4D-Printable Photocrosslinkable Polyurethane-Based Inks for Tissue Scaffold and Actuator Applications

4D printing recently emerges as an exciting evolution of conventional 3D printing, where a printed construct can quickly transform in response to a specific stimulus to switch between a temporary variable state and an original state. In this work, a photocrosslinkable polyethylene-glycol polyurethane ink is synthesized for light-assisted 4D printing of smart materials. The molecular weight distribution of the ink monomers is tunable by adjusting the copolymerization reaction time. Digital light processing (DLP) technique is used to program a differential swelling response in the printed constructs after humidity variation. Bioactive microparticles are embedded into the ink and the improvement of biocompatibility of the printed constructs is demonstrated for tissue engineering applications. Cell studies reveal above 90% viability in 1 week and ≈50% biodegradability after 4 weeks. Self-folding capillary scaffolds, dynamic grippers, and film actuators are made and activated in a humid environment. The approach offers a versatile platform for the fabrication of complex constructs. The ink can be used in tissue engineering and actuator applications, making the ink a promising avenue for future research.

3D Printing of Cellulase-Laden Cellulose Nanofiber/Chitosan Hydrogel Composites: Towards Tissue Engineering Functional Biomaterials with Enzyme-Mediated Biodegradation

The 3D printing of a multifunctional hydrogel biomaterial with bioactivity for tissue engineering, good mechanical properties and a biodegradability mediated by free and encapsulated cellulase was proposed. Bioinks of cellulase-laden and cellulose nanofiber filled chitosan viscous suspensions were used to 3D print enzymatic biodegradable and biocompatible cellulose nanofiber (CNF) reinforced chitosan (CHI) hydrogels. The study of the kinetics of CNF enzymatic degradation was studied in situ in fibroblast cell culture. To preserve enzyme stability as well as to guarantee its sustained release, the cellulase was preliminarily encapsulated in chitosan-caseinate nanoparticles, which were further incorporated in the CNF/CHI viscous suspension before the 3D printing of the ink. The incorporation of the enzyme within the CHI/CNF hydrogel contributed to control the decrease of the CNF mechanical reinforcement in the long term while keeping the cell growth-promoting property of chitosan. The hydrolysis kinetics of cellulose in the 3D printed scaffolds showed a slow but sustained degradation of the CNFs with enzyme, with approximately 65% and 55% relative activities still obtained after 14 days of incubation for the encapsulated and free enzyme, respectively. The 3D printed composite hydrogels showed excellent cytocompatibility supporting fibroblast cell attachment, proliferation and growth. Ultimately, the concomitant cell growth and biodegradation of CNFs within the 3D printed CHI/CNF scaffolds highlights the remarkable potential of CHI/CNF composites in the design of tissue models for the development of 3D constructs with tailored in vitro/in vivo degradability for biomedical applications.

Safety and efficacy of percutaneous nephrolithotomy for the treatment of paediatric urolithiasis

INTRODUCTION

Paediatric percutaneous nephrolithotomy (PCNL) has revolutionised the treatment of paediatric nephrolithiasis. Paediatric PCNL has been performed using both adult and paediatric instruments. Stone clearance rates and complications vary according to the technique used and surgeon experience. We present our experience with PCNL using adult instruments and a 28Fr access tract for large renal calculi in children under 18 years.

METHODS

All patients undergoing PCNL at our institution between 2000 and 2009 were reviewed. Demographics, surgical details and post-operative follow-up information were obtained to identify stone clearance rates and complications.

RESULTS

PCNL was performed in 32 renal units in 31 patients (mean age: 10.8 years). The mean stone diameter was 19mm (range: 5-40mm). Twenty-six cases required single puncture and six required multiple tracts. Overall, 11 staghorn stones, 10 multiple calyceal stones and 11 single stones were treated. Twenty-seven patients (84%) were completely stone free following initial PCNL. Two cases had extracorporeal shock wave lithotripsy for residual fragments, giving an overall stone free rate of 91% following treatment. There was no significant bleeding or sepsis encountered either during the operation or in the post-operative setting. No patient required or received a blood transfusion.

CONCLUSIONS

Paediatric PCNL can be performed safely with minimal morbidity using adult instruments for large stone burden, enabling rapid and complete stone clearance.

Substance use among university students at the St Augustine campus of the University of the West Indies

OBJECTIVE

Substance use and abuse is a well known public health risk that peaks in persons between 18 and 25 years of age and is prevalent among university students. While this has been repeatedly documented in developed nations, there have been limited studies in the English-speaking Caribbean. This study therefore sought to assess the prevalence of alcohol, tobacco and marijuana use among university students in the English-speaking Caribbean and any associated risk factors.

METHODS

The study was designed as a descriptive, cross-sectional study to assess substance use in full-time, undergraduate students of The University of the West Indies (UWI), Trinidad and Tobago, over a six-month period. Questionnaires were distributed and students asked to self-report on their use of alcohol, tobacco and marijuana during the preceding six months.

RESULTS

The six-month prevalence rate for alcohol was 70% and 28% of students were identified as regular users. Binge drinking was estimated at 31%. Muslims were least likely to have used alcohol when compared to other religious groupings. The prevalence rate for tobacco and marijuana was 17% and 13%, respectively Ten per cent used all three substances. The use of all three substances was associated with multiple problems.

CONCLUSION

We conclude that substance use is common among many students of the UWI but generally lower than reports from other regions of the world. Despite this, substance use is associated with a number of problems and immediate educational interventions may be necessary to assist students in making informed and responsible choices.

Uro-genital bleeding in pre-menarcheal girls: dilemmas of child abuse

Uro-genital bleeding in pre-menarcheal girls always raises concerns regarding child abuse. There are serious social issues involved; however, before labeling it as sexual abuse, all efforts must be made to rule out an organic pathology. We recently encountered two young girls of Afro-Caribbean origin who presented with vaginal bleeding with concerns from referring physicians about child/sexual abuse. On examination both had a rare condition of urethral prolapse. One of them underwent four-quadrant excision and the other was treated conservatively with urethral catherization.

"Total Gastric Dissociation (TGD)" in difficult clinical situations

BACKGROUND

Since the first report by Bianchi in 1997, TOGD has been found to be safe and effective in patients with gastro-oesophageal reflux (GOR) with neurological impairment. This paper explores the versatility of total gastric dissociation (TGD) in difficult clinical situations.

METHODS

The medical records of 11 neurologically normal children treated with TGD and gastrostomy after failure of conventional procedures between 1999 and 2004 were reviewed with respect to demographic data, initial diagnosis, previous operations, postoperative complications, feeding pattern, and follow-up.

RESULTS

There were 7 males and 4 females. The mean age at operation was 52.7 months (24 to 72 m). The indications were severe colo-oesophageal reflux in 3; 1 post-fundoplication necrotic stomach; 1 gastric remnant after subtotal gastrectomy for bleeding; 1 microgastria; 2 with severe oesophageal obstruction following repeated failed repair of congenital stenosis of the oesophagus and after fundoplication; 1 congenital short oesophagus with left-sided congenital diaphragmatic hernia; and 2 with severe dysfunctional oesophagus following repair of congenital tracheo-oesophageal cleft. Full oral or gastrostomy feeding was established by the 5th postoperative day. The average follow-up was 47.2 months (24-72 months). There were 4 late deaths in the group: 2 with respiratory failure, 1 with sepsis secondary to peritonitis (small bowel herniation into the thorax) and 1 with pneumococcal infection. Seven patients are alive and thriving with markedly reduced episodes of chest infections and hospitalizations.

CONCLUSIONS

In this study TGD presented with no peri-operative morbidity and mortality and had good long-term results. The procedure offers a safe alternative for neurologically normal children after the failure of conventional surgical procedures.

Pure esophageal atresia with no gap and associated intra-abdominal calcification

Pure esophageal atresia (PEA) is characterized by a long gap in between the two pouches. Primary anastomosis is usually not feasible and various techniques have been described in the literature to bridge this gap. We describe a case of PEA where there was no gap externally in between the two pouches and associated intra-abdominal calcification.

Epigastric heteropagus twins--a report of four cases

Asymmetrical conjoined twinning is an extremely rare congenital anomaly constituting only 1%-2% of all conjoined twins. In epigastric heteropagus twins (EHT), the dependent portion (parasite) is smaller than the host (autosite). The embryopathy is related to incomplete cleavage of the embryo at 2 weeks of gestation. However, some form of ischaemic insult in early gestation leads to selective atrophy of the cranial part of one of the monozygous twins. We report our experience with four cases of EHT and a review of the literature with a discussion of possible embryopathy.

Incarcerated diaphragmatic hernia secondary to plication for eventration of diaphragm

Diaphragmatic plication is the procedure of choice for congenital diaphragmatic eventration. In the absence of complications, most newborns with eventration do well after plication and have normal long-term respiratory functions. However complications are rare. Recurrence, ipsilateral pneumothorax and rupture of the diaphragm have been reported in literature. We report a case of incarcerated diaphragmatic hernia in a two-year-old child who had undergone plication for eventration of the diaphragm at six months of age.

Neonatal Hirschsprung's disease

Since the classic description of this disease by Harold Hirschsprung's. In 1886 just over a century ago, there has been a marked evolution in the diagnostic modalities, understanding of the pathophysiology, unraveling of genetic association and the treatment approach of this disease. Recent research on the molecular biology of the disease has bestowed us with a clearer understanding of the pathogenesis of the disease. Genetic deletions have been identified which explain the familial incidence of 3.6%-7.8%, and in some kindreds the inheritance rate approaches 50%. Improvement in the diagnostic approaches has evolved from full thickness rectal biopsy (under GA) to suction rectal biopsy. The development of the histochemical staining for acetylcholinesterase, allows rapid identification in the lamina propria of hypertrophied extrinsic nerve fibers which have proliferated in the absence of intrinsic ganglion cells. Frozen sections now permit screening for normal ganglia in the myenteric plexus from seromuscular biopsies during the definitive pull-through procedures or leveling colostomy. This service, however, requires significant infrastructure and an expert pathologist, not widely available. Hirschsprung's disease (HD) variants like intestinal neuronal dysplasia(IND), hypoganglionosis are better identified and treated with availability of histochemical staining. The three-stage procedure till date remains the gold standard; however, increasingly, the world over, two stage and even single stage procedures are being tried. In the era of minimally invasive surgery, perineal pull through procedure has been attempted with or without laparoscopic assistance.

A case of Fournier gangrene complicating idiopathic nephrotic syndrome of childhood

A 10-year-old boy presenting with steroid resistant nephrotic syndrome developed Fournier gangrene of the scrotum. Antimicrobial drug therapy, intravenous albumin, excision of necrotic scrotum and left orchidectomy followed by skin grafting 3 weeks later led to an excellent cosmetic and medical result. Six months later he remains nephrotic on diuretic and angiotensin converting enzyme inhibitor medication.

Total colonic aganglionosis: diagnosis and management in a 12-year-old boy

Total colonic aganglionosis (TCA) is an unusual form of Hirschsprung's disease, and most of these present within the first few weeks and nearly all by the end of the first year of life. Very few cases presenting in older childhood or adulthood have been reported. Without a high index of suspicion these cases can easily be missed and, therefore, patients undergo repeated laparotomies for subacute intestinal obstruction without relief of symptoms. The diagnosis is suspected on operative findings and confirmed by histological evaluation of seromuscular biopsy specimens. Proper diagnosis will prevent loss of bowel length caused by inadvertent resection and will help in performing an optimal procedure to treat these patients. Discussed herein is another case of TCA in a 12-year-old boy with review of relevant literature.

Surgical aspects of chronic constipation in children

Chronic constipation accounts for 3% of paediatric visits. These patients can be broadly classified into three groups: (a) medical group (60-70%), (b) surgical group (20-25%), (c) refractory constipation group (5-10%). The first two groups can be managed by dietary adjustments and surgery respectively. The recognition and management of refractory constipation is a slower process and needs close scrutiny and perseverance before a definite therapeutic option could be decided.

Neurogenic bladder: urodynamic and surgical aspects

Children with spina bifida often have vesico-urethral dysfunction manifesting either as upper urinary tract deterioration or voiding dysfunction, chiefly incontinence. Surgery of the back and presence of or increase in hydrocephalus may contribute to neuro-urologic worsening; secondary cord tethering and syrinx or hydromyelia may be additional factors coming into play later in life. Urodynamic assessment using simple modalities like uroflowmetry, external sphincter EMG, residual urine volume and cystometry provide data useful to classify patients according to detrusor and sphincter activity. Besides diagnosis, urodynamic studies are useful in guiding therapy of children with vesico-urethral dysfunction, and for their follow-up to detect sub-clinical deterioration. They also help to prognosticate risk of upper tract deterioration and the possible success of measures to contain incontinence. Urodynamic data in thirty one patients with spinal dysraphism who presented to us with urologic symptoms were analysed. Twenty-three children had hyper-reflexic bladders while in the other 8 the bladder was areflexic. 13 children showed upper tract dilatation. The leak point volume was significantly lower in this group of patients compared to those who did not show upper tract dilatation. Our results are comparable to earlier similar studies.

Haemodynamic studies during the management of severe tetanus

Detailed invasive haemodynamic studies were performed in 27 of 32 patients with severe tetanus. Nineteen had severe uncomplicated tetanus and eight had associated major complications, chiefly infection and pulmonary complications. The results were compared with those obtained from 15 healthy male volunteers who served as controls. There were two deaths in 32 patients (mortality 6.25 per cent). Severe tetanus without major complications was characterized by a high output hyperkinetic circulatory state with tachycardia (heart rate 131 (19.2) beats/minute), increased stroke volume index (43.1 (10.7) ml/m2), increased cardiac index (5.48 (0.94) l/min/m2) and a normal left ventricular stroke work index (60.5 (15.9) g/m/m2). Volume loading demonstrated a significant haemodynamic response and increased vascular capacitance. Even so the maximum percent rise from baseline values of these indices after volume load was significantly higher in controls (p < 0.001). Autonomic cardiovascular disturbances affected both sympathetic and parasympathetic activity. Hypertension and tachycardia alternating with hypotension and bradycardia were related to sudden fluctuations in systemic vascular resistance. Our studies suggested some degree of myocardial dysfunction in patients with severe uncomplicated tetanus. The haemodynamics of severe tetanus were masked and altered by complicating infection, pneumonia, and atelectasis.

Human rabies: clinical features, diagnosis, complications, and management

A case of rabies was treated with intensive medical support. This led to a prolongation of life to 25 days. The neurologic progression of the disease was monitored clinically and with serial EEG. This prolonged course enabled us to witness and manage a wide variety of unusual complications including the adult respiratory distress syndrome, hypothermia, myocarditis, and diabetes insipidus. This report documents the clinical features, diagnostic problems, complications, and management.

Tetanus and its complications: intensive care and management experience in 150 Indian patients

A total of 150 patients were treated for tetanus in the tetanus ward of the J. J. Hospital, Bombay, between October 1983 and January 1986. The complications of tetanus and the mode of management in the presence of restricted resources are outlined. Intensive care, proper nutrition, early tracheostomy and ventilator support in severe tetanus were chiefly responsible for an overall reduction in mortality from 30 to 12%. The mortality in severe tetanus was reduced from 70 to 23%. Sudden death due to unexpected cardiac arrest was an important complication in severe tetanus. We observed that an abrupt marked rise in rectal temperature (greater than 107 degrees F, 41.7 degrees C), if undetected, could lead to sudden circulatory collapse and death. Well-marked hypoxaemia was observed in all patients with severe tetanus, and was related to ventilation perfusion inequalities and to an increase in the true venous admixture (increased Qs/Qt) in the lungs. Bronchopulmonary infections and the adult respiratory distress syndrome added significantly to morbidity and mortality. Autonomic cardiovascular disturbances included bradycardia alternating with tachycardia, and hypertension which was either labile, paroxysmal or sustained. Persistent hypotension was of ominous significance. Amongst numerous complications involving other systems, sepsis and septic shock were associated with a high mortality.

Electron microscopic and electrophysiological studies on the carotid body following intracranial section of the glossopharyngeal nerve

1. The innervation of carotid body Type I cells has been investigated in seventeen cats. At a sterile operation the glossopharyngeal and vagus nerve roots were cut intracranially on one side.2. From 1(1/2) to 378 days after the operation the carotid bodies were fixed in situ and prepared for electron microscopy. Nerve endings on Type I cells were found to degenerate with a prolonged time course. In each cat there was a decrease in the number of nerve endings on the operated side as compared with the non-operated side.3. Before the carotid bodies were fixed, recordings were made from chemoreceptor, and baroreceptor, afferent fibres in the sinus nerve on the operated side. The chemoreceptors responded in the usual way to changes in arterial O(2), CO(2) and pH; the injection of cyanide evoked a brisk response.4. It is concluded that the nerve endings on Type I cells are efferent rather than afferent and the cell bodies of their axons are probably in the brain stem.

Reflex cardiovascular effects of epicardial stimulation by acetylstrophanthidin in dogs

Application of 25 to 100 µg of acetylstrophanthidin to the epicardium of the left ventricle of anesthetized and unanesthetized dogs caused hypotension and bradycardia without signs of discomfort. The response developed after an average latency of 8 seconds and lasted up to 12 minutes. Cooling the cervical vagi to 8 to 10°C or prior application of 0.1% procaine hydrochloride to the epicardium of the heart blocked the response. The response was, therefore, a reflex; the sensory receptors were located in the surface layers of the left ventricle. Electrophysiological recordings from single and multifiber preparations of the right recurrent cardiac nerve showed that the receptors for this reflex were mechanoreceptors whose fibers belonged to the C group. The sinus bradycardia caused by digitalis glycosides may result partly from excitation of these receptors.