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Biomedical subjects

R A Williams

Publications and source records attributed to R A Williams.

At least 19 recordsLinked to original sources
PubMed1995

Two thermostable type II restriction endonucleases from Icelandic strains of the genus Thermus: Tsp4C I (ACN/GT), a novel type II restriction endonuclease, and Tsp8E I, an isoschizomer of the mesophilic enzyme Bgl I (GCCNNNN/NGGC).

Sixteen isolates of thermophilic bacteria from the genus Thermus, isolated from neutral and alkaline hot water springs in the southwest region of Iceland, were tested for the presence of restriction endonucleases. Extracts from five of the isolates showed evidence of the presence of restriction endonuclease activity by producing discrete nucleotide fragments when incubated at 65 degrees C with lambda phage DNA. Two of the isolates (Tsp4C and Tsp8E) were found to have particularly high levels of restriction endonuclease activity, and the respective enzymes from these two Thermus isolates were partially purified and characterized and their recognition and cleavage sites were determined. Enzyme Tsp4C I is a novel Type II restriction endonuclease recognizing the interrupted palindromic tetranucleotide sequence ACNGT, where N can be any one of the four bases in DNA. Tsp4C I, which retains full enzyme activity when incubated for 10 min at temperatures up to 76 degrees C, hydrolyses the phosphodiester bond in both strands of a double-stranded DNA substrate between the third and fourth bases of the recognition sequence (ACN/GT), generating fragments with a single base 3'-OH overhang. Enzyme Tsp8E I is a thermostable isoschizomer of the mesophilic Type II restriction endonuclease Bgl I (GCCNNNN/NGGC) [Lee, Clanton and Chirikjiam (1979) Fed. Proc. 28, 294], generating fragments with a three base 3'-OH overhang. However, unlike Bgl I, Tsp8E I exhibits considerable thermal stability, retaining full enzyme activity when incubated for 10 min at temperatures up to 78 degrees C. Both Tsp4C I and Tsp8E I represent significant additions to the small but expanding list of the extremely thermostable restriction endonucleases.

Base Sequence↗
PubMed1995

Microbial transformation of steroids--IX. Purification of progesterone hydroxylase cytochrome P-450 from Phycomyces blakesleeanus.

Progesterone hydroxylase cytochrome P-450 was purified to homogeneity from Phycomyces blakesleeanus microsomes by a four step procedure. An M(r) value of 60,000 was determined for this protein by SDS-PAGE. The DEAE-cellulose and Blue-1 MIMETIC affinity fractions gave major peaks at 452 nm in a dithionite-reduced, carbon monoxide, difference spectrum. NaIO4-dependent progesterone hydroxylation was obtained by the pure enzyme without NADPH and NADPH-cytochrome P-450 reductase. NADPH-dependent hydroxylation required the addition of other Phycomyces microsomal proteins present in the Blue-1 fraction.

Chromatography, Affinity↗
PubMed1995

Managing choledocholithiasis in the laparoscopic era.

BACKGROUND: Management options for common bile duct stones have explained in the era of laparoscopic cholecystectomy (LC), and selecting the most appropriate method for each patient can be problematic due to the difficulty of predicting accurately which patients have choledocholithiasis (CDL). In order to improve selection of appropriate treatment for CDL, treatment options were analyzed for outcome retrospectively during a 25-month period beginning June 1, 1992. PATIENTS AND METHODS: Four hundred four patients underwent LC; 48 (12%) had CDL identified at preoperative endoscopic retrograde cholangiopancreatography (ERCP) or intraoperative cholangiogram (IOCG). Forty-seven patients were referred for preoperative ERCP for suspected CDL, 23 (49%) of whom had proven duct stones and underwent endoscopic sphincterotomy and stone retrieval with an 87% success rate. RESULTS: Of 357 patients scheduled for LC without preoperative ERCP, 236 had IOCG, of which 25 (11%) demonstrated CDL. Seven patients had open common bile duct exploration (CBDE). Sixteen patients had postoperative ERCP after positive IOCG, 7 (44%) of which were positive for CDL and whose stones were removed with 100% success. Two patients were observed, anticipating spontaneous passage of a small stone. CONCLUSIONS: Preoperative ERCP should be applied selectively. For the large majority of patients without preoperative evidence of CDL, we recommend routine IOCG; if CDL is demonstrated, an intraoperative decision can be made to proceed to postoperative ERCP in the usual case or to open CBDE for very large or multiple stones. Observation in anticipation of spontaneous passage may be appropriate for small, solitary common duct stones. Continuing advances in laparoscopic CBDE are likely to reduce further the need to rely on ERCP in managing CDL.

Cholangiography↗
PubMed1995

Symptoms of depression among female nursing students.

This study examines the extent to which depressive symptoms in female nursing students are affected by specific stressors and coping styles. Three hypotheses were examined for differences in symptoms of depression scores and a model was tested for predicting depression in female nursing students. Responses were gathered from three questionnaires (Hassles and Uplifts Scales, Symptoms of Stress Inventory, and Coping Styles) from 408 female baccalaureate, master's and doctoral students from a major Midwest research university. Symptoms of depression were not significantly different among the students and were as high as a comparative group of stress management clients. Path analysis was used to examine the patterns of stressors (hassles, uplifts, personal and student-related stress), coping (coping styles, habits, quitting school, and drug use), and a biological factor (depression around the menstrual cycle) that predicted symptoms of depression. All hypothesized variables had direct paths to symptoms of depression; the path model explained 58% of the variance. Results from this study support the biological and psychological theories of depression in women and raise important questions of particular relevance to women, nursing students and educators.

Adaptation, Psychological↗
PubMed1995

Multisystemic treatment of serious juvenile offenders: long-term prevention of criminality and violence.

This article examined the long-term effects of multisystemic therapy (MST) vs. individual therapy (IT) on the prevention of criminal behavior and violent offending among 176 juvenile offenders at high risk for committing additional serious crimes. Results from multiagent, multimethod assessment batteries conducted before and after treatment showed that MST was more effective than IT in improving key family correlates of antisocial behavior and in ameliorating adjustment problems in individual family members. Moreover, results from a 4-year follow-up of rearrest data showed that MST was more effective than IT in preventing future criminal behavior, including violent offending. The implications of such findings for the design of violence prevention programs are discussed.

Adolescent↗
PubMed1995

Surgical infections in AIDS patients.

Many patients with acquired immune deficiency syndrome (AIDS) and abdominal pain are evaluated by the surgeon, and the majority have gastroenteritis, which can be treated with specific antimicrobials. There are some, however, who need more extensive investigation or who have an intra-abdominal infective process that requires surgical treatment. The one and a half decades of experience with human immunodeficiency virus (HIV) and AIDS has defined the role of the surgeon in treating patients with HIV. Major infective processes that may require surgical involvement include cytomegalovirus infection of the intestinal tract; appendicitis, which may be due to opportunistic infections; spontaneous bacterial peritonitis; cholecystitis; and obstructive jaundice with underlying sclerosis of the biliary tree. Early diagnosis and prompt surgical treatment are critical in the management of HIV-infected patients. For example, cytomegalovirus affecting the gastrointestinal tract may lead to perforation with the development of generalized fecal peritonitis; the clinical presentation of acute appendicitis in HIV patients may not include the usual rise in white blood cell count; and bacterial peritonitis in patients with AIDS may be caused by opportunistic pathogens or, as in the classical case, a single gram-negative bacillus or pneumococcus. This review article focuses on intra-abdominal infections in patients with HIV and AIDS.

Abdominal Pain↗
PubMed1994

Intraoperative measurement of Javid shunt flow with transit-time ultrasound.

Transit-time ultrasound methods were used to measure blood flow in 37 patients undergoing carotid endarterectomy. Internal carotid flow before (ICFbef) and after (ICFaft) endarterectomy was measured with a 6 mm perivascular probe, and Javid shunt flow (SF) was measured with a clamp-on probe. For the entire group ICFbef averaged 117 +/- 67 ml/min and ICFaft was 173 +/- 67 ml/min. Shunt flow averaged 123 +/- 51 ml/min. The differences between ICFbef and ICFaft and between SF and ICFaft were significant (ANOVA, p < 0.01) but the difference between ICFbef and SF was not. The relationship between ICFbef and SF appeared to define two groups of patients. Those in whom SF was greater than ICFbef (SF > ICFbef) had more stenosis evident on preoperative arteriograms (64.7% +/- 14.55% maximum single diameter stenosis) and a greater average increase in ICF (151% +/- 159%) than those with SF < or = ICFbef (43.3% +/- 20.9% stenosis and 34% +/- 54% increase in ICF), suggesting that the relationship between SF and ICFbef defines groups with different hemodynamic responses. The similarity between SF and ICFbef indicates that Javid shunt flow offers adequate protection from cerebral ischemia. A practical benefit of the shunt clamp-on flow probe is the ability afforded to recognize shunt occlusions.

Anastomosis, Surgical↗
PubMed1994

Covalent immobilization of protein monolayers for biosensor applications.

Various sensor technologies require a monolayer of tightly bound proteins. Five methods for protein immobilization were evaluated, comprising two methods of linker attachment to a silicon nitride surface (CNBr, silanization) and three methods of linker attachment to the protein (via primary amines, carboxyl groups, and the aromatic rings of tyrosine and histidine). These covalent binding methods were evaluated by immobilization of the enzyme alkaline phosphatase and with monoclonal antibodies tagged with 125I. It was determined that approximately 75% of the protein on the "covalently" immobilized samples was simply adsorbed. Adsorption was reduced by varying the pH and ionic strength of the wash buffers as well as by adding chaotropes and competitors to the wash buffer. A more efficient method of reducing adsorption was to perform the immobilization in the presence of a detergent; 0.5% Tween 60 was the most effective detergent studied. The optimized procedure gives a surface loading of 1.20 x 10(12) MAb/cm2. of which approximately 10% was adsorbed protein. This surface density is consistent with a monolayer of immobilized protein. This protein was shown to be active by challenging immobilized antibodies with 35S-labelled antigen; only the antibody/antigen pair released radioactive material upon elution.

Antibodies, Monoclonal↗
PubMed1994

Microbial transformations of steroids--VIII. Transformation of progesterone by whole cells and microsomes of Aspergillus fumigatus.

The filamentous fungus, Aspergillus fumigatus, efficiently hydroxylated exogenous progesterone producing, after 3 h of incubation, 11 alpha- and 15 beta-hydroxyprogesterone as major products, 7 beta-hydroxyprogesterone as a minor product and trace amounts of 7 beta, 15 beta- and 11 alpha, 15 beta-dihydroxyprogesterone. After 72 h the dihydroxyprogesterones were the sole metabolites in the culture medium. Microsomes, prepared by Ca2+ precipitation, catalysed only monohydroxylation of progesterone at the same sites as whole cells. Hydroxylation was dependent on NADPH (but not NADH) which was replaceable by NaIO4. Hydroxylation was inhibited by carbon monoxide and by the azole fungicide, ketoconazole. Microsomes gave a dithionite-reduced, carbon monoxide difference absorbance spectrum with a peak at 448 nm and a Type-I progesterone-binding spectrum typical of cytochrome P450 interaction with substrate. Ketoconazole inhibition studies suggest the presence of two non-inducible cytochrome P450 progesterone hydroxylases, one possessing 7 beta site-selectivity, the other 11 alpha/15 beta site-selectivity.

Aspergillus fumigatus↗
PubMed1994

Changes in internal carotid blood flow after carotid endarterectomy correlate with preoperative stenosis.

BACKGROUND: The relationship between preoperative stenosis and the effect of carotid endarterectomy (CEA) upon internal carotid blood flow (ICF) is not well understood. With the intention of better characterizing this, we compared intraoperative measurements of internal carotid blood with the maximum single diameter stenosis found in preoperative angiograms. METHODS: Fifty-two patients undergoing 64 carotid endarterectomies (12 bilateral) had transit-time ultrasound perivascular probes used to measure ICF before and after CEA, and the percent change in ICF (% delta ICF) achieved was calculated. Maximum single-diameter stenosis was determined by comparing the least diameter in the flow path from the common carotid to the normal-appearing internal carotid just distal to bifurcation disease. RESULTS: The entire group had a mean of 53 +/- 21% stenosis found on preoperative angiograms, and % delta ICF averaged 64 +/- 92%. When divided into subgroups based on degree of stenosis, patients with 0% to 40% stenosis (n = 17) had % delta ICF of 32 +/- 46%, patients with 41% to 70% stenosis (n = 30) had % delta ICF of 72 +/- 105%, and patients with more than 70% stenosis had % delta ICF of 168 +/- 160%. The differences in % delta IC were significant for the > 70% group compared with the other groups (analysis of variance, P < 0.005), and marginally significant (P = 0.056) between the 0% to 40% and the 41% to 70% groups. The scatter plot of % delta ICF versus stenosis showed a significant second order direct correlation (r = 0.428, P < 0.001) and disproportionate increases in ICF above 60% stenosis. CONCLUSION: A curvilinear relationship between stenosis and immediate increase in ICF after CEA was demonstrated in agreement with theory, and in those patients with more than approximately 60% single-diameter stenosis, large disproportionate increases in blood flow were more frequently observed.

Analysis of Variance↗
PubMed1994

Dose-response relationships in hepatic injury produced by alcohol and carbon tetrachloride.

Dose-response relationships were examined for the production of hepatic fibrosis and cirrhosis by combined exposure of male Porton rats to alcohol and carbon tetrachloride. Alcohol was administered orally in Lieber-DeCarli liquid diet at levels of 75, 150, or 300 kcal/liter, giving mean daily intakes of 2.29, 4.61, and 8.16 g/kg/day, respectively. Carbon tetrachloride was administered by inhalation at concentrations of 10, 20, or 40 ppm, 6 hr/night, 5 nights/week. Liver biopsies were taken at intervals up to a maximum treatment period of 20 weeks. All four rats that received the high dose of both agents, and 1 of 4 that received the medium alcohol and high carbon tetrachloride treatments, were cirrhotic by 10 weeks. Two of the 4 rats that received the low alcohol and high carbon tetrachloride dose were cirrhotic at 20 weeks. Cirrhosis was not observed in rats that received the low or medium carbon tetrachloride dose, but some degree of hepatic fibrosis was observed in all treatment groups. Severity of fibrosis was significantly associated with both dose of alcohol and dose of carbon tetrachloride received. It is concluded that, in the alcohol-carbon tetrachloride rat model for chronic liver injury, both alcohol and carbon tetrachloride contribute to the response in a dose-related manner. Hepatic injury was observed even when relatively low doses of these agents are administered together.

Alcohol Drinking↗
PubMed1993

Can histopathologists reliably diagnose molar pregnancy?

AIMS: To assess the degree of difficulty in diagnosing partial mole by analysing intraobserver and interobserver agreement among a group of pathologists for these diagnoses. METHODS: Fifty mixed cases of partial mole, complete mole, and non-molar pregnancy were submitted to seven histopathologists, two of whom are expert gynaecological pathologists; the other five were district general hospital consultants, one of whom works in Australia. These participants gave each slide a firm diagnosis of either partial mole, complete mole, or non-molar pregnancy. Some 12 months later, the slides were recorded and again submitted for a second diagnostic round to assess intraobserver as well as interobserver agreement. Standard histological criteria for each diagnostic category were circulated with the slides. RESULTS: kappa statistics showed that complete mole could be reliably distinguished from non-molar pregnancy, but neither non-molar pregnancy nor complete mole could be easily differentiated from partial mole. In only 35 out of 50 cases was there agreement between five or more of the seven participants. Agreement between the expert gynaecological pathologists was no better than for others in the group. Interestingly, the intraobserver agreement for each pathologist was good to excellent. CONCLUSIONS: These results imply that the reported histological criteria are either not being applied consistently or that they are lacking in practical use. An atypical growth pattern of trophoblast, rather than the polar accentuation seen in normal first trimester pregnancies, seems to be the important diagnostic histological feature for partial mole. Ploidy studies might also help with problem cases.

Adult↗
PubMed1993

Straight segmental versus bifurcation grafts for repair of abdominal aortic aneurysm.

The decision of two surgical teams to repair an infrarenal aneurysm with a straight or bifurcation graft in 94 patients was investigated. Nine patients had an emergency operation and the two who died within 30 days of surgery (mortality rate 2%) had a ruptured aneurysm. Of 88 patients with follow-up data of at least 1 year (mean 3.5 years), 46 received bifurcation grafts and 42 tube grafts. The mean transverse diameter of the aneurysm on ultrasonography was 6.5 cm for straight and 6.1 cm for bifurcation grafts. The mean duration of operation was longer for bifurcation than straight grafts (4.2 versus 3.3 h, P < 0.05) and intraoperative blood loss greater for the former (2292 versus 1350 ml, P < 0.05). The incidences of late complications for the two grafts were not different. The only secondary aneurysm repair was a staged procedure on a descending thoracic aortic aneurysm. No postoperative iliac aneurysms were detected by routine physical examination and pelvic ultrasonography in patients receiving straight grafts. Even though there was no preselection of patients by disease status, one surgical team relying on preoperative arteriography successfully replaced 28 of 39 aneurysms (72%) with tube grafts while the other team using primarily intraoperative assessment placed straight grafts in only 14 of 49 patients (29%). In conclusion, straight grafts can be implanted in approximately two-thirds of patients undergoing aortic aneurysm repair with significantly less operating time and blood loss and without increase in the incidence of late iliac occlusion or dilatation.(ABSTRACT TRUNCATED AT 250 WORDS)

Anastomosis, Surgical↗
PubMed1992

Guidelines for surgical residents' working hours. Intent vs reality.

To comply with voluntary California medical school guidelines, our general surgery residency program reduced in-house call to 1 in 4 nights, and scheduled a 72-hour work-week. We assessed the effectiveness of these changes by prospectively surveying the actual working hours of surgical house staff through completion of a daily schedule for 1 month. Actual in-hospital hours averaged 98 per week, significantly exceeding the scheduled hours, and were greater for interns (100 hours) and junior residents (97 hours) than for chief residents (95 hours). Twenty hours (22%) of nonconference waking hours were spent on so-called scut work. Significant reduction of intern work hours could be accomplished by expansion of ancillary care, allowing more time for direct patient care. The effect on senior house staff hours would be less dramatic but might be sufficient to bring hours into compliance with proposed limits.

General Surgery↗
PubMed1992

The effect of fibrin glue on intraperitoneal contamination in rats treated with systemic antibiotics.

Intraperitoneal fibrin sealant lowers septic mortality in a rat model of peritoneal contamination (2 x 10(6) organism inoculum) at the cost of increased late intraabdominal abscesses. This study utilized parenteral antimicrobials to determine if the protective effect of intraperitoneal fibrin could be achieved without increasing the late abscess formation rate. One hundred and fifty-five rats were divided into four groups. Gelatin capsules containing various dilutions of feces (10(10) CFU/ml) and barium sulfate were placed into the abdomen in all groups. Group I controls had no antibiotics or fibrin. In group II, the capsule was surrounded by a solution of cryoprecipitate, thrombin, and calcium (fibrin "glue"). Groups III (no fibrin, antibiotics) and IV (fibrin, antibiotics) received a broad-spectrum cephalosporin intramuscularly postoperatively and then daily. Surviving rats were sacrificed on the tenth postoperative day. At a moderate volume of fecal inoculum (0.3 ml), fibrin reduced mortality from 100% in the control group to 0% in treated animals (P less than 0.001) that did not receive antibiotics. Abscesses formed in 10% of the surviving fibrin-treated rats which were implanted with 0.1 ml of inoculum. In the 0.2 and 0.3 ml inoculum groups substantially more abscesses occurred (75 and 70%, respectively). The protective effect of fibrin was not manifested in the antibiotic-treated rats since no deaths occurred in either group. At higher and lower inoculum doses, no significant differences between fibrin and control groups were observed in mortality or abscess formation, whether or not antibiotics were given.(ABSTRACT TRUNCATED AT 250 WORDS)

Abscess↗