Biomedical subjects
Publications and source records attributed to M Y Khan.
A case of fatal polymorphic reticulosis, currently considered to be a peripheral T cell lymphoma, that was initially seen as a nasolabial swelling with a left lower lobe pulmonary nodule in a 40-year-old woman is reported. At autopsy, it was found to be associated with disseminated cryptococcosis and Pneumocystis carinii pneumonia associated with secondary severe immunodeficiency of unknown origin.
This paper describes the history of brucellosis and the current public health picture in the Kingdom of Saudi Arabia. Health protection is made more difficult by several factors: (a) the local custom of drinking raw and warm milk of sheep, goats, and camels, (b) the animal reservoir of infection in the country complicated by importation of live animals both for sacrifice during Haj periods and to increase commercial flocks, and (c) by uncontrolled movements of humans and stock across political borders.
The in vitro activities of three quinolones (ofloxacin, difloxacin, and ciprofloxacin) were compared with those of trimethoprim-sulfamethoxazole, streptomycin, tetracycline, and rifampin against 47 Brucella melitensis strains. Ofloxacin was the most active of the test antimicrobial agents. It inhibited 90% of B. melitensis strains at a concentration of 0.02 micrograms/ml.
A manic-depressive diabetic man receiving lithium carbonate therapy had massive proteinuria, which dramatically improved after the withdrawal of lithium. The authors discuss previous cases of lithium-induced nephrotic syndrome in nondiabetics and draw attention to the possibility that lithium therapy aggravates protein excretion in diabetic patients.
Equilibrium and kinetic studies of the unfolding-refolding of goat spleen cathepsin B induced by urea are reported. Tryptophan fluorescence and enzyme activity were monitored. The activity of cathepsin B is lost reversibly at 1.2 M-urea. The enzyme unfolds in two main stages, having a stable intermediate (Y) between its native (N) and fully denatured (D) states. Enzyme activity and kinetic studies of these transitions indicate the existence of at least two intermediate forms (X1 and X2) between the N and Y states. The overall denaturation and renaturation scheme is thus suggested to be N in equilibrium with X1----X2 in equilibrium with Y in equilibrium with D. The multiplicity of the intermediate and fractional regaining of the activity up to a urea concentration of 2 M indicates the presence of multidomain structure in cathepsin B.
The effects of heparin and various related polysaccharides on the circular dichroic spectra of fibronectin and its 31-kDa NH2-terminal tryptic fragment were studied. These effects were evaluated with respect to (i) spectral features of the native proteins that are sensitive to pH denaturation and breaking of disulfide bonds, (ii) sensitivity of spectral changes to Ca2+, and (iii) the fibronectin-dependent interfacial interaction known as "matrix-driven translocation." We found that native heparin causes an attenuation of the positive CD peak at 228 nm with both the intact protein and the fragment, and causes a small but reproducible red shift in the spectrum of the fragment. All of these changes are analogous to spectral changes seen with denaturation or reduction of the proteins. In contrast to the situation with the intact protein, the heparin-induced spectral changes in the fragment were abolished in the presence of 10 mM Ca2+. Desulfation of heparin lessened or destroyed its ability to induce these changes, and carboxymethylated heparin and dextran sulfate induced different kinds of spectral alterations. Fibronectin and heparin determinants required for the induction of the characteristic spectral shift of the NH2-terminal domain corresponded to those required for matrix-driven translocation, suggesting that the associated conformational change in fibronectin plays a role in this biophysical effect.
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Clinical and necropsy findings in 13 intravenous drug abusers who died of the acquired immunodeficiency syndrome (AIDS) were reviewed and compared with findings in eight patients who acquired the infection through sexual exposure, the most common mode of transmission in AIDS. No differences were found in lymphocyte counts or duration of survival, despite reports that the degree of immunosuppression in intravenous drug abusers with AIDS differs from that in homosexuals. Neoplasms were found in 25 per cent of patients with sexual risks, but not in any drug abusers (0 per cent). Two opportunistic infections (toxoplasmosis and cytomegalovirus pneumonia and esophagitis) were more common in the intravenous drug abuser group. Although cytomegalovirus has been associated with Kaposi's sarcoma, this association was not found in this study. The postmortem findings in both groups were otherwise similar.
Urea-induced unfolding of bovine serum albumin and one of its fragments containing domain II + III has been studied by difference spectral and fluorescence emission measurements. The unfolding-refolding curves of both the proteins showed the presence of at least one stable intermediate when the transition was monitored at 288 nm. The presence of the intermediate was not detectable at 293 nm where only tryptophan contributed towards the protein absorption. However, both the proteins did show the presence of intermediate when the denaturation was monitored fluorometrically. Since domain III of the albumin is devoid of tryptophan, it is concluded that the formation of intermediate in the unfolding-refolding transition of serum albumin involves (i) unfolding of domain III, (ii) minor structural transformations in domain II, and/or (iii) the separation of the sub-domains of domain III from each other.
Brucellosis is common in the central region of Saudi Arabia. The major clue to the diagnosis is serologic testing. In 3 years, over 500 positive patients who had a titer of 1:160 or more were identified. Brucella species was the single organism most commonly recovered in all blood cultures, being found in 24% of patients with cultures positive for pathogenic bacteria. The expected greater number of Brucella cultures with high initial recorded titer was confirmed; 31% of the positive high-titer group had positive Brucella cultures. Conclusive correlation was uncommon below the 1:640 titer. The lower titers were less useful as indicators of active disease in this population, in which many people appear to have persistent low antibody levels.
Some properties of cathepsin B from a hitherto unstudied source (goat spleen) have been reported. The activity of the enzyme was optimal at pH 6.8 and it was fairly stable between pH 4.0-7.0. The maximum activity was observed at 37 degrees C and the enzyme could withstand temperature shocks up to 40 degrees C for 20 min without any significant loss of activity. Gamma-irradiation of the enzyme led to an increase in its activity in the beginning (up to 10 Gy) followed by a gradual decrease to about half of its activity at 1200 Gy. The enzyme was most active at an ionic strength of 0.022 and lost its activity substantially as the ionic strength was raised above the optimum value. The preferred protein substrate for the enzyme was found to be casein. The enzyme also hydrolyzed hemoglobin and serum albumin, but to lesser extents. In contrast to prevailing opinion, it was concluded that cathepsin B can act for a limited period even at physiological temperature, pH, etc. before it is inactivated.
Effect of salt concentration on the activity and stability of cathepsin B from buffalo spleen has been investigated. Catheptic activity was maximal at a buffer concentration of 5.5 x 10(-3) M. The enzyme was, however, highly unstable at a salt concentration lower than 1.5 x 10(-2) M. The use of 0.02 M sodium phosphate buffer has been suggested for the assay of cathepsin B activity. For storage of the enzyme, however, a 0.1 M sodium phosphate or other buffer of equivalent ionic strength has been recommended.
The domain III of bovine serum albumin containing residues 377-582 of the protein sequence was isolated and its behaviour in acid solution was studied. The fragment was found to undergo structural transformations over the pH range 3.5-4.5 known to cause N-F transition in serum albumin. On the other hand, an albumin fragment that was devoid of domain III was unable to exhibit such a transition. These results were consistent with a mechanism where N-F transition involves the separation of domain III from the rest of the albumin starts at about pH 4.3 and is completed at pH 3.5.
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A fragment of bovine serum albumin corresponding to positions 1-385 of the protein sequence has been prepared by peptic digestion. Acid-induced conformational changes in the fragment as well as in the intact albumin have been studied by hydrodynamic and spectral methods. Special emphasis has been given to the pH zone, which is known to cause the N-F transition in bovine serum albumin. In agreement with earlier reports we have shown that bovine serum albumin undergoes N-F transition in the neighbourhood of pH 4.0. Our results on the fragment showed that it was unable to exhibit the N-F transition under identical experimental conditions. Since bovine serum albumin and the peptic fragment differ in that the latter lacks the C-terminal portion (i.e. residues 386-582) of its parent molecule, we conclude that the separation of C-terminal region (from rest of bovine serum albumin molecule) and/or its unfolding is responsible for the N-F transition in bovine serum albumin.
Alcide is a germicidal preparation which has been shown to kill a wide range of common pathogenic bacteria as well as fungi, in vitro. This preparation is composed of Part A and Part B which contains sodium chlorite (NaClO2) and lactic acid as the active ingredients, respectively. The two parts are combined in equal volumes immediately prior to application resulting in the formation of chlorine dioxide (ClO2). Alcide gel was applied to the shaven backs of 18 female Sprague-Dawley rats in a 2.0-g/kg dose by combining 1 g of each part immediately prior to administration. This dose was applied for a period of 10 days to reach a steady state. On the 11th day, 36Cl-labeled Alcide gel, which contained Na36ClO2 in Part A, was administered to the animals in a 0.6-g dose (2.0 g/kg) containing 0.1 microCi. The half-life for 36Cl absorption was 22.1 hr while the elimination half-life was 64.0 hr. 36Cl was excreted by the kidneys with chloride (Cl-) and chlorite as the metabolites. Ninety-six hours after Alcide administration, radioactivity was highest in whole blood and lowest in fat. In a 90-day subchronic dermal toxicity study in rabbits, exposure to Alcide gel resulted in decreased glutathione concentrations in blood of the group receiving 2.0 g/kg Alcide as well as in the placebo gel group which received the same dose of gel.