George Gabriel Stokes as a biologist

It is universally acknowledged that George Gabriel Stokes (1819–1903) was a polymath who made major contributions to the fields of mathematics, chemistry, physics, fluidics and optics. However, his contributions to biology have received far less attention and this brief communication examines two of Stokes' major biological contributions, namely his description of the phenomenon of fluorescence and his studies on the changes in the colour of blood following oxidation and reduction. The paper on fluorescence is discussed because in it, Stokes demonstrates his wide-ranging biological knowledge and because the use of fluorescence is an invaluable experimental tool in biology. It was by developing the experimental approaches and equipment used to investigate fluorescence that Stokes then applied these to other investigations, including that of blood. From what we now know, what Stokes was describing in his paper on blood were the changes in the configuration of the haemoglobin molecule upon the acquisition and release of oxygen. This article is part of the theme issue ‘Stokes at 200 (part 2)'.

Newborn Screening for Sickle Cell Disease in Tanzania: The Past, Present and Future

Sickle Cell Disease (SCD) is an inherited disorder of the Haemoglobin molecule of the red blood cells that is associated with serious complications and reduced life expectancy. Over 75% of people with SCD live in Sub-Saharan Africa (SSA), and this proportion are projected to increase to 85% by the year 2050. In Tanzania, approximately 11,000 babies are born with SCD each year, ranking 5th in the world. The high prevalence of SCD in SSA is compounded by the disproportionately higher mortality compared to that observed in the high-income countries. In Tanzania, SCD is a major contributor to under-five mortality and is estimated to account for 7% of all-cause mortality in this age group. Newborn screening (NBS) is the practice of testing babies right after delivery to ascertain whether they have diseases that are potentially lethal if not treated early. Where routinely practiced, NBS has significantly reduced morbidity and mortality associated with such diseases. The Sickle Cell Programme at Muhimbili University of Health and Allied Sciences (MUHAS) in Dar-es-salaam and Bugando Medical Center in Mwanza have both conducted pilot NBS for SCD, showing that the intervention is generally feasible and acceptable in Tanzania. The successful introduction and expansion of NBS in Tanzania will require careful planning and advocacy at community to national level.

A New Model for the Oxyhaemoglobin Dissociation Curve

This paper describes a new model for the oxygen-haemoglobin dissociation curve in humans. The model is based on the known structural alterations that occur in the quaternary haemoglobin molecule during oxygenation and deoxygenation. The two alternative structures, tense and relaxed, are described using hyperbolic tangent curves and linked with a probability function to obtain the completed mathematical description of the oxygen-haemoglobin dissociation curve. Model accuracy is assessed by a bias/precision analysis of calculated logit (S) and P50 against gold standard data. A mechanism for the transition between the two structures involving the chloride ion as a major allosteric effector is proposed. Results were analysed against the Siggaard-Andersen model for bias, precision and calculated P50 in four saturation ranges—0.00<SO 2< 1.00, 0.20<SO 2< 0.80, 0.90<SO 2< 1.00 and 0.97<SO 2< 1.00. In each range except for 0.20<SO 2 <0.80, bias, precision and calculated P50 for the new model are significantly better (P<0.05). Analysis of calculated P50 across the entire saturation range revealed significant drift out of the acceptable range in the Siggaard-Andersen model for SO 2 >0.92. The new model remained within tolerance across the saturation range 0.00<SO 2 <1.00. The new model is significantly more accurate than the popular Siggaard-Andersen model, particularly in the range SO 2> 0.90.

Isolation of Fasciola hepatica haemoglobin

SUMMARYA haemoprotein released in vitro by adult Fasciola hepatica was purified by gel filtration chromatography on Sephacryl S-200 and ion-exchange chromatography on DEAE-Sepharose. The molecule, with an apparent molecular weight of > 200 kDa, contains a haem group and has absorption spectra characteristics similar to haemoglobins. N-terminal amino acid sequence analysis revealed no similarity between the F. hepatica haemoglobin and other vertebrate or invertebrate haemoglobins. Antibodies to the haemoglobin molecule can be detected in the sera of F. hepatica-infected bovines as early as 1 week after infection.