Machine learning to predict myocardial injury and death after non-cardiac surgery

Myocardial injury due to ischaemia within 30 days of non-cardiac surgery is prognostically relevant. We aimed to determine the discrimination, calibration, accuracy, sensitivity and specificity of single-layer and multiple-layer neural networks for myocardial injury and death within 30 postoperative days. We analysed data from 24,589 participants in the Vascular Events in Non-cardiac Surgery Patients Cohort Evaluation study. Validation was performed on a randomly selected subset of the study population. Discrimination for myocardial injury by single-layer vs. multiple-layer models generated areas (95%CI) under the receiver operating characteristic curve of: 0.70 (0.69-0.72) vs. 0.71 (0.70-0.73) with variables available before surgical referral, p < 0.001; 0.73 (0.72-0.75) vs. 0.75 (0.74-0.76) with additional variables available on admission, but before surgery, p < 0.001; and 0.76 (0.75-0.77) vs. 0.77 (0.76-0.78) with the addition of subsequent variables, p < 0.001. Discrimination for death by single-layer vs. multiple-layer models generated areas (95%CI) under the receiver operating characteristic curve of: 0.71 (0.66-0.76) vs. 0.74 (0.71-0.77) with variables available before surgical referral, p = 0.04; 0.78 (0.73-0.82) vs. 0.83 (0.79-0.86) with additional variables available on admission but before surgery, p = 0.01; and 0.87 (0.83-0.89) vs. 0.87 (0.85-0.90) with the addition of subsequent variables, p = 0.52. The accuracy of the multiple-layer model for myocardial injury and death with all variables was 70% and 89%, respectively.

979 Emphysematous Pyelonephritis in a Diabetic Patient with Horseshoe Kidney: Case Study and Literature Review

We present to you the case of a 54-year-old female with a background of horseshoe kidney presenting with a fever, right-sided flank pain, and raised inflammatory markers. This presentation was on a background of recurrent urinary tract infections which were managed conservatively with antibiotics. CT-KUB revealed pockets of gas in both kidneys and within the pelvis, with wall thickening of the left renal pelvis. She subsequently received broad spectrum antibiotics and a suprapubic catheter. Bilateral JJ stents were inserted, and ultrasound was performed in the days following to rule out hydronephrosis. Subsequently, a nephrostomy tube was inserted. The patient clinically improved over time. Horseshoe kidney is a rare anomaly, presenting multiple challenges when managing emphysematous pyelonephritis in these patients.

Emphysematous pyelonephritis (EPN) is a necrotising renal infection that leads to the formation of gas in the renal parenchyma, collecting ducts, and surrounding tissue. In the past, multiple eponyms have been used to describe these conditions: ‘renal emphysema’, ‘pneumonephritis’. The pathophysiology of this benign condition is multifactorial. The gas formation that occurs can be either focal or diffuse and has the capability of tracking into perinephric and paranephric spaces.

Approximately 90% of these patients have an underlying diagnosis of uncontrolled diabetes mellitus with pathogens that can produce gas, whilst 10% have urinary tract obstructions. EPN is rare, and the occurrence in a diabetic patient with horseshoe kidney has rarely been reported. The presence of a horseshoe kidney makes management more difficult. Few cases have been reported in the literature.

Neuroaxial Infantile Hemangiomas: Imaging Manifestations and Association with Hemangioma Syndromes

BACKGROUND AND PURPOSE

Infantile hemangiomas are common lesions in the pediatric population; in rare cases, an infantile hemangioma can be detected along the neural axis. The purposes of our study included determination of the incidence, location, and imaging appearance of neuroaxial infantile hemangiomas and their syndromic association. We also assessed additional features of cerebral and cardiovascular anomalies that may be associated with neuroaxial lesions.

MATERIALS AND METHODS

A retrospective cohort study was performed, searching the radiology database for patients with segmental infantile hemangiomas referred for assessment of possible hemangioma syndromes. We retrospectively reviewed brain and spine MR imaging studies, with particular attention paid to neuroaxial vascular lesions, as well as the relevant clinical data. Neuroaxial hemangioma imaging findings were described, and comparison of segmental cutaneous infantile hemangioma location with the imaging findings was performed in patients with confirmed hemangioma syndromes and in patients with isolated skin infantile hemangioma.

RESULTS

Ninety-five patients with segmental infantile hemangioma were included in the study, 42 of whom had a hemangioma syndrome; of those, 41 had posterior fossa brain malformations, hemangioma, arterial lesions, cardiac abnormalities, and eye abnormalities (PHACE) syndrome and 1 had diffuse neonatal hemangiomatosis. Neuroaxial involvement was detected in 20/42 patients (48%) with hemangioma syndromes and in no subjects with isolated segmental infantile hemangioma (P < .001). The most common intracranial hemangioma location was within the ipsilateral internal auditory canal (83%).

CONCLUSIONS

Many pediatric patients with segmental infantile hemangioma in the setting of hemangioma syndromes, especially those with PHACE, had neuroaxial hemangiomas. This finding may potentially lead to requiring additional clinical evaluation and management of these patients.

Assessing physical activity in people with mental illness: 23-country reliability and validity of the simple physical activity questionnaire (SIMPAQ)

BACKGROUND

Physical inactivity is a key contributor to the global burden of disease and disproportionately impacts the wellbeing of people experiencing mental illness. Increases in physical activity are associated with improvements in symptoms of mental illness and reduction in cardiometabolic risk. Reliable and valid clinical tools that assess physical activity would improve evaluation of intervention studies that aim to increase physical activity and reduce sedentary behaviour in people living with mental illness.

METHODS

The five-item Simple Physical Activity Questionnaire (SIMPAQ) was developed by a multidisciplinary, international working group as a clinical tool to assess physical activity and sedentary behaviour in people living with mental illness. Patients with a DSM or ICD mental illness diagnoses were recruited and completed the SIMPAQ on two occasions, one week apart. Participants wore an Actigraph accelerometer and completed brief cognitive and clinical assessments.

RESULTS

Evidence of SIMPAQ validity was assessed against accelerometer-derived measures of physical activity. Data were obtained from 1010 participants. The SIMPAQ had good test-retest reliability. Correlations for moderate-vigorous physical activity was comparable to studies conducted in general population samples. Evidence of validity for the sedentary behaviour item was poor. An alternative method to calculate sedentary behaviour had stronger evidence of validity. This alternative method is recommended for use in future studies employing the SIMPAQ.

CONCLUSIONS

The SIMPAQ is a brief measure of physical activity and sedentary behaviour that can be reliably and validly administered by health professionals.

Design of a Pilot SOFC System for the Combined Production of Hydrogen and Electricity under Refueling Station Requirements

The objective of the current work is to support the design of a pilot hydrogen and electricity producing plant that uses natural gas (or biomethane) as raw material, as a transition option towards a 100% renewable transportation system. The plant, with a solid oxide fuel cell (SOFC) as principal technology, is intended to be the main unit of an electric vehicle station. The refueling station has to work at different operation periods characterized by the hydrogen demand and the electricity needed for supply and self-consumption. The same set of heat exchangers has to satisfy the heating and cooling needs of the different operation periods. In order to optimize the operating variables of the pilot plant and to provide the best heat exchanger network, the applied methodology follows a systematic procedure for multi-objective, i.e. maximum plant efficiency and minimum number of heat exchanger matches, and multi-period optimization. The solving strategy combines process flow modeling in steady state, superstructure-based mathematical programming and the use of an evolutionary-based algorithm for optimization. The results show that the plant can reach a daily weighted efficiency exceeding 60%, up to 80% when considering heat utilization.

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

BACKGROUND

Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery.

METHODS

This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy.

RESULTS

Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI.

CONCLUSIONS

After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.

American Society of Functional Neuroradiology-Recommended fMRI Paradigm Algorithms for Presurgical Language Assessment

INTRODUCTION

Functional MR imaging is increasingly being used for presurgical language assessment in the treatment of patients with brain tumors, epilepsy, vascular malformations, and other conditions. The inherent complexity of fMRI, which includes numerous processing steps and selective analyses, is compounded by institution-unique approaches to patient training, paradigm choice, and an eclectic array of postprocessing options from various vendors. Consequently, institutions perform fMRI in such markedly different manners that data sharing, comparison, and generalization of results are difficult. The American Society of Functional Neuroradiology proposes widespread adoption of common fMRI language paradigms as the first step in countering this lost opportunity to advance our knowledge and improve patient care.

LANGUAGE PARADIGM REVIEW PROCESS

A taskforce of American Society of Functional Neuroradiology members from multiple institutions used a broad literature review, member polls, and expert opinion to converge on 2 sets of standard language paradigms that strike a balance between ease of application and clinical usefulness.

ASFNR RECOMMENDATIONS

The taskforce generated an adult language paradigm algorithm for presurgical language assessment including the following tasks: Sentence Completion, Silent Word Generation, Rhyming, Object Naming, and/or Passive Story Listening. The pediatric algorithm includes the following tasks: Sentence Completion, Rhyming, Antonym Generation, or Passive Story Listening.

DISCUSSION

Convergence of fMRI language paradigms across institutions offers the first step in providing a "Rosetta Stone" that provides a common reference point with which to compare and contrast the usefulness and reliability of fMRI data. From this common language task battery, future refinements and improvements are anticipated, particularly as objective measures of reliability become available. Some commonality of practice is a necessary first step to develop a foundation on which to improve the clinical utility of this field.

Association between vasoactive-inotropic score and mortality in pediatric septic shock

OBJECTIVE

To assess the association between Vasoactive Inotrope Score (vis) and mortality in children with fluid-refractory septic shock.

METHODS

A retrospective chart review of 71 children (age 1 mo-16y) admitted with fluid-refractory septic shock in pediatric intensive care unit during a two year period was done. We divided our cohort into two groups viz High vasoactive inotrope score (Group-H) and Low-vasoactive inotrope score (Group-L) based on a cut-off value of 20.

RESULTS

73% of the children were in Group-L. The mortality rate was 44% and 100% in Group L and Group H, respectively.

CONCLUSIONS

High inotropic score in children with septic shock is associated with high mortality rate.

Increased Susceptibility to Aphids of Flowering Wheat Plants Exposed to Low Temperatures

Frost is known to directly affect flowering wheat plants (Triticum aestivum L.) and lead to reduced grain yield. Additionally, it may increase wheat susceptibility to economically important pests, such as aphids (Hemiptera: Aphididae). Wheat plants at flowering stage were exposed to one of the three temperature treatments: ambient (11-12°C), 0°C, and -3°C for 60 min. Preference (3-choice) and performance (no-choice) bioassays with aphids (Rhopalosiphum padi L.) were conducted 1, 3, 6, and 12 d after temperature treatments to assess effects of temperature-induced stress over time. As an initial feasibility study of using remote sensing technologies to detect frost-induced stress in flowering wheat plants, hyperspectral imaging data were acquired from wheat plants used in preference bioassays. Element analysis of wheat plants was included to determine the effect of temperature-induced stress on the nutritional composition of flowering wheat plants. The results from this study support the following cause-effect scenario: a 60-min exposure to low temperatures caused a significant decrease in potassium and copper content of wheat plants 6 d after temperature exposure, and it coincided with a marked increase in preference by aphids of wheat plants. The preference exhibited by aphids correlated positively with performance of aphids, so the preference-performance hypothesis was confirmed and possibly driven by potassium and copper content of wheat plants. In addition, we demonstrated that hyperspectral imaging data can be used to detect frost-induced susceptibility to aphid infestation in flowering wheat plants. These findings justify further research into airborne remote sensing of frost-induced stress and the possible secondary effects on crop susceptibility to arthropod pests.

Treat to target in managing inflammatory arthritis

Treating to target has been used in many areas of medicine, including diabetes mellitus and cardiovascular disease risk. This principle has now been applied to rheumatological conditions, notably inflammatory arthritis. This article discusses the role and importance of this management approach in inflammatory arthritis.

"Dazed and diffused": making sense of diffusion abnormalities in neurologic pathologies

To review diffusion abnormalities seen in diffusion-weighted MRI in neurological pathologies. We examine the clinical significance of the abnormalities in a broad spectrum of neurological diseases and highlight our current understanding of their causes. Diffusion abnormalities seen on diffusion-weighted MRI can play an important role in the diagnosis and follow-up of a broad spectrum of neurological diseases. A thorough understanding of the appearance and significance of these abnormalities is critical in patient management.

Aspergillus infection and extracorporeal membrane oxygenation support

BACKGROUND

The clinical characteristics of patients with Aspergillus isolation while supported on extracorporeal membrane oxygenator (ECMO) remain unclear.

OBJECTIVES

We present a case report of angioinvasive Aspergillus infection on an infant supported on ECMO and also investigate outcomes among patients with Aspergillus infection reported to the Extracorporeal Life Support Organization (ELSO) registry.

DESIGN

Case report and retrospective analysis of ELSO registry data set from 1985 to 2009.

SETTING

One hundred and seventy ECMO centers contributing data to the ELSO registry.

PATIENTS

Single case report and patients 0 to 90 years of age with Aspergillus infection requiring ECMO support as reported to the ELSO registry.

METHODS

Besides presenting details of our institutional case, we compared clinical characteristics and outcomes between pediatric and adult patients with Aspergillus isolation. Risk factors for in-hospital mortality were investigated. Kaplan-Meier estimates for freedom from death on ECMO for pediatric and adult patients were investigated.

MEASUREMENTS AND MAIN RESULTS

(a) we report a case with Aspergillus supported on ECMO, (b) the ELSO registry yielded 46 patients with 59% (n = 27) in the pediatric data set (≤20 years of age) and 41% (n = 19) in the adult data set (>20 years of age) with Aspergillus infection requiring ECMO support. Overall survival to hospital discharge was 30% (14/46) with 22% (6/27) in children as compared to 42% (8/18) in adults (P = .19). Table 1 shows a comparison of clinical characteristics between children and adults. The comparison between adults and pediatric groups differed significantly in age (P = .0001), more use of venoarterial ECMO in children (P = .028). The median age of pediatric group was 1.95 years (range 0-17.3 years) versus 30.2 years (range 22-60 years) among adults.

CONCLUSIONS

Aspergillus infection/colonization is associated with a 70% overall mortality among patients supported on ECMO. The ELSO registry data confirms that Aspergillus infection among ECMO supported patients occurs often in hosts who do not have known immunodeficiencies. The case stresses the need for a high level of suspicion for Aspergillus infection in nonimproving lung disease in patients on ECMO support.

Genotype-phenotype study of familial haemophagocytic lymphohistiocytosis due to perforin mutations

BACKGROUND

PRF1 gene mutations are associated with familial haemophagocytic lymphohistiocytosis type 2 (FHL2). Genotype-phenotype analysis, previously hampered by limited numbers of patients, was for the first time performed by data pooling from five large centres worldwide.

PATIENTS AND METHODS

Members of the Histiocyte Society were asked to report cases of FHL2 on specific forms. Data were pooled in a common database and analysed.

RESULTS

The 124 patients had 63 different mutations (including 15 novel mutations): 11 nonsense, 10 frameshift, 38 missense and 4 in-frame deletions. Some mutations were found more commonly: 1122 G-->A (W374X), associated with Turkish origin, in 32 patients; 50delT (L17fsX22) associated with African/African American origin, in 21 patients; and 1090-91delCT (L364fsX), in 7 Japanese patients. Flow cytometry showed that perforin expression was absent in 40, reduced in 6 and normal in 4 patients. Patients presented at a median age of 3 months (quartiles: 2, 3 and 13 months), always with fever, splenomegaly and thrombocytopenia. NK activity was absent in 36 (51%), <or=2% in 18 (26%), 3-<or=5% in 10 (14%), >5% in 4 (6%), "reduced" in 2 (3%) (not reported, n = 54). Nonsense mutations were significantly associated with younger age at onset (p<0.001) and absent natural killer activity (p = 0.008).

CONCLUSION

PRF1 mutations are spread over the functional domains. Specific mutations are strongly associated with Turkish, African American and Japanese ethnic groups. Later onset and residual cytotoxic function are observed in patients with at least one missense mutation.

Performance of laser bonded glass/polyimide microjoints in cerebrospinal fluid

In this paper, laser bonded microjoints between glass and polyimide is considered to examine their potential applicability in encapsulating neural implants. To facilitate bonding between polyimide and glass, a thin titanium film with a thickness of 2 microm was deposited on borosilicate glass plates by a physical vapor deposition (PVD) process. Titanium coated glass was then joined with polyimide by using a cw fiber laser emitting at a wavelength of 1.1 microm (1.0 W) to prepare several tensile samples. Some of the samples were exposed to artificial cerebrospinal fluid (aCSF) at 37 degrees C for two weeks to assess long-term integrity of the joints. Both the as-received and aCSF soaked samples were subjected to uniaxial tensile loads for bond strengths measurements. The bond strengths for the as-received and aCSF soaked samples were measured to be 7.31 and 5.33 N/mm, respectively. Although the long-term exposure of the microjoints to aCSF has resulted in 26% reduction of bond strength, the samples still retain considerably high strength as compared with the titanium-polyimide samples. The failed glass/polyimide samples were also analyzed using optical microscopy, and failure mechanisms are discussed. In addition, a two dimensional finite element analysis (FEA) was conducted to understand the stress distribution within the substrate materials while the samples are in tension. The FEA results match reasonably well with the experimental load-displacement curves for as-received samples. Detailed discussion on various stress contours is presented in the paper, and the failure mechanisms observed from the experiment are shown in good agreement with the FEA predicted ones.

Accumulation of E. Coli bacteria in mini-channel flow

The objective of this research is to design and optimize a mini/micro-channel based surface-accumulator of E. coli bacteria to be detected by acoustic wave biosensors. A computational approach has been carried out using the state of the art software, CFD-ACE with water as bacteria bearing fluid. E. coli bacteria have been modeled as random discrete particles tracked by solving the Lagrangian equations. The design challenges are to achieve low shear force (pico-N), high concentration at accumulation, and high enough Reynolds number to avoid bacteria swimming. A range of low Reynolds number (Re) has been considered along with the effects of particle boundary interactions, gravity, Saffman lift, etc. More than two orders of magnitude higher concentration at the accumulation than the inlet concentration, and lower shear force of less than pico-N have been achieved in the optimized designs.

A comparison between glass/polyimide and titanium/polyimide microjoint performances in cerebrospinal fluid

Assessment of neural biocompatibility requires that materials be tested with exposure in neural fluids. Laser bonded microjoint samples made from Ti coated glass substrate and polyimide film (GPI) and titanium foil and polyimide film (TIPI) were evaluated for mechanical performance before and after exposure in artificial cerebrospinal fluid (CSF) for two, four, and 12 weeks at 37 degrees C. These samples represent a critical feature, i.e., the microjoint-a major weakness in the bioencapsulation system. Both material systems showed initial degradation up to 4 weeks which then stabilized afterwards and retained similar strength until 12 weeks. The TIPI system appears to exhibit better overall performance with less degradation compared to its as-received strength. The CSF exposed TIPI samples predominantly failed at the interface, while GPI samples had mixed glass and polyimide substrate and interface failure. The amount of glass failure decreases and interface failure increases with increase in CSF exposure time. The failure mechanism of the as-received (not exposed to CSF) GPI samples under tension was predominantly flexure type failure of the glass substrate.

Laser bonded microjoints between titanium and polyimide for applications in medical implants

Bioencapsulation of medical implant devices, and neural implant devices in particular, requires development of reliable hermetic joints between packaging materials that are often dissimilar. Titanium-polyimide is one of the biocompatible material systems, which are of interest to our research groups at Wayne State University and Fraunhofer USA. We have found processing conditions for successful joining of titanium with polyimide using near-infrared diode lasers or fiber lasers along transmission bonding lines with widths ranging from 200 to 300 microm. Laser powers of 2.2 and 3.8 W were used to create these joints. Laser-joined samples were tested in a microtester under tensile loading to determine joint strengths. In addition, finite element analysis (FEA) was conducted to understand the stress distribution within the bond area under tensile loading. The FEA model provides a full-field stress distribution in and around the joint that cause eventual failure. Results from the investigation provide an initial approach to characterize laser-fabricated microjoints between dissimilar materials that can be potentially used in optimization of bio-encapsulation design.

Vulnerability to homicide in Karachi: political activity as a risk factor

BACKGROUND

Previous studies analysing Karachi ambulance data from 1993 to 1995 identified neighbourhoods in Karachi disproportionately affected by homicide. As a step toward developing intervention programmes to curb violence, we conducted a study to identify risk factors for becoming a homicide victim in a high violence area of Karachi.

METHODS

We interviewed families of 35 cases, individuals intentionally killed through acts of violence between January 1994 and January 1997, and 85 community-based controls frequency matched by sex, from Orangi, a high violence area of Karachi.

RESULTS

Most of our cases and controls were male (97% and 92%, respectively) and had similar socioeconomic and ethnic backgrounds. All the victims were killed by firearms; 4 (11%) had been tortured prior to death. Most of the victims were killed in the streets (n = 25, 71%). Of these, 7 (36%) had been killed by law-enforcement officers, while 6 (24%) died from indiscriminate firing. People who were killed were 34 times more likely to have attended all political processions (29% versus 1%, odds ratio [OR] = 34; 95% CI: 4-749, P < 0.001), 19 times more likely to have attended political meetings (31% versus 2%, OR = 19; 95% CI: 4-136, P < 0.001), and 17 times more likely to have held an important position in a political party (29% versus 2%, OR = 17; 95% CI: 3-120, P < 0.001) than controls.

CONCLUSIONS

Homicide in Orangi was political. Efforts to improve trust between ethnic groups and to build legitimacy for non-violent forms of conflict resolution are important steps to limit future violence.

Suprapubic prostatectomy for benign prostatic hyperplasia in rural Asia: 200 consecutive cases

OBJECTIVES

To assess the safety and efficacy of a suprapubic prostatectomy technique performed in a rural hospital in Asia.

METHODS

A retrospective study of 200 consecutive suprapubic transvesical prostatectomies with a removable bladder neck partition suture for benign prostatic hyperplasia from 1995 to 1998 in a rural mission hospital in northern Pakistan was performed.

RESULTS

Despite preoperative comorbidities in 28% of patients, the postoperative morbidity (14%) and mortality (1%) was low. The partition suture is credited with a very low transfusion rate (1%) and a lower intensity of nursing care in the postoperative period. Patient satisfaction was high with regard to both relief of symptoms and cost.

CONCLUSIONS

This study demonstrated that suprapubic prostatectomy with a routine bladder neck partition suture for benign prostatic hyperplasia can be carried out with a high degree of safety and efficacy in a rural setting with limited facilities in a developing country.

Distribution of AB0 and RH blood group alleles in different populations of southern Punjab, Pakistan

The analysis of a sample of 1632 individuals from patients of the Nishtar Teaching Hospital, Multan, suggests that different ethnic groups (Araeen, Mughals, Syed, Jat, Rajputs, Baloch and Pathan) are not significantly different from another with regard to the distribution of RH blood group alleles (RH*d around 0.30). The distributions of the AB0 blood group alleles suggest that different ethnic groups are not significantly different from the average alele frequencies (AB0*A = 0.23, AB0*B = 0.33, AB0*0 = 0.47) except for the Pathan ethnic group (AB0*A = 0.35, AB0*B = 0.47, AB0*0 = 0.27). The populations of different geographic areas are not significantly different from the average allele frequencies, except for the southern district of Rahim Yar Khan (AB0*A = 0.12) and the northern district of Sahiwal (AB0*A = 0.19). The populations of Sahiwal (RH*d = 0.35) and Muzaffargarh (RH*d = 0.36) yield significantly different allele frequencies at the RH locus. The interpopulation differences can be explained by the geographic distance. There is a significant difference in the frequencies of the AB0 alleles between rural and urban populations, suggesting that rural populations maintain their isolation from urban populations. Rural and urban populations are not significantly different from one another concerning the allele frequencies at the RH locus.

Use of multivariate characterization, design and analysis in assay optimization

A procedure is proposed for utilizing information from previous work on development of LC assays in order to facilitate the analysis of novel compounds related to those previously analysed. The procedure employs a multivariate method from the field of chemometrics, partial least squares analysis (PLS) to combine quantitative information on the chemical properties of a compound with a quantitative description of the column and the mobile phase and then to use this information to form a regression model for the retention time. A test of the procedure was made by using data on nucleoside analogues studied in our laboratory. Data obtained from chromatographic studies of seven compounds tested in a total of 28 combinations of columns and mobile phases (3-5 per compound) were used to calculate a PLS model. The model was then used to predict retention times of nine other substances and the results were compared with experimental data. The predictions were (115 +/- 82%) (95% confidence interval) of the experimentally observed retention times. The results are encouraging and the method will be subject to further and extended investigations.

Genetic studies in some ethnic groups of Pakistan (Southern Punjab): colour blindness, ear lobe attachment and behavioural traits

Frequency distributions of colour blindness, adherent ear lobe, hand clasping, arm folding and leg folding are reported for different ethnic groups (Balochs, Rajputs, Syeds, Pathans, Araeen and Jats) for Pakistan (Southern Punjab). The F-analysis suggests an insignificant difference between these groups, though the LSD value indicates a significant difference of Balochs with the other groups. The association Chi-square values suggest the independence of the three behavioural traits.

Promoter variation in the ribosomal RNA genes in Drosophila melanogaster strains

The sequences of thirty D. melanogaster ribosomal DNA promoter regions have been determined. Fifteen of these were isolated from a wild population recently captured in North Wootten, England. The other fifteen were isolated from an inbred laboratory strain. The overall level of variation is almost twice as high in the North Wootten strain as in the inbred laboratory strain. Two mutations at nucleotides -17 and -21 relative to transcription start, fall directly within a region known to be transcriptionally important. The sequences are also compared to eight previously published sequences from another D. melanogaster strain, Oregon R. Two of these eight clones have a -17 mutation identical to the one found in this study, suggesting that this polymorphism is widespread. Strikingly, all eight of these clones carry two single base pair changes not found in any of the other thirty clones, indicating the extent with which promoter variants can be homogenized and fixed in a population. Polymorphisms show different levels of homogenization within the rDNA unit spacer repeats or between different arrays depending on the location of the polymorphism. This has implications for the evolution of the observed species-specific transcription of ribosomal RNA genes.

Effect of aneuploidy and neoplasia on human ribosomal DNA inheritance

A DNA length polymorphism in the nontranscribed spacer region of the repeating unit that codes for human ribosomal RNA produces a characteristic pattern or restriction fragments in each individual. Quantitative densitometric analysis of ribosomal ribosomal DNA fragment distribution in families demonstrates additive inheritance in those with chromosomally normal or aneuploid offspring. Differences between offspring and parental ribosomal DNA patterns could be explained by a heterogeneous distribution of length variants on the acrocentric chromosomes. New ribosomal DNA length variants of 9.0, 6.7, 5.5, and 5.2 kilobases were observed in normal individuals after BamHI restriction, and the former two were present in multiple copies. A panel of solid tumor specimens exhibited ribosomal DNA patterns that were generally characteristic of the patient rather than tumor type. However, novel ribosomal DNA length variants or changes in length variant proportions were noted in three of the four tumors for which adjacent normal tissue was available for comparison; these alterations occurred in a Burkitt lymphoma, a teratoma, and a Wilms tumor. A consistent karyotype of 50,XY in the Wilms tumor specimen supports previous evidence for increased repetitive DNA variation in aneuploid, neoplastic tissues.

Sterility enhancement in the mosquito. Culex tritaeniorhynchus

The sterilities of stocks with chromosomal aberrations were enhanced by re-irradiation. Males heterozygous for two independent aberrations were synthesized and their sterilities determined. The possible advantages of the double heterozygote males over either completely sterile males or those heterozygous for only one aberrational complex are discussed.

Linkage group-chromosome correlation in Culex tritaeniorhynchus

Linkage groups of a culicine mosquito, Culex tritaeniorhynchus, have been assigned to their respective chromosomes by genetic and cytologic observations of radiation-induced aberrations. Linkage group I is assigned to the smallest chromosome, linkage group II to the submetacentric chromosome, and linkage group III to the metacentric chromosome.