Asymmetric squares as standing waves in rayleigh-Benard convection

Possibility of thermal convection in the form of asymmetric squares in a thin layer of Boussinesq fluids of large lateral extension confined between stress-free and conducting flat boundaries is investigated numerically using a seven mode Lorenz-like model. For fluids with moderate and high Prandtl numbers (4<sigma<20) and in a narrow window of high Rayleigh numbers (12<R/R(c)<15), which depend on Prandtl number, the stationary rolls become unstable and asymmetric squares appear as standing waves at the onset of secondary instability. Asymmetric squares, two-dimensional rolls, and again asymmetric squares with their corners shifted by half a wavelength form a stable limit cycle. The oscillatory bifurcation is supercritical.

Tuberculosis of the gallbladder

Analysis of 5 patients with gallbladder tuberculosis who had open cholecystectomy and review of literature have shown that, although still rare it presents as a part of systemic miliary tuberculosis, abdominal tuberculosis, isolated gallbladder tuberculosis and as a calculus cholecystitis in anergic patients. There are no pathognomonic signs, the diagnosis depends on suspicion of tuberculosis, peroperative findings and histological examination.

Deep brain stimulation of the ventral intermediate nucleus of the thalamus for control of tremors in Parkinson's disease and essential tremor

The beneficial effects of ventral intermediate nucleus (VIM) stimulation were evaluated in 20 patients with tremor refractory to medical therapy. Thalamic stimulation is a non-ablative procedure which has the advantage of a reversible, non-destructive lesion. Eleven patients [7 with Parkinson's disease (PD) and 4 with essential tremor (ET)] received unilateral VIM implantation, while 9 patients had staged bilateral VIM implantation (4 with PD, 5 with ET). PD patients showed a significant improvement in contralateral arm and leg rest tremor and ipsilateral leg rest tremor (p < 0.02) at a mean follow-up period of 16.2 +/- 7.0 months. Patients with PD did not demonstrate any significant decrease in medication use at follow-up. ET patients demonstrated significant improvement in postural and action tremor in the contralateral arm (p < 0.001), but no significant improvement in the contralateral leg tremor at follow-up. Significant improvements were also seen in ET patients in the Clinical Rating Scale for Tremor (p < 0.001) with respect to several activities of daily living at a mean follow-up of 14.9 +/- 8. 1 months. Deep brain stimulation is a safe and effective treatment for severe tremor refractory to medications. It is a highly effective, reversible, adaptable, and predictable procedure which avoids the complication of cognitive deficit seen in patients with bilateral thalamotomies.

In-situ irradiation of keloid scars with Nd:YAG laser

In-situ coagulation of keloid with Nd:YAG laser irradiation was carried out in in a cohort study of 17 patients, each with one keloid scar situated on either the sternum (six), abdomen (seven), shoulder (two), hip (one), or ear lobe (one). The duration of scarring was three to 17 years and size varied from 3-8 cm long. One to two doses of laser irradiation was required for complete coagulation. At three months, 10 (58.8%) keloids had completely healed; but in seven (41.1%), 25-50% of residual keloid persisted. Intralesional triamcinolone injection, once in four patients and twice in three patients, produced complete resolution in all seven patients. At 18 months to five years follow-up, 14 patients remain keloid-free but in three keloid recurred and was re-treated with laser coagulation with complete resolution. The treatment was carried out as an outpatient procedure under local anaesthesia. There were no complications. The results of this initial study suggest that Nd:YAG laser irradiation coagulation is effective treatment for keloid scarring.

Neurological complications of congenital heart disease

Neurological complications contribute significantly to mortality and morbidity from congenital heart disease with serious long-term consequences. Congenital heart disease has also been shown to adversely influence the neuro-developmental outcome of children. In developing countries such as India, majority of congenital heart defects remains uncorrected and major neurological complications are frequently encountered. Stroke and brain abscess are the commonest neurological complications of unoperated congenital heart disease. In developed countries the focus has now shifted to neurological complications of cardiac surgery in the very young as a result of cardiopulmonary bypass and total hypothermic circulatory arrest. A variety of neurological disturbances are now being increasingly recognized and are currently the subject of intense investigations. In this review the neurological complications of uncorrected congenital heart disease and the common neurological complications that result from operations for congenital heart disease will be discussed.

Neurological complications of congenital heart disease

Neurological complications contribute significantly to mortality and morbidity from congenital heart disease with serious long-term consequences. Congenital heart disease has also been shown to adversely influence the neurodevelopmental outcome of children. In developing countries such as India, majority of congenital heart defects remains uncorrected and major neurological complications are frequently encountered. Stroke and brain abscess are the commonest neurological complications of unoperated congenital heart disease. In developed countries the focus has now shifted to neurological complications of cardiac surgery in the very young as a result of cardiopulmonary bypass and total hypothermic circulatory arrest. A variety of neurological disturbances are now being increasingly recognized and are currently the subject of intense investigations. In this review the neurological complications of uncorrected congenital heart disease and the common neurological complications that result from operations for congenital heart disease will be discussed.

Angiogenesis in a patient with ischemic limb induced by intramuscular injection of vascular endothelial growth factor and fibrin platform

Direct revascularization of critical ischemia of the limb is often unsuccessful due to the anatomic extent and distribution of arterial occlusive disease, and no pharmacologic treatment has proved effective in treating this condition. Patients with ischemic limb may eventually require amputation and may develop serious morbidity and mortality. The goal of limb salvage in these patients has stimulated research into alternative treatment methods, including angiogenesis. Attempts have been made to apply growth factors directly or to encode DNA for such factors, but it is unknown whether these factors remain at the target site long enough to be effective. We report our strategy of using vascular endothelial growth factor in a fibrin network, which enables the sustained release of biologic material at the target site.

A prototype electrochemical chromatographic column for use with proteins

We developed electrochemical hardware and media targeted for protein chromatography. Two types of stationary phases were investigated. The first comprised gold-plated stainless 316L beads coated with a self-assembled monolayer of 6-mercaptohexan-1-ol and was expected to behave like an ion-exchange resin in the presence of an electric field. The secondary stationary phase comprised the first stationary phase with further functionalization with immobilized heme moieties and was expected to behave like immobilized metal affinity resin. We tested apparatus with both stationary phases using ribonuclease A as a model protein and applied potentials from -0.3 to +0.3 V versus the saturated calomel electrode. Despite low binding capacities, we demonstrated that protein retention on both stationary phases could be controlled with an applied potential. The greatest extent of electromodulation was achieved with the mercaptohexanol-based ion-exchange media.

Bistability and Electrokinetic Oscillations

Nonlinear dynamic behavior and electrokinetic oscillations have been investigated for the membrane systems (a) 0.1 N NaCl/KCl parallel Millipore filter parallel 0.01 N NaCl/KCl; (b) 0.1 N NaCl/KCl parallel Whatman Inorganic filter parallel 0.01 N NaCl/KCl; and (c) 0.1 N NaCl/KCl parallel silver-coated filter parallel 0.01 N NaCl/KCl, from the viewpoint of testing the theories for the phenomena and elucidating the mechanism. To achieve these objectives, studies on hydrodynamic permeability, electroosmotic permeability, bistability, and electrokinetic oscillations were undertaken. Relaxation time for buildup and decay of electroosmotic pressures was experimentally determined. Bistability was not observed showing that it is not a prerequisite for oscillations and nonlinear relations between (J(v))(Deltarho=0) and Delta&phi; involving cubic or higher-order terms are necessary for bistability. The oscillations were studied at different current strengths. The period is found to be independent of current, while amplitude A is found to be linearly related to current I which is the bifurcation parameter. The bifurcation point occurs at approximately 0.4 mA. Studies have also been made with membranes of different pore size that show that amplitude increases with increase in pore size of the membranes. The validity of the two-variable model of Teorell was examined by comparing the experimental results with computer simulation based on parameters determined experimentally. Theory does not meet expectation and the results suggest that modification of theory is needed. The weakness of the theory has been critically examined. Copyright 1999 Academic Press.

High temperature induced antibiotic sensitivity changes in Pseudomonas aeruginosa

Pseudomonas aeruginosa, which was resistant to a wide variety of antibiotics, became sensitive to several of these antibiotics when grown and tested at 46 degrees C. Cell wall antibiotics such as penicillin G and ampicillin were only effective when added to cells growing at 46 degrees C prior to a temperature shift to 37 degrees C. Antibiotics which penetrate the cytoplasmic membrane to express their inhibiting action present a pattern different from those which are active against the outer cell wall. In order that these compounds be effective, the permeability of the cytoplasmic membrane must be further altered with agents such as EDTA which allow the penetration of actinomycin D. Inhibitors of protein synthesis, such as streptomycin and chloramphenicol, have increased access to their sites of action in cells grown at 46 degrees C. Cells grown at 46 degrees C have 40% less lipopolysaccharide (LPS) than cells grown at 37 degrees C and the LPS aggregates were of large molecular size in cells grown at 46 degrees C. Growth at 46 degrees C affects the permeability properties of the outer cell wall more than the permeability properties of the cytoplasmic membrane and this was due, in part, to the selective release of LPS of LPS-protein complexes at elevated growth temperatures.

Stereotactic cyst wall disruption and aspiration of colloid cysts of the third ventricle

BACKGROUND

Current strategies of surgical therapy for colloid cysts have been associated with low rates of initial success and high rates of morbidity, mortality and recurrence of cysts. Cyst recurrence following simple stereotactic aspiration has been hypothesized to be due to regrowth of the epithelium composing the cyst wall.

METHODS

We propose a procedure involving stereotactic disruption of the colloid cyst wall with the removal of a portion of the cyst wall followed by aspiration of cyst contents as a surgical therapy for colloid cysts.

RESULTS

This procedure was performed in 2 female and 3 male patients who were followed for an average of 49 months with all patients demonstrating immediate improvement of symptoms and resolution of the cyst verified with repeat computerized tomography (CT) scans. There was one incidence of recurrence in an asymptomatic patient at 75 months postoperatively.

CONCLUSION

We propose that stereotactic partial cyst wall disruption and content aspiration may limit recurrence of colloid cysts, thus offering an advantage over simple stereotactic aspiration alone.

Hypoxic-ischemic brain damage in perinatal age group

Cerebral hypoxia-ischemia in the perinatal period continues to be a major contributor to chronic neurologic impairment in children worldwide. Extensive research conducted in the past several years has led to a better understanding of the mechanisms involved in hypoxic-ischemic brain injury. Based on this understanding, the major potential therapeutic approaches being studied include antagonists of excitatory amino acids, calcium channel antagonists, free-radical scavengers, nitric oxide synthase inhibitors, anti-inflammatory agents, trophic factors, and hypothermia. Several agents are in clinical trial phases in adults. However, safety concerns and close relationship between pathomechanisms of hypoxic-ischemic cerebral injury and normal developmental processes have contributed to the slow pace in the neonatal trials. Large multicenter trials including an adequate number of infants will be needed to evaluate efficacy of therapeutic interventions in this particular age group. A large number of risk factors that predispose to hypoxic ischemic injury have been identified. It is important to control these factors and prevent brain damage in the first place. This is especially true for developing countries where resources for treatment with newer agents (when they become available) are likely to be limited. Recent information regarding mechanisms of injury and potential therapeutic measures related to perinatal age are presented in this paper.

The ligament augmentation device: an historical perspective

Anterior cruciate ligament (ACL) injury is the most common ligament injury in the knee, and a significant number of patients may develop progressive instability and disability despite aggressive rehabilitation. Various materials have been used for its reconstruction. These include autografts, allografts, prosthetic ligaments, and synthetic augmentation of the biological tissue. The concept of ligament augmentation device (LAD) arose from the observation that biological grafts undergo a phase of degeneration and loss of strength before being incorporated. The LAD is meant to protect the biological graft during this vulnerable phase. However, it provokes an inflammatory reaction in the knee, and has been found to delay maturation of autogenous graft in humans. In experimental situations, the LAD has been found to share loads in a composite graft. It has also been found to be substantially stronger than the biological graft. However, in clinical situations no significant advantages have been observed with the use of LAD to augment patellar tendon or hamstring reconstruction of the chronic ACL-deficient knee or in the acute setting to augment repair of the torn ACL. There are very few reports of the use of LAD in reconstruction of the posterior cruciate ligament, and again these do not suggest any advantage in its use. Insertion of the LAD implies the introduction of a foreign material into the knee, has been associated with complications such as reactive synovitis and effusions, and may also be associated with an increased risk of infection. At present, there is no evidence that its routine use should be advocated in uncomplicated reconstructions of the ACL using biological grafts.

Heap corrugation and hexagon formation of powder under vertical vibrations

We report free-surface instabilities in a deep bed of fine granular material of irregular shape under vertical vibrations. At low frequency of vibration, the conical heap due to convective flow becomes unstable above a critical amplitude of vibration and acquires an azimuthal dependence which makes the heap surface corrugated. At even higher amplitude, the heap is no longer stable and splits into small heaps on a hexagonal lattice. At high frequency, we observe standing waves (stripes) at the same frequency as the driving one. The main mechanism of these instabilities can be traced back to the presence of the surrounding gas, since they vanish under vacuum conditions.

Three-dimensional structure of ribonuclease T1 complexed with an isosteric phosphonate substrate analogue of GpU: alternate substrate binding modes and catalysis

The X-ray crystal structure of a complex between ribonuclease T1 and guanylyl(3'-6')-6'-deoxyhomouridine (GpcU) has been determined at 2. 0 A resolution. This ligand is an isosteric analogue of the minimal RNA substrate, guanylyl(3'-5')uridine (GpU), where a methylene is substituted for the uridine 5'-oxygen atom. Two protein molecules are part of the asymmetric unit and both have a GpcU bound at the active site in the same manner. The protein-protein interface reveals an extended aromatic stack involving both guanines and three enzyme phenolic groups. A third GpcU has its guanine moiety stacked on His92 at the active site on enzyme molecule A and interacts with GpcU on molecule B in a neighboring unit via hydrogen bonding between uridine ribose 2'- and 3'-OH groups. None of the uridine moieties of the three GpcU molecules in the asymmetric unit interacts directly with the protein. GpcU-active-site interactions involve extensive hydrogen bonding of the guanine moiety at the primary recognition site and of the guanosine 2'-hydroxyl group with His40 and Glu58. On the other hand, the phosphonate group is weakly bound only by a single hydrogen bond with Tyr38, unlike ligand phosphate groups of other substrate analogues and 3'-GMP, which hydrogen-bonded with three additional active-site residues. Hydrogen bonding of the guanylyl 2'-OH group and the phosphonate moiety is essentially the same as that recently observed for a novel structure of a RNase T1-3'-GMP complex obtained immediately after in situ hydrolysis of exo-(Sp)-guanosine 2',3'-cyclophosphorothioate [Zegers et al. (1998) Nature Struct. Biol. 5, 280-283]. It is likely that GpcU at the active site represents a nonproductive binding mode for GpU [Steyaert, J., and Engleborghs (1995) Eur. J. Biochem. 233, 140-144]. The results suggest that the active site of ribonuclease T1 is adapted for optimal tight binding of both the guanylyl 2'-OH and phosphate groups (of GpU) only in the transition state for catalytic transesterification, which is stabilized by adjacent binding of the leaving nucleoside (U) group.

Kala-azar epidemic in Varanasi district, India

Reports at the Sir Sunder Lal Hospital, Banaras Hindu University, of a large number of kala-azar cases from one particular village in Varanasi district, Uttar Pradesh, led us to carry out an epidemiological study of the situation using standard techniques. The overall prevalence and case fatality of the disease were 12.9% and 10.5%, respectively. A history of fever and hepatosplenomegaly was noted for all the cases. The case definition was the presence of parasites in bone marrow or splenic aspirate smears. The disease was more prevalent among adults, but occurred also among children. However, there was no clear linear relationship between the prevalence of the disease and age group. Kala-azar occurred among males and females, and its prevalence did not correlate significantly with income. Since the disease vector continues to be present in the study area, the health authorities should take strong steps to control the disease.

Microcystic adnexal carcinoma: a report of three cases

Microcystic adnexal carcinoma is an uncommon adnexal neoplasm. It is highly aggressive locally and its importance lies in the fact that it can be easily confused with benign adnexal tumours, particularly desmoplastic trichoepithelioma, trichoadenoma and syringoma. We report three cases of microcystic adnexal carcinoma of the skin, all three being on the face: two on the lips and one on the left eyebrow. Clinically, the neoplasms were slow growing indurated nodules or plaques. Two of the cases displayed benign features on initial biopsy and their malignant potential could not be established at that stage. On subsequent review, the three neoplasms showed all the characteristic features of microcystic adnexal carcinoma as described by Goldstein et al. and the University of Virginia study. All three patients were treated by surgery in the form of wide excision. They behaved in a highly locally malignant manner with excisions being incomplete in two of the lesions, in spite of taking an adequate margin around the clinically assessable margins. The other recurred after three years in spite of a histologically proven complete excision. Two of the tumours showed infiltration into the underlying muscle with perineural spread. Wider excision in the next stage with frozen section control achieved good clearance and after a five year follow-up period all are symptom free. None of these tumours showed any evidence of distant spread.

Reduction of laparoscopic-induced hypothermia, postoperative pain and recovery room length of stay by pre-conditioning gas with the Insuflow device: a prospective randomized controlled multi-center study

OBJECTIVE

To assess the efficacy and safety of Insuflow (Georgia BioMedical, Inc.) filter heater hydrator device in reducing the incidence, severity and extent of hypothermia, length of recovery room stay and postoperative pain at the time of laparoscopy.

DESIGN

Prospective, randomized, blinded, controlled multi-center study. Patients underwent gynecologic procedures via laparoscopy; surgeons, anesthesiologists and recovery room personnel assessed the results.

SETTING

Seven North American institutions.

PATIENTS

Seventy-two women for safety evaluation and efficacy studies.

INTERVENTIONS

Intraoperative pre-conditioning of laparoscopic gas with the Insuflow device (treatment) or standard raw gas (control) during laparoscopic surgery and postoperatively.

MAIN OUTCOME MEASURES

Incidence, severity and extent of hypothermia, postoperative pain perception and length of recovery room stay.

RESULTS

The Insuflow group had significantly less intraoperative hypothermia, reduced length of recovery room stay and reduced postoperative pain. Pre-conditioning of laparoscopic gas by filtering heating and hydrating was well tolerated with no adverse effects. The safety profile of the Insuflow pre-conditioned gas showed significant benefits compared to currently used raw gas.

CONCLUSIONS

Pre-conditioning laparoscopic gas by filtering heating and hydrating with the Insuflow device was significantly more effective than the currently used standard raw gas and was safe in reducing or eliminating laparoscopic-induced hypothermia, shortening recovery room length of stay and reducing postoperative pain.

Video-endoscopic and mini-endoscopic sympathectomy for hyperhidrosis

Video-endoscopic sympathectomy (VES) is currently the method of choice for the minimally invasive treatment of hyperhidrosis involving the palms, armpit and facial areas. Over a 7-year period from 1991 to 1997 our technique of performing VES has evolved during the performance of 800 endoscopic sympathectomies from the use of 3 ports to a single 10-mm port to finally a 3-mm port using a mini-endoscope. In comparison to standard VES, mini-endoscopic sympathectomy is simpler, less invasive, causes less postoperative discomfort and consistently allows patients to return home the same day.

Physician-hospital integration strategies: impact on physician involvement in hospital governance

This study investigated the impact of three physician-hospital contractual arrangements (PHCAs)--joint ventures, management service organizations, and not-for-profit foundations--on physician involvement in hospital governance and physician-hospital relationships. Analysis of data collected from a national sample of 1,013 hospitals revealed that PHCAs generate greater physician involvement in hospital decision making and result in lower physician-hospital conflict.

Epidural spinal cord stimulation for treatment of chronic pain--some predictors of success. A 15-year experience

BACKGROUND

We have used epidural spinal cord stimulation (SCS) for pain control for the past 15 years. An analysis of our series of 235 patients has clarified the value of specific prognostic parameters in the prediction of successful SCS.

METHODS

Patients were followed up for periods ranging from 6 months to 15 years with a mean follow-up of 66 months. The mean age of the 150 men and 85 women in the study was 51.4 years. Indications for SCS included failed back syndrome (114 patients), peripheral vascular disease (39 patients), peripheral neuropathy (30 patients), multiple sclerosis (13 patients), reflex sympathetic dystrophy (13 patients), and other etiologies of chronic intractable pain (26 patients).

RESULTS

One hundred and eighty-nine patients received permanent devices; 111 (59%) of these patients continue to receive satisfactory pain relief. Pain attributable to failed back syndrome, reflex sympathetic dystrophy, peripheral vascular disease of lower limbs, multiple sclerosis, and peripheral neuropathy responded favorably to spinal cord stimulation. In contrast, paraplegic pain, cauda equina syndrome, stump pain, phantom limb pain, and primary bone and joint disease pain did not respond as well. Cases of cauda equina injury had promising initial pain relief, but gradually declined after a few years. After long-term follow-up, 47 of the 111 successfully implanted patients were gainfully employed, compared with 22 patients before implantation. The successful patients reported improvements in daily living as well as a decrease in analgesic usage. Multipolar stimulation systems were significantly more reliable (p < 0.001) than unipolar systems. Complications included hardware malfunction, electrode displacement, infection, and tolerance.

CONCLUSION

Aside from etiologies of pain syndromes as a prognostic factor, we have identified other parameters of success. In patients who have undergone previous surgical procedures, the shorter the duration of time to implantation, the greater the rate of success (p < 0.001). The diagnosis of failed back syndrome must be considered a confounding factor in our analysis. Those patients whose pain did not follow a surgical procedure had better responses to SCS than patients who had multiple surgical procedures prior to their first implant. The advent of multipolar systems has significantly improved clinical reliability over unipolar systems. Age, sex, and laterality of pain did not prove to be of significance.