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Biomedical subjects

M Hussain

Publications and source records attributed to M Hussain.

At least 217 records · Page 12Linked to original sources
PubMed1987

Cloning and sequencing of the blaZ gene encoding beta-lactamase III, a lipoprotein of Bacillus cereus 569/H.

It has not been clear whether the membrane-bound beta-lactamase III of Bacillus cereus 569 is a separate enzyme or a modified form of the secreted beta-lactamase I. The membrane enzyme is an acyl-glyceride thioether-linked lipoprotein (J. B. K. Nielsen and J. O. Lampen, Biochemistry 22:4652-4656, 1983) and thus is probably a separate entity. We cloned the beta-lactamase III gene (blaZ) on a 4.9-kilobase-pair ClaI fragment from mutant strain 569/H (constitutive for high-level production of beta-lactamases I, II, and III), and the nucleotide sequence was determined. The structural gene was flanked by typical promoter, transcription termination, and translation initiation sequences. Expression of the cloned gene in Escherichia coli was low in exponential-phase cultures and increased only as the cultures reached the stationary phase. The deduced amino acid sequence indicates a pre-beta-lactamase III of 316 amino acid residues (35,021 daltons), with a 29-residue signal peptide and a mature lipoprotein form of approximately 32,500 daltons. The 12 NH2-terminal residues of a 21-kilodalton tryptic peptide from the B. cereus membrane enzyme were in agreement with the sequence deduced from the cloned gene. The amino acid sequence was highly homologous to the class A beta-lactamases, especially that of Bacillus licheniformis 749. beta-Lactamase III is a distinct class A enzyme and the product of a separate gene (blaZ).

Amino Acid Sequence↗
PubMed1986

A comparative study of prokallikreins and kallikreins from rat pancreatic tissue and juice.

Two zymogens, designated prokallikreins A and B, were isolated from homogenates of rat pancreatic tissue. The two forms of prokallikrein were found to be very similar in size and charge properties. They gave rise to very similar kallikreins on activation with exogenous trypsin. Differences in carbohydrate content of the two zymogens were probably responsible for differences seen in their behaviour on ion-exchange chromatography and immunoelectrophoresis. In contrast, only one form of prokallikrein was isolated from rat pancreatic juice. It showed almost identical behaviour on ion-exchange chromatography and identical mobility on electrophoresis to prokallikrein A. Thus it can be tentatively suggested that it is prokallikrein A which is secreted into the pancreatic juice and represents the physiologically important zymogen.

Animals↗
PubMed1986

Patterns of blood-vessel invasion by mammary tumor cells.

Rat mammary tumor TMT-081 was employed as a model for blood vessel invasion because its mode of metastasis resembles that of human tumors. The invasive mechanism was studied with two methods of serial transplantation: transfer of enzymatically dispersed solid tumors, and transfer of buffy coat containing circulating tumor cells. The latter method produced greater invasion of blood vessels, including larger veins and occasionally arteries, perhaps by obviating damage to tumor cells during enzyme treatment. The course of migration was traced by three-dimensional examination in the high voltage electron microscope, as well as the light microscope. Two broad patterns were found for the course of invasion of small and large vessels respectively.

Animals↗
PubMed1986

Esthesioneuroblastoma: cerebrospinal fluid rhinorrhea and widespread metastasis.

Esthesioneuroblastoma, a tumor of neural crest origin arising in the nasal cavity, is uncommon, may be difficult to diagnose, and frequently is not cured. We report a case that was originally diagnosed as an inflammatory polyp and recurred with extension into the anterior cranial fossa. Surgery and radiotherapy were followed by local recurrence and cerebrospinal fluid rhinorrhea. Despite initial negative results of investigation for metastases, recurrence appeared in cervical nodes and was followed by widespread bone, soft tissue, and cerebral metastasis. There was no response to multiple-agent chemotherapy. The results of surgery, radiation, and chemotherapy in this rare and lethal tumor are reviewed.

Adult↗
PubMed1985

Intravenous amrinone in left ventricular failure complicated by acute myocardial infarction.

Hemodynamic dose-response effects of intravenous amrinone were studied in 22 male patients aged 38 to 62 years with left ventricular failure occurring within 18 hours of acute myocardial infarction. After hemodynamic confirmation of a raised left-sided cardiac filling pressure--pulmonary artery occluded pressure greater than 20 mm Hg--patients were randomized to either low-dose infusion of amrinone (200 micrograms/kg/hr for 30 minutes, 400 micrograms/kg/hr for 30 minutes and then 800 micrograms/kg/hr for 30 minutes) or high-dose infusion of the drug (800, 1,600 and 3,200 micrograms/kg/hr sequentially, each for 30 minutes). Hemodynamic measurements were obtained at 1 hour before amrinone and at the end of each infusion step. Low-dose infusion of amrinone resulted in a progressive increase in cardiac output (p less than 0.05) and stroke volume (p less than 0.05) and progressive reductions in pulmonary artery occluded pressure (p less than 0.01) and systemic vascular resistance (p less than 0.05). Systemic blood pressure and heart rate were unchanged. High-dose infusion resulted in a similar increase in cardiac output (p less than 0.05) but no change in stroke volume owing to associated tachycardia (p less than 0.01). There was a significantly greater decrease in pulmonary artery occluded pressure compared with the low-dose infusion (p less than 0.05), and systemic arterial diastolic and mean pressures were also decreased (p less than 0.05). The decrease in systemic vascular resistance was of a similar order to that induced by the low-dose infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

The effect of digitoxose on insulin release, glucose oxidation and oxygen consumption by islets of lean and genetically obese diabetic (ob/ob) mice.

Digitoxose specifically and competitively inhibited glucose stimulated insulin release from islets of both lean and obese mice without affecting either the rate of glucose oxidation or the rate of glucose stimulated oxygen consumption. Obese mouse islets were marginally more resistant to the inhibitory effect of digitoxose than lean mouse islets. Digitoxose provides a means for dissociating glucose stimulated insulin release by isolated islets from their metabolism of glucose confirming that glucose metabolism per se is not a necessary prerequisite for the initiation of insulin release but is required to fuel the insulin secretory process.

Animals↗
PubMed1985

The effects on left ventricular performance of verapamil and metoprolol singly and together in exercise-induced angina pectoris.

Concurrent therapy with the calcium channel blocker, verapamil, and the beta-blocking group of compounds is usually felt to be clinically contraindicated due to the former's potent dromotropic and negative inotropic actions. The basis of this assumption was examined in a rest and exercise hemodynamic study of the effects of verapamil and the cardioselective beta-blocking drug, metoprolol, in 22 patients with stable angina pectoris and angiographically confirmed coronary artery disease. In a randomized study, 11 patients were assessed following intravenous verapamil (16 mg) alone, 11 following intravenous metoprolol (10 mg) alone, and all 22 were assessed on combination therapy. The plasma levels achieved at the time of each hemodynamic assessment were in the therapeutic range. At rest, verapamil alone significantly lowered systemic arterial pressure and vascular resistance; metoprolol alone lowered heart rate and increased systemic vascular resistance without change in systemic arterial pressure. Combination therapy reduced systemic arterial pressure and heart rate without change in cardiac output and systemic vascular resistance. During upright bicycle exercise, the changes were directionally similar. Depression of cardiac function (i.e., reduced cardiac output at increased pulmonary artery occluded pressure) occurred following metoprolol but not following verapamil; the addition of verapamil did not accentuate the depression of function induced by metoprolol. These results suggested that in patients with stable coronary artery disease, without manifest conduction system abnormality, the cardiac depressant actions of verapamil were countered by its vasodilator properties.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Cloning and sequencing of the metallothioprotein beta-lactamase II gene of Bacillus cereus 569/H in Escherichia coli.

The structural gene for beta-lactamase II (EC 3.5.2.6), a metallothioenzyme, from Bacillus cereus 569/H (constitutive for high production of the enzyme) was cloned in Escherichia coli, and the nucleotide sequence was determined. This is the first class B beta-lactamase whose primary structure has been reported. The amino acid sequence of the exoenzyme form, deduced from the DNA, indicates that beta-lactamase II, like other secreted proteins, is synthesized as a precursor with a 30-amino acid N-terminal signal peptide. The pre-beta-lactamase II (Mr, 28,060) is processed in E. coli and in B. cereus to a single mature protein (Mr, 24,932) which is totally secreted by B. cereus but in E. coli remains intracellular, probably in the periplasm. The expression of the gene in E. coli RR1 on the multicopy plasmid pRWHO12 was comparable to that in B. cereus, where it is presumably present as a single copy. The three histidine residues that are involved (along with the sole cysteine of the mature protein) in Zn(II) binding and hence in enzymatic activity against beta-lactams were identified. These findings will help to define the secondary structure, mechanism of action, and evolutionary lineage of B. cereus beta-lactamase II and other class B beta-lactamases.

Amino Acid Sequence↗
PubMed1985

A study of two diuretic/potassium combinations in heart failure.

The effect of potassium supplements was studied in 28 patients taking long term frusemide (40-80 mg daily). Plasma potassium fell when supplements were stopped, and rose towards prior values on the potassium/frusemide combination, Diumide K. In a crossover study in 14 of these patients comparing equivalent doses of frusemide, Diumide K (frusemide 40 mg, potassium 8 mmol), bumetanide, and Burinex K (bumetanide 0.5 mg, potassium 7.7 mmol) plasma potassium was lower on frusemide than on bumetanide. On Diumide K and Burinex K plasma potassium rose significantly but did not reach the levels on prior therapy. Small doses of potassium in combined formulations seem to be effective in countering the mild hypokalaemia caused by loop diuretics.

Adult↗
PubMed1985

Comparative haemodynamic effects of nicardipine and verapamil in coronary artery disease.

The haemodynamic relevance of the disparate electrophysiological and structural differences between agents blocking the slow-calcium channels in patients with exercise-induced angina pectoris is controversial. We therefore evaluated the effects of single intravenous and equivalent hypotensive doses of nicardipine (7.5 mg) or verapamil (16 mg) in a randomized single-blind study of 30 patients with angiographically documented coronary artery disease. The randomization process achieved comparable distribution of 15 patients with similar demographic data and cardiac function to each drug. Patients were evaluated at rest and during four minutes upright bicycle exercise at an individually titrated symptom-limited load in both control and post-drug assessments; the reproducibility of the haemodynamics during such tests has been previously demonstrated. Both nicardipine and verapamil induced similar reductions in systemic mean arterial blood pressure and vascular resistance; the reduction in afterload resulted in increased resting cardiac index and stroke volume index on each agent. The magnitude of the former increase was greater following nicardipine (p less than 0.05). The pulmonary artery occluded pressure (PAOP) increased following verapamil (p less than 0.01) without change following nicardipine. During dynamic exercise, neither drug improved cardiac stroke volume index, the PAOP was significantly higher following verapamil compared with nicardipine (p less than 0.05). Analysis of the cardiac performance curve demonstrated its significant depression following verapamil but not following nicardipine. Thus clear haemodynamic advantages were present, both at rest and during exercise-induced angina, for nicardipine; whether such haemodynamic effects will be reflected in symptomatic terms should be critically evaluated.

Adult↗