Clinical Vignette Delayed ("Blow-out") Perforation of Sigmoid Following Diagnostic Colonoscopy

A case has been described in which perforation of the sigmoid colon occurred three days following simple diagnostic colonoscopic examination. The desirability is indicated for including the possibility of this occurrence in the informed eonsent. Administration of stool softener and use of low-residue diet for several days following diagnostic and therapeutic colonoscopy may be of value in averting the occurrence of this catastrophe.     

Spectroscopic study on the structure and stability of beef liver arginase

The secondary and tertiary structure of the oligomeric arginase (EC 3.5.3.1) from beef liver was investigated by circular dichroism (CD) and fluorescence measurements. The far-ultraviolet CD spectrum of the enzyme at neutral pH is indicative of high helical content. The intrinsic fluorescence emission of the protein is due to tryptophan, the contribution of tyrsoine being small. Upon excitation at 295 nm, the maximum of emission occurs at 330 nm, implying that the trytophan residues are rather buried in a hydrophobic interior of the protein. Ethylenediaminetetraacetic acid (EDTA), which inactivates the enzyme by removing the functional Mn²⁺-ion from the enzyme, does not dissociate the enzyme into subunits, nor affect noticeably its secondary and tertiary structure. Inactivation occurs in the acid pH range, being complete at pH below 4. However, acidification up to pH 1.5 produced only limited changes in the far-ultraviolet CD spectrum and intrinsic fluorescence emission properties. The enzyme shows noteworthy thermal stability, as shown by measuring the residual activity after heating and by evaluating the temperature dependence of the CD signal at 220 nm and the intensity of emission fluorescence. A temperature of half inactivation (Tm) of 77° was determined upon heating the enzyme at pH 7.5 in the presence of Mn²⁺-ions for 10 min; in the presence of EDTA, Tm is shifted to 55°. Taken together, these observations indicate that the structural stability of beef liver arginase arises from a clustering of hydrophobic amino acids and from Mn²⁺-ion binding.     

Potential for Load-Induced Cervical Stress Concentration as a Function of Periodontal Support

Abstract: Purpose : The purpose was to determine, photoelastically, the locations of occlusal load-induced stress concentrations within a maxillary premolar as a function of degree of periodontal support.
Materials and Methods : Composite three-dimensional models of a maxillary first premolar were fabricated for quasi-three-dimensional photoelastic stress analysis. Individual materials were used to model enamel, dentin, periodontal ligament, and alveolar bone. Three levels of periodontal support reduction (0%, 20%, 25%) were simulated by varying the socket depth. Vertical loads of 10 lb were applied to: (1) tip of buccal cusp, (2) tip of lingual cusp, and (3) center of occlusal surface. The resulting stresses were monitored and recorded photographically in the field of a circular polariscope arrangement.
Results : Cuspal loading concentrated stress around the cervical region below the loaded cusp, being highest under buccal cusp loading. The location of the stress concentration shifted apically as periodontal support diminished.     

Familial mandibuloacral dysplasia

A family is described in which two sisters and their two female fifth-cousins were cases of mandibuloacral dysplasia. This syndrome is characterized by mandibular hypoplasia, delayed cranial suture closure, dysplastic clavicles, abbreviated terminal club-shaped phalanges associated with acroosteolysis and atrophy of the skin over hands and feet. Furthermore, in this family alopecia and loss of the lower teeth were noted. We stress the importance of the cutaneous alterations and the possible existence of partial forms of the disease as in one of the patients presented.     

FIXED AND DYNAMIC URETHRAL COMPRESSION FOR THE TREATMENT OF POST-PROSTATECTOMY URINARY INCONTINENCE: IS HISTORY REPEATING ITSELF?

PURPOSE: We reviewed the evolution of appliances and devices used for treating post-prostatectomy urinary incontinence. MATERIALS AND METHODS: We used the MEDLINE to search the literature from 1966 to March 2000 and then manually searched bibliographies to identify studies that our initial search may have missed. RESULTS: The evolution of treatment for post-prostatectomy urinary incontinence may be traced back to the 18th century. Two main schools of thoughts simultaneously evolved. The first fixed urethral compression devices were constructed to enable urethral obstruction by fixed resistance. This outlet resistance allows voiding after intra-abdominal and intravesical pressure is elevated but it is sufficient to prevent leakage between urinations. The other school of thought preferred creation of dynamic urethral compression in which outlet resistance is not fixed but may be decreased when voiding is desired or elevated between urinations. Therapeutic fixed and dynamic urethral compression interventions may be further divided into external or internal compressive devices or procedures. External fixed compression devices may be traced back to antiquity. A penile clamp, similar to the later Cunningham clamp, and a truss designed to compress the urethra by external perineal compression were presented in the Heister textbook of surgery, Institutiones Chirurgicae, as early as 1750. Dynamic compressive devices applied externally were developed much later, such as the first artificial urinary sphincter, described by Foley, in 1947 and the Vincent apparatus, described in 1960. The modern era of fixed urethral compression began in 1961 with Berry. Acrylic prostheses impregnated with bismuth to allow radiographic visualization were produced in various shapes and sizes, and used to compress the urethra against the urogenital diaphragm. In 1968 the University of California-Los Angeles group under the direction of Kaufman began to use cavernous crural crossover to compress the bulbous urethra (Kaufman I). Later 2 other modifications were described, including approximation of the crura in the midline using a polytetrafluoroethylene mesh tape (Kaufman II) and an implantable silicone gel prosthesis (Kaufman III). With the advent of the artificial urinary sphincter pioneered by Scott in 1973 interest in passive urethral compression disappeared in favor of the implantation of an inflatable circumferential prosthetic sphincter. Recently there has been a trend back to passive urethral compression. Synthetic bolsters have been described that passively compress the bulbar urethra to achieve urinary incontinence after radical prostatectomy. CONCLUSIONS: Much creativity has been dedicated to solve the complex and challenging problem of post-prostatectomy urinary incontinence. Devices used for treating this condition may be grouped according to the mechanism of action and how they are applied. Passive urethral compression, long abandoned in favor of dynamic implantable sphincters, has reemerged. Further research in this field may determine which school of thought may provide the best solution for treating post-prostatectomy urinary incontinence.