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Biomedical subjects

M Silverman

Publications and source records attributed to M Silverman.

At least 307 records · Page 17Linked to original sources

Increased bronchial responsiveness caused by ingestion of ice.

We studied 7 asthmatics who had a history of symptoms exacerbated by ice-cold drinks. Bronchial responsiveness to inhaled histamine was measured before and after ingestion of 40 ml of ice or water at room temperature. Although there was no change in baseline peak flow, a significant increase in bronchial responsiveness to histamine developed by 90 min after the ingestion of ice. No satisfactory explanation could be found.

Adolescent↗

Parathyroid carcinoma: the Lahey Clinic experience.

From 1942 to 1984, 301 operations were performed for hyperparathyroidism; nine patients (3%) had carcinoma. The mean serum calcium level of the patients with carcinoma was 14.0 mg/dl, whereas the mean serum calcium level of patients with benign hyperparathyroidism was 12.0 mg/dl. With follow-up ranging from 2 to 16 years, there has been one death 9 years after the initial operation caused by primary lung cancer. At autopsy the patient also had a recurrence of parathyroid carcinoma in the neck. There were no additional recurrences or deaths. Prognosis was not correlated with any laboratory or pathologic findings. The importance of intraoperative recognition at the time of the initial operation is stressed. En bloc resection is recommended, including ipsilateral thyroid lobectomy and dissection of the tracheoesophageal groove. Radical neck dissection is performed only for extensive cervical node metastases or for reoperations where scarring prevents accurate delineation of the extent of the tumor.

Adult↗

Further evidence of the validity of risk group definition in differentiated thyroid carcinoma.

Three hundred nine consecutive patients primarily treated at the Lahey Clinic Foundation for differentiated thyroid carcinoma between the years 1961 and 1980 were followed for a median of 13 years and a minimum of 5 years. The recurrence and survival rates of these patients are strikingly different in the low-risk group (men 40 years of age and under and women 50 years and under) compared with the high-risk group (all older patients). Only two patients died and eight others had recurrences but survived in 192 low-risk patients, whereas 18 died and 23 had recurrences in 117 high-risk patients. Thus 20% of patients with recurrence in the low-risk group died but 78% of patients with recurrence in the high-risk group died. Follicular carcinoma and major capsular invasion carries a poor prognosis, but only 22% of low-risk in contrast to 55% of high-risk patients died. The fact that low- and high-risk patients have a separate biology is emphasized by unique sex ratio differences. Low-risk patients have a constant male to female ratio of about 5:1, whereas high-risk patients have progressively increased from 1:3 to a male predominance during the past 5 decades. This study showing unique differences in results by age reemphasizes the concept of basic risk groups in differentiated thyroid cancer. The effect of this basic risk group, as in our previous report, supercedes the effect of pathologic type, extent of local disease, or aspects of therapy and exerts principal control over biologic behavior.

Adenocarcinoma↗

Computational analysis of models for cotransport.

The order of substrate interaction with a cotransport carrier is studied by numerically fitting theoretical models to empirical data for a Na+-D-glucose pathway. Our analysis is based on a least-squares minimization routine developed at CERN, and uses data derived from tracer flux of substrate under equilibrium exchange conditions. Random, Ordered mirror, and Ordered glide models are considered and the applicability of both Random and Glide systems to the experimental observations is demonstrated. A more detailed study of the Glide model provides an estimation of the relative values of the individual rate constants describing each kinetic step in the mechanism. We argue that parameterization of competing models can result in tests which will distinguish between them, even when these contain many unknowns in the proposed structure of the kinetic mechanism. The essence of this means of model discrimination is the ability to find a single set of parameter values that fits a variety of experimental observations. The ability to obtain numerical estimates of obtain numerical estimates of individual rate constants is also a useful tool in investigation of the kinetic fine structure of the carrier. For the data at hand we conclude that a complete parameterization of the Glide model cannot be attained, possibly due to a heterogeneity in the temperature at which the experiments have been performed. Three solutions to the Glide model are presented, each of which corresponds to a fit of the Glide model to a subset of the experimental data.

Biological Transport↗

Identification of genes and gene products necessary for bacterial bioluminescence.

Expression of luminescence in Escherichia coli was recently achieved by cloning genes from the marine bacterium Vibrio fischeri. One DNA fragment on a hybrid plasmid encoded regulatory functions and enzymatic activities necessary for light production. We report the results of a genetic analysis to identify the luminescence genes (lux) that reside on this recombinant plasmid. lux gene mutations were generated by hydroxylamine treatment, and these mutations were ordered on a linear map by complementation in trans with a series of polar transposon insertions on other plasmids. lux genes were defined by complementation of lux gene defects on pairs of plasmids in trans in E. coli. Hybrid plasmids were also used to direct the synthesis of polypeptides in the E. coli minicell system. Seven lux genes and the corresponding gene products were identified from the complementation analysis and the minicell programing experiments. These genes, in the order of their position on a linear map, and the apparent molecular weights of the gene products are luxR (27,000), luxI (25,000), luxC (53,000), luxD (33,000), luxA (40,000), luxB (38,000), and luxE (42,000). From the luminescence phenotypes of E. coli containing mutant plasmids, functions were assigned to these genes: luxA, luxB, luxC, luxD, and luxE encode enzymes for light production and luxR and luxI encode regulatory functions.

Cloning, Molecular↗

Oral tartrazine challenge in childhood asthma: effect on bronchial reactivity.

Ten asthmatic children who gave a history of cough or wheeze after orange drinks, were tested for tartrazine sensitivity. On separate days, either oral tartrazine (1 mg) or a placebo capsule were administered double blind. Bronchial reactivity was measured before, 30 and 60 min after ingestion by means of a histamine-inhalation challenge test. There was no change in baseline lung function after tartrazine, but histamine sensitivity (PC20) increased significantly in four of the children. No response was obtained to a larger dose of tartrazine (10 mg) in four of the non-responders. Alteration in the bronchial reactivity after an oral challenge, appears to be a sensitive means of detecting tartrazine sensitivity.

Adolescent↗

Transposon mutagenesis of marine Vibrio spp.

Coliphage P1 was used to transduce derivatives of transposons Tn5 and mini-Mu into marine Vibrio spp. Transposon Tn5 encoding tetracycline resistance (Tn5-132) was used to isolate mutants of Vibrio harveyi defective in genes for bioluminescence (lux). Insertion of transposon Tn5-132 into the lux gene region was demonstrated by intraspecific transduction with phage hv-1 and by Southern blot hybridization. Transposon mini-Mu, modified to specify tetracycline resistance, was employed to mutagenize genes for lateral flagella synthesis of Vibrio parahaemolyticus. Mini-Mu contains the lacZ structural gene, and transposition results in transcriptional fusion of Vibrio genes with the transposon lacZ gene. Thus, in these fusions, lacZ expression was proportional to the level of transcription of the target gene. Regulation of lateral flagella gene expression was studied in vivo by measuring beta-galactosidase activity, and conditions which activate transcription of these genes were identified. A method for gene cloning with transposon-induced mutations is discussed.

Coliphages↗

Bronchial responsiveness to hyperventilation in children with asthma: inhibition by ipratropium bromide.

Isocapnic hyperventilation dose response curves were constructed for 11 asthmatic children before and after pretreatment with placebo or ipratropium bromide, 40-1500 micrograms given by inhalation, on three separate days. The response before and after placebo was highly reproducible (within subject coefficient of variation 7.5%, 18%, and 22% for intervals of two hours, within two weeks, and over two weeks). It was independent of baseline lung function. Complete protection against hyperventilation induced asthma was achieved by ipratropium bromide 40 micrograms in six children and by 200 micrograms or more in a further four. The remaining child was unaffected by any dose of ipratropium up to 1500 micrograms. The dose of ipratropium required for protection was better related to the subjects' requirement for regular medication than to their sensitivity to hyperventilation or baseline lung function.

Adolescent↗

Glomerular and postglomerular permselectivity to anionic dextrans in the dog.

Glomerular (G) and postglomerular (PG) capillary permselectivity to anionic dextran markers was investigated using the multiple-indicator-dilution (MID) technique in anesthetized mongrel dogs (n = 14). A bolus of solutes that included sulfated [3H]dextran (SO4d) homogeneous fractions 15.0-28.5 A Stokes-Einstein radius, 125I-albumin (plasma reference), [14C]inulin (G reference), and creatinine (interstitial reference) was injected into the left renal artery. Serial samples of left renal venous and urine outflows were rapidly collected. Sulfated [3H]dextran was 100% recovered, indicating no secretion or reabsorption. The urine recovery of the extracellular indicators was a measure of G extraction (EG). Mean EGSO4d/EGi (+/- SD) ranged from 0.82 +/- 0.03 to 0.48 +/- 0.02 for SO4d's 15.0-28.5 A and was invariant with renal plasma flow (F). These values were 30-50% less than the fractional EG for neutral [3H]dextrans. Postglomerular capillary extraction (EPG) was calculated from the renal vein outflow curve upslope ratios. EPGso4d/EPGcreat varied inversely with F, confirming PG diffusion limitation. Mean permeability-surface area (PS) product ratios PSSO4d/PSi (+/- SD) ranged from 0.98 +/- 0.01 to 0.55 +/- 0.04 for SO4d's 15.0-28.5 A and were consistently larger than values for neutral [3H]dextrans of the same molecular size. In contrast to G charge limitation to anionic solute flux, the PG capillaries demonstrate an increase in apparent permeability to anionic relative to neutral dextrans.

Albuminuria↗

Glomerular and postglomerular transcapillary exchange in dog kidney.

The multiple-indicator dilution technique (MIDT) was used to study glomerular and postglomerular permselectivity to neutral dextran molecular weight markers in anesthetized dogs undergoing mannitol diuresis. Renal vein and urine outflow curves were obtained after an intraarterial pulse injection of 125I-labeled albumin (plasma reference), creatinine (extracellular reference), [14C]inulin, and chromatographically homogeneous 3H-labeled neutral dextrans. The urine recovery data reflect solute losses across the glomerulus. The renal vein outflow curves contain information about both glomerular and postglomerular extraction. For dextrans less than 13,500 daltons the urine transit pattern was superimposed on the glomerular markers creatinine and inulin. Relative to 125I-labeled albumin, the renal vein recoveries for creatinine, inulin, and dextrans (less than 13,500 daltons) were all equal. The renal vein mean transit time (tdextran) was greater than talbumin and less than tcreatinine. With increasing dextran size, tdextran progressively decreased. Eventually for dextrans greater than 15,500 daltons, tdextran became equal to talbumin in the renal vein, whereas urine recovery relative to inulin decreased with increasing size. Urine recovery of 3H-labeled dextran (ED) relative to inulin (Ei) provided a measure of unidirectional fractional glomerular extraction (ED/Ei). Constant infusion fractional clearance measurement of the same dextrans [U/P)D/(U/P)i) was found to equal ED/Ei obtained from the MIDT. Within the autoregulatory range of glomerular filtration, ED/Ei was invariant with reduction in renal plasma flow. Therefore, under the experimental conditions employed in the present study, diffusion across the glomerulus was negligible relative to convection. This permitted estimation of the reflection coefficients for the series of neutral dextrans. Postglomerular extraction was markedly flow dependent, which implies a major diffusion limitation. Application of a barrier-limited distributed model permitted quantitation of postglomerular capillary permeability coefficients for neutral markers of less than 5000 daltons.

Capillary Permeability↗

Multidisciplinary survey of erectile impotence.

A study was done of 220 men referred principally by family physicians to a multidisciplinary erectile dysfunction study group to determine the factors causing or contributing to impotence that had persisted for more than 2 months and for which no cause was apparent. The men were aged 21 to 79 (mean 50.3) years, and the duration of impotence was a few months to 15 years (mean 2.65 years). The men were to be assessed from general medical, endocrinologic/metabolic, psychiatric and urogenital viewpoints. The significance of the causal or contributory factors detected was scored by application of defined criteria and a four-point scale. The degree of loss of potency and of libido as well as level of concern were also scored by each specialist. Impotence was complete in 60%, and an associated decline in libido was reported by 38%. The level of concern was high--that is, normal--in 81% and slightly reduced in 9%. Full investigation by all the specialists was precluded by the severity of other conditions in 16 patients, by the return of potency following relief of anxiety/depression or genitourinary tract infection in 16 and for logistic or other reasons in 34. Although the cause of the impotence could be attributed in 186 of the patients, only 154 were fully assessed. Among these patients general medical factors were contributory in 46%, endocrinologic/metabolic factors in 44%, psychogenic factors (primary or secondary) in 60% and urogenital factors in 49%. Multiple contributing factors were identified in 65%, which underscores the importance of a multidisciplinary approach to assessing many cases of impotence.

Adult↗

Glucose polymer supplementation of feeds for very low birthweight infants.

The feeds of 14 very low birthweight infants (birth weight less than 1500 g) were supplemented with a glucose polymer (Caloreen) at the rate of 6 g/kg body weight daily. Seven day periods of supplementation were alternated with seven day periods of normal feeding. Adding the glucose polymer significantly increased the rate of weight gain in these infants from 105 g/week to 140 g/week; growth rates in terms of length and head circumference were not affected. No adverse effects were noted. Glucose polymer is a useful energy supplement for very low birthweight infants.

Body Weight↗

Erectile impotence: a clinical challenge.

The wide range of factors that may contribute to impotence is reviewed in an attempt to establish a systematized approach for assessing etiologic factors. The effects on potency of ageing, general fitness, weight, debilitating disease, use of therapeutic and other drugsincluding alcohol and neurogenic, vasculogenic, endocrine/metabolic, urogenital and psychogenic factors are considered and discussed. The review also affords a rationale for the methodology employed.

Aging↗