Controlled dissolution of freeform 3D printed carbohydrate glass scaffolds in hydrogels using a hydrophobic spray coating.

Freeform 3D printing combined with sacrificial molding promises to lead advances in production of highly complex tubular systems for biomedical applications. Here we leverage a purpose-built isomalt 3D printer to generate complex channel geometries in hydrogels which would be inaccessible with other techniques. To control the dissolution of the scaffold, we propose an enabling technology consisting of an automated nebulizer coating system which applies octadecane to isomalt scaffolds. Octadecane, a saturated hydrocarbon, protects the rigid mold from dissolution and provides ample time for gels to set around the sacrificial structure. With a simplified model of the nebulizer system, the robotic motion was optimized for uniform coating. Using a combination of stimulated Raman scattering (SRS) microscopy and X-ray computed tomography, the coating was characterized to assess surface roughness and consistency. Colorimetric measurements of dissolution rates allowed optimization of sprayer parameters, yielding a decrease in dissolution rates by at least 4 orders of magnitude. High fidelity channels are ensured by surfactant treatment of the coating, which prevents bubbles from clinging to the surface. Spontaneous Raman scattering microspectroscopy and white light microscopy indicate cleared channels are free of octadecane following gentle flushing. The capabilities of the workflow are highlighted with several complex channel architectures including helices, blind channels, and multiple independent channels within polyacrylamide hydrogels of varying stiffnesses.

Chitobiase, a new reporter enzyme.

N,N'-diacetylchitobiase (chitobiase) from the marine organism Vibrio harveyi is a highly stable reporter enzyme for gene fusions. This enzyme hydrolyzes the disaccharide chitobiose to N-acetyl glucosamine. The advantages of the reporter gene encoding chitobiase (chb) are: (i) that chitobiase and N-acetyl-beta-D-glucosaminidase activities are missing in E. coli strains, (ii) chitobiase can be monitored using blue/white colony indicator plates and (iii) convenient substrates for this enzyme are commercially available. The use of chitobiase as a reporter enzyme is generally applicable to the study of gene expression in those bacteria that do not contain N-acetyl-beta-D-glucosaminidases. We constructed plasmid vectors containing a multiple cloning site for producing in-frame fusions to chitobiase, the attP of lambda phase for movement into the bacterial chromosome for single-copy analysis, the gene encoding chloramphenicol acetyltransferase (cat), the pACYC184 origin of replication and the rrnBt1t2 terminator region upstream of the chb gene to prevent read-through from other promoters. In-frame fusions between the dnaA gene and chb were moved to the chromosome by site-specific recombination with the chromosomal attB site. These single-copy fusions were assayed for chitobiase to examine the effects of a deletion in the dnaA regulatory region.

The mathematics of screening mammography.

In an unselected population of women in their early fifties, about 7500 mammograms would have to be performed annually at a cost of U.S. $375,000 per survivor in order to find one woman who would: 1) have an incidental cancer in stage I which was not detectable by physical examination; and 2) owe her survival to the early detection of that cancer. Annual screening mammography has a poor cost-benefit ratio.

Selective utilization of clinical diagnosis in treatment of pharyngitis.

Exudate, adenopathy, and fever were used to predict clinically whether pharyngitis was streptococcal, nonstreptococcal, or questionable in 466 adults and 234 children. Clinical accuracy was: nonstreptococcal - adults 94.6 percent, children 86.9 percent; streptococcal - adults 44.2 percent, children 53.5 percent. Significance of results was determined by calculating the cost of routine cultures compared to risk of rheumatic fever. The economic justification of cultures was lowest in nonstreptococcal adults, streptococcal adults, and streptococcal children. Therapy of streptococcal patients presented an additional risk: anaphylaxis. The fatality risk after penicillin injection compared to the increased risk of rheumatic fever after oral penicillin is: adults 7.5 percent (clinical diagnosis), 3.3 percent (laboratory diagnosis); children 1.8 percent and 0.8 percent respectively. It is recommended that throat culture be obtained for all questionable patients and clinically nonstreptococcal children. Penicillin should be administered orally in the majority of adults.

Hypertension in a primary care practice.

The charts of 554 consecutive hypertensive patients seen at a primary care office were reviewed. The highest recorded blood pressure of hypertensive male patients averaged 177/113 mmHg. The most recent blood pressure of males under treatment for hypertension averaged 144/92 mmHg. For female patients the corresponding figures were 179/112 mmHg and 146/91 mmHg. The average yearly cost of treatment was $80. In theory, if these reductions were maintained in one hundred 55-year-old hypertensives for six years, coronary events would decrease by 4.3 events in men and 2.2 events in women. The cost per event prevented would be $11,000 in men and $21,000 in women. Diastolic blood pressures showed a greater correlation to the morbidity pattern found in coronary heart disease (a greater prevalence and severity in men than in women, especially under age 55 years) than did the systolic blood pressures. These findings suggest that for prevention of coronary heart disease, emphasis should be placed on the diagnosis and treatment of males under the age of 55 years who have diastolic hypertension.

HMO productivity: back to basics.

Significant reductions in health expenditures can best be achieved by a few inexpensive systemic changes in utilization of physicians rather than by multiple small savings from individual guidelines, pathways, etc. Capitation was a systemic change that removed the fee-for-service incentive to increase income by increasing visits. What is needed now is to change the scheduling patterns and demand needs of the population adopted under fee for service. By designing schedules to reduce no-shows, facilitating a reduction in the number of visits per patient per year, and preferentially accommodating acute primary care visits and consultations, HMOs can rapidly reduce demand and achieve substantial savings.

Coronary heart disease in treated hypertensive patients and risk-matched normotensive control subjects.

The incidence of coronary heart disease (CHD) was recorded prospectively for 543 persons--335 treated hypertensive patients and a group of 208 normotensive control subjects, individually matched to a subgroup of the hypertensive patients on the basis of seven risk factors. If antihypertensive therapy reduces CHD, CHD should have occurred at a rate predicted by initial blood pressure levels in the normotensive control subjects and at a rate predicted by post-treatment blood pressure levels in the hypertensive patients. A treatment effect seemed possible in hypertensive men, since CHD occurred at the rate predicted by post-treatment blood pressure levels. However, because the reduction was not statistically significant and was similar to a reduction observed in the normotensive control subjects, a treatment effect could not be confirmed. There was no evidence of a treatment effect in hypertensive women, since CHD occurred at a rate higher than that predicted by post-treatment blood pressure levels and the normotensive control subjects showed a lower than expected rate.

Five-year follow-up of asymptomatic patients with negative fecal occult blood test results in whom clinically significant colorectal pathology was detected.

OBJECTIVES: To determine from a 5-yr longitudinal study (a) rate of compliance with follow-up, (b) number of new clinically significant colorectal lesions discovered by sigmoidoscopy or colonoscopy at later examination, (c) number and causes of deaths, and (d) rate of diagnosis of new cancers among 36 asymptomatic patients with negative fecal occult blood tests in whom clinically significant colorectal lesions were found initially by 60-cm flexible sigmoidoscope. METHODS: For the 36 patients, medical records were reviewed throughout the 5-yr study period. These records included pathology reports, results from 60-cm sigmoidoscopy and colonoscopy examinations, and notations from visits to health facilities for reasons other than colorectal examinations. RESULTS: Seventy-one clinically significant lesions were removed during the 5-yr period; 58 were discovered by sigmoidoscopy and 13 by colonoscopy. Also, during the 5-yr period, noncolorectal cancer was diagnosed in six patients, and two patients died of cardiac disease. CONCLUSIONS: Patients who have clinically significant colorectal pathology found by 60-cm sigmoidoscope have a high prevalence of lesions beyond the view of this instrument. Therefore, colonoscopy should be performed when sigmoidoscopy shows clinically significant pathology. Because subsequent examinations show a high incidence of new lesions, rescreening is indicated.