A General Solution of the Problem of Mixing of Subpopulations and its Application to Risk- and Age-Structured Epidemic Models for the Spread of AIDS

A central aspect in the study of the dynamics of sexually transmitteddiseases is that of mixing. The study of the effects of socialstructure in disease dynamics has received considerable attentionover the last few years as a result of the AIDS epidemic. Inthis paper, we formulate a generalization of the Blythe andCastillo-Chavez social/sexual framework for human interactionsthrough the incorporation of age structure, and derive an explicitexpression in terms of a preference function for the generalsolution to this formulation. We emphasize the role played byproportionate mixing, the only separable solution to this mixingframework, through the discussion of several specific cases,and we formulate an age-structured epidemic model for a singlesexually active homosexual population, stratified by risk andage, with arbitrary risk- and age-dependent mixing as well asvariable infectivity. In the special case of proportionate mixingin age and risk, an explicit expression for the basic reproductivenumber is computed.     

2,3-Diphosphoglycerate Content and Oxygen Affinity as a Function of Red Cell Age in Normal Individuals

A parallel decline of 2,3-diphosphoglycerate (2,3-DPG) and P₅₀ of intracorpuscular hemoglobin is found in red bloodcells during their in vivo aging. After2,3-DPG depletion due to in vitro storage, the capacity to restore, 2,3-DPG inthe presence of inosine is significantlyimpaired in senescent cells as comparedwith young cells.

Submitted on April 5, 1971 Revised on May 11, 1971 Accepted on May 16, 1971     

SERUM CYFRA 21–1 IN PATIENTS WITH INVASIVE BLADDER CANCER AND ITS RELEVANCE AS A TUMOR MARKER DURING CHEMOTHERAPY

Purpose:

Previous studies have shown that serum levels of the degradation products of cytokeratins could be used as surrogate markers in the diagnosis and followup of patients with solid tumors, including tumors of the bladder.

Materials and Methods:

The soluble cytokeratin 19 fragment CYFRA 21-1 was measured by solid phase radioimmunoassay in the serum of 142 patients with invasive transitional cell cancer of the bladder. Of the patients 56 had clinical stage I to III locally confined disease (T1-4aN0M0) and 86 had stage IV metastatic disease with lymph node and/or distant metastases. A control group consisted of 33 healthy volunteers. In a subgroup of 49 patients with metastatic disease receiving combined platinum based chemotherapy serum CYFRA 21-1 was determined prior to the initiation of therapy and after the documentation of response.

Results:

Abnormal CYFRA 21-1 was observed in 7% of patients with locally invasive disease and in 66% of those with metastatic disease (p <0.0001). There was no correlation of CYFRA 21-1 with tumor differentiation. Patients with abnormal CYFRA 21-1 showed statistically significant worse median overall survival. Moreover, in the subgroup of patients with metastatic disease receiving chemotherapy CYFRA 21-1 levels correlated with the response to treatment.

Conclusions:

Patients with transitional cell cancer of the bladder with evidence of distant metastases showed a significant increase in serum CYFRA 21-1. During chemotherapy CYFRA 21-1 appears to be a potentially sensitive and useful indicator for monitoring treatment response.     

Intermittent P Wave Sensing in a Patient with DDD Pacemaker

We present the case of a patient with a DDD pacemaker and intermittent P wave sensing due to T wave oversensing by the ventricular lead. The T wave sensing caused initiation of an extended atrial refractory period and the P waves, falling within this period, were not sensed. The problem was solved by decreasing the ventricular sensitivity.     

Linear Ablation Following Pulmonary Vein Isolation in Patients with Atrial Fibrillation: A Meta‐Analysis

Previous studies have given conflicting data regarding the long‐term adjunctive efficacy of linear lesions (LLs) on top of pulmonary vein isolation (PVI) as an ablation strategy in patients with atrial fibrillation (AF). The aim of this meta‐analysis was to provide a detailed analysis of the available randomized controlled trials (RCTs) regarding the efficacy of LL following PVI in AF patients. Current databases were searched until October 2015. The primary outcome end point of the meta‐analysis was recurrence of any symptomatic or documented episode of AF or atrial tachycardia after a single ablation procedure with or without the use of antiarrhythmic drugs. Ten RCTs with a total of 1,446 patients were included in the meta‐analysis. The pooled analysis of five trials concerning persistent AF (PeAF) patients (400 in PVI plus LL group and 182 in PVI alone group) suggested that the addition of LL following PVI does not lead to a significant reduction in recurrent atrial tachyarrhythmias compared with PVI alone (relative ratio [RR] = 0.73, 95% confidence interval [CI]: 0.44–1.21, P = 0.22). Similarly, there was no incremental benefit of additional LL in long‐term outcomes in paroxysmal AF (PAF) patients (RR = 0.85, 95% CI: 0.68–1.05, P = 0.13). Pooling the results of all eligible trials suggested that PVI plus LL compared with PVI alone significantly increased radiofrequency time (P = 0.0002), fluoroscopy time (P < 0.00001), and procedure time (P < 0.0001). This meta‐analysis suggests that LL following PVI does not provide additional benefit to sinus rhythm maintenance in patients with PeAF and PAF.