Identical and Nonidentical Twins: Risk and Factors Involved in Development of Islet Autoimmunity and Type 1 Diabetes

OBJECTIVE

There are variable reports of risk of concordance for progression to islet autoantibodies and type 1 diabetes in identical twins after one twin is diagnosed. We examined development of positive autoantibodies and type 1 diabetes and the effects of genetic factors and common environment on autoantibody positivity in identical twins, nonidentical twins, and full siblings.

RESEARCH DESIGN AND METHODS

Subjects from the TrialNet Pathway to Prevention Study (N = 48,026) were screened from 2004 to 2015 for islet autoantibodies (GAD antibody [GADA], insulinoma-associated antigen 2 [IA-2A], and autoantibodies against insulin [IAA]). Of these subjects, 17,226 (157 identical twins, 283 nonidentical twins, and 16,786 full siblings) were followed for autoantibody positivity or type 1 diabetes for a median of 2.1 years.

RESULTS

At screening, identical twins were more likely to have positive GADA, IA-2A, and IAA than nonidentical twins or full siblings (all P < 0.0001). Younger age, male sex, and genetic factors were significant factors for expression of IA-2A, IAA, one or more positive autoantibodies, and two or more positive autoantibodies (all P ≤ 0.03). Initially autoantibody-positive identical twins had a 69% risk of diabetes by 3 years compared with 1.5% for initially autoantibody-negative identical twins. In nonidentical twins, type 1 diabetes risk by 3 years was 72% for initially multiple autoantibody-positive, 13% for single autoantibody-positive, and 0% for initially autoantibody-negative nonidentical twins. Full siblings had a 3-year type 1 diabetes risk of 47% for multiple autoantibody-positive, 12% for single autoantibody-positive, and 0.5% for initially autoantibody-negative subjects.

CONCLUSIONS

Risk of type 1 diabetes at 3 years is high for initially multiple and single autoantibody-positive identical twins and multiple autoantibody-positive nonidentical twins. Genetic predisposition, age, and male sex are significant risk factors for development of positive autoantibodies in twins.

The effects of withdrawing tegaserod treatment in comparison with continuous treatment in irritable bowel syndrome patients with abdominal pain/discomfort, bloating and constipation: a clinical study

BACKGROUND

The post-withdrawal characteristics of tegaserod treatment in patients with irritable bowel syndrome with constipation remain undefined.

AIM

To evaluate the effects of continuous tegaserod treatment, versus intermittent or withdrawal of treatment in patients with irritable bowel syndrome with constipation.

METHODS

In a randomized, open-label trial, all patients initially received tegaserod 6 mg b.d. Responders were randomized to continue or withdraw from treatment for 8 weeks and symptom recurrence was assessed. Tegaserod was re-introduced in withdrawal patients who experienced symptom recurrence, allowing an assessment of intermittent treatment. Two separate analyses assessed the effects of intermittent and withdrawal of treatment on symptom recurrence.

RESULTS

Five hundred irritable bowel syndrome with constipation patients initially received tegaserod; 410 completed treatment. Time to symptom recurrence was shorter in withdrawal patients than those maintained on tegaserod. Significantly more patients maintained on tegaserod had not experienced symptom recurrence by week 8, compared with intermittent (86.5% vs. 58.1%, respectively) or withdrawal of treatment (69.2% vs. 11.3%, respectively) (P < 0.0001 for both). Significant treatment effects were observed for bloating (P < 0.01) and abdominal pain/discomfort (P < 0.02). Most adverse events were mild to moderate.

CONCLUSIONS

Irritable bowel syndrome with constipation patients who receive continuous or intermittent tegaserod are less likely to experience symptom recurrence than patients withdrawn from treatment.

Outcome of Toxoplasma gondii mismatches in heart transplant recipients over a period of 8 years

Donor-related infection due to Toxoplasma gondii is a well-recorded complication of cardiac transplantation. In order to assess the efficacy of co-trimoxazole in small doses as prophylaxis for primary Toxoplasma gondii infection in seronegative heart and heart-lung transplant recipients receiving organs from seropositive donors, we reviewed the serostatus and clinical outcome of all such mismatched transplants performed at our unit over a period of 8 years. Of 310 transplants performed between May 1985 and May 1993, donor and recipient serum samples were available for 257 heart and 33 heart-lung transplants. Of these, 13 (4.5%) were toxoplasma mismatches. Post-transplant review serum samples were available for 3 months or longer for nine of the 13 mismatches. The first three patients received co-trimoxazole 480 mg bd orally for 3 months (regimen A) while the remainder received only the standard prophylaxis designed for Pneumocystis carinii i.e., 960 mg bd orally three times per week for 3 months (regimen B). Seroconversion was demonstrated in only one patient (regimen A). Furthermore, none of the mismatched patients developed serious infection compatible with primary toxoplasmosis. We therefore conclude that in centres with a low prevalence of toxoplasma seropositivity, testing of donor and recipient serum for Toxoplasma gondii antibody should be performed only when clinically indicated and, in addition, standard prophylaxis for Pneumocystis carinii may be adequate for preventing primary toxoplasmosis.

On the Nature of Paddle Cilia and Discocilia

Cilia with paddle-shaped or disc-shaped tips enclosing a curved end of the axoneme (paddle cilia or discocilia) have been described in a variety of marine invertebrates. Although numerous studies, in which fixed specimens were used, claimed that paddle cilia and discocilia are genuine structures of unknown function, several studies, in which fresh living material was used, reported that modified cilia are artifacts. We have re-investigated a recent SEM report that paddle cilia are genuine organelles in veliger larvae of marine bivalves (Campos and Mann, 1988). Using high-speed video and electronic flash DIC microscopy, we find no paddle cilia in living larvae of Spisula solidissima and Lyrodus pedicellatus. Hypotonic seawater, however, induces formation of paddle cilia and vesiculations of the ciliary membrane in these veligers, as does the hypotonic SEM fixative used by Campos and Mann (1988). Fixatives that are isosmotic with seawater, on the other hand, do not induce paddle cilia. We conclude that paddle cilia are artifacts, and we propose a unifying mechanism to explain their production in various animals under different conditions.

Testing for neutral-to-ground connections in new construction

A study was performed to seek out inadvertent connections between neutral and ground in the power distribution system of a newly constructed hospital, prior to occupancy. Such connections are not only violations of code but could cause medical device problems. Ground wires are not intended to carry load currents except during faults. When currents do flow in grounds, medical device chassis voltages are elevated and some devices may respond unpredictably. Suitable acceptance testing is not commonly done. In this study, a simple test method was developed that helped reveal and correct many neutral-ground misconnections. The authors advocate incorporating such a test into building construction contract specifications.