Intraoperative Diagnosis of Bilateral Upper Limb Arteriovenous Fistulae in a Child: A Case Report

Arteriovenous fistulae have not been extensively reported in pediatric patients and are rare for pediatric anesthesiologists to encounter in their routine practice. Awareness of these lesions enables clinicians to avoid giving medications through the anomalous vascular connections. We report a child scheduled for an excision of a sacrococcygeal mass in whom we incidentally diagnosed the presence of arteriovenous fistulae in both his upper limbs. The affected limbs should be avoided and the vessels of the lower limbs should be cannulated for administration of fluid and medications during surgery.

SARS-COV-2 reinfection after previous infection and vaccine breakthrough infection through the second wave of pandemic in India: An observational study

Background

There are sparse longitudinal data on SARS-CoV-2 infection after previous infection and after partial or full vaccination.

Methods

This study of a cohort of healthcare workers used Kaplan-Meier analysis with appropriate definition of events and censoring and used Cox models to assess outcomes, with data cut-off on June 18, 2021.

Results

A total of 1806 individuals with median age of 32 (18-64) years, 1483 (82.1%) with at least one vaccine dose, 1085 (60.1%) with 2 vaccine doses, 408 (22.6%) with at least one episode of SARS-CoV-2 infection, and 6 (1.47%) with 2 episodes of infection were included in the analysis. At median follow-up of 38.4 weeks after first SARS-CoV-2 infection (n=408), the 52-week probability of reinfection was 2.2% (95% CI, 1.0-4.91%); and at median follow-up of 13.3 weeks after second dose, the 16-week probability of breakthrough infection was 5.6% (95% CI, 4.33-7.23%), which was significantly higher among those without previous SARS-CoV-2 infection versus with previous infection (6.4% vs 1.8%, p=0.016, adjusted Cox HR=3.49, 95% CI, 1.09-11.20, p=0.036) and females versus males (7.9% vs 3.8%, p=0.007, adjusted Cox HR=2.06, 95% CI 1.19-3.56, p=0.01).

Conclusions

There was low probability of reinfection after previous SARS-CoV-2 infection and higher vaccine breakthrough infections among females and those without previous infection.

Clinical characteristics, laboratory parameters and outcomes of COVID-19 in cancer and non-cancer patients from a tertiary Cancer Centre in India

BACKGROUND

There is paucity of data regarding clinical characteristics, laboratory parameters and outcomes of coronavirus disease (COVID-19) in cancer versus non-cancer patients, particularly from India.

MATERIALS AND METHODS

This was an observational, single-centre, retrospective analysis of patients with laboratory-confirmed COVID-19 hospitalised in our institution between 22 May 2020 and 1 December 2020. We compared baseline clinical characteristics, laboratory parameters and outcomes of COVID-19 (overall mortality, time to discharge) between cancer and non-cancer patients.

RESULTS

A total of 200 COVID-19 infection episodes were analysed of which 109 (54.5%) were patients with cancer and 91 (45.5%) were patients without cancer. The median age was 43 (interquartile range [IQR]:32-57), 51 (IQR: 33-62) and 38 (IQR: 31.5-49.3) years; of whole cohort, cancer and non-cancer patients, respectively. Comparison of outcomes showed that oxygen requirement (31.2% [95% CI: 22.6-40.7] vs. 17.6% [95% CI: 10.4-26.9]; p = 0.03), median time to discharge (11 days [IQR: 6.75-16] vs. 6 days [IQR: 3-9.75]; p < 0.001) and mortality (10.0% [95% CI: 5.2-17.3] vs. 1.1% [95% CI: 0.03-5.9]; p = 0.017) were significantly higher in patients with cancer. In univariable analysis, factors associated with higher mortality in the whole cohort included diagnosis of cancer (10.1% vs. 1.1%; p = 0.027; odds ratio [OR]: 7.04), age ≥60 (17.4% vs. 2.6%; p = 0.001; OR: 7.38), oxygen requirement (22% vs. 0.6%; p < 0.001; OR: 29.01), chest infiltrates (19.2% vs. 1.4%; p < 0.001; OR: 22.65), baseline absolute lymphocyte count <1 × 109 /L (10.8% vs. 1.9%; p = 0.023; OR:5.1), C-reactive protein >1 mg% (12.8% vs. 0%; p = 0.027; OR: 24.69), serum procalcitonin >0.05 ng/ml (22.65% vs. 0%; p = 0.004; OR: 4.49) and interleukin-6 >6 pg/ml (10.8% vs. 1.3%; p = 0.036; OR: 3.08). In multivariable logistic regression, factors significantly associated with mortality were oxygen requirement (p = 0.005; OR: 13.11) and high baseline procalcitonin level (p = 0.014; OR: 37.6).

CONCLUSION

Cancer patients with COVID-19 have higher mortality and require longer hospital stay. High procalcitonin levels and oxygen requirement during admission are other factors that affect outcomes adversely.

Comprehensive immune cell profiling depicts an early immune response associated with severe coronavirus disease 2019 in cancer patients

Recent studies have highlighted multiple immune perturbations related to severe acute respiratory syndrome coronavirus 2 infection-associated respiratory disease [coronavirus disease 2019 (COVID-19)]. Some of them were associated with immunopathogenesis of severe COVID-19. However, reports on immunological indicators of severe COVID-19 in the early phase of infection in patients with comorbidities such as cancer are scarce. We prospectively studied about 200 immune response parameters, including a comprehensive immune-cell profile, inflammatory cytokines and other parameters, in 95 patients with COVID-19 (37 cancer patients without active disease and intensive chemo/immunotherapy, 58 patients without cancer) and 21 healthy donors. Of 95 patients, 41 had severe disease, and the remaining 54 were categorized as having a nonsevere disease. We evaluated the association of immune response parameters with severe COVID-19. By principal component analysis, three immune signatures defining characteristic immune responses in COVID-19 patients were found. Immune cell perturbations, in particular, decreased levels of circulating dendritic cells (DCs) along with reduced levels of CD4 T-cell subsets such as regulatory T cells (T_regs ), type 1 T helper (Th1) and Th9; additionally, relative expansion of effector natural killer (NK) cells were significantly associated with severe COVID-19. Compared with patients without cancer, the levels of terminal effector CD4 T cells, T_regs , Th9, effector NK cells, B cells, intermediate-type monocytes and myeloid DCs were significantly lower in cancer patients with mild and severe COVID-19. We concluded that severely depleted circulating myeloid DCs and helper T subsets in the initial phase of infection were strongly associated with severe COVID-19 independent of age, type of comorbidity and other parameters. Thus, our study describes the early immune response associated with severe COVID-19 in cancer patients without intensive chemo/immunotherapy.

Clinical course of severe COVID19 treated with tocilizumab and antivirals post-allogeneic stem cell transplant with extensive chronic GVHD

Recipients of allogeneic hematopoietic stem cell transplantation (allo‐HSCT) are an immunocompromised group who are likely to develop severe complications and mortality because of coronavirus disease 2019 (COVID‐19). We report here a 61‐year‐old male patient of primary myelofibrosis who underwent an allo‐HSCT 6 years earlier, had chronic graft‐versus‐host disease (cGVHD) involving the liver, lung, eyes, and skin, (with recurrent episodes of pulmonary infections) who developed severe COVID‐19. The patient was treated with tocilizumab, and a combination of lopinavir/ritonavir, ribavirin, interferon‐β1b. He was discharged after 31 days with full recovery. Tocilizumab, a humanized monoclonal antibody against IL6, has been shown to benefit respiratory manifestations in severe COVID19. However, this is first report, to our knowledge, of its use and benefit in a post HSCT recipient.

Unilateral acquired Brown's syndrome in systemic scleroderma: An unusual cause for diplopia

Brown's syndrome can be congenital or acquired with multiple causes. It has been described as a ocular complication in various rheumatic and nonrheumatic diseases. We describe a case of 27-year-old female patient with 5 years old history of systemic scleroderma who developed vertical diplopia, a left head tilt, and restriction of left eye on elevation in adduction. The patient responded to systemic steroids with resolution of diplopia.

A systematic review of radiographic definitions of foot osteoarthritis in population-based studies

OBJECTIVE

To identify the methods used in population-based epidemiological studies to diagnose radiographic foot osteoarthritis (OA) and to estimate the population prevalence of radiographic foot OA.

METHOD

Electronic databases searched included Medline, Embase, CINAHL and Ageline (inception to May 2009). The search strategy combined search terms for radiography, OA, foot, and specific foot joints. Predetermined selection criteria were applied. Data extracted from each paper included: sample population, radiographic views taken, foot joints examined, scoring system used, definition of OA applied, reliability of radiographic scoring and prevalence of radiographic OA in the foot.

RESULTS

Titles and abstracts of 1035 papers were reviewed and full-texts of 21 papers were obtained. Fifteen papers met inclusion criteria and a further 12 papers were included after screening references. Radiographic views were frequently not specified (NS) but a combination of antero-posterior (AP) and lateral (Lat) views was most commonly reported. The first metatarsophalangeal (MTP) joint was the most commonly examined joint (n=20, 74%). Nineteen studies (70%) used the Kellgren and Lawrence (K&L) grading system, 95% of which defined OA as K&L grade> or =2. Estimates of the prevalence of radiographic first MTP joint OA (defined as K&L> or =2) in middle-aged to older adults ranged from 6.3 to 39%. Significant statistical heterogeneity prevented pooling of prevalence estimates.

CONCLUSION

There are comparatively few studies examining radiographic foot OA. Existing studies mainly focus on the first MTP joint and use the K&L grading system. Future studies are needed to quantify the prevalence of radiographic OA at the different joint complexes within the foot.

Real-time patch-cram detection of intracellular cGMP reveals long-term suppression of responses to NO and muscarinic agonists

Cyclic GMP (cGMP) is a crucial intracellular messenger in neuronal, muscle, and endocrine cells. The intracellular concentration of cGMP is regulated by various neurotransmitters, including acetylcholine (ACh) and nitric oxide (NO). While much is known about the biochemical steps leading to cGMP synthesis, little is known about cGMP kinetics in intact cells. Here, we use "patch-cramming," in which an excised, inside-out membrane patch containing cyclic nucleotide-gated ion channels is used as a biosensor, to obtain the first real-time measurements of cGMP in intact cells. Patch-cramming experiments on neuroblastoma cells show that both muscarinic agonists and NO rapidly elevate cGMP. NO elicits cGMP responses repeatedly without decrement, whereas responses to muscarinic agonists exhibit a profound and prolonged desensitization. Remarkably, muscarinic agonists also cause long-term (>30 min) suppression (LTS) of cGMP responses elicited by NO. Biochemical measurements reveal that rat sympathetic neurons also exhibit LTS of cGMP, suggesting that LTS is a widespread mechanism that may contribute to synaptic plasticity.

Modulation of rod photoreceptor cyclic nucleotide-gated channels by tyrosine phosphorylation

Cyclic nucleotide-gated (CNG) channels in vertebrate photoreceptors are crucial for transducing light-induced changes in cGMP concentration into electrical signals. In this study, we show that both native and exogenously expressed CNG channels from rods are modulated by tyrosine phosphorylation. The cGMP sensitivity of CNG channels, composed of rod alpha-subunits expressed in Xenopus oocytes, gradually increases after excision of inside-out patches from the oocyte membrane. This increase in sensitivity is inhibited by a protein tyrosine phosphatase (PTP) inhibitor and is unaffected by three different Ser/Thr phosphatase inhibitors. Moreover, it is suppressed or reversed by application of ATP but not by a nonhydrolyzable ATP analog. Application of protein tyrosine kinase (PTK) inhibitors causes an increase in cGMP sensitivity, but only in the presence of ATP. Taken together, these results suggest that CNG channels expressed in oocytes are associated with active PTK(s) and PTP(s) that regulate their cGMP sensitivity by changing phosphorylation state. The cGMP sensitivity of native CNG channels from salamander rod outer segments also increases and decreases after incubation with inhibitors of PTP(s) and PTK(s), respectively. These results suggest that rod CNG channels are modulated by tyrosine phosphorylation, which may function as a novel mechanism for regulating the sensitivity of rods to light.

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Abnormal serum IGF-II transport in non-islet cell tumor hypoglycemia results from abnormalities of both IGF binding protein-3 and acid labile subunit and leads to elevation of serum free IGF-II

The syndrome of non-islet cell tumor hypoglycemia (NICTH) is the result of hypersecretion of IGF-II by a tumor although serum IGF-II is seldom elevated. This is attributable to abnormalities of the IGF binding proteins (IGFBPs) present in NICTH which is characterized by a marked decrease in the fraction of IGFBP-3 present in the 150 kD complex with acid labile subunit (ALS) and a 2- to 4-fold increase in IGFBP-2. We studied the impact of these changes in IGFBPs on the concentration of free IGF-II using a neutral C-18 Sep-Pak extraction procedure. We found that free IGF-II was increased 8- to 20-fold in NICTH. Thus there is no limitation of free IGF-II for complex formation. Additional experiments were conducted to determfine whether ALS deficiency limits 150 kD complex formation. We observed that addition of purified ALS to NICTH sera only partially succeeded in converting smaller complexes containing IGFBP-3 to large 150 kD complexes. We conclude that both a functional deficiency of ALS and IGFBP-3 are present in NICTH sera. The increased free IGF-II in NICTH sera contributes greatly to bioactivity and largely explains the marked hypoglycemia of NICTH patients even when total serum IGF-II concentrations may remain within normal limits.

Non-islet cell tumour induced hypoglycaemia with acromegaloid facial and acral swelling

The syndrome of non-islet cell tumour hypoglycaemia (NICTH) has been linked with the synthesis and secretion of 'big' IGF-II. We report a patient with a large pelvic clear cell sarcoma who developed recurrent severe hypoglycaemia and in addition presented with severe soft tissue facial swelling, skin tags and nuchal hyperpigmentation. After resection of the tumour serum 'big' IGF-II returned to normal and the acromegaloid skin changes remitted.

The diastrophic dysplasia gene encodes a novel sulfate transporter: positional cloning by fine-structure linkage disequilibrium mapping

Diastrophic dysplasia (DTD) is a well-characterized autosomal recessive osteochondrodysplasia with clinical features including dwarfism, spinal deformation, and specific joint abnormalities. The disease occurs in most populations, but is particularly prevalent in Finland owing to an apparent founder effect. DTD maps to distal chromosome 5q and, based on linkage disequilibrium studies in the Finnish population, we had previously predicted that the DTD gene should lie about 64 kb away from the CSF1R locus. Here, we report the positional cloning of the DTD gene by fine-structure linkage disequilibrium mapping. The gene lies in the predicted location, approximately 70 kb proximal to CSF1R, and encodes a novel sulfate transporter. Impaired function of its product is likely to lead to undersulfation of proteoglycans in cartilage matrix and thereby to cause the clinical phenotype of the disease. These results demonstrate the power of linkage disequilibrium mapping in isolated populations for positional cloning.

Prevalence of microalbuminuria in diabetic subjects

Total 193 diabetic patients were investigated to assess the prevalence of microalbuminuria. Urinary albumin excretion rate (UAER) was measured by radioimmunoassay (RIA) on 3 hours urine samples. The prevalence of microalbuminuria (UAER) > 15 micrograms/min was 41%. Microalbuminuria was commonly observed in patients having diabetes for more than 5 years. A significant correlation was found between duration of diabetes and microalbuminuria (p < 0.01). Glycemic control (fasting and postprandial blood sugar) did not show any correlation with UAER, whereas blood urea (r.39, p < 0.01), creatinine (r.26, p < 0.05) and chloride (r.24, p < 0.05) were positively correlated. A significant correlation was found between raised blood pressure and UAER (p < 0.01).

Serum "big insulin-like growth factor II" from patients with tumor hypoglycemia lacks normal E-domain O-linked glycosylation, a possible determinant of normal propeptide processing

The insulin-like growth factor II (IGF-II) gene is overexpressed in many mesenchymal tumors and can lead to non-islet-cell tumor hypoglycemia (NICTH). ProIGF-II consists of the 67 aa of IGF-II with a carboxyl 89-aa extension, the E domain. A derivative of proIGF-II containing only the first 21 aa of the E domain [proIGF-II-(E1-21)] has been isolated by others from normal serum and has O-linked glycosylation. We found that the "big IGF-II" of normal serum, as detected by an RIA directed against residues 1-21 of the E domain of proIGF-II, was reduced in size by treatment with neuraminidase and O-glycosidase. The big IGF-II, which is greatly increased in NICTH sera, was unaffected by neuraminidase and O-glycosidase treatment. We have also shown that big IGF-II from normal serum is retained by jacalin lectin columns and that big IGF-II from NICTH serum was not retained, indicating that it lacked O-glycosylation. Normal O-linked glycosylation may be required for proper peptidase processing of proIGF-II. The lack of normal O-linked glycosylation by tumors may explain the predominance of big IGF-II in NICTH sera. In normal serum, most of the IGF-II is present in a 150-kDa ternary complex with IGF-II binding protein (IGFBP) 3 and alpha subunit. In NICTH serum, however, the complexes carrying big IGF-II are < 50 kDa. We investigated whether big IGF-II of NICTH was responsible for this abnormality. Tumor big IGF-II and IGF-II were equally effective in forming the 150-kDa complex with purified IGFBP-3 and 125I-labeled alpha subunit. Both 125I-labeled IGF-II and 125I-labeled proIGF-II-(E1-21), when incubated with normal serum, formed the 150-kDa complex as detected by Superose 12 exclusion chromatography. We conclude that the nonglycosylated big IGF-II of NICTH serum can form normal complexes with serum IGFBPs. The defective binding in NICTH is attributable to defective IGFBP-3 binding.

Heterogeneity of serum peptides with immunoactivity detected by a radioimmunoassay for proinsulin-like growth factor-II E domain: description of a free E domain peptide in serum

We have reported that normal human sera contain immunoactivity (IA) detected by a RIA directed against the first 21 amino acids of the E domain of proinsulin-like growth factor-II (pro-IGF-II). Marked elevations of E-21 IA were found in the serum of patients with nonislet cell hypoglycemia (NICTH) and patients with renal failure receiving chronic hemodialysis. In this paper we describe some of the properties of the E-21 IA of normal and abnormal sera. The E-21 IA eluted from a calibrated acid Sephadex G-50 column as two major peaks. In normal serum the first major peak had a mol wt (Mr) between 14,000-15,000, and the second peak had a Mr between 5,000-6,000. When E-21 IA from serum of a patient with NICTH was similarly studied, most of the IA was present as a Mr 11,000 peak and only a small amount was present as a 5,000-6,000 Mr peak. In contrast, most of the E-21 IA present in the sera of patients on hemodialysis was present in the smaller molecular form, which eluted from a reverse phase column as a single component. This small Mr peak lacked determinants for the IGF-II monoclonal antibody (Amano), for pooled serum IGF-binding proteins, and for the IGF-I receptors on human placental membranes. We suggest that the 15- and 11-kilodalton peaks represent the glycated and unglycated forms of pro-IGF-II (E-21) reported by others. The glycated form appears to predominate in normal serum, whereas the nonglycated form predominates in the serum of patients with NICTH and renal failure. The 5,000-6,000 Mr E-21 IA probably represents a fragment of the free E domain of pro-IGF-II. Its size is consistent with cleavage of the free E domain between Arg46 and Arg47. The accumulation of this E-21 IA in renal failure is evidence that the kidney has a major role in the clearance of this fragment, which is not accomplished by the membranes used in hemodialysis.

Measurement of derivatives of proinsulin-like growth factor-II in serum by a radioimmunoassay directed against the E-domain in normal subjects and patients with nonislet cell tumor hypoglycemia

We describe a modified RIA using a rabbit polyclonal antiserum directed against the first 21 amino acids of the E-domain (E-21) of proinsulin-like growth factor-II (pro-IGF-II). For standardization, we purified big IGF-II from patients with nonislet cell tumor hypoglycemia (NICTH). Under the conditions of our assay there was no significant interference from IGF-binding proteins. The big IGF-II present in the serum of a patient with NICTH displaced [125I]E-(1-21) from antibody parallel to our big IGF-II standard. We found a progressive rise in E-21 immunoactivity (IA) during childhood, with somewhat higher values in girls than in boys. In normal adults the mean E-21 IA level was 138 +/- 49 (+/- SD) micrograms/L. Women with twin pregnancies had higher E-21 IA than women with single pregnancies (302 +/- 66 compared with 120 +/- 18 micrograms/L). We found a marked elevation of E-21 IA in patients with NICTH due to sarcomas (n = 3), hepatoma (n = 2), adrenal carcinoma (n = 1), and carcinoma of the lung (n = 1). No elevation of E-21 IA was present in the serum of a hypoglycemic patient with a hypernephroma or another patient with carcinoma of the lung. Marked elevation of E-21 IA was observed in the serum of patients with renal failure receiving chronic hemodialysis. We conclude that this assay will prove useful in the diagnosis of NICTH in patients who are not azotemic and the investigation of the role of the kidney in clearing products of pro-IGF-II processing.

Whole body nitrogen kinetics and their relationship to growth in short children treated with recombinant human growth hormone

We studied the effects of growth hormone on retention of 15N-labeled amino acids in 34 short, prepubertal, growth hormone-sufficient children and three growth hormone-deficient subjects. All 34 non-growth hormone-deficient children had apparently normal circulating growth hormone molecules and no mutations were detected in the growth hormone or IGF-I genes of any subjects. Fibroblasts from 34 children responded normally when challenged with recombinant human IGF-I. During the last 72 h of a 4-d challenge with recombinant human growth hormone (16 micrograms/kg body wt), retention of a mixed 15N-amino acid dose varied between 5.7 and 50.5%. Whole body protein synthesis, breakdown, and net anabolism calculated from the 15N kinetics were all increased by the acute growth hormone challenge. However, no routine clinical feature or laboratory determination correlated with the nitrogen retention response. After subsequent treatment (75 micrograms/kg three times a week) with recombinant human growth hormone for 1 y, there was a significant increase in height velocity, but this increase was not related significantly to pretreatment variables other than inversely to pretreatment height velocity. There was a significant (p = 0.03) correlation between the change in height velocity Z score and the degree of nitrogen retention to acute challenge with growth hormone, but this correlation was too weak (r = 0.37) to be of practical value in predicting the treatment growth response in an individual child.

Hypersomatotropism in pregnant women, as measured by a human liver radioreceptor assay

Radioreceptor assays (RRAs) provide useful information about the bioactivity of peptide hormones. We have developed a RRA for human GH using membranes prepared from human liver. The assay has 1% cross-reactivity with human PRL, 0.11% cross-reactivity with human chorionic somatomammotropin, and negligible cross-reactivity with bovine and rat GH. The assay has distinct advantages over the IM-9 lymphocyte RRA in having reduced nonspecific interference from serum proteins and providing a uniform source of receptors which can be stored for long periods at -70 C. The coefficient of variation of the assay is 13%. In studies of 55 sera from short children with normal or elevated serum GH concentrations the mean ratio of RRA GH to immunoradiometric assayed GH was 1.28. This assay provided important information about the total GH activity in pregnancy. There was a progressive rise in RRA GH during pregnancy, reaching 64.7 +/- 2.5 (+/- SE) micrograms/L at term. This level is 2-3 times higher than suggested by earlier estimates made with monoclonal antibody RIAs for pituitary GH. At term the contributions to total GH activity of serum are less than 3% from the pituitary, 12% from human chorionic somatomammotropin reacting with the GH receptor, and 85% from placental GH. Despite this great increase in receptor-reactive GH, somatomedin activity by bioassay is reduced, and IGF-I, determined by RIA after acid-gel filtration, is minimally elevated.

Embryotoxicity and fetotoxicity of orally administered hexavalent chromium in mice

The embryotoxic and fetotoxic potential of hexavalent chromium (Cr+6) in mice was investigated by administering 250, 500, and 1000 ppm of potassium dichromate daily through drinking water during the entire gestation period. An increase in embryonic deaths was observed; however, in the mothers treated with the highest dose, there was complete absence of implantation sites. No major abnormality was observed in the fetuses except that Cr+6 exposure increased the incidences and types of external and skeletal malformations. It is concluded that oral exposure to Cr+6 causes dose-dependent embryolethal effects in mice.

Release of growth hormone binding protein from IM-9 lymphocytes by endopeptidase is dependent on sulfhydryl group inactivation

The hydrophilic GH-binding protein of serum is a derivative of the GH receptor. Little is known how this GH binding protein is released from the receptor which is firmly anchored in the plasma membrane. The IM-9 lymphocytes provide a useful laboratory model for studying this process because they are richly endowed with GH receptors and, under special conditions, are able to shed these receptors during incubation. Incubation of IM-9 cells for 90 min at 30 C did not result in the appearance of significant [125I]hGH binding in conditioned medium as determined with an ultrogel AcA 44 minicolumn. When iodoacetamide, 20 mM, or N-ethylmaleimide, 5 mM, was added during incubation, the conditioned medium bound 20-35% of [125I]human(h)GH. p-Chloromercuriphenyl sulfonic acid was less effective in promoting shedding of GH-binding protein. In contrast, aprotinin, phenylmethylsulfonylfluoride (PMSF), bacitracin, leupeptin, pepstatin, phosphoramidon, or chloroquine did not promote release of GH binding protein and did not affect iodoacetamide-induced release. Release was not inhibited by the addition of serum lacking GH binding protein. GH binding protein release was markedly temperature sensitive and practically ceased at 4 C. GH binding protein incubated with [125I] hGH was cross-linked with disuccinimidyl suberate. After sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence of dithiothreitol the complex migrated with an estimated molecular weight of 100,000 whereas [125I]hGH cross-linked to the membrane-bound GH receptor of the IM-9 cells migrated with an estimated molecular weight of 135,000. The smaller size of the binding protein is consistent with its derivation from the extracellular domain of the GH receptor. Because the release of this GH binding is greatly augmented by iodoacetamide and N-ethylmaleimide, two known sulfhydryl reactive reagents, we suggest that a free sulfhydryl group, either on the GH receptor or on a neighboring protein normally maintains the integrity of the receptor. The loss of this sulfhydryl group destabilizes the receptor and permits a membrane endopeptidase to release the GH binding protein. Cleavage is not dependent on lysosomal action and is not inhibited by protease inhibitors.

Calcium compartmentation in isolated renal tubules in suspension

Substantial increases of total cell Ca2+ have been observed in suspensions of isolated rabbit proximal tubules subjected to hypoxic injury or treated with exogenous ATP followed by apparent recovery with reoxygenation of the hypoxic tubules or continued incubation of ATP-treated tubules. Ca2+ compartmentation studies using digitonin and metabolic inhibitors were done to clarify the basis for these changes. Digitonin, 40-90 micrograms/mg tubule protein, rapidly permeabilized the tubule cells and did not impair mitochondrial Ca2+ sequestration. Most of the increases of tubule cell Ca2+ produced by hypoxia and ATP were accounted for by pools which could be rapidly removed by exposure of tubules to EGTA and the uncoupler carbonyl cyanide m-chlorophenyl hydrazone without concomitant use of digitonin, suggesting that the changes of Ca2+ predominantly reflect sequestration by mitochondria in severely damaged cells or mitochondria already released to the medium from them. The time course of uptake followed by spontaneous release of mitochondrial Ca2+ from tubule cells deliberately permeabilized with digitonin, then incubated for prolonged periods, indicated that the decreases of tubule cell Ca2+ during reoxygenation of hypoxic suspensions and prolonged incubation of ATP-treated tubules were likely to be attributable to loss of Ca2+ from free mitochondria and those in damaged cells rather than to extrusion by intact cells.

Reduced 125I-hGH binding by serum of dwarf pigs but not by serum of dwarfed poodles

1. Normal and growth-deficient poodle and swine strains were characterized for serum growth hormone-binding protein (GH-BP) content as well as other growth-related hormones, and the relationship between these factors and body size was examined. 2. GH-BPs were found in all strains of pigs and poodles. Concentrations of GH-BPs (as expressed by specific bindings) did not vary among the poodle breeds, but did correlate with body size in pigs. 3. Insulin-like growth factors (IGFs) I and II were decreased 71 and 44% respectively in miniature compared to standard size poodles. 4. Only the Yucatan micro pig strain had reduced serum IGF-I concentrations compared to normal controls. 5. Growth hormone concentrations however were normal to elevated in all micro and miniature pig strains. 6. Serum triiodothyronine concentrations were reduced in Yucatan mini and micro pigs in spite of normal circulating levels of thyroxine. 7. Body size reductions in the swine and dog strains are probably attributable to different primary defects of various growth related hormones or hormone receptors. 8. Each species breed therefore could serve as a model for a different human growth-deficient condition.

The ontogeny of serum GH binding protein in man: a possible indicator of hepatic GH receptor development

Experiments in rabbits suggest that a serum GH binding protein (GH-BP) probably is derived largely from hepatic membrane bound GH receptors. Human serum contains a specific GH binding protein which can be easily measured by incubation with [125I] hGH and separation of [125I] hGH-BP complexes from free [125I] hGH by gel filtration through an Ultrogel AcA 44 minicolumn. In each assay GH-BP activity of a reference (normal young adult) serum is similarly run and the results are expressed as a percentage of the activity of the unknown serum divided by the GH-BP activity of the reference serum after correction for the expected inhibition of GH binding resulting from the GH content of the unknown serum. The mean relative specific GH binding protein (RSGH-BP) of cord serum from 11 premature infants was only 3.2 +/- 1.4% (SE) and of cord serum from 17 full term infants was 14.9 +/- 2.5%. During the first two decades of life there was a progressive rise of RSGH-BP with considerable individual variation. The mean serum RSGH-BP of 13 such subjects was 54.5 +/- 6.2%. More uniform RSGH-BP results were obtained in serum from 15 young adults, 91.7 +/- 7.4%. Lower RSGH-BP 77.2 +/- 5.4% was found in serum from 12 healthy older adults (age 60 to 70 years). The low levels of RSGH-BP in fetal serum are consistent with the reported low concentrations of GH receptors in sheep and rat fetal liver membranes. We suggest the measurement of GH-BP activity provides a simple, noninvasive measure of the ontogeny of GH receptors of human beings.

Absence of serum growth hormone binding protein in patients with growth hormone receptor deficiency (Laron dwarfism)

It has recently been recognized that human serum contains a protein that specifically binds human growth hormone (hGH). This protein has the same restricted specificity for hGH as the membrane-bound GH receptor. To determine whether the GH-binding protein is a derivative of, or otherwise related to, the GH receptor, we have examined the serum of three patients with Laron-type dwarfism, a condition in which GH refractoriness has been attributed to a defect in the GH receptor. The binding of 125I-labeled hGH incubated with serum has been measured after gel filtration of the serum through an Ultrogel AcA 44 minicolumn. Nonspecific binding was determined when 125I-hGH was incubated with serum in the presence of an excess of GH. Results are expressed as percent of specifically bound 125I-hGH and as specific binding relative to that of a reference serum after correction is made for endogenous GH. The mean +/- SEM of specific binding of sera from eight normal adults (26-46 years of age) was 21.6 +/- 0.45%, and the relative specific binding was 101.1 +/- 8.6%. Sera from 11 normal children had lower specific binding of 12.5 +/- 1.95% and relative specific binding of 56.6 +/- 9.1%. Sera from three children with Laron-type dwarfism lacked any demonstrable GH binding, whereas sera from 10 other children with other types of nonpituitary short stature had normal relative specific binding. We suggest that the serum GH-binding protein is a soluble derivative of the GH receptor. Measurement of the serum GH-binding protein may permit recognition of other abnormalities of the GH receptor.

Effect of respiratory acidosis on intracellular pH of the proximal tubule

In contrast to chronic metabolic acidosis, chronic respiratory acidosis does not result in an adaptation in either renal ammonia or glucose production. To examine the possibility that this might be explained by a difference in proximal tubule intracellular pH, the response of two pH-sensitive metabolites, citrate and alpha-ketoglutarate, were assessed. Metabolic acidosis of 3 days duration, induced by drinking 1.5% NH4Cl, significantly reduced urinary citrate excretion (172 to 15 mumol/day) and renal cortical citrate (1.33 to 0.88 mumol/g) and alpha-ketoglutarate (0.90 to 0.46 mumol/g) concentrations in comparison with normal rats. Chronic respiratory acidosis, produced by 3 days in a 10% CO2 environment, lowered systemic pH similar to metabolic acidosis but had no effect on either urinary citrate excretion or renal cortical citrate and alpha-ketoglutarate concentrations. By contrast, acute respiratory acidosis (3, 6, or 24 h duration) reduced urinary citrate excretion and renal cortical citrate and alpha-ketoglutarate concentrations in a fashion similar to acute metabolic acidosis. These data suggest that acute acidosis of either respiratory or metabolic origin lowers the intracellular pH of the proximal tubule. However, when the acid-base abnormality enters the chronic phase, proximal tubular intracellular pH remains low with metabolic acidosis but returns to normal values with respiratory acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of somatomedin binding in human serum by ultracentrifugation and gel filtration

It is known that the somatomedins exist in human serum complexed to specific binding proteins. The existence of unbound somatomedins in serum has never unequivocally been demonstrated. We have characterized the distribution of insulin-like growth factor (IGF) I in different fractions after gel filtration of serum through Sephadex G-200 in neutral buffer. IGF-I was measured by RIA after acid extraction. Seventy-two percent of serum IGF-I was associated with large complexes with an estimated size of about 150,000 daltons and 25% was associated with smaller complexes of about 50,000 daltons. No unbound IGF-I was detected. Ultracentrifugation of 10 ml fresh serum was carried out at 106,000 X g for 17 h, after which the tube was aspirated in 1-ml fractions beginning at the top. IGF-I by RIA in fractions 2 and 3 sedimented with albumin; in fractions 4 to 7, the sedimentation pattern approached that of immunoglobulin G. This shift is consistent with the size distribution of IGF-I complexes demonstrated by gel filtration. The failure to find any significant increase in the concentration of IGF-I relative to albumin in the top 30% of the tube (fractions 1-3) after centrifugation argues against the presence of measurable free IGF-I in these fractions. The ability of upper fractions to bind added [125I]IGF-II proved to closely approximate the binding of the initial serum, indicating little sedimentation of the accessible binding protein. The relative binding of [125I]IGF-II by serum aliquots proved to be markedly concentration dependent. At concentrations above 5% serum, the incremental increase of binding as a function of serum concentration was much reduced. We interpret this to indicate that with dilution there is a dissociation of complexes and an increase in accessible binding sites. This phenomenon may modify tissue delivery of somatomedins in interstitial fluid. The data suggest that in undiluted serum there is no significant concentration of free somatomedins but at the dilution of serum that exists in the interstitial fluid, dissociation of bound somatomedins may be facilitated.

Homologous IM-9 lymphocyte radioreceptor and receptor modulation assays for human serum growth hormone

Radioreceptor assays for human GH (hGH) have been developed using the IM-9 cultured human lymphoid cell receptor. Varying degrees of nonspecific interference with [125I] hGH binding to these cells occurs in the presence of serum. We have modified the traditional IM-9 competitive binding assay for hGH and abolished the nonspecific serum effects. The modified competitive assay is sensitive to as little as 2 ng/ml hGH, and it has been validated by the quantitative recovery of purified pituitary hGH in hypopituitary serum. Sera from stimulated normals, acromegalics, and patients with severe growth retardation were assayed. The RIA to radioreceptor assay ratios for these groups were 0.98 +/- 0.10, 0.97 +/- 0.18, and 2.43 +/- 0.54, respectively. The assay has potential usefulness in screening and predicting growth-retarded patients most likely to respond to exogenous hGH therapy. In addition, a sensitivity receptor modulation assay, which uses the ability of hGH to regulate its homologous IM-9 receptors, is described. This is 8- to 10-fold more sensitive than the nonregulatory assays and has been applied to the measurement of hGH in sera from unstimulated normals and acromegalics. The ratios of RIA to receptor modulation assay for the two groups were 1.17 +/-0.68 ad 1.07 +/- 0.26, respectively. These sensitive receptor assays offer a powerful technique for the measurement of biologically active and inactive GH peptide in serum, and may be particularly useful in the evaluation of statural growth disorders.

Measurement of somatomedin-related peptides in fetal, neonatal, and maternal rat serum by insulin-like growth factor (IGF) I radioimmunoassay, IGF-II radioreceptor assay (RRA), and multiplication-stimulating activity RRA after acid-ethanol extraction

Previous measurements of somatomedins (Sms) and insulin-like growth factors (IGFs) in maternal and fetal serum have yielded contradictory results. We have, therefore, measured maternal, fetal, and neonatal rat serum with two highly specific assays: 1) IGF-I/Sm-C RiA and 2) a highly specific IGF-II/rat placental membrane radioreceptor assay (RRA). In addition, we have made measurements with a less specific multiplication-stimulating activity (MSA)-rat placental membrane RRA. To avoid possible serious artifacts created by Sm-binding proteins, preliminary acid-ethanol extraction of serum was performed. Results are expressed in terms of a reference human serum with an assigned potency of 1 U/ml. Maternal RIA IGF-I fluctuated between 1.1-1.4 U/ml from the 17th day of pregnancy to the 25th day after delivery (nonpregnant rat serum pool, 1.25 +/- 0.22 U/ml). On day 21 of gestation, fetal serum radioimmunoassayable IGF-I was 1.03 +/- 0.03 U/ml. After birth, radioimmunoassayable IGF-I fell and reached .19 +/- 0.03 U/ml at 18 days of age, but rose to 0.71 +/- 0.04 U/ml at 25 days of age. At term, maternal radioreceptor assayable IGF-II was 2.18 +/- 0.27 U/ml (nonpregnant female pool, 1.4 +/- 0.12). By the 25th postpartum day, radioreceptor assayable IGF-II was 1.39 +/- 0.12 U/ml. Radioreceptor assayable IGF-II in fetal serum on day 19 was 3.26 +/- 0.48 U/ml and rose to 5.37 +/- 0.66 U/ml on the day of delivery. A further rise to 8.92 +/- 1.03 occurred on day 5. A subsequent fall to 2.41 +/- 0.05 U/ml was observed on day 25. The patterns of results of the MSA RRA in fetal and neonatal rat serum were similar to that obtained with the IGF-II RRA. We now conclude that radioimmunoassayable IGF-I is present in higher concentrations than previously reported in term fetal rat serum and that radioreceptor assayable IGF-II is selectively elevated in rat fetal and neonatal life and may have unique metabolic and growth-promoting significance.U

Measurement of insulin-like growth factor II by a specific radioreceptor assay in serum of normal individuals, patients with abnormal growth hormone secretion, and patients with tumor-associated hypoglycemia

A radioreceptor assay for insulin-like growth factor II (IGF-II) is described in which [125I]IGF-II is bound by rat placental membranes. IGF-I and other insulin-related peptides have less than 1% of the potency of IGF-II in displacing [125I]-IGF-II. IGF-II is extracted from its serum binding protein with a simple acid-ethanol step. After neutralization with Tris base, the extract is introduced directly into the radioreceptor assay. Results are expressed in terms of a reference serum with an assigned potency of 1 U/ml. By this method, serum from normal adults, 20-69 yr of age, had a mean (+/-SE)IGF-II activity of 0.73 +/- 0.03; higher concentrations were noted in adults more than 70 years of age (1.05 +/- 0.05), in cord serum (1.55 +/- 0.24), and in short children with normal GH secretion (0.88 +/- 0.42). In hypopituitary dwarfism, serum IGF-II activity was reduced (0.50 +/- 0.05), but in acromegaly, it was not increased (0.77 +/- 0.06). In 10 of 14 serum samples from patients with tumor-related hypoglycemia, the IGF-II exceeded the normal 95.5% confidence limits. In 8 of these sera, IGF-I by RIA was low, and in 5, it was essentially unmeasurable. These results with a new radioreceptor assay for IGF-II provide additional evidence that the regulation of this serum peptide differs from that of IGF-I.

The effect of hypophysectomy on rat chorionic somatomammotropin as measured by prolactin and growth hormone radioreceptor assays: possible significance in maintenance of somatomedin generation

We have previously reported that serum somatomedin concentrations are maintained in pregnant rats after hypophysectomy. Because rat chorionic somatomammotropin (rCS) might replace pituitary GH during pregnancy, the concentration of rCS was measured at intervals after hypophysectomy on day of pregnancy. By day 16 of pregnancy, the serum rCS of hypophysectomized (hypox) rats was actually higher than that of normal pregnant rats when measured by a lactogenic radioreceptor assay. Increased levels of lactogenic radioreceptor activity (L-RRA) were maintained in the serum of hypox rats throughout the remainder of pregnancy. The GH radioreceptor activity (GH-RRA) of serum of hypox pregnant rats was also greater than that of normal rats during the last days of pregnancy, but the activity was only about 1/20th that of the L-RRA with the assays employed. There was no significant difference between placental L-RRA and GH-RRA of normal and hypox pregnant rats. The difference in concentration could not be attributed to differences in the number of fetuses. We conclude that the high levels of rCS were sufficient to maintain serum somatomedin concentration in hypox pregnant rats. This effect of rCS could have been due to binding by GH or PRL receptors of the maternal liver.

Suppression of sleep-related prolactin secretion and enhancement of sleep-related growth hormone secretion

Methysergide, a clinically-used blocker of serotonin receptors, was administered to 10 normal young men at a dose of 2 mg every 6 h for 48 h. After drug treatment, serum levels of growth hormone during sleep were 41.9% higher than placebo values (less than 0.001). In contrast, drug treatment was associated with a 36.4% decrease in stimulated growth hormone secretion during insulin tolerance testing (P less than 0.01). These opposite effects of methysergide suggest that different mechanisms are responsible for sleep-related and insulin-induced growth hormone secretion. Accordingly, data obtained with pharmacologic stimuli may lead to erroneous inferences regarding physiologic growth hormone control mechanisms. Administration of methysergide profoundly suppressed sleep-related prolactin secretion; overall nocturnal mean prolactin fell by 70.3% from 4.30+/-0.19 to 1.28+/-0.06 ng/ml (P less than 0.0001). It appears that serotonin may be significant modulating neurotransmitter for the control of growth hormone secretion, limiting sleep-related release, and enhancing insulin-induced release. It seems likely from these data that the role of serotonin in the control of prolactin secretion is relatively more important, since serotonin receptor blockade dramatically reduced sleep-related prolactin secretion.