Feasibility study of using high-frequency ultrasonic Nakagami imaging for characterizing the cataract lens in vitro

A cataract is a clouding of the crystalline lens that reduces the amount of incoming light and impairs visual perception. Phacoemulsification is the most common surgical method for treating advanced cataracts, and determining the optimal phacoemulsification energy is dependent on measuring the hardness of the lens. This study explored the feasibility of using an ultrasonic parametric image based on the Nakagami distribution to quantify the lens hardness. Young's modulus was measured in porcine lenses in which cataracts had been artificially induced. High-frequency ultrasound at 35 MHz was used to obtain the B-mode and Nakagami images of the cataract lenses. The averaged integrated backscatter and Nakagami parameters were also estimated in the region of interest. The experimental results show that the conventional B-scan and integrated backscatter are inadequate for quantifying the lens hardness, whereas Nakagami imaging allows different degrees of lens hardening to be distinguished both globally and locally based on the concentration of fiber coemption therein.     

Estimation of equivalent threshold currents using different pulse widths for the epidural stimulation test in a porcine model

Background

The epidural stimulation test can help detect if a catheter is correctly positioned in the epidural space. Previous studies showed that a current of up to 16 mA was required to elicit a motor response, but few peripheral nerve stimulators can produce a current this high. Manipulating pulse width can produce a positive response at a lower current. To clarify the effects of pulse width on the epidural stimulation test, we performed a single-blinded study in a porcine model to estimate the equivalent current needed at varying pulse widths.

Methods

After obtaining local ethics approval, an 18G insulated Tuohy needle was advanced into the epidural space at the lower lumbar spinal level, and a 20G stimulating epidural catheter was advanced 30 cm cephalad. A gradually increasing electrical current was applied, and a motor response was elicited at pulse widths of 0.1, 0.2, 0.3, 0.5, and 1 msec. This was followed by a 1-2 cm catheter withdrawal, and the process was repeated for a total of 15 locations per pig.

Results

Recorded threshold currents ranged from 0.36-9.5 mA at a pulse width of 0.2 msec. Our results show a linear relationship between threshold current and pulse width.

Conclusions

In situations where different pulse widths are needed, the nomograms presented here may be useful to estimate the equivalent threshold current which is required to elicit a motor response according to previously published criteria for epidural stimulation tests.     

Reversal of high spinal anesthesia with cerebrospinal lavage after inadvertent intrathecal injection of local anesthetic in an obstetric patient

Purpose

High or total spinal anesthesia commonly results from accidental placement of an epidural catheter in the intrathecal space with subsequent injection of excessive volumes of local anesthetic. Cerebrospinal lavage has been shown to be effective at reversing the effects of high/total spinal anesthesia but is rarely considered in obstetric cases. Here, we describe the use of cerebrospinal lavage to prevent potential complications from high/total spinal anesthesia after unintentional placement of an intrathecal catheter in a labouring obstetric patient.

Clinical features

A 34-yr-old female presented to the labour and delivery unit in active labour. Epidural anesthesia was initiated, and after the first bolus dose, the patient experienced lower extremity motor block and shortness of breath. A high spinal was confirmed, and cerebrospinal lavage was performed. In total, 40 mL of cerebrospinal fluid (CSF) were exchanged for an equal volume of normal saline. The patient’s breathing difficulties and motor block resolved quickly, and a new epidural catheter was placed after removal of the spinal catheter. Pain control was effective, and the patient delivered a healthy baby.

Conclusion

We show that exchange of CSF for normal saline can be used successfully to manage a high spinal in an obstetric patient. Our results suggest that CSF lavage could potentially be an important and helpful adjunct to the conventional supportive management of obstetric patients in the event of inadvertent high or total spinal anesthesia.     

HIV and family planning service integration and voluntary HIV counselling and testing client composition in Ethiopia

Integrating voluntary HIV counselling and testing (VCT) with family planning and other reproductive health services may be one effective strategy for expanding VCT service delivery in resource poor settings. Using 30,257 VCT client records with linked facility characteristics from Ethiopian non-governmental, non-profit, reproductive health clinics, we constructed multi-level logistic regression models to examine associations between HIV and family planning service integration modality and three outcomes: VCT client composition, client-initiated HIV testing and client HIV status. Associations between facility HIV and family planning integration level and the likelihood of VCT clients being atypical family planning client-types, versus older (at least 25 years old), ever-married women were assessed. Relative to facilities co-locating services in the same compound, those offering family planning and HIV services in the same rooms were 2-13 times more likely to serve atypical family planning client-types than older, ever-married women. Facilities where counsellors jointly offered HIV and family planning services and served many repeat family planning clients were significantly less likely to serve single clients relative to older, married women. Younger, single men and older, married women were most likely to self-initiate HIV testing (78.2 and 80.6% respectively), while the highest HIV prevalence was seen among older, married men and women (20.5 and 34.2% respectively). Compared with facilities offering co-located services, those integrating services at room- and counsellor-levels were 1.9-7.2 times more likely to serve clients initiating HIV testing. These health facilities attract both standard material and child health (MCH) clients, who are at high risk for HIV in these data, and young, single people to VCT. This analysis suggests that client types may be differentially attracted to these facilities depending on service integration modality and other facility-level characteristics.     

Gamma-crystallin family of the mouse lens: structural and evolutionary relationships.

The heterogeneity inherent among gamma-crystallins of the mouse lens was investigated by sequence analysis of three gamma-crystallin-specific cDNAs. Comparison of the nucleotide sequence of these cDNAs and one previously reported by us revealed that the four gamma-cDNAs share 80-90% homology in nucleotide sequence. The entire 3' half of the coding region shows more variability than the 5' half, whereas the greatest variability is observed in the 3' untranslated region where numerous base substitutions, deletions, and insertions seem to have occurred. Alignment of the amino acid sequences of the four mouse gamma-crystallins according to the known four structural motifs of the major calf gamma-crystallin, gamma-II, suggests that all four mouse polypeptides are structurally very similar to calf gamma-II. However, most of the mouse polypeptides differ from gamma-II by the absence of one amino acid residue, resulting in a shorter connecting peptide between the two globular domains of the protein. Primary sequence alignment also revealed that the four mouse gamma-crystallins are most divergent in the third structural motif of the polypeptide. The significance of these differences in terms of the structure and function of the gamma-crystallins in the mouse lens is discussed.     

Allicin protects rat cardiomyoblasts (H9c2 cells) from hydrogen peroxide-induced oxidative injury through inhibiting the generation of intracellular reactive oxygen species

Oxidative stress is considered an important factor that promotes cell death in response to a variety of pathophysiological conditions. This study investigated the antioxidant properties of allicin, the principle ingredient of garlic, on preventing oxidative stress-induced injury. The antioxidant capacities of allicin were measured by using 1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay and hydrogen peroxide (H₂O₂)-induced cell damage on H9c2 cardiomyoblasts. Allicin (0.3–10?μM) pre-incubation could concentration-dependently attenuate the intracellular reactive oxygen species (ROS) increase induced by H₂O₂ on H9c2 cells. It could also protect H9c2 cells against H₂O₂-induced cell damage. However, the DPPH free radical scavenging activity of allicin was shown to be low. Therefore, it is believed that the protective effect of allicin on H9c2 cells could inhibit intracellular ROS production instead of scavenging extracellular H₂O₂ or free radicals. For the observed protective effect on H9c2 cells, allicin might also be effective in reducing free radical-induced myocardial cell death in ischemic condition.