Manipulation of peptide conformations by fine-tuning of the environment and/or the primary sequence

The widely observed phenomenon that peptides are capable of adopting multiple conformations in different environments suggests that secondary structure formation in a peptide segment is a process involving not only the peptide itself but also the surrounding solvent media. The influence of the primary sequence and the molecular environment on peptide conformations are now investigated using synthetic peptides of amino acid sequence H2N-(Ser-Lys)2-Ala-X-Gly-Ala-X-Gly-Trp-Ala-X-Gly-(Lys-Ser)3-OH, where X = Ile or Val. These two peptides, namely 3I (X = Ile) and 3V (X = Val), are found to lack defined secondary structure in aqueous buffer. However, discrete conformational states, e.g., alpha-helices and beta-sheets, are readily generated and interconverted for both peptides when the buffer is modulated with the addition of methanol, sodium dodecyl sulfate (SDS) micelles, or phospholipid vesicles. The role of the primary sequence in affecting peptide conformations is manifested in that peptides 3I and 3V, which differ respectively in their content of beta-branched Ile or Val residues, differ in their secondary structures at monomeric concentrations in 2 mM SDS and in mixed lipid vesicles of phosphatidic acid and phosphatidylcholine. The overall results suggest that peptide segments can be conformationally flexible entities poised to react to minor modulation in either the molecular environment or the primary sequence, a circumstance that may be relevant to protein functioning and folding.

Rapid culture and quantitation of human immunodeficiency virus type 1 from patient cells without the use of mitogen-stimulated donor cells

We report the development of a rapid, sensitive virus culture method for direct quantitation of human immunodeficiency virus (HIV) in peripheral blood mononuclear cells (PBMCs). This new method involves culturing 10(7) PBMCs from HIV-seropositive persons in 10 ml of medium containing phorbol 12-myristate 13-acetate and interleukin-2. Both agents stimulate cell activation and hence viral replication. Cell-associated virus and free virus are quantitated by a commercially available HIV p24 antigen capture enzyme immunoassay. Detection of cell-associated p24 antigen by flow cytometry was less sensitive than by the enzyme immunoassay. In this preliminary study, HIV was detected in 20 of 23 HIV-seropositive patients and in none of the 11 HIV seronegative low-risk individuals. One HIV-seronegative person with Guillain-Barré syndrome following high-risk activity was found to be rapid-HIV-culture positive. The overall sensitivity and specificity were 87 and 100%, respectively. By comparing the quantity of virus produced in infected cells with the amount of virus produced in chronically infected U1 monocytes and ACH-2 lymphocytes stimulated with phorbol 12-myristate 13-acetate and interleukin-2, the approximate number of infected cells per sample is calculated. In the same patient specimens, quantitation of the number of HIV infected cells by the HIV rapid-culture method correlated with the results of the 21-day cell dilution coculture assay (correlation coefficient r = 0.5; 95% confidence interval, 0.07 to 0.77). Advantages of the rapid HIV culture include no requirement for donor PBMCs or change of media, shortened culture time, and the ability to detect p24 viral antigen from cell-associated virus for quantitation of viral load.

Cyclosporin A sensitivity of the NF-kappa B site of the IL2R alpha promoter in untransformed murine T cells

We have investigated the characteristics of IL2R alpha gene induction in untransformed murine T cells. Induction of IL2R alpha mRNA by TCR/CD3 ligands in a murine T cell clone and in short-term splenic T cell cultures was inhibited by protein synthesis inhibitors and by CsA. This result was contrary to previous observations in JURKAT T leukemia cells and human peripheral blood T cells, suggesting a difference in the mechanisms of IL2R alpha gene induction in these different cell types. The CsA sensitivity of IL2R alpha mRNA induction represented a direct effect on the TCR/CD3 response, and was not due to CsA-sensitive release of the lymphokines IL2 or tumour necrosis factor alpha (TNF alpha) and consequent lymphokine-mediated induction of IL2R alpha mRNA. The NF-kappa B site of the IL2R alpha promoter was essential for gene induction through the TCR/CD3 complex, and the induction of reporter plasmids containing multimers of this site was significantly inhibited by CsA. Northern blotting analysis indicated that while the p65 subunit of NF-kappa B was constitutively expressed and not appreciably induced upon T cell activation, mRNA for the p105 precursor of p50 NF-kappa B was induced in response to TCR/CD3 stimulation and this induction was sensitive to CsA. Electrophoretic mobility shift assays and antiserum against the p50 subunit of NF-kappa B indicated that p50 was a component of the inducible nuclear complex that bound to the IL2R alpha kappa B site. Appearance of the kB-binding proteins was insensitive to CsA at early times after activation (approximately 15 min), but was partially sensitive to CsA at later times. Based on these results, we propose that the NF-kappa B site of the IL2R alpha promoter mediates at least part of the CsA sensitivity of IL2R alpha gene induction in untransformed T cells, possibly because de novo synthesis of p105 NF-kappa B is required for sustained IL2R alpha expression.

An analysis of 2361 cases of renal biopsy in Korea

To evaluate the distribution pattern of renal diseases based on needle biopsy, we analyzed 2361 cases of renal biopsy and necropsy material examined at the Department of Pathology from 1973 to 1988. The average age was 21.1 years for males and 23.7 years for females. The adult cases comprised 60.2% and the child cases 39.8%. The male to female ratio was 1.6: 1 in adults and 2.3:1 in children. Glomerular diseases were 97.8% of the total; primary glomerulonephritis (GN) 59.8% and secondary GN 27.6% The major glomerular diseases, in descending order of frequency, were; minimal change nephrotic syndrome (MCNS; 24.2%), IgA nephropathy (IgAN; 17.8%), benign recurrent hematuria (BRH; 8.8%), membranous GN (MGN; 7.9%), acute poststreptococcal GN (APSGN; 7.3%), mesangioproliferative GN (MspGN; 5.5%), minimal mesangiopathy (5.5%), membranoproliferative GN(4.1%), and focal segmental glomerulosclerosis (FSGS; 2.7%). GN of systemic disease included 77 cases of lupus nephritis, 157 cases of Henoch-Schönlein purpura nephritis (HSPN) and 7 cases of systemic infection excluding Hepatitis B viral hepatitis. The most common glomerular diseases were MCNS, IgAN, MGN and MspGN in adults, and MCNS, BRH, HSP-N and APSGN in children. HBs antigenemia was found in 71 cases, of which MGN and IgAN were the most frequent. HBs antigenemia-associated MGN was prevalent in male children, whereas IgAN was prevalent in adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Significance of mesangial IgA deposition in minimal change nephrotic syndrome: a study of 60 cases

We studied 60 cases of minimal change nephrotic syndrome (MCNS) with mesangial IgA deposits occurring over a 6 year period. There were 43 adults and 17 children. Hematuria occurred in 69.0% of the adults and 88.2% of the children. Two adults and six children had gross hematuria during the course of the disease. Mesangial IgA deposits were noted in 100% of the cases, and concomitant IgG or IgM deposits were found in 78.6% of adults and 73.7% of children. The fluorescent intensity of mesangial IgA deposits was trace (+/-) to 1+ in 86.1% and 70.6% of the adults and children respectively. Most of the patients showed electron microscopic findings consistent with minimal change nephrotic syndrome. We speculate that most of our cases are variants of minimal change nephrotic syndrome but are neither IgA nephropathy nor an overlapping syndrome, and that environmental or genetic factors may be related to the deposition of IgA in these MCNS patients.

[The prevalence of head louse infestation among urban and rural children in Korea]

The prevalence of head louse (Pediculus hamanus var. capitis) infestation in preschool and school children in 9 urban and 8 rural areas of Korea, was investigated. Of 11,865 children who were examined for head lice and nits, 2,900(24.4%) were found infested. The over-all infestation rate of rural children, 58.9%, was higher than that of urban children, 14.4%. There also existed significant differences in the infestation rate among various regions of urban as well as rural areas. Females were more infested than males. But there was no differences in infestation rate in either sex of preschool age. The infestation rate increased gradually from the age of 6, reached a plateau between 9-12 years of age and thereafter slowly decreased. The infestation rate of an orphanage children was higher than that of general childhood population. Health education and mass-delousing attempt are urgently required to lower such a high prevalence of head louse infestation in Korea.

Transluminal angioplasty in patients with bilateral renal artery stenosis or renal artery stenosis in a solitary functioning kidney

Renal angioplasty in patients with bilateral renal artery stenosis or with renal artery stenosis in a solitary functioning kidney has been thought to be relatively contraindicated. We report the results of renal artery angioplasty in 18 patients, 10 with severe bilateral renal artery stenosis and eight with severe renal artery stenosis in a solitary kidney. Twenty-five (89%) of 28 angioplasties were successful, with a mean improvement of the degree of stenosis from 85% to 18% after angioplasty and a restoration of renal blood flow. A significant drop in mean blood pressure at admission of 187/101 mm Hg to 154/87 mm Hg at discharge, 152/86 mm Hg at 3-month, and 146/82 mm Hg at 1-year follow-up was seen. Because of the decrease in blood pressure, 11 of the patients decreased or stopped taking diuretics and 15 decreased or stopped taking antihypertensive medications. Although no significant change in renal function was found by measuring mean serum creatinine levels over time, no patient had an elevated serum creatinine level at follow-up, indicating preservation of renal function. One major complication, cholesterol embolization to the bowel, was seen. Our results suggest that angioplasty is an acceptable treatment of hypertension in patients with bilateral renal artery stenosis or renal artery stenosis in a single kidney.

Steroid effects on minimal lesion nephrotic syndrome with and without immune deposits

A comparison was done between the two groups of MLNS (minimal lesion nephrotic syndrome) with and without mesangial deposits of immunoglobulin and complement. The subjects were 40 patients with MLNS whose kidney could be obtained by biopsy. No significant differences were found between the two groups in selective protein index, serum cholesterol level, serum albumin level, amount of 24 hour urine protein, hematuria, serum immunoglobulin level and response to steroid therapy. Ig M was deposited in eleven of fourteen patients with MLNS, Ig G three of fourteen, C3 thirteen of fourteen. There was no relationship between serum level and glomerular deposition of immunoglobulin and complement.

Cell-mediated immunity to cytomegalovirus in patients receiving immunosuppressive therapy

Employing the techniques of complement-fixation (CF), immunofluorescence (IF), and in vitro lymphocyte transformation (LTF), the humoral antibody response and cell-mediated immune (CMI) response to cytomegalovirus (CMV) were studied in the serum and peripheral blood lymphocytes in 19 normal children (controls) and 23 patients with renal disease who were receiving immunosuppressive therapy or undergoing hemodialysis. The LTF activity was determined by the whole blood microassay using two strains of CMV (AD-169 and Davis) and phytohemagglutinin (PHA). The antibody level responses to CMV in different groups of subjects were generally similar. The LTF response to PHA as evidenced by delta cpm activity was moderately depressed in immunosuppressed and hemodialyzed subjects compared to the response observed in the controls. The mean delta cpm activities in response to AD-169 and Davis strains of CMV in seropositive immunosuppressed patients were about one-fifth and one-third lower respectively than those of seropositive normal controls. These observations suggest that an impairment of CMV specific cellular immunity may be an important mechanism underlying the increased susceptibility to CMV infections in patients with chronic renal disease who receive immunosuppressive therapy.