not clearly demonstrated by the diagnostic studies. Intestinal resection was performed in two patients for ischemic bowel. There were no perioperative deaths. Postoperative complications consisted of a wound infection in one patient. Total relief of symptoms occurred in 64% of patients. All patients with volvulus or internal hernia had resolution of symptoms, and all patients reported partial relief of their chronic symptoms. Surgical therapy eliminates the possibility of loss of bowel from volvulus or internal hernia, which is not always evident on diagnostic radiographic examination. Surgery is also highly effective in alleviating the chronic symptoms in these children. We believe, therefore, that surgical treatment is clearly indicated in the older child with proven malrotation.

The protective role of enteral IgA supplementation in neonatal gut origin sepsis

Preterm infants and infants unable to breast feed are particularly susceptible to gut origin sepsis. Many studies have shown the benefits of breast milk in decreasing the incidence of bacterial infections in neonates. Little in vivo work has focused on prevention of neonatal gut origin sepsis with breast milk components. The aim of this study was to determine whether supplementation of a standard neonatal formula with exogenous, luminally administered, human secretory IgA protects against gut origin sepsis in a newborn rabbit model. Sixty New Zealand white rabbit pups were delivered by cesarean section 1 day preterm and divided into two groups--the IgA group (n = 26) and the non-IgA group (n = 34). Animals were gavage-fed a standard artificial formula (KMR) twice daily. The IgA group was supplemented on days 3 and 4 with 6.25 mg/kg of human secretory IgA. The non-IgA group received an equal volume of saline. On the evening of day 3, the animals were orally challenged with Escherichia coli K100. The quantity of bacteria that colonized the cecum was similar in the two groups. The quantity of bacteria that translocated to the mesenteric lymph node, liver, and spleen was significantly lower in the IgA group (P < .05). The incidence of translocation to the organs was also significantly lower in the IgA group (P < .05). The exogenous secretory IgA showed specificity to E coli K100 by ELISA. These data show that neonatal formula supplemented with human secretory IgA decreases the incidence and quantity of bacterial translocation of E coli K100 in a neonatal rabbit model.(ABSTRACT TRUNCATED AT 250 WORDS)

Gastric teratoma with intramural extension

Gastric teratoma is an extremely rare neoplasm which accounts for less than two percent of all teratomas. Unlike other teratomas, gastric teratomas are all benign and predominantly occur in males. As gastric teratomas generally present as a palpable abdominal mass, more aggressive solid masses of childhood must be excluded. In this case, CT imaging delineates both cystic and fatty components characteristic of teratoma and displays the rare gastric origin of the lesion.

The role of the mucus gel layer in intestinal bacterial translocation

The mucus gel layer is thought to be a vital component of the intestinal mucosal barrier. The purpose of this study is to determine if decreasing mucus production following ischemia and reoxygenation of the intestinal mucosa would alter bacterial translocation in an in vitro rat mucosal model. Clonidine was used to decrease mucus production associated with an ischemia/reoxygenation insult. Bacterial translocation was studied in a modified Ussing chamber using Escherichia coli K100. The quantity of mucus produced, as well as the incidence and quantity of bacteria translocating was measured. In the clonidine-treated animals, there was a significant decrease in the amount of mucus produced compared to the control animals. The clonidine animals also had a higher quantity of bacteria translocating during the reoxygenation period compared to the control animals. The mucus gel layer is protective against in vitro translocation of bacteria following an ischemia/reoxygenation insult.

Delayed gastric emptying in neurologically impaired children with gastroesophageal reflux: the role of pyloroplasty

The presence of delayed gastric emptying in neurologically impaired children with gastroesophageal reflux has led to controversy regarding appropriate surgical management. The authors reviewed the charts of neurologically impaired children requiring fundoplication to answer two questions: (1) is pyloroplasty needed in addition to fundoplication for delayed gastric emptying? and (2) Does delayed gastric emptying influence the morbidity associated with fundoplication? To answer the first question, 40 neurologically impaired children with delayed gastric emptying undergoing fundoplication were divided into two groups: Nissen and pyloroplasty (n = 21) and Nissen only (n = 19). The Nissen and pyloroplasty group had significantly more postoperative complications (23.8% v 5.0%) and took longer to reach full feeding (14.6 v 3.9) days. There were no differences in the incidence of recurrent symptoms, readmissions, or reoperations. To answer the second question, 58 neurologically impaired children undergoing fundoplication were grouped based on gastric emptying scan results: normal gastric emptying (> 32% in 1 hour) (n = 29) and delayed gastric emptying (n = 29). There were no differences in postoperative feeding tolerance, postoperative complications, recurrent symptoms, readmissions, or reoperations between the two groups. Delayed gastric emptying in neurologically impaired children with gastroesophageal reflux did not increase postoperative morbidity after fundoplication, and the addition of a pyloroplasty to fundoplication provided no additional benefit. The authors conclude that the procedure of choice for neurologically impaired children with gastroesophageal reflux is a fundoplication without pyloroplasty, regardless of the degree of delay in gastric emptying.