Acidification of formula reduces bacterial translocation and gut colonization in a neonatal rabbit model.

BACKGROUND/PURPOSE: The authors hypothesized that gastric acidity is protective because it is bactericidal. They tested acidified formula for protection against gut colonization and bacterial translocation. METHODS: In vitro: Formula was acidified to pH of 2, 3, 4, 5 and innoculated with Enterobacter. Growth over time was quantitatively assessed. In vivo: 442 premature rabbit pups were sorted randomly and fed formula of pH 2, 3, 4, or 7, with ranitidine. Two models were utilized: (1) with bacterial challenge using a known acid sensitive organism, (2) without bacterial challenge to simulate natural gut colonization and to test against organisms of unknown acid sensitivity. Normal acid animals received pH 7 formula, no ranitidine. On day 3, the mesenteric lymph nodes (MLN), spleen, liver, and cecum were harvested and cultured. RESULTS: Bacterial growth was inhibited at pH 2 and 3, growth was logarithmic above pH 4 (P<.001). Total and organ-specific translocation was reduced at pH 3 and below in both models (P<.05). Translocation with formula pH 3 equaled normal acid animals. Quantitative cecal colonization was reduced in pups receiving pH 3 and below in both models (P<.05). CONCLUSION: Acidification of formula below pH 4 is bactericidal to enteric organisms. Acidified formula decreases bacterial translocation and gut colonization.

Noninvasive optical polarimetric glucose sensing using a true phase measurement technique.

The focus of this paper was to describe the development and testing of a noninvasive true phase optical polarimetry sensing system to monitor in vivo glucose concentrations. To demonstrate the applicability of this optical sensor for glucose measurement, we first calibrated the system and then tested it in vitro using both a glass test cell filled with glucose solution in the physiologic range, with a path length of 0.9 cm to approximate one centimeter path length present in the anterior chamber of the eye, and then on an excised human eye. Our technique used helium neon laser light which was coupled through a rotating linear polarizer along with two stationary linear polarizers and two detectors to produce reference and signal outputs whose amplitudes varied sinusoidally with a frequency of twice the angular velocity of the rotating polarizer, and whose phase was proportional to the rotation of the linear polarization vector passing through the glucose solution.

Amplitude-modulated tone encoding behavior of cochlear nucleus neurons: modeling study.

A recent study of amplitude-modulated (AM) tone encoding behavior of dorsal and posteroventral cochlear nucleus (DCN and PVCN) neurons by Kim et al. [Hear. Res. 45, 95-113, 1990] observed that certain neurons (e.g., pause/build type-III neurons and chop-S neurons) tended to exhibit band-pass modulation transfer functions (MTFs) and intrinsic oscillations (IOs) whereas certain other neurons (e.g., chop-T neurons) tended to exhibit low-pass MTFs and no IOs. The goal of the present study was to develop models of these response characteristics in an attempt to understand the underlying neuronal mechanisms. We hypothesized that chopper neurons corresponded to stellate cells and pause/build neurons corresponded to fusiform cells. We also hypothesized that, with right input combination, appropriate models of a single stellate and fusiform cell could account for band-pass and low-pass MTFs as well as the associated IOs. The neuron models developed by Arle and Kim [Biol. Cybern. 64, 273-283, 1991] for the stellate and fusiform cells were used in this study. The models are modified versions of MacGregor type neuron model incorporating cell-specific nonlinear voltage-dependent conductances. The AM tone excitation via the auditory nerve fibers was represented by a current at the soma of the neuron model, which consisted of dc, ac and a zero-mean Gaussian noise. The dc, ac and noise represent a high-frequency carrier beyond the neuron's phase-locking limit, an envelope, and randomness of the system, respectively. With systematic variation of dc, ac and noise amplitudes, we observed the following: the band-pass MTF behaviors of pause/build and chop-S neurons were reproduced by the fusiform cell model and the stellate cell model with a strong dc/noise ratio, respectively. The low-pass MTF behavior of a chop-T neuron was reproduced by the stellate cell model with a weak dc/noise ratio. It was observed that the stellate cell model was more susceptible to the noise, in the sense that an increase in noise tended to abolish the IO and change the MTF of the model from band-pass to low-pass more readily in the stellate cell model than in the fusiform cell model. Kim et al. (1990) observed a close correlation between the IO frequency and the best envelope frequency (BEF). In the models, a similar correlation was observed between the two measures for both the stellate and fusiform cell models.(ABSTRACT TRUNCATED AT 400 WORDS)

A new approach to the modeling and control of postoperative pain.

The objective of this paper has been to explore contributions which the technology of control engineering can make to the relief of postoperative pain. A human-operated, closed-loop, analgesic drug injection system has been designed to alleviate chronic pain. In this system, a patient presses a button when pain relief is required. A computer interfaces the button to the patient's drug injection pump. A patient pain model has been developed to describe the dynamics of the human physiological and psychological responses to chronic pain. A pharmacokinetic model of analgesia is also included. The pain model has been validated by adjusting its parameters so that its behavior mimics actual button-pressing records of self-administered analgesia. A modified Smith delay compensator and IPFM controller are used to compensate for the inherent nonlinearity of the system and to obtain the high performance required. The results of this simulation study are promising. The nonlinear patient pain model represents a contribution to the description of the dynamics and quantification of pain. The control algorithms proposed have shown, through modeling studies, an improvement in the performance of self-administered analgesia systems. The simulated patients obtained good pain relief without excessive button-pressing, and without undesirable high concentrations of opioids being observed. The SDC/IPFM controller architecture has been found to be robust in the presence of pain noise and pharmacokinetic plant parameter changes.

An outbreak of congenital rubella in Chicago.

After an outbreak of rubella in Chicago in 1978, an intensive survey of local health care personnel and hospital records identified 31 infants with congenital rubella syndrome (CRS). Rubella virus was isolated from 11 infants; rubella-IgM antibodies were demonstrated in seven infants; ten babies had persistent high rubella hemagglutination-inhibition (HI) titers. The incidence of CRS in Chicago between July 1978 and June 1979 was 48.9 per 100,000 live births. Mothers of babies with CRS frequently remembered a crash-illness during pregnancy (56%), were unmarried (74%), and were primigravidas (64%). No mother had received rubella vaccine. Review of prenatal rubella HI testing and follow-up immunization in one hospital showed that only eight (10.8%) of 74 seronegative women received rubella vaccine physicians need to place increased emphasis on detection and vaccination of susceptible adult women.

Selective destruction of the outer hair cells in the chinchilla.

In the study of cochlear function an animal model in which apical outer hair cells could be destroyed with retention of inner hair cells would be valuable. Our object was to attempt to reproduce a reported method in a scientific manner. Behavioural response thresholds to pure tones were recorded in 7 monaural chinchillas. In 5, Kanamycin was administered in ototoxic dosage until the thresholds deteriorated. The other 2 served as controls. Cochlear histology was assessed from embedded surface preparations. In only one of the 5 animals was the aim achieved. In this animal outer hair cells were absent virtually throughout the cochlea and inner hair cell retention was basal. Ths thresholds were elevated on average 40 dB throughout the frequency range. This is in keeping with current concepts of cochlear function.

Microbial sampling variables and recreational water quality standards.

A study was conducted at two beaches on Lake Erie to evaluate the water sampling design for the collection of several microbiological indicator organisms in relation to day, time, and location of collection. The concentrations of these organisms were generally found to vary significantly (P less than 0.05) by the specific time of day and day of weekend that collection took place. However, the concentrations of these organisms did not vary significantly (P greater than 0.05) at various locations in the bathing area. Future studies investigating the health effects of recreational water as related to microbiological variables should be designed to collect water samples at the specific time of day and day of weekend that an individual was exposed. In addition, sampling at various locations in the bathing area should probably be considered for those beaches having poor dispersion of fecal waste sources.

RNA polymerase in mumps virion.

Mumps virions of the Enders' strain were examined for polymerase activity in vitro. An RNA-dependent RNA polymerase was found to be associated with the virion. The general properties of the reaction appear to be similar to those described for other paramyxoviruses.