Characterization of the X-linked murine centrin Cetn2 gene.

A multi-gene family (Cetn1, Cetn2, and Cetn3) encodes the calcium-binding protein, centrin, in the mouse. This work characterizes the Cetn2 gene. Structurally, Cetn2 consists of five exons and four introns, and contains a classical TATA-less promoter. Cetn2 has two alternate transcription start sites, and a single length 3' untranslated region. Fluorescence in situ hybridization demonstrates that Cetn2 is an X-linked gene whose alleles replicate asynchronously during S-phase. Cetn2 encodes a 172 amino acid protein, with a predicted molecular mass of 19,795 Da (pI=4.71), that contains all of the defining characteristics of centrin. Northern blot analysis indicates that Cetn2 is ubiquitously expressed in the tissues of adult mice. RT-PCR shows that Cetn2 and Cetn3, but not Cetn1, are expressed in NIH 3T3 cells. Immunofluorescence microscopy demonstrates that mouse centrin 2 protein localizes to the region immediately surrounding the centrioles in the centrosome of NIH 3T3 cells.

Expression and purification of two isozymes of clavaminate synthase and initial characterization of the iron binding site. General error analysis in polymerase chain reaction amplification.

Clavaminate synthase is an Fe(2+)-, O2-, and alpha-ketoglutarate-dependent oxygenase that catalyzes three transformations in the biosynthesis of the important beta-lactamase inhibitor clavulanic acid. The genes from Streptomyces clavuligerus encoding two isoenzymes of clavaminate synthase have been over-expressed in Escherichia coli to give soluble proteins whose reactions, kinetic properties, and molecular masses are in excellent agreement with the wild-type isozymes. Preliminary investigation of the active site of clavaminate synthase was undertaken using diethyl pyrocarbonate and N-ethylmaleimide. Each was inhibitory to catalytic activity. Protection from inactivation in the presence of these reagents by Fe2+, O2, and alpha-ketoglutaric acid was thwarted by the rapid self-inactivation of the enzyme in the absence of substrate. However, protection was achieved when Co2+, a potent competitive inhibitor of clavaminate synthase 2 with respect to Fe2+, was substituted. This is consistent with the presence of histidine and cysteine, respectively, at or near the active site and possibly involved in iron binding. In the course of constructing the expression vector, a simply applied general error analysis of the polymerase chain reaction was formulated to calculate the proportion of correctly replicated DNA and guide the design of experiments using this method.

Perineal hidradenitis suppurativa: presentation of two unusual complications and a review.

Two patients with advanced perineal hidradenitis suppurativa, complicated by fecal incontinence and squamous cell carcinoma, are presented. The first patient was a 58-year-old man who had a 30-year history of chronic recurring perianal abscesses and perineal sinuses. At the time of presentation, he had extensive perineal suppurative disease, and scarring and fixation of the anal sphincters with resultant fecal incontinence. He was treated with wide excision and skin graft closure. The second patient was a 27-year-old man with an 11-year history of recurrent gluteal abscesses and perineal sinuses. At the time of presentation, his inflammatory disease was only mildly active, but he had a nonhealing gluteal lesion. The nonhealing lesion was diagnosed as a squamous cell carcinoma and was managed with wide excision and primary closure. The inflammatory disease was excised and grafted. Complications of advanced hidradenitis suppurativa can be debilitating and life threatening. We review the etiology, pathophysiology, complications, and treatment options of hidradenitis suppurativa, including a literature review of the association with malignancy. We propose that the incidence of disabilities and complications may be reduced by early diagnosis and treatment, by emphasis on prevention of recurrence, and by more aggressive surgical intervention for recurrent and extensive disease.

Improved imaging of the augmented breast.

The breast containing an augmentation implant presents a challenge to the mammographer and is often considered unsuitable for adequate mammographic evaluation. A modified positioning technique is described. By displacing the implant posteriorly against the chest wall and pulling breast tissue over and in front of the implant, marked improvement in compression and visualization of substantially more breast tissue is achieved. Over 250 patients with augmentation implants have been successfully studied with this modified compression technique. After review of 50 consecutive cases, two experienced mammographers confirmed a significant improvement in image quality, amount of breast tissue visualized, and overall benefit of the modified technique. Modified positioning for women with breast implants substantially improves both image quality and amount of breast tissue imaged.

A mathematical overview of a computer simulation model of maternity histories with illustrative examples.

A mathematical overview of a stochastic computer simulation model of maternity histories is provided. Various components of human reproduction are accommodated in the model through distributions of waiting times among live births. Included in these components are distributions of age at first marriage in a cohort of women, waiting times to pregnancy for fecundable women, and the lengths of infecundable periods following live births. Probabilities that pregnancies end in either a live birth, induced abortion, or some other type of outcome are also included. Elements of renewal theory and semi-Markov processes in discrete time were the basic mathematical concepts used in the construction of the model. A brief description of an interactive software package called MATHIST, which may be used to implement the model on a computer, is also included. Four illustrative computer runs with MATHIST, pertinent to the operation of family planning programmes in Africa, are also described and discussed.