Characteristics associated with the transition to partial breastfeeding prior to 6 months of age: Data from seven sites in a birth cohort study

The WHO recommends exclusive breastfeeding for the first 6 months of life. However, the transition of the infants'' diet to partial breastfeeding with the addition of animal milks and/or solids typically occurs earlier than this. Here, we explored factors associated with the timing of an early transition to partial breastfeeding across seven sites of a birth cohort study in which twice weekly information on infant feeding practices was collected. Infant (size, sex, illness and temperament), maternal (age, education, parity and depressive symptoms), breastfeeding initiation practices (time of initiation, colostrum and pre‐lacteal feeding) and household factors (food security, crowding, assets, income and resources) were considered. Three consecutive caregiver reports of feeding animal milks and/or solids (over a 10‐day period) were characterized as a transition to partial breastfeeding, and Cox proportional hazard models with time (in days) to partial breastfeeding were used to evaluate associations with both fixed and time‐varying characteristics. Overall, 1470 infants were included in this analysis. Median age of transition to partial breastfeeding ranged from 59 days (South Africa and Tanzania) to 178 days (Bangladesh). Overall, higher weight‐for‐length z‐scores were associated with later transitions to partial breastfeeding, as were food insecurity, and infant cough in the past 30 days. Maternal depressive symptoms (evaluated amongst 1227 infants from six sites) were associated with an earlier transition to partial breastfeeding. Relative thinness or heaviness within each site was related to breastfeeding transitions, as opposed to absolute z‐scores. Further research is needed to understand relationships between local perceptions of infant body size and decisions about breastfeeding.     

CARBON-13 N.M.R. STUDY OF BLEOMYCIN-A2 PROTONATION

The acid-base titration of bleomycin-A₂ in D₂O solution at 35 ± 5° has been monitored by ¹³C n.m.r. spectroscopy at 67.89 MHz. The following pK^D_a values were obtained: 3.68 ± 0.05 (secondary amine), 5.29 ± 0.03 (imidazole), and 8.23 ± 0.19 (primary amine), where K^D_a is the dissociation constant in D₂O solution. The equilibrium isotope effects (pK^D_a -pK_a in H₂O) are: 0.70 ± 0.06 (secondary amine), 0.28 ± 0.04 (imidazole), and 0.85 ± 0.19 (primary amine). Titration of the imidazole group of Bleo-A₂ occurs at N^π, i.e. only N^π is protonated in basic solution. Significant protonation shifts are almost completely limited to carbons of the N-terminal tetrapeptide, suggesting that the C-terminal tripeptide extends into the solvent and interacts to a minimal extent with the rest of the molecule. Long range protonation shifts associated with titration of the imidazole and secondary amine groups indicate that protonation of one or both of these sites is probably accompanied by significant conformational changes. The observed protonation shifts generally fail to correlate with Zn(II) complexation shifts reported by Dabrowiak et al. (1973, Biochemistry 17, 4090) indicating that ligation sites cannot unambiguously be determined from these complexation shifts. The complexation shifts previously attributed to coordination of the imidazole and carbamoyl groups probably result from conformational changes.     

The Operational Characteristics of Ultrasonography for the Diagnosis of Plantar Intermetatarsal Neuroma

A retrospective study was carried out on 48 patients to correlate preoperative ultrasound findings with postoperative histopathology findings and to assess the sensitivity, specificity, positive predictive values, and negative predictive values of ultrasound in the diagnosis of Morton's interdigital neuroma. All case sheets of 48 patients operated on between 1997 and 2005 were reviewed in the medical record section of Ninewells Hospital, Dundee, Scotland, so that preoperative ultrasound reports were compared with the postoperative histopathological reports. A statistical analysis of the results was performed. Ultrasonography showed 43 true-positive cases, 1 true-negative case, and 4 false-negative cases out of 48 cases. Histopathology showed 47 true-positive cases and 1 true-negative case; statistical analysis performed on the results showed a sensitivity of 91.48%, a specificity of 100%, and 100% positive and 20% negative predictive values, respectively. In our analysis, the probability that ultrasound will confirm the presence of plantar intermetatarsal neuroma is 91.67%.     

Use of monoclonal antihapten antibodies for immunolocalisation of tissue antigens

The applicability of a hapten-antihapten sandwich technique incorporating a monoclonal antihapten bridge antibody to localisation of tissue antigen is described. The results show that the method is both versatile and selective and has the potential of being even more sensitive than currently used immunoperoxidase methods.     

Neural dynamics in a model of the thalamocortical system. II. The role of neural synchrony tested through perturbations of spike timing

Activity in the mammalian thalamocortical system is often accompanied by a synchronous discharge of cortical and thalamic neurons. Although many functions have been attributed to such synchronous firing, it is not known whether or how synchrony of firing per se affects thalamocortical operations. Direct experimental tests of the consequences of neuronal synchronization in vivo are hard to carry out, whereas theoretical studies based on single-neuron models cannot reveal the effects of synchrony at the system level. To overcome these limitations, we have used a perturbational approach to test the causal efficacy of synchrony per se in large-scale simulations of the thalamocortical system. The test consists of selectively disrupting firing synchrony by 'jittering' the timing of action potentials in the simulations and determining whether firing rates are modified by this perturbation. The simulations are based in detail on the known anatomy and physiology of the thalamocortical-visual system of the cat, and have been shown in a companion paper to produce episodes of fast synchronous activity at multiple levels. By carrying out the perturbation analysis, we established that neurons can have long membrane time constants (8-16 ms) and balanced synaptic activations, and yet function collectively in such a way that synchrony within a time window of 4 ms significantly affects the rates and selectivity of the responses to visual stimuli. The simulations also revealed a complex interplay, at the network level, between synchrony of firing and rate of firing. The dynamic consequences of firing synchrony were most evident when spike jittering was applied to specific polysynaptic loops involving corticocortical and corticothalamic connections. These results support the view that firing synchrony within thalamocortical and corticocortical loops plays a causal role in the cooperative and competitive neural interactions that produce pattern-selective responses in the cortex.