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Biomedical subjects

S Schultz

Publications and source records attributed to S Schultz.

At least 73 records · Page 4Linked to original sources
PubMed1998

Iron center, substrate recognition and mechanism of peptide deformylase.

Eubacterial proteins are synthesized with a formyl group at the N-terminus which is hydrolytically removed from the nascent chain by the mononuclear iron enzyme peptide deformylase. Catalytic efficiency strongly depends on the identity of the bound metal. We have determined by X-ray crystallography the Fe2+, Ni2+ and Zn2+ forms of the Escherichia coli enzyme and a structure in complex with the reaction product Met-Ala-Ser. The structure of the complex, with the tripeptide bound at the active site, suggests detailed models for the mechanism of substrate recognition and catalysis. Differences of the protein structures due to the identity of the bound metal are extremely small and account only for the observation that Zn2+ binds more tightly than Fe2+ or Ni2+. The striking loss of catalytic activity of the Zn2+ form could be caused by its reluctance to change between tetrahedral and five-fold metal coordination believed to occur during catalysis. N-terminal formylation and subsequent deformylation

Amidohydrolases↗
PubMed1996

Effect of background interference on accelerant detection by canines.

Additional studies were performed with respect to examining the lower limits at which canines can reliably detect products commonly used as accelerants and distinguish them from pyrolysis products or background hydrocarbons. As part of a testing exercise performed in conjunction with a national conference of the Canine Accelerant Detection Association (CADA), 34 canines were subjected to a series of tests, some of them were a recertification proficiency. In one of the tests, the dogs were nearly unanimously successful in locating one can (out of five) containing 50% evaporated gasoline at the 5 microL level on a burnt carpet matrix, and pinpointing the 6-in. square sector on a piece of plain carpeting where the same amount of gasoline (5 microL) was applied. However, only half were able to detect a second doped sample containing a lesser amount (0.05, 0.1, or 0.2 microL) of gasoline, and registered a number of alerts on samples containing only burnt carpeting material. The dogs were also tested on measured amounts (2 or 5 microL) of a variety of other light, medium, and heavy petroleum products applied to a variety of substances containing significant pyrolysis products. As a group, the canines were much less successful in pinpointing these products than they were with gasoline at this same level, and again registered a number of alerts on cans containing only pyrolysis products. The significant number of alerts by canines on samples not containing gasoline or other products points out the importance of obtaining laboratory confirmation on samples on which dogs alert, and on keeping accurate field and training records of canines to establish their credibility.

Animals↗
PubMed1995

Identification of nucleotide binding sites in the poliovirus RNA polymerase.

Poliovirus RNA polymerase (3Dpol) was cross-linked to [32P]ribonucleoside triphosphates (NTPs) by reduction of oxidized NTP-protein complexes. Cross-linked complexes were digested with cyanogen bromide, and resulting peptides were fractionated by reverse-phase HPLC. 32P-Labeled peptides were purified by secondary HPLC fractionation and/or additional digestion with endoproteinases Glu-C, TPCK-trypsin, or Asp-N followed by another HPLC fractionation. N-Terminal sequences of the major [32P]-peptides were determined, and approximate sizes of these peptides were obtained by SDS-polyacrylamide gel electrophoresis. Two major NTP binding sites in 3Dpol were found. One site was between Asp-266 and Met-286; possible binding residues in this fragment were Lys-276, Lys-278, or Lys-283. A second binding site was between Ala-57 and Met-74 with Lys-61 or Lys-66 as possible binding residues. Alignment of these regions on the known structure of HIV-1 reverse transcriptase allowed us to predict the position of the downstream nucleotide binding site in the conserved "fingers" subdomain present near the active site cleft of both RNA and DNA polymerases. The N-terminal nucleotide binding site is not contained within a region that is conserved among other polymerases.

Amino Acid Sequence↗
PubMed1995

Signal averaging and waveform analysis of laser Doppler flowmetry monitoring of porcine myocutaneous flaps: I. Acute assessment of flap viability.

Postoperative monitoring of microvascular free-tissue transfer is essential to the early identification and correction of vascular compromise. Laser Doppler flowmetry is a noninvasive monitor of capillary bed perfusion. Its current clinical use requires continuous monitoring and trend analysis to detect changes in capillary perfusion. This study investigated the hypothesis that signal averaging of laser Doppler flowmetry output triggered by a fixed point in the cardiac cycle would provide accurate information about the microvascular flow patterns not dependent on trend analysis. These results indicate that averaged waveform analysis allowed for a rapid, objective, and statistically significant distinction between a viable myocutaneous flap and one with vascular compromise in a porcine model. Moreover, this technique allows for distinction between venous and arterial insufficiency.

Animals↗
PubMed1995

Interventional radiology of the chest: image-guided percutaneous drainage of pleural effusions, lung abscess, and pneumothorax.

Percutaneous catheter drainage of intrathoracic collections has developed as a natural extension of similar interventional radiologic procedures in the abdomen. The advent of CT and sonography, which allow detection and characterization of pleural and parenchymal collections, combined with advances in drainage catheter design and interventional techniques, have made imaging-guided management of intrathoracic collections a safe and effective alternative to traditional surgical therapy. This article begins with a review of the etiology, pathophysiology, diagnosis, and treatment of parapneumonic pleural effusion, which remains the most common indication for image-guided percutaneous drainage. Subsequent sections consider issues related to percutaneous drainage of malignant pleural effusion, lung abscess, and pneumothorax.

Drainage↗
PubMed1994

Pneumonia in a nursing home.

The authors studied nursing home residents serologically to determine whether atypical organisms were causes of radiologic pneumonia. The study was conducted at the Wisconsin Veterans Home, a facility with on-site microbiology and x-ray. Over one year, serologic examinations for Legionella, Mycoplasma, and Chlamydia were conducted for the residents who had pneumonia. Cultures and mortality were reviewed. Fifty-six episodes were studied (mean resident age 78 years). There was no fourfold titer change. Seventeen quality sputum specimens revealed Streptococcus pneumoniae (5), normal flora (4), Hemophilus influenzae (4), Moraxella catarrhalis (3), Staphylococcus aureus (1), and beta-hemolytic Streptococcus, not group A (1). The two-month mortality was 21%. This study did not result in serologic confirmation of atypical organisms' causing pneumonia. Antibiotic choice should be based on coverage of prevalent organisms, including Hemophilus influenzae, Moraxella, and Staphylococcus, as well as clinical features.

Aged↗
PubMed1994

Relations of endogenous anabolic hormones and physical activity to bone mineral density and lean body mass in elderly men.

OBJECTIVE: It has been proposed that declining activities of the somatotrophic or gonadotrophic axes, or sedentary life style, are partial causes for geriatric losses of bone mineral density (BMD) and of lean body mass (LBM). The present study tested these hypotheses by determining, in both free-living and institutionalized elderly men, the correlations of bone mineral density (BMD), total body bone mineral content (TBBMC) and lean body mass (LBM) with the following predictor variables: age, body mass index, body weight, serum insulin-like growth factor I (IGF-I), serum testosterone, habitual physical activity and mobility. SUBJECTS: Forty-nine independent, community-dwelling older men, and 49 men of similar age residing in two Veterans Administration extended care facilities. The age range was 58-95 years. MEASUREMENTS: Serum IGF-I and testosterone were measured by radioimmunoassay. Habitual physical activity in the independent men and mobility in the institutionalized men were estimated by standard instruments. LBM and bone status at nine skeletal sites were determined by dual X-ray absorptiometry. RESULTS: The BMD and TBBMC values of the free living men were 4-20% higher than those of the institutionalized men. In the independent old men, serum testosterone was the strongest predictor of BMD and TBBMC, while age was the only predictor of LBM. In the chronically institutionalized men, age, body weight and immobility were the strongest predictors of body composition, and testosterone was correlated only with femoral neck BMD. CONCLUSIONS: In aging independent men, low levels of testosterone are associated with demineralization of the skeleton. Immobility and under-weight are associated with the osteopenia of old men residing in nursing homes. In this cross-sectional study of elderly men, there was no evidence of a relation of the somatotrophic axis to bone status or LBM, or of the gonadotrophic axis to LBM.

Activities of Daily Living↗
PubMed1994

Positive and negative symptoms of schizophrenia: past, present, and future.

The "group of schizophrenias," normally referred to with a single nominative, is phenomenologically heterogeneous. Its symptoms represent multiple psychological domains, including perception, inferential thinking, language, attention, social interaction, emotion expression, and volition. Studies of psychopathology have simplified this complex array in several ways; one has been a subdivision into positive and negative symptoms. Reports by our group and others suggest that the symptoms of schizophrenia fall into three natural dimensions: positive symptoms subdivided into psychotic and disorganized dimensions, while a third negative dimension also emerges. Since these dimensions have impressive consistency across studies, future work must examine their relationship to clinically relevant concepts such as prognosis or etiology and examine four different aspects: longitudinal course, neural mechanisms, relationship to treatment, and interrelationships in other pathological conditions.

Brain↗
PubMed1994

Diaspirin crosslinked hemoglobin (DCLHb): control of pressor effect with anti-hypertensive agents.

Diaspirin crosslinked hemoglobin (DCLHb) administration elevates mean arterial pressure (MAP). The purpose of this study was to determine whether commonly used antihypertensive agents could control this pressor effect in rats. Awake rats were injected intravenously (i.v.) with 280 mg/kg of DCLHb. Fifteen minutes later when MAP was 25-30% above baseline and heart rate (HR) was reciprocally decreased, prazosin (2 mg/kg;an alpha adrenergic blocker), nitroglycerine (NTG; 10-150 mcg/min; a nitrovasodilator), nicardipine (0.204-0.08 mg/hr; a calcium channel blocker) or labetalol (5 mg/kg; an alpha/beta adrenergic blocker) was administered i.v. All four classes of antihypertensive agents promptly restored MAP to baseline. Coincident with the return of MAP to baseline, HR was restored to baseline in prazosin and NTG treated animals, however, bradycardia persisted in those animals treated with nicardipine and labetalol, most likely due to the negative chronotropic properties of these agents. We conclude that the pressor effect of DCLHb can be readily controlled with at least four different classes of commonly used antihypertensive agents.

Animals↗
PubMed1994

Urinary retention in infants: unusual presentation of pelvic tumors.

Infants presenting with urinary retention must be evaluated for the presence of presacral neoplasm. Two cases--a newborn and a seven-month-old infant--are presented that illustrate the need for prompt radiologic evaluation in order to detect or exclude a pelvic tumor.

Female↗
PubMed1994

Hyposomatomedinemia and hypogonadism in hemiplegic men who live in nursing homes.

The purpose of this study was to determine the prevalence of low serum insulin-like growth factor-I (IGF-I) and testosterone in men with poststroke hemiplegia. Serum concentrations of IGF-I, total testosterone, and free testosterone were compared in healthy young men, healthy old men, and old men with poststroke hemiplegia. A low IGF-I level, below the lower 2.5 percentile of the healthy young men, occurred in 85% of the healthy old men, and in 88% of the poststroke hemiplegic patients. When a low IGF-I was defined as a value below the lower 2.5 percentile of the healthy old men, the prevalence in the hemiplegic men was 5%. For total testosterone, a value below the lower 2.5 percentile in the healthy young men occurred in 78% of the healthy old men and in 79% of the stroke survivors. Low total testosterone, defined as a value below the lower 2.5 percentile of the healthy old men, occurred in 17% of the hemiplegic men. The results with free testosterone were similar. Compared with healthy young men, most healthy old men have low serum IGF-I and testosterone levels. Old hemiplegic men resemble healthy old men in their IGF-I levels, but they have more cases of severe hypogonadism (total tostosterone < 193ng/dL). Because correction of IGF-I and testosterone deficiencies in younger adults improves muscle strength, work capacity, and quality of life, treatment with human growth hormone and testosterone may be a useful adjunct to physical measures in the rehabilitation of selected hemiplegic stroke survivors.

Adult↗