Ventilatory response to hypercapnia is increased after 4 h of head down bed rest.

Head-down bed rest (HDBR) has previously been shown to alter cerebrovascular and autonomic control. Previous work found that sustained HDBR (≥ 20 days) attenuates the hypercapnic ventilatory response (HCVR); however, little is known about shorter-term effects of HDBR nor the influence of HDBR on the hypoxic ventilatory response (HVR). We investigated the effect of 4-h HDBR on HCVR and HVR and hypothesized attenuated ventilatory responses due to greater carotid and brain blood flow. Cardiorespiratory responses of young men (n = 11) and women (n = 3) to 5% CO2 or 10% O2 before and after 4-h HDBR were examined. HDBR resulted in lower HR, lower cardiac output index, lower common carotid artery flow, higher SpO2, and higher pulse wave velocity. After HDBR, tidal volume and ventilation responses to 5% CO2 were enhanced (all P < 0.05), yet no other changes in cardiorespiratory variables were evident. There was no influence of HDBR on the cardiorespiratory responses to hypoxia (all P > 0.05). Short-duration HDBR does not alter the HVR, yet enhances the HCVR, which we hypothesize is a consequence of cephalic CO2 accumulation from cerebral congestion.

Ferrous sulphate oxidation using Thiobacillus ferrooxidans cells immobilised on sand for the purpose of treating acid mine-drainage.

Thiobacillus ferrooxidans was immobilised on sand (size 0.85 mm to 1.18 mm) for use in a repeated batch and continuously operated packed-bed bioreactor which has not been previously reported in the literature. Repeated batch operation resulted in the complete oxidation of ferrous to ferric iron. The bacteria were active immediately after 3-4 weeks in a non-aqueous medium; i.e. the sand was allowed to dry out, demonstrating the stability of the system. A lag phase of 28 days was recorded when the sand was stored dried in a sealed container for 16 weeks compared with a lag phase of 13 days for a sample frozen for 18 weeks. After a period of 10 days, continuous operation of the reactor at a dilution rate of 0.64 h(-1) resulted in 95-99% oxidation of ferrous iron or 0.31-0.33 kg m(-3) h(-1). With the use of a scanning electron microscope, images were recorded of Thiobacillus ferrooxidans on sand.

Probing the 121-136 domain of lecithin:cholesterol acyltransferase using antibodies.

Lecithin:cholesterol acyltransferase (LCAT) catalyzes the esterification of plasma lipoprotein cholesterol in mammals as part of the reverse cholesterol transport pathway. Studies of the natural mutations of LCAT revealed a region that is highly sensitive to mutations (residues 121-136) and it is highly conserved in six animal species. The purpose of these studies was to investigate the reactivity of wild type and several mutated forms of LCAT, with a series polyclonal antibodies to further characterize this specific domain (residues 121-136). Two polyclonal antibodies directed against the whole enzyme, one against human plasma LCAT and the other against purified recombinant LCAT, and one site specific polyclonal antibody, directed against the 121-136 region of LCAT, were employed. All three antibodies reacted with a recombinant form of purified LCAT; however, only the polyclonal antibodies directed against the whole enzyme were able to recognize the LCAT when it was adsorbed to a hydrophobic surface in a solid phase immunoassay, or when bound to HDL in a sink immunoassay. These findings indicate that the epitope(s) of the 121-136 region are not accessible to antibodies under these conditions. Three mutant forms of LCAT, representing alterations in the 121-136 region, were also examined for their immunoreactivity with the same panel of antibodies and compared to the wild-type enzyme. These studies demonstrate that in its native configuration the 121-136 region of LCAT is likely to reside on a surface of LCAT. Furthermore, mutations within this region appear to markedly impact the exposure of epitopes at additional sites. These findings suggest that the 121-136 region could play an important role in enzyme interaction with its hydrophobic lipoprotein substrates as mutations within this region appear to alter enzyme conformation, catalytic activity, and the specificity of LCAT.

Some factors affecting the size of nylon 6-10 microcapsules prepared by interfacial polymerization in a high-voltage electric field.

The effect of process variables such as nozzle size, flow-rate of dispersed phase, inter-electrode distance, and presence of an acid acceptor and a thickening agent in the dispersed phase, on the production and size distribution of nylon 6-10 microcapsules prepared by interfacial polymerization in a high-voltage electric field was studied. Factors which increased the intensity of the electrostatic forces acting upon the droplets formed, such as increasing nozzle diameter at constant aqueous phase flow-rate and decreasing inter-electrode distance, were found to decrease the capsule size while those which enhanced the availability of the aqueous phase monomer for the polymerization reaction, such as the addition of an acid acceptor and a thickening agent, resulted in an increase in the average size of the capsules obtained. Free flowing capsules and a reduction in the rate of diacid chloride hydrolysis during the process were also obtained with increasing concentration of the thickening agent in the aqueous phase.

X-linked spinomuscular atrophy: a kindred with associated abnormal androgen receptor binding.

We studied androgen receptor function in cultured scrotal skin fibroblasts from eight subjects with X-linked spinal and bulbar muscular atrophy (SBMA) (Kennedy's syndrome) from four families. The neuromuscular and endocrine features were similar in all patients. High-affinity dihydrotestosterone binding (Bmax) was decreased in three patients from one family (average, 11.1 fmol/mg) similar to values in subjects with androgen resistance syndromes. Bmax was normal in five SBMA patients from three other families (average, 26.0 fmol/mg). This finding provides direct evidence for abnormal androgen receptor function in some patients with SBMA. There was some correlation between severity of neuromuscular and endocrine dysfunction, providing further evidence that the two types of manifestations are related.

Innominate osteotomy in Perthes disease.

A retrospective study was performed in 27 patients who underwent innominate osteotomy for the treatment of severe Perthes disease. Time intervals between surgery and final follow-up ranged from 5 years to 16 years 4 months. Preoperative and postoperative periods of treatment were often more prolonged than those reported by Salter. One-half of the patients were less than 6 years of age at onset of the disease. A number of patients had significant deformity of the femoral head. Nevertheless, clinically good or fair results were obtained in 88% of the patients and poor results were found in 12%.

Influence of lung volume on the mixing defect for an inert gas.

UNLABELLED: For quantitative assessment of how gas mixing in the lung compares to the ideal of perfect mixing, it is necessary to measure pre-inspiratory lung volume as well as to study the inhaled and exhaled gas. Normal young-adult persons in the seated position assumed various lung volumes and then took 1-L test breaths (11% Ar, 22% O2 in N2). Integration of concentration at the mouth against volume yielded amounts of Ar inhaled, exhaled and retained; un-exhaled concentration in the lung after the single breath was calculated from amount retained divided by lung volume (measured by rebreathing). Retention was 60% of the inhaled amount when pre-inspiratory volume was above FRC and less when it was below. Series dead space increased with lung volume. End-tidal Ar was the same as, or slightly above, the concentration predicted for perfect mixing and un-exhaled Ar was slightly below the perfect-mix concentration. INTERPRETATION: three separable influences decrease the transfer of inspirate to the resident gas. A dilution effect, predictable from the volumes involved, decreases retention at low lung volumes. An enlarged series dead space decreases retention at high volumes. In normal persons, a mixing defect that is attributable to poor distribution or incomplete gas-phase diffusion is small and can be ascribed almost completely to the part of the expirate that gives rise to the slope of the alveolar plateau, except when breaths are taken at very low lung volumes.