Prognostication and Prediction of Outcomes in Patients with Organophosphorus and Carbamate Poisoning: A Prospective Cohort Study

Background

Organophosphorus (OP) and carbamate poisoning are significant concerns in developing nations. This study evaluates the effectiveness of the ChE check mobile, a cholinesterase-rapid bedside diagnostic test, in the diagnosis and management of OP and carbamate poisoning.

Materials and methods

We conducted this prospective observational study, involving patients with OP and carbamate poisoning over 1 year (June 2016 to June 2017) at a single tertiary care center. Levels of RBC cholinesterase (E-AChE), butyl cholinesterase (BChE), and various other determinants were systematically coded and analyzed.

Results

The study population (n = 60) consisted primarily of males (n = 43; 71.7%), with a mean age of 30.6 (SD: 13.7) years. Monocrotophos (n = 10; 20.4%) and carbofuran (n = 4; 8.1%) were the commonest OP and carbamate compounds, respectively. The median initial atropinization dose was 10 (IQR: 0, 61.5) mg, with a median total administered atropine dose of 116 (IQR: 32, 320) mg. A significant negative correlation was found between E-AChE levels and both the initial atropinization dose (ρ: -0.653, p-value < 0.001) and total atropine requirement (ρ: -0.659, p-value < 0.001) during admission. An E-AChE cut-off of 4 units/g hemoglobin provided an area under the curve of 0.73 (sensitivity: 80.0%, specificity: 68.6%, p-value < 0.001) for predicting moderate to severe peradeniya organophosphorus poisoning.

Conclusion

The check mobile device can be a valuable tool for prognosticating patients. There was a significant correlation between low E-AChE levels and the atropine requirement and severity.

How to cite this article

Jha A, Hazra D, Yadav B, Zachariah A, Alex R. Prognostication and Prediction of Outcomes in Patients with Organophosphorus and Carbamate Poisoning: A Prospective Cohort Study. Indian J Crit Care Med 2024;28(2):141-147.

Acute work-related hazardous eye exposures in a health care environment - An observational study from a tertiary care hospital in South India

Purpose:

Healthcare workers (HCW) are exposed to numerous occupation-related eye hazards. We studied the epidemiological distribution, risk factors, and severity of acute work-related hazardous exposure/infection (WRHEI) to the eyes of HCW in a tertiary healthcare institution in Southern India.

Methods:

In this prospective observational study, we included HCW who reported acute WRHEI between February 15, 2017 and August 14, 2017 from a total 11,628 HCWs (staff and students). Each HCW underwent a comprehensive eye examination. Information regarding WRHEI was collected by a structured questionnaire. Statistical analysis was performed using SPSS Version 20.0.

Results:

Cumulative incidence of acute WRHEI in 6 months was 0.8%, 95% CI (0.64–0.96). Among the 94 reporting WRHEI, 82 (87.2%) were staff and 12 (12.8%) students. Mean age was 31.53 ± 8.39 years and 65 (69%) were females. Exposures were reported more commonly among nurses (25.5%), followed by technicians (18%), and housekeeping staff (15.9%). Infectious eye hazards accounted for 50%. Noninfectious eye hazards included exposure to chemicals (28%) and blood and body fluid (8%). Among them, awareness regarding personal protective equipment (PPE) and its usage was present in 44.6 and 27.6%, respectively. Multivariable logistic regression analysis showed that HCWs working in clinical areas (adjusted odd’s ratio (AOR): 3.23, 95% CI: 1.12–9.34) and not wearing glasses (AOR: 3.72, 95% CI: 1.33–10.34) had a significantly higher risk of acute WRHEI.

Conclusion:

Cumulative Incidence of WRHEI eye was 8 per 1000 in 6 months. Infectious conjunctivitis is half the burden followed by chemical exposures. Awareness regarding eye safety and usage of PPE was low.

Clinical presentation of type 1 and type 2 pyrethroid poisoning in humans

BACKGROUND

It is unclear if the clinical presentation of poisoning with type 1 and type 2 pyrethroid compounds is different. This study was undertaken to detail the clinical profile and outcome of patients presenting with pyrethroid poisoning and to quantify serum pyrethroid levels.

PATIENTS AND METHODS

In this prospective study, patients were categorised as poisoning with type 1 pyrethroids or type 2 pyrethroids. Blood samples were sent for compound identification and quantification. Clinical features and outcomes were compared between the two groups. Factors associated with moderate and severe toxicity were explored using univariate logistic regression analysis and presented as odds ratio (OR) and 95% confidence intervals (CI).

RESULTS

Type 1 pyrethroids were implicated in 16 patients and type 2 in 43 patients. The incidence of nausea and vomiting (81.2% vs. 81.3%) and tremor (37.5% vs. 32.6%) were similar in type 1 and type 2 poisoning; paraesthesia (6.2% vs. 32.6%, p = 0.04), hypersalivation (0% vs. 20.9%, p = 0.04), seizures (0% vs. 7%, p = 0.29) and depressed sensorium (0% vs. 18.6%, p = 0.03.) were observed more frequently in type 2 pyrethroid poisoning. Pyrethroids were detected in the serum samples of 24 patients; quantification was possible in 22 patients in whom serum levels ranged from 1.1 to 453 μg/ml. The compounds were undetectable in 35 patients. Two patients (lambda-cyhalothrin poisoning and cypermethrin poisoning) required intubation for low sensorium and respiratory distress. The median (interquartile range) duration of hospitalization was 12 (12-24) hours. All patients survived. Factors associated with moderate and severe toxicity included ingestion of a type 2 pyrethroid, lambda-cyhalothrin (OR 7.81, 95%CI 1.55-39.37, p = 0.01) and volume ingested (OR 1.01, 95%CI 1.00-1.02, p = 0.02).

CONCLUSION

Patients with pyrethroid poisoning present predominantly with mild to moderate symptoms. Paraesthesia and hypersalivation are more frequent in type 2 poisoning. A favourable outcome can be expected.

Designing, optimization, and validation of whole blood direct T-ARMS PCR for precise and rapid genotyping of complex vertebral malformation in cattle

Background

DNA testing in the cattle industry undergoes multiple hurdles. Successful genotyping involves the transportation of samples from the field to the laboratory in a chilled environment followed by DNA extraction, and finally, a specific genotyping protocol is followed. Various researches are focused on overcoming these issues. Microcards offer blood transportation at ambient temperature. Direct PCR methods can save the time of DNA extraction but available only for simplex PCR. Tetra Primer-Amplification Refractory Mutation System based Polymerase Chain Reaction (T-ARMS PCR) can make DNA testing faster in a low-cost setting. The present study was aimed to design, optimize, and validate a T-ARMS PCR for faster DNA testing of SNP responsible for Complex Vertebral Malformation (CVM)-an important genetic disease of the cattle industry. Further, a direct T-ARMS PCR from whole blood was developed to avoid the DNA extraction steps. Lastly, using the optimized protocol, genotyping of blood spotted on Microcard eliminates the need for cold chain maintenance in the transportation of samples.

Results

The present study demonstrated a novel T-ARMS PCR-based genotyping of the SNP rs438228855, which is responsible for CVM. Here, wild genotypes were recognized by 389 bp and 199 bp bands in agarose gel, while the carrier genotype showed an additional 241 bp band. The developed protocol was validated using PCR-Primer Introduced Restriction Analysis (PCR-PIRA) and sequencing. The present study further established a direct T-ARMS PCR for this SNP from whole blood. Different conditions such as heparin and EDTA treated blood, the need for pre-treatment, and two different DNA Polymerases for the direct PCR were optimized. Finally, our optimized protocol successfully genotyped the whole blood samples dried on Insta™DNA cards.

Conclusions

The present study reported the usefulness of primer modified T-ARMS PCR for detecting CVM for the first time. To the best of our knowledge, direct PCR in T-ARMS PCR has never been reported. Lastly, the use of microcards in the developed protocol can make the assay useful in the DNA testing of field samples.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12896-021-00696-5.

Effects of heat stroke on surface ECG: a study on clinical outcomes

Aims

Classic heat stroke is associated with high in-hospital mortality and morbidity. The relation between the ECG findings in heat stroke and the clinical outcomes of these patients has not been studied. The aim of this study was to describe the electrocardiographic features in patients with classic heat stroke and to determine if there is any correlation of ECG findings with in-hospital outcomes.

Methods

We performed a retrospective study on 50 patients with classic heat stroke during summer months of 2016-2018. All 12-lead electrocardiographic recordings obtained from these patients were subjected to in-depth analysis. Statistical analysis was done to determine the correlation of electrocardiographic findings with in-hospital outcomes.

Results

37 patients were in sinus rhythm, while supraventricular arrhythmias including atrial fibrillation (n=6), ectopic atrial tachycardia (n=4) and atrial flutter (n=2) were observed in the rest. There was a high prevalence of QTc prolongation, low voltage P waves, conduction defects like incomplete right bundle branch block and repolarisation abnormalities. The ratio of QRS voltage in the limb leads to that in precordial leads was ≤0.5 in nearly three-fourths of the patients. Among the observed electrocardiographic features, low P-wave voltage (<0.01 mV) in lead II was found to have statistically significant correlation with adverse in-hospital outcome (OR 8.93, p=0.04), after adjustment for clinical covariates.

Conclusion

There was high incidence of atrial arrhythmias in patients with classic heat stroke. A low P-wave voltage (<0.01 mV) in lead II was predictive of adverse in-hospital outcome in this cohort of patients.

Prevalence and risk factors for neck pain among health care workers

Background: Work related neck pain (WRNP) is common among professionals. Its cause is multifactorial and results in loss of productivity and avoidable morbidity. Aims & Objectives: To estimate the prevalence and risk factors of WRNP among the support staff of a tertiary hospital. Material & Methods: 558 support staff were randomly selected to estimate the prevalence of neck pain. Staff with severe WRNP were then included in a nested case control study to identify risk factors. Results: 37% of workers reported neck pain in the preceding 3 months. Female gender, improper posture, jobs requiring repetitive movements, perception of decreased job control, high body mass index and psychosocial stress were identified as the significant risk factors. Conclusion: Better ergonomics, improving the perception of job control and encouraging micro breaks during the work time may decrease WRNP.

Antinuclear antibodies in scrub typhus: Transient occurrence during acute illness

Background & objectives

The pathological hallmark of scrub typhus infection is focal or disseminated vasculitis. As with other infections, antinuclear antibodies (ANA) have been previously described in scrub typhus. However, the underlying mechanisms and implications of this immunological phenomenon is not well understood. In the present work it was assessed whether ANA is associated with illness severity and outcomes.

Methods

In this prospective study spanning one year, patients fulfilling the diagnostic criteria for scrub typhus were recruited. Patients with other acute infective febrile illnesses were taken as controls. ANA positivity was compared between the cases and controls. ANA in scrub typhus was assessed for correlation with disease severity, organ dysfunction and outcomes.

Results

The cohort comprised of 149 patients (scrub 89; controls 60) with mean age 46.5 (SD=16.9) yr; 48.3% were female. ANA was detected in 48 (53.9%) patients with scrub typhus and 9(15%) controls (p < 0.001). The ANA pattern was predominantly speckled (93.8%) in both scrub typhus patients and controls. In patients with scrub typhus, ANA positivity was associated with increasing APACHE-III score [Odds ratio (OR) 1.01; 95% CI 0.99-1.03; p = 0.09]. On bivariate analysis, ANA tended to be correlated with acute respiratory distress syndrome (OR 2.32; 95% CI 0.98-5.46; p = 0.06), hepatic dysfunction (OR 2.25; 95% CI 0.94-5.39, p = 0.06) and aseptic meningitis (OR 6.83; 95% CI 0.80-58.05, p = 0.08). The presence of these antibodies did not correlate with duration of hospitalization or mortality. Convalescent sera on 31 ANA positive scrub typhus patients demonstrated persistence of ANA in only 5 (16.1%) patients.

Interpretation & conclusion

The disappearance of ANA during the convalescent phase suggests that ANA is expressed during the acute phase of scrub typhus infection. Its association with organ dysfunction warrants further study of the mechanisms and impact of autoantibody formation in scrub typhus.

Association analysis of novel polymorphisms in 2', 5'-oligoadenylate synthetase gene with reproductive traits in indigenous and cross-bred cattle of Indian Origin

2', 5'-Oligoadenylate synthetases (OAS) are important components of an interferon-mediated antiviral pathway. No polymorphisms in exonic regions of bovine OAS1 gene have been identified and associated with reproduction traits. The objective of the study was to detect and evaluate the effects of mutations in exonic region of bovine OAS1 gene with reproduction traits in cattle. DNA samples collected from 250 individual cows of two Indian dairy breeds (Sahiwal and Frieswal) of cattle were used in the study. The genetic variants of the OAS1 gene were identified with polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and sequence analysis using seven set of primer pairs. The PCR-SSCP analysis revealed polymorphism in the fragments comprising of exon 2, exon 5 and first fragment of exon 6 while the fragments of exons 1, 3, 4 and second fragment of exon 6 were monomorphic in Sahiwal and Frieswal cattle. The mutations in the amplified region comprising of exon 2 were found to have significant association with age at first breeding and calving, service period, dry period and pregnancy rate. Significant associations were found between SNPs in the exon 5 and service and dry periods of the animal, whereas the genetic variants in the first fragment of the exon 6 showed significant association with age at first breeding and calving. To our knowledge, this study demonstrated for the first time that the polymorphisms in OAS1 gene were associated with reproductive traits and it can be chosen as a candidate gene for improvement of reproductive performance of cattle.

LAMP assay for rapid diagnosis of cow DNA in goat milk and meat samples

Animal species detection is one of the crucial steps for consumer's food analysis. In the present study we developed an in-house built loop-mediated isothermal amplification (LAMP) assay for rapid detection of adulterated cow DNA in goat milk/meat samples. The cow milk/tissue DNA in goat milk/meat samples were identified in the developed LAMP assay by either naked eye visualizing with SYBR Green I dyes or by detecting the typical ladder pattern on gel electrophoresis. This test can detect up to minimum 5% level of cow components admixed in goat milk/meat samples and can be completed within 1 h 40 min starting from DNA extraction from milk/meat samples and can be performed in a water bath. Developed LAMP methodology is simple; rapid and sensitive techniques that can detect adulterant like cow components in goat milk/meat are more accurate than other existing DNA based technologies.

Compliance to treatment among type 2 diabetics receiving care at peripheral mobile clinics in a rural block of Vellore District, Southern India

Background:

Providing treatment to patients with diabetes mellitus in rural areas at a cost they can afford is a public health challenge.

Aims:

This study aims to measure the rate of compliance to oral hypoglycemic agents among patients with type 2 diabetes mellitus attending peripheral mobile clinics in rural South India. To study factors that impact glycemic control.

Setting and Design:

A cross-sectional study was done among patients attending peripheral mobile clinics in a rural block in Southern India.

Materials and Methods:

Pill counts were done to assess compliance. Participants' dietary intake was measured using a 24 h diet recall and their level of physical activity was measured using the WHO Global Physical Activity Questionnaire. Glycated hemoglobin (HbA1c) was measured for all participants.

Statistical Analyses Used:

Data were entered on EpiData and analyzed using SPSS. The prevalence of good glycemic control and good compliance was measured. A multiple linear regression was done to study factors affecting glycemic control.

Results:

Overall 52% of the participants were compliant to at least one drug and 50% had achieved good glycemic control. Compliance increased by 2.1% with every passing year since the diagnosis of diabetes. HbA1c reduced by 0.09% for every 10% increase in overall compliance.

Conclusions:

Levels of compliance and glycemic control achieved through this primary care team is comparable to those achieved through other systems.

Clinico-epidemiological Profile of Snake Bites over 6-year Period from a Rural Secondary Care Centre of Northern India: A Descriptive Study

Estimated deaths due to snake bites are more than 46,000 annually in India. Ninety-seven percent bites occur in rural areas. Data on snake bites from Jharkhand rural area are sparse. This study describes 6 years profile of snake bite patients from January, 2007 to December, 2012 at Nav Jivan Hospital in Palamu district, Jharkhand.

Purple urine bag syndrome: time for awareness

Purple urine bag syndrome occurs commonly in long-term catheterized patients causing significant stress for patients, care takers, and health care providers. This may lead to unwarranted investigation as well as treatment when not identified early. Demographic changes in Indian population with increasing geriatric care make it a case to increase awareness of this condition among health care providers in primary and secondary care settings.

Perceptions of farmers' and farmworkers' wives on the use and hazards of agrochemicals in rural Vellore

Poor handling, storage, and application of agrochemicals have resulted in a steep rise in mortality and morbidity associated with their use. This study aimed at assessing the awareness of wives of farmers and farmworkers in rural Vellore on the use and health effects of agrochemicals to identify gaps in their knowledge. A cross-sectional survey among 512 wives was conducted. Nearly 75 percent of the wives (384/512) did not know that agrochemicals could pass through skin. Also, wives who owned between 1 and 5 acres of land had a higher odds of knowing that agrochemicals were harmful (OR: 1.71(1.03-2-85), p < 0.05) and need to be disposed safely (OR: 4.76 (1.47-15.36), p < 0.05), than those owning less than an acre or no land. There is a need to educate women associated with agriculture in India on the harms and proper use of agrochemicals in order to better protect and inform their households and communities.

Overdose of mycophenolate mofetil managed in a secondary care hospital in South India

Mycophenolate mofetil (MMF) is a commonly used immunosuppressive agent and is considered relatively safe with minimal side-effects in therapeutic doses. However, data regarding the effects of an overdose is sparse and therefore, concerns remain regarding its safety. Here, we report the case of a 24-year-old young woman who consumed high dose (10 g) of MMF with suicidal intent. We did not observe any complications related to MMF overdose.

Melioidosis: a report of two cases

Melioidosis is increasingly being reported from India in the past few years. Since it can mimic tuberculosis during the initial presentation, treatment with antituberculosis drugs is common. It should be considered in the differential diagnosis of any pyrexia of unknown origin. We report two cases of melioidosis that presented with pyrexia of unknown origin and a localized cutaneous abscess over the chest wall.

Foot care knowledge and practices and the prevalence of peripheral neuropathy among people with diabetes attending a secondary care rural hospital in southern India

Background:

Diabetes mellitus is a multifaceted disease and foot ulceration is one of its most common complications. Poor foot care knowledge and practices are important risk factors for foot problems among people with diabetes.

Aims:

To assess the knowledge and practices regarding foot care and to estimate the proportion of people with peripheral neuropathy among people with diabetes.

Settings and Design:

The cross-sectional study was conducted in 212 consecutive diabetes patients attending the out-patient department of a rural secondary care hospital.

Materials and Methods:

A questionnaire which included demographic details, knowledge questionnaire, and Nottingham assessment of functional foot care was administered. The Michigan Neuropathy Screening Instrument was used to identify peripheral neuropathy.

Statistical Analysis Used:

Descriptive analysis with frequency distribution for knowledge and practice scores, univariate analysis, and multiple logistic regressions to find significant variables associated with good knowledge and practice scores.

Results:

About 75% had good knowledge score and 67% had good foot care practice score. Male gender (OR 2.36, 95% CI 1.16–4.79), poor education status (OR 2.40, 95% CI 1.19–4.28), and lesser duration of diabetes (OR 2.24, 95% CI 1.15–4.41) were significantly associated with poor knowledge on foot care. Poor knowledge was associated with poor foot care practices (OR 3.43, 95% CI 1.75–6.72). The prevalence of neuropathy was 47% (95% CI 40.14–53.85) and it was associated with longer duration of the disease (OR 2.18, 95% CI 1.18–4.04).

Conclusion:

There exist deficiencies in knowledge and practices regarding foot care. Male gender, low education, and lesser duration of diabetes are associated with poor knowledge scores. The prevalence of diabetic peripheral neuropathy is high.

Compatibilization of SBR/NBR Blends Using Chemically Modified Styrene Butadiene Rubber

The effect of dichlorocarbene modified styrene butadiene rubber (DCSBR) as a compatibilizer in blends of acrylonitrile butadiene rubber and styrene butadiene rubber (SBR/NBR) has been studied. The cure characteristics, physical properties, crosslink density, FTIR studies and low temperature transitions of the blends were determined as a function of chlorine content of DCSBR. Compatibilizing efficiency depended on the chlorine content of DCSBR and composition of blend constituents. Effective compatibilization was achieved when chlorine content of compatibilizer was 25% and SBR content of blend was either 50% or lower. FTIR studies, glass transition behavior measured by DSC and DMA showed that an appreciable extent of molecular level miscibility has been achieved in SBR/NBR blends by using DCSBR as a compatibilizer. Improvement in mechanical properties such as tensile strength, tear strength, resilience, hardness and compression set were achieved both when DCSBR was added and chlorine content of DCSBR increased up to 25%. The resistance of the vulcanizate towards air and oil aging improved with compatibilization. The change in technological properties correlated with crosslink density of the blends assessed from swelling studies and stress-strain data.

Born with low birth weight in rural Southern India: what are the metabolic consequences 20 years later?

OBJECTIVE

Low birth weight (LBW) is common in the Indian population and may represent an important predisposing factor for type 2 diabetes (T2D) and the metabolic syndrome. Intensive metabolic examinations in ethnic LBW Asian Indians have been almost exclusively performed in immigrants living outside India. Therefore, we aimed to study the metabolic impact of being born with LBW in a rural non-migrant Indian population.

SUBJECTS AND METHODS

One hundred and seventeen non-migrant, young healthy men were recruited from a birth cohort in a rural part of south India. The subjects comprised 61 LBW and 56 normal birth weight (NBW) men, with NBW men acting as controls. Subjects underwent a hyperinsulinaemic euglycaemic clamp, i.v. and oral glucose tolerance tests and a dual-energy X-ray absorptiometry scan. The parents' anthropometric status and metabolic parameters were assessed.

RESULTS

Men with LBW were shorter (167±6.4 vs 172±6.0 cm, P<0.0001), lighter (51.9±9 vs 55.4±7 kg, P=0.02) and had a reduced lean body mass (42.1±5.4 vs 45.0±4.5 kg, P=0.002) compared with NBW controls. After adjustment for height and weight, the LBW subjects had increased diastolic blood pressure (77±6 vs 75±6 mmHg, P=0.01). Five LBW subjects had impaired glucose tolerance. In vivo insulin secretion and peripheral insulin action were similar in both the groups. Mothers of the LBW subjects were 3 cm shorter than the control mothers.

CONCLUSION

Only subtle features of the metabolic syndrome and changes in body composition among LBW rural Indians were found. Whether other factors such as urbanisation and ageing may unmask more severe metabolic abnormalities may require a long-term follow-up.

Self-harm and self-poisoning in southern India: choice of poisoning agents and treatment

OBJECTIVE

To record cases of suicide and attempted suicide among a population of 108 000 people living in a primarily rural area of southern India, with the aim of guiding policies and strategies to restrict access to poisonous compounds at community level.

METHOD

Community-based surveillance over a period of 2 years.

RESULTS AND CONCLUSION

The overall suicide rate was 71.4 per 100 000 population; the highest burden was among men. Most people died through hanging (81, 54%) and self-poisoning (46, 31%). Of the 46 who died from self-poisoning, 78.3% had taken pesticides and 19.7% had eaten poisonous plants. Eighty per cent of the self-poisoning cases obtained the poisonous substance in or in close proximity to the home, highlighting the importance of safe storage in the domestic environment. Of the 110 fatal and non-fatal self-poisoning cases, 87 (57.5%) were taken for treatment; 50 (57.4%) went to government hospitals and 37 (42.5%) to private facilities. This indicates the importance of including the private sector in the efforts to improve case management. Furthermore, the fact that 31 (67%) of the self-poisoning patients, who eventually died, were alive after 4 h provides an incentive to focus on improved case management and access to health services.

Is nitrocellulose filter binding really a universal assay for protein-DNA interactions?

The ability to bind to nitrocellulose is commonly accepted as being a universal property of proteins and has been widely used in many different fields of study. This property was first exploited in the study of DNA-binding proteins 30 years ago, in studies involving DNA binding by the lactose repressor (LacR) of Escherichia coli. Termed the filter-binding assay, it remains the quickest and easiest assay available for the study of protein-DNA interactions. However, the exact mechanism by which proteins bind to nitrocellulose remains uncertain. Given the supposedly universal nature of the interaction, we were surprised to notice that certain LacR variants were completely unable to bind simultaneously to DNA containing a single lac operator and nitrocellulose. Investigation of this loss of binding suggests that LacR requires a protein region that is both hydrophobic in nature and more or less unstructured, in order to bind to both nitrocellulose and DNA. In the case of wild-type, tetrameric LacR, the DNA-recognition domain that is not bound to DNA suffices. Dimeric LacR variants will only bind if they have certain C-terminal extensions. These experiments sound a cautionary note for the use of filter binding as an assay of choice, particularly in applications involving screening for the DNA-binding site of putative DNA-binding proteins.

Active apical secretory efflux of the HIV protease inhibitors saquinavir and ritonavir in Caco-2 cell monolayers

PURPOSE

To investigate in vitro the mechanisms involved in the gastro-intestinal absorption of the HIV protease inhibitor, saquinavir mesylate (Invirase), whose oral bioavailability is low, variable, and significantly increased by co-administration with ritonavir, also an HIV protease inhibitor but with higher oral bioavailability.

METHODS

Confluent epithelial layers of human Caco-2 cells mimicking the intestinal barrier.

RESULTS

Both saquinavir and ritonavir showed polarized transport through Caco-2 cell monolayers in the basolateral to apical direction (secretory pathway), exceeding apical to basolateral transport (absorptive pathway) by factors of 50-70 and 15-25, respectively. Active efflux was temperature dependent, saturable and inhibited by verapamil and cyclosporin A. Saquinavir and ritonavir decreased each other's secretory permeability and hence elevated their net transport by the absorptive pathway.

CONCLUSIONS

Saquinavir and ritonavir are both substrates for an efflux mechanism in the gut, most likely P-glycoprotein, which acts as a counter-transporter for both drugs. Together with sensitivity to gutwall metabolism by cytochrome P-450 3A, this may partially account for the low and variable oral bioavailability of saquinavir in clinical studies and for its increased bioavailability after co-administration with ritonavir.

A basic tail increases repression by dimeric lac repressor

Tetrameric Lac repressor achieves cooperative repression by binding simultaneously to O1 and to one of the auxiliary operators O2 or O3, thereby forcing the intervening DNA into a loop. Dimeric Lac repressor is not able to form DNA loops and consequently shows no cooperative repression. We constructed a dimeric Lac repressor mutant which exhibits increased repression to the lac operon that does not depend on specific operator-repressor-operator loops. This Lac repressor carries a synthetic tail of basic residues attached to its C terminus. With this construct, we observe an increase of the in vivo repression upon addition of auxiliary lac operators to a chromosomal lac operon controlled by O1. This suggests that the basic tail enables dimeric Lac repressor to enhance its repression by additional non-specific DNA contacts.

Single exchanges of amino acids in the basic region change the specificity of N-Myc

We exchanged specific amino acids in the basic region of the murine N-Myc protein and tested the mutant proteins for their DNA binding specificity. The amino acids we exchanged were chosen in analogy to residues of the homologous basic regions of bHLH and bZIP proteins. Mutant N-Myc peptides were expressed in Escherichia coli and specific DNA binding was monitored by gel shift experiments. For this we used palindromic target sequences with systematic base pair exchanges. Several mutants with altered DNA binding specificity were identified. Amino acid exchanges of residues -14 or -10 of the basic region lead to specificity changes (we define leucine 402 of N-Myc as +1; comparable to GCN4 see (1)). The palindromic N-Myc recognition sequence 5'CACGTG is no longer recognized by the mutant proteins, but DNA fragments with symmetrical exchanges of the target sequence are. Exchanges at position -15 broaden the binding specificity. These data were used to build a computer based model of the putative interactions of the N-Myc basic DNA binding region with its target sequence.

Determination of the DNA sequence recognized by the bHLH-zip domain of the N-Myc protein

The DNA-binding domain of the murine N-Myc protein, comprising the basic helix-loop-helix-zipper (bHLH-zip) region was expressed as a fusion protein in E. coli. The affinity purified glutathione-S-transferase-N-Myc fusion protein (GST-N-MYC) was used to select the N-Myc specific DNA-recognition motif from a pool of random-sequence oligonucleotides. After seven rounds of binding-site selection, specifically enriched oligonucleotides were cloned and sequenced. Of 31 individual oligonucleotides whose sequences were determined, 30 contained a common DNA-motif, defining the hexameric consensus sequence CACGTG. We confirm by mutational analysis that binding of the N-Myc derived bHLH-zip domain to this motif is sequence-specific.

[Biodegradable gentamicin-depot implants made of beta-tricalcium phosphate ceramics. 3. In vivo studies on drug release, tissue tolerance, and biodegradation]

In vivo drug release properties and biocompatibility of gentamicin-loaded controlled release implants made of beta-tricalcium phosphate ceramics designed for the local antibiotic treatment of bone infections were investigated. Controlled release pellets containing 0.4 and 0.8 mg of gentamicin were implanted into the femoral bone of rats. Drug release was measured from renal excretion over a time period of 3 weeks. The excretion pattern can be described by an initial phase of increased drug release was faster at higher drug loading. Drug release from glyceride-containing controlled release pellets occurs at a significantly slower rate than from drug-loaded pellets without glycerides. Histological studies after implantation of the pure ceramic pellets and the controlled release pellets into the bone tissue of rats and rabbits are showing a high tissue tolerance and the biodegradability of the implants. However, the glyceride-containing pellets are degraded at a slower rate than the pure ceramic pellets.

Encapsulation of water-soluble drugs by a modified solvent evaporation method. I. Effect of process and formulation variables on drug entrapment

Pseudoephedrine HCl, a highly water-soluble drug, was entrapped within poly (methyl methacrylate) microspheres by a water/oil/water emulsification-solvent evaporation method. An aqueous drug solution was emulsified into a solution of the polymer in methylene chloride, followed by emulsification of this primary emulsion into an external aqueous phase to form a water/oil/water emulsion. The middle organic phase separated the internal drug-containing aqueous phase from the continuous phase. Microspheres were formed after solvent evaporation and polymer precipitation. The drug content of the microspheres increased with increasing theoretical drug loading, increasing amounts of organic solvent, polymer and polymeric stabilizer, and decreased with increasing stirring time, increasing pH of the continuous phase and increased volume of the internal and external aqueous phase.