Identification of a Frizzled-like cysteine rich domain in the extracellular region of developmental receptor tyrosine kinases

In Drosophila, members of the Frizzled family of tissue-polarity genes encode proteins that appear to function as cell-surface receptors for Wnts. The Frizzled genes belong to the seven transmembrane class of receptors (7TMR) and have on their extracellular region a cysteine-rich domain that has been implicated as the Wnt binding domain. This region has a characteristic spacing of ten cysteines, which has also been identified in FrzB (a secreted antagonist of Wnt signaling) and Smoothened (another 7TMR, which is involved in suppression of the hedgehog pathway). We have identified, using BLAST, sequence similarity between the cysteine-rich domain of Frizzled and several receptor tyrosine kinases, which have roles in development. These include the muscle-specific receptor tyrosine kinase (MuSK), the neuronal specific kinase (NSK2), and ROR1 and ROR2. At present, the ligands for these developmental tyrosine kinases are unknown. Our results suggest that Wnt-like ligands may bind to these developmental tyrosine kinases.

Chromium(III) decreases the fidelity of human DNA polymerase beta

Certain particulate compounds of hexavalent chromium are well-known occupational and environmental human carcinogens. Hexavalent chromium primarily enters the cells and undergoes metabolic reduction; however, the ultimate trivalent oxidation state of chromium, Cr(III), predominates within the cell. DNA-bound Cr(III) has been previously shown to decrease the fidelity of replication in the M13 phage mutation assay. This study was done to understand how Cr(III), in the presence of physiological concentrations of magnesium, affects the kinetic parameters of steady-state DNA synthesis in vitro across site-specific O6-methylguanine (m6dG) residues by DNA polymerase beta (pol beta). Cr(III) binds to the short oligomer templates in a dose-dependent manner and stimulates the activity of pol beta. Cr(III) stimulates the mutagenic incorporation of dTTP opposite m6dG more than the nonmutagenic incorporation of dCTP, and thereby Cr(III) further decreases the fidelity of DNA synthesis across m6dG by pol beta. In contrast, Cr(III) does not affect the fidelity of DNA synthesis across the normal template base, dG. Both the enhanced activity and the mutagenic lesion bypass in the presence of Cr(III) may be associated with Cr(III)-dependent stimulation of pol beta binding to DNA as reported here. This study shows some of the mechanisms by which mutagenic chromium affects DNA synthesis.

Dietary fish oil inhibits the expression of farnesyl protein transferase and colon tumor development in rodents

Although epidemiological and experimental studies indicate a strong relationship between different dietary fats and risk of colon cancer, the modulating effects of these nutritional factors at the molecular level are not fully elucidated. Activated ras genes have been implicated in the etiology of many human malignancies, including colon cancer. It is well established that the transforming ability of ras-p21 depends on its correct localization in plasma membrane. We have previously demonstrated that ingestion of a relatively higher amount of dietary fish oil leads to reduced plasma membrane levels of ras-p21 with concomitant increase in its cytoplasmic contents during the promotion and progression phases of chemically-induced colon tumorigenesis. In this follow-up experiment, we have found that intake of a high amount of corn oil, one of the most widely used fats in the American diet, enhances the expression of farnesyl protein transferase (FPTase). This enzyme catalyses farnesylation of ras precursors in a critical step during post-translational modification of ras oncoproteins, thereby enabling their anchorage to plasma membrane. In contrast, consumption of high amounts of fish oil, which is rich in omega-3 polyunsaturated fatty acids, reduces the levels of FPTase expression, thus inhibiting post-translational processing of ras precursors resulting in decreased ras function both in colonic mucosa as well as in colon tumors. These results correlate with increased incidence and multiplicity of grossly visibly colon tumors in carcinogen-treated animals fed a high corn oil diet versus decreased incidence and multiplicity of colon tumors in their counterparts fed the high fish oil diet. This dietary inhibition of FPTase may have a practical chemopreventive potential.

Coronary artery bypass grafting without cardiopulmonary bypass

Coronary artery bypass surgery on a beating heart is now an accepted modality to treat selected patients of ischaemic heart disease. From June '92 through Sep '97, 162 patients underwent this procedure. There was no mortality and none of the patients had any respiratory or neurological morbidity, though 24% of the patients form a high risk group for conventional coronary bypass surgery. It is definitely cost effective in comparison to any other modalities for treatment of ischaemic heart disease. We conclude that continous use of this technique is justified and all cardiac surgeons should have exposure to this procedure.

Endemic cholera in Delhi, 1995: analysis of data from a sentinel centre

Data on cholera cases admitted to the Delhi Infectious Diseases Hospital (IDH) are presented to describe the pattern of occurrence of cholera in Delhi in 1995. Rectal swabs from 4082 cases of acute diarrhoea admitted to the IDH were examined for excretion of Vibrio cholerae. Of them, 2004(49%) and 4(0.1%) were positive for V. cholerae O1 biotype El Tor and V. cholerae O139 respectively. Most cholera cases occurred during May-September (summer and monsoon months). The period from January to March (winter) was completely free from cholera. The urban areas were not affected uniformly. Of the 80 PIN (Postal Index Number) code areas, 10 contributed to 57% of the cases. The early cases were scattered in PIN code areas distant from one another. The hospitalisation rates for cholera were the highest in children aged less than five years and declined significantly with increasing patients' age. Males had significantly higher rates than females aged up to 20 years, whereas the situation was reversed in the 20 to 39 year age group. Four per cent of the affected families had multiple cases. An estimated 1% of the household contacts of hospitalised cases of cholera were themselves hospitalised for cholera within 2 days of the first admission. Of the 260 V. cholerae O1 isolates tested, 4%, 7%, 8%, 89%, 91% and 95% were resistant to tetracycline, nalidixic acid, chloramphenicol, co-trimoxazole, streptomycin, and furazolidone respectively. The study highlights the usefulness of surveillance data to identify groups, urban areas and seasons with increased risk for cholera and to allow control measures to be focussed on those in greatest need.

Ribosomes mask cytochrome b5 on rough microsomal vesicles

Cytochrome b5 is unmasked on the removal of ribosomes by chemical degranulation of rat liver microsomes. Reattachment of ribosomes to stripped membranes remasks this enzyme on the membrane surface. This haemoprotein may be involved either in the attachment of ribosomes to reticular membranes or in protein biosynthesis by membrane-bound ribosomes.

Effects of Momordica charantia fruit juice on islet morphology in the pancreas of the streptozotocin-diabetic rat

An investigation was made of the effect of Momordica charantia fruit juice on the distribution and number of alpha, beta and delta cells in the pancreas of streptozotocin (STZ)-induced diabetic rats using immunohistochemical methods. The results indicated that there was a significant (Student's t-test, P < 0.004) increase in the number of beta cells in M. charantia-treated animals when compared with untreated diabetics, however, their number was still significantly less than that obtained for normal rats. There was also a significant (P < 0.006) increase in the number of delta cells in STZ-diabetic rats compared to non-diabetic rats. This increase in the number of delta cells was not affected by M. charantia treatment. The number of alpha cells did not change significantly in M. charantia-treated rats when compared with untreated diabetic rats. Our results suggest that oral feeding of M. charantia fruit juice may have a role in the renewal of beta cells in STZ-diabetic rats or alternately may permit the recovery of partially destroyed beta cells.

The role of polar interactions in the molecular recognition of CD40L with its receptor CD40

CD40 Ligand (CD40L) is transiently expressed on the surface of T-cells and binds to CD40, which is expressed on the surface of B-cells. This binding event leads to the differentiation, proliferation, and isotype switching of the B-cells. The physiological importance of CD40L has been demonstrated by the fact that expression of defective CD40L protein causes an immunodeficiency state characterized by high IgM and low IgG serum levels, indicating faulty T-cell dependent B-cell activation. To understand the structural basis for CD40L/CD40 association, we have used a combination of molecular modeling, mutagenesis, and X-ray crystallography. The structure of the extracellular region of CD40L was determined by protein crystallography, while the CD40 receptor was built using homology modeling based upon a novel alignment of the TNF receptor superfamily, and using the X-ray structure of the TNF receptor as a template. The model shows that the interface of the complex is composed of charged residues, with CD40L presenting basic side chains (K143, R203, R207), and CD40 presenting acidic side chains (D84, E114, E117). These residues were studied experimentally through site-directed mutagenesis, and also theoretically using electrostatic calculations with the program Delphi. The mutagenesis data explored the role of the charged residues in both CD40L and CD40 by switching to Ala (K143A, R203A, R207A of CD40L, and E74A, D84A, E114A, E117A of CD40), charge reversal (K143E, R203E, R207E of CD40L, and D84R, E114R, E117R of CD40), mutation to a polar residue (K143N, R207N, R207Q of CD40L, and D84N, E117N of CD40), and for the basic side chains in CD40L, isosteric substitution to a hydrophobic side chain (R203M, R207M). All the charge-reversal mutants and the majority of the Met and Ala substitutions led to loss of binding, suggesting that charged interactions stabilize the complex. This was supported by the Delphi calculations which confirmed that the CD40/CD40L residue pairs E74-R203, D84-R207, and E117-R207 had a net stabilizing effect on the complex. However, the substitution of hydrophilic side chains at several of the positions was tolerated, which suggests that although charged interactions stabilize the complex, charge per se is not crucial at all positions. Finally, we compared the electrostatic surface of TNF/TNFR with CD40L/CD40 and have identified a set of polar interactions surrounded by a wall of hydrophobic residues that appear to be similar but inverted between the two complexes.

Assay of carcinogenicity of tobacco metabolites employing microsomal degranulation technique

Carcinogenicity of salivarty extracts of different types of tobaccos smoked and chewed in India and Pan Parag were tested using microsomal degranulation technique. Results obtained on the basis of RNA/protein ratios (Indices to confirm the detachment of ribosomes from microsomes) showed that tobaccos used for cigarette, bidi, hukah and chewing tobacco with lime as well as Pan Parag were positively carcinogenic. Two fractions out of 7 isolated chromatographically from salivary extract of chewing tobacco plus lime were found to be carcinogenic. Elemental and spectral analyses indicated that the fractions are possibly an aromatic compound with an aliphatic side chain and N-(buty1 nitrosamine)-1-(3-pyridyl)-4-hydroxy-1-butanone.

Age-related changes in morphology and secretory responses of male rat lacrimal gland

This study investigates the differences in the outward appearance and morphology of lacrimal glands, the morphology within the lacrimal acinar cells and the secretion of protein from acinar cells of young (3-5 months) and aged (20 and 24 months) male rats. The appearance of the glands, as seen by the naked eye, differed between the three age-groups. The lacrimal gland of young animals was a smooth pink tissue, while the tissue from aged animals appeared lobular and white in colour, thought to result from infiltration of fatty/connective tissue. Glands from 24 month old animals had a more pronounced lobular appearance than the glands from 20 month old animals. Light microscopy studies revealed that as the animals aged there was evidence of progressive morphological changes. These changes included thickening of the connective tissue sheath, chronic inflammation with increased infiltration by mast cells, patchy destruction of ductal and vascular tissues, enlargement of lacrimal ducts, luminal swelling of the acini, and changes in acinar type. Electron microscopy (EM) studies revealed the presence of 3 types of acini in the rat lacrimal gland: acini which contained only protein secretory granules (serous acini), acini which contained protein and mucous secretory granules (seromucous acini), and acini which contained only mucous secretory granules (mucous acini). In young glands the majority of acini were serous with a few seromucous acini and even fewer mucous acini. In aged glands there were significant reductions in serous acini (ANOVA; P < 0.01) when compared to the young glands. In 20-month-old glands, there were marked increases in the percentage occurrence of seromucous acini, while in 24 month old glands, there were large increases in the relative number of mucous acini. Qualitative EM studies demonstrated that the typical acini from young glands contained numerous protein secretory granules. Ageing was associated with a progressive loss of protein (serous) secretory granules. Furthermore, marked changes and patchy destruction of the endoplasmic reticulum and Golgi apparatus were observed in acini of glands from aged rats when compared to acini of glands from young rats. Measurement of total protein output from acini revealed a significant (Student's t-test, P < 0.05) decrease in protein secretion from aged glands compared to glands from young animals. These results suggest that not only is there considerable structural damage, chronic inflammation and mast cell infiltration to the lacrimal gland with ageing, but also possible redifferentiation of acini from serous to seromucous and then to mucous acini. Furthermore, the results also suggest a reduction or an inability of the acini to synthesise and to secrete protein from glands of aged animals compared to glands of young rats. All of these changes appear to occur more rapidly as the rats mature between 20 and 24 months. These findings provide a morphological basis to explain the phenomenon of reduced tear/protein secretion with ageing.

Biliary stenting is more effective than sphincterotomy in the resolution of biliary leaks

BACKGROUND

Biliary fistulae may occur following surgical injury, abdominal trauma, or inadequate closure of a cystic duct stump. These leaks are most often managed by drainage of the associate biloma and either endoscopic sphincterotomy or placement of a biliary endoprosthesis to decrease the pressure gradient between the bile duct and the duodenum created by the muscular contraction of the ampullary sphincter. In a previous study, we demonstrated a statistically significant reduction in ductal pressures following stent placement as compared to sphincterotomy. The goal of this present study was to determine if reduction in ductal pressures correlates clinically with the resolution of biliary leaks in an animal model.

METHODS

Fourteen mongrel dogs underwent laparotomy, cholecystectomy without closure of the cystic stump, and a lateral duodenotomy to identify the major papilla. The dogs were then randomized into three groups. Group I (n = 5) was a control group undergoing closure of the duodenotomy only. Group II (n = 4) underwent sphincterotomy. Group III (n = 5) underwent placement of a 7 Fr x 5 cm biliary endoprosthesis prior to duodenotomy closure. A drain was placed adjacent to the cystic duct stump in all groups. Drain output was recorded daily. The biliary leak was considered resolved when the output was < 10 cc/day. Regardless of suspected fistula closure, the drains were not removed until 2 weeks postprocedure. Necropsy was performed to identify undrained intraperitoneal bile. Statistical analysis was performed using Student's paired t test.

RESULTS

All dogs had bile leaks identified on postoperative day 1. The number of days required for resolution of bile leak in group I (mean +/- SEM) was 7.60 +/- 0.87 days, as compared to 6.75 +/- 0.80 days for group II and 2.60 +/- 0.24 days for group III. There was no significant difference in the duration of bile leak between groups I and II (p = 0.445). Group III, however, had a significant reduction in the duration of biliary fistulae as compared to both groups I and II (p < 0.005). At autopsy, persistent bilomas were identified in 80% of group I, 25% of group II, and 0% of group III. None of the dogs showed evidence of dehisence of the duodenotomy closure site as a source of bile leak.

CONCLUSION

Biliary stenting significantly reduces the time to resolution of cystic duct leaks as compared to sphincterotomy in a canine model. The results obtained in this study support the use of biliary endoprostheses in the management of biliary leaks and fistulae.

Synergistic effect of iontophoresis and a series of fatty acids on LHRH permeability through porcine skin

The effect of chemical penetration enhancers (e.g., fatty acids) in combination with iontophoresis was examined on the in vitro permeability of luteinizing hormone releasing hormone (LHRH) through porcine skin. Porcine epidermis was pretreated with either ethanol (EtOH) or 10% fatty acid/EtOH. The permeability coefficient of LHRH was significantly (p < 0.05) greater through EtOH, lauric acid/EtOH, palmitic acid/EtOH, oleic acid/EtOH, linoleic acid/EtOH, and linolenic acid/EtOH treated epidermis than the control (untreated epidermis). Iontophoresis further enhanced the permeability of LHRH (p < 0.05) through enhancer-pretreated epidermis in comparison with corresponding passive permeability. Among saturated fatty acids tested, 10% palmitic acid/iontophoresis showed the highest permeability coefficient [(59.52 +/- 2.40) x 10(-4) cm/h], which was approximately 16-fold higher than that of the control [(3.57 +/- 0.41) x 10(-4) cm/h]. Unsaturated cis-octadecenoic acids were more effective penetration enhancers when compared with octadecanoic acid. Among cis-octadecenoic acids in combination with EtOH, the greater iontophoretic permeability coefficient [(59.18 +/- 12.43) x 10(-4) cm/h] was obtained through linolenic acid treated epidermis, which was significantly greater (p < 0.05) than through saturated octadecanoic acid treated epidermis [(29.08 +/- 3.18) x 10(-4) cm/h]. Also, pretreatment of epidermis with 5% linolenic acid/propylene glycol (PG) resulted in greater (p < 0.05) iontophoretic flux of LHRH in comparison to 5% linolenic acid/EtOH. Furthermore, increases in the degree of unsaturation in octadecenoic acids did not produce corresponding increases in the degree of enhancement. Reversibility studies revealed that the postrecovery passive flux of LHRH through 5% linolenic acid in combination with EtOH or PG/iontophoresis treated epidermis was significantly (p < 0.05) reduced than the prerecovery value but could not completely recover to the baseline flux (i.e., flux of LHRH through untreated epidermis).

Sensitivity of poliomyelitis surveillance in India

OBJECTIVE

To estimate the sensitivity of poliomyelitis surveillance in India.

DESIGN

A comparison of two sets of data obtained from lameness surveys and routine surveillance system.

METHODS

Lameness surveys were undertaken by the Ministry of Health and Family Welfare in 1981, 1989 and 1992 using 30-cluster sampling technique. These data were compared with the number of polio cases reported through routine surveillance system.

RESULTS

Based on the 1981 survey which was undertaken near the initiation of routine immunization with oral polio vaccine (OPV) in India, poliomyelitis incidence was estimated at 25 cases per 100,000 population. Subsequent studies in 1989 and 1992 estimated a decrease in incidence rates to 15.7 and 6.3 cases per 100,000 population, respectively. Comparing the number of reported cases with the survey estimates provided a measure of the sensitivity of (completeness of reporting) surveillance; the sensitivity increased from 8% in 1981, to 20% in 1989, to 32% in 1992.

CONCLUSION

The results are encouraging when compared with the global estimates of 10% reporting in 1993. Nevertheless, there is a need for further improvement in the completeness of reporting of poliomyelitis cases to detect all the cases of acute flaccid paralysis to allow epidemiological investigations and effective follow-up action which is critical to interrupt wild virus transmission.

Carotid artery dissection presenting as a painless Horner's syndrome in a pilot: fit to fly?

We describe a case of a middle-aged Caucasian pilot who presented to us with a painless left Horner's syndrome due to a focal dissection of the infra-petrous portion of the ipsilateral internal carotid artery. He did not suffer symptoms of cerebral ischemia at the time of onset, or during the following 2 yr. The Horner's syndrome persisted unchanged throughout follow-up. Serial magnetic resonance angiograms showed some regression of the focal stenosis at 12 mo, with no further change over the next 10 mo. The literature suggests that the risk of stroke after onset of dissection is usually in the first month, and the risk of recurrence of dissection is about 1% per year after the first year. Our patient was prescribed aspirin 300 mg.d-1, and certified to fly as or with a co-pilot commencing 1 yr after onset of his symptoms.

Wegener's granulomatosis in a patient with apparent drug-induced acute interstitial nephritis

We describe a patient whose clinical presentation was suggestive of drug-induced acute interstitial nephritis (AIN). A renal biopsy and serologic testing led instead to the diagnosis of Wegener's granulomatosis (WG) with necrotizing crescentic glomerulonephritis. Treatment with corticosteroids and cyclophosphamide resulted initially in complete recovery of renal function, and an exacerbation of acute renal failure after doses of these agents had been tapered responded to resumption of the original regimen. We report this case to emphasize the potentially identical presentations of AIN and WG. Since the two conditions are treated differently, we suggest that the diagnosis of AIN should be accepted only after biopsy confirmation.

Effects of islet hormones on nerve-mediated and acetylcholine-evoked secretory responses in the isolated pancreas of normal and diabetic rats

This study employs the pancreas of normal and diabetic rats to investigate the relationship between the endocrine and exocrine pancreas in the control of exocrine secretion employing enzyme and immunohistochemical and physiological techniques. Acetylcholine esterase (ACh-E) positive nerves were distributed in the interacinar regions of the pancreas lying close to the exocrine cells. There was no difference between the cholinergic innervation of the pancreas in normal and diabetic rat. Insulin (INS) immunopositive cells were observed in the peripheral and central portions of the Islet of Langerhans in the pancreas of normal rat. In the diabetic animals the number of INS-positive cells were decreased. In contrast, glucagon (GLU) and somatostatin (SOM)-immunopositive cells were identified mainly in the peripheral parts of the Islets of Langerhans and their numbers increased markedly in the diabetic pancreas. Insulin alone had no significant effect on amylase secretion in the normal pancreas whereas GLU and SOM evoked small increases in amylase out compared to basal. In contrast, the islet hormones have no detectable secretory effect on the diabetic pancreas compared to control. Both electrical field stimulation (EFS) of intrinsic secretomotor nerves and exogenous application of acetylcholine (ACh) resulted in marked increases in amylase secretion. In pancreatic acini and acinar cells ACh evoked dose-dependent increases in amylase release. In normal pancreatic segments a combination of either INS or GLU with EFS or ACh resulted in marked potentiation of amylase output. In contrast, SOM inhibited the EFS-evoked amylase output but enhanced the secretory response to ACh. In pancreatic acini and acinar cells from normal rat and in pancreatic segments from diabetic rats, the islet hormones had no potentiating effect on the ACh-evoked secretory response. Similarly, in the diabetic rat the islet hormone had no effect on EFS-evoked amylase output. In fura-2 loaded pancreatic acinar cells ACh-induced a marked increase in intracellular free calcium concentration [Ca2+]i compared to basal. Either INS or GLU, but not SOM, elicited a small increase in [Ca2+]i. Combining either INS or GLU with ACh resulted in a potentiation of [Ca2+]i compared with ACh alone. In contrast, SOM had no significant effect on the ACh-induced [Ca2+]i compared to the response obtained with ACh alone. In pancreatic acinar cells of diabetic rat ACh-elicited similar magnitude of [Ca2+]i compared to acinar cells of normal rat. However, when the islet hormones were combined with ACh there was no enhancement of [Ca2+]i compared to ACh alone. The results indicate that the potentiation of either EFS or ACh-evoked secretory responses by the islet hormones seem to occur only in pancreatic segments which have intact viable Islets of Langerhans and not in either acini and acinar cells or from the pancreas of diabetic rat. Moreover, it is apparent that cellular Ca2+ is involved with the interaction of ACh with either INS or GLU.