Cloning and functional expression of a rat kidney extracellular calcium/polyvalent cation-sensing receptor

The maintenance of a stable extracellular concentration of ionized calcium depends on the integrated function of a number of specialized cells (e.g., parathyroid and certain kidney epithelial cells). We recently identified another G protein-coupled receptor (BoPCaRI) from bovine parathyroid that responds to changes in extracellular Ca2+ within the millimolar range and provides a key mechanism for regulating the secretion of parathyroid hormone. Using an homology-based strategy, we now report the isolation of a cDNA encoding an extracellular Ca2+/polyvalent cation-sensing receptor (RaKCaR) from rat kidney. The predicted RaKCaR protein shares 92% identity with BoPCaR1 receptor and features a seven membrane-spanning domain, characteristic of the G protein-coupled receptors, which is preceded by a large hydrophilic extracellular NH2 terminus believed to be involved in cation binding. RaKCaR cRNA-injected Xenopus oocytes responded to extracellular Ca2+, Mg2+, Gd3+, and neomycin with characteristic activation of inositol phospholipid-dependent, intracellular Ca(2+)-induced Cl- currents. In rat kidney, Northern analysis revealed RaKCaR transcripts of 4 and 7 kb, and in situ hybridization showed localization primarily in outer medulla and cortical medullary rays. Our results provide important insights into the molecular structure of an extracellular Ca2+/polyvalent cation-sensing receptor in rat kidney and provide another basis on which to understand the role of extracellular divalent cations in regulating kidney function in mineral metabolism.

Pleomorphic fibroma on the scalp

We present the eleventh case of benign pleomorphic fibroma arising on the scalp in a young Korean woman. Histopathologically these lesions were characterized by a polypoid or dome-shaped cutaneous fibrous mass with sparse cellularity but striking nuclear atypia and rare mitotic figures. They all showed benign clinical behavior, despite these histopathological findings.

Poliomyelitis and measles serosurvey in northern Malaysia

In 1990 the Institute for Medical Research carried out a serosurvey in the state of Kelantan to study the age stratified immune prevalence rates for measles and poliomyelitis. Our findings indicate that 981 out of 1,097 (89%) of the population screened had measles antibodies and more than 90% (366 out of 400) had antibodies to all three serotypes of poliovirus. The susceptible group for measles was infants below one year of age, of whom 53.3% (8/15) did not have measles antibody. Of 400 subjects, 125 (31.3%) who were either incompletely vaccinated or had not been vaccinated against poliomyelitis, had polio neutralizing antibodies to all three poliovirus serotypes, suggesting herd immunity in the population. No high risk age group could be identified for poliomyelitis.

Use of Fos-related antigens (FRAs) as markers of neuronal activity: FRA changes in dopamine neurons during proestrus, pregnancy and lactation

This manuscript describes the use of staining of Fos-related antigens (FRAs) as markers for changes in neuronal activity. The model system consisted of the tuberoinfundibular dopamine (TIDA) neurons located in the arcuate nucleus of the hypothalamus. Under normal conditions, these neurons are devoid of c-Fos staining even though the neurons are tonically active and can express FRAs. During specific neuroendocrine states the neurons undergo changes in activity, as described by other studies. At times when the activity is relatively high as in pregnancy and during proestrus, approximately 50%-60% of the TIDA neurons expressed FRA immunoreactivity. Moreover changes over the course of proestrus paralleled known shifts in TIDA activity (declining as the day progressed). At times when TIDA activity is suppressed, such as during lactation, FRA staining in TIDA neurons was markedly reduced or absent. Upon removal of the suckling stimulus, FRA staining rose to reach peak expression 12-24 h after pup removal (without coordinate induction of c-Fos). These data suggest that FRA staining can serve as a useful marker of activity in the TIDA neurons which permits not only assessment of stimulated activity but also suppressed function in the neurons. A cautionary note in using this approach along with acquisition of serial blood samples for hormone measurement is that surgical procedures for monitoring plasma hormone levels are associated with strong long-lived induction of FRAs (and c-Fos) in many neurons (including the TIDA neurons) that can confound interpretation of FRA staining.

L-NNA decreases cortical hyperemia and brain cGMP levels following CO2 inhalation in Sprague-Dawley rats

The role of nitric oxide (NO) in the response to 5% CO2 inhalation was investigated by measuring 1) regional cerebral blood flow (rCBF) by laser-Doppler flowmetry and pial vessel diameter through a closed cranial window after topical NG-nitro-L-arginine (L-NNA, 1 mM), and 2) the time-dependent changes in brain guanosine 3',5'-cyclic monophosphate (cGMP) levels after L-NNA (10 mg/kg ip). When L-NNA (but not NG-nitro-D-arginine) was applied topically for 30 or 60 min, the response to hypercapnia was significantly attenuated. A correlation was found between inhibition of brain NO synthase (NOS) activity and the rCBF response (r = 0.77; P < 0.01). However, L-NNA applied 15 min before hypercapnia did not attenuate the increase in rCBF but did attenuate the dilation to topical acetylcholine. Inhalation of CO2 (5%) elevated brain cGMP levels by 20-25%, and L-NNA reduced this response. These data from the rat suggest that 1) a product of NOS activity is associated with hypercapnic hyperemia and the attendant increase in brain cGMP levels, and 2) hypercapnic blood flow changes may not be dependent on endothelial NOS activity within pial vessels.

Blockade by oral or parenteral RPR 100893 (a non-peptide NK1 receptor antagonist) of neurogenic plasma protein extravasation within guinea-pig dura mater and conjunctiva

1. The ability of an NK1 receptor antagonist, RPR 100893, and its enantiomer, RPR 103253 to block neurogenic plasma protein extravasation in guinea-pig dura mater and conjunctiva was assessed following 125I-labelled bovine serum albumin ([125I]-BSA, 50 muCi kg-1, i.v.) and unilateral electrical stimulation of the trigeminal ganglion (0.6 mA, 5 ms, 5 Hz, 5 min) or capsaicin administration (150 micrograms kg-1, i.v.). 2. When administered p.o. 60 min prior to electrical stimulation, RPR 100893 (> or = 0.1 microgram kg-1) decreased plasma protein extravasation in dura mater in a dose-dependent manner, whereas the enantiomer (10 or 100 micrograms kg-1, p.o.) was inactive. 3. When given i.v. 30 min prior to electrical stimulation, RPR 100893 (> or = 0.5 ng kg-1) significantly inhibited plasma protein extravasation in the dura mater evoked by electrical stimulation in a dose-dependent manner. 4. RPR 100893 (100 micrograms kg-1, p.o.) also reduced the leakage when given 45 min before the guinea-pigs were killed and 10, 40 and 80 min after electrical trigeminal stimulation. 5. RPR 100893 given p.o. dose-dependently inhibited capsaicin-induced plasma protein extravasation with ID50S of 7.4 micrograms kg-1 and 82 micrograms kg-1 for dura mater and conjunctiva, respectively. 6. These results are consistent with the contention that NK1 receptors mediate neurogenic plasma protein leakage following trigeminal stimulation, and suggest that NK1 receptor antagonists of the perhydroisoindolone series may be useful for treating migraine and cluster headaches.

Molecular cloning, primary structure, and characterization of two members of the mammalian electroneutral sodium-(potassium)-chloride cotransporter family expressed in kidney

Electrically silent Na(+)-(K+)-Cl- transporter systems are present in a wide variety of cells and serve diverse physiological functions. In chloride secretory and absorbing epithelia, these cotransporters provide the chloride entry mechanism crucial for transcellular chloride transport. We have isolated cDNAs encoding the two major electroneutral sodium-chloride transporters present in the mammalian kidney, the bumetanide-sensitive Na(+)-K(+)-Cl- symporter and thiazide-sensitive Na(+)-Cl- cotransporter, and have characterized their functional activity in Xenopus laevis oocytes. Despite their differing sensitivities to bumetanide and thiazides and their different requirements for potassium, these approximately 115-kDa proteins share significant sequence similarity (approximately 60%) and exhibit a topology featuring 12 potential membrane-spanning helices flanked by long non-hydrophobic domains at the NH2 and COOH termini. Northern blot analysis and in situ hybridization indicate that these transporters are expressed predominantly in kidney with an intrarenal distribution consistent with their recognized functional localization. These proteins establish a new family of Na(+)-(K+)-Cl- cotransporters.

Acral Darier's disease: report of a case complicated by Kaposi's varicelliform eruption

We report a case of acral Darier's disease in a 16-year-old Korean boy that was complicated by Kaposi's varicelliform eruption. It is uncommon in Darier's disease for dyskeratotic papules to be limited to acral areas. In our patient, Kaposi's varicelliform eruption occurred on the face where there were no preexisting lesions of Darier's disease.

The high affinity Na+/glucose cotransporter. Re-evaluation of function and distribution of expression

We report the primary structure, functional characterization, and tissue distribution of the high affinity Na+/glucose cotransporter SGLT1 from rat kidney. Rat SGLT1 (665 amino acid residues) is 86-87% identical to SGLT1 from rabbit, pig, and human. High stringency Northern analysis demonstrated that SGLT1 is strongly expressed in small intestine and at lower levels in kidney, liver, and lung. In situ hybridization performed on kidney sections revealed that SGLT1 is predominantly present in S3 segments of the proximal tubule. In small intestine, SGLT1 message was located in cells of the lower two-thirds of intestinal villi. Expression of rat SGLT1 in Xenopus oocytes resulted in a large Na(+)-dependent uptake of [14C]-alpha-methyl-D-glucopyranoside (alpha MeGlc). Overall, the transport characteristics were similar to those of rabbit SGLT1. High affinity Na+/glucose cotransport in membrane vesicles was previously shown to be coupled to the cotransport of two Na+ ions (Turner, R. J., and Moran, A. (1982) J. Membr. Biol. 70, 37-45). Previous kinetic analysis of rat and rabbit SGLT1, however, demonstrated between second and first order dependence of sugar uptake on extracellular Na+ concentration, suggesting the existence of Na(+)-binding sites with different affinities. Here, we directly compared the initial rates of the alpha MeGlc uptake with alpha MeGlc-induced inward currents as an indicator of the Na+ flux. This analysis clearly revealed a Na+ to glucose coupling ratio of 2:1. In summary, our data provide important insights into the function and tissue distribution of the high affinity Na+/glucose cotransporter SGLT1 and clarify its role in the reabsorption mechanism of D-glucose in the kidney.

The biologic role of ganglioside in neuronal differentiation--effects of GM1 ganglioside on human neuroblastoma SH-SY5Y cells

Human neuroblastoma SH-SY5Y cell is a cloned cell line which has many attractive features for the study of neuronal proliferation and neurite outgrowth, because it has receptors for insulin, IGF-I and PDGF. Gangliosides are sialic acid containing glycosphingolipids which form an integral part of the plasma membrane of many mammalian cells. They inhibit cell growth mediated by tyrosine kinase receptors and ligand-stimulated tyrosine kinase activity, and autophosphorylation of EGF(epidermal growth factor) and PDGF receptors. The experiment was designed to study the effects of GM1 ganglioside on growth of human neuroblastoma SH-SY5Y cells stimulated with trophic factor in vitro. The cells were plated in Eagle's minimum essential medium without serum. The number and morphologic change of SH-SY5Y cells were evaluated in the serum free medium added GM1 ganglioside with insulin or PDGF. SH-SY5Y cells were maintained for six days in serum-free medium, and then cultured for over two weeks in serum-free medium containing either insulin or PDGF. The effect of insulin on cell proliferation developed earlier and was more potent than that of PDGF. These proliferative effects were inhibited by GM1 ganglioside, and the cells showed prominent neurites outgrowth. These findings suggest that GM1 ganglioside inhibits the cell proliferation mediated by tyrosine kinase receptors and directly induces neuritogenesis as one of the neurotrophic factors.

The zinc finger region of the adenovirus E1A transactivating domain complexes with the TATA box binding protein

The 289R E1A protein of adenovirus transactivates a variety of viral and cellular promoters through protein-protein interactions. In earlier studies, mutational analyses of the E1A transactivating domain identified residues that are critical for transactivation and implied that the zinc finger region of the transactivating domain binds a transcription factor. Also, the E1A activation domain was found to bind to the TATA box binding protein (TBP) in vitro. Here, we tested the significance of the E1A-TBP interaction for E1A transactivation by analyzing the effects of conservative substitutions at each of the 49 residues of the E1A activation domain. Seven of the substitutions significantly diminished TBP binding in vitro. All of these were in the zinc finger region and were defective for transactivation in vivo. The perfect correlation between reduced TBP binding and transactivation argues strongly that a direct interaction between the E1A activation domain and TBP is critical to the mechanism of E1A activation. This genetic analysis leads us to further suggest that another factor, which is limiting, is also necessary for E1A-mediated transactivation.

Cyclic AMP-dependent protein kinase does not regulate CTP:phosphocholine cytidylyltransferase activity in maturing type II cells

CTP:phosphocholine cytidylyltransferase catalyses a rate regulatory step in the de novo synthesis of surfactant phosphatidylcholine in alveolar type II cells. To investigate if cytidylyltransferase can be regulated by cAMP-dependent protein kinase, we first studied the ontogeny of cAMP-dependent protein kinase activity in type II cells of fetal rat lung. Total cAMP-dependent protein kinase activity, measured in the presence of 10 microM cAMP, as well as endogenous activity, measured without cAMP, increased with advancing gestation. Phosphocholine cytidylyltransferase activity showed a similar developmental profile. This temporal relationship between cAMP-dependent protein kinase and cytidylyltransferase supports a potential role for cAMP-dependent protein kinase in regulating cytidylyltransferase phosphorylation. Cytidylyltransferase purified from adult rat lung was, indeed, phosphorylated in vitro by cAMP-dependent protein kinase. Despite the phosphorylation, however, no change in cytidylyltransferase activity was noted. Pre-incubation of fetal type II cell cytosol with ATP and Mg2+ did not affect cytidylyltransferase activity. Addition of either cAMP, dibutyryl-cAMP or the catalytic subunit of cAMP-dependent protein kinase to the pre-incubation medium did also not alter cytidylyltransferase activity. Furthermore, neither cAMP-dependent protein kinase inhibitor peptide, nor H8, a cyclic nucleo-dependent protein kinase inhibitor, affected cytidylyltransferase activity in fetal type II cell cytosol. Treatment of intact fetal type II cells with either cAMP, dibutyryl-cAMP or 8-[4-chlorophenylthio]cAMP activated cAMP-dependent protein kinase activity but did not alter cytidylyltransferase activity. We conclude that the increase in cytidylyltransferase activity in fetal type II cells at late gestation is not regulated by the developmental activation of cAMP-dependent protein kinase.

Small intestine hexose transport in experimental diabetes. Increased transporter mRNA and protein expression in enterocytes

The effect of insulinopenic diabetes on the expression of glucose transporters in the small intestine was investigated. Enterocytes were sequentially isolated from jejunum and ileum of normal fed rats, streptozotocin-diabetic rats, and diabetic rats treated with insulin. Facilitative glucose transporter (GLUT) 2, GLUT5, and sodium-dependent glucose transporter 1 protein content was increased from 1.5- to 6-fold in enterocytes isolated from diabetic animals in both jejunum and ileum. Insulin was able to reverse the increase in transporter protein expression seen after induction of diabetes. There was a four- to eightfold increase in the amount of enterocyte glucose transporter mRNA after diabetes with greater changes in sodium-dependent glucose transporter 1 and GLUT2 than in GLUT5 levels. In situ hybridization showed that after the induction of diabetes there was new hybridization in lower villus and crypt enterocytes that was reversed by insulin treatment. Thus, the increase in total hexose transport caused by diabetes is due to a premature expression of hexose transporters by enterocytes along the crypt-villus axis, causing a cumulative increase in enterocyte transporter protein during maturation. These changes are likely to represent an adaptive response by the organism to increase nutrient absorption in a perceived state of tissue starvation. These adaptive changes may lead to exacerbation of hyperglycemia in uncontrolled diabetes.

Pharmacological evidence that calcitonin gene-related peptide is implicated in cerebral autoregulation

In anesthetized rats, we examined the possibility that calcitonin gene-related peptide (CGRP, a neuropeptide) released in response to transient hypotension may contribute to the reflex autoregulation of cerebral blood flow. Changes in pial arterial diameter (mean 33.0 +/- 1.1 microns) with changes in systemic arterial blood pressure (mean 101.9 +/- 2.7 mmHg) were observed directly through a closed cranial window. In capsaicin-treated rats (depletor of CGRP and substance P, 50 nmol capsaicin injected intracisternally 24 h before experiment), vasodilatation, which was evoked on transient hypotension, and vasoconstriction on reverse of hypotension were markedly attenuated or almost abolished. When changes in pial arterial diameter were plotted as a function of changes in blood pressure, the slopes of regression lines for vasodilatation and vasoconstriction were markedly reduced after capsaicin treatment. Similar reductions were evidenced under suffusion of CGRP antibody serum (1:1,000) and after CGRP receptor desensitization but not after substance P receptor desensitization. Pretreatment with glibenclamide, a K(+)-channel antagonist, also caused severe alterations in the autoregulatory vasomotor responses to hypotension and its reverse. Suffusion with mock cerebrospinal fluid, containing either CGRP or cromakalim, a K(+)-channel opener, dilated the pial artery in a concentration-dependent manner, and their effects were antagonized by glibenclamide. Substance P produced a vasodilatation, which was unaffected by glibenclamide.(ABSTRACT TRUNCATED AT 250 WORDS)

The human kidney low affinity Na+/glucose cotransporter SGLT2. Delineation of the major renal reabsorptive mechanism for D-glucose

The major reabsorptive mechanism for D-glucose in the kidney is known to involve a low affinity high capacity Na+/glucose cotransporter, which is located in the early proximal convoluted tubule segment S1, and which has a Na+ to glucose coupling ratio of 1:1. Here we provide the first molecular evidence for this renal D-glucose reabsorptive mechanism. We report the characterization of a previously cloned human kidney cDNA that codes for a protein with 59% identity to the high affinity Na+/glucose cotransporter (SGLT1). Using expression studies with Xenopus laevis oocytes we demonstrate that this protein (termed SGLT2) mediates saturable Na(+)-dependent and phlorizin-sensitive transport of D-glucose and alpha-methyl-D-glucopyranoside (alpha MeGlc) with Km values of 1.6 mM for alpha MeGlc and approximately 250 to 300 mM for Na+, consistent with low affinity Na+/glucose cotransport. In contrast to SGLT1, SGLT2 does not transport D-galactose. By comparing the initial rate of [14C]-alpha MeGlc uptake with the Na(+)-influx calculated from alpha MeGlc-evoked inward currents, we show that the Na+ to glucose coupling ratio of SGLT2 is 1:1. Using combined in situ hybridization and immunocytochemistry with tubule segment specific marker antibodies, we demonstrate an extremely high level of SGLT2 message in proximal tubule S1 segments. This level of expression was also evident on Northern blots and likely confers the high capacity of this glucose transport system. We conclude that SGLT2 has properties characteristic of the renal low affinity high capacity Na+/glucose cotransporter as previously reported for perfused tubule preparations and brush border membrane vesicles. Knowledge of the structural and functional properties of this major renal Na+/glucose reabsorptive mechanism will advance our understanding of the pathophysiology of renal diseases such as familial renal glycosuria and diabetic renal disorders.

Effects of N-methyl-D-aspartate receptor activation on cFos expression in luteinizing hormone-releasing hormone neurons in female rats

N-Methyl-D,L-aspartic acid (NMA), an agonist of N-methyl-D-aspartate (NMDA) excitatory amino acid receptors, stimulates the secretion of LH by increasing the release of LHRH. During proestrus, LHRH neurons express cFos in association with the LH surge. To determine the involvement of NMDA receptors in the activation of LHRH neurons on proestrus, we treated animals with an NMDA receptor blocker, MK-801. Treatment with MK-801 (0.3 mg/kg, sc) at 1130 h blocked both the LH and PRL surges and cFos expression in LHRH neurons. These data suggest that NMDA receptors are involved in the regulation of LHRH neuronal activation during the LH surge. We then determined whether NMA treatment could restore LH secretion and cFos expression in LHRH neurons in animals whose endogenous proestrous LH surges were blocked with pentobarbital. In the pentobarbital-blocked rats, NMA failed to induce cFos expression in LHRH neurons and increase LH secretion, but it did result in an increase in PRL secretion. To determine if NMA treatment alone could induce cFos expression in LHRH neurons, diestrous rats were treated with NMA by either systemic (40 mg/kg BW; four injections, 10 min apart) or third ventricular (2 micrograms in 2 microliters; four injections, 10 min apart) injections. NMA administration (regardless of the route of administration) caused an increase in LH secretion and significant cFos expression in many regions of the brain, including sites where the LHRH perikarya are concentrated. However, neither systemic nor intraventricular administration of NMA induced cFos expression in LHRH neurons. Thus, even though NMA results in increased activity of LHRH neurons, as evidenced by increased LH secretion, NMDA receptor activation alone appears to be insufficient to induce cFos expression in the LHRH neurons.

Conformationally restricted sumatriptan analogues, CP-122,288 and CP-122,638 exhibit enhanced potency against neurogenic inflammation in dura mater

CP-122,288 and CP-122,638 blocked plasma protein extravasation response within dura mater following trigeminal ganglion stimulation. The threshold (1 and 0.1 pmol/kg, respectively) was remarkably lower than for sumatriptan (7 nmol/kg), as was the dose at maximum response. As with sumatriptan, substance P-induced plasma leakage was unaffected by either compound, and metergoline only partially (27%) reversed the effects of CP-122,288. The data suggest the importance of modifications at the aminoethyl side chain to the actions of sumatriptan and possibly to the treatment of migraine headache.

Cloning and characterization of the vasopressin-regulated urea transporter

Urea is the principal end product of nitrogen metabolism in mammals. Movement of urea across cell membranes was originally thought to occur by lipid-phase permeation, but recent studies have revealed the existence of specialized transporters with a low affinity for urea (Km > 200 mM)2. Here we report the isolation of a complementary DNA from rabbit renal medulla that encodes a 397-amino-acid membrane glycoprotein, UT2, with the functional characteristics of the vasopressin-sensitive urea transporter previously described in in vitro-perfused inner medullary collecting ducts. UT2 is not homologous to any known protein and displays a unique pattern of hydrophobicity. Because of the central role of this transporter in fluid balance and nitrogen metabolism, the study of this protein will provide important insights into the urinary concentrating mechanism and nitrogen balance.

Psychiatric medication: what the occupational health nurse should know

1. Occupational health nurses need a general knowledge of psychiatric medications to work effectively with clients and their off site health providers. 2. Acquiring an understanding of the major classes of medications--anti-psychotic, anti-anxiety, anti-depressant, and antimanic--is important. 3. It is helpful to understand under what conditions and with which conditions psychotropic medications are helpful.

Role of transforming growth factor-beta 1 in the cellular growth response to angiotensin II

We have shown that angiotensin II (Ang II)-induced hypertrophy of vascular smooth muscle cells is dependent on the balance between proliferative and antiproliferative growth factors, specifically basic fibroblast growth factor and transforming growth factor-beta 1 (TGF-beta 1), respectively. We now present evidence, based on two phenotypically distinct cell cultures, that the ability to secrete the biologically active form of TGF-beta 1 is central to the growth response to Ang II. Two separate cultures were examined, one in which Ang II induces hypertrophy and the other in which Ang II induces hyperplasia. Ang II induces the expression of basic fibroblast growth factor twofold to fivefold in both cultures. Furthermore, both cultures express TGF-beta 1. In the culture that responds with hypertrophy, Ang II induces the expression of the active form of TGF-beta 1 twofold to threefold. However, in the culture that responds with hyperplasia, no active TGF-beta 1 was detected either at baseline or after Ang II exposure. Interestingly, all the TGF-beta 1 present was in the inactive, latent form. In the culture that responded with hyperplasia, Ang II induced a fourfold to fivefold increase in DNA synthesis. This increase could be abolished by the addition of active TGF-beta 1. Thus in these two cultures the ability to activate TGF-beta 1 dictates the cellular response to Ang II. These results support our hypothesis that a balance of proliferative and antiproliferative autocrine signals mediates the growth control of vascular smooth muscle cells.

The value of potency testing of poliomyelitis and measles vaccines as an integral part of cold chain surveillance

The Virology Division in the Institute for Medical Research, Kuala Lumpur, Malaysia performs potency tests on oral polio vaccines and live attenuated measles vaccines. Since these potency tests were introduced in 1981 a total of 752 tests have been performed on vaccine samples from peripheral immunization centers. Of 165 representative vaccine samples sent for potency evaluation after a cold chain breakdown 154 (87%) passed minimum potency requirements recommended for immunization of infants. In the absence of potency evaluation, those vaccines exposed to temperatures higher than the recommended storage range would be discarded, perhaps resulting in unnecessary wastage and economic loss. Results of the vaccine potency evaluation has enabled health authorities to indirectly monitor cold chain efficiency and ensure the high quality of viral vaccines used in our childhood immunization program.

Cloning and chromosomal localization of a human kidney cDNA involved in cystine, dibasic, and neutral amino acid transport

We have recently cloned, sequenced, and characterized a rat kidney cDNA (D2) that stimulates cystine as well as dibasic and neutral amino acid transport. In order to evaluate the role of this protein in human inherited diseases such as cystinuria, we have isolated a human D2 clone (D2H) by low stringency screening of a human kidney cDNA library using the radiolabeled D2 insert as a probe. The D2H cDNA is 2284 nucleotides long and encodes a 663 amino acid protein that is 80% identical to the rat D2 amino acid sequence and 86% to that of the rabbit homologue rBAT. Microinjection of in vitro transcribed D2H cRNA into Xenopus oocytes induced uptake of cystine as well as dibasic and neutral amino acids in a pattern similar to that of rat D2 and rabbit rBAT. Both neutral and dibasic amino acids inhibited the D2H-induced uptake of cystine. Northern blot analysis demonstrated that D2H, like D2 and rBAT, is expressed strongly in the kidney and intestine. Southern blot analysis of genomic DNA from a panel of mouse-human somatic cell hybrids showed that the human gene for D2H resides on chromosome 2.