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Biomedical subjects

A C Herman

Publications and source records attributed to A C Herman.

11 recordsLinked to original sources
PubMed2006

Discharge outcomes of extremely low birth weight infants with spontaneous intestinal perforations.

OBJECTIVE: To examine discharge outcomes of extremely low birth weight infants (ELBW) with spontaneous intestinal perforation (SIP). STUDY DESIGN: A single-center retrospective cohort study of all ELBW infants admitted to the University of Virginia neonatal intensive care unit between July 1996 and June 2004. RESULTS: We found 35 patients with SIP (incidence 8.4%). The median gestational age was 25 weeks, median birth weight was 722 g, and 71% of the infants were male. Most infants (n=28) with SIP were diagnosed secondary to pneumoperitoneum; however, one-third (7) of infants<25 weeks had occult presentations without pneumoperitoneum. When controlled for gestational age, gender, multiple gestation, indomethacin, and glucocorticoid exposure, infants with SIP have a higher risk of PVL and death than infants without perforation. SUMMARY: Periventricular leukomalacia and death are significantly associated with SIP in ELBW after adjusting for gestational age, multiple gestation, indomethacin, and glucocorticoid exposure.

Birth Weight↗
PubMed1996

Affinity chromatography with immunochemical detection applied to the analysis of human methionyl granulocyte colony stimulating factor in serum.

An on-line, automated, HPLC method was developed for the separation and detection of recombinant human methionyl granulocyte colony stimulating factor (GCSF) and GCSF modified with poly(ethylene glycol) (PEG-GCSF) in rat serum. The automated method consists of an initial immunoaffinity chromatography step, a microbore reverse phase separation, and postcolumn immunochemical detection. Calibration curves were constructed with a lower limit of 1.5 ng of GCSF (80 fmol) and 7.5 ng of PEG-GCSF in 120 microL of rat serum. In vivo serum samples from rats dosed with PEG-GCSF were also analyzed. The development of the method is discussed as well as its general application to the detection of metabolites of recombinant proteins in body fluids.

Animals↗
PubMed1994

Formation of mitogenically active PDGF-B dimer does not require interchain disulfide bonds.

Platelet-derived growth factor (PDGF), a major mitogen for mesenchymal cells, is a disulfide-bonded dimer of two subunit polypeptides named A and B. All of the three possible dimeric forms, i.e. AA, BB, and AB, exist in nature. The dimeric structure has been presumed to be necessary for biological activity, since reduction of the dimer results in loss of activity and simultaneous conversion to monomeric form as determined by SDS-gel electrophoresis. However, reduction of the native molecule destroys intrachain, as well as interchain, disulfide bonds, and it is possible that the former rather than the latter are critical for proper conformation of the active protein. We show here that PDGF-B polypeptides in which all 8 cysteines or the 2nd, 4th, 5th, and 8th cysteines have been mutated to serines fail to form covalent dimers and possess dramatically less mitogenic activity than native PDGF-BB. Another mutant, PDGF-B(C2,4S), in which just the 2 cysteines involved in interchain disulfides were converted to serine, ran as a monomer on SDS-polyacrylamide gels as expected. Somewhat unexpectedly, however, the mitogenic activity of the PDGF-B(C2,4S) analog was similar to the activity of wild-type PDGF-BB disulfide-bonded dimer under physiological conditions. The activity of the analog was more sensitive to the effect of low pH than was the activity of wild-type PDGF-BB. Molecular weight analysis utilizing light scattering and sedimentation equilibrium demonstrated that the PDGF-B(C2,4S) analog exists as a noncovalent dimer at pH 4-7 but dissociates to a monomer at pH 2.5. Disulfide analysis of the mutant protein demonstrated that the intrachain disulfide bonds are the same as those formed in wild-type PDGF-BB homodimers. We conclude that proper formation of intrachain disulfide bonds is critical to maintaining the correct conformation of PDGF monomers, but that appropriately folded monomers can associate into active noncovalent dimers in the absence of interchain disulfide bonds. Interchain disulfide bonds thus appear to increase the stability of the PDGF dimer rather than being crucial to its existence.

Amino Acid Sequence↗
PubMed1993

Isolation and characterization of three recombinant human granulocyte colony stimulating factor His-->Gln isoforms produced in Escherichia coli.

This report demonstrates that three variant isoforms of recombinant methionyl human granulocyte colony stimulating factor are present in small quantities in the crude preparation solubilized from Escherichia coli inclusion bodies. These isoforms were separated from the main form of the factor during purification and further isolated by a series of cationic exchange chromatographic separations. They exhibit full in vitro biological activity and have slightly lower pI's. Structural characterization of the intact proteins and their isolated peptides by sequence determination and mass spectrometric analysis revealed that they are methionyl granulocyte colony stimulating factors having a His-->Gln replacement at sequence position 53, 157, or 171, respectively. The specific His-->Gln change suggests the occurrence of mistranslation during protein synthesis. These variant forms are chromatographically separable during purification and are not detectable in the final purified form of the factor.

Amino Acid Sequence↗
PubMed1983

Production of purified hepatitis B surface antigen from Alexander hepatoma cells grown in artificial capillary units.

An artificial capillary system was devised for growth of hepatoma cells that yields very high titers of hepatitis B surface antigen (HBsAg). High yield of antigen was facilitated by slowing cellular metabolism through reduction of incubation temperature and addition of 0.1 mM caffeine. Deletion of serum from the medium did not reduce the yield of antigen. HBsAg prepared from the culture fluid by affinity chromatography and additional chemical and enzymatic steps was essentially pure and was indistinguishable from HBsAg prepared from infected human plasma. Preparation of HBsAg from the cell culture source presents advantages over that of human plasma and might be a source of HBsAg for vaccine preparation.

Caffeine↗