Colposcopic biopsies versus loop electrosurgical excision procedure cone histology in human immunodeficiency virus-positive women.

OBJECTIVE: To compare the discrepancy between colposcopically directed punch biopsy and excisional cone biopsy in human immunodeficiency-positive (HIV+) vs. HIV-negative (HIV-) women. STUDY DESIGN: We performed a case-control analysis of women treated with excisional cone biopsy after an abnormal colposcopic punch biopsy. Punch and cone biopsy histology were compared in 29 HIV+ (mean CD4 = 251 cells/mm3, 10 with the acquired immunodeficiency syndrome) and 31 HIV- women. Only patients with no prior treatment for cervical dysplasia, satisfactory colposcopy and cervical cytologic smears concordant with colposcopic biopsies were included. RESULTS: Disagreement between punch biopsy and cone histology was evident in 41% (12/29) of HIV+ patients and 48% (15/31) of seronegative women (chi 2, P = .78). The cone specimen had a higher grade lesion than the punch biopsy in 38% (11/29) of HIV+ patients and 32% (10/31) of seronegative women (P = .65). Overall, patients with HPV, cervical intraepithelial neoplasia (CIN) I or II on punch biopsy had CIN III on 30% of cone biopsies (5/23 HIV+ vs. 9/23 HIV-women, P = .2). In HIV+ women with HPV or CIN I on punch biopsy, 50% (9/18, 95% confidence interval 26-74%) had CIN II or III on the excisional cone vs. 18% (2/11) HIV-patients (Fisher's test, P = .13). However, in HIV+ patients with CIN II or III on cone biopsy, 47% (9/19) had only CIN I or human papillomavirus on punch biopsy as compared to 9% (2/22) HIV-patients (chi 2, P = .01). CONCLUSION: Colposcopically directed punch biopsies are poor predictors of cone histology in both HIV+ and HIV-patients. Based on confidence intervals, at least 26% and as many as 74% of HIV+ women with CIN I on punch biopsy may have a significantly worse lesion on cone biopsy despite satisfactory colposcopy. Though CIN I may be observed in immunocompetent women, due to the likelihood of a more advanced lesion, observation may not be justified in HIV+ women.

Glucose transport in primary cultured neurons.

UNLABELLED: In this study, we have examined glucose uptake and its regulation by insulin in primary cultured neurons. Glucose transport was assessed by measuring the initial rate of uptake of 3H-2-deoxyglucose, a glucose analog that is transported and phosphorylated but not further metabolized. The uptake of 2-deoxyglucose was saturable; measurements of the intracellular concentration of 2-deoxyglucose and 2-deoxyglucose-6-phosphate revealed that hexokinase activity rather than membrane transport is the rate-limiting step for glucose uptake. Insulin had no effect on 2-deoxyglucose uptake at low (0.2 mM) or high (20 mM) concentrations of substrate. The order of potency of other hexoses to competitively inhibit the accumulation of 2-deoxyglucose was D-glucose (0.2 mM) = D-mannose (0.2 mM) greater than 3-0-methylglucose (9 mM) greater than D-galactose (90 mM). Cytochalasin B was a potent inhibitor of 2-deoxyglucose uptake (IC50 = 500 nM) and phloretin was more potent than ploridzin in inhibiting uptake. The structure of glucose transporters was examined by photoaffinity labeling using 3H-cytochalasin B and by immunologic detection using antibodies raised against the human erythrocyte transporter. 3H-cytochalasin B labeled two proteins of 55 kDa and 43 kDa and the antibody recognized primarily a 43 kDa protein. The subcellular distribution of glucose transporters, estimated by measuring the number of specific cytochalasin B binding sites in subfractions of neuronal homogenates, showed 3.62 pmol/mg protein in the 11,000g pellet and 1.34 pmol/mg protein in the 200,000g pellet. IN CONCLUSION: 1) Neuronal glucose transport is not acutely regulated by insulin. 2) The kinetics of 2-deoxyglucose uptake into neurons are determined largely by hexokinase activity rather than membrane transport. 3) The apparent molecular weight of neuronal glucose transporters is similar to transporters in other tissues. 4) The number of glucose transporters per milligram of protein is relatively low in neurons compared to other tissues.

Functional properties of the subtype of insulin receptor found on neurons.

In this report, we have examined the structure, regulation, and function of insulin receptors in cultured neurons from fetal chicken brain. The apparent molecular weight of the alpha-subunit of neuronal insulin receptors, analyzed by photoaffinity labeling and sodium dodecyl sulfate gel electrophoresis under reducing conditions, was 115,000. The number of insulin receptors in the cultures increased from day 2 to day 4 during a period of extensive process formation. After 5 days in culture, there were approximately 40,000 high-affinity insulin receptors per neuron. When neurons were photoaffinity labeled at 16 degrees C and then warmed to 37 degrees C for 30 min, approximately 40% of the cell-surface receptors were recovered in the intracellular, trypsin-insensitive pool. Chronic exposure of neurons to insulin (100 ng/ml) resulted in a time-dependent loss of neuronal insulin receptors with a maximal decrease of 50% after 24 h. Insulin had no effect on glucose transport, glucose oxidation, or glycogen synthase activity in neurons. On the other hand, insulin supported the growth and differentiation of a fraction of neurons isolated from chick forebrain. We conclude that (1) cultured neurons from fetal chicken brain express the same subtype of insulin receptor previously identified in adult rat and human brain, (2) the neuronal subtype of insulin receptor undergoes internalization and down-regulation in response to insulin, and (3) neuronal insulin receptors do not acutely regulate glucose metabolism but mediate growth in neurons.

Angiodysplasia of the upper gastrointestinal tract.

I have reviewed the English language literature on angiodysplasia of the upper gastrointestinal tract. Angiodysplasia is a distinct mucosal vascular lesion associated with acute or chronic gastrointestinal bleeding. Its etiology is unknown, but theories of its pathogenesis have evolved from its similarity to colonic angiodysplasia and an association with renal failure. Despite recurrent gastrointestinal bleeding, the endoscopic diagnosis is difficult because the lesions are so small and so similar to fresh blood. Endoscopic ablation by electrocautery or laser photocoagulation can reduce bleeding or make it stop, but repeated treatments are often necessary.

Peptide mapping on Northern blot analyses of insulin receptors in brain and adipocytes.

Previous studies have demonstrated differences in the size of insulin receptor subunits in brain and adipocytes that appear to involve variations in glycosylation of the proteins. In this report, we examined the degree of homology in the protein backbones of insulin receptors in both tissues by peptide mapping and compared the mRNAs encoding the receptors by Northern blot analysis. Photoaffinity-labeled insulin receptors from rat brain and adipocytes were deglycosylated and then subjected to partial proteolysis by five different enzymes with differing substrate specificities. The intact receptors and their proteolytic fragments were analyzed by electrophoresis and autoradiography. Each enzyme yielded a unique pattern of fragments ranging from 70 to 11 kDa. In all cases, there was a striking similarity in the peptide maps generated from insulin receptors in brain and adipocytes. Northern hybridization experiments were carried out using poly(A)+ RNA from rat brain, rat adipocytes, and human hepatocarcinoma (HEP G2) cells. In rat brain, two bands of 9.5 and 7.4 kb were detected and, in rat adipocytes, the same two bands were observed. The two mRNA bands observed in rat tissues represented only two of the five mRNA species seen in human HEP G2 cells. The results indicate that the protein domains and the mRNAs encoding of insulin receptors in brain and adipocytes are very similar, if not identical.

Evidence for a subtype of insulin-like growth factor I receptor in brain.

We examined the structure of receptors for insulin-like growth factor I (IGF-I), insulin, and epidermal growth factor (EGF) in human brain and human placenta using affinity cross-linking procedures and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In human brain, proteins specifically cross-linked to 125I-IGF-I, 125I-insulin, and 125I-EGF had apparent molecular weights of 120,000, 115,000 and 170,000, respectively. In human placenta, proteins cross-linked to 125I-IGF-I and 125I-insulin were 10 kDa larger than the corresponding subunits in brain. The receptor labeled by 125I-EGF in placenta was indistinguishable from the EGF receptor in brain. The size discrepancy of IGF-I receptors in brain and placenta was no longer apparent after removing the carbohydrate moieties of the proteins with endo-beta-N-acetylglucosaminidase F (EndoF). Furthermore, the brain IGF-I receptor was not cleaved by neuraminidase, whereas, the placental IGF-I receptor had increased mobility on SDS gels following neuraminidase treatment. The results indicate that receptors for IGF-I and insulin in human brain are structurally distinct from the corresponding receptors in human placenta, the structural heterogeneity of the receptors involves differences in N-linked glycosylation, particularly the terminal processing steps, and EGF receptors are present in human brain and human placenta but are structurally similar in these tissues. We conclude that there is a selective modification in the glycosylation of receptors for IGF-I and insulin in brain.

Structural and functional characteristics of insulin receptors in rat neuroblastoma cells.

Insulin receptors were detected in a variety of rat neuroblastoma and glioma cell lines. The binding of 125I-insulin to B103 neuroblastoma cells had characteristics typical of insulin receptors in other tissues, including high affinity for insulin, low affinity for insulin-like growth factor I (IGF-I), and curvilinear Scatchard plots. Using photoaffinity labeling procedures and sodium dodecyl sulfate (SDS) gel electrophoresis to analyze the subunit structure of insulin receptors in B103 cells, the predominantly labeled protein had an apparent molecular weight of 125K and the mobility of this protein was shifted after removal of sialic acid residues. On the basis of size and susceptibility to neuraminidase, the insulin binding subunit in neuroblastoma cells was identical to the alpha-subunit of insulin receptors in adipocytes and different from the 115K subunit found in brain. The presence of an "adipocyte" form of the insulin receptor in clonal cells derived from brain is probably a consequence of transformation and results from more extensive oligosaccharide processing of the 115K receptor expressed in normal brain cells. The fully glycosylated receptors in neuroblastoma cells were capable of exerting functions typical of insulin receptors in adipocytes such as internalization of insulin and stimulation of glucose transport.