Situational analysis of varying models of adherence support and loss to follow up rates; findings from 27 treatment facilities in eight resource limited countries

OBJECTIVES

Large-scale provision of ART in the absence of viral load monitoring, resistance testing, and limited second-line treatment options places adherence support as a vital therapeutic intervention. We aimed to compare patient loss to follow up rates with the degree of adherence support through a retrospective review of patients enrolled in the AIDSRelief program between August 2004 and June 2005.

METHODS

Loss to follow up data were analysed and programs were categorised into one of four tiered levels of adherence support models: Tier I, II, III, and IV which increase from lowest to highest support. Bivariate and t-test analyses were used to test for significant differences between the models.

RESULTS

13,391 patients at 27 treatment facilities from six African and two Caribbean countries began antiretroviral therapy within the first year of the AIDSRelief program. The mean loss to follow up within the first year was 7.5%. Eight facilities were Tier I, three (Tier II), nine (Tier III), and seven (Tier IV). Facilities in Tier I had a loss to follow up rate of 14%, Tier II (10%), Tier III (5%), and Tier IV (1%). The proportion of loss to follow up for Tier I and Tier III were significantly different from each other (P < 0.02), as were Tier I and Tier IV (P < 0.006). There were differences between Tier II and Tier IV (P < 0.009) as well as Tier III and Tier IV (P < 0.017).

CONCLUSION

These data strongly support the use of proactive adherence support programs, beyond routine patient counselling and defaulter tracking to support the'public health approach'to ART.

Serum and seminal plasma hormonal profiles of infertile Nigerian male

Male infertility constitutes a worldwide problem, especially in Nigeria where most men do not readily accept that they may contribute to the couple's infertility. In order to assess hormonal disturbances in the male infertility we compared male reproductive hormonal levels in human serum and seminal plasma and evaluated the hypothalamic-pituitary-testicular-axis in infertile Nigerian males. The biophysical semen parameters were assessed by W.H.O. standard manual method. Serum and seminal plasma male reproductive hormones (Leutinizing hormones, Follicular stimulating hormone, Prolactin and Testosterone) were measured by Enzyme Immunoassay (EIA) technique of W.H.O. in sixty (60) infertile adult male Nigerians (Oligospermic; n = 40 and azoopermic; n = 20) and forty controls of proven fertility (Normospermic subjects; n = 40). The results show that the serum concentrations of gonadotropins (LH and FSH) were significantly higher (P<0.05) in infertile subjects than controls. Patterns of serum prolactin levels were similar. The values of gonadotropins in serum were significantly higher (P<0.05) than those of seminal plasma. Seminal plasma testosterone in infertile subjects was significantly higher (P<0.005) than that of controls but the serum levels of testosterone were significantly higher (P<0.05) in azoospermic than oligospermic subjects and controls. There was no significant correlation between serum hormonal level and seminal plasma hormonal level in all the groups (P<0.05). We concluded that male infertility in Nigerians is characterized by hyperprolactinaemia, raised serum gonadotropins (LH, FSH), and raised seminal plasma testosterone. Hormonal profiles in serum and seminal plasma were not significantly correlated, and hence cannot be used as exclusive alternative in male infertility investigations. The observed spermogram in spite of significant elevation of seminal plasma testosterone in infertile males investigated suggests Sertoli cells malfunction.

In search of susceptibility genes for type 2 diabetes in West Africa: the design and results of the first phase of the AADM study

PURPOSE

The purpose of this study is to map type 2 diabetes susceptibility genes in West African ancestral populations of African-Americans, through an international collaboration between West African and US investigators.

DESIGN AND METHODS

Affected sib-pairs (ASP) along with unaffected spouse controls are being enrolled and examined in West Africa, with two sites established in Ghana (Accra and Kumasi) and three in Nigeria (Enugu, Ibadan, and Lagos). Eligible participants are invited to study clinics to obtain detailed epidemiologic, family, and medical history information. Blood samples are drawn from each participant to measure glucose, insulin, C-peptide, total cholesterol, LDL, HDL, triglycerides, albumin, creatinine, urea, uric acid, total calcium and to detect autoantibodies to glutamic acid decarboxylase (GAD). DNA is isolated from frozen white blood cells obtained from 20 ml of EDTA whole blood samples.

RESULTS

With full informed consent, 162 individuals from 78 families have been enrolled and examined since the Africa America Diabetes Mellitus (AADM) study began in June of 1997. Logistics of field examinations and specimen shipping have been successfully established. At the end of the third year of field activity (September 2000) the AADM study will have enrolled and performed comprehensive examination on 400 ASP with type 2 diabetes, for a minimum of 800 cases and 200 controls from Ghana and Nigeria. At the current participation rate, the goal of 400 sib-pairs and 200 controls will be met before the scheduled closing date.

CONCLUSIONS

The AADM study will create a comprehensive epidemiologic and genetic resource that will facilitate a powerful genome-wide search for West African susceptibility genes to type 2 diabetes.

Predictive value of abdominal obesity cut-off points for hypertension in blacks from west African and Caribbean island nations

BACKGROUND

Waist circumferences (WC) >/=94 cm for men and >/=80 cm for women (action level I) and >/=102 cm for men and >/=88 cm for women (action level II) have been suggested as limits for health promotion purposes to alert the general public to the need for weight loss. In this analysis we examined the ability of the above cut-off points to correctly identify subjects with or without hypertension in Nigeria, Cameroon, Jamaica, St Lucia and Barbados. We also determined population- and gender-specific abdominal adiposity cut-off points for epidemiological identification of risk of hypertension.

METHODS

Waist measurement was made at the narrowest part of the torso as seen from the front or at midpoint between the bottom of the rib cage and 2 cm above the top of the iliac crest. Sensitivity and specificity of the established WC cut-off points for hypertension were compared across sites. With receiver operating characteristics (ROC), population- and gender-specific cut-off points associated with risk of hypertension were determined over the entire range of WC values.

RESULTS

Predictive abilities of the established WC cut-off points for hypertension were poor compared to the specific cut-off points estimated for each population. Different values of WC were associated with increased risk of hypertension in these populations. In men, WC cut-off points of 76, 81, 80, 83 and 87 cm provided the highest sensitivity for identifying hypertensives in Nigeria, Cameroon, Jamaica, St Lucia and Barbados, respectively. The analogous cut-off points in women were 72, 82, 85, 86 and 88 cm.

CONCLUSIONS

The waist cut-off points from this study represent values for epidemiological identification of risk of hypertension. For the purpose of health promotion, the decision on what cut-off points to use must be made by considering other additional factors including overall impact on health due to intervention (e.g. weight reduction) and potential burden on health services if a low cut-off point is employed. There is a need to develop abdominal adiposity cut-off points associated with increased risks for cardiovascular diseases in different societies, especially for those populations where the distribution of obesity and associated risk factors tends to be very different from those of the technologically advanced nations. International Journal of Obesity (2000) 24, 180-186

Association of waist circumference with risk of hypertension and type 2 diabetes in Nigerians, Jamaicans, and African-Americans

OBJECTIVE

Prior studies have supported that waist circumference correlates better with visceral adipose tissue and is a better predictor of cardiovascular disease than are BMI and waist-to-hip ratio. In this study, we reexamine the role of waist size on the risk of hypertension and type 2 diabetes in African-origin populations from three contrasting environments.

RESEARCH DESIGN AND METHODS

A cross-sectional survey was conducted of 5,042 men and women 25-74 years of age from Nigeria, Jamaica, and the U.S. The relationship between waist, blood pressure, and fasting blood glucose was assessed using multiple linear regression analyses. Logistic regression analyses using sex-specific empirical waist cut-points were used to determine the risks of hypertension and type 2 diabetes.

RESULTS

Waist circumference was positively correlated with blood pressure and fasting blood glucose (P < 0.05). Increasing waist quartiles were significantly associated with higher risks of hypertension in the three populations, as estimated from age-adjusted odds ratios obtained from sex-specific logistic regression models. A highly elevated risk of type 2 diabetes-10-fold for Jamaican men and 23-fold for African-American women-was observed in the comparison of lowest to highest quartiles of waist circumference.

CONCLUSIONS

Substantial reduction in hypertension and diabetes in men and women is achievable if the waist size is decreased in these populations. Intervention programs designed to reduce waist circumference through lifestyle modification, including exercise and diet, may have significant public health significance in reducing the incidence of hypertension and adult-onset diabetes in these populations.

The prevalence of hypertension in seven populations of west African origin

OBJECTIVES

This study was undertaken to describe the distribution of blood pressures, hypertension prevalence, and associated risk factors among seven populations of West African origin.

METHODS

The rates of hypertension in West Africa (Nigeria and Cameroon), the Caribbean (Jamaica, St. Lucia, Barbados), and the United States (metropolitan Chicago, Illinois) were compared on the basis of a highly standardized collaborative protocol. After researchers were given central training in survey methods, population-based samples of 800 to 2500 adults over the age of 25 were examined in seven sites, yielding a total sample of 10014.

RESULTS

A consistent gradient of hypertension prevalence was observed, rising from 16% in West Africa to 26% in the Caribbean and 33% in the United States. Mean blood pressures were similar among persons aged 25 to 34, while the increase in hypertension prevalence with age was twice as steep in the United States as in Africa. Environmental factors, most notably obesity and the intake of sodium and potassium, varied consistently with disease prevalence across regions.

CONCLUSION

The findings demonstrate the determining role of social conditions in the evolution of hypertension risk in these populations.

Standardization of blood pressure measurement in an international comparative study

In the context of a collaborative study on the epidemiology of hypertension in populations of West African origin procedures for standardization of the measurement of blood pressure were evaluated. Comparisons of mean levels of blood pressure, which in large part determine prevalence rates, are highly sensitive to differences in technique. While rotating a single field team may be the ideal approach to multisite studies, it is not practical in international collaborative research. Appropriate techniques to standardize multiple teams over a long period of time have not been well developed, however. In the present study 8981 individuals were examined in eight sites in six countries with the standard mercury sphygmomanometer. An evaluation of the effectiveness of central training, site visits, monitoring of digit preference, and the use of an electronic device for internal standardization is described. In all but one of the sites reliability was high and comparable to the observers at the Coordinating Center. Digit preference for the entire set of measurements was limited (frequency of terminal zero = 23.5% for systolic and 28.9% for diastolic readings) and could be shown to have virtually no effect on prevalence rates or correlation estimates. Mean differences among observers within a given site and between sites were small (+/- 0-5 mmHg). While logistically complex, these methods can provide the basis for standardization in international comparative blood pressure surveys.

Distribution of anthropometric variables and the prevalence of obesity in populations of west African origin: the International Collaborative Study on Hypertension in Blacks (ICSHIB)

A survey of the prevalence of hypertension and associated risk factors including obesity was carried out among persons of West African heritage currently living in societies at different stages of social, economic and technological development. We present here the distribution of several anthropometric variables and the prevalence of obesity in these populations. Using a standard protocol with centralized training of field staff, 7,439 men and women aged 24 to 75 from six multinational sites were recruited and examined. Although men were taller, women were more obese across sites. Body mass index (BMI) and consequently the prevalence of overweight and obesity increased with westernization from rural African subsistence farming communities to suburban Chicago. Average BMI increased with age until about age 54, and then began to decline or at least level off. The mean BMI for African-American men and women was 27.1kg/m2 and 30.8kg/m2, respectively. Men displayed high levels of centripetal fatness, measured as the waist-to-hip ratio (WHR), compared to the women across site. Based on the US Department of Agriculture guidelines, 22.6% and 56.9% of the African-American men and women had elevated WHR. Although account must be taken of the important contribution of an individual's genetic background, this multinational study of persons with similar heritage clearly shows the potent impact of current environmental factors on the distribution and level of obesity.

Plasma immunoglobulin, total protein and albumin levels during Norplant use by Nigerian women

OBJECTIVE

To determine the effect of Norplant on plasma immunoglobulins, albumin and total proteins.

DESIGN

A longitudinal prospective study of Norplant (six capsules) subdermal contraceptive implant acceptors.

SETTING

Family Planning Clinic, University College Hospital, Ibadan, Nigeria.

PATIENTS

36 women volunteers aged 18-40 years on Norplant.

MAIN OUTCOME MEASURES

Serum immunoglobulins, albumin and total protein before, one, three and 12 months after Norplant insertion.

RESULTS

No statistically significant changes were observed in plasma levels of IgA, IgM and total proteins but plasma levels of IgG showed statistically significant increases after one, three and 12 months on Norplant.

CONCLUSION

Norplant does not seem to alter IgM, IgA, albumin and total protein levels over a period of 12 months. It, however, induces significant changes in IgG levels at one, three and 12 months after insertion. These changes are less marked by the end of 12 months.

Blood pressure and educational level among factory workers in Ibadan, Nigeria

An epidemiological survey of blood pressure was carried out among men employed at a single factory in Ibadan, Nigeria. All available employees participated, with only four persons excluded at the time of analysis for missing data. Hypertension was uncommon (blood pressure greater than or equal to 160/95 = 8%) and little rise in mean blood pressure was observed with age. Obesity was likewise uncommon, although body mass index was related to blood pressure (r = 0.22; P less than 0.01). Contrary to reports from Western industrialised countries, education was found to have a significant positive association with blood pressure, and this finding was independent of age, body mass index, pulse, and alcohol consumption. The process of modernisation is associated with rising blood pressure in West Africa at the present time, but the absolute risk remains low.

Plasma levels of digitalis-like substance in pregnancy-induced hypertension in Nigeria

Digitalis-like substance or plasma inhibitor factor was measured by a competitive binding method in 56 subjects comprising: (1) 12 normotensive normally menstruating non-pregnant women without a family history of hypertension; (2) 13 normotensive normally menstruating non-pregnant women with a family history of hypertension; (3) 15 normotensive pregnant subjects without a family history of hypertension; and (4) 16 subjects with clinical features of pregnancy-induced hypertension. Even though the mean value (1.14 +/- 0.12) of the inhibitor factor (expressed as KD ratios) in the non-pregnant women with family history was slightly higher than the mean value (0.95 +/- 0.12) in the non-pregnant women without a family history, the difference did not attain statistical significance. The mean value (1.25 +/- 0.24) of the inhibitor factor in the pregnant subjects without family history was, however, significantly elevated when compared with the non-pregnant subject without family history (P less than 0.05). The inhibitor factor levels in the subjects with pregnancy-induced hypertension were generally lower than those of the normotensive pregnant subjects, although the difference was not statistically significant. The relevance of these results to the understanding of the pathophysiology of pregnancy-induced hypertension is discussed.

Uraemia and adrenocortical function in Nigerian subjects

In assessing the pituitary-adrenal axis of uraemic Nigerians, we investigated the circadian rhythm of plasma cortisol secretion, the response to the overnight dexamethasone (1 mg) suppression test and the pattern of excretion of urinary free cortisol (UFC) in 10 uraemic subjects and nine non-uraemic controls. Basal (0800 h) plasma cortisol levels were similar in both uraemic (mean +/- s.e.m.; 224 +/- 36 nmol/l) and non-uraemic (218 +/- 47 nmol/l) subjects. The non-uraemic subjects demonstrated the normal late night (2300 h) reduction in cortisol levels but this was absent in uraemic subjects in whom the basal and late night values were similar. Post-dexamethasone (0800 h) values were suppressed by 80% in non-uraemic subjects (P less than 0.01) from 218 +/- 47 nmol/l (at 2300 h) to 44 +/- 16 nmol/l (at 0800 h), whereas there was lack of suppression (P greater than 0.05) in values from uraemic subjects (224 +/- 36 nmol/l at 2300 h and 210 +/- 39 nmol/l at 0800 h). Irrespective of the degree of renal impairment in uraemic subjects, the 24 h UFC excretion was significantly greater (P less than 0.05) (1126 +/- 403 nmol/24 h) compared with non-uraemic subjects (342 +/- 94 nmol/24 h). These results confirm previous observations in Caucasians and reaffirm the existence of a pseudo-Cushingoid state in uraemia which may contribute to the associated hypertension and electrolyte abnormalities.

Plasma levels of digitalis-like substance in Nigerians with essential hypertension

A plasma Na+-K+ ATPase inhibitor, which is estimated by a technique in which it competes with ouabain for binding on red cells, was measured in three groups of individuals: (a) normotensive subjects without a family history of hypertension, (b) normotensive subjects with a family history of hypertension, (c) untreated essential hypertensive subjects. The mean value of the inhibitor in group (b) subjects was significantly higher than the mean value in group (a). The mean value in group (c) subjects was also significantly higher than in group (a) subjects. However, the means of the values in groups (b) and (c) were not significantly different. There was a significant positive correlation between the levels of the inhibitor and the urinary Na+ excretion in all subjects. However, there was no correlation between the inhibitor levels and mean arterial pressure. The relevance of these results to the pathophysiology of hypertension in the black African subject is discussed.

Nitrogen balance study in young Nigerian adult males using four levels of protein intake

1. The present study was carried out to estimate precisely, via the nitrogen balance technique, the protein requirement of Nigerians (earlier estimated via the obligatory N method) using graded levels of protein intake. 2. Fifteen medical students of the University of Ibadan who volunteered to participate in the study were given graded levels of protein (0.3, 0.45, 0.6 and 0.75 g/kg body-weight per d) derived from foods similar to those usually consumed by the subjects. 3. Each subject was given each of the dietary protein levels for a period of 10 d. Subjects were divided into two groups and the feeding pattern followed a criss-cross design with one group starting with the highest level of protein intake (0.3 g). Mean energy intake during each of the eleven experimental periods was maintained at 0.2 MJ/kg per d. After an initial 5 d adaptation period in each experimental period, 24 h urine and faecal samples were collected in marked containers for five consecutive days for N determination. 4. Mean N balance during consumption of the four protein levels (0.30, 0.45, 0.6 and 0.75 g/kg) were -11.02 (SD 8.07), -9.90 (SD 6.64), +9.70 (SD 4.15) and +5.13 (SD 4.62) respectively. Using regression analysis, the mean daily N requirement was estimated at 110.25 mg N/kg body-weight (0.69 g protein/kg body-weight). Estimates of allowances for individual variations to cover 97.5% of the population adjusted this value to 0.75 g protein/kg body-weight. Net protein utilization for the diet at maintenance level was estimated at 57.5.

Plasma renin activity and plasma aldosterone concentrations in normotensive pregnant Nigerians

Plasma renin activity (PRA) and plasma aldosterone concentrations were determined in thirty-four normotensive pregnant subjects, sixteen subjects who were examined 6 weeks post-partum and sixteen non-pregnant controls. Plasma renin activity and plasma aldosterone concentrations increased sequentially in pregnancy i.e. there were progressive significant increases when the values of the first, second and third trimesters were compared. The values for the post-partum subjects and the non-pregnant controls were not significantly different. There was no significant correlation between any pair of the following indices: mean arterial pressure (MAP), PRA and plasma aldosterone. The results are discussed in the light of the present state of knowledge of the pathogenesis of pregnancy-induced hypertension (PIH).

Sequential hormone measurements after first trimester abortion in normal Nigerian women

This study looks at the dynamics of the pituitary hormones and progesterone in normal adult Nigerian females during their first postabortal cycle. Serial determinations of serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PrL) and progesterone were carried out on eleven normal Nigerian women during the first postabortal period after menstrual regulation. Nine out of the eleven subjects (82%) attained LH peaks within the first 22 days after menstrual regulation, seven had discernible FSH peaks and seven had serum progesterone concentrations greater than 6 nmol/l during the second half of the study period. Subjects probably ovulated during the first postabortal cycle; serial LH seems to be the most reliable index of ovulation in our subjects. We hope these data will aid in development of effective family planning strategies for women in the first postabortal cycle.

Sequential hormone measurements after menstrual regulation in normal Nigerian women

The objective of this study was to examine the dynamics of the pituitary hormones (LH, FSH and Prolactin) and Progesterone in normal adult Nigerian women during the first cycle after a menstrual regulation for delayed periods. Hence, eleven healthy volunteers aged between 19 and 35 years were recruited. All the subjects had consulted the Family Planning Clinic for menstrual regulation. Venepuncture was performed immediately before and every other day after the procedure until the onset of the first menstrual period. Serum from the samples were stored at -20 degrees C and later assayed for LH, FSH, Prolactin and Progesterone. The results showed that nine patients (82%) had a demonstrable LH peak whilst seven patients (64%) had a luteal phase serum progesterone in excess of 6 nmol/l. These criteria were used for the diagnosis of ovulation. The combination of two or three indices i.e. LH + FSH peak (64%) LH + Progesterone (64%) LH + FSH + Progesterone (55%) did not seem to confer any special advantages in terms of the diagnosis of ovulation. These results are considered as further evidence for the need to provide contraception in the first cycle after an abortion in women who do not wish to get pregnant immediately.

Plasma renin activity and plasma aldosterone concentrations in untreated Nigerians with essential hypertension

On the basis of existing information we set out to test an hypothesis that 'the blood volume and more specifically total body sodium and sodium disposition in the body play a more important role in blood-pressure regulation and the pathophysiology of hypertension than other regulatory mechanisms in the indigenous African'. To achieve our objective, ninety-eight newly diagnosed unmedicated hypertensives with adequate renal function were admitted to the study. Fifty-one (52%) of the subjects were males while forty-seven (48%) were females. Their ages ranged between 21 and 70 years. All grades of the disease were adequately represented with thirty (31%) being mild, fifty (51%) moderate and eighteen (18.4%) in severe phase of the disease. Blood-pressure measurements and blood samples were obtained in the supine position in all the patients after adequate preparation. Plasma renin activity (PRA) and plasma aldosterone concentrations were measured by specific radioimmunoassays. Contrary to what obtains elsewhere, seventy-six (77%) of our patients were of the low renin status, twelve (12%) of whom had undetectable levels by our assay system. Eighteen (18.4%) had PRA levels in the medium range and five (5.1%) in the high range. In a cohort, forty-two (43%) of our ninety-eight patients, we estimated plasma aldosterone levels. The results obtained showed that the plasma aldosterone concentrations were significantly higher in hypertensives than in our normal controls (P less than 0.01). There was lack of correlation between PRA or plasma aldosterone when compared to mean arterial pressure or serum Na+. These results are discussed in relation to the management of hypertension in our environment.

HbA1C measured by a colorimetric method in normal and diabetic Nigerian subjects

Glycosylation of haemoglobin was evaluated in 30 normal adult Nigerians and 60 diabetic adult Nigerians who were at various stages of blood glucose control, by measuring ketoamine-linked hexoses in haemoglobin. These hexoses were converted by digestion with 1 M oxalic acid for 4.5 h at 100 degrees C to 5-hydroxymethylfurfural, which was measured by reaction with 2 thiobarbituric acid. Glycosylation of haemoglobin was expressed as micromoles (mumol) of fructose per 5% haemoglobin. A mean fructose concentration of 91.0 mumol/1 (s.d. +/- 9.3) was obtained for normal subjects; that for diabetic adult Nigerians was 175.3 mumol/l (s.d. +/- 26.4). There was significant correlation between fasting blood glucose levels and glycosylated haemoglobins in both normal adults (r = 0.77, P less than 0.001) and diabetic adults (r = 0.90, P less than 0.001). The colorimetric method was found to be precise and accurate with an interassay variability of 1.44% and an intra-assay variability of 0.98%.

Serum thyroxine, triiodothyronine, reverse triiodothyronine, thyroid stimulating hormone, thyroxine binding globulin and thyroxine binding pre-albumin concentrations in healthy African adults

A study of the serum concentrations of the thyroid hormones thyroxine (T4), triiodothyronine (T3) and reverse triiodothyronine (rT3), thyrotropin (TSH) and the thyroid hormone binding proteins (thyroxine binding globulin (TBG), and thyroxine binding pre-albumin (TBPA)) in non-hospitalized adult Nigerian African subjects was conducted. The subjects were divided into three subgroups, male subjects, non-pregnant female subjects and pregnant female subjects to highlight peculiarities of each sub-group. All three subgroups showed elevation of TBG concentration as compared to British subjects. A statistically significant difference was observed in the concentrations of T4, T3, and TBG in the pregnant female subjects compared to the male and the non-pregnant subjects. A statistically significant difference was also observed between the concentrations rT3 in the male and pregnant female subjects compared to the non-pregnant female subjects. No statistically significant difference was observed between the concentrations of TSH, and TBPA, in all three subgroups, although the mean values for TSH were highest in the pregnant female subjects and the mean values for TBPA and albumin were lowest in this same group. The significance of these findings are discussed in relation to the evaluation of thyroid function in the adult African subject.

Measurement of membrane potentials (psi) of erythrocytes and white adipocytes by the accumulation of triphenylmethylphosphonium cation

The accumulation of the lipophilic cation, triphenylmethylphosphonium, has been employed to determine the resting membrane potential in human erythrocytes, turkey erythrocytes, and rat white adipocytes. The triphenylmethylphosphonium cation equilibrates rapidly in human erythrocytes in the presence of low concentrations of the hydrophobic anion, tetraphenylborate. Tetraphenylborate does not accelerate the uptake of triphenylmethylphosphonium ion by adipocytes. The cell associated vs. extracellular distribution of the triphenylmethylphosphonium ion is proportional to changes in membrane potential. The distribution of this ion reflects the membrane potential determining concentration of the ion with dominant permeability in a "Nernst" fashion. The resting membrane potentials for the human erythrocyte, turkey erythrocyte, and rat white adipocyte were found to be -8.4 +/- 1.3, -16.8 +/- 1.1, and -58.3 +/- 5.0 mV, respectively, values which compare favorably with values obtained by other methods. In addition, changes in membrane potential can be assessed by following triphenylmethylphosphonium uptake without determining the intracellular water space. The method has been successfully applied to a study of hormonally induced changes in membrane potential of rat white adipocytes.

Serum thyroglobulin measurement in various thyroidal disorders

A specific double antibody radioimmunoassay for human serum thyroglobulin was established. Serum thyroglobulin concentrations were measured in euthyroid non-goitrous subjects and in patients with various specific pathologies of the thyroid gland. Thyroglobulin was detectable in the serum of most euthyroid non-goitrous subjects studied. The serum thyroglobulin concentrations obtained in patients with hyper or hypofunctioning thyroid glands seem to mirror gland activity in terms of hormone production, being high in thyrotoxicosis and low in hypothyroidism. Elevation of serum thyroglobulin concentrations were observed in patients with non-toxic goitres. There was a great deal of overlap in the values obtained in patients with benign goitres and those with malignant lesions making serum thyroglobulin concentration an unreliable discriminant. However, it would seem that once histological diagnosis is established serum thyroglobulin measurements could be useful in the management and follow-up of patients with differentiated primary thyroid malignancies. The likely mechanism(s) of release of thyroglobulin in different thyroidal states and the clinical potential of this new entry into thyroidology are extensively discussed.