Copula bivariate probit models: with an application to medical expenditures

The bivariate probit model is frequently used for estimating the effect of an endogenous binary regressor (the ‘treatment’) on a binary health outcome variable. This paper discusses simple modifications that maintain the probit assumption for the marginal distributions while introducing non‐normal dependence using copulas. In an application of the copula bivariate probit model to the effect of insurance status on the absence of ambulatory health care expenditure, a model based on the Frank copula outperforms the standard bivariate probit model. Copyright © 2011 John Wiley & Sons, Ltd.     

Septic sequelae after splenectomy for trauma in adults

Of 619 trauma patients who underwent splenectomy, 503 lived more than 10 days postoperatively. In this group systemic sepsis developed in 114 patients (22.7 percent). The most frequent septic focus was intraabdominal abscess (59 patients). The incidence of postoperative septic complications increased with the severity of trauma. Of the 41 patients who died after the 10th postoperative day, 36 died from sepsis. There were no septic complications or deaths in the 13 patients under age 15 years. Septic morbidity and mortality rates in splenectomized patients were significantly (p less than 0.01) greater than those in 2,368 consecutive trauma patients treated from 1978 to 1979. Long-term follow-up information was obtained in 242 patients. Follow-up encompassed 1,046 patient-years, with a mean patient follow-up interval of 4.4 years. Severe bacterial infections have occurred in six patients (2.5 percent). Thus far there have been no deaths from overwhelming sepsis. Interestingly, 11.5 percent of the patients complained of more severe viral infections after splenectomy. Our data support the concept of preserving the traumatized spleen whenever possible.     

Carrageenin-induced arthritis: V. A morphologic study of the development of inflammation in acute arthritis

Following a single injection of the polysaccharide carrageenin into the rabbit knee joint, a rapid inflammatory process occurs in the joint space and synovial membrane, followed by changes in the articular cartilage. Initially there is an influx of cells, mainly PMNs, into the synovial fluid, accompanied by proliferation of the synovial lining cells and infiltration of the synovial membrane. The numbers of synovial fluid cells decline gradually after 24 hr. The reaction in the synovial membrane is greatest at day 7, and inflammation is still evident at day 21. Initially, the infiltrate consists mainly of PMNs, but by day 7 it is predominantly mononuclear, with small clusters of lymphocytes.The articular cartilage shows loss of metachromasia with toluidine blue at 3–14 days after injection, but stains normally after day 21. Electron microscopy shows damage to the chondrocytes at days 1 and 7, with complete destruction of cells in the surface layer. At day 7 cells in the deeper layers have lost the apparatus required for proteoglycan synthesis, but at day 21 the cells appear virtually normal.There was no evidence for a direct inhibitory effect of carrageenin on proteoglycan biosynthesis. Most labeled carrageenin was rapidly cleared from the joint space, but about 10% was retained in the synovial membrane and 0.6% in articular cartilage at 48 hr after injection.Since the increase and decline in PMN numbers respectively precede the cartilage damage and recovery, it is suggested that there may be a correlation between the clinical activity of arthritis and the number of PMNs in the synovial fluid.     

Effects of allopurinol, propranolol and methylprednisolone on infarct size in experimental myocardial infarction.

With use of a canine model of occlusion of the left anterior descending coronary artery and an intracellular lactic dehydrogenase stain to measure infarct size directly, the effects of allopurinol, methylprednisolone sodium succinate and propranolol were studied. Allopurinol did not influence the extent of myocardial necrosis, whereas both methylprednisolone and propranolol significantly reduced myocardial infarct size. Possible mechanisms of action and clinical applicability of these agents are discussed.     

The axoplasmic transport of 4S RNA within the sciatic nerve of the chicken

Following the introduction of [³H]uridine into the adult chicken spinal cord, a preferential labelling of 4S RNA with respect to rRNA was detected in the sciatic nerve at 2 and 4 days post-injection. No such proferential incorporation was observed within the spinal cord at the times examined nor in the sciatic nerve at 1 day post-injection. The results suggest that about 40% of the radioactivity in the sciatic nerve RNA after 4 days is due to tRNA transported from the spinal cord. Autoradiographic studies have shown that about 40% of radioactivity labelled RNA within the chicken sciatic nerve at 7–9 days post- injection is intraaxonal. It is concluded that RNA, but probably not rRNA, is transported within the axoplasm of the chicken sciatic nerve at approx. 20–25 mm/day.