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Biomedical subjects

H Khan

Publications and source records attributed to H Khan.

85 records · Page 5Linked to original sources
PubMed1985

Site-directed mutagenesis of the Klebsiella pneumoniae nifL and nifH promoters and in vivo analysis of promoter activity.

The role of conserved nucleotides in nitrogen-fixation promoter function has been examined using both oligonucleotide and chemical mutagenesis to introduce base changes in the Klebsiella pneumoniae nifL and nifH promoters. Among ten mutations analysed, including six spontaneous mutations, base changes at -12, -13, -14, and -26, located in previously identified conserved sequences, perturbed the activity of the promoters, demonstrating that these sequences are required for transcription. Not all base changes produced similar strong promoter down phenotypes when the nifL and nifH promoters were compared: activation of the nifH promoter by the nifA gene product was less sensitive to base changes in conserved nucleotides than was activation of the equivalently altered nifL promoter by the nifA or ntrC products. We have found that the nifH promoter can be weakly activated by the ntrC product; this activation shows the same down response to base changes seen with ntrC activation of the nifL promoter. We present evidence that the efficient activation of the nifH promoter by nifA (but not ntrC) can be attributed to specific upstream sequences present in the nifH promoter.

Anti-Bacterial Agents↗
PubMed1977

Skin barrier properties in the newborn. Transepidermal water loss and carbon dioxide emission rates.

Relative permeabilities of newborn and adult skin to small molecules were determined by measuring emission of carbon dioxide and water vapor through skin. Transepidermal water loss (TEWL) measured on the forearm of 22 term infants was lower than that observed in 30 control adults (0.31 +/- 0.09 vs. 0.39 +/- 0.15 mg/cm2/h). There was no significant difference between newborn carbon dioxide emission rates (CDER) and adults CDER. When environmental temperature was raised from 74 to 80 derees F, large dramatic increases in adult TEWL were observed in contrast to small increases in newborns. This phenomenon suggests diminished eccrine activity in the newborn. No correlation of TEWL or CDER with respect to birth weight, sex, age or gestational age was observed. Similar permeability to carbon dioxide in neonates and adults and a decreased TEWL in neonates compared to adults suggest that even at birth the skin functions as an efficient barrier to these molecules, penetration rates, in adults, of other polar compounds should be similar to those in neonates.

Adult↗
PubMed1969

Effect of histalog, insulin and reserpine on gastric emptying and secretion in man.

Four different groups of subjects were given Histalog, insulin or reserpine or acted as controls. Changes were noted in gastric emptying, acid, chloride, parietal and non-parietal secretions and neutral chloride. Gastric emptying and secretion were measured by the Hunt and Spurrell test meal as modified by us for drug testing.Histalog stimulated gastric secretion but not emptying. Insulin stimulated both secretion and emptying. Reserpine stimulated secretion but it stimulated emptying only in one-half of the subjects.After Histalog and reserpine the rise in hydrogen and chloride secretion was equal, so the neutral chloride did not increase. After insulin the rise of chloride was proportionately greater than the rise of hydrogen, so that neutral chloride was increased.

Gastric Acidity Determination↗
PubMedDate not supplied

Cytologic diagnosis of isolated pancreatic alveolar hydatid disease with immunologic and PCR analyses. A case report.

BACKGROUND: Alveolar hydatid disease (AHD) is a rare and severe parasitic infection caused by the larval stage of the fox tapeworm, Echinococcus multilocularis. AHD mainly involves the liver, and although it may extend progressively to the pancreas, isolated pancreatic localization has not been reported previously. CASE: A 68-year-old white female presented with a multicystic mass in the pancreas. Fine needle aspiration showed some protoscolices, free hooklets and fragments of laminated layer, which are pathognomonic features of echinococcosis. Serologic analyses by an enzyme-linked immunosorbent assay using Em2plus antigen showed high antibody reactivity of the patient's serum, which is indicative of an infection with E multilocularis. Diagnosis was finally confirmed by molecular and immunologic analyses of the cytologic material by polymerase chain reaction and direct immunofluorescence. CONCLUSION: This case illustrates the value of cytology in the identification of echinococcosis, particularly when it involves extrahepatic sites, where the risk of misdiagnosis may be related to its extremely rare occurrence. Precise parasitologic tying of E multilocularis in endemic areas is important.

Aged↗
PubMedDate not supplied

Hras1 VNTR alleles as susceptibility markers for lung cancer: relationship to microsatellite instability in tumors.

PURPOSE: To further evaluate lung cancer risk associated with rare Hras1 VNTR alleles and possible biological mechanisms. MATERIALS AND METHODS: The Hras1 VNTR was genotyped in 295 lung cancer patients and 500 healthy controls by PCR and high resolution electrophoresis. Microsatellite alterations were examined in 168 tumors by PCR and capillary electrophoresis. RESULTS: 35 Hras1 VNTR alleles were found, of which 24 were defined as rare. A relative risk of 3.3 (95% CI; 1.9-6.0) associated with rare alleles was obtained using the total groups. Increased risk was significant both for males and females. When a matched control group was used, a relative risk of 12.7 (95% CI; 1.7-93.9) was calculated for individuals with rare alleles at the Hras1 VNTR locus. A low frequency of microsatellite alterations was observed (4.7%) in lung tumors. The frequency of altered microsatellite loci was higher among patients with rare Hras1 VNTR alleles than among patients with common alleles. CONCLUSION: Rare Hras1 VNTR alleles are associated with lung cancer risk, and a genetic mechanism which increases allelic diversity may be involved.

Adult↗
PubMedDate not supplied

Experimental study on a large animal model of a new thermoablation technique.

BACKGROUND: A novel technique of thermoablation, using a microtube to deliver pulses of hot water vapour, was tested on a large animal model in order to evaluate its efficacy and potential adverse effects. MATERIALS AND METHODS: The medical device consisted of a microtube extension connected to a hydropneumatic pump. Pulses of pure water were injected though the microtube where they were heated and delivered as vapour into the target zone. The method was tested on the liver of 12 healthy pigs, either during open surgery or percutaneously under ultrasounds. RESULTS: The technique was efficient and well-tolerated by the animals. Large volumes of necrotic tissue were created in a significantly short time compared to concurrent thermoablative techniques. CONCLUSION: Anticipating human application, this experimental study demonstrated a safe and efficient innovative thermoablation technique. The first human applications have been successfully performed and will be reported soon.

Animals↗
PubMedDate not supplied

Incidental neck symptoms in high energy trauma victims.

We conducted a prospective study into the incidence of neck symptoms in victims of high energy trauma. Thirty consecutive patients were questioned regarding neck and jaw pain and stiffness initially and at six weeks. Despite suffering extensive skeletal injuries as a result of road traffic accidents, only two patients had such symptoms. We conclude that the incidence of 'whip lash' is surprisingly low in victims of high energy trauma.

Accidents, Traffic↗