The GIP receptor displays higher basal activity than the GLP-1 receptor but does not recruit GRK2 or arrestin3 effectively

Background and Objectives

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are important regulators of insulin secretion, and their functional loss is an early characteristic of type 2 diabetes mellitus (T2DM). Pharmacological levels of GLP-1, but not GIP, can overcome this loss. GLP-1 and GIP exert their insulinotropic effects through their respective receptors expressed on pancreatic β-cells. Both the GLP-1 receptor (GLP-1R) and the GIP receptor (GIPR) are members of the secretin family of G protein-coupled receptors (GPCRs) and couple positively to adenylate cyclase. We compared the signalling properties of these two receptors to gain further insight into why GLP-1, but not GIP, remains insulinotropic in T2DM patients.

Methods

GLP-1R and GIPR were transiently expressed in HEK-293 cells, and basal and ligand-induced cAMP production were investigated using a cAMP-responsive luciferase reporter gene assay. Arrestin3 (Arr3) recruitment to the two receptors was investigated using enzyme fragment complementation, confocal microscopy and fluorescence resonance energy transfer (FRET).

Results

GIPR displayed significantly higher (P<0.05) ligand-independent activity than GLP-1R. Arr3 displayed a robust translocation to agonist-stimulated GLP-1R but not to GIPR. These observations were confirmed in FRET experiments, in which GLP-1 stimulated the recruitment of both GPCR kinase 2 (GRK2) and Arr3 to GLP-1R. These interactions were not reversed upon agonist washout. In contrast, GIP did not stimulate recruitment of either GRK2 or Arr3 to its receptor. Interestingly, arrestin remained at the plasma membrane even after prolonged (30 min) stimulation with GLP-1. Although the GLP-1R/arrestin interaction could not be reversed by agonist washout, GLP-1R and arrestin did not co-internalise, suggesting that GLP-1R is a class A receptor with regard to arrestin binding.

Conclusions

GIPR displays higher basal activity than GLP-1R but does not effectively recruit GRK2 or Arr3.

Functional coupling of Cys-226 and Cys-296 in the glucagon-like peptide-1 (GLP-1) receptor indicates a disulfide bond that is close to the activation pocket

G protein-coupled receptors (GPCRs) are seven transmembrane α-helical (7TM) integral membrane proteins that play a central role in both cell signaling and in the action of many pharmaceuticals. The crystal structures of several Family A GPCRs have shown the presence of a disulfide bond linking transmembrane helix 3 (TM3) to the second extracellular loop (ECL2), enabling ECL2 to stabilize and contribute to the ligand binding pocket. Family B GPCRs share no significant sequence identity with those in Family A but nevertheless share two conserved cysteines in topologically equivalent positions. Since there are no available crystal structures for the 7TM domain of any Family B GPCR, we used mutagenesis alongside pharmacological analysis to investigate the role of ECL2 and the conserved cysteine residues. We mutated Cys-226, at the extracellular end of TM3 of the glucagon-like peptide-1 (GLP-1) receptor, to alanine and observed a 38-fold reduction in GLP-1 potency. Interestingly, this potency loss was restored by the additional substitution of Cys-296 in ECL2 to alanine. Alongside the complete conservation of these cysteine residues in Family B GPCRs, this functional coupling suggested the presence of a disulfide bond. Further mutagenesis demonstrated that the low potency observed at the C226A mutant, compared with the C226A-C296A double mutant, was the result of the bulky nature of the released Cys-296 side chain. Since this suggested that ECL2 was in close proximity to the agonist activation pocket, an alanine scan of ECL2 was carried out which confirmed the important role of this loop in agonist-induced receptor activation.

The major determinant of exendin-4/glucagon-like peptide 1 differential affinity at the rat glucagon-like peptide 1 receptor N-terminal domain is a hydrogen bond from SER-32 of exendin-4

BACKGROUND AND PURPOSE

Exendin-4 (exenatide, Ex4) is a high-affinity peptide agonist at the glucagon-like peptide-1 receptor (GLP-1R), which has been approved as a treatment for type 2 diabetes. Part of the drug/hormone binding site was described in the crystal structures of both GLP-1 and Ex4 bound to the isolated N-terminal domain (NTD) of GLP-1R. However, these structures do not account for the large difference in affinity between GLP-1 and Ex4 at this isolated domain, or for the published role of the C-terminal extension of Ex4. Our aim was to clarify the pharmacology of GLP-1R in the context of these new structural data.

EXPERIMENTAL APPROACH

The affinities of GLP-1, Ex4 and various analogues were measured at human and rat GLP-1R (hGLP-1R and rGLP-1R, respectively) and various receptor variants. Molecular dynamics coupled with in silico mutagenesis were used to model and interpret the data.

KEY RESULTS

The membrane-tethered NTD of hGLP-1R displayed similar affinity for GLP-1 and Ex4 in sharp contrast to previous studies using the soluble isolated domain. The selectivity at rGLP-1R for Ex4(9-39) over Ex4(9-30) was due to Ser-32 in the ligand. While this selectivity was not observed at hGLP-1R, it was regained when Glu-68 of hGLP-1R was mutated to Asp.

CONCLUSIONS AND IMPLICATIONS

GLP-1 and Ex4 bind to the NTD of hGLP-1R with similar affinity. A hydrogen bond between Ser32 of Ex4 and Asp-68 of rGLP-1R, which is not formed with Glu-68 of hGLP-1R, is responsible for the improved affinity of Ex4 at the rat receptor.

Genetic and functional analyses of FH mutations in multiple cutaneous and uterine leiomyomatosis, hereditary leiomyomatosis and renal cancer, and fumarate hydratase deficiency

Germline mutations of the fumarate hydratase (FH, fumarase) gene are found in the recessive FH deficiency syndrome and in dominantly inherited susceptibility to multiple cutaneous and uterine leiomyomatosis (MCUL). We have previously reported a number of germline FH mutations from MCUL patients. In this study, we report additional FH mutations in MCUL and FH deficiency patients. Mutations can readily be found in about 75% of MCUL cases and most cases of FH deficiency. Some of the more common FH mutations are probably derived from founding individuals. Protein-truncating FH mutations are functionally null alleles. Disease-associated missense FH changes map to highly conserved residues, mostly in or around the enzyme's active site or activation site; we predict that these mutations severely compromise enzyme function. The mutation spectra in FH deficiency and MCUL are similar, although in the latter mutations tend to occur earlier in the gene and, perhaps, are more likely to result in a truncated or absent protein. We have found that not all mutation-carrier parents of FH deficiency children have a strong predisposition to leiomyomata. We have confirmed that renal carcinoma is sometimes part of MCUL, as part of the variant hereditary leiomyomatosis and renal cancer (HLRCC) syndrome, and have shown that these cancers may have either type II papillary or collecting duct morphology. We have found no association between the type or site of FH mutation and any aspect of the MCUL phenotype. Biochemical assay for reduced FH functional activity in the germline of MCUL patients can indicate carriers of FH mutations with high sensitivity and specificity, and can detect reduced FH activity in some patients without detectable FH mutations. We conclude that MCUL is probably a genetically homogeneous tumour predisposition syndrome, primarily resulting from absent or severely reduced fumarase activity, with currently unknown functional consequences for the smooth muscle or kidney cell.

Women's perception of provider, social, and program support in an outpatient drug treatment program

The purpose of this study was to explore perceptions of pregnant and parenting substance-abusing women in an outpatient drug treatment program regarding provider and social support. Also identified were aspects of the rehabilitation program perceived by the women as assisting them to maintain abstinence from substance use. Data were collected through a demographic questionnaire and a tool designed by the authors based on the Social Stress Model of Substance Abuse (Lindenberg et al., 1993) and the literature of social support. The majority of the women were satisfied with their social support from family and friends. Sixty-seven percent of the women felt the support received from medical providers were not adequate. Also, the majority of the women received no information on risks of drug use and pregnancy from their medical providers. The women felt the program helped maintain abstinence by providing education, coping mechanisms, resources, 12-step programs, and spiritual guidance.

Synapsins as major neuronal Ca2+/S100A1-interacting proteins

The mammalian S100A1 protein can activate the invertebrate myosin-associated giant protein kinase twitchin in a Ca(2+)-dependent manner by more than 1000-fold in vitro; however, no mammalian S100-dependent protein kinases are known. In an attempt to identify novel mammalian Ca(2+)/S100A1-regulated protein kinases, brain extracts were subjected to combined Ca(2+)-dependent affinity chromatography with S100A1 and an ATP analogue. This resulted in the purification to near-homogeneity of the four major synapsin isoforms Ia, Ib, IIa and IIb. All four synapsins were specifically affinity-labelled with the ATP analogue 5'-p-fluorosulphonylbenzoyladenosine. S100A1 bound to immobilized synapsin IIa in BIAcore experiments in a Ca(2+)-dependent and Zn(2+)-enhanced manner with submicromolar affinity; this interaction could be competed for with synthetic peptides of the proposed S100A1-binding sites of synapsin. Double-labelling confocal immunofluorescence microscopy demonstrated that synapsins and S100A1 are both present in the soma and neurites of PC12 cells, indicating their potential to interact in neurons in vivo.

Expression of the AMP-activated protein kinase beta1 and beta2 subunits in skeletal muscle

A heterotrimeric member of the AMP-activated protein kinase (AMPK) isoenzyme family was purified from rat skeletal muscle by immunoaffinity chromatography, consisting of an alpha2 catalytic and two non-catalytic subunits, beta2 and gamma1. The AMPK beta2 cDNA (271 amino acids (aa), molecular weight (MW)=30¿ omitted¿307, pI 6. 3) was cloned from skeletal muscle and found to share an overall identity of 70% with beta1 (270 aa, MW=30¿ omitted¿475, pI 6.0). In the liver AMPK beta1 subunit, Ser-182 is constitutively phosphorylated whereas in skeletal muscle beta2 isoform, we find that Ser-182 is only partially phosphorylated. In addition, the autophosphorylation sites Ser-24, Ser-25 found in the beta1 are replaced by Ala-Glu in the beta2 isoform. beta2 contains seven more Ser and one less Thr residues than beta1, raising the possibility of differential post-translational regulation. Immunoblot analysis further revealed that soleus muscle (slow twitch) contains exclusively beta1 associated with alpha2, whereas extensor digitorum longus muscle alpha2 (EDL, fast twitch) associates with beta2 as well as beta1. Sequence analysis revealed that glycogen synthase, a known AMPK substrate, co-immunoprecipitated with the AMPK alpha2beta2gamma1 complex.

The personal experience of pregnancy for African-American women

This study describes the personal experiences of pregnancy for African-American women. Data were obtained from two group interviews with four African-American nurse-midwives who had experienced pregnancy and had extensive professional experience in the provision of health care services to pregnant African Americans. Three major themes were constructed from the interview narratives. The first concerned the experience of pregnancy as a transition experience from childhood to adulthood and from womanhood to motherhood, involving heightened senses of maturity, self-esteem, and intimacy. The second identified stresses experienced by African-American women, including the lack of material resources and emotional support. The last theme concerned the provision of effective support in pregnancy. The significance of interpersonal relationships with the pregnant women's mothers, other significant women, and their partners was described. Implications for practice included suggestions for the provision of effective emotional support from health care professionals such as attentive listening and the elimination of environmental factors that communicate lowered personal value.

Transgenic mice with chronically elevated luteinizing hormone are infertile due to anovulation, defects in uterine receptivity, and midgestation pregnancy failure

Elevated levels of LH have been associated with infertility and miscarriage in women. Previously, we have reported generating a transgenic mouse model that hypersecretes LH. Female transgenics exhibit extensive pathology including enlarged, cystic, and hemorrhagic ovaries; elevated testosterone:estradiol ratios; and infertility primarily due to anovulation. Here we show that anovulation can be reversed in transgenics and that, despite development within a pathological ovary, oocytes from transgenics are remarkably healthy. Fertilized ova from transgenics are capable of normal development to term when transferred into nontransgenic pseudopregnant recipients. However, reciprocal transfers of nontransgenic embryos into transgenic recipients failed due to lack of uterine receptivity. In addition, while superovulated and mated transgenics appear to have normal early pregnancy, embryos are resorbed at midgestation due to maternal hormonal defects. Transgenic infertility can be rescued by ovariectomy with progesterone and estradiol replacement. These studies are particularly intriguing in light of data indicating an increased rate of miscarriage among women undergoing infertility treatments who are diagnosed with polycystic ovarian syndrome.

Cellular distribution and developmental expression of AMP-activated protein kinase isoforms in mouse central nervous system

The mammalian AMP-activated protein kinase is a heterotrimeric serine/threonine protein kinase with multiple isoforms for each subunit (alpha, beta, and gamma) and is activated under conditions of metabolic stress. It is widely expressed in many tissues, including the brain, although its expression pattern throughout the CNS is unknown. We show that brain mRNA levels for the alpha2 and beta2 subunits were increased between embryonic days 10 and 14, whereas expression of alpha1, beta1, and gamma1 subunits was consistent at all ages examined. Immunostaining revealed a mainly neuronal distribution of all isoforms. The alpha2 catalytic subunit was highly expressed in neurons and activated astrocytes, whereas the alpha1 catalytic subunit showed low expression in neuropil. The gamma1 noncatalytic subunit was highly expressed by neurons, but not by astrocytes. Expression of the beta1 and beta2 noncatalytic subunits varied, but some neurons, such as granule cells of olfactory bulb, did not express detectable levels of either beta isoform. Preferential nuclear localization of the alpha2, beta1, and gamma1 subunits suggests new functions of the AMP-activated protein kinase, and the different expression patterns and cellular localization between the two catalytic subunits alpha1 and alpha2 point to different physiological roles.

A model for the cleft lip nasal deformity

The underlying pathology of the cleft lip nasal deformity has yet to be fully realized, and cleft lip rhinoplasty continues to challenge the reconstructive surgeon. A new model is proposed, which is composed of elements that represent known anatomical structures of the nose. These structures are considered elemental to the mechanism of the primary cleft lip nasal deformity. The lobule is reduced to four arches. Five points on the skull provide foundations for these arches, which react interdependently to extrinsic forces and positional change. When certain changes are imposed on the model, predictable alterations in the configuration of the model imitate the observed deformities in the spectrum of the cleft lip nasal deformity, unilateral and bilateral, mild through severe. The model is described with illustrations, anatomic dissection, physical models, and selected clinical cases. A better understanding of the mechanisms of the cleft nasal deformities can be obtained through analysis of the model.

Biomolecular interaction analysis of IFN gamma-induced signaling events in whole-cell lysates: prevalence of latent STAT1 in high-molecular weight complexes

The basic framework for the JAK/STAT pathway is well documented. Recruitment of latent cytoplasmic STAT transcription factors to tyrosine phosphorylated docking sites on cytokine receptors and their JAK-mediated phosphorylation instigates their translocation to the nucleus and their ability to bind DNA. The biochemical processes underlying recruitment and activation of this pathway have commonly been studied in reconstituted in vitro systems using previously defined recombinant signaling components. We have dissected the Interferon gamma (IFN gamma) signal transduction pathway in crude extracts from wild-type and STAT1-negative mutant cell lines by real-time BIAcore analysis, size-exclusion (SE) chromatography and immuno-detection. The data indicate that in detergent-free cell extracts: (1) the phospho-tyrosine (Y440P)-containing peptide motif of the IFN gamma-receptor alpha-chain interacts directly with STAT1, or STAT1 complexes, and no other protein; (2) non-activated STAT1 is present in a higher molecular weight complex(es) and, at least for IFN gamma-primed cells, is available for recruitment to the activated IFN gamma-receptor from only a subset of such complexes; (3) activated STAT1 is released from the receptor as a monomer.

Chronically elevated luteinizing hormone depletes primordial follicles in the mouse ovary

A few years before reproductive senescence, primordial follicles are depleted from the ovary at a dramatically accelerated rate. It has been proposed that this depletion is due to transient increases in gonadotropin levels. To test this hypothesis, we used mice that produce chronically elevated levels of serum LH via expression of an LHbeta subunit transgene. Ovaries were collected from transgenic and control mice, and complete serial sections were prepared for histological examination. Each section was scanned for morphological abnormalities, and every fifth section was sampled to estimate the total number of primordial, primary, and large preantral follicles per ovary. Until 3 wk postpartum, ovaries from transgenic and control mice were morphologically similar. By 5 wk, control ovaries contained many healthy primordial, primary, and large preantral follicles as well as atretic follicles. Transgenic ovaries contained blood-filled cysts, misshapen granulosa cells, luteinized cells, and approximately 45% fewer primordial follicles than controls. By 3 mo, transgenic ovaries had about 68% fewer primordial follicles and 53% fewer primary follicles than controls. These results suggest that, in addition to having profound effects on growing follicles, chronically elevated LH levels deplete the primordial follicle pool and thus may hasten the onset of reproductive senescence.

Interaction of the recombinant S100A1 protein with twitchin kinase, and comparison with other Ca2+-binding proteins

The giant myosin-associated twitchin kinase, a member of the Ca2+-regulated protein kinase superfamily, is activated by the EF-hand protein S100A1 in a Ca2+-dependent and Zn2+-enhanced manner. We used recombinant S100A1 to further characterize the interaction between the two proteins. Zn2+ enhanced the binding of Ca2+/S100A1 to twitchin kinase fragments (Kd < 50 nM) in assays using a BIAcore biosensor by reducing the S100A1 off rate. Other Ca2+-binding proteins (S100A6, calmodulin, and the calmodulin-like domain of Ca2+-dependent protein kinase alpha) bound to the kinase but did not activate it. These results indicate that binding of Ca2+-binding proteins alone is insufficient to trigger the intramolecular rearrangement of kinase autoinhibitory contacts required for twitchin kinase activation that is specifically elicited by the S100A1 protein. Kinase fragments that contained only the autoinhibited catalytic sequence or an additional immunoglobulin-like domain had very similar properties, indicating that the tethered immunoglobulin-like domain does not modulate kinase regulation.

Bilateral buccal flaps with double opposing Z-plasty for wider palatal clefts

Described is a technique that has evolved from the challenges of closure of larger cleft palate defects and that we are now using in preference over other techniques to repair a wide variety of clefts. Soft-palate closure and muscular sling reconstruction are accomplished using a modified Furlow technique. An associated cleft of the hard palate and the gaps produced by posterior displacement of the reconstructed soft palate are closed by adding tissue, buccal flaps, rather than by closure under tension or leaving residual raw surfaces. Palate lengthening is achieved both by the Z-plasty effect and by the interposition of buccal flaps between the hard and soft palate. Seventy-six palates have been repaired using this procedure. There were three postoperative fistulas.

Ligand for EPH-related kinase (LERK) 7 is the preferred high affinity ligand for the HEK receptor

HEK is a member of the EPH-like receptor tyrosine kinase family, which appear to have roles in development and oncogenesis. Recently, we purified a soluble HEK ligand which is also a ligand (AL1) for the HEK-related receptor EHK1. Promiscuity appears to be a characteristic feature of interactions between the EPH-like receptors and their ligands, termed ligands for EPH-related kinases (LERKs). This prompted us to analyze the interactions between the HEK exodomain and fusion proteins comprising candidate LERKs and the Fc portion of human IgG1 (Fc) or a FLAGTM-peptide tag by surface plasmon resonance, size exclusion high performance liquid chromatography, sedimentation equilibrium, and transphosphorylation. Our results indicate that AL1/LERK7 is the preferred high-affinity ligand for HEK, forming a stable 1:1 complex with a dissociation constant of 12 nM. As expected the apparent affinities of bivalent fusion proteins of LERKs and the Fc portion of human IgG1 had significantly reduced dissociation rates compared with their monovalent, FLAGTM-tagged derivatives. High-avidity binding of monovalent ligands can be achieved by antibody-mediated cross-linking of monovalent ligands and with LERK7 results in specific phosphorylation of the receptor. By extrapolation, our findings indicate that some of the reported LERK-receptor interactions are a consequence of the use of bivalent ligand or receptor constructs and may be functionally irrelevant.

Purification of a ligand for the EPH-like receptor HEK using a biosensor-based affinity detection approach

Advances in screening technologies allowing the identification of growth factor receptors solely by virtue of DNA or protein sequence comparison call for novel methods to isolate corresponding ligand growth factors. The EPH-like receptor tyrosine kinase (RTK) HEK (human EPH-like kinase) was identified previously as a membrane antigen on the LK63 human pre-B-cell line and overexpression in leukemic specimens and cell lines suggested a role in oncogenesis. We developed a biosensor-based approach using the immobilized HEK receptor exodomain to detect and monitor purification of the HEK ligand. A protein purification protocol, which included HEK affinity chromatography, achieved a 1.8 X 10(6)-fold purification of an approximately 23-kDa protein from human placental conditioned medium. Analysis of specific sHEK (soluble extracellular domain of HEK) ligand interactions in the first and final purification steps suggested a ligand concentration of 40 pM in the source material and a Kd of 2-3 nM. Since the purified ligand was N-terminally blocked, we generated tryptic peptides and N-terminal amino acid sequence analysis of 7 tryptic fragments of the S-pyridylethylated protein unequivocally matched the sequence for AL-1, a recently reported ligand for the related EPH-like RTK REK7 (Winslow, J.W., Moran, P., Valverde, J., Shih, A., Yuan, J.Q., Wong, S.C., Tsai, S.P., Goddard, A., Henzel, W.J., Hefti, F., Beck, K.D., & Caras, I.W. (1995) Neuron 14, 973-981). Our findings demonstrate the application of biosensor technology in ligand purification and show that AL-1, as has been found for other ligands of the EPH-like RTK family, binds more than one receptor.

Clinical practice guidelines: implications for use

The differences between standards and clinical practice guidelines are discussed. Implications for using guidelines in nursing practice in defining scope of practice, evaluating careless or negligent practice, practicing outside of clinical guidelines, and using clinical guidelines for cost containment are presented.

Selected factors that influence responses to antihypertensives. Choosing therapy for the uncomplicated patient

Numerous factors may influence an individual patient's response to antihypertensive therapy. The physician should select therapy that is more likely to effectively control the patient's blood pressure. In addition to age and race, specific properties of the drugs plus the method of administration can influence response. Most antihypertensives can be given once or twice daily without the need for sustained-release dosage forms. The appropriate selection of regular-release products can significantly reduce the cost of therapy and improve adherence to the regimen. Because most antihypertensives exist as isomers of two compounds, response to a given agent can be influenced by the type of product (eg, sustained-release) or the method of administration. When these variables are considered for individual patients, it is more likely that a given drug will be effective.

The dorsal skin-flap model in the rat: factors influencing survival

Several authors have postulated that the standard McFarlane-type dorsal rat flap model can survive as a graft. Therefore, in an effort to better understand the metabolic support governing the survival of this flap, five flap designs on the dorsal surface of the rat were studied. Each was manipulated to control progressively for the metabolic support to the flap by means of skin-graft and/or skin-flap physiology. The flap designs included (1) a standard McFarlane flap (n = 10), (2) a full-thickness "flap" graft (n = 10), (3) a McFarlane flap separated from the bed with plastic sheeting (n = 9), (4) a McFarlane flap separated from the bed by closing the wound beneath the flap (n = 29), and (5) flaps raised as in group 4 after a 2-week delay procedure (n = 9). Based on direct comparisons of both the pattern of necrosis and the surviving surface area in each group, we conclude that (1) the distal aspect of the dorsal rat flap can survive as a graft when in contact with the underlying bed, (2) the "take" of the flap as a graft is variable, and (3) to serve as a reasonable indicator of human flap behavior, the skin-graft effect must be controlled for by separating the flap from the underlying bed.

Extrarenal Wilms' tumor. Unusual presentation in the lumbosacral region

True extrarenal Wilms' tumor is a rare malignant neoplasm most frequently presenting in the retroperitoneal or inguinal regions. We report an unusual subcutaneous lumbosacral (LS) region extrarenal Wilms' tumor without associated teratomatous tumor elements or associated neural tube defect in a 2 1/2-year-old girl. Pathologic review revealed features of true extrarenal Wilms' tumor, and the patient remains in complete remission following surgery and combination chemotherapy. This report illustrates the importance of early surgical intervention and pathologic examination of similar soft tissue masses in children.

Metal ion-dependent binding of gastrin to albumin

Binding of 125I-[Nle15]gastrin to albumin purified from porcine serum, from porcine gastric mucosal cytosol, and from bovine serum has been demonstrated by covalent cross-linking and ultracentrifugation. Binding was enhanced in the presence of Zn2+, Ni2+, Cu2+, Co2+, and Cd2+, but not Ca2+, Mg2+, or Mn2+. The best fit to the binding data for bovine serum albumin was obtained with a model assuming two nonequivalent binding sites. The affinity of both sites for gastrin was increased in the presence of 100 microM Zn2+ or Ni2+ ions. The highest association constant observed was 2.3 X 10(5) M-1 in the presence of 100 microM Zn2+ ions. The similarity of the Zn(2+)-dependence of binding for bovine and porcine serum albumins, despite the replacement of His3 by Tyr, suggested that the N-terminal metal ion-binding site was not involved. Although all gastrin affinities were reduced by 50% in the presence of 150 mM NaCl, the Zn(2+)-dependence of binding was retained. We therefore propose that the ternary complex of gastrin, Zn2+ ions, and albumin may play a physiological role in the serum transport of Zn2+ ions and in the uptake of Zn2+ ions from the lumen of the gastrointestinal tract.

Controlled tissue expansion of a groin flap for upper extremity reconstruction

A large upper extremity defect in an 8-year-old girl was resurfaced with an expanded groin flap. Tissue expansion allowed complete coverage of the defect while minimizing the donor deformity. Pretransfer expansion of pedicled flaps offers an alternative to free-flap reconstruction of complex upper extremity defects. This is especially valuable in the pediatric patient, in whom donor-site morbidity can be significant.

Wrist pain: correlation of clinical and plain film findings with arthrographic results

A technique adding digital subtraction to otherwise standard wrist arthrography allows more precise determination of the site of radiocarpal-midcarpal communications. Since arthrographic results often do not correlate with clinical findings, we became interested in correlating these various modalities. The precision of our arthrographic interpretation makes these correlations meaningful. In 72 consecutive patients who had digital subtraction wrist arthrograms, both clinical sites of pain and plain film abnormalities were correlated with arthrographic findings. The results indicate that those patients with ulnar-sided pain more commonly have perforations in that region (88%). Radial-sided pain is a poor indicator of a radial site of perforation. Scapholunate dissociation does not correlate highly with scapholunate perforation (26%).

Submuscular transposition of the ulnar nerve

A retrospective study of 26 submuscular ulnar nerve transpositions was performed with the specific use of grip and pinch analysis to evaluate this form of objective testing. Twenty-six patients were treated by submuscular transposition of the ulnar nerve between 1981 and 1985 and were followed an average of 21 months. Preoperative and postoperative analysis consisted of subjective questioning, clinical examination, quantitative two-point discrimination, quantitative pinch and grip analysis, and electromyographic (EMG) and nerve conduction velocity (NCV) evaluation. Many of the patients suffered from associated problems such as alcohol abuse, diabetes mellitus, and concurrent Guyon's canal compression, which adversely affected the outcome. Subjectively, 62% were improved, 31% were no better, and 7% were worse. Clinical examination demonstrated 46% improved, 35% no better, and 19% worse. Quantitative two-point discrimination was better in 59%, unchanged in 26%, and worse in 15%. Quantitative pinch and grip analysis revealed 28% improved, 56% with little improvement, or the same, and 16% worse, while EMG/NCV showed one-third of the patients in each category postoperatively. Quantitative pinch and grip analysis provided good preoperative and postoperative documentation, which is absent from previous studies in the literature concerning ulnar nerve transportation.

Simultaneous fractures of the distal radius and scaphoid

Simultaneous fractures of the distal radius and scaphoid are uncommon injuries for which the treatment is controversial. Nine patients with these fractures are presented. Five patients were available for long-term followup. In the series, there were five Colles and four Smith's fractures of the distal radius. All scaphoid fractures occurred at the anatomic waist. All injuries resulted from falls of considerable force producing hyperextension at the wrist. The ages of the patients ranged from 21 to 90 years (median, 34). All fractures were placed in a thumb spica cast with the wrist in neutral position. Five fractures required a second reduction of the radius and were placed in external skeletal fixation. No scaphoid fracture was displaced by this treatment, and all scaphoid fractures progressed to union. The principal deformity at followup was an average 16 degrees loss of volar tilt. Residual pain or functional disability was not noted. We conclude that these fractures can be successfully treated by reduction of the radius and immobilization by whatever means necessary to maintain an acceptable position. Scaphoid reduction and healing seemed unaffected by the method of treatment used to treat the distal radius fracture in this series.

Extracutaneous sporotrichosis

Although an uncommon cause of arthritis, sporotrichosis may mimic other forms of joint disease and should be considered in the differential diagnosis of a patient with a chronic monoarticular arthritis or if granulomatous synovitis is recognized by histologic examination. Characteristic skin findings may be absent, repeated cultures may be necessary, severe osseous destructive changes can occur, and surgical extirpation of the diseased tissue combined with amphotericin B chemotherapy is recommended.

The stability of internal fixation in the proximal phalanx

A biomechanical study was performed to assess quantitative differences in the stability obtained with five commonly used types of internal fixation used in proximal phalangeal fractures. The techniques included dorsal plating, dorsal plating combined with an interfragmentary lag screw, two interfragmentary lag screws, tension-band technique, and crossed Kirschner wires. Rigidity and strength in apex palmar bending were determined after oblique osteotomy and fixation of the proximal phalanx. The failure modes for each fixation technique were also observed and described. The results showed that both of the techniques that used interfragmentary lag screws across the oblique osteotomies provided significantly more rigidity than did dorsal plating alone or the wired configurations but that measurements of strength were similar between all techniques tested. Dorsal plates were at a mechanical disadvantage on the compression surface in our apex palmar bend test and consequently provided no more rigidity and strength than did the wired techniques. The tension band technique represented a combination of stiff and flexible intraosseous wires without strict application of tension band principles and provided intermediate rigidity and strength. Rigidity and strength in intact proximal phalanges in the controls were significantly greater than in all techniques tested.

Comparison of internal fixation techniques in metacarpal fractures

A biomechanical study assessed quantitative differences in the stability that was obtained by five commonly used types of internal fixation employed in metacarpal fractures. The techniques included dorsal plating, dorsal plating combined with an interfragmentary lag screw, crossed Kirschner wires, a single intraosseous wire combined with a single oblique Kirschner wire, and a single intraosseous wire alone. Rigidity and strength in torsion and bending were determined after transverse osteotomy and fixation of the metacarpal were performed. The failure modes for each fixation technique were also observed and described. Significant differences in rigidity were found between the plated configurations (with or without an interfragmentary lag screw) and the wired configurations in both apex dorsal bending and axial torsion. The three wired configurations were not significantly different from each other except in torsion. Analysis of the bending moments that were required to produce both yield and failure in apex dorsal bending and also the energy absorbed to yield showed similar disparity between plated and wired techniques. For metacarpal fixation, dorsal plating with or without lag screws provides significantly more stability than do wired techniques and approaches that provided by intact bones.

Chondroblastoma of a metacarpal. Report of a case and review of the literature

A 25-year-old white man had a tender mass on the dorsum of his hand. Routine examination and radiographs revealed a benign lytic neoplasm in the base of the ring metacarpal. The primary treatment consisted of curettage and cancellous bone grafting. The biopsy diagnosis was chondroblastoma. The patient is asymptomatic and has a normal radiograph after a follow-up period of one year. This unusual tumor has seldom been reported at sites distal to the wrist. The report of this chondroblastoma serves as a reminder that not all benign lytic processes in the hand are enchondromas.

Small intestinal permeability to sugars in patients with atopic eczema

Absorption of lactulose and mannitol was measured in eleven patients with atopic eczema and lactulose/mannitol excretion ratios were calculated. Mean lactulose absorption was increased in the patients with exzema and their excretion ratios were higher than those of controls. There was no correlation between either eczema extent or severity and the excretion ratio. We conclude that small intestinal passive permeability is increased in some patients with atopic eczema.

Cutaneous anaesthesia in necrobiosis lipoidica

Cutaneous sensation in plaques of necrobiosis lipoidica was assessed in five non-diabetic and seven diabetic patients. Eleven of the twelve showed partial or complete anaesthesia of the affected skin. These findings are important in the differential diagnosis of tuberculoid leprosy. Further studies of nerve function in cutaneous granulomas need to be carried out.

Septic arthritis of the wrist

Twenty-eight patients (two of them children) with septic arthritis of twenty-nine wrists were treated with early surgical drainage, parenteral antibiotics, and early motion after surgical decompression. The etiology was trauma in seventeen patients, and Staphylococcus aureus was the organism that was most commonly recovered on culture. In twenty-two patients (twenty-three wrists) who were followed for six months to nine years there were no recurrences. The results were evaluated in terms of range of motion, grip strength, and subjective complaints of discomfort and disability. Of the ten wrists with a good or excellent result, all had had the arthrotomy within ten hours after diagnosis, and of the thirteen with a fair or poor result, surgery had been delayed for sixteen hours or longer. The long-term results deteriorated in direct proportion to increasing time until treatment and the number of procedures performed.