Insulin and glucose excursion following premeal insulin lispro or repaglinide in cystic fibrosis-related diabetes

OBJECTIVE

Insulin and glucose levels in response to premeal insulin lispro or repaglinide were evaluated in adult patients with cystic fibrosis-related diabetes (CFRD) without fasting hyperglycemia.

RESEARCH DESIGN AND METHODS

Seven patients with CFRD were fed 1,000-kcal liquid mixed meals. Three study conditions were administered in random order on separate mornings: 1) no premeal diabetes medication, 2) insulin lispro, 0.1 unit/kg body wt premeal and 3) repaglinide 1 mg premeal. Glucose and insulin levels were measured every 20 min for 5 h.

RESULTS

Fasting insulin and glucose levels were normal in patients with CFRD, but the peak glucose level was elevated. Insulin lispro significantly decreased the peak glucose level (P = 0.0004) and the 2-h (P = 0.001) and 5-h (P < 0.0001) glucose area under the curve (AUC). Repaglinide significantly decreased the 5-h glucose AUC (P = 0.03). Neither drug completely normalized cystic fibrosis glucose excursion at the doses used for this study. Insulin lispro significantly increased the 5-h insulin AUC (P = 0.04).

CONCLUSIONS

In response to subcutaneous insulin lispro, postprandial glucose excursion was significantly diminished and insulin secretion was enhanced compared with a control meal in which no medication was given to patients with CFRD. The oral agent repaglinide resulted in lesser corrections in these parameters. Neither drug completely normalized glucose or insulin levels, suggesting that the doses chosen for this study were suboptimal. Placebo-controlled longitudinal studies comparing the effectiveness of repaglinide and insulin on glucose metabolic control as well as overall nutrition and body weight are needed to help determine optimal medical treatment of CFRD.

A zinc-sensing receptor triggers the release of intracellular Ca2+ and regulates ion transport

Changes in extracellular zinc concentration participate in modulating fundamental cellular processes such as proliferation, secretion, and ion transport in a mechanism that is not well understood. Here, we show that a micromolar concentration of extracellular zinc triggers a massive release of calcium from thapsigargin-sensitive intracellular pools in the colonocytic cell line HT29. Calcium release was blocked by a phospholipase-C inhibitor, indicating that formation of inositol 1,4,5-triphosphate is required for zinc-dependent calcium release. Zinc influx was not observed, indicating that extracellular zinc triggered the release. The Ca(i)2+ release was zinc specific and could not be triggered by other heavy metals. Furthermore, zinc failed to activate the Ca(2+)-sensing receptor heterologously expressed in HEK293 cells. The zinc-induced Ca(i)2+ rise stimulated the activity of the Na(+)/H(+) exchanger in HT29 cells. Our results indicate that a previously uncharacterized extracellular, G protein-coupled, Zn(2+)-sensing receptor is functional in colonocytes. Because Ca(i)2+ rise is known to regulate key cellular and signal-transduction processes, the zinc-sensing receptor may provide the missing link between extracellular zinc concentration changes and the regulation of cellular processes.

Functional analysis of patient-derived mutations in the Fanconi anemia gene, FANCG/XRCC9

OBJECTIVE

Fanconi anemia (FA) is an autosomal-recessive cancer susceptibility syndrome with seven complementation groups. Six of the FA genes have been cloned (corresponding to subtypes A, C, D2, E, F, and G) and the encoded proteins interact in a common pathway. Patient-derived mutations in FA genes have been helpful in delineating functional domains of FA proteins. The purpose of this work was to subtype FA patient-derived cell lines in our repository and to identify FA gene mutations.

METHODS

We subtyped 62 FA patients as type A, G, C, or non-ACG by using a combination of retroviral gene transfer and immunoblot analysis. Among these FA patients, we identified six FA-G patients for further analysis. We used a strategy involving amplification of FANCG/XRCC9 exons and direct sequencing to identify novel FANCG mutations in cell lines derived from these FA-G patients. We functionally analyzed FANCG mutant alleles by transducing the corresponding cDNAs into a known FA-G indicator cell line and scoring correction of MMC sensitivity.

RESULTS

Our results demonstrate a wide range of mutations in the FANCG gene (splice, nonsense, and missense mutations). Based on this mutational screen, a carboxy terminal functional domain of the FANCG protein appears to be required for complementation of FA-G cells and for normal assembly of the FANCA/FANCG/FANCC protein complex.

CONCLUSION

The identification of patient-derived mutant alleles of FA genes can provide important insights to the function of FA proteins. FA subtyping is also a necessary precondition for gene therapy.

Protein metabolism in clinically stable adult cystic fibrosis patients with abnormal glucose tolerance

Cystic fibrosis (CF) patients are reported to experience chronic protein catabolism. Since diabetes or impaired glucose tolerance (IGT) is common in CF, we hypothesized that their protein catabolic state is related to reduced insulin secretion or reduced insulin action. A total of 12 clinically stable adult CF patients with abnormal glucose tolerance and 12 age-, sex-, and lean body mass-matched healthy control subjects underwent protein turnover studies using L-[1-(13)C]leucine, L-[(15)N]phenylalanine, and L-[(2)H(4)]tyrosine, with and without exogenous insulin infusion. In the baseline fasting state, protein metabolism was entirely normal in CF patients, with no evidence of increased protein catabolism. In contrast, striking abnormalities were seen in CF patients when insulin was infused, since they did not experience normal suppression of the appearance rates of leucine, phenylalanine, or tyrosine (indexes of protein breakdown). At an insulin concentration of 45 +/- 2 microU/ml, normal control subjects suppressed the leucine appearance rate by 19 +/- 5% (P < 0.01), ketoisocaproate appearance rate by 10 +/- 3% (P = 0.03), tyrosine appearance rate by 11 +/- 2% (P = 0.03), and phenylalanine appearance rate by 6 +/- 3% (P = 0.07). Phenylalanine conversion to tyrosine decreased by 22 +/- 7% (P = 0.03). At a similar insulin concentration of 44 +/- 3 microU/ml, normal suppression of amino acid appearance did not occur in CF. The leucine appearance rate decreased by 4 +/- 2% (P = 0.65), ketoisocaproate appearance rate by 1 +/- 2% (P = 0.94), tyrosine appearance rate by 0 +/- 6% (P = 0.56), phenylalanine appearance rate by 5 +/- 6% (P = 0.34), and phenylalanine conversion to tyrosine by 5 +/- 6% (P = 0.95). Poor suppression of the amino acid appearance rate in CF was not related to previously documented glucose tolerance status (IGT or CF-related diabetes without fasting hyperglycemia), fasting insulin levels, the acute insulin response, insulin sensitivity, cytokine or counterregulatory hormone levels, resting energy expenditure, caloric intake, pulmonary function, or clinical status. Protein synthesis was not significantly affected by insulin infusion in either normal control subjects or CF patients. In conclusion, clinically stable adult CF patients have normal indexes of protein breakdown and synthesis in the fasting state. In contrast, elevation of plasma insulin to physiological postprandial levels fails to normally suppress indexes of protein breakdown. It is therefore likely that inability to spare protein during the postprandial state is the cause of protein catabolism in these patients.

Adiposity in childhood predicts obesity and insulin resistance in young adulthood

OBJECTIVE

To determine whether adiposity in children predicts adiposity, insulin resistance, and abnormal lipid levels in young adults.

STUDY DESIGN

Children (n = 31) were recruited into an epidemiologic study at age 13.3 +/- 0.3 years and had blood pressure, weight, and height measured. They were reevaluated at age 21.8 +/- 0.3 years at which time the measurements were repeated, a euglycemic insulin clamp was performed, and fasting lipid levels were measured. All values are expressed as mean +/- SEM. Data were analyzed by analysis of variance and linear regression analysis.

RESULTS

Body mass index (BMI) in childhood (22.6 +/- 0.6) was highly correlated with BMI in young adulthood (26.9 +/- 0.9). Childhood BMI was also inversely correlated with young adult glucose utilization (r = -0.5, P = .006) and positively correlated with total cholesterol (r = 0.37, P = .05), and low-density lipoprotein (LDL) cholesterol (r = 0.48, P = .01).

CONCLUSIONS

These data confirm that adiposity in childhood is a strong predictor of young adult adiposity. In addition, these results demonstrate that cardiovascular risk in young adulthood is highly related to the degree of adiposity as early as age 13.

Smoking and quitting among Irish teenage males

Nicotine addiction in adulthood is usually preceded by exposure to cigarettes in adolescence. A minimal exposure may be sufficient to produce addiction. Strategies to reduce adult smoking must address those factors, which influence teenage smoking. In this study we aimed to establish the prevalence of smoking in male secondary schools, to measure the association between student's smoking status and parental, peer and sibling smoking and to describe attempted quitting. An anonymous questionnaire was given to 1070 male secondary school pupils in two schools in County Louth. Twenty-seven percent of respondents smoked every day or on most days. Having a best friend who smoked was associated with personal smoking (O.R. 11.75, C.I. 8.6-16.08) as was sibling smoking (O.R. 3.49, C.I. 2.67-4.57.) Seventy percent of smokers stated that they wanted to stop and 75% that they had tried to stop. Only five smokers (1.2%) had been advised to quit by their general practitioner. We conclude that smoking is as prevalent among teenage boys in Ireland as it has been shown to be elsewhere and that most teenagers are unable rather than unwilling to stop.

Dorsal cortex lesions impair habituation in turtles (Chrysemys picta)

Two experiments investigated habituation in painted turtles (Chrysemys picta). In the first, turtles were given lesions of the dorsal cortex or sham lesions and then trained on a restraint. Although the sham-lesioned turtles learned to tolerate the restraint, the lesioned animals continued to struggle against it. Thus dorsal cortex lesions disrupted habituation to restraint. In order to test habituation to a looming stimulus in a second experiment, all animals were habituated to the restraint before surgery. Postoperatively they continued to be habituated to the restraint. The looming stimulus was a circular shadow that enlarged suddenly on a screen in front of the turtle. It was presented 5 times per day for 15 days. Between-day or long-term habituation was impaired by dorsal cortex lesions.

Atopic eczema is associated with delayed maturation of the antibody response to pneumococcal vaccine

The aim of this study was to investigate a previously undocumented observation, that children with atopic eczema under 9 years of age tended to have a poor antibody response to Pneumococcal vaccination. Thirty-five children (mean age 8.8 years, range 3-16 years) with moderate to severe atopic eczema but no history of systemic infection were studied retrospectively. Pneumococcal antibody responses after immunization with Pneumovax II were compared with a hospital control group consisting of 36 children (mean age 6.0 years, range 3-16 years) with recurrent upper respiratory tract infections. Only 17% of children with atopic eczema aged 3-8 years responded to Pneumovax. This response was significantly poorer than that of the controls (57%) (odds ratio 0.20, 95% confidence interval (CI) 0.05-0.84, P = 0.03). There were no significant differences in the levels of total IgG2, the component of IgG associated with protective antibody responses to Pneumococcus between the two groups. Delay in maturation of the total IgG and IgG2 antibody response to Pneumococcus is a feature in this group of children with moderately severe atopic eczema.

Stress down regulates milk yield in cows by plasmin induced beta-casein product that blocks K+ channels on the apical membranes

Stress and stress related hormones such as glucocorticoids inhibit lactation in cows. In the present study we propose a novel mechanism connecting stress with plasminogen-plasmin system (PPS) (an enzymatic mechanism in milk, which leads to the breakdown of the major milk protein casein). We show that stress activates the PPS leading to an increase in plasmin activity, and that a distinct plasmin-induced beta-casein breakdown product (fraction 1-28) is a potent blocker of potassium channels in mammary epithelia apical membranes. The reduction in milk production due to dehydration stress or glucocorticoid (dexamethsone) was correlated with the activities of plasmin and channel blocking activity in the milk of the tested cows. The notion that the axis Stress-PPS-beta-casein fraction 1-28 is responsible for the reduction in milk yield is supported by the results of experiments showing that injecting solution composed of casein digest enriched with beta-casein fraction 1-28 to the udder lumen leads to a transient reduction in milk production. Furthermore, injecting a pure beta-casein fraction 1-28 to the udder lumen of goat's lead also to a transient reduction in milk production with kinetics that was similar to the kinetics observed in cows.

Carboxy terminal region of the Fanconi anemia protein, FANCG/XRCC9, is required for functional activity

Fanconi anemia (FA) is an autosomal recessive cancer susceptibility syndrome with eight complementation groups. Four of the FA genes have been cloned, and at least three of the encoded proteins, FANCA, FANCC, and FANCG/XRCC9, interact in a nuclear complex, required for the maintenance of normal chromosome stability. In the current study, mutant forms of the FANCA and FANCG proteins have been generated and analyzed with respect to protein complex formation, nuclear translocation, and functional activity. The results demonstrate that the amino terminal two-thirds of FANCG (FANCG amino acids 1-428) binds to the amino terminal nuclear localization signal (NLS) of the FANCA protein. On the basis of 2-hybrid analysis, the FANCA/FANCG binding is a direct protein-protein interaction. Interestingly, a truncated mutant form of the FANCG protein, lacking the carboxy terminus, binds in a complex with FANCA and translocates to the nucleus; however, this mutant protein fails to bind to FANCC and fails to correct the mitomycin C sensitivity of an FA-G cell line. Taken together, these results demonstrate that binding of FANCG to the amino terminal FANCA NLS sequence is necessary but not sufficient for the functional activity of FANCG. Additional amino acid sequences at the carboxy terminus of FANCG are required for the binding of FANCC in the complex. (Blood. 2000;96:1625-1632)

Trends in pulmonary function in patients with cystic fibrosis correlate with the degree of glucose intolerance at baseline

In patients with cystic fibrosis, CF-related diabetes mellitus (CFRD) has been associated with increased morbidity and mortality. Whether glucose intolerance is also associated with poor outcomes is unclear. To better define these relationships we prospectively followed a group of 152 patients with CF without diabetes for 4 yr. Patients were classified as having normal glucose tolerance (NGT), impaired glucose tolerance (IGT), or CFRD without fasting hyperglycemia (CFRD-No FH). FEV(1), FVC, and body mass index (BMI) were measured at baseline and quarterly. At baseline 45% of the patients had NGT, 38.8% had IGT, and 15.8% had CFRD-No FH. FEV(1), FVC, and BMI at baseline were comparable among these groups (all p > 0.1). After 4 yr an overall decline in FEV(1) and FVC occurred, with no change in BMI. The rates of decline for FEV(1) and FVC correlated with the glucose tolerance groups, with the highest rates of decline occurring among the CFRD-No FH group. In addition, patients in the lowest quartile for insulin production at baseline experienced the highest rates of pulmonary function decline over time, suggesting a relationship between insulin deficiency and clinical deterioration. We conclude that the degree of glucose intolerance is a strong determinant of future lung function decline in patients with CF.

Colonic metastasis of breast carcinoma

Metastasis of breast carcinoma to the colon is a rare occurrence. We report here the case of a 65-year-old patient who presented a stenosing tumor of breast origin, located in the right colon. Some of the regional lymph nodes were infiltrated but no distant metastasis were detected. The primary breast lesion was a 4-cm infiltrating adenocarcinoma, operated 4 years earlier. Surgical removal of the lesion was followed by Endoxan-Epirubicin and 5-Fluororacil chemotherapy and the patient remained disease-free during the 3 years of follow-up. We could find only 2 similar cases reported in the world literature until now. Profound anemia in a patient with a past history of breast carcinoma may indicate colonic metastasis; treatment should be surgery followed by chemotherapy.

Tissue-engineered valved conduits in the pulmonary circulation

OBJECTIVE

Bioprosthetic and mechanical valves and valved conduits are unable to grow, repair, or remodel. In an attempt to overcome these shortcomings, we have evaluated the feasibility of creating 3-leaflet, valved, pulmonary conduits from autologous ovine vascular cells and biodegradable polymers with tissue-engineering techniques.

METHODS

Endothelial cells and vascular medial cells were harvested from ovine carotid arteries. Composite scaffolds of polyglycolic acid and polyhydroxyoctanoates were formed into a conduit, and 3 leaflets (polyhydroxyoctanoates) were sewn into the conduit. These constructs were seeded with autologous medial cells on 4 consecutive days and coated once with autologous endothelial cells. Thirty-one days (+/-3 days) after cell harvesting, 8 seeded and 1 unseeded control constructs were implanted to replace the pulmonary valve and main pulmonary artery on cardiopulmonary bypass. No postoperative anticoagulation was given. Valve function was assessed by means of echocardiography. The constructs were explanted after 1, 2, 4, 6, 8, 12, 16, and 24 weeks and evaluated macroscopically, histologically, and biochemically.

RESULTS

Postoperative echocardiography of the seeded constructs demonstrated no thrombus formation with mild, nonprogressive, valvular regurgitation up to 24 weeks after implantation. Histologic examination showed organized and viable tissue without thrombus. Biochemical assays revealed increasing cellular and extracellular matrix contents. The unseeded construct developed thrombus formation on all 3 leaflets after 4 weeks.

CONCLUSION

This experimental study showed that valved conduits constructed from autologous cells and biodegradable matrix can function in the pulmonary circulation. The progressive cellular and extracellular matrix formation indicates that the remodeling of the tissue-engineered structure continues for at least 6 months.

Cystic fibrosis-related diabetes: an approach to diagnosis and management

Diabetes is a common complication of cystic fibrosis (CF). Because of evidence that it is associated with increased morbidity and mortality, prompt diagnosis and aggressive management of CF-related diabetes (CFRD) is important. The Cystic Fibrosis Foundation held a consensus conference in 1998 to define the current standards for the diagnosis and care of this disease [Moran A, Hardin D, Rodman D et al. Diagnosis, screening, and management of CFRD: a consensus conference report. J Diabetes Res Clin Pract 1999: 45: 61-73]. This article reviews those recommendations, and presents the practical approach to the management of CFRD used at the University of Minnesota.

Absence of a numerical memory span advantage in Japanese Kanji

Research suggests that people's memory span for Arabic numerals is consistently greater than that for digit words written in an alphabet, even when these stimuli have been matched for word length, lexicality, and semantics. It is not clear whether this "numeral advantage" holds true for other scripts. The present study tested this possibility in the case of Japanese kanji (the Chinese characters used in Japanese). 23 Japanese adults responded to stimuli comprised of two sets of random number sequences, one set presented in Arabic numerals and the other in digit word kanji. Each set began with three two-item sequences followed by three three-item sequences and so on, until three 12-item sequences were presented. Consecutive repetition of stimuli was avoided. Memory span was measured as the length of the last correctly recalled item sequence. Results indicated no numeral advantage effect, as there was no significant difference between people's recall of numerals and digit words. Memory strategy in dealing with kanji appears to bear more resemblance to numerals than to words in English.

Diabetes mellitus in cystic fibrosis

Glucose intolerance and diabetes are common complications of cystic fibrosis (CF), affecting up to 75% of the adult population. This article discusses the prevalence and pathophysiology of glucose tolerance abnormalities in CF, and reviews recent recommendations for diagnosis, screening, and management of CF-related diabetes (CFRD).

Guidelines for the diagnosis and therapy of diabetes mellitus in cystic fibrosis

Diabetes is a common complication of cystic fibrosis. Because it is associated with increased morbidity and mortality, prompt diagnosis and aggressive management of cystic fibrosis-related diabetes is important. The Cystic Fibrosis Foundation held a consensus conference in 1998 to define the standards of care for patients with this disease [1[symbol: see text]]. In this article, pathophysiology and management of cystic fibrosis-related diabetes are reviewed.

Insulin resistance during puberty: results from clamp studies in 357 children

Insulin resistance may be an important cause of a constellation of cardiovascular risk factors in adults, and onset of this syndrome may occur in childhood. However, children normally experience transient insulin resistance at puberty. There were 357 normal children (159 girls, 198 boys) age 10-14 years who underwent euglycemic clamp studies to assess the effects of Tanner stage (T), sex, ethnicity, and BMI on insulin resistance. Insulin resistance increased immediately at the onset of puberty (T2), but returned to near prepubertal levels by the end of puberty (T5). Its peak occurred at T3 in both sexes, and girls were more insulin resistant than boys at all T stages. White boys appeared to be more insulin resistant than black boys; no difference was seen between white and black girls. Insulin resistance was strongly related to BMI, triceps skinfold thickness, and waist circumference, and this relationship was independent of Tanner stage or sex. Differences in BMI and adiposity did not, however, entirely explain the insulin resistance of puberty. These results demonstrate that 1) significant differences in insulin resistance are present between boys and girls; 2) insulin resistance increases significantly at T2, T3, and T4, but decreases to near prepubertal levels at T5; and 3) while insulin resistance is related to BMI and anthropometric measures of fatness, these factors do not completely explain the insulin resistance that occurs during the Tanner stages of puberty.

Regulation by P2 agonists of the intracellular calcium concentration in epithelial cells freshly isolated from rat trachea

Epithelial cells were isolated from rat trachea by incubation of the organ in a calcium-free medium. The intracellular concentration of calcium ([Ca(2+)](i)) was measured with the calcium-sensitive fluorescent dye fura2. In resting conditions, the cells maintained a low [Ca(2+)](i) in spite of the presence of millimolar concentration of calcium in the incubation medium. These cells had retained intracellular stores of calcium which were emptied after exposure of the cells to thapsigargin, an inhibitor of intracellular calcium ATPases. Substance P (125 nM) transiently increased 2.5-fold the [Ca(2+)](i). ATP (1 mM) doubled the [Ca(2+)](i) after a few seconds and further induced a sustained increase of the [Ca(2+)](i). Coomassie blue fully blocked the response to ATP and extracellular magnesium only inhibited the delayed response to ATP. Among purinergic analogs, only benzoyl-ATP (Bz-ATP), an agonist on P2X ionotropic purinergic receptors, reproduced the response to ATP. UTP and 2-methylthioATP (two agonists on P2Y metabotropic purinergic receptors) transiently increased the [Ca(2+)](i). Thapsigargin, ATP and Bz-ATP increased the uptake of extracellular calcium. RT-PCR analysis revealed that two metabotropic receptors (P2Y(1) and P2Y(2)) and two ionotropic receptors (P2X(4) and P2X(7)) were expressed by the cells present in the suspension. It is concluded that purinergic agonists can modulate the response of rat tracheal epithelial cells by several mechanisms. The activation of metabotropic receptors should mobilize intracellular IP(3)-sensitive calcium pools. The activation of the ionotropic receptors should not only open a non-specific cation channel leading to the entry of calcium but should also induce the formation of pores in cells expressing the P2X(7) receptors, which could be deleterious to these cells.

Morphometry of the dorsal raphe nucleus serotonergic neurons in suicide victims

BACKGROUND

The serotonin deficiency hypothesis of suicide has been important heuristically. Few studies have directly examined the brainstem dorsal raphe nucleus (DRN) serotonin neurons. We determined the number and morphometry of DRN serotonergic neurons in suicide victims (n = 7) compared to controls (n = 6).

METHODS

Brainstems were collected at autopsy, fixed and cryoprotected. Tissue was sectioned, stained for Nissl and processed with an antiserum that cross-reacts with tryptophan hydroxylase. All DRN neurons were identified, counted and analyzed every 1000 microns. Neuron morphometry was characterized by soma area (micron 2), sphericity, perimeter, length and density (neurons per mm3).

RESULTS

Neuron number and density was higher in suicide victims (1,780 +/- 127 neurons/mm3) than controls (1,349 +/- 68). The DRN volume did not differ between groups (66 +/- 9 mm3 for controls vs. 67 +/- 5 mm3 for suicides). Mean neuronal area and sphericity did not differ between suicides and controls. The total number and the density of DRN neurons did not correlate with age.

CONCLUSIONS

The finding of an increased number of neurons indicates that impaired serotonergic transmission found in association with serious suicide attempts is not due to fewer neurons.

Effect of heat acclimation and heat shock on oscillations of carbamyl-choline-evoked Ca2+ signal in HSY cell line

We studied effects of heat acclimation (HA) and acute heat stress (HS) on Ca2+ signal oscillations following supramaximal carbamyl-choline (CCh) stimulation, using HSY cell line as a model. In the control cells, oscillations decreased their amplitude with time. HS alone did not change either oscillation amplitude or frequency, although calcium release to the cytosol upon CCh stimulation was faster. HA increased maximal oscillation amplitude only. There was no change in basal cytosolic calcium level and peak evoked signal in all experimental conditions. Collectively, the data suggest that HA affects the oscillation profile. Changes in the oscillation profile did not correlate with changes in the resting and evoked Ca2+ signal, which suggests that the oscillations are a separate target for heat acclimation.

Defective antibody production in patients with rheumatoid arthritis and bronchiectasis

Bronchiectasis (BR) occurs in about 3% of patients with rheumatoid arthritis (RA). Defective antibody production is a rare but well-recognised cause of both BR and inflammatory arthritis. We examined the hypothesis that subtle specific antibody defects might play a role in the pathogenesis of BR associated with RA. Identification of defects in antibody production is important because substantial benefits may be gained from immunoglobulin replacement. Specific antibody production was assessed in 20 patients with RA and BR, 20 with BR alone, 20 with RA alone and 20 healthy controls (all groups matched for age and sex). All had normal total IgG. IgA and IgM and IgG subclass levels. Specific antibody production was assessed by assay of antibodies to representative polysaccharide and protein antigens. Subjects with subprotective titres were challenged with the appropriate vaccine. Defective antibody production was defined as a subprotective level despite immunisation. Three out of 20 patients with RA and BR had a defective IgG2 response to the polysaccharide antigen, but normal responses to the protein antigen. All of the subjects in the BR alone or healthy control group had normal antibody production. Two out of 20 patients with RA alone had defective production of antibodies against both protein and polysaccharide antigens; both were receiving gold therapy, a recognised cause of functional antibody defects. It was concluded that some patients with RA and BR have functional antibody defects and may benefit from antibody replacement. An unexpectedly high proportion of patients with RA alone also have functional antibody defects, possibly secondary to gold therapy.

Purines, a new class of agonists in salivary glands?

The response of rat submandibular glands to extracellular purines was tested. In crude cellular suspensions, ATP increased the [Ca2+]i mostly by promoting uptake of extracellular calcium. ATP caused the pHi to drop, a response blocked by chloride channel inhibitors. ATP also inhibited the basal and isoproterenol-stimulated activity of the Na+ -K+ -2Cl-cotransporter. These effects were reproduced by benzoyl-ATP, an agonist of ionotropic purinoceptors. In pure ductal suspensions, ATP activated a metabotropic P2Y1 purinergic receptor coupled to phospholipase C and opened a non-specific cation channel coupled to a P2X7 receptor. Activation of these receptors stimulated a Ca2+ -dependent and a Ca2+ -independent phospholipase A2, the latter resulting in kallikrein secretion. We conclude that purinergic agonists can modulate the activity of both acinar and ductal phases of secretion. Activation of metabotropic receptors coupled to phospholipase C could lead to responses resembling those to muscarinic or adrenergic agonists. Activation of ionotropic receptors could stimulate new intracellular responses also involved in secretory function.