Intravenous formulations of the enantiomers of thalidomide: pharmacokinetic and initial pharmacodynamic characterization in man

Thalidomide, a racemate, is coming into clinical use as an immunomodulating and antiinflammatory drug. These effects may chiefly be exerted by S-thalidomide, but the enantiomers are interconverted in-vivo. Thalidomide is given orally, although parenteral administration would be desirable in some clinical situations. The aim of this study was to prepare solutions of the enantiomers of thalidomide for intravenous administration and to investigate their pharmacokinetics and sedative effects following infusion in man. Solubility and stability of the enantiomers in 5% glucose solution was investigated. After a dose-determination experiment in one subject, six healthy male volunteers received R- and S-thalidomide separately by 1-h infusions in a randomized double-blind cross-over study. Blood was sampled over 22h and sedative effects were recorded. Blood concentrations of the enantiomers were determined by stereospecific HPLC. A four-compartment model consisting of a two-compartment model for each enantiomer, with elimination from both compartments, connected by rate constants for chiral inversion was fitted to the concentration data, while the sedative effects were correlated with the blood concentrations of R- and S-thalidomide by means of logistic regression. The enantiomers of thalidomide were chemically stable in solution for at least a week at room temperature. The infusions were well tolerated. Sedation, which was the only observed effect, was related to the blood concentration of R-thalidomide. Inter-individual variation in the disposition of the enantiomers was modest (e.g. terminal half-lives ranged between 3.9 and 5.3h). Pharmacokinetic modelling predicted that varying the infusion time of a fixed dose of S-thalidomide between 10 min and 6h would have little influence on the maximal blood concentration of formed R-thalidomide. To our knowledge this is the first time that thalidomide has been administered intravenously.

Drug concentration effect relationship of estradiol from two matrix transdermal delivery systems: Menorest and Climara

OBJECTIVES

To relate the pharmacokinetics of estradiol to pharmacological effects.

METHODS

Drug concentration effect relationship of estradiol from two matrix transdermal delivery systems, Menorest and Climara, was studied in a single centre, open, randomised, comparative crossover study. The trial consisted of two treatment periods, 14 days for each patch separated by a 4-week washout period. Blood hormone levels were followed during the second week of each treatment. Estradiol levels during treatments were related to three concentration levels previously proposed as efficacy or safety limits. The effect of treatment on FSH-levels was examined and the relationship between the levels of estradiol and FSH was described using an inhibitory sigmoidal I(max) model. Estrone levels and estradiol/estrone before and during treatment were followed.

RESULTS

The C(average) of FSH during treatment was 38% lower than baseline plasma levels. Estradiol had an inhibitory effect on FSH with an I(max) of 0.68 and an IC(50) of 19 pg/ml. The fraction of time above the minimum concentration for therapeutic effect and the tolerability limit did not differ between the two treatments, whereas the fraction of time above the suggested threshold for osteoporosis prophylaxis was significantly larger for Menorest than for Climara (P<0.05). The low baseline estradiol/estrone ratios increased towards pre-menopausal levels during treatment.

CONCLUSIONS

The drug concentration effect relationship of estradiol may be of use in evaluation of the effects of prophylactic estrogen therapy and to facilitate comparisons between different forms of estrogen treatments.

Clustering of private mutations in the congenital chloride diarrhea/down-regulated in adenoma gene

An inherited defect in intestinal anion exchange, congenital chloride diarrhea (CLD), was recently shown to be caused by mutations in the down-regulated in adenoma (DRA) gene. A three base pair deletion resulting in the loss of an amino acid valine (V317del) in the predicted CLD/DRA protein was shown to be responsible for all CLD cases in a Finnish founder population. Two additional mutations, H124L and 344delT, were found in Polish CLD patients. Here, we screened for additional mutations in a set of 14 CLD families of Polish, Swedish, North American, and Finnish origin using primers that allowed mutation searches directly from genomic DNA samples. We found eight novel mutations in the CLD/DRA gene. The mutations included two transversions, one transition, one insertion, and four small deletions. Of 11 sequence alterations detected so far, nine lie clustered in three short segments that are 49 bp, 39 bp, and 65 bp in size, respectively. These short segments span only 6.7% of the total cDNA length, suggesting functional importance or mutation-prone DNA regions of the corresponding CLD/DRA protein domains.

Inherited disorders of ion transport in the intestine

Within the past year, it has been established that the gene mutated in the human disorder congenital chloride diarrhea encodes a major Cl-/HCO3- exchanger at the apical membrane of gut epithelial cells. A major apical Na+/H+ exchanger has also been identified. New insight into metal ion absorption has been gained, and several new transporters without cognate diseases have been cloned.

The congenital chloride diarrhea gene is expressed in seminal vesicle, sweat gland, inflammatory colon epithelium, and in some dysplastic colon cells

Congenital chloride diarrhea (CLD) is an autosomal recessive disorder of intestinal electrolyte transportation caused by mutations in the anion transporter protein encoded by the down-regulated in adenoma (DRA), or CLD, gene. In this study, in situ hybridization and immunohistochemistry were performed to investigate the expression of CLD in extraintestinal normal epithelia and in intestinal inflammatory and neoplastic epithelia. The expression of the closely related anion transporter diastrophic dysplasia sulfate transporter, DTDST, was also examined and compared with that of CLD in colon. The only extraintestinal tissues showing CLD expression were eccrine sweat glands and seminal vesicles. In inflammatory bowel disease and ischemic colitis, expression of CLD mRNA in colon epithelium was similar to histologically normal colon epithelium, but the protein was found deeper in crypts, including proliferative epithelial cells. In intestinal tumors, the expression pattern of CLD was dependent on the differentiation status of the tissue studied: epithelial polyps with no or minor dysplasia showed abundant expression, whereas adenocarcinomas were negative. The DTDST gene was abundantly expressed in the upper crypt epithelium of colonic mucosa.

CT and MR imaging of the liver. Clinical importance of nutritional status

PURPOSE

In an experimental study in rats a correlation between nutritional status and hepatic attenuation in CT and signal intensities in MR imaging was shown. Is physiological nutritional status of importance in clinical CT and MR imaging?

MATERIAL AND METHODS

In a cross-over study including 12 healthy volunteers (6 women and 6 men, mean age 34 years), CT and MR imaging of the liver were performed with nutritional status at three different levels, i.e., normal, fasting and after glycogen-rich meals. CT and MR were performed on clinical imaging systems and hepatic attenuation and signal intensity, respectively, were assessed. In MR, T1-weighted, proton density-weighted and T2-weighted pulse-sequences were used.

RESULTS

In CT there were significantly (p<0.01) higher liver attenuations in normal nutritional status and after glycogen rich-meals compared to the fasting condition. The difference between fasting and glycogen-rich meals were 10.5 HU for men, 7.4 for women and mean 8.8 HU for all 12 volunteers. In MR imaging the differences were small and non-significant. The results of this study are in accordance with an earlier experimental study in rats.

CONCLUSION

In CT it may be of importance not to have patients in a fasting condition as it lowers the attenuation in normal liver tissue. The findings are important for planning of clinical studies where hepatic attenuation will be assessed and may be of some importance in clinical CT. In MR imaging the results indicate that the nutritional status is of less importance.

Absorption and disposition including enterohepatic circulation of (14C) roquinimex after oral administration to healthy volunteers

The absorption and disposition of roquinimex (Linomide) were studied in four male and two female healthy volunteers. The subjects received a single oral aqueous solution of 14C-labelled roquinimex, about 0.1 mg/kg, after an overnight fast. Blood samples were taken and urine and faeces were collected for 10 days after dosing. The plasma, urine and faeces concentrations of roquinimex and metabolites were determined by high-performance liquid chromatography (HPLC) with radiochemical detection. The metabolites were identified by HPLC-mass spectroscopy (MS). The plasma concentration-time profiles of roquinimex exhibited a rapid absorption followed by a bi-exponential disposition. A secondary peak was observed between 6 and 8 h, indicating enterohepatic circulation (EHC) of roquinimex. The terminal disposition half-life was estimated as 27 h. The primary metabolic pathways of roquinimex were hydroxylation, demethylation and conjugation. The major compound in plasma was roquinimex; metabolites were only occasionally detected. In urine and faeces, roquinimex accounted for 2% of the dose and conjugated and hydroxylated metabolites each accounted for about 30% of the dose. A model was derived for the plasma concentrations of roquinimex and the amount of urinary excreted roquinimex to take into account EHC. This model improved the goodness-of-fit according to common goodness-of-fit criteria. The values of the pharmacokinetic parameters were similar using compartmental and non-compartmental methods, indicating that the contribution of EHC of roquinimex is of minor importance in the evaluation of the pharmacokinetics of roquinimex.

Differential effects on T cell and NK cell development by tissue-specific expression of H-2D(d) transgene

The effect of tissue-specific expression of the MHC class I molecule H-2D(d) on T cell and NK cell specificity was studied in transgenic mice expressing the H-2D(d) gene under the control of the mouse metallothionein-I promoter. MTD mice expressed high amounts of H-2D(d) in the liver, intestine and testis, but only minute amounts in the thymus, spleen and kidney. Zinc administration resulted in a 1.5- and 8.5-fold increase in H-2D(d) expression in the liver and the intestine, respectively, but did not affect expression in the other organs tested. T cell tolerance developed towards H-2D(d) in MTD mice, even in the absence of zinc. In contrast, NK cell-mediated natural resistance against lymphoma grafts was not seen in MTD mice, despite zinc administration. NK cells in MTD mice also failed to develop self tolerance to H-2D(d). The lack of functional effects did not result from inability of NK cells in MTD mice to interact with H-2D(d), as down-regulation of Ly49A receptor expression was observed on liver NK cells in MTD mice. Our data reveal a difference between T cells and NK cells in their requirements for MHC class I molecules in specificity development.

Bioavailability of estradiol from two matrix transdermal delivery systems: Menorest and Climara

OBJECTIVES

To compare two estradiol transdermal matrix systems with regard to bioavailability, pharmacokinetics and tolerability.

METHODS

A single centre, open, randomized, comparative cross-over study in 20 healthy postmenopausal women. Menorest with 3 or 4 days of suggested use and Climara with 7 days of suggested use (both 50 microg/24 h) were compared at steady state. Two 14-day treatment periods were separated by a 4 week washout. Plasma levels of estradiol were monitored during the second week of each treatment. Tolerability was assessed by open questions and inspection of the application site.

RESULTS

There were no differences between the two treatments with regards to AUC, Cmax, Cmin, Caverage or fluctuations of plasma estradiol. Tmax was significantly shorter for Menorest than Climara. Cmax and Cmin were significantly higher for the second Menorest patch during the monitoring period compared to the first. All local reactions were mild and there were three cases of erythema with Menorest and a total of 21 skin reactions in 15 subjects with Climara. Systemic tolerability was similar between treatments with eight estrogen-related adverse events in eight subjects (period pains, uterine bleeding, mastodynia, headache and vaginal discharge) with Menorest and 13 events in ten subjects with Climara.

CONCLUSIONS

The bioavailability of estradiol from the two matrix transdermal delivery systems Menorest and Climara was similar, but the products were not bioequivalent because Tmax was significantly shorter for Menorest than for Climara. Tolerability of treatment was good for both patches but with a higher number of local reactions and estrogen related adverse events for Climara.

Gastrointestinal damage induced by cytostatic treatment does not affect the bioavailability of co-trimoxazole

Twelve lymphoma patients received prophylaxis with co-trimoxazole during cytostatic treatment according to the MACOP-B regimen with cyclophosphamide, doxorubicin, vincristine, methotrexate, bleomycin, folinic acid and prednisone. Gastrointestinal mucosal damage from cytostatic treatment was estimated by WHO toxicity scores. No correlation was found between the degree of gastrointestinal damage and the presumed bioavailability of co-trimoxazole as estimated from serum levels of trimethoprim and sulphamethoxazole. The serum concentrations were above the minimum inhibitory concentration for Escherichia coli, Staphylococcus aureus and coagulase-negative staphylococci irrespective of the degree of toxicity. There is no apparent reason to change the dosing regimen of prophylactic co-trimoxazole when there is clinical evidence of damage to the gastrointestinal mucosa induced by chemotherapy.

Dissolution rate-limited absorption and complete bioavailability of roquinimex in man

In order to investigate the bioavailability and the rate-limiting step of the absorption of roquinimex, an oral solution and a tablet formulation (Linomide(R)) were given to healthy volunteers. The study was conducted as a randomized three-period crossover study in seven male and seven female healthy volunteers. The subjects received an intravenous infusion, an oral solution and an oral tablet formulation, each of 5 mg (about 0.07 mg kg(-1)), as single doses after an overnight fast on three occasions, with a wash-out period of 3 weeks in between. Venous blood samples were taken over 7 days and the plasma concentrations of roquinimex were determined by high-performance liquid chromatography (HPLC) with ultraviolet (UV)-detection. The pharmacokinetics of roquinimex was characterized by a low plasma clearance, 4.9 mL h(-1) kg(-1) and a small volume of distribution, 0.22 L kg(-1). The oral bioavailability of the drug was complete for both the solution and the tablet formulation. The absorption rate was faster for the solution than for the tablet. The disposition of roquinimex was biphasic, with a terminal disposition half-life of 32 h. Between 4 and 8 hours after dosing, a secondary plasma peak was observed, indicating enterohepatic circulation of the drug. No major sex differences were shown in the pharmacokinetics of roquinimex. In conclusion, dissolution rate-limited absorption of roquinimex was shown, which demonstrates that disintegration and dissolution of the tablet play a major role in the absorption process of roquinimex. Despite the delayed absorption after administration of the tablet, the extent of absorption was complete.

Indirect-response modeling of desmopressin at different levels of hydration

The objective of the present study was to investigate the pharmacokinetics (PK) and pharmacodynamics (PD) of desmopressin in healthy male subjects at different levels of overhydration. Also, we examined if an indirect-response model could be related to renal physiology and the pharmacological action of desmopressin. Eight healthy male subjects participated in this open, randomized crossover study with three periods. Each subject was orally water loaded (0 to 20 ml.kg-1 body weight) on 3 study days in order to achieve three different levels of hydration. After the initial water load, urine was voided every 15 min and the volumes were measured. To ensure continuous overhydration the subjects replaced their fluid loss with drinking-water. When a steady-state diuresis was achieved after approximately 2 hr, 0.396 microgram of desmopressin was administered intravenously as a bolus injection. Blood was sampled and urine was collected at intervals throughout the study day (10 hr). An indirect-response model, where desmopressin was assumed to inhibit the elimination of response, was fit to the urine osmolarity data. There were no statistically significant effects of different levels of hydration, as expressed by urine flow rate at baseline, on the estimates of the PK and PD model parameters. The calculated terminal half-lives of elimination (t1/2 beta) ranged between 2.76 and 8.37 hr with an overall mean of 4.36 hr. The overall means of plasma clearance and the volumes of distribution of the central compartment (Vc) and at steady state (Vss) were estimated to be 1.34 (SD 0.35) ml.min-1.kg-1, 151 (SD28) ml.kg-1, and 386 (SD 63) ml.kg-1, respectively. High urine flow rate, indicating overhydration, produced a diluted urine and thus a low osmolarity at baseline (R0). The effect of the urine flow rate on the urine osmolarity at baseline was highly significant (p < 0.0001). The mean values for IC50 and the sigmodicity factor (gamma) were 3.7 (SD 1.2) pg ml-1 and 13.0 (SD 3.5), respectively. In most cases when there was a high urine flow rate at baseline, the model and the estimated PD parameters could be related to the pharmacological action of desmopressin and renal physiology. Thus, the indirect-response model used in this study offers a mechanistic approach of modeling the effect of desmopressin in overhydrated subjects.

Perceived problems of pharmacotherapy: a problem detection study among physicians and nurses at a Swedish university hospital

As a first step toward obtaining quality assurance regarding use and handling of drugs at Malmö University Hospital, a problem detection study (PDS) was performed, drug related problems being collected from nurses, physicians and pharmacists. Problem questionnaires relevant for physicians (67 items) and nurses (82 items) were prepared and sent to chief physicians and head nurses for distribution to colleagues. The problems identified covered all aspects of drug use and handling such as availability, prescription, dispensing, information and monitoring. Fifty-six per cent (79/141) of the physicians and 68 per cent (88/130) of the nurses responded. The main problems were related to information, chart order sheets and follow up. The item 'Uncertain whether patients take their medicine correctly after discharge' scored highest among physicians. The two main problems for the nurses were that 'newly licensed drugs and drugs used on a named-patient basis are not included in FASS' (the Swedish national formulary). The problem detection technique proved useful for the identification of drug-related problems, and the results will provide a basis for further improvement in quality assurance in pharmacotherapy at the hospital.

Natural killing of MHC class I(-) lymphoblasts by NK cells from long-term bone marrow culture requires effector cell expression of Ly49 receptors

NK cells from long-term bone marrow culture (LTBMC) were compared with IL-2-activated splenic NK cells [short-term spleen cell culture (STSC)] with regard to expression of inhibitory Ly49 receptors and cytotoxic function. In the LTBMC, the total number of NK cells expressing either one of the Ly49 molecules A, C/I and G2 was strongly reduced (10-15% of NK1.1(+) cells) compared to the STSC (80-90% of NK1.1(+) cells). With regard to cytotoxic function, we confirmed that LTBMC-derived NK cells efficiently killed the prototype NK target YAC-1. However, against other targets, killing was more variable. First, while STSC-derived NK cells clearly distinguished MHC class I(-) from MHC class I(+) tumor cell targets, LTBMC-derived NK cells did not; they either killed both targets equally well or not at all. Secondly, LTBMC-derived NK cells were largely incapable of killing lymphoblast targets deficient in MHC class I expression. To test whether this cytotoxic defect was due to the low number of Ly49(+) NK cells in the LTBMC, we separated Ly49(+) and Ly49(-) NK cells by cell sorting and tested them individually. This experiment showed that only Ly49(+) NK cells in the LTBMC were able to kill MHC class I(-) lymphoblasts (and to distinguish them from MHC class I(+)), despite good cytotoxicity against YAC-1 cells in both populations. These data suggest that certain modes of NK cell triggering are dependent on Ly49 receptor expression. From our results, we speculate that inhibitory receptors are expressed before triggering receptors for normal self cells during NK cell development, which may be an important mechanism to preserve self tolerance during the early stages of NK cell maturation.

Pharmacokinetics and antidiuretic effect of a new vasopressin analogue (F992) in overhydrated male volunteers

OBJECTIVE

The aim of the present study was to study the pharmacokinetics, the antidiuretic effects and the safety of [D-Phe2, Thi3, alpha-Me-Abu4, Hyp7, D-Arg8]dC1-vasopressin, a new antidiuretic peptide (F992, Ferring, Sweden), administered as intravenous infusion to orally overhydrated male volunteers.

METHODS

Eight healthy male volunteers participated in this open study consisting of two parts: a dose titration study and a safety study. In the dose titration study ascending doses of F992 were administered to volunteers in pairs in order to find a dose that within 1 h after the infusion, in both subjects, caused a reduction of the urine flow rate to below 5 ml x min(-1) (target dose). Subsequently, this target dose was administered to all volunteers. In the safety study the target dose was doubled and given to all volunteers. On each study occasion, in both study parts, the subjects were orally overhydrated with water. F992 was administered as i.v. infusion approximately 1.5 h after the start of the hydration procedure. Throughout the study days, blood was sampled for determination of plasma concentrations of F992 and for safety evaluation. Urine was collected at intervals in order to estimate flow rate and osmolality.

RESULTS

The target dose was found to be 4.0 microg as this dose fulfilled the criteria regarding antidiuretic effect, consequently 8.0 microg was administered to all subjects in the safety study. After infusion of 4.0 and 8.0 microg, the median half-lives of elimination were 4.72 (range 3.99-6.53) h and 3.85 (range 3.04-11.08) h, respectively. The plasma clearance and the volume of distribution at steady state were estimated to be 0.88 (SD 0.24) ml x min(-1) x kg(-1) and 326 (SD 68) ml x kg(-1)] after infusion of 4 microg. After the highest dose (8 microg), the corresponding estimates were 0.86 (SD 0.32) ml x min(-1) x kg(-1) and 299 (SD 81) ml x kg(-1), respectively. Significantly (P = 0.033) different maximum mean urine osmolalities were produced after infusion of 4.0 and 8.0 microg of F992 (534 (SD 318) vs 732 (SD 189) mOsmol x kg(-1)). The median times to reach these values showed some tendency to be longer for the highest dose, however statistical significance was not reached. No serious adverse events were observed during the study.

CONCLUSION

We found it safe to administer F992 as infusion to overhydrated male volunteers. The results suggest that F992 has a longer half-life and a lower potency than the widely used peptide desmopressin.

Different modes of pathogenesis in T-cell-dependent autoimmunity: clues from two TCR transgenic systems

T lymphocytes constantly flirt with reactivity to self peptides, a price they pay for their ability to recognize foreign peptides presented by self-MHC molecules, and autoreactivity in the T compartment occasionally gives rise to autoimmune disease. Pathology from T-cell autoimmunity can manifest itself through radically different strategies, as we have observed recently in two transgenic models. In the BDC2.5 diabetes model, T cells express a transgene-encoded T-cell receptor (TCR) with reactivity against a pancreatic antigen. This leads to a massive, if often controlled, infiltration of the pancreatic islets. Target cell destruction then results from the local consequences of this local immune/inflammatory process. On the other hand, the arthritic manifestations of the KRN transgenic model are indirect: the transgenic TCR confers a broad autoreactivity, through which T cells stimulate B cells to produce arthritogenic immunoglobulins. These molecules are then sufficient to produce the disease, even in the complete absence of any lymphocytes. Although important questions subsist in this model--how the KRN T cells interfere with B-cell tolerance, what the target of arthritogenic IgG is--its implication is that an isolated T-cell dysregulation may manifest itself through an Ig-mediated disease.

Changes in gastrointestinal motility influence the absorption of desmopressin

OBJECTIVE

The antidiuretic effect of desmopressin is widely utilized in the treatment of neurogenic diabetes insipidus and nocturnal enuresis in children. The objective of the present study was to assess how changes in gastrointestinal motility, induced by erythromycin and loperamide, influence the pharmacokinetics of orally administered desmopressin.

METHODS

This study was conducted using an open randomized, three-period, three-treatment design in 18 healthy subjects. On each study day a single oral dose of 400 microg desmopressin was administered in the morning. The desmopressin dose was either given alone (reference) or after pretreatment with either loperamide tablets (4 mg at -24, -12 h and -1 h) or erythromycin capsules (250 mg q.i.d, with the first dose in the morning 3 days before the study day and the last dose at -1 h). On each study day, blood was sampled up to 8 h after dosing for assessment of desmopressin concentration.

RESULTS

Compared with administration of 400 microg of desmopressin alone, pretreatment with loperamide produced significantly (P < 0.05) altered pharmacokinetics of desmopressin as the endpoints; area under the curve up to infinity (AUC), area up to the last determinable plasma concentration (AUCt) and maximum plasma concentration (Cmax) increased 3.1-fold (95% CI 2.3-4.2), 3.2 (2.3-4.4) and 2.3 (1.6 3.2), respectively. Although the estimates were lower, pretreatment with erythromycin did not result in any significant changes in these endpoints. There were no significant changes observed between the three treatments regarding the terminal elimination half-life (t1/2). However, significant (P < 0.05) changes in the time to reach Cmax (tmax) values (median and range) were observed as, compared with administration of desmopressin alone (1.3 h and 0.5-4.0), it was longer after pretreatment with loperamide (2.0 h and 0.5-3.0) and shorter following pre-treatment with erythromycin (0.9 h and 0.5-1.3).

CONCLUSION

Presumably due to slower gastrointestinal motility, pretreatment with loperamide significantly increases the gastrointestinal absorption of desmopressin. Except for a shortening of tmax pretreatment with erythromycin did not significantly influence absorption of the drug.

Molecular characterization of deletion at 11q22.1-23.3 in mantle cell lymphoma

Chromosomal deletions at 11q21-23 have recently been reported to be common aberrations in mantle cell lymphoma (MCL). To characterize the structure of the deletion, we studied 41 cases of MCL by fluorescence in situ hybridization using a YAC contig, which spans the region at 11q22.1-23.3. 17 MCLs were studied using a set of 20 yeast artificial chromosomes (YACs) in a contig, and nine of these cases showed deletion of 11q22-23. The deletion spanned several megabases in all but one case, where only YAC 755b11 at 11q23.1, covering approximately a 1.6 Mb of DNA, was deleted. Analysis of additional 24 MCLs with YAC 755b11 revealed the deletion in 49% of all cases (20/41). The deleted region at 11q22.1-23.3 was discontinuous in five lymphomas and in the majority of the cases the distal breakpoint occurred between YACs 785e12 and 911f2 at 11q23.3. We conclude that the deletion of 11q22-23 and particularly the deletion of YAC 755b11 are very common in MCL and may be important in the genesis or progression of the disease.

Initiation of autoimmune diabetes by developmentally regulated presentation of islet cell antigens in the pancreatic lymph nodes

Little is known about the events triggering lymphocyte invasion of the pancreatic islets in prelude to autoimmune diabetes. For example, where islet-reactive T cells first encounter antigen has not been identified. We addressed this issue using BDC2.5 T cell receptor transgenic mice, which express a receptor recognizing a natural islet beta cell antigen. In BDC2.5 animals, activated T cells were found only in the islets and the lymph nodes draining them, and there was a close temporal correlation between lymph node T cell activation and islet infiltration. When naive BDC2.5 T cells were transferred into nontransgenic recipients, proliferating cells were observed only in pancreatic lymph nodes, and this occurred significantly before insulitis was detectable. Surprisingly, proliferation was not seen in 10-day-old recipients. This age-dependent dichotomy was reproduced in a second transfer system based on an unrelated antigen artificially expressed on beta cells. We conclude that beta cell antigens are transported specifically to pancreatic lymph nodes, where they trigger reactive T cells to invade the islets. Systemic or extrapancreatic T cell priming, indicative of activation via molecular mimicry or superantigens, was not seen. Compromised presentation of beta cell antigens in the pancreatic lymph nodes of juvenile animals may be the root of a first "checkpoint" in diabetes progression.

Downregulated in adenoma gene encodes a chloride transporter defective in congenital chloride diarrhea

Congenital chloride diarrhea (CLD) is a recessively inherited disorder characterized by massive loss of chloride in stool. We previously identified mutations in the downregulated in adenoma (DRA) gene in patients with CLD and demonstrated that DRA encodes an intestine-specific sulfate transporter. To determine whether DRA is an intestinal chloride transporter and how mutations affect transport, Xenopus oocytes were injected with wild-type and mutagenized DRA cRNA and uptake of Cl- and SO2-4 was assayed. Both Cl- and SO2-4 were transported by wild-type DRA and an outwardly directed pH gradient stimulated Cl- uptake, consistent with Cl-/OH- exchange. Among three mutants, C307W transported both anions as effectively as wild-type, whereas transport activity was lost in V317del and the double mutant identified in 32 of 32 Finnish CLD patients. We conclude that DRA is a chloride transporter defective in CLD and that V317del is a functional mutation and C307W a silent polymorphism.

Genetic Disorders of Membrane Transport III. Congenital chloride diarrhea

Congenital chloride diarrhea (CLD) is a recessively inherited disorder of intestinal electrolyte absorption that involves, specifically, Cl-/HCO-3 exchange. CLD is caused by mutations in a chromosome 7 gene, first known as DRA (for downregulated in adenoma). The disease occurs in all parts of the world but is more common in some populations with genetic founder effects. More than 20 mutations in the gene are known to date. The CLD (or DRA) gene encodes a transmembrane protein belonging to the sulfate transporter family with three known members in humans, all associated with a distinct genetic disease. Members of the gene family can transport other anions as well that may turn out to be physiologically more important than sulfate transport. The gene family is well conserved in many prokaryotic and eukaryotic species and is expected to be much larger than presently known.

Pharmacokinetics and antidiuretic effect of intravenous administration of desmopressin in orally overhydrated male volunteers

In order to study the antidiuretic activity of desmopressin in healthy human subjects, a study design has previously been used with subjects orally hydrated. The objective of the present study was to investigate the pharmacokinetics and the antidiuretic activity of desmopressin administered as an intravenous infusion to eight orally hydrated male volunteers. After initial ingestion of water corresponding to 15 ml.kg-1 body weight, the overhydration was maintained by replacing the urinary fluid loss by drinking-water. Desmopressin (4 micrograms) was administered intravenously over 10 min. 1.5 hr after the start of the hydration procedure. Blood was sampled and urine was collected at intervals throughout the study day (9.5 hr). The terminal half-life of elimination (t1/2,) of desmopressin was calculated to be 2.97 +/- 0.24 (S.E.M.) hr while the clearance was 1.77 +/- 0.10 ml.min.-1.kg-1 and the volume of distribution at steady state was 373 +/- 30 ml.kg-1. The infusion caused a marked and long-lasting reduction of the urine flow rate. Four hr after the start of the infusion the mean urine osmolality was 909 +/- 46 mOsm.kg-1.

External and internal calibration of the MHC class I-specific receptor Ly49A on murine natural killer cells

Expression of the H-2Dd-specific inhibitory receptor Ly49A on murine NK cells is subject to MHC class I-dependent modulation in vivo. As a result, NK cells in H-2Dd-transgenic mice express low cell surface levels of Ly49A, whereas NK cells from nontransgenic C57BL/6 (B6) mice express high levels. The purpose of this study was to assess the role of MHC class I molecules on the NK cell itself vs those on surrounding cells in this calibration and to test whether the Ly49A levels are subject to regulation in mature NK cells also. Analysis of transgenic mice with mosaic expression of an H-2Dd/Ld transgene showed that MHC class I molecules on surrounding cells (external ligands) and on the NK cell itself (internal ligands) played distinct roles in the determination of Ly49A levels. External ligands were involved in down-regulation of Ly49A levels in vivo, whereas internal ligands kept the down-regulated levels of Ly49A low upon NK cell activation in vitro. Furthermore, in an experimental system based on adoptive transfer of spleen cells, receptor down-regulation of Ly49A occurred as a rapid adaptation process in mature NK cells after interaction with the H-2Dd ligand in vivo. This suggests that Ly49 levels are not fixed but can be changed in mature NK cells when they are exposed to a changed MHC class I environment.

Alpha1/alpha2 domains of H-2D(d), but not H-2L(d), induce "missing self" reactivity in vivo--no effect of H-2L(d) on protection against NK cells expressing the inhibitory receptor Ly49G2

Introduction of the MHC class I transgene H-2Dd on C57BL/6 (B6) background conveys NK cell-mediated "missing self" reactivity against transgene-negative cells, and down-regulates expression of the inhibitory receptors Ly49A and Ly49G2 in NK cells. We here present an analysis of transgenic mice expressing chimeric H-2Dd/Ld MHC class I transgenes, and show that the alpha1/alpha2 domains of H-2Dd were necessary and sufficient to induce "missing self" recognition and to down-modulate Ly49A and Ly49G2 receptors. In contrast, transgenes containing the alpha1/alpha2 domains of H-2Ld induced none of these changes, suggesting that not all MHC class I alleles in a host necessarily take part in NK cell education. The lack of effect of the alpha1/alpha2 domains of H-2Ld on NK cell specificity was surprising, considering that both H-2Ld and H-2Dd have been reported to interact with Ly49G2. Therefore, the role of H-2Ld for protection against NK cells expressing Ly49G2 was re-investigated in a transfection system. In contradiction to earlier reports, we show that H-2Dd, but not H-2Ld, abolished killing by sorted Ly49G2+ NK cells, indicating that H-2Ld does not inhibit NK cells via the Ly49G2 receptor.

Hydroxylated metabolites of thalidomide: formation in-vitro and in-vivo in man

There is renewed interest in the clinical use of thalidomide, because of its unique immunomodulating action. Because data on the metabolism of thalidomide in man are very sparse, the aim of this study was to develop HPLC assays for the 5-hydroxy, 5,6-dihydroxy, 4,5-dihydroxy and 5'-hydroxy metabolites of thalidomide and to investigate their possible formation in man-in-vitro in liver homogenates and in-vivo in healthy volunteers. Reversed-phase HPLC assays with UV detection were developed for quantification of the metabolites in the low ng mL(-1) range in plasma and incubate samples. The stability of the metabolites was investigated and degradation was avoided by rapid chilling and acidification of the samples. After incubation of thalidomide with fraction S9 from human liver, formation of the 5-hydroxy and 5'-hydroxy metabolites could be demonstrated. The 5'-hydroxy metabolite was found, in low concentrations, in plasma samples from eight healthy male volunteers who had received thalidomide orally. The other three metabolites could not be found by HPLC with detection limits of 1-2 ng mL(-1). Thus the formation of two hydroxylated metabolites of thalidomide in the liver in man was demonstrated, but only one of these could be detected in the circulation.