Alginate microparticles loaded with lipopolysaccharide subunit antigen for mucosal vaccination against Klebsiella pneumoniae.

Klebsiella pneumoniae (K. pneumoniae) is one of the commonest causes of nosocomial infections in human beings. Since K. pneumoniae infections are air borne type, controlling it by mucosal vaccination through nasal and pulmonary route could be a promising approach in order to simulate the natural infection. New vaccines such as subunit vaccines are safer than traditional vaccines, but they are less immunogenic. Therefore to enhance their immunogenicity, there is a need to develop potent and safe adjuvants and delivery systems. It has been established that micro-particles are one of the most potent adjuvants available for mucosal delivery of vaccines and they do so by improving uptake of encapsulated antigen by antigen presenting cells (APCs). Lipopolysaccharide (LPS), the antigenic fraction was extracted from K. pneumoniae by hot phenol extraction method. LPS loaded sodium alginate microparticles were prepared by emulsion ionic gelation method. Microparticles with particle size less than 5 µm were obtained. Loading efficiency of the LPS loaded microparticles ranged from 76 to 82 %. Comparative in vivo immunogenicity studies were carried for free LPS and encapsulated LPS, administered via intramuscular, intratracheal and intranasal routes in Swiss albino mice. The study revealed that LPS encapsulated microparticles exhibit greater efficacy when administered by intra-tracheal route as compared to free LPS vaccine.

The use of thoracic computed tomography scanning and EBUS-TBNA to diagnose tuberculosis of the central nervous system: two case reports.

Herein, we report two cases of tuberculosis (TB) of the central nervous system where accessing the cerebrospinal fluid for diagnostic purposes was relatively or absolutely contraindicated at presentation. The finding of mediastinal lymphadenopathy on thoracic computed tomography scans, which was not visible on plain chest radiography, allowed endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) of these lymph nodes to support the diagnosis of TB in each patient and rule out other disease processes. EBUS-TBNA is a new bronchoscopic technique and in this case report appears to be a safe and useful option in the diagnosis of TB. Moreover, it proved to be so in cases where the main focus of disease was outside the thorax.

Role of experience and oscillations in transforming a rate code into a temporal code.

In the vast majority of brain areas, the firing rates of neurons, averaged over several hundred milliseconds to several seconds, can be strongly modulated by, and provide accurate information about, properties of their inputs. This is referred to as the rate code. However, the biophysical laws of synaptic plasticity require precise timing of spikes over short timescales (<10 ms). Hence it is critical to understand the physiological mechanisms that can generate precise spike timing in vivo, and the relationship between such a temporal code and a rate code. Here we propose a mechanism by which a temporal code can be generated through an interaction between an asymmetric rate code and oscillatory inhibition. Consistent with the predictions of our model, the rate and temporal codes of hippocampal pyramidal neurons are highly correlated. Furthermore, the temporal code becomes more robust with experience. The resulting spike timing satisfies the temporal order constraints of hebbian learning. Thus, oscillations and receptive field asymmetry may have a critical role in temporal sequence learning.

Neuronal dynamics of predictive coding.

A critical task of the central nervous system is to learn causal relationships between stimuli to anticipate events in the future, such as the position of a moving prey or predator. What are the neuronal phenomena underlying anticipation? In this article, I review recent results in hippocampal electrophysiology that shed light on this issue. It is shown that hippocampal spatial receptive fields show large and rapid anticipatory changes in their firing characteristics. These changes are experience- and environment-dependent and can be explained by a computational model based on NMDA-dependent synaptic plasticity during behavior. Striking similarities between the anticipatory network dynamics of widely different neural circuits, such as the hippocampus and primary visual cortex, are discussed. These experimental and theoretical results indicate how the microscopic laws of synaptic plasticity give rise to emergent anticipatory properties of receptive fields and behavior.

Experience-dependent asymmetric shape of hippocampal receptive fields.

We propose a novel parameter, namely, the skewness, or asymmetry, of the shape of a receptive field to characterize two properties of hippocampal place fields. First, a majority of hippocampal receptive fields on linear tracks are negatively skewed, such that during a single pass the firing rate is low as the rat enters the field but high as it exits. Second, while the place fields are symmetric at the beginning of a session, they become highly asymmetric with experience. Further experiments suggest that these results are likely to arise due to synaptic plasticity during behavior. Using a purely feed forward neural network model, we show that following repeated directional activation, NMDA-dependent long-term potentiation/long-term depotentiation (LTP/LTD) could result in an experience-dependent asymmetrization of receptive fields.

Cystic hygroma: Presentation of two casfes with a review of the literature.

Two interesting cases of cystic hygroma are being reported. One presented with dyspneoa and the other one with macroglosia and mediastinal cystic hygroma. The foetal chromosomal anomalies associated with cystic hygroma, intrauterine diagnosis and treatment of cystic hygroma as well as pathogenesis, classification, surgical and non-surgical management of cystic hygroma has been discussed in detail in the review of the literature.

Experience-dependent, asymmetric expansion of hippocampal place fields.

Theories of sequence learning based on temporally asymmetric, Hebbian long-term potentiation predict that during route learning the spatial firing distributions of hippocampal neurons should enlarge in a direction opposite to the animal's movement. On a route AB, increased synaptic drive from cells representing A would cause cells representing B to fire earlier and more robustly. These effects appeared within a few laps in rats running on closed tracks. This provides indirect evidence for Hebbian synaptic plasticity and a functional explanation for why place cells become directionally selective during route following, namely, to preserve the synaptic asymmetry necessary to encode the sequence direction.

Loss of frequencies in autocorrelations and a procedure to recover them.

We show that the standard methods, like the autocorrelation of a discrete time series, such as a spike train, can often miss prominent oscillation frequencies. In particular, if a phenomenon involves bursting and oscillations at two or more frequencies, the higher frequencies, with a lesser number of spikes per burst, can be often missed by the conventional methods. It is argued that on should separate the intraburst phenomena from the interburst phenomena by identifying bursts as single events. The distribution of oscillation frequencies should then computed by evaluating the autocorrelation of these events. A method is also developed for situations where intraburst and interburst time scales overlap significantly. It is shown that the correct estimate of strengths of various frequencies is found by using different thresholds for burst identification. The method is applied to data from a neuron in the subthalamic nucleus of a Parkinsonian (MPTP-treated) monkey. The conventional analysis shows that the neuron oscillates at only 6 Hz, whereas the new analysis reveals the presence of an additional, predominant, oscillation frequency of 18 Hz.

A neural network model for kindling of focal epilepsy: basic mechanism.

A simple neural network model is proposed for kindling--the phenomenon of generating epilepsy by means of repeated electrical stimulation. The model satisfies Dale's hypothesis, incorporates a Hebb-like learning rule and has low periodic activity in absence of shocks. Many of the experimental observations are reproduced and some new experiments are suggested. It is proposed that the main reason for kindling is the formation of a large number of excitatory synaptic connections due to learning.

Why go endocapsular?

A prospective randomized clinical trial was carried out to compare the intercapsular or the endocapsular technique of IOL insertion and conventional posterior chamber IOL insertion after can opener capsulotomy. Age and sex matched groups of 76 patients each underwent surgery by the two techniques. The corneal and the uveal reaction was evaluated on the first day after the surgery and specular counts were done at six weeks. Though the difference between the two groups was not statistically significant, a trend in favour of intercapsular technique emerged strongly.

Pupillary dilatation during cataract surgery--relative efficacy of indomethacin and flurbiprofen.

In a prospective, randomized, double-blind trial, we evaluated the relative efficacy of indomethacin and flurbiprofen when used as adjuvants to routinely used mydriatics for maintenance of pupillary dilatation in patients with heavily pigmented iris undergoing extracapsular cataract extraction. The drugs were administered orally as well as topically according to a fixed regimen. The pupillary diameters, measured with calipers at various surgical steps, were significantly larger at every step in the study groups in which either of the adjuvants had been used than they were in the control group (P less than .001). Flurbiprofen tended to help maintain a larger pupillary diameter in the later stages of surgery than indomethacin, but this difference was not statistically significant. We conclude that it is important to use prostaglandin synthetase inhibitors as adjuvants to routine mydriatics, and that flurbiprofen may be somewhat more effective than indomethacin in this capacity.

Argon laser suturotomy: a technique for the correction of surgically induced astigmatism.

We prospectively studied 40 eyes with intraocular lenses and astigmatism of 4 or more diopters to evaluate the efficacy and safety of argon laser suture ablation as contrasted with surgical suture removal. Two groups of 10 eyes underwent argon laser suturotomy (ALS) 4 and 6 weeks, respectively, after surgery. Sutures were removed surgically in a third group of 10 eyes 6 weeks after surgery. The final group of 10 eyes served as controls. Serial keratometry and refraction demonstrated that ALS was as effective as surgical suture removal in reducing postoperative astigmatism, and complications associated with the procedure were negligible.

Pitfalls in aphakic contact lens fitting.

We examined 23 consecutive cases of unilateral aphakia reporting to the contact lens office for endothelial count and morphology, corneal thickness and toricity. The fellow eye served as a control in all the cases. It was found that there is a significant drop in the central endothelial cell density, and change in the size and shape of the cells. These observations indicate a thermodynamically unstable state. The aphakic corneas were thicker than the controls but not to a significant extent. The cell count and pachymetry had no statistical correlation. Toricity of the aphakic corneas make successful fitting of a lens difficult. Since prolonged use of extended wear gas permeable as well as hydrogel lenses have a deleterious effect on the endothelium it is suggested that a careful case selection be made and strict monitoting carried out at follow up. These corneas are liable for decompensation with only mild noxious stimuli. This article is intended to acquaint the ophthalmologist with the pitfalls in aphakic contact lens fitting so that a cautious follow up may be planned.

Linear scleroderma. A unique presentation.

A rare case of linear scleroderma with plaques of morphea in hemicorporeal distribution and subclinical systemic involvement is presented. Its possibility of progression into systemic sclerosis, which has not been reported earlier, is discussed.

Specular microscopy of unilateral hard contact lens wearers.

The effects of long term wear of PMMA contact lenses on the corneal endothelium used on a daily wear basis were determined by examining 8 patients who had been prescribed lenses in one eye only. The patients excluded unilateral aphakes. It was found that a significant reduction in the cell density and a change in the cell size and shape was induced by PMMA lenses. These changes reflect an endothelial metabolic stress and emphasize the need to find newer lens materials that are more oxygen permeable and produce little interference with the corneal metabolism.

Is the test patch useful in determining safety against operative infection?

The practice of pre-operative 'Test Patch' on any eye continues to be an important, conventional step at a number of eye infirmaries. The present study was carried out on eighty seven eyes to determine the relevance of Test Patch as a prelude to surgery. After a critical analysis of the result of investigation, it is concluded that the 'Test Patch' does not provide a statistically reliable information regarding potential bacterial infection since there is no correlation between pre-patching and post-patching clinical appearance, and bacterial isolates in a given case. Presence of polymorphs or organisms in the Grams stained conjunctival smears did not make any difference with regard to a positive or negative bacterial growth in a given eye. It is concluded that 'Test Patch' neither predicts nor helps in any way in a case waiting to undergo intra ocular surgery. The Test Patch, therefore, at best, can serve as an acclimatizing exercise that simulates bandaging in the post-operative period.