CURRENT TRENDS IN PRESCRIBING PATTERN OF ANTI-MIGRAINE DRUGS IN PATIENTS OF MIGRAINE AT A TERTIARY CARE TEACHING HOSPITAL

Background. An inappropriate prescribing pattern of antimigraine drugs by doctors may often encourage inappropriate self-medication by patients because of the asymmetry of medical information. Objective. The study is aimed to assess the current trends in prescribing patterns of anti-migraine drugs, rationality of prescription, and pattern of migraine severity in patients of migraine. Methods. A cross sectional study was conducted at a tertiary care teaching hospital. All the prescribing details including patient’s demographic details, diagnosis, details of drug therapy (drug name, dose, duration, and frequency) were recorded. Rationality of prescription was assessed using the WHO core drug prescribing indicators and the pattern of severity of migraine was assessed using MIDAS scoring system. Results. Out of 85 patients, 71 were female (83.5%), mostly around 21-30 years of age, and 27 (31.7%) patients had other comorbidities. Naproxen was the most commonly used NSAID for termination of acute migraine attack (15.3 %). The most common drugs prescribed for prophylaxis included beta adrenergic blockers (Propranolol, 14.66%), antidepressants (Amitriptyline, 9.33% and Fluoxetine 3.33%), and antipsychotics (Prochlorperazine, 4.66%). Domperidone (17.30%) was the most commonly prescribed antiemetic. Prescription of triptans was low (2.66%) with Rizatriptan as the most commonly prescribed triptan. Conclusions. The current study revealed that further improvements are required in prescribing practices especially in average number of drugs per prescription, prescription of drugs with generic names, and prescription of drugs of the essential drugs list.

942 Outcome of Image Guided Intra-Articular Thumb Base Steroid Injections-Retrospective Study of Consecutive Patient Over 4 Years in A Plastic and Hand Surgery Unit in West Lothian, Scotland

Introduction

Osteoarthritis of the thumb base is a common condition. Usually effects the elderly population causing significant disability. Modalities of treatment of osteoarthritis which includes conservative measures, non-operative interventions, and surgery.

In this study we endeavored to assess how effective are image guided steroid injections for base of thumb Osteoarthritis as assessed by subjective pain relief perceived by patient and what percentage of these patients proceed to operative treatment.

Method

Retrospective data between January 2015 and December 2018 of the patients who underwent Steroid injections to the Base of thumb joints (CMCJ and/or STTJ) for Osteoarthritis under image intensifier guidance was collected from Hospital management system –TRAK and eHealth services. Follow up of the patients were done for Maximum 1 to 5 years.

Results

A total number of 692 patients with thumb base osteoarthritis were included in the study of which 546 patients underwent Image guided steroid injection to the thumb base. The mean Age of patients was 64.5 years and the Female: Male ratio was 401:145. Mean number of injections each patient received- 3.25 (1 – 7 times). Pain relief after first, second and third injections were 3.15 months, 2.63 and 1.75 months, respectively. 127 (23.2% of injections patients) underwent trapeziectomy. Mean time between first injection & Surgery was 1.3yrs (6 months -2 years)

Conclusions

This study demonstrates the effectiveness of image guided steroid injections for thumb base osteoarthritis. Though about a quarter of these patients proceed to operative management, steroid injections can delay the same considerably.

Gap Analysis in Workforce and Infrastructure in the Subcenters for Upgradation to Health and Wellness Center in a Community Development Block of Purba Bardhaman District, West Bengal

Context:

The government of India has recently decided to upgrade subcenters (SCs) to health and wellness centers (HWCs) for providing comprehensive quality services.

Aims:

The present study was undertaken to determine workforce- and infrastructure-wise gaps in the SCs for upgradation to HWCs and assess knowledge of the auxiliary nurse midwives (ANMs) regarding services to be delivered through HWCs.

Settings and Design:

This cross-sectional study was conducted in Bhatar block of Purba Bardhaman district between August and October 2019.

Subjects and Methods:

Workforce and infrastructure availability was assessed using a checklist in 38 SCs and knowledge was assessed using a questionnaire among ANMs.

Statistical Analysis Used:

Data entry and analysis was done in Microsoft™ Excel™.

Results:

No Subcentre had Community Health Officer and 23.7% of Subcentre were without second ANM. 28.9% of the ANMs had adequate knowledge about services to be delivered through HWCs. Infrastructurally, lack of staff residential facility (76.3%), water supply (34.2%), and inadequate civil construction (34.2%) were major barriers.

Conclusions:

Adequate recruitment of HCWs, infrastructure upliftment, and proper training of HCWs in the SCs are the need of the hour.

Acceleration of cutaneous wound healing by Lucilia sericata maggots in diabetic Wistar rats

The study was aimed to evaluate the effectiveness of maggot therapy in healing of cutaneous infected wound in streptozotocin (STZ) induced diabetic Wistar rat. For live maggots, the sterilized eggs of Lucilia sericata were obtained from colonies established in laboratory. Diabetes model was established in 48 male Wister rat by intra-peritoneal injection of STZ at the dose of 60 mg/kg body-weight. Cutaneous wounds exposed with mixed colonies of bacteria like Staphylococcus aureus, E. coli and Pseudomonas aeruginosa were prepared in all rat. The animals equally divided in 4 groups with 12 rats each being presented as treatment group of control, antibiotic, maggot and maggot with antibiotic in combination. All treatments were done once and hold for 24 hours. Wound kinetics and bacterial bio burden were measured at weekly interval to till complete healing. Significant reduction in wound area with maximum contraction was found (>95%) in maggot treated group when compared to antibiotic treated (79%) and control (72%). In maggot as well as maggot and antibiotic in combination group showed early elimination of bacterial bio-burden 7.88±0.03log CFU/ml to 1.12±0.65log CFU/ml and 7.86±0.04) log CFU/ml to 1.54±0.52log CFU/ml respectively in three weeks of time. Early healing indication was also experienced on histomorphological examination of wounded tissue of maggot treated groups by early and better epithelialization, collagenation and neovascularization with complete healing of wound in three weeks in comparison to antibiotic and control respectively. However, the present study did not show any difference in healing of wound with use of maggot alone or in antibiotic combination. Live maggot of Lucilia sericata effectively lower bacterial bioburden and and accelerate healing of infected cutaneous wound in diabetic conditions.

Variant morphology and arterial supply of diaphragmatic crura with probe patent foramen ovale

Crura are the posterior pillars of the tendino-muscular partition between thoracic and abdominal cavity. This study highlights bilaterally an unfamiliar morphology of diaphragmatic crura with uncommon origin of inferior phrenic artery and accompanying atrial septal defect in a 63-years-old female cadaver with scoliosis. An attempt is made to portray the clinical implications of these variations. In addition authors have discussed the embryological and genetic basis of these variations. In the recent few decades, surgical correction of scoliosis involving intervention with the crura has gained pace. Knowledge about the normal as well as variant crural morphology is imperative for the surgeons to decide the correct approach during spinal corrective surgeries and for radiologist to prevent any diagnostic pitfall. Familiarity about the variant origin of inferior phrenic artery may prevent complications during treatment of pathological conditions related to inferior phrenic artery. Preoperative awareness about the coexisting atrial septal defect is vital for anesthesiologists promoting them to administer cardioprotective anesthetic drugs. To the best of our knowledge, description of such a combination of variations in anatomical literature is rare and scarcely reported. Awareness of these anatomical variations is relevant for operating surgeons, radiologists, anesthesiologists and anatomists.

Therapeutic use of Lucilia sericata maggot in controlling bacterial bio-burden in Rat wound model

Delayed wound healing due to extraneous bacterial contamination, antibacterial resistance and other associated factors are of great concern in dealing patients having chronically infected wound. Medicinal properties of certain maggots of Calliphoridae family are known for its effective wound debridement therapy. The objective of the study was to evaluate the wound healing potential of maggots of Lucilia sericata in an experimentally infected cutaneous wound model in Wistar rat. The study was carried out by using male Wistar rats (n=48) by creating excisional wounds and later contaminated with mixed population of gram positive and gram-negative bacteria. Animals were divided randomly in to four groups with 12 individuals each, being denominated as control, antibiotic treated, maggot treated, and antibiotic plus maggot combination treated group. Ten pre-sterilized maggots were applied per centimetre square wound bed for 24 hours. Different wound kinetics in L. sericata maggot treated wounds revealed significant reduction in wound area with maximum contraction, early elimination of bacterial bioburden as compared to group of infected control and group of rats receiving only antibiotic treatment. The histopathological examination of wounded tissue of maggot treated groups showed early and better epithelialization, collagenation and neovascularization with complete healing of wound in two weeks. The maggot effects on healing when used singly or in combination with antibiotic were recorded to be similar. The results of the present study clearly demonstrate that the maggots of L. sericata possesses a definite antibacterial action along with removal of dead tissues and effectively reduced the bacterial bio-burden in infected wound and induced wound healing quickly.

Evidence for magnetic Weyl fermions in a correlated metal

Weyl fermions have been observed as three-dimensional, gapless topological excitations in weakly correlated, inversion-symmetry-breaking semimetals. However, their realization in spontaneously time-reversal-symmetry-breaking phases of strongly correlated materials has so far remained hypothetical. Here, we report experimental evidence for magnetic Weyl fermions in Mn₃Sn, a non-collinear antiferromagnet that exhibits a large anomalous Hall effect, even at room temperature. Detailed comparison between angle-resolved photoemission spectroscopy (ARPES) measurements and density functional theory (DFT) calculations reveals significant bandwidth renormalization and damping effects due to the strong correlation among Mn 3d electrons. Magnetotransport measurements provide strong evidence for the chiral anomaly of Weyl fermions-namely, the emergence of positive magnetoconductance only in the presence of parallel electric and magnetic fields. Since weak magnetic fields (approximately 10 mT) are adequate to control the distribution of Weyl points and the large fictitious fields (equivalent to approximately a few hundred T) produced by them in momentum space, our discovery lays the foundation for a new field of science and technology involving the magnetic Weyl excitations of strongly correlated electron systems such as Mn₃Sn.

Infections in infancy and the presence of antinuclear antibodies in adult life

There has been limited success defining environmental factors important to the development of connective tissue diseases such as systemic lupus erythematosus (SLE). Recent work has suggested that the perinatal environment may be important. To investigate this we measured antinuclear antibodies (ANA) in a general population with well-defined early lives to see whether fetal and infant growth and infections were associated with ANA positivity in adult life. Included in our investigation were 1334 individuals (668 men, 666 women) from the Hertfordshire cohort study. ANA was measured using an ANA ELISA and confirmed using immunofluorescence. We investigated associations between the presence of ANA and early growth and infectious exposure in infancy in men and women combined, but with adjustment for gender throughout. A positive ANA was present in 73 (10.9%) of men and 81 (12.2%) women. Of these, 26 women and 14 men were positive using IF on HEP2 cells. Sharing a bedroom during childhood was associated with a higher risk of being ANA positive (odds ratio (OR), 1.42, 95% confidence interval (CI) 1.00-2.01, P = 0.05). A record of diarrhoeal illness (OR 2.12 95% CI 1.07, 4.23, P = 0.03) and rubella or mumps during the first year of life (OR 16.12, 95% CI 2.92, 88.94, P = 0.001) was also significantly associated with ANA in adult life. Higher ANA titres by Inova ELISA were associated with infections in the first year of life from mumps (2.74-fold higher, 95% CI 0.98, 7.64, P = 0.05) and rubella (3.90-fold higher, 95% CI 1.89, 8.04, P < 0.001). In addition, higher ANA titres were also associated with mumps (1.26-fold higher, 95% CI 1.02, 1.56, P = 0.03) between one and five years of age. Our results suggest that a developing immune system exposed to increased infection is more likely to produce ANA in adult life and perhaps begin the pathological process that leads to SLE.

Parametric Study of Electrospun Cellulose Acetate in Relation to Fibre Diameter

The objective was to identify the main factors and interactions influencing the fibre diameter in the production of electrospun cellulose acetate (CA) webs. A systematic parameter study was completed for producing electrospun CA fibres that were substantially free of bead defects and the effect of different process parameters during electrospinning CA were evaluated in respect of mean fibre diameter. The experiments were planned using factorial designs. Altogether three parameters, each at three levels, were selected for this study. The results indicate that polymer concentration, voltage and flow rate interact so that the magnitude of any change in the mean fibre diameter is dependent upon the level of the other factors. Furthermore, stable electrospinning conditions for CA were confirmed using an acetone: N, N-dimethylacetamide (DMAc) (2:1) solvent system that minimised the presence of structural defects in the web and promoted uniform fibre diameters.

Incidence of Haemoproteus columbae in pigeons of Jammu district

Haemoproteus columbae is the major protozoan infection reported in pigeon and appeared in the erythrocyte of the peripheral circulation. Incidence and parasitaemia of H. columbae in pigeon was studied in different localities of Jammu, India for a period from April to September 2010 using thin blood smear examination. Of the 150 pigeons (wild: 70, domestic: 80), 92 (61.33 %) were found to be infected with H. columbae. Domestic pigeon showed higher incidence rate (74.28 %) than the wild (50 %). Mature and immature gametocyte encircled the erythrocyte nucleus to form a halter shaped appearance were characteristic feature of the parasite. Pseudolynchia canariensis, the vector for H. columbae was also recovered from beneath the feathers of pigeons. No other haemoprotozoan parasite was observed in the blood smear of examined pigeon. Counting of infected erythrocyte revealed higher affection of 1-2 erythrocytes indicative of milder infection in the birds. A long term study within bird population is essential in order to disclose seasonal variation in parasite, vector density and age of infection such as nesting area.

Lung cancer statistics in Luxembourg from 1981 to 2008

Lung cancer is the leading cause of cancer-related death in the world and in Luxembourg. As a part of "The health science initiative focused on personalized medicine", Luxembourg aims to participate by developing diagnostics to improve the detection and treatment of lung cancer. In line with this objective, this study made a review of evolution of lung cancer in Luxembourg from 1981 to 2008 and compared this statistics to the situation in the Nordic countries, Europe in general and the World. Incidence data of the national morphological tumour registry and mortality data of the service of statistics of the national ministry of health is depicted in charts with trend lines, in the framework of a statistical evaluation of relevant parameters. The data indicate that while male lung cancer incidence decreased in Luxembourg, the incidence in women and its mortality have doubled over the 28-year span considered. Notwithstanding this increase, the female lung cancer incidence and mortality remain low compared to the Nordic countries and Europe. Interestingly, the study also potentially suggests that the lung cancer pattern follows the smoking pattern in incidence and mortality.

Structural and functional abnormalities in lungs in patients with achalasia

Dilatation and oesophageal body aperistalsis in achalasia can lead to stasis which in turn can induce repeated microaspiration. It is therefore conceivable that patients with achalasia may also have abnormalities in lungs secondary to repeated episodes of microaspiration. There is a lack of systematic study on involvement of lungs in patients with achalasia. Thirty patients with achalasia underwent pulmonary function tests (spirometry, and carbon mono-oxide diffusion capacity) and high resolution computerized tomography (HRCT) of the chest. The mean age of patients and mean duration of disease were 33.5 +/- 10.9 years and 28.1 +/- 27.3 months respectively. Regurgitation was present in 22 (73.3%) of them. Respiratory symptoms in them were dry cough in 17 (56.6%), and chest pain in 18 (60%). The oesophagus was dilated in 26 (86.6%) and 13 (43.3%) had residue in oesophagus. Sixteen (53.3%) patients had either anatomical changes as seen on HRCT or functional changes as observed on pulmonary function tests. Of those with functional abnormalities, five (16.6%) and one (3.3%) had restrictive and obstructive airways disease respectively. While evidence of tracheo-bronchial compression by dilated oesophagus was present in eight (26.6%), 10 (33.3%) patients had parenchymal lung disease [nodular opacities in five (16.6%), ground glass appearance six (20%), patchy pulmonary fibrosis five (16.6%), air trapping two (6.6%), consolidation and bronchiectasis one (3.3%) each]. There was a significant association between presence of regurgitation and dilatation of oesophagus (P = 0.032). More than half (53.3%) of patients with achalasia have structural and/or functional abnormalities in lungs.

Klebsiella meningitis. A case report

Acute bacterial meningitis is a severe CNS infection occurring mostly in infants and older children. Bacterial meningitis caused by gram-negative bacteria is usually fatal. Klebsiella pneumoniae is an uncommon gram-negative bacteria causing meningitis with a poor outcome. Though the commonest presentation of bacterial meningitis is fever, patients usually seek medical attention for uncontrolled seizure and features of raised ICP. The commonest complications of gram-negative bacterial meningitis including Klebsiella meningitis are subdural hygroma / empyema, hydrocephalus, infarcts (both arterial and venous) and cortical blindness due to hypoxic ischaemic insult. MRI is the best modality for evaluating these patients for early diagnosis. Early institution of treatment significantly reduces the mortality and morbidity. We describe a case of acute bacterial meningitis caused by Klebsiella pneumoniae with MR evidence of sinus thrombosis, venous infarcts and subdural hygroma.

Chronic Tuberculous Retropharyngeal Abscess Due to Vertebral Tuberculosis with Associated Calvarial Tuberculosis

The occurrence of chronic tuberculous retropharyngeal abscess and calvarial tuberculosis is rare, even in isolated form. Chronic tuberculous retropharyngeal abscess is usually due to vertebral tuberculosis in adults. Calvarial tuberculosis is a rare manifestation of extra-pulmonary tuberculosis with limited reports in medical literature. We describe a rare case of chronic tuberculous retropharyngeal abscess due to vertebral tuberculosis with associated calvarial tuberculosis.

The autoantibody rheumatoid factor may be an independent risk factor for ischaemic heart disease in men

BACKGROUND

Subjects with rheumatoid arthritis have an increased prevalence of ischaemic heart disease (IHD). This is most likely in those people with the autoantibody rheumatoid factor (RF). RF is strongly associated with rheumatoid arthritis (RA) but is also present in up to 15% of all adults.

OBJECTIVE

To determine whether RF might identify people in a general population who also share an increased likelihood of developing IHD.

METHODS

Subjects from the Hertfordshire Cohort Study were investigated for the presence of RF. Subjects completed a questionnaire and attended a clinic where a history of IHD was recorded (ECG, coronary artery bypass grafting, Rose chest pain). Associations between the presence of RF, antinuclear antibodies (ANA), anticardiolipin antibodies (ACA) and IHD in 567 men and 589 women were investigated and compared with traditional risk factors for IHD.

RESULTS

RF was associated with an increased likelihood of IHD in men (odds ratio (OR) = 3.1, 95% CI 1.7 to 5.4, p<0.001). This increased risk could not be explained by traditional risk factors for IHD (mutually adjusted OR for RF 2.9 (95% CI 1.6 to 5.3), p<0.001). There was no significant association between RF in women or between ANA or ACA with IHD in men or women.

CONCLUSION

This work suggests that RF is an independent risk factor for IHD in the general population. It lends support to the importance of inflammation in atherosclerosis and suggests that autoimmune processes may be involved. In addition, it raises the intriguing possibility that RF may have a direct role in the pathogenesis of IHD in some subjects.

Pyomyositis: a diagnostic problem

A case of a 45-year-old lady presenting with symptoms suggestive of pancreatitis is described. Initially the findings on Imaging were ambiguous while the enzyme studies were against the diagnosis of pancreatitis. Recurrence of symptoms and with Increased intensity prompted repeated imaging and further investigations. Finally, by a combination of CT scan, MR imaging and muscle biopsy the rare diagnosis of pyomyositis was established. The fact that this case was difficult to diagnose because of its rarity and its mimicking pencreatitis is discussed.

Growth and infectious exposure during infancy and the risk of rheumatoid factor in adult life

BACKGROUND

The contribution of the environment to rheumatoid arthritis (RA) remains uncertain. Intrauterine and early postnatal life may be important. Rheumatoid factor (RF) found in around 10% of the normal population confers a risk of developing RA and may be present years before onset of clinical disease. The immune pathology leading to RA and RF may have similar genetic and environmental influences.

OBJECTIVE

To measure RF in people for whom data on birth weight, infant growth, and markers of infectious exposure during infancy and childhood, had been previously recorded.

METHODS

675 men and 668 women aged 59-67 years, born and still resident in Hertfordshire, UK, were studied. RF was measured with an ELISA. Associations between presence of RF, early growth, and markers of hygiene in infancy, were investigated.

RESULTS

RF was detected in 112/675 (16.6%) men and 79/668 (11.8%) women. No significant relationships existed between early growth and presence of RF in men or women. Among women, sharing a bedroom during childhood was associated with a lower risk of RF positivity (OR = 0.48, 95% CI 0.30 to 0.78, p = 0.003).

CONCLUSIONS

A developing immune system exposed to increased infectious exposure is less likely to produce RF in adult life; this may reduce the pathological process which leads to RA.

A case of disseminated hydatidosis

A young lady initially found to have hydatid cysts in the lung only, subsequently within a very short period was found to develop cysts in the liver. Soon after, she developed cysts in the subcutaneous tissue over the anterolateral chest wall, which, on investigation, revealed hepatic cysts herniating through the chest wall defects caused by previous operations. The unique features of this case include the degree of dissemination, the multiplicity of sites and the peculiar nature of herniation of the hepatic cysts into the parietes.

Mitotically active haemorrhagic cellular (apoplectic) leiomyoma

Apoplectic leiomyoma is a distinctive smooth muscle tumour usually occurring in women either taking oral contraceptives or who are pregnant or recently postpartum. Most of these tumours show 0-2 mitoses per 10 high power fields, but a mitotic index of up to 8 per 10 high power fields is allowed in such tumours. We describe an apoplectic leiomyoma with a number of atypical features including a high mitotic index (up to 20 per 10 high power fields) in a 47-year-old woman. Follow-up clinically and by computerised tomography (CT) for 3 years demonstrates no recurrence.

Heat shock inhibits radiation-induced activation of NF-kappaB via inhibition of I-kappaB kinase

Radiation stimulates signaling cascades that result in the activation of several transcription factors that are believed to play a central role in protective response(s) to ionizing radiation (IR). It is also well established that heat shock alters the regulation of signaling cascades and transcription factors and is a potent radiosensitizing agent. To explore the hypothesis that heat disrupts or alters the regulation of signaling factors activated by IR, the effect of heat shock on IR-induced activation of NF-kappaB was determined. Irradiated HeLa cells demonstrated transient increases in NF-kappaB DNA binding activity and NF-kappaB protein nuclear localization. In addition, irradiated cells demonstrated increased I-kappaB phosphorylation and decreased I-kappaBalpha cytoplasmic protein levels, corresponding temporally with the increase of NF-kappaB DNA binding. Heat shock prior to IR inhibited the increase in NF-kappaB DNA binding activity, nuclear localization of NF-kappaB, and the phosphorylation and subsequent degradation of I-kappaB. I-kappaB kinase (IKK) immunoprecipitation assays demonstrated an increase in IKK catalytic activity in response to IR that was inhibited by pretreatment with heat. Kinetic experiments determined that heat-induced inhibition of NF-kappaB activation in response to IR decayed within 5 h after heating. Furthermore, pretreatment with cycloheximide, to block de novo protein synthesis, did not alter heat shock inhibition of IR induction of NF-kappaB. These experiments demonstrate that heat shock transiently inhibits IR induction of NF-kappaB DNA binding activity by preventing IKK activation and suggests a mechanism independent of protein synthesis.

Intron sequences and the length of the downstream second exon affect the binding of hnRNP C proteins in an in vitro splicing reaction

The proteins that are in direct contact with the pre-mRNA in an in vitro splicing reaction were analyzed by UV cross-linking experiments. Six major proteins (120, 55, 44, 42, 39 and 38 KD) and three minor polypeptides (84, 72 and 63 KD) were detected. The predominant proteins 44, 42 KD belong to the class of hnRNP C proteins since they were immunoprecipitated by monoclonal antibodies directed against hnRNP C proteins. The cross-linked proteins were not detected in the absence of Mg2+, ATP or when RNA lacking introns were used as substrates in the splicing reactions. The effect of exon sequences on the binding efficiency for the photocrosslinked proteins was investigated. Transcripts containing a second exon of 24 nucleotides for the beta-globin or 107 nucleotides for the mouse insulin, yielded a reduced amount of cross-linked proteins when compared with "full length" pre-mRNAs. Sequences within the first exon of the beta-globin pre-mRNA did not affect the binding efficiency of these proteins. The reduced binding efficiency of the cross-linked proteins for the truncated beta-globin or mouse insulin pre-mRNAs correlated with the lower efficiency for in vitro splicing. Substitutions with unrelated sequences in the beta-globin second exon restore the binding of the cross-linked proteins indicating that the length of the second exon and not specific sequences are relevant for the binding efficiency of these proteins. The SP6/mouse insulin oligonucleotides cross-linked to the hnRNP C proteins were isolated and sequenced. A 17-mer was located in the second exon (134 nucleotides downstream from the 3' splice site) and a 14-mer in the intron region (25 nucleotides downstream the 5' splice site). The beta-globin oligonucleotides cross-linked to the hnRNP C proteins were a 13-mer in the second exon (28 nucleotides downstream the 3' splice site) and an 8-mer in the first exon (81 nucleotides downstream the 5' end of the pre-mRNA). Our results indicate that the hnRNP C proteins interact with those oligonucleotides located in different regions of the pre-mRNA. The binding efficiency of those proteins, however, depends on the length of the second exon and the presence of intron sequences (secondary and/or tertiary pre-mRNA structure).

The secondary structure of a messenger RNA precursor probed with psoralen is melted in an in vitro splicing reaction

The secondary structure of the SP6/mouse insulin precursor RNA was determined by psoralen cross-linking experiments. A series of long-range contacts occur within the left half of the pre-mRNA that contains the intervening sequence. Multiple secondary structures for the pre-mRNA exist since some of the interactions share common sites. In splicing buffer but without the splicing extract added, many of these interactions are stable up to at least 50 degrees C. These interactions, however, are dissociated during the in vitro splicing reaction. This dissociation requires ATP and it occurs during the first 30 min. of the splicing reaction. Pre-mRNAs containing psoralen cross-links in different locations within the RNA molecule were purified and used as substrates for in vitro splicing. Psoralen cross-links at any of the double-stranded regions resulted in complete inhibition of the splicing reaction. This indicates that destabilization of the secondary structure of the SP6/mouse insulin pre-mRNA is necessary for in vitro splicing.