Lung mechanics--the inverse problem.

The mechanical properties of the lung are important determinants of its efficacy as a gas exchanging organ. These properties are reflected to a precise degree in the relationships between pressure and flow measured at the mouth. Together with oesophageal pressure, which reflects the pressure in the pleural space, these quantities allow one to usefully indulge in inverse modelling of the lung - that is, identify mathematical models of lung mechanics that give insight into its structure and may be diagnostic of certain diseases. The complexity of such models, however, is limited by the number of distinct components that can be unambiguously resolved from the measured signals. The development of more detailed models requires the availability of experimental methods for obtaining additional input-output information from the lungs. One such method is the so-called alveolar capsule technique which allows alveolar pressures at several sites on the lung surface to be measured directly. This technique has been used in animals to show that the mechanical behaviour of normal lungs in the breathing frequency range is well described by a homogeneously ventilated compartment surrounded by viscoelastic tissue. During bronchoconstriction, however, the lungs can become markedly inhomogeneous resulting from differences in regional resistive and elastic properties. Model ambiguity problems again appear as it becomes impossible to distinguish changes in local resistance from changes in elastance using only the information obtained from alveolar capsules. To push the inverse modelling of the lung one step further, we have recently developed a new technique for quantifying changes in local resistance and elastance by applying broad-band oscillations in flow to the lung through a small hole in the pleura, thereby obtaining an alveolar input impedance.     

Malakoplakia and colorectal adenocarcinoma.

We report a case of malakoplakia in association with colonic adenocarcinoma. Tumour-associated malakoplakia in the gastrointestinal tract is a rare finding, generally confined to the colon. It may be locally aggressive, with invasion of pericolic tissues, but is always located adjacent to the tumour. This contrasts with the often more diffuse, multifocal distribution of colonic malakoplakia in association with other pathologies.     

Zinc in breast milk during prolonged lactation: comparison between the UK and the Gambia

A total of 580 breast milk samples were collected from 56 lactating women living in a rural village community in The Gambia, West Africa, and 92 samples were obtained from 57 lactating women living in Cambridge, England. Total zinc content of each sample was measured by atomic absorption spectrometry, and pooled samples of the Gambian breast milks, representing successive periods of lactation, were fractionated into fat, whey and insoluble casein fractions, to examine zinc distribution. The two sets of milks both exhibited a dramatic decline in total zinc concentrations with increasing duration of lactation, in common with previous studies. However, the UK milks unexpectedly had lower zinc contents at all stages than the Gambian milks. Milk zinc levels were not significantly related to either maternal age or parity in the Gambian women. The proportion of zinc found in the sedimentable fraction remained nearly constant with increasing duration of lactation, but the proportion found in the fat fraction increased and the proportion in the whey fraction declined. These observations are potentially relevant for estimations of milk zinc availability and the fulfillment of zinc requirements by infants, and hence for infant feeding practices.     

The relationship between subtalar and knee joint function as a possible mechanism for running injuries

The purposes of the study were: (1) to evaluate the effects of different surfaces on the relationship between subtalar and knee joint function, and (2) to examine/explore alternative approaches to the evaluation of these relationships. Five subjects ran under four different surface conditions of various hardness, while both rear and sagittal view kinematic data were collected (200 Hz). Critical parameters describing the knee angle and rearfoot motion were examined in conjunction with a curve analysis technique which incorporated slope differences and curve correlations. A repeated measure ANOVA design (surface × subject) was used along with single subject procedures. The results of the study support a strong inter-relationship between pronation and knee joint function via tibial rotation and underlined it as a possible mechanism for injury. Moreover, discrete point analysis might not be the most appropriate methodology for evaluating dynamic functions such as rearfoot motion and knee angle. Extreme methodological care must be exercised when evaluating these functions to avoid oversmoothing and/or masking correlations and differences due to differential subject responses and individual variability. The fact that increased impact force facilitated timing discrepancies between subtalar and knee joint function resulting in a transition of the pronation curve from a unimodal to bimodal configuration, is hypothesized as a possible explanation to better understand the inter-relationships among these lower extremity functions and their relationship to running injuries.     

A novel G protein-coupled receptor kinase gene cloned from 4p16.3.

Within the Huntington's disease (HD) candidate region of 4p16.3, the D4S127 locus displays strong linkage disequilibrium with the defect and anchors a conserved haplotype found on many HD chromosomes. To isolate genes from this region we have applied the exon amplification technique to overlapping cosmids spanning D4S127. Here, we report the discovery of a new gene encoding a novel member of a family of protein kinases that specifically phosphorylate the activated forms of G protein-coupled receptors. Such kinases are thought to participate in desensitization of specific receptors, thereby blocking further signal transduction. This gene must now be carefully scrutinized to determine whether it might be involved in HD.     

Spinal MR findings in neurofibromatosis types 1 and 2.

PURPOSE: To evaluate the frequency and nature of spinal pathology, the frequency of clinically silent lesions, and the potential benefit of screening spinal MR in neurofibromatosis patients. PATIENTS AND METHODS: 28 neurofibromatosis type-1 (NF-1) patients and nine neurofibromatosis type-2 (NF-2) patients were studied with postcontrast spinal MR imaging. RESULTS: NF-1: One patient had a biopsy-proven low-grade glioma; five patients, intradural, extramedullary masses (N = 23); one patient, extradural masses (N = 2) (neurofibromas); 16 patients had bony abnormalities; and three patients thecal sac abnormalities. NF-2: Five patients demonstrated intramedullary masses (five/eight ependymomas); nine patients, intradural, extramedullary masses (meningiomas, schwannomas); and four patients, bony abnormalities. Eight/10 NF-1 and four/nine NF-2 patients had asymptomatic masses. CONCLUSION: Intradural disease is common, often asymptomatic, and often presents at a young age in NF-1 and NF-2 patients. Because of the propensity to develop significant asymptomatic as well as symptomatic intradural disease, screening of the entire spine with MR is recommended in both NF-1 and NF-2 patients.