Mapping of QTL for downy mildew resistance in maize

Quantitative trait loci (QTLs) of maize involved in mediating resistance to Peronosclerospora sorghi, the causative agent of sorghum downy mildew (SDM), were detected in a population of recombinant inbred lines (RILs) derived from the Zea mays L. cross between resistant (G62) and susceptible (G58) inbred lines. Field tests of 94 RILs were conducted over two growing seasons using artificial inoculation. Heritability of the disease reaction was high (around 70%). The mapping population of the RILs was also scored for restriction fragment length polymorphic (RFLP) markers. One hundred and six polymorphic RFLP markers were assigned to ten chromosomes covering 1648 cM. Three QTLs were detected that significantly affected resistance to SDM combined across seasons. Two of these mapped quite close together on chromosome 1, while the third one was on chromosome 9. The percentage of phenotypic variance explained by each QTL ranged from 12.4% to 23.8%. Collectively, the three QTLs identified in this study explained 53.6% of the phenotypic variation in susceptibility to the infection. The three resistant QTLs appeared to have additive effects. Increased susceptibility was contributed by the alleles of the susceptible parent. The detection of more than one QTL supports the hypothesis that several qualitative and quantitative genes control resistance to P. sorghi.

Effect of total hepatic vascular exclusion during liver resection on hepatic ultrastructure

The aim of this investigation was to observe ultrastructural changes in the liver in response to warm ischemia during liver surgery. In 11 noncirrhotic patients, hepatic resection was performed under total vascular exclusion (TVE). The mean duration of warm ischemia was 28 minutes (range 16-48 minutes). Three specimens were taken from each patient: before clamping, at the end of TVE, and after reperfusion. Biopsy specimens were studied by light microscopy and by transmission electron microscopy (EM). At the end of the ischemic phase sinusoids were collapsed with resultant loss of normal hepatic architecture. Morphological changes to hepatocytes included focal chromatin condensation at the nuclear margins, distended nuclear envelope, and swelling of both mitochondria and endoplasmic reticulum. After reperfusion these changes reversed. The phenomenon of sinusoidal and hepatocellular recovery after TVE was seen in all the cases of this study, irrespective of age, sex, disease, type and severity of surgical intervention, and duration of TVE. It can be concluded that TVE over a period of 48 minutes has no irreversible deleterious effects on the ultrastructure of the noncirrhotic liver.

Why is colonoscopy more difficult in women?

BACKGROUND

In our experience colonoscopy in women is more difficult than in men. A retrospective review of 2194 colonoscopies performed by a single experienced endoscopist (CBW) showed that 31% of examinations in women were considered technically difficult compared with 16% in men.

METHODS

To investigate a possible anatomic basis for this finding, normal barium enema series from 183 female and 162 male patients were identified. From these barium enemas, measurements of colonic length and mobility were independently taken by two physicians who were unaware of each patient's gender.

RESULTS

Total colonic length was greater in women (median, 155 cm) compared to men (median, 145 cm), p = 0.005, despite women's smaller stature (p < 0.0001). Although there were no significant differences in rectum plus sigmoid, descending, or ascending plus cecum segmental lengths, women had longer transverse colons (female median length, 48 cm; male median length, 40 cm), p < 0.0001. There were no differences in mobility of the descending colon and transverse colon between the sexes, but the transverse colon reached the true pelvis more often in women (62%) than in men (26%), p < 0.001.

CONCLUSIONS

Colonoscopy appears to be a technically more difficult procedure in women. The reason for this may be due in part to an inherently longer colon.

Repeated resection for malignant liver tumours

Fifteen repeat hepatic resections were performed on 12 patients with either recurrent or residual malignant tumours of the liver. Of these, one patient underwent three repeat resections and another underwent two. Five had primary liver liver tumours and seven had liver metastases. Planned, 'staged', repeat resections were performed on three patients because of multiple deposits of tumour, cirrhosis or extensive disease at initial presentation. There was no operative mortality. The period of follow-up from the time of repeat sections ranged between 4 months and 36 months during which two patients died from recurrent disease. The mean survival after the repeat resection was 16.8 months (range 4-36 months). Although technically demanding, repeat hepatectomy is feasible and provide similar benefits.

Can barium enema indicate when colonoscopy will be difficult?

The barium enemas of 48 consecutive patients, who were technically difficult to intubate at colonoscopy, were compared to those of 46 patients who were not. Measurements were taken of colonic length and mobility, and an assessment made of diverticular disease. Rectosigmoid length (mean difficult group = 61 cm, mean control = 54 cm, P = 0.01) and total colonic length (mean difficult group = 157 cm, mean control = 140 cm, P < 0.0001) were greater in the difficult colonoscopy group as were transverse colon mobility (mean difficult group = 10 cm, mean control = 7 cm, P = 0.003) or redundancy (transverse colon reaching the true pelvis on the erect film); 65% difficult group vs 17% control group, P < 0.0001. The presence of moderate or severe diverticular disease was also greater in the difficult (23%) compared to the control (4%) group, P = 0.02. When available, assessment of a previous barium enema is a useful guide to probable technical difficulty of colonscopy. It may allow appropriate allocation of potentially difficult cases to specialist endoscopy lists.